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2013


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Theory of scattering of crystal electrons at magnons

Haag, Michael, Illg, C., Fähnle, M.

{Physical Review B}, Published by the American Physical Society through the American Institute of Physics, Woodbury, NYAmerican Institute of Physics, Woodbury, NY, 2013 (article)

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DOI [BibTex]

2013


DOI [BibTex]


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The effect of magnetocrystalline anisotropy on the domain structure of patterned Fe2CrSi Heusler alloy thin films

Miyawaki, T., Foerster, M., Finizio, S., Vaz, C. A. F., Mawass, M.-A., Inagaki, K., Fukatani, N., Le Guyader, L., Nolting, F., Ueda, K., Asano, H., Kläui, M.

{Journal of Applied Physcis}, 114(7), American Institute of Physics, New York, NY, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Ion beam lithography for Fresnel zone plates in X-ray microscopy

Keskinbora, K., Grévent, C., Bechtel, M., Weigand, M., Goering, E., Nadzeyka, A., Lloyd, P., Rehbein, S., Schneider, G., Follath, R., Vila-Comamala, J., Yan, H., Schütz, G.

{Optics Express}, 21(10):11747-11756, Optical Society of America, Washington, DC, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Is the angular momentum of a ferromagnetic sample after exposure to a fs laser pulse conserved?

Fähnle, M., Haag, M., Illg, C.

{Journal of Magnetism and Magnetic Materials}, 347, pages: 45-46, North-Holland, Amsterdam, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Grain boundaries as the controlling factor for the ferromagnetic behaviour of Co-doped ZnO

Straumal, B. B., Mazilkin, A. A., Protasova, S. G., Straumal, P. B., Myatiev, A. A., Schütz, G., Goering, E. J., Tietze, T., Baretzky, B.

{Philosophical Magazine}, 93(10-12):1371-1383, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetic properties of electrochemically prepared crystalline films of Prussian blue-based molecular magnets Kj CrIIk [CrIII(CN)6] l \mbox⋅ mH2O

Bhatt, P., Yusuf, S. M., Bhatt, R., Schütz, G.

{Journal of Solid State Electrochemistry}, 17, pages: 1285-1293, Springer-Verlag Germany, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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H2/D2 adsorption and desorption studies on carbon molecular sieves with different pore structures

Krkljus, I., Steriotis, T., Charalambopoulou, G., Gotzias, A., Hirscher, M.

{Carbon}, 57, pages: 239-247, Elsevier Science, Amsterdam [u.a.], 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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X-ray magnetic circular dichroism strongly influenced by non-magnetic cover layers

Zafar, K., Audehm, P., Schütz, G., Goering, E., Pathak, M., Chetry, K. B., LeClair, P. R., Gupta, A.

{Journal of Electron Spectroscopy and Related Phenomena}, 191, pages: 1-6, Elsevier, Amsterdam, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Structural learning

Braun, D

Scholarpedia, 8(10):12312, October 2013 (article)

Abstract
Structural learning in motor control refers to a metalearning process whereby an agent extracts (abstract) invariants from its sensorimotor stream when experiencing a range of environments that share similar structure. Such invariants can then be exploited for faster generalization and learning-to-learn when experiencing novel, but related task environments.

ei

DOI [BibTex]

DOI [BibTex]


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The effect of model uncertainty on cooperation in sensorimotor interactions

Grau-Moya, J, Hez, E, Pezzulo, G, Braun, DA

Journal of the Royal Society Interface, 10(87):1-11, October 2013 (article)

Abstract
Decision-makers have been shown to rely on probabilistic models for perception and action. However, these models can be incorrect or partially wrong in which case the decision-maker has to cope with model uncertainty. Model uncertainty has recently also been shown to be an important determinant of sensorimotor behaviour in humans that can lead to risk-sensitive deviations from Bayes optimal behaviour towards worst-case or best-case outcomes. Here, we investigate the effect of model uncertainty on cooperation in sensorimotor interactions similar to the stag-hunt game, where players develop models about the other player and decide between a pay-off-dominant cooperative solution and a risk-dominant, non-cooperative solution. In simulations, we show that players who allow for optimistic deviations from their opponent model are much more likely to converge to cooperative outcomes. We also implemented this agent model in a virtual reality environment, and let human subjects play against a virtual player. In this game, subjects' pay-offs were experienced as forces opposing their movements. During the experiment, we manipulated the risk sensitivity of the computer player and observed human responses. We found not only that humans adaptively changed their level of cooperation depending on the risk sensitivity of the computer player but also that their initial play exhibited characteristic risk-sensitive biases. Our results suggest that model uncertainty is an important determinant of cooperation in two-player sensorimotor interactions.

ei

DOI [BibTex]

DOI [BibTex]


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Exchange bias in La0.7Sr0.3MnO3 / SrMnO3 / La0.7Sr0.3MnO3 trilayers

Jungbauer, M., Hühn, S., Michelmann, M., Goering, E., Moshnyaga, V.

{Journal of Applied Physcis}, 113(17), American Institute of Physics, New York, NY, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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General decoupling procedure for expectation values of four-operator products in electron-phonon quantum kinetics

Teeny, N., Fähnle, M.

{Journal of Physics A: Mathematical and Theoretical}, 46(38), IOP Pub., London, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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SPD-induced changes of structure and magnetic properties in the Cu-Co alloys

Straumal, B. B., Protasova, S. G., Mazilkin, A. A., Kogtenkova, O. A., Kurmanaeva, L., Baretzky, B., Schütz, G., Korneva, A., Zieba, P.

{Materials Letters}, 98, pages: 217-221, Elsevier, Amsterdam, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Ferromagnetic behaviour of Fe-doped ZnO nanograined films

Straumal, B. B., Protasova, S. G., Mazilkin, A. A., Tietze, T., Goering, E., Schütz, G., Straumal, P. B., Baretzky, B.

{Beilstein Journal of Nanotechnology}, 4, pages: 361-369, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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The effect of magnetic anisotropy on the spin configurations of patterned La0.7Sr0.3MnO3 elements

Wohlhüter, P., Rhensius, J., Vaz, C. A. F., Heidler, J., Körner, H. S., Bisig, A., Foerster, M., Méchin, L., Gaucher, F., Locatelli, A., Niño, M. A., El Moussaoui, S., Nolting, F., Goering, E., Heyderman, L. J., Kläui, M.

{Journal of Physics: Condensed Matter}, 25, IOP Pub., Bristol, UK, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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The avalanche process in gold covered MgB2 films

Stahl, C., Treiber, S., Schütz, G., Albrecht, J.

{Superconductor Science and Technology}, 26, IOP Pub., Bristol, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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MFU-4 - A metal-organic framework for highly effective H2/D2 separation

Teufel, J., Oh, H., Hirscher, M., Wahiduzzaman, M., Zhechkov, L., Kuc, A., Heine, T., Denysenko, D., Volkmer, D.

{Advanced Materials}, 25(4):635-639, Wiley-VCH Verlag, Weinheim, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Delayed magnetic vortex core reversal

Kammerer, M., Sproll, M., Stoll, H., Noske, M., Weigand, M., Illg, C., Fähnle, M., Schütz, G.

{Applied Physics Letters}, 102, American Institute of Physics, Melville, NY, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Self-organized state formation in magnonic vortex crystals

Adolff, C. F., Hänze, M., Vogel, A., Weigand, M., Martens, M., Meier, G.

{Physical Review B}, 88(22), American Physical Society, Woodbury, NY, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Erratum: Generalized Gilbert equation including inertial damping: Derivation from an extended breathing Fermi surface model [Phys. Rev. B 84, 172403 (2011)]

Fähnle, M., Steiauf, D., Illg, C.

{Physical Review B}, 88, American Physical Society, Woodbury, NY, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Strain and composition dependence of orbital polarization in nickel oxide superlattices

Wu, M., Benckiser, E., Haverkort, M. W., Franco, A., Lu, J., Nwankwo, U., Brück, S., Audehm, P., Goering, E., Macke, S., Hinkov, V., Wochner, P., Christiani, G., Heinze, S., Logvenov, G., Habermeier, H., Keimer, B.

{Physical Review B}, 88, Published by the American Physical Society through the American Institute of Physics, Woodbury, NY, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Efficient focusing of 8 keV X-rays with multilayer Fresnel zone plates fabricated by atomic layer deposition and focused ion beam milling

Mayer, M., Keskinbora, K., Grévent, C., Szeghalmi, A., Knez, M., Weigand, M., Snigirev, A., Snigereva, I., Schütz, G.

{Journal of Synchrotron Radiation}, 20, pages: 433-440, Published for the International Union of Crystallography by Munksgaard, Copenhagen, Denmark, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Rapid prototyping of Fresnel zone plates via direct Ga+ ion beam lithography for high-resolution x-ray imaging

Keskinbora, K., Grévent, C., Eigenthaler, U., Weigand, M., Schütz, G.

{ACS Nano}, 7(11):9788-9797, American Chemical Society, Washington, DC, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Eine kryoflexible kovalente organische Gerüststruktur für die effiziente Trennung von Wasserstoffisotopien durch Quantensieben

Oh, H., Kalidindi, S. B., Um, Y., Bureekaew, S., Schmid, R., Fischer, R. A., Hirscher, M.

{Angewandte Chemie}, 125(50):13461-13464, Wiley-VCH Verl., Weinheim, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Ultrafast demagnetization after laser irradiation in transition metals: Ab initio calculations of the spin-flip electron-phonon scattering with reduced exchange splitting

Illg, C., Haag, M., Fähnle, M.

{Physical Review B}, 88, American Physical Society, Woodbury, NY, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Phase diagram for magnetic vortex core switching studied by ferromagnetic absorption spectroscopy and time-resolved transmission x-ray microscopy

Martens, M., Kamionka, T., Weigand, M., Stoll, H., Tyliszczak, T., Meier, G.

{Physical Review B}, 87, Published by the American Physical Society through the American Institute of Physics, Woodbury, NY, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Thermodynamics as a theory of decision-making with information-processing costs

Ortega, PA, Braun, DA

Proceedings of the Royal Society of London A, 469(2153):1-18, May 2013 (article)

Abstract
Perfectly rational decision-makers maximize expected utility, but crucially ignore the resource costs incurred when determining optimal actions. Here, we propose a thermodynamically inspired formalization of bounded rational decision-making where information processing is modelled as state changes in thermodynamic systems that can be quantified by differences in free energy. By optimizing a free energy, bounded rational decision-makers trade off expected utility gains and information-processing costs measured by the relative entropy. As a result, the bounded rational decision-making problem can be rephrased in terms of well-known variational principles from statistical physics. In the limit when computational costs are ignored, the maximum expected utility principle is recovered. We discuss links to existing decision-making frameworks and applications to human decision-making experiments that are at odds with expected utility theory. Since most of the mathematical machinery can be borrowed from statistical physics, the main contribution is to re-interpret the formalism of thermodynamic free-energy differences in terms of bounded rational decision-making and to discuss its relationship to human decision-making experiments.

ei

DOI [BibTex]

DOI [BibTex]


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Switching modes in easy and hard axis magnetic reversal in a self-assembled antidot array

Haering, F., Wiedwald, U., Nothelfer, S., Koslowski, B., Ziemann, P., Lechner, L., Wallucks, A., Lebecki, K., Nowak, U., Gräfe, J., Goering, E., Schütz, G.

{Nanotechnology}, 24, IOP Pub., Bristol, UK, 2013 (article)

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DOI Project Page [BibTex]

DOI Project Page [BibTex]


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Time-resolved imaging of nonlinear magnetic domain-wall dynamics in ferromagnetic nanowires

Stein, F.-U., Bocklage, L., Weigand, M., Meier, G.

{Scientific Reports}, 3, Nature Publishing Group, London, UK, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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A cryogenically flexible covalent organic framework for efficient hydrogen isotrope separation by quantum sieving

Oh, H., Kalidindi, S. B., Um, Y., Bureekaew, S., Schmid, R., Fischer, R. A., Hirscher, M.

{Angewandte Chemie International Edition in English}, 52(50):13219-13222, Wiley-VCH Verlag GmbH & Co. KGaA, D-69451 Weinheim, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Unexpected room-temperature ferromagnetism in bulk ZnO

Chen, Y., Goering, E., Jeurgens, L., Wang, Z., Phillipp, F., Baier, J., Tietze, T., Schütz, G.

{Applied Physics Letters}, (103), American Institute of Physics, Melville, NY, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Large-area hard magnetic L10-FePt and composite L10-FePt based nanopatterns

Goll, D., Bublat, T.

{Physica Status Solidi A-Applications and Materials Science}, 210(7):1261-1271, Wiley-VCH, Weinheim, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Wave modes of collective vortex gyration in dipolar-coupled-dot-array magnonic crystals

Han, D., Vogel, A., Jung, H., Lee, K., Weigand, M., Stoll, H., Schütz, G., Fischer, P., Meier, G., Kim, S.

{Scientific Reports}, 3, Nature Publishing Group, London, UK, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Ferromagnetism of zinc oxide nanograined films

Straumal, B. B., Protasova, S. G., Mazilkin, A. A., Schütz, G., Goering, E., Baretzky, B., Straumal, P. B.

{Journal of Experimental and Theoretical Physics Letters}, 97(6):367-377, Pleiades Publishing, Inc., 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Hydrogen adsorption properties of platinum decorated hierarchically structured templated carbons

Oh, H., Gennett, T., Atanassov, P., Kurttepeli, M., Bals, S., Hurst, K. E., Hirscher, M.

{Microporous and Mesoporous Materials}, pages: 66-74, Elsevier, Amsterdam, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Extended s-d models for the dynamics of noncollinear magnetization: Short review of two different approaches

Fähnle, M., Zhang, S.

{Journal of Magnetism and Magnetic Materials}, 326, pages: 232-234, NH, Elsevier, Amsterdam, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Correlation between spin structure oscillations and domain wall velocities

Bisig, A., Stärk, M., Mawass, M., Moutafis, C., Rhensius, J., Heidler, J., Büttner, F., Noske, M., Weigand, M., Eisebitt, S., Tyliszczak, T., Van Wayenberge, B., Stoll, H., Schütz, G., Kläui, M.

{Nature Communications}, 4, Nature Publishing Group, London, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Recent advances in use of atomic layer deposition and focused ion beams for fabrication of Fresnel zone plates for hard x-rays

Keskinbora, K., Robisch, A., Mayer, M., Grévent, C., Szeghalmi, A. V., Knez, M., Weigand, M., Snigireva, I., Snigirev, A., Salditt, T., Schütz, G.

{Proceedings of SPIE (The International Society for Optical Engineering)}, 8851, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetic states in low-pinning high-anisotropy material nanostructures suitable for dynamic imaging

Büttner, F., Moutafis, C., Bisig, A., Wohlhüter, P., Günther, C. M., Mohanty, J., Geilhufe, J., Schneider, M., v. Korff Schmising, C., Schaffert, S., Pfau, B., Hantschmann, M., Riemeier, M., Emmel, M., Finizio, S., Jakob, G., Weigand, M., Rhensius, J., Franken, J. H., Lavrijsen, R., Swagten, H. J. M., Stoll, H., Eisebitt, S., Kläui, M.

{Physical Review B}, 87, Published by the American Physical Society through the American Institute of Physics, Woodbury, NY, 2013 (article)

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DOI [BibTex]

DOI [BibTex]


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Experimental and theoretical study of D2/H2 quantum sieving in a carbon molecular sieve

Gotzias, A., Charalambopoulou, G., Ampoumogli, A., Krkljus, I., Hirscher, M., Steriotis, T.

{Adsorption}, 19(2-4):373-379, Springer Science+Business Media, New York, 2013 (article)

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DOI [BibTex]

DOI [BibTex]

2005


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Kernel Methods for Measuring Independence

Gretton, A., Herbrich, R., Smola, A., Bousquet, O., Schölkopf, B.

Journal of Machine Learning Research, 6, pages: 2075-2129, December 2005 (article)

Abstract
We introduce two new functionals, the constrained covariance and the kernel mutual information, to measure the degree of independence of random variables. These quantities are both based on the covariance between functions of the random variables in reproducing kernel Hilbert spaces (RKHSs). We prove that when the RKHSs are universal, both functionals are zero if and only if the random variables are pairwise independent. We also show that the kernel mutual information is an upper bound near independence on the Parzen window estimate of the mutual information. Analogous results apply for two correlation-based dependence functionals introduced earlier: we show the kernel canonical correlation and the kernel generalised variance to be independence measures for universal kernels, and prove the latter to be an upper bound on the mutual information near independence. The performance of the kernel dependence functionals in measuring independence is verified in the context of independent component analysis.

ei

PDF PostScript PDF [BibTex]

2005


PDF PostScript PDF [BibTex]


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A Unifying View of Sparse Approximate Gaussian Process Regression

Quinonero Candela, J., Rasmussen, C.

Journal of Machine Learning Research, 6, pages: 1935-1959, December 2005 (article)

Abstract
We provide a new unifying view, including all existing proper probabilistic sparse approximations for Gaussian process regression. Our approach relies on expressing the effective prior which the methods are using. This allows new insights to be gained, and highlights the relationship between existing methods. It also allows for a clear theoretically justified ranking of the closeness of the known approximations to the corresponding full GPs. Finally we point directly to designs of new better sparse approximations, combining the best of the existing strategies, within attractive computational constraints.

ei

PDF [BibTex]

PDF [BibTex]


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Maximal Margin Classification for Metric Spaces

Hein, M., Bousquet, O., Schölkopf, B.

Journal of Computer and System Sciences, 71(3):333-359, October 2005 (article)

Abstract
In order to apply the maximum margin method in arbitrary metric spaces, we suggest to embed the metric space into a Banach or Hilbert space and to perform linear classification in this space. We propose several embeddings and recall that an isometric embedding in a Banach space is always possible while an isometric embedding in a Hilbert space is only possible for certain metric spaces. As a result, we obtain a general maximum margin classification algorithm for arbitrary metric spaces (whose solution is approximated by an algorithm of Graepel. Interestingly enough, the embedding approach, when applied to a metric which can be embedded into a Hilbert space, yields the SVM algorithm, which emphasizes the fact that its solution depends on the metric and not on the kernel. Furthermore we give upper bounds of the capacity of the function classes corresponding to both embeddings in terms of Rademacher averages. Finally we compare the capacities of these function classes directly.

ei

PDF PDF DOI [BibTex]

PDF PDF DOI [BibTex]


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Selective integration of multiple biological data for supervised network inference

Kato, T., Tsuda, K., Asai, K.

Bioinformatics, 21(10):2488 , October 2005 (article)

ei

PDF [BibTex]

PDF [BibTex]


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Assessing Approximate Inference for Binary Gaussian Process Classification

Kuss, M., Rasmussen, C.

Journal of Machine Learning Research, 6, pages: 1679 , October 2005 (article)

Abstract
Gaussian process priors can be used to define flexible, probabilistic classification models. Unfortunately exact Bayesian inference is analytically intractable and various approximation techniques have been proposed. In this work we review and compare Laplace‘s method and Expectation Propagation for approximate Bayesian inference in the binary Gaussian process classification model. We present a comprehensive comparison of the approximations, their predictive performance and marginal likelihood estimates to results obtained by MCMC sampling. We explain theoretically and corroborate empirically the advantages of Expectation Propagation compared to Laplace‘s method.

ei

PDF PDF [BibTex]

PDF PDF [BibTex]


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Clustering on the Unit Hypersphere using von Mises-Fisher Distributions

Banerjee, A., Dhillon, I., Ghosh, J., Sra, S.

Journal of Machine Learning Research, 6, pages: 1345-1382, September 2005 (article)

Abstract
Several large scale data mining applications, such as text categorization and gene expression analysis, involve high-dimensional data that is also inherently directional in nature. Often such data is L2 normalized so that it lies on the surface of a unit hypersphere. Popular models such as (mixtures of) multi-variate Gaussians are inadequate for characterizing such data. This paper proposes a generative mixture-model approach to clustering directional data based on the von Mises-Fisher (vMF) distribution, which arises naturally for data distributed on the unit hypersphere. In particular, we derive and analyze two variants of the Expectation Maximization (EM) framework for estimating the mean and concentration parameters of this mixture. Numerical estimation of the concentration parameters is non-trivial in high dimensions since it involves functional inversion of ratios of Bessel functions. We also formulate two clustering algorithms corresponding to the variants of EM that we derive. Our approach provides a theoretical basis for the use of cosine similarity that has been widely employed by the information retrieval community, and obtains the spherical kmeans algorithm (kmeans with cosine similarity) as a special case of both variants. Empirical results on clustering of high-dimensional text and gene-expression data based on a mixture of vMF distributions show that the ability to estimate the concentration parameter for each vMF component, which is not present in existing approaches, yields superior results, especially for difficult clustering tasks in high-dimensional spaces.

ei

PDF [BibTex]

PDF [BibTex]


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Support Vector Machines for 3D Shape Processing

Steinke, F., Schölkopf, B., Blanz, V.

Computer Graphics Forum, 24(3, EUROGRAPHICS 2005):285-294, September 2005 (article)

Abstract
We propose statistical learning methods for approximating implicit surfaces and computing dense 3D deformation fields. Our approach is based on Support Vector (SV) Machines, which are state of the art in machine learning. It is straightforward to implement and computationally competitive; its parameters can be automatically set using standard machine learning methods. The surface approximation is based on a modified Support Vector regression. We present applications to 3D head reconstruction, including automatic removal of outliers and hole filling. In a second step, we build on our SV representation to compute dense 3D deformation fields between two objects. The fields are computed using a generalized SVMachine enforcing correspondence between the previously learned implicit SV object representations, as well as correspondences between feature points if such points are available. We apply the method to the morphing of 3D heads and other objects.

ei

PDF [BibTex]

PDF [BibTex]


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Fast Protein Classification with Multiple Networks

Tsuda, K., Shin, H., Schölkopf, B.

Bioinformatics, 21(Suppl. 2):59-65, September 2005 (article)

Abstract
Support vector machines (SVM) have been successfully used to classify proteins into functional categories. Recently, to integrate multiple data sources, a semidefinite programming (SDP) based SVM method was introduced Lanckriet et al (2004). In SDP/SVM, multiple kernel matrices corresponding to each of data sources are combined with weights obtained by solving an SDP. However, when trying to apply SDP/SVM to large problems, the computational cost can become prohibitive, since both converting the data to a kernel matrix for the SVM and solving the SDP are time and memory demanding. Another application-specific drawback arises when some of the data sources are protein networks. A common method of converting the network to a kernel matrix is the diffusion kernel method, which has time complexity of O(n^3), and produces a dense matrix of size n x n. We propose an efficient method of protein classification using multiple protein networks. Available protein networks, such as a physical interaction network or a metabolic network, can be directly incorporated. Vectorial data can also be incorporated after conversion into a network by means of neighbor point connection. Similarly to the SDP/SVM method, the combination weights are obtained by convex optimization. Due to the sparsity of network edges, the computation time is nearly linear in the number of edges of the combined network. Additionally, the combination weights provide information useful for discarding noisy or irrelevant networks. Experiments on function prediction of 3588 yeast proteins show promising results: the computation time is enormously reduced, while the accuracy is still comparable to the SDP/SVM method.

ei

PDF Web DOI [BibTex]

PDF Web DOI [BibTex]


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Iterative Kernel Principal Component Analysis for Image Modeling

Kim, K., Franz, M., Schölkopf, B.

IEEE Transactions on Pattern Analysis and Machine Intelligence, 27(9):1351-1366, September 2005 (article)

Abstract
In recent years, Kernel Principal Component Analysis (KPCA) has been suggested for various image processing tasks requiring an image model such as, e.g., denoising or compression. The original form of KPCA, however, can be only applied to strongly restricted image classes due to the limited number of training examples that can be processed. We therefore propose a new iterative method for performing KPCA, the Kernel Hebbian Algorithm which iteratively estimates the Kernel Principal Components with only linear order memory complexity. In our experiments, we compute models for complex image classes such as faces and natural images which require a large number of training examples. The resulting image models are tested in single-frame super-resolution and denoising applications. The KPCA model is not specifically tailored to these tasks; in fact, the same model can be used in super-resolution with variable input resolution, or denoising with unknown noise characteristics. In spite of this, both super-resolution a nd denoising performance are comparable to existing methods.

ei

Web DOI [BibTex]

Web DOI [BibTex]


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Phenotypic characterization of chondrosarcoma-derived cell lines

Schorle, C., Finger, F., Zien, A., Block, J., Gebhard, P., Aigner, T.

Cancer Letters, 226(2):143-154, August 2005 (article)

Abstract
Gene expression profiling of three chondrosarcoma derived cell lines (AD, SM, 105KC) showed an increased proliferative activity and a reduced expression of chondrocytic-typical matrix products compared to primary chondrocytes. The incapability to maintain an adequate matrix synthesis as well as a notable proliferative activity at the same time is comparable to neoplastic chondrosarcoma cells in vivo which cease largely cartilage matrix formation as soon as their proliferative activity increases. Thus, the investigated cell lines are of limited value as substitute of primary chondrocytes but might have a much higher potential to investigate the behavior of neoplastic chondrocytes, i.e. chondrosarcoma biology.

ei

Web [BibTex]

Web [BibTex]