Search results for "DIPOLE"
showing 10 items of 982 documents
Dynamic fluctuations of dipolar semiflexible filaments
2005
On the basis of the model of a flexible magnetic filament, the characteristics of their thermal fluctuations are considered. The crossover of the time dependence of the mean quadratic displacement from t(3/4) to t(1/2) at the magnetic field increase is found. Two characteristic mechanisms of the magnetization relaxation time distribution--straightening of the thermal undulations and excitation of the bending modes of the free ends under the action of an ac magnetic field--are described. In both cases, the characteristic scaling law omega(-3/4) of the magnetic susceptibility in a high-frequency range is found.
Site selectivity in excited-state intramolecular proton transfer in flavonols
2001
Abstract To investigate 4′-(diethylamino) (FET) and 4′-N-(15-azacrown-5) (FCR) derivatives of 3-hydroxyflavone in binary solvents and erythrocyte ghosts, we used the red-edge excitation spectroscopy (REES). The results obtained prove the existence of spectral heterogeneity of flavonols in the studied systems. The effect manifests itself in the dependence of the efficiency of excited-state intramolecular proton transfer (ESIPT) on the excitation frequency. The electro-optical absorption method (EOAM) was used to measure the dipole moments of the normal form of FET. The electric dipole moments in the ground (μg) and excited Franck–Condon ( μ e FC ) states have the values 22.7×10−30 and 53.3×1…
Reinterpretation of Classic Proton Charge Form Factor Measurements
2020
In 1963, a proton radius of $0.805(11)~\mathrm{fm}$ was extracted from electron scattering data and this classic value has been used in the standard dipole parameterization of the form factor. In trying to reproduce this classic result, we discovered that there was a sign error in the original analysis and that the authors should have found a value of $0.851(19)~\mathrm{fm}$. We additionally made use of modern computing power to find a robust function for extracting the radius using this 1963 data's spacing and uncertainty. This optimal function, the Pad\'{e} $(0,1)$ approximant, also gives a result which is consistent with the modern high precision proton radius extractions.
Laser control of the radiationless decay in pyrazine using the dynamic Stark effect
2014
The laser control of the radiationless decay between the B(3u)(nπ*) and B(2u)(ππ*) states of pyrazine using the dynamic Stark effect has been investigated. A vibronic coupling model Hamiltonian in diabatic representation, including potential energy, transition dipole, and static polarizability surfaces as a function of the four most important vibrational modes of the molecule has been parametrized using multi-reference electronic structure calculations. The interaction of the molecule with a strong non-resonant laser pulse has been analyzed in terms of dressed potential energy surfaces. Because of the large polarizability difference between the vibronically coupled B(3u)(nπ*) and B(2u)(ππ*)…
Interacting induced dipoles polarization model for molecular polarizabilities: application to benzothiazole (A)-benzobisthiazole (B) oligomers AB13A
1998
Abstract We have outlined a method for the calculation of atomic net charges and molecular dipole-dipole, α , dipole-quadrupole, A , and quadrupole-quadrupole, C , polarizabilities which we have successfully applied to benzothiazole (A)-benzobisthiazole (B) oligomers in the series AB1A to AB13A, and the results have been extrapolated to give predictions for polybenzobisthiazole. The calculation of α , A and C has been carried out by the interacting induced dipoles polarization model that calculates tensor effective anisotropic point polarizabilities (method of Applequist). The mean effective atomic αeffpolarizabilities for the monomeric unit are of the same order of magnitud…
Intermolecular coupling influence on conformations of molecules in solution
1994
Abstract The influence of non-specific intermolecular interactions on conformational equilibria of organic molecules is investigated with the help of the London-Debye-Keesom pair coupling potentials. It is shown that in a series of apolar solvents equilibrium constant logarithms are proportional to ζα ≡ Z αs/ R 6s,d, and in a series of polar solvents equilibrium constants logarithms are proportional to ζμ ≡ Z μ2s/ R 6s,d, where Z is the average number of neighbours of a solute molecule in the first coordination sphere, αs is the polarizability, μs the dipole moment of solvent molecules, and R s,d = R s + R d is the sum of the radii of spherical volumes per molecule of solvent (s) and dissol…
Theoretical study of excitation transfer from modified B800 rings of the LH II antenna complex of Rps. acidophila
2002
The recently developed configuration interaction exciton model has been applied to study spectral shifts and B800 to B850 energy transfer rates in a series of modified LH2 light harvesting antenna complexes of the purple bacterium Rhodopseudomonas acidophila. Complexes, where the in vivo B800 bacteriochlorophyll a chromophores are exchanged with different tetrapyrroles including chlorophyll a were studied. Absorption spectra of the modified complexes were simulated by using quantum chemical methods to evaluate site and interaction energies and exciton theory to generate the eigenstates of the chromophore assemblies. Four experimental input parameters: the transition moment of Bchl a, the di…
Effective approach for calculations of absolute stability of proteins using focused dielectric constants
2009
The ability to predict the absolute stability of proteins based on their corresponding sequence and structure is a problem of great fundamental and practical importance. In this work, we report an extensive, refinement and validation of our recent approach (Roca et al., FEBS Lett 2007;581:2065-2071) for predicting absolute values of protein stability DeltaG(fold). This approach employs the semimacroscopic protein dipole Langevin dipole method in its linear response approximation version (PDLD/S-LRA) while using the best fitted values of the dielectric constants epsilon'(p) and epsilon'(eff) for the self energy and charge-charge interactions, respectively. The method is validated on a divers…
The Modelling of Cell Membrane Electrodynamics
2013
Main electrical processes in cells are defined by membranes. The membrane maintains a biochemical environment inside the cell that differs from the outside one, keeping the electrical potential negative inside the cell and organizing the selective transport across the surface. In the paper, it is attempted to explain the cell membrane electrodynamics using modelling experiments with magnetic dipoles. It is shown that the membrane has a definite symmetry or handenness. In addition, a characteristic mechanism of the excited state physics is given. The modelling experiments have also shown that a membrane with different symmetry can exist. Since the electrical processes in these cases are diff…
Strong CP-violation in an effective chiral lagrangian approach
1991
21 páginas, 2 figuras.-- CERN-TH-6071-91