bluuebunny/crossref_metadata_2025 huggingface dataset:
Plant neurobiology and green plant intelligence: science, metaphors and nonsense
Authors: Struik Paul C , Yin Xinyou , Meinke Holger
Published: December 2007

This paper analyses the recent debates on the emerging science of plant neurobiology, which claims that the individual green plant should be considered as an intelligent organism. Plant neurobiology tries to use elements from animal physiology as elegant metaphors to trigger the imagination in solving complex plant physiological elements of signalling, internal and external plant communication and whole‐plant organisation. Plant neurobiology proposes useful concepts that stimulate discussions on plant behaviour. To be considered a new science, its added value to existing plant biology needs to be presented and critically evaluated. A general, scientific approach is to follow the so‐called ‘parsimony principle’, which calls for simplest ideas and the least number of assumptions for plausible explanation of scientific phenomena. The extent to which plant neurobiology agrees with or violates this general principle needs to be examined. Nevertheless, innovative ideas on the complex mechanisms of signalling, communication, patterning and organisation in higher plants are badly needed. We present current views on these mechanisms and the specific role of auxins in regulating them. Copyright © 2007 Society of Chemical Industry
Differential effect of organic cultivation on the levels of phenolics, peroxidase and capsidiol in sweet peppers
Authors: del Amor Francisco M , Serrano‐Martínez Ana , Fortea Isabel , Núñez‐Delicado Estrella
Published: December 2007

BACKGROUND: Coincident with the changes in agricultural practices from conventional to organic, changes in the nutrient composition of fresh fruits and vegetables have been identified. The levels of peroxidase, total phenolics content, and capsidiol activity in organic as compared with conventional sweet pepper fruit were examined in this study. In order to avoid interferences of environmental factors on the studied parameters, the sweet peppers were grown (organically and conventionally) in a greenhouse under the same soil and climate conditions.

RESULTS: Peroxidase was partially purified using the Triton X‐114 method and both organic and conventional peppers had the same isoenzymatic form. However, peroxidase activity in organic sweet peppers was higher than in conventional ones, in both maturity stages studied. The level of total phenolics compunds was also higher in organic than in conventional sweet peppers. With respect to the capsidiol activity, expressed as inhibition of fungus growth, it was not affected by the cultivation method at the green mature stage. However, at the red mature stage, organic sweet peppers showed higher capsidiol activity than those grown under the conventional system.

CONCLUSION: Sweet peppers grown under organic culture have a maturity‐related response, with high levels of phenolic compounds, and peroxidase and capsidiol activity that contribute to disease resistance in organic farming. Copyright © 2007 Society of Chemical Industry
Simultaneous determination of iridoids, phenolic acids, flavonoids, and saponins in Flos Lonicerae and Flos Lonicerae Japonicae by HPLC‐DAD‐ELSD coupled with principal component analysis
Authors: Chen Chun‐Yun , Qi Lian‐Wen , Li Hui‐Jun , Li Ping , Yi Ling , Ma Hong‐Liang , Tang Dan
Published: December 2007

A method, HPLC coupled with diode‐array and evaporative light scattering detectors (HPLC‐DAD‐ELSD), was newly developed to evaluate the quality of Flos Lonicerae (FL) and Flos Lonicerae Japonicae (FLJ), through a simultaneous determination of multiple types of bioactive components. By employing DAD, the detection wavelengths were set at 240 nm for the determination of iridoids, 330 nm for phenolic acids, and 360 nm for flavonoids, respectively. While ELSD, connected in series after DAD, was applied to the determination of saponins. This assay was fully validated with respect to precision, repeatability, and accuracy. Moreover, principal component analysis (PCA) was used for the similarity evaluation of different samples, and it was proven straightforward and reliable to differentiate FL and FLJ samples from different origins. For PCA, two principal components have been extracted. Principal component 1 (PC1) influences the separation between different sample sets, capturing 54.598% variance, while principal component 2 (PC2) affects differentiation within sample sets, capturing 12.579% variance. In conclusion, simultaneous quantification of bioactive components by HPLC‐DAD‐ELSD coupled with PCA would be a well‐acceptable strategy to differentiate the sources and to comprehensively control the quality of the medicinal plants FL and FLJ.
Pore structural characteristics, size exclusion properties and column performance of two mesoporous amorphous silicas and their pseudomorphically transformed MCM‐41 type derivatives
Authors: Bayram‐Hahn Zöfre , Grimes Brian A. , Lind Anna M. , Skudas Romas , Unger Klaus K. , Galarneau Anne , Iapichella Julien , Fajula François
Published: December 2007

Highly ordered mesoporous silicas such as, mobile composition of matter, MCM‐41, MCM‐48, and the SBA‐types of materials have helped to a large extent to understand the formation mechanisms of the pore structure of adsorbents and to improve the methods of pore structural characterization. It still remains an open question whether the high order, the regularity of the pore system, and the narrow pore size distribution of the materials will lead to a substantial benefit when these materials are employed in liquid phase separation processes. MCM‐41 type 10 μm beads are synthesized following the route of pseudomorphic transformation of highly porous amorphous silicas. Highly porous silicas and the pseudomorphically transformed derivatives are characterized by nitrogen sorption at 77 K and by inverse size‐exclusion chromatography (ISEC) employing polystyrene standards. Applying the network model developed by Grimes, we calculated the pore connectivity nT of the materials. The value of nT varies between the percolation threshold of the lattice and values of nT > 10, the latter being the limiting value above which the material can be considered to be almost infinitely connected such that the ISEC behavior of the material calculated with the pore network model is the same when calculated with a parallel pore model which assumes an infinite connectivity. One should expect that the pore connectivity is reflected in the column performance, when these native and unmodified materials are packed into columns and tested with low molecular weight analytes in the Normal Phase LC mode. As found in a previous study on monolithic silicas and highly porous silicas, the slope of the plate height (HETP) – linear velocity (u) curve decreased significantly with enhanced pore connectivity of the materials. First results on the pseudomorphically transformed MCM‐41 type silicas and their highly porous amorphous precursors showed that (i) the transformation did not change the pore connectivity (within the limits detectable by ISEC) from the starting material to the final product and (ii) the slope of the HETP versus u curve for dibutylphtalate did not change significantly after the pseudomorphic transformation.
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

Resveratrol 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

A 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

A 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

Iodine 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

Poly(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.

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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

A 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°.

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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

The 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.

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Noble Metal Decoration and Alignment of Carbon Nanotubes in Carboxymethyl Cellulose
Authors: Nadagouda Mallikarjuna N. , Varma Rajender S.
Published: December 2007

A 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.

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A Precursor Route to Supramolecular Oligo(p‐phenylene terephthalamide) Block Copolymers
Authors: Schleuss Tobias W. , Schollmeyer Dieter , Kilbinger Andreas F. M.
Published: December 2007

New 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.

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On‐Chip Alginate Microencapsulation of Functional Cells
Authors: Workman Victoria L. , Dunnett Stephen B. , Kille Peter , Palmer Daniel D.
Published: December 2007

We 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.

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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

A 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.

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Formation of Glycopolyamide Nanofibers
Authors: Gress Anja , Smarsly Bernd , Schlaad Helmut
Published: December 2007

A 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.

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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

Summary: 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

Summary: 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

Summary: 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

Summary: 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

Summary: 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

Summary: 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

Summary: 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

Summary: 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

Summary: 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

Summary: 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.
Homogeneous Phase Polymerization of Vinylidene Fluoride in Supercritical CO2: Surfactant Free Synthesis and Kinetics
Authors: Beuermann Sabine , Imran‐ul‐haq M.
Published: December 2007

Summary: Vinylidene fluoride (VDF) polymerizations were carried out in homogeneous phase with supercritical carbon dioxide (scCO2) at 120 °C and 1500 bar. To control molecular weight perfluorohexyl iodide was used. Molecular weight analysis by size‐exclusion chromatography indicates that polymers of low polydispersities ranging from 1.5 to 1.2 at the highest iodide concentration of 0.25 mol · L−1 were obtained. In addition, polymer molecular weight increases linearly with reaction time, indicating that living conditions were established. The “livingness” is based on the labile C‐I bond. The weakness of the C‐I bond is associated with a fast decomposition of the original hexyl iodide, thus, contributing to initiation and to a significant increase in the initiation rate in the initial phase of the polymerization.
Phase‐Equilibrium Measurements of the Polystyrene/Styrene/Carbon Dioxide Ternary System at Elevated Pressures Using ATR‐FTIR Spectroscopy
Authors: Görnert Michael , Sadowski Gabriele
Published: December 2007

Summary: In this paper a novel ATR‐IR spectroscopic setup for phase‐equilibrium studies of polymer systems in supercritical carbon dioxide is presented. A calibration procedure for the spectroscopic investigations has been developed and verified. The results of isothermal phase‐equilibrium measurements of the polystyrene/styrene/carbon dioxide ternary system are presented and compared to results of well‐established cloud‐point measurements. The phase behaviour was determined at 338.15 K, at two pressures (10 MPa and 15 MPa), and for two polystyrene samples having different molecular weights (6 kg/mol, 105 kg/mol) and narrow molecular‐weight distributions.
Modeling the Chain‐Length Differentiated Polymer Microstructure of α‐Olefins
Authors: Busch Markus , Becker Katrin
Published: December 2007

Summary: Due to a complex polymerization scheme, incorporating besides propagation, termination and transfer to monomer and chain transfer agents in addition intra‐ and inter‐molecular transfer to polymer as well as β‐scission, α‐olefin (co)polymers feature a quite complex polymeric microstructure. It is demanding to design a kinetic model that describes these in a predictive manner in order to have a tool for computer‐aided product design. The molecular weight distribution and branching indices together with the composition are the subjects of interest in this case. The latter quantities are often provided as being averaged over the molecular weight distribution. Modern coupled analytical techniques of size exclusion chromatography provide even more insight. The combination of size exclusion chromatography with fractionation techniques provide under adequate processing of the data branching indices and co‐polymer composition differentiated with respect to chain‐lengths. This contribution will inspect how good a model for predicting the chain‐length differentiated co‐polymer composition in high‐pressure high‐temperature ethene – vinyl acetate‐co‐polymerizations will coincide with analytical results of technical products.
A Study of L‐Lactide Ring‐Opening Polymerization Kinetics
Authors: Puaux Jean‐Pierre , Banu Ionut , Nagy Iosif , Bozga Grigore
Published: December 2007

Summary: The paper presents an experimental study of L‐lactide polymerization in molten state using as initiator the Stannous Octoate. The experiments were performed in a Haake mixer. The operating temperatures were between 170 and 195°C, the reaction time up to 60 min and monomer to initiator initial molecular ratio between 102 and 5 · 103. The conversion was determined by using 1H NMR and the molecular weights distributions by SEC. A preliminary mathematical modeling study was also performed, based on experimental data and a previously published reaction scheme.
Ab Initio Calculation of the Propagation Kinetics in Free Radical Polymerization: Chain Length and Penultimate Effects
Authors: Moscatelli Davide , Dossi Marco , Cavallotti Carlo , Storti Giuseppe
Published: December 2007

Summary: In this work, Quantum Chemistry is applied to investigate the propagation kinetics in free radical polymerization. Energies, structures and transition state geometries are determined using density functional theory, which combines good accuracy with reasonable computational demand. In particular, B3LYP functional is used to evaluate the exchange and correlation energy with the 6‐311+G(d,p) basis sets. The capabilities of the approach with respect to the prediction of the kinetic constants of elementary processes relevant to polymeric systems (propagation reactions) is first tested using literature experimental data as reference values.1 Namely, two different monomers of industrial relevance have been selected, acrylonitrile and styrene. For such systems, the effect of chain‐length on the propagation rate coefficient is examined. Finally, for the selected monomer pair, the relative reactivity (so‐called reactivity ratios) is also analyzed, in particular considering the penultimate effect.
Temperature and pH Dependency of Copolymerization Parameters of Acrylic Acid and 2‐Hydroxypropyl Acrylate
Authors: Blaszk Christoph , Grünitz Jan , Möller Maike , Pauer Werner , Moritz Hans‐Ulrich , Schwede Christian
Published: December 2007

Summary: Since copolymerization parameters of acrylic acid (AA) and 2‐hydroxypropyl acrylate (HPA) in aqueous solutions are scarcely investigated a new method and different experimental setups were developed to run copolymerization experiments at different temperatures and pH values. The experiments were done with UV‐ or azo‐ initiation and analyzed by residual monomer analytics with HPLC and GPC methods. Based on the data obtained the conversion and copolymerization parameters were calculated with different mathematical models.
Reaction Inhibition as a Method for Preventing Thermal Runaway in Industrial Processes
Authors: Russo Alessandra , Maschio Giuseppe , Ampelli Claudio
Published: December 2007

Summary: In this work inhibitors were used to prevent runaway reactions during methylmethacrylate suspension polymerization processes. The main problem that may more frequently occur in chemical reactors, carrying out free radical polymerization reactions, is the loss of temperature control. The addition of an inhibitor during polymerization processes can be considered as a good method to stop or at the least slow down the reaction. In this work two inhibitors were used: hydroquinone and 1,4‐benzoquinone in a series of polymerization experiments. In order to identify situations that can lead to a runaway reaction, an early warning detection system based on the divergence criterion was used. When this system signalled an alarm, small amounts of inhibitor were added to the reaction mixture. The results showed that hydroquinone and 1,4‐benzoquinone behave slightly differently and the reactor temperature can be kept within safe limits.
Advanced Calorimetric Techniques in Polymer Engineering
Authors: Grolier Jean‐Pierre E. , Dan Florin
Published: December 2007

Summary: In polymer synthesis, reaction calorimetry (RC) is an appropriate technique for on‐line process monitoring, since polymerization reactions are highly exothermic. Measurements are noninvasive, rapid, and straightforward. Nowadays RC is the technique recognized as the most powerful way to study such process in near‐to‐the‐ industrial conditions. Our approach was focused on temperature oscillation calorimetry (TOC). Two different reaction calorimeters were used, i.e. a isoperibolic calorimeter and a Calvet type high sensitivity differential calorimeter, respectively. A special attention was paid to the interpretation of the measured signals in order to obtain reliable calorimetric data. The evolution of heat transfer coefficient UA was followed by performing appropriate Joule effect calibrations, before and after the reaction. A convolution differential method of the measured heat flow by the generated one was used for determining the time constants and deconvoluting the measured heat flow.
Online‐Analysis on Acoustically Levitated Droplets
Authors: Biedasek Silke , Abboud Mohammed , Moritz Hans‐Ulrich , Stammer Achim
Published: December 2007

Summary: Aqueous solutions of acrylic acid were levitated in a 40 kHz acoustic levitator. The monomer amount in the levitated droplets was monitored by Raman spectroscopy relating to an internal standard. Thus evaporation of the monomer as well as polymerization reactions initiated by a redox system were investigated by Raman spectroscopy and resultant data were compared to HPLC data. Decreases in monomer amount due to evaporation can be clearly distinguished from polymerization reactions. Additionally, temperature measurement within the droplet throughout a polymerization reaction shows the typical temperature course originating from the heat of polymerization.
What Kind of Image is Drawn by a MALDI‐Experiment of Grafted Nanoparticles? ‐ How to Distinguish between Chemically and Physically Adsorbed Parts
Authors: Dempwolf Wibke , Nothdurft Lars , Schmidt‐Naake Gudrun
Published: December 2007

Summary: The modern MALDI‐TOF mass spectrometry is a powerful technique for the fast and accurate determination of a number of polymer characteristics like end group analysis. It can also be used to analyze the grafted shell around silane modified nanoparticles. This shell contains physically and chemically adsorbed parts. It is a question of great interest what kind of adsorbent can be visualized by using MALDI‐TOF mass spectrometry, while it is not possible to ionize the whole AEROSIL® particle. Therefore we chose the system MPTMS/AEROSIL®200 to address this issue. We grafted AEROSIL®200 with methacryloxy(propyl)‐trimethoxysilane (MPTMS) under acid conditions. The grafted nanoparticles were treated via Soxhlet extraction. The resulting fractions (the washed nanoparticles and the Soxhlet extract) were systematically analyzed by using MALDI‐TOF MS as well as the grafted nanoparticles themselves. As a crosscheck MPTMS was homopolymerized and analyzed. Our results show that for the system under investigation there is strong evidence that only the physically adsorbed part can be analyzed via MALDI‐TOF MS.
Cued task‐specific training is better than exercise in improving sit‐to‐stand in patients with Parkinson's disease: A randomized controlled trial
Authors: Mak Margaret K.Y. , Hui‐Chan Christina W.Y.
Published: December 2007

We examined whether 4 weeks of audio‐visual (AV) cued task‐specific training could enhance sit‐to‐stand (STS) and whether the treatment effects could outlast the treatment period by 2 weeks. Fifty‐two subjects with PD completed the study. They were randomly allocated to receive 4 weeks of AV cued task‐specific training, conventional exercise (Ex), or no treatment (control). Each subject was assessed before, at the end of 2 and 4 weeks of treatment, and 2 weeks after treatment ended. After 2 weeks of training, the AV group significantly increased the peak horizontal velocity (by 13%, P<0.01) when compared with the Ex group. After 4 weeks of training, AV group increased both peak horizontal and vertical velocities, respectively by 18% and 51%, and reduced the time taken to complete STS by 25%. These improvements were greater than those of the Ex group, who showed 8% (nonsignificant between‐group) and 20% (P<0.05 between‐group) increases respectively for peak horizontal and vertical velocities, and 10% decrease in movement time (P<0.05). Worth‐noting is the improvements in AV group could be carried over to 2 weeks after treatment ended. These findings provided concrete evidence for the use of AV cued task‐specific training to reeducate STS in patients with PD. © 2007 Movement Disorder Society
Novel biomimetic composite based on collagen and poly(γ‐benzyl L‐glutamate)‐co‐poly(glutamic acid)
Authors: Zhou Xiumiao , Wang Yingjun , Ren Li , Wang Lingyun
Published: December 2007

Novel biomimetic composite was prepared by the reaction of collagen and poly(γ‐benzyl L‐glutamate)‐co‐poly(glutamic acid) (PBLG‐co‐PGA), which were crosslinked by non‐toxic crosslinking reagents 1‐ethyl‐(dimethylaminopropyl) carbodiimide (EDC) and N‐hydroxysuccinimide (NHS). The composite was characterized by FTIR and DSC. FTIR results confirmed that the collagen in the composite was successfully crosslinked with PBLG‐co‐PGA. DSC results showed that the composites possessed higher shrinkage temperature and higher thermal stability than the collagen. The water absorption test showed that the water absorbency of the composites increased with the increase in PBLG‐co‐PGA content in the composite. The studies of collagenase degradation and the tensile strength showed that the biostability and the tensile strength of the composites were significantly improved in comparison with that of the collagen. According to the investigations of cell adherent ratio and cell proliferation in vitro, the composite possessed good biocompatibility. Copyright © 2007 John Wiley & Sons, Ltd.
Theoretical prediction of linear free energy relationships using proton nucleomers
Authors: Macchia Giovanni La , Gagliardi Laura , Carlson Geoffrey S. , Jay Ashley N. , Davis Erik , Cramer Christopher J.
Published: December 2007

Values of σ and σ+, for use in linear free energy relationships, are determined for para hydrogen atoms having nuclear charges other than 1 (nucleomers). Hammett ρ values for a variety of free energies of activation, reaction, and other extrathermodynamic properties (e.g., vibrational frequencies) are computed therefrom and compared to those computed using typical para functional groups. The nucleomer correlations show excellent qualitative agreement with standard correlations but the quantitative agreement is less good, typically underestimating the standard ρ‐value by 10–60%. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis and Characterization of First Generation Dendritic Azidoesters
Authors: Pant Chandra Shekhar , Wagh Rashmi M. , Nair Jaya K. , Gore Girish M. , Thekkekara Mukundan , Venugopalan Sethuramasharma
Published: December 2007

A new class of first generation azido‐terminated dendritic esters have been synthesized by four step processes. The final products and the intermediates are characterized by IR, 1H NMR, and elemental analysis. Thermal studies revealed that these dendritic esters were thermally stable up to ∼190 °C and the glass transition temperature was found to be −54 and −32 °C, respectively.
Studies of Free Field and Confined Explosions of Aluminium Enriched RDX Compositions
Authors: Trzciński Waldemar A. , Cudziło Stanisław , Paszula Józef
Published: December 2007

Research on the effect of aluminium contents and its particle size on free field and confined explosions characteristics of RDX‐based compositions containing 15–60% aluminium was carried out. Parameters of blast waves produced by charges of the investigated explosives detonating in an open space were measured by the use of piezoelectric gauges. Simultaneously, photodiode set‐ups were used to measure light output of the detonating charges. Quasi‐static pressure measurements were conducted in steel chambers of 0.15 and 7 m3 volume filled with air. Moreover, the heat of detonation was measured with a calorimetric set in a 5.6 dm3 bomb filled with argon. The results of QSP and detonation heat measurements were compared with those obtained from thermochemical calculations.
Study of Confined Pyrotechnic Compositions for Medium/Large Calibre Gun Igniter Applications
Authors: Gransden Joseph I. , Taylor Michael J.
Published: December 2007

With the continued shift towards more insensitive munitions and the subsequent development of low vulnerability propellants, the study of novel gun igniters is playing a significant role in the design of future direct and in‐direct fire charge systems. Previously, concepts such as electrothermal plasma ignition have offered high performance ignition solutions. However, using current technology they lack practical, in‐service applicability and will be difficult to incorporate into near future combat systems at a low cost.