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Sample records for reaction rates sigma

  1. Sigma: Web Retrieval Interface for Nuclear Reaction Data

    Energy Technology Data Exchange (ETDEWEB)

    Pritychenko,B.; Sonzogni, A.A.

    2008-06-24

    The authors present Sigma, a Web-rich application which provides user-friendly access in processing and plotting of the evaluated and experimental nuclear reaction data stored in the ENDF-6 and EXFOR formats. The main interface includes browsing using a periodic table and a directory tree, basic and advanced search capabilities, interactive plots of cross sections, angular distributions and spectra, comparisons between evaluated and experimental data, computations between different cross section sets. Interactive energy-angle, neutron cross section uncertainties plots and visualization of covariance matrices are under development. Sigma is publicly available at the National Nuclear Data Center website at www.nndc.bnl.gov/sigma.

  2. The energy dependence of the pp->K+ n Sigma+ reaction close to threshold

    CERN Document Server

    Valdau, Yu; Büscher, M; Chiladze, D; Dymov, S; Dzyuba, A; Hartmann, M; Kacharava, A; Keshelashvili, I; Khoukaz, A; Koptev, V; Kulessa, P; Merzliakov, S; Mielke, M; Mikirtychiants, S; Nekipelov, M; Ohm, H; Papenbrock, M; Rathmann, F; Serdyuk, V; Ströher, H; Trusov, S; Wilkin, C

    2010-01-01

    The production of the Sigma+ hyperon through the pp->K+nSigma+ reaction has been investigated at four energies close to threshold, 1.826, 1.920, 1.958, and 2.020 GeV. At low energies, correlated K+pi+ pairs can only originate from Sigma+ production so that their measurement allows the total cross section for the reaction to be determined. The results obtained are completely consistent with the values extracted from the study of the K+-proton correlation spectra obtained in the same experiment. These spectra, as well as the inclusive K+ momentum distributions, also provide conservative upper limits on the Sigma+ production rates. The measurements show a Sigma+ production cross section that varies roughly like phase space and, in particular, none of the three experimental approaches used supports the anomalously high near-threshold pp->K+ nSigma+ total cross section previously reported [T. Rozek et al., Phys. Lett. B 643, 251 (2006)].

  3. Examination and experimental constraints of the stellar reaction rate factor $N_A < \\sigma v >$ of the $^{18}$Ne($\\alpha$,$p$)$^{21}$Na reaction at temperatures of X-Ray Bursts

    CERN Document Server

    Mohr, P

    2013-01-01

    The $^{18}$Ne($\\alpha$,$p$)$^{21}$Na reaction is one key for the break-out from the hot CNO-cycles to the $rp$-process. Recent papers have provided reaction rate factors $N_A $ which are discrepant by at least one order of magnitude. The compatibility of the latest experimental results is tested, and a partial explanation for the discrepant $N_A$ is given. A new rate factor is derived from the combined analysis of all available data. The new rate factor is located slightly below the higher rate factor by Matic {\\it et al.}\\ at low temperatures and significantly below at higher temperatures whereas it is about a factor of five higher than the lower rate factor recently published by Salter {\\it et al.}

  4. Applying Lean Six Sigma methodology to reduce cesarean section rate.

    Science.gov (United States)

    Chai, Ze-Ying; Hu, Hua-Min; Ren, Xiu-Ling; Zeng, Bao-Jin; Zheng, Ling-Zhi; Qi, Feng

    2017-06-01

    This study aims to reduce cesarean section rate and increase rate of vaginal delivery. By using Lean Six Sigma (LSS) methodology, the cesarean section rate was investigated and analyzed through a 5-phase roadmap consisting of Define, Measure, Analyze, Improve, and Control. The principal causes of cesarean section were identified, improvement measures were implemented, and the rate of cesarean section before and after intervention was compared. After patients with a valid medical reason for cesarean were excluded, the main causes of cesarean section were maternal request, labor pain, parturient women assessment, and labor observation. A series of measures was implemented, including an improved parturient women assessment system, strengthened pregnancy nutrition guidance, implementation of painless labor techniques, enhanced midwifery team building, and promotion of childbirth-assist skills. Ten months after introduction of the improvement measures, the cesarean section rate decreased from 41.83% to 32.00%, and the Six Sigma score (ie, Z value) increased from 1.706 to 1.967 (P cesarean section. © 2016 John Wiley & Sons, Ltd.

  5. An evaluation of the rate of absorption of solar radiation in the O2(X3Sigma-g - b1Sigma-g) transition

    Science.gov (United States)

    Mlynczak, Martin G.

    1993-01-01

    The rate at which molecular oxygen absorbs radiation in the O2(X3Sigma-g - b1Sigma-g) transition is calculated using a line-by-line radiative transfer model. This rate is critical to the determination of the population of the O2(b1Sigma-g) state required for studies of the O2(b1Sigma-g - X3Sigma-g) dayglow, the O2(a1Delta-g - X3Sigma-g) dayglow, and possibly the rates of oxidation of H2 and N2O. Previous evaluations of this rate (which is sometimes called the g-factor) have significantly overestimated its value. The rate is tabulated as a function of altitude, pressure, and solar zenith angle.

  6. A polymerase chain reaction-based approach to cloning sigma factors from eubacteria and its application to the isolation of a sigma-70 homolog from Chlamydia trachomatis.

    Science.gov (United States)

    Engel, J N; Ganem, D

    1990-05-01

    Taking advantage of the known sequence conservation of portions of bacterial sigma factor proteins, we have designed degenerate oligonucleotides corresponding to these domains and used these synthetic DNA sequences as primers in a polymerase chain reaction (PCR) to amplify DNA sequences from the chlamydial genome. The PCR products were used as a probe to recover the genomic fragments from a library of cloned murine Chlamydia trachomatis DNA. Sequence analysis of one of these clones revealed striking homology to the sigma-70 protein of Escherichia coli and the sigma-43 protein of Bacillus subtilis, strongly implying that this locus (sigA) encodes the major vegetative sigma factor of murine C. trachomatis. This PCR-based approach will be broadly applicable to the cloning of major sigma factors from other eubacteria.

  7. The role of the P sub 1 sub 1 (1710) in the NN->N SIGMA K reaction

    CERN Document Server

    Sibirtsev, A A; Cassing, W; Thomas, A W

    1999-01-01

    Using the resonance model, which was successfully applied for the study of the pp->p LAMBDA K sup + reaction, we investigate NN->N SIGMA K reactions that are expected to provide cleaner information about resonance excitations and meson exchange contributions. For this purpose we demonstrate that the invariant mass distribution for the SIGMA K system, as well as the Dalitz plot for the NN->N SIGMA K reaction, provide direct information about the SIGMA K production mechanism, which can be tested in the near future by experiments at COSY.

  8. On the {Sigma}N cusp in the pp {yields} pK{sup +}{Lambda} reaction

    Energy Technology Data Exchange (ETDEWEB)

    Abd El-Samad, S. [Atomic Energy Authority NRC Cairo, Cairo (Egypt); Borodina, E.; Dzhygadlo, R.; Gast, W.; Gillitzer, A.; Grzonka, D.; Kilian, K.; Ritman, J.; Roderburg, E.; Roeder, M.; Sefzick, T.; Wintz, P. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany); Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (Germany); Brinkmann, K.T. [Physikalisches Institut Justus-Liebig-Universitaet, Giessen (Germany); Clement, H.; Doroshkevich, E.; Ehrhardt, K.; Erhardt, A.; Wagner, G.J. [Physikalisches Institut der Universitaet Tuebingen, Tuebingen (Germany); University of Tuebingen, Kepler Center for Astro and Particle Physics, Tuebingen (Germany); Eyrich, W.; Krapp, M.; Schulte-Wissermann, M. [Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen (Germany); Freiesleben, H. [Technische Universitaet Dresden, Institut fuer Kern- und Teilchenphysik, Dresden (Germany); Hanhart, C. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany); Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (Germany); Forschungszentrum Juelich, Institute for Advanced Simulation, Juelich (Germany); Hauenstein, F.; Klaja, P.; Schroeder, W. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany); Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (Germany); Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Erlangen (Germany); Wuestner, P. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany); Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (Germany); Forschungszentrum Juelich, Zentralinstitut fuer Elektronik, Juelich (Germany); Collaboration: COSY-TOF Collaboration

    2013-03-15

    Measurements of the pp {yields} pK {sup +} {Lambda} reaction at T{sub p} = 2.28 GeV have been carried out at COSY-TOF. In addition to the {Lambda}p FSI and N {sup *} resonance excitation effects a pronounced narrow structure is observed in the Dalitz plot and in its projection on the p {Lambda} invariant mass. The strongly asymmetric structure appears at the pp {yields} NK {sup +} {Sigma} threshold and is interpreted as the {Sigma}N cusp effect. The observed width of about 20 MeV/c {sup 2} is substantially broader than anticipated from previous measurements as well as theoretical predictions. Angular distributions of this cusp structure are shown to be dissimilar to those in the residual pK {sup +} {Lambda} channel, but similar to those observed in the pK {sup +} {Sigma} {sup 0} channel. (orig.)

  9. On the SigmaN cusp in the pp -> pK+Lambda reaction

    CERN Document Server

    El-Samad, S Abd; Brinkmann, K -Th; Clement, H; Doroshkevich, E; Dzhygadlo, R; Ehrhardt, K; Erhardt, A; Eyrich, W; Freiesleben, H; Gast, W; Gillitzer, A; Grzonka, D; Hanhart, C; Hauenstein, F; Klja, P; Kilian, K; Krapp, M; Ritman, J; Roderburg, E; Roeder, M; Schulte-Wissermann, M; Schroeder, W; Sfzick, T; Wagner, G J; Wintz, P; Wuestner, P

    2012-01-01

    Measurements of the $pp \\to pK^+\\Lambda$ reaction at $T_p$ = 2.28 GeV have been carried out at COSY-TOF. In addition to the $\\Lambda p$ FSI and $N^*$ resonance excitation effects a pronounced narrow structure is observed in the Dalitz plot and in its projection on the $p\\Lambda$-invariant mass. The structure appears at the $pp \\to $N$K^+\\Sigma$ threshold and is interpreted as $\\Sigma$N cusp effect. The observed width of 20 MeV/$c^2$ is substantially broader than anticipated from previous inclusive measurements. Angular distributions of this cusp structure are shown to be dissimilar to those in the residual $pK^+\\Lambda$ channel, but similar to those observed in the $pK^+\\Sigma^0$ channel.

  10. Charged-Particle Thermonuclear Reaction Rates: II. Tables and Graphs of Reaction Rates and Probability Density Functions

    CERN Document Server

    Iliadis, Christian; Champagne, Art; Coc, Alain; Fitzgerald, Ryan

    2010-01-01

    Numerical values of charged-particle thermonuclear reaction rates for nuclei in the A=14 to 40 region are tabulated. The results are obtained using a method, based on Monte Carlo techniques, that has been described in the preceding paper of this series (Paper I). We present a low rate, median rate and high rate which correspond to the 0.16, 0.50 and 0.84 quantiles, respectively, of the cumulative reaction rate distribution. The meaning of these quantities is in general different from the commonly reported, but statistically meaningless expressions, "lower limit", "nominal value" and "upper limit" of the total reaction rate. In addition, we approximate the Monte Carlo probability density function of the total reaction rate by a lognormal distribution and tabulate the lognormal parameters {\\mu} and {\\sigma} at each temperature. We also provide a quantitative measure (Anderson-Darling test statistic) for the reliability of the lognormal approximation. The user can implement the approximate lognormal reaction rat...

  11. Measurement of the g p -> K^0 Sigma^+ reaction with the Crystal Ball/TAPS detectors at the Mainz Microtron

    CERN Document Server

    Aguar-Bartolomé, P; Arends, H J; Bantawa, K; Beck, R; Bekrenev, V; Berghäuser, H; Braghieri, A; Briscoe, W J; Brudvik, J; Cherepnya, S; Codling, R F B; Demissie, B; Dieterle, M; Downie, E J; Drexler, P; Fil'kov, L V; Glazier, D I; Gregor, R; Hamilton, D; Heid, E; Hornidge, D; Howdle, D; Isaksson, L; Jaegle, I; Jahn, O; Jude, T C; Kashevarov, V L; Keshelashvili, I; Kondratiev, R; Korolija, M; Kotulla, M; Koulbardis, A; Kruglov, S; Krusche, B; Lisin, V; Livingston, K; MacGregor, I J D; Maghrbi, Y; Mancel, J; Manley, D M; McNicoll, E F; Mekterovic, D; Metag, V; Mushkarenkov, A; Nefkens, B M K; Nikolaev, A; Novotny, R; Oberle, M; Ortega, H; Ostrick, M; Ott, P; Otte, P B; Oussena, B; Pedroni, P; Pheron, F; Polonski, A; Prakhov, S; Robinson, J; Rosner, G; Rostomyan, T; Schumann, S; Sikora, M H; Sober, D I; Starostin, A; Strakovsky, I I; Suarez, I M; Supek, I; Tarbert, C M; Thiel, M; Thomas, A; Unverzagt, M; Watts, D P; Werthmüller, D; Witthauer, L; Zehr, F

    2013-01-01

    The g p -> K^0 Sigma^+ reaction has been measured from threshold to Eg=1.45~GeV (W_cm=1.9~GeV) using the Crystal Ball and TAPS multiphoton spectrometers together with the photon tagging facility at the Mainz Microtron MAMI. In the present experiment, this reaction was searched for in the 3pi^0 p final state, assuming K^0_S -> pi^0 pi^0 and Sigma^+ -> pi^0 p. The experimental results include total and differential cross sections as well as the polarization of the recoil hyperon. The new data significantly improve the empirical knowledge about the g p -> K^0 Sigma^+ reaction in the measured energy range. The results are compared to previous measurements and model predictions. It was demonstrated that adding the present g p -> K^0 Sigma^+ results to existing data allowed a better description of this reaction with various models.

  12. Differential cross sections and recoil polarizations for the reaction gamma p -> K+ Sigma0

    CERN Document Server

    Dey, B; Bellis, M; McCracken, M E; Williams, M

    2010-01-01

    High-statistics measurements of differential cross sections and recoil polarizations for the reaction $\\gamma p \\rightarrow K^+ \\Sigma^0$ have been obtained using the CLAS detector at Jefferson Lab. We cover center-of-mass energies ($\\sqrt{s}$) from 1.69 to 2.84 GeV, with an extensive coverage in the $K^+$ production angle. Independent measurements were made using the $K^{+}p\\pi^{-}$($\\gamma$) and $K^{+}p$($\\pi^-, \\gamma$) final-state topologies, and were found to exhibit good agreement. Our differential cross sections show good agreement with earlier CLAS, SAPHIR and LEPS results, while offering better statistical precision and a 300-MeV increase in $\\sqrt{s}$ coverage. Above $\\sqrt{s} \\approx 2.5$ GeV, $t$- and $u$-channel Regge scaling behavior can be seen at forward- and backward-angles, respectively. Our recoil polarization ($P_\\Sigma$) measurements represent a substantial increase in kinematic coverage and enhanced precision over previous world data. At forward angles we find that $P_\\Sigma$ is of the s...

  13. Structure of the $\\Lambda(1405)$ and the $K^-d\\rightarrow\\pi\\Sigma n$ reaction

    CERN Document Server

    Ohnishi, Shota; Hyodo, Tetsuo; Weise, Wolfram

    2015-01-01

    The $\\Lambda(1405)$ resonance production reaction is investigated within the framework of the coupled-channels Alt-Grassberger-Sandhas (AGS) equations. We perform full three-body calculations for the $\\bar{K}NN-\\pi YN$ amplitudes on the physical real energy axis and investigate how the signature of the $\\Lambda(1405)$ appears in the cross sections of the $K^-d\\rightarrow \\pi\\Sigma n$ reactions, also in view of the planned E31 experiment at J-PARC. Two types of meson-baryon interaction models are considered: an energy-dependent interaction based on chiral $SU(3)$ effective field theory, and an energy-independent version that has been used repeatedly in phenomenological approaches. These two models have different off-shell properties that imply correspondingly different behavior in the three-body system. We investigate how these features show up in differential cross sections of $K^- d\\rightarrow \\pi\\Sigma n$ reactions. Characteristic patterns distinguishing between the two models are found in the invariant mas...

  14. A Six Sigma approach to the rate and clinical effect of registration errors in a laboratory.

    Science.gov (United States)

    Vanker, Naadira; van Wyk, Johan; Zemlin, Annalise E; Erasmus, Rajiv T

    2010-05-01

    Laboratory errors made during the pre-analytical phase can have an impact on clinical care. Quality management tools such as Six Sigma may help improve error rates. To use elements of a Six Sigma model to establish the error rate of test registration onto the laboratory information system (LIS), and to deduce the potential clinical impact of these errors. In this retrospective study, test request forms were compared with the tests registered onto the LIS, and all errors were noted before being rectified. The error rate was calculated. The corresponding patient records were then examined to determine the actual outcome, and to deduce the potential clinical impact of the registration errors. Of the 47 543 tests requested, 72 errors were noted, resulting in an error rate of 0.151%, equating to a sigma score of 4.46. The patient records reviewed indicated that these errors could, in various ways, have impacted on clinical care. This study highlights the clinical effect of errors made during the pre-analytical phase of the laboratory testing process. Reduction of errors may be achieved through implementation of a Six Sigma programme.

  15. A Six Sigma Trial For Reduction of Error Rates in Pathology Laboratory.

    Science.gov (United States)

    Tosuner, Zeynep; Gücin, Zühal; Kiran, Tuğçe; Büyükpinarbaşili, Nur; Turna, Seval; Taşkiran, Olcay; Arici, Dilek Sema

    2016-01-01

    A major target of quality assurance is the minimization of error rates in order to enhance patient safety. Six Sigma is a method targeting zero error (3.4 errors per million events) used in industry. The five main principles of Six Sigma are defining, measuring, analysis, improvement and control. Using this methodology, the causes of errors can be examined and process improvement strategies can be identified. The aim of our study was to evaluate the utility of Six Sigma methodology in error reduction in our pathology laboratory. The errors encountered between April 2014 and April 2015 were recorded by the pathology personnel. Error follow-up forms were examined by the quality control supervisor, administrative supervisor and the head of the department. Using Six Sigma methodology, the rate of errors was measured monthly and the distribution of errors at the preanalytic, analytic and postanalytical phases was analysed. Improvement strategies were reclaimed in the monthly intradepartmental meetings and the control of the units with high error rates was provided. Fifty-six (52.4%) of 107 recorded errors in total were at the pre-analytic phase. Forty-five errors (42%) were recorded as analytical and 6 errors (5.6%) as post-analytical. Two of the 45 errors were major irrevocable errors. The error rate was 6.8 per million in the first half of the year and 1.3 per million in the second half, decreasing by 79.77%. The Six Sigma trial in our pathology laboratory provided the reduction of the error rates mainly in the pre-analytic and analytic phases.

  16. Valence quark and meson cloud contributions for the gamma* Lambda -> Lambda* and gamma* Sigma0 -> Lambda* reactions

    CERN Document Server

    Ramalho, G; Tsushima, K

    2012-01-01

    We estimate the valence quark contributions for the gamma* Y -> Lambda* (Y=Lambda, Sigma0) electromagnetic transition form factors. We focus particularly on the case Lambda*=Lambda(1670) as an analog reaction with gamma* N -> N(1535). The results are compared with those obtained from chiral unitary model, where the Lambda* resonance is dynamically generated and thus the electromagnetic structure comes directly from the meson cloud excitation of the baryon ground states. The form factors for the case Y=Sigma0 in particular, depend crucially on the two real phase (sign) combination, a phase between the Lambda and Lambda* states, and the other, the phase between the Lambda and Sigma0 radial wave functions. Depending on the combination of these two phases, the form factors for the gamma* Sigma0 -> Lambda* reaction can be enhanced or suppressed. Therefore, there is a possibility to determine the phase combination by experiments.

  17. The reactions K/sup -/p to pi /sup -or+/ Sigma /sup +or-/(1385) at 42 GeV/c

    CERN Document Server

    Holmgren, S O; Barreiro, F; Hemingway, R J; Kittel, E W; Kluyver, J C; Losty, Michael J; Massaro, G G G; Van de Walle, R T; Worden, R P; Zatz, J

    1977-01-01

    The total and differential cross sections are presented. Amplitude analyses are performed and the complete sigma /sup +or-/(1385) helicity spin density matrices are extracted. The results are compared with the predictions of the additive quark model and exchange degeneracy. A substantial cross section is observed for the reaction K /sup -/p to pi /sup +/ Sigma /sup -/(1385) in the forward direction, which implies exotic meson quantum numbers in the t-channel. One possible interpretation of this process provides an explanation for the small but significant violations of the additive quark model predictions observed in the reaction K/sup -/p to pi /sup -/ Sigma /sup +/(1385) at low four-momentum transfer. In the backward direction unnatural parity exchange is shown to give a larger contribution to K /sup -/p to Sigma /sup -/(1385) pi /sup +/ than natural parity exchange. (25 refs).

  18. Measurement of the reaction gamma p --> K0 Sigma+ at photon energies up to 2.6 GeV

    CERN Document Server

    Lawall, R; Bennhold, C; Glander, K H; Goers, S; Hannappel, J; Jöpen, N; Klein, F; Klempt, E; Mart, T; Menze, D; Ostrick, M; Paul, E; Schulday, I; Schwille, W J; Wieland, F W; Wu, C

    2005-01-01

    The reaction gamma p --> K0 Sigma+ was measured in the photon energy range from threshold up to 2.6 GeV with the SAPHIR detector at the electron stretcher facility, ELSA, in Bonn. Results are presented on the reaction cross section and the polarization of the Sigma+ as a function of the kaon production angle in the centre-of-mass system, cos(Theta_K^{c.m.}), and the photon energy. The cross section is lower and varies less with photon energy and kaon production angle than that of gamma p --> K+ Sigma0. The Sigma+ is polarized predominantly at cos(Theta_K^{c.m.}) \\approx 0. The data presented here are more precise than previous ones obtained with SAPHIR and extend the photon energy range to higher values. They are compared to isobar model calculations.

  19. Reducing patients' falls rate in an Academic Medical Center (AMC) using Six Sigma "DMAIC" approach.

    Science.gov (United States)

    Kuwaiti, Ahmed Al; Subbarayalu, Arun Vijay

    2017-05-08

    Purpose The purpose of this paper is to evaluate the impact of adopting the Six Sigma define, measure, analyze, improve and control (DMAIC) approach in reducing patients fall rate in an Academic Medical Center, Saudi Arabia. Design/methodology/approach A prospective study design was adopted and this study was conducted at King Fahd Hospital of the University (KFHU) during the year 2014. Based on the historical data of the patients' falls reported at KFHU during the year 2013, the goal was fixed to reduce the falls rate from 7.18 toSix Sigma "DMAIC" approach improves the processes related to the prevention of falls. A greater reduction in patients falls rate (over 70 percent) was observed after the implementation of the improvement strategy.

  20. The pp->p Lambda K+ and pp->p Sigma0 K+ reactions with chiral dynamics

    CERN Document Server

    Xie, Ju-Jun; Oset, E

    2011-01-01

    We report on a theoretical study of the pp->p Lambda K+ and pp->p Sigma0 K+ reactions near threshold using a chiral dynamical approach. The production process is described by single-pion and single-kaon exchange. The final state interactions of nucleon-hyperon, K-hyperon and K-nucleon systems are also taken into account. We show that our model leads to a fair description of the experimental data on the total cross section of the pp->p Lambda K+ and pp->p Sigma0 K+ reactions. We find that the experimental observed strong suppression of Sigma0 production compared to Lambda production at the same excess energy can be explained. However, ignorance of phases between some amplitudes does not allow to properly account for the nucleon-hyperon final state interaction for the pp->p Sigma0 K+ reaction. We also demonstrate that the invariant mass distribution and the Dalitz plot provide direct information about the Lambda and Sigma0 production mechanism, and can be tested by experiments at COSY or HIRFL-CSR.

  1. Investigation of the pp{yields}K{sup +}n{sigma}{sup +} reaction at the magnetic spectrometer ANKE-COSY

    Energy Technology Data Exchange (ETDEWEB)

    Valdau, Yury

    2009-10-20

    This thesis describes measurements of the pp{yields}K{sup +}n{sigma}{sup +} reaction near threshold. The work was largely motivated by the lack of data for {sigma}{sup +} hyperon production in pp collisions and, in particular, by recent measurements of pp{yields}K{sup +}n{sigma}{sup +} by the COSY11 collaboration. The experiment performed by this group using a neutron detector reported surprisingly high {sigma}{sup +} cross sections that are hard to reconcile with isospin considerations. The experiment discussed in the thesis has been performed at the ANKE-COSY facility at four close-to-threshold energies. It relies on the almost background-free K{sup +} identification using the delayed-veto technique and the fact that below the threshold for pp{yields}K{sup +}n{lambda}{pi}{sup +} there is no source of the K{sup +}{pi}{sup +} correlations other than the {sigma}{sup +}{yields}n{pi}{sup +} decay. Thus, the detection of K{sup +}{pi}{sup +} pairs allows one to identify the pp{yields}K{sup +}n{sigma}{sup +} reaction without the need for a neutron detector. The analysis of three simultaneously measured spectra has been carried out, searching for any signal from a possible high {sigma}{sup +} cross section. All the K{sup +} production channels allowed at the energy of the experiment contribute to the K{sup +} inclusive and K{sup +}p correlation spectra. In the K{sup +} inclusive distributions, signals from the different production channels are summed and can only be isolated using theoretical models. In the K{sup +}p correlation spectra, there are not only signals from the direct reaction protons but also protons from hyperon decays can be observed. Thus, the signal from {sigma}{sup +}{yields}p{pi}{sup 0} decay contributes to the K{sup +}p missing mass. The study of the K{sup +}{pi}{sup +} correlations allows one to identify the {sigma}{sup +} reaction channels and to estimate the total production cross section. This method has been successfully applied to existing ANKE

  2. Reaction Rate Constant for Radiative Association of CF$^+$

    CERN Document Server

    Öström, Jonatan; Nyman, Gunnar; Gustafsson, Magnus

    2015-01-01

    Reaction rate constants and cross sections are computed for the radiative association of carbon cations ($\\text{C}^+$) and fluorine atoms ($\\text{F}$) in their ground states. We consider reactions through the electronic transition $1^1\\Pi \\rightarrow X^1\\Sigma^+$ and rovibrational transitions on the $X^1\\Sigma^+$ and $a^3\\Pi$ potentials. Semiclassical and classical methods are used for the direct contribution and Breit--Wigner theory for the resonance contribution. Quantum mechanical perturbation theory is used for comparison. A modified formulation of the classical method applicable to permanent dipoles of unequally charged reactants is implemented. The total rate constant is fitted to the Arrhenius--Kooij formula in five temperature intervals with a relative difference of $<3\\:\\%$. The fit parameters will be added to the online database KIDA. For a temperature of $10$ to $250\\:\\text{K}$, the rate constant is about $10^{-21}\\:\\text{cm}^3\\text{s}^{-1}$, rising toward $10^{-16}\\:\\text{cm}^3\\text{s}^{-1}$ fo...

  3. Cross sections of the pp{yields}K{sup +{Sigma}+}n reaction close to threshold

    Energy Technology Data Exchange (ETDEWEB)

    Budzanowski, A. [Institute of Nuclear Physics, Polish Academy of Sciences, Krakow (Poland); Chatterjee, A. [Nuclear Physics Division, BARC, Mumbai (India); Clement, H.; Dorochkevitch, E. [Physikalisches Institut, Universitaet Tuebingen (Germany); Hawranek, P. [Institute of Physics, Jagellonian University, Krakow (Poland); Hinterberger, F.; Jahn, R.; Joosten, R. [Helmholtz-Institut fuer Strahlen- und Kernphysik der Universitaet Bonn, Bonn (Germany); Kilian, K. [Institut fuer Kernphysik, Forschungszentrum Juelich, Juelich (Germany); Juelich Centre for Hadron Physics, Forschungszentrum Juelich, Juelich (Germany); Kliczewski, S. [Institute of Nuclear Physics, Polish Academy of Sciences, Krakow (Poland); Kirillov, Da. [Institut fuer Kernphysik, Forschungszentrum Juelich, Juelich (Germany); Juelich Centre for Hadron Physics, Forschungszentrum Juelich, Juelich (Germany); Fachbereich Physik, Universitaet Duisburg-Essen, Duisburg (Germany); Kirillov, Di. [Laboratory for High Energies, JINR Dubna (Russian Federation); Kolev, D. [Physics Faculty, University of Sofia, Sofia (Bulgaria); Kravcikova, M. [Technical University Kosice, Kosice (Slovakia); Lesiak, M. [Institute of Physics, Jagellonian University, Krakow (Poland); Institut fuer Kernphysik, Forschungszentrum Juelich, Juelich (Germany); Juelich Centre for Hadron Physics, Forschungszentrum Juelich, Juelich (Germany); Machner, H., E-mail: h.machner@fz-juelich.d [Institut fuer Kernphysik, Forschungszentrum Juelich, Juelich (Germany); Juelich Centre for Hadron Physics, Forschungszentrum Juelich, Juelich (Germany); Fachbereich Physik, Universitaet Duisburg-Essen, Duisburg (Germany); Magiera, A. [Institute of Physics, Jagellonian University, Krakow (Poland); Martinska, G. [P.J. Safarik University, Kosice (Slovakia); Piskunov, N. [Laboratory for High Energies, JINR Dubna (Russian Federation)

    2010-08-16

    We have measured inclusive data on K{sup +}-meson production in pp collisions at COSY Juelich close to the hyperon production threshold and determined the hyperon-nucleon invariant mass spectra. The spectra were decomposed into three parts: {Lambda}p, {Sigma}{sup 0}p and {Sigma}{sup +}n. The cross section for the {Sigma}{sup +}n channel was found to be much smaller than a previous measurement in that excess energy region. The data together with previous results at higher energies are compatible with a phase space dependence.

  4. Cross section of the $pp\\to K^+\\Sigma^+n$ reaction close to threshold

    CERN Document Server

    Budzanowski, A; Clement, H; Dorochkevitch, E; Hawranek, P; Hinterberger, F; Jahn, R; Joosten, R; Kilian, K; Kliczewski, S; Kirillov, Da; Kirillov, Di; Kolev, D; Kravcikova, M; Lesiak, M; Magiera, A; Martinska, G; Piskunov, N; Protic, D; Ritman, J; von Rossen, P; Sibirtsev, A; Sitnik, I; Siudak, R; Tsenov, R; Ulbrich, K; Urban, J; Wagner, G J

    2010-01-01

    We have measured inclusive data on $K^+$-meson production in $pp$ collisions at COSY J\\"ulich close to the hyperon production threshold and determined the hyperon-nucleon invariant mass spectra. The spectra were decomposed into three parts: $\\Lambda p$, $\\Sigma^0p$ and $\\Sigma^+n$. The cross section for the $\\Sigma^+n$ channel was found to be much smaller than a previous measurement in that excess energy region. The data together with previous results at higher energies are compatible with a phase space dependence.

  5. $\\Sigma^- p$ emission rates in $K^-$ absorptions at rest on $^6$Li, $^7$Li, $^{9}$Be, $^{13}$C and $^{16}$O

    CERN Document Server

    Agnello, M; Bertani, M; Bonomi, G; Botta, E; Bregant, M; Bressani, T; Bufalino, S; Busso, L; Calvo, D; Camerini, P; Dalena, B; De Mori, F; D'Erasmo, G; Feliciello, A; Filippi, A; Fiore, E M; Fontana, A; Fujioka, H; Genova, P; Gianotti, P; Grion, N; Lucherini, V; Marcello, S; Morra, O; Nagae, T; Outa, H; Pantaleo, A; Paticchio, V; Piano, S; Rui, R; Simonetti, G; Wheadon, R; Zenoni, A

    2015-01-01

    An experimental study of the $K^-_{stop}A\\rightarrow \\Sigma^- p A'$ reaction on $A=^6$Li, $^7$Li, $^9$Be, $^{13}$C and $^{16}$O $p$-shell nuclei is presented. The data were collected by the FINUDA spectrometer operating at the DA$\\Phi$NE $\\phi$-factory (LNF-INFN, Italy). Emission rates for the reaction in the mentioned nuclei are measured and compared with the few existing data. The spectra of several observables are discussed; indications of Quasi-Free absorptions by a $(np)$ pair embedded in the $A$ nucleus can be obtained from the study of the missing mass distributions.

  6. Towards establishing low-lying $\\Lambda$ and $\\Sigma$ hyperon resonances with $\\bar K + d \\to \\pi + Y + N$ reaction

    CERN Document Server

    Kamano, H

    2016-01-01

    A model for the $\\bar K d \\to \\pi Y N$ reactions with $Y=\\Lambda, \\Sigma$ is developed, aiming at establishing the low-lying $\\Lambda$ and $\\Sigma$ hyperon resonances through analyzing the forthcoming data from the J-PARC E31 experiment. The off-shell amplitudes generated from the dynamical coupled-channels (DCC) model, which was developed in Phys. Rev. C 90, 065204 (2014), are used as input to the calculations of the elementary $\\bar K N \\to \\bar K N$ and $\\bar K N \\to \\pi Y$ subprocesses in the $\\bar K d \\to \\pi Y N$ reactions. It is shown that the cross sections for the J-PARC E31 experiment with a rather high incoming-$\\bar{K}$ momentum, $|\\vec p_{\\bar K}|= 1$ GeV, can be predicted reliably only when the input $\\bar K N \\to \\bar K N$ amplitudes are generated from a $\\bar KN$ model, such as the DCC model used in this investigation, which describes the data of the $\\bar K N$ reactions at energies far beyond the $\\bar K N$ threshold. We find that the data of the threefold differential cross section $d\\sigma/...

  7. The pp{yields}nK{sup +}{sigma}{sup +} reaction at 2.95 GeV/c

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Bary, M.; Abdel-Samad, S.; Filges, D.; Gillitzer, A.; Hesselbarth, D.; Kilian, K.; Marwinski, S.; Morsch, H.P.; Paul, N.; Ritman, J.; Roderburg, E.; Sefzick, T.; Wintz, P. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany); Bilger, R.; Eyrich, W.; Fritsch, M.; Georgi, J.; Schroeder, W.; Stinzig, F.; Teufel, A.; Wagner, M.; Wirth, S. [Universitaet Erlangen-Nuernberg, Physikalisches Institut, Erlangen (Germany); Brinkmann, K.T. [Technische Universitaet Dresden, Institut fuer Kern- und Teilchenphysik, Dresden (Germany); Rheinische Friedrich-Wilhelms-Universitaet Bonn, Helmholtz Institut fuer Strahlen- und Kernphysik, Bonn (Germany); Clement, H.; Doroshkevich, E.; Erhardt, A.; Kress, J.; Wagner, G.J. [Universitaet Tuebingen, Physikalisches Institut, Tuebingen (Germany); Dshemuchadse, S.; Freiesleben, H.; Jakob, B.; Karsch, L.; Kuhlmann, E.; Plettner, C.; Richter, M.; Schoenmeier, P.; Schulte-Wissermann, M.; Sun, G.Y. [Technische Universitaet Dresden, Institut fuer Kern- und Teilchenphysik, Dresden (Germany); Filippi, A.; Marcello, S. [INFN Torino, Torino (Italy); Koch, H.; Mauro, S.; Steinke, M.; Wilms, A. [Ruhr-Universitaet Bochum, Institut fuer Experimentalphysik, Bochum (Germany); Michel, P.; Moeller, K.; Naumann, L.; Schamlott, A. [Forschungszentrum Dresden-Rossendorf, Institut fuer Kern- und Hadronenphysik, Dresden (Germany)

    2012-03-15

    The total cross-section of the pp{yields}nK{sup +}{sigma}{sup +} reaction was measured at COSY using a proton beam with a momentum of p{sub beam} = 2.95 GeV/c, corresponding to an excess energy of {epsilon} = 129 MeV. The neutron detector COSYnus was added to the time-of-flight spectrometer COSY-TOF which tracks charged primary and secondary particles. Thus a complete reconstruction of the exit channel was feasible by exploiting for both neutron and kaon their time and direction of flight as well as the decay of the {sigma}{sup +}-hyperon into a neutral and a charged particle. The cross-section was determined to be between {sigma} = 2.0 and 5.9 {mu}b with 68% confidence. The experimental data published so far by various groups for this reaction are assessed as a whole. We conclude that either the theoretical models lack some important aspect of the reaction mechanism if one takes the experimental data at face value, or the experimental data are inconsistent and therefore theoretical descriptions must fail. (orig.)

  8. Monte Carlo analysis of uncertainty propagation in a stratospheric model. 2: Uncertainties due to reaction rates

    Science.gov (United States)

    Stolarski, R. S.; Butler, D. M.; Rundel, R. D.

    1977-01-01

    A concise stratospheric model was used in a Monte-Carlo analysis of the propagation of reaction rate uncertainties through the calculation of an ozone perturbation due to the addition of chlorine. Two thousand Monte-Carlo cases were run with 55 reaction rates being varied. Excellent convergence was obtained in the output distributions because the model is sensitive to the uncertainties in only about 10 reactions. For a 1 ppby chlorine perturbation added to a 1.5 ppby chlorine background, the resultant 1 sigma uncertainty on the ozone perturbation is a factor of 1.69 on the high side and 1.80 on the low side. The corresponding 2 sigma factors are 2.86 and 3.23. Results are also given for the uncertainties, due to reaction rates, in the ambient concentrations of stratospheric species.

  9. Reaction Order Ambiguity in Integrated Rate Plots

    Science.gov (United States)

    Lee, Joe

    2008-01-01

    Integrated rate plots are frequently used in reaction kinetics to determine orders of reactions. It is often emphasised, when using this methodology in practice, that it is necessary to monitor the reaction to a substantial fraction of completion for these plots to yield unambiguous orders. The present article gives a theoretical and statistical…

  10. Cross sections of the $pp\\to K^+\\Sigma^+n$ reaction close to threshold

    CERN Document Server

    Budzanowski, A; Clement, H; Dorochkevitch, E; Hawranek, P; Hinterberger, F; Jahn, R; Joosten, R; Kilian, K; Kliczewski, S; Kirilov, Da; Kirillov, Di; Kolev, D; Kravcikova, M; Lesiak, M; Machner, H; Magiera, A; Martinska, G; Piskunov, N; Ritman, J; von Rossen, P; Roy, B J; Sibirtsev, A; Sitnik, I; Siudak, R; Tsenov, R; Ulbrich, K; Urban, J; Wagner, G J

    2009-01-01

    We have measured inclusive data on $K^+$-meson production in $pp$ collisions at COSY Juelich close to the hyperon production threshold and determined the hyperon-nucleon invariant mass spectra. The spectra were decomposed into three parts: $\\Lambda p$, $\\Sigma^0p$ and $\\Sigma^+n$. The cross sections for the later channel were found to be much smaller than a previous measurement in that excess energy region. The data together with previous results at higher energies are compatible with a phase space dependence.

  11. Reaction rates for reaction-diffusion kinetics on unstructured meshes

    Science.gov (United States)

    Hellander, Stefan; Petzold, Linda

    2017-02-01

    The reaction-diffusion master equation is a stochastic model often utilized in the study of biochemical reaction networks in living cells. It is applied when the spatial distribution of molecules is important to the dynamics of the system. A viable approach to resolve the complex geometry of cells accurately is to discretize space with an unstructured mesh. Diffusion is modeled as discrete jumps between nodes on the mesh, and the diffusion jump rates can be obtained through a discretization of the diffusion equation on the mesh. Reactions can occur when molecules occupy the same voxel. In this paper, we develop a method for computing accurate reaction rates between molecules occupying the same voxel in an unstructured mesh. For large voxels, these rates are known to be well approximated by the reaction rates derived by Collins and Kimball, but as the mesh is refined, no analytical expression for the rates exists. We reduce the problem of computing accurate reaction rates to a pure preprocessing step, depending only on the mesh and not on the model parameters, and we devise an efficient numerical scheme to estimate them to high accuracy. We show in several numerical examples that as we refine the mesh, the results obtained with the reaction-diffusion master equation approach those of a more fine-grained Smoluchowski particle-tracking model.

  12. Resonances and the thermonuclear reaction rate

    CERN Document Server

    Hussein, M S; Sargeant, A J; Pato, M P

    2003-01-01

    We present an approximate analytic expression for thermonuclear reaction rate of charged particles when the cross section contains a single narrow or wide resonance described by a Breit-Wigner shape. The resulting expression is uniformly valid as the effective energy and resonance energy coalesce. We use our expressions to calculate the reaction rate for $^{12}$C(p,$\\gamma$)$^{13}$N.

  13. Screened Thermonuclear Reaction Rates on Magnetar Surfaces

    Institute of Scientific and Technical Information of China (English)

    LIU Hong-Lin; LUO Zhi-Quan; LIU Jing-Jing; LAI Xiang-Jun

    2008-01-01

    Improving Salpeter's method, we discuss the effect of superstrong magnetic fields (such as those of magnetars) on thermonuclear reaction rates. These most interesting reactions, including the hydrogen burning by the CNO cycle and the helium burning by the triple alpha reaction, are investigated as examples on the magnetar surfaces. The obtained result shows that the superstrong magnetic fields can increase the thermonuclear reaction rates by many orders of magnitude. The enhancement may have significant influence for further study research of the magnetars, especially for the x-ray luminosity observation and the evolution of magnetars.

  14. Measurement of the reaction $\\gamma p \\rightarrow K^ + \\Sigma^{\\pm}\\pi^{\\mp}$ at photon energies up to 2.6 GeV

    CERN Document Server

    Schulday, I; Barth, J; Glander, K -H; Goers, S; Hannappel, J; Jöpen, N; Klein, F; ~Klempt, E; Menze, D; Paul, E; Schwille, W J

    2010-01-01

    The reactions $\\gamma p \\rightarrow K^{+}\\Sigma^{\\pm}\\pi^{\\mp}$ were studied with the SAPHIR detector using a tagged photon beam at the electron stretcher facility ELSA in Bonn. The decays $\\Sigma^{-} \\rightarrow n\\pi^{-}$ and $\\Sigma^{+} \\rightarrow n\\pi^{+}, p\\pi^0$ were fully reconstructed. Reaction cross sections were measured as a function of the photon energy from threshold up to $2.6\\,$GeV with considerably improved statistics compared to a previous bubble chamber measurement. The cross sections rise monotonously with increasing photon energy. The two-particle mass distributions of $\\Sigma^{\\pm}\\pi^{\\mp}$ and $K^+\\pi^-$ show substantial production of resonant states.

  15. Production of Sigma{\\pm}pi?pK+ in p+p reactions at 3.5 GeV beam energy

    CERN Document Server

    Agakishiev, G; Belver, D; Belyaev, A; Berger-Chen, J C; Blanco, A; Boehmer, M; Boyard, J L; Cabanelas, P; Castro, E; Chernenko, S; Destefanis, T Christ M; Dohrmann, F; Dybczak, A; Epple, E; Fabbietti, L; Fateev, O; Finocchiaro, P; Fonte, P; Friese, J; Fröhlich, I; Galatyuk, T; Garzon, J A; Gernhäuser, R; Gilardi, C; Golubeva, M; Gonza'lez-Di'az, D; Guber, F; Gumberidze, M; Heinz, T; Hennino, T; Holzmann, R; Ierusalimov, A; Iori, I; Ivashkin, A; Jurkovic, M; Kämpfer, B; Kanaki, K; Karavicheva, T; Koenig, I; Koenig, W; Kolb, B W; Kotte, R; Kr'asa, A; Krizek, F; Krücken, R; Kuc, H; Kuehn, W; Kugler, A; Kurepin, A; Lalik, R; Lang, S; Lange, J S; Lapidus, K; Liu, T; Lopes, L; Lorenz, M; Maier, L; Mangiarotti, A; Markert, J; Metag, V; Michalska, B; Michel, J; Morinie're, E; Mousa, J; Müntz, C; Naumann, L; Otwinowski, J; Pachmayer, Y C; Palka, M; Parpottas, Y; Pechenov, V; Pechenova, O; Pietraszko, J; Przygoda, W; Ramstein, B; Reshetin, A; Rustamov, A; Sadovsky, A; Salabura, P; Schmah, A; Schwab, E; Siebenson, J; Sobolev, Yu G; Spataro, S; Spruck, B; Ströbele, H; Stroth, J; Sturm, C; Tarantola, A; Teilab, K; Tlusty, P; Traxler, M; Trebacz, R; Tsertos, H; Wagner, V; Weber, M; Wendisch, C; Wüstenfeld, J; Yurevich, S; Zanevsky, Y

    2012-01-01

    We study the production of Sigma^+-pi^+-pK^+ particle quartets in p+p reactions at 3.5 GeV kinetic beam energy. The data were taken with the HADES experiment at GSI. This report evaluates the contribution of resonances like Lambda(1405$, Sigma(1385)^0, Lambda(1520), Delta(1232), N^* and K^*0 to the Sigma^+- pi^-+ p K+ final state. The resulting simulation model is compared to the experimental data in several angular distributions and it shows itself as suitable to evaluate the acceptance corrections properly.

  16. Regge-plus-resonance treatment of the p(gamma,K^+)Sigma^0 and p(gamma,K^0)Sigma^+ reactions at forward kaon angles

    CERN Document Server

    Corthals, T; Ryckebusch, J; Van Cauteren, T

    2006-01-01

    An effective-Lagrangian framework for K Sigma photoproduction from the proton is presented. The proposed model is applicable at forward kaon angles and photon lab energies from threshold up to 16 GeV. The high-energy part of the p(gamma,K^+)Sigma^0 and p(gamma,K^0)Sigma^+ amplitudes is expressed in terms of Regge-trajectory exchange in the t channel. By supplementing this Regge background with a number of s-channel resonances, the model is extended towards the resonance region. The resulting ``Regge-plus-resonance'' (RPR) approach has the advantage that the background contributions involve only a few parameters, which can be largely constrained by the high-energy data. This work compares various implementations of the RPR model, and explores which resonance contributions are required to fit the data presently at hand. It is demonstrated that, through the inclusion of one K and two K* trajectories, the RPR framework provides an efficient and unified description of the K^+ Sigma^0 and K^0 Sigma^+ photoproductio...

  17. How is entropy production rate related to chemical reaction rate?

    CERN Document Server

    Banerjee, Kinshuk

    2013-01-01

    The entropy production rate is a key quantity in irreversible thermodynamics. In this work, we concentrate on the realization of entropy production rate in chemical reaction systems in terms of the experimentally measurable reaction rate. Both triangular and linear networks have been studied. They attain either thermodynamic equilibrium or a non-equilibrium steady state, under suitable external constraints. We have shown that the entropy production rate is proportional to the square of the reaction velocity only around equilibrium and not any arbitrary non-equilibrium steady state. This feature can act as a guide in revealing the nature of a steady state, very much like the minimum entropy production principle. A discussion on this point has also been presented.

  18. Reaction rates for mesoscopic reaction-diffusion kinetics.

    Science.gov (United States)

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-01

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.

  19. Reaction rates for mesoscopic reaction-diffusion kinetics

    Science.gov (United States)

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-01

    The mesoscopic reaction-diffusion master equation (RDME) is a popular modeling framework frequently applied to stochastic reaction-diffusion kinetics in systems biology. The RDME is derived from assumptions about the underlying physical properties of the system, and it may produce unphysical results for models where those assumptions fail. In that case, other more comprehensive models are better suited, such as hard-sphere Brownian dynamics (BD). Although the RDME is a model in its own right, and not inferred from any specific microscale model, it proves useful to attempt to approximate a microscale model by a specific choice of mesoscopic reaction rates. In this paper we derive mesoscopic scale-dependent reaction rates by matching certain statistics of the RDME solution to statistics of the solution of a widely used microscopic BD model: the Smoluchowski model with a Robin boundary condition at the reaction radius of two molecules. We also establish fundamental limits on the range of mesh resolutions for which this approach yields accurate results and show both theoretically and in numerical examples that as we approach the lower fundamental limit, the mesoscopic dynamics approach the microscopic dynamics. We show that for mesh sizes below the fundamental lower limit, results are less accurate. Thus, the lower limit determines the mesh size for which we obtain the most accurate results.

  20. The attractive quartet potential energy surface for the CH(a{sup 4}{sigma}{sup {minus}}) + CO reaction: A role for the a {sup 4}A`` state of the ketenyl radical in combustion?

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, H.F. III [Univ. of Georgia, Athens (United States)

    1993-12-01

    Ab initio quantum mechanical techniques, including the self-consistent field (SCF), single and double excitation configuration interaction (CISD), single and double excitation double cluster (CCSD), and the single, double and perturbative triple excitation coupled cluster [CCSD(T)] methods have been applied to study the HCCO(a {sup 4}A{open_quotes}) energy hypersurface. Rate constant measurements suggest an attractive potential for the reaction of CH(a {sup 4}{sigma}{sup -}) with CO, and a vanishingly small energy barrier is predicted here in the CH(a {sup 4}{sigma}{sup -}) + CO reaction channel. The {sup 4}A{open_quotes} state of HCCO is predicted to be bound by about 30 kcal/mol with respect to separated CH(a {sup 4}{sigma}{sup -}) + CO. The authors propose that a spin-forbidden electronic deactivation of CH(a {sup 4}{sigma}{sup -}) might occur through through an intersystem crossing involving the {sup 4}A{open_quotes} state of HCCO. The energetics and the geometries of the reactants and products on both quartet and doublet energy surfaces are presented. The relationship between this research and experimental combustion chemistry has been explored.

  1. Reaction rates for a generalized reaction-diffusion master equation.

    Science.gov (United States)

    Hellander, Stefan; Petzold, Linda

    2016-01-01

    It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach, in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model and show in two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is of the order of the reaction radius of a reacting pair of molecules.

  2. Reaction rates for a generalized reaction-diffusion master equation

    Science.gov (United States)

    Hellander, Stefan; Petzold, Linda

    2016-01-01

    It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach, in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model and show in two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is of the order of the reaction radius of a reacting pair of molecules.

  3. Reactions of aromatic nitro-compounds. LV. Anionic sigma-complexes of sym-trinitrobenzene with the alkoxides of dihydric alcohols

    Energy Technology Data Exchange (ETDEWEB)

    Mel' nikov, A.I.; Gitis, S.S.; Kaminskii, A.Ya.

    1986-12-20

    The reactions of alkoxides of dihydric alcohols with 2,4,6-trinitroanisole and picryl chloride have been studied. The reaction between 2,4,6-trinitroanisole and sodium 2-hydroxyethoxide, 3-hydroxypropoxide, 4-hydroxybutoxide, and 2-methoxyethoxide gives the unsymmetrical 1-methoxy-1-hydroxyalkoxy-2,4,6-trinitrocyclohexa-2,5-dienate sigma-complexes, which are converted on heating into the 1,1-dihydroxyalkoxy-2,4-6-trinitrocyclohexa-2,5-dienate sigma-complexes. In the case of sodium 1-methoxy-1-(..beta..-hydroxyethoxy)-2,4,6-trinitrocyclohexa-2,5-dienate, heating results in intramolecular spirocyclization of the ..beta..-hydroxyethoxy grouping to give sodium 6,8,10-trinitro-1,4-dioxaspiro(4,5)deca-6,9-dienate. The reaction of sodium 3-hydroxy-propoxide, 4-hydroxybutoxide, 2-methoxyethoxide, and diethyleneglycolate with picryl chloride gives the symmetrical 1,1-dihyroxyalkoxy sigma-complexes, while sodium 2-hydroxyethoxide forms a sigma-complex with a 1,3-dioxolane spiro-ring. The composition and structures of the sigma-complexes, isolated as their sodium salts, were established by their elemental analyses and PMR and IR spectroscopy.

  4. Production of $\\Xi^*$ resonances in $\\Sigma ^{-}$ induced reactions at 345 GeV/c

    CERN Document Server

    Adamovich, M I; Baranov, S P; Barberis, D; Beck, M; Bérat, C; Beusch, Werner; Boss, M; Brons, S; Brückner, W; Buénerd, M; Busch, C; Büscher, C; Charignon, F; Chauvin, J; Chudakov, E A; Dersch, U; Dropmann, F; Engelfried, J; Faller, F; Fournier, A; Gerassimov, S G; Godbersen, M; Grafström, P; Haller, T; Heidrich, M; Hubbard, E L; Hurst, R B; Königsmann, K C; Konorov, I; Keller, N; Martens, K; Martin, P; Masciocchi, S; Michaels, R; Müller, U; Neeb, H; Newbold, D; Newsom, C R; Paul, S; Pochodzalla, J; Potashnikova, I K; Povh, B; Ransome, R D; Ren, Z; Epherre-Rey-Campagnolle, Marcelle; Rosner, G; Rossi, L; Rudolph, H; Scheel, C V; Schmitt, L; Siebert, Hans-Wolfgang; Simon, A; Smith, V; Thilmann, O; Trombini, A; Vesin, E; Volkemer, B; Vorwalter, K; Walcher, T; Wälder, G; Werding, R; Witmann, E; Zavertyaev, M V

    1999-01-01

    We report on a measurement of the differential and total cross sections of inclusive production of Xi * resonances in Sigma /sup -/- nucleus collisions at 345 GeV/c. The cross section for inclusive Xi /sub 1530//sup 0/ production is about a factor of 5 below that of Xi /sub 1320//sup -/ hyperons. The products of cross section and branching ratio for the observed channels Xi /sub 1690//sup 0/ to Xi /sup -/ pi /sup +/, Xi /sub 1820//sup -/ to Xi /sub 1530//sup 0/ pi /sup -/ and Xi /sub 1950//sup -/ to Xi /sub 1530//sup 0/ pi /sup -/ are lower by yet another order of magnitude. The Xi /sub 1820//sup -/ and Xi /sub 1950//sup -/ resonances show significantly harder x/sub F / and p/sub t/ distributions than Xi /sup -/ and Xi /sub 1530//sup 0/ hyperons. A comparison of the x/sub F/-distribution to PYTHIA and QGSM predictions provides only a partial agreement. (29 refs).

  5. Dynamical coupled-channels model of $K^- p$ reactions (II): Extraction of $\\Lambda^*$ and $\\Sigma^*$ hyperon resonances

    CERN Document Server

    Kamano, H; Lee, T -S H; Sato, T

    2015-01-01

    Resonance parameters (pole masses and residues) associated with the excited states of hyperons, Lambda^* and Sigma^*, are extracted within a dynamical coupled-channels model developed recently in Phys. Rev. C 90, 065204 (2014) through a comprehensive partial-wave analysis of the K^- p --> barK N, pi Sigma, pi Lambda, eta Lambda, K Xi data up to invariant mass W = 2.1 GeV. We confirm the existence of resonances corresponding to most, if not all, of the four-star resonances rated by the Particle Data Group. We also find several new resonances, and in particular propose a possible existence of a new narrow J^P=3/2^+ Lambda resonance that couples strongly to the eta Lambda channel. The J^P=1/2^- Lambda resonances located below the barK N threshold are also discussed. Comparing our extracted pole masses with the ones from a recent analysis by the Kent State University group, some significant differences in the extracted resonance parameters are found, suggesting the need of more extensive and accurate data of K^- ...

  6. Thermonuclear Reaction Rate Parameterization for Nuclear Astrophysics

    Science.gov (United States)

    Sharp, Jacob; Kozub, Raymond L.; Smith, Michael S.; Scott, Jason; Lingerfelt, Eric

    2004-10-01

    The knowledge of thermonuclear reaction rates is vital to simulate novae, supernovae, X-ray bursts, and other astrophysical events. To facilitate dissemination of this knowledge, a set of tools has been created for managing reaction rates, located at www.nucastrodata.org. One tool is a rate parameterizer, which provides a parameterization for nuclear reaction rate vs. temperature values in the most widely used functional form. Currently, the parameterizer uses the Levenberg-Marquardt method (LMM), which requires an initial estimate of the best-fit parameters. The initial estimate is currently provided randomly from a preselected pool. To improve the quality of fits, a new, active method of selecting parameters has been developed. The parameters of each set in the pool are altered for a few iterations to replicate the input data as closely as possible. Then, the set which most nearly matches the input data (based on chi squared) is used in the LMM as the initial estimate for the final fitting procedure. A description of the new, active algorithm and its performance will be presented. Supported by the U. S. Department of Energy.

  7. Untangling the Energetics and Dynamics of Boron Monoxide Radical Reactions (11BO; X2Sigma+)

    Science.gov (United States)

    2015-04-15

    energy-density molecules and builds up on our previously successful synthesis of higher carbon oxides COx (x=3-6). Higher-order carbon sulfides - carbon...3.1. Crossed Beam Reactions of Boron Monoxide with Acetylene anmd Ethylene (P1, P8) The reaction dynamics of boron monoxide (BO; X2Σ...with acetylene (C2H2; X1Σg+) and with ethylene (C2H4; X1Ag) were investigated under single collision conditions at collision energy of 12 to 13 kJ mol

  8. Two-temperature reaction and relaxation rates

    Science.gov (United States)

    Kolesnichenko, E.; Gorbachev, Yu.

    2016-09-01

    Within the method of solving the kinetic equations for gas mixtures with internal degrees of freedom developed by the authors and based on the approximate summational invariants (ASI) concept, gas-dynamic equations for a multi-temperature model for the spatially inhomogeneous case are derived. For the two-temperature case, the expressions for the non-equilibrium reaction and relaxation rates are obtained. Special attention is drawn to corresponding thermodynamic equations. Different possibilities of introducing the gas-dynamic variables related to the internal degrees of freedom are considered. One is based on the choice of quantum numbers as the ASI, while the other is based on the choice of internal (vibrational) energy as the ASI. Limits to a one-temperature situation are considered in all the cases. For the cutoff harmonic oscillator model, explicit expressions for the reaction and relaxation rates are derived.

  9. Quantum theory of chemical reaction rates

    Energy Technology Data Exchange (ETDEWEB)

    Miller, W.H. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States). Chemical Sciences Div.

    1994-10-01

    If one wishes to describe a chemical reaction at the most detailed level possible, i.e., its state-to-state differential scattering cross section, then it is necessary to solve the Schroedinger equation to obtain the S-matrix as a function of total energy E and total angular momentum J, in terms of which the cross sections can be calculated as given by equation (1) in the paper. All other physically observable attributes of the reaction can be derived from the cross sections. Often, in fact, one is primarily interested in the least detailed quantity which characterizes the reaction, namely its thermal rate constant, which is obtained by integrating Eq. (1) over all scattering angles, summing over all product quantum states, and Boltzmann-averaging over all initial quantum states of reactants. With the proper weighting factors, all of these averages are conveniently contained in the cumulative reaction probability (CRP), which is defined by equation (2) and in terms of which the thermal rate constant is given by equation (3). Thus, having carried out a full state-to-state scattering calculation to obtain the S-matrix, one can obtain the CRP from Eq. (2), and then rate constant from Eq. (3), but this seems like ``overkill``; i.e., if one only wants the rate constant, it would clearly be desirable to have a theory that allows one to calculate it, or the CRP, more directly than via Eq. (2), yet also correctly, i.e., without inherent approximations. Such a theory is the subject of this paper.

  10. Hyperon production in photonuclear reactions on protons and deuterons : The Kappa(0)Sigma(+) channel

    NARCIS (Netherlands)

    Lohner, H; Bacelar, J; Castelijns, R; Messchendorp, J; Shende, S; Maeda, K; Tamura, H; Nakamura, SN; Hashimoto, O

    2004-01-01

    With the combined setup of the Crystal Barrel and TAPS photonspectrometers at ELSA in Bonn we have studied photonuclear reactions on protons and deuterons. From the series of experiments on single and multiple neutral meson emission we concentrate here on the hyperon production off protons and deute

  11. Reaction Rate Parameterization for Nuclear Astrophysics Research

    Science.gov (United States)

    Scott, J. P.; Lingerfelt, E. J.; Smith, M. S.; Hix, W. R.; Bardayan, D. W.; Sharp, J. E.; Kozub, R. L.; Meyer, R. A.

    2004-11-01

    Libraries of thermonuclear reaction rates are used in element synthesis models of a wide variety of astrophysical phenomena, such as exploding stars and the inner workings of our sun. These computationally demanding models are more efficient when libraries, which may contain over 60000 rates and vary by 20 orders of magnitude, have a uniform parameterization for all rates. We have developed an on-line tool, hosted at www.nucastrodata.org, to obtain REACLIB parameters (F.-K. Thielemann et al., Adv. Nucl. Astrophysics 525, 1 (1987)) that represent reaction rates as a function of temperature. This helps to rapidly incorporate the latest nuclear physics results in astrophysics models. The tool uses numerous techniques and algorithms in a modular fashion to improve the quality of the fits to the rates. Features, modules, and additional applications of this tool will be discussed. * Managed by UT-Battelle, LLC, for the U.S. D.O.E. under contract DE-AC05-00OR22725 + Supported by U.S. D.O.E. under Grant No. DE-FG02-96ER40955

  12. Bayesian Estimation of Thermonuclear Reaction Rates

    CERN Document Server

    Iliadis, Christian; Coc, Alain; Timmes, Frank; Starrfield, Sumner

    2016-01-01

    The problem of estimating non-resonant astrophysical S-factors and thermonuclear reaction rates, based on measured nuclear cross sections, is of major interest for nuclear energy generation, neutrino physics, and element synthesis. Many different methods have been applied in the past to this problem, all of them based on traditional statistics. Bayesian methods, on the other hand, are now in widespread use in the physical sciences. In astronomy, for example, Bayesian statistics is applied to the observation of extra-solar planets, gravitational waves, and type Ia supernovae. However, nuclear physics, in particular, has been slow to adopt Bayesian methods. We present the first astrophysical S-factors and reaction rates based on Bayesian statistics. We develop a framework that incorporates robust parameter estimation, systematic effects, and non-Gaussian uncertainties in a consistent manner. The method is applied to the d(p,$\\gamma$)$^3$He, $^3$He($^3$He,2p)$^4$He, and $^3$He($\\alpha$,$\\gamma$)$^7$Be reactions,...

  13. Bayesian Estimation of Thermonuclear Reaction Rates

    Science.gov (United States)

    Iliadis, C.; Anderson, K. S.; Coc, A.; Timmes, F. X.; Starrfield, S.

    2016-11-01

    The problem of estimating non-resonant astrophysical S-factors and thermonuclear reaction rates, based on measured nuclear cross sections, is of major interest for nuclear energy generation, neutrino physics, and element synthesis. Many different methods have been applied to this problem in the past, almost all of them based on traditional statistics. Bayesian methods, on the other hand, are now in widespread use in the physical sciences. In astronomy, for example, Bayesian statistics is applied to the observation of extrasolar planets, gravitational waves, and Type Ia supernovae. However, nuclear physics, in particular, has been slow to adopt Bayesian methods. We present astrophysical S-factors and reaction rates based on Bayesian statistics. We develop a framework that incorporates robust parameter estimation, systematic effects, and non-Gaussian uncertainties in a consistent manner. The method is applied to the reactions d(p,γ)3He, 3He(3He,2p)4He, and 3He(α,γ)7Be, important for deuterium burning, solar neutrinos, and Big Bang nucleosynthesis.

  14. What is Six Sigma?

    OpenAIRE

    Gulcin Daglioglu; Inal, Tamer C.; Kiymet Aksoy

    2009-01-01

    Sigma (σ) refers to Standard Deviation which is a measure of variation in statistics. Methodology of Six Sigma is a management philosophy that is based on the theory that parameters can be cotrolled. Six Sigma applications follow the process of identifying and defining defects, analyzing the defects using various measures, suggesting improvements and having metrics or controls in place to achieve the goals of the business. The error rate is defined as the number of error in a million. An...

  15. CHLORINATION OF AMINO ACIDS: REACTION PATHWAYS AND REACTION RATES.

    Science.gov (United States)

    How, Zuo Tong; Linge, Kathryn; Busetti, Francesco; Joll, Cynthia A

    2017-03-15

    Chlorination of amino acids can result in the formation of organic monochloramines or organic dichloramines, depending on the chlorine to amino acid ratio (Cl:AA). After formation, organic chloramines degrade into aldehydes, nitriles and N-chloraldimines. In this paper, the formation of organic chloramines from chlorination of lysine, tyrosine and valine were investigated. Chlorination of tyrosine and lysine demonstrated that the presence of a reactive secondary group can increase the Cl:AA ratio required for the formation of N,N-dichloramines, and potentially alter the reaction pathways between chlorine and amino acids, resulting in the formation of unexpected by-products. In a detailed investigation, we report rate constants for all reactions in the chlorination of valine, for the first time, using experimental results and modelling. At Cl:AA = 2.8, the chlorine was found to first react quickly with valine (5.4x104 M-1 s-1) to form N-monochlorovaline, with a slower subsequent reaction with N-monochlorovaline to form N,N-dichlorovaline (4.9x102 M-1 s-1), although some N-monochlorovaline degraded into isobutyraldehyde (1.0x10-4 s-1). The N,N-dichlorovaline then competitively degraded into isobutyronitrile (1.3x10-4 s-1) and N-chloroisobutyraldimine (1.2x10-4 s-1). In conventional drinking water disinfection, N-chloroisobutyraldimine can potentially be formed in concentrations higher than its odour threshold concentration, resulting in aesthetic challenges and an unknown health risk.

  16. Improved study of a possible $\\Theta^{+} production in the pp /to p K^{0} \\Sigma^{+}$ reaction with the COSY-TOF spectrometer

    CERN Document Server

    Abdel-Bary, M; Brinkmann, K T; Castelijns, R; Clement, H; Dietrich, J; Dshemuchadse, S; Dorochkevitch, E; Eyrich, W; Ehrhardt, K; Erhardt, A; Freiesleben, H; Gast, W; Georgi, J; Gillitzer, A; Karsch, L; Kilian, K; Krapp, M; Kuhlmann, E; Lehmann, A; Morsch, H P; Paul, N; Pinna, L; Pizzolotto, C; Roderburg, J; Ritman, E; Schadmand, S; Schonmeier, P; Schulte-Wissermann, M; Schroeder, W; Sefzick, T; Teufel, A; Ucar, A; Ullrich, W; Wenzel, R; Wintz, P; Wüstner, P; Zupranski, P

    2007-01-01

    The pp -> p K0 Sigma+ reaction was investigated with the TOF spectrometer at COSY at 3.059 GeV/c incident beam momentum. The main objective was to clarify wether or not a narrow exotic S = +1 resnance, the Theta+ pentaquark, is populated at 1.53 GeV/c2 in the K0 p subsystem with a data sample of much higher statistical significance compared to the previously reported data in this channel. An analysis of these data does not confirm the existence of the Theta+ pentaquark. This is expressed as an upper limit for the cross section sigma (pp -> p K0 Sigma+) < 0.3 microbarn at the 95 percent confidence level.

  17. December Sigma-Virginids

    Science.gov (United States)

    Shiba, Yasuo; Ueda, Masayoshi

    2013-02-01

    We studied the December sigma-Virginids from the TV meteor observation network database in Japan (the "SonotaCo Network"). The December sigma-Virginids are a minor annual meteor shower that has a broad peak around December 20 and about 40 days active duration. The visual maximum zenithal hourly rate (ZHR) is estimated at 1.5.

  18. Rate constant for the reaction of atomic oxygen with phosphine at 298 K

    Science.gov (United States)

    Stief, L. J.; Payne, W. A.; Nava, D. F.

    1987-01-01

    The rate constant for the reaction of atomic oxygen with phosphine has been measured at 298 K using flash photolysis combined with time-resolved detection of O(3P) via resonance fluorescence. Atomic oxygen was produced by flash photolysis of N2O or NO highly diluted in argon. The results were shown to be independent of (PH3), (O), total pressure and the source of O(3P). The mean value of all the experiments is k1 = (3.6 + or -0.8) x 10 to the -11th cu cm/s (1 sigma). Two previous measurements of k1 differed by more than an order of magnitude, and the results support the higher value obtained in a discharge flow-mass spectrometry study. A comparison with rate data for other atomic and free radical reactions with phosphine is presented, and the role of these reactions in the aeronomy or photochemistry of Jupiter and Saturn is briefly considered.

  19. Reaction weakening and emplacement of crystalline thrusts: Diffusion control on reaction rate and strain rate

    Science.gov (United States)

    O'Hara, Kieran

    2007-08-01

    In the southern Appalachians, the Blue Ridge-Piedmont crystalline thrust sheet was emplaced onto low-grade Late Precambrian and Paleozoic sedimentary rocks in the footwall along a basal detachment consisting of phyllosilicate-rich mylonites (phyllonites). The phyllonites developed first by mechanical breakdown of feldspar followed by chemical breakdown to white mica in the presence of a pore fluid. Diffusion of solute in the pore fluid is the rate limiting step in controlling reaction rate and also the strain rate. Assuming solute diffusion follows the Stokes-Einstein equation, the shear strain rate is given by ⅆγ/ⅆt=2ωkT/5ηrx for shear stress ≥20 MPa, where n is a constant, ω is a geometric factor, k is Boltzmann's constant, T is absolute temperature, η is water viscosity, r is the atomic radius of the diffusing species, and x is the diffusion distance. A bulk diffusion coefficient in the range of ˜10 -10 to 10 -12 m 2/s over distances of 10-100 m results in strain rates of 10 -14 to 10 -13 s -1 in the temperature range 200-400 °C. It is concluded that greenschist grade crystalline thrust sheets develop on pre-existing basement faults that become weak during reaction softening and localize into high strain phyllonite zones in which pore fluid diffusion controls reaction rate and strain rate.

  20. What is Six Sigma?

    Directory of Open Access Journals (Sweden)

    Gulcin Daglioglu

    2009-04-01

    Full Text Available Sigma (σ refers to Standard Deviation which is a measure of variation in statistics. Methodology of Six Sigma is a management philosophy that is based on the theory that parameters can be cotrolled. Six Sigma applications follow the process of identifying and defining defects, analyzing the defects using various measures, suggesting improvements and having metrics or controls in place to achieve the goals of the business. The error rate is defined as the number of error in a million. An increase in Sigma means decrease in the number of error, and lower values of Sigma correspond to higher number of error. The Six Sigma philosophy aims to bring about improvements in processes that have zero error. The Six Sigma approach is to implement methodologies that aim at reaching world standard quality which is 6 Sigma or more. The Six Sigma methodology used in clinical laboratories appears to be a quality management tool involving statistical calculations, process parameter based, and reports about the process performance. [Archives Medical Review Journal 2009; 18(2.000: 132-139

  1. Inclusive $\\Sigma^{+}$ and $\\Sigma^{0}$ Production in Hadronic Z Decays

    CERN Document Server

    Acciarri, M; Adriani, O; Aguilar-Benítez, M; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alviggi, M G; Ambrosi, G; Anderhub, H; Andreev, V P; Angelescu, T; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Bajo, A; Baksay, L; Balandras, A; Banerjee, S; Banerjee, Sw; Barczyk, A; Barillère, R; Barone, L; Bartalini, P; Basile, M; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Bellucci, L; Berbeco, R; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Bhattacharya, S; Biasini, M; Biland, A; Blaising, J J; Blyth, S C; Bobbink, Gerjan J; Böhm, A; Boldizsar, L; Borgia, B; Bourilkov, D; Bourquin, Maurice; Braccini, S; Branson, J G; Brigljevic, V; Brochu, F; Buffini, A; Buijs, A; Burger, J D; Burger, W J; Cai, X D; Campanelli, M; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A M; Casaus, J; Castellini, G; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada-Canales, M; Cesaroni, F; Chamizo-Llatas, M; Chang, Y H; Chaturvedi, U K; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chiefari, G; Cifarelli, Luisa; Cindolo, F; Civinini, C; Clare, I; Clare, R; Coignet, G; Colijn, A P; Colino, N; Costantini, S; Cotorobai, F; Cozzoni, B; de la Cruz, B; Csilling, Akos; Cucciarelli, S; Dai, T S; van Dalen, J A; D'Alessandro, R; De Asmundis, R; Déglon, P L; Degré, A; Deiters, K; Della Volpe, D; Denes, P; De Notaristefani, F; De Salvo, A; Diemoz, M; Van Dierendonck, D N; Di Lodovico, F; Dionisi, C; Dittmar, Michael; Dominguez, A; Doria, A; Dova, M T; Duchesneau, D; Dufournaud, D; Duinker, P; Durán, I; El-Mamouni, H; Engler, A; Eppling, F J; Erné, F C; Extermann, Pierre; Fabre, M; Faccini, R; Falagán, M A; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, Marta; Ferguson, T; Ferroni, F; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, Frank; Fisher, P H; Fisk, I; Forconi, G; Fredj, L; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gataullin, M; Gau, S S; Gentile, S; Gheordanescu, N; Giagu, S; Gong, Z F; Grenier, G; Grimm, O; Grünewald, M W; Guida, M; van Gulik, R; Gupta, V K; Gurtu, A; Gutay, L J; Haas, D; Hasan, A; Hatzifotiadou, D; Hebbeker, T; Hervé, A; Hidas, P; Hirschfelder, J; Hofer, H; Holzner, G; Hoorani, H; Hou, S R; Hu, Y; Iashvili, I; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Khan, R A; Kaur, M; Kienzle-Focacci, M N; Kim, D; Kim, J K; Kirkby, Jasper; Kiss, D; Kittel, E W; Klimentov, A; König, A C; Kopp, A; Koutsenko, V F; Kräber, M H; Krämer, R W; Krenz, W; Krüger, A; Kunin, A; Ladrón de Guevara, P; Laktineh, I; Landi, G; Lassila-Perini, K M; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Lee, H J; Le Goff, J M; Leiste, R; Leonardi, E; Levchenko, P M; Li Chuan; Likhoded, S A; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lü, Y S; Lübelsmeyer, K; Luci, C; Luckey, D; Lugnier, L; Luminari, L; Lustermann, W; Ma Wen Gan; Maity, M; Malgeri, L; Malinin, A; Maña, C; Mangeol, D J J; Mans, J; Marchesini, P A; Marian, G; Martin, J P; Marzano, F; Massaro, G G G; Mazumdar, K; McNeil, R R; Mele, S; Merola, L; Meschini, M; Metzger, W J; Von der Mey, M; Mihul, A; Milcent, H; Mirabelli, G; Mnich, J; Mohanty, G B; Molnár, P; Monteleoni, B; Moulik, T; Muanza, G S; Muheim, F; Muijs, A J M; Musy, M; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Niessen, T; Nisati, A; Nowak, H; Organtini, G; Oulianov, A; Palomares, C; Pandoulas, D; Paoletti, S; Paolucci, P; Paramatti, R; Park, H K; Park, I H; Pascale, G; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Pedace, M; Pensotti, S; Perret-Gallix, D; Petersen, B; Piccolo, D; Pierella, F; Pieri, M; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Postema, H; Pothier, J; Produit, N; Prokofev, D; Prokofiev, D O; Quartieri, J; Rahal-Callot, G; Rahaman, M A; Raics, P; Raja, N; Ramelli, R; Rancoita, P G; Raspereza, A V; Raven, G; Razis, P A; Ren, D; Rescigno, M; Reucroft, S; Van Rhee, T; Riemann, S; Riles, K; Robohm, A; Rodin, J; Roe, B P; Romero, L; Rosca, A; Rosier-Lees, S; Rubio, Juan Antonio; Ruschmeier, D; Rykaczewski, H; Saremi, S; Sarkar, S; Salicio, J; Sánchez, E; Sanders, M P; Sarakinos, M E; Schäfer, C; Shchegelskii, V; Schmidt-Kärst, S; Schmitz, D; Schopper, Herwig Franz; Schotanus, D J; Schwering, G; Sciacca, C; Sciarrino, D; Seganti, A; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shumilov, E; Shvorob, A V; Siedenburg, T; Son, D; Smith, B; Spillantini, P; Steuer, M; Stickland, D P; Stone, A; Stone, H; Stoyanov, B; Strässner, A; Sudhakar, K; Sultanov, G G; Sun, L Z; Suter, H; Swain, J D; Szillási, Z; Sztaricskai, T; Tang, X W; Tauscher, Ludwig; Taylor, L; Tellili, B; Timmermans, C; Ting, Samuel C C; Ting, S M; Tonwar, S C; Tóth, J; Tully, C; Tung, K L; Uchida, Y; Ulbricht, J; Valente, E; Vesztergombi, G; Vetlitskii, I; Vicinanza, D; Viertel, Gert M; Villa, S; Vivargent, M; Vlachos, S; Vodopyanov, I; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Vorvolakos, A; Wadhwa, M; Wallraff, W; Wang, M; Wang, X L; Wang, Z M; Weber, A; Weber, M; Wienemann, P; Wilkens, H; Wu, S X; Wynhoff, S; Xia, L; Xu, Z Z; Yamamoto, J; Yang, B Z; Yang, C G; Yang, H J; Yang, M; Ye, J B; Yeh, S C; Zalite, A; Zalite, Yu; Zhang, Z P; Zhu, G Y; Zhu, R Y; Zichichi, A; Zilizi, G; Zöller, M

    2000-01-01

    We report on measurements of the inclusive production rate of $\\Sigma^+$ and $\\Sigma^0$ baryons in hadronic Z decays collected with the L3 detector at LEP. The $\\Sigma^+$ baryons are detected through the decay $\\Sigma^+ \\rightarrow {\\rm p} \\pi^0$, while the $\\Sigma^0$ baryons are detected via the decay mode $\\Sigma^0 \\rightarrow \\Lambda \\gamma$. The average numbers of $\\Sigma^+$ and $\\Sigma^0$ per hadronic Z decay are measured to be: \\begin{eqnarray*} \\left + \\left & = & 0.114 \\pm 0.011_{\\mbox{\\it \\small stat}} \\pm 0.009_{\\mbox{\\it \\small syst}} \\\\ \\left + \\left & = & 0.095 \\pm 0.015_{\\mbox{\\it \\small stat}} \\pm 0.013_{\\mbox{\\it \\small syst}} \\ \\mbox{.} \\end{eqnarray*} These rates are found to be higher than the predictions from Monte Carlo hadronization models and analytical parameterizations of strange baryon production.

  2. Narrow Sigma -hypernuclear states

    CERN Document Server

    Gal, A

    1980-01-01

    It is shown that the spin-isospin dependence of low-energy Sigma N to Lambda N conversion leads to substantial quenching of nuclear-matter estimates of the widths of some Sigma -hypernuclear states produced in (K/sup -/, pi ) reactions, to a level below 10 MeV. The estimated widths compare favorably with those of the Sigma -hypernuclear peaks recently observed at CERN for /sup 7/Li, /sup 9/Be, and /sup 12/C. Tentative quantum number assignments are suggested for these states. (10 refs).

  3. Development of a group contribution method to predict aqueous phase hydroxyl radical (HO*) reaction rate constants.

    Science.gov (United States)

    Minakata, Daisuke; Li, Ke; Westerhoff, Paul; Crittenden, John

    2009-08-15

    The hydroxyl radical (HO*) is a strong oxidant that reacts with electron-rich sites of organic compounds and initiates complex chain mechanisms. In order to help understand the reaction mechanisms, a rule-based model was previously developed to predict the reaction pathways. For a kinetic model, there is a need to develop a rate constant estimator that predicts the rate constants for a variety of organic compounds. In this study, a group contribution method (GCM) is developed to predict the aqueous phase HO* rate constants for the following reaction mechanisms: (1) H-atom abstraction, (2) HO* addition to alkenes, (3) HO* addition to aromatic compounds, and (4) HO* interaction with sulfur (S)-, nitrogen (N)-, or phosphorus (P)-atom-containing compounds. The GCM hypothesizes that an observed experimental rate constant for a given organic compound is the combined rate of all elementary reactions involving HO*, which can be estimated using the Arrhenius activation energy, E(a), and temperature. Each E(a) for those elementary reactions can be comprised of two parts: (1) a base part that includes a reactive bond in each reaction mechanism and (2) contributions from its neighboring functional groups. The GCM includes 66 group rate constants and 80 group contribution factors, which characterize each HO* reaction mechanism with steric effects of the chemical structure groups and impacts of the neighboring functional groups, respectively. Literature-reported experimental HO* rate constants for 310 and 124 compounds were used for calibration and prediction, respectively. The genetic algorithms were used to determine the group rate constants and group contribution factors. The group contribution factors for H-atom abstraction and HO* addition to the aromatic compounds were found to linearly correlate with the Taft constants, sigma*, and electrophilic substituent parameters, sigma+, respectively. The best calibrations for 83% (257 rate constants) and predictions for 62% (77

  4. Study of the quasi-two body processes including {sigma}(1385) production in {pi}{sup -}p and K{sup -} reactions at 4 GeV/c; Estudio de procesos cuasi-dos cuerpos con produccion de {sigma} (1385) en interacciones {pi}{sup -}p y K{sup p} A 4 GeV/c

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar-Benitez, M.; Salicio, J.

    1981-07-01

    An analysis of (1385) production in reactions of the type 0{sup +} 1/z 4 +{yields}>-1{sup +} 3+/2 and 0{sup -} + 1/2+{yields} 0{sup -} + 3*/2 is presented. A determination of the {sigma}(1385) production parameters Is performed and the results are compared with the predictions from several models. A transversity amplitudes reconstruction describing the processes {pi} {sup p} ->K(890) {sigma}(1385) and K{sup -}p {yields} 3{yields}{phi}(1385), {zeta}{sup -}{sigma}(1385) is obtained in a model independent way. We observe dominance of unnatural partly exchange in the production mechanisms. Exchanges of exotic quantum numbers are established by the study of {pi}p {yields} K{sup 0}+ {sigma}(1385)s and K{sup -} p{yields}>{pi}+{sigma}(1385){+-} processes. Additive quark model predictions are reasonable agreement with the experimental data. (Author)

  5. Study of the reaction {gamma}p{yields}K{sup +}{sigma}{sup -}{pi}{sup +} for photon energies up to 2.65 GeV with the SAPHIR detector at ELSA; Untersuchung der Reaktion {gamma}p{yields}K{sup +}{sigma}{sup -}{pi}{sup +} fuer Photonenenergien bis 2.65 GeV mit dem SAPHIR-Detektor an ELSA

    Energy Technology Data Exchange (ETDEWEB)

    Schulday, I.

    2004-10-01

    The reaction {gamma}p{yields}K{sup +}{sigma}{sup -}{pi}{sup +} was measured in the photon energy range from threshold up to 2.65 GeV. The cross section is dominated by the production of the resonances {sigma}(1385), {lambda}(1405) and {lambda}(1520) which decay into {sigma}{sup -}{pi}{sup +}. Cross sections were obtained as a function of the photon energy and the K{sup +} production angle for the reaction and the resonance production. The cross section for {lambda}(1520) rises up to (0.230{+-}0.029) {mu}b in the photon energy range 1.80sigma}/dt) distribution yields a slope parameter b=-2.41{+-}0.37 GeV{sup -2}. The polar decay angular distribution is consistent with being flat. (orig.)

  6. Search for $\\Sigma$ Hypernuclear States using the Strangeness Exchange Reactions $(K^{-},\\pi^{-})$ and $(K^{-},\\pi^{+})$

    CERN Multimedia

    2002-01-01

    In previous $\\Lambda$ hypernuclei experiments details of the $\\Lambda$ nucleus interaction have been deduced, the most outstanding being a very small spin orbit interaction in p$^{-}$ and sd shell $\\Lambda$ hypernuclei. This kind of information is decisive in the understanding of the baryon interaction and will contribute to distinguish between the boson exchange and the QCD motivated picture of the baryon baryon interaction. To further exploit the hyperon nucleus interaction one has to investigate hypernuclei with hyperons of different quark configuration, i.e. $\\Sigma$ hypernuclei. Since the $\\Sigma\\$ particle can, in contrast to the $\\Lambda$, decay by strong interaction in the nucleus, the existence of narrow states was not obvious. A small momentum transfer guarantees that the spectra are dominated by a few strong transitions to narrow hypernuclear states with the same spin and space quantum numbers as the target nucleus. Therefore a new kaon beamline was built with a lower momentum of 400~MeV/c and a co...

  7. Statistical Methods for Thermonuclear Reaction Rates and Nucleosynthesis Simulations

    CERN Document Server

    Iliadis, Christian; Coc, Alain; Timmes, F X; Champagne, Art E

    2014-01-01

    Rigorous statistical methods for estimating thermonuclear reaction rates and nucleosynthesis are becoming increasingly established in nuclear astrophysics. The main challenge being faced is that experimental reaction rates are highly complex quantities derived from a multitude of different measured nuclear parameters (e.g., astrophysical S-factors, resonance energies and strengths, particle and gamma-ray partial widths). We discuss the application of the Monte Carlo method to two distinct, but related, questions. First, given a set of measured nuclear parameters, how can one best estimate the resulting thermonuclear reaction rates and associated uncertainties? Second, given a set of appropriate reaction rates, how can one best estimate the abundances from nucleosynthesis (i.e., reaction network) calculations? The techniques described here provide probability density functions that can be used to derive statistically meaningful reaction rates and final abundances for any desired coverage probability. Examples ...

  8. On the sigma sigma term

    CERN Document Server

    Bruns, Peter C

    2016-01-01

    We give some estimates for the light-quark mass dependence of the pole position of the sigma ($f_{0}(500)$) resonance in the complex energy plane, with the help of a chiral Lagrangian for the resonance field and some input from hadronic models constrained by Chiral Perturbation Theory and elastic unitarity. We also speculate on the fate of the sigma resonance when the quark masses become unphysically large.

  9. Enzymatic spectrophotometric reaction rate determination of aspartame

    Directory of Open Access Journals (Sweden)

    Trifković Kata T.

    2015-01-01

    Full Text Available Aspartame is an artificial sweetener of low caloric value (approximately 200 times sweeter than sucrose. Aspartame is currently permitted for use in food and beverage production in more than 90 countries. The application of aspartame in food products requires development of rapid, inexpensive and accurate method for its determination. The new assay for determination of aspartame was based on set of reactions that are catalyzed by three different enzymes: α-chymotrypsin, alcohol oxidase and horseradish peroxidase. Optimization of the proposed method was carried out for: (i α-chymotrypsin activity; (ii time allowed for α-chymotrypsin action, (iii temperature. Evaluation of the developed method was done by determining aspartame content in “diet” drinks, as well as in artificial sweetener pills. [Projekat Ministarstva nauke Republike Srbije, br. III46010

  10. MCSCF potential energy surface for the high barrier adiabatic 1 /sup 4/. sigma. /sup -/ pathway of the O/sup +/(/sup 4/S)+N/sub 2/(X /sup 1/. sigma. /sub g//sup +/). -->. NO/sup +/(X /sup 1/. sigma. /sup +/) +N(/sup 4/S) reaction

    Energy Technology Data Exchange (ETDEWEB)

    Hopper, D.G.

    1980-03-15

    The collinear /sup 4/..sigma../sup -/ pathway for the state-specific O/sup +/(/sup 4/S)+N/sub 2/(X /sup 1/..sigma../sub g//sup +/) ..-->..NO/sup +/(X /sup 1/..sigma../sup +/)+N(/sup 4/S) reaction has been surveyed with ab initio calculations. A ninety-nine configuration, fifteen orbital multiconfiguration self-consistent field (MCSCF) wave function, involving the use of a double-zeta plus polarization one-electron basis, was developed for the long range /sup 4/..sigma../sup -/ state. This long range /sup 4/..sigma../sup -/ state has the character of O/sup +/+N/sub 2/ for long R/sub NO/, or of N+NO/sup +/ for long R/sub NN/, and is for most geometries, the lowest, or 1 /sup 4/..sigma../sup -/, state. The ab initio exothermicity computed with the present wave function is 0.93 eV, compared to an accurate experimental value of 1.10 eV. The saddle-point in the energy surface is 8.0 eV above O/sup +/+N/sub 2/, with critical values of R*/sub NN/=1.48 +- 0.02 A and R*/sub NO/ =1.38 +- 0.02 A. These values are 0.38 and 0.32 A greater than the equilibrium bond lengths of N/sub 2/(X /sup 1/..sigma../sub g//sup +/) and NO/sup +/(X /sup 1/..sigma../sup +/). The present wave function reproduces the experimental bond lengths of these two diatomics to within 0.01 A when the third atom is removed to 500 a.u. (264.6 A). Preceding the barrier on the O/sup +/+N/sub 2/ side is an appreciable polarization well. With the present wave function the attributes of this well are D/sup 0/ (N/sub 2/--O/sup +/) =0.38 eV, R/sub NN//sup E/=1.108 A, R/sub NO//sup e/ =2.350 A, theta/sup e//sub NNO/=180/sup 0/, k/sup e//sub NN/=24.679 md/A, k/sup e//sub NO/=0.295 md/A, k/sub theta/=0.0366 md/A. There is also a smaller polarization well on the N+NO/sup +/ side. Although the ion--atom interaction is more stable at C/sub s/ the latter well is bound by 0.02 eV at 180/sup 0/ with R/sup e//sub NN/=3.34 A, and R/sup e//sub NO/=1.07 A.

  11. Six sigma.

    Science.gov (United States)

    Carter, Pam

    2010-12-01

    When I was first introduced to the Six Sigma process, I resisted it with every ounce of energy I had. I continuously fabricated reasons so that I was unable to complete the training that my company required. When it came time for my performance review, I could not hide the truth from my manager; I had not completed the required training. It was then that I began my journey into the world of Six Sigma. Once I understood that a black belt and a green belt certification had nothing to do with karate, I felt much better.

  12. APPRAISAL OF STUDENT RATING AS A MEASURE TO MANAGE THE QUALITY OF HIGHER EDUCATION IN INDIA: AN INSTITUTIONAL STUDY USING SIX SIGMA MODEL APPROACH

    Directory of Open Access Journals (Sweden)

    Arun Vijay

    2013-09-01

    Full Text Available Students' rating of teaching is one of the most widely accepted methods of measuring the quality in Higher Education worldwide. The overall experience gained by the students during their academic journey in their respective college is a key factor to determine the Institutional Quality. This study was conducted among the Physical Therapy students with an objective to capture the overall experience related to various aspects of their Academic environment including teaching and learning process adopted in their college. To facilitate that, a unique questionnaire called, "Academic Environment Evaluation Questionnaire (AEEQwas developed covering all the important teaching elements of the Higher Education Institutions. The students' opinion was captured and analyzed through six sigma analytical tool using Poisson distribution model. From the non-conformance level captured through the responses from the students about the various categories of teaching and learning elements, the corresponding Sigma rating for each teaching element was measured. Accordingly, a six point Quality rating system was developed customizing to each sigma values. This study brings a new, innovative student driven Quality rating system for the Higher Education Institutions in India.

  13. APPRAISAL OF STUDENT RATING AS A MEASURE TO MANAGE THE QUALITY OF HIGHER EDUCATION IN INDIA: AN INSTITUTIONAL STUDY USING SIX SIGMA MODEL APPROACH

    Directory of Open Access Journals (Sweden)

    Arun Vijay

    2013-12-01

    Full Text Available Students' rating of teaching is one of the most widely accepted methods of measuring the quality in Higher Education worldwide. The overall experience gained by the students during their academic journey in their respective college is a key factor to determine the Institutional Quality. This study was conducted among the Physical Therapy students with an objective to capture the overall experience related to various aspects of their Academic environment including teaching and learning process adopted in their college. To facilitate that, a unique questionnaire called,"Academic Environment Evaluation Questionnaire (AEEQ was developed covering all the important teaching elements of the Higher Education Institutions. The students' opinion was captured and analyzed through six sigma analytical tool using Poisson distribution model. From the non-conformance level captured through the responses from the students about the various categories of teaching and learning elements, the corresponding Sigma rating for each teaching element was measured. Accordingly, a six point Quality rating system was developed customizing to each sigma values. This study brings a new, innovative student driven Quality rating system for the Higher Education Institutions in India.

  14. Measurement of the reaction {gamma}p{yields}K{sup 0}{sigma}{sup +} for photon energies up to 2.65 GeV with the SAPHIR detector at ELSA; Messung der Reaktion {gamma}p {yields} K{sup 0}{sigma}{sup +} fuer Photonenergien bis 2.65 GeV mit dem SAPHIR-Detektor an ELSA

    Energy Technology Data Exchange (ETDEWEB)

    Lawall, R.

    2004-01-01

    The reaction {gamma}p {yields} K{sup 0}{sigma}{sup +} was measured with the SAPHIR-detector at ELSA during the run periods 1997 and 1998. Results were obtained for cross sections in the photon energy range from threshold up to 2.65 GeV for all production angles and for the {sigma}{sup +}-polarization. Emphasis has been put on the determination and reduction of the contributions of background reactions and the comparison with other measurements and theoretical predictions. (orig.)

  15. Energy diffusion controlled reaction rate in dissipative Hamiltonian systems

    Institute of Scientific and Technical Information of China (English)

    Deng Mao-Lin; Zhu Wei-Qiu

    2007-01-01

    In this paper the energy diffusion controlled reaction rate in dissipative Hamiltonian systems is investigated by using the stochastic averaging method for quasi Hamiltonian systems. The boundary value problem of mean first-passage time (MFPT) of averaged system is formulated and the energy diffusion controlled reaction rate is obtained as the inverse of MFPT. The energy diffusion controlled reaction rate in the classical Kramers bistable potential and in a two-dimensional bistable potential with a heat bath are obtained by using the proposed approach respectively. The obtained results are then compared with those from Monte Carlo simulation of original systems and from the classical Kramers theory. It is shown that the reaction rate obtained by using the proposed approach agrees well with that from Monte Carlo simulation and is more accurate than the classical Kramers rate.

  16. Quantum Mechanics Rate Constant for the N+ND Reaction

    Institute of Scientific and Technical Information of China (English)

    Ai-jie Zhang; Guo-zhong He

    2011-01-01

    We present nonadiabatic quantum dynamical calculations on the two coupled potential energy surfaces (12A' and 22A') [J.Theor.Comput.Chem.8,849 (2009)] for the reaction.Initial state-resolved reaction probabilities and cross sections for the N+ND→N2+D reaction and N'+ND→N+N'D reaction for collision energies of 5 meV to 1.0 eV are determined,respectively.It is found that the N+ND→N2+D reaction is dominated in the N+ND reaction.In addition,we obtained the rate constants for the N+ND→N2+D reaction which demand further experimental investigations.

  17. Sign ambiguity in the K Sigma channel

    CERN Document Server

    Anisovich, A V; Nikonov, V A; Sarantsev, A V; Thoma, U

    2013-01-01

    Ambiguities of the signs of $N\\to \\Sigma K$ coupling constants are studied in a multichannel partial wave analysis of a large body of pion and photo-induced reactions. It is shown that the signs are not free from some ambiguities, and further experimental data are needed. Data on the reactions $\\pi^+p\\to \\Sigma^+K^+$ and $\\gamma p\\to K^+\\Sigma^0$ define rather well the isospin 3/2 contributions to these channels. However the lack of information on polarization observables for the reactions $\\pi^-p\\to \\Sigma^0K^0$, $\\pi^-p\\to \\Sigma^-K^+$ and $\\gamma p\\to K^0\\Sigma^+$ does not allow us to fix uniquely the signs of $N\\to \\Sigma K$ coupling constants. As a consequence, also the contributions of nucleon resonances to these channels remain uncertain.

  18. Cross Sections for the $\\gamma p \\to K^{*0}\\Sigma^+$ Reaction at $E_\\gamma = 1.7 - 3.0$ GeV

    Energy Technology Data Exchange (ETDEWEB)

    I. Hleiqawi; K. Hicks; D.Carman; T.Mibe

    2007-04-01

    Differential cross sections for the reaction $\\gamma p \\to K^{*0} \\Sigma^+$ are presented at nine bins in photon energy in the range from 1.7 to 3.0 GeV. The \\kstar was detected by its decay products, $K^+\\pi^-$, in the CLAS detector at Jefferson Lab. These data are the first \\kstar photoproduction cross sections ever published over a broad range of angles. Comparison with a theoretical model based on the vector and tensor $K^*$-quark couplings shows good agreement with the data in general, after adjusting the model's two parameters in a fit to our data. Disagreement between the data at forward angles and the global angle-energy fit to the model suggests that the role of scalar $\\kappa$ meson exchange in $t$-channel diagrams should be investigated.

  19. Cross Sections for the $\\gamma p \\to K^{*0}\\Sigma^+$ Reaction at $E_\\gamma = 1.7 - 3.0$ GeB

    CERN Document Server

    Hleiqawi, I; Hicks, K; Mibe, T; al, et

    2007-01-01

    Differential cross sections for the reaction $\\gamma p \\to K^{*0} \\Sigma^+$ are presented at nine bins in photon energy in the range from 1.7 to 3.0 GeV. The \\kstar was detected by its decay products, $K^+\\pi^-$, in the CLAS detector at Jefferson Lab. These data are the first \\kstar photoproduction cross sections ever published over a broad range of angles. Comparison with a theoretical model based on the vector and tensor $K^*$-quark couplings shows good agreement with the data in general, after adjusting the model's two parameters in a fit to our data. Disagreement between the data at forward angles and the global angle-energy fit to the model suggests that the role of scalar $\\kappa$ meson exchange in $t$-channel diagrams should be investigated.

  20. Non-resonant triple alpha reaction rate at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, T.; Tamii, A.; Aoi, N.; Fujita, H.; Hashimoto, T.; Miki, K.; Ogata, K. [Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Carter, J.; Donaldson, L.; Sideras-Haddad, E. [Schools of Physics, University of Witwatersrand, Johannesburg 2050 (South Africa); Furuno, T.; Kawabata, T. [Departments of Physics, Kyoto University, Sakyo, Kyoto, 606-8502 (Japan); Kamimura, M. [RIKEN Nishina Center, Wako, Saitama, 351-0198 (Japan); Nemulodi, F.; Neveling, R.; Smit, F. D.; Swarts, C. [iThemba Laboratory for Accelerator Based Sciences Somerset, West, 7129 (South Africa)

    2014-05-02

    Our experimental goal is to study the non-resonant triple alpha reaction rate at low temperture (T < 10{sup 8} K). The {sup 13}C(p,d) reaction at 66 MeV has been used to probe the alpha-unbound continuum state in {sup 12}C just below the 2{sup nd} 0{sup +} state at 7.65 MeV. The transition strength to the continuum state is predicted to be sensitive to the non-resonant triple alpha reaction rate. The experiment has been performed at iThemba LABS. We report the present status of the experiment.

  1. On the 14C(alpha,gamma) reaction rate

    CERN Document Server

    Johnson, E D; Mitchell, J; Miller, L; Kemper, K W

    2009-01-01

    The 14C(alpha,gamma) reaction rate at temperatures below 0.3 GK depends on the properties of two near threshold resonances in 18O, the 1- at 6.198 MeV and the 3- at 6.404 MeV. The alpha+14C Asymptotic Normalization Coefficients (ANCs) for these resonances were determined using the alpha-transfer reactions 14C(7Li,t) and 14C(6Li,d) at sub-Coulomb energies. The 14C(alpha,gamma) reaction rate at low temperatures has been evaluated. Implications of the new reaction rate on the evolution of accreting helium white dwarfs and on the nucleosynthesis of low mass stars during the asymptotic giant branch (AGB) phase are discussed.

  2. Dependence of Reaction Rate Constants on Density in Supercritical Fluids

    Institute of Scientific and Technical Information of China (English)

    WANGTao; SHENZhongyao

    2002-01-01

    A new method,which correlates rate constants of chemical reactions and density or pressure in supercritical fluids,was developed.Based on the transition state theory and thermodynamic principles, the rate constant can be reasonably correlated with the density of the supercritical fluid,and a correlation equation was obtained. Coupled with the equation of state (EOS) of a supercritical solvent,the effect of pressure on reaction rate constant could be represented.Two typical systems were used to test this method.The result indicates that this method is suitable for dilute supercritical fluid solutions.

  3. Extension of a Kinetic-Theory Approach for Computing Chemical-Reaction Rates to Reactions with Charged Particles

    Science.gov (United States)

    Liechty, Derek S.; Lewis, Mark J.

    2010-01-01

    Recently introduced molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction rate information) are extended to include reactions involving charged particles and electronic energy levels. The proposed extensions include ionization reactions, exothermic associative ionization reactions, endothermic and exothermic charge exchange reactions, and other exchange reactions involving ionized species. The extensions are shown to agree favorably with the measured Arrhenius rates for near-equilibrium conditions.

  4. State Space Path Integrals for Electronically Nonadiabatic Reaction Rates

    CERN Document Server

    Duke, Jessica Ryan

    2016-01-01

    We present a state-space-based path integral method to calculate the rate of electron transfer (ET) in multi-state, multi-electron condensed-phase processes. We employ an exact path integral in discrete electronic states and continuous Cartesian nuclear variables to obtain a transition state theory (TST) estimate to the rate. A dynamic recrossing correction to the TST rate is then obtained from real-time dynamics simulations using mean field ring polymer molecular dynamics. We employ two different reaction coordinates in our simulations and show that, despite the use of mean field dynamics, the use of an accurate dividing surface to compute TST rates allows us to achieve remarkable agreement with Fermi's golden rule rates for nonadiabatic ET in the normal regime of Marcus theory. Further, we show that using a reaction coordinate based on electronic state populations allows us to capture the turnover in rates for ET in the Marcus inverted regime.

  5. Reaction rate in an evanescent random walkers system

    CERN Document Server

    Ré, Miguel A

    2015-01-01

    Diffusion mediated reaction models are particularly ubiquitous in the description of physical, chemical or biological processes. The random walk schema is a useful tool for formulating these models. Recently, evanescent random walk models have received attention in order to include finite lifetime processes. For instance, activated chemical reactions, such as laser photolysis, exhibit a different asymptotic limit when compared with immortal walker models. A diffusion limited reaction model based on a one dimensional continuous time random walk on a lattice with evanescent walkers is presented here. The absorption probability density and the reaction rate are analytically calculated in the Laplace domain. A finite absorption rate is considered, a model usually referred to as imperfect trapping. Short and long time behaviors are analyzed.

  6. Effects of Surfactants on the Rate of Chemical Reactions

    Directory of Open Access Journals (Sweden)

    B. Samiey

    2014-01-01

    Full Text Available Surfactants are self-assembled compounds that depend on their structure and electric charge can interact as monomer or micelle with other compounds (substrates. These interactions which may catalyze or inhibit the reaction rates are studied with pseudophase, cooperativity, and stoichiometric (classical models. In this review, we discuss applying these models to study surfactant-substrate interactions and their effects on Diels-Alder, redox, photochemical, decomposition, enzymatic, isomerization, ligand exchange, radical, and nucleophilic reactions.

  7. Reaction rates between water and the Karl Fischer reagent.

    Science.gov (United States)

    Cedergren, A

    1974-04-01

    Reaction rates between water and the Karl Fischer reagent have been determined by potentiometric measurement for various compositions of the Karl Fischer reagent. The study has been made with an iodine complex concentration of 0.3-1.2 mM and sulphur dioxide complex at 0.01-0.5M. The concentration of excess of pyridine had no measurable effect on the rate of the main reaction. The reaction was found to be first-order with respect to iodine complex, to sulphur dioxide complex, and to water. The rate constant was (1.2+/-0.2) x 10(3) 1(2). mole(-2). sec(-1). In an ordinary titration it is therefore essential to keep the sulphur dioxide concentration high for the reaction to go to completion within a reasonable time. The extent of side-reactions was found to be independent of the iodine concentration at low concentrations. The side-reactions increased somewhat with increasing sulphur dioxide pyridine concentrations and decreased to about 60% when the temperature was lowered from 24 degrees to 7 degrees.

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

    KAUST Repository

    Suleimanov, Yu.V.

    2013-03-01

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

  9. Liquid Film Diffusion on Reaction Rate in Submerged Biofilters

    DEFF Research Database (Denmark)

    Christiansen, Pia; Hollesen, Line; Harremoës, Poul

    1995-01-01

    Experiments were carried out in order to investigate the influence of liquid film diffusion on reaction rate in a submerged biofilter with denitrification and in order to compare with a theoretical study of the mass transfer coefficient. The experiments were carried out with varied flow, identified...... by the empty bed velocity of inflow and recirculation, respectively 1.3, 2.8, 5.6 and 10.9 m/h. The filter material consisted of 3 mm biostyren spheres. The results indicate that the influence of liquid film diffusion on reaction rate can be ignored....

  10. Analysis of the Crystal Ball data on $K^-p\\to\\pi^0\\Sigma^0$ reaction with center-of-mass energies of $1536\\sim 1676$ MeV

    CERN Document Server

    Shi, Jun

    2014-01-01

    With an effective Lagrangian approach, we analyze the $K^-p\\to \\pi^0\\Sigma^0$ reaction to study the $\\Lambda$ hyperon resonances by fitting the Crystal Ball data on differential cross sections and $\\Sigma^0$ polarization with the center-of-mass energies of $1536\\sim 1676$ MeV. Besides well established PDG 4-star $\\Lambda$ resonances around this energy range, the $\\Lambda(1600){1\\over 2}^+$ resonance, listed as a 3-star resonance in PDG, is found to be definitely needed. In addition, there is strong evidence for the existence of a new $\\Lambda({3\\over 2}^+)$ resonance around 1680 MeV.

  11. Experimental measurements of low temperature rate coefficients for neutral-neutral reactions of interest for atmospheric chemistry of Titan, Pluto and Triton: reactions of the CN radical.

    Science.gov (United States)

    Morales, Sébastien B; Le Picard, Sébastien D; Canosa, André; Sims, Ian R

    2010-01-01

    The kinetics of the reactions of cyano radical, CN (X2sigma+) with three hydrocarbons, propane (CH3CH2CH3), propene (CH3CH=CH2) and 1-butyne (CH[triple band]CCH2CH3) have been studied over the temperature range of 23-298 K using a CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in Uniform Supersonic Flow) apparatus combined with the pulsed laser photolysis-laser induced fluorescence technique. These reactions are of interest for the cold atmospheres of Titan, Pluto and Triton, as they might participate in the formation of nitrogen and carbon bearing molecules, including nitriles, that are thought to play an important role in the formation of hazes and biological molecules. All three reactions are rapid with rate coefficients in excess of 10(-10) cm3 molecule(-1) s(-1) at the lowest temperatures of this study and show behaviour characteristic of barrierless reactions. Temperature dependences, different for each reaction, are compared to those used in the most recent photochemical models of Titan's atmosphere.

  12. Massive Star Evolution Nucleosynthesis and Nuclear Reaction Rate Uncertainties

    CERN Document Server

    Heger, A; Rauscher, T; Hoffman, R D; Boyes, M M

    2002-01-01

    We present a nucleosynthesis calculation of a 25 solar mass star of solar composition that includes all relevant isotopes up to polonium. In particular, all stable isotopes and necessary nuclear reaction rates are covered. We follow the stellar evolution from hydrogen burning till iron core collapse and simulate the explosion using a ``piston'' approach. We discuss the influence of two key nuclear reaction rates, C12(a,g) and Ne22(a,n), on stellar evolution and nucleosynthesis. The former significantly influences the resulting core sizes (iron, silicon, oxygen) and the overall presupernova structure of the star. It thus has significant consequences for the supernova explosion itself and the compact remnant formed. The later rate considerably affects the s-process in massive stars and we demonstrate the changes that different currently suggested values for this rate cause.

  13. A compilation of charged-particle induced thermonuclear reaction rates

    CERN Document Server

    Angulo, C; Rayet, M; Descouvemont, P; Baye, D; Leclercq-Willain, C; Coc, A; Barhoumi, S; Aguer, P; Rolfs, C; Kunz, R; Hammer, J W; Mayer, A; Paradelis, T; Kossionides, S; Chronidou, C; Spyrou, K; Degl'Innocenti, S; Fiorentini, G; Ricci, B; Zavatarelli, S; Providência, C; Wolters, H; Soares, J; Grama, C; Rahighi, J; Shotter, A; Rachti, M L

    1999-01-01

    Low-energy cross section data for 86 charged-particle induced reactions involving light (1 <= Z <= 14), mostly stable, nuclei are compiled. The corresponding Maxwellian-averaged thermonuclear reaction rates of relevance in astrophysical plasmas at temperatures in the range from 10 sup 6 K to 10 sup 1 sup 0 K are calculated. These evaluations assume either that the target nuclei are in their ground state, or that the target states are thermally populated following a Maxwell-Boltzmann distribution, except in some cases involving isomeric states. Adopted values complemented with lower and upper limits of the rates are presented in tabular form. Analytical approximations to the adopted rates, as well as to the inverse/direct rate ratios, are provided.

  14. A compilation of charged-particle induced thermonuclear reaction rates

    Energy Technology Data Exchange (ETDEWEB)

    Angulo, C.; Arnould, M.; Rayet, M.; Descouvemont, P.; Baye, D.; Leclercq-Willain, C.; Coc, A.; Barhoumi, S.; Aguer, P.; Rolfs, C.; Kunz, R.; Hammer, J.W.; Mayer, A.; Paradellis, T.; Kossionides, S.; Chronidou, C.; Spyrou, K.; Degl' Innocenti, S.; Fiorentini, G.; Ricci, B.; Zavatarelli, S.; Providencia, C.; Wolters, H.; Soares, J.; Grama, C.; Rahighi, J.; Shotter, A.; Rachti, M. Lamehi

    1999-08-23

    Low-energy cross section data for 86 charged-particle induced reactions involving light (1 {<=} Z {<=} 14), mostly stable, nuclei are compiled. The corresponding Maxwellian-averaged thermonuclear reaction rates of relevance in astrophysical plasmas at temperatures in the range from 10{sup 6} K to 10{sup 10} K are calculated. These evaluations assume either that the target nuclei are in their ground state, or that the target states are thermally populated following a Maxwell-Boltzmann distribution, except in some cases involving isomeric states. Adopted values complemented with lower and upper limits of the rates are presented in tabular form. Analytical approximations to the adopted rates, as well as to the inverse/direct rate ratios, are provided.

  15. Nuclear reaction rates and opacity in massive star evolution calculations

    Energy Technology Data Exchange (ETDEWEB)

    Bahena, D [Astronomical Institute of the Academy of Sciences, BocnI II 1401, 14131 Praha 4 (Czech Republic); Klapp, J [Instituto Nacional de Investigaciones Nucleares, Km. 36.5 Carr. Mexico-Toluca, 52750 Edo. de Mexico (Mexico); Dehnen, H, E-mail: jaime.klapp@inin.gob.m [Universitaet Konstanz, Fachbereich Physik, Fach M568, D-78457 Konstanz (Germany)

    2010-07-01

    Nuclear reaction rates and opacity are important parameters in stellar evolution. The input physics in a stellar evolution code determines the main theoretical characteristics of the stellar structure, evolution and nucleosynthesis of a star. For different input physics, in this work we calculate stellar evolution models of very massive first stars during the hydrogen and helium burning phases. We have considered 100 and 200M{sub s}un galactic and pregalactic stars with metallicity Z = 10{sup -6} and 10{sup 9}, respectively. The results show important differences from old to new formulations for the opacity and nuclear reaction rates, in particular the evolutionary tracks are significantly affected, that indicates the importance of using up to date and reliable input physics. The triple alpha reaction activates sooner for pregalactic than for galactic stars.

  16. Prediction of Rate Constants for Catalytic Reactions with Chemical Accuracy.

    Science.gov (United States)

    Catlow, C Richard A

    2016-08-01

    Ex machina: A computational method for predicting rate constants for reactions within microporous zeolite catalysts with chemical accuracy has recently been reported. A key feature of this method is a stepwise QM/MM approach that allows accuracy to be achieved while using realistic models with accessible computer resources.

  17. Helium Burning Reaction Rate Uncertainties and Consequences for Supernovae

    Science.gov (United States)

    Tur, C.; Heger, A.; Austin, S. M.

    2007-10-01

    The triple alpha and ^12C(,)^16O reaction rates determine the carbon to oxygen ratio at the completion of core helium burning in stars, which, in turn, influences the later stellar burning stages. We explored the dependence of massive star evolution and nucleosynthesis yields on the experimental uncertainties in the triple alpha rate (10 to 12%) and the ^12C(,)^16O rate (25 to 35%) using full stellar models followed to core collapse and including supernova explosion. The production factors of medium-weight elements obtained by using the Lodders (2003) solar abundances for the initial star composition, rather than the abundances of Anders & Grevesse (1989), provide a less stringent constraint on the ^12C(,)^16O rate. Variations within the current uncertainties in both reaction rates, however, induce significant changes in the central carbon abundance at core carbon ignition and in the mass of the supernova remnant. An experiment is being carried out by an NSCL/WMU collaboration to improve the accuracy of the triple alpha reaction rate.

  18. Noise slows the rate of Michaelis-Menten reactions.

    Science.gov (United States)

    Van Dyken, J David

    2017-10-07

    Microscopic randomness and the small volumes of living cells combine to generate random fluctuations in molecule concentrations called "noise". Here I investigate the effect of noise on biochemical reactions obeying Michaelis-Menten kinetics, concluding that substrate noise causes these reactions to slow. I derive a general expression for the time evolution of the joint probability density of chemical species in arbitrarily connected networks of non-linear chemical reactions in small volumes. This equation is a generalization of the chemical master equation (CME), a common tool for investigating stochastic chemical kinetics, extended to reaction networks occurring in small volumes, such as living cells. I apply this equation to a generalized Michaelis-Menten reaction in an open system, deriving the following general result: 〈p〉≤p¯ and 〈s〉≥s¯, where s¯ and p¯ denote the deterministic steady-state concentration of reactant and product species, respectively, and 〈s〉 and 〈p〉 denote the steady-state ensemble average over independent realizations of a stochastic reaction. Under biologically realistic conditions, namely when substrate is degraded or diluted by cell division, 〈p〉≤p¯. Consequently, noise slows the rate of in vivo Michaelis-Menten reactions. These predictions are validated by extensive stochastic simulations using Gillespie's exact stochastic simulation algorithm. I specify the conditions under which these effects occur and when they vanish, therefore reconciling discrepancies among previous theoretical investigations of stochastic biochemical reactions. Stochastic slowdown of reaction flux caused by molecular noise in living cells may have functional consequences, which the present theory may be used to quantify. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Control of serpentinisation rate by reaction-induced cracking

    Science.gov (United States)

    Malvoisin, Benjamin; Brantut, Nicolas; Kaczmarek, Mary-Alix

    2017-10-01

    Serpentinisation of mantle rocks requires the generation and maintenance of transport pathways for water. The solid volume increase during serpentinisation can lead to stress build-up and trigger cracking, which ease fluid penetration into the rock. The quantitative effect of this reaction-induced cracking mechanism on reactive surface generation is poorly constrained, thus hampering our ability to predict serpentinisation rate in geological environments. Here we use a combined approach with numerical modelling and observations in natural samples to provide estimates of serpentinisation rate at mid-ocean ridges. We develop a micromechanical model to quantify the propagation of serpentinisation-induced cracks in olivine. The maximum crystallisation pressure deduced from thermodynamic calculations reaches several hundreds of megapascals but does not necessary lead to crack propagation if the olivine grain is subjected to high compressive stresses. The micromechanical model is then coupled to a simple geometrical model to predict reactive surface area formation during grain splitting, and thus bulk reaction rate. Our model reproduces quantitatively experimental kinetic data and the typical mesh texture formed during serpentinisation. We also compare the model results with olivine grain size distribution data obtained on natural serpentinised peridotites from the Marum ophiolite and the Papuan ultramafic belt (Papua New Guinea). The natural serpentinised peridotites show an increase of the number of olivine grains for a decrease of the mean grain size by one order of magnitude as reaction progresses from 5 to 40%. These results are in agreement with our model predictions, suggesting that reaction-induced cracking controls the serpentinisation rate. We use our model to estimate that, at mid-ocean ridges, serpentinisation occurs up to 12 km depth and reaction-induced cracking reduces the characteristic time of serpentinisation by one order of magnitude, down to values

  20. Abundances in Astrophysical Environments: Reaction Network Simulations with Reaction Rates from Many-nucleon Modeling

    Science.gov (United States)

    Amason, Charlee; Dreyfuss, Alison; Launey, Kristina; Draayer, Jerry

    2017-01-01

    We use the ab initio (first-principle) symmetry-adapted no-core shell model (SA-NCSM) to calculate reaction rates of significance to type I X-ray burst nucleosynthesis. We consider the 18O(p,γ)19F reaction, which may influence the production of fluorine, as well as the 16O(α,γ)20Ne reaction, which is key to understanding the production of heavier elements in the universe. Results are compared to those obtained in the no-core sympletic shell model (NCSpM) with a schematic interaction. We discuss how these reaction rates affect the relevant elemental abundances. We thank the NSF for supporting this work through the REU Site in Physics & Astronomy (NSF grant #1560212) at Louisiana State University. This work was also supported by the U.S. NSF (OCI-0904874, ACI -1516338) and the U.S. DOE (DE-SC0005248).

  1. Astrophysical reaction rate for $\\alpha(\\alpha n,\\gamma)$

    CERN Document Server

    Sumiyoshi, K; Goko, S; Kajino, T

    2002-01-01

    We study the astrophysical reaction rate for the formation of $^{9}$Be through the three body reaction $\\alpha(\\alpha n,\\gamma)$. This reaction is one of the key reactions which could bridge the mass gap at A = 8 nuclear systems to produce intermediate-to-heavy mass elements in alpha- and neutron-rich environments such as r-process nucleosynthesis in supernova explosions, s-process nucleosynthesis in asymptotic giant branch (AGB) stars, and primordial nucleosynthesis in baryon inhomogeneous cosmological models. To calculate the thermonuclear reaction rate in a wide range of temperatures, we numerically integrate the thermal average of cross sections assuming a two-steps formation through a metastable $^{8}$Be. Off-resonant and on-resonant contributions from the ground state in $^{8}$Be are taken into account. As input cross section, we adopt the latest experimental data by photodisintegration of $^{9}$Be with laser-electron photon beams, which covers all relevant resonances in $^{9}$Be. We provide the reactio...

  2. The temperature-dependence of elementary reaction rates: beyond Arrhenius.

    Science.gov (United States)

    Smith, Ian W M

    2008-04-01

    The rates of chemical reactions and the dependence of their rate constants on temperature are of central importance in chemistry. Advances in the temperature-range and accuracy of kinetic measurements, principally inspired by the need to provide data for models of combustion, atmospheric, and astrophysical chemistry, show up the inadequacy of the venerable Arrhenius equation--at least, over wide ranges of temperature. This critical review will address the question of how to reach an understanding of the factors that control the rates of 'non-Arrhenius' reactions. It makes use of a number of recent kinetic measurements and shows how developments in advanced forms of transition state theory provide satisfactory explanations of complex kinetic behaviour (72 references).

  3. Rate Constant Calculation for Thermal Reactions Methods and Applications

    CERN Document Server

    DaCosta, Herbert

    2011-01-01

    Providing an overview of the latest computational approaches to estimate rate constants for thermal reactions, this book addresses the theories behind various first-principle and approximation methods that have emerged in the last twenty years with validation examples. It presents in-depth applications of those theories to a wide range of basic and applied research areas. When doing modeling and simulation of chemical reactions (as in many other cases), one often has to compromise between higher-accuracy/higher-precision approaches (which are usually time-consuming) and approximate/lower-preci

  4. Adjustable Nyquist-rate System for Single-Bit Sigma-Delta ADC with Alternative FIR Architecture

    Science.gov (United States)

    Frick, Vincent; Dadouche, Foudil; Berviller, Hervé

    2016-09-01

    This paper presents a new smart and compact system dedicated to control the output sampling frequency of an analogue-to-digital converters (ADC) based on single-bit sigma-delta (ΣΔ) modulator. This system dramatically improves the spectral analysis capabilities of power network analysers (power meters) by adjusting the ADC's sampling frequency to the input signal's fundamental frequency with a few parts per million accuracy. The trade-off between straightforwardness and performance that motivated the choice of the ADC's architecture are preliminary discussed. It particularly comes along with design considerations of an ultra-steep direct-form FIR that is optimised in terms of size and operating speed. Thanks to compact standard VHDL language description, the architecture of the proposed system is particularly suitable for application-specific integrated circuit (ASIC) implementation-oriented low-power and low-cost power meter applications. Field programmable gate array (FPGA) prototyping and experimental results validate the adjustable sampling frequency concept. They also show that the system can perform better in terms of implementation and power capabilities compared to dedicated IP resources.

  5. Resonances in the Sigma NN system

    Science.gov (United States)

    Gibson, B. F.; Afnan, I. R.

    We first review certain unique aspects of few-body Lambda-hypernuclei and then explore the physics of Sigma-hypernuclei that would produce structure near the Sigma threshold in few-body elastic scattering and reactions. In particular, we discuss a predicted enhancement in the lambda(d) cross section near the Sigma NN threshold in terms of poles in the Tau = 0 Y N N amplitude. A brief discussion of anticipated poles in the Tau = 1 amplitudes is also given.

  6. Application of semiclassical methods to reaction rate theory

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez, R.

    1993-11-01

    This work is concerned with the development of approximate methods to describe relatively large chemical systems. This effort has been divided into two primary directions: First, we have extended and applied a semiclassical transition state theory (SCTST) originally proposed by Miller to obtain microcanonical and canonical (thermal) rates for chemical reactions described by a nonseparable Hamiltonian, i.e. most reactions. Second, we have developed a method to describe the fluctuations of decay rates of individual energy states from the average RRKM rate in systems where the direct calculation of individual rates would be impossible. Combined with the semiclassical theory this latter effort has provided a direct comparison to the experimental results of Moore and coworkers. In SCTST, the Hamiltonian is expanded about the barrier and the ``good`` action-angle variables are obtained perturbatively; a WKB analysis of the effectively one-dimensional reactive direction then provides the transmission probabilities. The advantages of this local approximate treatment are that it includes tunneling effects and anharmonicity, and it systematically provides a multi-dimensional dividing surface in phase space. The SCTST thermal rate expression has been reformulated providing increased numerical efficiency (as compared to a naive Boltzmann average), an appealing link to conventional transition state theory (involving a ``prereactive`` partition function depending on the action of the reactive mode), and the ability to go beyond the perturbative approximation.

  7. Estimation of the Polymerization Rate of Liquid Propylene Using Adiabatic Reaction Calorimetry and Reaction Dilatometry

    NARCIS (Netherlands)

    Al-haj Ali, Mohammad; Betlem, Ben; Roffel, Brian; Weickert, Günter

    2007-01-01

    The use of pressure-drop and constant-pressure dilatometry for obtaining rate data for liquid propylene polymerization in filled batch reactors was examined. The first method uses reaction temperature and pressure as well as the compressibility of the reactor contents to calculate the polymerization

  8. Differential cross section and. lambda. -polarization in the hypercharge exchange reaction. pi. /sup -/p. -->. K/sup 0/. lambda. /. sigma. /sup 0/ at large mod(t) between 3 and 8 GeV/c

    Energy Technology Data Exchange (ETDEWEB)

    De Bellefon, A.; Billoir, P.; Brunet, J.M.; Tristram, G. (College de France, 75 - Paris); Gago, J. (Junta de Energia Nuclear, Lisbon (Portugal)); Sonderegger, P. (European Organization for Nuclear Research, Geneva (Switzerland)); Bachman, L.; Bogdanski, M.; Perrin, D.; Schwarz, R. (Neuchatel Univ. (Switzerland). Inst. de Physique)

    1982-11-15

    During the WA13 experiment at the ..cap omega.. spectrometer at CERN, elastic and hypercharge exchange reactions were recorded in the RF separated S1-beam. A surprisingly high negative ..lambda..-polarization has been found in the ..pi../sup -/p..-->..K/sup 0/..lambda../..sigma../sup 0/ sample. This result and the shape of the differential cross sections at large angles between 3 and 8 GeV/c are compared with Regge model and quark parton model.

  9. Optimized reaction mechanism rate rules for ignition of normal alkanes

    KAUST Repository

    Cai, Liming

    2016-08-11

    The increasing demand for cleaner combustion and reduced greenhouse gas emissions motivates research on the combustion of hydrocarbon fuels and their surrogates. Accurate detailed chemical kinetic models are an important prerequisite for high fidelity reacting flow simulations capable of improving combustor design and operation. The development of such models for many new fuel components and/or surrogate molecules is greatly facilitated by the application of reaction classes and rate rules. Accurate and versatile rate rules are desirable to improve the predictive accuracy of kinetic models. A major contribution in the literature is the recent work by Bugler et al. (2015), which has significantly improved rate rules and thermochemical parameters used in kinetic modeling of alkanes. In the present study, it is demonstrated that rate rules can be used and consistently optimized for a set of normal alkanes including n-heptane, n-octane, n-nonane, n-decane, and n-undecane, thereby improving the predictive accuracy for all the considered fuels. A Bayesian framework is applied in the calibration of the rate rules. The optimized rate rules are subsequently applied to generate a mechanism for n-dodecane, which was not part of the training set for the optimized rate rules. The developed mechanism shows accurate predictions compared with published well-validated mechanisms for a wide range of conditions.

  10. Mass splittings in $\\Sigma_b$ and $\\Sigma_b^*$

    OpenAIRE

    Rosner, Jonathan L.

    2006-01-01

    The charged $\\Sigma_b$ and $\\Sigma^*_b$ states have recently been reported by the CDF Collaboration. The relation of their reported charge-averaged masses to expectations based on the quark model is reviewed briefly. A relation is proved among the $\\Delta I = 1$ electromagnetic mass differences $\\Sigma_1 \\equiv M(\\Sigma^+) - M(\\Sigma^-)$, $\\Sigma^*_1 \\equiv M(\\Sigma^{*+})- M(\\Sigma^{*-})$, $\\Sigma_{b1} \\equiv M(\\Sigma_b^+) - M(\\Sigma_b^-)$, and $\\Sigma^*_{b1} \\equiv M(\\Sigma_b^{*+}) - M(\\Sigm...

  11. Toward understanding the rates of reactions at mineral surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Casey, W.H. [Univ. of California Davis, CA (United States). Dept. of Land, Air and Water Resources and Dept. of Geology; Ludwig, C. [EAWAG, Swiss Federal Institute for Environmental Science and Technolgy, Dubendorf (Switzerland). Dept. of Resources and Waste management; Holmen, B. [Univ. of California Davis, CA (United States). Dept. of Land, Air and Water Resources

    1998-12-31

    Environmental geo chemists are commonly called upon to make predictions over long scales of time and distance. In many cases, these predictions involve disequilibrium reactions, such as the decomposition of ozone-depleting gases or the migration rates of groundwater contaminants. These groundwater contaminants interact with mineral surfaces in a complicated fashion that is not understood quantitatively. However, in a real sense, mineral dissolution studies are to the aqueous geo chemists what Escherichia coli are to microbiologists: an inexpensive model system to map out important kinetic relations that can then be extended qualitatively to other settings. This chapter explains that is enormously useful to draw analogies between reactions at mineral surfaces and at dissolved metal-ligand complexes. In this approach, the reactivities of bond between a metal and a water molecule or ligand in the inner-coordination-sphere of the dissolved complex are proxies for bonds between a metal and oxygen at the mineral surface, which cannot be studied directly.

  12. Reaction rate constant for radiative association of CF{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Öström, Jonatan, E-mail: jonatan.ostrom@gmail.com; Gustafsson, Magnus, E-mail: magnus.gustafsson@ltu.se [Applied Physics, Division of Materials Science, Department of Engineering Science and Mathematics, Luleå University of Technology, 97187 Luleå (Sweden); Bezrukov, Dmitry S. [Department of Chemistry, M. V. Lomonosov Moscow State University, Moscow, 119991 (Russian Federation); Nyman, Gunnar [Department of Chemistry and Molecular Biology, University of Gothenburg, 41296 Gothenburg (Sweden)

    2016-01-28

    Reaction rate constants and cross sections are computed for the radiative association of carbon cations (C{sup +}) and fluorine atoms (F) in their ground states. We consider reactions through the electronic transition 1{sup 1}Π → X{sup 1}Σ{sup +} and rovibrational transitions on the X{sup 1}Σ{sup +} and a{sup 3}Π potentials. Semiclassical and classical methods are used for the direct contribution and Breit–Wigner theory for the resonance contribution. Quantum mechanical perturbation theory is used for comparison. A modified formulation of the classical method applicable to permanent dipoles of unequally charged reactants is implemented. The total rate constant is fitted to the Arrhenius–Kooij formula in five temperature intervals with a relative difference of <3%. The fit parameters will be added to the online database KIDA. For a temperature of 10–250 K, the rate constant is about 10{sup −21} cm{sup 3} s{sup −1}, rising toward 10{sup −16} cm{sup 3} s{sup −1} for a temperature of 30 000 K.

  13. Evaluation of antioxidants using oxidation reaction rate constants

    Institute of Scientific and Technical Information of China (English)

    SHI Yan; ZHAN Xiancheng; MA Lie; LI Linli; LI Chengrong

    2007-01-01

    An evaluation method for the capacity of antioxidants to protect drugs against oxidation is presented.As a new viewpoint,to determine the priority of the competitive oxidations between the antioxidant and the protected drug,and to compare the drug-protection capacity of antioxidants,it is important to determine their oxidation rate constants using chemical kinetics instead of standard oxidation (or reduction) potentials.Sodium sulfite,sodium bisulfite and sodium pyrosulfite were used as models for the determination of oxidation reaction rate constants in aqueous solutions.In the experiments,sufficient air was continually infused into the solution to keep the concentration of dissolved oxygen constant.The residual concentrations of the antioxidants were determined by iodimetry,and the concentration of dissolved oxygen by oxygen electrode.The data were fitted by linear regressions to obtain the reaction rate constants.It was found that the degradation of sodium sulfite,sodium bisulfite or sodium pyrosulfite obeyed pseudo zero-order kinetics in the buffer solutions.Because of the ionization equilibrium,these three antioxidants have the same ion form in solutions at a definite pH value and therefore their apparent rate constants were essentially the same.The average apparent rate constants of the three antioxidants at 25~C are (1.34±0.03)×10-3 at pH 6.8,(1.20±0.02) x 10-3 at pH 4.0 and (6.58±0.02)×10-3 mol.L-1.h-1 at pH 9.2,respectively.

  14. Infrared identification of the {sigma}-complex of Cl-C{sub 6}H{sub 6} in the reaction of chlorine atom and benzene in solid para-hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Bahou, Mohammed; Witek, Henryk [Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan (China); Lee, Yuan-Pern [Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, 1001 Ta-Hsueh Road, Hsinchu 30010, Taiwan (China); Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China)

    2013-02-21

    The reaction of a chlorine atom with benzene (C{sub 6}H{sub 6}) is important in organic chemistry, especially in site-selective chlorination reactions, but its product has been a subject of debate for five decades. Previous experimental and theoretical studies provide no concrete conclusion on whether the product is a {pi}- or {sigma}-form of the Cl-C{sub 6}H{sub 6} complex. We took advantage of the diminished cage effect of para-hydrogen (p-H{sub 2}) to produce Cl in situ to react with C{sub 6}H{sub 6} (or C{sub 6}D{sub 6}) upon photolysis of a Cl{sub 2}/C{sub 6}H{sub 6} (or C{sub 6}D{sub 6})/p-H{sub 2} matrix at 3.2 K. The infrared spectrum, showing intense lines at 1430.5, 833.6, 719.8, 617.0, and 577.4 cm{sup -1}, and several weaker ones for Cl-C{sub 6}H{sub 6}, and the deuterium shifts of observed new lines unambiguously indicate that the product is a 6-chlorocyclohexadienyl radical, i.e., the {sigma}-complex of Cl-C{sub 6}H{sub 6}. Observation of the {sigma}-complex rather than the {pi}-complex indicates that the {sigma}-complex is more stable in solid p-H{sub 2} at 3.2 K. The spectral information is crucial for further investigations of the Cl + C{sub 6}H{sub 6} reaction either in the gaseous or solution phase.

  15. The optical model potential of the $\\Sigma$ hyperon in nuclear matter

    OpenAIRE

    Dabrowski, J; Rozynek, J.

    2009-01-01

    We present our attempts to determine the optical model potential $U_\\Sigma = V_\\Sigma -iW_\\Sigma$ of the $\\Sigma$ hyperon in nuclear matter. We analyze the following sources of information on $U_\\Sigma$: $\\Sigma N$ scattering, $\\Sigma^-$ atoms, and final state interaction of $\\Sigma$ hyperons in the $(\\pi,K^+)$ and $(K^-.\\pi)$ reactions on nuclear targets. We conclude that $V_\\Sigma$ is repulsive inside the nucleus and has a shallow a tractive pocket at the nuclear surface. These features of ...

  16. Determination of the Astrophysical S(E) Factors or Rates for Radiative Capture Reaction with One Nucleon Transfer Reaction%Determination of the Astrophysical S(E) Factors or Rates for Radiative Capture Reaction with One Nucleon Transfer Reaction

    Institute of Scientific and Technical Information of China (English)

    李志宏; 郭冰; 李云居; 苏俊; 李二涛; 白希祥; 王友宝; 曾晟; 王宝祥; 颜胜权; 李志常; 刘建成; 连钢; 金孙均; 刘鑫; 柳卫平

    2012-01-01

    The radiative capture reaction plays an important role in nuclear astrophysics. We have indirectly measured the astrophysical S(E) factors for some proton capture reactions and reaction rates for several neutron capture reactions with one nucleon transfer reactions at HI-13 tandem accelerator in recent years. Some of them are compiled into IAEA EXFOR database and JINA REACLIB project, and used in the network calculations of Big Bang nucleosynthesis and type-I X-ray bursts.

  17. A Comparison of Longitudinal and Transverse Cross Sections in the p (e,e'K)/Lambda and p(e,e'K)/Sigma Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Richard Mohring

    1999-10-01

    Jefferson Lab Experiment E93-018 measured kaon electroproduction in hydrogen in two hyperon channels, p(e, e'K{sup +})Lambda and p(e,e'K{sup +})Sigma{sup 0}. Data in both channels were taken at three (3) different values of the virtual photon transverse linear polarization, epsilon, for each of four (4) values of Q{sup 2} = (0.52, 0.75, 1.00, 2.00) GeV{sup 2}. Cross sections averaged over the azimuthal angle, phi, were extracted (i.e., sigma{sub T} + epsilon sigma{sub L}) at each of these twelve points for each hyperon. Rosenbluth separations were performed to separate the longitudinal and transverse production cross sections.

  18. The gamma + p to K+ + Lambda and gamma + p to K+ + Sigma0 reactions at forward angles with photon energies from 1.5 to 2.4 GeV

    CERN Document Server

    Sumihama, M

    2006-01-01

    Differential cross sections and photon beam asymmetries for the gamma p rightarrow K+ Lambda and gamma p rightarrow K+ Sigma0 reactions have been measured in the photon energy range from 1.5 GeV to 2.4 GeV and in the angular range from Theta_{cm} = 0 to 60 of the K+ scattering angle in the center of mass system at the SPring-8/LEPS facility. The photon beam asymmetries for both the reactions have been found to be positive and to increase with the photon energy. The measured differential cross sections agree with the data measured by the CLAS collaboration at cosTheta_{cm}0.9. In the K+Lambda reaction, the resonance-like structure found in the CLAS and SAPHIR data at W=1.96 GeV is confirmed. The differential cross sections at forward angles suggest a strong K-exchange contribution in the t-channel for the K+Lambda reaction, but not for the K+Sigma0 reaction.

  19. Reaction rate theory of radiation exposure: Effects of the dose rate on mutation frequencies

    CERN Document Server

    Manabe, Yuichiro; Nakamura, Issei

    2014-01-01

    We develop a kinetic reaction model for the cells having the irradiated DNA molecules due to the ionizing radiation exposure. Our theory simultaneously accounts for the time-dependent reactions of the DNA damage, the DNA mutation, the DNA repair, and the proliferation and apoptosis of cells in a tissue with a minimal set of model parameters. In contrast to the existing theories for the radiation exposition, we do not assume the relationships between the total dose and the induced mutation frequency. We show good agreement between theory and experiment. Importantly, our result shows a new perspective that the key ingredient in the study of the irradiated cells is the rate constants depending on the dose rate. Moreover, we discuss the universal scaling function for mutation frequencies due to the irradiation at low dose rates.

  20. Formation of the 1,3,5-hexatriynyl radical (C6H(X(2)Pi)) via the crossed beams reaction of dicarbon (C2(X(1)Sigma(g)+/a(3)Pi(u))), with diacetylene (C4H2(X(1)Sigma(g)+)).

    Science.gov (United States)

    Zhang, Fangtong; Kim, Seol; Kaiser, Ralf I; Mebel, Alexander M

    2009-02-19

    Crossed molecular beams experiments were conducted to investigate the chemical dynamics of the reaction of dicarbon molecules, C(2)(X(1)Sigma(g)(+)/a(3)Pi(u)), with diacetylene, C(4)H(2)(X(1)Sigma(g)(+)) at two collision energies of 12.1 and 32.8 kJ mol(-1). The dynamics were found to be indirect, involved C(6)H(2) intermediates, and were dictated by an initial addition of the dicarbon molecule to the carbon-carbon triple bond of diacetylene. The initial collision complexes could isomerize. On the singlet surface, the resulting linear triacetylene molecule (C(6)H(2)(X(1)Sigma(g)(+))) decomposed without an exit barrier to form the linear 1,3,5-hexatriynyl radical (C(6)H(X(2)Pi)). On the triplet surface, the dynamics suggested at least a tight exit transition state involved in the fragmentation of a triplet C(6)H(2) intermediate to yield the 1,3,5-hexatriynyl radical (C(6)H(X(2)Pi)) plus atomic hydrogen. On the basis of the experimental data, we recommend an experimentally determined enthalpy of formation of the 1,3,5-hexatriynyl radical of 1014 +/- 27 kJ mol(-1) at 0 K. Our experimental results and the derived reaction mechanisms gain full support from electronic structure calculations on the singlet and triplet C(6)H(2) potential-energy surfaces. The identification of the 1,3,5-hexatriynyl radical under single collision conditions implies that the neutral-neutral reaction of dicarbon with diacetylene can lead to the formation of 1,3,5-hexatriynyl radicals in the interstellar medium and possibly in the hydrocarbon-rich atmospheres of planets and their moons such as Saturn's satellite Titan.

  1. Improved resonance reaction rate calculation for lattice physics subsystem

    Energy Technology Data Exchange (ETDEWEB)

    Finch, D.R.

    1974-02-08

    The resonance capture calculations of the HAMMER System and HAMBUR System are derived from a consistent statement of the integral slowing down equation and definitions of the resonance integral. The assumptions made in these treatments are explicitly stated, and and an attempt is made to estimate the possible error in the resonance integral arising from these assumptions. This analysis is made to pin-point those parts of the calculation that can be improved and updated. Based on the analysis of existing calculations a method of calculation is derived which avoids most of the problems encountered in HAMMER and HAMBUR. The chief improvements that result are as follows: Careful attention is paid to calculation of the resonance flux as most errors in existing calculations result from consistently overpredicting fluxes in all regions of a lattice cell. The calculation can be modified to produce as crude or detailed a resonance calculation, at the expense of computer time, as required by the user. Resonances that overlap group boundaries contribute the correct contribution to each group's reaction rates. Overlap between resonances of different isotopes is correctly accounted for. Up-to-date resonance formalisms are used including the Adler-Adler multi-level formulations. Provision is made to easily add new formalisms when required. Streaming effects from neutron leaking into a cell may optionally be included in the calculation of resonance reaction rates. A complete description of the physics contained in this new computational module is provided along with additional information on the numerical techniques employed in the module.

  2. Analysis of reaction rates of single molecules on metal surfaces

    Science.gov (United States)

    Ueba, H.

    2017-10-01

    The experimental results of the action spectra i.e., reaction rate R(V) as a function of a bias voltage V are analyzed for rotation of a single CCH (D) molecule on a Cu (100) surface [5] and hopping of a single H(D)2O molecule on Pd(111) surface [6]. In the former system it is identified that rotation occurs if enough energy stored in the C-H (D) in-plane bending (IPB) mode excited by tunneling electron is transferred to the C-H (D) out of plane bending (OPB) mode (reaction coordinate mode) via the anharmonic mode coupling in a single electron process. The calculated R(V) shows an excellent agreement with the experimental results except at the low bias voltages below V ≃ 60 mV where no experimental data is available for the nonlinear current I dependence of R(I). A reproduction of the experimental R(V) at the higher voltage region allows us to determine the vibrational density of states of the C-H IPB mode and its coupling rate to the C-H (D) OPB mode as well as the inelastic tunneling current to excite IPB mode. A change of a conductance upon excitation of the C-H IPB mode enables us to evaluate the electron-vibration coupling strength inducing the rotation motion of CCH molecule. In the latter system investigated at a high temperature of about 40 K, the constant R(V) due to thermal hopping followed by the rapid increase is satisfactory explained by anharmonic inter-mode coupling between the scissor mode excited by tunneling electrons and the frustrated translation mode for H(D)2O molecule on Pd(111).

  3. Manual Choice Reaction Times in the Rate-Domain

    Directory of Open Access Journals (Sweden)

    Chris eHarris

    2014-06-01

    Full Text Available Over the last 150 years, human manual reaction times (RTs have been recorded countless times. Yet, our understanding of them remains remarkably poor. RTs are highly variable with positively skewed frequency distributions, often modelled as an inverse Gaussian distribution reflecting a stochastic rise to threshold (diffusion process. However, latency distribution of saccades are very close to the reciprocal Normal, suggesting that ‘rate’ (reciprocal RT may be the more fundamental variable. We explored whether this phenomenon extends to choice manual RTs. We recorded two-alternative choice RTs from 24 subjects, each with 4 blocks of 200 trials with two task difficulties (easy vs. difficult discrimination and two instruction sets (urgent vs. accurate. We found that rate distributions were, indeed, very close to Normal, shifting to lower rates with increasing difficulty and accuracy, and for some blocks subjects they appeared to become left-truncated, but still close to Normal. Using autoregressive techniques, we found temporal sequential dependencies for lags of at least 3. We identified a transient and steady-state component in each block. Because rates were Normal, we were able to estimate autoregressive weights using the Box-Jenkins technique, and convert to a moving average model using z-transforms to show explicit dependence on stimulus input. We also found a spatial sequential dependence for the previous 3 lags depending on whether the laterality of previous trials was repeated or alternated. This was partially dissociated from temporal dependency as it only occurred in the easy tasks. We conclude that 2-alternative choice manual RT distributions are close to reciprocal Normal and not the inverse Gaussian. This is not consistent with stochastic rise to threshold models, and we propose a simple optimality model in which reward is maximized to yield to an optimal rate, and hence an optimal time to respond. We discuss how it might be

  4. What is Six Sigma ?

    Directory of Open Access Journals (Sweden)

    Prof. Ph.D. Sorin-George Toma

    2008-12-01

    Full Text Available Over the past decades, several business improvement methods were launched, includingthe one known as Six Sigma. The Six Sigma implies the application of scientific principles to business processesand allows companies to obtain better, faster and cheaper products and services. Motorola was thefirst company that introduced and implemented Six Sigma in its business processes in the 1980s.

  5. Hyperon polarization at high P/sub T/ in the reactions. pi. /sup -/p. -->. K/sup 0/anti-. lambda. /. sigma. /sup 0/ and anti-pp. -->. lambda lambda. /. sigma. /sup 0/ between 3 and 12 GeV/c

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, R.; Bachman, L.; Bogdanski, M.; Perrin, D.; Gago, J.; Sonderegger, P.; de Bellefon, A.; Billoir, P.; Brunet, J.M.; Tristram, G.

    1983-01-01

    ..lambda.. and anti-..lambda.. polarizations have been measured in exclusive ..pi../sup -/p and anti-pp reactions at 3-5 GeV/c and in semi-inclusive reactions at 3-12 GeV/c covering transverse momentum values up to 1.5 GeV/c. The main result is a large and negative polarization which may provide a clear and severe test for theoretical models. 11 references, 2 figures.

  6. Beam-Recoil Polarization Transfer in the Nucleon Resonance Region in the Exclusive $\\vec{e}p \\to e'K^+\\vec{\\Lambda}$ and $\\vec{e}p \\to e'K^+\\vec{\\Sigma}^0$ Reactions at CLAS

    Energy Technology Data Exchange (ETDEWEB)

    D.S. Carman, B.A. Raue, for the CLAS Collaboration

    2009-06-01

    Beam-recoil transferred polarizations for the exclusive $\\vec{e}p \\to e'K^+ \\vec{\\Lambda},\\vec{\\Sigma}^0$ reactions have been measured using the CLAS spectrometer at Jefferson Laboratory. New measurements have been completed at beam energies of 4.261 and 5.754~GeV that span a range of momentum transfer $Q^2$ from 0.7 to 5.4~GeV$^2$, invariant energy $W$ from 1.6 to 2.6~GeV, and the full center-of-mass angular range of the $K^+$ meson. These new data add to the existing CLAS $K^+\\Lambda$ measurements at 2.567~GeV, and provide the first-ever data for the $K^+\\Sigma^0$ channel in electroproduction. Comparisons of the data with several theoretical models are used to study the sensitivity to $s$-channel resonance contributions and the underlying reaction mechanism. Interpretations within two semi-classical partonic models are made to probe the underlying reaction mechanism and the $s\\bar{s}$ quark-pair creation dynamics.

  7. Beam-Recoil Polarization Transfer in the Nucleon Resonance Region in the Exclusive $\\vec{e}p \\to e'K^+\\vec{\\Lambda}$ and $\\vec{e}p \\to e'K^+\\vec{\\Sigma}^0$ Reactions at CLAS

    CERN Document Server

    Carman, D S

    2009-01-01

    Beam-recoil transferred polarizations for the exclusive $\\vec{e}p \\to e'K^+ \\vec{\\Lambda},\\vec{\\Sigma}^0$ reactions have been measured using the CLAS spectrometer at Jefferson Laboratory. New measurements have been completed at beam energies of 4.261 and 5.754 GeV that span a range of momentum transfer $Q^2$ from 0.7 to 5.4 GeV$^2$, invariant energy $W$ from 1.6 to 2.6 GeV, and the full center-of-mass angular range of the $K^+$ meson. These new data add to the existing CLAS $K^+\\Lambda$ measurements at 2.567 GeV, and provide the first-ever data for the $K^+\\Sigma^0$ channel in electroproduction. Comparisons of the data with several theoretical models are used to study the sensitivity to s-channel resonance contributions and the underlying reaction mechanism. Interpretations within two semi-classical partonic models are made to probe the underlying reaction mechanism and the $s\\bar{s}$ quark-pair creation dynamics.

  8. On the mechanism of effective chemical reactions with turbulent mixing of reactants and finite rate of molecular reactions

    Science.gov (United States)

    Vorotilin, V. P.

    2017-01-01

    A generalization of the theory of chemical transformation processes under turbulent mixing of reactants and arbitrary values of the rate of molecular reactions is presented that was previously developed for the variant of an instantaneous reaction [13]. The use of the features of instantaneous reactions when considering the general case, namely, the introduction of the concept of effective reaction for the reactant volumes and writing a closing conservation equation for these volumes, became possible due to the partition of the whole amount of reactants into "active" and "passive" classes; the reactants of the first class are not mixed and react by the mechanism of instantaneous reactions, while the reactants of the second class approach each other only through molecular diffusion, and therefore their contribution to the reaction process can be neglected. The physical mechanism of reaction for the limit regime of an ideal mixing reactor (IMR) is revealed and described. Although formally the reaction rate in this regime depends on the concentration of passive fractions of the reactants, according to the theory presented, the true (hidden) mechanism of the reaction is associated only with the reaction of the active fractions of the reactants with vanishingly small concentration in the volume of the reactor. It is shown that the rate constant of fast chemical reactions can be evaluated when the mixing intensity of reactants is much less than that needed to reach the mixing conditions in an IMR.

  9. SIGMA WEB INTERFACE FOR REACTOR DATA APPLICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Pritychenko,B.; Sonzogni, A.A.

    2010-05-09

    We present Sigma Web interface which provides user-friendly access for online analysis and plotting of the evaluated and experimental nuclear reaction data stored in the ENDF-6 and EXFOR formats. The interface includes advanced browsing and search capabilities, interactive plots of cross sections, angular distributions and spectra, nubars, comparisons between evaluated and experimental data, computations for cross section data sets, pre-calculated integral quantities, neutron cross section uncertainties plots and visualization of covariance matrices. Sigma is publicly available at the National Nuclear Data Center website at http://www.nndc.bnl.gov/sigma.

  10. On the ambiguity of the reaction rate constants in multivariate curve resolution for reversible first-order reaction systems.

    Science.gov (United States)

    Schröder, Henning; Sawall, Mathias; Kubis, Christoph; Selent, Detlef; Hess, Dieter; Franke, Robert; Börner, Armin; Neymeyr, Klaus

    2016-07-13

    If for a chemical reaction with a known reaction mechanism the concentration profiles are accessible only for certain species, e.g. only for the main product, then often the reaction rate constants cannot uniquely be determined from the concentration data. This is a well-known fact which includes the so-called slow-fast ambiguity. This work combines the question of unique or non-unique reaction rate constants with factor analytic methods of chemometrics. The idea is to reduce the rotational ambiguity of pure component factorizations by considering only those concentration factors which are possible solutions of the kinetic equations for a properly adapted set of reaction rate constants. The resulting set of reaction rate constants corresponds to those solutions of the rate equations which appear as feasible factors in a pure component factorization. The new analysis of the ambiguity of reaction rate constants extends recent research activities on the Area of Feasible Solutions (AFS). The consistency with a given chemical reaction scheme is shown to be a valuable tool in order to reduce the AFS. The new methods are applied to model and experimental data.

  11. Molecule-based approach for computing chemical-reaction rates in upper atmosphere hypersonic flows.

    Energy Technology Data Exchange (ETDEWEB)

    Gallis, Michail A.; Bond, Ryan Bomar; Torczynski, John Robert

    2009-08-01

    This report summarizes the work completed during FY2009 for the LDRD project 09-1332 'Molecule-Based Approach for Computing Chemical-Reaction Rates in Upper-Atmosphere Hypersonic Flows'. The goal of this project was to apply a recently proposed approach for the Direct Simulation Monte Carlo (DSMC) method to calculate chemical-reaction rates for high-temperature atmospheric species. The new DSMC model reproduces measured equilibrium reaction rates without using any macroscopic reaction-rate information. Since it uses only molecular properties, the new model is inherently able to predict reaction rates for arbitrary nonequilibrium conditions. DSMC non-equilibrium reaction rates are compared to Park's phenomenological non-equilibrium reaction-rate model, the predominant model for hypersonic-flow-field calculations. For near-equilibrium conditions, Park's model is in good agreement with the DSMC-calculated reaction rates. For far-from-equilibrium conditions, corresponding to a typical shock layer, the difference between the two models can exceed 10 orders of magnitude. The DSMC predictions are also found to be in very good agreement with measured and calculated non-equilibrium reaction rates. Extensions of the model to reactions typically found in combustion flows and ionizing reactions are also found to be in very good agreement with available measurements, offering strong evidence that this is a viable and reliable technique to predict chemical reaction rates.

  12. Low-Mass (M<1.2 Gev/c^2) Sigma0 - Meson Produced in the System Pi+Pi- from the Reaction np --> np Pi+Pi- at Pn = 5.20 Gev/c^2

    CERN Document Server

    Troyan, Yu A; Troyan, A Y; Plekhanov, E B; Jerusalimov, A P; Arakelian, S G; Troyan, Yu. A.

    2006-01-01

    The production and properties of the resonances in the system of Pi+Pi- were studied in the reaction np --> npPi+Pi- at the momentum of incident neutrons Pn=(5.20 +/- 0.12)GeV/c. In this work in comparison with previous ones we made more hard selection of events taking into account track measurement precise. In the distribution of the Pi+Pi- combinations effective masses we have found 8 peculiarities. All the observable peculiarities have spins equal to zero. There were no corresponding picks in the Pi-PI- and Pi-Pi0 - systems in the reactions np --> npPi+Pi- Pi- and np --> npPi-Pi0. So, we have observed a row of resonances with a set of quantum numbers 0+(0++) -- SIGMA0 - mesons decaying on the channel SIGMA0 --> Pi+Pi-. The obtained in other experiments masses coincide with the sequence of masses observed in our experiment. Especially good coincidence can be obtained in the K-matrix approach (see RPP).

  13. Nonequilibrium Thermodynamic Formalism of Nonlinear Chemical Reaction Systems with Waage-Guldberg's Law of Mass Action

    CERN Document Server

    Ge, Hao

    2016-01-01

    Macroscopic entropy production $\\sigma^{(tot)}$ in the general nonlinear isothermal chemical reaction system with mass action kinetics is decomposed into a free energy dissipation and a house-keeping heat: $\\sigma^{(tot)}=\\sigma^{(fd)}+\\sigma^{(hk)}$; $\\sigma^{(fd)}=-\\rd A/\\rd t$, where $A$ is a generalized free enegy function. This yields a novel nonequilibrium free energy balance equation $\\rd A/\\rd t=-\\sigma^{(tot)}+\\sigma^{(hk)}$, which is on a par with celebrated entropy balance equation $\\rd S/\\rd t=\\sigma^{(tot)}+\\eta^{(ex)}$ where $\\eta^{(ex)}$ is the rate of entropy exchange with the environment.For kinetic system with complex balance,$\\sigma^{(fd)},\\sigma^{(hk)}\\ge 0$: $\\sigma^{(fd)}$ characterizes the irreversibility of a transient relaxation kinetics; while $\\sigma^{(hk)}$ is positive even in a steady state, representing irreversibility in open,driven chemical systems with a chemostat.For kinetic system withoutcomplex balance, negative $\\sigma^{(fd)}$ is a necessary condition for multistability, w...

  14. Bridging silyl groups in sigma-bond metathesis and [1, 2] shifts. An experimental and computational study of the reaction between cerium metallocenes and MeOSiMe3

    Energy Technology Data Exchange (ETDEWEB)

    Werkema, Evan; Yahia, Ahmed; Maron, Laurent; Eisenstein, Odile; Andersen, Richard

    2010-04-21

    The reaction of Cp'2CeH (Cp' = 1,2,4-(Me3C)3C5H2 ) with MeOSiMe3 gives Cp'2CeOMe and HSiMe3 and the reaction of the metallacycle, Cp'[(Me3C)2C5H2C(Me) 2CH2]Ce, with MeOSiMe3 yields Cp'2CeOCH2SiMe3, formed from hypothetical Cp'2CeCH2OSiMe3 by a [1, 2] shift also known as a silyl-Wittig rearrangement. Although both cerium products are alkoxides, they are formed by different pathways. DFT calculations on the reaction of the model metallocene, Cp2CeH, and MeOSiMe3 show that the lowest energy pathway is a H for OMe exchange at Ce that occurs by way of a sigma-bond metathesis transition state as SiMe3 exchanges partners. The formation of Cp2CeOCH2SiMe3 occurs by way of a low activation barrier [1, 2]shift of the SiMe3 group in Cp2CeCH2OSiMe3. Calculations on a model metallacycle, Cp[C5H4C(Me)2CH2]Ce, show that the metallacycle favors CH bond activation over sigma-bond metathesis involving the transfer of the SiMe3 group in good agreement with experiment. The sigma-bond metathesis involving the transfer of SiMe3 and the [1, 2]shift of SiMe3 reactions have in common a pentacoordinate silicon at the transition states. A molecular orbital analysis illustrates the connection between these two Si-O bond cleavage reactions and traces the reason why they occur for a silyl but not for an alkyl group to the difference in energy required to form a pentacoordinate silicon or carbon atom in the transition state. This difference clearly distinguishes a silyl from an alkyl group as shown in the study of"Pyrolysis of Tetramethylsilane Yielding Free d-orbitals by Seyferth and Pudvin in ChemTech 1981, 11, 230-233".

  15. Bridging silyl groups in sigma-bond metathesis and [1, 2] shifts. An experimental and computational study of the reaction between cerium metallocenes and MeOSiMe3

    Energy Technology Data Exchange (ETDEWEB)

    Werkema, Evan; Yahia, Ahmed; Maron, Laurent; Eisenstein, Odile; Andersen, Richard

    2010-04-21

    The reaction of Cp'2CeH (Cp' = 1,2,4-(Me3C)3C5H2 ) with MeOSiMe3 gives Cp'2CeOMe and HSiMe3 and the reaction of the metallacycle, Cp'[(Me3C)2C5H2C(Me) 2CH2]Ce, with MeOSiMe3 yields Cp'2CeOCH2SiMe3, formed from hypothetical Cp'2CeCH2OSiMe3 by a [1, 2] shift also known as a silyl-Wittig rearrangement. Although both cerium products are alkoxides, they are formed by different pathways. DFT calculations on the reaction of the model metallocene, Cp2CeH, and MeOSiMe3 show that the lowest energy pathway is a H for OMe exchange at Ce that occurs by way of a sigma-bond metathesis transition state as SiMe3 exchanges partners. The formation of Cp2CeOCH2SiMe3 occurs by way of a low activation barrier [1, 2]shift of the SiMe3 group in Cp2CeCH2OSiMe3. Calculations on a model metallacycle, Cp[C5H4C(Me)2CH2]Ce, show that the metallacycle favors CH bond activation over sigma-bond metathesis involving the transfer of the SiMe3 group in good agreement with experiment. The sigma-bond metathesis involving the transfer of SiMe3 and the [1, 2]shift of SiMe3 reactions have in common a pentacoordinate silicon at the transition states. A molecular orbital analysis illustrates the connection between these two Si-O bond cleavage reactions and traces the reason why they occur for a silyl but not for an alkyl group to the difference in energy required to form a pentacoordinate silicon or carbon atom in the transition state. This difference clearly distinguishes a silyl from an alkyl group as shown in the study of"Pyrolysis of Tetramethylsilane Yielding Free d-orbitals by Seyferth and Pudvin in ChemTech 1981, 11, 230-233".

  16. Six Sigma software development

    CERN Document Server

    Tayntor, Christine B

    2002-01-01

    Since Six Sigma has had marked success in improving quality in other settings, and since the quality of software remains poor, it seems a natural evolution to apply the concepts and tools of Six Sigma to system development and the IT department. Until now however, there were no books available that applied these concepts to the system development process. Six Sigma Software Development fills this void and illustrates how Six Sigma concepts can be applied to all aspects of the evolving system development process. It includes the traditional waterfall model and in the support of legacy systems,

  17. New Astrophysical Reaction Rate for the $^{12}\\textrm{C}(\\alpha,\\gamma)^{16}\\textrm{O}$ Reaction

    CERN Document Server

    An, Z D; Fan, G T; Li, Y J; Chen, Z P; Sun, Y Y

    2016-01-01

    A new astrophysical reaction rate for $^{12}$C($\\alpha,\\gamma$)$^{16}$O has been evaluated on the basis of a global R-matrix fitting to the available experimental data. The reaction rates of $^{12}$C($\\alpha,\\gamma$)$^{16}$O for stellar temperatures between 0.04 $\\leq$ $T_9$ $\\leq$ 10 are provided in a tabular form and by an analytical fitting expression. At $T_9$ = 0.2, the reaction rate is (7.83 $\\pm$ 0.35)$\\times10^{15}$ $\\rm{cm^3 mol^{-1} s^{-1}}$, where stellar helium burning occurs.

  18. Refit to numerically problematic UMIST reaction rate coefficients

    CERN Document Server

    Röllig, M

    2011-01-01

    Aims. Chemical databases such as the UMIST Database for Astrochemistry (UDFA) are indispensable in the numerical modeling of astrochemical networks. Several of the listed reactions in the UDFA have properties that are problematic in numerical computations: Some are parametrized in a way that leads to extremely divergent behavior for low kinetic temperatures. Other reactions possess multiple entries that are each valid in a different temperature regime, but have no smooth transition when switching from one to another. Numerically, this introduces many difficulties.We present corrected parametrizations for these sets of reactions in the UDFA06 database. Methods. From the tabulated parametrization in UDFA, we created artificial data points and used a Levenberg-Marquardt algorithm to find a set of improved fit parameters without divergent behavior for low temperatures. For reactions with multiple entries in the database that each possess a different temperature regime, we present one joint parametrization that is...

  19. Pop-It Beads to Introduce Catalysis of Reaction Rate and Substrate Depletion Effects

    Science.gov (United States)

    Gehret, Austin U.

    2017-01-01

    A kinesthetic classroom activity was designed to help students understand enzyme activity and catalysis of reaction rate. Students served the role of enzymes by manipulating Pop-It Beads as the catalytic event. This activity illuminates the relationship between reaction rate and reaction progress by allowing students to experience first-hand the…

  20. Apparent Rate Constant for Diffusion-Controlled Three molecular (catalytic) reaction

    OpenAIRE

    Burlatsky, S. F.; Moreau, M

    1996-01-01

    We present simple explicit estimates for the apparent reaction rate constant for three molecular reactions, which are important in catalysis. For small concentrations and $d> 1$, the apparent reaction rate constant depends only on the diffusion coefficients and sizes of the particles. For small concentrations and $d\\le 1$, it is also time -- dependent. For large concentrations, it gains the dependence on concentrations.

  1. Reaction rate oscillations during catalytic CO oxidation: A brief overview

    Science.gov (United States)

    Tsotsis, T. T.; Sane, R. C.

    1987-04-01

    It is not the intent here to present a comprehensive review of the dynamic behavior of the catalytic oxidation of CO. This reaction is one of the most widely studied in the field of catalysis. A review paper by Engel and Ertl has examined the basic kinetic and mechanistic aspects, and a comprehensive paper by Razon and Schmitz was recently devoted to its dynamic behavior. Those interested in further study of the subject should consult these reviews and a number of general review papers on catalytic reaction dynamics. The goal is to present a brief overview of certain interesting aspects of the dynamic behavior of this reaction and to discuss a few questions and issues, which are still the subject of study and debate.

  2. SIX SIGMA: A METRIC, A METHODOLOGY AND A MANAGEMENT SYSTEM

    Directory of Open Access Journals (Sweden)

    Mureşan Ioana

    2010-07-01

    Full Text Available This article is a theoretical article regarding Six Sigma. Six Sigma has been interpreted over time within quality theory as a metric, methodology or a management system. We explain Six Sigma using a logistics context: Delivery-On-Time (DOT rate problem. It is a theoretical context useful both for academic users and practitioners. At the beginning of the paper the DOT problem is generally described, while Sigma is presented according to statisticians view in the second part of the paper. Six Sigma is then presented as a metric for process’ capability. The fourth part of this article contains details regarding Six Sigma usage as a methodology for improvement, while the fifth part of this article refers to Six Sigma as a management system which can be used at firms’ level. The last chapter is dedicated to conclusions regarding the possible use of Six Sigma in Romania.

  3. "Depletion": A Game with Natural Rules for Teaching Reaction Rate Theory.

    Science.gov (United States)

    Olbris, Donald J.; Herzfeld, Judith

    2002-01-01

    Depletion is a game that reinforces central concepts of reaction rate theory through simulation. Presents the game with a set of follow-up questions suitable for either a quiz or discussion. Also describes student reaction to the game. (MM)

  4. Six Sigma in healthcare delivery.

    Science.gov (United States)

    Liberatore, Matthew J

    2013-01-01

    The purpose of this paper is to conduct a comprehensive review and assessment of the extant Six Sigma healthcare literature, focusing on: application, process changes initiated and outcomes, including improvements in process metrics, cost and revenue. Data were obtained from an extensive literature search. Healthcare Six Sigma applications were categorized by functional area and department, key process metric, cost savings and revenue generation (if any) and other key implementation characteristics. Several inpatient care areas have seen most applications, including admission, discharge, medication administration, operating room (OR), cardiac and intensive care. About 42.1 percent of the applications have error rate as their driving metric, with the remainder focusing on process time (38 percent) and productivity (18.9 percent). While 67 percent had initial improvement in the key process metric, only 10 percent reported sustained improvement. Only 28 percent reported cost savings and 8 percent offered revenue enhancement. These results do not favorably assess Six Sigma's overall effectiveness and the value it offers healthcare. Results are based on reported applications. Future research can include directly surveying healthcare organizations to provide additional data for assessment. Future application should emphasize obtaining improvements that lead to significant and sustainable value. Healthcare staff can use the results to target promising areas. This article comprehensively assesses Six Sigma healthcare applications and impact.

  5. Generalized Poisson sigma models

    CERN Document Server

    Batalin, I; Batalin, Igor; Marnelius, Robert

    2001-01-01

    A general master action in terms of superfields is given which generates generalized Poisson sigma models by means of a natural ghost number prescription. The simplest representation is the sigma model considered by Cattaneo and Felder. For Dirac brackets considerably more general models are generated.

  6. Six Sigma in Education

    Science.gov (United States)

    LeMahieu, Paul G.; Nordstrum, Lee E.; Cudney, Elizabeth A.

    2017-01-01

    Purpose: This paper is one of seven in this volume that aims to elaborate different approaches to quality improvement in education. It delineates a methodology called Six Sigma. Design/methodology/approach: The paper presents the origins, theoretical foundations, core principles and a case study demonstrating an application of Six Sigma in a…

  7. Six Sigma in Education

    Science.gov (United States)

    LeMahieu, Paul G.; Nordstrum, Lee E.; Cudney, Elizabeth A.

    2017-01-01

    Purpose: This paper is one of seven in this volume that aims to elaborate different approaches to quality improvement in education. It delineates a methodology called Six Sigma. Design/methodology/approach: The paper presents the origins, theoretical foundations, core principles and a case study demonstrating an application of Six Sigma in a…

  8. Quick and Easy Rate Equations for Multistep Reactions

    Science.gov (United States)

    Savage, Phillip E.

    2008-01-01

    Students rarely see closed-form analytical rate equations derived from underlying chemical mechanisms that contain more than a few steps unless restrictive simplifying assumptions (e.g., existence of a rate-determining step) are made. Yet, work published decades ago allows closed-form analytical rate equations to be written quickly and easily for…

  9. Classical reaction probabilities, cross sections and rate constants for the O( 1D) + H2 → OH + H reaction

    Science.gov (United States)

    Alexander, A. J.; Aoiz, F. J.; Bañares, L.; Brouard, M.; Herrero, V. J.; Simons, J. P.

    1997-10-01

    Reaction probabilitiers total reaction cross sections as a function of collision energy, and rate constants have been calculated using the quasi-classical trajectory (QCT) method for the O( 1D) + H 2 reaction on several ab initio potential energy surfaces (PES), including the recent one by Ho, Hollebeck, Rabitz, Harding and Schatz. Detailed QCT results on the Schinke and Lester PES are compared with recent time-dependent wavepacket calculations on the same PES, showing good agreement. The QCT thermal rate constants calculated on the PES of Ho et al. are in better accord with the experimental determinations than those calculated on the Schinke-Lester PES.

  10. Rate constants of reactions of {kappa}-carrageenan with hydrated electron and hydroxyl radical

    Energy Technology Data Exchange (ETDEWEB)

    Abad, L.V. [Nuclear Professional School, School of Engineering Laboratory, University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1188 (Japan); Philippine Nuclear Research Institute, Commonwealth Avenue, Diliman, Quezon City (Philippines)], E-mail: lvabad@pnri.dost.gov.ph; Saiki, S.; Kudo, H.; Muroya, Y.; Katsumura, Y. [Nuclear Professional School, School of Engineering Laboratory, University of Tokyo, 2-22 Shirakata-Shirane, Tokai, Naka, Ibaraki 319-1188 (Japan); Rosa, A.M. de la [Philippine Nuclear Research Institute, Commonwealth Avenue, Diliman, Quezon City (Philippines)

    2007-12-15

    The rate constants for the reactions of {kappa}-carrageenan with hydrated electron and hydroxyl radical was investigated by pulse radiolysis and laser photolysis. The kinetics of the reaction of hydrated electron indicates no seeming reaction with {kappa}-carrageenan. On the other hand, hydroxyl radical reacts very rapidly with {kappa}-carrageenan at a rate constant of approximately 1.2 x 10{sup 9} M{sup -1} s{sup -1}. This rate constant varies with pH.

  11. for the inference of Furan combustion reaction rate

    KAUST Repository

    Long, Quan

    2016-01-06

    We carry out the design of experiments for the identification of the reaction parameters in Furan combustion. The lacks of information on the true value of the control parameters, specifically, the initial temperature and the initial TBHP concentration, are considered in the design procedure by errors-invariables models. We use two types of observables. The first is a scaler observable, i.e., half decay time of the [TBHP]. The second is the time history of the concentration.

  12. Collective plasma corrections to thermonuclear reactions rates in dense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Tsytovich, V.N. [General Physics Institute, Moscow (Russian Federation)

    2002-01-01

    General kinetic equations for nuclear reaction in dense plasmas are obtained. They take into account the first order collective plasma effects. Together with previously known corrections proportional to Z{sub i}Z{sub j}, the product of the charges Z{sub i} and Z{sub j} of two interacting nuclei, it is shown that there exist corrections proportional to the squares Z{sub i}{sup 2} and Z{sub j}{sup 2} of the charges. It is shown that the Salpeter's [1] correction due to the plasma screening of the interaction potential is at least r/d smaller (r is the nuclei size and d is Debye screening length) than previously thought and is zero in the approximation when the terms of the order r/d are neglected. But the correlation effects in the first approximation in the parameter 1/N{sub d} (where N{sub d} is the number of particle in the Debye sphere) give corrections which often coincide with the first order Salpeter's corrections (found by expansion in another small parameter, the ratio of thermal energy to Gamov's energy). The correlation corrections are {proportional_to} Z{sub i}Z{sub j}, have a different physical meaning than the corrections [1], can have a different sign and are present for reactions where the Salpeter's corrections are zero. Previously in astrophysical applications it was widely used the interpolation formulas between weak and strong Salpeter's screening corrections. Since the correlation correction take place the previously known Salpeter's corrections and the strong correlation corrections is difficult to describe analytically, the interpolation formulas between the weak and strong correlations cannot be yet found. A new type of corrections are found here which are proportional to the square of the charges. They are due to collective change in electrostatic self-energy of the plasma system during the nuclear reactions. The latter corrections are found by taking into account the changes of plasma particle fluctuations by

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

    Science.gov (United States)

    Zheng, Jingjing; Truhlar, Donald G

    2012-01-01

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

  14. Evidence for a narrow resonance at 1530 MeV/c2 in the K0 p - system of the reaction pp --> Sigma+ K0 p from the COSY-TOF experiment

    CERN Document Server

    Abdel-Bary, M; Brinkmann, K T; Clement, H; Doroshkevich, E A; Drochner, M; Dshemuchadze, S V; Erhardt, A; Eyrich, W; Filges, D; Filippi, A; Freiesleben, H; Fritsch, M; Georgi, J; Gillman, A R; Hesselbarth, D; Jaekel, R; Jakob, B; Karsch, L; Kilian, K; Koch, H; Kress, J; Kuhlmann, E; Marcello, S; Marwinski, S; Meier, R; Michel, P; Möller, K; Moertel, H; Morsch, H P; Paul, N; Pinna, L; Pizzolotto, C; Richter, M; Roderburg, E; Schoenmeier, P; Schroeder, W; Schulte-Wissermann, M; Sefzick, T; Stinzing, F; Sun, G Y; Teufel, A; Ucar, A; Wagner, G J; Wagnerc, M; Wilms, A; Wintz, P; Wirth, S; Wüstner, P; Wirth, St.

    2004-01-01

    The hadronic reaction pp --> Sigma+ K0 p was measured exclusively at a beam momentum of 2.95 GeV/c using the TOF detector at the COSY storage ring. A narrow peak was observed in the invariant mass spectrum of the K0 p subsystem at 1530 +- 5 MeV/c2 with a significance of 4 - 6 standard deviations, depending on background assumptions. The upper limit of 18 +- 4 MeV/c2 (FWHM) for its width is given by the experimental resolution. The corresponding total cross section is estimated to be about 0.4 +- 0.1(stat) +- 0.1(syst) microbarn. Since a resonance in this subsystem must have strangeness S = + 1 we claim it to be the Theta+ state for which very recently evidence was found in various experiments.

  15. Vibrational population distributions of the product of the chemiluminescent charge transfer reaction: O + (2D)+HCl --> O+HCl + (A 2Sigma + )

    Science.gov (United States)

    Shiraishi, Yasushi; Kusunoki, Isao

    1987-12-01

    The chemiluminescent charge transfer reaction of O+ (2 D)ions with HCl has been studied in the energy range of 7 to 100 eVc.m. . The vibrational population distributions of the HCl+(A 2 Σ+,v') product have been analyzed from the emission spectra of the A→X transition. At low collision energy the distribution has a peak at v'=3. The partial reaction cross section σ(3) for this level increases with decreasing collision energy. The features of the reaction are very similar to the F+ +CO→ F+CO+ (A) reaction reported previously. The mechanism has been discussed on the basis of curve crossing between the initial and final states along the HCl vibrational coordinate in the asymptotic region of the [O-HCl]+ system. The projectile ions C+ and N+ have also been tested for the charge transfer reaction of HCl(X)→HCl+(A).

  16. Interlaboratory reaction rate program. 12th progress report, November 1976-October 1979

    Energy Technology Data Exchange (ETDEWEB)

    Lippincott, E.P.; McElroy, W.N.; Preston, C.C. (comps.)

    1980-09-01

    The Interlaboratory Reaction Rate UILRR) program is establishing the capability to accurately measure neutron-induced reactions and reaction rates for reactor fuels and materials development programs. The goal for the principal fission reactions, /sup 235/U, /sup 238/U and /sup 239/Pu, is an accuracy to within +- 5% at the 95% confidence level. Accurate measurement of other fission and nonfission reactions is also required, but to a lesser accuracy, between +- 5% and 10% at the 95% confidence level. A secondary program objective is improvement in knowledge of the nuclear parameters involved in the standarization of fuels and materials dosimetry measurements of neutron flux, spectra, fluence and burnup.

  17. Evolutionary implications of the new triple-alpha nuclear reaction rate for low mass stars

    CERN Document Server

    Dotter, Aaron

    2009-01-01

    Context: Ogata et al. (2009; hereafter OKK) presented a theoretical determination of the triple-alpha nuclear reaction rate. Their rate differs from the NACRE rate by many orders of magnitude at temperatures relevant for low mass stars. Aims: We explore the evolutionary implications of adopting the OKK triple-alpha reaction rate in low mass stars and compare the results with those obtained using the NACRE rate. Methods: The triple-alpha reaction rates are compared by following the evolution of stellar models at 1 and 1.5 Msol with Z=0.0002 and Z=0.02. Results: Results show that the OKK rate has severe consequences for the late stages of stellar evolution in low mass stars. Most notable is the shortening--or disappearance--of the red giant phase. Conclusions: The OKK triple-alpha reaction rate is incompatible with observations of extended red giant branches and He burning stars in old stellar systems.

  18. Supersymmetric sigma models

    Energy Technology Data Exchange (ETDEWEB)

    Bagger, J.A.

    1984-09-01

    We begin to construct the most general supersymmetric Lagrangians in one, two and four dimensions. We find that the matter couplings have a natural interpretation in the language of the nonlinear sigma model.

  19. Sigma photoproduction in the resonance region

    CERN Document Server

    Janssen, S; Debruyne, D; Van Cauteren, T

    2002-01-01

    A study of p(gamma,K)Sigma processes in an isobar model at tree level is reported. By comparing model calculations to the published SAPHIR data, we explore the possible role of different isospin I=1/2 (N*) and I=3/2 (Delta*) resonances in the reaction dynamics. In our analysis, the inclusion of the ``missing'' D_{13}(1895) resonance does only slightly improve the global description of the Sigma photoproduction data. More convincing signals for the presence of such a ``missing'' resonance emerged in the analysis of the isospin related p(gamma,K+)Lambda reaction. Various implementations of the nonresonant part of the Sigma photoproduction amplitude are presented. The sensitivity of the computed observables and extracted resonance parameters to the uncertainties inherent to the treatment of the nonresonant (background) diagrams are discussed.

  20. Theoretical reaction rates of the $^{12}$C($\\alpha$,$\\gamma$)$^{16}$O reaction from the potential model

    CERN Document Server

    Katsuma, M

    2015-01-01

    The radiative capture cross sections of $^{12}$C($\\alpha$,$\\gamma$)$^{16}$O and derived reaction rates are calculated from the direct capture potential model. The resulting $S$-factor at low energies is found to be dominated by $E$2 transition to the $^{16}$O ground state. The $E$1 and $E$2 $S$-factors at $E_{c.m.}=0.3$ MeV are $S_{E1}\\approx3$ keV~b and $S_{E2}=150^{+41}_{-17}$ keV~b, respectively. The sum of the cascade transition through the excited state of $^{16}$O is $S_{\\rm casc}= 18\\pm4.5$ keV~b. The derived reaction rates at low temperatures seem to be concordant with those from the previous evaluation. For astrophysical applications, our reaction rates below $T_9=3$ are provided in an analytic expression.

  1. Critical evaluation and rate constants of chemoselective ligation reactions for stoichiometric conjugations in water.

    Science.gov (United States)

    Saito, Fumito; Noda, Hidetoshi; Bode, Jeffrey W

    2015-04-17

    Chemoselective ligation reactions have contributed immensely to the development of organic synthesis and chemical biology. However, the ligation of stoichiometric amounts of large molecules for applications such as protein-protein conjugates is still challenging. Conjugation reactions need to be fast enough to proceed under dilute conditions and chemoselective in the presence of unprotected functional groups; the starting materials and products must be stable under the reaction conditions. To compare known ligation reactions for their suitability under these conditions, we determined the second-order rate constants of ligation reactions using peptide substrates with unprotected functional groups. The reaction conditions, the chemoselectivity of the reactions, and the stability of the starting materials and products were carefully evaluated. In some cases, the stability could be improved by modifying the substrate structure. These data obtained under the ligation conditions provide a useful guide to choose an appropriate ligation reaction for synthesis of large molecules by covalent ligation reactions of unprotected substrates in water.

  2. Reaction rates between water and some modified rapidly-reacting Karl Fischer reagents.

    Science.gov (United States)

    Cedergren, A

    1978-04-01

    Rate constants were determined for the reaction between water and various modified Karl Fischer reagents containing formamide, dimethylformamide or N-methylformamide. It was shown that the reaction rate can be increased by a factor of 100 by using a reagent containing 40% v/v formamide in pyridine compared to that obtained by use of the conventional methanolic reagent.

  3. Rate of reaction of dimethylmercury with oxygen atoms in the gas phase

    DEFF Research Database (Denmark)

    Egsgaard, Helge

    1986-01-01

    The rate constant for the reaction of atomic oxygen (O(3P)) with dimethylmercury has been measured at room temperature at a pressure of about 1 Torr using a fast flow system with electron paramagnetic resonance and mass spectrometric detection. Some reaction products were identified. The rate...

  4. Controlling the emotional heart: heart rate biofeedback improves cardiac control during emotional reactions.

    Science.gov (United States)

    Peira, Nathalie; Fredrikson, Mats; Pourtois, Gilles

    2014-03-01

    When regulating negative emotional reactions, one goal is to reduce physiological reactions. However, not all regulation strategies succeed in doing that. We tested whether heart rate biofeedback helped participants reduce physiological reactions in response to negative and neutral pictures. When viewing neutral pictures, participants could regulate their heart rate whether the heart rate feedback was real or not. In contrast, when viewing negative pictures, participants could regulate heart rate only when feedback was real. Ratings of task success paralleled heart rate. Participants' general level of anxiety, emotion awareness, or cognitive emotion regulation strategies did not influence the results. Our findings show that accurate online heart rate biofeedback provides an efficient way to down-regulate autonomic physiological reactions when encountering negative stimuli.

  5. BRUSLIB and NETGEN: the Brussels nuclear reaction rate library and nuclear network generator for astrophysics

    CERN Document Server

    Aikawa, M; Goriely, S; Jorissen, A; Takahashi, K

    2005-01-01

    Nuclear reaction rates are quantities of fundamental importance in astrophysics. Substantial efforts have been devoted in the last decades to measure or calculate them. The present paper presents for the first time a detailed description of the Brussels nuclear reaction rate library BRUSLIB and of the nuclear network generator NETGEN so as to make these nuclear data packages easily accessible to astrophysicists for a large variety of applications. BRUSLIB is made of two parts. The first one contains the 1999 NACRE compilation based on experimental data for 86 reactions with (mainly) stable targets up to Si. The second part of BRUSLIB concerns nuclear reaction rate predictions calculated within a statistical Hauser-Feshbach approximation, which limits the reliability of the rates to reactions producing compound nuclei with a high enough level density. These calculations make use of global and coherent microscopic nuclear models for the quantities entering the rate calculations. The use of such models is utterl...

  6. Sigma factors in Pseudomonas aeruginosa.

    Science.gov (United States)

    Potvin, Eric; Sanschagrin, François; Levesque, Roger C

    2008-01-01

    In Pseudomonas aeruginosa, as in most bacterial species, the expression of genes is tightly controlled by a repertoire of transcriptional regulators, particularly the so-called sigma (sigma) factors. The basic understanding of these proteins in bacteria has initially been described in Escherichia coli where seven sigma factors are involved in core RNA polymerase interactions and promoter recognition. Now, 7 years have passed since the completion of the first genome sequence of the opportunistic pathogen P. aeruginosa. Information from the genome of P. aeruginosa PAO1 identified 550 transcriptional regulators and 24 putative sigma factors. Of the 24 sigma, 19 were of extracytoplasmic function (ECF). Here, basic knowledge of sigma and ECF proteins was reviewed with particular emphasis on their role in P. aeruginosa global gene regulation. Summarized data are obtained from in silico analysis of P. aeruginosasigma and ECF including rpoD (sigma(70)), RpoH (sigma(32)), RpoF (FliA or sigma(28)), RpoS (sigma(S) or sigma(38)), RpoN (NtrA, sigma(54) or sigma(N)), ECF including AlgU (RpoE or sigma(22)), PvdS, SigX and a collection of uncharacterized sigma ECF, some of which are implicated in iron transport. Coupled to systems biology, identification and functional genomics analysis of P. aeruginosasigma and ECF are expected to provide new means to prevent infection, new targets for antimicrobial therapy, as well as new insights into the infection process.

  7. Accessing reaction rate constants in on-column reaction chromatography: an extended unified equation for reaction educts and products with different response factors.

    Science.gov (United States)

    Trapp, Oliver; Bremer, Sabrina; Weber, Sven K

    2009-11-01

    An extension of the unified equation of chromatography to directly access reaction rate constants k(1) of first-order reaction in on-column chromatography is presented. This extended equation reflects different response factors in the detection of the reaction educt and product which arise from structural changes by elimination or addition, e.g., under pseudo-first-order reaction conditions. The reaction rate constants k(1) and Gibbs activation energies DeltaG(double dagger) of first-order reactions taking place in a chromatographic system can be directly calculated from the chromatographic parameters, i.e., retention times of the educt E and product P (t(R)(A) and t(R)(B)), peak widths at half height (w(A) and w(B)), the relative plateau height (h(p)) of the conversion profile, and the individual response factors f(A) and f(B). The evaluation of on-column reaction gas chromatographic experiments is exemplified by the evaluation of elution profiles obtained by ring-closing metathesis reaction of N,N-diallytrifluoroacetamide in presence of Grubbs second-generation catalyst, dissolved in polydimethylsiloxane (GE SE 30).

  8. Simulation of biochemical reactions with time-dependent rates by the rejection-based algorithm

    Energy Technology Data Exchange (ETDEWEB)

    Thanh, Vo Hong, E-mail: vo@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Priami, Corrado, E-mail: priami@cosbi.eu [The Microsoft Research - University of Trento Centre for Computational and Systems Biology, Piazza Manifattura 1, Rovereto 38068 (Italy); Department of Mathematics, University of Trento, Trento (Italy)

    2015-08-07

    We address the problem of simulating biochemical reaction networks with time-dependent rates and propose a new algorithm based on our rejection-based stochastic simulation algorithm (RSSA) [Thanh et al., J. Chem. Phys. 141(13), 134116 (2014)]. The computation for selecting next reaction firings by our time-dependent RSSA (tRSSA) is computationally efficient. Furthermore, the generated trajectory is exact by exploiting the rejection-based mechanism. We benchmark tRSSA on different biological systems with varying forms of reaction rates to demonstrate its applicability and efficiency. We reveal that for nontrivial cases, the selection of reaction firings in existing algorithms introduces approximations because the integration of reaction rates is very computationally demanding and simplifying assumptions are introduced. The selection of the next reaction firing by our approach is easier while preserving the exactness.

  9. A simple expression for the apparent reaction rate of large wood char gasification with steam.

    Science.gov (United States)

    Umeki, Kentaro; Roh, Seon-Ah; Min, Tai-Jin; Namioka, Tomoaki; Yoshikawa, Kunio

    2010-06-01

    A simple expression for the apparent reaction rate of large wood char gasification with steam is proposed. Large char samples were gasified under steam atmosphere using a thermo-balance reactor. The apparent reaction rate was expressed as the product of the intrinsic rate and the effective factor. The effective factor was modified to include the effect of change in char diameter and intrinsic reaction rate during the reaction. Assuming uniform conversion ratio throughout a particle, the simplified reaction scheme was divided into three stages. In the initial stage, the local conversion ratio increases without particle shrinkage. In the middle stage, the particle shrinks following the shrinking core model without change in the local conversion ratio. In the final stage, the local conversion ratio increases without particle shrinkage. The validity of the modified effective value was confirmed by comparison with experimental results.

  10. Rate constants for the reaction of CF3O radicals with hydrocarbons at 298 K

    DEFF Research Database (Denmark)

    Kelly, C.; Treacy, J.; Sidebottom, H.W.;

    1993-01-01

    Rate constant ratios of the reactions of CF3O radicals with a number of hydrocarbons have been determined at 298 +/- 2 K and atmospheric pressure using a relative rate method. Using a previously determined value k(CF30 + C2H6) = 1.2 x 10(-12) cm3 molecule-1 s-1 these rate constant ratios provide......-1. The importance of the reactions of CF3O radicals with hydrocarbons under atmospheric conditions is discussed....

  11. VizieR Online Data Catalog: Brussels nuclear reaction rate library (Aikawa+, 2005)

    Science.gov (United States)

    Aikawa, M.; Arnould, M.; Goriely, S.; Jorissen, A.; Takahashi, K.

    2005-07-01

    The present data is part of the Brussels nuclear reaction rate library (BRUSLIB) for astrophysics applications and concerns nuclear reaction rate predictions calculated within the statistical Hauser-Feshbach approximation and making use of global and coherent microscopic nuclear models for the quantities (nuclear masses, nuclear structure properties, nuclear level densities, gamma-ray strength functions, optical potentials) entering the rate calculations. (4 data files).

  12. K^0 pi^0 Sigma^+ and K^*0 Sigma^+ photoproduction off the proton

    CERN Document Server

    Nanova, M; Bantes, B; Bartholomy, O; Bayadilov, D; Beck, R; Beloglasov, Yu A; Castelijns, R; Credé, V; Dutz, H; Ehmanns, A; Elsner, D; Essig, K; Ewald, R; Fabry, I; Fornet-Ponse, K; Fuchs, M; Funke, C; Gothe, R; Gregor, R; Gridnev, A B; Gutz, E; Hoffmeister, P; Horn, I; Jaegle, I; Junkersfeld, J; Kalinowsky, H; Kammer, S; Kleber, V; Klein, Frank; Klein, Friedrich; Klempt, E; Konrad, M; Kotulla, M; Krusche, B; Lang, M; Langheinrich, J; Löhner, H; Lopatin, I V; Lotz, J; Lugert, S; Menze, D; Messchendorp, J G; Mertens, T; Metag, V; Morales, C; Novinski, D V; Novotny, R; Ostrick, M; Pant, L M; Van Pee, H; Pfeiffer, M; Radkov, A; Roy, A; Schadmand, S; Schmidt, C; Schmieden, H; Schoch, B; Shende, S V; Sokhoyan, V; Sule, A; Sumachev, V V; Szczepanek, T; Thoma, U; Trnka, D; Varma, R; Walther, D; Weinheimer, C; Wendel, C

    2008-01-01

    The exclusive reactions $\\gamma p \\to K^{*0} \\Sigma^+(1189)$ and $\\gamma p \\to K^{0} \\pi^{0}\\Sigma^+(1189)$, leading to the p 4$\\pi^{0}$ final state, have been measured with a tagged photon beam for incident energies from threshold up to 2.5 GeV. The experiment has been performed at the tagged photon facility of the ELSA accelerator (Bonn). The Crystal Barrel and TAPS detectors were combined to a photon detector system of almost 4$\\pi$ geometrical acceptance. Differential and total cross sections are reported. At energies close to the threshold, a flat angular distribution has been observed for the reaction $\\gamma p\\to K^{0} \\pi^{0}\\Sigma^+$ suggesting dominant s-channel production. $\\Sigma^*(1385)$ and higher lying hyperon states have been observed. An enhancement in the forward direction in the angular distributions of the reaction $\\gamma p \\to K^{*0}\\Sigma^+$ indicates a $t$-channel exchange contribution to the reaction mechanism. The experimental data are in reasonable agreement with recent theoretical ...

  13. Sigma models on supercosets

    Energy Technology Data Exchange (ETDEWEB)

    Mitev, Vladimir

    2010-08-15

    The purpose of this thesis is to deepen our understanding of the fundamental properties and defining features of non-linear sigma models on superspaces. We begin by presenting the major concepts that we have used in our investigation, namely Lie superalgebras and supergroups, non-linear sigma models and two dimensional conformal field theory. We then exhibit a method, called cohomological reduction, that makes use of the target space supersymmetry of non-linear sigma models to compute certain correlation functions. We then show how the target space supersymmetry of Ricci flat Lie supergroups simplifies the perturbation theory of suitable deformed Wess-Zumino-Witten models, making it possible to compute boundary conformal weights to all orders. This is then applied to the OSP (2S+2 vertical stroke 2S) Gross-Neveu Model, leading to a dual description in terms of the sigma model on the supersphere S{sup 2S+1} {sup vertical} {sup stroke} {sup 2S}. With this results in mind, we then turn to the similar, yet more intricate, theory of the non-linear sigma model on the complex projective superspaces CP{sup N-1} {sup vertical} {sup stroke} {sup N}. The cohomological reduction allows us to compute several important quantities non-perturbatively with the help of the system of symplectic fermions. Combining this with partial perturbative results for the whole theory, together with numerical computations, we propose a conjecture for the exact evolution of boundary conformal weights for symmetry preserving boundary conditions. (orig.)

  14. Characterization of shock-dependent reaction rates in an aluminum/perfluoropolyether pyrolant

    Science.gov (United States)

    Wilson, Dennis; Granier, John; Johnson, Richard; Littrell, Donald

    2017-01-01

    Energetic formulations of perfluoropolyether (PFPE) and aluminum are highly non-ideal. They release energy via a fast self-oxidized combustion wave rather than a true self-sustaining detonation. Unlike high explosives, the reactions are shock dependent and can be overdriven to control energy release rate. Reaction rate experiments show that the velocity can vary from 1.25 to 3 km/s. This paper examines the effect of the initial shock conditions upon the reaction rate of the explosive. The following conditions were varied in a series of reaction rate experiments: the high explosive booster mass and geometry; shock attenuation; confinement; and rate stick diameter and length. Several experiments designed to isolate and quantify these dependencies are described and summarized.

  15. $K^0$-$\\Sigma^+$ Photoproduction with SAPHIR

    CERN Document Server

    Bennhold, C

    1998-01-01

    Preliminary results of the analysis of the reaction p(gamma,K0)Sigma+ are presented. We show the first measurement of the differential cross section and much improved data for the total cross section than previous data. The data are compared with model predictions from different isobar and quark models that give a good description of p(gamma,K+)Lambda and p(gamma,K+)Sigma0 data in the same energy range. None of the models yield an adequate description of the data at all energies.

  16. Comparing transfusion reaction rates for various plasma types: a systematic review and meta-analysis/regression.

    Science.gov (United States)

    Saadah, Nicholas H; van Hout, Fabienne M A; Schipperus, Martin R; le Cessie, Saskia; Middelburg, Rutger A; Wiersum-Osselton, Johanna C; van der Bom, Johanna G

    2017-09-01

    We estimated rates for common plasma-associated transfusion reactions and compared reported rates for various plasma types. We performed a systematic review and meta-analysis of peer-reviewed articles that reported plasma transfusion reaction rates. Random-effects pooled rates were calculated and compared between plasma types. Meta-regression was used to compare various plasma types with regard to their reported plasma transfusion reaction rates. Forty-eight studies reported transfusion reaction rates for fresh-frozen plasma (FFP; mixed-sex and male-only), amotosalen INTERCEPT FFP, methylene blue-treated FFP, and solvent/detergent-treated pooled plasma. Random-effects pooled average rates for FFP were: allergic reactions, 92/10(5) units transfused (95% confidence interval [CI], 46-184/10(5) units transfused); febrile nonhemolytic transfusion reactions (FNHTRs), 12/10(5) units transfused (95% CI, 7-22/10(5) units transfused); transfusion-associated circulatory overload (TACO), 6/10(5) units transfused (95% CI, 1-30/10(5) units transfused); transfusion-related acute lung injury (TRALI), 1.8/10(5) units transfused (95% CI, 1.2-2.7/10(5) units transfused); and anaphylactic reactions, 0.8/10(5) units transfused (95% CI, 0-45.7/10(5) units transfused). Risk differences between plasma types were not significant for allergic reactions, TACO, or anaphylactic reactions. Methylene blue-treated FFP led to fewer FNHTRs than FFP (risk difference = -15.3 FNHTRs/10(5) units transfused; 95% CI, -24.7 to -7.1 reactions/10(5) units transfused); and male-only FFP led to fewer cases of TRALI than mixed-sex FFP (risk difference = -0.74 TRALI/10(5) units transfused; 95% CI, -2.42 to -0.42 injuries/10(5) units transfused). Meta-regression demonstrates that the rate of FNHTRs is lower for methylene blue-treated compared with FFP, and the rate of TRALI is lower for male-only than for mixed-sex FFP; whereas no significant differences are observed between plasma types for allergic

  17. Astrophysical Reaction Rates of the 8Li(p,γ)9Beg.s. Direct Capture Reaction

    Institute of Scientific and Technical Information of China (English)

    Su Jun; WANG You-Bao; LI Zhi-Hong; GUO Bing; LIU Wei-Ping; BAI Xi-Xiang; ZENG Sheng; LIAN Gang; YAN Sheng-Quan; WANG Bao-Xiang

    2006-01-01

    Based 0n the angular distribution of the 8Li(d,n)9Beg.s. reaction at Ec.m.=8.0 MeV and distorted wave Born approximation analysis,the single particle spectroscopic factor S1,3/2 for the ground state of 9Be=8Li(×)p is derived to be 0.64±0.21.In addition,we deduce the astrophysical S-factors and rates of the 8Li(p,γ)9Beg.s. direct capture reaction at energies of astrophysical interests.

  18. Astrophysical S-Factors and Reaction Rates of Threshold (p, n)-Reactions on 99-102Ru

    Science.gov (United States)

    Skakun, Ye.; Rauscher, T.

    2010-08-01

    Astrophysical S-factors of (p, n) reactions on 99Ru, 100Ru, 101Ru, and 102Ru were derived from the sum of experimental isomeric and ground states cross sections measured in the incident proton energy range of 5-9 MeV. They were compared with Hauser-Feshbach statistical model predictions of the NON-SMOKER code. Good agreement was found in the majority of cases. Reaction rates were derived up to 8.7 GK stellar temperature by combining experiment and theory.

  19. Combustion of Bimodal Nano/Micro Aluminum Suspension with New Reaction Rate Model

    Directory of Open Access Journals (Sweden)

    M. Bidabadi

    2008-01-01

    Full Text Available In this study a mathematical model for combustion of bimodal particle in lean flow was developed. The difference between structure of flame in this work and previous ones was that, in those flame was divided by five zones and reaction rate was considered to be constant in reaction zones and also zero in post flame zone. In reality it was obvious with respect to shape and size of different particles in dust, reaction didn't end suddenly. In the present research the heat loss term, which was assumed to be linearly proportional to temperature difference, was added to the energy conservation equation and reaction rate was considered proportional to available amount of fuel, leading to exponentially decreasing of reaction rate. The flame speed and temperature distribution were obtained by solving the energy equation in each zone and matching the temperature and heat flux at the interfacial boundaries. Calculated values of flame speed were in good agreement with experimental data.

  20. Reaction rate estimation of controlled-release antifouling paint binders: Rosin-based systems

    DEFF Research Database (Denmark)

    Meseguer Yebra, Diego; Kiil, Søren; Dam-Johansen, Kim

    2005-01-01

    at product optimisation and innovation (e.g. incorporation of natural active agents). This study seeks to attain scientifically founded knowledge of the reaction mechanisms and the rate of reaction with sea water of a Zn-carboxylate of a synthetic rosin compound. The kinetic expression attained can be used...... have shown that mathematical coating models based on a fundamental knowledge of the underlying mechanisms of A/F paints is a promising tool for accelerated product testing at different operational conditions of a sailing ship or a paint rotor. Such models can also be used for generation of ideas aiming...... rather than pointing at a certain diffusion control in the reaction rate experiments. The reverse reaction is found not to affect the hydrolysis rate within the pores, of antifouling paints significantly. It is concluded, from the reaction mechanism proposed, that the observed partial exchange of Zn2...

  1. Development of Theoretical Methods for Predicting Solvent Effects on Reaction Rates in Supercritical Water Oxidation Processes

    Science.gov (United States)

    2007-11-02

    Tucker, manuscript in preparation. “Examination of Nonequilibrium Solvent Effects on an SN2 Reaction in Supercritical Water,” R. Behera, B...DATES COVERED Final: 7/1/99 - 12/31/02 4. TITLE AND SUBTITLE Development of theoretical methods for predicting solvent effects on reactions ...computational methods for predicting how reaction rate constants will vary with thermodynamic condition in supercritical water (SCW). Towards this

  2. The Relation Between Damping and Reaction Rates of Fermions in Hot Gauge Theories

    CERN Document Server

    Ayala, A P; Weber, A; Ayala, Alejandro; Olivo, Juan Carlos D'; Weber, Axel

    1998-01-01

    We examine the relation between the damping rate of a chiral fermion mode propagating in a hot plasma and the rate at which the mode approaches equilibrium. We show that these two quantities, obtained from the imaginary part of the fermion self-energy, are equal provided the reaction rate is defined using the appropriate wave function of the mode in the medium.

  3. The Reaction Mechanism and Rate Constants in the Radiolysis of Fe2+-Cu2+ Solutions

    DEFF Research Database (Denmark)

    Bjergbakke, Erling; Sehested, Knud; Rasmussen, O. Lang

    1976-01-01

    Pulse radiolysis and gamma radiolysis have been used to study the reaction mechanism in the radiolysis of aqueous solutions of Fe2+ and Cu2+. A reaction scheme has been developed and confirmed by computation of the corresponding complete set of differential equations. The rate constants for some...

  4. Determining astrophysical three-body radiative capture reaction rates from inclusive Coulomb break-up measurements

    CERN Document Server

    Casal, J; Arias, J M; Gómez-Camacho, J

    2016-01-01

    A relationship between the Coulomb inclusive break-up probability and the radiative capture reaction rate for weakly-bound three-body systems is established. This direct link provides a robust procedure to estimate the reaction rate for nuclei of astrophysical interest by measuring inclusive break-up processes at different energies and angles. This might be an advantageous alternative to the determination of reaction rates from the measurement of $B(E1)$ distributions through exclusive Coulomb break-up experiments. In addition, it provides a reference to assess the validity of different theoretical approaches that have been used to calculate reaction rates. The procedure is applied to $^{11}$Li ($^{9}$Li+n+n) and $^6$He ($^{4}$He+n+n) three-body systems for which some data exist.

  5. Determining astrophysical three-body radiative capture reaction rates from inclusive Coulomb break-up measurements

    Science.gov (United States)

    Casal, J.; Rodríguez-Gallardo, M.; Arias, J. M.; Gómez-Camacho, J.

    2016-04-01

    A relationship between the Coulomb inclusive break-up probability and the radiative capture reaction rate for weakly bound three-body systems is established. This direct link provides a robust procedure to estimate the reaction rate for nuclei of astrophysical interest by measuring inclusive break-up processes at different energies and angles. This might be an advantageous alternative to the determination of reaction rates from the measurement of B (E 1 ) distributions through exclusive Coulomb break-up experiments. In addition, it provides a reference to assess the validity of different theoretical approaches that have been used to calculate reaction rates. The procedure is applied to 11Li (9Li+n +n ) and 6He (4He+n +n ) three-body systems for which some data exist.

  6. Reaction mechanisms and rate constants of waste degradation in landfill bioreactor systems with enzymatic-enhancement.

    Science.gov (United States)

    Jayasinghe, P A; Hettiaratchi, J P A; Mehrotra, A K; Kumar, S

    2014-06-01

    Augmenting leachate before recirculation with peroxidase enzymes is a novel method to increase the available carbon, and therefore the food supply to microorganisms at the declining phase of the anaerobic landfill bioreactor operation. In order to optimize the enzyme-catalyzed leachate recirculation process, it is necessary to identify the reaction mechanisms and determine rate constants. This paper presents a kinetic model developed to ascertain the reaction mechanisms and determine the rate constants for enzyme catalyzed anaerobic waste degradation. The maximum rate of reaction (Vmax) for MnP enzyme-catalyzed reactors was 0.076 g(TOC)/g(DS).day. The catalytic turnover number (k(cat)) of the MnP enzyme-catalyzed was 506.7 per day while the rate constant (k) of the un-catalyzed reaction was 0.012 per day.

  7. Neutron Scattering in Hydrogenous Moderators, Studied by Time Dependent Reaction Rate Method

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, L.G.; Moeller, E.; Purohit, S.N.

    1966-03-15

    The moderation and absorption of a neutron burst in water, poisoned with the non-1/v absorbers cadmium and gadolinium, has been followed on the time scale by multigroup calculations, using scattering kernels for the proton gas and the Nelkin model. The time dependent reaction rate curves for each absorber display clear differences for the two models, and the separation between the curves does not depend much on the absorber concentration. An experimental method for the measurement of infinite medium reaction rate curves in a limited geometry has been investigated. This method makes the measurement of the time dependent reaction rate generally useful for thermalization studies in a small geometry of a liquid hydrogenous moderator, provided that the experiment is coupled to programs for the calculation of scattering kernels and time dependent neutron spectra. Good agreement has been found between the reaction rate curve, measured with cadmium in water, and a calculated curve, where the Haywood kernel has been used.

  8. Shell and explosive hydrogen burning. Nuclear reaction rates for hydrogen burning in RGB, AGB and Novae

    Energy Technology Data Exchange (ETDEWEB)

    Boeltzig, A. [Gran Sasso Science Institute, L' Aquila (Italy); Bruno, C.G.; Davinson, T. [University of Edinburgh, SUPA, School of Physics and Astronomy, Edinburgh (United Kingdom); Cavanna, F.; Ferraro, F. [Dipartimento di Fisica, Universita di Genova (Italy); INFN, Genova (Italy); Cristallo, S. [Osservatorio Astronomico di Collurania, INAF, Teramo (Italy); INFN, Napoli (Italy); Depalo, R. [Dipartimento di Fisica e Astronomia, Universita di Padova, Padova (Italy); INFN, Padova (Italy); DeBoer, R.J.; Wiescher, M. [University of Notre Dame, Institute for Structure and Nuclear Astrophysics, Joint Institute for Nuclear Astrophysics, Notre Dame, Indiana (United States); Di Leva, A.; Imbriani, G. [Dipartimento di Fisica, Universita di Napoli Federico II, Napoli (Italy); INFN, Napoli (Italy); Marigo, P. [Dipartimento di Fisica e Astronomia, Universita di Padova, Padova (Italy); Terrasi, F. [Dipartimento di Matematica e Fisica Seconda Universita di Napoli, Caserta (Italy); INFN, Napoli (Italy)

    2016-04-15

    The nucleosynthesis of light elements, from helium up to silicon, mainly occurs in Red Giant and Asymptotic Giant Branch stars and Novae. The relative abundances of the synthesized nuclides critically depend on the rates of the nuclear processes involved, often through non-trivial reaction chains, combined with complex mixing mechanisms. In this paper, we summarize the contributions made by LUNA experiments in furthering our understanding of nuclear reaction rates necessary for modeling nucleosynthesis in AGB stars and Novae explosions. (orig.)

  9. The Effect of the Triple-α Reaction Rate on Stellar Evolution at Low-Metallicity

    Science.gov (United States)

    Suda, Takuma; Hirschi, Raphael; Fujimoto, Masayuki Y.

    2010-06-01

    We investigate the effect of the triple-α reaction rates on the evolution of low-mass stars and massive stars. The former is compared with the observations of metal-poor stars known to date. For the latter, we discuss the impact of recent calculation of triple-α reaction rate by Ogata et al. (2009, PTP, 122, 1055) on the evolution until carbon burning.

  10. Six Sigma and Implementations of Six Sigma in Finance Sector

    OpenAIRE

    Gokhan Senol; Adem Anbar

    2010-01-01

    Quality is a one of the critical factors for achieving competitive advantage. Six sigma approach is a business strategy which usage has increased gradually in last years for quality improvement initiative. Although six sigma established by a manufacturing firm and it has been successfully implemented in many manufacturing firms, service firms have began to use six sigma for reducing cost, enhanced quality of service, increasing customer satisfaction and profitability. In this paper, six sigma...

  11. Supersymmetric Sigma Model Geometry

    OpenAIRE

    Ulf Lindström

    2012-01-01

    This is a review of how sigma models formulated in Superspace have become important tools for understanding geometry. Topics included are: The (hyper)k\\"ahler reduction; projective superspace; the generalized Legendre construction; generalized K\\"ahler geometry and constructions of hyperk\\"ahler metrics on Hermitean symmetric spaces.

  12. DESIGN FOR SIX SIGMA

    OpenAIRE

    Liem Ferryanto

    2007-01-01

    This article provides a step by step process of executing analytical or computer based Design for Six Sigma using a Sliding Door project as an example. It comprises of identification of Voice Of the Customer (VOC), transformation of VOC to what it is called Critical To Quality characteristics (CTQs), modeling of system transfers function, optimal and robust solutions, and tolerance design approach

  13. Supersymmetric Sigma Model geometry

    CERN Document Server

    Lindström, Ulf

    2012-01-01

    This is a review of how sigma models formulated in Superspace have become important tools for understanding geometry. Topics included are: The (hyper)k\\"ahler reduction; projective superspace; the generalized Legendre construction; generalized K\\"ahler geometry and constructions of hyperk\\"ahler metrics on Hermitean symmetric spaces.

  14. Sodium Enrichment in Yellow Supergiants: a Perspective from the Uncertainties of Reaction Rates

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Sodium overabundance in yellow supergiants has stumped people for more than 20 years. The purpose of this paper is to explore this problem from the perspective of nuclear physics. We investigate carefully the CNO and NeNa cycles that are responsible for sodium production. We investigate some key reactions in the appropriate network. We show whether and how the sodium output can be affected by the rate uncertainties in these reactions. In this way, we evaluate if a reaction is important enough to deserve a better determination of its rate in terrestrial laboratories.

  15. STARLIB: A Next-Generation Reaction-Rate Library for Nuclear Astrophysics

    CERN Document Server

    Sallaska, A L; Champagne, A E; Goriely, S; Starrfield, S; Timmes, F X

    2013-01-01

    STARLIB is a next-generation, all-purpose nuclear reaction-rate library. For the first time, this library provides the rate probability density at all temperature grid points for convenient implementation in models of stellar phenomena. The recommended rate and its associated uncertainties are also included. Currently, uncertainties are absent from all other rate libraries, and, although estimates have been attempted in previous evaluations and compilations, these are generally not based on rigorous statistical definitions. A common standard for deriving uncertainties is clearly warranted. STARLIB represents a first step in addressing this deficiency by providing a tabular, up-to-date database that supplies not only the rate and its uncertainty but also its distribution. Because a majority of rates are lognormally distributed, this allows the construction of rate probability densities from the columns of STARLIB. This structure is based on a recently suggested Monte Carlo method to calculate reaction rates, w...

  16. New determination of 12C(α,γ)16O reaction rate

    Science.gov (United States)

    Oulebsir, N.

    2015-12-01

    The reaction 12C(α,γ)16O was investigated through the direct α-transfer reaction (7Li,t) at 28 and 34 MeV incident energies. We determined the reduced α-widths of the sub-threshold 2+ and 1- states of 16O from the DWBA analysis of the transfer reaction 12C(7Li,t)16O performed at two incident energies. The obtained result for the 2+ and 1- sub-threshold resonances as introduced in the R-matrix fitting of radiative capture and elastic-scattering data to determine the E2 and E1 S-factor from 0.01MeV to 4.2MeV in the center-of-mass energy. After determining the astrophysic factor of 12C(α,γ)16O S(E) with Pierre Descouvement code, I determined numerically the new reaction rate of this reaction at a different stellar temperature (0.06 Gk-2 GK). The 12C(α,γ)16O reaction rate at T9 = 0.2 is [7.21-2.25+2.15] × 10-15 cm3 s-1 mol-1. Some comparisons and discussions about our new 12C(α,γ)16O reaction rate are presented. The agreements of the reaction rate below T9 = 2 between our results and with those proposed by NACRE indicate that our results are reliable, and they could be included in the astrophysical reaction rate network.

  17. The Effects of Thermonuclear Reaction Rate Variations on Nova Nucleosynthesis A Sensitivity Study

    CERN Document Server

    Iliadis, C; José, J; Starrfield, S; Tupper, P; Iliadis, Christian; Champagne, Art; Jose, Jordi; Starrfield, Sumner; Tupper, Paul

    2002-01-01

    We investigate the effects of thermonuclear reaction rate uncertainties on nova nucleosynthesis. One-zone nucleosynthesis calculations have been performed by adopting temperature-density-time profiles of the hottest hydrogen-burning zone (i.e., the region in which most of the nucleosynthesis takes place). We obtain our profiles from 7 different, recently published, hydrodynamic nova simulations covering peak temperatures in the range from Tpeak=0.145-0.418 GK. For each of these profiles, we individually varied the rates of 175 reactions within their associated errors and analyzed the resulting abundance changes of 142 isotopes in the mass range below A=40. In total, we performed 7350 nuclear reaction network calculations. We use the most recent thermonuclear reaction rate evaluations for the mass ranges A=1-20 and A=20-40. For the theoretical astrophysicist, our results indicate the extent to which nova nucleosynthesis calculations depend on presently uncertain nuclear physics input, while for the experimenta...

  18. Calorimetric determination of rate constants and enthalpy changes for zero-order reactions.

    Science.gov (United States)

    Almeida e Sousa, Luis; Beezer, Anthony E; Hansen, Lee D; Clapham, David; Connor, Joseph A; Gaisford, Simon

    2012-06-07

    Calorimetry is a general method for determination of the rates of zero-order processes, but analysis of the data for the rate constant and reaction enthalpy is difficult because these occur as a product in the rate equation so evaluation of one requires knowledge of the other. Three methods for evaluation of both parameters, without prior knowledge, are illustrated with examples and compared with literature data. Method 1 requires the reaction to be studied in two buffers with different enthalpies of ionization. Method 2 is based on calculation of reaction enthalpy from group additivity functions. Method 3 applies when reaction progresses to completion. The methods are applied to the enzymatic hydrolysis of urea, the hydrolysis of acetylsalicylic acid, and the photodegradation of nifedipine, respectively.

  19. BRUSLIB and NETGEN: the Brussels nuclear reaction rate library and nuclear network generator for astrophysics

    Science.gov (United States)

    Aikawa, M.; Arnould, M.; Goriely, S.; Jorissen, A.; Takahashi, K.

    2005-10-01

    Nuclear reaction rates are quantities of fundamental importance in astrophysics. Substantial efforts have been devoted in the last decades to measuring or calculating them. This paper presents a detailed description of the Brussels nuclear reaction rate library BRUSLIB and of the nuclear network generator NETGEN. BRUSLIB is made of two parts. The first one contains the 1999 NACRE compilation based on experimental data for 86 reactions with (mainly) stable targets up to Si. BRUSLIB provides an electronic link to the published, as well as to a large body of unpublished, NACRE data containing adopted rates, as well as lower and upper limits. The second part of BRUSLIB concerns nuclear reaction rate predictions to complement the experimentally-based rates. An electronic access is provided to tables of rates calculated within a statistical Hauser-Feshbach approximation, which limits the reliability of the rates to reactions producing compound nuclei with a high enough level density. These calculations make use of global and coherent microscopic nuclear models for the quantities entering the rate calculations. The use of such models makes the BRUSLIB rate library unique. A description of the Nuclear Network Generator NETGEN that complements the BRUSLIB package is also presented. NETGEN is a tool to generate nuclear reaction rates for temperature grids specified by the user. The information it provides can be used for a large variety of applications, including Big Bang nucleosynthesis, the energy generation and nucleosynthesis associated with the non-explosive and explosive hydrogen to silicon burning stages, or the synthesis of the heavy nuclides through the s-, α- and r-, rp- or p-processes.

  20. Six Sigma and Implementations of Six Sigma in Finance Sector

    Directory of Open Access Journals (Sweden)

    Gokhan Senol

    2010-04-01

    Full Text Available Quality is a one of the critical factors for achieving competitive advantage. Six sigma approach is a business strategy which usage has increased gradually in last years for quality improvement initiative. Although six sigma established by a manufacturing firm and it has been successfully implemented in many manufacturing firms, service firms have began to use six sigma for reducing cost, enhanced quality of service, increasing customer satisfaction and profitability. In this paper, six sigma was examined in a view of finance sector and applications of six sigma within the finance sector were evaluated.

  1. Determination of the enzyme reaction rate in a differential fixed-bed reactor: a case study

    Directory of Open Access Journals (Sweden)

    Baruque Filho E.A.

    2001-01-01

    Full Text Available The reaction rate of starch hydrolysis catalyzed by a glucoamylase covalently bound to chitin particles was measured in a Differential Fixed-Bed Reactor (DFBR. Under selected test conditions the initial reaction rate may represent biocatalyst activity. Some aspects which influence measurement of the initial reaction rate of an immobilized enzyme were studied: the amount of desorbed enzyme and its hydrolytic activity, the extent of pore blockage of the biocatalyst caused by substrate solution impurities and the internal and external diffusional mass transfer effects. The results showed that the enzyme glucoamylase was firmly bound to the support, as indicated by the very low amount of desorbed protein found in the recirculating liquid. Although this protein was very active, its contribution to the overall reaction rate was negligible. It was observed that the biocatalyst pores were susceptible to being blocked by the impurities of the starch solution. This latter effect was accumulative, increasing with the number of sequential experiments carried out. When the substrate solution was filtered before use, very reliable determinations of immobilized enzyme reaction rates could be performed in the DFBR. External and internal diffusional resistences usually play a significant role in fixed-bed reactors. However, for the experimental system studied, internal mass transfer effects were not significant, and it was possible to select an operational condition (recirculation flow rate value that minimized the external diffusional limitations.

  2. REACLIB: A Reaction Rate Library for the Era of Collaborative Science

    Science.gov (United States)

    Meisel, Zachary

    2008-10-01

    Thermonuclear reaction rates and weak decay rates are of great importance to modern nuclear astrophysics. They are critical in the study of many topics such as Big Bang Nucleosynthesis, X-ray bursts, Supernovae, and S-process element formation, among others. The Joint Institute for Nuclear Astrophysics (JINA) has been created to increase connectivity amongst nuclear astrophysicists in our modern age of highly collaborative science. Within JINA there has been an effort to create a frequently updated and readily accessible database of thermonuclear reactions and weak decay rates. This database is the REACLIB library, which can be accessed at the web address: http://www.nscl.msu.edu/˜nero/db/. Here I will discuss the JINA REACLIB Project, including a new procedure to fit reaction rates as a function of temperature that takes full advantage of physicality. With these updated reaction rates, astrophysical modelers will no longer have to worry about the adverse effects of using obsolete reaction rate libraries lacking physical behavior.

  3. Rate constant and reaction coordinate of Trp-cage folding in explicit water

    NARCIS (Netherlands)

    Juraszek, J.; Bolhuis, P.G.

    2008-01-01

    We report rate constant calculations and a reaction coordinate analysis of the rate-limiting folding and unfolding process of the Trp-cage mini-protein in explicit solvent using transition interface sampling. Previous transition path sampling simulations revealed that in this (un)folding process the

  4. Does \\Sigma -\\Sigma -\\alpha Form a Quasi-Bound State?

    CERN Document Server

    Htun Oo, H; Kamada, H; Glöckle, W

    2004-01-01

    We have investigated the possible existence of a quasi-bound state for the \\Sigma -\\Sigma -\\alpha system in the framework of Faddeev calculations. We are particularly interested in the state of total iso-spin T=2, since for an inert \\alpha particle there is no strong conversion to \\Xi -N-\\alpha or \\Lambda -\\Lambda -\\alpha possible. A \\Sigma -\\alpha optical potential based on Nijmegen model D and original \\Sigma -\\Sigma interactions of the series of Nijmegen potentials NSC97 as well a simulated Gaussian type versions thereof are used. Our investigation of the \\Sigma -\\Sigma -\\alpha system leads to a quasi bound state where, depending on the potential parameters, the energy ranges between -1.4 and -2.4 MeV and the level width is about 0.2MeV.

  5. Sign ambiguity in the K{Sigma} channel

    Energy Technology Data Exchange (ETDEWEB)

    Anisovich, A.V.; Nikonov, V.A.; Sarantsev, A.V. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany); Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Klempt, E.; Thoma, U. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik, Bonn (Germany)

    2013-12-15

    Ambiguities of the signs of N {yields} {Sigma}K coupling constants are studied in a multichannel partial wave analysis of a large body of pion- and photo-induced reactions. It is shown that the signs are not free from some ambiguities, and further experimental data are needed. Data on the reactions {pi}{sup +} p {yields} {Sigma}{sup +} K{sup +} and {gamma}p {yields} K{sup +} {Sigma}{sup 0} define rather well the isospin 3/2 contributions to these channels. However the lack of information on polarization observables for the reactions {pi}{sup -} p {yields} {Sigma}{sup 0} K{sup 0}, {pi}{sup -} p {yields} {Sigma}{sup -} K{sup +} and {gamma}p {yields} K{sup 0} {Sigma}{sup +} does not allow us to fix uniquely the signs of N {yields} {Sigma}K coupling constants. As a consequence, also the contributions of nucleon resonances to these channels remain uncertain. (orig.)

  6. Momentum Dependent Vertices $\\sigma \\gamma \\gamma$, $\\sigma \\rho \\gamma$ and $\\sigma \\rho \\rho$ : The NJL Scalar Hidden by Chiral Symmetry

    OpenAIRE

    Bajc, B.; Blin, A. H.; Hiller, B.; Nemes, M. C.; Rosina, M.

    1994-01-01

    We calculate the momentum dependence of three particle vertices $\\sigma \\gamma \\gamma$, $\\sigma \\rho \\gamma$ and $\\sigma \\rho \\rho$ in the context of a Nambu Jona Lasinio type model. We show how they influence the processes $\\gamma \\gamma \\rightarrow \\sigma \\rightarrow \\pi \\pi$, $\\rho \\rightarrow \\gamma \\sigma$ and $\\gamma \\gamma \\rightarrow \\rho \\rho$ and how chiral symmetry shadows the presence of the $\\sigma$.

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

    CERN Document Server

    Suleimanov, Yury V; Guo, Hua

    2016-01-01

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

  8. Chemical Reaction Rate Coefficients from Ring Polymer Molecular Dynamics: Theory and Practical Applications.

    Science.gov (United States)

    Suleimanov, Yury V; Aoiz, F Javier; Guo, Hua

    2016-11-03

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

  9. 运用精益六西格玛降低分立器件芯片测试设备的故障率%Reduce the Use of Lean Six Sigma Discrete Chip Testing Equipment Failure Rate

    Institute of Scientific and Technical Information of China (English)

    易华波

    2013-01-01

    目的:为了提高芯片测试工序的测试产能,通过改进分立器件芯片测试工序的设备管理与流程,降低生产设备的故障率。方法:采用精益六西格玛,并通过其定义、测量、分析、改进、控制5个步骤研究,改进我公司分立器件芯片测试工序的设备管理与流程。结果:设备故障率由改进前的2.5%降低到1.4%。结论:精益六西格玛可减少设备管理与流程中存在的缺陷,降低分立器件生产设备的故障率,以便进一步提高芯片测试产能和设备管理水平。%Objective: To improve the test process test chip production capacity through improved discrete chip testing equip-ment management processes and procedures to reduce the failure rate of production equipment. Methods:Using Lean Six Sigma, and through its definition, measure, analyze, improve, control 5 steps to study and improve my company discrete chip testing equipment management processes and procedures. Results: Improved equipment failure rate decreased to 2.5% before to 1.4%Conclusion:Lean Six Sigma to reduce device management and process defects, reduce discrete manufacturing equipment failure rate, in order to further improve productivity and chip testing equipment management.

  10. A numerical evaluation of prediction accuracy of CO2 absorber model for various reaction rate coefficients

    Directory of Open Access Journals (Sweden)

    Shim S.M.

    2012-01-01

    Full Text Available The performance of the CO2 absorber column using mono-ethanolamine (MEA solution as chemical solvent are predicted by a One-Dimensional (1-D rate based model in the present study. 1-D Mass and heat balance equations of vapor and liquid phase are coupled with interfacial mass transfer model and vapor-liquid equilibrium model. The two-film theory is used to estimate the mass transfer between the vapor and liquid film. Chemical reactions in MEA-CO2-H2O system are considered to predict the equilibrium pressure of CO2 in the MEA solution. The mathematical and reaction kinetics models used in this work are calculated by using in-house code. The numerical results are validated in the comparison of simulation results with experimental and simulation data given in the literature. The performance of CO2 absorber column is evaluated by the 1-D rate based model using various reaction rate coefficients suggested by various researchers. When the rate of liquid to gas mass flow rate is about 8.3, 6.6, 4.5 and 3.1, the error of CO2 loading and the CO2 removal efficiency using the reaction rate coefficients of Aboudheir et al. is within about 4.9 % and 5.2 %, respectively. Therefore, the reaction rate coefficient suggested by Aboudheir et al. among the various reaction rate coefficients used in this study is appropriate to predict the performance of CO2 absorber column using MEA solution. [Acknowledgement. This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF, funded by the Ministry of Education, Science and Technology (2011-0017220].

  11. Dependence of X-Ray Burst Models on Nuclear Reaction Rates

    Science.gov (United States)

    Cyburt, R. H.; Amthor, A. M.; Heger, A.; Johnson, E.; Keek, L.; Meisel, Z.; Schatz, H.; Smith, K.

    2016-10-01

    X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars, and reliable burst models are needed to interpret observations in terms of properties of the neutron star and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p, γ), (α, γ), and (α, p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophysical conditions. A two-step approach first identified sensitive nuclear reaction rates in a single-zone model with ignition conditions chosen to match calculations with a state-of-the-art 1D multi-zone model based on the Kepler stellar evolution code. All relevant reaction rates on neutron-deficient isotopes up to mass 106 were individually varied by a factor of 100 up and down. Calculations of the 84 changes in reaction rate with the highest impact were then repeated in the 1D multi-zone model. We find a number of uncertain reaction rates that affect predictions of light curves and burst ashes significantly. The results provide insights into the nuclear processes that shape observables from X-ray bursts, and guidance for future nuclear physics work to reduce nuclear uncertainties in X-ray burst models.

  12. Ab Initio Calculation of Rate Constants for Molecule–Surface Reactions with Chemical Accuracy

    Science.gov (United States)

    Piccini, GiovanniMaria; Alessio, Maristella

    2016-01-01

    Abstract The ab initio prediction of reaction rate constants for systems with hundreds of atoms with an accuracy that is comparable to experiment is a challenge for computational quantum chemistry. We present a divide‐and‐conquer strategy that departs from the potential energy surfaces obtained by standard density functional theory with inclusion of dispersion. The energies of the reactant and transition structures are refined by wavefunction‐type calculations for the reaction site. Thermal effects and entropies are calculated from vibrational partition functions, and the anharmonic frequencies are calculated separately for each vibrational mode. This method is applied to a key reaction of an industrially relevant catalytic process, the methylation of small alkenes over zeolites. The calculated reaction rate constants (free energies), pre‐exponential factors (entropies), and enthalpy barriers show that our computational strategy yields results that agree with experiment within chemical accuracy limits (less than one order of magnitude). PMID:27008460

  13. DESIGN FOR SIX SIGMA

    Directory of Open Access Journals (Sweden)

    Liem Ferryanto

    2007-01-01

    Full Text Available This article provides a step by step process of executing analytical or computer based Design for Six Sigma using a Sliding Door project as an example. It comprises of identification of Voice Of the Customer (VOC, transformation of VOC to what it is called Critical To Quality characteristics (CTQs, modeling of system transfers function, optimal and robust solutions, and tolerance design approach

  14. Metodologie Six Sigma

    OpenAIRE

    Zajícová, Hana

    2010-01-01

    Bachelor thesis deals with the desription of the statistical foundations and individual steps of Six Sigma, which are descibed by the DMAIC model. The thesis focuses on statistical process control and control charts. The main goal is to evaluate the possible use of control charts for attributes, namely the control chart for fraction nonconforming or p-diagram and to describe its properties expressed by the operating characteristic (OC). The influence of the sample size on the OC curve is exam...

  15. Gravitating $\\sigma$ Model Solitons

    OpenAIRE

    Kim, Yoonbai; Moon, Sei-Hoon

    1998-01-01

    We study axially symmetric static solitons of O(3) nonlinear $\\sigma$ model coupled to (2+1)-dimensional anti-de Sitter gravity. The obtained solutions are not self-dual under static metric. The usual regular topological lump solution cannot form a black hole even though the scale of symmetry breaking is increased. There exist nontopological solitons of half integral winding in a given model, and the corresponding spacetimes involve charged Ba$\\tilde n$ados-Teitelboim-Zanelli black holes with...

  16. Six Sigma pricing.

    Science.gov (United States)

    Sodhi, ManMohan S; Sodhi, Navdeep S

    2005-05-01

    Many companies are now good at managing costs and wringing out manufacturing efficiencies. The TQM movement and the disciplines of Six Sigma have seen to that. But the discipline so often brought to the cost side of the business equation is found far less commonly on the revenue side. The authors describe how a global manufacturer of industrial equipment, which they call Acme Incorporated, recently applied Six Sigma to one major revenue related activity--the price-setting process. It seemed to Acme's executives that pricing closely resembled many manufacturing processes. So, with the help of a Six Sigma black belt from manufacturing, a manager from Acme's pricing division recruited a team to carry out the five Six Sigma steps: Define what constitutes a defect. At Acme, a defect was an item sold at an unauthorized price. Gather data and prepare it for analysis. That involved mapping out the existing pricing-agreement process. Analyze the data. The team identified the ways in which people failed to carry out or assert effective control at each stage. Recommend modifications to the existing process. The team sought to decrease the number of unapproved prices without creating an onerous approval apparatus. Create controls. This step enabled Acme to sustain and extend the improvements in its pricing procedures. As a result of the changes, Acme earned dollar 6 million in additional revenue on one product line alone in the six months following implementation--money that went straight to the bottom line. At the same time, the company removed much of the organizational friction that had long bedeviled its pricing process. Other companies can benefit from Acme's experience as they look for ways to exercise price control without alienating customers.

  17. Kinetics of the benzyl + O(3P) reaction: a quantum chemical/statistical reaction rate theory study.

    Science.gov (United States)

    da Silva, Gabriel; Bozzelli, Joseph W

    2012-12-14

    The resonance stabilized benzyl radical is an important intermediate in the combustion of aromatic hydrocarbons and in polycyclic aromatic hydrocarbon (PAH) formation in flames. Despite being a free radical, benzyl is relatively stable in thermal, oxidizing environments, and is predominantly removed through bimolecular reactions with open-shell species other than O(2). In this study the reaction of benzyl with ground-state atomic oxygen, O((3)P), is examined using quantum chemistry and statistical reaction rate theory. C(7)H(7)O energy surfaces are generated at the G3SX level, and include several novel pathways. Transition state theory is used to describe elementary reaction kinetics, with canonical variational transition state theory applied for barrierless O atom association with benzyl. Apparent rate constants and branching ratios to different product sets are obtained as a function of temperature and pressure from solving the time-dependent master equation, with RRKM theory for microcanonical k(E). These simulations indicate that the benzyl + O reaction predominantly forms the phenyl radical (C(6)H(5)) plus formaldehyde (HCHO), with lesser quantities of the C(7)H(6)O products benzaldehyde, ortho-quinone methide, and para-quinone methide (+H), along with minor amounts of the formyl radical (HCO) + benzene. Addition of O((3)P) to the methylene site in benzyl produces a highly vibrationally excited C(7)H(7)O* adduct, the benzoxyl radical, which can β-scission to benzaldehyde + H and phenyl + HCHO. In order to account for the experimental observation of benzene as the major reaction product, a roaming radical mechanism is proposed that converts the nascent products phenyl and HCHO to benzene + HCO. Oxygen atom addition at the ortho and para ring sites in benzyl, which has not been previously considered, is shown to lead to the quinone methides + H; these species are less-stable isomers of benzaldehyde that are proposed as important combustion intermediates, but

  18. Depletion: A Game with Natural Rules for Teaching Reaction Rate Theory

    Science.gov (United States)

    Olbris, Donald J.; Herzfeld, Judith

    2002-10-01

    Depletion is a game that reinforces central concepts of reaction rate theory through simulation. Each player buys chemicals and guides them through a series of reactions, thereby earning money to buy more chemicals. The reactions occur when players roll a high enough value on two dice to overcome an activation barrier. The reactions may be accelerated by buying heat (which allows the player to roll three dice instead of two) or catalysts (which lower the activation barrier). The value of acceleration derives from the increasing price of fresh chemicals as resources are depleted and waste products accumulate. The player who nets the most money wins the game. The details of the game are presented, with a set of follow-up questions suitable for either a quiz or discussion. Student reaction to the game is also described.

  19. Measurements of sigma(e^+ e^- -> Upsilon(nS)pi^+pi^-) and sigma(e^+ e^- -> b bbar) in the Upsilon(10860) and Upsilon(11020) resonance regions

    CERN Document Server

    Santel, D; Chang, P; Abdesselam, A; Adachi, I; Aihara, H; Said, S Al; Arinstein, K; Asner, D M; Aushev, T; Ayad, R; Bakich, A M; Bansal, V; Bhuyan, B; Bobrov, A; Bondar, A; Bonvicini, G; Bračko, M; Browder, T E; Červenkov, D; Chekelian, V; Cheon, B G; Chilikin, K; Cho, K; Chobanova, V; Choi, S -K; Choi, Y; Cinabro, D; Dalseno, J; Danilov, M; Dingfelder, J; Doležal, Z; Drásal, Z; Drutskoy, A; Eidelman, S; Farhat, H; Fast, J E; Ferber, T; Gaur, V; Gabyshev, N; Garmash, A; Getzkow, D; Gillard, R; Goh, Y M; Haba, J; Hara, T; Hayasaka, K; Hayashii, H; He, X H; Hou, W -S; Hyun, H J; Iijima, T; Inami, K; Ishikawa, A; Itoh, R; Iwasaki, Y; Jaegle, I; Joffe, D; Julius, T; Kang, K H; Kato, E; Kawasaki, T; Kiesling, C; Kim, D Y; Kim, H J; Kim, J B; Kim, J H; Kim, M J; Kim, S H; Kim, Y J; Ko, B R; Kodyš, P; Korpar, S; Križan, P; Krokovny, P; Kuzmin, A; Lange, J S; Lee, I S; Li, Y; Gioi, L Li; Libby, J; Liventsev, D; Lukin, P; Matvienko, D; Miyabayashi, K; Miyata, H; Mizuk, R; Mohanty, G B; Moll, A; Mori, T; Mussa, R; Nakano, E; Nakao, M; Nanut, T; Natkaniec, Z; Nisar, N K; Nishida, S; Ogawa, S; Okuno, S; Olsen, S L; Oswald, C; Pakhlov, P; Pakhlova, G; Park, C W; Park, H; Pedlar, T K; Petrič, M; Piilonen, L E; Ribežl, E; Ritter, M; Rostomyan, A; Ryu, S; Sakai, Y; Sandilya, S; Santelj, L; Sanuki, T; Savinov, V; Schneider, O; Schnell, G; Schwanda, C; Schwartz, A J; Senyo, K; Sevior, M E; Shebalin, V; Shibata, T -A; Shiu, J -G; Shwartz, B; Sibidanov, A; Simon, F; Sohn, Y -S; Solovieva, E; Starič, M; Steder, M; Tamponi, U; Tatishvili, G; Teramoto, Y; Trabelsi, K; Uchida, M; Uglov, T; Unno, Y; Uno, S; Van Hulse, C; Vanhoefer, P; Varner, G; Vinokurova, A; Wagner, M N; Wang, P; Wang, X L; Watanabe, M; Watanabe, Y; Won, E; Yamaoka, J; Yang, Y -P; Yashchenko, S; Yook, Y; Yusa, Y; Zhang, Z P; Zhilich, V; Zhulanov, V; Zupanc, A

    2016-01-01

    We report new measurements of $R_{\\Upsilon\\pi\\pi}\\equiv\\sigma(e^+e^-\\to \\Upsilon(n{\\rm S})\\pi^+\\pi^-)/\\sigma^0_{\\mu\\mu}$ ($n$ = 1, 2, 3) and $R_b\\equiv\\sigma(e^+e^-\\to b\\bar b)/\\sigma^0_{\\mu\\mu}$ (where $\\sigma^0_{\\mu\\mu}$ is the muon-pair Born cross section) in the region $\\sqrt{s} = 10.63$-$11.05$ GeV, based on data collected with the Belle detector. Distributions in $R_{\\Upsilon\\pi\\pi}$ and $R_b$ are fit for the masses and widths of the $\\Upsilon(10860)$ and $\\Upsilon(11020)$ resonances. Unlike $R_b$, which includes a large non-resonant $b\\bar{b}$ component, we find that $R_{\\Upsilon\\pi\\pi}$ is dominated by the two resonances. With $R_{\\Upsilon\\pi\\pi}$ as the basis, the total rate at the $\\Upsilon(10860)$ peak for known final states containing bottomonium(-like) resonances is estimated. We find that $\\Upsilon(10860)$ is essentially saturated by such modes, raising doubts about the validity of masses measured using $R_b$. With $R_{\\Upsilon\\pi\\pi}$, we measure $M_{10860}=(10891.1\\pm3.2^{+0.6}_{-1.5})$ MeV/$c...

  20. Unified equation for access to rate constants of first-order reactions in dynamic and on-column reaction chromatography.

    Science.gov (United States)

    Trapp, O

    2006-01-01

    A unified equation to evaluate elution profiles of reversible as well as irreversible (pseudo-) first-order reactions in dynamic chromatography and on-column reaction chromatography has been derived. Rate constants k1 and k(-1) and Gibbs activation energies are directly obtained from the chromatographic parameters (retention times tR(A) and tR(B) of the interconverting or reacting species A and B, the peak widths at half-height wA and wB, and the relative plateau height h(p)), the initial amounts A0 and B0 of the reacting species, and the equilibrium constant K(A/B). The calculation of rate constants requires only a few iterative steps without the need of performing a computationally extensive simulation of elution profiles. The unified equation was validated by comparison with a data set of 125,000 simulated elution profiles to confirm the quality of this equation by statistical means and to predict the minimal experimental requirements. Surprisingly, the recovery rate from a defined data set is on average 35% higher using the unified equation compared to the evaluation by iterative computer simulation.

  1. Generalization of the Activated Complex Theory of Reaction Rates. I. Quantum Mechanical Treatment

    Science.gov (United States)

    Marcus, R. A.

    1964-01-01

    In its usual form activated complex theory assumes a quasi-equilibrium between reactants and activated complex, a separable reaction coordinate, a Cartesian reaction coordinate, and an absence of interaction of rotation with internal motion in the complex. In the present paper a rate expression is derived without introducing the Cartesian assumption. The expression bears a formal resemblance to the usual one and reduces to it when the added assumptions of the latter are introduced.

  2. Measurement of reaction rates of interest in stellar structure and evolution

    Energy Technology Data Exchange (ETDEWEB)

    Terrasi, F.; D`Onofrio, A. [Dipt. di Scienze Ambientali, Seconda Univ. di Napoli, Caserta (Italy)]|[INFN, Napoli (Italy); Campajola, L.; Imbriani, G. [INFN, Napoli (Italy)]|[Dipt. di Scienze Fisiche, Univ. Federico II, Napoli (Italy); Gialanella, L. [INFN, Napoli (Italy)]|[Dipt. di Scienze Fisiche, Univ. Federico II, Napoli (Italy)]|[Inst. fuer Experimentalphysik III, Ruhr-Univ. Bochum, Bochum (Germany); Greife, U.; Rolfs, C.; Strieder, F.; Trautvetter, H.P. [Inst. fuer Experimentalphysik III, Ruhr-Univ. Bochum, Bochum (Germany); Roca, V.; Romano, M. [INFN, Napoli (Italy)]|[Dipt. di Scienze Fisiche, Univ. Federico II, Napoli (Italy); Straniero, O. [Osservatorio Astronomico di Collurania, Teramo (Italy)

    1998-06-01

    Accurate determinations of reaction rates at astrophysical energies are very important in stellar structure and evolution studies. The cases of two key reactions, namely {sup 7}Be(p,{gamma}){sup 8}B and {sup 12}C({alpha},{gamma}){sup 16}O are discussed, both from the point of view of their astrophysical interest and of the experimental difficulties in the measurement of their cross section. (orig.)

  3. Perturbation theory in the catalytic rate constant of the Henri-Michaelis-Menten enzymatic reaction.

    Science.gov (United States)

    Bakalis, Evangelos; Kosmas, Marios; Papamichael, Emmanouel M

    2012-11-01

    The Henry-Michaelis-Menten (HMM) mechanism of enzymatic reaction is studied by means of perturbation theory in the reaction rate constant k (2) of product formation. We present analytical solutions that provide the concentrations of the enzyme (E), the substrate (S), as well as those of the enzyme-substrate complex (C), and the product (P) as functions of time. For k (2) small compared to k (-1), we properly describe the entire enzymatic activity from the beginning of the reaction up to longer times without imposing extra conditions on the initial concentrations E ( o ) and S ( o ), which can be comparable or much different.

  4. Considerations Based on Reaction Rate on Char Gasification Behavior in Two-stage Gasifier for Biomass

    Science.gov (United States)

    Taniguchi, Miki; Nishiyama, Akio; Sasauchi, Kenichi; Ito, Yusuke; Akamatsu, Fumiteru

    In order to develop a small-scale gasifier in which biomass can be converted to energy with high efficiency, we planned a gasification process that consists of two parts: pyrolysis part (rotary kiln) and gasification part (downdraft gasifier). We performed fundamental experiments on gasification part and discussed the appropriate conditions such as air supply location, air ratio, air temperature and hearth load. We considered the results by calculating reaction rates of representative reactions on char gasification part and found that water gas reaction is dominant in the reduction area and its behavior gives important information to decide the adequate length of the char layer.

  5. Combustion of Bimodal Nano/Micro Aluminum Suspension with New Reaction Rate Model

    OpenAIRE

    M. Bidabadi; N. Moallemi; I. Shafieenejad; M. Jadidi

    2008-01-01

    In this study a mathematical model for combustion of bimodal particle in lean flow was developed. The difference between structure of flame in this work and previous ones was that, in those flame was divided by five zones and reaction rate was considered to be constant in reaction zones and also zero in post flame zone. In reality it was obvious with respect to shape and size of different particles in dust, reaction didn't end suddenly. In the present research the heat loss term, which was as...

  6. Rate constants for chemical reactions in high-temperature nonequilibrium air

    Science.gov (United States)

    Jaffe, R. L.

    1986-01-01

    In the nonequilibrium atmospheric chemistry regime that will be encountered by the proposed Aeroassisted Orbital Transfer Vehicle in the upper atmosphere, where air density is too low for thermal and chemical equilibrium to be maintained, the detailed high temperature air chemistry plays a critical role in defining radiative and convective heating loads. Although vibrational and electronic temperatures remain low (less than 15,000 K), rotational and translational temperatures may reach 50,000 K. Attention is presently given to the effects of multiple temperatures on the magnitudes of various chemical reaction rate constants, for the cases of both bimolecular exchange reactions and collisional excitation and dissociation reactions.

  7. Comparison of mass loss rate in reaction of silica with carbon from different investigation results

    Directory of Open Access Journals (Sweden)

    J. Węgrzyn

    2015-07-01

    Full Text Available In the process of carbothermic reaction of SiO2 + mC, key reactions appear on the surfaces of both SiO2 and C grains. However, the values of these surfaces are not known. Assuming the simplest case, quartzite and carbon grains are spheres, total surfaces of reaction were calculated for grains of carbon and quartzite respectively. This enabled to determine the rate of weight loss referred to the unit area of C and SiO2.

  8. Mineral/solution reaction rates in a mixed flow reactor: Wollastonite hydrolysis

    Science.gov (United States)

    Rimstidt, J. Donald; Dove, Patricia M.

    1986-11-01

    A newly developed mixed flow reactor was used to measure the rate of hydrolysis of wollastonite over the pH range of 3 to 8. This design avoids abrasion of the solid sample by confining it within a nylon mesh while the reacting solution is circulated over it by a stirrer. The rate of reaction was determined from the difference of the compositions of the input and output solutions following the methods used by chemical engineers for the analysis of mixed flow reactors, also called continuously stirred tank reactors (CSTR). This apparatus, constructed from easily obtainable parts, avoids many of the problems inherent in studying mineral/solution reaction kinetics in batch reactors. The hydrolysis of wollastonite CaSiO3 + 2 H+ + H2O = Ca2+ + H4SiO4 can be fit to a rate law of the form: dnH+/ dt = kadKH+mH+/(1.0 + KH+mH+) where kad = 9.80 × 10 -8molm-2sec-1 and KH+ = 2.08 × 10 5. Over the pH range of 4 to 7, the data also may fit a simple linear form: dnH+/ dt = - Ak+( aH+) 0.40 where k+ = 3.80 × 10 -6 sec -1 at 25°C. The presence of calcium ion in the solution at concentrations up to 1.0 mol kg -1 produces only a minor reduction of the reaction rate. The activation energy for this reaction is 79.2 kJ mol -1. Examination of the surfaces of the reacted grains showed no evidence of incongruent reaction leading to a product layer but did show the extensive development of etch pits leading to a rapid increase in the specific surface area. At large extents of reaction at low pH, diffusion of ions into or from these deep etch pits may limit the reaction rate.

  9. The Influence of Reaction Rates on the Final p-Abundances

    CERN Document Server

    Rapp, W; Schatz, H; Käppeler, F K

    2004-01-01

    The astrophysical p-process is responsible for the origin of the proton rich nuclei,which are heavier than iron. A huge network involving thousands of reaction rates is necessary to calculate the final p-abundances. But not all rates included in the network have a strong influence on the p-nuclei abundances. The p-process was investigated using a full nuclear reaction network for a type II supernovae explosion when the shock front passes through the O/Ne layer. Calculations were done with a multi-layer model adopting the seed of a pre-explosion evolution of a 25 mass star. In extensive simulations we investigated the impact of single reaction rates on the final p-abundances. The results are important for the strategy of future experiments in this field.

  10. Sensitivity of Type I X-Ray Bursts to rp-Process Reaction Rates

    CERN Document Server

    Amthor, A M; Heger, A; Sakharuk, A; Schatz, H; Smith, K; Galaviz, Daniel; Heger, Alexander; Sakharuk, Alexander; Schatz, Hendrik; Smith, Karl

    2006-01-01

    First steps have been taken in a more comprehensive study of the dependence of observables in Type I X-ray bursts on uncertain (p,gamma) reaction rates along the rp-process path. We use the multizone hydrodynamics code KEPLER which implicitly couples a full nuclear reaction network of more than 1000 isotopes, as needed, to follow structure and evolution of the X-ray burst layer and its ashes. This allows us to incorporate the full rp-process network, including all relevant nuclear reactions, and individually study changes in the X-ray burst light curves when modifying selected key nuclear reaction rates. In this work we considered all possible proton captures to nuclei with 10 < Z < 28 and N <= Z. When varying individual reaction rates within a symmetric full width uncertainty of a factor of 10000, early results for some rates show changes in the burst light curve as large as 10 percent of peak luminosity. This is very large compared to the current sensitivity of X-ray observations. More precise reac...

  11. Ab-Initio Based Computation of Rate Constants for Spin Forbidden Metalloprotein-Substrate Reactions

    Science.gov (United States)

    Ozkanlar, Abdullah; Rodriguez, Jorge H.

    2007-03-01

    Some chemical and biochemical reactions are non-adiabatic processes whereby the total spin angular momentum, before and after the reaction, is not conserved. These are named spin- forbidden reactions. The application of ab-initio methods, such as spin density functional theory (SDFT), to the prediction of rate constants is a challenging task of fundamental and practical importance. We apply non-adiabatic transition state theory (NA-TST) in conjuntion with SDFT to predict the rate constant of the spin- forbidden recombination of carbon monoxide with iron tetracarbonyl. To model the surface hopping probability between singlet and triplet states, the Landau-Zener formalism is used. The lowest energy point for singlet-triplet crossing, known as minimum energy crossing point (MECP), was located and used to compute, in a semi-quantum approach, reaction rate constants at 300 K. The predicted rates are in very good agreement with experiment. In addition, we present results for the spin- forbidden ligand binding reactions of iron-containing heme proteins such as myoglobin.

  12. An accurate analytic representation of the temperature dependence of nonresonant nuclear reaction rate coefficients

    Science.gov (United States)

    Shizgal, Bernie D.

    2016-12-01

    There has been intense interest for several decades by different research groups to accurately model the temperature dependence of a large number of nuclear reaction rate coefficients for both light and heavy nuclides. The rate coefficient, k(T) , is given by the Maxwellian average of the reactive cross section expressed in terms of the astrophysical factor, S(E) , which for nonresonant reactions is generally written as a power series in the relative energy E. A computationally efficient algorithm for the temperature dependence of nuclear reaction rate coefficients is required for fusion reactor research and for models of nucleosynthesis and stellar evolution. In this paper, an accurate analytical expression for the temperature dependence of nuclear reaction rate coefficients is provided in terms of τ = 3(b / 2) 2/3 or equivalently, T - 1/3 , where b = B /√{kB T }, B is the Gamow factor and kB is the Boltzmann constant. The methodology is appropriate for all nonresonant nuclear reactions for which S(E) can be represented as a power series in E. The explicit expression for the rate coefficient versus temperature is derived with the asymptotic expansions of the moments of w(E) = exp(- E /kB T - B /√{ E }) in terms of τ. The zeroth order moment is the familiar Gaussian approximation to the rate coefficient. Results are reported for the representative reactions D(d, p)T, D(d, n)3He and 7Li(p, α) α and compared with several different fitting procedures reported in the literature.

  13. Temperature dependence of electrocatalytic and photocatalytic oxygen evolution reaction rates using NiFe oxide

    KAUST Repository

    Nurlaela, Ela

    2016-01-25

    The present work compares oxygen evolution reaction (OER) in electrocatalysis and photocatalysis in aqueous solutions using nanostructured NiFeOx as catalysts. The impacts of pH and reaction temperature on the electrocatalytic and photocatalytic OER kinetics were investigated. For electrocatalysis, a NiFeOx catalyst was hydrothermally decorated on Ni foam. In 1 M KOH solution, the NiFeOx electrocatalyst achieved 10 mA cm-2 at an overpotential of 260 mV. The same catalyst was decorated on the surface of Ta3N5 photocatalyst powder. The reaction was conducted in the presence of 0.1 M Na2S2O8 as a strong electron scavenger, thus likely leading to the OER being kinetically relevant. When compared with the bare Ta3N5, NiFeOx/Ta3N5 demonstrated a 5-fold improvement in photocatalytic activity in the OER under visible light irradiation, achieving a quantum efficiency of 24 % at 480 nm. Under the conditions investigated, a strong correlation between the electrocatalytic and photocatalytic performances was identified: an improvement in electrocatalysis corresponded with an improvement in photocatalysis without altering the identity of the materials. The rate change at different pH was likely associated with electrocatalytic kinetics that accordingly influenced the photocatalytic rates. The sensitivity of the reaction rates with respective to the reaction temperature resulted in an apparent activation energy of 25 kJ mol-1 in electrocatalysis, whereas that in photocatalysis was 16 kJ mol-1. The origin of the difference in these activation energy values is likely attributed to the possible effects of temperature on the individual thermodynamic and kinetic parameters of the reaction process. The work described herein demonstrates a method of “transferring the knowledge of electrocatalysis to photocatalysis” as a strong tool to rationally and quantitatively understand the complex reaction schemes involved in photocatalytic reactions.

  14. Observation of double pygmy resonances in $^{195,196}$Pt and enhanced astrophysical reaction rates

    CERN Document Server

    Giacoppo, F; Eriksen, T K; Görgen, A; Guttormsen, M; Hagen, T W; Larsen, A C; Kheswa, B V; Klintefjord, M; Koehler, P E; Nyhus, H T; Renstr\\om, T; Sahin, E; Siem, S; Tornyi, T G

    2014-01-01

    Our measurements of $^{195,196}$Pt $\\gamma$-strength functions show a double-humped enhancement in the $E_{\\gamma}= 4-8$ MeV region. For the first time, the detailed shape of these resonances is revealed for excitation energies in the quasicontinuum. We demonstrate that the corresponding neutron-capture cross sections and astrophysical reaction rates are increased by up to a factor of 2 when these newly observed pygmy resonances are included. These results lend credence to theoretical predictions of enhanced reaction rates due to such pygmy resonances and hence are important for a better understanding of r-process nucleosynthesis.

  15. Effect of macromolecular crowding on the rate of diffusion-limited enzymatic reaction

    Indian Academy of Sciences (India)

    Manish Agrawal; S B Santra; Rajat Anand; Rajaram Swaminathan

    2008-08-01

    The cytoplasm of a living cell is crowded with several macromolecules of different shapes and sizes. Molecular diffusion in such a medium becomes anomalous due to the presence of macromolecules and diffusivity is expected to decrease with increase in macromolecular crowding. Moreover, many cellular processes are dependent on molecular diffusion in the cell cytosol. The enzymatic reaction rate has been shown to be affected by the presence of such macromolecules. A simple numerical model is proposed here based on percolation and diffusion in disordered systems to study the effect of macromolecular crowding on the enzymatic reaction rates. The model qualitatively explains some of the experimental observations.

  16. Reaction rate of H atoms with N2O in hot water

    Science.gov (United States)

    Sargent, Leanne; Sterniczuk, Marcin; Bartels, David M.

    2017-06-01

    The rate constant of H• atoms with N2O in water has been measured by a competition method up to 300 °C. Radiolysis with 2.5 MeV electrons generated H• atoms, and the HD product from their reaction with deuterated tetrahydrofuran (THF-d8) was measured with mass spectroscopy. The concentration of THF-d8 was changed by an order of magnitude in the presence of 25 mM N2O to obtain the ratio of rate constants. To determine the rate constant of H• with THF-d8, a similar competition vs. 0.2 mM OH- ion was also measured. The reaction rate of H• with OH- has been accurately determined vs. temperature in previous work, allowing the two unknown rate constants to be deduced. Rate constant of H• with THF-d8 follows the Arrhenius law ln(k/M-1s-1)=27.33 - (32.30 kJ/mol)/RT. Rate constant of H• with N2O follows the Arrhenius law ln(k/M-1s-1)=24.50 - (30.42 kJ/mol)/RT. In all likelihood, the N2O reaction proceeds via cis-HNNO• radical intermediate as in the gas phase, but with participation of a bridging water molecule in the 1,3 hydrogen shift to form N2 and •OH products.

  17. Examining the reaction of monetary policy to exchange rate changes: A nonlinear ARDL approach

    Science.gov (United States)

    Manogaran, Lavaneesvari; Sek, Siok Kun

    2017-04-01

    Previous studies showed the exchange rate changes can have significant impacts on macroeconomic performance. Over fluctuation of exchange rate may lead to economic instability. Hence, monetary policy rule tends to react to exchange rate changes. Especially, in emerging economies where the policy-maker tends to limit the exchange rate movement through interventions. In this study, we seek to investigate how the monetary policy rule reacts to exchange rate changes. The nonlinear autoregressive distributed lag (NARDL) model is applied to capture the asymmetric effect of exchange rate changes on monetary policy reaction function (interest rate). We focus the study in ASEAN5 countries (Indonesia, Malaysia, Philippines, Thailand and Singapore). The results indicated the existence of asymmetric effect of exchange rates changes on the monetary reaction function for all ASEAN5 countries in the long-run. Where, in majority of the cases the monetary policy is reacting to the appreciation and depreciation of exchange rate by raising the policy rate. This affirms the intervention of policymakers with the `fear of floating' behavior.

  18. Mutational analysis of phenylalanine ammonia lyase to improve reactions rates for various substrates.

    Science.gov (United States)

    Bartsch, Sebastian; Bornscheuer, Uwe T

    2010-12-01

    Phenylalanine ammonia lyases (PAL) catalyze the reversible, non-reductive amination of trans-cinnamic acid to l-phenylalanine in the presence of high ammonia concentrations. Since neither cofactor recycling nor other additives are needed and by this asymmetric synthesis theoretical yields of 100% can be reached, it is an interesting reaction for industrial processes. In this study we demonstrate the superior properties of p-nitro-cinnamic acid (p-n-CA) in the amination reaction using the PAL from Petroselinum crispum (pcPAL). By focused-directed evolution, three mutants were identified showing increased reaction rates and decreased substrate inhibition. Together, the F137V mutant with p-n-CA showed a 15-fold increased reaction rate compared with the pcPAL WT with the natural cinnamic acid. The high reaction rates were also proven in preparative scale experiments. Activities towards other p-substituted cinnamic acids showing different electronic effects of the substituent were analyzed. Focused-directed evolution around the carboxylic acid- and amine-binding site always decreased PAL activity, due to a sensitive H-bond network.

  19. Gravitating $\\sigma$ Model Solitons

    CERN Document Server

    Kim, Y; Kim, Yoonbai; Moon, Sei-Hoon

    1998-01-01

    We study axially symmetric static solitons of O(3) nonlinear $\\sigma$ model coupled to (2+1)-dimensional anti-de Sitter gravity. The obtained solutions are not self-dual under static metric. The usual regular topological lump solution cannot form a black hole even though the scale of symmetry breaking is increased. There exist nontopological solitons of half integral winding in a given model, and the corresponding spacetimes involve charged Ba$\\tilde n$ados-Teitelboim-Zanelli black holes without non-Abelian scalar hair.

  20. The rate constant for the CO + H2O2 reaction

    DEFF Research Database (Denmark)

    Glarborg, Peter; Marshall, Paul

    2009-01-01

    The rate constant for the reaction CO + H2O2 -> HOCO + OH (R1) at 713 K is determined based on the batch reactor experiments of Baldwin et al. [ R. R. Baldwin, R. W. Walker, S. J. Webster, Combust. Flame 15 (1970) 167] on decomposition of H2O2 sensitized by CO. The value, k(1) (713 K) = 8.1 x 10...... in combustion. The present analysis reconciles the batch reactor data of Baldwin et al. with recent high-level theoretical work on the CO + HO2 reaction.......(2) cm(3) mol(-1) s(-1), is consistent with spin-unrestricted density functional theory. Extrapolation to a wider temperature range through ab initio calculations yields the rate constant k(1) = 3.6 x 10(4)T(2.5) exp(-14425[K]/T) cm(3) mol(-1) s(-1). The reaction is probably of minor importance...

  1. Reaction Rates and Kinetic Isotope Effects of H$_2$ + OH $\\rightarrow$ H$_2$O + H

    CERN Document Server

    Meisner, Jan

    2016-01-01

    We calculated reaction rate constants including atom tunneling of the reaction of dihydrogen with the hydroxy radical down to a temperature of 50 K. Instanton theory and canonical variational theory with microcanonical optimized multidimensional tunneling (CVT/$\\mu$OMT) were applied using a fitted potential energy surface [J. Chem. Phys. 138, 154301 (2013)]. All possible protium/deuterium isotopologues were considered. Atom tunneling increases at about 250 K (200 K for deuterium transfer). Even at 50 K the rate constants of all isotopologues remain in the interval $ 4 \\cdot 10^{-20}$ to $4 \\cdot 10^{-17}$ cm$^3$ s$^{-1}$ , demonstrating that even deuterated versions of the title reaction are possibly relevant to astrochemical processes in molecular clouds. The transferred hydrogen atom dominates the kinetic isotope effect at all temperatures.

  2. Investigating rare events with nonequilibrium work measurements. II. Transition and reaction rates.

    Science.gov (United States)

    Moradi, Mahmoud; Sagui, Celeste; Roland, Christopher

    2014-01-21

    We present a formalism for investigating transition pathways and transition probabilities for rare events in biomolecular systems. The formalism is based on combining Transition Path Theory with the results of nonequilibrium work relations, and shows that the equilibrium and nonequilibrium transition rates are in fact related. Aside from its fundamental importance, this allows for the calculation of relative equilibrium reaction rates with driven nonequilibrium simulations such as Steered Molecular Dynamics. The workings of the formalism are illustrated with a few typical numerical examples.

  3. SENSMG: First-Order Sensitivities of Neutron Reaction Rates, Reaction-Rate Ratios, Leakage, keff, and α Using PARTISN

    Energy Technology Data Exchange (ETDEWEB)

    Favorite, Jeffrey A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-11-21

    SENSMG is a tool for computing first-order sensitivities of neutron reaction rates, reaction-rate ratios, leakage, keff, and α using the PARTISN multigroup discrete-ordinates code. SENSMG computes sensitivities to all of the transport cross sections and data (total, fission, nu, chi, and all scattering moments), two edit cross sections (absorption and capture), and the density for every isotope and energy group. It also computes sensitivities to the mass density for every material and derivatives with respect to all interface locations. The tool can be used for one-dimensional spherical (r) and two-dimensional cylindrical (r-z) geometries. The tool can be used for fixed-source and eigenvalue problems. The tool implements Generalized Perturbation Theory (GPT) as discussed by Williams and Stacey. Section II of this report describes the theory behind adjoint-based sensitivities, gives the equations that SENSMG solves, and defines the sensitivities that are output. Section III describes the user interface, including the input file and command line options. Section IV describes the output. Section V gives some notes about the coding that may be of interest. Section VI discusses verification, which is ongoing. Section VII lists needs and ideas for future work. Appendix A lists all of the input files whose results are presented in Sec. VI.

  4. Energy Dependence of the Lambda-Sigma0 Production in Proton-Proton Collisions

    CERN Document Server

    Dillig, M

    2006-01-01

    The energy dependence of the reactions pp -> p Lambda K+ and pp -> p Sigma0 K+ and the ratio R(Lambda/Sigma0} is studied in a constituent quark-gluon model, including the excitation of the baryon resonances N*(1650), N*(1710) and N*(1720) near the Lambda/Sigma0 thresholds. Representing the baryons as quark-diquark objects, the energy dependent ratio Lambda/Sigma0, which is qualitatively reproduced up to excess energies of 60 MeV above threshold, provides detailed information on the momentum spectrum of axial diquarks in the proton and the Sigma0.

  5. Efficient Computation of Transition State Resonances and Reaction Rates from a Quantum Normal Form

    NARCIS (Netherlands)

    Schubert, Roman; Waalkens, Holger; Wiggins, Stephen

    2006-01-01

    A quantum version of a recent formulation of transition state theory in phase space is presented. The theory developed provides an algorithm to compute quantum reaction rates and the associated Gamov-Siegert resonances with very high accuracy. The algorithm is especially efficient for multi-degree-o

  6. Modified landfill gas generation rate model of first-order kinetics and two-stage reaction

    Institute of Scientific and Technical Information of China (English)

    Jiajun CHEN; Hao WANG; Na ZHANG

    2009-01-01

    This investigation was carried out to establish a new domestic landfill gas (LFG) generation rate model that takes into account the impact ofleachate recirculation. The first-order kinetics and two-stage reaction (FKTSR) model of the LFG generation rate includes mechanisms of the nutrient balance for biochemical reaction in two main stages. In this study, the FKTSR model was modified by the introduction of the outflow function and the organic acid conversion coefficient in order to represent the in-situ condition of nutrient loss through leachate. Laboratory experiments were carried out to simulate the impact of leachate recirculation and verify the modified FKTSR model. The model calibration was then calculated by using the experimental data. The results suggested that the new model was in line with the experimental data. The main parameters of the modified FKTSR model, including the LFG production potential (L0), the reaction rate constant in the first stage (K1), and the reaction rate constant in the second stage (K2) of 64.746 L, 0.202 d-1, and 0.338 d-1,respectively, were comparable to the old ones of 42.069 L,0.231 d-1, and 0.231 d-1. The new model is better able to explain the mechanisms involved in LFG generation.

  7. Should Thermostatted Ring Polymer Molecular Dynamics be used to calculate reaction rates?

    CERN Document Server

    Hele, Timothy J H

    2015-01-01

    We apply Thermostatted Ring Polymer Molecular Dynamics (TRPMD), a recently-proposed approximate quantum dynamics method, to the computation of thermal reaction rates. Its short-time Transition-State Theory (TST) limit is identical to rigorous Quantum Transition-State Theory, and we find that its long-time limit is independent of the location of the dividing surface. TRPMD rate theory is then applied to one-dimensional model systems, the atom-diatom bimolecular reactions H+H$_2$, D+MuH and F+H$_2$, and the prototypical polyatomic reaction H+CH$_4$. Above the crossover temperature, the TRPMD rate is virtually invariant to the strength of the friction applied to the internal ring-polymer normal modes, and beneath the crossover temperature the TRPMD rate generally decreases with increasing friction, in agreement with the predictions of Kramers theory. We therefore find that TRPMD is less accurate than Ring Polymer Molecular Dynamics (RPMD) for symmetric reactions, and in certain asymmetric systems closer to the q...

  8. Dependence of X-Ray Burst Models on Nuclear Reaction Rates

    CERN Document Server

    Cyburt, R H; Heger, A; Johnson, E; Keek, L; Meisel, Z; Schatz, H; Smith, K

    2016-01-01

    X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars and reliable burst models are needed to interpret observations in terms of properties of the neutron star and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p,$\\gamma$), ($\\alpha$,$\\gamma$), and ($\\alpha$,p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophysical conditions. A two-step approach first identified sensitive nuclear reaction rates in a single-zone model with ignition conditions chosen to match calculations with a state-of-the-art 1D multi-zone model based on the {\\Kepler} stellar evolution code. All relevant reaction rates on neutron deficient isotopes up to mass 106 were individually varied by a factor of 100 up and down. Calculations of the 84 highest impact reaction rate changes were then repeated in the 1D multi-zone model. We find a number of uncertain reac...

  9. The influence of SPS heating rates on the synthesis reaction of tantalum diboride

    Directory of Open Access Journals (Sweden)

    Jolanta Laszkiewicz-Łukasik

    2016-07-01

    Full Text Available TaB2 is a material from the Ultra High Temperature Ceramics group and is rather unexplored because it is difficult to procure the raw materials and to densify TaB2. Using SPS technique to realize reactive sintering processes of powders mixture according to the reaction Ta + 2B → TaB2 makes it possible to achieve TaB2 in one technological step. The aim of the study was to determine the influence of heating rates on the synthesis reaction and on the multistage densification mechanisms during SPS processes. The mixture was sintered at constant parameters of 2200 °C, 48 MPa for 5 min with the usage of heating rates from 50 °C/min up to 400 °C/min. The densification processes were studied through analyzing the shrinkage of powder compacts during SPS (Spark Plasma Sintering processes. The comparison of the densification curves indicates that the reactions do not proceed completely at slow heating rates. Namely, too low heating rates contribute to the sintering of tantalum before the synthesis reaction and demonstrate the presence of boron in liquid state. The best material obtained in this study has Young's modulus 571 GPa, Vickers hardness 20.7 GPa (HV1 and indentation fracture toughness KIC 4.7 MPa m1/2.

  10. Should thermostatted ring polymer molecular dynamics be used to calculate thermal reaction rates?

    Energy Technology Data Exchange (ETDEWEB)

    Hele, Timothy J. H., E-mail: tjhh2@cam.ac.uk [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Suleimanov, Yury V. [Computation-based Science and Technology Research Center, Cyprus Institute, 20 Kavafi St., Nicosia 2121 (Cyprus); Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States)

    2015-08-21

    We apply Thermostatted Ring Polymer Molecular Dynamics (TRPMD), a recently proposed approximate quantum dynamics method, to the computation of thermal reaction rates. Its short-time transition-state theory limit is identical to rigorous quantum transition-state theory, and we find that its long-time limit is independent of the location of the dividing surface. TRPMD rate theory is then applied to one-dimensional model systems, the atom-diatom bimolecular reactions H + H{sub 2}, D + MuH, and F + H{sub 2}, and the prototypical polyatomic reaction H + CH{sub 4}. Above the crossover temperature, the TRPMD rate is virtually invariant to the strength of the friction applied to the internal ring-polymer normal modes, and beneath the crossover temperature the TRPMD rate generally decreases with increasing friction, in agreement with the predictions of Kramers theory. We therefore find that TRPMD is approximately equal to, or less accurate than, ring polymer molecular dynamics for symmetric reactions, and for certain asymmetric systems and friction parameters closer to the quantum result, providing a basis for further assessment of the accuracy of this method.

  11. Effect of Conceptual Change Approach on Students' Understanding of Reaction Rate Concepts

    Science.gov (United States)

    Kingir, Sevgi; Geban, Omer

    2012-01-01

    The purpose of the present study was to investigate the effect of conceptual change text oriented instruction compared to traditional instruction on 10th grade students' understanding of reaction rate concepts. 45 students from two classes of the same teacher in a public high school participated in this study. Students in the experimental group…

  12. The Effect of Conceptual Change Pedagogy on Students' Conceptions of Rate of Reaction

    Science.gov (United States)

    Calik, Muammer; Kolomuc, Ali; Karagolge, Zafer

    2010-01-01

    This paper reports on an investigation of the effect of conceptual change pedagogy on students' conceptions of "rate of reaction" concepts. The study used a pre-test/post-test non-equivalent comparison group design approach and the sample consisted of 72 Turkish grade-11 students (aged 16-18 years) selected from two intact classrooms.…

  13. Generalization of the Activated Complex Theory of Reaction Rates. II. Classical Mechanical Treatment

    Science.gov (United States)

    Marcus, R. A.

    1964-01-01

    In its usual classical form activated complex theory assumes a particular expression for the kinetic energy of the reacting system -- one associated with a rectilinear motion along the reaction coordinate. The derivation of the rate expression given in the present paper is based on the general kinetic energy expression.

  14. Probing the Rate-Determining Step of the Claisen-Schmidt Condensation by Competition Reactions

    Science.gov (United States)

    Mak, Kendrew K. W.; Chan, Wing-Fat; Lung, Ka-Ying; Lam, Wai-Yee; Ng, Weng-Cheong; Lee, Siu-Fung

    2007-01-01

    Competition experiments are a useful tool for preliminary study of the linear free energy relationship of organic reactions. This article describes a physical organic experiment for upper-level undergraduates to identify the rate-determining step of the Claisen-Schmidt condensation of benzaldehyde and acetophenone by studying the linear free…

  15. Automated Prediction of Catalytic Mechanism and Rate Law Using Graph-Based Reaction Path Sampling.

    Science.gov (United States)

    Habershon, Scott

    2016-04-12

    In a recent article [ J. Chem. Phys. 2015 , 143 , 094106 ], we introduced a novel graph-based sampling scheme which can be used to generate chemical reaction paths in many-atom systems in an efficient and highly automated manner. The main goal of this work is to demonstrate how this approach, when combined with direct kinetic modeling, can be used to determine the mechanism and phenomenological rate law of a complex catalytic cycle, namely cobalt-catalyzed hydroformylation of ethene. Our graph-based sampling scheme generates 31 unique chemical products and 32 unique chemical reaction pathways; these sampled structures and reaction paths enable automated construction of a kinetic network model of the catalytic system when combined with density functional theory (DFT) calculations of free energies and resultant transition-state theory rate constants. Direct simulations of this kinetic network across a range of initial reactant concentrations enables determination of both the reaction mechanism and the associated rate law in an automated fashion, without the need for either presupposing a mechanism or making steady-state approximations in kinetic analysis. Most importantly, we find that the reaction mechanism which emerges from these simulations is exactly that originally proposed by Heck and Breslow; furthermore, the simulated rate law is also consistent with previous experimental and computational studies, exhibiting a complex dependence on carbon monoxide pressure. While the inherent errors of using DFT simulations to model chemical reactivity limit the quantitative accuracy of our calculated rates, this work confirms that our automated simulation strategy enables direct analysis of catalytic mechanisms from first principles.

  16. Ion-neutral gas reactions in a collision/reaction cell in inductively coupled plasma mass spectrometry: Correlation of ion signal decrease to kinetic rate constants

    Energy Technology Data Exchange (ETDEWEB)

    Gray, Patrick J. [Trace Element Research Laboratory, School of Earth Sciences, The Ohio State University, 125 S. Oval Mall, Columbus, OH 43210 (United States); Department of Chemistry, The Ohio State University, 120 18th Avenue, Columbus, OH 43210 (United States); Olesik, John W., E-mail: olesik.2@osu.edu [Trace Element Research Laboratory, School of Earth Sciences, The Ohio State University, 125 S. Oval Mall, Columbus, OH 43210 (United States)

    2015-03-01

    Reaction gas flow rate dependent Ar{sub 2}{sup +} and Ar{sup +} signals are correlated to fundamental kinetic rate coefficients. A simple calculation, assuming that gas exits the reaction cell due only to effusion, is described to estimate the gas pressure in the reaction cell. The value of the product of the kinetic rate constant and the ion residence time in the reaction cell can be determined from experimental measurement of the decrease in an ion signal as a function of reaction gas flow rate. New kinetic rate constants are determined for the reaction of CH{sub 3}F with Ar{sup +} and Ar{sub 2}{sup +}. - Highlights: • How to determine pressure and the product of the kinetic rate constant times the ion residence time in reaction cell • Relate measured ICP-DRC-MS signals versus gas flow rate to kinetic rate constants measured previously using SIFT-MS • Describe how to determine previously unmeasured kinetic rate constants using ICP-DRC-MS.

  17. Quantifying plyometric intensity via rate of force development, knee joint, and ground reaction forces.

    Science.gov (United States)

    Jensen, Randall L; Ebben, William P

    2007-08-01

    Because the intensity of plyometric exercises usually is based simply upon anecdotal recommendations rather than empirical evidence, this study sought to quantify a variety of these exercises based on forces placed upon the knee. Six National Collegiate Athletic Association Division I athletes who routinely trained with plyometric exercises performed depth jumps from 46 and 61 cm, a pike jump, tuck jump, single-leg jump, countermovement jump, squat jump, and a squat jump holding dumbbells equal to 30% of 1 repetition maximum (RM). Ground reaction forces obtained via an AMTI force plate and video analysis of markers placed on the left hip, knee, lateral malleolus, and fifth metatarsal were used to estimate rate of eccentric force development (E-RFD), peak ground reaction forces (GRF), ground reaction forces relative to body weight (GRF/BW), knee joint reaction forces (K-JRF), and knee joint reaction forces relative to body weight (K-JRF/BW) for each plyometric exercise. One-way repeated measures analysis of variance indicated that E-RFD, K-JRF, and K-JRF/BW were different across the conditions (p 0.05). Results indicate that there are quantitative differences between plyometric exercises in the rate of force development during landing and the forces placed on the knee, though peak GRF forces associated with landing may not differ.

  18. Astrophysical reaction rate for alpha(alpha n,gamma) sup 9 Be by photodisintegration

    CERN Document Server

    Sumiyoshi, K; Goko, S; Kajino, T

    2002-01-01

    We study the astrophysical reaction rate for the formation of sup 9 Be through the three body reaction alpha(alpha n,gamma). This reaction is one of the key reactions which could bridge the mass gap at A=8 nuclear systems to produce intermediate-to-heavy mass elements in alpha- and neutron-rich environments such as r-process nucleosynthesis in supernova explosions, s-process nucleosynthesis in asymptotic giant branch (AGB) stars, and primordial nucleosynthesis in baryon inhomogeneous cosmological models. To calculate the thermonuclear reaction rate in a wide range of temperatures, we numerically integrate the thermal average of cross sections assuming a two-steps formation through a metastable sup 8 Be, alpha+alpha[rlhar2] sup 8 Be(n,gamma) sup 9 Be. Off-resonant and on-resonant contributions from the ground state in sup 8 Be are taken into account. As input cross section, we adopt the latest experimental data by photodisintegration of sup 9 Be with laser-electron photon beams, which covers all relevant reson...

  19. A randomised controlled trial of two infusion rates to decrease reactions to antivenom.

    Directory of Open Access Journals (Sweden)

    Geoffrey K Isbister

    Full Text Available BACKGROUND: Snake envenoming is a major clinical problem in Sri Lanka, with an estimated 40,000 bites annually. Antivenom is only available from India and there is a high rate of systemic hypersensitivity reactions. This study aimed to investigate whether the rate of infusion of antivenom reduced the frequency of severe systemic hypersensitivity reactions. METHODS AND FINDINGS: This was a randomized comparison trial of two infusion rates of antivenom for treatment of non-pregnant adult patients (>14 y with snake envenoming in Sri Lanka. Snake identification was by patient or hospital examination of dead snakes when available and confirmed by enzyme-immunoassay for Russell's viper envenoming. Patients were blindly allocated in a 11 randomisation schedule to receive antivenom either as a 20 minute infusion (rapid or a two hour infusion (slow. The primary outcome was the proportion with severe systemic hypersensitivity reactions (grade 3 by Brown grading system within 4 hours of commencement of antivenom. Secondary outcomes included the proportion with mild/moderate hypersensitivity reactions and repeat antivenom doses. Of 1004 patients with suspected snakebites, 247 patients received antivenom. 49 patients were excluded or not recruited leaving 104 patients allocated to the rapid antivenom infusion and 94 to the slow antivenom infusion. The median actual duration of antivenom infusion in the rapid group was 20 min (Interquartile range[IQR]:20-25 min versus 120 min (IQR:75-120 min in the slow group. There was no difference in severe systemic hypersensitivity reactions between those given rapid and slow infusions (32% vs. 35%; difference 3%; 95%CI:-10% to +17%;p = 0.65. The frequency of mild/moderate reactions was also similar. Similar numbers of patients in each arm received further doses of antivenom (30/104 vs. 23/94. CONCLUSIONS: A slower infusion rate would not reduce the rate of severe systemic hypersensitivity reactions from current high

  20. α-Terpineol reactions with the nitrate radical: Rate constant and gas-phase products

    Science.gov (United States)

    Jones, Brian T.; Ham, Jason E.

    The bimolecular rate constant of k rad +α-terpineol (16 ± 4) × 10 -12 cm 3 molecule -1 s -1 was measured using the relative rate technique for the reaction of the nitrate radical (NO 3rad ) with α-terpineol (2-(4-methyl-1-cyclohex-3-enyl)propan-2-ol) at 297 ± 3 K and 1 atmosphere total pressure. To more clearly define part of α-terpineol's indoor environment degradation mechanism, the products of α-terpineol + NO 3rad reaction were investigated. The identified reaction products were: acetone, glyoxal (HC( dbnd O)C( dbnd O)H), and methylglyoxal (CH 3C( dbnd O)C( dbnd O)H). The use of derivatizing agents O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) and N, O-bis(trimethylsilyl) trifluoroacetamide (BSTFA) were used to propose the other major reaction products: 6-hydroxyhept-5-en-2-one, 4-(1-hydroxy-1-methylethyl)-1-methyl-2-oxocyclohexyl nitrate, 5-(1-hydroxy-1-methylethyl)-2-oxocyclohexyl nitrate, 1-formyl-5-hydroxy-4-(hydroxymethyl)-1,5-dimethylhexyl nitrate, and 1,4-diformyl-5-hydroxy-1,5-dimethylhexyl nitrate. The elucidation of these products was facilitated by mass spectrometry of the derivatized reaction products coupled with plausible α-terpineol + NO 3rad reaction mechanisms based on previously published volatile organic compound + NO 3rad gas-phase mechanisms. The additional gas-phase products (2,6,6-trimethyltetrahydro-2 H-pyran-2,5-dicarbaldehyde and 2,2-dimethylcyclohexane-1,4-dicarbaldehyde) are proposed to be the result of cyclization through a reaction intermediate.

  1. Helium Ignition on Accreting Neutron Stars with a New Triple-α Reaction Rate

    Science.gov (United States)

    Peng, Fang; Ott, Christian D.

    2010-12-01

    We investigate the effect of a new triple-α reaction rate from Ogata et al. on helium ignition conditions on accreting neutron stars and on the properties of the subsequent type I X-ray burst. We find that the new rate leads to significantly lower ignition column density for accreting neutron stars at low accretion rates. We compare the results of our ignition models for a pure helium accretor to observations of bursts in ultracompact X-ray binaries (UCXBs), which are believed to have nearly pure helium donors. For \\dot{m}> 0.001 \\dot{m}_{{Edd}}, the new triple-α reaction rate from Ogata et al. predicts a maximum helium ignition column of ~3 × 109 g cm-2, corresponding to a burst energy of ~4 × 1040 erg. For \\dot{m}˜ 0.01 \\dot{m}_{{Edd}} at which intermediate long bursts occur, the predicted burst energies are at least a factor of 10 too low to explain the observed energies of such bursts in UCXBs. This finding adds to the doubts cast on the triple-α reaction rate of Ogata et al. by the low-mass stellar evolution results of Dotter & Paxton.

  2. Helium Ignition on Accreting Neutron Stars with a New Triple-alpha Reaction Rate

    CERN Document Server

    Peng, Fang

    2010-01-01

    We investigate the effect of a new triple-alpha reaction rate from Ogata et al. (2009) on helium ignition conditions on accreting neutron stars and on the properties of the subsequent type I X-ray burst. We find that the new rate leads to significantly lower ignition column density for accreting neutron stars at low accretion rates. We compare the results of our ignition models for a pure helium accretor to observations of bursts in ultra-compact X-ray binary (UCXBs), which are believed to have nearly pure helium donors. For mdot > 0.001 mdot_Edd, the new triple-alpha reaction rate from Ogata et al. (2009) predicts a maximum helium ignition column of ~ 3 x 10^9 g cm^{-2}, corresponding to a burst energy of ~ 4 x 10^{40} ergs. For mdot ~ 0.01 mdot_Edd at which intermediate long bursts occur, the predicted burst energies are at least a factor of 10 too low to explain the observed energies of such bursts in UCXBs. This finding adds to the doubts cast on the triple-alpha reaction rate of Ogata et al. (2009) by th...

  3. Quantum three-body calculation of the nonresonant triple-\\alpha reaction rate at low temperatures

    CERN Document Server

    Ogata, Kazuyuki; Kamimura, Masayasu

    2009-01-01

    The triple-\\alpha reaction rate is re-evaluated by directly solving the three-body Schroedinger equation. The resonant and nonresonant processes are treated on the same footing using the continuum-discretized coupled-channels method for three-body scattering. Accurate description of the \\alpha-\\alpha nonresonant states significantly quenches the Coulomb barrier between the two-\\alpha's and the third \\alpha particle. Consequently, the \\alpha-\\alpha nonresonant continuum states below the resonance at 92.04 keV, i.e., the ground state of 8Be, give markedly larger contribution at low temperatures than in foregoing studies. We find about 20 orders-of-magnitude enhancement of the triple-\\alpha reaction rate around 10^7 K compared to the rate of the NACRE compilation.

  4. Reaction rates for the s-process neutron source 22Ne+{\\alpha}

    CERN Document Server

    Longland, Richard; Karakas, Amanda I

    2012-01-01

    The 22Ne({\\alpha},n)25Mg reaction is an important source of neutrons for the s-process. In massive stars responsible for the weak component of the s-process, 22Ne({\\alpha},n)25Mg is the dominant source of neutrons, both during core helium burning and in shell carbon burning. For the main s-process component produced in Asymptotic Giant Branch (AGB) stars, the 13C({\\alpha},n)16O reaction is the dominant source of neutrons operating during the interpulse period, with the 22Ne+{\\alpha} source affecting mainly the s-process branchings during a thermal pulse. Rate uncertainties in the competing 22Ne({\\alpha},n)25Mg and 22Ne({\\alpha},{\\gamma})26Mg reactions result in large variations of s-process nucleosynthesis. Here, we present up-to-date and statistically rigorous 22Ne+{\\alpha} reaction rates using recent experimental results and Monte Carlo sampling. Our new rates are used in post-processing nucleosynthesis calculations both for massive stars and AGB stars. We demonstrate that the nucleosynthesis uncertainties ...

  5. Reevaluation of thermonuclear reaction rate of 50Fe(p,gamma)51Co

    CERN Document Server

    Zhang, L P; Chai, W D; Hou, S Q; Zhang, L Y

    2016-01-01

    The thermonuclear rate of the 50Fe(p,gamma)51Co reaction in the Type I X-ray bursts (XRBs) temperature range has been reevaluated based on a recent precise mass measurement at CSRe lanzhou, where the proton separation energy Sp=142+/-77 keV has been determined firstly for the 51Co nucleus. Comparing to the previous theoretical predictions, the experimental Sp value has much smaller uncertainty. Based on the nuclear shell model and mirror nuclear structure information, we have calculated two sets of thermonuclear rates for the 50Fe(p,gamma)51Co reaction by utilizing the experimental Sp value. It shows that the statistical-model calculations are not ideally applicable for this reaction primarily because of the low density of low-lying excited states in 51Co. In this work, we recommend that a set of new reaction rate based on the mirror structure of 51Cr should be incorporated in the future astrophysical network calculations.

  6. Nuclear Reaction Rates in a Plasma The Effect of Highly Damped Modes

    CERN Document Server

    Opher, M; Opher, Merav; Opher, Reuven

    2000-01-01

    The fluctuation-dissipation theorem is used to evaluate the screening factor of nuclear reactions due to the electromagnetic fluctuations in a plasma. We show that the commonly used Saltpeter factor is obtained if only fluctuations near the plasma eigenfrequency are assumed to be important (\\omega \\sim \\omega_{pe}\\ll T (\\hbar=k_{B}=1)). By taking into account all the fluctuations, the highly damped ones, with \\omega >\\omega_{pe}, as well as those with \\omega\\leq\\omega_{pe}, we find that nuclear reaction rates are higher than those obtained using the Saltpeter factor, for many interesting plasmas.

  7. APPRAISAL OF STUDENT RATING AS A MEASURE TO MANAGE THE QUALITY OF HIGHER EDUCATION IN INDIA: AN INSTITUTIONAL STUDY USING SIX SIGMA MODEL APPROACH

    OpenAIRE

    Arun Vijay

    2013-01-01

    Students' rating of teaching is one of the most widely accepted methods of measuring the quality in Higher Education worldwide. The overall experience gained by the students during their academic journey in their respective college is a key factor to determine the Institutional Quality. This study was conducted among the Physical Therapy students with an objective to capture the overall experience related to various aspects of their Academic environment including teaching and learning process...

  8. Observation of the Heavy Baryons Sigma b and Sigma b*.

    Science.gov (United States)

    Aaltonen, T; Abulencia, A; Adelman, J; Affolder, T; Akimoto, T; Albrow, M G; Amerio, S; Amidei, D; Anastassov, A; Anikeev, K; Annovi, A; Antos, J; Aoki, M; Apollinari, G; Arisawa, T; Artikov, A; Ashmanskas, W; Attal, A; Aurisano, A; Azfar, F; Azzi-Bacchetta, P; Azzurri, P; Bacchetta, N; Badgett, W; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Bartsch, V; Bauer, G; Beauchemin, P-H; Bedeschi, F; Behari, S; Bellettini, G; Bellinger, J; Belloni, A; Benjamin, D; Beretvas, A; Beringer, J; Berry, T; Bhatti, A; Binkley, M; Bisello, D; Bizjak, I; Blair, R E; Blocker, C; Blumenfeld, B; Bocci, A; Bodek, A; Boisvert, V; Bolla, G; Bolshov, A; Bortoletto, D; Boudreau, J; Boveia, A; Brau, B; Brigliadori, L; Bromberg, C; Brubaker, E; Budagov, J; Budd, H S; Budd, S; Burkett, K; Busetto, G; Bussey, P; Buzatu, A; Byrum, K L; Cabrera, S; Campanelli, M; Campbell, M; Canelli, F; Canepa, A; Carillo, S; Carlsmith, D; Carosi, R; Carron, S; Casal, B; Casarsa, M; Castro, A; Catastini, P; Cauz, D; Cavalli-Sforza, M; Cerri, A; Cerrito, L; Chang, S H; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, I; Cho, K; Chokheli, D; Chou, J P; Choudalakis, G; Chuang, S H; Chung, K; Chung, W H; Chung, Y S; Cilijak, M; Ciobanu, C I; Ciocci, M A; Clark, A; Clark, D; Coca, M; Compostella, G; Convery, M E; Conway, J; Cooper, B; Copic, K; Cordelli, M; Cortiana, G; Crescioli, F; Cuenca Almenar, C; Cuevas, J; Culbertson, R; Cully, J C; DaRonco, S; Datta, M; D'Auria, S; Davies, T; Dagenhart, D; de Barbaro, P; De Cecco, S; Deisher, A; De Lentdecker, G; De Lorenzo, G; Dell'Orso, M; Delli Paoli, F; Demortier, L; Deng, J; Deninno, M; De Pedis, D; Derwent, P F; Di Giovanni, G P; Dionisi, C; Di Ruzza, B; Dittmann, J R; D'Onofrio, M; Dörr, C; Donati, S; Dong, P; Donini, J; Dorigo, T; Dube, S; Efron, J; Erbacher, R; Errede, D; Errede, S; Eusebi, R; Fang, H C; Farrington, S; Fedorko, I; Fedorko, W T; Feild, R G; Feindt, M; Fernandez, J P; Field, R; Flanagan, G; Forrest, R; Forrester, S; Franklin, M; Freeman, J C; Furic, I; Gallinaro, M; Galyardt, J; Garcia, J E; Garberson, F; Garfinkel, A F; Gay, C; Gerberich, H; Gerdes, D; Giagu, S; Giannetti, P; Gibson, K; Gimmell, J L; Ginsburg, C; Giokaris, N; Giordani, M; Giromini, P; Giunta, M; Giurgiu, G; Glagolev, V; Glenzinski, D; Gold, M; Goldschmidt, N; Goldstein, J; Golossanov, A; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Goulianos, K; Gresele, A; Grinstein, S; Grosso-Pilcher, C; Grundler, U; Guimaraes da Costa, J; Gunay-Unalan, Z; Haber, C; Hahn, K; Hahn, S R; Halkiadakis, E; Hamilton, A; Han, B-Y; Han, J Y; Handler, R; Happacher, F; Hara, K; Hare, D; Hare, M; Harper, S; Harr, R F; Harris, R M; Hartz, M; Hatakeyama, K; Hauser, J; Hays, C; Heck, M; Heijboer, A; Heinemann, B; Heinrich, J; Henderson, C; Herndon, M; Heuser, J; Hidas, D; Hill, C S; Hirschbuehl, D; Hocker, A; Holloway, A; Hou, S; Houlden, M; Hsu, S-C; Huffman, B T; Hughes, R E; Husemann, U; Huston, J; Incandela, J; Introzzi, G; Iori, M; Ivanov, A; Iyutin, B; James, E; Jang, D; Jayatilaka, B; Jeans, D; Jeon, E J; Jindariani, S; Johnson, W; Jones, M; Joo, K K; Jun, S Y; Jung, J E; Junk, T R; Kamon, T; Karchin, P E; Kato, Y; Kemp, Y; Kephart, R; Kerzel, U; Khotilovich, V; Kilminster, B; Kim, D H; Kim, H S; Kim, J E; Kim, M J; Kim, S B; Kim, S H; Kim, Y K; Kimura, N; Kirsch, L; Klimenko, S; Klute, M; Knuteson, B; Ko, B R; Kondo, K; Kong, D J; Konigsberg, J; Korytov, A; Kotwal, A V; Kraan, A C; Kraus, J; Kreps, M; Kroll, J; Krumnack, N; Kruse, M; Krutelyov, V; Kubo, T; Kuhlmann, S E; Kuhr, T; Kulkarni, N P; Kusakabe, Y; Kwang, S; Laasanen, A T; Lai, S; Lami, S; Lammel, S; Lancaster, M; Lander, R L; Lannon, K; Lath, A; Latino, G; Lazzizzera, I; LeCompte, T; Lee, J; Lee, J; Lee, Y J; Lee, S W; Lefèvre, R; Leonardo, N; Leone, S; Levy, S; Lewis, J D; Lin, C; Lin, C S; Lindgren, M; Lipeles, E; Lister, A; Litvintsev, D O; Liu, T; Lockyer, N S; Loginov, A; Loreti, M; Lu, R-S; Lucchesi, D; Lujan, P; Lukens, P; Lungu, G; Lyons, L; Lys, J; Lysak, R; Lytken, E; Mack, P; MacQueen, D; Madrak, R; Maeshima, K; Makhoul, K; Maki, T; Maksimovic, P; Malde, S; Malik, S; Manca, G; Manousakis, A; Margaroli, F; Marginean, R; Marino, C; Marino, C P; Martin, A; Martin, M; Martin, V; Martínez, M; Martínez-Ballarín, R; Maruyama, T; Mastrandrea, P; Masubuchi, T; Matsunaga, H; Mattson, M E; Mazini, R; Mazzanti, P; McFarland, K S; McIntyre, P; McNulty, R; Mehta, A; Mehtala, P; Menzemer, S; Menzione, A; Merkel, P; Mesropian, C; Messina, A; Miao, T; Miladinovic, N; Miles, J; Miller, R; Mills, C; Milnik, M; Mitra, A; Mitselmakher, G; Miyamoto, A; Moed, S; Moggi, N; Mohr, B; Moon, C S; Moore, R; Morello, M; Movilla Fernandez, P; Mülmenstädt, J; Mukherjee, A; Muller, Th; Mumford, R; Murat, P; Mussini, M; Nachtman, J; Nagano, A; Naganoma, J; Nakamura, K; Nakano, I; Napier, A; Necula, V; Neu, C; Neubauer, M S; Nielsen, J; Nodulman, L; Norniella, O; Nurse, E; Oh, S H; Oh, Y D; Oksuzian, I; Okusawa, T; Oldeman, R; Orava, R; Osterberg, K; Pagliarone, C; Palencia, E; Papadimitriou, V; Papaikonomou, A; Paramonov, A A; Parks, B; Pashapour, S; Patrick, J; Pauletta, G; Paulini, M; Paus, C; Pellett, D E; Penzo, A; Phillips, T J; Piacentino, G; Piedra, J; Pinera, L; Pitts, K; Plager, C; Pondrom, L; Portell, X; Poukhov, O; Pounder, N; Prakoshyn, F; Pronko, A; Proudfoot, J; Ptohos, F; Punzi, G; Pursley, J; Rademacker, J; Rahaman, A; Ramakrishnan, V; Ranjan, N; Redondo, I; Reisert, B; Rekovic, V; Renton, P; Rescigno, M; Richter, S; Rimondi, F; Ristori, L; Robson, A; Rodrigo, T; Rogers, E; Rolli, S; Roser, R; Rossi, M; Rossin, R; Roy, P; Ruiz, A; Russ, J; Rusu, V; Saarikko, H; Safonov, A; Sakumoto, W K; Salamanna, G; Saltó, O; Santi, L; Sarkar, S; Sartori, L; Sato, K; Savard, P; Savoy-Navarro, A; Scheidle, T; Schlabach, P; Schmidt, E E; Schmidt, M A; Schmidt, M P; Schmitt, M; Schwarz, T; Scodellaro, L; Scott, A L; Scribano, A; Scuri, F; Sedov, A; Seidel, S; Seiya, Y; Semenov, A; Sexton-Kennedy, L; Sfyrla, A; Shalhout, S Z; Shapiro, M D; Shears, T; Shepard, P F; Sherman, D; Shimojima, M; Shochet, M; Shon, Y; Shreyber, I; Sidoti, A; Sinervo, P; Sisakyan, A; Slaughter, A J; Slaunwhite, J; Sliwa, K; Smith, J R; Snider, F D; Snihur, R; Soderberg, M; Soha, A; Somalwar, S; Sorin, V; Spalding, J; Spinella, F; Spreitzer, T; Squillacioti, P; Stanitzki, M; Staveris-Polykalas, A; St Denis, R; Stelzer, B; Stelzer-Chilton, O; Stentz, D; Strologas, J; Stuart, D; Suh, J S; Sukhanov, A; Sun, H; Suslov, I; Suzuki, T; Taffard, A; Takashima, R; Takeuchi, Y; Tanaka, R; Tecchio, M; Teng, P K; Terashi, K; Tesarek, R J; Thom, J; Thompson, A S; Thomson, E; Tipton, P; Tiwari, V; Tkaczyk, S; Toback, D; Tokar, S; Tollefson, K; Tomura, T; Tonelli, D; Torre, S; Torretta, D; Tourneur, S; Trischuk, W; Tsuno, S; Tu, Y; Turini, N; Ukegawa, F; Uozumi, S; Vallecorsa, S; van Remortel, N; Varganov, A; Vataga, E; Vazquez, F; Velev, G; Vellidis, C; Veramendi, G; Veszpremi, V; Vidal, M; Vidal, R; Vila, I; Vilar, R; Vine, T; Vogel, M; Vollrath, I; Volobouev, I; Volpi, G; Würthwein, F; Wagner, P; Wagner, R G; Wagner, R L; Wagner, J; Wagner, W; Wallny, R; Wang, S M; Warburton, A; Waters, D; Weinberger, M; Wester, W C; Whitehouse, B; Whiteson, D; Wicklund, A B; Wicklund, E; Williams, G; Williams, H H; Wilson, P; Winer, B L; Wittich, P; Wolbers, S; Wolfe, C; Wright, T; Wu, X; Wynne, S M; Yagil, A; Yamamoto, K; Yamaoka, J; Yamashita, T; Yang, C; Yang, U K; Yang, Y C; Yao, W M; Yeh, G P; Yoh, J; Yorita, K; Yoshida, T; Yu, G B; Yu, I; Yu, S S; Yun, J C; Zanello, L; Zanetti, A; Zaw, I; Zhang, X; Zhou, J; Zucchelli, S

    2007-11-16

    We report an observation of new bottom baryons produced in pp collisions at the Tevatron. Using 1.1 fb(-1) of data collected by the CDF II detector, we observe four Lambda b 0 pi+/- resonances in the fully reconstructed decay mode Lambda b 0-->Lambda c + pi-, where Lambda c+-->pK* pi+. We interpret these states as the Sigma b(*)+/- baryons and measure the following masses: m Sigma b+=5807.8 -2.2 +2.0(stat.)+/-1.7(syst.) MeV/c2, m Sigma b- =5815.2+/-1.0(stat.)+/-1.7(syst.) MeV/c2, and m(Sigma b*)-m(Sigma b)=21.2-1.9 +2.0(stat.)-0.3+0.4(syst.) MeV/c2.

  9. Two effects relevant for the study of astrophysical reaction rates: gamma transitions in capture reactions and Coulomb suppression of the stellar enhancement

    CERN Document Server

    Rauscher, T

    2008-01-01

    Nucleosynthesis processes involve reactions on several thousand nuclei, both close to and far off stability. The preparation of reaction rates to be used in astrophysical investigations requires experimental and theoretical input. In this context, two interesting aspects are discussed: (i) the relevant gamma transition energies in astrophysical capture reactions, and (ii) the newly discovered Coulomb suppression of the stellar enhancement factor. The latter makes a number of reactions with negative Q value more favorable for experimental investigation than their inverse reactions, contrary to common belief.

  10. On the Temperature Dependence of the Rate Constant of the Bimolecular Reaction of two Hydrated Electrons

    Directory of Open Access Journals (Sweden)

    S.L. Butarbutar

    2013-08-01

    Full Text Available It has been a longstanding issue in the radiation chemistry of water that, even though H2 is a molecular product, its “escape” yield g(H2 increases with increasing temperature. A main source of H2 is the bimolecular reaction of two hydrated electrons (eaq. The temperature dependence of the rate constant of this reaction (k1, measured under alkaline conditions, reveals that the rate constant drops abruptly above ~150°C. Recently, it has been suggested that this temperature dependence should be regarded as being independent of pH and used in high-temperature modeling of near-neutral water radiolysis. However, when this drop in the eaq self-reaction rate constant is included in low (isolated spurs and high (cylindrical tracks linear energy transfer (LET modeling calculations, g(H2 shows a marked downward discontinuity at ~150°C which is not observed experimentally. The consequences of the presence of this discontinuity in g(H2 for both low and high LET radiation are briefly discussed in this communication. It is concluded that the applicability of the sudden drop in k1 observed at ~150°C in alkaline water to near-neutral water is questionable and that further measurements of the rate constant in pure water are highly desirable.

  11. Formulation of a universal first-order rate constant for enzymatic reactions.

    Science.gov (United States)

    Imoto, Taiji

    2013-01-01

    It is a common practice to employ k(cat)[E]₀/K(m) as a first-order rate constant for the analysis of an enzymatic reaction, where [E]₀ is the total enzyme concentration. I describe in this report a serious shortcoming in analyzing enzymatic reactions when kcat[E]₀/K(m) is employed and show that k(cat)[E]₀/K(m) can only be applied under very limited conditions. I consequently propose the use of a more universal first-order rate constant, k(cat)[ES](K)/[S]₀, where [ES](K) is the initial equilibrium concentration of the ES-complex derived from [E]₀, [S]₀ and K(m). Employing k(cat)[ES](K)/[S]₀ as the first-order rate constant enables all enzymatic reactions to be reasonably simulated under a wide range of conditions, and the catalytic and binding contributions to the rate constant of any enzyme can be determined under any and all conditions.

  12. Rate constant for the reaction SO + BrO yields SO2 + Br

    Science.gov (United States)

    Brunning, J.; Stief, L.

    1986-01-01

    The rate of the radical-radical reaction SO + BrO yields SO2 + Br has been determined at 298 K in a discharge flow system near 1 torr pressure with detection of SO and BrO via collision-free sampling mass spectrometry. The rate constant was determined using two different methods: measuring the decay of SO radicals in the presence of an excess of BrO and measuring the decay of BrO radicals in excess SO. The results from the two methods are in reasonable agreement and the simple mean of the two values gives the recommended rate constant at 298 K, k = (5.7 + or - 2.0) x 10 to the -11th cu cm/s. This represents the first determination of this rate constant and it is consistent with a previously derived lower limit based on SO2 formation. Comparison is made with other radical-radical reactions involving SO or BrO. The reaction SO + BrO yields SO2 + Br is of interest for models of the upper atmosphere of the earth and provides a potential coupling between atmospheric sulfur and bromine chemistry.

  13. 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.

  14. An efficient Monte Carlo method for calculating ab initio transition state theory reaction rates in solution

    CERN Document Server

    Iftimie, R; Schofield, J P; Iftimie, Radu; Salahub, Dennis; Schofield, Jeremy

    2003-01-01

    In this article, we propose an efficient method for sampling the relevant state space in condensed phase reactions. In the present method, the reaction is described by solving the electronic Schr\\"{o}dinger equation for the solute atoms in the presence of explicit solvent molecules. The sampling algorithm uses a molecular mechanics guiding potential in combination with simulated tempering ideas and allows thorough exploration of the solvent state space in the context of an ab initio calculation even when the dielectric relaxation time of the solvent is long. The method is applied to the study of the double proton transfer reaction that takes place between a molecule of acetic acid and a molecule of methanol in tetrahydrofuran. It is demonstrated that calculations of rates of chemical transformations occurring in solvents of medium polarity can be performed with an increase in the cpu time of factors ranging from 4 to 15 with respect to gas-phase calculations.

  15. Light elements burning reaction rates at stellar temperatures as deduced by the Trojan Horse measurements

    Energy Technology Data Exchange (ETDEWEB)

    Lamia, L. [Dipartimento di Fisica e Astronomia, Università degli Studi di Catania, Catania (Italy); Spitaleri, C. [Dipartimento di Fisica e Astronomia, Università degli Studi di Catania, Catania, Italy and INFN-Laboratori Nazionali del Sud, Catania (Italy); La Cognata, M.; Palmerini, S.; Sergi, M. L. [INFN-Laboratori Nazionali del Sud, Catania (Italy); Puglia, S. M. R. [INFN-Laboratori Nazionali del Sud, Catania, Italy and Dipartimento di Fisica e Astronomia, Università degli Studi di Catania, Catania (Italy)

    2015-02-24

    Experimental nuclear astrophysics aims at determining the reaction rates for astrophysically relevant reactions at their Gamow energies. For charged-particle induced reactions, the access to these energies is usually hindered, in direct measurements, by the presence of the Coulomb barrier between the interacting particles or by electron screening effects, which make hard the determination of the bare-nucleus S(E)-factor of interest for astrophysical codes. The use of the Trojan Horse Method (THM) appears as one of the most suitable tools for investigating nuclear processes of interest for astrophysics. Here, in view of the recent TH measurements, the main destruction channels for deuterium ({sup 2}H), for the two lithium {sup 6,7}Li isotopes, for the {sup 9}Be and the one for the two boron {sup 10,11}B isotopes will be discussed.

  16. Reaction Rate Distributions and Ratios in FR0 Assemblies 1, 2 and 3

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, T.L.

    1966-06-15

    The spatial distribution of different reaction rates and reaction ratios in Assemblies 1, 2 and 3 of the fast reactor FR0 was measured by fission chamber scans and foil activation technique. Assemblies 1 and 2 had cores of undiluted fuel (uranium metal enriched to 20 % U{sup 235}) while the core of Assembly 3 was diluted with about 30 vol. % graphite. All the systems had a thick copper reflector, The experimental results were compared with calculated values obtained from DSN and TDC multigroup spectra and group cross-section sets for the reactions. Good agreement between experiment and calculations is generally obtained in the core region but in the reflector the neutron spectrum is calculated too hard.

  17. Mathematical Formalism of Nonequilibrium Thermodynamics for Nonlinear Chemical Reaction Systems with General Rate Law

    Science.gov (United States)

    Ge, Hao; Qian, Hong

    2017-01-01

    This paper studies a mathematical formalism of nonequilibrium thermodynamics for chemical reaction models with N species, M reactions, and general rate law. We establish a mathematical basis for J. W. Gibbs' macroscopic chemical thermodynamics under G. N. Lewis' kinetic law of entire equilibrium (detailed balance in nonlinear chemical kinetics). In doing so, the equilibrium thermodynamics is then naturally generalized to nonequilibrium settings without detailed balance. The kinetic models are represented by a Markovian jumping process. A generalized macroscopic chemical free energy function and its associated balance equation with nonnegative source and sink are the major discoveries. The proof is based on the large deviation principle of this type of Markov processes. A general fluctuation dissipation theorem for stochastic reaction kinetics is also proved. The mathematical theory illustrates how a novel macroscopic dynamic law can emerges from the mesoscopic kinetics in a multi-scale system.

  18. Electron capture rates in stars studied with heavy ion charge exchange reactions

    CERN Document Server

    Bertulani, C A

    2015-01-01

    Indirect methods using nucleus-nucleus reactions at high energies (here, high energies mean $\\sim$ 50 MeV/nucleon and higher) are now routinely used to extract information of interest for nuclear astrophysics. This is of extreme relevance as many of the nuclei involved in stellar evolution are short-lived. Therefore, indirect methods became the focus of recent studies carried out in major nuclear physics facilities. Among such methods, heavy ion charge exchange is thought to be a useful tool to infer Gamow-Teller matrix elements needed to describe electron capture rates in stars and also double beta-decay experiments. In this short review, I provide a theoretical guidance based on a simple reaction model for charge exchange reactions.

  19. Learned cardiac control with heart rate biofeedback transfers to emotional reactions.

    Directory of Open Access Journals (Sweden)

    Nathalie Peira

    Full Text Available Emotions involve subjective feelings, action tendencies and physiological reactions. Earlier findings suggest that biofeedback might provide a way to regulate the physiological components of emotions. The present study investigates if learned heart rate regulation with biofeedback transfers to emotional situations without biofeedback. First, participants learned to decrease heart rate using biofeedback. Then, inter-individual differences in the acquired skill predicted how well they could decrease heart rate reactivity when later exposed to negative arousing pictures without biofeedback. These findings suggest that (i short lasting biofeedback training improves heart rate regulation and (ii the learned ability transfers to emotion challenging situations without biofeedback. Thus, heart rate biofeedback training may enable regulation of bodily aspects of emotion also when feedback is not available.

  20. Learned cardiac control with heart rate biofeedback transfers to emotional reactions.

    Science.gov (United States)

    Peira, Nathalie; Pourtois, Gilles; Fredrikson, Mats

    2013-01-01

    Emotions involve subjective feelings, action tendencies and physiological reactions. Earlier findings suggest that biofeedback might provide a way to regulate the physiological components of emotions. The present study investigates if learned heart rate regulation with biofeedback transfers to emotional situations without biofeedback. First, participants learned to decrease heart rate using biofeedback. Then, inter-individual differences in the acquired skill predicted how well they could decrease heart rate reactivity when later exposed to negative arousing pictures without biofeedback. These findings suggest that (i) short lasting biofeedback training improves heart rate regulation and (ii) the learned ability transfers to emotion challenging situations without biofeedback. Thus, heart rate biofeedback training may enable regulation of bodily aspects of emotion also when feedback is not available.

  1. Determination of collisional quenching rate coefficient of {{\\rm{N}}}_{2}({{\\rm{A}}}^{3}{{\\rm{\\Sigma }}}_{{\\rm{u}}}^{+}) by H2O

    Science.gov (United States)

    Suzuki, S.; Itoh, H.

    2017-06-01

    The measurement of the effective lifetime of {{{N}}}2({{{A}}}3{{{Σ }}}{{u}}+) in mixtures of nitrogen and small amounts of H2O (10.2 and 103 ppm) was carried out while observing the transient ionization current after turning off the ultraviolet (UV) light illuminating the cathode in a non-self-sustained Townsend discharge region. The transient current was formed by the emitted current sustained by the γ m action of metastable excited molecules {{{N}}}2({{{A}}}3{{{Σ }}}{{u}}+), which were produced by the impact of electrons with nitrogen molecules in the gap, and returned to the cathode by diffusion. Then, the collisional quenching rate coefficient of {{{N}}}2({{{A}}}3{{{Σ }}}{{u}}+) by H2O, the diffusion coefficient of {{{N}}}2({{{A}}}3{{{Σ }}}{{u}}+), and the reflection coefficient of {{{N}}}2({{{A}}}3{{{Σ }}}{{u}}+) at the cathode surface were determined from the observed effective lifetime of {{{N}}}2({{{A}}}3{{{Σ }}}{{u}}+) by an analytical procedure based on solving the diffusion equation. The obtained collisional quenching rate coefficient of {{{N}}}2({{{A}}}3{{{Σ }}}{{u}}+,{v}=0) by H2O was (5.7 ± 0.6) × 10-13 cm3 s-1.

  2. The effects of physical and geochemical heterogeneities on hydro-geochemical transport and effective reaction rates.

    Science.gov (United States)

    Atchley, Adam L; Navarre-Sitchler, Alexis K; Maxwell, Reed M

    2014-09-01

    The role of coupled physical and geochemical heterogeneities in hydro-geochemical transport is investigated by simulating three-dimensional transport in a heterogeneous system with kinetic mineral reactions. Ensembles of 100 physically heterogeneous realizations were simulated for three geochemical conditions: 1) spatially homogeneous reactive mineral surface area, 2) reactive surface area positively correlated to hydraulic heterogeneity, and 3) reactive surface area negatively correlated to hydraulic heterogeneity. Groundwater chemistry and the corresponding effective reaction rates were calculated at three transverse planes to quantify differences in plume evolution due to heterogeneity in mineral reaction rates and solute residence time (τ). The model is based on a hypothetical CO2 intrusion into groundwater from a carbon capture utilization and storage (CCUS) operation where CO2 dissolution and formation of carbonic acid created geochemical dis-equilibrium between fluids and the mineral galena that resulted in increased aqueous lead (Pb(2+)) concentrations. Calcite dissolution buffered the pH change and created conditions of galena oversaturation, which then reduced lead concentrations along the flow path. Near the leak kinetic geochemical reactions control the release of solutes into the fluid, but further along the flow path mineral solubility controls solute concentrations. Simulation results demonstrate the impact of heterogeneous distribution of geochemical reactive surface area in coordination with physical heterogeneity on the effective reaction rate (Krxn,eff) and Pb(2+) concentrations within the plume. Dissimilarities between ensemble Pb(2+) concentration and Krxn,eff are attributed to how geochemical heterogeneity affects the time (τeq) and therefore advection distance (Leq) required for the system to re-establish geochemical equilibrium. Only after geochemical equilibrium is re-established, Krxn,eff and Pb(2+) concentrations are the same for all

  3. Rate constants of quenching and vibrational relaxation in the OH({{A}^{2}}{{ \\Sigma }^{+}},v=0,1 ), manifold with various colliders

    Science.gov (United States)

    Martini, L. M.; Gatti, N.; Dilecce, G.; Scotoni, M.; Tosi, P.

    2017-03-01

    Laser induced fluorescence is intensively used for the detection of OH in many atmospheric pressure discharge devices. At this pressure, a quantitative knowledge of the collision phenomena in the upper excited state is critical. Here we report the measurement at T  =  300 K of a set of rate constants of electronic quenching and vibrational relaxation of the OH≤ft({{A}2}{{ Σ }+},{{v}\\prime}=0,1\\right) electronic state, by collision with N2, O2, H2O, CO2, CO, H2, D2, CH4, C2H2, C2H4, C2H6. These are the main gases in applications like plasma medicine, hydrocarbons reforming and CO2 conversion. Available literature data are revisited, and new data are added, mostly relevant to {{v}\\prime}=1 quenching and vibrational relaxation.

  4. Rate parameters for the reaction of atomic hydrogen with dimethyl ether and dimethyl sulfide

    Science.gov (United States)

    Lee, J. H.; Machen, R. C.; Nava, D. F.; Stief, L. J.

    1981-03-01

    Absolute rate constants for the reaction of atomic hydrogen with dimethyl ether (DME) and dimethyl sulfide (DMS) were obtained using the flash photolysis-resonance fluorescence technique. Under conditions where secondary reactions are avoided, rate constants for the H+DME reaction over the temperature range 273-426 K are well represented by the Arrhenius expression k1=(4.38±0.59)×10-12 exp(-1956±43/T) cm3 molecule-1 s-1. The corresponding Arrhenius expression for the H+DMS reaction over the temperature range 212-500 K is k2=(1.30±0.43)×10-11exp(-1118±81/T) cm3 molecule-1 s-1. The Arrhenius plot for k2 shows signs of curvature, however, and separate Arrhenius expressions are derived for the data above and below room temperature. These results are discussed and comparisons are made with previous determinations which employed flow discharge and product analysis techniques.

  5. Transition path sampling with quantum/classical mechanics for reaction rates.

    Science.gov (United States)

    Gräter, Frauke; Li, Wenjin

    2015-01-01

    Predicting rates of biochemical reactions through molecular simulations poses a particular challenge for two reasons. First, the process involves bond formation and/or cleavage and thus requires a quantum mechanical (QM) treatment of the reaction center, which can be combined with a more efficient molecular mechanical (MM) description for the remainder of the system, resulting in a QM/MM approach. Second, reaction time scales are typically many orders of magnitude larger than the (sub-)nanosecond scale accessible by QM/MM simulations. Transition path sampling (TPS) allows to efficiently sample the space of dynamic trajectories from the reactant to the product state without an additional biasing potential. We outline here the application of TPS and QM/MM to calculate rates for biochemical reactions, by means of a simple toy system. In a step-by-step protocol, we specifically refer to our implementation within the MD suite Gromacs, which we have made available to the research community, and include practical advice on the choice of parameters.

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

    Science.gov (United States)

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

    2016-06-28

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

  7. Reaction rate constants of H-abstraction by OH from large ketones: Measurements and site-specific rate rules

    KAUST Repository

    Badra, Jihad

    2014-01-01

    Reaction rate constants of the reaction of four large ketones with hydroxyl (OH) are investigated behind reflected shock waves using OH laser absorption. The studied ketones are isomers of hexanone and include 2-hexanone, 3-hexanone, 3-methyl-2-pentanone, and 4-methl-2-pentanone. Rate constants are measured under pseudo-first-order kinetics at temperatures ranging from 866 K to 1375 K and pressures near 1.5 atm. The reported high-temperature rate constant measurements are the first direct measurements for these ketones under combustion-relevant conditions. The effects of the position of the carbonyl group (CO) and methyl (CH3) branching on the overall rate constant with OH are examined. Using previously published data, rate constant expressions covering, low-to-high temperatures, are developed for acetone, 2-butanone, 3-pentanone, and the hexanone isomers studied here. These Arrhenius expressions are used to devise rate rules for H-abstraction from various sites. Specifically, the current scheme is applied with good success to H-abstraction by OH from a series of n-ketones. Finally, general expressions for primary and secondary site-specific H-abstraction by OH from ketones are proposed as follows (the subscript numbers indicate the number of carbon atoms bonded to the next-nearest-neighbor carbon atom, the subscript CO indicates that the abstraction is from a site next to the carbonyl group (CO), and the prime is used to differentiate different neighboring environments of a methylene group):P1,CO = 7.38 × 10-14 exp(-274 K/T) + 9.17 × 10-12 exp(-2499 K/T) (285-1355 K)S10,CO = 1.20 × 10-11 exp(-2046 K/T) + 2.20 × 10-13 exp(160 K/T) (222-1464 K)S11,CO = 4.50 × 10-11 exp(-3000 K/T) + 8.50 × 10-15 exp(1440 K/T) (248-1302 K)S11′,CO = 3.80 × 10-11 exp(-2500 K/T) + 8.50 × 10-15 exp(1550 K/T) (263-1370 K)S 21,CO = 5.00 × 10-11 exp(-2500 K/T) + 4.00 × 10-13 exp(775 K/T) (297-1376 K) © 2014 the Partner Organisations.

  8. Effects of network dissolution changes on pore-to-core upscaled reaction rates for kaolinite and anorthite reactions under acidic conditions

    KAUST Repository

    Kim, Daesang

    2013-11-01

    We have extended reactive flow simulation in pore-network models to include geometric changes in the medium from dissolution effects. These effects include changes in pore volume and reactive surface area, as well as topological changes that open new connections. The computed changes were based upon a mineral map from an X-ray computed tomography image of a sandstone core. We studied the effect of these changes on upscaled (pore-scale to core-scale) reaction rates and compared against the predictions of a continuum model. Specifically, we modeled anorthite and kaolinite reactions under acidic flow conditions during which the anorthite reactions remain far from equilibrium (dissolution only), while the kaolinite reactions can be near-equilibrium. Under dissolution changes, core-scale reaction rates continuously and nonlinearly evolved in time. At higher injection rates, agreement with predictions of the continuum model degraded significantly. For the far-from-equilibrium reaction, our results indicate that the ability to correctly capture the heterogeneity in dissolution changes in the reactive mineral surface area is critical to accurately predict upscaled reaction rates. For the near-equilibrium reaction, the ability to correctly capture the heterogeneity in the saturation state remains critical. Inclusion of a Nernst-Planck term to ensure neutral ionic currents under differential diffusion resulted in at most a 9% correction in upscaled rates.

  9. Solute transport predicts scaling of surface reaction rates in porous media: Applications to silicate weathering

    CERN Document Server

    Hunt, Allen G; Ghanbarian, Behzad

    2013-01-01

    We apply our theory of conservative solute transport, based on concepts from percolation theory, directly and without modification to reactive solute transport. This theory has previously been shown to predict the observed range of dispersivity values for conservative solute transport over ten orders of magnitude of length scale. We now show that the temporal dependence derived for the solute velocity accurately predicts the time-dependence for the weathering of silicate minerals over nine orders of magnitude of time scale, while its predicted length dependence agrees with data obtained for reaction rates over five orders of magnitude of length scale. In both cases, it is possible to unify lab and field results. Thus, net reaction rates appear to be limited by solute transport velocities. We suggest the possible relevance of our results to landscape evolution of the earth's terrestrial surface.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-12-09

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

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

    Science.gov (United States)

    Kustova, Elena V.; Kremer, Gilberto M.

    2014-12-01

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

  12. Probing the interplay between factors determining reaction rates on silica gel using termolecular systems.

    Science.gov (United States)

    Kirkpatrick, Iain; Worrall, David R; Williams, Siân L; Buck, Craig J T; Meseguer, Rafael G

    2012-10-01

    In this study we have compared energy and electron transfer reactions in termolecular systems using a nanosecond diffuse reflectance laser flash photolysis technique. We have previously investigated these processes on silica gel surfaces for bimolecular systems and electron transfer in termolecular systems. The latter systems involved electron transfer between three arene molecules with azulene acting as a molecular shuttle. In this study we present an alternative electron transfer system using trans β-carotene as an electron donor in order to effectively immobilise all species except the shuttle, providing the first unambiguous evidence for radical ion mobility. In the energy transfer system we use naphthalene, a structural isomer of azulene, as the shuttle, facilitating energy transfer from a selectively excited benzophenone sensitiser to 9-cyanoanthracene. Bimolecular rate constants for all of these processes have been measured and new insights into the factors determining the rates of these reactions on silica gel have been obtained.

  13. Reaction rate distribution measurement and the core performance evaluation in the prototype FBR Monju

    Energy Technology Data Exchange (ETDEWEB)

    Usami, S.; Suzuoki, Z.; Deshimaru, T. [Monju Construction Office, Japan Nuclear Cycle Development Institute, Fukui-ken (Japan); Nakashima, F. [Tsuruga head Office, Japan Nuclear Cycle Development Institute, Fukui-ken (Japan)

    2001-07-01

    Monju is a prototype fast breeder reactor designed to have an output of 280 MW (714 MWt), fueled with mixed oxides of plutonium and uranium and cooled by liquid sodium. The principal data on plant design and performance are shown in Table 1. Monju attained initial criticality in April 1994 and the reactor physics tests were carried out from May through November 1994. The reaction rate distribution measurement by the foil activation method was one of these tests and was carried out in order to verify the core performance and to contribute to the development of the core design methods. On the basis of the reaction rate measurement data, the Monju initial core breeding ratio and the power distribution were evaluated. (author)

  14. The 23Na({\\alpha},p) 26Mg reaction rate at astrophysically relevant energies

    CERN Document Server

    Howard, A M; Fynbo, H O U; Kirsebom, O S; Laursen, K L; Diget, C Aa; Hubbard, N J

    2015-01-01

    The production of 26 Al in massive stars is sensitive to the 23 Na(a,p) 26 Mg cross section. Recent experimental data suggest the currently recommended cross sections are underestimated by a factor of 40. We present here differential cross sections for the 23 Na(a,p) 26 Mg reaction measured in the energy range E c.m. = 1.7 - 2.5 MeV. Concurrent measurements of Rutherford scattering provide absolute normalisations which are independent of variations in target properties. Angular distributions were measured for both p 0 and p 1 permitting the determination of total cross sections. The results show no significant deviation from the statistical model calculations upon which the recommended rates are based. We therefore retain the previous recommendation without the increase in cross section and resulting stellar reaction rates of a factor of 40, impacting on the 26 Al yield from massive stars by more than a factor of three.

  15. Rate of diffusion-limited reactions for a fractal aggregate of reactive spheres

    Science.gov (United States)

    Tseng, Chin-Yao; Tsao, Heng-Kwong

    2002-08-01

    We study the reaction rate for a fractal cluster of perfectly absorbing, stationary spherical sinks in a medium containing a mobile reactant. The effectiveness factor eta, which is defined as the ratio of the total reaction rate of the cluster to that without diffusional interactions, is calculated. The scaling behavior of eta is derived for arbitrary fractal dimension based on the Kirkwood-Riseman approximation. The asymptotic as well as the finite size scaling of eta are confirmed numerically by the method of multipole expansion, which has been proven to be an excellent approximation. The fractal assembly is made of N spheres with its dimension varying from D1, eta][approx(ln N)-1 for D=1, and eta][approxN0 for D1 the screening effect of diffusive interactions grows with the size, for Ddecays with decreasing D. The conclusion is also applicable to transport phenomena like dissolution, heat conduction, and sedimentation.

  16. Absolute rate constants for the reaction of hypochlorous acid with protein side chains and peptide bonds

    DEFF Research Database (Denmark)

    Pattison, D I; Davies, Michael Jonathan

    2001-01-01

    , absolute second-order rate constants for the reactions of HOCl with protein side chains, model compounds, and backbone amide (peptide) bonds have been determined at physiological pH values. The reactivity of HOCl with potential reactive sites in proteins is summarized by the series: Met (3.8 x 10(7) M(-1......) x s(-1)) > backbone amides (10-10(-3) M(-1) x s(-1)) > Gln(0.03 M(-1) x s(-1)) approximately Asn (0.03 M(-1) x s(-1)). The rate constants for reaction of HOCl with backbone amides (peptide bonds) vary by 4 orders of magnitude with uncharged peptide bonds reacting more readily with HOCl than those...

  17. Reactivity and reaction rate studies on the fourth loading of ZENITH

    Energy Technology Data Exchange (ETDEWEB)

    Cameron, I.R.; Freemantle, R.G.; Reed, D.L.; Wilson, D.J. [General Reactor Physics Division, Atomic Energy Establishment, Winfrith, Dorchester, Dorset (United Kingdom)] (and others)

    1963-08-15

    The determination of the excess reactivity, control rod worths, prompt neutron lifetime, flux fine structure, and reaction rates of various nuclides for the fourth loading of the heated zero energy reactor ZENITH is described. The core contains 7.76 kg of U235, giving a carbon/U235 atom ratio of 7578, and forms the most dilute of the range studied. Comparisons of the experimental results with calculations using multigroup diffusion codes are presented. (author)

  18. The effect of learning models and emotional intelligence toward students learning outcomes on reaction rate

    Science.gov (United States)

    Sutiani, Ani; Silitonga, Mei Y.

    2017-08-01

    This research focused on the effect of learning models and emotional intelligence in students' chemistry learning outcomes on reaction rate teaching topic. In order to achieve the objectives of the research, with 2x2 factorial research design was used. There were two factors tested, namely: the learning models (factor A), and emotional intelligence (factor B) factors. Then, two learning models were used; problem-based learning/PBL (A1), and project-based learning/PjBL (A2). While, the emotional intelligence was divided into higher and lower types. The number of population was six classes containing 243 grade X students of SMAN 10 Medan, Indonesia. There were 15 students of each class were chosen as the sample of the research by applying purposive sampling technique. The data were analyzed by applying two-ways analysis of variance (2X2) at the level of significant α = 0.05. Based on hypothesis testing, there was the interaction between learning models and emotional intelligence in students' chemistry learning outcomes. Then, the finding of the research showed that students' learning outcomes in reaction rate taught by using PBL with higher emotional intelligence is higher than those who were taught by using PjBL. There was no significant effect between students with lower emotional intelligence taught by using both PBL and PjBL in reaction rate topic. Based on the finding, the students with lower emotional intelligence were quite hard to get in touch with other students in group discussion.

  19. Experimental results for studies of the 40Ca(α,γ)44Ti reaction rates

    Science.gov (United States)

    Robertson, Daniel; Becker, Hans-Werner; Bowers, Matt; Collon, Philippe; Goerres, Joachim; Lu, Wenting; Schmitt, Chris; Wiescher, Michael

    2011-10-01

    Observational studies of galactic γ emitters such as 44Ti have highlighted their use in nucleosynthesis studies of massive stars in their late stage stellar evolution and final explosive demise in core collapse supernova events. Models used in the simulation of such γ emitters rely heavily upon reliable reaction rates for both the creation and annihilation of these isotopes over large temperature ranges. The production of 44Ti mainly through the 40Ca(α,γ)44Ti reaction is thought to take place primarily in the α-rich freeze out phase of a core collapse supernova. However, current supernova models predict lower 44Ti to 56Ni ratios than observed, creating a need for more information about its production mechanism. A number of previous studies include prompt γ-ray measurements, recoil mass separator experiments and the use of AMS, all giving greatly different reaction rates. Aiding in the refinement of these needed rates, the results of experiments at the DTL, Bochum and NSL, Notre Dame will be presented against the backdrop of these previous measurements. Work supported by grant # 0758100 and # 0822648.

  20. Decays of Baryon Resonances into K Lambda, K^+ Sigma^0 and K^0 Sigma^+

    CERN Document Server

    Sarantsev, A V; Anisovich, A V; Klempt, E; Thoma, U

    2005-01-01

    Cross sections, beam asymmetries, and recoil polarisations for the reactions gamma p to K^+ Lambda ; gamma to K^+ Sigma^0, and gamma p to K^0 Sigma^+ have been measured by the SAPHIR, CLAS, and LEPS collaborations with high statistics and good angular coverage for centre-of-mass energies between 1.6 and 2.3 GeV. The combined analysis of these data with data from pi and eta photoproduction reveals evidence for new baryon resonances in this energy region. A new P_{11} state with mass 1840 MeV and width 140 MeV was observed contributing to most of the fitted reactions. The data demand the presence of two D_{13} states at 1870 and 2170 MeV.

  1. Quantum Tunneling Rates of Gas-Phase Reactions from On-the-Fly Instanton Calculations.

    Science.gov (United States)

    Beyer, Adrian N; Richardson, Jeremy O; Knowles, Peter J; Rommel, Judith; Althorpe, Stuart C

    2016-11-03

    The instanton method obtains approximate tunneling rates from the minimum-action path (known as the instanton) linking reactants to the products at a given temperature. An efficient way to find the instanton is to search for saddle-points on the ring-polymer potential surface, which is obtained by expressing the quantum Boltzmann operator as a discrete path-integral. Here we report a practical implementation of this ring-polymer form of instanton theory into the Molpro electronic-structure package, which allows the rates to be computed on-the-fly, without the need for a fitted analytic potential-energy surface. As a test case, we compute tunneling rates for the benchmark H + CH4 reaction, showing how the efficiency of the instanton method allows the user systematically to converge the tunneling rate with respect to the level of electronic-structure theory.

  2. Reaction Rate Theory in Coordination Number Space: An Application to Ion Solvation

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Santanu; Baer, Marcel D.; Mundy, Christopher J.; Schenter, Gregory K.

    2016-04-14

    Understanding reaction mechanisms in many chemical and biological processes require application of rare event theories. In these theories, an effective choice of a reaction coordinate to describe a reaction pathway is essential. To this end, we study ion solvation in water using molecular dynamics simulations and explore the utility of coordination number (n = number of water molecules in the first solvation shell) as the reaction coordinate. Here we compute the potential of mean force (W(n)) using umbrella sampling, predicting multiple metastable n-states for both cations and anions. We find with increasing ionic size, these states become more stable and structured for cations when compared to anions. We have extended transition state theory (TST) to calculate transition rates between n-states. TST overestimates the rate constant due to solvent-induced barrier recrossings that are not accounted for. We correct the TST rates by calculating transmission coefficients using the reactive flux method. This approach enables a new way of understanding rare events involving coordination complexes. We gratefully acknowledge Liem Dang and Panos Stinis for useful discussion. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. SR, CJM, and GKS were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. MDB was supported by MS3 (Materials Synthesis and Simulation Across Scales) Initiative, a Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory (PNNL). PNNL is a multiprogram national laboratory operated by Battelle for the U.S. Department of Energy.

  3. A study of the photocatalytic effects of aqueous suspensions of platinized semiconductor materials on the reaction rates of candidate redox reactions

    Science.gov (United States)

    Miles, A. M.

    1982-01-01

    The effectiveness of powdered semiconductor materials in photocatalyzing candidate redox reactions was investigated. The rate of the photocatalyzed oxidation of cyanide at platinized TiO2 was studied. The extent of the cyanide reaction was followed directly using an electroanalytical method (i.e. differential pulse polarography). Experiments were performed in natural or artificial light. A comparison was made of kinetic data obtained for photocatalysis at platinized powders with rate data for nonplatinized powders.

  4. Effect of Solvents on the Product Distribution and Reaction Rate of a Buchwald-Hartwig Amination Reaction

    DEFF Research Database (Denmark)

    Christensen, H.; Kiil, Søren; Dam-Johansen, Kim;

    2006-01-01

    The Buchwald-Hartwig amination reaction between p-bromotoluene and piperazine in the presence of the homogeneous catalytic system Pd(dba)(2)/(+/-)-BINAP and the base NaO-t-Bu was investigated in two different classes of solvents: aprotic, nonpolar and aprotic, polar. The reaction was carried out...... solvent for the Buchwald-Hartwig amination reaction under the conditions applied was m-xylene....

  5. Nuclear halo effect on nucleon capture reaction rates at stellar energies

    Institute of Scientific and Technical Information of China (English)

    Liu Zu-Hua; Zhou Hong-Yu

    2005-01-01

    The capture cross sections at stellar energies are very difficult to measure directly. Hence, data are usually evaluated by using indirect methods or extrapolations from the experimental data obtained at the lowest possible energies. The asymptotic normalization coefficient (ANC) approach of the transfer reactions provides a reliable way for the determination of the capture cross sections at stellar energies. By virtue of its reliability, we have calculated the capture cross sections of the 10Be(n,γ)11Be reaction by using nuclear ANC method. 11Be is a well-known neutron halo nucleus with two weakly bound states. As a typical example, we have shown that the radiative cross sections for a nucleon captured into a halo state are obviously enhanced. The enormous enhancement of the capture cross section is just due to the large overlap of the incident neutron wave with the extended tail of the halo. The 10Be(n,γ)11Be capture reaction is involved in the inhomogeneous big-bang nucleosynthesis. We have evaluated its reaction rates at stellar energies with the nuclear ANC method.

  6. Correlation between discrete probability and reaction front propagation rate in heterogeneous mixtures

    Science.gov (United States)

    Naine, Tarun Bharath; Gundawar, Manoj Kumar

    2017-09-01

    We demonstrate a very powerful correlation between the discrete probability of distances of neighboring cells and thermal wave propagation rate, for a system of cells spread on a one-dimensional chain. A gamma distribution is employed to model the distances of neighboring cells. In the absence of an analytical solution and the differences in ignition times of adjacent reaction cells following non-Markovian statistics, invariably the solution for thermal wave propagation rate for a one-dimensional system with randomly distributed cells is obtained by numerical simulations. However, such simulations which are based on Monte-Carlo methods require several iterations of calculations for different realizations of distribution of adjacent cells. For several one-dimensional systems, differing in the value of shaping parameter of the gamma distribution, we show that the average reaction front propagation rates obtained by a discrete probability between two limits, shows excellent agreement with those obtained numerically. With the upper limit at 1.3, the lower limit depends on the non-dimensional ignition temperature. Additionally, this approach also facilitates the prediction of burning limits of heterogeneous thermal mixtures. The proposed method completely eliminates the need for laborious, time intensive numerical calculations where the thermal wave propagation rates can now be calculated based only on macroscopic entity of discrete probability.

  7. Astrophysical reaction rates from a symmetry-informed first-principles perspective

    Science.gov (United States)

    Dreyfuss, Alison; Launey, Kristina; Baker, Robert; Draayer, Jerry; Dytrych, Tomas

    2017-01-01

    With a view toward a new unified formalism for studying bound and continuum states in nuclei, to understand stellar nucleosynthesis from a fully ab initio perspective, we studied the nature of surface α-clustering in 20Ne by considering the overlap of symplectic states with cluster-like states. We compute the spectroscopic amplitudes and factors, α-decay width, and absolute resonance strength - characterizing major contributions to the astrophysical reaction rate through a low-lying 1- resonant state in 20Ne. As a next step, we consider a fully microscopic treatment for the n+4 He system, based on the successful first-principles No-Core Shell Model/Resonating Group Method (NCSM/RGM) for light nuclei, but with the capability to reach intermediate-mass nuclei. The new model takes advantage of the symmetry-based concept central to the Symmetry-Adapted No-Core Shell Model (SA-NCSM) to reduce computational complexity in physically-informed and methodical way, with sights toward first-principles calculations of rates for important astrophysical reactions, such as the 23 Al(p , γ) 24 Si reaction, believed to have a strong influence on X-ray burst light curves. Supported by the U.S. NSF (OCI-0904874, ACI -1516338) and the U.S. DOE (DE-SC0005248), and benefitted from computing resources provided by Blue Waters and the LSU Center for Computation & Technology.

  8. Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Iron

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2009-01-01

    DESIG: E 263 09 ^TITLE: Standard Test Method for Measuring Fast-Neutron Reaction Rates by Radioactivation of Iron ^SIGNUSE: Refer to Guide E 844 for guidance on the selection, irradiation, and quality control of neutron dosimeters. Refer to Practice E 261 for a general discussion of the determination of fast-neutron fluence rate with threshold detectors. Pure iron in the form of foil or wire is readily available and easily handled. Fig. 1 shows a plot of cross section as a function of neutron energy for the fast-neutron reaction 54Fe(n,p)54Mn (1). This figure is for illustrative purposes only to indicate the range of response of the 54Fe(n,p)54Mn reaction. Refer to Guide E 1018 for descriptions of recommended tabulated dosimetry cross sections. 54Mn has a half-life of 312.13 days (3) (2) and emits a gamma ray with an energy of 834.845 keV (5). (2) Interfering activities generated by neutron activation arising from thermal or fast neutron interactions are 2.57878 (46)-h 56Mn, 44.95-d (8) 59Fe, and 5.27...

  9. Spectra of coset sigma models

    Energy Technology Data Exchange (ETDEWEB)

    Candu, Constantin [Institut fuer Theoretische Physik, Zuerich (Switzerland); Mitev, Vladimir [Humboldt-Universitaet, Berlin (Germany). Inst. fuer Mathematik; Humboldt-Universitaet, Berlin (Germany). Inst. fuer Physik; Schomerus, Volker [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Theory Group

    2013-08-15

    We compute the complete 1-loop spectrum of anomalous dimensions for the bulk fields of non-linear sigma models on symmetric coset (super)spaces G/H, both with and without world-sheet supersymmetry. In addition, we provide two new methods for the construction of partition functions in the infinite radius limit and demonstrate their efficiency in the case of (super)sphere sigma models. Our results apply to a large number of target spaces including superspheres and superprojective spaces such as the N=2 sigma model on CP{sup 3} {sup vertical} {sup stroke} {sup 4}.

  10. Six sigma for revenue retrieval.

    Science.gov (United States)

    Plonien, Cynthia

    2013-01-01

    Deficiencies in revenue retrieval due to failures in obtaining charges have contributed to a negative bottom line for numerous hospitals. Improving documentation practices through a Six Sigma process improvement initiative can minimize opportunities for errors through reviews and instill structure for compliance and consistency. Commitment to the Six Sigma principles with continuous monitoring of outcomes and constant communication of results to departments, management, and payers is a strong approach to reducing the financial impact of denials on an organization's revenues and expenses. Using Six Sigma tools can help improve the organization's financial performance not only for today, but also for health care's uncertain future.

  11. Modeling microbial reaction rates in a submarine hydrothermal vent chimney wall

    Science.gov (United States)

    LaRowe, Douglas E.; Dale, Andrew W.; Aguilera, David R.; L'Heureux, Ivan; Amend, Jan P.; Regnier, Pierre

    2014-01-01

    The fluids emanating from active submarine hydrothermal vent chimneys provide a window into subseafloor processes and, through mixing with seawater, are responsible for steep thermal and compositional gradients that provide the energetic basis for diverse biological communities. Although several models have been developed to better understand the dynamic interplay of seawater, hydrothermal fluid, minerals and microorganisms inside chimney walls, none provide a fully integrated approach to quantifying the biogeochemistry of these hydrothermal systems. In an effort to remedy this, a fully coupled biogeochemical reaction-transport model of a hydrothermal vent chimney has been developed that explicitly quantifies the rates of microbial catalysis while taking into account geochemical processes such as fluid flow, solute transport and oxidation-reduction reactions associated with fluid mixing as a function of temperature. The metabolisms included in the reaction network are methanogenesis, aerobic oxidation of hydrogen, sulfide and methane and sulfate reduction by hydrogen and methane. Model results indicate that microbial catalysis is generally fastest in the hottest habitable portion of the vent chimney (77-102 °C), and methane and sulfide oxidation peak near the seawater-side of the chimney. The fastest metabolisms are aerobic oxidation of H2 and sulfide and reduction of sulfate by H2 with maximum rates of 140, 900 and 800 pmol cm-3 d-1, respectively. The maximum rate of hydrogenotrophic methanogenesis is just under 0.03 pmol cm-3 d-1, the slowest of the metabolisms considered. Due to thermodynamic inhibition, there is no anaerobic oxidation of methane by sulfate (AOM). These simulations are consistent with vent chimney metabolic activity inferred from phylogenetic data reported in the literature. The model developed here provides a quantitative approach to describing the rates of biogeochemical transformations in hydrothermal systems and can be used to constrain the

  12. Quantifying metabolic rates in submarine hydrothermal vent chimneys: A reaction transport model

    Science.gov (United States)

    LaRowe, D.; Dale, A.; Aguilera, D.; Amend, J. P.; Regnier, P.

    2012-12-01

    The fluids emanating from active submarine hydrothermal vent chimneys provide a window into subseafloor processes and, through mixing with seawater, are responsible for steep thermal and compositional gradients that provide the energetic basis for diverse biological communities. Although several models have been developed to better understand the dynamic interplay of seawater, hydrothermal fluid, minerals and microorganisms inside chimney walls, none provide a fully integrated approach to quantifying the biogeochemistry of these hydrothermal systems. In an effort to remedy this, a fully coupled biogeochemical reaction transport model of a hydrothermal vent chimney has been developed that explicitly quantifies the rate of microbial catalysis while taking into account geochemical processes such as fluid flow, solute transport and oxidation-reduction reactions associated with fluid mixing as a function of temperature. Methanogenesis, hydrogen oxidation by oxygen and sulfate, sulfide oxidation by oxygen and methane oxidation by oxygen and sulfate are the metabolisms included in the reaction network. Model results indicate that microbial catalysis is fastest in the hottest habitable portion of the vent chimney except for methane oxidation by oxygen, which peaks near the seawater-side of the chimney at 20 nmol /cm^3 yr. The dominant metabolisms in the chimney are hydrogen oxidation by sulfate and oxygen and sulfide oxidation at peak rates 3200 , 300 and 900 nmol /cm^3 yr, respectively. The maximum rate of hydrogenotrophic methanogensis is just under 0.07 nmol /cm^3 yr, the slowest of the metabolisms considered. Due to thermodynamic inhibition, there is no anaerobic oxidation of methane by sulfate (AOM). The model developed here provides a quantitative approach to understanding the rates of biogeochemical transformations in hydrothermal systems and can be used to better understand the role of microbial activity in the deep subsurface.

  13. Lean Six Sigma

    OpenAIRE

    N, Vivekananthamoorthy; S, ankar

    2011-01-01

    Методология Lean Six Sigma, которая идеально подходит для проектов, направленных на уменьшение объема потерь, длительности бизнес-циклов, их вариаций, а также для увеличения качества продукта, может служить основой для улучшения бизнес-процессов.

  14. Non-explosive hydrogen and helium burnings: abundance predictions from the NACRE reaction rate compilation

    Science.gov (United States)

    Arnould, M.; Goriely, S.; Jorissen, A.

    1999-07-01

    The abundances of the isotopes of the elements from C to Al produced by the non-explosive CNO, NeNa and MgAl modes of hydrogen burning, as well as by helium burning, are calculated with the thermonuclear rates recommended by the European compilation of reaction rates for astrophysics (NACRE). The impact of nuclear physics uncertainties on the derived abundances is discussed in the framework of a simple parametric astrophysical model. These calculations have the virtue of being a guide in the selection of the nuclear uncertainties that have to be duly analyzed in detailed model stars, particularly in order to perform meaningful confrontations between abundance observations and predictions. They are also hoped to help nuclear astrophysicists pinpointing the rate uncertainties that have to be reduced most urgently. An electronic version of this paper, with colour figures, is available at {\\it http://astro.ulb.ac.be}

  15. A reaction-diffusion-based coding rate control mechanism for camera sensor networks.

    Science.gov (United States)

    Yamamoto, Hiroshi; Hyodo, Katsuya; Wakamiya, Naoki; Murata, Masayuki

    2010-01-01

    A wireless camera sensor network is useful for surveillance and monitoring for its visibility and easy deployment. However, it suffers from the limited capacity of wireless communication and a network is easily overflown with a considerable amount of video traffic. In this paper, we propose an autonomous video coding rate control mechanism where each camera sensor node can autonomously determine its coding rate in accordance with the location and velocity of target objects. For this purpose, we adopted a biological model, i.e., reaction-diffusion model, inspired by the similarity of biological spatial patterns and the spatial distribution of video coding rate. Through simulation and practical experiments, we verify the effectiveness of our proposal.

  16. Size dependence of surface thermodynamic properties of nanoparticles and its determination method by reaction rate constant

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wenjiao; Xue, Yongqiang, E-mail: xyqlw@126.com; Cui, Zixiang

    2016-08-15

    Surface thermodynamic properties are the fundamental properties of nanomaterials, and these properties depend on the size of nanoparticles. In this paper, relations of molar surface thermodynamic properties and surface heat capacity at constant pressure of nanoparticles with particle size were derived theoretically, and the method of obtaining the surface thermodynamic properties by reaction rate constant was put forward. The reaction of nano-MgO with sodium bisulfate solution was taken as a research system. The influence regularities of the particle size on the surface thermodynamic properties were discussed theoretically and experimentally, which show that the experimental regularities are in accordance with the corresponding theoretical relations. With the decreasing of nanoparticle size, the molar surface thermodynamic properties increase, while the surface heat capacity decreases (the absolute value increases). In addition, the surface thermodynamic properties are linearly related to the reciprocal of nanoparticle diameter, respectively.

  17. Temperature dependence of the absolute rate constant for the reaction of ozone with dimethyl sulfide

    Institute of Scientific and Technical Information of China (English)

    WANG Hai-tao; ZHANG Yu-jie; MU Yu-jing

    2007-01-01

    Absolute rate constants for the reaction of ozone with dimethyl sulfide (DMS) were measured in a 200-L Teflon chamber over the temperature range of 283-353 K. Measurements were carried out using DMS in large excess over ozone of 10 to 1 or greater. Over the indicated temperature range,the data could be fit to the simple Arrhenius expression as KDMS = (9.96±3.61)×10-11exp(-(7309.7±1098.2)/T)cm3/(molecule·s). A compared investigation of the reaction between ozone and ethene had a kc2H4 value of(1.35±0.11)×10-18 cm3/(molecule·s) at room temperature.

  18. Measurement of absolute reaction rates in Be,Pb and Fe spherical systems

    Institute of Scientific and Technical Information of China (English)

    LiuRong; ChenYuan; 等

    1998-01-01

    The absolute reaction rates in Be,Pb and Fe have been measured by using the activation foil technique with different reaction energy thresholds.Thicknesses of Be,Pb and Fe spheres were 5.3,19.1 and 31.9cm.respectively,Eight kinds of activation folis were used for Fe,and four kinds each for Be and Pb,The total experimental er5ror was about 5-7%.The measured results were compared to the values calculated with the 1-D ANISN code and the ENDF/B-VI library data.The average ratio of the experimental to the calculational is less than 7% for Be and Pb,about 5-30% for Fe.

  19. Application of Six Sigma towards improving surgical outcomes.

    Science.gov (United States)

    Shukla, P J; Barreto, S G; Nadkarni, M S

    2008-01-01

    Six Sigma is a 'process excellence' tool targeting continuous improvement achieved by providing a methodology for improving key steps of a process. It is ripe for application into health care since almost all health care processes require a near-zero tolerance for mistakes. The aim of this study is to apply the Six Sigma methodology into a clinical surgical process and to assess the improvement (if any) in the outcomes and patient care. The guiding principles of Six Sigma, namely DMAIC (Define, Measure, Analyze, Improve, Control), were used to analyze the impact of double stapling technique (DST) towards improving sphincter preservation rates for rectal cancer. The analysis using the Six Sigma methodology revealed a Sigma score of 2.10 in relation to successful sphincter preservation. This score demonstrates an improvement over the previous technique (73% over previous 54%). This study represents one of the first clinical applications of Six Sigma in the surgical field. By understanding, accepting, and applying the principles of Six Sigma, we have an opportunity to transfer a very successful management philosophy to facilitate the identification of key steps that can improve outcomes and ultimately patient safety and the quality of surgical care provided.

  20. High-precision (p,t) reaction measurement to determine Ne-18(alpha,p)Na-21 reaction rates

    NARCIS (Netherlands)

    Matic, A.; van den Berg, A. M.; Harakeh, M. N.; Wörtche, H. J.; Berg, G. P. A.; Couder, M.; Fisker, J. L.; Goerres, J.; LeBlanc, P.; O'Brien, S.; Wiescher, M.; Fujita, K.; Hatanaka, K.; Sakemi, Y.; Shimizu, Y.; Tameshige, Y.; Tamii, A.; Yosoi, M.; Adachi, T.; Fujita, Y.; Shimbara, Y.; Fujita, H.; Wakasa, T.; Hess, P. O.; Brown, B. A.; Schatz, H.

    2009-01-01

    x-ray bursts are identified as thermonuclear explosions in the outer atmosphere of accreting neutron stars. The thermonuclear runaway is fueled by the alpha p process that describes a sequence of (alpha,p) reactions triggered by the Ne-18(alpha,p)Na-21 breakout reaction from the hot CNO cycles. We

  1. Accurate quantum thermal rate constants for the three-dimensional H+H2 reaction

    Science.gov (United States)

    Park, Tae Jun; Light, J. C.

    1989-07-01

    The rate constants for the three-dimensional H+H2 reaction on the Liu-Siegbahn-Truhlar-Horowitz (LSTH) surface are calculated using Pack-Parker hyperspherical (APH) coordinates and a C2v symmetry adapted direct product discrete variable representation (DVR). The C2v symmetry decomposition and the parity decoupling on the basis are performed for the internal coordinate χ. The symmetry decomposition results in a block diagonal representation of the flux and Hamiltonian operators. The multisurface flux is introduced to represent the multichannel reactive flux. The eigenvalues and eigenvectors of the J=0 internal Hamiltonian are obtained by sequential diagonalization and truncation. The individual symmetry blocks of the flux operator are propagated by the corresponding blocks of the Hamiltonian, and the J=0 rate constant k0(T) is obtained as a sum of the rate constants calculated for each block. k0(T) is compared with the exact k0(T) obtained from thermal averaging of the J=0 reaction probabilities; the errors are within 5%-20% up to T=1500 K. The sequential diagonalization-truncation method reduces the size of the Hamiltonian greatly, but the resulting Hamiltonian matrix still describes the time evolution very accurately. For the J≠0 rate constant calculations, the truncated internal Hamiltonian eigenvector basis is used to construct reduced (JKJ) blocks of the Hamiltonian. The individual (JKJ) blocks are diagonalized neglecting Coriolis coupling and treating the off-diagonal KJ±2 couplings by second order perturbation theory. The full wave function is parity decoupled. The rate constant is obtained as a sum over J of (2J+1)kJ(T). The time evolution of the flux for J≠0 is again very accurately described to give a well converged rate constant.

  2. Structural and dynamical control of the reaction rate in protein electron transfer

    Science.gov (United States)

    Balabin, Ilya A.

    Electron transfer (ET) reactions in proteins are key steps in many vital bioenergetic processes, and the reaction rate is known to be highly sensitive to the protein structure in some cases. For most bioenergetic reactions, as described by the Fermi Golden rule, the rate is proportional to a product of the average square of the effective electronic donor to acceptor coupling and a Franck-Condon factor, which accounts for the nuclear control of the energy gap. The nuclear factor is reasonably well described in Marcus theory and its modifications, and this work is focused on the mechanisms that control the effective coupling. About ten years ago, the Pathways model described for the first time how protein environment may control the effective coupling. In this work, a novel theoretical approach is developed to explore the mechanisms of structural and dynamical control beyond the qualitative level of the Pathways model. In Chapter 1, the assumptions of the Pathways model, its limitations and effects of the structure and the electronic Hamiltonian are investigated for model chain-like bridges using the Dyson's equations. In Chapter II, the framework to explore the sensitivity of the effective coupling to quality of the electronic Hamiltonian, the interference among the dominant pathways and the bridge dynamics is presented. This analysis employs the Green's function technique and includes combined molecular dynamics and electronic structure calculations. Finally, in Chapter III, this framework is tested on the bacterial photosynthetic reaction center, and the mechanisms of the structural and dynamical control for different ET steps are discussed.

  3. A kinetic-theory approach for computing chemical-reaction rates in upper-atmosphere hypersonic flows.

    Science.gov (United States)

    Gallis, Michael A; Bond, Ryan B; Torczynski, John R

    2009-09-28

    Recently proposed molecular-level chemistry models that predict equilibrium and nonequilibrium reaction rates using only kinetic theory and fundamental molecular properties (i.e., no macroscopic reaction-rate information) are investigated for chemical reactions occurring in upper-atmosphere hypersonic flows. The new models are in good agreement with the measured Arrhenius rates for near-equilibrium conditions and with both measured rates and other theoretical models for far-from-equilibrium conditions. Additionally, the new models are applied to representative combustion and ionization reactions and are in good agreement with available measurements and theoretical models. Thus, molecular-level chemistry modeling provides an accurate method for predicting equilibrium and nonequilibrium chemical-reaction rates in gases.

  4. New reaction rates for improved primordial D /H calculation and the cosmic evolution of deuterium

    Science.gov (United States)

    Coc, Alain; Petitjean, Patrick; Uzan, Jean-Philippe; Vangioni, Elisabeth; Descouvemont, Pierre; Iliadis, Christian; Longland, Richard

    2015-12-01

    Primordial or big bang nucleosynthesis (BBN) is one of the three historically strong evidences for the big bang model. Standard BBN is now a parameter-free theory, since the baryonic density of the Universe has been deduced with an unprecedented precision from observations of the anisotropies of the cosmic microwave background radiation. There is a good agreement between the primordial abundances of 4He, D, 3He, and 7Li deduced from observations and from primordial nucleosynthesis calculations. However, the 7Li calculated abundance is significantly higher than the one deduced from spectroscopic observations and remains an open problem. In addition, recent deuterium observations have drastically reduced the uncertainty on D /H , to reach a value of 1.6%. It needs to be matched by BBN predictions whose precision is now limited by thermonuclear reaction rate uncertainties. This is especially important as many attempts to reconcile Li observations with models lead to an increased D prediction. Here, we reevaluate the d (p ,γ )3He, d (d ,n ) 3H3, and d (d ,p ) 3H reaction rates that govern deuterium destruction, incorporating new experimental data and carefully accounting for systematic uncertainties. Contrary to previous evaluations, we use theoretical ab initio models for the energy dependence of the S factors. As a result, these rates increase at BBN temperatures, leading to a reduced value of D /H =(2.45 ±0.10 )×10-5 (2 σ ), in agreement with observations.

  5. Non-explosive hydrogen and helium burnings Abundance predictions from the NACRE reaction rate compilation

    CERN Document Server

    Arnould, M; Jorissen, A

    1999-01-01

    The abundances of the isotopes of the elements from C to Al produced by the non-explosive CNO, NeNa and MgAl modes of hydrogen burning, as well as by helium burning, are calculated with the thermonuclear rates recommended by the European compilation of reaction rates for astrophysics (NACRE: details about NACRE may be found at http://astro.ulb.ac.be. This electronic address provides many data of nuclear astrophysics interest and also offers the possibility of generating interactively tables of reaction rates for networks and temperature grids selected by the user). The impact of nuclear physics uncertainties on the derived abundances is discussed in the framework of a simple parametric astrophysical model. These calculations have the virtue of being a guide in the selection of the nuclear uncertainties that have to be duly analyzed in detailed model stars, particularly in order to perform meaningful confrontations between abundance observations and predictions. They are also hoped to help nuclear astrophysici...

  6. Shock tube measurements of the rate constant for the reaction ethanol + OH.

    Science.gov (United States)

    Stranic, Ivo; Pang, Genny A; Hanson, Ronald K; Golden, David M; Bowman, Craig T

    2014-02-06

    The overall rate constant for the reaction ethanol + OH → products was determined experimentally from 900 to 1270 K behind reflected shock waves. Ethan(18)ol was utilized for these measurements in order to avoid the recycling of OH radicals following H-atom abstraction at the β-site of ethanol. Similar experiments were also performed with unlabeled ethan(16)ol in order to infer the rate constant that excludes reactivity at the β-site. The two data sets were used to directly infer the branching ratio for the reaction at the β-site. Experimental data in the current study and in previous low-temperature studies for the overall rate constant are best fit by the expression koverall = 5.07 × 10(5) T[K](2.31) exp(608/T[K]) cm(3) mol(-1) s(-1), valid from 300 to 1300 K. Measurements indicate that the branching ratio of the β-site is between 20 and 25% at the conditions studied. Pseudo-first-order reaction conditions were generated using tert-butylhydroperoxide (TBHP) as a fast source of (16)OH with ethanol in excess. (16)OH mole fraction time-histories were measured using narrow-line width laser absorption near 307 nm. Measurements were performed at the linecenter of the R22(5.5) transition in the A-X(0,0) band of (16)OH that does not overlap with any absorption features of (18)OH, thus producing a measurement of the (16)OH mole fraction that is insensitive to the presence of (18)OH.

  7. Plasticity of Performance Curves Can Buffer Reaction Rates from Body Temperature Variation in Active Endotherms

    Directory of Open Access Journals (Sweden)

    Frank Seebacher

    2017-08-01

    Full Text Available Endotherms regulate their core body temperature by adjusting metabolic heat production and insulation. Endothermic body temperatures are therefore relatively stable compared to external temperatures. The thermal sensitivity of biochemical reaction rates is thought to have co-evolved with body temperature regulation so that optimal reaction rates occur at the regulated body temperature. However, recent data show that core body temperatures even of non-torpid endotherms fluctuate considerably. Additionally, peripheral temperatures can be considerably lower and more variable than core body temperatures. Here we discuss whether published data support the hypothesis that thermal performance curves of physiological reaction rates are plastic so that performance is maintained despite variable body temperatures within active (non-torpid endotherms, and we explore mechanisms that confer plasticity. There is evidence that thermal performance curves in tissues that experience thermal fluctuations can be plastic, although this question remains relatively unexplored for endotherms. Mechanisms that alter thermal responses locally at the tissue level include transient potential receptor ion channels (TRPV and TRPM and the AMP-activated protein kinase (AMPK both of which can influence metabolism and energy expenditure. Additionally, the thermal sensitivity of processes that cause post-transcriptional RNA degradation can promote the relative expression of cold-responsive genes. Endotherms can respond to environmental fluctuations similarly to ectotherms, and thermal plasticity complements core body temperature regulation to increase whole-organism performance. Thermal plasticity is ancestral to endothermic thermoregulation, but it has not lost its selective advantage so that modern endotherms are a physiological composite of ancestral ectothermic and derived endothermic traits.

  8. Unimolecular reaction rate constants of NO{sub 2} just above D{sub 0}

    Energy Technology Data Exchange (ETDEWEB)

    Bezel, I.; Stolyarov, D.; Wittig, C.

    1999-12-09

    Photoinitiated unimolecular decomposition on a barrierless potential energy surface (PES) has been studied for the reaction NO{sub 2} {yields} O({sup 3}P{sub 2}) + NO(X{sup 2}{Pi}{sub 1/2}, {nu} = 0) for excess energies up to approximately 17 cm{sup {minus}1} above the dissociation threshold (i.e., D{sub 0} for nonrotating molecules) by using expansion-cooled samples and the time-resolved pump-probe technique. To examine the threshold region with enough energy resolution to discern abrupt changes in the rate constant, should they occur, a pump-probe cross-correlation temporal width of {approximately}25 ps and a pump line width {le}2 cm{sup {minus}1} has been used. These are the first direct observations of the reaction rate constants in this energy regime. The rate constant was found to increase by an order of magnitude, varying from {approximately}2 x 10{sup 10} s{sup {minus}1} to {ge}10{sup 11} s{sup {minus}1}, the latter being a rough lower bound imposed by the experimental arrangement. The rate constant does not display the energy dependence predicted by using phase space theory, at least in detail. Rather, it appears to reflect the highly complex nature of the levels and the multiple PESs that are believed to be responsible for the anomalously high vibronic level density which has been observed just below D{sub 0}. These results bridge the gap between spectroscopic studies which have been carried out at energies just above D{sub 0} and ultrafast experiments which have measured rate constants in this energy region with pump laser spectral widths of {approximately}30 cm{sup {minus}1}.

  9. Chemical reaction rates using the semiclassical Van-Vleck initialvalue representation

    Energy Technology Data Exchange (ETDEWEB)

    Venkataraman, Charulatha; Miller, William H.

    2006-11-29

    A semiclassical IVR formulation using the Van-Vleck propagator has been used to calculate the flux correlation function and thereby reaction rate constants. This Van-Vleck formulation of the flux-flux correlation function is computationally as simple as the classical Wigner model. However unlike the latter, it has the ability to capture quantum interference/coherence effects. Classical trajectories are evolved starting from the dividing surface that separates reactants and products, and are evolved negatively in time. This formulation has been tested on model problems ranging from the Eckart barrier, double well to the collinear H + H{sub 2}.

  10. Rates of reaction and process design data for the Hydrocarb Process

    Energy Technology Data Exchange (ETDEWEB)

    Steinberg, M.; Kobayashi, Atsushi [Brookhaven National Lab., Upton, NY (United States); Tung, Yuanki [Hydrocarb Corp., New York, NY (United States)

    1992-08-01

    In support of studies for developing the coprocessing of fossil fuels with biomass by the Hydrocarb Process, experimental and process design data are reported. The experimental work includes the hydropryolysis of biomass and the thermal decomposition of methane in a tubular reactor. The rates of reaction and conversion were obtained at temperature and pressure conditions pertaining to a Hydrocarb Process design. A Process Simulation Computer Model was used to design the process and obtain complete energy and mass balances. Multiple feedstocks including biomass with natural gas and biomass with coal were evaluated. Additional feedstocks including green waste, sewage sludge and digester gas were also evaluated for a pilot plant unit.

  11. THE ASYMPTOTIC LIMIT FOR A COMBUSTION MODEL IN REGARD TO INFINITE REACTION RATE

    Institute of Scientific and Technical Information of China (English)

    Ying Longan

    2008-01-01

    The Zeldovich-von Neumann-Doring model and the Chapman-Jouguet model for a simplified combustion model-Majda's model is studied. The author proves a uniform maximum norm estimate, then proves that as the rate of chemical reaction tends to infinity the solutions to the Zeldovich-von Neumann-Doring model tend to that of the Chapman-Jouguet model. The type of combustion waves is studied. This result is compared with the result of the projection and finite difference method for the same model.

  12. Shock tube/laser absorption measurements of the reaction rates of OH with ethylene and propene.

    Science.gov (United States)

    Vasu, Subith S; Hong, Zekai; Davidson, David F; Hanson, Ronald K; Golden, David M

    2010-11-04

    Reaction rates of hydroxyl (OH) radicals with ethylene (C₂H₄) and propene (C₃H₆) were studied behind reflected shock waves. OH + ethylene → products (rxn 1) rate measurements were conducted in the temperature range 973-1438 K, for pressures from 2 to 10 atm, and for initial concentrations of ethylene of 500, 751, and 1000 ppm. OH + propene → products (rxn 2) rate measurements spanned temperatures of 890-1366 K, pressures near 2.3 atm, and initial propene concentrations near 300 ppm. OH radicals were produced by shock-heating tert-butyl hydroperoxide, (CH₃)₃-CO-OH, and monitored by laser absorption near 306.7 nm. Rate constants for the reactions of OH with ethylene and propene were extracted by matching modeled and measured OH concentration time-histories in the reflected shock region. Current data are in excellent agreement with previous studies and extend the temperature range of OH + propene data. Transition state theory calculations using recent ab initio results give excellent agreement with our measurements and other data outside our temperature range. Fits (in units of cm³/mol/s) to the abstraction channels of OH + ethylene and OH + propene are k₁ = 2.23 × 10⁴ (T)(2.745) exp(-1115 K/T) for 600-2000 K and k₂ = 1.94 × 10⁶ (T)(2.229) exp(-540 K/T) for 700-1500 K, respectively. A rate constant determination for the reaction TBHP → products (rxn 3) was also obtained in the range 745-1014 K using OH data from behind both incident and reflected shock waves. These high-temperature measurements were fit with previous low-temperature data, and the following rate expression (0.6-2.6 atm), applicable over the temperature range 400-1050 K, was obtained: k₃ (1/s) = 8.13 × 10⁻¹² (T)(7.83) exp(-14598 K/T).

  13. Selected specific rates of reactions of transients from water in aqueous solution. Hydrated electron, supplemental data. [Reactions with transients from water, with inorganic solutes, and with solutes

    Energy Technology Data Exchange (ETDEWEB)

    Ross, A.B.

    1975-06-01

    A compilation of rates of reactions of hydrated electrons with other transients and with organic and inorganic solutes in aqueous solution appeared in NSRDS-NBS 43, and covered the literature up to early 1971. This supplement includes additional rates which have been published through July 1973.

  14. The interplay between transport and reaction rates as controls on nitrate attenuation in permeable, streambed sediments

    Science.gov (United States)

    Lansdown, K.; Heppell, C. M.; Trimmer, M.; Binley, A.; Heathwaite, A. L.; Byrne, P.; Zhang, H.

    2015-06-01

    Anthropogenic nitrogen fixation and subsequent use of this nitrogen as fertilizer have greatly disturbed the global nitrogen cycle. Rivers are recognized hot spots of nitrogen removal in the landscape as interaction between surface water and sediments creates heterogeneous redox environments conducive for nitrogen transformations. Our understanding of riverbed nitrogen dynamics to date comes mainly from shallow sediments or hyporheic exchange flow pathways with comparatively little attention paid to groundwater-fed, gaining reaches. We have used 15N techniques to quantify in situ rates of nitrate removal to 1 m depth within a groundwater-fed riverbed where subsurface hydrology ranged from strong upwelling to predominantly horizontal water fluxes. We combine these rates with detailed hydrologic measurements to investigate the interplay between biogeochemical activity and water transport in controlling nitrogen attenuation along upwelling flow pathways. Nitrate attenuation occurred via denitrification rather than dissimilatory nitrate reduction to ammonium or anammox (range = 12 to >17,000 nmol 15N L-1 h-1). Overall, nitrate removal within the upwelling groundwater was controlled by water flux rather than reaction rate (i.e., Damköhler numbers rates of denitrification and short water residence time close to the riverbed surface balanced by slower rates of denitrification and water flux at depth. Within this permeable riverbed >80% of nitrate removal occurs within sediments not exposed to hyporheic exchange flows under base flow conditions, illustrating the importance of deep sediments as nitrate sinks in upwelling systems.

  15. Running Head: Implementing Six Sigma Efforts

    Science.gov (United States)

    Lindsay, Jamie Eleaitia Mae

    2005-01-01

    Six Sigma is an organization wide program that provides common set of goals, language, and methodology for improving the overall quality of the processes within the organization (Davis & Heineke 2004). Six Sigma main concern is for the customer. What will the customers want? Need? Six Sigma has a model that helps Sigma get implemented DMAIC model…

  16. Elementary reaction rate measurements at high temperatures by tunable-laser flash-absorption

    Energy Technology Data Exchange (ETDEWEB)

    Hessler, J.P. [Argonne National Laboratory, IL (United States)

    1993-12-01

    The major objective of this program is to measure thermal rate coefficients and branching ratios of elementary reactions. To perform these measurements, the authors constructed an ultrahigh-purity shock tube to generate temperatures between 1000 and 5500 K. The tunable-laser flash-absorption technique is used to measure the rate of change of the concentration of species which absorb below 50,000 cm{sup {minus}1} e.g.: OH, CH, and CH{sub 3}. This technique is being extended into the vacuum-ultraviolet spectral region where one can measure atomic species e.g.: H, D, C, O, and N; and diatomic species e.g.: O{sub 2}, CO, and OH.

  17. Noise-induced convergence of the low flow rate chaos in the Belousov-Zhabotinsky reaction

    Science.gov (United States)

    Yoshimoto, Minoru; Nakaiwa, Masaru; Akiya, Takaji; Ohmori, Takao; Yamaguchi, Tomohiko

    The effect of noise on the low flow-rate chaos in the Belousov-Zhabotinsky (BZ) reaction was studied. The chaos was simulated using the three-variable model of Györgyi and Field. Gaussian white noise was imposed on the flow-rate of the reactant solutions fed into CSTR to simulate the so-called type P noise. The range of average noise amplitudes was chosen between 0.01% and 1% related to the inverse residence time. The calculated time series were analyzed on the basis of their Fourier spectra, maximum Lyapunov exponent, Kolmogorov entropies, return maps and invariant density. We found that the noise induces partial order of the period-3-like oscillations in the low flowrate chaos.

  18. Rate Constant and Branching Fraction for the NH2 + NO2 Reaction

    DEFF Research Database (Denmark)

    Klippenstein, Stephen J.; Harding, Lawrence B.; Glarborg, Peter

    2013-01-01

    The NH2 + NO2 reaction has been studied experimentally and theoretically. On the basis of laser photolysis/LIF experiments, the total rate constant was determined over the temperature range 295–625 K as k1,exp(T) = 9.5 × 10–7(T/K)−2.05 exp(−404 K/T) cm3 molecule–1 s–1. This value is in the upper...... may facilitate a small flux between the adducts. High- and low-pressure limit rate coefficients for the various product channels of NH2 + NO2 are determined from the ab initio TST-based master equation calculations for the temperature range 300–2000 K. The theoretical predictions are in good agreement...

  19. Scanning electrochemical microscopy of metallic biomaterials: reaction rate and ion release imaging modes.

    Science.gov (United States)

    Gilbert, J L; Smith, S M; Lautenschlager, E P

    1993-11-01

    The Scanning Electrochemical Microscope (SECM) is a nonoptical scanning microscopic instrument capable of imaging highly localized electrical currents associated with charge transfer reactions on metallic biomaterials surfaces. The SECM operates as an aqueous electrochemical cell under bipotentiostatic control with a microelectrode and sample independently biased as working electrodes. Microelectrode current and position is recorded as it is scanned very near a metallurgically polished planar sample surface. To date, the SECM has imaged metallic biomaterials surfaces in oxygen reaction rate imaging (ORRI) and ion release and deposition imaging (IRDI) modes. In ORRI, sample and microelectrode are biased at sufficiently negative potentials to reduce absorbed oxygen. As the microelectrode scans areas of active oxygen reduction, localized diffusion fields with decreased oxygen solution concentrations are encountered and resultant decrements in microelectrode current are observed. In IRDI mode the sample is positively biased and the microelectrode is negatively biased. The microelectrode detects anodic dissolution products with highest currents being observed over the most active areas. Performance of the SECM has been evaluated on Ni minigrids, gamma-1 Hg-Ag dental amalgam crystals, and sintered beads of Co-Cr-Mo alloy which represent significantly different geometries and corrosion processes to help demonstrate the potential of this instrument. The SECM is a valuable tool for imaging microelectrochemical processes on the surfaces of metallurgically polished metallic biomaterials samples and a wide variety of other surfaces of biological interest where charge transfer reactions occur. The SECM allows selective biasing of metallic biomaterials surfaces and Faradaic reactions can be selectively imaged while the surface is in the active, passive, or transpassive state.

  20. \\textit{Ab initio} study of reactive collisions between Rb($^{2}S$) or Rb($^{2}P$) and OH$^{-}$($^{1}\\Sigma^{+}$)

    CERN Document Server

    Kas, Milaim; Liévin, Jacques; Vaeck, Nathalie

    2016-01-01

    A theoretical rate constant for the associative detachment reaction Rb($^{2}S$)$+$OH$^{-}$($^{1}\\Sigma^{+}$)$\\rightarrow \\,$ RbOH($^{1}\\Sigma^{+}$)$+\\,e^{-}$ of 4$\\,\\times$10$^{-10}$cm$^{3}$s$^{-1}$ at 300 K has been calculated. This result agrees with the experimental rate constant of 2$^{+2}_{-1}\\,\\times10^{-10}$cm$^{3}$s$^{-1}$ obtained by Deiglmayr \\textit{et al.} (Phys. Rev. A 86, 2012) for a temperature between 200 K and 600 K. A Langevin-based dynamics which depends on the crossing point between the anion (RbOH$^{-}$) and neutral (RbOH) potential energy surfaces has been used. The calculation were performed using the ECP28MDF effective core potential to describe the rubidium atom at the CCSD(T) level of theory and extended basis sets. The effect of ECPs and basis set on the height of the crossing point, and hence the rate constant, has been investigated. The temperature dependence of the latter is also discussed. Preliminary work on the potential energy surface for the excited reaction channel Rb($^{2}...

  1. Reaction rate uncertainties and 26Al in AGB silicon carbide stardust

    CERN Document Server

    van Raai, M A; Karakas, A I; Iliadis, C

    2007-01-01

    Stardust is a class of presolar grains each of which presents an ideally uncontaminated stellar sample. Mainstream silicon carbide (SiC) stardust formed in the extended envelopes of carbon-rich asymptotic giant branch (AGB) stars and incorporated the radioactive nucleus 26Al as a trace element. The aim of this paper is to analyse in detail the effect of nuclear uncertainties, in particular the large uncertainties of up to four orders of magnitude related to the 26Al_g+(p,gamma)27Si reaction rate, on the production of 26Al in AGB stars and compare model predictions to data obtained from laboratory analysis of SiC stardust grains. Stellar uncertainties are also briefly discussed. We use a detailed nucleosynthesis postprocessing code to calculate the 26Al/27Al ratios at the surface of AGB stars of different masses (M = 1.75, 3, and 5 M_sun) and metallicities (Z = 0.02, 0.012, and 0.008). For the lower limit and recommended value of the 26Al_g(p,gamma)27Si reaction rate, the predicted 26Al/27Al ratios replicate t...

  2. Deep Mixing in Evolved Stars: I. The Effect of Reaction Rate Revisions from C to Al

    CERN Document Server

    Palmerini, S; Cristallo, S; Busso, M

    2010-01-01

    We present computations of nucleosynthesis in low-mass red-giant-branch and asymptotic-giant-branch stars of Population I experiencing extended mixing. We adopt the updated version of the FRANEC evolutionary model, a new post-process code for non-convective mixing and the most recent revisions for solar abundances. In this framework, we discuss the effects of recent improvements in relevant reaction rates for proton captures on intermediate-mass nuclei (from carbon to aluminum). For each nucleus we briefly discuss the new choices and their motivations. The calculations are then performed on the basis of a parameterized circulation, where the effects of the new nuclear inputs are best compared to previous works. We find that the new rates (and notably the one for the 14N(p,g)15O reaction) imply considerable modifications in the composition of post-main sequence stars. In particular, the slight temperature changes due to the reduced efficiency of proton captures on 14N induce abundance variations at the first d...

  3. Thermal behaviors, nonisothermal decomposition reaction kinetics, thermal safety and burning rates of BTATz-CMDB propellant.

    Science.gov (United States)

    Yi, Jian-Hua; Zhao, Feng-Qi; Wang, Bo-Zhou; Liu, Qian; Zhou, Cheng; Hu, Rong-Zu; Ren, Ying-Hui; Xu, Si-Yu; Xu, Kang-Zhen; Ren, Xiao-Ning

    2010-09-15

    The composite modified double base (CMDB) propellants (nos. RB0601 and RB0602) containing 3,6-bis (1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine (BTATz) without and with the ballistic modifier were prepared and their thermal behaviors, nonisothermal decomposition reaction kinetics, thermal safety and burning rates were investigated. The results show that there are three mass-loss stages in TG curve and two exothermic peaks in DSC curve for the BTATz-CMDB propellant. The first two mass-loss stages occur in succession and the temperature ranges are near apart, and the decomposition peaks of the two stages overlap each other, inducing only one visible exothermic peak appear in DSC curve during 350-550 K. The reaction mechanisms of the main exothermal decomposition processes of RB0601 and RB0602 are all classified as chemical reaction, the mechanism functions are f(alpha)=(1-alpha)(2), and the kinetic equations are dalpha/dt = 10(19.24)(1-alpha)(2)e(-2.32x10(4)/T) and dalpha/dt = 10(20.32)(1-alpha)(2)e(-2.32x10(4)/T). The thermal safety evaluation on the BTATz-CMDB propellants was obtained. With the substitution of 26% RDX by BTATz and with the help of the ballistic modifier in the CMDB propellant formulation, the burning rate can be improved by 89.0% at 8 MPa and 47.1% at 22 MPa, the pressure exponent can be reduced to 0.353 at 14-20 MPa.

  4. Thermal behaviors, nonisothermal decomposition reaction kinetics, thermal safety and burning rates of BTATz-CMDB propellant

    Energy Technology Data Exchange (ETDEWEB)

    Yi Jianhua [Xi' an Modern Chemistry Research Institute, Xi' an 710065 (China); Zhao Fengqi, E-mail: yiren@nwu.edu.cn [Xi' an Modern Chemistry Research Institute, Xi' an 710065 (China); Wang Bozhou; Liu Qian; Zhou Cheng; Hu Rongzu [Xi' an Modern Chemistry Research Institute, Xi' an 710065 (China); Ren Yinghui [School of Chemical Engineering, Northwest University, Xi' an 710069 (China); Xu Siyu [Xi' an Modern Chemistry Research Institute, Xi' an 710065 (China); Xu, Kang-Zhen [School of Chemical Engineering, Northwest University, Xi' an 710069 (China); Ren Xiaoning [Xi' an Modern Chemistry Research Institute, Xi' an 710065 (China)

    2010-09-15

    The composite modified double base (CMDB) propellants (nos. RB0601 and RB0602) containing 3,6-bis (1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine (BTATz) without and with the ballistic modifier were prepared and their thermal behaviors, nonisothermal decomposition reaction kinetics, thermal safety and burning rates were investigated. The results show that there are three mass-loss stages in TG curve and two exothermic peaks in DSC curve for the BTATz-CMDB propellant. The first two mass-loss stages occur in succession and the temperature ranges are near apart, and the decomposition peaks of the two stages overlap each other, inducing only one visible exothermic peak appear in DSC curve during 350-550 K. The reaction mechanisms of the main exothermal decomposition processes of RB0601 and RB0602 are all classified as chemical reaction, the mechanism functions are f({alpha}) = (1 - {alpha}){sup 2}, and the kinetic equations are d{alpha}/dt=10{sup 19.24}(1-{alpha}){sup 2}e{sup -2.32x10{sup 4/T}} and d{alpha}/dt=10{sup 20.32}(1-{alpha}){sup 2}e{sup -2.43x10{sup 4/T}}. The thermal safety evaluation on the BTATz-CMDB propellants was obtained. With the substitution of 26% RDX by BTATz and with the help of the ballistic modifier in the CMDB propellant formulation, the burning rate can be improved by 89.0% at 8 MPa and 47.1% at 22 MPa, the pressure exponent can be reduced to 0.353 at 14-20 MPa.

  5. The Effects of Mixing, Reaction Rates, and Stoichiometry on Yield for Mixing Sensitive Reactions—Part II: Design Protocols

    Directory of Open Access Journals (Sweden)

    Syed Imran A. Shah

    2012-01-01

    Full Text Available Competitive-consecutive and competitive-parallel reactions are both mixing sensitive reactions where the yield of desired product depends on how fast the reactants are brought together. Recent experimental results have suggested that the magnitude of the mixing effect may depend strongly on the stoichiometry of the reactions. To investigate this, a 1D, dimensionless, reaction-diffusion model was developed at the micromixing scale, yielding a single general Damköhler number. Dimensionless reaction rate ratios were derived for both reaction schemes. A detailed investigation of the effects of initial mixing condition (striation thickness, dimensionless reaction rate ratio, and reaction stoichiometry on the yield of desired product showed that the stoichiometry has a considerable effect on yield. All three variables were found to interact strongly. Model results for 12 stoichiometries are used to determine the mixing scale and relative rate ratio needed to achieve a specified yield for each reaction scheme. The results show that all three variables need to be considered when specifying reactors for mixing sensitive reactions.

  6. Study of the $\\Lambda p$ Interaction Close to the $\\Sigma^+n$ and $\\Sigma^0p$ Thresholds

    CERN Document Server

    Machner, H; Hinterberger, F; Magiera, A; Niskanen, J A; Ritman, J; Siudak, R

    2013-01-01

    The $\\Lambda p$ interaction close to the $\\Sigma N$ threshold is considered. Specifically, the pronounced structure seen in production reactions like $K^-d \\to \\pi^- \\Lambda p$ and $pp\\to K^+ \\Lambda p$ around the $\\Sigma N$ threshold is analyzed. Modern interaction models of the coupled $\\Lambda N - \\Sigma N$ systems generate such a structure either due to the presence of a (deuteron-like) unstable bound state or of an inelastic virtual state. % A determination of the position of the prominent peak as observed in various experiments for the two aforementioned reactions leads to values that agree quite well with each other. Furthermore, the deduced mean value of $2128.7\\pm 0.3$ MeV for the peak position coincides practically with the threshold energy of the $\\Sigma^+ n$ channel. This supports the interpretation of the structure as a genuine cusp, signaling an inelastic virtual state in the $^3S_1-^3D_1$ partial wave of the $\\Sigma N$ isospin 1/2 channel. % There is also evidence for a second peak (or shoulder...

  7. Study of the Reaction Rate of Gold Nanotube Synthesis from Sacrificial Silver Nanorods through the Galvanic Replacement Method

    OpenAIRE

    Sunil Kwon; Hyunbae Dong; Sang-Yup Lee

    2010-01-01

    An investigation was carried out about the gold nanotube synthesis via a galvanic replacement reaction. The progress of the gold nanotube synthesis was investigated using electron microscopy and UV-Vis spectroscopy. In addition, the reaction rates of gold nanotube formation in the early stage of the reaction were studied. The chlorine ion concentration linearly increased with the gold precursor concentration but deviated from the stoichiometric amounts. This deviation was probably due to AgCl...

  8. Stress-associated cardiovascular reaction masks heart rate dependence on physical load in mice.

    Science.gov (United States)

    Andreev-Andrievskiy, A A; Popova, A S; Borovik, A S; Dolgov, O N; Tsvirkun, D V; Custaud, M; Vinogradova, O L

    2014-06-10

    When tested on the treadmill mice do not display a graded increase of heart rate (HR), but rather a sharp shift of cardiovascular indices to high levels at the onset of locomotion. We hypothesized that under test conditions cardiovascular reaction to physical load in mice is masked with stress-associated HR increase. To test this hypothesis we monitored mean arterial pressure (MAP) and heart rate in C57BL/6 mice after exposure to stressful stimuli, during spontaneous locomotion in the open-field test, treadmill running or running in a wheel installed in the home cage. Mice were treated with β1-adrenoblocker atenolol (2mg/kg ip, A), cholinolytic ipratropium bromide (2mg/kg ip, I), combination of blockers (A+I), anxiolytic diazepam (5mg/kg ip, D) or saline (control trials, SAL). MAP and HR in mice increased sharply after handling, despite 3weeks of habituation to the procedure. Under stressful conditions of open field test cardiovascular parameters in mice were elevated and did not depend on movement speed. HR values did not differ in I and SAL groups and were reduced with A or A+I. HR was lower at rest in D pretreated mice. In the treadmill test HR increase over speeds of 6, 12 and 18m/min was roughly 1/7-1/10 of HR increase observed after placing the mice on the treadmill. HR could not be increased with cholinolytic (I), but was reduced after sympatholytic (A) or A+I treatment. Anxiolytic (D) reduced heart rate at lower speeds of movement and its overall effect was to unmask the dependency of HR on running speed. During voluntary running in non-stressful conditions of the home cage HR in mice linearly increased with increasing running speeds. We conclude that in test situations cardiovascular reactions in mice are governed predominantly by stress-associated sympathetic activation, rendering efforts to evaluate HR and MAP reactions to workload unreliable. Copyright © 2014 Elsevier Inc. All rights reserved.

  9. Pressure-Dependent Rate Rules for Intramolecular H-Migration Reactions of Hydroperoxyalkylperoxy Radicals in Low Temperature.

    Science.gov (United States)

    Yao, Qian; Sun, Xiao-Hui; Li, Ze-Rong; Chen, Fang-Fang; Li, Xiang-Yuan

    2017-04-27

    Intramolecular H-migration reaction of hydroperoxyalkylperoxy radicals ((•)O2QOOH) is one of the most important reaction families in the low-temperature oxidation of hydrocarbon fuels. This reaction family is first divided into classes depending upon H atom transfer from -OOH bonded carbon or non-OOH bonded carbon, and then the two classes are further divided depending upon the ring size of the transition states and the types of the carbons from which the H atom is transferred. High pressure limit rate rules and pressure-dependent rate rules for each class are derived from the rate constants of a representative set of reactions within each class using electronic structure calculations performed at the CBS-QB3 level of theory. For the intramolecular H-migration reactions of (•)O2QOOH radicals for abstraction from an -OOH substituted carbon atom (-OOH bonded case), the result shows that it is acceptable to derive the rate rules by taking the average of the rate constants from a representative set of reactions with different sizes of the substitutes. For the abstraction from a non-OOH substituted carbon atom (non-OOH bonded case), rate rules for each class are also derived and it is shown that the difference between the rate constants calculated by CBS-QB3 method and rate constants estimated from the rate rules may be large; therefore, to get more reliable results for the low-temperature combustion modeling of alkanes, it is better to assign each reaction its CBS-QB3 calculated rate constants, instead of assigning the same values for the same reaction class according to rate rules. The intramolecular H-migration reactions of (•)O2QOOH radicals (a thermally equilibrated system) are pressure-dependent, and the pressure-dependent rate constants of these reactions are calculated by using the Rice-Ramsberger-Kassel-Marcus/master-equation theory at pressures varying from 0.01 to 100 atm. The impact of molecular size on the pressure-dependent rate constants of the

  10. The role of advanced reactive surface area characterization in improving predictions of mineral reaction rates

    Science.gov (United States)

    Beckingham, L. E.; Zhang, S.; Mitnick, E.; Cole, D. R.; Yang, L.; Anovitz, L. M.; Sheets, J.; Swift, A.; Kneafsey, T. J.; Landrot, G.; Mito, S.; Xue, Z.; Steefel, C. I.; DePaolo, D. J.; Ajo Franklin, J. B.

    2014-12-01

    Geologic sequestration of CO2 in deep sedimentary formations is a promising means of mitigating carbon emissions from coal-fired power plants but the long-term fate of injected CO2 is challenging to predict. Reactive transport models are used to gain insight over long times but rely on laboratory determined mineral reaction rates that have been difficult to extrapolate to field systems. This, in part, is due to a lack of understanding of mineral reactive surface area. Many models use an arbitrary approximation of reactive surface area, applying orders of magnitude scaling factors to measured BET or geometric surface areas. Recently, a few more sophisticated approaches have used 2D and 3D image analyses to determine mineral-specific reactive surface areas that account for the accessibility of minerals. However, the ability of these advanced surface area estimates to improve predictions of mineral reaction rates has yet to be determined. In this study, we fuse X-ray microCT, SEM QEMSCAN, XRD, SANS, and SEM-FIB analysis to determine mineral-specific accessible reactive surface areas for a core sample from the Nagaoka pilot CO2 injection site (Japan). This sample is primarily quartz, plagioclase, smectite, K-feldspar, and pyroxene. SEM imaging shows abundant smectite cement and grain coatings that decrease the fluid accessibility of other minerals. However, analysis of FIB-SEM images reveals that smectite nano-pores are well connected such that access to underlying minerals is not occluded by smectite coatings. Mineral-specific accessible surfaces are determined, accounting for the connectivity of the pore space with and without connected smectite nano-pores. The large-scale impact of variations in accessibility and dissolution rates are then determined through continuum scale modeling using grid-cell specific information on accessible surface areas. This approach will be compared with a traditional continuum scale model using mineral abundances and common surface area

  11. The reaction rate for dissociative adsorption of N-2 on stepped Ru(0001): Six-dimensional quantum calculations

    DEFF Research Database (Denmark)

    van Harrevelt, Rob; Honkala, Johanna Karoliina; Nørskov, Jens Kehlet

    2005-01-01

    Quantum-mechanical calculations of the reaction rate for dissociative adsorption of N-2 on stepped Ru(0001) are presented. Converged six-dimensional quantum calculations for this heavy-atom reaction have been performed using the multiconfiguration time-dependent Hartree method. A potential...

  12. Two Optimization Methods to Determine the Rate Constants of a Complex Chemical Reaction Using FORTRAN and MATLAB

    Directory of Open Access Journals (Sweden)

    Abdel-Latif A. Seoud

    2010-01-01

    Full Text Available Problem statement: For chemical reactions, the determination of the rate constants is both very difficult and a time consuming process. The aim of this research was to develop computer programs for determining the rate constants for the general form of any complex reaction at a certain temperature. The development of such program can be very helpful in the control of industrial processes as well as in the study of the reaction mechanisms. Determination of the accurate values of the rate constants would help in establishing the optimum conditions of reactor design including pressure, temperature and other parameters of the chemical reaction. Approach: From the experimental concentration-time data, initial values of rate constants were calculated. Experimental data encountered several types of errors, including temperature variation, impurities in the reactants and human errors. Simulations of a second order consecutive irreversible chemical reaction of the saponification of diethyl ester were presented as an example of the complex reactions. The rate equations (system of simultaneous differential equations of the reaction were solved to get the analytical concentration versus time profiles. The simulation results were compared with experimental results at each measured point. All deviations between experimental and calculated values were squared and summed up to form a new function. This function was fed into a minimizer routine that gave the optimal rate constants. Two optimization techniques were developed using FORTRAN and MATLAB for accurately determining the rate constants of the reaction at certain temperature from the experimental data. Results: Results showed that the two proposed programs were very efficient, fast and accurate tools to determine the true rate constants of the reaction with less 1% error. The use of the MATLAB embedded subroutines for simultaneously solving the differential equations and minimization of the error function

  13. Analysis of turbulent free jet hydrogen-air diffusion flames with finite chemical reaction rates

    Science.gov (United States)

    Sislian, J. P.

    1978-01-01

    The nonequilibrium flow field resulting from the turbulent mixing and combustion of a supersonic axisymmetric hydrogen jet in a supersonic parallel coflowing air stream is analyzed. Effective turbulent transport properties are determined using the (K-epsilon) model. The finite-rate chemistry model considers eight reactions between six chemical species, H, O, H2O, OH, O2, and H2. The governing set of nonlinear partial differential equations is solved by an implicit finite-difference procedure. Radial distributions are obtained at two downstream locations of variables such as turbulent kinetic energy, turbulent dissipation rate, turbulent scale length, and viscosity. The results show that these variables attain peak values at the axis of symmetry. Computed distributions of velocity, temperature, and mass fraction are also given. A direct analytical approach to account for the effect of species concentration fluctuations on the mean production rate of species (the phenomenon of unmixedness) is also presented. However, the use of the method does not seem justified in view of the excessive computer time required to solve the resulting system of equations.

  14. Venting Design for Di-tert-butyl Peroxide Runaway Reaction Based on Accelerating Rate Calorimeter Test

    Institute of Scientific and Technical Information of China (English)

    魏彤彤; 蒋慧灵

    2012-01-01

    In order to design the relief system size of di-tert-butyl peroxide(DTBP) storage tanks,the runaway re-action of DTBP was simulated by accelerating rate calorimeter(ARC).The results indicated that under adiabatic conditions the initial exothermic temperature was 102.6 ℃,the maximum self-heating rate was 3.095×107 ℃·min-1,the maximum self-heating temperature was 375.9 ℃,and the pressure produced by unit mass was 4.512 MPa·g-1.Judged by ARC test,the emergency relief system for DTBP was a hybrid system.Based on Design Institute for Emergency Relief System(DIERS) method,the releasing mass flow rate W was determined by Leung methods,and the mass velocity G was calculated by two modified Omega methods.The two relief sizes calculated by monograph Omega method and arithmetic Omega method are close,with only 0.63% relative error.The monograph Omega method is more convenient to apply.

  15. The form of the rate constant for elementary reactions at equilibrium from MD: framework and proposals for thermokinetics

    CERN Document Server

    Jesudason, C G

    2006-01-01

    The rates or formation and concentration distributions of a dimer reaction showing hysteresis behavior are examined in an ab initio chemical reaction designed as elementary and where the hysteresis structure precludes the formation of transition states (TS) with pre-equilibrium and internal sub-reactions. It was discovered that the the reactivity coefficients, defined as a measure of departure from the zero density rate constant for the forward and backward steps had a ratio that was equal to the activity coefficient ratio for the product and reactant species. From the above observations, a theory is developed with the aid of some proven elementary theorems in thermodynamics, and expressions are derived whereby a feasible experimental and computational method for determining the activity coefficients from the rate constants may be obtained The theory developed is applied to ionic reactions where the standard Bronsted-Bjerrum rate equation and exceptions to this are rationalized, and by viewing ion association...

  16. Monte carlo simulations of Yttrium reaction rates in Quinta uranium target

    Directory of Open Access Journals (Sweden)

    Suchopár M.

    2017-01-01

    Full Text Available The international collaboration Energy and Transmutation of Radioactive Waste (E&T RAW performed intensive studies of several simple accelerator-driven system (ADS setups consisting of lead, uranium and graphite which were irradiated by relativistic proton and deuteron beams in the past years at the Joint Institute for Nuclear Research (JINR in Dubna, Russia. The most recent setup called Quinta, consisting of natural uranium target-blanket and lead shielding, was irradiated by deuteron beams in the energy range between 1 and 8 GeV in three accelerator runs at JINR Nuclotron in 2011 and 2012 with yttrium samples among others inserted inside the setup to measure the neutron flux in various places. Suitable activation detectors serve as one of possible tools for monitoring of proton and deuteron beams and for measurements of neutron field distribution in ADS studies. Yttrium is one of such suitable materials for monitoring of high energy neutrons. Various threshold reactions can be observed in yttrium samples. The yields of isotopes produced in the samples were determined using the activation method. Monte Carlo simulations of the reaction rates leading to production of different isotopes were performed in the MCNPX transport code and compared with the experimental results obtained from the yttrium samples.

  17. Influence of the excitation light intensity on the rate of fluorescence quenching reactions: pulsed experiments.

    Science.gov (United States)

    Angulo, Gonzalo; Milkiewicz, Jadwiga; Kattnig, Daniel; Nejbauer, Michał; Stepanenko, Yuriy; Szczepanek, Jan; Radzewicz, Czesław; Wnuk, Paweł; Grampp, Günter

    2017-02-22

    The effect of multiple light excitation events on bimolecular photo-induced electron transfer reactions in liquid solution is studied experimentally. It is found that the decay of fluorescence can be up to 25% faster if a second photon is absorbed after a first cycle of quenching and recombination. A theoretical model is presented which ascribes this effect to the enrichment of the concentration of quenchers in the immediate vicinity of fluorophores that have been previously excited. Despite its simplicity, the model delivers a qualitative agreement with the observed experimental trends. The original theory by Burshtein and Igoshin (J. Chem. Phys., 2000, 112, 10930-10940) was created for continuous light excitation though. A qualitative extrapolation from the here presented pulse experiments to the continuous excitation conditions lead us to conclude that in the latter the order of magnitude of the increase of the quenching efficiency upon increasing the light intensity of excitation, must also be on the order of tens of percent. These results mean that the rate constant for photo-induced bimolecular reactions depends not only on the usual known factors, such as temperature, viscosity and other properties of the medium, but also on the intensity of the excitation light.

  18. Origin of the Non-Arrhenius Behavior of the Rates of Enzymatic Reactions.

    Science.gov (United States)

    Roy, Subhendu; Schopf, Patrick; Warshel, Arieh

    2017-07-13

    The origin of the non-Arrhenius behavior of the rate constant for hydride transfer enzymatic reactions has been a puzzling problem since its initial observation. This effect has been used originally to support the idea that enzymes work by dynamical effects and more recently to suggest an entropy funnel model. Our analysis, however, has advanced the idea that the reason for the non-Arrhenius trend reflects the temperature dependence of the rearrangements of the protein polar groups in response to the change in the charge distribution of the reacting system during the transition from the ground state (GS) to the transition state (TS). Here we examine the validity of our early proposal by simulating the catalytic reaction of alcohol dehydrogenase (ADH) and determine the microscopic origin of the entropic and enthalpic contributions to the activation barrier. The corresponding analysis establishes the origin of the non-Arrhenius behaviors and quantifies our original suggestion that the classical effect is due to the entropic contributions of the environment. We also find that the quantum effects reflect in part the temperature dependence of the donor-acceptor distance.

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

    Science.gov (United States)

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

    2013-01-01

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

  20. Metabolic control analysis of biochemical pathways based on a thermokinetic description of reaction rates

    DEFF Research Database (Denmark)

    Nielsen, Jens Bredal

    1997-01-01

    Metabolic control analysis is a powerful technique for the evaluation of flux control within biochemical pathways. Its foundation is the elasticity coefficients and the flux control coefficients (FCCs). On the basis of a thermokinetic description of reaction rates it is here shown...... affinity. This parameter can often be determined from experiments in vitro. The methodology is applicable only to the analysis of simple two-step pathways, but in many cases larger pathways can be lumped into two overall conversions. In cases where this cannot be done it is necessary to apply an extension...... be much more widely applied, although it was originally based on linearized kinetics. The methodology of determining elasticity coefficients directly from pool levels is illustrated with an analysis of the first two steps of the biosynthetic pathway of penicillin. The results compare well with previous...

  1. CORAL: QSPR modeling of rate constants of reactions between organic aromatic pollutants and hydroxyl radical.

    Science.gov (United States)

    Toropov, A A; Toropova, A P; Rasulev, B F; Benfenati, E; Gini, G; Leszczynska, D; Leszczynski, J

    2012-09-05

    The rate constants (K(OH)) of reactions between 78 organic aromatic pollutants and hydroxyl radical were examined. Simplified molecular input line entry system was used as representation of the molecular structure of the pollutants. Quantitative structure-property relationships was developed using CORAL software (http://www.insilico.eu/CORAL) for four random splits of the data into the subtraining, calibration, and test sets. The obtained results reveal good predictive potential of the applied approach: correlation coefficients (r(2)) for the test sets of the four random splits are 0.75, 0.91, 0.84, and 0.80. Using the Monte Carlo method CORAL software generated the optimal descriptors for one-variable models. The reproducibility of each model was tested performing three runs of the Monte Carlo optimization. The current data were compared to previous results and discussed. Copyright © 2012 Wiley Periodicals, Inc.

  2. Gauging the Poisson sigma model

    CERN Document Server

    Zucchini, Roberto

    2008-01-01

    We show how to carry out the gauging of the Poisson sigma model in an AKSZ inspired formulation by coupling it to the a generalization of the Weil model worked out in ref. arXiv:0706.1289 [hep-th]. We call the resulting gauged field theory, Poisson--Weil sigma model. We study the BV cohomology of the model and show its relation to Hamiltonian basic and equivariant Poisson cohomology. As an application, we carry out the gauge fixing of the pure Weil model and of the Poisson--Weil model. In the first case, we obtain the 2--dimensional version of Donaldson--Witten topological gauge theory, describing the moduli space of flat connections on a closed surface. In the second case, we recover the gauged A topological sigma model worked out by Baptista describing the moduli space of solutions of the so--called vortex equations.

  3. A kinetic study of the reactions between H2O2 and Cu,Zn superoxide dismutase; evidence for an electrostatic control of the reaction rate.

    Science.gov (United States)

    Viglino, P; Scarpa, M; Rotilio, G; Rigo, A

    1988-01-04

    H2O2 was shown to reduce the copper ion of native bovine Cu,Zn superoxide dismutase (superoxide:superoxide oxidoreductase, EC 1.15.1.1) (ECu2+) and to oxidize the reduced enzyme (ECu+). The time-course of these processes was monitored by NMR measurement of the longitudinal relaxation rate of the water protons. A steady-state characterized by the same ratio [ECu2+]/[( EC2+] + [ECu+]) was obtained either by starting from the oxidized or the reduced enzyme. The kinetics of these processes appear to be quite complex, since different reactions between H2O2, or its reaction products, and the enzyme-bound copper control the reaction rate. The solution of the differential equations describing the kinetic processes showed that the oxidation and the reduction of the copper ion by H2O2 are first-order with respect to the copper ion itself only when these processes approach the steady-state. The rate constants of the reduction and oxidation reactions were calculated according to these equations and were found to have comparable values which are in the range 5-80 and 5-45 M-1.min-1, respectively, changing the pH from 5.6 to 7 at 0.21 M ionic strength. This result, together with the dependence of the reaction rates on pH and ionic strength, points to HO2- as the reactive species in both processes, and indicates that the electrostatic control of the access of the peroxide to the active site is the rate-determining step of the two redox reactions.

  4. Evaluation of the FBR MONJU core breeding ratio and the power distribution from the reaction rate distribution measurement

    Energy Technology Data Exchange (ETDEWEB)

    Usami, Shin; Suzuki, Takayuki; Sasaki, Kenji; Deshimaru, Takehide [Power Reactor and Nuclear Fuel Development Corp., Tsuruga, Fukui (Japan). Monju Construction Office; Nakashima, Fumiaki

    1996-09-01

    In MONJU, reaction rate distribution measurements were made by foil activation methods from May through September 1994. On the basis of the reaction rate measurement data, the MONJU initial core breeding ratio and the power distribution, etc. were evaluated. As a result, the evaluated values and the calculated values showed good agreement, and we confirmed that the core performance of MONJU and the method of core calculations were satisfactory. (author)

  5. The extracytoplasmic function (ECF) sigma factors.

    Science.gov (United States)

    Helmann, John D

    2002-01-01

    Bacterial sigma (sigma) factors are an essential component of RNA polymerase and determine promoter selectivity. The substitution of one sigma factor for another can redirect some or all of the RNA polymerase in a cell to activate the transcription of genes that would otherwise be silent. As a class, alternative sigma factors play key roles in coordinating gene transcription during various stress responses and during morphological development. The extracytoplasmic function (ECF) sigma factors are small regulatory proteins that are quite divergent in sequence relative to most other sigma factors. Many bacteria, particularly those with more complex genomes, contain multiple ECF sigma factors and these regulators often outnumber all other types of sigma factor combined. Examples include Bacillus subtilis (7 ECF sigma factors), Mycobacterium tuberculosis (10), Caulobacter crescentus (13), Pseudomonas aeruginosa (approximately 19), and Streptomyces coelicolor (approximately 50). The roles and mechanisms of regulation for these various ECF sigma factors are largely unknown, but significant progress has been made in selected systems. As a general trend, most ECF sigma factors are cotranscribed with one or more negative regulators. Often, these include a transmembrane protein functioning as an anti-sigma factor that binds, and inhibits, the cognate sigma factor. Upon receiving a stimulus from the environment, the sigma factor is released and can bind to RNA polymerase to stimulate transcription. In many ways, these anti-sigma:sigma pairs are analogous to the more familiar two-component regulatory systems consisting of a transmembrane histidine protein kinase and a DNA-binding response regulator. Both are mechanisms of coordinating a cytoplasmic transcriptional response to signals perceived by protein domains external to the cell membrane. Here, I review current knowledge of some of the better characterized ECF sigma factors, discuss the variety of experimental approaches

  6. Kinetics of low-temperature transitions and a reaction rate theory from non-equilibrium distributions

    Science.gov (United States)

    Aquilanti, Vincenzo; Coutinho, Nayara Dantas; Carvalho-Silva, Valter Henrique

    2017-03-01

    This article surveys the empirical information which originated both by laboratory experiments and by computational simulations, and expands previous understanding of the rates of chemical processes in the low-temperature range, where deviations from linearity of Arrhenius plots were revealed. The phenomenological two-parameter Arrhenius equation requires improvement for applications where interpolation or extrapolations are demanded in various areas of modern science. Based on Tolman's theorem, the dependence of the reciprocal of the apparent activation energy as a function of reciprocal absolute temperature permits the introduction of a deviation parameter d covering uniformly a variety of rate processes, from those where quantum mechanical tunnelling is significant and d 0, corresponding to the Pareto-Tsallis statistical weights: these generalize the Boltzmann-Gibbs weight, which is recovered for d = 0. It is shown here how the weights arise, relaxing the thermodynamic equilibrium limit, either for a binomial distribution if d > 0 or for a negative binomial distribution if d kinetics, where transport phenomena accelerate processes as the temperature increases; (ii) the sub-Arrhenius kinetics, where quantum mechanical tunnelling propitiates low-temperature reactivity; (iii) the anti-Arrhenius kinetics, where processes with no energetic obstacles are rate-limited by molecular reorientation requirements. Particular attention is given for case (i) to the treatment of diffusion and viscosity, for case (ii) to formulation of a transition rate theory for chemical kinetics including quantum mechanical tunnelling, and for case (iii) to the stereodirectional specificity of the dynamics of reactions strongly hindered by the increase of temperature. This article is part of the themed issue 'Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'.

  7. Helium effects on microstructural change in RAFM steel under irradiation: Reaction rate theory modeling

    Science.gov (United States)

    Watanabe, Y.; Morishita, K.; Nakasuji, T.; Ando, M.; Tanigawa, H.

    2015-06-01

    Reaction rate theory analysis has been conducted to investigate helium effects on the formation kinetics of interstitial type dislocation loops (I-loops) and helium bubbles in reduced-activation-ferritic/martensitic steel during irradiation, by focusing on the nucleation and growth processes of the defect clusters. The rate theory model employs the size and chemical composition dependence of thermal dissociation of point defects from defect clusters. In the calculations, the temperature and the production rate of Frenkel pairs are fixed to be T = 723 K and PV = 10-6 dpa/s, respectively. And then, only the production rate of helium atoms was changed into the following three cases: PHe = 0, 10-7 and 10-5 appm He/s. The calculation results show that helium effect on I-loop formation quite differs from that on bubble formation. As to I-loops, the loop formation hardly depends on the existence of helium, where the number density of I-loops is almost the same for the three cases of PHe. This is because helium atoms trapped in vacancies are easily emitted into the matrix due to the recombination between the vacancies and SIAs, which induces no pronounced increase or decrease of vacancies and SIAs in the matrix, leading to no remarkable impact on the I-loop nucleation. On the other hand, the bubble formation depends much on the existence of helium, in which the number density of bubbles for PHe = 10-7 and 10-5 appm He/s is much higher than that for PHe = 0. This is because helium atoms trapped in a bubble increase the vacancy binding energy, and suppress the vacancy dissociation from the bubble, resulting in a promotion of the bubble nucleation. And then, the helium effect on the promotion of bubble nucleation is very strong, even the number of helium atoms in a bubble is not so large.

  8. The Effect of Screening Factors and Thermonuclear Reaction Rates in the Pre-main Sequence Evolution of Low Mass Stars

    Indian Academy of Sciences (India)

    İ. Küçük; Ş. Çalışkan

    2010-09-01

    In understanding the nucleosynthesis of the elements in stars, one of the most important quantities is the reaction rate and it must be evaluated in terms of the stellar temperature , and its determination involves the knowledge of the excitation function () of the specific nuclear reaction leading to the final nucleus. In this paper, the effect of thermonuclear reaction rates to the pre-main sequence evolution of low mass stars having masses 0.7, 0.8, 0.9 and 1 M⊙ are studied by using our modified Stellar Evolutionary Program.

  9. Evaluation of the reaction rate constants for the gas-phase Al-CH4-air combustion chemistry

    Science.gov (United States)

    Sharipov, A. S.; Titova, N. S.; Starik, A. M.

    2012-10-01

    The most likely reaction pathways and reaction products in the Al-CH4-O2-N2 system are investigated using density functional theory and ab initio calculations. The B3LYP functional with extended 6-311+G(3df,2p) basis set as well as the CBS-QB3 composite method are mainly utilised. Theoretical analysis of corresponding reaction rate constants is also performed with the use of simple theoretical models. A critical overview of current knowledge on combustion-relevant reactions with aluminium compounds is given. On the basis of critical comparison of available experimental kinetic data with theoretical calculations, the approximations for rate constants for 44 reversible elementary reactions involving Al-containing species are recommended for use in combustion issues.

  10. The LHCb pentaquark as a $\\bar{D}^*\\Sigma_c-\\bar{D}^*\\Sigma_c^*$ molecular state

    CERN Document Server

    Roca, L.; Oset, E.

    2015-01-01

    We perform a theoretical analysis of the $\\Lambda_b \\to J/\\psi K^- p$ reaction from where a recent LHCb experiment extracts a $\\Lambda(1405)$ contribution in the $K^- p$ spectrum close to threshold and two baryon states of hidden charm in the $J/\\psi\\,p$ spectrum. We recall that baryon states of this type have been theoretically predicted matching the mass, width and $J^P$ of the experiment, concretely some states built up from the $J/\\psi\\, N$, $\\bar D^* \\Lambda_c$, $\\bar D^* \\Sigma_c$, $\\bar D \\Sigma^*_c$ and $\\bar D^* \\Sigma^*_c$ coupled channels. We assume that the observed narrow state around 4450 MeV has this nature and we are able to describe simultaneously the shapes and relative strength of the the $K^- p$ mass distribution close to threshold and the peak of the $J/\\psi\\,p$ distribution, with values of the $J/\\psi\\, p$ coupling to the resonance in line with the theoretical ones. The non trivial matching of many properties gives support to a $J^P=3/2^-$ assignment to this state and to its nature as a ...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-12-05

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

  12. Spectra of conformal sigma models

    Energy Technology Data Exchange (ETDEWEB)

    Tlapak, Vaclav

    2015-04-15

    In this thesis the spectra of conformal sigma models defined on (generalized) symmetric spaces are analysed. The spaces where sigma models are conformal without the addition of a Wess-Zumino term are supermanifolds, in other words spaces that include fermionic directions. After a brief review of the general construction of vertex operators and the background field expansion, we compute the diagonal terms of the one-loop anomalous dimensions of sigma models on semi-symmetric spaces. We find that the results are formally identical to the symmetric case. However, unlike for sigma models on symmetric spaces, off diagonal terms that lead to operator mixing are also present. These are not computed here. We then present a detailed analysis of the one-loop spectrum of the supersphere S{sup 3} {sup vertical} {sup stroke} {sup 2} sigma model as one of the simplest examples. The analysis illustrates the power and simplicity of the construction. We use this data to revisit a duality with the OSP(4 vertical stroke 2) Gross-Neveu model that was proposed by Candu and Saleur. With the help of a recent all-loop result for the anomalous dimension of (1)/(2)BPS operators of Gross-Neveu models, we are able to recover the entire zero-mode spectrum of the supersphere model. We also argue that the sigma model constraints and its equations of motion are implemented correctly in the Gross-Neveu model, including the one-loop data. The duality is further supported by a new all-loop result for the anomalous dimension of the ground states of the sigma model. However, higher-gradient operators cannot be completely recovered. It is possible that this discrepancy is related to a known instability of the sigma model. The instability of sigma models is due to symmetry preserving high-gradient operators that become relevant at arbitrarily small values of the coupling. This feature has been observed long ago in one-loop calculations of the O(N)-vector model and soon been realized to be a generic

  13. INTEGRATING SIX-SIGMA AND HEALTHCARE QUALITY IMPROVEMENT CIRCLES IN REDUCING THE NEEDLE STICKING

    OpenAIRE

    Sen-Ji Chen; Frank F. C. Pan; Hsuen C. H. Chen

    2008-01-01

    Six-Sigma (SS) is a managerial philosophy used in detecting the error rate of a particular (set) of activities. This research applies six sigma concepts in dealing with troublesome needle-stick events that occurred in a Taiwan hospital. This research integrates several advanced managerial instruments into one framework, grounded in Continuous Quality Improvement and Total Quality Management. This framework combines Six-Sigma and Health Quality Improvement circle practices. The project suggest...

  14. New Astrophysical Reaction Rates for 18F(p, α)15O and 18F(p, γ)19Ne

    Institute of Scientific and Technical Information of China (English)

    SHU Neng-Chuan(舒能川); D. W. Bardayan; J. C. Blackmon; CHEN Yong-Shou(陈永寿); R. L. Kozub; P. D. Parker; M. S. Smith

    2003-01-01

    The rates of the thermonuclear 18F(p, α)15O and 18F(p,γ)19Ne reactions in hot astrophysical environments are needed to understand gamma-ray emission from nova explosions. The rates for these reactions have been uncertain due to discrepancies in recent measurements, as well as to a lack of a comprehensive examination of the available structure information in the compound nucleus 19Ne. We have examined the latest experimental measurements with radioactive and stable beams, and made estimates of the unmeasured 19Ne nuclear level parameters, to generate new rates with uncertainties for these reactions. The rates are expressed as numerical values over the temperature range relevant for stellar explosions, as well as analytical expressions as functions of temperature in a format suitable for use in astrophysical simulations. Comparisons with the previous rate calculations are carried out, and the astrophysical implications are briefly discussed.

  15. Study of the Reaction Rate of Gold Nanotube Synthesis from Sacrificial Silver Nanorods through the Galvanic Replacement Method

    Directory of Open Access Journals (Sweden)

    Sunil Kwon

    2010-01-01

    Full Text Available An investigation was carried out about the gold nanotube synthesis via a galvanic replacement reaction. The progress of the gold nanotube synthesis was investigated using electron microscopy and UV-Vis spectroscopy. In addition, the reaction rates of gold nanotube formation in the early stage of the reaction were studied. The chlorine ion concentration linearly increased with the gold precursor concentration but deviated from the stoichiometric amounts. This deviation was probably due to AgCl precipitates formed by the reaction of chlorine ions with dissolved silver ions. The replacement reaction was promoted with increased temperature and was nonlinearly proportional to the gold ion concentration. The outcomes of this research will enhance the current understanding of the galvanic replacement reaction.

  16. Standard and Nonstandard Neutrino-Nucleus Reactions Cross Sections and Event Rates to Neutrino Detection Experiments

    Directory of Open Access Journals (Sweden)

    D. K. Papoulias

    2015-01-01

    Full Text Available In this work, we explore ν-nucleus processes from a nuclear theory point of view and obtain results with high confidence level based on accurate nuclear structure cross sections calculations. Besides cross sections, the present study includes simulated signals expected to be recorded by nuclear detectors and differential event rates as well as total number of events predicted to be measured. Our original cross sections calculations are focused on measurable rates for the standard model process, but we also perform calculations for various channels of the nonstandard neutrino-nucleus reactions and come out with promising results within the current upper limits of the corresponding exotic parameters. We concentrate on the possibility of detecting (i supernova neutrinos by using massive detectors like those of the GERDA and SuperCDMS dark matter experiments and (ii laboratory neutrinos produced near the spallation neutron source facilities (at Oak Ridge National Lab by the COHERENT experiment. Our nuclear calculations take advantage of the relevant experimental sensitivity and employ the severe bounds extracted for the exotic parameters entering the Lagrangians of various particle physics models and specifically those resulting from the charged lepton flavour violating μ-→e- experiments (Mu2e and COMET experiments.

  17. Kinetics of low-temperature transitions and a reaction rate theory from non-equilibrium distributions.

    Science.gov (United States)

    Aquilanti, Vincenzo; Coutinho, Nayara Dantas; Carvalho-Silva, Valter Henrique

    2017-04-28

    This article surveys the empirical information which originated both by laboratory experiments and by computational simulations, and expands previous understanding of the rates of chemical processes in the low-temperature range, where deviations from linearity of Arrhenius plots were revealed. The phenomenological two-parameter Arrhenius equation requires improvement for applications where interpolation or extrapolations are demanded in various areas of modern science. Based on Tolman's theorem, the dependence of the reciprocal of the apparent activation energy as a function of reciprocal absolute temperature permits the introduction of a deviation parameter d covering uniformly a variety of rate processes, from those where quantum mechanical tunnelling is significant and d  0, corresponding to the Pareto-Tsallis statistical weights: these generalize the Boltzmann-Gibbs weight, which is recovered for d = 0. It is shown here how the weights arise, relaxing the thermodynamic equilibrium limit, either for a binomial distribution if d > 0 or for a negative binomial distribution if d theory for chemical kinetics including quantum mechanical tunnelling, and for case (iii) to the stereodirectional specificity of the dynamics of reactions strongly hindered by the increase of temperature.This article is part of the themed issue 'Theoretical and computational studies of non-equilibrium and non-statistical dynamics in the gas phase, in the condensed phase and at interfaces'. © 2017 The Author(s).

  18. Analysis of turbulent free-jet hydrogen-air diffusion flames with finite chemical reaction rates

    Science.gov (United States)

    Sislian, J. P.; Glass, I. I.; Evans, J. S.

    1979-01-01

    A numerical analysis is presented of the nonequilibrium flow field resulting from the turbulent mixing and combustion of an axisymmetric hydrogen jet in a supersonic parallel ambient air stream. The effective turbulent transport properties are determined by means of a two-equation model of turbulence. The finite-rate chemistry model considers eight elementary reactions among six chemical species: H, O, H2O, OH, O2 and H2. The governing set of nonlinear partial differential equations was solved by using an implicit finite-difference procedure. Radial distributions were obtained at two downstream locations for some important variables affecting the flow development, such as the turbulent kinetic energy and its dissipation rate. The results show that these variables attain their peak values on the axis of symmetry. The computed distribution of velocity, temperature, and mass fractions of the chemical species gives a complete description of the flow field. The numerical predictions were compared with two sets of experimental data. Good qualitative agreement was obtained.

  19. Influence of regulatory measures on the rate of spontaneous adverse drug reaction reporting in Italy.

    Science.gov (United States)

    Motola, Domenico; Vargiu, Antonio; Leone, Roberto; Conforti, Anita; Moretti, Ugo; Vaccheri, Alberto; Velo, Giampaolo; Montanaro, Nicola

    2008-01-01

    The reporting of adverse drug reactions (ADRs) is the mainstay of post-marketing surveillance systems. Under-reporting and selective reporting are considered the main limitations of a spontaneous reporting-based pharmacovigilance system. However, excessive reporting induced by external events may also impair signal detection by increasing the noise level. The aim of this study was to examine the influence of regulatory measures and other external factors on the rate of ADR reporting in Italy, focusing on four situations occurring in the last 10 years: ACE inhibitor-induced cough; HMG-CoA reductase inhibitors ('statins') and rhabdomyolysis; nimesulide and hepatic toxicity; and cyclo-oxygenase (COX)-2 selective inhibitors ('coxibs') and increase in cardiovascular risk. The study was based on data from spontaneous reporting in six Italian regions collected from January 1995 to December 2005. We analysed a 10-year period as a reasonable time interval around the four situations of interest, highlighting the influence of regulatory measures on the rate of ADR reporting (number of reports per million inhabitants). Chi-squared tests were used to assess the statistical significance of any changes in ADR reporting. Drug sales data were also studied to examine possible changes in drug use. Sales data were expressed as daily defined dose per 1000 inhabitants per day. ACE inhibitors: a 5-fold increase in the reporting rate of ACE inhibitor-induced cough was observed in 1998 and 1999 following a restriction on reimbursement for angiotensin receptor blockers introduced in 1998 and removed at the end of 1999. Statins: after the withdrawal of cerivastatin in 2001, the ADR reporting rate increased more than 4-fold, with musculoskeletal ADRs representing about 60% of all the ADRs reported in that year, and progressively decreased in the following years. Nimesulide: an increase in hepatic ADR reporting was observed after withdrawal of the drug from the Finnish and Spanish markets in

  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. Incorporating IPMVP and Six Sigma Strategies into Monitoring and Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, Kathleen [Verified, Inc. (United States); Mowris, Robert; Jones, Ean [Robert Mowris and Associates (United States)

    2007-07-01

    Increased emphasis on energy efficiency to reduce energy use and mitigate global warming requires rigorous evaluations based on the International Performance Measurement and Verification Protocol (IPMVP). The California Public Utilities Commission, New York State Energy Research and Development Authority (NYSERDA), the World Bank, and many state and federal agencies require adherence to IPMVP. The World Resources Inst. recommends evaluation standards such as IPMVP for the Kyoto Protocol. Increased emphasis on customer satisfaction and resource efficiency to improve profitability has motivated businesses worldwide to adopt Six Sigma strategies. Motorola, General Electric, Sony, Honda, Toyota, and many other companies have adopted Six Sigma to decrease costs and increase profitability and market share. The objectives of IPMVP and Six Sigma are similar to IEA Annex 40 which provides tools, guidelines, and recommendations for commissioning HVAC systems to optimize building energy efficiency. IPMVP provides a framework to measure, verify, and commission energy efficiency and renewable energy savings. Six Sigma provides a framework to measure and verify energy efficiency performance metrics at critical steps in the market chain (i.e., design, manufacturing, installation). Incorporating IPMVP and Six Sigma into monitoring and evaluation will help program implementers, utilities, consumers, corporations, and government agencies better understand the value of energy efficiency.This paper provides an example of how to incorporate IPMVP and Six Sigma strategies into monitoring and evaluation studies of four residential air conditioner incentive programs implemented by public utilities in California. The net realization rates for the four residential air conditioner programs are 0.53 {+-} 0.1 for kWh and 0.58 {+-} 0.04 for kW. The net realization rates are lower than anticipated due to lower baseline usage, lower ex post savings, and lower net-to-gross ratios. Findings for the

  2. A sensitivity study of s-process: the impact of uncertainties from nuclear reaction rates

    Science.gov (United States)

    Vinyoles, N.; Serenelli, A.

    2016-01-01

    The slow neutron capture process (s-process) is responsible for the production of about half the elements beyond the Fe-peak. The production sites and the conditions under which the different components of s-process occur are relatively well established. A detailed quantitative understanding of s-process nucleosynthesis may yield light in physical processes, e.g. convection and mixing, taking place in the production sites. For this, it is important that the impact of uncertainties in the nuclear physics is well understood. In this work we perform a study of the sensitivity of s-process nucleosynthesis, with particular emphasis in the main component, on the nuclear reaction rates. Our aims are: to quantify the current uncertainties in the production factors of s-process elements originating from nuclear physics and, to identify key nuclear reactions that require more precise experimental determinations. In this work we studied two different production sites in which s-process occurs with very different neutron exposures: 1) a low-mass extremely metal-poor star during the He-core flash (nn reaching up to values of ∼ 1014cm-3); 2) the TP-AGB phase of a M⊙, Z=0.01 model, the typical site of the main s-process component (nn up to 108 — 109cm-3). In the first case, the main variation in the production of s-process elements comes from the neutron poisons and with relative variations around 30%-50%. In the second, the neutron poison are not as important because of the higher metallicity of the star that actually acts as a seed and therefore, the final error of the abundances are much lower around 10%-25%.

  3. Theoretical study of the mechanism and rate constant of the B + CO2 reaction.

    Science.gov (United States)

    Poully, Benjamin; Bergeat, Astrid; Hannachi, Yacine

    2008-09-04

    The different stationary points on the potential energy surface relative to the title reaction have been reinvestigated at the B3LYP/aug-cc-pVDZ level with relative energies computed at the CCSD(T)/aug-cc-pVTZ level with B3LYP/aug-cc-pVDZ optimized geometries and by using the G3B3 composite method. Two entrance channels have been identified. The first one corresponds to boron addition at one of the oxygen atoms of the CO 2 molecule leading to trans-BOCO, which is found to be about 27 kcal/mol exothermic with a potential energy barrier of 16.4 kcal/mol (G3B3). The second channel, which has not been identified in previous theoretical works, corresponds to a direct insertion of the boron atom into a CO bond and leads to OBCO. The B + CO 2 --> OBCO step is found to be about 84 kcal/mol exothermic and needs to overcome a potential energy barrier of only 3.6 kcal/mol (G3B3). The rate constant at 300 K of the insertion step, calculated by using TST theory with G3B3 calculated activation energy value, is 5.4 10 (-14) cm (3) molecule (-1) s (-1), in very good agreement with the experimental data ((7.0 +/- 2.8) 10 (-14) cm (3) molecule (-1) s (-1), DiGiuseppe, T. G.; Davidovits, P. J. Chem. Phys. 1981, 74, 3287). The one corresponding to the addition process is found to be several orders of magnitude smaller because of a much higher potential energy barrier. The addition channel would not contribute to the title reaction even at high temperature. A modified Arrhenius equation has been fitted in the 300-1000 K temperature range, which might be useful for chemical models.

  4. Influence of changing particle structure on the rate of gas-solid gasification reactions. Final report, July 1981-March 1984

    Energy Technology Data Exchange (ETDEWEB)

    1984-04-04

    The objetive of this work is to determine the changes in the particle structure of coal as it undergoes the carbon/carbon dioxide reaction (C + CO/sub 2/ ..-->.. 2CO). Char was produced by heating the coal at a rate of 25/sup 0/C/min to the reaction temperatures of 800/sup 0/C, 900/sup 0/C, 1000/sup 0/C and 1100/sup 0/C. The changes in surface area and effective diffusivity as a result of devolitization were determined. Changes in effective diffusivity and surface area as a function of conversion have been measured for reactions conducted at 800, 900, 1000 and 1100/sup 0/C for Wyodak coal char. The surface areas exhibit a maximum as a function of conversion in all cases. For the reaction at 1000/sup 0/C the maximum in surface area is greater than the maxima determined at all other reaction temperatures. Thermogravimetric rate data were obtained for five coal chars; Wyodak, Wilcox, Cimmeron, Illinois number 6 and Pittsburgh number 6 over the temperature range 800-1100/sup 0/C. All coal chars exhibit a maximum in reaction rate. Five different models for gas-solid reactions were evaluated. The Bhatia/Perlmutter model seems to best represent the data. 129 references, 67 figures, 37 tables.

  5. Application of the compensated Arrhenius formalism to explain the dielectric constant dependence of rates for Menschutkin reactions.

    Science.gov (United States)

    Petrowsky, Matt; Glatzhofer, Daniel T; Frech, Roger

    2013-11-21

    The dependence of the reaction rate on solvent dielectric constant is examined for the reaction of trihexylamine with 1-bromohexane in a series of 2-ketones over the temperature range 25-80 °C. The rate constant data are analyzed using the compensated Arrhenius formalism (CAF), where the rate constant assumes an Arrhenius-like equation that also contains a dielectric constant dependence in the exponential prefactor. The CAF activation energies are substantially higher than those obtained using the simple Arrhenius equation. A master curve of the data is observed by plotting the prefactors against the solvent dielectric constant. The master curve shows that the reaction rate has a weak dependence on dielectric constant for values approximately less than 10 and increases more rapidly for dielectric constant values greater than 10.

  6. Generalized Temporal Acceleration Scheme for Kinetic Monte Carlo Simulations of Surface Catalytic Processes by Scaling the Rates of Fast Reactions.

    Science.gov (United States)

    Dybeck, Eric Christopher; Plaisance, Craig Patrick; Neurock, Matthew

    2017-02-14

    A novel algorithm has been developed to achieve temporal acceleration during kinetic Monte Carlo (KMC) simulations of surface catalytic processes. This algorithm allows for the direct simulation of reaction networks containing kinetic processes occurring on vastly disparate timescales which computationally overburden standard KMC methods. Previously developed methods for temporal acceleration in KMC have been designed for specific systems and often require a priori information from the user such as identifying the fast and slow processes. In the approach presented herein, quasi-equilibrated processes are identified automatically based on previous executions of the forward and reverse reactions. Temporal acceleration is achieved by automatically scaling the intrinsic rate constants of the quasi-equilibrated processes, bringing their rates closer to the timescales of the slow kinetically relevant non-equilibrated processes. All reactions are still simulated directly, although with modified rate constants. Abrupt changes in the underlying dynamics of the reaction network are identified during the simulation and the reaction rate constants are rescaled accordingly. The algorithm has been utilized here to model the Fischer-Tropsch synthesis reaction over ruthenium nanoparticles. This reaction network has multiple timescale-disparate processes which would be intractable to simulate without the aid of temporal acceleration. The accelerated simulations are found to give reaction rates and selectivities indistinguishable from those calculated by an equivalent mean-field kinetic model. The computational savings of the algorithm can span many orders of magnitude in realistic systems and the computational cost is not limited by the magnitude of the timescale disparity in the system processes. Furthermore, the algorithm has been designed in a generic fashion and can easily be applied to other surface catalytic processes of interest.

  7. Chemical reaction rates of ozone in water infusions of wheat, beech, oak and pine leaves of different ages

    Science.gov (United States)

    Potier, Elise; Loubet, Benjamin; Durand, Brigitte; Flura, Dominique; Bourdat-Deschamps, Marjolaine; Ciuraru, Raluca; Ogée, Jérôme

    2017-02-01

    In this study we present results from a laboratory experiment designed to evaluate the first-order chemical reaction rate (k) of ozone in water films on plant leaves occurring during dew or rain events. Ozone deposition to wet cuticles is indeed known to be a significant pathway of ozone deposition, but the underlying processes are not yet well understood. Leaf infusions obtained by infusing plant leaves with water at room temperature were introduced into a wet effluent denuder fed with a flux of ozone-rich air. Ozone, water vapour concentrations and temperature were measured in both inlet and outlet airflows in order to compute ozone reaction rates kr using an ozone reaction-diffusion model in the water film. Ascorbate solutions were used to validate the set up and led to kr = 3.6 107 M-1 s-1 consistent with the literature. Ozone reaction rates were determined for wheat, beech, oak and pine leaves infusions at several developmental stages, as well as for rain samples. Leaf infusions reaction rates were between 240 s-1 and 3.4 105 s-1 depending on species and developmental stage, while k for rain water ranged from 130 to 830 s-1. Wheat leaves solutions showed significantly (P ascorbate and VOCs as well as the reaction products of ozone with these compounds.

  8. Bethe Ansatz in Stringy Sigma Models

    OpenAIRE

    Klose, T.; Zarembo, K.

    2006-01-01

    We compute the exact S-matrix and give the Bethe ansatz solution for three sigma-models which arise as subsectors of string theory in AdS(5)xS(5): Landau-Lifshitz model (non-relativistic sigma-model on S(2)), Alday-Arutyunov-Frolov model (fermionic sigma-model with su(1|1) symmetry), and Faddeev-Reshetikhin model (string sigma-model on S(3)xR).

  9. Rate Coefficients of the Reaction of OH with Allene and Propyne at High Temperatures

    KAUST Repository

    Es-Sebbar, Et Touhami

    2016-09-28

    Allene (H2C═C═CH2; a-C3H4) and propyne (CH3C≡CH; p-C3H4) are important species in various chemical environments. In combustion processes, the reactions of hydroxyl radicals with a-C3H4 and p-C3H4 are critical in the overall fuel oxidation system. In this work, rate coefficients of OH radicals with allene (OH + H2C═C═CH2 → products) and propyne (OH + CH3C≡CH → products) were measured behind reflected shock waves over the temperature range of 843–1352 K and pressures near 1.5 atm. Hydroxyl radicals were generated by rapid thermal decomposition of tert-butyl hydroperoxide ((CH3)3–CO–OH), and monitored by narrow line width laser absorption of the well-characterized R1(5) electronic transition of the OH A–X (0,0) electronic system near 306.7 nm. Results show that allene reacts faster with OH radicals than propyne over the temperature range of this study. Measured rate coefficients can be expressed in Arrhenius form as follows: kallene+OH(T) = 8.51(±0.03) × 10–22T3.05 exp(2215(±3)/T), T = 843–1352 K; kpropyne+OH(T) = 1.30(±0.07) × 10–21T3.01 exp(1140(±6)/T), T = 846–1335 K.

  10. Lean Six Sigma in financial services

    NARCIS (Netherlands)

    de Koning, H.; Does, R.J.M.M.; Bisgaard, S.

    2008-01-01

    Lean Thinking and Six Sigma are typically considered as separate approaches to process innovation, with complementary strengths. When combined as Lean Six Sigma, this approach provides a unified framework for systematically developing innovations. Lean Six Sigma can also bring about significant resu

  11. Lean Six Sigma in financial services

    NARCIS (Netherlands)

    de Koning, H.; Does, R.J.M.M.; Bisgaard, S.

    2008-01-01

    Lean Thinking and Six Sigma are typically considered as separate approaches to process innovation, with complementary strengths. When combined as Lean Six Sigma, this approach provides a unified framework for systematically developing innovations. Lean Six Sigma can also bring about significant

  12. New reaction rates for improved primordial D/H calculation and the cosmic evolution of deuterium

    CERN Document Server

    Coc, Alain; Uzan, Jean-Philippe; Vangioni, Elisabeth; Descouvemont, Pierre; Illiadis, Christian; Longland, Richard

    2015-01-01

    Primordial or big bang nucleosynthesis (BBN) is one of the three historical strong evidences for the big bang model. Standard BBN is now a parameter free theory, since the baryonic density of the Universe has been deduced with an unprecedented precision from observations of the anisotropies of the cosmic microwave background (CMB) radiation. There is a good agreement between the primordial abundances of 4He, D, 3He and 7Li deduced from observations and from primordial nucleosynthesis calculations. However, the 7Li calculated abundance is significantly higher than the one deduced from spectroscopic observations and remains an open problem. In addition, recent deuterium observations have drastically reduced the uncertainty on D/H, to reach a value of 1.6%. It needs to be matched by BBN predictions whose precision is now limited by thermonuclear reaction rate uncertainties. This is especially important as many attempts to reconcile Li observations with models lead to an increased D prediction. Here, we re-evalua...

  13. Predicting reaction rate constants of ozone with organic compounds from radical structures

    Science.gov (United States)

    Yu, Xinliang; Yi, Bing; Wang, Xueye; Chen, Jianfang

    2012-05-01

    The reaction rate constants of ozone with organic compounds in the atmosphere were predicted by a quantitative structure-activity relationship (QSAR) model. Density functional theory (DFT) calculations, for the first time, were carried out on the radicals from organic compounds, at the UB3LYP level of theory with 6-31G(d) basis set. A set of quantum chemical descriptors calculated from the radicals, the energy of the highest occupied molecular orbital of beta spin states (EβHOMO), the molecular average polarizability (α), and the total energy (ET), were used to build the general QSAR model for aliphatic compounds, applying the genetic algorithm (GA) technique and support vector machine (SVM) regression. The root mean square errors (RMSE) are 0.680 for the training set (68 compounds), 0.777 for the validation set (36 compounds) and 0.709 for the test set (35 compounds). Investigated results indicate that the SVM model given here has good predictivity for aliphatic compounds.

  14. Reaction rates, depositional history and sources of indium in sediments from Appalachian and Canadian Shield lakes

    Science.gov (United States)

    Tessier, André; Gobeil, Charles; Laforte, Lucie

    2014-07-01

    Sediment cores were collected at the deepest site of twelve headwater lakes from the Province of Québec, Canada that receive contaminants only from atmospheric deposition, either directly to the lake surface or indirectly from the watershed. Several of the lakes are located within relatively short distance (In2S3(s) do not precipitate in the sediments and that adsorption of In onto sedimentary FeS(s) does not occur. However, similarities in the In and Fe porewater profiles, and the presence of In in the authigenic Fe-rich solids, reveal that part of the In becomes associated with authigenic Fe oxyhydroxides in the perennially oxic lake and is coupled to the Fe redox cycling. Comparison of the In/Corg and In/Fe molar ratios in the authigenic Fe-rich material and in surface sediments (0-0.5 cm) of this lake suggests that most non-lithogenic In was bound to humic substances. From the magnitude of the net In reaction rates, we infer that the post-depositional redistribution of this element is quantitatively not important and that the In sedimentary record represents accurately In deposition at the sampling sites. Reconstructed chronologies of the anthropogenic In deposition and comparison of In inventories among lakes point to non-ferrous metal smelters as a past significant source of atmospheric In contamination and to a significant reduction of industrial In emissions into the North American atmosphere in recent decades.

  15. Type Ia supernovae and the ^{12}C+^{12}C reaction rate

    CERN Document Server

    Bravo, E; Domínguez, I; Straniero, O; Isern, J; Escartín, J A

    2011-01-01

    The experimental determination of the cross-section of the ^{12}C+^{12}C reaction has never been made at astrophysically relevant energies (E<2 MeV). The profusion of resonances throughout the measured energy range has led to speculation that there is an unknown resonance at E\\sim1.5 MeV possibly as strong as the one measured for the resonance at 2.14 MeV. We study the implications that such a resonance would have for the physics of SNIa, paying special attention to the phases that go from the crossing of the ignition curve to the dynamical event. We use one-dimensional hydrostatic and hydrodynamic codes to follow the evolution of accreting white dwarfs until they grow close to the Chandrasekhar mass and explode as SNIa. In our simulations, we account for a low-energy resonance by exploring the parameter space allowed by experimental data. A change in the ^{12}C+^{12}C rate similar to the one explored here would have profound consequences for the physical conditions in the SNIa explosion, namely the centra...

  16. NMR-based screening method for transglutaminases: rapid analysis of their substrate specificities and reaction rates.

    Science.gov (United States)

    Shimba, Nobuhisa; Yokoyama, Kei-ichi; Suzuki, Ei-ichiro

    2002-03-13

    Incorporation of inter- or intramolecular covalent cross-links into food proteins with microbial transglutaminase (MTG) improves the physical and textural properties of many food proteins such as tofu, boiled fish paste, and sausage. Other transglutaminases (TGases) are expected to be used in the same way, and also to extend the scope of industrial applications to materials, drugs, and so on. The TGases have great diversity, not only in amino acid sequence and size, but also in their substrate specificities and catalytic activities, and therefore, it is quite difficult to estimate their reactivity. We have developed an NMR-based method using the enzymatic labeling technique (ELT) for simultaneous analysis of the substrate specificities and reaction rates of TGases. It is quite useful for comparing the existing TGases and for screening new TGases or TGases variants. This method has shown that MTG is superior for industrial use because of its lower substrate specificity compared with those of guinea pig liver transglutaminase (GTG) and red sea bream liver transglutaminase (FTG). We have also found that an MTG variant lacking an N-terminal aspartic acid residue has higher activity than that of the native enzyme.

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

    Science.gov (United States)

    Kustova, Elena V.; Kremer, Gilberto M.

    2014-12-01

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

  18. Superconducting bandpass delta-sigma modulator

    Science.gov (United States)

    Bulzacchelli, J. F.; Lee, H.-S.; Misewich, J. A.; Ketchen, M. B.

    1999-11-01

    Bandpass delta-sigma modulators digitize narrowband signals with high dynamic range and linearity. The required sampling rate is only a few times higher than the centre frequency of the input. This paper presents a superconducting bandpass delta-sigma modulator for direct analogue-to-digital conversion of RF signals in the GHz range. The input signal is capacitively coupled to one end of a microstrip transmission line, and a single flux quantum balanced comparator quantizes the current flowing out of the other end. Quantization noise is suppressed at the quarter-wave resonance of the transmission line (about 2 GHz in our design). Circuit performance at a 20 GHz sampling rate has been studied with several long JSIM simulations. Full-scale (FS) input sensitivity is 20 mV (rms), and in-band noise is -53 dBFS and -57 dBFS over bandwidths of 39 MHz and 19.5 MHz, respectively. In-band intermodulation distortion is better than -69 dBFS.

  19. Superconducting bandpass delta-sigma modulator

    Energy Technology Data Exchange (ETDEWEB)

    Bulzacchelli, J.F.; Lee, H.-S. [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Misewich, J.A.; Ketchen, M.B. [IBM Research Division, T. J. Watson Research Center, Yorktown Heights, NY 10598 (United States)

    1999-11-01

    Bandpass delta-sigma modulators digitize narrowband signals with high dynamic range and linearity. The required sampling rate is only a few times higher than the centre frequency of the input. This paper presents a superconducting bandpass delta-sigma modulator for direct analogue-to-digital conversion of RF signals in the GHz range. The input signal is capacitively coupled to one end of a microstrip transmission line, and a single flux quantum balanced comparator quantizes the current flowing out of the other end. Quantization noise is suppressed at the quarter-wave resonance of the transmission line (about 2 GHz in our design). Circuit performance at a 20 GHz sampling rate has been studied with several long JSIM simulations. Full-scale (FS) input sensitivity is 20 mV (rms), and in-band noise is -53 dBFS and -57 dBFS over bandwidths of 39 MHz and 19.5 MHz, respectively. In-band intermodulation distortion is better than -69 dBFS. (author)

  20. Capture cross-section and rate of the 14C(, )15C reaction from the Coulomb dissociation of 15C

    Indian Academy of Sciences (India)

    Shubhchintak; Neelam; R Chatterjee

    2014-10-01

    We calculate the Coulomb dissociation of 15C on a Pb target at 68 MeV/u incident beam energy within the fully quantum mechanical distorted wave Born approximation formalism of breakup reactions. The capture cross-section and the subsequent rate of the 14C(, )15C reaction are calculated from the photodisintegration of 15C, using the principle of detailed balance. Our theoretical model is free from the uncertainties associated with the multipole strength distributions of the projectile.

  1. Ab initio and density functional theory evidence on the rate-limiting step in the Morita-Baylis-Hillman reaction.

    Science.gov (United States)

    Roy, Dipankar; Sunoj, Raghavan B

    2007-11-08

    The first ab initio and DFT studies on the mechanism of the MBH reaction show that the rate-limiting step involves an intramolecular proton transfer in the zwitterionic intermediate generated by the addition of enolate to electrophile. The activation barrier for the C-C bond-formation is found to be 20.2 kcal/mol lower than the proton-transfer step for the MBH reaction between methyl vinyl ketone and benzaldehyde catalyzed by DABCO.

  2. Topography of Slow Sigma Power during Sleep is Associated with Processing Speed in Preschool Children.

    Science.gov (United States)

    Doucette, Margaret R; Kurth, Salome; Chevalier, Nicolas; Munakata, Yuko; LeBourgeois, Monique K

    2015-11-04

    Cognitive development is influenced by maturational changes in processing speed, a construct reflecting the rapidity of executing cognitive operations. Although cognitive ability and processing speed are linked to spindles and sigma power in the sleep electroencephalogram (EEG), little is known about such associations in early childhood, a time of major neuronal refinement. We calculated EEG power for slow (10-13 Hz) and fast (13.25-17 Hz) sigma power from all-night high-density electroencephalography (EEG) in a cross-sectional sample of healthy preschool children (n = 10, 4.3 ± 1.0 years). Processing speed was assessed as simple reaction time. On average, reaction time was 1409 ± 251 ms; slow sigma power was 4.0 ± 1.5 μV²; and fast sigma power was 0.9 ± 0.2 μV². Both slow and fast sigma power predominated over central areas. Only slow sigma power was correlated with processing speed in a large parietal electrode cluster (p power predicted faster reaction time. Our findings indicate regional correlates between sigma power and processing speed that are specific to early childhood and provide novel insights into the neurobiological features of the EEG that may underlie developing cognitive abilities.

  3. Evidence for a narrow resonance at 1530 MeV/c{sup 2} in the K{sup 0}p-system of the reaction pp{yields}{sigma}{sup +}K{sup 0}p from the COSY-TOF experiment

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Bary, M.; Abdel-Samad, S.; Brinkmann, K.-Th.; Clement, H.; Doroshkevich, E.; Drochner, M.; Dshemuchadse, S.; Erhardt, A.; Eyrich, W.; Filges, D.; Filippi, A.; Freiesleben, H.; Fritsch, M.; Georgi, J.; Gillitzer, A.; Hesselbarth, D.; Jaekel, R.; Jakob, B.; Karsch, L.; Kilian, K.; Koch, H.; Kress, J.; Kuhlmann, E.; Naumann, L.; Marcello, S.; Marwinski, S.; Meier, R.; Michel, P.; Moeller, K.; Moertel, H.; Morsch, H.P.; Paul, N.; Pinna, L.; Pizzolotto, C.; Richter, M.; Roderburg, E.; Schoenmeier, P.; Schroeder, W.; Schulte-Wissermann, M.; Sefzick, T.; Stinzing, F.; Sun, G.Y.; Teufel, A.; Ucar, A.; Wagner, G.J.; Wagner, M.; Wilms, A.; Wintz, P.; Wirth, St.; Wuestner, P

    2004-08-12

    The hadronic reaction pp{yields}{sigma}{sup +}K{sup 0}p was measured exclusively at a beam momentum of 2.95 GeV/c using the TOF detector at the COSY storage ring. A narrow peak was observed in the invariant mass spectrum of the K{sup 0}p-subsystem at 1530{+-}5 MeV/c{sup 2} with a significance of 4-6 standard deviations, depending on background assumptions. The upper limit of 18{+-}4 MeV/c{sup 2} (FWHM) for its width is given by the experimental resolution. The corresponding total cross section is estimated to be about 0.4{+-}0.1 (stat){+-}0.1(syst) {mu}b. Since a resonance in this subsystem must have strangeness S=+1 we claim it to be the {theta}{sup +} state for which very recently evidence was found in various experiments.

  4. Rate constants and isotope effects for the reaction of H-atom abstraction from RH substrates by PINO radicals

    Science.gov (United States)

    Opeida, I. A.; Litvinov, Yu. E.; Kushch, O. V.; Kompanets, M. A.; Shendrik, A. N.; Matvienko, A. G.; Novokhatko, A. A.

    2016-11-01

    The kinetics of the reactions of hydrogen atom abstraction from the C-H bonds of substrates of different structures by phthalimide- N-oxyl radicals is studied. The rate constants of this reaction are measured and the kinetic isotope effects are determined. It is shown that in addition to the thermodynamic factor, Coulomb forces and donor-acceptor interactions affect the reaction between phthalimide- N-oxyl radicals and substrate molecules, altering the shape of the transition state. This favors the tunneling of hydrogen atoms and leads to a substantial reduction in the activation energy of the process.

  5. Measurement of rate constant for gas-phase reaction of DDVP with OH radical by using LP-FTIR

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Pollution caused by organic pesticides has received increasing attention. Until now, studies on organic pesticides pollution are mainly focused on soil and water. For reactions of organic pesticides in gas-phase, there are very little research results reported. Using a long path quartz reactor to simulate the atmospheric reaction of dimethyl_dichloro_vinyl_phosphate(DDVP) with OH radicals, the rate constant for the reaction at room temperature is measured at (3.06±0.46)×10-11 cm3 s-1 with Fourier transform infrared spectrograph.The result indicates that DDVP degrades relatively fast in the atmosphere and is unlikely to cause persistent pollution.

  6. Rate of influenza vaccination and its adverse reactions seen in health care personnel in a single tertiary hospital in Korea.

    Science.gov (United States)

    Lee, Chang-Seop; Lee, Kang-Hyu; Jung, Min-Hee; Lee, Heung-Bum

    2008-11-01

    To determine the vaccination rate and its adverse reactions after influenza vaccination, we administered an anonymous questionnaire survey during the last three influenza seasons from 2005-2006 to 2007-2008. In total, the rate of Influenza vaccination was 82.3% in health-care personnel. Dividing the subjects into four groups by work category, the vaccine coverage rates were as follows: physicians 67.9%; nurses and nursing assistants 91.2%; technicians, pharmacists, therapists, and administrative personnel 80.2%; and other personnel not directly involved in patient care but having the potential of being exposed to infectious agents 89%. The most frequent adverse reaction after vaccination was soreness at the injection site in 33.4%, followed by skin redness in 18.1%, myalgia in 17.7%, fatigue in 17%, and febrile sensation in 15.2%. After vaccination, such adverse reactions began within 24 h in 70.6% of subjects. Eighty-nine percent of those adverse reactions persisted for 1-3 days, but 11% persisted more than 4 days. Serious adverse reactions were not noted; the reported adverse reactions were relatively minor and transient. Surprisingly, among those who were vaccinated, the physicians' participation was the lowest. We believe that influenza vaccination is safe and that physicians should be more concerned with influenza vaccination and its impact on the health-care community.

  7. Variational RRKM calculation of thermal rate constant for C–H bond fission reaction of nitro methane

    Directory of Open Access Journals (Sweden)

    Afshin Taghva Manesh

    2017-02-01

    Full Text Available The present work provides quantitative results for the rate constants of unimolecular C–H bond fission reactions in the nitro methane at elevated temperatures up to 2000 K. In fact, there are three different hydrogen atoms in the nitro methane. The potential energy surface for each C–H bond fission reaction of nitro methane was investigated by ab initio calculations. The geometry and vibrational frequencies of the species involved in this process were optimized at the MP2 level of theory, using the cc-pvdz basis set. Since C–H bond fission channel is a barrierless reaction, we have used variational RRKM theory to predict rate coefficients. By means of calculated rate coefficients at different temperatures, the Arrhenius expression of the channel over the temperature range of 100–2000 K is k(T = 5.9E19∗exp(−56274.6/T.

  8. Shell model based reaction rates for rp-process nuclei in the mass range A=44-63

    CERN Document Server

    Fisker, J L; Görres, J; Langanke, K; Martínez-Pinedo, G; Wiescher, M C

    2001-01-01

    We have used large-scale shell-model diagonalization calculations to determine the level spectra, proton spectroscopic factors, and electromagnetic transition probabilities for proton rich nuclei in the mass range A=44-63. Based on these results and the available experimental data, we calculated the resonances for proton capture reactions on neutron deficient nuclei in this mass range. We also calculated the direct capture processes on these nuclei in the framework of a Woods-Saxon potential model. Taking into account both resonant and direct contributions, we determined the ground-state proton capture reaction rates for these nuclei under hot hydrogen burning conditions for temperatures between 10 sup 8 and 10 sup 1 sup 0 K. The calculated compound-nucleus level properties and the reaction rates are presented here; the rates are also available in computer-readable format from the authors.

  9. A 3rd Order Low Power Switched Current Sigma-Delta Modulator

    DEFF Research Database (Denmark)

    Jørgensen, Ivan Herald Holger; Bogason, Gudmundur

    1996-01-01

    This paper presents a 3rd order switched current Sigma-Delta modulator. The Sigma-Delta modulator operates at a sampling rate of 600kHz and the signal band is 5.5kHz, i.e. an oversampling factor of 54.5 is used. Multiple input signals are used to reduce the internal signal swings which results...

  10. Low-Temperature Mechanical Behavior of Super Duplex Stainless Steel with Sigma Precipitation

    Directory of Open Access Journals (Sweden)

    Seul-Kee Kim

    2015-09-01

    Full Text Available Experimental studies in various aspects have to be conducted to maintain stable applications of super duplex stainless steels (SDSS because the occurrence rate of sigma phase, variable temperature and growth direction of sigma phase can influence mechanical performances of SDSS. Tensile tests of precipitated SDSS were performed under various temperatures to analyze mechanical and morphological behavior.

  11. Determination of the 36Mg(n ,γ )37Mg reaction rate from Coulomb dissociation of 37Mg

    Science.gov (United States)

    Shubhchintak; Chatterjee, R.; Shyam, R.

    2017-08-01

    We use the Coulomb dissociation (CD) method to calculate the rate of the 36Mg(n ,γ )37Mg radiative capture reaction. The CD cross sections of the 37Mg nucleus on a 208Pb target at the beam energy of 244 MeV/nucleon, for which new experimental data have recently become available, were calculated within the framework of a finite-range distorted-wave Born approximation theory that is extended to include the projectile deformation effects. Invoking the principle of detailed balance, these cross sections are used to determine the excitation function and subsequently the rate of the 36Mg(n ,γ )37Mg reaction. We compare these rates to those of the 36Mg(α ,n )39Si reaction calculated within a Hauser-Feshbach model. We find that for T9 as large as up to 1.0 (in units of 109 K) the 36Mg(n ,γ )37Mg reaction is much faster than the 36Mg(α ,n )39Si one. The inclusion of the effects of 37Mg projectile deformation in the breakup calculations enhances the (n ,γ ) reaction rate even further. Therefore, it is highly unlikely that the (n ,γ )β -decay r -process flow will be broken at the 36Mg isotope by the α process.

  12. EFFECTS OF PORE STRUCTURE CHANGE AND MULTI-SCALE HETEROGENEITY ON CONTAMINANT TRANSPORT AND REACTION RATE UPSCALING

    Energy Technology Data Exchange (ETDEWEB)

    Peters, Catherine A [Princeton University

    2013-05-15

    This project addressed the scaling of geochemical reactions to core and field scales, and the interrelationship between reaction rates and flow in porous media. We targeted reactive transport problems relevant to the Hanford site specifically the reaction of highly caustic, radioactive waste solutions with subsurface sediments, and the immobilization of 90Sr and 129I through mineral incorporation and passive flow blockage, respectively. We addressed the correlation of results for pore-scale fluid-soil interaction with field-scale fluid flow, with the specific goals of (i) predicting attenuation of radionuclide concentration; (ii) estimating changes in flow rates through changes of soil permeabilities; and (iii) estimating effective reaction rates. In supplemental work, we also simulated reactive transport systems relevant to geologic carbon sequestration. As a whole, this research generated a better understanding of reactive transport in porous media, and resulted in more accurate methods for reaction rate upscaling and improved prediction of permeability evolution. These scientific advancements will ultimately lead to better tools for management and remediation of DOE legacy waste problems.

  13. The sausage sigma model revisited

    Science.gov (United States)

    Suneeta, Vardarajan

    2015-06-01

    Fateev’s sausage sigma models in two and three dimensions are known to be integrable. We study their stability under renormalization group (RG) flow in the target space by using results from the mathematics of Ricci flow. We show that the three-dimensional sausage is unstable, whereas the two-dimensional sausage appears to be stable at least at leading order as it approaches the sphere. We speculate that the stability results obtained are linked to the classification of ancient solutions to Ricci flow (i.e., sigma models that are nonperturbative in the infrared regime) in two and three dimensions. We also describe a class of perturbations of the three-dimensional sausage (with the same continuous symmetries) which remarkably decouple. This indicates that there could be a new solution to RG flow, which is described at least perturbatively as a deformation of the sausage.

  14. Rate Constants and Activation Energies for Gas‐Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical

    Science.gov (United States)

    Safron, Andreas; Strandell, Michael; Kierkegaard, Amelie

    2015-01-01

    ABSTRACT Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second‐order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140‐mL gas‐phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D4 and D5 with the OH radical are 1.9 × 10−12 (95% confidence interval (CI): (1.7–2.2) × 10−12) and 2.6 × 10−12 (CI: (2.3–2.9) × 10−12) cm3 molecule−1 s−1, respectively, which are 1.9× and 1.7× faster than previous measurements. Our measured rate constant for D6 is 2.8 × 10−12 (CI: (2.5–3.2) × 10−12) cm3 molecule−1 s−1 and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D5 were 33% higher than for D4 (CI: 30–37%), whereas the rates for D6 were only 8% higher than for D5 (CI: 5–10%). The activation energies of the reactions of D4, D5, and D6 with OH were not statistically different and had a value of 4300 ± 2800 J/mol. PMID:27708500

  15. Rate Constants and Activation Energies for Gas-Phase Reactions of Three Cyclic Volatile Methyl Siloxanes with the Hydroxyl Radical.

    Science.gov (United States)

    Safron, Andreas; Strandell, Michael; Kierkegaard, Amelie; Macleod, Matthew

    2015-07-01

    Reaction with hydroxyl radicals (OH) is the major pathway for removal of cyclic volatile methyl siloxanes (cVMS) from air. We present new measurements of second-order rate constants for reactions of the cVMS octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) with OH determined at temperatures between 313 and 353 K. Our measurements were made using the method of relative rates with cyclohexane as a reference substance and were conducted in a 140-mL gas-phase reaction chamber with online mass spectrometry analysis. When extrapolated to 298 K, our measured reaction rate constants of D4 and D5 with the OH radical are 1.9 × 10(-12) (95% confidence interval (CI): (1.7-2.2) × 10(-12)) and 2.6 × 10(-12) (CI: (2.3-2.9) × 10(-12)) cm(3) molecule(-1) s(-1), respectively, which are 1.9× and 1.7× faster than previous measurements. Our measured rate constant for D6 is 2.8 × 10(-12) (CI: (2.5-3.2) × 10(-12)) cm(3) molecule(-1) s(-1) and to our knowledge there are no comparable laboratory measurements in the literature. Reaction rates for D5 were 33% higher than for D4 (CI: 30-37%), whereas the rates for D6 were only 8% higher than for D5 (CI: 5-10%). The activation energies of the reactions of D4, D5, and D6 with OH were not statistically different and had a value of 4300 ± 2800 J/mol.

  16. Kinetics analysis for development of a rate constant estimation model for ultrasonic degradation reaction of methylene blue.

    Science.gov (United States)

    Kobayashi, Daisuke; Honma, Chiemi; Matsumoto, Hideyuki; Takahashi, Tomoki; Kuroda, Chiaki; Otake, Katsuto; Shono, Atsushi

    2014-07-01

    Ultrasound has been used as an advanced oxidation method for wastewater treatment. Sonochemical degradation of organic compounds in aqueous solution occurs by pyrolysis and/or reaction with hydroxyl radicals. Moreover, kinetics of sonochemical degradation has been proposed. However, the effect of ultrasonic frequency on degradation rate has not been investigated. In our previous study, a simple model for estimating the apparent degradation rate of methylene blue was proposed. In this study, sonochemical degradation of methylene blue was performed at various frequencies. Apparent degradation rate constant was evaluated assuming that sonochemical degradation of methylene blue was a first-order reaction. Specifically, we focused on effects of ultrasonic frequency and power on rate constant, and the applicability of our proposed model was demonstrated. Using this approach, maximum sonochemical degradation rate was observed at 490 kHz, which agrees with a previous investigation into the effect of frequency on the sonochemical efficiency value evaluated by KI oxidation dosimetry. Degradation rate increased with ultrasonic power at every frequency. It was also observed that threshold power must be reached for the degradation reaction to progress. The initial methylene blue concentration and the apparent degradation rate constant have a relation of an inverse proportion. Our proposed model for estimating the apparent degradation rate constant using ultrasonic power and sonochemical efficiency value can apply to this study which extended the frequency and initial concentration range.

  17. Topological sigma models on supermanifolds

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Bei, E-mail: beijia@physics.utexas.edu

    2017-02-15

    This paper concerns constructing topological sigma models governing maps from semirigid super Riemann surfaces to general target supermanifolds. We define both the A model and B model in this general setup by defining suitable BRST operators and physical observables. Using supersymmetric localization, we express correlation functions in these theories as integrals over suitable supermanifolds. In the case of the A model, we obtain an integral over the supermoduli space of “superinstantons”. The language of supergeometry is used extensively throughout this paper.

  18. Topological sigma models on supermanifolds

    Science.gov (United States)

    Jia, Bei

    2017-02-01

    This paper concerns constructing topological sigma models governing maps from semirigid super Riemann surfaces to general target supermanifolds. We define both the A model and B model in this general setup by defining suitable BRST operators and physical observables. Using supersymmetric localization, we express correlation functions in these theories as integrals over suitable supermanifolds. In the case of the A model, we obtain an integral over the supermoduli space of "superinstantons". The language of supergeometry is used extensively throughout this paper.

  19. Topological Sigma Models On Supermanifolds

    CERN Document Server

    Jia, Bei

    2016-01-01

    This paper concerns constructing topological sigma models governing maps from semirigid super Riemann surfaces to general target supermanifolds. We define both the A model and B model in this general setup by defining suitable BRST operators and physical observables. Using supersymmetric localization, we express correlation functions in these theories as integrals over suitable supermanifolds. In the case of the A model, we obtain an integral over the supermoduli space of "superinstantons". The language of supergeometry is used extensively throughout this paper.

  20. Lean six sigma in healthcare.

    Science.gov (United States)

    de Koning, Henk; Verver, John P S; van den Heuvel, Jaap; Bisgaard, Soren; Does, Ronald J M M

    2006-01-01

    Healthcare, as with any other service operation, requires systematic innovation efforts to remain competitive, cost efficient, and up-to-date. This article outlines a methodology and presents examples to illustrate how principles of Lean Thinking and Six Sigma can be combined to provide an effective framework for producing systematic innovation efforts in healthcare. Controlling healthcare cost increases, improving quality, and providing better healthcare are some of the benefits of this approach.

  1. Charting an Alternate Pathway to Reaction Orders and Rate Laws in Introductory Chemistry Courses

    Science.gov (United States)

    Rushton, Gregory T.; Criswell, Brett A.; McAllister, Nicole D.; Polizzi, Samuel J.; Moore, Lamesha A.; Pierre, Michelle S.

    2014-01-01

    Reaction kinetics is an axiomatic topic in chemistry that is often addressed as early as the high school course and serves as the foundation for more sophisticated conversations in college-level organic, physical, and biological chemistry courses. Despite the fundamental nature of reaction kinetics, students can struggle with transforming their…

  2. An Interactive Classroom Activity Demonstrating Reaction Mechanisms and Rate-Determining Steps

    Science.gov (United States)

    Jennings, Laura D.; Keller, Steven W.

    2005-01-01

    An interactive classroom activity that includes two-step reaction of unwrapping and eating chocolate candies is described which brings not only the reaction intermediate, but also the reactants and products into macroscopic view. The qualitative activation barriers of both steps can be adjusted independently.

  3. Pyrite oxidation in unsaturated aquifer sediments. Reaction stoichiometry and rate of oxidation

    DEFF Research Database (Denmark)

    Andersen, Martin Søgaard; Larsen, Flemming; Postma, Diederik Jan

    2001-01-01

    the reaction stoichiometry and partitioning of gases between the solution and the gas phase. Pyrite oxidation with concurrent calcite dissolution was found to be consistent with the experimental data while organic carbon oxidation was not. The reaction involves changes in the total volume of the gas phase...

  4. The sigma Orionis substellar population

    CERN Document Server

    Barrado y Navascués, D; Mundt, R; Martín, E L; Rebolo, R; Zapatero-Osorio, M R; Bailer-Jones, C A L; Navascu\\'es, David Barrado y; Mundt, Reinhard; Mart\\'{\\i}n, Eduardo L.; Rebolo, Rafael; Osorio, Mar\\'{\\i}a Rosa Zapatero; Bailer-Jones, Coryn A.L.

    2003-01-01

    VLT/FORS spectroscopy and 2MASS near-infrared photometry, together with previously known data, have been used to establish the membership and the properties of a sample of low-mass candidate members of the sigma Orionis cluster with masses spanning from 1 Msun down to about 0.013 Msun (i.e., deuterium-burning mass limit). We have observed K-band infrared excess and remarkably intense H(alpha) emission in various cluster members, which, in addition to the previously detected forbidden emision lines and the presence of LiI in absorption at 6708 A, have allowed us to tentatively classify sigma Orionis members as classical or weak-line TTauri stars and substellar analogs. Variability of the H(alpha) line has been investigated and detected in some objects. Based on the K-band infrared excesses and the intensity of H(alpha) emission, we estimate that the minimum disk frequency of the sigma Orionis low-mass population is in the range 5-12%.

  5. Sigma-class glutathione transferases.

    Science.gov (United States)

    Flanagan, Jack U; Smythe, Mark L

    2011-05-01

    Mammalian cytosolic glutathione transferases (GSTs) can be grouped into seven classes. Of these, the sigma class is also widely distributed in nature, with isoforms found in both vertebrates and invertebrates. It contains examples of proteins that have evolved specialized functions, such as the cephalopod lens S-crystallins, the mammalian hematopoietic prostaglandin D(2) synthase, and the helminth 28-kDa antigen. In mammals, the sigma-class GST has both anti- and proinflammatory functions, depending on the type of immune response, and an immunomodulatory function is also associated with the enzyme from helminth parasites. In the fly, it is associated with a specific detoxication activity toward lipid oxidation products. Mice genetically depleted of the sigma-class GST, or transgenically overexpressing it, have provided insight into the physiological roles of the GST. Inhibitors of the mammalian enzyme developed by structure-based methods are effective in controlling allergic response. This review covers the structure, function, and pharmacology of vertebrate and invertebrate GSTs.

  6. The sausage sigma model revisited

    CERN Document Server

    Suneeta, Vardarajan

    2014-01-01

    Fateev's sausage sigma models in two and three dimensions are known to be integrable. We study their stability under RG flow in the target space by using results from the mathematics of Ricci flow. We show that the three dimensional sausage is unstable, whereas the two dimensional sausage appears to be stable at least at leading order as it approaches the sphere. The $n$-sphere, corresponding to the integrable O(n) sigma model, is geometrically stable and an attractor for nearby solutions to RG flow. We speculate that the stability results obtained seem to be linked to the classification of ancient solutions to Ricci flow (i.e., sigma models which are asymptotically free in the UV and nontrivial in the IR) in two and three dimensions. We also describe a class of perturbations of the three dimensional sausage (with the same continuous symmetries) which remarkably decouple. This indicates that there could be a new solution to RG flow which is described at least perturbatively as a deformation of the sausage.

  7. All optical asynchronous binary delta-sigma modulator

    Science.gov (United States)

    Tafazoli, M.; Davoudzadeh, N.; Sayeh, M. R.

    2013-03-01

    We present the first all optical delta-sigma modulator using a bistable device and a leaky integrator. In this paper, a novel tri-coupled ring geometry is utilized, resulting in resonance which is a building block for delta-sigma modulator. In each ring, the main active element is a semiconductor optical amplifier (SOA). The experimental result of the implemented setup is in a good agreement with our presented theory. Applying optical discrete components leads to a sampling rate of 660 kS/s. The higher frequency can be reached easily by using faster bistable devices and shorter loops.

  8. Effect of low and high heating rates on reaction path of Ni(V)/Al multilayer

    Energy Technology Data Exchange (ETDEWEB)

    Maj, Łukasz, E-mail: l.maj@imim.pl [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta St., 30-059 Kraków (Poland); Morgiel, Jerzy; Szlezynger, Maciej [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta St., 30-059 Kraków (Poland); Bała, Piotr; Cios, Grzegorz [AGH University of Science and Technology, Academic Centre for Materials and Nanotechnology, 30 Kawiory St., 30-055 Kraków (Poland)

    2017-06-01

    The effect of heating rates of Ni(V)/Al NanoFoils{sup ®} was investigated with transmission electron microscopy (TEM). The Ni(V)/Al were subjected to heating by using differential scanning calorimetry (DSC), in-situ TEM or electric pulse. Local chemical analysis was carried out using energy dispersive X-ray spectroscopy (EDS). Phase analysis was done with X-ray diffractions (XRD) and selected area electron diffractions (SAED). The experiments showed that slow heating in DSC results in development of separate exothermic effects at ∼230 °C, ∼280 °C and ∼390 °C, corresponding to precipitation of Al{sub 3}Ni, Al{sub 3}Ni{sub 2} and NiAl phases, respectively, i.e. like in vanadium free Ni/Al multilayers. Further heating to 700 °C allowed to obtain a single phase NiAl foil. The average grain size (g.s.) of NiAl phase produced in the DSC heat treated foil was comparable with the Ni(V)/Al multilayer period (∼50 nm), whereas in the case of reaction initiated with electric pulse the g.s. was in the micrometer range. Upon slow heating vanadium tends to segregate to zones parallel to the original multilayer internal interfaces, while in SHS process vanadium-rich phases precipitates at grain boundaries of the NiAl phase. - Highlights: • Peaks in DSC heating of Ni(V)/Al were explained by in-situ TEM observations. • Nucleation of Al{sub 3}Ni, Al{sub 3}Ni{sub 2} and NiAl at slow heating of Ni(V)/Al was documented. • Near surface NiAl obtained from NanoFoil show Ag precipitates at grain boundaries.

  9. SISGR - In situ characterization and modeling of formation reactions under extreme heating rates in nanostructured multilayer foils

    Energy Technology Data Exchange (ETDEWEB)

    Hufnagel, Todd C.

    2014-06-09

    Materials subjected to extreme conditions, such as very rapid heating, behave differently than materials under more ordinary conditions. In this program we examined the effect of rapid heating on solid-state chemical reactions in metallic materials. One primary goal was to develop experimental techniques capable of observing these reactions, which can occur at heating rates in excess of one million degrees Celsius per second. One approach that we used is x-ray diffraction performed using microfocused x-ray beams and very fast x-ray detectors. A second approach is the use of a pulsed electron source for dynamic transmission electron microscopy. With these techniques we were able to observe how the heating rate affects the chemical reaction, from which we were able to discern general principles about how these reactions proceed. A second thrust of this program was to develop computational tools to help us understand and predict the reactions. From atomic-scale simulations were learned about the interdiffusion between different metals at high heating rates, and about how new crystalline phases form. A second class of computational models allow us to predict the shape of the reaction front that occurs in these materials, and to connect our understanding of interdiffusion from the atomistic simulations to measurements made in the laboratory. Both the experimental and computational techniques developed in this program are expected to be broadly applicable to a wider range of scientific problems than the intermetallic solid-state reactions studied here. For example, we have already begun using the x-ray techniques to study how materials respond to mechanical deformation at very high rates.

  10. 光学Sigma-Delta模数转换器的研究进展%Research and development of optical sigma-delta analog to digital converter

    Institute of Scientific and Technical Information of China (English)

    周雯; 王目光; 李博

    2012-01-01

    Optical analog to digital conversion techniques have been the developing trend of analog to digital converter(ADC) with high conversion rate and high bit accuracy in recent years. As a kind of optical ADC, optical Sigma-Delta ADC has distinguished advantages such as high conversion accuracy and simple analog circuitry. Basic principle of optical Sigma-Delta ADC is introduced. The structures of several typical optical Sigma-Delta ADCs are described detailedly.Finally the merits and demerits of optical Sigma-Delta ADCs with different structures are summed up.%采用光学模数转换技术已经成为高转换速率、高比特精度模数转换器(ADC)的发展趋势.光学Sigma-Delta ADC作为一种光学ADC,具有转换精度高和模拟电路简单等显著优点.介绍了光学Sigma-Delta ADC的基本原理,详细阐述了几种典型的光学Sigma-Delta ADC的系统结构,对不同结构的光学Sigma-Delta ADC的优缺点进行了归纳总结.

  11. Determination of the reaction rate coefficient of sulphide mine tailings deposited under water.

    Science.gov (United States)

    Awoh, Akué Sylvette; Mbonimpa, Mamert; Bussière, Bruno

    2013-10-15

    The efficiency of a water cover to limit dissolved oxygen (DO) availability to underlying acid-generating mine tailings can be assessed by calculating the DO flux at the tailings-water interface. Fick's equations, which are generally used to calculate this flux, require knowing the effective DO diffusion coefficient (Dw) and the reaction (consumption) rate coefficient (Kr) of the tailings, or the DO concentration profile. Whereas Dw can be accurately estimated, few studies have measured the parameter Kr for submerged sulphide tailings. The objective of this study was to determine Kr for underwater sulphide tailings in a laboratory experiment. Samples of sulphide mine tailings (an approximately 6 cm layer) were placed in a cell under a water cover (approximately 2 cm) maintained at constant DO concentration. Two tailings were studied: TA1 with high sulphide content (83% pyrite) and TA2 with low sulphide content (2.8% pyrite). DO concentration was measured with a microelectrode at various depths above and below the tailings-water interface at 1 mm intervals. Results indicate that steady-state condition was rapidly attained. As expected, a diffusive boundary layer (DBL) was observed in all cases. An iterative back-calculation process using the numerical code POLLUTEv6 and taking the DBL into account provided the Kr values used to match calculated and experimental concentration profiles. Kr obtained for tailings TA1 and TA2 was about 80 d(-1) and 6.5 d(-1), respectively. For comparison purposes, Kr obtained from cell tests on tailings TA1 was lower than Kr calculated from the sulphate production rate obtained from shake-flask tests. Steady-state DO flux at the water-tailings interface was then calculated with POLLUTEv6 using tailings characteristics Dw and Kr. For the tested conditions, DO flux ranged from 608 to 758 mg O2/m(2)/d for tailings TA1 and from 177 to 221 mg O2/m(2)/d for tailings TA2. The impact of placing a protective layer of inert material over

  12. On the Sensitivity of Massive Star Nucleosynthesis and Evolution to Solar Abundances and to Uncertainties in Helium Burning Reaction Rates

    CERN Document Server

    Tur, Clarisse; Austin, Sam M

    2007-01-01

    We explore the dependence of pre-supernova evolution and supernova nucleosynthesis yields on the uncertainties in helium burning reaction rates. Using the revised solar abundances of Lodders (2003) for the initial stellar composition, instead of those of Anders & Grevesse (1989), changes the supernova yields and limits the constraints that those yields place on the 12C(a,g)16O reaction rate. The production factors of medium-weight elements (A = 16 to 40) were found to be in reasonable agreement with observed solar ratios within the current experimental uncertainties in the triple alpha reaction rate. Simultaneous variations by the same amount in both reaction rates or in either of them separately, however, can induce significant changes in the central 12C abundance at core carbon ignition and in the mass of the supernova remnant. It therefore remains important to have experimental determinations of the helium burning rates so that their ratio and absolute values are known with an accuracy of 10% or better...

  13. The role of reaction affinity and secondary minerals in regulating chemical weathering rates at the Santa Cruz Soil Chronosequence, California

    Energy Technology Data Exchange (ETDEWEB)

    Maher, K.; Steefel, C. I.; White, A.F.; Stonestrom, D.A.

    2009-02-25

    In order to explore the reasons for the apparent discrepancy between laboratory and field weathering rates and to determine the extent to which weathering rates are controlled by the approach to thermodynamic equilibrium, secondary mineral precipitation and flow rates, a multicomponent reactive transport model (CrunchFlow) was used to interpret soil profile development and mineral precipitation and dissolution rates at the 226 ka marine terrace chronosequence near Santa Cruz, CA. Aqueous compositions, fluid chemistry, transport, and mineral abundances are well characterized (White et al., 2008, GCA) and were used to constrain the reaction rates for the weathering and precipitating minerals in the reactive transport modeling. When primary mineral weathering rates are calculated with either of two experimentally determined rate constants, the nonlinear, parallel rate law formulation of Hellmann and Tisser and [2006] or the aluminum inhibition model proposed by Oelkers et al. [1994], modeling results are consistent with field-scale observations when independently constrained clay precipitation rates are accounted for. Experimental and field rates, therefore, can be reconciled at the Santa Cruz site. Observed maximum clay abundances in the argillic horizons occur at the depth and time where the reaction fronts of the primary minerals overlap. The modeling indicates that the argillic horizon at Santa Cruz can be explained almost entirely by weathering of primary minerals and in situ clay precipitation accompanied by undersaturation of kaolinite at the top of the profile. The rate constant for kaolinite precipitation was also determined based on model simulations of mineral abundances and dissolved Al, SiO{sub 2}(aq) and pH in pore waters. Changes in the rate of kaolinite precipitation or the flow rate do not affect the gradient of the primary mineral weathering profiles, but instead control the rate of propagation of the primary mineral weathering fronts and thus total

  14. Machine Process Capability Information Through Six Sigma

    Energy Technology Data Exchange (ETDEWEB)

    Lackner, M.F.

    1998-03-13

    A project investigating details concerning machine process capability information and its accessibility has been conducted. The thesis of the project proposed designing a part (denoted as a machine capability workpiece) based on the major machining features of a given machine. Parts are machined and measured to gather representative production, short-term variation. The information is utilized to predict the expected defect rate, expressed in terms of a composite sigma level process capability index, for a production part. Presently, decisions concerning process planning, particularly what machine will statistically produce the minimum amount of defects based on machined features and associated tolerances, are rarely made. Six sigma tools and methodology were employed to conduct this investigation at AlliedSignal FM and T. Tools such as the thought process map, factor relationship diagrams, and components of variance were used. This study is progressing toward completion. This research study was an example of how machine process capability information may be gathered for milling planar faces (horizontal) and slot features. The planning method used to determine where and how to gather variation for the part to be designed is known as factor relationship diagramming. Components-of-variation is then applied to the gathered data to arrive at the contributing level of variation illustrated within the factor relationship diagram. The idea of using this capability information beyond process planning to the other business enterprise operations is proposed.

  15. Under the knife: a national survey of six sigma programs in US healthcare organizations.

    Science.gov (United States)

    Feng, Qianmei; Manuel, Chris M

    2008-01-01

    Medical and policy literature reports many six sigma applications at specific healthcare organizations. However, there is a lack of studies that investigate the broader status of six sigma in US healthcare systems. The purpose of this paper is to present the results from a national survey of six sigma programs in US healthcare organizations. Through the design, distribution, and analysis of a nationwide survey, this paper assesses the implementation of six sigma in healthcare facilities. Two sets of surveys were designed based on whether an organization has adopted six sigma or not. Findings from this paper indicate the common six sigma projects implemented in healthcare organizations, typical implementation durations, cost benefits, and major barriers in implementation, and so on. This paper is limited by the low-response rate owing to time and budget constraints. Through the dissemination of this paper, it is hoped that more organizations will become interested in this subject and participate in future studies. This work is the first study to investigate the implementation status of six sigma in US healthcare systems. It will share experiences amongst six sigma institutions and promote its application in many institutions. The findings will provide instructive information to six sigma practitioners and researchers, and particularly to health care management.

  16. A model SN2 reaction ‘on water’ does not show rate enhancement

    Science.gov (United States)

    Nelson, Katherine V.; Benjamin, Ilan

    2011-05-01

    Molecular dynamics calculations of the benchmark nucleophilic substitution reaction (SN2) Cl- + CH3Cl are carried out at the water liquid/vapor interface. The reaction free energy profile and the activation free energy are determined as a function of the reactants' location normal to the surface. The activation free energy remains almost constant relative to that in bulk water, despite the fact that the barrier is expected to significantly decrease as the reaction is carried out near the vapor phase. We show that this is due to the combined effects of a clustering of water molecules around the nucleophile and a relatively weak hydration of the transition state.

  17. Does the {sigma}(1580)((3)/(2)){sup -} resonance exist?

    Energy Technology Data Exchange (ETDEWEB)

    Olmsted, J.; Prakhov, S.; Manley, D.M.; Allgower, C.E.; Bekrenev, V.S.; Briscoe, W.J.; Clajus, M.; Comfort, J.R.; Craig, K.; Grosnick, D.; Isenhower, D.; Knecht, N.; Koetke, D.D.; Kozlenko, N.G.; Kruglov, S.; Kulbardis, A.A.; Lolos, G.; Lopatin, I.V.; Manweiler, R.; Marusic, A.; McDonald, S.; Nefkens, B.M.K.; Papandreou, Z.; Peaslee, D.C.; Phaisangittisakul, N.; Price, J.W.; Ramirez, A.F.; Sadler, M.; Shafi, A.; Spinka, H.; Stanislaus, T.D.S.; Starostin, A.; Staudenmaier, H.M.; Strakovsky, I.I.; Supek, I.; Tippens, W.B

    2004-05-20

    Precise new data for the reaction K{sup -}p{yields}{pi}{sup 0}{lambda} are presented in the c.m. energy range 1565 to 1600 MeV. Our analysis of these data sheds new light on claims for the {sigma}(1580)((3)/(2)){sup -} resonance, which (if it exists with the specified quantum numbers) must be an exotic baryon because of its very low mass. Our results show no evidence for this state.

  18. Does the Sigma(1580)3/2- resonance exist?

    CERN Document Server

    Olmsted, J A; Manley, D M; Allgower, C E; Bekrenev, V S; Briscoe, W J; Clajus, M; Comfort, J R; Craig, K; Grosnick, D P; Isenhower, D; Knecht, N; Koetke, D D; Kozlenko, N G; Kruglov, S; Kulbardis, A A; Lolos, G J; Lopatin, I V; Manweiler, R; Marusic, A; McDonald, S; Nefkens, B M K; Papandreou, Z; Peaslee, D C; Phaisangittisakul, N; Price, J W; Ramírez, A F; Sadler, M E; Shafi, A; Spinka, H M; Stanislaus, T D S; Starostin, A S; Staudenmaier, H M; Strakovsky, I I; Supek, I; Tippens, W B; Tippens, and W.B.

    2003-01-01

    Precise new data for the reaction $K^- p \\to \\pi^0 \\Lambda$ are presented in the c.m. energy range 1565 to 1600 MeV. Our analysis of these data sheds new light on claims for the $\\Sigma(1580){3/2}^-$ resonance, which (if it exists with the specified quantum numbers) must be an exotic baryon because of its very low mass. Our results are decisive and show no evidence for this state.

  19. Electrochemical reaction rates in a dye-sensitised solar cell - the iodide/tri-iodide redox system

    DEFF Research Database (Denmark)

    Bay, L.; West, K.; Winther-Jensen, B.

    2006-01-01

    The electrochemical reaction rate of the redox couple iodide/tri-iodide in acetonitrile is characterised by impedance spectroscopy. Different electrode materials relevant for the function of dye-sensitised solar cells (DSSC) are investigated. Preferably, the reaction with the iodide....../tri-iodide couple should be fast at the counter electrode, i.e. this electrode must have a high catalytic activity towards the redox couple, and the same reaction must be slow on the photo electrode. The catalytic activity is investigated for platinum, poly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole (PPy......), and polyaniline (PANI)-all deposited onto fluorine-doped tin oxide (FTO) glass. Both Pt and PEDOT are found to have sufficiently high catalytic activities for practical use as counter electrodes in DSSC. The reaction resistance on FTO and anatase confirmed the beneficial effect of a compact anatase layer on top...

  20. THE STORY OF SIGMA HYPERNUCLEI - A MODERN FABLE.

    Energy Technology Data Exchange (ETDEWEB)

    CHRIEN,R.E.

    1999-02-19

    The reality of {Sigma} hypernuclei has been the subject of intense concern among experimenters and theoreticians for more than 20 years. The possible existence of {Sigma} hypernuclei was first suggested by a pioneering experiment on a {sup 9}Be target at the CERN PS. There were reported to be two narrow ({Gamma} < 8 MeV) peaks in the continuum region. This finding was quite unexpected since the widths of {Sigma} states were believed to be large due to the strong conversion process. It is obvious that if such relatively long-lived systems were confirmed unambiguously by experiment, their masses and widths provide important constraints on the {Sigma}N effective interaction and its relation to the {Lambda}N and NN interactions. Since the {Sigma} carries isospin, the role of isospin and isospin conservation in hadronic reactions could be explored. This report stimulated a number of subsequent experiments at the BNL-AGS and KEK, along with further experiments with a specially created short kaon beam at the CERN PS. Experimental data were reported for different targets at different momenta and at different conditions. Various tagging techniques were employed to suppress backgrounds, but always at the expense of a reduction in statistical quality. Because of problems with resolution and statistics, contradictions among the different sets of data resulted more often in clouding the issues than clarifying them. Thus, up until a few years ago, there was no statistically clear confirmation of this surprising finding. In the last few years, however, a series of definitive experiments has been performed at the BNL-AGS in an effort to resolve the discrepancies and settle the controversy. Besides repeating the initial experiment on Be, a target of {sup 6}Li was run. The earlier stopped kaon data on {sup 4}He was repeated in an in-flight experiment, and the suggestion of a {Sigma} bound state, with virtually pure isospin, confirmed. We now have a better understanding of the role

  1. Strong screening by lattice confinement and resultant fusion reaction rates in fcc metals

    Science.gov (United States)

    Prados-Estévez, F. M.; Subashiev, A. V.; Nee, H. H.

    2017-09-01

    The effects of electronic screening on the cross sections and reactivities for the nuclear reactions between light nuclei in Pd and Ni is studied. We consider the applicability of the theory of thermonuclear burning in stars to the D-D nuclear reaction in metals. The screening model based on the mean field potential of the electron cloud in the metal plasma is used. We discuss the specifics of the screening for the H (D) atoms embedded in vacancies and divacancies. High concentration of hydrogen isotopes segregated to monovacancies and divacancies in face-centered cubic (fcc) metals such as Ni and Pd with densities of ∼ 6 ×1023atom /cm3 , makes the hydrogen cluster a favorable active site for the fusion reaction. Still the observation of a nuclear reaction requires an accumulation of energy in D nuclei of at least several eV, which is far above what can be achieved in the thermal heating experiments.

  2. Bacterial Sigma Factors and Anti-Sigma Factors: Structure, Function and Distribution.

    Science.gov (United States)

    Paget, Mark S

    2015-06-26

    Sigma factors are multi-domain subunits of bacterial RNA polymerase (RNAP) that play critical roles in transcription initiation, including the recognition and opening of promoters as well as the initial steps in RNA synthesis. This review focuses on the structure and function of the major sigma-70 class that includes the housekeeping sigma factor (Group 1) that directs the bulk of transcription during active growth, and structurally-related alternative sigma factors (Groups 2-4) that control a wide variety of adaptive responses such as morphological development and the management of stress. A recurring theme in sigma factor control is their sequestration by anti-sigma factors that occlude their RNAP-binding determinants. Sigma factors are then released through a wide variety of mechanisms, often involving branched signal transduction pathways that allow the integration of distinct signals. Three major strategies for sigma release are discussed: regulated proteolysis, partner-switching, and direct sensing by the anti-sigma factor.

  3. [Determination of rate constants of gas-phase reactions of alpha-pinene and beta-pinene with ozone].

    Science.gov (United States)

    Liu, Z R; Hu, D

    2001-10-01

    alpha-pinene and beta-pinene are the most dominating species among natural terpenes. Terpenes are mainly emitted from forest trees, flowers and grass. In the lower troposphere terpenes can react fast with OH radical, ozone, NO3 radical and ground state oxygen atom. These reactions may contribute to the occurring of aerosols, peroxides (hydrogen peroxide and organic peroxide), carbon cycle (mainly CO), acid rain (organic acids, NO3- and SO4(2-), ozone and active radicals such as OH radical. Reactions with ozone occur both in the daytime and in the night. The study in this field in China began in the late 1980. The main work focus on the source emission and the experimental simulation has just started. It is most of our group's work. In this paper preliminary experimental simulation of the gas-phase reactions of alpha-pinene and beta-pinene with ozone were carried out in the quartz chamber. The rate constants of these reactions were measured using long-path Fourier transform infra-red combined with relative rate constant method. And the rate constants for the gas-phase reactions of alpha-pinene, beta-pinene with ozone were determined as 2.83 x 10(17) cm3.molecule-1.s-1 and 1.48 x 10(17) cm3.molecule-1.s-1 at 1.0 x 10(5) Pa and 296 +/- 3 K. The results are quite similar to the data from Atkinson group. No cyclohexane was added to the reaction system during the measurement to restrain the formation of OH radical. The formation of OH radical could not be quantified, so that the effect of subsidiary reactions induced by OH radical has not been calculated. In the later simulation study and model this effect should be considered.

  4. Nacre II:. AN Update and Extension of the Nacre Compilation of Charged-Particle Thermonuclear Reaction Rates for Astrophysics

    Science.gov (United States)

    Xu, Y.; Takahashi, K.; Goriely, S.; Arnould, M.

    2013-03-01

    The status of a new evaluation of astrophysical nuclear reaction rates, referred as NACRE- II, is reported. It includes 19 radiative capture and 15 transfer reactions on targets with mass numbers A < 16. This work is meant to supersede the NACRE compilation. Post-NACRE experimental data are taken into account. Extrapolations of the astrophysical S-factor to largely sub-Coulomb energies are based on the use of the potential model and of the distorted wave Born approximation (DWBA) for capture and transfer reactions, respectively. Adopted rates and their lower and upper limits are provided. Here, we illustrate with some results the general procedure followed in the construction of NACRE-II.

  5. Effects of a new triple-$\\alpha$ reaction rate on the helium ignition of accreting white dwarfs

    CERN Document Server

    Saruwatari, Motoaki

    2010-01-01

    Effects of a new triple-alpha reaction rate on the ignition of carbon-oxygen white dwarfs accreting helium in a binary systems have been investigated. The ignition points determine the properties of a thermonuclear explosion of a Type Ia supernova. We examine the cases of different accretion rates of helium and different initial masses of the white dwarf, which was studied in detail by Nomoto. We find that for all cases from slow to intermediate accretion rates, nuclear burnings are ignited at the helium layers. As a consequence, carbon deflagration would be triggered for the lower accretion rate compared to that of $dM/dt\\simeq 4\\times10^{-8} M_{\\odot} \\rm yr^{-1}$ which has been believed to the lower limit of the accretion rate for the deflagration supernova. Furthermore, off-center helium detonation should result for intermediate and slow accretion rates and the region of carbon deflagration for slow accretion rate is disappeared.

  6. K{sup 0}{pi}{sup 0}{sigma} and K{sup *0}{sigma}{sup +} photoproduction off the proton

    Energy Technology Data Exchange (ETDEWEB)

    Nanova, M.; Gregor, R.; Kotulla, M.; Lugert, S.; Metag, V.; Novotny, R.; Pant, L.M.; Pfeiffer, M.; Roy, A.; Schadmand, S.; Trnka, D.; Varma, R. [Universitaet Giessen, II. Physikalisches Institut (Germany); Bacelar, J.C.S.; Castelijns, R.; Loehner, H.; Messchendorp, J.G.; Shende, S.V. [Kernfysisch Versneller Institut, Groningen (Netherlands); Bantes, B.; Dutz, H.; Elsner, D.; Ewald, R.; Fornet-Ponse, K.; Gothe, R.; Kammer, S.; Kleber, V.; Klein, Frank; Klein, Friedrich; Konrad, M.; Langheinrich, J.; Menze, D.; Morales, C.; Ostrick, M.; Schmieden, H.; Schoch, B.; Suele, A. [Universitaet Bonn, Physikalisches Institut (Germany); Bartholomy, O.; Beck, R.; Ehmanns, A.; Essig, K.; Fabry, I.; Fuchs, M.; Funke, C.; Gutz, E.; Hoffmeister, P.; Horn, I.; Junkersfeld, J.; Kalinowsky, H.; Klempt, E.; Lang, M.; Lotz, J.; Pee, H. van; Schmidt, C.; Sokhoyan, V.; Szczepanek, T.; Weinheimer, C.; Wendel, C. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- u. Kernphysik (Germany); Bayadilov, D. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- u. Kernphysik (Germany); Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Beloglazov, Y.A.; Gridnev, A.B.; Lopatin, I.V.; Novinski, D.V.; Radkov, A.; Sumachev, V.V. [Petersburg Nuclear Physics Institute, Gatchina (Russian Federation); Crede, V. [Florida State University, Department of Physics, Tallahassee, FL (United States); Jaegle, I.; Krusche, B.; Mertens, T. [Universitaet Basel, Physikalisches Institut (Switzerland); Thoma, U. [Universitaet Giessen, II. Physikalisches Institut (Germany); Universitaet Bonn, Helmholtz-Institut fuer Strahlen- u. Kernphysik (Germany); Walther, D. [Universitaet Bonn, Physikalisches Institut (Germany); Universitaet Bonn, Helmholtz-Institut fuer Strahlen- u. Kernphysik (Germany)

    2008-03-15

    The exclusive reactions {gamma}p{yields}K{sup *0}{sigma}{sup +}(1189) and {gamma}p{yields}K{sup 0}{pi}{sup 0}{sigma}{sup +}(1189), leading to the p4{pi}{sup 0} final state, have been measured with a tagged photon beam for incident energies from threshold up to 2.5GeV. The experiment has been performed at the tagged photon facility of the ELSA accelerator (Bonn). The Crystal Barrel and TAPS detectors were combined to a photon detector system of almost 4{pi} geometrical acceptance. Differential and total cross-sections are reported. At energies close to the threshold, a flat angular distribution has been observed for the reaction {gamma}p{yields}K{sup 0}{pi}{sup 0}{sigma}{sup +} suggesting dominant s-channel production. {sigma}{sup *}(1385) and higher-lying hyperon states have been observed. An enhancement in the forward direction in the angular distributions of the reaction {gamma}p{yields}K{sup *0}{sigma}{sup +} indicates a t-channel exchange contribution to the reaction mechanism. The experimental data are in reasonable agreement with recent theoretical predictions. (orig.)

  7. Rate and mechanism of the reactions of OH and Cl with 2-methyl-3-buten-2-ol

    Science.gov (United States)

    Ferronato, C.; Orlando, J. J.; Tyndall, G. S.

    1998-10-01

    An environmental chamber/Fourier transform infrared system was used to determine the rate coefficient k1 for the gas-phase reaction of OH with 2-methyl-3-buten-2-ol (MBO, (CH3)2C(OH)CH=CH2), relative to the rate of its reaction with ethylene (k2) and propylene (k3). Experiments performed at 295±1 K, in 700 torr total pressure of air, gave k1 = (6.9±1.0) × 10-11 cm3 molecule-1 s-1. At 295±1 K, the reaction of OH with MBO yielded, on a per mole basis, (52±5)% acetone, (50±5)% glycolaldehyde, and (35±4)% formaldehyde. The production of acetone from the oxidation of MBO may be of significance globally. The kinetics and mechanism of the reaction of chlorine atoms with MBO (k15) have also been studied at 700 torr total pressure of air and 295±1 K. The rate coefficient was determined using a relative rate technique, with ethane (k16), ethylene (k17), and cyclohexane (k18) as reference compounds. The value of k15 was found to be (3.3±0.4) × 10-10 cm3 molecule-1 s-1 at 295 K. The major carbon-containing products obtained in the Cl-atom oxidation of MBO were acetone (47±5)%, chloroacetaldehyde (53±5)%, HCOCl (<11%), and formaldehyde (6 ± 2)%.

  8. First measurement of the 34S(p ,γ )35Cl reaction rate through indirect methods for presolar nova grains

    Science.gov (United States)

    Gillespie, S. A.; Parikh, A.; Barton, C. J.; Faestermann, T.; José, J.; Hertenberger, R.; Wirth, H.-F.; de Séréville, N.; Riley, J. E.; Williams, M.

    2017-08-01

    Sulphur isotopic ratio measurements may help to establish the astrophysical sites in which certain presolar grains were formed. Nova model predictions of the 34S/32S ratio are, however, unreliable due to the lack of an experimental 34S(p ,γ )35Cl reaction rate. To this end, we have measured the 34S(3He,d )35Cl reaction at 20 MeV using a high resolution quadrupole-dipole-dipole-dipole magnetic spectrograph. Twenty-two levels over 6.2 MeV transfer spectroscopic factors have been measured for the first time over the energy range relevant for novae. With this new spectroscopic information a new 34S(p ,γ )35Cl reaction rate has been determined using a Monte Carlo method. Hydrodynamic nova model calculations have been performed using this new reaction rate. These models show that remaining uncertainties in the 34S(p ,γ ) rate affect nucleosynthesis predictions by less than a factor of 1.4, and predict a 34S/32S isotopic ratio of 0.014-0.017. Since recent type II supernova models predict 34S/32S=0.026 -0.053 , the 34S/32S isotopic ratio may be used, in conjunction with other isotopic signatures, to distinguish presolar grains from oxygen-neon nova and type II supernova origin. Our results address a key nuclear physics uncertainty on which recent considerations discounting the nova origin of several grains depend.

  9. Standard Test Method for Determining Thermal Neutron Reaction Rates and Thermal Neutron Fluence Rates by Radioactivation Techniques

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 The purpose of this test method is to define a general procedure for determining an unknown thermal-neutron fluence rate by neutron activation techniques. It is not practicable to describe completely a technique applicable to the large number of experimental situations that require the measurement of a thermal-neutron fluence rate. Therefore, this method is presented so that the user may adapt to his particular situation the fundamental procedures of the following techniques. 1.1.1 Radiometric counting technique using pure cobalt, pure gold, pure indium, cobalt-aluminum, alloy, gold-aluminum alloy, or indium-aluminum alloy. 1.1.2 Standard comparison technique using pure gold, or gold-aluminum alloy, and 1.1.3 Secondary standard comparison techniques using pure indium, indium-aluminum alloy, pure dysprosium, or dysprosium-aluminum alloy. 1.2 The techniques presented are limited to measurements at room temperatures. However, special problems when making thermal-neutron fluence rate measurements in high-...

  10. Hypertriton:. Lambda. leftrightarrow. Sigma. conversion and tensor forces

    Energy Technology Data Exchange (ETDEWEB)

    Afnan, I.R. (School of Physical Sciences, The Flinders University of South Australia, Bedford Park, South Australia 5042, (Australia)); Gibson, B.F. (Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (USA))

    1990-06-01

    The separable potential equations that describe the hypertriton when {Lambda}{ital N}-{Sigma}{ital N} coupling and noncentral {ital NN} and {ital YN} forces are included, are formulated. Numerical solution of the equations for various potential models shows that {Lambda}-{Sigma} conversion in the {ital YN} interaction plays a significant role, even in the lightly bound {sub {Lambda}}{sup 3}H. When the {Sigma}{ital N} channel is formally eliminated, the dispersive energy dependence of the resulting {Lambda}{ital N} effective interaction is repulsive, whereas the resulting {Lambda}{ital NN} three-body force is attractive. The contribution of the {Lambda}{ital N} tensor force is shown to depend upon the inclusion of the {ital NN} tensor force and the relative sign of the {sup 3}{ital S}{sub 1}-{sup 3}{ital D}{sub 1} {ital NN} and {Lambda}{ital N} tensor coupling. Also, a model which supports a {Sigma}{ital N} bound state in the continuum appears to severely overbind the {sub {Lambda}}{sup 3}H system, indicating that such a phenomenon is not present in the {ital K}{sup {minus}}{ital d}{r arrow}{Lambda}{ital N}{pi} reaction.

  11. Relationship between severity of the local skin reactions and the rate of local skin reaction resolution in patients treated with ingenol mebutate gel

    Directory of Open Access Journals (Sweden)

    Jim On SC

    2016-08-01

    Full Text Available Shelbi C Jim On,1 Kim Mark Knudsen,2 Torsten Skov,2 Mark Lebwohl,1 1Department of Dermatology, Mount Sinai School of Medicine, New York, NY, USA; 2LEO Pharma A/S, Biostatistics, Ballerup, Denmark Background: Ingenol mebutate gel is a topical field treatment for actinic keratosis (AK. The treatment elicits application-site reactions in most patients. This analysis evaluated the relationship between the severity of reactions and the speed of their resolution.  Methods: Patients in Phase III studies were treated for AKs on the face (n=218, scalp (n=56, and trunk and extremities (n=209. All of the patients were treated with either ingenol mebutate gel 0.015% once daily for three consecutive days (face/scalp or ingenol mebutate gel 0.05% once daily for two consecutive days (trunk/extremities. Local skin reactions (LSRs were assessed on a 5-point scale from 0 to 4 in six categories, yielding composite scores in the range of 0 to 24. Results: The composite LSR score on the day after the last application of ingenol mebutate gel was an important predictor of the speed of resolution of LSRs. The rate of resolution was greatest for AKs treated on the face, followed by the scalp, and then the trunk and extremities. All patients were expected to have minimal LSR scores for the face and scalp at 2 weeks, and for the trunk and extremities at 4 weeks. Conclusion: The absolute reduction in LSR scores was proportional to the composite LSR score on the day after the last application of ingenol mebutate gel treatment. The rate of resolution for LSRs was dependent on the anatomic site treated as well as the day 4 composite score. Keywords: ingenol mebutate, local skin reaction, actinic keratosis

  12. Application of an Artificial Neural Network to the Prediction of OH Radical Reaction Rate Constants for Evaluating Global Warming Potential.

    Science.gov (United States)

    Allison, Thomas C

    2016-03-03

    Rate constants for reactions of chemical compounds with hydroxyl radical are a key quantity used in evaluating the global warming potential of a substance. Experimental determination of these rate constants is essential, but it can also be difficult and time-consuming to produce. High-level quantum chemistry predictions of the rate constant can suffer from the same issues. Therefore, it is valuable to devise estimation schemes that can give reasonable results on a variety of chemical compounds. In this article, the construction and training of an artificial neural network (ANN) for the prediction of rate constants at 298 K for reactions of hydroxyl radical with a diverse set of molecules is described. Input to the ANN consists of counts of the chemical bonds and bends present in the target molecule. The ANN is trained using 792 (•)OH reaction rate constants taken from the NIST Chemical Kinetics Database. The mean unsigned percent error (MUPE) for the training set is 12%, and the MUPE of the testing set is 51%. It is shown that the present methodology yields rate constants of reasonable accuracy for a diverse set of inputs. The results are compared to high-quality literature values and to another estimation scheme. This ANN methodology is expected to be of use in a wide range of applications for which (•)OH reaction rate constants are required. The model uses only information that can be gathered from a 2D representation of the molecule, making the present approach particularly appealing, especially for screening applications.

  13. The role of reaction affinity and secondary minerals in regulating chemical weathering rates at the Santa Cruz Soil Chronosequence, California

    Science.gov (United States)

    Maher, K.; Steefel, Carl; White, A.F.; Stonestrom, D.A.

    2009-01-01

    In order to explore the reasons for the apparent discrepancy between laboratory and field weathering rates and to determine the extent to which weathering rates are controlled by the approach to thermodynamic equilibrium, secondary mineral precipitation, and flow rates, a multicomponent reactive transport model (CrunchFlow) was used to interpret soil profile development and mineral precipitation and dissolution rates at the 226 ka Marine Terrace Chronosequence near Santa Cruz, CA. Aqueous compositions, fluid chemistry, transport, and mineral abundances are well characterized [White A. F., Schulz M. S., Vivit D. V., Blum A., Stonestrom D. A. and Anderson S. P. (2008) Chemical weathering of a Marine Terrace Chronosequence, Santa Cruz, California. I: interpreting the long-term controls on chemical weathering based on spatial and temporal element and mineral distributions. Geochim. Cosmochim. Acta 72 (1), 36-68] and were used to constrain the reaction rates for the weathering and precipitating minerals in the reactive transport modeling. When primary mineral weathering rates are calculated with either of two experimentally determined rate constants, the nonlinear, parallel rate law formulation of Hellmann and Tisserand [Hellmann R. and Tisserand D. (2006) Dissolution kinetics as a function of the Gibbs free energy of reaction: An experimental study based on albite feldspar. Geochim. Cosmochim. Acta 70 (2), 364-383] or the aluminum inhibition model proposed by Oelkers et al. [Oelkers E. H., Schott J. and Devidal J. L. (1994) The effect of aluminum, pH, and chemical affinity on the rates of aluminosilicate dissolution reactions. Geochim. Cosmochim. Acta 58 (9), 2011-2024], modeling results are consistent with field-scale observations when independently constrained clay precipitation rates are accounted for. Experimental and field rates, therefore, can be reconciled at the Santa Cruz site. Additionally, observed maximum clay abundances in the argillic horizons occur at

  14. Anisotropic transverse mixing and its effect on reaction rates in multi-scale, 3D heterogeneous porous media

    Science.gov (United States)

    Engdahl, N. B.

    2016-12-01

    Mixing rates in porous media have been a heavily research topic in recent years covering analytic, random, and structured fields. However, there are some persistent assumptions and common features to these models that raise some questions about the generality of the results. One of these commonalities is the orientation of the flow field with respect to the heterogeneity structure, which are almost always defined to be parallel each other if there is an elongated axis of permeability correlation. Given the vastly different tortuosities for flow parallel to bedding and flow transverse to bedding, this assumption of parallel orientation may have significant effects on reaction rates when natural flows deviate from this assumed setting. This study investigates the role of orientation on mixing and reaction rates in multi-scale, 3D heterogeneous porous media with varying degrees of anisotropy in the correlation structure. Ten realizations of a small flow field, with three anisotropy levels, were simulated for flow parallel and transverse to bedding. Transport was simulated in each model with an advective-diffusive random walk and reactions were simulated using the chemical Langevin equation. The reaction system is a vertically segregated, transverse mixing problem between two mobile reactants. The results show that different transport behaviors and reaction rates are obtained by simply rotating the direction of flow relative to bedding, even when the net flux in both directions is the same. This kind of behavior was observed for three different weightings of the initial condition: 1) uniform, 2) flux-based, and 3) travel time based. The different schemes resulted in 20-50% more mass formation in the transverse direction than the longitudinal. The greatest variability in mass was observed for the flux weights and these were proportionate to the level of anisotropy. The implications of this study are that flux or travel time weights do not provide any guarantee of a fair

  15. Sigma Factors for Cyanobacterial Transcription

    Directory of Open Access Journals (Sweden)

    Sousuke Imamura

    2009-04-01

    Full Text Available Cyanobacteria are photosynthesizing microorganisms that can be used as a model for analyzing gene expression. The expression of genes involves transcription and translation. Transcription is performed by the RNA polymerase (RNAP holoenzyme, comprising a core enzyme and a sigma (σ factor which confers promoter selectivity. The unique structure, expression, and function of cyanobacterial σ factors (and RNAP core subunits are summarized here based on studies, reported previously. The types of promoter recognized by the σ factors are also discussed with regard to transcriptional regulation.

  16. Topological sigma models on supermanifolds

    Directory of Open Access Journals (Sweden)

    Bei Jia

    2017-02-01

    Full Text Available This paper concerns constructing topological sigma models governing maps from semirigid super Riemann surfaces to general target supermanifolds. We define both the A model and B model in this general setup by defining suitable BRST operators and physical observables. Using supersymmetric localization, we express correlation functions in these theories as integrals over suitable supermanifolds. In the case of the A model, we obtain an integral over the supermoduli space of “superinstantons”. The language of supergeometry is used extensively throughout this paper.

  17. Cohomological reduction of sigma models

    Energy Technology Data Exchange (ETDEWEB)

    Candu, Constantin; Mitev, Vladimir; Schomerus, Volker [DESY, Hamburg (Germany). Theory Group; Creutzig, Thomas [North Carolina Univ., Chapel Hill, NC (United States). Dept. of Physics and Astronomy

    2010-01-15

    This article studies some features of quantum field theories with internal supersymmetry, focusing mainly on 2-dimensional non-linear sigma models which take values in a coset superspace. It is discussed how BRST operators from the target space super- symmetry algebra can be used to identify subsectors which are often simpler than the original model and may allow for an explicit computation of correlation functions. After an extensive discussion of the general reduction scheme, we present a number of interesting examples, including symmetric superspaces G/G{sup Z{sub 2}} and coset superspaces of the form G/G{sup Z{sub 4}}. (orig.)

  18. Effect of Composition on the Formation of Sigma during Single-Pass Welding of Mo-Bearing Stainless Steels

    Science.gov (United States)

    Perricone, M. J.; Anderson, T. D.; Robino, C. V.; Dupont, J. N.; Michael, J. R.

    2007-09-01

    A series of 64 Mo-bearing stainless steel compositions ranging from 0 to 10 wt pct Mo and over a broad range of Ni and Cr contents were analyzed over a variety of cooling rates. Alloys were created using the arc button melting process, and laser welds were prepared on each alloy at constant power and travel speeds ranging from 4.2 to 42 mm/s. The presence of the σ-sigma intermetallic was observed in several primary γ-austenite alloys with Mo contents ≥2.5 wt pct Mo and in several primary δ-ferrite alloys with Mo contents ≥6 wt pct Mo. However, its formation cannot be explained by the eutectic solidification reaction previously explored in this class of materials by the present authors. Instead, σ-sigma was determined to form by the eutectoid decomposition of δ-ferrite ( δ → γ + σ) in the as-solidified arc melt buttons in both primary γ-austenite and primary δ-ferrite alloys. The high cooling rates in the laser welds (estimated to range from 104 °C/s to 105 °C/s) largely prevented this transformation from occurring, resulting in the retention of metastable δ-ferrite to room temperature. A correlation was observed between the composition of the δ-ferrite in the microstructure and the calculated onset temperature of sigma stability. By combining multicomponent liquidus projections and isothermal sections, a good correlation of δ-ferrite compositions that decompose to γ-austenite + σ-sigma upon cooling is presented. It is suggested that the absence of the chi ( χ) phase, often observed in a similar composition range at high Mo contents, could be attributed to the extremely low carbon content in these alloys.

  19. Rate of pozzolanic reaction of two kinds of activated coal gangue

    Institute of Scientific and Technical Information of China (English)

    ZHOU Shuang-xi

    2009-01-01

    Two kinds of activated ways are used to prepare activated coal gangue fine powder,one is calcining coal gangue at 800 ℃ (gangue A),and the other is calcining coal gangue with a certain calcite at 800 ℃ (gangue B).The experiment shows that strengths of blended cement mortar with coal gangue B are higher than that of blended cement with coal gangue A.Hydration of cements with the two kinds of activated coal gangue is investigated through a differential thermal analysis.The weight loss due to Ca(OH)2 decomposition of hydration products by differential thermal anaiysis/thermo gravimetric (DTA/TG) can be used to quantify the pozzolanic reaction.A new method based on the composition of hydration cement is proposed to determine the degree of pozzolanic reaction.The results obtained suggest that the degree of pozzolanic reaction of gangue B is faster than that of gangue A.

  20. Determination of 8B(p,gamma)9C reaction rate from 9C breakup

    CERN Document Server

    Fukui, Tokuro; Minomo, Kosho; Yahiro, Masanobu

    2012-01-01

    The astrophysical factor of the 8B(p,gamma)9C at zero energy, S18(0), is determined from three-body model analysis of 9C breakup processes. The elastic breakup 208Pb(9C,p8B)208Pb at 65 MeV/nucleon and the one-proton removal reaction of 9C at 285 MeV/nucleon on C and Al targets are calculated with the continuum-discretized coupled-channels method (CDCC) and the eikonal reaction theory (ERT), respectively. The asymptotic normalization coefficient (ANC) of 9C in the p-8B configuration extracted from the two reactions show good consistency, in contrast to in the previous studies. As a result of the present analysis, S18(0) = 66 \\pm 10 eVb is obtained.

  1. Significance of vapor phase chemical reactions on CVD rates predicted by chemically frozen and local thermochemical equilibrium boundary layer theories

    Science.gov (United States)

    Gokoglu, Suleyman A.

    1988-01-01

    This paper investigates the role played by vapor-phase chemical reactions on CVD rates by comparing the results of two extreme theories developed to predict CVD mass transport rates in the absence of interfacial kinetic barrier: one based on chemically frozen boundary layer and the other based on local thermochemical equilibrium. Both theories consider laminar convective-diffusion boundary layers at high Reynolds numbers and include thermal (Soret) diffusion and variable property effects. As an example, Na2SO4 deposition was studied. It was found that gas phase reactions have no important role on Na2SO4 deposition rates and on the predictions of the theories. The implications of the predictions of the two theories to other CVD systems are discussed.

  2. Non-steady state mass action dynamics without rate constants: dynamics of coupled reactions using chemical potentials

    Science.gov (United States)

    Cannon, William R.; Baker, Scott E.

    2017-10-01

    Comprehensive and predictive simulation of coupled reaction networks has long been a goal of biology and other fields. Currently, metabolic network models that utilize enzyme mass action kinetics have predictive power but are limited in scope and application by the fact that the determination of enzyme rate constants is laborious and low throughput. We present a statistical thermodynamic formulation of the law of mass action for coupled reactions at both steady states and non-stationary states. The formulation uses chemical potentials instead of rate constants. When used to model deterministic systems, the method corresponds to a rescaling of the time dependent reactions in such a way that steady states can be reached on the same time scale but with significantly fewer computational steps. The relationships between reaction affinities, free energy changes and generalized detailed balance are central to the discussion. The significance for applications in systems biology are discussed as is the concept and assumption of maximum entropy production rate as a biological principle that links thermodynamics to natural selection.

  3. Conserved and Variable Functions of the sigma(E Stress Response in Related Genomes.

    Directory of Open Access Journals (Sweden)

    2005-12-01

    Full Text Available Bacteria often cope with environmental stress by inducing alternative sigma (sigma factors, which direct RNA polymerase to specific promoters, thereby inducing a set of genes called a regulon to combat the stress. To understand the conserved and organism-specific functions of each sigma, it is necessary to be able to predict their promoters, so that their regulons can be followed across species. However, the variability of promoter sequences and motif spacing makes their prediction difficult. We developed and validated an accurate promoter prediction model for Escherichia coli sigma(E, which enabled us to predict a total of 89 unique sigma(E-controlled transcription units in E. coli K-12 and eight related genomes. sigma(E controls the envelope stress response in E. coli K-12. The portion of the regulon conserved across genomes is functionally coherent, ensuring the synthesis, assembly, and homeostasis of lipopolysaccharide and outer membrane porins, the key constituents of the outer membrane of Gram-negative bacteria. The larger variable portion is predicted to perform pathogenesis-associated functions, suggesting that sigma(E provides organism-specific functions necessary for optimal host interaction. The success of our promoter prediction model for sigma(E suggests that it will be applicable for the prediction of promoter elements for many alternative sigma factors.

  4. On the structure of a distinguished-limit quasi-isothermal deflagration for the generalized reaction-rate model

    Directory of Open Access Journals (Sweden)

    W. B. Bush

    1997-01-01

    are the activation, adiabatic-flame (and/or burned-gas, and unburned-gas temperatures, respectively]; and (2 the exponent, a, which characterizes the pre-exponential thermal dependence of the reaction-rate term, unity. The examination indicates that, as in the order-unity heat-addition case, this deflagration has a four-region structure: the upstream diffusion-convection and downstream diffusion-reaction regions, and the far-upstream (or cold-boundary and the far-downstream (or hot-boundary regions.

  5. The Effect of Nuclear Reaction Rates & Convective Mixing on the Evolution of a 6M$_{\\odot}$ Star

    CERN Document Server

    Halabi, Ghina M

    2014-01-01

    We present the evolution of a 6M$_{\\odot}$ star, of solar-like initial metallicity, and investigate the effects of key nuclear reaction rates, as well as the treatment of the convective mixing on its evolution along the Cepheid instability strip. In particular, we study the effect of recent estimates of the $^{14}$N(p,{\\gamma})$^{15}$O reaction on the formation and extension of the blue loop during core helium burning. We also investigate the effects induced on this blue loop by the adoption of non-standard convective mixing prescriptions, as well as the implications of modifying the Mixing Length Theory.

  6. Using Arrested Solid-Solid Multiphase Reactions in Geological Materials to Deduce the Rate of Crustal Uplift

    Energy Technology Data Exchange (ETDEWEB)

    Glassley, W.E.; Meike, A.

    2000-03-13

    The history geological terrains experience can be traced as a series of temperature and pressure changes. Each change drives the system toward a new state of thermodynamic equilibrium. The resultant overprinted rock fabrics, textures and chemical heterogeneities can be difficult to interpret. However, if carefully chosen, features from the scale of kilometers to nanometers can be used to reconstruct the history of mountain systems. Uplift of the Sri Lankan Central Highlands was rapid enough to preserve well-developed symplectite textures, some of which represent arrested solid-state diffusion-controlled reactions of garnet + O{sub 2} to form orthopyroxene + plagioclase + magnetite, as the rocks were exhumed from over 30 km in the earth's crust. Our objective has been to determine the reaction mechanisms responsible for symplectite development, and to establish the time interval over which these reactions occurred, to constrain the rate of mountain uplift. Considering that the most rapid mechanism is solid state grain-boundary diffusion of oxygen, the reaction time can be constrained by bounding the rate of oxygen supply to the reaction site. The solid state grain boundary diffusion rate of oxygen has been inferred to be ca. 10{sup -14}m{sup 2}-sec (Farver and Yund, 1991), but is sensitive to inferred grain boundary width. The range of rates thus determined allows the distinction between rapid uplift similar to that of the Himalayan Mountains, and the slow and progressive erosion of a less dramatic terrain. Further constraints on diffusion control and energetic relationships are determined from crystallographic relationships between the reactant and product phases, and submicron scale microstructure.

  7. The bi Hermitian topological sigma model

    CERN Document Server

    Zucchini, R

    2006-01-01

    BiHermitian geometry, discovered long ago by Gates, Hull and Roceck, is the most general sigma model target space geometry allowing for (2,2) world sheet supersymmetry. By using the twisting procedure proposed by Kapustin and Li, we work out the type A and B topological sigma models for a general biHermtian target space, we write down the explicit expression of the sigma model's action and BRST transformations and present a computation of the topological gauge fermion.

  8. Lean Six Sigma in financial services

    OpenAIRE

    Koning, H.; Does, R.J.M.M.; Bisgaard, S.

    2008-01-01

    Lean Thinking and Six Sigma are typically considered as separate approaches to process innovation, with complementary strengths. When combined as Lean Six Sigma, this approach provides a unified framework for systematically developing innovations. Lean Six Sigma can also bring about significant results and breakthrough improvements in financial services, as demonstrated with four case studies from Dutch multinational insurance companies. These cases demonstrate the importance of incremental i...

  9. Dual mode cobaloxime crystals: Acceleration of trans-cis photochromic reaction rate by photoisomerization

    Science.gov (United States)

    Sekine, Akiko

    2016-08-01

    Our recent results on the photochromic reactions in dual mode cobaloxime crystals containing azobenzene derivatives are briefly reviewed. This work represents the first step toward the design of functional materials which can be controlled by two independent external stimuli, one by visible light and the other by UV radiation.

  10. Electrochemical reaction rates in a dye sentisised solar cell - the iodide/tri-iodide redox system

    DEFF Research Database (Denmark)

    Bay, Lasse; West, Keld; Winter-Jensen, Bjørn

    2006-01-01

    -iodide couple should be fast at the counter electrode, i.e. this electrode must have a high catalytic activity towards the redox couple, and the same reaction must be slow on the photo electrode. The catalytic activity is investigated for platinum, poly(3,4-ethylenedioxythiophene) (PEDOT), polypyrrole (PPy...

  11. On the relationship between structure and reaction rate in olefin ring-closing metathesis.

    Science.gov (United States)

    Ashworth, Ian W; Carboni, Davide; Hillier, Ian H; Nelson, David J; Percy, Jonathan M; Rinaudo, Giuseppe; Vincent, Mark A

    2010-10-14

    In the RCM reactions of a series of simple α,ω-dienes, the relative order of reactivity has been unambiguously determined showing that cyclohexene forms faster than cyclopentene or cycloheptene. 1,5-Hexadiene inhibits the RCM of 1,7-octadiene; 1,5-hexadiene cannot progress to the RCM product (cyclobutene) but forms an unexpectedly stable cyclic η(2)-complex.

  12. Defense Nuclear Agency Reaction Rate Handbook. Second Edition. Revision Number 6

    Science.gov (United States)

    1972-03-01

    257 (1972). 17-55. Gilmore, F. R., J. Quant. Spectry. Radiative Transfer S_t 369(1965). 17-56. Herzberg , G., Electronic Spectra of...1F»O •BBS • \\ CHAPTER 19 19. NEUTRAL REACTIONS Frederick Kaufman, University of Pittsburgh (Latest Revision 14 May 1975) o 19.1

  13. Applying Sigma Metrics to Reduce Outliers.

    Science.gov (United States)

    Litten, Joseph

    2017-03-01

    Sigma metrics can be used to predict assay quality, allowing easy comparison of instrument quality and predicting which tests will require minimal quality control (QC) rules to monitor the performance of the method. A Six Sigma QC program can result in fewer controls and fewer QC failures for methods with a sigma metric of 5 or better. The higher the number of methods with a sigma metric of 5 or better, the lower the costs for reagents, supplies, and control material required to monitor the performance of the methods.

  14. Surface reaction rate and probability of ozone and alpha-terpineol on glass, polyvinyl chloride, and latex paint surfaces.

    Science.gov (United States)

    Shu, Shi; Morrison, Glenn C

    2011-05-15

    Ozone can react homogeneously with unsaturated organic compounds in buildings to generate undesirable products. However, these reactions can also occur on indoor surfaces, especially for low-volatility organics. Conversion rates of ozone with α-terpineol, a representative low-volatility compound, were quantified on surfaces that mimic indoor substrates. Rates were measured for α-terpineol adsorbed to beads of glass, polyvinylchloride (PVC), and dry latex paint, in a plug flow reactor. A newly defined second-order surface reaction rate coefficient, k(2), was derived from the flow reactor model. The value of k(2) ranged from 0.68 × 10(-14) cm(4)s(-1)molecule(-1) for α-terpineol adsorbed to PVC to 3.17 × 10(-14) cm(4)s(-1)molecule(-1) for glass, but was insensitive to relative humidity. Further, k(2) is only weakly influenced by the adsorbed mass but instead appears to be more strongly related to the interfacial activity α-terpineol. The minimum reaction probability ranged from 3.79 × 10(-6) for glass at 20% RH to 6.75 × 10(-5) for PVC at 50% RH. The combination of high equilibrium surface coverage and high reactivity for α-terpineol suggests that surface conversion rates are fast enough to compete with or even overwhelm other removal mechanisms in buildings such as gas-phase conversion and air exchange.

  15. Reduction of Large Detailed Chemical Kinetic Mechanisms for Autoignition Using Joint Analyses of Reaction Rates and Sensitivities

    Energy Technology Data Exchange (ETDEWEB)

    Saylam, A; Ribaucour, M; Pitz, W J; Minetti, R

    2006-11-29

    A new technique of reduction of detailed mechanisms for autoignition, which is based on two analysis methods is described. An analysis of reaction rates is coupled to an analysis of reaction sensitivity for the detection of redundant reactions. Thresholds associated with the two analyses have a great influence on the size and efficiency of the reduced mechanism. Rules of selection of the thresholds are defined. The reduction technique has been successfully applied to detailed autoignition mechanisms of two reference hydrocarbons: n-heptane and iso-octane. The efficiency of the technique and the ability of the reduced mechanisms to reproduce well the results generated by the full mechanism are discussed. A speedup of calculations by a factor of 5.9 for n-heptane mechanism and by a factor of 16.7 for iso-octane mechanism is obtained without losing accuracy of the prediction of autoignition delay times and concentrations of intermediate species.

  16. Atmospheric reactions of methylcyclohexanes with Cl atoms and OH radicals: determination of rate coefficients and degradation products.

    Science.gov (United States)

    Ballesteros, Bernabé; Ceacero-Vega, Antonio A; Jiménez, Elena; Albaladejo, José

    2015-04-01

    As the result of biogenic and anthropogenic activities, large quantities of chemical compounds are emitted into the troposphere. Alkanes, in general, and cycloalkanes are an important chemical class of hydrocarbons found in diesel, jet and gasoline, vehicle exhaust emissions, and ambient air in urban areas. In general, the primary atmospheric fate of organic compounds in the gas phase is the reaction with hydroxyl radicals (OH). The oxidation by Cl atoms has gained importance in the study of atmospheric reactions because they may exert some influence in the boundary layer, particularly in marine and coastal environments, and in the Arctic troposphere. The aim of this paper is to study of the atmospheric reactivity of methylcylohexanes with Cl atoms and OH radicals under atmospheric conditions (in air at room temperature and pressure). Relative kinetic techniques have been used to determine the rate coefficients for the reaction of Cl atoms and OH radicals with methylcyclohexane, cis-1,4-dimethylcyclohexane, trans-1,4-dimethylcyclohexane, and 1,3,5-trimethylcyclohexane at 298 ± 2 K and 720 ± 5 Torr of air by Fourier transform infrared) spectroscopy and gas chromatography-mass spectrometry (GC-MS) in two atmospheric simulation chambers. The products formed in the reaction under atmospheric conditions were investigated using a 200-L Teflon bag and employing the technique of solid-phase microextraction coupled to a GC-MS. The rate coefficients obtained for the reaction of Cl atoms with the studied compounds are the following ones (in units of 10(-10) cm(3) molecule(-1) s(-1)): (3.11 ± 0.16), (2.89 ± 0.16), (2.89 ± 0.26), and (2.61 ± 0.42), respectively. For the reactions with OH radicals the determined rate coefficients are (in units of 10(-11) cm(3) molecule(-1) s(-1)): (1.18 ± 0.12), (1.49 ± 0.16), (1.41 ± 0.15), and (1.77 ± 0.23), respectively. The reported error is twice the standard deviation. A detailed

  17. The low-lying 2-sigma-minus states of OH

    Science.gov (United States)

    Van Dishoeck, E. F.; Langhoff, S. R.; Dalgarno, A.

    1983-01-01

    The configuration-interaction method is used to determine the electronic wave functions of the two lowest 2-sigma-minus states of OH using four different atomic orbital basis sets. Potential energy curves, transition moments, oscillator strengths, and photodissociation cross sections are obtained. Electronic transition dipole moments connecting the excited 1 2-sigma-minus and 2(D)2-sigma-minus states with each other and with the ground chi-2-pi state are presented as functions of internuclear distance. The theoretical absorption oscillator strengths for the D-2-sigma-minus(v prime = 0) from chi-2-pi(v double prime = 0) transition are in good agreement with the empirical value derived from astronomical measurement. The photodissociation cross sections for absorption from the v prime = 0, 1, and 2 levels of the ground state into the continuum of the 1 2-sigma-minus state are calculated, and the interstellar and cometary photodissociation rates are derived.

  18. Narrow structure in [Lambda]d scattering near the [Sigma] threshold ([sub [Sigma

    Energy Technology Data Exchange (ETDEWEB)

    Gibson, B.F. (Los Alamos National Lab., NM (United States). Theoretical Div.); Afnan, I.R. (Flinders Univ. of South Australia, Bedford Park (Australia). School of Physical Sciences)

    1992-09-14

    A separable-potential, Faddeev-type calculation of [Lambda]-deuteron scattering near the threshold for [Sigma] production is shown to produce structure (a resonance peak) in the cross section which lies below the [Sigma] threshold for two different Y N ([Lambda]N - [Sigma]N coupled-channel) potential models. In one case the [Sigma]NN eigenvalue corresponds to a pole which lies below threshold (bound) and in the second case the pole lies above the threshold. (orig.).

  19. Narrow structure in. Lambda. d scattering near the. Sigma. threshold ( sub. Sigma. sup 3 He states)

    Energy Technology Data Exchange (ETDEWEB)

    Gibson, B.F. (Los Alamos National Lab., NM (United States)); Afnan, I.R. (Flinders Univ. of South Australia, Bedford Park (Australia). School of Physical Sciences)

    1991-01-01

    A separable-potential, Faddeev-type calculation of {Lambda}-deuteron scattering near the threshold for {Sigma} production is shown to produce structure (a resonance peak) in the cross section which lies below the {Sigma} threshold for two different YN ({Lambda}N-{Sigma}N coupled-channel) potential models. In one case the {Sigma}NN eigenvalue corresponds to a pole which lies below threshold (bound) and in the second case the poles lies above the threshold.

  20. Bacterial Sigma Factors and Anti-Sigma Factors: Structure, Function and Distribution

    OpenAIRE

    Paget, Mark S.

    2015-01-01

    Sigma factors are multi-domain subunits of bacterial RNA polymerase (RNAP) that play critical roles in transcription initiation, including the recognition and opening of promoters as well as the initial steps in RNA synthesis. This review focuses on the structure and function of the major sigma-70 class that includes the housekeeping sigma factor (Group 1) that directs the bulk of transcription during active growth, and structurally-related alternative sigma factors (Groups 2–4) that control ...

  1. Nucleon-resonance decay by the K-0 Sigma(+) channel near threshold

    NARCIS (Netherlands)

    Castelijns, R; Lohner, H

    2002-01-01

    For the combined setup of the Crystal Barrel and TAPS at ELSA in Bonn we have proposed to study the reaction gammap --> K(0)Sigma(+). The reaction is characterised by the final state of 6 photons and a forward emitted proton. Here we report on results of simulations to demonstrate the feasibility of

  2. Role of $\\sigma$ exchange in the $\\gamma p\\to \\phi p$ process and the scaling from the Reggeized model

    CERN Document Server

    Kong, Kook-Jin; Yu, Byung-Geel

    2016-01-01

    We investigate the role driven by the $\\sigma$ exchange in the photoproduction of $\\phi$ meson off a proton by using the Reggeized model. In this reaction, in addition to the Pomeron exchange which constitutes the background contribution extending to high energies, the $\\sigma$ Regge-pole exchange is found to give an interesting contribution to the reaction process near threshold. In particular, the $\\sigma$ exchange can reproduce reasonably well the bump structure at the forward angle in the differential cross section as well as the peaking behavior in the total cross section observed in the CLAS collaboration. We also show that our calculation reproduces well the recent data for the differential cross section from the LEPS and CLAS at low energies. Moreover, the scaled cross section $s^7d\\sigma /dt$ at the production angle $\\theta=90^{\\circ}$ obtained from the CLAS data is found to be consistent with the calculation using the canonical phase of the $\\sigma$ Regge-pole.

  3. 12位Sigma-Delta模数转换器的降采样滤波器设计%Decimation Filter Design for 12-bit Sigma-Delta ADC

    Institute of Scientific and Technical Information of China (English)

    黄博志

    2014-01-01

    The paper presents a signal-noise-ratio (SNR) based design method for the decimation filter of a 12-bit Sigma-Delta ADC (analog-to-digital converter). Sigma-Delta ADC consists of Sigma-Delta modulatorand decimation filter. Sigma-Delta modulatoris used for signal modulation and over-sampling quantization. Decimation filter is used for down-sampling the digital signal to its normal frequency and the quantization noise is filtered at the same time. Sigma-Delta ADC has higher sampling frequency, higher precision and less hardware cost than traditional ADC. There are two specifications for decimation filter:down-sampling rate and filter performance. This filter design method is driven by SNR and two solutions are applied. Simulation is done using MATLAB and the result is met the requirement of 12-bit Sigma-Delta ADC with SNR larger than 74 dB.%一种由SNR(信噪比)驱动的滤波器设计,用于12位Sigma-Delta模数转换器。Sigma-Delta模数转换器包括Sigma-Delta调制器和降采样滤波器两部分,首先用Sigma-Delta调制器对信号进行过采样率量化,然后通过降采样滤波器进行数字信号处理,将信号还原到原始采样率并去除量化噪声。和传统的模数转换器相比,Sigma-Delta模数转换器具有采样率高、精度高、面积小等优点。Sigma-Delta模数转换器的滤波器设计有降采样率和滤波性能两个指标要求,该设计方法由SNR驱动并采用了两种滤波器方案,设计结果在MATLAB里进行了仿真,其SNR大于74 dB,达到12位Sigma-Delta模数转换器的要求。

  4. Precision measurement of the {Sigma}{sup 0} hyperon mass

    Energy Technology Data Exchange (ETDEWEB)

    Wang, M.H.L.S.; Hartouni, E.P.; Kreisler, M.N. [and others

    1998-02-17

    The research that is described in this paper is part of a program to study strong interaction mechanisms in proton proton collisions. The program consists of two experiments: Brookhaven E766 in which we studied the reactions pp {yields} p+ all charged particles with 27.5 GeV/c incident protons and Fermilab E690 in which we studied the reactions pp {yields} p+ all charged particles with 800 GeV/c incident protons. In these experiments, we employed state-of-the-art data acquisition sys- tems and acquired large samples of data: at Brookhaven we amassed 300 million high multiplicity events and at Fermilab, 5.5 billion events. Our uncertainty in the {Sigma}{sup 0} mass is more than 7 times smaller than the best previous result and was based on 16 times the statistics. Likewise, the {Sigma}{sup 0} - {Lambda}{sup 0} mass difference is more than 14 times more accurate than the previous best result. Finally, we note that this measurement is the first direct measurement of the {Sigma}{sup 0} mass.

  5. Experimental and theoretical studies of rate coefficients for the reaction O(3P)+CH3OH at high temperatures.

    Science.gov (United States)

    Lu, Chih-Wei; Chou, Shen-Long; Lee, Yuan-Pern; Xu, Shucheng; Xu, Z F; Lin, M C

    2005-06-22

    Rate coefficients of the reaction O((3)P) + CH(3)OH in the temperature range of 835-1777 K were determined using a diaphragmless shock tube. O atoms were generated by photolysis of SO(2) with a KrF excimer laser at 248 nm or an ArF excimer laser at 193 nm; their concentrations were monitored via atomic resonance absorption excited by emission from a microwave-discharged mixture of O(2) and He. The rate coefficients determined for the temperature range can be represented by the Arrhenius equation, k(T) = (2.29 +/- 0.18) x 10(-10) exp[-(4210 +/- 100)T] cm(3) molecule(-1) s(-1); unless otherwise noted, all the listed errors represent one standard deviation in fitting. Combination of these and previous data at lower temperature shows a non-Arrhenius behavior described as the three-parameter equation, k(T) = (2.74 +/- 0.07) x 10(-18)T(2.25 +/- 0.13) exp[-(1500 +/- 90)T] cm(3)molecule(-1) s(-1). Theoretical calculations at the Becke-3-Lee-Yang-Parr (B3LYP)6-311 + G(3df,2p) level locate three transition states. Based on the energies computed with coupled clusters singles, doubles (triples) [CCSD(T)]/6-311 + G(3df,2p)B3LYP6-311 + G(3df,2p), the rate coefficients predicted with canonical variational transition state theory with small curvature tunneling corrections agree satisfactorily with the experimental observations. The branching ratios of two accessible reaction channels forming OH + CH(2)OH (1a) and OH + CH(3)O (1b) are predicted to vary strongly with temperature. At 300 K, reaction (1a) dominates, whereas reaction (1b) becomes more important than reaction (1a) above 1700 K.

  6. The triple alpha reaction rate and the 2$^+$ resonances in $^{12}$C

    CERN Document Server

    de Diego, R; Fedorov, D V; ~Jensen, A S

    2010-01-01

    The triple alpha rate is obtained from the three-body bound and continuum states computed in a large box. The results from this genuine full three-body calculation are compared with standard reference rates obtained by two sequential two-body processes. The fairly good agreement relies on two different assumptions about the lowest $2^+$ resonance energy. With the same $2^+$ energy the rates from the full three-body calculation are smaller than those of the standard reference. We discuss the rate dependence on the experimentally unknown $2^+$ energy. Substantial deviations from previous results appear for temperatures above $3$~GK.

  7. Sigma Receptors in Oncology : Therapeutic and Diagnostic Applications of Sigma Ligands

    NARCIS (Netherlands)

    van Waarde, Aren; Rybczynska, Anna A.; K. Ramakrishnan, Nisha; Ishiwata, Kiichi; Elsinga, Philip H.; Dierckx, Rudi A. J. O.

    2010-01-01

    Sigma receptors (subtypes sigma-1 and sigma-2) are a unique class of binding sites expressed throughout the mammalian body. The endogenous ligand for these sites has not been identified, but steroid hormones (particularly progesterone), sphingolipid-derived amines and N,N-dimethyltryptamine can bind

  8. Sigma Receptors in Oncology : Therapeutic and Diagnostic Applications of Sigma Ligands

    NARCIS (Netherlands)

    van Waarde, Aren; Rybczynska, Anna A.; K. Ramakrishnan, Nisha; Ishiwata, Kiichi; Elsinga, Philip H.; Dierckx, Rudi A. J. O.

    2010-01-01

    Sigma receptors (subtypes sigma-1 and sigma-2) are a unique class of binding sites expressed throughout the mammalian body. The endogenous ligand for these sites has not been identified, but steroid hormones (particularly progesterone), sphingolipid-derived amines and N,N-dimethyltryptamine can bind

  9. Low-Mass (M<1.2 Gev/c^2) Sigma0 - Meson Produced in the System Pi+Pi- from the Reaction np --> np Pi+Pi- at Pn = 5.20 Gev/c^2

    OpenAIRE

    Troyan, Yu. A.; Beljaev, A. V.; Troyan, A. Yu.; Plekhanov, E. B.; Jerusalimov, A. P.; Arakelian, S. G.

    2006-01-01

    The production and properties of the resonances in the system of Pi+Pi- were studied in the reaction np --> npPi+Pi- at the momentum of incident neutrons Pn=(5.20 +/- 0.12)GeV/c. In this work in comparison with previous ones we made more hard selection of events taking into account track measurement precise. In the distribution of the Pi+Pi- combinations effective masses we have found 8 peculiarities. All the observable peculiarities have spins equal to zero. There were no corresponding picks...

  10. Measurement and analysis of the 238U(n, 2n) reaction rate in depleted uranium/polyethylene shells

    Institute of Scientific and Technical Information of China (English)

    YAN Xiao-Song; LIU Rong; LU Xin-Xin; JIANG Li; WEN Zhong-Wei; HAN Zi-Jie

    2012-01-01

    In order to check the conceptual design of the subcritical blanket in a fnsion-fission hybrid reactor,a depleted uranium/polyethylene simulation device with alternate shells has been established.The measurement of the 238U(n,2n) reaction rate was carried out using an activation technique,by measuring the 208 keV γ rays emitted from 237 U.The self-absorption of depleted uranium foils with different thicknesses was experimentally corrected.The distribution of the 238U(n,2n) reaction rate at 90° to the incident D+ beam was obtained,with uncertainty between 5.3% and 6.0%.The experiment was analyzed using MCNP5 code with the ENDF/BVI library,and the calculated results are all about 5% higher than the measured results.

  11. Geometric Scaling for a Detonation Wave Governed by a Pressure-Dependent Reaction Rate and Yielding Confinement

    CERN Document Server

    Jianling, Li; Higgins, Andrew J

    2014-01-01

    The propagation of detonation waves in reactive media bounded by an inert, compressible layer is examined via computational simulations in two different geometries, axisymmetric cylinders and two dimensional, planar slabs. For simplicity, an ideal gas equation of state is used with a pressure-dependent reaction rate that results in a stable detonation wave structure. The detonation is initiated as an ideal Chapman-Jouguet (CJ) detonation with a one-dimensional structure, and then allowed to propagate into a finite diameter or thickness layer of explosive surrounded by an inert layer. The yielding confinement of the inert layer results in the detonation wave decaying to a sub-CJ steady state velocity or failing entirely. Simulations are performed with different values of the reaction rate pressure exponent (n = 2 and 3) and different impedance confinement (greater than, less than, and equal to the confinement of the explosive). The velocity decrement and critical dimension (critical diameter or thickness) are ...

  12. NACRE II: An Update of the NACRE Compilation of Atarget<16 Charged-Particle Thermonuclear Reaction Rates for Astrophysics

    Science.gov (United States)

    Xu, Y.; Takahashi, K.; Goriely, S.; Arnould, M.

    2011-10-01

    We report on the status of a new evaluation of the rates in astrophysical conditions of 19 capture and 15 transfer reactions on stable targets with mass numbers A<16, referred as NACRE-II. This work is meant to supersede the NACRE compilation. Post-NACRE experimental data are taken into account. Extrapolations of the astrophysical S-factor to largely sub-Coulomb energies are based on the use of the potential model and of the distorted wave Born approximation for capture and transfer reactions, respectively. Adopted rates and their lower and upper limits are provided. Here, we illustrate the general procedure followed in the NACRE-II construction with two examples.

  13. Dramatic effects of halogen substitution and solvent on the rates and mechanisms of nucleophilic substitution reactions of aziridines.

    Science.gov (United States)

    Banks, Harold D

    2008-04-04

    In a previous study we reported that fluorine substitution at the carbon positions of aziridine results in profound enhancements of the rate of reaction with ammonia, a typical nucleophile, in the gas phase. In this study the investigation is extended to include chloro- and bromoaziridines. Because syntheses are largely performed in the condensed phase, the present computational investigation [(MP2(Full)/6-311++G(d,p)//MP2(Full)/6-31+G(d) level] was conducted with three typical solvents that cover a wide range of polarity: THF, CH3CN, and H2O. Nucleophiles can react with haloaziridines 1 by displacing a substituted amide ion by means of an SN2 mechanism (pathway a), producing 1,2-diaminohaloethanes (from the initially formed dipolar species 2). Alternatively, a rearrangement mechanism involving rate-determining departure of a halide ion (pathway b) to form an imidoyl halide, 3, is possible. Transition-state theory was used to compute relative reaction rates of these mechanistic possibilities and to assess the role of the halogen substituents and the reaction solvent. Gas-phase results provided the basis of mechanistic insights that were more apparent in the absence of intermolecular interactions. Fluoroaziridines were found to react at accelerated rates relative to aziridine exclusively by means of the a Menshutkin-type mechanism (SN2) in each solvent tested, while the reactions of the chloro- and bromoaziridines could be directed toward 2 in the highly nonpolar solvent, cyclohexane, or toward 3 in the more polar solvents. An assessment is made of the feasibility of using this chemistry of the haloazirdines in the synthetic laboratory.

  14. Enzymatic hydrolysis of nylons: quantification of the reaction rate of nylon hydrolase for thin-layered nylons.

    Science.gov (United States)

    Nagai, Keisuke; Iida, Kazuki; Shimizu, Kimiaki; Kinugasa, Ryo; Izumi, Motoki; Kato, Dai-Ichiro; Takeo, Masahiro; Mochiji, Kozo; Negoro, Seiji

    2014-10-01

    Nylon hydrolase degrades various aliphatic nylons, including nylon-6 and nylon-66. We synthesized a nylon-66 copolymer (M w = 22,900, M n = 7,400), in which a part of an adipoyl unit (32 % molar ratio) of nylon-66 was replaced with a succinyl unit by interfacial polymerization. To quantify the reaction rate of the enzymatic hydrolysis of nylons at the surface of solid polymers, we prepared a thin layer of nylons on the bottom surface of each well in a polystyrene-based micro-assay plate. The thickness of the nylon layer was monitored by imaging analysis of the photographic data. More than 99 % of the copolymer with thicknesses of 260 nm (approximately 600 layers of polymer strands) were converted to water-soluble oligomers by nylon hydrolase (3 mg enzyme ml(-1)) at 30 °C within 60 h. These results were further confirmed by TLC analysis of the reaction products and by assay of liberated amino groups in the soluble fractions. The degradation rate of the thin-layered nylon-6 was similarly analyzed. We demonstrate that this assay enables a quantitative evaluation of the reaction rate of hydrolysis at the interface between the solid and aqueous phases and a quantitative comparison of the degradability for various polyamides.

  15. The H2 + CO ↔ H2CO Reaction: Rate Constants and Relevance to Hot and Dense Astrophysical Media

    Science.gov (United States)

    Vichietti, R. M.; Spada, R. F. K.; da Silva, A. B. F.; Machado, F. B. C.; Haiduke, R. L. A.

    2016-07-01

    A theoretical thermochemical and kinetic investigation of the thermal H2 + CO ↔ H2CO reaction was performed for a temperature range from 200 to 4000 K. Geometries and vibrational frequencies of reactants, product, and transition state (TS) were obtained at CCSD/cc-pVxZ (x = T and Q) levels and scaling factors were employed to consider anharmonicity effects on vibrational frequencies, zero-point energies, and thermal corrections provided by these methodologies. Enthalpies Gibbs energies, and rate constants for this reaction were determined by including a complete basis set extrapolation correction for the electronic properties calculated at CCSD(T)/cc-pVyZ (y = Q and 5) levels. Our study indicates that enthalpy changes for this reaction are highly dependent on temperature. Moreover, forward and reverse (high-pressure limit) rate constants were obtained from variational TS theory with quantum tunneling corrections. Thus, modified Arrhenius’ equations were fitted by means of the best forward and reverse rate constant values, which provide very reliable estimates for these quantities within the temperature range between 700 and 4000 K. To our knowledge, this is the first kinetic study done for the forward H2 + CO \\to H2CO process in a wide temperature range. Finally, these results can be used to explain the formaldehyde abundance in hot and dense interstellar media, possibly providing data about the physical conditions associated with H2CO masers close to massive star-forming regions.

  16. High-level theoretical study of the reaction between hydroxyl and ammonia: Accurate rate constants from 200 to 2500 K

    Science.gov (United States)

    Nguyen, Thanh Lam; Stanton, John F.

    2017-10-01

    Hydrogen abstraction from NH3 by OH to produce H2O and NH2—an important reaction in combustion of NH3 fuel—was studied with a theoretical approach that combines high level quantum chemistry and advanced chemical kinetics methods. Thermal rate constants calculated from first principles agree well (within 5%-20%) with available experimental data over a temperature range that extends from 200 to 2500 K. Quantum mechanical tunneling effects were found to be important; they lead to a decided curvature and non-Arrhenius behavior for the rate constant.

  17. Creep properties of aged duplex stainless steels containing [sigma] phase

    Energy Technology Data Exchange (ETDEWEB)

    Shek, C.H.; Wong, K.W.; Lai, J.K.L. (City Univ. of Hong Kong, Kowloon (Hong Kong). Dept. of Physics and Materials Science); Li, D.J. (Department of Materials Engineering, Dalian University of Technology, Dalian 116 024 (China))

    1999-06-30

    The creep properties of a cast of duplex stainless steel were characterized at temperatures 550-800 C under different loading conditions. For fully aged specimens containing [sigma], the stress exponent for creep was close to 3 and the activation energy was 281[+-]9 kJ mol[sup -1]. The results suggested that the creep mechanism in the samples in this investigation was controlled by dislocation movement. Extensive [sigma]/[gamma][sub 2] interfaces introduced during ageing improved the creep resistance of the material and related to a reduction of the creep rate in Stage II creep and an increase in the creep rupture strength of the material. Microstructural studies revealed the dependence of the creep properties on the morphology of the microstructure. Among the aged specimens containing [sigma], the creep strength and ductility were higher for specimens having larger [gamma] grain thickness measured on the longitudinal plane. This characteristic was related to the crack propagation and interconnection of voids within [gamma] matrix during tertiary creep. With appropriate solution treatment, the creep strength of [sigma]-containing steels can be improved to a value exceeding that of type 316 steels. (orig.) 14 refs.

  18. Application of Six Sigma methodology to a cataract surgery unit.

    Science.gov (United States)

    Taner, Mehmet Tolga

    2013-01-01

    The article's aim is to focus on the application of Six Sigma to minimise intraoperative and post-operative complications rates in a Turkish public hospital cataract surgery unit. Implementing define-measure-analyse-improve and control (DMAIC) involves process mapping, fishbone diagrams and rigorous data-collection. Failure mode and effect analysis (FMEA), pareto diagrams, control charts and process capability analysis are applied to redress cataract surgery failure root causes. Inefficient skills of assistant surgeons and technicians, low quality of IOLs used, wrong IOL placement, unsystematic sterilisation of surgery rooms and devices, and the unprioritising network system are found to be the critical drivers of intraoperative-operative and post-operative complications. Sigma level was increased from 2.60 to 3.75 subsequent to extensive training of assistant surgeons, ophthalmologists and technicians, better quality IOLs, systematic sterilisation and air-filtering, and the implementation of a more sophisticated network system. This article shows that Six Sigma measurement and process improvement can become the impetus for cataract unit staff to rethink their process and reduce malpractices. Measuring, recording and reporting data regularly helps them to continuously monitor their overall process and deliver safer treatments. This is the first Six Sigma ophthalmology study in Turkey.

  19. Geometry of Membrane Sigma Models

    CERN Document Server

    Vysoky, Jan

    2015-01-01

    String theory still remains one of the promising candidates for a unification of the theory of gravity and quantum field theory. One of its essential parts is relativistic description of moving multi-dimensional objects called membranes (or p-branes) in a curved spacetime. On the classical field theory level, they are described by an action functional extremalising the volume of a manifold swept by a propagating membrane. This and related field theories are collectively called membrane sigma models. Differential geometry is an important mathematical tool in the study of string theory. It turns out that string and membrane backgrounds can be conveniently described using objects defined on a direct sum of tangent and cotangent bundles of the spacetime manifold. Mathematical field studying such object is called generalized geometry. Its integral part is the theory of Leibniz algebroids, vector bundles with a Leibniz algebra bracket on its module of smooth sections. Special cases of Leibniz algebroids are better ...

  20. TA-55 and Sigma Overview

    Energy Technology Data Exchange (ETDEWEB)

    Spearing, Dane Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Safeguards Science and Technology Group (NEN-1)

    2016-11-29

    These are slides from a facility overview presentation for visiting agencies to Los Alamos National Laboratory (LANL). The TA-55 Plutonium Facility (PF-4) is discussed in detail. PF-4 is a unique resource for US plutonium programs. The basic design is flexible and has adapted to changing national needs. It is a robust facility with strong safety and security implementation. It supports a variety of national programs. It will continue for many years into the future. Sigma is then discussed in detail, which handles everything from hydrogen to uranium. It has been in long term service to the Nation (nearly 60 years). It has a flexible authorization basis to handle almost the entire periodic table. It has a wide breadth of prototyping and characterization capabilities. It has integrated program and line management.