Mechanical relaxations in polybutene-1 and poly-4-methylpentene-1

Dynamic mechanical measurements between — 180°C and 180°C were made on both isotropic and drawn samples of polybutene-1 (PB-1) and poly-4-methylpentene-1 (P4MB1) over a wide frequency range by the use of a torsional pendulum (0.3–3 Hz), a viscoelastic spectrometer (5–90 Hz) and ultrasonic technique (3 MHz). The relaxation peaks were identified and the associated activation energies determined from Arrhenius plots. For PB-1 it was observed that orientation reduces the height and shifts up the temperature of the α_a-peak associated with large scale main-chain motion in the amorphous regions, but has little effect on the β-peak associated with side-group motion. In addition to the α_a and β relaxations a high-temperature crystalline relaxation (α_c) is also observed in P4MP1. For both the α_c and β relaxations the mechanical loss at 45° to the draw direction is much larger than that at 90°, which indicates that shear processes are involved in these relaxations.     

纺牵—步法中粗旦丙纶长丝沸水收缩率初探

在纺牵联合一步法纺丝机上研究了丙纶切片的熔融指数对纤维沸水收缩率的影响，发现熔融指数高的切片，其纤维的沸水收缩率变化大。沸水收缩率随热定型的温度升高而下降。沸水收缩率可根据用户提供中心值（Ｍ）通过实验确定，一般以Ｍ±１．５为宜。     

Toughening by Metallic Lamina in Nickel/Alumina Composites

Tape casting and hot-pressing were used to produce metal/ alumina laminate composites. The mechanical behavior of these laminates was characterized. The strength and toughness of the laminates were greatly improved in comparison to that of monolithic alumina. Indentation strength values of the laminates remained approximately constant for indent loads between 10 and 100 N. Thus, this type of laminate appears to be a good candidate for damage-tolerant composite material design.     

High-impact poly(ethylene terephthalate) blends

Rubbers of different kind were tested as toughening agents of poly(ethylene terephthalate) (PET), noting significant morphological and mechanical differences. In particular, good results were obtained by using an ethylene–ethyl acrylate–glycidyl methacrylate copolymer. The resulting blend evidenced good particle distribution, and the latter was related to chemical interactions between the rubber epoxy groups and PET terminal groups, including the effect of low molecular weight and polymeric amine catalysts, and to extrusion conditions. © 1995 John Wiley & Sons, Inc.     

Comparison of selective cytotoxicity of alkyl lysophospholipids

Alkyl lysophospholipids have been shown to be cytooxic to a number of neoplastic tissues. One, ET-18-OCH₃, has been used to selectively purge leukemic cells from mixtures with normal marrow progenitor cells,in vitro andin vivo. We have measured the 50% inhibitory (IC₅₀) effect of a series of ether, lipids (EL) on leukemic cells (HL60, K562, Daudi, KG-1, KG-1a) and normal marrow progenitor cells. Cells were incubated with varying concentrations of EL for 4 hr and assayed for viability, [³H]thymidine incorporation and clonogenicity in semi-solid media. The effect on protein kinase C (PKC) activity was assayed for each compound. Compounds tested included three glycerophosphocholine analogs-ET-18-OCH₃, ET-16-NHCOCH₃, and BM 41.440. In addition, a lipoidal amine, CP 46665, an ethyleneglycolphospholipid, AEPL, and four single chain alkylphosphocholine analogs, HePC₂, HePC₃, HePC₄ and HePC₆ were also tested. During the period of incubation, the cells remained viable (>70%) as judged by trypan blue dye exclusion. The glycerophosphocholines were the most active and showed the highest therapeutic index. The lipoidal amine was active, but toxic to normal marrow progenitor cells. The ethyleneglycolphospholipid was active against HL60, but not against the other cell lines. The single chain alkylphosphocholine analogs were less active. All of the compounds inhibited PKC activity; however, the glycerophosphocholines were the most inhibitory. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Polyether-metal salt complexes: 1. The elevation of the glass transition temperature of polyethers by metal salts

Various metal halides have been dispersed in high and low molecular weight, amorphous poly(propylene oxide), by solution blending techniques, to give single phase polymeric complexes which remained thermoplastic even at very high salt loadings. These complexes were amorphous and showed a single well-defined glass transition temperature (T_g) by differential thermal analysis with the T_g of the complex up to 140°C greater than the T_g of the parent polymer. The T_g elevation depended upon both the amount and the type of salt added and for a given salt the elevation followed a sigmoidal curve which levelled out at high salt concentrations. The T_g data have been interpreted in terms of a chelate ring model involving the co-ordination of two adjacent ether oxygen atoms in the polymer backbone to the salt. Using this model it was possible to consider the complex as a random copolymer consisting of complexed and uncomplexed monomer units. The contribution of crosslinking by metal salts to the elevation of T_g was assessed by studying poly(tetramethylene glycol)-zinc chloride complexes in which chelate formation is entropically unfavourable. Mechanical data are reported for ZnCl₂ complexes with high molecular weight poly(propylene oxide). The results indicate that ZnCl₂ increased the rubbery modulus and this has been interpreted in terms of ZnCl₂ forming a few, weak intermolecular crosslinks.     

Non-insulin dependent diabetes mellitus in Psammomys obesus is independent of changes in tissue fatty acid composition

Recently it has been postulated that membrane fatty acid composition may be involved in the pathogenesis of insulin resistance and non-insulin dependent diabetes mellitus (NIDDM). The aim of this study was to determine whether alterations in tissue phospholipid (PL) fatty acids are present in hyperglycemic and hyperinsulinemic Psammomys obesus. On a native diet of salt bush, P. obesus (Israeli sand rat) remains lean and free of diabetes; however, when placed on a normal laboratory chow, a significant proportion of these animals develops a number of metabolic disorders associated with NIDDM, providing an ideal animal model of obesity and NIDDM. Four groups of mature P. obesus were studied: group A; normoglycemic and normoinsulinemic; group B: normoglycemic and hyperinsulinemic; group C: hyperglycemic and hyperinsulinemic; and group D: hyperglycemic hypoinsulinemic. In liver and red gastrocnemius muscle, there were no significant differences between groups, A, B, and in fatty acid composition of PL. Minor differences in individual fatty acids were demonstrated in group D animals (increased liver 20∶4n-6 and increased muscle 22∶5n-3); however, the unsaturation indices in liver and muscle were not significantly different between any of the groups. In considering that the minor changes in group D animals were not demonstrated in hyperinsulinemic group B animals or hyperglycemic, hyperinsulinemic group C animals, it is likely that the differences in group D animals were secondary to the more severe disturbances in glucose homeostasis and hypoinsulinemia present in these animals. The results of this study suggest that in this rodent diabetic model significant disturbances in glucose homeostasis and hyperinsulinemia may develop independently of changes in tissue fatty acid composition.     

Zukünftige Aufgaben der Verfahrenstechnik im Wasser- und Kohlenstoffkreislauf unserer Erde

Future Tasks of Processing Technology in Water and Carbon Cycle of the Earth The consumption of water and energy is very high in the modern industrial society. Energy is produced mostly from fossil fuels. From the material viewpoint, the planet earth is a system with closed cycles. One must therefore ask about the consequences of such high consumption on this cycle. Several contributions of processing technology to intensification of water and carbon cycle are shown. These solutions are compared with processes that have been developed for the maintenance of important cycles in spacecrafts.