Process of end-capping a polyimide system

A process of endcapping a polyimide system with an endcapping agent in order to achieve a controlled decrease in molecular weight and melt viscosity along with predictable fracture resistance of the molded products is disclosed. The uncapped system is formed by combining an equimolar ratio of 4,4'-bis (3,4-dicarboxyphenoxy) diphenylsulfide dianhydride (BDSDA) and 1,-bis (aminophenoxy) benzene (APB) dissolved in bis (2-methoxyethyl)ether. The endcapped system is formed by dissolving APB in bis-(2-methoxyethyl)ether, adding the BDSDA. By varying the amount of endcapping from 0 to 4%, molecular weight is decreased from 13,900 to 8660. At a processing temperature of 250 C, there is a linear relationship between molecular weight and viscosity, with the viscosity decreasing by two orders of magnitude as the molecular weight decreased from 13,900 to 8660

Polyimide adhesives

A process was developed for preparing aromatic polyamide acids for use as adhesives by reacting an aromatic dianhydride to an approximately equimolar amount of an aromatic diamine in a water or lower alkanol miscible ether solvent. The polyamide acids are converted to polyimides by heating to the temperature range of 200 - 300 C. The polyimides are thermally stable and insoluble in ethers and other organic solvents

Copolyimide with a combination of flexibilizing groups

Copolyimides are prepared by reacting one or more aromatic dianhydrides with a meta-substituted phenylene diamine and an aromatic bridged diamine. The incorporation of meta-substituted phenylene diamine derived units and bridged aromatice diamine derived units into the linear aromatic polymer backbone results in a copolyimide of improved flexibility, processability, and melt-flow characteristics. The copolyimides are especially useful as thermoplastic hot-melt adhesives

Functional reasoning in diagnostic problem solving

This work is one facet of an integrated approach to diagnostic problem solving for aircraft and space systems currently under development. The authors are applying a method of modeling and reasoning about deep knowledge based on a functional viewpoint. The approach recognizes a level of device understanding which is intermediate between a compiled level of typical Expert Systems, and a deep level at which large-scale device behavior is derived from known properties of device structure and component behavior. At this intermediate functional level, a device is modeled in three steps. First, a component decomposition of the device is defined. Second, the functionality of each device/subdevice is abstractly identified. Third, the state sequences which implement each function are specified. Given a functional representation and a set of initial conditions, the functional reasoner acts as a consequence finder. The output of the consequence finder can be utilized in diagnostic problem solving. The paper also discussed ways in which this functional approach may find application in the aerospace field

Strategies for adding adaptive learning mechanisms to rule-based diagnostic expert systems

Rule-based diagnostic expert systems can be used to perform many of the diagnostic chores necessary in today's complex space systems. These expert systems typically take a set of symptoms as input and produce diagnostic advice as output. The primary objective of such expert systems is to provide accurate and comprehensive advice which can be used to help return the space system in question to nominal operation. The development and maintenance of diagnostic expert systems is time and labor intensive since the services of both knowledge engineer(s) and domain expert(s) are required. The use of adaptive learning mechanisms to increment evaluate and refine rules promises to reduce both time and labor costs associated with such systems. This paper describes the basic adaptive learning mechanisms of strengthening, weakening, generalization, discrimination, and discovery. Next basic strategies are discussed for adding these learning mechanisms to rule-based diagnostic expert systems. These strategies support the incremental evaluation and refinement of rules in the knowledge base by comparing the set of advice given by the expert system (A) with the correct diagnosis (C). Techniques are described for selecting those rules in the in the knowledge base which should participate in adaptive learning. The strategies presented may be used with a wide variety of learning algorithms. Further, these strategies are applicable to a large number of rule-based diagnostic expert systems. They may be used to provide either immediate or deferred updating of the knowledge base

Association analysis of Neuregulin 1 candidate regions in schizophrenia and bipolar disorder

Schizophrenia (SCZ) and bipolar disorder (BPD) are severe heritable psychiatric disorders involving a complex genetic aetiology. Neuregulin 1 (NRG1) is a leading candidate gene for SCZ, and has recently been implicated in BPD. We previously reported association of two NRG1 haplotypes with SCZ and BPD in a Scottish case–control sample. One haplotype is located at the 5′ end of the gene (region A), and the other is located at the 3′ end (region B). Here, association to haplotypes within regions A and B was assessed in patients with SCZ and BPD in a second Scottish case–control sample and in the two Scottish samples combined. Association to region B was also assessed in patients with SCZ and BPD in a German case–control sample, and in all three samples combined. No evidence was found for association in the new samples when analysed individually; however, in the joint analysis of the two Scottish samples, a region B haplotype comprising two SNPs (rs6988339 and rs3757930) was associated with SCZ and the combined case group (SCZ: p = 0.0037, OR = 1.3, 95% CI: 1.1–1.6; BPD + SCZ: p = 0.0080, OR = 1.2, 95% CI: 1.1–1.5), with these associations withstanding multiple testing correction at the single-test level (SCZ: pst = 0.022; BPD + SCZ: pst = 0.044). This study supports the involvement of NRG1 variants in the less well studied 3′ region in conferring susceptibility to SCZ and BPD in the Scottish population

The Trichoptera barcode initiative: a strategy for generating a species-level Tree of Life

DNA barcoding was intended as a means to provide species-level identifications through associating DNA sequences from unknown specimens to those from curated reference specimens. Although barcodes were not designed for phylogenetics, they can be beneficial to the completion of the Tree of Life. The barcode database for Trichoptera is relatively comprehensive, with data from every family, approximately two-thirds of the genera, and one-third of the described species. Most Trichoptera, as with most of life’s species, have never been subjected to any formal phylogenetic analysis. Here, we present a phylogeny with over 16 000 unique haplotypes as a working hypothesis that can be updated as our estimates improve. We suggest a strategy of implementing constrained tree searches, which allow larger datasets to dictate the backbone phylogeny, while the barcode data fill out the tips of the tree. We also discuss how this phylogeny could be used to focus taxonomic attention on ambiguous species boundaries and hidden biodiversity. We suggest that systematists continue to differentiate between ‘Barcode Index Numbers’ (BINs) and ‘species’ that have been formally described. Each has utility, but they are not synonyms. We highlight examples of integrative taxonomy, using both barcodes and morphology for species description. This article is part of the themed issue ‘From DNA barcodes to biomes’

Evaluation of a Real-Time Nucleic Acid Sequence-Based Amplification Assay Using Molecular Beacons for Detection of Human Immunodeficiency Virus Type 1

We evaluated the performance characteristics of a new, real-time nucleic acid sequence-based amplification (NASBA) assay that incorporates molecular beacon technology for detection of human immunodeficiency virus type 1 (HIV-1). The quantitative results were comparable to those obtained with three leading commercially available assays. The analytical sensitivity was 37 IU/ml. The NASBA assay detected clinically relevant recombinant viruses and all group M HIV-1 subtypes