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101.
Barone V Bloino J Monti S Pedone A Prampolini G 《Physical chemistry chemical physics : PCCP》2011,13(6):2160-2166
Classical all-atom molecular dynamics (MD) simulations and quantum mechanical (QM) time-dependent density functional theory (TD-DFT) calculations are employed to study the conformational and photophysical properties of the first emitter excited state of tetramethyl-rhodamine iso-thiocyanate fluorophore in aqueous solution. For this purpose, a specific and accurate force field has been parameterised from QM data to model the fluorophore's first bright excited state. During the MD simulations, the consequences of the π→π* electronic transition on the structure and microsolvation sphere of the dye has been analysed in some detail and compared to the ground state behaviour. Thereafter, fluorescence has been calculated at the TD-DFT level on configurations sampled from the simulated MD trajectories, allowing us to include time dependent solvent effects in the computed emission spectrum. The latter, when compared with the absorption spectrum, reproduces well the experimental Stokes shift, further validating the proposed multilevel computational procedure. 相似文献
102.
Bravo I Díaz-de-Mera Y Aranda A Moreno E Nutt DR Marston G 《Physical chemistry chemical physics : PCCP》2011,13(38):17185-17193
Density Functional Theory (DFT) has been used with an empirically-derived correction for the wavenumbers of vibrational band positions to predict the infrared spectra of several fluorinated esters (FESs). Radiative efficiencies (REs) were then determined using the method of Pinnock et al. and these were used with atmospheric lifetimes from the literature to determine the direct global warming potentials of FESs. FESs, in particular fluoroalkylacetates, alkylfluoroacetates and fluoroalkylformates, are potential greenhouse gases and their likely long atmospheric lifetimes and relatively large REs, compared to their parent HFEs, make them active contributors to global warming. Here, we use the concept of indirect global warming potential (indirect GWP) to assess the contribution to the warming of several commonly used HFEs emitted from the Earth's surface, explicitly taking into account that these HFEs will be converted into the corresponding FESs in the troposphere. The indirect GWP can be calculated using the radiative efficiencies and lifetimes of the HFE and its degradation FES products. We found that the GWPs of those studied HFEs which have the smallest direct GWP can be increased by 100-1600% when taking account of the cumulative effect due to the secondary FESs formed during HFE atmospheric oxidation. This effect may be particularly important for non-segregated HFEs and some segregated HFEs, which may contribute significantly more to global warming than can be concluded from examination of their direct GWPs. 相似文献
103.
Ringkøbing Fjord is a large and shallow brackish lagoon on the west coast of Denmark that has gone through two environmental regime shifts in recent decades. Different intervention strategies, including nutrient abatement and the construction of facilities to increase the water exchange between the lagoon and the outside sea, have been proposed to achieve good water quality in terms of trophic state and conditions for waterfowl. The selection of an intervention strategy is a complex decision-making problem in which several conflicting objectives, like costs of application and environmental or social impacts, must be taken into account simultaneously. We propose a PC-based decision support system, called the Generic Multi-Attribute Analysis system, to deal with such interdisciplinary analyses. It evaluates the intervention strategies by means of an additive multiattribute utility model accounting for imprecision of the various components of the analysis, such as intervention strategy performances and decision-makers’ preferences. Also, it implements what is known as decision making with partial information, through the application of Monte Carlo simulation techniques. This enables a straightforward analysis of the difference between an anthropocentrist and an ecocentrist view of the problem, from which a final recommendation can be reached. 相似文献
104.
We introduce a new method to study compact spaceliken-submanifolds in de Sitter spacesS
q
n+q
by means of certain integral formulas which have a very clear geometric meaning. As a first application of them we obtain
a Bernstein type result for complete maximal submanifolds inS
q
n+q
. As for surfaces, we also get a uniqueness result for compact spacelike surfaces inS
q
2+q
with parallel mean curvature vector field.
Partially supported by a DGICYT Grant No. PB91-0705-C02-02
Partially supported by a DGICYT Grant No. PB91-0731 相似文献
105.
106.
3-Hydroxy-1-phenyl-2-pyrazolin-5-one 1 reacts with primary, secondary and allylic alcohols under catalytic acidic conditions and in the presence of 3 Å molecular sieves, to afford 3-alkoxy-1-phenyl-2-pyrazolin-5-ones 3 . 相似文献
107.
Duc Hanh Nguyen Frdric Hebrard Josep Duran Alfonso Polo Martine Urrutigoíty Philippe Kalck 《应用有机金属化学》2005,19(1):30-34
Three different kinds of representative monoterpenic alcohol are involved in the palladium‐catalysed cyclocarbonylation reaction. Lactone formation is shown to occur when cyclic ( 1 ), tertiary ( 3 ) and primary allylic alcohol ( 7 ) functions are reacted, in the presence of CO with [HPd(SnCl3)L2] as the active catalytic species. Good yields and selectivities can easily be reached for isopulegol ( 1 ), and dihydromyrcenol ( 3 ). However, more modest results are obtained for the functionalization of geraniol into the original lactone ( 9 ). This lactone can be largely favoured by using a basic chelating diphosphine ligand such as 1,4‐bis(diphenylphosphino)butane. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
108.
Francesca Lionetto Alfonso Maffezzoli 《Journal of Polymer Science.Polymer Physics》2005,43(5):596-602
Ultrasonic wave propagation, dynamic mechanical analysis, and dielectric analysis were used to monitor relaxation phenomena during the nonisothermal postcure of unsaturated polyester networks. The measurements covered 6 decades of frequency. As a result, the residual reactive groups, immobilized in the glassy state by vitrification during an isothermal cure step, gained molecular mobility, which promoted the formation of additional crosslinks. After the postcure, the reaction was complete, and the maximum achievable glass‐transition temperature was reached. Moreover, the frequency and temperature dependence of the two relaxations, one related to the glass‐transition temperature of the partially cured sample and the other to the glass transition of the fully cured sample, was evaluated. The Williams–Landel–Ferry equation was used to model the frequency dependence of the main α‐relaxation data obtained with the different techniques. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 596–602, 2005 相似文献
109.
A necessary and sufficient condition of correctness of extremal problems for lower semicontinuous functionals defined in metric spaces is given.This work was performed under the auspices of the Italian Research Council, Grant No. 115-3083-0-5179. 相似文献
110.
Alfonso Reinoza 《Mathematical Programming》1985,31(3):307-320
Global Newton methods for computing solutions of nonlinear systems of equations have recently received a great deal of attention.
By using the theory of generalized equations, a homotopy method is proposed to solve problems arising in complementarity and
mathematical programming, as well as in variational inequalities. We introduce the concepts of generalized homotopies and
regular values, characterize the solution sets of such generalized homotopies and prove, under boundary conditions similar
to Smale’s [10], the existence of a homotopy path which contains an odd number of solutions to the problem. We related our
homotopy path to the Newton method for generalized equations developed by Josephy [3]. An interpretation of our results for
the nonlinear programming problem will be given. 相似文献