Universal features of the melt elasticity of interacting polymer nanocomposites.

We study the structure and linear viscoelasticity of interacting polymer nanocomposites based on mixtures of poly(ethylene oxide) and fumed silica particles. The filler is dispersed within the polymer using two different techniques which lead to different dispersion states. The analysis of the dynamic response of our systems highlights the formation of a stress-bearing network above a critical volume fraction, Φ(c). Extending a two-phase model used to describe weakly interacting systems, we show that above Φ(c) the melt-state elasticity of the composites arises from the independent contributions of a polymer-particle network and a viscous matrix. We also find that, although Φ(c) depends on the initial state of dispersion, the network elasticity scales with volume fraction following a universal power-law, with an exponent ν ≈ 1.8. Such a scaling law has been recently predicted for the stress-bearing mechanism governed by polymer-mediated interactions.

Use of microwaves for in-situ removal of pollutant compounds from solid matrices.

Thermal treatments are the most used methods to remediate contaminated solids. However, they may seriously damage the otherwise recoverable matrices, especially when mild operating conditions cannot be used. Microwaves recently raised as a powerful tool in industrial engineering for their ability, among other advantages, to offer a selected heating, thus allowing to treat and remove only the undesired components of a matrix. This work approaches the microwave assisted thermal treatments of waste from a physical-chemical point of view. Two recovering operations have been performed, respectively, on a soil contaminated by volatile organic compounds and on a ceramic filter spoiled by soot, using two specially designed prototypes, both realized on pre-pilot scale. The heat and mass transfer balances have then been analyzed in their more general form, and terms related to the use of microwaves outlined. Solutions of the differential equations have been applied to interpret the effects of microwaves on rate and efficiency of the remediation processes.

Surveillance of post-operative infections and management of antibiotic surgical prophylaxis in an Italian region.

The aim of the study was to evaluate the incidence of post-surgical infections and to assess management of antibiotic surgical prophylaxis. The survey was carried out by means of a questionnaire in order to obtain diverse information such as demographics, length of pre- and post-operative hospitalization, type of surgery, intervention duration, possible antibiotic prophylaxis and onset of post-surgical infections also monitored by post-discharge ambulatory controls. Four General Surgery and five Obstetrics and Gynecology Departments in Campania (southern Italy) participated in the study, which was carried out from December 2001-January 2002. Overall, 410 questionnaires were collected, referring to as many patients; antibiotic prophylaxis was performed in 385 (93.9%) patients. Antibiotic prophylaxis was generally managed not according to the general principles suggested by the international guidelines either for timing, for its duration or for the route of administration. Substantial differences were also noted in patient selection and antibiotic choice. Surgical site infections were recorded in 0.9% of patients undergoing clean surgery and in 3.6% of patients undergoing clean-contaminated surgery. Distant infections occurred in 1.5% in clean-contaminated surgery. The results of the present study suggest the need for continuous and accurate monitoring of post-surgical infections and the need to adopt appropriate guidelines to improve the management of surgical prophylaxis.

Relationships between processing-structure-migration properties for recycled polypropylene in food packaging.

In this work the relationships between processing, structure and migration properties of recycled polypropylene (PP) were analysed in relation to the possible use of recycled PP in food packaging applications. PP containers used in food packaging were contaminated with food and then washed, reduced into a processable size, dried and reprocessed by injection moulding. Gel Permeation Chromatography (GPC) analysis, mechanical, and total migration tests were performed on injection moulded samples to verify the effect of the recycling process on the structure and properties of PP. In order to evaluate the effect of the molecular weight on the properties of the recycled polymer, the study was conducted on containers produced by injection moulding made from a low molecular weight (LMW) PP and on containers produced by thermoforming made from a high molecular weight (HMW) PP.