The taming of absorption: generating a constant intensity beam in a lossy medium

We report the first observation (to our best knowledge) of a constant intensity, quasi-Bessel/nondiffracting beam in an absorbing medium generated by a novel optical element, "exicon," or exponential intensity axicon. Such absorption-compensated and diffraction-resistant beams can find applications in illumination, remote sensing, free-space communications, imaging in biological tissues, nonlinear optics, and other situations where absorption and diffraction hinder light propagation.     

Counterexamples in calculus of variations in L∞ through the vectorial Eikonal equation

We show that, for any regular bounded domain $\mathrm{\Omega }?{\mathbb{R}}^n$, $n=2,3$, there exist infinitely many global diffeomorphisms equal to the identity on ?Ω that solve the Eikonal equation. We also provide explicit examples of such maps on annular domains. This implies that the ∞-Laplace system arising in vectorial calculus of variations in $L^{\infty }$ does not suffice to characterise either limits of p-Harmonic maps as $p\to \infty$ or absolute minimisers in the sense of Aronsson.     

On the smoothing properties of the SIMPLE pressure-correction algorithm

A local mode Fourier analysis is used to assess the suitability of the SIMPLE pressure-correction algorithm to act as a smoother in a multigrid method. The necessary ellipticity of the Navier-Stokes equations and their discrete representation are established. The theoretical analysis is compared with practical results.     

Vibrational relaxation of KrF* and XeCl* by rare gases

A steady-state, chemiluminescence technique has been used to measure effective rate constants for vibrational relaxation as a function of vibrational level for KrF^* in collisions with He, Ne, and Ar and XeCl^* with Ar. The effective rate constants reported include contributions to relaxation due to intersystem crossing between theB andC states, in addition to direct relaxation within theB state. The relevance of these results to the understanding of previous measurements in KrF and XeCl lasers is discussed.     

Novel glass-forming liquid crystals. II. Systems containing 1-phenyl-2-(6-cyanonaphth-2-yl)ethyne as a high optical birefringence moiety

A new series of glass-forming molecular materials have been synthesized that incorporate 1-phenyl-2-(6-cyanonaphth-2-yl)ethyne as the high optical birefringence nematogenic moiety and a diphenylacetylenic group as part of the chiral moiety containing (S)-(-)-1-phenylethanol. To facilitate the preparation of chiral nematic systems, the key intermediate, i.e. 1,3,5-cyclohex-anetricarboxylic anhydride chloride, was synthesized and characterized. The thermotropic and optical properties of all products and the blends prepared therefrom were characterized by polarizing optical microscopy, differential scanning calorimetry, and UV-VIS-NIR spectrophotometry. It was found that all the resultant molecular materials readily form glasses with a T_g of around 60°C while showing no residual crystallinity below T_g or tendency toward crystallization by heating above T_g. Furthermore, binary blends showed a decreasing degree of miscibility at an increasing extent of structural dissimilarity with the all-chiral/all-nematic systems exhibiting significant phase separation at a chiral mole fraction of 0.16.     

A comparative thermodynamic analysis of InP and GaAs deposition

A PCl₃ transport system for epitaxial InP deposition has been considered from an equilibrium point of view and compared with a similar arsenic trichloride process for GaAs deposition. Thermochemical values for all species pertinent to these two systems were compiled and employed in conjunction with an iterative Gibbs energy minimization program to compute the gas phase equilibrium concentrations and the maximum extent of deposition. The results are presented as functions of three independent variables: the source and deposition temperatures and the initial concentration of Group III trichloride. The degree of gas phase supersaturation is presented as a function of the temperature differential between the source and deposition regions.     

On determining the dimension of chaotic flows

We describe a method for determining the approximate fractal dimension of an attractor. Our technique fits linear subspaces of appropriate dimension to sets of points on the attractor. The deviation between points on the attractor and this local linear subspace is analyzed through standard multilinear regression techniques. We show how the local dimension of attractors underlying physical phenomena can be measured even when only a single time-varying quantity is available for analysis. These methods are applied to several dissipative dynamical systems.     

Fused s-Triazino heterocycles. VI. 1,9,9b-Triazaphenalenes

Derivatives of 1,9,b-triazaphenalene have been prepared by reacting alkyl-N-cyanoimidates with 2,6-bis(cyanomethyl)pyridine.