bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copper(I) Chelate Complexes with Novel π-Conjugated 1,2-Bis(2-pyridylethynyl)benzene Ligands: Synthesis, Structure, and Reactivity
Authors: Kawano Tomikazu , Kuwana Jun , Shinomaru Tatsuji , Du Chong-Xu , Ueda Ikuo 
Published: April 2003

Abstract
Novel π-conjugated nitrogen ligands, 1,2-bis(2-pyridylethynyl)benzenes, and their Cu(I) complexes have been synthesized and structurally characterized: the reactivity of the complexes for radical cyclization has also been examined.
Conformational Change Forced by Cesium Ion Complexation in Crystal Violet Derivative Possessing Tris(monoaza-15-crown-5) Structure
Authors: Uda Ryoko M , Oue Masatoshi , Kimura Keiichi 
Published: April 2003

Abstract
A Crystal Violet derivative incorporating a tris(monoaza-15-crown-5) structure exhibits an anomalous absorbance change in the absorption spectrum of its acetonitrile solution, which was induced only by cesium ion but not by other alkali metal ions. A consideration about its complex conformation explains the cesium ion specificity and a molecular orbital calculation suggests the correlation between the conformation and absorbance.
Synthesis of PPV-Based Conjugated Oligomer Containing Tropone in Main Chain
Authors: Takagi Koji , Nishikawa Yukimi , Kunisada Hideo , Yuki Yasuo 
Published: April 2003

Abstract
The synthesis of a tropone-containing PPV-based conjugated oligomer by the Wittig polycondensation was investigated, where the tropone unit was introduced as the conjugated segment. Although the NMR and IR studies revealed the low molecular weight of the resulting product, no side reaction toward the carbonyl group in the tropone ring occurred to maintain the tropone structure as evidenced by the MALDI(Matrix-Assisted Laser Desorption Ionization)-TOFMS spectrum. The UV–vis and PL spectra gave preliminary information on the optical property of the tropone-containing conjugated oligomer.
Unique Fluorescent Properties of 1-Aryl-3,4-diphenylpyrido[1,2-a]benzimidazoles
Authors: Hirano Keisuke , Oderaotoshi Yoji , Minakata Satoshi , Komatsu Mitsuo 
Published: April 2003

Abstract
Novel fluorophores, 1-aryl-3,4-diphenylpyrido[1,2-a]benzimidazoles were synthesized. They emit intense blue to green fluorescence in solution (Φ: ca. 0.7) and show weak negative solvatofluorochromism by about 10 nm which was caused by the combination of π–π* and n–π* transitions. In the powdered form, they emit intense fluorescence whose intensity is at least two times stronger than that of Alq3.
Porphyrin Polygons: A New Synthetic Strategy for Cyclic Porphyrin Oligomers Utilizing a Porphyrin Double Decker Structure
Authors: Ikeda Masato , Sugasaki Atsushi , Kubo Yohei , Sugiyasu Kazunori , Takeuchi Masayuki , Shinkai Seiji 
Published: April 2003

Abstract
A novel synthetic scheme for constructing cyclic porphyrin oligomers is presented: bisporphyrin derivative 1 reacts with La(acac)3 in 1,2,4-trichlorobenzene to yield porphyrin polygons, such as cyclic dimer 12·2La(III) and cyclic trimer 13·3La(III).
Microporous Structure of Titanium Oxide Prepared by a Salt Catalytic Sol–Gel Process
Authors: Tanaka Kazuhiko , Murakami Yasushi , Imai Tomohito , Matsumoto Taki , Furuno Shinsuke , Sugimoto Wataru , Takasu Yoshio 
Published: April 2003

Abstract
A microporous structure (dpore &lt; 1 nm) of titanium oxide was synthesized by a salt catalytic sol–gel process of dilute titanium tetra-n-butoxide (Ti(n-C4H9O)4) and H2O solution without any template molecule. The specific surface area of titanium oxide after the calcinations at 300–350 °C was 310 m2 g−1. It decreased significantly by calcinations above 400 °C because the microporous structure collapsed with crystallization into anatase.
Structure of the First Tetranuclear Ni(II) Complex Derived from N-(2-hydroxybenzylidene)-4,6-O-ethylidene-β-d-glucopyranosylamine
Authors: Sah Ajay K , Rao Chebrolu P , Saarenketo Pauli K , Rissanen Kari 
Published: April 2003

Abstract
In order to understand the binding nature of the glycosylamines possessing imine functionality, a novel tetranuclear Ni(II) complex of N-(2-hydroxybenzylidene)-4,6-O-ethylidene-β-d-glucopyranosylamine having twisted Ni4O4 cubane core was synthesized and structurally characterized.
Synthesis of New Photoresponsive Polymers Containing Trifluoromethyl-Substituted Norbornadiene Moieties
Authors: Nagai Takabumi , Shimada Miwa , Nishikubo Tadatomi 
Published: April 2003

Abstract
Polymers containing trifluoromethyl (CF3)-substituted donor−acceptor NBD moieties in the side chain or in the main chain were synthesized by substitution or addition with CF3-NBD-carboxylic acid derivatives, or by polycondensation of CF3-NBD-dicarboxylic acid derivatives, and the durability of the resulting polymers was examined.
Molybdenum Hydrido Complex Containing a Novel Quinquidentate (P,P,Ge,P,P) Ligand
Authors: Minato Makoto , Hirabayashi Ryo , Matsumoto Takaomi , Yamaguchi Yoshitaka , Ito Takashi 
Published: April 2003

Abstract
The reaction of [MoH4(Ph2PCH2CH2PPh2)2] with PhGeH3 or Ph2GeH2 resulted in the formation of a novel molybdenum–germyl complex [MoH3{[Ph2PCH2CH2P(Ph)C6H4-o]2(Ph)Ge-P,P,P,P,Ge}] (4) with a quinquidentate ligand comprised of a P∼P∼Ge∼P∼P framework, where activation of Ge–H bonds, two C–H bonds, and, in the case of Ph2GeH2, a Ge–C bond took place concurrently.
Synthesis and Fluorescence Emission Behavior of anti-[2.3](3,10)Phenanthrenophane: Overlap between Phenanthrene Rings Required for Excimer Formation
Authors: Nakamura Yosuke , Fujii Takahiro , Nishimura Jun 
Published: April 2003

Abstract
Novel anti-[2.3](3,10)phenanthrenophane 3, prepared by the intramolecular [2 + 2] photocycloaddition of 1,3-bis(3-vinyl-10-phenanthryl)propane, exhibited monomer fluorescence. This is in a remarkable contrast with the excimer fluorescence emission from anti-[2.3](3,9)phenanthrenophane 2 with slightly larger overlap between phenanthrene rings than in anti-3.
Pyrolyse organischer Verbindungen im Mikrowellenofen
Authors: Lühken Arnim , Bader Hans Joachim 
Published: April 2003

AbstractDIE PYROLYSE CHEMISCHER VERBINDUNGEN wird im Chemieunterricht in unterschiedlichen Zusammenhängen thematisiert und sollte deshalb auch im Experiment nachvollzogen werden. Beispiele aus dem Bereich der Organischen Chemie sind das Cracken von Erdöl zur Gewinnung von Benzin und die thermische Zersetzung von Ethanol zur Darstellung von Ethen. In der Anorganischen Chemie sind pyrolytische Vorgänge ebenfalls von Bedeutung, werden jedoch meist als Calcinieren oder Brennen bezeichnet.Mit zunehmender Relevanz der Themen „Umweltschutz, Stoffkreisläufe und Recycling”︁ wurden von verschiedenen Autoren auch Experimente zur Pyrolyse von Kunststoffen und Altreifen zur Demonstration des rohstofflichen Recycling ausgearbeitet [z.B. 1‐3].In den Versuchsvorschriften zur Pyrolyse organischer Verbindungen wird das Ausgangsmaterial meist mit einem Wärmeüberträger (z.B. Sand) vermengt und über der Flamme eines oder mehrerer Gasbrenner unter Luftausschluss erhitzt. Die Thermolyse geschieht dann meist an einem ebenfalls erhitzten Festkörper‐Katalysator. Als problematisch erweist sich bei der Durchführung dieser Versuchsvorschriften eine ausreichende Wärmezufuhr für die vollständige Pyrolyse der Materialmenge, da die Wärmeübertragung nicht optimal gelingt.In diesem Beitrag wird eine Methode beschrieben, deren Besonderheit zunächst die Zufuhr der zur Pyrolyse erforderlichen Wärmeenergie durch Mikrowellenstrahlung ist. Dadurch gelingt ein schnelles und gleichmäßiges Erhitzen des Pyrolysematerials. Das eingesetzte Medium zur Wärmeübertragung und dessen hohe Temperatur bedingen ein Produktspektrum, das sich überraschend von dem der klassischen Pyrolyse unterscheidet und zu interessanten Fragestellungen und didaktischen Aspekten führt.
Analytical SPLITT cell fractionation: Linearity and resolution study
Authors: Contado Catia , Dondi Francesco 
Published: April 2003

AbstractIn this paper the analytical SPLITT (split flow thin cell) procedure is used to characterize the percentage composition of micronic polydisperse particulate samples at a given cut‐off size. The linearity and resolution of the separation method have been tested using specifically prepared starch samples, in order to compare the analytical process with two continuous (preparative) SPLITT procedures. Linearity has been checked by injecting a series of suspensions (at different concentrations) under five different flow rate conditions. Retrieval factors F were evaluated to verify the relative amount of sample exiting the cell outlets. The effective resolution has been assessed by inspecting the SPLITT fractions with an optical microscope, counting the granules, and evaluating the percentage of granules of expected size. It has been found that the resolution is very good (around 90%) and independent of sample distribution. It is seen from the comparison that in the analytical SPLITT mode sample resolution is usually around 85–90% and it is significantly better than that of the continuous SPLITT modes, thus making the analytical mode valuable in characterizing polydisperse samples. The method was tested for the characterization of a commercial starch sample.
Optimization of headspace sampling using solid‐phase microextraction for chloroanisoles in cork stoppers and gas chromatography–ion‐trap tandem mass spectrometric analysis
Authors: Bianchi Federica , Careri Maria , Mangia Alessandro , Musci Marilena 
Published: April 2003

AbstractIn a study aiming to characterize cork off‐flavour for quality control purposes, chloroanisoles were extracted and identified from cork stoppers by means of solid‐phase microextraction (SPME)–gas chromatography–ion‐trap mass spectrometry (GC–ITMS). An experimental design procedure was used to investigate the effects of some experimental parameters on the SPME of 2,4‐dichloroanisole, 2,6‐dichloroanisole, and 2,4,6‐trichloroanisole from cork stoppers by using a Carboxen‐PDMS 75 μm fibre. Variables such as extraction temperature, extraction time, and percentage of ethanol added to the matrix were optimized to improve extraction efficiency of chloroanisoles onto SPME fibre. Instrumental analysis was performed by GC–ITMS in the MS/MS mode. Preliminary analyses on standard solutions allowed selection of the appropriate ionization mode (i. e. electron impact or chemical ionization), providing for each analyte the highest instrumental response. In order to find polynomial functions describing the relationships between variables and responses, the analytical responses, i.e. the chromatographic peak areas, were processed by using the backward multiple regression analysis. For all the analytes the operating conditions providing the highest extraction yield inside the experimental domain considered were found.
HPLC of humic substances fractionated by Flow FFF
Authors: Benincasa Maria‐Anna , Cartoni Giampaolo , Imperia Nadia 
Published: April 2003

AbstractThis communication reports a study of the effect of ionic strength and electrolyte composition on fractions, separately collected by flow FFF, of a mixture of humic substances. Reverse phase HPLC analysis of three early eluting fractions suggests that the components released by the column behave as organic acids. The baseline‐resolved peaks of the first two fractions, subject to higher retention in solutions of lower pH and/or higher polarity, substantiate this suggestion. The fraction with larger components, as measured by flow FFF, also appears to contain acidic species. Their retention level, however, may not be accurately modulated by varying the mobile phase properties as these species are either totally retained in acidic phases or released before the void peak at pH ≥ 4.2. Besides showing the effective separation achieved in the flow FFF channel, this study reveals the pronounced difference in the physicochemical properties of some components of a humic mixture even with very close particle size.
Novel Biodegradable and Thermosensitive Dex‐AI/PNIPAAm Hydrogel
Authors: Zhang Xian‐Zheng , Wu Da‐Qing , Sun Guo‐Ming , Chu Chih‐Chang 
Published: April 2003

AbstractThe dextran‐allyl isocyanate/poly(N‐isopropylacrylamide) (Dex‐AI/PNIPAAm) hydrogel was designed and prepared by copolymerization of the modified dextran with N‐isopropylacrylamide (NIPAAm). This novel Dex‐AI/PNIPAAm hydrogel is biodegradable and intelligent due to its biodegradable dextran linkage and thermosensitive PNIPAAm moiety. With an increase in dextran content, it exhibits the increased lower critical solution temperature (LCST) and decreased porous microstructure. Also, the thermosensitivity of this hydrogel is also controllable and adjustable depending on the different compositions.SEM micrographs of the Dex‐AI/PNIPAAm hydrogels.magnified imageSEM micrographs of the Dex‐AI/PNIPAAm hydrogels.
Conical diffraction by periodic structures: Variation of interfaces and gradient formulas
Authors: Elschner J. , Schmidt G. 
Published: April 2003

AbstractThis paper studies the dependence of solutions to conical diffraction problems upon geometric parameters of non–smooth profiles and interfaces between different materials of diffractive gratings. This problem arises in the design of those optical devices to diffract time–harmonic oblique incident plane waves to a specified far–field pattern. We prove the stability of solutions and give analytic formulas for the derivatives of reflection and transmission coefficients with respect to Lipschitz perturbations of interfaces. These derivatives are expressible as contour integrals involving the direct and adjoint solutions of conical diffraction problems.
On 1–dimensional dissipative Schrödinger–type operators their dilations and eigenfunction expansions
Authors: Kaiser H.–Ch. , Neidhardt H. , Rehberg J. 
Published: April 2003

AbstractWe study in detail Schrödinger–type operators on a bounded interval of R with dissipative boundary conditions. The characteristic function of this operator is computed, its minimal self–adjoint dilation is constructed and the generalized eigenfunction expansion for the dilation is developed. The problem is motivated by semiconductor physics.
Strategien zur Verbesserung der Fahrdynamik durch aktive Stelleingriffe an den Rädern
Authors: Heinzl Ph. , Plöchl M. , Lugner P. 
Published: April 2003

AbstractDurch aktive Eingriffe eines Regelungssystems in die Fahrdynamik eines Kraftfahrzeugs können kritische Fahrsituationen verhindert oder der Fahrer bei der Bewältigung dieser unterstützt werden. Ein solches System beeinflußt in der Regel aktiv die Gierbewegung des Fahrzeugs. Als Erweiterung scheint es aber sinnvoll, auch den Schwimmwinkel des Fahrzeugs zu regeln. Dieser kombinierten Regelung ist ein ABS überlagert, das die vom Fahrer oder Regler vorgegebenen Bremsmomente beschränkt.Der simulierte Regelkreis besteht aus einem Fahrzeugmodell mit ausreichend genau abgebildeten Reifenkräften, aus einem Zustandsbeobachter zur Schätzung des Schwimmwinkels und einem Gleitregler (sliding control). Der Ausgang des Reglers ist eine Kombination zweier der drei möglichen Stelleingriffe: Zusatzlenken der Vorderräder, der Hinterräder und im Falle des einseitigen Zusatzbremsens ein zusätzliches Giermoment. Die Simulationsergebnisse der Fahrmanöver ‘Lenkwinkelsprung’ und ‘Bremsen in der Kurve’ veranschaulichen die Verbesserung der aktiven Fahrsicherheit durch alle drei möglichen Regelstrategien; bei starkem Kurvenbremsen verhält sich die Kombination Zusatzlenken der Vorderräder und Zusatzbremsen ungünstiger als die beiden anderen Kombinationen zufolge der Stellgrößenbeschränkung des übergeordneten ABS.
Low‐rank approximation of FE matrix inverses for operators with jumping coefficients
Authors: Bebendorf M. , Hackbusch W. 
Published: April 2003

AbstractThis article deals with the existence of blockwise low‐rank approximants, so called ℋ︁‐matrices, to inverses of FE matrices in the case of uniformly elliptic operators with L∞‐coefficients. Unlike operators arising from boundary element methods for which the ℋ︁‐matrix theory has been extensively developed the inverses of these operators do not benefit from the smoothness of the kernel function. However, it will be shown that this does not affect the existence of low‐rank approximants. Numerical examples show the correctness of our estimates.
A Scharfetter–Gummel Type Discretization of the Quantum Drift Diffusion Model
Authors: Pinnau René 
Published: April 2003

AbstractWe derive a generalized Scharfetter–Gummel discretization of the Quantum Drift Diffusion Model in one space dimension. The scheme relies on the introduction of a generalized potential which identifies the quantum drift term. Further, the new scheme is stable in the semiclassical limit recovering the SG scheme for the classical drift diffusion equations. Numerical results for a ballistic diode are presented.
Instability of Unbalance Excited Synchronous Forward Whirl at Rotor‐Stator‐Contact
Authors: Ehehalt Ulrich , Markert Richard 
Published: April 2003

AbstractNormally rotor unbalance causes synchronous forward whirl of rotor‐stator systems, even if rub occurs due to rotorstatorcontact. This synchronous forward whirl has to be stable in order to avoid destructive self‐excited dry friction backward whirl, chaotic motions or sub‐ and superharmonic vibrations. However, friction between rotor and stator can cause the synchronous forward whirl to become unstable within certain rotor speed ranges. In the present paper the stability of the synchronous forward whirl caused by unbalance is investigated for rotor motions under contact with the stator. To analyse the stability of synchronous forward whirl the equations of motion are linearised around the stationary synchronous motion. The characteristic polynomial of the perturbations is calculated and the stability is checked by the Hurwitz criterion.
Prevention of Stick‐Slip Vibrations by Passive Normal Force Control
Authors: Rudolph Martin , Popp Karl 
Published: April 2003

AbstractThe classical stick‐slip oscillator is extended by an additional degree of freedom which couples the slipping motion to the normal force. Using this, the effective friction force can be altered without changing the friction‐velocity characteristic. The paper deals with the optimization problem of finding parameters of the additional system that prevent stick‐slip motion or minimize the amplitude of the residual limit cycle. Another goal is to increase the decay rate of vibration. Results were achieved by numerical integration based on analytical investigations.
Vertikaldynamik von Straßenfahrzeugen mit Gas‐Feder‐Dämpfer‐Elementen
Authors: Duwensee Maik , Heim Andreas , Woernle Christoph 
Published: April 2003

AbstractGas‐Feder‐Dämpfer‐Elemente (GFD) sind Luftfedern, die mittels pneumatischer Drosseln bedämpft werden, wodurch separate Schwingungsdämpfer entfallen. Sie stellen ein neues Bauelement zur Aufbaufederung und Dämpfung im Fahrzeug dar. Um sie der Simulation z.B. in einem Viertelfahrzeug‐Schwingungsmodell zugänglich zu machen, muss ihr Verhalten mathematisch modelliert werden. Ihr Steifigkeits‐ sowie Dämpfungsverhalten bei unterschiedlichen Anregungsfrequenzen wird vorgestellt.
Erzwungene Schwingungen von elastischen Mehrkörpersystemen mit Reibkontakten
Authors: Genzo A. , Sextro W. , Popp K. 
Published: April 2003

AbstractIm Folgenden wird eine Berechnungsmethode vorgestellt, die es erlaubt, das räumliche Schwingungsverhalten eines elastischen Mehrkörpersystems (EMKS) mit Reibkontakten in rechenzeit‐ und speicherplatzsparender Form zu analysieren. Der von trockener Reibung und Mikroschlupf geprägte, nichtlineare Dämpfungsmechanismus in den Reibkontakten eines EMKS wird dabei realitätsnahe abgebildet. Die Plausibilität der mit der Methode gewonnenen Berechnungsergebnisse wird beispielhaft an einem einfachen EMKS, einem in Längsrichtung geteilten, einseitig eingespannten Balken gezeigt. Für den geteilten Balken werden die Frequenzgänge des Torsionswinkels um die Längsachse und der Auslenkung um die biegeweiche Achse berechnet.
Adaptive Schwingungskompensation eines Parallelroboters
Authors: Schüller J. , Rose M. , Sachau D. 
Published: April 2003

AbstractBei der Entwicklung von Parallelrobotern stehen vor allem hohe Geschwindigkeiten und Beschleunigungen im Vordergrund, wie sie im Anwendungsfeld der Handhabung und Montage erforderlich sind. Das Streben nach immer leichteren Bauweisen bedingt hierdurch zwangsläufig eine größere Schwingungsanfälligkeit der einzelnen Elemente. In diesem Zusammenhang wird eine ebene und geschlossene kinematische Kette als Vorstudie zur Parallelrobotik untersucht. Mit adaptiven Stäben wird eine aktive Schwingungsreduktion des Robotors realisiert. Das System liegt als elastisches Mehrkörpermodell vor. Anhand der linearisierten Systemgleichungen wird die Beobachtbarkeit und die Steuerbarkeit der Struktur in verschiedenen Posen betrachtet. Mit einer prädiktiv adaptiven Zustandsregelung wird eine aktive Schwingungskompensation des Ende.ektors erreicht und in der nichtlinearen Simulation überprüft.
Construction of polyconvex, anisotropic free‐energy functions
Authors: Schröder J. , Neff P. 
Published: April 2003

AbstractThe existence of minimizers of some variational principles in finite elasticity is based on the concept of quasiconvexity, introduced by Morrey [6]. This integral inequality is rather complicated to handle. Thus, the sufficient condition for quasiconvexity, the polyconvexity condition in the sense of Ball [1], is a more important concept for practical applications, see also Ciarlet [4] and Dacorogna [5]. In the case of isotropy there exist some models which satisfy this condition. Furthermore, there does not exist a systematic treatment of anisotropic, polyconvex free‐energies in the literature. In the present work we discuss some aspects of the formulation of polyconvex, anisotropic free‐energy functions in the framework of the invariant formulation of anisotropic constitutive equations and focus on transverse isotropy.
Zum reversiblen thermomechnischen Kopplungseffekt bei idealen Kristallen
Authors: Schweizer B. , Wauer J. 
Published: April 2003

AbstractDurch eine spezielle Analyse von Gitterschwingungen wird der thermomechanische Kopplungseffekt (Gough‐Joule‐Effekt) bei Festkörpern untersucht. Verwendet wird ein nichtlineares, unkorreliertes Teilchenmodell, das sog. Einstein‐Modell. Die Berechnung beschränkt sich auf ideale Kristalle mit nur einer Sorte von Gitterteilchen (Debyescher Festkörper). Ein Vergleich zwischen der bekannten makroskopischen Theorie und den hier vorgestellten mikroskopischen Ergebnissen wird gezogen.
Numerische Berechnung von Mikrostrukturen bei inelastischen Materialien mittels relaxierter Energien
Authors: Hoppe U. , Hackl K. 
Published: April 2003

AbstractDie Verwendung eines inkrementellen Variationsprinzips ermöglicht die Berechnung der Mikrostrukturentwicklung bei inelastischen Materialien. Das Berechnungsverfahren beruht auf einer partiellen Rang‐1‐Konvexifizierung der reduzierten Energiefunktion und wird numerisch als globales Minimierungsproblem umgesetzt. Die Schwierigkeiten hinsichtlich der globalen Minimierung werden diskutiert.