A short synthesis of 4-aryioxymethyl-δ3-chromenes and 3-(β-aryloxy)ethylbenzofurans

A direct and short route to the synthesis of 4-aryloxymethyl-δ³ -chromenes and 3-(β-aryloxy)-ethylbenzofurans is described. Hydration of I,4-diaryloxy-2-butynes with mercuric oxide and sulfuric acid affords, instead of a ketone, the cyclization product of the ketone. In three of the diaryloxy-butynes studied, the corresponding aryloxyethylbenzofurans are formed. In no instance could the ketone be isolated from the hydration reaction.     

Mathematical modelling of flows in recessed wall flame holder

A finite difference procedure has been employed to predict the flow situation in a recessed wall flame holder with and without combustion. Turbulence has been modelled by an ad hoc effective viscosity law. A single step chemical reaction has been assumed in dealing with the flows involving combustion. The predicted physical parameters have been compared with the experimental results. It has been argued that with the simplifying assumptions on turbulence and chemical kinetics the numerical procedure is adequately accurate to predict the important design parameters such as flame length and blow-off velocity. However, there are significant discrepancies between the predicted and measured distribution of velocity and temperature which could be attributed mainly to the inadequate turbulence modelling.     

Connectivity constant of the kagomé lattice

From the computation of self-avoiding walks on the kagomé lattice, its connectivity constant is found to be 2·569 ± 0·008.     

Three-pion interferometry results from central Pb+Pb collisions at 158A GeV/c

Three-particle correlations have been measured for identified pi(-) from central 158A GeV Pb+Pb collisions by the WA98 experiment at CERN. A substantial contribution of the genuine three-body correlation has been found as expected for a mainly chaotic and symmetric source.     

Coarsening in the presence of kinetic disorders: analogy to granular compaction

We study the zero temperature dynamics in an Ising chain in the presence of a dynamically induced field that favors locally the " -" phase compared to the " +" phase. At late times, while the " +" domains coarsen as t(1/2), the " -" domains coarsen as t(1/2)log(t). Hence, at late times, the magnetization decays slowly as m(t) = -1+const/log(t). We establish this behavior both analytically within an independent interval approximation and numerically. Our model can be viewed as a simple model for granular compaction, where the system decays into a fully compact state (with all spins " -") in a slow logarithmic manner as seen in recent experiments on granular systems.     

Particle motion and gravitational lensing in the metric of a dilaton black hole in a de Sitter universe

We consider the metric exterior to a charged dilaton black hole in a de Sitter universe. We study the motion of a test particle in this metric. Conserved quantities are identified and the Hamilton–Jacobi method is employed for the solutions of the equations of motion. At large distances from the black hole the Hubble expansion of the universe modifies the effective potential such that bound orbits could exist up to an upper limit of the angular momentum per mass for the orbiting test particle. We then study the phenomenon of strong field gravitational lensing by these black holes by extending the standard formalism of strong lensing to the non-asymptotically flat dilaton-de Sitter metric. Expressions for the various lensing quantities are obtained in terms of the metric coefficients.     

Diffusion with stochastic resetting

We study simple diffusion where a particle stochastically resets to its initial position at a constant rate r. A finite resetting rate leads to a nonequilibrium stationary state with non-Gaussian fluctuations for the particle position. We also show that the mean time to find a stationary target by a diffusive searcher is finite and has a minimum value at an optimal resetting rate r*. Resetting also alters fundamentally the late time decay of the survival probability of a stationary target when there are multiple searchers: while the typical survival probability decays exponentially with time, the average decays as a power law with an exponent depending continuously on the density of searchers.     

Entanglement witness operator for quantum teleportation

The ability of entangled states to act as a resource for teleportation is linked to a property of the fully entangled fraction. We show that the set of states with their fully entangled fraction bounded by a threshold value required for performing teleportation is both convex and compact. This feature enables the existence of Hermitian witness operators, the measurement of which could distinguish unknown states useful for performing teleportation. We present an example of such a witness operator illustrating it for different classes of states.     

Room temperature weak ferromagnetism and magnetoconductance in functional CuO film

The granular CuO films are deposited on n-Si (1 0 0) and sapphire substrates using sol-gel route. Small microstrain leads to ∼5 times larger grain sizes (200-300 nm) and ∼2.5 times larger film thickness (∼0.57 μm) for sapphire than n-Si substrate, which are confirmed by X-ray diffraction and Atomic Force Microscopy. A diode-like current-voltage characteristics are observed for film deposited on n-Si substrate, which is absent for sapphire substrate. Typical manifestation of ferromagnetic character is observed for CuO films, which are strongly influenced by the substrates. Magnetic anisotropy is larger for sapphire substrate than n-Si substrate. At room temperature considerably large magnetoconductance ∼21% and soft ferromagnetic character of CuO film on n-Si substrate are attractive for functional applications.