The morphology and properties of high modulus polypropylenes (PP) are characterized over a wide range of material variables. These variables include the tacticity, room temperature xylene solubles (XSRT), molecular weight, melt flow rate (MFR), and polydispersity index (PI). Flexural modulus in quench‐cooled compression moldings of propylene homopolymer can be correlated to the volume fraction crystallinity, ϕc, by an empirical logarithmic dependence. The quantitative zero orientation results for the quench‐cooled compression moldings provide an approximate crystallinity normalization for oriented moldings. WAXS analyses of crystalline orientation were determined over a range of melt temperatures and mold locations and correlated to the skin area fraction by optical microscopy. WAXS analysis of the balance of orientations for the crystallographic axes suggest that the orientation balance is primarily determined by the “melt orientability” of the resin type. An empirical description of flexural modulus in injection molded PP is developed for the range of material variables and molding conditions studied. This description is represented as a function of crystallinity‐normalized modulus vs. the frozen‐in crystalline orientation.
The influence of variations in beryllium content on the mechanical properties of copper-beryllium alloy strip is discussed. Four tempers of each of five alloys varying in beryllium content from 1.60 to 2.05 per cent were investigated, both in the solution heat-treated and strain-hardened conditions and after precipitation heat treatment. The mechanical properties evaluated include tensile strength, proportional limit, 0.01 and 0.2 per cent offset yield strengths, modulus of elasticity, elongation, fatigue strength in reversed bending at cycle lives ranging from 105 to 168, Rockwell and Rockwell superficial hardness. The effect of surface treatments on fatigue life, including furnace atmospheres and shot peening, is shown. Hardness response curves are given for the five alloys for various periods of time ranging from 1/2 to 5 hr at temmperatures of 575 to 700 F in increments of 25 F. From these studies the correlation between Rockwell B and Rockwell 30T hardness values, and Rockwell C and Rockwell 30N hardness values for each of the alloys was established. Data are also presented showing the resistance of the two commercial copper-beryllium alloys (No. 25 and No. 165) to stress corrosion cracking.
The success of the macrolide-rifampicin combination relies on the synergistic action of these 2 agents. Resistance to rifampicin will reduce the therapeutic efficacy of this treatment. It is of serious concern that the resistant isolates were all recently collected. Hopefully, recent research will lead to fewer asymptomatic foals receiving antimicrobials which will in turn reduce the likelihood of ongoing development of resistance. Ethical animal research: All organisms in this study were received by the laboratory from diagnostic accessions. Sources of funding: Funding for the study was provided by Rural Industries Research and Development Corporation and the University of Melbourne. G. Herbert was the recipient of a RN McCarthy scholarship from the Faculty of Veterinary Science. Competing interests: None declared.
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