Melt‐processable rubber: Chlorinated waste tire rubber‐filled polyvinyl chloride

Chlorinated ground rubber tire (Cl‐GRT) particles were used as filler in a plasticized polyvinylchloride (PVC) to develop a melt‐processable rubber composition. Physical properties of the Cl‐GRT‐filled PVC compound showed improvement compared to the nonchlorinated counterpart. Interaction between Cl‐GRT and PVC was examined on the basis of results of stress relaxation, dynamic mechanical thermal analysis, and solvent swelling studies. The Cl‐GRT could be loaded upto 40 parts per hundred parts of PVC, and the composition still retains the elastomeric characteristics. The Cl‐GRT‐filled composite was found to be reprocessable like the unfilled PVC compound. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 622–631, 2002; DOI 10.1002/app.10352     

Factors influencing magnetic polymer microspheres prepared by dispersion polymerization

Magnetic iron oxide (Fe₃O₄) was prepared by a coprecipitation method. Core–shell composite magnetic polymer microspheres with carboxyl groups were synthesized by the dispersion polymerization of styrene and acrylic acid in the presence of magnetic oxide, and dibenzoyl peroxide was used as an initiator. The synthesized magnetic polymer microspheres were characterized with X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and so forth. The results indicated that the product was single‐phase Fe₃O₄, and its average size was about 10 nm. The configuration of the microspheres, which contained carboxyl groups, was spherical, and the average size was about 2 μm. The results of vibrating sample magnetometry tests showed that the magnetic powders produced by different surfactants had different saturation magnetizations. When poly(ethylene glycol) with a weight‐average molecular weight of 4000 was used as a surfactant, the saturation magnetization of the samples reached 69.2 emu/g. The factors that affected the shape, magnetism, size, and distribution of the microspheres were also studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Re-examining the causal structure of information technology impact research

About 20 years ago, Markus and Robey noted that most research on IT impacts had been guided by deterministic perspectives and had neglected to use an emergent perspective, which could account for contradictory findings. They further observed that most research in this area had been carried out using variance theories at the expense of process theories. Finally, they suggested that more emphasis on multilevel theory building would likely improve empirical reliability. In this paper, we reiterate the observations and suggestions made by Markus and Robey on the causal structure of IT impact theories and carry out an analysis of empirical research published in four major IS journals, Management Information Systems Quarterly (MISQ), Information Systems Research (ISR), the European Journal of Information Systems (EJIS), and Information and Organization (I&O), to assess compliance with those recommendations. Our final sample consisted of 161 theory-driven articles, accounting for approximately 21% of all the empirical articles published in these journals. Our results first reveal that 91% of the studies in MISQ, ISR, and EJIS focused on deterministic theories, while 63% of those in I&O adopted an emergent perspective. Furthermore, 91% of the articles in MISQ, ISR, and EJIS adopted a variance model; this compares with 71% from I&O that applied a process model. Lastly, mixed levels of analysis were found in 14% of all the surveyed articles. Implications of these findings for future research are discussed.     

Analysis of the inappropriate utilization of the emergency service of a third-level hospital

OBJECTIVE: a) To find the reasons for inadequate use of Hospital Casualty Departments (HCDs); b) to discover the general population's levels of information concerning non-hospital Emergency Services (NESs); c) to analyse the relationship between the type of Primary Care Centre (PCC), i.e. whether reformed or not, and inadequate use of HCDs. DESIGN: A crossover study. SETTING: The Germans Trias i Pujol Hospital Casualty Department, Badalona. PATIENTS: A random sample of 321 patients over 14 years old, who were attended for pathologies considered emergencies not requiring hospital treatment. MEASUREMENTS AND MAIN RESULTS: The variables gathered were: age, gender, where the patient came from, reason for hospital use, knowledge of NESs and subsequent referral. 83.2% of patients attended on their own initiative. The main reasons given were "advantages of a hospital" and "the persistence of symptoms." 49% of the patients stated they knew of the NESs. 80% of the patients proceeded from PCCs which had not been reformed. There were no statistically significant differences (p > 0.05) when the variables "reason for use" and "knowledge of NESs" were compared in relation to where the patient came from (i.e. reformed or non-reformed PCC). CONCLUSIONS: General practitioners in reformed PCCs are less likely to refer to HCDs. Knowledge and use of NESs should be actively supported.     

A modified expectation maximization algorithm for penalized likelihood estimation in emission tomography

The maximum likelihood (ML) expectation maximization (EM) approach in emission tomography has been very popular in medical imaging for several years. In spite of this, no satisfactory convergent modifications have been proposed for the regularized approach. Here, a modification of the EM algorithm is presented. The new method is a natural extension of the EM for maximizing likelihood with concave priors. Convergence proofs are given.