Incremental Exact Min-Cut in Poly-logarithmic Amortized Update Time

We present a deterministic incremental algorithm for exactly maintaining the size of a minimum cut with ~O(1) amortized time per edge insertion and O(1) query time. This result partially answers an open question posed by Thorup [Combinatorica 2007]. It also stays in sharp contrast to a polynomial conditional lower-bound for the fully-dynamic weighted minimum cut problem. Our algorithm is obtained by combining a recent sparsification technique of Kawarabayashi and Thorup [STOC 2015] and an exact incremental algorithm of Henzinger [J. of Algorithm 1997]. We also study space-efficient incremental algorithms for the minimum cut problem. Concretely, we show that there exists an O(n log n/epsilon^2) space Monte-Carlo algorithm that can process a stream of edge insertions starting from an empty graph, and with high probability, the algorithm maintains a (1+epsilon)-approximation to the minimum cut. The algorithm has ~O(1) amortized update-time and constant query-time

Interface conditions for limits of the Navier--Stokes--Korteweg model

In this contribution we will study the behaviour of the pressure across phase boundaries in liquid-vapour flows. As mathematical model we will consider the static version of the Navier-Stokes-Korteweg model which belongs to the class of diffuse interface models. From this static equation a formula for the pressure jump across the phase interface can be derived. If we perform then the sharp interface limit we see that the resulting interface condition for the pressure seems to be inconsistent with classical results of hydrodynamics. Therefore we will present two approaches to recover the results of hydrodynamics in the sharp interface limit at least for special situations

The impact of unilateral brain damage on weight perception, sensorimotor anticipation, and fingertip force adaptation

PublishedJournal ArticleResearch Support, Non-U.S. Gov'tDamage to the left parietal cortex can lead to apraxia - a selective deficit in tool use and action planning. There is conflicting evidence as to whether this disorder affects more fundamental motor parameters, such as applying the appropriate forces to lift objects based upon how heavy they look. Here we examined how individuals with left and right-lateralized brain damage lift and perceive the weight of objects of the same mass which vary in their size and material properties. No clear differences emerged between the groups in terms of how visual material properties affected their perceptions of object weight or their initial application of grip and load forces. There was, however, some evidence that unilateral brain injury impaired the use of size cues for the parameterization of grip forces.This project was funded with a grant to support the initiation of international collaboration from the Deutsche Forschungsgemeinschaft (DFG). We thank Prof. G. Goldenberg, head of the Clinic for Neuropsychology at Hospital München-Bogenhausen for his support providing us with access to the patients tested in this study

Web-basierte Atlanten als Instrumente zur Lösung raumbezogener Problemstellungen. Ein generisches Informationsmodell als semantische Brücke zwischen Daten und Diensten

Die Arbeit beschreibt Konzeption, Entwicklung, Aufbau und Betrieb eines generischen Informationsmodells in der Verwaltung der Stadt Köln. Das Modell ist praxiserprobt und in der Fachwelt bekannt. Einige Komponenten beginnen, sich als Standard für Geoinformationssysteme durchzusetzen. In seiner Gesamtheit ist das Modell einzigartig. Über Lizenzen findet es Verbreitung in Städten und Unternehmen. Teile waren immer wieder Richtungsgeber und Schrittmacher der technologischen Entwicklung. Der Verfasser, nach Konzeption, Entwicklung und Aufbau des Modells nun mit den nicht minder schwierigen Alltäglichkeiten des Betriebs befasst, schaut visionär voraus. Er sieht zusätzlich zur technischen Weiterentwicklung die Öffnung des bisher verwaltungsinternen Informationsmodells nach außen als erstrebenswert an. Informationsbeteiligung wäre nicht nur ein auch politikwirksames Zeichen modernen Verwaltungsmanagements, sondern sicherlich auch ein willkommener Beitrag zur wohlverstandenen Informationsgesellschaft. Ein generisches Informationsmodell kann flexibel auf raumbezogene Informations-wünsche reagieren. Allein Geodaten reichen dazu aber nicht aus; sie sind um Sach-daten aus den Verwaltungsverfahren zu ergänzen. Erst dadurch ist es möglich, die umfangreichen Datenschätze einer Kommunalverwaltung in Werte umzusetzen und für vielfältige geographische Fragestellungen zu nutzen. Als Grundlage des als Semantic Data Dictionary bezeichneten Informationsmodells war ein raumbezogenes Data Warehouse zu konzipieren, zu realisieren und aufzu-bauen. Das Besondere daran ist die Verbindung eines Spatial Data Warehouse mit einem Business Data Warehouse. Das bedeutet nicht nur die Verknüpfung von Geo- und Sachdaten für Raumanalysen, sondern auch die Zusammenführung komplexer Wertschöpfungsprozesse für eine integrierte Informationsproduktion. Der Nutzer hat dadurch Zugriff auf laufend aktuelle Sachdaten für beliebige räumliche Strukturen. Die aus unterschiedlichen Quellen zusammengeführten und verdichteten Informationen werden auf der Basis einer modernen IT-Architektur als raum-bezogene Dienste im Sinne von Spatial Business Intelligence bereitgestellt. Das dahinter stehende Content Management System ermöglicht den Aufbau und die Pflege von raumbezogenen Diensten, aber auch die schnelle Reaktion auf neue Informationszusammenstellungen und unterstützt dabei Verfahren zur Informations-gewinnung. Die als Web Services angebotenen Atlanten ermöglichen dem Nutzer unterschiedliche Sichten auf Struktur, Inhalt, Funktionalität und Sprache und damit eine neue Dimension sachbezogener Raumanalysen. Am Beispiel ausgewählter Indikatoren wird der gesamte innovative Produktions-prozess von den Verwaltungsdaten über die Datenmodellierung im Data Warehouse und die Informationsmodellierung bis zu interaktiven Atlanten im Web aufgezeigt. Dazu werden Sachdaten aus unterschiedlichen Quellen kleinräumig aufbereitet und analysiert. Die Grundlagendaten und die daraus abgeleiteten Ergebnisse sind in verschiedenen Planungsatlanten nutzbar. Dieses Wertschöpfungsnetzwerk ist auf andere raumbezogene Problemstellungen übertragbar

Dissipation characteristics of quantized spin waves in nano-scaled magnetic ring structures

The spatial profiles and the dissipation characteristics of spin-wave quasi-eigenmodes are investigated in small magnetic Ni$_{81}$Fe$_{19}$ ring structures using Brillouin light scattering microscopy. It is found, that the decay constant of a mode decreases with increasing mode frequency. Indications for a contribution of three-magnon processes to the dissipation of higher-order spin-wave quasi-eigenmodes are found

Torque-planning errors affect the perception of object properties and sensorimotor memories during object manipulation in uncertain grasp situations.

This is the author accepted manuscript. The final version is available from American Physiological Society via the DOI in this record.Predicting instead of only reacting to the properties of objects we grasp is crucial to dexterous object manipulation. Although we normally plan our grasps according to well-learned associations, we rely on implicit sensorimotor memories when we learn to interact with novel or ambiguous objects. However, little is known about the influence of sensorimotor predictions on subsequent perception and action. Here, young and elderly subjects repeatedly lifted an object in which the center of mass (CoM) was randomly varied between trials straight upward with the aim of preventing object tilts. After each lift, subjects indicated the location of the perceived CoM and reported how heavy the object felt. Surprisingly, we found that sensorimotor torque memories eventually causing initial lifting errors had substantial effects on the perception of torques, weight, and the torque planning for the next lift. Whereas subjects tended to partly retain their previous erroneous sensorimotor memories (instead of solely relying on the previously encountered torque for the upcoming motor plan), they perceived encountered torques to be stronger when they erroneously predicted them. Additionally, we found that torque prediction errors, as well as the actual torques, made the object feel heavier. By contrast, perception did not influence upcoming motor control. There were no major differences observed between the age groups. The sensorimotor impact on torque perception can be explained by internal feedforward prediction highlighting task-relevant errors, while the partial retention and adaptation of sensorimotor torque memories is reconciled with the trial-to-trial learning rule for motor adaptation. NEW & NOTEWORTHY The current study is the first to demonstrate in an object manipulation task in uncertainty that errors in the sensorimotor prediction of torques influence the perception of both torques and weight, whereas sensorimotor torque memories are partly retained and partly adapted to planning errors. Our results provide novel insights into the predictive mechanisms underpinning the common everyday task of object manipulation and further support theories about the predictive modulation of perception established in other neuroscientific disciplines

Target Uncertainty During Motor Decision-Making: The Time Course of Movement Variability Reveals the Effect of Different Sources of Uncertainty on the Control of Reaching Movements

The processes underlying motor decision-making have recently caught considerable amount of scientific attention, focusing on the integration of empirical evidence from sensorimotor control research with psychological theories and computational models on decision-making. Empirical studies on motor decision-making suggest that the kinematics of goal-directed reaching movements are sensitive to the level of target uncertainty during movement planning. However, the source of uncertainty as a relevant factor influencing the process of motor decision-making has not been sufficiently considered, yet. In this study, we test the assumption that the source of target uncertainty has an effect on motor decision-making, which can be proven by analyzing movement variability during the time course of movement execution. Ten healthy young adults performed three blocks with 66 trials of goal-directed reaching movements in each block, across which the source and level of reach target uncertainty at movement onset were manipulated (“no uncertainty”, “extrinsic uncertainty”, and “intrinsic uncertainty”). Fingertip position of the right index finger was recorded using an optical motion tracking system. Standard kinematic measures (i.e., path length and movement duration) as well as variability of fingertip position across the time course of movement execution and at movement end were analyzed. In line with previous studies, we found that a high level of extrinsic target uncertainty leads to increased overall movement duration, which could be attributed to increased path length in this condition, as compared to intrinsic and no target uncertainty (all p < 0.001). Movement duration and path length did not show any differences between the latter two conditions. However, the time course analysis of movement variability revealed significant differences between these two conditions, with increased variability of fingertip position in the presence of intrinsic target uncertainty (Condition × Sampling point: p = 0.01), though considerably less than under high extrinsic target uncertainty (p ≤ 0.001). These findings suggest that both the level and source of uncertainty have a significant effect on the processing of potential action plans during motor decision-making, which can be revealed through the analysis of the time course of movement variability at the end-effector level

Use of Biological Motion based Cues and Ecological Sounds in the Neurorehabilitation of Apraxia

Technological progress in the area of informatics and human interface platforms create a window of opportunities for the neurorehablitation of patients with motor impairments. The CogWatch project (www.cogwatch.eu) aims to create an intelligent assistance system to improve motor planning and execution in patients with apraxia during their daily activities. Due to the brain damage caused by cardiovascular incident these patients suffer from impairments in the ability to use tools, and to sequence actions during daily tasks (such as making breakfast). Based on the common coding theory (Hommel et al., 2001) and mirror neuron primate research (Rizzolatti et al., 2001) we aim to explore use of cues, which incorporate aspects of biological motion from healthy adults performing everyday tasks requiring tool use and ecological sounds linked to the action goal. We hypothesize that patients with apraxia will benefit from supplementary sensory information relevant to the task, which will reinforce the selection of the appropriate motor plan. Findings from this study determine the type of sensory guidance in the CogWatch interface. Rationale for the experimental design is presented and the relevant literature is discussed