An investigation of amorphous phase separation, leachability and surface area of an ionomer glass system and a sodium-boro-silicate glass system

Glasses from a complex SiO₂-Al₂O₃-P₂O₅-CaO-CaF₂ glass series, known as 'ionomer glasses' were investigated. For comparison, a sodium-boro-silicate (s-b-s) glass system, which is known to undergo amorphous phase separation was also investigated. Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX) and BET surface area and pore distribution analysis were the principal analytical techniques used in this study. SEM analysis of the ionomer glass compositions revealed smooth spherical droplets of 2–15 nm while the background morphology appeared rough and speckled. A classic interconnected structure was observed for the s-b-s glass. EDX analysis of the s-b-s glass confirmed that the sodium-borate phase was removed by leaching with 0.3 M HNO₃, leaving behind a silica-rich structure. EDX analysis of ionomer glasses leached with 10% NaOH showed that the calcium and phosphate phases were being removed, although not to completion. For the base s-b-s glass a surface area of m 8² g^–1 was recorded. However, the base glass after extraction with 0.3 M HNO₃ of the sodium borate rich phase gave a BET surface area of 330 m² g^–1 indicating that it had already undergone phase separation on quenching from the melt, giving rise to a fine scale interconnected structure. The leached s-b-s glasses exhibited type 4 adsorption/desorption isotherms characteristic of mesoporous materials. Glasses which had been heat treated at 580°C for 4 h exhibited a surface area of 62 m² g^–1. This indicates that the as-quenched glass is already phase separated and that the phase separated microstructure is coarsening on heat treatment. A surface area of 4 m² g^–1 was measured for the base ionomer glasses. After leaching with 10% NaOH this value rose 10-fold with a maximum surface area of 44.1 m² g^–1 being recorded. The ionomer glasses also exhibited adsorption/desorption isotherms characteristic of mesoporous materials.     

Protein kinase C and the cytoskeleton

In this work we take under examination the aromatic polycyclic hydrocarbons (APHs) as a class of organic micropolluting agents which have a considerable impact in the life and in the working environment of man. The authors decided to expressly start this study by proposing the changes pattern cause by APHs according to their chemical-physical reactivity characteristics, in order to realise a qualitative and quantitative evaluation of their toxicologic impact. Therefore, the specific aspects of chemism (reactions of substitution, aromatic electrophilia and addition) of these organic micropolluting agents are studied with particular reference to their chemical structure and to the properties which are the main important cause of every effect of diffusion both in productive environments and of toxicity in the human body. In this way, come toxicologic risk sources, responsible, within some technological cycles for the APHs emission in the working areas, are identified, shown and evaluated; carrying factors, not much investigated till now, which represent a synergic effect to the introduction and absorption of the APHs by the human body. For the necessity of a useful environmental monitoring which could be applied to different matrices, the techniques and the methods useful for carrying out sampling and analytical evaluation in a correct way, are introduced as well. Lastly, the Authors stress on the engagement and discuss the measures of prevention and protection, technically performable on the basis of the chemico-physical-granulometric properties of APHs, with the goal of safeguarding at best health of people occupationally exposed.     

Influence of gender and the endocrine environment on the distribution of androgen receptors in the lacrimal gland

Androgens are known to regulate both the structure and function of lacrimal tissue in a variety of species. To explore the endocrine basis for this hormone action, the following study was designed to: (1) determine the cellular distribution of androgen receptors in the lacrimal gland; and (2) examine the influence of gender and the endocrine environment on the glandular content of these binding sites. Lacrimal glands were obtained from intact, castrated, hypophysectomized, diabetic or sham-operated male or female adult rats, mice or hamsters, as well as from orchiectomized rats exposed to placebo compounds or physiological levels of testosterone. The cellular location of androgen receptors was evaluated by utilizing an immunoperoxidase protocol, in which a purified rabbit polyclonal antibody to the rat androgen receptor was used as the first antibody. Our findings with lacrimal glands showed that: (1) androgen receptors are located almost exclusively in nuclei of epithelial cells; (2) the cellular distribution or intranuclear density of these binding sites is far more extensive in glands of males, as compared to females; (3) orchiectomy or hypophysectomy, but not sham-surgery or diabetes, lead to a dramatic reduction in the immunocytochemical expression of androgen receptors; and (4) testosterone administration to orchiectomized rats induces a marked increase in androgen receptor content, relative to that in placebo-exposed glands. Our results also reveal that a 10 kb androgen receptor mRNA exists in the rat lacrimal gland. Overall, these findings demonstrate that gender and the endocrine system may significantly influence the distribution of androgen binding sites in rat lacrimal tissue. Moreover, our results show that androgens up-regulate their own lacrimal gland receptors.     

Thermal oxidation and photo-oxidation of poly(2,6-dimethyl-1,4-phenylene oxide)

The thermal oxidation and photo-oxidation of poly(2,6-dimethyl-1,4-phenylene oxide) have been examined. Oxidation of the plastic results in the evolution of carbon dioxide, nitrogen and traces of hydrogen, the introduction of considerable crosslinking, and increased absorption in the hydroxyl and carbonyl regions of the infrared spectrum. A free-radical oxidation mechanism is postulated.     

Photo-oxidation of phenoxy resin

A study has been made of the photolysis and photo-oxidation of phenoxy resin. Photolysis results in the evolution of hydrogen, methane, ethane, propene, propane, toluene, and the oxides of carbon. Also observed are increased yellowing, a rapid rise in gel content, and a decrease in intrinsic viscosity and elongation. Photo-oxidation causes similar changes, but produces oxidized chain fragments, more gel, and less yellowing as well as broad absorptions in the hydroxyl and carbonyl regions of the infrared spectrum. A free-radical mechanism is proposed in which both chain scission and crosslinking occur.     

Hydrolysis of polycarbonate to yield BPA

Elevated temperatures and high humidity decrease the molecular weight and impact strength of polycarbonate. Hydrolysis of injection molded polycarbonate (PC) bars stored in glass containers at 85°C and 96% relative humidity (RH) produced brown surface crystals within 30 days. Aging of PC bars at 96% RH and temperatures of 70°C and lower for longer periods of time formed a brown liquid coating on the PC. X-ray, DSC, and GPC measurements indicated that about 70 wt% of the surface crystals were bisphenol A (BPA). The remaining portion of hydrolysis products appeared to be higher molecular weight oligomers of BPA. The brown liquid was composed of supercooled liquid BPA, BPA oligomers, and water. Initial growth of BPA on the surface of a PC bar took place at the interface between the PC and the glass wall of the container. Apparently a water soluble extract from the glass container accelerated the hydrolytic degradation of PC; nevertheless, hydrolysis of PC occurred in the absence of glass—although at a slower rate. Hydrolysis studies were carried out on several commercial PC formulations. The PC resin containing only a heat stabilizer was least affected. Of the fiame retardant grades, the brominated PC hydrolyzed less rapidly than these particular compositions containing alkali metal sulfonic acid salts. A glass fiber reinforced PC was less stable than its unfilled parent compound. A hydrolytic stabilizer was ineffective against the attack of water under these conditions.