Results for "Gregory R. Brady"

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Phase-Retrieval-Based Wavefront Metrology for High Contrast CoronagraphyMar 05 2019We discuss the use of parametric phase-diverse phase retrieval as an in-situ high-fidelity wavefront measurement method to characterize and optimize the transmitted wavefront of a high-contrast coronagraphic instrument. We apply our method to correct ... More
Searching for periodic sources with LIGO. II: Hierarchical searchesDec 04 1998The detection of quasi-periodic sources of gravitational waves requires the accumulation of signal-to-noise over long observation times. If not removed, Earth-motion induced Doppler modulations, and intrinsic variations of the gravitational-wave frequency ... More
Cauchy horizon singularity without mass inflationNov 20 1992A perturbed Reissner-Nordstr\"om-de Sitter solution is used to emphasize the nature of the singularity along the Cauchy horizon of a charged spherically symmetric black hole. For these solutions, conditions may prevail under which the mass function is ... More
Critical phenomena in gravitational collapseDec 21 1998This article reviews classical and quantum aspects of critical phenomena in gravitational collapse. We pay special attention to the origin of the scaling law for black hole mass, and to phase transitions in which black hole formation turns on at finite ... More
Integration of fluorescence collection optics with a microfabricated surface electrode ion trapAug 17 2010Sep 23 2010We have successfully demonstrated an integrated optical system for collecting the fluorescence from a trapped ion. The system, consisting of an array of transmissive, dielectric micro-optics and an optical fiber array, has been intimately incorporated ... More
High-contrast Imager for Complex Aperture Telescopes (HiCAT): 6. Software Control Infrastructure and CalibrationMar 07 2019High contrast imaging using coronagraphy is one of the main avenues to enable the search for life on extrasolar Earth analogs. The HiCAT testbed aims to demonstrate coronagraphy and wavefront control for segmented on-axis space telescopes as envisioned ... More
A note on the affine-invariant plank problemApr 02 2016Suppose that $C$ is a bounded convex subset of $\mathbb{R}^n$, and that $P_1, \dots, P_k$ are planks which cover $C$ in respective directions $v_1, \dots, v_k$ and with widths $w_1, \dots, w_k$. In 1951, Bang conjectured that $$\sum_{i=1}^k \frac{w_i}{w_{v_i}(C)} ... More
Proof of the Log-Convex Density ConjectureNov 16 2013Mar 15 2015We completely characterize isoperimetric regions in R^n with density e^h, where h is convex, smooth, and radially symmetric. In particular, balls around the origin constitute isoperimetric regions of any given volume, proving the Log-Convex Density Conjecture ... More
On the Classification of Legendrian Rational TanglesNov 12 2014We show that under certain conditions the flyping operation on rational tangles, which produces topologically isotopic tangles, may also produce tangles which are not Legendrian isotopic when viewed in the standard contact structure on $\mathbb{R}^3$. ... More
A constitutive model for brittle granular materials considering the competition between breakage and dilationFeb 20 2019A constitutive model is presented for brittle granular materials based on a recent reformulation of the breakage mechanics theory. Compared with previous breakage mechanics-based models, the proposed model is improved to capture strain softening towards ... More
Geometric stability of the Coulomb energyJul 08 2014Jul 06 2015The Coulomb energy of a charge that is uniformly distributed on some set is maximized (among sets of given volume) by balls. It is shown here that near-maximizers are close to balls.
Optimal sweepouts of a Riemannian 2-sphereNov 24 2014Jun 25 2016Given a sweepout of a Riemannian 2-sphere which is composed of curves of length less than L, we construct a second sweepout composed of curves of length less than L which are either constant curves or simple curves. This result, and the methods used to ... More
Cohomology of One-dimensional Mixed Substitution Tiling SpacesDec 07 2011Mar 06 2012We compute the Cech cohomology with integer coefficients of one-dimensional tiling spaces arising from not just one, but several different substitutions, all acting on the same set of tiles. These calculations involve the introduction of a universal version ... More
Monotone homotopies and contracting discs on Riemannian surfacesNov 13 2013Oct 05 2016We prove a "gluing" theorem for monotone homotopies; a monotone homotopy is a homotopy through simple contractible closed curves which themselves are pairwise disjoint. We show that two monotone homotopies which have appropriate overlap can be replaced ... More
Beyond primitivity for one-dimensional substitution tiling spacesApr 05 2016We study the topology and dynamics of subshifts and tiling spaces associated to non-primitive substitutions in one dimension. We identify a property of a substitution, which we call tameness, in the presence of which most of the possible pathological ... More
Splitting a contraction of a simple curve traversed $m$ timesOct 12 2015Suppose that $M$ is a $2$-dimensional oriented Riemannian manifold, and let $\gamma$ be a simple closed curve on $M$. Let $m \gamma$ denote the curve formed by tracing $\gamma$ $m$ times. We prove that if $m \gamma$ is contractible through curves of length ... More
Beyond primitivity for one-dimensional substitution subshifts and tiling spacesApr 05 2016Jul 17 2017We study the topology and dynamics of subshifts and tiling spaces associated to non-primitive substitutions in one dimension. We identify a property of a substitution, which we call tameness, in the presence of which most of the possible pathological ... More
High-contrast imager for complex aperture telescopes (HiCAT): 5. first results with segmented-aperture coronagraph and wavefront controlMar 13 2019Segmented telescopes are a possibility to enable large-aperture space telescopes for the direct imaging and spectroscopy of habitable worlds. However, the complexity of their aperture geometry, due to the central obstruction, support structures and segment ... More
General divisor function inequalities and the third cumulantSep 14 2015We extend a lower bound of Munshi on sums over divisors of a number $n$ which are less than a fixed power of $n$ from the squarefree case to the general case. In the process we prove a lower bound on the entropy of a geometric distribution with finite ... More
Existence of minimal hypersurfaces in complete manifolds of finite volumeSep 13 2016We prove that every complete non-compact manifold of finite volume contains a (possibly non-compact) minimal hypersurface of finite volume.
Perimeter under multiple Steiner symmetrizationsSep 20 2012Steiner symmetrization along n linearly independent directions transforms every compact subset of R^n into a set of finite perimeter.
Converting homotopies to isotopies and dividing homotopies in half in an effective wayNov 04 2013Jan 09 2014We prove two theorems about homotopies of curves on 2-dimensional Riemannian manifolds. We show that, for any epsilon > 0, if two simple closed curves are homotopic through curves of bounded length L, then they are also isotopic through curves of length ... More
Existence of minimal hypersurfaces in complete manifolds of finite volumeSep 13 2016Nov 11 2016We prove that every complete non-compact manifold of finite volume contains a (possibly non-compact) minimal hypersurface of finite volume.
Chromatic numbers of directed hypergraphs with no "bad" cyclesJun 03 2018Imagine that you are handed a rule for determining whether a cycle in a digraph is "good" or "bad", based on which edges of the cycle are traversed in the forward direction and which edges are traversed in the backward direction. Can you then construct ... More
Quantum Effects in Black Hole InteriorsOct 23 1992The Weyl curvature inside a black hole formed in a generic collapse grows, classically without bound, near to the inner horizon, due to partial absorption and blueshifting of the radiative tail of the collapse. Using a spherical model, we examine how ... More
Synchrotron radiation, pair production and longitudinal electron motion during 10-100PW laser solid interactionsDec 18 2013At laser intensities above 1023W/cm2 the interaction of a laser with a plasma is qualitatively different to the interactions at lower intensities. In this intensity regime solid targets start to become relativistically underdense, gamma-ray production ... More
The Intrinsic Fractions and Radio Properties of Low Ionization Broad Absorption Line QuasarsApr 05 2010Apr 12 2011Low-ionization (MgII, FeII, FeIII) broad absorption line quasars (LoBALs) probe a relatively obscured quasar population, and could be at an early evolutionary stage for quasars. We study the intrinsic fractions of LoBALs using the SDSS, 2MASS, and FIRST ... More
A note on automatic continuityOct 13 2017We present new results regarding automatic continuity, unifying some diagonalization concepts that have been developed over the years. For example, any homomorphism from a completely metrizable topological group to Thompson's group $F$ has open kernel. ... More
A Critical Look At Massive Scalar Field CollapseOct 02 1997We present the findings of an investigation of critical behavior in the collapse of spherically symmetric distributions of massive scalar field. Two distinct types of phase transition are observed at the verge of black hole formation and a criterion for ... More
Self-affine ManifoldsFeb 12 2014Nov 09 2015This paper studies closed 3-manifolds which are the attractors of a system of finitely many affine contractions that tile $\mathbb{R}^3$. Such attractors are called self-affine tiles. Effective characterization and recognition theorems for these 3-manifolds ... More
Derivative-free optimization of rate parameters of capsid assembly models from bulk in vitro dataJul 07 2015The assembly of virus capsids from free coat proteins proceeds by a complicated cascade of association and dissociation steps, the great majority of which cannot be directly experimentally observed. This has made capsid assembly a rich field for computational ... More
Some anomalous examples of lifting spacesAug 02 2017An inverse limit of a sequence of covering spaces over a given space $X$ is not, in general, a covering space over $X$ but is still a lifting space, i.e. a Hurewicz fibration with unique path lifting property. Of particular interest are inverse limits ... More
Topological Defects, Surface Geometry and Cohesive Energy of Twisted Filament BundlesMar 06 2013Jul 05 2013Cohesive assemblies of filaments are a common structural motif found in diverse contexts, ranging from biological materials such as fibrous proteins, to artificial materials such as carbon nanotube ropes and micropatterned filament arrays. In this paper, ... More
On Boundary -- Value Problems for the Laplacian in Boundedand in Unbounded Domains Withperforated BoundariesMar 04 2003In the paper we consider boundary -- value problems with rapidly alternating type of boundary conditions, including problems in domains with perforated boundaries. We present the classification of homogenized (limit) problems depending on the ratio of ... More
Ergodic properties of folding maps on spheresSep 08 2015Nov 13 2016We consider the trajectories of points on $\mathbb{S}^{d - 1}$ under sequences of certain folding maps associated with reflections. The main result characterizes collections of folding maps that produce dense trajectories. The minimal number of maps in ... More
2MASS Reveals a Large Intrinsic Fraction of BALQSOsApr 22 2007Sep 18 2007The intrinsic fraction of broad absorption line quasars (BALQSOs) is important in constraining geometric and evolutionary models of quasars. We present the fraction of BALQSOs in 2MASS detected quasars within the SDSS DR3 sample in the redshift range ... More
Quantitative nullhomotopy and rational homotopy typeNov 10 2016Mar 14 2018In \cite{GrOrang}, Gromov asks the following question: given a nullhomotopic map $f:S^m \to S^n$ of Lipschitz constant $L$, how does the Lipschitz constant of an optimal nullhomotopy of $f$ depend on $L$, $m$, and $n$? We establish that for fixed $m$ ... More
Archipelago groupsOct 30 2014The classical archipelago is a non-contractible subset of $\mathbb{R}^3$ which is homeomorphic to a disk except at one non-manifold point. Its fundamental group, $\mathcal{A}$, is the quotient of the topologist's product of $\mathbb Z$, the fundamental ... More
Snowflake geometry in CAT(0) groupsFeb 26 2016Aug 15 2017We construct CAT(0) groups containing subgroups whose Dehn functions are given by $x^s$, for a dense set of numbers $s \in [2, \infty)$. This significantly expands the known geometric behavior of subgroups of CAT(0) groups.
Braids, posets and orthoschemesSep 25 2009In this article we study the curvature properties of the order complex of a graded poset under a metric that we call the ``orthoscheme metric''. In addition to other results, we characterize which rank 4 posets have CAT(0) orthoscheme complexes and by ... More
Dehn functions of subgroups of right-angled Artin groupsSep 12 2017We show that for each positive integer $k$ there exist right-angled Artin groups containing free-by-cyclic subgroups whose monodromy automorphisms grow as $n^k$. As a consequence we produce examples of right-angled Artin groups containing finitely presented ... More
Lattices in finite real reflection groupsJan 28 2005For a finite real reflection group $W$ with Coxeter element $\gamma$ we give a uniform proof that the closed interval, $[I, \gamma]$ forms a lattice in the partial order on $W$ induced by reflection length. The proof involves the construction of a simplicial ... More
From Permutahedron to AssociahedronApr 15 2008For each finite real reflection group $W$, we identify a copy of the type-$W$ simplicial generalised associahedron inside the corresponding simplicial permutahedron. This defines a bijection between the facets of the generalised associahedron and the ... More
Origin and reduction of wakefields in photonic crystal accelerator cavitiesSep 04 2013Sep 09 2013Photonic crystal (PhC) defect cavities that support an accelerating mode tend to trap unwanted higher-order modes (HOMs) corresponding to zero-group-velocity PhC lattice modes at the top of the bandgap. The effect is explained quite generally from photonic ... More
Why quantum computing is hard - and quantum cryptography is not provably secureJan 30 2013Despite high hopes for quantum computation in the 1990s, progress in the past decade has been slow; we still cannot perform computation with more than about three qubits and are no closer to solving problems of real interest than a decade ago. Separately, ... More
Factoring euclidean isometriesDec 30 2013Every isometry of a finite dimensional euclidean space is a product of reflections and the minimum length of a reflection factorization defines a metric on its full isometry group. In this article we identify the structure of intervals in this metric ... More
Detecting transient gravitational waves in non-Gaussian noise with partially redundant analysis methodsJan 13 2012Apr 25 2012There is a broad class of astrophysical sources that produce detectable, transient, gravitational waves. Some searches for transient gravitational waves are tailored to known features of these sources. Other searches make few assumptions about the sources. ... More
Likelihood-ratio ranking of gravitational-wave candidates in a non-Gaussian backgroundJan 13 2012Jan 17 2012We describe a general approach to detection of transient gravitational-wave signals in the presence of non-Gaussian background noise. We prove that under quite general conditions, the ratio of the likelihood of observed data to contain a signal to the ... More
Investigation of the Vertical Movement of an Isothermal Line at the Density Maximum in H2O and D2OMar 05 2008We studied the cooling of a column of water, primarily in a freezer, and analyzed the development and movement of an isothermal line at ~4 degC in H2O and ~11 degC in D2O. Our experiments show that the vertical velocity of the symmetrical isothermal line ... More
Open String Star as a Continuous Moyal ProductFeb 14 2002Apr 14 2002We establish that the open string star product in the zero momentum sector can be described as a continuous tensor product of mutually commuting two dimensional Moyal star products. Let the continuous variable $\kappa \in [~0,\infty)$ parametrize the ... More
Nb/InAs nanowire proximity junctions from Josephson to quantum dot regimesNov 26 2016The superconducting proximity effect is probed experimentally in Josephson junctions fabricated with InAs nanowires contacted by Nb leads. Contact transparencies $t \sim 0.7$ are observed. The electronic phase coherence length at low temperatures exceeds ... More
Quantum Logic with Interacting Bosons in 1DJan 18 2015Mar 05 2015We present a scheme for implementing high-fidelity quantum logic gates using the quantum walk of a few interacting bosons on a one-dimensional lattice. The gate operation is carried out by a single compact lattice described by a one-dimensional Bose-Hubbard ... More
Gasser-Leutwyler coefficients: A progress reportSep 19 2002Last year, we reported our first results on the determination of Gasser-Leutwyler coefficients using partially quenched lattice QCD with three flavors of dynamical staggered quarks. We give an update on our progress in determining two of these coefficients, ... More
Two dimensional heteroclinic attractor in the generalized Lotka-Volterra systemSep 15 2015We study a simple dynamical model exhibiting sequential dynamics. We show that in this model there exist sets of parameter values for which a cyclic chain of saddle equilibria, $O_k$, $k=1, \ldots, p$, have two dimensional unstable manifolds that contain ... More
MLtuner: System Support for Automatic Machine Learning TuningMar 20 2018MLtuner automatically tunes settings for training tunables (such as the learning rate, the momentum, the mini-batch size, and the data staleness bound) that have a significant impact on large-scale machine learning (ML) performance. Traditionally, these ... More
Quantum optical neural networksAug 29 2018Sep 20 2018Physically motivated quantum algorithms for specific near-term quantum hardware will likely be the next frontier in quantum information science. Here, we show how many of the features of neural networks for machine learning can naturally be mapped into ... More
Area of convex disksJan 23 2017This paper considers metric balls $B(p,R)$ in two dimensional Riemannian manifolds when $R$ is less than half the convexity radius. We prove that $Area(B(p,R)) \geq \frac{8}{\pi}R^2$. This inequality has long been conjectured for $R$ less than half the ... More
Education and Outreach for the Pierre Auger ObservatoryJul 25 2007The scale and scope of the physics studied at the Auger Observatory offer significant opportunities for original outreach work. Education, outreach, and public relations of the Auger collaboration are coordinated in a task of its own whose goals are to ... More
Quantitative null-cobordismOct 16 2016Jul 24 2017For a given null-cobordant Riemannian $n$-manifold, how does the minimal geometric complexity of a null-cobordism depend on the geometric complexity of the manifold? In [Gro99], Gromov conjectured that this dependence should be linear. We show that it ... More
Modelling Gamma Ray Emission and Pair Production in High-Intensity Laser-Matter InteractionsNov 21 2013In high-intensity (> 10^21W/cm^2) laser-matter interactions gamma-ray photon emission by the electrons can strongly affect the electron's dynamics and copious numbers of electron-positron pairs can be produced by the emitted photons. We show how these ... More
Dense Electron-Positron Plasmas and Ultra-Intense Bursts of Gamma-Rays from Laser-Irradiated SolidsFeb 13 2012Jun 06 2012In simulations of a 10PW laser striking a solid we demonstrate the possibility of producing a pure electron-positron plasma by the same processes as those thought to operate in high-energy astrophysical environments. A maximum positron density of 10^26/m^3 ... More
Computing arithmetic invariants for hyperbolic reflection groupsAug 15 2007We describe a collection of computer scripts written in PARI/GP to compute, for reflection groups determined by finite-volume polyhedra in $\mathbb{H}^3$, the commensurability invariants known as the invariant trace field and invariant quaternion algebra. ... More
Formal Concept Analysis with Many-sorted AttributesOct 12 2018This paper unites two problem-solving traditions in computer science: (1) constraint-based reasoning, and (2) formal concept analysis. For basic definitions and properties of networks of constraints, we follow the foundational approach of Montanari and ... More
Short-time transport properties of bidisperse suspensions and porous media: a Stokesian Dynamics studyDec 28 2014We present a comprehensive computational study of the short-time transport properties of bidisperse neutral colloidal suspensions and the corresponding porous media. Our study covers bidisperse particle size ratios up to $4$, and total volume fractions ... More
Kepler-1656b: a Dense Sub-Saturn With an Extreme EccentricitySep 22 2018Kepler-1656b is a 5 $R_E$ planet with an orbital period of 32 days initially detected by the prime Kepler mission. We obtained precision radial velocities of Kepler-1656 with Keck/HIRES in order to confirm the planet and to characterize its mass and orbital ... More
Three-generator Artin groups of large type are biautomaticSep 29 1998In this article we construct a piecewise Euclidean, non-positively curved 2-complex for the 3-generator Artin groups of large type. As a consequence we show that these groups are biautomatic. A slight modification of the proof shows that many other Artin ... More
Refining Exoplanet Ephemerides and Transit Observing StrategiesSep 30 2009Transiting planet discoveries have yielded a plethora of information regarding the internal structure and atmospheres of extra-solar planets. These discoveries have been restricted to the low-periastron distance regime due to the bias inherent in the ... More
Constrained Spacecraft Relative Motion Planning Exploiting Periodic Natural Motion Trajectories and InvarianceMar 18 2017Jun 21 2017Spacecraft relative motion planning is concerned with the design and execution of maneuvers relative to a nominal target. These types of maneuvers are frequently utilized in missions such as rendezvous and docking, satellite inspection and formation flight ... More
Short-time diffusion in concentrated bidisperse hard-sphere suspensionsOct 31 2014Diffusion in bidisperse Brownian hard-sphere suspensions is studied by Stokesian Dynamics (SD) computer simulations and a semi-analytical theoretical scheme for colloidal short-time dynamics, based on Beenakker and Mazur's method [Physica 120A, 388 (1983) ... More
Amorphous and ordered states of concentrated hard spheres under oscillatory shearJan 12 2016Hard sphere colloidal particles are a basic model system for general research into phase behavior, ordering and out-equilibrium glass transitions. Experimentally it has been shown that oscillatory shearing of a monodisperse hard sphere glass, produces ... More
Morse theory and conjugacy classes of finite subgroups IIMay 01 2009We construct a hyperbolic group with a finitely presented subgroup, which has infinitely many conjugacy classes of finite-order elements. We also use a version of Morse theory with high dimensional horizontal cells and use handle cancellation arguments ... More
Non-crossing partitions and Milnor fibersSep 22 2017For a finite real reflection group $W$ we use non-crossing partitions of type $W$ to construct finite cell complexes with the homotopy type of the Milnor fiber of the associated $W$-discriminant $\Delta_W$ and that of the Milnor fiber of the defining ... More
Census of the Local Universe (CLU) I: Characterization of Galaxy Catalogs from Preliminary FieldsOct 13 2017We present a Census of the Local Universe (CLU) -- a combination of the largest area H$\alpha$ survey for nearby emission-line galaxies to date as well as a compilation of all publicly available galaxy catalogs out to a distance of 200 Mpc. With the Palomar ... More
Turn graphs and extremal surfaces in free groupsApr 27 2011This note provides an alternate account of Calegari's rationality theorem for stable commutator length in free groups.
Trace Asymptotics for C*-Algebras from Smale SpacesAug 24 2012We consider C*-algebras associated with stable and unstable equivalence in hyperbolic dynamical systems known as Smale spaces. These systems include shifts of finite type, in which case these C*-algebras are both AF-algebras. These algebras have fundamental ... More
Shellability of noncrossing partition latticesMar 01 2005We give a case-free proof that the lattice of noncrossing partitions associated to any finite real reflection group is EL-shellable. Shellability of these lattices was open for the groups of type $D_n$ and those of exceptional type and rank at least three. ... More
Hierarchical Nystrom Methods for Constructing Markov State Models for Conformational DynamicsJan 06 2013Markov state models (MSMs) have become a popular approach for investigating the conformational dynamics of proteins and other biomolecules. MSMs are typically built from numerous molecular dynamics simulations by dividing the sampled configurations into ... More
The impact of mergers on relaxed X-ray clusters - III. Effects on compact cool coresApr 09 2008(Abridged) We use the simulations presented in Poole et al. 2006 to examine the effects of mergers on compact cool cores in X-ray clusters. We propose a scheme for classifying the morphology of clusters based on their surface brightness and entropy profiles. ... More
Control of catalytic efficiency by a co-evolving network of catalytic and non-catalytic residuesApr 14 2014The active sites of enzymes consist of residues necessary for catalysis, and structurally important non-catalytic residues that together maintain the architecture and function of the active site. Examples of evolutionary interactions between active site ... More
On the representation of many-body interactions in waterJun 17 2015Aug 11 2015Recent work has shown that the many-body expansion of the interaction energy can effectively be used to develop analytical representations of global potential energy surfaces (PESs) for water. In this study, the role of short- and long-range contri- butions ... More
Non-contact method for measurement of the microwave conductivity of grapheneApr 04 2013We report a non-contact method for conductivity and sheet resistance measurements of graphene samples using a high Q microwave dielectric resonator perturbation technique, with the aim of fast and accurate measurement of microwave conductivity and sheet ... More
System-size convergence of nonthermal particle acceleration in relativistic plasma turbulenceMay 22 2018We apply collisionless particle-in-cell simulations of relativistic pair plasmas to explore whether driven turbulence is a viable high-energy astrophysical particle accelerator. We characterize nonthermal particle distributions for varying system sizes ... More
Unveiling the Intrinsic X-ray Properties of Broad Absorption Line Quasars with a Relatively Unbiased SampleSep 23 2013Feb 25 2014There is growing evidence of a higher intrinsic fraction of broad absorption line quasars (BALQSOs) than that obtained in optical surveys, on which most previous X-ray studies of BALQSOs have focused. Here we present Chandra observations of 18 BALQSOs ... More
Suzaku Observations of Three FeLoBAL QSOs, SDSS J0943+5417, J1352+4239, and J1723+5553Nov 18 2010May 29 2011We present Suzaku observations of three iron low-ionization broad absorption line quasars (FeLoBALs). We detect J1723+5553 (3\sigma) in the observed 2--10 keV band, and constrain its intrinsic nh column density to nh > 6\times10^{23} \cmsq by modeling ... More
Topological Methods for Exploring Low-density States in Biomolecular Folding PathwaysDec 17 2008Characterization of transient intermediate or transition states is crucial for the description of biomolecular folding pathways, which is however difficult in both experiments and computer simulations. Such transient states are typically of low population ... More
Trapped charge dynamics in InAs nanowiresSep 14 2012Oct 11 2012We study random telegraph noise in the conductance of InAs nanowire field-effect transistors due to single electron trapping in defects. The electron capture and emission times are measured as functions of temperature and gate voltage for individual traps, ... More
Electron Transport in InAs-InAlAs Core-Shell NanowiresSep 13 2012Sep 10 2014Evidence is given for the effectiveness of InAs surface passivation by the growth of an epitaxial InAlAs shell. The electron mobility is measured as a function of temperature for both core-shell and unpassivated nanowires, with the core-shell nanowires ... More
Tumour Ellipsification in Ultrasound Images for Treatment Prediction in Breast CancerJan 13 2017Recent advances in using quantitative ultrasound (QUS) methods have provided a promising framework to non-invasively and inexpensively monitor or predict the effectiveness of therapeutic cancer responses. One of the earliest steps in using QUS methods ... More
Finding the centre: corrections for asymmetry in high-throughput sequencing datasetsApr 06 2017High throughput sequencing is a technology that allows for the generation of millions of reads of genomic data regarding a study of interest, and data from high throughput sequencing platforms are usually count compositions. Subsequent analysis of such ... More
Constructing monotone homotopies and sweepoutsApr 20 2017Aug 26 2017This article investigates when homotopies can be converted to monotone homotopies without increasing the lengths of curves. A monotone homotopy is one which consists of curves which are simple or constant, and in which curves are pairwise disjoint. We ... More
X-ray Emission from Young Stars in the TW Hya AssociationAug 18 2014The 9 Myr old TW Hya Association (TWA) is the nearest group (typical distances of $\sim$50 pc) of pre-main-sequence (PMS) stars with ages less than 10 Myr and contains stars with both actively accreting disks and debris disks. We have studied the coronal ... More
Model for SU(3) vacuum degeneracy using light-cone coordinatesJan 11 2001Working in light-cone coordinates, we study the zero-modes and the vacuum in a 2+1 dimensional SU(3) gauge model. Considering the fields as independent of the tranverse variables, we dimensionally reduce this model to 1+1 dimensions. After introducing ... More
Dissecting a Small InfiniBand Application Using the Verbs APIMay 10 2011May 24 2011InfiniBand is a switched fabric interconnect. The InfiniBand specification does not define an API. However the OFED package, libibverbs, has become the default API on Linux and Solaris systems. Sparse documentation exists for the verbs API. The simplest ... More
Decidability of theories of modules over canonical algebras of tubular typeMar 10 2016We show that the common theory of all modules over a canonical algebra of tubular type (over a recursively given algebraically closed field) is decidable. This result supports a long standing conjecture of Mike Prest which says that a finite-dimensional ... More
Liouville Type Theorem for Stationary Navier-Stokes EquationsDec 09 2015It is shown that any smooth solution to the stationary Navier-Stokes system in $R^3$ with the velocity field, belonging globally to $L_6$ and $BM0^{-1}$, must be zero.
Nodal count of graph eigenfunctions via magnetic perturbationOct 24 2011We establish a connection between the stability of an eigenvalue under a magnetic perturbation and the number of zeros of the corresponding eigenfunction. Namely, we consider an eigenfunction of discrete Laplacian on a graph and count the number of edges ... More
Metric contraction of the cone divisor by the conical Kähler-Ricci flowApr 02 2017We use the momentum construction of Calabi to study the conical K\"ahler-Ricci flow on Hirzebruch surfaces with cone angle along the exceptional curve, and show that either the flow Gromov-Hausdorff converges to the Riemann sphere or a single point in ... More
The Rational Toomer Invariant and Certain Elliptic SpacesSep 24 2003We give an explicit formula for the rational category of an elliptic space whose minimal model has a homogeneous-length differential. We also show that for such a space, there are no gaps in the sequence of integers realized as the rational Toomer invariant ... More
Random Delaunay triangulations and metric uniformizationOct 31 2000Nov 01 2000In this paper a new connection between the discrete conformal geometry problem of disk pattern construction and the continuous conformal geometry problem of metric uniformization is presented. In a nutshell, we discuss how to construct disk patterns by ... More
Searching for line transitive, point imprimitive, linear spacesApr 25 2006A finite linear space is a finite set of points and lines, where any two points lie on a unique line. Well known examples include projective planes. This project focuses on linear spaces which admit certain types of symmetries. Symmetries of the space ... More