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2015


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Macroscopic drift current in the inverse Faraday effect

Hertel, R., Fähnle, M.

{Physical Review B}, 91(2), American Physical Society, Woodbury, NY, 2015 (article)

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DOI [BibTex]

2015


DOI [BibTex]


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Single-step 3D nanofabrication of kinoform optics via gray-scale focused ion beam lithography for efficient X-ray focusing

Keskinbora, K., Grévent, C., Hirscher, M., Weigand, M., Schütz, G.

{Advanced Optical Materials}, 3, pages: 792-800, WILEY-VCH Verlag GmbH Co. KGaA, Weinheim, 2015 (article)

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DOI [BibTex]

DOI [BibTex]


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Band structure engineering of two-dimensional magnonic vortex crystals

Behncke, C., Hänze, M., Adolff, C. F., Weigand, M., Meier, G.

{Physical Review B}, 91(22), American Physical Society, Woodbury, NY, 2015 (article)

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DOI [BibTex]

DOI [BibTex]


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Towards denoising XMCD movies of fast magnetization dynamics using extended Kalman filter

Kopp, M., Harmeling, S., Schütz, G., Schölkopf, B., Fähnle, M.

{Ultramicroscopy}, 148, pages: 115-122, North-Holland, Amsterdam, 2015 (article)

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DOI [BibTex]

DOI [BibTex]


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A Reward-Maximizing Spiking Neuron as a Bounded Rational Decision Maker

Leibfried, F, Braun, DA

Neural Computation, 27(8):1686-1720, July 2015 (article)

Abstract
Rate distortion theory describes how to communicate relevant information most efficiently over a channel with limited capacity. One of the many applications of rate distortion theory is bounded rational decision making, where decision makers are modeled as information channels that transform sensory input into motor output under the constraint that their channel capacity is limited. Such a bounded rational decision maker can be thought to optimize an objective function that trades off the decision maker's utility or cumulative reward against the information processing cost measured by the mutual information between sensory input and motor output. In this study, we interpret a spiking neuron as a bounded rational decision maker that aims to maximize its expected reward under the computational constraint that the mutual information between the neuron's input and output is upper bounded. This abstract computational constraint translates into a penalization of the deviation between the neuron's instantaneous and average firing behavior. We derive a synaptic weight update rule for such a rate distortion optimizing neuron and show in simulations that the neuron efficiently extracts reward-relevant information from the input by trading off its synaptic strengths against the collected reward.

ei

DOI [BibTex]

DOI [BibTex]


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Magnetic moments induce strong phonon renormalization in FeSi

Krannich, S., Sidis, Y., Lamago, D., Heid, R., Mignot, J., von Löhneysen, H., Ivanov, A., Steffens, P., Keller, T., Wang, L., Goering, E., Weber, F.

{Nature Communications}, 6, Nature Publishing Group, London, 2015 (article)

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DOI [BibTex]

DOI [BibTex]


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Transfer of angular momentum from the spin system to the lattice during ultrafast magnetization

Tsatsoulis, T.

Universität Stuttgart, Stuttgart, 2015 (mastersthesis)

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[BibTex]

[BibTex]


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Robot Learning

Peters, J., Lee, D., Kober, J., Nguyen-Tuong, D., Bagnell, J. A., Schaal, S.

In Springer Handbook of Robotics 2nd Edition, pages: 1371-1394, Springer Berlin Heidelberg, Berlin, Heidelberg, 2015 (incollection)

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[BibTex]

[BibTex]


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Model-based strategy selection learning

Lieder, F., Griffiths, T. L.

The 2nd Multidisciplinary Conference on Reinforcement Learning and Decision Making, 2015 (article)

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Project Page [BibTex]

Project Page [BibTex]


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What is epistemic value in free energy models of learning and acting? A bounded rationality perspective

Ortega, PA, Braun, DA

Cognitive Neuroscience, 6(4):215-216, December 2015 (article)

Abstract
Free energy models of learning and acting do not only care about utility or extrinsic value, but also about intrinsic value, that is, the information value stemming from probability distributions that represent beliefs or strategies. While these intrinsic values can be interpreted as epistemic values or exploration bonuses under certain conditions, the framework of bounded rationality offers a complementary interpretation in terms of information-processing costs that we discuss here.

ei

DOI [BibTex]

DOI [BibTex]


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Derivation of phenomenological expressions for transition matrix elements for electron-phonon scattering

Illg, C., Haag, M., Müller, B. Y., Czycholl, G., Fähnle, M.

2015 (misc)

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link (url) [BibTex]


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Quantum kinetic theory of ultrafast demagnetization by electron-phonon scattering

Briones Paz, J. Z.

Universität Stuttgart, Stuttgart, 2015 (mastersthesis)

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[BibTex]

[BibTex]


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Perpendicular magnetisation from in-plane fields in nano-scaled antidot lattices

Gräfe, J., Haering, F., Tietze, T., Audehm, P., Weigand, M., Wiedwald, U., Ziemann, P., Gawronski, P., Schütz, G., Goering, E. J.

{Nanotechnology}, 26(22), IOP Pub., Bristol, UK, 2015 (article)

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DOI Project Page [BibTex]

DOI Project Page [BibTex]


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Theory of ultrafast demagnetization after femtosecond laser pulses

Fähnle, M., Illg, C., Haag, M., Teeny, N.

{Acta Physica Polonica A}, 127(2):170-175, Państwowe Wydawnictwo Naukowe, Warszawa, 2015 (article)

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DOI [BibTex]

DOI [BibTex]


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Non-linear radial spinwave modes in thin magnetic disks

Helsen, M., Gangwar, Ajay, De Clercq, J., Vansteenkiste, A., Weigand, M., Back, C. H., Van Waeyenberge, B.

{Applied Physics Letters}, 106(3), American Institute of Physics, Melville, NY, 2015 (article)

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DOI [BibTex]

DOI [BibTex]


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Hydrogen isotope separation in metal-organic frameworks: Kinetic or chemical affinity quantum-sieving?

Savchenko, I., Mavrandonakis, A., Heine, T., Oh, H., Teufel, J., Hirscher, M.

{Microporous and Mesoporous Materials}, 216, pages: 133-137, Elsevier, Amsterdam, 2015 (article)

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DOI [BibTex]

DOI [BibTex]


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High-resolution dichroic imaging of magnetic flux distributions in superconductors with scanning x-ray microscopy

Ruoß, S., Stahl, C., Weigand, M., Schütz, G., Albrecht, J.

{Applied Physics Letters}, 106, American Institute of Physics, Melville, NY, 2015 (article)

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DOI [BibTex]

DOI [BibTex]


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Preparation and characterisation of epitaxial Pt/Cu/FeMn/Co thin films on (100)-oriented MgO single crystals

Schmidt, M., Gräfe, J., Audehm, P., Phillipp, F., Schütz, G., Goering, E.

{Physica Status Solidi A}, 212(10):2114-2123, Wiley-VCH, Weinheim, 2015 (article)

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DOI [BibTex]

DOI [BibTex]


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Probing the magnetic moments of [MnIII6CrIII]3+ single-molecule magnets - A cross comparison of XMCD and spin-resolved electron spectroscopy

Helmstedt, A., Dohmeier, N., Müller, N., Gryzia, A., Brechling, A., Heinzmann, U., Hoeke, V., Krickemeyer, E., Glaser, T., Leicht, P., Fonin, M., Tietze, T., Joly, L., Kuepper, K.

{Journal of Electron Spectroscopy and Related Phenomena}, 198, pages: 12-19, Elsevier B.V., Amsterdam, 2015 (article)

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DOI [BibTex]

DOI [BibTex]

2001


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Anabolic and Catabolic Gene Expression Pattern Analysis in Normal Versus Osteoarthritic Cartilage Using Complementary DNA-Array Technology

Aigner, T., Zien, A., Gehrsitz, A., Gebhard, P., McKenna, L.

Arthritis and Rheumatism, 44(12):2777-2789, December 2001 (article)

ei

Web [BibTex]

2001


Web [BibTex]


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Generalization performance of regularization networks and support vector machines via entropy numbers of compact operators

Williamson, R., Smola, A., Schölkopf, B.

IEEE Transactions on Information Theory, 47(6):2516-2532, September 2001 (article)

Abstract
We derive new bounds for the generalization error of kernel machines, such as support vector machines and related regularization networks by obtaining new bounds on their covering numbers. The proofs make use of a viewpoint that is apparently novel in the field of statistical learning theory. The hypothesis class is described in terms of a linear operator mapping from a possibly infinite-dimensional unit ball in feature space into a finite-dimensional space. The covering numbers of the class are then determined via the entropy numbers of the operator. These numbers, which characterize the degree of compactness of the operator can be bounded in terms of the eigenvalues of an integral operator induced by the kernel function used by the machine. As a consequence, we are able to theoretically explain the effect of the choice of kernel function on the generalization performance of support vector machines.

ei

DOI [BibTex]

DOI [BibTex]


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Centralization: A new method for the normalization of gene expression data

Zien, A., Aigner, T., Zimmer, R., Lengauer, T.

Bioinformatics, 17, pages: S323-S331, June 2001, Mathematical supplement available at http://citeseer.ist.psu.edu/574280.html (article)

Abstract
Microarrays measure values that are approximately proportional to the numbers of copies of different mRNA molecules in samples. Due to technical difficulties, the constant of proportionality between the measured intensities and the numbers of mRNA copies per cell is unknown and may vary for different arrays. Usually, the data are normalized (i.e., array-wise multiplied by appropriate factors) in order to compensate for this effect and to enable informative comparisons between different experiments. Centralization is a new two-step method for the computation of such normalization factors that is both biologically better motivated and more robust than standard approaches. First, for each pair of arrays the quotient of the constants of proportionality is estimated. Second, from the resulting matrix of pairwise quotients an optimally consistent scaling of the samples is computed.

ei

PDF PostScript Web [BibTex]

PDF PostScript Web [BibTex]


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Regularized principal manifolds

Smola, A., Mika, S., Schölkopf, B., Williamson, R.

Journal of Machine Learning Research, 1, pages: 179-209, June 2001 (article)

Abstract
Many settings of unsupervised learning can be viewed as quantization problems - the minimization of the expected quantization error subject to some restrictions. This allows the use of tools such as regularization from the theory of (supervised) risk minimization for unsupervised learning. This setting turns out to be closely related to principal curves, the generative topographic map, and robust coding. We explore this connection in two ways: (1) we propose an algorithm for finding principal manifolds that can be regularized in a variety of ways; and (2) we derive uniform convergence bounds and hence bounds on the learning rates of the algorithm. In particular, we give bounds on the covering numbers which allows us to obtain nearly optimal learning rates for certain types of regularization operators. Experimental results demonstrate the feasibility of the approach.

ei

PDF [BibTex]

PDF [BibTex]


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Variationsverfahren zur Untersuchung von Grundzustandseigenschaften des Ein-Band Hubbard-Modells

Eichhorn, J.

Biologische Kybernetik, Technische Universität Dresden, Dresden/Germany, May 2001 (diplomathesis)

Abstract
Using different modifications of a new variational approach, statical groundstate properties of the one-band Hubbard model such as energy and staggered magnetisation are calculated. By taking into account additional fluctuations, the method ist gradually improved so that a very good description of the energy in one and two dimensions can be achieved. After a detailed discussion of the application in one dimension, extensions for two dimensions are introduced. By use of a modified version of the variational ansatz in particular a description of the quantum phase transition for the magnetisation should be possible.

ei

PostScript [BibTex]

PostScript [BibTex]


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Failure Diagnosis of Discrete Event Systems

Son, HI., Kim, KW., Lee, S.

Journal of Control, Automation and Systems Engineering, 7(5):375-383, May 2001, In Korean (article)

ei

[BibTex]

[BibTex]


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Pattern Selection Using the Bias and Variance of Ensemble

Shin, H., Cho, S.

Journal of the Korean Institute of Industrial Engineers, 28(1):112-127, March 2001 (article)

Abstract
[Abstract]: A useful pattern is a pattern that contributes much to learning. For a classification problem those patterns near the class boundary surfaces carry more information to the classifier. For a regression problem the ones near the estimated surface carry more information. In both cases, the usefulness is defined only for those patterns either without error or with negligible error. Using only the useful patterns gives several benefits. First, computational complexity in memory and time for learning is decreased. Second, overfitting is avoided even when the learner is over-sized. Third, learning results in more stable learners. In this paper, we propose a pattern “utility index” that measures the utility of an individual pattern. The utility index is based on the bias and variance of a pattern trained by a network ensemble. In classification, the pattern with a low bias and a high variance gets a high score. In regression, on the other hand, the one with a low bias and a low variance gets a high score. Based on the distribution of the utility index, the original training set is divided into a high-score group and a low-score group. Only the high-score group is then used for training. The proposed method is tested on synthetic and real-world benchmark datasets. The proposed approach gives a better or at least similar performance.

ei

[BibTex]

[BibTex]


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Structure and Functionality of a Designed p53 Dimer.

Davison, TS., Nie, X., Ma, W., Lin, Y., Kay, C., Benchimol, S., Arrowsmith, C.

Journal of Molecular Biology, 307(2):605-617, March 2001 (article)

Abstract
P53 is a homotetrameric tumor suppressor protein involved in transcriptional control of genes that regulate cell proliferation and death. In order to probe the role that oligomerization plays in this capacity, we have previously designed and characterized a series of p53 proteins with altered oligomeric states through hydrophilc substitution of residues Met340 or Leu344 in the normally tetrameric oligomerization domain. Although such mutations have little effect on the overall secondary structural content of the oligomerization domain, both solubility and the resistance to thermal denaturation are substantially reduced relative to that of the wild-type domain. Here, we report the design and characterization of a double-mutant p53 with alterations of residues at positions Met340 and Leu344. The double-mutations Met340Glu/Leu344Lys and Met340Gln/Leu344Arg resulted in distinct dimeric forms of the protein. Furthermore, we have verified by NMR structure determination that the double-mutant Met340Gln/Leu344Arg is essentially a "half-tetramer". Analysis of the in vivo activities of full-length p53 oligomeric mutants reveals that while cell-cycle arrest requires tetrameric p53, transcriptional transactivation activity of monomers and dimers retain roughly background and half of the wild-type activity, respectively.

ei

Web [BibTex]

Web [BibTex]


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An Introduction to Kernel-Based Learning Algorithms

Müller, K., Mika, S., Rätsch, G., Tsuda, K., Schölkopf, B.

IEEE Transactions on Neural Networks, 12(2):181-201, March 2001 (article)

Abstract
This paper provides an introduction to support vector machines, kernel Fisher discriminant analysis, and kernel principal component analysis, as examples for successful kernel-based learning methods. We first give a short background about Vapnik-Chervonenkis theory and kernel feature spaces and then proceed to kernel based learning in supervised and unsupervised scenarios including practical and algorithmic considerations. We illustrate the usefulness of kernel algorithms by discussing applications such as optical character recognition and DNA analysis

ei

DOI [BibTex]

DOI [BibTex]


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Estimating the support of a high-dimensional distribution.

Schölkopf, B., Platt, J., Shawe-Taylor, J., Smola, A., Williamson, R.

Neural Computation, 13(7):1443-1471, March 2001 (article)

Abstract
Suppose you are given some data set drawn from an underlying probability distribution P and you want to estimate a “simple” subset S of input space such that the probability that a test point drawn from P lies outside of S equals some a priori specified value between 0 and 1. We propose a method to approach this problem by trying to estimate a function f that is positive on S and negative on the complement. The functional form of f is given by a kernel expansion in terms of a potentially small subset of the training data; it is regularized by controlling the length of the weight vector in an associated feature space. The expansion coefficients are found by solving a quadratic programming problem, which we do by carrying out sequential optimization over pairs of input patterns. We also provide a theoretical analysis of the statistical performance of our algorithm. The algorithm is a natural extension of the support vector algorithm to the case of unlabeled data.

ei

Web DOI [BibTex]

Web DOI [BibTex]


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Cerebellar Control of Robot Arms

Peters, J.

Biologische Kybernetik, Technische Univeristät München, München, Germany, 2001 (diplomathesis)

ei

[BibTex]

[BibTex]


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The psychometric function: II. Bootstrap-based confidence intervals and sampling

Wichmann, F., Hill, N.

Perception and Psychophysics, 63 (8), pages: 1314-1329, 2001 (article)

ei

PDF [BibTex]

PDF [BibTex]


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The psychometric function: I. Fitting, sampling and goodness-of-fit

Wichmann, F., Hill, N.

Perception and Psychophysics, 63 (8), pages: 1293-1313, 2001 (article)

Abstract
The psychometric function relates an observer'sperformance to an independent variable, usually some physical quantity of a stimulus in a psychophysical task. This paper, together with its companion paper (Wichmann & Hill, 2001), describes an integrated approach to (1) fitting psychometric functions, (2) assessing the goodness of fit, and (3) providing confidence intervals for the function'sparameters and other estimates derived from them, for the purposes of hypothesis testing. The present paper deals with the first two topics, describing a constrained maximum-likelihood method of parameter estimation and developing several goodness-of-fit tests. Using Monte Carlo simulations, we deal with two specific difficulties that arise when fitting functions to psychophysical data. First, we note that human observers are prone to stimulus-independent errors (or lapses ). We show that failure to account for this can lead to serious biases in estimates of the psychometric function'sparameters and illustrate how the problem may be overcome. Second, we note that psychophysical data sets are usually rather small by the standards required by most of the commonly applied statistical tests. We demonstrate the potential errors of applying traditional X^2 methods to psychophysical data and advocate use of Monte Carlo resampling techniques that do not rely on asymptotic theory. We have made available the software to implement our methods

ei

PDF [BibTex]

PDF [BibTex]


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On Unsupervised Learning of Mixtures of Markov Sources

Seldin, Y.

Biologische Kybernetik, The Hebrew University of Jerusalem, Israel, 2001 (diplomathesis)

ei

PDF [BibTex]

PDF [BibTex]


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Extracting egomotion from optic flow: limits of accuracy and neural matched filters

Dahmen, H-J., Franz, MO., Krapp, HG.

In pages: 143-168, Springer, Berlin, 2001 (inbook)

ei

[BibTex]

[BibTex]


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The control structure of artificial creatures

Zhou, D., Dai, R.

Artificial Life and Robotics, 5(3), 2001, invited article (article)

ei

Web [BibTex]

Web [BibTex]


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Markovian domain fingerprinting: statistical segmentation of protein sequences

Bejerano, G., Seldin, Y., Margalit, H., Tishby, N.

Bioinformatics, 17(10):927-934, 2001 (article)

ei

PDF Web [BibTex]

PDF Web [BibTex]


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Support Vector Machines: Theorie und Anwendung auf Prädiktion epileptischer Anfälle auf der Basis von EEG-Daten

Lal, TN.

Biologische Kybernetik, Institut für Angewandte Mathematik, Universität Bonn, 2001, Advised by Prof. Dr. S. Albeverio (diplomathesis)

ei

ZIP [BibTex]

ZIP [BibTex]


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Isotropic second-order nonlinear optical susceptibilities

Fischer, P., Buckingham, A., Albrecht, A.

PHYSICAL REVIEW A, 64(5), 2001 (article)

Abstract
The second-order nonlinear optical susceptibility, in the electric dipole approximation, is only nonvanishing for materials that are noncentrosymmetric. Should the medium be isotropic, then only a chiral system. such as an optically active liquid, satisfies this symmetry requirement. We derive the quantum-mechanical form of the isotropic component of the sum- and difference-frequency susceptibility and discuss its unusual spectral properties. We show that any coherent second-order nonlinear optical process in a system of randomly oriented molecules requires the medium to be chiral. and the incident frequencies to be different and nonzero. Furthermore, a minimum of two nondegenerate excited molecular states are needed for the isotropic part of the susceptibility to be nonvanishing. The rotationally invariant susceptibility is zero in the static field limit and shows exceptionally sensitive resonance and dephasing effects that are particular to chiral centers.

pf

DOI [BibTex]

DOI [BibTex]


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Reply to “Comment on ‘Phenomenological damping in optical response tensors’”

Buckingham, A., Fischer, P.

PHYSICAL REVIEW A, 63(4), 2001 (article)

Abstract
We show that damping factors must not be incorporated in the perturbation of the ground state by a static electric field. If they are included, as in the theory of Stedman et al. {[}preceding Comment. Phys. Rev. A 63, 047801 (2001)], then there would be an electric dipole in the y direction induced in a hydrogen atom in the M-s = + 1/2 state by a static electric field in the x direction. Such a dipole is excluded by symmetry.

pf

DOI [BibTex]


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The coercivity of the melt-spun Sm-Fe-Ga-C permanent magnets and the effect of additives (Nb, Cu and Zr)

Zhang, J. X., Kleinschroth, I., Goll, D., Cuevas, F., Kronmüller, H.

{Journal of Physics-Condensed Matter}, 13(46):10487-10496, 2001 (article)

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[BibTex]

[BibTex]


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Hardness-depth profile of a carbon-implanted Ti-6Al-4V alloy and its relation to composition and microstructure

Kunert, M., Kienzle, O., Baretzky, B., Baker, S. P., Mittemeijer, E. J.

{Journal of Materials Research}, 16(8):2321-2335, 2001 (article)

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[BibTex]

[BibTex]


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Kritische Ströme über Kleinwinkelkorngrenzen in YBCO

Albrecht, J.

Universität Stuttgart, Stuttgart, 2001 (phdthesis)

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[BibTex]

[BibTex]


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New Sm(Co, Fe, Cu, Zr)(z) magnets with better temperature stability

Tang, W., Zhang, Y., Goll, D., Hadjipanayis, G. C., Kronmüller, H.

{Journal of Magnetism and Magnetic Materials}, 226(Sp. Iss. SI):1365-1366, 2001 (article)

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[BibTex]

[BibTex]


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Hydrogen in nanostructured vanadium-hydrogen systems

Orimo, S., Kimmerle, F., Majer, G.

{Physical Review B}, 63(9), 2001 (article)

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[BibTex]

[BibTex]


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Diffusion of hydrogen in heterogeneous systems

Herrmann, A., Schimmele, L., Mössinger, J., Hirscher, M., Kronmüller, H.

{Applied Physics A-Materials Science \& Processing}, 72(2):197-208, 2001 (article)

mms

[BibTex]

[BibTex]


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Von der elektronischen Struktur zum makroskopischen Verhalten: Eine Multi-Skalen Analyse der Plastizität

Kohlhammer, S.

Universität Stuttgart, Stuttgart, 2001 (phdthesis)

mms

[BibTex]


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Structural vacancies in B2-CoAl and NiAl

Meyer, B., Bester, G., Fähnle, M.

{Scripta Materialia}, 44, pages: 2485-2488, 2001 (article)

mms

[BibTex]

[BibTex]


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Grain boundary phase transition in the Cu-Bi system

Straumal, B. B., Prokofyev, S. I., Chang, L.-S., Sluchanko, N. E., Baretzky, B., Gust, W., Mittemeijer, E. J.

{Diffusion and Defect Forum}, 194-199, pages: 1343-1348, 2001 (article)

mms

[BibTex]

[BibTex]


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Carbon nanostructures: an efficient hydrogen storage medium for fuel cells

Atkinson, K., Roth, S., Hirscher, M., Grünwald, W.

{Fuel Cells Bulletin}, 4(38):9-12, 2001 (article)

mms

[BibTex]

[BibTex]


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Magnetic domains in nanostructured media studied with M-TXM

Fischer, P., Eimüller, T., Schütz, G., Bayreuther, G., Tsunashima, S., Tagaki, N., Denbeaux, G., Attwood, D.

{Journal of Synchrotron Radiation}, 8, pages: 325-327, 2001 (article)

mms

[BibTex]

[BibTex]