cssi/SciSciGPT-SciSciNet huggingface dataset:
Exceptionally Active Yttrium−Salen Complexes for the Catalyzed Ring Opening of Epoxides by TMSCN and TMSN3

Halide or alkoxide free yttrium−salen complexes are excellent catalysts for the ring opening of epoxides mediated by TMSCN and TMSN3. Substrate to catalyst ratios up to 10000 have been realized in these potentially useful reactions, which can be run under solvent-free conditions. Even though the enantioselectivities for the TMSCN-mediated reaction remains modest (best 77% ee), these studies with a highly tunable ligand system may provide further impetus for work in this important area of catalysis. Even though attempts to isolate a Y−cyanide complex, which was detected by in situ IR spectroscopy, failed, a related dimeric hydroxide complex was isolated. A kinetic study using in situ IR spectroscopy did not provide conclusive data to assign an order with respect to Y in this reaction.
Early-Transition-Metal Silyl Complexes Free of Anionic π-Ligands. A Comparison of Alkyl and Silyl Ligands

Abstract A new family of silyl complexes, (RCH2)3MSiR'3 (M = Ti, Zr), (RCH2)2Ta(=CHR)SiR'3 and (RCH2)2W(=CR)SiR'3, which are free of cyclopentadienyl (Cp) or other supporting anionic Ω-ligands, have been prepared and characterized. The silyl ligands are found to be more reactive than the alkyl ligands in the silyl alkyl and silyl alkylidene complexes. Silane (HSiR'3) elimination to form metal—carbon multiple bonds is preferred over alkane (RCH3) elimination. In the formation of (Me3SiCH2)2Ta(=CHSiMe3)Si(SiMe3)3 from the reaction of (Me3SiCH2)3TaCl2 with 2 equiv of Li(THF)3Si(SiMe3)3, an intermediate (Me3SiCH2)3Ta(Cl)Si(SiMe3)3 was identified. The first step in the conversion of this intermediate to (Me3SiCH2)2Ta(=CHSiMe3)Si(SiMe3)3 is a silane [HSi(SiMe3)3] elimination reaction to form “(Me3SiCH2)2Ta(=CHSiMe3)Cl”. The dimer of “(Me3SiCH2)2Ta(=CHSiMe3)Cl”, (Me3SiCH2)4(Cl)2Ta2(=CHSiMe3)2, was observed in the formation of (Me3SiCH2)2Ta(=CHSiMe3)Si(SiMe3)3 and in the decomposition of (Me3SiCH2)3Ta(Cl)Si(SiMe3...
Formation of Radical Anions in the Reaction of p-Benzoquinone and C60 with Alkoxide Ions

Reactions of p-benzoquinone and its derivatives with hydroxide and alkoxide ions (RO-: R = H, Me, Et, i-Pr, PhCH2) in acetonitrile (MeCN) result in formation of the corresponding semiquinone radic...
Synthesis of angular quinoid heterocycles from 2-(2-nitrovinyl)-1,4- benzoquinone

Reactions of 2-(2-nitrovinyl)-1,4-benzoquinone with furans, indoles, and endocyclic enol ethers form angular fused heterocyclic quinoid ring systems. The reaction proceeds by a formal inverse electron-demand [4 + 2] cycloaddition reaction of the nitrovinylquinone and a double bond of the heterocycle. The initial quinoid cycloadducts can be readily tautomerized to hydroquinoid species, which may be dehydrogenated to fully aromatic quinones. In the case of furans, the tautomerized adducts may be ring-opened to give 6,7-di- or 5,6,7-tri-substituted-1,4-naphthalenediols. In the case of endocyclic enol ethers, formation of benzofuran products competes with [4 + 2] cycloaddition.
Supercritical Fluid−Liquid−Solid Synthesis of Gallium Phosphide Nanowires

A new GaP nanowire synthesis method is employed to produce a high yield of single crystalline wires. Reaction at 500 °C in supercritical hexane using gold seed particles results in wires that average 20 nm in diameter and tens of micrometers in length. Some wires generate twinning faults orthogonal to the wire growth direction.
Catalytic hydrogenolysis on metals

Two issues of broad interest in catalysis are reaction mechanisms and comparisons of catalytic activities of different substances. Metal-catalyzed hydrogenolysis reactions of simple molecules provide examples in which both issues have been investigated in some detail. While hydrogenolysis of carbon-carbon bonds in alkanes has received most of the attention to date, some work has also been reported on the hydrogenolysis of carbon-nitrogen bonds in amines and of carbon-halogen bonds in alkyl halides. General mechanistic features of hydrogenolysis reactions on metals and comparisons of catalytic activities of metals for such reactions are considered in this brief review.
Flagellar Synchronization Is a Simple Alternative to Cell Cycle Synchronization for Ciliary and Flagellar Studies.

ABSTRACT The unicellular green alga Chlamydomonas reinhardtii is an ideal model organism for studies of ciliary function and assembly. In assays for biological and biochemical effects of various factors on flagellar structure and function, synchronous culture is advantageous for minimizing variability. Here, we have characterized a method in which 100% synchronization is achieved with respect to flagellar length but not with respect to the cell cycle. The method requires inducing flagellar regeneration by amputation of the entire cell population and limiting regeneration time. This results in a maximally homogeneous distribution of flagellar lengths at 3 h postamputation. We found that time-limiting new protein synthesis during flagellar synchronization limits variability in the unassembled pool of limiting flagellar protein and variability in flagellar length without affecting the range of cell volumes. We also found that long- and short-flagella mutants that regenerate normally require longer and shorter synchronization times, respectively. By minimizing flagellar length variability using a simple method requiring only hours and no changes in media, flagellar synchronization facilitates the detection of small changes in flagellar length resulting from both chemical and genetic perturbations in Chlamydomonas. This method increases our ability to probe the basic biology of ciliary size regulation and related disease etiologies. IMPORTANCE Cilia and flagella are highly conserved antenna-like organelles that found in nearly all mammalian cell types. They perform sensory and motile functions contributing to numerous physiological and developmental processes. Defects in their assembly and function are implicated in a wide range of human diseases ranging from retinal degeneration to cancer. Chlamydomonas reinhardtii is an algal model system for studying mammalian cilium formation and function. Here, we report a simple synchronization method that allows detection of small changes in ciliary length by minimizing variability in the population. We find that this method alters the key relationship between cell size and the amount of protein accumulated for flagellar growth. This provides a rapid alternative to traditional methods of cell synchronization for uncovering novel regulators of cilia.
Synthesis, assembly and physical properties of magnetic nanoparticles

Compared with the top-down lithographic techniques, bottom-up chemical synthesis and self-assembly approaches offer much more flexibilities in creating magnetic nanostructures with controlled size, shape, composition and physical properties. This review summarizes some of the latest developments in this field, with emphasis mainly on transition metals, their alloys and metal oxide nanoparticles. The focus is directed towards the conditions of individual particles as well as large assemblies of particles through colloidal chemistry. Furthermore, some of the future directions in nanomagnetism from the perspective of physical chemists is also presented.
Middle-way flexible docking: Pose prediction using mixed-resolution Monte Carlo in estrogen receptor α

There is a vast gulf between the two primary strategies for simulating protein-ligand interactions. Docking methods significantly limit or eliminate protein flexibility to gain great speed at the price of uncontrolled inaccuracy, whereas fully flexible atomistic molecular dynamics simulations are expensive and often suffer from limited sampling. We have developed a flexible docking approach geared especially for highly flexible or poorly resolved targets based on mixed-resolution Monte Carlo (MRMC), which is intended to offer a balance among speed, protein flexibility, and sampling power. The binding region of the protein is treated with a standard atomistic force field, while the remainder of the protein is modeled at the residue level with a Gō model that permits protein flexibility while saving computational cost. Implicit solvation is used. Here we assess three facets of the MRMC approach with implications for other docking studies: (i) the role of receptor flexibility in cross-docking pose prediction; (ii) the use of non-equilibrium candidate Monte Carlo (NCMC) and (iii) the use of pose-clustering in scoring. We examine 61 co-crystallized ligands of estrogen receptor α, an important cancer target known for its flexibility. We also compare the performance of the MRMC approach with Autodock smina. Adding protein flexibility, not surprisingly, leads to significantly lower total energies and stronger interactions between protein and ligand, but notably we document the important role of backbone flexibility in the improvement. The improved backbone flexibility also leads to improved performance relative to smina. Somewhat unexpectedly, our implementation of NCMC leads to only modestly improved sampling of ligand poses. Overall, the addition of protein flexibility improves the performance of docking, as measured by energy-ranked poses, but we do not find significant improvements based on cluster information or the use of NCMC. We discuss possible improvements for the model including alternative coarse-grained force fields, improvements to the treatment of solvation, and adding additional types of NCMC moves.
Characterizing the reproductive transcriptomic correlates of acute dehydration in males in the desert-adapted rodent, Peromyscus eremicus.

The understanding of genomic and physiological mechanisms related to how organisms living in extreme environments survive and reproduce is an outstanding question facing evolutionary and organismal biologists. One interesting example of adaptation is related to the survival of mammals in deserts, where extreme water limitation is common. Research on desert rodent adaptations has focused predominantly on adaptations related to surviving dehydration, while potential reproductive physiology adaptations for acute and chronic dehydration have been relatively neglected. This study aims to explore the reproductive consequences of acute dehydration by utilizing RNAseq data in the desert-specialized cactus mouse (Peromyscus eremicus). We exposed 22 male cactus mice to either acute dehydration or control (fully hydrated) treatment conditions, quasimapped testes-derived reads to a cactus mouse testes transcriptome, and then evaluated patterns of differential transcript and gene expression. Following statistical evaluation with multiple analytical pipelines, nine genes were consistently differentially expressed between the hydrated and dehydrated mice. We hypothesized that male cactus mice would exhibit minimal reproductive responses to dehydration; therefore, this low number of differentially expressed genes between treatments aligns with current perceptions of this species’ extreme desert specialization. However, these differentially expressed genes include Insulin-like 3 (Insl3), a regulator of male fertility and testes descent, as well as the solute carriers Slc45a3 and Slc38a5, which are membrane transport proteins that may facilitate osmoregulation. These results suggest that in male cactus mice, acute dehydration may be linked to reproductive modulation via Insl3, but not through gene expression differences in the subset of other a priori tested reproductive hormones. Although water availability is a reproductive cue in desert-rodents exposed to chronic drought, potential reproductive modification via Insl3 in response to acute water-limitation is a result which is unexpected in an animal capable of surviving and successfully reproducing year-round without available external water sources. Indeed, this work highlights the critical need for integrative research that examines every facet of organismal adaptation, particularly in light of global climate change, which is predicted, amongst other things, to increase climate variability, thereby exposing desert animals more frequently to the acute drought conditions explored here.
Quantitative reconstruction of time-varying 3D cell forces with traction force optical coherence microscopy.

Cellular traction forces (CTFs) play an integral role in both physiological processes and disease, and are a topic of interest in mechanobiology. Traction force microscopy (TFM) is a family of methods used to quantify CTFs in a variety of settings. State-of-the-art 3D TFM methods typically rely on confocal fluorescence microscopy, which can impose limitations on acquisition speed, volumetric coverage, and temporal sampling or coverage. In this report, we present the first quantitative implementation of a new TFM technique: traction force optical coherence microscopy (TF-OCM). TF-OCM leverages the capabilities of optical coherence microscopy and computational adaptive optics (CAO) to enable the quantitative reconstruction of 3D CTFs in scattering media with minute-scale temporal sampling. We applied TF-OCM to quantify CTFs exerted by isolated NIH-3T3 fibroblasts embedded in Matrigel, with five-minute temporal sampling, using images spanning a 500 × 500 × 500 μm3 field-of-view. Due to the reliance of TF-OCM on computational imaging methods, we have provided extensive discussion of the equations, assumptions, and failure modes of these methods. By providing high-throughput, label-free, volumetric imaging in scattering media, TF-OCM is well-suited to the study of 3D CTF dynamics, and may prove advantageous for the study of large cell collectives, such as the spheroid models prevalent in mechanobiology.
Deconfinement and chiral transition with the highly improved staggered quark (HISQ) action

We report on investigations of the chiral and deconfinement aspects of the finite temperature transition in 2+1 flavor QCD using the Highly Improved Staggered Quark (HISQ) action on lattices with temporal extent N? = 6 and N? = 8. We have performed the calculations for physical values of the strange quark mass ms and the light quark masses ml = 0.2ms and 0.05ms. Several finite temperature observables, including the renormalized Polyakov loop, the renormalized chiral condensate and the chiral susceptibility have been calculated. We also study the fluctuations and correlations of different conserved charges as well as the trace anomaly at finite temperature. We compare our findings with previous calculations that use different improved staggered fermion formulations: asqtad, p4 and stout.
Equilibrium Acidities and Homolytic Bond Dissociation Enthalpies of the Acidic C−H Bonds in P-(Para-substituted benzyl)triphenylphosphonium Cations and Related Cations

Equilibrium acidities (pKHA) of six P-(para-substituted benzyl)triphenylphosphonium (p-GC6H4CH2PPh3+) cations, P-allyltriphenylphosphonium cation, P-cinnamyltriphenylphosphonium cation, and As-(p-cyanobenzyl)triphenylarsonium cation, together with the oxidation potentials [Eox(A-)] of their conjugate anions (ylides) have been measured in dimethyl sulfoxide (DMSO) solution. The acidifying effects of the α-triphenylphosphonium groups on the acidic C−H bonds in toluene and propene were found to be ca 25 pKHA units (34 kcal/mol). Introduction of an electron-withdrawing group such as 4-NO2, 4-CN, or 4-Br into the para position of the benzyl ring in p-GC6H4CH2PPh3+ cations resulted in an additional acidity increase, but introduction of the 4-OEt electron-donating group decreases the acidity. The equilibrium acidities of p-GC6H4CH2PPh3+ cations were nicely linearly correlated with the Hammett σ- constants of the substituents (G) with a slope of 4.78 pKHA units (R2 = 0.992) (Figure 1). Reversible oxidation potent...
The effect of carbon subsidies on marine planktonic niche partitioning and recruitment during biofilm assembly.

The influence of resource availability on planktonic and biofilm microbial community membership is poorly understood. Heterotrophic bacteria derive some to all of their organic carbon (C) from photoautotrophs while simultaneously competing with photoautotrophs for inorganic nutrients such as phosphorus (P) or nitrogen (N). Therefore, C inputs have the potential to shift the competitive balance of aquatic microbial communities by increasing the resource space available to heterotrophs (more C) while decreasing the resource space available to photoautotrophs (less mineral nutrients due to increased competition from heterotrophs). To test how resource dynamics affect membership of planktonic communities and assembly of biofilm communities we amended a series of flow-through mesocosms with C to alter the availability of C among treatments. Each mesocosm was fed with unfiltered seawater and incubated with sterilized microscope slides as surfaces for biofilm formation. The highest C treatment had the highest planktonic heterotroph abundance, lowest planktonic photoautotroph abundance, and highest biofilm biomass. We surveyed bacterial 16S rRNA genes and plastid 23S rRNA genes to characterize biofilm and planktonic community membership and structure. Regardless of resource additions, biofilm communities had higher alpha diversity than planktonic communities in all mesocosms. Heterotrophic plankton communities were distinct from heterotrophic biofilm communities in all but the highest C treatment where heterotrophic plankton and biofilm communities resembled each other after 17 days. Unlike the heterotrophs, photoautotrophic plankton communities were different than photoautotrophic biofilm communities in composition in all treatments including the highest C treatment. Our results suggest that although resource amendments affect community membership and structure, microbial lifestyle (biofilm versus planktonic) has a stronger influence on community composition.
Simple and practical routes to enantiomerically pure 5-(trialkylsilyl)-2-cyclohexenones.

Enantiomerically pure chiral 5-silylated 2-cyclohexenones are easily prepared in high yield using as a key step kinetic resolution with a commercially available lipase. Fully active enzyme can be r...
A Temperature-Dependent Kinetics Study of the Important Stratospheric Reaction O(3P) + NO2 → O2 + NO

A laser flash photolysis-resonance fluorescence technique has been employed to investigate the kinetics of the important stratospheric reaction O(3P) + NO2 → O2 + NO (k1) as a function of temperatu...
Ring‐Closing Metathesis at Room Temperature within Nanometer Micelles using Water as the Only Solvent

Simply mixing a water-insoluble diolefinic substrate and Grubbs second generation catalyst in pure water containing small amounts of the amphiphile polyoxyethanyl α-tocopheryl sebacate (PTS) leads to efficient ring-closing metathesis.
The regiospecific synthesis of angularly-fused xanthones via the benzannulation of 1,2-adducts derived from 3-(o-anisoyl)-4-substituted cyclobutenediones and their dithianyl derivatives

Abstract Described in this paper is a new synthetic approach to angularly-fused and simpler substituted xanthones that is based upon the benzannulation of 2-(o-anisoyl)-4-heteroaryl-2-cyclobutenones and 2-(2-(o-anisyl)-1,3-dithian-2-yl)-4-alkenyl-2-cyclobutenones followed by facile intramolecular loss of methanol and cyclization to the xanthone.
Does an integrated focus on fractions and decimals improve at-risk students’ rational number magnitude performance?

Abstract The purpose of this study was to assess whether intervention with an integrated focus on fraction and decimal magnitude provides added value in improving rational number performance over intervention focused exclusively on fractions. We randomly assigned 4th graders with poor whole-number performance to 3 conditions: a business-as-usual control group and 2 variants of a validated fraction magnitude (FM) intervention. One variant of FM intervention included an integrated component on fraction-decimal magnitude (FM + DM); the other included a fraction applications component (FM + FAPP) to more closely mirror the validated FM intervention and to control for intervention time. Cross-classified partially-nested analyses (N = 225) provided the basis for 3 conclusions. First, FM intervention improves 4th-graders’ fraction understanding and applications. Second, effects of FM intervention, even without a focus on decimals, transfer to decimal number line performance. Third, an intervention component integrating fraction-decimal magnitude does not provide added value over FM intervention on fraction or decimal performance, except on decimal tasks paralleling intervention tasks.
HIV Infection and Incidence of Cardiovascular Diseases: An Analysis of a Large Healthcare Database

Background People living with HIV (PLWH) experience higher risk of myocardial infarction (MI) and heart failure (HF) compared with uninfected individuals. Risk of other cardiovascular diseases (CVD...
Joint estimation of the Epoch of Reionization power spectrum and foregrounds

The power spectrum of redshifted 21 cm emission brightness temperature fluctuations is a powerful probe of the Epoch of Reionization (EoR). However, bright foreground emission presents a significant impediment to its unbiased recovery from interferometric data. We build on the Bayesian power spectral estimation methodology introduced in Sims et al. 2016 and demonstrate that incorporating a priori knowledge of the spectral structure of foregrounds in the large spectral scale component of the data model enables significantly improved modelling of the foregrounds without increasing the model complexity. We explore two astrophysically motivated parametrisations of the large spectral scale model: (i) a constant plus power law model of the form $q_{0}+q_{1}(\nu/\nu_{0})^{b_{1}}$ for two values of $b_{1}$: $b_{1} = _\mathrm{GDSE}$ and $b_{1} = _\mathrm{EGS}$, the mean spectral indices of the Galactic diffuse synchrotron emission and extragalactic source foreground emission, respectively, and (ii) a constant plus double power law model of the form $q_{0}+q_{1}(\nu/\nu_{0})^{b_{1}}+q_{2}(\nu/\nu_{0})^{b_{2}}$ with $b_{1} = _\mathrm{GDSE}$ and $b_{2} = _\mathrm{EGS}$. We estimate the EoR power spectrum from simulated interferometric data consisting of an EoR signal, Galactic diffuse synchrotron emission, extragalactic sources and diffuse free-free emission from the Galaxy. We show that, by jointly estimating a model of the EoR signal with the constant plus double power law parametrisation of the large spectral scale model, unbiased estimates of the EoR power spectrum are recoverable on all spatial scales accessible in the data set, including on the large spatial scales that were found to be contaminated in earlier work.
The 2017 ISO New England System Operational Analysis and Renewable Energy Integration Study (SOARES)

Abstract The bulk electric power system in New England is fundamentally changing. The representation of nuclear, coal and oil generation facilities is set to dramatically fall, and natural gas, wind and solar facilities will come to fill their place. The introduction of variable energy resources (VERs) like solar and wind, however, necessitates fundamental changes in the power grid’s dynamic operation. VER forecasts are uncertain, and their profiles are intermittent; thus requiring greater quantities of operating reserves. This paper describes the methodology and the key findings of the 2017 ISO New England System Operational Analysis and Renewable Energy Integration Study (SOARES). This study was commissioned by the ISO New England stakeholders to investigate the effect of several scenarios of varying generation mix on normal operating reserves. The project was conducted using the holistic assessment approach called the Electric Power Enterprise Control System (EPECS) simulator. The study finds a minimal impact on current normal operating conditions in the ISO-NE system for scenarios with relatively low penetration of VERs. Nevertheless, for scenarios with a significant presence of VERs, the system may require additional amounts of both upward and downward load following reserves and upward and downward ramping reserves to effectively maintain reliable operations. In these scenarios, the curtailment of semi-dispatchable resources also becomes an integral part of balancing performance; in part to complement operating reserves and in part to mitigate the topological limitations of the system. Indeed, the integration of significant amounts of VERs in relatively remote regions significantly increases the potential of congestion on several key interfaces. In many of these scenarios, the system experiences heavy saturations of regulation reserves and their increase would enhance the response to residual imbalances. The concludes with final insights into the emerging roles of curtailment, energy storage, and demand response as integral parts of normal balancing performance.
BugSwarm: mining and continuously growing a dataset of reproducible failures and fixes

Fault-detection, localization, and repair methods are vital to software quality; but it is difficult to evaluate their generality, applicability, and current effectiveness. Large, diverse, realistic datasets of durably-reproducible faults and fixes are vital to good experimental evaluation of approaches to software quality, but they are difficult and expensive to assemble and keep current. Modern continuous-integration (CI) approaches, like Travis-CI, which are widely used, fully configurable, and executed within custom-built containers, promise a path toward much larger defect datasets. If we can identify and archive failing and subsequent passing runs, the containers will provide a substantial assurance of durable future reproducibility of build and test. Several obstacles, however, must be overcome to make this a practical reality. We describe BugSwarm, a toolset that navigates these obstacles to enable the creation of a scalable, diverse, realistic, continuously growing set of durably reproducible failing and passing versions of real-world, open-source systems. The BugSwarm toolkit has already gathered 3,091 fail-pass pairs, in Java and Python, all packaged within fully reproducible containers. Furthermore, the toolkit can be run periodically to detect fail-pass activities, thus growing the dataset continually.
Optimal terminal dimensionality reduction in Euclidean space

Let e∈(0,1) and X⊂d be arbitrary with |X| having size n>1. The Johnson-Lindenstrauss lemma states there exists f:X→m with m = O(e−2logn) such that ∀ x∈ X ∀ y∈ X, ||x−y||2 ≤ ||f(x)−f(y)||2 ≤ (1+e)||x−y||2 . We show that a strictly stronger version of this statement holds, answering one of the main open questions posed by Mahabadi et al. in STOC 2018: “∀ y∈ X” in the above statement may be replaced with “∀ y∈d”, so that f not only preserves distances within X, but also distances toX from the rest of space. Previously this stronger version was only known with the worse bound m = O(e−4logn). Our proof is via a tighter analysis of (a specific instantiation of) the embedding recipe of Mahabadi et al.
Endofunctors of Quandles and Racks

We show that the only endofunctors of the category of quandles commuting with the forgetful functor to sets are the power operations. We also give a similar statement for racks.
Jack polynomials and the coinvariant ring of $G(r,p,n)$

We study the coinvariant ring of the complex reflection group G(r,p,n) as a module for the corresponding rational Cherednik algebra H and its generalized graded affine Hecke subalgebra H. We construct a basis consisting of non-symmetric Jack polynomials and, using this basis, decompose the coinvariant ring into irreducible modules for H. The basis consists of certain non-symmetric Jack polynomials whose leading terms are the "descent monomials" for G(r,p,n) recently studied by Adin, Brenti, and Roichman as well as Bagno and Biagoli. The irreducible H-submodules of the coinvariant ring are their "colored descent representations".
Doubly robust off-policy value evaluation for reinforcement learning

We study the problem of off-policy value evaluation in reinforcement learning (RL), where one aims to estimate the value of a new policy based on data collected by a different policy. This problem is often a critical step when applying RL to real-world problems. Despite its importance, existing general methods either have uncontrolled bias or suffer high variance. In this work, we extend the doubly robust estimator for bandits to sequential decision-making problems, which gets the best of both worlds: it is guaranteed to be unbiased and can have a much lower variance than the popular importance sampling estimators. We demonstrate the estimator's accuracy in several benchmark problems, and illustrate its use as a subroutine in safe policy improvement. We also provide theoretical results on the inherent hardness of the problem, and show that our estimator can match the lower bound in certain scenarios.
Particle Transport in a 3D Duct by Adding and Doubling

ABSTRACTHow particles are transported through a duct by Lambertian reflection from duct walls is again considered. This popular transport example has been solved with most numerical transport metho...
Van der Corput's difference theorem: Some modern developments

Abstract We discuss various forms of the classical van der Corput’s difference theorem and explore applications to and connections with the theory of uniform distribution, ergodic theory, topological dynamics and combinatorics.
Emergent Predication Structure in Hidden State Vectors of Neural Readers.

A significant number of neural architectures for reading comprehension have recently been developed and evaluated on large cloze-style datasets. We present experiments supporting the emergence of “predication structure” in the hidden state vectors of these readers. More specifically, we provide evidence that the hidden state vectors represent atomic formulas 𝛷c where 𝛷 is a semantic property (predicate) and c is a constant symbol entity identifier.
On the multiple membranes problem

Abstract We establish the optimal regularity for solutions to the multiple membranes problem, and perform a blow-up analysis at points on the free boundary with the highest multiplicity. This leads to a complete classification of blow-up profiles in the plane. The main technical tool is a Weiss-type monotonicity formula.
Nearest-Neighbor and Contact Distance Distributions for Thomas Cluster Process

We characterize the statistics of nearest-neighbor and contact distance distributions for Thomas cluster process (TCP), which is a special case of Poisson cluster process. In particular, we derive the cumulative distribution function of the distance to the nearest point of TCP from a reference point for three different cases: 1) reference point is not a part of the point process; 2) it is chosen uniformly at random from the TCP; and 3) it is a randomly chosen point from a cluster chosen uniformly at random from the TCP. While the first corresponds to the contact distance distribution, the other two provide two different viewpoints for the nearest-neighbor distance distribution. Closed-form bounds are also provided for the first two cases.
Accumulation points of real Schur roots

Abstract Let k be an algebraically closed field and Q be an acyclic quiver with n vertices. Consider the category rep ( Q ) of finite dimensional representations of Q over k. The exceptional representations of Q, that is, the indecomposable objects of rep ( Q ) without self-extensions, correspond to the so-called real Schur roots of the usual root system attached to Q. These roots are special elements of the Grothendieck group Z n of rep ( Q ) . When we identify the dimension vectors of the representations (that is, the non-negative vectors of Z n ) up to positive multiple, we see that the real Schur roots can accumulate in some directions of R n ⊃ Z n . This paper is devoted to the study of these accumulation points. After giving new properties of the canonical decomposition of dimension vectors, we show how to use this decomposition to describe the rational accumulation points. Finally, we study the irrational accumulation points and we give a complete description of them in case Q is of weakly hyperbolic type.
Inherent Trade-Offs in the Fair Determination of Risk Scores

Recent discussion in the public sphere about algorithmic classification has involved tension between competing notions of what it means for a probabilistic classification to be fair to different groups. We formalize three fairness conditions that lie at the heart of these debates, and we prove that except in highly constrained special cases, there is no method that can satisfy these three conditions simultaneously. Moreover, even satisfying all three conditions approximately requires that the data lie in an approximate version of one of the constrained special cases identified by our theorem. These results suggest some of the ways in which key notions of fairness are incompatible with each other, and hence provide a framework for thinking about the trade-offs between them.
Galois groups in a family of dynatomic polynomials

Abstract For every nonconstant polynomial f ∈ Q [ x ] , let Φ 4 , f denote the fourth dynatomic polynomial of f. We determine here the structure of the Galois group and the degrees of the irreducible factors of Φ 4 , f for every quadratic polynomial f. As an application we prove new results related to a uniform boundedness conjecture of Morton and Silverman. In particular we show that if f is a quadratic polynomial, then, for more than 39 % of all primes p, f does not have a point of period four in Q p .
Smoothed analysis of the low-rank approach for smooth semidefinite programs

We consider semidefinite programs (SDPs) of size $n$ with equality constraints. In order to overcome scalability issues, Burer and Monteiro proposed a factorized approach based on optimizing over a matrix $Y$ of size $n\times k$ such that $X=YY^*$ is the SDP variable. The advantages of such formulation are twofold: the dimension of the optimization variable is reduced, and positive semidefiniteness is naturally enforced. However, optimization in $Y$ is non-convex. In prior work, it has been shown that, when the constraints on the factorized variable regularly define a smooth manifold, provided $k$ is large enough, for almost all cost matrices, all second-order stationary points (SOSPs) are optimal. Importantly, in practice, one can only compute points which approximately satisfy necessary optimality conditions, leading to the question: are such points also approximately optimal? To this end, and under similar assumptions, we use smoothed analysis to show that approximate SOSPs for a randomly perturbed objective function are approximate global optima, with $k$ scaling like the square root of the number of constraints (up to log factors). We particularize our results to an SDP relaxation of phase retrieval.
Uniquely $K_r$-Saturated Graphs

A graph $G$ is uniquely $K_r$-saturated if it contains no clique with $r$ vertices and if for all edges $e$ in the complement, $G+e$ has a unique clique with $r$ vertices. Previously, few examples of uniquely $K_r$-saturated graphs were known, and little was known about their properties. We search for these graphs by adapting orbital branching, a technique originally developed for symmetric integer linear programs. We find several new uniquely $K_r$-saturated graphs with $4 \leq r \leq 7$, as well as two new infinite families based on Cayley graphs for $\mathbb{Z}_n$ with a small number of generators.
Variational Inference for Sparse and Undirected Models

Undirected graphical models are applied in genomics, protein structure prediction, and neuroscience to identify sparse interactions that underlie discrete data. Although Bayesian methods for inference would be favorable in these contexts, they are rarely used because they require doubly intractable Monte Carlo sampling. Here, we develop a framework for scalable Bayesian inference of discrete undirected models based on two new methods. The first is Persistent VI, an algorithm for variational inference of discrete undirected models that avoids doubly intractable MCMC and approximations of the partition function. The second is Fadeout, a reparameterization approach for variational inference under sparsity-inducing priors that captures a posteriori correlations between parameters and hyperparameters with noncentered parameterizations. We find that, together, these methods for variational inference substantially improve learning of sparse undirected graphical models in simulated and real problems from physics and biology.
SE3-nets: Learning rigid body motion using deep neural networks

We introduce SE3-Nets which are deep neural networks designed to model and learn rigid body motion from raw point cloud data. Based only on sequences of depth images along with action vectors and point wise data associations, SE3-Nets learn to segment effected object parts and predict their motion resulting from the applied force. Rather than learning point wise flow vectors, SE3-Nets predict SE(3) transformations for different parts of the scene. Using simulated depth data of a table top scene and a robot manipulator, we show that the structure underlying SE3-Nets enables them to generate a far more consistent prediction of object motion than traditional flow based networks. Additional experiments with a depth camera observing a Baxter robot pushing objects on a table show that SE3-Nets also work well on real data.
Euler–Mahonian statistics and descent bases for semigroup algebras

Abstract We consider quotients of the unit cube semigroup algebra by particular Z r ≀ S n -invariant ideals. Using Grobner basis methods, we show that the resulting graded quotient algebra has a basis where each element is indexed by colored permutations ( π , ϵ ) ∈ Z r ≀ S n and each element encodes the negative descent and negative major index statistics on ( π , ϵ ) . This gives an algebraic interpretation of these statistics that was previously unknown. This basis of the Z r ≀ S n -quotients allows us to recover certain combinatorial identities involving Euler–Mahonian distributions of statistics.
Learning Sensor Multiplexing Design through Back-propagation

Recent progress on many imaging and vision tasks has been driven by the use of deep feed-forward neural networks, which are trained by propagating gradients of a loss defined on the final output, back through the network up to the first layer that operates directly on the image. We propose back-propagating one step further---to learn camera sensor designs jointly with networks that carry out inference on the images they capture. In this paper, we specifically consider the design and inference problems in a typical color camera---where the sensor is able to measure only one color channel at each pixel location, and computational inference is required to reconstruct a full color image. We learn the camera sensor's color multiplexing pattern by encoding it as layer whose learnable weights determine which color channel, from among a fixed set, will be measured at each location. These weights are jointly trained with those of a reconstruction network that operates on the corresponding sensor measurements to produce a full color image. Our network achieves significant improvements in accuracy over the traditional Bayer pattern used in most color cameras. It automatically learns to employ a sparse color measurement approach similar to that of a recent design, and moreover, improves upon that design by learning an optimal layout for these measurements.
STABLE DECOMPOSITIONS OF CERTAIN REPRESENTATIONS OF THE FINITE GENERAL LINEAR GROUPS

We prove that the irreducible decomposition of the permutation representation of GLn $$ \left({\mathbb{F}}_q\right) $$ on GLn $$ \left({\mathbb{F}}_q\right)/{GL}_{n-m}\left({\mathbb{F}}_q\right) $$ stabilizes for large n. We deduce, as a consequence, a representation stability theorem for finitely generated VIC-modules.
Constructing permutation arrays from groups

Let M(n, d) be the maximum size of a permutation array on n symbols with pairwise Hamming distance at least d. We use various combinatorial, algebraic, and computational methods to improve lower bounds for M(n, d). We compute the Hamming distances of affine semilinear groups and projective semilinear groups, and unions of cosets of AGL(1, q) and PGL(2, q) with Frobenius maps to obtain new, improved lower bounds for M(n, d). We give new randomized algorithms. We give better lower bounds for M(n, d) also using new theorems concerning the contraction operation. For example, we prove a quadratic lower bound for $$M(n,n-2)$$ for all $$n\equiv 2 \pmod 3$$ such that $$n+1$$ is a prime power.
A Formality Quasi-Isomorphism for Hochschild Cochains Over Rationals can be Constructed Recursively

It is believed arXiv:0808.2762, arXiv:math/9904055 that, among the coefficients entering Kontsevich's formality quasi-isomorphism arXiv:q-alg/9709040, there are irrational (possibly even transcendental) numbers. In this paper, we prove that a formality quasi-isomorphism for Hochschild cochains of a polynomial algebra over rationals can be constructed recursively. The proof that the proposed recursive algorithm works, is based on the existence of formality quasi-isomorphism over reals. However, the algorithm requires no explicit knowledge of the coefficients entering Kontsevich's construction. Although this algorithm completely bypasses Tamarkin's approach arXiv:math/0003052, arXiv:math/9803025, the construction is inspired by Proposition 5.8 from the classical paper (Algebra i Analiz, 1990) by V. Drinfeld.
Associativity properties of the symplectic sum

In this note we apply a 4-fold sum operation to develop an associativity rule for the pairwise symplectic sum. This allows us to show that certain diffeomorphic symplectic 4-manifolds made out of elliptic surfaces are in fact symplectically deformation equivalent. We also show that blow-up points can be traded from one side of a symplectic sum to another without changing the symplectic deformation class of the resulting manifold.
Group actions and rational ideals

We develop the theory of rational ideals for arbitrary associative algebras R without assuming the standard finiteness conditions, noetherianness or the Goldie property. The Amitsur-Martindale ring of quotients replaces the classical ring of quotients which underlies the previous definition of rational ideals but is not available in a general setting. Our main result concerns rational actions of an affine algebraic group G on R. Working over an algebraically closed base field, we prove an existence and uniqueness result for generic rational ideals in the sense of Dixmier: for every G-rational ideal I of R, the closed subset of the rational spectrum RatR that is defined by I is the closure of a unique G-orbit in RatR. Under additional Goldie hypotheses, this was established earlier by Mœglin and Rentschler (in characteristic 0) and by Vonessen (in arbitrary characteristic), answering a question of Dixmier.
The large scale geometry of strongly aperiodic subshifts of finite type

Abstract A subshift on a group G is a closed, G-invariant subset of A G , for some finite set A. It is said to be a subshift of finite type (SFT) if it is defined by a finite collection of “forbidden patterns”, to be strongly aperiodic if all point stabilizers are trivial, and weakly aperiodic if all point stabilizers are infinite index in G. We show that groups with at least 2 ends have a strongly aperiodic SFT, and that having such an SFT is a QI invariant for finitely presented groups. We show that a finitely presented torsion free group with no weakly aperiodic SFT must be QI-rigid. The domino problem on G asks whether the SFT specified by a given set of forbidden patterns is empty. We show that decidability of the domino problem is a QI invariant.
DeepDRR -- A Catalyst for Machine Learning in Fluoroscopy-guided Procedures

Machine learning-based approaches outperform competing methods in most disciplines relevant to diagnostic radiology. Interventional radiology, however, has not yet benefited substantially from the advent of deep learning, in particular because of two reasons: (1) Most images acquired during the procedure are never archived and are thus not available for learning, and (2) even if they were available, annotations would be a severe challenge due to the vast amounts of data. When considering fluoroscopy-guided procedures, an interesting alternative to true interventional fluoroscopy is in silico simulation of the procedure from 3D diagnostic CT. In this case, labeling is comparably easy and potentially readily available, yet, the appropriateness of resulting synthetic data is dependent on the forward model. In this work, we propose DeepDRR, a framework for fast and realistic simulation of fluoroscopy and digital radiography from CT scans, tightly integrated with the software platforms native to deep learning. We use machine learning for material decomposition and scatter estimation in 3D and 2D, respectively, combined with analytic forward projection and noise injection to achieve the required performance. On the example of anatomical landmark detection in X-ray images of the pelvis, we demonstrate that machine learning models trained on DeepDRRs generalize to unseen clinically acquired data without the need for re-training or domain adaptation. Our results are promising and promote the establishment of machine learning in fluoroscopy-guided procedures.
Linear Convergence of Stochastic Iterative Greedy Algorithms With Sparse Constraints

Motivated by recent work on stochastic gradient descent methods, we develop two stochastic variants of greedy algorithms for possibly non-convex optimization problems with sparsity constraints. We prove linear convergence 1 in expectation to the solution within a specified tolerance. This generalized framework is specialized to the problems of sparse signal recovery in compressed sensing and low-rank matrix recovery, giving methods with provable convergence guarantees that often outperform their deterministic counterparts. We also analyze the settings, where gradients and projections can only be computed approximately, and prove the methods are robust to these approximations. We include many numerical experiments, which align with the theoretical analysis and demonstrate these improvements in several different settings. 1 Linear convergence is sometimes called exponential convergence.
Global solution curves for self-similar equations

Abstract We consider positive solutions of a semilinear Dirichlet problem Δ u + λ f ( u ) = 0 , for | x | 1 , u = 0 , when | x | = 1 on a unit ball in R n . For four classes of self-similar equations it is possible to parameterize the entire (global) solution curve through the solution of a single initial value problem. This allows us to derive results on the multiplicity of solutions, and on their Morse indices. In particular, we easily recover the classical results of D.D. Joseph and T.S. Lundgren [6] on the Gelfand problem. Surprisingly, the situation turns out to be different for the generalized Gelfand problem, where infinitely many turns are possible for any space dimension n ≥ 3 . We also derive detailed results for the equation modeling electrostatic micro-electromechanical systems (MEMS), in particular we easily recover the main result of Z. Guo and J. Wei [4] , and we show that the Morse index of the solutions increases by one at each turn. We also consider the self-similar Henon's equation.