cssi/SciSciGPT-SciSciNet huggingface dataset:
Catalyst controlled regioselective Suzuki cross-coupling of 2-(4-bromophenyl)-5-chloropyrazine

Abstract The Suzuki cross-coupling between 2-(4-bromophenyl)-5-chloropyrazine and a range of aryl boronic acids has been investigated. The regioselectivity of the reaction can be switched between the aryl bromide and pyrazinyl chloride positions by changing the ligand associated with the palladium catalyst. Xantphos has shown excellent selectivity for the pyrazinyl chloride, with most other ligands showing preferential selectivity for the aryl bromide.
iCn3D, a web-based 3D viewer for sharing 1D/2D/3D representations of biomolecular structures.

Motivation Build a web-based 3D molecular structure viewer focusing on interactive structural analysis. Results iCn3D (I-see-in-3D) can simultaneously show 3D structure, 2D molecular contacts and 1D protein and nucleotide sequences through an integrated sequence/annotation browser. Pre-defined and arbitrary molecular features can be selected in any of the 1D/2D/3D windows as sets of residues and these selections are synchronized dynamically in all displays. Biological annotations such as protein domains, single nucleotide variations, etc. can be shown as tracks in the 1D sequence/annotation browser. These customized displays can be shared with colleagues or publishers via a simple URL. iCn3D can display structure-structure alignments obtained from NCBI's VAST+ service. It can also display the alignment of a sequence with a structure as identified by BLAST, and thus relate 3D structure to a large fraction of all known proteins. iCn3D can also display electron density maps or electron microscopy (EM) density maps, and export files for 3D printing. The following example URL exemplifies some of the 1D/2D/3D representations: https://www.ncbi.nlm.nih.gov/Structure/icn3d/full.html?mmdbid=1TUP&showanno=1&show2d=1&showsets=1. Availability and implementation iCn3D is freely available to the public. Its source code is available at https://github.com/ncbi/icn3d. Supplementary information Supplementary data are available at Bioinformatics online.
Syntheses of methylpyridine and methylpyridine N-oxide decorated benzoxazine and naphthoxazine platforms

Abstract Simple, aqueous-based syntheses of methylpyridine and methylpyridine N-oxide decorated 3,4-dihydro-2H-naphthoxazine and 2,3-dihydro-1H-naphthoxazine monomers, as well as thermally promoted syntheses of 3,4-dihydro-2H-benzoxazine monomers and bisoxazine methylpyridine derivatives of substituted 1,5-, 2,6-, and 2,7-dihydroxynaphthalenes are described. The crystal structures of two derivatives are presented.
Modeling heterogeneous melting in phase change memory devices

We present thermodynamic crystallization and melting models and calculate phase change velocities in Ge2Sb2Te5 based on kinetic and thermodynamic parameters with a focus on the impacts of grain boundary melting. The calculated phase change velocities are strong functions of grain size, with smaller grains beginning to melt at lower temperatures. Phase change velocities are continuous functions of temperature which determine crystallization and melting rates. Hence, set and reset times as well as power and peak current requirements for switching are strong functions of grain size. Grain boundary amorphization can lead to a sufficient increase in cell resistance for small-grain phase change materials even if the whole active region does not completely amorphize. Isolated grains left in the amorphous regions, the quenched-in nuclei, facilitate templated crystal growth and significantly reduce set times for phase change memory cells. We demonstrate the significance of heterogeneous melting through 2-D electrothermal simulations coupled with a dynamic material phase change model. Our results show reset and set times on the order of ∼1 ns for 30 nm wide confined nanocrystalline (7.5 nm–25 nm radius crystals) phase change memory cells.
Allylic aminations with hindered secondary amine nucleophiles catalyzed by heterobimetallic Pd-Ti complexes.

Phosphinoamide-scaffolded heterobimetallic palladium–titanium complexes are highly effective catalysts for allylic aminations of allylic chlorides with hindered secondary amine nucleophiles. Three titanium-containing ligands are shown to assemble active catalysts in situ and enable catalysis at room temperature. A variety of sterically bulky secondary amines are efficiently allylated in high yields with as little as 1 mol % palladium catalyst. Piperidine and pyrrolidine products are also efficiently generated via intramolecular aminations with hindered amine nucleophiles.
Cs[Si3O6(OH)] and Rb[Si2O4(OH)]: two novel phyllosilicates

The crystal structures of two novel phyl­losilicates with compositions Cs[Si3O6(OH)] (caesium hydroxo­hexa­oxotetra­otri­silicate) and Rb[Si2O4(OH)] (rubidium hydroxo­hexa­oxotetrao­di­silicate) have been characterized by X-ray diffraction. The topology of the caesium phyl­losilicate silica sheet consists of interconnected four- and six-membered rings and thus differs from all of the previously reported phyl­losilicates. The topology of the rubidium phyl­losilicate silica sheet consists of six-membered rings only, in boat conformations, resulting in a corrugated sheet similar to that observed in δ-Na2Si2O5. Both of the title compounds exhibit the characteristic sandwich structure of sheet silicates, with the Cs atom ninefold coordinated and the Rb atom eightfold coordinated to the framework O atoms.
Stereoselective aldol coupling of α,β-acetylenic ketones promoted by MgI2

A highly stereoselective synthesis of (Z)-β-iodovinyl ketone has been achieved with the tandem formation of CC and CI bonds in a three-component reaction. This new catalysis utilizes MgI2 as a Lewis acid as well as an iodine source for a Michael-type addition. α,β-Acetylenic ketone is initially converted to an active β-iodo allenolate intermediate and then can be attacked by a variety of aldehydes to afford Z-selective Baylis–Hillman adducts in excellent yields.
Kinetic resolution in palladium-catalyzed asymmetric allylic alkylations by a P,O ligand system.

Through the investigation of peptide-based phosphine oxazoline ligands, a simple P,O ligand system was developed. This system provides palladium complexes that are capable of a very high degree of kinetic resolution of 1,3-diphenylprop-2-enyl acetate. The isolated palladium complex was synthesized, characterized, and determined to be an effective procatalyst.
On the number of siblings and p-th cousins in a large population sample

The number of individuals in a random sample with close relatives in the sample is a quantity of interest when designing Genome Wide Association Studies and other cohort based genetic, and non-genetic, studies. In this paper, we develop expressions for the distribution and expectation of the number of p-th cousins in a sample from a population of size N under two diploid Wright–Fisher models. We also develop simple asymptotic expressions for large values of N. For example, the expected proportion of individuals with at least one p-th cousin in a sample of K individuals, for a diploid dioecious Wright–Fisher model, is approximately $$1-e^{-(2^{2p-1})K/N}$$ . Our results show that a substantial fraction of individuals in the sample will have at least a second cousin if the sampling fraction (K / N) is on the order of $$10^{-2}$$ . This confirms that, for large cohort samples, relatedness among individuals cannot easily be ignored.
Chemistry of fluoroalkanoyl peroxides, 1980–1998

Abstract A fluoroalkanoyl peroxide is a convenient tool for the preparation of various fluoroalkylated endcapped oligomers via a radical process. These new oligomers have high potential for new functional fluorinated materials through their surfactant, biological and gelling properties.
The ring opening of cyclopropylidene to allene: global features of the reaction surface

The global features of the groundstate ring opening of cyclopropylidene to allene are studied by means ofab-initio FORS MCSCF calculations based on a minimal AO basis set. The energy surface is completely mapped out in terms of three reaction coordinates, namely the CCC ring-opening angle and two angles describing the rotations of the CH2 groups. For each choice of these three variables, the twelve remaining internal coordinates are optimized by energy minimization. In the initial phase of the reaction, as the CCC angle opens, the CH2 groups rotate in a disrotatory manner, maintainingC s symmetry. This uphill reaction path leads to a transition region which occurs early, for a CCC angle of about 84°. In this transition region the reaction path branches into two pathways which are each others' mirror images. The system exhibits thus abifurcating transition region. Passed this region, the two pathways are overall conrotatory in character. However, these downhill reaction paths to the products are poorly defined because, from a CCC opening angle of about 90° on,the CH 2 groups can rotate freely and isoenergetically in a synchronized, cogwheel-like manner and this disrotatory motion can mix unpredictably with the conrotatory downhill motion. There is no preference for any one of the two reaction pathways yielding the two stereoisomers of allene and the reaction is thereforenonstereospecific with respect to the numbered hydrogen atoms. The global surface is documented by means of contour maps representing slices corresponding to constant CCC angles. The bifurcating transition region is mapped in detail.
Ecology, not distance, explains community composition in parasites of sky-island Audubon’s Warblers

Abstract Haemosporidian parasites of birds are ubiquitous in terrestrial ecosystems, but their coevolutionary dynamics remain poorly understood. If species turnover in parasites occurs at a finer scale than turnover in hosts, widespread hosts would encounter diverse parasites, potentially diversifying as a result. Previous studies have shown that some wide-ranging hosts encounter varied haemosporidian communities throughout their range, and vice-versa. More surveys are needed to elucidate mechanisms that underpin spatial patterns of diversity in this complex multi-host multi-parasite system. We sought to understand how and why a community of avian haemosporidian parasites varies in abundance and composition across elevational transects in eight sky islands in southwestern North America. We tested whether bird community composition, environment, or geographic distance explain haemosporidian parasite species turnover in a widespread host that harbors a diverse haemosporidian community, the Audubon’s Warbler (Setophaga auduboni). We tested predictors of infection using generalized linear models, and predictors of bird and parasite community dissimilarity using generalized dissimilarity modeling. Predictors of infection differed by parasite genus: Parahaemoproteus was predicted by elevation and climate, Leucocytozoon varied idiosyncratically among mountains, and Plasmodium was unpredictable, but rare. Parasite turnover was nearly three-fold higher than bird turnover and was predicted by elevation, climate, and bird community composition, but not geographic distance. Haemosporidian communities vary strikingly at fine spatial scales (hundreds of kilometers), across which the bird community varies only subtly. The finer scale of turnover among parasites implies that their ranges may be smaller than those of their hosts. Avian host species should encounter different parasite species in different parts of their ranges, resulting in spatially varying selection on host immune systems. The fact that parasite turnover was predicted by bird turnover, even when considering environmental characteristics, implies that host species or their phylogenetic history plays a role in determining which parasite species will be present in a community.
Regioselective C-2 and C-6 Substitution of (S)-Nicotine and Nicotine Derivatives

Regioselective deprotonations of (S)-nicotine and derivatives at the C-2 and C-6 positions of the pyridine ring were performed in good to excellent yields. These methodologies allow the direct introduction of a plethora of functional groups onto the pyridine ring of nicotine.
Synthesis of 4-(N,N-Dialkylamino)benzyltriphenylphosphonium Iodides from Hydroxymethyltriphenylphosphonium Iodide and N,N-Dialkylaniline

Abstract Reinvestigation of the one-pot synthesis of 4-(N,N-dialkylamino)benzyltriphenylphosphonium iodides has shown that the product forms after the initial condensation of triphenylphosphine upon formaldehyde.
Stereoselective synthesis of conformationally constrained reverse turn dipeptide mimetics

Abstract Peptide side chains play critical roles in the event of molecular recognition. In order to study the bioactive conformation of parent peptides, a concise and straightforward five-step synthesis of [5.5]-bicyclic reverse turn dipeptide mimetic scaffolds with side chain functionality at the i +1 and i +2 positions has been developed. In the bicyclic structure, two dihedral angles ( ψ 2 and φ 3 ) are greatly restricted.
Gamma-ray burst spectra and time histories from 2 to 400 keV

Abstract The Gamma-Ray burst detector on Ginga consisted of a proportional counter to observe the x-rays and a scintillation counter to observe the gamma-rays. It was ideally suited to study the x-rays associated with gamma-ray bursts (GRBs). Ginga detected ∼ 120 GRBs and 22 of them had sufficient statistics to determine spectra from 2 to 400 keV. Although the Ginga and BATSE trigger criteria were very similar, the distribution of spectral parameters was different. Ginga observed bend energies in the spectra down to 2 keV and had a larger fraction of bursts with low energy power law indexes greater than zero. The average ration of energy in the x-ray band (2 to 10 keV) compared to the gamma-ray band (50 to 300 keV) was 24%. Some events had more energy in the x-ray band than in the gamma-ray band. One Ginga event had a period of time preceding the gamma rays that was effectively pure x-ray emission. This x-ray “preactivity” might be due to the penchant for the GRB time structure to be broader at lower energy rather than a different physical process. The x-rays tend to rise and fall slower than the gamma rays but they both tend to peak at about the same time. This argues against models involving the injection of relativistic electrons that cool by synchrotron radiation.
Strongly birefringent pb3o2cl2 nanobelts.

Orthorhombic Pb3O2Cl2 (mendipite) nanobelts micrometers in length and tens of nanometers wide were synthesized by a solventless thermolysis of a single-source precursor in the presence of capping l...
Regio-controlled ene-yne photochemical [2 + 2] cycloaddition using silicon as a tether

Abstract Substituted cyclobutenes were synthesized by irradiation of silicon tethered ene-ynes. Irradiation of a silicon tethered bis-phenylalkyne resulted in cycloaddition and rearrangement to a substituted naphthalene. A diradical intermediate which resembles known DNA cleaving molecules is proposed.
Asymmetric nitroaldol reaction catalyzed by a C2-symmetric bisoxazolidine ligand.

A C2-symmetric bisoxazolidine was found to effectively catalyze the asymmetric Henry reaction of aliphatic and aromatic aldehydes. β-Hydroxy nitroalkanes were produced in up to 99% yield and 95% ee. The bisoxazolidine-catalyzed nitroaldol formation requires relatively short reaction times, proceeds under mild conditions and is applicable to a wide range of substrates including sterically hindered aldehydes.
A simple and rapid entry to 5-alkyl (aryl)-5-hydroxy-3,4-diarylfuranones and 3a-hydroxy-1-aryl-2,3a, 4,5-tetrahydronaphthofuranones via a tandem esterification and oxidative cyclization process

A synthesis of 5-hydroxy-3,4-diarylfuranones and related derivatives is accomplished by the reaction of arylacetic acid with α-bromoketone in the presence of base and atmospheric oxygen. A variety of compounds were synthesized in good to excellent yield and many are of potential biological interest.
A Novel Synthesis of the Fluorene Skeleton

Abstract 1,4,6-Trimethyl-9-trifluoroacetylfluorene 1 has been synthesized in one pot from 2-chloro-p-xylene 2 and has been characterized by single-crystal X-ray diffraction. © 1997 Elsevier Science Ltd.
NaCeP2Se6, Cu0.4Ce1.2P2Se6, Ce4(P2Se6)3, and the Incommensurately Modulated AgCeP2Se6: New Selenophosphates Featuring the Ethane-Like [P2Se6]4- Anion

NaCeP(2)Se(6), Cu(0.4)Ce(1.2)P(2)Se(6), and AgCeP(2)Se(6) were prepared from nearly stoichiometric proportions of the starting materials plus extra selenium at 750-850 degrees C. Ce(1.33)P(2)Se(6) (or Ce(4)(P(2)Se(6))(3)) was obtained from the same reaction that produced Cu(0.4)Ce(1.2)P(2)Se(6). The structure of all four compounds was determined by single-crystal X-ray diffraction. NaCeP(2)Se(6), Cu(0.4)Ce(1.2)P(2)Se(6), and Ce(1.33)P(2)Se(6) crystallize in the monoclinic space group, P2(1)/c, with a = 12.1422(2), b = 7.6982(1), c = 11.7399(2) A, beta = 111.545(1) degrees and Z = 4 for NaCeP(2)Se(6); a = 12.040(1), b = 7.6418(8), c = 11.700(1) A, beta = 111.269(2) degrees and Z = 4 for Cu(0.4)Ce(1.2)P(2)Se(6); and a = 6.8057(5), b = 22.969(2), c = 11.7226(8) A, beta = 124.096(1) degrees and Z = 6 for Ce(1.33)P(2)Se(6). NaCeP(2)Se(6) has a two-dimensional character and is isostructural to the KLnP(2)Q(6) family of compounds, where Ln = La, Ce, and Pr for Q = Se and Ln = La for Q = S. The structure consists of [CeP(2)Se(6)](n)(n-) layers which are separated by Na(+) cations. Each layer contains CeSe(9) distorted, tricapped trigonal prisms and [P(2)Se(6)](4-) ethane-like anions. Cu(0.4)Ce(1.2)P(2)Se(6) possesses a similar structure; however, substitution of the alkali metal by copper and cerium atoms renders the structure three dimensional. Ce(1.33)P(2)Se(6) is the pure lanthanide member of this structure type. In this three-dimensional structure, there are three cerium metal sites which are partially occupied. The structure of AgCeP(2)Se(6) was solved in the superspace group P2(1)/c(alpha0gamma) and represents an incommensurately modulated version of the KLnP(2)Q(6) structure type, with a = 9.971(5), b = 7.482(3), c = 11.757(4) A, beta = 145.630(9) degrees, q = 0.3121(18)a + 0.4116(19)c, and Z = 2. The structures of the compounds reported here and those of the KLnP(2)Q(6) family are highly related to the monoclinic-II, M(II)PQ(3) structure type (where M = Pb, Sn, Ca, and Sr for Q = S and M = Pb and Sn for Q = Se). Optical and vibrational spectroscopic characterization is also reported.
Catalytic conversion of β-hydroxy carboxylic acids to olefins by tungsten(Vi) complexes: A new acyl group transfer catalyst

Oxotungsten tetrachloride catalyzes the conversion of {beta}-hydroxy carboxylic acids to olefins, in the presence of base. The reaction proceeds in high yield, stereospecifically, and with high catalyst turnover. Examination of the likely stoichiometric steps for {beta}-hydroxy carboxylic acid activation shows the formation of intermediate chelates, structures of which were studied by {sup 1}H NMR. The role of the base was probed by using both {sup 1}H and {sup 183}W NMR, and it was shown that base simply deprotonates the chelate; base does not coordinate to the W center. {beta}-Lactones were the initial products of this sequence from which decarboxylation occurred to give the olefinic product.
Calcium-induced differentiation in normal human colonoid cultures: Cell-cell / cell-matrix adhesion, barrier formation and tissue integrity.

Background and aims The goal of the study was to assess calcium alone and Aquamin, a multi-mineral natural product that contains magnesium and detectable levels of 72 trace elements in addition to calcium, for capacity to affect growth and differentiation in colonoid cultures derived from histologically-normal human colon tissue. Methods Colonoid cultures were maintained in a low-calcium (0.25 mM) medium or in medium supplemented with an amount of calcium (1.5–3.0 mM), either from calcium alone or Aquamin for a period of two weeks. This was shown in a previous study to induce differentiation in colonoids derived from large adenomas. Changes in growth, morphological features and protein expression profile were assessed at the end of the incubation period using a combination of phase-contrast and scanning electron microscopy, histology and immunohistology, proteomic assessment and transmission electron microscopy. Results Unlike the previously-studied tumor-derived colonoids (which remained un-differentiated in the absence of calcium-supplementation), normal tissue colonoids underwent differentiation as indicated by gross and microscopic appearance, a low proliferative index and high-level expression of cytokeratin 20 in the absence of intervention (i.e., in control condition). Only modest additional changes were seen in these parameters with either calcium alone or Aquamin (providing up to 3.0 mM calcium). In spite of this, proteomic analysis and immunohistochemistry revealed that both interventions induced strong up-regulation of proteins that promote cell-cell and cell-matrix adhesive functions, barrier formation and tissue integrity. Transmission electron microscopy revealed an increase in desmosomes in response to intervention. Conclusions These findings demonstrate that colonoids derived from histologically normal human tissue can undergo differentiation in the presence of a low ambient calcium concentration. However, higher calcium levels induce elaboration of proteins that promote cell-cell and cell-matrix adhesion. These changes could lead to improved barrier function and improved colon tissue health.
Does Forecast‐Accuracy‐Based Allocation Induce Customers to Share Truthful Order Forecasts?

Through a behavioral study, we investigate buyers’ strategic order forecasting behavior in a multi-period setting under a forecast accuracy based allocation policy, where the supplier allocates (proportionally) more inventory to the buyer with the better order forecast accuracy in case of scarce supply. We developed an interactive game that simulates a supply chain in which one supplier sells a key component to two buyers, who in turn sell to consumers. In each period, buyers share forecasts of future orders with their supplier. The participants in the game play the role of a buyer, while the supplier is automated. Our experimental findings suggest that rewarding forecast accuracy in allocating inventory can significantly improve the order forecast accuracy of the buyers and reduce their forecast inflation behavior. Interestingly, even without communication of the policy, buyers learn over time that more accurate forecasts lead to better service from their supplier and improve their order forecast accuracy.
Circuit Models of Low-Dimensional Shared Variability in Cortical Networks.

Summary Trial-to-trial variability is a reflection of the circuitry and cellular physiology that make up a neuronal network. A pervasive yet puzzling feature of cortical circuits is that despite their complex wiring, population-wide shared spiking variability is low dimensional. Previous model cortical networks cannot explain this global variability, and rather assume it is from external sources. We show that if the spatial and temporal scales of inhibitory coupling match known physiology, networks of model spiking neurons internally generate low-dimensional shared variability that captures population activity recorded in vivo. Shifting spatial attention into the receptive field of visual neurons has been shown to differentially modulate shared variability within and between brain areas. A top-down modulation of inhibitory neurons in our network provides a parsimonious mechanism for this attentional modulation. Our work provides a critical link between observed cortical circuit structure and realistic shared neuronal variability and its modulation.
Synthesis and tubulin interaction of thiocolchicines containing an isothiocyanato group. Synthesis of C(2)-deuterated and C(2)-14C-labeled 7-isothiocyanatodeacetamidothiocolchicine

Synthesis of isothiocyanato substituted thiocolchicines XI - XIV is described. Introduction of an isotope label is demonstrated with the deuterated isothiocyanate XII and the 14 C-labeled analog XIII . These isothiocyanates inhibit tubulin polymerization at low concentration. In addition, the 14 C-labeled XIII forms covalent bond(s) with tubulin. Unfortunately, the covalent reaction while rapid, is not inhibited by preincubation of tubulin with colchicine. The covalent interaction of XIII with tubulin thus appears to be nonspecific, limiting its use as a marker of the colchicine binding site on tubulin.
Practical hydroxymethylation of aldehydes and ketones via pinacol cross-coupling reactions with paraformaldehyde

Abstract A general and practical method for the direct hydroxymethylation of aldehydes and ketones via pinacol cross-coupling with paraformaldehyde is described. The reaction is promoted by vanadium(II) ions which are conveniently generated from the reduction of VCl 3 (THF) 3 with zinc dust. Excellent yields of terminal diols are obtained and stereoselective coupling is observed with some chiral aldehydes and ketones.
Technological Changes, Offshoring, and the Labor Share

Existing studies on the downward trend in the labor share of income mostly focus on changes within individual countries. I document, however, that half of the global decline in the labor share of income can be traced to the relocation of activities between countries. I develop a two-country model to show that when the relative price of investment goods falls, production activities with a small elasticity of substitution between capital and labor tend to get offshored from high- to low-wage countries. The model provides an explanation as to why such relocation may drive the labor share down in both developed and developing economies, as well as globally.
A Vector Threshold Model for the Simultaneous Spread of Correlated Influence

Spread of influence is one of the most widely studied propagation processes in the literature on complex networks. Examples include the rise of collective action to join a riot and diffusion of beliefs, norms, and cultural fads, to name a few. Most existing works on modeling influence propagation consider a single content (e.g., an opinion, decision, product, political view, etc.) spreading over a network independent from everything else. However, most real-life examples involve multiple correlated contents spreading simultaneously and exhibiting positive (e.g., opinions on same-sex marriage and gun control) or negative (e.g., opinions on universal health care and tax-relief for the &#x201C;rich&#x201D;) correlation. To accommodate these cases, this paper proposes the vector threshold model, as an extension of the widely used Watts threshold model for complex contagions. Here, the state of a node is represented by a binary vector representing their opinion on a number of content items. Nodes switch their states based on the influence they receive from their neighbors in the network. The influence is represented by a vector containing the proportion of neighbors who support each content; both positively and negatively correlated contents can be captured in this formulation by using different rules for switching node states. Our main result is concerned with the expected size of global cascades, i.e., cases where a randomly chosen node can initiate a propagation that eventually reaches a positive fraction of the whole population. We also derive conditions on network structure for global cascades to be possible. Analytic results are supported by a numerical study.
Variance Components and Generalized Sobol' Indices ∗

This paper introduces generalized Sobol' indices, compares strategies for their estimation, and makes a systematic search for efficient estimators. Of particular interest are contrasts, sums of squares, and indices of bilinear form which allow a reduced number of function evaluations compared to alternatives. The bilinear framework includes some efficient estimators from Saltelli [Comput. Phys. Comm., 145 (2002), pp. 280--297] and Mauntz [Global Sensitivity Analysis of General Nonlinear Systems, Master's thesis, Imperial College, London, 2002] as well as some new estimators for specific variance components and mean dimensions. This paper also provides a bias corrected version of the estimator of Janon et al. [Asymptotic Normality and Efficiency of Two Sobol' Index Estimators, technical report, INRIA, Rocquencourt, France] and extends the bias correction to generalized Sobol' indices. Some numerical comparisons are given.
Intrinsic chirality of graphs in 3-manifolds

The main result of this paper is that for every closed, connected, orientable, irreducible 3-manifold $M$, there is an integer $ n_M$ such that any abstract graph with no automorphism of order 2 which has a 3-connected minor whose genus is more than $n_M$ has no achiral embedding in $M$. By contrast, the paper also proves that for every graph $\gamma$, there are infinitely many closed, connected, orientable, irreducible 3-manifolds $M$ such that some embedding of $\gamma$ in $M$ is pointwise fixed by an orientation reversing involution of $M$.
On the Lebesgue constant of weighted Leja points for Lagrange interpolation on unbounded domains

This work focuses on weighted Lagrange interpolation on an unbounded domain, and analyzes the Lebesgue constant for a sequence of weighted Leja points. The standard Leja points are a nested sequence of points defined on a compact subset of the real line, and can be extended to unbounded domains with the introduction of a weight function $w:\mathbb{R}\rightarrow [0,1]$. Due to a simple recursive formulation in one dimension, such abscissas provide a foundation for high-dimensional approximation methods such as sparse grid collocation, deterministic least squares, and compressed sensing. Just as in the unweighted case of interpolation on a compact domain, we use results from potential theory to prove that the Lebesgue constant for the Leja points grows subexponentially with the number of interpolation nodes.
The branch locus for one-dimensional Pisot tiling spaces

If phi is a Pisot substitution of degree d, then the inflation and substitution homeomorphism Phi on the tiling space T_Phi factors via geometric realization onto a d-dimensional solenoid. Under this realization, the collection of Phi-periodic asymptotic tilings corresponds to a finite set that projects onto the branch locus in a d-torus. We prove that if two such tiling spaces are homeomorphic, then the resulting branch loci are the same up to the action of certain affine maps on the torus.
Fast Maximization of Non-Submodular, Monotonic Functions on the Integer Lattice

The optimization of submodular functions on the integer lattice has received much attention recently, but the objective functions of many applications are non-submodular. We provide two approximation algorithms for maximizing a non-submodular function on the integer lattice subject to a cardinality constraint; these are the first algorithms for this purpose that have polynomial query complexity. We propose a general framework for influence maximization on the integer lattice that generalizes prior works on this topic, and we demonstrate the efficiency of our algorithms in this context.
Unsupervised Word Mapping Using Structural Similarities in Monolingual Embeddings

Most existing methods for automatic bilingual dictionary induction rely on prior alignments between the source and target languages, such as parallel corpora or seed dictionaries. For many language...
Small-Noise Analysis and Symmetrization of Implicit Monte Carlo Samplers

Implicit samplers are algorithms for producing independent, weighted samples from multivariate probability distributions. These are often applied in Bayesian data assimilation algorithms. We use Laplace asymptotic expansions to analyze two implicit samplers in the small noise regime. Our analysis suggests a symmetrization of the algorithms that leads to improved implicit sampling schemes at a relatively small additional cost. Computational experiments confirm the theory and show that symmetrization is effective for small noise sampling problems.© 2016 Wiley Periodicals, Inc.
Nonlinear sequential accepts and rejects for identification of top arms in stochastic bandits

We address the M-best-arm identification problem in multi-armed bandits. A player has a limited budget to explore K arms (M < K), and once pulled, each arm yields a reward drawn (independently) from a fixed, unknown distribution. The goal is to find the top M arms in the sense of expected reward. We develop an algorithm which proceeds in rounds to deactivate arms iteratively. At each round, the budget is divided by a nonlinear function of remaining arms, and the arms are pulled correspondingly. Based on a decision rule, the deactivated arm at each round may be accepted or rejected. The algorithm outputs the accepted arms that should ideally be the top M arms. We characterize the decay rate of the misidentification probability and establish that the nonlinear budget allocation proves to be useful for different problem environments (described by the number of competitive arms). We provide comprehensive numerical experiments showing that our algorithm outperforms the state-of-the-art using suitable nonlinearity.
Algorithmic Connections between Active Learning and Stochastic Convex Optimization

Interesting theoretical associations have been established by recent papers between the fields of active learning and stochastic convex optimization due to the common role of feedback in sequential querying mechanisms. In this paper, we continue this thread in two parts by exploiting these relations for the first time to yield novel algorithms in both fields, further motivating the study of their intersection. First, inspired by a recent optimization algorithm that was adaptive to unknown uniform convexity parameters, we present a new active learning algorithm for one-dimensional thresholds that can yield minimax rates by adapting to unknown noise parameters. Next, we show that one can perform d-dimensional stochastic minimization of smooth uniformly convex functions when only granted oracle access to noisy gradient signs along any coordinate instead of real-valued gradients, by using a simple randomized coordinate descent procedure where each line search can be solved by 1-dimensional active learning, provably achieving the same error convergence rate as having the entire real-valued gradient. Combining these two parts yields an algorithm that solves stochastic convex optimization of uniformly convex and smooth functions using only noisy gradient signs by repeatedly performing active learning, achieves optimal rates and is adaptive to all unknown convexity and smoothness parameters.
Post-Selection Inference for ℓ1-Penalized Likelihood Models.

We present a new method for post-selection inference for l1 (lasso)-penalized likelihood models, including generalized regression models. Our approach generalizes the post-selection framework presented in Lee et al. (2013). The method provides p-values and confidence intervals that are asymptotically valid, conditional on the inherent selection done by the lasso. We present applications of this work to (regularized) logistic regression, Cox's proportional hazards model and the graphical lasso. We do not provide rigorous proofs here of the claimed results, but rather conceptual and theoretical sketches.
To Adjust or Not to Adjust? Sensitivity Analysis of M-Bias and Butterfly-Bias

"M-Bias," as it is called in the epidemiologic literature, is the bias introduced by conditioning on a pretreatment covariate due to a particular "M-Structure" between two latent factors, an observed treatment, an outcome, and a "collider." This potential source of bias, which can occur even when the treatment and the outcome are not confounded, has been a source of considerable controversy. We here present formulae for identifying under which circumstances biases are inflated or reduced. In particular, we show that the magnitude of M-Bias in linear structural equation models tends to be relatively small compared to confounding bias, suggesting that it is generally not a serious concern in many applied settings. These theoretical results are consistent with recent empirical findings from simulation studies. We also generalize the M-Bias setting (1) to allow for the correlation between the latent factors to be nonzero, and (2) to allow for the collider to be a confounder between the treatment and the outcome. These results demonstrate that mild deviations from the M-Structure tend to increase confounding bias more rapidly than M-Bias, suggesting that choosing to condition on any given covariate is generally the superior choice. As an application, we re-examine a controversial example between Professors Donald Rubin and Judea Pearl.
The c=1 String Theory S-Matrix Revisited

We revisit the perturbative S-matrix of c = 1 string theory from the worldsheet perspective. We clarify the origin of the leg pole factors, the non-analyticity of the string amplitudes, and the validity as well as limitations of earlier computations based on resonance momenta. We compute the tree level 4-point amplitude and the genus one 2-point reflection amplitude by numerically integrating Virasoro conformal blocks with DOZZ structure constants on the sphere and on the torus, with sufficiently generic complex Liouville momenta, and find agreement with known answers from the c = 1 matrix model.
Efficient estimation of quantiles in missing data models

Abstract We propose a novel targeted maximum likelihood estimator (TMLE) for quantiles in semiparametric missing data models. Our proposed estimator is locally efficient, n -consistent, asymptotically normal, and doubly robust, under regularity conditions. We use Monte Carlo simulation to compare our proposed method to existing estimators. Our proposed estimator has superior performance, with relative efficiency up to three times smaller than the inverse probability weighted estimator (IPW), and up to two times smaller than the augmented IPW. This research is motivated by a causal inference research question with highly variable treatment assignment probabilities, and a heavy tailed, highly variable outcome. Estimation of causal effects on the mean is a hard problem in such scenarios because the information bound is generally small. In our application, the efficiency bound for estimating the effect on the mean is possibly infinite. This rules out n -consistent inference and reduces the power for testing hypothesis of no treatment effect on the mean. In our simulations, using the effect on the median allows us to test a location-shift hypothesis with 30% more power. This allows us to make claims about the effectiveness of treatment that would have been hard to make for the effect on the mean. We provide R code to implement the proposed estimators.
Ramification theory for Artin–Schreier extensions of valuation rings

Abstract The goal of this paper is to generalize and refine the classical ramification theory of complete discrete valuation rings to more general valuation rings, in the case of Artin–Schreier extensions. We define refined versions of invariants of ramification in the classical ramification theory and compare them. Furthermore, we can treat the defect case.
An overview of the current understanding of Gamma Ray Bursts in the Fermi era

Gamma-ray bursts are the most luminous explosions in the Universe, and their origin as well as mechanism are the focus of intense research and debate. More than three decades since their serendipitous discovery, followed by several breakthroughs from space-borne and ground-based observations, they remain one of the most interesting astrophysical phenomena yet to be completely understood. Since the launch of Fermi with its unprecedented energy band width spanning seven decades, the study of gamma-ray burst research has entered a new phase. Here we review the current theoretical understanding and observational highlights of gamma-ray burst astronomy and point out some of the potential promises of multi-wavelength observations in view of the upcoming ground based observational facilities .
Entire downward translating solitons to the mean curvature flow in Minkowski space

In this paper, we study entire translating solutions $u(x)$ to a mean curvature flow equation in Minkowski space. We show that if $\Sigma=\{(x, u(x))| x\in\mathbb{R}^n\}$ is a strictly spacelike hypersurface, then $\Sigma$ reduces to a strictly convex rank k soliton in $\mathbb{R}^{k, 1}$ (after splitting off trivial factors) whose "blowdown" converges to a multiple $\lambda\in(0, 1)$ of a positively homogeneous degree one convex function in $\mathbb{R}^k$. We also show that there is nonuniqueness as the rotationally symmetric solution may be perturbed to a solution by an arbitrary smooth order one perturbation.
Conjugacy of Cartan Subalgebras in Solvable Leibniz Algebras and Real Leibniz Algebras

We extend conjugacy results from Lie algebras to their Leibniz algebra generalizations. The proofs in the Lie case depend on anti-commutativity. Thus it is necessary to find other paths in the Leibniz case. Some of these results involve Cartan subalgebras. Our results can be used to extend other results on Cartan subalgebras. We show an example here and others will be shown in future work.
Use of dempster-shafer conflict metric to detect interpretation inconsistency

A model of the world built from sensor data may be incorrect even if the sensors are functioning correctly. Possible causes include the use of inappropriate sensors (e.g. a laser looking through glass walls), sensor inaccuracies accumulate (e.g. localization errors), the a priori models are wrong, or the internal representation does not match the world (e.g. a static occupancy grid used with dynamically moving objects). We are interested in the case where the constructed model of the world is flawed, but there is no access to the ground truth that would allow the system to see the discrepancy, such as a robot entering an unknown environment. This paper considers the problem of determining when something is wrong using only the sensor data used to construct the world model. It proposes 11 interpretation inconsistency indicators based on the Dempster-Shafer conflict metric, Con, and evaluates these indicators according to three criteria: ability to distinguish true inconsistency from sensor noise (classification), estimate the magnitude of discrepancies (estimation), and determine the source(s) (if any) of sensing problems in the environment (isolation). The evaluation is conducted using data from a mobile robot with sonar and laser range sensors navigating indoor environments under controlled conditions. The evaluation shows that the Gambino indicator performed best in terms of estimation (at best 0.77 correlation), isolation, and classification of the sensing situation as degraded (7% false negative rate) or normal (0% false positive rate). While the evaluation is limited to 2D world models, the use of the Dempster-Shafer conflict metric to detect significant inconsistencies in data appears useful and could lead to systems which autonomously switch information sources to ensure the best mission performance, learn the relative contribution and reliability of sources for different environments, and reason about which sources to use under what circumstances.
On maximum, typical and generic ranks

We show that for several notions of rank including tensor rank, Waring rank, and generalized rank with respect to a projective variety, the maximum value of rank is at most twice the generic rank. We show that over the real numbers, the maximum value of the real rank is at most twice the smallest typical rank, which is equal to the (complex) generic rank.
Length Four Polynomial Automorphisms

We study the structure of length four polynomial automorphisms of R[X, Y] when R is a unique factorization domain. The results from this study are used to prove that, if SL m (R[X 1, X 2,…, X n ]) ...
The Kazhdan–Lusztig polynomial of a matroid

Abstract We associate to every matroid M a polynomial with integer coefficients, which we call the Kazhdan–Lusztig polynomial of M, in analogy with Kazhdan–Lusztig polynomials in representation theory. We conjecture that the coefficients are always non-negative, and we prove this conjecture for representable matroids by interpreting our polynomials as intersection cohomology Poincare polynomials. We also introduce a q-deformation of the Mobius algebra of M, and use our polynomials to define a special basis for this deformation, analogous to the canonical basis of the Hecke algebra. We conjecture that the structure coefficients for multiplication in this special basis are non-negative, and we verify this conjecture in numerous examples.
Spatially transformed adversarial examples

Recent studies show that widely used deep neural networks (DNNs) are vulnerable to carefully crafted adversarial examples. Many advanced algorithms have been proposed to generate adversarial examples by leveraging the $\mathcal{L}_p$ distance for penalizing perturbations. Researchers have explored different defense methods to defend against such adversarial attacks. While the effectiveness of $\mathcal{L}_p$ distance as a metric of perceptual quality remains an active research area, in this paper we will instead focus on a different type of perturbation, namely spatial transformation, as opposed to manipulating the pixel values directly as in prior works. Perturbations generated through spatial transformation could result in large $\mathcal{L}_p$ distance measures, but our extensive experiments show that such spatially transformed adversarial examples are perceptually realistic and more difficult to defend against with existing defense systems. This potentially provides a new direction in adversarial example generation and the design of corresponding defenses. We visualize the spatial transformation based perturbation for different examples and show that our technique can produce realistic adversarial examples with smooth image deformation. Finally, we visualize the attention of deep networks with different types of adversarial examples to better understand how these examples are interpreted.
Rigid components in fixed-lattice and cone frameworks.

We study the fundamental algorithmic rigidity problems for generic frameworks periodic with respect to a xed lattice or a
Testing homogeneity of proportions from sparse binomial data with a large number of groups

In this paper, we consider testing the homogeneity for proportions in independent binomial distributions, especially when data are sparse for large number of groups. We provide broad aspects of our proposed tests such as theoretical studies, simulations and real data application. We present the asymptotic null distributions and asymptotic powers for our proposed tests and compare their performance with existing tests. Our simulation studies show that none of tests dominate the others; however, our proposed test and a few tests are expected to control given sizes and obtain significant powers. We also present a real example regarding safety concerns associated with Avandia (rosiglitazone) in Nissen and Wolski (New Engl J Med 356:2457–2471, 2007).