Stepwise-Graded Si3N4–SiC Ceramics with Improved Wear Properties

The processing of stepwise graded Si₃N₄/SiC ceramics by pressureless co-sintering is described. Here, SiC (high elastic modulus, high thermal expansion coefficient) forms the substrate and Si₃N₄ (low elastic modulus, low thermal expansion coefficient) forms the top contact surface, with a stepwise gradient in composition existing between the two over a depth of ∼1.7 mm. The resulting Si₃N₄ contact surface is fine-grained and dense, and it contains only 2 vol% yttrium aluminum garnet (YAG) additive. This graded ceramic shows resistance to cone-crack formation under Hertzian indentation, which is attributed to a combined effect of the elastic-modulus gradient and the compressive thermal-expansion-mismatch residual stress present at the contact surface. The presence of the residual stress is corroborated and quantified using Vickers indentation tests. The graded ceramic also possesses wear properties that are significantly improved compared with dense, monolithic Si₃N₄ containing 2 vol% YAG additive. The improved wear resistance is attributed solely to the large compressive stress present at the contact surface. A modification of the simple wear model by Lawn and co-workers is used to rationalize the wear results. Results from this work clearly show that the introduction of surface compressive residual stresses can significantly improve the wear resistance of polycrystalline ceramics, which may have important implications for the design of contact-damage-resistant ceramics.     

A variable radius roll adhesion test (VaRRAT) suitable for measuring the adhesion of paint to metal

Early trials and analysis of a new adhesion test are discussed. The test is designed for measuring the adhesion of paint to deformable steel sheets as used in building, automotive, and other cladding applications, and does not require detailed knowledge of the paint mechanical properties. A stiff overlay, such as an epoxy resin, is applied to the coating, and the steel substrate is peeled away using a roll of well-defined radius to which the steel substrate is constrained. The propagation of a crack within the paint or at some interface in the paint/metal system depends mostly on the mechanical properties and thickness of the overlay and the radius of the constraining roll. The test is shown to discriminate better than existing practical adhesion tests between paints of expected differing adhesion/cohesion, but also presents some inconsistencies that require further work to resolve. BHP Institute of Steel Processing and Products, Wollongong NSW 2522, Australia.     

Obtaining Characteristic 4f–4f Luminescence from Rare Earth Organic Chelates

We report a study of a series of heavy rare earth tris‐8‐hydroxyquinolines (REQ₃s), using UV‐visible absorption spectroscopy, infrared absorption spectroscopy, and photoluminescence (PL) measurements. We show that the heavy REQ₃s are all chemically similar to each other and to aluminium tris‐8‐hydroxyquinoline, at least in terms of the ligand behavior. Characteristic rare earth 4f–4f luminescence is only observed for ErQ₃ and YbQ₃ due to the relatively low energy of the ligand triplet state. We show that a triplet transfer mechanism cannot be responsible for the observed Yb 4f–4f luminescence observed in YbQ₃. Instead, an internal chemiluminescent process is shown to be energetically favorable. The thin film PL spectra of all the heavy REQ₃s are dominated by triplet emission, except for that of ErQ₃, for which transfer to the Er³⁺ ion represents an efficient alternative. The PL spectra of powder samples, which would be expected to consist of approximately equal amounts of both isomers, are dominated by singlet emission. This is in contrast to the results from the thin films, and suggests that the isomer which predominates in the thin films has a much higher intersystem crossing rate than the other isomer.     

Toward automatic phenotyping of developing embryos from videos.

We describe a trainable system for analyzing videos of developing C. elegans embryos. The system automatically detects, segments, and locates cells and nuclei in microscopic images. The system was designed as the central component of a fully automated phenotyping system. The system contains three modules 1) a convolutional network trained to classify each pixel into five categories: cell wall, cytoplasm, nucleus membrane, nucleus, outside medium; 2) an energy-based model, which cleans up the output of the convolutional network by learning local consistency constraints that must be satisfied by label images; 3) a set of elastic models of the embryo at various stages of development that are matched to the label images.     

A reliable and manufacturable method to induce a stress of >1 GPa on a P-channel MOSFET in high volume manufacturing

This letter discusses a reliable and manufacturable integration technique to induce greater than 1 GPa of stress into a p-channel MOSFET, which will be required to increase the drive current beyond 1 mA//spl mu/m at the sub-90-nm process generation. Uniaxial compressive stress is introduced into the p-channel by both a selective deposition of SiGe in the source/drain and an engineered 2.5-GPa compressively stressed nitride. The highest to date compressively stressed SiN film is obtained by heavy ion bombardment during the deposition of the film.     

Synthesis and applications of heterobifunctional poly(ethylene oxide) oligomers

Poly(ethylene oxide) (PEO) oligomers are employed extensively in pharmaceutical and biomedical arenas mainly due to their excellent physical and biological properties, including solubility in water and organic solvents, lack of toxicity, and absence of immunogenicity. PEO can be chemically modified and reacted with, or adsorbed onto, other molecules and surfaces. Sophisticated applications for PEO have increased the demand for PEO oligomers with tailored functionalities, and heterobifunctional PEOs are often needed. This review discusses the synthesis and applications of heterobifunctional PEO oligomers possessing amine, carboxylate, thiol, and maleimide functional groups.     

Self-service reservation in the fieldforce

On-line service reservation is becoming increasingly popular in the service industry. As services become more complex, requiring co-ordination among individual actions, the planning for making service appointments is normally conducted manually by the operators, often resulting in slow responses to customers. To tackle this problem, we have developed a real-time service reservation portal that takes an order from a user and works out appointment options, based on the availability of enterprise resources, for the user to book on-line. The portal is capable of dealing with complex workflow appointing, supporting interactive fine-tuning in individual appointments, respecting customer preferences and work policies, monitoring progress of workflow, informing the customer of status changes in job scheduling, dispatching and execution, as well as handling exceptions automatically. We have integrated the portal, code-named FieldReserve, with other components in the BT fieldforce optimisation suite (FOS) that covers functions of resource planning, scheduling and execution for the fieldforce to demonstrate the feasibility and potential benefits of this technology. Benefits demonstrated are to provide customers with instant response of service reservation, to provide volume control on reservation, to break away from one-size-fits-all lead times for service fulfilment, to provide customers with equal access to service provision, and to bring transparency of service progress to customers. Currently, we are actively engaging with businesses and have obtained strong support to downstream the key values of this technology in commercial contexts.