Tandem enzyme-catalysed oxidations of alkyl phenyl sulfides and alkyl benzenes: enantiocomplementary routes to chiral phenols.

Dioxygenase-catalysed trioxygenation of alkyl phenyl sulfides and alkyl benzenes yields enantiopure cis-dihydrodiol sulfoxides and triols respectively; naphthalene cis-dihydrodiol dehydrogenase-catalysed aromatisation of these diastereoisomers gives enantiopure catechols of either configuration.

Chiral discrimination within disordered adlayers on metal surfaces

Using a novel non-linear optical technique enantiomeric excess within a translationally disordered overlayer on a metal surface has been monitored for the first time.

Compressive membrane action in composite floor slabs in the Cardington LBTF

This paper presents the results of an experimental study (the ultimate load capacity of composite metal decking/concrete floor slabs. Full-scale in situ testing of composite floor slabs was carried out in the Building Research Establishment's Large Building Test Facility (LBTF) at Cardington. A parallel laboratory test programme, which compared the behaviour of composite floor slabs strips, also carried out at Queen's University Belfast (QUB). Articular attention was paid to the contribution of compressive membrane action to the load carrying capacity. The results of both test programmes were compared with predictions by yield line theory and a theoretical prediction method in which the amount of horizontal restraint mid be assessed. The full-scale tests clearly demon-wed the significant contribution of compressive membrane effects to the load capacity of interior floor panels with a lesser contribution to edge/corner panels.

Load Testing of Floor Slabs in a Full-Scale Reinforced Concrete Building

A series of short and long term service load tests were undertaken on the sixth floor of the full-scale, seven storey, reinforced concrete building at the Large Building Test Facility of the Building Research Establishment at Cardington. By using internally strain gauged reinforcing bars cast into an internal and external floor bay during the construction process it was possible to gain a detailed record of slab strains resulting from the application of several arrangements of test loads. Short term tests were conducted in December 1998 and long term monitoring then ensued until April 2001. This paper describes the test programmes and presents results to indicate slab behaviour for the various loading regimes.

Arching action in high strength concrete slabs

The corrosion of reinforcement in bridge deck slabs has been the cause of major deterioration and high costs in repair and maintenance.This problem could be overcome by reducing the amount of reinforcement and/or altering the location.This is possible because, in addition to the strength provided by the reinforcement, bridge deck slabs have an inherent strength due to the in-plane arching forces set up as a result of restraint provided by the slab boundary conditions. This is known as arching action or Compressive Membrane Action (CMA). It has been recognised for some time that laterally restrained slabs exhibit strengths far in excess of those predicted by most design codes but the phenomenon has not been recognised by the majority of bridge design engineers. This paper presents the results of laboratory tests on fifteen reinforced concrete slab strips typical of a bridge deck slab and compares them to predicted strengths using the current codes and CMA theory. The tests showed that the strength of laterally restrained slabs is sensitive to both the degree of external lateral restraint and the concrete compressive strength.The tests particularly highlighted the benefits in strength obtained from very high strength concrete slabs. The theory extends the existing knowledge of CMA in slabs with concrete compressive strengths up to 100 N/mm[2] and promotes more economical and durable bridge deck construction by utilising the benefits of high strength concrete.

Serviceability of bridge deck slabs with arching action

The deterioration of infrastructure, such as bridges, has been one of the major challenges facing both the designers and the owners of such utilities. Sustainable development and a climate of increasing commercialism has led to a requirement for more accurate means of structural analysis. Bridge assessment is one area where this is particularly relevant. It has been known for some time that bridge deck slabs have inherent enhanced strength due to the presence of arching or compressive membrane action (CMA) but only in recent years has there been some acceptance of a rational treatment of this phenomenon for design and assessment purposes. To use the benefits of arching action, this paper presents the results of tests carried out on a reinforced-concrete beam and slab bridge in Northern Ireland that incorporated novel reinforcement type and position. The research was aimed at extending previous laboratory tests on 1/3scale bridge deck edge panels. The measured crack widths and deflections have been compared with the current code requirements.

Ab initio simulation of charged slabs at constant chemical potential

We present a practical scheme for performing ab initio supercell calculations of charged slabs at constant electron chemical potential mu, rather than at constant number of electrons N-e. To this end, we define the chemical potential relative to a plane (or "reference electrode") at a finite distance from the slab (the distance should reflect the particular geometry of the situation being modeled). To avoid a net charge in the supercell, and thus make possible a standard supercell calculation, we restore the electroneutrality of the periodically repeated unit by means of a compensating charge, whose contribution to the total energy and potential is subtracted afterwards. The "constant mu" mode enables one to perform supercell calculation on slabs, where the slab is kept at a fixed potential relative to the reference electrode. We expect this to be useful in modeling many experimental situations, especially in electro-chemistry. (C) 2001 American Institute of Physics.