bluuebunny/crossref_metadata_2025 huggingface dataset:
Empirical formulas for distributions of air velocity/temperature along the spinline of a dual slot die
Authors: Wang Xiaomei , Ke Qinfei
Published: June 2005

Empirical formulas, which describe the air velocity and air temperature decays along the spinline of a dual slot die, are improved by introducing the influence of the ratio of die end width to air slot width. The thus‐improved empirical formulas include more die geometry parameters and are more accurate than the existing ones. The fiber diameters of nonwoven web are predicted by incorporating these new empirical formulas into a one‐dimensional theoretical model for melt‐blowing process. The agreement between the predicted results and the experimental data cited from literature is very good, which confirms the reliability and the accuracy of these new formulas. POLYM. ENG. SCI., 45:1092–1097, 2005. © 2005 Society of Plastics Engineers
Prediction of residual stresses in cross‐linked polyethylene cable insulation
Authors: Olasz L. , Gudmundson P.
Published: June 2005

Modeling of the manufacturing process of high‐voltage power cables was performed with the aim of predicting residual stresses in the cable insulation. A viscoelastic power law‐type constitutive model was used which incorporates temperature and crystallinity dependence of the parameters. In this way the mechanical problem is coupled to the heat transfer and crystallization problems. In order to illustrate the effects of relaxation, a comparison to a thermoelastic material model is made. POLYM. ENG. SCI., 45:1132–1139, 2005. © 2005 Society of Plastics Engineers
Nucleation effect of polyamide on polyoxymethylene
Authors: Hu Youliang , Ye Lin
Published: June 2005

The crystallization behavior and morphology of polyoxymethylene (POM) and POM with polyamide (PA) were studied by polarized light microscopy (PLM), isothermal and nonisothermal differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The isothermal crystallization kinetics were analyzed with the Avrami equation. Compared with the virgin POM, the addition of PA can reduce the spherulites size and improve the crystallization growth rate and crystallinity (Xc) of POM, which demonstrates that the nucleation effect of PA as the high‐molecular nucleus is favorable to the mechanical properties and dimension stability of POLYM. ENG. SCI., 45:1174–1179, 2005. © 2005 Society of Plastics Engineers
Increased flow property of polycarbonate by adding hollow glass beads
Authors: Chen Peng , Zhang Jun , He Jiasong
Published: June 2005

The steady shear viscosity and dynamic viscoelastic properties of glass beads (GB) filled polycarbonate (PC) melts were studied at varying filler diameters and concentrations. The PC/GB composites containing small amounts of GB bore lower melt viscosity and dynamic modulus than those of pure PC at studied frequencies and shear rates, showing a “ball‐bearings” effect. For highly filled systems, the viscosity and dynamic modulus were decreased further at higher frequencies and shear rates. This ball‐bearings effect was enhanced by changing the GB from larger to smaller one. The oscillatory experiments with modified shear stress showed a stress‐dependent decrease of the viscoelastic properties, and revealed an interfacial slip mechanism, combined with the polymer chains disentanglement at melt/solid interfaces. The scaling relationship between the relative viscosity and the mean interparticle gap confirmed that the interfacial slip and polymer chains disentanglement were induced by the extremely high local shear developed in the narrow gaps between the nearby rotating spheres. POLYM. ENG. SCI., 45:1119–1131, 2005. © 2005 Society of Plastics Engineers
Evaluation of mechanical properties of adjacent flow weldline
Authors: Yamada Koji , Tomari Kiyotaka , Ishiaku Umaru Semo , Hamada Hiroyuki
Published: June 2005

Weldlines occur at the interface of two adjacent flows of material behind an obstructive pin in a cavity in injection molding (meldline or hot weldline). Tensile strength of such “adjacent flow weldline” in injection molded polystyrene plates was evaluated by a mechanical step‐by‐step milling technique. The strength when the milling depth was 1/5 of the thickness from each surface was about the same and independent of the distance from the pin. In contrast, the strength without milling decreased once and then increased along the flow direction. This demonstrates that the strength of a weldline is predominantly dependent on the properties of the surface layer of the weldline. The depth of the surface layer was defined as the depth of the weld, Dw. Dw reduced monotonously along the flow direction and faded away with the V‐notch, resulting in an increase of strength along the direction. On the other hand, it was considered that the farther from the pin, the flow‐induced molecular orientation in the surface layer is greater. It caused a decrease of the strength along the flow direction. The sequence of decrease and increase in tensile strength of adjacent flow weldline is due to the complex effect of these two contradictory factors. POLYM. ENG. SCI., 45:1180–1186, 2005. © 2005 Society of Plastics Engineers
Thermal and rheological properties of maleated polypropylene modified asphalt
Authors: Yeh Pei‐Hung , Nien Yu‐Hsun , Chen Jean‐Hong , Chen Wei‐Chyum , Chen Jian‐Shiuh
Published: June 2005

Modified asphalts using polymeric additives, such as isotactic polypropylene (iPP) and maleated polypropylene (MPP), for asphalt binders were prepared and characterized for potential usages in pavement construction. The differential scanning calorimetry (DSC) studies show that most of the crystallinity of iPP remains intact in the asphalt binders, but MPP exhibits more interaction with the asphalt due to the increase of the amorphous region of MPP. The phase distributions and rheological properties of the modified asphalts were examined by scanning electron microscope (SEM) and dynamic shear rheometer (DSR), respectively. The images of SEM show that the MPP‐rich phase is larger than the iPP‐rich phase in asphalt blends, which contributes to more dispersion of the polymer into the asphalt phase in the asphalt/MPP blend. From the rheological studies, the asphalt blends containing iPP exhibit higher viscosity in terms of higher temperature to get Newtonian behavior and have a higher performance grade for rutting resistance at high temperature and frequency. POLYM. ENG. SCI., 45:1152–1158, 2005. © 2005 Society of Plastics Engineers
The effect of nanoclays on the processibility of polyolefins
Authors: Hatzikiriakos Savvas G. , Rathod Nimish , Muliawan Edward B.
Published: June 2005

The influence of a new processing additive (particles of organically modified nanoclays) on the processibility of polyolefins in extrusion is studied. The equipment used includes an Instron capillary rheometer with two types of dies, namely capillary dies and special annular dies (Nokia Maillefer wire coating crosshead) attached to the rheometer. Ziegler Natta and metallocene polyethylenes and one polypropylene were tested using these two pieces of equipment. It was found that the nanoclay additive had a significant effect on the extrudate appearance of polyethylene. It eliminates surface melt fracture and postpones the critical shear rate for the onset of gross melt fracture to significantly higher values depending on resin type, temperature, and additive concentration (typically 0.05 to 0.5 wt%). To explain the possible mechanism for the effect of the additive on the processibility of the resins, shear and extensional rheological measurements were carried out for the pure resins as well those loaded with the nanoclay additives. It seems that the presence of nanoclays suppresses the development of extensional stresses to such high levels that can cause melt fracture phenomena. Finally, it was found that the combination of nanoclays with traditional processing aids such as fluoropolymers produce an enhanced processing aid that can increase the critical shear rates for the onset of melt fracture to levels much higher than the individual constituents when they are used independently. POLYM. ENG. SCI., 45:1098–1107, 2005. © 2005 Society of Plastics Engineers
Crystallization and melting behavior of homogeneous and heterogeneous linear low‐density polyethylene resins
Authors: Feng Lijun , Kamal Musa R.
Published: June 2005

The crystallization behavior of homogeneous and heterogeneous linear low‐density polyethylenes (LLDPE) was investigated by evaluating the characteristics of melting traces obtained by differential scanning calorimetry (DSC). Based on the isothermal experimental results, the concept of the effective nucleation induction time is suggested. In the initial crystallization stage, the Avrami equation in conjunction with the effective induction time can be used to successfully describe the overall crystallization kinetics. Avrami exponents 2, 1.5, and 1 were found to apply in regimes III, II, and IM, respectively, as identified by the modified Hoffman‐Lauritzen (MHL) equation. The kinetic parameters estimated from evaluating the linear crystallization behavior during spherulitic growth experiments using polarized light microscopy (PLM) are in agreement with the overall crystallization kinetic parameters obtained from DSC experiments. POLYM. ENG. SCI., 45:1140–1151, 2005. © 2005 Society of Plastics Engineers
Defining the configuration of co‐rotating twin‐screw extruders with multiobjective evolutionary algorithms
Authors: Gaspar‐Cunha A. , Covas J.A. , Vergnes B.
Published: June 2005

Multiobjective evolutionary algorithms have already been used for the optimization of the processing conditions of a co‐rotating twin screw extruder. In the present paper, we develop this approach for the optimization of the screw geometry, in terms of the most adequate location of a pre‐selected set of screw elements, in order to maximize a prescribed performance. Experimental validation shows the pertinence of this approach, which is computationally more rapid and less expensive than the classical trial and error procedure. An application to the complex case of reactive extrusion is also presented. POLYM. ENG. SCI., 45:1159–1173, 2005. © 2005 Society of Plastics Engineers
Die Dunkle Energie: Kosmologie
Authors: Börner Gerhard
Published: June 2005

Beobachtungen der Ausdehnung des Weltalls und der Temperaturschwankungen der kosmischen Hintergrundstrahlung führen zu einer präzisen Bestimmung aller kosmischen Parameter. Das überraschende Ergebnis ist, dass die kosmische Expansion gegenwärtig beschleunigt verläuft, angetrieben von einer rätselhaften Dunklen Energie. Diese macht etwa 70% der gesamten Materie und Energiekomponenten im Kosmos aus und wirkt wie eine abstoßende Gravitation. Man vermutet, dass diese Größe mit der Vakuumenergie der Quantenfeldtheorie zusammenhängt. Theoretische Deutungsversuche sind aber bisher nicht sehr erfolgreich.
Quantenwelt im Nanozylinder: Elektronische Eigenschaften von Kohlenstoff‐Nanoröhrchen
Authors: Strunk Christoph
Published: June 2005

Kohlenstoff‐Nanoröhren sind einzelne oder mehrfach ineinander gesteckte molekulare Hohlzylinder. In ihnen bilden Kohlenstoffatome ein Graphit ähnliches Kristallgitter. Diese Fullerene zeichnen sich durch eine außerordentlich hohe Elastizität und Zugfestigkeit aus. In ihren elektronischen Eigenschaften verhalten sie sich entweder wie Halbleiter oder wie metallische Leiter. Aus halbleitenden Nanoröhren konnten bereits winzige Feldeffekttransistoren hergestellt werden, ein erster Schritt hin zu einer molekularen Elektronik. Die Grundlagenforscher interessiert vor allem das Verhalten metallischer Nanoröhren bei tiefen Temperaturen. An ihren elektronischen Systemen lassen sich zum Beispiel Quanteninterferenzphänomene oder Elektron‐Elektron‐Wechselwirkungen untersuchen.
Einsteins Spuren in den Archiven der Wissenschaft: Physikgeschichte
Authors: Marx Werner
Published: June 2005

Die Erwähnungen und Zitierungen von Einsteins Arbeiten dokumentieren lediglich den quantifizierbaren Anteil von Einsteins Beitrag zur Physik. Gleichwohl belegen sie die außergewöhnliche Resonanz und Langzeitwirkung seiner Arbeiten. Die Häufigkeit der Zitierungen entspricht nicht der allgemeinen Einschätzung ihrer Bedeutung. Insbesondere die Pionierarbeiten werden inzwischen als bekannt vorausgesetzt und nicht mehr explizit zitiert. Interessanterweise ist seine nach 1945 meist zitierte Arbeit nicht eine der Pionierarbeiten zur Quantenphysik oder Relativitätstheorie, sondern jene aus dem Jahr 1935 zum berühmten Einstein‐Podolsky‐Rosen‐Paradoxon.
Kriechschädigung dreidimensional sichtbar gemacht
Authors: Pyzalla Anke Rita , Reimers Walter
Published: June 2005

Erstmals gelang es einem Forscherteam, die innere Schädigung eines Werkstoffs bei mechanischer und thermischer Beanspruchung sichtbar zu machen. Die Ergebnisse geben Einblicke in die zeitabhängige Verformung von Bauteilen, und sie versprechen einen entscheidenden Fortschritt im Verständnis des Verhaltens von Hochtemperaturwerkstoffen.
Genauere Hyperfeinstruktur
Authors: Vogel Manuel , Winters Danyal F.A. , Thompson Richard C.
Published: June 2005

Übergänge zwischen Hyperfeinstruktur‐Niveaus liegen im Bereich der Mikrowellen und entziehen sich daher hoch genauen Messungen mit Lasern. Am Imperial College London wird derzeit in Zusammenarbeit mit der Gesellschaft für Schwerionenforschung (GSI) in Darmstadt ein Experiment aufgebaut, das solche Messungen an gespeicherten, nahezu ruhenden Ionen zulässt.
Pentaquarks – existieren sie wirklich?
Authors: Ziegler Thomas
Published: June 2005

Für viel Wirbel sorgte vor zwei Jahren die Entdeckung eines “Pentaquarks”, eines bis dahin unbekannten Teilchens, das aus vier Quarks und einem Antiquark besteht. Seitdem hat es jedoch Experimente gegeben, welche die Messung nicht bestätigen konnten. Physiker vom Jefferson‐Laboratorium in den USA haben nun kürzlich die Ergebnisse eines Experimentes mit sehr hoher Statistik vorgestellt. Auch sie fanden das Pentaquark nicht. Gibt es das Teilchen also gar nicht?
Im Doppelschatten
Authors: Schlichting H. Joachim
Published: June 2005

Hin und wieder beobachtet man zwei Schatten eines Gegenstandes oder einer Person, obwohl nur eine Lichtquelle vorhanden ist. Diese verblüffenden Doppelschatten entstehen, wenn ein Gegenstand nicht nur direkt, sondern gleichzeitig von reflektiertem Sonnenlicht getroffen wird.
Lernen am Phänomen
Authors: Junge Michel
Published: June 2005

Science Center sollen die Naturwissenschaften und insbesondere die Physik erfahrbar machen, mit Phänomenen faszinieren und den Besucher selbst experimentieren lassen. Das Technorama im schweizerischen Winterthur war eines der ersten Science Center in Europa. Von hier einige Impressionen und Ideen.
Lebensende in Princeton
Authors: Hoffmann Dieter
Published: June 2005

“Princeton ist ein wundervolles Stückchen Erde und dabei ein ungemein drolliges zeremonielles Krähwinkel winziger stelzbeiniger Halbgötter”, so beschrieb Einstein in seiner spöttisch‐distanzierenden Art den Eindruck, den das beschauliche Universitätsstädtchen südlich von New York auf den Neuankömmling machte.
Das Experiment von Einstein und de Haas
Authors: Engels Wolfgang
Published: June 2005

Als Einstein sich 1915 mitten in der Entwicklung der Allgemeinen Relativitätstheorie befand, widmete er sich einem alten physikalischen Problem: Wie lässt sich der Magnetismus auf atomarer Ebene erklären? Mit dem niederländischen Physiker Wander Johannes de Haas realisierte er ein Experiment, das nach den beiden Forschern benannt wurde.
Kleine Pastis‐Kunde
Authors: Vilgis Thomas
Published: June 2005

Mediterran angehauchte Zeitgenossen genehmigen sich gern einen Pastis, natürlich mit Wasser verdünnt und einem Eiswürfel gekühlt. Wird der Aperitiv zu wässerig, setzt eine starke Trübung ein. Die Ursache finden wir in dem Verhalten des Geschmacksstoffs Anethol.
Interfacial ion exchange between monovalent and divalent anions in cationic micelles, revised in the light of correlation analysis
Authors: Blagoeva Iva B. , Ouarti Nadia , El Seoud Omar A. , Ruasse Marie‐Françoise
Published: June 2005

The pH changes of an aqueous carbonate buffer solution (9 × 10−3 M Na2CO3, 10−3 M NaHCO3, pHo 10.79), induced by addition of cetyltrimethylammonium chloride (CTA+Cl−) in concentrations varying from 10−3 to 10−1 M, are employed to determine the concentration of dianionic base in the water pseudophase. The pH decreases markedly up to −0.6 pH units at 0.1 M CTA+. The pH profile is analysed in terms of the pseudophase ion‐exchange model from which the equations for mono‐/divalent anion exchanges are derived. The fit of the pH data to these equations is satisfactory only when a [CTA+] dependence of β (the degree of counterion binding) is considered: β = 0.5 + 2[CTA+]. The resulting exchange constant, K = (6.75 ± 0.22) × 10−2, is markedly larger than that measured previously at only one surfactant concentration without taking into account the β variation. This surfactant concentration dependence of β is discussed in terms of recent results on salt effects on the composition of micellar interfaces, which also show that β depends on the surfactant concentration in the presence or absence of any added salt. Copyright © 2005 John Wiley & Sons, Ltd.
Tautomeric equilibria, H‐bonding and π‐electron delocalization in o‐nitrosophenol. A B3LYP/6–311 + G(2df,2p) study
Authors: Raczyńska Ewa D. , Krygowski Tadeusz M. , Zachara Joanna E. , Ośmiałowski Borys , Gawinecki Ryszard
Published: June 2005

Tautomeric interconversions (keto–enol and nitroso–oxime combined according to the 1,5‐proton shift into nitrosoenol–ketoxime) and related variations of π‐electron delocalization were studied for o‐nitrosophenol at the B3LYP/6–311 + G(2df,2p) level. The geometry‐ and magnetism‐based indices (HOMA and NICS) were applied to estimate π‐electron delocalization. The relative electronic (ΔE) and Gibbs free energies (ΔG) between the tautomers–rotamers were calculated to estimate tautomeric equilibrium and percentage content of the tautomeric mixture. Aromaticity of the phenyl ring and intramolecular H‐bonding were found to be the main factors stabilizing tautomeric forms (two isomeric nitrosoenols and one ketoxime) via increasing π‐electron delocalization in the chelating (quasi) ring and lowering push–pull interaction between ortho substituents. Copyright © 2005 John Wiley & Sons, Ltd.
First diphosphinoamine ligand bearing a polymerizable side chain: Complexation with copper(I)
Authors: Ahuja Ritu , Samuelson Ashoka G.
Published: June 2005

A diphosphinoamine ligand with a polymerizable side chain, (PPh2)2NCH2C6H4CHCH2 (vbzpnp or 1), was synthesized. The ligand could be polymerized by anionic polymerization with n‐butyllithium as the initiator. Polyvbzpnp was soluble in tetrahydrofuran and chloroform but was insoluble in methanol and was characterized with NMR, IR, and gel permeation chromatography. The number‐average and weight‐average molecular weights were 40,050 and 55,690, respectively, and the polydispersity index was 1.39. [Cu(CH3CN)4]ClO4 formed a bischelated complex with the monomer and produced [Cu(1)2]ClO4 (2), and CuCl formed a tetramer, Cu4(1)2Cl4 (3). All the compounds (1, 2, and 3) were characterized with single‐crystal‐structure determination, NMR, and IR spectroscopy. The addition of [Cu(CH3CN)4]ClO4 to polyvbzpnp resulted in an insoluble crosslinked polymer, which was characterized with solid‐state 31P {1H} magic‐angle‐spinning NMR. The copolymerization of styrene and 1 produced a styrene–vbzpnp copolymer that was found to be soluble in common organic solvents. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3411–3420, 2005
Cationic copolymerization of cycloaliphatic epoxy resin with a spirobislactone with lanthanum triflate as initiator: I. Characterization and shrinkage
Authors: Fernandez Xavier , Salla Josep Maria , Serra Angels , Mantecón Ana , Ramis Xavier
Published: June 2005

3,4‐Epoxycyclohexylmethyl 3,4‐epoxycyclohexane carboxylate (ECH) was cured with different proportions of 1,6‐dioxaspiro [4,4]nonane‐2,7‐dione (s(γ‐BL)) using lanthanum triflate as a catalyst. The shrinkage undergone during curing was monitored by means of thermomechanical analysis (TMA) in isothermal experiments. Fourier transform infrared spectroscopy in attenuated‐total‐reflection mode (FTIR/ATR) was used to study the evolution of lactone, epoxide, and intermediate spiroorthoester (SOE) groups to identify the different reactions that take place during the curing process. DSC was used to study the thermal characteristics of the curing process and to assess the glass‐transition temperature (Tg) of the cured material. The dynamic mechanical properties of the cured material were determined based on the data obtained by DMTA. An increase in the proportion of s(γ‐BL) led to a decrease in the gelation time and the shrinkage after gelation. By combining the data obtained by TMA and FTIR/ATR, it was also possible to identify the reactive processes responsible for the shrinkage. It was observed that an increase in the proportion of s(γ‐BL) also increases the speed of the curing process and modifies the structure of the material, thus giving rise to more flexible materials. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3421–3432, 2005
Synthesis and characterization of micron‐sized monodisperse superparamagnetic polymer particles with amino groups
Authors: Ma Zhiya , Guan Yueping , Liu Huizhou
Published: June 2005

Micron‐sized monodisperse superparamagnetic polyglycidyl methacrylate (PGMA) particles with functional amino groups were prepared by a process involving: (1) preparation of parent monodisperse PGMA particles by the dispersion polymerization method, (2) chemical modification of the PGMA particles with ethylenediamine (EDA) to yield amino groups, and (3) impregnation of iron ions (Fe2+ and Fe3+) inside the particles and subsequently precipitating them with ammonium hydroxide to form magnetite (Fe3O4) nanoparticles within the polymer particles. The resultant magnetic PGMA particles with amino groups were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X‐ray diffractometry (XRD), and vibrating sample magnetometry (VSM). SEM showed that the magnetic particles had an average size of 2.6 μm and were highly monodisperse. TEM demonstrated that the magnetite nanoparticles distributed evenly within the polymer particles. The existence of amino groups in the magnetic polymer particles was confirmed by FTIR. XRD indicated that the magnetic nanoparticles within the polymer were pure Fe3O4 with a spinel structure. VSM results showed that the magnetic polymer particles were superparamagnetic, and saturation magnetization was found to be 16.3 emu/g. The Fe3O4 content of the magnetic particles was 24.3% based on total weight. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3433–3439, 2005
Effect of ligand on the synthesis of star polymers by resorcinarene‐based ATRP initiators
Authors: Strandman Satu , Pulkkinen Petri , Tenhu Heikki
Published: June 2005

The effect of the steric hindrance on the initiating properties of two multifunctional resorcinarene‐based initiators in atom transfer radical polymerization (ATRP) was studied by using Cu(I)‐complexes of three multidentate amine ligands in the polymerization of tert‐butyl acrylate and methyl methacrylate. These ligands are less sterically hindered and have higher activities in the catalysis of ATRP of (meth)acrylates than 2,2′‐bipyridine. The polymerizations were faster and more controlled than with the 2,2′‐bipyridyl catalyst, but the tendency for bimolecular coupling increased. Even though the initiator was octafunctional, the resulting star polymers had only four arms. This indicates that the steric hindrance arising from the conformations of the initiators determines the structure of the polymer, but the ligand noticeably affects the controllability of the polymerization © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3349–3358, 2005
Structures and properties of liquid‐crystalline polymers based on laterally attached oligo p‐phenylenes
Authors: Lu Xuehong , He Chaobin , Liu Puwei , Griffin Anslem C.
Published: June 2005

The structures and properties of liquid‐crystalline polymers containing laterally attached p‐terphenyl and p‐pentaphenyl have been studied. In contrast to their mesogenic groups, that is, p‐terphenyl and p‐pentaphenyl, the polymers have much lower crystallinity and also lower nematic‐to‐isotropic transition temperatures. The significant depression in crystallinity can be attributed to flexible chain segments laterally attached to the oligo p‐phenylene rods, which prevent close packing of the rods and thus disrupt the crystallization. The destabilization of the liquid‐crystalline phase is due to the diluting effect of the flexible polymer backbones; that is, the concentration of the mesogenic groups is reduced. The polymer containing p‐pentaphenyl can still exhibit good solubility in common solvents and emit light at about 402 nm in the solvent tetrahydrofuran. In the solid state, the emission redshifts to 418 nm, which is fairly close to the blue‐light emission. An interdigitated packing structure of mesogenic groups has been proposed to represent the structure of the polymer in the oriented state. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3394–3402, 2005
Review of melt‐processed nanocomposites based on EVOH/organoclay
Authors: Artzi N. , Narkis M. , Siegmann A.
Published: June 2005

EVOH nanocomposites containing organically treated clays are unique systems in which the clay is strongly attracted to EVOH, thus affecting the morphology and the resultant thermal and mechanical properties. A strong effect of the processing conditions on morphology, thermal, and mechanical properties was observed. In highly interacting systems, under dynamic mixing conditions, in addition to a fracturing process of the clay particles, an onion‐like delamination process is suggested. EVA‐g‐MA and LLDPE‐g‐MA, having polar groups, were studied as compatibilizers to further induce clay intercalation and exfoliation. The compatibilizers affected both the thermal and mechanical properties of the composites at different levels. Thermal analysis showed that with increasing compatibilizer content lower crystallinity levels result, until at a certain content no crystallization has taken place. A Ny‐6 (nylon‐6)/EVOH blend is an interesting host matrix for incorporation of low organoclay contents. The Ny‐6/EVOH blend is a unique system that tends to hydrogen bond and also to in situ chemically react during melt mixing. The addition of clay seems to interrupt the chemical reaction between the two host polymers at certain compositions, leading to lower melt blending torque levels when clay is present. A competition between Ny‐6 and EVOH regarding the intercalation process takes place. However, Ny‐6 seems to lead to exfoliated structures, whereas EVOH forms intercalated structures, as revealed from combined XRD and TEM experiments, owing to thermodynamic considerations and preferential localization of the clay in Ny‐6. Of special interest is the increased storage modulus seen by the presence of only 1 wt % clay, which was achieved by extrusion under high shear forces, leading to a completely exfoliated structure. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1931–1943, 2005
An observation of accelerated exfoliation in iPP/organoclay nanocomposite as induced by repeated shear during melt solidification
Authors: Wang Ke , Liang Si , Zhang Qin , Du Rongni , Fu Qiang
Published: June 2005

A well‐exfoliated morphology is usually observed for polar polymer/clay nanocomposites via dynamic melt processing techniques, whereas only an intercalated or a partially intercalated/partially exfoliated morphology is often obtained for nonpolar polymer/clay nanocomposites, even though some polar compatibilzer is used. In this study, an accelerated exfoliation effect was observed for the first time in iPP/organoclay nanocomposites prepared through so‐called dynamic packing injection molding, in which the specimen is forced to move repeatedly in a chamber by two pistons that move reversibly with the same frequency as the solidification progressively occurs from the mold wall to the molding core part. The disordered level and exfoliated degree of clay was found to dramatically increase from the skin to the core of the prepared samples and eventually the WAXD reflections of interlayer d‐spacing diminished in the core. The changed degree of exfoliation was also proved directly by TEM observation. The prolongation of processing time, the gradual growth of solidification front, the increased melts viscosity, and the shear amplification effect were considered to explain the higher degree of exfoliation in the center zone of mold chamber. Our result suggests that a critical shear force may be needed to break down clay into exfoliated structure. This can be also well used to explain at least partially the intercalated morphology, which is commonly observed for nonpolar polymer/clay nanocomposites via conventional processing. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2005–2012, 2005
Morphology and dynamics of the poly(ϵ‐caprolactone)‐b‐poly(L‐lactide) diblock copolymer and its inclusion compound with α‐cyclodextrin: A solid‐state 13C NMR study
Authors: Porbeni Francis E. , Shin I. Daniel , Shuai Xintao , Wang Xingwu , White Jeffery L. , Jia Xin , Tonelli Alan E.
Published: June 2005

A biodegradable diblock copolymer of poly(ϵ‐caprolactone) (PCL) and poly(L‐lactide) (PLLA) was synthesized and characterized. The inclusion compound (IC) of this copolymer with α‐cyclodextrin (α‐CD) was formed and characterized. Wide‐angle X‐ray diffraction showed that in the IC crystals α‐CDs were packed in the channel mode, which isolated and restricted the individual guest copolymer chains to highly extended conformation. Solid‐state 13C NMR techniques were used to investigate the morphology and dynamics of both the bulk and α‐CD‐IC isolated PCL‐b‐PLLA chains. The conformation of the PCL blocks isolated within the α‐CD cavities was similar to the crystalline conformation of PCL blocks in the bulk copolymer. Spin–lattice relaxation time (T1C) measurements revealed a dramatic difference in the mobilities of the semicrystalline bulk copolymer chains and those isolated in the α‐CD‐IC channels. Carbon‐observed proton spin–lattice relaxation in the rotating frame measurements (T1ρH) showed that the bulk copolymer was phase‐separated, while, in the IC, exchange of proton magnetization through spin‐diffusion between the isolated guest polymer chains and the host α‐CD was not complete. The two‐dimensional solid‐state heteronuclear correlation (HetCor) method was also employed to monitor proton communication in these samples. Intrablock exchange of proton magnetization was observed in both the bulk semicrystalline and IC copolymer samples at short mixing times; however, even at the longest mixing time, interblock proton communication was not observed in either sample. In spite of the physical closeness between the isolated included guest chains and the host α‐CD molecules, efficient proton spin diffusion was not observed between them in the IC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2086–2096, 2005
Poly(acrylonitrile) ultrafiltration membranes. I. Polymer‐salt‐solvent interactions
Authors: Phadke Madhuri A. , Musale Deepak A. , Kulkarni Sudhir S. , Karode Sandeep K.
Published: June 2005

Fourier transform infrared spectroscopy was used to study the interactions among LiCl, ZnCl2, and AlCl3 with N,N‐dimethylformamide (DMF) and poly(acrylonitrile) (PAN). It was observed that all three salts complex with DMF as well as PAN. The strength of the cation interaction with the >CO oxygen of DMF was found to be higher than that with the CN group of PAN. The >CO stretching frequency of DMF with ZnCl2 was red shifted, indicating stronger complex formation compared with other two cations. With the addition of salt, the salt–DMF pseudo solvent was found to become a θ solvent for PAN compared with neat DMF. This change in PAN solvation power was primarily the result of DMF–salt complexation. As a result of the complexation, Mark‐Houwink constant a, was found to reduce from 0.75 (for pure DMF) to ∼0.6 for DMF–salt solvents, indicating decreased PAN chain expansion. Comparison of intrinsic viscosity [η] values indicated that addition of salts to PAN–DMF solutions resulted in: (i) decrease in the DMF solvation power, which causes less expanded polymer coils, and (ii) increased interpolymer chain entanglements via salt‐promoted chain association. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2061–2073, 2005
Poly(acrylonitrile) ultrafiltration membranes. II. Membrane morphology and permeation characteristics
Authors: Phadke Madhuri A. , Kulkarni Sudhir S. , Karode Sandeep K. , Musale Deepak A.
Published: June 2005

The rheology and phase‐boundary characteristics of various solutions comprising three polyacrylonitrile (PAN) grades dissolved in solutions of N,N‐dimethylformamide + salt (LiCl, ZnCl2, or AlCl3) additives were correlated with the resulting membrane morphology as determined by microscopy and permeability measurements. The phase separation characteristics of the dope solution were not markedly affected by the PAN molecular weight (MW); however, they were affected by the salt additive. For higher MW grades, the effect of salt addition can also be masked by the increased self‐association tendency of the polymer chains. PAN‐B and ‐C membranes were clearly less asymmetric in structure than the lower MW PAN‐A–based membranes. This is attributed to the higher viscosity/lower diffusivity of the PAN‐B and ‐C solutions, which results in slower solvent–nonsolvent exchange during the phase inversion process. Two factors reduce the incidence of surface defects (increased bubble points): (a) higher solution viscosity dampens surface perturbations during phase inversion, and (b) phase inversion pathways resulting in more homogenous morphology lead to membranes with higher bubble points. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2074–2085, 2005
Rheology of cellulose/KSCN/ethylenediamine solutions and coagulation into filaments and films
Authors: Frey Margaret W. , Chan Hester , Carranco Kristen
Published: June 2005

Dissolution of cellulose in ethylenediamine/potassium thiocyanate (KSCN) was studied as a function of cellulose and KSCN concentration. Concentrations of up to 9% (w/w) cellulose were obtained. Large variations in solution rheology with salt and cellulose concentration were observed, and phases including flowing solutions and gels were identified visually. Rheological data indicated that viscosity decreased with increasing salt or cellulose concentration in certain composition ranges. Viscosity decrease with concentration increase is associated with either onset of liquid crystalline ordering or phase separation in the system. Both of these are quite likely in the cellulose/ethylenediamine/KSCN system, depending on composition. Additionally, comparison of loss (G′′) and storage (G′) moduli confirmed that compositions that exhibited gel behavior at zero shear became liquid at shear rates as low as 1 Hz. Solutions were coagulated into filaments and films using ethanol (CH3CH2OH) and methanol (CH3OH). Infrared spectroscopy (FTIR) indicated that significant quantities of KSCN salt remained in the fibers and films after coagulation. Subsequent washing removed residual KSCN and improved physical properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2013–2022, 2005
Nitrogen plasma modification on polyimide films for copper metallization on microelectronic flex substrates
Authors: Lin Yung‐Sen , Liu Huang‐Ming , Tsai Chung‐Wei
Published: June 2005

Surface modification of polyimide films Kapton E(N) and Upilex S by nitrogen plasmas were investigated for their enhanced adhesion strength with sputtered coppers. Peel tests demonstrate this improvement, with peel strengths of 7 and 12 N/m for unmodified Kapton E(N) and Upilex S, and 1522 and 1401 N/m for nitrogen plasma‐modified Kapton E(N) and Upilex S at certain plasma conditions. Atomic force microscopy (AFM) and the sessile drop method indicated the surface roughness, and the surface energy of polyimide films were highly increased by nitrogen plasmas. This study shows the enhanced adhesion strengths of polyimide films with sputtered coppers by nitrogen plasmas, and these nitrogen plasmas were strongly affected by the surface characteristics of polyimide films. Electron spectroscopy for chemical analysis (ESCA) observed the increased surface energy on polyimide films by nitrogen plasmas was due to the increased surface composition of O and the increased chemical bond of CO. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2023–2038, 2005
Assessment of CAPRI predictions in rounds 3–5 shows progress in docking procedures
Authors: Méndez Raúl , Leplae Raphaël , Lensink Marc F. , Wodak Shoshana J.
Published: June 2005

The current status of docking procedures for predicting protein–protein interactions starting from their three‐dimensional (3D) structure is reassessed by evaluating blind predictions, performed during 2003–2004 as part of Rounds 3–5 of the community‐wide experiment on Critical Assessment of PRedicted Interactions (CAPRI). Ten newly determined structures of protein–protein complexes were used as targets for these rounds. They comprised 2 enzyme–inhibitor complexes, 2 antigen–antibody complexes, 2 complexes involved in cellular signaling, 2 homo‐oligomers, and a complex between 2 components of the bacterial cellulosome. For most targets, the predictors were given the experimental structures of 1 unbound and 1 bound component, with the latter in a random orientation. For some, the structure of the free component was derived from that of a related protein, requiring the use of homology modeling. In some of the targets, significant differences in conformation were displayed between the bound and unbound components, representing a major challenge for the docking procedures. For 1 target, predictions could not go to completion. In total, 1866 predictions submitted by 30 groups were evaluated. Over one‐third of these groups applied completely novel docking algorithms and scoring functions, with several of them specifically addressing the challenge of dealing with side‐chain and backbone flexibility. The quality of the predicted interactions was evaluated by comparison to the experimental structures of the targets, made available for the evaluation, using the well‐agreed‐upon criteria used previously. Twenty‐four groups, which for the first time included an automatic Web server, produced predictions ranking from acceptable to highly accurate for all targets, including those where the structures of the bound and unbound forms differed substantially. These results and a brief survey of the methods used by participants of CAPRI Rounds 3–5 suggest that genuine progress in the performance of docking methods is being achieved, with CAPRI acting as the catalyst. Proteins 2005;60:150–169. © 2005 Wiley‐Liss, Inc.
The targets of CAPRI rounds 3–5
Authors: Janin Joël
Published: June 2005

Ten protein–protein complexes have been offered by X‐ray crystallographers as targets for structure prediction in Rounds 3–5 of the CAPRI experiment. They illustrate molecular recognition in several domains of biology: enzyme regulation, antigen–antibody recognition, signal transduction, and oligomer assembly. The targets presented various degrees of difficulty to the predictors, depending on their status (bound when components were taken from the complex, unbound when coming from independent structures of the free proteins), the amplitude of conformation changes, and the amount of biological information available. Predictors produced high‐quality models of 6 of the targets, good models of 3 others, and failed only in 1 case, where the conformation change was particularly large. This result demonstrates significant progress relative to earlier rounds of CAPRI. Proteins 2005;60:170–175. © 2005 Wiley‐Liss, Inc.
Classification of protein complexes based on docking difficulty
Authors: Vajda Sandor
Published: June 2005

Based on the results of several groups using different docking methods, the key properties that determine the expected success rate in protein–protein docking calculations are measures of conformational change, interface area, and hydrophobicity. A classification of protein complexes in terms of these measures provides a prediction of docking difficulty. This classification is used to study the targets of the CAPRI docking experiment. Results show that targets with a moderate expected difficulty were indeed predicted well by a number of groups, whereas the use of additional a priori information was necessary to obtain good results for some very difficult targets. The analysis indicates that CAPRI and other relatively large‐scale docking studies represent very important steps toward understanding the capabilities and limitations of current protein–protein docking methods. Proteins 2005;60:176–180. © 2005 Wiley‐Liss, Inc.
CAPRI rounds 3–5 reveal promising successes and future challenges for RosettaDock
Authors: Daily Michael D. , Masica David , Sivasubramanian Arvind , Somarouthu Sony , Gray Jeffrey J.
Published: June 2005

CAPRI Rounds 3, 4, and 5 are the first public test of the published RosettaDock algorithm. The targets cover a wide range of sizes and shapes. For most targets, published biological information indicated the region of the binding site on at least one docking partner. The RosettaDock algorithm produced high accuracy predictions for three targets, medium‐accuracy predictions for two targets, and an acceptable prediction for one target. RosettaDock predicted all five targets with less than 450 residues to high or medium accuracy, but it predicted only one of seven targets with above 450 residues to acceptable accuracy. RosettaDock's high‐accuracy predictions for small to moderately large targets reveal the predictive power and fidelity of the algorithm, especially the high‐resolution refinement and scoring protocol. In addition, RosettaDock can predict complexes from at least one homology‐modeled docking partner with comparable accuracy to unbound cases of similar size. Larger targets present a more intensive sampling problem, and some large targets present repulsive barriers to entering the binding site. Ongoing improvements to RosettaDock's low‐resolution search may alleviate this problem. This first public test suggests that RosettaDock can be useful in a significant range of applications in biochemistry and cell biology. Proteins 2005;60:181–186. © 2005 Wiley‐Liss, Inc.
Progress in protein–protein docking: Atomic resolution predictions in the CAPRI experiment using RosettaDock with an improved treatment of side‐chain flexibility
Authors: Schueler‐Furman Ora , Wang Chu , Baker David
Published: June 2005

RosettaDock uses real‐space Monte Carlo minimization (MCM) on both rigid‐body and side‐chain degrees of freedom to identify the lowest free energy docked arrangement of 2 protein structures. An improved version of the method that uses gradient‐based minimization for off‐rotamer side‐chain optimization and includes information from unbound structures was used to create predictions for Rounds 4 and 5 of CAPRI. First, large numbers of independent MCM trajectories were carried out and the lowest free energy docked configurations identified. Second, new trajectories were started from these lowest energy structures to thoroughly sample the surrounding conformation space, and the lowest energy configurations were submitted as predictions. For all cases in which there were no significant backbone conformational changes, a small number of very low‐energy configurations were identified in the first, global search and subsequently found to be close to the center of the basin of attraction in the free energy landscape in the second, local search. Following the release of the experimental coordinates, it was found that the centers of these free energy minima were remarkably close to the native structures in not only the rigid‐body orientation but also the detailed conformations of the side‐chains. Out of 8 targets, the lowest energy models had interface root‐mean‐square deviations (RMSDs) less than 1.1 Å from the correct structures for 6 targets, and interface RMSDs less than 0.4 Å for 3 targets. The predictions were top submissions to CAPRI for Targets 11, 12, 14, 15, and 19. The close correspondence of the lowest free energy structures found in our searches to the experimental structures suggests that our free energy function is a reasonable representation of the physical chemistry, and that the real space search with full side‐chain flexibility to some extent solves the protein–protein docking problem in the absence of significant backbone conformational changes. On the other hand, the approach fails when there are significant backbone conformational changes as the steric complementarity of the 2 proteins cannot be modeled without incorporating backbone flexibility, and this is the major goal of our current work. Proteins 2005;60:187–194. © 2005 Wiley‐Liss, Inc.
Docking to single‐domain and multiple‐domain proteins: Old and new challenges
Authors: Ben‐Zeev E. , Kowalsman N. , Ben‐Shimon A. , Segal D. , Atarot T. , Noivirt O. , Shay T. , Eisenstein M.
Published: June 2005

The diverse selection of targets in the CAPRI experiments provides grounds for determining the limits of our rigid‐body docking program MolFit, and for extending it. We find that the sensitivity of MolFit is high, enabling it to produce reasonably accurate docking solutions when the structures undergo moderate local conformation changes upon complex formation or when the docked molecules are modeled. Yet the ranks of these solutions are sometimes too low to meet the requirements of CAPRI assessment. This indicates that the selectivity of MolFit, which was optimized for docking of unbound X‐ray structures, and which relies on the availability of external data from biochemical and bioinformatic sources, needs readjustment in order to meet the challenges presented by NMR or modeled structures. A different challenge is presented by large global conformation changes such as movements of domains. We show that such changes can be accommodated within the rigid‐body approximation by employing rigid multibody multistage docking procedures. We also address the difficulty of ranking results from 2‐body and multibody docking scans in cases in which there are no external data favoring one option over the other. Proteins 2005;60:195–201. © 2005 Wiley‐Liss, Inc.
Modeling oligomers with Cn or Dn symmetry: Application to CAPRI target 10
Authors: Berchanski Alexander , Segal Dadi , Eisenstein Miriam
Published: June 2005

The abundance of oligomeric proteins makes them a frequent target for structure prediction. However, homologous proteins sometimes adopt different oligomerization states, rendering the prediction of structures of whole oligomers beyond the scope of comparative modeling. This obstacle can be overcome by combining comparative modeling of the single subunit of an oligomer with docking techniques, designed for predicting subunit–subunit interfaces. We present here algorithms for predicting the structures of homo‐oligomers with Cn or Dn (n > 2) symmetry. The prediction procedure includes a symmetry‐restricted docking step followed by a Cn or Dn oligomer‐forming step, in which the dimers from the docking step are assembled to oligomers. The procedure is applied to each of the crystallographically independent subunits in 8 Cn and 3 Dn oligomers, producing very accurate predictions. It is further applied to a single monomer of the tick‐borne encephalitis virus coat protein E (Target 10 of the CAPRI experiment). The predicted trimer ranked 30, obtained via rigid‐body geometric–hydrophobic docking followed by Cn oligomer formation, is very similar to the experimentally observed trimer formed by domain II of this protein. Furthermore, the predicted trimer formed from the separated domain I is also close to the experimental structure. Proteins 2005;60:202–206. © 2005 Wiley‐Liss, Inc.