bluuebunny/crossref_metadata_2025 huggingface dataset:
A Semantic Differential Measure of Attitudes Toward Black American Patients
Authors: Morgan Barbara Sawyer
Published: April 2007

The development of an instrument measuring attitudes toward black American patients using a semantic differential technique is described. Subjects were 242 white senior students enrolled in baccalaureate degree, associate degree, and diploma nursing programs. The instrument consisted of 20 bipolar adjective scales for positive and negative racial stereotypes. A factor analysis resulted in five factors which accounted for the majority of the variance, with 30.2% for Factor I Evaluation. An alpha reliability of .84 for the same factor revealed a high level of internal consistency. To obtain an attitude score, the eight bipolar adjective scales comprising Factor I were summed and the scores obtained were in the neutral range. There were no significant differences among the attitudes of baccalaureate degree, associate degree, or diploma nursing students. Comparisons also were made between the perceptions of students toward black Americans and toward black American patients, with the latter perceived more favorably.
Perceived Uncertainty and Stress in Illness
Authors: Mishel Merle H.
Published: April 2007

A structural model was proposed to explain the stress resulting from hospitalization for a medical problem. Perceived uncertainty about symptoms, treatment, and outcome was examined as a major predictor of stress. Other variables proposed in the model included seriousness of illness, age, education, and recency of rehospitalization. Testing of the model with hospitalized medical patients indicated support for the relationship of uncertainty to stress. Uncertainty also had the predicted mediating role between seriousness of illness and stress. The only other variable supporting the proposed model was age which related inversely to stress. Much of the unexplained variance in the model is attributed to the heterogeneity of diagnoses in the sample. Suggestions for future testing of the model are presented.
Effect of Advance Organizers on Learning Medical Surgical Nursing Content by Baccalaureate Nursing Students
Authors: Gillies Dee Ann
Published: April 2007

The hypothesis for this study was that a verbal advance organizer would increase learning and retention of class content more in subjects with greater field independence and with higher scholastic aptitude. The sample was 43 junior baccalaureate nursing students, randomly assigned to experimental and control groups. Sophomore cumulative grade point averages were used as a measure of scholastic aptitude and Group Embedded Figures Test scores as measures of field independence. An expository organizer was presented to experimental subjects and a passage of nonorganizing historical information to control subjects at the beginning of each of six classes. Class quizzes were used to measure initial learning, and end‐of‐unit and final examinations were used to measure intermediate and long range retention of class content. Increased initial learning occurred with exposure to a verbal advance organizer in subjects with above average scholastic ability and below average field independence (p < .05), but intermediate and long‐term retention were not significantly higher in these subjects.
An economic application of the Dubovitskii–Milyutin version of the Maximum Principle
Authors: Leung Siu Fai
Published: April 2007

The Pontryagin Maximum Principle is well known in economics. There is a different and more general version of the Maximum Principle, first established by Dubovitskii and Milyutin (Dokl. Acad. Nauk SSSR 1963; 149:759–762; Zh. Vychisl. Mat. Mat. Fiz. 1965; 5:393–453), which is little known in economics and has never been applied to solve an economic optimal control problem. This paper introduces the Dubovitskii–Milyutin version of the Maximum Principle to economics and offers an economic application to illustrate the limitation of the conventional Maximum Principle and the usefulness of the Dubovitskii–Milyutin version. The Dubovitskii–Milyutin Maximum Principle should be an integral part of the economist's toolbox and be included in economics textbooks on dynamic optimization. Copyright © 2007 John Wiley & Sons, Ltd.
Numerical method for weights adjustment in minimax multi‐model LQ‐control
Authors: Poznyak Alexander , Bejarano Francisco Javier , Fridman Leonid
Published: April 2007

The minimax linear quadratic problem, where ‘max’ is taken over a finite set of indices (models) and ‘min’ is taken over the set of admissible controls, is considered. The solution is obtained by the robust optimal control application. The control turns out to be a linear combination of the controls optimal for each individual model. This paper develops a numerical method for the optimal weights adjustment. An example shows a quick convergence of the proposed procedure. Copyright © 2007 John Wiley & Sons, Ltd.
Computational optimal control of the terminal bunt manoeuvre—Part 1: minimum altitude case
Authors: Subchan S. , Zbikowski R.
Published: April 2007

This two‐part paper studies trajectory shaping of a generic cruise missile attacking a fixed target from above. This guidance problem is reinterpreted using optimal control theory resulting in two formulations: (1) minimum time‐integrated altitude (part 1) and (2) minimum flight time (part 2). Each formulation entails non‐linear, two‐dimensional (vertical plane) missile flight dynamics, boundary conditions and path constraints, including pure state constraints. The focus here is on informed use of the tools of computational optimal control, rather than their development. Each of the formulations is solved using a three‐stage approach. In stage 1, the problem is discretized, effectively transforming it into a non‐linear programming problem, and hence suitable for approximate solution DIRCOL and NUDOCCCS. The results are used to discern the structure of the optimal solution, i.e. type of constraints active, time of their activation, switching and jump points. This qualitative
analysis, employing the results of stage 1 and optimal control theory, constitutes stage 2. Finally, in stage 3, the insights of stage 2 are made precise by rigorous mathematical formulation of the relevant two‐point boundary value problems (TPBVPs), using the appropriate theorems of optimal control theory. The TPBVPs are then solved using BNDSCO and the results compared with the appropriate solutions of stage 1. For each formulation (minimum altitude and minimum time) the influence of boundary conditions on the structure of the optimal solution and the performance index is investigated. The results are then interpreted from the operational and computational perspectives. Copyright © 2007 John Wiley & Sons, Ltd.
A mood moderation of the Extrinsic Affective Simon Task
Authors: Vermeulen Nicolas , Corneille Olivier , Luminet Olivier
Published: April 2007

Using an Extrinsic Affective Simon Task (EAST), we provide the first‐ever systematic examination of the role of affective states (negative and positive affectivity, depression, anxiety) and personality traits (alexithymia, optimism) in automatic evaluation effects. Results revealed that the EAST effect was negatively associated with depressive mood even if others affective states and traits were simultaneously entered in a regression model. These findings could reflect a preference for a systematic information processing style elicited during sadness. More generally, the present findings suggest that implicit attitudes measures that capitalise on automatic evaluation effects may lack validity when measuring attitudes of individuals who have negative emotional states. Individual measures relating to affective differences may thus contribute to better predicting the implicit attitude‐behaviour link. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis and characterization of new aromatic sulfone ether polyamides containing pendant pentadecyl groups
Authors: Jadhav Arun S. , Vernekar Subhash P. , Maldar Noormahmad N.
Published: April 2007

A series of new polyamides and copolyamides containing aromatic sulfone ether linkages was synthesized from 4,4′‐[sulfonyl‐bis(4,1‐phenyleneoxy‐3‐pentadecyl)]bisphenylamine (SPPBA) and isophthaloyl chloride (IPC), terephthaloyl chloride (TPC), bis(4‐chlorocarbonylphenyl)dimethylsilane (DMSC) and bis(4‐chlorocarbonylphenyl)diphenylsilane (DPSC) by a low‐temperature inter‐facial polymerization technique. SPPBA was prepared from 4,4′‐dichlorodiphenyl sulfone and 4‐amino‐3‐pentadecyl phenol derived from cashew‐nut shell liquid and was characterized by spectral methods and elemental analysis, whereas the polyamides were characterized by solution viscosity, IR spectroscopy, thermogravimetric analysis, X‐ray diffraction and solubility. These polyamides showed enhanced solubility in organic solvents and no weight loss below 405°C in nitrogen. The effect of pendant penladecyl substituents and silicon in the main chain of polyamides on the properties of these polymers was studied by comparing their properties with those of unsubstituted polyamides prepared from 4,4′‐[sulfonylbis(4,1 ‐phenyleneoxy)] bisphenylamine.
Electrical properties of laminated epoxy‐carbon fiber composite
Authors: Jawad S. A. , Ahmad M. , Ramadin Y. , Zihlif A. , Paesano A. , Martuscelli E. , Ragosta G.
Published: April 2007

This work deals with the effect of temperature on the electrical properties of laminated epoxy composites containing 60% by volume of commercial unidirectional carbon fibers. The temperature was varied from 30°C to 120°C and the frequency range was from 10 Hz to 10 kHz. It is found that the impedance decreases with increasing temperature and is inversely proportional to the number of layers in the specimen. The calculated dielectric constants show a strong dependence on the frequency below 100 Hz, and attain relatively constant values for frequencies greater than 100 Hz. The decrease in impedance with increasing number of layers was explained in terms of the existence of electrical contacts and bridges both between and within the fibers, in the carbon fiber layers. The activation energy results indicate that there are two conduction mechanisms in this laminated composite.
The kinetics of dissociation of blocked 2,4‐diisocyanatotoluene (tdi) in amines
Authors: Kamath Prathima , Srinivasan M.
Published: April 2007

The kinetics of dissociation of blocked diisocyanates based on commercial diisocyanatotoluene (TDI) (80/20 mixture of 2,4‐ and 2,6‐ isomers) in the presence of amino compounds was studied by a volumetric method and Fourier Transform IR (FTIR) spectral data. Second‐order rate constants for the dissociation of TDI adducts (with phenol, thiophenol and p‐chlorophenol) in the presence of amines (dibenzyl, benzyl, cyclohexyl, n‐hexyl and di‐n‐butyl) in cyclohexanone solvent are reported. The relative effects of various blocking agents, basicity of the amines and temperature on the dissociation of blocked TDI have been determined. An FTIR spectroscopic method was used to study the dissociation of blocked TDI (with blocking agents such as phenol, thiophenol, p‐chlorophenol,p‐nitrophenol,p‐cresol, α‐naphthol and resorcinol) in the presence of excess triethylamine and in cyclohexanone solvent. Pseudo‐first‐order rate constants were calculated from NCO concentrations as determined from FTIR spectra.
A new technique for the study of the kinetics of adsorption of polymers onto surfaces
Authors: Bajpai U. D. N. , Bajpai A. K.
Published: April 2007

A new and simpler technique is described for the study of the kinetics of adsorption of poly(methylmethacrylale) (PPMA) on a glass surface at 30°C. The kinetics of adsorption were followed gravimetrically by knowing the amount of polymer adsorbed on glass balls at various time intervals. A simple kinetic model for rate of adsorption has been proposed, and from the scheme outlined various adsorption parameters such as adsorption coefficient, surface coverage and film thickness have been evaluated. From the available experimental data, adsorption isotherms have been drawn, and the effect of molecular weight of PMMA on adsorption behaviour has been studied.
Sorption and diffusion of aldehydes and ketones into elastomers
Authors: Aminabhavi Tejraj M. , Munnolli Ravindra S.
Published: April 2007

The results of the sorption and diffusion of aldehydes and ketones into structurally different elastomers such as ethylene propylene diene terpolymer, styrene butadiene rubber, nitrile butadiene rubber, neoprene and natural rubber are described in the temperature interval of 25‐60°C. From these data, the Arrhenius parameters for the processes of diffusion and permeation are determined. The activation parameters for the diffusion of ketones range from 10.29 to 49.62 kJ/mol and for aldehydes, from 13.18 to 50.42 kJ/mol; these values fall in the range expected for rubbery polymers well above their glass transition temperatures. Transport data are affected by the nature of the interacting solvent molecule rather than its size and also by the structural variations of the elastomers. For all the solvents, the polymers remained intact; however, natural rubber in the presence of benzaldehyde showed degradative reactions at higher temperatures. Volumetric expansions of the elastomers have been measured from the dimensional response in the presence of aggressive solvents.
Anionic synthesis and characterization of poly(4‐vinylpyridine)‐poly(dimethylsiloxane) block copolymers
Authors: Nugay N. , Küçükyavuz Z. , Küçükyavuz S.
Published: April 2007

Poly(4‐vinylpyridine)‐b‐Poly(dimethylsiloxane) (P4VP‐b‐PDMS) copolymers have been synthesized by sequential anionic polymerization of 4VP and hexamethylcyclotrisiloxane at — 70°C. The initiator was sodium naphthenate. The solvent used during reactions has a very critical role in an homogeneous polymerization medium. A 1:1 pyridine/THF mixture was found to be the most suitable. The products were characterized by 1H‐NMR spectroscopy, transmission electron microscopy (TEM) and differential scanning calorimetry (DSC) techniques. All the results indicated the formation of 4‐vinylpyridine‐siloxane block copolymers. Also, the P4VP blocks can be completely quaternized with methyl iodide as indicated by 1H‐NMR and FTIR spectroscopies.
Adsorption and desorption dynamics of associative polymers onto particulates of titanium dioxide, alumina and quartz
Authors: Filippov Leonid K. , Silebi Cesar A. , El‐Aasser Mohamed S.
Published: April 2007

The authors have been investigating the adsorption and desorption dynamics of nonionic water soluble polymers on inorganic particles. The influence of the nature of polymers with and without associating hydrophobic end groups, the nature of adsorbents [TiO2, Al2O3 (neutral, acid and basic), and SiO2], polymer concentrations, linear velocity of fluids, and mutual diffusion of polymer molecules on the patterns of adsorption and desorption distribution of polymer concentrations are shown. The model polymer is a nonionic polyurethane polymer based on ethylene oxide. The polymer's structure is R‐O‐(DI‐PEO)6‐DI‐O‐R (R is C16H33, DI is isophorone diisocyanate, and PEO is CARBOWAXTM with a molecular weight of 8200). The phenomenological models of association and dissociation kinetics of associative polymers are suggested. The half‐lives of clusters into adsorption and desorption layers are estimated. It is shown that heats of desorption of associative polymers are dependent essentially on heats of dissociation of clusters.
Influence of a monomeric plasticizer on the water‐sorption behaviour of food‐grade plastics packaging materials
Authors: Kalaouzis Panagiotis J. , Demertzis Panagiotis G.
Published: April 2007

The interaction of water with poly(vinylchloride) and poly(vinylidene chloride‐vinylchloride) (p(VdC‐VC)) plasticized with different amounts of a monomeric plasticizer (dioctylphthalate) has been studied using inverse gas chromatography. The present work was focused on the effect of temperature and plasticizer content on the water sorption behaviour of these plastics packaging materials. Values for thermodynamic parameters such as Gibb's free energy (ΔGs), enthalpy (ΔHs), entropy (ΔSs) and activity coefficient (γ) corresponding to sorption of water by the polymers have been calculated using chromatographic retention data. It was found that the sorption of water vapours increases with increasing the amount of plasticizer and decreases with increasing temperature. The Van Deemter equation was found to be applicable to these systems and was used to determine diffusion coefficients and activation energies for diffusion. Diffusion coefficient values increase with increasing amounts of plasticizer and they also increase with increasing temperature; this latter increase is accompanied by a decrease in the activation energy for diffusion. Present results were also compared to our own previous data, using a polymeric plasticizer.
Radiation‐initiated graft copolymerization of acrylic acid and vinyl acetate onto LDPE films in two individual steps
Authors: El‐Sawy Naeem M. , Hegazy El‐Sayed A. , Rabie A. M. , Hamed A. , Miligy G. A.
Published: April 2007

Radiation‐induced grafting of vinyl acetate (VAc) and acrylic acid (AAc) onto low‐density polyethylene (LDPE) films was carried out in two individual steps: initially, the polymer substrate was grafted either with VAc or AAc and the grafted film thus obtained was grafted with the other monomer. The graft copolymerization of AAc onto LDPE‐g‐PVAc films was enhanced when the content of PVAc is low. This is due to the high polarity and hydrophilicity of AAc. On the other hand, the grafting of VAc onto LDPE‐g‐PAAc films was restricted due to the difficulties of VAc diffusion through the crosslinked grafted chains of PAAc. The influence of inhibitor and monomer concentration on the degree of grafting was studied. The addition of 2wt% of Mohr's salt effectively reduced the homopolymerization of monomer during the irradiation process. The dependence of the grafting rate upon VAc concentration was found to be of 1.5 order. Some selected properties of the graft copolymers, swelling behaviour and electrical properties, were investigated.
Retarding behaviour of organic solvents in permanganate‐sulphite‐initiated polymerization of acrylamide
Authors: Bajpai U. D. N. , Bajpai A. K. , Jain A.
Published: April 2007

Redox polymerization of acrylamide initiated by a new redox couple, potassium permanganate‐sodium sulphite, has been studied under atmospheric oxygen at 35 ± 0.2° C. The rate of polymerization has been found to vary with the half power of the redox components and the first power of the monomer concentration. The energy of activation has been calculated to be 8.29 kcal/(deg. mol.). The effect of various additives such as neutral salts and surface‐active agents has been studied qualitatively. The retarding effect of organic solvents on the rate of polymerization has also been studied both qualitatively and quantitatively. An interpretation of the observed results has been proposed.
Dipolar relaxation behaviour in poly(methyl methacrylate)/4‐nitroaniline solid solutions
Authors: Dionísio Madalena , Ramos Joaquim J. Moura , Williams Graham
Published: April 2007

In the present paper the dielectric properties of solid solutions of 4‐nitroaniline in a poly(methyl methacrylate) matrix have been measured in the frequency range 20‐106 Hz and the obtained data have been compared with those for pure poly(methyl methacrylate). It is shown that the presence of the solute has a strong influence on the relaxation process of the polymer and this is ascribed to the formation of hydrogen bonds between the amino group of the solute and acetate side groups of the polymer.
Gelatin renaturation and viscosity of dilute gelatin solutions
Authors: Horský Jiři , Švantner Jiří
Published: April 2007

Mechanical melting temperatures of gelatin gels determined by the ball‐drop method are decreased by several degrees if 0.5m potassium thiocyanate aqueous solution is used as solvent instead of pure water. In agreement with that, the growth with time of the viscosity of dilute gelatin solutions occurs at lower temperatures in 0.5m potassium thiocyanate. Surprisingly enough, the reduced specific viscosity after five hours at 5° C is lower in pure water. This is because the temperature dependence of this quantity in water is not monotonic, and the temperature 5° C is below that at which a distinct maximum is reached. No similar maximum has been reported so far for the temperature and time dependences of the extent of renaturation determined by optical techniques. The difference between the results of these two methods could be ascribed to the fact that the viscosity of solutions of partially renaturated gelatin is given not only by the fraction of monomer units in the helical conformation but also by the average length of created helices.
Redox polymerisation—kinetics of polymerisation of acrylamide initiated by the Mn3+‐citric acid redox system
Authors: Sailaja G. , Raju K. Mohana , Raju M. Subramanyam
Published: April 2007

The kinetics and mechanism of polymerisation of acrylamide initiated by manganese(III) acetate‐citric acid (CA) redox system in aqueous acetic acid and sulphuric acid medium were studied over the temperature range 30‐50° C. The overall rates of polymerisation (Rp), disappearance of manganic ion (—Rm), and degree of polymerisation (X̄n) were measured with variation in [monomer], [Mn3+], [CA], [H+], μ and temperature. The polymerisation is initiated by the organic free radical arising from the Mn3+‐CA reaction and the termination is by metal ions. The various rate parameters were evaluated and discussed.
Permeability of PHEMA membranes prepared by photoinitiation
Authors: Arica M. Yakup , Hasirci Vasif N.
Published: April 2007

Poly(2‐hydroxyethyl methacrylate) membranes were prepared in aqueous media with different ions and ionic strengths. The enzyme glucose oxidase was incorporated into some of these membranes. It was found that membrane water contents and ionic strengths have a linear relationship as long as the salt is not changed. When the salt was varied, only a relationship between salt concentration and water content could be observed. The membrane permeabilities were all found to be of the same order (10−8cm2s−1) but the membranes were slightly more permeable to chromate ions than glucose. Incorporation of enzyme distinctly increased the water content of the membrane and permeability to both solutes.
Free radical copolymerization in the presence of lewis acids—III: Alternating copolymerization of butyl acrylate and styrene in the presence of Al2Et3Cl3: Solvent effect
Authors: Yuan Yumin , Hao Xiaojuan , Jian Xigao , Xu Late Guojin
Published: April 2007

Photo‐initiated alternating copolymerization of butyl acrylate (BA) and styrene (St) in the presence of Al2Et3Cl3 was investigated in tetrachloroethylene (TCE) and toluene (TOL) solution. The results showed that copolymers with equimolar compositions were obtained over a wide range of reactant composition. The 13C nuclear magnetic resonance spectrum confirmed their alternating structure. Solvent could greatly affect kinetic behaviour, in TCE solution, the optimum rate of copolymerization was observed near equimolar monomer ratio; while in TOL solution the rate of copolymerization increased rapidly at lower [BA], tended to a constant rate at higher [BA] and increased slightly with increasing [St]. Electron spin resonance spectra indicated that the St radical was the only one to be detected. The effect of solvent as well as Lewis acid on alternating mechanism is also discussed.
Living functionalization of polymethacrylates by group transfer polymerization (GTP) using low ceiling temperature monomers
Authors: Quirk Roderic P. , Ren Jie
Published: April 2007

A living functionalization method for group transfer polymerization (GTP) has been developed for poly(alkyl methacrylates) using the sterically hindered monomer, methyl‐2‐phenylpropenoate (MPHA). The end‐capping reactions of MPHA with living trimethylsilyl ketene acetal‐ended poly(methyl methacrylate) (PMMA) chain ends have been systematically studied and characterized by size exclusion chromatography, vapor pressure osmometry, ultraviolet‐visible, 1H and 13C nuclear magnetic resonance spectroscopy. Although oligomerization of MPHA is observed at ‐ 78° C, this is reversible and only monoaddition is observed at room temperature. In principle, various functional groups can be introduced into poly(alkyl methacrylates) via substituents on the aromatic ring of MPHA and related monomers. Amino‐functionalized PMMA was prepared by end‐capping reactions of living trimethylsilyl ketene acetal‐ended PMMA with methyl E‐3‐(2‐dimethylaminophenyl)‐2‐phenylacrylate.
Synthesis and characterisation of PP‐g‐butyl acrylate copolymers
Authors: Sathe Sachin N. , Srinivasarao G. S. , Devi Surekha
Published: April 2007

Butyl acrylate was grafted onto isotactic polypropylene using benzoyl peroxide as an initiator and toluene as a solvent. Effects of various parameters such as monomer and initiator concentration, reaction time and temperature on rates of polymerization, percentage grafting and grafting efficiency were studied. The extent of grafting achieved was 2.85%. The graft copolymers were characterized by IR, thermal, viscometric and contact‐angle studies. Improved thermal stability and decreased intrinsic viscosity and critical surface tension were observed for graft copolymers.
Epoxy/amine systems with monodisperse modifiers: thermodynamic analysis of the phase separation process taking the polymer polydispersity into account
Authors: Riccardi Carmen C. , Borrajo Julio
Published: April 2007

Phase separation during polymerisation was studied by taking into account in the thermodynamic analysis the generated distribution of polymer species. A model system consisting of a diepoxide based on diglycidylether of bisphenol A, a diamine and castor oil as modifier was considered. One‐and two‐step polymerisation processes were simulated (in the two‐step process a first step was carried out with an epoxy excess up to a particular conversion, stoichiometry was balanced and the reaction continued in a second step). A thermodynamic analysis for a monodisperse modifier‐epoxy/amine system was performed taking the polydispersity of the polymer into account. It was shown that the cloud point conversion was decreased when the polymerisation was carried out in two steps. This effect was enhanced for lower stoichiometric ratios (higher epoxy excesses) and higher epoxy conversions in the first step. The dispersed phase became richer in low molecular weight species than the continuous one. In particular both monomers increased their concentration in the dispersed phase.
Effect of alkyl phthalate plasticizers on permeation of water vapour through PVC membranes
Authors: Shailaja D. , Yaseen M.
Published: April 2007

PVC membranes plasticized with various concentrations of a di‐n‐alkylphthalate (methyl, ethyl, butyl or octyl) were studied for their water vapour permeation (WVP) properties. The rates of WVP through them were estimated under steady state by permeating the vapour through the membrane under the vapour pressure differential of approximately 100% to 0% relative humidities at 25°C. The rates of WVP were found to decrease with an increase in the size of the alkyl group of the phthalate but increased with its concentration. The maintenance of the property by the membranes being critical for their long‐term applications, the measurements were also repeated on the membranes aged for 250 days at intervals of 50 days. The WVP data indicate that membranes containing medium concentrations, i.e. 17.5‐20% of the plasticizers have better maintenance of the property during ageing and also in handling with good mechanical strength.
Kinetics of heterogeneous cyanoethylation of cellulose
Authors: Sefain Magdi Z. , Fadl Mohamed H. , Elwakil Nahla A. , Naoum Magdi M.
Published: April 2007

Heterogeneous sodium and potassium hydroxide‐catalysed cyanoethylation of cotton linter and viscose grade wood pulp, investigated by analysing the nitrogen content of the cyanoethylated product as a function of the time of reaction, were shown to follow a first‐order rate equation. A new procedure was elaborated and a computer program was written to estimate the number of hydroxyl groups accessible for cyanoethylation per anhydroglucose unit and the specific rate constant from the rate curves. The effect of the type of alkali, its solution‐to‐cellulose ratio, temperature of reaction, mode of agitation, and the degree of polymerisation and packing density of cellulose fibres on the kinetics of cyanoethylation reaction were investigated.
Synthesis and characterisation of poly(amide‐hydrazides) containing many flexible spacer groups
Authors: Joseph K. Abraham , Srinivasan M.
Published: April 2007

A set of 12 fully aromatic poly(amide‐hydrazides) were synthesised by the direct polycondensation phosphorylation reaction. Four different diamines containing preformed hydrazide units were condensed with three diacids in a mixture of N‐methylpyrrolidinone and pyridine. The polymers were obtained in 70‐85% yield and characterised by infrared and elemental analysis. The thermal stability, crystallinity, density and solubility were also measured.
Polymerisation control in casting of methylmethacrylate
Authors: Ramaseshan Vinod , Trivedi M. K. , Raghunathan T. S.
Published: April 2007

This paper reports a technique for the controlled bulk polymerisation of methylmethacrylate initiated by benzoyl peroxide. Due to the high exothermic nature of this polymerisation process, casting of thin sheets and profiles must generally be carried out at relatively low temperatures and over extended intervals of time at a constant rate. Curing profiles of 6‐12 h have been considered incorporating the kinetic features of polymerisation which includes a gel effect. The influence of the gel effect on the propagation and termination rate constants can be divided into two regions: one up to 20% conversion, and the other beyond it. In the first range the gel effect is independent of conversion while in the latter stage its influence is characterised by Ross‐Laurence parameters. The study indicates that no advantage is gained through the employment of two‐stage initiator loading. Curing cycles of longer duration can be generated for thicker castings from the analysis given.
Kinetics of phase separation in polyurethane/polystyrene semi‐1 interpenetrating polymer networks. 1. Light transmission studies
Authors: He Xiongwei , Widmaier Jean‐Michel , Meyer Guy C.
Published: April 2007

The phase separation of different in‐situ semi‐1 interpenetrating polymer networks (IPNs) based on polyurethane and polystyrene has been followed by light transmission. The effect of the presence ab initio of small amounts of homopolystyrene in the initial reaction mixture on the phase separation process has also been examined. If gelation of the polyurethane occurs before the onset of phase separation, the latter is impeded or strongly limited, and transparent semi‐1 IPNs are obtained. In the opposite case, phase separation is macroscopic and the material is turbid.
Kinetics of phase separation in polyurethane/polystyrene semi‐1 interpenetrating polymer networks. 2. Microscopy observations and theoretical approach
Authors: He Xiongwei , Widmaier Jean‐Michel , Meyer Guy C.
Published: April 2007

The phase separation process of in‐situ polyurethane/polystyrene semi‐1 interpenetrating polymer networks has been followed by optical microscopy completed by image analysis. The final morphology has been examined by scanning electron microscopy, and its relation to the phase separation process has been established. When phase separation occurs before gelation of the medium, polystyrene is dispersed both as large and small noduli in the polyurethane network; a polyurethane‐rich interphase separates the noduli from the matrix. These observations explain the previous results on the turbidity of such systems measured by light transmission. In the opposite cases, no visible phase separation is observed on the micrographs. The thermodynamics of the phase separation process has also been examined.
Crosslinking of PVC and NBR blends
Authors: Oravec Jan , Oishi Yoshiyuki , Hirahara Hidetoshi , Mori Kunio
Published: April 2007

The purpose of our work is to control the interfacial bonds between PVC and NBR using the ammonium salts of triazine thiols and dithiodimorpholine (DTDM) and thereby reveal the relation between the interfacial bonds and the final mechanical properties of products.

In the experimental work a two‐stage process was used. At first, an NBR/PVC blend was mixed with a mono‐tetra‐n‐butylammonium salt of triazine trithiol at a temperature of 100°C on a two‐roll mill to give the branching structure of triazine thiols into PVC. In the second stage branched NBR/PVC reacted with DTDM to afford the branched PVC containing trithiomorphonyl groups. In the presence of ZnO at 160°C trithiomorphonyl groups react with NBR to form a crosslinking structure between NBR and PVC.

The mechanical properties of cured NBR/PVC blends were markedly improved by the treatment process and after addition of tetramethylthiuram monosulphide also. The mechanical properties were not improved by increasing the concentration of TT‐TBA (tetrabutylammonium salt of 1,3,5‐triazine‐2,4,6‐trithiol) over 4.2 phr.
Synthesis and properties of aromatic ionenes
Authors: Hochberg Gerd C. , Schulz Rolf C.
Published: April 2007

Cationic polyelectrolytes with aromatic segments can be synthesized by a repetitive alkylation reaction. The structure of the products, their synthesis and their solubility are described. All ionenes are not, or only in small amounts, water soluble. The best solubility can be achieved by mixtures of polar protic and aprotic solvents. Variations of the counterion produces sufficient solubility in THF. All ionenes show a typical polyelectrolyte effect. The thermal stability of aromatic ionenes and the glass transition temperature is dominated by the nature of the counterion. The molecular weight of oligomers can be described by using a combination of a conductive titration method and an ion selective electrode.
Thermal behaviour of nylon 6 synthesized using urethane‐based initiator system
Authors: Desai Manish R. , Pandya Madhav V.
Published: April 2007

Using ϵ‐caprolactam capped urethane molecule as an initiator, nylon 6 was prepared by anionic method using sodium metal as catalyst. Two different aromatic diisocyanates were used to prepare the initiator. The effect of the nature and concentration of the initiator molecules on the physical and thermal properties of polyamide 6 is discussed.
Mechanical properties of blends of nylon with chemically modified ABS
Authors: Nelson T. J. , Subramanian N.
Published: April 2007

Tensile, flexural and impact properties were measured of a heterogeneous polymer blend system, consisting of nylon 6 and a chemically modified ABS (MABS). It was found from the tensile tests that nylon‐richer blends show yielding behaviour and nylon‐leaner blends show necking behaviour. The addition of MABS increases the modulus, whereas the tensile strength and percentage elongation at break decrease and go through a minimum. The impact strength is increased to a maximum of approximately three times when 20 wt% of MABS is added to nylon 6. In order to interpolate the mechanical properties observed, empirical equations are given which are found to describe the experimental data rather well. Photomicrographs were taken of the tensile fractured surfaces using a scanning electron microscope.
Rubber‐modified epoxies. I. Influence of presence of a low level of rubber on the polymerization
Authors: Chen Dong , Pascault Jean Pierre , Sautereau Henry
Published: April 2007

Butadiene‐acrylonitrile random copolymers with various molecular weights and end‐groups were introduced into a system consisting of the diglycidyl ether of bisphenol A (DGEBA) and 3,3′‐dimethyl‐4,4′‐diamino dicyclohexyl methane (3DCM) cured at 50°C. We studied the influence of a low level of soluble additive on the polymerization rate, evolution of viscosity, gelation and vitrification times, and the final network in the cases of different additive molecular weight and end groups of the additive. It was found that the additive influences the final network only by dissolving in the matrix and that the dilution effect plays a minor role, but the catalytic effect of an additive can play a significant role on the polymerization depending on the additive end groups. However, in all the rubber‐modified systems, the phase separation has no direct influence on the polymerization rate and the change of viscosity.
Dielectric properties of amorphous cellulose acetate‐butyrate polymer films
Authors: Reddy N. Venugopal , Kumar C. Ramesh , Rao V. V. R. Narasimha
Published: April 2007

The dielectric constant, loss tangent and AC conductivity of solution grown cellulose acetate‐butyrate films of 5μm thickness were studied as a function of temperature (300‐450 K) in the frequency range 10 Hz‐10 MHz. The decrease in dielectric constant was observed with the increase in frequency as well as with temperature. A loss peak was observed in the dielectric loss spectra and was identified as the β‐relaxation peak. The frequency‐dependent conductivity was also studied. The results were interpreted in terms of electronic conduction via hopping processes.
Azeotropy in terpolymerisation reactions of glycidylmethacrylate with alkyl acrylates and acrylonitrile
Authors: El‐Hamouly S. H.
Published: April 2007

Ternary copolymerisation of glycidylmethacrylate (GMA), with different alkyl acrylates (methylacrylate (MA), methylmethacrylate (MMA), butylacrylate (BuA) and n‐butylmethacrylate (n‐BuMA)) and acrylonitrile (AN)) were carried out in solution at 65°C in the presence of a free radical initiator. Experimental terpolymerisation data agree well with calculations based on the Alfrey‐Goldfinger equation. The determination of unitary, binary and ternary azeotropes of the various systems studied was easily handled by a computer. Ternary azeotropic compositions for GMA‐MMA‐AN and GMA‐nBuMA‐AN systems were found to be 17‐50:68‐50:14‐00 and 51‐00:3‐00:46‐00 mol%, respectively. Also, 'pseudo‐azeotropic' regions were identified where the deviation between feed and polymer compositions was very small.
Use of glycidyls in the modification of polyurethane membrane structures
Authors: Bezdadea Mariana , Savin Alexandru , Ciobanu Gabriela
Published: April 2007

Aromatic glycidyl ethers have been used for modifying the structure of polyurethane membranes and improving their properties. The changes of chemical structure of the polyurethane in the membrane network have been followed by IR spectroscopy. The structural uniformity of the membrane has been elucidated by osmotic measurements and SEM. The structure of the membranes obtained has been related to their permeability towards distilled water.
Photosensitive polymers containing pendent chalcone moieties via oxyethylene group
Authors: Akelah A. , Selim A. , El‐Deen N. Salah
Published: April 2007

Vinylchalcone derivatives were prepared by the reaction of the sodium salt of 4‐hydroxychalcone with 2‐chloroethanol, followed by esterfication of the hydroxy groups with methacryloyl chloride in the presence of triethylamine as a base. The photosensitive monomers, 4‐(methacryloyloxyethoxy)chalcone and its 4′‐methyl and 4′‐chloro‐derivatives, have been homo‐ and copolymerized with p‐nitrophenylmethacrylate under free radical conditions to give the copolymers containing different ratios of photosensitizer group. The photosensitivities of the polymeric chalcone derivatives were investigated through their photochemical reactions on exposure to UV light and measuring the changes in UV spectra before and after irradiation. The results of these measurements indicate that the insolubilization percentage, i.e. the rate of the double bond disappearance depends on the effects of (i) the time of exposure to UV light, (ii) the position of the substituent in the phenyl ring of the chalcone, (iii) the spacer between the active moiety and the polymer backbone, and (iv) the ratio of the photosensitizer group.
Experimental and theoretical push‐pull Chemo‐ and regioselectivity in 1,3‐Dipolar cycloaddition reactions: the case of benzotriazepin‐5‐one with mesitylnitrile oxide
Authors: Azzouzi Saida , Jalal Rachid , El Messaoudi Malika , Domingo Luis R. , Esseffar M'hamed , Aurell M. José
Published: April 2007

A novel heterocyclic compound 3‐mesityl‐5‐methyl‐4,5,11,11a‐tetrahydro‐6H‐[1,2,4]oxadiazolo [5,4‐b][1,3,4]benzotriazépin‐6‐one 4 has been synthesised by a 1,3 dipolar cycloaddition (13DC) reaction of 1,3,4‐benzotriazepin‐5‐one 1 with mesitylnitrile oxide 3. The reaction, beside its synthetic interest, has shown to be completely chemo‐ and regioselective. The structure of the compound was determined by X‐ray crystallography and analysed by spectral methods (NMR and mass spectrometry). The molecular mechanism for the reaction has been studied using quantum mechanical calculations at the B3LYP/6‐31G* theory level. Two mechanisms are possible for the formation of the cycloadduct 4. The first one involves a 13DC reaction between 1, as dipolarophile and 3, as dipole. Analysis of the results indicates that it takes place along asynchronous concerted bond‐formation process with a very low polar character. The regioselectivity obtained from the calculations are in complete agreement with the unique formation of the cycloadduct 4. The second mechanism is initiated by the nucleophilic attack of the N3 nitrogen of the tautomer form of 2, to the C5 carbon of the nitrile oxide 3 to yield an amidoxime. However, the large energy involved in this addition prevents this mechanism. The large energy difference between the tautomers 1 and 2, makes that only the CN site of benzotriazepin‐5‐one 1 could act as a dipolarophile site. This fact makes the 13DC reaction to be chemoselective. The analysis of global electrophilicity of the reagents allows explaining the low polar character of these 13DC reactions. Copyright © 2007 John Wiley & Sons, Ltd.
A novel probe for determination of electrical surface potential of surfactant micelles: N,N'‐di‐n‐octadecylrhodamine
Authors: Mchedlov‐Petrossyan Nikolay O. , Vodolazkaya Natalya A. , Yakubovskaya Anna G. , Grigorovich Aleksey V. , Alekseeva Vera I. , Savvina Lyubov P.
Published: April 2007

The peculiarities of the structure of the fluorescent dye N,N'‐di‐n‐octadecylrhodamine advantage its using as an interfacial acid–base probe in aqueous micellar solution of colloidal surfactants. Two long hydrocarbon tails of the dye provide similar orientation of both cation and zwitterion on the micelle/water interface, with the ionizing group COOH exposed to the Stern region in all the systems studied. Further, the charge type of the acid–base couple, A+B±, ensures similar values of the ‘intrinsic’ contribution, pK, to the ‘apparent’ pK value in micelles of different surfactants. This makes the indicator suitable for determination of electrical surface potentials, Ψ. The pKs have been obtained in cationic, anionic, zwitterionic, and nonionic surfactant systems, at various salt background. In total 17 systems were studied. At bulk counterion concentration of ca. 0.05 M, the pK values vary from 2.14 ± 0.07 in n–C18H37N(CH3)Cl– micelles to 5.48 ± 0.06 in n–C16H33OSONa+ micelles. The Ψ values, corresponding to the Stern region of micelles, have been evaluated as Ψ = 59.16 pK–pK for T = 298.15 K. The pK parameter was equated to the average value of 4.23 in nonionic surfactants (4.12–4.32, depending on the surfactant type). For cetyltrimethylammonium bromide and sodium n‐dodecylsulfate micelles, the Ψ values (±(7–11) mV) appeared to be +118 mV and at bulk Br− concentration 0.019 M and −76 mV at bulk Na+ concentration 0.020 M, respectively. This satisfactorily agrees with the theoretical values +111 and −84 mV, estimated using the Oshima, Healy, and White equation for these well‐defined colloidal systems. Finally, not only absorption, but also fluorescence spectra display the same response to changes in bulk pH. Copyright © 2007 John Wiley & Sons, Ltd.
Modulating testosterone stimulated prostate growth by phenethyl isothiocyanate via Sp1 and androgen receptor down‐regulation
Authors: Beklemisheva Anastasia A. , Feng Jingyang , Yeh Yunshin Albert , Wang L. G. , Chiao J. W.
Published: April 2007

BACKGROUND

The effects of phenethyl isothiocyanate (PEITC), present naturally in cruciferous vegetables, on androgen‐influenced growth of the prostate such as benign hyperplasia, was investigated.

METHODS

Rats dosed with cyproterone acetate and testosterone, were fed at the same time with either PEITC or vehicle control. The growth of the prostates was compared to untreated rats.

RESULTS

While testosterone increased the prostate mass (30%) and hyperplastic seminiferous tubules as compared to the untreated rats, PEITC feeding decreased the prostate mass and hyperplasia to roughly the levels of untreated rats (P < 0.05). PEITC negated the testosterone‐mediated enhancement of the androgen receptor (AR), via down‐regulating transcription factor Sp1 expression and Sp1 binding complex formation. Cell cycle progression was attenuated with decreases of cyclins, Rb, and up‐regulates p27.

CONCLUSIONS

PEITC modulates the testosterone‐influenced growth by repressing Sp1, thus down‐regulating AR and proliferation. PEITC from cruciferous vegetables may represent a regulator for hormone‐dependent growth of the prostate. Prostate 67: 863–870, 2007. © 2007 Wiley‐Liss, Inc.
Orientational vibrations of 2D molecular layers with quadrupolar interaction
Authors: Lykah V. A. , Syrkin E. S.
Published: April 2007

Molecular layers with rotational degrees of freedom and quadrupolar interaction between linear molecules are investigated theoretically. Rotation of the molecules in the plane of an adsorbing surface is considered; centers of gravity of the molecules are pinned to sites of a rectangular lattice. The energy of the system contains an additional parameter ρ (ratio of the lattice constants of a 2D system), in comparison with the 1D case. It is found that alternating orientation of the adsorbed molecules along both sides of the rectangular unit cell corresponds to the minimum of the energy. Equations of rotational movement are derived for linear oscillations of molecules near the equilibrium positions in a 2D lattice. Dispersion relations are obtained and analyzed. The Brillouin zone cannot be divided as in the 1D case after unit‐cell doubling. The parameter B (k), which describes the topology of the dispersion surfaces, is introduced. It is shown that both branches of the spectrum have optical behavior. The gaps and bandwidths are found as functions of ρ. The method of calculation of the density of states (DOS) for translational oscillations of a 2D rectangular lattice with one atom per unit cell is generalized for rotational oscillations of a 2D two‐sublattice molecular lattice. The diagram describing three regions with different analytical properties of the DOS which correspond to different topologies of the isofrequency lines is introduced. This diagram is a portrait in the plane of the parameters B and ρ. The DOS is found in terms of complete elliptic integrals of the first kind. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)