Nonterminal unsaturated silane coupling agents for mineral-filled ethylene–propylene rubber

This paper describes the results of an experimental investigation concerning the effect of reactive organofunctional unsaturated silanes on mechanical properties of mineral-filled ethylene–propylene elastomers. The tested group of the unsaturated silanes was prepared by hydrosilylation syntheses. The experimental silanes, 2,6-octadienyltriethoxysilane, cis-2-butenyltriethoxysilane, 2-(3-cyclohexenylethyl)triethoxysilane, and 2-(3-cyclohexenylethyl)methyldiethoxysilane, led to a considerable improvement in mechanical and electrical properties of mineral-filled vulcanizates based on peroxide-cured ethylene–propylene elastomers. From the tested silanes, the 3-cyclohexenylethylsilanes impart an improvement comparable with the action of vinyltris(2-methoxyethoxy)silane, presently used as a standard coupling agent in mineral-filled peroxide-cured elastomers.     

Reactive polymers,XXXVII. An investigation of the internal structure of polymeric sorbents based on poly(2,3-epoxypropyl methacrylate-co-ethylene dimethacrylate)

The internal structure of polymeric sorbents based on 2,3-epoxypropyl methacrylateethylene dimethacrylate was investigated by means of mercury porosimetry and by employing the sorption method. The results were confronted with characteristic chromatographic data and helped to elucidate the relationships existing between the internal structure of copolymers and their chromatographic properties.     

Influence of temperature on the reactivity of limestone particles with sulfur dioxide

A modified version of the grain theory was used to analyse the effect of temperature on the sulfation reaction. The theory combines the influence of temperature on the grain size, its effect on the rate of transport of SO₂ and the chemical reaction. An efficient numerical procedure is presented for solving the model equations which take into account the radial gradient of the effective diffusivity in a particle.     

Fracture of the anterior superior process of the calcaneus: an often misdiagnosed fracture

Fracture of the anterior superior process of the calcaneus has been considered an unusual injury. Following a sudden twist there is immediate pain on the outer aspect of the mid-portion of the foot and discomfort on weight-bearing. Three mechanisms of injury have been reported to cause the fracture. The diagnosis is often missed, and prolonged disability and local pain at the calcaneocuboid joint deserve further consideration. Oblique X-rays of the foot are helpful to visualize the fracture. Type III fractures may cause cartilage lesions and arthrosis; therefore, one should not wait long before excision or refixation of the fragment.     

Extrahierbarkeit der Organozinnstabilisatoren aus Hart-Polyvinylehlorid-Folien

Zusammenfassung Wegen der biologischen Aktivität von Organozinnverbindungen, die als Stabilisatoren für PVC-Mischungen verwendet werden, und ihrer bewiesenen Auslaugung aus Folien scheint es erforderlich, deren Anwendung in der Lebensmittelindustrie einzuschränken. Ein endgültiges Ergebnis kann erst nach Abschluß der biologischen Versuche gefällt werden.Sollte ein Organozinnstabilisator untoxisch sein, so kann seine Verwendung erst dann erwogen werden, wenn eine verläßliche Methode seiner Erfassung im Kunststoff ausgearbeitet ist, d. h. eine Methode für die Bestimmung des organischen Radikals und nicht nur für die Bestimmung des Zinns.     

Does nitric oxide act in the ventromedial preoptic area to mediate oestrogen negative feedback in the seasonally anoestrous ewe?

Seasonal anoestrus in the ewe results from enhanced oestrogen negative feedback. Recent data have implicated the ventromedial preoptic area (vmPOA) as an important site of oestrogen action. This study addressed whether NO acts within the vmPOA to inhibit LH during seasonal anoestrus. In Experiment 1, microimplants containing Nomega-nitro-l-arginine methyl ester (l-NAME, NOS inhibitor), S-methyl thiocitrulline (SMTC, neural NOS (nNOS) inhibitor) or empty implants (control) were administered during mid-anoestrus to the vmPOA. l-NAME, but not SMTC, significantly increased LH pulse frequency. For Experiment 2, ewes in late anoestrus were administered 7-nitroindazole (7NI; nNOS inhibitor), l-NAME, SMTC, or empty implants. 7NI, but not l-NAME or SMTC, increased LH pulse frequency. In Experiment 3, the effects of microimplants and microinjections of l-NAME were compared in mid-anoestrus. Microinjections of l-NAME (300 nl at 10 microg/microl) increased LH pulse frequency, but microimplants did not. In late anoestrus, similar microinjections were ineffective. Taken together, the results of Experiments 1-3 suggested that NO inhibition may be stronger during the middle than at the end of seasonal anoestrus. To test this hypothesis, ewes in Experiment 4 received microinjection of l-NAME or vehicle thrice during the non-breeding season; none of the treatments increased LH pulse frequency. These results indicate that NO plays a role in the vmPOA in suppressing LH secretion during seasonal anoestrus because NOS inhibitors were consistently stimulatory when LH pulse frequency was low. However, the inconsistent and modest effects of these inhibitors suggest that NO actions in this area cannot completely account for the effects of inhibitory photoperiod.