Results for "Thomas Meier"

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Dynamics of short time--scale energy relaxation of optical excitations due to electron--electron scattering in the presence of arbitrary disorderNov 11 2002Apr 11 2003A non--equilibrium occupation distribution relaxes towards the Fermi--Dirac distribution due to electron--electron scattering even in finite Fermi systems. The dynamic evolution of this thermalization process assumed to result from an optical excitation ... More
Model Checking CTL is Almost Always Inherently SequentialMar 25 2011Nov 15 2011The model checking problem for CTL is known to be P-complete (Clarke, Emerson, and Sistla (1986), see Schnoebelen (2002)). We consider fragments of CTL obtained by restricting the use of temporal modalities or the use of negations---restrictions already ... More
The Complexity of Satisfiability for Sub-Boolean Fragments of ALCJan 24 2010Mar 29 2010The standard reasoning problem, concept satisfiability, in the basic description logic ALC is PSPACE-complete, and it is EXPTIME-complete in the presence of unrestricted axioms. Several fragments of ALC, notably logics in the FL, EL, and DL-Lite family, ... More
Generalized Satisfiability for the Description Logic ALCMar 04 2011The standard reasoning problem, concept satisfiability, in the basic description logic ALC is PSPACE-complete, and it is EXPTIME-complete in the presence of unrestricted axioms. Several fragments of ALC, notably logics in the FL, EL, and DL-Lite families, ... More
Small Seifert fibered surgery on hyperbolic pretzel knotsOct 29 2012Jul 23 2013We complete the classification of hyperbolic pretzel knots admitting Seifert fibered surgeries. This is the final step in understanding all exceptional surgeries on hyperbolic pretzel knots. We also present results toward similar classifications for non-pretzel ... More
Additive decompositions for rings of modular formsOct 10 2017Feb 02 2018We study rings of integral modular forms for congruence subgroups as modules over the ring of integral modular forms for the full modular group. In many cases these modules are free or decompose at least into well-understood pieces. We apply this to characterize ... More
Thermodynamics and Spin Tunneling Dynamics in Ferric Wheels with Excess SpinJul 02 2001We study theoretically the thermodynamic properties and spin dynamics of a class of magnetic rings closely related to ferric wheels, antiferromagnetic ring systems, in which one of the Fe (III) ions has been replaced by a dopant ion to create an excess ... More
Alignment of the CMS Silicon Tracker -- and how to improve detectors in the futureOct 11 2010The complex system of the CMS all-silicon Tracker, with 15\,148 silicon strip and 1440 silicon pixel modules, requires sophisticated alignment procedures. In order to achieve an optimal track-parameter resolution, the position and orientation of its modules ... More
Orbit equivalence of higher-rank graphsMar 17 2019We study the notions of continuous orbit equivalence and eventual one-sided conjugacy of finitely-aligned higher-rank graphs and two-sided conjugacy of row-finite higher-rank graphs with finitely many vertices and no sinks or sources. We show that there ... More
Neuromorphic Learning towards Nano Second PrecisionSep 17 2013Sep 18 2013Temporal coding is one approach to representing information in spiking neural networks. An example of its application is the location of sounds by barn owls that requires especially precise temporal coding. Dependent upon the azimuthal angle, the arrival ... More
The Complexity of Reasoning for Fragments of Autoepistemic LogicJun 01 2010Autoepistemic logic extends propositional logic by the modal operator L. A formula that is preceded by an L is said to be "believed". The logic was introduced by Moore 1985 for modeling an ideally rational agent's behavior and reasoning about his own ... More
The Complexity of Propositional ImplicationNov 06 2008Aug 12 2009The question whether a set of formulae G implies a formula f is fundamental. The present paper studies the complexity of the above implication problem for propositional formulae that are built from a systematically restricted set of Boolean connectives. ... More
Algebraic Cuntz-Pimsner ringsOct 17 2008May 12 2009From a system consisting of a right non-degenerate ring $R$, a pair of $R$-bimodules $Q$ and $P$ and an $R$-bimodule homomorphism $\psi:P\otimes Q\longrightarrow R$ we construct a $\Z$-graded ring $\mathcal{T}_{(P,Q,\psi)}$ called the Toeplitz ring and ... More
The Complexity of Reasoning for Fragments of Default LogicAug 28 2008Aug 23 2010Default logic was introduced by Reiter in 1980. In 1992, Gottlob classified the complexity of the extension existence problem for propositional default logic as $\SigmaPtwo$-complete, and the complexity of the credulous and skeptical reasoning problem ... More
Observation of Nuclear Quantum Effects and Hydrogen Bond Symmetrisation in High Pressure IceMar 19 2018Hydrogen bond symmetrisations in H-bonded systems triggered by pressure induced nuclear quantum effects (NQEs) is a long-known concept1 but experimental evidences in high-pressure ices have remained elusive with conventional methods2,3. Theoretical works ... More
Neuromorphic Hardware learns to learnMar 15 2019Mar 18 2019Hyperparameters and learning algorithms for neuromorphic hardware are usually chosen by hand. In contrast, the hyperparameters and learning algorithms of networks of neurons in the brain, which they aim to emulate, have been optimized through extensive ... More
On the Parameterized Complexity of Default Logic and Autoepistemic LogicOct 04 2011Oct 06 2011We investigate the application of Courcelle's Theorem and the logspace version of Elberfeld etal. in the context of the implication problem for propositional sets of formulae, the extension existence problem for default logic, as well as the expansion ... More
The Complexity of Monotone Hybrid Logics over Linear Frames and the Natural NumbersApr 05 2012Jun 12 2012Hybrid logic with binders is an expressive specification language. Its satisfiability problem is undecidable in general. If frames are restricted to N or general linear orders, then satisfiability is known to be decidable, but of non-elementary complexity. ... More
The Complexity of Satisfiability for Fragments of Hybrid Logic -- Part IJun 08 2009The satisfiability problem of hybrid logics with the downarrow binder is known to be undecidable. This initiated a research program on decidable and tractable fragments. In this paper, we investigate the effect of restricting the propositional part of ... More
NMR close to Mega-Bar PressuresMar 14 2018The past 15 years have seen an astonishing increase in Nuclear Magnetic Resonance (NMR) sensitivity and accessible pressure range in high-pressure NMR experiments, owing to a series of new developments of NMR spectroscopy applied to the diamond anvil ... More
Fast alignment of a complex tracking detector using advanced track modelsMar 21 2011The inner silicon detector of the Compact Muon Solenoid experiment (CMS) at CERN's LHC consists of 16588 modules. Charged-particle tracks in the detector are used to improve the accuracy to which the position and orientation of the modules is known. This ... More
Stop the ChaseJan 26 2009May 06 2009The chase procedure, an algorithm proposed 25+ years ago to fix constraint violations in database instances, has been successfully applied in a variety of contexts, such as query optimization, data exchange, and data integration. Its practicability, however, ... More
Foundations of SPARQL Query OptimizationDec 19 2008Jan 26 2009The SPARQL query language is a recent W3C standard for processing RDF data, a format that has been developed to encode information in a machine-readable way. We investigate the foundations of SPARQL query optimization and (a) provide novel complexity ... More
Multi-Label Wireless Interference Identification with Convolutional Neural NetworksApr 12 2018The steadily growing use of license-free frequency bands require reliable coexistence management and therefore proper wireless interference identification (WII). In this work, we propose a WII approach based upon a deep convolutional neural network (CNN) ... More
A tale of clusters: No resolvable periodicity in the terrestrial impact cratering recordJan 31 2017Rampino & Caldeira (2015) carry out a circular spectral analysis (CSA) of the terrestrial impact cratering record over the past 260 million years (Ma), and suggest a ~26 Ma periodicity of impact events. For some of the impacts in that analysis, new accurate ... More
Apate - A Linux Kernel Module for High Interaction HoneypotsJul 11 2015Honeypots are used in IT Security to detect and gather information about ongoing intrusions, e.g., by documenting the approach of an attacker. Honeypots do so by presenting an interactive system that seems just like a valid application to an attacker. ... More
Wireless Interference Identification with Convolutional Neural NetworksMar 02 2017The steadily growing use of license-free frequency bands requires reliable coexistence management for deterministic medium utilization. For interference mitigation, proper wireless interference identification (WII) is essential. In this work we propose ... More
A Whitehead theorem for periodic homotopy groupsNov 09 2018We show that $v_n$-periodic homotopy groups detect homotopy equivalences between simply-connected finite CW-complexes.
Distribution Network Topology Detection with Time Series Measurement Data AnalysisApr 22 2015This paper proposes a novel approach for detecting the topology of distribution networks based on the analysis of time series measurements. The time-based analysis approach draws on data from high-precision phasor measurement units (PMUs or synchrophasors) ... More
The Euler characteristic of the Whitehead automorphism group of a free productJan 28 2006A combinatorial summation identity over the lattice of labelled hypertrees is established that allows one to gain concrete information on the Euler characteristics of various automorphism groups of free products of groups.
Charged domain walls in improper ferroelectric hexagonal manganites and gallatesJun 16 2018Jul 04 2018Ferroelectric domain walls are attracting broad attention as atomic-scale switches, diodes and mobile wires for next-generation nanoelectronics. Charged domain walls in improper ferroelectrics are particularly interesting as they offer multifunctional ... More
Microscopic modeling of photoluminescence of strongly disordered semiconductorsMay 09 2005Feb 07 2006A microscopic theory for the luminescence of ordered semiconductors is modified to describe photoluminescence of strongly disordered semiconductors. The approach includes both diagonal disorder and the many-body Coulomb interaction. As a case study, the ... More
Optically induced coherent intra-band dynamics in disordered semiconductorsNov 21 2001On the basis of a tight-binding model for a strongly disordered semiconductor with correlated conduction- and valence band disorder a new coherent dynamical intra-band effect is analyzed. For systems that are excited by two, specially designed ultrashort ... More
Is a 4-bit synaptic weight resolution enough? - Constraints on enabling spike-timing dependent plasticity in neuromorphic hardwareJan 30 2012Nov 28 2014Large-scale neuromorphic hardware systems typically bear the trade-off between detail level and required chip resources. Especially when implementing spike-timing-dependent plasticity, reduction in resources leads to limitations as compared to floating ... More
Propagation of Coulomb-correlated electron-hole pairs in semiconductors with correlated and anticorrelated disorderFeb 28 2000Local ultrafast optical excitation of electron-hole pairs in disordered semiconductors provides the possibility to observe experimentally interaction-assisted propagation of correlated quantum particles in a disordered environment. In addition to the ... More
Generalized Seismic Phase Detection with Deep LearningMay 03 2018Jan 11 2019To optimally monitor earthquake-generating processes, seismologists have sought to lower detection sensitivities ever since instrumental seismic networks were started about a century ago. Recently, it has become possible to search continuous waveform ... More
Magnetic Flux Tailoring through Lenz Lenses in Toroidal Diamond Indenter Cells: A New Pathway to High Pressure Nuclear Magnetic ResonanceMay 24 2017A new pathway to nuclear magnetic resonance spectroscopy in high pressure diamond anvil cells is introduced, using inductively coupled broadband passive electro-magnetic lenses to locally amplify the magnetic flux at the isolated sample, leading to an ... More
Signatures of Many-Particle Correlations in Two-Dimensional Fourier-Transform Spectra of Semiconductor NanostructuresFeb 05 2007On the basis of a microscopic theory, the signatures of many-particle correlations in Two-Dimensional Fourier-Transform Spectra (2D-FTS) of semiconductor nanostructures are identified and compared to experimental data. Spectra in the photon energy range ... More
Dynamics of Coulomb-correlated electron-hole pairs in disordered semiconductor nanowiresNov 23 2001The dynamics of optically generated electron-hole pairs is investigated in a disordered semiconductor nanowire. The particle pairs are generated by short laser pulses and their dynamics is followed using the Heisenberg equation of motion. Is is shown ... More
The effect of heterogeneity on decorrelation mechanisms in spiking neural networks: a neuromorphic-hardware studyNov 28 2014Jun 09 2016High-level brain function such as memory, classification or reasoning can be realized by means of recurrent networks of simplified model neurons. Analog neuromorphic hardware constitutes a fast and energy efficient substrate for the implementation of ... More
Macro pose based non-invasive thermal comfort perception for energy efficiencyNov 12 2018Dec 20 2018Individual thermal comfort perception gives important feedback signals for energy efficient control of smart buildings. However, there is no effective method to measure real-time thermal comfort status of individual occupant until now. For overcoming ... More
Joule heating in nanowiresDec 20 2010Aug 30 2011We study the effect of Joule heating from electric currents flowing through ferromagnetic nanowires on the temperature of the nanowires and on the temperature of the substrate on which the nanowires are grown. The spatial current density distribution, ... More
PhaseLink: A Deep Learning Approach to Seismic Phase AssociationSep 08 2018Jan 10 2019Seismic phase association is a fundamental task in seismology that pertains to linking together phase detections on different sensors that originate from a common earthquake. It is widely employed to detect earthquakes on permanent and temporary seismic ... More
Interacting electrons in a one-dimensional random array of scatterers - A Quantum Dynamics and Monte-Carlo studyMar 28 2002The quantum dynamics of an ensemble of interacting electrons in an array of random scatterers is treated using a new numerical approach for the calculation of average values of quantum operators and time correlation functions in the Wigner representation. ... More
Generalized Complexity of ALC SubsumptionMay 03 2012The subsumption problem with respect to terminologies in the description logic ALC is EXPTIME-complete. We investigate the computational complexity of fragments of this problem by means of allowed Boolean operators. Hereto we make use of the notion of ... More
Compactly supported cohomology of buildingsJun 15 2008We compute the compactly supported cohomology of the standard realization of any locally finite building.
Vector Bundles on the Moduli Stack of Elliptic CurvesJul 31 2013Apr 20 2015We study vector bundles on the moduli stack of elliptic curves over a local ring R. If R is a field or a discrete valuation ring of (residue) characteristic not 2 or 3, all these vector bundles are sums of line bundles. For R the 3-local integers, we ... More
Inducing strong convergence into the asymptotic behaviour of proximal splitting algorithms in Hilbert spacesSep 06 2016Nov 18 2017Proximal splitting algorithms for monotone inclusions (and convex optimization problems) in Hilbert spaces share the common feature to guarantee for the generated sequences in general weak convergence to a solution. In order to achieve strong convergence, ... More
Distinguishing topologically and smoothly doubly slice knotsJan 06 2014Nov 03 2014We construct an infinite family of smoothly slice knots that we prove are topologically doubly slice. Using the correction terms coming from Heegaard Floer homology, we show that none of these knots is smoothly doubly slice. We use these knots to show ... More
Spectral Sequences in String TopologyJan 27 2010Aug 08 2015In this paper, we investigate the behaviour of the Serre spectral sequence with respect to the algebraic structures of string topology in generalized homology theories, specificially with the Chas-Sullivan product and the corresponding coproduct and module ... More
Perturb-and-MPM: Quantifying Segmentation Uncertainty in Dense Multi-Label CRFsMar 01 2017Mar 02 2017This paper proposes a novel approach for uncertainty quantification in dense Conditional Random Fields (CRFs). The presented approach, called Perturb-and-MPM, enables efficient, approximate sampling from dense multi-label CRFs via random perturbations. ... More
(Topological) modular forms with level structures: decompositions and dualitySep 29 2016The present article studies decompositions of vector bundles on the moduli stack of elliptic curves that are pushforwards of vector bundles on moduli of elliptic curves with level structure. These imply decomposition results for rings of modular forms ... More
Magnetically-Dominated Accretion Flows (MDAFs) and Jet Production in the Low/Hard STateApr 22 2005In this paper I propose that the inner part of a black hole accretion inflow ($< 100 r_{g}$) may enter a magnetically-dominated, magnetosphere-like phase in which the strong, well-ordered fields play a more important role than weak, turbulent fields. ... More
Mercury (Hg) in meteorites: variations in abundance, thermal release profile, mass-dependent and mass-independent isotopic fractionationMar 07 2016We have measured the concentration, isotopic composition and thermal release profiles of Mercury (Hg) in a suite of meteorites, including both chondrites and achondrites. We find large variations in Hg concentration between different meteorites (ca. 10 ... More
Fibration Categories are Fibrant Relative CategoriesMar 06 2015Apr 20 2015A relative category is a category with a chosen class of weak equivalences. Barwick and Kan produced a model structure on the category of all relative categories, which is Quillen equivalent to the Joyal model structure on simplicial sets and the Rezk ... More
(Topological) modular forms with level structures: decompositions and dualitySep 29 2016Feb 20 2017The present article studies decompositions of vector bundles on the moduli stack of elliptic curves that are pushforwards of vector bundles on moduli of elliptic curves with level structure. These imply decomposition results for rings of modular forms ... More
Object Recognition with Multi-Scale Pyramidal Pooling NetworksJul 07 2012We present a Multi-Scale Pyramidal Pooling Network, featuring a novel pyramidal pooling layer at multiple scales and a novel encoding layer. Thanks to the former the network does not require all images of a given classification task to be of equal size. ... More
Physics Performance with the CMS Pixel DetectorDec 17 2014A large fraction of the results produced by the LHC experiments during the first run were made possible by precision vertexing detectors. The all-silicon tracking detector of the CMS experiment uses a pixel detector to do vertexing. This conference report ... More
First Alignment of the Complete CMS TrackerMar 12 2010This conference proceeding presents the first results of the full CMS Tracker alignment based on several million reconstructed tracks from the cosmic data taken during the commissioning runs with the detector in its final position and magnetic field present. ... More
A note on cabled slice knots and reducible surgeriesJul 16 2015We consider the question of when a slice knot admits a reducible Dehn surgery. By analyzing the correction terms associated to such a surgery, we show that slice knots cannot admit surgeries with more than two summands. We also give a necessary Heegaard ... More
Resource Allocation for a Wireless Coexistence Management System Based on Reinforcement LearningMay 24 2018In industrial environments, an increasing amount of wireless devices are used, which utilize license-free bands. As a consequence of these mutual interferences of wireless systems might decrease the state of coexistence. Therefore, a central coexistence ... More
Shock Structure and Shock Heating in the Galactic Central Molecular ZoneFeb 20 2014We present maps of a large number of dense molecular gas tracers across the Central Molecular Zone of our Galaxy. The data were taken with the CSIRO/CASS Mopra telescope in Large Projects in the 1.3cm, 7mm, and 3mm wavelength regimes. Here, we focus on ... More
Topological modular forms with level structure: decompositions and dualityJun 18 2018Topological modular forms with level structure were introduced in full generality by Hill and Lawson. We will show that these decompose additively in many cases into a few simple pieces and give an application to equivariant $TMF$. Furthermore, we show ... More
Pairing gaps near ferromagnetic quantum critical pointsNov 14 2014Feb 22 2015We address the quantum-critical behavior of a two-dimensional itinerant ferromagnetic systems described by a spin-fermion model in which fermions interact with close to critical bosonic modes. We consider Heisenberg ferromagnets, Ising ferromagnets, and ... More
Learning Sensor Feedback Models from Demonstrations via Phase-Modulated Neural NetworksOct 24 2017Mar 15 2018In order to robustly execute a task under environmental uncertainty, a robot needs to be able to reactively adapt to changes arising in its environment. The environment changes are usually reflected in deviation from expected sensory traces. These deviations ... More
Characterization of Disorder in Semiconductors via Single-Photon InterferometryNov 15 2006The method of angular photonic correlations of spontaneous emission is introduced as an experimental, purely optical scheme to characterize disorder in semiconductor nanostructures. The theoretical expression for the angular correlations is derived and ... More
Step size of the rotary proton motor in single FoF1-ATP synthase from a thermoalkaliphilic bacterium by DCO-ALEX FRETFeb 05 2012Thermophilic enzymes can operate at higher temperatures but show reduced activities at room temperature. They are in general more stable during preparation and, accordingly, are considered to be more rigid in structure. Crystallization is often easier ... More
Finitely additive beliefs and universal type spacesFeb 28 2006The probabilistic type spaces in the sense of Harsanyi [Management Sci. 14 (1967/68) 159--182, 320--334, 486--502] are the prevalent models used to describe interactive uncertainty. In this paper we examine the existence of a universal type space when ... More
Enumeration in Incremental FPT-TimeApr 20 2018Aug 27 2018In this paper, we study the relationship of parametrised enumeration complexity classes defined by Creignou et al. (MFCS 2013). Specifically, we introduce two hierarchies (IncFPTa and CapIncFPTa) of enumeration complexity classes for incremental fpt-time ... More
Theory of filtered type-II PDC in the continuous-variable domain: Quantifying the impacts of filteringMar 12 2014Aug 16 2014Parametric down-conversion (PDC) forms one of the basic building blocks for quantum optical experiments. However, the intrinsic multimode spectral-temporal structure of pulsed PDC often poses a severe hindrance for the direct implementation of the heralding ... More
Beyond Whittle: Nonparametric correction of a parametric likelihood with a focus on Bayesian time series analysisJan 17 2017The Whittle likelihood is widely used for Bayesian nonparametric estimation of the spectral density of stationary time series. However, the loss of efficiency for non-Gaussian time series can be substantial. On the other hand, parametric methods are more ... More
On the Definition of Cyber-Physical Resilience in Power SystemsApr 22 2015Jun 01 2015In recent years, advanced sensors, intelligent automation, communication networks, and information technologies have been integrated into the electric grid to enhance its performance and efficiency. Integrating these new technologies has resulted in more ... More
Using Simulation to Improve Sample-Efficiency of Bayesian Optimization for Bipedal RobotsMay 07 2018Learning for control can acquire controllers for novel robotic tasks, paving the path for autonomous agents. Such controllers can be expert-designed policies, which typically require tuning of parameters for each task scenario. In this context, Bayesian ... More
Curious iLQR: Resolving Uncertainty in Model-based RLApr 15 2019Curiosity as a means to explore during reinforcement learning problems has recently become very popular. However, very little progress has been made in utilizing curiosity for learning control. In this work, we propose a model-based reinforcement learning ... More
Sélection de la structure d'un perceptron multicouches pour la réduction dun modèle de simulation d'une scierieDec 05 2008Simulation is often used to evaluate the relevance of a Directing Program of Production (PDP) or to evaluate its impact on detailed sc\'enarii of scheduling. Within this framework, we propose to reduce the complexity of a model of simulation by exploiting ... More
Infinite reduced words and the Tits boundary of a Coxeter groupJan 05 2013Sep 18 2014Let (W,S) be a finite rank Coxeter system with W infinite. We prove that the limit weak order on the blocks of infinite reduced words of W is encoded by the topology of the Tits boundary of the Davis complex X of W. We consider many special cases, including ... More
How deals with discrete data for the reduction of simulation models using neural networkJun 10 2009Simulation is useful for the evaluation of a Master Production/distribution Schedule (MPS). Also, the goal of this paper is the study of the design of a simulation model by reducing its complexity. According to theory of constraints, we want to build ... More
Thermodynamic formalism for transport coefficients with an application to the shear modulus and shear viscosityDec 07 2016We discuss Onsager's thermodynamic formalism for transport coefficients and apply it to the calculation of the shear modulus and shear viscosity of a monodisperse system of repulsive particles. We focus on the concept of extensive "distance" and intensive ... More
An optimization principle for the computation of MHD equilibria in the solar coronaDec 21 2006AIMS: We develop an optimization principle for computing stationary MHD equilibria. METHODS: Our code for the self-consistent computation of the coronal magnetic fields and the coronal plasma uses non-force-free MHD equilibria. Previous versions of the ... More
On the boundedness of an iteration involving points on the hypersphereJan 11 2010Oct 05 2010For a finite set of points $X$ on the unit hypersphere in $\mathbb{R}^d$ we consider the iteration $u_{i+1}=u_i+\chi_i$, where $\chi_i$ is the point of $X$ farthest from $u_i$. Restricting to the case where the origin is contained in the convex hull of ... More
Nef reduction and anticanonical bundlesOct 31 2003We investigate the structure of smooth projective 3-folds X with -K_X nef and K_X^3=0.
Causes and Explanations in the Structural-Model Approach: Tractable CasesDec 12 2012In this paper, we continue our research on the algorithmic aspects of Halpern and Pearl's causes and explanations in the structural-model approach. To this end, we present new characterizations of weak causes for certain classes of causal models, which ... More
Transient photon echoes from donor-bound excitons in ZnO epitaxial layersFeb 16 2017The coherent optical response from 140~nm and 65~nm thick ZnO epitaxial layers is studied using transient four-wave-mixing spectroscopy with picosecond temporal resolution. Resonant excitation of neutral donor-bound excitons results in two-pulse and three-pulse ... More
Pressure induced Hydrogen-Hydrogen interaction in metallic FeH revealed by NMRFeb 08 2019Knowledge of the behavior of hydrogen in metal hydrides is the key for understanding their electronic properties. So far, no experimental methods exist to access these properties beyond 100 GPa, where high-Tc superconductivity emerges. Here, we present ... More
Six networks on a universal neuromorphic computing substrateOct 26 2012Feb 21 2013In this study, we present a highly configurable neuromorphic computing substrate and use it for emulating several types of neural networks. At the heart of this system lies a mixed-signal chip, with analog implementations of neurons and synapses and digital ... More
Non-uniqueness of Solutions to the Conformal FormulationOct 08 2012Dec 04 2012It is well-known that solutions to the conformal formulation of the Einstein constraint equations are unique in the cases of constant mean curvature (CMC) and near constant mean curvature (near-CMC). However, the new far-from-constant mean curvature (far-from-CMC) ... More
Multi-Dimensional Astrophysical Structural and Dynamical Analysis I. Development of a Nonlinear Finite Element ApproachJun 19 1998Nov 10 1998A new field of numerical astrophysics is introduced which addresses the solution of large, multidimensional structural or slowly-evolving problems (rotating stars, interacting binaries, thick advective accretion disks, four dimensional spacetimes, etc.). ... More
Doubly slice knots with low crossing numberApr 13 2015A knot in the three-sphere is doubly slice if it is the cross-section of an unknotted two-sphere in the four-sphere. For low-crossing knots, the most complete work to date gives a classification of doubly slice knots through 9 crossings. We extend that ... More
Fibered ribbon disksOct 17 2014Oct 19 2015We study the relationship between fibered ribbon 1-knots and fibered ribbon 2-knots by studying fibered slice disks with handlebody fibers. We give a characterization of fibered homotopy-ribbon disks and give analogues of the Stallings twist for fibered ... More
The Bieri-Neumann-Strebel invariants for graph groupsOct 12 1993Given a finite simplicial graph ${\cal G}$, the graph group $G{\cal G}$" is the group with generators in one-to-one correspondence with the vertices of ${\cal G}$ and with relations stating two generators commute if their associated vertices are adjacent ... More
Analytical Model for IEEE 802.15.4 Multi-Hop Networks with Improved Handling of Acknowledgements and RetransmissionsJan 29 2015The IEEE 802.15.4 standard allows for the deployment of cost-effective and energy-efficient multi-hop networks. This document features an in-depth presentation of an analytical model for assessing the performance of such networks. It considers a generic, ... More
Learning to recognize Abnormalities in Chest X-Rays with Location-Aware Dense NetworksMar 12 2018Chest X-ray is the most common medical imaging exam used to assess multiple pathologies. Automated algorithms and tools have the potential to support the reading workflow, improve efficiency, and reduce reading errors. With the availability of large scale ... More
In situ transformation and cleaning of tin-drop contamination on mirrors for extreme ultraviolet lightJan 19 2018Tin-drop contamination was cleaned from multilayer-coated mirrors by induction of phase transformation. The {\beta} - {\alpha} phase transition of tin was induced to initiate material embrittlement and enable facile removal of thick tin deposits. The ... More
Learning Neural Models for End-to-End ClusteringJul 11 2018We propose a novel end-to-end neural network architecture that, once trained, directly outputs a probabilistic clustering of a batch of input examples in one pass. It estimates a distribution over the number of clusters $k$, and for each $1 \leq k \leq ... More
Consistency of extended Nelson-Siegel curve families with the Ho-Lee and Hull and White short rate modelsJul 08 2017Nelson and Siegel curves are widely used to fit the observed term structure of interest rates in a particular date. By the other hand, several interest rate models have been developed such their initial forward rate curve can be adjusted to any observed ... More
Enhancing clinical MRI Perfusion maps with data-driven maps of complementary nature for lesion outcome predictionJun 12 2018Stroke is the second most common cause of death in developed countries, where rapid clinical intervention can have a major impact on a patient's life. To perform the revascularization procedure, the decision making of physicians considers its risks and ... More
Anomalous condensate fluctuations in strongly interacting superfluidsJun 23 1999Aug 12 1999We show that the condensate occupation of a superfluid Bose liquid quite generally exhibits anomalously large fluctuations at finite temperatures. In three dimensions, the variance scales like T^2 V^{4/3} at low T, generalizing the result obtained by ... More
The Theory and Simulation of Relativistic Jet Formation: Towards a Unified Model For Micro- and MacroquasarsDec 02 2003I review recent progress in the theory of relativistic jet production, with special emphasis on unifying black hole sources of stellar and supermassive size. Observations of both classes of objects, as well as theoretical considerations, indicate that ... More
A Magnetically-Switched, Rotating Black Hole Model For the Production of Extragalactic Radio Jets and the Fanaroff and Riley Class DivisionOct 21 1998Jul 30 1999A model is presented in which both Fanaroff and Riley class I and II extragalactic jets are produced by magnetized accretion disk coronae in the ergospheres of rotating black holes. While the jets are produced in the accretion disk itself, the output ... More
Push is Fast on Sparse Random GraphsAug 27 2014We consider the classical push broadcast process on a large class of sparse random multigraphs that includes random power law graphs and multigraphs. Our analysis shows that for every $\varepsilon>0$, whp $O(\log n)$ rounds are sufficient to inform all ... More