Effect of outdoor aging on acrylic sheet

One of the prime contenders for solar reflectors or concentrators is acrylic plastic. Other than the basic requirement of being a highly efficient reflector or transmitter of the solar spectrum, it must offer excellent long-term weatherability with minimum cost. The weatherability of acrylic polymers, although known to be good compared to other polymers, has been an unknown with regard to actual exposure data in the southwestern United States, where the potential is high for solar energy installations. This report is a compilation of data obtained from an acrylic panel that has been exposed for over 17 years in the semi-arid desert terrain south of Albuquerque. New Mexico. A comparison is made with unexposed material having a very similar polymer structure.In general, chemical changes are not detectable while mechanical response shows some evidence of embrittlement. In spite of these, the decrease in optical transmission is surprisingly low. The as-recovered material (with dust-eroded surface) had an integrated or total transmittance which was 10 per cent less than the control material, based on a solar radiation spectrum. In order to isolate the degradation loss due to change in the basic polymer, a polished specimen of aged material was tested and showed only a 3 per cent drop in transmission across the solar spectrum. It appears reasonable that this low loss could be duplicated in a solar reflector provided the mirror is coated with an abrasion-resistant glass resin system.     

Formulation,Quality Control and Shelf Life of the Experimental Cytostatic Drug Cyclopentenyl Cytosine

ABSTRACT

This paper describes the formulation and quality control of an aqueous sterilized formulation of the experimental cytostatic drug cyclopentenyl cytosine (CPEC) to be used in Phase I/II clinical trials. The raw drug substance was extensively tested. A High Pressure Liquid Chromotography (HPLC) method was validated for the quality control of the formulated product. The aqueous formulation was found to be stable for at least 2 years at 2–8°C. Sterilization (15 min at 121°C) showed no influence on drug stability. The results show that CPEC can be formulated in an aqueous solution. The described HPLC method is a useful tool in the pharmaceutical quality control.     

Network characterisation of end-linked poly(dimethylsiloxane) by 1H-NMR-spin-spin relaxation

Summary Above the glass transition temperature ¹H-NMR-spinspin relaxation curves of elastomers usually consist of two main components, a Gauss-like decay and a longer exponential decay. They can be attributed to inter-crosslink chains and free dangling chain ends, respectively, in accordance with basic ideas of the dynamics of polymer chains. By using an increasing amount of end-linking agent during the network synthesis of poly(dimethyl siloxane), the portion of the long decay is considerably reduced while the shape and the decay times remain approximately constant. This gives experimental evidence of the common classification of the decay components for the first time. Finally, the theoretical model for network dynamics used, which includes common phantom network properties and a concept of two independent motion scales, provides two mean correlation times and an average molecular mass of inter-crosslink chains.     

Effect of Ca++ on triphosphoinositide extraction in fusing myoblasts

Ca⁺⁺-dependent degradation of triphosphoinositide has been postulated to regulate levels of membrane-bound Ca⁺⁺ and to generate a 1,2-diacylglycerol fusogen in cell fusion. Triphosphoinositide metabolism was therefore studied during Ca⁺⁺-induced fusion of cultured chick embryo myoblasts. Using a frequently cited extraction procedure, it was found that apparent Ca⁺⁺-dependent triphosphoinositide degradation was actually due to inhibition of extraction. A new procedure using the ion-pairing reagent tetrabutylammonium sulfate was developed which was unaffected by Ca⁺⁺ and gave 2- to 20-fold greater extraction of triphosphoinositide than existing procedures. With this procedure, no changes in triphosphoinositide metabolism were found during myoblast fusion.     

Untersuchung zur Rißbildung im Schweißgut legierter Stähle mit Hilfe des instrumentierten Einspann-Schweißversuchs

Instrumentierte Einspann-Schweißversuche zum Einfluß der chemischen Zusammensetzung und des Gefügeaufbaus auf Reaktionskräfte und Rißverlauf des Schweißguts legierter Kohlenstoffstähle. Rißeinleitung durch Heißrisse im Endkraterbereich. Bevorzugtes Rißwachstum bei mittleren Kohlenstoffgehalten im Temperaturbereich der Zwischenstufenausscheidung. Bedeutung der Plastifizierung. Verzögertes Rißwachstum in Abhängigkeit von Kohlenstoff- und Chromgehalten.     

Verminderung des Cadmium-Gehaltes von Rohphosphaten und Mineraldüngern

Reducing the cadmium content of crude phosphates and mineral fertilizers . Crude sedimentary phosphates generally contain cadmium together with traces of other heavy metals. These Cd traces generally end up in fertilizers produced from the crude phosphates. Processes have therefore been developed to separate the Cd from the crude phosphate or from the crude phosphoric acids arising therefrom as intermediates. In this way, the Cd content of the crude phosphate can be reduced to less the 10% of its original value, and to 50% thereof by extractive treatment with acidic calcium nitrate solution. Older calcination processes for crude phosphate have been improved to give residual Cd contents of 10 to 50% at temperatures of 800 to 1000°C. Cadmium can be removed almost quantitatively from crude phosphate by means of dialkyl dithiophosphoric acid esters by extraction, binding to adsorbents, or ion flotation. Cadmium can be extracted from crude acids in high yield by long-chained amines. After partial neutralization of the crude acids, precipitation as cadmium sulphide is also possible.