bluuebunny/crossref_metadata_2025 huggingface dataset:
PV thermal systems: PV panels supplying renewable electricity and heat
Authors: van Helden Wim G. J. , van Zolingen Ronald J. Ch. , Zondag Herbert A.
Published: September 2004

With PV Thermal panels sunlight is converted into electricity and heat simultaneously. Per unit area the total efficiency of a PVT panel is higher than the sum of the efficiencies of separate PV panels and solar thermal collectors. During the last 20 years research into PVT techniques and concepts has been widespread, but rather scattered. This reflects the number of possible PVT concepts and the accompanying research and development problems, for which it is the general goal to optimise both electrical and thermal efficiency of a device simultaneously. The aspects that can be optimised are, amongst others, the spectral characteristics of the PV cell, its solar absorption and the internal heat transfer between cells and heat‐collecting system. Another important level of optimisation is for the PVT device geometry and the integration into a system. The electricity and heat demand and the temperature level of the heat determine the choice for a certain system set‐up. With an optimal design, PVT systems can supply buildings with 100% renewable electricity and heat in a more cost‐effective manner than separate PV and solar thermal systems and thus contribute to the long‐term international targets on implementation of renewable energy in the built environment. Copyright © 2004 John Wiley & Sons, Ltd.
Regenbögen in Raum und Zeit: Ultrakurze Laserpulse
Authors: Grunwald Rüdiger , Steinmeyer Günter
Published: August 2004

Fortschritte auf dem Gebiet der Ultrakurzpulslaser stellen an Forschung und Technik neue Herausforderungen hinsichtlich Formung und Diagnostik komplexer Lichtfelder. Für die Kontrolle der zeitlichen und räumlichen Spektraleigenschaften werden neuartige Optiken entwickelt. Spiegel aus Mehrfachschichten mit trickreichem Design gestatten optimale Pulskompression. Mit verbesserter SPIDER‐Technik werden kürzeste Femtosekundenpulse messbar. Dispersionsarme Dünnschicht‐Mikrooptiken erlauben eine Analyse von Wellenpaketen in Raum und Zeit. Mit derartigen Komponenten können auch optische Riesenwellen, so genannte X‐Pulse, erzeugt werden.
Falten und fliegen: Papierflieger und ihre Physik
Authors: Gruber Werner
Published: August 2004

Mit Papierfliegern können wichtige Eigenschaften der Aerodynamik anschaulich vermittelt werden: ein Blatt Papier, ein paar Faltungen und schon kann man experimentieren. Allerdings sind beim Trimmen des Fliegers einige Punkte zu beachten. Besonders wichtig ist die Y‐Stellung der Flügel, die ihm Flugstabilität verleiht. Ist der Flieger fertig, dann gilt es, die dem Modell am besten angepasste Wurftechnik herauszufinden. Dazu variiert man Wurfgeschwindigkeit und Abwurfwinkel. Den Boden kann ein Papierflieger auf vier prinzipiell verschiedenen Flugkurven erreichen: Optimal ist die Gerade, dann fliegt er am weitesten.
Weltlabor im Herzen Europas: 50 Jahre CERN
Authors: Schopper Herwig
Published: August 2004

Vor 50 Jahren wurde unter dem Dach der UNESCO das europäische Teilchenlabor CERN gegründet. Erstes Hauptziel war der Bau des Protonen‐Synchrotrons, das einen Umfang von 200 m hatte und eine maximale Energie von 28 GeV lieferte. Eine neue Ära begann mit dem Protonenbeschleuniger mit einer Energie von 400 GeV, dem Super‐Proton‐Synchrotron, SPS. Mit ihm wurden 1983 die W‐ und Z‐Bosonen der schwachen Wechselwirkung entdeckt. Es folgte 1989 als bislang größte Anlage der Large Elektron‐Positron‐Collider, LEP, mit 27 km Umfang. Er wurde im Oktober 2000 stillgelegt, um im Tunnel Platz für das neue Projekt Large Hadron Collider, LHC, zu schaffen.
Lavalampen: Spielwiese
Authors: Ucke Christian
Published: August 2004

Im Innern eine Lavalampe befinden sich zwei nicht mischbare Flüssigkeiten unterschiedlicher Dichte und unterschiedlicher temperaturabhängiger Wärmeausdehnung. Bei der Erwärmung kommt es zum Auftrieb der “Lava” in der “Matrix.” Für den Dauerbetrieb muss sich die Matrix in ausreichendem Maße abkühlen können, sonst kommt der Vorgang zum Erliegen. Beim Bau einer Riesenlavalampe an der TU München zeigte es sich, dass eine einfache lineare Vergrößerung aller Bauteile nicht zu einer funktionierenden Lampe führt.
Quarks & Gluonen im Superrechner: Quantenchromodynamik auf dem Gitter
Authors: Gattringer Christof
Published: August 2004

Die Quantenchromodynamik (QCD) ist die heute gültige Quantenfeldtheorie der starken Wechselwirkung. Sie beschreibt die Dynamik des Zusammenspiels von Quarks und Gluonen. Weil die Gluonen mit sich selbst wechselwirken können, ist der traditionelle Zugang über eine Störungsentwicklung nur bei sehr hohen Energien anwendbar. Die elegante Übertragung auf ein vierdimensionales Raumzeit‐Gitter macht die QCD der numerischen Berechnung auf Supercomputern zugänglich. Damit können zentrale Probleme wie etwa Hadronmassen oder Matrixelemente bestimmt werden. Heute ist die Gitter‐QCD so weit entwickelt, dass sie ein tieferes Verständnis von der Natur der starken Wechselwirkung ermöglicht.
Hybrid‐Solarzellen mit Nanopartikeln
Authors: Leute Angelika
Published: August 2004

Die organische Photovoltaik auf der Basis halbleitender Polymere bietet eine kostengünstige Alternative zu Solarzellen aus Silizium. Allerdings weisen die organischen Materialien relativ schlechte Ladungstransporteigenschaften auf. Hybrid‐Solarzellen, in denen Polymere mit geeigneten anorganischen Halbleitern kombiniert sind, besitzen einerseits die praktischen Vorteile der Organik und andererseits die hohe Elektronenbeweglichkeit der anorganischen Materialien. Wissenschaftler der Technischen Universität Eindhoven haben kürzlich Hybrid‐Solarzellen vorgestellt, die aus einem halbleitenden Polymer mit Zinkoxid‐Nanopartikeln bestehen.
Gezielte Umladung einzelner Goldatome
Authors: Repp Jascha , Meyer Gerhard
Published: August 2004

Mit einem Rastertunnelmikroskop lassen sich nicht nur Oberflächen atomar abbilden, es kann auch dazu genutzt werden, Atome auf einer Oberfläche zu manipulieren. Auf diese Weise ist es erstmals gelungen, den Ladungszustand einzelner Goldatome zu verändern, ohne diese dabei seitlich zu verschieben.
Besucher vom Mond
Authors: TB
Published: August 2004

Ein in Oman entdeckter Meteorit mit dem Namen Sayh al Uhaymir (SaU) 169 kam vom Mond. Forscher der Universität Bern ermittelten die chemische Zusammensetzung des himmlischen Gesteins und konnten daraus durch Vergleich mit Gestein der Apollo‐Missionen und Satellitendaten den Herkunftsort relativ genau eingrenzen. Demnach stammt SaU 169 aus dem Bereich des 25 km großen Kraters Lalande im Mare Imbrium.
Ein Rastertunnelmikroskop im Selbstbau
Authors: Panzer Oliver , Fuchs Harald
Published: August 2004

Seit Anfang der achtziger Jahre macht das Rastertunnelmikroskop die Untersuchung von Oberflächen mit atomarer Genauigkeit möglich. Engagierte Schüler und Studienanfänger haben nun die Möglichkeit, sich selbst ein Bild des “Sub‐Mikrokosmos” zu machen: die Universität Münster präsentiert im Internet eine komplette Anleitung für den Aufbau eines einfachen Rastertunnelmikroskops für unter 1000 €.
Einstein in Prag
Authors: Hoffmann Dieter
Published: August 2004

Im Dezember 1910 meldete das Prager Tageblatt die Berufung Albert Einsteins als Professor für mathematische Physik an die Deutsche Universität Prag. Doch erst im Januar unterzeichnete der österreichische Kaiser Franz Joseph die Berufungsurkunde, und zum Frühjahrssemester 1911 nahm Einstein seine Tätigkeit in der Moldaumetropole auf.
Schatten, Bild und Spiegelung
Authors: Schlichting H. Joachim
Published: August 2004

Wenn Licht von einer Fläche sowohl spiegelnd als auch diffus reflektiert wird, kann es zu überraschenden Situationen kommen. Spiegelbild und Schatten sehen sich beide oft zum Verwechseln ähnlich – wenn man nicht genau genug hinschaut.
Das Rastertunnelmikroskop – von der Störstellenanalyse zum Nanowerkzeug
Authors: Hennig Jochen
Published: August 2004

Mit dem Rastertunnelmikroskop steht der Forschung ein Instrument zur atomgenauen Oberflächenuntersuchung zur Verfügung, das seit seiner Entwicklung 1982 bereits eine wechselhafte Geschichte hinter sich hat.
Der rastlose Amerikaner
Authors: Loos Andreas
Published: August 2004

In der Schule, die er mit acht Jahren zum ersten Mal von innen sah, hielt man ihn nicht für allzu helle – schließlich hinkte der Kleine oft hinter der Klasse her. Und es hat etwas Tragisches, wenn der wohl berühmteste Erfinder aller Zeiten und Halter von 2000 Patenten im Alter über seinen Vater sagt: “Er dachte, ich sei dumm. Und ich meinte schon fast selbst, ich sei ein Dummkopf.”
Mayonnaise, Aioli & Co
Authors: Vilgis Thomas
Published: August 2004

Hätten Sie einmal Lust auf selbst gemachte Mayonnaise? Oder ein cremiges, nach Knoblauch duftendes Aioli? Mögen Sie Fisch und eine kräftige Remoulade? Kein Problem, vor allem für Physiker, denn sie wissen, was zu tun ist, schließlich gehorchen all diese Kulinarien bestimmten molekularen Prinzipien.
Poly(vinyl acetate‐co‐dibutyl maleate) latex films in the presence of grafted and post‐added poly(vinyl alcohol)
Authors: Wu Jun , Li Huxi , Winnik Mitchell A. , Farwaha Rajeev , Rademacher Jude
Published: August 2004

We describe the synthesis and characterization of a series of poly(vinyl acetate‐co‐dibutyl maleate) [P(VAc‐DBM)] latex particles (monomer molar ratio 10.6:1). One set of samples [high‐MandM250kSDS‐P(VAc‐DBM), gel content 50% and 0%] was prepared in the presence of an anionic surfactant sodium dodecyl sulfate. The other two sets of samples [high‐MandM250kPVOH–P(VAc‐DBM)] were prepared in the presence of poly(vinyl alcohol) (PVOH). These polymers differ in gel content (50 and 0%) and the extent of PVOH grafting (30 and 15%). Polymer diffusion across cell boundaries in the latex films was monitored by fluorescence resonant energy transfer (ET) experiments. First, we examinedM250ksamples in the presence of grafted and post‐added PVOH. The presence of post‐added PVOH (5%) causes a small but detectable retardation on the rate of polymer diffusion, whereas the presence of grafted PVOH (degree of grafting: 15%) significantly promotes the polymer diffusion rate. For the high‐MP(VAc‐DBM), the presence of post‐added PVOH also retards the polymer diffusion. Strikingly, the presence of grafted PVOH (degree of grafting: 30%) in the high‐MPVOH‐P(VAc‐DBM) promotes the polymer diffusion to such an extent that the diffusion was complete in the freshly prepared films. Our data also suggest that under our experimental conditions, the rate of P(VAc‐DBM) diffusion increases with an increase of the degree of PVOH grafting. To confirm these results, we carried out fluorescence microscopy experiments to monitor the fate of PVOH in these latex films and found that in newly formed PVOH–P(VAc‐DBM) films, the PVOH was either uniformly distributed in the P(VAc‐DBM) matrix or the domains were too small to be resolved (i.e., < 0.5 μm). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5005–5020, 2004
Synthesis and characterization of alkylated N‐vinylformamide monomers and their polymers
Authors: Shi Lianjun , Boduch‐Lee Keri A. , Henssler John T. , Beckman Eric J. , Chapman Toby M.
Published: August 2004

N‐alkyl‐N‐vinylformamide monomers (alkyl: n‐butyl, hexyl, decyl, and dodecyl) are synthesized in two steps: first, preparation of N‐vinylformamide potassium salt by the reaction of N‐vinylformamide (NVF) with potassium t‐butoxide, then reaction with alkyl bromide. All four monomers are liquid and are characterized by IR, 1H NMR, 13C NMR, and mass spectra. They exist as rotomers in solution and a 2D NOE experiment on the N‐hexyl containing polymer shows the E isomer to be favored. The polymerizability of the four monomers is from good to fair, depending upon the length of alkyl chain on the N‐atom‐‐the longer the chain length, the lower lower the polymerizability of monomer. The hydrolysis of poly(N‐hexyl‐N‐vinylformamide) and poly(N‐dodecyl‐N‐vinylformamide) under acidic and basic conditions was examined. Studies show that hydrolytic cleavage of formyl groups of poly (N‐alkylated‐N‐vinylformamide) depends on the hydrophobicity of the alkyl substituent on the N‐atom under acidic conditions; both polymers were hydrolyzed to only a minor extent under alkaline conditions. The N‐alkylated monomers can copolymerize with NVF and demonstrate amphiphilic properties. The copolymers demonstrate a critical aggregation concentration above which they can solubilize a water insoluble dye; the N‐hexyl containing copolymer stabilizes a castor oil‐in‐water emulsion. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4994–5004, 2004
D. P. Chatterjee, U. Chatterjee, and B. M. Mandal, "Atom transfer radical polymerization of methyl methacrylate at ambient temperature using soluble Cu(I) complex catalysts formed with mixed ligands of multidentate amines and halide ions," J Polym Sci Part A: Polym Chem (2004) 42(17) 4132–4142
Authors: Chatterjee Dhruba P. , Chatterjee Uma , Mandal Broja M.
Published: August 2004

The original article to which this Erratum refers was published in J Polym Sci Part A: Polym Chem (2004) 42(17) 4132–4142

No abstract.
Gallium nitride nanowires with a metal initiated metal‐organic chemical vapor deposition (MOCVD) approach
Authors: Lee Sang‐Kwon , Choi Heon‐Jin , Pauzauskie Peter , Yang Peidong , Cho Nam‐Kyu , Park Hyo‐Derk , Suh Eun‐Kyung , Lim Kee‐Young , Lee Hyung‐Jae
Published: August 2004

We have studied structural and electrical properties of one dimensionally grown single crystalline gallium nitride (GaN) nanowires (NWs) for nanoscale devices using a metal‐initiated metal‐organic chemical vapor deposition (MOCVD). GaN nanowires were formed via the vapor‐liquid‐solid (VLS) mechanism with gold, iron, or nickel as growth initiators and were found to have triangular cross‐sections with widths of 15 ∼ 200 nm and lengths of 5 ∼ 20 μm. TEM confirmed that the nanowires were single crystalline and were well oriented along the [210] or [110] direction on substrate depending on the metal initiators. For electrical transport properties of un‐doped GaN nanowires, the back‐gated field effect transistors (FET) were also fabricated by standard e‐beam lithography. In our electrical measurement, the carrier concentration and mobility were ≈2 ∼ 4 × 1018 cm–3 and 60 ∼ 70 cm2/V s, respectively. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A study of magnetic clusters in Co‐doped ZnO using neutron scattering
Authors: Lee Hyeon‐Jun , Ryu Gi‐Hun , Kim Sung‐Kyu , Kim Shin Ae , Lee Chang‐Hee , Jeong Se‐Young , Cho Chae Ryong
Published: August 2004

We report on a study of magnetic cluster in Co‐doped ZnO using neutron diffraction. The samples are fabricated by the sol–gel process and the structural properties are characterized by X‐ray diffraction and neutron diffraction. The diffraction data obtained by neutron are compared with the results of X‐ray diffraction and refined by the Rietveld refinement method. The secondary phases are detected by neutron diffraction in above 5 mol% Co‐doping of ZnO samples and the fractions of the phases in the samples are calculated. In particular, the Co metal phase is clearly observed in 30 mol% Co‐doped ZnO. However, these secondary phases are not detected by X‐ray diffraction due to reasons such as X‐ray absorption by CoK‐edge and incoherent X‐ray scattering. We discuss the advantage of using neutron diffraction in studying the secondary phase and suggest the solubility limit of Co‐doping. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence and Raman scattering in Mg and P co‐implanted GaN epitaxial layers
Authors: Liu K. T. , Su Y. K. , Chang S. J. , Onomitsu K. , Horikoshi Y.
Published: August 2004

Optical properties of P–Mg co‐implanted GaN epitaxial layers with P/Mg concentration ratios of 0–0.5 have been studied. It is found that the photoluminescence intensity significantly increases with the P/Mg ratio, probably due to the suppression of N vacancy generation by co‐implanted P atoms. New photoluminescence lines caused by P‐related transitions are observed for samples with a large P/Mg ratio. Unlike the usual donor‐acceptor pair emission peaks, these newly observed peaks exhibit clear red shifts when the temperature is increased. The P‐related emission is found to be associated with the recombination of electrons on the shallow native donors with holes on isoelectronic P traps. The photoluminescence study suggests that the isoelectronic P trap forms a stable charged state in the P–Mg co‐implanted GaN with a hole binding energy of approximately 220 meV. In addition, Raman measurements indicate that the P–Mg co‐implanted GaN layers are to be annealed at 1200 °C for 10s to achieve a sufficient recovery of crystal quality. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photo‐induced absorption change for InGaN film by violet laser diode
Authors: Nomura Masahiro , Arita Munetaka , Ashihara Satoshi , Nishioka Masao , Arakawa Yasuhiko , Shimura Tsutomu , Kuroda Kazuo
Published: August 2004

We have investigated photo‐induced absorption changes for In0.10Ga0.90N multiple quantum wells and a thin film induced by a continuous‐wave (cw) beam and a femtosecond pulse in the violet region. For the thin‐film sample, nearly the same absorption changes were observed in cw pumping and pulse pumping measurements. Screening of the piezoelectric field in InGaN heterostructures causes absorption changes around the band edge. This screening results from spatial separation of electron–hole pairs to the opposite sides of the InGaN epilayer. These spatially separated carriers are trapped in deep levels and maintain the absorption changes. The trapped charges are considered to be thermally excited to the conduction band and diffuse to attain the equilibrium state. This process takes on the order of 100 μs and such a long decay time of absorption changes allows us to have large absorption changes even by low‐intensity cw pumping. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Eu concentration dependence on structural and optical properties of Eu‐doped GaN
Authors: Bang Hyungjin , Morishima Shinichi , Tsukamoto Takaharu , Li Zhiqiang , Sawahata Junji , Seo Jongwon , Takiguchi Mikio , Bando Yoshio , Akimoto Katsuhiro
Published: August 2004

The structural and optical properties of europium‐doped GaN were studied. The Eu‐related luminescence was observed at 622 nm and originated from the intra‐4f transition of the Eu3+ ion. The intensity of the luminescence increased as the Eu concentration increased up to about 3 at%, and then abruptly decreased. In‐situ reflection high‐energy electron diffraction (RHEED) and X‐ray diffraction (XRD) were carried out to study this luminescence quenching, and it was discovered that there is a close relationship between the luminescence intensity at 622 nm and the structural properties. The cause of the concentration quenching is likely related to the polycrystalline growth as well as to the formation of EuN. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Epitaxial growth of hexagonal and cubic InN films
Authors: Nishida K. , Kitamura Y. , Hijikata Y. , Yaguchi H. , Yoshida S.
Published: August 2004

We have grown InN films on 3C‐SiC (001) substrates with and without cubic GaN underlayers by RF‐N2 plasma MBE. It was found that, in the case of direct growth on 3C‐SiC (001), hexagonal InN grows with the crystal orientation as hexagonal InN (1 $ \bar 1 $00)//3C‐SiC (110), while, in the case of the growth on cubic GaN underlayers, cubic InN grows with the crystal orientation as cubic InN (110)//cubic GaN (110). Photoluminescence emissions from the cubic and hexagonal InN films were clearly observed at around 0.7 eV. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effects of strained sapphire (0001) substrate on the structural quality of GaN epilayer
Authors: Cho Yong Suk , Kim Jeakyun , Park Young Ju , Na Hyunseok , Kim Hee Jin , Kim Hyun Jin , Yoon Euijoon , Kim Young Woon
Published: August 2004

We investigated the structural properties of GaN epilayers grown on strained sapphire (0001) substrate by metal‐organic chemical vapor deposition (MOCVD). To minimize the mismatch in lattice constants and thermal expansion coefficients between the sapphire substrate and the GaN epilayer, we imposed the strain onto the sapphire (0001) substrate using high‐energy O+, Cl+, and As+ ion implantation. The strained sapphire surfaces result in the different behaviors of defect generation in the GaN epilayer. Not only the ionic species but also the thickness of the low‐temperature GaN buffer layer on sapphire affected the structural quality of the GaN epilayer. The present results show that O+ ion‐implanted substrate can provide an improved GaN epilayer using only a thin (∼5 nm) buffer layer rather than using a thicker one. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First‐principle study on electronic properties of gallium nitride and aluminium nitride nanowires
Authors: Doi Kentaro , Higashimaki Nobuyuki , Kawakami Yoshihiko , Nakamura Koichi , Tachibana Akitomo
Published: August 2004

In this work, one‐dimensional wire structures of gallium nitride (GaN) and aluminium nitride (AlN) are studied by first‐principle methods. These wire structures have interesting properties different from those of the bulks. We devised two types of wire structures named axial joint model and equatorial joint model. These initial structures are optimized and energy band structures of these optimized structures are calculated. The energy band gaps of GaN nanowires are 0.26 eV in the axial bond model and 0.08 eV in the equatorial one and those of AlN nanowires are 2.68 eV in the axial model and 0.16 eV in the equatorial one. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Polarity control of ZnO films grown with high temperature N‐polar GaN intermediate layers by plasma‐assisted molecular beam epitaxy
Authors: Roh O. H. , Tomita Y. , Ohsugi M. , Wang X. , Ishitani Y. , Yoshikawa A.
Published: August 2004

ZnO epilayers were grown on nitridated c‐Al2O3 substrates by plasma‐assisted molecular beam epitaxy and the effect of the deposition temperature for GaN buffer and/or intermediate layers on the polarity of ZnO epilayer was investigated. First, it was found that the polarity of the ZnO epilayers grown on low temperature‐grown GaN buffer and/or intermediate layers was uncertain and it became often +c polarity, i.e., Zn‐polarity. This seems strange because the polarity of the GaN‐underlying layer was –c polarity, i.e., N‐polarity, and then the polarity of the under layer was not kept unchanged by the following epilayer. On the other hand, when the growth temperature of the GaN buffer/intermediate layer was increased above 850 °C, it was found that the polarity of the GaN layer was followed by the ZnO epilayers; the polarity became –c polarity, i.e., O‐polarity. This reason was estimated by the effect of surface oxides on GaN which were formed just before the deposition of ZnO buffer layer on it. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Direct heteroepitaxial lateral overgrowth of GaN on stripe‐patterned sapphire substrates with very thin SiO2 masks
Authors: Cheong H. S. , Yoo M. K. , Kim H. G. , Bae S. J. , Kim C. S. , Hong C.‐H. , Baek J. H. , Kim H. J. , Yu Y. M. , Cho H. K.
Published: August 2004

Direct heteroeptaxial lateral overgrowth of GaN was performed on sapphire substrates by low‐pressure metalorganic chemical vapor deposition. The substrates were patterned with very thin SiO2 stripes with the thickness of 200∼300 Å. The growth was carried out by a two‐step condition. In the first step for facet‐controlled epitaxy, the formation of a triangular cross‐section of GaN stripes grown directly on the patterned sapphire was achieved to terminate threading dislocations (TDs) in the opening regions on the inclined {11–22} facets. During the second step for lateral growth, the TDs were bended completely by strong lateral overgrowth. The densities of the step terminations in atomic force microscopic images, corresponding screw‐ or mixed‐type TDs were effectively reduced to less than 107 cm–2 over the entire region. The crystallographic tilt between the mask and the opening regions was also well suppressed by using the very thin SiO2 mask as thick as GaN nucleation layer. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Applicability criterion for semiclassical Bohmian dynamics
Authors: Garashchuk Sophya , Rassolov Vitaly A.
Published: August 2004

In this paper we develop a criterion of the applicability for the trajectory‐based semiclassical propagation methods that are exact for Gaussian wavepackets in locally quadratic potentials. The error estimate takes into account a deviation of the wavefunction from the Gaussian form due to the anharmonicity of a potential. The derivation is based on the time‐dependent noncoherent solutions of the Schrödinger equation for a general quadratic potential that form a complete orthonormal time‐dependent basis. The anharmonicity is treated as a time‐dependent cubic perturbation, which is further related to the nonlinearity of a force acting on trajectories. The criterion is expressed in terms of scalar products of the average force, its first moments, and dispersion of the wavefunction and is efficient in the context of dynamics with the Bohmian trajectories. We give an application for the Bohmian dynamics with the approximate quantum potential, for the Gaussian wavepacket dynamics and for the semiclassical initial value representation propagator. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Ensemble‐averaged variational transition state theory with optimized multidimensional tunneling for enzyme kinetics and other condensed‐phase reactions
Authors: Truhlar Donald G. , Gao Jiali , Garcia‐Viloca Mireia , Alhambra Cristobal , Corchado Jose , Luz Sanchez Maria , Poulsen Tina D.
Published: August 2004

This paper provides an overview of a new method developed to include quantum mechanical effects and free energy sampling in calculations of reaction rates in enzymes. The paper includes an overview of variational transition state theory with optimized multidimensional tunneling for simple gas‐phase reactions and then shows how this is extended to incorporate free energy effects and to include protein motions in the reaction coordinate by ensemble averaging. Finally we summarize recent comparisons to experiment for primary and secondary kinetic isotope effects for proton and hydride transfer reactions catalyzed by enzymes. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Theoretical study of stabling function of the NO to the (CH3)3CO · radical
Authors: Zhao Hongmei , Liu Kun , Ma Siyu , Li Zonghe
Published: August 2004

The stabling function of the NO to the (CH3)3CO · radical has been theoretically investigated. Density functional theory (DFT) calculations are performed to optimize the geometries of relevant species. The single‐point energy is evaluated at CCSD(T)/6‐31++G** level. Three reaction channels of (CH3)3CO · + NO in the singlet state are considered. The calculations indicate that NO is a stable reagent of active radical (CH3)3CO. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Neural membrane field effects in a cytoskeleton corral: Microdomain regulation of impulse propagation
Authors: Wallace Ron
Published: August 2004

This article proposes that electrostatic interaction between transiently polarized neural‐membrane ethenes and charged residues of an unfolded ion‐channel protein regulate channel closing and electrical signaling in neurons. Field effects are confined by a cytoskeleton corral that gates movement of membrane lipids from one corralled region to another. Cytoskeleton gating permits stepwise changes in the concentration of unsaturated lipids and thereby modulates ion‐channel activity. The system is hypothesized to operate at axonal branch points where impulse conduction has a low safety factor. Throughout the discussion the A‐current delayed‐rectifier potassium channel is used as an example. Implications of the model for molecular networks are briefly discussed. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Application of transfer Hamiltonian quantum mechanics to multi‐scale modeling
Authors: Mallik Aditi , Taylor DeCarlos E. , Runge Keith , Dufty James W.
Published: August 2004

In quantum mechanical/classical mechanical (QM/CM) partitioning methods for multi‐scale modeling, one is often forced to introduce uncontrolled phenomenological effects of the environment (CM) in the quantum (QM) domain, as ab initio quantum calculations are computationally too intensive to be applied to the whole sample. We propose a method in which two qualitatively different components of the information about the state of the CM region are incorporated into the QM calculations. First, pseudoatoms constructed to describe the chemistry of the nearest‐neighbor exchange interactions replace the atoms at the boundary of the CM and the QM regions. Second, the remaining effect of the CM bulk environment due to long‐range Coulombic interactions is modeled in terms of dipoles. We have tested this partitioning method in a silica nanorod and a three‐membered silica ring for which ab initio quantum data for the whole system are available to assess the quality of the proposed partitioning method. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Fast preparation method of effective pure states for NMR‐quantum computer with controlled‐not gates
Authors: Kawamura Minaru , Sawae Ryuichi , Kumaya Takashi , Takarabe Kenichi , Manmoto Yoshinori , Sakata Toshio
Published: August 2004

A fast method to prepare effective pure states for NMR‐quantum computer in homo‐nuclear spin system is proposed. The temporal averaging method has been introduced to prepare an effective pure state in NMR‐quantum computer, but the method requires many experiments, whose number increases exponentially with the number of quantum bits (qubits), and it seems that a huge number of logical gates are required. The proposed method avoids this problem by eliminating a part of elements in the density matrices. This method requires only one ancillary qubit and two different experiments; the steps have been confirmed to be proportional to the number of qubits up to four‐qubit. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Determination of the absolute configuration of calliactine by quantum chemical calculations
Authors: Voloshina Elena , Raabe Gerhard , Estermeier Michael , Steffan Bert , Fleischhauer Jörg
Published: August 2004

The chiroptical properties of calliactine (2) have been studied experimentally as well as by quantum chemical calculations based on density functional theory (DFT). According to the DFT calculations, the four energetically lowest conformers of the title compound lie within a range of 1.1 kcal/mol and are separated from other conformers by an energy gap of nearly 9 kcal/mol. Based on their geometries, the excitation energies and rotational strengths have been calculated using time‐dependent DFT (TDDFT) and the dipole velocity formalism. The circular dichroism (CD) spectrum of calliactine has been obtained as a Boltzmann‐weighted superposition of the spectra of each of the four structures. By comparison of the calculated and experimental CD spectra, the absolute configuration of calliactine has been elucidated as S. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
J‐model for magnetism and superconductivity of triangular, kagome, and related spin lattice systems
Authors: Yamanaka Shusuke , Yamaki Daisuke , Takeda Ryo , Nagao Hidemi , Yamaguchi Kizashi
Published: August 2004

A previous theoretical model, the J‐model, for superconductivity of triangular, Kagome, and related spin lattice systems, has been reinvestigated in relation to the recent discovery of superconductivity in NaxCoO2 · yH2O. To elucidate a possible interrelationship between magnetism and superconductivity, effective exchange integrals (Jab) for magnetic clusters with triangular lattices are calculated by ab initio generalized Hartree–Fock (GHF) and generalized density functional theory (GDFT) methods through the use of general spin orbitals (GSO). From the computational results, several model Hamiltonians such as J‐ and t–J‐models are derived for elucidation of the electronic properties of molecule‐based materials with triangular, Kagome, and related spin lattice systems. The theoretical possibilities of spin‐mediated superconductivity are examined on the basis of the J‐model in the intermediate region for metal–insulator transitions. The interplay of spin exchange or spin fluctuation and other effects for superconductivity of strong correlation systems is also feasible both on theoretical and on experimental grounds, supporting the cooperative mechanism toward high‐Tc superconductivity. The implications of the calculated results are discussed in relation to theoretical possibilities of non‐Bardeen–Cooper–Schrieffer (BCS) superconductivity on the basis of cooperative mechanisms of electron correlation (or spin fluctuation) and multi‐band effects in magnetic clusters with icosidodecahedral and related symmetries. Noncoplanarity of spins in molecule‐based magnets is finally discussed to elucidate spin chirality, which is related to a persistent electron current and anomalous Hall effect in triangular and Kagome spin lattices. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Testing graphs for colorability properties*
Authors: Fischer Eldar
Published: August 2004

Let P be a property of graphs. An ϵ‐test for P is a randomized algorithm which, given the ability to make queries whether a desired pair of vertices of an input graph G with n vertices are adjacent or not, distinguishes, with high probability, between the case of G satisfying P and the case that it has to be modified by adding and removing more than ϵ() edges to make it satisfy P. The property P is called testable if for every ϵ there exists an ϵ‐test for P whose total number of queries is independent of the size of the input graph. Goldreich, Goldwasser, and Ron [Property testing and its connection to learning and approximation, J ACM 45 (1998), 653–750] showed that certain graph properties, like k‐colorability, admit an ϵ‐test. In Alon, Fischer, Krivelevich, and Szegedy [Efficient testing of large graphs, Combinatorica 20 (2000), 451–476] a first step towards a logical characterization of the testable graph properties was made by proving that all first order properties of type “∃∀” are testable, while there exist first‐order graph properties of type “∃∀” that are not testable. For proving the positive part, it was shown that all properties describable by a very general type of coloring problem are testable. While this result is tight from the standpoint of first order expressions, further steps towards the characterization of the testable graph properties can be taken by considering the coloring problem instead. It is proven here that other classes of graph properties, describable by various generalizations of the coloring notion used in Alon et al. [Combinatorica 20 (2000), 451–476], are testable, showing that this approach can broaden the understanding of the nature of the testable graph properties. The proof combines some generalizations of the methods used in Alon et al. with additional methods. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2005
Monte Carlo calculation using a personal computer for electron probe microanalysis
Authors: Osada Yoshio
Published: August 2004

Monte Carlo simulation for calculating x‐ray spectra under electron impact is carried out by a personal computer. Reduction of the CPU time by reducing the number of incident electrons for calculation is performed. One of the methods used to reduce the number of incident electrons to obtain the results within an acceptable error is provided. We limit the present report to five typical compounds: an oxide (Al2O3), a nitride (TiN), a carbide (Al4C3), a light–light element compound (BN), and a heavy–light element compound (PbS). We calculate the relative x‐ray intensity generated from the five compounds listed above with the change of the number of the incident electrons. The calculated x‐ray intensity is then converted into the mass % by the ZAF method. Comparisons are made between the calculation and experiment for Al4C3 and PbS. It is found that the present Monte Carlo method is useful for investigating a relationship between the number of incident electrons and the acceptable error. The results of 150 incident electrons can be applied in practical analysis, and the calculation time is less than 2 min. Copyright © 2004 John Wiley & Sons, Ltd.
Study of the deterioration of sandstone due to acid rain and humid SO2 gas
Authors: Holynska Barbara , Gilewicz‐Wolter Jolanta , Ostachowicz Beata , Bielewski Marek , Streli Christina , Wobrauschek Peter
Published: August 2004

The aim of this work was to study the deterioration of various kinds of sandstone due to acid rain and SO2 gas. The samples were taken from three quarries in Poland and one sample was from a tomb about 100 years old. To elucidate the mechanism of stone deterioration, simple experiments were performed. The sandstone samples were immersed for several weeks in SO2 aqueous solution of pH ≈ 4. Similar experiments were performed using SO2 aqueous solution of pH ≈ 1.5. The concentrations of Ca, Mg and Fe leached from the sandstone samples were measured with TXRF. An additional experiment was carried out with the use of radioactive 35SO2. The samples were exposed to both 35SO2 aqueous solution and to 35SO2 gas. The autoradiograms obtained from the sample cross‐sections indicated that sulfur penetrated to the interior parts of sandstone samples, especially from SO2 gas. Copyright © 2004 John Wiley & Sons, Ltd.
Inelastic and elastic scattering differential cross‐sections of 59.5 keV photons for Cu and Zn targets
Authors: Şimşek Ö. , Ertuǧrul M. , Budak G. , Karabulut A.
Published: August 2004

Differential cross‐sections for incoherent and coherent scattering of 59.54 keV photons were measured for Cu and Zn targets at scattering angles of 40–135° in a reflection geometry setup with a graded shielding arrangement. The ratio of these cross‐sections, which can be determined with higher precision than absolute values, is given. A method was used to determine differential incoherent and coherent scattering cross‐sections of elements. This method is based on simultaneous measurement of fluorescence radiation and scattered radiation, thus avoiding problems with measuring source strength and source‐to‐detector solid angle. The measurements were performed using a point source of Am‐241 radioisotope and an Si(Li) detector. The experimental results, which complement earlier results, were compared with the theories of incoherent scattering function and form factor. Copyright © 2004 John Wiley & Sons, Ltd.
Quantitative thickness determination using x‐ray fluorescence: application to multiple layers
Authors: Nygård K. , Hämäläinen K. , Manninen S. , Jalas P. , Ruottinen J.‐P.
Published: August 2004

The fundamental parameter method using x‐ray fluorescence was applied to the quantitative determination of single and multiple layer thicknesses using a compact experimental setup. Focused white‐beam radiation was obtained from a high‐voltage Mo x‐ray tube and the fluorescence spectra were acquired using a Peltier‐cooled Si solid‐state detector. The results show that in the case of single layers the accuracy of the thicknesses obtained is very good whereas for multiple layer structures the agreement is poorer, especially for the thinnest layers. This indicates a possible drawback of the standard‐free thickness determination scheme based on fundamental parameters for complex samples. Copyright © 2004 John Wiley & Sons, Ltd.
Fahreignung bei Demenz: Eine Herausforderung für neuropsychologische Diagnostik und Beratung
Authors: Mix Stefan , Lämmler Gernot , Steinhagen-Thiessen Elisabeth
Published: August 2004

Zusammenfassung: Immer häufiger ist die Demenz-Diagnostik und -Beratung mit der Frage der Beurteilung der Fahreignung konfrontiert. Auch wenn eine Demenz im Verlauf sicher zur Fahruntauglichkeit führt, gibt es doch bisher keine verlässlichen Maßstäbe, wann nicht mehr gefahren werden darf. Internationale Studien kommen zu keinen einheitlichen Ergebnissen. Die deutsche Gesetzgebung lässt sowohl dem Kraftfahrer als auch der medizinisch-psychologischen Beurteilung weite Spielräume. So ist eine differenzierte Exploration des kognitiven Leistungsvermögens, der Alltagskompetenz, der Verhaltenskontrolle und der Ressourcen des Betroffenen erforderlich. Erst dann kann eine differenzierte Beratung hinsichtlich der Fahreignung erfolgen. Dies ist eine Herausforderung, für die die Neuropsychologie mit ihrer Kompetenz zum Einsatz quantitativer und qualitativer diagnostischer Verfahren und der Beratung zur Alltagsbewältigung bei hirnorganisch bedingten Behinderungen gut gerüstet ist.
Do Patients Volunteer Their Life Weariness and Suicidal Ideations? A Sri Lankan Study
Authors: Sumathipala Athula , Siribaddana Sisira , Samaraweera Sudath D.
Published: August 2004

Summary: Objectives: Sri Lanka has a high suicide rate. The importance of suicidal ideations and their relationship to the common mental disorders (CMD) have not been adequately explored. This study examined whether patients harboring suicidal thoughts or life weariness would volunteer them. It also examined the relationship between life weariness, suicidal ideations, and the probability of underlying CMD. Method: A case control study was nested within a cross-sectional survey of attendees to the outpatients department in a general hospital. The index group consisted of patients presenting with multiple complaints and repeated visits, the control group was 100 patients randomly selected from a total of 5,767 between 16 and 65 years of age, not fulfilling criteria for the index group. Presence of underlying CMD was assessed by the General Health Questionnaire 30 (GHQ-30). The two groups were compared for symptoms volunteered, response to questions from GHQ-30 on suicidal ideations, and hopelessness. Results: Somatic symptoms were the most common in both groups. Eighty-one patients (81%) in the index group and 34 patients (34%) in the control group had probable CMD. No patient in either group volunteered suicidal ideation as a symptom. However, 59% of index patients and 26% of controls admitted life weariness, and 51/59 index patients and 15/26 controls who had life weariness also had underlying CMD as defined by GHQ scores. Conclusion: Patients who have suicidal thoughts do not volunteer them unless directly asked. There is a strong relationship between suicidal ideation and the probability of underlying CMD.
Psychological and Psychosocial Interventions After Attempted Suicide
Authors: Hepp Urs , Wittmann Lutz , Schnyder Ulrich , Michel Konrad
Published: August 2004

Summary: A literature search was conducted to collect randomized controlled studies evaluating the outcome of psychological and psychosocial interventions after attempted suicide and deliberate self-harm. Twenty-five studies meeting the inclusion criteria were identified. The studies are grouped according to the psychological approach chosen for the intervention. They are discussed with regard to both the various therapeutic strategies and models used, and the repetition of self-harming behavior as the main outcome.
Police Referral to Victim Support
Authors: Winkel Frans Willem , Wohlfarth Tamar , Blaauw Eric
Published: August 2004

One of the basic rights of crime victims granted under victim-orientated legislation introduced during the last 20 years in more than 100 countries worldwide is the right to be referred to victim support by the police. The under-utilization of psychological services by crime victims who are objectively in need of external support is substantial. Current legal procedures tend to perpetuate this unwanted condition. Programs aimed at the early detection and prevention of persistent postvictimization distress are more in line with the ideals of therapeutic jurisprudence. The RISK (10) screening instrument, which was specifically developed to be administered by police officers, may provide a basis for early detection. RISK (10) consists of a selection of 10 Risk factors with prior empirical evidence and theoretical significance. The focus of the present study was to examine the predictive and diagnostic power of RISK (10) components to detect persistent future psychological distress, among other things, in terms of Adjustment Disorder. Analyses were based on a sample of 93 crime victims who participated in the police and (3 months) follow-up parts of the study. Findings provided initial validation for the predictive accuracy of most RISK (10) components, and confirm the diagnostic value (in terms of specificity, sensitivity, positive and negative predictive power) of risk factors, such as engaging in character attributions, upward comparison processes, fatalistic appraisals of the episode, and the initial reporting of expected deficiencies in social support. The clinical utility of RISK (10) for early detection in police stations is confirmed.
Assessing Suicide Risk in Cluster C Personality Disorders
Authors: Chioqueta Andrea P. , Stiles Tore C.
Published: August 2004

Abstract: The aim of the study was to assess suicide risk in psychiatric outpatients with specific cluster C personality disorders (avoidant, dependent, and obsessive-compulsive). A sample of 142 psychiatric outpatients was used for the study. The sample was composed of 87 outpatients meeting diagnostic criteria for a personality disorder and 53 psychiatric outpatients meeting criteria for an axis I disorder only. The results showed that dependent, but not avoidant or obsessive-compulsive, personality disorders, as well as the clusters A and B personality disorders, were significantly associated with suicide attempts. This association remained significant after controlling for both a lifetime depressive disorder and severity of depression for the cluster A and the cluster B personality disorders, but not for dependent personality disorder. The results underline the importance of assessing suicide risk in patients with cluster A and cluster B personality disorders, while the assessment of suicide risk in patients with cluster C personality disorders seems to be irrelevant as long as assessment of a comorbid depressive disorder is appropriately conducted.
What Helps and What Hinders the Process of Surviving the Suicide of Somebody Close?
Authors: Grad Onja T. , Clark Sheila , Dyregrov Kari , Andriessen Karl
Published: August 2004

Abstract: This paper presents similar findings about the lack of support and understanding for people bereaved through suicide from four different countries and reports on each country's unique response to this challenge. This paper reports on presentations made at the conference workshop of the International Association for Suicide Prevention meeting in Chennai in 2001, and on participants' suggestions of how best to help the bereaved.
Blood Types and National Suicide Rates
Authors: Lester David
Published: August 2004

Summary: In a sample of 51 nations, the suicide rates were negatively associated with the proportion of people with Type O blood, while homicide rates were positively associated with this proportion.