An index inequality for embedded pseudoholomorphic curves in symplectizations

Let Σ be a surface with a symplectic form, let φ be a symplectomorphism of Σ, and let Y be the mapping torus of φ. We show that the dimensions of moduli spaces of embedded pseudoholomorphic curves in ℝ×Y, with cylindrical ends asymptotic to periodic orbits of φ or multiple covers thereof, are bounded from above by an additive relative index. We deduce some compactness results for these moduli spaces.?This paper establishes some of the foundations for a program with Michael Thaddeus, to understand the Seiberg-Witten Floer homology of Y in terms of such pseudoholomorphic curves. Analogues of our results should also hold in three dimensional contact topology. Received November 2, 2000 / final version received December 16, 2001?Published online November 19, 2002     

Introduction to Entity-relationship Modelling for OR Analysts

A software engineering tool, viz. data analysis, is proposed as a method for constructing the data structures needed for software development in the field of operational research. An introduction to entity-relationship modelling is given, and the technique is applied to two areas, namely critical path analysis and simulation.     

Conversion electron Mössbauer spectroscopy of plasma immersion ion implanted H13 tool steel

Conversion electron Mössbauer spectroscopy (CEMS) has been used to investigate nitride formation in AISI-H13 tool steel after treatment by plasma immersion ion implantation (PI³) at 350 °C. With only slight variation in the plasma conditions, it is possible to influence the kinetics of nitride precipitation so as to obtain nitrogen concentrations that range from those associated with -Fe₂N through -Fe₃N to -Fe₄N. The CEMS results enable a more definite identification of the nitrides than that obtained by glancing-angle X-ray diffraction and nuclear reaction analysis alone.     

Palladium and gold-palladium catalysts for the direct synthesis of hydrogen peroxide

Today hydrogen peroxide is produced by an indirect process in which an alkyl anthraquinone is sequentially hydrogenated and oxidized. In this way hydrogen and oxygen are kept separate during the manufacturing process. A process where molecular oxygen is directly hydrogenated could be preferred if control of the sequential hydrogenation can be achieved, particularly if high rates can be attained under intrinsically safe, non-explosive conditions. Herein we describe recent progress in the direct synthesis of hydrogen peroxide using supported palladium and gold-palladium alloy catalysts and consider some of the problems that have to be overcome.     

Gold--an introductory perspective

We introduce the collection of reviews in this thematic issue of Chemical Society Reviews that demonstrate and discuss the current cutting edge research in the field of gold chemistry and materials science as it stands today. We also highlight achievements in the fields of gold catalysis, gold nanoparticles and the preparative, structural and theoretical chemistry of gold, and discuss the remaining challenges and opportunities. Our aim is to inspire further discovery in these new and deeply fascinating fields.     

Nanocrystalline gold and gold palladium alloy catalysts for chemical synthesis

Catalysis by gold has become one of the most studied new topics in chemistry in recent years, and yet for many gold acting as a catalyst is, perhaps, a most unlikely possibility since bulk gold is a relatively non-reactive, immutable, ductile metal that is prized for its great beauty and value rather than for the depth of its chemistry. However, when prepared in nanocrystalline form, as a collection of a few hundreds of atoms, it displays remarkable activity as a heterogeneous catalyst for a broad range of redox reactions. Of particular note is the ability of gold, either alone or alloyed with palladium, to catalyse selective oxidation reactions, e.g. alkene epoxidation, alcohol oxidation, and the direct synthesis of hydrogen peroxide by the hydrogenation of molecular oxygen. In this article the recent advances in this exciting new field are explored.     

The preparation, characterization, and X-ray structural analysis of dichlorobis[1-methyl-3-(2-propyl) -2(3H)-imidazolethione]mercury(II)

A new compound of mercury(II) chloride complexed to 1-methyl-3-(2-propyl) -2(3H)-imidazolethione (mipit) has been prepared and characterized via standard methods and X-ray crystallography. The structural significance of this study is that it shows one of the few monomeric examples of a mercury(II) chloride thione complex reported to date. The compound crystallizes in space group P2₁/c with a = 17.143(6) Å, b = 17.047(6) Å, c = 14.759(5) Å, = 105.899(5)°, V = 4148(2) ų, Z = 8. The coordination sphere is distorted tetrahedral with Hg–S bonds and Hg–Cl bond distances falling within the normally expected ranges. Bond angles ranged from 108.11(4)° to 115.51(4)° with the widest angle being observed for the S–Hg–S linkage. Ligand bond distances and angles including the C=S distance are within the normally expected values observed for this compound.