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Heightened perception of gastrointestinal sensation is termed visceral hypersensitivity (VH) and is commonly observed in patients with gastrointestinal disorders. VH is thought to be a major contributory factor in oesophageal disease, particularly gastro-oesophageal reflux disease that does not respond to standard (proton pump inhibitor) treatment, and in functional heartburn. Clinical tools that can help phenotype according to the mechanism of chronic pain and thus allow targeted drug treatment (e.g. with pain modulator therapy) would be very desirable. A technique that produces repeatable and controllable thermal stimuli within the oesophagus could meet this need. The aims of this study were to develop a method for linear control of the heat stimulation in the oesophagus, to assess the reproducibility of this method, and obtain normal thermal sensitivity values in the distal and proximal oesophagus. The 7 mm diameter Peltier-based thermal device was investigated on 27 healthy subjects using a heating ramp of 0.2 °C s(-1). The pain detection threshold (PDT) temperature was recorded. To assess the reproducibility of the device, each subject underwent the procedure twice, with a minimum of two weeks between each procedure. The mean PDT temperature measured in the distal oesophagus, was 53.8 ± 2.9 °C and 53.6 ± 2.6 °C, for visits 1 and 2 respectively. The mean PDT temperature measured in the proximal oesophagus was 54.1 ± 2.4 °C and 54.0 ± 2.8 °C, for visits 1 and 2 respectively. The reproducibility of the PDT temperature in the distal and proximal oesophagus, was good (intra-class correlation >0.6). Future studies should be aimed to determine whether oesophageal thermal sensitivity can act as a biomarker of transient receptor potential vallanoid 1 upregulation.

Ferroelectric liquid crystal displays offer an attractive matrix addressed alternative for complex displays. However, their potential can only be realised by using novel addressing schemes suitable for the fast responding, DC sensitive, ferroelectric electro-optic effect. Over a period of several years, a high performance, novel, ferroelectric drive scheme1 has been developed in a UK, JOERS/Alvey funded, collaborative programme. The JOERS/Alvey drive scheme is based on monopulse strobe waveforms2,3,4 and utilises the response time - voltage minimum5,6 found in certain materials. Using this novel drive scheme, complex ferroelectric displays with a high contrast ratio, wide operating range and fast addressing times have been made7,8,9,10 The JOERS/Alvey drive scheme is described, compared with other published drive schemes, and the operating principles discussed.

The authors constructed a contact therapy unit based around the RT50 tube. The characteristics of the constituent parts, their assembly into a contact X-ray therapy unit and a brief comparison with the original RT50 machine are presented.

This paper presents a FELC/VLSI spatial light modulator which has been built as a component for optoelectronic neural networks. The device exhibits analogue optical modulation and is capable of optical memory. It is the first parallel optical device that implements a learning algorithm in its pixels.

The use of free-space optics to perform high bandwidth connections for computing applications has been widely discussed in the literature. In this paper we present the practical results of a free-space optical crossbar switch which uses a ferroelectric liquid crystal spatial light modulator as the active switching element. This work has formed part of a collaborative project entitled OCPM which is concerned with developing optical free-space crossbar switching technology for use as the communications fabric for parallel computing systems. The OCPM project (Optically Connected Parallel Machines) is a collaboration between British Aerospace (Sowerby Research Centre), Meiko, BNR Europe, Heriot-Watt University, the University of Bath and Thorn EMI CRL. The project is coordinated by British Aerospace and is funded in part by the DTI and SERC.

A single stage optical crossbar switch has been developed as part of a collaborative project entitled Optically Connected Parallel Machines (OCPM). The aim of this project is to develop electronically controlled, free-space optical systems capable of inter-connecting large numbers of advanced electronic processors and arbitrarily switching high bandwidth signals between them. The implications of this high performance communications technology for parallel computing architectures is being analysed by way of simulations and technology demonstrators. The optoelectronic interconnect system consists of an electronically addressed spatial light modulator positioned at the centre of a single stage optical crossbar configuration formed with holographic and bulk optical elements. This paper describes the development of the optical crossbar switch and both its current and predicted performance.

We consider the addressing requirements associated with some analogue and binary electro- optic effects in chiral smectic liquid crystals driven from silicon VLSI backplanes. This class of liquid crystals offers major improvements in switching speed over electro-optic effects in nematic liquid crystals, but their non-RMS response to impressed voltages leads to addressing difficulties. Their spontaneous polarization also leads to limitations in using pixel drive circuits resembling dynamic random access memory cells (DRAMs), which are commonplace in display technology. Some illustrative examples of the performance of electro-optic effects with currently available materials are given, followed by a discussion of the problems associated with the charging phenomena occurring when ferroelectric liquid crystals are driven from active backplane drive circuits. Addressing schemes are then considered, particularly those that are aimed at providing electro-optic modulators with continuous optical access and with no temporal noise in their transfer characteristic, such as might be needed in optical switching devices. Some examples of experimental pixel circuits are given.

The development of a ferroelectric liquid-crystal-over-single-crystal-silicon spatial light modulator is described. The reflective SLM has an array of 176 X 176 pixels over a clear aperture of 5.28 mm X 5.28 mm. Prototype devices driven from a specially designed high speed frame store have been operated at frame rates of approximately equals 1 kHz.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

[1] An experimental method, using simultaneous vertical and slant observations, has been derived for estimating the effective shell height for electron content measurement by GPS reception. At a latitude of approximately 53° north, Lancashire is well placed as an observing site since GPS satellite orbits are inclined at 55° to the Earth's equatorial plane and, as a result, many GPS tracks pass almost directly overhead, giving true zenithal measurements. This paper focuses on the question of oblique-to-zenithal correction and related matters. In particular, plasmaspheric effective height and satellite bias corrections are determined by measuring the total electron content (TEC) from pairs of satellites to a single ground station, each pair giving simultaneous observations of oblique and zenithal TEC. Additional bias corrections are determined by extracting the TEC using pairs of satellites with the same elevation at the same time. The Chapman Production Function Model and the Sheffield University Plasmasphere and Ionosphere Model are both used to determine a theoretical value for the plasmaspheric effective height. The results indicate that the plasmaspheric effective height used in the oblique-to-zenithal thin shell conversion is considerably greater than the commonly adopted value of 350 km. It is suggested, on the basis of all the available evidence, that a value between 600 and 1200 km is preferred. Assuming a lower value could produce an error of 15 to 30% or more in the electron content.

The paper describes the features and attributes of the CORE requirements analysis tool in a simulation environment and the associated implementation via the FORSS software package. This method is applied to the analysis of a proposed automated manufacturing facility which involves the integration of a power-and-free conveyor system into the paint sprayshop of a manual treatments facility. Practical results for the simulation model are presented.

An instrument and associated mechanical assembly is described which combines the measurement of two parameters from a linear accelerator. The overlaid display of the radiation field flatness and the optical field size markers allows examination of the radiation beam symmetry to be combined with a comparison of radiation and optical field size against the machine's collimator settings.

Two bipolar integrated circuits are described which provide the write and sense functions required by magnetic bubble memory systems, both organized in four-channel format to minimize board area occupied. The write driver circuit has a 300 mA drive capability and includes on-chip circuitry which prevents fusing of the delicate bubble `hairpin' structure under fault conditions. The sense amplifier has programmable sensitivity in the range of 1 mV to 10 mV and allows the bubble device to be directly coupled to the differential input while tolerating DC offsets of up to /spl plusmn/150 mV without significantly modifying sensitivity.

A monolithic wideband amplifier (5 MHz to 200 MHz) is described which, in conjunction with a D to A, has been used to realise a subsystem with 48 dB of digital gain control.

Coughing was induced in seven normal and eight asthmatic subjects by giving successive inhalations of citric acid aerosols of progressively higher concentration (range 0.5-32%). A baseline cough response was obtained on each of four experimental days, and there was no significant difference between days in this respect. Then the subjects received by inhalation either a bronchodilator (salbutamol 5 mg or ipratropium 1 mg) or placebo, in a paired double blind crossover design. A second citric acid run followed and was used for paired drug-placebo comparisons. In the asthmatic subjects the cough response was diminished by both bronchodilators (p less than 0.05), and the cough threshold was significantly higher after ipratropium but not salbutamol. In normal subjects no significant effects were found. Airways calibre was assessed, by an oscillatory technique that measures the resistance of the respiratory system (Siemens Siregnost FD 5), in four of the seven normal and all eight asthmatic subjects. The mean respiratory resistance was higher in asthmatic than in normal subjects, and fell significantly after both bronchodilators. In normal subjects smaller decreases in respiratory resistance occurred, significant only with salbutamol. The simplest hypothesis which explains the results relates change in cough response to altered neuroreceptor sensitivity associated with rapid changes in bronchial calibre.

This paper describes how C.O.R.E. (Controlled Requirements Expression) may be used as a structured analysis and design methodology to develop system simulation software.’ The application of C.O.R.E. to the modelling and simulation of an automated manufacturing facility in the aerospace industry is discussed. In particular the paper explains how a manufacturing ‘target system’ is defined in a bounded form for subsequent decomposition into process modules for simulation studies. The structure notation requirements of the C.O.R.E. methodology are outlined, and the attributes of modularity, functionality, visibility of structure and operational considerations are discussed. The simulation of a small-parts manufacturing system is described, and a typical set of practical results of the simulation study are presented.