WorldWideScience

Sample records for total rate constants

  1. Arrhenius Rate: constant volume burn

    Energy Technology Data Exchange (ETDEWEB)

    Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-12-06

    A constant volume burn occurs for an idealized initial state in which a large volume of reactants at rest is suddenly raised to a high temperature and begins to burn. Due to the uniform spatial state, there is no fluid motion and no heat conduction. This reduces the time evolu tion to an ODE for the reaction progress variable. With an Arrhenius reaction rate, two characteristics of thermal ignition are illustrated: induction time and thermal runaway. The Frank-Kamenetskii approximation then leads to a simple expression for the adiabatic induction time. For a first order reaction, the analytic solution is derived and used to illustrate the effect of varying the activation temperature; in particular, on the induction time. In general, the ODE can be solved numerically. This is used to illustrate the effect of varying the reaction order. We note that for a first order reaction, the time evolution of the reaction progress variable has an exponential tail. In contrast, for a reaction order less than one, the reaction completes in a nite time. The reaction order also affects the induction time.

  2. Direct measurements of the total rate constant of the reaction NCN + H and implications for the product branching ratio and the enthalpy of formation of NCN.

    Science.gov (United States)

    Fassheber, Nancy; Dammeier, Johannes; Friedrichs, Gernot

    2014-06-21

    The overall rate constant of the reaction (2), NCN + H, which plays a key role in prompt-NO formation in flames, has been directly measured at temperatures 962 K rate constants are best represented by the combination of two Arrhenius expressions, k2/(cm(3) mol(-1) s(-1)) = 3.49 × 10(14) exp(-33.3 kJ mol(-1)/RT) + 1.07 × 10(13) exp(+10.0 kJ mol(-1)/RT), with a small uncertainty of ±20% at T = 1600 K and ±30% at the upper and lower experimental temperature limits.The two Arrhenius terms basically can be attributed to the contributions of reaction channel (2a) yielding CH + N2 and channel (2b) yielding HCN + N as the products. A more refined analysis taking into account experimental and theoretical literature data provided a consistent rate constant set for k2a, its reverse reaction k1a (CH + N2 → NCN + H), k2b as well as a value for the controversial enthalpy of formation of NCN, ΔfH = 450 kJ mol(-1). The analysis verifies the expected strong temperature dependence of the branching fraction ϕ = k2b/k2 with reaction channel (2b) dominating at the experimental high-temperature limit. In contrast, reaction (2a) dominates at the low-temperature limit with a possible minor contribution of the HNCN forming recombination channel (2d) at T < 1150 K.

  3. Dose rate constants for new dose quantities

    International Nuclear Information System (INIS)

    Tschurlovits, M.; Daverda, G.; Leitner, A.

    1992-01-01

    Conceptual changes and new quantities made is necessary to reassess dose rate quantities. Calculations of the dose rate constant were done for air kerma, ambient dose equivalent and directional dose equivalent. The number of radionuclides is more than 200. The threshold energy is selected as 20 keV for the dose equivalent constants. The dose rate constant for the photon equivalent dose as used mainly in German speaking countries as a temporary quantity is also included. (Author)

  4. Elongational flow of polymer melts at constant strain rate, constant stress and constant force

    Science.gov (United States)

    Wagner, Manfred H.; Rolón-Garrido, Víctor H.

    2013-04-01

    Characterization of polymer melts in elongational flow is typically performed at constant elongational rate or rarely at constant tensile stress conditions. One of the disadvantages of these deformation modes is that they are hampered by the onset of "necking" instabilities according to the Considère criterion. Experiments at constant tensile force have been performed even more rarely, in spite of the fact that this deformation mode is free from necking instabilities and is of considerable industrial relevance as it is the correct analogue of steady fiber spinning. It is the objective of the present contribution to present for the first time a full experimental characterization of a long-chain branched polyethylene melt in elongational flow. Experiments were performed at constant elongation rate, constant tensile stress and constant tensile force by use of a Sentmanat Extensional Rheometer (SER) in combination with an Anton Paar MCR301 rotational rheometer. The accessible experimental window and experimental limitations are discussed. The experimental data are modelled by using the Wagner I model. Predictions of the steady-start elongational viscosity in constant strain rate and creep experiments are found to be identical, albeit only by extrapolation of the experimental data to Hencky strains of the order of 6. For constant stress experiments, a minimum in the strain rate and a corresponding maximum in the elongational viscosity is found at a Hencky strain of the order of 3, which, although larger than the steady-state value, follows roughly the general trend of the steady-state elongational viscosity. The constitutive analysis also reveals that constant tensile force experiments indicate a larger strain hardening potential than seen in constant elongation rate or constant tensile stress experiments. This may be indicative of the effect of necking under constant elongation rate or constant tensile stress conditions according to the Considère criterion.

  5. Inflation with a constant rate of roll

    International Nuclear Information System (INIS)

    Motohashi, Hayato; Starobinsky, Alexei A.; Yokoyama, Jun'ichi

    2015-01-01

    We consider an inflationary scenario where the rate of inflaton roll defined by ·· φ/H φ-dot remains constant. The rate of roll is small for slow-roll inflation, while a generic rate of roll leads to the interesting case of 'constant-roll' inflation. We find a general exact solution for the inflaton potential required for such inflaton behaviour. In this model, due to non-slow evolution of background, the would-be decaying mode of linear scalar (curvature) perturbations may not be neglected. It can even grow for some values of the model parameter, while the other mode always remains constant. However, this always occurs for unstable solutions which are not attractors for the given potential. The most interesting particular cases of constant-roll inflation remaining viable with the most recent observational data are quadratic hilltop inflation (with cutoff) and natural inflation (with an additional negative cosmological constant). In these cases even-order slow-roll parameters approach non-negligible constants while the odd ones are asymptotically vanishing in the quasi-de Sitter regime

  6. Dissociative electron attachment to ozone: rate constant

    International Nuclear Information System (INIS)

    Skalny, J.D.; Cicman, P.; Maerk, T.D.

    2002-01-01

    The rate constant for dissociative electron attachment to ozone has been derived over the energy range of 0-10 eV by using previously measured cross section data revisited here in regards to discrimination effect occurring during the extraction of ions. The obtained data for both possible channels exhibit the maximum at mean electron energies close to 1 eV. (author)

  7. On determining dose rate constants spectroscopically

    International Nuclear Information System (INIS)

    Rodriguez, M.; Rogers, D. W. O.

    2013-01-01

    Purpose: To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of 125 I and 103 Pd seeds [Z. Chen and R. Nath, Phys. Med. Biol. 55, 6089–6104 (2010)] including the accuracy of using a line or dual-point source approximation as done in their method, and the accuracy of ignoring the effects of the scattered photons in the spectra. Additionally, the authors investigate the accuracy of the literature's many different spectra for bare, i.e., unencapsulated 125 I and 103 Pd sources. Methods: Spectra generated by 14 125 I and 6 103 Pd seeds were calculated in vacuo at 10 cm from the source in a 2.7 × 2.7 × 0.05 cm 3 voxel using the EGSnrc BrachyDose Monte Carlo code. Calculated spectra used the initial photon spectra recommended by AAPM's TG-43U1 and NCRP (National Council of Radiation Protection and Measurements) Report 58 for the 125 I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for 103 Pd seeds. The emitted spectra were treated as coming from a line or dual-point source in a Monte Carlo simulation to calculate the dose rate constant. The TG-43U1 definition of the dose rate constant was used. These calculations were performed using the full spectrum including scattered photons or using only the main peaks in the spectrum as done experimentally. Statistical uncertainties on the air kerma/history and the dose rate/history were ⩽0.2%. The dose rate constants were also calculated using Monte Carlo simulations of the full seed model. Results: The ratio of the intensity of the 31 keV line relative to that of the main peak in 125 I spectra is, on average, 6.8% higher when calculated with the NCRP Report 58 initial spectrum vs that calculated with TG-43U1 initial spectrum. The 103 Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak when calculated with the TG-43U1 rather than the NNDC(2000) initial spectrum. The measured values from three different

  8. Constant displacement rate testing at elevated temperatures

    International Nuclear Information System (INIS)

    Pepe, J.J.; Gonyea, D.C.

    1989-01-01

    A short time test has been developed which is capable of determining the long time notch sensitivity tendencies of CrMoV rotor forging materials. This test is based on Constant Displacement Rate (CDR) testing of a specific notch bar specimen at 1200 0 F at 2 mils/in/hour displacement rate. These data were correlated to conventional smooth and notch bar rupture behavior for a series of CrMoV materials with varying long time ductility tendencies. The purpose of this paper is to describe the details of this new test procedure and some of the relevant mechanics of material information generated during its development

  9. VMATc: VMAT with constant gantry speed and dose rate

    International Nuclear Information System (INIS)

    Peng, Fei; Romeijn, H Edwin; Epelman, Marina A; Jiang, Steve B

    2015-01-01

    This article considers the treatment plan optimization problem for Volumetric Modulated Arc Therapy (VMAT) with constant gantry speed and dose rate (VMATc). In particular, we consider the simultaneous optimization of multi-leaf collimator leaf positions and a constant gantry speed and dose rate. We propose a heuristic framework for (approximately) solving this optimization problem that is based on hierarchical decomposition. Specifically, an iterative algorithm is used to heuristically optimize dose rate and gantry speed selection, where at every iteration a leaf position optimization subproblem is solved, also heuristically, to find a high-quality plan corresponding to a given dose rate and gantry speed. We apply our framework to clinical patient cases, and compare the resulting VMATc plans to idealized IMRT, as well as full VMAT plans. Our results suggest that VMATc is capable of producing treatment plans of comparable quality to VMAT, albeit at the expense of long computation time and generally higher total monitor units. (paper)

  10. 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.

  11. Biased Brownian dynamics for rate constant calculation.

    OpenAIRE

    Zou, G; Skeel, R D; Subramaniam, S

    2000-01-01

    An enhanced sampling method-biased Brownian dynamics-is developed for the calculation of diffusion-limited biomolecular association reaction rates with high energy or entropy barriers. Biased Brownian dynamics introduces a biasing force in addition to the electrostatic force between the reactants, and it associates a probability weight with each trajectory. A simulation loses weight when movement is along the biasing force and gains weight when movement is against the biasing force. The sampl...

  12. Recent developments in semiclassical mechanics: eigenvalues and reaction rate constants

    International Nuclear Information System (INIS)

    Miller, W.H.

    1976-04-01

    A semiclassical treatment of eigenvalues for a multidimensional non-separable potential function and of the rate constant for a chemical reaction with an activation barrier is presented. Both phenomena are seen to be described by essentially the same semiclassical formalism, which is based on a construction of the total Hamiltonian in terms of the complete set of ''good'' action variables (or adiabatic invariants) associated with the minimum in the potential energy surface for the eigenvalue case, or the saddle point in the potential energy surface for the case of chemical reaction

  13. ADSORPTION RATE CONSTANTS OF EOSIN IN HUMIN

    OpenAIRE

    anshar, andi muhammad

    2015-01-01

    Eosin is one of the dyes commonly used in the industry and has the potential to cause pollution of the water environment. The Eosin pollution treatment methods used in this study was the adsorption method using humin fraction obtained from the peat land comes from Kalimantan. From the research data showed that the adsorption of eosin in humin result of washing with HCl / HF optimum at pH 4 and a contact time of 60 minutes with the adsorption-order rate was 8,4 x 10-3 min-1

  14. Le budget total du CERN restera plus ou moins constant

    CERN Document Server

    Van der Boon, J E

    2002-01-01

    The Director of Administration at CERN has written to the paper following an article titled "Licenciements chez les sous-traitants du CERN" : dismissals amongst CERN sub-contractors. As the CERN budget will remain constant and a greater part will be devoted to building the LHC, changes will be made to staffing balances (0.5 page)

  15. Determination of Biological Oxygen Demand Rate Constant and ...

    African Journals Online (AJOL)

    Determination of Biological Oxygen Demand Rate Constant and Ultimate Biological Oxygen Demand for Liquid Waste Generated from Student Cafeteria at Jimma University: A Tool for Development of Scientific Criteria to Protect Aquatic Health in the Region.

  16. Rate constants for the reaction of OH radicals with 1-chloroalkanes at 295 K

    DEFF Research Database (Denmark)

    Markert, F.; Nielsen, O.J.

    1992-01-01

    The rate constants for the reaction of OH radicals with a series of 1-chloroalkanes were measured at 295 K and at a total pressure of 1 atm. The rate constants were obtained by using the absolute technique of pulse radiolysis combined with kinetic UV-spectroscopy. The results are discussed in terms...

  17. Empirical correlation for prediction of the elutriation rate constant

    Directory of Open Access Journals (Sweden)

    Stojkovski Valentino

    2003-01-01

    Full Text Available In vessels containing fluidized solids, the gas leaving carries some suspended particles. This flux of solids is called entrainment, E or carryover and the bulk density of solids on this leaving gas stream is called the holdup. For design we need to know the rate of this entrainment and the size distribution of these entrained particles Rim in relation to the size distribution in the bed, Rib, as well as the variation of both these quantities with gas and solids properties, gas flow rate, bed geometry and location of the leaving gas stream. Steady-state elutriation experiments have been done in a fluidized bed 0,2 m diameter by 2,94 m high freeboard with superficial gas velocities up to 1 m/s using solids ranging in mean size from 0,15 to 0,58 mm and with particle density 2660 kg/m3. When the fine and coarse particles were mixed, the total entrainment flux above the freeboard was increased. None of the published correlations for estimating the elutriation rate constant were useful. A new simple equation, which is developed on the base of experimental results and theory of dimensional analyses, is presented.

  18. Rate constant for reaction of hydroxyl radicals with bicarbonate ions

    International Nuclear Information System (INIS)

    Buxton, G.V.; Elliot, A.J.

    1986-01-01

    The rate constant for reaction of hydroxyl radicals with the bicarbonate ion has been determined to be 8.5 x 10 6 dm 3 mol -1 s -1 . This value was calculated from: the measured rate of formation of the CO 3 - radical in pulsed electron irradiation of bicarbonate solutions over the pH range 7.0 to 9.4; the pK for the equilibrium HCO 3 - = CO 3 2- + H + ; and the rate constant for hydroxyl radicals reacting with the carbonate ion. (author)

  19. Rate constant for reaction of atomic hydrogen with germane

    Science.gov (United States)

    Nava, David F.; Payne, Walter A.; Marston, George; Stief, Louis J.

    1990-01-01

    Due to the interest in the chemistry of germane in the atmospheres of Jupiter and Saturn, and because previously reported kinetic reaction rate studies at 298 K gave results differing by a factor of 200, laboratory measurements were performed to determine the reaction rate constant for H + GeH4. Results of the study at 298 K, obtained via the direct technique of flash photolysis-resonance fluorescence, yield the reaction rate constant, k = (4.08 + or - 0.22) x 10(exp -12) cu cm/s.

  20. Sensitivity of molecular vibrational dynamics to energy exchange rate constants

    International Nuclear Information System (INIS)

    Billing, G D; Coletti, C; Kurnosov, A K; Napartovich, A P

    2003-01-01

    The sensitivity of molecular vibrational population dynamics, governing the CO laser operated in fundamental and overtone transitions, to vibration-to-vibration rate constants is investigated. With this aim, three rate constant sets have been used, differing in their completeness (i.e. accounting for single-quantum exchange only, or for multi-quantum exchange with a limited number of rate constants obtained by semiclassical calculations, and, finally, with an exhaustive set of rate constants including asymmetric exchange processes, as well) and in the employed interaction potential. The most complete set among these three is introduced in this paper. An existing earlier kinetic model was updated to include the latter new data. Comparison of data produced by kinetic modelling with the above mentioned sets of rate constants shows that the vibrational distribution function, and, in particular, the CO overtone laser characteristics, are very sensitive to the choice of the model. The most complete model predicts slower evolution of the vibrational distribution, in qualitative agreement with experiments

  1. Accurate and approximate thermal rate constants for polyatomic chemical reactions

    International Nuclear Information System (INIS)

    Nyman, Gunnar

    2007-01-01

    In favourable cases it is possible to calculate thermal rate constants for polyatomic reactions to high accuracy from first principles. Here, we discuss the use of flux correlation functions combined with the multi-configurational time-dependent Hartree (MCTDH) approach to efficiently calculate cumulative reaction probabilities and thermal rate constants for polyatomic chemical reactions. Three isotopic variants of the H 2 + CH 3 → CH 4 + H reaction are used to illustrate the theory. There is good agreement with experimental results although the experimental rates generally are larger than the calculated ones, which are believed to be at least as accurate as the experimental rates. Approximations allowing evaluation of the thermal rate constant above 400 K are treated. It is also noted that for the treated reactions, transition state theory (TST) gives accurate rate constants above 500 K. TST theory also gives accurate results for kinetic isotope effects in cases where the mass of the transfered atom is unchanged. Due to neglect of tunnelling, TST however fails below 400 K if the mass of the transferred atom changes between the isotopic reactions

  2. Impact of Constant Rate Factor on Objective Video Quality Assessment

    Directory of Open Access Journals (Sweden)

    Juraj Bienik

    2017-01-01

    Full Text Available This paper deals with the impact of constant rate factor value on the objective video quality assessment using PSNR and SSIM metrics. Compression efficiency of H.264 and H.265 codecs defined by different Constant rate factor (CRF values was tested. The assessment was done for eight types of video sequences depending on content for High Definition (HD, Full HD (FHD and Ultra HD (UHD resolution. Finally, performance of both mentioned codecs with emphasis on compression ratio and efficiency of coding was compared.

  3. a comparative study of the drying rate constant, drying efficiency

    African Journals Online (AJOL)

    The drying rate constants for the solar dryer and open- air sun dried bitter leaf were 0.8 and ... of cost benefit but the poorest when other considerations ... J. I. Eze, National Centre for Energy Research and Development (NCERD), University of ...

  4. High-temperature rate constant measurements for OH+xylenes

    KAUST Repository

    Elwardani, Ahmed Elsaid; Badra, Jihad; Farooq, Aamir

    2015-01-01

    The overall rate constants for the reactions of hydroxyl (OH) radicals with o-xylene (k 1), m-xylene (k 2), and p-xylene (k 3) were measured behind reflected shock waves over 890-1406K at pressures of 1.3-1.8atm using OH laser absorption near 306

  5. Semiclassical Calculation of Reaction Rate Constants for Homolytical Dissociations

    Science.gov (United States)

    Cardelino, Beatriz H.

    2002-01-01

    There is growing interest in extending organometallic chemical vapor deposition (OMCVD) to III-V materials that exhibit large thermal decomposition at their optimum growth temperature, such as indium nitride. The group III nitrides are candidate materials for light-emitting diodes and semiconductor lasers operating into the blue and ultraviolet regions. To overcome decomposition of the deposited compound, the reaction must be conducted at high pressures, which causes problems of uniformity. Microgravity may provide the venue for maintaining conditions of laminar flow under high pressure. Since the selection of optimized parameters becomes crucial when performing experiments in microgravity, efforts are presently geared to the development of computational OMCVD models that will couple the reactor fluid dynamics with its chemical kinetics. In the present study, we developed a method to calculate reaction rate constants for the homolytic dissociation of III-V compounds for modeling OMCVD. The method is validated by comparing calculations with experimental reaction rate constants.

  6. Critical Review of rate constants for reacitons of hydrated electrons

    International Nuclear Information System (INIS)

    Buxton, G.V.; Greenstock, C.L.; Phillips Helman, W.; Ross, A.B.

    1988-01-01

    Kinetic data for the radicals Hx and xOH in aqueous solution,and the corresponding radical anions, xO - and e/sub =/, have been critically reviewed. Reactions of the radicals in aqueous solution have been studied by pulse radiolysis, flash photolysis and other methods. Rate constants for over 3500 reaction are tabulated, including reaction with molecules, ions and other radicals derived from inorganic and organic solutes

  7. High-temperature rate constant measurements for OH+xylenes

    KAUST Repository

    Elwardani, Ahmed Elsaid

    2015-06-01

    The overall rate constants for the reactions of hydroxyl (OH) radicals with o-xylene (k 1), m-xylene (k 2), and p-xylene (k 3) were measured behind reflected shock waves over 890-1406K at pressures of 1.3-1.8atm using OH laser absorption near 306.7nm. Measurements were performed under pseudo-first-order conditions. The measured rate constants, inferred using a mechanism-fitting approach, can be expressed in Arrhenius form as:k1=2.93×1013exp(-1350.3/T)cm3mol-1s-1(890-1406K)k2=3.49×1013exp(-1449.3/T)cm3mol-1s-1(906-1391K)k3=3.5×1013exp(-1407.5/T)cm3mol-1s-1(908-1383K)This paper presents, to our knowledge, first high-temperature measurements of the rate constants of the reactions of xylene isomers with OH radicals. Low-temperature rate-constant measurements by Nicovich et al. (1981) were combined with the measurements in this study to obtain the following Arrhenius expressions, which are applicable over a wider temperature range:k1=2.64×1013exp(-1181.5/T)cm3mol-1s-1(508-1406K)k2=3.05×109exp(-400/T)cm3mol-1s-1(508-1391K)k3=3.0×109exp(-440/T)cm3mol-1s-1(526-1383K) © 2015 The Combustion Institute.

  8. Uniaxial tension test on Rubber at constant true strain rate

    Directory of Open Access Journals (Sweden)

    Sourne H.L.

    2012-08-01

    Full Text Available Elastomers are widely used for damping parts in different industrial contexts because of their remarkable dissipation properties. Indeed, they can undergo severe mechanical loading conditions, i.e., high strain rates and large strains. Nevertheless, the mechanical response of these materials can vary from purely rubber-like to glassy depending on the strain rate undergone. Classically, uniaxial tension tests are made in order to find a relation between the stress and the strain in the material at various strain rates. However, even if the strain rate is searched to be constant, it is the nominal strain rate that is considered. Here we develop a test at constant true strain rate, i.e. the strain rate that is experienced by the material. In order to do such a test, the displacement imposed by the machine is an exponential function of time. This test has been performed with a high speed hydraulic machine for strain rates between 0.01/s and 100/s. A specific specimen has been designed, yielding a uniform strain field (and so a uniform stress field. Furthermore, an instrumented aluminum bar has been used to take into account dynamic effects in the measurement of the applied force. A high speed camera enables the determination of strain in the sample using point tracking technique. Using this method, the stress-strain curve of a rubber-like material during a loading-unloading cycle has been determined, up to a stretch ratio λ = 2.5. The influence of the true strain rate both on stiffness and on dissipation of the material is then discussed.

  9. Divided Saddle Theory: A New Idea for Rate Constant Calculation.

    Science.gov (United States)

    Daru, János; Stirling, András

    2014-03-11

    We present a theory of rare events and derive an algorithm to obtain rates from postprocessing the numerical data of a free energy calculation and the corresponding committor analysis. The formalism is based on the division of the saddle region of the free energy profile of the rare event into two adjacent segments called saddle domains. The method is built on sampling the dynamics within these regions: auxiliary rate constants are defined for the saddle domains and the absolute forward and backward rates are obtained by proper reweighting. We call our approach divided saddle theory (DST). An important advantage of our approach is that it requires only standard computational techniques which are available in most molecular dynamics codes. We demonstrate the potential of DST numerically on two examples: rearrangement of alanine-dipeptide (CH3CO-Ala-NHCH3) conformers and the intramolecular Cope reaction of the fluxional barbaralane molecule.

  10. Dose rate constant and energy spectrum of interstitial brachytherapy sources

    International Nuclear Information System (INIS)

    Chen Zhe; Nath, Ravinder

    2001-01-01

    In the past two years, several new manufacturers have begun to market low-energy interstitial brachytherapy seeds containing 125 I and 103 Pd. Parallel to this development, the National Institute of Standards and Technology (NIST) has implemented a modification to the air-kerma strength (S K ) standard for 125 I seeds and has also established an S K standard for 103 Pd seeds. These events have generated a considerable number of investigations on the determination of the dose rate constants (Λ) of interstitial brachytherapy seeds. The aim of this work is to study the general properties underlying the determination of Λ and to develop a simple method for a quick and accurate estimation of Λ. As the dose rate constant of clinical seeds is defined at a fixed reference point, we postulated that Λ may be calculated by treating the seed as an effective point source when the seed's source strength is specified in S K and its source characteristics are specified by the photon energy spectrum measured in air at the reference point. Using a semi-analytic approach, an analytic expression for Λ was derived for point sources with known photon energy spectra. This approach enabled a systematic study of Λ as a function of energy. Using the measured energy spectra, the calculated Λ for 125 I model 6711 and 6702 seeds and for 192 Ir seed agreed with the AAPM recommended values within ±1%. For the 103 Pd model 200 seed, the agreement was 5% with a recently measured value (within the ±7% experimental uncertainty) and was within 1% with the Monte Carlo simulations. The analytic expression for Λ proposed here can be evaluated using a programmable calculator or a simple spreadsheet and it provides an efficient method for checking the measured dose rate constant for any interstitial brachytherapy seed once the energy spectrum of the seed is known

  11. Determination of rate constants for the oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Racz, A.; Walter, T.; Stimming, U. [Munich Technical Univ., Garching (Germany). Dept. of Physics

    2008-07-01

    The oxygen reduction reaction (ORR) in fuel cells is a complex and fundamental electrochemical reaction. However, greater insight is needed into this multi-electron reaction in order to develop efficient and innovative catalysts. The rotating ring disc electrode (RRDE) is a useful tool for studying reaction intermediates of the ORR and to better understand the reaction pathway. Carbon materials such as carbon nanofilaments-platelets (CNF-PL) have high electrical conductivity and may be considered for fuel cells. In particular Pt and RuSe{sub x}, deposited on CNF-PL materials could act as efficient catalysts in fuel cells. This study used the RRDE to evaluate the oxygen reduction kinetics of these catalysts in oxygen-saturated, diluted sulphuric acid at room temperature. Kinetic data and hydrogen peroxide formation were determined by depositing a thin-film of the catalyst on the Au disc. The values for the constants k1, k2 and k3 were obtained using diagnostic criteria and expressions to calculate the rate constants of the cathodic oxygen reduction reaction for RuSe on new carbon supports. A potential dependency of the constants k1 and k2 for RuSe{sub x}/CNF-PL was observed. The transition of the Tafel slopes for this catalyst was obtained. 4 refs., 1 fig.

  12. Phototransformation rate constants of PAHs associated with soot particles

    International Nuclear Information System (INIS)

    Kim, Daekyun; Young, Thomas M.; Anastasio, Cort

    2013-01-01

    Photodegradation is a key process governing the residence time and fate of polycyclic aromatic hydrocarbons (PAHs) in particles, both in the atmosphere and after deposition. We have measured photodegradation rate constants of PAHs in bulk deposits of soot particles illuminated with simulated sunlight. The photodegradation rate constants at the surface (k p 0 ), the effective diffusion coefficients (D eff ), and the light penetration depths (z 0.5 ) for PAHs on soot layers of variable thickness were determined by fitting experimental data with a model of coupled photolysis and diffusion. The overall disappearance rates of irradiated low molecular weight PAHs (with 2–3 rings) on soot particles were influenced by fast photodegradation and fast diffusion kinetics, while those of high molecular weight PAHs (with 4 or more rings) were apparently controlled by either the combination of slow photodegradation and slow diffusion kinetics or by very slow diffusion kinetics alone. The value of z 0.5 is more sensitive to the soot layer thickness than the k p 0 value. As the thickness of the soot layer increases, the z 0.5 values increase, but the k p 0 values are almost constant. The effective diffusion coefficients calculated from dark experiments are generally higher than those from the model fitting method for illumination experiments. Due to the correlation between k p 0 and z 0.5 in thinner layers, D eff should be estimated by an independent method for better accuracy. Despite some limitations of the model used in this study, the fitted parameters were useful for describing empirical results of photodegradation of soot-associated PAHs. - Highlights: ► PAHs on soot were evaluated by a model of coupled photolysis and diffusion. ► Photodegradation rate at the surface, diffusion coefficient, and light penetration path were determined. ► Low MW PAHs were influenced by fast photodegradation and fast diffusion. ► High MW PAHs were controlled either by slow

  13. Studies on the catalytic rate constant of ribosomal peptidyltransferase.

    Science.gov (United States)

    Synetos, D; Coutsogeorgopoulos, C

    1987-02-20

    A detailed kinetic analysis of a model reaction for the ribosomal peptidyltransferase is described, using fMet-tRNA or Ac-Phe-tRNA as the peptidyl donor and puromycin as the acceptor. The initiation complex (fMet-tRNA X AUG X 70 S ribosome) or (Ac-Phe-tRNA X poly(U) X 70 S ribosome) (complex C) is isolated and then reacted with excess puromycin (S) to give fMet-puromycin or Ac-Phe-puromycin. This reaction (puromycin reaction) is first order at all concentrations of S tested. An important asset of this kinetic analysis is the fact that the relationship between the first order rate constant kobs and [S] shows hyperbolic saturation and that the value of kobs at saturating [S] is a measure of the catalytic rate constant (k cat) of peptidyltransferase in the puromycin reaction. With fMet-tRNA as the donor, this kcat of peptidyltransferase is 8.3 min-1 when the 0.5 M NH4Cl ribosomal wash is present, compared to 3.8 min-1 in its absence. The kcat of peptidyltransferase is 2.0 min-1 when Ac-Phe-tRNA replaces fMet-tRNA in the presence of the ribosomal wash and decreases to 0.8 min-1 in its absence. This kinetic procedure is the best method available for evaluating changes in the activity of peptidyltransferase in vitro. The results suggest that peptidyltransferase is subjected to activation by the binding of fMet-tRNA to the 70 S initiation complex.

  14. Rate Constant and Temperature Dependence for the Reaction of Hydroxyl Radicals with 2-Flouropropane (FC-281ea) and Comparison with an Estimated Rate Constant

    Science.gov (United States)

    DeMore, W.; Wilson, E., Jr.

    1998-01-01

    Relative rate experiments were used to measure the rate constant and temperature dependence of the reaction of OH radicals with 2-fluoropropane (HFC-281ea), using ethane, propane, ethyl chloride as reference standards.

  15. The Rate Constant for the Reaction H + C2H5 at T = 295 - 150K

    Science.gov (United States)

    Pimentel, Andre S.; Payne, Walter A.; Nesbitt, Fred L.; Cody, Regina J.; Stief, Louis J.

    2004-01-01

    The reaction between the hydrogen atom and the ethyl (C2H3) radical is predicted by photochemical modeling to be the most important loss process for C2H5 radicals in the atmospheres of Jupiter and Saturn. This reaction is also one of the major sources for the methyl radicals in these atmospheres. These two simplest hydrocarbon radicals are the initial species for the synthesis of larger hydrocarbons. Previous measurements of the rate constant for the H + C2H5 reaction varied by a factor of five at room temperature, and some studies showed a dependence upon temperature while others showed no such dependence. In addition, the previous studies were at higher temperatures and generally higher pressures than that needed for use in planetary atmospheric models. The rate constant for the reaction H + C2H5 has been measured directly at T = 150, 202 and 295 K and at P = 1.0 Torr He for all temperatures and additionally at P = 0.5 and 2.0 Torr He at T = 202 K. The measurements were performed in a discharge - fast flow system. The decay of the C2H5 radical in the presence of excess hydrogen was monitored by low-energy electron impact mass spectrometry under pseudo-first order conditions. H atoms and C2H5 radicals were generated rapidly and simultaneously by the reaction of fluorine atoms with H2 and C2H6, respectively. The total rate constant was found to be temperature and pressure independent. The measured total rate constant at each temperature are: k(sub 1)(295K) = (1.02+/-0.24)x10(exp -10), k(sub 1)(202K) = (1.02+/-0.22)x10(exp -10) and k(sub 1)(150K) = (0.93+/-0.21)x10(exp -10), all in units of cu cm/molecule/s. The total rate constant derived from all the combined measurements is k(sub 1) = (l.03+/-0.17)x10(exp -10) cu cm/molecule/s. At room temperature our results are about a factor of two higher than the recommended rate constant and a factor of three lower than the most recently published study.

  16. Assessment of the analgesic potency of constant rate infusion of ...

    African Journals Online (AJOL)

    Parameters determined were heart and respiratory rates, blood glucose level, pain score and body weight. Results showed that mean heart rate, respiratory rate and body weight were not differed significantly (p > 0.05) within and among the groups. Mean blood glucose level of group 4 was significantly higher (p < 0.05) ...

  17. Biodegradation testing of chemicals with high Henry’s constants – separating mass and effective concentration reveals higher rate constants

    DEFF Research Database (Denmark)

    Birch, Heidi; Andersen, Henrik Rasmus; Comber, Mike

    Microextraction (HS-SPME) was applied directly on the test systems to measure substrate depletion by biodegradation relative to abiotic controls. HS-SPME was also applied to determine air to water partitioning ratios. Water phase biodegradation rate constants, kwater, were up to 72 times higher than test system...

  18. Exergy analysis of integrated photovoltaic thermal solar water heater under constant flow rate and constant collection temperature modes

    NARCIS (Netherlands)

    Tiwari, A.; Dubey, Swapnil; Sandhu, G.S.; Sodha, M.S.; Anwar, S.I.

    2009-01-01

    In this communication, an analytical expression for the water temperature of an integrated photovoltaic thermal solar (IPVTS) water heater under constant flow rate hot water withdrawal has been obtained. Analysis is based on basic energy balance for hybrid flat plate collector and storage tank,

  19. Reaction rate constant for uranium in water and water vapor

    Energy Technology Data Exchange (ETDEWEB)

    TRIMBLE, D.J.

    1998-11-09

    The literature on uranium oxidation in water and oxygen free water vapor was reviewed. Arrhenius rate equations were developed from the review data. These data and equations will be used as a baseline from which to compare reaction rates measured for K Basin fuel.

  20. Low-Temperature Experimental and Theoretical Rate Constants for the O(1D) + H2 Reaction.

    Science.gov (United States)

    Hickson, Kevin M; Suleimanov, Yury V

    2017-03-09

    In the present joint experimental and theoretical study, we report thermal rate constants for the O( 1 D) + H 2 reaction within the 50-300 K temperature range. Experimental kinetics measurements were performed using a continuous supersonic flow reactor coupled with pulsed laser photolysis for O( 1 D) production and pulsed laser-induced fluorescence in the vacuum ultraviolet wavelength range (VUV LIF) for O( 1 D) detection. Theoretical rate constants were obtained using the ring polymer molecular dynamics (RPMD) approach over the two lowest potential energy surfaces 1 1 A' and 1 1 A″, which possess barrierless and thermally activated energy profiles, respectively. Both the experimental and theoretical rate constants exhibit a weak temperature dependence. The theoretical results show the dominant role of the 1 1 A' ground state and that contribution of the 1 1 A″ excited state to the total thermal rate decreases dramatically at lower temperature. Agreement between the experimental and theoretical results is good, and the discrepancy does not exceed 25%. It is argued that these differences are likely to be due to nonadiabatic couplings between the 1 1 A' and 2 1 A' surfaces.

  1. Reaction rate constants of HO2 + O3 in the temperature range 233-400 K

    Science.gov (United States)

    Wang, Xiuyan; Suto, Masako; Lee, L. C.

    1988-01-01

    The reaction rate constants of HO2 + O3 were measured in the temperature range 233-400 K using a discharge flow system with photofragment emission detection. In the range 233-253 K, the constants are approximately a constant value, and then increase with increasing temperature. This result suggests that the reaction may have two different channels. An expression representing the reaction rate constants is presented.

  2. A model for turbulent dissipation rate in a constant pressure ...

    Indian Academy of Sciences (India)

    J Dey

    the logarithmic region. However, measurement of the. Taylor microscale remains a difficult task, as it involves correlation function [1]. Consequently, an appreciation of the Taylor microscale, dissipation rate, etc., is lacking in practice due to complexity involved in estimating these quantities. Segalini et al [2] have proposed a ...

  3. Constant temperatures and the rate of seed germination in maize ...

    African Journals Online (AJOL)

    The rate of germination of the NEM cultivar was faster than that of the QPM cultivar at all temperatures. The thermal times for median germination were 46 for QPM and 40.7 oCd for the NEM cultivar. The cardinal temperatures (base, Tb, optimum, To and ceiling, Tc) for the NEM cultivar were Tb: 7, To: 30 and Tc: 48.2 oC.

  4. Atmospheric fate of a series of carbonyl nitrates: photolysis frequencies and OH-oxidation rate constants.

    Science.gov (United States)

    Suarez-Bertoa, R; Picquet-Varrault, B; Tamas, W; Pangui, E; Doussin, J-F

    2012-11-20

    Multifunctional organic nitrates are potential NO(x) reservoirs whose atmospheric chemistry is somewhat little known. They could play an important role in the spatial distribution of reactive nitrogen species and consequently in ozone formation and distribution in remote areas. In this work, the rate constants for the reaction with OH radical and the photolysis frequencies of α-nitrooxyacetone, 3-nitrooxy-2-butanone, and 3-methyl-3-nitrooxy-2-butanone have been determined at room temperature at 1000 mbar total pressure of synthetic air. The rate constants for the OH oxidation were measured using the relative rate technique, with methanol as reference compound. The following rate constants were obtained for the reaction with OH: k(OH) = (6.7 ± 2.5) × 10(-13) cm(3) molecule(-1) s(-1) for α-nitrooxyacetone, (10.6 ± 4.1) × 10(-13) cm(3) molecule(-1) s(-1) for 3-nitrooxy-2-butanone, and (2.6 ± 0.9) × 10(-13) cm(3) molecule(-1) s(-1) for 3-methyl-3-nitrooxy-2-butanone. The corresponding photolysis frequencies extrapolated to typical atmospheric conditions for July first at noon at 40° latitude North were (4.8 ± 0.3) × 10(-5) s(-1), (5.7 ± 0.3) × 10(-5) s(-1), and (7.4 ± 0.2) × 10(-5) s(-1), respectively. The data show that photolysis is a major atmospheric sink for these organic nitrates.

  5. Constrained least squares methods for estimating reaction rate constants from spectroscopic data

    NARCIS (Netherlands)

    Bijlsma, S.; Boelens, H.F.M.; Hoefsloot, H.C.J.; Smilde, A.K.

    2002-01-01

    Model errors, experimental errors and instrumental noise influence the accuracy of reaction rate constant estimates obtained from spectral data recorded in time during a chemical reaction. In order to improve the accuracy, which can be divided into the precision and bias of reaction rate constant

  6. Estimating reaction rate constants: comparison between traditional curve fitting and curve resolution

    NARCIS (Netherlands)

    Bijlsma, S.; Boelens, H. F. M.; Hoefsloot, H. C. J.; Smilde, A. K.

    2000-01-01

    A traditional curve fitting (TCF) algorithm is compared with a classical curve resolution (CCR) approach for estimating reaction rate constants from spectral data obtained in time of a chemical reaction. In the TCF algorithm, reaction rate constants an estimated from the absorbance versus time data

  7. Rate constants for some electrophilic reactions of benzyl, benzhydryl, and trityl cations in solution

    International Nuclear Information System (INIS)

    Ujdak, R.J.; Jones, R.L.; Dorfman, L.M.

    1976-01-01

    Absolute rate constants have been determined by the pulse radiolysis technique for several electrophilic reactions of the benzyl, the benzhydryl, and the trityl cation in 1,2-dichloroethane solution. The rate constants for the reactions of these carbonium ions with chloride ion, with bromide ion, and with iodide ion are all very nearly the same, namely 6 x 10 10 M -1 s -1 at 24 0 C. The values very likely represent the diffusion controlled limit for the ion combination reactions. The rate constants for the reactions with triethylamine, tri-n-propylamine, and tri-n-butylamine range from 2.0 x 10 9 to 7 x 10 6 M -1 s -1 at 24 0 C. With increasing phenyl substitution, the decreasing trend in the magnitude of the rate constant is consistent with the combined electronic and steric effects. With increasing size of the amine, the decrease in the value of the rate constant seems to indicate that the steric effect predominates. The values of the rate constants for reactions of benzyl and benzhydryl cation with methanol, ethanol, and 2-propanol indicate the following. The rate constant is higher for reaction with the alcohol dimer in solution than with alcohol monomer. The rate constants for reaction with alcohol monomer have values of 1 x 10 8 M -1 s -1 or lower

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

    KAUST Repository

    Badra, Jihad; Elwardani, Ahmed Elsaid; Farooq, Aamir

    2014-01-01

    -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

  9. Rate Constants for the Reactions of Hydroxyl Radical with Several Alkanes, Cycloalkanes, and Dimethyl Ether

    Science.gov (United States)

    DeMore, W.; Bayes, K.

    1998-01-01

    Relative rate experiements were used to measure rate constants and temperature denpendencies of the reactions of OH with propane, n-butane, n-pentane, n-hexane, cyclopropane, cyclobutane, cyclopentane, and dimethyl ether.

  10. Alternative approach to estimate the hydrolysis rate constant of particulate material from batch data

    International Nuclear Information System (INIS)

    Koch, Konrad; Drewes, Jörg E.

    2014-01-01

    Highlights: • An alternative to the commonly used first-order approach is presented. • A relationship between k h and the 1% criterion of the VDI 4630 is deduced. • Equation is proposed to directly calculate k h without the need for data fitting. • Hydrolysis constant k h can then easily be read-off from a table. - Abstract: As anaerobic batch tests are easy to conduct, they are commonly used to assess the effects of different operational factors on the anaerobic digestion process. Hydrolysis of particulate material is often assumed to be the rate limiting step in anaerobic digestion. Its velocity is often estimated by data fitting from batch tests. In this study, a Monod-type alternative to the commonly used first-order approach is presented. The approach was adapted from balancing a continuously stirred-tank reactor and better accommodates the fact that even after a long incubation time, some of the methane potential of the substrate remains untapped in the digestate. In addition, an equation is proposed to directly calculate the hydrolysis constant from the time when the daily gas production is less than 1% of the total gas production. The hydrolysis constant can then easily be read-off from a table when the batch test duration is known

  11. 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.

  12. A calculation of the surface recombination rate constant for hydrogen isotopes on metals

    International Nuclear Information System (INIS)

    Baskes, M.J.

    1980-01-01

    The surface recombination rate constant for hydrogen isotopes on a metal has been calculated using a simple model whose parameters may be determined by direct experimental measurements. Using the experimental values for hydrogen diffusivity, solubility, and sticking coefficient at zero surface coverage a reasonable prediction of the surface recombination constant may be made. The calculated recombination constant is in excellent agreement with experiment for bcc iron. A heuristic argument is developed which, along with the rate constant calculation, shows that surface recombination is important in those metals in which hydrogen has an exothermic heat of solution. (orig.)

  13. Effects of Water Molecule on CO Oxidation by OH: Reaction Pathways, Kinetic Barriers, and Rate Constants.

    Science.gov (United States)

    Zhang, Linyao; Yang, Li; Zhao, Yijun; Zhang, Jiaxu; Feng, Dongdong; Sun, Shaozeng

    2017-07-06

    The water dilute oxy-fuel combustion is a clean combustion technology for near-zero emission power; and the presence of water molecule could have both kinetic and dynamic effects on combustion reactions. The reaction OH + CO → CO 2 + H, one of the most important elementary reactions, has been investigated by extensive electronic structure calculations. And the effects of a single water molecule on CO oxidation have been studied by considering the preformed OH(H 2 O) complex reacts with CO. The results show little change in the reaction pathways, but the additional water molecule actually increases the vibrationally adiabatic energy barriers (V a G ). Further thermal rate constant calculations in the temperature range of 200 to 2000 K demonstrate that the total low-pressure limit rate constant for the water assisted OH(H 2 O) + CO → CO 2 + H 2 O + H reaction is 1-2 orders lower than that of the water unassisted one, which is consistent with the change of V a G . Therefore, the hydrated radical OH(H 2 O) would actually slow down the oxidation of CO. Meanwhile, comparisons show that the M06-2X/aug-cc-pVDZ method gives a much better estimation in energy and thus is recommended to be employed for direct dynamics simulations.

  14. The time dependence of rate constants of esub(aq)sup(-) reactions

    International Nuclear Information System (INIS)

    Burcl, R.; Byakov, V.M.; Grafutin, V.I.

    1982-01-01

    Published data about the time dependence of rate constants k(esub(aq)sup(-)+Ac) of esub(aq)sup(-) reactions with the acceptor Ac are analyzed, using the results of rate constant k(Ps+Ac) measurements for positronium reactions. It is shown that neither esub(aq)sup(-) nor Ps reaction rate constants depend on time in the observable range. Experimentally found concentration dependence of k(esub(aq)sup(-)+Ac) is due to other factors, connected with the existence of electric charge of esub(aq)sup(-), e.g. ionic strength, tunnelling effect etc. (author)

  15. Determination of rate constants of N-alkylation of primary amines by 1H NMR spectroscopy.

    Science.gov (United States)

    Li, Chenghong

    2013-09-05

    Macromolecules containing N-diazeniumdiolates of secondary amines are proposed scaffolds for controlled nitrogen oxide (NO) release medical applications. Preparation of these compounds often involves converting primary amine groups to secondary amine groups through N-alkylation. However, N-alkylation results in not only secondary amines but tertiary amines as well. Only N-diazeniumdiolates of secondary amines are suitable for controlled NO release; therefore, the yield of secondary amines is crucial to the total NO load of the carrier. In this paper, (1)H NMR spectroscopy was used to estimate the rate constants for formation of secondary amine (k1) and tertiary amine (k2) for alkylation reagents such as propylene oxide (PO), methyl acrylate (MA), and acrylonitrile (ACN). At room temperature, the ratio of k2/k1 for the three reactions was found to be around 0.50, 0.026, and 0.0072.

  16. On the estimate of the rate constant in the homogeneous dissolution model

    Czech Academy of Sciences Publication Activity Database

    Čupera, Jakub; Lánský, Petr

    2013-01-01

    Roč. 39, č. 10 (2013), s. 1555-1561 ISSN 0363-9045 Institutional support: RVO:67985823 Keywords : dissolution * estimation * rate constant Subject RIV: FR - Pharmacology ; Medidal Chemistry Impact factor: 2.006, year: 2013

  17. Measuring Protein Synthesis Rate In Living Object Using Flooding Dose And Constant Infusion Methods

    OpenAIRE

    Ulyarti, Ulyarti

    2018-01-01

    Constant infusion is a method used for measuring protein synthesis rate in living object which uses low concentration of amino acid tracers. Flooding dose method is another technique used to measure the rate of protein synthesis which uses labelled amino acid together with large amount of unlabelled amino acid.  The latter method was firstly developed to solve the problem in determination of precursor pool arise from constant infusion method.  The objective of this writing is to com...

  18. The correlation schemes in calculations of the rate constants of some radiation chemical reactions

    International Nuclear Information System (INIS)

    Zagorets, P.A.; Shostenko, A.G.; Kim, V.

    1983-01-01

    The various correlation relationships of the evaluation of the rate constants of radiation chemical reactions of addition, abstraction and isomerization were considered. It was shown that neglection of the influence of solvent can result in errors in calculations of rate constants equalling two orders in magnitude. Several examples of isokinetic relationship are given. The methods of calculation of transmission coefficient of reaction addition have been discussed. (author)

  19. Glucose consumption and rate constants for sup 18 F-fluorodeoxyglucose in human gliomas

    Energy Technology Data Exchange (ETDEWEB)

    Ishikawa, Masatsune; Kikuchi, Haruhiko; Nagata, Izumi; Yamagata, Sen; Taki, Waro; Yonekura, Yoshiharu; Nishizawa, Sadahiko; Iwasaki, Yasushi; Mukai, Takao [Kyoto Univ. (Japan). Faculty of Medicine

    1990-06-01

    To investigate the value of direct measurement of the rate constants by performing {sup 18}F-labeled fluorodeoxyglucose (FDG) studies of glucose consumption in human gliomas in vivo, a kinetic method with 3- and 4-parameter rate constant models for FDG uptake was used to analyze data from dynamic scans obtained by positron emission tomography after injection of FDG into 14 patients with glioma. The results were compared with those obtained by the autoradiographic method using 3- and 4-parameter rate constant models. There were no significant differences in the glucose consumption calculated by the four different methods both in the gliomas and in the contralateral intact cortex. It was found that the rate constant k4 could be neglected in calculation of glucose consumption in gliomas as well as in the contralateral intact cortex. The rate constant k3, an index of hexokinase function, was higher in malignant gliomas than in benign gliomas and was close to that in the contralateral cortex. This study indicates that the 3-parameter autoradiographic method, which is the most common one used in clinical practice, is reliable for the calculation of glucose consumption in human gliomas. Furthermore, direct measurement of the regional rate constants for FDG by the kinetic method was found to be useful for evaluation of the biochemical and physiological characteristics of human gliomas in vivo. (author).

  20. Selected hydraulic test analysis techniques for constant-rate discharge tests

    International Nuclear Information System (INIS)

    Spane, F.A. Jr.

    1993-03-01

    The constant-rate discharge test is the principal field method used in hydrogeologic investigations for characterizing the hydraulic properties of aquifers. To implement this test, the aquifer is stressed by withdrawing ground water from a well, by using a downhole pump. Discharge during the withdrawal period is regulated and maintained at a constant rate. Water-level response within the well is monitored during the active pumping phase (i.e., drawdown) and during the subsequent recovery phase following termination of pumping. The analysis of drawdown and recovery response within the stress well (and any monitored, nearby observation wells) provides a means for estimating the hydraulic properties of the tested aquifer, as well as discerning formational and nonformational flow conditions (e.g., wellbore storage, wellbore damage, presence of boundaries, etc.). Standard analytical methods that are used for constant-rate pumping tests include both log-log type-curve matching and semi-log straight-line methods. This report presents a current ''state of the art'' review of selected transient analysis procedures for constant-rate discharge tests. Specific topics examined include: analytical methods for constant-rate discharge tests conducted within confined and unconfined aquifers; effects of various nonideal formation factors (e.g., anisotropy, hydrologic boundaries) and well construction conditions (e.g., partial penetration, wellbore storage) on constant-rate test response; and the use of pressure derivatives in diagnostic analysis for the identification of specific formation, well construction, and boundary conditions

  1. Glucose consumption and rate constants for 18F-fluorodeoxyglucose in human gliomas

    International Nuclear Information System (INIS)

    Ishikawa, Masatsune; Kikuchi, Haruhiko; Nagata, Izumi; Yamagata, Sen; Taki, Waro; Yonekura, Yoshiharu; Nishizawa, Sadahiko; Iwasaki, Yasushi; Mukai, Takao

    1990-01-01

    To investigate the value of direct measurement of the rate constants by performing 18 F-labeled fluorodeoxyglucose (FDG) studies of glucose consumption in human gliomas in vivo, a kinetic method with 3- and 4-parameter rate constant models for FDG uptake was used to analyze data from dynamic scans obtained by positron emission tomography after injection of FDG into 14 patients with glioma. The results were compared with those obtained by the autoradiographic method using 3- and 4-parameter rate constant models. There were no significant differences in the glucose consumption calculated by the four different methods both in the gliomas and in the contralateral intact cortex. It was found that the rate constant k4 could be neglected in calculation of glucose consumption in gliomas as well as in the contralateral intact cortex. The rate constant k3, an index of hexokinase function, was higher in malignant gliomas than in benign gliomas and was close to that in the contralateral cortex. This study indicates that the 3-parameter autoradiographic method, which is the most common one used in clinical practice, is reliable for the calculation of glucose consumption in human gliomas. Furthermore, direct measurement of the regional rate constants for FDG by the kinetic method was found to be useful for evaluation of the biochemical and physiological characteristics of human gliomas in vivo. (author)

  2. Higher success rate with transcranial electrical stimulation of motor-evoked potentials using constant-voltage stimulation compared with constant-current stimulation in patients undergoing spinal surgery.

    Science.gov (United States)

    Shigematsu, Hideki; Kawaguchi, Masahiko; Hayashi, Hironobu; Takatani, Tsunenori; Iwata, Eiichiro; Tanaka, Masato; Okuda, Akinori; Morimoto, Yasuhiko; Masuda, Keisuke; Tanaka, Yuu; Tanaka, Yasuhito

    2017-10-01

    During spine surgery, the spinal cord is electrophysiologically monitored via transcranial electrical stimulation of motor-evoked potentials (TES-MEPs) to prevent injury. Transcranial electrical stimulation of motor-evoked potential involves the use of either constant-current or constant-voltage stimulation; however, there are few comparative data available regarding their ability to adequately elicit compound motor action potentials. We hypothesized that the success rates of TES-MEP recordings would be similar between constant-current and constant-voltage stimulations in patients undergoing spine surgery. The objective of this study was to compare the success rates of TES-MEP recordings between constant-current and constant-voltage stimulation. This is a prospective, within-subject study. Data from 100 patients undergoing spinal surgery at the cervical, thoracic, or lumbar level were analyzed. The success rates of the TES-MEP recordings from each muscle were examined. Transcranial electrical stimulation with constant-current and constant-voltage stimulations at the C3 and C4 electrode positions (international "10-20" system) was applied to each patient. Compound muscle action potentials were bilaterally recorded from the abductor pollicis brevis (APB), deltoid (Del), abductor hallucis (AH), tibialis anterior (TA), gastrocnemius (GC), and quadriceps (Quad) muscles. The success rates of the TES-MEP recordings from the right Del, right APB, bilateral Quad, right TA, right GC, and bilateral AH muscles were significantly higher using constant-voltage stimulation than those using constant-current stimulation. The overall success rates with constant-voltage and constant-current stimulations were 86.3% and 68.8%, respectively (risk ratio 1.25 [95% confidence interval: 1.20-1.31]). The success rates of TES-MEP recordings were higher using constant-voltage stimulation compared with constant-current stimulation in patients undergoing spinal surgery. Copyright © 2017

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

    Science.gov (United States)

    Badra, Jihad; Elwardany, Ahmed E; Farooq, Aamir

    2014-06-28

    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 (C=O) 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 (C=O), and the prime is used to differentiate different neighboring environments of a methylene group):

  4. Estimation of uptake rate constants for PCB congeners accumulated by semipermeable membrane devices and brown treat (Salmo trutta)

    Science.gov (United States)

    Meadows, J.C.; Echols, K.R.; Huckins, J.N.; Borsuk, F.A.; Carline, R.F.; Tillitt, D.E.

    1998-01-01

    The triolein-filled semipermeable membrane device (SPMD) is a simple and effective method of assessing the presence of waterborne hydrophobic chemicals. Uptake rate constants for individual chemicals are needed to accurately relate the amounts of chemicals accumulated by the SPMD to dissolved water concentrations. Brown trout and SPMDs were exposed to PCB- contaminated groundwater in a spring for 28 days to calculate and compare uptake rates of specific PCB congeners by the two matrixes. Total PCB congener concentrations in water samples from the spring were assessed and corrected for estimated total organic carbon (TOC) sorption to estimate total dissolved concentrations. Whole and dissolved concentrations averaged 4.9 and 3.7 ??g/L, respectively, during the exposure. Total concentrations of PCBs in fish rose from 0.06 to 118.3 ??g/g during the 28-day exposure, while concentrations in the SPMD rose from 0.03 to 203.4 ??g/ g. Uptake rate constants (k1) estimated for SPMDs and brown trout were very similar, with k1 values for SPMDs ranging from one to two times those of the fish. The pattern of congener uptake by the fish and SPMDs was also similar. The rates of uptake generally increased or decreased with increasing K(ow), depending on the assumption of presence or absence of TOC.The triolein-filled semipermeable membrane device (SPMD) is a simple and effective method of assessing the presence of waterborne hydrophobic chemicals. Uptake rate constants for individual chemicals are needed to accurately relate the amounts of chemicals accumulated by the SPMB to dissolved water concentrations. Brown trout and SPMDs were exposed to PCB-contaminated groundwater in a spring for 28 days to calculate and compare uptake rates of specific PCB congeners by the two matrixes. Total PCB congener concentrations in water samples from the spring were assessed and corrected for estimated total organic carbon (TOC) sorption to estimate total dissolved concentrations. Whole and

  5. Convergence analysis of Chauvin's PCA learning algorithm with a constant learning rate

    International Nuclear Information System (INIS)

    Lv Jiancheng; Yi Zhang

    2007-01-01

    The convergence of Chauvin's PCA learning algorithm with a constant learning rate is studied in this paper by using a DDT method (deterministic discrete-time system method). Different from the DCT method (deterministic continuous-time system method), the DDT method does not require that the learning rate converges to zero. An invariant set of Chauvin's algorithm with a constant learning rate is obtained so that the non-divergence of this algorithm can be guaranteed. Rigorous mathematic proofs are provided to prove the local convergence of this algorithm

  6. Convergence analysis of Chauvin's PCA learning algorithm with a constant learning rate

    Energy Technology Data Exchange (ETDEWEB)

    Lv Jiancheng [Computational Intelligence Laboratory, School of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610054 (China); Yi Zhang [Computational Intelligence Laboratory, School of Computer Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610054 (China)]. E-mail: zhangyi@uestc.edu.cn

    2007-05-15

    The convergence of Chauvin's PCA learning algorithm with a constant learning rate is studied in this paper by using a DDT method (deterministic discrete-time system method). Different from the DCT method (deterministic continuous-time system method), the DDT method does not require that the learning rate converges to zero. An invariant set of Chauvin's algorithm with a constant learning rate is obtained so that the non-divergence of this algorithm can be guaranteed. Rigorous mathematic proofs are provided to prove the local convergence of this algorithm.

  7. 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. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. 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

  9. Airborne and total gamma absorbed dose rates at Patiala - India

    International Nuclear Information System (INIS)

    Tesfaye, Tilahun; Sahota, H.S.; Singh, K.

    1999-01-01

    The external gamma absorbed dose rate due to gamma rays originating from gamma emitting aerosols in air, is compared with the total external gamma absorbed dose rate at the Physics Department of Punjabi University, Patiala. It has been found out that the contribution, to the total external gamma absorbed dose rate, of radionuclides on particulate matter suspended in air is about 20% of the overall gamma absorbed dose rate. (author)

  10. Microscopic Rate Constants of Crystal Growth from Molecular Dynamic Simulations Combined with Metadynamics

    Directory of Open Access Journals (Sweden)

    Dániel Kozma

    2012-01-01

    Full Text Available Atomistic simulation of crystal growth can be decomposed into two steps: the determination of the microscopic rate constants and a mesoscopic kinetic Monte Carlo simulation. We proposed a method to determine kinetic rate constants of crystal growth. We performed classical molecular dynamics on the equilibrium liquid/crystal interface of argon. Metadynamics was used to explore the free energy surface of crystal growth. A crystalline atom was selected at the interface, and it was displaced to the liquid phase by adding repulsive Gaussian potentials. The activation free energy of this process was calculated as the maximal potential energy density of the Gaussian potentials. We calculated the rate constants at different interfacial structures using the transition state theory. In order to mimic real crystallization, we applied a temperature difference in the calculations of the two opposite rate constants, and they were applied in kinetic Monte Carlo simulation. The novelty of our technique is that it can be used for slow crystallization processes, while the simple following of trajectories can be applied only for fast reactions. Our method is a possibility for determination of elementary rate constants of crystal growth that seems to be necessary for the long-time goal of computer-aided crystal design.

  11. An exclusion process on a tree with constant aggregate hopping rate

    International Nuclear Information System (INIS)

    Mottishaw, Peter; Waclaw, Bartlomiej; Evans, Martin R

    2013-01-01

    We introduce a model of a totally asymmetric simple exclusion process (TASEP) on a tree network where the aggregate hopping rate is constant from level to level. With this choice for hopping rates the model shows the same phase diagram as the one-dimensional case. The potential applications of our model are in the area of distribution networks, where a single large source supplies material to a large number of small sinks via a hierarchical network. We show that mean-field theory (MFT) for our model is identical to that of the one-dimensional TASEP and that this MFT is exact for the TASEP on a tree in the limit of large branching ratio, b (or equivalently large coordination number). We then present an exact solution for the two level tree (or star network) that allows the computation of any correlation function and confirm how mean-field results are recovered as b → ∞. As an example we compute the steady-state current as a function of branching ratio. We present simulation results that confirm these results and indicate that the convergence to MFT with large branching ratio is quite rapid. (paper)

  12. Consideration of demand rate in overall equipment effetiveness (OEE on equipment with constant process time

    Directory of Open Access Journals (Sweden)

    Perumal Puvanasvaran

    2013-06-01

    Full Text Available Purpose: The paper is primarily done on the purpose of introducing new concept in defining the Overall Equipment Effectiveness (OEE with the consideration of both machine utilization and customer demand requested. Previous literature concerning the limitation and difficulty of OEE implementation has been investigated in order to track out the potential opportunities to be improved, since the OEE has been widely accepted by most of the industries regardless their manufacturing environment.Design/methodology/approach: The paper is conducting the study based on literature review and the computerized data collection. In details, the novel definition and method of processing the computerized data are all interpreted based on similar studies performed by others and supported by related journals in proving the validation of the output. Over the things, the computerized data are the product amount and total time elapsed on each production which is automatically recorded by the system at the manufacturing site.Findings: The finding of this paper is firstly the exposure and emphasis of limitation exists in current implementation of OEE, which showing that high utilization of the machine is encouraged regardless of the customer demand and is having conflict with the inventory handling cost. This is certainly obvious with overproduction issue especially during low customer demand period. The second limitation in general implementation of OEE is the difficulty in obtaining the ideal cycle time, especially those equipments with constant process time. The section of this paper afterward comes out with the proposed solution in fixing this problem through the definition of performance ratio and then usage of this definition in measuring the machine utilization from time to time. Before this, the time available for the production is calculated incorporating the availability of OEE, which is then used to get the Takt time.Research limitations/implications: Future

  13. Extraction of elementary rate constants from global network analysis of E. coli central metabolism

    Directory of Open Access Journals (Sweden)

    Broderick Gordon

    2008-05-01

    Full Text Available Abstract Background As computational performance steadily increases, so does interest in extending one-particle-per-molecule models to larger physiological problems. Such models however require elementary rate constants to calculate time-dependent rate coefficients under physiological conditions. Unfortunately, even when in vivo kinetic data is available, it is often in the form of aggregated rate laws (ARL that do not specify the required elementary rate constants corresponding to mass-action rate laws (MRL. There is therefore a need to develop a method which is capable of automatically transforming ARL kinetic information into more detailed MRL rate constants. Results By incorporating proteomic data related to enzyme abundance into an MRL modelling framework, here we present an efficient method operating at a global network level for extracting elementary rate constants from experiment-based aggregated rate law (ARL models. The method combines two techniques that can be used to overcome the difficult properties in parameterization. The first, a hybrid MRL/ARL modelling technique, is used to divide the parameter estimation problem into sub-problems, so that the parameters of the mass action rate laws for each enzyme are estimated in separate steps. This reduces the number of parameters that have to be optimized simultaneously. The second, a hybrid algebraic-numerical simulation and optimization approach, is used to render some rate constants identifiable, as well as to greatly narrow the bounds of the other rate constants that remain unidentifiable. This is done by incorporating equality constraints derived from the King-Altman and Cleland method into the simulated annealing algorithm. We apply these two techniques to estimate the rate constants of a model of E. coli glycolytic pathways. The simulation and statistical results show that our innovative method performs well in dealing with the issues of high computation cost, stiffness, local

  14. Extraction of elementary rate constants from global network analysis of E. coli central metabolism

    Science.gov (United States)

    Zhao, Jiao; Ridgway, Douglas; Broderick, Gordon; Kovalenko, Andriy; Ellison, Michael

    2008-01-01

    Background As computational performance steadily increases, so does interest in extending one-particle-per-molecule models to larger physiological problems. Such models however require elementary rate constants to calculate time-dependent rate coefficients under physiological conditions. Unfortunately, even when in vivo kinetic data is available, it is often in the form of aggregated rate laws (ARL) that do not specify the required elementary rate constants corresponding to mass-action rate laws (MRL). There is therefore a need to develop a method which is capable of automatically transforming ARL kinetic information into more detailed MRL rate constants. Results By incorporating proteomic data related to enzyme abundance into an MRL modelling framework, here we present an efficient method operating at a global network level for extracting elementary rate constants from experiment-based aggregated rate law (ARL) models. The method combines two techniques that can be used to overcome the difficult properties in parameterization. The first, a hybrid MRL/ARL modelling technique, is used to divide the parameter estimation problem into sub-problems, so that the parameters of the mass action rate laws for each enzyme are estimated in separate steps. This reduces the number of parameters that have to be optimized simultaneously. The second, a hybrid algebraic-numerical simulation and optimization approach, is used to render some rate constants identifiable, as well as to greatly narrow the bounds of the other rate constants that remain unidentifiable. This is done by incorporating equality constraints derived from the King-Altman and Cleland method into the simulated annealing algorithm. We apply these two techniques to estimate the rate constants of a model of E. coli glycolytic pathways. The simulation and statistical results show that our innovative method performs well in dealing with the issues of high computation cost, stiffness, local minima and uncertainty

  15. Big bang nucleosynthesis with a varying fine structure constant and nonstandard expansion rate

    International Nuclear Information System (INIS)

    Ichikawa, Kazuhide; Kawasaki, Masahiro

    2004-01-01

    We calculate the primordial abundances of light elements produced during big bang nucleosynthesis when the fine structure constant and/or the cosmic expansion rate take nonstandard values. We compare them with the recent values of observed D, 4 He, and 7 Li abundances, which show a slight inconsistency among themselves in the standard big bang nucleosynthesis scenario. This inconsistency is not solved by considering either a varying fine structure constant or a nonstandard expansion rate separately but solutions are found by their simultaneous existence

  16. An Empirical Rate Constant Based Model to Study Capacity Fading in Lithium Ion Batteries

    Directory of Open Access Journals (Sweden)

    Srivatsan Ramesh

    2015-01-01

    Full Text Available A one-dimensional model based on solvent diffusion and kinetics to study the formation of the SEI (solid electrolyte interphase layer and its impact on the capacity of a lithium ion battery is developed. The model uses the earlier work on silicon oxidation but studies the kinetic limitations of the SEI growth process. The rate constant of the SEI formation reaction at the anode is seen to play a major role in film formation. The kinetics of the reactions for capacity fading for various battery systems are studied and the rate constants are evaluated. The model is used to fit the capacity fade in different battery systems.

  17. Reaction rate constant of HO2+O3 measured by detecting HO2 from photofragment fluorescence

    Science.gov (United States)

    Manzanares, E. R.; Suto, Masako; Lee, Long C.; Coffey, Dewitt, Jr.

    1986-01-01

    A room-temperature discharge-flow system investigation of the rate constant for the reaction 'HO2 + O3 yields OH + 2O2' has detected HO2 through the OH(A-X) fluorescence produced by photodissociative excitation of HO2 at 147 nm. A reaction rate constant of 1.9 + or - 0.3 x 10 to the -15th cu cm/molecule per sec is obtained from first-order decay of HO2 in excess O3; this agrees well with published data.

  18. Impact of uncertainties in inorganic chemical rate constants on tropospheric composition and ozone radiative forcing

    Directory of Open Access Journals (Sweden)

    B. Newsome

    2017-12-01

    Full Text Available Chemical rate constants determine the composition of the atmosphere and how this composition has changed over time. They are central to our understanding of climate change and air quality degradation. Atmospheric chemistry models, whether online or offline, box, regional or global, use these rate constants. Expert panels evaluate laboratory measurements, making recommendations for the rate constants that should be used. This results in very similar or identical rate constants being used by all models. The inherent uncertainties in these recommendations are, in general, therefore ignored. We explore the impact of these uncertainties on the composition of the troposphere using the GEOS-Chem chemistry transport model. Based on the Jet Propulsion Laboratory (JPL and International Union of Pure and Applied Chemistry (IUPAC evaluations we assess the influence of 50 mainly inorganic rate constants and 10 photolysis rates on tropospheric composition through the use of the GEOS-Chem chemistry transport model. We assess the impact on four standard metrics: annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime. Uncertainty in the rate constants for NO2 + OH →M  HNO3 and O3 + NO  →  NO2 + O2 are the two largest sources of uncertainty in these metrics. The absolute magnitude of the change in the metrics is similar if rate constants are increased or decreased by their σ values. We investigate two methods of assessing these uncertainties, addition in quadrature and a Monte Carlo approach, and conclude they give similar outcomes. Combining the uncertainties across the 60 reactions gives overall uncertainties on the annual mean tropospheric ozone burden, surface ozone and tropospheric OH concentrations, and tropospheric methane lifetime of 10, 11, 16 and 16 %, respectively. These are larger than the spread between models in recent model intercomparisons. Remote

  19. Determination of reaction rate constants for alkylation of 4-(p-nitrobenzyl) pyridine by different alkylating agents.

    Science.gov (United States)

    Walles, S A

    1980-02-01

    The rate constants have been determined for the reaction between some different alkylating agents and 4-(p-nitrobenzyl) pyridine (NBP) in methanol. These constants have been compared with those for alkylation of aniline in water. All the constants were lower in methanol than in water but in different degrees. The rate constants of the different alkylating agents have been calculated at a nucleophilic strength n=2. The genetic risk defined as the degree of alkylation of a nucleophile (n=2) is equivalent to the rate constant kn=2 and the target dose. The dependence of the genetic risk on the rate constant (kn=2) is discussed.

  20. Free energy correlation of rate constants for electron transfer between organic systems in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Meisel, D

    1975-07-15

    Recent experimental data concerning the rate constants for electron transfer reactions of organic systems in aqueous solutions and their equilibrium constants is examined for possible correlation. The data is correlated quite well by the Marcus theory, if a reorganization parameter, lambda, of 18 kcal/mole is used. Assuming that the only contribution to lambda is the free energy of rearrangement of the water molecules, an effective radius of 5 A for the reacting entities is estimated. For the zero free energy change reaction, i.e., electron exchange between a radical ion and its parent molecule, a rate constant of about 5 X 10/sup 7/ M/sup -1/ s/sup -1/ is predicted. (auth)

  1. Order of current variance and diffusivity in the rate one totally asymmetric zero range process

    NARCIS (Netherlands)

    Balázs, M.; Komjáthy, J.

    2008-01-01

    We prove that the variance of the current across a characteristic is of order t 2/3 in a stationary constant rate totally asymmetric zero range process, and that the diffusivity has order t 1/3. This is a step towards proving universality of this scaling behavior in the class of one-dimensional

  2. Application of accelerated evaluation method of alteration temperature and constant dose rate irradiation on bipolar linear regulator LM317

    International Nuclear Information System (INIS)

    Deng Wei; Wu Xue; Wang Xin; Zhang Jinxin; Zhang Xiaofu; Zheng Qiwen; Ma Wuying; Lu Wu; Guo Qi; He Chengfa

    2014-01-01

    With different irradiation methods including high dose rate irradiation, low dose rate irradiation, alteration temperature and constant dose rate irradiation, and US military standard constant high temperature and constant dose rate irradiation, the ionizing radiation responses of bipolar linear regulator LM317 from three different companies were investigated under the operating and zero biases. The results show that compared with constant high temperature and constant dose rate irradiation method, the alteration temperature and constant dose rate irradiation method can not only very rapidly and accurately evaluate the dose rate effect of three bipolar linear regulators, but also well simulate the damage of low dose rate irradiation. Experiment results make the alteration temperature and constant dose rate irradiation method successfully apply to bipolar linear regulator. (authors)

  3. Separating the effect of respiration from the heart rate variability for cases of constant harmonic breathing

    Directory of Open Access Journals (Sweden)

    Kircher Michael

    2015-09-01

    Full Text Available Heart Rate Variability studies are a known measure for the autonomous control of the heart rate. In special situations, its interpretation can be ambiguous, since the respiration has a major influence on the heart rate variability. For this reason it has often been proposed to measure Heart Rate Variability, while the subjects are breathing at a constant respiration rate. That way the spectral influence of the respiration is known. In this work we propose to remove this constant respiratory influence from the heart rate and the Heart Rate Variability parameters to gain respiration free autonomous controlled heart rate signal. The spectral respiratory component in the heart rate signal is detected and characterized. Subsequently the respiratory effect on Heart Rate Variability is removed using spectral filtering approaches, such as the Notch filter or the Raised Cosine filter. As a result new decoupled Heart Variability parameters are gained, which could lead to new additional interpretations of the autonomous control of the heart rate.

  4. Some chaotic behaviors in a MCA learning algorithm with a constant learning rate

    International Nuclear Information System (INIS)

    Lv Jiancheng; Yi Zhang

    2007-01-01

    Douglas's minor component analysis algorithm with a constant learning rate has both stability and chaotic dynamical behavior under some conditions. The paper explores such dynamical behavior of this algorithm. Certain stability and chaos of this algorithm are derived. Waveform plots, Lyapunov exponents and bifurcation diagrams are presented to illustrate the existence of chaotic behavior

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

    KAUST Repository

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

    2017-01-01

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

  6. Determination of rate constants in second-order kinetics using UV-visible spectroscopy

    NARCIS (Netherlands)

    Bijlsma, S.; Boelens, H. F. M.; Smilde, A. R.

    2001-01-01

    A general method for estimating reaction rate constants of chemical reactions using ultraviolet-visible (UV-vis) spectroscopy is presented. The only requirement is that some of the chemical components involved be spectroscopically active. The method uses the combination of spectroscopic measurements

  7. The ruin probability of a discrete time risk model under constant interest rate with heavy tails

    NARCIS (Netherlands)

    Tang, Q.

    2004-01-01

    This paper investigates the ultimate ruin probability of a discrete time risk model with a positive constant interest rate. Under the assumption that the gross loss of the company within one year is subexponentially distributed, a simple asymptotic relation for the ruin probability is derived and

  8. Constant savings rates and quasi-arithmetic population growth under exhaustible resource constraints

    NARCIS (Netherlands)

    Asheim, G.B.; Buchholz, W.; Hartwick, J.M.; Mitra, T.; Withagen, C.A.A.M.

    2007-01-01

    In the Dasgupta–Heal–Solow–Stiglitz (DHSS) model of capital accumulation and resource depletion we show the following equivalence: if an efficient path has constant (gross and net of population growth) savings rates, then population growth must be quasi-arithmetic and the path is a maximin or a

  9. 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.

  10. USE OF ROUGH SETS AND SPECTRAL DATA FOR BUILDING PREDICTIVE MODELS OF REACTION RATE CONSTANTS

    Science.gov (United States)

    A model for predicting the log of the rate constants for alkaline hydrolysis of organic esters has been developed with the use of gas-phase min-infrared library spectra and a rule-building software system based on the mathematical theory of rough sets. A diverse set of 41 esters ...

  11. Competitive kinetics as a tool to determine rate constants for reduction of ferrylmyoglobin by food components

    DEFF Research Database (Denmark)

    Jongberg, Sisse; Lund, Marianne Nissen; Pattison, David I.

    2016-01-01

    Competitive kinetics were applied as a tool to determine apparent rate constants for the reduction of hypervalent haem pigment ferrylmyoglobin (MbFe(IV)=O) by proteins and phenols in aqueous solution of pH 7.4 and I = 1.0 at 25 °C. Reduction of MbFe(IV)=O by a myofibrillar protein isolate (MPI) f...

  12. Neural estimation of kinetic rate constants from dynamic PET-scans

    DEFF Research Database (Denmark)

    Fog, Torben L.; Nielsen, Lars Hupfeldt; Hansen, Lars Kai

    1994-01-01

    A feedforward neural net is trained to invert a simple three compartment model describing the tracer kinetics involved in the metabolism of [18F]fluorodeoxyglucose in the human brain. The network can estimate rate constants from positron emission tomography sequences and is about 50 times faster ...

  13. Quantum chemical and conventional TST calculations of rate constants for the OH + alkane reaction

    International Nuclear Information System (INIS)

    Bravo-Perez, Graciela; Alvarez-Idaboy, J. Raul; Jimenez, Annia Galano; Cruz-Torres, Armando

    2005-01-01

    Reactions of OH with methane, ethane, propane, i-butane, and n-butane have been modeled using ab initio (MP2) and hybrid DFT (BHandHLYP) methods, and the 6-311G(d,p) basis set. Furthermore, single-point calculations at the CCSD(T) level were carried out at the optimized geometries. The rate constants have been calculated using the conventional transition-state theory (CTST). Arrhenius equations are proposed in the temperature range of 250-650 K. Hindered Internal Rotation partition functions calculations were explicitly carried out and included in the total partition functions. These corrections showed to be relevant in the determination of the pre-exponential parameters, although not so important as in the NO 3 + alkane reactions [G. Bravo-Perez, J.R. Alvarez-Idaboy, A. Cruz-Torres, M.E. Ruiz, J. Phys. Chem. A 106 (2002) 4645]. The explicit participation of the tunnel effect has been taken into account. The calculated rate coefficients provide a very good agreement with the experimental data. The best agreement for the overall alkane + OH reactions seemed to occur when the BHandHLYP geometries and partition functions are used. For propane and i-butane, in addition to the respective secondary and tertiary H-abstraction channels, the primary one has been considered. These pathways are confirmed to be significant in spite of the large differences in activation energies between primary and secondary or primary and tertiary channels, respectively of propane and i-butane reactions and should not be disregarded

  14. Three-minute constant rate step test for detecting exertional dyspnea relief after bronchodilation in COPD

    Directory of Open Access Journals (Sweden)

    Borel B

    2016-11-01

    Full Text Available Benoit Borel,1,2 Courtney A Wilkinson-Maitland,3 Alan Hamilton,4 Jean Bourbeau,5 Hélène Perrault,6 Dennis Jensen,3,5,7 François Maltais2 1Laboratoire HAVAE, Université de Limoges, Limoges, France; 2Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, 3Clinical Exercise and Respiratory Physiology Laboratory, Department of Kinesiology and Physical Education, McGill University, Montréal, QC, 4Boehringer Ingelheim (Canada Limited, Burlington, ON, 5Respiratory Epidemiology and Clinical Research Unit, Montreal Chest Institute, McGill University Health Center, Montreal, QC, 6Faculty of Health Sciences, University of Ottawa, Ottawa, ON, 7Translational Research in Respiratory Diseases Program, Research Institute of the McGill University Health Centre, Montreal, QC, Canada Background: The aim of this study was to evaluate the responsiveness of the 3-minute constant rate step test (3-MST to detect the relief of exertional dyspnea (respiratory discomfort after acute bronchodilation in COPD patients. Patients and methods: A total of 40 patients with moderate-to-severe COPD (mean forced expiratory volume in 1 second: 45.7 (±14.7, % predicted performed four 3-MSTs at randomly assigned stepping rates of 14, 16, 20 and 24 steps/min after inhalation of nebulized ipratropium bromide (500 µg/salbutamol (2.5 mg and saline placebo, which were randomized to order. Patients rated their intensity of perceived dyspnea at the end of each 3-MST using Borg 0–10 category ratio scale. Results: A total of 37 (92.5%, 36 (90%, 34 (85% and 27 (67.5% patients completed all 3 minutes of exercise at 14, 16, 20 and 24 steps/min under both treatment conditions, respectively. Compared with placebo, ipratropium bromide/salbutamol significantly decreased dyspnea at the end of the third minute of exercise at 14 steps/min (by 0.6±1.0 Borg 0–10 scale units, P<0.01 and 16 steps/min (by 0.7±1.3 Borg 0–10 scale

  15. Absolute rate constants for the reaction of NO with a series of peroxy radicals in the gas at 295 K

    DEFF Research Database (Denmark)

    Sehested, J.; Nielsen, O.J.; Wallington, T.J.

    1993-01-01

    The rate constants for the reaction of NO with a series of peroxy radicals: CH3O2, C2H5O2, (CH3)3CCH2O2, (CH3)3CC(CH3)2CH2O2, CH2FO2, CH2ClO2, CH2BrO2, CHF2O2, CF2ClO2, CHF2CF2O2, CF3CF2O2, CFCl2CH2O2 and CF2ClCH2O2 were measured at 298 K and a total pressure of 1 atm. The rate constants were...

  16. Accelerated Testing Methodology in Constant Stress-Rate Testing for Advanced Structural Ceramics: A Preloading Technique

    Science.gov (United States)

    Choi, Sung R.; Gyekenyesi, John P.; Huebert, Dean; Bartlett, Allen; Choi, Han-Ho

    2001-01-01

    Preloading technique was used as a means of an accelerated testing methodology in constant stress-rate (dynamic fatigue) testing for two different brittle materials. The theory developed previously for fatigue strength as a function of preload was further verified through extensive constant stress-rate testing for glass-ceramic and CRT glass in room temperature distilled water. The preloading technique was also used in this study to identify the prevailing failure mechanisms at elevated temperatures, particularly at lower test rates in which a series of mechanisms would be associated simultaneously with material failure, resulting in significant strength increase or decrease. Two different advanced ceramics including SiC whisker-reinforced composite silicon nitride and 96 wt% alumina were used at elevated temperatures. It was found that the preloading technique can be used as an additional tool to pinpoint the dominant failure mechanism that is associated with such a phenomenon of considerable strength increase or decrease.

  17. Efficient quantum-classical method for computing thermal rate constant of recombination: application to ozone formation.

    Science.gov (United States)

    Ivanov, Mikhail V; Babikov, Dmitri

    2012-05-14

    Efficient method is proposed for computing thermal rate constant of recombination reaction that proceeds according to the energy transfer mechanism, when an energized molecule is formed from reactants first, and is stabilized later by collision with quencher. The mixed quantum-classical theory for the collisional energy transfer and the ro-vibrational energy flow [M. Ivanov and D. Babikov, J. Chem. Phys. 134, 144107 (2011)] is employed to treat the dynamics of molecule + quencher collision. Efficiency is achieved by sampling simultaneously (i) the thermal collision energy, (ii) the impact parameter, and (iii) the incident direction of quencher, as well as (iv) the rotational state of energized molecule. This approach is applied to calculate third-order rate constant of the recombination reaction that forms the (16)O(18)O(16)O isotopomer of ozone. Comparison of the predicted rate vs. experimental result is presented.

  18. Constant rate natural gas production from a well in a hydrate reservoir

    International Nuclear Information System (INIS)

    Ji Chuang; Ahmadi, Goodarz; Smith, Duane H.

    2003-01-01

    Using a computational model, production of natural gas at a constant rate from a well that is drilled into a confined methane hydrate reservoir is studied. It is assumed that the pores in the reservoir are partially saturated with hydrate. A linearized model for an axisymmetric condition with a fixed well output is used in the analysis. For different reservoir temperatures and various well outputs, time evolutions of temperature and pressure profiles, as well as the gas flow rate in the hydrate zone and the gas region, are evaluated. The distance of the decomposition front from the well as a function of time is also computed. It is shown that to maintain a constant natural gas production rate, the well pressure must be decreased with time. A constant low production rate can be sustained for a long duration of time, but a high production rate demands unrealistically low pressure at the well after a relatively short production time. The simulation results show that the process of natural gas production in a hydrate reservoir is a sensitive function of reservoir temperature and hydrate zone permeability

  19. Determination of Methane and Carbon Dioxide Formation Rate Constants for Semi-Continuously Fed Anaerobic Digesters

    Directory of Open Access Journals (Sweden)

    Jan Moestedt

    2015-01-01

    Full Text Available To optimize commercial-scale biogas production, it is important to evaluate the performance of each microbial step in the anaerobic process. Hydrolysis and methanogenesis are usually the rate-limiting steps during digestion of organic waste and by-products. By measuring biogas production and methane concentrations on-line in a semi-continuously fed reactor, gas kinetics can be evaluated. In this study, the rate constants of the fermentative hydrolysis step (kc and the methanogenesis step (km were determined and evaluated in a continuously stirred tank laboratory-scale reactor treating food and slaughterhouse waste and glycerin. A process additive containing Fe2+, Co2+ and Ni2+ was supplied until day 89, after which Ni2+ was omitted. The omission resulted in a rapid decline in the methanogenesis rate constant (km to 70% of the level observed when Ni2+ was present, while kc remained unaffected. This suggests that Ni2+ mainly affects the methanogenic rather than the hydrolytic microorganisms in the system. However, no effect was initially observed when using conventional process monitoring parameters such as biogas yield and volatile fatty acid concentration. Hence, formation rate constants can reveal additional information on process performance and km can be used as a complement to conventional process monitoring tools for semi-continuously fed anaerobic digesters.

  20. 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.

  1. 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...... estimates of the rate constants: k(CF3O + CH4) = (1.2 +/- 0.1) x 10(-14), k(CF3O + c-C3H6) = (3.6 +/- 0.2) x 10(-13), k(CF3O + C3H8) = (4.7 +/- 0.7) x 10(-12), k(CF3O + (CH3)3CH) = (7.2 +/- 0.5) x 10(-12), k(CF3O + C2H4) = (3.0 +/- 0.1) x 10(-11) and k(CF3O + C6H6) = (3.6 +/- 0.1) x 10(-11) cm3 molecule-1 s......-1. The importance of the reactions of CF3O radicals with hydrocarbons under atmospheric conditions is discussed....

  2. Effects of the anion salt nature on the rate constants of the aqueous proton exchange reactions.

    Science.gov (United States)

    Paredes, Jose M; Garzon, Andres; Crovetto, Luis; Orte, Angel; Lopez, Sergio G; Alvarez-Pez, Jose M

    2012-04-28

    The proton-transfer ground-state rate constants of the xanthenic dye 9-[1-(2-methyl-4-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (TG-II), recovered by Fluorescence Lifetime Correlation Spectroscopy (FLCS), have proven to be useful to quantitatively reflect specific cation effects in aqueous solutions (J. M. Paredes, L. Crovetto, A. Orte, J. M. Alvarez-Pez and E. M. Talavera, Phys. Chem. Chem. Phys., 2011, 13, 1685-1694). Since these phenomena are more sensitive to anions than to cations, in this paper we have accounted for the influence of salts with the sodium cation in common, and the anion classified according to the empirical Hofmeister series, on the proton transfer rate constants of TG-II. We demonstrate that the presence of ions accelerates the rate of the ground-state proton-exchange reaction in the same order than ions that affect ion solvation in water. The combination of FLCS with a fluorophore undergoing proton transfer reactions in the ground state, along with the desirable feature of a pseudo-dark state when the dye is protonated, allows one unique direct determination of kinetic rate constants of the proton exchange chemical reaction. This journal is © the Owner Societies 2012

  3. Likelihood inference of non-constant diversification rates with incomplete taxon sampling.

    Science.gov (United States)

    Höhna, Sebastian

    2014-01-01

    Large-scale phylogenies provide a valuable source to study background diversification rates and investigate if the rates have changed over time. Unfortunately most large-scale, dated phylogenies are sparsely sampled (fewer than 5% of the described species) and taxon sampling is not uniform. Instead, taxa are frequently sampled to obtain at least one representative per subgroup (e.g. family) and thus to maximize diversity (diversified sampling). So far, such complications have been ignored, potentially biasing the conclusions that have been reached. In this study I derive the likelihood of a birth-death process with non-constant (time-dependent) diversification rates and diversified taxon sampling. Using simulations I test if the true parameters and the sampling method can be recovered when the trees are small or medium sized (fewer than 200 taxa). The results show that the diversification rates can be inferred and the estimates are unbiased for large trees but are biased for small trees (fewer than 50 taxa). Furthermore, model selection by means of Akaike's Information Criterion favors the true model if the true rates differ sufficiently from alternative models (e.g. the birth-death model is recovered if the extinction rate is large and compared to a pure-birth model). Finally, I applied six different diversification rate models--ranging from a constant-rate pure birth process to a decreasing speciation rate birth-death process but excluding any rate shift models--on three large-scale empirical phylogenies (ants, mammals and snakes with respectively 149, 164 and 41 sampled species). All three phylogenies were constructed by diversified taxon sampling, as stated by the authors. However only the snake phylogeny supported diversified taxon sampling. Moreover, a parametric bootstrap test revealed that none of the tested models provided a good fit to the observed data. The model assumptions, such as homogeneous rates across species or no rate shifts, appear to be

  4. Likelihood inference of non-constant diversification rates with incomplete taxon sampling.

    Directory of Open Access Journals (Sweden)

    Sebastian Höhna

    Full Text Available Large-scale phylogenies provide a valuable source to study background diversification rates and investigate if the rates have changed over time. Unfortunately most large-scale, dated phylogenies are sparsely sampled (fewer than 5% of the described species and taxon sampling is not uniform. Instead, taxa are frequently sampled to obtain at least one representative per subgroup (e.g. family and thus to maximize diversity (diversified sampling. So far, such complications have been ignored, potentially biasing the conclusions that have been reached. In this study I derive the likelihood of a birth-death process with non-constant (time-dependent diversification rates and diversified taxon sampling. Using simulations I test if the true parameters and the sampling method can be recovered when the trees are small or medium sized (fewer than 200 taxa. The results show that the diversification rates can be inferred and the estimates are unbiased for large trees but are biased for small trees (fewer than 50 taxa. Furthermore, model selection by means of Akaike's Information Criterion favors the true model if the true rates differ sufficiently from alternative models (e.g. the birth-death model is recovered if the extinction rate is large and compared to a pure-birth model. Finally, I applied six different diversification rate models--ranging from a constant-rate pure birth process to a decreasing speciation rate birth-death process but excluding any rate shift models--on three large-scale empirical phylogenies (ants, mammals and snakes with respectively 149, 164 and 41 sampled species. All three phylogenies were constructed by diversified taxon sampling, as stated by the authors. However only the snake phylogeny supported diversified taxon sampling. Moreover, a parametric bootstrap test revealed that none of the tested models provided a good fit to the observed data. The model assumptions, such as homogeneous rates across species or no rate shifts, appear

  5. Frost heave susceptibility of saturated soil under constant rate of freezing

    Science.gov (United States)

    Ryokai, K.; Iguro, M.; Yoneyama, K.

    Introduced are the results of experiments carried out to quantitatively obtain the frost heave pressure and displacement of soil subjected to artificial freezing or freezing around in-ground liquefied natural gas storage tanks. This experiment is conducted to evaluate the frost heave susceptibility of saturated soil under overconsolidation. In other words, this experiment was carried out to obtain the relation of the over-burden pressure and freezing rate to the frost heave ratio by observing the frost heave displacement and freezing time of specimens by freezing the specimens at a constant freezing rate under a constant overburden pressure, while letting water freely flow in and out of the system. Introduced are the procedures for frost heave test required to quantitatively obtain the frost heave displacement and pressure of soil. Furthermore, the relation between the frost heave susceptibility and physical properties of soil obtained by this test is reported.

  6. Electron attachment rate constant measurement by photoemission electron attachment ion mobility spectrometry (PE-EA-IMS)

    International Nuclear Information System (INIS)

    Su, Desheng; Niu, Wenqi; Liu, Sheng; Shen, Chengyin; Huang, Chaoqun; Wang, Hongmei; Jiang, Haihe; Chu, Yannan

    2012-01-01

    Photoemission electron attachment ion mobility spectrometry (PE-EA-IMS), with a source of photoelectrons induced by vacuum ultraviolet radiation on a metal surface, has been developed to study electron attachment reaction at atmospheric pressure using nitrogen as the buffer gas. Based on the negative ion mobility spectra, the rate constants for electron attachment to tetrachloromethane and chloroform were measured at ambient temperature as a function of the average electron energy in the range from 0.29 to 0.96 eV. The experimental results are in good agreement with the data reported in the literature. - Highlights: ► Photoemission electron attachment ion mobility spectrometry (PE-EA-IMS) was developed to study electron attachment reaction. ► The rate constants of electron attachment to CCl 4 and CHCl 3 were determined. ► The present experimental results are in good agreement with the previously reported data.

  7. Rate constant for the reaction of O(3P) with diacetylene from 210 to 423 K

    Science.gov (United States)

    Mitchell, M. B.; Nava, D. F.; Stief, L. J.

    1986-01-01

    The absolute rate constant for the reaction of O(3P) with diacetylene (C4H2) has been measured as a function of pressure and temperature by the flash-photolysis/resonance-fluorescence method. At 298 K and below, no pressure dependence of the rate constant was observed, but at 423 K a moderate (factor-of-2) increase was detected in the range 3 to 75 torr Ar.Results at or near the high-pressure limit are represented by an Arrhenius expression over the temperature range 210 to 423 K. The results are compared with previous determinations, all of which employed the discharge-flow/mass-spectrometry technique. The mechanism of the reaction is considered, including both primary and secondary processes. The heats of formation of the reactants, adducts, and products for the O(3P) + C4H2 reaction are discussed and contrasted with those for O(3P) + C2H2.

  8. 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...

  9. A photon spectrometric dose-rate constant determination for the Advantage™ Pd-103 brachytherapy source

    OpenAIRE

    Chen, Zhe Jay; Bongiorni, Paul; Nath, Ravinder

    2010-01-01

    Purpose: Although several dosimetric characterizations using Monte Carlo simulation and thermoluminescent dosimetry (TLD) have been reported for the new Advantage™ Pd-103 source (IsoAid, LLC, Port Richey, FL), no AAPM consensus value has been established for the dosimetric parameters of the source. The aim of this work was to perform an additional dose-rate constant (Λ) determination using a recently established photon spectrometry technique (PST) that is independent of the published TLD and ...

  10. Rate constant of free electrons and holes recombination in thin films CdSe

    International Nuclear Information System (INIS)

    Radychev, N.A.; Novikov, G.F.

    2006-01-01

    Destruction kinetics of electrons generated in thin films CdSe by laser impulse (wave length is 337 nm, period of impulse - 8 nc) is studied by the method of microwave photoconductivity (36 GHz) at 295 K. Model of the process was suggested using the analysis of kinetics of photo-responses decay, and it allowed determination of rate constant of recombination of free electrons and holes in cadmium selenide - (4-6)x10 -11 cm 3 s -1 [ru

  11. Biotransformation of trace organic chemicals during groundwater recharge: How useful are first-order rate constants?

    KAUST Repository

    Regnery, J.

    2015-05-29

    This study developed relationships between the attenuation of emerging trace organic chemicals (TOrC) during managed aquifer recharge (MAR) as a function of retention time, system characteristics, and operating conditions using controlled laboratory-scale soil column experiments simulating MAR. The results revealed that MAR performance in terms of TOrC attenuation is primarily determined by key environmental parameters (i.e. redox, primary substrate). Soil columns with suboxic and anoxic conditions performed poorly (i.e. less than 30% attenuation of moderately degradable TOrC) in comparison to oxic conditions (on average between 70-100% attenuation for the same compounds) within a residence time of three days. Given this dependency on redox conditions, it was investigated if key parameter-dependent rate constants are more suitable for contaminant transport modeling to properly capture the dynamic TOrC attenuation under field-scale conditions. Laboratory-derived first-order removal kinetics were determined for 19 TOrC under three different redox conditions and rate constants were applied to MAR field data. Our findings suggest that simplified first-order rate constants will most likely not provide any meaningful results if the target compounds exhibit redox dependent biotransformation behavior or if the intention is to exactly capture the decline in concentration over time and distance at field-scale MAR. However, if the intention is to calculate the percent removal after an extended time period and subsurface travel distance, simplified first-order rate constants seem to be sufficient to provide a first estimate on TOrC attenuation during MAR.

  12. Biotransformation of trace organic chemicals during groundwater recharge: How useful are first-order rate constants?

    Science.gov (United States)

    Regnery, J; Wing, A D; Alidina, M; Drewes, J E

    2015-08-01

    This study developed relationships between the attenuation of emerging trace organic chemicals (TOrC) during managed aquifer recharge (MAR) as a function of retention time, system characteristics, and operating conditions using controlled laboratory-scale soil column experiments simulating MAR. The results revealed that MAR performance in terms of TOrC attenuation is primarily determined by key environmental parameters (i.e., redox, primary substrate). Soil columns with suboxic and anoxic conditions performed poorly (i.e., less than 30% attenuation of moderately degradable TOrC) in comparison to oxic conditions (on average between 70-100% attenuation for the same compounds) within a residence time of three days. Given this dependency on redox conditions, it was investigated if key parameter-dependent rate constants are more suitable for contaminant transport modeling to properly capture the dynamic TOrC attenuation under field-scale conditions. Laboratory-derived first-order removal kinetics were determined for 19 TOrC under three different redox conditions and rate constants were applied to MAR field data. Our findings suggest that simplified first-order rate constants will most likely not provide any meaningful results if the target compounds exhibit redox dependent biotransformation behavior or if the intention is to exactly capture the decline in concentration over time and distance at field-scale MAR. However, if the intention is to calculate the percent removal after an extended time period and subsurface travel distance, simplified first-order rate constants seem to be sufficient to provide a first estimate on TOrC attenuation during MAR. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Constant Growth Rate Can Be Supported by Decreasing Energy Flux and Increasing Aerobic Glycolysis

    Directory of Open Access Journals (Sweden)

    Nikolai Slavov

    2014-05-01

    Full Text Available Fermenting glucose in the presence of enough oxygen to support respiration, known as aerobic glycolysis, is believed to maximize growth rate. We observed increasing aerobic glycolysis during exponential growth, suggesting additional physiological roles for aerobic glycolysis. We investigated such roles in yeast batch cultures by quantifying O2 consumption, CO2 production, amino acids, mRNAs, proteins, posttranslational modifications, and stress sensitivity in the course of nine doublings at constant rate. During this course, the cells support a constant biomass-production rate with decreasing rates of respiration and ATP production but also decrease their stress resistance. As the respiration rate decreases, so do the levels of enzymes catalyzing rate-determining reactions of the tricarboxylic-acid cycle (providing NADH for respiration and of mitochondrial folate-mediated NADPH production (required for oxidative defense. The findings demonstrate that exponential growth can represent not a single metabolic/physiological state but a continuum of changing states and that aerobic glycolysis can reduce the energy demands associated with respiratory metabolism and stress survival.

  14. An optimal policy for deteriorating items with time-proportional deterioration rate and constant and time-dependent linear demand rate

    Science.gov (United States)

    Singh, Trailokyanath; Mishra, Pandit Jagatananda; Pattanayak, Hadibandhu

    2017-12-01

    In this paper, an economic order quantity (EOQ) inventory model for a deteriorating item is developed with the following characteristics: (i) The demand rate is deterministic and two-staged, i.e., it is constant in first part of the cycle and linear function of time in the second part. (ii) Deterioration rate is time-proportional. (iii) Shortages are not allowed to occur. The optimal cycle time and the optimal order quantity have been derived by minimizing the total average cost. A simple solution procedure is provided to illustrate the proposed model. The article concludes with a numerical example and sensitivity analysis of various parameters as illustrations of the theoretical results.

  15. Prediction of ozone tropospheric degradation rate constant of organic compounds by using artificial neural networks

    International Nuclear Information System (INIS)

    Fatemi, M.H.

    2006-01-01

    Ozone tropospheric degradation of organic compound is very important in environmental chemistry. The lifetime of organic chemicals in the atmosphere can be calculated from the knowledge of the rate constant of their reaction with free radicals such as OH and NO 3 or O 3 . In the present work, the rate constant for the tropospheric degradation of 137 organic compounds by reaction with ozone, the least widely and successfully modeled degradation process, are predicted by quantitative structure activity relationships modeling based on a variety of theoretical descriptors, which screened and selected by genetic algorithm variable subset selection procedure. These descriptors which can be used as inputs for generated artificial neural networks are; HOMO-LUMO gap, number of double bonds, number of single bonds, maximum net charge on C atom, minimum (>0.1) bond order of C atom and Minimum e-e repulsion of H atom. After generation, optimization and training of artificial neural network, network was used for the prediction of log KO 3 for the validation set. The root mean square error for the neural network calculated log KO 3 for training, prediction and validation set are 0.357, 0.460 and 0.481, respectively, which are smaller than those obtained by multiple linear regressions model (1.217, 0.870 and 0.968, respectively). Results obtained reveal the reliability and good predictivity of neural network model for the prediction of ozone tropospheric degradations rate constant of organic compounds

  16. 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.

  17. An Analysis of Total Lightning Flash Rates Over Florida

    Science.gov (United States)

    Mazzetti, Thomas O.; Fuelberg, Henry E.

    2017-12-01

    Although Florida is known as the "Sunshine State", it also contains the greatest lightning flash densities in the United States. Flash density has received considerable attention in the literature, but lightning flash rate has received much less attention. We use data from the Earth Networks Total Lightning Network (ENTLN) to produce a 5 year (2010-2014) set of statistics regarding total flash rates over Florida and adjacent regions. Instead of tracking individual storms, we superimpose a 0.2° × 0.2° grid over the study region and count both cloud-to-ground (CG) and in-cloud (IC) flashes over 5 min intervals. Results show that the distribution of total flash rates is highly skewed toward small values, whereas the greatest rate is 185 flashes min-1. Greatest average annual flash rates ( 3 flashes min-1) are located near Orlando. The southernmost peninsula, North Florida, and the Florida Panhandle exhibit smaller average annual flash rates ( 1.5 flashes min-1). Large flash rates > 100 flashes min-1 can occur during any season, at any time during the 24 h period, and at any location within the domain. However, they are most likely during the afternoon and early evening in East Central Florida during the spring and summer months.

  18. Extrapolation of rate constants of reactions producing H2 and O2 in radiolysis of water at high temperatures

    International Nuclear Information System (INIS)

    Leblanc, R.; Ghandi, K.; Hackman, B.; Liu, G.

    2014-01-01

    One target of our research is to extrapolate known data on the rate constants of reactions and add corrections to estimate the rate constants at the higher temperatures reached by the SCWR reactors. The focus of this work was to extrapolate known data on the rate constants of reactions that produce Hydrogen or Oxygen with a rate constant below 10 10 mol -1 s -1 at room temperature. The extrapolation is done taking into account the change in the diffusion rate of the interacting species and the cage effect with thermodynamic conditions. The extrapolations are done over a wide temperature range and under isobaric conditions. (author)

  19. Propargyl Recombination: Estimation of the High Temperature, Low Pressure Rate Constant from Flame Measurements

    DEFF Research Database (Denmark)

    Rasmussen, Christian Lund; Skjøth-Rasmussen, Martin Skov; Jensen, Anker

    2005-01-01

    The most important cyclization reaction in hydrocarbon flames is probably recombination of propargyl radicals. This reaction may, depending on reaction conditions, form benzene, phenyl or fulvene, as well as a range of linear products. A number of rate measurements have been reported for C3H3 + C3H......3 at temperatures below 1000 K, while data at high temperature and low pressure only can be obtained from flames. In the present work, an estimate of the rate constant for the reaction at 1400 +/- 50 K and 20 Torr is obtained from analysis of the fuel-rich acetylene flame of Westmoreland, Howard...

  20. Gas-phase reaction rate constants for atmospheric pressure ionization in ion-mobility spectrometry

    International Nuclear Information System (INIS)

    Vandiver, V.J.

    1987-01-01

    Ion-mobility spectrometry (IMS) is an instrumental technique in which gaseous ions are formed from neutral molecules by proton and charge transfer from reactant ions through collisional ionization. An abbreviated rate theory has been proposed for atmospheric pressure ionization (API) in IMS, but supporting experimental measurements have not been reported. The objectives of this thesis were (1) assessment of existing API rate theory using positive and negative product ions in IMS, (2) measurement of API equilibria and kinetics for binary mixtures, and (3) investigating of cross-ionizations with multiple-product ions in API reactions. Although IMS measurements and predictions from rate theory were comparable, shapes and slopes of response curves for both proton transfer and electron capture were not described exactly by existing theory. In particular, terms that are needed for calculation of absolute rate constants were unsuitable in the existing theory. These included recombination coefficients,initial number of reactant ions, and opposing ion densities

  1. Shock tube measurements of the rate constants for seven large alkanes+OH

    KAUST Repository

    Badra, Jihad

    2015-01-01

    Reaction rate constants for seven large alkanes + hydroxyl (OH) radicals were measured behind reflected shock waves using OH laser absorption. The alkanes, n-hexane, 2-methyl-pentane, 3-methyl-pentane, 2,2-dimethyl-butane, 2,3-dimethyl-butane, 2-methyl-heptane, and 4-methyl-heptane, were selected to investigate the rates of site-specific H-abstraction by OH at secondary and tertiary carbons. Hydroxyl radicals were monitored using narrow-line-width ring-dye laser absorption of the R1(5) transition of the OH spectrum near 306.7 nm. The high sensitivity of the diagnostic enabled the use of low reactant concentrations and pseudo-first-order kinetics. Rate constants were measured at temperatures ranging from 880 K to 1440 K and pressures near 1.5 atm. High-temperature measurements of the rate constants for OH + n-hexane and OH + 2,2-dimethyl-butane are in agreement with earlier studies, and the rate constants of the five other alkanes with OH, we believe, are the first direct measurements at combustion temperatures. Using these measurements and the site-specific H-abstraction measurements of Sivaramakrishnan and Michael (2009) [1,2], general expressions for three secondary and two tertiary abstraction rates were determined as follows (the subscripts indicate the number of carbon atoms bonded to the next-nearest-neighbor carbon): S20=1.58×10-11exp(-1550K/T)cm3molecule-1s-1(887-1327K)S30=2.37×10-11exp(-1850K/T)cm3molecule-1s-1(887-1327K)S21=4.5×10-12exp(-793.7K/T)cm3molecule-1s-1(833-1440K)T100=2.85×10-11exp(-1138.3K/T)cm3molecule-1s-1(878-1375K)T101=7.16×10-12exp(-993K/T)cm3molecule-1s-1(883-1362K) © 2014 The Combustion Institute.

  2. Laser Measurements of the H Atom + Ozone Rate Constant at Atmospheric Temperatures

    Science.gov (United States)

    Liu, Y.; Smith, G. P.; Peng, J.; Reppert, K. J.; Callahan, S. L.

    2015-12-01

    The exothermic H + O3 reaction produces OH(v) Meinel band emissions, used to derive mesospheric H concentrations and chemical heating rates. We have remeasured its rate constant to reduce resulting uncertainties and the measurement extend to lower mesospheric temperatures using modern laser techniques. H atoms are produced by pulsed ultraviolet laser trace photolysis of O3, followed by reaction of O(D) with added H2. A second, delayed, frequency-mixed dye laser measures the reaction decay rate with the remaining ozone by laser induced fluorescence. We monitor either the H atom decay by 2 photon excitation at 205 nm and detection of red fluorescence, or the OH(v=9) product time evolution with excitation of the B-X (0,9) band at 237 nm and emission in blue B-A bands. By cooling the enclosed low pressure flow cell we obtained measurements from 146-305 K. Small kinetic modeling corrections are made for secondary regeneration of H atoms. The results fully confirm the current NASA JPL recommendation for this rate constant, and establish its extrapolation down to the lower temperatures of the mesosphere. This work was supported by the NSF Aeronomy Program and an NSF Physics summer REU student grant.

  3. Ozonation of norfloxacin and levofloxacin in water: Specific reaction rate constants and defluorination reaction.

    Science.gov (United States)

    Ling, Wencui; Ben, Weiwei; Xu, Ke; Zhang, Yu; Yang, Min; Qiang, Zhimin

    2018-03-01

    The degradation kinetics and mechanism of two typical fluoroquinolones (FQs), norfloxacin (NF) and levofloxacin (LOF), by ozone in water were investigated. Semi-continuous mode and competition kinetics mode experiments were conducted to determine the reaction rate constants of target FQs with ozone and OH, separately. Results indicate that both NF and LOF were highly reactive toward ozone, and the reactivity was strongly impacted by the solution pH. The specific reaction rate constants of the diprotonated, monoprotonated and deprotonated species were determined to be 7.20 × 10 2 , 8.59 × 10 3 , 4.54 × 10 5  M -1  s -1 respectively for NF and 1.30 × 10 3 , 1.40 × 10 4 , 1.33 × 10 6  M -1  s -1 respectively for LOF. The reaction rate constants of target FQs toward OH were measured to be (4.81-7.41) × 10 9  M -1  s -1 in the pH range of 6.3-8.3. Furthermore, NF was selected as a model compound to clarify the degradation pathways, with a particular focus on the defluorination reaction. The significant release of F - ions and the formation of three F-free organic byproducts indicated that defluorination was a prevalent pathway in ozonation of FQs, while six F-containing organic byproducts indicated that ozone also attacked the piperazinyl and quinolone moieties. Escherichia coli growth inhibition tests revealed that ozonation could effectively eliminate the antibacterial activity of target FQ solutions, and the residual antibacterial activity had a negative linear correlation with the released F - concentration. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. Rate Constant of the Reaction between CH3O2 Radicals and OH Radicals Revisited.

    Science.gov (United States)

    Assaf, Emmanuel; Song, Bo; Tomas, Alexandre; Schoemaecker, Coralie; Fittschen, Christa

    2016-11-17

    The reaction between CH 3 O 2 and OH radicals has been studied in a laser photolysis cell using the reaction of F atoms with CH 4 and H 2 O for the simultaneous generation of both radicals, with F atoms generated through 248 nm photolysis of XeF 2 . An experimental setup combining cw-Cavity Ring Down Spectroscopy (cw-CRDS) and high repetition rate laser-induced fluorescence (LIF) to a laser photolysis cell has been used. The absolute concentration of CH 3 O 2 was measured by cw-CRDS, while the relative concentration of OH(v = 0) radicals was determined by LIF. To remove dubiety from the quantification of CH 3 O 2 by cw-CRDS in the near-infrared, its absorption cross section has been determined at 7489.16 cm -1 using two different methods. A rate constant of k 1 = (1.60 ± 0.4) × 10 -10 cm 3 s -1 has been determined at 295 K, nearly a factor of 2 lower than an earlier determination from our group ((2.8 ± 1.4) × 10 -10 cm 3 s -1 ) using CH 3 I photolysis as a precursor. Quenching of electronically excited I atoms (from CH 3 I photolysis) in collision with OH(v = 0) is suspected to be responsible for a bias in the earlier, fast rate constant.

  5. Addition and spin exchange rate constants by longitudinal field μSR: the Mu + NO reaction

    International Nuclear Information System (INIS)

    Senba, Masayoshi; Gonzalez, A.C.; Kempton, J.R.; Arseneau, D.J.; Pan, J.J.; Tempelmann, A.; Fleming, D.G.

    1991-01-01

    The addition reaction Mu + NO + M → MuNO + M and the spin exchange reaction Mu(↑) + NO(↓)→Mu(↓)+NO(↑) have been measured by longitudinal field μSR at room temperature in the presence of up to 58 atm of N 2 as inert collider. The pressure dependence of the longitudinal relaxation rate due to the addition reaction (λ c ) demonstrates that the system is still in the low pressure regime in this pressure range. The corresponding termolecular rate constant has been determined as k 0.Mu =(1.10±0.25)x10 -32 cm 6 molecules -2 s -1 , almost 4 times smaller than the corresponding H atom reaction k 0,H =3.90x10 -32 cm 6 molecules -2 s -1 . The average value of the spin exchange rate constants in the 2.5-58 atm pressure range, k SE = (3.16±0.06)x10 -10 cm 3 molecule -1 s -1 , is in good agreement with previous values obtained by transverse field μSR. (orig.)

  6. Rate constant computation on some elementary reactions of Hg during combustion

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qing; Yang, Bo-wen; Bai, Jing-ru [Northeast Dianli Univ., Jilin (China). Inst. of Energy and Power Engineering

    2013-07-01

    The geometry optimizations of reactants, products and transition states were made by the quantum chemistry MP2 method at the SDD basis function level for Hg, and 6-311++G(3df, 3pd) for others. The properties of stable minimums were validated by vibration frequencies analysis. Furthermore, the microcosmic chemical reaction mechanisms of reactions were investigated by ab initio calculations of quantum chemistry. On the basis of the geometry optimization, reaction rate constants within 298-2,000 K are calculated neither from experimental data nor by estimated, but directly from Quantum Chemistry software-Khimera.

  7. Power consumption analysis of constant bit rate data transmission over 3G mobile wireless networks

    DEFF Research Database (Denmark)

    Wang, Le; Ukhanova, Ann; Belyaev, Evgeny

    2011-01-01

    This paper presents the analysis of the power consumption of data transmission with constant bit rate over 3G mobile wireless networks. Our work includes the description of the transition state machine in 3G networks, followed by the detailed energy consumption analysis and measurement results...... of the radio link power consumption. Based on these description and analysis, we propose power consumption model. The power model was evaluated on the smartphone Nokia N900, which follows a 3GPP Release 5 and 6 supporting HSDPA/HSPA data bearers. Further we propose method of parameters selection for 3GPP...... transition state machine that allows to decrease power consumption on the mobile device....

  8. Pseudo-extravasation rate constant of dynamic susceptibility contrast-MRI determined from pharmacokinetic first principles.

    Science.gov (United States)

    Li, Xin; Varallyay, Csanad G; Gahramanov, Seymur; Fu, Rongwei; Rooney, William D; Neuwelt, Edward A

    2017-11-01

    Dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI) is widely used to obtain informative perfusion imaging biomarkers, such as the relative cerebral blood volume (rCBV). The related post-processing software packages for DSC-MRI are available from major MRI instrument manufacturers and third-party vendors. One unique aspect of DSC-MRI with low-molecular-weight gadolinium (Gd)-based contrast reagent (CR) is that CR molecules leak into the interstitium space and therefore confound the DSC signal detected. Several approaches to correct this leakage effect have been proposed throughout the years. Amongst the most popular is the Boxerman-Schmainda-Weisskoff (BSW) K 2 leakage correction approach, in which the K 2 pseudo-first-order rate constant quantifies the leakage. In this work, we propose a new method for the BSW leakage correction approach. Based on the pharmacokinetic interpretation of the data, the commonly adopted R 2 * expression accounting for contributions from both intravascular and extravasating CR components is transformed using a method mathematically similar to Gjedde-Patlak linearization. Then, the leakage rate constant (K L ) can be determined as the slope of the linear portion of a plot of the transformed data. Using the DSC data of high-molecular-weight (~750 kDa), iron-based, intravascular Ferumoxytol (FeO), the pharmacokinetic interpretation of the new paradigm is empirically validated. The primary objective of this work is to empirically demonstrate that a linear portion often exists in the graph of the transformed data. This linear portion provides a clear definition of the Gd CR pseudo-leakage rate constant, which equals the slope derived from the linear segment. A secondary objective is to demonstrate that transformed points from the initial transient period during the CR wash-in often deviate from the linear trend of the linearized graph. The inclusion of these points will have a negative impact on the accuracy of the leakage

  9. Methane combustion kinetic rate constants determination: an ill-posed inverse problem analysis

    Directory of Open Access Journals (Sweden)

    Bárbara D. L. Ferreira

    2013-01-01

    Full Text Available Methane combustion was studied by the Westbrook and Dryer model. This well-established simplified mechanism is very useful in combustion science, for computational effort can be notably reduced. In the inversion procedure to be studied, rate constants are obtained from [CO] concentration data. However, when inherent experimental errors in chemical concentrations are considered, an ill-conditioned inverse problem must be solved for which appropriate mathematical algorithms are needed. A recurrent neural network was chosen due to its numerical stability and robustness. The proposed methodology was compared against Simplex and Levenberg-Marquardt, the most used methods for optimization problems.

  10. Rate Constants for Reactions of Radiation-Produced Transients in Aqueous Solutions of Actinides

    International Nuclear Information System (INIS)

    Gordon, S.; Sullivan, J.C.; Ross, A.B.

    1986-01-01

    Rate constants have been critically compiled for reactions of ions of the actinides Am, Cf, Cm, Np, Pu, Th, and U, as well as the element Tc, in different oxidation states with various chemical species in aqueous solution. The reactants include products of the radiolysis of water (hydrated electrons, hydrogen atoms, hydroxyl radicals, hydrogen peroxide) and transient species derived from other solutes (e.g., carbonate radical). The data are useful in the estimation of migration properties of actinides, which are relevant to waste management studies

  11. Sex differences in obesity associated with total fertility rate.

    Directory of Open Access Journals (Sweden)

    Robert Brooks

    Full Text Available The identification of biological and ecological factors that contribute to obesity may help in combating the spreading obesity crisis. Sex differences in obesity rates are particularly poorly understood. Here we show that the strong female bias in obesity in many countries is associated with high total fertility rate, which is well known to be correlated with factors such as low average income, infant mortality and female education. We also document effects of reduced access to contraception and increased inequality of income among households on obesity rates. These results are consistent with studies that implicate reproduction as a risk factor for obesity in women and that suggest the effects of reproduction interact with socioeconomic and educational factors. We discuss our results in the light of recent research in dietary ecology and the suggestion that insulin resistance during pregnancy is due to historic adaptation to protect the developing foetus during famine. Increased access to contraception and education in countries with high total fertility rate might have the additional benefit of reducing the rates of obesity in women.

  12. Rapid estimation of glucosinolate thermal degradation rate constants in leaves of Chinese kale and broccoli (Brassica oleracea) in two seasons.

    Science.gov (United States)

    Hennig, Kristin; Verkerk, Ruud; Bonnema, Guusje; Dekker, Matthijs

    2012-08-15

    Kinetic modeling was used as a tool to quantitatively estimate glucosinolate thermal degradation rate constants. Literature shows that thermal degradation rates differ in different vegetables. Well-characterized plant material, leaves of broccoli and Chinese kale plants grown in two seasons, was used in the study. It was shown that a first-order reaction is appropriate to model glucosinolate degradation independent from the season. No difference in degradation rate constants of structurally identical glucosinolates was found between broccoli and Chinese kale leaves when grown in the same season. However, glucosinolate degradation rate constants were highly affected by the season (20-80% increase in spring compared to autumn). These results suggest that differences in glucosinolate degradation rate constants can be due to variation in environmental as well as genetic factors. Furthermore, a methodology to estimate rate constants rapidly is provided to enable the analysis of high sample numbers for future studies.

  13. Relativistic quasiparticle random-phase approximation calculation of total muon capture rates

    International Nuclear Information System (INIS)

    Marketin, T.; Paar, N.; Niksic, T.; Vretenar, D.

    2009-01-01

    The relativistic proton-neutron quasiparticle random phase approximation (pn-RQRPA) is applied in the calculation of total muon capture rates on a large set of nuclei from 12 C to 244 Pu, for which experimental values are available. The microscopic theoretical framework is based on the relativistic Hartree-Bogoliubov (RHB) model for the nuclear ground state, and transitions to excited states are calculated using the pn-RQRPA. The calculation is fully consistent, i.e., the same interactions are used both in the RHB equations that determine the quasiparticle basis, and in the matrix equations of the pn-RQRPA. The calculated capture rates are sensitive to the in-medium quenching of the axial-vector coupling constant. By reducing this constant from its free-nucleon value g A =1.262 by 10% for all multipole transitions, the calculation reproduces the experimental muon capture rates to better than 10% accuracy.

  14. A note on total muon capture rates in heavy nuclei

    International Nuclear Information System (INIS)

    Parthasarathy, R.

    1978-03-01

    The results of calculations of the total capture rates in heavy nuclei, into account the nucleon velocity-dependent terms in the Fujii-Primakoff Hamiltonian and the effective mass of nucleons inside the nucleus, are presented along with the recent experimental data. The results are in general agreement with experiment. However, they indicate a possible deviation from SU(4) symmetry and, in some nuclei, support the Salam-Strathdee idea of the vanishing of the Cabibbo angle at large magnetic fields.

  15. Failure rate of cemented and uncemented total hip replacements

    DEFF Research Database (Denmark)

    Makela, K. T.; Matilainen, M.; Pulkkinen, P.

    2014-01-01

    ). Participants 347 899 total hip replacements performed during 1995-2011. Main outcome measures Probability of implant survival (Kaplan-Meier analysis) along with implant survival with revision for any reason as endpoint (Cox multiple regression) adjusted for age, sex, and diagnosis in age groups 55-64, 65......Objective To assess the failure rate of cemented, uncemented, hybrid, and reverse hybrid total hip replacements in patients aged 55 years or older. Design Register study. Setting Nordic Arthroplasty Register Association database (combined data from Sweden, Norway, Denmark, and Finland......-74, and 75 years or older. Results The proportion of total hip replacements using uncemented implants increased rapidly towards the end of the study period. The 10 year survival of cemented implants in patients aged 65 to 74 and 75 or older (93.8%, 95% confidence interval 93.6% to 94.0% and 95.9%, 95...

  16. Basic study on relationship between estimated rate constants and noise in FDG kinetic analysis

    International Nuclear Information System (INIS)

    Kimura, Yuichi; Toyama, Hinako; Senda, Michio.

    1996-01-01

    For accurate estimation of the rate constants in 18 F-FDG dynamic study, the shape of the estimation function (Φ) is crucial. In this investigation, the relationship between the noise level in tissue time activity curve and the shape of the least squared estimation function which is the sum of squared error between a function of model parameters and a measured data is calculated in 3 parameter model of 18 F-FDG. In the first simulation, by using actual plasma time activity curve, the true tissue curve was generated from known sets of rate constants ranging 0.05≤k 1 ≤0.15, 0.1≤k 2 ≤0.2 and 0.01≤k 3 ≤0.1 in 0.01 step. This procedure was repeated under various noise levels in the tissue time activity curve from 1 to 8% of the maximum value in the tissue activity. In the second simulation, plasma and tissue time activity curves from clinical 18 F-FDG dynamic study were used to calculate the Φ. In the noise-free case, because the global minima is separated from neighboring local minimums, it was easy to find out the optimum point. However, with increasing noise level, the optimum point was buried in many neighboring local minima. Making it difficult to find out the optimum point. The optimum point was found within 20% of the convergence point by standard non-linear optimization method. The shape of Φ for the clinical data was similar to that with the noise level of 3 or 5% in the first simulation. Therefore direct search within the area extending 20% from the result of usual non-linear curve fitting procedure is recommended for accurate estimation of the constants. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Greene, Samuel M., E-mail: samuel.greene@chem.ox.ac.uk; Shan, Xiao, E-mail: xiao.shan@chem.ox.ac.uk; Clary, David C., E-mail: david.clary@chem.ox.ac.u [Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ (United Kingdom)

    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.

  18. 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 ...... 10^{8}$ and $1.3\\times 10^{8}\\ {\\rm mol}^{-1}\\ {\\rm sec}^{-1}$ in pH 2.1 H2 SO4 and HClO4, respectively.......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...... of the reactions have been determined at different pH's. $k_{{\\rm Cu}^{+}+{\\rm O}_{2}}=4.6\\times 10^{5}$ and $1.0\\times 10^{6}\\ {\\rm mol}^{-1}\\ {\\rm sec}^{-1}$, $k_{{\\rm Cu}^{+}+{\\rm Fe}^{3+}}=5.5\\times 10^{6}$ and $1.3\\times 10^{7}\\ {\\rm mol}^{-1}\\ {\\rm sec}^{-1}$, $k_{{\\rm Cu}({\\rm III)}+{\\rm Fe}^{2+}}=3.3\\times...

  19. Estimation of Anaerobic Debromination Rate Constants of PBDE Pathways Using an Anaerobic Dehalogenation Model.

    Science.gov (United States)

    Karakas, Filiz; Imamoglu, Ipek

    2017-04-01

    This study aims to estimate anaerobic debromination rate constants (k m ) of PBDE pathways using previously reported laboratory soil data. k m values of pathways are estimated by modifying a previously developed model as Anaerobic Dehalogenation Model. Debromination activities published in the literature in terms of bromine substitutions as well as specific microorganisms and their combinations are used for identification of pathways. The range of estimated k m values is between 0.0003 and 0.0241 d -1 . The median and maximum of k m values are found to be comparable to the few available biologically confirmed rate constants published in the literature. The estimated k m values can be used as input to numerical fate and transport models for a better and more detailed investigation of the fate of individual PBDEs in contaminated sediments. Various remediation scenarios such as monitored natural attenuation or bioremediation with bioaugmentation can be handled in a more quantitative manner with the help of k m estimated in this study.

  20. Estimation of rate constants of PCB dechlorination reactions using an anaerobic dehalogenation model.

    Science.gov (United States)

    Karakas, Filiz; Imamoglu, Ipek

    2017-02-15

    This study aims to estimate anaerobic dechlorination rate constants (k m ) of reactions of individual PCB congeners using data from four laboratory microcosms set up using sediment from Baltimore Harbor. Pathway k m values are estimated by modifying a previously developed model as Anaerobic Dehalogenation Model (ADM) which can be applied to any halogenated hydrophobic organic (HOC). Improvements such as handling multiple dechlorination activities (DAs) and co-elution of congeners, incorporating constraints, using new goodness of fit evaluation led to an increase in accuracy, speed and flexibility of ADM. DAs published in the literature in terms of chlorine substitutions as well as specific microorganisms and their combinations are used for identification of pathways. The best fit explaining the congener pattern changes was found for pathways of Phylotype DEH10, which has the ability to remove doubly flanked chlorines in meta and para positions, para flanked chlorines in meta position. The range of estimated k m values is between 0.0001-0.133d -1 , the median of which is found to be comparable to the few available published biologically confirmed rate constants. Compound specific modelling studies such as that performed by ADM can enable monitoring and prediction of concentration changes as well as toxicity during bioremediation. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Computational study of the rate constants and free energies of intramolecular radical addition to substituted anilines

    Directory of Open Access Journals (Sweden)

    Andreas Gansäuer

    2013-08-01

    Full Text Available The intramolecular radical addition to aniline derivatives was investigated by DFT calculations. The computational methods were benchmarked by comparing the calculated values of the rate constant for the 5-exo cyclization of the hexenyl radical with the experimental values. The dispersion-corrected PW6B95-D3 functional provided very good results with deviations for the free activation barrier compared to the experimental values of only about 0.5 kcal mol−1 and was therefore employed in further calculations. Corrections for intramolecular London dispersion and solvation effects in the quantum chemical treatment are essential to obtain consistent and accurate theoretical data. For the investigated radical addition reaction it turned out that the polarity of the molecules is important and that a combination of electrophilic radicals with preferably nucleophilic arenes results in the highest rate constants. This is opposite to the Minisci reaction where the radical acts as nucleophile and the arene as electrophile. The substitution at the N-atom of the aniline is crucial. Methyl substitution leads to slower addition than phenyl substitution. Carbamates as substituents are suitable only when the radical center is not too electrophilic. No correlations between free reaction barriers and energies (ΔG‡ and ΔGR are found. Addition reactions leading to indanes or dihydrobenzofurans are too slow to be useful synthetically.

  2. Reaction of H2 with O2 in Excited Electronic States: Reaction Pathways and Rate Constants.

    Science.gov (United States)

    Pelevkin, Alexey V; Loukhovitski, Boris I; Sharipov, Alexander S

    2017-12-21

    Comprehensive quantum chemical analysis with the use of the multireference state-averaged complete active space self-consistent field approach was carried out to study the reactions of H 2 with O 2 in a 1 Δ g , b 1 Σ g + , c 1 Σ u - , and A' 3 Δ u electronically excited states. The energetically favorable reaction pathways and possible intersystem crossings have been revealed. The energy barriers were refined employing the extended multiconfiguration quasi-degenerate second-order perturbation theory. It has been shown that the interaction of O 2 (a 1 Δ g ) and O 2 (A' 3 Δ u ) with H 2 occurs through the H-abstraction process with relatively low activation barriers that resulted in the formation of the HO 2 molecule in A″ and A' electronic states, respectively. Meanwhile, molecular oxygen in singlet sigma states (b 1 Σ g + and c 1 Σ u - ) was proved to be nonreactive with respect to the molecular hydrogen. Appropriate rate constants for revealed reaction and quenching channels have been estimated using variational transition-state theory including corrections for the tunneling effect, possible nonadiabatic transitions, and anharmonicity of vibrations for transition states and reactants. It was demonstrated that the calculated reaction rate constant for the H 2 + O 2 (a 1 Δ g ) process is in reasonable agreement with known experimental data. The Arrhenius approximations for these processes have been proposed for the temperature range T = 300-3000 K.

  3. Bimolecular Rate Constants for FAD-Dependent Glucose Dehydrogenase from Aspergillus terreus and Organic Electron Acceptors.

    Science.gov (United States)

    Tsuruoka, Nozomu; Sadakane, Takuya; Hayashi, Rika; Tsujimura, Seiya

    2017-03-10

    The flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) from Aspergillus species require suitable redox mediators to transfer electrons from the enzyme to the electrode surface for the application of bioelectrical devices. Although several mediators for FAD-GDH are already in use, they are still far from optimum in view of potential, kinetics, sustainability, and cost-effectiveness. Herein, we investigated the efficiency of various phenothiazines and quinones in the electrochemical oxidation of FAD-GDH from Aspergillus terreus . At pH 7.0, the logarithm of the bimolecular oxidation rate constants appeared to depend on the redox potentials of all the mediators tested. Notably, the rate constant of each molecule for FAD-GDH was approximately 2.5 orders of magnitude higher than that for glucose oxidase from Aspergillus sp. The results suggest that the electron transfer kinetics is mainly determined by the formal potential of the mediator, the driving force of electron transfer, and the electron transfer distance between the redox active site of the mediator and the FAD, affected by the steric or chemical interactions. Higher k ₂ values were found for ortho-quinones than for para-quinones in the reactions with FAD-GDH and glucose oxidase, which was likely due to less steric hindrance in the active site in the case of the ortho-quinones.

  4. Bimolecular Rate Constants for FAD-Dependent Glucose Dehydrogenase from Aspergillus terreus and Organic Electron Acceptors

    Directory of Open Access Journals (Sweden)

    Nozomu Tsuruoka

    2017-03-01

    Full Text Available The flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH from Aspergillus species require suitable redox mediators to transfer electrons from the enzyme to the electrode surface for the application of bioelectrical devices. Although several mediators for FAD-GDH are already in use, they are still far from optimum in view of potential, kinetics, sustainability, and cost-effectiveness. Herein, we investigated the efficiency of various phenothiazines and quinones in the electrochemical oxidation of FAD-GDH from Aspergillus terreus. At pH 7.0, the logarithm of the bimolecular oxidation rate constants appeared to depend on the redox potentials of all the mediators tested. Notably, the rate constant of each molecule for FAD-GDH was approximately 2.5 orders of magnitude higher than that for glucose oxidase from Aspergillus sp. The results suggest that the electron transfer kinetics is mainly determined by the formal potential of the mediator, the driving force of electron transfer, and the electron transfer distance between the redox active site of the mediator and the FAD, affected by the steric or chemical interactions. Higher k2 values were found for ortho-quinones than for para-quinones in the reactions with FAD-GDH and glucose oxidase, which was likely due to less steric hindrance in the active site in the case of the ortho-quinones.

  5. Constant strain accumulation rate between major earthquakes on the North Anatolian Fault.

    Science.gov (United States)

    Hussain, Ekbal; Wright, Tim J; Walters, Richard J; Bekaert, David P S; Lloyd, Ryan; Hooper, Andrew

    2018-04-11

    Earthquakes are caused by the release of tectonic strain accumulated between events. Recent advances in satellite geodesy mean we can now measure this interseismic strain accumulation with a high degree of accuracy. But it remains unclear how to interpret short-term geodetic observations, measured over decades, when estimating the seismic hazard of faults accumulating strain over centuries. Here, we show that strain accumulation rates calculated from geodetic measurements around a major transform fault are constant for its entire 250-year interseismic period, except in the ~10 years following an earthquake. The shear strain rate history requires a weak fault zone embedded within a strong lower crust with viscosity greater than ~10 20  Pa s. The results support the notion that short-term geodetic observations can directly contribute to long-term seismic hazard assessment and suggest that lower-crustal viscosities derived from postseismic studies are not representative of the lower crust at all spatial and temporal scales.

  6. Dynamic Monte Carlo rate constants for magnetic Hamiltonians coupled to a phonon bath

    Science.gov (United States)

    Solomon, Lazarus; Novotny, Mark

    2007-03-01

    For quantitative comparisons between experimental time- dependent measurements and dynamic Monte Carlo simulations, a relation between the time constant in the simulation and real time is necessary. We calculate the transition rate for spin S system using the lattice frame method for a rigid spin cluster in an elastic medium [1]. We compare this with the transition rate for an Ising spin 12 system using the quantum- mechanical density-matrix method [2] with the results of ref [1,3]. These transition probabilities are different from those of either the Glauber or the Metropolis dynamics, and reflect the properties of the bosonic bath. Comparison with recent experiments [4] will be discussed. [1] E. M. Chudnovsky, D. A. Garanin, and R. Schilling (PRB 72, 2006) [2] K. Park, M. A. Novotny, and P. A. Rikvold (PRE 66, 2002) [3] K Saito, S. Takesue, and S. Miyashita, (PRE 61, 2002) [4] T. Meunier et al (Condensed Matter, 2006)

  7. Endo- and exocytic rate constants for spontaneous and protein kinase C-activated T cell receptor cycling

    DEFF Research Database (Denmark)

    Menné, Charlotte; Møller Sørensen, Tine; Siersma, Volkert

    2002-01-01

    To determine the rate constants of spontaneous and activated TCR cycling, we examined TCR endo- and exocytosis in the human T cell line Jurkat by three different methods. Using a simple kinetic model for TCR cycling and non-linear regression analyses, we found that the spontaneous endocytic rate...... constant of the TCR was low (approximately 0.012 min(-1)) whereas the spontaneous exocytic rate constant was similar to that of other cycling receptors (approximately 0.055 min(-1)). Following protein kinase C activation (PKC) the endocytic rate constant was increased tenfold (to approximately 0.128 min(-1......)) whereas the exocytic rate constant was unaffected. Thus, the TCR becomes a rapidly cycling receptor with kinetics similar to classical cycling receptors subsequent to PKC activation. This results in a reduction of the half-life of cell surface expressed TCR from approximately 58 to 6 min and allows rapid...

  8. Estimation in adults of the glomerular filtration rate in [99mTc] DTPA renography - the rate constant method

    International Nuclear Information System (INIS)

    Carlsen, Ove

    2004-01-01

    The purpose of this study was to design an alternative and robust method for estimation of glomerular filtration rate (GFR) in [ 99 mTc]-diethylenetriaminepentaacetic acid ([ 99 mTc] -DTPA renography with a reliability not significantly lower than that of the conventional Gates' method. Methods: The method is based on renographies lasting 40 min in which regions of interest (ROIs) are manually created over selected parts of certain blood pools (e.g. heart, lungs, spleen, and liver). For each ROI the corresponding time-activity curve (TAC) was generated, decay corrected and exposed to a monoexponential fit in the time interval 10 to 40 min postinjection. The rate constant in min-1 of the monoexponential fit was denoted BETA. Following an iterative procedure comprising usually 5-10 manually created ROIs, the monoexponential fit with the maximum rate constant (BETA max ) was used for estimation of GFR. Results: In a patient material of 54 adult subjects in whom GFR was determined with multiple or one sample techniques with [ 51 Cr]-ethylenediaminetetraacetic acid ([ 51 Cr]-EDTA) the regression curve of standard GFR (GFR std ) (i.e. GFR adjusted to 1.73 m 2 body surface area) showed a close, non-linear relationship with BETA max with a correlation coefficient of 95%. The standard errors of estimate (SEE) were 6.6, 10.6 and 16.8 for GFR std equal to 30, 60, and 120 ml/(min .73 m 2 ), respectively. The corresponding SEE values for almost the same patient material using Gates' method were 8.4, 11.9, and 16.8 ml/(min 1.73 m 2 ). Conclusions: The alternative rate constant method yields estimates of GFR std with SEE values equal to or slightly smaller than in Gates' method. The two methods provide statistically uncorrelated estimates of GFR std . Therefore, pooled estimates of GFR std can be calculated with SEE values approximately 1.41 times smaller than those mentioned above. The reliabilities of the pooled estimate of GFR std separately and of the multiple samples method

  9. Extension of the master sintering curve for constant heating rate modeling

    Science.gov (United States)

    McCoy, Tammy Michelle

    The purpose of this work is to extend the functionality of the Master Sintering Curve (MSC) such that it can be used as a practical tool for predicting sintering schemes that combine both a constant heating rate and an isothermal hold. Rather than just being able to predict a final density for the object of interest, the extension to the MSC will actually be able to model a sintering run from start to finish. Because the Johnson model does not incorporate this capability, the work presented is an extension of what has already been shown in literature to be a valuable resource in many sintering situations. A predicted sintering curve that incorporates a combination of constant heating rate and an isothermal hold is more indicative of what is found in real-life sintering operations. This research offers the possibility of predicting the sintering schedule for a material, thereby having advanced information about the extent of sintering, the time schedule for sintering, and the sintering temperature with a high degree of accuracy and repeatability. The research conducted in this thesis focuses on the development of a working model for predicting the sintering schedules of several stabilized zirconia powders having the compositions YSZ (HSY8), 10Sc1CeSZ, 10Sc1YSZ, and 11ScSZ1A. The compositions of the four powders are first verified using x-ray diffraction (XRD) and the particle size and surface area are verified using a particle size analyzer and BET analysis, respectively. The sintering studies were conducted on powder compacts using a double pushrod dilatometer. Density measurements are obtained both geometrically and using the Archimedes method. Each of the four powders is pressed into ¼" diameter pellets using a manual press with no additives, such as a binder or lubricant. Using a double push-rod dilatometer, shrinkage data for the pellets is obtained over several different heating rates. The shrinkage data is then converted to reflect the change in relative

  10. Direct Dynamics Simulation of the Thermal 3CH2 + 3O2 Reaction. Rate Constant and Product Branching Ratios.

    Science.gov (United States)

    Lakshmanan, Sandhiya; Pratihar, Subha; Machado, Francisco Bolivar Correto; Hase, William Louis

    2018-04-26

    The reaction of 3CH2 with 3O2 is of fundamental importance in combustion and the reaction is complex as a result of multiple extremely exothermic product channels. In the present study, direct dynamics simulations were performed to study the reaction on both the singlet and triplet potential energy surfaces (PESs). The simulations were performed at the UM06/6-311++G(d,p) level of theory. Trajectories were calculated at a temperature of 300 K and all reactive trajectories proceeded through the carbonyl oxide Criegee intermediate, CH2OO, on both the singlet and triplet PESs. The triplet surface leads to only one product channel, H2CO + O(3P), while the singlet surface leads to 8 product channels with their relative importance as: CO + H2O > CO + OH + H ~ H2CO + O(1D) > HCO + OH ~ CO2 + H2 ~ CO + H2 + O(1D) > CO2 + H + H > HCO + O(1D) + H. Reaction on the singlet PES is barrierless, consistent with experiment and the total rate constant on the singlet surface is 0.93 ± 0.22 x 10-12 cm3molecule-1s-1 in comparison to the recommended experimental rate constant of 3.3 x 10-12 cm3molecule-1s-1. The simulation product yields for the singlet PES are compared with experiment and the most significant differences are for H, CO2, and H2O. Reaction on the triplet surface is also barrierless, inconsistent with experiment. A discussion is given of the need for future calculations to address the: (1) barrier on the triplet PES for 3CH2 + 3O2 → 3CH2OO; (2) temperature dependence of the 3CH2 + 3O2 reaction rate constant and product branching ratios; and (3) possible non-RRKM dynamics of the 1CH2OO Criegee intermediate.

  11. A photon spectrometric dose-rate constant determination for the Advantage Pd-103 brachytherapy source

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhe Jay; Bongiorni, Paul; Nath, Ravinder [Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06520 (United States)

    2010-02-15

    Purpose: Although several dosimetric characterizations using Monte Carlo simulation and thermoluminescent dosimetry (TLD) have been reported for the new Advantage Pd-103 source (IsoAid, LLC, Port Richey, FL), no AAPM consensus value has been established for the dosimetric parameters of the source. The aim of this work was to perform an additional dose-rate constant ({Lambda}) determination using a recently established photon spectrometry technique (PST) that is independent of the published TLD and Monte Carlo techniques. Methods: Three Model IAPD-103A Advantage Pd-103 sources were used in this study. The relative photon energy spectrum emitted by each source along the transverse axis was measured using a high-resolution germanium spectrometer designed for low-energy photons. For each source, the dose-rate constant was determined from its emitted energy spectrum. The PST-determined dose-rate constant ({sub PST}{Lambda}) was then compared to those determined by TLD ({sub TLD}{Lambda}) and Monte Carlo ({sub MC}{Lambda}) techniques. A likely consensus {Lambda} value was estimated as the arithmetic mean of the average {Lambda} values determined by each of three different techniques. Results: The average {sub PST}{Lambda} value for the three Advantage sources was found to be (0.676{+-}0.026) cGyh{sup -1} U{sup -1}. Intersource variation in {sub PST}{Lambda} was less than 0.01%. The {sub PST}{Lambda} was within 2% of the reported {sub MC}{Lambda} values determined by PTRAN, EGSnrc, and MCNP5 codes. It was 3.4% lower than the reported {sub TLD}{Lambda}. A likely consensus {Lambda} value was estimated to be (0.688{+-}0.026) cGyh{sup -1} U{sup -1}, similar to the AAPM consensus values recommended currently for the Theragenics (Buford, GA) Model 200 (0.686{+-}0.033) cGyh{sup -1} U{sup -1}, the NASI (Chatsworth, CA) Model MED3633 (0.688{+-}0.033) cGyh{sup -1} U{sup -1}, and the Best Medical (Springfield, VA) Model 2335 (0.685{+-}0.033) cGyh{sup -1} U{sup -1} {sup 103}Pd

  12. A photon spectrometric dose-rate constant determination for the Advantage Pd-103 brachytherapy source

    International Nuclear Information System (INIS)

    Chen, Zhe Jay; Bongiorni, Paul; Nath, Ravinder

    2010-01-01

    Purpose: Although several dosimetric characterizations using Monte Carlo simulation and thermoluminescent dosimetry (TLD) have been reported for the new Advantage Pd-103 source (IsoAid, LLC, Port Richey, FL), no AAPM consensus value has been established for the dosimetric parameters of the source. The aim of this work was to perform an additional dose-rate constant (Λ) determination using a recently established photon spectrometry technique (PST) that is independent of the published TLD and Monte Carlo techniques. Methods: Three Model IAPD-103A Advantage Pd-103 sources were used in this study. The relative photon energy spectrum emitted by each source along the transverse axis was measured using a high-resolution germanium spectrometer designed for low-energy photons. For each source, the dose-rate constant was determined from its emitted energy spectrum. The PST-determined dose-rate constant ( PST Λ) was then compared to those determined by TLD ( TLD Λ) and Monte Carlo ( MC Λ) techniques. A likely consensus Λ value was estimated as the arithmetic mean of the average Λ values determined by each of three different techniques. Results: The average PST Λ value for the three Advantage sources was found to be (0.676±0.026) cGyh -1 U -1 . Intersource variation in PST Λ was less than 0.01%. The PST Λ was within 2% of the reported MC Λ values determined by PTRAN, EGSnrc, and MCNP5 codes. It was 3.4% lower than the reported TLD Λ. A likely consensus Λ value was estimated to be (0.688±0.026) cGyh -1 U -1 , similar to the AAPM consensus values recommended currently for the Theragenics (Buford, GA) Model 200 (0.686±0.033) cGyh -1 U -1 , the NASI (Chatsworth, CA) Model MED3633 (0.688±0.033) cGyh -1 U -1 , and the Best Medical (Springfield, VA) Model 2335 (0.685±0.033) cGyh -1 U -1 103 Pd sources. Conclusions: An independent Λ determination has been performed for the Advantage Pd-103 source. The PST Λ obtained in this work provides additional information

  13. Rate constants and mechanisms for the crystallization of Al nano-goethite under environmentally relevant conditions

    Science.gov (United States)

    Bazilevskaya, Ekaterina; Archibald, Douglas D.; Martínez, Carmen Enid

    2012-07-01

    Mobile inorganic and organic nanocolloidal particles originate-from and interact-with bulk solid phases in soil and sediment environments, and as such, they contribute to the dynamic properties of environmental systems. In particular, ferrihydrite and (nano)goethite are the most abundant of nanocolloidal Fe oxy(hydr)oxides in these environments. We therefore investigated the ferrihydrite to goethite phase transformation using experimental reaction conditions that mimicked environmental conditions where the formation of nanocolloidal Fe oxy(hydr)oxides may occur: slow titration of dilute solutions to pH 5 at 25 °C with and without 2 mol% Al. Subsequently, the rate constants from 54-d nano-goethite aging/crystallization experiments at 50 °C were determined using aliquots pulled for vibrational spectroscopy (including multivariate curve resolution, MCR, analyses of infrared spectra) and synchrotron-based X-ray diffraction (XRD). We also present a mechanistic model that accounts for the nano-goethite crystallization observed by the aforementioned techniques, and particle structural characteristics observed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). In contrast to the common assumption that metastable ferrihydrite precipitates first, before it transforms to goethite, the presence of characteristic infrared bands in freshly synthesized nanoparticle suspensions indicate goethite can precipitate directly from solution under environmentally relevant conditions: low Fe concentration, ambient temperature, and pH maintained at 5. However, the presence of 2 mol% Al prevented direct goethite precipitation. Rate constants obtained by fitting the contributions from the MCR-derived goethite-like component to the OH-stretching region were (7.4 ± 1.1) × 10-7 s-1 for 0% Al and (4.2 ± 0.4) × 10-7 s-1 for 2 mol% Al suspensions. Rate constants derived from intensities of OH-bending infrared vibrations (795 and 895 cm-1) showed similar values

  14. Uptake rate constants and partition coefficients for vapor phase organic chemicals using semipermeable membrane devices (SPMDs)

    Science.gov (United States)

    Cranor, W.L.; Alvarez, D.A.; Huckins, J.N.; Petty, J.D.

    2009-01-01

    To fully utilize semipermeable membrane devices (SPMDs) as passive samplers in air monitoring, data are required to accurately estimate airborne concentrations of environmental contaminants. Limited uptake rate constants (kua) and no SPMD air partitioning coefficient (Ksa) existed for vapor-phase contaminants. This research was conducted to expand the existing body of kinetic data for SPMD air sampling by determining kua and Ksa for a number of airborne contaminants including the chemical classes: polycyclic aromatic hydrocarbons, organochlorine pesticides, brominated diphenyl ethers, phthalate esters, synthetic pyrethroids, and organophosphate/organosulfur pesticides. The kuas were obtained for 48 of 50 chemicals investigated and ranged from 0.03 to 3.07??m3??g-1??d-1. In cases where uptake was approaching equilibrium, Ksas were approximated. Ksa values (no units) were determined or estimated for 48 of the chemicals investigated and ranging from 3.84E+5 to 7.34E+7. This research utilized a test system (United States Patent 6,877,724 B1) which afforded the capability to generate and maintain constant concentrations of vapor-phase chemical mixtures. The test system and experimental design employed gave reproducible results during experimental runs spanning more than two years. This reproducibility was shown by obtaining mean kua values (n??=??3) of anthracene and p,p???-DDE at 0.96 and 1.57??m3??g-1??d-1 with relative standard deviations of 8.4% and 8.6% respectively.

  15. Rate constants for the slow Mu + propane abstraction reaction at 300 K by diamagnetic RF resonance.

    Science.gov (United States)

    Fleming, Donald G; Cottrell, Stephen P; McKenzie, Iain; Ghandi, Khashayar

    2015-08-14

    The study of kinetic isotope effects for H-atom abstraction rates by incident H-atoms from the homologous series of lower mass alkanes (CH4, C2H6 and, here, C3H8) provides important tests of reaction rate theory on polyatomic systems. With a mass of only 0.114 amu, the most sensitive test is provided by the rates of the Mu atom. Abstraction of H by Mu can be highly endoergic, due to the large zero-point energy shift in the MuH bond formed, which also gives rise to high activation energies from similar zero-point energy corrections at the transition state. Rates are then far too slow near 300 K to be measured by conventional TF-μSR techniques that follow the disappearance of the spin-polarised Mu atom with time. Reported here is the first measurement of a slow Mu reaction rate in the gas phase by the technique of diamagnetic radio frequency (RF) resonance, where the amplitude of the MuH product formed in the Mu + C3H8 reaction is followed with time. The measured rate constant, kMu = (6.8 ± 0.5) × 10(-16) cm(3) s(-1) at 300 K, is surprisingly only about a factor of three slower than that expected for H + C3H8, indicating a dominant contribution from quantum tunneling in the Mu reaction, consistent with elementary transition state theory calculations of the kMu/kH kinetic isotope effect.

  16. Hysteresis behaviour of silver sputtered in different plasma atmospheres at constant flow rates

    International Nuclear Information System (INIS)

    Rizk, A.; Makar, L.N.; Rizk, N.S.; Shinoda, R.

    1990-01-01

    The effects of ion bombardment on sputtering behaviour of pure silver targets in inert and active gas atmospheres were investigated, using a dc planar magnetron sputtering system. The obtained current-voltage characteristics showed the formation of hysteresis loops without noticeable sharp transitions. Redeposited layers of silver nitride or silver oxide on the target surface when using nitrogen or oxygen in the glow discharge, residual ionization when using dry argon atmosphere were considered the main reasons for the occurrence of these loops. The results indicate that films of AgN x and AgO x can be deposited with controlled x in the range 0 ≤ x ≤ 1 using voltage control at constant gas flow rates. (author)

  17. Power consumption analysis of constant bit rate video transmission over 3G networks

    DEFF Research Database (Denmark)

    Ukhanova, Ann; Belyaev, Evgeny; Wang, Le

    2012-01-01

    This paper presents an analysis of the power consumption of video data transmission with constant bit rate over 3G mobile wireless networks. The work includes the description of the radio resource control transition state machine in 3G networks, followed by a detailed power consumption analysis...... and measurements of the radio link power consumption. Based on this description and analysis, we propose our power consumption model. The power model was evaluated on a smartphone Nokia N900, which follows 3GPP Release 5 and 6 supporting HSDPA/HSUPA data bearers. We also propose a method for parameter selection...... for the 3GPP transition state machine that allows to decrease power consumption on a mobile device taking signaling traffic, buffer size and latency restrictions into account. Furthermore, we discuss the gain in power consumption vs. PSNR for transmitted video and show the possibility of performing power...

  18. 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......Hypochlorous acid (HOCl) is a potent oxidant, which is produced in vivo by activated phagocytes. This compound is an important antibacterial agent, but excessive or misplaced production has been implicated in a number of human diseases, including atherosclerosis, arthritis, and some cancers....... Proteins are major targets for this oxidant, and such reaction results in side-chain modification, backbone fragmentation, and cross-linking. Despite a wealth of qualitative data for such reactions, little absolute kinetic data is available to rationalize the in vitro and in vivo data. In this study...

  19. Stress relaxation of entangled polystyrene solution after constant-rate, uniaxial elongation

    DEFF Research Database (Denmark)

    Matsumiya, Yumi; Masubuchi, Yuichi; Watanabe, Hiroshi

    For an entangled solution of linear polystyrene (PS 545k; M = 545k) in dibutyl phthalate (DBP), the stress relaxation after constant-rate uniaxial elongation was examined with an extensional viscosity fixture mounted on ARES (TA Instruments). The PS concentration, c = 52 wt%, was chosen in a way...... that the entanglement density M/Me of the solution coincided with that of PS 290k melt (M = 290k). After the elongation at the Rouse-based Weissenberg number Wi(R) ~ 3 up to the Hencky strain of 3, the short time stress relaxation of the solution was accelerated by a factor of ~4, which was less significant compared...... and the lack of monotonic thinning observed for the semidilute solutions. Results for less concentrated solutions will be also presented on site....

  20. Constant extension rate testing of Type 304L stainless steel in simulated waste tank environments

    International Nuclear Information System (INIS)

    Wiersma, B.J.

    1992-01-01

    New tanks for storage of low level radioactive wastes will be constructed at the Savannah River Site (SRS) of AISI Type 304L stainless steel (304L). The presence of chlorides and fluorides in the wastes may induce Stress Corrosion Cracking (SCC) in 304L. Constant Extension Rate Tests (CERT) were performed to determine the susceptibility of 304L to SCC in simulated wastes. In five of the six tests conducted thus far 304L was not susceptible to SCC in the simulated waste environments. Conflicting results were obtained in the final test and will be resolved by further tests. For comparison purposes the CERT tests were also performed with A537 carbon steel, a material similar to that utilized for the existing nuclear waste storage tanks at SRS

  1. A constant velocity Moessbauer spectrometer free of long-term instrumental drifts in the count rate

    International Nuclear Information System (INIS)

    Sarma, P.R.; Sharma, A.K.; Tripathi, K.C.

    1979-01-01

    Two new control circuits to be used with a constant velocity Moessbauer spectrometer with a loud-speaker drive have been described. The wave-forms generated in the circuits are of the stair-case type instead of the usual square wave-form, so that in each oscillation of the source it remains stationary for a fraction of the time-period. The gamma-rays counted during this period are monitored along with the positive and negative velocity counts and are used to correct any fluctuation in the count rate by feeding these pulses into the timer. The associated logic circuits have been described and the statistical errors involved in the circuits have been computed. (auth.)

  2. Surface hopping, transition state theory, and decoherence. II. Thermal rate constants and detailed balance

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Amber; Subotnik, Joseph E., E-mail: subotnik@sas.upenn.edu [Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104 (United States)

    2015-10-07

    We investigate a simple approach to compute a non-adiabatic thermal rate constant using the fewest switches surface hopping (FSSH) dynamics. We study the effects of both decoherence (using our augmented-FSSH (A-FSSH) algorithm) and forbidden hops over a large range of parameters, including high and low friction regimes, and weak and strong electronic coupling regimes. Furthermore, when possible, we benchmark our results against exact hierarchy equations of motion results, where we usually find a maximum error of roughly a factor of two (at reasonably large temperatures). In agreement with Hammes-Schiffer and Tully, we find that a merger of transition state theory and surface hopping can be both accurate and efficient when performed correctly. We further show that detailed balance is followed approximately by A-FSSH dynamics.

  3. Sedative and cardiorespiratory effects of detomidine constant rate infusion in sheep.

    Science.gov (United States)

    de Moura, Rauane Sousa; Bittar, Isabela Plazza; da Silva, Luiz Henrique; Villela, Ana Carolina Vasquez; Dos Santos Júnior, Marcelo Borges; Borges, Naida Cristina; Franco, Leandro Guimarães

    2018-02-01

    The use of sheep in experiments is widespread and is increasing worldwide, and so is the need to develop species-specific anaesthetic techniques to ensure animal safety. Previous studies have mentioned several protocols involving the administration of alpha-2 adrenergic agonists in sheep; however, assessment of the efficacy and safety of these infusion techniques is still relatively new. Thus, the aim of the present study is to assess the effectiveness of detomidine constant rate infusion (CRI) in sheep by measuring the cardiovascular and respiratory parameters, blood gas variables and sedation scores. Eight adult female Santa Inês sheep received 20 µg/kg of detomidine hydrochloride intravenously as a bolus loading dose, followed by an infusion rate of 60 µg/kg/h. The heart rates and respiratory rates changed continuously during the CRI period. No arrhythmias were observed. The reduction in arterial partial pressure of oxygen (PaO 2 ) was not significant, but one animal showed signs of hypoxaemia (minimum PaO 2 of 66.9 mmHg). The arterial partial pressure of carbon dioxide (PaCO 2 ) increased, but the animals did not become hypercapnic. The bicarbonate (HCO 3- ), pH and base excess (BE) tended towards metabolic alkalosis. The cardiac output (CO), stroke volume (SV), cardiac index (CI) and ejection fraction (EF%) showed no significant changes. The fractional shortening (FS%) decreased slightly, starting at T 45min . Sedation scores varied between 3 (0/10) after sedation and during recovery and 7 (0/10) during CRI. We concluded that administering detomidine at an infusion rate of 60 µg/kg/h in Santa Inês sheep is a simple technique that produces satisfactory sedation for minimally invasive procedures.

  4. Direct measurements of methoxy removal rate constants for collisions with CH4, Ar, N2, Xe, and CF4 in the temperature range 673--973K

    International Nuclear Information System (INIS)

    Wantuck, P.J.; Oldenborg, R.C.; Baugchum, S.L.; Winn, K.R.

    1988-01-01

    Removal rate constants for CH 3 O by CH 4 , Ar, N 2 , Xe, and CF 4 were measured over a 400K temperature range using a laser photolysis/laser-induced fluorescence technique. Rapid methoxy removal rates are observed for the non-reactive collision partners (Ar, N 2 , Xe, and CF 4 ) at elevated temperatures showing that the dissociation and isomerization channels for CH 3 O are indeed important. The total removal rate constant (reaction /plus/ dissociation and/or isomerization) for CH 4 exhibits a linear dependence on temperature and has a removal rate constant, k/sub r/ /equals/ (1.2 +- 0.6) /times/ 10/sup /minus/8/exp[(/minus/101070 +- 350)/T]cm 3 molecule/sup /minus/1/s/sup /minus/1/. Assuming that the removal rate constant due to dissociation and/or isomerization are similar for CH 4 and CF 4 , the reaction rate constant for CH 3 O /plus/ CH 4 is equal to (1.7 +- 1.0) /times/ 10/sup /minus/10/exp[(/minus/7480 +- 1100)/T]cm 3 molecule/sup /minus/1/s/sup /minus/1/. 7 refs., 4 figs

  5. A Unified Kinetics and Equilibrium Experiment: Rate Law, Activation Energy, and Equilibrium Constant for the Dissociation of Ferroin

    Science.gov (United States)

    Sattar, Simeen

    2011-01-01

    Tris(1,10-phenanthroline)iron(II) is the basis of a suite of four experiments spanning 5 weeks. Students determine the rate law, activation energy, and equilibrium constant for the dissociation of the complex ion in acid solution and base dissociation constant for phenanthroline. The focus on one chemical system simplifies a daunting set of…

  6. Assessment of volumetric-modulated arc therapy for constant and variable dose rates

    Directory of Open Access Journals (Sweden)

    Mariluz De Ornelas-Couto

    2017-01-01

    Full Text Available Purpose: The aim of this study is to compare the effects of dose rate on volumetric-modulated arc therapy plans to determine optimal dose rates for prostate and head and neck (HN cases. Materials and Methods: Ten prostate and ten HN cases were retrospectively studied. For each case, seven plans were generated: one variable dose rate (VDR and six constant dose rate (CDR (100–600 monitor units [MUs]/min plans. Prescription doses were: 80 Gy to planning target volume (PTV for the prostate cases, and 70, 60, and 54 Gy to PTV1, PTV2, and PTV3, respectively, for HN cases. Plans were normalized to 95% of the PTV and PTV1, respectively, with the prescription dose. Plans were assessed using Dose-Volume-Histogram metrics, homogeneity index, conformity index, MUs, and delivery time. Results: For the prostate cases, significant differences were found for rectum D35 between VDR and all CDR plans, except CDR500. Furthermore, VDR was significantly different than CDR100 and 200 for bladder D50. Delivery time for all CDR plans and MUs for CDR400–600 were significantly higher when compared to VDR. HN cases showed significant differences between VDR and CDR100, 500 and 600 for D2 to the cord and brainstem. Significant differences were found for delivery time and MUs for all CDR plans, except CDR100 for number of MUs. Conclusion: The most significant differences were observed in delivery time and number of MUs. All-in-all, the best CDR for prostate cases was found to be 300 MUs/min and 200 or 300 MUs/min for HN cases. However, VDR plans are still the choice in terms of MU efficiency and plan quality.

  7. Determination of hydroxyl rate constants by a high-throughput fluorimetric assay: towards a unified reactivity scale for antioxidants

    International Nuclear Information System (INIS)

    Louit, G.; Renault, J.P.; Pin, S.; Coffigny, H.; Hanedanian, M.; Taran, F.; Renault, J.P.; Pin, S.

    2009-01-01

    We describe in this article the development of a new method for the determination of rate constants of reaction of the hydroxyl radical, generated by radiolysis of water, with almost any possible molecule. It has been designed to provide a fast and reliable screening of antioxidant banks using microplates. Our particular approach is based on the use of the coumarin molecule as a competitor against the tested molecules: after a fast pulse of low dose irradiation, the fluorescence of 7-hydroxycoumarin produced by the oxidation of coumarin is measured and is inversely proportional to the scavenging ability of the tested antioxidant. We have validated our protocol using 32 molecules whose rate constants with HO . had already been evaluated and found a good agreement between our rate constants and the latter ones. The scopes and limitations of our method, as well as those of other rate constant determination methods, are discussed. (authors)

  8. Theoretical growth rates, periods, and pulsation constants for long-period variables

    International Nuclear Information System (INIS)

    Fox, M.W.; Wood, P.R.

    1982-01-01

    Theoretical values of the growth rate, period, and pulsation constant for the first three radial pulsation modes in red giants (Population II and galactic disk) and supergiants have been derived in the linear, nonadiabatic approximation. The effects of altering the surface boundary conditions, the effective temperature (or mixing length), and the opacity in the outer layers have been explored. In the standard models, the Q-value for the first overtone can be much larger (Q 1 1 roughly-equal0.04); in addition, the Q-value for the fundamental mode is reduced from previous values, as is the period ratio P 0 /P 1 . The growth rate for the fundamental mode is found to increase with luminosity on the giant branch while the growth rate for the first overtone decreases. Dynamical instabilities found in previous adiabatic models of extreme red giants do not occur when nonadiabatic effects are included in the models. In some massive, luminous models, period ratios P 0 /P 1 approx.7 occur when P 0 approx.2000--5000 days; it is suggested that the massive galactic supergiants and carbon stars which have secondary periods Papprox.2000--7000 days and primary periods Papprox.300--700 days are first-overtone pulsators in which the long secondary periods are due to excitation of the fundamental mode. Some other consequences of the present results are briefly discussed, with particular emphasis on the mode of pulsation of the Mira variables. Subject headings: stars: long-period variables: stars: pulsation: stars: supergiants

  9. Study of optical non-linear properties of a constant total effective length multiple quantum wells system

    International Nuclear Information System (INIS)

    Solaimani, M.; Morteza, Izadifard; Arabshahi, H.; Reza, Sarkardehi Mohammad

    2013-01-01

    In this work, we have studied the effect of the number of the wells, in a multiple quantum wells structure with constant total effective length, on the optical properties of multiple quantum wells like the absorption coefficient and the refractive index by means of compact density matrix approach. GaAs/Al x Ga (1−x) As multiple quantum wells systems was selected as an example. Besides, the effect of varying number of wells on the subband energies, wave functions, number of bound states, and the Fermi energy have been also investigated. Our calculation revealed that the number of wells in a multiple quantum well is a criterion with which we can control the amount of nonlinearity. This study showed that for the third order refractive index change there is two regimes of variations and the critical well number was six. In our calculations, we have used the same wells and barrier thicknesses to construct the multiple quantum wells system. - Highlights: ► OptiOptical Non-Linear. ► Total Effective Length. ► Multiple Quantum Wells System - genetic algorithm ► Schrödinger equation solution. ► Nanostructure.

  10. Experimental determination of the high-temperature rate constant for the reaction of OH with sec-butanol.

    Science.gov (United States)

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

    2012-10-04

    The overall rate constant for the reaction of OH with sec-butanol [CH(3)CH(OH)CH(2)CH(3)] was determined from measurements of the near-first-order OH decay in shock-heated mixtures of tert-butylhydroperoxide (as a fast source of OH) with sec-butanol in excess. Three kinetic mechanisms from the literature describing sec-butanol combustion were used to examine the sensitivity of the rate constant determination to secondary kinetics. The overall rate constant determined can be described by the Arrhenius expression 6.97 × 10(-11) exp(-1550/T[K]) cm(3) molecule(-1) s(-1), valid over the temperature range of 888-1178 K. Uncertainty bounds of ±30% were found to adequately account for the uncertainty in secondary kinetics. To our knowledge, the current data represent the first efforts toward an experimentally determined rate constant for the overall reaction of OH with sec-butanol at combustion-relevant temperatures. A rate constant predicted using a structure-activity relationship from the literature was compared to the current data and previous rate constant measurements for the title reaction at atmospheric-relevant temperatures. The structure-activity relationship was found to be unable to correctly predict the measured rate constant at all temperatures where experimental data exist. We found that the three-parameter fit of 4.95 × 10(-20)T(2.66) exp(+1123/T[K]) cm(3) molecule(-1) s(-1) better describes the overall rate constant for the reaction of OH with sec-butanol from 263 to 1178 K.

  11. SU-G-201-06: Directional Low-Dose Rate Brachytherapy: Determination of the TG-43 Dose-Rate Constant Analog for a New Pd-103 Source

    Energy Technology Data Exchange (ETDEWEB)

    Aima, M; Culberson, W; Hammer, C; Micka, J; DeWerd, L [Department of Medical Physics, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI (United States)

    2016-06-15

    Purpose: The aim of this work is to determine the TG-43 dose-rate constant analog for a new directional low-dose rate brachytherapy source based on experimental methods and comparison to Monte Carlo simulations. The CivaSheet™ is a new commercially available planar source array comprised of a variable number of discrete directional source elements called “CivaDots”. Given the directional nature and non-conventional design of the source, modifications to the AAPM TG-43 protocol for dosimetry are required. As a result, various parameters of the TG-43 dosimetric formalism have to be adapted to accommodate this source. This work focuses on the dose-rate constant analog determination for a CivaDot. Methods: Dose to water measurements of the CivaDot were performed in a polymethyl methacrylate phantom (20×20×12 cm{sup 3}) using thermoluminescent dosimeters (TLDs) and Gafchromic EBT3 film. The source was placed in the center of the phantom, and nine TLD micro-cubes were irradiated along its central axis at a distance of 1 cm. For the film measurements, the TLDs were substituted by a (3×3) cm{sup 2} EBT3 film. Primary air-kerma strength measurements of the source were performed using a variable-aperture free-air chamber. Finally, the source was modeled using the Monte Carlo N-Particle Transport Code 6. Results: Dose-rate constant analog observed for a total of eight CivaDots using TLDs and five CivaDots using EBT3 film was within ±7.0% and ±2.9% of the Monte Carlo predicted value respectively. The average difference observed was −4.8% and −0.1% with a standard deviation of 1.7% and 2.1% for the TLD and the film measurements respectively, which are both within the comparison uncertainty. Conclusion: A preliminary investigation to determine the doserate constant analog for a CivaDot was conducted successfully with good agreement between experimental and Monte Carlo based methods. This work will aid in the eventual realization of a clinically-viable dosimetric

  12. Multi-target QSPR modeling for simultaneous prediction of multiple gas-phase kinetic rate constants of diverse chemicals

    Science.gov (United States)

    Basant, Nikita; Gupta, Shikha

    2018-03-01

    The reactions of molecular ozone (O3), hydroxyl (•OH) and nitrate (NO3) radicals are among the major pathways of removal of volatile organic compounds (VOCs) in the atmospheric environment. The gas-phase kinetic rate constants (kO3, kOH, kNO3) are thus, important in assessing the ultimate fate and exposure risk of atmospheric VOCs. Experimental data for rate constants are not available for many emerging VOCs and the computational methods reported so far address a single target modeling only. In this study, we have developed a multi-target (mt) QSPR model for simultaneous prediction of multiple kinetic rate constants (kO3, kOH, kNO3) of diverse organic chemicals considering an experimental data set of VOCs for which values of all the three rate constants are available. The mt-QSPR model identified and used five descriptors related to the molecular size, degree of saturation and electron density in a molecule, which were mechanistically interpretable. These descriptors successfully predicted three rate constants simultaneously. The model yielded high correlations (R2 = 0.874-0.924) between the experimental and simultaneously predicted endpoint rate constant (kO3, kOH, kNO3) values in test arrays for all the three systems. The model also passed all the stringent statistical validation tests for external predictivity. The proposed multi-target QSPR model can be successfully used for predicting reactivity of new VOCs simultaneously for their exposure risk assessment.

  13. Bioaccessibility of metal cations in soil is linearly related to its water exchange rate constant.

    Science.gov (United States)

    Laird, Brian D; Peak, Derek; Siciliano, Steven D

    2011-05-01

    Site-specific risk assessments often incorporate the concepts of bioaccessibility (i.e., contaminant fraction released into gastrointestinal fluids) or bioavailability (i.e., contaminant fraction absorbed into systemic circulation) into the calculation of ingestion exposure. We evaluated total and bioaccessible metal concentrations for 19 soil samples under simulated stomach and duodenal conditions using an in vitro gastrointestinal model. We demonstrated that the median bioaccessibility of 23 metals ranged between exchange rates of metal cations (k(H₂O)) indicated that desorption kinetics may influence if not control metal bioaccessibility.

  14. Determination of the rate constant for neuronal and extra-neuronal monoamine oxidase

    International Nuclear Information System (INIS)

    Cassis, L.; Ludwig, J.; Trendelenburg, U.

    1986-01-01

    In the rat vas deferens, neuronal deamination of 3 H-(-) noradrenaline ( 3 H-NA) to 3 H-dihydroxyphenethylglycol ( 3 HDOPEG) cannot be inhibited by pretreatment with a monoamine oxidase (MAO) inhibitor. However, in the extraneuronal compartment of the rat heart, inhibition of MAO abolishes the formation of 3 HDOPEG. To clarify this discrepancy, the authors determined the rate constant for MAO (/sup k/mao/) neuronally (rat vas deferens) and extraneuronally (rat heart). For neuronal /sup k/mao, vasa deferentia were incubated with 3 HNA for 300 minutes, and the cumulative formation of 3 HDOPEG measured. The delay in time before 3 HDOPEG achieves steady state (/sup tau/system), is inversely proportional to /sup k/mao. Because /sup tau/system is very short for neuronal MAO, an appreciable delay was only achieved after partial inhibition of MAO with various parglyline concentrations. To relate to the uninhibited enzyme, the percentage inhibition by pargyline was then determined in homogenate preparations. For extraneuronal MAO, a similar procedure was performed in perfused rat hearts. Results show a significantly greater /sup k/mao of neuronal origin, (/sup k/mao = .57min - 1) which when related to the fractional size of the neuronal compartment suggests a very high activity of neuronal MAO

  15. Application of the constant rate of pressure change method to improve jet pump performance

    International Nuclear Information System (INIS)

    Long, X P; Yang, X L

    2012-01-01

    This paper adopts a new method named the constant rate of pressure change (CRPC) to improve the jet pump performance. The main contribution of this method is that the diffuser generates uniform pressure gradient. The performance of the jet pump with new diffusers designed by the CRPC method, obtained by CFD methods, was compared with that of the jet pump with traditional conical diffusers. It is found that the CRPC diffuser produces a linear pressure increase indeed. The higher friction loss and the separation decrease the CRPC diffuser efficiency and then lower the pump efficiency. The pump with shorter throats has higher efficiency at small flow ratio while its efficiency is lower than the original pump at lager flow ratio and the peak efficiency of the pumps with the throat length of 5-6 Dt is higher than that of the pumps with other throat length. When the throat length is less than 4 Dt, the CRPC diffuser efficiency is higher than the conical diffuser. The CRPC method could also be used to design the nozzle and other situations needing the pressure change gradually.

  16. Detection of exudates in fundus imagery using a constant false-alarm rate (CFAR) detector

    Science.gov (United States)

    Khanna, Manish; Kapoor, Elina

    2014-05-01

    Diabetic retinopathy is the leading cause of blindness in adults in the United States. The presence of exudates in fundus imagery is the early sign of diabetic retinopathy so detection of these lesions is essential in preventing further ocular damage. In this paper we present a novel technique to automatically detect exudates in fundus imagery that is robust against spatial and temporal variations of background noise. The detection threshold is adjusted dynamically, based on the local noise statics around the pixel under test in order to maintain a pre-determined, constant false alarm rate (CFAR). The CFAR detector is often used to detect bright targets in radar imagery where the background clutter can vary considerably from scene to scene and with angle to the scene. Similarly, the CFAR detector addresses the challenge of detecting exudate lesions in RGB and multispectral fundus imagery where the background clutter often exhibits variations in brightness and texture. These variations present a challenge to common, global thresholding detection algorithms and other methods. Performance of the CFAR algorithm is tested against a publicly available, annotated, diabetic retinopathy database and preliminary testing suggests that performance of the CFAR detector proves to be superior to techniques such as Otsu thresholding.

  17. Constant strain rate experiments and constitutive modeling for a class of bitumen

    Science.gov (United States)

    Reddy, Kommidi Santosh; Umakanthan, S.; Krishnan, J. Murali

    2012-08-01

    The mechanical properties of bitumen vary with the nature of the crude source and the processing methods employed. To understand the role of the processing conditions played in the mechanical properties, bitumen samples derived from the same crude source but processed differently (blown and blended) are investigated. The samples are subjected to constant strain rate experiments in a parallel plate rheometer. The torque applied to realize the prescribed angular velocity for the top plate and the normal force applied to maintain the gap between the top and bottom plate are measured. It is found that when the top plate is held stationary, the time taken by the torque to be reduced by a certain percentage of its maximum value is different from the time taken by the normal force to decrease by the same percentage of its maximum value. Further, the time at which the maximum torque occurs is different from the time at which the maximum normal force occurs. Since the existing constitutive relations for bitumen cannot capture the difference in the relaxation times for the torque and normal force, a new rate type constitutive model, incorporating this response, is proposed. Although the blended and blown bitumen samples used in this study correspond to the same grade, the mechanical responses of the two samples are not the same. This is also reflected in the difference in the values of the material parameters in the model proposed. The differences in the mechanical properties between the differently processed bitumen samples increase further with aging. This has implications for the long-term performance of the pavement.

  18. Rate constant measurements for the overall reaction of OH + 1-butanol → products from 900 to 1200 K.

    Science.gov (United States)

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

    2012-03-15

    The rate constant for the overall reaction OH + 1-butanol → products was determined in the temperature range 900 to 1200 K from measurements of OH concentration time histories in reflected shock wave experiments of tert-butyl hydroperoxide (TBHP) as a fast source of OH radicals with 1-butanol in excess. Narrow-linewidth laser absorption was employed for the quantitative OH concentration measurement. A detailed kinetic mechanism was constructed that includes updated rate constants for 1-butanol and TBHP kinetics that influence the near-first-order OH concentration decay under the present experimental conditions, and this mechanism was used to facilitate the rate constant determination. The current work improves upon previous experimental studies of the title rate constant by utilizing a rigorously generated kinetic model to describe secondary reactions. Additionally, the current work extends the temperature range of experimental data in the literature for the title reaction under combustion-relevant conditions, presenting the first measurements from 900 to 1000 K. Over the entire temperature range studied, the overall rate constant can be expressed in Arrhenius form as 3.24 × 10(-10) exp(-2505/T [K]) cm(3) molecule(-1) s(-1). The influence of secondary reactions on the overall OH decay rate is discussed, and a detailed uncertainty analysis is performed yielding an overall uncertainty in the measured rate constant of ±20% at 1197 K and ±23% at 925 K. The results are compared with previous experimental and theoretical studies on the rate constant for the title reaction and reasonable agreement is found when the earlier experimental data were reinterpreted.

  19. Effect of selecting a fixed dephosphorylation rate on the estimation of rate constants and rCMRGlu from dynamic [18F] fluorodeoxyglucose/PET data

    International Nuclear Information System (INIS)

    Dhawan, V.; Moeller, J.R.; Strother, S.C.; Evans, A.C.; Rottenberg, D.A.

    1989-01-01

    Several publications have discussed the estimation and physiologic significance of regional [ 18 F]fluorodeoxyglucose (FDG) rate constants and metabolic rates. Most of these studies analyzed dynamic data collected over 45-60 min; three rate constants (k1-k3) and blood volume (Vb) were estimated and the regional cerebral metabolic rate for glucose (rCMRGlu) was subsequently derived using the measured blood glucose value and a regionally invariant value of the lumped constant (LC). The dephosphorylation rate constant (k4) was either neglected, or a fixed value was used in the estimation procedure to obtain the remaining parameters. To compare the rate constants obtained by different authors using different values of k4 is impossible without knowledge of the effect of selecting different fixed values of k4 (including zero) on the estimated rate constants and rCMRGlu. Based on our analysis of FDG/PET data from nine normal volunteer subjects, we conclude that inclusion of a fixed value for k4, in spite of a scaling effect on the absolute values of model parameters, has no effect on the coefficient of variation (CV) of within- and between-subject parameter estimates and glucose metabolic rates

  20. The dissolution rate constant of magnetite in water at different temperatures and pH conditions

    International Nuclear Information System (INIS)

    Mohajery, Khatereh; Deydier de Pierrefeu, Laurent; Lister, Derek H.

    2012-09-01

    Under the nominal conditions of power system coolants, the corrosion of components made of carbon steel is limited by the magnetite films that develop on surfaces. In some situations, the magnetite film loses much of its protective ability and corrosion and loss of iron to the system are exacerbated. Common examples of such situations occur when the system is non-isothermal so that temperature gradients cause differences in magnetite solubility around the circuit; the resulting areas of under-saturation in iron give rise to dissolution of normally protective films. Condensing steam in two-phase systems may also promote oxide dissolution. When the turbulence in the system is high, oxide degradation is aggravated and flow-accelerated corrosion (FAC) results. The subsequent increased loading of systems with iron leads to fouling of flow passages and heat transfer surfaces and in reactor primary coolants to rising radiation fields, while FAC can have disastrous results in terms of pipe wall thinning and eventual rupture. Magnetite dissolution is clearly a key contributor to these processes. Thus, the conventional mechanistic description of FAC postulates magnetite dissolution in series with mass transfer of iron from the film to the bulk coolant. In the resulting equations, if the dissolution rate constant is considerably less than the mass transfer coefficient for a particular situation, dissolution will control and flow should have no effect. This is clearly untenable for FAC, so it is often assumed that mass transfer controls and the contribution from oxide dissolution is ignored - on occasion when data on dissolution kinetics are available and sometimes when those data show that dissolution should control. In most cases, however, dissolution rate constants for magnetite are not available. At UNB Nuclear we have a research program using a high-temperature loop to measure dissolution rates of magnetite in water under various conditions of flow, temperature and

  1. 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.

  2. 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. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Study of supersonic flow in a constant rate of momentum change (CRMC) ejector with frictional effects

    International Nuclear Information System (INIS)

    Kumar, Virendra; Singhal, Gaurav; Subbarao, P.M.V.

    2013-01-01

    The constant rate of momentum change (CRMC) is a new approach towards design of supersonic ejectors. CRMC methodology was first proposed by Eames [1] in a study which was primarily based on isentropic flow inside the diffusing region of a supersonic ejector. The prime benefit that accrues from employing a CRMC ejector is that it can effectively eliminate the irreversibility associated with occurrence of thermodynamic shock process. The present study examines the supersonic flow in a CRMC ejector from the perspective of an adiabatic flow with frictional effects inside the variable cross-section of supersonic ejector, which is apparently more realistic. An analytical model has been discussed for the prediction of flow parameter variation in a space marching formulation taking into account change in localized frictional coefficient due to corresponding changes at each step. The analytical results have been validated by conducting a computational study based on 2-D axi-symmetric viscous compressible flow formulation with turbulence in FLUENT. The results are in good agreement at on-design conditions. The predictions especially for the recovered pressure made through the analytical formulation incorporating friction are found to be in significantly better agreement than the isentropic approach. The experimental validation for the approach has also been presented with the results being in close agreement with analytically predicted values. -- Highlights: • CRMC ejector eliminates the irreversibility due to occurrence of thermodynamic shock. • Frictional effect based apparently present more realistic solution for ejector. • Static pressure variation between proposed model and numerical study is nearly 2.29%. • Static pressure variation between analytical and experimental values is nearly 4%. • Experimentally observed entrainment ratio shows 3% variation w.r.t. design point value

  4. A new variable interval schedule with constant hazard rate and finite time range.

    Science.gov (United States)

    Bugallo, Mehdi; Machado, Armando; Vasconcelos, Marco

    2018-05-27

    We propose a new variable interval (VI) schedule that achieves constant probability of reinforcement in time while using a bounded range of intervals. By sampling each trial duration from a uniform distribution ranging from 0 to 2 T seconds, and then applying a reinforcement rule that depends linearly on trial duration, the schedule alternates reinforced and unreinforced trials, each less than 2 T seconds, while preserving a constant hazard function. © 2018 Society for the Experimental Analysis of Behavior.

  5. Site-specific reaction rate constant measurements for various secondary and tertiary H-abstraction by OH radicals

    KAUST Repository

    Badra, Jihad; Farooq, Aamir

    2015-01-01

    absorption of the R1(5) transition of OH spectrum near 306.69nm.Previous low-temperature rate constant measurements are added to the current data to generate three-parameter rate expressions that successfully represent the available direct measurements over a

  6. 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. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. A first-passage scheme for determination of overall rate constants for non-diffusion-limited suspensions

    Science.gov (United States)

    Lu, Shih-Yuan; Yen, Yi-Ming

    2002-02-01

    A first-passage scheme is devised to determine the overall rate constant of suspensions under the non-diffusion-limited condition. The original first-passage scheme developed for diffusion-limited processes is modified to account for the finite incorporation rate at the inclusion surface by using a concept of the nonzero survival probability of the diffusing entity at entity-inclusion encounters. This nonzero survival probability is obtained from solving a relevant boundary value problem. The new first-passage scheme is validated by an excellent agreement between overall rate constant results from the present development and from an accurate boundary collocation calculation for the three common spherical arrays [J. Chem. Phys. 109, 4985 (1998)], namely simple cubic, body-centered cubic, and face-centered cubic arrays, for a wide range of P and f. Here, P is a dimensionless quantity characterizing the relative rate of diffusion versus surface incorporation, and f is the volume fraction of the inclusion. The scheme is further applied to random spherical suspensions and to investigate the effect of inclusion coagulation on overall rate constants. It is found that randomness in inclusion arrangement tends to lower the overall rate constant for f up to the near close-packing value of the regular arrays because of the inclusion screening effect. This screening effect turns stronger for regular arrays when f is near and above the close-packing value of the regular arrays, and consequently the overall rate constant of the random array exceeds that of the regular array. Inclusion coagulation too induces the inclusion screening effect, and leads to lower overall rate constants.

  8. Linear free energy relationships between aqueous phase hydroxyl radical reaction rate constants and free energy of activation.

    Science.gov (United States)

    Minakata, Daisuke; Crittenden, John

    2011-04-15

    The hydroxyl radical (HO(•)) is a strong oxidant that reacts with electron-rich sites on organic compounds and initiates complex radical chain reactions in aqueous phase advanced oxidation processes (AOPs). Computer based kinetic modeling requires a reaction pathway generator and predictions of associated reaction rate constants. Previously, we reported a reaction pathway generator that can enumerate the most important elementary reactions for aliphatic compounds. For the reaction rate constant predictor, we develop linear free energy relationships (LFERs) between aqueous phase literature-reported HO(•) reaction rate constants and theoretically calculated free energies of activation for H-atom abstraction from a C-H bond and HO(•) addition to alkenes. The theoretical method uses ab initio quantum mechanical calculations, Gaussian 1-3, for gas phase reactions and a solvation method, COSMO-RS theory, to estimate the impact of water. Theoretically calculated free energies of activation are found to be within approximately ±3 kcal/mol of experimental values. Considering errors that arise from quantum mechanical calculations and experiments, this should be within the acceptable errors. The established LFERs are used to predict the HO(•) reaction rate constants within a factor of 5 from the experimental values. This approach may be applied to other reaction mechanisms to establish a library of rate constant predictions for kinetic modeling of AOPs.

  9. QSARs for phenols and phenolates: oxidation potential as a predictor of reaction rate constants with photochemically produced oxidants.

    Science.gov (United States)

    Arnold, William A; Oueis, Yan; O'Connor, Meghan; Rinaman, Johanna E; Taggart, Miranda G; McCarthy, Rachel E; Foster, Kimberley A; Latch, Douglas E

    2017-03-22

    Quantitative structure-activity relationships (QSARs) for prediction of the reaction rate constants of phenols and phenolates with three photochemically produced oxidants, singlet oxygen, carbonate radical, and triplet excited state sensitizers/organic matter, are developed. The predictive variable is the one-electron oxidation potential (E 1 ), which is calculated for each species using density functional theory. The reaction rate constants are obtained from the literature, and for singlet oxygen, are augmented with new experimental data. Calculated E 1 values have a mean unsigned error compared to literature values of 0.04-0.06 V. For singlet oxygen, a single linear QSAR that includes both phenols and phenolates is developed that predicts experimental rate constants, on average, to within a factor of three. Predictions for only 6 out of 87 compounds are off by more than a factor of 10. A more limited data set for carbonate radical reactions with phenols and phenolates also gives a single linear QSAR with prediction of rate constant being accurate to within a factor of three. The data for the reactions of phenols with triplet state sensitizers demonstrate that two sensitizers, 2-acetonaphthone and methylene blue, most closely predict the reactivity trend of triplet excited state organic matter with phenols. Using sensitizers with stronger reduction potentials could lead to overestimation of rate constants and thus underestimation of phenolic pollutant persistence.

  10. Variable dose rate single-arc IMAT delivered with a constant dose rate and variable angular spacing

    International Nuclear Information System (INIS)

    Tang, Grace; Earl, Matthew A; Yu, Cedric X

    2009-01-01

    Single-arc intensity-modulated arc therapy (IMAT) has gained worldwide interest in both research and clinical implementation due to its superior plan quality and delivery efficiency. Single-arc IMAT techniques such as the Varian RapidArc(TM) deliver conformal dose distributions to the target in one single gantry rotation, resulting in a delivery time in the order of 2 min. The segments in these techniques are evenly distributed within an arc and are allowed to have different monitor unit (MU) weightings. Therefore, a variable dose-rate (VDR) is required for delivery. Because the VDR requirement complicates the control hardware and software of the linear accelerators (linacs) and prevents most existing linacs from delivering IMAT, we propose an alternative planning approach for IMAT using constant dose-rate (CDR) delivery with variable angular spacing. We prove the equivalence by converting VDR-optimized RapidArc plans to CDR plans, where the evenly spaced beams in the VDR plan are redistributed to uneven spacing such that the segments with larger MU weighting occupy a greater angular interval. To minimize perturbation in the optimized dose distribution, the angular deviation of the segments was restricted to ≤± 5 deg. This restriction requires the treatment arc to be broken into multiple sectors such that the local MU fluctuation within each sector is reduced, thereby lowering the angular deviation of the segments during redistribution. The converted CDR plans were delivered with a single gantry sweep as in the VDR plans but each sector was delivered with a different value of CDR. For four patient cases, including two head-and-neck, one brain and one prostate, all CDR plans developed with the variable spacing scheme produced similar dose distributions to the original VDR plans. For plans with complex angular MU distributions, the number of sectors increased up to four in the CDR plans in order to maintain the original plan quality. Since each sector was

  11. Tempo of Diversification of Global Amphibians: One-Constant Rate, One-Continuous Shift or Multiple-Discrete Shifts?

    OpenAIRE

    Youhua Chen

    2014-01-01

    In this brief report, alternative time-varying diversification rate models were fitted onto the phylogeny of global amphibians by considering one-constant-rate (OCR), one-continuous-shift (OCS) and multiplediscrete- shifts (MDS) situations. The OCS diversification model was rejected by γ statistic (γ=-5.556, p⁄ 0.001), implying the existence of shifting diversification rates for global amphibian phylogeny. Through model selection, MDS diversification model outperformed OCS and OCR...

  12. Comments to "Analysis of constant rate period of spray drying of slurry" by Liang et al., 2001

    DEFF Research Database (Denmark)

    Jørgensen, Kåre; Jensen, Anker Degn; Sloth, Jakob

    2006-01-01

    In the study by Liang et al. [2001. Analysis of constant rate period of spray drying of slurry. Chemical Engineering Science 56, 2205-2213] the Darcy flow of liquid through a pore system of primary particles to the surface of a slurry droplet was applied for the constant rate period. Steep primary...... particle concentration gradients inside -25 mu m droplets with a primary particle size of 0.2 mu m were observed. Unfortunately, the boundary condition at the droplet surface for the parabolic second-order PDE did not conserve the solid mass in the droplet, and the plots for the primary particle...

  13. Estimating time-based instantaneous total mortality rate based on the age-structured abundance index

    Science.gov (United States)

    Wang, Yingbin; Jiao, Yan

    2015-05-01

    The instantaneous total mortality rate ( Z) of a fish population is one of the important parameters in fisheries stock assessment. The estimation of Z is crucial to fish population dynamics analysis, abundance and catch forecast, and fisheries management. A catch curve-based method for estimating time-based Z and its change trend from catch per unit effort (CPUE) data of multiple cohorts is developed. Unlike the traditional catch-curve method, the method developed here does not need the assumption of constant Z throughout the time, but the Z values in n continuous years are assumed constant, and then the Z values in different n continuous years are estimated using the age-based CPUE data within these years. The results of the simulation analyses show that the trends of the estimated time-based Z are consistent with the trends of the true Z, and the estimated rates of change from this approach are close to the true change rates (the relative differences between the change rates of the estimated Z and the true Z are smaller than 10%). Variations of both Z and recruitment can affect the estimates of Z value and the trend of Z. The most appropriate value of n can be different given the effects of different factors. Therefore, the appropriate value of n for different fisheries should be determined through a simulation analysis as we demonstrated in this study. Further analyses suggested that selectivity and age estimation are also two factors that can affect the estimated Z values if there is error in either of them, but the estimated change rates of Z are still close to the true change rates. We also applied this approach to the Atlantic cod ( Gadus morhua) fishery of eastern Newfoundland and Labrador from 1983 to 1997, and obtained reasonable estimates of time-based Z.

  14. Dynamics of chest wall volume regulation during constant work rate exercise in patients with chronic obstructive pulmonary disease

    Energy Technology Data Exchange (ETDEWEB)

    Takara, L.S.; Cunha, T.M.; Barbosa, P.; Rodrigues, M.K.; Oliveira, M.F.; Nery, L.E. [Setor de Função Pulmonar e Fisiologia Clínica do Exercício, Disciplina de Pneumologia, Departamento de Medicina, Universidade Federal de São Paulo, São Paulo, SP (Brazil); Neder, J.A. [Setor de Função Pulmonar e Fisiologia Clínica do Exercício, Disciplina de Pneumologia, Departamento de Medicina, Universidade Federal de São Paulo, São Paulo, SP (Brazil); Division of Respiratory and Critical Care Medicine, Department of Medicine, Queen' s University, Kingston, ON (Canada)

    2012-10-15

    This study evaluated the dynamic behavior of total and compartmental chest wall volumes [(V{sub CW}) = rib cage (V{sub RC}) + abdomen (V{sub AB})] as measured breath-by-breath by optoelectronic plethysmography during constant-load exercise in patients with stable chronic obstructive pulmonary disease. Thirty males (GOLD stages II-III) underwent a cardiopulmonary exercise test to the limit of tolerance (Tlim) at 75% of peak work rate on an electronically braked cycle ergometer. Exercise-induced dynamic hyperinflation was considered to be present when end-expiratory (EE) V{sub CW} increased in relation to resting values. There was a noticeable heterogeneity in the patterns of V{sub CW} regulation as EEV{sub CW} increased non-linearly in 17/30 “hyperinflators” and decreased in 13/30 “non-hyperinflators” (P < 0.05). EEV{sub AB} decreased slightly in 8 of the “hyperinflators”, thereby reducing and slowing the rate of increase in end-inspiratory (EI) V{sub CW} (P < 0.05). In contrast, decreases in EEV{sub CW} in the “non-hyperinflators” were due to the combination of stable EEV{sub RC} with marked reductions in EEV{sub AB}. These patients showed lower EIV{sub CW} and end-exercise dyspnea scores but longer Tlim than their counterparts (P < 0.05). Dyspnea increased and Tlim decreased non-linearly with a faster rate of increase in EIV{sub CW} regardless of the presence or absence of dynamic hyperinflation (P < 0.001). However, no significant between-group differences were observed in metabolic, pulmonary gas exchange and cardiovascular responses to exercise. Chest wall volumes are continuously regulated during exercise in order to postpone (or even avoid) their migration to higher operating volumes in patients with COPD, a dynamic process that is strongly dependent on the behavior of the abdominal compartment.

  15. A new analytical method for estimating lumped parameter constants of linear viscoelastic models from strain rate tests

    Science.gov (United States)

    Mattei, G.; Ahluwalia, A.

    2018-04-01

    We introduce a new function, the apparent elastic modulus strain-rate spectrum, E_{app} ( \\dot{ɛ} ), for the derivation of lumped parameter constants for Generalized Maxwell (GM) linear viscoelastic models from stress-strain data obtained at various compressive strain rates ( \\dot{ɛ}). The E_{app} ( \\dot{ɛ} ) function was derived using the tangent modulus function obtained from the GM model stress-strain response to a constant \\dot{ɛ} input. Material viscoelastic parameters can be rapidly derived by fitting experimental E_{app} data obtained at different strain rates to the E_{app} ( \\dot{ɛ} ) function. This single-curve fitting returns similar viscoelastic constants as the original epsilon dot method based on a multi-curve global fitting procedure with shared parameters. Its low computational cost permits quick and robust identification of viscoelastic constants even when a large number of strain rates or replicates per strain rate are considered. This method is particularly suited for the analysis of bulk compression and nano-indentation data of soft (bio)materials.

  16. Rate constant for reaction of vitamin C with protein radicals in γ-irradiated aqueous albumin solution at 295K

    International Nuclear Information System (INIS)

    Miyazaki, Tetsuo; Yoshimura, Toru; Mita, Kazuya; Suzuki, Keiji; Watanabe, Masami

    1995-01-01

    When an aqueous solution of albumin (0.1 kg dm -3 ) is irradiated by γ-rays at 295 K, albumin radicals with a long lifetime are observed by ESR. The reaction of vitamin C with the albumin radicals has been studied at 295 K in the albumin solution, which is considered as a model of cells. The rate constant for the reaction of vitamin C with the albumin radicals was measured as 0.014 dm 3 mol -1 S -1 , which is much smaller than the reported constants (10 6 -10 10 dm 3 mol -1 s -1 ) for the reaction of vitamin C with radicals in a dilute aqueous solution. The small rate constant for the reaction of vitamin C is ascribed to the reaction in polymer coils in the albumin solution, since vitamin C and albumin radicals diffuse very slowly in the coils. (author)

  17. 38 CFR 4.15 - Total disability ratings.

    Science.gov (United States)

    2010-07-01

    ... must be given to unusual physical or mental effects in individual cases, to peculiar effects of occupational activities, to defects in physical or mental endowment preventing the usual amount of success in overcoming the handicap of disability and to the effect of combinations of disability. Total disability will...

  18. EFRT M-12 Issue Resolution: Caustic Leach Rate Constants from PEP and Laboratory-Scale Tests

    Energy Technology Data Exchange (ETDEWEB)

    Mahoney, Lenna A.; Rassat, Scot D.; Eslinger, Paul W.; Aaberg, Rosanne L.; Aker, Pamela M.; Golovich, Elizabeth C.; Hanson, Brady D.; Hausmann, Tom S.; Huckaby, James L.; Kurath, Dean E.; Minette, Michael J.; Sundaram, S. K.; Yokuda, Satoru T.

    2009-08-14

    concentrated to nominally 20 wt% solids using cross-flow ultrafiltration before adding caustic. The work described in this report addresses the kinetics of caustic leach under WTP conditions, based on tests performed with a Hanford waste simulant. The tests were completed at the lab-scale and in the PEP, which is a 1/4.5-scale mock-up of key PTF process equipment. The purpose of this report is to summarize the results from both scales that are related to caustic leach chemistry to support a scale-up factor for the submodels to be used in the G2 model, which predicts WTP operating performance. The scale-up factor will take the form of an adjustment factor for the rate constant in the boehmite leach kinetic equation in the G2 model.

  19. EFRT M-12 Issue Resolution: Caustic Leach Rate Constants from PEP and Laboratory-Scale Tests

    International Nuclear Information System (INIS)

    Mahoney, Lenna A.; Rassat, Scot D.; Eslinger, Paul W.; Aaberg, Rosanne L.; Aker, Pamela M.; Golovich, Elizabeth C.; Hanson, Brady D.; Hausmann, Tom S.; Huckaby, James L.; Kurath, Dean E.; Minette, Michael J.; Sundaram, S. K.; Yokuda, Satoru T.

    2009-01-01

    to nominally 20 wt% solids using cross-flow ultrafiltration before adding caustic. The work described in this report addresses the kinetics of caustic leach under WTP conditions, based on tests performed with a Hanford waste simulant. The tests were completed at the lab-scale and in the PEP, which is a 1/4.5-scale mock-up of key PTF process equipment. The purpose of this report is to summarize the results from both scales that are related to caustic leach chemistry to support a scale-up factor for the submodels to be used in the G2 model, which predicts WTP operating performance. The scale-up factor will take the form of an adjustment factor for the rate constant in the boehmite leach kinetic equation in the G2 model

  20. The constant failure rate model for fault tree evaluation as a tool for unit protection reliability assessment

    International Nuclear Information System (INIS)

    Vichev, S.; Bogdanov, D.

    2000-01-01

    The purpose of this paper is to introduce the fault tree analysis method as a tool for unit protection reliability estimation. The constant failure rate model applies for making reliability assessment, and especially availability assessment. For that purpose an example for unit primary equipment structure and fault tree example for simplified unit protection system is presented (author)

  1. Bibliographies on radiation chemistry: Pt. 12; Rate constants for reactions of nonmetallic inorganic radicals in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Helman, W P; Ross, A B [Notre Dame Univ., IN (USA). Radiation Chemistry Data Center

    1990-01-01

    Rate constants have been determined by pulse radiolysis, flash photolysis, and other methods, for a wide variety of reactions involving transient radicals in aqueous solution. Reliable rate constants have been established for reactions of radicals from water (e{sub aq}{sup -}, {center dot}H, {center dot}OH/{center dot}O{sup -}) and the data have been tabulated (Buxton, 1988) through 1986. Kinetic data for HO{sub 2}{center dot}/O{sub 2}{center dot}{sup -} were tabulated. (Bielski, 1985) from papers published through 1983. A compilation of rate constants, from the literature through Mid-1987, for other nonmetallic inorganic radicals has also appeared recently (Neta, 1988). Together, these compilations contain rate constants for more than 6,000 different reactions, reported in about 2,000 references. The present bibliography provides a list of relevant references which have been collected since the publication of the above-mentioned compilations. The list contains references received through the end of December, 1989. (author).

  2. Measuring in-stream retention of copper by means of constant-rate additions.

    Science.gov (United States)

    Serra, A; Guasch, H; Martí, E; Geiszinger, A

    2009-06-01

    Human practices entail inputs of nutrients and toxicants such as heavy metals to the fluvial ecosystems. While nutrient dynamics in fluvial ecosystems have been widely studied for over three decades, dynamics of toxicants still remain unclear. In this investigation, the nutrient spiraling concept and associated methodologies to quantify nutrient retention in streams were applied to study copper (Cu) dynamics in streams. The present study aimed to quantify total dissolved Cu retention using a simplified system of indoor channels colonized with fluvial biofilms. Cu retention was studied at sub-toxic concentrations to avoid negative/lethal effects on biota. In addition, Cu retention was compared with retention estimates of a macronutrient, phosphate (PO(4)(3-)), which has been widely studied within the context of the nutrient spiraling concept. The methodology used allowed a successful quantification of Cu and PO(4)(3-) retention. The results showed higher retention efficiency for PO(4)(3-) than for Cu. The biofilm played a key role in retaining both solutes. Although retention efficiency for both solutes was higher in the experiments with colonized substrata compared to uncolonized substrata, we found a positive relationship between uptake rate and chlorophyll-a only for PO(4)(3-). Finally, retention efficiency for both solutes was influenced by water discharge, showing lower retention efficiencies under higher flow conditions. These results suggest that the fate and toxic effects of copper on stream biota may be strongly influenced by the prevailing environmental conditions. Our results indicate that the experimental approach considered can provide new insights into the investigation of retention of toxic compounds in fluvial systems and their controlling mechanisms.

  3. Variational transition-state theory study of the rate constant of the DMS·OH scavenging reaction by O2.

    Science.gov (United States)

    Ramírez-Anguita, Juan M; González-Lafont, Àngels; Lluch, José M

    2011-07-30

    The chemical tropospheric dimethyl sulfide (DMS, CH3SCH3) degradation involves several steps highly dependent on the environmental conditions. So, intensive efforts have been devoted during the last years to enhance the understanding of the DMS oxidation mechanism under different conditions. The reaction of DMS with OH is considered to be the most relevant process that initiates the whole oxidation process. The experimental observations have been explained by a two-channel mechanism consisting of a H-abstraction process leading to CH3S(O)CH3 and HO2 and an addition reaction leading to the DMS·OH adduct. In the presence of O2, the DMS·OH adduct is competitively scavenged increasing the contribution of the addition channel to the overall DMS oxidation. Recent experimental measurements have determined from a global fit that the rate constant of this scavenging process is independent of pressure and temperature but this rate constant cannot be directly measured. In this article, a variational transition-state theory calculation of the low- and high-pressure rate constants for the reaction between DMS·OH and O2 has been carried out as a function of temperature. Our proposal is that the slight temperature dependence of the scavenging rate constant can only be explained if the H-abstraction bottleneck is preceded by a dynamical bottleneck corresponding to the association process between the DMS·OH adduct and the O2 molecule. The agreement between the low-pressure and high-pressure rate constants confirms the experimental observations. Copyright © 2011 Wiley Periodicals, Inc.

  4. Absolute rate constants for the reaction of NO3 radicals with a series of dienes at 295 K

    DEFF Research Database (Denmark)

    Ellermann, T.; Nielsen, O.J.; Skov, H.

    1992-01-01

    The rate constants for the reaction of NO3 radicals with a series of 7 dienes, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, trans-1,3-pentadiene, cis-1,3-pentadiene, trans,trans-2,4-hexadiene, and 1,3-cyclohexadiene, were measured at 295 K and at a total pressure of 1 atm. The rate consta...... were obtained using the absolute technique of pulse radiolysis combined with kinetic UV-VIS spectroscopy. The results are discussed in terms of reactivity trends and previous literature data....

  5. Photon spectrometry for the determination of the dose-rate constant of low-energy photon-emitting brachytherapy sources

    International Nuclear Information System (INIS)

    Chen, Zhe Jay; Nath, Ravinder

    2007-01-01

    Accurate determination of dose-rate constant (Λ) for interstitial brachytherapy sources emitting low-energy photons (<50 keV) has remained a challenge in radiation dosimetry because of the lack of a suitable absolute dosimeter for accurate measurement of the dose rates near these sources. Indeed, a consensus value of Λ taken as the arithmetic mean of the dose-rate constants determined by different research groups and dosimetry techniques has to be used at present for each source model in order to minimize the uncertainties associated with individual determinations of Λ. Because the dosimetric properties of a source are fundamentally determined by the characteristics of the photons emitted by the source, a new technique based on photon spectrometry was developed in this work for the determination of dose-rate constant. The photon spectrometry technique utilized a high-resolution gamma-ray spectrometer to measure source-specific photon characteristics emitted by the low-energy sources and determine their dose-rate constants based on the measured photon-energy spectra and known dose-deposition properties of mono-energetic photons in water. This technique eliminates many of the difficulties arising from detector size, the energy dependence of detector sensitivity, and the use of non-water-equivalent solid phantoms in absolute dose rate measurements. It also circumvents the uncertainties that might be associated with the source modeling in Monte Carlo simulation techniques. It was shown that the estimated overall uncertainty of the photon spectrometry technique was less than 4%, which is significantly smaller than the reported 8-10% uncertainty associated with the current thermo-luminescent dosimetry technique. In addition, the photon spectrometry technique was found to be stable and quick in Λ determination after initial setup and calibration. A dose-rate constant can be determined in less than two hours for each source. These features make it ideal to determine

  6. Flowing afterglow: construction of an apparatus, measurement of rate constants, and consideration of the diffusive behavior of charges

    International Nuclear Information System (INIS)

    Matsuoka, Shingo; Nakamura, Hirone; Tamura, Takaaki; Fujii, Toshihiro.

    1984-01-01

    A flowing afterglow apparatus was constructed and the operation of the afterglow system including data analysis was tested by measuring the rate constants for the reactions N + + NO, N 2 + + NO, He + + N 2 , and SF 6 + e; the results were 5.8 x 10 -10 , 3.9 x 10 -10 , 1.20 x 10 -9 , and 2.1 x 10 -7 cm 3 s -1 respectively. In the measurements an extraction voltage for ion sampling was not applied to the nose cone in order not to introduce an electric field into the reaction region. A ''non-ambipolar'' model developed by us was used for the data analysis of the ion/molecule reactions. For the data analysis of the electron attachment, a typical curve fit mehtod to the product ion signal was used. However, no theoretical curves fit the experimental points. This disagreement is attributed to a change of the ion-sampling efficiency through the nose-cone aperture arising from a change of the electron-dominated plasma to a negative-ion-dominated plasma with an increasing flow rate of SF 6 . Nevertheless, the attachment rate could be determined by fitting the theoretical and experimantal curves in the limited region of the SF 6 flow rate where the negative-ion-dominated plasma is established at the sampling aperture. All the rate constants obtained here agree reasonably well with literature values. Next, errors in the positive ion/molecule reaction rate constants, which would occur if the diffusion coefficients of the ions and neutrals each have a + 10 % error were calculated for the flow model to be -0.4 and +1.2 % respectively, demonstrating that these parameters are not important in the analysis of data. This insensitivity explains why the nose-cone voltage applied in a typical flowing afterglow operation has not caused a significant error in the published rate constants although it disturbs the ion diffusive behavior. (author)

  7. The chemistry of bromine in the stratosphere: Influence of a new rate constant for the reaction BrO + HO2

    Science.gov (United States)

    Pirre, Michel; Marceau, Francois J.; Lebras, Georges; Maguin, Francoise; Poulet, Gille; Ramaroson, Radiela

    1994-01-01

    The impact of new laboratory data for the reaction BrO + HO2 yields HOBr + O2 in the depletion of global stratospheric ozone has been estimated using a one-dimensional photochemical model taking into account the heterogeneous reaction on sulphate aerosols which converts N2O5 into HNO3. Assuring an aerosol loading 2 times as large as the 'background' and a reaction probability of 0.1 for the above heterogeneous reaction, the 6 fold increase in the measured rate constant for the reaction of BrO with HO2 increases the computed depletion of global ozone produced by 20 ppt of total bromine from 2.01 percent to 2.36 percent. The use of the higher rate constant increases the HOBr mixing ratio and makes the bromine partitioning and the ozone depletion very sensitive to the branching ratio of the potential channel forming HBr in the BrO + HO2 reaction.

  8. Site-specific reaction rate constant measurements for various secondary and tertiary H-abstraction by OH radicals

    KAUST Repository

    Badra, Jihad

    2015-02-01

    Reaction rate constants for nine site-specific hydrogen atom (H) abstraction by hydroxyl radicals (OH) have been determined using experimental measurements of the rate constants of Alkane+OH→Products reactions. Seven secondary (S 20, S 21, S 22, S 30, S 31, S 32, and S 33) and two tertiary (T 100 and T 101) site-specific rate constants, where the subscripts refer to the number of carbon atoms (C) connected to the next-nearest-neighbor (N-N-N) C atom, were obtained for a wide temperature range (250-1450K). This was done by measuring the reaction rate constants for H abstraction by OH from a series of carefully selected large branched alkanes. The rate constant of OH with four different alkanes, namely 2,2-dimethyl-pentane, 2,4-dimethyl-pentane, 2,2,4-trimethyl-pentane (iso-octane), and 2,2,4,4-tetramethyl-pentane were measured at high temperatures (822-1367K) using a shock tube and OH absorption diagnostic. Hydroxyl radicals were detected using the narrow-line-width ring-dye laser absorption of the R1(5) transition of OH spectrum near 306.69nm.Previous low-temperature rate constant measurements are added to the current data to generate three-parameter rate expressions that successfully represent the available direct measurements over a wide temperature range (250-1450. K). Similarly, literature values of the low-temperature rate constants for the reaction of OH with seven normal and branched alkanes are combined with the recently measured high-temperature rate constants from our group [1]. Subsequent to that, site-specific rate constants for abstractions from various types of secondary and tertiary H atoms by OH radicals are derived and have the following modified Arrhenius expressions:. S20=8.49×10-17T1.52exp(73.4K/T)cm3molecule-1s-1(250-1450K) S21=1.07×10-15T1.07exp(208.3K/T)cm3molecule-1s-1(296-1440K) S22=2.88×10-13T0.41exp(-291.5K/T)cm3molecule-1s-1(272-1311K) S30=3.35×10-18T1.97exp(323.1K/T)cm3molecule-1s-1(250-1366K) S31=1.60×10-18T2.0exp(500.0K/T)cm3

  9. A Constant Rate of Spontaneous Mutation in DNA-Based Microbes

    Science.gov (United States)

    Drake, John W.

    1991-08-01

    In terms of evolution and fitness, the most significant spontaneous mutation rate is likely to be that for the entire genome (or its nonfrivolous fraction). Information is now available to calculate this rate for several DNA-based haploid microbes, including bacteriophages with single- or double-stranded DNA, a bacterium, a yeast, and a filamentous fungus. Their genome sizes vary by ≈6500-fold. Their average mutation rates per base pair vary by ≈16,000-fold, whereas their mutation rates per genome vary by only ≈2.5-fold, apparently randomly, around a mean value of 0.0033 per DNA replication. The average mutation rate per base pair is inversely proportional to genome size. Therefore, a nearly invariant microbial mutation rate appears to have evolved. Because this rate is uniform in such diverse organisms, it is likely to be determined by deep general forces, perhaps by a balance between the usually deleterious effects of mutation and the physiological costs of further reducing mutation rates.

  10. Constant growth rate can be supported by decreasing energy flux and increasing aerobic glycolysis

    NARCIS (Netherlands)

    Slavov, Nikolai; Budnik, Bogdan A; Schwab, David; Airoldi, Edoardo M; van Oudenaarden, Alexander

    2014-01-01

    Fermenting glucose in the presence of enough oxygen to support respiration, known as aerobic glycolysis, is believed to maximize growth rate. We observed increasing aerobic glycolysis during exponential growth, suggesting additional physiological roles for aerobic glycolysis. We investigated such

  11. Effect of detomidine or romifidine constant rate infusion on plasma lactate concentration and inhalant requirements during isoflurane anaesthesia in horses.

    Science.gov (United States)

    Niimura Del Barrio, M C; Bennett, Rachel C; Hughes, J M Lynne

    2017-05-01

    Influence of detomidine or romifidine constant rate infusion (CRI) on plasma lactate concentration and isoflurane requirements in horses undergoing elective surgery. Prospective, randomised, blinded, clinical trial. A total of 24 adult healthy horses. All horses were administered intramuscular acepromazine (0.02 mg kg -1 ) and either intravenous detomidine (0.02 mg kg -1 ) (group D), romifidine (0.08 mg kg -1 ) (group R) or xylazine (1.0 mg kg -1 ) (group C) prior to anaesthesia. Group D was administered detomidine CRI (10 μg kg -1 hour -1 ) in lactated Ringer's solution (LRS), group R romifidine CRI (40 μg kg -1 hour -1 ) in LRS and group C an equivalent amount of LRS intraoperatively. Anaesthesia was induced with ketamine and diazepam and maintained with isoflurane in oxygen. Plasma lactate samples were taken prior to anaesthesia (baseline), intraoperatively (three samples at 30 minute intervals) and in recovery (at 10 minutes, once standing and 3 hours after end of anaesthesia). End-tidal isoflurane percentage (Fe'Iso) was analysed by allocating values into three periods: Prep (15 minutes after the start anaesthesia-start surgery); Surgery 1 (start surgery-30 minutes later); and Surgery 2 (end Surgery 1-end anaesthesia). A linear mixed model was used to analyse the data. A value of pdetomidine or romifidine CRI in horses did not result in a clinically significant increase in plasma lactate compared with control group. Detomidine and romifidine infusions decreased isoflurane requirements during surgery. Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.

  12. Mineralization Rate Constants, Half-Lives and Effects of Two Organic

    African Journals Online (AJOL)

    INTRODUCTION. Low soil fertility is one the ... important for maintenance of fertility of tropical soils. ... soil N. Thus, total N in the soil and the amount released for plant uptake depend on its content of organic ... capacity for productivity, nutrient cycling, filtering and buffering ... (Steel and Torrie, 1981) and, thereafter, Fischer's.

  13. In situ and laboratory determined first-order degradation rate constants of specific organic compounds in an aerobic aquifer

    DEFF Research Database (Denmark)

    Nielsen, P.H.; Bjerg, P.L.; Nielsen, P.

    1996-01-01

    In situ microcosms (ISM) and laboratory batch microcosms (LBM) were used for determination of the first-order degradation rate constants of benzene, toluene, o-xylene, nitrobenzene, naphthalene, biphenyl, o- and p-dichlorobenzene, 1,1,1 -trichloroethane, tetrachlorometane, trichloroethene......, tetrachloroethene, phenol, o-cresol, 2,4- and 2,6-dichlorophenol, 4,6-o-dichlorocresol, and o- and p-nitrophenol in an aerobic aquifer, All aromatic hydrocarbons were degraded in ISM and LBM experiments. The phenolic hydrocarbons were ail degraded in ISM experiments, but some failed to degrade in LBM experiments....... Chlorinated aliphatic hydrocarbons were degraded neither in ISM nor LBM experiments. Degradation rate constants were determined by a model accounting for kinetic sorption (bicontinuum model), lag phases, and first-order degradation. With a few exceptions, lag phases were less than 2 weeks in both ISM and LBM...

  14. First-Principles Computed Rate Constant for the O + O2 Isotopic Exchange Reaction Now Matches Experiment.

    Science.gov (United States)

    Guillon, Grégoire; Honvault, Pascal; Kochanov, Roman; Tyuterev, Vladimir

    2018-04-19

    We show, by performing exact time-independent quantum molecular scattering calculations, that the quality of the ground electronic state global potential energy surface appears to be of utmost importance in accurately obtaining even as strongly averaged quantities as kinetic rate constants. The oxygen isotope exchange reaction, 18 O + 32 O 2 , motivated by the understanding of a complex long-standing problem of isotopic ozone anomalies in the stratosphere and laboratory experiments, is explored in this context. The thermal rate constant for this key reaction is now in quantitative agreement with all experimental data available to date. A significant recent progress at the frontier of three research domains, advanced electronic structure calculations, ultrasensitive spectroscopy, and quantum scattering calculations, has therefore permitted a breakthrough in the theoretical modeling of this crucial collision process from first principles.

  15. Rate constant and thermochemistry for K + O2 + N2 = KO2 + N2

    DEFF Research Database (Denmark)

    Sorvajärvi, Tapio; Viljanen, Jan; Toivonen, Juha

    2015-01-01

    in the form of double exponential decays of [K], which yielded both kR1 and the equilibrium constant for KO2 formation. kR1 can be summarized as 1.07 × 10-30(T/1000 K)-0.733 cm6 molecule-2 s-1. Combination with literature values leads to a recommended kR1 of 5.5 × 10-26T-1.55 exp(-10/T) cm6 molecule-2 s-1...... over 250-1320 K, with an error limit of a factor of 1.5. A vant Hoff analysis constrained to fit the computed ΔS298 yields a K-O2 bond dissociation enthalpy of 184.2 ± 4.0 kJ mol-1 at 298 K and ΔfH298(KO2) = -95.2 ± 4.1 kJ mol-1. The corresponding D0 is 181.5 ± 4.0 kJ mol-1. This value compares well...

  16. Regional Distribution of Epifascial Swelling and Epifascial Lymph Drainage Rate Constants in Breast Cancer-Related Lymphedema

    OpenAIRE

    MODI, STEPHANIE; STANTON, ANTHONY W. B.; MELLOR, RUSSELL H.; MICHAEL PETERS, A.; RODNEY LEVICK, J.; MORTIMER, PETER S.

    2005-01-01

    Background: The view that breast cancer-related lymphedema (BCRL) is a simple, direct mechanical result of axillary lymphatic obstruction (‘stopcock’ mechanism) appears incomplete, because parts of the swollen limb (e.g., hand) can remain nonswollen. The lymph drainage rate constant (k) falls in the swollen forearm but not in the spared hand, indicating regional differences in lymphatic function. Here the generality of the hypothesis that regional epifascial lymphatic failure underlies region...

  17. Interaction of hydrated electron with dietary flavonoids and phenolic acids. Rate constants and transient spectra studied by pulse radiolysis

    International Nuclear Information System (INIS)

    Cai, Zhongli; Li, Xifeng; Katsumura, Yosuke

    2000-01-01

    The reaction rate constants and transient spectra of 11 flavonoids and 4 phenolic acids reacting with e aq - at neutral pH were measured. The results suggest that C 4 keto group is the active site for e aq - to attack on flavonoids and phenolic acids, while the o-dihydroxy structure in B-ring, the C 2,3 double bond, the C 3 -OH group and glycosylation have little effects on the e aq - scavenging activities. (author)

  18. Rate constants for a mechanism including intermediates in the interconversion of ternary complexes by horse liver alcohol dehydrogenase

    International Nuclear Information System (INIS)

    Sekhar, V.C.; Plapp, B.V.

    1990-01-01

    Transient kinetic data for partial reactions of alcohol dehydrogenase and simulations of progress curves have led to estimates of rate constants for the following mechanism, at pH 8.0 and 25 degrees C: E in equilibrium E-NAD+ in equilibrium *E-NAD+ in equilibrium E-NAD(+)-RCH2OH in equilibrium E-NAD+-RCH2O- in equilibrium *E-NADH-RCHO in equilibrium E-NADH-RCHO in equilibrium E-NADH in equilibrium E. Previous results show that the E-NAD+ complex isomerizes with a forward rate constant of 620 s-1. The enzyme-NAD(+)-alcohol complex has a pK value of 7.2 and loses a proton rapidly (greater than 1000 s-1). The transient oxidation of ethanol is 2-fold faster in D 2 O, and proton inventory results suggest that the transition state has a charge of -0.3 on the substrate oxygen. Rate constants for hydride ion transfer in the forward or reverse reactions were similar for short-chain aliphatic substrates (400-600 s-1). A small deuterium isotope effect for transient oxidation of longer chain alcohols is apparently due to the isomerization of the E-NAD+ complex. The transient reduction of aliphatic aldehydes showed no primary deuterium isotope effect; thus, an isomerization of the E-NADH-aldehyde complex is postulated, as isomerization of the E-NADH complex was too fast to be detected. The estimated microscopic rate constants show that the observed transient reactions are controlled by multiple steps

  19. Rate constants for the reaction of e-aq with EDTA and some metal EDTA-complexes

    International Nuclear Information System (INIS)

    Buitenhuis, R.; Bakker, C.M.N.; Stock, F.R.; Louwrier, P.W.F.

    1977-01-01

    The rate constants for the reaction e - aq + EDTA were measured as a function of the pH by the pulse-radiolysis technique. Between pH = 6and pH = 10 this rate constant can be represented by the equation k = 4.7 x 10 6 x (fraction of HEDTA 3- )+1.0 x 10 8 x (fraction H 2 EDTA 2 -)M -1 s -1 . Also the rate constants for reactions of e - aq with the following metal-EDTA complexes were measured: CuEDTA 2- , HgEDTA 2- , CoEDTA 2- , InEDTA - , NiEDTA 2- , GaEDTA - , MnEDTA 2- , ZnEDTA 2- , CdEDTA 2- , PbEDTA 2- . Ionic strength variation indicates that the reacting ions are not hydrolized to an appreciable amount at pH = 11.5. It is found that some of the products show light absorption in the region between 300 and 400 nm. (orig.) [de

  20. The dissolution rate constant of magnetite in water at different temperatures and neutral or ammoniated chemistry conditions

    International Nuclear Information System (INIS)

    Mohajery, K.; Lister, D.H.

    2012-01-01

    In this study, the dissolution rate constants of magnetite were measured at various water chemistry conditions and different temperatures, corresponding to several feedwater conditions of water-cooled reactors. Sintered magnetite pellets were used as the dissolving material and these were mounted in a jet-impingement apparatus in a recirculating water loop. Exposures were carried out at temperatures of 25, 55 and 140 o C and pHs of neutral and 9.2 in which many FAC (Flow Accelerated Corrosion) studies have been conducted. Average dissolution rate constants were estimated by measuring the volume of lost material with a profilometry technique. The excellent correspondent between the calculated value of dissolution rate constant of 2.20 mm/s for the synthesized magnetite and 2.05 mm/s for the single crystal of magnetite at neutral condition shows that the particle removal from the synthesized pellets is not an obstruction in this technique. Also, good agreement between the values calculated in duplicated runs at neutral condition at room temperature supports the accuracy of the method. (author)

  1. Radiative lifetimes and two-body collisional deactivation rate constants in argon for Kr(4p 55p) and Kr(4p 55p') states

    International Nuclear Information System (INIS)

    Chang, R.S.F.; Horiguchi, H.; Setser, D.W.

    1980-01-01

    The radiative lifetimes and collisional deactivation rate constants, in argon, of eight Kr(4p 5 [ 2 P/sub 1/2/]5p and [ 2 P/sub 3/2/]5p) levels have been measured by a time-resolved laser-induced fluorescence technique in a flowing afterglow apparatus. The measured radiative lifetimes are compared with other experimental values and with theoretical calculations. Radiative branching ratios of these excited states also were measured in order to assign the absolute transition probabilities of the Kr(5p,5p'--5s, 5s') transition array from the radiative lifetimes. In addition to the total deactivation rate constants, product states from two-body collisions between Kr(5p and 5p') atoms and ground state argon atoms were identified from the laser-induced emission spectra, and product formation rate constants were assigned. Two-body intermultiplet transfer from Kr(4p 5 [ 2 P/sub 1/2/]5p) to the Kr(4p 5 [ 2 P/sub 3/2/]4d) levels occurs with ease. Intermultiplet transfer from the lowest level in the (4p 5 5p) configuration to the Kr(4p 5 5s and 5s') manifold was fast despite the large energy defect. However, this was the only Kr(5p) level that gave appreciable transfer to the Kr(5s or 5s') manifold. Generally the favored product states are within a few kT of the entrance channel

  2. Rate Constant Change of Photo Reaction of Bacteriorhodopsin Observed in Trimeric Molecular System.

    Science.gov (United States)

    Tsujiuchi, Yutaka; Masumoto, Hiroshi; Goto, Takashi

    2016-04-01

    To elucidate the time evolution of photo reaction of bacteriorhodopsin in glycerol mixed purple membrane at around 196 K under irradiation by red light, a kinetic model was constructed. The change of absorption with irradiation at times of 560 nm and 412 nm was analyzed for the purpose of determining reaction rates of photo reaction of bacteriorhodopsin and its product M intermediate. In this study it is shown that reaction rates of conversion from bacteriorhodopsin to the M intermediate can be explained by a set of linear differential equations. This model analysis concludes that bacteriorhodopsin in which constitutes a trimer unit with other two bacteriorhodopsin molecules changes into M intermediates in the 1.73 of reaction rate, in the initial step, and according to the number of M intermediate in a trimer unit, from three to one, the reaction rate of bacteriorhodopsin into M intermediates smaller as 1.73, 0.80, 0.19 which caused by influence of inter-molecular interaction between bacteriorhodopsin.

  3. Non-Constant Learning Rates in Retrospective Experience Curve Analyses and their Correlation to Deployment Programs

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Max [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Smith, Sarah J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Sohn, Michael D. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2015-07-16

    A key challenge for policy-makers and technology market forecasters is to estimate future technology costs and in particular the rate of cost reduction versus production volume. A related, critical question is what role should state and federal governments have in advancing energy efficient and renewable energy technologies? This work provides retrospective experience curves and learning rates for several energy-related technologies, each of which have a known history of federal and state deployment programs. We derive learning rates for eight technologies including energy efficient lighting technologies, stationary fuel cell systems, and residential solar photovoltaics, and provide an overview and timeline of historical deployment programs such as state and federal standards and state and national incentive programs for each technology. Piecewise linear regimes are observed in a range of technology experience curves, and public investments or deployment programs are found to be strongly correlated to an increase in learning rate across multiple technologies. A downward bend in the experience curve is found in 5 out of the 8 energy-related technologies presented here (electronic ballasts, magnetic ballasts, compact fluorescent lighting, general service fluorescent lighting, and the installed cost of solar PV). In each of the five downward-bending experience curves, we believe that an increase in the learning rate can be linked to deployment programs to some degree. This work sheds light on the endogenous versus exogenous contributions to technological innovation and highlights the impact of exogenous government sponsored deployment programs. This work can inform future policy investment direction and can shed light on market transformation and technology learning behavior.

  4. 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 (D 4 ), decamethylcyclopentasiloxane (D 5 ), and dodecamethylcyclohexasiloxane (D 6 ) 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 D 4 and D 5 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 D 6 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 D 5 were 33% higher than for D 4 (CI: 30-37%), whereas the rates for D 6 were only 8% higher than for D 5 (CI: 5-10%). The activation energies of the reactions of D 4 , D 5 , and D 6 with OH were not statistically different and had a value of 4300 ± 2800 J/mol.

  5. 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

  6. Extrapolation of rate constants of reactions producing H{sub 2} and O{sub 2} in radiolysis of water at high temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Leblanc, R.; Ghandi, K.; Hackman, B.; Liu, G. [Mount Allison Univ., Sackville, NB (Canada)

    2014-07-01

    One target of our research is to extrapolate known data on the rate constants of reactions and add corrections to estimate the rate constants at the higher temperatures reached by the SCWR reactors. The focus of this work was to extrapolate known data on the rate constants of reactions that produce Hydrogen or Oxygen with a rate constant below 10{sup 10} mol{sup -1} s{sup -1} at room temperature. The extrapolation is done taking into account the change in the diffusion rate of the interacting species and the cage effect with thermodynamic conditions. The extrapolations are done over a wide temperature range and under isobaric conditions. (author)

  7. Direct quantum mechanical calculation of the F + H{sub 2} {yields} HF + H thermal rate constant

    Energy Technology Data Exchange (ETDEWEB)

    Moix, Marc [Computer Simulation and Modeling (COSMO) Lab, Parc Cientific de Barcelona, Josep Samitier 5, 08028 Barcelona (Spain); Institut de Quimica Teorica i Computacional de la UB (IQTCUB), Universitat de Barcelona (Spain); Huarte-Larranaga, Fermin [Computer Simulation and Modeling (COSMO) Lab, Parc Cientific de Barcelona, Josep Samitier 5, 08028 Barcelona (Spain); Institut de Quimica Teorica i Computacional de la UB (IQTCUB), Universitat de Barcelona (Spain)], E-mail: fhuarte@pcb.ub.es

    2008-07-03

    Accurate full-dimensional quantum mechanical thermal rate constant values have been calculated for the F+H{sub 2}{yields}HF+H reaction on the Stark-Werner ab initio potential energy surface. These calculations are based on a flux correlation functions and employ a rigorous statistical sampling scheme to account for the overall rotation and the MCTDH scheme for the wave packet propagation. Our results shed some light on discrepancies on the thermal rate found for previous flux correlation based calculations with respect to accurate reactive scattering results. The resonance pattern of the all-J cumulative reaction probability is analyzed in terms of the partial wave contributions.

  8. Slopes, nearly constant loss, universality, and hopping rates for dispersive ionic conduction

    International Nuclear Information System (INIS)

    Macdonald, J Ross; Ahmad, Mohamad M

    2007-01-01

    The title topics are investigated, discussed, and new insights provided by considering isothermal frequency response data for seven different materials having quite different conductivity spans and involving different electrode polarization effects and temperatures. These data sets were fitted using several different models, including the Kohlrausch-related K0 and K1 ones derived from stretched-exponential response in the temporal domain. The quasi-universal UN model, the K1 with its shape parameter, β 1 , fixed at 1/3, fitted most of the data very well, and its fits of such data were used to compare its predictions for hopping rate with those derived from fitting with the conventional 'universal dynamic response' Almond-West real-part-of-conductivity model. The K1-model theoretical hopping rate, involving the mean waiting time for a hop and derived from microscopic stochastic analysis, was roughly twice as large as the empirical Almond-West rate for most of the materials considered and should be used in place of it. Its use in a generalized Nernst-Einstein equation led to comparison of estimates of the concentration of fully dissociated mobile charge carriers in superionic PbSnF 4 with earlier estimates of Ahmad using an Almond-West hopping rate value. Agreement with an independent structure-derived value was relatively poor. Fitting results obtained using the K0 model, for Na 2 SO 4 data sets for two different polycrystalline material phases, and involving severely limited conductivity variation, were far superior to those obtained using the K1 model. The estimated values of the K0 shape parameter, β 0 , were close to 1/3 for both phases, strongly suggesting that the charge motion was one dimensional for each phase, even though they involved different crystalline structures

  9. Determination of photoformation rates and scavenging rate constants of hydroxyl radicals in natural waters using an automatic light irradiation and injection system

    International Nuclear Information System (INIS)

    Nakatani, Nobutake; Hashimoto, Norichika; Shindo, Hirotaka; Yamamoto, Masatoshi; Kikkawa, Megumi; Sakugawa, Hiroshi

    2007-01-01

    Photoformation rates and scavenging rate constants of hydroxyl radicals (·OH) in natural water samples were determined by an automatic determination system. After addition of benzene as a chemical probe to a water sample in a reaction cell, light irradiation and injection of irradiated water samples into an HPLC as a function of time were performed automatically. Phenol produced by the reaction between ·OH and the benzene added to the water sample was determined to quantify the ·OH formation rate. The rate constants of ·OH formation from the photolysis of nitrate ions, nitrite ions and hydrogen peroxide were comparable with those obtained in previous studies. The percent of expected ·OH photoformation rate from added nitrate ion were high in drinking water (97.4%) and river water (99.3%). On the other hand, the low percent (65.0%) was observed in seawater due to the reaction of ·OH with the high concentrations of chloride and bromide ions. For the automatic system, the coefficient of variance for the determination of the ·OH formation rate was less than 5.0%, which is smaller than that in the previous report. When the complete time sequence of analytical cycle was 40 min for one sample, the detection limit of the photoformation rate and the sample throughput were 8 x 10 -13 M s -1 and 20 samples per day, respectively. The automatic system successfully determined the photoformation rates and scavenging rate constants of ·OH in commercial drinking water and the major source and sink of ·OH were identified as nitrate and bicarbonate ions, respectively

  10. Simple analytical approximation for rotationally inelastic rate constants based on the energy corrected sudden scaling law

    International Nuclear Information System (INIS)

    Smith, N.; Pritchard, D.E.

    1981-01-01

    We have recently demonstrated that the energy corrected sudden (ECS) scaling law of De Pristo et al. when conbined with the power law assumption for the basis rates k/sub l/→0proportional[l(l+1)]/sup -g/ can accurately fit a wide body of rotational energy transfer data. We develop a simple and accurate approximation to this fitting law, and in addition mathematically show the connection between it and our earlier proposed energy based law which also has been successful in describing both theoretical and experimental data on rotationally inelastic collisions

  11. The effect of solvation on the radiation damage rate constants for adenine

    DEFF Research Database (Denmark)

    Milhøj, Birgitte Olai; Sauer, Stephan P. A.

    2016-01-01

    in calculations of Gibbs free energies and reaction rates for the reaction between the OH radical and the DNA nucleobase adenine using Density Functional Theory at the ωB97X-D/6-311++G(2df,2pd) level with the Eckart tunneling correction. The solvent, water, has been included through either the implicit...... polarizable continuum model (PCM) or through explicit modelling of micro-solvation by a single water molecule at the site of reaction as well as the combination of both. Scrutiny of the thermodynamics and kinetics of the individual sub-reactions suggests that the qualitative differences introduced...

  12. Effect of selected calculation routines and dissociation constants on the determination of total carbon dioxide in seawater

    NARCIS (Netherlands)

    Stoll, M.H.C.; Rommets, J.W.; Baar, H.J.W. de

    1993-01-01

    During the 1989 and 1990 JGOFS North Atlantic Pilot Study a comparison was made between the Coulometric and the acid titration method for determination of total carbon dioxide (TCO2) in seawater. TCO2 and alkalinity have been calculated from acid titration using either the modified Gran plot or the

  13. Tempo of Diversification of Global Amphibians: One-Constant Rate, One-Continuous Shift or Multiple-Discrete Shifts?

    Directory of Open Access Journals (Sweden)

    Youhua Chen

    2014-01-01

    Full Text Available In this brief report, alternative time-varying diversification rate models were fitted onto the phylogeny of global amphibians by considering one-constant-rate (OCR, one-continuous-shift (OCS and multiplediscrete- shifts (MDS situations. The OCS diversification model was rejected by γ statistic (γ=-5.556, p⁄ 0.001, implying the existence of shifting diversification rates for global amphibian phylogeny. Through model selection, MDS diversification model outperformed OCS and OCR models using “laser” package under R environment. Moreover, MDS models, implemented using another R package “MEDUSA”, indicated that there were sixteen shifts over the internal nodes for amphibian phylogeny. Conclusively, both OCS and MDS models are recommended to compare so as to better quantify rate-shifting trends of species diversification. MDS diversification models should be preferential for large phylogenies using “MEDUSA” package in which any arbitrary numbers of shifts are allowed to model.

  14. Constant strain rate test and SCC-behaviour of stainless steels

    International Nuclear Information System (INIS)

    Krauss, H.; Speckhardt, H.

    1979-01-01

    In the present work, the stress corrosion cracking behaviour in boiling aqueous 35% magnesium chloride solution under conditions of no external current was investigated as a function of the defined extension rates for the two austenitic steels X 2 CrNi 189 and X 2 CrNiSi 1815, as well as for both ferritic austenitic steels X 6 CrNiMoCu 217 and X 2 CrNiMoN 225. The endurance time found until cracking, the maximum tensile stress, the sample stretching up to cracking and the relative rupture energy were determined for the evaluation, as well as metallographic investigations to describe the crack picture, test surface appearance and attack picture carried out. (orig.) 891 RW/orig. 892 BRE [de

  15. Rate constants for the reactions of OH with CH3Cl, CH2Cl2, CHCl3, and CH3Br

    Science.gov (United States)

    Hsu, K.-J.; Demore, W. B.

    1994-01-01

    Rate constants for the reactions of OH with CH3Cl, CH2Cl2, CHCl3, and CH3Br have been measured by a relative rate technique in which the reaction rate of each compound was compared to that of HFC-152a (CH3CHF2) and (for CH2Cl2) HFC-161 (CH3CH2F). Using absolute rate constants for HFC-152a and HFC-161, which we have determined relative to those for CH4, CH3CCl3, and C2H6, temperature dependent rate constants of both compounds were derived. The derived rate constant for CH3Br is in good agreement with recent absolute measurements. However, for the chloromethanes all the rate constants are lower at atmospheric temperatures than previously reported, especially for CH2Cl2 where the present rate constant is about a factor of 1.6 below the JPL 92-20 value. The new rate constant appears to resolve a discrepancy between the observed atmospheric concentrations and those calculated from the previous rate constant and estimated release rates.

  16. 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.

  17. Evaluation of Chemical Kinetic for Mathematics Model Reduction of Cadmium Reaction Rate, Constant and Reaction Orde in to Electrochemical Process

    International Nuclear Information System (INIS)

    Prayitno

    2007-01-01

    The experiment was reduction of cadmium rate with electrochemical influenced by time process, concentration, current strength and type of electrode plate. The aim of the experiment was to know the influence, mathematic model reduction of cadmium the reaction rate, reaction rate constant and reaction orde influenced by time process, concentration, current strength and type of electrode plate. Result of research indicate the time processing if using plate of copper electrode is during 30 minutes and using plate of aluminium electrode is during 20 minutes. Condition of strong current that used in process of electrochemical is only 0.8 ampere and concentration effective is 5.23 mg/l. The most effective type Al of electrode plate for reduction from waste and the efficiency of reduction is 98 %. (author)

  18. Nonmonotonic Temperature Dependence of the Pressure-Dependent Reaction Rate Constant and Kinetic Isotope Effect of Hydrogen Radical Reaction with Benzene Calculated by Variational Transition-State Theory.

    Science.gov (United States)

    Zhang, Hui; Zhang, Xin; Truhlar, Donald G; Xu, Xuefei

    2017-11-30

    The reaction between H and benzene is a prototype for reactions of radicals with aromatic hydrocarbons. Here we report calculations of the reaction rate constants and the branching ratios of the two channels of the reaction (H addition and H abstraction) over a wide temperature and pressure range. Our calculations, obtained with an accurate potential energy surface, are based on variational transition-state theory for the high-pressure limit of the addition reaction and for the abstraction reaction and on system-specific quantum Rice-Ramsperger-Kassel theory calibrated by variational transition-state theory for pressure effects on the addition reaction. The latter is a very convenient way to include variational effects, corner-cutting tunneling, and anharmonicity in falloff calculations. Our results are in very good agreement with the limited experimental data and show the importance of including pressure effects in the temperature interval where the mechanism changes from addition to abstraction. We found a negative temperature effect of the total reaction rate constants at 1 atm pressure in the temperature region where experimental data are missing and accurate theoretical data were previously missing as well. We also calculated the H + C 6 H 6 /C 6 D 6 and D + C 6 H 6 /C 6 D 6 kinetic isotope effects, and we compared our H + C 6 H 6 results to previous theoretical data for H + toluene. We report a very novel nonmonotonic dependence of the kinetic isotope effect on temperature. A particularly striking effect is the prediction of a negative temperature dependence of the total rate constant over 300-500 K wide temperature ranges, depending on the pressure but generally in the range from 600 to 1700 K, which includes the temperature range of ignition in gasoline engines, which is important because aromatics are important components of common fuels.

  19. Reaction F + C2H4: Rate Constant and Yields of the Reaction Products as a Function of Temperature over 298-950 K.

    Science.gov (United States)

    Bedjanian, Yuri

    2018-03-29

    The kinetics and products of the reaction of F + C 2 H 4 have been studied in a discharge flow reactor combined with an electron impact ionization mass spectrometer at nearly 2 Torr total pressure of helium in the temperature range 298-950 K. The total rate constant of the reaction, k 1 = (1.78 ± 0.30) × 10 -10 cm 3 molecule -1 s -1 , determined under pseudo-first-order conditions, monitoring the kinetics of F atom consumption in excess of C 2 H 4 , was found to be temperature independent in the temperature range used. H, C 2 H 3 F, and HF were identified as the reaction products. Absolute measurements of the yields of these species allowed to determine the branching ratios, k 1b / k 1 = (0.73 ± 0.07) exp(-(425 ± 45)/ T) and k 1a / k 1 = 1 - (0.73 ± 0.07) exp(-(425 ± 45)/ T) and partial rate constants for addition-elimination (H + C 2 H 3 F) and H atom abstraction (HF + C 2 H 3 ) pathways of the title reaction: k 1a = (0.80 ± 0.07) × 10 -10 exp(189 ± 37/ T) and k 1b = (1.26 ± 0.13) × 10 -10 exp(-414 ± 45/ T) cm 3 molecule -1 s -1 , respectively, at T = 298-950 K and with 2σ quoted uncertainties. The overall reaction rate constant can be adequately described by both the temperature independent value and as a sum of k 1a and k 1b . The kinetic and mechanistic data from the present study are discussed in comparison with previous absolute and relative measurements and theoretical calculations.

  20. Time-Dependent Quantum Wave Packet Study of the Si + OH → SiO + H Reaction: Cross Sections and Rate Constants.

    Science.gov (United States)

    Rivero Santamaría, Alejandro; Dayou, Fabrice; Rubayo-Soneira, Jesus; Monnerville, Maurice

    2017-03-02

    The dynamics of the Si( 3 P) + OH(X 2 Π) → SiO(X 1 Σ + ) + H( 2 S) reaction is investigated by means of the time-dependent wave packet (TDWP) approach using an ab initio potential energy surface recently developed by Dayou et al. ( J. Chem. Phys. 2013 , 139 , 204305 ) for the ground X 2 A' electronic state. Total reaction probabilities have been calculated for the first 15 rotational states j = 0-14 of OH(v=0,j) at a total angular momentum J = 0 up to a collision energy of 1 eV. Integral cross sections and state-selected rate constants for the temperature range 10-500 K were obtained within the J-shifting approximation. The reaction probabilities display highly oscillatory structures indicating the contribution of long-lived quasibound states supported by the deep SiOH/HSiO wells. The cross sections behave with collision energies as expected for a barrierless reaction and are slightly sensitive to the initial rotational excitation of OH. The thermal rate constants show a marked temperature dependence below 200 K with a maximum value around 15 K. The TDWP results globally agree with the results of earlier quasi-classical trajectory (QCT) calculations carried out by Rivero-Santamaria et al. ( Chem. Phys. Lett. 2014 , 610-611 , 335 - 340 ) with the same potential energy surface. In particular, the thermal rate constants display a similar temperature dependence, with TDWP values smaller than the QCT ones over the whole temperature range.

  1. Modeling the downward transport of 210Pb in Peatlands: Initial Penetration‐Constant Rate of Supply (IP-CRS) model

    International Nuclear Information System (INIS)

    Olid, Carolina; Diego, David; Garcia-Orellana, Jordi; Cortizas, Antonio Martínez; Klaminder, Jonatan

    2016-01-01

    The vertical distribution of 210 Pb is commonly used to date peat deposits accumulated over the last 100–150 years. However, several studies have questioned this method because of an apparent post-depositional mobility of 210 Pb within some peat profiles. In this study, we introduce the Initial Penetration–Constant Rate of Supply (IP-CRS) model for calculating ages derived from 210 Pb profiles that are altered by an initial migration of the radionuclide. This new, two-phased, model describes the distribution of atmospheric-derived 210 Pb ( 210 Pb xs ) in peat taking into account both incorporation of 210 Pb into the accumulating peat matrix as well as an initial flushing of 210 Pb through the uppermost peat layers. The validity of the IP-CRS model is tested in four anomalous 210 Pb peat records that showed some deviations from the typical exponential decay profile not explained by variations in peat accumulation rates. Unlike the most commonly used 210 Pb-dating model (Constant Rate of Supply (CRS)), the IP-CRS model estimates peat accumulation rates consistent with typical growth rates for peatlands from the same areas. Confidence in the IP-CRS chronology is also provided by the good agreement with independent chronological markers (i.e. 241 Am and 137 Cs). Our results showed that the IP-CRS can provide chronologies from peat records where 210 Pb mobility is evident, being a valuable tool for studies reconstructing past environmental changes using peat archives during the Anthropocene. - Highlights: • Accurate age dating of peat and sediment cores is critical for evaluating change. • A new 210 Pb dating model that includes vertical transport of 210 Pb was developed. • The IP-CRS model provided consistent peat accumulation rates. • The IP-CRS ages were consistent with independent chronological markers. • The IP-CRS model derives peat ages where downward 210 Pb transport is evidenced.

  2. Creatine kinase rate constant in the human heart measured with 3D‐localization at 7 tesla

    Science.gov (United States)

    Robson, Matthew D.; Neubauer, Stefan; Rodgers, Christopher T.

    2016-01-01

    Purpose We present a new Bloch‐Siegert four Angle Saturation Transfer (BOAST) method for measuring the creatine kinase (CK) first‐order effective rate constant kf in human myocardium at 7 tesla (T). BOAST combines a variant of the four‐angle saturation transfer (FAST) method using amplitude‐modulated radiofrequency pulses, phosphorus Bloch‐Siegert B1+‐mapping to determine the per‐voxel flip angles, and nonlinear fitting to Bloch simulations for postprocessing. Methods Optimal flip angles and repetition time parameters were determined from Monte Carlo simulations. BOAST was validated in the calf muscle of two volunteers at 3T and 7T. The myocardial CK forward rate constant was then measured in 10 volunteers at 7T in 82 min (after 1H localization). Results BOAST kfCK values were 0.281 ± 0.002 s−1 in the calf and 0.35 ± 0.05 s−1 in myocardium. These are consistent with literature values from lower fields. Using a literature values for adenosine triphosphate concentration, we computed CK flux values of 4.55 ± 1.52 mmol kg−1 s−1. The sensitive volume for BOAST depends on the B1 inhomogeneity of the transmit coil. Conclusion BOAST enables measurement of the CK rate constant in the human heart at 7T, with spatial localization in three dimensions to 5.6 mL voxels, using a 10‐cm loop coil. Magn Reson Med 78:20–32, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:27579566

  3. The D(+) + H2 reaction: differential and integral cross sections at low energy and rate constants at low temperature.

    Science.gov (United States)

    González-Lezana, Tomás; Scribano, Yohann; Honvault, Pascal

    2014-08-21

    The D(+) + H2 reaction is investigated by means of a time independent quantum mechanical (TIQM) and statistical quantum mechanical (SQM) methods. Differential cross sections and product rotational distributions obtained with these two theoretical approaches for collision energies between 1 meV and 0.1 eV are compared to analyze the dynamics of the process. The agreement observed between the TIQM differential cross sections and the SQM predictions as the energy increases revealed the role played by the complex-forming mechanism. The importance of a good description of the asymptotic regions is also investigated by calculating rate constants for the title reaction at low temperature.

  4. A Simulation Analysis of Errors in the Measurement of Standard Electrochemical Rate Constants from Phase-Selective Impedance Data.

    Science.gov (United States)

    1987-09-30

    RESTRICTIVE MARKINGSC Unclassif ied 2a SECURIly CLASSIFICATION ALIIMOA4TY 3 DIS1RSBj~jiOAVAILAB.I1Y OF RkPORI _________________________________ Approved...of the AC current, including the time dependence at a growing DME, at a given fixed potential either in the presence or the absence of an...the relative error in k b(app) is ob relatively small for ks (true) : 0.5 cm s-, and increases rapidly for ob larger rate constants as kob reaches the

  5. A survey of the reaction rate constants for the thermal dissociation and recombination of nitrogen and oxygen

    Science.gov (United States)

    Marraffa, Lionel; Dulikravich, George S.; Keeney, Timothy C.; Deiwert, George S.

    1988-01-01

    The objective of the present report is to survey the various values of forward and backward reaction rate constants used by investigators in the field of high-temperature (T greater than 2000 K) gas reactions involving nitrogen and oxygen only. The objective is to find those values that correlate well so that they can be used for the studies of hypersonic flow and supersonic combustion with reasonable confidence. Relatively good agreement among these various values is observed for temperatures lower than 10,000 K.

  6. Interaction of hydrated electron with dietary flavonoids and phenolic acids. Rate constants and transient spectra studied by pulse radiolysis

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Zhongli; Li, Xifeng; Katsumura, Yosuke [Tokyo Univ., Tokai, Ibaraki (Japan). Nuclear Engineering Research Lab

    2000-03-01

    The reaction rate constants and transient spectra of 11 flavonoids and 4 phenolic acids reacting with e{sub aq}{sup -} at neutral pH were measured. The results suggest that C{sub 4} keto group is the active site for e{sub aq}{sup -} to attack on flavonoids and phenolic acids, while the o-dihydroxy structure in B-ring, the C{sub 2,3} double bond, the C{sub 3}-OH group and glycosylation have little effects on the e{sub aq}{sup -} scavenging activities. (author)

  7. The WiggleZ Dark Energy Survey: constraining the evolution of Newton's constant using the growth rate of structure

    International Nuclear Information System (INIS)

    Nesseris, Savvas; Blake, Chris; Davis, Tamara; Parkinson, David

    2011-01-01

    We constrain the evolution of Newton's constant using the growth rate of large-scale structure measured by the WiggleZ Dark Energy Survey in the redshift range 0.1 m (assuming General Relativity), and use this to construct a diagnostic to detect the presence of an evolving Newton's constant. Secondly we directly measure the evolution of Newton's constant, G eff , that appears in Modified Gravity theories, without assuming General Relativity to be true. The novelty of these approaches are that, contrary to other methods, they do not require knowledge of the expansion history of the Universe, H(z), making them model independent tests. Our constraints for the second derivative of Newton's constant at the present day, assuming it is slowly evolving as suggested by Big Bang Nucleosynthesis constraints, using the WiggleZ data is G double-dot eff (t 0 ) = −1.19 ± 0.95·10 −20 h 2 yr −2 , where h is defined via H 0 = 100 h km s −1 Mpc −1 , while using both the WiggleZ and the Sloan Digital Sky Survey Luminous Red Galaxy (SDSS LRG) data is G double-dot eff (t 0 ) = −3.6 ± 6.8·10 −21 h 2 yr −2 , both being consistent with General Relativity. Finally, our constraint for the rms mass fluctuation σ 8 using the WiggleZ data is σ 8 = 0.75 ± 0.08, while using both the WiggleZ and the SDSS LRG data σ 8 = 0.77 ± 0.07, both in good agreement with the latest measurements from the Cosmic Microwave Background radiation

  8. Rate constants for the reactions of OH with HFC-134a (CF3CH2F) and HFC-134 (CHF2CHF2)

    Science.gov (United States)

    Demore, W. B.

    1993-01-01

    Measurements of rate constants for HFC-134 (CF2HCF2H) relative to CH3CCl3, HFC-125, and HFC-134a are reported. The measurements were made in a slow-flow, temperature controlled photochemical reactor, and were based on relative rates of disappearance of the parent compounds as measured by FTIR spectroscopy. Hydroxyl radicals were generated by 254-nm photolysis of O3 in the presence of water vapor. NASA/JPL rate constants for the reference compounds are used to derive temperature-dependent rate constants of both compounds. Rate constants obtained from the different reference compounds are in excellent agreement. The presently recommended rate constant for HFC-134a is about 25 percent too high.

  9. Measurement of nucleotide exchange rate constants in single rabbit soleus myofibrils during shortening and lengthening using a fluorescent ATP analog.

    Science.gov (United States)

    Shirakawa, I; Chaen, S; Bagshaw, C R; Sugi, H

    2000-02-01

    The kinetics of displacement of a fluorescent nucleotide, 2'(3')-O-[N[2-[[Cy3]amido]ethyl]carbamoyl]-adenosine 5'-triphosphate (Cy3-EDA-ATP), bound to rabbit soleus muscle myofibrils were studied using flash photolysis of caged ATP. Use of myofibrils from this slow twitch muscle allowed better resolution of the kinetics of nucleotide exchange than previous studies with psoas muscle myofibrils (, Biophys. J. 73:2033-2042). Soleus myofibrils in the presence of Cy3-EDA-nucleotides (Cy3-EDA-ATP or Cy3-EDA-ADP) showed selective fluorescence staining of the A-band. The K(m) for Cy3-EDA-ATP and the K(d) for Cy3-EDA-ADP binding to the myofibril A-band were 1.9 microM and 3.8 microM, respectively, indicating stronger binding of nucleotide to soleus cross-bridges compared to psoas cross-bridges (2.6 microM and 50 microM, respectively). After flash photolysis of caged ATP, the A-band fluorescence of the myofibril in the Cy3-EDA-ATP solution under isometric conditions decayed exponentially with a rate constant of 0.045 +/- 0.007 s(-1) (n = 32) at 10 degrees C, which was about seven times slower than that for psoas myofibrils. When a myofibril was allowed to shorten with a constant velocity, the nucleotide displacement rate constant increased from 0.066 s(-1) (isometric) to 0.14 s(-1) at 20 degrees C with increasing shortening velocity up to 0.1 myofibril length/s (V(max), the shortening velocity under no load was approximately 0. 2 myofibril lengths/s). The rate constant was not significantly affected by an isovelocity stretch of up to 0.1 myofibril lengths/s. These results suggest that the cross-bridge kinetics are not significantly affected at higher strain during lengthening but depend on the lower strain during shortening. These data also indicate that the interaction distance between a cross-bridge and the actin filament is at least 16 nm for a single cycle of the ATPase.

  10. Appropriate control time constant in relation to characteristics of the baroreflex vascular system in 1/R control of the total artificial heart.

    Science.gov (United States)

    Mizuta, Sora; Saito, Itsuro; Isoyama, Takashi; Hara, Shintaro; Yurimoto, Terumi; Li, Xinyang; Murakami, Haruka; Ono, Toshiya; Mabuchi, Kunihiko; Abe, Yusuke

    2017-09-01

    1/R control is a physiological control method of the total artificial heart (TAH) with which long-term survival was obtained with animal experiments. However, 1/R control occasionally diverged in the undulation pump TAH (UPTAH) animal experiment. To improve the control stability of the 1/R control, appropriate control time constant in relation to characteristics of the baroreflex vascular system was investigated with frequency analysis and numerical simulation. In the frequency analysis, data of five goats in which the UPTAH was implanted were analyzed with first Fourier transform technique to examine the vasomotion frequency. The numerical simulation was carried out repeatedly changing baroreflex parameters and control time constant using the elements-expanded Windkessel model. Results of the frequency analysis showed that the 1/R control tended to diverge when very low frequency band that was an indication of the vasomotion frequency was relative high. In numerical simulation, divergence of the 1/R control could be reproduced and the boundary curves between the divergence and convergence of the 1/R control varied depending on the control time constant. These results suggested that the 1/R control tended to be unstable when the TAH recipient had high reflex speed in the baroreflex vascular system. Therefore, the control time constant should be adjusted appropriately with the individual vasomotion frequency.

  11. Temperature dependence of the rate constant for reactions of hydrated electrons with H, OH and H2O2

    DEFF Research Database (Denmark)

    Christensen, H.; Sehested, K.; Løgager, T.

    1994-01-01

    The temperature dependence of the rate constants, for the reactions of hydrated electrons with H atoms, OH radicals and H2O2 has been determined. The reaction with H atoms, studied in the temperature range 20-250-degrees-C gives k(20-degrees-C) = 2.4 x 10(10) M-1 s-1 and the activation energy E......-1 and E(A) = 15.6 kJ mol-1 (3.7 kcal mol-1) measured from 5-150-degrees-C. Thus, the activation energy for all three fast reactions is close to that expected for diffusion controlled reactions. As phosphates were used as buffer system, the rate constant and activation energy for the reaction......(A) = 14.0 kJ mol-1 (3.3 kcal mol-1). For reaction with OH radicals the corresponding values are, k(20-degrees-C) = 3.1 x 10(10) M-1 s-1 and E(A) = 14.7 kJ mol-1 (3.5 kcal mol-1) determined in the temperature range 5-175-degrees-C. For reaction with H2O2 the values are, k(20-degrees-C) = 1.2 x 10(10) M-1 s...

  12. Determination of the stability constants of a number of metal fluoride complexes and their rates of formation

    International Nuclear Information System (INIS)

    Hammer, R.R.

    1979-08-01

    The stability constants of the fluoride complexes of Al +3 , H 3 BO 3 , Cr +3 , Cr +6 , Fe +3 , Gd +3 , Nb +5 , UO 2 +2 , and Zr +4 were determined in 0.96 and 2.88 M HNO 3 solutions in the temperature range 25 to 60 0 C with a fluoride specific ion electrode. These data can be used to calculate the concentration of chemical species in solution and will be used to correlate solution properties with solution composition. The solubilities of some fluoride precipitates were also measured in nitric acid solutions. The rates of formation of the fluoborates, aluminum fluoride, and zirconium fluoride complexes were measured with a fluoride specific ion electrode at 25, 35, and 45 0 C. The rates of formation of all complexes, except BF 4 - , AlF +2 , and a fluoride complex with aluminum containing more than three fluorides associated with it, were too fast to measure with the instrumentation used

  13. Determination of constant of chemical reaction rate in the process of steel treatment in the endothermal atmosphere

    International Nuclear Information System (INIS)

    Gyulikhandanov, E.L.; Kislenkov, V.V.

    1978-01-01

    The high-temperature method was applied to measuring a relative variation in the electrical resistance of a thin steel foil prepared from the 12KhN3A, 18Kh2N4VA, 20KhGNR, and 20Kh3MVF steels during its carburization and decarburization, and determined was the temperature dependence of the reaction rate of the interaction of the endothermal atmosphere of different compositions with the analloyed γ-Fe. A connection has been established between the reaction rate constant and the thermodynamic activity of carbon in the alloyed austenite at the temperature of about 925 deg C, corresponding to the cementation temperature. This provides the quantitative estimation of the above value for any alloyed steels and with the presence of numerical values of diffusion coefficients; this also enables one to carry out an accurate calculation of the distribution of carbon throughout the depth of a layer when effecting the cementation in the endothermal atmosphere

  14. Tissue vitamin concentrations are maintained constant by changing the urinary excretion rate of vitamins in rats' restricted food intake.

    Science.gov (United States)

    Shibata, Katsumi; Fukuwatari, Tsutomu

    2014-01-01

    We previously reported that mild food restriction induces a reduction in tryptophan-nicotinamide conversion, which helps to explain why death secondary to pellagra is pandemic during the hungry season. In this study, we investigated the levels of B-group vitamins in the liver, kidney, blood, and urine in rats that underwent gradual restriction of food intake (80, 60, 40, and 20% restriction vs. ad libitum food intake). No significant differences in the B-group vitamin concentrations (mol/g tissue) in the liver and kidney were observed at any level of food restriction. However, the urine excretion rates exhibited some characteristic phenomena that differed by vitamin. These results show that the tissue concentrations of B-group vitamins were kept constant by changing the urinary elimination rates of vitamins under various levels of food restriction. Only vitamin B12 was the only (exception).

  15. The reaction of atomic hydrogen with germane - Temperature dependence of the rate constant and implications for germane photochemistry in the atmospheres of Jupiter and Saturn

    Science.gov (United States)

    Nava, David F.; Payne, Walter A.; Marston, George; Stief, Louis J.

    1993-01-01

    Studies of the formation and loss processes for GeH4 are required in order to provide data to help determine the major chemical form in which germanium exists in the atmospheres of Jupiter and Saturn. The reaction of hydrogen atoms with germane is one of the most important of these reactions. The absolute rate constant for this reaction as a function of temperature and pressure is studied. Flash photolysis of dilute mixtures of GeH4 in argon, combined with time-resolved detection of H atoms via Lyman alpha resonance fluorescence, is employed to measure the reaction rate. The reaction is shown to be moderately rapid, independent of total pressure, but possessing a positive temperature dependence.

  16. Constant strain rate and peri-implant bone modeling: an in vivo longitudinal micro-CT analysis.

    Science.gov (United States)

    De Smet, Els; Jaecques, Siegfried V N; Wevers, Martine; Sloten, Jos Vander; Naert, Ignace E

    2013-06-01

    Strain, frequency, loading time, and strain rate, among others, determine mechanical parameters in osteogenic loading. We showed a significant osteogenic effect on bone mass (BM) by daily peri-implant loading at 1.600µε.s(-1) after 4 weeks. To study the peri-implant osteogenic effect of frequency and strain in the guinea pig tibia by in vivo longitudinal micro-computed tomography (CT) analysis. One week after implant installation in both hind limb tibiae, one implant was loaded daily for 10' during 4 weeks, while the other served as control. Frequencies (3, 10, and 30Hz) and strains varied alike in the three series to keep the strain rate constant at 1.600µε.s(-1) . In vivo micro-CT scans were taken of both tibiae: 1 week after implantation but before loading (v1) and after 2 (v2) and 4 weeks (v3) of loading as well as postmortem (pm). BM (BM (%) bone-occupied area fraction) was calculated as well as the difference between test and control sides (delta BM) RESULTS: All implants (n=78) were clinically stable at 4 weeks. Significant increase in BM was measured between v1 and v2 (pimplant marrow 500 Region of Interest already 2 weeks after loading (p=.01) and was significantly larger (11%) in series 1 compared with series 2 (p=.006) and 3 (p=.016). Within the constraints of constant loading time and strain rate, the effect of early implant loading on the peri-implant bone is strongly dependent on strain and frequency. This cortical bone model has shown to be most sensitive for high force loading at low frequency. © 2011 Wiley Periodicals, Inc.

  17. Creatine kinase rate constant in the human heart measured with 3D-localization at 7 tesla.

    Science.gov (United States)

    Clarke, William T; Robson, Matthew D; Neubauer, Stefan; Rodgers, Christopher T

    2017-07-01

    We present a new Bloch-Siegert four Angle Saturation Transfer (BOAST) method for measuring the creatine kinase (CK) first-order effective rate constant k f in human myocardium at 7 tesla (T). BOAST combines a variant of the four-angle saturation transfer (FAST) method using amplitude-modulated radiofrequency pulses, phosphorus Bloch-Siegert B1+-mapping to determine the per-voxel flip angles, and nonlinear fitting to Bloch simulations for postprocessing. Optimal flip angles and repetition time parameters were determined from Monte Carlo simulations. BOAST was validated in the calf muscle of two volunteers at 3T and 7T. The myocardial CK forward rate constant was then measured in 10 volunteers at 7T in 82 min (after 1 H localization). BOAST kfCK values were 0.281 ± 0.002 s -1 in the calf and 0.35 ± 0.05 s -1 in myocardium. These are consistent with literature values from lower fields. Using a literature values for adenosine triphosphate concentration, we computed CK flux values of 4.55 ± 1.52 mmol kg -1 s -1 . The sensitive volume for BOAST depends on the B 1 inhomogeneity of the transmit coil. BOAST enables measurement of the CK rate constant in the human heart at 7T, with spatial localization in three dimensions to 5.6 mL voxels, using a 10-cm loop coil. Magn Reson Med 78:20-32, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

  18. Calculated Third Order Rate Constants for Interpreting the Mechanisms of Hydrolyses of Chloroformates, Carboxylic Acid Halides, Sulfonyl Chlorides and Phosphorochloridates

    Directory of Open Access Journals (Sweden)

    T. William Bentley

    2015-05-01

    Full Text Available Hydrolyses of acid derivatives (e.g., carboxylic acid chlorides and fluorides, fluoro- and chloroformates, sulfonyl chlorides, phosphorochloridates, anhydrides exhibit pseudo-first order kinetics. Reaction mechanisms vary from those involving a cationic intermediate (SN1 to concerted SN2 processes, and further to third order reactions, in which one solvent molecule acts as the attacking nucleophile and a second molecule acts as a general base catalyst. A unified framework is discussed, in which there are two reaction channels—an SN1-SN2 spectrum and an SN2-SN3 spectrum. Third order rate constants (k3 are calculated for solvolytic reactions in a wide range of compositions of acetone-water mixtures, and are shown to be either approximately constant or correlated with the Grunwald-Winstein Y parameter. These data and kinetic solvent isotope effects, provide the experimental evidence for the SN2-SN3 spectrum (e.g., for chloro- and fluoroformates, chloroacetyl chloride, p-nitrobenzoyl p-toluenesulfonate, sulfonyl chlorides. Deviations from linearity lead to U- or V-shaped plots, which assist in the identification of the point at which the reaction channel changes from SN2-SN3 to SN1-SN2 (e.g., for benzoyl chloride.

  19. The effect of surfaces on AGR coolant chemistry: critical assessment of gas-phase rate constants relevant to ethane pyrolysis

    International Nuclear Information System (INIS)

    Gonzales, M.D.U.; Norfolk, D.J.

    1988-02-01

    Previous work has shown the ability of a chemical kinetic model, applied using the FACSIMILE computer code, to predict the thermal decomposition of ethane in a silica flow reactor. To optimise the performance of the model, the present report reviews the literature data on the twenty reactions which it incorporates. Critical assessment has shown some discrepancies in the previously used rate constants, especially those leading to ethyne formation. Table 2 of the report gives the kinetic data which, as a result of the present evaluation, are recommended for future work. Use of these data gives significantly improved agreement between the model and the experimental results, particularly for ethyne formation, which had previously been underestimated. (author)

  20. Reaction paths and rate constants of the reaction of hydroxyl radicals with environmental species under tropospheric conditions

    International Nuclear Information System (INIS)

    Leonard, C.; Wahner, A.; Zetzsch, C.

    1987-01-01

    The uv-laser absorption technique in a multipath cell (with excimer-laser photolysis for radical production) is used to investigate the rate constants of the reaction of OH with carbon monoxide. The pressure dependence and the influence of collision partners (measurements in pure oxygen up to one atmosphere) of this important atmospheric chemical reaction are determined. In the kinetic measurements detection limits of 10 7 OH cm -3 are reached with millisecond time resolution. Furthermore the application of the cw-Laser for stationary OH measurements (for example in smog chambers or the free troposphere) is described. The possibilities and limits of different detection methods are discussed with respect to of noise spectra. Modifications of the apparatus with a frequency modulation technique are presented, with an extrapolated detection limit of 10 5 OH cm -3 . (orig.) With 43 refs., 16 figs [de

  1. Water Exchange Rate Constant as a Biomarker of Treatment Efficacy in Patients With Brain Metastases Undergoing Stereotactic Radiosurgery

    Energy Technology Data Exchange (ETDEWEB)

    Mehrabian, Hatef, E-mail: hatef.mehrabian@sri.utoronto.ca [Medical Biophysics, University of Toronto, Toronto, Ontario (Canada); Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario (Canada); Desmond, Kimberly L. [Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario (Canada); Chavez, Sofia [Research Imaging Centre, Centre for Addiction and Mental Health, Toronto, Ontario (Canada); Bailey, Colleen [Computer Science Department, University College London, London (United Kingdom); Rola, Radoslaw [Neurosurgery and Pediatric Neurosurgery, Medical University, Lublin (Poland); Sahgal, Arjun [Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario (Canada); Radiation Oncology, Sunnybrook Health Sciences Centre, Toronto, Ontario (Canada); Czarnota, Gregory J. [Medical Biophysics, University of Toronto, Toronto, Ontario (Canada); Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario (Canada); Radiation Oncology, Sunnybrook Health Sciences Centre, Toronto, Ontario (Canada); Soliman, Hany [Radiation Oncology, Sunnybrook Health Sciences Centre, Toronto, Ontario (Canada); Martel, Anne L. [Medical Biophysics, University of Toronto, Toronto, Ontario (Canada); Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario (Canada); Stanisz, Greg J. [Medical Biophysics, University of Toronto, Toronto, Ontario (Canada); Physical Sciences, Sunnybrook Research Institute, Toronto, Ontario (Canada); Neurosurgery and Pediatric Neurosurgery, Medical University, Lublin (Poland)

    2017-05-01

    Purpose: This study was designed to evaluate whether changes in metastatic brain tumors after stereotactic radiosurgery (SRS) can be seen with quantitative MRI early after treatment. Methods and Materials: Using contrast-enhanced MRI, a 3-water-compartment tissue model consisting of intracellular (I), extracellular-extravascular (E), and vascular (V) compartments was used to assess the intra–extracellular water exchange rate constant (k{sub IE}), efflux rate constant (k{sub ep}), and water compartment volume fractions (M{sub 0,I}, M{sub 0,E}, M{sub 0,V}). In this prospective study, 19 patients were MRI-scanned before treatment and 1 week and 1 month after SRS. The change in model parameters between the pretreatment and 1-week posttreatment scans was correlated to the change in tumor volume between pretreatment and 1-month posttreatment scans. Results: At 1 week k{sub IE} differentiated (P<.001) tumors that had partial response from tumors with stable and progressive disease, and a high correlation (R=−0.76, P<.001) was observed between early changes in the k{sub IE} and tumor volume change 1 month after treatment. Other model parameters had lower correlation (M{sub 0,E}) or no correlation (k{sub ep}, M{sub 0,V}). Conclusions: This is the first study that measured k{sub IE} early after SRS, and it found that early changes in k{sub IE} (1 week after treatment) highly correlated with long-term tumor response and could predict the extent of tumor shrinkage at 1 month after SRS.

  2. Water Exchange Rate Constant as a Biomarker of Treatment Efficacy in Patients With Brain Metastases Undergoing Stereotactic Radiosurgery

    International Nuclear Information System (INIS)

    Mehrabian, Hatef; Desmond, Kimberly L.; Chavez, Sofia; Bailey, Colleen; Rola, Radoslaw; Sahgal, Arjun; Czarnota, Gregory J.; Soliman, Hany; Martel, Anne L.; Stanisz, Greg J.

    2017-01-01

    Purpose: This study was designed to evaluate whether changes in metastatic brain tumors after stereotactic radiosurgery (SRS) can be seen with quantitative MRI early after treatment. Methods and Materials: Using contrast-enhanced MRI, a 3-water-compartment tissue model consisting of intracellular (I), extracellular-extravascular (E), and vascular (V) compartments was used to assess the intra–extracellular water exchange rate constant (k IE ), efflux rate constant (k ep ), and water compartment volume fractions (M 0,I , M 0,E , M 0,V ). In this prospective study, 19 patients were MRI-scanned before treatment and 1 week and 1 month after SRS. The change in model parameters between the pretreatment and 1-week posttreatment scans was correlated to the change in tumor volume between pretreatment and 1-month posttreatment scans. Results: At 1 week k IE differentiated (P<.001) tumors that had partial response from tumors with stable and progressive disease, and a high correlation (R=−0.76, P<.001) was observed between early changes in the k IE and tumor volume change 1 month after treatment. Other model parameters had lower correlation (M 0,E ) or no correlation (k ep , M 0,V ). Conclusions: This is the first study that measured k IE early after SRS, and it found that early changes in k IE (1 week after treatment) highly correlated with long-term tumor response and could predict the extent of tumor shrinkage at 1 month after SRS.

  3. Combination of poroelasticity theory and constant strain rate test in modelling land subsidence due to groundwater extraction

    Science.gov (United States)

    Pham, Tien Hung; Rühaak, Wolfram; Sass, Ingo

    2017-04-01

    Extensive groundwater extraction leads to a drawdown of the ground water table. Consequently, soil effective stress increases and can cause land subsidence. Analysis of land subsidence generally requires a numerical model based on poroelasticity theory, which was first proposed by Biot (1941). In the review of regional land subsidence accompanying groundwater extraction, Galloway and Burbey (2011) stated that more research and application is needed in coupling of stress-dependent land subsidence process. In geotechnical field, the constant rate of strain tests (CRS) was first introduced in 1969 (Smith and Wahls 1969) and was standardized in 1982 through the designation D4186-82 by American Society for Testing and Materials. From the reading values of CRS tests, the stress-dependent parameters of poroelasticity model can be calculated. So far, there is no research to link poroelasticity theory with CRS tests in modelling land subsidence due to groundwater extraction. One dimensional CRS tests using conventional compression cell and three dimension CRS tests using Rowe cell were performed. The tests were also modelled by using finite element method with mixed elements. Back analysis technique is used to find the suitable values of hydraulic conductivity and bulk modulus that depend on the stress or void ratio. Finally, the obtained results are used in land subsidence models. Biot, M. A. (1941). "General theory of three-dimensional consolidation." Journal of applied physics 12(2): 155-164. Galloway, D. L. and T. J. Burbey (2011). "Review: Regional land subsidence accompanying groundwater extraction." Hydrogeology Journal 19(8): 1459-1486. Smith, R. E. and H. E. Wahls (1969). "Consolidation under constant rates of strain." Journal of Soil Mechanics & Foundations Div.

  4. Predicting the Rate Constant of Electron Tunneling Reactions at the CdSe-TiO2 Interface.

    Science.gov (United States)

    Hines, Douglas A; Forrest, Ryan P; Corcelli, Steven A; Kamat, Prashant V

    2015-06-18

    Current interest in quantum dot solar cells (QDSCs) motivates an understanding of the electron transfer dynamics at the quantum dot (QD)-metal oxide (MO) interface. Employing transient absorption spectroscopy, we have monitored the electron transfer rate (ket) at this interface as a function of the bridge molecules that link QDs to TiO2. Using mercaptoacetic acid, 3-mercaptopropionic acid, 8-mercaptooctanoic acid, and 16-mercaptohexadecanoic acid, we observe an exponential attenuation of ket with increasing linker length, and attribute this to the tunneling of the electron through the insulating linker molecule. We model the electron transfer reaction using both rectangular and trapezoidal barrier models that have been discussed in the literature. The one-electron reduction potential (equivalent to the lowest unoccupied molecular orbital) of each molecule as determined by cyclic voltammetry (CV) was used to estimate the effective barrier height presented by each ligand at the CdSe-TiO2 interface. The electron transfer rate (ket) calculated for each CdSe-ligand-TiO2 interface using both models showed the results in agreement with the experimentally determined trend. This demonstrates that electron transfer between CdSe and TiO2 can be viewed as electron tunneling through a layer of linking molecules and provides a useful method for predicting electron transfer rate constants.

  5. Effects of a constant rate infusion of detomidine on cardiovascular function, isoflurane requirements and recovery quality in horses.

    Science.gov (United States)

    Schauvliege, Stijn; Marcilla, Miguel Gozalo; Verryken, Kirsten; Duchateau, Luc; Devisscher, Lindsey; Gasthuys, Frank

    2011-11-01

    To examine the influence of a detomidine constant rate infusion (CRI) on cardiovascular function, isoflurane requirements and recovery quality in horses undergoing elective surgery. Prospective, randomized, blinded, clinical trial. Twenty adult healthy horses. After sedation (detomidine, 10 μg kg(-1) intravenously [IV]) and induction of anaesthesia (midazolam 0.06 mg kg(-1) , ketamine 2.2 mg kg(-1) IV), anaesthesia was maintained with isoflurane in oxygen/air (inspiratory oxygen fraction 55%). When indicated, the lungs were mechanically ventilated. Dobutamine was administered when MAPdetomidine (5 μg kg(-1)  hour(-1) ) (D) or saline (S) CRI, with the anaesthetist unaware of the treatment. Monitoring included end-tidal isoflurane concentration, arterial pH, PaCO(2) , PaO(2) , dobutamine administration rate, heart rate (HR), arterial pressure, cardiac index (CI), systemic vascular resistance (SVR), stroke index and oxygen delivery index (ḊO(2) I). For recovery from anaesthesia, all horses received 2.5 μg kg(-1) detomidine IV. Recovery quality and duration were recorded in each horse. For statistical analysis, anova, Pearson chi-square and Wilcoxon rank sum tests were used as relevant. Heart rate (p=0.0176) and ḊO(2) I (p= 0.0084) were lower and SVR higher (p=0.0126) in group D, compared to group S. Heart rate (p=0.0011) and pH (p=0.0187) increased over time. Significant differences in isoflurane requirements were not detected. Recovery quality and duration were comparable between treatments. A detomidine CRI produced cardiovascular effects typical for α(2) -agonists, without affecting isoflurane requirements, recovery duration or recovery quality. © 2011 The Authors. Veterinary Anaesthesia and Analgesia. © 2011 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.

  6. Nonadiabatic rate constants for proton transfer and proton-coupled electron transfer reactions in solution: Effects of quadratic term in the vibronic coupling expansion.

    Science.gov (United States)

    Soudackov, Alexander V; Hammes-Schiffer, Sharon

    2015-11-21

    Rate constant expressions for vibronically nonadiabatic proton transfer and proton-coupled electron transfer reactions are presented and analyzed. The regimes covered include electronically adiabatic and nonadiabatic reactions, as well as high-frequency and low-frequency proton donor-acceptor vibrational modes. These rate constants differ from previous rate constants derived with the cumulant expansion approach in that the logarithmic expansion of the vibronic coupling in terms of the proton donor-acceptor distance includes a quadratic as well as a linear term. The analysis illustrates that inclusion of this quadratic term in the framework of the cumulant expansion framework may significantly impact the rate constants at high temperatures for proton transfer interfaces with soft proton donor-acceptor modes that are associated with small force constants and weak hydrogen bonds. The effects of the quadratic term may also become significant in these regimes when using the vibronic coupling expansion in conjunction with a thermal averaging procedure for calculating the rate constant. In this case, however, the expansion of the coupling can be avoided entirely by calculating the couplings explicitly for the range of proton donor-acceptor distances sampled. The effects of the quadratic term for weak hydrogen-bonding systems are less significant for more physically realistic models that prevent the sampling of unphysical short proton donor-acceptor distances. Additionally, the rigorous relation between the cumulant expansion and thermal averaging approaches is clarified. In particular, the cumulant expansion rate constant includes effects from dynamical interference between the proton donor-acceptor and solvent motions and becomes equivalent to the thermally averaged rate constant when these dynamical effects are neglected. This analysis identifies the regimes in which each rate constant expression is valid and thus will be important for future applications to proton

  7. Nonadiabatic rate constants for proton transfer and proton-coupled electron transfer reactions in solution: Effects of quadratic term in the vibronic coupling expansion

    International Nuclear Information System (INIS)

    Soudackov, Alexander V.; Hammes-Schiffer, Sharon

    2015-01-01

    Rate constant expressions for vibronically nonadiabatic proton transfer and proton-coupled electron transfer reactions are presented and analyzed. The regimes covered include electronically adiabatic and nonadiabatic reactions, as well as high-frequency and low-frequency proton donor-acceptor vibrational modes. These rate constants differ from previous rate constants derived with the cumulant expansion approach in that the logarithmic expansion of the vibronic coupling in terms of the proton donor-acceptor distance includes a quadratic as well as a linear term. The analysis illustrates that inclusion of this quadratic term in the framework of the cumulant expansion framework may significantly impact the rate constants at high temperatures for proton transfer interfaces with soft proton donor-acceptor modes that are associated with small force constants and weak hydrogen bonds. The effects of the quadratic term may also become significant in these regimes when using the vibronic coupling expansion in conjunction with a thermal averaging procedure for calculating the rate constant. In this case, however, the expansion of the coupling can be avoided entirely by calculating the couplings explicitly for the range of proton donor-acceptor distances sampled. The effects of the quadratic term for weak hydrogen-bonding systems are less significant for more physically realistic models that prevent the sampling of unphysical short proton donor-acceptor distances. Additionally, the rigorous relation between the cumulant expansion and thermal averaging approaches is clarified. In particular, the cumulant expansion rate constant includes effects from dynamical interference between the proton donor-acceptor and solvent motions and becomes equivalent to the thermally averaged rate constant when these dynamical effects are neglected. This analysis identifies the regimes in which each rate constant expression is valid and thus will be important for future applications to proton

  8. Acceleration and sensitivity analysis of lattice kinetic Monte Carlo simulations using parallel processing and rate constant rescaling.

    Science.gov (United States)

    Núñez, M; Robie, T; Vlachos, D G

    2017-10-28

    Kinetic Monte Carlo (KMC) simulation provides insights into catalytic reactions unobtainable with either experiments or mean-field microkinetic models. Sensitivity analysis of KMC models assesses the robustness of the predictions to parametric perturbations and identifies rate determining steps in a chemical reaction network. Stiffness in the chemical reaction network, a ubiquitous feature, demands lengthy run times for KMC models and renders efficient sensitivity analysis based on the likelihood ratio method unusable. We address the challenge of efficiently conducting KMC simulations and performing accurate sensitivity analysis in systems with unknown time scales by employing two acceleration techniques: rate constant rescaling and parallel processing. We develop statistical criteria that ensure sufficient sampling of non-equilibrium steady state conditions. Our approach provides the twofold benefit of accelerating the simulation itself and enabling likelihood ratio sensitivity analysis, which provides further speedup relative to finite difference sensitivity analysis. As a result, the likelihood ratio method can be applied to real chemistry. We apply our methodology to the water-gas shift reaction on Pt(111).

  9. Energy dependence of the reaction rate constants of Ar+, Ar++ and N2+ ions with Cl2

    International Nuclear Information System (INIS)

    Lukac, P.; Holubcik, L.; Morva, I.; Lindinger, W.

    2002-01-01

    Dry etching processes using low temperature plasmas in Cl 2 and in Cl 2 -noble gas or nitrogen mixtures are common in the manufacture of semiconductor devices, but their chemical mechanisms are often poorly understood. Results are given for the reaction rate constant measurements of Ar + , Ar ++ , N 2 + ions with chlorine as a function of mean relative kinetic energy. The experiments were performed by using the innsbruck flow drift tube (IFDT) apparatus. Measurements were done at various E/N values, where E is the electric field strength and N the buffer gas density in the drift section. The mean relative kinetic energy KE CM between the ions and the neutral chlorine Cl 2 was calculated using the Wanniers formula. It was found that The N 2 + , Ar + and Ar ++ positive ions react with chlorine Cl 2 very fast and the corresponding reaction rate coefficients depend on the mean relative kinetic energy. For the reaction of Ar - with Cl 2 , its reaction coefficient depends also on the buffer gas. It can imply the enhancement of Cl 2 + ions during etching of Si in the Ar/Cl 2 mixtures. (nevyjel)

  10. SU-E-T-421: Feasibility Study of Volumetric Modulated Arc Therapy with Constant Dose Rate for Endometrial Cancer

    Energy Technology Data Exchange (ETDEWEB)

    Yang, R; Wang, J [Peking University Third Hospital, Beijing, Beijing (China)

    2014-06-01

    Purpose: To investigate the feasibility, efficiency, and delivery accuracy of volumetric modulated arc therapy with constant dose rate (VMAT-CDR) for whole-pelvic radiotherapy (WPRT) of endometrial cancer. Methods: The nine-Field intensity-modulated radiotherapy (IMRT), VMAT with variable dose-rate (VMAT-VDR), and VMAT-CDR plans were created for 9 patients with endometrial cancer undergoing WPRT. The dose distribution of planning target volume (PTV), organs at risk (OARs), and normal tissue (NT) were compared. The monitor units (MUs) and treatment delivery time were also evaluated. For each VMAT-CDR plan, a dry Run was performed to assess the dosimetric accuracy with MatriXX from IBA. Results: Compared with IMRT, the VMAT-CDR plans delivered a slightly greater V20 of the bowel, bladder, pelvis bone, and NT, but significantly decreased the dose to the high-dose region of the rectum and pelvis bone. The MUs Decreased from 1105 with IMRT to 628 with VMAT-CDR. The delivery time also decreased from 9.5 to 3.2 minutes. The average gamma pass rate was 95.6% at the 3%/3 mm criteria with MatriXX pretreatment verification for 9 patients. Conclusion: VMAT-CDR can achieve comparable plan quality with significant shorter delivery time and smaller number of MUs compared with IMRT for patients with endometrial cancer undergoing WPRT. It can be accurately delivered and be an alternative to IMRT on the linear accelerator without VDR capability. This work is supported by the grant project, National Natural; Science Foundation of China (No. 81071237)

  11. 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.

  12. Do illness rating systems predict discharge location, length of stay, and cost after total hip arthroplasty?

    Directory of Open Access Journals (Sweden)

    Sarah E. Rudasill, BA

    2018-06-01

    Conclusions: These findings suggest that although ASA classifications predict discharge location and SOI scores predict length of stay and total costs, other factors beyond illness rating systems remain stronger predictors of discharge for THA patients.

  13. Dependence of total dose response of bipolar linear microcircuits on applied dose rate

    International Nuclear Information System (INIS)

    McClure, S.; Will, W.; Perry, G.; Pease, R.L.

    1994-01-01

    The effect of dose rate on the total dose radiation hardness of three commercial bipolar linear microcircuits is investigated. Total dose tests of linear bipolar microcircuits show larger degradation at 0.167 rad/s than at 90 rad/s even after the high dose rate test is followed by a room temperature plus a 100 C anneal. No systematic correlation could be found for degradation at low dose rate versus high dose rate and anneal. Comparison of the low dose rate with the high dose rate anneal data indicates that MIL-STD-883, method 1019.4 is not a worst-case test method when applied to bipolar microcircuits for low dose rate space applications

  14. 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.

  15. First-principles method for calculating the rate constants of internal-conversion and intersystem-crossing transitions.

    Science.gov (United States)

    Valiev, R R; Cherepanov, V N; Baryshnikov, G V; Sundholm, D

    2018-02-28

    A method for calculating the rate constants for internal-conversion (k IC ) and intersystem-crossing (k ISC ) processes within the adiabatic and Franck-Condon (FC) approximations is proposed. The applicability of the method is demonstrated by calculation of k IC and k ISC for a set of organic and organometallic compounds with experimentally known spectroscopic properties. The studied molecules were pyrromethene-567 dye, psoralene, hetero[8]circulenes, free-base porphyrin, naphthalene, and larger polyacenes. We also studied fac-Alq 3 and fac-Ir(ppy) 3 , which are important molecules in organic light emitting diodes (OLEDs). The excitation energies were calculated at the multi-configuration quasi-degenerate second-order perturbation theory (XMC-QDPT2) level, which is found to yield excitation energies in good agreement with experimental data. Spin-orbit coupling matrix elements, non-adiabatic coupling matrix elements, Huang-Rhys factors, and vibrational energies were calculated at the time-dependent density functional theory (TDDFT) and complete active space self-consistent field (CASSCF) levels. The computed fluorescence quantum yields for the pyrromethene-567 dye, psoralene, hetero[8]circulenes, fac-Alq 3 and fac-Ir(ppy) 3 agree well with experimental data, whereas for the free-base porphyrin, naphthalene, and the polyacenes, the obtained quantum yields significantly differ from the experimental values, because the FC and adiabatic approximations are not accurate for these molecules.

  16. Th isotopes in the Santa Monica basin: temporal variation, long-term mass balance and model rate constants

    International Nuclear Information System (INIS)

    Huh, Chih-An

    1995-01-01

    Distribution and flux of 234 Th, 232 Th and 230 Th in the water column of central Santa Monica basin observed over a period of seven years show seasonal and interannual variabilities. A steady-state model is applied to the integrated data to calculate long term average flux and model rate constants of Th isotopes. Mass balance calculations show that the basin acts like a closed system for short-lived 234 Th, but not for the long-lived isotopes 230 Th and 232 Th. Most 230 Th in the basin is transported from elsewhere. Of the incoming Th, 40-55% of the 230 Th and 14-26% of the 232 Th enter the surface water in dissolved form. In the upper 100m, the residence time of dissolved Th with respect to adsorption onto suspended particulates, 70-80 days, is about one order of magnitude higher than the residence time of suspended particles with respect to aggregation into sinking particles, 7-10 days. (author)

  17. Three Rate-Constant Kinetic Model for Permanganate Reactions Autocatalyzed by Colloidal Manganese Dioxide: The Oxidation of L-Phenylalanine.

    Science.gov (United States)

    Perez-Benito, Joaquin F; Ferrando, Jordi

    2014-12-26

    The reduction of permanganate ion to MnO(2)-Mn(2)O(3) soluble colloidal mixed oxide by l-phenylalanine in aqueous phosphate-buffered neutral solutions has been followed by a spectrophotometric method, monitoring the decay of permanganate ion at 525 nm and the formation of the colloidal oxide at 420 nm. The reaction is autocatalyzed by the manganese product, and three rate constants have been required to fit the experimental absorbance-time kinetic data. The reaction shows base catalysis, and the values of the activation parameters at different pHs have been determined. A mechanism including both the nonautocatalytic and the autocatalytic reaction pathways, and in agreement with the available experimental data, has been proposed. Some key features of this mechanism are the following: (i) of the two predominant forms of the amino acid, the anionic form exhibits a stronger reducing power than the zwitterionic form; (ii) the nonautocatalytic reaction pathway starts with the transfer of the hydrogen atom in the α position of the amino acid to permanganate ion; and (iii) the autocatalytic reaction pathway involves the reduction of Mn(IV) to Mn(II) by the amino acid and the posterior reoxidation of Mn(II) to Mn(IV) by permanganate ion.

  18. Dose rate constants for the quantity H{sub p}(3) for frequently used radionuclides in nuclear medicine

    Energy Technology Data Exchange (ETDEWEB)

    Szermerski, Bastian; Bruchmann, Iris; Geworski, Lilli [Medical School Hannover (Germany). Dept. for Radiation Protection and Medical Physics; Behrens, Rolf [Physikalisch-Technische Bundesanstalt (PTB), Braunschweig (Germany)

    2016-07-01

    According to recent studies, the human eye lens is more sensitive to ionising radiation than previously assumed. Therefore, the dose limit for personnel occupationally exposed to ionising radiation will be lowered from currently 150 mSv to 20 mSv per year. Currently, no data base for a reliable estimation of the dose to the lens of the eye is available for nuclear medicine. Furthermore, the dose is usually not monitored. The aim of this work was to determine dose rate constants for the quantity H{sub p}(3), which is supposed to estimate the dose to the lens of the eye. For this, H{sub p}(3)-dosemeters were fixed to an Alderson Phantom at different positions. The dosemeters were exposed to radiation from nuclides typically used in nuclear medicine in their geometries analog to their application in nuclear medicine, e.g. syringe or vial. The results show that the handling of high-energy beta (i.e. electron or positron) emitters may lead to a relevant dose to the lens of the eye. For low-energy beta emitters and gamma emitters, an exceeding of the lowered dose limit seems to be unlikely.

  19. Benthic Uptake Rate due to Hyporheic Exchange: The Effects of Streambed Morphology for Constant and Sinusoidally Varying Nutrient Loads

    Directory of Open Access Journals (Sweden)

    Daniele Tonina

    2015-01-01

    Full Text Available Hyporheic exchange carries reactive solutes, which may include biological oxygen demand (BOD, dissolved oxygen (DO and reactive dissolved inorganic nitrogen (Nr, into the sediment, where biochemical reactions consume DO. Here, we study the impact of streambed morphology, stream-reactive solute loads and their diel oscillations on the DO benthic uptake rate (BUR due to hyporheic processes. Our model solves the hyporheic flow field and the solute transport equations analytically, within a Lagrangian framework, considering advection, longitudinal diffusion and reactions modeled as first order kinetics. The application of the model to DO field measurements over a gravel bar-pool sequence shows a good match with measured DO concentrations with an overall agreement of 58% and a kappa index of 0.46. We apply the model to investigate the effects of daily constant and sinusoidally time varying stream BOD, DO and Nr loads and of the morphodynamic parameters on BUR. Our modeling results show that BUR varies as a function of bedform size and of nutrient loads and that the hyporheic zone may consume up to 0.06% of the stream DO at the pool-riffle bedform scale. Daily oscillations of stream BOD and DO loads have small effects on BUR, but may have an important influence on local hyporheic processes and organisms’ distribution.

  20. Reversible conformational transition gives rise to 'zig-zag' temperature dependence of the rate constant of irreversible thermoinactivation of enzymes.

    Science.gov (United States)

    Levitsky VYu; Melik-Nubarov, N S; Siksnis, V A; Grinberg VYa; Burova, T V; Levashov, A V; Mozhaev, V V

    1994-01-15

    We have obtained unusual 'zig-zag' temperature dependencies of the rate constant of irreversible thermoinactivation (k(in)) of enzymes (alpha-chymotrypsin, covalently modified alpha-chymotrypsin, and ribonuclease) in a plot of log k(in) versus reciprocal temperature (Arrhenius plot). These dependencies are characterized by the presence of both ascending and descending linear portions which have positive and negative values of the effective activation energy (Ea), respectively. A kinetic scheme has been suggested that fits best for a description of these zig-zag dependencies. A key element of this scheme is the temperature-dependent reversible conformational transition of enzyme from the 'low-temperature' native state to a 'high-temperature' denatured form; the latter form is significantly more stable against irreversible thermoinactivation than the native enzyme. A possible explanation for a difference in thermal stabilities is that low-temperature and high-temperature forms are inactivated according to different mechanisms. Existence of the suggested conformational transition was proved by the methods of fluorescence spectroscopy and differential scanning calorimetry. The values of delta H and delta S for this transition, determined from calorimetric experiments, are highly positive; this fact underlies a conclusion that this heat-induced transition is caused by an unfolding of the protein molecule. Surprisingly, in the unfolded high-temperature conformation, alpha-chymotrypsin has a pronounced proteolytic activity, although this activity is much smaller than that of the native enzyme.

  1. Application of Constant Rate of Supply model (CRS) in dating of Guanabara Bay sediments using 210Pb measures

    International Nuclear Information System (INIS)

    Braganca, Maura Julia Camara da Silva

    1992-09-01

    A geochronological study of the Guanabara Bay (Rio de Janeiro, Brazil) based on 210P b dating technique to determine sedimentation rates and using the Constant Rate of Supply model (CRS) is presented in this work. Sediment samples were collected from river-head of Estrela, Sao Joao de Meriti, Guapimirim, Guaxindiba e Imbuacu. A low energy gamma spectrometry ( 210P b, samples taken from the Estrela and Sao Joao de Meriti rivers. Radiochemical method was applied to determine the amount of 210P b in samples collected near Guapimirim, Guaxindiba and Imbuacu Rivers. Atomic absorption spectrometry with air-acetylene flame technique was used to determine the amount of copper in all these samples. Experimental data shown the following variation in the concentration levels of copper and 210P b: (i) copper; from 2.5 μg/g to 37.1 μg/g (Imbuacu River); from 3.6 to 228.1 μg/g (Estrela River); from 11.6 to 73.4 μg/g (Guapimirim River); from 12.0 to 52.9 μg/g (Guaxindiba River) and from 90.8 to to 237.7 μg/g (Sao Joao de Meriti River), (ti) 210P b; from 2.0 Bq/kg to 27.0 Bq/kg (Imbuacu River); from 25.2 to 136.6 Bq/kg (Estrela River); from 40.0 to 90.0 Bq/kg (Sao Joao de Meriti River); from 7.0 to 70.0 Bq/kg (Guapimirim River); from 10.0 to 48.0 Bq/kg (Guaxindiba River). The sedimentation rates ranged from 0.30 cm/y in the Imbuacu River for a depth below of 35 cm to 1.3 cm/y for 0-30 cm depth in Guaxindiba River. It was concluded that the experimental data found in this work are consistent with those published in the scientific literature and that they can be predicted by the CRS model. (author)

  2. The rate constant of the reaction NCN + H2 and its role in NCN and NO modeling in low pressure CH4/O2/N2-flames.

    Science.gov (United States)

    Faßheber, Nancy; Lamoureux, Nathalie; Friedrichs, Gernot

    2015-06-28

    Bimolecular reactions of the NCN radical play a key role in modeling prompt-NO formation in hydrocarbon flames. The rate constant of the so-far neglected reaction NCN + H2 has been experimentally determined behind shock waves under pseudo-first order conditions with H2 as the excess component. NCN3 thermal decomposition has been used as a quantitative high temperature source of NCN radicals, which have been sensitively detected by difference UV laser absorption spectroscopy at [small nu, Greek, tilde] = 30383.11 cm(-1). The experiments were performed at two different total densities of ρ≈ 4.1 × 10(-6) mol cm(-3) and ρ≈ 7.4 × 10(-6) mol cm(-3) (corresponding to pressures between p = 324 mbar and p = 1665 mbar) and revealed a pressure independent reaction. In the temperature range 1057 K rate constant can be represented by the Arrhenius expression k/(cm(3) mol(-1) s(-1)) = 4.1 × 10(13) exp(-101 kJ mol(-1)/RT) (Δlog k = ±0.11). The pressure independent reaction as well as the measured activation energy is consistent with a dominating H abstracting reaction channel yielding the products HNCN + H. The reaction NCN + H2 has been implemented together with a set of reactions for subsequent HNCN and HNC chemistry into the detailed GDFkin3.0_NCN mechanism for NOx flame modeling. Two fuel-rich low-pressure CH4/O2/N2-flames served as examples to quantify the impact of the additional chemical pathways. Although the overall NCN consumption by H2 remains small, significant differences have been observed for NO yields with the updated mechanism. A detailed flux analysis revealed that HNC, mainly arising from HCN/HNC isomerization, plays a decisive role and enhances NO formation through a new HNC → HNCO → NH2→ NH → NO pathway.

  3. Rate Constant and RRKM Product Study for the Reaction Between CH3 and C2H3 at T = 298K

    Science.gov (United States)

    Thorn, R. Peyton, Jr.; Payne, Walter A., Jr.; Chillier, Xavier D. F.; Stief, Louis J.; Nesbitt, Fred L.; Tardy, D. C.

    2000-01-01

    The total rate constant k1 has been determined at P = 1 Torr nominal pressure (He) and at T = 298 K for the vinyl-methyl cross-radical reaction CH3 + C2H3 yields products. The measurements were performed in a discharge flow system coupled with collision-free sampling to a mass spectrometer operated at low electron energies. Vinyl and methyl radicals were generated by the reactions of F with C2H4 and CH4, respectively. The kinetic studies were performed by monitoring the decay of C2H3 with methyl in excess, 6 rate coefficient was determined to be k1(298 K) = (1.02 +/- 0.53)x10(exp -10) cubic cm/molecule/s with the quoted uncertainty representing total errors. Numerical modeling was required to correct for secondary vinyl consumption by reactions such as C2H3 + H and C2H3 + C2H3. The present result for k1 at T = 298 K is compared to two previous studies at high pressure (100-300 Torr He) and to a very recent study at low pressure (0.9-3.7 Torr He). Comparison is also made with the rate constant for the similar reaction CH3 + C2H5 and with a value for k1 estimated by the geometric mean rule employing values for k(CH3 + CH3) and k(C2H3 + C2H3). Qualitative product studies at T = 298 K and 200 K indicated formation of C3H6, C2H2, and C2H5 as products of the combination-stabilization, disproportionation, and combination-decomposition channels, respectively, of the CH3 + C2H3 reaction. We also observed the secondary C4H8 product of the subsequent reaction of C3H5 with excess CH3; this observation provides convincing evidence for the combination-decomposition channel yielding C3H5 + H. RRKM calculations with helium as the deactivator support the present and very recent experimental observations that allylic C-H bond rupture is an important path in the combination reaction. The pressure and temperature dependencies of the branching fractions are also predicted.

  4. Infrared optical constants of aqueous sulfate-nitrate-ammonium multi-component tropospheric aerosols from attenuated total reflectance measurements: Part II. An examination of mixing rules

    International Nuclear Information System (INIS)

    Boer, Gregory J.; Sokolik, Irina N.; Martin, Scot T.

    2007-01-01

    We examine the performance of several mixing rules that are commonly used in modeling optical constants of aerosol mixtures either in remote sensing or radiation transfer/climate studies employing the new refractive index data reported in Part I. We demonstrate that the optical constants of the considered mixtures are not accurately modeled using pure solute optical constants (e.g., ammonium sulfate optical constants and the optical constants of pure water) due to the complex ion-ion and ion-water interactions. On the other hand, we do find that ternary and quaternary mixtures can be well modeled by applying the mixing rules to lower order multi-component optical constants data, e.g., binary data to determine ternary optical constants, or binary and ternary data to determine quaternary optical constants. By using lower order optical constants data sets, much of the ion-ion and ion-water effects are captured. Both mass-fraction and volume-fraction weighting of the 'component' optical constants yield satisfactory results, performing as well or better than the more complicated mixing rules. These findings will be of practical use in remote sensing and radiation transfer/climate studies as well as help guide the decision on what optical constants measurements will be required

  5. Relationship of dose rate and total dose to responses of continuously irradiated beagles

    International Nuclear Information System (INIS)

    Fritz, T.E.; Norris, W.P.; Tolle, D.V.; Seed, T.M.; Poole, C.M.; Lombard, L.S.; Doyle, D.E.

    1978-01-01

    Young-adult beagles were exposed continuously (22 hours/day) to 60 Co γ rays in a specially constructed facility. The exposure rates were either 5, 10, 17, or 35 R/day, and the exposures were terminated at either 600, 1400, 2000, or 4000 R. A total of 354 dogs were irradiated; 221 are still alive as long-term survivors, some after more than 2000 days. The data on survival of these dogs, coupled with data from similar preliminary experiments, allow an estimate of the LD 50 for γ-ray exposures given at a number of exposure rates. They also allow comparison of the relative importance of dose rate and total dose, and the interaction of these two variables, in the early and late effects after protracted irradiation. The LD 50 for the beagle increases from 258 rad delivered at 15 R/minute to approximately 3000 rad at 10 R/day. Over this entire range, the LD 50 is dependent upon hematopoietic damage. At 5 R/day and less, no meaningful LD 50 can be determined; there is nearly normal continued hematopoietic function, survival is prolonged, and the dogs manifest varied individual responses in other organ systems. Although the experiment is not complete, interim data allow several important conclusions. Terminated exposures, while not as effective as radiation continued until death, can produce myelogenous leukemia at the same exposure rate, 10 R/day. More importantly, at the same total accumulated dose, lower exposure rates are more damaging than higher rates on the basis of the rate and degree of hematological recovery that occurs after termination of irradiation. Thus, the rate of hematologic depression, the nadir of the depression, and the rate of recovery are dependent upon exposure rate; the latter is inversely related and the former two are directly related to exposure rate

  6. Relationship of dose rate and total dose to responses of continuously irradiated beagles

    International Nuclear Information System (INIS)

    Fritz, T.E.; Norris, W.P.; Tolle, D.V.; Seed, T.M.; Poole, C.M.; Lombard, L.S.; Doyle, D.E.

    1978-01-01

    Young-adult beagles were exposed continuously (22 hours/day) to 60 Co gamma rays in a specially constructed facility. The exposure rates were 5, 19, 17 or 35 R/day, and the exposures were terminated at 600, 1400, 2000 or 4000 R. A total of 354 dogs were irradiated; 221 are still alive as long-term survivors, some after more than 2000 days. The data on survival of these dogs, coupled with data from similar preliminary experiments, allow an estimate of the LD 50 for gamma-ray exposures given at a number of exposure rates. They also allow comparison of the relativeimportance of dose rate and total dose, and the interaction of these two variables, in the early and late effects after protracted irradiation. The LD 50 for the beagle increases from 344 R (258 rads) delivered at 15 R/minute to approximately 4000 R (approximately 3000 rads) at 10 R/day. Over this entire range, the LD 50 is dependent upon haematopoietic damage. At 5 R/day and less, no definitive LD 50 can be determined; there is nearly normal continued haematopoietic function, survival is prolonged, and the dogs manifest varied individual responses in the organ systems. Although the experiment is not complete, interim data allow serveral important conclusions. Terminated exposures, while not as effective as irradiation continued until death, can produce myelogenous leukaemia at the same exposure rate, 10 R/day. More importantly, at the same total accumulated dose, lower exposure rates appear more damaging than higher rates on the basis of the rate and degree of haematological recovery that occurs after termination of irradiation. Thus, the rate of haematologic depression, the nadir of the depression and the rate of recovery are dependent upon exposure rate; the latter is inversely related and the first two are directly related to exposure rate. ( author)

  7. A systematic evaluation of the dose-rate constant determined by photon spectrometry for 21 different models of low-energy photon-emitting brachytherapy sources.

    Science.gov (United States)

    Chen, Zhe Jay; Nath, Ravinder

    2010-10-21

    The aim of this study was to perform a systematic comparison of the dose-rate constant (Λ) determined by the photon spectrometry technique (PST) with the consensus value ((CON)Λ) recommended by the American Association of Physicists in Medicine (AAPM) for 21 low-energy photon-emitting interstitial brachytherapy sources. A total of 63 interstitial brachytherapy sources (21 different models with 3 sources per model) containing either (125)I (14 models), (103)Pd (6 models) or (131)Cs (1 model) were included in this study. A PST described by Chen and Nath (2007 Med. Phys. 34 1412-30) was used to determine the dose-rate constant ((PST)Λ) for each source model. Source-dependent variations in (PST)Λ were analyzed systematically against the spectral characteristics of the emitted photons and the consensus values recommended by the AAPM brachytherapy subcommittee. The values of (PST)Λ for the encapsulated sources of (103)Pd, (125)I and (131)Cs varied from 0.661 to 0.678 cGyh(-1) U(-1), 0.959 to 1.024 cGyh(-1)U(-1) and 1.066 to 1.073 cGyh(-1)U(-1), respectively. The relative variation in (PST)Λ among the six (103)Pd source models, caused by variations in photon attenuation and in spatial distributions of radioactivity among the source models, was less than 3%. Greater variations in (PST)Λ were observed among the 14 (125)I source models; the maximum relative difference was over 6%. These variations were caused primarily by the presence of silver in some (125)I source models and, to a lesser degree, by the variations in photon attenuation and in spatial distribution of radioactivity among the source models. The presence of silver generates additional fluorescent x-rays with lower photon energies which caused the (PST)Λ value to vary from 0.959 to 1.019 cGyh(-1)U(-1) depending on the amount of silver used by a given source model. For those (125)I sources that contain no silver, their (PST)Λ was less variable and had values within 1% of 1.024 cGyh(-1)U(-1). For the 16

  8. Impact of Total, Internal and External Government Debt on Interest Rate in Pakistan

    OpenAIRE

    Perveen, Asma; Munir, Kashif

    2017-01-01

    The objective of the study is to examine impact of total, internal and external government debt on nominal interest rate in Pakistan. To attain these objectives, the study used annual time series data from 1973 to 2016. The study used loanable fund theory as theoretical model and ARDL bound testing approach for cointegration and Granger causality test to estimate the results. The results of the study found negative relation between total government debt, external debt and nominal interest rat...

  9. High Re-Operation Rates Using Conserve Metal-On-Metal Total Hip Articulations

    DEFF Research Database (Denmark)

    Mogensen, S L; Jakobsen, Thomas; Christoffersen, Hardy

    2016-01-01

    INTRODUCTION: Metal-on-metal hip articulations have been intensely debated after reports of adverse reactions and high failure rates. The aim of this study was to retrospectively evaluate the implant of a metal-on.metal total hip articulation (MOM THA) from a single manufacture in a two-center st......INTRODUCTION: Metal-on-metal hip articulations have been intensely debated after reports of adverse reactions and high failure rates. The aim of this study was to retrospectively evaluate the implant of a metal-on.metal total hip articulation (MOM THA) from a single manufacture in a two...

  10. Comparison of three continuous positive airway pressure (CPAP) interfaces in healthy Beagle dogs during medetomidine-propofol constant rate infusions.

    Science.gov (United States)

    Meira, Carolina; Joerger, Fabiola B; Kutter, Annette P N; Waldmann, Andreas; Ringer, Simone K; Böehm, Stephan H; Iff, Samuel; Mosing, Martina

    2018-03-01

    To compare the efficacy of three continuous positive airway pressure (CPAP) interfaces in dogs on gas exchange, lung volumes, amount of leak during CPAP and rebreathing in case of equipment failure or disconnection. Randomized, prospective, crossover, experimental trial. Ten purpose-bred Beagle dogs. Dogs were in dorsal recumbency during medetomidine-propofol constant rate infusions, breathing room air. Three interfaces were tested in each dog in a consecutive random order: custom-made mask (M), conical face mask (FM) and helmet (H). End-expiratory lung impedance (EELI) measured by electrical impedance tomography was assessed with no interface (baseline), with the interface only (No-CPAP for 3 minutes) and at 15 minutes of 7 cmH 2 O CPAP (CPAP-delivery). PaO 2 was assessed at No-CPAP and CPAP-delivery, partial pressure of inspired carbon dioxide (PICO 2 ; rebreathing assessment) at No-CPAP and the interface leak (ΔP leak ) at CPAP-delivery. Mixed-effects linear regression models were used for statistical analysis (pCPAP-delivery, all interfaces increased EELI by 7% (pCPAP, less rebreathing occurred with M (0.5 kPa, 4 mmHg) than with FM (1.8 kPa, 14 mmHg) and with H (1.4 kPa, 11 mmHg), but also lower PaO 2 was measured with M (9.3 kPa, 70 mmHg) than with H (11.9 kPa, 90 mmHg) and FM (10.8 kPa, 81 mmHg). All three interfaces can be used to provide adequate CPAP in dogs. The leak during CPAP-delivery and the risk of rebreathing and hypoxaemia, when CPAP is not maintained, can be significant. Therefore, animals should always be supervised during administration of CPAP with any of the three interfaces. The performance of the custom-made M was not superior to the other interfaces. Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.

  11. Low-dose-rate total lymphoid irradiation: a new method of rapid immunosuppression

    International Nuclear Information System (INIS)

    Blum, J.E.; de Silva, S.M.; Rachman, D.B.; Order, S.E.

    1988-01-01

    Total Lymphoid Irradiation (TLI) has been successful in inducing immunosuppression in experimental and clinical applications. However, both the experimental and clinical utility of TLI are hampered by the prolonged treatment courses required (23 days in rats and 30-60 days in humans). Low-dose-rate TLI has the potential of reducing overall treatment time while achieving comparable immunosuppression. This study examines the immunosuppressive activity and treatment toxicity of conventional-dose-rate (23 days) vs low-dose-rate (2-7 days) TLI. Seven groups of Lewis rats were given TLI with 60Co. One group was treated at conventional-dose-rates (80-110 cGy/min) and received 3400 cGy in 17 fractions over 23 days. Six groups were treated at low-dose-rate (7 cGy/min) and received total doses of 800, 1200, 1800, 2400, 3000, and 3400 cGy over 2-7 days. Rats treated at conventional-dose-rates over 23 days and at low-dose-rate over 2-7 days tolerated radiation with minimal toxicity. The level of immunosuppression was tested using allogeneic (Brown-Norway) skin graft survival. Control animals retained allogeneic skin grafts for a mean of 14 days (range 8-21 days). Conventional-dose-rate treated animals (3400 cGy in 23 days) kept their grafts 60 days (range 50-66 days) (p less than .001). Low-dose-rate treated rats (800 to 3400 cGy total dose over 2-7 days) also had prolongation of allogeneic graft survival times following TLI with a dose-response curve established. The graft survival time for the 3400 cGy low-dose-rate group (66 days, range 52-78 days) was not significantly different from the 3400 cGy conventional-dose-rate group (p less than 0.10). When the total dose given was equivalent, low-dose-rate TLI demonstrated an advantage of reduced overall treatment time compared to conventional-dose-rate TLI (7 days vs. 23 days) with no increase in toxicity

  12. Effect of survey design and catch rate estimation on total catch estimates in Chinook salmon fisheries

    Science.gov (United States)

    McCormick, Joshua L.; Quist, Michael C.; Schill, Daniel J.

    2012-01-01

    Roving–roving and roving–access creel surveys are the primary techniques used to obtain information on harvest of Chinook salmon Oncorhynchus tshawytscha in Idaho sport fisheries. Once interviews are conducted using roving–roving or roving–access survey designs, mean catch rate can be estimated with the ratio-of-means (ROM) estimator, the mean-of-ratios (MOR) estimator, or the MOR estimator with exclusion of short-duration (≤0.5 h) trips. Our objective was to examine the relative bias and precision of total catch estimates obtained from use of the two survey designs and three catch rate estimators for Idaho Chinook salmon fisheries. Information on angling populations was obtained by direct visual observation of portions of Chinook salmon fisheries in three Idaho river systems over an 18-d period. Based on data from the angling populations, Monte Carlo simulations were performed to evaluate the properties of the catch rate estimators and survey designs. Among the three estimators, the ROM estimator provided the most accurate and precise estimates of mean catch rate and total catch for both roving–roving and roving–access surveys. On average, the root mean square error of simulated total catch estimates was 1.42 times greater and relative bias was 160.13 times greater for roving–roving surveys than for roving–access surveys. Length-of-stay bias and nonstationary catch rates in roving–roving surveys both appeared to affect catch rate and total catch estimates. Our results suggest that use of the ROM estimator in combination with an estimate of angler effort provided the least biased and most precise estimates of total catch for both survey designs. However, roving–access surveys were more accurate than roving–roving surveys for Chinook salmon fisheries in Idaho.

  13. High bacterial contamination rate of electrocautery tips during total hip and knee arthroplasty.

    Science.gov (United States)

    Abdelaziz, Hussein; Zahar, Akos; Lausmann, Christian; Gehrke, Thorsten; Fickenscher, Helmut; Suero, Eduardo M; Gebauer, Matthias; Citak, Mustafa

    2018-04-01

    The aim of the study was to quantify the bacterial contamination rate of electrocautery tips during primary total joint replacement (TJR), as well as during aseptic and septic revision TJR. A total of 150 electrocautery tips were collected between April and July 2017. TJR surgeries were divided into three groups: (1) primary, (2) aseptic and (3) septic revisions. In each group, a total of 50 electrocautery tips were collected. A monopolar electrocautery with a reusable stainless-steel blade tip was used in all cases. The rate of bacterial contamination was determined for all groups. Correlation of exposure time and type of surgery was analyzed. The overall bacterial contamination rate was 14.7% (95% CI 9.4 to 21.4%). The highest contamination rate occurred in the septic revision group (30.0%; 95% CI 17.9 to 44.6%), followed by the primary cases group (10.0%; 95% CI 3.3 to 21.8%) and the aseptic revision group (4.0%; 95% CI 0.5 to 13.7%). Exposure time did not affect the bacterial contamination rate. In 12 out of 15 (80%) contaminations identified in the septic group, we found the same causative microorganism of the prosthetic joint infection on the electrocautery tip. The bacterial contamination of the electrocautery tips is relatively high, especially during septic hip revision arthroplasty. Electrocautery tips should be changed after debridement of infected tissue.

  14. Comparing 30-day all-cause readmission rates between tibiotalar fusion and total ankle replacement.

    Science.gov (United States)

    Merrill, Robert K; Ferrandino, Rocco M; Hoffman, Ryan; Ndu, Anthony; Shaffer, Gene W

    2018-01-12

    End-stage ankle arthritis is a debilitating condition that negatively impacts patient quality of life. Tibiotalar fusion and total ankle replacement are treatment options for managing ankle arthritis. Few studies have examined short term readmission rates of these two procedures. The objective of this study was compare all-cause 30-day readmission rates between patients undergoing tibiotalar fusion vs. total ankle replacement. This study queried the Nationwide Readmission Database (NRD) from 2013-2014 and used international classification of disease, 9th revision (ICD-9) procedure codes to identify all patients who underwent a tibiotalar fusion or a total ankle replacement. Comorbidities, insurance status, hospital characteristics, and readmission rates were statistically compared between the two cohorts. Risk factors were then identified for 30-day readmission. A total of 5660 patients were analyzed with 2667 in the tibiotalar fusion cohort and 2993 in the total ankle replacement cohort. Univariate analysis revealed that the readmission rate after tibiotalar fusion (4.4%) was statistically greater than after total ankle replacement (1.4%). Multivariable regression analysis indicated that deficiency anemia (OR 2.18), coagulopathy (OR 3.51), renal failure (OR 2.83), other insurance relative to private (OR 3.40), and tibiotalar fusion (OR 2.51) were all statistically significant independent risk factors for having a readmission within 30-days. These findings suggest that during the short-term period following discharge from the hospital, patients who received a tibiotalar fusion are more likely to experience a 30-day readmission. These findings are important for decision making when a surgeon encounters a patient with end stage ankle arthritis. Level III, cohort study. Published by Elsevier Ltd.

  15. The impact of the total tax rate reduction on public services provided in Romania

    Directory of Open Access Journals (Sweden)

    Adina TRANDAFIR

    2014-09-01

    Full Text Available Against the background of economic globalization, governments tend to take tax measures disadvantageous to society in order to increase the attractiveness of the business environment. A common measures for this purpose is the reduction in tax rate. According to the classical theory of tax competition such measure leads to under the provision of public goods. This article aims to show, through an econometric analysis, whether in Romania, in the period 2006-2013, reducing total tax rate had a negative impact on public services. For this, using linear regression technique, the article analysed the correlation between total tax rate and the variation in the share of the main public service spending in GDP.

  16. Concentration and chemical status of arsenic in the blood of pregnant hamsters during critical embryogenesis. 1. Subchronic exposure to arsenate utilizing constant rate administration

    Energy Technology Data Exchange (ETDEWEB)

    Hanlon, D.P.; Ferm, V.H.

    1986-08-01

    The concentration, availability, and chemical status of radiolabeled arsenic has been determined in the blood of pregnant hamsters at the beginning (morning of Day 8) and the end (morning of Day 9) of the critical period of embryogenesis. Hamster dams were exposed to teratogenic doses of arsenate by means of osmotic minipumps implanted on the morning of Day 6 of the gestation period. Whole blood arsenic concentrations were the same for 48 and 72 hr postimplant. The arsenic concentration of plasma equaled that of red cells. Plasma arsenic was not bound to macromolecules and had the same chemical status 48 and 72 hr postimplant. Arsenate was the dominant form (67% of the total). However, the presence of dimethylarsinic acid and arsenite indicates that the pentavalent species was metabolized. Red cell arsenic was bound to macromolecules in the cell sap. Seventy percent of red cell sap arsenic was dialyzable 48 hr postimplant, but only 56% 72 hr postimplant. Arsenate was the dominant dialyzable red cell species on Day 8 and arsenite was the major dialyzable form on Day 9. The authors findings demonstrate a relationship between the maternal blood concentration and chemical status of arsenic and the presence of malformations resulting from a constant rate exposure of pregnant hamsters to arsenate via the osmotic minipump.

  17. Concentration and chemical status of arsenic in the blood of pregnant hamsters during critical embryogenesis. 1. Subchronic exposure to arsenate utilizing constant rate administration

    International Nuclear Information System (INIS)

    Hanlon, D.P.; Ferm, V.H.

    1986-01-01

    The concentration, availability, and chemical status of radiolabeled arsenic has been determined in the blood of pregnant hamsters at the beginning (morning of Day 8) and the end (morning of Day 9) of the critical period of embryogenesis. Hamster dams were exposed to teratogenic doses of arsenate by means of osmotic minipumps implanted on the morning of Day 6 of the gestation period. Whole blood arsenic concentrations were the same for 48 and 72 hr postimplant. The arsenic concentration of plasma equaled that of red cells. Plasma arsenic was not bound to macromolecules and had the same chemical status 48 and 72 hr postimplant. Arsenate was the dominant form (67% of the total). However, the presence of dimethylarsinic acid and arsenite indicates that the pentavalent species was metabolized. Red cell arsenic was bound to macromolecules in the cell sap. Seventy percent of red cell sap arsenic was dialyzable 48 hr postimplant, but only 56% 72 hr postimplant. Arsenate was the dominant dialyzable red cell species on Day 8 and arsenite was the major dialyzable form on Day 9. The authors findings demonstrate a relationship between the maternal blood concentration and chemical status of arsenic and the presence of malformations resulting from a constant rate exposure of pregnant hamsters to arsenate via the osmotic minipump

  18. Effect of improved TLD dosimetry on the determination of dose rate constants for 125I and 103Pd brachytherapy seeds

    International Nuclear Information System (INIS)

    Rodriguez, M.; Rogers, D. W. O.

    2014-01-01

    Purpose: To more accurately account for the relative intrinsic energy dependence and relative absorbed-dose energy dependence of TLDs when used to measure dose rate constants (DRCs) for 125 I and 103 Pd brachytherapy seeds, to thereby establish revised “measured values” for all seeds and compare the revised values with Monte Carlo and consensus values. Methods: The relative absorbed-dose energy dependence, f rel , for TLDs and the phantom correction, P phant , are calculated for 125 I and 103 Pd seeds using the EGSnrc BrachyDose and DOSXYZnrc codes. The original energy dependence and phantom corrections applied to DRC measurements are replaced by calculated (f rel ) −1 and P phant values for 24 different seed models. By comparing the modified measured DRCs to the MC values, an appropriate relative intrinsic energy dependence, k bq rel , is determined. The new P phant values and relative absorbed-dose sensitivities, S AD rel , calculated as the product of (f rel ) −1 and (k bq rel ) −1 , are used to individually revise the measured DRCs for comparison with Monte Carlo calculated values and TG-43U1 or TG-43U1S1 consensus values. Results: In general, f rel is sensitive to the energy spectra and models of the brachytherapy seeds. Values may vary up to 8.4% among 125 I and 103 Pd seed models and common TLD shapes. P phant values depend primarily on the isotope used. Deduced (k bq rel ) −1 values are 1.074 ± 0.015 and 1.084 ± 0.026 for 125 I and 103 Pd seeds, respectively. For (1 mm) 3 chips, this implies an overall absorbed-dose sensitivity relative to 60 Co or 6 MV calibrations of 1.51 ± 1% and 1.47 ± 2% for 125 I and 103 Pd seeds, respectively, as opposed to the widely used value of 1.41. Values of P phant calculated here have much lower statistical uncertainties than literature values, but systematic uncertainties from density and composition uncertainties are significant. Using these revised values with the literature’s DRC measurements, the

  19. An Adaptive, Multi-Rate Linear Quadratic Regulator for a Shipboard MVDC Distribution System with Constant Power Loads

    Science.gov (United States)

    2017-09-01

    investigation into the factors which most strongly influence ROA size would be instructive. The genetic algorithm could be modified to assess ROA size and an...DISTRIBUTION SYSTEM WITH CONSTANT POWER LOADS 5. FUNDING NUMBERS REL95 REK4K 6. AUTHOR(S) Adam J. Mills 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS...ES) Naval Postgraduate School Monterey, CA 93943-5000 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING /MONITORING AGENCY NAME(S) AND

  20. Approximation for the Finite-Time Ruin Probability of a General Risk Model with Constant Interest Rate and Extended Negatively Dependent Heavy-Tailed Claims

    Directory of Open Access Journals (Sweden)

    Yang Yang

    2011-01-01

    Full Text Available We propose a general continuous-time risk model with a constant interest rate. In this model, claims arrive according to an arbitrary counting process, while their sizes have dominantly varying tails and fulfill an extended negative dependence structure. We obtain an asymptotic formula for the finite-time ruin probability, which extends a corresponding result of Wang (2008.

  1. Determination of first order rate constants by natural logarithm of the slope plot exemplified by analysis of Aspergillus niger in batch culture

    NARCIS (Netherlands)

    Poulsen, B.R.; Ruiter, G.; Visser, J.; Iversen, J.J.L.

    2003-01-01

    Finding rate constants from experimental data is often difficult because of offset and noise. A computer program was developed to average experimental data points, reducing the effect of noise, and to produce a loge of slope plot - a plot of the natural logarithm of the slope of a curve -

  2. QSAR models for oxidation of organic micropollutants in water based on ozone and hydroxyl radical rate constants and their chemical classification

    KAUST Repository

    Sudhakaran, Sairam; Amy, Gary L.

    2013-01-01

    . In this study, quantitative structure activity relationships (QSAR) models for O3 and AOP processes were developed, and rate constants, kOH and kO3, were predicted based on target compound properties. The kO3 and kOH values ranged from 5 * 10-4 to 105 M-1s-1

  3. Determination of H-atom reaction rate constants by the competition kinetic technique using riboflavin as a standard solute [Paper No. RD-7

    International Nuclear Information System (INIS)

    Kishore, Kamal; Moorthy, P.N.; Rao, K.N.

    1982-01-01

    Riboflavin has been used as a standard solute to evaluate H-atom rate constants of other solutes by steady state radiolytic competition kinetic method. The bleaching of absorbance of riboflavin at 445 nm as a result of its reaction with H-atoms is made use of in estimating its decomposition. The merits and demerits of this method are discussed. (author)

  4. Room-temperature and temperature-dependent QSRR modelling for predicting the nitrate radical reaction rate constants of organic chemicals using ensemble learning methods.

    Science.gov (United States)

    Gupta, S; Basant, N; Mohan, D; Singh, K P

    2016-07-01

    Experimental determinations of the rate constants of the reaction of NO3 with a large number of organic chemicals are tedious, and time and resource intensive; and the development of computational methods has widely been advocated. In this study, we have developed room-temperature (298 K) and temperature-dependent quantitative structure-reactivity relationship (QSRR) models based on the ensemble learning approaches (decision tree forest (DTF) and decision treeboost (DTB)) for predicting the rate constant of the reaction of NO3 radicals with diverse organic chemicals, under OECD guidelines. Predictive powers of the developed models were established in terms of statistical coefficients. In the test phase, the QSRR models yielded a correlation (r(2)) of >0.94 between experimental and predicted rate constants. The applicability domains of the constructed models were determined. An attempt has been made to provide the mechanistic interpretation of the selected features for QSRR development. The proposed QSRR models outperformed the previous reports, and the temperature-dependent models offered a much wider applicability domain. This is the first report presenting a temperature-dependent QSRR model for predicting the nitrate radical reaction rate constant at different temperatures. The proposed models can be useful tools in predicting the reactivities of chemicals towards NO3 radicals in the atmosphere, hence, their persistence and exposure risk assessment.

  5. Estimating reaction rate constants from a two-step reaction: a comparison between two-way and three-way methods

    NARCIS (Netherlands)

    Bijlsma, S.; Smilde, A. K.

    2000-01-01

    In this paper, two different spectral datasets are used in order to estimate reaction rate constants using different algorithms. Dataset 1 consists of short-wavelength near-infrared (SW NIR) spectra taken in time of the two-step epoxidation of 2,5-di-tert-butyl-1,4-benzoquinone using tert-butyl

  6. USING IN VIVO GAS UPDATE STUDIES TO ESTIMATE METABOLIC RATE CONSTANTS FOR CCL CHEMICALS: 1,1-DICHLOROPROPANE AND 2,2-DICHLOROPROPANE

    Science.gov (United States)

    USING IN VIVO GAS UPTAKE STUDIES TO ESTIMATE METABOLIC RATE CONSTANTS FOR CCL CHEMICALS: 1,1-DICHLOROPROPENE AND 2,2-DICHLOROPROPANE. Mitchell, C T, Evans, M V, Kenyon, E M. NHEERL, U.S. EPA, ORD, ETD, RTP, NC The Safe Drinking Water Act Amendments of 1996 required ...

  7. Dose rate and dose fractionation studies in total body irradiation of dogs

    International Nuclear Information System (INIS)

    Kolb, H.J.; Netzel, B.; Schaffer, E.; Kolb, H.

    1979-01-01

    Total body irradiation (TBI) with 800-900 rads and allogeneic bone marrow transplantation according to the regimen designated by the Seattle group has induced remissions in patients with otherwise refractory acute leukemias. Relapse of leukemia after bone marrow transplantation remains the major problem, when the Seattle set up of two opposing 60 Co-sources and a low dose rate is used in TBI. Studies in dogs with TBI at various dose rates confirmed observations in mice that gastrointestinal toxicity is unlike toxicity against hemopoietic stem cells and possibly also leukemic stem cells depending on the dose rate. However, following very high single doses (2400 R) and marrow infusion acute gastrointestinal toxicity was not prevented by the lowest dose rate studied (0.5 R/min). Fractionated TBI with fractions of 600 R in addition to 1200 R (1000 rads) permitted the application of total doses up to 300 R followed by marrow infusion without irreversible toxicity. 26 dogs given 2400-3000 R have been observed for presently up to 2 years with regard to delayed radiation toxicity. This toxicity was mild in dogs given single doses at a low dose rate or fractionated TBI. Fractionated TBI is presently evaluated with allogeneic transplants in the dog before being applied to leukemic patients

  8. Efficient Total Nitrogen Removal in an Ammonia Gas Biofilter through High-Rate OLAND

    DEFF Research Database (Denmark)

    De Clippeleir, Haydée; Courtens, Emilie; Mosquera, Mariela

    2012-01-01

    Ammonia gas is conventionally treated in nitrifying biofilters; however, addition of organic carbon to perform post-denitrification is required to obtain total nitrogen removal. Oxygen-limited autotrophic nitrification/denitrification (OLAND), applied in full-scale for wastewater treatment, can...... offer a cost-effective alternative for gas treatment. In this study, the OLAND application thus was broadened toward ammonia loaded gaseous streams. A down flow, oxygen-saturated biofilter (height of 1.5 m; diameter of 0.11 m) was fed with an ammonia gas stream (248 ± 10 ppmv) at a loading rate of 0...... at water flow rates of 1.3 ± 0.4 m3 m–2 biofilter section d–1. Profile measurements revealed that 91% of the total nitrogen activity was taking place in the top 36% of the filter. This study demonstrated for the first time highly effective and sustainable autotrophic ammonia removal in a gas biofilter...

  9. Fitting the elementary rate constants of the P-gp transporter network in the hMDR1-MDCK confluent cell monolayer using a particle swarm algorithm.

    Directory of Open Access Journals (Sweden)

    Deep Agnani

    Full Text Available P-glycoprotein, a human multidrug resistance transporter, has been extensively studied due to its importance to human health and disease. In order to understand transport kinetics via P-gp, confluent cell monolayers overexpressing P-gp are widely used. The purpose of this study is to obtain the mass action elementary rate constants for P-gp's transport and to functionally characterize members of P-gp's network, i.e., other transporters that transport P-gp substrates in hMDR1-MDCKII confluent cell monolayers and are essential to the net substrate flux. Transport of a range of concentrations of amprenavir, loperamide, quinidine and digoxin across the confluent monolayer of cells was measured in both directions, apical to basolateral and basolateral to apical. We developed a global optimization algorithm using the Particle Swarm method that can simultaneously fit all datasets to yield accurate and exhaustive fits of these elementary rate constants. The statistical sensitivity of the fitted values was determined by using 24 identical replicate fits, yielding simple averages and standard deviations for all of the kinetic parameters, including the efflux active P-gp surface density. Digoxin required additional basolateral and apical transporters, while loperamide required just a basolateral tranporter. The data were better fit by assuming bidirectional transporters, rather than active importers, suggesting that they are not MRP or active OATP transporters. The P-gp efflux rate constants for quinidine and digoxin were about 3-fold smaller than reported ATP hydrolysis rate constants from P-gp proteoliposomes. This suggests a roughly 3∶1 stoichiometry between ATP hydrolysis and P-gp transport for these two drugs. The fitted values of the elementary rate constants for these P-gp substrates support the hypotheses that the selective pressures on P-gp are to maintain a broad substrate range and to keep xenobiotics out of the cytosol, but not out of the

  10. Weight suppression predicts total weight gain and rate of weight gain in outpatients with anorexia nervosa.

    Science.gov (United States)

    Carter, Frances A; Boden, Joseph M; Jordan, Jennifer; McIntosh, Virginia V W; Bulik, Cynthia M; Joyce, Peter R

    2015-11-01

    The present study sought to replicate the finding of Wildes and Marcus, Behav Res Ther, 50, 266-274, 2012 that higher levels of weight suppression at pretreatment predict greater total weight gain, faster rate of weight gain, and bulimic symptoms amongst patients admitted with anorexia nervosa. Participants were 56 women with anorexia nervosa diagnosed by using strict or lenient weight criteria, who were participating in a randomized controlled psychotherapy trial (McIntosh et al., Am J Psychiatry, 162, 741-747, 2005). Thirty-five women completed outpatient treatment and post-treatment assessment. Weight suppression was the discrepancy between highest lifetime weight at adult height and weight at pretreatment assessment. Outcome variables were total weight gain, rate of weight gain, and bulimic symptoms in the month prior to post-treatment assessment [assessed using the Eating Disorders Examination (Fairburn et al., Binge-Eating: Nature, Assessment and Treatment. New York: Guilford, 1993)]. Weight suppression was positively associated with total weight gain and rate of weight gain over treatment. Regression models showed that this association could not be explained by covariates (age at onset of anorexia nervosa and treatment modality). Weight suppression was not significantly associated with bulimic symptoms in the month prior to post-treatment assessment, regardless of whether bulimic symptoms were examined as continuous or dichotomous variables. The present study reinforces the previous finding that weight suppression predicts total weight gain and rate of weight gain amongst patients being treated for anorexia nervosa. Methodological issues may explain the failure of the present study to find that weight suppression predicts bulimic symptoms. Weight suppression at pretreatment for anorexia nervosa should be assessed routinely and may inform treatment planning. © 2015 Wiley Periodicals, Inc.

  11. Insight into the Physical and Dynamical Processes that Control Rapid Increases in Total Flash Rate

    Science.gov (United States)

    Schultz, Christopher J.; Carey, Lawrence D.; Schultz, Elise V.; Blakeslee, Richard J.; Goodman, Steven J.

    2015-01-01

    Rapid increases in total lightning (also termed "lightning jumps") have been observed for many decades. Lightning jumps have been well correlated to severe and hazardous weather occurrence. The main focus of lightning jump work has been on the development of lightning algorithms to be used in real-time assessment of storm intensity. However, in these studies it is typically assumed that the updraft "increases" without direct measurements of the vertical motion, or specification of which updraft characteristic actually increases (e.g., average speed, maximum speed, or convective updraft volume). Therefore, an end-to-end physical and dynamical basis for coupling rapid increases in total flash rate to increases in updraft speed and volume must be understood in order to ultimately relate lightning occurrence to severe storm metrics. Herein, we use polarimetric, multi-Doppler, and lightning mapping array measurements to provide physical context as to why rapid increases in total lightning are closely tied to severe and hazardous weather.

  12. Ratiometric analysis in hyperpolarized NMR (I): test of the two-site exchange model and the quantification of reaction rate constants.

    Science.gov (United States)

    Li, Lin Z; Kadlececk, Stephen; Xu, He N; Daye, Dania; Pullinger, Benjamin; Profka, Harrilla; Chodosh, Lewis; Rizi, Rahim

    2013-10-01

    Conventional methods for the analysis of in vivo hyperpolarized (13) C NMR data from the lactate dehydrogenase (LDH) reaction usually make assumptions on the stability of rate constants and/or the validity of the two-site exchange model. In this study, we developed a framework to test the validity of the assumption of stable reaction rate constants and the two-site exchange model in vivo via ratiometric fitting of the time courses of the signal ratio L(t)/P(t). Our analysis provided evidence that the LDH enzymatic kinetics observed by hyperpolarized NMR are in near-equilibrium and satisfy the two-site exchange model for only a specific time window. In addition, we quantified both the forward and reverse exchange rate constants of the LDH reaction for the transgenic and mouse xenograft models of breast cancer using the ratio fitting method developed, which includes only two modeling parameters and is less sensitive to the influence of instrument settings/protocols, such as flip angles, degree of polarization and tracer dosage. We further compared the ratio fitting method with a conventional two-site exchange modeling method, i.e. the differential equation fitting method, using both the experimental and simulated hyperpolarized NMR data. The ratio fitting method appeared to fit better than the differential equation fitting method for the reverse rate constant on the mouse tumor data, with less relative errors on average, whereas the differential equation fitting method also resulted in a negative reverse rate constant for one tumor. The simulation results indicated that the accuracy of both methods depends on the width of the transport function, noise level and rate constant ratio; one method may be more accurate than the other based on the experimental/biological conditions aforementioned. We were able to categorize our tumor models into specific conditions of the computer simulation and to estimate the errors of rate quantification. We also discussed possible

  13. Relative effect of radiation dose rate on hemopoietic and nonhemopoietic lethality of total-body irradiation

    International Nuclear Information System (INIS)

    Peters, L.J.; McNeill, J.; Karolis, C.; Thames, H.D. Jr.; Travis, E.L.

    1986-01-01

    Experiments were undertaken to determine the influence of dose rate on the toxicity of total-body irrdiation (TBI) with and without syngeneic bone-marrow rescue in mice. The results showed a much greater dose-rate dependence for death from nonhemopoietic toxicity than from bone-marrow ablation, with the ratio of LD 50 's increasing from 1.73 at 25 cGy/min to 2.80 at 1 cGy/min. At the higher dose rates, dose-limiting nonhemopoietic toxicity resulted from late organ injury, affecting the lungs, kidneys, and liver. At 1 cGy/min the major dose-limiting nonhemopoietic toxicity was acute gastrointestinal injury. The implications of these results in the context of TBI in preparation for bone-marrow transplantation are discussed. 15 refs., 4 figs

  14. Effects of respiratory rate and tidal volume on gas exchange in total liquid ventilation.

    Science.gov (United States)

    Bull, Joseph L; Tredici, Stefano; Fujioka, Hideki; Komori, Eisaku; Grotberg, James B; Hirschl, Ronald B

    2009-01-01

    Using a rabbit model of total liquid ventilation (TLV), and in a corresponding theoretical model, we compared nine tidal volume-respiratory rate combinations to identify a ventilator strategy to maximize gas exchange, while avoiding choked flow, during TLV. Nine different ventilation strategies were tested in each animal (n = 12): low [LR = 2.5 breath/min (bpm)], medium (MR = 5 bpm), or high (HR = 7.5 bpm) respiratory rates were combined with a low (LV = 10 ml/kg), medium (MV = 15 ml/kg), or high (HV = 20 ml/kg) tidal volumes. Blood gases and partial pressures, perfluorocarbon gas content, and airway pressures were measured for each combination. Choked flow occurred in all high respiratory rate-high volume animals, 71% of high respiratory rate-medium volume (HRMV) animals, and 50% of medium respiratory rate-high volume (MRHV) animals but in no other combinations. Medium respiratory rate-medium volume (MRMV) resulted in the highest gas exchange of the combinations that did not induce choke. The HRMV and MRHV animals that did not choke had similar or higher gas exchange than MRMV. The theory predicted this behavior, along with spatial and temporal variations in alveolar gas partial pressures. Of the combinations that did not induce choked flow, MRMV provided the highest gas exchange. Alveolar gas transport is diffusion dominated and rapid during gas ventilation but is convection dominated and slow during TLV. Consequently, the usual alveolar gas equation is not applicable for TLV.

  15. Determination of rate constants and branching ratios for TCE degradation by zero-valent iron using a chain decay multispecies model.

    Science.gov (United States)

    Hwang, Hyoun-Tae; Jeen, Sung-Wook; Sudicky, Edward A; Illman, Walter A

    2015-01-01

    The applicability of a newly-developed chain-decay multispecies model (CMM) was validated by obtaining kinetic rate constants and branching ratios along the reaction pathways of trichloroethene (TCE) reduction by zero-valent iron (ZVI) from column experiments. Changes in rate constants and branching ratios for individual reactions for degradation products over time for two columns under different geochemical conditions were examined to provide ranges of those parameters expected over the long-term. As compared to the column receiving deionized water, the column receiving dissolved CaCO3 showed higher mean degradation rates for TCE and all of its degradation products. However, the column experienced faster reactivity loss toward TCE degradation due to precipitation of secondary carbonate minerals, as indicated by a higher value for the ratio of maximum to minimum TCE degradation rate observed over time. From the calculated branching ratios, it was found that TCE and cis-dichloroethene (cis-DCE) were dominantly dechlorinated to chloroacetylene and acetylene, respectively, through reductive elimination for both columns. The CMM model, validated by the column test data in this study, provides a convenient tool to determine simultaneously the critical design parameters for permeable reactive barriers and natural attenuation such as rate constants and branching ratios. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Rate and Risk Factors for Periprosthetic Joint Infection Among 36,494 Primary Total Hip Arthroplasties.

    Science.gov (United States)

    Triantafyllopoulos, Georgios K; Soranoglou, Vasileios G; Memtsoudis, Stavros G; Sculco, Thomas P; Poultsides, Lazaros A

    2018-04-01

    As periprosthetic joint infections (PJIs) can have tremendous health and socioeconomic implications, recognizing patients at risk before surgery is of great importance. Therefore, we sought to determine the rate of and risk factors for deep PJI in patients undergoing primary total hip arthroplasty (THA). Clinical characteristics of patients treated with primary THA between January 1999 and December 2013 were retrospectively reviewed. These included patient demographics, comorbidities (including the Charlson/Deyo comorbidity index), length of stay, primary diagnosis, total/allogeneic transfusion rate, and in-hospital complications, which were grouped into local and systemic (minor and major). We determined the overall deep PJI rate, as well as the rates for early-onset (occurring within 2 years after index surgery) and late-onset PJI (occurring more than 2 years after surgery). A Cox proportional hazards regression model was constructed to identify risk factors for developing deep PJI. Significance level was set at 0.05. A deep PJI developed in 154 of 36,494 primary THAs (0.4%) during the study period. Early onset PJI was found in 122 patients (0.3%), whereas late PJI occurred in 32 patients (0.1%). Obesity, coronary artery disease, and pulmonary hypertension were identified as independent risk factors for deep PJI after primary THA. The rate of deep PJIs of the hip is relatively low, with the majority occurring within 2 years after THA. If the optimization of modifiable risk factors before THA can reduce the rate of this complication remains unknown, but should be attempted as part of good practice. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. Increased Total Anesthetic Time Leads to Higher Rates of Surgical Site Infections in Spinal Fusions.

    Science.gov (United States)

    Puffer, Ross C; Murphy, Meghan; Maloney, Patrick; Kor, Daryl; Nassr, Ahmad; Freedman, Brett; Fogelson, Jeremy; Bydon, Mohamad

    2017-06-01

    A retrospective review of a consecutive series of spinal fusions comparing patient and procedural characteristics of patients who developed surgical site infections (SSIs) after spinal fusion. It is known that increased surgical time (incision to closure) is associated with a higher rate of postoperative SSIs. We sought to determine whether increased total anesthetic time (intubation to extubation) is a factor in the development of SSIs as well. In spine surgery for deformity and degenerative disease, SSI has been associated with operative time, revealing a nearly 10-fold increase in SSI rates in prolonged surgery. Surgical time is associated with infections in other surgical disciplines as well. No studies have reported whether total anesthetic time (intubation to extubation) has an association with SSIs. Surgical records were searched in a retrospective fashion to identify all spine fusion procedures performed between January 2010 and July 2012. All SSIs during that timeframe were recorded and compared with the list of cases performed between 2010 and 2012 in a case-control design. There were 20 (1.7%) SSIs in this fusion cohort. On univariate analyses of operative factors, there was a significant association between total anesthetic time (Infection 7.6 ± 0.5 hrs vs. no infection -6.0 ± 0.1 hrs, P operative time (infection 5.5 ± 0.4 hrs vs. no infection - 4.4 ± 0.06 hrs, P infections, whereas level of pathology and emergent surgery were not significant. On multivariate logistic analysis, BMI and total anesthetic time remained independent predictors of SSI whereas ASA status and operative time did not. Increasing BMI and total anesthetic time were independent predictors of SSIs in this cohort of over 1000 consecutive spinal fusions. 3.

  18. Radionuclide mass transfer rates from a pinhole in a waste container for an inventory-limited and a constant concentration source

    International Nuclear Information System (INIS)

    LeNeveu, D.M.

    1996-03-01

    Analytical solutions for transient and steady state diffusive mass transfer rates from a pinhole in a waste container are developed for constant concentration and inventory-limited source conditions. Mass transport in three media are considered, inside the pinhole (medium 2), outside the container (medium 3) and inside the container (medium 1). Simple equations are developed for radionuclide mass transfer rates from a pinhole. It is shown that the medium with the largest mass transfer resistance need only be considered to provide a conservative estimate of mass transfer rates. (author) 11 refs., 3 figs

  19. The effect of addition of primary positive salts, complex salt, on the ionic strength and rate constant at various temperatures by reaction kinetics

    Science.gov (United States)

    Kurade, S. S.; Ramteke, A. A.

    2018-05-01

    In this work, we have investigated the rate of reaction by using ionic strength at different temperatures. The main goal of this experiment is to determine the relation between ionic strength with reaction rate, reaction time and rate constant with temperature. It is observed that the addition of positive salt indicate the increasing ionic strength with increase in run time at various temperatures. Thus the temperature affects the speed of reaction and mechanism by which chemical reaction occurs and time variable plays vital role in the progress of reaction at different temperatures.

  20. Evaluation of total energy-rate feedback for glidescope tracking in wind shear

    Science.gov (United States)

    Belcastro, C. M.; Ostroff, A. J.

    1986-01-01

    Low-altitude wind shear is recognized as an infrequent but significant hazard to all aircraft during take-off and landing. A total energy-rate sensor, which is potentially applicable to this problem, has been developed for measuring specific total energy-rate of an airplane with respect to the air mass. This paper presents control system designs, with and without energy-rate feedback, for the approach to landing of a transport airplane through severe wind shear and gusts to evaluate application of this sensor. A system model is developed which incorporates wind shear dynamics equations with the airplance equations of motion, thus allowing the control systems to be analyzed under various wind shears. The control systems are designed using optimal output feedback and are analyzed using frequency domain control theory techniques. Control system performance is evaluated using a complete nonlinear simulation of the airplane and a severe wind shear and gust data package. The analysis and simulation results indicate very similar stability and performance characteristics for the two designs. An implementation technique for distributing the velocity gains between airspeed and ground speed in the simulation is also presented, and this technique is shown to improve the performance characteristics of both designs.

  1. Total dose and dose rate models for bipolar transistors in circuit simulation.

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, Phillip Montgomery; Wix, Steven D.

    2013-05-01

    The objective of this work is to develop a model for total dose effects in bipolar junction transistors for use in circuit simulation. The components of the model are an electrical model of device performance that includes the effects of trapped charge on device behavior, and a model that calculates the trapped charge densities in a specific device structure as a function of radiation dose and dose rate. Simulations based on this model are found to agree well with measurements on a number of devices for which data are available.

  2. Total skin high-dose-rate electron therapy dosimetry using TG-51

    International Nuclear Information System (INIS)

    Gossman, Michael S.; Sharma, Subhash C.

    2004-01-01

    An approach to dosimetry for total skin electron therapy (TSET) is discussed using the currently accepted TG-51 high-energy calibration protocol. The methodology incorporates water phantom data for absolute calibration and plastic phantom data for efficient reference dosimetry. The scheme is simplified to include the high-dose-rate mode conversion and provides support for its use, as it becomes more available on newer linear accelerators. Using a 6-field, modified Stanford technique, one may follow the process for accurate determination of absorbed dose

  3. [Rates of total and free PSA prescriptions in France (2012-2014)].

    Science.gov (United States)

    Tuppin, Philippe; Leboucher, Claire; Peyre-Lanquar, Gabrielle; Lamy, Pierre-Jean; Gabach, Pierre; Rébillard, Xavier

    2017-10-01

    In 2010, the French Haute Autorité de santé (National Health Authority) confirmed the limited value of prostate cancer (PCa) screening by total prostate-specific antigen (PSA) assay. This study was designed to determine the modalities of ordering total PSA or free PSA assays (in the absence of PCa) according to various parameters and the corresponding sums reimbursed. Men aged 40 years and older covered by the national health insurance general scheme (73% of the French population) between 2012 and 2014 were selected. Data were derived from the Système national d'information inter-régimes de l'assurance maladie (Sniiram) (National health insurance information system) database. In 2014, 27% of the 11.6 million men 40 years and older underwent at least one total PSA assay and 5.6% underwent at least one free PSA assay, with marked variations according to the presence or absence of treated lower urinary tract symptoms (LUTS) (53% and 15% vs 24% and 5%) and from one administrative department to another. The peak total PSA assay rate was observed between the ages of 65 and 74 years: 64% of men with LUTS, 46% without LUTS. Between 2012 and 2014, men in whom at least one PSA assay had been performed underwent a mean of 1.8 total PSA assays and 1.7 free PSA assays, with means of 2.3 and 2, respectively, in the presence of LUTS. General practice specialists ordered 91% of the PSA tests reimbursed in 2014 (92% for total PSA and 87% for free PSA) and urologists ordered 4% of reimbursed tests. The total sum reimbursed was €28.5 million, comprising €8.7 million for free PSA. An average of 10 laboratory tests was performed at the same time as the PSA assay in the absence of treated LUTS. Total PSA and free PSA assays are performed in a large number of men, although the value of these tests as first-line test before biopsy remains controversial. These PSA assays are associated with many other laboratory tests looking for possible abnormalities, especially in younger

  4. Emesis as a Screening Diagnostic for Low Dose Rate (LDR) Total Body Radiation Exposure.

    Science.gov (United States)

    Camarata, Andrew S; Switchenko, Jeffrey M; Demidenko, Eugene; Flood, Ann B; Swartz, Harold M; Ali, Arif N

    2016-04-01

    Current radiation disaster manuals list the time-to-emesis (TE) as the key triage indicator of radiation dose. The data used to support TE recommendations were derived primarily from nearly instantaneous, high dose-rate exposures as part of variable condition accident databases. To date, there has not been a systematic differentiation between triage dose estimates associated with high and low dose rate (LDR) exposures, even though it is likely that after a nuclear detonation or radiologic disaster, many surviving casualties would have received a significant portion of their total exposure from fallout (LDR exposure) rather than from the initial nuclear detonation or criticality event (high dose rate exposure). This commentary discusses the issues surrounding the use of emesis as a screening diagnostic for radiation dose after LDR exposure. As part of this discussion, previously published clinical data on emesis after LDR total body irradiation (TBI) is statistically re-analyzed as an illustration of the complexity of the issue and confounding factors. This previously published data includes 107 patients who underwent TBI up to 10.5 Gy in a single fraction delivered over several hours at 0.02 to 0.04 Gy min. Estimates based on these data for the sensitivity of emesis as a screening diagnostic for the low dose rate radiation exposure range from 57.1% to 76.6%, and the estimates for specificity range from 87.5% to 99.4%. Though the original data contain multiple confounding factors, the evidence regarding sensitivity suggests that emesis appears to be quite poor as a medical screening diagnostic for LDR exposures.

  5. A study on the influence of fast amide exchange on the accuracy of (15)N relaxation rate constants.

    Science.gov (United States)

    Jurt, Simon; Zerbe, Oliver

    2012-12-01

    (15)N relaxation rates of amide moieties provide insight both into global as well as local backbone dynamics of peptides and proteins. As the differences in the relaxation rates in general are small, their accurate determination is of prime importance. One potential source of error is fast amide exchange. It is well known that in its presence the effects of saturation transfer and H/D exchange may result in erroneous apparent relaxation rates R (1) and R (2). Here, the extent of these errors is rigorously examined. Theoretical considerations reveal that even when saturation effects are absent, H/D exchange will easily result in significant deviations from the true values. In particular overestimations of up to 10 % in R (1) and up to 5 % in R (2) are observed. An alternative scheme for fitting the relaxation data to the corresponding exponentials is presented that in the best cases not only delivers more accurate relaxation rates but also allows extracting estimates for the exchange rates. The theoretical computations were tested and verified for the case of ubiquitin.

  6. A study on the influence of fast amide exchange on the accuracy of 15N relaxation rate constants

    International Nuclear Information System (INIS)

    Jurt, Simon; Zerbe, Oliver

    2012-01-01

    15 N relaxation rates of amide moieties provide insight both into global as well as local backbone dynamics of peptides and proteins. As the differences in the relaxation rates in general are small, their accurate determination is of prime importance. One potential source of error is fast amide exchange. It is well known that in its presence the effects of saturation transfer and H/D exchange may result in erroneous apparent relaxation rates R 1 and R 2 . Here, the extent of these errors is rigorously examined. Theoretical considerations reveal that even when saturation effects are absent, H/D exchange will easily result in significant deviations from the true values. In particular overestimations of up to 10 % in R 1 and up to 5 % in R 2 are observed. An alternative scheme for fitting the relaxation data to the corresponding exponentials is presented that in the best cases not only delivers more accurate relaxation rates but also allows extracting estimates for the exchange rates. The theoretical computations were tested and verified for the case of ubiquitin.

  7. Two-dimensional analytical solutions for chemical transport in aquifers. Part 1. Simplified solutions for sources with constant concentration. Part 2. Exact solutions for sources with constant flux rate

    International Nuclear Information System (INIS)

    Shan, C.; Javandel, I.

    1996-05-01

    Analytical solutions are developed for modeling solute transport in a vertical section of a homogeneous aquifer. Part 1 of the series presents a simplified analytical solution for cases in which a constant-concentration source is located at the top (or the bottom) of the aquifer. The following transport mechanisms have been considered: advection (in the horizontal direction), transverse dispersion (in the vertical direction), adsorption, and biodegradation. In the simplified solution, however, longitudinal dispersion is assumed to be relatively insignificant with respect to advection, and has been neglected. Example calculations are given to show the movement of the contamination front, the development of concentration profiles, the mass transfer rate, and an application to determine the vertical dispersivity. The analytical solution developed in this study can be a useful tool in designing an appropriate monitoring system and an effective groundwater remediation method

  8. Rate constants and temperature effects for reactions of Cl2sm-bullet- with unsaturated alcohols and hydrocarbons in aqueous and acetonitrile/water solutions

    International Nuclear Information System (INIS)

    Padmaja, S.; Neta, P.; Huie, R.E.

    1992-01-01

    Absolute rate constants for reactions of the dichlorine radical anion, Cl 2 sm-bullet- , with unsaturated alcohols and hydrocarbons have been measured at various temperatures. The alcohol reactions were measured in aqueous solutions and the hydrocarbon reactions in 1:1 aqueous acetonitirle (ACN) solutions. The rate constants for two alcohols and one hydrocarbon were also examined as a function of solvent composition. The room temperature rate constants varied between 10 6 and 10 9 M -1 s -1 . The pre-exponential factors, A, were about (1-5) x 10 9 M -1 s -1 for the alcohols in aqueous solutions and about (0.1-1) x 10 9 M -1 s -1 for the hydrocarbons in aqueous ACN solutions. The activation energies, E a , varied considerably, between 4 and 12 kJ mol -1 for the alcohols and between 2 and 8 kJ mol -1 for the hydrocarbons. The rate constants, k 298 , decrease with increasing ionization potential (IP) of the unsaturated compound, in agreement with an electrophilic addition mechanism. The activation energies for the unsaturated alcohols decrease when the IP decreases from 9.7 to 9.1 eV but appear to level off at lower IP. Most alkenes studied had IP a . Upon addition of ACN to the aqueous solution, the values of log k 298 decreased linearly by more than 1 order of magnitude with increasing ACN mole fraction. This decrease appears to result from a combination of changes in the activation energy and in the pre-exponential factor. The reason for these changes may lie in changes in the solvation shell of the Cl 2 sm-bullet- radical, which will affect the A factor, in combination with changes in solvation of Cl - , which will affect the energetics of the reactions as well. 20 refs., 7 figs., 6 tabs

  9. Absolute rate constants for the reaction of CF3O2 and CF3O radicals with NO at 295 K

    DEFF Research Database (Denmark)

    Sehested, J.; Nielsen, O.J.

    1993-01-01

    Using a pulse radiolysis UV absorption technique and subsequent simulations of experimental NO2 and FNO absorption transients, rate constants for reaction between CF3O and CF3O2 radicals with NO were determined, CF3O2+NO-->CF3O+NO2 (3), CF3O+NO-->CF2O+FNO (5). k3 was derived to be (1.68+/-0.26)x10...

  10. Simultaneous measurement of glucose blood–brain transport constants and metabolic rate in rat brain using in-vivo 1H MRS

    Science.gov (United States)

    Du, Fei; Zhang, Yi; Zhu, Xiao-Hong; Chen, Wei

    2012-01-01

    Cerebral glucose consumption and glucose transport across the blood–brain barrier are crucial to brain function since glucose is the major energy fuel for supporting intense electrophysiological activity associated with neuronal firing and signaling. Therefore, the development of noninvasive methods to measure the cerebral metabolic rate of glucose (CMRglc) and glucose transport constants (KT: half-saturation constant; Tmax: maximum transport rate) are of importance for understanding glucose transport mechanism and neuroenergetics under various physiological and pathological conditions. In this study, a novel approach able to simultaneously measure CMRglc, KT, and Tmax via monitoring the dynamic glucose concentration changes in the brain tissue using in-vivo 1H magnetic resonance spectroscopy (MRS) and in plasma after a brief glucose infusion was proposed and tested using an animal model. The values of CMRglc, Tmax, and KT were determined to be 0.44±0.17 μmol/g per minute, 1.35±0.47 μmol/g per minute, and 13.4±6.8 mmol/L in the rat brain anesthetized with 2% isoflurane. The Monte-Carlo simulations suggest that the measurements of CMRglc and Tmax are more reliable than that of KT. The overall results indicate that the new approach is robust and reliable for in-vivo measurements of both brain glucose metabolic rate and transport constants, and has potential for human application. PMID:22714049

  11. Parametric imaging of the rate constant K[sub i] using 18Fluoro-L-dopa positron emission tomography in progressive supranuclear palsy

    Energy Technology Data Exchange (ETDEWEB)

    Cordes, M. (Neurodegenerative Disorders Centre, Univ. Hospital, Univ. of British Columbia, Vancouver, BC (Canada) Strahlenklinik und Poliklinik, Universitaetsklinikum Rudolf-Virchow, Berlin (Germany)); Snow, B.J. (Neurodegenerative Disorders Centre, Univ. Hospital, Univ. of British Columbia, Vancouver, BC (Canada)); Morrison, S. (TRIUMF, Univ. of British Columbia, Vancouver, BC (Canada)); Sossi, V. (TRIUMF, Univ. of British Columbia, Vancouver, BC (Canada)); Ruth, T.J. (TRIUMF, Univ. of British Columbia, Vancouver, BC (Canada)); Calne, D.B. (Neurodegenerative Disorders Centre, Univ. Hospital, Univ. of British Columbia, Vancouver, BC (Canada))

    1993-01-01

    Positron emission tomography (PET) studies using 18F-L-dopa were carried out in 9 patients with supranuclear palsy and 13 controls. For quantification of PET data a rate constant K[sub i] was calculated for the radiotracer using a graphical method. Corrections for nonspecific activity were performed in both arterial plasma and brain tissue. The purpose of this study was to test the hypothesis that parametric images of the rate constant K mapping can be obtained on a pixel-by-pixel basis using an appropriate mathematical algorithm. K[sub i] values from these parametric images and the graphical approach were compared. Both correlated closely, with y=0.013+0.947[sup *]x, r=0.992 and y=-0.052+1.048[sup *]x, r=0.965 in patients and controls, respectively. Contrast measurements were also performed and showed a striking increase in contrast on parametric images. K mapping offers several advantages over the graphical approach, since parametric images are time-independent, i.e. one image represents the quantitative result of the study. In addition, parmetric images of the rate constant are normalized to arterial plasma radioactivity and corrected for tissue metabolites. Thus, parametric images of K[sub i] in different individuals can be compared directly without further processing in order to assess the nigrostriatal integrity. (orig.)

  12. QSAR models for oxidation of organic micropollutants in water based on ozone and hydroxyl radical rate constants and their chemical classification

    KAUST Repository

    Sudhakaran, Sairam

    2013-03-01

    Ozonation is an oxidation process for the removal of organic micropollutants (OMPs) from water and the chemical reaction is governed by second-order kinetics. An advanced oxidation process (AOP), wherein the hydroxyl radicals (OH radicals) are generated, is more effective in removing a wider range of OMPs from water than direct ozonation. Second-order rate constants (kOH and kO3) are good indices to estimate the oxidation efficiency, where higher rate constants indicate more rapid oxidation. In this study, quantitative structure activity relationships (QSAR) models for O3 and AOP processes were developed, and rate constants, kOH and kO3, were predicted based on target compound properties. The kO3 and kOH values ranged from 5 * 10-4 to 105 M-1s-1 and 0.04 to 18 * (109) M-1 s-1, respectively. Several molecular descriptors which potentially influence O3 and OH radical oxidation were identified and studied. The QSAR-defining descriptors were double bond equivalence (DBE), ionisation potential (IP), electron-affinity (EA) and weakly-polar component of solvent accessible surface area (WPSA), and the chemical and statistical significance of these descriptors was discussed. Multiple linear regression was used to build the QSAR models, resulting in high goodness-of-fit, r2 (>0.75). The models were validated by internal and external validation along with residual plots. © 2012 Elsevier Ltd.

  13. Ab initio calculation of the transition-state properties and addition rate constants for H + C2H2 and selected isotopic analogues

    International Nuclear Information System (INIS)

    Harding, L.B.; Wagner, A.F.; Bowman, J.M.; Schatz, G.C.; Christoffel, K.

    1982-01-01

    GVB-POL-CI ab initio calculations of the geometries, energetics, and normal mode frequencies of C 2 H 2 , C 2 H 3 , and the transition state for the addition reaction of H + C 2 H 2 are presented. In addition, normal mode frequencies for the isotopic variants D + C 2 D 2 , D + C 2 H 2 , and H + C 2 D 2 are preented. These results are compared to experimental values for C 2 H 2 and to ab initio values of Hagase and Kern, and semiempirical values of Keil, Lynch, Cowfer, and Michael. The results are also used to calculate the apparent bimolecular addition rate constant using conventional RRKM theory for chemical activation. The calculated rate constants and their isotopic variants are compared as a function of temperature and pressure to available experimental information. The agreement is little different from that obtained by Keil et al. with a similar calculation using semiempirical values for acetylene, transition-state, and vinyl radical properties. In particular, the calculated high-pressure limit of the rate constant appears to be at least 1 order of magnitude higher than the experimental limit. Several possible reasons for this discrepancy are discussed

  14. Rate constant for the H˙ + H2O → ˙OH + H2 reaction at elevated temperatures measured by pulse radiolysis.

    Science.gov (United States)

    Muroya, Y; Yamashita, S; Lertnaisat, P; Sanguanmith, S; Meesungnoen, J; Jay-Gerin, J-P; Katsumura, Y

    2017-11-22

    Maintaining the structural integrity of materials in nuclear power plants is an essential issue associated with safe operation. Hydrogen (H 2 ) addition or injection to coolants is a powerful technique that has been widely applied such that the reducing conditions in the coolant water avoid corrosion and stress corrosion cracking (SCC). Because the radiation-induced reaction of ˙OH + H 2 → H˙ + H 2 O plays a crucial role in these systems, the rate constant has been measured at operation temperatures of the reactors (285-300 °C) by pulse radiolysis, generating sufficient data for analysis. The reverse reaction H˙ + H 2 O → ˙OH + H 2 is negligibly slow at ambient temperature; however, it accelerates considerably quickly at elevated temperatures. Although the reverse reaction reduces the effectiveness of H 2 addition, reliable rate constants have not yet been measured. In this study, the rate constants have been determined in a temperature range of 250-350 °C by pulse radiolysis in an aqueous I - solution.

  15. Investigation of the Flow Rate Effect Upstream of the Constant-Geometry Throttle on the Gas Mass Flow

    Directory of Open Access Journals (Sweden)

    Yu. M. Timofeev

    2016-01-01

    Full Text Available The turbulent-flow throttles are used in pneumatic systems and gas-supply ones to restrict or measure gas mass flow. It is customary to install the throttles in joints of pipelines (in teejoints and cross tees or in joints of pipelines with pneumatic automation devices Presently, in designing the pneumatic systems and gas-supply ones a gas mass flow through a throttle is calculated by a known equation derived from the Saint-Venant-Vantсel formula for the adiabatic flow of ideal gas through a nozzle from an unrestrictedly high capacity tank. Neglect of gas velocity at the throttle inlet is one of the assumptions taken in the development of the above equation. As may be seen in practice, in actual systems the diameters of the throttle and the pipe wherein it is mounted can be commensurable. Neglect of the inlet velocity therewith can result in an error when determining the required throttle diameter in design calculation and a flow rate in checking calculation, as well as when measuring a flow rate in the course of the test. The theoretical study has revealed that the flow velocity at the throttle inlet is responsible for two parameter values: the outlet flow velocity and the critical pressure ratio, which in turn determine the gas mass flow value. To calculate the gas mass flow, the dependencies are given in the paper, which allow taking into account the flow rate at the throttle inlet. The analysis of obtained dependencies has revealed that the degree of influence of inlet flow rate upon the mass flow is defined by two parameters: pressure ratio at the throttle and open area ratio of the throttle and the pipe wherein it is mounted. An analytical investigation has been pursued to evaluate the extent to which the gas mass flow through the throttle is affected by the inlet flow rate. The findings of the investigation and the indications for using the present dependencies are given in this paper. By and large the investigation allowed the

  16. A mathematical analysis of Prx2-STAT3 disulfide exchange rate constants for a bimolecular reaction mechanism.

    Science.gov (United States)

    Langford, Troy F; Deen, William M; Sikes, Hadley D

    2018-03-22

    Appreciation of peroxiredoxins as the major regulators of H 2 O 2 concentrations in human cells has led to a new understanding of redox signaling. In addition to their status as the primary reducers of H 2 O 2 to water, the oxidized peroxiredoxin byproduct of this reaction has recently been shown capable of participation in H 2 O 2 -mediated signaling pathways through disulfide exchange reactions with the transcription factor STAT3. The dynamics of peroxidase-transcription factor disulfide exchange reactions have not yet been considered in detail with respect to how these reactions fit into the larger network of competing reactions in human cells. In this study, we used a kinetic model of oxidation and reduction reactions related to H 2 O 2 metabolism in the cytosol of human cells to study the dynamics of peroxiredoxin-2 mediated oxidation of the redox-regulated transcription factor STAT3. In combination with previously reported experimental data, the model was used to estimate the rate coefficient of a biomolecular reaction between Prx2 and STAT3 for two sets of assumptions that constitute lower and upper bound cases. Using these estimates, we calculated the relative rates of the reaction of oxidized peroxiredoxin-2 and STAT3 and other competing reactions in the cytosol. These calculations revealed that peroxiredoxin-2-mediated oxidation of STAT3 likely occurs at a much slower rate than competing reactions in the cytosol. This analysis suggests the existence of more complex mechanisms, potentially involving currently unknown protein-protein recognition partners, which facilitate disulfide exchange reactions between peroxiredoxin-2 and STAT3. Copyright © 2018 Elsevier Inc. All rights reserved.

  17. Nuclear constants

    International Nuclear Information System (INIS)

    Foos, J.

    1999-01-01

    This paper is written in two tables. The first one describes the different particles (bosons and fermions). The second one gives the isotopes nuclear constants of the different elements, for Z = 1 to 56. (A.L.B.)

  18. Nuclear constants

    International Nuclear Information System (INIS)

    Foos, J.

    2000-01-01

    This paper is written in two tables. The first one describes the different particles (bosons and fermions). The second one gives the isotopes nuclear constants of the different elements, for Z = 56 to 68. (A.L.B.)

  19. Nuclear constants

    International Nuclear Information System (INIS)

    Foos, J.

    1998-01-01

    This paper is made of two tables. The first table describes the different particles (bosons and fermions) while the second one gives the nuclear constants of isotopes from the different elements with Z = 1 to 25. (J.S.)

  20. Nuclear constants

    International Nuclear Information System (INIS)

    Foos, J.

    1999-01-01

    This paper is written in two tables. The first one describes the different particles (bosons and fermions). The second one gives the isotopes nuclear constants of the different elements, for Z = 56 to 68. (A.L.B.)

  1. Surface displacements and energy release rates for constant stress drop slip zones in joined elastic quarter spaces

    Science.gov (United States)

    Rodgers, Michael J.; Wen, Shengmin; Keer, Leon M.

    2000-08-01

    A three-dimensional quasi-static model of faulting in an elastic half-space with a horizontal change of material properties (i.e., joined elastic quarter spaces) is considered. A boundary element method is used with a stress drop slip zone approach so that the fault surface relative displacements as well as the free surface displacements are approximated in elements over their respective domains. Stress intensity factors and free surface displacements are calculated for a variety of cases to show the phenomenological behavior of faulting in such a medium. These calculations showed that the behavior could be distinguished from a uniform half-space. Slip in a stiffer material increases, while slip in a softer material decreases the energy release rate and the free surface displacements. Also, the 1989 Kalapana earthquake was located on the basis of a series of forward searches using this method and leveling data. The located depth is 8 km, which is the closer to the seismically inferred depth than that determined from other models. Finally, the energy release rate, which can be used as a fracture criterion for fracture at this depth, is calculated to be 11.1×106 J m-2.

  2. Do Insect Populations Die at Constant Rates as They Become Older? Contrasting Demographic Failure Kinetics with Respect to Temperature According to the Weibull Model.

    Directory of Open Access Journals (Sweden)

    Petros Damos

    Full Text Available Temperature implies contrasting biological causes of demographic aging in poikilotherms. In this work, we used the reliability theory to describe the consistency of mortality with age in moth populations and to show that differentiation in hazard rates is related to extrinsic environmental causes such as temperature. Moreover, experiments that manipulate extrinsic mortality were used to distinguish temperature-related death rates and the pertinence of the Weibull aging model. The Newton-Raphson optimization method was applied to calculate parameters for small samples of ages at death by estimating the maximum likelihoods surfaces using scored gradient vectors and the Hessian matrix. The study reveals for the first time that the Weibull function is able to describe contrasting biological causes of demographic aging for moth populations maintained at different temperature regimes. We demonstrate that at favourable conditions the insect death rate accelerates as age advances, in contrast to the extreme temperatures in which each individual drifts toward death in a linear fashion and has a constant chance of passing away. Moreover, slope of hazard rates shifts towards a constant initial rate which is a pattern demonstrated by systems which are not wearing out (e.g. non-aging since the failure, or death, is a random event independent of time. This finding may appear surprising, because, traditionally, it was mostly thought as rule that in aging population force of mortality increases exponentially until all individuals have died. Moreover, in relation to other studies, we have not observed any typical decelerating aging patterns at late life (mortality leveling-off, but rather, accelerated hazard rates at optimum temperatures and a stabilized increase at the extremes.In most cases, the increase in aging-related mortality was simulated reasonably well according to the Weibull survivorship model that is applied. Moreover, semi log- probability hazard

  3. Differentiating inflamed and normal lungs by the apparent reaction rate constants of lactate dehydrogenase probed by hyperpolarized (13)C labeled pyruvate.

    Science.gov (United States)

    Xu, He N; Kadlececk, Stephen; Shaghaghi, Hoora; Zhao, Huaqing; Profka, Harilla; Pourfathi, Mehrdad; Rizi, Rahim; Li, Lin Z

    2016-02-01

    Clinically translatable hyperpolarized (HP) (13)C-NMR can probe in vivo enzymatic reactions, e.g., lactate dehydrogenase (LDH)-catalyzed reaction by injecting HP (13)C-pyruvate into the subject, which is converted to (13)C labeled lactate by the enzyme. Parameters such as (13)C-lactate signals and lactate-to-pyruvate signal ratio are commonly used for analyzing the HP (13)C-NMR data. However, the biochemical/biological meaning of these parameters remains either unclear or dependent on experimental settings. It is preferable to quantify the reaction rate constants with a clearer physical meaning. Here we report the extraction of the kinetic parameters of the LDH reaction from HP (13)C-NMR data and investigate if they can be potential predictors of lung inflammation. Male Sprague-Dawley rats (12 controls, 14 treated) were used. One dose of bleomycin (2.5 U/kg) was administered intratracheally to the treatment group. The lungs were removed, perfused, and observed by the HP-NMR technique, where a HyperSense dynamic nuclear polarization system was used to generate the HP (13)C-pyruvate for injecting into the lungs. A 20 mm (1)H/(13)C dual-tuned coil in a 9.4-T Varian vertical bore NMR spectrometer was employed to acquire the (13)C spectral data every 1 s over a time period of 300 s using a non-selective, 15-degree radiofrequency pulse. The apparent rate constants of the LDH reaction and their ratio were quantified by applying ratiometric fitting analysis to the time series data of (13)C labeled pyruvate and lactate. The apparent forward rate constant kp =(3.67±3.31)×10(-4) s(-1), reverse rate constant kl =(4.95±2.90)×10(-2) s(-1), rate constant ratio kp /kl =(7.53±5.75)×10(-3) for the control lungs; kp =(11.71±4.35)×10(-4) s(-1), kl =(9.89±3.89)×10(-2) s(-1), and kp /kl =(12.39±4.18)×10(-3) for the inflamed lungs at the 7(th) day post treatment. Wilcoxon rank-sum test showed that the medians of these kinetic parameters of the 7-day cohort were significantly

  4. Total Body Capacitance for Estimating Human Basal Metabolic Rate in an Egyptian Population

    Science.gov (United States)

    M. Abdel-Mageed, Samir; I. Mohamed, Ehab

    2016-01-01

    Determining basal metabolic rate (BMR) is important for estimating total energy needs in the human being yet, concerns have been raised regarding the suitability of sex-specific equations based on age and weight for its calculation on an individual or population basis. It has been shown that body cell mass (BCM) is the body compartment responsible for BMR. The objectives of this study were to investigate the relationship between total body capacitance (TBC), which is considered as an expression for BCM, and BMR and to develop a formula for calculating BMR in comparison with widely used equations. Fifty healthy nonsmoking male volunteers [mean age (± SD): 24.93 ± 4.15 year and body mass index (BMI): 25.63 ± 3.59 kg/m2] and an equal number of healthy nonsmoking females matched for age and BMI were recruited for the study. TBC and BMR were measured for all participants using octopolar bioelectric impedance analysis and indirect calorimetry techniques, respectively. A significant regressing equation based on the covariates: sex, weight, and TBC for estimating BMR was derived (R=0.96, SEE=48.59 kcal, and P<0.0001), which will be useful for nutritional and health status assessment for both individuals and populations. PMID:27127453

  5. Rate Constants for the Reactions of OH with CO, NO and NO2, and of HO2 with NO2 in the Presence of Water Vapour at Lower-Tropospheric Conditions

    Science.gov (United States)

    Rolletter, Michael; Fuchs, Hendrik; Novelli, Anna; Ehlers, Christian; Hofzumahaus, Andreas

    2016-04-01

    Recent studies have shown that the chemistry of gaseous nitrous acid (HONO) in the lower troposphere is not fully understood. Aside from heterogenous reactions, the daytime HONO formation in the gas-phase is not well understood (Li et al., Science, 2014). For a better understanding of HONO in the gas-phase, we have reinvestigated the reaction rate constants of important tropospheric reactions of the HOx radical family (OH and HO2) with nitrogen oxides at realistic conditions of the lower troposphere (at ambient temperature/pressure and in humid air). In this study we apply a direct pump and probe technique with high accuracy, using small radical concentrations to avoid secondary chemistry. Pulsed laser photolysis/laser-induced fluorescence (LP/LIF) was used to investigate the reaction rate constants of OH with CO, NO, NO2, and HO2 with NO2 in synthetic air at different water vapor concentrations (up to 5 x 1017 molecules cm-3). Photolysis of ozone in the presence of gaseous water was the source of OH. The reactions took place in a flow-tube at room temperature and atmospheric pressure. The chemical decay of the radicals was monitored by laser-induced fluorescence detection in a low-pressure cell, which sampled air continuously from the end of the flow-tube. Knowing the reactant concentrations subsequently allowed to calculate the bimolecular reaction rate constants at 1 atm from the pseudo-first-order decays. In order to observe HO2 reactions, OH was converted into HO2 with an excess of CO in the flow-tube. The newly measured rate constants for OH with CO, NO and NO2 agree very well with current recommendations by NASA/JPL and IUPAC and have an improved accuracy (uncertainty < 5%). These rate coefficients are independent of the presence of water vapour. The measured rate constant of HO2 with NO2 was found to depend significantly on the water-vapour concentration (probably due to formation of HO2*H2O complexes) and to exceed current recommendations by NASA/JPL and

  6. A parsimonious characterization of change in global age-specific and total fertility rates

    Science.gov (United States)

    2018-01-01

    This study aims to understand trends in global fertility from 1950-2010 though the analysis of age-specific fertility rates. This approach incorporates both the overall level, as when the total fertility rate is modeled, and different patterns of age-specific fertility to examine the relationship between changes in age-specific fertility and fertility decline. Singular value decomposition is used to capture the variation in age-specific fertility curves while reducing the number of dimensions, allowing curves to be described nearly fully with three parameters. Regional patterns and trends over time are evident in parameter values, suggesting this method provides a useful tool for considering fertility decline globally. The second and third parameters were analyzed using model-based clustering to examine patterns of age-specific fertility over time and place; four clusters were obtained. A country’s demographic transition can be traced through time by membership in the different clusters, and regional patterns in the trajectories through time and with fertility decline are identified. PMID:29377899

  7. Body mass and weight thresholds for increased prosthetic joint infection rates after primary total joint arthroplasty.

    Science.gov (United States)

    Lübbeke, Anne; Zingg, Matthieu; Vu, Diemlan; Miozzari, Hermes H; Christofilopoulos, Panayiotis; Uçkay, Ilker; Harbarth, Stephan; Hoffmeyer, Pierre

    2016-01-01

    Obesity increases the risk of deep infection after total joint arthroplasty (TJA). Our objective was to determine whether there may be body mass index (BMI) and weight thresholds indicating a higher prosthetic joint infection rate. We included all 9,061 primary hip and knee arthroplasties (mean age 70 years, 61% women) performed between March 1996 and December 2013 where the patient had received intravenous cefuroxime (1.5 g) perioperatively. The main exposures of interest were BMI (5 categories: prosthetic joint infection. The mean follow-up time was 6.5 years (0.5-18 years). 111 prosthetic joint infections were observed: 68 postoperative, 16 hematogenous, and 27 of undetermined cause. Incidence rates were similar in the first 3 BMI categories (infection from the early postoperative period onward (adjusted HR = 2.1, 95% CI: 1.3-3.6). BMI ≥ 35 or weight ≥ 100 kg may serve as a cutoff for higher perioperative dosage of antibiotics.

  8. Are fundamental constants really constant

    International Nuclear Information System (INIS)

    Norman, E.B.

    1986-01-01

    Reasons for suspecting that fundamental constants might change with time are reviewed. Possible consequences of such variations are examined. The present status of experimental tests of these ideas is discussed

  9. Standard Glbbs Energy of Formation of the Hydroxyl Radical in Aqueous Solution. Rate Constants for the Reaction C102- -t O3 S 03- -t CIO,

    DEFF Research Database (Denmark)

    Klaning, U. K.; Sehested, Knud; Holcman, J.

    1985-01-01

    The rate constants of the following reactions were determined by pulse radiolysis and stopped-flow experiments: C102- + O3 + C102 + 03-(k f= (4 f 1) X lo6 dm3 mol-' s-', k, = (1.8 f 0.2) X lo5 dm3 mol-' s-]); C102 + OH - C103- + H+ (k = (4.0 * 0.4) X lo9 dm3 mol-' s-l); C102 + 0- - C103- (k = (2.......7 * 0.4) X lo9 dm3 mol-' s-l); and O3 + C102 - C103 + O2 (k = (1.05 f 0.10) X lo3 dm3 mol-l s-'), where kf is the forward rate of reaction and k, is the reverse rate of reaction. The standard Gibbs energy of formation of OH in aqueous solution A&O,,(OH) and the corresponding standard oxidation potential...

  10. Determination of the strong coupling constant α{sub s} (m{sub Z}) from measurements of the total cross section for top-antitop-quark production

    Energy Technology Data Exchange (ETDEWEB)

    Klijnsma, Thomas; Dissertori, Guenther [ETH Zurich, Institute for Particle Physics, Zurich (Switzerland); Bethke, Siegfried [Max-Planck-Institute of Physics, Munich (Germany); Salam, Gavin P. [CERN, Theoretical Physics Department, Geneva (Switzerland); CNRS, UMR 7589, LPTHE, Paris (France)

    2017-11-15

    We present a determination of the strong coupling constant α{sub s} (m{sub Z}) using inclusive top-quark pair production cross section measurements performed at the LHC and at the Tevatron. Following a procedure first applied by the CMS Collaboration, we extract individual values of α{sub s} (m{sub Z}) from measurements by different experiments at several centre-of-mass energies, using QCD predictions complete in NNLO perturbation theory, supplemented with NNLL approximations to all orders, and suitable sets of parton distribution functions. The determinations are then combined using a likelihood-based approach, where special emphasis is put on a consistent treatment of theoretical uncertainties and of correlations between various sources of systematic uncertainties. Our final combined result is α{sub s} (m{sub Z}) = 0.1177{sup +0.0034}{sub -0.0036}. (orig.)

  11. 12 CFR Appendix K to Part 226 - Total Annual Loan Cost Rate Computations for Reverse Mortgage Transactions

    Science.gov (United States)

    2010-01-01

    ... Appendix K to Part 226—Total Annual Loan Cost Rate Computations for Reverse Mortgage Transactions (a... loan cost rate for various transactions, as well as instructions, explanations, and examples for.... (2) Term of the transaction. For purposes of total annual loan cost disclosures, the term of a...

  12. Rates and equilibrium constants of the ligand-induced conformational transition of an HCN ion channel protein domain determined by DEER spectroscopy.

    Science.gov (United States)

    Collauto, Alberto; DeBerg, Hannah A; Kaufmann, Royi; Zagotta, William N; Stoll, Stefan; Goldfarb, Daniella

    2017-06-14

    Ligand binding can induce significant conformational changes in proteins. The mechanism of this process couples equilibria associated with the ligand binding event and the conformational change. Here we show that by combining the application of W-band double electron-electron resonance (DEER) spectroscopy with microfluidic rapid freeze quench (μRFQ) it is possible to resolve these processes and obtain both equilibrium constants and reaction rates. We studied the conformational transition of the nitroxide labeled, isolated carboxy-terminal cyclic-nucleotide binding domain (CNBD) of the HCN2 ion channel upon binding of the ligand 3',5'-cyclic adenosine monophosphate (cAMP). Using model-based global analysis, the time-resolved data of the μRFQ DEER experiments directly provide fractional populations of the open and closed conformations as a function of time. We modeled the ligand-induced conformational change in the protein using a four-state model: apo/open (AO), apo/closed (AC), bound/open (BO), bound/closed (BC). These species interconvert according to AC + L ⇌ AO + L ⇌ BO ⇌ BC. By analyzing the concentration dependence of the relative contributions of the closed and open conformations at equilibrium, we estimated the equilibrium constants for the two conformational equilibria and the open-state ligand dissociation constant. Analysis of the time-resolved μRFQ DEER data gave estimates for the intrinsic rates of ligand binding and unbinding as well as the rates of the conformational change. This demonstrates that DEER can quantitatively resolve both the thermodynamics and the kinetics of ligand binding and the associated conformational change.

  13. Estimation of salivary flow rate, pH, buffer capacity, calcium, total protein content and total antioxidant capacity in relation to dental caries severity, age and gender.

    Science.gov (United States)

    Pandey, Pallavi; Reddy, N Venugopal; Rao, V Arun Prasad; Saxena, Aditya; Chaudhary, C P

    2015-03-01

    The aim of the study was to evaluate salivary flow rate, pH, buffering capacity, calcium, total protein content and total antioxidant capacity in relation to dental caries, age and gender. The study population consisted of 120 healthy children aged 7-15 years that was further divided into two groups: 7-10 years and 11-15 years. In this 60 children with DMFS/dfs = 0 and 60 children with DMFS/dfs ≥5 were included. The subjects were divided into two groups; Group A: Children with DMFS/dfs = 0 (caries-free) Group B: Children with DMFS/dfs ≥5 (caries active). Unstimulated saliva samples were collected from all groups. Flow rates were determined, and samples analyzed for pH, buffer capacity, calcium, total protein and total antioxidant status. Salivary antioxidant activity is measured with spectrophotometer by an adaptation of 2,2'-azino-di-(3-ethylbenzthiazoline-6-sulphonate) assays. The mean difference of the two groups; caries-free and caries active were proved to be statistically significant (P salivary calcium, total protein and total antioxidant level for both the sexes in the age group 7-10 years and for the age 11-15 years the mean difference of the two groups were proved to be statistically significant (P salivary calcium level for both the sexes. Salivary total protein and total antioxidant level were proved to be statistically significant for male children only. In general, total protein and total antioxidants in saliva were increased with caries activity. Calcium content of saliva was found to be more in caries-free group and increased with age.

  14. Stress corrosion crack initiation of Zircaloy-4 cladding tubes in an iodine vapor environment during creep, relaxation, and constant strain rate tests

    Science.gov (United States)

    Jezequel, T.; Auzoux, Q.; Le Boulch, D.; Bono, M.; Andrieu, E.; Blanc, C.; Chabretou, V.; Mozzani, N.; Rautenberg, M.

    2018-02-01

    During accidental power transient conditions with Pellet Cladding Interaction (PCI), the synergistic effect of the stress and strain imposed on the cladding by thermal expansion of the fuel, and corrosion by iodine released as a fission product, may lead to cladding failure by Stress Corrosion Cracking (SCC). In this study, internal pressure tests were conducted on unirradiated cold-worked stress-relieved Zircaloy-4 cladding tubes in an iodine vapor environment. The goal was to investigate the influence of loading type (constant pressure tests, constant circumferential strain rate tests, or constant circumferential strain tests) and test temperature (320, 350, or 380 °C) on iodine-induced stress corrosion cracking (I-SCC). The experimental results obtained with different loading types were consistent with each other. The apparent threshold hoop stress for I-SCC was found to be independent of the test temperature. SEM micrographs of the tested samples showed many pits distributed over the inner surface, which tended to coalesce into large pits in which a microcrack could initiate. A model for the time-to-failure of a cladding tube was developed using finite element simulations of the viscoplastic mechanical behavior of the material and a modified Kachanov's damage growth model. The times-to-failure predicted by this model are consistent with the experimental data.

  15. Geochronological study of the Guanabara Bay (Rio de Janeiro State, Brazil) using 2'10 Pb dating technique and the constant rate of supply model

    International Nuclear Information System (INIS)

    Silva Braganca, Maura Julia Camara da; Oliveira Godoy, Jose Marcos de

    1995-01-01

    A geochronological study of the Guanabara Bay (RJ, Brazil) based on 210 Pb dating technique using the Constant Rate of Supply Model CRS is presented. A low energy gamma spectrometry ( 210 Pb for samples collected from Estrela and Sao Joao de Meriti rivers. Radiochemical method was applied to determine the amount of 210 Pb in samples from Guapimirim, Guaxindiba and Imbuacu rivers. Atomic absorption spectrometry with air-acetylene flame technique was used to determine the amount of copper in all the samples. The CRS model showed adequate in this estuarine system. (author). 19 refs., 5 figs., 6 tabs

  16. Theoretical study and rate constant calculation for the reactions of SH (SD) with Cl2, Br2, and BrCl.

    Science.gov (United States)

    Wang, Li; Liu, Jing-Yao; Li, Ze-Sheng; Sun, Chia-Chung

    2005-01-30

    The mechanisms of the SH (SD) radicals with Cl2 (R1), Br2 (R2), and BrCl (R3) are investigated theoretically, and the rate constants are calculated using a dual-level direct dynamics method. The optimized geometries and frequencies of the stationary points are calculated at the MP2/6-311G(d,p) and MPW1K/6-311G(d,p) levels. Higher-level energies are obtained at the approximate QCISD(T)/6-311++G(3df, 2pd) level using the MP2 geometries as well as by the multicoefficient correlation method based on QCISD (MC-QCISD) using the MPW1K geometries. Complexes with energies less than those of the reactants or products are located at the entrance or the exit channels of these reactions, which indicate that the reactions may proceed via an indirect mechanism. The enthalpies of formation for the species XSH/XSD (X = Cl and Br) are evaluated using hydrogenation working reactions method. By canonical variational transition-state theory (CVT), the rate constants of SH and SD radicals with Cl2, Br2, and BrCl are calculated over a wide temperature range of 200-2000 K at the a-QCISD(T)/6-311++G(3df, 2pd)//MP2/6-311G(d, p) level. Good agreement between the calculated and experimental rate constants is obtained in the measured temperature range. Our calculations show that for SH (SD) + BrCl reaction bromine abstraction (R3a or R3a') leading to the formation of BrSH (BrSD) + Cl in a barrierless process dominants the reaction with the branching ratios for channels 3a and 3a' of 99% at 298 K, which is quite different from the experimental result of k3a'/k3' = 54 +/- 10%. Negative activation energies are found at the higher level for the SH + Br2 and SH + BrCl (Br-abstraction) reactions; as a result, the rate constants show a slightly negative temperature dependence, which is consistent with the determination in the literature. The kinetic isotope effects for the three reactions are "inverse". The values of kH/kD are 0.88, 0.91, and 0.69 at room temperature, respectively, and they increase

  17. Site-Specific Rate Constant Measurements for Primary and Secondary H- and D-Abstraction by OH Radicals: Propane and n -Butane

    KAUST Repository

    Badra, Jihad; Nasir, Ehson F.; Farooq, Aamir

    2014-01-01

    Site-specific rate constants for hydrogen (H) and deuterium (D) abstraction by hydroxyl (OH) radicals were determined experimentally by monitoring the reaction of OH with two normal and six deuterated alkanes. The studied alkanes include propane (C3H8), propane 2,2 D2 (CH 3CD2CH3), propane 1,1,1-3,3,3 D6 (CD 3CH2CD3), propane D8 (C3D 8), n-butane (n-C4H10), butane 2,2-3,3 D4 (CH3CD2CD2CH3), butane 1,1,1-4,4,4 D6 (CD3CH2CH2CD3), and butane D10 (C4D10). Rate constant measurements were carried out over 840-1470 K and 1.2-2.1 atm using a shock tube and OH laser absorption. Previous low-temperature data were combined with the current high-temperature measurements to generate three-parameter fits which were then used to determine the site-specific rate constants. Two primary (P1,H and P 1,D) and four secondary (S00,H, S00,D, S 01,H, and S01,D) H- and D-abstraction rate constants, in which the subscripts refer to the number of C atoms connected to the next-nearest-neighbor C atom, are obtained. The modified Arrhenius expressions for the six site-specific abstractions by OH radicals are P1,H = 1.90 × 10-18T2.00 exp(-340.87 K/T) cm 3molecule-1s-1 (210-1294 K); P1,D= 2.72 × 10-17 T1.60 exp(-895.57 K/T) cm 3molecule-1s-1 (295-1317 K); S00,H = 4.40 × 10-18 T1.93 exp(121.50 K/T) cm 3molecule-1s-1 (210-1294 K); S00,D = 1.45 × 10-20 T2.69 exp(282.36 K/T) cm 3molecule-1s-1 (295-1341 K); S01,H = 4.65 × 10-17 T1.60 exp(-236.98 K/T) cm 3molecule-1s-1 (235-1407 K); S01,D = 1.26 × 10-18 T2.07 exp(-77.00 K/T) cm 3molecule-1s-1 (294-1412 K). © 2014 American Chemical Society.

  18. Determination of the absolute second-order rate constant for the reaction Na + O3 → NaO + O2

    International Nuclear Information System (INIS)

    Husain, David; Marshall, Paul; Plane, J.M.C.

    1985-01-01

    The absolute second-order rate constant for the reaction Na + O 3 -> NaO + O 2 (k 1 ) has been determined by time-resolved atomic resonance absorption spectroscopy at lambda = 589 nm [Na(3 2 Psub(j)) 2 Ssub(1/2))] following pulsed irradiation, coupled with monitoring of O 3 by light absorption in the ultra-violet; this yields k 1 (500 K) = 4(+4,-2) x 10 -10 cm 3 molecule -1 s -1 , resolving large differences for various estimates of this important quantity used in modelling the sodium layer in the mesosphere. (author)

  19. Direct determination of the rate constant of propagation by pseudo-stationary polymerization technique: screening investigation for the (implicit) penultimate effect

    International Nuclear Information System (INIS)

    Schnoll-Bitai, I.; Friedrich Olaj, O.; Liu Song Yu

    1999-01-01

    The systems styrene-p-methylstyrene, styrene-p-chlorostyrene, methyl methacrylate-p-methylstyrene and methyl methacrylate-p-chlorostyrene were polymerized under pseudo-stationary conditions (rotating sector or pulsed laser) at 25 degree C, 40 degree C and 50 degree C. The respective molecular weight distributions measured by GPC were analysed in order to derive directly the phenomenological rate constant of propagation, κ sub ρ. Copolymer compositions as a function of monomer feed could be described by the terminal model, whereas the kinetic results could only be interpreted in terms of the restricted penultimate model

  20. Virtual Instrument for Determining Rate Constant of Second-Order Reaction by pX Based on LabVIEW 8.0.

    Science.gov (United States)

    Meng, Hu; Li, Jiang-Yuan; Tang, Yong-Huai

    2009-01-01

    The virtual instrument system based on LabVIEW 8.0 for ion analyzer which can measure and analyze ion concentrations in solution is developed and comprises homemade conditioning circuit, data acquiring board, and computer. It can calibrate slope, temperature, and positioning automatically. When applied to determine the reaction rate constant by pX, it achieved live acquiring, real-time displaying, automatical processing of testing data, generating the report of results; and other functions. This method simplifies the experimental operation greatly, avoids complicated procedures of manual processing data and personal error, and improves veracity and repeatability of the experiment results.

  1. Possibility of reconstructing the mechanism and rate constants of elementary processes in the gas-discharge plasma of a rapid-flow laser

    International Nuclear Information System (INIS)

    Gontar, V.G.; Pashkin, S.V.; Surguchenko, S.A.

    1982-01-01

    The procedure is given for reconstructing the mechanism of elementary processes in the plasma of a gas-discharge laser on the basis of a statistical analysis of the experimental data. The method of writing the initial equations described here permits automation of the procedure for constructing a mathematical model of the discharge. A new iteration procedure for estimating the rate constants of the elementary processes by the method of least squares is proposed which has a wide region of convergence. The proposed methods are analyzed on test problems

  2. Site-Specific Rate Constant Measurements for Primary and Secondary H- and D-Abstraction by OH Radicals: Propane and n -Butane

    KAUST Repository

    Badra, Jihad

    2014-07-03

    Site-specific rate constants for hydrogen (H) and deuterium (D) abstraction by hydroxyl (OH) radicals were determined experimentally by monitoring the reaction of OH with two normal and six deuterated alkanes. The studied alkanes include propane (C3H8), propane 2,2 D2 (CH 3CD2CH3), propane 1,1,1-3,3,3 D6 (CD 3CH2CD3), propane D8 (C3D 8), n-butane (n-C4H10), butane 2,2-3,3 D4 (CH3CD2CD2CH3), butane 1,1,1-4,4,4 D6 (CD3CH2CH2CD3), and butane D10 (C4D10). Rate constant measurements were carried out over 840-1470 K and 1.2-2.1 atm using a shock tube and OH laser absorption. Previous low-temperature data were combined with the current high-temperature measurements to generate three-parameter fits which were then used to determine the site-specific rate constants. Two primary (P1,H and P 1,D) and four secondary (S00,H, S00,D, S 01,H, and S01,D) H- and D-abstraction rate constants, in which the subscripts refer to the number of C atoms connected to the next-nearest-neighbor C atom, are obtained. The modified Arrhenius expressions for the six site-specific abstractions by OH radicals are P1,H = 1.90 × 10-18T2.00 exp(-340.87 K/T) cm 3molecule-1s-1 (210-1294 K); P1,D= 2.72 × 10-17 T1.60 exp(-895.57 K/T) cm 3molecule-1s-1 (295-1317 K); S00,H = 4.40 × 10-18 T1.93 exp(121.50 K/T) cm 3molecule-1s-1 (210-1294 K); S00,D = 1.45 × 10-20 T2.69 exp(282.36 K/T) cm 3molecule-1s-1 (295-1341 K); S01,H = 4.65 × 10-17 T1.60 exp(-236.98 K/T) cm 3molecule-1s-1 (235-1407 K); S01,D = 1.26 × 10-18 T2.07 exp(-77.00 K/T) cm 3molecule-1s-1 (294-1412 K). © 2014 American Chemical Society.

  3. Oil flow rate measurements using 198Au and total count technique

    International Nuclear Information System (INIS)

    Goncalves, Eduardo R.; Crispim, Verginia R.

    2013-01-01

    In industrial plants, oil and oil compounds are usually transported by closed pipelines with circular cross-section. The use of radiotracers in oil transport and processing industrial facilities allows calibrating flowmeters, measuring mean residence time in cracking columns, locate points of obstruction or leak in underground ducts, as well as investigating flow behavior or industrial processes such as in distillation towers. Inspection techniques using radiotracers are non-destructive, simple, economic and highly accurate. Among them, Total Count, which uses a small amount of radiotracer with known activity, is acknowledged as an absolute technique for flow rate measurement. A viscous fluid transport system, composed by four PVC pipelines with 13m length (12m horizontal and 1m vertical) and 1/2, 3/4, 1 and 2-inch gauges, respectively, interconnected by maneuvering valves was designed and assembled in order to conduct the research. This system was used to simulate different flow conditions of petroleum compounds and for experimental studies of flow profile in the horizontal and upward directions. As 198 Au presents a single photopeak (411,8 keV), it was the radioisotope chosen for oil labeling, in small amounts (6 ml) or around 200 kBq activity, and it was injected in the oil transport lines. A NaI scintillation detector 2'x 2', with well-defined geometry, was used to measure total activity, determine the calibration factor F and, positioned after a homogenization distance and interconnected to a standardized electronic set of nuclear instrumentation modules (NIM), to detect the radioactive cloud. (author)

  4. Water turnover rate and total body water affected by different physiological factors under Egyptian environmental conditions

    International Nuclear Information System (INIS)

    Kamal, T.H.

    1982-01-01

    The tritiated water dilution technique was used to determine the total body water (TBW) and water turnover rate (WTR), which is assumed to be similar to water intake, in water buffalo, Red Danish cattle, fat-tailed Osemi sheep and crossed Nubian-Bedouin goats and camels (Camelus dromedarius). There was a significant (P < 0.05) effect of species on TBW and WTR. The combined data of buffalo, cattle and sheep revealed a significant (P < 0.05) effect of pregnancy on TBW, but not on WTR. The combined data of buffalo and cattle showed a significantly lower TBW (P < 0.01) and a higher WTR (P < 0.05) in lactating animals than in heifers. In buffalo WTR was on average 81% higher in summer grazing (SG) than in spring. It was also 118 and 20% higher in summer non-grazing (SNG), than in either spring or SG, respectively. The differences between treatments in heifers, pregnant and lactating, were significant (P<0.01), except between spring and SG in heifers. The TBW was on average 12% higher in SG than in spring. It was also 18 and 5% higher in SNG than in either spring or SG, respectively. The differences between treatments in heifers, pregnant and lactating, were significant, except between SG and SNG in heifers and lactating cows and between spring and SG in lactating cows. (author)

  5. Quantum mechanical calculations of state-to-state cross sections and rate constants for the F + DCl → Cl + DF reaction.

    Science.gov (United States)

    Bulut, Niyazi; Kłos, Jacek; Roncero, Octavio

    2015-06-07

    We present accurate state-to-state quantum wave packet calculations of integral cross sections and rate constants for the title reaction. Calculations are carried out on the best available ground 1(2)A' global adiabatic potential energy surface of Deskevich et al. [J. Chem. Phys. 124, 224303 (2006)]. Converged state-to-state reaction cross sections have been calculated for collision energies up to 0.5 eV and different initial rotational and vibrational excitations, DCl(v = 0, j = 0 - 1; v = 1, j = 0). Also, initial-state resolved rate constants of the title reaction have been calculated in a temperature range of 100-400 K. It is found that the initial rotational excitation of the DCl molecule does not enhance reactivity, in contract to the reaction with the isotopologue HCl in which initial rotational excitation produces an important enhancement. These differences between the isotopologue reactions are analyzed in detail and attributed to the presence of resonances for HCl(v = 0, j), absent in the case of DCl(v = 0, j). For vibrational excited DCl(v = 1, j), however, the reaction cross section increases noticeably, what is also explained by another resonance.

  6. Electron exchange by hexakis(tert-butyl-isocyanide)- and hexakis(cyclohexyl isocyanide)manganese(I,II). Solvent effect on the rate constant and the volume of activation

    International Nuclear Information System (INIS)

    Stebler, M.; Nielson, R.M.; Siems, W.F.; Hunt, J.P.; Dodgen, H.W.; Wherland, H.W.

    1988-01-01

    The rate of electron self-exchange of Mn(CNC(CH 3 ) 3 ) 6 +/2+ and Mn(CNC 6 H 11 ) 6 +/2+ as the BF 4 - salts has been measured by 55 Mn NMR line broadening as a function of pressure, temperature, and concentration in acetonitrile, bromobenzene, benzonitrile, acetone, diethyl ketone, methanol, ethanol, methylene chloride, and trimethyl phosphate, and various binary mixtures of methylene chloride, bromobenzene, and acetonitrile. The values of ΔV double dagger obtained are negative and cover a range of ca. 12 cm 3 /mol, which is limited by ion pairing in the solvents of lower dielectric constant. The variation of the ambient pressure rate constant with solvent is qualitatively different for Mn(CNC(CH 3 ) 3 ) 6 +/2+ reaction than was observed for the Mn(CNC 6 H 11 ) 6 +/2+ reaction. This is taken as further evidence for a significant influence of rather subtle differences in solvation on the molecular level that are not approximated by dielectric continuum models. 30 references, 3 tables

  7. On the Theory of Oxidation-Reduction Reactions Involving Electron Transfer. V. Comparison and Properties of Electrochemical and Chemical Rate Constants

    Science.gov (United States)

    Marcus, R. A.

    1962-01-01

    Using a theory of electron transfers which takes cognizance of reorganization of the medium outside the inner coordination shell and of changes of bond lengths inside it, relations between electrochemical and related chemical rate constants are deduced and compared with the experimental data. A correlation is found, without the use of arbitrary parameters. Effects of weak complexes with added electrolytes are included under specified conditions. The deductions offer a way of coordinating a variety of data in the two fields, internally as well as with each those in another. For example, the rate of oxidation or reduction of a series of related reactants by one reagent is correlated with that of another and with that of the corresponding electrochemical oxidation-reduction reaction, under certain specified conditions. These correlations may also provide a test for distinguishing an electron from an atom transfer mechanism. (auth)

  8. Mechanistic kinetic modeling generates system-independent P-glycoprotein mediated transport elementary rate constants for inhibition and, in combination with 3D SIM microscopy, elucidates the importance of microvilli morphology on P-glycoprotein mediated efflux activity.

    Science.gov (United States)

    Ellens, Harma; Meng, Zhou; Le Marchand, Sylvain J; Bentz, Joe

    2018-06-01

    In vitro transporter kinetics are typically analyzed by steady-state Michaelis-Menten approximations. However, no clear evidence exists that these approximations, applied to multiple transporters in biological membranes, yield system-independent mechanistic parameters needed for reliable in vivo hypothesis generation and testing. Areas covered: The classical mass action model has been developed for P-glycoprotein (P-gp) mediated transport across confluent polarized cell monolayers. Numerical integration of the mass action equations for transport using a stable global optimization program yields fitted elementary rate constants that are system-independent. The efflux active P-gp was defined by the rate at which P-gp delivers drugs to the apical chamber, since as much as 90% of drugs effluxed by P-gp partition back into nearby microvilli prior to reaching the apical chamber. The efflux active P-gp concentration was 10-fold smaller than the total expressed P-gp for Caco-2 cells, due to their microvilli membrane morphology. The mechanistic insights from this analysis are readily extrapolated to P-gp mediated transport in vivo. Expert opinion: In vitro system-independent elementary rate constants for transporters are essential for the generation and validation of robust mechanistic PBPK models. Our modeling approach and programs have broad application potential. They can be used for any drug transporter with minor adaptations.

  9. Rate Constants of PSII Photoinhibition and its Repair, and PSII Fluorescence Parameters in Field Plants in Relation to their Growth Light Environments.

    Science.gov (United States)

    Miyata, Kazunori; Ikeda, Hiroshi; Nakaji, Masayoshi; Kanel, Dhana Raj; Terashima, Ichiro

    2015-09-01

    The extent of photoinhibition of PSII is determined by a balance between the rate of photodamage to PSII and that of repair of the damaged PSII. It has already been indicated that the rate constants of photodamage (kpi) and repair (krec) of the leaves differ depending on their growth light environment. However, there are no studies using plants in the field. We examined these rate constants and fluorescence parameters of several field-grown plants to determine inter-relationships between these values and the growth environment. The kpi values were strongly related to the excess energy, EY, of the puddle model and non-regulated energy dissipation, Y(NO), of the lake model, both multiplied by the photosynthetically active photon flux density (PPFD) level during the photoinhibitory treatment. In contrast, the krec values corrected against in situ air temperature were very strongly related to the daily PPFD level. The plants from the fields showed higher NPQ than the chamber-grown plants, probably because these field plants acclimated to stronger lightflecks than the averaged growth PPFD. Comparing chamber-grown plants and the field plants, we showed that kpi is determined by the incident light level and the photosynthetic capacities such as in situ rate of PSII electron transport and non-photochemical quenching (NPQ) [e.g. Y(NO)×PPFD] and that krec is mostly determined by the growth light and temperature levels. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  10. Constant Fault Slip-Rates Over Hundreds of Millenia Constrained By Deformed Quaternary Palaeoshorelines: the Vibo and Capo D'Orlando Faults, Southern Italy.

    Science.gov (United States)

    Meschis, M.; Roberts, G.; Robertson, J.; Houghton, S.; Briant, R. M.

    2017-12-01

    Whether slip-rates on active faults accumulated over multiple seismic events is constant or varying over tens to hundreds of millenia timescales is an open question that can be addressed through study of deformed Quaternary palaeoshorelines. It is important to know the answer so that one can judge whether shorter timescale measurements (e.g. Holocene palaeoseismology or decadal geodesy) are suitable for determining earthquake recurrence intervals for Probabilistic Seismic Hazard Assessment or more suitable for studying temporal earthquake clustering. We present results from the Vibo Fault and the Capo D'Orlando Fault, that lie within the deforming Calabrian Arc, which has experienced damaging seismic events such as the 1908 Messina Strait earthquake ( Mw 7) and the 1905 Capo Vaticano earthquake ( Mw 7). These normal faults deform uplifted Late Quaternary palaeoshorelines, which outcrop mainly within their hangingwalls, but also partially in their footwalls, showing that a regional subduction and mantle-related uplift outpaces local fault-related subsidence. Through (1) field and DEM-based mapping of palaeoshorelines, both up flights of successively higher, older inner edges, and along the strike of the faults, and (2) utilisation of synchronous correlation of non-uniformly-spaced inner edge elevations with non-uniformly spaced sea-level highstand ages, we show that slip-rates decrease towards fault tips and that slip-rates have remained constant since 340 ka (given the time resolution we obtain). The slip-rates for the Capo D'Orlando Fault and Vibo Fault are 0.61mm/yr and 1mm/yr respectively. We show that the along-strike gradients in slip-rate towards fault tips differ for the two faults hinting at fault interaction and also discuss this in terms of other regions of extension like the Gulf of Corinth, Greece, where slip-rate has been shown to change through time through the Quaternary. We make the point that slip-rates may change through time as fault systems grow

  11. Rate constant for the reaction of OH with CH3CCl2F (HCFC-141b) determined by relative rate measurements with CH4 and CH3CCl3

    Science.gov (United States)

    Huder, Karin; Demore, William B.

    1993-01-01

    Determination of accurate rate constants for OH abstraction is of great importance for the calculation of lifetimes for HCFCs and their impact on the atmosphere. For HCFC-141b there has been some disagreement in the literature for absolute measurements of this rate constant. In the present work rate constant ratios for HCFC-141b were measured at atmospheric pressure in the temperature range of 298-358 K, with CH4 and CH3CCl3 as reference gases. Ozone was photolyzed at 254 nm in the presence of water vapor to produce OH radicals. Relative depletions of 141b and the reference gases were measured by FTIR. Arrhenius expressions for 141b were derived from each reference gas and found to be in good agreement with each other. The combined expression for HCFC-141b which we recommend is 1.4 x 10 exp -12 exp(-1630/T) with k at 298 K being 5.9 x 10 exp -15 cu cm/molec-s. This value is in excellent agreement with the JPL 92-20 recommendation.

  12. Dose rate constants for 125I, 103Pd, 192Ir and 169Yb brachytherapy sources: an EGS4 Monte Carlo study

    International Nuclear Information System (INIS)

    Mainegra, Ernesto; Capote, Roberto; Lopez, Ernesto

    1998-01-01

    An exhaustive revision of dosimetry data for 192 Ir, 125 I, 103 Pd and 169 Yb brachytherapy sources has been performed by means of the EGS4 simulation system. The DLC-136/PHOTX cross section library, water molecular form factors, bound Compton scattering and Doppler broadening of the Compton-scattered photon energy were considered in the calculations. The absorbed dose rate per unit contained activity in a medium at 1 cm in water and air-kerma strength per unit contained activity for each seed model were calculated, allowing the dose rate constant (DRC) Λ to be estimated. The influence of the calibration procedure on source strength for low-energy brachytherapy seeds is discussed. Conversion factors for 125 I and 103 Pd seeds to obtain the dose rate in liquid water from the dose rate measured in a solid water phantom with a detector calibrated for dose to water were calculated. A theoretical estimate of the DRC for a 103 Pd model 200 seed equal to 0.669±0.002 cGy h -1 U -1 is obtained. Comparison of obtained DRCs with measured and calculated published results shows agreement within 1.5% for 192 Ir, 169 Yb and 125 I sources. (author)

  13. The reaction O((3)P) + HOBr: Temperature dependence of the rate constant and importance of the reaction as an HOBr stratospheric loss process

    Science.gov (United States)

    Nesbitt, F. L.; Monks, P. S.; Payne, W. A.; Stief, L. J.; Toumi, R.

    1995-01-01

    The absolute rate constant for the reaction O((3)P) + HOBr has been measured between T = 233K and 423K using the discharge-flow kinetic technique coupled to mass spectrometric detection. The value of the rate coefficient at room temperature is (2.5 +/- 0.6) x 10(exp -11)cu cm/molecule/s and the derived Arrhenius expression is (1.4 +/- 0.5) x 10(exp -10) exp((-430 +/- 260)/T)cu cm/molecule/s. From these rate data the atmospheric lifetime of HOBr with respect to reaction with O((3)P) is about 0.6h at z = 25 km which is comparable to the photolysis lifetime based on recent measurements of the UV cross section for HOBr. Implications for HOBr loss in the stratosphere have been tested using a 1D photochemical box model. With the inclusion of the rate parameters and products for the O + HOBr reaction, calculated concentration profiles of BrO increase by up to 33% around z = 35 km. This result indicates that the inclusion of the O + HOBr reaction in global atmospheric chemistry models may have an impact on bromine partitioning in the middle atmosphere.

  14. Modeling the downward transport of {sup 210}Pb in Peatlands: Initial Penetration‐Constant Rate of Supply (IP-CRS) model

    Energy Technology Data Exchange (ETDEWEB)

    Olid, Carolina, E-mail: olid.carolina@gmail.com [Department of Ecology and Environmental Science, Umeå University, SE-90187, Umeå (Sweden); Diego, David [Department of Earth Science, University of Bergen, NO-5020 Bergen (Norway); Garcia-Orellana, Jordi [Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain); Institut de Ciència i Tecnologia Ambientals (ICTA), Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain); Cortizas, Antonio Martínez [Departamento de Edafoloxía e Química Agrícola, Universidade de Santiago de Compostela, E-15782 Santiago de Compostela (Spain); Klaminder, Jonatan [Department of Ecology and Environmental Science, Umeå University, SE-90187, Umeå (Sweden)

    2016-01-15

    The vertical distribution of {sup 210}Pb is commonly used to date peat deposits accumulated over the last 100–150 years. However, several studies have questioned this method because of an apparent post-depositional mobility of {sup 210}Pb within some peat profiles. In this study, we introduce the Initial Penetration–Constant Rate of Supply (IP-CRS) model for calculating ages derived from {sup 210}Pb profiles that are altered by an initial migration of the radionuclide. This new, two-phased, model describes the distribution of atmospheric-derived {sup 210}Pb ({sup 210}Pb{sub xs}) in peat taking into account both incorporation of {sup 210}Pb into the accumulating peat matrix as well as an initial flushing of {sup 210}Pb through the uppermost peat layers. The validity of the IP-CRS model is tested in four anomalous {sup 210}Pb peat records that showed some deviations from the typical exponential decay profile not explained by variations in peat accumulation rates. Unlike the most commonly used {sup 210}Pb-dating model (Constant Rate of Supply (CRS)), the IP-CRS model estimates peat accumulation rates consistent with typical growth rates for peatlands from the same areas. Confidence in the IP-CRS chronology is also provided by the good agreement with independent chronological markers (i.e. {sup 241}Am and {sup 137}Cs). Our results showed that the IP-CRS can provide chronologies from peat records where {sup 210}Pb mobility is evident, being a valuable tool for studies reconstructing past environmental changes using peat archives during the Anthropocene. - Highlights: • Accurate age dating of peat and sediment cores is critical for evaluating change. • A new {sup 210}Pb dating model that includes vertical transport of {sup 210}Pb was developed. • The IP-CRS model provided consistent peat accumulation rates. • The IP-CRS ages were consistent with independent chronological markers. • The IP-CRS model derives peat ages where downward {sup 210}Pb transport is

  15. 38 CFR 3.342 - Permanent and total disability ratings for pension purposes.

    Science.gov (United States)

    2010-07-01

    ... applied with other types of disabilities requiring hospitalization for indefinite periods. The need for... permanency of total disability contained in § 3.340, the following special considerations apply in pension... permanence of total disability will be established as of the earliest date consistent with the evidence in...

  16. Ab initio calculation of transition state normal mode properties and rate constants for the H(T)+CH4(CD4) abstraction and exchange reactions

    International Nuclear Information System (INIS)

    Schatz, G.C.; Walch, S.P.; Wagner, A.F.

    1980-01-01

    We present ab initio (GVB--POL--CI) calculations for enough of the region about the abstraction and exchange saddle points for H(T)+CH 4 (CD 4 ) to perform a full normal mode analysis of the transition states. The resulting normal mode frequencies are compared to four other published surfaces: an ab initio UHF--SCF calculation by Carsky and Zahradnik, a semiempirical surface by Raff, and two semiempirical surfaces by Kurylo, Hollinden, and Timmons. Significant quantitative and qualitative differences exist between the POL--CI results and those of the other surfaces. Transition state theory rate constants and vibrationally adiabatic reaction threshold energies were computed for all surfaces and compared to available experimental values. For abstraction, the POL--CI rates are in good agreement with experimental rates and in better agreement than are the rates of any of the other surfaces. For exchange, uncertainties in the experimental values and in the importance of vibrationally nonadiabatic effects cloud the comparison of theory to experiment. Tentative conclusions are that the POL--CI barrier is too low by several kcal. Unless vibrationaly nonadiabatic effects are severe, the POL--CI surface is still in better agreement with experiment than are the other surfaces. The rates for a simple 3-atom transition state theory model (where CH 3 is treated as an atom) are compared to the rates for the full 6-atom model. The kinetic energy coupling of reaction coordinate modes to methyl group modes is identified as being of primary importance in determining the accuracy of the 3-atom model for this system. Substantial coupling in abstraction, but not exchange, causes the model to fail for abstraction but succeed for exchange

  17. Development of a kinetic model, including rate constant estimations, on iodine and caesium behaviour in the primary circuit of LWR's under accident conditions

    International Nuclear Information System (INIS)

    Alonso, A.; Buron, J.M.; Fernandez, S.

    1991-07-01

    In this report, a kinetic model has been developed with the aim to try to reproduce the chemical phenomena that take place in a flowing system containing steam, hydrogen and iodine and caesium vapours. The work is divided into two different parts. The first part consists in the estimation, through the Activited Complex Theory, of the reaction rate constants, for the chosen reactions, and the development of the kinetic model based on the concept of ideal tubular chemical reactor. The second part deals with the application of such model to several cases, which were taken from the Phase B 'Scoping Calculations' of the Phebus-FP Project (sequence AB) and the SFD-ST and SFD1.1 experiments. The main conclusion obtained from this work is that the assumption of instantaneous equilibrium could be inacurrate in order to estimate the iodine and caesium species distribution under severe accidents conditions

  18. Absolute rate constants for the reaction of O(3P) atoms with ethylene, propylene, and propylene-d6 over the temperature range 258--861 K

    International Nuclear Information System (INIS)

    Perry, R.A.

    1984-01-01

    Absolute rate constants for the reaction of O( 3 P) with ethylene, propylene, and propylene-d6 were determined over the temperature range 258--861 K using a laser photolysis-chemiluminescence technique. The following empirical expressions are the best fits to the data: k/sub ethylene/ = 2.12 x 10 -13 T -63 e -1370 /sup ///sup R//sup T/, k/sub propylene/ = 3.40 x 10 -19 T/sup 2.56/e/sup 1130/RT/, and k/sub propylene-d/6 = 3.40 x 10 -19 T/sup 2.53/ e/sup 1210/R/T cm 3 molecule -1 s -1 . A simple transition state theory model is shown to provide a reasonable explanation for non-Arrhenius temperature behavior

  19. Time since death and decay rate constants of Norway spruce and European larch deadwood in subalpine forests determined using dendrochronology and radiocarbon dating

    Science.gov (United States)

    Petrillo, M.; Cherubini, P.; Fravolini, G.; Ascher, J.; Schärer, M.; Synal, H.-A.; Bertoldi, D.; Camin, F.; Larcher, R.; Egli, M.

    2015-09-01

    Due to the large size and highly heterogeneous spatial distribution of deadwood, the time scales involved in the coarse woody debris (CWD) decay of Picea abies (L.) Karst. and Larix decidua Mill. in Alpine forests have been poorly investigated and are largely unknown. We investigated the CWD decay dynamics in an Alpine valley in Italy using the five-decay class system commonly employed for forest surveys, based on a macromorphological and visual assessment. For the decay classes 1 to 3, most of the dendrochronological samples were cross-dated to assess the time that had elapsed since tree death, but for decay classes 4 and 5 (poorly preserved tree rings) and some others not having enough tree rings, radiocarbon dating was used. In addition, density, cellulose and lignin data were measured for the dated CWD. The decay rate constants for spruce and larch were estimated on the basis of the density loss using a single negative exponential model. In the decay classes 1 to 3, the ages of the CWD were similar varying between 1 and 54 years for spruce and 3 and 40 years for larch with no significant differences between the classes; classes 1-3 are therefore not indicative for deadwood age. We found, however, distinct tree species-specific differences in decay classes 4 and 5, with larch CWD reaching an average age of 210 years in class 5 and spruce only 77 years. The mean CWD rate constants were 0.012 to 0.018 yr-1 for spruce and 0.005 to 0.012 yr-1 for larch. Cellulose and lignin time trends half-lives (using a multiple-exponential model) could be derived on the basis of the ages of the CWD. The half-lives for cellulose were 21 yr for spruce and 50 yr for larch. The half-life of lignin is considerably higher and may be more than 100 years in larch CWD.

  20. Density functional theory study on aqueous aluminum-fluoride complexes: exploration of the intrinsic relationship between water-exchange rate constants and structural parameters for monomer aluminum complexes.

    Science.gov (United States)

    Jin, Xiaoyan; Qian, Zhaosheng; Lu, Bangmei; Yang, Wenjing; Bi, Shuping

    2011-01-01

    Density functional theory (DFT) calculation is carried out to investigate the structures, (19)F and (27)Al NMR chemical shifts of aqueous Al-F complexes and their water-exchange reactions. The following investigations are performed in this paper: (1) the microscopic properties of typical aqueous Al-F complexes are obtained at the level of B3LYP/6-311+G**. Al-OH(2) bond lengths increase with F(-) replacing inner-sphere H(2)O progressively, indicating labilizing effect of F(-) ligand. The Al-OH(2) distance trans to fluoride is longer than other Al-OH(2) distance, accounting for trans effect of F(-) ligand. (19)F and (27)Al NMR chemical shifts are calculated using GIAO method at the HF/6-311+G** level relative to F(H(2)O)(6)(-) and Al(H(2)O)(6)(3+) references, respectively. The results are consistent with available experimental values; (2) the dissociative (D) activated mechanism is observed by modeling water-exchange reaction for [Al(H(2)O)(6-i)F(i)]((3-i)+) (i = 1-4). The activation energy barriers are found to decrease with increasing F(-) substitution, which is in line with experimental rate constants (k(ex)). The log k(ex) of AlF(3)(H(2)O)(3)(0) and AlF(4)(H(2)O)(2)(-) are predicted by three ways. The results indicate that the correlation between log k(ex) and Al-O bond length as well as the given transmission coefficient allows experimental rate constants to be predicted, whereas the correlation between log k(ex) and activation free energy is poor; (3) the environmental significance of this work is elucidated by the extension toward three fields, that is, polyaluminum system, monomer Al-organic system and other metal ions system with high charge-to-radius ratio.

  1. 75 FR 47258 - Determination of Total Amounts of Fiscal Year 2011 Tariff-Rate Quotas for Raw Cane Sugar and...

    Science.gov (United States)

    2010-08-05

    ... Determination of Total Amounts of Fiscal Year 2011 Tariff-Rate Quotas for Raw Cane Sugar and Certain Sugars...) 2011 in-quota aggregate quantity of the raw, as well as, refined and specialty sugar Tariff-Rate Quotas (TRQ) as required under the U.S. World Trade Organization (WTO) commitments. The FY 2011 raw cane sugar...

  2. Laboratory Bioaccumulation, Depuration And Total Dose Rate Of Waterborne Th-232 In Freshwater Fish Of Anabas Testudineus

    International Nuclear Information System (INIS)

    Zal U'yun Wan Mahmood; Norfaizal Mohamed; Nita Salina Abu Bakar

    2014-01-01

    Preliminary results on the study of bioaccumulation, depuration and total dose rate of Th-232 in the whole body of Anabas testudineus are presented. The objective of this study was to evaluate the effect of Th-232 concentration activity on the laboratory bioaccumulation, depuration and total dose rate in Anabas testudineus. Anabas testudineus adults were exposed to different waterborne Th-232 levels: 0 BqL -1 (control), 50 BqL -1 and 100 BqL -1 for 30 day (uptake phase), followed by exposure to radionuclide-free water for 30 days (loss phase). Radionuclide concentration ratios between the whole body levels and water levels, percentage of Th-232 remaining in fish were calculated and total dose rates using ERICA Assessment Tool were also estimated. The results showed the increase of waterborne Th-232 concentration corresponded to a progressive increase of Th accumulation and total dose rate (internal and external) in the whole body of Anabas testudineus. Considering the ERICA dose rate screening value of 10 μGyh -1 , the findings can be concluded the estimated of total dose rate (< 5 μGyh -1 ) in Anabas testudineus is in order of small magnitude. Nevertheless, these preliminary results showed that the Anabas testudineus has a potential to accumulate thorium. (author)

  3. Constant conditional entropy and related hypotheses

    International Nuclear Information System (INIS)

    Ferrer-i-Cancho, Ramon; Dębowski, Łukasz; Moscoso del Prado Martín, Fermín

    2013-01-01

    Constant entropy rate (conditional entropies must remain constant as the sequence length increases) and uniform information density (conditional probabilities must remain constant as the sequence length increases) are two information theoretic principles that are argued to underlie a wide range of linguistic phenomena. Here we revise the predictions of these principles in the light of Hilberg’s law on the scaling of conditional entropy in language and related laws. We show that constant entropy rate (CER) and two interpretations for uniform information density (UID), full UID and strong UID, are inconsistent with these laws. Strong UID implies CER but the reverse is not true. Full UID, a particular case of UID, leads to costly uncorrelated sequences that are totally unrealistic. We conclude that CER and its particular cases are incomplete hypotheses about the scaling of conditional entropies. (letter)

  4. Cinética de sinterização para sistemas à base de SnO2 por taxa de aquecimento constante Sintering kinetics for SnO2-based systems by constant heating rate

    Directory of Open Access Journals (Sweden)

    S. M. Tebcheran

    2003-04-01

    in small concentrations as densifying aids for this oxide. In the present study the sintering kinetics of tin oxide was studied considering the effect of sintering atmosphere and of the MnO2 concentration. SnO2-MnO2 systems were prepared from the polymeric precursors method and the obtained powders were characterized by surface area by the BET method. SnO2 powders with varied MnO2 concentrations were pressed in cylindrical shape, and sintered in a dilatometer furnace with constant heating rate and controlled atmospheres. Sintered samples were characterized by scanning electron microscopy. The influence of atmosphere (argon, air or CO2 as well as of the MnO2 concentrations on the sintering kinetics was determined. The kinetics data of linear shrinkage were analyzed in terms of kinetic models for the initial stage of sintering (Woolfrey and Bannister as well as for the global sintering (Su e Johnson allowing the determination of the apparent activation energy. Following the determination of the master sintering curve the apparent activation energy of all sintering process were determined as well as its dependence with the atmosphere and manganese concentrations. Based on these values and on the n exponent, determined by the classical grain growth equation, it was concluded that the most probable sintering mechanism is grain boundary diffusion with surface redistribution controlling the kinetics.

  5. The H + HeH(+) → He + H2(+) reaction from the ultra-cold regime to the three-body breakup: exact quantum mechanical integral cross sections and rate constants.

    Science.gov (United States)

    De Fazio, Dario

    2014-06-21

    In this work, we present a quantum mechanical scattering study of the title reaction from 1 mK to 2000 K. Total integral cross sections and thermal rate constants are compared with previous theoretical and experimental data and with simpler theoretical models to understand the range of validity of the approximations used in the previous studies. The obtained quantum reactive observables have been found to be nearly insensitive to the roto-vibrational energy of the reactants at high temperatures. More sensitive to the reactant's roto-vibrational energy are the data in the cold and ultra-cold regimes. The implications of the new data presented here in the early universe scenario are also discussed and analyzed.

  6. Time since death and decay rate constants of Norway spruce and European larch deadwood in subalpine forests determined using dendrochronology and radiocarbon dating

    Science.gov (United States)

    Petrillo, Marta; Cherubini, Paolo; Fravolini, Giulia; Marchetti, Marco; Ascher-Jenull, Judith; Schärer, Michael; Synal, Hans-Arno; Bertoldi, Daniela; Camin, Federica; Larcher, Roberto; Egli, Markus

    2016-03-01

    Due to the large size (e.g. sections of tree trunks) and highly heterogeneous spatial distribution of deadwood, the timescales involved in the coarse woody debris (CWD) decay of Picea abies (L.) Karst. and Larix decidua Mill. in Alpine forests are largely unknown. We investigated the CWD decay dynamics in an Alpine valley in Italy using the chronosequence approach and the five-decay class system that is based on a macromorphological assessment. For the decay classes 1-3, most of the dendrochronological samples were cross-dated to assess the time that had elapsed since tree death, but for decay classes 4 and 5 (poorly preserved tree rings) radiocarbon dating was used. In addition, density, cellulose, and lignin data were measured for the dated CWD. The decay rate constants for spruce and larch were estimated on the basis of the density loss using a single negative exponential model, a regression approach, and the stage-based matrix model. In the decay classes 1-3, the ages of the CWD were similar and varied between 1 and 54 years for spruce and 3 and 40 years for larch, with no significant differences between the classes; classes 1-3 are therefore not indicative of deadwood age. This seems to be due to a time lag between the death of a standing tree and its contact with the soil. We found distinct tree-species-specific differences in decay classes 4 and 5, with larch CWD reaching an average age of 210 years in class 5 and spruce only 77 years. The mean CWD rate constants were estimated to be in the range 0.018 to 0.022 y-1 for spruce and to about 0.012 y-1 for larch. Snapshot sampling (chronosequences) may overestimate the age and mean residence time of CWD. No sampling bias was, however, detectable using the stage-based matrix model. Cellulose and lignin time trends could be derived on the basis of the ages of the CWD. The half-lives for cellulose were 21 years for spruce and 50 years for larch. The half-life of lignin is considerably higher and may be more than

  7. Toward elimination of discrepancies between theory and experiment: The rate constant of the atmospheric conversion of SO3 to H2SO4

    Science.gov (United States)

    Loerting, Thomas; Liedl, Klaus R.

    2000-01-01

    The hydration rate constant of sulfur trioxide to sulfuric acid is shown to depend sensitively on water vapor pressure. In the 1:1 SO3-H2O complex, the rate is predicted to be slower by about 25 orders of magnitude compared with laboratory results [Lovejoy, E. R., Hanson, D. R. & Huey, L. G. (1996) J. Phys. Chem. 100, 19911–19916; Jayne, J. T., Pöschl, U., Chen, Y.-m., Dai, D., Molina, L. T., Worsnop, D. R., Kolb, C. E. & Molina, M. J. (1997) J. Phys. Chem. A 101, 10000–10011]. This discrepancy is removed mostly by allowing a second and third water molecule to participate. An asynchronous water-mediated double proton transfer concerted with the nucleophilic attack and a double proton transfer accompanied by a transient H3O+ rotation are predicted to be the fastest reaction mechanisms. Comparison of the predicted negative apparent “activation” energies with the experimental finding indicates that in our atmosphere, different reaction paths involving two and three water molecules are taken in the process of forming sulfate aerosols and consequently acid rain. PMID:10922048

  8. The use of digital simulation to improve the cyclic voltammetric determination of rate constants for homogeneous chemical reactions following charge transfers

    International Nuclear Information System (INIS)

    Mozo, J.D.; Carbajo, J.; Sturm, J.C.; Nunez-Vergara, L.J.; Moscoso, R.; Squella, J.A.

    2011-01-01

    Cyclic voltammetry (CV) is a very useful electrochemical tool used to study reaction systems that include chemical steps that are coupled to electron transfers. This type of system generally involves the chemical reaction of an electrochemically generated free radical. Published methods exist that are used to determine the kinetics of electrochemically initiated chemical reactions from the measurements of the peak current ratio (i pa /i pc ) of a cyclic voltammogram. The published method requires working curves to relate a kinetic parameter to the peak current ratio. In the presented work, a digital simulation package was used to obtain improved working curves for specific working conditions. The curves were compared with the published results for the first- and second-order chemical reactions following the charge transfer step mechanisms. According to the presented results, the previously published working curve is reliable for a mechanism with a first-order chemical reaction; however, a change in the switching potential requires a recalculation of the curve. In the case of mechanisms with a second-order step (dimerisation and disproportionation), several different views exist on how the second-order chemical term should be expressed so that different values of the constant are obtained. Parameters such as electrode type, electrode area, electroactive species concentration, switching potential, scan rate and method for peak current ratio calculation modify the working curves and must always be specified. We propose a standardised method to obtain the most reliable kinetic constant values. The results of this work will permit researchers who handle simulation software to construct their own working curves. Additionally, those who do not have the simulation software could use the working curves described here. The revelations of the presented experiments may be useful to a broad chemistry audience because this study presents a simple and low-cost procedure for the

  9. A comparison of methods to estimate anaerobic capacity: Accumulated oxygen deficit and W' during constant and all-out work-rate profiles.

    Science.gov (United States)

    Muniz-Pumares, Daniel; Pedlar, Charles; Godfrey, Richard; Glaister, Mark

    2017-12-01

    This study investigated (i) whether the accumulated oxygen deficit (AOD) and curvature constant of the power-duration relationship (W') are different during constant work-rate to exhaustion (CWR) and 3-min all-out (3MT) tests and (ii) the relationship between AOD and W' during CWR and 3MT. Twenty-one male cyclists (age: 40 ± 6 years; maximal oxygen uptake [V̇O 2max ]: 58 ± 7 ml · kg -1 · min -1 ) completed preliminary tests to determine the V̇O 2 -power output relationship and V̇O 2max . Subsequently, AOD and W' were determined as the difference between oxygen demand and oxygen uptake and work completed above critical power, respectively, in CWR and 3MT. There were no differences between tests for duration, work, or average power output (P ≥ 0.05). AOD was greater in the CWR test (4.18 ± 0.95 vs. 3.68 ± 0.98 L; P = 0.004), whereas W' was greater in 3MT (9.55 ± 4.00 vs. 11.37 ± 3.84 kJ; P = 0.010). AOD and W' were significantly correlated in both CWR (P W' in CWR and 3MT, between-test differences in the magnitude of AOD and W', suggest that both measures have different underpinning mechanisms.

  10. Predictors of low self-rated health in patients aged 65+ after total hip replacement (THA)

    DEFF Research Database (Denmark)

    Hørdam, Britta; Hemmingsen, Lars

    2013-01-01

    predicting low self-rated health after surgery. Material and method: A cross-sectional study including 287 patients aged 65+, who had had THR within 12-months were performed. Patients from five Danish counties received a mailed questionnaire assessing health status and demographic data. Short Form-36...

  11. Predicting temporal trends in total absenteeism rates for civil service employees of a federal public health agency.

    Science.gov (United States)

    Spears, D Ross; McNeil, Carrie; Warnock, Eli; Trapp, Jonathan; Oyinloye, Oluremi; Whitehurst, Vanessa; Decker, K C; Chapman, Sandy; Campbell, Morris; Meechan, Paul

    2014-06-01

    This study evaluates the predictability in temporal absences trends due to all causes (total absenteeism) among employees at a federal agency. The objective is to determine how leave trends vary within the year, and determine whether trends are predictable. Ten years of absenteeism data from an attendance system were analyzed for rates of total absence. Trends over a 10-year period followed predictable and regular patterns during a given year that correspond to major holiday periods. Temporal trends in leave among small, medium, and large facilities compared favorably with the agency as a whole. Temporal trends in total absenteeism rates for an organization can be determined using its attendance system. The ability to predict employee absenteeism rates can be extremely helpful for management in optimizing business performance and ensuring that an organization meets its mission.

  12. Modeling the pH and temperature dependence of aqueousphase hydroxyl radical reaction rate constants of organic micropollutants using QSPR approach.

    Science.gov (United States)

    Gupta, Shikha; Basant, Nikita

    2017-11-01

    Designing of advanced oxidation process (AOP) requires knowledge of the aqueous phase hydroxyl radical ( ● OH) reactions rate constants (k OH ), which are strictly dependent upon the pH and temperature of the medium. In this study, pH- and temperature-dependent quantitative structure-property relationship (QSPR) models based on the decision tree boost (DTB) approach were developed for the prediction of k OH of diverse organic contaminants following the OECD guidelines. Experimental datasets (n = 958) pertaining to the k OH values of aqueous phase reactions at different pH (n = 470; 1.4 × 10 6 to 3.8 × 10 10  M -1  s -1 ) and temperature (n = 171; 1.0 × 10 7 to 2.6 × 10 10  M -1  s -1 ) were considered and molecular descriptors of the compounds were derived. The Sanderson scale electronegativity, topological polar surface area, number of double bonds, and halogen atoms in the molecule, in addition to the pH and temperature, were found to be the relevant predictors. The models were validated and their external predictivity was evaluated in terms of most stringent criteria parameters derived on the test data. High values of the coefficient of determination (R 2 ) and small root mean squared error (RMSE) in respective training (> 0.972, ≤ 0.12) and test (≥ 0.936, ≤ 0.16) sets indicated high generalization and predictivity of the developed QSPR model. Other statistical parameters derived from the training and test data also supported the robustness of the models and their suitability for screening new chemicals within the defined chemical space. The developed QSPR models provide a valuable tool for predicting the ● OH reaction rate constants of emerging new water contaminants for their susceptibility to AOPs.

  13. Total dose and dose rate radiation characterization of EPI-CMOS radiation hardened memory and microprocessor devices

    International Nuclear Information System (INIS)

    Gingerich, B.L.; Hermsen, J.M.; Lee, J.C.; Schroeder, J.E.

    1984-01-01

    The process, circuit discription, and total dose radiation characteristics are presented for two second generation hardened 4K EPI-CMOS RAMs and a first generation 80C85 microprocessor. Total dose radiation performance is presented to 10M rad-Si and effects of biasing and operating conditions are discussed. The dose rate sensitivity of the 4K RAMs is also presented along with single event upset (SEU) test data

  14. Impact of Inpatient Versus Outpatient Total Joint Arthroplasty on 30-Day Hospital Readmission Rates and Unplanned Episodes of Care.

    Science.gov (United States)

    Springer, Bryan D; Odum, Susan M; Vegari, David N; Mokris, Jeffrey G; Beaver, Walter B

    2017-01-01

    This article describes a study comparing 30-day readmission rates between patients undergoing outpatient versus inpatient total hip (THA) and knee (TKA) arthroplasty. A retrospective review of 137 patients undergoing outpatient total joint arthroplasty (TJA) and 106 patients undergoing inpatient (minimum 2-day hospital stay) TJA was conducted. Unplanned hospital readmissions and unplanned episodes of care were recorded. All patients completed a telephone survey. Seven inpatients and 16 outpatients required hospital readmission or an unplanned episode of care following hospital discharge. Readmission rates were higher for TKA than THA. The authors found no statistical differences in 30-day readmission or unplanned care episodes. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Rate Constants for the Reactions of OH with CH(sub 3)Cl, CH(sub 2) C1(sub 2), CHC1(sub 3)and CH(sub 3)Br

    Science.gov (United States)

    Hsu, H-J.; DeMore, W.

    1994-01-01

    Rate constants for the reactions of OH with CH3C1, CH2Cl2, CHCl3 and CH3Br have been measured by a relative rate technique in which the reaction rate of each compound was compared to that of HFC-152a (CH3CHF2)and for CH2Cl2, HFC-161 (CH3CH2F).

  16. The effects of dose rate in total body irradiation of dogs

    International Nuclear Information System (INIS)

    Kolb, H.J.; Bodenberger, U.; Holler, E.; Thierfelder, S.; Eckstein, R.

    1986-01-01

    In summary the studies in dogs show that the dose rate or exposure time has a great impact on survival of acute radiation syndromes. In contrast the inactivation of colony forming hemopoietic precursors is less influenced by the dose rate. The potential of hemopoietic recovery is determined by the survival of hemopoietic precursor cells. Therefore in patients with a suspected whole body exposure of more than 1.50 Gy, bacterial and fungal decontamination and reverse isolation in a sterile environment has to be started immediately. Human patients treated with about 10 Gy of TBI frequently developed nausea, elevated temperatures and swelling of the parotic glands at the first and second day. The extent of these changes varies from patient to patient. The temperature is rarely elevated above 38.5 0 C. The swelling of parotics and the nausea subside within 48 hours. The presence of such systemic symptoms may suggest the exposure to a lethal dose of radiation. The disappearance of immature red cells, i.e. reticulocytes, and bandforms of granulocytes within the first 5 days supports this suggestion. HLA typing of the victim and his family should be performed as soon as possible after the accident. An HLA-identical sibling would be a suitable bone marrow donor. Unlike therapeutic TBI accidental exposures bring about uncertainties in the calculation of dose, dose distribution and dose rate. Early after irradiation biological changes are extremely variable. Both biological and physical data have to be considered, when microbiological decontamination, reverse isolation and transplantation of bone marrow are to be decided upon. Obviously these intensive therapeutic efforts are limited to a small number of victims. (orig.)

  17. Reduction of the hydraulic retention time at constant high organic loading rate to reach the microbial limits of anaerobic digestion in various reactor systems.

    Science.gov (United States)

    Ziganshin, Ayrat M; Schmidt, Thomas; Lv, Zuopeng; Liebetrau, Jan; Richnow, Hans Hermann; Kleinsteuber, Sabine; Nikolausz, Marcell

    2016-10-01

    The effects of hydraulic retention time (HRT) reduction at constant high organic loading rate on the activity of hydrogen-producing bacteria and methanogens were investigated in reactors digesting thin stillage. Stable isotope fingerprinting was additionally applied to assess methanogenic pathways. Based on hydA gene transcripts, Clostridiales was the most active hydrogen-producing order in continuous stirred tank reactor (CSTR), fixed-bed reactor (FBR) and anaerobic sequencing batch reactor (ASBR), but shorter HRT stimulated the activity of Spirochaetales. Further decreasing HRT diminished Spirochaetales activity in systems with biomass retention. Based on mcrA gene transcripts, Methanoculleus and Methanosarcina were the predominantly active in CSTR and ASBR, whereas Methanosaeta and Methanospirillum activity was more significant in stably performing FBR. Isotope values indicated the predominance of aceticlastic pathway in FBR. Interestingly, an increased activity of Methanosaeta was observed during shortening HRT in CSTR and ASBR despite high organic acids concentrations, what was supported by stable isotope data. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Convergence of high order memory kernels in the Nakajima-Zwanzig generalized master equation and rate constants: Case study of the spin-boson model

    Science.gov (United States)

    Xu, Meng; Yan, Yaming; Liu, Yanying; Shi, Qiang

    2018-04-01

    The Nakajima-Zwanzig generalized master equation provides a formally exact framework to simulate quantum dynamics in condensed phases. Yet, the exact memory kernel is hard to obtain and calculations based on perturbative expansions are often employed. By using the spin-boson model as an example, we assess the convergence of high order memory kernels in the Nakajima-Zwanzig generalized master equation. The exact memory kernels are calculated by combining the hierarchical equation of motion approach and the Dyson expansion of the exact memory kernel. High order expansions of the memory kernels are obtained by extending our previous work to calculate perturbative expansions of open system quantum dynamics [M. Xu et al., J. Chem. Phys. 146, 064102 (2017)]. It is found that the high order expansions do not necessarily converge in certain parameter regimes where the exact kernel show a long memory time, especially in cases of slow bath, weak system-bath coupling, and low temperature. Effectiveness of the Padé and Landau-Zener resummation approaches is tested, and the convergence of higher order rate constants beyond Fermi's golden rule is investigated.

  19. Rate Constants and H-Atom Product Yields for the Reactions of O(1D) Atoms with Ethane and Acetylene from 50 to 296 K.

    Science.gov (United States)

    Nunez-Reyes, Dianailys; Hickson, Kevin M

    2018-05-01

    The gas phase reactions of atomic oxygen in its first excited state with ethane and acetylene have been investigated in a continuous supersonic flow reactor over the temperature range 50 K to 296 K. O(1D) atoms were produced by pulsed laser photolysis of ozone at 266 nm. Two different types of experiments, kinetics measurements and H-atom product yield determinations, were performed by detecting O(1D) atoms and H(2S) atoms respectively by vacuum ultraviolet laser induced fluorescence. The measured rate constants are in agreement with previous work at room temperature and little or no temperature dependence was observed as the temperature is decreased to 50 K. H-atoms yields were found to be independent of temperature for the reaction of O(1D) with ethane. These product yields are discussed in the context of earlier dynamics measurements at higher temperature. Due to the influence of secondary reactions, no H-atom yields could be obtained for the reaction of O(1D) with acetylene.

  20. Comparison of constant-rate pumping test and slug interference test results at the Hanford Site B pond multilevel test facility

    International Nuclear Information System (INIS)

    Spane, F.A. Jr.; Thorne, P.D.

    1995-10-01

    Pacific Northwest Laboratory (PNL), as part of the Hanford Site Ground-Water Surveillance Project, is responsible for monitoring the movement and fate of contamination within the unconfined aquifer to ensure that public health and the environment are protected. To support the monitoring and assessment of contamination migration on the Hanford Site, a sitewide 3-dimensional groundwater flow model is being developed. Providing quantitative hydrologic property data is instrumental in development of the 3-dimensional model. Multilevel monitoring facilities have been installed to provide detailed, vertically distributed hydrologic characterization information for the Hanford Site unconfined aquifer. In previous reports, vertically distributed water-level and hydrochemical data obtained over time from these multi-level monitoring facilities have been evaluated and reported. This report describes the B pond facility in Section 2.0. It also provides analysis results for a constant-rate pumping test (Section 3.0) and slug interference test (Section 4.0) that were conducted at a multilevel test facility located near B Pond (see Figure 1. 1) in the central part of the Hanford Site. A hydraulic test summary (Section 5.0) that focuses on the comparison of hydraulic property estimates obtained using the two test methods is also presented. Reference materials are listed in Section 6.0

  1. Calculations with spectroscopic accuracy for energies, transition rates, hyperfine interaction constants, and Landé gJ-factors in nitrogen-like Kr XXX

    Science.gov (United States)

    Wang, K.; Li, S.; Jönsson, P.; Fu, N.; Dang, W.; Guo, X. L.; Chen, C. Y.; Yan, J.; Chen, Z. B.; Si, R.

    2017-01-01

    Extensive self-consistent multi-configuration Dirac-Fock (MCDF) calculations and second-order many-body perturbation theory (MBPT) calculations are performed for the lowest 272 states belonging to the 2s22p3, 2s2p4, 2p5, 2s22p23l, and 2s2p33l (l=s, p, d) configurations of N-like Kr XXX. Complete and consistent data sets of level energies, wavelengths, line strengths, oscillator strengths, lifetimes, AJ, BJ hyperfine interaction constants, Landé gJ-factors, and electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), magnetic quadrupole (M2) transition rates among all these levels are given. The present MCDF and MBPT results are compared with each other and with other available experimental and theoretical results. The mean relative difference between our two sets of level energies is only about 0.003% for these 272 levels. The accuracy of the present calculations are high enough to facilitate identification of many observed spectral lines. These accurate data can be served as benchmark for other calculations and can be useful for fusion plasma research and astrophysical applications.

  2. Energy matrices evaluation and exergoeconomic analysis of series connected N partially covered (glass to glass PV module) concentrated-photovoltaic thermal collector: At constant flow rate mode

    International Nuclear Information System (INIS)

    Tripathi, Rohit; Tiwari, G.N.; Dwivedi, V.K.

    2017-01-01

    Highlights: • Fluid, other than water has been chosen for achieving higher outlet temperature. • Mass flow rate and number of collector have been optimized. • Three PVT systems have been compared for evaluating annual energy and exergy. • Life cycle cost analysis has been evaluated to obtain exergetic cost. • Proposed PVT systems have been compared on the basis of energy matrices. - Abstract: In present analysis, a comparative study has been carried out to evaluate the annual performances of three systems or cases at constant flow rate, namely: case (i): partially covered (25% PV module) N concentrated photovoltaic thermal collectors connected in series, case (ii): fully covered (100% PV module) N concentrated photovoltaic thermal collectors in series and case (iii): N (0% PV module) convectional compound parabolic concentrator collector connected in series. Comparison for three cases has also been carried out by considering fluid namely: ethylene glycol for higher outlet temperature and better thermal performance which can be applicable for heating and steaming or small industry purpose. The embodied energy, energy matrices, uniform annual cost, exergetic cost and carbon credits are also evaluated for same systems. The energy payback time is found to be 5.58 years and energy production factor is to be 0.17 on energy basis for case (iii) which is maximum. The exergetic cost has computed as 17.85 Rs/kW h for 30 years of life time of the system. It is observed that N conventional compound parabolic concentrator collector [case (iii)] is most suitable for steam cooking or space heating but not self-sustainable to run the dc power motor due to unavailability of electrical power.

  3. A system for accurate on-line measurement of total gas consumption or production rates in microbioreactors

    NARCIS (Netherlands)

    van Leeuwen, Michiel; Heijnen, Joseph J.; Gardeniers, Johannes G.E.; Oudshoorn, Arthur; Noorman, Henk; Visser, Jan; van der Wielen, Luuk A.M.; van Gulik, Walter M.

    2009-01-01

    A system has been developed, based on pressure controlled gas pumping, for accurate measurement of total gas consumption or production rates in the nmol/min range, applicable for on-line monitoring of bioconversions in microbioreactors. The system was validated by carrying out a bioconversion with

  4. Monitoring of German fertility: Estimation of monthly and yearly total fertility rates on the basis of preliminary monthly data

    NARCIS (Netherlands)

    G. Doblhammer (Gabriele); Milewski, N. (Nadja); F. Peters (Frederick)

    2010-01-01

    textabstractThis paper introduces a set of methods for estimating fertility indicators in the absence of recent and short-term birth statistics. For Germany, we propose a set of straightforward methods that allow for the computation of monthly and yearly total fertility rates (mTFR) on the basis of

  5. Low revision rate after total hip arthroplasty in patients with pediatric hip diseases

    DEFF Research Database (Denmark)

    Engesæter, Lars B; Engesæter, Ingvild Ø; Fenstad, Anne Marie

    2012-01-01

    Background The results of primary total hip arthroplasties (THAs) after pediatric hip diseases such as developmental dysplasia of the hip (DDH), slipped capital femoral epiphysis (SCFE), or Perthes' disease have been reported to be inferior to the results after primary osteoarthritis of the hip (OA.......9%) were operated due to pediatric hip diseases (3.1% for Denmark, 8.8% for Norway, and 1.9% for Sweden) and 288,435 THAs (77.8%) were operated due to OA. Unadjusted 10-year Kaplan-Meier survival of THAs after pediatric hip diseases (94.7% survival) was inferior to that after OA (96.6% survival......). Consequently, an increased risk of revision for hips with a previous pediatric hip disease was seen (risk ratio (RR) 1.4, 95% CI: 1.3-1.5). However, after adjustment for differences in sex and age of the patients, and in fixation of the prostheses, no difference in survival was found (93.6% after pediatric hip...

  6. Reaction kinetics aspect of U3O8 kernel with gas H2 on the characteristics of activation energy, reaction rate constant and O/U ratio of UO2 kernel

    International Nuclear Information System (INIS)

    Damunir

    2007-01-01

    The reaction kinetics aspect of U 3 O 8 kernel with gas H 2 on the characteristics of activation energy, reaction rate constant and O/U ratio of UO 2 kernel had been studied. U 3 O 8 kernel was reacted with gas H 2 in a reduction furnace at varied reaction time and temperature. The reaction temperature was varied at 600, 700, 750 and 850 °C with a pressure of 50 mmHg for 3 hours in gas N 2 atmosphere. The reation time was varied at 1, 2, 3 and 4 hours at a temperature of 750 °C using similar conditions. The reaction product was UO 2 kernel. The reaction kinetic aspect between U 3 O 8 and gas H 2 comprised the minimum activation energy (ΔE), the reaction rate constant and the O/U ratio of UO 2 kernel. The minimum activation energy was determined from a straight line slope of equation ln [{D b . R o {(1 - (1 - X b ) ⅓ } / (b.t.Cg)] = -3.9406 x 10 3 / T + 4.044. By multiplying with the straight line slope -3.9406 x 10 3 , the ideal gas constant (R) 1.985 cal/mol and the molarity difference of reaction coefficient 2, a minimum activation energy of 15.644 kcal/mol was obtained. The reaction rate constant was determined from first-order chemical reaction control and Arrhenius equation. The O/U ratio of UO 2 kernel was obtained using gravimetric method. The analysis result of reaction rate constant with chemical reaction control equation yielded reaction rate constants of 0.745 - 1.671 s -1 and the Arrhenius equation at temperatures of 650 - 850 °C yielded reaction rate constants of 0.637 - 2.914 s -1 . The O/U ratios of UO 2 kernel at the respective reaction rate constants were 2.013 - 2.014 and the O/U ratios at reaction time 1 - 4 hours were 2.04 - 2.011. The experiment results indicated that the minimum activation energy influenced the rate constant of first-order reaction and the O/U ratio of UO 2 kernel. The optimum condition was obtained at reaction rate constant of 1.43 s -1 , O/U ratio of UO 2 kernel of 2.01 at temperature of 750 °C and reaction time of 3

  7. Is volumetric modulated arc therapy with constant dose rate a valid option in radiation therapy for head and neck cancer patients?

    Science.gov (United States)

    Didona, Annamaria; Lancellotta, Valentina; Zucchetti, Claudio; Panizza, Bianca Moira; Frattegiani, Alessandro; Iacco, Martina; Di Pilato, Anna Concetta; Saldi, Simonetta; Aristei, Cynthia

    2018-01-01

    Intensity-modulated radiotherapy (IMRT) improves dose distribution in head and neck (HN) radiation therapy. Volumetric-modulated arc therapy (VMAT), a new form of IMRT, delivers radiation in single or multiple arcs, varying dose rates (VDR-VMAT) and gantry speeds, has gained considerable attention. Constant dose rate VMAT (CDR-VMAT) associated with a fixed gantry speed does not require a dedicated linear accelerator like VDR-VMAT. The present study explored the feasibility, efficiency and delivery accuracy of CDR-VMAT, by comparing it with IMRT and VDR-VMAT in treatment planning for HN cancer. Step and shoot IMRT (SS-IMRT), CDR-VMAT and VDR-VMAT plans were created for 15 HN cancer patients and were generated by Pinnacle 3 TPS (v 9.8) using 6 MV photon energy. Three PTVs were defined to receive respectively prescribed doses of 66 Gy, 60 Gy and 54 Gy, in 30 fractions. Organs at risk (OARs) included the mandible, spinal cord, brain stem, parotids, salivary glands, esophagus, larynx and thyroid. SS-IMRT plans were based on 7 co-planar beams at fixed gantry angles. CDR-VMAT and VDR-VMAT plans, generated by the SmartArc module, used a 2-arc technique: one clockwise from 182° to 178° and the other one anti-clockwise from 178° to 182°. Comparison parameters included dose distribution to PTVs ( D mean , D 2% , D 50% , D 95% , D 98% and Homogeneity Index), maximum or mean doses to OARs, specific dose-volume data, the monitor units and treatment delivery times. Compared with SS-IMRT, CDR-VMAT significantly reduced the maximum doses to PTV1 and PTV2 and significantly improved all PTV3 parameters, except D 98% and D 95% . It significantly spared parotid and submandibular glands and was associated with a lower D mean to the larynx. Compared with VDR-VMAT, CDR-VMAT was linked to a significantly better D mean , to the PTV3 but results were worse for the parotids, left submandibular gland, esophagus and mandible. Furthermore, the D mean to the larynx was also worse

  8. Utilizing the Total Design Method in medicine: maximizing response rates in long, non-incentivized, personal questionnaire postal surveys.

    Science.gov (United States)

    Kazzazi, Fawz; Haggie, Rebecca; Forouhi, Parto; Kazzazi, Nazar; Malata, Charles M

    2018-01-01

    Maximizing response rates in questionnaires can improve their validity and quality by reducing non-response bias. A comprehensive analysis is essential for producing reasonable conclusions in patient-reported outcome research particularly for topics of a sensitive nature. This often makes long (≥7 pages) questionnaires necessary but these have been shown to reduce response rates in mail surveys. Our work adapted the "Total Design Method," initially produced for commercial markets, to raise response rates in a long (total: 11 pages, 116 questions), non-incentivized, very personal postal survey sent to almost 350 women. A total of 346 women who had undergone mastectomy and immediate breast reconstruction from 2008-2014 (inclusive) at Addenbrooke's University Hospital were sent our study pack (Breast-Q satisfaction questionnaire and support documents) using our modified "Total Design Method." Participants were sent packs and reminders according to our designed schedule. Of the 346 participants, we received 258 responses, an overall response rate of 74.5% with a useable response rate of 72.3%. One hundred and six responses were received before the week 1 reminder (30.6%), 120 before week 3 (34.6%), 225 before the week 7 reminder (64.6%) and the remainder within 3 weeks of the final pack being sent. The median age of patients that the survey was sent to, and the median age of the respondents, was 54 years. In this study, we have demonstrated the successful implementation of a novel approach to postal surveys. Despite the length of the questionnaire (nine pages, 116 questions) and limitations of expenses to mail a survey to ~350 women, we were able to attain a response rate of 74.6%.

  9. Quantitative estimation of 123I-MIBG scintigraphy in neuroblastoma. Usefulness of the total body retention rate

    International Nuclear Information System (INIS)

    Okuyama, Chio; Ushijima, Yo; Sugihara, Hiroki; Nishimura, Tunehiko

    2000-01-01

    A new method of easily and simply quantifying 123 I-MIBG accumulation as a criterion for curative effect of chemotherapy in infants with neuroblastoma was developed. This method uses the data from two images: an early image (at 5-7.5 hr) and a delayed image (at 25-32 hr). Twenty infants with untreated neuroblastoma which showed clear accumulation of 123 I-MIBG at the primary site were examined. The differences between the accumulation counts on the early image and the delayed image showed that washout of 123 I-MIBG in the neuroblastomas was delayed in tumor regions. This finding indicated that the total body 123 I-MIBG retention rate reflects the total volume of the neuroblastoma. The 123 I-MIBG retention rate was significantly higher in patients with advanced stage neuroblastoma with systemic metastases, and there was a good correlation between the retention rate and tumor markers (VMA and HVA values in urine). The response to chemotherapy paralleled the change in markers. These results suggested that the total body 123 I-MIBG retention rate is useful as a criterion for curative effect in advanced neuroblastoma. (K.H.)

  10. Non Lyapunov stability of the constant spatially developing 1-D gas flow in presence of solutions having strictly positive exponential growth rate

    Science.gov (United States)

    Balint, Stefan; Balint, Agneta M.

    2017-01-01

    Different types of stabilities (global, local) and instabilities (global absolute, local convective) of the constant spatially developing 1-D gas flow are analyzed in the phase space of continuously differentiable functions, endowed with the usual algebraic operations and the topology generated by the uniform convergence on the real axis. For this purpose the Euler equations linearized at the constant flow are used. The Lyapunov stability analysis was presented in [1] and this paper is a continuation of [1].

  11. Interference in the gg→h→γγ On-Shell Rate and the Higgs Boson Total Width.

    Science.gov (United States)

    Campbell, John; Carena, Marcela; Harnik, Roni; Liu, Zhen

    2017-11-03

    We consider interference between the Higgs signal and QCD background in gg→h→γγ and its effect on the on-shell Higgs rate. The existence of sizable strong phases leads to destructive interference of about 2% of the on-shell cross section in the standard model. This effect can be enhanced by beyond the standard model physics. In particular, since it scales differently from the usual rates, the presence of interference allows indirect limits to be placed on the Higgs width in a novel way, using on-shell rate measurements. Our study motivates further QCD calculations to reduce uncertainties. We discuss possible width-sensitive observables, both using total and differential rates and find that the HL-LHC can potentially indirectly constrain widths of order tens of MeV.

  12. RATE CONSTANTS FOR THE REACTIONS OF OH RADICALS AND CL ATOMS WITH DI-N-PROPYL ETHER AND DI-N-BUTYL ETHER AND THEIR DEUTERATED ANALOGS. (R825252)

    Science.gov (United States)

    Using relative rate methods, rate constants for the gas-phase reactions of OH radicals and Cl atoms with di-n-propyl ether, di-n-propyl ether-d14, di-n-butyl ether and di-n-butyl ether-d18 have been measured at 296 ? 2 K and atmos...

  13. Total- and methyl-mercury concentrations and methylation rates across the freshwater to hypersaline continuum of the Great Salt Lake, Utah, USA

    Science.gov (United States)

    Johnson, William P.; Swanson, Neil; Black, Brooks; Rudd, Abigail; Carling, Gregory; Fernandez, Diego P.; Luft, John; Van Leeuwen, Jim; Marvin-DiPasquale, Mark C.

    2015-01-01

    We examined mercury (Hg) speciation in water and sediment of the Great Salt Lake and surrounding wetlands, a locale spanning fresh to hypersaline and oxic to anoxic conditions, in order to test the hypothesis that spatial and temporal variations in Hg concentration and methylation rates correspond to observed spatial and temporal trends in Hg burdens previously reported in biota. Water column, sediment, and pore water concentrations of methylmercury (MeHg) and total mercury (THg), as well as related aquatic chemical parameters were examined. Inorganic Hg(II)-methylation rates were determined in selected water column and sediment subsamples spiked with inorganic divalent mercury (204Hg(II)). Net production of Me204Hg was expressed as apparent first-order rate constants for methylation (kmeth), which were also expanded to MeHg production potential (MPP) rates via combination with tin reducible ‘reactive’ Hg(II) (Hg(II)R) as a proxy for bioavailable Hg(II). Notable findings include: 1) elevated Hg concentrations previously reported in birds and brine flies were spatially proximal to the measured highest MeHg concentrations, the latter occurring in the anoxic deep brine layer (DBL) of the Great Salt Lake; 2) timing of reduced Hg(II)-methylation rates in the DBL (according to both kmeth and MPP) coincides with reduced Hg burdens among aquatic invertebrates (brine shrimp and brine flies) that act as potential vectors of Hg propagation to the terrestrial ecosystem; 3) values ofkmeth were found to fall within the range reported by other studies; and 4) MPP rates were on the lower end of the range reported in methodologically comparable studies, suggesting the possibility that elevated MeHg in the anoxic deep brine layer results from its accumulation and persistence in this quasi-isolated environment, due to the absence of light (restricting abiotic photo demethylation) and/or minimal microbiological demethylation.

  14. Anesthesia Preoperative Clinic Referral for Elevated Hba1c Reduces Complication Rate in Diabetic Patients Undergoing Total Joint Arthroplasty

    OpenAIRE

    Kallio, Peter J.; Nolan, Jenea; Olsen, Amy C.; Breakwell, Susan; Topp, Richard; Pagel, Paul S.

    2015-01-01

    Background: Diabetes mellitus (DM) is risk factor for complications after orthopedic surgery. Objectives: We tested the hypothesis that anesthesia preoperative clinic (APC) referral for elevated glycosylated hemoglobin (HbA1c) reduces complication rate after total joint arthroplasty (TJA). Patients and Methods: Patients (n = 203) with and without DM were chosen from 1,237 patients undergoing TJA during 2006 - 12. Patients evaluated in the APC had surgery in 2006 - 8 regardless of HbA1c (uncon...

  15. Warming and organic matter sources impact the proportion of dissolved to total activities in marine extracellular enzymatic rates

    KAUST Repository

    Baltar, Federico

    2017-04-19

    Extracellular enzymatic activities (EEAs) are the rate-limiting step in the degradation of organic matter. Extracellular enzymes can be found associated to cells or dissolved in the surrounding water. The proportion of cell-free EEA constitutes in many marine environments more than half of the total activity. This high proportion causes an uncoupling between hydrolysis rates and the actual bacterial activity. However, we do not know what factors control the proportion of dissolved relative to total EEA, nor how this may change in the future ocean. To resolve this, we performed laboratory experiments with water from the Great Barrier Reef (Australia) to study the effects of temperature and dissolved organic matter sources on EEA and the proportion of dissolved EEA. We found that warming increases the rates of organic matter hydrolysis and reduces the proportion of dissolved relative to total EEA. This suggests a potential increase of the coupling between organic matter hydrolysis and heterotrophic activities with increasing ocean temperatures, although strongly dependent on the organic matter substrates available. Our study suggests that local differences in the organic matter composition in tropical coastal ecosystems will strongly affect the proportion of dissolved EEA in response to ocean warming.

  16. Effect Of Adding Sago Flour In Yoghurt Based On Viscosity, Overrun, Melting Rate And Total Solid Of Yoghurt Ice Cream

    Directory of Open Access Journals (Sweden)

    Ika Ayu Wijayanti

    2017-03-01

    Full Text Available The purpose of this research was to find out the best concentration of adding sago flour in yoghurt based on viscosity, overrun, melting rate and total solid of yoghurt ice cream. The experiment was designed by Completely Randomized Design (CRD using four treatments were 0 %, 2 %, 4 %, 6 % from volume of fresh milk and four replication. The data were analyzed by using Analysis of Variance (ANOVA and continued by Duncan’s Multiple Range Test (DMRT. Result of this research showed that concentration of adding sago flour in yoghurt gave highly significant difference effect (P<0.01 on viscosity, overrun, melting rate and total solid of yoghurt ice cream. It can be concluded that the adding of sago flour 2% in yoghurt gave the best result with the viscosity was 1750.75 cP, overrun was 25.14%, melting rate was 39.13 minutes/50 g, total solid was 36.20% and gave the best quality of yoghurt ice cream.

  17. Estimates of the Tempo-adjusted Total Fertility Rate in Western and Eastern Germany, 1955-2008

    Directory of Open Access Journals (Sweden)

    Marc Luy

    2011-09-01

    Full Text Available In this article we present estimates of the tempo-adjusted total fertility rate in Western and Eastern Germany from 1955 to 2008. Tempo adjustment of the total fertility rate (TFR requires data on the annual number of births by parity and age of the mother. Since official statistics do not provide such data for West Germany as well as Eastern Germany from 1990 on we used alternative data sources which include these specific characteristics. The combined picture of conventional TFR and tempo-adjusted TFR* provides interesting information about the trends in period fertility in Western and Eastern Germany, above all with regard to the differences between the two regions and the enormous extent of tempo effects in Eastern Germany during the 1990s. Compared to corresponding data for populations from other countries, our estimates of the tempo-adjusted TFR* for Eastern and Western Germany show plausible trends. Nevertheless, it is important to note that the estimates of the tempo-adjusted total fertility rate presented in this paper should not be seen as being on the level of or equivalent to official statistics since they are based on different kinds of data with different degrees of quality.

  18. Comparison of the rate constants for energy transfer in the light-harvesting protein, C-phycocyanin, calculated from Foerster`s theory and experimentally measured by time-resolved fluorescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Debreczeny, Martin Paul [Univ. of California, Berkeley, CA (United States)

    1994-05-01

    We have measured and assigned rate constants for energy transfer between chromophores in the light-harvesting protein C-phycocyanin (PC), in the monomeric and trimeric aggregation states, isolated from Synechococcus sp. PCC 7002. In order to compare the measured rate constants with those predicted by Fdrster`s theory of inductive resonance in the weak coupling limit, we have experimentally resolved several properties of the three chromophore types ({beta}{sub 155} {alpha}{sub 84}, {beta}{sub 84}) found in PC monomers, including absorption and fluorescence spectra, extinction coefficients, fluorescence quantum yields, and fluorescence lifetimes. The cpcB/C155S mutant, whose PC is missing the {beta}{sub 155} chromophore, was, useful in effecting the resolution of the chromophore properties and in assigning the experimentally observed rate constants for energy transfer to specific pathways.

  19. SU-E-P-55: The Reaserch of Cervical Cancer Delivered with Constant Dose Rate and Gantry Speed Arc Therapy(CDR-CAS-IMAT) On Conventional Linac

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, R; Bai, W; Chi, Z; Gao, C; Xiaomei, F [The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei (China); Gao, Y [Hebei General Hospital, Shijiazhuang, Hebei (China)

    2015-06-15

    Purpose: Postoperative cervical cancer patients with large target volume and the target shape is concave, treatmented with static intensity-modulated radiotherapy (IMRT) is time consuming. The purpose of this study is to investigate using constant dose rate and gantry speed arc therapy(CDR-CAS-IMAT) on conventional linear accelrator, by comparing with the IMRT technology to evaluate the performance of CDR-CAS-IMAT on postoperative cervical cancer patients. Methods: 18 cervical cancer patients treated with IMRT on Varian 23IX were replanted using CDR-CAS-IMAT. The plans were generated on Oncentra v4.1 planning system, PTV was prescribed to 50.4 Gy in 28 fractions. Plans were evaluated based on the ability to meet the dose volume histogram. The homogeneity index (HI), conformity index (CI) of target volume, the dose of organs at risk, radiation delivery time and monitor units were also compared. SPSS 19.0 software paired T-test analysis was carried out on the two sets of data. Results: Compared with the IMRT plans PTV’s CI (t= 3.85, P =0.001), CTV’s CI, HI, D90, D95, D98, V95, V98, V100 (t=4.21, −3.18, 2.13, 4.65, 7.79, 2.29, 6.00, 2.13, p=0.001, 0.005, 0.049, 0.000, 0.000, 0.035, 0.000, 0.049), and cord D2 and rectum V40 (t=−2.65, −2.47, p= P =0.017, 0.025), and treatment time and MU (t=−36.0, −6.26, P =0.000, 0.000) were better than that of IMRT group. But the IMRT plans in terms of decreasing bladder V50, bowel V30 (t=2.14, 3.00, P =0.048, 0.008) and low dose irradiation volume were superior to that of CDR-CAS-IMAT plans. There were no significant differences in other statistical index. Conclusion: Cervical cancer patients with CDR-CAS-IMAT on Varian Clinical 23IX can get equivalent or superior dose distribution compared with the IMRT technology. IMAT have much less treatment time and MU can reduce the uncertainty factor and patient discomfort in treatment. This work was supported by the Medical Science Foundation of the health department of Hebei

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

    Science.gov (United States)

    Rangel, Cipriano; Espinosa-Garcia, Joaquin

    2018-02-07

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

  1. Rate constants of hydroxyl radical oxidation of polychlorinated biphenyls in the gas phase: A single−descriptor based QSAR and DFT study

    International Nuclear Information System (INIS)

    Yang, Zhihui; Luo, Shuang; Wei, Zongsu; Ye, Tiantian; Spinney, Richard; Chen, Dong; Xiao, Ruiyang

    2016-01-01

    The second‒order rate constants (k) of hydroxyl radical (·OH) with polychlorinated biphenyls (PCBs) in the gas phase are of scientific and regulatory importance for assessing their global distribution and fate in the atmosphere. Due to the limited number of measured k values, there is a need to model the k values for unknown PCBs congeners. In the present study, we developed a quantitative structure–activity relationship (QSAR) model with quantum chemical descriptors using a sequential approach, including correlation analysis, principal component analysis, multi−linear regression, validation, and estimation of applicability domain. The result indicates that the single descriptor, polarizability (α), plays an important role in determining the reactivity with a global standardized function of lnk = −0.054 × α ‒ 19.49 at 298 K. In order to validate the QSAR predicted k values and expand the current k value database for PCBs congeners, an independent method, density functional theory (DFT), was employed to calculate the kinetics and thermodynamics of the gas‒phase ·OH oxidation of 2,4′,5-trichlorobiphenyl (PCB31), 2,2′,4,4′-tetrachlorobiphenyl (PCB47), 2,3,4,5,6-pentachlorobiphenyl (PCB116), 3,3′,4,4′,5,5′-hexachlorobiphenyl (PCB169), and 2,3,3′,4,5,5′,6-heptachlorobiphenyl (PCB192) at 298 K at B3LYP/6–311++G**//B3LYP/6–31 + G** level of theory. The QSAR predicted and DFT calculated k values for ·OH oxidation of these PCB congeners exhibit excellent agreement with the experimental k values, indicating the robustness and predictive power of the single–descriptor based QSAR model we developed. - Highlights: • We developed a single−descriptor based QSAR model for ·OH oxidation of PCBs. • We independently validated the QSAR predicted k values of five PCB congeners with the DFT method. • The QSAR predicted and DFT calculated k for the five PCB congeners exhibit excellent agreement. - We developed a single

  2. TU-CD-304-04: Scanning Field Total Body Irradiation Using Dynamic Arc with Variable Dose Rate and Gantry Speed

    Energy Technology Data Exchange (ETDEWEB)

    Yi, B; Xu, H; Mutaf, Y; Prado, K [Univ. of Maryland School Of Medicine, Baltimore, MD (United States)

    2015-06-15

    Purpose: Enable a scanning field total body irradiation (TBI) technique, using dynamic arcs, which is biologically equivalent to a moving couch TBI. Methods: Patient is treated slightly above the floor and the treatment field scans across the patient by a moving gantry. MLC positions change during gantry motion to keep same field opening at the level of the treatment plane (170 cm). This is done to mimic the same geometry as the moving couch TBI technique which has been used in our institution for over 10 years. The dose rate and the gantry speed are determined considering a constant speed of the moving field, variations in SSD and slanted depths resulting from oblique gantry angles. An Eclipse (Varian) planning system is commissioned to accommodate the extended SSD. The dosimetric foundations of the technique have been thoroughly investigated using phantom measurements. Results: Dose uniformity better than 2% across 180 cm length at 10cm depth is achieved by moving the gantry from −55 to +55 deg. Treatment range can be extended by increasing gantry range. No device such as a gravity-oriented compensator is needed to achieve a uniform dose. It is feasible to modify the dose distribution by adjusting the dose rate at each gantry angle to compensate for body thickness differences. Total treatment time for 2 Gy AP/PA fields is 40–50 minutes excluding patient set up time, at the machine dose rate of 100 MU/min. Conclusion: This novel yet transportable moving field technique enables TBI treatment in a small treatment room with less program development preparation than other techniques. Treatment length can be extended per need, and. MLC-based thickness compensation and partial lung blocking are also possible.

  3. Determination of total flow rate and flow rate of every operating branch in commissioning of heavy water loop for ARR-2

    International Nuclear Information System (INIS)

    Han Yan

    1997-01-01

    The heavy water loop (i,e, RCS) for ARR-2 in Algeria is a complex loop. Flow regulating means are not provided by the design in order to operate the reactor safely and simplify operating processes. How to determine precisely the orifice diameters of resistance parts for the loop is a key point for decreasing deviation between practical and design flow rates. Commissioning tests shall ensure that under every one of combined operating modes for the pumps, total coolant flow rate is about the same (the number of pumps operating in parallel is the same) and is consistent with design requirement, as well as the distribution of coolant flow rate to every branch is uniform. The flow Determination is divided into two steps. First and foremost, corresponding resistance part at each pump outlet is determined in commissioning test of shorted heavy water loop with light water, so that the problem about uniform distribution of the flow rate to each branch is solved, Secondly, resistance part at the reactor inlet is determined in commissioning test of heavy water loop connected with the vessel, so that the problem about that total heavy water flow rate is within optimal range is solved. According to practical requirements of the project, a computer program of hydraulic calculation and analysis for heavy water loop has been developed, and hydraulic characteristics test for a part of loop has been conducted in order to correct calculation error. By means of program calculation combining with tests in site, orifice diameters of 9 resistance parts has been determined rapidly and precisely and requirements of design and operation has been met adequately

  4. Four-dimensional dose distributions of step-and-shoot IMRT delivered with real-time tumor tracking for patients with irregular breathing: Constant dose rate vs dose rate regulation

    International Nuclear Information System (INIS)

    Yang Xiaocheng; Han-Oh, Sarah; Gui Minzhi; Niu Ying; Yu, Cedric X.; Yi Byongyong

    2012-01-01

    Purpose: Dose-rate-regulated tracking (DRRT) is a tumor tracking strategy that programs the MLC to track the tumor under regular breathing and adapts to breathing irregularities during delivery using dose rate regulation. Constant-dose-rate tracking (CDRT) is a strategy that dynamically repositions the beam to account for intrafractional 3D target motion according to real-time information of target location obtained from an independent position monitoring system. The purpose of this study is to illustrate the differences in the effectiveness and delivery accuracy between these two tracking methods in the presence of breathing irregularities. Methods: Step-and-shoot IMRT plans optimized at a reference phase were extended to remaining phases to generate 10-phased 4D-IMRT plans using segment aperture morphing (SAM) algorithm, where both tumor displacement and deformation were considered. A SAM-based 4D plan has been demonstrated to provide better plan quality than plans not considering target deformation. However, delivering such a plan requires preprogramming of the MLC aperture sequence. Deliveries of the 4D plans using DRRT and CDRT tracking approaches were simulated assuming the breathing period is either shorter or longer than the planning day, for 4 IMRT cases: two lung and two pancreatic cases with maximum GTV centroid motion greater than 1 cm were selected. In DRRT, dose rate was regulated to speed up or slow down delivery as needed such that each planned segment is delivered at the planned breathing phase. In CDRT, MLC is separately controlled to follow the tumor motion, but dose rate was kept constant. In addition to breathing period change, effect of breathing amplitude variation on target and critical tissue dose distribution is also evaluated. Results: Delivery of preprogrammed 4D plans by the CDRT method resulted in an average of 5% increase in target dose and noticeable increase in organs at risk (OAR) dose when patient breathing is either 10% faster or

  5. Comparison of 3 Types of Readmission Rates for Measuring Hospital and Surgeon Performance After Primary Total Hip and Knee Arthroplasty.

    Science.gov (United States)

    Bottle, Alex; Loeffler, Mark D; Aylin, Paul; Ali, Adam M

    2018-02-26

    All-cause 30-day hospital readmission is in widespread use for monitoring and incentivizing hospital performance for patients undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA). However, little is known on the extent to which all-cause readmission is influenced by hospital or surgeon performance and whether alternative measures may be more valid. This is an observational study using multilevel modeling on English administrative data to determine the interhospital and intersurgeon variation for 3 readmission metrics: all-cause, surgical, and return-to-theater. Power calculations estimated the likelihood of identifying whether the readmission rate for a surgeon or hospital differed from the national average by a factor of 1.25, 1.5, 2, or 3 times, for both average and high-volume providers. 259,980 THAs and 311,033 TKAs were analyzed. Variations by both surgeons and hospitals were smaller for the all-cause measure than for the surgical or return-to-theater metrics, although statistical power to detect differences was higher. Statistical power to detect surgeon-level rates of 1.25 or 1.5 times the average was consistently low. However, at the hospital level, the surgical readmission measure showed more variation by hospital while maintaining excellent power to detect differences in rates between hospitals performing the average number of THA or TKA cases per year in England. In practice, more outliers than expected from purely random variation were found for all-cause and surgical readmissions, especially at hospital level. The 30-day surgical readmission rate should be considered as an adjunctive measure to 30-day all-cause readmission rate when assessing hospital performance. Copyright © 2018 Elsevier Inc. All rights reserved.

  6. Comparison of reconstructed radial pin total fission rates with experimental results in full scale BWR fuel elements

    Energy Technology Data Exchange (ETDEWEB)

    Giust, Flavio [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Nordostschweizerische Kraftwerke AG, Parkstrasse 23, CH-5401 Baden (Switzerland); Grimm, Peter; Jatuff, Fabian [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Chawla, Rakesh [Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland)

    2008-07-01

    Total fission rate measurements have been performed on full size BWR fuel assemblies of type SVEA-96+ in the zero power reactor PROTEUS at the Paul Scherrer Institute. This work presents comparisons of reconstructed 2D pin fission rates in two configurations, I-1A and I-2A. Both configurations contain, in the central test zone, an array of 3x3 SVEA-96+ fuel elements moderated with light water at 20 deg. C. In configuration I-2A, an L-shaped hafnium control blade (half of a real cruciform blade) is inserted adjacent to the NW corner of the central fuel element. To minimize the impact of the surroundings, all measurements were done in fuel pins belonging to the central assembly. The 3x3 experimental configuration was modeled using the core monitoring and design tools that are applied at the Leibstadt Nuclear Power Plant (KKL). These are the 2D transport code HELIOS, used for the cross-section generation, and the 3D, 2-group nodal diffusion code PRESTO-2. The exterior is represented, in the axial and radial directions, by 2-group albedos calculated at the test zone boundary using a full-core 3D MCNPX model. The calculated-to-experimental (C/E) ratios of the total fission rates have a standard deviation of 1.3% in configuration I-1A (uncontrolled) and 3.2% in configuration I-2A (controlled). Sensitivity cases are analyzed to show the impact of certain parameters on the calculated fission rate distribution and reactivity. It is shown that the relative pin fission rate is only weakly dependent on these parameters. In cases without a control blade, the pin power reconstruction methodology delivers the same level of accuracy as 2D transport calculations. On the other hand, significant deviations, that are inherent to the use of reflected geometry in the lattice calculations, are observed in cases when the control blade is inserted. (authors)

  7. Effect of γ-dose rate and total dose interrelation on the polymeric hydrogel: A novel injectable male contraceptive

    International Nuclear Information System (INIS)

    Jha, Pradeep K.; Jha, Rakhi; Gupta, B.L.; Guha, Sujoy K.

    2010-01-01

    Functional necessity to use a particular range of dose rate and total dose of γ-initiated polymerization to manufacture a novel polymeric hydrogel RISUG (reversible inhibition of sperm under guidance) made of styrene maleic anhydride (SMA) dissolved in dimethyl sulphoxide (DMSO), for its broad biomedical application explores new dimension of research. The present work involves 16 irradiated samples. They were tested by fourier transform infrared spectroscopy, matrix assisted laser desorption/ionization-TOF, field emission scanning electron microscopy, high resolution transmission electron microscopy, etc. to see the interrelation effect of gamma dose rates (8.25, 17.29, 20.01 and 25.00 Gy/min) and four sets of doses (1.8, 2.0, 2.2 and 2.4 kGy) on the molecular weight, molecular weight distribution and porosity analysis of the biopolymeric drug RISUG. The results of randomized experiment indicated that a range of 18-24 Gy/min γ-dose rate and 2.0-2.4 kGy γ-total doses is suitable for the desirable in vivo performance of the contraceptive copolymer.

  8. Discovery of a Significant Acetone•Hydroperoxy Adduct Chaperone Effect and Its Impact on the Determination of Room Temperature Rate Constants for Acetonylperoxy/Hydroperoxy Self-Reactions and Cross Reaction Via Infrared Kinetic Spectroscopy.

    Science.gov (United States)

    Grieman, F. J.; Hui, A. O.; Okumura, M.; Sander, S. P.

    2017-12-01

    In order to model the upper troposphere/lower stratosphere in regions containing acetone properly, the kinetics of the acetonylperoxy/hydroperoxy self-reactions and cross reaction have been studied over a wide temperature range using Infrared Kinetic Spectroscopy. We report here the determination of different rate constants for the acetonylperoxy chemistry that we obtained at 298 K compared to currently accepted values. A considerable increase in the observed HO2 self-reaction rate constant due to rate enhancement via the chaperone effect from the reaction between HO2 and the (CH3)2CO•HO2 hydrogen-bonded adduct, even at room temperature, was discovered that was previously ignored. Correct determination of the acetonylperoxy and hydroperoxy kinetics must include this dependence of the HO2 self-reaction rate on acetone concentration. Via excimer laser flash photolysis to create the radical reactants, HO2 absorption was monitored in the infrared by diode laser wavelength modulation detection simultaneously with CH3C(O)CH2O2absorption monitored in the ultraviolet at 300 nm as a function of time. Resulting decay curves were fit concurrently first over a short time scale to obtain the rate constants minimizing subsequent product reactions. Modeling/fitting with a complete reaction scheme was then performed to refine the rate constants and test their veracity. Experiments were carried out over a variety of concentrations of acetone and methanol. Although no effect due to methanol concentration was found at room temperature, the rate constant for the hydroperoxy self-reaction was found to increase linearly with acetone concentration which is interpreted as the adduct being formed and resulting in a chaperone mechanism that enhances the self-reaction rate: (CH3)2CO·HO2 + HO2 → H2O2 + O2 + (CH3)2CO Including this effect, the resulting room temperature rate constants for the cross reaction and the acetonylperoxy self-reaction were found to be 2-3 times smaller than

  9. Fractional rate of degradation (kd) of starch in the rumen and its relation to in vivo rumen and total digestibility

    DEFF Research Database (Denmark)

    Hvelplund, Torben; Larsen, Mogens; Lund, Peter

    2009-01-01

    in different ways both chemically and physically. The starch sources were fed in mixed diets together with grass silage and soya bean meal and allocated ad libitum to fistulated dairy cows. The starch content varied between 13 and 35% in ration dry matter for the different starch sources. The design...... was a series of cross-over experiments with two cows and two periods. Ruminal starch pool was estimated from rumen evacuation and starch flow was estimated by duodenal and faeces sampling. Fractional rate of rumen degradation was estimated from the equation [kd = rumen degraded/rumen pool] and rumen and total...

  10. Radiobiological basis of total body irradiation with different dose rate and fractionation: repair capacity of hemopoietic cells

    International Nuclear Information System (INIS)

    Song, C.W.; Kim, T.H.; Khan, F.M.; Kersey, J.H.; Levitt, S.H.

    1981-01-01

    Total body irradiation (TBI) followed by bone marrow transplantation is being used in the treatment of malignant or non-malignant hemopoietic disorders. It has been believed that the ability of hemopoietic cells to repair sublethal radiation damage is negligible. Therefore, several schools of investigators suggested that TBI in a single exposure at extremely low dose rate (5 rad/min) over several hours, or in several fractions in 2-3 days, should yield a higher therapeutic gain, as compared with a single exposure at a high dose rate (26 rad/min). We reviewed the existing data in the literature, in particular, the response of hemopoietic cells to fractionated doses of irradiation and found that the repair capacity of both malignant and non-malignant hemopoietic cells might be greater than has been thought. It is concluded that we should not underestimate the ability of hemopoietic cells to repair sublethal radiation damage in using TBI

  11. Monitoring of German Fertility: Estimation of Monthly and Yearly Total Fertility Rates on the Basis of Preliminary Monthly Data

    Directory of Open Access Journals (Sweden)

    Gabriele Doblhammer

    2011-02-01

    Full Text Available This paper introduces a set of methods for estimating fertility indicators in the absence of recent and short-term birth statistics. For Germany, we propose a set of straightforward methods that allow for the computation of monthly and yearly total fertility rates (mTFR on the basis of preliminary monthly data, including a confidence interval. The method for estimating most current fertility rates can be applied when no information on the age structure and the number of women exposed to childbearing is available. The methods introduced in this study are useful for calculating monthly birth indicators, with minimal requirements for data quality and statistical effort. In addition, we suggest an approach for projecting the yearly TFR based on preliminary monthly information up to June.

  12. Social life factors affecting the mortality, longevity, and birth rate of total Japanese population: effects of rapid industrialization and urbanization.

    Science.gov (United States)

    Araki, S; Uchida, E; Murata, K

    1990-12-01

    employment were positively related to the birth rate. The birth rate is higher in rural areas. Mortality of professional, engineering, and administrative workers was slightly lower than the total working population, while sales workers, those in farming, fishing, and forestry, and in personal and domestic service had significantly higher mortality. The mortality of the nonworking population was 6-8 times higher than sales, transportation, and communication, and personal and domestic service as well as the total population.

  13. Fluence of dielectric constant (D), (H/sup +/) and (SO/sub 4/sup -2/) on the rate of redox reaction between tris (2,2-bipyridine) iron (II) and ceric sulphate in aqueous sulphuric acid medium

    International Nuclear Information System (INIS)

    Khattak, R.; Naqvi, I.I.; Farrukh, M.A.

    2007-01-01

    Kinetic of the redox reaction between tris (2,2-bipyridine)iron(II) cation and ceric sulphate has been studied in aqueous sulphuric acid medium. Different methods were employed for the determination of order of reaction. The order of reaction is found to be first with respect to reductant however retarding effect of increasing initial concentration of oxidant is found. Influence of (H/sup +/), (SO/sub 4/sup 2-) and dielectric constant (D) on the rate of redox reaction has also been studied. Increase in (H/sup +/) and dielectric constant of the medium retard the rate while enhancement of the (SO/sub 4/sup 2-/) accelerates the rate first and then the reaction goes towards retardation. Effects of (H/sup +/) and (SO/sub 4/sup 2-/) were studied by using acetic acid-sodium acetate buffer for the first one and varying ionic concentrations of the salt sodium sulphate for the latter one, whereas dielectric constant was varied by using 0%, 10% and 20% ethanol-water mixtures. Results of effects of each one of the factors i.e., H/sup +/, SO/sub 4/sup 2-/ and dielectric constant (D) have been compared and on the basis of these factors, (Ce(SO/sub 4/ )/sub 3/)/sup 2-/ is suggested to be the active species of cerium(IV). However a rate law consistent with the observed kinetic data has also been derived supporting the proposed mechanism. (author)

  14. Anesthesia Preoperative Clinic Referral for Elevated Hba1c Reduces Complication Rate in Diabetic Patients Undergoing Total Joint Arthroplasty.

    Science.gov (United States)

    Kallio, Peter J; Nolan, Jenea; Olsen, Amy C; Breakwell, Susan; Topp, Richard; Pagel, Paul S

    2015-06-01

    Diabetes mellitus (DM) is risk factor for complications after orthopedic surgery. We tested the hypothesis that anesthesia preoperative clinic (APC) referral for elevated glycosylated hemoglobin (HbA1c) reduces complication rate after total joint arthroplasty (TJA). Patients (n = 203) with and without DM were chosen from 1,237 patients undergoing TJA during 2006 - 12. Patients evaluated in the APC had surgery in 2006 - 8 regardless of HbA1c (uncontrolled). Those evaluated between in subsequent two-year intervals were referred to primary care for HbA1c ≥ 10% and ≥ 8%, respectively, to improve DM control before surgery. Complications and mortality were quantified postoperatively and at three, six, and twelve months. Length of stay (LOS) and patients requiring a prolonged LOS (> 5 days) were recorded. Patients (197 men, 6 women) underwent 71, 131, and 1 total hip, knee, and shoulder replacements, respectively. Patients undergoing TJA with uncontrolled HbA1c and those with HbA1c patients without DM. An increase in complication rate was observed in DM patients with uncontrolled HbA1c versus patients without DM (P patients with preoperative HbA1c that was uncontrolled or ≥ 10% required prolonged LOS versus those without DM (P diabetics undergoing TJA.

  15. Effects of seeding date and seeding rate on yield, proximate composition and total tannins content of two Kabuli chickpea cultivars

    Directory of Open Access Journals (Sweden)

    Roberto Ruggeri

    2017-09-01

    Full Text Available Experiments were conducted in open field to assess the effect of seeding season and density on the yield, the chemical composition and the accumulation of total tannins in grains of two chickpea (Cicer arietinum L. cultivars (Pascià and Sultano. Environmental conditions and genetic factors considerably affected grain yield, nutrient and total tannins content of chickpea seeds, giving a considerable range in its qualitative characteristics. Results confirmed cultivar selection as a central factor when a late autumn-early winter sowing is performed. In effect, a more marked resistance to Ascochyta blight (AB of Sultano, allowed better agronomic performances when favourable-to-AB climatic conditions occur. Winter sowing appeared to be the best choice in the Mediterranean environment when cultivating to maximise the grain yield (+19%. Spring sowing improved crude protein (+10% and crude fibre (+8% content, whereas it did not significantly affect the accumulation of anti-nutrients compounds such as total tannins. The most appropriate seeding rate was 70 seeds m–2, considering that plant density had relatively little effect on the parameters studied.

  16. Calculation of the total plasma concentration of nonvolatile weak acids and the effective dissociation constant of nonvolatile buffers in plasma for use in the strong ion approach to acid-base balance in cats.

    Science.gov (United States)

    McCullough, Sheila M; Constable, Peter D

    2003-08-01

    To determine values for the total concentration of nonvolatile weak acids (Atot) and effective dissociation constant of nonvolatile weak acids (Ka) in plasma of cats. Convenience plasma samples of 5 male and 5 female healthy adult cats. Cats were sedated, and 20 mL of blood was obtained from the jugular vein. Plasma was tonometered at 37 degrees C to systematically vary PCO2 from 8 to 156 mm Hg, thereby altering plasma pH from 6.90 to 7.97. Plasma pH, PCO2, and concentrations of quantitatively important strong cations (Na+, K+, and Ca2+), strong anions (Cl-, lactate), and buffer ions (total protein, albumin, and phosphate) were determined. Strong ion difference was estimated from the measured strong ion concentrations and nonlinear regression used to calculate Atot and Ka from the measured pH and PCO2 and estimated strong ion difference. Mean (+/- SD) values were as follows: Atot = 24.3 +/- 4.6 mmol/L (equivalent to 0.35 mmol/g of protein or 0.76 mmol/g of albumin); Ka = 0.67 +/- 0.40 x 10(-7); and the negative logarithm (base 10) of Ka (pKa) = 7.17. At 37 degrees C, pH of 7.35, and a partial pressure of CO2 (PCO2) of 30 mm Hg, the calculated venous strong ion difference was 30 mEq/L. These results indicate that at a plasma pH of 7.35, a 1 mEq/L decrease in strong ion difference will decrease pH by 0.020, a 1 mm Hg decrease in PCO2 will increase plasma pH by 0.011, and a 1 g/dL decrease in albumin concentration will increase plasma pH by 0.093.

  17. Determination of the rate constant for the OH(X2Π) + OH(X2Π) → H2O + O(3P) reaction over the temperature range 295 to 701 K.

    Science.gov (United States)

    Altinay, Gokhan; Macdonald, R Glen

    2014-01-09

    The rate constant for the radical-radical reaction OH(X(2)Π) + OH(X(2)Π) → H2O + O((3)P) has been measured over the temperature and pressure ranges 295-701 K and 2-12 Torr, respectively, in mixtures of CF4, N2O, and H2O. The OH radical was produced by the 193 nm laser photolysis of N2O. The resulting O((1)D) atoms reacted rapidly with H2O to produce the OH radical. The OH radical was detected by high-resolution time-resolved infrared absorption spectroscopy using a single Λ-doublet component of the OH(1,0) P1e/f(4.5) fundamental vibrational transition. A detailed kinetic model was used to determine the reaction rate constant as a function of temperature. These experiments were conducted in a new temperature controlled reaction chamber. The values of the measured rate constants are quite similar to the previous measurements from this laboratory of Bahng and Macdonald (J. Phys. Chem. A 2007 , 111 , 3850 - 3861); however, they cover a much larger temperature range. The results of the present work do not agree with recent measurements of Sangwan and Krasnoperov (J. Phys. Chem. A 2012 , 116 , 11817 - 11822). At 295 K the rate constant of the title reaction was found to be (2.52 ± 0.63) × 10(-12) cm(3) molecule(-1) s(-1), where the uncertainty includes both experimental scatter and an estimate of systematic errors at the 95% confidence limit. Over the temperature range of the experiments, the rate constant can be represented by k1a = 4.79 × 10(-18)T(1.79) exp(879.0/T) cm(3) molecule(-1) s(-1) with a uncertainty of ±24% at the 2σ level, including experimental scatter and systematic error.

  18. Measurement Properties of Performance-Specific Pain Ratings of Patients Awaiting Total Joint Arthroplasty as a Consequence of Osteoarthritis

    Science.gov (United States)

    Stratford, Paul W.; Kennedy, Deborah M.; Woodhouse, Linda J.; Spadoni, Gregory

    2008-01-01

    Purpose: To estimate the test–retest reliability of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain sub-scale and performance-specific assessments of pain, as well as the association between these measures for patients awaiting primary total hip or knee arthroplasty as a consequence of osteoarthritis. Methods: A total of 164 patients awaiting unilateral primary hip or knee arthroplasty completed four performance measures (self-paced walk, timed up and go, stair test, six-minute walk) and the WOMAC. Scores for 22 of these patients provided test–retest reliability data. Estimates of test–retest reliability (Type 2,1 intraclass correlation coefficient [ICC] and standard error of measurement [SEM]) and the association between measures were examined. Results: ICC values for individual performance-specific pain ratings were between 0.70 and 0.86; SEM values were between 0.97 and 1.33 pain points. ICC estimates for the four-item performance pain ratings and the WOMAC pain sub-scale were 0.82 and 0.57 respectively. The correlation between the sum of the pain scores for the four performance measures and the WOMAC pain sub-scale was 0.62. Conclusion: Reliability estimates for the performance-specific assessments of pain using the numeric pain rating scale were consistent with values reported for patients with a spectrum of musculoskeletal conditions. The reliability estimate for the WOMAC pain sub-scale was lower than typically reported in the literature. The level of association between the WOMAC pain sub-scale and the various performance-specific pain scales suggests that the scores can be used interchangeably when applied to groups but not for individual patients. PMID:20145758

  19. Effect of radiation dose rate and cyclophosphamide on pulmonary toxicity after total body irradiation in a mouse model

    International Nuclear Information System (INIS)

    Safwat, Akmal; Nielsen, Ole S.; El-Badawy, Samy; Overgaard, Jens

    1996-01-01

    Purpose: Interstitial pneumonitis (IP) is still a major complication after total body irradiation (TBI) and bone marrow transplantation (BMT). It is difficult to determine the exact role of radiation in this multifactorial complication, especially because most of the experimental work on lung damage was done using localized lung irradiation and not TBI. We have thus tested the effect of radiation dose rate and combining cyclophosphamide (CTX) with single fraction TBI on lung damage in a mouse model for BMT. Methods and Materials: TBI was given as a single fraction at a high dose rate (HDR, 0.71 Gy/min) or a low dose rate (LDR, 0.08 Gy/min). CTX (250 mg/kg) was given 24 h before TBI. Bone marrow transplantation (BMT) was performed 4-6 h after the last treatment. Lung damage was assessed using ventilation rate (VR) and lethality between 28 and 180 days (LD (50(28))-180 ). Results: The LD 50 for lung damage, ± standard error (SE), increased from 12.0 (± 0.2) Gy using single fraction HDR to 15.8 (± 0.6) Gy using LDR. Adding CTX shifted the dose-response curves towards lower doses. The LD 50 values for the combined treatment were 5.3 (± 0.2) and 3.5 (± 0.2) Gy for HDR and LDR, respectively. This indicates that the combined effect of CTX and LDR was more toxic than that of combined CTX and HDR. Lung damage evaluated by VR demonstrated two waves of VR increase. The first wave of VR increase occurred after 6 weeks using TBI only and after 3 weeks in the combined CTX-TBI treatment, irrespective of total dose or dose rate. The second wave of VR elevation resembled the IP that follows localized thoracic irradiation in its time of occurrence. Conclusions: Lung damage following TBI could be spared using LDR. However, CTX markedly enhances TBI-induced lung damage. The combination of CTX and LDR is more toxic to the lungs than combining CTX and HDR

  20. Estimation of salivary glucose, salivary amylase, salivary total protein and salivary flow rate in diabetics in India.

    Science.gov (United States)

    Panchbhai, Arati S; Degwekar, Shirish S; Bhowte, Rahul R

    2010-09-01

    Diabetes is known to influence salivary composition and function, eventually affecting the oral cavity. We thus evaluated saliva samples for levels of glucose, amylase and total protein, and assessed salivary flow rate in diabetics and healthy non-diabetics. We also analyzed these parameters with regard to duration and type of diabetes mellitus and gender, and aimed to assess the interrelationships among the variables included in the study. A total of 120 age- and sex-matched participants were divided into 3 groups of 40 each; the uncontrolled diabetic group, the controlled diabetic group and the healthy non-diabetic group. Salivary investigations were performed using unstimulated whole saliva. Mean salivary glucose levels were found to be significantly elevated in both uncontrolled and controlled diabetics, as compared to healthy non-diabetics. There were significant decreases in mean salivary amylase levels in controlled diabetics when compared to healthy non-diabetics. Other than salivary glucose, no other parameters were found to be markedly affected in diabetes mellitus. Further research is needed to explore the clinical implications of these study results.

  1. Constant physics and characteristics of fundamental constant

    International Nuclear Information System (INIS)

    Tarrach, R.

    1998-01-01

    We present some evidence which supports a surprising physical interpretation of the fundamental constants. First, we relate two of them through the renormalization group. This leaves as many fundamental constants as base units. Second, we introduce and a dimensional system of units without fundamental constants. Third, and most important, we find, while interpreting the units of the a dimensional system, that is all cases accessible to experimentation the fundamental constants indicate either discretization at small values or boundedness at large values of the corresponding physical quantity. (Author) 12 refs

  2. Total intravenous anaesthesia by boluses or by continuous rate infusion of propofol in mute swans (Cygnus olor).

    Science.gov (United States)

    Müller, Kerstin; Holzapfel, Judith; Brunnberg, Leo

    2011-07-01

    To investigate intravenous (IV) propofol given by intermittent boluses or by continuous rate infusion (CRI) for anaesthesia in swans. Prospective randomized clinical study. Twenty mute swans (Cygnus olor) (eight immature and 12 adults) of unknown sex undergoing painless diagnostic or therapeutic procedures. Induction of anaesthesia was with 8 mg kg(-1) propofol IV. To maintain anaesthesia, ten birds (group BOLI) received propofol as boluses, whilst 10 (group CRI) received propofol as a CRI. Some physiological parameters were measured. Anaesthetic duration was 35 minutes. Groups were compared using Mann-Whitney U-test. Results are median (range). Anaesthetic induction was smooth and tracheal intubation was achieved easily in all birds. Bolus dose in group BOLI was 2.9 (1.3-4.3) mg kg(-1); interval between and number of boluses required were 4 (1-8) minutes and 6 (4-11) boluses respectively. Total dose of propofol was 19 (12.3-37.1) mg kg(-1). Awakening between boluses was very abrupt. In group CRI, propofol infusion rate was 0.85 (0.8-0.9) mg kg(-1) minute(-1), and anaesthesia was stable. Body temperature, heart and respiratory rates, oxygen saturation (by pulse oximeter) and reflexes did not differ between groups. Oxygen saturations (from pulse oximeter readings) were low in some birds. Following anaesthesia, all birds recovered within 40 minutes. In 55% of all, transient signs of central nervous system excitement occurred during recovery. 8 mg kg(-1) propofol appears an adequate induction dose for mute swans. For maintenance, a CRI of 0.85 mg kg(-1) minute(-1) produced stable anaesthesia suitable for painless clinical procedures. In contrast bolus administration, was unsatisfactory as birds awoke very suddenly, and the short intervals between bolus requirements hampered clinical procedures. Administration of additional oxygen throughout anaesthesia might reduce the incidence of low arterial haemoglobin saturation. © 2011 The Authors. Veterinary Anaesthesia and

  3. Rate constant and mechanism of the reaction Cl + CFCl₂H → CFCl₂ + HCl over the temperature range 298-670 K in N₂ or N₂/O₂ diluent.

    Science.gov (United States)

    Kaiser, E W; Jawad, Khadija M

    2014-05-08

    The rate constant of the reaction Cl + CFCl2H (k1) has been measured relative to the established rate constant for the reaction Cl + CH4 (k2) at 760 Torr. The measurements were carried out in Pyrex reactors using a mixture of CFCl2H, CH4, and Cl2 in either N2 or N2/O2 diluent. Reactants and products were quantified by GC/FID analysis. Cl atoms were generated by irradiation of the mixture with 360 nm light to dissociate the Cl2 for temperatures up to ~550 K. At higher temperature, the Cl2 dissociated thermally, and no irradiation was used. Over the temperature range 298-670 K, k1 is consistently a factor of ~5 smaller than that of k2 with a nearly identical temperature dependence. The optimum non-Arrhenius rate constant is represented by the expression k1 = 1.14 × 10(-22) T(3.49) e(-241/T) cm(3) molecule(-1) s(-1) with an estimated uncertainty of ±15% including uncertainty in the reference reaction. CFCl3 formed from the reaction CFCl2 + Cl2 (k3) is the sole product in N2 diluent. In ~20% O2 at 298 K, the CFCl3 product is suppressed. The rate constant of reaction 3 was measured relative to that of reaction 4 [CFCl2 + O2 (k4)] giving the result k3/k4 = 0.0031 ± 0.0005 at 298 K. An earlier experiment by others observed C(O)FCl to be the major product of reaction channel 4 [formed via the sequence, CFCl2(O2) → CFCl2O → C(O)FCl + Cl]. Our current experiments verified that there is a Cl atom chain reaction in the presence of O2 as required by this mechanism.

  4. The reaction of fluorine atoms with methanol: yield of CH3O/CH2OH and rate constant of the reactions CH3O + CH3O and CH3O + HO2.

    Science.gov (United States)

    Assaf, Emmanuel; Schoemaecker, Coralie; Vereecken, Luc; Fittschen, Christa

    2018-04-25

    Xenondifluoride, XeF2, has been photolysed in the presence of methanol, CH3OH. Two reaction pathways are possible: F + CH3OH → CH2OH + HF and F + CH3OH → CH3O + HF. Both products, CH2OH and CH3O, will be converted to HO2 in the presence of O2. The rate constants for the reaction of both radicals with O2 differ by more than 3 orders of magnitude, which allows an unequivocal distinction between the two reactions when measuring HO2 concentrations in the presence of different O2 concentrations. The following yields have then been determined from time-resolved HO2 profiles: φCH2OH = (0.497 ± 0.013) and φCH3O = (0.503 ± 0.013). Experiments under low O2 concentrations lead to reaction mixtures containing nearly equal amounts of HO2 (converted from the first reaction) and CH3O (from the second reaction). The subsequent HO2 decays are very sensitive to the rate constants of the reaction between these two radicals and the following rate constants have been obtained: k(CH3O + CH3O) = (7.0 ± 1.4) × 10-11 cm3 s-1 and k(CH3O + HO2) = (1.1 ± 0.2) × 10-10 cm3 s-1. The latter reaction has also been theoretically investigated on the CCSD(T)//M06-2X/aug-cc-pVTZ level of theory and CH3OH + O2 have been identified as the main products. Using μVTST, a virtually pressure independent rate constant of k(CH3O + HO2) = 4.7 × 10-11 cm3 s-1 has been obtained, in good agreement with the experiment.

  5. Title: Elucidation of Environmental Fate of Artificial Sweeteners (Aspartame, Acesulfame K and Saccharin) by Determining Bimolecular Rate Constants with Hydroxyl Radical at Various pH and Temperature Conditions and Possible Reaction By-Products

    Science.gov (United States)

    Teraji, T.; Arakaki, T.; Suzuka, T.

    2012-12-01

    Use of artificial sweeteners in beverages and food has been rapidly increasing because of their non-calorie nature. In Japan, aspartame, acesulfame K and sucralose are among the most widely used artificial sweeteners. Because the artificial sweeteners are not metabolized in human bodies, they are directly excreted into the environment without chemical transformations. We initiated a study to better understand the fate of artificial sweeteners in the marine environment. The hydroxyl radical (OH), the most potent reactive oxygen species, reacts with various compounds and determines the environmental oxidation capacity and the life-time of many compounds. The steady-state OH concentration and the reaction rate constants between the compound and OH are used to estimate the life-time of the compound. In this study, we determine the bimolecular rate constants between aspartame, acefulfame K and saccharin and OH at various pH and temperature conditions using a competition kinetics technique. We use hydrogen peroxide as a photochemical source of OH. Bimolecular rate constant we obtained so far for aspartame was (2.6±1.2)×109 M-1 s-1 at pH = 3.0 and (4.9±2.3)×109 M-1 s-1 at pH = 5.5. Little effect was seen by changing the temperatures between 15 and 40 oC. Activation energy (Ea) was calculated to be -1.0 kJ mol-1 at pH = 3.0, +8.5 kJ mol-1 at pH = 5.5, which could be regarded as zero. We will report bimolecular rate constants at different pHs and temperatures for acesulfame K and saccharin, as well. Possible reaction by-products for aspartame will be also reported. We will further discuss the fate of aspartame in the coastal environment.

  6. Rate constants of the equilibrium reactions SO⨪4 + HNO3 ⇄ HSO-4 + NO3 and SO⨪4 + NO-3 ⇄ SO2-4 + NO3

    DEFF Research Database (Denmark)

    Løgager, T.; Sehested, K.; Holcman, J.

    1993-01-01

    Rate constants of the following equilibrium reactions were determined by pulse radiolysis at high solute concentrations: SO4.- + HNO, half arrow right over half arrow left HSO4- + NO3. [k(f) = (2.7 +/- 0.5) x 10(6) M-1 s-1, k(r) = (5.6 +/- 1.0) x 10(3) M-1 s-1] and SO4.- + NO3- half arrow right...

  7. The reaction set, rate constants and g-values for the simulation of the radiolysis of light water over the range 20 deg to 350 deg C based on information available in 2008

    International Nuclear Information System (INIS)

    Elliot, A.J.; Bartels, D.M.

    2009-08-01

    An understanding of the aqueous radiolysis-induced chemistry in nuclear reactors is an important key to the understanding of materials integrity issues in reactor systems. Significant materials and chemistry issues have emerged in Pressurized Water Reactors (PWR), Boiling Water Reactors (BWR) and CANDU reactors that have required a detailed understanding of the radiation chemistry of the coolant. For each reactor type, specific computer radiolysis models have been developed to gain insight into radiolysis processes and to make chemistry control adjustments to address the particular issues. The objective of this report is to compile and review the radiolysis data now available and, where possible, correct the reported g-values and rate constants to provide a recommendation for the best values to use in high temperature modelling of light water radiolysis up to 350 o C. With a few exceptions, the review has been limited to those reactions that occur in slightly acid and slightly alkaline solutions, e.g., it does not address reactions involving the oxide radical anion, O - , or ionized forms of hydrogen peroxide, HO 2 - , beyond their acid-base equilibria reactions. However, a few reactions have been included where the rate constant for a reaction involving O - is significantly larger than the corresponding hydroxyl radical reaction rate constant and thus can influence the chemistry below the pK A of the hydroxyl radical. (author)

  8. Beyond the Hubble Constant

    Science.gov (United States)

    1995-08-01

    about the distances to galaxies and thereby about the expansion rate of the Universe. A simple way to determine the distance to a remote galaxy is by measuring its redshift, calculate its velocity from the redshift and divide this by the Hubble constant, H0. For instance, the measured redshift of the parent galaxy of SN 1995K (0.478) yields a velocity of 116,000 km/sec, somewhat more than one-third of the speed of light (300,000 km/sec). From the universal expansion rate, described by the Hubble constant (H0 = 20 km/sec per million lightyears as found by some studies), this velocity would indicate a distance to the supernova and its parent galaxy of about 5,800 million lightyears. The explosion of the supernova would thus have taken place 5,800 million years ago, i.e. about 1,000 million years before the solar system was formed. However, such a simple calculation works only for relatively ``nearby'' objects, perhaps out to some hundred million lightyears. When we look much further into space, we also look far back in time and it is not excluded that the universal expansion rate, i.e. the Hubble constant, may have been different at earlier epochs. This means that unless we know the change of the Hubble constant with time, we cannot determine reliable distances of distant galaxies from their measured redshifts and velocities. At the same time, knowledge about such change or lack of the same will provide unique information about the time elapsed since the Universe began to expand (the ``Big Bang''), that is, the age of the Universe and also its ultimate fate. The Deceleration Parameter q0 Cosmologists are therefore eager to determine not only the current expansion rate (i.e., the Hubble constant, H0) but also its possible change with time (known as the deceleration parameter, q0). Although a highly accurate value of H0 has still not become available, increasing attention is now given to the observational determination of the second parameter, cf. also the Appendix at the

  9. Comparison of pregnancy rates in pre-treatment male infertility and low total motile sperm count at insemination.

    Science.gov (United States)

    Xiao, Cheng Wei; Agbo, Chioma; Dahan, Michael H

    2016-01-01

    In intrauterine insemination (IUI), total motile sperm count (TMSC) is an important predictor of pregnancy. However, the clinical significance of a poor TMSC on the day of IUI in a patient with prior normal semen analysis (SA) is unclear. We performed this study to determine if these patients perform as poorly as those who had male factor infertility diagnosed prior to commencing treatment. 147 males with two abnormal SA based on the 2010 World Health Organization criteria underwent 356 IUI with controlled ovarian hyper-stimulation (COH). Their pregnancy rates were compared to 120 males who had abnormal TMSC at the time of 265 IUI with COH, in a retrospective university-based study. The two groups were comparable in female age (p = 0.11), duration of infertility (p = 0.17), previous pregnancies (p = 0.13), female basal serum FSH level (p = 0.54) and number of mature follicles on the day of ovulation trigger (p = 0.27). Despite better semen parameters on the day of IUI in the pre-treatment male factor infertility group (TMSC mean ± SD: 61 ± 30 million vs. 3.5 ± 2 million, p male factor infertility. More studies should be performed to confirm these findings.

  10. Total Absorption Spectroscopy Study of the Beta Decay of 60Mn to Constrain the Neutron Capture Rate of 60Fe

    Science.gov (United States)

    Richman, Debra; Spyrou, Artemis; Dombos, Alex; Couture, Aaron; e15034 Collaboration

    2017-09-01

    Interest in 60Fe, a long lived radioisotope synthesized in massive stars, has recently peaked. The signature of its decay allows us to probe astrophysical processes, events such as the early formation of the solar system and nucleosynthesis. To understand these observations a complete understanding of the creation, destruction and nuclear properties of 60Fe in the astrophysical environment are required. Using the beta decay of 60Mn in conjunction with total absorption spectroscopy (TAS), made possible by the high efficiency gamma ray calorimeter SuN (Summing NaI detector) at the National Superconducting Cyclotron Laboratory (NSCL), to study the distribution of beta-decay intensity over the daughter-nucleus 60Fe, provides information about the structure of the daughter and improves the predictive power of astrophysical models. In addition to the ongoing TAS analysis, The Beta-Oslo method will be used to extract the nuclear level density and gamma-strength function of 60Fe providing much needed constraints on the neutron capture reaction rate responsible for the creation of this nucleus.

  11. Estimating the reproductive number, total outbreak size, and reporting rates for Zika epidemics in South and Central America

    Directory of Open Access Journals (Sweden)

    Deborah P. Shutt

    2017-12-01

    Full Text Available As South and Central American countries prepare for increased birth defects from Zika virus outbreaks and plan for mitigation strategies to minimize ongoing and future outbreaks, understanding important characteristics of Zika outbreaks and how they vary across regions is a challenging and important problem. We developed a mathematical model for the 2015/2016 Zika virus outbreak dynamics in Colombia, El Salvador, and Suriname. We fit the model to publicly available data provided by the Pan American Health Organization, using Approximate Bayesian Computation to estimate parameter distributions and provide uncertainty quantification. The model indicated that a country-level analysis was not appropriate for Colombia. We then estimated the basic reproduction number to range between 4 and 6 for El Salvador and Suriname with a median of 4.3 and 5.3, respectively. We estimated the reporting rate to be around 16% in El Salvador and 18% in Suriname with estimated total outbreak sizes of 73,395 and 21,647 people, respectively. The uncertainty in parameter estimates highlights a need for research and data collection that will better constrain parameter ranges.

  12. Estimating the reproductive number, total outbreak size, and reporting rates for Zika epidemics in South and Central America.

    Science.gov (United States)

    Shutt, Deborah P; Manore, Carrie A; Pankavich, Stephen; Porter, Aaron T; Del Valle, Sara Y

    2017-12-01

    As South and Central American countries prepare for increased birth defects from Zika virus outbreaks and plan for mitigation strategies to minimize ongoing and future outbreaks, understanding important characteristics of Zika outbreaks and how they vary across regions is a challenging and important problem. We developed a mathematical model for the 2015/2016 Zika virus outbreak dynamics in Colombia, El Salvador, and Suriname. We fit the model to publicly available data provided by the Pan American Health Organization, using Approximate Bayesian Computation to estimate parameter distributions and provide uncertainty quantification. The model indicated that a country-level analysis was not appropriate for Colombia. We then estimated the basic reproduction number to range between 4 and 6 for El Salvador and Suriname with a median of 4.3 and 5.3, respectively. We estimated the reporting rate to be around 16% in El Salvador and 18% in Suriname with estimated total outbreak sizes of 73,395 and 21,647 people, respectively. The uncertainty in parameter estimates highlights a need for research and data collection that will better constrain parameter ranges. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  13. Cosmological Hubble constant and nuclear Hubble constant

    International Nuclear Information System (INIS)

    Horbuniev, Amelia; Besliu, Calin; Jipa, Alexandru

    2005-01-01

    The evolution of the Universe after the Big Bang and the evolution of the dense and highly excited nuclear matter formed by relativistic nuclear collisions are investigated and compared. Values of the Hubble constants for cosmological and nuclear processes are obtained. For nucleus-nucleus collisions at high energies the nuclear Hubble constant is obtained in the frame of different models involving the hydrodynamic flow of the nuclear matter. Significant difference in the values of the two Hubble constant - cosmological and nuclear - is observed

  14. New N2(C 3Πu, v) collision quenching and vibrational relaxation rate constants: 2. PG emission diagnostics of high-pressure discharges

    International Nuclear Information System (INIS)

    Dilecce, G; Ambrico, P F; De Benedictis, S

    2007-01-01

    The present paper deals with the determination of discharge parameters using N 2 (C 3 Π u , v) populations deduced from 2.PG emission spectra, focusing on the influence of N 2 (C 3 Π u , v) collision rate coefficients on these determinations. In particular it is shown that the new set of quenching and vibrational relaxation rate coefficients of N 2 (C 3 Π u , v 0-4) vibronic levels recently measured by optical-optical double resonance laser induced fluorescence (LIF) have a large effect on discharge parameter determination in high-pressure discharges. In the present paper we explore this effect, evidencing the differences with respect to the old data set case, in both simulated and real cases of N 2 (C 3 Π u , v) vibrational distributions measured at high pressure in a dielectric barrier discharge. Finally we point out the improved potentiality of 2.PG spectroscopy as a diagnostic technique: with the new rate coefficients, and measurement of the N 2 (C 3 Π u , v) distribution up to at least v = 3, it is possible to have a quasi-independent evaluation of the electron temperature and of the first level vibrational temperature of the N 2 ground state

  15. Whole-Body Docosahexaenoic Acid Synthesis-Secretion Rates in Rats Are Constant across a Large Range of Dietary α-Linolenic Acid Intakes.

    Science.gov (United States)

    Domenichiello, Anthony F; Kitson, Alex P; Metherel, Adam H; Chen, Chuck T; Hopperton, Kathryn E; Stavro, P Mark; Bazinet, Richard P

    2017-01-01

    Docosahexaenoic acid (DHA) is an ω-3 (n-3) polyunsaturated fatty acid (PUFA) thought to be important for brain function. Although the main dietary source of DHA is fish, DHA can also be synthesized from α-linolenic acid (ALA), which is derived from plants. Enzymes involved in DHA synthesis are also active toward ω-6 (n-6) PUFAs to synthesize docosapentaenoic acid n-6 (DPAn-6). It is unclear whether DHA synthesis from ALA is sufficient to maintain brain DHA. The objective of this study was to determine how different amounts of dietary ALA would affect whole-body DHA and DPAn-6 synthesis rates. Male Long-Evans rats were fed an ALA-deficient diet (ALA-D), an ALA-adequate (ALA-A) diet, or a high-ALA (ALA-H) diet for 8 wk from weaning. Dietary ALA concentrations were 0.07%, 3%, and 10% of the fatty acids, and ALA was the only dietary PUFA that differed between the diets. After 8 wk, steady-state stable isotope infusion of labeled ALA and linoleic acid (LA) was performed to determine the in vivo synthesis-secretion rates of DHA and DPAn-6. Rats fed the ALA-A diet had an ∼2-fold greater capacity to synthesize DHA than did rats fed the ALA-H and ALA-D diets, and a DHA synthesis rate that was similar to that of rats fed the ALA-H diet. However, rats fed the ALA-D diet had a 750% lower DHA synthesis rate than rats fed the ALA-A and ALA-H diets. Despite enrichment into arachidonic acid, we did not detect any labeled LA appearing as DPAn-6. Increasing dietary ALA from 3% to 10% of fatty acids did not increase DHA synthesis rates, because of a decreased capacity to synthesize DHA in rats fed the ALA-H diet. Tissue concentrations of DPAn-6 may be explained at least in part by longer plasma half-lives. © 2017 American Society for Nutrition.

  16. Effects of Postacute Settings on Readmission Rates and Reasons for Readmission Following Total Knee Arthroplasty.

    Science.gov (United States)

    Welsh, Rodney Laine; Graham, James E; Karmarkar, Amol M; Leland, Natalie E; Baillargeon, Jacques G; Wild, Dana L; Ottenbacher, Kenneth J

    2017-04-01

    Examine the effects of postacute discharge setting on unplanned hospital readmissions following total knee arthroplasty (TKA) in older adults. Secondary analyses of 100% Medicare (inpatient) claims files. Acute hospitals across the United States. Medicare fee-for-service beneficiaries ≥66 years of age who were discharged from an acute hospital following TKA in 2009-2011 (n = 608,031). The outcome measure was unplanned readmissions at 30, 60, and 90 days. The independent variable of interest was postacute discharge setting: inpatient rehabilitation facility (IRF), skilled nursing facility (SNF), or community. Covariates included demographic, clinical, and facility-level factors. The top 10 reasons for readmission were tabulated for each discharge setting across the 3 consecutive 30-day time periods. A total of 32,226 patients (5.3%) were re-admitted within 30 days. Compared with community discharge, patients discharged to IRF and SNF had 44% and 40% higher odds of 30-day readmission, respectively. IRF and SNF discharge settings were also associated with 48% and 45% higher odds of 90-day readmission, respectively, compared with community discharge. The largest increase in readmission rates occurred within the first 30 days of hospital discharge for each discharge setting. From 1 to 30 days, postoperative and post-traumatic infections were among the top causes for readmission in all 3 discharge settings. From 31 to 60 days, postoperative or traumatic infections remained in the top 5-7 reasons for readmission in all settings, but they were not in the top 10 at 61 to 90 days. Patients discharged to either SNF or IRF, in comparison with those discharged to the community, had greater likelihood of readmission within 30 and 90 days. The reasons for readmission were relatively consistent across discharge settings and time periods. These findings provide new information relevant to the delivery of postacute care to older adults following TKA. Copyright © 2017

  17. Communication: Charge-transfer rate constants in zinc-porphyrin-porphyrin-derived dyads: A Fermi golden rule first-principles-based study

    International Nuclear Information System (INIS)

    Manna, Arun K.; Dunietz, Barry D.

    2014-01-01

    We investigate photoinduced charge transfer (CT) processes within dyads consisting of porphyrin derivatives in which one ring ligates a Zn metal center and where the rings vary by their degree of conjugation. Using a first-principles approach, we show that molecular-scale means can tune CT rates through stabilization affected by the polar environment. Such means of CT tuning are important for achieving high efficiency optoelectronic applications using organic semiconducting materials. Our fully quantum mechanical scheme is necessary for reliably modeling the CT process across different regimes, in contrast to the pervading semi-classical Marcus picture that grossly underestimates transfer in the far-inverted regime

  18. Comparative analysis of the heat transfer rates in constant (CAV) and variable (VAV) volumes type multi zone acclimation system operating in hot and humid climate; Analise comparativa das taxas transferencia de calor em sistemas de climatizacao do tipo volume de ar constante (CAV) e volume de ar variavel (VAV) multizona operando em clima quente e umido

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Cesar A.G.; Correa, Jorge E. [Para Univ., Belem (Brazil). Centro Tecnologico. Dept. de Engenharia Mecanica]. E-mails: gsantos@ufpa.br; jecorrea@amazon.com.br

    2000-07-01

    This work performs a comparative analysis among the constant and variable air volume multi zones acclimation systems, used for provide the thermal comfort in buildings. The work used the simulation HVAC2KIT computer program. The results of sensible and latent heats transfer rates on the cooling and dehumidification, inflating fan capacity, and heat transfer on the final heating condenser were obtained and analysed for the climate conditions of the Brazilian city of Belem from Para State, presenting hot and humid climate during all the year.

  19. Cheap but accurate calculation of chemical reaction rate constants from ab initio data, via system-specific, black-box force fields.

    Science.gov (United States)

    Steffen, Julien; Hartke, Bernd

    2017-10-28

    Building on the recently published quantum-mechanically derived force field (QMDFF) and its empirical valence bond extension, EVB-QMDFF, it is now possible to generate a reliable potential energy surface for any given elementary reaction step in an essentially black box manner. This requires a limited and pre-defined set of reference data near the reaction path and generates an accurate approximation of the reference potential energy surface, on and off the reaction path. This intermediate representation can be used to generate reaction rate data, with far better accuracy and reliability than with traditional approaches based on transition state theory (TST) or variational extensions thereof (VTST), even if those include sophisticated tunneling corrections. However, the additional expense at the reference level remains very modest. We demonstrate all this for three arbitrarily chosen example reactions.

  20. Direct measurements of rate constants for the reactions of CH3 radicals with C2H6, C2H4, and C2H2 at high temperatures.

    Science.gov (United States)

    Peukert, S L; Labbe, N J; Sivaramakrishnan, R; Michael, J V

    2013-10-10

    The shock tube technique has been used to study the reactions CH3 + C2H6 → C2H4 + CH4 + H (1), CH3 + C2H4 → Products + H (2), and CH3 + C2H2 → Products + H (3). Biacetyl, (CH3CO)2, was used as a clean high temperature thermal source for CH3-radicals for all the three reactions studied in this work. For reaction 1, the experiments span a T-range of 1153 K ≤ T ≤ 1297 K, at P ~ 0.4 bar. The experiments on reaction 2 cover a T-range of 1176 K ≤ T ≤ 1366 K, at P ~ 1.0 bar, and those on reaction 3 a T-range of 1127 K ≤ T ≤ 1346 K, at P ~ 1.0 bar. Reflected shock tube experiments performed on reactions 1-3, monitored the formation of H-atoms with H-atom Atomic Resonance Absorption Spectrometric (ARAS). Fits to the H-atom temporal profiles using an assembled kinetics model were used to make determinations for k1, k2, and k3. In the case of C2H6, the measurements of [H]-atoms were used to derive direct high-temperature rate constants, k1, that can be represented by the Arrhenius equation k1(T) = 5.41 × 10(-12) exp(-6043 K/T) cm(3) molecules(-1) s(-1) (1153 K ≤ T ≤ 1297 K) for the only bimolecular process that occurs, H-atom abstraction. TST calculations based on ab initio properties calculated at the CCSD(T)/CBS//M06-2X/cc-pVTZ level of theory show excellent agreement, within ±20%, of the measured rate constants. For the reaction of CH3 with C2H4, the present rate constant results, k2', refer to the sum of rate constants, k(2b) + k(2c), from two competing processes, addition-elimination, and the direct abstraction CH3 + C2H4 → C3H6 + H (2b) and CH3 + C2H4 → C2H2 + H + CH4 (2c). Experimental rate constants for k2' can be represented by the Arrhenius equation k2'(T) = 2.18 × 10(-10) exp(-11830 K/T) cm(3) molecules(-1) s(-1) (1176 K ≤ T ≤ 1366 K). The present results are in excellent agreement with recent theoretical predictions. The present study provides the only direct measurement for the high-temperature rate constants for these channels

  1. Development of a chemical kinetic measurement apparatus and the determination of the reaction rate constants for lithium-lead/water interaction

    International Nuclear Information System (INIS)

    Biney, P.O.

    1993-04-01

    An experimental set-up for accurate measurement of hydrogen generation rate in Lithium-Lead (Li 17 Pb 83 ) Steam or water interactions has been designed. The most important features of the design include a pneumatic actuated quick opening and closing high temperature all stainless steel valve used to control the reaction time and the placement of most measuring devices below a water line to minimize leakage of the hydrogen collected. A PC based data acquisition and control system provides remote process sequencing, acquisition and control of all major components of the set-up. Initial tests indicate that the first design objective of maintaining leakproof gas collection chamber has been achieved. Initial pressure tests indicated that the pressure drop over a time span of 30 minutes was within the tolerance of the pressure transducer used to measure the pressure (within 0.690 kPa) at a nominal system pressure of 685 kPa. The experimental system hardware, data acquisition and control programs and data analysis program have been completed, tested and are currently functional

  2. FORMATION CONSTANTS AND THERMODYNAMIC ...

    African Journals Online (AJOL)

    KEY WORDS: Metal complexes, Schiff base ligand, Formation constant, DFT calculation ... best values for the formation constants of the proposed equilibrium model by .... to its positive charge distribution and the ligand deformation geometry.

  3. Ion exchange equilibrium constants

    CERN Document Server

    Marcus, Y

    2013-01-01

    Ion Exchange Equilibrium Constants focuses on the test-compilation of equilibrium constants for ion exchange reactions. The book first underscores the scope of the compilation, equilibrium constants, symbols used, and arrangement of the table. The manuscript then presents the table of equilibrium constants, including polystyrene sulfonate cation exchanger, polyacrylate cation exchanger, polymethacrylate cation exchanger, polysterene phosphate cation exchanger, and zirconium phosphate cation exchanger. The text highlights zirconium oxide anion exchanger, zeolite type 13Y cation exchanger, and

  4. Relationship of Total Motile Sperm Count and Percentage Motile Sperm to Successful Pregnancy Rates Following Intrauterine Insemination

    OpenAIRE

    Pasqualotto, Eleonora B.; Daitch, James A.; Hendin, Benjamin N.; Falcone, Tommaso; Thomas, Anthony J.; Nelson, David R.; Agarwal, Ashok

    1999-01-01

    Purpose:This study sought (i) to investigate the relationship between postwash total motile sperm count and postwash percentage motile sperm in predicting successful intrauterine insemination and (ii) to determine the minimal postwash total motile sperm count required to achieve pregnancy with intrauterine insemination.

  5. Calculating constants of the rates of the reactions of excitation, ionization, and atomic exchange: A model of a shock oscillator with a change of the Hamiltonian of the system

    Science.gov (United States)

    Tsyganov, D. L.

    2017-11-01

    A new model for calculating the rates of reactions of excitation, ionization, and atomic exchange is proposed. Diatomic molecule AB is an unstructured particle M upon the exchange of elastic-vibrational (VT) energy, i.e., a model of a shock forceful oscillator with a change in Hamiltonian (SFOH). The SFOH model is based on the quantum theory of strong perturbations. The SFOH model allows generalization in simulating the rates of the reactions of excitation, ionization, and atomic exchange in the vibrational-vibrational (VV) energy exchange of diatomic molecules, and the exchange of VV- and VT-energy of polyatomic molecules. The rate constants of the excitation of metastables A 3Σ u +, B 3Π g , W 3Δ u , B'3Σ u -, a'3Σ u -, and the ionization of a nitrogen molecules from ground state X2Σ g + upon a collision with a heavy structureless particle (a nitrogen molecule), are found as examples.

  6. I. Activation energies for the gas phase reactions of hydrogen atom with carbon monoxide and with ethylene. II. Rate constants for the reactions of benzyl cation with triethylphosphine and with triethylarsine in 1,2-dichloroethane

    International Nuclear Information System (INIS)

    Wang, H.Y.

    1976-01-01

    Two H-atom reactions H + CO + H 2 → HCO + H 2 and H + C 2 H 4 → C 2 H 5 * were separately studied from room temperature to about 100 0 C, and the activation energies for these two reactions were determined in this temperature range. For H + C 2 H 4 system, a small activation energy of 0.2 kcal/mole was obtained in the present narrow temperature range. The low activation energy indicates that the pre-exponential factor has a predominant contribution to the rate constant of this reaction and has about the same magnitude as that of the rate constant. For H + CO system, a fairly large activation energy of more than 7 kcal/mole was speculated in the potential energy surfaces of the system. The activation energy obtained in the present work, however, has a low value of about 2 kcal/mole. This low value reveals the low level of crossing of this reaction in the potential energy surface and thus indicates considerable complexity involved in the surface. Carbonium ions can be formed from chosen solutes in pulse-irradiated 1,2-dichloroethane (RCl) solutions. Upon irradiation, the electrons generated from the ionization of the solvent become localized on chloride ions as a result of their reaction with the neutral solvent molecules. The solvent counterion, RCl + , on the other hand, is free to exchange charge with the solute molecule. By choosing appropriate solutes, carbonium ion can be formed through a dissociative ionization process in the exchange. The benzyl cation was formed from its precursor compound dibenzylmercury and its reactions with two nucleophiles, triethylphosphine and triethylarsine, were separately studied. The formation and decay of benzyl cation were observed at 363 nm, the position of the maximum of its absorption band, and the second-order rate constants for the two reactions were determined at room temperature

  7. Determination of the rate constants of the reactions CO/sub 2/+OH/sup -/ -> HCO/sub 3//sup -/ and barbituric acid -> barbiturate anion -> H/sup -/ using the pulse radiolyse technique

    Energy Technology Data Exchange (ETDEWEB)

    Schuchmann, M.N.; von Sonntag, C.

    1982-09-01

    The kinetics of the reactions of CO/sub 2/ + OH /sup -/-> HCO/sub 3//sup -/ (i) and barbituric acid -> barbiturate anion + H/sup +/ (ii) have been remeasured using as a new approach the pulse radiolysis technique with optical and conductivity detection. The rate constants obtained in the present study, ksub(j) (21/sup 0/C) = 6900 +- 700 M/sup -1/ s/sup -1/ and ksub(II) (19/sup 0/C) = 22 +- 2 s/sup -1/ agree within experimental errors with values obtained earlier by other methods.

  8. Total dose and dose-rate effects on start-up current in anti-fuse FPGA

    International Nuclear Information System (INIS)

    Wang, J.; Wong, W.; McCollum, J.; Cronquist, B.; Katz, R.; Kleyner, I.; Kleyner, F.

    1999-01-01

    Radiation enhanced start-up current (RESC) in an anti-fuse FPGA, A1280A, is thoroughly investigated and a comprehensive transistor-level mechanism is proposed. Low dose-rate testing, appropriate for civilian space applications, and annealing at room temperature shows RESC to be negligible for the lot of parts tested with a fixed power supply slew rate. (authors)

  9. Time-dependent 31P saturation transfer in the phosphoglucomutase reaction. Characterization of the spin system for the Cd(II) enzyme and evaluation of rate constants for the transfer process

    International Nuclear Information System (INIS)

    Post, C.B.; Ray, W.J. Jr.; Gorenstein, D.G.

    1989-01-01

    Time-dependent 31 P saturation-transfer studies were conducted with the Cd 2+ -activated form of muscle phosphoglucomutase to probe the origin of the 100-fold difference between its catalytic efficiency (in terms of k cat ) and that of the more efficient Mg 2+ -activated enzyme. The present paper describes the equilibrium mixture of phosphoglucomutase and its substrate/product pair when the concentration of the Cd 2+ enzyme approaches that of the substrate and how the nine-spin 31 P NMR system provided by this mixture was treated. It shows that the presence of abortive complexes is not a significant factor in the reduced activity of the Cd 2+ enzyme since the complex of the dephosphoenzyme and glucose 1,6-bisphosphate, which accounts for a large majority of the enzyme present at equilibrium, is catalytically competent. It also shows that rate constants for saturation transfer obtained at three different ratios of enzyme to free substrate are mutually compatible. These constants, which were measured at chemical equilibrium, can be used to provide a quantitative kinetic rationale for the reduced steady-state activity elicited by Cd 2+ relative to Mg 2+ . They also provide minimal estimates of 350 and 150 s -1 for the rate constants describing (PO 3 - ) transfer from the Cd 2+ phosphoenzyme to the 6-position of bound glucose 1-phosphate and to the 1-position of bound glucose 6-phosphate, respectively. These minimal estimates are compared with analogous estimates for the Mg 2+ and Li + forms of the enzyme in the accompanying paper

  10. Warming and organic matter sources impact the proportion of dissolved to total activities in marine extracellular enzymatic rates

    KAUST Repository

    Baltar, Federico; Moran, Xose Anxelu G.; Lø nborg, Christian

    2017-01-01

    Extracellular enzymatic activities (EEAs) are the rate-limiting step in the degradation of organic matter. Extracellular enzymes can be found associated to cells or dissolved in the surrounding water. The proportion of cell-free EEA constitutes

  11. Short communication: Effect of straw inclusion rate in a dry total mixed ration on the behavior of weaned dairy calves

    NARCIS (Netherlands)

    Groen, M.J.; Steele, M.A.; DeVries, T.J.

    2015-01-01

    The primary objective of this study was to determine the effect of straw inclusion levels on the feeding behavior of young, weaned calves adapted to a dry total mixed ration (TMR) composed of a multitextured concentrate and chopped straw. A secondary objective was to determine how developed feeding

  12. 38 CFR 3.22 - DIC benefits for survivors of certain veterans rated totally disabled at time of death.

    Science.gov (United States)

    2010-07-01

    ... benefits under paragraph (a) of this section receives any money or property pursuant to a judicial... amount of money received and the fair market value of the property received. The provisions of this... veteran. The amount to be reported is the total of the amount of money received and the fair market value...

  13. The dramatic increase in total knee replacement utilization rates in the United States cannot be fully explained by growth in population size and the obesity epidemic.

    Science.gov (United States)

    Losina, Elena; Thornhill, Thomas S; Rome, Benjamin N; Wright, John; Katz, Jeffrey N

    2012-02-01

    Total knee replacement utilization in the United States more than doubled from 1999 to 2008. Although the reasons for this increase have not been examined rigorously, some have attributed the increase to population growth and the obesity epidemic. Our goal was to investigate whether the rapid increase in total knee replacement use over the past decade can be sufficiently attributed to changes in these two factors. We used data from the Nationwide Inpatient Sample to estimate changes in total knee replacement utilization rates from 1999 to 2008, stratified by age (eighteen to forty-four years, forty-five to sixty-four years, and sixty-five years or older). We obtained data on obesity prevalence and U.S. population growth from federal sources. We compared the rate of change in total knee replacement utilization with the rates of population growth and change in obesity prevalence from 1999 to 2008. In 2008, 615,050 total knee replacements were performed in the United States adult population, 134% more than in 1999. During the same time period, the overall population size increased by 11%. While the population of forty-five to sixty-four-year-olds grew by 29%, the number of total knee replacements in this age group more than tripled. The number of obese and non-obese individuals in the United States increased by 23% and 4%, respectively. Assuming unchanged indications for total knee replacement among obese and non-obese individuals with knee osteoarthritis over the last decade, these changes fail to account for the 134% growth in total knee replacement use. Population growth and obesity cannot fully explain the rapid expansion of total knee replacements in the last decade, suggesting that other factors must also be involved. The disproportionate increase in total knee replacements among younger patients may be a result of a growing number of knee injuries and expanding indications for the procedure.

  14. A comparison of post-op haemoglobin levels and allogeneic blood transfusion rates following total knee arthroplasty without drainage or with reinfusion drains.

    Science.gov (United States)

    Hazarika, Shariff; Bhattacharya, Rajarshi; Bhavikatti, Mainudden; Dawson, Matthew

    2010-02-01

    The effects of re-infusion drains on the rate of allogeneic blood transfusion and post-op haemoglobin levels in Total Knee Arthroplasty were examined. A group of 22 patients undergoing primary Total Knee Arthroplasty using a CBCII Constavac Stryker re-infusion drainage system were compared with a group of 30 patients, matched for age, sex and type of prosthesis but without any drain usage. The re-infusion drain.group had a significantly lower day 1 and day 3 post-operative haemoglobin compared to the non-drainage group. The re-infusion drain group had a higher allogenic transfusion rate compared to the non-drainage group. There were no significant differences between the two groups regarding the rate of wound and transfusion related complications and mean length of post-operative stay. We found that reinfusion drains were ineffective in reducing allogeneic transfusion requirements as compared with non-drainage in total knee arthroplasty.

  15. The Fine Structure Constant

    Indian Academy of Sciences (India)

    IAS Admin

    The article discusses the importance of the fine structure constant in quantum mechanics, along with the brief history of how it emerged. Al- though Sommerfelds idea of elliptical orbits has been replaced by wave mechanics, the fine struc- ture constant he introduced has remained as an important parameter in the field of ...

  16. Studies on the distribution of radioactivity in the organism during constant intravenous infusion of tracer amino acids and on the calculation of the rate of tissue protein synthesis in rats

    International Nuclear Information System (INIS)

    Simon, O.; Bergner, H.; Wolf, E.

    1978-01-01

    Male wistar rats (100 p body weight) were infused into the tail vein with 14 C-leucine and 14 C-lysine simultaneously for 0.5; 1.0; 2.0; 3.0; 4.5; 6.0 and 7.0 hours. At the end of the infusion the specific radioactivity was determined of the free leucine and lysine in the blood plasma, liver, M. gastrocnemius, small intestine, and colon as well as of the protein-bound leucine and lysine. In all the tissues tested the specific radioactivity of the free amino acids attained a plateau during the 6-hour and 7-hour infusions. The rate constants for the increase were calculated for each organ tested. The two amino acids used are suitable for calculating the fractional rate of protein synthesis in tissues. The values of the fractional rate of protein synthesis calculated on the basis of the 6-hour and 7-hour infusions were: 54+-7.7%/day for the liver, 9.4+-1.2%/day for the muscles, 89+-12.2%/day for the small intestine, and 42+-5.9%/day for the colon. The simultaneous application of two tracer amino acids is recommendable for estimating the precursor pool of the protein synthesis and the more accurate calculation of the rate of protein synthesis. (author)

  17. Systematics of constant roll inflation

    Science.gov (United States)

    Anguelova, Lilia; Suranyi, Peter; Wijewardhana, L. C. R.

    2018-02-01

    We study constant roll inflation systematically. This is a regime, in which the slow roll approximation can be violated. It has long been thought that this approximation is necessary for agreement with observations. However, recently it was understood that there can be inflationary models with a constant, and not necessarily small, rate of roll that are both stable and compatible with the observational constraint ns ≈ 1. We investigate systematically the condition for such a constant-roll regime. In the process, we find a whole new class of inflationary models, in addition to the known solutions. We show that the new models are stable under scalar perturbations. Finally, we find a part of their parameter space, in which they produce a nearly scale-invariant scalar power spectrum, as needed for observational viability.

  18. The Impact of use of Double Set-up on Infection Rates in Revision Total Knee Replacement and Limb Salvage Procedures

    Directory of Open Access Journals (Sweden)

    Jennifer Waterman

    2015-03-01

    Full Text Available A retrospective analysis was performed to determine the impact of utilizing a double set-up procedure on reducing infection rates revision total knee and limb salvage procedures in patients with known joint infection.  Eighteen cases fit selection criteria.  The recurrence rate of infection was 5.5% which is less than reported recent literature review.   This suggests the use of a double set-up in combination with other infection reducing protocols may help further reduce recurrent infection.  Keywords: double set-up, infection, revision total knee arthroplasty, limb-salvage

  19. Use of an exchange method to estimate the association and dissociation rate constants of cadmium complexes formed with low-molecular-weight organic acids commonly exuded by plant roots.

    Science.gov (United States)

    Schneider, André; Nguyen, Christophe

    2011-01-01

    Organic acids released from plant roots can form complexes with cadmium (Cd) in the soil solution and influence metal bioavailability not only due to the nature and concentration of the complexes but also due to their lability. The lability of a complex influences its ability to buffer changes in the concentration of free ions (Cd); it depends on the association (, m mol s) and dissociation (, s) rate constants. A resin exchange method was used to estimate and (m mol s), which is the conditional estimate of depending on the calcium (Ca) concentration in solution. The constants were estimated for oxalate, citrate, and malate, three low-molecular-weight organic acids commonly exuded by plant roots and expected to strongly influence Cd uptake by plants. For all three organic acids, the and estimates were around 2.5 10 m mol s and 1.3 × 10 s, respectively. Based on the literature, these values indicate that the Cd- low-molecular-weight organic acids complexes formed between Cd and low-molecular-weight organic acids may be less labile than complexes formed with soil soluble organic matter but more labile than those formed with aminopolycarboxylic chelates. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  20. Postprandial appetite ratings are reproducible and moderately related to total day energy intakes, but not ad libitum lunch energy intakes, in healthy young women.

    Science.gov (United States)

    Tucker, Amy J; Heap, Sarah; Ingram, Jessica; Law, Marron; Wright, Amanda J

    2016-04-01

    Reproducibility and validity testing of appetite ratings and energy intakes are needed in experimental and natural settings. Eighteen healthy young women ate a standardized breakfast for 8 days. Days 1 and 8, they rated their appetite (Hunger, Fullness, Desire to Eat, Prospective Food Consumption (PFC)) over a 3.5 h period using visual analogue scales, consumed an ad libitum lunch, left the research center and recorded food intake for the remainder of the day. Days 2-7, participants rated their at-home Hunger at 0 and 30 min post-breakfast and recorded food intake for the day. Total area under the curve (AUC) over the 180 min period before lunch, and energy intakes were calculated. Reproducibility of satiety measures between days was evaluated using coefficients of repeatability (CR), coefficients of variation (CV) and intra-class coefficients (ri). Correlation analysis was used to examine validity between satiety measures. AUCs for Hunger, Desire to Eat and PFC (ri = 0.73-0.78), ad libitum energy intakes (ri = 0.81) and total day energy intakes (ri​ = 0.48) were reproducible; fasted ratings were not. Average AUCs for Hunger, Desire to Eat and PFC, Desire to Eat at nadir and PFC at fasting, nadir and 180 min were correlated to total day energy intakes (r = 0.50-0.77, P < 0.05), but no ratings were correlated to lunch consumption. At-home Hunger ratings were weakly reproducible but not correlated to reported total energy intakes. Satiety ratings did not concur with next meal intake but PFC ratings may be useful predictors of intake. Overall, this study adds to the limited satiety research on women and challenges the accepted measures of satiety in an experimental setting. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Epicardial, pericardial and total cardiac fat and cardiovascular disease in type 2 diabetic patients with elevated urinary albumin excretion rate

    DEFF Research Database (Denmark)

    Christensen, Regitse H.; Von Scholten, Bernt J.; Hansen, Christian S.

    2017-01-01

    of 200 patients with type 2 diabetes and elevated urinary albumin excretion rate (UAER). Methods Cardiac adipose tissue was measured from baseline echocardiography. The composite endpoint comprised incident cardiovascular disease and all-cause mortality. Coronary artery calcium, carotid intima media.......7, p = 0.017) models. Cardiac adipose tissue (p = 0.033) was associated with baseline coronary artery calcium (model 1) and interleukin-8 (models 1-3, all p type 2 diabetes patients without coronary artery disease, high cardiac adipose tissue levels were associated...

  2. Direct and Indirect Determinations of Elementary Rate Constants H + O2: Chain Branching; the Dehydration of tertiary-Butanol; the Retro Diels-Alder Reaction of Cyclohexene; the Dehydration of Isopropanol

    Science.gov (United States)

    Heyne, Joshua S.

    Due to growing environmental concern over the continued use of fossil fuels, methods to limit emissions and partially replace fossil fuel use with renewable biofuels are of considerable interest. Developing chemical kinetic models for the chemistry that affects combustion properties is important to understanding how new fuels affect combustion energy conversion processes in transportation devices. This thesis reports the experimental study of several important reactions (the H + O2 branching reaction, the key decomposition reactions of tertiary-butanol, the dehydration reaction of isopropanol, and the retro Diels-Alder reaction of cyclohexene) and develops robust analysis methods to estimate the absolute uncertainties of specific elementary rate constants derived from the experimental data. In the study of the above reactions, both a direct and indirect rate constant determination technique with associated uncertainty estimation methodologies are developed. In the study of the decomposition reactions, a direct determination technique is applied to experimental data gathered in preparation of this thesis. In the case of the dehydration reaction of tertiary-butanol and the retro Diels-Alder reaction of cyclohexene, both of which are used as internal standards for relative rate studies (Herzler et al. 1997) and chemical thermometry (Rosado-Reyes et al. 2013) , analysis showed an ˜20 K difference in the reaction rate between the reported results and the previous recommendations. In light of these discrepancies, an uncertainty estimation of previous recommendations illuminated an uncertainty of at least 20 K for the dehydration reaction of tertiary-butanol and the retro Diels-Alder reaction of cyclohexene, thus resolving the discrepancies. The determination of the H + O2 branching reaction and decomposition reactions of isopropanol used an indirect determination technique. The uncertainty of the H + O2 branching reaction rate is shown to be underestimated by previous

  3. Mathematical modeling of radiation-chemical processes in HNO3 solutions of Pu. 5. Effect of [HNO3] on rate constants of radiation-chemical and chemical reactions of Pu ions

    International Nuclear Information System (INIS)

    Vladimirova, M.V.

    1993-01-01

    Dependences of rate constants on [HNO 3 ] are obtained for the reactions Pu(IV) + OH, Pu(IV) + NO 3 , Pu(V) + NO 2 , Pu(III) + NO 2 , Pu(V) + Pu(III), Pu(IV) + Pu(IV), and Pu(V) + Pu(V). These dependences are obtained for [HNO 3 ] = 0.3-6 M using existing experimental and literature data and the data obtained using mathematical modeling. The correctness of the resulting dependences is checked by comparing the calculated and experimental kinetic laws for the behavior of Pu in 0.3, 0.4, 0.6, and 1.6 M HNO 3 . 17 refs., 15 figs., 2 tabs

  4. Cosmological constants and variations

    International Nuclear Information System (INIS)

    Barrow, John D

    2005-01-01

    We review properties of theories for the variation of the gravitation and fine structure 'constants'. We highlight some general features of the cosmological models that exist in these theories with reference to recent quasar data that is consistent with time-variation in the fine structure 'constant' since a redshift of 3.5. The behaviour of a simple class of varying alpha cosmologies is outlined in the light of all the observational constraints. We also discuss some of the consequences of varying 'constants' for oscillating universes and show by means of exact solutions that they appear to evolve monotonically in time even though the scale factor of the universe oscillates

  5. Transition state theory thermal rate constants and RRKM-based branching ratios for the N((2)D) + CH(4) reaction based on multi-state and multi-reference ab initio calculations of interest for the Titan's chemistry.

    Science.gov (United States)

    Ouk, Chanda-Malis; Zvereva-Loëte, Natalia; Scribano, Yohann; Bussery-Honvault, Béatrice

    2012-10-30

    Multireference single and double configuration interaction (MRCI) calculations including Davidson (+Q) or Pople (+P) corrections have been conducted in this work for the reactants, products, and extrema of the doublet ground state potential energy surface involved in the N((2)D) + CH(4) reaction. Such highly correlated ab initio calculations are then compared with previous PMP4, CCSD(T), W1, and DFT/B3LYP studies. Large relative differences are observed in particular for the transition state in the entrance channel resolving the disagreement between previous ab initio calculations. We confirm the existence of a small but positive potential barrier (3.86 ± 0.84 kJ mol(-1) (MR-AQCC) and 3.89 kJ mol(-1) (MRCI+P)) in the entrance channel of the title reaction. The correlation is seen to change significantly the energetic position of the two minima and five saddle points of this system together with the dissociation channels but not their relative order. The influence of the electronic correlation into the energetic of the system is clearly demonstrated by the thermal rate constant evaluation and it temperature dependance by means of the transition state theory. Indeed, only MRCI values are able to reproduce the experimental rate constant of the title reaction and its behavior with temperature. Similarly, product branching ratios, evaluated by means of unimolecular RRKM theory, confirm the NH production of Umemoto et al., whereas previous works based on less accurate ab initio calculations failed. We confirm the previous findings that the N((2)D) + CH(4) reaction proceeds via an insertion-dissociation mechanism and that the dominant product channels are CH(2)NH + H and CH(3) + NH. Copyright © 2012 Wiley Periodicals, Inc.

  6. 78 FR 56646 - Determination of Total Amounts of Fiscal Year 2014 WTO Tariff-Rate Quotas for Raw Cane Sugar and...

    Science.gov (United States)

    2013-09-13

    ... Secretary Determination of Total Amounts of Fiscal Year 2014 WTO Tariff- Rate Quotas for Raw Cane Sugar and Certain Sugars, Syrups and Molasses AGENCY: Office of the Secretary, USDA. ACTION: Notice. SUMMARY: The... sugar at 1,117,195 metric tons raw value (MTRV). The Secretary also announces the establishment of the...

  7. Repeatability and individual correlates of basal metabolic rate and total evaporative water loss in birds : A case study in European stonechats

    NARCIS (Netherlands)

    Versteegh, Maaike A.; Heim, Barbara; Dingemanse, Niels J.; Tieleman, B. Irene

    Basal metabolic rate (BMR) and total evaporative water loss (TEWL) are thought to have evolved in conjunction with life history traits and are often assumed to be characteristic features of an animal. Physiological traits can show large intraindividual variation at short and long timescales, yet

  8. Impact of total PSA, PSA doubling time and PSA velocity on detection rates of 11C-Choline positron emission tomography in recurrent prostate cancer

    NARCIS (Netherlands)

    Rybalov, Maxim; Breeuwsma, Anthonius J.; Leliveld, Anna M.; Pruim, Jan; Dierckx, Rudi A.; de Jong, Igle J.

    PURPOSE: To evaluate the effect of total PSA (tPSA) and PSA kinetics on the detection rates of (11)C-Choline PET in patients with biochemical recurrence (BCR) after radical prostatectomy (RP) or external beam radiotherapy (EBRT). METHODS: We included 185 patients with BCR after RP (PSA >0.2 ng/ml)

  9. The cosmological constant problem

    International Nuclear Information System (INIS)

    Dolgov, A.D.

    1989-05-01

    A review of the cosmological term problem is presented. Baby universe model and the compensating field model are discussed. The importance of more accurate data on the Hubble constant and the Universe age is stressed. 18 refs

  10. Water cut measurement of oil–water flow in vertical well by combining total flow rate and the response of a conductance probe

    International Nuclear Information System (INIS)

    Chen, Jianjun; Xu, Lijun; Cao, Zhang; Zhang, Wen; Liu, Xingbin; Hu, Jinhai

    2015-01-01

    In this paper, a conductance probe-based well logging instrument was developed and the total flow rate is combined with the response of the conductance probe to estimate the water cut of the oil–water flow in a vertical well. The conductance probe records the time-varying electrical characteristics of the oil–water flow. Linear least squares regression (LSR) and nonlinear support vector regression (SVR) were used to establish models to map the total flow rate and features extracted from the probe response onto the water cut, respectively. Principal component analysis (PCA) and partial least squares analysis (PLSA) techniques were employed to reduce data redundancy within the extracted features. An experiment was carried out in a vertical pipe with an inner diameter of 125 mm and a height of 24 m in an experimental multi-phase flow setup, Daqing Oilfield, China. In the experiment, oil–water flow was used and the total flow rate varied from 10 to 200 m 3 per day and the water cut varied from 0% to 100%. As a direct comparison, the cases were also studied when the total flow rate was not used as an independent input to the models. The results obtained demonstrate that: (1) the addition of the total flow rate as an input to the regression models can greatly improve the accuracy of water cut prediction, (2) the nonlinear SVR model performs much better than the linear LSR model, and (3) for the SVR model with the total flow rate as an input, the adoption of PCA or PLSA not only decreases the dimensions of inputs, but also increases prediction accuracy. The SVR model with five PCA-treated features plus the total flow rate achieves the best performance in water cut prediction, with a coefficient of determination (R 2 ) as high as 0.9970. The corresponding root mean squared error (RMSE) and mean quoted error (MQE) are 0.0312% and 1.99%, respectively. (paper)

  11. Increased mortality by septicemia, interstitial pneumonitis and pulmonary fibrosis among bone marrow transplant recipients receiving an increased mean dose rate of total irradiation

    International Nuclear Information System (INIS)

    Ringden, O.; Baaryd, I.; Johansson, B.

    1983-01-01

    Seven bone marrow transplant recipients with acute lymphoblastic leukemia receiving a mean dose rate of 0.07 Gy/min of total body irradiation towards the pelvic midpoint and the lungs had an increased (p<0.01) overall death rate of 86 per cent compared with 33 per cent among 27 patients with acute non-lymphoblastic leukemia or acute lymphoblastic leukemia treated with a mean dose rate of 0.04 Gy/min. Among the patients receiving the higher dose rate there was an increased mortality in causes related to radiation toxicity like early septicemia, interstitial pneumonitis and pulmonary fibrosis, compared with all patients receiving the lower dose rate (p<0.01) and also with 10 patients from this group with acute lymphoblastic leukemia (p<0.02). (Auth.)

  12. Isotopic and chemical dilution effects on the vibrational relaxation rate of some totally symmetric motions of liquid acetonitrile

    International Nuclear Information System (INIS)

    Marri, E.; Morresi, A.; Paliani, G.; Cataliotti, R.S.; Giorgini, M.G.

    1999-01-01

    The vibrational dephasing of the ν 1 (C-H, C-D stretching) and ν 3 (C-H, C-D bending) symmetric motions of liquid acetonitrile in its light and fully deuterated forms has been studied in the frame of the vibrational time correlation functions obtained as Fourier transforms of the isotropic Raman spectral distributions and interpreted within the Kubo theory. In addition, the experimental isotropic profiles have been analysed within the bandshape approach formulated by analytical Fourier transformation of the Kubo vibrational time correlation functions in order to derive the relaxation parameters in the frequency domain. The effects of the isotopic (CH 3 CN/CD 3 CN and vice versa) and chemical (CCl 4 ) dilution on the bandshapes and on the vibrational relaxation parameters have been studied. It was observed that the decay rate of ν 1 mode is insensitive to the isotopic dilution but varies appreciably with chemical (CCl 4 ) dilution. The vibrational dephasing of ν 3 mode is qualitatively, but not quantitatively, affected in the same way by chemical dilution and shows a slower modulation regime than that exhibited by the stretching mode. Unlikely from the latter, the ν 3 mode results are slightly affected by the isotopic dilution. Phase relaxation mechanisms of these two motions of acetonitrile in the liquid state are proposed on the basis of these data, and a comparison is made with the results earlier published. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  13. Determinação das constantes cinéticas de degradação do ácido ascórbico em purê de pêssego: efeito da temperatura e concentração Determination of reaction rate constants for ascorbic acid degradation in peach pureé: effect of temperature and concentration

    Directory of Open Access Journals (Sweden)

    Ricardo Peraça Toralles

    2008-03-01

    Full Text Available O ácido ascórbico, vitamina C, é usado extensivamente na indústria de alimentos, não só devido ao seu valor nutricional, mas devido a suas contribuições funcionais na qualidade do produto. Existem muitos estudos sobre a estabilidade cinética do ácido ascórbico em bebidas, mas nenhum estudo foi encontrado sobre as constantes cinéticas de degradação do ácido ascórbico adicionado em purê de pêssego. Neste trabalho, estudou-se a cinética de degradação do ácido ascórbico em purê de pêssego da cultivar Jade, em condições anaeróbicas e na faixa de 70 a 90 °C. As concentrações de purês testadas foram 12, 22 e 32 °Brix. A análise cinética dos dados sugere que a degradação foi significativamente representada pelos modelos cinéticos de zero e primeira ordem. A velocidade de degradação do ácido ascórbico foi dependente da temperatura. A energia de ativação média foi de 45 kJ.mol-1 e independente da concentração de sólidos solúveis.Ascorbic acid (vitamin C is extensively used in the food industry, not only for its nutritional value, but also for its many functional contributions to product quality. There have been many studies on the stability of ascorbic acid in different beverages, but no study was found on the reaction rate constants for ascorbic acid degradation in peach purée. In this work, the degradation of ascorbic acid in Jade peach purée was studied in anaerobic conditions and from 70-90 °C. The peach purée concentrations tested were 12, 22 and 32 °Brix. The kinetic analysis of the data suggests that the degradation was significantly represented by zero and first-order kinetic models. The rate of ascorbic acid degradation in peach purée was temperature dependent. The average activation energy was 45 kJ.mol-1 and independent of the concentration of soluble solids.

  14. Challenges in assessing hospital-level stroke mortality as a quality measure: comparison of ischemic, intracerebral hemorrhage, and total stroke mortality rates.

    Science.gov (United States)

    Xian, Ying; Holloway, Robert G; Pan, Wenqin; Peterson, Eric D

    2012-06-01

    Public reporting efforts currently profile hospitals based on overall stroke mortality rates, yet the "mix" of hemorrhagic and ischemic stroke cases may impact this rate. Using the 2005 to 2006 New York state data, we examined the degree to which hospital stroke mortality rankings varied regarding ischemic versus hemorrhagic versus total stroke. Observed/expected ratio was calculated using the Agency for Healthcare Research and Quality Inpatient Quality Indicator software. The observed/expected ratio and outlier status based on stroke types across hospitals were examined using Pearson correlation coefficients (r) and weighted κ. Overall 30-day stroke mortality rates were 15.2% and varied from 11.3% for ischemic stroke and 37.3% for intracerebral hemorrhage. Hospital risk-adjusted ischemic stroke observed/expected ratio was weakly correlated with its own intracerebral hemorrhage observed/expected ratio (r=0.38). When examining hospital performance group (mortality better, worse, or no different than average), disagreement was observed in 35 of 81 hospitals (κ=0.23). Total stroke mortality observed/expected ratio and rankings were correlated with intracerebral hemorrhage (r=0.61 and κ=0.36) and ischemic stroke (r=0.94 and κ=0.71), but many hospitals still switched classification depending on mortality metrics. However, hospitals treating a higher percent of hemorrhagic stroke did not have a statistically significant higher total stroke mortality rate relative to those treating fewer hemorrhagic strokes. Hospital stroke mortality ratings varied considerably depending on whether ischemic, hemorrhagic, or total stroke mortality rates were used. Public reporting of stroke mortality measures should consider providing risk-adjusted outcome on separate stroke types.

  15. Short communication: Effect of straw inclusion rate in a dry total mixed ration on the behavior of weaned dairy calves.

    Science.gov (United States)

    Groen, M J; Steele, M A; DeVries, T J

    2015-04-01

    The primary objective of this study was to determine the effect of straw inclusion levels on the feeding behavior of young, weaned calves adapted to a dry total mixed ration (TMR) composed of a multitextured concentrate and chopped straw. A secondary objective was to determine how developed feeding patterns persist after calves were switched to a conventional silage-based diet. Ten Holstein bull calves (91 ± 2.4d of age, weighing 136 ± 12.3 kg) were assigned to 1 of 2 treatments: a TMR containing [dry matter (DM) basis] either (1) 85% concentrate and 15% chopped straw for 10 wk (wk 1 to 10) or (2) 85% concentrate and 15% chopped straw for 5 wk (wk 1 to 5), then 70% concentrate and 30% chopped straw for 5 wk (wk 6 to 10). After 10 wk, all animals were transitioned to a TMR containing (DM basis) 42.3% corn silage and 57.7% haylage for 2 wk (wk 11 to 12). During wk 1 to 5, all calves had similar DMI (5.5 kg/d), average daily gain (1.7 kg/d), feed efficiency (3.5 kg of DM/kg of gain), and eating time (151.9 min/d). During wk 6 to 10, calves transitioned to the 70% diet ate less DM (5.5 vs. 7.4 kg/d), grew more slowly (1.3 vs. 1.6 kg/d), sorted more against long forage particles (62.8 vs. 103.8%), and had greater feeding times (194.9 vs. 102.6 min/d). The difference in feeding time occurred only during the first 8 h after feed delivery. Despite similar DMI (5.2 kg/d) and average daily gain (1.1 kg/d) in wk 11 to 12, differences in behavior were observed resulting from previous diets. In wk 11 to 12, calves previously fed the 70% diet continued to have a longer meal immediately after feed delivery. Overall, the results indicate that diluting a dry TMR containing a multitextured concentrate and chopped straw with more straw resulted in calves spending more time feeding and having longer meals immediately after feed delivery; this feeding pattern carried over after calves were transitioned to a silage-based ration. Copyright © 2015 American Dairy Science Association

  16. Constant Proportion Debt Obligations (CPDOs)

    DEFF Research Database (Denmark)

    Cont, Rama; Jessen, Cathrine

    2012-01-01

    be made arbitrarily small—and thus the credit rating arbitrarily high—by increasing leverage, but the ratings obtained strongly depend on assumptions on the credit environment (high spread or low spread). More importantly, CPDO loss distributions are found to exhibit a wide range of tail risk measures......Constant Proportion Debt Obligations (CPDOs) are structured credit derivatives that generate high coupon payments by dynamically leveraging a position in an underlying portfolio of investment-grade index default swaps. CPDO coupons and principal notes received high initial credit ratings from...... the major rating agencies, based on complex models for the joint transition of ratings and spreads for all names in the underlying portfolio. We propose a parsimonious model for analysing the performance of CPDO strategies using a top-down approach that captures the essential risk factors of the CPDO. Our...

  17. The relation of putamen nucleus 6-[18F]fluoro-L-m-tyrosine uptake to total Unified Parkinson's Disease Rating Scale scores

    International Nuclear Information System (INIS)

    Buchy, R.

    2002-01-01

    The contribution of dopaminergic deficiency in the striatum to the severity of locomotor disability in Parkinson's disease has been consistently shown with 6-[ 18 F]fluoro-L-DOPA in positron emission tomography. Recently, 6-[ 18 F]fluoro-L-m-tyrosine, an alternative tracer with similar distribution kinetics has been used to facilitate data analysis. Locomotor disability in Parkinson's disease can be measured using the Unified Parkinson's Disease Rating Scale. The Unified Parkinson's Disease Rating Scale was used in conjunction with 6-[ 18 F]fluoro-L-m-tyrosine -PET to clinically examine a group of five Parkinson's disease patients. An inverse relation similar to that previously demonstrated with 6-[ 18 F]fluoro-L-DOPA was found between the putamen nucleus 6-[ 18 F]fluoro-L-m-tyrosine influx constant and Unified Parkinson's Disease Rating Scale score. This finding suggests that like 6-[ 18 F]fluoro-L-m-tyrosine can be used to accurately measure the degree of locomotor disability caused by Parkinson's disease. (author)

  18. Effects of radiation and α-tocopherol on saliva flow rate, amylase activity, total protein and electrolyte levels in oral cavity cancer

    Directory of Open Access Journals (Sweden)

    Chitra S

    2008-01-01

    Full Text Available Objective: The objective of the present study was to evaluate early and late effects of radiation and a-tocopherol on the secretion rate of saliva and on selected saliva salivary parameters in oral cavity cancer patients. Patients & Methods: Eighty-nine histologically confirmed oral cavity cancer patients (OCC were enrolled in the study. Resting whole saliva was collected before, during and at the end of the radiation therapy (RT and simultaneous supplementation with α - tocopherol to the radiation treated patients (RT + AT. Results: Salivary flow rate, pH, amylase activity, total protein, sodium and potassium were analyzed. Increased pH, potassium and decreased flow rate, amylase activity, protein content and sodium were observed in 6 weeks of radiation treated patients when compared to OCC patients. A significant improvement of those parameters was observed on α - tocopherol supplementation in RT + AT patients. Conclusion: Supplementation with α - tocopherol improves the salivary flow rate thereby, maintains salivary parameters.

  19. Radiographic constant exposure technique

    DEFF Research Database (Denmark)

    Domanus, Joseph Czeslaw

    1985-01-01

    The constant exposure technique has been applied to assess various industrial radiographic systems. Different X-ray films and radiographic papers of two producers were compared. Special attention was given to fast film and paper used with fluorometallic screens. Radiographic image quality...... was tested by the use of ISO wire IQI's and ASTM penetrameters used on Al and Fe test plates. Relative speed and reduction of kilovoltage obtained with the constant exposure technique were calculated. The advantages of fast radiographic systems are pointed out...

  20. Revision rates for metal-on-metal hip resurfacing and metal-on-metal total hip arthroplasty – a systematic review

    DEFF Research Database (Denmark)

    Ras Sørensen, Sofie-amalie L.; Jørgensen, Henrik L.; Sporing, Sune L.

    2016-01-01

    Purpose To compare revision rates of metal-on-metal (MoM) hip resurfacing (HRS) and MoM total hip arthroplasty (THA), as well as the primary causes for revisions. Methods The PubMed database was queried for potentially relevant articles addressing MoMTHA and MoMHRS, a total of 51 articles were....... The odds ratio was 1.25 (1.03:1.53) 95% CI (p = 0.03) (MoMHRS vs. MoMTHA). The studies of hip prostheses were separated into 2 categories of short- and long-term (more or less than 5 years). Short-term revision rate for MoMTHA was 4.5% after 4.8 years, and for MoMHRS 4.0% after 4.2 years. The odds ratio...