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2016


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Bio-inspired feedback-circuit implementation of discrete, free energy optimizing, winner-take-all computations

Genewein, T, Braun, DA

Biological Cybernetics, 110(2):135–150, June 2016 (article)

Abstract
Bayesian inference and bounded rational decision-making require the accumulation of evidence or utility, respectively, to transform a prior belief or strategy into a posterior probability distribution over hypotheses or actions. Crucially, this process cannot be simply realized by independent integrators, since the different hypotheses and actions also compete with each other. In continuous time, this competitive integration process can be described by a special case of the replicator equation. Here we investigate simple analog electric circuits that implement the underlying differential equation under the constraint that we only permit a limited set of building blocks that we regard as biologically interpretable, such as capacitors, resistors, voltage-dependent conductances and voltage- or current-controlled current and voltage sources. The appeal of these circuits is that they intrinsically perform normalization without requiring an explicit divisive normalization. However, even in idealized simulations, we find that these circuits are very sensitive to internal noise as they accumulate error over time. We discuss in how far neural circuits could implement these operations that might provide a generic competitive principle underlying both perception and action.

ei

DOI [BibTex]

2016


DOI [BibTex]


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Collective modes in three-dimensional magnonic vortex crystals

Hänze, M., Adolff, C. F., Schulte, B., Möller, J., Weigand, M., Meier, G.

{Scientific Reports}, 6, Nature Publishing Group, London, UK, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Spin wave mediated unidirectional vortex core reversal by two orthogonal monopolar field pulses: The essential role of three-dimensional magnetization dynamics

Noske, M., Stoll, H., Fähnle, M., Gangwar, A., Woltersdorf, G., Slavin, A., Weigand, M., Dieterle, G., Förster, J., Back, C. H., Schütz, G.

{Journal of Applied Physics}, 119(17), AIP Publishing, New York, NY, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetic vortex cores as tunable spin-wave emitters

Wintz, S., Tiberkevich, V., Weigand, M., Raabe, J., Lindner, J., Erbe, A., Slavin, A., Fassbender, J.

{Nature Nanotechnology}, 11(11):948-953, Nature Publishing Group, London, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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The usable capacity of porous materials for hydrogen storage

Schlichtenmayer, M., Hirscher, M.

{Applied Physics A}, 122(4), Springer-Verlag Heidelberg, Heidelberg, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Ferromagnetic behaviour of ZnO: the role of grain boundaries

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

{Beilstein Journal of Nanotechnology}, 7, pages: 1936-1947, Beilstein-Institut, Frankfurt am Main, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Localized domain wall nucleation dynamics in asymmetric ferromagnetic rings revealed by direct time-resolved magnetic imaging

Richter, K., Krone, A., Mawass, M., Krüger, B., Weigand, M., Stoll, H., Schütz, G., Kläui, M.

{Physical Review B}, 94(2), American Physical Society, Woodbury, NY, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Observation of room-temperature magnetic skyrmions and their current-driven dynamics in ultrathin metallic ferromagnets

Woo, S., Litzius, K., Krüger, B., Im, M., Caretta, L., Richter, K., Mann, M., Krone, A., Reeve, R. M., Weigand, M., Agrawal, P., Lemesh, I., Mawass, M., Fischer, P., Kläui, M., Beach, G. S. D.

{Nature Materials}, 15(5):501-506, Nature Pub. Group, London, UK, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Decision-Making under Ambiguity Is Modulated by Visual Framing, but Not by Motor vs. Non-Motor Context: Experiments and an Information-Theoretic Ambiguity Model

Grau-Moya, J, Ortega, PA, Braun, DA

PLoS ONE, 11(4):1-21, April 2016 (article)

Abstract
A number of recent studies have investigated differences in human choice behavior depending on task framing, especially comparing economic decision-making to choice behavior in equivalent sensorimotor tasks. Here we test whether decision-making under ambiguity exhibits effects of task framing in motor vs. non-motor context. In a first experiment, we designed an experience-based urn task with varying degrees of ambiguity and an equivalent motor task where subjects chose between hitting partially occluded targets. In a second experiment, we controlled for the different stimulus design in the two tasks by introducing an urn task with bar stimuli matching those in the motor task. We found ambiguity attitudes to be mainly influenced by stimulus design. In particular, we found that the same subjects tended to be ambiguity-preferring when choosing between ambiguous bar stimuli, but ambiguity-avoiding when choosing between ambiguous urn sample stimuli. In contrast, subjects’ choice pattern was not affected by changing from a target hitting task to a non-motor context when keeping the stimulus design unchanged. In both tasks subjects’ choice behavior was continuously modulated by the degree of ambiguity. We show that this modulation of behavior can be explained by an information-theoretic model of ambiguity that generalizes Bayes-optimal decision-making by combining Bayesian inference with robust decision-making under model uncertainty. Our results demonstrate the benefits of information-theoretic models of decision-making under varying degrees of ambiguity for a given context, but also demonstrate the sensitivity of ambiguity attitudes across contexts that theoretical models struggle to explain.

ei

DOI [BibTex]


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Outlook and challenges for hydrogen storage in nanoporous materials

Broom, D. P., Webb, C. J., Hurst, K. E., Parilla, P. A., Gennett, T., Brown, C. M., Zacharia, R., Tylianakis, E., Klontzas, E., Froudakis, G. E., Steriotis, T. A., Trikalitis, P. N., Anton, D. L., Hardy, B., Tamburello, D., Corgnale, C., van Hassel, B. A., Cossement, D., Chahine, R., Hirscher, M.

{Applied Physics A}, 122(3), Springer-Verlag Heidelberg, Heidelberg, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Quantum sieving for separation of hydrogen isotopes using MOFs

Oh, H., Hirscher, M.

{European Journal of Inorganic Chemistry}, 2016(27):4278-4289, Wiley-VCH, Weinheim, Germany, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Direct patterning of vortex generators on a fiber tip using a focused ion beam

Vayalamkuzhi, P., Bhattacharya, S., Eigenthaler, U., Keskinbora, K., Salman, C. T., Hirscher, M., Spatz, J. P., Viswanathan, N. K.

{Optics Letters}, 41(10):2133-2136, Optical Society of America, Washington, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Two-body problem of core-region coupled magnetic vortex stacks

Hänze, M., Adolff, C. F., Velten, S., Weigand, M., Meier, G.

{Physical Review B}, 93(5), American Physical Society, Woodbury, NY, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Irreproducibility in hydrogen storage material research

Broom, D. P., Hirscher, M.

{Energy \& Environmental Science}, 9(11):3368-3380, Royal Society of Chemistry, Cambridge, UK, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Effect of surface configurations on the room-temperature magnetism of pure ZnO

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

{Journal of Materials Chemistry C}, 4(19):4166-4175, Royal Society of Chemistry, London, UK, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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On the synthesis and microstructure analysis of high performance MnBi

Chen, Y., Sawatzki, S., Ener, S., Sepehri-Amin, H., Leineweber, A., Gregori, G., Qu, F., Muralidhar, S., Ohkubo, T., Hono, K., Gutfleisch, O., Kronmüller, H., Schütz, G., Goering, E.

{AIP Advances}, 6(12), 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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The role of individual defects on the magnetic screening of HTSC films

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

{New Journal of Physics}, 18(10), IOP Publishing, Bristol, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Magnetic switching of nanoscale antidot lattices

Wiedwald, U., Gräfe, J., Lebecki, K. M., Skripnik, M., Haering, F., Schütz, G., Ziemann, P., Goering, E., Nowak, U.

{Beilstein Journal of Nanotechnology}, 7, pages: 733-750, Beilstein-Institut, Frankfurt am Main, 2016 (article)

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DOI Project Page [BibTex]

DOI Project Page [BibTex]


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Hydrogen-based energy storage (IEA-HIA Task 32)

Buckley, C. E., Chen, P., van Hassel, B. A., Hirscher, M.

{Applied Physics A}, 122(2), Springer-Verlag Heidelberg, Heidelberg, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Local domain-wall velocity engineering via tailored potential landscapes in ferromagnetic rings

Richter, K., Krone, A., Mawass, M., Krüger, B., Weigand, M., Stoll, H., Schütz, G., Kläui, M.

{Physical Review Applied}, 5(2), American Physical Society, College Park, Md. [u.a.], 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Geometric control of the magnetization reversal in antidot lattices with perpendicular magnetic anisotropy

Gräfe, J., Weigand, M., Träger, N., Schütz, G., Goering, E. J., Skripnik, M., Nowak, U., Haering, F., Ziemann, P., Wiedwald, U.

{Physical Review B}, 93(10), American Physical Society, Woodbury, NY, 2016 (article)

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DOI Project Page Project Page [BibTex]

DOI Project Page Project Page [BibTex]


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Growth and characterizationof large weak topological insulator Bi2Tel single crystal by Bismuth self-flux method

Ryu, G., Son, K., Schütz, G.

{Journal of Crystal Growth}, 440, pages: 26-30, North-Holland, Amsterdam, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Additive interfacial chiral interaction in multilayers for stabilization of small individual skyrmions at room temperature

Moreau-Luchaire, C., Moutafis, C., Reyren, N., Sampaio, J., Vaz, C. A. F., Van Horne, N., Bouzehouane, K., Garcia, K., Deranlot, C., Warnicke, P., Wohlhüter, P., George, J.-M., Weigand, M., Raabe, J., Cros, V., Fert, A.

{Nature Nanotechnology}, 11(5):444-448, Nature Publishing Group, London, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Surface defect free growth of a spin dimer TlCuCl3 compound crystals and investigations on its optical and magnetic properties

Ryu, G., Son, K.

{Journal of Solid State Chemistry}, 237, pages: 358-363, Academic Press, Orlando, Fla., 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Physical and mathematical justification of the numerical Brillouin zone integration of the Boltzmann rate equation by Gaussian smearing

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

{Journal of Theoretical and Applied Physics}, 10(1):1-6, Springer, Berlin, Heidelberg, Tehran, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Pinned orbital moments - A new contribution to magnetic anisotropy

Audehm, P., Schmidt, M., Brück, S., Tietze, T., Gräfe, J., Macke, S., Schütz, G., Goering, E.

{Scientific Reports}, 6, Nature Publishing Group, London, UK, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Comparative study of ALD SiO2 thin films for optical applications

Pfeiffer, K., Shestaeva, S., Bingel, A., Munzert, P., Ghazaryan, L., van Helvoirt, C., Kessels, W. M. M., Sanli, U. T., Grévent, C., Schütz, G., Putkonen, M., Buchanan, I., Jensen, L., Ristau, D., Tünnermann, A., Szeghalmi, A.

{Optical materials express}, 6(2):660-670, OSA, Washington, DC, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Combined first-order reversal curve and x-ray microscopy investigation of magnetization reversal mechanisms in hexagonal antidot lattices

Gräfe, J., Weigand, M., Stahl, C., Träger, N., Kopp, M., Schütz, G., Goering, E. J., Haering, F., Ziemann, P., Wiedwald, U.

{Physical Review B}, 93(1), American Physical Society, Woodbury, NY, 2016 (article)

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DOI Project Page Project Page [BibTex]

DOI Project Page Project Page [BibTex]


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Switching probabilities of magnetic vortex core reversal studied by table top magneto optic Kerr microscopy

Dieterle, G., Gangwar, A., Gräfe, J., Noske, M., Förster, J., Woltersdorf, G., Stoll, H., Back, C. H., Schütz, G.

{Applied Physics Letters}, 108(2), American Institute of Physics, Melville, NY, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Ultrafast demagnetization after femtosecond laser pulses: Transfer of angular momentum from the electronic system to magnetoelastic spin-phonon modes

Tsatsoulis, T., Illg, C., Haag, M., Müller, B. Y., Zhang, L., Fähnle, M.

{Physical Review B}, 93(13), American Physical Society, Woodbury, NY, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Developments in the Ni-Nb-Zr amorphous alloy membranes

Sarker, S., Chandra, D., Hirscher, M., Dolan, M., Isheim, D., Wermer, J., Viano, D., Baricco, M., Udovic, T. J., Grant, D., Palumbo, O., Paolone, A., Cantelli, R.

{Applied Physics A}, 122(3), Springer-Verlag Heidelberg, Heidelberg, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Resistance to the transport of H2 through the external surface of as-made and modified silicalite-1 (MFI)

Kalantzopoulos, G. N., Policicchio, A., Maccallini, E., Krkljus, I., Ciuchi, F., Hirscher, M., Agostino, R. G., Golemme, G.

{Microporous and Mesoporous Materials}, 220, pages: 290-297, Elsevier, Amsterdam, 2016 (article)

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DOI [BibTex]

DOI [BibTex]


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Observation of pseudopartial grain boundary wetting in the NdFeB-based alloy

Straumal, B. B., Mazilkin, A. A., Protasova, S. G., Schütz, G., Straumal, A. B., Baretzky, B.

{Journal of Materials Engineering and Performance}, 25(8):3303-3309, 2016 (article)

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DOI [BibTex]

DOI [BibTex]

2013


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3-D Object Reconstruction of Symmetric Objects by Fusing Visual and Tactile Sensing

Illonen, J., Bohg, J., Kyrki, V.

The International Journal of Robotics Research, 33(2):321-341, Sage, October 2013 (article)

Abstract
In this work, we propose to reconstruct a complete 3-D model of an unknown object by fusion of visual and tactile information while the object is grasped. Assuming the object is symmetric, a first hypothesis of its complete 3-D shape is generated. A grasp is executed on the object with a robotic manipulator equipped with tactile sensors. Given the detected contacts between the fingers and the object, the initial full object model including the symmetry parameters can be refined. This refined model will then allow the planning of more complex manipulation tasks. The main contribution of this work is an optimal estimation approach for the fusion of visual and tactile data applying the constraint of object symmetry. The fusion is formulated as a state estimation problem and solved with an iterative extended Kalman filter. The approach is validated experimentally using both artificial and real data from two different robotic platforms.

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Web DOI Project Page [BibTex]

2013


Web DOI Project Page [BibTex]


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Correlation of Simultaneously Acquired Diffusion-Weighted Imaging and 2-Deoxy-[18F] fluoro-2-D-glucose Positron Emission Tomography of Pulmonary Lesions in a Dedicated Whole-Body Magnetic Resonance/Positron Emission Tomography System

Schmidt, H., Brendle, C., Schraml, C., Martirosian, P., Bezrukov, I., Hetzel, J., Müller, M., Sauter, A., Claussen, C., Pfannenberg, C., Schwenzer, N.

Investigative Radiology, 48(5):247-255, May 2013 (article)

ei

Web [BibTex]

Web [BibTex]


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Learning and Optimization with Submodular Functions

Sankaran, B., Ghazvininejad, M., He, X., Kale, D., Cohen, L.

ArXiv, May 2013 (techreport)

Abstract
In many naturally occurring optimization problems one needs to ensure that the definition of the optimization problem lends itself to solutions that are tractable to compute. In cases where exact solutions cannot be computed tractably, it is beneficial to have strong guarantees on the tractable approximate solutions. In order operate under these criterion most optimization problems are cast under the umbrella of convexity or submodularity. In this report we will study design and optimization over a common class of functions called submodular functions. Set functions, and specifically submodular set functions, characterize a wide variety of naturally occurring optimization problems, and the property of submodularity of set functions has deep theoretical consequences with wide ranging applications. Informally, the property of submodularity of set functions concerns the intuitive principle of diminishing returns. This property states that adding an element to a smaller set has more value than adding it to a larger set. Common examples of submodular monotone functions are entropies, concave functions of cardinality, and matroid rank functions; non-monotone examples include graph cuts, network flows, and mutual information. In this paper we will review the formal definition of submodularity; the optimization of submodular functions, both maximization and minimization; and finally discuss some applications in relation to learning and reasoning using submodular functions.

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arxiv link (url) [BibTex]

arxiv link (url) [BibTex]


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Replacing Causal Faithfulness with Algorithmic Independence of Conditionals

Lemeire, J., Janzing, D.

Minds and Machines, 23(2):227-249, May 2013 (article)

Abstract
Independence of Conditionals (IC) has recently been proposed as a basic rule for causal structure learning. If a Bayesian network represents the causal structure, its Conditional Probability Distributions (CPDs) should be algorithmically independent. In this paper we compare IC with causal faithfulness (FF), stating that only those conditional independences that are implied by the causal Markov condition hold true. The latter is a basic postulate in common approaches to causal structure learning. The common spirit of FF and IC is to reject causal graphs for which the joint distribution looks ‘non-generic’. The difference lies in the notion of genericity: FF sometimes rejects models just because one of the CPDs is simple, for instance if the CPD describes a deterministic relation. IC does not behave in this undesirable way. It only rejects a model when there is a non-generic relation between different CPDs although each CPD looks generic when considered separately. Moreover, it detects relations between CPDs that cannot be captured by conditional independences. IC therefore helps in distinguishing causal graphs that induce the same conditional independences (i.e., they belong to the same Markov equivalence class). The usual justification for FF implicitly assumes a prior that is a probability density on the parameter space. IC can be justified by Solomonoff’s universal prior, assigning non-zero probability to those points in parameter space that have a finite description. In this way, it favours simple CPDs, and therefore respects Occam’s razor. Since Kolmogorov complexity is uncomputable, IC is not directly applicable in practice. We argue that it is nevertheless helpful, since it has already served as inspiration and justification for novel causal inference algorithms.

ei

PDF Web DOI [BibTex]

PDF Web DOI [BibTex]


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What can neurons do for their brain? Communicate selectivity with bursts

Balduzzi, D., Tononi, G.

Theory in Biosciences , 132(1):27-39, Springer, March 2013 (article)

Abstract
Neurons deep in cortex interact with the environment extremely indirectly; the spikes they receive and produce are pre- and post-processed by millions of other neurons. This paper proposes two information-theoretic constraints guiding the production of spikes, that help ensure bursting activity deep in cortex relates meaningfully to events in the environment. First, neurons should emphasize selective responses with bursts. Second, neurons should propagate selective inputs by burst-firing in response to them. We show the constraints are necessary for bursts to dominate information-transfer within cortex, thereby providing a substrate allowing neurons to distribute credit amongst themselves. Finally, since synaptic plasticity degrades the ability of neurons to burst selectively, we argue that homeostatic regulation of synaptic weights is necessary, and that it is best performed offline during sleep.

ei

PDF Web DOI [BibTex]

PDF Web DOI [BibTex]


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Apprenticeship Learning with Few Examples

Boularias, A., Chaib-draa, B.

Neurocomputing, 104, pages: 83-96, March 2013 (article)

Abstract
We consider the problem of imitation learning when the examples, provided by an expert human, are scarce. Apprenticeship learning via inverse reinforcement learning provides an efficient tool for generalizing the examples, based on the assumption that the expert's policy maximizes a value function, which is a linear combination of state and action features. Most apprenticeship learning algorithms use only simple empirical averages of the features in the demonstrations as a statistics of the expert's policy. However, this method is efficient only when the number of examples is sufficiently large to cover most of the states, or the dynamics of the system is nearly deterministic. In this paper, we show that the quality of the learned policies is sensitive to the error in estimating the averages of the features when the dynamics of the system is stochastic. To reduce this error, we introduce two new approaches for bootstrapping the demonstrations by assuming that the expert is near-optimal and the dynamics of the system is known. In the first approach, the expert's examples are used to learn a reward function and to generate furthermore examples from the corresponding optimal policy. The second approach uses a transfer technique, known as graph homomorphism, in order to generalize the expert's actions to unvisited regions of the state space. Empirical results on simulated robot navigation problems show that our approach is able to learn sufficiently good policies from a significantly small number of examples.

ei

Web DOI [BibTex]

Web DOI [BibTex]


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Quasi-Newton Methods: A New Direction

Hennig, P., Kiefel, M.

Journal of Machine Learning Research, 14(1):843-865, March 2013 (article)

Abstract
Four decades after their invention, quasi-Newton methods are still state of the art in unconstrained numerical optimization. Although not usually interpreted thus, these are learning algorithms that fit a local quadratic approximation to the objective function. We show that many, including the most popular, quasi-Newton methods can be interpreted as approximations of Bayesian linear regression under varying prior assumptions. This new notion elucidates some shortcomings of classical algorithms, and lights the way to a novel nonparametric quasi-Newton method, which is able to make more efficient use of available information at computational cost similar to its predecessors.

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website+code pdf link (url) [BibTex]

website+code pdf link (url) [BibTex]


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Regional effects of magnetization dispersion on quantitative perfusion imaging for pulsed and continuous arterial spin labeling

Cavusoglu, M., Pohmann, R., Burger, H. C., Uludag, K.

Magnetic Resonance in Medicine, 69(2):524-530, Febuary 2013 (article)

Abstract
Most experiments assume a global transit delay time with blood flowing from the tagging region to the imaging slice in plug flow without any dispersion of the magnetization. However, because of cardiac pulsation, nonuniform cross-sectional flow profile, and complex vessel networks, the transit delay time is not a single value but follows a distribution. In this study, we explored the regional effects of magnetization dispersion on quantitative perfusion imaging for varying transit times within a very large interval from the direct comparison of pulsed, pseudo-continuous, and dual-coil continuous arterial spin labeling encoding schemes. Longer distances between tagging and imaging region typically used for continuous tagging schemes enhance the regional bias on the quantitative cerebral blood flow measurement causing an underestimation up to 37% when plug flow is assumed as in the standard model.

ei

Web DOI [BibTex]

Web DOI [BibTex]


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The multivariate Watson distribution: Maximum-likelihood estimation and other aspects

Sra, S., Karp, D.

Journal of Multivariate Analysis, 114, pages: 256-269, February 2013 (article)

Abstract
This paper studies fundamental aspects of modelling data using multivariate Watson distributions. Although these distributions are natural for modelling axially symmetric data (i.e., unit vectors where View the MathML source are equivalent), for high-dimensions using them can be difficult—largely because for Watson distributions even basic tasks such as maximum-likelihood are numerically challenging. To tackle the numerical difficulties some approximations have been derived. But these are either grossly inaccurate in high-dimensions [K.V. Mardia, P. Jupp, Directional Statistics, second ed., John Wiley & Sons, 2000] or when reasonably accurate [A. Bijral, M. Breitenbach, G.Z. Grudic, Mixture of Watson distributions: a generative model for hyperspherical embeddings, in: Artificial Intelligence and Statistics, AISTATS 2007, 2007, pp. 35–42], they lack theoretical justification. We derive new approximations to the maximum-likelihood estimates; our approximations are theoretically well-defined, numerically accurate, and easy to compute. We build on our parameter estimation and discuss mixture-modelling with Watson distributions; here we uncover a hitherto unknown connection to the “diametrical clustering” algorithm of Dhillon et al. [I.S. Dhillon, E.M. Marcotte, U. Roshan, Diametrical clustering for identifying anticorrelated gene clusters, Bioinformatics 19 (13) (2003) 1612–1619].

ei

Web DOI [BibTex]

Web DOI [BibTex]


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How the result of graph clustering methods depends on the construction of the graph

Maier, M., von Luxburg, U., Hein, M.

ESAIM: Probability & Statistics, 17, pages: 370-418, January 2013 (article)

Abstract
We study the scenario of graph-based clustering algorithms such as spectral clustering. Given a set of data points, one rst has to construct a graph on the data points and then apply a graph clustering algorithm to nd a suitable partition of the graph. Our main question is if and how the construction of the graph (choice of the graph, choice of parameters, choice of weights) in uences the outcome of the nal clustering result. To this end we study the convergence of cluster quality measures such as the normalized cut or the Cheeger cut on various kinds of random geometric graphs as the sample size tends to in nity. It turns out that the limit values of the same objective function are systematically di erent on di erent types of graphs. This implies that clustering results systematically depend on the graph and can be very di erent for di erent types of graph. We provide examples to illustrate the implications on spectral clustering.

ei

PDF DOI [BibTex]

PDF DOI [BibTex]


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Explicit eigenvalues of certain scaled trigonometric matrices

Sra, S.

Linear Algebra and its Applications, 438(1):173-181, January 2013 (article)

ei

DOI [BibTex]

DOI [BibTex]


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How Sensitive Is the Human Visual System to the Local Statistics of Natural Images?

Gerhard, H., Wichmann, F., Bethge, M.

PLoS Computational Biology, 9(1):e1002873, January 2013 (article)

Abstract
Several aspects of primate visual physiology have been identified as adaptations to local regularities of natural images. However, much less work has measured visual sensitivity to local natural image regularities. Most previous work focuses on global perception of large images and shows that observers are more sensitive to visual information when image properties resemble those of natural images. In this work we measure human sensitivity to local natural image regularities using stimuli generated by patch-based probabilistic natural image models that have been related to primate visual physiology. We find that human observers can learn to discriminate the statistical regularities of natural image patches from those represented by current natural image models after very few exposures and that discriminability depends on the degree of regularities captured by the model. The quick learning we observed suggests that the human visual system is biased for processing natural images, even at very fine spatial scales, and that it has a surprisingly large knowledge of the regularities in natural images, at least in comparison to the state-of-the-art statistical models of natural images.

ei

DOI [BibTex]

DOI [BibTex]


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A neural population model for visual pattern detection

Goris, R., Putzeys, T., Wagemans, J., Wichmann, F.

Psychological Review, 120(3):472–496, 2013 (article)

ei

DOI [BibTex]

DOI [BibTex]


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Accurate indel prediction using paired-end short reads

Grimm, D., Hagmann, J., Koenig, D., Weigel, D., Borgwardt, KM.

BMC Genomics, 14(132), 2013 (article)

ei

Web DOI [BibTex]

Web DOI [BibTex]


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Counterfactual Reasoning and Learning Systems: The Example of Computational Advertising

Bottou, L., Peters, J., Quiñonero-Candela, J., Charles, D., Chickering, D., Portugualy, E., Ray, D., Simard, P., Snelson, E.

Journal of Machine Learning Research, 14, pages: 3207-3260, 2013 (article)

ei

Web link (url) [BibTex]

Web link (url) [BibTex]


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When luminance increment thresholds depend on apparent lightness

Maertens, M., Wichmann, F.

Journal of Vision, 13(6):1-11, 2013 (article)

ei

DOI [BibTex]

DOI [BibTex]


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Efficient network-guided multi-locus association mapping with graph cuts

Azencott, C., Grimm, D., Sugiyama, M., Kawahara, Y., Borgwardt, K.

Bioinformatics, 29(13):i171-i179, 2013 (article)

ei

DOI [BibTex]

DOI [BibTex]