cssi/SciSciGPT-SciSciNet huggingface dataset:
Uncertainty Principles for Fourier Multipliers

The admittable Sobolev regularity is quantified for a function, w, which has a zero in the d-dimensional torus and whose reciprocal $$u=1/w$$ is a (p, q)-multiplier. Several aspects of this problem are addressed, including zero-sets of positive Hausdorff dimension, matrix valued Fourier multipliers, and non-symmetric versions of Sobolev regularity. Additionally, we make a connection between Fourier multipliers and approximation properties of Gabor systems and shift-invariant systems. We exploit this connection and the results on Fourier multipliers to refine and extend versions of the Balian–Low uncertainty principle in these settings.
Leveraging Independent Double-Gate FinFET Devices for Machine Learning Classification

Mixed-signal machine learning (ML) classification has recently been demonstrated as an efficient alternative for classification with power expensive digital MOSFET circuits. In this paper, a topology based on independent double-gate (IDG) FinFET devices is proposed for classifying high-dimensional input data into multi-class output space with less power and area as compared with state-of-the-art MOSFET classifiers. To facilitate a high-resolution multiplication as a part of the classifier predictions, ML features and feature weights are, respectively, fed to the back and front gate inputs of the individual IDG-FinFET transistors. A classifier that considers the decisions of the individual predictors is designed at 30 nm FinFET technology node and operates at 333 MHZ with nominal supply voltage of one volt. To evaluate the performance of the classifier, a reduced MNIST dataset is generated. The original resolution is reduced from 28×28 features to 9×9 features and the most important features are selected with sequential backward selection algorithm. The system is simulated in SPICE, exhibiting prediction accuracy of 90%, energy consumption of 25 pJ per classification (over four times lower than similar state-of-the-art classifiers), area of 1,365 μm2, and a stable response under a wide range of system variations.
Jointly defining cell types from multiple single-cell datasets using LIGER.

High-throughput single-cell sequencing technologies hold tremendous potential for defining cell types in an unbiased fashion using gene expression and epigenomic state. A key challenge in realizing this potential is integrating single-cell datasets from multiple protocols, biological contexts, and data modalities into a joint definition of cellular identity. We previously developed an approach, called linked inference of genomic experimental relationships (LIGER), that uses integrative nonnegative matrix factorization to address this challenge. Here, we provide a step-by-step protocol for using LIGER to jointly define cell types from multiple single-cell datasets. The main stages of the protocol are data preprocessing and normalization, joint factorization, quantile normalization and joint clustering, and visualization. We describe how to jointly define cell types from single-cell RNA-seq (scRNA-seq) and single-nucleus ATAC-seq (snATAC-seq) data, but similar steps apply across a wide range of other settings and data types, including cross-species analysis, single-nucleus DNA methylation, and spatial transcriptomics. Our protocol contains examples of expected results, describes common pitfalls, and relies only on our freely available, open-source R implementation of LIGER. We also provide R Markdown tutorials showing the outputs from each individual code segment. The analysis process can be performed in 1–4 h, depending on dataset size, and assumes no specialized bioinformatics training. Here, the authors describe step-by-step procedures for integrating single-cell sequencing datasets from different experiments or modalities to identify common and distinct cell types using the R-based software tool LIGER.
Optimal UAV Deployment for Rate Maximization in IoT Networks

We consider multiple unmanned aerial vehicles (UAVs) at a common altitude serving as data collectors to a network of IoT devices. First, using a probabilistic line of sight channel model, the optimal assignment of IoT devices to the UAVs is determined. Next, for the asymptotic regimes of a large number of UAVs and/or large UAV altitudes, we propose closed-form analytical expressions for the optimal data rate and characterize the corresponding optimal UAV deployments. We also propose a simple iterative algorithm to find the optimal deployments with a small number of UAVs at high altitudes. Globally optimal numerical solutions to the general rate maximization problem are found using particle swarm optimization.
Cardiogenic shock following cardiac tamponade and Takotsubo in COVID-19.

Introduction: Takotsubo is often described as stress-induced cardiomyopathy and is a known cause of heart failure. Objective: Review the clinical course of a young coronavirus disease 2019 (COVID-19) patient who developed Takotsubo following cardiac tamponade. Case presentation: A 42-year-old woman presented to the emergency department with fever, altered mental status and hypoxia. She was ultimately found to be in cardiac tamponade and within 2 hours of a pericardiocentesis she developed Takotsubo and was in cardiogenic shock. Her family decided to place her on comfort measures and she died the same day. Discussion: This case illustrates the increasing number of cardiovascular complications being reported in COVID-19 and highlights the importance of clinicians to be aware of these challenges. Conclusion: Here, we report a distinct presentation of cardiogenic shock in a young COVID-19 patient. The rapid onset of her suspected Takotsubo and the severity of her disease were striking features in this case.
Reliability of P3 Event-Related Potential During Working Memory Across the Spectrum of Cognitive Aging

Event-related potentials (ERPs) offer unparalleled temporal resolution in tracing distinct electrophysiological processes related to normal and pathological cognitive aging. The stability of ERPs in older individuals with a vast range of cognitive ability has not been established. In this test-retest reliability study, 39 older individuals (age 74.10 (5.4) years; 23 (59%) women; 15 non β-amyloid elevated, 16 β-amyloid elevated, 8 cognitively impaired) with scores on the Montreal Cognitive Assessment (MOCA) ranging between 3 and 30 completed a working memory (n-back) test with three levels of difficulty at baseline and 2-week follow-up. The main aim was to evaluate stability of the ERP on grand averaged task effects for both visits in the total sample (n = 39). Secondary aims were to evaluate the effect of age, group (non β-amyloid elevated; β-amyloid elevated, cognitively impaired), cognitive status (MOCA), and task difficulty on ERP reliability. P3 peak amplitude and latency were measured in predetermined channels. P3 peak amplitude at Fz, our main outcome variable, showed excellent reliability in 0-back (intraclass correlation coefficient (ICC), 95% confidence interval = 0.82 (0.67-0.90) and 1-back (ICC = 0.87 (0.76-0.93), however, only fair reliability in 2-back (ICC = 0.53 (0.09-0.75). Reliability of P3 peak latencies was substantially lower, with ICCs ranging between 0.17 for 2-back and 0.54 for 0-back. Generalized linear mixed models showed no confounding effect of age, group, or task difficulty on stability of P3 amplitude and latency of Fz. By contrast, MOCA scores tended to negatively correlate with P3 amplitude of Fz (p = 0.07). We conclude that P3 peak amplitude, and to lesser extent P3 peak latency, provide a stable measure of electrophysiological processes in older individuals.
Randomly aggregated least squares for support recovery

Abstract We study the problem of exact support recovery: given an (unknown) vector θ * ∈ { − 1 , 0 , 1 } D with known sparsity k = ∥ θ * ∥ 0 , we are given access to the noisy measurement y = X θ * + ω , where X ∈ R N × D is a (known) Gaussian matrix and the noise ω ∈ R N is an (unknown) Gaussian vector. How small can N be for reliable recovery of the support of θ * ? We present RAWLS (Randomly Aggregated unWeighted Least Squares Support Recovery): the main idea is to take random subsets of the N equations, perform least squares over this reduced bit of information, and average over many random subsets. We show that the proposed procedure can provably recover an approximation of θ * and demonstrate its use through numerical examples. We use numerical simulations to demonstrate that the proposed procedure is beneficial for the task of support recovery. Finally, we observe that RAWLS is at par with several strong baselines in the low information regime (i.e. N is small or k is large).
Structure of two-loop SMEFT anomalous dimensions via on-shell methods

We describe on-shell methods for computing one- and two-loop anomalous dimensions in the context of effective field theories containing higher-dimension operators. We also summarize methods for computing one-loop amplitudes, which are used as inputs to the computation of two-loop anomalous dimensions, and we explain how the structure of rational terms and judicious renormalization scheme choices can lead to additional vanishing terms in the anomalous dimension matrix at two loops. We describe the two-loop implications for the Standard Model Effective Field Theory (SMEFT). As a by-product of this analysis we verify a variety of one-loop SMEFT anomalous dimensions computed by Alonso, Jenkins, Manohar and Trott.
Machine learning assisted quantum state estimation

We build a general quantum state tomography framework that makes use of machine learning techniques to reconstruct quantum states from a given set of coincidence measurements. For a wide range of pure and mixed input states we demonstrate via simulations that our method produces functionally equivalent reconstructed states to that of traditional methods with the added benefit that expensive computations are front-loaded with our system. Further, by training our system with measurement results that include simulated noise sources we are able to demonstrate a significantly enhanced average fidelity when compared to typical reconstruction methods. These enhancements in average fidelity are also shown to persist when we consider state reconstruction from partial tomography data where several measurements are missing. We anticipate that the present results combining the fields of machine intelligence and quantum state estimation will greatly improve and speed up tomography-based quantum experiments.
Pre-ADS Superpotential from Confined Monopoles

According to the standard lore only single monopoles contribute to the superpotential on the Coulomb branch of 3D $$ \mathcal{N}=2 $$ SUSY gauge theories. However we argue that multi-monopole configurations can also generate superpotential terms in the presence of squark VEVs on the mixed Higgs-Coulomb branch. The new ingredient is the confinement of monopoles via Nielsen-Olesen flux tubes. Such confined multi-monopoles will yield a pre-ADS superpotential which depends both on the local Coulomb moduli and matter superfields but has no fractional powers. Once the lifted moduli are integrated out the familiar ADS superpotential is obtained. Our results demonstrate the important role multi-monopoles can play in generating non-perturbative effects and also sheds light on the still somewhat mysterious dynamical origin of the general 4D ADS superpotential.
Possibility of triple magic trapping of clock and Rydberg states of divalent atoms in optical lattices

We predict the possibility of 'triply magic' optical lattice trapping of neutral divalent atoms. In such a lattice, the and clock states and an additional Rydberg state experience identical optical potentials, fully mitigating detrimental effects of the motional decoherence. In particular, we show that this triply magic trapping condition can be satisfied for Yb atom at optical wavelengths and for various other divalent systems (Ca, Mg, Hg and Sr) in the UV region. We assess the quality of triple magic trapping conditions by estimating the probability of excitation out of the motional ground state as a result of the excitations between the clock and the Rydberg states. We also calculate trapping laser-induced photoionization rates of divalent Rydberg atoms at magic frequencies. We find that such rates are below the radiative spontaneous-emission rates, due to the presence of Cooper minima in photoionization cross-sections.
Homotopical resolutions associated to deformable adjunctions

Given an adjunction FaG connecting reasonable categories with weak equivalences, we define a new derived bar and cobar construction associated to the adjunction. This yields homotopical models of the completion and cocompletion associated to the monad and comonad of the adjunction. We discuss applications of these resolutions to spectral sequences for derived completions and Goodwillie calculus in general model categories. 55U35; 18G55, 18G10
Note: Investigation of a Marx generator imitating a Tesla transformer

A compact Marx generator was built to mimic a spark-gap Tesla transformer. The generator produced radio-frequency pulses of up to ±200 kV and ±15 A with a frequency between 110 and 280 kHz at a repetition rate of 120 Hz. The generator tolerated larger circuit-parameter perturbations than is expected for conventional Tesla transformers. Possible applications include research on the control and laser guiding of spark discharges.
Cp Symmetry and Fermion Masses in O(10) Grand Unification Models

O(10) grand unification models which do not necessarily have an extra global symmetry are discussed, taking the model with one 10-plet in the Yukawa sector as an example. A strong correlation between mass ratios and CP is found. The mass relation mt/mb=vu/vd is recovered when GW=0; and another special relation mt/mb=GE/GW appears when vd=0, where GE,W are Yukawa coupling constants and vu,d are vevs. To facilitate this discussion, a set of O(10) γ-matrices is offered based on a physical representation of the spinors and that of the vector of the SO(10) group. Flavor changing neutral currents in such models are also discussed.
Efficient stochastic sampling of first-passage times with applications to self-assembly simulations

Models of reaction chemistry based on the stochastic simulation algorithm (SSA) have become a crucial tool for simulating complicated biological reaction networks due to their ability to handle extremely complicated networks and to represent noise in small-scale chemistry. These methods can, however, become highly inefficient for stiff reaction systems, those in which different reaction channels operate on widely varying time scales. In this paper, we develop two methods for accelerating sampling in SSA models: an exact method and a scheme allowing for sampling accuracy up to any arbitrary error bound. Both methods depend on the analysis of the eigenvalues of continuous time Markov models that define the behavior of the SSA. We show how each can be applied to accelerate sampling within known Markov models or to subgraphs discovered automatically during execution. We demonstrate these methods for two applications of sampling in stiff SSAs that are important for modeling self-assembly reactions: sampling breakage times for multiply connected bond networks and sampling assembly times for multisubunit nucleation reactions. We show theoretically and empirically that our eigenvalue methods provide substantially reduced sampling times for a large class of models used in simulating self-assembly. These techniques are also likely to have broader use in accelerating SSA models so as to apply them to systems and parameter ranges that are currently computationally intractable.
A Bijective Proof of a False Theta Function Identity from Ramanujan’s Lost Notebook

In his lost notebook, Ramanujan listed five identities related to the false theta function: \( f(q) = \sum_{n=0}^{\infty} (-1)^nq^n(n+1)/2 . \) A new combinatorial interpretation and a proof of one of these identities are given. The methods of the proof allow for new multivariate generalizations of this identity. Additionally, the same technique can be used to obtain a combinatorial interpretation of another one of the identities.
Penalized Variable Selection Procedure for Cox Models with Semiparametric Relative Risk

We study the Cox models with semiparametric relative risk, which can be partially linear with one nonparametric component, or multiple additive or nonadditive nonparametric components. A penalized partial likelihood procedure is proposed to simultaneously estimate the parameters and select variables for both the parametric and the nonparametric parts. Two penalties are applied sequentially. The first penalty, governing the smoothness of the multivariate nonlinear covariate effect function, provides a smoothing spline ANOVA framework that is exploited to derive an empirical model selection tool for the nonparametric part. The second penalty, either the smoothly-clipped-absolute-deviation (SCAD) penalty or the adaptive LASSO penalty, achieves variable selection in the parametric part. We show that the resulting estimator of the parametric part possesses the oracle property, and that the estimator of the nonparametric part achieves the optimal rate of convergence. The proposed procedures are shown to work well in simulation experiments, and then applied to a real data example on sexually transmitted diseases.
LLMapReduce: Multi-level map-reduce for high performance data analysis

The map-reduce parallel programming model has become extremely popular in the big data community. Many big data workloads can benefit from the enhanced performance offered by supercomputers. LLMapReduce provides the familiar map-reduce parallel programming model to big data users running on a supercomputer. LLMapReduce dramatically simplifies map-reduce programming by providing simple parallel programming capability in one line of code. LLMapReduce supports all programming languages and many schedulers. LLMapReduce can work with any application without the need to modify the application. Furthermore, LLMapReduce can overcome scaling limits in the map-reduce parallel programming model via options that allow the user to switch to the more efficient single-program-multiple-data (SPMD) parallel programming model. These features allow users to reduce the computational overhead by more than 10x compared to standard map-reduce for certain applications. LLMapReduce is widely used by hundreds of users at MIT. Currently LLMapReduce works with several schedulers such as SLURM, Grid Engine and LSF.
MEASUREMENTS OF THE SUN'S HIGH-LATITUDE MERIDIONAL CIRCULATION

The meridional circulation at high latitudes is crucial to the buildup and reversal of the Sun's polar magnetic fields. Here, we characterize the axisymmetric flows by applying a magnetic feature cross-correlation procedure to high-resolution magnetograms obtained by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory. We focus on Carrington rotations 2096-2107 (2010 April to 2011 March)—the overlap interval between HMI and the Michelson Doppler Imager (MDI). HMI magnetograms averaged over 720 s are first mapped into heliographic coordinates. Strips from these maps are then cross-correlated to determine the distances in latitude and longitude that the magnetic element pattern has moved, thus providing meridional flow and differential rotation velocities for each rotation of the Sun. Flow velocities were averaged for the overlap interval and compared to results obtained from MDI data. This comparison indicates that these HMI images are rotated counterclockwise by 0075 with respect to the Sun's rotation axis. The profiles indicate that HMI data can be used to reliably measure these axisymmetric flow velocities to at least within 5° of the poles. Unlike the noisier MDI measurements, no evidence of a meridional flow counter-cell is seen in either hemisphere with the HMI measurements: poleward flow continues all the way to the poles. Slight north-south asymmetries are observed in the meridional flow. These asymmetries should contribute to the observed asymmetries in the polar fields and the timing of their reversals.
Spillover Effects in the Presence of Unobserved Networks

When experimental subjects can interact with each other, the outcome of one individual may be affected by the treatment status of others. In many social science experiments, such spillover effects may occur through multiple networks, for example, through both online and offline face-to-face networks in a Twitter experiment. Thus, to understand how people use different networks, it is essential to estimate the spillover effect in each specific network separately. However, the unbiased estimation of these network-specific spillover effects requires an often-violated assumption that researchers observe all relevant networks. We show that, unlike conventional omitted variable bias, bias due to unobserved networks remains even when treatment assignment is randomized and when unobserved networks and a network of interest are independently generated. We then develop parametric and nonparametric sensitivity analysis methods, with which researchers can assess the potential influence of unobserved networks on causal findings. We illustrate the proposed methods with a simulation study based on a real-world Twitter network and an empirical application based on a network field experiment in China.
Multi-wavelength high-resolution observations of a small-scale emerging magnetic flux event and the chromospheric and coronal response

State-of-the-art solar instrumentation is now revealing magnetic activity of the Sun with unprecedented temporal and spatial resolutions. Observations with the 1.6 m aperture New Solar Telescope (NST) of the Big Bear Solar Observatory are making next steps in our understanding of the solar surface structure. Granular-scale magnetic flux emergence and the response of the solar atmosphere are among the key research topics of high-resolution solar physics. As part of a joint observing program with NASA's Interface Region Imaging Spectrograph (IRIS) mission on 2013 August 7, the NST observed active region NOAA 11,810 in the photospheric TiO 7057 A band with a resolution of pixel size of 0.''034 and chromospheric He I 10830 A and Hα 6563 A wavelengths. Complementary data are provided by the Solar Dynamics Observatory (SDO) and Hinode space-based telescopes. The region displayed a group of solar pores, in the vicinity of which we detect a small-scale buoyant horizontal magnetic flux tube causing granular alignments and interacting with the preexisting ambient field in the upper atmospheric layers. Following the expansion of distorted granules at the emergence site, we observed a sudden appearance of an extended surge in the He I 10830 A data (bandpass of 0.05 A). Themore » IRIS transition region imaging caught ejection of a hot plasma jet associated with the He I surge. The SDO/HMI data used to study the evolution of the magnetic and Doppler velocity fields reveal emerging magnetic loop-like structures. Hinode/Ca II H and IRIS filtergrams detail the connectivities of the newly emerged magnetic field in the lower solar chromosphere. From these data, we find that the orientation of the emerging magnetic field lines from a twisted flux tube formed an angle of ∼45° with the overlying ambient field. Nevertheless, the interaction of emerging magnetic field lines with the pre-existing overlying field generates high-temperature emission regions and boosts the surge/jet production. The localized heating is detected before and after the first signs of the surge/jet ejection. We compare the results with previous observations and theoretical models and propose a scenario for the activation of plasma jet/surges and confined heating triggered by buoyant magnetic flux tubes rising up into a magnetized upper environment. Such process may play a significant role in the mass and energy flow from the interior to the corona.« less
Set-based corral control in stochastic dynamical systems: Making almost invariant sets more invariant

We consider the problem of stochastic prediction and control in a time-dependent stochastic environment, such as the ocean, where escape from an almost invariant region occurs due to random fluctuations. We determine high-probability control-actuation sets by computing regions of uncertainty, almost invariant sets, and Lagrangian coherent structures. The combination of geometric and probabilistic methods allows us to design regions of control, which provide an increase in loitering time while minimizing the amount of control actuation. We show how the loitering time in almost invariant sets scales exponentially with respect to the control actuation, causing an exponential increase in loitering times with only small changes in actuation force. The result is that the control actuation makes almost invariant sets more invariant.
Computationally tractable pairwise complexity profile

Quantifying the complexity of systems consisting of many interacting parts has been an important challenge in the field of complex systems in both abstract and applied contexts. One approach, the complexity profile, is a measure of the information to describe a system as a function of the scale at which it is observed. We present a new formulation of the complexity profile, which expands its possible application to high-dimensional real-world and mathematically defined systems. The new method is constructed from the pairwise dependencies between components of the system. The pairwise approach may serve as both a formulation in its own right and a computationally feasible approximation to the original complexity profile. We compare it to the original complexity profile by giving cases where they are equivalent, proving properties common to both methods, and demonstrating where they differ. Both formulations satisfy linear superposition for unrelated systems and conservation of total degrees of freedom (sum rule). The new pairwise formulation is also a monotonically nonincreasing function of scale. Furthermore, we show that the new formulation defines a class of related complexity profile functions for a given system, demonstrating the generality of the formalism. © 2013 Wiley Periodicals, Inc. Complexity 18:20–27, 2013
Using braids to quantify interface growth and coherence in a rotor-oscillator flow

The growth rate of material interfaces is an important proxy for mixing and reaction rates in fluid dynamics. Within experimental limits, mathematical braids can be used to identify regions of coherence within the flow that are distinct from regions of high mixing and to estimate growth rates of material interfaces.
Evolution of an N-level system via automated vectorization of the Liouville equations and application to optically controlled polarization rotation

The Liouville equation governing the evolution of the density matrix for an atomic/molecular system is expressed in terms of a commutator between the density matrix and the Hamiltonian, along with terms that account for decay and redistribution. To find solutions of this equation, it is convenient first to reformulate the Liouville equation by defining a vector corresponding to the elements of the density operator, and determining the corresponding time-evolution matrix. For a system of N energy levels, the size of the evolution matrix is N2 × N2. When N is very large, evaluating the elements of these matrices becomes very cumbersome. We describe a novel algorithm that can produce the evolution matrix in an automated fashion for an arbitrary value of N. As a non-trivial example, we apply this algorithm to a 15-level atomic system used for producing optically controlled polarization rotation. We also point out how such a code can be extended for use in an atomic system with arbitrary number of energy levels.
MODELING THE NEARLY ISOTROPIC COMET POPULATION IN ANTICIPATION OF LSST OBSERVATIONS

We run simulations to determine the expected distribution of orbital elements of nearly isotropic comets (NICs) in the outer solar system, assuming that these comets originate in the Oort Cloud at thousands of au and are perturbed into the planetary region by the Galactic tide. We show that the Large Synoptic Survey Telescope should detect and characterize the orbits of hundreds to thousands of NICs with perihelion distance outside 5 au. Observing NICs in the outer solar system is our only way of directly detecting comets from the inner Oort Cloud, as these comets are dynamically excluded from the inner solar system by the giant planets. Thus, the distribution of orbital elements constrains the spatial distribution of comets in the Oort Cloud and the environment in which the solar system formed. Additionally, comet orbits can be characterized more precisely when they are seen far from the Sun as they have not been affected by nongravitational forces.
Symmetry Reduction of Optimal Control Systems and Principal Connections

This paper explores the role of symmetries and reduction in nonlinear control and optimal control systems. The focus of the paper is to give a geometric framework of symmetry reduction of optimal control systems as well as to show how to obtain explicit expressions of the reduced system by exploiting the geometry. In particular, we show how to obtain a principal connection to be used in the reduction for various choices of symmetry groups, as opposed to assuming such a principal connection is given or choosing a particular symmetry group to simplify the setting. Our result synthesizes some previous works on symmetry reduction of nonlinear control and optimal control systems. Affine and kinematic optimal control systems are of particular interest: We explicitly work out the details for such systems and also show a few examples of symmetry reduction of kinematic optimal control problems.
THE EXTREME OPTICAL VARIABILITY OF J0948+0022

We report on observations of the optical variability of the radio-loud, narrow-line Seyfert 1 galaxy J0948+0022 on timescales ranging from minutes to years. Implications regarding recent suggestions that the object may constitute a prototype for an emerging class of blazar-like objects similar to FSRQs are discussed. The optical microvariability observed for J0948+0022 is found to be similar to that found for a typical low energy peaked BL Lac object. Based on observations of J0948+0022 in a flaring state and a significantly lower state, one can demonstrate that these rapid variations most likely originate in the relativistic jet and not in the accretion disk.
Two are better than one: Fundamental parameters of frame coherence

Abstract This paper investigates two parameters that measure the coherence of a frame: worst-case and average coherence. We first use worst-case and average coherence to derive near-optimal probabilistic guarantees on both sparse signal detection and reconstruction in the presence of noise. Next, we provide a catalog of nearly tight frames with small worst-case and average coherence. Later, we find a new lower bound on worst-case coherence; we compare it to the Welch bound and use it to interpret recently reported signal reconstruction results. Finally, we give an algorithm that transforms frames in a way that decreases average coherence without changing the spectral norm or worst-case coherence.
On uniqueness of end sums and $1$–handles at infinity

For oriented manifolds of dimension at least 4 that are simply connected at infinity, it is known that end summing is a uniquely defined operation. Calcut and Haggerty showed that more complicated fundamental group behavior at infinity can lead to nonuniqueness. We examine how and when uniqueness fails. Examples are given, in the categories top, pl and diff, of nonuniqueness that cannot be detected in a weaker category (including the homotopy category). In contrast, uniqueness is proved for Mittag-Leffler ends, and generalized to allow slides and cancellation of (possibly infinite) collections of 0 – and 1 –handles at infinity. Various applications are presented, including an analysis of how the monoid of smooth manifolds homeomorphic to ℝ 4 acts on the smoothings of any noncompact 4 –manifold.
Geometric control of a quadrotor UAV transporting a payload connected via flexible cable

We derived a coordinate-free form of equations of motion for a complete model of a quadrotor UAV with a payload which is connected via a flexible cable according to Lagrangian mechanics on a manifold. The flexible cable is modeled as a system of serially-connected links and has been considered in the full dynamic model. A geometric nonlinear control system is presented to asymptotically stabilize the position of the quadrotor while aligning the links to the vertical direction below the quadrotor. Numerical simulation and experimental results are presented and a rigorous stability analysis is provided to confirm the accuracy of our derivations. These results will be particularly useful for aggressive load transportation that involves large deformation of the cable.
Observational tests of the properties of turbulence in the Very Local Interstellar Medium

Abstract. The Very Local Interstellar Medium (VLISM) contains clouds which consist of partially-ionized plasma. These clouds can be effectively diagnosed via high resolution optical and ultraviolet spectroscopy of the absorption lines they form in the spectra of nearby stars. Information provided by these spectroscopic measurements includes values for ξ, the root-mean-square velocity fluctuation due to turbulence in these clouds, and T, the ion temperature, which may be partially determined by dissipation of turbulence. We consider whether this turbulence resembles the extensively studied and well-diagnosed turbulence in the solar wind and solar corona. Published observations are used to determine if the velocity fluctuations are primarily transverse to a large-scale magnetic field, whether the temperature perpendicular to the large scale field is larger than that parallel to the field, and whether ions with larger Larmor radii have higher temperatures than smaller gyroradius ions. We ask if the spectroscopically-deduced parameters such as ξ and T depend on the direction on the sky. We also consider the degree to which a single temperature T and turbulence parameter ξ account for the spectral line widths of ions with a wide range of masses. A preliminary examination of the published data shows no evidence for anisotropy of the velocity fluctuations or temperature, nor Larmor radius-dependent heating. These results indicate differences between solar wind and Local Cloud turbulence. Possible physical reasons for these differences are discussed.
A Precise Distance to IRAS 00420+5530 via H2O Maser Parallax with the VLBA

We have used the Very Long Baseline Array to measure the annual parallax of the H2O masers in the star-forming region IRAS 00420+5530. This measurement yields a direct distance estimate of 2.17 ? 0.05 kpc (an error of less than 3%), which disagrees substantially with the standard kinematic distance estimate of ~4.6 kpc (according to the rotation curve of Brand & Blitz), as well as most of the broad range of distances (1.7-7.7 kpc) used in various astrophysical analyses in the literature. The three-dimensional space velocity of IRAS 00420+5530 at this new, more accurate distance implies a substantial noncircular and anomalously slow Galactic orbit, consistent with similar observations of W3(OH) (Xu et?al. and Hachisuka et?al.), as well as line-of-sight velocity residuals in the rotation curve analysis of Brand & Blitz. The Perseus spiral arm of the Galaxy is thus more than a factor of 2 closer than previously presumed, and exhibits motions substantially at odds with axisymmetric models of the rotating Galaxy.
An equation-by-equation method for solving the multidimensional moment constrained maximum entropy problem

An equation-by-equation (EBE) method is proposed to solve a system of nonlinear equations arising from the moment constrained maximum entropy problem of multidimensional variables. The design of the EBE method combines ideas from homotopy continuation and Newton’s iterative methods. Theoretically, we establish the local convergence under appropriate conditions and show that the proposed method, geometrically, finds the solution by searching along the surface corresponding to one component of the nonlinear problem. We will demonstrate the robustness of the method on various numerical examples, including (1) a six-moment one-dimensional entropy problem with an explicit solution that contains components of order 1 0 0 – 1 0 3 in magnitude, (2) four-moment multidimensional entropy problems with explicit solutions where the resulting systems to be solved range from 7 0 – 3 1 0 equations, and (3) four- to eight-moment of a two-dimensional entropy problem, whose solutions correspond to the densities of the two leading EOFs of the wind stress-driven large-scale oceanic model. In this case, we find that the EBE method is more accurate compared to the classical Newton’s method, the Matlab generic solver, and the previously developed BFGS-based method, which was also tested on this problem. The fourth example is four-moment constrained of up to five-dimensional entropy problems whose solutions correspond to multidimensional densities of the components of the solutions of the Kuramoto–Sivashinsky equation. For the higher-dimensional cases of this example, the EBE method is superior because it automatically selects a subset of the prescribed moment constraints from which the maximum entropy solution can be estimated within the desired tolerance. This selection feature is particularly important since the moment constrained maximum entropy problems do not necessarily have solutions in general.
Radio frequency charge sensing in InAs nanowire double quantum dots

We demonstrate charge sensing of an InAs nanowire double quantum dot (DQD) coupled to a radio frequency (rf) circuit. We measure the rf signal reflected by the resonator using homodyne detection. Clear single dot and DQD behavior are observed in the resonator response. rf-reflectometry allows measurements of the DQD charge stability diagram in the few-electron regime even when the dc current through the device is too small to be measured. For a signal-to-noise ratio of one, we estimate a minimum charge detection time of 350 μs at interdot charge transitions and 9 μs for charge transitions with the leads.
Comparative Analysis and Evaluation of Two Prestressed Girder Bridges

A comparative analysis of two bridges constructed with the most commonly used girder types in Florida is carried out. The girder types that the bridges are employed for this study are AASHTO Type III (American Association of State Highway and Transportation Officials) and Florida I-Beam. Two bridges that have exactly the same specifications but with different girder type are analyzed under baseline state and different prestress loss cases. Finite element models of these bridges are utilized and the FE models are subjected to two types of virtual load tests of Florida legal loads namely C5 and SU4. Florida I-Beam tends to have higher load carrying capacity, higher lateral stiffness, cost efficiency and better element level reliability when compared to AASHTO Type girders.
Onset of fast reconnection in Hall magnetohydrodynamics mediated by the plasmoid instability

The role of a super-Alfvenic plasmoid instability in the onset of fast reconnection is studied by means of the largest Hall magnetohydrodynamics simulations to date, with system sizes up to 104 ion skin depths (di). It is demonstrated that the plasmoid instability can facilitate the onset of rapid Hall reconnection, in a regime where the onset would otherwise be inaccessible because the Sweet–Parker width is significantly above di. However, the topology of Hall reconnection is not inevitably a single stable X-point. There exists an intermediate regime where the single X-point topology itself exhibits instability, causing the system to alternate between a single X-point geometry and an extended current sheet with multiple X-points produced by the plasmoid instability. Through a series of simulations with various system sizes relative to di, it is shown that system size affects the accessibility of the intermediate regime. The larger the system size is, the easier it is to realize the intermediate regime. A...
Long-time behavior of 3–dimensional Ricci flow, B : Evolution of the minimal area of simplicial complexes under Ricci flow

In this second part of a series of papers on the long-time behavior of Ricci flows with surgery, we establish a bound on the evolution of the infimal area of simplicial complexes inside a 3–manifold under the Ricci flow. This estimate generalizes an area estimate of Hamilton, which we will recall in the first part of the paper. We remark that in this paper we will mostly be dealing with nonsingular Ricci flows. The existence of surgeries will not play an important role.
Entanglement of disjoint blocks in the one-dimensional spin-1 VBS

Starting with the valence-bond solid (VBS) ground state of the 1D AKLT Hamiltonian, we make a partition of the system in two subsystems A and B, where A is a block of L consecutive spins and B is its complement. In that setting we compute the partial transpose density matrix with respect to A, . We obtain the spectrum of the transposed density matrix of the VBS pure system. Subsequently, we define two disjoint blocks, A and B, containing LA and LB spins, respectively, separated by L sites. Tracing away the spins which do not belong to A?B, we find an expression for the reduced density matrix of the A and B blocks, ?(A, B). With this expression (in the thermodynamic limit), we compute the entanglement spectrum and other several entanglement measures, such as the purity P = tr(?(A, B)2), the negativity and the mutual entropy.
Spectropolarimetric Clues to the Structure and Evolutionary Status of MWC 349A

We present visible wavelength spectropolarimetric measurements of the emission-line star MWC 349A and its close optical companion MWC 349B, conducted with the HPOL spectropolarimeter on both the 0.9 m telescope at the University of Wisconsin's Pine Bluff Observatory and the 3.5 m WIYN telescope on Kitt Peak. Our measurements allow us to estimate the interstellar polarization contribution and thus constrain the intrinsic polarization of MWC 349A, which we find to be consistent in position angle with the dusty disk seen perpendicular to the bipolar outflow. Our analysis reopens the possibility that MWC 349A may be part of the Cyg OB2 association, suggests that it is not a physical companion to MWC 349B, and supports the classification of MWC 349A as a pre–main-sequence B[e] star.
First-Passage Time and Large-Deviation Analysis for Erasure Channels With Memory

This paper considers the performance of digital communication systems transmitting messages over finite-state erasure channels with memory. Information bits are protected from channel erasures using error-correcting codes; successful receptions of codewords are acknowledged at the source through instantaneous feedback. The primary focus of this research is on delay-sensitive applications, codes with finite block lengths, and, necessarily, nonvanishing probabilities of decoding failure. The contribution of this paper is twofold. A methodology to compute the distribution of the time required to empty a buffer is introduced. Based on this distribution, the mean hitting time to an empty queue and delay-violation probabilities for specific thresholds can be computed explicitly. The proposed techniques apply to situations where the transmit buffer contains a predetermined number of information bits at the onset of the data transfer. Furthermore, as additional performance criteria, large deviation principles are obtained for the empirical mean service time and the average packet-transmission time associated with the communication process. This rigorous framework yields a pragmatic methodology to select code rate and block length for the communication unit as functions of the service requirements. Examples motivated by practical systems are provided to further illustrate the applicability of these techniques.
The Barkas effect in plasma transport

Molecular dynamics simulations reveal that a fundamental symmetry of the plasma kinetic theory is broken at moderate to strong Coulomb coupling: the collision rate depends on the signs of the colliding charges. This symmetry breaking is analogous to the Barkas effect observed in charged-particle stopping experiments and gives rise to significantly enhanced electron-ion collision rates. It is expected to affect any neutral plasma with moderate to strong Coulomb coupling such as ultracold neutral plasmas (UNPs) and the dense plasmas of inertial confinement fusion and laser-matter interaction experiments. The physical mechanism responsible is the screening of binary collisions by the correlated plasma medium, which causes an asymmetry in the dynamics of large-angle scattering. Because the effect pertains only to close interactions, it is not predicted by traditional transport models based on cut-off Coulomb collisions or linear dielectric response. A model for the effective screened interaction potential is presented which is suitable for the coupling strengths achieved in UNP experiments. Transport calculations based on this potential and the effective potential kinetic theory agree with the simulated relaxation rates and predict that the Barkas effect can cause up to a 70% increase in the electron-ion collision rate at the conditions of present UNP experiments. The influence of the Barkas effect in other transport processes is also considered.Molecular dynamics simulations reveal that a fundamental symmetry of the plasma kinetic theory is broken at moderate to strong Coulomb coupling: the collision rate depends on the signs of the colliding charges. This symmetry breaking is analogous to the Barkas effect observed in charged-particle stopping experiments and gives rise to significantly enhanced electron-ion collision rates. It is expected to affect any neutral plasma with moderate to strong Coulomb coupling such as ultracold neutral plasmas (UNPs) and the dense plasmas of inertial confinement fusion and laser-matter interaction experiments. The physical mechanism responsible is the screening of binary collisions by the correlated plasma medium, which causes an asymmetry in the dynamics of large-angle scattering. Because the effect pertains only to close interactions, it is not predicted by traditional transport models based on cut-off Coulomb collisions or linear dielectric response. A model for the effective screened interaction potential is ...
Currents and flat chains associated to varifolds, with an application to mean curvature flow

We prove under suitable hypotheses that convergence of integral varifolds implies convergence of associated mod 2 flat chains and subsequential convergence of associated integer-multiplicity rectifiable currents. The convergence results imply restrictions on the kinds of singularities that can occur in mean curvature flow