4,413 research outputs found

    New polyimide polymer has excellent processing characterisitcs with improved thermo-oxidative and hydrolytic stabilities

    Get PDF
    Polyimide P10P and its processing technique apply to most high temperature plastic products, devices and castings. Prepolymer, when used as varnish, impregnates fibers directly and is able to be processed into advanced composities. Material may also be used as molding powder and adhesive

    Thermally stable laminating resins Final report

    Get PDF
    Polyimide resin and resin reinforced composite

    Reinforced structural plastics

    Get PDF
    Reinforced polyimide structures are described. Reinforcing materials are impregnated with a suspension of polyimide prepolymer and bonded together by heat and pressure to form a cured, hard-reinforced, polyimide structure

    New rapid-curing, stable polyimide polymers with high-temperature strength and thermal stability

    Get PDF
    Additive-type polymerization reaction forms thermally stable polyimide polymers, thereby eliminating the volatile matter attendant with the condensation reaction. It is based on the utilization of reactive alicyclic rings positioned on the ends of polyimide prepolymers having relatively low molecular weights

    A mechanophysical phase transition provides a dramatic example of colour polymorphism: the tribochromism of a substituted tri(methylene)tetrahydrofuran-2-one

    Get PDF
    BACKGROUND: Derivatives of fulgides have been shown to have interesting photochromic properties. We have synthesised a number of such derivatives and have found, in some cases, that crystals can be made to change colour on crushing, a phenomenon we have termed "tribochromism". We have studied a number of derivatives by X-ray crystallography, to see if the colour is linked to molecular structure or crystal packing, or both, and our structural results have been supported by calculation of molecular and lattice energies. RESULTS: A number of 5-dicyanomethylene-4-diphenylmethylene-3-disubstitutedmethylene-tetrahydrofuran-2-one compounds have been prepared and structurally characterised. The compounds are obtained as yellow or dark red crystals, or, in one case, both. In two cases where yellow crystals were obtained, we found that crushing the crystals gave a deep red powder. Structure determinations, including those of the one compound which gave both coloured forms, depending on crystallisation conditions, showed that the yellow crystals contained molecules in which the structure comprised a folded conformation at the diphenylmethylene site, whilst the red crystals contained molecules in a twisted conformation at this site. Lattice energy and molecular conformation energies were calculated for all molecules, and showed that the conformational energy of the molecule in structure IIIa (yellow) is marginally higher, and the conformation thus less stable, than that of the molecule in structure IIIb (red). However, the van der Waals energy for crystal structure IIIa, is slightly stronger than that of structure IIIb - which may be viewed as a hint of a metastable packing preference for IIIa, overcome by the contribution of a more stabilising Coulomb energy to the overall more favourable lattice energy of structure IIIb. CONCLUSIONS: Our studies have shown that the crystal colour is correlated with one of two molecular conformations which are different in energy, but that the less stable conformation can be stabilised by its host crystal lattice. Graphical abstractGraphical representation of the structural and colour change in the tribochromic compound (III)

    Phosphorylation site sequence of smooth muscle myosin light chain (Mr = 20 000)

    Get PDF
    AbstractThe amino terminal sequence of the myosin light chain (Mr = 20 000) isolated from chicken gizzards was found to be acetyl-Ser-Ser-Lys-Arg-Ala-Lys-Ala-Lys-Thr-Thr-Lys-Lys-Arg-Pro-Gln-Arg-Ala-Thr-Ser(P)-Asn-Val-Phe. This sequence assignment differs from that reported by Maita et al. [(1981) European J. Biochem. 117, 417] in the order of the tryptic peptides. The revised amino acid sequence exhibits greater homology with the phosphorylation site sequences of the regulatory light chains from cardiac and skeletal muscle. Moreover it is now apparent why synthetic peptides corresponding to the previously reported sequence were very poor substrates for the myosin light chain kinase

    Detection of Gravitational Lensing in the Cosmic Microwave Background

    Full text link
    Gravitational lensing of the cosmic microwave background (CMB), a long-standing prediction of the standard cosmolgical model, is ultimately expected to be an important source of cosmological information, but first detection has not been achieved to date. We report a 3.4 sigma detection, by applying quadratic estimator techniques to all sky maps from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, and correlating the result with radio galaxy counts from the NRAO VLA Sky Survey (NVSS). We present our methodology including a detailed discussion of potential contaminants. Our error estimates include systematic uncertainties from density gradients in NVSS, beam effects in WMAP, Galactic microwave foregrounds, resolved and unresolved CMB point sources, and the thermal Sunyaev-Zeldovich effect.Comment: 27 pages, 20 figure

    Relational trauma and its impact on late-adopted children

    Get PDF
    This paper describes work with two children, placed for late adoption who have suffered relational trauma. The paper explores the long-term consequences of such trauma, which includes problems with affect regulation, difficulties in generalising from one experience to another and shifts between phantasies of omnipotent control and sudden helplessness. Using drawings from one boy's therapy, it is argued that many children adopted at a later age live in two worlds, both internal and external, and internal objects and memories from the past vie with new experiences and representations for ascendancy within the child's mind. Which is more real: the world of the past or the present? The paper describes how these children experienced sudden and troubling shifts in focus as they were catapulted from feeling states belonging to one world to the other. The paper ends with a consideration of how findings from neuroscience may help us to understand these sudden shifts and overall argues for a pulling together of psychoanalytic thinking and child development research findings to support the child in psychotherapy
    corecore