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941.
Scalmani G Frisch MJ Mennucci B Tomasi J Cammi R Barone V 《The Journal of chemical physics》2006,124(9):94107
In this paper we present the theory and implementation of analytic derivatives of time-dependent density functional theory (TDDFT) excited states energies, both in vacuo and including solvent effects by means of the polarizable continuum model. The method is applied to two case studies: p-nitroaniline and 4-(dimethyl)aminobenzonitrile. For both molecules PCM-TDDFT is shown to be successful in supporting the analysis of experimental data with useful insights for a better understanding of photophysical and photochemical pathways in solution. 相似文献
942.
Arfaoui I Bermúdez V Bottari G De Nadai C Jalkanen JP Kajzar F Leigh DA Lubomska M Mendoza SM Niziol J Rudolf P Zerbetto F 《The journal of physical chemistry. B》2006,110(15):7648-7652
Surface enhanced second harmonic generation (SE SHG) experiments on molecular structures, macrocycles, catenanes, and rotaxanes, deposited as monolayers and multilayers by vacuum sublimation on silver, are reported. The measurements show that the molecules form ordered thin films, where the highest degree of order is observed in the case of macrocycle monolayers and the lowest in the case of rotaxane multilayers. The second harmonic generation activity is interpreted in terms of electric field induced second harmonic (EFISH) generation where the electric field is created by the substrate silver atoms. The measured second order nonlinear optical susceptibility for a rotaxane thin film is compared with that obtained by considering only EFISH contribution to SHG intensity. The electric field on the surface of a silver layer is calculated by using the Delphi4 program for structures obtained with TINKER molecular mechanics/dynamics simulations. An excellent agreement is observed between the calculated and the measured SHG susceptibilities. 相似文献
943.
Moggio L De Napoli L Di Blasio B Di Fabio G D'Onofrio J Montesarchio D Messere A 《Organic letters》2006,8(10):2015-2018
[structure: see text] A new and versatile on-line automated solid-phase approach to obtain cyclic PNA (I and III) and cyclic PNA-DNA chimeras (II) in highly pure form has been developed. Starting from a Tentagel matrix functionalized with a 3-chloro-4-hydroxyphenylacetic linker, the synthesis of representative, new cyclic molecules by standard peptide and phosphoramidite-based chemistry has been achieved. 相似文献
944.
Giovanni Colombo Antonio Marigonda 《Calculus of Variations and Partial Differential Equations》2006,25(1):1-31
Closed sets K ⊂
satisfying an external sphere condition with uniform radius (called ϕ-convexity or proximal smoothness) are considered. It
is shown that for
-a.e. x ∊ ∂K the proximal normal cone to K at x has dimension one. Moreover if K is the closure of an open set satisfying a (sharp) nondegeneracy condition, then the De Giorgi reduced boundary is equivalent
to ∂ K and the unit proximal normal equals
-a.e. the (De Giorgi) external normal. Then lower semicontinuous functions f :
with ϕ-convex epigraph are shown, among other results, to be locally BV and twice
-a.e. differentiable; furthermore, the lower dimensional rectifiability of the singular set where f is not differentiable is studied. Finally we show that for
-a.e. x there exists δ (x) > 0 such that f is semiconvex on B(x,δ(x)). We remark that such functions are neither convex nor locally Lipschitz, in general. Methods of nonsmooth analysis and
of geometric measure theory are used.
Work partially supported by M.I.U.R., project “Viscosity, metric, and control theoretic methods for nonlinear partial differential
equations.” 相似文献
945.
[reaction: see text] A novel synthetic pathway to benzoquinazolines from naphthylamines is reported. Benzoquinazoline nucleus was cyclized in good yield from N-protected naphthylamines using hexamethylenetetramine in TFA and potassium ferricyanide in aqueous ethanolic KOH. This method is efficient and convenient with respect to previously reported synthetic pathways. 相似文献
946.
D'Acquarica I Gasparrini F Pierini M Villani C Zappia G 《Journal of separation science》2006,29(10):1508-1516
Dynamic HPLC on enantioselective stationary phases has become a well-established technique to investigate chiral molecules with internal motions that result in stereoinversion and occur on the time scale of the separation process. Kinetic parameters for the on-column interconversion phenomena can be extracted from experimental peak profiles by computer simulation or by direct calculation methods. The technique has been used in a wide range of temperatures and is complementary in scope to dynamic NMR spectroscopy. 相似文献
947.
We report the statistical analysis of the movement of a submicron particle confined in a harmonic potential in the presence of a torque. The absolute value of the torque can be found from the auto- and cross-correlation functions of the particle's coordinates. We experimentally prove this analysis by detecting the torque produced onto an optically trapped particle by an optical beam with orbital angular momentum. 相似文献
948.
Gibbs free-energy calculations based on density functional theory have been used to determine the possible source of failure of boron carbide just above the Hugoniot elastic limit (HEL). A range of B4C polytypes is found to be stable at room pressure. The energetic barrier for shock amorphization of boron carbide is by far the lowest for the B12(CCC) polytype, requiring only 6 GPa approximately = P(HEL) for collapse under hydrostatic conditions. The results clearly demonstrate that the collapse of the B12(CCC) phase leads to segregation of B12 and amorphous carbon in the form of 2-3 nm bands along the (113) lattice direction, in excellent agreement with recent transmission electron microscopy results. 相似文献
949.
Surface plasmon radiation forces 总被引:1,自引:0,他引:1
We report the first experimental observation of momentum transfer from a surface plasmon to a single dielectric sphere. Using a photonic force microscope, we measure the plasmon radiation forces on different polystyrene beads as a function of their distance from the metal surface. We show that the force magnitude at resonance is strongly enhanced compared to a nonresonant illumination. Measurements performed as a function of the probe particle size indicate that optical manipulation by plasmon fields has a strong potential for optical sorting. 相似文献
950.
We present a method for finding exact solutions of Max-Cut, the problem of finding a cut of maximum weight in a weighted graph.
We use a Branch-and-Bound setting that applies a dynamic version of the bundle method as bounding procedure. This approach
uses Lagrangian duality to obtain a “nearly optimal” solution of the basic semidefinite Max-Cut relaxation, strengthened by
triangle inequalities. The expensive part of our bounding procedure is solving the basic semidefinite relaxation of the Max-Cut
problem, which has to be done several times during the bounding process. We review other solution approaches and compare the
numerical results with our method. We also extend our experiments to instances of unconstrained quadratic 0–1 optimization
and to instances of the graph equipartition problem. The experiments show that our method nearly always outperforms all other
approaches. In particular, for dense graphs, where linear programming-based methods fail, our method performs very well. Exact
solutions are obtained in a reasonable time for any instance of size up to n = 100, independent of the density. For some problems of special structure we can solve even larger problem classes. We could
prove optimality for several problems of the literature where, to the best of our knowledge, no other method is able to do
so.
Supported in part by the EU project Algorithmic Discrete Optimization (ADONET), MRTN-CT-2003-504438. 相似文献