cssi/SciSciGPT-SciSciNet huggingface dataset:
In situ X-ray diffraction study of cesium exchange in synthetic umbite.

The exchange of Cs{sup +} into H{sub 1.22}K{sub 0.84}ZrSi{sub 3}O{sub 9} {center_dot} 2.16H{sub 2}O (umbite-(HK)) was followed in situ using time-resolved X-ray diffraction at the National Synchrotron Light Source. The umbite framework (space group P2{sub 1}/c with cell dimensions of a = 7.2814(3) {angstrom}, b = 10.4201(4) {angstrom}, c = 13.4529(7) {angstrom}, and {beta} = 90.53(1){sup o}) consists of wollastonite-like silicate chains linked by isolated zirconia octahedra. Within umbite-(HK) there are two unique ion exchange sites in the tunnels running parallel to the a-axis. Exchange Site 1 is marked by 8 member-ring (MR) windows in the bc-plane and contains K{sup +} cations. Exchange Site 2 is marked by a larger 8-MR channel parallel to [100], and contains H{sub 2}O molecules. The occupancy of the Cs{sup +} cations through these channels was modeled by Rietveld structure refinements of the diffraction data and demonstrated that there is a two-step exchange process. The incoming Cs{sup +} ions populated the larger 8-MR channel (Exchange Site 2) first and then migrated into the smaller 8-MR channel. During the exchange process a structural change occurs, transforming the exchanger from monoclinic P2{sub 1}/c to orthorhombic P2{sub 1}2{sub 1}2{sub 1}. This structural change occurs when Cs{sup +} occupancymore » in the small cavity becomes greater than 0.50. The final in situ ion exchange diffraction pattern was refined to yield umbite-(CsK) with the molecular formula H{sub 0.18}K{sub 0.45}Cs{sub 1.37}ZrSi{sub 3}O{sub 9} {center_dot} 0.98H{sub 2}O and possessing an orthorhombic unit cell with dimensions a = 10.6668(8) {angstrom}, b = 13.5821(11) {angstrom}, c = 7.3946(6) {angstrom}. Solid state {sup 133}Cs MAS NMR showed there is only a slight difference between the two cavities electronically. Valence bond sums for the completely occupied Exchange Site 1 demonstrate that Cs-O bonds of up to 3.8 {angstrom} contribute to the coordination of the Cs{sup +} cation.« less
Diastereoselective Free Radical Halogenation, Azidation, and Rearrangement of β-Silyl Barton Esters

Barton esters of β-silylcarboxylic acids were decomposed by photolysis alone in organic solvents or in the presence of ethanesulfonyl azide or bromotrichloromethane. Products of the reaction, β-silylthiopyridyl ethers, β-silyl azides, or alkenes, were formed with significant control of stereochemistry.
ON SOLVING GENERAL LINEAR EQUATIONS IN THE SET OF NATURAL NUMBERS

The utility of this article is that it establishes if the number of the natural solutions of a general linear equation is limited or not. We will show also a method of solving, using integer numbers, the equation ax - by = c (which represents a generalization of lemmas 1 and 2 of [4]), an example of solving a linear equation with 3 unknowns in N, and some considerations on solving, using natural numbers, equations with n unknowns.
On binocular vision: The geometric horopter and Cyclopean eye.

We study geometric properties of horopters defined by the criterion of equality of angle. Our primary goal is to derive the precise geometry for anatomically correct horopters. When eyes fixate on points along a curve in the horizontal visual plane for which the vergence remains constant, this curve is the larger arc of a circle connecting the eyes' rotation centers. This isovergence circle is known as the Vieth-Muller circle. We show that, along the isovergence circular arc, there is an infinite family of horizontal horopters formed by circular arcs connecting the nodal points. These horopters intersect at the point of symmetric convergence. We prove that the family of 3D geometric horopters consists of two perpendicular components. The first component consists of the horizontal horopters parametrized by vergence, the point of the isovergence circle, and the choice of the nodal point location. The second component is formed by straight lines parametrized by vergence. Each of these straight lines is perpendicular to the visual plane and passes through the point of symmetric convergence. Finally, we evaluate the difference between the geometric horopter and the Vieth-Muller circle for typical near fixation distances and discuss its possible significance for depth discrimination and other related functions of vision that make use of disparity processing.
Patterning a surface so as to speed nucleation from solution

Motivated by the question of how to pattern a surface in order to best speed nucleation from solution, we build on the work of Page and Sear [Phys. Rev. Lett., 2006, 97, 65701] and calculate rates and free energy profiles for nucleation in the 3d Ising model in the presence of cuboidal pores. Pores of well-chosen aspect ratio can dramatically speed nucleation relative to a planar surface made of the same material, while badly chosen pores provide no such enhancement. For a given pore, the maximum nucleation rate is achieved when one of its two horizontal dimensions attains a critical length, largely irrespective of the other dimension (provided that the latter is large enough). This observation implies that patterning a surface with repeated copies of a well-chosen pore is a better strategy for speeding nucleation than e.g. scoring long grooves in it.
Palladium-catalyzed carbene insertion into vinyl halides and trapping with amines.

Palladium is shown to catalyze the three-component coupling of vinyl halides, trimethylsilyldiazomethane, and amines to generate allylamines. The mechanism is believed to involve formation of an R−...
Dynamic Brain Interactions during Picture Naming

Brain computations involve multiple processes by which sensory information is encoded and transformed to drive behavior. These computations are thought to be mediated by dynamic interactions between populations of neurons. Here, we demonstrate that human brains exhibit a reliable sequence of neural interactions during speech production. We use an autoregressive Hidden Markov Model (ARHMM) to identify dynamical network states exhibited by electrocorticographic signals recorded from human neurosurgical patients. Our method resolves dynamic latent network states on a trial-by-trial basis. We characterize individual network states according to the patterns of directional information flow between cortical regions of interest. These network states occur consistently and in a specific, interpretable sequence across trials and subjects: the data support the hypothesis of a fixed-length visual processing state, followed by a variable-length language state, and then by a terminal articulation state. This empirical evidence validates classical psycholinguistic theories that have posited such intermediate states during speaking. It further reveals these state dynamics are not localized to one brain area or one sequence of areas, but are instead a network phenomenon.
Single-crystal growth of Ln2MIn8 (Ln = La, Ce; M = Rh, Ir): Implications for the heavy-fermion ground state

The structures of the heavy-fermion compounds, Ce2MIn8 (M = Rh, Ir), and the nonmagnetic analogues, La2MIn8 (M = Rh, Ir), were determined by single-crystal X-ray diffraction. These materials adopt a tetragonal structure in the space group P4/mmm, Z = 1. Lattice parameters are a = 4.6670(4) A and c = 12.247(4) A for Ce2RhIn8, a = 4.6897(6) A and c = 12.1950(11) A for Ce2IrIn8, a = 4.6980(2) A and c = 12.3440(4) A for La2RhIn8, and a = 4.70600(10) A and c = 12.3120(4) A for La2IrIn8. Antiferromagnetism and/or unconventional superconductivity at low temperature have been found in CeCoIn5, CeRhIn5, CeIrIn5, and Ce2RhIn8. We compare structural trends with properties of the ground states of these materials. The LnnMIn3n+2 (n = 1, 2, ∞; Ln = La, Ce; M = Rh, Ir) intergrowth homologous series presents a unique opportunity to study structure−property relationships in this new family of heavy-fermions.
Thermal stability of hexagonal OsB2

The synthesis of novel hexagonal ReB{sub 2}-type OsB{sub 2} ceramic powder was performed by high energy ball milling of elemental Os and B powders. Two different sources of B powder have been used for this mechanochemical synthesis. One B powder consisted of a mixture of amorphous and crystalline phases and a mixture of {sup 10}B and {sup 11}B isotopes with a fine particle size, while another B powder was a purely crystalline (rhombohedral) material consisting of enriched {sup 11}B isotope with coarse particle size. The same Os powder was used for the synthesis in both cases. It was established that, in the first case, the hexagonal OsB{sub 2} phase was the main product of synthesis with a small quantity of Os{sub 2}B{sub 3} phase present after synthesis as an intermediate product. In the second case, where coarse crystalline {sup 11}B powder was used as a raw material, only Os{sub 2}B{sub 3} boride was synthesized mechanochemically. The thermal stability of hexagonal OsB{sub 2} powder was studied by heating under argon up to 876 °C and cooling in vacuo down to −225 °C. During the heating, the sacrificial reaction 2OsB{sub 2}+3O{sub 2}→2Os+2B{sub 2}O{sub 3} took place due to presence of O{sub 2}/watermore » vapor molecules in the heating chamber, resulting in the oxidation of B atoms and formation of B{sub 2}O{sub 3} and precipitation of Os metal out of the OsB{sub 2} lattice. As a result of such phase changes during heating, the lattice parameters of hexagonal OsB{sub 2} changed significantly. The shrinkage of the a lattice parameter was recorded in 276–426 °C temperature range upon heating, which was attributed to the removal of B atoms from the OsB{sub 2} lattice due to oxidation followed by the precipitation of Os atoms and formation of Os metal. While significant structural changes occurred upon heating due to presence of O{sub 2}, the hexagonal OsB{sub 2} ceramic demonstrated good phase stability upon cooling in vacuo with linear shrinkage of the lattice parameters and no phase changes detected during cooling. - Graphical abstract: The in situ high temperature XRD contour plot (A) and XRD patterns (B) of h-OsB{sub 2} upon heating and cooling under an argon atmosphere. - Highlights: • Different boron sources were compared for the synthesis of h-OsB{sub 2}. • The phase stability and thermal behavior of h-OsB{sub 2} were studied by in situ XRD. • Shrinkage of the a lattice parameter was observed from 276 °C to 426 °C upon heating. • Oxidation of OsB{sub 2} produced B vacancies led to the shrinkage of a lattice parameter.« less
Next Generation Muon g − 2 Experiments

I report on the progress of two new muon anomalous magnetic moment experiments, which are in advanced design and construction phases. The goal of Fermilab E989 is to reduce the experimental uncertainty of $$a_\mu$$ from Brookhaven E821 by a factor of 4; that is, $$\delta a_\mu \sim 16 \times 10^{-11}$$, a relative uncertainty of 140~ppb. The method follows the same magic-momentum storage ring concept used at BNL, and pioneered previously at CERN, but muon beam preparation, storage ring internal hardware, field measuring equipment, and detector and electronics systems are all new or upgraded significantly. In contrast, J-PARC E34 will employ a novel approach based on injection of an ultra-cold, low-energy, muon beam injected into a small, but highly uniform magnet. Only a small magnetic focusing field is needed to maintain storage, which distinguishes it from CERN, BNL and Fermilab. E34 aims to roughly match the previous BNL precision in their Phase~1 installation.
The ion channel ppk301 controls freshwater egg-laying in the mosquito Aedes aegypti.

When they bite humans, mosquitoes can transmit dangerous diseases. For example, the Aedes aegypti mosquito spreads the viruses that cause yellow fever, Zika and dengue fever. Only the female mosquitoes feed on blood so they can obtain the nutrients they need to develop their eggs. Once they are ready, the insects lay their eggs in carefully selected sites where fresh water collects: if instead they choose places where the water is too salty, their offspring will die. To find a suitable site, a mosquito ‘tastes’ the water by dipping in its legs and mouthparts, which activates the insect’s sensory neurons and sends signals to its brain. However, it remains unclear exactly how the mosquitoes can distinguish between fresh and salty water. To address this question, Matthews, Younger and Vosshall used a combination of genetic and imaging approaches to study female Ae. aegypti mosquitoes. These experiments identified a gene known as ppk301 that is necessary for the mosquitoes to successfully lay their eggs in the right type of water. Mutant Ae. aegypti mosquitoes lacking the ppk301 gene did not properly lay eggs in fresh water even when given the opportunity. Further experiments found that ppk301 was present in specific neurons in the legs and mouthparts of the mosquitoes. In leg neurons, ppk301 played a crucial role in sensing the presence of water and in stimulating the mosquitoes to lay eggs in water containing low levels of salt. However, these cells still responded to salt, even when lacking ppk301: other unidentified genes must therefore also be involved in preventing the mosquitoes from breeding in water that is too salty. Every year, Aedes aegypti and other mosquitoes infect hundreds of millions of people and cause 500,000 deaths. Knowing exactly how mosquitoes breed could help to develop traps, repellents and other strategies to stop the insects from multiplying.
Assortative mating can impede or facilitate fixation of underdominant alleles

Underdominant mutations have fixed between divergent species, yet classical models suggest that rare underdominant alleles are purged quickly except in small or subdivided populations. We predict that underdominant alleles that also influence mate choice, such as those affecting coloration patterns visible to mates and predators alike, can fix more readily. We analyze a mechanistic model of positive assortative mating in which individuals have n chances to sample compatible mates. This one-parameter model naturally spans random mating (n=1) and complete assortment (n→∞), yet it produces sexual selection whose strength depends non-monotonically on n. This sexual selection interacts with viability selection to either inhibit or facilitate fixation. As mating opportunities increase, underdominant alleles fix as frequently as neutral mutations, even though sexual selection and underdominance independently each suppress rare alleles. This mechanism allows underdominant alleles to fix in large populations and illustrates how life history can affect evolutionary change.
Copper-Catalyzed Electrophilic Amination of Organoboron Compounds

A new procedure for direct transformation of alkenes to tertiary alkylamines based on hydroboration and copper-catalyzed amination of alkylboranes is described. The new method is presented in a broader context provided by a brief analysis of various approaches to the formation of anti-Markovnikov hydroamination products. A short discussion of the reaction development, scope, and the mechanism are also provided. Finally, the extension of this methodology to the preparation of hindered anilines from aryl ­boronic esters is presented.
Turbulent pressure support in the outer parts of galaxy clusters

We use 3D magnetohydrodynamics simulations with anisotropic thermal conduction to study turbulence due to the magnetothermal instability (MTI) in the intracluster medium (ICM) of galaxy clusters. The MTI grows on time-scales of ≲1 Gyr and is capable of driving vigorous, sustained turbulence in the outer parts of galaxy clusters if the temperature gradient is maintained in spite of the rapid thermal conduction. If this is the case, turbulence due to the MTI can provide up to 5–30 per cent of the pressure support beyond r500 in galaxy clusters, an effect that is strongest for hot, massive clusters. The turbulence driven by the MTI is generally additive to other sources of turbulence in the ICM, such as that produced by structure formation. This new source of non-thermal pressure support reduces the observed Sunyaev–Zel’dovich (SZ) signal and X-ray pressure gradient for a given cluster mass and introduces a cluster mass and temperature-gradient-dependent bias in SZ and X-ray mass estimates of clusters. This additional physics may also need to be taken into account when estimating the matter power spectrum normalization, σ8, through simulation templates from the observed amplitude of the SZ power spectrum.
Topological and kinetic determinants of the modal matrices of dynamic models of metabolism

Large-scale kinetic models of metabolism are becoming increasingly comprehensive and accurate. A key challenge is to understand the biochemical basis of the dynamic properties of these models. Linear analysis methods are well-established as useful tools for characterizing the dynamic response of metabolic networks. Central to linear analysis methods are two key matrices: the Jacobian matrix (J) and the modal matrix (M-1) arising from its eigendecomposition. The modal matrix M-1 contains dynamically independent motions of the kinetic model near a reference state, and it is sparse in practice for metabolic networks. However, connecting the structure of M-1 to the kinetic properties of the underlying reactions is non-trivial. In this study, we analyze the relationship between J, M-1, and the kinetic properties of the underlying network for kinetic models of metabolism. Specifically, we describe the origin of mode sparsity structure based on features of the network stoichiometric matrix S and the reaction kinetic gradient matrix G. First, we show that due to the scaling of kinetic parameters in real networks, diagonal dominance occurs in a substantial fraction of the rows of J, resulting in simple modal structures with clear biological interpretations. Then, we show that more complicated modes originate from topologically-connected reactions that have similar reaction elasticities in G. These elasticities represent dynamic equilibrium balances within reactions and are key determinants of modal structure. The work presented should prove useful towards obtaining an understanding of the dynamics of kinetic models of metabolism, which are rooted in the network structure and the kinetic properties of reactions.
A synthesis of abemaciclib utilizing a Leuckart–Wallach reaction

Abstract A concise total synthesis of CDK 4/6 inhibitor abemaciclib is described. The synthesis uses a Suzuki coupling, followed by a Hartwig–Buchwald amination to join three of the four subunits. The final step is a reductive amination utilizing Leuckart–Wallach conditions. Key to the Leuckart–Wallach reaction was the addition of trimethyl orthoformate to remove water formed during the reaction, allowing the reaction to go to completion.
m-Terphenyl Anchored Palladium Diphosphinite PCP-Pincer Complexes That Promote the Suzuki−Miyaura Reaction Under Mild Conditions

Diphosphinite PCP-pincer pro-ligands anchored by a meta-terphenyl backbone were synthesized. These pro-ligands, [2,6-(2-Ph2POC6H4)2C6H3X] (3a X = I, 3b X = Br) and [2,6-(2-iPr2POC6H4)2C6H3X] (4a X = I, 4b X = Br) upon reaction with Pd2(dba)3 yield PCP palladium pincer complexes [2,6-(2-Ph2POC6H4)2C6H3PdX] (5a X = I, 5b X = Br) and [2,6-(2-iPr2POC6H4)2C6H3PdX] (6a X = I, 6b X = Br). The structures of 5a−b and 6a−b were determined by single crystal X-ray diffraction analyses. Complexes 5b and 6b were evaluated for their efficacy in promoting catalytic Suzuki−Miyaura CC coupling reactions. A variety of aryl bromides efficiently underwent CC coupling reactions with p-tolylboronic acid with high yields in the presence of either 5b or 6b. Compound 6b also proved to be a very active pro-catalyst for the coupling of aryl chlorides with p-tolylboronic acid. Excellent to good yields (in some cases greater than 90%) were achieved even with electron rich or sterically hindered aryl chlorides.
Yeast Ded1 promotes 48S translation pre-initiation complex assembly in an mRNA-specific and eIF4F-dependent manner

DEAD-box RNA helicase Ded1 is thought to resolve secondary structures in mRNA 5'-untranslated regions (5'-UTRs) that impede 48S preinitiation complex (PIC) formation at the initiation codon. We reconstituted Ded1 acceleration of 48S PIC assembly on native mRNAs in a pure system, and recapitulated increased Ded1-dependence of mRNAs that are Ded1-hyperdependent in vivo. Stem-loop (SL) structures in 5'-UTRs of native and synthetic mRNAs increased the Ded1 requirement to overcome their intrinsically low rates of 48S PIC recruitment. Ded1 acceleration of 48S assembly was greater in the presence of eIF4F, and domains mediating one or more Ded1 interactions with eIF4G or helicase eIF4A were required for efficient recruitment of all mRNAs; however, the relative importance of particular Ded1 and eIF4G domains were distinct for each mRNA. Our results account for the Ded1 hyper-dependence of mRNAs with structure-prone 5'-UTRs, and implicate an eIF4E·eIF4G·eIF4A·Ded1 complex in accelerating 48S PIC assembly on native mRNAs.
The ring opening of cyclopropylidene to allene and the isomerization of allene:ab initio interpretation of the electronic rearrangements in terms of quasi-atomic orbitals

A full optimized reaction space (FORS) remains invariant under arbitrary orthogonal transformations among its configuration-generating molecular orbitals. Localization of the latter for a FORS wavefunction yields molecular orbitals withquasi-atomic character which can be interpreted asmolecule-adapted minimal-basis-set atomic orbitals. In terms of these quasi-atomic FORS MOs, the configuration mixing in the FORS wavefunction, the representation of the density matrix, and the expansions of the natural orbitals provide information about the interactions that are responsible for the molecular energy changes. A basis-set-independent population analysis can be formulated which accomplishes the objectives of Mulliken's population analysis without the drawbacks stemming from the basis-set dependence of the latter. Through application of these procedures, explanations can be found for various features of the potential energy surface governing the ring opening of cyclopropylidene and the isomerization of allene.
Variation in pigmentation gene expression is associated with distinct aposematic color morphs in the poison frog Dendrobates auratus

Color and pattern phenotypes have clear implications for survival and reproduction in many species. However, the mechanisms that produce this coloration are still poorly characterized, especially at the genomic level. Here we have taken a transcriptomics-based approach to elucidate the underlying genetic mechanisms affecting color and pattern in a highly polytypic poison frog. We sequenced RNA from the skin from four different color morphs during the final stage of metamorphosis and assembled a de novo transcriptome. We then investigated differential gene expression, with an emphasis on examining candidate color genes from other taxa. Overall, we found differential expression of a suite of genes that control melanogenesis, melanocyte differentiation, and melanocyte proliferation (e.g., tyrp1, lef1, leo1, and mitf) as well as several differentially expressed genes involved in purine synthesis and iridophore development (e.g., arfgap1, arfgap2, airc, and gart). Our results provide evidence that several gene networks known to affect color and pattern in vertebrates play a role in color and pattern variation in this species of poison frog.
Synthesis of Nucleosides Utilizing Condensation Reaction

Many nucleoside analogues, which lack 2'-substituents, have been known to be a useful compound as anticancer and anti-virus agents. On the other hand, synthesis of these derivatives utilizing the condensation reactions between sugars and nucleic bases have a difficulty in the stereoselectivity of these reactions. In this paper, our investigation on the condensation reactions with some 2-deoxysugars are discussed in the point of stereoselectivity. Transformations to 2', 3'-dideoxynucleosides and 2', 3'-didehydro-2', 3'-dideoxynucleosides are also described.
Gold-catalyzed intramolecular cyclization of alkynones with pyridine anhydrobases

Abstract 4-Alkylpyridines functionalized with alkynyl amide substituents can be converted to pyridyl-substituted lactams via Au-catalyzed cyclization at the pyridine benzylic carbon. These transformations proceed through alkylidene dihydropyridine (anhydrobase) intermediates and demonstrate the ability to utilize these species in metal-catalyzed C–C bond forming reactions.
A microbial perspective on the life‐history evolution of marine invertebrate larvae: If, where and when to feed

The feeding environment for planktotrophic larvae has a major impact on development and progression towards competency for metamorphosis. High phytoplankton environments that promote growth often have a greater microbial load and incidence of pathogenic microbes, while areas with lower food availability have a lower number of potential pathogens. Trade-offs between metabolic processes associated with growth and immune functionality have been described throughout the animal kingdom and may influence the life-history evolution of marine invertebrate planktotrophic larvae in these environments. Namely, to avoid potential incidences of microbial-mediated mortality and/or dysbiosis, larvae should regulate time spent between these two feeding environments. We describe here transcriptomic and microbiome data that supports this trade-off in larvae, where larvae in a well-fed environment upregulate genes associated with metabolism and may regularly enter a state of dysbiosis, resulting in mortality. To address the hypothesis that the environmental microbiota is a selective force on if, where, and when planktotrophic larvae should feed, we present a strategy for determining the specific interactions of larvae and microbes at a scale representative of their larger pelagic environment.
Spatiotemporal dynamics of the bacterial microbiota on lacustrine Cladophora glomerata (Chlorophyta).

The branched periphytic green alga Cladophora glomerata, often abundant in nearshore waters of lakes and rivers worldwide, plays important ecosystem roles, some mediated by epibiotic microbiota that benefit from host-provided surface, organic C, and O2 . Previous microscopy and high-throughput sequencing studies have indicated surprising epibiont taxonomic and functional diversity, but have not included adequate consideration of sample replication or the potential for spatial and temporal variation. Here, we report the results of 16S rRNA amplicon-based phylum-to-genus taxonomic analysis of Cladophora-associated bacterial epibiota sampled in replicate from three microsites and at six times during the open-water season of 2014, from the same lake locale (Picnic Point, Lake Mendota, Dane Co., WI, USA) explored by high-throughput sequencing studies in two previous years. Statistical methods were used to test null hypotheses that the bacterial community: (i) is homogeneous across microsites tested, and (ii) does not change over the course of a growth season or among successive years. Results indicated a dynamic microbial community that is more strongly influenced by sampling day during the growth season than by microsite variation. A surprising diversity of bacterial genera known to be associated with the key function of methane-oxidation (methanotrophy), including relatively high-abundance of Crenothrix, Methylomonas, Methylovulum, and Methylocaldum-showed intraseasonal and interannual variability possibly related to temperature differences, and microsite preferences possibly related to variation in methane abundance. By contrast, a core assemblage of bacterial genera seems to persist over a growth season and from year to year, possibly transmitted by a persistent attached host resting stage.
Ring opening reactions of 6-oxo-substituted spiro-pyrrolidinediones: Synthesis of 4-substituted-1,5-dihydro-3-hydroxy-2-oxo-1,5-diphenyl-2H-pyrroles

Reaction of 2-oxocylalkaneglyoxylate esters with N-phenylmethyleneaniline yields spiro compounds such as 2-aza-3,4,6,-trioxo-1,2-diphenylspiro[4.4]nonane 4 and cycloalkane-2-aza-3,4,6-trioxo-1,2-diphenylspiro-[4.5]decanes 5–7. These undergo solvolytic opening of the the oxocycloalkane ring to yield 4-substituted-1,5-dihydro-3-hydroxy-2-oxo-1,5-diphenyl-2H-pyrroles 12–17.
Synthesis of β,β-Dimethylated Amino Acid Building Blocks Utilizing the 9-Phenylfluorenyl Protecting Group

Optically pure β,β-dimethylated amino acid building blocks with functionalized side chains have been prepared from d-aspartic acid. The dimethylation was accomplished by regioselective dialkylation of 9-phenylfluorenyl (PhFl)-protected aspartate diesters. The bulk of the PhFl protecting group also allowed for a variety of functional group manipulations to be carried out on the side chain without affecting the Cα ester of the aspartate. As a result, the derivatives of the following novel amino acids were synthesized in this study: β,β-dimethyl-d-aspartic acid, β,β-dimethyl-d-homoserine, 3,3-dimethyl-d-2,4-diaminobutyric acid, β,β-dimethyl-d-lysine, β,β-dimethyl-d-homoglutamate, β,β-dimethyl-d-ornithine, and 3,3-dimethylazetidine-2-carboxylic acid. The β,β-dimethylated amino acids were synthesized in high enantiomeric excess as determined by coupling the novel building blocks to chiral reagents.
Fluidigm2PURC: Automated processing and haplotype inference for double-barcoded PCR amplicons.

Premise of the Study Targeted enrichment strategies for phylogenomic inference are a time- and cost-efficient way to collect DNA sequence data for large numbers of individuals at multiple, independent loci. Automated and reproducible processing of these data is a crucial step for researchers conducting phylogenetic studies. Methods and Results We present Fluidigm2PURC, an open source Python utility for processing paired-end Illumina data from double-barcoded PCR amplicons. In combination with the program PURC (Pipeline for Untangling Reticulate Complexes), our scripts process raw FASTQ files for analysis with PURC and use its output to infer haplotypes for diploids, polyploids, and samples with unknown ploidy. We demonstrate the use of the pipeline with an example data set from the genus Thalictrum (Ranunculaceae). Conclusions Fluidigm2PURC is freely available for Unix-like operating systems on GitHub (https://github.com/pblischak/fluidigm2purc) and for all operating systems through Docker (https://hub.docker.com/r/pblischak/fluidigm2purc).
Synthesis and structure of BiMnPO5

Abstract The new compound BiMnPO 5 was prepared, and its structure determined using powder neutron diffraction data. The space group is P2 1 /n with a =7.4339(3) A, b =11.356(4) A, c =5.3577(2) A, β =109.19(2)°, and Z =4. The structure may be viewed as connected Bi 2 O 10 , Mn 2 O 10 , and PO 4 groups.
Synthesis, Structure, and Characterization of a New Second-Harmonic-Generating Tellurite: Na2TeW2O9

The synthesis, structure, and characterization of a new noncentrosymmetric tellurite, Na2TeW2O9, is reported. The oxide exhibits a three-dimensional structure comprising distorted W6+O6 octahedra linked to asymmetric Te4+O3 groups. Both cations are in local acentric environments attributable to second-order Jahn−Teller effects. Single crystals of Na2TeW2O9 were synthesized through supercritical hydrothermal methods, utilizing NaOH(aq), WO3, and TeO2 as reagents. Polycrystalline Na2TeW2O9 was synthesized by combining stoichiometric amounts of Na2CO3, WO3, and TeO2 through standard solid-state methods. Na2TeW2O9 crystallizes in the noncentrosymmetric space group Ia (No. 9) with a = 13.1394(5) A, b = 7.3202(3) A, c = 31.4435(11) A, and β = 95.0270(10)°. Powder SHG measurements, using 1064-nm radiation, on polycrystalline Na2TeW2O9 indicated a strong SHG intensity of approximately 500× SiO2. Additional SHG measurements revealed the material is phase-matchable (Type I).
Cycloadditions of o -quinone dimethides with p -quinol derivatives: regiocontrolled formation of anthracyclic ring systems

Abstract Regioselective cycloadditions between the cyclohexadienones 12–14 and the ortho-quinone dimethide 19 , which is thermally generated from the corresponding 1,3-dihydro-1-methoxy-2,2-dioxide benzo[c]thiophene 27 , are reported. The synthetic sequence provides rapid access to highly substituted anthracyclic system and may be of use for construction of the natural product (+)-rishirilide B.
Microwave-assisted synthesis of 1-aryl-1H-indazoles via one-pot two-step Cu-catalyzed intramolecular N-arylation of arylhydrazones

Abstract A highly efficient one-pot two-step microwave procedure was developed for the synthesis of 1-aryl-1 H -indazoles. Microwave heating of 2-halobenzaldehydes or 2-haloacetophenones with phenylhydrazines at 160 °C for 10 min quantitatively yielded the arylhydrazones, which were further cyclized to give 1-aryl-1 H -indazoles via CuI/diamine-catalyzed N -arylation under microwave heating (160 °C, 10 min). Good to excellent yields were observed for 2-iodo, 2-bromo, and 2-chloro benzaldehydes or acetophenones.
Convex hull realizations of the multiplihedra

Abstract We present a simple algorithm for determining the extremal points in Euclidean space whose convex hull is the n th polytope in the sequence known as the multiplihedra. This answers the open question of whether the multiplihedra could be realized as convex polytopes. We use this realization to unite the approach to A n -maps of Iwase and Mimura to that of Boardman and Vogt. We include a review of the appearance of the n th multiplihedron for various n in the studies of higher homotopy commutativity, (weak) n -categories, A ∞ -categories, deformation theory, and moduli spaces. We also include suggestions for the use of our realizations in some of these areas as well as in related studies, including enriched category theory and the graph-associahedra.
Asymptotics and Formulas for Cubic Exponential Sums

Several asymptotic expansions and formulas for cubic exponential sums are derived. The expansions are most useful when the cubic coefficient is in a restricted range. This generalizes previous results in the quadratic case and helps to clarify how to numerically approximate cubic exponential sums and how to obtain upper bounds for them in some cases.
On Symmetric and Asymmetric LSHs for Inner Product Search

We consider the problem of designing locality sensitive hashes (LSH) for inner product similarity, and of the power of asymmetric hashes in this context. Shrivastava and Li (2014a) argue that there is no symmetric LSH for the problem and propose an asymmetric LSH based on different mappings for query and database points. However, we show there does exist a simple symmetric LSH that enjoys stronger guarantees and better empirical performance than the asymmetric LSH they suggest. We also show a variant of the settings where asymmetry is in-fact needed, but there a different asymmetric LSH is required.
Determinant-Preserving Sparsification of SDDM Matrices with Applications to Counting and Sampling Spanning Trees

We show variants of spectral sparsification routines can preserve the totalspanning tree counts of graphs, which by Kirchhoffs matrix-tree theorem, isequivalent to determinant of a graph Laplacian minor, or equivalently, of any SDDM matrix. Our analyses utilizes this combinatorial connection to bridge between statisticalleverage scores / effective resistances and the analysis of random graphsby [Janson, Combinatorics, Probability and Computing 94]. This leads to a routine that in quadratic time, sparsifies a graph down to aboutn^(1.5) edges in ways that preserve both the determinant and the distributionof spanning trees (provided the sparsified graph is viewed as a random object). Extending this algorithm to work with Schur complements and approximateCholesky factorizations leads to algorithms for counting andsampling spanning trees which are nearly optimal for dense graphs.We give an algorithm that computes a (1 +/- &#x03B4;) approximation to the determinantof any SDDM matrix with constant probability in about n^2 / &#x03B4;^2 time. This is the first routine for graphs that outperforms general-purpose routines for computingdeterminants of arbitrary matrices. We also give an algorithm that generates in about n^2 / &#x03B4;^2 time a spanning tree ofa weighted undirected graph from a distribution with total variationdistance of &#x03B4; from the w-uniform distribution.
Proof mining and effective bounds in differential polynomial rings

Abstract Using the functional interpretation from proof theory, we analyze nonconstructive proofs of several central theorems about polynomial and differential polynomial rings. We extract effective bounds, some of which are new to the literature, from the resulting proofs. In the process we discuss the constructive content of Noetherian rings and the Nullstellensatz in both the classical and differential settings. Sufficient background is given to understand the proof-theoretic and differential-algebraic framework of the main results.
On the dimension of Z-sets

Abstract We offer a short and elementary proof that, for a Z -set A in a finite-dimensional ANR Y , dim A dim Y . This result is relevant to the study of group boundaries. The original proof by Bestvina and Mess relied on cohomological dimension theory.
Resilient and decentralized control of multi-level cooperative mobile networks to maintain connectivity under adversarial environment

Network connectivity plays an important role in the information exchange between different agents in the multi-level networks. In this paper, we establish a game-theoretic framework to capture the uncoordinated nature of the decision-making at different layers of the multi-level networks. Specifically, we design a decentralized algorithm that aims to maximize the algebraic connectivity of the global network iteratively. In addition, we show that the designed algorithm converges to a Nash equilibrium asymptotically and yields an equilibrium network. To study the network resiliency, we introduce three adversarial attack models and characterize their worst-case impacts on the network performance. Case studies based on a two-layer mobile robotic network are used to corroborate the effectiveness and resiliency of the proposed algorithm and show the interdependency between different layers of the network during the recovery processes.
Simulation methods for stochastic storage problems: a statistical learning perspective

We consider solution of stochastic storage problems through regression Monte Carlo methods. Taking a statistical learning perspective, we develop the dynamic emulation algorithm (DEA) that unifies the different existing approaches in a single modular template. We then investigate the two central aspects of regression architecture and experimental design that constitute DEA. For the regression piece, we discuss various non-parametric approaches, in particular introducing the use of Gaussian process regression in the context of stochastic storage. For simulation design, we compare the performance of traditional design (grid discretization), against space-filling, and several adaptive alternatives. The overall DEA template is illustrated with multiple examples drawing from natural gas storage valuation and optimal control of back-up generator in a microgrid.
Simultaneous oxygen and boron trifluoride functionalization of hexagonal boron nitride: a designer cathode material for energy storage

Covalent functionalization is a way to tune the electrochemical properties of hexagonal boron nitride (h-BN) monolayers. The wide bandgap insulator h-BN may become metallic conductor upon functionalization with strong oxidants, such as (fluorosulfonyl)oxy radicals (·OSO $$_{2}$$ F), as known since 1978 ( Bartlett et al in J Chem Soc Chem Commun 5:200, 1978), with electrical conductivity of 1.5 S/cm (Shen et al in J Solid State Chem 147:74, 1999) that greatly surpasses commercial cathode material Li $$_{x}$$ CoO $$_{2}$$ while retaining excellent ionic conductivity. Functionalized boron nitrides (FBN-s) have great potential for cathode applications in energy storage devices, for example, in solid-state batteries. While (fluorosulfonyl)oxy functionalization is unlikely to result in rechargeable cathodes, similarly to graphene fluoride (CF $$_{x}$$ ), some other FBN-s discussed here may do. In the present work, fluorene, oxygen and combined oxygen and boron trifluoride functionalizations are studied, on the basis of band structure calculations. Due to the open surfaces of FBN-s, fast ionic diffusion with Li, Na and Mg ions is possible, enabling batteries with voltages of 2.1–5.6 V, theoretical energy densities of 800–1200 Wh/kg and fast charge and discharge.
Log canonical thresholds in positive characteristic

In this paper, we study the singularities of pairs in arbitrary characteristic via jet schemes. For a smooth variety X in characteristic 0, Ein, Lazarsfeld and Mustaţǎ showed that there is a correspondence between irreducible closed cylinders and divisorial valuations on X. Via this correspondence, one can relate the codimension of a cylinder to the log discrepancy of the corresponding divisorial valuation. We now extend this result to positive characteristic. In particular, we prove Mustaţǎ’s log canonical threshold formula avoiding the use of log resolutions, making the formula available also in positive characteristic. As a consequence, we get a comparison theorem via reduction modulo p and a version of inversion of adjunction in positive characteristic.
Verification of the Jones unknot conjecture up to 22 crossings

We proved by computer enumeration that the Jones polynomial distinguishes the unknot for knots up to 22 crossings. Following an approach of Yamada, we generated knot diagrams by inserting algebraic...
Transit time derivation for hot planet bow-shocks

We present an analytical estimate of hot planet bow-shock transit times that will be useful for planning observations of such signatures.
Product function need recognition via semi-supervised attention network

Functionality is of utmost importance to customers when they purchase products. However, it is unclear to customers whether a product can really satisfy their needs on functions. Further, missing functions may be intentionally hidden by the manufacturers or the sellers. As a result, a customer needs to spend a fair amount of time before purchasing or just purchase the product on his/her own risk. In this paper, we first identify a novel QA corpus that is dense on product functionality information 1. We then design a neural network called Semi-supervised Attention Network (SAN) to discover product functions from questions. This model leverages unlabeled data as contextual information to perform semi-supervised sequence labeling. We conduct experiments to show that the extracted function have both high coverage and accuracy, compared with a wide spectrum of baselines.
Localization for the Ising Model in a Transverse Field with Generic Aperiodic Disorder

We show that the transverse field Ising model undergoes a zero temperature phase transition for a Gδ set of ergodic transverse fields. We apply our results to the special case of quasiperiodic transverse fields, in one dimension we find a sharp condition for the existence of a phase transition.
Learning and free energies for vector approximate message passing

Vector approximate message passing (VAMP) is a computationally simple approach to the recovery of a signal x from noisy linear measurements y = Ax + w. Like the AMP proposed by Donoho, Maleki, and Montanari in 2009, VAMP is characterized by a rigorous state evolution (SE) that holds under certain large random matrices and that matches the replica prediction of optimality. But while AMP's SE holds only for large i.i.d. sub-Gaussian A, VAMP's SE holds under the much larger class: right-rotationally invariant A. To run VAMP, however, one must specify the statistical parameters of the signal and noise. This work combines VAMP with Expectation-Maximization to yield an algorithm, EM-VAMP, that can jointly recover x while learning those statistical parameters. The fixed points of the proposed EM-VAMP algorithm are shown to be stationary points of a certain constrained free-energy, providing a variational interpretation of the algorithm. Numerical simulations show that EM-VAMP is robust to highly ill-conditioned A with performance nearly matching oracle-parameter VAMP.
The Consistency of Arithmetic

In 2010, Vladimir Voevodsky gave a lecture on "What If Current Foundations of Mathematics Are Inconsistent?" Among other things he said that he was seriously suspicious that an inconsistency in PA (first-order Peano arithmetic) might someday be found. About a year later, Edward Nelson announced that he had discovered an inconsistency not just in PA, but in a small fragment of primitive recursive arithmetic. Soon, Daniel Tausk and Terence Tao independently found a fatal error, and Nelson withdrew his claim, stating that consistency of PA was an "open problem." Many mathematicians may find such claims bewildering. Is the consistency of PA really an open problem? If so, would the discovery of an inconsistency in PA cause all of mathematics to come crashing down like a house of cards? This expository article attempts to address these questions, by sketching and discussing existing proofs of the consistency of PA (including Gentzen's proof and Friedman's relative consistency proof that appeals to the Bolzano-Weierstrass theorem). Since Nelson was a self-avowed formalist, the article also examines the implications of formalism.
Natural Language Inference from Multiple Premises

We define a novel textual entailment task that requires inference over multiple premise sentences. We present a new dataset for this task that minimizes trivial lexical inferences, emphasizes knowledge of everyday events, and presents a more challenging setting for textual entailment. We evaluate several strong neural baselines and analyze how the multiple premise task differs from standard textual entailment.
Panel data models with nonadditive unobserved heterogeneity: Estimation and inference

This paper considers fixed effects estimation and inference in linear and nonlinear panel data models with random coefficients and endogenous regressors. The quantities of interest—means, variances, and other moments of the random coefficients—are estimated by cross sectional sample moments of generalized method of moments (GMM) estimators applied separately to the time series of each individual. To deal with the incidental parameter problem introduced by the noise of the within-individual estimators in short panels, we develop bias corrections. These corrections are based on higher-order asymptotic expansions of the GMM estimators and produce improved point and interval estimates in moderately long panels. Under asymptotic sequences where the cross sectional and time series dimensions of the panel pass to infinity at the same rate, the uncorrected estimators have asymptotic biases of the same order as their asymptotic standard deviations. The bias corrections remove the bias without increasing variance. An empirical example on cigarette demand based on Becker, Grossman, and Murphy (1994) shows significant heterogeneity in the price effect across U.S. states.
Learning Without Mixing: Towards A Sharp Analysis of Linear System Identification

We prove that the ordinary least-squares (OLS) estimator attains nearly minimax optimal performance for the identification of linear dynamical systems from a single observed trajectory. Our upper bound relies on a generalization of Mendelson's small-ball method to dependent data, eschewing the use of standard mixing-time arguments. Our lower bounds reveal that these upper bounds match up to logarithmic factors. In particular, we capture the correct signal-to-noise behavior of the problem, showing that more unstable linear systems are easier to estimate. This behavior is qualitatively different from arguments which rely on mixing-time calculations that suggest that unstable systems are more difficult to estimate. We generalize our technique to provide bounds for a more general class of linear response time-series.