ESR as a fast technique to dissolve nitrogen-rich inclusions in titanium

 Nitrogen-rich inclusions can lead to a reduction in fatigue life of highly stressed titanium-alloy components (found in the compressor sections of power generation gas turbines, turbine sections of power generation steam turbines, wing sections of aircraft air frames, and compressor and fan sections of aircraft jet engines, for example). It is the ”crack starting” nature of the nitrogen-rich inclusions that is the problem, not the presence of nitrogen in the system, per se. This paper covers the theory and laboratory experiments used to evaluate ESR (electro-slag refining) as an alternative technique for rapid dissolution of nitrogen-rich inclusions in titanium and titanium alloys. Five variations of melt rate, slag temperature and inclusion type were evaluated. One variant showed complete dissolution of the inclusions. Several of the other variants showed partial dissolution of the inclusions. The kinetics were observed to occur at a rate 100 to 1000 times faster than the rate of dissolution of nitrogen-rich inclusions by immersion in liquid titanium. Received: 14 December 1998 / Reviewed and accepted: 17 December 1998     

Three-dimensional nanostructuring with femtosecond laser pulses

The development of simple laser-based technologies for the fabrication of complicated three-dimensional (3-D) microstructures with a structure size down to 100 nm is reported. These technologies are based on nonlinear multiphoton laser-matter interaction processes allowing to overcome the diffraction limit and to fabricate 3-D structures inside transparent materials. Examples on nanostructuring of metals, dielectrics, and polymers are presented.     

Distributed or centralised energy-from-waste policy? Implications of technology and scale at municipal level

Energy-from-waste (EfW) policies can provide an essential part of landfill diversion and climate change strategies. Many UK waste disposal authorities (WDAs) are currently deciding which energy-from-waste policies are most suitable for their respective municipal areas. Such decisions are challenging since the environmental, economic and social implications of any EfW policy must be fully considered, now that planning guidelines require a full Sustainability Assessment. More specifically, WDAs must identify suitable site locations for facilities, and the optimal scale and number of facilities. This paper reports the results from a study that has developed and appraised EfW policy options using Geographical Information Systems and Multi Criteria Analysis modelling. These methods were used to evaluate and compare the impacts of several EfW strategies in the UK administrative areas of Cornwall and Warwickshire. Different strategies have been defined by the size and number of the EfW facilities, as well as the technology chosen, which includes conventional incineration and advanced thermal treatment. The overall conclusion of this work is that distributed small-scale EfW facilities score most highly overall on the chosen decision criteria and that scale is more important than technology design in determining overall EfW policy impact.     

Useful models for simulating policies to induce technological change

Conventional top-down and bottom-up energy–economy models have limitations that affect their usefulness to policy-makers. Efforts to develop hybrid models, that incorporate valuable aspects of these two frameworks, may be more useful by representing technologies in the energy–economy explicitly while also representing more realistically the way in which businesses and consumers choose between those technologies. This representation allows for the realistic simulation of a wide range of technology-specific regulations and fiscal incentives alongside economy-wide fiscal incentives and disincentives. These policies can be assessed based on the costs required to reach a goal in the medium term, as well as on the degree to which they induce technological change that affects costs over long time periods.     

Peuchtebedingte Längenänderungen von Holzwerkstoffen in Plattenebene

A review of important factors influencing hygroscopic inplane swelling and shrinkage of wood-based panels (panel structure and components, measurement method, specimen size, conditioning of specimens) is given. Measurements of in-plane swelling and shrinkage on resin- and mineral-bonded particleboard, wet and dry process fibreboard, OSB, three-layer solid wood panel, and plywood are reported. The direct transfer of specimens from standard climate (20 °C/65% rel. humidity) to a dry (20/35) and a humid (20/85) climate, respectively, was compared with a two-step conditioning process involving intermediate steps, i.e. 20/75 and 20/50, respectively. In-plane swelling and shrinkage as well as equilibrium moisture contents of the panels at 20°C and 35, 50, 65, 75, and 85% relative humidity, respectively, are tabulated. From the results, important conclusions can be drawn with regard to a revision of EN 318. They also emphasise the influence of the conditioning procedure on swelling and shrinkage, and show that a quick test renders reliable results with regard to quality control on wood-based panels.     

Transient changes of the conformation of hemagglutinin of influenza virus at low pH detected by time-resolved circular dichroism spectroscopy

Membrane fusion of influenza virus is mediated by a conformational change of the viral membrane protein hemagglutinin (HA) triggered by low pH. By near UV CD spectroscopy, which is sensitive to the arrangement and mobility of aromatic amino acids in proteins, we have monitored continuously with a time resolution of 5 s the kinetics of structural alterations of the ectodomain of HA isolated from different influenza virus strains (H1 (A/PR 8/34), H2 (A/Japan), and H3 (X31)). To establish a functional correlation to structural alterations of the HA ectodomain reflected by the CD, we have measured the kinetics of the virus-erythrocyte fusion and of the inactivation of fusion by low pH preincubation of viruses. At acidic pH we found a multiphasic behavior of the CD signal recorded at 283 nm. Upon lowering the pH we detected first an increase of the CD amplitude, which is associated with the formation of a fusion-competent state of HA. The initial increase was followed by a continuous decline of CD amplitude, which can be ascribed to a transformation into a fusion-inactivated conformation that is in its early phase reversible as found for A/Japan. The half-time of the different phases of the CD signal depended on the virus strain, the temperature, and the acidic pH. The results support recent hypotheses that the fusion-competent conformation is an intermediate of the fusion-inactivated structure of HA.     

Differential pressure characteristics of wood impregnated with compressed gases, liquids and supercritical fluids

Pressure difference characteristics at high pressure impregnation of two hardwood and three softwood species with CO₂, ethanol, hexane and supercritical mixtures were analysed in a high pressure autoclave. The investigation shows that typical penetration characteristics of wood depending on species measured in terms of pressure difference between the surrounding and the centre are true for gases, liquids and supercritical fluids. The known fact that pressures higher than 16 bar may cause wood destruction is confirmed once more. In contrast to known investigations we can show that pressures up to 175 bar can be applied to wood samples without wood destruction if the pressure difference between surrounding and centre does not exceed 16 bar. The supercritical phase of ethanol/CO₂-mixture is a potential media for technical application. It allows fast penetration at high pressures increasing at 16 bar/5 min combined with low pressure differences even at high pressure levels of 175 bar without wood destruction.     

Contamination of carcasses, offals, and the environment with yadA-positive Yersinia enterocolitica in a pig slaughterhouse

This study was carried out in order to evaluate the contamination of the pig-slaughtering line with pathogenic Yersinia enterocolitica carrying the yadA gene. A total of 292 samples were collected from the slaughterhouse; 131 swab samples from pig carcasses, ears, livers, kidneys, and hearts; 89 swab samples from the environment; and 72 sedimentation samples from the air. All surface samples were studied with both the polymerase chain reaction (PCR) and culture methods. The contamination rate of edible pig offals was high with both methods. Using PCR, the detection rates of yadA-positive Y. enterocolitica for livers, kidneys, and hearts were 38, 86, and 63%, respectively, and using the culture method, the detection rates were 31, 69, and 50%, respectively. Pathogenic Y. enterocolitica was also detected from different environmental sites in the slaughterhouse. Using PCR, 13% of the surface samples from the environment were contaminated with yadA-positive Y. enterocolitica. PCR-positive samples were found on the brisket saw, the hook from which the pluck set (heart, lungs, esophagus, trachea, diaphragm, liver, kidneys, and tongue with tonsils) hang, the knife used for evisceration, the floors in the eviscerating area and the weighing area, the meat-cutting table, the aprons used by trimming workers, the computer used in the meat-inspection area, and the coffeemaker used by slaughterhouse workers. The respective detection rate (6%) was considerably lower when we used the culture method. Pathogenic Y. enterocolitica was isolated from the air in the bleeding area. Bioserotype 4/O:3 was the only pathogenic bioserotype isolated in this study. A total of 113 isolates of type 4/O:3 were characterized with pulsed-field gel electrophoresis using NotI and XbaI digests. By combining these profiles, nine different pulsotypes were obtained, the most common of which (1a) was found in 19 (61%) of 31 samples from different sites. This is the same type that has dominated in pig tonsils, which suggests that tonsils may be the source of Y. enterocolitica contamination in the slaughterhouse. The four pulsotypes (1a, 4g, 6g, and 19q) found on edible offals were the same as those found in tonsils, which supports our hypothesis that tonsils are the contamination source for the liver, heart, and kidneys.     

Drawing Time

Head of the Department of Architecture and Landscape Architecture at the University of Greenwich, Nic Clear is renowned for his role in championing film and animation techniques in architectural education. Here he challenges architects to put aside their assigned roles as mere imagers or practice technicians and embrace ‘the spatial possibilities offered by a whole range of emerging design activities - actual, augmented and virtual’.