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2005


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Kernel Constrained Covariance for Dependence Measurement

Gretton, A., Smola, A., Bousquet, O., Herbrich, R., Belitski, A., Augath, M., Murayama, Y., Schölkopf, B., Logothetis, N.

AISTATS, January 2005 (talk)

Abstract
We discuss reproducing kernel Hilbert space (RKHS)-based measures of statistical dependence, with emphasis on constrained covariance (COCO), a novel criterion to test dependence of random variables. We show that COCO is a test for independence if and only if the associated RKHSs are universal. That said, no independence test exists that can distinguish dependent and independent random variables in all circumstances. Dependent random variables can result in a COCO which is arbitrarily close to zero when the source densities are highly non-smooth. All current kernel-based independence tests share this behaviour. We demonstrate exponential convergence between the population and empirical COCO. Finally, we use COCO as a measure of joint neural activity between voxels in MRI recordings of the macaque monkey, and compare the results to the mutual information and the correlation. We also show the effect of removing breathing artefacts from the MRI recording.

ei

PostScript [BibTex]

2005


PostScript [BibTex]


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Composite adaptive control with locally weighted statistical learning

Nakanishi, J., Farrell, J. A., Schaal, S.

Neural Networks, 18(1):71-90, January 2005, clmc (article)

Abstract
This paper introduces a provably stable learning adaptive control framework with statistical learning. The proposed algorithm employs nonlinear function approximation with automatic growth of the learning network according to the nonlinearities and the working domain of the control system. The unknown function in the dynamical system is approximated by piecewise linear models using a nonparametric regression technique. Local models are allocated as necessary and their parameters are optimized on-line. Inspired by composite adaptive control methods, the proposed learning adaptive control algorithm uses both the tracking error and the estimation error to update the parameters. We first discuss statistical learning of nonlinear functions, and motivate our choice of the locally weighted learning framework. Second, we begin with a class of first order SISO systems for theoretical development of our learning adaptive control framework, and present a stability proof including a parameter projection method that is needed to avoid potential singularities during adaptation. Then, we generalize our adaptive controller to higher order SISO systems, and discuss further extension to MIMO problems. Finally, we evaluate our theoretical control framework in numerical simulations to illustrate the effectiveness of the proposed learning adaptive controller for rapid convergence and high accuracy of control.

am

link (url) [BibTex]

link (url) [BibTex]


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Invariance of Neighborhood Relation under Input Space to Feature Space Mapping

Shin, H., Cho, S.

Pattern Recognition Letters, 26(6):707-718, 2005 (article)

Abstract
If the training pattern set is large, it takes a large memory and a long time to train support vector machine (SVM). Recently, we proposed neighborhood property based pattern selection algorithm (NPPS) which selects only the patterns that are likely to be near the decision boundary ahead of SVM training [Proc. of the 7th Pacific-Asia Conference on Knowledge Discovery and Data Mining (PAKDD), Lecture Notes in Artificial Intelligence (LNAI 2637), Seoul, Korea, pp. 376–387]. NPPS tries to identify those patterns that are likely to become support vectors in feature space. Preliminary reports show its effectiveness: SVM training time was reduced by two orders of magnitude with almost no loss in accuracy for various datasets. It has to be noted, however, that decision boundary of SVM and support vectors are all defined in feature space while NPPS described above operates in input space. If neighborhood relation in input space is not preserved in feature space, NPPS may not always be effective. In this paper, we sh ow that the neighborhood relation is invariant under input to feature space mapping. The result assures that the patterns selected by NPPS in input space are likely to be located near decision boundary in feature space.

ei

PDF PDF [BibTex]

PDF PDF [BibTex]


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Approximate Inference for Robust Gaussian Process Regression

Kuss, M., Pfingsten, T., Csato, L., Rasmussen, C.

(136), Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2005 (techreport)

Abstract
Gaussian process (GP) priors have been successfully used in non-parametric Bayesian regression and classification models. Inference can be performed analytically only for the regression model with Gaussian noise. For all other likelihood models inference is intractable and various approximation techniques have been proposed. In recent years expectation-propagation (EP) has been developed as a general method for approximate inference. This article provides a general summary of how expectation-propagation can be used for approximate inference in Gaussian process models. Furthermore we present a case study describing its implementation for a new robust variant of Gaussian process regression. To gain further insights into the quality of the EP approximation we present experiments in which we compare to results obtained by Markov chain Monte Carlo (MCMC) sampling.

ei

PDF [BibTex]

PDF [BibTex]


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Theory of Classification: A Survey of Some Recent Advances

Boucheron, S., Bousquet, O., Lugosi, G.

ESAIM: Probability and Statistics, 9, pages: 323 , 2005 (article)

Abstract
The last few years have witnessed important new developments in the theory and practice of pattern classification. We intend to survey some of the main new ideas that have lead to these important recent developments.

ei

PDF DOI [BibTex]

PDF DOI [BibTex]


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Support Vector Machines and Kernel Algorithms

Schölkopf, B., Smola, A.

In Encyclopedia of Biostatistics (2nd edition), Vol. 8, 8, pages: 5328-5335, (Editors: P Armitage and T Colton), John Wiley & Sons, NY USA, 2005 (inbook)

ei

[BibTex]

[BibTex]


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Moment Inequalities for Functions of Independent Random Variables

Boucheron, S., Bousquet, O., Lugosi, G., Massart, P.

To appear in Annals of Probability, 33, pages: 514-560, 2005 (article)

Abstract
A general method for obtaining moment inequalities for functions of independent random variables is presented. It is a generalization of the entropy method which has been used to derive concentration inequalities for such functions cite{BoLuMa01}, and is based on a generalized tensorization inequality due to Lata{l}a and Oleszkiewicz cite{LaOl00}. The new inequalities prove to be a versatile tool in a wide range of applications. We illustrate the power of the method by showing how it can be used to effortlessly re-derive classical inequalities including Rosenthal and Kahane-Khinchine-type inequalities for sums of independent random variables, moment inequalities for suprema of empirical processes, and moment inequalities for Rademacher chaos and $U$-statistics. Some of these corollaries are apparently new. In particular, we generalize Talagrands exponential inequality for Rademacher chaos of order two to any order. We also discuss applications for other complex functions of independent random variables, such as suprema of boolean polynomials which include, as special cases, subgraph counting problems in random graphs.

ei

PDF [BibTex]

PDF [BibTex]


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Visual perception I: Basic principles

Wagemans, J., Wichmann, F., de Beeck, H.

In Handbook of Cognition, pages: 3-47, (Editors: Lamberts, K. , R. Goldstone), Sage, London, 2005 (inbook)

ei

[BibTex]

[BibTex]


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Maximum-Margin Feature Combination for Detection and Categorization

BakIr, G., Wu, M., Eichhorn, J.

Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2005 (techreport)

Abstract
In this paper we are concerned with the optimal combination of features of possibly different types for detection and estimation tasks in machine vision. We propose to combine features such that the resulting classifier maximizes the margin between classes. In contrast to existing approaches which are non-convex and/or generative we propose to use a discriminative model leading to convex problem formulation and complexity control. Furthermore we assert that decision functions should not compare apples and oranges by comparing features of different types directly. Instead we propose to combine different similarity measures for each different feature type. Furthermore we argue that the question: ”Which feature type is more discriminative for task X?” is ill-posed and show empirically that the answer to this question might depend on the complexity of the decision function.

ei

PDF [BibTex]

PDF [BibTex]


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Towards a Statistical Theory of Clustering. Presented at the PASCAL workshop on clustering, London

von Luxburg, U., Ben-David, S.

Presented at the PASCAL workshop on clustering, London, 2005 (techreport)

Abstract
The goal of this paper is to discuss statistical aspects of clustering in a framework where the data to be clustered has been sampled from some unknown probability distribution. Firstly, the clustering of the data set should reveal some structure of the underlying data rather than model artifacts due to the random sampling process. Secondly, the more sample points we have, the more reliable the clustering should be. We discuss which methods can and cannot be used to tackle those problems. In particular we argue that generalization bounds as they are used in statistical learning theory of classification are unsuitable in a general clustering framework. We suggest that the main replacements of generalization bounds should be convergence proofs and stability considerations. This paper should be considered as a road map paper which identifies important questions and potentially fruitful directions for future research about statistical clustering. We do not attempt to present a complete statistical theory of clustering.

ei

PDF [BibTex]

PDF [BibTex]


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A tutorial on v-support vector machines

Chen, P., Lin, C., Schölkopf, B.

Applied Stochastic Models in Business and Industry, 21(2):111-136, 2005 (article)

Abstract
We briefly describe the main ideas of statistical learning theory, support vector machines (SVMs), and kernel feature spaces. We place particular emphasis on a description of the so-called -SVM, including details of the algorithm and its implementation, theoretical results, and practical applications. Copyright © 2005 John Wiley & Sons, Ltd.

ei

PDF [BibTex]

PDF [BibTex]


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Robust EEG Channel Selection Across Subjects for Brain Computer Interfaces

Schröder, M., Lal, T., Hinterberger, T., Bogdan, M., Hill, J., Birbaumer, N., Rosenstiel, W., Schölkopf, B.

EURASIP Journal on Applied Signal Processing, 2005(19, Special Issue: Trends in Brain Computer Interfaces):3103-3112, (Editors: Vesin, J. M., T. Ebrahimi), 2005 (article)

Abstract
Most EEG-based Brain Computer Interface (BCI) paradigms come along with specific electrode positions, e.g.~for a visual based BCI electrode positions close to the primary visual cortex are used. For new BCI paradigms it is usually not known where task relevant activity can be measured from the scalp. For individual subjects Lal et.~al showed that recording positions can be found without the use of prior knowledge about the paradigm used. However it remains unclear to what extend their method of Recursive Channel Elimination (RCE) can be generalized across subjects. In this paper we transfer channel rankings from a group of subjects to a new subject. For motor imagery tasks the results are promising, although cross-subject channel selection does not quite achieve the performance of channel selection on data of single subjects. Although the RCE method was not provided with prior knowledge about the mental task, channels that are well known to be important (from a physiological point of view) were consistently selected whereas task-irrelevant channels were reliably disregarded.

ei

Web DOI [BibTex]

Web DOI [BibTex]


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Approximate Bayesian Inference for Psychometric Functions using MCMC Sampling

Kuss, M., Jäkel, F., Wichmann, F.

(135), Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2005 (techreport)

Abstract
In psychophysical studies the psychometric function is used to model the relation between the physical stimulus intensity and the observer's ability to detect or discriminate between stimuli of different intensities. In this report we propose the use of Bayesian inference to extract the information contained in experimental data estimate the parameters of psychometric functions. Since Bayesian inference cannot be performed analytically we describe how a Markov chain Monte Carlo method can be used to generate samples from the posterior distribution over parameters. These samples are used to estimate Bayesian confidence intervals and other characteristics of the posterior distribution. In addition we discuss the parameterisation of psychometric functions and the role of prior distributions in the analysis. The proposed approach is exemplified using artificially generate d data and in a case study for real experimental data. Furthermore, we compare our approach with traditional methods based on maximum-likelihood parameter estimation combined with bootstrap techniques for confidence interval estimation. The appendix provides a description of an implementation for the R environment for statistical computing and provides the code for reproducing the results discussed in the experiment section.

ei

PDF [BibTex]

PDF [BibTex]


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Nonlinear optical spectroscopy of chiral molecules

Fischer, P., Hache, F.

CHIRALITY, 17(8):421-437, 2005 (article)

Abstract
We review nonlinear optical processes that are specific to chiral molecules in solution and on surfaces. In contrast to conventional natural optical activity phenomena, which depend linearly on the electric field strength of the optical field, we discuss how optical processes that are nonlinear (quadratic, cubic, and quartic) functions of the electromagnetic field strength may probe optically active centers and chiral vibrations. We show that nonlinear techniques open entirely new ways of exploring chirality in chemical and biological systems: The cubic processes give rise to nonlinear circular dichroism and nonlinear optical rotation and make it possible to observe dynamic chiral processes at ultrafast time scales. The quadratic second-harmonic and sum-frequency-generation phenomena and the quartic processes may arise entirely in the electric-dipole approximation and do not require the use of circularly polarized light to detect chirality: They provide surface selectivity and their observables can be relatively much larger than in linear optical activity. These processes also give rise to the generation of light at a new color, and in liquids this frequency conversion only occurs if the solution is optically active. We survey recent chiral nonlinear optical experiments and give examples of their application to problems of biophysical interest. (C) 2005 Wiley-Liss, Inc.

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DOI [BibTex]

DOI [BibTex]


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Negative refraction at optical frequencies in nonmagnetic two-component molecular media

Chen, Y., Fischer, P., Wise, F.

PHYSICAL REVIEW LETTERS, 95(6), 2005 (article)

Abstract
There is significant motivation to develop media with negative refractive indices at optical frequencies, but efforts in this direction are hampered by the weakness of the magnetic response at such frequencies. We show theoretically that a nonmagnetic medium with two atomic or molecular constituents can exhibit a negative refractive index. A negative index is possible even when the real parts of both the permittivity and permeability are positive. This surprising result provides a route to isotropic negative-index media at optical frequencies.

pf

DOI [BibTex]

DOI [BibTex]


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A model of smooth pursuit based on learning of the target dynamics using only retinal signals

Shibata, T., Tabata, H., Schaal, S., Kawato, M.

Neural Networks, 18, pages: 213-225, 2005, clmc (article)

Abstract
While the predictive nature of the primate smooth pursuit system has been evident through several behavioural and neurophysiological experiments, few models have attempted to explain these results comprehensively. The model we propose in this paper in line with previous models employing optimal control theory; however, we hypothesize two new issues: (1) the medical superior temporal (MST) area in the cerebral cortex implements a recurrent neural network (RNN) in order to predict the current or future target velocity, and (2) a forward model of the target motion is acquired by on-line learning. We use stimulation studies to demonstrate how our new model supports these hypotheses.

am

link (url) [BibTex]

link (url) [BibTex]


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Linear and Nonlinear Estimation models applied to Hemodynamic Model

Theodorou, E.

Technical Report-2005-1, Computational Action and Vision Lab University of Minnesota, 2005, clmc (techreport)

Abstract
The relation between BOLD signal and neural activity is still poorly understood. The Gaussian Linear Model known as GLM is broadly used in many fMRI data analysis for recovering the underlying neural activity. Although GLM has been proved to be a really useful tool for analyzing fMRI data it can not be used for describing the complex biophysical process of neural metabolism. In this technical report we make use of a system of Stochastic Differential Equations that is based on Buxton model [1] for describing the underlying computational principles of hemodynamic process. Based on this SDE we built a Kalman Filter estimator so as to estimate the induced neural signal as well as the blood inflow under physiologic and sensor noise. The performance of Kalman Filter estimator is investigated under different physiologic noise characteristics and measurement frequencies.

am

PDF [BibTex]

PDF [BibTex]


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From colloidal Co/CoO core/shell nanoparticles to arrays of metallic nanomagnets: surface modification and magnetic properties

Wiedwald, U., Fauth, K., Hessler, M., Boyen, H. G., Weigl, F., Hilgendorff, M., Giersig, M., Schütz, G., Ziemann, P., Farle, M.

{ChemPhysChem}, 6(12):2522-2526, 2005 (article)

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[BibTex]

[BibTex]


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Competition between order and phase separation in Au-Ni

Reichert, H., Schöps, A., Ramsteiner, I. B., Bugaev, V. N., Shchyglo, O., Udyansky, A., Dosch, H., Asta, M., Drautz, R., Honkimäki, V.

{Physical Review Letters}, 95(23), 2005 (article)

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[BibTex]

[BibTex]


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Influence of faceting-roughening on triple-junction migration in zinc

Straumal, B. B., Sursaeva, V. G., Gomakova, A. S.

{Zeitschrift f\"ur Metallkunde}, 96(10):1147-1151, 2005 (article)

mms

[BibTex]

[BibTex]


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Damping of spin dynamics in nanostructures: an ab initio study

Steiauf, D., Fähnle, M.

{Physical Review B}, 72, 2005 (article)

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[BibTex]

[BibTex]


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Test of the hypothesis of transient molten state diffusion for swift-heavy-ion induced mixing

Srivastava, S. K.., Avasthi, D. K., Assmann, W., Wang, Z. G., Kucal, H., Jaquet, E., Carstanjen, H. D., Toulemonde, M.

{Physical Review B}, 71, 2005 (article)

mms

[BibTex]

[BibTex]


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Hydrogen physisorption in metal-organic porous crystals

Panella, B., Hirscher, M.

{Advanced Materials}, 17(5):538-541, 2005 (article)

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[BibTex]

[BibTex]


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The influence of misorientation deviation on the faceting of \Sigma3 grain boundaries in aluminium

Kogtenkova, O., Straumal, B., Protasova, S., Tsurekawa, S., Watanabe, T.

{Zeitschrift f\"ur Metallkunde}, 96(2):216-219, 2005 (article)

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[BibTex]

[BibTex]


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Metal-oxide interfacial reactions: encapsulation of Pd on TiO2(110)

Fu, Q., Wagner, Th., Olliges, S., Carstanjen, H. D.

{Journal of Physical Chemistry B}, 109, pages: 944-951, 2005 (article)

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[BibTex]

[BibTex]


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Faceting of \Sigma3 and \Sigma9 grain boundaries in Cu-Bi alloys

Straumal, B. B., Polyakov, S. A., Bischoff, E., Gust, W., Baretzky, B.

{Acta Materialia}, 53(2):247-254, 2005 (article)

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[BibTex]

[BibTex]


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Dependence of damage efficiency of ions in diamond on electronic stopping

Friedland, E., Carstanjen, H. D., Myberg, G., Nasr, M. A.

{Nuclear Instruments and Methods in Physics Research B}, 230, pages: 129-132, 2005 (article)

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[BibTex]

[BibTex]


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Volumetric measurement of hydrogen storage in HCl-treated polyaniline and polypyrrole

Panella, B., Kossykh, L., Dettlaff-Weglikowska, U., Hirscher, M., Zerbi, G., Roth, S.

{Synthetic Metals}, 151, pages: 208-210, 2005 (article)

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[BibTex]

[BibTex]


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Permanent magnet alloys based on Sm2Co17; phase evolution in the quinary system Sm-Zr-FeCo-Cu

Stadelmaier, H. H., Goll, D., Kronmüller, H.

{Zeitschrift f\"ur Metallkunde}, 96(1):17-23, 2005 (article)

mms

[BibTex]

[BibTex]


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Parametric and Non-Parametric approaches for nonlinear tracking of moving objects

Hidaka, Y, Theodorou, E.

Technical Report-2005-1, 2005, clmc (article)

am

PDF [BibTex]

PDF [BibTex]


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Anisotropic temperature-dependent current densities in vicinal YBCO

Djupmyr, M., Cristiani, G., Habermeier, H.-U., Albrecht, J.

{Physical Review B}, 72, 2005 (article)

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[BibTex]

[BibTex]


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Effects of catalysts on the dehydriding of alanates monitored by proton NMR

Majer, G., Stanik, E., Valiente-Banuet, L. E., Grinberg, F., Kircher, O., Fichtner, M.

{Journal of Alloys and Compounds}, 404, pages: 738-742, 2005 (article)

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[BibTex]

[BibTex]


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Kinetics of carbon precipitation and re-solution in low Si-content silicon iron

Walz, F., Wakisaka, T., Kronmüller, H.

{Physica Status Solidi A}, 202(14):2667-2678, 2005 (article)

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[BibTex]

[BibTex]


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Highly homogeneous MgB2 films prepared by a new post-annealing process

Matveev, A., Albrecht, J., Konuma, M., Stuhlhofer, B., Starke, U., Habermeier, H.-U.

{Superconductor Science and Technology}, 18, pages: 1313-1316, 2005 (article)

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[BibTex]

[BibTex]


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Spin-polarized quasiparticle injection effects in YBCO thin films

Soltan, S., Albrecht, J., Habermeier, H.-U.

{Solid State Communications}, 135, pages: 461-465, 2005 (article)

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[BibTex]

[BibTex]


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Thermodynamic properties from ab-initio calculations: New theoretical developments, and applications to various materials systems

Fähnle, M., Drautz, R., Lechermann, F., Singer, R., Diaz-Ortiz, A., Dosch, H.

{Physica Status Solidi (B)}, 242, pages: 1159-1173, 2005 (article)

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[BibTex]

[BibTex]


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Nuclear magnetic resonance measurements of the hydrogen dynamics in nanocrystalline graphite

Stanik, E., Majer, G., Orimo, S., Ichikawa, T., Fujii, H.

{Journal of Applied Physics}, 98, 2005 (article)

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[BibTex]

[BibTex]


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Oxygen K-edge shift at the Verwey transition of magnetite

Goering, E., Gold, S., Lafkioti, M., Schütz, G., Brabers, V. A. M.

{Physical Review B}, 72, 2005 (article)

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[BibTex]

[BibTex]


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First-principles investigation of the Ni-Fe-Al system

Lechermann, F., Fähnle, M., Sanchez, J. M.

{Intermetallics}, 13((10)):1096-1109, 2005 (article)

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[BibTex]

[BibTex]


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GdN thin films: Bulk and local electronic and magnetic properties

Leuenberger, F., Parge, A., Felsch, W., Fauth, K., He\ssler, M.

{Physical Review B}, 72(1), 2005 (article)

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[BibTex]

[BibTex]


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Hydrogen permeation through Pd/Fe and Pd/Ni multilayer systems

Yamakawa, K., Ege, M., Hirscher, M., Ludescher, B., Kronmüller, H.

{Journal of Alloys and Compounds}, 393(1-2):5-10, 2005 (article)

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[BibTex]

[BibTex]


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Parametrization of the magnetic energy at the atomic level

Drautz, R., Fähnle, M.

{Physical Review B}, 72, 2005 (article)

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[BibTex]


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Time-scales of electronic processes in Fe3O4 - An attempt to resolve a recently accentuated controversy

Fähnle, M., Kronmüller, H., Walz, F.

{Physica B}, 369, pages: 177-180, 2005 (article)

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[BibTex]

[BibTex]


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Interlayer contraction in MgB2 upon replacement of Mg by Al: Effect of the covalent bond energy

Bester, G., Fähnle, M.

{Physical Review B}, 72, 2005 (article)

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[BibTex]

[BibTex]


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First-principles atomistic modeling of ordering phenomena and phase diagrams

Fähnle, M., Drautz, R., Lechermann, F., Singer, R., Diaz-Ortiz, A., Dosch, H.

{TMS Letters}, 2(1):7-8, 2005 (article)

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[BibTex]

[BibTex]


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Constrained spin-density functional theory for excited magnetic configurations in an adiabatic approximation

Singer, R., Fähnle, M., Bihlmayer, G.

{Physical Review B}, 71, 2005 (article)

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[BibTex]

[BibTex]


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The influence of magnetism on atomic defects and diffusion: model calculations and ab initio electron theory

Fähnle, M., Schimmele, L.

{Defect and Diffusion Forum}, 237-240, pages: 19-29, 2005 (article)

mms

[BibTex]

[BibTex]


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X-ray magnetic circular dichroism sum rule correction for the light transition metals

Goering, E.

{Philosophical Magazine}, 85, pages: 2895-2911, 2005 (article)

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[BibTex]

[BibTex]


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Temperature dependence of the magnetocrystalline anisotropy energy and projected microscopic magnetic moments in epitaxial CrO2 films

Gold, S., Goering, E., König, C., Rüdiger, U., Güntherodt, G., Schütz, G.

{Physical Review B}, 71(22), 2005 (article)

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On the imaging of the flux-line lattice of a type-II superconductor by soft X-ray absorption spectroscopy

Fähnle, M., Albrecht, J., Eimüller, T., Fisher, P., Goering, E., Steiauf, D., Schütz, G.

{Journal of Synchrotron Radiation}, 12, pages: 251-253, 2005 (article)

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[BibTex]

[BibTex]