bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pioniere in der Supraleiter‐ und Supraflüssigkeitsforschung
Authors: Huebener Rudolf 
Published: November 2003

AbstractDie Königlich Schwedische Akademie der Wissenschaften vergab in diesem Jahr den Physik‐Nobelpreis zu gleichen Teilen an Aleksej Abrikossow, Witalij Ginsburg und Anthony Leggett für ihre „pionierhaften Beiträge zur Theorie der Supraleiter und Supraflüssigkeiten.”︁http://www.nobel.se
„Eine neue Eigenschaft der Materie”︁
Authors: Jacobi Manfred 
Published: November 2003

AbstractIm Jahre 1903 erhielten Henri Becquerel sowie Marie und Pierre Curie den Physik‐Nobelpreis für die Entdeckung der Radioaktivität. Schon damals stellte Pierre Curie die Frage nach Nutzen und Gefahr dieser neuen Eigenschaft von Materie. Er war der Überzeugung, dass der Fortschritt letztlich mehr zum Nutzen als zum Schaden der Menschen beitrage.
Das Elektron auf der Präzisionswaage
Authors: Vogel Manuel , Werth Günther 
Published: November 2003

AbstractDie Elektronenmasse ist eine der Fundamentalkonstanten der Physik. Entsprechend gibt es viele, zumeist indirekte Ansätze zu ihrer Bestimmung. Physikern der Universität Mainz gelang es jüngst, den Wert um einen Faktor vier zu verbessern. Sie nutzten dafür die Messung des anomalen magnetischen Moments des Elektrons in wasserstoffartigen Ionen.
Neutronen in Hiroshima
Authors: Rugel Georg 
Published: November 2003

AbstractMünchner Physikern gelang es kürzlich in Zusammenarbeit mit Kollegen aus den USA, in Kupferproben aus Hiroshima Reaktionsprodukte schneller Neutronen von der damaligen Atombomben‐Explosion nachzuweisen. Dies ermöglichte es erstmals, die Neutronendosen, denen die Überlebenden ausgesetzt gewesen waren, experimentell zu bestimmen [1].
Physik mit Gewehr und Eiern
Authors: Loos Andreas 
Published: November 2003

AbstractEs fing schon gut an: Mit zehn Jahren saß der begabte Junge bereits in der Universität, wo ihn kein Geringerer als sein Vater persönlich unterrichtete. Damit schlug dieser zwei Fliegen mit einer Klappe: Sein Sohn lernte etwas Gescheites, und er war zugleich in sicherer Obhut.
Von Weihnachtsplätzchen und anderen granularen Backwerken
Authors: Vilgis Thomas 
Published: November 2003

AbstractWeihnachten steht vor der Tür, und aus den Backöfen duften die ersten Plätzchen als Vorboten. Die isst man auch bei Physikers so gern, dass kaum ein Krumen übrig bleibt. Dabei sind die Krümel besonders interessant, denn sie zeigen eine Vielzahl von Merkmalen und lassen auf die verschiedenen Teigarten schließen, deren Reiz nicht nur im Geschmack, sondern auch in Herstellungsweise und Teigklasse liegt.
Synthesis and characterization of fillers of controlled structure based on polyhedral oligomeric silsesquioxane cages and their use in reinforcing siloxane elastomers
Authors: Pan Guirong , Mark James E. , Schaefer Dale W. 
Published: November 2003

AbstractFour polyhedral oligomeric silsesquioxane (POSS) cages with vinyl groups were linked to a central siloxane core by hydrosilylation. The goal was to obtain filler particles of sizes between those of the POSS cages themselves and the much larger silica particles typically used to reinforce elastomers. The hydrosilylation reaction was monitored with Fourier transform infrared spectroscopy and proton nuclear magnetic resonance, and the resulting structure was confirmed by mass spectrometry. Simply blending these POSS‐based fillers into silanol‐terminated poly(dimethylsiloxane) (PDMS) had little effect on the mechanical properties, but bonding them to PDMS provided considerable reinforcement. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3314–3323, 2003
Influence of polymer matrix composition and architecture on polymer nanocomposite formation: Coarse‐grained molecular dynamics simulation
Authors: Sinsawat Anuchai , Anderson Kelly L. , Vaia Richard A. , Farmer B. L. 
Published: November 2003

AbstractCoarse‐grained molecular dynamics simulations of stacks of two‐dimensional platelets immersed in a polymer melt were performed to investigate aspects of the polymer matrix that promote the formation of intercalated or exfoliated nanocomposite structures. Such factors include temperature, copolymer architecture, and blend composition. Increasing the polymer‐sheet attractive interaction led to binding of the sheets, where individual beads simultaneously attract two neighboring sheets, thus kinetically blocking intercalation by occupying the perimeter of the affected gallery. Polymers with a small polymer‐sheet attraction, but having a strongly attractive chain end (end‐functionalized polymers) minimized the bonding of adjacent sheets. These systems exhibited some sheet sliding because a majority of the confined polymer beads only interacted weakly with adjacent sheets; however, the number density of intercalated polymer was low. Mixtures of end‐functionalized and nonfunctionalized polymers, however, yielded better intercalation efficiency. For the mixed system, the reduced number of highly attractive beads provided sufficient interaction for intercalation to occur, enabling greater intercalation rates, less sheet‐bridging, and incorporation of the nonfunctionalized polymers into the galleries. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3272–3284, 2003
Melt‐processable syndiotactic polystyrene/montmorillonite nanocomposites
Authors: Wang Z. M. , Chung T. C. , Gilman J. W. , Manias E. 
Published: November 2003

AbstractMonoalkyl‐ and dialkyl‐imidazolium surfactants were used to prepare organically modified montmorillonites with markedly improved thermal stability in comparison with their alkyl‐ammonium equivalents (the decomposition temperatures increased by ca. 100 °C). Such an increase in the thermal stability affords the opportunity to form syndiotactic polystyrene (s‐PS)/imidazolium‐montmorillonite nanocomposites even under static melt‐intercalation conditions in the absence of high shear rates or solvents. Upon nanocomposite formation, s‐PS exhibited an improvement in the thermal stability in comparison with neat s‐PS, and the β‐crystal form of s‐PS became dominant. This crystallization response agrees with previous studies of s‐PS/pyridinium‐montmorillonite hybrids and is tentatively attributed to a heterogeneous nucleation action by the inorganic fillers. © 2003 Wiley Periodicals, Inc.* J Polym Sci Part B: Polym Phys 41: 3173–3187, 2003
Analysis of small‐angle scattering of suspensions of organically modified montmorillonite: Implications to phase behavior of polymer nanocomposites
Authors: Vaia Richard A. , Liu Weidong , Koerner Hilmar 
Published: November 2003

AbstractA generalized model for scattering from a collection of independent (isolated) stacks of layers enabled predictions of and parameterized fits to small‐angle X‐ray scattering from layered silicate dispersions. From this fundamental development, example investigations that use small‐angle scattering to examine the structure of organically modified montmorillonite dispersions in toluene and toluene–acetone blends provided detailed information on the distribution of the stacks (relative concentrations, K and fraction of individual layers, χ) and characteristics of the intercalated crystallite (mean number of layers per stack, 〈N〉; layer repeat distance, D; and fractional stack disorder, δ). The analysis initially supported correlations with discotic phase behavior, which provides concise definitions for various morphologies (exfoliated, intercalated, and mixed). Finally, examination of the deviations between the scattering model and the experiment provided insights for improved experimental technique, more complete utilization of the scattering data, a sound basis for real‐time observations, insight into inconsistencies between scattering and microscopy, and minimization of incorrect or overinterpretation of data. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3214–3236, 2003
Glass transition of polymer/single‐walled carbon nanotube composite films
Authors: Pham Joseph Q. , Mitchell Cynthia A. , Bahr Jeffrey L. , Tour James M. , Krishanamoorti Ramanan , Green Peter F. 
Published: November 2003

AbstractThe glass‐transition temperatures (Tg's) of nanocomposites of polystyrene (PS) and single‐walled carbon nanotubes were measured in the bulk and in thin films with differential scanning calorimetry and spectroscopic ellipsometry, respectively. The bulk Tg of the nanocomposites increased by approximately 3 °C and became much broader than that of PS. For the nanocomposite films thinner than 45 nm, Tg decreased with decreasing film thickness [i.e., ΔTg(nano) < 0]. This phenomenon also occurred in thin PS films, the magnitude of the depression in PS [ΔTg(PS)] being somewhat larger. The film thickness dependence and the differences in the magnitude of ΔTg in the two systems were examined in light of current theory, and a quantitative comparison was made. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3339–3345, 2003
Hybrid epoxy‐based thermosets based on polyhedral oligosilsesquioxane: Cure behavior and toughening mechanisms
Authors: Kim G.‐M. , Qin H. , Fang X. , Sun F. C. , Mather P. T. 
Published: November 2003

AbstractPolyhedral oligosilsesquioxane (POSS)‐reinforced thermosets based on octaglycidyl epoxy polyhedral oligosilsesquioxane cured with 4,4′‐diaminodiphenyl sulfone (DDS) were prepared and studied for their cure, thermomechanical, and microstructural characteristics. Particular attention was paid to nanometer‐scale deformation processes responsible for toughening, as revealed by transmission electron microscopy (TEM) in conjunction with the thermal properties. A cure analysis investigated with calorimetry and rheometry showed a significant dependence of the cure mechanism and kinetics on the DDS content, but all hybrid thermosets reacted completely below 300 °C into rigid solids. A dynamic mechanical analysis of this hybrid resin system showed that increasing the DDS concentration used during cure increased the dynamic storage modulus in the glassy (temperature < glass‐transition temperature) and rubbery (temperature > glass‐transition temperature) states, simply through an increase in the crosslink density. The phase structures revealed by TEM with selective POSS staining were drastically affected by the DDS concentration and manifested as altered nanomechanical deformation structures. It was qualitatively found that the main toughening mechanism in the studied POSS‐reinforced thermosets was void formation at the nanometer scale, possibly templated by limited POSS aggregation. As the crosslinking density increased with the DDS concentration, microshear yielding between voids prevailed, providing a balance of stiffness, strength, and toughness. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3299–3313, 2003
Electrical characterization of poly(ethylene oxide)–clay nanocomposites prepared by microwave irradiation
Authors: Aranda Pilar , Mosqueda Yodalgis , Pérez‐Cappe Eduardo , Ruiz‐Hitzky Eduardo 
Published: November 2003

AbstractPoly(ethylene oxide) (PEO)–clay (montmorillonite, hectorite, and laponite) nanocomposites were prepared by a melting intercalation procedure induced by microwave irradiation. The influence of parameters such as the time of irradiation, power, amount and relative ratio of the reagents, and relative humidity was investigated. X‐ray diffraction, differential scanning calorimetry, elemental microanalysis, Fourier transform infrared, and scanning electron microscopy techniques were applied to characterize the resulting nanocomposites. Techniques involving impedance spectroscopy, thermoelectric power, and electrical polarization in the solid state were used to characterize the electrical properties of the nanocomposites. The electrical behavior of these PEO–silicate nanocomposites, including those containing an excess of alkaline metal salts in comparison with that of similar systems prepared by alternative procedures such as direct intercalation from polymer solutions or melting intercalation, was also examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3249–3263, 2003
Investigation of nanodispersion in polystyrene–montmorillonite nanocomposites by solid‐state NMR
Authors: Bourbigot Serge , VanderHart David L. , Gilman Jeffrey W. , Awad Walid H. , Davis Rick D. , Morgan Alexander B. , Wilkie Charles A. 
Published: November 2003

AbstractNanocomposites result from combinations of materials with vastly different properties in the nanometer scale. These materials exhibit many unique properties such as improved thermal stability, reduced flammability, and improved mechanical properties. Many of the properties associated with polymer–clay nanocomposites are a function of the extent of exfoliation of the individual clay sheets or the quality of the nanodispersion. This work demonstrates that solid‐state NMR can be used to characterize, quantitatively, the nanodispersion of variously modified montmorillonite (MMT) clays in polystyrene (PS) matrices. The direct influence of the paramagnetic Fe3+, embedded in the aluminosilicate layers of MMT, on polymer protons within about 1 nm from the clay surfaces creates relaxation sources, which, via spin diffusion, significantly shorten the overall proton longitudinal relaxation time (T). Deoxygenated samples were used to avoid the particularly strong contribution to the T of PS from paramagnetic molecular oxygen. We used T as an indicator of the nanodispersion of the clay in PS. This approach correlated reasonably well with X‐ray diffraction and transmission electron microscopy (TEM) data. A model for interpreting the saturation‐recovery data is proposed such that two parameters relating to the dispersion can be extracted. The first parameter, f, is the fraction of the potentially available clay surface that has been transformed into polymer–clay interfaces. The second parameter, ϵ, is a relative measure of the homogeneity of the dispersion of these actual polymer–clay interfaces. Finally, a quick assay of T is reported for samples equilibrated with atmospheric oxygen. Included are these samples as well as 28 PS/MMT nanocomposite samples prepared by extrusion. These measurements are related to the development of high‐throughput characterization techniques. This approach gives qualitative indications about dispersion; however, the more time‐consuming analysis, of a few deoxygenated samples from this latter set, offers significantly greater insight into the clay dispersion. A second, probably superior, rapid‐analysis method, applicable to oxygen‐containing samples, is also demonstrated that should yield a reasonable estimate of the f parameter. Thus, for PS/MMT nanocomposites, one has the choice of a less complete NMR assay of dispersion that is significantly faster than TEM analysis, versus a slower and more complete NMR analysis with sample times comparable to TEM, information rivaling that of TEM, and a substantial advantage that this is a bulk characterization method. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3188–3213, 2003
New poly(butylene succinate)/layered silicate nanocomposites. II. Effect of organically modified layered silicates on structure, properties, melt rheology, and biodegradability
Authors: Okamoto Kazuaki , Sinha Ray Suprakas , Okamoto Masami 
Published: November 2003

AbstractA series of new poly(butylene succinate) (PBS)/layered silicate nanocomposites were prepared successfully by simple melt extrusion of PBS and organically modified layered silicates (OMLS). Three different types of OMLS were used for the preparation of nanocomposites: two functionalized ammonium salts modified montmorillonite and a phosphonium salt modified saponite. The structure of the nanocomposites in the nanometer scale was characterized with wide‐angle X‐ray diffraction and transmission electron microscopic observations. With three different types of layered silicates modified with three different types of surfactants, the effect of OMLS in nanocomposites was investigated by focusing on four major aspects: structural analysis, materials properties, melt rheological behavior, and biodegradability. Interestingly, all these nanocomposites exhibited concurrent improvements of material properties when compared with pure PBS. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3160–3172, 2003
Poly(styrene‐block‐isoprene) nanocomposites: Kinetics of intercalation and effects of copolymer on intercalation behaviors
Authors: Chen Hua , Schmidt Daniel F. , Pitsikalis Marinos , Hadjichristidis Nikos , Zhang Yuangming , Wiesner Ulrich , Giannelis Emmanuel P. 
Published: November 2003

AbstractIn addition to phase morphology, diffusion, and dynamics in the bulk, the behavior of block copolymers in the confined state has been of great interest. Although random and graft copolymers have been used in polymer‐layered silicate nanocomposites, well‐defined block copolymers have received relatively little attention. In this study, the kinetics of intercalation of a series of poly(styrene‐b‐isoprene) block copolymers into a layered silicate were examined via X‐ray diffraction. Intercalation was observed even when the copolymer was in the ordered state, with no discontinuity around the order–disorder transition of the copolymer. As the size of the polystyrene block was increased, slower intercalation kinetics were observed, possibly because of the increased glass‐transition temperature of the polystyrene segment. Finally, the clearing temperature of the copolymer in the nanocomposites as measured by small‐angle X‐ray scattering showed a large heating‐rate dependence suggesting that the nanoparticles act as kinetics barriers to the disordering of the copolymer. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3264–3271, 2003
The hot carrier dynamics in InGaN multi‐quantum well structure
Authors: Shikanai A. , Kojima K. , Omae K. , Kawakami Y. , Narukawa Y. , Mukai T. , Fujita Sg. 
Published: November 2003

AbstractWe investigated the hot carrier dynamics in InGaN mutli‐quantum wells using phtoluminescence, time‐resolved photoruminescence (TRPL) and white‐light pump and probe methods at room temperature. The pump and probe spectra or ΔOD spectra have not reflected the screening of electric field by photoexcited carriers but the distribution of hot carriers. It reflects the band filling of the tail state in lower energy side and Maxwell–Boltzmann‐like tail of hot carriers on the higher energy side. ΔOD spectra in 1.5 ps rose in the observed spectral region, which indicates that thermalization among carriers is very fast. It is because of carrier‐LO phonon and carrier‐carrier interaction. After 2 ps ΔOD spectra are red shifted as increasing the time delay. At 40 ps time delay, the Maxwell–Boltzmann‐like tail shows still the high temperature of carriers. This slow cooling is likely due to the hot phonon effects where the nonequilibrium phonon population may lead to a reabsorption of phonons by photoexcited carriers. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Isoelectronic doping of AlGaN alloys
Authors: Novikov S. V. , Zhao L. X. , Harrison I. , Foxon C. T. 
Published: November 2003

AbstractIsoelectronic doping of AlxGa1−xN alloys with arsenic in films grown by molecular beam epitaxy has been investigated. In photoluminescence spectra of these AlxGa1−xN layers, there is a gradual increase of the band gap and a smaller progressive shift of the position of blue emission band to the higher energies as the Al content increases. To explain the change in the energy of the blue band in As‐doped AlxGa1−xN alloys a model has been proposed, which predicts the shift in the blue band energy to be equal to the valence band offset from AlGaN to GaN. This prediction is consistent with the experimental results. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of nitrogen on self‐assembled GaInNAs quantum dots grown on GaAs
Authors: Nishikawa A. , Hong Y. G. , Tu C. W. 
Published: November 2003

AbstractWe investigate the effect of nitrogen on self‐assembled GaInNAs quantum dots (QDs) grown on GaAs (001) substrates by gas‐source molecular beam epitaxy. The dot density of GaInNAs QDs decreases with increasing nitrogen. The reduced strain resulted from nitrogen incorporation decreases dot density of QDs. However, we find that the dot density of Ga0.3In0.7N0.02As0.98 QDs is still significantly lower than that of Ga0.4In0.6As QDs, even though they have comparable nominal strain. This difference can be explained by the composition fluctuation in the wetting layer. The inhomogeneous local strain due to the composition fluctuation decreases the number of dots when the dots begin to form, resulting in lower dot density after QD growth. The dot density difference between GaInNAs QDs and GaInAs QDs becomes smaller with decreasing growth temperature. Therefore, the PL intensity of GaInNAs QDs grown at low temperature (450 °C) improved to be comparable to that of GaInAs QDs, while the PL intensity of the GaInNAs QDs grown at high temperature (520 °C) dramatically decreased with increasing nitrogen composition. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Localization characteristics of photoluminescence decay dynamics in an InxGa1−xAs1−yNy/GaAs single quantum well
Authors: Nakayama M. , Tokuoka K. , Nomura K. , Yamada T. , Moto A. , Takagishi S. 
Published: November 2003

AbstractWe have investigated photoluminescence (PL) properties of an InxGa1−xAs1−yNy/GaAs single quantum well from an aspect of carrier localization. The sample was grown on a (001) GaAs substrate by metalorganic vapor phase epitaxy: the InxGa1−xAs1−−yNy thickness is 8 nm, and the alloy compositions of x and y are 0.15 and 0.034, respectively. The PL spectra at low temperatures lie on the low energy side of the band edge confirmed by photoreflectance spectroscopy, and the PL peak energy approaches to the band edge with increasing excitation power. These results demonstrate the localization characteristics of the PL process. It has been found that the PL decay of localized carriers exhibits a stretched exponential profile that is a typical decay phenomenon in a disordered system. From the energy dependence and temperature dependence of the stretched exponential profile, we conclude that the PL decay dynamics at low temperatures are dominated by random potentials due to alloy disordering of InGaAsN. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nitrides as spintronic materials
Authors: Dietl Tomasz 
Published: November 2003

AbstractA report on the progress in spintronics‐related works involving group III nitrides is given, emphasizing contradictory opinions concerning the basic characteristics of these materials. The actual position of magnetic impurities in the GaN lattice as well as a possible role of magnetic precipitates is discussed. The question as to whether the hole introduced by Mn impurities is localized tightly on the Mn d levels or rather on the hybridized p–d bonding states is addressed. The nature of spin–spin interactions and magnetic phases, as provided by theoretical and experimental findings, is outlined and the possible origins of the high‐temperature ferromagnetism observed in (Ga, Mn)N are presented. Experimental studies aimed at evaluating characteristic times of spin coherence and dephasing in GaN are described. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)