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91.
Gómez-Carrasco S Roncero O González-Sánchez L Hernández ML Alvariño JM Paniagua M Aguado A 《The Journal of chemical physics》2005,123(11):114310
Global three-dimensional adiabatic potential-energy surfaces for the excited 2(3)A" and 1(3)A' triplet states of OHF are obtained to study the F(2P)+OH(2pi)-->O(3P)+HF(1sigma+) reaction. Highly accurate ab initio calculations are obtained for the two excited electronic states and fitted to analytical functions with small deviations. The reaction dynamics is studied using a wave-packet treatment within a centrifugal sudden approach, which is justified by the linear transition state of the two electronic states studied. The reaction efficiency presents a marked preference for perpendicular orientation of the initial relative velocity vector and the angular momentum of the OH reagent, consistent in the body-fixed frame used with an initial collinear geometry which facilitates the access to the transition state. It is also found that the reaction cross section presents a rather high threshold so that, in an adiabatic picture, the two excited triplet states do not contribute to the rate constant at room temperature. Thus, only the lowest triplet state leads to reaction under these conditions and the simulated rate constants are too low as compared with the experimental ones. Such disagreement is likely to be due to nonadiabatic transitions occurring at the conical intersections near the transition state for this reaction. 相似文献
92.
Seidel S Bionta RM Blewitt G Bratton CB Casper D Ciocio A Claus R Dye ST Errede S Foster GW Gajewski W Ganezer KS Goldhaber M Haines TJ Jones TW Kielczewska D Kropp WR Learned JG LoSecco JM Matthews J Park HS Price L Reines F Schultz J Shumard E Sinclair D Sobel HW Stone JL Sulak L Svoboda R Thornton G van der Velde JC Wuest C 《Physical review letters》1988,61(22):2522-2525
93.
94.
Jaime Fernandez Rico Rafael Lapez Miguel Paniagua Jose Ignacio Fernandez-Alonso 《International journal of quantum chemistry》1986,29(5):1155-1164
In a previous paper we have shown that the long-range potential generated by the two-center distributions can be written as a sum of two multipolar expansions centered at the terminal atoms and defined so that the two series of multipoles be minimal. In this paper we show that both charge distributions and short-range potentials can also be separated in atomic contributions in a way consistent with the above mentioned partition of the long-range potentials. 相似文献
95.
González-Lezana T Aguado A Paniagua M Roncero O 《The Journal of chemical physics》2005,123(19):194309
The H(+)+D(2) and D(+)+H(2) reactive collisions are studied using a recently proposed adiabatic potential energy surface of spectroscopic accuracy. The dynamics is studied using an exact wave packet method on the adiabatic surface at energies below the curve crossing occurring at approximately 1.5 eV above the threshold. It is found that the reaction is very well described by a statistical quantum method for a zero total angular momentum (J) as compared with the exact ones, while for higher J some discrepancies are found. For J >0 different centrifugal sudden approximations are proposed and compared with the exact and statistical quantum treatments. The usual centrifugal sudden approach fails by considering too high reaction barriers and too low reaction probabilities. A new statistically modified centrifugal sudden approach is considered which corrects these two failures to a rather good extent. It is also found that an adiabatic approximation for the helicities provides results in very good agreement with the statistical method, placing the reaction barrier properly. However, both statistical and adiabatic centrifugal treatments overestimate the reaction probabilities. The reaction cross sections thus obtained with the new approaches are in rather good agreement with the exact results. In spite of these deficiencies, the quantum statistical method is well adapted for describing the insertion dynamics, and it is then used to evaluate the differential cross sections. 相似文献
96.
S. Solís J. Paniagua J. C. Martínez M. Asomoza 《Journal of Sol-Gel Science and Technology》2006,37(2):125-127
The enzyme papain was adsorbed on mesoporous silica at 4°C and pH values between 3 and 11. From the adsorption kinetic data,
the rate constant for the process was evaluated. The concentration of the enzyme in solution was calculated by monitoring
the absorbance at 280 nm, and the quantity of papain bound to the solid was evaluated from the initial and residual soluble
enzyme concentrations. The best results were observed for papain adsorption at pH 5.0; under these conditions, the desorption
of the enzyme was <5%. 相似文献
97.
S. Solís J. C. Martínez J. Paniagua M. Asomoza 《Journal of Sol-Gel Science and Technology》2006,37(2):121-123
The adsorption of a cysteine enzyme, on mesoporous silica with high specific surface area synthesized by the sol-gel method,
was studied in a heat flow calorimeter, to determine the energy involved in the adsorption process of the protein. The adsorption
was carried out at a constant temperature of 30°C to avoid the denaturation of the enzyme. The observed results indicate that
the obtained biomaterials (silica-enzyme) have possibilities for their application in several biotechnology processes.
The heat of papain adsorption and the solid-enzyme (SiO2-Papain) interactions at different pH are presented. 相似文献
98.
99.
A. Baeza M. Del Rio C. Miro J. Paniagua 《Journal of Radioanalytical and Nuclear Chemistry》1991,152(1):175-188
With the object of quantifying the radiological impact that the Almaraz Nuclear Power Station, situated beside the Tajo river in Spain, induces on its ecosystem, since 1986 we have been carrying out multiple gamma-spectrometric studies and determinations of90Sr concentrations on the receptor media: surface waters, sediments, fishes, aerosols, and soils, in the two likeliest critical transmission pathways of transmission of the radioactive contamination. The principal results are summarized in the present work, and they allow the impact to be quantified, as well as the most probable source to be assigned for each of the levels detected. 相似文献
100.
Arati Nanda Pati Kehinde Ladipo David Paniagua Roland Glowinski 《Mathematical and Computer Modelling》2011,53(1-2):21-41
In this article we discuss an application of a Lagrange multiplier based fictitious domain method for the simulation of moving leaflets in an unsteady flow generated by pressure gradients during the systolic phase of the cardiac cycle in three dimensional geometry. The mathematical model includes the Navier–Stokes equations coupled with the Euler–Newton equations describing fluid–structure interaction for the generalized Neumann boundary conditions on upstream and downstream boundaries. The solution method includes the finite element method combined with an operator-splitting scheme, where the fictitious formulation allows the flow calculations to be in a fixed rectangular parallelepiped to predict the dynamic structural positions and flow field during the valve opening and closing phases. 相似文献