bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantenwelt im Nanozylinder: Elektronische Eigenschaften von Kohlenstoff‐Nanoröhrchen
Authors: Strunk Christoph 
Published: June 2005

AbstractKohlenstoff‐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

AbstractDie 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

AbstractErstmals 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

AbstractÜbergänge 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

AbstractFür 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

AbstractHin 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

AbstractScience 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

Abstract“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

AbstractAls 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

AbstractMediterran 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

AbstractThe 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

AbstractTautomeric 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

AbstractA 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

Abstract3,4‐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

AbstractMicron‐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

AbstractThe 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

AbstractThe 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

AbstractEVOH 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

AbstractA 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

AbstractA 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

AbstractFourier 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

AbstractThe 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