bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spin correlation functions by generalized spin orbital density functional and multireference approaches
Authors: Yamanaka S. , Takeda R. , Kawakami T. , Nakano S. , Yamaki D. , Yamada S. , Nakata K. , Sakuma T. , Takada T. , Yamaguchi K. 
Published: October 2003

AbstractWe presented the comparative study of spin correlation functions of generalized spin orbital density functional theory (GSO‐DFT) and configuration interaction (CI) wave function (WF) approaches, in particular for simple models. The differences between them are ascribed to that of their symmetry frameworks, which is similar to that between the Heisenberg (HB) model and its mean‐field approximation. Therefore, the prescriptions to spin‐frustrated and ‐degenerated systems are examined from the viewpoint of the HB model and its solutions. Both nondynamic electron correlation and spin‐dependent interactions are found to be important in the surface crossing regions. The GSO complete‐active‐space (CAS) CI and CAS self‐consistent field (SCF) are also discussed as the multireference approaches for the systems. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Energy relaxation dynamics and universal scaling laws in organic light‐emitting diodes
Authors: Bittner Eric R. , Karabunarliev Stoyan 
Published: October 2003

AbstractElectron–hole (e–h) capture in luminescent conjugated polymers (LCPs) is modeled by the dissipative dynamics of a multilevel electronic system coupled to a phonon bath. Electroinjected e–h pairs are simulated by a mixed quantum state, which relaxes via phonon‐driven internal conversions to low‐lying charge‐transfer (CT) and excitonic (XT) states. The underlying two‐band polymer model reflects PPV and spans monoexcited configuration interaction singlets (S) and triplets (T), coupled to Franck–Condon active CC stretches and ring torsions. Focusing entirely upon long PPV chains, we consider the recombination kinetics of an initially separated CT pair. Our model calculations indicate that S and T recombination proceeds according to a branched, two‐step mechanism dictated by near e–h symmetry. The initial relaxation occurs rapidly with nearly half of the population going into excitons (SXT or TXT), while the remaining portion remains locked in metastable CT states. While formation rates of SCT and TCT are nearly equal, SXT is formed about twice as fast TXT in concurrence with experimental observations of these systems. Further, breaking e–h symmetry suppresses the XT to CT branching ratio for triplets and opens a slow CT → XT conversion channel exclusively for singlets due to dipole–dipole interactions between geminate and nongeminate configurations. Finally, our calculations yield a remarkable linear relation between chain length and singlet/triplet branching ratio that can be explained in terms of the binding energies of the respective final excitonic states and the scaling of singlet–triplet energy gap with chain length. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Electronic and charge aspects of potential endocrine disruptors: Applications to pharmacological clustering
Authors: King James W. , Molnar Stephen P. 
Published: October 2003

AbstractQuantitative structure–activity relationships in a series of 37 substituted indoles with endocrine disruptor potential were performed using the structural indices FTe (electronic) and FTc (charge), in conjunction with a clustering technique, to relate substitution patterns to reported relative binding affinities for the calf estrogen receptor. Data clusters were generated by a primary numerically descending sort of the structure indices with a concurrent secondary numerically descending sort of the binding data. Reversal of the numerical descent of the latter served to delineate cluster boundaries. Analysis within the clusters defined the effect of substituents and their molecular positions on the pharmacological data. These results confirmed in detail a similar previous study in the same series using the more general FTm index and again suggested the same structure of a molecule with greater receptor binding ability than any in the database. The methodology used in these studies permits a rational presentation and subsequent interpretation of data that initially appear to be totally random and devoid of recoverable information content. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Quasilocal defects in regular planar networks: Categorization for molecular cones
Authors: Klein D. J. 
Published: October 2003

AbstractGraphical networks are cast into structural equivalence classes, with special focus on ones related to two‐dimensional regular translationally symmetric nets (or lattices). A quasilocal defect in a regular net is defined as consisting of a finite subnet surrounded outside this region by an infinitely extended network of which arbitrary, simply connected regions are isomorphic to those of the regular undefected net. The global equivalence classes for such quasilocal defects are identified by a “circum‐matching” characteristic. One or more such classes are identified as a “turn” number, or equivalently as a discrete “combinatorial curvature” κ, which associates closely to the geometric Gaussian curvature of “physically reasonable” embeddings of the net in Euclidean space. Then for positive κ, geometric cones result; for κ = 0, the network is flat overall; and for negative κ, fluted or crenalated cones result. As κ orqvaries through its discrete range, the number of defect classes varies between 1 and ∞ and repeats with a period depending on the parent regular net. For the square‐planar net, the numbers of defect classes at succeeding turn numbers (q) starting atq= 0 are ∞, 2, 3, 2, repeating with a period of 4. For the hexagonal and triangular nets, the numbers of classes at suceedingqstarting atq= 0 are ∞, 1, 2, 2, 2, 1, repeating with a period of 6. A further refinement of the classes of quasilocal defects breaks these classes up into “irrotational” subclasses, as are relevant for multiwall cones. The subclasses are identified via a “quasispin” characteristic, which is conveniently manipulatable for the categorization of multiwall cones. Besides the development of the overall comprehensive topo‐combinatoric categorization scheme for quasilocal defects, some consequences are briefly indicated, and combining rules for the characteristics of pairs of such defects are briefly considered. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Optimization of numerical orbitals in molecular MO‐LCAO calculations
Authors: Talman James D. 
Published: October 2003

AbstractThe problem of the numerical determination of the atomic orbitals used in the construction of molecular orbitals in MO‐LCAO calculations is studied. This gives rise to a two‐fold optimization problem; the Roothaan–Hall Hartree–Fock problem of minimizing the energy with respect to the molecular orbital expansion coefficients and the variational problem of optimizing the atomic orbitals. The variational equations for the atomic orbitals are derived and the methods of solution described. The methods of computing the required multicenter integrals for numerical orbitals using Fourier transform methods are also reviewed. The calculation of energy gradients within this framework is discussed. Results are presented for a number of small molecules. Possible advantages of this approach are smaller basis sets are required and the wave functions at the nuclei can be much better approximated than with Gaussian‐type orbitals. As well, the fact that orbitals are better approximated implies that basis set superposition errors for dissociation energies calculated in the Hartree–Fock approximation will be reduced. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Utility of chemical indices for transition structures of pericyclic reactions: Case study of the cope rearrangement
Authors: Isobe Hiroshi , Yamanaka Shusuke , Yamaguchi Kizashi 
Published: October 2003

AbstractStabilization effects of nonsynchronous transition structures (TSs) of the Cope rearrangements of phenyl‐substituted 1,5‐hexadienes were examined by the hybrid density functional theory (DFT) and UHF methods. Natural orbital analyses of the hybrid UDFT and UHF solutions were performed to analyze the instability of molecular orbitals at nonsynchronous TSs. It was found that the chemical characteristics at the TSs are made explicit in the behavior of the information entropy and related chemical indices, which are defined by the occupation numbers of natural orbitals. The computational results are discussed in connection with the utility of chemical indices and the applicability of the hybrid DFT methods for pericyclic reactions of large systems. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
On the Stability of Zero Dynamics of a Single‐Link Flexible Manipulator for a Class of Parametrized Outputs
Authors: Yuan K. , Liu L. Y. 
Published: October 2003

AbstractIn order to correct the misinterpretation which has occurred in two recent works concerning the stability of infinite‐dimensional zero dynamics, the stability of zero dynamics of a noncollocated single‐link flexible manipulator is considered in this article for a class of outputs containing a constant parameter. The characteristic equation governing the eigenvalues of zero dynamics is derived. The distribution of these eigenvalues on the complex plane (which depends on the values of the constant parameter) can be found analytically by using the methods of infinite product expansion and root locus. The equivalence of the eigenvalues of zero dynamics and the zeros of the transfer function is also verified. © 2003 Wiley Periodicals, Inc.
Neural Networks Based Control of Mobile Robots: Development and Experimental Validation
Authors: Corradini M. L. , Ippoliti G. , Longhi S. 
Published: October 2003

AbstractThe paper proposes a neural networks approach to the solution of the tracking problem for mobile robots. Neural networks based controllers are investigated in order to exploit the nonlinear approximation capabilities of the nets for modeling the kinematic behavior of the vehicle and for reducing unmodeled tracking errors contributions. The training of the nets and the control performances analysis have been done in a real experimental setup. The proposed solutions are implemented on a PC‐based control architecture for the real‐time control of the LabMate mobile base and are compared with classical kinematic control schemes. Experimental results are satisfactory in terms of tracking errors and computational efforts. © 2003 Wiley Periodicals, Inc.
A Unified Dynamic Model Formulation for Robotic Manipulator Systems
Authors: Swain Anjan Kumar , Morris Alan S. 
Published: October 2003

AbstractThis paper addresses the problem of the formulation of a unified dynamic model for sundry robotic manipulator systems derived from the first principle of mechanics instead of the existing formulation based on linear separability principle. It provides a systematic derivation, evaluation, and subsequent conceptual interpretation of manipulator dynamics model. Further, it analyzes the generality of the unified model over a wide range of manipulator configurations. In addition, it describes the implementation aspects of the unified model. © 2003 Wiley Periodicals, Inc.
Robust Navigation and Mapping Architecture for Large Environments
Authors: Masson Favio , Guivant Jose , Nebot Eduardo 
Published: October 2003

AbstractThis paper addresses the problem of Simultaneous Localization and Mapping (SLAM) for very large environments. A hybrid architecture is presented that makes use of the Extended Kalman Filter to perform SLAM in a very efficient form and a Monte Carlo localizer to resolve data association problems potentially present when returning to a known location after a large exploration period. Algorithms to improve the convergence of the Monte Carlo filter are presented that consider vehicle and sensor uncertainty. The proposed algorithm incorporates significant integrity to the standard SLAM algorithms by providing the ability to handle multimodal distributions over robot pose in real time during the re‐localization process. Experimental results in outdoor environments are presented to demonstrate the performance of the algorithm proposed. © 2003 Wiley Periodicals, Inc.
Experimente zur Gasreibung zwischen 10–3 und 10 mbar bei 330 K. Friction Experiments at 330 K with Gases in the Pressure Range between 10–3 und 10 mbar
Authors: Beyer Chr. , Brezina J. , Engländer H. , Klingner P.J. , Schittko F.J. , Seckel I. 
Published: October 2003

AbstractEin zylinderförmiges Reibsystem wurde auf der Antriebseinheit einer Turbomolekularvakuumpumpe TMP 340 M aufgebaut. Die Versuche befassten sich mit der Gasreibung von Argon, Krypton und Helium im Druckbereich von 10−3 bis 10 mbar. Die innere der zylindrischen Reibflächen war ein CFK Rohr, das im Drehzahlbereich zwischen 220 und 860 Hz rotierte. Die Außenreibfläche im Abstand von 0.4 und später 0.8 mm bildete ein Rohr aus einer Aluminium‐Legierung. Das Gehäuse, in dem das Rohr befestigt war, wurde thermostatisch auf 330 K gehalten. In den Versuchen wurden die auf das rotierende Rohr wirkenden Bremskräfte bestimmt. Die Berechnung der Viskosität erfolgte mit einer einfachen Formel, die sich aus der Definitionsgleichung ableiten ließ. Die Ergebnisse zeigen den Anstieg der Viskosität im Druckbereich zwischen 10−3 und 10 mbar. Als wichtig haben sich Grenzkurvensysteme zwischen Saug‐ und Widerstandsgebieten herausgestellt. Für die Zusammenhänge der Versuchsergebnisse wurden Linearisierungsverfahren versucht. Weiterhin erhielten wir Hinweise auf Grenzschichteffekte.
Hochstrom‐Filterbogen: eine neue Technik zur Abscheidung von Kohlenstoffschutzschichten in der Magnetspeichertechnologie. High Current Filtered Arc: a new Deposition Technique for Protecting Carbon Overcoats in Magnetic Storage Devices
Authors: Petereit B. , Schneider H. H. , Siemroth P. , Hilgers H. 
Published: October 2003

AbstractEine Zunahme der Speicherkapazität auf Magnetspeicherplatten setzt eine Verkleinerung der speichernden, magnetischen Domänen voraus. Damit die dadurch schwächeren Signale dennoch gelesen werden können, muss gleichzeitig der Abstand der Schreib‐Lese‐Köpfe zur Magnetschicht verringert werden. Da zur Funktionalität eine ausreichende Flughöhe der Köpfe eingehalten werden muss, kann eine Abstandsverringerung nur durch eine zusätzliche Verringerung der Schichtdicke der schützenden Kohlenstoffschicht erreicht werden.Zur Abscheidung ultradünnen Kohlenstoffschichten auf Magnetspeicherplatten (Disk) wurde ein gepulster Hochstrom‐Filterbogen (HCA High Current Arc) für den Einsatz in der industriellen Festplattenproduktion untersucht. Die mit der HCA‐Quelle erzeugten Schichten zeigen eine weitaus höhere Kratzhärte und eine vielfach geringere RMS‐Rauhigkeit als konventionell gesputterte Kohlenstoffschichten. Es konnte zudem gezeigt werden, dass die mit dem Hochstrom‐Filterbogen abgeschiedenen, nur 2 nm dicken Kohlenstoffschichten frei von sog. pin‐holes sind und einen ausreichenden Korrosionsschutz aufweisen. Die Abscheiderate der HCA‐Quelle liegt zwischen 0,07 nm und 0,3 nm pro Puls, d. h. für die Beschichtung einer Disk werden weniger als 2 Sekunden benötigt. Die empfindliche Magnetschicht wird durch dieses Verfahren nicht beschädigt. Zur Vermeidung von Makropartikeln wurde ein magnetisches Filtersystem eingesetzt und iterativ weiterentwickelt. Durch wiederholte Versuchsserien mit einem anschließenden Funktionstest (glide yield) der Disks hat sich der magnetische Filter als sehr wirkungsvoll erwiesen.Insgesamt konnte gezeigt werden, dass die HCA‐Quelle eine vielversprechende Technik zur Beschichtung von Kohlenstoffschutzschichten auf Magnetspeicherplatten darstellt. In Testreihen, die den industriellen Produktionskriterien entsprechen, wurde eine Ausbeute an funktionierenden Disks von bis über 90 % erreicht.
Characterisation of amorphous carbon coatings for magnetic storage devices via AFM‐Nanoscratching devices. AFM‐Nanoscratching an amorphen Kohlenstoffschichten für die Speichertechnologie
Authors: Jacoby B. , Wienss A. , v. Gradowski M. , Ohr R. , Petereit B. , Hilgers H. 
Published: October 2003

AbstractThe mechanical properties of ultra‐thin amorphous carbon films used as protective coatings for magnetic storage devices were investigated by means of atomic force microscopy (AFM). Diamond‐tipped cantilevers were used in order to generate scratches with residual scratch depths of only a few Angstroms and even below. The presented method simulates mechanical strains at the head‐disk interface. A driftcompensating image subtracting technique allows the visualisation of these ultra‐shallow scratches and enables the mechanical characterisation of only few Nanometer films widely independent from the hardness of the substrate. The scratch resistance as it is defined here correlates well with the mass density and the sp3 content of the investigated films.
Barriereschichten für medizinische elektronische Implantate. Barrier coatings for medical electronic implants
Authors: Lechleitner T. , Nagl M. , Pulker H.K. , Hochmaier E. 
Published: October 2003

AbstractDie zunehmende Bedeutung von aktiven elektronischen Implantaten in der Medizintechnik und die Fortschritte in der Verpackungstechnologie eröffnen ein neues Anwendungsfeld für langzeitstabile Verpackungen auf Kunststoff‐Basis als Ersatz für die teuren und relativ empfindlichen keramischen Gehäuse. Dazu bietet sich ein Schichtsystem aus hochgefülltem Kunststoff mit mindestens einer anorganischen Barriereschicht an. In diesem Beitrag soll ein möglicher Weg skizziert werden, der zur Zeit an der Universität Innsbruck untersucht wird.
Neue Vorvakuumpumpe: Schnelles Evakuieren dank Membran‐ Stabilisierungssystem. New roughing pump: Fast Evacuation thanks to Diaphragm Stabilization System
Authors: Rothe Uwe 
Published: October 2003

AbstractMembranpumpen werden an Turbo‐Molekularpumpen eingesetzt, um Grobvakuum zu erzeugen. Sie zeichnen sich durch ein hohes Saugvermögen aus, das allerdings bei abnehmendem Arbeitsdruck nachlässt. Die Ursache dafür ist der Unterschied zwischen dem Arbeitsdruck der Pumpe und dem Umgebungsdruck. Je größer dieser Druckunterschied ist, desto stärker beult sich die elastische Membrane aus und verringert das effektive Schöpfvolumen der Pumpe. Abhilfe schafft ein neu entwickeltes Membran‐Stabilisierungssystem. Membran‐Vorvakuumpumpen, die mit diesem System ausgestattet sind, evakuieren schneller als Pumpen ohne das System und gewährleisten aufgrund des besseren Saugvermögens eine höhere Prozesssicherheit.Erstmals kommt das zum Patent angemeldete Membran‐Stabilisierungssystem in einer neuentwickelten Membran‐Vorvakuumpumpe zum Einsatz. Angetrieben wird die Pumpe von einem bürstenlosen Gleichstrommotor mit sehr hohem Wirkungsgrad und geringer Baugröße. Die Pumpe ist in 24 Volt Gleichspannungsausführung und 90 – 264 Volt, 50/60 Hz, Wechselspannungsausführung erhältlich. Einbau‐ und tragbare Versionen stehen zur Wahl.
Antagonists of the κ‐opioid receptor enhance allodynia in rats and mice after sciatic nerve ligation
Authors: Obara I , Mika J , Schäfer M K ‐H , Przewlocka B 
Published: October 2003

The administration of κ‐opioid receptor antagonists, nor‐binaltorphimine (norBNI) and 5′‐guanidinonaltrindole (GNTI) enhanced allodynia in rats and mice after sciatic nerve ligation. In order to understand the mechanism underlying this effect, we examined the possible involvement of the endogenous ligand of κ‐opioid receptor dynorphin.
The experiments were carried out on male Wistar rats and on Albino‐Swiss mice. The rats had been implanted with a catheter 7 days earlier in the subarachnoid space of the spinal cord. Intrathecal (i.t.) administrations in mice were made by lumbar puncture. The animals were i.t. injected with norBNI, GNTI (κ‐opioid receptor antagonists), dynorphin A1–17 antiserum (DYN A/S), ketamine (NMDA receptor antagonist) and their combinations. The nociceptive sensitivity was assessed using the mechanical (von Frey) and therma allodynia tests on days 2–4 and 8–10 after the sciatic nerve ligation.
Both antagonists, norBNI and GNTI, significantly enhanced mechanical and therma allodynia in rats and mice with neuropathic pain. The potentiation of allodynia after the administration of norBNI or GNTI was inhibited by earlier administration of DYN A/S or by ketamine.
Our results suggest that allodynia is mediated through nonopioid effect of the endogenous opioid peptide, dynorphin. The nonopioid action is potentiated by the blockade of κ‐opioid receptors, and corresponding to the elevation of prodynorphin mRNA level in neuropathic pain. Furthermore, the potentiation of allodynia after the administration of the above drugs appears to be mediated through the activation of NMDA receptors directly by dynorphin.

British Journal of Pharmacology (2003) 140, 538–546. doi:10.1038/sj.bjp.0705427
On the selectivity of superoxide dismutase mimetics and its importance in pharmacological studies
Authors: Muscoli Carolina , Cuzzocrea Salvatore , Riley Dennis P , Zweier Jay L , Thiemermann Christoph , Wang Zhi‐Qiang , Salvemini Daniela 
Published: October 2003

The list of pathophysiological conditions associated with the overproduction of superoxide expands every day. Much of the knowledge compiled on the role of this radical in disease has been gathered using the native superoxide dismutase enzyme and, more recently, by the use of superoxide dismutase knockout models or transgenic models that overexpress the various isoforms of the enzyme. Although the native enzyme has shown promising anti‐inflammatory properties in both preclinical and clinical studies, there were drawbacks and issues associated with its use as a therapeutic agent and pharmacological tool. Based on the concept that removal of superoxide modulates the course of inflammation, synthetic, low‐molecular‐weight mimetics of the superoxide dismutase enzymes that could overcome some of the limitations associated with the use of the native enzyme have been designed. In this review, we will discuss the advances made using various superoxide dismutase mimetics that led to the proposal that superoxide (and/or the product of its interaction with nitric oxide, peroxynitrite) is an important mediator of inflammation, and to the conclusion that superoxide dismutase mimetics can be utilized as therapeutic agents in diseases of various etiologies. The importance of the selectivity of such compounds in pharmacological studies will be discussed.British Journal of Pharmacology (2003) 140, 445–460. doi:10.1038/sj.bjp.0705430