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The corrosion behaviour of the chromia forming metallic alloys, Nimonic 86 and Hastelloy X, has been examined in nitrogen containing 0.04% oxygen during 1005 h isothermal exposure at 950°C. Particular attention has been directed to the influence of crevices where depletion of oxidising species, due to restricted gas replenishment, would enhance competition between nitridation and oxidation.

A comparative study of the counterbore dual damascene (CBDD) and self-aligned dual damascene (SADD) approaches with aluminum interconnects was carried out for application to 0.18 /spl mu/m ULSI multilevel interconnects. It is shown that the defect density is lower with the SADD approach. Yield degradation with the CBDD approach is explained by photoresist residues in the bottom of vias, which are difficult to remove due to the high aspect ratio of the holes. The Al-CMP process was optimized by introducing dummy structures to reduce Al dishing on wide interconnect lines. Equivalent yield was demonstrated with the SADD approach in comparison with the standard subtractive aluminum etch process on 0.25 /spl mu/m SRAM technology.

The authors describe a WSi/sub x/ process using SiH/sub 2/Cl/sub 2/ chemistry, which is characterized by higher deposition rate, better film adhesion and integrity on polysilicon, and lower impurity concentration compared to the conventional SiH/sub 4/ chemistry. The nonselective W process (WF/sub 6/+H/sub 2/) developed for deposition on dielectric material is characterized by simplicity, excellent adhesion, and low resistivity without the need for a sticking layer. A selective W process (WF/sub 6/+H/sub 2/) developed for TiSi/sub 2/ contacts is characterized by high deposition rate, low contact resistance, low junction leakage, no lateral encroachment, and no silicon consumption in the vertical direction. The problems of silicon consumption and lateral encroachment associated with the tungsten deposition by hydrogen reduction is eliminated by the use of silane reduction. The silane reduction also leads to high deposition rates at low temperatures suitable for W deposition on aluminum layers. Blanket W deposition using silane reduction has good step coverage. >

A scalable submicron contact technology has been developed using a fully conformal LPCVD (low-pressure chemical vapor deposition) titanium nitride barrier metal that provides low contact resistance to salicide, low leakage, excellent adhesion, and high thermal stability. Owing to the uniform step coverage, especially in deep, straight wall contacts, the CVD TiN overcomes the metal reliability and junction leakage issues associated with the physical sputtering of metals in high-aspect-ratio, submicron contacts. LPCVD TiN withstands 550 degrees C thermal stress, maintaining low contact resistance and leakage, while physically deposited TiN fails at 500 degrees C. The applicability of CVD TiN barrier technology to VLSI devices has been successfully demonstrated on production circuits. >

Protecting people and the environment is an essential design and operational criteria for the Kutubu Petroleum Development Project to minimize the physical, social and economic impacts on the local people and their environment in Papua New Guinea. This paper describes how Kutubu was implemented, and how World Wildlife Fund is assisting the neighboring communities to utilize their natural resources for long term benefit. The objectives and first year expectations of a three year integrated conservation and development project are identified, and the progress is summarized.

The Savannah River Site (SRS) Safety Analysis Report (SAR) covering K reactor operation assesses a spectrum of design basis accidents. The assessment includes estimation of the dose consequences from the analyzed accidents. This report discusses the methodology used to perform the dose analysis reported in the SAR and also includes the quantified doses. Doses resulting from postulated design basis reactor accidents in Chapter 15 of the SAR are discussed, as well as an accident in which three percent of the fuel melts. Doses are reported for both atmospheric and aqueous releases. The methodology used to calculate doses from these accidents as reported in the SAR is consistent with NRC guidelines and industry standards. The doses from the design basis accidents for the SRS reactors are below the limits set for commercial reactors by the NRC and also meet industry criteria. A summary of doses for various postulated accidents is provided.

Protein extracts from 6- to 11-day-old rat enamel organs were applied to columns of carboxymethyl-52 cellulose. Protein eluted from the columns was assayed for acid phosphatase activity with substrates para-nitrophenylphosphate (p-NPP), beta-glycerolphosphate (beta-GP), ATP and phosphocasein. A weakly-bound peak of activity (A) emerged first which was insensitive to stimulation by iron and ascorbic acid. This enzyme hydrolysed only the phosphomonoester substrates (p-NPP and beta-GP). A strongly bound peak of activity (B) emerged later and was completely separated from the first activity. It hydrolysed all substrates except beta-GP, and was stimulated at least 10-fold by 0.1 mM ferrous ion (Fe2+) in the presence of a strong reducing agent (1.0 mM ascorbic acid). Both substances were more effective as stimulators when used together than they were when each was used separately. Dependency on these co-factors for the development of full activity increased with purification, especially when phosphocasein was substrate. The results were similar for each age of rat used. These properties of enzyme B are parallel with those of the acid phosphoprotein phosphatases of liver and spleen, and the tartrate-resistant acid phosphatase of rat bone. We conclude that enzyme B requires iron and a reducing agent for full activity and has properties that distinguishes it from the classical acid phosphatases (E.C. 3.1.3.2.).

The oxidation behaviour of adjusted uranium has been examined in air, at atmospheric pressure, at 348–765 K. Particular emphasis has been directed to the role of swelling resulting from prior irradiation of the metal to a burn-up of 5600–9100 MWd/t and an addition of 2.5 × 104 vpm water vapour to the air. Pre-irradiation of uranium enhanced its attack by air at 348–523 K, the enhancement increasing progressively with percentage swelling. This effect resulted primarily from the break-up of the uranium surface during oxidation with the generation of a greater reaction surface area and was independent of the temperature of oxidation in dry air and also above 423 K in wet air. At lower temperatures, however, the water vapour addition increased the effective reaction rate, possibly by the transitory involvement of uranium hydride. The influence of the water vapour increased with swelling of the irradiated uranium and was greater than that exerted on the oxidation of unirradiated uranium at comparable temperatures. With increasing temperature above 623 K, swelling had a progressively decreasing influence upon the attack of irradiated uranium in both environments.

1. 1. Haemolymph osmotic pressure was measured in four species of woodlouse after pre-treatment in 100% R.H. followed by progressive desiccation. 2. 2. Considering sexes together it was found that Oniscus asellus cannot osmoregulate but that Porcellio scaber and Armadillidium depressum can. Ligia oceanica showed a greater osmoregulatory ability during aerial desiccation than some other “more terrestrial” species. All species except A. depressum showed considerable sexual variation in their response to desiccation even though the pre-treatment values were similar. 3. 3. Sodium levels were monitored with progressive desiccation in O. asellus and P. scaher. Contrary to expectation the former species showed greater sodium control than the latter.

Acoustic emission (AE) monitoring was used both during the formation of scale on the 20Cr25NiNb stabilised stainless steel, during isothermal exposures to carbon dioxide at 1123–1273 K and on subsequent furnace cooling to ambient temperature. Developments are reported whereby the AE technique may be used in conjunction with a controlled-atmosphere microbalance to provide simultaneously two parameters describing the phenomenon occurring. Results obtained on cooling concerning the initiation and kinetics of spallation are discussed in terms of a strain-energy model.

Rabbit eyes were removed and held in temperature-regulated chambers and irrigated with saline. A dose of 0.1 ml of test irritant was applied to each eye (six eyes per test material) and the induced change in corneal thickness measured over a 5-hour period, using a Zeiss photoslit-lamp microscope. A total of sixty materials were assessed and the results graded and compared with in vivo effects. The results show that this in vitro test can be relied upon to provide a rapid, accurate prediction of the irritancy potential in vivo, with a wide range of chemicals and, as such, offers a reliable alternative to the use of live animals.

The chick chorioallantoic membrane (CAM) is a vascularized membrane which lacks sensory innervation and has been advocated as an alternative to the rabbit eye for assessing chemical irritancy. The method has been assessed using a variety of irritant and non-irritant chemicals. The CAMs were prepared by withdrawing 2 ml of albumin on day 2 of incubation, cutting a window in the shell and then sealing it with tape. On day 12 the window was opened, 0.1 ml of test material was applied to the membrane and the degrees of injection and haemorrhage were scored at 0.5, 2, 5 and 10 min. The results show that the test provides a rapid but not very accurate qualitative separation of non-irritant chemicals from those causing chemosis in vivo . Of the 30 chemicals tested, 23 were correctly identified as irritant or non-irritant, five were incorrectly identified as irritant and two were incorrectly identified as non-irritant. With the irritant chemicals there was no correlation between the intensity of the CAM response and the severity of the in vivo effects. The CAM test does not, therefore, appear to be a useful predictor of irritancy potential.