The C-terminal domains of gammaS-crystallin pair about a distorted twofold axis

The 2-domain gammaS-crystallin, a highly conserved early evolutionary off-shoot of the gamma-crystallin family, is located in the water-rich region of eye lenses. The expressed C-terminal domain, gammaS-C, has been crystallized and the 2.56 A X-ray structure determined. There are two domains in the asymmetric unit which pair about a distorted twofold axis. One of the domains has an altered conformation in a highly conserved region of the protein, the tyrosine corner. The distorted gammaS-C dimer of domains is compared with the highly symmetrical, equivalent recombinant dimer of C-terminal domains from gammaB- crystallin. Sequence changes close to the interface, that distinguish gammaS from the other gamma-crystallins, are examined in order to evaluate their role in symmetrical domain pairing.      

Creep behaviour of δ-phase of U-Zr system by impression creep technique

In this study, the impression creep behaviour of δ-phase of U-50 wt.% Zr (U-72.29 at.% Zr) system was studied in the temperature range 525-575 °C at different stresses. The velocity of the punch at different stresses and temperatures were evaluated for the above alloy. The stress exponents and thermal activation parameters of the above alloy were determined. A power law behaviour is displayed with the stress exponents range from 6.5 to 7. The activation enthalpy for the δ-UZr₂ was found to be independent of stress with an average value of 106 kJ/mol.     

Condition monitoring of power transformers

This article summarises some of the recent developments in devices and systems for monitoring the condition of power transformers as presented at an IEE Colloquium organised by Professional Group S2 (Materials Science and Technology) and held at Savoy Place, London, UK, on 19th June 1997     

Expression of an antigen homologous to the human CO17-1A/GA733 colon cancer antigen in animal tissues

The CO17-1A/GA733 antigen is associated with human carcinomas and some normal epithelial tissues. This antigen has shown promise as a target in approaches to passive and active immunotherapy of colorectal cancer. The relevance of animal models for studies of immunotherapy targeting this antigen in patients is dependent on the expression of the antigen on normal animal tissues. Immunohistoperoxidase staining with polyclonal rabbit antibodies to the human antigen revealed the human homologue on normal small intestine, colon and liver of mice, rats and non-human primates, whereas mouse monoclonal antibodies to the CO17-1A or GA733 epitopes on the human antigen did not detect the antigen. Polyclonal rabbit antibodies, elicited by the murine antigen homologue derived from recombinant baculovirus-infected insect cells, immunoprecipitated the antigen from mouse small intestine, colon, stomach, kidney and lung. The isolated recombinant murine protein bound polyclonal, but not monoclonal, antibodies to the human CO17-1A/GA733 antigen, and recombinant human antigen bound polyclonal antibodies elicited by the murine antigen homologue. Thus, the antigen homologue expressed by animal tissues is similar, but not identical, to the human antigen. These results have important implications for experimental active and passive immunotherapy targeting the CO17-1A/GA733 antigen.     

Calibration of a two-color imaging pyrometer and its use for particle measurements in controlled air plasma spray experiments

Advances in digital imaging technology have enabled the development of sensors that can measure the temperature and velocity of individual thermal spray particles over a large volume of the spray plume simultaneously using imaging pyrometry (IP) and particle streak velocimetry (PSV). This paper describes calibration, uncertainty analysis, and particle measurements with a commercial IP-PSV particle sensor designed for measuring particles in an air plasma spray (APS) process. Yttria-stabilized zirconia (YSZ) and molybdenum powders were sprayed in the experiments. An energy balance model of the spray torch was used to manipulate the average particle velocity and temperature in desired ways to test the response of the sensor to changes in the spray characteristics. Time-resolved particle data were obtained by averaging particle streaks in each successive image acquired by the sensor. Frame average particle velocity and temperature were found to fluctuate by 10% during 6 s acquisition periods. These fluctuations, caused by some combination of arc instability, turbulence, and unsteady powder feeding, contribute substantially to the overall particle variability in the spray plume.     

Three-dimensional finite element analysis of multi-stage hot forming of railway wheels

Three-dimensional finite element analyses has been carried out using DEFORM 3D software on multi-stage hot forming of railway wheels involving the processes of upsetting, forging, and punching of wheels. Thermal analysis related to heating the blank in furnace and all intermediate heat transfer stages between deforming operations have been conducted. Rigid viscoplastic finite element method has been utilized for coupled thermo-mechanical analysis of the processes. Modeling of punching the wheel bore has been carried out using Cockcroft and Latham fracture criterion. Evolution of thermo-mechanical parameters at selected points within the workpiece has been studied in detail. The method of simulating the effects of various process parameters has been explained using relevant mathematical relations. This study shows that design, optimization, and analysis of process perturbations for multi-stage railway wheel manufacturing process can be done efficiently in three-dimensional finite element simulations instead of conventional time and cost intensive trials. It might be necessary to use the results of finite element analysis in shop-floor to enhance productivity and reduce wheel rejection.     

Effect of oxygen flow rate and radio-frequency power on the photoconductivity of highly ultraviolet sensitive ZnO thin films grown by magnetron sputtering

We have investigated the effect of oxygen flow rate and radio-frequency (RF) power on the photoconductivity properties of ZnO thin films grown by magnetron sputtering and correlated the changes to the structural qualities. The electrical measurements show that the carrier concentration decreases with increase in the oxygen flow rate which is attributed to the probable increase in the oxygen vacancy (V_O)-related defects. The photocurrent spectra show that as the oxygen content increases, the films become lesser and more sensitive to the visible and ultraviolet (UV) lights respectively. As a result, the photo-to-dark current ratio (gain) increases to a value of 1.10 × 10⁶. As the RF power increases from 50 W to 150 W, the films become more conducting. The photoconductivity results show that as the RF power increases, the UV gain decreases slowly indicating that highly UV sensitive films can be grown at lower RF power.     

An integrated flow reactor-membrane filtration system for heterogeneous photocatalysis. Part II: Experiments on the ultrafiltration unit and combined operation

A batch-recirculated photoreactor was combined with a hollow-fibre membrane ultrafiltration (UF) unit for heterogeneous photocatalysis applications. This paper focuses on the operation and modelling of the UF process component and on the performance of the integrated photoreactor–UF process assembly. Methylene blue and titanium dioxide (Degussa P-25) were used as the test pollutant and photocatalyst, respectively. The influence of cross-flow velocity, transmembrane pressure, and TiO₂ dose on the permeate flux through the hollow fibre membrane is described. These data are modelled on the basis of concentration polarization and gel layer formation at the membrane surface/feed slurry boundary. The operation of the integrated photoreactor–UF assembly over ten repeat cycles is described. Photocatalyst separation was complete as gauged by nephelometric turbidity measurements. However, a systematic degradation in the photocatalyst performance was noted with each repeat cycle. Dynamic laser light scattering data are consistent with agglomeration of the TiO₂ particles as a result of the UF process, and suggest a possible factor in the degraded photocatalytic activity. Possible solutions to this problem are finally presented.