Preparation of Silicon Carbide/Aluminum Nitride Ceramics Using Organometallic Precursors

Solid solutions of 2H -SiC/AlN can be prepared at temperatures less than 1600°C by rapid pyrolysis ("hot drop") of mixtures of [(Me₃Si)_0.80((CH₂=CH)MeSi)_1.0(MeHSi)_0.35] _n (VPS) or [MeHSiCH₂] _n (MPCS) with [R₂AlNH₂]₃, where R=Et, i -Bu or simply by slow pyrolysis of the precursor mixture in the case of [Et₂AlNH₂]₃. In contrast, slow pyrolysis of mixtures of VPS or MPCS with [ i -Bu₂AlNH₂]₃ yields a composite of 2 H -AlN and 3 C -SiC at 1600°C, which transforms into a single 2 H -SiC/AlN solid solution on heating to 2000°C. The influences of the nature of the precursor and processing conditions on the structure, composition, and purity of the SiC/AlN materials are discussed.     

Composite rectilinear deformation for stretch and squish navigation

We present the first scalable algorithm that supports the composition of successive rectilinear deformations. Earlier systems that provided stretch and squish navigation could only handle small datasets. More recent work featuring rubber sheet navigation for large datasets has focused on rendering and on application-specific issues. However, no algorithm has yet been presented for carrying out such navigation methods; our paper addresses this problem. For maximum flexibility with large datasets, a stretch and squish navigation algorithm should allow for millions of potentially deformable regions. However, typical usage only changes the extents of a small subset k of these n regions at a time. The challenge is to avoid computations that are linear in n, because a single deformation can affect the absolute screen-space location of every deformable region. We provide an O(klogn) algorithm that supports any application that can lay out a dataset on a generic grid, and show an implementation that allows navigation of trees and gene sequences with millions of items in sub-millisecond time.     

Some opportunities and challenges of producing bio-composites from non-wood residues

Plant-based composites (bio-composites) may in the future, become materials to replace polymer based composites and wood in terms of their attractive specific properties, lower cost, simple processing technologies, eco-friendliness, and ability to be recycled after use. The quality and performance of plant fibre-based composites can further be improved by adopting appropriate engineering techniques. Although plant-based fibres have these advantages, they also have some limitations. One of the serious problems of plant fibres is their strong polar character, which creates many problems of incompatibility with most thermosetting and thermoplastic matrices. Production of bio-composites with high quality and performance is therefore based on adjusting the properties of the constituents to meet the requirements of the composite material i.e. a product with consistent, uniform, predictable, and reproducible properties. Such adjustments involve creating strong interfacial bonds between the lignocellulosic substrates and the binder. Successful development of bio-composites therefore stem from a careful understanding of the influence of these adjustments on the composite properties. This paper suggests some opportunities available in producing bio-composites from non-wood resources, and the challenges that must be overcome to make this technology commercially viable. Gaps in knowledge and information required before full commercialisation of these materials are identified.     

Gender, Alcohol Consumption, and Differing Alcohol Expectancy Dimensions in College Drinkers.

Examinations of gender differences in alcohol expectancies among college drinkers typically have used self-report measures to assess single expectancy dimensions and often have been confounded by drinking level. This study examined gender differences in alcohol expectancies using 2 assessment methods. College students (N = 88) completed self-report questionnaires, including expectancy likelihood and subjective evaluation endorsements of expectancies, and a computerized expectancy accessibility task. Expectancy accessibility and endorsement were modestly correlated, with higher alcohol consumption and female gender linked to greater accessibility and endorsement of social enhancement expectancies. Gender moderated the relation between consumption and sociability expectancy accessibility; among men, heavier drinking was associated with more rapid activation of expectancies. Findings suggest complexity in associations among these variables and underscore the need to capture the multidimensionality of the expectancy construct and its relationship to alcohol use. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The polyurea structure and the role of Amine-Terminated Polyethers and Polyesters in Polyurethanes

The Reaction Injection Molding (RIM) technology has made it possible to master the fast reaction of di- and polyamines with di- and polyisocyanates, leading to the preferred polyurea structure. Telechelics with amino end groups are gaining increased interest for the manufacture of polyurethane-polyurea materials by this technology. They make it possible to substitute all urethane groups in the elastomers with urea groups. The telechelics which are considered are amine-terminated polyethers (ATPE) and polyesters based on the typical soft-segment forming polycondensation polymers which are widely used in polyurethane chemistry. Isocyanate-terminated prepolymers of toluene diisocyanate and polyether polyols can be hydrolyzed in aqueous alkaline media via the carbamate intermediate to the amineterminated prepolymers. The reactivity of these aromatic ATPEs was ideally fit for the RIM process. ATPEs by the hydrolysis process are somewhat limited if products with low viscosities are required. In the reaction of chloro-nitrobenzenes with polyether polyols followed by the hydrogenation of the nitro groups of the terminal phenoxy moieties, we found a path for the synthesis of low viscosity aromatic ATPEs. Capping of polyether polyols with acetoacetate groups and subsequent reaction of the acetoacetylated polyethers with amines, leads to polyethers with terminal imine or enamine groups, which are derivates of aminocrotonic acid. We determined that this approach is a universal method for the synthesis of a large variety of aromatic as well as aliphatic ATPEs with low viscosities. Trifluoroacetic acid turned out to be the ideal catalyst for the reaction of the acetoacetylated polyethers with aromatic diamines, one amino group forming the imine link, the second one remaining intact and providing the desired reactivity towards isocyanates. Aliphatic diamines do not require a catalyst for this reaction. They lead to aminocrotonates with aliphatic amino groups that have high reactivity towards isocyanates, which is to be expected from aliphatic amines. The reaction of the chloroformates of polyether polyols with diamines can also be used to synthesize a variety of ATPEs. We recently developed an approach to low viscosity ATPEs having secondary amino end groups. The hydroxyl groups of the polyether polyols are converted to chloride or methanesulfonyl. The polyethers terminated with these leaving-groups are reacted with primary aliphatic or aromatic amines to give the secondary ATPEs in very good yields.     

Achieving Dependability in the Configuration, Integration and Testing of Healthcare Technologies

This paper presents two case studies, which highlight the practical work involved in developing and deploying dependable healthcare systems. It shows how dependability is a thoroughgoingly practical, contexted achievement. We show how dependability is an outcome of the reasoning and argumentation processes that stakeholders engage in, in situations such as design and testing. What becomes relevant during these interactions stands as the dependability criteria that must be achieved. Furthermore, we examine the way in which different dependability criteria need to be managed, and even relatively prioritised, before finally discussing the types of work this provokes at the boundaries of organisations, particularly when integrating work and technologies.     

Diagnostic value of antibodies to filaggrin in rheumatoid arthritis

OBJECTIVE: To determine the prevalence of antibodies to filaggrin in a cross sectional sample of patients with rheumatoid arthritis (RA). METHODS: Filaggrin from human skin was either extracted with 0.05% Nonidet P-40 and then partially purified by precipitating in ethanol and resuspending in water (Nonidet preparation) or extracted with 9 M urea and then purified by sequential fractionation on a DEAE Sephadex column and on a strong cation exchange column (purified preparation). Antibodies to filaggrin were detected using immunoblotting techniques with sera diluted 1:50. Antikeratin antibodies (AKA) were detected using indirect immunofluorescence microscopy on sections of rat esophagus. RESULTS: Antibodies to filaggrin were detected in 5 of 30 sera of patients with RA using filaggrin from the Nonidet preparation and 6 of 49 sera using filaggrin from the purified preparation. AKA were detected in 13 of 40 sera. A positive correlation existed between the presence of AKA and the presence of antibodies to filaggrin using the purified preparation (p=0.017). CONCLUSION: These data indicate that the reactivity of RA sera with filaggrin is not identical to the presence of AKA and is variable depending upon the preparation of filaggrin used. The diagnostic value of antibodies to filaggrin remains to be proven.     

Expression and functions of FGF-3 in Xenopus development

We have analyzed the expression pattern of the Xenopus FGF-3 gene during early development and examined its biological activity in three different bioassays using Xenopus embryos. We show that from the early gastrula stage there is a domain of expression around the blastopore which becomes a posterior domain as the blastopore closes. An anterior ectodermal domain becomes detectable from mid-gastrula stages in the prospective hind-brain, and there are several later domains of expression: the midbrain-hindbrain junction, the otocyst, the pharyngeal pouches and the tailbud region. By using double whole-mount in situ hybridizations we show that the XFGF-3 expression in the brain is dynamically regulated both in time and space during development. The anterior domain of early neurula stage embryos corresponds to the prospective rhombomeres 3-5. By the time the neural tube is closed, XFGF-3 expression is restricted to r4 and later a new domain of expression is established at the midbrain/hindbrain junction. In addition, we show that, despite its difference in receptor specificity, XFGF-3 can induce the formation of mesoderm from animal caps similarly to other FGFs. It also displays a posteriorizing activity on whole embryos similar to other FGFs. Although the absence of maternal expression makes it unlikely that XFGF-3 is involved in mesoderm induction in vivo, its posterior domain of expression during gastrulation and its posteriorizing activity suggests that it participates in the maintenance of mesodermal gene expression and in the FGF mediated patterning of the anteroposterior axis during gastrulation.