cssi/SciSciGPT-SciSciNet huggingface dataset:
Astrophysics: Most distant cosmic blast seen.

The most distant γ-ray burst yet sighted is the earliest astronomical object ever observed in cosmic history. This ancient beacon offers a glimpse of the little-known cosmic dark ages. Two groups present redshift determinations and other spectroscopic data for the γ-ray burst GRB 090423 — now the earliest and most distant astronomical object known. Salvaterra et al. report its initial detection with the Swift satellite on 23 April 2009, and a redshift determination with the Telescopio Nazionale Galileo on La Palma 14 hours after the burst, obtaining z ≈ 8.1. Tanvir et al. used the United Kingdom Infrared Telescope, Hawaii, from about 20 minutes after the burst and arrive at z ≈ 8.2. The previous highest redshift known for any object was z = 6.96 for a Lyman-α emitting galaxy. These measurements imply that massive stars were being produced and were dying as γ-ray bursts as early as about 600 million years after the Big Bang, and that their properties are very similar to those stars producing γ-ray bursts 10 billion years later.
AMINOALANE DIMERS AND TRIMERS. AN EXAMINATION OF STRUCTURAL AND STERIC TRENDS

Abstract Reaction of aluminum alkyls with primary or secondary amines readily affords dimeric or trimeric aminoalanes. Steric constraints of the substituents on aluminum and nitrogen substantially affect the structural nature of the products. Ring size, conformational data, and structural trends are reported for a number of dimeric and trimeric aminoalanes.
Nickel-catalyzed carbonylative Negishi cross-coupling reactions

Abstract Catalytic carbonylative Negishi cross-coupling reactions are described. This method readily provides various enones from enol triflates and diorganozinc reagents with catalytic amounts of nickel(II) chloride–4,4′-dimethoxyl-2,2′-bipyridyl under carbon monoxide atmosphere. The rate of carbon monoxide insertion is increased by the addition of lithium or magnesium halides and the use of polar solvents. Alkenyl iodides can also be used in place of enol triflates.
A novel and practical synthesis of polycyclic fluoranthenes

Abstract A novel and general preparation of polycyclic fluoranthenes is described. The synthesis involves a Michael addition of silyl enol ethers to dibenzofulvene followed by cyclization and aromatization.
1-(1-Alkenyl)benzotriazoles: Novel α-Hydroxyacyl Anion Equivalents for the Synthesis of α-Hydroxy Ketones

Abstract α-Lithiated 1-(1-alkenyl)benzotriazoles, generated from the reactions of 1-(1-alkenyl)benzotriazoles with n-BuLi, react with a variety of electrophiles to afford α-substituted 1-(1-alkenyl)benzotriazoles which undergo epoxidation with m-CPBA followed by hydrolysis to give α-hydroxy ketones in good yields. Thus, 1-(1-alkenyl)benzotriazoles behave as α-hydroxyacyl anion equivalents.
A Study of the Products of the Reaction of Phosphorus and Dioxygen

The products of the reaction of laser-ablated red phosphorus and dioxygen have been studied using experiment and theory. The bands at 480.3 and 1273.3 cm-l, previously attributed to PO3 in the matrix isolation IR experiments, are reassigned to PO3-. Also observed in experiment are PO2, PO2-, P2O, OPOPO, P4, and higher oxides.
Phase Diagram of the Nitric Acid/Water System: Implications for Polar Stratospheric Clouds

We have investigated the HNO3/H2O binary liquid/solid phase diagram using a highly sensitive differential scanning calorimeter (DSC) and infrared spectroscopy of thin films. In particular we have sought to investigate the nitric acid trihydrate (NAT) and nitric acid dihydrate (NAD) regions. We report here a detailed stability region for NAD, including comment on the preferential freezing of NAD vs NAT. We have found metastability for NAD and pure HNO3 outside of their normal thermodynamic stability. We have deciphered and more clearly defined the many eutectic transitions in the region of NAT, NAD, and nitric acid monohydrate (NAM). We also report a new solid phase mentioned previously in the literature that undergoes a transition at ∼228 K for samples in the range 54−75 wt % HNO3. We have also detected other new phases that we deem either minor or not relevant for polar stratospheric clouds (PSCs). Finally, we have calculated the fraction of each solid that exists in a frozen sample on the basis of our m...
Direct deprotonation of aliphatic sulfides

Alkylmethyl sulfides are regioselectively deprotonated by n-butyllithium and potassium tert-butoxide at the methyl group in good yields. Thiolane and thiane are deprotonated under the same conditions at the α-position in good yield.
Complete stereochemistry of tetrafibricin.

With use of the NMR databases in achiral and chiral solvents, the complete stereochemistry of tetrafibricin (1) has been elucidated without degradation of the carbon framework.
Elucidation of carbene ambiphilicity leading to the discovery of reversible ammonia activation.

An N,N′-diamidocarbene (DAC) was found to activate a broad range of primary as well as secondary aliphatic and aromatic amines. The relative rates measured for the insertion of the DAC into the primary amines were consistent with an electrophilic activation mechanism; in contrast, the DAC functioned as a nucleophile upon treatment with secondary aryl amines. Collectively, these results constituted the first ambiphilic process for an isolable carbene. By comparison, an analogous diaminocarbene was found to serve exclusively as a nucleophile under similar conditions and led to the discovery of the first organic reagent to reversibly activate ammonia.
Omitted Variable Bias in GLMs of Neural Spiking Activity.

Generalized linear models (GLMs) have a wide range of applications in systems neuroscience describing the encoding of stimulus and behavioral variables, as well as the dynamics of single neurons. H...
Iridium-catalyzed C-C bond forming hydrogenation: direct regioselective reductive coupling of alkyl-substituted alkynes to activated ketones.

We report the first hydrogen-mediated C−C bond formations catalyzed by iridium. Hydrogenation of commercially available alkyl-substituted alkynes, 3-hexyne 1a and 1-phenylpropyne 1b, in the presence of α-ketoesters 2a−2g using cationic iridium precatalysts results in reductive C−C coupling to afford β,γ-unsaturated α-hydroxyesters 3a−3f and 4a−4e and 4g, which are formed in excellent yield, with complete control of olefin geometry and, in most cases, with excellent regiocontrol. Similar levels of selectivity are observed across a range of alkynes 1c−1h. Reductive coupling of 3-hexyne 1a and α-ketoester 2a under an atmosphere of elemental deuterium provides the monodeuterated product deuterio-3a, consistent with a catalytic mechanism involving alkyne−carbonyl oxidative coupling followed by hydrogenolysis of the resulting oxametallacycle.
Intermolecular transition metal-catalyzed [4 + 2 + 2] cycloaddition reactions: A new approach to the construction of eight-membered rings

Transition metal-catalyzed cycloaddition reactions represent powerful methods for the construction of complex polycyclic systems. We have developed a new intermolecular metal-catalyzed [4 + 2 + 2] cycloaddition of heteroatom-tethered enyne derivatives with 1,3-butadiene. This study demonstrates that excellent selectivity can be obtained for the heterocycloaddition adducts through the judicious choice of silver salt. The development of the tandem rhodium-catalyzed allylic substitution [4 + 2 + 2] cycloaddition provides a convenient three-component coupling that circumvents the prior formation of the enyne derivative. Finally, the introduction of a stereogenic center at C-2 leads to a diastereoselective cycloaddition, which provides a powerful new method for the construction of bicyclic octanoid ring systems applicable to target directed synthesis.
Structure−Property Relationship of Permutite-like Amorphous Silicates, Nax+2yM3+xSi1-xO2+y (M3+ = Al, Mn, Fe, Y), for Ion-Exchange Reactions

A series of amorphous silicate materials with the general formula Na{sub x+2y}M{sub x}{sup 3+}Si{sub 1-x}O{sub 2+y}(M{sup 3+} = Al, Mn, Fe, Y) were studied. Samples were synthesized by a precipitation reaction at room temperature. The results indicate that the ion-exchange capacity (IEC) decreases as follows: Al > Fe > Mn > Y. Additionally, the IEC increases with increasing aluminum concentration. Structural studies show that the relative amount of octahedrally coordinated aluminum increases with increasing Al content, as does the total amount of AlO{sub 4} species increases. The data suggest that the IEC value of these amorphous aluminosilicates is dependent on the tetrahedrally coordinated aluminum. Regeneration of the Al-silicate with acetic acid does not decrease the IEC significantly.
The role of imine–enamine tautomerism in effecting cross-aldol condensations

An indirect method to effect cross-aldol coupling of two nonequivalent enolizable aldehydes is reported that involves initial conversion of one aldehyde to an imine derivative possessing an N-3° alkyl substituent. In sharp contrast to the related couplings (e.g., the use of α-lithiated imines at low temperature), condensation between the imine and several representative aldehydes occurs readily at ambient temperature in the presence of a catalytic amount of cobalt(II) chloride.
Experimental determination of the H2SO4/HNO3/H2O phase diagram in regions of stratospheric importance

We have investigated the region of the H2SO4/HNO3/H2O ternary liquid/solid phase diagram bounded by ice, nitric acid trihydrate (NAT), and sulfuric acid tetrahydrate (SAT) using differential scanning calorimetry and IR spectroscopy of thin films. We report measurements and analysis of the eutectic melting curves in the ternary system of the hydrates mentioned as well as the temperature of the eutectics ice/SAT/NAT, ice/sulfuric acid hemihexahydrate (SAH)/NAT, and SAT/NAT. We report for the first time an analysis of the content of the solid phase of completely frozen samples and find that sulfuric acid octahydrate (SAO) is often present in frozen ternary samples and can be a significant portion of the solid phase. We provide a description of how the melting path of a frozen ternary sample can be predicted using the ternary phase diagram. We have parametrized our melting point data and provide equations to generate the ternary melting surface. Finally, we compare our results to the historic work of Carpente...
An analytical approach to bistable biological circuit discrimination using real algebraic geometry

Biomolecular circuits with two distinct and stable steady states have been identified as essential components in a wide range of biological networks, with a variety of mechanisms and topologies giving rise to their important bistable property. Understanding the differences between circuit implementations is an important question, particularly for the synthetic biologist faced with determining which bistable circuit design out of many is best for their specific application. In this work we explore the applicability of Sturm's theorem—a tool from nineteenth-century real algebraic geometry—to comparing ‘functionally equivalent’ bistable circuits without the need for numerical simulation. We first consider two genetic toggle variants and two different positive feedback circuits, and show how specific topological properties present in each type of circuit can serve to increase the size of the regions of parameter space in which they function as switches. We then demonstrate that a single competitive monomeric activator added to a purely monomeric (and otherwise monostable) mutual repressor circuit is sufficient for bistability. Finally, we compare our approach with the Routh–Hurwitz method and derive consistent, yet more powerful, parametric conditions. The predictive power and ease of use of Sturm's theorem demonstrated in this work suggest that algebraic geometric techniques may be underused in biomolecular circuit analysis.
High Pressure Synthesis of Solid State Materials

Within the ASU MRSEC, we are using a combination of high pressure synthesis techniques (multi-anvil, piston cylinder), combined with in situ studies in diamond anvil cells, and ab initio calculations, to prepare a range of new materials at high pressure, and to study their physical properties under extreme conditions of pressure and temperature. Work in progress includes experiments on nitrides, particularly glasses and crystalline materials based in the P 3 N 5 -HPN 2 -PON system, silicate and germanate perovskites and related vanadates and niobates, and high hardness materials in the B-C-N-0 system. Some of our recent results are presented.
A facile synthesis of aryl iodides via potassium aryltrifluoroborates

Aryl- and heteroaryltrifluoroborates are rapidly converted to aryl and heteroaryl iodides under mild conditions using sodium iodide in the presence of mild oxidizing agents.
2- and 4-Nitrobenzenesulfonamides: Exceptionally versatile means for preparation of secondary amines and protection of amines

Abstract 2- and 4-Nitrobenzenesulfonamides, readily prepared from primary amines, undergo smooth alkylation by Mitsunobu reaction or by conventional methods to give N-alkylated sulfonamides in near quantitative yields. These sulfonamides could be deprotected readily via Meisenheimer complexes upon treatment with thiolates in DMF at room temperature, giving secondary amines in high yields.
Mixed-Valence and Neutral Framework Inorganic−Organic Hybrid Materials: Synthesis, Characterization, and Magnetic Properties of [{Co(N(CH)4N)}(V2O5)2] and [{Co(N(CH)4N)}V2O6]

Two inorganic−organic hybrid materials [{Co(N(CH)4N)}(V2O5)2] (1) and [{Co(N(CH)4N)}V2O6] (2) have been synthesized and characterized by FT-IR spectroscopy, thermogravimetric analysis, elemental analysis, manganometric titration, temperature-dependent magnetic susceptibility measurement, bond valence sum calculations, and single-crystal X-ray diffraction analyses. The neutral framework materials were prepared by the amalgamation of vanadium oxide chains and layers with metal−organoamine coordination polymers. The three-dimensional framework structures of the crystals in 1 and 2 are composed of vanadium oxide layers (1) and chains (2) combined with {Co(N(CH)4N)}2+ motifs that cross-link the reduced vanadium oxide layers (containing mixed-valent vanadium centers) in 1 and oxovanadium chains in 2. Besides crosslinking the metal oxide chains and layers in these materials, cationic metal−pyrazine polymers provide charge balance leading to the neutral framework in these solids. The compounds show good thermal s...
An Optimized Recurrent Unit for Ultra-Low-Power Keyword Spotting

There is growing interest in being able to run neural networks on sensors, wearables and internet-of-things (IoT) devices. However, the computational demands of neural networks make them difficult to deploy on resource-constrained edge devices. To meet this need, our work introduces a new recurrent unit architecture that is specifically adapted for on-device low power acoustic event detection (AED). The proposed architecture is based on the gated recurrent unit ('GRU' -- introduced by Cho et al. [9]) but features optimizations that make it implementable on ultra-low power micro-controllers such as the Arm Cortex M0+. Our new architecture, the Embedded Gated Recurrent Unit (eGRU) is demonstrated to be highly efficient and suitable for short-duration AED and keyword spotting tasks. A single eGRU cell is 60× faster and 10× smaller than a GRU cell. Despite its optimizations, eGRU compares well with GRU across tasks of varying complexities. The practicality of eGRU is investigated in a wearable acoustic event detection application. An eGRU model is implemented and tested on the Arm Cortex M0-based Atmel ATSAMD21E18 processor. The Arm M0+ implementation of the eGRU model compares favorably with a full precision GRU that is running on a workstation. The embedded eGRU model achieves a classification accuracy 95.3%, which is only 2% less than the full precision GRU.
Aligning High-Aspect-Ratio Particles in User-Specified Orientations with Ultrasound-Directed Self-Assembly

Ultrasound-directed self-assembly (DSA) enables the arranging of particles into user-specified patterns, but not explicitly accounting for particle orientation has long hampered the potential for high-aspect-ratio particles. The authors demonstrate accurate control over the orientation of such particles, by maximizing the curvature of the acoustic radiation potential orthogonal to the chosen orientation. This knowledge makes it possible to use ultrasound DSA as a processing method for engineered materials based on $e.g.$ fibers in a polymer matrix.
Computability and categoricity of weakly ultrahomogeneous structures

This paper investigates the effective categoricity of ultrahomogeneous structures. It is shown that any computable ultrahomogeneous structure is $\Delta^0_2$ categorical. A structure A is said to be weakly ultrahomogeneous if there is a finite (exceptional) set of elements $a_1,\dots,a_n$ such that A becomes ultrahomogeneous when constants representing these elements are added to the language. Characterizations are obtained for weakly ultrahomogeneous linear orderings, equivalence structures, injection structures and trees, and these are compared with characterizations of the computably categorical and $\Delta^0_2$ categorical structures. Index sets are used to determine the complexity of the notions of ultrahomegenous and weakly ultrahomogeneous for various families of structures.
The uniform content of partial and linear orders

Abstract The principle ADS asserts that every linear order on ω has an infinite ascending or descending sequence. This has been studied extensively in the reverse mathematics literature, beginning with the work of Hirschfeldt and Shore [16] . We introduce the principle ADC , which asserts that every such linear order has an infinite ascending or descending chain. The two are easily seen to be equivalent over the base system RCA 0 of second order arithmetic; they are even computably equivalent. However, we prove that ADC is strictly weaker than ADS under Weihrauch (uniform) reducibility. In fact, we show that even the principle SADS , which is the restriction of ADS to linear orders of type ω + ω ⁎ , is not Weihrauch reducible to ADC . In this connection, we define a more natural stable form of ADS that we call General - SADS , which is the restriction of ADS to linear orders of type k + ω , ω + ω ⁎ , or ω + k , where k is a finite number. We define General - SADC analogously. We prove that General - SADC is not Weihrauch reducible to SADS , and so in particular, each of SADS and SADC is strictly weaker under Weihrauch reducibility than its general version. Finally, we turn to the principle CAC , which asserts that every partial order on ω has an infinite chain or antichain. This has two previously studied stable variants, SCAC and WSCAC , which were introduced by Hirschfeldt and Jockusch [16] , and by Jockusch, Kastermans, Lempp, Lerman, and Solomon [19] , respectively, and which are known to be equivalent over RCA 0 . Here, we show that SCAC is strictly weaker than WSCAC under even computable reducibility.
1/Nc - Chiral Perturbation Theory in the One-Baryon Sector

In this contribution, baryon axial-vector couplings are studied in the framework of the combined 1/N{sub c} and chiral expansions. This framework is implemented on the basis of the emergent spin-flavor symmetry in baryons at large N{sub c} and HBChPT, and linking both expansions ({xi}-expansion), where 1/N{sub c} is taken to be a quantity order p. The study is carried out including one-loop contributions, which corresponds to order xi to the third for baryon masses and order {xi} square for the axial couplings.
Composition properties of inferential privacy for time-series data

With the proliferation of mobile devices and the internet of things, developing principled solutions for privacy in time series applications has become increasingly important. While differential privacy is the gold standard for database privacy, many time series applications require a different kind of guarantee, and a number of recent works have used some form of inferential privacy to address these situations. However, a major barrier to using inferential privacy in practice is its lack of graceful composition — even if the same or related sensitive data is used in multiple releases that are safe individually, the combined release may have poor privacy properties. In this paper, we study composition properties of a form of inferential privacy called Pufferfish when applied to time-series data. We show that while general Pufferfish mechanisms may not compose gracefully, a specific Pufferfish mechanism, called the Markov Quilt Mechanism, which was recently introduced by [10], has strong composition properties comparable to that of pure differential privacy.
Central Limits and Homogenization in Random Media

We consider the perturbation of elliptic pseudodifferential operators $P(\mathbf{x},\mathbf{D})$ with more than square integrable Green's functions by random, rapidly varying, sufficiently mixing, potentials of the form $q(\frac{\mathbf{x}}{\varepsilon},\omega)$. We analyze the source and spectral problems associated with such operators and show that the rescaled difference between the perturbed and unperturbed solutions may be written asymptotically as $\varepsilon \to 0$ as explicit Gaussian processes. Such results may be seen as central limit corrections to homogenization (law of large numbers). Similar results are derived for more general elliptic equations with random coefficients in one dimension of space. The results are based on the availability of a rapidly converging integral formulation for the perturbed solutions and on the use of classical central limit results for random processes with appropriate mixing conditions.
The Effect of Pets on Happiness: A Large-Scale Multi-Factor Analysis Using Social Multimedia

From reducing stress and loneliness, to boosting productivity and overall well-being, pets are believed to play a significant role in people’s daily lives. Many traditional studies have identified that frequent interactions with pets could make individuals become healthier and more optimistic, and ultimately enjoy a happier life. However, most of those studies are not only restricted in scale, but also may carry biases by using subjective self-reports, interviews, and questionnaires as the major approaches. In this article, we leverage large-scale data collected from social media and the state-of-the-art deep learning technologies to study this phenomenon in depth and breadth. Our study includes five major steps: (1) collecting timeline posts from around 20,000 Instagram users; (2) using face detection and recognition on 2 million photos to infer users’ demographics, relationship status, and whether having children, (3) analyzing a user’s degree of happiness based on images and captions via smiling classification and textual sentiment analysis; (4) applying transfer learning techniques to retrain the final layer of the Inception v3 model for pet classification; and (5) analyzing the effects of pets on happiness in terms of multiple factors of user demographics. Our main results have demonstrated the efficacy of our proposed method with many new insights. We believe this method is also applicable to other domains as a scalable, efficient, and effective methodology for modeling and analyzing social behaviors and psychological well-being. In addition, to facilitate the research involving human faces, we also release our dataset of 700K analyzed faces.
Coordination-driven Learning in Multi-agent Problem Spaces.

We discuss the role of coordination as a direct learning objective in multi-agent reinforcement learning (MARL) domains. To this end, we present a novel means of quantifying coordination in multi-agent systems, and discuss the implications of using such a measure to optimize coordinated agent policies. This concept has important implications for adversary-aware RL, which we take to be a sub-domain of multi-agent learning.
Analytical SLAM without linearization

We apply a combination of linear time varying (LTV) Kalman filtering and nonlinear contraction tools to the problem of simultaneous mapping and localization (SLAM), in a fashion which avoids linearized approximations altogether. By exploiting virtual synthetic measurements, the LTV Kalman observer avoids errors and approximations brought by the linearization process in the EKF SLAM. Furthermore, conditioned on the robot position, the covariances between landmarks are fully decoupled, making the algorithm easily scalable. Contraction analysis is used to establish stability of the algorithm and quantify its convergence rate. We propose four versions based on different combinations of sensor information, ranging from traditional bearing measurements and radial measurements to optical flows and time-to-contact measurements. As shown in simulations, the proposed algorithm is simple and fast, and it can solve SLAM problems in both 2D and 3D scenarios with guaranteed convergence rates in a full nonlinear context.
Finding a most biased coin with fewest flips

We study the problem of learning a most biased coin among a set of coins by tossing the coins adaptively. The goal is to minimize the number of tosses until we identify a coin whose posterior probability of being most biased is at least 1 for a given . Under a particular probabilistic model, we give an optimal algorithm, i.e., an algorithm that minimizes the expected number of future tosses. The problem is closely related to finding the best arm in the multi-armed bandit problem using adaptive strategies. Our algorithm employs an optimal adaptive strategy—a strategy that performs the best possible action at each step after observing the outcomes of all previous coin tosses. Consequently, our algorithm is also optimal for any given starting history of outcomes. To our knowledge, this is the first algorithm that employs an optimal adaptive strategy under a Bayesian setting for this problem. Our proof of optimality employs mathematical tools from the area of Markov games.
Horizon instability of extremal black holes

We show that axisymmetric extremal horizons are unstable under linear scalar perturbations. Specifically, we show that translation invariant derivatives of generic solutions to the wave equation do not decay along such horizons as advanced time tends to infinity, and in fact, higher order derivatives blow up. This result holds in particular for extremal Kerr-Newman and Majumdar-Papapetrou spacetimes and is in stark contrast with the subextremal case for which decay is known for all derivatives along the event horizon.
A piecewise smooth control-Lyapunov function framework for switching stabilization

Abstract This paper studies switching stabilization problems for general switched nonlinear systems. A piecewise smooth control-Lyapunov function (PSCLF) approach is proposed and a constructive way to design stabilizing switching laws is developed. The switching law is constructed via directional derivative of the PSCLF with a careful discussion on various technical issues that may occur on the nonsmooth surface. Sufficient conditions are derived to ensure stability of closed-loop Filippov solutions including possible sliding motions. The proposed PSCLF approach provides a unified framework to study switching stabilization problems with a systematic consideration of sliding motions. Application to stabilization of switched nonlinear systems is illustrated through a numerical example.
Statistical inference for SPDEs: an overview

The aim of this work is to give an overview of the recent developments in the area of statistical inference for parabolic stochastic partial differential equations. Significant part of the paper is devoted to the spectral approach, which is the most studied sampling scheme under which the observations are done in the Fourier space over some finite time interval. We also discuss the practically important case of discrete sampling of the solution. Other relevant methodologies and some open problems are briefly addressed over the course of the manuscript.
Fast sampling with Gaussian scale mixture priors in high-dimensional regression

We propose an efficient way to sample from a class of structured multivariate Gaussian distributions. The proposed algorithm only requires matrix multiplications and linear system solutions. Its computational complexity grows linearly with the dimension, unlike existing algorithms that rely on Cholesky factorizations with cubic complexity. The algorithm is broadly applicable in settings where Gaussian scale mixture priors are used on high-dimensional parameters. Its effectiveness is illustrated through a high-dimensional regression problem with a horseshoe prior on the regression coefficients. Other potential applications are outlined.
A Representation Stability Theorem for VI-modules

Let VI be the category whose objects are the finite dimensional vector spaces over a finite field of order q and whose morphisms are the injective linear maps. A VI-module over a ring is a functor from the category VI to the category of modules over the ring. A VI-module gives rise to a sequence of representations of the finite general linear groups. We prove that the sequence obtained from any finitely generated VI-module over an algebraically closed field of characteristic zero is representation stable - in particular, the multiplicities which appear in the irreducible decompositions eventually stabilize. We deduce as a consequence that the dimension of the representations in the sequence {Vn} obtained from a finitely generated VI-module V over a field of characteristic zero is eventually a polynomial in qn. Our results are analogs of corresponding results on representation stability and polynomial growth of dimension for FI-modules (which give rise to sequences of representations of the symmetric groups) proved by Church, Ellenberg, and Farb.
Chiral symmetry and lattice fermions

Lattice gauge theory and chiral perturbation theory are among the primary tools for understanding non-perturbative aspects of QCD. I review several subtle and sometimes controversial issues that arise when combining these techniques. Among these are one failure of partially quenched chiral perturbation theory when the valence quarks become lighter than the average sea quark mass and a potential ambiguity in comparisons of perturbative and lattice properties of non-degenerate quarks.
Noise-weighted angular differential imaging

Angular differential imaging (ADI) (Marois et al. 2006) is an observational technique in high contrast imaging where the telescope is used in pupil tracking mode so that the image of the sky rotates with respect to the optical surfaces. Bright "speckle" light caused by optical errors remains fixed in the image, while planets and disks rotate with the sky. The resulting dataset is then post-processed to remove the speckles, de-rotated to undo the sky motion, and median-collapsed to create a final data product. The postprocessing algorithms to remove the speckles are an active area of research and beyond the scope of this note. We consider the derotation and median-combination, where we show gains in signal-to-noise ratio are possible with a small change to the algorithm.
Integrality and gauge dependence of Hennings TQFTs

Abstract We provide a general construction of integral TQFTs over a general commutative ring, k , starting from a finite Hopf algebra over k which is Frobenius and double balanced. These TQFTs specialize to the Hennings invariants of the respective doubles on closed 3-manifolds. We show the construction applies to index 2 extensions of the Borel parts of Lusztig's small quantum groups for all simple Lie types, yielding integral TQFTs over the cyclotomic integers for surfaces with one boundary component. We further establish and compute isomorphisms of TQFT functors constructed from Hopf algebras that are related by a strict gauge transformation in the sense of Drinfeld. Formulas for the natural isomorphisms are given in terms of the gauge twist element. These results are combined and applied to show that the Hennings invariant associated to quantum- sl 2 takes values in the cyclotomic integers. Using prior results of Chen et al. we infer integrality also of the Witten–Reshetikhin–Turaev S O ( 3 ) invariant for rational homology spheres. As opposed to most other approaches the methods described in this article do not invoke calculations of skeins, knots polynomials, or representation theory, but follow a combinatorial construction that uses only the elements and operations of the underlying Hopf algebras.
Hybrid generative/discriminative learning for automatic image annotation

Automatic image annotation (AIA) raises tremendous challenges to machine learning as it requires modeling of data that are both ambiguous in input and output, e.g., images containing multiple objects and labeled with multiple semantic tags. Even more challenging is that the number of candidate tags is usually huge (as large as the vocabulary size) yet each image is only related to a few of them. This paper presents a hybrid generative-discriminative classifier to simultaneously address the extreme data-ambiguity and overfitting-vulnerability issues in tasks such as AIA. Particularly: (1) an Exponential-Multinomial Mixture (EMM) model is established to capture both the input and output ambiguity and in the meanwhile to encourage prediction sparsity; and (2) the prediction ability of the EMM model is explicitly maximized through discriminative learning that integrates variational inference of graphical models and the pairwise formulation of ordinal regression. Experiments show that our approach achieves both superior annotation performance and better tag scalability.
Planning and navigation of climbing robots in low-gravity environments

Advances in planetary robotics have led to wheeled robots that have beamed back invaluable science data from the surface of the Moon and Mars. However, these large wheeled robots are unable to access rugged environments such as cliffs, canyons and crater walls that contain exposed rock-faces and are geological time-capsules into the early Moon and Mars. We have proposed the SphereX robot with a mass of 3 kg, 30 cm diameter that can hop, roll and fly short distances. A single robot may slip and fall, however, a multirobot system can work cooperatively by being interlinked using spring-tethers and work much like a team of mountaineers to systematically climb a slope. We consider a team of four or more robots that are interlinked with tethers in an “x” configuration. Each robot secures itself to a slope using spiny gripping actuators, and one by one each robot moves upwards by crawling, rolling or hopping up the slope. Apart from climbing, path planning, and navigation is another critical challenge that needs to be solved to make the whole approach feasible. For climbing navigation, a multirobot system needs to have up to date info of its location, together with a macroscopic map of the climbing surface and a detailed map ahead. This system with limited sensor range needs to discern and identify feasible pathways to make the next climbing step much like a human mountaineer. These climbing pathways consist of a series of anchor points for the robot to grip onto next. Identifying one or more feasible pathways is a critical challenge as the terrain ahead needs to be acquired, followed by identification and ranking of anchor points to grip. The climbing task resembles a maze with wrong pathways leading to dead-end. The multirobot systems need to autonomously explore climbing pathways and know when to give up. In this paper, we present a human devised autonomous climbing algorithm and evaluate it using a high-fidelity dynamics simulator. The climbing surfaces contain impassable obstacles and some loosely held rocks that can dislodge. Under these conditions, the robots need to autonomously map, plan and navigate up or down these steep environments. Autonomous mapping and navigation capability is evaluated using simulated lasers, vision sensors. The human devised planning algorithm uses a new algorithm called bounded-leg A∗. Our early simulation results show much promise in these techniques and our future plans include demonstration on real robots in a controlled laboratory environment and outdoors in the canyons of Arizona.
Finite-time extinction of the Kähler–Ricci flow

We investigate the limiting behavior of the unnormalized Kahler-Ricci flow on a Kahler manifold with a polarized initial Kahler metric. We prove that the Kahler-Ricci flow becomes extinct in finite time if and only if the manifold has positive first Chern class and the initial Kahler class is proportional to the first Chern class of the manifold. This proves a conjecture of Tian for the smooth solutions of the Kahler-Ricci flow.
Dynamic signal tracking in a simple v1 spiking model

This work is part of an effort to understand the neural basis for our visual system's ability, or failure, to accurately track moving visual signals. We consider here a ring model of spiking neurons, intended as a simplified computational model of a single hypercolumn of the primary visual cortex of primates. Signals that consist of edges with time-varying orientations localized in space are considered. Our model is calibrated to produce spontaneous and driven firing rates roughly consistent with experiments, and our two main findings, for which we offer dynamical explanation on the level of neuronal interactions, are the following. First, we have documented consistent transient overshoots in signal perception following signal switches due to emergent interactions of the E-and I-populations. Second, for continuously moving signals, we have found that accuracy is considerably lower at reversals of orientation than when continuing in the same direction as when the signal is a rotating bar. To measure performance, we use two metrics, called fidelity and reliability, to compare signals reconstructed by the system to the ones presented and assess trial-to-trial variability. We propose that the same population mechanisms responsible for orientation selectivity also impose constraints on dynamic signal tracking that manifest in perception failures consistent with psychophysical observations.
Higher Stanley-Reisner rings and Toric Residues

We give a purely algebraic proof of the hypersurface case of the Toric Residue Mirror Conjecture recently proposed by Batyrev and Materov.
Uncertainty in Multi-Commodity Routing Networks: When does it help?

We study the equilibrium quality in a multicommodity selfish routing game with many types of users, where each user type experiences a different level of uncertainty. We consider a new model of uncertainty where each user-type over- or under-estimates their congestion costs by a multiplicative constant. We present a variety of theoretical results showing that when users under-estimate their costs, the network congestion decreases at equilibrium, whereas overestimation of costs leads to increased equilibrium congestion. Motivated by applications in urban transportation networks, we perform simulations consisting of parking users and through traffic on synthetic network topologies. Our results strongly indicate that while users' perception of network costs can significantly impact the equilibrium quality, optimism in the face of uncertainty leads to favorable network conditions.
Symmetrizing Tableaux and the 5th Case of the Foulkes Conjecture

Abstract The Foulkes conjecture states that the multiplicities in the plethysm Sym a ( Sym b V ) are at most as large as the multiplicities in the plethysm Sym b ( Sym a V ) for all a ≤ b . This conjecture has been known to be true for a ≤ 4 . The main result of this paper is its verification for a = 5 . This is achieved by performing a combinatorial calculation on a computer and using a propagation theorem of Tom McKay from 2008. Moreover, we obtain a complete representation theoretic decomposition of the vanishing ideal of the 5th Chow variety in degree 5, we show that there are no degree 5 equations for the 6th Chow variety, and we also find some representation theoretic degree 6 equations for the 6th Chow variety.
Computational Complexity of Certifying Restricted Isometry Property

Given a matrix A with n rows, a number k 0 and any arbitrarily small constant 0<delta<1, there exists some k such that given a matrix M, it is SSE-Hard to distinguish the following two cases: i) (Highly RIP) M is (k,delta)-RIP; ii) (Far away from RIP) M is not (k/C,1-delta)-RIP. Most of the previous results on the topic of hardness of RIP certification only hold for certification when delta=o(1). In practice, it is of interest to understand the complexity of certifying a matrix with delta being close to sqrt(2) - 1, as it suffices for many real applications to have matrices with delta=sqrt(2)-1. Our hardness result holds for any constant delta. Specifically, our result proves that even if delta is indeed very small, i.e. the matrix is in fact strongly RIP, certifying that the matrix exhibits weak RIP itself is SSE-Hard. In order to prove the hardness result, we prove a variant of the Cheeger's Inequality for sparse vectors.
SOME COMPUTATIONS OF 1-COHOMOLOGY GROUPS AND CONSTRUCTION OF NON-ORBIT-EQUIVALENT ACTIONS

For each group has uncountably many non-stably orbit-equivalent actions. We also calculate 1-cohomology groups and show existence of ‘many’ non-stably orbit-equivalent actions for free products of groups as above.
Colored Morton-Franks-Williams inequalities

We generalize the Morton-Franks-Williams inequality to the colored $\mathfrak{sl}(N)$ link homology defined in arXiv:0907.0695, which gives infinitely many new bounds for the braid index and the self linking number. A key ingredient of our proof is a composition product for the general MOY graph polynomial, which generalizes that of Wagner arXiv:math/0702230v1.
Temporal correlation detection using computational phase-change memory

Conventional computers based on the von Neumann architecture perform computation by repeatedly transferring data between their physically separated processing and memory units. As computation becomes increasingly data centric and the scalability limits in terms of performance and power are being reached, alternative computing paradigms with collocated computation and storage are actively being sought. A fascinating such approach is that of computational memory where the physics of nanoscale memory devices are used to perform certain computational tasks within the memory unit in a non-von Neumann manner. We present an experimental demonstration using one million phase change memory devices organized to perform a high-level computational primitive by exploiting the crystallization dynamics. Its result is imprinted in the conductance states of the memory devices. The results of using such a computational memory for processing real-world data sets show that this co-existence of computation and storage at the nanometer scale could enable ultra-dense, low-power, and massively-parallel computing systems. New computing paradigms, such as in-memory computing, are expected to overcome the limitations of conventional computing approaches. Sebastian et al. report a large-scale demonstration of computational phase change memory (PCM) by performing high-level computational primitives using one million PCM devices.
Real rank boundaries and loci of forms

In this article, we study forbidden loci and typical ranks of forms with respect to the embeddings of P1×P1 given by the line bundles (2, 2d). We introduce the Ranestad–Schreyer locus corresponding...
A Computational Model of Commonsense Moral Decision Making

We introduce a computational model for building moral autonomous vehicles by learning and generalizing from human moral judgments. We draw on a cognitively inspired model of how people and young children learn moral theories from sparse and noisy data and integrate observations made from different people in different groups. The problem of moral learning for autonomous vehicles is cast as learning how to weigh the different features of the dilemma using utility calculus, with the goal of making these trade-offs reflect how people make them in a wide variety of moral dilemma. By modeling the structures of individuals and groups in a hierarchical Bayesian model, we show that an individual's moral values -- as well as a group's shared values -- can be inferred from sparse and noisy data. We evaluate our approach with data from the Moral Machine, a web application that collects human judgments on moral dilemmas involving autonomous vehicles, and show that the model rapidly and accurately infers people's preferences and can predict the difficulty of moral dilemmas from limited data.
Neumann-Neumann Waveform Relaxation Algorithm in Multiple subdomains for Hyperbolic Problems in 1D and 2D

We present a Waveform Relaxation (WR) version of the Neumann–Neumann algorithm for the wave equation in space-time. The method is based on a nonoverlapping spatial domain decomposition, and the iteration involves subdomain solves in space-time with corresponding interface conditions, followed by a correction step. Using a Fourier-Laplace transform argument, for a particular relaxation parameter, we prove convergence of the algorithm in a finite number of steps for the finite time intervals. The number of steps depends on the size of the subdomains and the time window length on which the algorithm is employed. We illustrate the performance of the algorithm with numerical results, followed by a comparison with classical and optimized Schwarz WR methods.© 2016 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2016
Spectral analysis of inhomogeneities shows that the elastic stiffness of random composites decreases with increasing heterogeneity

Abstract Investigation of inhomogeneities has wide applications in different areas of mechanics including the study of composite materials. Here, we analytically study an arbitrarily-shaped isotropic inhomogeneity embedded in a finite-sized heterogeneous medium. By modal decomposition of the influence of the inhomogeneity on the deformation of the composite, an exact relation is presented that determines the variation of effective elastic stiffness caused by the presence of the inhomogeneity. This relation indicates that the effective elastic stiffness of a composite is always a concave function of the elastic modulus of the inhomogeneity, embedded inside the composite. Therefore, as the heterogeneity of elastic random composites increases, the rate of increase in effective stiffness caused by the stiffer constituents is smaller than the rate of its decrease due to the softer constitutions. So, weakly heterogeneous random composites become softer and less conductive with increasing heterogeneity at the same mean of constituent properties. We numerically evaluated the effective properties of about ten thousand composites to empirically support these results, characterize the nonaffinity of the displacement field in random composites, characterize the sample to sample variability of the effective properties and extend the results to the thermal conductivity of composites.
On the minimum size of signed sumsets in elementary abelian groups

For a finite abelian group G and positive integers m and h, we let ρ(G,m,h)=min⁡{|hA|:A⊆G,|A|=m} and ρ±(G,m,h)=min⁡{|h±A|:A⊆G,|A|=m}, where hA and h±A denote the h-fold sumset and the h-fold signed sumset of A, respectively. The study of ρ(G,m,h) has a 200-year-old history and is now known for all G, m, and h. In previous work we provided an upper bound for ρ±(G,m,h) that we believe is exact, and proved that ρ±(G,m,h) agrees with ρ(G,m,h) when G is cyclic. Here we study ρ±(G,m,h) for elementary abelian groups G; in particular, we determine all values of m for which ρ±(Zp2,m,2) equals ρ(Zp2,m,2) for a given prime p.