bluuebunny/crossref_metadata_2025_split huggingface dataset:
Batch Emulsion Polymerization of Styrene Stabilized by a Hydrophilic Macro‐RAFT Agent
Authors: Manguian Maggy , Save Maud , Charleux Bernadette 
Published: March 2006

AbstractSummary: A well‐defined homopolymer of 2‐(diethylamino)ethyl methacrylate has been synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization using (4‐cyanopentanoic acid)‐4‐dithiobenzoate as a chain transfer agent. The corresponding protonated homopolymer with a very reactive dithiobenzoate end group has been used as a water‐soluble macromolecular chain transfer agent in the batch emulsion polymerization of styrene without any surfactant. The reaction leads to a stable latex, as a result of the in‐situ formation of an amphiphilic block copolymer stabilizer, via transfer reaction to the dithioester functions during the nucleation step. The work does not intend to apply controlled free‐radical polymerization in an aqueous dispersed system but takes advantage of the RAFT technique to create a well‐defined polyelectrolyte, with a high chain‐end reactivity.Schematic of the formation of the stabilized latex by the in situ formation of an amphiphilic block copolymer stabilizer.magnified imageSchematic of the formation of the stabilized latex by the in situ formation of an amphiphilic block copolymer stabilizer.
Novel Hierarchic Structures in Polymer Blends
Authors: Buxton Gavin A. , Clarke Nigel 
Published: March 2006

AbstractWe use computer simulations to investigate the dissolution and phase separation process in polymer blends. In particular, we take initial cylindrical and spherical structures and allow them to dissolve in the one phase region. Before the structure can completely dissolve, however, we thrust the system into the two‐phase region. Phase separation then occurs such that hierarchic structures are formed both inside and outside the confines of the original structure. These novel hierarchic structures can be of significant technological importance.
Recent Developments for EPDM‐Based Thermoplastic Vulcanisates
Authors: van Duin Martin 
Published: March 2006

AbstractAn overview will be given on thermoplastic vulcanisates (TPVs). Like other thermoplastic elastomers, TPVs combine the elastic and mechanical properties of thermoset cross‐linked rubbers with the melt processability of thermoplastics. Emphasis will be on general‐purpose TPVs, based on resol‐cross‐linked EPDM/PP/oil blends. The following recent scientific developments will be discussed in detail: resol cross‐linking chemistry, extruder dynamic vulcanisation, TPV morphology, oil distribution, TPV elasticity model and TPV rheology. A series of scientific questions and technological problems, which are challenging future TPV developments, will be put forward at the end.
Waxy Maize Starch Nanocrystals as Filler in Natural Rubber
Authors: Angellier Hélène , Molina‐Boisseau Sonia , Dufresne Alain 
Published: March 2006

AbstractStarch nanocrystals obtained from acid hydrolysis of waxy maize starch granules consist in crystalline nanoplatelets about 6–8 nm thick with a length of 20–40 nm and a width of 15–30 nm. New nanocomposite materials, i.e. natural rubber (NR) filled with waxy maize starch nanocrystals were processed by casting. Dynamic mechanical analysis has shown that starch nanocrystals were a good reinforcing agent for NR at temperatures higher than the glass transition temperature of NR. Tensile tests have shown that until a weight fraction of 20 wt%, this new filler presented the advantage to reinforce natural rubber without decreasing significantly the strain at break of the material. These properties may be due to both the morphological nature of starch nanocrystals, and the formation of a percolating starch nanocrystals network within the NR matrix, resulting from hydrogen bonding forces between starch aggregates.
Role of Polyelectrolytes in Crystallogenesis of Calcium Carbonate
Authors: Jada Amane , Jradi Khalil 
Published: March 2006

AbstractThe effects anionic polyelectrolytes, having various molecular weights and repeating unit structures, on the crystallization of calcium carbonate in supersaturated solutions are studied. The induction times of the crystals grown in the presence of the polymers were optically evaluated; X‐ray diffraction and Scanning Electronic Microscopy (SEM) analyses were performed to determine, respectively, their crystalline structures and morphologies. The polyelectrolyte is found to lengthen the induction time and to reduce the size of CaCO3 nanocrystallites, to an extent depending on the interaction efficiency between the polymer anionic repeating units and the calcium ions. Further, depending on their sizes and their crystalline structures (calcite, vaterite) the nanocrystallites aggregate and yield final calcium carbonate particles having various sizes and morphologies. The data indicate that nanocrystals having vaterite structure, as determined by X‐ray analysis, give spherical CaCO3 final particles, while nanocrystals having calcite structure lead to either acicular or flower shapes of CaCO3 final particles.
Microstructure of Nanocomposites of Styrenic Polymers
Authors: Carastan Danilo Justino , Demarquette Nicole Raymonde 
Published: March 2006

AbstractNanocomposites of three different styrenic polymers (polystyrene – PS, styrene‐butadiene‐styrene triblock copolymer – SBS, and styrene‐ethylene/butylene‐styrene triblock copolymer – SEBS) containing organophilic silicates have been prepared using three different techniques. The materials were prepared by melt mixing, solution casting and a process in which a highly filled masterbatch prepared by solution is mixed in the melt with the pure polymer. These composites were characterized by X‐ray diffraction (XRD), optical microscopy (OM), transmission electron microscopy (TEM) and small amplitude oscillatory shear analysis (SAOS). The results obtained showed that the nanocomposites of PS formed an intercalated microstructure, while those of SBS and especially SEBS are more easily exfoliated. To achieve this better silicate dispersion it was shown that it is necessary to use solution casting as one of the stages in the nanocomposite preparation. The masterbatch process showed to be an effective method to disperse the clay because it combines the advantages of the solution casting technique, which is good to dissolve coarse clay aggregates, and the shear provided by melt mixing.
Synthesis, Characterization and Properties of (Vinyl Triethoxy Silane‐grafted PP)/Silica Nanocomposites
Authors: Jain S. , Goossens J.G.P. , van Duin M. 
Published: March 2006

AbstractA new route has been developed to produce PP/silica nanocomposites starting from porous PP reactor powder and making use of sol‐gel chemistry. Silica‐like, nano‐sized particles were prepared in the pores of the PP reactor powder with a controlled degree of adhesion between PP and silica. Magic‐angle spinning (MAS) 29Si NMR spectra showed that the chemical building blocks of the silica‐like clusters are of Q3 and Q4‐type. For (vinyl triethoxy silane (VTES)‐grafted PP)/silica nanocomposites, VTES was grafted via solid‐state modification (SSM) in porous PP particles. Subsequently, silica particles were prepared by sol‐gel technology in the VTES‐grafted PP. MAS 29Si NMR and FT‐IR spectroscopy showed that the grafted VTES becomes part of the in‐situ formed silica particles. The study on the mechanical properties of (VTES‐grafted PP)/silica nanocomposites showed that the silica particles improved the impact toughness of PP by a factor of 2, when there is no chemical interaction between the particles and the matrix, while for (VTES‐grafted PP)/silica nanocomposites the impact toughness decreased. This indicates that chemical bonding between the filler particles and the PP‐matrix results in brittle failure and supports the hypothesis that debonding is necessary for improving the impact toughness of PP with inorganic fillers.
Nanocomposites from Untreated Clay : A Myth ?
Authors: Fedullo Nicolas , Sclavons Michel , Bailly Christian , Lefebvre Jean‐Marc , Devaux Jacques 
Published: March 2006

AbstractPolyamide 6 and pristine montmorillonite have been melt blended in an extruder and water was injected into the melt in order to produce nanocomposites. The pristine clay was found to be exfoliated and dispersed homogenously in the nanocomposites. A mechanism explaining the formation of such nanocomposites is presented.
Influence of Morphology on PTC in Conducting Polypropylene‐Silver Composites
Authors: Boiteux Gisèle , Boullanger Christophe , Cassagnau Philippe , Fulchiron René , Seytre Gérard 
Published: March 2006

AbstractBlends of polypropylene with silver particles of controlled morphology are performed to elaborate polymer‐metal conductive composites which can present a PTC effect to be used for a specific current limited function. The samples present quite low percolation threshold around 22% in volume of Ag and a resistivity at room temperature around 100 ohm.cm. Looking at the results of the analysis of the PTC effect, it can be observed that the electrical behaviour of the samples is depending of the crystalline morphology of the systems which is governed by the specific nucleation effect of the silver filler on the polypropylene matrix.
Kinetics of Temperature‐induced and Reaction‐induced Phase Separation Studied by Modulated Temperature DSC
Authors: Pieters Ronny , Miltner Hans E. , Van Assche Guy , Van Mele Bruno 
Published: March 2006

AbstractTemperature‐induced phase separation of P(EO75‐ran‐PO25)/PES and reaction‐induced phase separation of DGEBA/MDA modified with PVME are studied using MTDSC as an in‐situ tool. Phase separation can be probed by the onset of an ‘excess’ contribution in the MTDSC heat capacity signal, in good correspondence with the cloud point temperature. This feature enables the complete construction of the state diagram of P(EO75‐ran‐PO25)/PES. The detection of phase separation‐induced partial vitrification of the high‐Tg phase (PES‐rich phase) enables to sub‐divide the LCST‐type heterogeneous region in a zone 1 (no interference of partial vitrification) and a zone 2 (interference of partial vitrification of the PES‐rich phase). This sub‐division of the heterogeneous region has drastic implications on the remixing behavior of demixed blends. In DGEBA/MDA modified with PVME, reaction‐induced phase separation accompanied by an increase in reaction rate, followed by a vitrification step of the epoxy‐amine phase can be detected in‐situ. In non‐isothermal conditions, a diffusion‐controlled reaction after vitrification and a final devitrification of the system is also observed.
Mechanical and Rheological Behavior of Unvulcanized and Dynamically Vulcanized i‐PP/EPDM Blends
Authors: Prut Eduard , Medintseva Tatiana , Dreval Vadim 
Published: March 2006

AbstractThe mechanical and rheological behavior of dynamically vulcanized PP/EPDM blends is examined and compared with those of unvulcanized blends. The effect of blend ratio and dynamic vulcanization of EPDM rubber on tensile properties and flow are investigated. The mechanical properties of the blends are strongly influenced by the blend ratio. With the increasing of EPDM content the value of yield stress in a solid state decreases with the elastomer volume fractions less than 0.45 for the unvulcanized blends. For the dynamically vulcanized blends the interval of EPDM content, at which the yield peak is seen, is rather limited below 0.25 elastomer volume fractions. It is shown that dynamic vulcanization changes the deformational behavior of PP/EPDM blends. The rheological properties of dynamically vulcanized blends depending on the ratio of the components may be similar to the properties of polymer composites containing the highly disperse structuring filler. The distinction between the rheological behavior of unvulcanized and dynamically vulcanized blends is related to differences of their structures and viscoelastic characteristics of unvulcanized and vulcanized EPDM phase.
Contracting for management: Assessing management capacity under alternative service delivery arrangements
Authors: Brown Trevor , Potoski Matt 
Published: March 2006

AbstractContracting critics suggest that when governments outsource, they reduce their capacity to produce services and manage service delivery. In this paper, we decompose the service delivery decision into service production and service management components. When governments contract for service production, they may also choose to contract for a portion of service delivery management. Studies that only compare the management activities of contracting and direct service delivery governments, without examining the management activities contracted to vendors, are likely to be incomplete and biased. Drawing on a unique survey of governmental refuse collection service directors, matched with a survey of refuse collection vendors operating under municipal contracts, we show that the vendors' management activities offset the decline in management capacity that occurs when governments contract for service delivery for this particular service. Governments can “buy” management activities when contracting for service production. © 2006 by the Association for Public Policy Analysis and Management
Utility of PET scans to predict disease relapse in pediatric patients with Hodgkin lymphoma
Authors: Meany Holly J. , Gidvani Vinod K. , Minniti Caterina P. 
Published: March 2006

AbstractBackgroundPositron emission tomography (PET) differentiates normal from abnormal cells based on metabolic activity. Numerous studies report that PET scan offers increased sensitivity, specificity and predictive values as compared to computed tomography (CT) in adult lymphoma patients.ProcedureTwenty‐three consecutive pediatric Hodgkin lymphoma (HL) patients were evaluated with PET scan either at diagnosis or during treatment, then at therapy completion and in follow‐up.ResultsTwenty two of the 23 patients had a negative PET scan at the end of therapy; however, ten later developed a positive scan for a total of 11 (47.8%) patients with a positive post treatment PET scan. Six tissue biopsies were performed in five patients; four specimens were negative for disease and two confirmed HL relapse. Six patients were monitored clinically and remained asymptomatic; four had resolution of abnormalities on repeat PET while two had persistently positive, but stable PET scan findings and continue to be in remission at 11 and 40 months following treatment. Twelve (52.2%) patients of the original cohort have had consistently negative PET scans and have not relapsed.ConclusionsPET is a sensitive (100%), but not a specific (57.1%) method for evaluating post‐treatment pediatric HL patients with a strong negative predictive value (NPV; 100%), but poor positive predictive value (PPV; 18.2%). We do not recommend treatment decisions be based solely on PET scan results. Pediatr Blood Cancer © 2006 Wiley‐Liss, Inc.
Anionic/nonionic mixed surfactants templates preparation of hollow polymer spheres via emulsion polymerization
Authors: Song Linyong , Ge Xuewu , Wang Mozhen , Zhang Zhicheng , Li Shicheng 
Published: March 2006

AbstractWe herein report a facile, convenient, and economical method to prepare hollow polymer spheres (HSs). By virtue of the phase transformation of nonionic surfactant at its cloud point, hollow spheres of polystyrene were prepared from vesicle templates formed by potassium oleate (KO) and alkyl‐phenol polyoxyethylene (n) ether (n = 10, OP) at 70–80 °C. The morphologies of the HSs were characterized by field‐emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The diameter of the HSs varies from 200 to 800 nm, and the shell thickness is uniformly c.a. 30–50 nm. The weight ratio of monomer/surfactant was as high as 7/1. The microstructure of the HSs was very stable and remained unchanged after drying or resuspension in water. The mechanism of the formation of HSs was explained on the theory of vesicles. Furthermore, the factors affecting the formation of the hollow structure were discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2533–2541, 2006
Synthesis and properties of polyacetylenes with directly attached bis(4‐alkoxyphenyl)terephthalate mesogens as pendants
Authors: Chen Lie , Chen Yiwang , Zha Daijun , Yang Yan 
Published: March 2006

AbstractLiquid‐crystalline, monosubstituted polyacetylenes containing lateral pendants of bis(4‐alkoxyphenyl)terephthalate with no flexible spacers and alkoxy tails {RO, where R is CH3 [P(1)] or C6H13 [P(6)]} were synthesized, and the effects of the backbone structure and alkoxy tails on the properties of the polymers were investigated. The polymerizations of acetylene monomers were carried out with chloronorbornadiene rhodium(I) dimer as a 1,2‐insertion catalyst in toluene. The structures and properties of the monosubstituted polyacetylenes were characterized and evaluated with nuclear magnetic resonance, infrared spectroscopy, thermogravimetry, differential scanning calorimetry, polarized optical microscopy, ultraviolet spectroscopy, and photoluminescence analyses. The molecular weights of the polymers were measured by gel permeation chromatography. The polymer with long tails (p‐hexyloxy), that is, P(6), formed a smectic mesophase upon heating above the melting temperature, but the other one with short tails (p‐methoxy), that is, P(1), could not exhibit liquid crystallinity at elevated temperatures. The steric effect of bulky, liquid‐crystalline mesogens and a direct connection with the main chain prevented the planar conformation of the polyene backbone and, therefore, led to the lower absorption and emission wavelength of the polymers. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2499–2509, 2006
Polyglutamine repeats and β‐helix structure: Molecular dynamics study
Authors: Merlino Antonello , Esposito Luciana , Vitagliano Luigi 
Published: March 2006

AbstractNeurodegenerative diseases are often associated with the formation of highly insoluble aggregates. Despite the efforts devoted to the characterization of these aggregates, their structure remains elusive. Several neurodegenerative diseases are characterized by the expansion of CAG repeats, which code for Gln. Among the structural models proposed for the aggregates observed in polyQ‐linked diseases, the nanotube β‐helix model proposed by Perutz and colleagues Proc Natl Acad Sci U S A 2002;99:5591–5595 has been influential. In the present study, the stability of this β‐helix model has been investigated by performing molecular dynamics simulations on polyQ fragments of different lengths. The results indicate that models shorter than two full β‐helix turns are unstable and collapse toward irregular structures. On the other hand, longer β‐helix models, containing more than 40 residues, achieve a dynamic regular structure. This finding is in line with the observed threshold of Gln repeats (≈ 40) correlated with the insurgence of the disease. Notably, the structure of the final state of the models longer than 40 residues strictly depends on their size. A compact stable ellipsoidal structure is formed by the model made of two full helical turns (41 residues), whereas water filled tubular structures emerge from simulation on longer polypeptides. These results have been interpreted taking into account the experimental data on polyQ aggregates. A structural interpretation of the literature data has been proposed by assuming that different β‐helical models are involved in the different stages of the aggregation process. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Carbon nanodots made on diamond surface by focused ion beam
Authors: Zaitsev Alexander M. , Dobrinets Inga A. 
Published: March 2006

AbstractCarbon nanodots were made on the polished surface of a single crystal CVD diamond by a focused 30 keV Ga+ ion beam. The electrical conductance via the nanodots was measured in two types of structures: single nanodots embedded in the gaps of broken carbon nanowires and linear chains of nanodots. Changes of the conductance with annealing temperature allow to make the conclusion that the size of the electrically conductive area of the nanodots increases from a few nanometers to 20 nm after annealing from 500 to 1000 °C. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development and validation of a technique to measure and compare the opening characteristics of tamper‐evident bottle closures
Authors: Carus D. A. , Grant C. , Wattie R. , Pridham M. S. 
Published: March 2006

AbstractLarge sections of the population encounter difficulty in opening consumer packaging of many kinds. Screw‐caps in particular can cause problems for a range of people with a variety of impairments. This paper describes the development and initial testing of a novel multi‐axial force and torque transducer, designed for the study of loading conditions when tamper‐evident bottle closures are opened manually. The transducer, which comprises seven beams that are sensitive to direct forces and torques in each of three axes, can provide comprehensive information on the loading conditions that occur when an instrumented bottle is opened. Importantly, the transducer has been designed to fit inside a typical 500 ml capacity plastic soft drinks bottle so that it does not interfere with the way in which the subject grips the bottle and cap, or applies forces and torques, in order to open the bottle. The method to obtain load data from the calibration matrix, along with initial opening force and torque test data from two user groups, elderly and young, is described. It is clear from the results of these tests that the elderly and young groups exhibit significantly different torque and force profiles to open bottles. It is anticipated that the transducer will be a valuable tool in future studies of opening strategies. Copyright © 2006 John Wiley & Sons, Ltd.
Sustainable natural resource use and economic development in small states: the tuna fisheries in Fiji and Samoa
Authors: Read Robert 
Published: March 2006

AbstractThis paper is concerned with the sustainable management of the Western Pacific tuna fishery given its critical contribution to the economies of many small island developing states in the region. The paper focuses on contrasting the operation, regulation and management of the tuna fisheries in two Pacific island states, Fiji and Samoa, in the light of progress in regional fishery co‐operation, and is based upon research undertaken in 2003. The analysis identifies critical shortcomings in implementation and enforcement of sustainable management policies in Fiji, which compare unfavourably with Samoa's attempts to ensure the long‐term sustainability of a crucial economic sector. The principal differences in the effectiveness of these policies can be ascribed to the quality of governance as well as the general coherence of national economic policies. The paper attempts to highlight some of the problems faced by small developing states in ensuring the long‐term sustainability of an important migratory marine resource. Copyright © 2006 John Wiley & Sons, Ltd and ERP Environment.
Lehrter Bahnhof Berlin: Das Nord‐Süd‐Dach
Authors: Gugeler Jochen , Havemann Kathrin , Schober Hans 
Published: March 2006

AbstractSeit Herbst 2002 überspannt eine gläserne Bahnsteighalle die oberirdische Trasse des neuen Hauptbahnhofs von Berlin. Das zweite filigrane Tonnendach – das Nord‐Süd‐Dach – wird gerade vollendet. Anstelle der Pfetten historischer Bahnsteighallen spannt eine effiziente Stabschale zwischen schlanken Seilbindern. Das gesamte Dach sowie die abschließenden Seilfassaden stellen höchste Anforderungen an Statik und Detailplanung. Zahlreiche Sonderkonstruktionen, umfangreiche Versuche und nicht zuletzt die Montage bei laufendem Bahnverkehr waren eine große Herausforderung für alle Beteiligten.