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Shah R, Barrett TJ, Colcelli A, Oručević F, Trombettoni A, Krüger P. Probing the Degree of Coherence through the Full 1D to 3D Crossover. Phys Rev Lett 2023; 130:123401. [PMID: 37027886 DOI: 10.1103/physrevlett.130.123401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 08/03/2022] [Accepted: 01/09/2023] [Indexed: 06/19/2023]
Abstract
We experimentally study a gas of quantum degenerate ^{87}Rb atoms throughout the full dimensional crossover, from a one-dimensional (1D) system exhibiting phase fluctuations consistent with 1D theory to a three-dimensional (3D) phase-coherent system, thereby smoothly interpolating between these distinct, well-understood regimes. Using a hybrid trapping architecture combining an atom chip with a printed circuit board, we continuously adjust the system's dimensionality over a wide range while measuring the phase fluctuations through the power spectrum of density ripples in time-of-flight expansion. Our measurements confirm that the chemical potential μ controls the departure of the system from 3D and that the fluctuations are dependent on both μ and the temperature T. Through a rigorous study we quantitatively observe how inside the crossover the dependence on T gradually disappears as the system becomes 3D. Throughout the entire crossover the fluctuations are shown to be determined by the relative occupation of 1D axial collective excitations.
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Affiliation(s)
- R Shah
- Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH, United Kingdom
| | - T J Barrett
- Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH, United Kingdom
| | - A Colcelli
- SISSA and INFN, Sezione di Trieste, Via Bonomea 265, I-34136 Trieste, Italy
| | - F Oručević
- Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH, United Kingdom
| | - A Trombettoni
- SISSA and INFN, Sezione di Trieste, Via Bonomea 265, I-34136 Trieste, Italy
- Department of Physics, University of Trieste, Strada Costiera 11, I-34151 Trieste, Italy
| | - P Krüger
- Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH, United Kingdom
- Physikalisch-Technische Bundesanstalt, 10587 Berlin, Germany
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2
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Simon JM, Krüger P, Schnell SK, Vlugt TJH, Kjelstrup S, Bedeaux D. Kirkwood-Buff integrals: From fluctuations in finite volumes to the thermodynamic limit. J Chem Phys 2022; 157:130901. [PMID: 36209013 DOI: 10.1063/5.0106162] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The Kirkwood-Buff theory is a cornerstone of the statistical mechanics of liquids and solutions. It relates volume integrals over the radial distribution function, so-called Kirkwood-Buff integrals (KBIs), to particle number fluctuations and thereby to various macroscopic thermodynamic quantities such as the isothermal compressibility and partial molar volumes. Recently, the field has seen a strong revival with breakthroughs in the numerical computation of KBIs and applications to complex systems such as bio-molecules. One of the main emergent results is the possibility to use the finite volume KBIs as a tool to access finite volume thermodynamic quantities. The purpose of this Perspective is to shed new light on the latest developments and discuss future avenues.
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Affiliation(s)
- J-M Simon
- Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR-6303 CNRS - Université de Bourgogne Franche-Comté, F-21078 Dijon, France
| | - P Krüger
- Graduate School of Science and Engineering, Molecular Chirality Research Center, Chiba University, Chiba 263-8522, Japan
| | - S K Schnell
- Department of Materials Science and Engineering, NTNU - Norwegian University of Science and Technology, N-7491 Trondheim, Norway
| | - T J H Vlugt
- Process & Energy Department, Delft University of Technology, Leeghwaterstraat 39, 2628CB Delft, The Netherlands
| | - S Kjelstrup
- Center of Excellence PoreLab, Department of Chemistry, Faculty of Natural Sciences, NTNU - Norwegian University of Science and Technology, Trondheim, Norway
| | - D Bedeaux
- Center of Excellence PoreLab, Department of Chemistry, Faculty of Natural Sciences, NTNU - Norwegian University of Science and Technology, Trondheim, Norway
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3
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Zschech E, Löffler M, Krüger P, Gluch J, Kutukova K, Zgłobicka I, Silomon J, Rosenkranz R, Standke Y, Topal E. Laboratory Computed X-Ray Tomography – A Nondestructive Technique for 3D Microstructure Analyis of Materials. ACTA ACUST UNITED AC 2018. [DOI: 10.3139/147.110537] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- E. Zschech
- Fraunhofer Institute for Ceramic Technologies and Systems Dresden , Maria-Reiche-Strasse 2, 01109 Dresden , Germany; e-mail:
| | - M. Löffler
- Dresden University of Technology , Dresden Center for Nanoanalysis, 01062 Dresden , Germany
| | - P. Krüger
- Fraunhofer Institute for Ceramic Technologies and Systems Dresden , Maria-Reiche-Strasse 2, 01109 Dresden , Germany; e-mail:
| | - J. Gluch
- Fraunhofer Institute for Ceramic Technologies and Systems Dresden , Maria-Reiche-Strasse 2, 01109 Dresden , Germany; e-mail:
| | - K. Kutukova
- Fraunhofer Institute for Ceramic Technologies and Systems Dresden , Maria-Reiche-Strasse 2, 01109 Dresden , Germany; e-mail:
| | - I. Zgłobicka
- Warsaw University of Technology , ul. Woloska 141, 02 – 507 Warszawa , Poland
| | - J. Silomon
- Fraunhofer Institute for Ceramic Technologies and Systems Dresden , Maria-Reiche-Strasse 2, 01109 Dresden , Germany; e-mail:
| | - R. Rosenkranz
- Fraunhofer Institute for Ceramic Technologies and Systems Dresden , Maria-Reiche-Strasse 2, 01109 Dresden , Germany; e-mail:
| | - Y. Standke
- Fraunhofer Institute for Ceramic Technologies and Systems Dresden , Maria-Reiche-Strasse 2, 01109 Dresden , Germany; e-mail:
| | - E. Topal
- Dresden University of Technology , Dresden Center for Nanoanalysis, 01062 Dresden , Germany
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4
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Saint R, Evans W, Zhou Y, Barrett T, Fromhold TM, Saleh E, Maskery I, Tuck C, Wildman R, Oručević F, Krüger P. 3D-printed components for quantum devices. Sci Rep 2018; 8:8368. [PMID: 29849028 PMCID: PMC5976634 DOI: 10.1038/s41598-018-26455-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 05/09/2018] [Indexed: 11/18/2022] Open
Abstract
Recent advances in the preparation, control and measurement of atomic gases have led to new insights into the quantum world and unprecedented metrological sensitivities, e.g. in measuring gravitational forces and magnetic fields. The full potential of applying such capabilities to areas as diverse as biomedical imaging, non-invasive underground mapping, and GPS-free navigation can only be realised with the scalable production of efficient, robust and portable devices. We introduce additive manufacturing as a production technique of quantum device components with unrivalled design freedom and rapid prototyping. This provides a step change in efficiency, compactness and facilitates systems integration. As a demonstrator we present an ultrahigh vacuum compatible ultracold atom source dissipating less than ten milliwatts of electrical power during field generation to produce large samples of cold rubidium gases. This disruptive technology opens the door to drastically improved integrated structures, which will further reduce size and assembly complexity in scalable series manufacture of bespoke portable quantum devices.
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Affiliation(s)
- R Saint
- School of Physics and Astronomy, The University of Nottingham, Nottingham, NG7 2RD, United Kingdom
- Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom
| | - W Evans
- School of Physics and Astronomy, The University of Nottingham, Nottingham, NG7 2RD, United Kingdom
- Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom
| | - Y Zhou
- School of Physics and Astronomy, The University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - T Barrett
- School of Physics and Astronomy, The University of Nottingham, Nottingham, NG7 2RD, United Kingdom
- Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom
| | - T M Fromhold
- School of Physics and Astronomy, The University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - E Saleh
- Faculty of Engineering, EPSRC Centre for Innovative Manufacturing in Additive Manufacturing, University of Nottingham, Nottingham, United Kingdom
| | - I Maskery
- Faculty of Engineering, EPSRC Centre for Innovative Manufacturing in Additive Manufacturing, University of Nottingham, Nottingham, United Kingdom
| | - C Tuck
- Faculty of Engineering, EPSRC Centre for Innovative Manufacturing in Additive Manufacturing, University of Nottingham, Nottingham, United Kingdom
| | - R Wildman
- Faculty of Engineering, EPSRC Centre for Innovative Manufacturing in Additive Manufacturing, University of Nottingham, Nottingham, United Kingdom
| | - F Oručević
- School of Physics and Astronomy, The University of Nottingham, Nottingham, NG7 2RD, United Kingdom
- Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom
| | - P Krüger
- School of Physics and Astronomy, The University of Nottingham, Nottingham, NG7 2RD, United Kingdom.
- Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom.
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5
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Dawass N, Krüger P, Schnell SK, Bedeaux D, Kjelstrup S, Simon JM, Vlugt TJH. Finite-size effects of Kirkwood–Buff integrals from molecular simulations. Molecular Simulation 2017. [DOI: 10.1080/08927022.2017.1416114] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- N. Dawass
- Process & Energy Laboratory, Delft University of Technology, Delft, The Netherlands
| | - P. Krüger
- Graduate School of Science and Engineering, Molecular Chirality Research Center, Chiba University, Chiba, Japan
- ICB, UMR 6303 CNRS – Université de Bourgogne, Dijon, France
| | - S. K. Schnell
- Department of Materials Science and Engineering, Norwegian University of Science and Technology, NTNU, Trondheim, Norway
| | - D. Bedeaux
- PoreLab, Department of Chemistry, Norwegian University of Science and Technology, NTNU, Trondheim, Norway
| | - S. Kjelstrup
- Process & Energy Laboratory, Delft University of Technology, Delft, The Netherlands
- PoreLab, Department of Chemistry, Norwegian University of Science and Technology, NTNU, Trondheim, Norway
| | - J. M. Simon
- ICB, UMR 6303 CNRS – Université de Bourgogne, Dijon, France
| | - T. J. H. Vlugt
- Process & Energy Laboratory, Delft University of Technology, Delft, The Netherlands
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6
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Paris-Mandoki A, Shearring J, Mancarella F, Fromhold TM, Trombettoni A, Krüger P. Superfluid flow above the critical velocity. Sci Rep 2017; 7:9070. [PMID: 28831070 PMCID: PMC5567279 DOI: 10.1038/s41598-017-08941-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 07/18/2017] [Indexed: 11/09/2022] Open
Abstract
Superfluidity and superconductivity have been widely studied since the last century in many different contexts ranging from nuclear matter to atomic quantum gases. The rigidity of these systems with respect to external perturbations results in frictionless motion for superfluids and resistance-free electric current flow in superconductors. This peculiar behaviour is lost when external perturbations overcome a critical threshold, i.e. above a critical magnetic field or a critical current for superconductors. In superfluids, such as liquid helium or ultracold gases, the corresponding quantities are a critical rotation rate and a critical velocity respectively. Enhancing the critical values is of great fundamental and practical value. Here we demonstrate that superfluidity can be completely restored for specific, arbitrarily large flow velocities above the critical velocity through quantum interference-induced resonances providing a nonlinear counterpart of the Ramsauer-Townsend effect occurring in ordinary quantum mechanics. We illustrate the robustness of this phenomenon through a thorough analysis in one dimension and prove its generality by showing the persistence of the effect in non-trivial 2d systems. This has far reaching consequences for the fundamental understanding of superfluidity and superconductivity and opens up new application possibilities in quantum metrology, e.g. in rotation sensing.
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Affiliation(s)
- A Paris-Mandoki
- Midlands Ultracold Atom Research Centre, School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom.,5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, 70569, Stuttgart, Germany.,Instituto de Física, Universidad Nacional Autónoma de México, P.O.B. 20-364, Mexico City, 01000, Mexico
| | - J Shearring
- Midlands Ultracold Atom Research Centre, School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - F Mancarella
- Nordic Institute for Theoretical Physics (NORDITA), SE-106 91, Stockholm, Sweden.,Stockholm University, SE-106 91, Stockholm, Sweden
| | - T M Fromhold
- Midlands Ultracold Atom Research Centre, School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - A Trombettoni
- CNR-IOM DEMOCRITOS Simulation Center, Via Bonomea 265, I-34136, Trieste, Italy.,SISSA and INFN, Sezione di Trieste, Via Bonomea 265, I-34136, Trieste, Italy
| | - P Krüger
- Midlands Ultracold Atom Research Centre, School of Physics & Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom. .,Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH, United Kingdom.
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7
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Krüger P, Schmidt F, Otto S, Lange A, Langner S. Röntgenaufnahmen des pädiatrischen Thorax im Kontext der aktuellen Leitlinien der Europäischen Kommission – Sind die Vorgaben in der täglichen Routine realisierbar? ROFO-FORTSCHR RONTG 2017. [DOI: 10.1055/s-0037-1600486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- P Krüger
- Universitätsmedizin Greifswald, Institut für Diagnostische Radiologie und Neuroradiologie, Greifswald
| | - F Schmidt
- Universitätsmedizin Greifswald, Institut für Diagnostische Radiologie und Neuroradiologie, Greifswald
| | - S Otto
- Universitätsmedizin Greifswald, Institut für Diagnostische Radiologie und Neuroradiologie, Greifswald
| | - A Lange
- Universitätsmedizin Greifswald, Klinik und Poliklinik für Kinder- und Jugendmedizin, Greifswald
| | - S Langner
- Universitätsmedizin Greifswald, Institut für Diagnostische Radiologie und Neuroradiologie, Greifswald
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8
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Moser S, Fatale S, Krüger P, Berger H, Bugnon P, Magrez A, Niwa H, Miyawaki J, Harada Y, Grioni M. Electron-Phonon Coupling in the Bulk of Anatase TiO2 Measured by Resonant Inelastic X-Ray Spectroscopy. Phys Rev Lett 2015; 115:096404. [PMID: 26371668 DOI: 10.1103/physrevlett.115.096404] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Indexed: 06/05/2023]
Abstract
We investigate the polaronic ground state of anatase TiO2 by bulk-sensitive resonant inelastic x-ray spectroscopy (RIXS) at the Ti L3 edge. We find that the formation of the polaron cloud involves a single 95 meV phonon along the c axis, in addition to the 108 meV ab-plane mode previously identified by photoemission. The coupling strength to both modes is the same within error bars, and it is unaffected by the carrier density. These data establish RIXS as a directional bulk-sensitive probe of electron-phonon coupling in solids.
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Affiliation(s)
- S Moser
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut de Physique des Nanostructures, CH-1015 Lausanne, Switzerland
| | - S Fatale
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut de Physique des Nanostructures, CH-1015 Lausanne, Switzerland
| | - P Krüger
- Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage, Chiba 263-8522, Japan
| | - H Berger
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut de Physique des Nanostructures, CH-1015 Lausanne, Switzerland
| | - P Bugnon
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut de Physique des Nanostructures, CH-1015 Lausanne, Switzerland
| | - A Magrez
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut de Physique des Nanostructures, CH-1015 Lausanne, Switzerland
| | - H Niwa
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8526, Japan
- Synchrotron Radiation Research Organization, University of Tokyo, Sayo-cho, Sayo, Hyogo 679-5198, Japan
| | - J Miyawaki
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8526, Japan
- Synchrotron Radiation Research Organization, University of Tokyo, Sayo-cho, Sayo, Hyogo 679-5198, Japan
| | - Y Harada
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8526, Japan
- Synchrotron Radiation Research Organization, University of Tokyo, Sayo-cho, Sayo, Hyogo 679-5198, Japan
| | - M Grioni
- Ecole Polytechnique Fédérale de Lausanne (EPFL), Institut de Physique des Nanostructures, CH-1015 Lausanne, Switzerland
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9
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Abstract
X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) support the idea that during nitrogen doping of TiO2 nanoribbons N2 molecules may be formed and trapped in the nanostructures.
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Affiliation(s)
- C. Bittencourt
- Chimie des Interactions Plasma Surface
- CIRMAP
- University of Mons
- B-7000 Mons
- Belgium
| | - M. Rutar
- Jožef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
- Jožef Stefan International Postgraduate School
- SI-1000 Ljubljana
| | - P. Umek
- Jožef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
| | - A. Mrzel
- Jožef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
| | - K. Vozel
- Jožef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
| | - D. Arčon
- Jožef Stefan Institute
- SI-1000 Ljubljana
- Slovenia
- Faculty of Mathematics and Physics
- University of Ljubljana
| | - K. Henzler
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH
- Institute for Soft Matter and Functional Materials
- D-12489 Berlin
- Germany
| | - P. Krüger
- Graduate School of Advanced Integration Science
- Chiba University
- Chiba 263-8522
- Japan
| | - P. Guttmann
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH
- Institute for Soft Matter and Functional Materials
- D-12489 Berlin
- Germany
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10
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Simpson DP, Gangardt DM, Lerner IV, Krüger P. One-dimensional transport of bosons between weakly linked reservoirs. Phys Rev Lett 2014; 112:100601. [PMID: 24679274 DOI: 10.1103/physrevlett.112.100601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Indexed: 06/03/2023]
Abstract
We study a flow of ultracold bosonic atoms through a one-dimensional channel that connects two macroscopic three-dimensional reservoirs of Bose-condensed atoms via weak links implemented as potential barriers between each of the reservoirs and the channel. We consider reservoirs at equal chemical potentials so that a superflow of the quasicondensate through the channel is driven purely by a phase difference 2Φ imprinted between the reservoirs. We find that the superflow never has the standard Josephson form ∼sin2Φ. Instead, the superflow discontinuously flips direction at 2Φ=±π and has metastable branches. We show that these features are robust and not smeared by fluctuations or phase slips. We describe a possible experimental setup for observing these phenomena.
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Affiliation(s)
- D P Simpson
- School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - D M Gangardt
- School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - I V Lerner
- School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - P Krüger
- Midlands Ultracold Atom Research Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
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11
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Braun S, Kubec A, Menzel M, Niese S, Krüger P, Seiboth F, Patommel J, Schroer C. Multilayer Laue Lenses with Focal Length of 10 mm. ACTA ACUST UNITED AC 2013. [DOI: 10.1088/1742-6596/425/5/052019] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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12
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Abstract
Polarized second-order Raman scattering spectra of CuO single crystals are reported. It is shown that for some scattering geometries the second-order processes dominate the inelastic light scattering spectra. Group-theoretical symmetry analysis of the selection rules for the first- and second-order scattering processes is performed and phonon dispersion relations are calculated within density functional theory. The main spectral features of the two-phonon spectra are assigned to overtones of the vibrational branches at various special points across the Brillouin zone.
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Affiliation(s)
- A P Litvinchuk
- Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5002, USA.
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13
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Gray AX, Cooke DW, Krüger P, Bordel C, Kaiser AM, Moyerman S, Fullerton EE, Ueda S, Yamashita Y, Gloskovskii A, Schneider CM, Drube W, Kobayashi K, Hellman F, Fadley CS. Electronic structure changes across the metamagnetic transition in FeRh via hard X-ray photoemission. Phys Rev Lett 2012; 108:257208. [PMID: 23004654 DOI: 10.1103/physrevlett.108.257208] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2011] [Indexed: 06/01/2023]
Abstract
Stoichiometric FeRh undergoes a temperature-induced antiferromagnetic (AFM) to ferromagnetic (FM) transition at ~350 K. In this Letter, changes in the electronic structure accompanying this transition are investigated in epitaxial FeRh thin films via bulk-sensitive valence-band and core-level hard x-ray photoelectron spectroscopy with a photon energy of 5.95 keV. Clear differences between the AFM and FM states are observed across the entire valence-band spectrum and these are well reproduced using density-functional theory. Changes in the 2p core levels of Fe are also observed and interpreted using Anderson impurity model calculations. These results indicate that significant electronic structure changes over the entire valence-band region are involved in this AFM-FM transition.
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Affiliation(s)
- A X Gray
- Stanford Institute for Materials and Energy Science, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94029, USA
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14
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Krüger P, Jupille J, Bourgeois S, Domenichini B, Verdini A, Floreano L, Morgante A. Intrinsic nature of the excess electron distribution at the TiO2(110) surface. Phys Rev Lett 2012; 108:126803. [PMID: 22540610 DOI: 10.1103/physrevlett.108.126803] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Indexed: 05/31/2023]
Abstract
The gap state that appears upon reduction of TiO2 plays a key role in many of titania's interesting properties but its origin and spatial localization have remained unclear. In the present work, the TiO2(110) surface is reduced in a chemically controlled way by sodium adsorption. By means of resonant photoelectron diffraction, excess electrons are shown to be distributed mainly on subsurface Ti sites strikingly similar to the defective TiO2(110) surface, while any significant contribution from interstitial Ti ions is discarded. In agreement with first principles calculations, these findings demonstrate that the distribution of the band gap charge is an intrinsic property of TiO2(110), independent of the way excess electrons are produced.
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Affiliation(s)
- P Krüger
- ICB, UMR 6303 CNRS-Université de Bourgogne, BP 47870, F-21078 Dijon, France.
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15
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Walle LE, Agnoli S, Svenum IH, Borg A, Artiglia L, Krüger P, Sandell A, Granozzi G. High resolution photoemission and x-ray absorption spectroscopy of a lepidocrocite-like TiO2 nanosheet on Pt(110) (1 × 2). J Chem Phys 2011; 135:054706. [DOI: 10.1063/1.3623271] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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16
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Nowarra C, Krüger P. QM-Zertifikat...- und was dann? ROFO-FORTSCHR RONTG 2011. [DOI: 10.1055/s-0031-1279517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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17
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Krüger P, Hofferberth S, Mazets IE, Lesanovsky I, Schmiedmayer J. Weakly interacting Bose gas in the one-dimensional limit. Phys Rev Lett 2010; 105:265302. [PMID: 21231675 DOI: 10.1103/physrevlett.105.265302] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 09/18/2010] [Indexed: 05/30/2023]
Abstract
We prepare a chemically and thermally one-dimensional (1D) quantum degenerate Bose gas in a single microtrap. We introduce a new interferometric method to distinguish the quasicondensate fraction of the gas from the thermal cloud at finite temperature. We reach temperatures down to kT≈0.5ℏω(⊥) (transverse oscillator eigenfrequency ω(⊥)) when collisional thermalization slows down as expected in 1D. At the lowest temperatures the transverse-momentum distribution exhibits a residual dependence on the line density n(1D), characteristic for 1D systems. For very low densities the approach to the transverse single-particle ground state is linear in n(1D).
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Affiliation(s)
- P Krüger
- Midlands Ultracold Atom Research Centre (MUARC), School of Physics and Astronomy, The University of Nottingham, Nottingham, United Kingdom
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18
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Cheynet M, Pokrant S, Irsen S, Krüger P. New fine structures resolved at the ELNES Ti-L2,3 edge spectra of anatase and rutile: Comparison between experiment and calculation. Ultramicroscopy 2010. [DOI: 10.1016/j.ultramic.2010.03.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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19
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Krüger P, Vockelmann C, Nowarra C, Matyssek K, Doering T, Mathias K. Das perfekte QM-Handbuch (QMH). ROFO-FORTSCHR RONTG 2010. [DOI: 10.1055/s-0030-1253059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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20
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Abstract
Optical dipole traps and atom chips are two very powerful tools for the quantum manipulation of neutral atoms. We demonstrate that both methods can be combined by creating an optical lattice potential on an atom chip. A red-detuned laser beam is retroreflected using the atom chip surface as a high-quality mirror, generating a vertical array of purely optical oblate traps. We transfer thermal atoms from the chip into the lattice and observe cooling into the two-dimensional regime. Using a chip-generated Bose-Einstein condensate, we demonstrate coherent Bloch oscillations in the lattice.
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Affiliation(s)
- D Gallego
- Physikalisches Institut, Universität Heidelberg, 69120 Heidelberg, Germany
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21
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Turek M, Heiden W, Riesen A, Chhabda T, Schubert J, Zander W, Krüger P, Keusgen M, Schöning M. Artificial intelligence/fuzzy logic method for analysis of combined signals from heavy metal chemical sensors. Electrochim Acta 2009. [DOI: 10.1016/j.electacta.2009.03.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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22
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Vockelmann C, Nowarra C, Krüger P, Mathias K. Verbesserung der organisatorischen Abläufe in der interventionellen Angiographie. ROFO-FORTSCHR RONTG 2009. [DOI: 10.1055/s-0029-1221759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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23
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Bartels T, Fischer B, Krüger P, Koch E, Ryll M, Krautwald-Junghanns ME. [3D-X-ray microcomputer tomography and optical coherence tomography as methods for the localization of the blastoderm in the newly laid unincubated chicken egg]. Dtsch Tierarztl Wochenschr 2008; 115:182-188. [PMID: 18547018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The routine culling of the male offspring of hybrid layer type chickens is met with increasing public disapproval for both ethical and legal reasons. Until now practice-oriented methods for reliable sex diagnosis prior to hatch could not be developed. Molecular genetical analysis of blastodermic cells can be used for sex determination in unincubated eggs; however, knowledge of the precise localization of the germinal disc is crucial for the extraction of a carefully directed cell biopsy. In principle, 3D-X-ray micro computed tomography (3D-CT) has been proven a suitable method to localize the germinal disk in the unincubated egg without damaging the egg shell. No negative effects on embryogenesis and hatching rate of irradiated hatching eggs were established. The pictorial representation of the germinal disk using optical coherence tomography (OCT) failed in the unopened egg. The egg shell formed an impenetrable barrier for the currently available measuring method which utilized near infrared (NIR) wavelength regions. After opening the egg shell, the germinal disk could be visualized without any difficulties. In conclusion, technical possibilities for localization of the germinal disk in the unincubated egg already exist, but regarding technical parameters, the procedures have to be adapted to the specific purpose.
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Affiliation(s)
- T Bartels
- Klinik für Vögel und Reptilien der Universität Leipzig.
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24
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Krüger P, Bourgeois S, Domenichini B, Magnan H, Chandesris D, Le Fèvre P, Flank AM, Jupille J, Floreano L, Cossaro A, Verdini A, Morgante A. Defect states at the TiO2(110) surface probed by resonant photoelectron diffraction. Phys Rev Lett 2008; 100:055501. [PMID: 18352385 DOI: 10.1103/physrevlett.100.055501] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Revised: 11/02/2007] [Indexed: 05/26/2023]
Abstract
The charge distribution of the defect states at the reduced TiO(2)(110) surface is studied via a new method, the resonant photoelectron diffraction. The diffraction pattern from the defect state, excited at the Ti-2p-3d resonance, is analyzed in the forward scattering approach and on the basis of multiple scattering calculations. The defect charge is found to be shared by several surface and subsurface Ti sites with the dominant contribution on a specific subsurface site in agreement with density functional theory calculations.
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Affiliation(s)
- P Krüger
- Institut Carnot de Bourgogne, UMR 5209 CNRS-Université de Bourgogne, BP 47870, 21078 Dijon Cedex, France
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25
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Luo X, Krüger P, Brugger K, Wildermuth S, Gimpel H, Klein MW, Groth S, Folman R, Bar-Joseph I, Schmiedmayer J. Atom fiber for omnidirectional guiding of cold neutral atoms. Opt Lett 2004; 29:2145-2147. [PMID: 15460884 DOI: 10.1364/ol.29.002145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We present an omnidirectional matter waveguide on an atom chip. The guide is based on a combination of two current-carrying wires and a bias field pointing perpendicular to the chip surface. Thermal atoms are guided for more than two complete turns along a 25-mm-long spiral path (with curve radii as short as 200 microm) at various atom-surface distances (35-450 microm). An extension of the scheme for the guiding of Bose-Einstein condensates is outlined.
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Affiliation(s)
- X Luo
- Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg, Germany
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26
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Krüger P, Luo X, Klein MW, Brugger K, Haase A, Wildermuth S, Groth S, Bar-Joseph I, Folman R, Schmiedmayer J. Trapping and manipulating neutral atoms with electrostatic fields. Phys Rev Lett 2003; 91:233201. [PMID: 14683179 DOI: 10.1103/physrevlett.91.233201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2003] [Indexed: 05/24/2023]
Abstract
We report on experiments with cold thermal (7)Li atoms confined in combined magnetic and electric potentials. A novel type of three-dimensional trap was formed by modulating a magnetic guide using electrostatic fields. We observed atoms trapped in a string of up to six individual such traps, a controlled transport of an atomic cloud over a distance of 400 microm, and a dynamic splitting of a single trap into a double well potential. Applications for quantum information processing are discussed.
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Affiliation(s)
- P Krüger
- Physikalisches Institut, Universität Heidelberg, 69120 Heidelberg, Germany.
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27
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Caetano W, Ferreira M, Tabak M, Mosquera Sanchez MI, Oliveira ON, Krüger P, Schalke M, Lösche M. Cooperativity of phospholipid reorganization upon interaction of dipyridamole with surface monolayers on water. Biophys Chem 2001; 91:21-35. [PMID: 11403881 DOI: 10.1016/s0301-4622(01)00145-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Results from various surface sensitive characterization techniques suggest a model for the interaction of the piperidinopyrimidine dipyridamole (DIP)--known as a vasodilator and inhibitor of P-glycoprotein associated multidrug resistance of tumor cells--with phospholipid monolayers in which the drug is peripherally associated with the membrane, binding (up to) five phospholipids at a time. These multiple interactions are responsible for a very strong association of the drug with the lipid monolayer even at exceedingly low concentrations (approximately 0.2 mol%). Electrostatic interactions and hydrogen bonding are likely involved in the binding of DIP to DPPC. Cooperative effects among the lipids are invoked to explain the macroscopically measurable changes of lipid monolayer properties even when only one out of 100 DPPC molecules is directly associated with a DIP molecule. A reversal of the observed changes upon drug association with the membrane as the DIP concentration surpasses a threshold concentration (c(crit)approximately 0.5 mol%) may be explained by cooperativity in a different context, the self-aggregation of drug molecules. With its implications for the interaction of DIP with phospholipid films, this work provides a first approach to the explanation of the high sensitivity of cell membranes to piperidinopyrimidine drugs on a molecular level.
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Affiliation(s)
- W Caetano
- Instituto de Química de São Carlos, USP, Cx. Postal 780, 13560-970 São Carlos, SP, Brazil
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28
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Krüger P, Verheyden S, Declerck PJ, Engelborghs Y. Extending the capabilities of targeted molecular dynamics: simulation of a large conformational transition in plasminogen activator inhibitor 1. Protein Sci 2001; 10:798-808. [PMID: 11274471 PMCID: PMC2373958 DOI: 10.1110/ps.40401] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Plasminogen activator inhibitor type 1 (PAI-1) is an inhibitor of plasminogen activators such as tissue-type plasminogen activator or urokinase-type plasminogen activator. For this molecule, different conformations are known. The inhibiting form that interacts with the proteinases is called the active form. The noninhibitory, noncleavable form is called the latent form. X-ray and modeling studies have revealed a large change in position of the reactive center loop (RCL), responsible for the interaction with the proteinases, that is inserted into a beta-sheet (s4A) in the latent form. The mechanism underlying this spontaneous conformational change (half-life = 2 h at 37 degrees C) is not known in detail. This investigation attempts to predict a transition path from the active to the latent structure at the atomic level, by using simulation techniques. Together with targeted molecular dynamics (TMD), a plausible assumption on a rigid body movement of the RCL was applied to define an initial guess for an intermediate. Different pathways were simulated, from the active to the intermediate, from the intermediate to the latent structure and vice versa under different conditions. Equilibrium simulations at different steps of the path also were performed. The results show that a continuous pathway from the active to the latent structure can be modeled. This study also shows that this approach may be applied in general to model large conformational changes in any kind of protein for which the initial and final three-dimensional structure is known.
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Affiliation(s)
- P Krüger
- Laboratory of Biomolecular Dynamics, Katholieke Universiteit Leuven, 3001 Leuven, Belgium
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29
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Lehmann W, Skupin H, Tolksdorf C, Gebhard E, Zentel R, Krüger P, Lösche M, Kremer F. Giant lateral electrostriction in ferroelectric liquid-crystalline elastomers. Nature 2001; 410:447-50. [PMID: 11260707 DOI: 10.1038/35068522] [Citation(s) in RCA: 341] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Mechanisms for converting electrical energy into mechanical energy are essential for the design of nanoscale transducers, sensors, actuators, motors, pumps, artificial muscles, and medical microrobots. Nanometre-scale actuation has to date been mainly achieved by using the (linear) piezoelectric effect in certain classes of crystals (for example, quartz), and 'smart' ceramics such as lead zirconate titanate. But the strains achievable in these materials are small--less than 0.1 per cent--so several alternative materials and approaches have been considered. These include grafted polyglutamates (which have a performance comparable to quartz), silicone elastomers (passive material--the constriction results from the Coulomb attraction of the capacitor electrodes between which the material is sandwiched) and carbon nanotubes (which are slow). High and fast strains of up to 4 per cent within an electric field of 150 MV x m(-1) have been achieved by electrostriction (this means that the strain is proportional to the square of the applied electric field) in an electron-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer. Here we report a material that shows a further increase in electrostriction by two orders of magnitude: ultrathin (less than 100 nanometres) ferroelectric liquid-crystalline elastomer films that exhibit 4 per cent strain at only 1.5 MV x m(-1). This giant electrostriction was obtained by combining the properties of ferroelectric liquid crystals with those of a polymer network. We expect that these results, which can be completely understood on a molecular level, will open new perspectives for applications.
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Affiliation(s)
- W Lehmann
- Institut für experimentelle Physik I, Universität Leipzig, Linnéstrabetae 5, 04103 Leipzig, Germany
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30
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Wurlitzer A, Politsch E, Huebner S, Krüger P, Weygand M, Kjaer K, Hommes P, Nuyken O, Cevc G, Lösche M. Conformation of Polymer Brushes at Aqueous Surfaces Determined with X-ray and Neutron Reflectometry. 2. High-Density Phase Transition of Lipopolyoxazolines. Macromolecules 2001. [DOI: 10.1021/ma000932n] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A. Wurlitzer
- Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, D-04103 Leipzig, Germany; Institute of Medical Biophysics, Technical University of Munich, Ismaninger Str. 22, D-81675 München, Germany; Department of Condensed Matter Physics and Chemistry, Risø National Laboratory, DK-4000 Roskilde, Denmark; and Institute of Technical Chemistry, Technical University of Munich, D-85747 München, Germany
| | - E. Politsch
- Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, D-04103 Leipzig, Germany; Institute of Medical Biophysics, Technical University of Munich, Ismaninger Str. 22, D-81675 München, Germany; Department of Condensed Matter Physics and Chemistry, Risø National Laboratory, DK-4000 Roskilde, Denmark; and Institute of Technical Chemistry, Technical University of Munich, D-85747 München, Germany
| | - S. Huebner
- Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, D-04103 Leipzig, Germany; Institute of Medical Biophysics, Technical University of Munich, Ismaninger Str. 22, D-81675 München, Germany; Department of Condensed Matter Physics and Chemistry, Risø National Laboratory, DK-4000 Roskilde, Denmark; and Institute of Technical Chemistry, Technical University of Munich, D-85747 München, Germany
| | - P. Krüger
- Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, D-04103 Leipzig, Germany; Institute of Medical Biophysics, Technical University of Munich, Ismaninger Str. 22, D-81675 München, Germany; Department of Condensed Matter Physics and Chemistry, Risø National Laboratory, DK-4000 Roskilde, Denmark; and Institute of Technical Chemistry, Technical University of Munich, D-85747 München, Germany
| | - M. Weygand
- Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, D-04103 Leipzig, Germany; Institute of Medical Biophysics, Technical University of Munich, Ismaninger Str. 22, D-81675 München, Germany; Department of Condensed Matter Physics and Chemistry, Risø National Laboratory, DK-4000 Roskilde, Denmark; and Institute of Technical Chemistry, Technical University of Munich, D-85747 München, Germany
| | - K. Kjaer
- Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, D-04103 Leipzig, Germany; Institute of Medical Biophysics, Technical University of Munich, Ismaninger Str. 22, D-81675 München, Germany; Department of Condensed Matter Physics and Chemistry, Risø National Laboratory, DK-4000 Roskilde, Denmark; and Institute of Technical Chemistry, Technical University of Munich, D-85747 München, Germany
| | - P. Hommes
- Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, D-04103 Leipzig, Germany; Institute of Medical Biophysics, Technical University of Munich, Ismaninger Str. 22, D-81675 München, Germany; Department of Condensed Matter Physics and Chemistry, Risø National Laboratory, DK-4000 Roskilde, Denmark; and Institute of Technical Chemistry, Technical University of Munich, D-85747 München, Germany
| | - O. Nuyken
- Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, D-04103 Leipzig, Germany; Institute of Medical Biophysics, Technical University of Munich, Ismaninger Str. 22, D-81675 München, Germany; Department of Condensed Matter Physics and Chemistry, Risø National Laboratory, DK-4000 Roskilde, Denmark; and Institute of Technical Chemistry, Technical University of Munich, D-85747 München, Germany
| | - G. Cevc
- Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, D-04103 Leipzig, Germany; Institute of Medical Biophysics, Technical University of Munich, Ismaninger Str. 22, D-81675 München, Germany; Department of Condensed Matter Physics and Chemistry, Risø National Laboratory, DK-4000 Roskilde, Denmark; and Institute of Technical Chemistry, Technical University of Munich, D-85747 München, Germany
| | - M. Lösche
- Institute of Experimental Physics I, University of Leipzig, Linnéstr. 5, D-04103 Leipzig, Germany; Institute of Medical Biophysics, Technical University of Munich, Ismaninger Str. 22, D-81675 München, Germany; Department of Condensed Matter Physics and Chemistry, Risø National Laboratory, DK-4000 Roskilde, Denmark; and Institute of Technical Chemistry, Technical University of Munich, D-85747 München, Germany
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Krüger P, Lösche M. Molecular chirality and domain shapes in lipid monolayers on aqueous surfaces. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 2000; 62:7031-7043. [PMID: 11102059 DOI: 10.1103/physreve.62.7031] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2000] [Indexed: 05/23/2023]
Abstract
The shapes of domain boundaries in the mesoscopic phase separation of phospholipids in aqueous surface monolayers are analyzed with particular attention to the influence of molecular chirality. We have calculated equilibrium shapes of such boundaries, and show that the concept of spontaneous curvature-derived from an effective pair potential between the chiral molecules-yields an adequate description of the contribution of chirality to the total energy of the system. For enantiomeric dipalmitoylphosphatidylcholine in pure monolayers, and in mixtures with impurities that adsorb preferentially at the (one-dimensional) boundary line between the isotropic and anisotropic fluid phases, such as cyanobiphenyl (5CB), a total energy term that includes line tension, electrostatic dipole-dipole interaction, and spontaneous curvature is sufficient to describe the shapes of well-separated domain boundaries in full detail. As soon as interdomain distances fall below the domain sizes upon compression of a monolayer, fluctuations take over in determining its detailed structural morphology. Using Minkowski measures for the well-studied dimyristoyl phosphatidic acid (DMPA)/cholesterol system, we show that calculations accounting for line tension, electrostatic repulsion, and molecular chirality yield boundary shapes that are of the same topology as the experimentally observed structures. At a fixed molecular area in the phase coexistence region, the DMPA/cholesterol system undergoes an exponential decay of the line tension lambda with decreasing subphase temperature T.
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Affiliation(s)
- P Krüger
- Institute of Experimental Physics I, Leipzig University, Linnéstrasse 5, D-04103 Leipzig, Germany
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Abstract
A new approach to the data refinement of X-ray reflection measurements from lipid surface monolayers, applied to DMPA on pure water, reveals the structural organization of the lipid in unprecedented detail and provides new insights into headgroup conformation and hydration as a function of lateral pressure. While conventional box models are incapable of modeling the experimental data at high momentum transfer satisfactorily, a quasimolecular composition-space refinement approach using distribution functions to map the spatial organization of submolecular headgroup fragments yields a much better description and overcomes inherent difficulties of box models. Upon going from the fluid liquid-expanded (LE) phase to the hexatic liquid-condensed (LC) phase, the orientation of the headgroup is tightly coupled to the ordering of the acyl chains. Headgroups tilt toward the surface normal to accommodate for the large reduction in available area per lipid molecule. The spread of the headgroup fragment distribution is considerably larger than the global interface roughness and increases slightly with compression. In distinction to earlier work on DMPE using the two-box approach, we find that the phosphate hydration stays essentially constant across the whole isotherm. The discrepancy between the results observed with the different models is attributed to intrinsic deficiencies of the box model.
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Affiliation(s)
- M Schalke
- Institute of Experimental Physics I, Leipzig University, Linnéstr. 5, D-04103, Leipzig, Germany
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34
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Forst J, Krüger P, Forst R. Value of myofibrillar protein catabolic rate in Duchenne muscular dystrophy. A study after lower limb surgery. Arch Orthop Trauma Surg 2000; 120:38-41. [PMID: 10653102 DOI: 10.1007/pl00021213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Previous studies have shown a decreased progression of the course in Duchenne muscular dystrophy (DMD) patients treated by lower limb surgery in early childhood. The use of 3-methylhistidine (3-MH) excretion and 3-MH/creatinine excretion ratio as an appropriate indicator for the myofibrillar protein catabolic rate (MPCR) in muscle disorders is discussed controversially. To explore this issue we studied the renal excretion of (3-MH) over a period up to 24 months (on average 20.8 +/- 1.4) after operation in 15 consecutive DMD patients with an average age at operation of 8.75 (+/- 2.43 years) to evaluate the myofibrillar protein catabolic rate. No significant change of the MPCR could be found in our population over the follow-up period. However, the formula for the calculation of the MPCR contains quantities which are not precisely known in DMD or assumed to be constant over the progressive course of DMD. Summarizing MPCR cannot be recommended for the assessment of therapeutic efficacy in DMD.
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Affiliation(s)
- J Forst
- Orthopaedic Department RWTH Aachen, Germany.
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35
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Krüger P, Schalke M, Wang Z, Notter RH, Dluhy RA, Lösche M. Effect of hydrophobic surfactant peptides SP-B and SP-C on binary phospholipid monolayers. I. Fluorescence and dark-field microscopy. Biophys J 1999; 77:903-14. [PMID: 10423435 PMCID: PMC1300381 DOI: 10.1016/s0006-3495(99)76941-9] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
The influence of the hydrophobic proteins SP-B and SP-C, isolated from pulmonary surfactant, on the morphology of binary monomolecular lipid films containing phosphocholine and phosphoglycerol (DPPC and DPPG) at the air-water interface has been studied using epifluorescence and dark-field microscopy. In contrast to previously published studies, the monolayer experiments used the entire hydrophobic surfactant protein fraction (containing both the SP-B and SP-C peptides) at physiologically relevant concentrations (approximately 1 wt %). Even at such low levels, the SP-B/C peptides induce the formation of a new phase in the surface monolayer that is of lower intrinsic order than the liquid condensed (LC) phase that forms in the pure lipid mixture. This presumably leads to a higher structural flexibility of the surface monolayer at high lateral pressure. Variation of the subphase pH indicates that electrostatic interaction dominates the association of the SP-B/C peptides with the lipid monolayer. As evidenced from dark-field microscopy, monolayer material is excluded from the DPPC/DPPG surface film on compression and forms three-dimensional, surface-associated structures of micron dimensions. Such exclusion bodies formed only with SP-B/C peptides. This observation provides the first direct optical evidence for the squeeze-out of pulmonary surfactant material in situ at the air-water interface upon increasing monolayer surface pressures.
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Affiliation(s)
- P Krüger
- Institute of Experimental Physics I, University of Leipzig, D-04103 Leipzig, Germany
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36
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37
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Hassiepen U, Federwisch M, Mülders T, Lenz VJ, Gattner HG, Krüger P, Wollmer A. Analysis of protein self-association at constant concentration by fluorescence-energy transfer. Eur J Biochem 1998; 255:580-7. [PMID: 9738896 DOI: 10.1046/j.1432-1327.1998.2550580.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Fluorescence-resonance-energy transfer from subunits labelled with a fluorescence donor group to subunits labelled with a fluorescence acceptor group can be used for quantitative analysis of protein self-association. The present approach evaluates fluorescence measurements on mixtures of equimolar solutions of donor-labelled and acceptor-labelled protein composed by systematic variation of the volume ratio. Its attractive feature is that it allows the determination of equilibrium constants at fixed total concentration. Problems encountered by most other methods, which require the equilibria to be followed to high dilution, are avoided. Conditions to be fulfilled are that a reactive site is available on the protein for specific introduction of the labels and that labelling neither affects the conformation nor interferes with the intermolecular interactions. It is desirable that the Forster distance of the donor/acceptor pair complies with its separation. While dimerisation constants can be determined exclusively by fluorescence measurements, the analysis of more complex cases of self-association depends on additional independent information. This communication reports on an application of the approach to the association/dissociation equilibrium between insulin monomers and dimers. Labelling of insulin at the epsilon-amino group of LysB29 does not disturb the conformation nor does it affect dimerisation. 2-Aminobenzoyl and 3-nitrotyrosyl residues served as the donor/acceptor pairs. Because they are less bulky than most other fluorescence labels and are of balanced polarity they do not alter the chemical nature of the protein. Their Forster distance of 29 A matches their 32-A separation in the insulin dimer. Energy transfer was measured as a function of the molar fractions of donor-insulin and acceptor-insulin at constant total concentration. Evaluation of this dependence resulted in a dimerisation constant, K12, of 0.72x10(5) M(-1). Its agreement with values obtained with other methods demonstrates that the present approach is a reliable alternative.
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Affiliation(s)
- U Hassiepen
- Institut für Biochemie, Rheinisch-Westfälische Technische Hochschule Aachen, Germany
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38
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Abstract
CD spectra of bovine pancreatic ribonuclease A (RNase A) and its subtilisin-modified from (RNase S) have been calculated, based upon high-resolution structures from x-ray diffraction. All known transitions in the peptide and side-chain groups, especially the aromatic and disulfide groups, have been included. Calculations have been performed with both the matrix method and with first-order perturbation theory. A newly developed method for treating the electrostatic interactions among transition charge densities and between static charge distributions and transition charge densities is used. The effects of local electrostatic fields upon the group transition energies are included for all transitions. Rotational strengths generated by the matrix method were combined with Gaussian band shapes to generate theoretical CD spectra. The calculated spectra reproduce the signs and approximate magnitudes of the near-uv CD bands of both RNase A and S. Agreement is most satisfactory for the negative 275 nm band, dominated by tyrosine contributions. In agreement with two previous studies by other workers, coupling between Tyr 73 and Tyr 115 is the single most important factor in this band. The positive band observed near 240 nm is dominated by disulfide contributions, according to our results. The far-uv CD spectrum is poorly reproduced by the calculations. The observed 208 nm band, characteristic of alpha-helices, is absent from the calculated spectrum, probably because the helices in RNase are short. A strong positive couplet centered near 190 nm is predicted but not observed. Possible reasons for these incorrect predictions of the current theoretical model in the far-uv are discussed.
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Affiliation(s)
- G Kurapkat
- Institut für Biochemie, RWTH Aachen, Germany
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Abstract
CD spectra of bovine pancreatic ribonuclease A (RNase A) and its subtilisin-modified from (RNase S) have been calculated, based upon high-resolution structures from x-ray diffraction. All known transitions in the peptide and side-chain groups, especially the aromatic and disulfide groups, have been included. Calculations have been performed with both the matrix method and with first-order perturbation theory. A newly developed method for treating the electrostatic interactions among transition charge densities and between static charge distributions and transition charge densities is used. The effects of local electrostatic fields upon the group transition energies are included for all transitions. Rotational strengths generated by the matrix method were combined with Gaussian band shapes to generate theoretical CD spectra. The calculated spectra reproduce the signs and approximate magnitudes of the near-uv CD bands of both RNase A and S. Agreement is most satisfactory for the negative 275 nm band, dominated by tyrosine contributions. In agreement with two previous studies by other workers, coupling between Tyr 73 and Tyr 115 is the single most important factor in this band. The positive band observed near 240 nm is dominated by disulfide contributions, according to our results. The far-uv CD spectrum is poorly reproduced by the calculations. The observed 208 nm band, characteristic of alpha-helices, is absent from the calculated spectrum, probably because the helices in RNase are short. A strong positive couplet centered near 190 nm is predicted but not observed. Possible reasons for these incorrect predictions of the current theoretical model in the far-uv are discussed.
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Affiliation(s)
- G Kurapkat
- Institut für Biochemie, RWTH Aachen, Germany
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Rohlfing M, Krüger P, Pollmann J. Quasiparticle band structures of clean, hydrogen-, and sulfur-terminated Ge(001) surfaces. Phys Rev B Condens Matter 1996; 54:13759-13766. [PMID: 9985293 DOI: 10.1103/physrevb.54.13759] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Krüger P, Elmouhssine O, Demangeat C, Parlebas JC. Magnetic structures of bct manganese in the bulk and at the (001) surface. Phys Rev B Condens Matter 1996; 54:6393-6400. [PMID: 9986657 DOI: 10.1103/physrevb.54.6393] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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42
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Vogel D, Krüger P, Pollmann J. Self-interaction and relaxation-corrected pseudopotentials for II-VI semiconductors. Phys Rev B Condens Matter 1996; 54:5495-5511. [PMID: 9986510 DOI: 10.1103/physrevb.54.5495] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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43
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Sabisch M, Krüger P, Mazur A, Rohlfing M, Pollmann J. First-principles calculations of beta -SiC(001) surfaces. Phys Rev B Condens Matter 1996; 53:13121-13132. [PMID: 9982991 DOI: 10.1103/physrevb.53.13121] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Jacoby E, Krüger P, Schlitter J, Röper D, Wollmer A. Simulation of a complex protein structural change: the T <--> R transition in the insulin hexamer. Protein Eng 1996; 9:113-25. [PMID: 9005432 DOI: 10.1093/protein/9.2.113] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The T <--> R transition in the insulin hexamer is an outstanding model for protein structural changes in terms of its extent and complexity: the limiting structures T(6), T(3)R(3) and R(6) have been defined by X-ray crystallography. The transition occurs cooperatively within trimers. It involves displacements of >30 A and a secondary structural rearrangement of 15% of the peptide chain between extended and helical conformations. Experimental data for the transition are plentiful. Theoretical methods to simulate pathways without constraints would never succeed with such substantial transitions. We have developed two approaches, targeted energy minimization (TEM) and targeted molecular dynamics (TMD). Previously successful in simulating the T <--> R transition of the insulin monomer, these procedures are also shown here to be effective in the hexamer. With TMD, more conformational space is explored and pathways are found at 500 kJ/mol lower energy than with TEM. Because the atoms have to meet distance constraints in sum rather than individually, a high degree of conformational freedom and independence is implied. T(6) --> T(3)R(3) and T(3)R(3) --> T(6) pathways do not coincide because the transformation is directed. One subunit enters a dead end pathway in one direction of the TMD simulation, which shows that constraint and freedom are critically balanced. The ensemble of productive pathways represents a plausible corridor for the transition. A video display of the transformations is available.
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Affiliation(s)
- E Jacoby
- Institut für Biochemie, Rheinisch-Westfälische Technische Hochschule Aachen, Germany
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46
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Rohlfing M, Krüger P, Pollmann J. Metallic nature of the symmetric dimer model of Si(001)-(2 x 1). Phys Rev B Condens Matter 1995; 52:13753-13756. [PMID: 9980581 DOI: 10.1103/physrevb.52.13753] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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47
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Vogel D, Krüger P, Pollmann J. Ab initio electronic-structure calculations for II-VI semiconductors using self-interaction-corrected pseudopotentials. Phys Rev B Condens Matter 1995; 52:14316-14319. [PMID: 9980748 DOI: 10.1103/physrevb.52.r14316] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Rohlfing M, Krüger P, Pollmann J. Efficient scheme for GW quasiparticle band-structure calculations with applications to bulk Si and to the Si(001)-(2 x 1) surface. Phys Rev B Condens Matter 1995; 52:1905-1917. [PMID: 9981258 DOI: 10.1103/physrevb.52.1905] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Sabisch M, Krüger P, Pollmann J. Ab initio calculations of SiC(110) and GaAs(110) surfaces: A comparative study and the role of ionicity. Phys Rev B Condens Matter 1995; 51:13367-13380. [PMID: 9978141 DOI: 10.1103/physrevb.51.13367] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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