bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simultaneous measurement of resistance and viscoelastic responses of carbon black‐filled high‐density polyethylene subjected to dynamic torsion
Authors: Zhou Jianfeng , Song Yihu , Shangguan Yonggang , Zheng Qiang 
Published: August 2008

AbstractThe conduction and viscoelastic responses to temperature are measured simultaneously for carbon black (CB) filled high‐density polyethylene (HDPE) subjected to dynamic torsion. PTC/NTC transition was correlated with the loss tangent peak and the quasi modulus plateau, which was ascribed to the filler network. The bond‐bending model of elastic percolation networks was used to reveal the structural mechanisms for the cyclic resistance changes at different temperatures. The resistance changes at lower temperatures depended on the deformation of the polymer matrix, while the changes in melting state were mainly attributed to the rearrangement of the CB network. A simple scaling law is derived to relate resistance and dynamic storage modulus in the melting region. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Porous versus novel compact Ziegler–Natta catalyst particles and their fragmentation during the early stages of bulk propylene polymerization
Authors: Vestberg Torvald , Denifl Peter , Wilén Carl‐Eric 
Published: August 2008

AbstractThe effect of the porosity of Ziegler–Natta catalyst particles on early fragmentation, nascent polymer morphology, and activity were studied. The bulk polymerization of propylene was carried out with three different heterogeneous Ziegler–Natta catalysts under industrial conditions at low temperatures, that is, with a novel self‐supported catalyst (A), a SiO2‐supported catalyst (B), and a MgCl2‐supported catalyst (C), with triethyl aluminum as a cocatalyst and dicyclopentyl dimethoxy silane as an external donor. The compact catalyst A exhibited no measurable porosity and a very low surface area (<5 m2/g) by Brunauer–Emmet–Teller analysis, whereas catalysts B and C showed surface areas of 63 and 250 m2/g, respectively. The surface and cross‐sectional morphologies of the resulting polymer particles at different stages of particle growth were analyzed by scanning electron microscopy and transmission electron microscopy. The compact catalyst A showed homogeneous and instantaneous fragmentation already in the very early stages of polymerization, which is typically observed for porous MgCl2‐supported Ziegler–Natta catalysts. Moreover, the compact catalyst particles gave rise to almost perfectly spherical polymer particles with a smooth surface. In contrast, the silica‐supported catalyst B gave rise to particles having a cauliflower morphology, and the second reference catalyst C produced fairly spherical polymer particles with a rough surface. All of the three catalysts exhibited similar activities of 450 g of polypropylene/g of catalyst after 30 min of polymerization, and most interestingly, the comparative kinetic data presented indicated that the reaction rates were not influenced by the porosity of the catalyst. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.
Protein separation by cellulose acetate/sulfonated poly(ether imide) blend ultrafiltration membranes
Authors: Nagendran A. , Mohan D. 
Published: August 2008

AbstractA process for purifying aqueous solutions containing macromolecular proteins such as bovine serum albumin (BSA), egg albumin (EA), pepsin, and trypsin has been investigated. Protein removal from food and biorelated industrial waste streams are gaining increased visibility due to environmental concern and saving precious materials. Ultrafiltration (UF) processes are largely being applied for protein separation from aqueous streams. In this work, an attempt has been made to separate the valuable proteins using cellulose acetate (CA)/sulfonated poly(ether imide) (SPEI) blend UF membranes prepared in the absence and presence of the additive, polyethyleneglycol (PEG600) in various compositions. The blend membranes were subjected to the determination of pore statistics and molecular weight cut‐off (MWCO). Porosity and pore size of the membranes increased with increasing concentrations of SPEI and PEG600 in the casting solution. Similarly, the MWCOs of the blend membranes ranged from 20 to greater than 69 kDa, depending on the various polymer blend compositions. Surface morphology of the blend membranes were analyzed using scanning electron microscopy. Studies were carried out to find the rejection and permeate flux of proteins. On increasing the concentration of SPEI and PEG600, the rejection of proteins is decreasing, whereas the permeate flux has an increasing trend. The effect of hydrophilicity of SPEI on fouling of protein for CA/SPEI blend membranes was also discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Electrospun nano‐scaled glass fiber reinforcement of bis‐GMA/TEGDMA dental composites
Authors: Gao Yi , Sagi Sriramaraju , Zhang Lifeng , Liao Yiliang , Cowles David M. , Sun Yuyu , Fong Hao 
Published: August 2008

AbstractThe objective of this study was to investigate the electrospun nano‐scaled glass fiber reinforcement of 2,2′‐bis[4‐(methacryloxypropoxy)‐phenyl]‐propane/triethylene glycol dimethacrylate (Bis‐GMA/TEGDMA) dental composites. The hypothesis was that incorporation of the surface‐silanized electrospun nano‐scaled glass fibers into Bis‐GMA/TEGDMA dental composites would result in substantial improvement on mechanical properties. To test the hypothesis, photo‐cured Bis‐GMA/TEGDMA dental composites filled with various mass fractions of surface‐silanized electrospun nano‐scaled glass fibers were systematically fabricated; and their mechanical properties were then evaluated. The results indicated that small mass fraction substitutions (1, 2.5, 5, and 7.5%) of conventional dental filler with the surface‐silanized electrospun nano‐scaled glass fibers, significantly improved the flexural strength, elastic modulus, and work of fracture values of 70% (mass fraction) filled composites, by as much as 44%, 29%, and 66%, respectively. The mechanical properties of the composites could be further improved by optimizing the chemical compositions and the surface treatment methods of the fibers. We envision that the electrospun nano‐scaled glass fibers could be utilized to develop the next generation dental composites, which would be particularly useful for large posterior restorations. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Morphology and mechanical properties of catalytic coke/polypropylene composites
Authors: Muangmaithong Kingkan , Praserthdam Piyasan , Thongyai Supakanok , Wacharawichanant Sirirat 
Published: August 2008

AbstractPolypropylene (PP) composites with filler of catalytic coke (CC) or fresh catalyst (FC) of Ni/SiO2.MgO were prepared by melt mixing technique in a twin screw extruder. The catalytic coke, that has the fibril of carbon, is the waste from petrochemical industry and can be obtain cheaply in high volume. The composites were examined by assessing their mechanical properties, thermal properties, and the morphology of fracture surface of the PP matrix. The improvement of some mechanical properties of the CC filler such as Young's modulus and slightly improvement of tensile strength were observed whereas the elongation at break and toughness decreased with the increase in CC or FC. Both degradation temperature of CC or FC composites decreased with increased filler content but lesser in the case of CC. The structures of fracture surfaces were supported by the results from mechanical properties measurement. The CC composite in PP matrix (CCPP) exhibits the fibrils and the plastic deformation of the matrix, while the FC composite in PP matrix (FCPP) presents similar fracture roughness as the nascent PP. The catalytic coke can be utilized as the filler to improve the Young's modulus while the fresh catalyst cannot be utilized as filler because of the adverse effects. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and characterization of polyparaphenylene from cis‐dihydrocatechol
Authors: Li Song , Li Zibiao , Fang Xiaobin , Chen Guo‐Qiang , Huang Yuanming , Xu Kaitian 
Published: August 2008

AbstractConducting polymer polyparaphenylene (PPP) was synthesized from cis‐dihydrocatechol (DHCD) obtained from bacterial transformation of benzene. Results showed that the DHCD to DHCD‐DA (diacetate) synthesis process produced some byproducts as impurities including trace amounts of phenol, quinone, and phenyl acetate derived from phenol. These impurities played a negative role in the polymerization process of DHCD‐DA to P(DHCD‐DA). In this study, a distillation fractionation method was employed to obtain monomer DHCD‐DA with high purity and high yield. Four different polymerization methods using the purified DHCD‐DA, including bulk polymerization initiated by different catalyst systems, solution polymerization as well as emulsion polymerization, were compared. A very high P(DHCD‐DA) yield of 92% with a molecular weight of 84,500 was obtained under an optimized condition using the bulk polymerization process initiated by (di)benzoyl peroxide (BPO) and ferrous sulfate. A standard curve was established to evaluate the aromatization degree of P(DHCD‐DA) to PPP under different temperatures based on the intensity of FTIR absorption and functional groups on the PPP. The glass transition temperature and the crystallinity of PPP increased with the degree of aromatization of the prepolymer P(DHCD‐DA). Thermal analysis indicated that the PPP possessed high thermal stability both in nitrogen and in air atmospheres. All these results would help the synthesis of PPP. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Modeling the stress‐relaxation behavior of wool fibers
Authors: Liu H. L. , Yu W. D. , Jin H. B. 
Published: August 2008

AbstractThe stress‐relaxation behavior of wool fibers after a pretreatment with a chemical solution is particularly important for evaluating the efficiency of the pretreatment. In this study, three viscoelastic models, including the Maxwell, two Maxwell unit, and modified two Maxwell unit models, were established first. To verify the feasibility of the models, stress‐relaxation experiments for wool fibers were performed. The wool fibers were pretreated with a sodium bisulfite solution (1 and 3%) at various temperatures (293, 298, 303, 308, 313, and 318 K). Then, the experimental values were fitted to the three models to obtain the rate constants of relaxation. The activation energy of the wool fibers was calculated with the Arrhenius equation. The results showed that the modified two Maxwell unit model provided the best fit for the experimental data of the wool fibers. The stress‐relaxation process of the wool fibers could be divided into two stages, a rapid stage followed by a slow stage. The rapid relaxation of stress was attributed to the weak bonds in the wool fibers, and the following slow relaxation stage was attributed to strong bonds. The Arrhenius equation could describe the stress‐relaxation process of the wool fibers very well. Furthermore, the activation energy decreased in the presence of sodium bisulfite. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Rheological and thermal properties of poly(ethylene oxide)/multiwall carbon nanotube composites
Authors: Abraham T. N. , Ratna Debdatta , Siengchin S. , Karger‐Kocsis J. 
Published: August 2008

AbstractPoly(ethylene oxide) (PEO) based nanocomposites were prepared by the dispersion of multiwall carbon nanotubes (MWCNTs) in aqueous solution. MWCNTs were added up to 4 wt % of the PEO matrix. The dynamic viscoelastic behavior of the PEO/MWCNT nanocomposites was assessed with a strain‐controlled parallel‐plate rheometer. Prominent increases in the shear viscosity and storage modulus of the nanocomposites were found with increasing MWCNT content. Dynamic and isothermal differential scanning calorimetry studies indicated a significant decrease in the crystallization temperature as a result of the incorporation of MWCNTs; these composites can find applications as crystallizable switching components for shape‐memory polymer systems with adjustable switching temperatures. The solid‐state, direct‐current conductivity was also enhanced by the incorporation of MWCNTs. The dispersion level of the MWCNTs was investigated with scanning electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and characterization of new monomeric and polymeric phthalocyanines
Authors: Bilgin A. , Yağcı Ç. , Mendi A. , Yıldız U. 
Published: August 2008

AbstractMonomeric (M = 2Li or 2H) and polymeric (M = 2H, Zn, Cu, Co, or Ni), where M is metal or hydrogen, phthalocyanines were prepared by the tetramerization reaction of bisphthalonitrile monomer with appropriate materials. The electrical conductivities of the polymeric phthalocyanines, which were measured as gold sandwiches, were found to be 10−10–10−7 S/cm in vacuo and in air. The binding property of a Co‐containing polymeric phthalocyanine (10) toward alkali, alkaline‐earth, and some heavy cations was studied in tetrahydrofuran. The extraction affinity of 10 for K+ was found to be the highest in the heterogeneous phase extraction experiments. The disaggregation property of a Ni‐containing polymeric phthalocyanine (11) was investigated with K+, Na+, and NH4+ cations. The intrinsic viscosities of all polymers were also measured by means of viscometry. All the novel compounds were characterized with elemental analysis, ultraviolet–visible, Fourier transform infrared, NMR, and mass spectrometry spectral data, and differential thermal analysis/thermogravimetry. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Microspheres of new alternating copolyesters derived from glycolic acid units for controlled drug release
Authors: Martínez‐Palau Meritxell , Franco Lourdes , Puiggalí Jordi 
Published: August 2008

AbstractTwo new copolyesters consisting of an alternating disposition of glycolic acid units and 4‐hydroxybutyric or 6‐hydroxyhexanoic units were assayed in the form of microspheres as drug delivery systems. Despite their similar chemical constitutions, great differences in properties such as the melting point and glass‐transition temperature were found between the two polymers. Microspheres could be successfully prepared by the oil/water emulsification/solvent evaporation method and revealed different morphological features depending on the polymer matrix. The encapsulation and release of triclosan in a cell medium and in a Sörensen solution were evaluated. The release profiles, which were clearly different in both polymers when the hydrophobic cell medium was employed, indicated that the release reached an asymptotic value that was always lower than the maximum release expected for the drug loading. No significant degradation occurred during drug release. The charged microspheres of both polymers were highly crystalline, and the incorporation of drug particles into the polymer crystalline domains was feasible. No trace of single triclosan crystals was found in differential scanning calorimetry or X‐ray synchrotron experiments. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Synthesis and characterization of novel poly(arylenevinylene) derivative
Authors: Se‐Yong Song , Kang‐Su Kim , Young‐Bin Lee , Jin‐Sung Kwak , Kim Eun‐Kyung , Yong‐Kuk Cho , Kwon Soon‐Ki , Zhao Qinghua , Jung Won‐Ik , Kim Jang‐Joo , Kim Yun‐Hi 
Published: August 2008

AbstractThe new poly(arylenevinylene) derivative composed naphthalene phenylene vinylene backbone was developed. The theoretical calculation showed that the model compound of the obtained polymer was highly distorted between the stryl and naphthalene units as well as between the backbone and fluorene side units. The polymer was synthesized by the palladium catalyzed Suzuki coupling reaction with 2,6‐(1′,2′‐ethylborate)‐1,5‐dihexyloxynaphtalene and 1,2‐bis(4′‐bromophenyl)‐1‐(9″,9″‐dihexyl‐3‐fluorenyl)ethene. The structure of the polymer was confirmed by 1H NMR, IR, and elemental analysis. The weight–average molecular weight of the polymer is 29,800 with the polydispersity index of 1.87. The new polymer showed good thermal stability with high Tg of 195°C. The bright blue fluorescence (λmax = 475 nm) was observed both in solution and film of new polymer with naphthalene phenylene vinylene backbone. Double layer LED devices with the configuration of ITO/PEDOT/polymer/LiF/Ca/Al showed a turn‐on voltage at around 4.5 V, the maximum luminance of 150 cd/m2, and the maximum efficiency of 0.1 cd/A. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Preparation of microcapsules containing TMBA (1,3,5‐trimethylbarbituric acid) by the drying‐in‐liquid method and its application
Authors: Fuchigami Kiyomi , Taguchi Yoshinari , Tanaka Masato 
Published: August 2008

Abstract1,3,5‐trimethylbarbituric acid (TMBA), an amphiphilic material used widely for redox catalysts, such as organic peroxide, aromatic tertiary amine, and anhydride, was microencapsulated by the drying‐in‐liquid method with polyethylene methacrylate (PEMA) as a wall material. To prevent osmotically induced leakage of the core material into the continuous water phase during the microencapsulation process, TMBA was beforehand dissolved into the continuous water phase. In the experiment, the amount of TMBA dissolved and holdup of the dispersed oil phase were changed. The microencapsulation efficiency increased with the increase in the amount of TMBA dissolved but remained 36% at the highest even with the saturated level of TMBA. Also, the microencapsulation efficiency decreased with increase in holdup. The microcapsules containing TMBA were used for preparing a biological hard tissue‐adhesive material and estimated for the microencapsulation effects. The adhesives containing the microencapsules were found to have excellent bonding properties and high storage stability. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Modeling of multifilament PET fiber melt‐spinning
Authors: Jeon Young‐Pyo , Cox Christopher L. 
Published: August 2008

AbstractA fundamental issue in the polymer fiber melt‐spinning process is the control of final properties. Most available melt‐spinning models simulate only a single fiber, providing an incomplete representation of the actual industrial multifilament process. Variations across the fiber bundle in cooling air velocity and temperature result in nonuniformity in fiber properties. Simulation can provide insight into this cause‐and‐effect relationship and lead to better process design to control differences between fibers. The few multifilament models in existence typically use a Newtonian constitutive model for the polymer, failing to capture nonlinear effects which often play a significant role in the process. Experimental validation of multifilament simulation is lacking. We present a nonisothermal multifilament spinning model, applicable for a variety of polymer and process conditions. The model combines the flow‐enhanced crystallization (FEC) fiber spinning model of McHugh et al. with a generalization of Dutta's multifilament model. The model predicts fiber properties such as stress, degree of crystallinity, fiber radius and temperature as a function of distance from the spinneret, along with quench air cross velocity and temperature throughout the fiber bundle region. The McHugh FEC model for single fiber spinning, based on a modified Giesekus constitutive model and Avrami‐type crystallization kinetics, has been experimentally validated. In this work we show that results of the multifilament quench air model compare favorably to experimental measurements. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Using information behaviors to evaluate the functionality and usability of electronic resources: From Ellis's model to evaluation
Authors: Makri Stephann , Blandford Ann , Cox Anna L. 
Published: August 2008

AbstractInformation behavior (IB) research involves examining how people look for and use information, often with the sole purpose of gaining insights into the behavior displayed. However, it is also possible to examine IB with the purpose of using the insights gained to design new tools or improve the design of existing tools to support information seeking and use. This approach is advocated by David Ellis who, over two decades ago, presented a model of information seeking behaviors and made suggestions for how electronic tools might be designed to support these behaviors. Ellis also recognized that IBs might be used as the basis for evaluating as well as designing electronic resources. In this article, we present the IB evaluation methods. These two novel methods, based on an extension of Ellis's model, use the empirically observed IBs of lawyers as a framework for structuring user‐centered evaluations of the functionality and usability of electronic resources. In this article, we present the IB methods and illustrate their use through the discussion of two examples. We also discuss benefits and limitations, grounded in specific features of the methods.
Mangroven: Vergessene Wälder? Maßnahmen zum Schutz tropischer Küsten
Authors: Saint‐Paul Ulrich , Schnack Christiane 
Published: August 2008

AbstractEtwa ein Viertel der Fläche der ursprünglichen Mangrovenwälder ist in den vergangenen Jahrzehnten weltweit zerstört worden. Mangrovenwälder schützen die Küste vor Erosion, mindern die Wirkung von tropischen Stürmen, fördern als Sedimentfallen die Verlandung, binden CO2 und sind damit für das Weltklima relevant. Betroffen sind vor allem die armen Bevölkerungsgruppen in den Tropen, die nicht nur ihre Lebensgrundlage mit dem Verschwinden der Mangrovenwälder verlieren, sondern die darüber hinaus verstärkt unter anderem tropischen Stürmen ausgesetzt sind. In Vietnam untersucht das Bremer Zentrum für Marine Tropenökologie die Ökologie wieder aufgeforsteter Mangrovenwälder. Wiederaufforstungen degradierter Mangrovenflächen sind für den Küstenschutz in den Tropen zwingend notwendig.
Landei oder Wasserei?
Authors: Wendler Silke 
Published: August 2008

AbstractFrösche haben im Laufe der Evolution zwei Strategien des Ablaichens entwickelt: Entweder der Laich wird im Wasser abgesetzt oder an Land; dort bevorzugt auf Blättern, die über einem Gewässer hängen. In beiden Lebensräumen droht dem Nachwuchs Gefahr – Austrocknung an Land, Räuber und Sauerstoffunterversorgung im Wasser. Deshalb sind die Eier speziell an den jeweiligen Lebensraum angepasst und schließen eine Überlebensmöglichkeit im anderen Element normalerweise aus. Die Weibchen des Bromelienlaubfrosches (Dendropsophus ebraccatus) sind jedoch in der Lage, je nach Umweltbedingungen im Wasser oder an Land abzulaichen.
Web 2.0 – auf dem Weg zur offenen Wissenschaft
Authors: Waldminghaus Torsten 
Published: August 2008

AbstractVor einigen Monaten wurde zum ersten Mal ein Fußballverein von einer Online‐Gemeinschaft gekauft, moderner Wahlkampf spielt sich zu einem großen Teil auf Youtube ab und das Internetsystem StudiVZ hat zweieinhalb Jahre nach seiner Gründung bereits acht Millionen Mitglieder. Nach der Internetrevolution in den 1990er Jahren zeichnet sich aktuell eine neue Entwicklung ab: das Web 2.0, eine neue Form der Kommunikation und Kooperation, die zunehmend auch von Wissenschaftlern genutzt wird.
Werkzeuge der Molekularbiologie: Restriktionsenzyme
Authors: Schrödel Andrea 
Published: August 2008

AbstractAn einen Laboralltag ohne Restriktionsenzyme ist heute nicht mehr zu denken. Der Griff in die Gefriertruhe zur Suche nach dem passenden Enzym ist so selbstverständlich geworden, wie der Restriktionsverdau selbst. Kaum vorstellbar, dass die so genannten Restriktionsenzyme erst vor 30 Jahren entdeckt wurden. 1978 bekamen Werner Arber, Daniel Nathans und Hamilton Othanel Smith dafür den Nobelpreis verliehen.