bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrodynamic Activation of the Batch‐Polymerization of Methyl methacrylate in a Taylor‐Couette Reactor
Authors: Liu Zhen , Kádár Roland , Kind Matthias 
Published: March 2011

AbstractSummary:In this work, the free radical batch polymerization of methyl methacrylate (MMA) premixed with xylene as a solvent, in the presence of an initiator, 2,2‐azoisobutyronitrile (AIBN), in the Taylor‐Couette reactor was studied. We observed an unexpected influence of hydrodynamic process parameters, i.e. angular velocity ω, on the polymer conversion, molecular weight and viscosity of the produced polymer. The polymerization process seems to be activated by hydrodynamic process parameters. Hydrodynamic activation is a promoting effect of process parameters on polymer product properties. The hydrodynamic activation is found to depend on the reaction time and the angular velocity of the inner cylinder. In addition, our results highlight both the reaction kinetics and the hydrodynamics during the polymerization. The conversion exhibits a significant difference between tests with and without the angular velocity of the inner cylinder. The conversion and the molecular weight strongly increase with the increase of the angular velocity of the inner cylinder, whereas the viscosity is less strongly dependent. There is more increase with decreasing solvent concentration. The radial Reynolds number decreases with increasing conversion. The polymerization is faster with a low solvent concentration, and the molecular weight is higher compared to the case of high solvent concentration.
Electrical, Film and Surface Properties of Water‐Based Latexes Prepared by Semicontinuous Emulsion Polymerization
Authors: Kahraman Ayça , Sarac Ayfer 
Published: March 2011

AbstractSummary: In this study, the results obtained with latexes prepared by semicontinuous emulsion polymerization with conventional anionic and nonionic emulsifiers and their different mixtures were presented. For this study, vinyl acetate‐butyl acrylate latexes with a conventional anionic emulsifier (sodium lauril ether sulfate) and a nonionic emulsifier (30 mole nonyl phenol ethoxylate), of which films can be easily cast, were used. The latex properties in terms of mechanical stability, film‐water absorption, and film‐emulsifier exudation, and surface and electrical properties were assessed and compared.
Computational Analysis of Mixing and Scale‐Up in Emulsion Polymerization Reactors
Authors: Pohn Jordan , Heniche Mourad , Fradette Louis , Cunningham Michael , McKenna Timothy 
Published: March 2011

AbstractSummary: A hybrid multi‐zonal/computational fluid dynamics (CFD) framework is currently being developed to aid in the scale‐up of high solid content latex production and processing. Poly3D, a commercial laminar CFD code tailored to modelling the mixing of non‐Newtonian fluids, has been coupled to a population balance model via a customized interface. CFD is used to generate flow fields inside a series of reactors; this information is then transferred to a multi‐zone population balance model to assess the impact of non‐homogenous mixing on the evolution of the latex particle size distribution (PSD) when concentrated latex suspension is altered via the addition of a coagulant. The rheological properties of high solid content latexes are sensitive to changes in the PSD, so the flow field is periodically updated if significant changes in the rheological properties of the latex are detected in any of the zones. The details of the models comprising the framework are presented and the utility of the framework is demonstrated.
A Density Functional Theory Study of Poly (vinyl chloride) (PVC) Free Radical Polymerization
Authors: Cuccato Danilo , Dossi Marco , Moscatelli Davide , Storti Giuseppe 
Published: March 2011

AbstractSummary: Quantum chemistry was applied to the free radical polymerization of Vinyl Chloride with the aim of elucidating the reaction kinetics and especially the formation of structural defects and low molecular weight polymer. The radical reactions were studied using the Density Functional Theory. All calculations were performed with B3LYP functionals and in particular the 6‐31G(d,p) basis set was selected to evaluate the exchange and correlation energies. The computational method was first validated by predicting the rate constant of the propagation step and comparing the calculated values to experimental ones. Then intramolecular chain transfer, β‐scission and branching reactions were also investigated, due to their direct connection with the production of defects in the growing chains. A comparison of the evaluated kinetic constants of such secondary reactions with other computational evaluations and experimental data was finally made.
Microwave Effects Due to Anionic or Cationic Initiators in Emulsion Polymerization Reactions
Authors: Costa Cristiane , Santos Verusca H. S. , Sayer Claudia , Araujo Pedro H. H. , Santos Alexandre F. , Fortuny Montserrat 
Published: March 2011

AbstractSummary: Emulsion polymerization reactions were performed under microwave irradiation and conventional heating using anionic or cationic initiators and surfactants. Microwave irradiation promoted higher reaction rates for both initiators and surfactants, in comparison with the conventional heating. The effect of high power microwave irradiation was studied using a method of cycles of heating and cooling, where rapid polymerization reactions were obtained. In the reactions with anionic initiator and surfactant, a decrease in the particle diameters was observed with microwave heating, and even smaller particles were obtained using high power microwave irradiation. Moreover, the decrease in the particle size was acompanied by an increase in the polymer molecular weight. On the other hand, these effects were not observed for reactions with cationic initiator and surfactant.
Modelling of the High‐Impact Polystyrene Morphogenesis
Authors: Vonka Michal , Šeda Libor , Kosek Juraj 
Published: March 2011

AbstractSummary: High‐impact polystyrene (HIPS) is a hetero‐phase polymer with the so‐called salami morphology. Salami morphology is formed by a continuous PS phase containing micron‐sized PB domains. PB domains contain submicron‐sized irregular PS occlusions. In our modeling work we addressed several weak points of Cahn‐Hilliard model of HIPS salami morphology evolution. The weakest point of Cahn‐Hilliard model is the inherently present Ostwald ripening destabilizing or competing with graft‐stabilized domains. Two mechanism of formation of HIPS morphology are supported by the model: (i) encapsulation of graft‐stabilized PS‐rich domains in PB particles, and (ii) polymerization of styrene dissolved in PB‐rich phase and subsequent phase separation leading to PS occlusions in PB domains.
Data Reconciliation and Control in Styrene‐Butadiene Emulsion Polymerizations
Authors: Souza Paula Naomi , Soares Matheus , Amaral Marcelo M. , Lima Enrique Luis , Pinto José Carlos 
Published: March 2011

AbstractSummary: A nonlinear model‐based predictive control (NLMPC) method was developed using a First Principles model of an emulsion copolymerization of carboxylated styrene butadiene rubber (XSBR). Copolymer composition, conversion and average molecular weights of the copolymer were chosen as the controlled variables due to their influence on the final product properties and quality. These properties, however, are rarely measured in‐line due to the operational difficulties associated with their measurement. For this reason a soft‐sensor using reaction calorimetry techniques was developed and used to infer reaction conditions, rates, species concentrations and polymer properties in a industrial scale emulsion polymerization reactor.
Design and Simulation of a New Reactor for the Production of High‐Viscosity Polymer Melts
Authors: Rieckmann Thomas , Frei Fabian , Völker Susanne 
Published: March 2011

AbstractSummary: Innovative reactor internals consisting of a number of vertically stacked perforated plates have been proposed to increase mass transfer rates of volatiles from highly viscous polymer melts. A mathematical model comprising mass and enthalpy balances for the polycondensation of polyamide 6 has been used to evaluate the new reactor design. According to the simulation, the alternating arrangement of devolatilization and residence zones leads to an effective removal of reaction water from the polymer melt. Compared to the VK‐tube reactor, which is most commonly used to produce high quality PA‐6, the new reactor design produces high quality polymer with a high degree of polymerization within a considerably shorter residence time. The application of the proposed reactor internals is not limited to PA‐6 production, since the removal of volatiles is of the same major importance during all reversible polycondensation reactions, e.g. the production of PET.
A Detailed Polymerization Model for Cerenol® Polyols
Authors: Mueller Philipp A. , Murphy Edward R. , Rajagopalan Bhuma , Congalidis John P. , Minter Aaron R. 
Published: March 2011

AbstractSummary: A mathematical model of the acid catalyzed 1,3‐propanediol polymerization has been developed. Two catalysts investigated include sulfuric acid and superacid (tetrafluoroethane sulfonic acid or triflic acid). Based on a detailed reaction mechanism, population and mass balance equations have been derived for small molecules as well as for polymeric species of numerous chain distributions, which are distinguishable in terms of protonation state and end group functionality. Due to the interaction of the sulfuric acid catalyst with the polymer ends, a novel, dual index polymer chain distribution was derived and implemented.The model has been validated with various sets of experimental data obtained in a lab‐scale reactor setup. Dynamic model outputs such as monomer concentration, molecular weight averages, unsaturated and sulfate end groups, water evaporation rate and sulfate middle groups have been compared with experimental data of sulfuric and super acid catalyzed polymerization runs. Very good agreement between model predictions and experimental data has been obtained for both catalyst systems over an extended range of conditions using the same set of model parameter values. It is worth noting that the model is also capable of predicting polymerization equilibrium.
Safety and Quality Aspects of Acrylic Monomers
Authors: Hartwig Ali , Brand Raphael H. , Pfeifer Christian , Dürr Nadine , Drochner Alfons , Vogel Herbert 
Published: March 2011

AbstractSummary: Acrylic monomers are important intermediates for the chemical industry. Especially acrylic acid (AA) is the basis for various reactions, such as polymerizations and esterifications and is, therefore, responsible for high product diversity. Spontaneous polymerization is a safety problem during the transportation and storage of acrylic monomers. In the production process, polymerization leads to blockages in the apparatus. For the prevention of these issues, special stabilizer systems are used such as hydroquinone monomethyl ether (MeHQ)/oxygen and phenothiazine (PTZ). The reactions of these stabilizer systems are not well understood at the moment. Therefore a lot of expertise and experience are necessary to guarantee safe handling. In this paper some methods for the investigation of stability related reaction kinetics are presented. A better comprehension of the mechanism of the polymerization inhibition is generated by the kinetic simulation with these data.
Polymerization Kinetics of Water‐Soluble N‐Vinyl Monomers in Aqueous and Organic Solution
Authors: Santanakrishnan Sandhya , Hutchinson Robin A. , Učňová Lucia , Stach Marek , Lacík Igor , Buback Michael 
Published: March 2011

AbstractSummary: Free‐radical batch polymerization (FRP) of N‐vinyl pyrrolidone (NVP) and N‐vinyl formamide (NVF) monomers in aqueous solution as well as NVP polymerization in organic (n‐butanol) solution has been studied. The differences found in rate of monomer conversion with monomer and solvent choice correlates well with the differences in values of the propagation rate coefficients (kp) and their variation with monomer concentration measured in independent pulsed‐laser polymerization studies, a result demonstrating that a generalized understanding of water‐soluble vinyl monomers can be obtained once their kp differences have been accounted for. A reasonable representation of polymer molecular mass averages and the complete molecular mass distributions for the three systems was obtained by assuming that the rate coefficient for transfer to monomer, polymer, and organic solvent also vary as a function of monomer concentration.
Molecular Versus Conventional Kinetics of Emulsion Polymerization
Authors: Tauer Klaus , Hernandez Hugo , Weber Nancy , Roohi Farnoosh 
Published: March 2011

AbstractSummary: Experimental data are discussed challenging the deterministic kinetics of emulsion polymerization. Examples are given for the overall rate of polymerization, in‐situ stabilizer formation, and swelling of latex particles. Improving the deterministic view on emulsion polymerization kinetics requires the consideration of results of molecular modelling and the application of multiscale integration techniques.
Order and Phase Behavior of a Cylinder Forming Diblock Copolymers and Nano‐Particles Mixture in Confinement: A Molecular Dynamics Study
Authors: Shagolsem Lenin S. , Sommer Jens‐Uwe 
Published: March 2011

AbstractWe study a coarse grained model of cylinder forming diblock copolymers and nano‐particles (NPs) mixture confined between Lennard–Jones hard walls. Two models for non‐selective interactions between monomers and NPs are applied. In the case of purely repulsive interactions between NPs and monomers (athermal case) strong segregation of NPs at the film surfaces and the formation of droplets of particles inside the copolymer film can be observed. For weakly attractive interactions between NPs and monomers (thermal case) formation of droplets of particles disappears and segregation on the film surfaces depend on temperature. The uptake of NPs by the copolymer film in the thermal case displays a non‐monotonic dependence on temperature which can be qualitatively explained by a mean‐field model. In both cases of non‐selective interactions NPs are preferentially localized at the interface between the microphase domains. magnified image
Targeting PKC‐β II and PKB Connection: Design of Dual Inhibitors
Authors: Jain Kapil , Ajay Dara , Sobhia M. Elizabeth 
Published: March 2011

AbstractProtein kinase C (PKC) has been the center of many cell signaling pathways. PKC isoforms, specifically PKC‐β II is linked to both diabetic complications as well as in promotion of angiogenesis and regulation of cancers. PKC‐β II activates the PKB/Akt pathway. Enzastaurin, a selective PKC‐β II inhibitor has been found to inhibit PKB/Akt by suppressing the regulation of various cancerous pathways. In the present work, we carried out an in depth study on the binding mode of inhibitors of PKC‐β II, enzastaurin and ruboxistaurin with the active site residues of PKB and PKC‐β II. A ligand based approach has been further used to determine the pharmacophoric features and spatial arrangement of molecules, having common properties necessary for appropriate binding to the active site of both targets. Virtual screening of the respective pharmacophores of both proteins led to identification of hits which may be useful for treatment of diabetic complications and cancer. The study has highlighted important features that may be considered in the future for designing novel inhibitors.
Prilocaine–cyclodextrin–liposome: effect of pH variations on the encapsulation and topology of a ternary complex using 1H NMR
Authors: Cabeça Luís Fernando , Figueiredo Isis Martins , Paula Eneida de , Marsaioli Anita Jocelyne 
Published: March 2011

AbstractA better comprehension of the prilocaine (PLC)–β‐cyclodextrin (β‐CD) complex liberation to membranes was provided by studying the architectural supramolecular arrangements of PLC, β‐CD and egg phosphatidylcholine (EPC) liposomes, a membrane model. The topologies and possible interactions of mixtures of PLC, β‐CD and EPC liposomes were investigated by nuclear magnetic resonances combining experimental 1H‐NMR (1D ROESY, STD and DOSY) at different pHs. The results indicate that in the mixture PLC/β‐CD/EPC at pH 10 the PLC molecules are almost totally embedded into the liposomes and little interaction was observed between PLC and β‐CD. However, at pH 5.5 not only was PLC imbedded in the EPC bilayer, but PLC was also interacting with β‐CD. These results were rationalized as a spontaneous PLC release from β‐CD to liposomes vesicles, whereas the PLC/EPC complex formation was higher at pH 10 than pH 5.5. Copyright © 2011 John Wiley & Sons, Ltd.
NMR assignment in regioisomeric hydroquinones
Authors: Dobado Jose A. , Gómez‐Tamayo José C. , Calvo‐Flores Francisco G. , Martínez‐García Henar , Cardona Wilson , Weiss‐López Boris , Ramírez‐Rodríguez Oney , Pessoa‐Mahana Hernán , Araya‐Maturana Ramiro 
Published: March 2011

AbstractA set of regioisomeric pairs of tricyclic hydroquinones, analogues of antitumor 9,10‐dihydroxy‐4,4‐dimethyl‐5,8‐dihydroanthracen‐1(4H)‐one (1) and other derivatives, were synthesized and their regiochemistry and NMR spectra assigned by using 1H‐detected one‐bond (CH) HMQC and long‐range CH HMBC, in good agreement with theoretical O3LYP/Alhrichs‐pVTZ calculations. The 5‐hydroxymethyl derivatives (11, 15, 19) showed a 3JH, H coupling constant of methylene protons evidencing the presence of a seven‐membered intramolecular hydrogen bonded ring, not observed for the 8‐hydroxymethyl isomers. Copyright © 2011 John Wiley & Sons, Ltd.
Steroids and an oxylipin from an algicolous isolate of Aspergillus flavus
Authors: Qiao Ming‐Feng , Ji Nai‐Yun , Miao Feng‐Ping , Yin Xiu‐Li 
Published: March 2011

AbstractA new oxylipin, (8E,12Z)‐10,11‐dihydroxyoctadeca‐8,12‐dienoic acid (1), a new steroid, 3β,4α‐dihydroxy‐26‐methoxyergosta‐7,24(28)‐dien‐6‐one (2), and four known steroids, episterol (3), (22E,24R)‐ergosta‐7,22‐dien‐3β,5α,6α‐triol (4), (22E,24R)‐ergosta‐5,22‐dien‐3β‐ol (5), and (22E,24R)‐ergosta‐4,6,8(14),22‐tetraen‐3‐one (6), were isolated from the cultures of Aspergillus flavus, an endophytic fungus isolated from the marine red alga Corallina officinalis. Their structures and relative stereochemistry were elucidated by 1D, 2D NMR and mass spectroscopic techniques. 1 and 2 exhibited low activity to inhibit acetylcholinesterase and no activity against plant pathogenic fungi Colletotrichum lagenarium and Fusarium oxysporum. Copyright © 2011 John Wiley & Sons, Ltd.
Saturation‐dependent nuclear magnetic resonance relaxation of fluids confined inside porous media with micrometer‐sized pores
Authors: Simina Marius , Nechifor Ruben , Ardelean Ioan 
Published: March 2011

AbstractIn the present study, we investigate the relationship between the relaxation rate and the filling factor in partially saturated porous media. The filling fluids are polar (water, acetone) and nonpolar (cyclohexane, hexane). The porous sample is a silica glass (Vitrapor#5) with the nominal mean pore size of d = 1 µm ( ± 0.6 µm). All nuclear magnetic resonance relaxation experiments are performed at 20 °C using a NMR instrument operable at 20 MHz proton resonance frequency. The experimental results are compared with a two‐phase exchange model providing us information on the strength of surface relaxation and fluid distribution inside pores. These results will affect the NMR estimations about fluid content of porous media. Copyright © 2011 John Wiley & Sons, Ltd.
Complete NMR data of methoxylated cis‐ and trans‐stilbenes as well as 1,2‐diphenylethanes
Authors: Jo Geunhyeong , Hyun Jiye , Hwang Doseok , Lee Young Han , Koh Dongsoo , Lim Yoongho 
Published: March 2011

AbstractResveratrol is a polyphenol isolated from many natural sources including grapes, mulberries, eucalyptus, spruce, lilies, and peanuts. The hydroxyl groups in polyphenols can be substituted with various functional groups, allowing production of multiple derivatives. NMR spectroscopy is used to identify new derivatives. Since the complete NMR data of the known derivatives can be useful for identification of the newly isolated derivatives, here, we report the synthesis of 14 methoxylated stilbenes and four 1,2‐diphenylethanes and their NMR data. Copyright © 2011 John Wiley & Sons, Ltd.
Conformational analysis and diastereotopic assignments in the series of selenium‐containing heterocycles by means of 77Se‐1H spin‐spin coupling constants: a combined theoretical and experimental study
Authors: Rusakov Yury Yu. , Krivdin Leonid B. , Potapov Vladimir A. , Penzik Maxim V. , Amosova Svetlana V. 
Published: March 2011

AbstractA combined theoretical and experimental study on the stereochemical behavior of 77Se‐1H spin‐spin coupling constants has been performed at the second‐order polarization propagator approach level together with heteronuclear multiple‐bond correlation technique in the series of selenium‐containing four‐, five‐ and six‐membered heterocycles including the derivatives of thiaselenetane, selenasilole, thiaselenole, thiaselenolane and dihydrothiaselenine. Geminal and vicinal 77Se‐1H spin‐spin couplings were shown to have the pronounced stereochemical dependences in respect with the topology of the coupling pathway, internal rotation of the side‐chain substituents and ring inversion providing a straightforward tool for the conformational analysis and diastereotopic assignments in the chiral organoselenium compounds. Copyright © 2011 John Wiley & Sons, Ltd.
Effects of pharmaceutical counselling on antimicrobial use in surgical wards: intervention study with historical control group,
Authors: Grill Eva , Weber Alexandra , Lohmann Stefanie , Vetter‐Kerkhoff Cornelia , Strobl Ralf , Jauch Karl‐Walter 
Published: March 2011

ABSTRACTPurposeThe objective of this study was to assess the impact of pharmaceutical consulting on the quality of antimicrobial use in a surgical hospital department in a prospective controlled intervention study.MethodsPatients receiving pharmaceutical intervention (intervention group, IG, n = 317) were compared with a historical control group (control group, CG, n = 321). During the control period, antimicrobial use was monitored without intervention. During the subsequent intervention period, a clinical pharmacist reviewed the prescriptions and gave advice on medication.ResultsIntervention reduced the length of antimicrobial courses (IG = 10 days, CG = 11 days, incidence rate ratio for i.v. versus o.p. = 0.88, 95% confidence interval 0.84 to 0.93) and shortened i.v. administration (IG = 8 days, CG = 10 days, hazard rate = 1.76 in favour of switch from i.v. to p.o., 95% confidence interval 1.23 to 2.52). Intervention also helped to avoid useless combination therapy and reduced total costs for antimicrobials.ConclusionsA clinical pharmacist who reviews prescriptions can promote an increase in efficiency, for example, by shortening the course of treatment. Counselling by ward‐based clinical pharmacists was shown to be effective to streamline antimicrobial therapy in surgical units and to increase drug safety. Copyright © 2011 John Wiley & Sons, Ltd.
On the testing of large PV arrays
Authors: Martínez‐Moreno F. , Lorenzo E. , Muñoz J. , Moretón R. 
Published: March 2011

ABSTRACTThis paper reports on the IES‐UPM experience from 2006 to 2010 in the field of the characterization of PV arrays of commercial large PV plants installed in Spain within the framework of the profitable economic scenarios associated to feed‐in tariff laws. This experience has extended to 200 MW and has provided valuable lessons to minimize uncertainty, which plays a key role in quality assurance procedures. The paper deals not only with classic I–V measurements but also with watt‐metering‐based procedures. Particular attention is paid to the selection of irradiance and cell temperature sensors. Copyright © 2011 John Wiley & Sons, Ltd.