bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reaction kinetics of graft copolymerization and thermochemical studies of the degradation of poly(vinyl alcohol) graft copolymer
Authors: Aggour Yassin A 
Published: August 2002

AbstractPoly(vinyl alcohol) (PVA) is a water‐soluble and biomedical polymer. 2‐Acrylamido‐2‐methyl‐1‐propanesulfonic acid was grafted onto PVA using ammonium persulfate as radical initiator. The influences of synthesis conditions such as temperature, concentrations of initiator, PVA and monomer were investigated. Both the initial rate of grafting and the final percentage of grafting were increased by an increase in reaction temperature. The reaction kinetics were studied to determine the rate constants of the first‐order reactions. An activation energy of 16.3 kJ mol−1 was found for the grafting reaction. The graft copolymers were characterized by IR and intrinsic viscosity measurements. A proposed mechanism of the grafting reaction is discussed. Kinetics of the thermal degradation were studied using a thermogravimetric method and the order of thermal stabilities are given. The apparent activation thermodynamic parameters, Ea, ΔH*, ΔS* and ΔG* were determined and correlated to the thermal stabilities of the homo‐ and grafted polymers.© 2001 Society of Chemical Industry
Dispersion polymerization of aniline using hydroxypropylcellulose as stabilizer: role of rate of polymerization
Authors: Chattopadhyay Dipankar , Chakraborty Mukut , Mandal Broja M 
Published: August 2002

AbstractHydroxypropylcellulose (HPC) has been used as a steric stabilizer for preparing polyaniline dispersions using the route of oxidative dispersion polymerization of aniline. Using strongly acidic conditions (1 mol l−1 HCl), low temperature of about 2 °C and a concentration of aniline as low as 0.5%, ammonium peroxodisulfate at 1.25% and hydroxypropylcellulose concentrations at 0.5–1 g d l−1, unstable dispersions were obtained not only in water but also in aqueous alcohols (ethanol and methanol) up to at least 70 vol% alcohol. In contrast, dispersions that remained stable for at least 72 h were obtained when the alcohol concentration of the medium was as high as about 80 vol%. Kinetic studies of the polymerization systems suggested that success in the latter case was due to a lowering of the rate of polymerization. Transmission electron microscopy studies showed that dispersion particles prepared in 80 vol% alcohol media are spherical in shape and their diameter decreases with increasing stabilizer concentration. However, a change of morphology from spherical to aggregated needle‐shaped was observed when the rate was increased by increasing the aniline concentration from 0.5% to 0.75% g d l−1 in the above recipe. The aggregated particles were found to be broken down to spherical nanoparticles when the as‐prepared dispersions were sonicated for about 30 min. The sonicated dispersion on drying showed the presence of fractal clusters of polyaniline particles in the dried film. The fractal dimension was determined to be 1.77 which agreed well with the theoretical value determined by computer simulation based on a diffusion limited cluster–cluster aggregation model in three dimensions.© 2001 Society of Chemical Industry
Structure and properties of poly(vinyl alcohol)/κ‐carrageenan blends
Authors: Tanaka Toshihisa , Lu Tong , Yuasa Shingo , Yamaura Kazuo 
Published: August 2002

AbstractBlends of a commercial atactic poly(vinyl alcohol) (a‐PVA) derived from vinyl acetate and κ‐carrageenan were prepared by mixing the aqueous solutions of both samples. Blend films prepared by casting were transparent. In the DSC curves of the blend films, the endothermic peaks shifted to lower temperature with an increase of the content of κ‐carrageenan. The Young's modulus and the strength at break increased with an increase of the content of a‐PVA. As the standing temperature of the blend solutions decreased, the gelation region increased also at high content of carrageenan. In the amorphous regions of blend films, a‐PVA and κ‐carrageenan were miscible.© 2001 Society of Chemical Industry
Externalizing behavior problems in young children: Contributing factors and early intervention
Authors: Stormont Melissa 
Published: August 2002

AbstractEarly intervention should begin as soon as relatively stable problem behavior is detected in young children. Once professionals have identified young children who are at risk for stable externalizing behavior problems, it is important that they use and/or recommend research‐based interventions. Therefore, the first purpose of this article is to present research on specific child (e.g., temperament), family (e.g., family adversity), and transactional characteristics that have been documented to contribute to the manifestation of externalizing disorders in young children. School factors that may also support externalizing behavior in young children will also be presented and include negative teacher interactions and limited support for appropriate behavior. The second purpose of this manuscript is to present screening and intervention strategies that school psychologists could may use with young children who have externalizing behavior prior to or as soon as they enter the kindergarten setting. © 2002 Wiley Periodicals, Inc.
Exploring the relationship between school discipline referrals and delinquency
Authors: Sprague Jeffery , Walker Hill M. , Stieber Steve , Simonsen Brandi , Nishioka Vicki , Wagner Linda 
Published: August 2002

AbstractThere is a growing concern about violent and destructive behaviors of youth that require intervention by juvenile justice and youth‐serving agencies. This concern has led many to conclude that schools and community agencies must increase efforts to prevent juvenile delinquency and to provide programs that will facilitate rehabilitation, education, and vocational training for youth already involved. A clear understanding of the nature and range of behaviors that result in juvenile crime is needed in order to develop programs and interventions that can be expected to lead to beneficial changes for youth and for society as a whole. The purpose of this article is to describe the relationship between school behaviors and youth characteristics in school (e.g., discipline referrals, teacher nominations, nomothetic ratings) and referrals to juvenile authorities (e.g., illegal behaviors). We describe a strategy of using teacher nominations, school discipline referrals, and community arrest data to predict delinquent and violent behavior in youth. We outline data from a group of socially maladjusted middle school youth to illustrate the relationship between the two data sources and recommendations for identification and treatment of youth at risk for delinquency and antisocial behavior. © 2001 John Wiley & Sons, Inc.
Manganese‐based transition metal complexes as new catalysts for olefin polymerizations
Authors: Ban Hoang The , Kase Toshio , Murata Masahide 
Published: August 2002

AbstractThree manganese complexes, Mn(acac)3 (acac = acetylacetonate), Cp2Mn (Cp = cyclopentadienyl), and Mn(salen)Cl [salen = 1,2‐cyclohexanediamino‐N,N′‐bis(3,5‐dit‐butyl‐salicylidene)], were used for ethylene and propylene polymerizations. These complexes, in combination with an alkylaluminum cocatalyst such as methylaluminoxane (MAO) or diethyl aluminum chloride (AlEt2Cl), could promote ethylene polymerizations that yielded extremely high molecular weight linear polymers, but were inactive for propylene polymerizations. The counterparts supported on MgCl2 showed activities even for propylene polymerizations and had remarkably enhanced activities for ethylene polymerizations. In the presence of an electron donor such as ethylbenzoate, the MgCl2‐supported manganese‐based catalysts yielded a highly isotactic polypropylene with a high molecular weight. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3733–3738, 2001
Sulfobetaine zwitterionomers based on n‐butyl acrylate and 2‐ethoxyethyl acrylate: Monomer synthesis and copolymerization behavior
Authors: Gauthier Mario , Carrozzella Tony , Penlidis Alexander 
Published: August 2002

AbstractNew materials with potential applications for adhesives and coatings, based on copolymers containing zwitterionic pendent groups, were investigated. n‐Butyl acrylate and 2‐ethoxyethyl acrylate were copolymerized with a series of five zwitterionic sulfobetaine monomers. The structure of the monomers was varied in terms of the zwitterion intercharge spacing and the bulkiness of the alkyl substituents at the quaternary ammonium unit. Four of the five zwitterionic sulfobetaine methacrylate (SBM) monomers used in the study were synthesized. An evaluation of the reactivity ratios for the copolymer systems was performed with programs based on statistically sound techniques such as the error‐in‐variables model and the nonlinear‐least‐squares method. Reactivity ratio estimates for all 10 comonomer pairs were obtained, and they showed clear variations in reactivity with the structure of the SBM. In general, the more hydrophobic the SBM was, the lower its reactivity was with respect to the acrylate monomers. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 511–523, 2002; DOI 10.1002/pola.10138
Polymer‐supported reagents, catalysts, and sorbents: Evolution and exploitation—A personalized view
Authors: Sherrington D. C. 
Published: August 2002

AbstractThe solid‐phase method for oligopeptide synthesis was introduced by Professor Bruce Merrifield in 1963, but in practice the origins of polymer‐supported reagents, catalysts, and so forth trace back to the early development of ion exchange and catalysis by sulfonic acid resins. This highlight summarizes how the evolution of solid‐phase organic synthesis occurred in parallel with the development of supported reactive species and indicates the interchange between these areas in the last 30 years or so. The treatment is essentially a personalized one as seen from the author's own laboratory in the United Kingdom and is not intended to review the whole field. The emergence of the international series of conferences on polymer‐supported organic chemistry is emphasized as a key development that stimulated and maintained the area before its importance was recognized more widely by both academic and industrial chemists. The requirement of robotic technologies, as the basis for high‐throughput combinatorial and parallel synthesis in the pharmaceutical industry, has brought the relevance of supported chemistry to the attention of all synthetic chemists. At the same time, the recognition that all industrial chemical processes need to meet appropriate environmental standards has focused attention on the use of heterogenized reactive species as a potentially important technology for achieving the greening of chemistry. These two factors have brought polymer‐supported reactive chemistry to center stage, so to speak, and the early principles laid down over 2 decades ago are now being developed and exploited at an amazing rate. From a rather slow start, through a number of ups and downs in its development, the area of polymer‐supported chemistry now seems poised to join the more routine world of synthesis and to become a methodology used by all as and when appropriate. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2364–2377, 2001
Various silicon‐containing polymers with Si(H)CC units
Authors: Itoh Masayoshi , Iwata Kenji , Ishikawa Jun‐Ichi , Sukawa Hiroshi , Kimura Hideaki , Okita Koichi 
Published: August 2002

AbstractNine new kinds of thermosetting polymers with the Si(H)CC unit were synthesized by dehydrogenative polycondensation reactions between hydrosilanes and diethynyl compounds in the presence of a magnesia catalyst. Phenylsilane, silane, vinylsilane, and n‐octylsilane were used as the hydrosilanes, and 1,3‐diethynylbenzene, 1,4‐diethynylbenzene, 4,4′‐diethynyldiphenyl ether, and 1,3‐diethynyl‐1,1,3,3‐tetramethyldisiloxane were used as the diethynyl compounds. All the polymers were thermosetting, highly heat‐resistant, easily soluble in a solvent, and moldable. In particular, Si(R)HCCC6H4CC (R = H or CHCH2) showed high thermal stability; the temperature of 5% weight loss was greater than 800 °C, and the residue at 1000 °C was over 90%. The thermal stabilities of the polymers were attributed to the crosslinking reaction of the SiH and CC bonds. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2658–2669, 2001
Study of hydrogen‐bonding strength in poly(ϵ‐caprolactone) blends by DSC and FTIR
Authors: Kuo Shiao Wei , Huang Chih Feng , Chang Feng Chih 
Published: August 2002

AbstractThe hydrogen‐bonding strength of poly(ϵ‐caprolactone) (PCL) blends with three different well‐known hydrogen‐bonding donor polymers [i.e., phenolic, poly(vinyl‐phenol) (PVPh), and phenoxy] was investigated with differential scanning calorimetry and Fourier transform infrared spectroscopy. All blends exhibited a single glass‐transition temperature with differential scanning calorimetry, which is characteristic of a miscible system. The strength of interassociation depended on the hydrogen‐bonding donor group in the order phenolic/PCL > PVPh/PCL > phenoxy/PCL, which corresponds to the q value of the Kwei equation. In addition, the interaction energy density parameter calculated from the melting depression of PCL with the Nishi–Wang equation resulted in a similar trend in terms of the hydrogen‐bonding strength. Quantitative analyses on the fraction of hydrogen‐bonded carbonyl groups in the molten state were made with Fourier transform infrared spectroscopy for all systems, and good correlations between thermal behaviors and infrared results were observed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1348–1359, 2001
Modeling of particle‐dispersed melting mechanism and its application in corotating twin‐screw extrusion
Authors: Zhu Linjie , Narh K. A. , Geng Xiaozheng 
Published: August 2002

AbstractParticle‐dispersed melting is a complex but important melting mechanism in the corotating twin‐screw extruder. In this study, the complex multi‐particle‐dispersed system was simplified into a single‐particle melting model. The finite‐difference method was introduced to solve this problem. The simulation results show that the melting of a particle may involve two steps: the heating stage and melting stage. The heating time and melting time depend on solid concentration, initial melt and solid temperature, and shear rate. Calculations indicate that high solid concentration and solid temperature, low melt temperature and shear rate will result in a more uniform temperature distribution after polymer melting. The model offers valuable information for designing the melting zone in a corotating twin‐screw extruder, especially at high screw speed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2461–2468, 2001
Communication between physicians and cancer patients about complementary and alternative medicine: exploring patients' perspectives
Authors: Tasaki Katsuya , Maskarinec Gertraud , Shumay Dianne M. , Tatsumura Yvonne , Kakai Hisako 
Published: August 2002

AbstractThe aim of this paper is to identify barriers to communication between physicians and cancer patients regarding complementary and alternative medicine (CAM) by exploring the perspectives of patients. In face of the recent popularity of CAM use among cancer patients, the lack of communication is a serious problem. A number of CAM therapies may interfere with conventional treatments and thus impact patients' well‐being and chances of survival. In addition, lack of communication is problematic in the health care context because the development of openness and trust between health care providers and clients is contingent upon effective interpersonal communication. We conducted semi‐structured interviews with 143 cancer patients to explore their experiences with CAM use. Using a qualitative research method, we examined interview data from 93 CAM users who provided sufficient information about communication issues. As a result, three themes emerged describing barriers to unsuccessful communication as perceived from the patient's point of view: physicians' indifference or opposition toward CAM use, physicians' emphasis on scientific evidence, and patients' anticipation of a negative response from their physician. Increasing education about CAM and regular assessment of CAM use may help physicians to be more aware of their patients' CAM use. As a result, physicians may provide patients with information on risks and benefits of CAM use and refer patients to other services that may address unmet needs. Given a difference in epistemiologic beliefs about cancer and its treatment, the challenge is to find a common ground for an open discussion in which physicians consider that scientific evidence is not all that counts in the life of an individual facing a serious disease. Copyright © 2002 John Wiley & Sons, Ltd.
Efficacy of sublingual immunotherapy in children with asthma and rhinitis: A double‐blind, placebo‐controlled study
Authors: Bahçeciler Nerin N. , Işik Uğur , Barlan Işil B. , Başaran Müjdat M. 
Published: August 2002

AbstractTo evaluate the efficacy of specific sublingual immunotherapy (SLIT), we enrolled 15 children with asthma and rhinitis (7 girls, 8 boys,mean ± SD age of 11.7 ± 3.3) allergic to house dust mite (HDM) into a double‐blind, placebo‐controlled study. After a run‐in period, patients were randomized to receive either placebo (n = 7) or SLIT (n = 8) with a standardized Dermatophagoides pteronyssinus (D. pteronyssinus) + Dermatophagoides farinea (D. farinea) 50/50 extract. They received increasing doses up to 100 index units of reactivity (IR) every day for 4 weeks, then 100 IR/day for another 4 weeks, followed by maintenance therapy consisting of 20 drops 2 times a week for 4 months. Efficacy was assessed at the end of 6 months of therapy according to symptom and medication scores, serum total IgE levels, results of lung function tests, methacholine provocation tests, and skin prick tests.Daily means for the asthma score and use of inhaled beta‐2‐mimetics decreased significantly in the SLIT group (P = 0.05, P = 0.028, respectively), whereas no such difference was observed in the placebo group. At the end of follow‐up, mean daily doses of intranasal steroids needed for control of rhinitis symptoms decreased significantly in the SLIT group (P = 0.04). Baseline skin sensitivity to D. pteronyssinus and D. farinea was not significantly different between in the two groups, whereas end‐point wheal diameter obtained with D. pteronyssinus extract was significantly less in the SLIT vs. the placebo group (P = 0.026). At the end of 6 months, peak expiratory flow (PEF) values in the placebo group was significantly lower than in the SLIT group (P = 0.049). Throughout the treatment period, the SLIT group was found to have less asthma exacerbations than the placebo group (P = 0.007). The provocation concentration causing a 20% drop in forced expired volume in 1 sec did not change throughout the treatment period in either groups. None of the patients reported local or systemic side effects from SLIT.Results of this study suggests that SLIT may be a useful alternative or additional therapy in the treatment of children with asthma/rhinitis due to HDM. Pediatr Pulmonol. 2001; 32:49–55. © 2001 Wiley‐Liss, Inc.
Impact of a pediatric asthma clinical pathway on hospital cost and length of stay*
Authors: Wazeka April , Valacer David J. , Cooper Mary , Caplan David W. , DiMaio Mary 
Published: August 2002

AbstractThis study sought to determine if a clinical pathway developed and executed by specialists in pediatric asthma would reduce hospital costs and length of stay (LOS). The study design was a retrospective, nonrandomized, controlled trial. Subjects were children aged 2–18 years (N = 1,004) with a history of recurrent wheezing, hospitalized with a diagnosis of acute asthma exacerbation between 1995–1998 at the New York Hospital‐Weill Cornell Medical Center and treated via the pathway, as well as a control group of 206 children ages 2–18 hospitalized for acute asthma exacerbation in 1994, the year prior to pathway implementation.Patients were treated via the pathway under the supervision of an asthma specialist. The pathway provided guidelines for: 1) frequency of patient assessment; 2) bronchodilator usage; 3) corticosteroid use; 4) laboratory evaluation; 5) vital signs, oxygen saturation, and peak flow measurements; 6) chest x‐rays; 7) social work intervention; and 8) discharge planning. The main outcome measures were hospital length of stay, cost per hospitalization, nursing, medication, laboratory and radiology costs, and relapse rate. Total charges for admission and average LOS for 1995–1998 were calculated, and compared with 1994, the year preceding implementation of the pathway.LOS decreased from 4.2 days to 2.7 days (P < 0.0001). The annual total charges for pediatric asthma admissions decreased from $2 million to $1.4 million (P < 0.005). Nursing and laboratory costs showed a statistically significant decrease. Follow‐up study at 8 months showed a readmission rate of 0.02%.The implementation of a pediatric asthma clinical pathway, directed by specialists, resulted in significantly decreased length of stay and overall cost, without an increased rate of readmission. Pediatr Pulmonol. 2001; 32:211–216. © 2001 Wiley‐Liss, Inc.
Thermal unfolding molecular dynamics simulation of Escherichia coli dihydrofolate reductase: Thermal stability of protein domains and unfolding pathway
Authors: Sham Yuk Yin , Ma Buyong , Tsai Chung‐Jung , Nussinov Ruth 
Published: August 2002

AbstractTemperature‐induced unfolding of Escherichia coli dihydrofolate reductase was carried out by using molecular dynamic simulations. The simulations show that the unfolding generally involves an initial end‐to‐end collapse of the adenine binding domain into partially extended loops, followed by a gradual breakdown of the remaining β‐sheet core structure. The core, which consists of β‐strands 5–7, was observed to be the most resistant to thermal unfolding. This region, which is made up of part of the N‐terminus domain and part of the large domain of the E. coli dihydrofolate reductase, may constitute the nucleation site for protein folding and may be important for the eventual formation of both domains. The unfolding of different domains at different stages of the unfolding process suggests that protein domains vary in stability and that the rate at which they unfold can affect the overall outcome of the unfolding pathway. This observation is compared with the recently proposed hierarchical folding model. Finally, the results of the simulation were found to be consistent with a previous experimental study (Frieden, Proc Natl Acad Sci USA 1990;87:4413–4416) which showed that the folding process of E. coli dihydrofolate reductase involves sequential formation of the substrate‐binding sites. Proteins 2002;46:308–320. © 2002 Wiley‐Liss, Inc.