Header logo is


2006


no image
Weighting of experimental evidence in macromolecular structure determination

Habeck, M., Rieping, W., Nilges, M.

Proceedings of the National Academy of Sciences of the United States of America, 103(6):1756-1761, February 2006 (article)

Abstract
The determination of macromolecular structures requires weighting of experimental evidence relative to prior physical information. Although it can critically affect the quality of the calculated structures, experimental data are routinely weighted on an empirical basis. At present, cross-validation is the most rigorous method to determine the best weight. We describe a general method to adaptively weight experimental data in the course of structure calculation. It is further shown that the necessity to define weights for the data can be completely alleviated. We demonstrate the method on a structure calculation from NMR data and find that the resulting structures are optimal in terms of accuracy and structural quality. Our method is devoid of the bias imposed by an empirical choice of the weight and has some advantages over estimating the weight by cross-validation.

ei

Web DOI [BibTex]

2006


Web DOI [BibTex]


no image
Cross-Validation Optimization for Structured Hessian Kernel Methods

Seeger, M., Chapelle, O.

Max-Planck Institute for Biological Cybernetics, Tübingen, Germany, February 2006 (techreport)

Abstract
We address the problem of learning hyperparameters in kernel methods for which the Hessian of the objective is structured. We propose an approximation to the cross-validation log likelihood whose gradient can be computed analytically, solving the hyperparameter learning problem efficiently through nonlinear optimization. Crucially, our learning method is based entirely on matrix-vector multiplication primitives with the kernel matrices and their derivatives, allowing straightforward specialization to new kernels or to large datasets. When applied to the problem of multi-way classification, our method scales linearly in the number of classes and gives rise to state-of-the-art results on a remote imaging task.

ei

PDF Web [BibTex]

PDF Web [BibTex]


no image
Subspace identification through blind source separation

Grosse-Wentrup, M., Buss, M.

IEEE Signal Processing Letters, 13(2):100-103, February 2006 (article)

Abstract
Given a linear and instantaneous mixture model, we prove that for blind source separation (BSS) algorithms based on mutual information, only sources with non-Gaussian distribution are consistently reconstructed independent of initial conditions. This allows the identification of non-Gaussian sources and consequently the identification of signal and noise subspaces through BSS. The results are illustrated with a simple example, and the implications for a variety of signal processing applications, such as denoising and model identification, are discussed.

ei

PDF Web DOI [BibTex]

PDF Web DOI [BibTex]


no image
Classification of Faces in Man and Machine

Graf, A., Wichmann, F., Bülthoff, H., Schölkopf, B.

Neural Computation, 18(1):143-165, January 2006 (article)

ei

PDF Web [BibTex]

PDF Web [BibTex]


no image
Dimension Reduction as a Deflation Method in ICA

Zhang, K., Chan, L.

IEEE Signal Processing Letters, 13(1):45-48, 2006 (article)

ei

Web [BibTex]

Web [BibTex]


no image
Symbol Recognition with Kernel Density Matching

Zhang, W., Wenyin, L., Zhang, K.

IEEE Transactions on Pattern Analysis and Machine Intelligence, 28(12):2020-2024, 2006 (article)

Abstract
We propose a novel approach to similarity assessment for graphic symbols. Symbols are represented as 2D kernel densities and their similarity is measured by the Kullback-Leibler divergence. Symbol orientation is found by gradient-based angle searching or independent component analysis. Experimental results show the outstanding performance of this approach in various situations.

ei

Web [BibTex]

Web [BibTex]


no image
An adaptive method for subband decomposition ICA

Zhang, K., Chan, L.

Neural Computation, 18(1):191-223, 2006 (article)

Abstract
Subband decomposition ICA (SDICA), an extension of ICA, assumes that each source is represented as the sum of some independent subcomponents and dependent subcomponents, which have different frequency bands. In this article, we first investigate the feasibility of separating the SDICA mixture in an adaptive manner. Second, we develop an adaptive method for SDICA, namely band-selective ICA (BS-ICA), which finds the mixing matrix and the estimate of the source independent subcomponents. This method is based on the minimization of the mutual information between outputs. Some practical issues are discussed. For better applicability, a scheme to avoid the high-dimensional score function difference is given. Third, we investigate one form of the overcomplete ICA problems with sources having specific frequency characteristics, which BS-ICA can also be used to solve. Experimental results illustrate the success of the proposed method for solving both SDICA and the over-complete ICA problems.

ei

Web DOI [BibTex]

Web DOI [BibTex]


Thumb xl toc image
Chiral molecules split light: Reflection and refraction in a chiral liquid

Ghosh, A., Fischer, P.

PHYSICAL REVIEW LETTERS, 97(17), 2006, Featured highlight ‘Fundamental optical physics: Refraction’ Nature Photonics, Nov. 2006. (article)

Abstract
A light beam changes direction as it enters a liquid at an angle from another medium, such as air. Should the liquid contain molecules that lack mirror symmetry, then it has been predicted by Fresnel that the light beam will not only change direction, but will actually split into two separate beams with a small difference in the respective angles of refraction. Here we report the observation of this phenomenon. We also demonstrate that the angle of reflection does not equal the angle of incidence in a chiral medium. Unlike conventional optical rotation, which depends on the path-length through the sample, the reported reflection and refraction phenomena arise within a few wavelengths at the interface and thereby suggest a new approach to polarimetry that can be used in microfluidic volumes.

Featured highlight ‘Fundamental optical physics: Refraction’ Nature Photonics, Nov. 2006.

pf

DOI [BibTex]

DOI [BibTex]


Thumb xl screen shot 2018 02 03 at 7.14.23 pm
Passive compliance for a RC servo-controlled bouncing robot

Meyer, F., Spröwitz, A., Berthouze, L.

Advanced Robotics, 20(8):953-961, 2006 (article)

Abstract
A novel and low-cost passively compliant mechanism is described that can be used with RC servos to actuate legged robots in tasks involving high dynamic loads such as bouncing. Compliance is achieved by combining visco-elastic material and metal parts. Joint response to dynamic loads is evaluated using real-world experiments and force data are obtained from a Lagrangian analysis of the system. The experimental results demonstrate the applicative potential of this mechanism.

dlg

DOI [BibTex]

DOI [BibTex]


Thumb xl toc image
Direct chiral discrimination in NMR spectroscopy

Buckingham, A., Fischer, P.

CHEMICAL PHYSICS, 324(1):111-116, 2006 (article)

Abstract
Conventional nuclear magnetic resonance spectroscopy is unable to distinguish between the two mirror-image forms (enantiomers) of a chiral molecule. This is because the NMR spectrum is determined by the chemical shifts and spin-spin coupling constants which - in the absence of a chiral solvent - are identical for the two enantiomers. We discuss how chirality may nevertheless be directly detected in liquid-state NMR spectroscopy: In a chiral molecule, the rotating nuclear magnetic moment induces an electric dipole moment in the direction perpendicular to itself and to the permanent magnetic field of the spectrometer. We present computations of the precessing electric polarization following a pi/2 pulse. Our estimates indicate that the electric polarization should be detectable in favourable cases. We also predict that application of an electrostatic field induces a chirally sensitive magnetization oscillating in the direction of the permanent magnetic field. We show that the electric-field-perturbed chemical shift tensor, the nuclear magnetic shielding polarizability, underlies these chiral NMR effects. (c) 2005 Elsevier B.V. All rights reserved.

pf

DOI [BibTex]

DOI [BibTex]


no image
An ultrasonic standing-wave-actuated nano-positioning walking robot: piezoelectric-metal composite beam modeling

Son, K. J., Kartik, V., Wickert, J. A., Sitti, M.

Journal of vibration and control, 12(12):1293-1309, Sage Publications, 2006 (article)

pi

[BibTex]

[BibTex]


Thumb xl toc image
Ring-resonator-based frequency-domain optical activity measurements of a chiral liquid

Vollmer, F., Fischer, P.

OPTICS LETTERS, 31(4):453-455, 2006 (article)

Abstract
Chiral liquids rotate the plane of polarization of linearly polarized light and are therefore optically active. Here we show that optical rotation can be observed in the frequency domain. A chiral liquid introduced in a fiber-loop ring resonator that supports left and right circularly polarized modes gives rise to relative frequency shifts that are a direct measure of the liquid's circular birefringence and hence of its optical activity. The effect is in principle not diminished if the circumference of the ring is reduced. The technique is similarly applicable to refractive index and linear birefringence measurements. (c) 2006 Optical Society of America.

pf

DOI [BibTex]


Thumb xl toc image
Sign of the refractive index in a gain medium with negative permittivity and permeability

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

JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS, 23(1):45-50, 2006 (article)

Abstract
We show how the sign of the refractive index in any medium may be derived using a rigorous analysis based on Einstein causality. In particular, we consider left-handed materials, i.e., media that have negative permittivities and permeabilities at the frequency of interest. We find that the consideration of gain in such media can give rise to a positive refractive index. (c) 2006 Optical Society of America.

pf

DOI [BibTex]

DOI [BibTex]


Thumb xl screen shot 2012 06 06 at 11.31.38 am
Implicit Wiener Series, Part II: Regularised estimation

Gehler, P., Franz, M.

(148), Max Planck Institute, 2006 (techreport)

ei ps

pdf [BibTex]

pdf [BibTex]


no image
IEEE TRANSACTIONS ON ROBOTICS

VOLZ, RICHARD A, TARN, TJ, MACIEJEWSKI, ANTHONY A, LEE, SUKHAN, BICCHI, ANTONIO, DE LUCA, ALESSANDRO, LUH, PETER B, TAYLOR, RUSSELL H, BEKEY, GEORGE A, ARAI, HIROHIKO, others

2006 (article)

pi

[BibTex]

[BibTex]


no image
Design methodology for biomimetic propulsion of miniature swimming robots

Behkam, B., Sitti, M.

Trans.-ASME Journal of Dynamic Systems Measurement and Control, 128(1):36, ASME, 2006 (article)

pi

Project Page [BibTex]

Project Page [BibTex]


no image
Augmented reality user interface for an atomic force microscope-based nanorobotic system

Vogl, W., Ma, B. K., Sitti, M.

IEEE transactions on nanotechnology, 5(4):397-406, IEEE, 2006 (article)

pi

[BibTex]

[BibTex]


no image
Friction enhancement via micro-patterned wet elastomer adhesives on small intestinal surfaces

Kwon, J., Cheung, E., Park, S., Sitti, M.

Biomedical Materials, 1(4):216, IOP Publishing, 2006 (article)

pi

[BibTex]

[BibTex]


no image
Statistical Learning of LQG controllers

Theodorou, E.

Technical Report-2006-1, Computational Action and Vision Lab University of Minnesota, 2006, clmc (techreport)

am

PDF [BibTex]

PDF [BibTex]


no image
Influence of the substrate on the magnetic anisotropy of monatomic wires

Komelj, M., Steiauf, D., Fähnle, M.

{Physical Review B}, 73, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Mechanical properties of single-walled carbon nanotubes based on higher order Cauchy-Born rule

Guo, X., Wang, J. B., Zhang, H. W.

{International Journal of Solids and Structures}, 43, pages: 1276-1290, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Vanishing Fe 3d orbital moments in single-crystalline magnetite

Goering, E., Gold, S., Lafkioti, M., Schütz, G.

{Europhysics Letters}, 73(1):97-103, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Enhancement of L10 phase formation in FePt nanoparticles by nitrogenization

Dmitrieva, O., Acet, M., Dumpich, G., Kästner, J., Antoniak, C., Farle, M., Fauth, K.

{Journal of Physics D}, 39, pages: 4741-4745, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Structure of historical brass tonques and shallots from baroque organs

Baretzky, B., Friesel, M., Petelin, A., Mazilkin, A., Straumal, B.

{Defect and Diffusion Forum}, 249, pages: 275-280, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Three-dimensional modeling of mechanical forces in the extra-cellular matrix during epithelial lumen formation

Zeng, D., Ferrari, A., Ulmer, J., Veligodskiy, A., Fischer, P., Spatz, J. P., Ventikos, Y., Poulikakos, D., Kroschewski, R.

{Biophysical Journal}, 90(12):4380-4391, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Compliant and low-cost humidity nanosensors using nanoporous polymer membranes

Yang, B., Aksak, B., Lin, Q., Sitti, M.

Sensors and Actuators B: Chemical, 114(1):254-262, Elsevier, 2006 (article)

pi

[BibTex]

[BibTex]


no image
Task-based and stable telenanomanipulation in a nanoscale virtual environment

Kim, S., Sitti, M.

IEEE Transactions on automation science and engineering, 3(3):240-247, IEEE, 2006 (article)

pi

[BibTex]

[BibTex]


no image
Drawing suspended polymer micro-/nanofibers using glass micropipettes

Nain, A. S., Wong, J. C., Amon, C., Sitti, M.

Applied Physics Letters, 89(18):183105, AIP, 2006 (article)

pi

[BibTex]

[BibTex]


no image
Dynamic Hebbian learning in adaptive frequency oscillators

Righetti, L., Buchli, J., Ijspeert, A.

Physica D: Nonlinear Phenomena, 216(2):269-281, 2006 (article)

Abstract
Nonlinear oscillators are widely used in biology, physics and engineering for modeling and control. They are interesting because of their synchronization properties when coupled to other dynamical systems. In this paper, we propose a learning rule for oscillators which adapts their frequency to the frequency of any periodic or pseudo-periodic input signal. Learning is done in a dynamic way: it is part of the dynamical system and not an offline process. An interesting property of our model is that it is easily generalizable to a large class of oscillators, from phase oscillators to relaxation oscillators and strange attractors with a generic learning rule. One major feature of our learning rule is that the oscillators constructed can adapt their frequency without any signal processing or the need to specify a time window or similar free parameters. All the processing is embedded in the dynamics of the adaptive oscillator. The convergence of the learning is proved for the Hopf oscillator, then numerical experiments are carried out to explore the learning capabilities of the system. Finally, we generalize the learning rule to non-harmonic oscillators like relaxation oscillators and strange attractors.

mg

link (url) DOI [BibTex]

link (url) DOI [BibTex]


Thumb xl evatr
HumanEva: Synchronized video and motion capture dataset for evaluation of articulated human motion

Sigal, L., Black, M. J.

(CS-06-08), Brown University, Department of Computer Science, 2006 (techreport)

ps

pdf abstract [BibTex]

pdf abstract [BibTex]


Thumb xl neuralcomp
Bayesian population decoding of motor cortical activity using a Kalman filter

Wu, W., Gao, Y., Bienenstock, E., Donoghue, J. P., Black, M. J.

Neural Computation, 18(1):80-118, 2006 (article)

Abstract
Effective neural motor prostheses require a method for decoding neural activity representing desired movement. In particular, the accurate reconstruction of a continuous motion signal is necessary for the control of devices such as computer cursors, robots, or a patient's own paralyzed limbs. For such applications, we developed a real-time system that uses Bayesian inference techniques to estimate hand motion from the firing rates of multiple neurons. In this study, we used recordings that were previously made in the arm area of primary motor cortex in awake behaving monkeys using a chronically implanted multielectrode microarray. Bayesian inference involves computing the posterior probability of the hand motion conditioned on a sequence of observed firing rates; this is formulated in terms of the product of a likelihood and a prior. The likelihood term models the probability of firing rates given a particular hand motion. We found that a linear gaussian model could be used to approximate this likelihood and could be readily learned from a small amount of training data. The prior term defines a probabilistic model of hand kinematics and was also taken to be a linear gaussian model. Decoding was performed using a Kalman filter, which gives an efficient recursive method for Bayesian inference when the likelihood and prior are linear and gaussian. In off-line experiments, the Kalman filter reconstructions of hand trajectory were more accurate than previously reported results. The resulting decoding algorithm provides a principled probabilistic model of motor-cortical coding, decodes hand motion in real time, provides an estimate of uncertainty, and is straightforward to implement. Additionally the formulation unifies and extends previous models of neural coding while providing insights into the motor-cortical code.

ps

pdf preprint pdf from publisher abstract [BibTex]

pdf preprint pdf from publisher abstract [BibTex]


no image
Theoretical justification of ground-state moment analysis of magnetic dichroic x-ray absorption spectra for 3d transition metals

Dörfler, F., Fähnle, M.

{Physical Review B}, 74, 2006 (article)

Abstract
{(6 pages)}

mms

[BibTex]


no image
Vortex dynamics in coupled ferromagnetic multilayer structures

Chou, K., Puzic, A., Stoll, H., Schütz, G., Van Waeyenberge, B., Tyliszczak, T., Rott, K., Reiss, G., Brückl, H., Neudecker, I., Weiss, D., Back, C. H.

{Journal of Applied Physics}, 99, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Electrical transport, magnetic and thermal properties of icosahedral Al-Pd-Mn quasicrystals

Poddar, A., Das, S., Plachke, D., Carstanjen, H.D.

{Journal of Magnetism and Magnetic Materials}, 300(2):263-272, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Aqueous solution deposition of indium hydroxide and indium oxide columnar type thin films

Qiu, Y., Gerstel, P., Jiang, L., Lipowsky, P., Pitta Bauermann, L., Bill, J.

{International Journal of Materials Research}, 97(6):808-811, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Enhanced orbital magnetism in Fe50Pt50 nanoparticles

Antoniak, C., Lindner, J., Spasova, M., Sudfeld, D., Acet, M., Farle, M., Fauth, K., Wiedwald, U., Boyen, H.-G., Ziemann, P., Wilhelm, F., Rogalev, A., Sun, S.

{Physical Review Letters}, 97, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Biologically inspired polymer microfibers with spatulate tips as repeatable fibrillar adhesives

Kim, S., Sitti, M.

Applied Physics Letters, 89(26):261911-261911, AIP, 2006 (article)

pi

Project Page [BibTex]


no image
Converting polycrystals into single crystals - Selective grain growth by high-energy ion bombardment

Olliges, S., Gruber, P., Bardill, A., Ehrler, D., Carstanjen, H. D., Spolenak, R.

{Acta Materialia}, 54(20):5393-5399, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Topological k-space refinement of the configurational energy of alloys

Shchyglo, O., Bugaev, V.N., Drautz, R., Udyanskyy, A., Reichert, H., Dosch, H.

{Physical Review B}, 72, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Synthesis of MgB2 films in Mg vapour flow and their characterization

Matveev, A. T., Albrecht, J., Konuma, M., Christiani, G., Krockenberger, Y., Starke, U., Schütz, G., Habermeier, H.

{Superconductor Science and Technology}, 19, pages: 299-305, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Analysis of switching times of inhomogeneous magnetization processes in thin platelets

Goll, D., Schütz, G., Kronmüller, H.

{Physica B: Condensed Matter}, 372(1-2):273-276, 2006 (article)

mms

[BibTex]

[BibTex]


no image
The initial oxidation of magnesium: an in situ study with XPS, HERDA and ellipsometry.

Kurth, M., Graat, P. C. J., Carstanjen, H. D., Mittemeijer, E. J.

{Surface and Interface Analysis}, 38, pages: 931-940, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Temperature influence of the faceting of \sum3 and \sum9 grain boundaries in Cu

Straumal, B. B., Polyakov, S. A., Mittemeijer, E. J.

{Acta Materialia}, 54, pages: 167-172, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Coercivity of 2 : 17 based permanent magnets

Kronmüller, H., Goll, D.

{Journal of the Iron and Steel Research International}, 13(Suppl. 1):39-47, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Hydrogen adsorption in a nickel based coordination polymer with open metal sites in the cylindrical cavities of the desolvated framework

Dietzel, P. D. C., Panella, B., Hirscher, M., Blom, R., Fjellvag, H.

{Chemical Communications}, [2006], pages: 959-961, 2006 (article)

mms

DOI [BibTex]

DOI [BibTex]


no image
Magnetic ground states and the role of vortices in ferromagnetic hollow nanospheres

Goll, D., Macke, S., Berkowitz, A., Bertram, H. N.

{Physica B: Condensed Matter}, 372(1-2):282-285, 2006 (article)

mms

[BibTex]

[BibTex]


no image
Two-dimensional vision-based autonomous microparticle manipulation using a nanoprobe

Pawashe, C., Sitti, M.

Journal of Micromechatronics, 3(3):285-306, Brill, 2006 (article)

pi

[BibTex]

[BibTex]