cssi/SciSciGPT-SciSciNet huggingface dataset:
Brain amyloid and the transition to dementia in Down syndrome.

Author(s): Keator, David B; Doran, Eric; Taylor, Lisa; Phelan, Michael J; Hom, Christy; Tseung, Katherine; van Erp, Theo GM; Potkin, Steven G; Brickman, Adam M; Rosas, Diana H; Yassa, Michael A; Silverman, Wayne; Lott, Ira T | Abstract: IntroductionDown syndrome (DS) is associated with elevated risk for Alzheimer's disease (AD) due to amyloid beta (Aβ) lifelong accumulation. We hypothesized that the spatial distribution of brain Aβ predicts future dementia conversion in individuals with DS.MethodsWe acquired 18F-florbetapir positron emission tomography scans from 19 nondemented individuals with DS at baseline and monitored them for 4 years, with five individuals transitioning to dementia. Machine learning classification using an independent test set determined features on 18F-florbetapir standardized uptake value ratio maps that predicted transition.ResultsIn addition to "AD signature" regions including the inferior parietal cortex, temporal lobes, and the cingulum, we found that Aβ cortical binding in the prefrontal and superior frontal cortices distinguished subjects who transitioned to dementia. Classification did well in predicting transitioners.DiscussionOur study suggests that specific regional profiles of brain amyloid in older adults with DS may predict cognitive decline and are informative in evaluating the risk for dementia.
AN HST SURVEY FOR 100–1000 au COMPANIONS AROUND YOUNG STELLAR OBJECTS IN THE ORION MOLECULAR CLOUDS: EVIDENCE FOR ENVIRONMENTALLY DEPENDENT MULTIPLICITY

We present a near-IR survey for the visual multiples in the Orion molecular clouds region at separations between 100 and 1000 AU. These data were acquired at 1.6~$\mu$m with the NICMOS and WFC3 cameras on the Hubble Space Telescope. Additional photometry was obtained for some of the sources at 2.05~$\mu$m with NICMOS and in the $L'$-band with NSFCAM2 on the IRTF. Towards 129 protostars and 197 pre-main sequence stars with disks observed with WFC3, we detect 21 and 28 candidate companions between the projected separations of 100---1000 AU, of which less than 5 and 8, respectively, are chance line of sight coincidences. The resulting companion fraction ($CF$) after the correction for the line of sight contamination is 14.4$^{+1.1}_{-1.3}$% for protostars and 12.5$^{+1.2}_{-0.8}$% for the pre-main sequence stars. These values are similar to those found for main sequence stars, suggesting that there is little variation in the $CF$ with evolution, although several observational biases may mask a decrease in the $CF$ from protostars to the main sequence stars. After segregating the sample into two populations based on the surrounding surface density of YSOs, we find that the $CF$ in the high stellar density regions ($\Sigma_{YSO} > 45$~pc$^{-2}$) is approximately 50% higher than that found in the low stellar density regions ($\Sigma_{YSO} < 45$~pc$^{-2}$). We interpret this as evidence for the elevated formation of companions at 100 to 1000 AU in the denser environments of Orion. We discuss possible reasons for this elevated formation.
Patterns of Activity in A Global Model of A Solar Active Region

In this work we investigate the global activity patterns predicted from a model active region heated by distributions of nanoflares that have a range of frequencies. What differs is the average frequency of the distributions. The activity patterns are manifested in time lag maps of narrow-band instrument channel pairs. We combine hydrodynamic and forward modeling codes with a magnetic field extrapolation to create a model active region and apply the time lag method to synthetic observations. Our aim is not to reproduce a particular set of observations in detail, but to recover some typical properties and patterns observed in active regions. Our key findings are the following. (1) Cooling dominates the time lag signature and the time lags between the channel pairs are generally consistent with observed values. (2) Shorter coronal loops in the core cool more quickly than longer loops at the periphery. (3) All channel pairs show zero time lag when the line of sight passes through coronal loop footpoints. (4) There is strong evidence that plasma must be re-energized on a timescale comparable to the cooling timescale to reproduce the observed coronal activity, but it is likely that a relatively broad spectrum of heating frequencies are operating across active regions. (5) Due to their highly dynamic nature, we find nanoflare trains produce zero time lags along entire flux tubes in our model active region that are seen between the same channel pairs in observed active regions.
A surgery triangle for lattice cohomology

Lattice cohomology, defined by Nemethi in [Publ. Res. Inst. Math. Sci. 44 (2008) 507–543], is an invariant of negative definite plumbed 3–manifolds which conjecturally computes their Heegaard Floer homology HF+. We prove a surgery exact triangle for the lattice cohomology analogous to the one for HF+. This is a step towards relating these two invariants.
ANOMALOUS CHIRAL ACTION FROM THE PATH INTEGRAL

By generalizing the Fujikawa approach, we show in the path integral formalism: (1) how the infinitesimal variation of the fermion measure can be integrated to obtain the full anomalous chiral action; (2) how the action derived in this way can be identified as the Chern–Simons term in five dimensions, if the anomaly is consistent; (3) how the regularization can be carried out, so as to lead to the consistent anomaly and not to the covariant anomaly. We consider a massless left-handed fermion interacting with a non-Abelian gauge field. The gauge field also interacts with a set of Goldstone bosons, so that a gauge-invariant configuration of the gauge field exists. We use Schwinger's "proper time" representation of the Green's function and the guage-invariant point-splitting technique, and find that the consistency requirement and the point-splitting technique allow both an anomalous and a nonanomalous action. In the end, the nature of the vacuum determines whether we have an anomalous theory or a nonanomalous theory.
Random Spiking and Systematic Evaluation of Defenses Against Adversarial Examples

Image classifiers often suffer from adversarial examples, which are generated by strategically adding a small amount of noise to input images to trick classifiers into misclassification. Over the years, many defense mechanisms have been proposed, and different researchers have made seemingly contradictory claims on their effectiveness. We present an analysis of possible adversarial models, and propose an evaluation framework for comparing different defense mechanisms. As part of the framework, we introduce a more powerful and realistic adversary strategy. Furthermore, we propose a new defense mechanism called Random Spiking (RS), which generalizes dropout and introduces random noises in the training process in a controlled manner. Evaluations under our proposed framework suggest RS delivers better protection against adversarial examples than many existing schemes.
Melvin magnetic fluxtube/cosmology correspondence

We explore a correspondence between Melvin magnetic fluxtubes and anisotropic cosmological solutions, which we call 'Melvin cosmologies'. The correspondence via analytic continuation provides useful information in both directions. Solution generating techniques known on the fluxtube side can also be used for generating cosmological backgrounds. Melvin cosmologies interpolate between different limiting Kasner behaviors at early and late times. This has an analogue on the fluxtube side between limiting Levi-Civita behavior at small and large radii. We construct generalized Melvin fluxtubes and cosmologies in both Einstein–Maxwell theory and dilaton gravity and show that similar properties hold.
Is single-mode lasing possible in an infinite periodic system?

In this Letter, we present a rigorous method to study the stability of periodic lasing systems. In a linear model, the presence of a continuum of modes (with arbitrarily close lasing thresholds) gives the impression that stable single-mode lasing cannot be maintained in the limit of an infinite system. However, we show that nonlinear effects of the Maxwell–Bloch equations can lead to stable systems near threshold given a simple stability condition on the sign of the laser detuning compared to the band curvature. We examine band edge (1D) and bound-in-continuum (2D) lasing modes and validate our stability results against time-domain simulations.
Tutorial: Time-domain thermoreflectance (TDTR) for thermal property characterization of bulk and thin film materials

Measuring thermal properties of materials is not only of fundamental importance in understanding the transport processes of energy carriers (electrons and phonons in solids) but also of practical interest in developing novel materials with desired thermal properties for applications in energy conversion and storage, electronics, and photonic systems. Over the past two decades, ultrafast laser-based time-domain thermoreflectance (TDTR) has emerged and evolved as a reliable, powerful, and versatile technique to measure the thermal properties of a wide range of bulk and thin film materials and their interfaces. This tutorial discusses the basics as well as the recent advances of the TDTR technique and its applications in the thermal characterization of a variety of materials. The tutorial begins with the fundamentals of the TDTR technique, serving as a guideline for understanding the basic principles of this technique. Several variations of the TDTR technique that function similarly as the standard TDTR but with their own unique features are introduced, followed by introducing different advanced TDTR configurations that were developed to meet different measurement conditions. This tutorial closes with a summary that discusses the current limitations and proposes some directions for future development.
MMT HYPERVELOCITY STAR SURVEY. II. FIVE NEW UNBOUND STARS

We present the discovery of five new unbound hypervelocity stars (HVSs) in the outer Milky Way halo. Using a conservative estimate of Galactic escape velocity, our targeted spectroscopic survey has now identified 16 unbound HVSs as well as a comparable number of HVSs ejected on bound trajectories. A Galactic center origin for the HVSs is supported by their unbound velocities, the observed number of unbound stars, their stellar nature, their ejection time distribution, and their Galactic latitude and longitude distribution. Other proposed origins for the unbound HVSs, such as runaway ejections from the disk or dwarf galaxy tidal debris, cannot be reconciled with the observations. An intriguing result is the spatial anisotropy of HVSs on the sky, which possibly reflects an anisotropic potential in the central 10-100 pc region of the Galaxy. Further progress requires measurement of the spatial distribution of HVSs over the southern sky. Our survey also identifies seven B supergiants associated with known star-forming galaxies; the absence of B supergiants elsewhere in the survey implies there are no new star-forming galaxies in our survey footprint to a depth of 1-2 Mpc.
Continuum electrodynamics and the Abraham-Minkowski momentum controversy

Michael E. Crenshaw US Army Aviation and Missile Research, Development, and Engineering CenterRMDR-WDS-W, Redstone Arsenal, AL 35898, USAABSTRACTContinuum electrodynamics is an axiomatic formal theory based on the macroscopic Maxwell equations andthe constitutive relations. We apply the formal theory to a thermodynamically closed system consisting of anantireection coated block of dielectric situated in free-space and illuminated by a quasimonochromatic eld.We show that valid theorems of the formal theory are proven false by relativity and by conservation laws. Thenthe axioms of the formal theory are proven false at a fundamental level of mathematical logic. We derive a newformal theory of continuum electrodynamics for macroscopic electric and magnetic elds in a four-dimensionalat non-Minkowski material spacetime in which the speed of light is c=n.Keywords: Classical Electrodynamics, Maxwell's equations, energy{momentum tensor, Abraham{Minkowski controversy
Piezoelectric Transduction of a Wavelength-Scale Mechanical Waveguide

We present a piezoelectric transducer in thin-film lithium niobate that converts a 1.7-GHz microwave signal to a mechanical wave in a single mode of a 1-$\ensuremath{\mu}\mathrm{m}$-wide waveguide. We measure a $\ensuremath{-}12$-dB conversion efficiency that is limited by material loss. The design method we employ is widely applicable to transduction in wavelength-scale structures in emerging phononic circuits such as those needed for efficient piezo-optomechanical converters and spin-phonon transducers.
A MODIFIED VERSION OF TAYLOR’S HYPOTHESIS FOR SOLAR PROBE PLUS OBSERVATIONS

The Solar Probe Plus (SPP) spacecraft will explore the near-Sun environment, reaching heliocentric distances less than  R 10 . Near Earth, spacecraft measurements of fluctuating velocities and magnetic fields taken in the time domain are translated into information about the spatial structure of the solar wind via Taylor’s “frozen turbulence” hypothesis. Near the perihelion of SPP, however, the solar-wind speed is comparable to the Alfven speed, and Taylor’s hypothesis in its usual form does not apply. In this paper, we show that under certain assumptions, a modified version of Taylor’s hypothesis can be recovered in the near-Sun region. We consider only the transverse, non-compressive component of the fluctuations at length scales exceeding the proton gyroradius, and we describe these fluctuations using an approximate theoretical framework developed by Heinemann and Olbert. We show that fluctuations propagating away from the Sun in the plasma frame obey a relation analogous to Taylor’s hypothesis when ^  V z sc, and +-  z z , where ^ Vsc, is the component of the spacecraft velocity perpendicular to the mean magnetic field and + z ( z ) is the Elsasser variable corresponding to transverse, non-compressive fluctuations propagating away from (toward) the Sun in the plasma frame. Observations and simulations suggest that, in the near-Sun solar wind, the above inequalities are satisfied and + z fluctuations account for most of the fluctuation energy. The modified form of Taylor’s hypothesis that we derive may thus make it possible to characterize the spatial structure of the energetically dominant component of the turbulence encountered by SPP.
Revisiting The Riemann Zeta Function at Positive Even Integers

Using Parseval’s identity for the Fourier coefficients of xk, we provide a new proof that ζ(2k) = (−1)k+1B2k(2π)2k 2(2k)!.
Robust temporal logic model predictive control

Control synthesis from temporal logic specifications has gained popularity in recent years. In this paper, we use a model predictive approach to control discrete time linear systems with additive bounded disturbances subject to constraints given as formulas of signal temporal logic (STL). We introduce a (conservative) computationally efficient framework to synthesize control strategies based on mixed integer programs. The designed controllers satisfy the temporal logic requirements, are robust to all possible realizations of the disturbances, and optimal with respect to a cost function. In case the temporal logic constraint is infeasible, the controller satisfies a relaxed, minimally violating constraint. An illustrative case study is included.
Why Are There Dwarf Spheroidal Galaxies

There appears to exist a conflict between the standard structure formation theory and the existence of the faint dwarf spheroidal galaxies in the Local Group. Theoretical considerations suggest that a cold dark matter universe has been a very hostile place for the formation of small galaxies. In particular, gas would not have been able to cool and condense to form stars inside dark matter halos with velocity dispersions ≤10 km s-1 since before the cosmological reionization epoch. In other words, one should not expect to see any major star formation activities in dwarf galaxies with velocity dispersions ≤10 km s-1 during the past 12 Gyr, according to the current structure formation theory. The real universe, on the other hand, shows that all dwarf spheroidal galaxies in the Local Group have velocity dispersions ≤10 km s-1 and that extended and recent star formation activities are quite common in them. This apparent conflict between cold dark matter models and local observations can be resolved, if one allows the cold dark matter particles to decay relatively recently. The resolution comes about in that the dwarf spheroidal galaxies with velocity dispersions of ~10 km s-1 seen today were born, in this picture, in a small fraction of halos with velocity dispersions of ~20 km s-1, where gas can be retained and is able to cool and contract to form stars. The presently observed lower velocity dispersions (~10 km s-1) of these dwarf spheroidal galaxies is a consequence of the decay of one-half of the dark matter in the halos and the subsequent expansion of the halos since redshift z ~ 2.
Magnetotransport Properties of Quasi-Free-Standing Epitaxial Graphene Bilayer on SiC: Evidence for Bernal Stacking

We investigate the magnetotransport properties of quasi-free-standing epitaxial graphene bilayer on SiC, grown by atmospheric pressure graphitization in Ar, followed by H2 intercalation. At the charge neutrality point, the longitudinal resistance shows an insulating behavior, which follows a temperature dependence consistent with variable range hopping transport in a gapped state. In a perpendicular magnetic field, we observe quantum Hall states (QHSs) both at filling factors (ν) multiples of four (ν = 4, 8, 12), as well as broken valley symmetry QHSs at ν = 0 and ν = 6. These results unambiguously show that the quasi-free-standing graphene bilayer grown on the Si-face of SiC exhibits Bernal stacking.
Monotonic convergence of a general algorithm for computing optimal designs

Monotonic convergence is established for a general class of multiplicative algorithms introduced by Silvey, Titterington and Torsney [Comm. Statist. Theory Methods 14 (1978) 1379–1389] for computing optimal designs. A conjecture of Titterington [Appl. Stat. 27 (1978) 227–234] is confirmed as a consequence. Optimal designs for logistic regression are used as an illustration.
Worst-case source for distributed compression with quadratic distortion

We consider the k-encoder source coding problem with a quadratic distortion measure. We show that among all source distributions with a given covariance matrix K, the jointly Gaussian source requires the highest rates in order to meet a given set of distortion constraints.
Resource Letter BH-2: Black Holes

This Resource Letter is designed to guide students, educators, and researchers through (some of) the literature on black holes. We discuss both the physics and astrophysics of black holes. We emphasize breadth over depth, and review articles over primary sources. We include resources ranging from nontechnical discussions appropriate for broad audiences to technical reviews of current research. Topics addressed include classification of stationary solutions, perturbations and stability of black holes, numerical simulations, collisions, the production of gravity waves, black-hole thermodynamics and Hawking radiation, quantum treatments of black holes, black holes in both higher and lower dimensions, and connections to nuclear and condensed-matter physics. On the astronomical end, we also cover the physics of gas accretion onto black holes, relativistic jets, gravitationally redshifted emission lines, evidence for stellar-mass black holes in binary systems and supermassive black holes at the centers of galax...
Asymptotic stability of shear-flow solutions to incompressible viscous free boundary problems with and without surface tension

This paper concerns the dynamics of a layer of incompressible viscous fluid lying above a rigid plane and with an upper boundary given by a free surface. The fluid is subject to a constant external force with a horizontal component, which arises in modeling the motion of such a fluid down an inclined plane, after a coordinate change. We consider the problem both with and without surface tension for horizontally periodic flows. This problem gives rise to shear-flow equilibrium solutions, and the main thrust of this paper is to study the asymptotic stability of the equilibria in certain parameter regimes. We prove that there exists a parameter regime in which sufficiently small perturbations of the equilibrium at time $$t=0$$ give rise to global-in-time solutions that return to equilibrium exponentially in the case with surface tension and almost exponentially in the case without surface tension. We also establish a vanishing surface tension limit, which connects the solutions with and without surface tension.
A Highly Parallel FPGA Implementation of Sparse Neural Network Training

This paper describes the development of an FPGA implementation of a parallel and reconfigurable architecture for sparse neural networks, capable of on-chip training and inference. The network connectivity uses pre-determined, structured sparsity to significantly reduce complexity by lowering memory and computational requirements. The architecture uses a notion of edge-processing, leading to efficient pipelining and parallelization. Moreover, the device can be reconfigured to trade off resource utilization with training time to fit networks and datasets of varying sizes. The combined effects of complexity reduction and easy reconfigurability enable greater exploration of network hyperparameters and structures on-chip. As proof of concept, we show implementation results on an Artix-7 FPGA.
The Volume Fraction of Ionized Intergalactic Gas at Redshift z = 6.5

The observed number density of Lyα sources implies a minimum volume of the intergalactic medium that must be ionized, in order to allow the Lyα photons to escape attenuation. We estimate this volume by assigning to each Lyα emitter the minimum ionized bubble that would allow half its Lyα photons to escape. This implies a lower limit to the ionized gas volume fraction of 20%-50% at z = 6.5. This is a lower limit in two ways: First, we conservatively assume that the Lyα sources seen (at a relatively bright flux limit) are the only ones present, and second, we assume the smallest ionized bubble volume that will allow the photons to escape. This limit is completely independent of what ionizing photon sources produced the bubbles. Deeper Lyα surveys are possible with present technology and can strengthen these limits by detecting a higher density of Lyα galaxies.
Probing light sbottoms with B decays

Abstract We discuss recently reported experimental hints for a bottom squark with mass around 3.5 GeV decaying as b →cl ν ∗ . We correlate the sbottom lifetime with the decay rates for b→ b ν ν ∗ and b→ b ν ν in the framework of a minimal supersymmetric model extended by right-handed (s)neutrinos. Confronting our results with the well-measured semileptonic branching ratio of B mesons we conclude that the light sbottom interpretation of the experimental anomalies is ruled out, unless m b ⩽m b +m ν .
Discussion of Likelihood Inference for Models with Unobservables: Another View

Lee and Nelder identify important issues and pro vide excellent advice and warnings associated with inferences and interpretations for models with unob served, latent variables (random effects). Their discus sion of prediction versus estimation goals is insight ful and I have some sympathy with their call for use of comprehensive probability models. They provide a clear explanation of their h-likelihood approach and a spirited promotion of it. Unfortunately, the value and impact of the their advice are compromised by their singular focus on promoting h-likelihood. Their claim that it is an almost universally preferred approach is, to put it mildly, a stretch. The h-likelihood approach by no means "trumps" all competitors and has its own deficits. Over promotion makes the article more of an opinion-piece than a scientific comparison of ap proaches.
Modern Observations of Hubble’s First-discovered Cepheid in M31

ABSTRACT.We present a modern ephemeris and modern light curve of the first-discovered Cepheid variable in M31, Edwin Hubble’s M31-V1. Observers of the American Association of Variable Star Observers (AAVSO) undertook these observations during the latter half of 2010. The observations were in support of an outreach program by the Space Telescope Science Institute’s Hubble Heritage project, but the resulting data are the first concentrated observations of M31-V1 made in modern times. AAVSO observers obtained 214 VV-band, RcRc-band, and unfiltered observations from which a current ephemeris was derived. The ephemeris derived from these observations is JDMax = 2,455,430.5( ± 0.5) + 31.4( ± 0.1)EJDMax=2,455,430.5(±0.5)+31.4(±0.1)E. The period derived from the 2010 data is in agreement with the historic values of the period, but the single season of data precludes a more precise determination of the period or measurement of the period change using these data alone. However, using an ephemeris based upon the per...
Computational complexity and the conjugacy problem

The conjugacy problem for a finitely generated group $G$ is the two-variable problem of deciding for an arbitrary pair $(u,v)$ of elements of $G$, whether or not $u$ is conjugate to $v$ in $G$. We construct examples of finitely generated, computably presented groups such that for every element $u_0$ of $G$, the problem of deciding if an arbitrary element is conjugate to $u_0$ is decidable in quadratic time but the worst-case complexity of the global conjugacy problem is arbitrary: it can be any c.e. Turing degree , can exactly mirror the Time Hierarchy Theorem, or can be $\mathcal{NP}$-complete. Our groups also have the property that the conjugacy problem is generically linear time: that is, there is a linear time partial algorithm for the conjugacy problem whose domain has density $1$, so hard instances are very rare. We also consider the complexity relationship of the "half-conjugacy" problem to the conjugacy problem. In the last section we discuss the extreme opposite situation: groups with algorithmically finite conjugation.
Traveling Wave Model for Frequency Comb Generation in Single-Section Quantum Well Diode Lasers

We present a traveling wave model for a semiconductor diode laser based on quantum wells. The gain model is carefully derived from first principles and implemented with as few phenomenological constants as possible. The transverse energies of the quantum well confined electrons are discretized to automatically capture the effects of spectral and spatial hole burning, the gain asymmetry, and the linewidth enhancement factor. We apply this model to semiconductor optical amplifiers and single-section phase-locked lasers. We are able to reproduce the experimental results. The calculated frequency modulated comb shows potential to be a compact, chip-scale comb source without additional external components.
Stability Diagram, Hysteresis, and Critical Time Delay and Frequency for the Kuramoto Model with Heterogeneous Interaction Delays

We investigate the dynamics of large, globally-coupled systems of Kuramoto oscillators with heterogeneous interaction delays. For the case of exponentially distributed time delays we derive the ful...
Topologically massive Yang–Mills theory and link invariants

Topologically massive Yang–Mills theory is studied in the framework of geometric quantization. Since this theory has a mass gap proportional to the topological mass m, Yang–Mills contribution decays exponentially at very large distances compared to 1/m, leaving a pure Chern–Simons theory with level number k. In this paper, the near Chern–Simons limit is studied where the distance is large enough to give an almost topological theory, with a small contribution from the Yang–Mills term. It is shown that this almost topological theory consists of two copies of Chern–Simons with level number k/2, very similar to the Chern–Simons splitting of topologically massive AdS gravity. Also, gauge invariance of these half-Chern–Simons theories is discussed. As m approaches to infinity, the split parts add up to give the original Chern–Simons term with level k. Reduction of the phase space is discussed in this limit. Finally, a relation between the observables of topologically massive Yang–Mills theory and Chern–Simons theory is shown. One of the two split Chern–Simons pieces is shown to be associated with Wilson loops while the other with 't Hooft loops. This allows one to use skein relations to calculate topologically massive Yang–Mills theory observables in the near Chern–Simons limit.
The Rapidly Fading Afterglow from the Gamma-Ray Burst of 1999 May 6

We report on the discovery of the radio afterglow from the gamma-ray burst of 1999 May 6 (GRB 990506) using the Very Large Array. The radio afterglow was detected at early times (Δt = 1.5 days) but began to fade rapidly sometime between 1 and 5 days after the burst. If we attribute the radio emission to the forward shock from an expanding fireball, then this rapid onset of the decay in the radio predicts that the corresponding optical transient began to decay between 1 and 5 minutes after the burst. This could explain why no optical transient for GRB 990506 was detected in spite of numerous searches. The cause of the unusually rapid onset of the decay for the afterglow is probably the result of an isotropically energetic fireball expanding into a low-density circumburst environment. At the location of the radio afterglow, we find a faint (R ~ 24 mag) host galaxy with a double morphology.
Diffusion-driven transition between two regimes of viscous fingering

Diffusion between miscible fluids in the viscous-fingering instability produces an unexpected transition into a novel pattern. Usually thought of as a two-dimensional phenomena, this works shows the importance of three-dimensional structure to the patterns that form.
OPTICAL STRUCTURE AND EVOLUTION OF THE Arp 104 INTERACTING GALAXY SYSTEM

Arp 104 is a pair of luminous interacting galaxies consisting of NGC 5216, an elliptical, and NGC 5218, a disturbed disk galaxy and joined by a stellar bridge. We obtained optical imaging to support photometric and color studies of the system. NGC 5216 lies on the red sequence, while the unusual distribution of stellar population properties in combination with intense central star formation in a dusty region result in NGC 5218 being a nearby example of an intermediate color (green valley) system. The stellar bridge has remarkably uniform optical surface brightness, with colors consistent with its stars coming from the outskirts of NGC 5218, but is relatively gas-poor while the northern tidal tail is rich in H I. While both galaxies contain shells, the shell structures in NGC 5218 are pronounced, and some appear to be associated with counter-rotating gas. This combination of features suggests that Arp 104 could be the product of distinct multiple interactions in a small galaxy group, possibly resulting from a hierarchical merging process, and likely leading to the birth of a relatively massive and isolated early-type galaxy.
The Origin and Evolution of Transition Discs: Successes, Problems, and Open Questions

Transition discs are protoplanetary discs that show evidence for large holes or wide gaps (with widths comparable to their radii) in their dust component. These discs could be giving us clues about the disc destruction mechanism or hints about the location and time-scales for the formation of planets. However, at the moment there remain key gaps in our theoretical understanding. The vast majority of transition discs are accreting onto their central stars, indicating that—at least close to the star—dust has been depleted from the gas by a very large amount. In this review, we discuss evidence for two distinct populations of transition discs: mm-faint—those with low mm-fluxes, small holes (≲ 10 AU), and low accretion rates (~ 10−10 − 10−9 M⊙ yr−1) and mm-bright—discs with large mm-fluxes, large holes (≳ 20 AU), and high accretion rates ~ 10−8 M⊙ yr−1. MM-faint transition discs are consistent with what would naively be expected from a disc undergoing dispersal; however, mm-bright discs are not, and are likely to be rare and long-lived objects. We discuss the two commonly proposed mechanisms for creating transition discs: photoevaporation and planet–disc interactions, with a particular emphasis on how they would evolve in these models, comparing these predictions to the observed population. More theoretical work on explaining the lack of optically thick, non-accreting transition discs is required in both the photoevaporation and planetary hypothesis, before we can start to use transition discs to constrain models of planet formation. Finally, we suggest that the few discs with primordial looking spectral energy distribution, but serendipitously imaged showing large cavities in the mm (e.g. MWC758 and WSB 60) may represent a hidden population of associated objects. Characterising and understanding how these objects fit into the overall paradigm may allow us to unravel the mystery of transition discs.
ActiveRemediation: The Search for Lead Pipes in Flint, Michigan

We detail our ongoing work in Flint, Michigan to detect pipes made of lead and other hazardous metals. After elevated levels of lead were detected in residents' drinking water, followed by an increase in blood lead levels in area children, the state and federal governments directed over $125 million to replace water service lines, the pipes connecting each home to the water system. In the absence of accurate records, and with the high cost of determining buried pipe materials, we put forth a number of predictive and procedural tools to aid in the search and removal of lead infrastructure. Alongside these statistical and machine learning approaches, we describe our interactions with government officials in recommending homes for both inspection and replacement, with a focus on the statistical model that adapts to incoming information. Finally, in light of discussions about increased spending on infrastructure development by the federal government, we explore how our approach generalizes beyond Flint to other municipalities nationwide.
The use of strain to tailor electronic thermoelectric transport properties: A first principles study of 2H-phase CuAlO2

Using first principles calculations, the use of strain to adjust electronic transport and the resultant thermoelectric (TE) properties are discussed using 2H phase CuAlO2 as a test case. Transparent oxide materials, such as CuAlO2, a p-type transparent conducting oxide (TCO), have recently been studied for high temperature TE power generators and coolers for waste heat. Given TCO materials with relative ease of fabrication, low cost of materials, and non-toxicity, the ability to tailor them to specific temperature ranges, power needs, and size requirements through the use of strain opens an interesting avenue. We find that strain can have a significant effect on these properties, in some cases detrimental and in others beneficial, including the potential for n-type power factors larger than the highest p-type case. The physical reasons for this behavior are explained in terms of the TE transport distribution and the Landauer distribution of modes.Using first principles calculations, the use of strain to adjust electronic transport and the resultant thermoelectric (TE) properties are discussed using 2H phase CuAlO2 as a test case. Transparent oxide materials, such as CuAlO2, a p-type transparent conducting oxide (TCO), have recently been studied for high temperature TE power generators and coolers for waste heat. Given TCO materials with relative ease of fabrication, low cost of materials, and non-toxicity, the ability to tailor them to specific temperature ranges, power needs, and size requirements through the use of strain opens an interesting avenue. We find that strain can have a significant effect on these properties, in some cases detrimental and in others beneficial, including the potential for n-type power factors larger than the highest p-type case. The physical reasons for this behavior are explained in terms of the TE transport distribution and the Landauer distribution of modes.
Ubiquitous Water Masers in Nearby Star-Forming Galaxies

We report the detection of water maser emission from four nearby galaxies hosting ultradense H II (UDHII) regions, He 2-10, the Antennae galaxies (NGC 4038/4039), NGC 4214, and NGC 5253, with the Green Bank Telescope. Our detection rate is 100%, and all of these H2O "kilomasers" (LH2O < 10 L☉) are located toward regions of known star formation as traced by UDHII regions and bright 24 μm emission. Some of the newly discovered H2O masers have luminosities 1-2 orders of magnitude less than previous extragalactic studies and the same order of magnitude as those typical of Galactic massive star-forming regions. The unusual success of this minisurvey suggests that H2O maser emission may be very common in starburst galaxies, and the paucity of detections to date is due to a lack of sufficient sensitivity. While the galaxy sample was selected by the presence of UDHII regions, and the UDHII regions lie within the telescope beam, in the absence of H2O spectral line maps the connection between H2O masers and UDHII regions has not yet been demonstrated.
Perturbed Proximal Descent to Escape Saddle Points for Non-convex and Non-smooth Objective Functions

We consider the problem of finding local minimizers in non-convex and non-smooth optimization. Under the assumption of strict saddle points, positive results have been derived for first-order methods. We present the first known results for the non-smooth case, which requires different analysis and a different algorithm. This is the extended version of the paper that contains the proofs.
The bond-algebraic approach to dualities

An algebraic theory of dualities is developed based on the notion of bond algebras. It deals with classical and quantum dualities in a unified fashion explaining the precise connection between quantum dualities and the low temperature (strong-coupling)/high temperature (weak-coupling) dualities of classical statistical mechanics (or (Euclidean) path integrals). Its range of applications includes discrete lattice, continuum field and gauge theories. Dualities are revealed to be local, structure-preserving mappings between model-specific bond algebras that can be implemented as unitary transformations, or partial isometries if gauge symmetries are involved. This characterization permits us to search systematically for dualities and self-dualities in quantum models of arbitrary system size, dimensionality and complexity, and any classical model admitting a transfer matrix or operator representation. In particular, special dualities such as exact dimensional reduction, emergent and gauge-reducing dualities th...
An integrated mirror and surface ion trap with a tunable trap location

We report a demonstration of a surface ion trap fabricated directly on a highly reflective mirror surface, which includes a secondary set of radio frequency (RF) electrodes allowing for translation of the quadrupole RF null location. We introduce a position-dependent photon scattering rate for a 174Yb+ ion in the direction perpendicular to the trap surface using a standing wave of retroreflected light off the mirror surface directly below the trap. Using this setup, we demonstrate the capability of fine-tuning the RF trap location with nanometer scale precision and characterize the charging effects of the dielectric mirror surface upon exposure to ultra-violet light.
Scale Invariance and Dynamic Phase Transitions in Diffusion-Limited Reactions

Many systems that can be described in terms of diffusion-limited 'chem- ical' reactions display non-equilibrium continuous transitions separating active from inactive, absorbing states, where stochastic fluctuations cease entirely. Their critical properties can be analyzed via a path-integral representation of the corresponding classical master equation, and the dynamical renormalization group. An overview over the ensuing universality classes in single-species processes is given, and gen- eralizations to reactions with multiple particle species are discussed as well. The generic case is represented by the processes AA+A ,a ndA →∅ ,w hich map onto Reggeon field theory with the critical exponents of directed percolation (DP). For branching and annihilating random walks (BARW) A → (m +1 )A and A + A →∅ , the mean-field rate equation predicts an active state only. Yet BARW with odd m display a DP transition for d ≤ 2. For even offspring number m, the particle number parity is conserved locally. Below d � ≈ 4/3, this leads to the emergence of an inac- tive phase that is characterized by the power laws of the pair annihilation process. The critical exponents at the transition are those of the 'parity-conserving' (PC) universality class. For local processes without memory, competing pair or triplet annihilation and fission reactions kA → (k − l)A, kA → (k + m)A with k =2 , 3a p- pear to yield the only other universality classes not described by mean-field theory. In these reactions, site occupation number restrictions play a crucial role.
Investigating the Anisotropic Scintillation Response in Anthracene through Neutron, Gamma-Ray, and Muon Measurements

This paper reports a series of measurements that characterize the directional dependence of the scintillation response of crystalline anthracene to incident DT neutrons, DD neutrons, $^{137}{\rm Cs}$ gamma rays, and, for the first time, cosmic ray muons. The neutron measurements give the amplitude and pulse shape dependence on the proton recoil direction over one hemisphere of the crystal, confirming and extending previous results in the literature. In similar measurements using incident gamma rays, no directional effect is evident, and any anisotropy with respect to the electron recoil direction is constrained to have a magnitude of less than a tenth of that present in the proton recoil events. Cosmic muons are measured at two directions, and no anisotropy is observed. This set of observations indicates that high $dE/dx$ is necessary for an anisotropy to be present for a given type of scintillation event, which in turn could be used to discriminate among different hypotheses for the underlying causes of the anisotropy, which are not well understood.
Normal distributions of finite Markov chains

We show that the stationary distribution of a finite Markov chain can be expressed as the sum of certain normal distributions. These normal distributions are associated to planar graphs consisting ...
Photon isolation and jet substructure

We introduce soft drop isolation, a new photon isolation criterion inspired by jet substructure techniques. Soft drop isolation is collinear safe and is equivalent to Frixione isolation at leading non-trivial order in the small R limit. However, soft drop isolation has the interesting feature of being democratic, meaning that photons can be treated equivalently to hadrons for initial jet clustering. Taking advantage of this democratic property, we define an isolated photon subjet: a photon that is not isolated from its parent jet but is isolated within its parent subjet after soft drop declustering. The kinematics of this isolated photon subjet can be used to expose the QED splitting function, in which a quark radiates a photon, and we verify this behavior using both a parton shower generator and a perturbative calculation in the collinear limit.
Decoupling of translational and rotational diffusion in quasi-2D colloidal fluids

We observe the translational and rotational diffusion of dimer tracer particles in quasi-2D colloidal samples. The dimers are in dense samples of two different sizes of spherical colloidal particles, with the area fraction ϕ of the particles varying from dilute to nearly glassy. At low ϕ, rotational and translational diffusion have a ratio set by the dimer size, as expected. At higher ϕ, dimers become caged by their neighboring particles, and both rotational and translational diffusion become slow. For short dimers, we observe rapid reorientations so that the rotational diffusion is faster than the translational diffusion: the two modes of diffusion are decoupled and have different ϕ dependence. Longer dimers do not exhibit fast rotations, and we find that their translational and rotational diffusion stay coupled for all ϕ. Our results bridge prior results that used spheres (very fast rotation) and long ellipsoids (very slow rotation).
Eleven Exoplanet Host Star Angular Diameters from the Chara Array

We directly measured the angular diameters for 11 exoplanet host stars using Georgia State University's CHARA Array interferometer and calculated their linear radii and effective temperatures. The sample tends toward evolving or evolved stars and includes one dwarf, four subgiants, and six giants. We then estimated masses and ages for the stars using our effective temperatures combined with metallicity measurements from the literature.
Limits of (certain) CAT(0) groups, I: Compactification

The purpose of this paper is to investigate torsion-free groups which act properly and cocompactly on CAT(0) metric spaces which have isolated flats, as defined by Hruska [18]. Our approach is to seek results analogous to those of Sela, Kharlampovich and Miasnikov for free groups and to those of Sela (and Rips and Sela) for torsion-free hyperbolic groups. This paper is the first in a series. In this paper we extract an R-tree from an asymptotic cone of certain CAT(0) spaces. This is analogous to a construction of Paulin, and allows a great deal of algebraic information to be inferred, most of which is left to future work.
SRCLock: SAT-Resistant Cyclic Logic Locking for Protecting the Hardware

In this paper, we claim that cyclic obfuscation, when properly implemented, poses exponential complexity on SAT or CycSAT attack. The CycSAT, in order to generate the necessary cycle avoidance clauses, uses a pre-processing step. We show that this pre-processing step has to compose its cycle avoidance condition on all cycles in a netlist, otherwise, a missing cycle could trap the SAT solver in an infinite loop or force it to return an incorrect key. Then, we propose several techniques by which the number of cycles is exponentially increased with respect to the number of inserted feedbacks. We further illustrate that when the number of feedbacks is increased, the pre-processing step of CycSAT faces an exponential increase in complexity and runtime, preventing the correct composition of loop avoidance clauses in a reasonable time before invoking the SAT solver. On the other hand, if the pre-processing is not completed properly, the SAT solver will get stuck or return incorrect key. Hence, when the cyclic obfuscation in accordance to the conditions proposed in this paper is implemented, it would impose an exponential complexity with respect to the number of inserted feedback, even when the CycSAT solution is used.
Characterizing Driving Context from Driver Behavior

Because of the increasing availability of spatiotemporal data, a variety of data-analytic applications have become possible. Characterizing driving context, where context may be thought of as a combination of location and time, is a new challenging application. An example of such a characterization is finding the correlation between driving behavior and traffic conditions. This contextual information enables analysts to validate observation-based hypotheses about the driving of an individual. In this paper, we present DriveContext, a novel framework to find the characteristics of a context, by extracting significant driving patterns (e.g., a slow-down), and then identifying the set of potential causes behind patterns (e.g., traffic congestion). Our experimental results confirm the feasibility of the framework in identifying meaningful driving patterns, with improvements in comparison with the state-of-the-art. We also demonstrate how the framework derives interesting characteristics for different contexts, through real-world examples.