The high temperature behavior of superalloys exposed to sodium chloride: II. corrosion

The corrosion behavior of various superalloys in molten NaCl has been examined by weight loss measurements, analysis of corrosion products, and potentiostatic polarization curves. Corrosion rates were higher in platinum than in quartz crucibles, relatively independent of alloy composition, but highly dependent on oxygen pressure. The high corrosion rates and the shape of the polarization curves indicate that the oxides formed in molten NaCl are not protective. Analysis of the sodium content in the alloy after exposure to molten NaCl indicates diffusion of sodium into the bulk of the metal. The effect of oxygen and the highercorrosion rates in platinum crucibles are explained by thermodynamic and kinetic considerations.     

Effects of shearing conditions on crystalline orientation and relaxation in polyethylene

The effects of shearing conditions (i.e., shear temperature and shear rate) on the degree of orientation of polyethylene (Marlex 6006) and to what extent the induced orientation could be relaxed were examined in this study. Two types of samples were prepared: namely, SIC (shear-induced crystallization) and non-SIC samples. The SIC samples show induction times and possess a high degree of c-axis orientation along the shear direction. The induced orientation of SIC samples can be relaxed to a small extent but does not reach a steady value. Non-SIC samples do not show induction times and they show low degrees of c-axis orientation. The induced orientation of non-SIC samples can be relaxed to a steady state value with an activation energy of 90 kJ/mole. Our results also indicate that, when the shear temperature is at and above 145°C, polyethylene can be sheared up to 200X without introducing any significant molecular orientation even at very high shear rates.     

Integrated dielectric wavelength filters on InGaAs PIN photodetectors

There is an increasing desire to employ wavelength division multiplexing (WDM) techniques in optical communication systems to increase the useable capacity of optical fibre links. WDM transmitters usually consist of several narrow linewidth lasers, with their operating wavelengths suitably spaced. WDM demultiplexers or receivers employ either discrete gratings or discrete transmission filters to separate the various wavelengths. The disadvantage of such demultiplexers is that precise mechanical alignment of the many components is required. Together with the high cost of components such as gratings this makes such demultiplexers unsuitable for mass production. The authors describe a method of producing a dielectric wavelength filter integrated onto an InGaAs PIN photodiode for use in WDM systems and give results for the transmission characteristics of the filters and quantum efficiency of the whole structure.<>     

Nuclear morphometry of the myocardial cells as a diagnostic tool in cases of sudden death due to coronary thrombosis

One general signalling mechanism used to transfer the information delivered by agonists into appropriate intracellular compartments involves the rapid redistribution of ionised calcium throughout the cell, which results in transient elevations of the cytosolic free Ca2+ concentration. Various physiological stimuli increase [Ca2+]i transiently and, thereby, induce cellular responses. However, under pathological conditions, changes of [Ca2+]i are generally more pronounced and sustained. Marked elevations of [Ca2+]i activate hydrolytic enzymes, lead to exaggerated energy expenditure, impair energy production, initiate cytoskeletal degradation, and ultimately result in cell death. Such Ca(2+)-induced cytotoxicity may play a major role in several diseases, including neuropathological conditions such as chronic neurodegenerative diseases and acute neuronal losses (e.g. in stroke).     

Zinc release and the sequence of biochemical events during triggering of Bacillus megaterium KM spore germination

Zinc release is the first quantitatively significant event detected during the triggering of Bacillus megaterium KM spore germination. Of the total spore Zn2+ pool 25% is released from non-heat-activated spores within 4 min of triggering germination. During this period only 10% of the spore population becomes irreversibly committed to germinate. The investigation of a putative role for Zn2+ in the germination trigger mechanism has established a relationship between the rate and extent of Zn2+ release and the stimulation of spore germination by heat activation. Furthermore, a correlation can be demonstrated between the extent of zinc release from spore populations and the time required to obtain 50% commitment of these populations to germinate over a wide temperature range. These findings have been used to expand a recently published model for the triggering of bacterial spore germination.     

Salicylic acid in fresh and canned fruit and vegetables

The salicylic acid concentration in a range of fresh and canned fruit and vegetables was determined using a sensitive spectrofluorimetric technique. Concentrations in fresh fruit ranged from 0.02 mg kg-¹ in kiwifruit to 0.10 mg kg-¹ in New Zealand grapefruit, and in fresh vegetables from 0.01 mg kg-¹ in cabbage to 0.10 mg kg-¹ in whole kernel sweet corn. In canned products, salicylic acid levels ranged from 0.01 mg kg-¹ in pears to 0.82 mg kg-¹ in cream-style sweet corn. Canned sweet corn and some tomato products had higher levels than the corresponding fresh vegetables. Evidence was obtained to suggest that, in the case of whole kernel sweet corn, the application of heat increased the concentration of free salicylic acid.     

A study of vapour phase epitaxy of indium phosphide

The results of a study of the preparation of epitaxial layers of indium phosphide on indium phosphide substrates by means of the PCl₃-In-InP process are presented. The limitations of the process as discovered in this study are described. It is proposed that the major reaction species is phosphine and the unpredictable break-down of this compound, along with the presence of oxyhalides in the phosphorus trihalides, are the significant causes of the observed variation of the parameters of the epitaxial layers.