bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isocratic chromatography of resveratrol and piceid after previous generation of fluorescent photoproducts: Wine analysis without sample preparation
Authors: Galeano‐Díaz Teresa , Durán‐Merás Isabel , Airado‐Rodríguez Diego 
Published: December 2007

AbstractResveratrol and its 3‐glucoside (piceid), are stilbene‐like molecules produced by plants. Both of them are weakly fluorescent, but highly fluorescent compounds are obtained when their hydroethanolic solutions are UV‐irradiated, which implies a substantial improvement in the sensitivity of analytical methods. Experimental design (central composite design) together with the response surface methodology have been used to find optimum conditions for the fast, sensitive, and precise chromatographic analysis (with isocratic elution) of resveratrol and piceid in wine samples. These compounds have been UV‐transformed into their respective photoproducts, which have been separated in a C18 column (Novapack C18 150×3.9 mm, 4 μm) by isocratic elution, using a mobile phase made up of acetonitrile and 4.1 vol% aqueous acetic acid, 19:81 v/v, at a flow rate of 0.8 mL/min, and fluorimetrically detected at 364 nm (λexc = 260 nm). Detection limits (S/N = 3) are 0.29 and 0.28 μg/L for resveratrol and piceid, respectively. The method has been applied to the analysis of these compounds in wine samples without a clean‐up step. The analysis is completed in only 20 min. The standard addition method has been applied to the analysis of a commercial red wine and average recoveries near 100% were obtained for resveratrol and piceid. Three wine pools were satisfactorily analysed by external calibration.
Quality evaluation of Yin Chen Hao Tang extract based on fingerprint chromatogram and simultaneous determination of five bioactive constituents
Authors: Wang Xijun , Lv Haitao , Sun Hui , Jiang Xingang , Wu Zeming , Sun Wenjun , Wang Ping , Liu Lian , Bi Kaishun 
Published: December 2007

AbstractA completely validated method based on HPLC coupled with photodiode array detector (HPLC‐UV) was described for evaluating and controlling quality of Yin Chen Hao Tang extract (YCHTE). First, HPLC‐UV fingerprint chromatogram of YCHTE was established for preliminarily elucidating amount and chromatographic trajectory of chemical constituents in YCHTE. Second, for the first time, five mainly bioactive constituents in YCHTE were simultaneously determined based on fingerprint chromatogram for furthermore controlling the quality of YCHTE quantitatively. The developed method was applied to analyze 12 batches of YCHTE samples which consisted of herbal drugs from different places of production, showed acceptable linearity, intraday (RSD <5%), interday precision (RSD <4.80%), and accuracy (RSD <2.80%). As a result, fingerprint chromatogram determined 15 representative general fingerprint peaks, and the fingerprint chromatogram resemblances are all better than 0.9996. The contents of five analytes in different batches of YCHTE samples do not indicate significant difference. So, it is concluded that the developed HPLC‐UV method is a more fully validated and complete method for evaluating and controlling the quality of YCHTE.
The effectiveness of blood cholesterol lowering is a question of duration as well as magnitude
Authors: Stanley John C. 
Published: December 2007

AbstractA high circulating LDL‐cholesterol level is a risk factor for cardiovascular disease. LDL‐cholesterol is cleared from the circulation by the LDL receptor and hence the more receptors an individual possesses the lower the circulating LDL‐cholesterol level will be. Statins increase the synthesis of new LDL receptors and hence reduce circulating LDL‐cholesterol levels and lower the risk of developing cardiovascular disease. However, low circulating levels of LDL resulting from 5 years of statin treatment are not as effective at lowering the risk of developing cardiovascular disease as lifelong exposure to low circulating levels of LDL resulting from loss of function mutations in the gene for PSCK9 a protein which breaks down the LDL receptor. This implies that the effectiveness of statins depends not only on the magnitude of cholesterol lowering but also on its duration.
Iodine value and biodiesel: Is limitation still appropriate?
Authors: Schober Sigurd , Mittelbach Martin 
Published: December 2007

AbstractIodine value (IV) limitation of biodiesel is currently one of the most discussed topics within the different world‐wide biofuel specifications. Claims concerning engine operability on high IV feedstocks and biodiesel are interrelated. Also, the limitation of feedstock is a major problem for producers as well as for biodiesel trade. In this context, it might be time to re‐evaluate the IV parameter. Based on available data, reports, and experience in this field the enclosed considerations maybe will help to answer the (admittedly provocative) question: Is IV limitation still appropriate?
Electrochromic Response of Nanostructured Poly(3,4‐ethylenedioxythiophene) Films Grown in an Aqueous Micellar Solution
Authors: Deepa Melepurath , Bhandari Shweta , Arora Manju , Kant Rama 
Published: December 2007

AbstractPoly(3,4‐ethylenedioxythiophene) (PEDOT) films have been electropolymerized from an aqueous micellar solution encompassing the monomer (EDOT) and the moieties sodium dodecyl sulfate (SDS) and lithium triflate. The presence of these anionic dopants in the polymer matrix and a doping level of 0.26 have been confirmed by X‐ray photoemission and electron paramagnetic resonance (EPR) spectroscopy. The hydrophobic micellar core encompassing the monomer orchestrates the growth of a uniform homogeneous polymer deposit as electron microscopy and atomic force microscopy studies reveal the film to be composed of a continuous interlinked network of quasi‐spherical grains (50–150 nm in dimensions) and pores alongwith a low surface roughness. The film exhibits a large coloration efficiency of 153 cm2 · C−1 and a transmission modulation of 62% (λ = 632.8 nm), which are manifestations of the open ion‐permeable morphology. The Q(inserted/extracted) ratio ranges between 1.2 and 1.4 when cycled back and forth between the clear and blue states 2 500 times, thereby affirming the suitability of these films for practical electrochromic smart windows.magnified image
Synthesis of Polyurethane/Poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate) Particles in Supercritical Carbon Dioxide
Authors: Renault Benjamin , Cloutet Eric , Lacroix‐Desmazes Patrick , Cramail Henri 
Published: December 2007

AbstractA new range of end‐functionalized poly(1,1,2,2‐tetrahydroperfluorodecyl acrylate)s was synthesized by ATRP. Such macromonomers were used as reactive and steric stabilizers for the preparation of original core‐shell polyurethane particles in supercritical carbon dioxide. The nature of the chain end functionality, as well as the molar mass of the reactive stabilizer, were varied in order to investigate the role of such parameters on the properties of the resulting materials. Due to the low surface energy of PFDA combined with the high surface roughness induced by the specific microstructure of particles deposited on a silica plate, PUR materials exhibited super‐hydrophobic behavior with a water CA above 150°.magnified image
Reactivities of endo versus exo Isomers of Ester‐Substituted Norbornenes in their Addition Copolymerizations Catalyzed by Cyclopentadienyl Nickel Complexes
Authors: Shikada Chie , Kaita Shojiro , Maruyama Yooichiroh , Takei Masayuki , Wakatsuki Yasuo 
Published: December 2007

AbstractThe addition copolymerization of 5‐norbornene‐2‐carboxylic acid methyl ester (NBCM) with norbornene (NB) catalyzed by CpNi‐based (Cp = η5‐C5H5) systems, i.e., CpNi(PPh3)Me/B(C6F5)3 and CpNi(PPh3)Cl/AlMe3/B(C6F5)3, was studied with particular focus on the reactivities of the endo‐ versus exo‐isomers of NBCM. Unlike the well‐known higher reactivity of the exo‐isomer in PdII‐catalyzed polymerizations, the CpNi system showed a small but noticeable preference for the endo‐ isomer. The better reactivity of the endo‐isomer is more pronounced in the copolymerization of cis‐5‐norbornene‐2,3‐dicarboxylic acid dimethyl ester (NBCD) with NB, where only the endo‐isomer gave the copolymer when the NB/NBCD feed ratio was 6/4.magnified image
Noble Metal Decoration and Alignment of Carbon Nanotubes in Carboxymethyl Cellulose
Authors: Nadagouda Mallikarjuna N. , Varma Rajender S. 
Published: December 2007

AbstractA facile microwave method (MW) is described that accomplishes alignment and decoration of noble metals on carbon nanotubes (CNT) wrapped with carboxymethyl cellulose (CMC). Carbon nanotubes such as single‐ and multi‐walled, and Buckminsterfullerene (C‐60) are well dispersed using the sodium salt of CMC under sonication. Addition of respective noble metal salts then generates noble metal‐decorated CNT composites at room temperature. However, aligned nanocomposites of CNTs could only be generated by exposing the above nanocomposites to MW irradiation. The CNT composites are characterized using scanning electron microscopy, energy dispersive X‐ray analysis, X‐ray mapping, transmission electron microscopy, and UV‐visible spectroscopy. The general preparative procedure is versatile and provides a simple route to manufacturing useful metal‐coated CNT nanocomposites.magnified image
A Precursor Route to Supramolecular Oligo(p‐phenylene terephthalamide) Block Copolymers
Authors: Schleuss Tobias W. , Schollmeyer Dieter , Kilbinger Andreas F. M. 
Published: December 2007

AbstractNew soluble precursors for the step‐wise synthesis of oligo(p‐phenylene terephthalamide) block copolymers are described. Kevlar‐like aramide oligomers up to the hexamer (six phenyl groups) were prepared in a polymer‐analogous manner. Activating the carboxylic‐acid‐carrying oligomers as carbonyl chlorides while reversibly transforming the aromatic amides into imidoyl chlorides gave access to soluble precursors. The dimer and tetramer precursor were prepared and used in block copolymer synthesis. Single‐crystal XRD confirmed the structure of the dimer precursor. Above a critical rod length, the Kevlar‐like rod‐coil block copolymers show strong aggregation in non‐polar solvents such as chloroform.magnified image
On‐Chip Alginate Microencapsulation of Functional Cells
Authors: Workman Victoria L. , Dunnett Stephen B. , Kille Peter , Palmer Daniel D. 
Published: December 2007

AbstractWe report the use of a PTFE‐based microfluidic device for the encapsulation of living, therapeutically‐active cells within monodisperse alginate microspheres. We present a novel microfluidic platform and a flexible experimental method for the production of alginate microspheres. Cell lines HEK293, U‐2 OS and PC12 were separately encapsulated using this method, with minimal loss of cell viability.magnified image
Self‐Organization on Multiple Length Scales in “Hairy Rod”‐Coil Block Copolymer Supramolecular Complexes
Authors: Hammond Matthew R. , Klok Harm‐Anton , Mezzenga Raffaele 
Published: December 2007

AbstractA peptide‐synthetic hybrid block copolymer, poly(ethylene oxide)‐block‐poly(L‐glutamic acid), is shown to form supramolecular complexes with primary alkylamines of varying alkyl chain lengths (8 to 18 methylene units) in organic solvents via acid‐base proton transfer and subsequent ionic bonding. The peptidic block being in theα‐helical conformation, these materials behave as coil‐“hairy rod” block copolymers, and show hierarchically self‐organized nanostructures in the solid state. X‐ray scattering measurements show mesomorphic behavior at the length scales of both the overall block copolymer and the polypeptide‐alkylammonium complex.magnified image
Formation of Glycopolyamide Nanofibers
Authors: Gress Anja , Smarsly Bernd , Schlaad Helmut 
Published: December 2007

AbstractA hydrophilic glycopolyamide homopolymer is described, consisting of a tertiary polyamide backbone and D‐glucose side chains, which upon direct dissolution in water can self‐assemble into spherical vesicles and nanofibers. Based on TEM, SFM, and SAXS data, it is proposed that the nanofibers are hollow nanotubes with a cross‐sectional radius of about 3 nm and a wall thickness of about 1 nm. The wall should be constructed of chains forming a sheet through intermolecular hydrogen bonding between amide and glucose units, as evidenced by CD spectroscopy.magnified image
Miniemulsification: An Analysis of the Use of Rotor Stators as Emulsification Devices
Authors: El‐Jaby Ula , McKenna Timothy F. L. , F. Cunningham Michael 
Published: December 2007

AbstractSummary: Production of polymeric latexes by miniemulsion techniques is clearly attracting more and more attention for a number of reasons. However, one of the limiting factors in the acceptance of miniemulsion polymerisation as a commercialisible technique was that in early laboratory studies ultrasonication was the only method considered for the generation of polymerisable droplets. It is shown in the current paper that rotor stator mixers are an promising alternative. In addition to demonstrating the feasibility of these techniques, an investigation of the evolution of the particle size distribution during polymerisation revealed that controlled coalescence can occur for reasons that are difficult to identify.
Development and Modeling of a Continuous Dispersion Copolymerization Process in the Presence of a Stabilizing Agent Elaborated in situ
Authors: Pla Fernand , Fonteix Christian , Hoppe Sandrine , Schrauwen Cornelius , Van der Wal Hanno , Van Damme Freddy 
Published: December 2007

AbstractSummary: This work deals with the development of a process for the radical copolymerization of acrylonitrile and styrene in a dispersed medium. This process was carried out in a continuous stirred tank reactor, in the presence of a stabilizing agent produced in situ during the polymerization. The continuous phase is a polyol. Besides all elementary chemical mechanisms related to the copolymerization and to the synthesis and grafting of the stabilizing agent, this process involves several complex physical phenomena.A tendency model of the whole process was developed, using the corresponding mass balances and thermodynamics. Its unknown parameters were identified by use of an evolutionary algorithm and experimental data resulting from an adapted experimental strategy. This model was then validated and allowed to predict monomers and transfer agent conversions, amounts of solids and average molar masses, versus the operating conditions.
Modeling Nd‐Catalyzed Butadiene Rubber Production
Authors: Tracht Ursula , Kloppenburg Heike 
Published: December 2007

AbstractSummary: A simulation tool was developed for the industrial solution polymerization of 1,3‐butadiene with a Nd‐based homogeneous Ziegler‐Natta catalyst system. Insight into underlying reaction mechanisms was gained from laboratory experiments. Besides the chain growth reaction, the following steps were identified: catalyst formation, deactivation reactions, and molecular weight control reactions. A kinetic model based on this reaction scheme was developed to quantitatively describe butadiene conversion and product molecular weight distribution. By including process characteristics, the laboratory (batch) model was transferred to the industrial production process. A correlation function relates product molecular weight to the relevant product property Mooney viscosity. This polymerization model was successfully applied, e.g. to optimize product grade transitions and to maintain high product quality by predicting the influence of process changes.
Design of Blends with an Extremely Low Viscosity Ratio between the Dispersed and Continuous Phases. Dependence of the Dispersed Phase Size on the Processing Parameters
Authors: Leblanc Jonathan , Mercier Mathilde , Fonteix Christian , Pla Fernand 
Published: December 2007

AbstractSummary: This work deals with the development of the dispersed phase morphology in immiscible blends of poly(ethylene glycol)/polyamide 66 (PEG/PA) with an extremely low viscosity ratio. The blends were obtained, under different operating conditions, by melt blending in an internal mixer. The objective was to examine the influence of the main processing parameters on the particles size of the minor phase (PEG). A model was elaborated to describe the dependence of the particle size on interfacial tension, PEG concentration, shear rate and viscosity ratio between the two blend components.
Model Development in Thermal Styrene Polymerization
Authors: Matthews Bryan , Villa Carlos , Pierini Pete 
Published: December 2007

AbstractSummary: The thermal polymerization of styrene is usually modeled by relying on a reaction scheme and a set of equations that were developed more than three decades ago by Hui and Hamielec. Many detailed models of styrene polymerization are available in the open literature and they are mostly based on the work of Hui and Hamielec, which nearly makes this the standard to follow in explaining the behavior of polystyrene reactors. The model of Hui and Hamielec does a very nice job of describing monomer conversion data but discrepancies are seen between observed and predicted values of number and weight average molecular weights, Mn and Mw. Discrepancies in number average molecular weight seem to be the result of random noise. Discrepancies in weight average molecular weight grow as the polymerization temperature decreases and some of the trends observed in the residuals over the entire temperature range cannot be attributed to random noise. Hui and Hamielec attributed the observed deficiencies to a standard deviation of ±10% in their GPC measurements. A new data set with an experimental error of 2% for average molecular weights is presented. The set contains measured values of Mn, Mw and Mz, so the polymerization scheme has been extended to include third order moments. The data set also includes the effect of ethylbenzene as a chain transfer agent. We present the results of comparing model predictions to our measurements and the adjustments made in the original set of kinetic parameters published by Hui and Hamielec.
Time Programmed Feed of Semi‐Batch Reactors with Non‐Linear Radical Copolymerizations: An Experimental Study of the System Styrene + Divinylbenzene Using SEC/MALLS
Authors: Gonçalves Miguel A. D. , Dias Rolando C. S. , Costa Mário Rui P. F. N. 
Published: December 2007

AbstractSummary: The radical crosslinking copolymerization of mono and divinyl monomers was experimentally studied with a 2.5 dm3 semi‐batch reactor using styrene + divinylbenzene as a model system. The analysis of products was carried out by SEC with a MALLS detector. The influence of the feed policy of divinylbenzene on the time evolution of the copolymer molecular weights and z‐average mean square radius of gyration was assessed. A detailed kinetic model, in the absence of intramolecular reactions but taking into account the presence of the two isomers m‐ and p‐ in the commercial divinylbenzene and the different reactivities of the various radicals and double bonds was developed; most parameters have been collected from previous kinetic studies, and only two have been regressed using our measured molecular weights. These results can be used to improve the production of branched/crosslinked polymers with controlled molecular architecture.
Fluidized Bed Polyethylene Reactor Modeling in Condensed Mode Operation
Authors: Mirzaei Ahmad , Kiashemshaki Ali , Emami Mehrsa 
Published: December 2007

AbstractSummary: Modeling of fluidized bed reactor for polyethylene production in the condensed mode operation is proposed in this paper. A two‐phase model including the emulsion and bubble phases with the constant bubble size is employed to describe hydrodynamic behavior of the reactor. The kinetics of Ziegler‐Natta polymerization is also modeled with a two active site model. The phase behavior and solubility of low molecular weight components in polyethylene are estimated with the Sanchez‐Lacombe equation of state. The validation of the model is carried out with industrial data for an ethylene and 1‐butene copolymerization with the isopentane as a condensable component. The simulation results are in good agreement with industrial data. The model is also used to study quantitatively the effect of the inlet stream temperature to the reactor and isopentane concentration in the reactor on the production rate. For instance, in a typical process, when the inlet stream temperature changes 10 °C, the production rate will alter about 40%. Furthermore, the change of the isopentane concentration around 1 mole percentage leads to a variation of production rate about 14%.
Composite Polymer Nanoparticles via Transitional Phase Inversion Emulsification and Polymerisation
Authors: Jahanzad Fatemeh , Chauhan Gini , Mustafa Sherif , Saha Basu , Sajjadi Shahriar , Brooks Brian W. 
Published: December 2007

AbstractSummary: A new route was employed to produce composite polymer nanoparticles. First, a model polymer (a low molecular‐weight polyisobutene) was dissolved in a model monomer (styrene) and then the solution was emulsified in water containing a pair of nonionic surfactants via a transitional phase inversion route. After phase inversion, which produced an oil‐in‐water miniemulsion, polymerisation of the vinyl monomer gave composite polymer particles. Low temperature emulsification was not practical because the inverted oil‐in‐water emulsions reinverted to water‐in‐oil emulsions upon raising the temperature to the reaction temperature. Miniemulsions prepared at the reaction temperature with low monomer content in the oil phase showed good stabilty in the course of polymerisation and produced latexes with a particle size similar to the size of drops in the initial miniemulsions.
Semibatch Atom Transfer Radical Copolymerization of Styrene and Butyl Acrylate
Authors: Fu Yao , Cunningham Michael F. , Hutchinson Robin A. 
Published: December 2007

AbstractSummary: Batch and semibatch butyl acrylate (BA) polymerizations are carried out using a heterogeneous atom transfer radical polymerization (ATRP) catalyst system, with excellent molecular weight (MW) control maintained at temperatures below 80 °C. A kinetic model, using rate coefficients from literature and catalyst solubility data from this study, provides a good representation of the experimental results, after modifying the model to account for the decrease in rate caused by intramolecular chain transfer. It is also demonstrated experimentally that well‐defined random, gradient, and block styrene/BA copolymers can be synthesized by manipulating monomer feed profiles in the ATRP semibatch process.
Poly(propylene carbonate), old CO2 Copolymer with New Attractiveness
Authors: Luinstra Gerrit A. , Molnar Ferenc 
Published: December 2007

AbstractSummary: The catalytic synthesis of poly(propylene carbonate) (PPC) from propylene oxide and CO2 is mediated by zinc glutarate and chromium salen complexes. The determined solid state structure of the zinc glutarate was taken to model the polymerisation of ethylene oxide. It has a low activation energy for a reaction path involving two zinc atoms, where one binds the nucleophilic alkoxy chain end and one activates the epoxide. A similar pathway may operate in the alternating copolymerization PO/CO2 as is shown in the homogeneous chromium salen catalyst system. The material profile was determined of PPC with 93% carbonate linkages. A study of the transparent blend with poly(lactic acid) (PLA) shows that the polymers are not miscible, but rather compatible as they are finely dispersed and show linear behaviour in the mechanic properties. The permeability of oxygen, carbon dioxide and water of the composite PPC/PLA are also reported.