Ultrafast spectroscopy of the solvent dependence of electron transfer in a perylenebisimide dimer

We investigate the photoinduced intramolecular electron-transfer (IET) behavior of a perylenebisimide dimer in a variety of solvents using femtosecond transient absorption spectroscopy. Overlapping photoinduced absorptions and stimulated emission give rise to complicated traces, but they are well fit with a simple kinetic model. IET rates were found to depend heavily on solvent dielectric constant. Good quantitative agreement with rates derived from fluorescence quantum yield and time-resolved fluorescence measurements was found for forward electron transfer and charge recombination rates.     

L 0 - phonon instability in the free-carrier absorption in semiconductors under strong magnetic fields

The LO- phonon damping in an electron-phonon system in the presence of a laser beam and a d. c. magnetic field is discussed. It is shown that near the laser-cyclotron resonance, and for the laser beam propagating perpendicularly to the magnetic field the LO-phonon population in a relatively narrow range of $\text{K}$ may grow with time.     

Circular carrier-frequency photography for observing phase objects

A circular grating is photographed through a phase object which deforms the image of the grating lines. By super-imposing these deformed lines with a master grating on photographic film, moiré patterns are observed. These patterns are interpreted as fringes of constant radial derivative.     

Induced rotational effects in relativity

Using the Kerr metric the angular velocity of the locally nonrotating frame (LNRF) shell is shown to be equal to the value obtained by Thirring. It is established that perfect dragging as seen by a distant observer occurs when the red shift becomes infinite, while no such effect is observed in the LNRF.The work in this paper was commenced while the author was at the Department of Mathematics, University of Sri Lanka Peradeniya Campus, Sri Lanka.     

On nearly pseudocompact spaces

A completely regular space X is called nearly pseudocompact if υX?X is dense in βX?X, where βX is the Stone-?ech compactification of X and υX is its Hewitt realcompactification. After characterizing nearly pseudocompact spaces in a variety of ways, we show that X is nearly pseudocompact if it has a dense locally compact pseudocompact subspace, or if no point of X has a closed realcompact neighborhood. Moreover, every nearly pseudocompact space X is the union of two regular closed subsets X₁, X₂ such that Int X₁ is locally compact, no points of X₂ has a closed realcompact neighborhood, and $\text{Int(X}{}_1\text{?X}{}_2\text{)=?}$. It follows that a product of two nearly pseudocompact spaces, one of which is locally compact, is also nearly pseudocompact.     

Mathematical programming methods for the optimal design of turbine blade shapes

This paper describes some optimization techniques for the design of turbine blade profiles with a vibration constraint. The vibration characteristics were modelled by a Timoshenko beam with idealized boundary conditions permitting the system dynamics to be simulated by differential equations. Elliptical cross-sectional shapes were assumed, resulting in an optimization problem in a finite number of variables. The methods used were (1) a direct handling of the differential equations describing the system, in which penalty function transformations were used, and (2) a finite difference discretization with the system equations replaced by finite difference approximations. In the latter formulation the vibrational frequencies are the eigenvalues of the system while in the former case they are regarded as control parameters.This paper includes a numerical study of these methods and their implementation together with a discussion of results.     

Les séries de multipôles des physiciens et la théorie des ultradistributions

Sans résuméÀ MonsieurGottfried Köthe, à l'occasion de son 60^me anniversaire