Results for "Amy B. Knudsen"

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A fully non-linear optimization approach to acousto-electric tomographyApr 07 2018Jul 04 2018This paper considers the non-linear inverse problem of reconstructing an electric conductivity distribution from the interior power density in a bounded domain. Applications include the novel tomographic method known as acousto-electric tomography, in ... More
A spectral stacking analysis to search for faint outflow signatures in z~6 quasarsAug 29 2019Outflows in quasars during the early epochs of galaxy evolution are an important part of the feedback mechanisms potentially affecting the evolution of the host galaxy. However, systematic observations of outflows are only now becoming possible with the ... More
Characterization and valuation of uncertainty of calibrated parameters in stochastic decision modelsJun 11 2019We evaluated the implications of different approaches to characterize uncertainty of calibrated parameters of stochastic decision models (DMs) in the quantified value of such uncertainty in decision making. We used a microsimulation DM of colorectal cancer ... More
Fundamental solution for (Delta - lambda_z)^n on a symmetric space G/KApr 21 2011Jun 13 2012We determine a fundamental solution for the differential operator (Delta - lambda_z)^n on the Riemannian symmetric space G/K, where G is any complex semi-simple Lie group, and K is a maximal compact subgroup. We develop a global zonal spherical Sobolev ... More
Tree Descent Polynomials: Unimodality and Central Limit TheoremAug 30 2019For a poset whose Hasse diagram is a rooted plane forest $F$, we consider the corresponding tree descent polynomial $A_F(q)$, which is a generating function of the number of descents of the labelings of $F$. When the forest is a path, $A_F(q)$ specializes ... More
A General Mathematical Framework Suitable for Studying Signaling CascadesAug 03 2010Dec 13 2011We define a general mathematical framework for studying post-translational modification processes under the assumption of mass action kinetics.
Subdivisional spaces and graph braid groupsAug 08 2017Mar 03 2019We study the problem of computing the homology of the configuration spaces of a finite cell complex $X$. We proceed by viewing $X$, together with its subdivisions, as a subdivisional space--a kind of diagram object in a category of cell complexes. After ... More
Almost Optimal Tensor SketchSep 03 2019We construct a matrix $M\in R^{m\otimes d^c}$ with just $m=O(c\,\lambda\,\varepsilon^{-2}\text{poly}\log1/\varepsilon\delta)$ rows, which preserves the norm $\|Mx\|_2=(1\pm\varepsilon)\|x\|_2$ of all $x$ in any given $\lambda$ dimensional subspace of ... More
Self-Similar Grooving Solutions to the Mullins' EquationJun 17 2019Aug 14 2019In 1957, Mullins proposed surface diffusion motion as a model for thermal grooving. By adopting a small slope approximation, he reduced the model to the Mullins' linear surface diffusion equation, \begin{equation} \nonumber ({\rm{ME}})\quad\quad y_t + ... More
Evolution of cosmic star formation in the SCUBA-2 Cosmology Legacy SurveyJul 14 2016Jan 05 2017We present a new exploration of the cosmic star-formation history and dust obscuration in massive galaxies at redshifts $0.5< z<6$. We utilize the deepest 450 and 850$\mu$m imaging from SCUBA-2 CLS, covering 230arcmin$^2$ in the AEGIS, COSMOS and UDS ... More
Fast hashing with Strong Concentration BoundsMay 01 2019May 02 2019Previous work on tabulation hashing of P\v{a}tra\c{s}cu and Thorup from STOC'11 on simple tabulation and from SODA'13 on twisted tabulation offered Chernoff-style concentration bounds on hash based sums, but under some quite severe restrictions on the ... More
Fast hashing with Strong Concentration BoundsMay 01 2019Previous work on tabulation hashing of P\v{a}tra\c{s}cu and Thorup from STOC'11 on simple tabulation and from SODA'13 on twisted tabulation offered Chernoff-style concentration bounds on hash based sums, but under some quite severe restrictions on the ... More
High-precision methanol spectroscopy with a widely tunable SI-traceable frequency-comb-based mid-infrared QCLJul 23 2019There is an increasing demand for precise molecular spectroscopy, in particular in the mid-infrared fingerprint window that hosts a considerable number of vibrational signatures, whether it be for modeling our atmosphere, interpreting astrophysical spectra ... More
First industrial-grade coherent fiber link for optical frequency standard disseminationSep 13 2019We report on a fully bi-directional 680~km fiber link connecting two cities for which the equipment, the set up and the characterization are managed for the first time by an industrial consortium. The link uses an active telecommunication fiber network ... More
New CO detections of lensed submillimeter galaxies in A2218: Probing molecular gas in the LIRG regime at high redshiftDec 17 2008Context: Submillimeter galaxies (SMGs) are distant, dusty galaxies undergoing star formation at prodigious rates. Recently there has been major progress in understanding the nature of the bright SMGs (i.e. S(850um)>5mJy). The samples for the fainter SMGs ... More
Characterizing Demand Graphs for (Fixed-Parameter) Shallow-Light Steiner NetworkFeb 28 2018We consider the Shallow-Light Steiner Network problem from a fixed-parameter perspective. Given a graph $G$, a distance bound $L$, and $p$ pairs of vertices $(s_1,t_1),\cdots,(s_p,t_p)$, the objective is to find a minimum-cost subgraph $G'$ such that ... More
On the matrix equation $XA + AX^T = 0$Aug 02 2012Oct 24 2012The matrix equation $XA + AX^T = 0$, which has relevance to the study of Lie algebras, was recently studied by De Teran and Dopico. They reduced the study of this equation to several special cases and produced explicit solutions in most instances. In ... More
Classifying Convex Bodies by their Contact and Intersection GraphsFeb 05 2019Suppose that $A$ is a convex body in the plane and that $A_1,\dots,A_n$ are translates of $A$. Such translates give rise to an intersection graph of $A$, $G=(V,E)$, with vertices $V=\{1,\dots,n\}$ and edges $E=\{uv\mid A_u\cap A_v\neq \emptyset\}$. The ... More
Evaluating race and sex diversity in the world's largest companies using deep neural networksJul 09 2017Diversity is one of the fundamental properties for the survival of species, populations, and organizations. Recent advances in deep learning allow for the rapid and automatic assessment of organizational diversity and possible discrimination by race, ... More
The integration of variable generation and storage into electricity capacity marketsJul 12 2019We show how to value both variable generation and energy storage in such a way as to enable them to be integrated fairly (from the point of view of capacity providers) and optimally (from the point of view of society) into electricity capacity markets, ... More
Wetzel's Problem, Paul Erdos, and the Continuum Hypothesis: a mathematical mysteryJun 19 2014Oct 23 2014This is a short historical note concerning the evolution of Wetzel's problem and Erdos' solution.
Linked and Knotted Gravitational RadiationFeb 16 2014Aug 15 2014We show that the torus knot topology is inherent in electromagnetic and gravitational radiation by constructing spin-$N$ fields based on this topology from the elementary states of twistor theory. The twistor functions corresponding to the elementary ... More
Some new aspects of the coupon-collector's problemApr 16 2003We extend the classical coupon collector's problem to one in which two collectors are simultaneously and independently seeking collections of $d$ coupons. We find, in finite terms, the probability that the two collectors finish at the same trial, and ... More
An Improved Implementation and Abstract Interface for HybridNov 01 2011Hybrid is a formal theory implemented in Isabelle/HOL that provides an interface for representing and reasoning about object languages using higher-order abstract syntax (HOAS). This interface is built around an HOAS variable-binding operator that is ... More
Adsorption of CO on the Fe3O4(001) SurfaceApr 13 2018The interaction of CO with the Fe3O4(001)-(rt2xrt2)R45{\deg} surface was studied using temperature programmed desorption (TPD), scanning tunneling microscopy (STM) and x-ray photoelectron spectroscopy (XPS), the latter both under ultrahigh vacuum (UHV) ... More
Betti numbers and stability for configuration spaces via factorization homologyMay 26 2014Aug 14 2015Using factorization homology, we realize the rational homology of the unordered configuration spaces of an arbitrary manifold $M$, possibly with boundary, as the homology of a Lie algebra constructed from the compactly supported cohomology of $M$. By ... More
Configuration spaces in algebraic topologyMar 29 2018These expository notes are dedicated to the study of the topology of configuration spaces of manifolds. We give detailed computations of many invariants, including the fundamental group of the configuration spaces of $\mathbb{R}^2$, the integral cohomology ... More
Higher enveloping algebrasMay 04 2016We provide Lie algebras with enveloping algebras over the operad of little $n$-dimensional disks for any choice of $n$, and we give two complementary descriptions of these objects. The first description is an abstract characterization by a universal mapping ... More
Integrated Optical Polarization of Nearby GalaxiesJan 11 2012We performed an integrated optical polarization survey of 70 nearby galaxies to study the relationship between linear polarization and galaxy properties. To date this is the largest survey of its kind. The data were collected at McDonald Observatory using ... More
Massive and massless modes of the triplet phase of neutron matterAug 21 2014Sep 12 2014Neutron matter at densities of the order of the nuclear saturation density is believed to have neutrons paired in the 3P2 channel. We study the low lying modes of this phase and find two massless modes (angulons), resulting from the spontaneous breaking ... More
Suzuki-invariant codes from the Suzuki curveNov 23 2014Nov 25 2014In this paper we consider the Suzuki curve $y^q + y = x^{q_0}(x^q + x)$ over the field with $q = 2^{2m+1}$ elements. The automorphism group of this curve is known to be the Suzuki group $Sz(q)$ with $q^2(q-1)(q^2+1)$ elements. We construct AG codes over ... More
Spatial Statistical Downscaling for Constructing High-Resolution Nature Runs in Global Observing System Simulation ExperimentsNov 01 2017Aug 31 2018Observing system simulation experiments (OSSEs) have been widely used as a rigorous and cost-effective way to guide development of new observing systems, and to evaluate the performance of new data assimilation algorithms. Nature runs (NRs), which are ... More
Learning Equilibria of Simulation-Based GamesMay 31 2019We tackle a fundamental problem in empirical game-theoretic analysis (EGTA), that of learning equilibria of simulation-based games. Such games cannot be described in analytical form; instead, a black-box simulator can be queried to obtain noisy samples ... More
Compaction and Melt Transport in Ammonia-Rich Ice Shells: Implications for the Evolution of TritonNov 27 2018Ammonia, if present in the ice shells of icy satellites, could lower the temperature for the onset of melting to 176 K and create a large temperature range where partial melt is thermally stable. The evolution of regions of ammonia-rich partial melt could ... More
Number-Theoretic Characterizations of Some Restricted Clifford+T CircuitsAug 16 2019Kliuchnikov, Maslov, and Mosca proved in 2012 that a $2\times 2$ unitary matrix $V$ can be exactly represented by a single-qubit Clifford+$T$ circuit if and only if the entries of $V$ belong to the ring $\mathbb{Z}[1/\sqrt{2},i]$. Later that year, Giles ... More
A New Sample of (Wandering) Massive Black Holes in Dwarf Galaxies from High Resolution Radio ObservationsSep 10 2019We present a sample of nearby dwarf galaxies with radio-selected accreting massive black holes (BHs), the majority of which are non-nuclear. We observed 111 galaxies using sensitive, high-resolution observations from the Karl G. Jansky Very Large Array ... More
Constructing a class of topological solitons in magnetohydrodynamicsOct 16 2013Apr 26 2014We present a class of topological plasma configurations characterized by their toroidal and poloidal winding numbers, $n_t$ and $n_p$ respectively. The special case of $n_t=1$ and $n_p=1$ corresponds to the Kamchatnov-Hopf soliton, a magnetic field configuration ... More
SDSS-IV MaNGA: The Spatially Resolved Stellar Initial Mass Function in $\sim$400 Early-Type GalaxiesMar 22 2018MaNGA provides the opportunity to make precise spatially resolved measurements of the IMF slope in galaxies owing to its unique combination of spatial resolution, wavelength coverage and sample size. We derive radial gradients in age, element abundances ... More
The Gould's Belt Distances Survey (GOBELINS) III. The distance to the Serpens/Aquila Molecular ComplexOct 10 2016We report on new distances and proper motions to seven stars across the Serpens/Aquila complex. The observations were obtained as part of the Gould's Belt Distances Survey (GOBELINS) project between September 2013 and April 2016 with the Very Long Baseline ... More
The Gould's Belt Distances Survey (GOBELINS) II. Distances and structure towards the Orion Molecular CloudsSep 13 2016Oct 04 2016We present the results of the Gould's Belt Distances Survey (GOBELINS) of young star forming regions towards the Orion Molecular Cloud Complex. We detected 36 YSOs with the Very Large Baseline Array (VLBA), 27 of which have been observed in at least 3 ... More
Modeling microbial abundances and dysbiosis with beta-binomial regressionFeb 07 2019Using a sample from a population to estimate the proportion of the population with a certain category label is a broadly important problem. In the context of microbiome studies, this problem arises when researchers wish to use a sample from a population ... More
Monte Carlo Particle Lists: MCPLSep 09 2016A binary format with lists of particle state information, for interchanging particles between various Monte Carlo simulation applications, is presented. Portable C code for file manipulation is made available to the scientific community, along with converters ... More
3D Reconstruction for Partial Data Electrical Impedance Tomography Using a Sparsity PriorDec 19 2014In electrical impedance tomography the electrical conductivity inside a physical body is computed from electro-static boundary measurements. The focus of this paper is to extend recent result for the 2D problem to 3D. Prior information about the sparsity ... More
Distinguishability revisited: depth dependent bounds on reconstruction quality in electrical impedance tomographyFeb 11 2016Jan 26 2017The reconstruction problem in electrical impedance tomography is highly ill-posed, and it is often observed numerically that reconstructions have poor resolution far away from the measurement boundary but better resolution near the measurement boundary. ... More
Paradigms in Physics Education ResearchJul 16 2013Jan 07 2015In this paper, we describe two paradigms in physics education research (PER): recurrence- oriented and case-oriented PER. We connect theory on research methodologies in the social sciences to interviews with physics education researchers and examples ... More
Multi-class Twitter Data Categorization and Geocoding with a Novel Computing FrameworkMay 08 2019Transportation data analysis is becoming a major area of computing application. Operation and management of transportation system have been transforming with the advancements in computing technology. This study presents such an advancement in transportation ... More
Paradigms in Physics Education ResearchJul 16 2013Jan 11 2018In this paper, we describe two paradigms in physics education research (PER): recurrence-oriented and case-oriented PER. We connect theory on research methodologies in the social sciences to interviews with physics education researchers and examples of ... More
Astro2020 APC White Paper: The Early Career Perspective on the Coming Decade, Astrophysics Career Paths, and the Decadal Survey ProcessJul 02 2019Jul 12 2019In response to the need for the Astro2020 Decadal Survey to explicitly engage early career astronomers, the National Academies of Sciences, Engineering, and Medicine hosted the Early Career Astronomer and Astrophysicist Focus Session (ECFS) on October ... More
Selection, Generalization, and Theories of Cause in Case-Oriented Physics Education ResearchJul 16 2013Jan 07 2015Case-oriented physics education research - which seeks to refine and develop theory by linking that theory to cases - incorporates distinct practices for selecting data for analysis, generalizing results, and making causal claims. Unanswered questions ... More
z~1 Lya Emitters I. The Luminosity FunctionJan 23 2014We construct a flux-limited sample of 135 candidate z~1 Lya emitters (LAEs) from Galaxy Evolution Explorer (GALEX) grism data using a new data cube search method. These LAEs have luminosities comparable to those at high redshifts and lie within a 7 Gyr ... More
Reconstruction of less regular conductivities in the planeOct 26 2001We study the inverse conductivity problem of how to reconstruct an isotropic electrical conductivity distribution $\gamma$ in an object from static electrical measurements on the boundary of the object. We give an exact reconstruction algorithm for the ... More
A Kuenneth theorem for configuration spacesOct 04 2018We construct a spectral sequence converging to the homology of the ordered configuration spaces of a product of parallelizable manifolds. To identify the second page of this spectral sequence, we introduce a version of the Boardman--Vogt tensor product ... More
Photometric Amplitude Distribution of Stellar Rotation of Kepler KOIs-Indication for Spin-Orbit Alignment of Cool Stars and High Obliquity for Hot StarsJan 06 2015The observed amplitude of the rotational photometric modulation of a star with spots should depend on the inclination of its rotational axis relative to our line of sight. Therefore, the distribution of observed rotational amplitudes of a large sample ... More
EUVE Observations of the Magnetic Cataclysmic Variable QQ VulpeculaeNov 30 1999We present simultaneous X-ray (lambda_peak ~ 44A) and EUV (lambda_peak = 89A) light curves for the magnetic cataclysmic variable QQ Vulpeculae, obtained with the EUVE satellite. We find that the unique shape of the X-ray light curve is different from ... More
Multi-class Twitter Data Categorization and Geocoding with a Novel Computing FrameworkMay 08 2019Aug 28 2019This study details the progress in transportation data analysis with a novel computing framework in keeping with the continuous evolution of the computing technology. The computing framework combines the Labelled Latent Dirichlet Allocation (L-LDA)-incorporated ... More
Non-uniform Information Dissemination for Sensor NetworksAug 10 2004Future smart environments will be characterized by multiple nodes that sense, collect, and disseminate information about environmental phenomena through a wireless network. In this paper, we define a set of applications that require a new form of distributed ... More
Simulation Tools for Detector and Instrument DesignAug 07 2017The high performance requirements at the European Spallation Source have been driving the technological advances on the neutron detector front. Now more than ever is it important to optimize the design of detectors and instruments, to fully exploit the ... More
Multi-class Twitter Data Categorization and Geocoding with a Novel Computing FrameworkMay 08 2019Jul 18 2019This study details the progress in transportation data analysis with a novel computing framework in keeping with the continuous evolution of the computing technology. The computing framework combines the Labelled Latent Dirichlet Allocation (L-LDA)-incorporated ... More
Bayesian Local Extrema SplinesApr 04 2016We consider the problem of shape restricted nonparametric regression on a closed set X ?\in R; where it is reasonable to assume the function has no more than H local extrema interior to X: Following a Bayesian approach we develop a nonparametric prior ... More
Elucidating the sign problem through noise distributionsOct 26 2012Due to the presence of light pions in the theory, lattice QCD at finite densities suffers from issues with noise in both grand canonical and canonical formulations. We study two different formulations of the Nambu-Jona-Lasinio model reduced to 2+1 dimensions ... More
Additive Spanners and Distance Oracles in Quadratic TimeApr 14 2017Let $G$ be an unweighted, undirected graph. An additive $k$-spanner of $G$ is a subgraph $H$ that approximates all distances between pairs of nodes up to an additive error of $+k$, that is, it satisfies $d_H(u,v) \le d_G(u,v)+k$ for all nodes $u,v$, where ... More
Sparsity prior for electrical impedance tomography with partial dataMay 26 2014Dec 22 2014This paper focuses on prior information for improved sparsity reconstruction in electrical impedance tomography with partial data, i.e. data measured only on subsets of the boundary. Sparsity is enforced using an $\ell_1$ norm of the basis coefficients ... More
Determining nonsmooth first order terms from partial boundary measurementsSep 05 2006We extend results of Dos Santos Ferreira-Kenig-Sjoestrand-Uhlmann (math.AP/0601466) to less smooth coefficients, and we show that measurements on part of the boundary for the magnetic Schroedinger operator determine uniquely the magnetic field related ... More
Depth dependent bounds on distinguishability of inclusions in electrical impedance tomographyFeb 11 2016May 04 2016The inverse problem of electrical impedance tomography is highly ill-posed, and it is often observed that inclusions far from the boundary are difficult to reconstruct. This paper provides rigorous results supporting the intuition. Indeed, lower and upper ... More
Linear Hashing is AwesomeJun 08 2017We consider the hash function $h(x) = ((ax+b) \bmod p) \bmod n$ where $a,b$ are chosen uniformly at random from $\{0,1,\ldots,p-1\}$. We prove that when we use $h(x)$ in hashing with chaining to insert $n$ elements into a table of size $n$ the expected ... More
Additive Spanners: A Simple ConstructionMar 02 2014Nov 23 2014We consider additive spanners of unweighted undirected graphs. Let $G$ be a graph and $H$ a subgraph of $G$. The most na\"ive way to construct an additive $k$-spanner of $G$ is the following: As long as $H$ is not an additive $k$-spanner repeat: Find ... More
A closer look at the stacks of stable pointed curvesJun 08 2011Apr 03 2012In the theory of the moduli-stacks of n-pointed stable curves, there are two fundamental functors, contraction and stabilization. These functors are constructed in [4], where they are used to show that the various \bar{M_{g,n}}'s are DM-stacks. We give ... More
Deep Learning Features for Robust Detection of Acoustic Events in Sleep-Disordered BreathingApr 05 2019Sleep-disordered breathing (SDB) is a serious and prevalent condition, and acoustic analysis via consumer devices (e.g. smartphones) offers a low-cost solution to screening for it. We present a novel approach for the acoustic identification of SDB sounds, ... More
Analyzing Basket Trials under Multisource Exchangeability AssumptionsAug 01 2019Basket designs are prospective clinical trials that are devised with the hypothesis that the presence of selected molecular features determine a patient's subsequent response to a particular "targeted" treatment strategy. Basket trials are designed to ... More
Investigating Evaluation of Open-Domain Dialogue Systems With Human Generated Multiple ReferencesJul 24 2019Sep 08 2019The aim of this paper is to mitigate the shortcomings of automatic evaluation of open-domain dialog systems through multi-reference evaluation. Existing metrics have been shown to correlate poorly with human judgement, particularly in open-domain dialog. ... More
Atmospheric waves and dynamics beneath Jupiter's clouds from radiowavelength observationsJan 12 2017Jan 19 2017We observed Jupiter at wavelengths near 2 cm with the Karl G. Jansky Very Large Array in February 2015. These frequencies are mostly sensitive to variations in ammonia abundance and probe between ~0.5-2.0 bars of pressure in Jupiter's atmosphere; within ... More
Sign problems, noise, and chiral symmetry breaking in a QCD-like theoryAug 28 2012Jan 24 2013The Nambu-Jona-Lasinio model reduced to 2+1 dimensions has two different path integral formulations: at finite chemical potential one formulation has a severe sign problem similar to that found in QCD, while the other does not. At large N, where N is ... More
Gravitational HopfionsFeb 06 2013Feb 16 2014The electromagnetic hopfion (EM hopfion) is a topologically nontrivial solution to the vacuum Maxwell equations with the property that any two field lines belonging to either the electric, magnetic, or Poynting vector fields (EBS fields) are closed and ... More
Sub-stellar companions of the young weak-line TTauri Star DoAr21Sep 05 2019The compact, non-thermal emission in DoAr21 has been studied with the VLBA to investigate the possibility that the residuals of the astrometry fitting are due to the reflex motion induced by a possible companion. We find that the fitting of VLBA astrometric ... More
Robust Graph IdealsSep 29 2013Let I be a toric ideal. We say I is robust if its universal Groebner basis is a minimal generating set. We show that any robust toric ideal arising from a graph G is also minimally generated by its Graver basis. We then completely characterize all graphs ... More
Predicting the Long-Term Outcomes of Biologics in Psoriasis Patients Using Machine LearningAug 25 2019Background. Real-world data show that approximately 50% of psoriasis patients treated with a biologic agent will discontinue the drug because of loss of efficacy. History of previous therapy with another biologic, female sex and obesity were identified ... More
Recommendation or Discrimination?: Quantifying Distribution Parity in Information Retrieval SystemsSep 13 2019Information retrieval (IR) systems often leverage query data to suggest relevant items to users. This introduces the possibility of unfairness if the query (i.e., input) and the resulting recommendations unintentionally correlate with latent factors that ... More
Assessing Fashion Recommendations: A Multifaceted Offline Evaluation ApproachSep 05 2019Fashion is a unique domain for developing recommender systems (RS). Personalization is critical to fashion users. As a result, highly accurate recommendations are not sufficient unless they are also specific to users. Moreover, fashion data is characterized ... More
Electron-hole transport and photovoltaic effect in gated MoS2 Schottky junctionsJun 26 2012Apr 09 2013Atomically thin MoS2 has recently emerged as a very attractive material for nanoscale optoelectronic devices. While n-type transport in MoS2 devices has been demonstrated, hole conduction has been more challenging. Here we show work-function engineering ... More
On the matrix equation $XA+AX^T =0$, II: Type 0-I interactionsMar 13 2013Sep 20 2013The matrix equation $XA + AX^T = 0$ was recently introduced by De Ter\'an and Dopico to study the dimension of congruence orbits. They reduced the study of this equation to a number of special cases, several of which have not been explicitly solved. In ... More
EMU: Evolutionary Map of the UniverseJun 16 2011EMU is a wide-field radio continuum survey planned for the new Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The primary goal of EMU is to make a deep (rms ~ 10 microJy/beam) radio continuum survey of the entire Southern Sky at 1.3 GHz, ... More
A new relation between pressure and fractional flow in two-phase flow in porous mediaFeb 16 2001Jan 30 2002We study average flow properties in porous media using a two-dimensional network simulator. It models the dynamics of two-phase immiscible bulk flow where film flow can be neglected. The boundary conditions are biperiodic which provide a means of studying ... More
Two-phase flow in porous media: dynamical phase transitionJul 18 2003Two-phase flow systems in porous media have complex dynamics. It is well established that a wide range of system parameters like viscosities and porosity as well as flow parameters such as pressure gradient and fluid saturation have strong impact on the ... More
Diamagnetic Susceptibility and Current Distributions in Granular Superconductors at PercolationJun 09 1999Jan 06 2000Comments: 4 pages RevTeX, 4 Postscript figures. References added. We study a two-dimensional granular superconducting network at the percolation threshold under the influence of an external perpendicular magnetic field. By numerical simulations on the ... More
Non-inner amenability of the Thompson groups T and VSep 16 2016In this paper we prove that the Thompson groups $T$ and $V$ are not inner amenable. In particular, their group von Neumann algebras do not have property $\Gamma$. Moreover, we prove that if the reduced group $C^\ast$-algebra of $T$ is simple, then the ... More
Snell's Law for Shear Zone Refraction in Granular MaterialsApr 27 2009We present experiments on slow shear flow in a split-bottom linear shear cell, filled with layered granular materials. Shearing through two different materials separated by a flat material boundary is shown to give narrow shear zones, which refract at ... More
Breakdown of disordered media by surface loadsOct 12 2004We model an interface layer connecting two parts of a solid body by N parallel elastic springs connecting two rigid blocks. We load the system by a shear force acting on the top side. The springs have equal stiffness but are ruptured randomly when the ... More
Managing your Private and Public Data: Bringing down Inference Attacks against your PrivacyAug 16 2014We propose a practical methodology to protect a user's private data, when he wishes to publicly release data that is correlated with his private data, in the hope of getting some utility. Our approach relies on a general statistical inference framework ... More
Secure Communications using Nonlinear Silicon Photonic KeysNov 04 2017Feb 05 2018We present a secure communication system constructed using pairs of nonlinear photonic physical unclonable functions (PUFs) that harness physical chaos in integrated silicon micro-cavities. Compared to a large, electronically stored one-time pad, our ... More
Two-Branch Fiber Link for International Clock NetworksSep 04 2019We present our work on realizing two-branch fiber links enabling multiple-partner clock comparisons in Europe. We report in detail on the setup connecting two long haul links, and report for the relative frequency stability and accuracy. We report on ... More
HCOOH high resolution spectroscopy in the 9.18$μ$m regionJul 15 2007We report on higly accurate absolute frequency measurement against a femtosecond frequency comb of 6 saturated absorption lines of formic acid (HCOOH) with an accuracy of 1 kHz. We also report the frequency measurement of 17 other lines with an accuracy ... More
Generic differential equation for fractional flow of steady two-phase flow in porous mediaJun 06 2002We report on generic relations between fractional flow and pressure in steady two-phase flow in porous media. The main result is a differential equation for fractional flow as a function of phase saturation. We infer this result from two underlying observations ... More
Species richness estimation with high diversity but spurious singletonsApr 09 2016The presence of uncommon taxa in high-throughput sequenced ecological samples pose challenges to the microbial ecologist, bioinformatician and statistician. It is rarely certain whether these taxa are truly present in the sample or the result of sequencing ... More
Conjugates of characteristic Sturmian words generated by morphismsAug 31 2007This article is concerned with characteristic Sturmian words of slope $\alpha$ and $1-\alpha$ (denoted by $c_\alpha$ and $c_{1-\alpha}$ respectively), where $\alpha \in (0,1)$ is an irrational number such that $\alpha = [0;1+d_1,\bar{d_2,...,d_n}]$ with ... More
Information-Dense Nonlinear Photonic Physical Unclonable FunctionNov 06 2017We present a comprehensive investigation into the complexity of a new private key storage apparatus: a novel silicon photonic physical unclonable function (PUF) based on ultrafast nonlinear optical interactions in a chaotic silicon microcavity that is ... More
Confidence sets for phylogenetic treesJul 28 2016Inferring evolutionary histories (phylogenetic trees) has important applications in biology, criminology and public health. However, phylogenetic trees are complex mathematical objects that reside in a non-Euclidean space, which complicates their analysis. ... More
Towards Large-scale Functional Verification of Universal Quantum CircuitsMay 17 2018Jan 29 2019We introduce a framework for the formal specification and verification of quantum circuits based on the Feynman path integral. Our formalism, built around exponential sums of polynomial functions, provides a structured and natural way of specifying quantum ... More
Results from a 2016 Pilot Survey on Math Post-docsMar 16 2017A pilot survey was sent to chairs of 14 doctoral math departments asking for three types of data: (1) category on job-placements for research post-docs leaving their department in three recent years; (2) category of jobs from which their new faculty hires ... More
Sea Spider development: How the encysting Anoplodactylus eroticus matures from a buoyant nymph to a grounded adultJan 06 2013In order to understand how animals evolved over time, biologists must learn how their body parts form during their development. The following is a detailed description of how one species of sea spider transforms from a hatchling to an 8-legged adult. ... More
A Brief History of Quaternions and of the Theory of Holomorphic Functions of Quaternionic VariablesNov 25 2011In this paper I will give a brief history of the discovery (Hamilton, 1843) of quaternions. I will address the issue of why a theory of triplets (the original goal of Hamilton) could not be developed. Finally, I will discuss briefly the history of various ... More