Monolithically integrated four-channel receiver array using diffused InGaAs (JFET technology)

Four-channel receiver arrays have been fabricated by monolithically integrating diffused InGaAs JFET-based electronics with InGaAs pin photodiodes. Cascode and simple inverter transimpedance amplifier circuits have been produced, both of which use a micro-FET as a tunable feedback element to vary bandwidth between 20 and 800 MHz. A sensitivity of -28.2 dBm was achieved at 1.25 Gbit/s with crosstalk between adjacent channels of -50 dB (electrical).<>     

Application of structural analysis to the mechanical behaviour of the cornea.

Structural engineering analysis tools have been used to improve the understanding of the biomechanical behaviour of the cornea. The research is a multi-disciplinary collaboration between structural engineers, mathematical and numerical analysts, ophthalmologists and clinicians. Mathematical shell analysis and nonlinear finite-element modelling have been used in conjunction with laboratory experiments to study the behaviour of the cornea under different loading states and to provide improved predictions of the mechanical response to disease and injury. The initial study involved laboratory tests and mathematical back analysis to determine the corneal material properties and topography. These data were then used to facilitate the construction of accurate finite-element models that are able to reliably trace the performance of cornea upon exposure to disease, injury or elevated intra-ocular pressure. The models are being adapted to study the response to keratoconus (a disease causing loss of corneal tissue) and to tonometry procedures, which are used to measure the intra-ocular pressure. This paper introduces these efforts as examples of the application of structural engineering analysis tools and shows their potential in the field of corneal biomechanics.     

Environmental change in river channels: a neglected element. Towards geomorphological typologies,standards and monitoring

Rivers integrate the impacts of change in atmospheric and terrestrial systems; they then deliver these to the coast. En route geomorphological processes create dynamic and diverse habitats, both in-stream and in riparian/floodplain ecotones. The dynamics of channel change conflict with human resource development, the outcome is that many river and riparian environments have been significantly modified, complicating the interpretation of change. Collection of geomorphological data on both form and process has to date been overwhelmingly an academic pursuit; standard measurement networks and long-term monitoring have, as a result been largely absent-as in the Environmental Change Network (ECN), despite the emerging requirements of legislation such as the EU Water Framework Directive. In this paper, we utilise a unique set of repeat channel surveys and long-term bed-load sediment yields to provide guidance on both definitions of change and those variables and survey techniques which might form the basis, in future, of improved national-scale monitoring. The Environment Agency's River Habitat Surveys suggest the basis for channel typologies that could structure a sampling framework and rationalise the variables to be monitored. We also point to the value of more detailed geomorphological procedures in use at the catchment/project scale-Catchment Baseline Surveys and Fluvial Audits-as a standardised basis for monitoring the detail of change in the fluvial sediment system. A perfect opportunity to lay foundations for such monitoring activity has been provided in England and Wales by the winter floods of 2000/2001.     

Interferometric fibre-optic sensor using a short-coherence-length source

A fibre-optic sensor system exploiting the principles of white-light interferometry is demonstrated. A digital feedback servo ensures that theMach-Zehnder interferometric system is maintained at near-zero optical path difference.     

Effect of residual doping on optimum structure of multiquantum-well optical modulators

Using a variational method we have calculated the effect of residual doping on the optimum structure of multiquantum-well (MQW) optical modulators which utilise the quantum confined Stark effect. Residual doping gives a nonuniform electric field and a degraded modulation depth. For example, for a structure consisting of 100 ? GaAs wells and 100 ? Ga0.7A10.3As barriers, we calculate the optimum number of wells to be 20 for a doping of 5 × 1015 cm?3.     

Chromosomal localization of mouse Cenpa gene

Using a previously isolated mouse centromere protein A (Cenpa) probe, we have localized the gene to the proximal region of mouse Chromosome 5, between the known Il6 and Yes1 loci near [Adra2C-D5H4S43-Hdh]. Comparison of this localization with that of human CENPA, which maps to chromosome 2, is consistent with the presence of a new region of conserved synteny between the two species.     

The development of enhanced heat transfer condenser tubing

Methods for manufacturing a variety of shapes of enhanced heat transfer condenser tubing have been developed. 32 different tubes have been studied, in a vertical orientation, for their overall heat transfer and pressure drop characteristics. All experiments were conducted with atmospheric steam condensing on the outside of the tube and water in forced convective flow on the inside, the heated length of the tube being 45 ins. (114 cm). The results show that, on the condensing steam side, coefficients up to 6 times comparable smooth tube values were obtained, and on the forced convective side up to 2$\text{1}\text{2}$times. The results are linked to tube shape, and appropriate theoretical analyses are presented.     

STUDIES OF MAGNETITE DEPOSITION FROM A FLOWING SUSPENSION

The deposition of magnetite from flowing water suspensions is a problem particularly important in boiler plant. Measurements have been made of the rate of deposition of magnetite particles from suspension in demincraliscd water pumped through vertical aluminium tubes of 19 mm bore over a range of temperatures I2-75°C and Reynolds number 7900 to 88500 under isothermal conditions. Bulk concentrations of magnetite particles (of the order of 2 μm diameter) were in the range 200-600 ppm.

It would appear that deposition is mass transfer controlled. The initial deposilion rate for a given temperature and concentration varies as the suspension velocity to the power 0.73. The measured asymptotic deposition quantity varies as the suspension velocity to the power -0.66.

The conclusions imply a sticking probability for the magnetite on to the aluminium lube walls as 1 for the experimental conditions.     

39 GHz monolithic coplanar waveguide amplifier using doped channel HFET technology on InP

A single-state amplifier has been designed and fabricated using 0.25 mu m gate length, doped-channel HFET technology on InP substrates. Coplanar waveguide (CPW) was used for impedance matching. A gain of 14.4 dB was measured at 39 GHz.<>