The hot compaction behaviour of woven oriented polypropylene fibres and tapes. I. Mechanical properties

The aim of this work was to establish the important parameters that control the hot compaction behaviour of woven oriented polypropylene. Five commercial woven cloths, based on four different polypropylene polymers, were selected so that the perceived important variables could be studied. These include the mechanical properties of the original oriented tapes or fibres, the geometry of the oriented reinforcement (fibres or tapes), the mechanical properties of the base polymer (which are crucially dependant on the molecular weight and morphology), and the weave style. The five cloths were chosen so as to explore the boundaries of these various parameters, i.e. low and high molecular weight: circular or rectangular reinforcement (fibres or tapes): low or high tape initial orientation: coarse or fine weave.A vital aspect of this study was the realisation that hot compacted polypropylene could be envisaged as a composite, comprising an oriented ‘reinforcement’ bound together by a matrix phase, formed by melting and recrystallisation of the original oriented material. We have established the crucial importance of the properties of the melted and recrystallised matrix phase, especially the level of ductility, in controlling the properties of the hot compacted composite.     

Polymeric prodrugs of mitomycin C designed for tumour tropism and sustained activation

Prodrugs of mitomycin C (MMC) based on soluble poly-[N-(2-hydroxyethyl)-L-glutamine] (pHEG) polymers have been evaluated as tumour-targeted drugs. These materials are designed to exploit the enhanced permeability of tumour vasculature, combining a passive tumour tropism with decreased systemic liberation of free MMC. A tri- or tetrapeptide linkage (e.g. Gly-Phe-Ala-Leu) between pHEG and the aziridine nitrogen of MMC can combine good hydrolytic stability with rapid cleavage by lysosomal enzymes, releasing free MMC. The conjugates showed decreased systemic toxicity and could be administered to mice at a total MMC dose of 15 mg/kg i.v., compared with just 6 mg/kg for free MMC. Conjugates also showed better activity against animal models of established tumours, achieving up to 77% increased life span (ILS) against solid P388 leukaemia, compared with only 23% for free MMC, and up to 121% ILS against solid C26 colorectal carcinoma, compared with no activity for the free drug. Improving the therapeutic index of anticancer drugs by combining tumour tropism with decreased systemic toxicity is a versatile approach that should produce a new generation of improved anticancer agents.     

Metastasis induced by overexpression of p185neu-T after orthotopic injection into a prostatic epithelial cell line (NbE)

The effects of the composition of bacteriological growth media on the light output in a chemiluminometric assay of beta-galactosidase in Escherichia coli using 1,2-dioxetane substrates has been studied. In this assay a basic conflict exists between conditions that promote optimal bacterial growth and those conducive to maximal chemiluminescence. Common medium ingredients such as yeast or beef extract, protein hydrolysates and lactose suppress light emission and/or lead to high backgrounds. Quenching of light emission is probably partly due to light absorption by medium ingredients such as oxgall, and partly to interference with the reaction triggering the chemiluminescent process. Elevated backgrounds are caused by the presence of high concentrations of protein hydrolysates, which interact with the alkali in the accelerator solution. Only two purposely developed media, i.e. ILM and Colicult are shown to reconcile the requirements of growth support with that of optimal luminescent properties.     

The spinal muscular atrophy gene region at 5q13.1 has a paralogous chromosomal region at 6p21.3

We have examined acetaminophen (paracetamol) dosing for outpatient management of posttonsillectomy pain in children. Forty children, 5-15 years of age, undergoing tonsillectomy and their parents were randomly assigned to use a scheduled administration of acetaminophen in weight appropriate doses, 60 mg.kg-1.24h-1 orally, 90 mg.kg-1.24h-1 rectally, or to use acetaminophen 'as needed' according to present standards (control group). Postoperative pain was assessed by the child using the poker chip tool for the first three days after discharge. The prevalence of pain amongst all the children was high. The second day after discharge 22%-64% of the children in the study group and 36%-73% of the children in the control group rated severe pain. Recommended dose ranges of acetaminophen do not provide sufficient pain relief in children following tonsillectomy. Further studies are required to determine, whether higher doses of acetaminophen or analgesics with different analgesic properties will lead to improved analgesia in children following tonsillectomy.     

Ultrastructure of the spermatozoa and eggs of the ocean pout (Macrozoarces americanus L.), an internally fertilizing marine fish

Ultrastructure of sperm and eggs of the ocean pout (Macrozoarces americanus L.), an internally fertilizing marine teleost, was examined by scanning and transmission electron microscopy. The results showed that the sperm do not have an acrosome but have a very long mid-piece (one to two times the sperm head length) containing numerous well-developed elongated mitochondria. The sperm also have two tails (is biflagellate) each consisting of nine peripheral and one central pair (9 +/- 2) of microtubules. This long mid-piece and the biflagellate nature of the sperm appear to be associated with the long life-span of the sperm and with sperm dispersal in the ovary to fertilize the eggs internally. The ocean pout eggs are enveloped by a porous chorionic membrane similar to that found in other teleosts but have two micropyles, a condition likely related to a mechanism of egg fertilization which increases the egg fertility in the presence of low sperm numbers. Following insemination, some biochemically undefined excretions appeared on the surface of fertilized eggs and led to the acquisition of adherent capability of the eggs which formed a tightly associated egg mass in sea water.     

Localization of G-proteins in macrophages and E. coli during phagocytosis

Heterotrimeric GTP-binding proteins (G-proteins) have been shown to play an important role in cellular signalling. However, G-protein involvement in the intracellular spreading of bacterial pathogens is still poorly understood. In this study, antibodies, that recognize G-protein alpha-subunits (anti-G alpha), were used to investigate the localization of G-proteins in the macrophage-like cell line P388D1 and E. coli, also in their L-forms, during phagocytosis. In E. coli, anti-G alpha-binding sites were detected preferably in the cell wall and septa of the whole bacterial forms as well as in the cytoplasm of L-forms. Western blotting of bacterial lysates demonstrated protein bands with positive immunoreaction to antibodies against Gs alpha, Gi alpha, and Gcommon alpha with a higher affinity to the antibody against Gs alpha. Immunoreaction with the anti-Gs alpha-antibody was markedly higher in pathogenic strains of E. coli. Because of the conserved structure in all GTP-binding proteins which seem to derive from a single primordial protein involved in signal transduction mechanisms, it is reasonable to assume that some anti-Ga-positive proteins in E. coli might be related to G-proteins of higher organisms. A putative candidate for bacterial G-proteins seems to be a 36 kDa protein. Enhancement in G-protein immunostaining in the cytoplasm of macrophages around the internalized bacteria testifies to the involvement of G-proteins in mediation of endocytosis responses of phagocytes.     

Geometric model for nuclear absorption from microscopic theory

A parameter-free geometric model for nuclear absorption is derived from microscopic theory. The expression for the absorption cross section in the eikonal approximation taken in integral form is separated into a geometric contribution, described by an energy-dependent effective radius, and two surface terms which are shown to cancel in an asymptotic series expansion. For collisions of light nuclei, an expression for the effective radius is derived using harmonic-oscillator nuclear density functions. A direct extension to heavy nuclei with Woods-Saxon densities is made by identifying the equivalent half density radius for the harmonic-oscillator functions. Coulomb corrections are incorporated and a simplified geometric form of the Bradt-Peters type obtained. Results spanning the energy range of 1 MeV/nucleon to 1 GeV/nucleon are presented. Good agreement with experimental results are obtained.     

Statistical studies of branched ester latex and paint properties

Vinyl versatate, butyl acrylate and 2-ethylhexyl acrylate were compared as comonomer, for colloid-stabilized vinyl acetate latex polymers to assess their impact on latex coating properties. Vinyl versatate afforded advantages in scrub resistance, gloss, hydrophobicity and higher glass transition temperatures. Butyl acrylate developed better wet adhesion efficiency, gel content and hiding efficiency. 2-Ethylhexyl acrylate offered performance comparable to butyl acrylate in hiding efficiency, lowering copolymer glass transition temperatures, and gloss development. Combinations of these monomers, in many instances, afforded a better balance of performance properties than individual monomers alone. In the subject study, a simplex-centroid design was utilized to statistically map polymer compositions for determining the effect of comonomer composition on latex and paint film properties. In addition to developing contour maps of polymer and paint properties as a function of composition, a technique for studying structure-property relationships is presented.