Spectral Properties of the Cauchy Operator and Its Product with Bergman's Projection on a Bounded Domain

In this paper exact asymptotic formulae are found for singularvalues of the Cauchy operator and the logarithmic potentialtype operator (on a bounded domain), as well as their productswith Bergman's projection. It is shown that these spectral characteristicsdetect geometric properties of a domain (area and the lengthof the boundary). The hypothesis "can we hear the shape of adrum", from a paper by J.M. Anderson, D. Khavinson, and V. Lomonosov[‘Spectral properties of some integral operators arisingin potential theory’, Quart. J. Math. Oxford (2) 43 (1992)387-407], is correct in the above sense. 1991 Mathematics SubjectClassification: 47B10.     

Far downstream analysis for the Blasius boundary-layer stability problem

In this paper, we examine the large Reynolds number (Re) asymptoticstructure of the wave number in the Orr–Sommerfeld regionfor the Blasius boundary layer on a semi-infinite flat plategiven by Goldstein (1983, J. Fluid Mech., 127, 59–81).We show that the inclusion of the term which contains the leading-ordernon-parallel effects, at O(Re^{– 1/2}), leads to a non-uniformexpansion. By considering the far downstream form of each termin the asymptotic expansion, we derive a length scale at whichthe non-uniformity appears, and compare this position with theposition seen in plots of the wave number.     

Wrap-around partitioning for block bidiagonal linear systems

A stable vector algorithm for the solution of block diagonallinear systems is obtained by a permutation of the unknownscalled wrap-around partitioning combined with standard QR factorization.Wrap-around partitioning uses blocking and selects the unknownsin the blocks in turns. After a suitable orthogonal eliminationstep one ends up with a reduced system which is again blockbidiagonal and so wrap-around partitioning can be applied again.Using a simple model for vectorization overhead it is shownthat small block sizes give best performance. The minimal blocksize 2, which corresponds to cyclic reduction, is suboptimaldue to memory bank conflicts.     

The formation of nickel ferrite

The solid state reaction between NiO and Fe₂O₃ to form NiFe₂O₄ proceeds through an intermediate oxygen deficient phase. Material containing this intermediate phase is found to exhibit magnetite like properties. A similar phenomenon also occurs during zinc ferrite formation.We wish to thank Mr. M. T. G. Powell for help and advice with the X-ray measurement.One of us, C. J. T., wishes to express his gratitude to the Governors of Portsmouth College of Technology for the tenure of a research award.     

On the accuracy and convergence of conjugate flux approximations

We prove that the L²-projections of derivatives of piecewise bilinear or linear finite element approximations of smooth solutions of elliptic boundary-value problems on the interior of uniform meshes, converge in L² and L^∞ at a rate faster than that of derivatives of the approximations themselves.     

Absolute Intensities of the 10-µm Bands of (16)O(3)

Two hundred ninety experimental absolute intensities of nu(1) and nu(3) transitions of ozone have been measured, with good accuracy (<2%). They are used to derive the transition-moment parameters for these bands. The agreement between our observed and calculated line intensities is satisfactory. This work shows that the intensities of these two bands are on average 4% smaller than those used in the literature. In addition, 20 intensities of the nu(2) + nu(3) - nu(2) band confirm this value. Also, 42 line intensities of the 2nu(1)-nu(3) band are reported. Copyright 2001 Academic Press.     

Complex organizing centers in groups of oscillatory particles

We investigate the origin and evolution of spatiotemporal complexity in a system of locally coupled Belousov-Zhabotinsky chemical oscillators. Using a combination of high resolution microscopy and fine grain numerical modeling, we demonstrate that the behavior arises from an initial phase heterogeneity of the oscillators. This heterogeneity produces wave breaks in the system with the free ends becoming pinned to holes in the medium. The fastest of these pinned tips behave as reentrant circuits that phase set the rest of the medium. The slower tips are repeatedly destroyed and then re-created by the central circuit. The resulting spatiotemporal pattern repeats with the frequency of the reentrant circuit, with its spatial structure depending on the location of the initial wave breaks.