Catalytic action of metallic salts in autoxidation and polymerization: 11. Polymerization of methacrylic acid esters with sodium hexanitrocobaltate in methanol-water

The polymerization of a series of methacrylic acid esters (methyl, ethyl, isopropyl and n-butyl) with sodium hexanitrocobaltate, Na₃[Co(NO₂)₆] was carried out in a methanol-water mixed solvent. The homogeneity of the polymerization system was dependent on the composition of the mixed solvent and greatly affected the rate of the polymerization. A maximum rate was obtained at approximately equimolar fractions of methanol and water in the polymerization of methyl methacrylate. The effect of bulkiness of ester groups on the polymerizability of each monomer was indistinguishable in the mixed solvent system. Kinetic study of the polymerization of methyl methacrylate in a mixed solvent of about an equimolar fraction of methanol and water gave the following polymerization equation: $\text{R}{}_{\mathrm{p}}\text{= k[l]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{[}\text{M}\text{]}{}^2$, and an apparent activation energy of 10.6 kcal/mol. The copolymerization of methyl methacrylate and styrene with the initiator suggested that polymerization proceeded via a radical mechanism. The possibility of a certain interaction between initiator, solvent and monomer in the initial stage of the polymerization is discussed on the basis of the kinetic data, properties of oligomers of methyl methacrylate, spectroscopic and other data.     

E.s.r. studies on free radicals generated in poly[p-(2-hydroxyethoxy) benzoic acid] fibres at low temperatures

Free radicals generated in stretched and ground poly [p-(2-hydroxyethoxy) benzoic acid] (PEOB) were studied by e.s.r. spectroscopy in an effort to isolate those formed by main chain scission. PEOB fibres stretched at ?86°C in a dry nitrogen atmosphere gave an asymmetric spectrum, which had patterns characteristic of both phenoxy and peroxy radicals in addition to some unknown peaks. The shape of the spectrum changed with increasing temperatures, finally becoming identical to that of phenoxy radicals at room temperature. The phenoxy radical was observed in all PEOB films ground or γ-irradiated in liquid nitrogen. In some cases a small peak of peroxy radical was observed. Theoretical spectra calculated for possible radical species or combinations of them were compared with those observed. No direct evidence was observed of the formation of alkyl type and radicals which were assumed to be formed with phenoxy radicals upon main chain rupture of PEOB. However, the relatively unstable peroxy radical observed in these experiments is thought to arise from them.     

Effect of water-Insoluble Powder Addition on Physical Properties of Gelatin Gel

Water-insoluble powder is often dispersed in shells of commercial soft capsules for various reasons, but little reports have been published about the effect of powder addition on the physical properties of the gelatin gel. Glass powder, titanium oxide, calcium carbonate and γ-orizanol were used as model of powder. Changes of Young modulus obtained from the tensile test showed that any powder addition to the gelatin sheet made the gelatin sheet hard not by the surface effect of powder but by the volumetric effect of it. In this test, any powders had no effect on the tensile strength of the gelatin sheet because there was little interaction between each powder and the gelatin gel in the break point. The limiting strain was decreased a little up to the specific amount of each powder and then beyond the specific amount that decreased steeply in the case of glass powder and γ-orizanol. There might be a suitable range of the amount of powder for the gelatin sheet to keep the plastic flow similar to the gelatin sheet containing no powder. In this work, it was shown that the physical properties of the gelatin shell would be regulated by powder addition to the gelatin sheet.     

Finite element analysis of wave motion

To estimate wave motion, the finite element method is presented based on the linear interpolation function and two-step explicit numerical integration in time. For the determination of free surface position, the two-step scheme based on the Eulerian technique is usefully employed. Travel and run-up of solitary wave have been analysed and compared with the analytical solution. Both results are reasonably well in agreement. This method is applied to estimate the wave force on the practical breakwater to show the validity of the method.     

Effect of polymer matrices on magnetic properties of plastic magnets

Plastic magnets were prepared using commercial polyamide (Nylon 12), polystyrene and ethylene-vinylacetate copolymer, and three kinds of ferrite magnetic powders with different concentration levels (20, 35 and 50 vol%). Their magnetic properties and thermal stability are discussed comparing viscoelasticity and thermal properties of the polymers and plastic magnets. Magnetic properties of the anisotropic plastic magnets were largely dependent on the concentration of the magnetic powder and its degree of orientation in the matrix. The degree of the orientation was mainly affected by the interaction between polymer matrix and magnetic powder, and viscoelastic property of the matrix polymer. It was also affected to some extent by the shape of the magnetic particles. The order of the interaction of the polymers to the magnetic powders was as follows: PA > EVA copolymer > PS, and PA-bonded magnets gave the highest magnetic properties among the matrices examined. The decrease in magnetic properties due to the change in the orientation of magnetic powder rarely occurred during thermal treatment.     

Regulation of tissue plasminogen activator production in cultured human fetal mesangial cells

This study was designed to determine the persistence of culturable bacteria versus DNA in the presence of a middle ear effusion in a chinchilla model of otitis media. Cohorts of animals were either infected with an ampicillin-resistant Haemophilus influenzae strain or injected with a tripartite inoculum consisting of freeze-thawed Streptococcus pneumoniae; pasteurized Moraxella catarrhalis; and DNA from H influenzae. The H influenzae-infected animals displayed culture positivity and polymerase chain reaction positivity through day 35. In the chinchillas infected with the low-copy number inocula of S pneumoniae, DNA was not detectable after day 1 from the co-inoculated pasteurized M catarrhalis bacteria or the purified H influenzae DNA; however, amplifiable DNA from the live low-copy number bacteria persisted through day 21 even though they were not culture-positive past day 3. These results demonstrate that DNA, and DNA from intact but nonviable bacteria, does not persist in an amplifiable form for more than a day in the presence of an effusion; however, live bacteria, while not culturable, persist in a viable state for weeks.     

Measurement of Rising R-Curve Behavior in Toughened Silicon Nitride by Stable Crack Propagation in Bending

A simple procedure for measuring the R -curve properties of ceramics by a stable fracture test in three-point bending is described. As a typical case, data are displayed for a Si₃N₄ material toughened by the presence of acicular grains in situ grown during the sintering process. The fracture mechanics specimen was a single-edge double-notched beam (SEDNB), whose notch was sharpened to a radius of <10 μm in order to reduce the amount of elastic energy stored at its root prior to crack extension. Furthermore, a stabilizer, specially designed for the bending geometry, was used to control crack stability. During stable extension, the crack could be easily arrested at selected locations of the load-displacement curve, the load quickly released, and the stable crack extension directly measured by the die-penetration technique. The crack resistance, K _R, of the material was calculated from the measured crack extent and the onset load value before unloading. This method enabled us to precisely monitor the critical load value at which the load-displacement curve deviated from linear behavior, as well as crack extensions from a few tens of micrometers to about 1 mm. As an application of this method, the fracture resistance of a Si₃N₄ material with rising R -curve behavior was measured and found to increase from about 5.5 to 9.0 MPaμm^1/2 within a 0.8-mm extension.     

Effects of ACE inhibitor on renal anemia in predialysis patients

Enterocolitis necroticans or pigbel is a rare condition characteristically affecting chronically malnourished people who abruptly increase their intake of protein. The classic presentation of the disease as seen in the highlands of Papua New Guinea is that of a necrotising enterocolitis after the ritual ingestion of contaminated pork. In this context, the presentation of the same disease in a well nourished white vegetarian in Oxford was all the more intriguing.