Calculation of two-photon absorption spectra of donor-pi-acceptor compounds in solution using quadratic response time-dependent density functional theory

Linear and quadratic response time-dependent density functional theories have been applied to calculate the photophysical properties of donor-pi-acceptor molecules which are known to have large nonlinear absorption. The linear absorption and two-photon absorption spectra predicted using hybrid functionals, including the Coulomb-attenuated model, with continuum solvation models are reported and compared to experiment and to previous theoretical predictions. While the quadratic response with these functionals overestimated the TPA cross sections relative to experiment when a Gaussian linewidth function was used, a fairly good agreement was obtained when a Lorentzian linewidth function was applied. In addition, the comparison of the TPA cross sections calculated by the sum over states with those calculated by the two-state approximation indicates the importance of the higher energy states in TPA, particularly in nondegenerate experiments.     

Prediction of peptide conformation: The adaptive simulated annealing approach

We report the application of the adaptive simulated annealing (ASA) method as a global optimization approach to biomolecular structure determination, using the ECEPP/2 (empirical conformation energy program for peptides) potential energy form. As applied to Met-enkephalin, our optimization results in a conformation that is in agreement with other studies. In addition, a dominant right-handed α-helical conformation is predicted for a 14-residue poly (L-alanine) model peptide in a limited search range. These results show that ASA is an efficient and robust algorithm for conformational analysis. © 1997 by John Wiley & Sons, Inc.     

INDO-FPT calculations of the dihedral angle dependence of 1J(CH) in groups adjacent to a cationic carbon atom

INDO-FPT calculations of ¹J(CH) in the hypothetical ethyl cation are presented in support of a recently derived empirical relationship which describes the effect of a cationic carbon on ¹J(CH) in an adjacent CH_n group.     

On the max-min pursuit game

The max-min linear pursuit game with quadratic performance measure is examined by means of an approximation by a finite sequence of ‘open-loop’ max-min control stages. It is shown that under mild conditions the finite approximation provides a satisfactory representation of the actual game. The limiting behaviour (as the number of stages approaches infinity) is also discussed.     

The Complete Differential Game of Active Target Defense

In the Target–Attacker–Defender differential game, an Attacker missile strives to capture a Target aircraft. The Target tries to escape the Attacker and is aided by a Defender missile which aims at intercepting the Attacker, before the latter manages to close in on the Target. The conflict between these intelligent adversaries is naturally modeled as a zero-sum differential game. The Game of Degree when the Attacker is able to win the Target–Attacker–Defender differential game has not been fully solved, and it is addressed in this paper. Previous attempts at designing the players’ strategies have not been proven to be optimal in the differential game sense. In this paper, the optimal strategies of the Game of Degree in the Attacker’s winning region of the state space are synthesized. Also, the value function is obtained, and it is shown that it is continuously differentiable, and it is the solution of the Hamilton–Jacobi–Isaacs equation. The obtained state feedback strategies are compared to recent results addressing this differential game. It is shown that the correct solution of the Target–Attacker–Defender differential game that provides a semipermeable Barrier surface is synthesized and verified in this paper.

     

Gold Nanocage Assemblies for Selective Second Harmonic Generation Imaging of Cancer Cell

Second harmonic generation (SHG) imaging using near infrared laser light is the key to improving penetration depths, leading to biological understanding. Unfortunately, currently SHG imaging techniques have limited capability due to the poor signal‐to‐noise ratio, resulting from the low SHG efficiency of available dyes. Targeted tumor imaging over nontargeted tissues is also a challenge that needs to be overcome. Driven by this need, in this study, the development of two‐photon SHG imaging of live cancer cell lines selectively by enhancement of the nonlinear optical response of gold nanocage assemblies is reported. Experimental results show that two‐photon scattering intensity can be increased by few orders of magnitude by just developing nanoparticle self‐assembly. Theoretical modeling indicates that the field enhancement values for the nanocage assemblies can explain, in part, the enhanced nonlinear optical properties. Our experimental data also show that A9 RNA aptamer conjugated gold nanocage assemblies can be used for targeted SHG imaging of the LNCaP prostate cancer cell line. Experimental results with the HaCaT normal skin cell lines show that bioconjugated nanocage‐based assemblies demonstrate SHG imaging that is highly selective and will be able to distinguish targeted cancer cell lines from other nontargeted cell types. After optimization, this reported SHG imaging assay could have considerable application for biology.     

A molecular simulation study of a cyclic siloxane with attached biphehylyl 4-allyloxybenzoate mesogens

A molecular simulation study of a cyclic siloxane macromolecule based on a pentamethylcyclosiloxane core and biphenylyl 4-allyloxybenzoate mesogenic units is reported. Molecular dynamics and semi-empirical calculations were used to provide insight into the conformation and the dielectric properties of the material. Out of three proposed conformations of the molecules, a cylindrical conformation was found to be the most probable. The intermolecular interactions were found to be optimized for the case where the mesogenic groups were planar and parallel to each other. The calculated mesogen length and inter-mesogen distances were consistent with available X-ray data. Electrostatic interactions were found to make a very significant contribution to the total energy. For the cylindrical model, the major component of the dipole was calculated to be along the long axis of the molecules. This is consistent with the alignment of the molecules parallel to a low frequency applied electric field as found experimentally.     

Detection of partially resolved carbon-13–proton couplings with selective population inversion (SPI)

In a heteronuclear ¹³C? {¹H} selective population inversion ¹³C NMR spectrum a splitting, resulting from a (CH) coupling over more than one bond, can be detected even when no splitting is observed in the single-frequency ¹³C NMR spectrum. The relationship between the observed splitting, coupling constant and line width is discussed. A method is proposed from which the value of the coupling constant can be estimated, and its application illustrated by the splittings observed in the ¹³C NMR spectra of the mycotoxin, ochratoxin A.