bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of decoherence in a NMR quantum computer using tetrafluoropyridine
Authors: Tei Minaru , Mizuno Yoichi , Manmoto Yoshinori , Sawae Ryuichi , Takarabe Kenichi
Published: October 2003

Recently, quantum algorithms have been realized on a quantum computer by using a nuclear magnetic resonance technique. The nuclear magnetic resonance quantum computer (NMR‐QC) consists of nuclear spins of molecules that are coupled by J‐coupling to each other and the nuclear spins take a role of quantum bits (qubits). In performing quantum algorithms on NMR‐QC, the decoherence effects are a key problem. We studied the decoherence effects in the four‐qubit NMR‐QC using the fluorine nuclear spins of tetrafluoropyridine molecules. The nitrogen nuclear spin in the tetrafluoropyridine molecule increases the transverse relaxation rate of nearby fluorine nuclear spins about 10 times because of its quadrupole moment. In this study we evaluated the decoherence effects in the NMR‐QC by utilizing controlled‐not quantum gates. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Interface structures of III–V semiconductor heterostructures
Authors: Kim Seong‐Gon , Kim Sungho , Shen Jun , Nosho B. Z. , Erwin S. C. , Whitman L. J.
Published: October 2003

We report first‐principles calculations of the electronic and geometric structure of the (110) cross‐sectional surfaces on InAs/GaSb superlattices and compare the results to scanning tunneling microscopy images of filled electronic states. We also study the atomic scale structure of (001) interface surfaces and the adsorption of deposited atoms on these surfaces to simulate the process occurring during the heterostructure growth. In both the predicted and measured images the InAs (110) surfaces appear lower than GaSb, a height difference we show is caused primarily by differences in the electronic structure of the two materials. In contrast, local variations in the apparent height of (110) surface atoms at InSb‐ or GaAs‐like interfaces arise primarily from geometric distortions associated with local differences in bond length. We further observed that both Ga‐ and Sb‐terminating (001) surfaces showed dimerization of surface atoms. Ga‐terminating (001) surfaces exhibited substantial buckling of surface atoms while Sb‐terminating (001) surfaces did not show appreciable buckling. The adsorption of arsenic atoms occurred preferably at the bridge sites between the dimerized Sb atoms on Sb‐terminating (001) surfaces. Indium atoms, on the other hand, were observed to have somewhat equal probabilities to be adsorbed at a few different sites on Ga‐terminating (001) surfaces. Our calculated energies for atomic intermixing indicate that anion exchanges are exothermic for As atoms on Ga‐terminating (001) interfaces but endothermic for In atoms on Sb‐terminating (001) interfaces. This difference may explain why GaAs interfaces are typically more disordered than InSb interfaces in these heterostructures. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Electronic polarization of 1H‐benzotriazole in water: Ground and first excited‐state dipole moments
Authors: Ludwig Valdemir , Coutinho Kaline , Borin Antonio Carlos , Canuto Sylvio
Published: October 2003

Sequential Monte Carlo and quantum mechanical calculations of the electronic polarization of the ground and first vertical excited states of 1H‐benzotriazole in water are made. Using statistically uncorrelated configurations and CASSCF ab initio calculations the increase in the ground and excited state dipole moments of 1H‐benzotriazole from gas phase to aqueous environment are obtained as 2.89 ± 0.10 and 2.75 ± 0.11 D, leading to total moments of 6.89 ± 0.10 and 6.40 ± 0.11 D, respectively. Structures are sampled using the statistical correlation interval obtained from the autocorrelation function of the energy and statistical convergence of the calculated dipole moments is shown. These water‐polarized dipole moments of 1H‐benzotriazole are used to obtain the solvatochromic shift of the first absorption transition. The resulting theoretical blue shift of 570 cm−1 for the strong and characteristic π → π* transition is in good agreement with the inferred experimental value of ∼700 cm−1. The use of the gas‐phase values of the dipole moments are useful for the qualitative understanding of the shift but the polarization of the solvent is required to achieve quantitative agreement. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
One‐ and two‐exciton migration dynamics of a dendritic molecular aggregate
Authors: Takahata Masahiro , Nakano Masayoshi , Yamada Satoru , Yamaguchi Kizashi
Published: October 2003

The two‐exciton dynamics in a dendritic molecular aggregate composed of monomers coupled with each other by the dipole–dipole interaction is performed to investigate the effect of two‐exciton states on the exciton migration using the master equation approach. Although the spatial unique feature of exciton migration from the periphery to the core in the one‐exciton model is also observed in the two‐exciton model, about 36% of such exciton migration is found to be carried out by the relaxation among two‐exciton states in the present model. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Time‐dependent density functional theory calculations of X‐ray absorption
Authors: Rehr J. J. , Ankudinov A. L.
Published: October 2003

There has been dramatic progress in recent years both in calculations and in the interpretation of X‐ray absorption spectra (XAS). Often an independent‐electron approximation with final state potentials is adequate. However, for soft X‐rays (i.e., energies less than about 1 keV) local field effects can be important. Such local fields arise from the dynamic screening of both the external X‐ray field and the coupling to the core hole created in the absorption process. These effects require a theory that goes beyond the independent‐electron approximation. We developed an efficient approach for treating such effects in molecules and solids based on a generalization of time‐dependent density functional theory (TDDFT), with a local approximation for the screening response. The approach has been implemented in our self‐consistent, real‐space Green's function code FEFF8 in terms of screened dipole transition matrix elements. Typical results are discussed for the XAS of the N4,5 edges of solid Xe and for the L2,3 edges of 3d transition metals. Our approach accounts for the deviations of the L3/L2 intensity branching ratio from the 2:1 value of the independent electron approximation. For the N4,5 edges of Xe, the approach also accounts for the observed fine structure. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Derivation and efficient implementation of a recursion formula to calculate harmonic Franck–Condon factors for polyatomic molecules
Authors: Hazra Anirban , Nooijen Marcel
Published: October 2003

We present a simple derivation of a recursion formula for calculating harmonic Franck–Condon (FC) overlap integrals for polyatomic molecules. We also provide an efficient algorithm for computer implementation of the recursion formula. The algorithm resolves the problems associated with earlier implementations and has the following features: (1) It allows obtaining convergence of the series of FC overlap integrals to the degree desired (the measure of convergence is the sum of the FC factors, which is unity for the converged series); (2) the maximal number of quanta in the normal modes does not have to be specified a priori; (3) there is no computer memory bottleneck to do large FC calculations with many normal modes; (4) the algorithm uses binary trees to store data, thus making data retrieval fast and the algorithm highly efficient. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
n‐Electron problem and its formulation in terms ofk‐particle density cumulants
Authors: Kutzelnigg Werner
Published: October 2003

Approaches to the solution of then‐electron problem in terms of the reducedk‐particle density matricesγkor their cumulantsλkare critically reviewed. The advantages of a cumulant‐based theory are outlined, especially its extensivity, which implies a connected‐diagram theorem. A perturbative analysis of the hierarchy ofk‐particle approximations, based on the irreducible contracted Schrödinger equations (ICSEk) (which are conditions for the stationarity of the energy), reveals that the three‐particle approximation is necessary to obtain the energy correct to the MP2 (second‐order Møller–Plesset) level. This disqualifies the naive use of thek‐particle hierarchy, in a linearly converging iterative scheme, as ineffective (compared, e.g., to coupled‐cluster theory). A promising alternative is, however, a quadratically convergent iterative scheme based on successive unitary transformations in Fock space. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Monte Carlo Wave Function (MCWF) approach to dissipative quantum systems interacting with a single‐mode quantized field
Authors: Nakano Masayoshi , Yamaguchi Kizashi
Published: October 2003

We investigate the quantum dynamics of a dissipative molecular system interacting with a single‐mode coherent field (with an initial average photon number 8) using the Monte Carlo wave function (MCWF) method. As quantum dissipation, we consider cavity relaxation (the dissipation of an internal single mode to outer mode) and molecular population relaxation and molecular coherent (phase) relaxation caused by nuclear vibration. In this study, we elucidate the effects of these dissipations on the unique quantum dynamic behaviors of this coupled system, e.g., collapse–revival behavior of Rabi oscillations, using the diagonal and off‐diagonal molecular density matrices. It is found that although slight cavity relaxation suppresses the revival of molecular population similarly to other relaxation effects with larger decay rates the cavity relaxation hardly suppresses the increase in the off‐diagonal molecular density matrix (representing the degree of coherency between the ground and excited states) in the quiescent region, the feature of which is related to the generation of the Schrödinger cat state, in contrast to molecular phase and population relaxations. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
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

We 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

Electron–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

Quantitative 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

Graphical 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

The 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

Stabilization 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

In 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

The 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

This 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

This 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

Ein 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

Eine 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

The 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

Die 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

Membranpumpen 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.
Glacial flow of floating marine ice in “Snowball Earth”
Authors: Goodman Jason C. , Pierrehumbert Raymond T.
Published: October 2003

Simulations of frigid Neoproterozoic climates have not considered the tendency of thick layers of floating marine ice to deform and spread laterally. We have constructed a simple model of the production and flow of marine ice on a planetary scale, and determined ice thickness and flow in two situations: when the ocean is globally ice‐covered (“hard snowball”) and when the tropical waters remain open (“soft snowball”). In both cases, ice flow strongly affects the distribution of marine ice. Flowing ice probably carries enough latent heat and freshwater to significantly affect the transition into a Snowball Earth climate. We speculate that flowing marine ice, rather than continental ice sheets, may be the erosive agent that created some Neoproterozoic glacial deposits.
Modeling the drift of ridged sea ice: A view from below
Authors: Debernard Jens
Published: October 2003

The influence of long parallel pressure‐ridge keels on the ice‐water drag and the fluid velocity under ice in a rotating, non‐stratified ocean is studied using a numerical model. Turbulence in the water is modeled by a two‐equation eddy‐viscosity model, designed for adverse pressure‐gradient flow along both smooth and rough ice without assuming the logarithmic law‐of‐the‐wall to be valid. The simulations show the violation of this law in flow beneath the ice keels. The numerical results demonstrate that the orientation of the ice keels relative to the ice‐drift direction and the ice keel depth have a significant influence on the ice‐water drag coefficient, the drag‐turning angle, the near‐ice velocity and the turbulence fields. Application to free‐drifting, wind‐driven sea ice yields changes in the deflection angle between the wind stress and ice‐drift directions of about 40°, depending on the pressure‐ridge orientation relative to the drift direction. In addition, the results define a region where the ice‐drift direction is sensitive to changes in the wind stress direction.
Equilibrium surface elevation distribution in a baroclinic ocean with realistic bottom topography
Authors: Dobricic Srdjan
Published: October 2003

The objective of this study is to theoretically determine the equilibrium surface elevation distribution for the given density field in the ocean with the realistic bottom topography. It is first experimentally demonstrated in a barotropic ocean model experiment that during the process of the geostrophic adjustment in the ocean with the realistic bottom topography the equilibrium surface elevation rapidly adjusts to the most stable state independent of initial conditions. It follows from this result that in a baroclinic ocean the equilibrium gradient of the potential energy that can be converted into the kinetic energy of the vertically averaged flow is rapidly minimized, giving the theoretical solution for the equilibrium surface elevation field. This application of the minimum potential energy principle is experimentally validated in a numerical model simulation of the free surface geostrophic adjustment in the North Atlantic.
Reflected and locally wind‐forced interannual equatorial Kelvin waves in the western Pacific Ocean
Authors: Boulanger Jean‐Philippe , Cravatte Sophie , Menkes Christophe
Published: October 2003

Evaluating long equatorial wave reflections at the Pacific western boundary has been a concern for many past studies in order to discuss whether the delayed action oscillator mechanism may indeed be at work to terminate El Niño events. In the present study, we investigate the respective contributions of Rossby wave reflection and wind forcing in the generation of interannual long equatorial Kelvin waves in the western Pacific Ocean using satellite data over the 1993–2001 period. The reflection efficiency of the western Pacific boundary (east of 165°E) is found to be about 80–90% of a perfect wall at interannual timescales. This result would suggest that the delayed action oscillator mechanism is indeed at work during that period. However, the wind contribution increases significantly from 145°E to 175°E and actually represents more than 80% of the Kelvin wave variance at 175°E. As a conclusion, although Rossby wave reflection is efficient and sufficient to theoretically terminate an El Niño event, easterly wind anomalies in the western Pacific during the mature phase of the 1997–1998 event mostly contribute to the upwelling Kelvin signal involved in the termination of the event confirming previous studies mainly based on other methods. If such a mechanism were found to be at work during other El Niño events, then the negative feedback mechanism of the delayed action oscillator mechanism would be a combination of easterly wind anomalies and wave reflection with a significant role played by easterly wind anomalies. Our result may support some aspects of the western Pacific oscillator paradigm.
Influence of the North Atlantic SST tripole on northwest African rainfall
Authors: Li Shuanglin , Robinson Walter A. , Peng Shiling
Published: October 2003

The sea‐surface temperature (SST) tripole, with warm anomalies off the east coast of the United States and cold anomalies north of 40°N and south of 25°N, is the leading mode of interannual variability in wintertime North Atlantic SST. Its influence on northwest African rainfall is investigated by using a large‐ensemble of GCM simulations. Firstly the modeled basin‐scale rainfall impact is displayed, and the results suggest: in early‐mid winter (November–January), a positive SST tripole causes a reduced rainfall extending from the tropical North Atlantic northeastward to Mediterranean while a negative SST causes a south‐north increased rainfall across the central Atlantic from the subtropics to the midlatitude. In late winter (February–April) a positive SST tripole causes a reduced rainfall in the central Atlantic from the subtropics to the midlatitude while a negative SST tripole induces a zonal increased rainfall from the subtropics to Mediterranean. The asymmetry and seasonal dependence of the SST influence on the basin‐scale rainfall is consistent with the nonlinear response of the large‐scale atmospheric circulation. Under the large‐scale impact background, northwest Africa regional rainfall response is also nonlinear and seasonally dependent. In early‐mid winter a positive SST tripole causes reduced rainfall, while a negative SST has little effect. In late winter a negative SST tripole induces increased rainfall, while a positive tripole has little effect. A similarly large‐scale asymmetric association between SST and rainfall‐circulation exists in observations in late winter, while the observed seasonal dependence of this association is relatively weak. Also, a similar SST tripole association with the regional rainfall over the northwest coast of Africa exists in observations.
Mineral aerosol particles collected in Dunhuang, China, and their comparison with chemically modified particles collected over Japan
Authors: Trochkine D. , Iwasaka Y. , Matsuki A. , Yamada M. , Kim Y.‐S. , Nagatani T. , Zhang D. , Shi G.‐Y. , Shen Z.
Published: October 2003

Continental China has been recognized as one of the most important sources of atmospheric mineral dust particles (called Kosa in Japan, which literally means yellow sand). Many investigators have pointed out the importance of study of the long‐range transport of mineral dust particles and their modifications in this process even during the nondust storm periods. Because of these modifications, particles can change their radiative properties and their ability to be a condensation nucleus. Therefore it is important to examine the composition of individual mineral particles in their source region and compare these particles with those after long‐range transport. A number of investigations have been carried out on the subject; however, the amount of data is still insufficient. Samples of aerosol particles were collected in Dunhuang, China, in different seasons in 2001 and 2002 during the ACE‐Asia campaign. The collected particles were examined using a scanning electron microscope equipped with an energy dispersive X‐ray analyzer. The particles in all the samples were mainly mineral particles. Similar types of mineral particles were found in the free troposphere over Japan. A number of differences were found between the particles collected in China and those collected over Japan, and these differences can be explained by chemical modifications that occurred in the particles during their transport from China to Japan. Approximately 40–45% of mineral particles mixed internally with sulphate during their transport in the troposphere. Also, the particles collected over Japan were found to be different from those obtained in ground‐based measurements in Nagasaki, Nagoya, and Fukuoka, Japan (reported by other research groups). The portion of mineral particles that mixed internally with sea salt and sulphates was considerably smaller than for the samples obtained in Japan near the ground. It is important to take this fact into account while investigating the impact of mineral particles on the biogeochemical cycle and climate.
Path‐averaged ocean measurements in the deep, stratified tidal channel of Hood Canal using acoustical scintillation
Authors: Di Iorio D. , Barton A. D.
Published: October 2003

Path‐averaged current speed, effective refractive index fluctuations, and stratification measurements were made using high‐frequency (67 kHz) acoustical scintillation measurements in the northern entrance to Hood Canal, Puget Sound, Washington. This experiment made use of a four‐transmitter and four‐receiver array configured in a T‐shape; the two‐dimensional feature of this array was designed to measure both along‐channel small‐scale properties as a result of advection and vertical properties as a result of acoustic refraction from temperature/salinity stratification. With long path lengths and stratified conditions, acoustic propagation resulted in multipath arrivals which were separable for most of the measurement period. A maximum likelihood estimation algorithm is developed that tracks both the direct path signal at approximately 25–30 m depth and the upward refracted signal into the near surface and calculates amplitude, phase, and travel time for each. The acoustical signals are then inverted to estimate path‐averaged along‐channel flow properties, turbulent effective refractive index levels, and changes in stratification. Along‐channel flows approach 50 cm s−1, and the acoustic measurement agrees very well with a simple tidal model of the currents and shows some deviations from independent measurements during maximum flood tide. Current velocity contributions to the effective refractive index fluctuations are analyzed, and results indicate that both sound speed and velocity fluctuations contribute to the acoustic scattering. The vertical acoustic arrival angle to first order appears to be a sensitive indicator of small changes in stratification.
Gravity‐wave forcing in the stratosphere: Observational constraints from the Upper Atmosphere Research Satellite and implications for parameterization in global models
Authors: Alexander M. Joan , Rosenlof Karen H.
Published: October 2003

Global models that include parameterized gravity‐wave effects have an excessively broad range of tuning parameters to choose from that allow a very broad range of gravity‐wave momentum forcing distributions. We derive a set of constraints on gravity‐wave characteristics near the tropopause from databased estimates of gravity‐wave effects in the stratosphere. We use 5.6 years of Upper Atmosphere Research Satellite data and UK Met Office‐analyzed wind and temperature fields to first derive estimates of the gravity‐wave mean flow forcing in the stratosphere. We then compare these estimates to a suite of gravity‐wave model calculations to infer the constraints on the gravity‐wave characteristics near the tropopause. These constraints apply to the portion of the gravity‐wave spectrum that dissipates in the stratosphere and does not include those that dissipate and drive the mesosphere. We focus on equatorial and extratropical regions separately and find substantially different wave characteristics between the two. We also find a seasonal variation in gravity‐wave characteristics in the extratropics. Near the equator, gravity waves assist in driving the quasibiennial and semiannual oscillations, and our constraints on “gravity waves” likely include a blend of characteristics of both ordinary gravity waves and some Kelvin‐wave modes. In the extratropics, gravity‐wave forcing primarily assists in the annual winter‐to‐summer transition from westward‐to‐eastward winds.
Gravity wave generation in the lower stratosphere due to passage of the typhoon 9426 (Orchid) observed by the MU radar at Shigaraki (34.85°N, 136.10°E)
Authors: Dhaka S. K. , Takahashi M. , Shibagaki Y. , Yamanaka M. D. , Fukao S.
Published: October 2003

Intense gravity wave activities were investigated in the lower stratosphere during the typhoon 9426. Strong vertical winds were observed just a few hours before the arrival of the typhoon‐center at the MU radar site. About 30 min to 1 hour after the typhoon‐center had passed, a considerable reduction in vertical wind amplitude was detected. Dominant gravity waves showed time period in the range of 7–8 min, 15 min, and 40–60 min in the upper troposphere and lower stratosphere. In the vicinity of the central region of the typhoon, a gravity wave was observed, which was monochromatic in nature with a vertical wavelength ∼3 km between 1.5 km and 23 km height. In the lower stratosphere, the horizontal wavelength for the prominent period was detected in the range of 10–15 km (for 15 min wave period) and 25–50 km (for 40–60 min wave period). The vertical wavelength of these waves was examined from 2.5 km to 4.0 km. In the horizontal direction, the intrinsic group velocity was estimated between 9 ± 2 and 11 ± 2 m/s. Near the tropopause, the average direction of group velocity was assessed at about 20° ± 3° from the horizontal. The generation of gravity wave like features, in the lower stratosphere, is believed induced by convection, as the low temperature of the clouds indicates a deep penetration over the radar region as seen in the satellite GMS images.
Molecular density retrieval and temperature climatology for 40–60 km from SAGE II
Authors: Burton S. P. , Thomason L. W.
Published: October 2003

The Stratospheric Aerosol and Gas Experiment (SAGE) II is a spaceborne solar occultation instrument that makes long‐term stable measurements of atmospheric transmission at seven wavelengths between the ultraviolet and the near infrared. It provides near‐global coverage (from about 75°S to 75°N latitude) and a data record spanning over 18 years starting in late 1984. Recently, a self‐consistent molecular density retrieval was developed which uses SAGE II version 6.10 transmission data above 40 km altitude. Since at this altitude attenuation of solar radiation due to aerosols can be neglected, there is enough independent information in five SAGE II channels (386–600 nm) to separate the absorption due to ozone and nitrogen dioxide from Rayleigh scattering. Vertical inversion to obtain profiles of these quantities from 40 to 60 km proceeds as in the standard SAGE II algorithm, using a matrix of refracted path lengths. The density gradient information for averaged profiles is converted to temperature. The data are sorted into 20° latitude bands from 70°S to 70°N latitude, and the time series are fitted to provide a mean climatology and long‐term trend estimates. The climatology agrees well with published climatologies for the northern midlatitudes and includes results for the other latitude bands as well. Analysis of long‐term variation finds no statistically significant effect from the solar cycle or quasi‐biennial oscillation and no statistically significant trend. An upper bound on a possible cooling trend of 3 or 4 K/decade is derived for high and middle latitudes between 40 and 45 km altitude.
Dynamic science on the Stardust mission
Authors: Anderson John D. , Lau Eunice L. , Bird Michael K. , Clark Benton C. , Giampieri Giacomo , Pätzold Martin
Published: October 2003

Radio Doppler and ranging data at X band (∼8.4 GHz), optical navigation data, and spacecraft attitude control data can be used to characterize the dust environment surrounding comet 81P/Wild 2 and possibly the mass and bulk density of its nucleus. As a secondary objective, a favorable solar conjunction prior to the cometary encounter on 2 January 2004 can be used to sound the Sun's corona at X band.
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