Redox-initiated vinyl graft copolymerization onto wool with thiourea as the reductant. III. Di-tert.-butyl peroxide thiourea system

Graft copolymerization of wool with methyl methacrylate (MMA) induced by di-tert.-butyl peroxide (DTBP)/thiourea (TU) system in acid medium was studied. The rate of the copolymerization reaction depends on concentrations of DTBP, TU and MMA, temperature as well as kind of acid and solvent used. The graft yield increases by increasing the concentration of DTBP and MMA. Increasing the temperature enhances also the graft formation; 60°C produces higher grafting than 50°C. Carrying out the graft polymerization reaction in acid medium by using nitric acid has proved to be the best in comparison with sulphuric and formic acid. There is an optimal concentration of TU (0.4 M); lower grafting is achieved below and above this concentration. A mixture of isopropanol/water at a ratio of 10:90 constitutes the most favourable reaction medium since increasing the solvent content is accompanied by a reduction in the graft yield. The kind of solvent does affect the graft yield: for the solvent studied, the graft yield follows the order: isopropanol < acetone < dimethylsulphoxide. Incorporation of an acid dye in the polymerization system to affect concurrent dyeing and grafting was carried out and the properties of the products so obtained were examined. The changes in alkali solubility of wool by grafting was also investigated. In addition, a reaction mechanism based essentially on complexes formed between DTBP and wool and/or DTBP and TU and their subsequent dissociation to give wool macroradicals was suggested.     

离子交换树脂催化酯化研究进展

与传统的无机催化剂相比,离子交换树脂表现出良好的催化性能并且能回收再利用。本文简单介绍了离子交换树脂的种类,重点介绍了离子交换树催化剂在酯化反应中的应用进展。     

Signal threshold adaptation for vertical handoff in heterogeneous wireless networks

The convergence of heterogeneous wireless access technologies has been envisioned to characterize the next generation wireless networks. In such converged systems, the seamless and efficient handoff between different access technologies (vertical handoff) is essential and remains a challenging problem. The heterogeneous co-existence of access technologies with largely different characteristics results in handoff asymmetry that differs from the traditional intra-network handoff (horizontal handoff) problem. In the case where one network is preferred, the vertical handoff decision should be carefully executed, based on the wireless channel state, network layer characteristics, as well as application requirements. In this paper, we study the performance of vertical handoff using the integration of 3G cellular and wireless local area networks as an example. In particular, we investigate the effect of an application-based signal strength threshold on an adaptive preferred-network lifetime-based handoff strategy, in terms of the signalling load, available bandwidth, and packet delay for an inter-network roaming mobile. We present an analytical framework to evaluate the converged system performance, which is validated by computer simulation. We show how the proposed analytical model can be used to provide design guidelines for the optimization of vertical handoff in the next generation integrated wireless networks. This article is the extended version of a paper presented in IFIP Networking 2005 Ahmed H. Zahran is a Ph.D. candidate at the Department of Electrical and Computer Engineering, University of Toronto. He received both his M.Sc. and B.Sc. in Electrical Engineering from Electronics and Electrical Communication Department in the Faculty of Engineering, Cairo University in 2002 and 2000 respectively, where he was holding teaching and research positions. Since September 2003, he has been working as a research assistant in the Department of Electrical and Computer Engineering, University of Toronto under the supervision of Professor Ben Liang. His research interest is wireless communication and networking with an emphasis on the design and analysis of networking protocols and algorithms. Ben Liang received honors simultaneous B.Sc. (valedictorian) and M.Sc. degrees in Electrical Engineering from Polytechnic University in Brooklyn, New York, in 1997 and the PhD degree in Electrical Engineering with Computer Science minor from Cornell University in Ithaca, New York, in 2001. In the 2001–2002 academic year, he was a visiting lecturer and post-doctoral research associate at Cornell University. He joined the Department of Electrical and Computer Engineering at the University of Toronto as an Assistant Professor in 2002. His current research interests are in the areas of mobile networking and wireless multimedia systems. He is a member of Tau Beta Pi, IEEE, and ACM and serves on the organization and technical program committees of a number of major conferences each year. Aladdin Saleh earned his Ph.D. degree in Electrical Engineering from London University, England. Since March 1998, Dr. Saleh has been working in the Wireless Technology Department of Bell Canada, the largest service provider of wireless, wire-line, and Internet in Canada. He worked as a senior application architect in the wireless data group working on several projects among them the wireless application protocol (WAP) and the location-based services. Later, he led the work on several key projects in the broadband wireless network access planning group including planning of the IEEE 802.16/ Wimax, the IEEE 802.11/ WiFi, and the integration of these technologies with the 3G cellular network including Mobile IP (MIP) deployment. Dr. Saleh also holds the position of Adjunct Full Professor at the Department of Electrical and Computer Engineering of Waterloo University, Canada since January 2004. He is currently conducting several joint research projects with the University of Waterloo and the University of Toronto on IEEE 802.16-Wimax, MIMO technology, interworking of IEEE 802.11 WLAN and 3G cellular networks, and next generation wireless networks. Prior to joining Bell Canada, Dr. Saleh worked as a faculty member at different universities and was Dean and Chairman of Department for several years. Dr. Saleh is a Fellow of IEE and a Senior Member of IEEE.     

Diagnostic comorbidity in panic disorder: effect on treatment outcome and course of comorbid diagnoses following treatment

The impact and course of additional diagnoses was examined in 126 patients undergoing cognitive-behavioral treatment for panic disorder. With the Anxiety Disorders Interview Schedule--Revised, a high comorbidity rate (51%) was observed at pretreatment. Pretreatment comorbidity was not predictive of premature termination, nor did it have a substantial impact on short-term treatment outcome. However, patients with comorbidity at posttreatment were more likely to have sought additional treatment over the follow-up interval. Although a significant and dramatic decline in the overall comorbidity rate was found at posttreatment (17%), at 24-month follow-up this rate had increased to a level (30.2%) that was no longer significantly different from pretreatment. This was despite the fact that patients maintained or improved on treatment gains for panic disorder over this interval. The implications of these findings for the treatment, conceptualization, and classification of emotional disorders are discussed.     

Feasibility of an immunoassay for mevalonolactone

Trace eyeblink classical conditioning was assessed in patients with bilateral medial-temporal amnesia and matched control participants who had previously shown equivalent delay eyeblink conditioning (J. D. E. Gabrieli et al., 1995). The silent trace interval varied for durations of 500, 750, or 1,000 ms in successive sessions separated by at least 2 weeks; extinction trials followed each session. Patients with amnesia produced significantly fewer conditioned responses (CRs) than did control participants at all trace intervals. Both groups produced fewer CRs as the trace interval lengthened. Thus, the temporal lobe memory system in humans makes an essential contribution to normal acquisition in trace, but not delay, classical eyeblink conditioning.     

A general-purpose CMOS associative processor IC and system

An associative processor architecture that integrates the functionality of content-addressable memory (CAM), functional memory (FM), and associative parallel processors (APPs) in a single-chip architecture is described. The hardware design, environment and applications of the Coherent Processor, a microchannel memory device designed by combining 16 such chips, are discussed. It is shown that the processor's writable control store permits quick execution of application-specific microcoded operations     

Efficacy and safety of pravastatin in African Americans with primary hypercholesterolemia

BACKGROUND: Coronary artery disease strikes early and may prove particularly severe in persons of African-American descent. Therefore, we studied the lipid-lowering efficacy and safety of pravastatin sodium (20 mg/d), a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, in 245 African-American patients with primary hypercholesterolemia. METHODS: After 4 weeks on an American Heart Association phase I low-fat diet, patients were randomized in a double-blind manner to either pravastatin or placebo in a 3:1 ratio. RESULTS: After 12 weeks of pravastatin treatment, low-density lipoprotein cholesterol levels declined 25.8%, total cholesterol levels 20.3%, and triglyceride levels 6.2%, while high-density lipoprotein cholesterol levels remained essentially unchanged. Overall, 72% of pravastatin-treated patients achieved reductions in low-density lipoprotein cholesterol level in excess of 20%, and 44% attained declines in excess of 30% (both P < .01 vs placebo). Pravastatin was generally well tolerated in this population, with one patient (0.5%) exhibiting a reversible myopathy with creatine kinase elevations to 10 times the upper limit of normal. No substantial elevations of aminotransferase levels of two to three times the upper limit of normal occurred in either the pravastatin or the placebo group. Drug compliance was high, exceeding 90%. CONCLUSION: Pravastatin appears to be an effective and safe lipid-lowering agent and is the first 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor to be studied extensively in this underrepresented population.