cssi/SciSciGPT-SciSciNet huggingface dataset:
Squarepants in a tree: Sum of subtree clustering and hyperbolic pants decomposition

We provide efficient constant-factor approximation algorithms for the problems of finding a hierarchical clustering of a point set in any metric space, minimizing the sum of minimimum spanning tree lengths within each cluster, and in the hyperbolic or Euclidean planes, minimizing the sum of cluster perimeters. Our algorithms for the hyperbolic and Euclidean planes can also be used to provide a pants decomposition, that is, a set of disjoint simple closed curves partitioning the plane minus the input points into subsets with exactly three boundary components, with approximately minimum total length. In the Euclidean case, these curves are squares; in the hyperbolic case, they combine our Euclidean square pants decomposition with our tree clustering method for general metric spaces.
Synthesis of Cyclopropylpyrrolidines via Reaction of N-Allyl-N-propargylamides with a Molybdenum Carbene Complex. Effect of Substituents and Reaction Conditions

Previous studies have demonstrated that group 6 carbene complexes react with α,ω-enynes to form vinylcyclopropane derivatives in good to excellent yield, and that the length and composition of the tether between the alkyne and the alkene often has a dramatic impact on the viability of this reaction pathway. The reactivity of allylpropargyl amine derivatives with pentacarbonyl(1-methoxypentylidene)molybdenum(0) (14a) was investigated in order to provide further insight into the steric and electronic factors controlling this reaction. Treatment of allylpropargyl amines with 14a failed to produce the desired cyclization products while treatment of allylpropargyl amides with 14a led to the expected cyclopropylpyrrolidine systems in good to excellent yields. Higher yields are obtained when the reaction is conducted in a sealed vial in the presence of atmospheric oxygen.
Synthesis of 2,3-Dihydro-1,3-oxazin-4-ones via a Mild Formal [4+2] Cycloaddition of Acylketenes with Aldimines

A mild and efficient silver-mediated synthesis of 2,3-dihydro-1,3-oxazin-4-ones through a formal [4+2] cycloaddition reaction of aldimines and acylketene intermediates is described. A variety of functionalized and potentially biologically relevant heterocycles have been accessed in moderate to high yields through this process.
Cross-linked poly(4-vinylpyridine/styrene) copolymers as a support for immobilization of ytterbium triflate

Abstract Eight cross-linked poly(4-vinylpyridine/styrene) (P/S) resins (as beads) were prepared by radical suspension polymerization. Ytterbium triflate was immobilized in the range of 0.10–0.24 mmol/g by mixing with the P/S resins. The ytterbium triflate-immobilized P/S resins exhibited good activity in two Lewis acid-catalyzed reactions. Low pyridine containing resins were recycled with no loss of activity, while a slight loss of activity was observed with the higher pyridine containing resins.
Oxidation of Hydrazines with Carbon Tetrachloride

Some hydrazines, especially 1,2-dialkylhydrazines are oxidized to the corresponding diazenes (azo compounds) by carbon tetrachloride presumably via nucleophilic attack by nitrogen on chlorine. Monacylhydrazines are converted to the corresponding diacylhydrazines.
Hydrothermal synthesis and structures of the open-framework copper silicates Na2[Cu2Si4O11](H2O)2 (CuSH-2Na), Na2[CuSi3O8] (CuSH-3Na), Cs2Na4[Cu2Si12O27(OH)2](OH)2 (CuSH-4NaCs), and Na2[Cu2Si5O13](H2O)3 (CuSH-6Na)

A series of open-framework copper silicates has been synthesized under mild hydrothermal conditions. The frameworks are based on double chains, single layers or double layers of SiO4 tetrahedra interconnected by CuO4 squares or tetrahedra or CuO5 tetragonal pyramids. The structures contain 8-ring or 10-ring channel systems with apertures up to 2.7 × 5.9 A which are filled by alkali metal cations and water molecules.  2005 Elsevier SAS. All rights reserved.
PISEMA Solid-State NMR Spectroscopy

Abstract Gone are the days when solid-state NMR spectroscopy was considered to be untouchable-like as it provided unappealing spectral lines due to poor resolution and sensitivity. Introduction of a number of powerful concepts dramatically increased the resolution and sensitivity of the spectroscopy and paved numerous avenues for researchers from all walks of science. Now, the new era is harvesting the valuable technique’s applications on chemical, material, biological, and pharmaceutical systems in all types of non-isotropic phases such as single crystal, liquid crystal, fibre, powder, and amorphous. One of the most powerful solid-state NMR techniques is PISEMA, which provides very high resolution of the correlation and the precise measurement of chemical shift and heteronuclear dipolar coupling interactions. It is a combination of polarization inversion, that doubles the sensitivity, and spin exchange at the magic angle (SEMA) among dipolar coupled heteronuclear spins. The SEMA pulse sequence suppresses dipole–dipole interaction among protons and simultaneously generates a doubly rotating frame to have no role for chemical shifts of 1H and S nuclei (such as 13C and 15N). The PISEMA pulse sequence has a high dipolar scaling factor, and the dipolar resolution in the PISEMA spectrum is up to 10 times higher than in spectra obtained by the conventional separated-local-field method. A 2D PISEMA spectrum can be viewed as an image that could be used to determine the secondary structure and topology of aligned molecules. In fact, this was the first solid-state NMR technique that rendered complete resolution and partial assignment of resonances, and the structure and the topology of uniformly labeled membrane proteins. Fascinated by the efficiency of PISEMA, a family of multidimensional pulse sequences has been designed to further increase the resolution and applied to study the structure of biological solids, particularly membrane-associated peptides and proteins which are increasingly important, but notorious in general to investigate. In this review, the pulse sequence, line-narrowing mechanism, experimental set-up, applications and limits of 2D PISEMA and related techniques, and different types of PISEMA spectra are discussed. Multi-dimensional solid-state NMR experiments designed based on 2D PISEMA and their applications are reviewed. A new one-dimensional 1H-detected PISEMA pulse sequence to enhance the sensitivity of the experiment is also presented.
Rhodium(I)-Catalyzed [4+2+2] Cycloadditions of 1,3-Dienes, Alkenes, and Alkynes for the Synthesis of Cyclooctadienes

The first [4+2+2] cycloadditions involving terminal alkynes and diene-enes, including a fully intramolecular example, are reported resulting in the formation of cyclooctadienes using [RhCl(CO)2]2 (5 mol %) treated with AgSbF6 (10 mol %) as a precatalyst. The reaction is general for a variety of terminal alkynes, as well as variously substituted diene-enes (yields up to 88%).
Multiple Mechanisms Inactivate the LIN-41 RNA-Binding Protein To Ensure a Robust Oocyte-to-Embryo Transition in Caenorhabditis elegans .

In the nematode Caenorhabditis elegans, the conserved LIN-41 RNA-binding protein is a translational repressor that coordinately controls oocyte growth and meiotic maturation. LIN-41 exerts these effects, at least in part, by preventing the premature activation of the cyclin-dependent kinase CDK-1 Here we investigate the mechanism by which LIN-41 is rapidly eliminated upon the onset of meiotic maturation. Elimination of LIN-41 requires the activities of CDK-1 and multiple SCF (Skp1, Cul1, and F-box protein)-type E3 ubiquitin ligase subunits, including the conserved substrate adaptor protein SEL-10/Fbw7/Cdc4, suggesting that LIN-41 is a target of ubiquitin-mediated protein degradation. Within the LIN-41 protein, two nonoverlapping regions, Deg-A and Deg-B, are individually necessary for LIN-41 degradation; both contain several potential phosphodegron sequences, and at least one of these sequences is required for LIN-41 degradation. Finally, Deg-A and Deg-B are sufficient, in combination, to mediate SEL-10-dependent degradation when transplanted into a different oocyte protein. Although LIN-41 is a potent inhibitor of protein translation and M phase entry, the failure to eliminate LIN-41 from early embryos does not result in the continued translational repression of LIN-41 oocyte messenger RNA targets. Based on these observations, we propose a model for the elimination of LIN-41 by the SEL-10 E3 ubiquitin ligase and suggest that LIN-41 is inactivated before it is degraded. Furthermore, we provide evidence that another RNA-binding protein, the GLD-1 tumor suppressor, is regulated similarly. Redundant mechanisms to extinguish translational repression by RNA-binding proteins may both control and provide robustness to irreversible developmental transitions, including meiotic maturation and the oocyte-to-embryo transition.
2,4,6-Trifluoropyrimidine. Reactions with nitrogen nucleophiles

In a continuation of our studies involving the nucleophilic displacement of one of the chlorines from 2,4,6-trichloropyrimidine, we now report the initial displacement of one of the fluorine atoms from 2,4,6-trifluoropyrimidine using both aliphatic and aromatic amines. The monosubstitution products favor 2-substitution with ammonia and ethanolamine while aniline gave the 4-substituted derivative as the preferred product.
One-pot synthesis of nitroolefins using zeolite

Abstract Nitroolefins, versatile intermediates in organic synthesis, are conveniently prepared in good yields by nitration of olefins using nitric oxide and zeolite as described.
Synthesis of 2-Indanones via [4 + 1] Annulation Reactions of (Trialkylsilyl)arylketenes

[reaction: see text] (Trialkylsilyl)arylketenes combine with (trimethylsilyl)diazomethane in a new [4 + 1] annulation process leading to 2-indanone derivatives. The (trialkylsilyl)arylketene annulation substrates are available via the photochemical Wolff rearrangement of alpha-silyl-alpha-diazo ketones, which are themselves prepared by silylation of the corresponding diazo ketones. The mechanism of the annulation reaction is proposed to involve the formation of a 2,3-bis(silyl)cyclopropanone, which is in equilibrium with an oxyallylic cation. Electrocyclic closure of this intermediate forms the new cyclopentenone ring.
A novel synthesis of piperidin-3-ones via an intramolecular Amadori-type reaction

Abstract 1-Methoxycarbonyl-2-(3,5-dimethoxy-4-benzyloxyphenyl)-piperidin-3-one1 and rac-5R, 8aS-5-(3,5-dimethoxy-4-t-butyldimethylsiloxyphenyl)-oxazolo[3,4:1,6]piperidin-3,6-dione2 were synthesized via an intramolecular adaptation of the biochemically well-characterized Amadori reaction.
22 kHz and 55 kHz ultrasonic vocalizations differentially influence neural and behavioral outcomes: Implications for modeling anxiety via auditory stimuli in the rat.

Abstract The communicative role of ultrasonic vocalizations (USVs) in rats is well established, with distinct USVs indicative of different affective states. USVs in the 22 kHz range are typically emitted by adult rats when in anxiety- or fear-provoking situations (e.g. predator odor, social defeat), while 55 kHz range USVs are typically emitted in appetitive situations (e.g., play, anticipation of reward). Previous work indicates that USVs (real-time and playback) can effectively communicate these affective states and influence changes in behavior and neural activity of the receiver. Changes in cFos activation following 22 kHz USVs have been seen in cortical and limbic regions involved in anxiety, including the basolateral amygdala (BLA). However, it is unclear how USV playback influences cFos activity within the bed nucleus of the stria terminalis (BNST), a region also thought to be critical in processing anxiety-related information, and the nucleus accumbens, a region associated with reward. The present work sought to characterize distinct behavioral, physiological, and neural responses in rats presented with aversive (22 kHz) compared to appetitive (55 kHz) USVs or silence. Our findings show that rats exposed to 22 kHz USVs: 1) engage in anxiety-like behaviors in the elevated zero maze, and 2) show distinct patterns of cFos activation within the BLA and BNST that contrast those seen in 55 kHz playback and silence. Specifically, 22 kHz USVs increased cFos density in the anterodorsal nuclei, while 55 kHz playback increased cFos in the oval nucleus of the BNST, without significant changes within the nucleus accumbens. These results provide important groundwork for leveraging ethologically-relevant stimuli in the rat to improve our understanding of anxiety-related responses in both typical and pathological populations.
2,6-Bis(triisopropylsilyl)pyridine, an extreme example of the effect of strong steric screening on basicity

Abstract 2,6-Bis(triisopropylsilyl)pyridine ( 1 ) has been synthesized from 2,6-dibromopyridine. It is a very weak base in water since it does not dissolve in 6N hydrochloric acid, but does undergo protonation in nonaqueous media by triflic acid.
[Ni(H2O)4]3[U(OH,H2O)(UO2)8O12(OH)3], crystal structure and comparison with uranium minerals with U3O8-type sheets

Abstract The new U(VI) compound, [Ni(H2O)4]3[U(OH,H2O)(UO2)8O12(OH)3], was synthesized by mild hydrothermal reaction of uranyl and nickel nitrates. The crystal-structure was solved in the P-1 space group, a=8.627(2), b=10.566(2), c=12.091(4) A and α=110.59(1), β=102.96(2), γ=105.50(1)°, R=0.0539 and wR=0.0464 from 3441 unique observed reflections and 151 parameters. The structure of the title compound is built from sheets of uranium polyhedra closely related to that in β-U3O8. Within the sheets [(UO2)(OH)O4] pentagonal bipyramids share equatorial edges to form chains, which are cross-linked by [(UO2)O4] and [UO4(H2O)(OH)] square bipyramids and through hydroxyl groups shared between [(UO2)(OH)O4] pentagonal bipyramids. The sheets are pillared by sharing the apical oxygen atoms of the [(UO2)(OH)O4] pentagonal bipyramids with the oxygen atoms of [NiO2(H2O)4] octahedral units. That builds a three-dimensional framework with water molecules pointing towards the channels. On heating [Ni(H2O)4]3[U(OH,H2O)(UO2)8O12(OH)3] decomposes into NiU3O10.
Rif1 inhibits replication fork progression and controls DNA copy number in Drosophila.

Control of DNA copy number is essential to maintain genome stability and ensure proper cell and tissue function. In Drosophila polyploid cells, the SNF2-domain-containing SUUR protein inhibits replication fork progression within specific regions of the genome to promote DNA underreplication. While dissecting the function of SUUR’s SNF2 domain, we identified an interaction between SUUR and Rif1. Rif1 has many roles in DNA metabolism and regulates the replication timing program. We demonstrate that repression of DNA replication is dependent on Rif1. Rif1 localizes to active replication forks in a partially SUUR-dependent manner and directly regulates replication fork progression. Importantly, SUUR associates with replication forks in the absence of Rif1, indicating that Rif1 acts downstream of SUUR to inhibit fork progression. Our findings uncover an unrecognized function of the Rif1 protein as a regulator of replication fork progression.
An Intramolecular Nitrone-Olefin Dipolar Cycloaddition-Based Approach to Total Synthesis of the Cylindricine and Lepadiformine Marine Alkaloids.

A synthetic route to the cylindricine skeleton as well as to the reported structure of the marine alkaloid lepadiformine has been achieved using an intramolecular nitrone/1,3-diene dipolar cycloaddition as the key step. The synthesis began with sequential alkylations of acetone oxime to afford key intermediate oxime 30, which contains all of the carbons necessary to form the tricyclic skeleton of the alkaloids. Nitrone 40, available from oxime 30 by standard transformations, underwent an intramolecular 1,3-dipolar cycloaddition to provide isoxazolidine 43. Related 1,3-dipolar cycloadditions were also explored on two additional nitrone−olefin substrates 41 and 42, which were prepared in a manner similar to that of 40. The tricyclic alkaloid core 52 was formed stereoselectively by a tandem oxidation−Michael addition of amino alcohol 49 derived from isoxazolidine 43. Cleavage of the O-phenyl ether of 52 provided 2-epi-cylindricine C (53). Several unsuccessful attempts were made to convert 52 to cylindricine ...
Synthesis of β-mannopyranosides from α-epimers by radical inversion : 1,6-hydrogen transfer reactions of 2-O-(2-bromoaryl)dimethylsilyl-α-methyl-d-mannopyranosides

Abstract Intramolecular hydrogen transfer reactions of 3-O-acyl-α-methyl- d -mannopyranosides occur in a 1,6-fashion to give inverted β-mannopyranosides. The yields are limited by competing 1,5-hydrogen transfer reactions that give isomeric α-glucopyranosides.
Low-temperature synthesis of hydrated zinco(beryllo)-phosphate and arsenate molecular sieves

ALUMINOSILICATE (zeolite) molecular sieves, both natural and synthetic, have been studied extensively because of their utility in commercial processes such as petroleum cracking, water treatment and gas absorption 1–3. Although aluminium and silicon may be replaced by a variety of other tetrahedrally coordinated elements, there are few examples of molecular sieves that contain neither aluminium nor silicon: several gallophosphates are known4,5, and cacoxenite, a basic ferric oxyphosphate, occurs naturally6. Recently, two new beryllophosphate minerals have been identified7,8: tiptopite, isotypic with cancrinite, and pahasapaite (Li, Ca beryllophosphate), which has the structure of zeolite RHO. Harvey and Meier9 have prepared five new beryllophosphates, with structures analogous to RHO (Li), gismondine (Na), edingtonite (K), pollucite (Cs), and a new structure, BPH, that has no aluminosilicate analogue. Here we describe the preparation of new families of hydrated zincophosphates/arsenates and beryllo-phosphates/arsenates with structures that are also related to zeolitic aluminosilicates. These materials may be prepared from gels over a much wider range of pH and at much lower temperatures than are possible for aluminophosphates, perhaps because of the greater solubility of the framework elements: analogues of hydro-sodalite and zeolites RHO, Li-A(BW) and X are easily prepared at pH values ranging from 2 to 12 and between 4 and 100 °C. Growth of crystals adequate for X-ray structural analyses seems to be easier than is the case for aluminosilicate/phosphate materials.
Synthesis of fluoro and trifluoromethyl derivatives of 2-phenylquinolin-4-ol

A tert-butoxide base-mediated cyclization of fluoro- and trifluoromethyl-substituted Schiff bases 12-19 produces 4-tert-butoxyquinolines 23-30 which are hydrolyzed to quinolin-4-ols 31-38.
Tetrakis(tetramethylammonium) tricarbonatodioxidouranate octahydrate.

The environment of the U atom in the title compound, (C4H12N)4[UO2(CO3)3]·8H2O, presents a typical hexa­gonal bipyramidal geometry found in many actinide complexes. It is a model for actinide species and consists of common environmental moieties (carbonate, water and ammonia species). The structure displays a sheet-like hydrogen-bonding network formed from crystallization water mol­ecules and carbonate ligands. The compound is isomorphous with a previously described Np isolog [Grigorev et al. (1997). Radiokhimiya (Russ. Radiochem.), 39, 325–329].
The “β-Fluorine Effect” in the Non-Metal Hydride Radical Deoxygenation of Fluorine-Containing Nucleoside Xanthates

Abstract An alternative method to conduct a Barton-McCombie deoxygenation in nucleosides is described. The utility of the procedure is limited to structures with an electronegative substituent, particularly fluorine, in the β-position relative to the radical center. The process is radical in nature and triggered by peroxides. The abstraction of hydrogen from the solvent is favorably influenced by the presence of a β-fluorine.
Mammalian alkaloids: Synthesis and O‐methylation of (S)‐ and (R)‐3′‐hydroxycoclaurine and their N‐methylated analogues with S‐adenosyl‐L‐[methyl‐14C]methionine in presence of mammalian catechol O‐methyltransferase

O-Methylation of the optically active 3′-hydroxycoclaurines 3a and 3b and of the N-methylated analogs 5a,b with S-adenosyl-L-[methyl-14C]methionine in presence of mammalian COMT was investigated in vitro. The N-unsubstituted (1S)- and (1R )-isomers 3a and 3b, respectively, afforded almost equal amounts of the corresponding N-norreticuline 4 and N-nororientaline 19, besides two unknown by-products (see Fig. and Table 1). The N-methylated (1S)-isoquinoline 5a, on the other hand, afforded largely (S)-orientaline ((S)-19), while an almost equal mixture of (R)-reticuline (6b) and (R)-orientaline ((R)-19) was obtained from the (1R)-enantiomer 5b. The isoquinolines 3a,b and 5a,b were prepared by a Bischler-Napieralski cyclization yielding O-benzyl-protected isoquinoline 10 (Scheme 1). The optical resolution of 10 was accomplished with 2′-bromotartranilic acid. The N-methylated isoquinolines were prepared by N-formylation of 10a,b and reduction of the formamides 13a,b with diborane ( 14a,b). Deblocking of the benzyl-ether moieties of 10a,b and 14a,b was accomplished by catalytic hydrogenation in presence of HCl, affording directly 3a,b·HCl and 5a,b·HCl, respectively.
Dopamine, inference, and uncertainty

The hypothesis that the phasic dopamine response reports a reward prediction error has become deeply entrenched. However, dopamine neurons exhibit several notable deviations from this hypothesis. A coherent explanation for these deviations can be obtained by analyzing the dopamine response in terms of Bayesian reinforcement learning. The key idea is that prediction errors are modulated by probabilistic beliefs about the relationship between cues and outcomes, updated through Bayesian inference. This account can explain dopamine responses to inferred value in sensory preconditioning, the effects of cue preexposure latent inhibition, and adaptive coding of prediction errors when rewards vary across orders of magnitude. We further postulate that orbitofrontal cortex transforms the stimulus representation through recurrent dynamics, such that a simple error-driven learning rule operating on the transformed representation can implement the Bayesian reinforcement learning update.
Ligand Influences in Copper-Dioxygen Complex-Formation and Substrate Oxidations

Publisher Summary This chapter discusses ligand influences in copper-dioxygen complex-formation and substrate oxidations. The chapter describes how ligand modifications can often result in different dioxygen reactivity. The rates and thermodynamics of O 2 -binding are influenced by the structural, electronic, or geometric properties of the supporting ligand. The chapter also discusses ligand effects on the subsequent reactivity of the dioxygen adduct produced. Intramolecular and intermolecular oxidations by copper-dioxygen compounds are well documented. The reaction of Cu(I) with molecular oxygen is of considerable interest for understanding the inherent reactivity tendencies of copper ion in biological enzymes, as well as in synthetic systems. The low cost and availability, and the broad range of oxidative potential make copper reagents or catalysts potentially very attractive. It is of interest to elucidate different possible copper-dioxygen compound structures, and to understand their bonding interactions and associated spectroscopic signatures. Oxidative transformations carried out by the reaction of copper(I) and O 2 in nature are widespread in terms of the variety of substrates and in copper active-site structures.
PfClpC Is an Essential Clp Chaperone Required for Plastid Integrity and Clp Protease Stability in Plasmodium falciparum

Summary The deadly malaria parasite Plasmodium falciparum contains a nonphotosynthetic plastid, known as the apicoplast, that functions to produce essential metabolites, and drugs that target the apicoplast are clinically effective. Several prokaryotic caseinolytic protease (Clp) genes have been identified in the Plasmodium genome. Using phylogenetic analysis, we focused on the Clp members that may form a regulated proteolytic complex in the apicoplast. We genetically targeted members of this complex and generated conditional mutants of the apicoplast-localized PfClpC chaperone and PfClpP protease. Conditional inhibition of the PfClpC chaperone resulted in growth arrest and apicoplast loss and was rescued by addition of the essential apicoplast-derived metabolite IPP. Using a double-conditional mutant parasite line, we discovered that the chaperone activity is required to stabilize the mature protease, revealing functional interactions. These data demonstrate the essential function of PfClpC in maintaining apicoplast integrity and its role in regulating the proteolytic activity of the Clp complex.
Concerning the Origin of the High β-Selectivity of Glycosidation Reactions of 2-Deoxy-2-iodo-glucopyranosyl Trichloroacetimidates

Studies on the glycosidation reactions of conformationally constrained glycosyl imidates 8a and 8b were performed to evaluate the possible involvement of “conformationally inverted” oxonium ion int...
Palladium-catalyzed reactions of Di-tert-butylsiliranes with electron-deficient alkynes and investigations of the catalytic cycle

Siliranes undergo palladium-catalyzed reactions with alkynes to give a variety of silacycles depending upon the alkyne. When terminal and electron-poor alkynes (DMAD and methyl 2-butynoate) are employed, silole formation is favored. Silirenes are formed preferentially when more electron-rich internal alkynes are involved. Control experiments provide evidence that palladium(0) species are the active catalysts. By evaluation of product distributions in these reactions, a catalytic cycle that accounts for the production of all silacycles can be proposed.
Single crystal growth and characterization of the first reduced lanthanum molybdenum oxychloride, La20Mo12O63Cl4, with an unusual trigonal prismatic MoO6 unit

Abstract The use of a KCl/CsCl alkali eutectic flux under reducing conditions facilitated the crystal growth of the mixed valent Mo(V)/Mo(VI) compound La20Mo12O63Cl4. La20Mo12O63Cl4 crystallizes in the noncentrosymmetric hexagonal space group P-62m with a = 10.2241(2) A and c = 15.0768(4) A, which represents a new structure type exhibiting a three-dimensional crystal structure containing three different molybdenum coordination environments, MoO5 square pyramids, MoO6 trigonal prisms, and MoO5 trigonal bipyramids. The temperature dependence of the magnetic susceptibility was measured and La20Mo12O63Cl4 was found to be paramagnetic across the entire 2–300 K temperature range measured. Although noncentrosymmetric, La20Mo12O63Cl4 was not found to be second harmonic generation active. La20Mo12O63Cl4 was further characterized by UV/Vis spectroscopy.
Vanadogermanate cluster anions.

Three novel vanadogermanate cluster anions have been synthesized by hydrothermal reactions. The cluster anions are derived from the {V18O42} Keggin cluster shell by substitution of VO2+ “caps” by Ge2O(OH)24+ species. In Cs8[Ge4V16O42(OH)4]·4.7H2O, 1, (monoclinic, space group C2/c (No. 15), Z = 8, a = 44.513(2) A, b = 12.7632(7) A, c = 22.923(1) A, β = 101.376(1)°) and (pipH2)4(pipH)4[Ge8V14O50·(H2O)] (pip = C4N2H10), 2 (tetragonal, space group P42/nnm (No. 134), Z = 2, a = 14.9950(7) A, c = 18.408(1) A), two and four VO2+ caps are replaced, respectively, and each cluster anion encapsulates a water molecule. In K5H8Ge8V12SO52·10H2O, 3, (tetragonal, space group I4/m (No. 87), Z = 2, a = 15.573(1) A, c = 10.963(1) A), four VO2+ caps are replaced by Ge2O(OH)24+ species, and an additional two are omitted. The cluster ion in 3 contains a sulfate anion disordered over two positions. The cluster anions are analogous to the vanadoarsenate anions [V18-nAs2nO42(X)]m- (X = SO3, SO4, Cl; n = 3, 4) previously reported.
Synthesis and structural studies of selected multifunctional phosphonate and phosphonic acid ligands

Abstract The carbanion [(RO)2P(O)][C(O)NEt2]CH− is used to prepare several new carbamoylmethyl phosphonates of the general type [(RO)2P(O)][C(O)NEt2]CH(X), XCH3, C2H5, (CH2)2CN, CH2CH[(RO)2P(O)][C(O)NEt2], (CH2)3OH and CH2C(O)OCH3. In addition, an interesting intramolecular transesterification process for the molecule with X(CH2)3OH and novel hydrolysis chemistry that produces useful phosphonic acids are described. The molecular structure determinations of two compounds, {[(i-PrO)2P(O)][C(O)NEt2]CH}2CH2 (4b) and [ NH 2 C(CH 3 ) 2 CH 2 C(O)CH 2 C(C H3)2+][(HO)PO2CH2C(O)NEt2−] (bd11) are outlined. Compound (bd4b) crystallizes in the triclinic space group P1, with a=9.0996(24), b=12.6604(31), c=16.5711(48) A, α=68.655(20), β=78.714(22), γ=70.742(19)° and Z=2. The molecular structure confirms that two carbamoylmethyl phosphonate fragments are bonded to a central methyl group. Compound 11 crystallizes in the triclinic space group P1, with a=9.2384(21), b=9.8404(21), c=11.0702(25) A, α=85.276(18), β=74.477(17), γ=78.644(17)° and Z=2. The molecular structure contains a 2,2,6,6-tetramethyl piperidone cation and a carbamoylmethyl phosphonic acid anion.
Radical-based methodology for efficient generation of acyclic N-acylimines

Abstract α-Methoxybenzamides 11 , which are convenient precursors of acyclic N -acylimines, can be cleanly generated in high yields via a free radical process starting from an o -aminobenzamide 16 derived from an N - t -butyl or N -cumyl secondary amine.
Mechanism and resistance for antimycobacterial activity of a fluoroquinophenoxazine compound

We have previously reported the inhibition of bacterial topoisomerase I activity by a fluoroquinophenoxazine compound (FP-11g) with a 6-bipiperidinyl lipophilic side chain that exhibited promising antituberculosis activity (MIC = 2.5 μM against Mycobacterium tuberculosis, SI = 9.8). Here, we found that the compound is bactericidal towards Mycobacterium smegmatis, resulting in greater than 5 Log10 reduction in colony-forming units [cfu]/mL following a 10 h incubation at 1.25 μM (4X MIC) concentration. Growth inhibition (MIC = 50 μM) and reduction in cfu could also be observed against a clinical isolate of Mycobacterium abscessus. Stepwise isolation of resistant mutants of M. smegmatis was conducted to explore the mechanism of resistance. Mutations in the resistant isolates were identified by direct comparison of whole-genome sequencing data from mutant and wild-type isolates. These include mutations in genes likely to affect the entry and retention of the compound. FP-11g inhibits Mtb topoisomerase I and Mtb gyrase with IC50 of 0.24 and 27 μM, respectively. Biophysical analysis showed that FP-11g binds DNA as an intercalator but the IC50 for inhibition of Mtb topoisomerase I activity is >10 fold lower than the compound concentrations required for producing negatively supercoiled DNA during ligation of nicked circular DNA. Thus, the DNA-binding property of FP-11g may contribute to its antimycobacterial mechanism, but that alone cannot account for the observed inhibition of Mtb topoisomerase I.
Selective Oxidation of Olefins within Organic Dye Cation-Exchanged Zeolites

This paper reports selectivity in the products during single oxygen mediated oxidation of olefins included within dye-exchanged X and Y zeolites. Singlet oxygen is generated within a zeolite by irradiating a thiazine dye exchanged into zeolites. Oxazine and thiazine dye molecules can be readily exchanged for alkali cations present in the interior of faujasite (X and Y) zeolites. Depending on the status of hydration, these dye molecules exist either in monomeric or dimeric forms. We show here that when a thiazine dye molecule is present in its monomeric form within a zeolite, it serves as an excellent singlet oxygen sensitizer. Utilizing zeolite supercages as `active reaction cavities`, we have directed the reactive oxygen toward a particular face of the olefin and obtained a high selectivity in the products of oxidation. 18 refs., 4 figs.
Strong Preferential Ion Heating is Limited to within the Solar Alfvén Surface

The decay of the solar wind helium-to-hydrogen temperature ratio due to Coulomb thermalization can be used to measure how far from the Sun strong preferential ion heating occurs. Previous work has shown that a zone of preferential ion heating, resulting in mass-proportional temperatures, extends about 20–40 R ⊙ from the Sun on average. Here we look at the motion of the outer boundary of this zone with time and compare it to other physically meaningful distances. We report that the boundary moves in lockstep with the Alfven point over the solar cycle, contracting and expanding with solar activity with a correlation coefficient of better than 0.95 and with an rms difference of 4.23 R ⊙. Strong preferential ion heating is apparently predominately active below the Alfven surface. To definitively identify the underlying preferential heating mechanisms, it will be necessary to make in situ measurements of the local plasma conditions below the Alfven surface. We predict that the Parker Solar Probe (PSP) will be the first spacecraft to directly observe this heating in action, but only a couple of years after launch as activity increases, the zone expands, and PSP's perihelion drops.
Multifaceted protein-protein interaction prediction based on Siamese residual RCNN.

Motivation Sequence-based protein-protein interaction (PPI) prediction represents a fundamental computational biology problem. To address this problem, extensive research efforts have been made to extract predefined features from the sequences. Based on these features, statistical algorithms are learned to classify the PPIs. However, such explicit features are usually costly to extract, and typically have limited coverage on the PPI information. Results We present an end-to-end framework, PIPR (Protein-Protein Interaction Prediction Based on Siamese Residual RCNN), for PPI predictions using only the protein sequences. PIPR incorporates a deep residual recurrent convolutional neural network in the Siamese architecture, which leverages both robust local features and contextualized information, which are significant for capturing the mutual influence of proteins sequences. PIPR relieves the data pre-processing efforts that are required by other systems, and generalizes well to different application scenarios. Experimental evaluations show that PIPR outperforms various state-of-the-art systems on the binary PPI prediction problem. Moreover, it shows a promising performance on more challenging problems of interaction type prediction and binding affinity estimation, where existing approaches fall short. Availability and implementation The implementation is available at https://github.com/muhaochen/seq_ppi.git. Supplementary information Supplementary data are available at Bioinformatics online.
Pharmacokinetics of dexmedetomidine during administration of vatinoxan in male neutered cats anesthetized with isoflurane

Dexmedetomidine is an alpha-2 adrenoceptor agonist, and vatinoxan is an alpha-2 antagonist believed to poorly cross the blood-brain barrier in cats. Dexmedetomidine-vatinoxan combinations are of interest in anesthetized cats because the anesthetic sparing effect of dexmedetomidine may be preserved while vatinoxan attenuates the adverse cardiovascular effects of dexmedetomidine. The aim of this study was to characterize the pharmacokinetics of dexmedetomidine in cats during administration of isoflurane and vatinoxan. Six healthy adult male castrated cats were anesthetized with isoflurane in oxygen. Vatinoxan was administered using a target-controlled infusion system intended to maintain a plasma concentration of 4 µg/ml. Dexmedetomidine, 35 µg/kg was administered intravenously over 5 min. Plasma dexmedetomidine and vatinoxan concentrations were measured at selected time points ranging from prior to 8 hr after dexmedetomidine administration using liquid chromatography/tandem mass spectrometry. Compartment models were fitted to the time-concentration data using nonlinear mixed-effect modeling. A three-compartment model best fitted the data. Typical value (% interindividual variability) for the three-compartment volumes (ml/kg), the metabolic clearance and the two intercompartment distribution clearances (ml min-1 kg-1 ) were 168 (259), 318 (35), 1,425 (18), 12.4 (31), 39.1 (18), and 29.6 (17), respectively. Mean ± standard deviation plasma vatinoxan concentration was 2.6 ± 0.6 µg/ml.
Exponential Error Rates of SDP for Block Models: Beyond Grothendieck’s Inequality

In this paper, we consider the cluster estimation problem under the stochastic block model. We show that the semidefinite programming (SDP) formulation for this problem achieves an error rate that decays exponentially in the signal-to-noise ratio. The error bound implies weak recovery in the sparse graph regime with bounded expected degrees as well as exact recovery in the dense regime. An immediate corollary of our results yields error bounds under the censored block model. Moreover, these error bounds are robust, continuing to hold under heterogeneous edge probabilities and a form of the so-called monotone attack. Significantly, this error rate is achieved by the SDP solution itself without any further pre- or post-processing and improves upon existing polynomially decaying error bounds proved using the Grothendieck’s inequality. Our analysis builds on two key ingredients: 1) showing that the graph has a well-behaved spectrum, even in the sparse regime, after discounting an exponentially small number of edges and 2) an order-statistics argument that governs the final error rate. Both arguments highlight the implicit regularization effect of the SDP formulation.
Invariant distributions and tensor tomography for Gaussian thermostats

In this paper we consider the Gaussian thermostat ray transform on both closed Riemannian surfaces and compact Riemannian surfaces with boundary. We establish certain results on the injectivity of the thermostat ray transform and the surjectivity of its adjoint.
Variations on a Theorem of Tate

Let F be a number field. These notes explore Galois-theoretic, automorphic, and motivic analogues and refinements of Tate’s basic result that continuous projective representations Gal(F/F)→ PGLn(C) lift to GLn(C). We take special interest in the interaction of this result with algebraicity (for automorphic representations) and geometricity (in the sense of Fontaine-Mazur). On the motivic side, we study refinements and generalizations of the classical Kuga-Satake construction. Some auxiliary results touch on: possible infinity-types of algebraic automorphic representations; comparison of the automorphic and Galois “Tannakian formalisms”; monodromy (independenceof-`) questions for abstract Galois representations.
Energy, momentum, and center of mass in general relativity

These notions in the title are of fundamental importance in any branch of physics. However, there have been great difficulties in finding physically acceptable definitions of them in general relativity since Einstein's time. I shall explain these difficulties and progresses that have been made. In particular, I shall introduce new definitions of center of mass and angular momentum at both the quasi-local and total levels, which are derived from first principles in general relativity and by the method of geometric analysis. With these new definitions, the classical formula p=mv is shown to be consistent with Einstein's field equation for the first time. This paper is based on joint work [14][15] with Po-Ning Chen and Shing-Tung Yau.
Vector bundles whose restriction to a linear section is Ulrich

An Ulrich sheaf on an n-dimensional projective variety \(X \subseteq \mathbb {P}^{N}\) is an initialized ACM sheaf which has the maximum possible number of global sections. Using a construction based on the representation theory of Roby–Clifford algebras, we prove that every normal ACM variety admits a reflexive sheaf whose restriction to a general 1-dimensional linear section is Ulrich; we call such sheaves \(\delta \)-Ulrich. In the case \(n=2,\) where \(\delta \)-Ulrich sheaves satisfy the property that their direct image under a general finite linear projection to \(\mathbb {P}^2\) is a semistable instanton bundle on \(\mathbb {P}^{2}\), we show that some high Veronese embedding of X admits a \(\delta \)-Ulrich sheaf with a global section.
UAV circumnavigating an unknown target under a GPS-denied environment with range-only measurements

One typical application of unmanned aerial vehicles (UAVs) is the intelligence, surveillance, and reconnaissance mission, where the objective is to improve situation awareness through information acquisition. For example, an efficient way to gather information regarding a target is to deploy UAV in such a way that it orbits around this target at a desired distance. Such a UAV motion is called circumnavigation. The objective of this paper is to design a control algorithm such that this circumnavigation mission is achieved under a GPS-denied environment when only range measurement is used. The control algorithm is constructed in two steps. The first step is to design a control algorithm by assuming the availability of both range and range rate measurements, where the associated control input is always bounded. The second step is to further eliminate the use of range rate measurement by using an estimated range rate, obtained via a sliding-mode estimator based on range measurement, to replace actual range rate measurement. Such a controller design technique is applicable in other UAV navigation and control missions when a GPS-denied environment is considered.
On coupling kinetic and Schrödinger equations

Abstract We consider in this paper a system coupling a linear quantum Boltzmann equation and a defocussing cubic nonlinear Schrodinger equation. The Schrodinger equation reflects the dynamics of the wave function of the Bose–Einstein Condensate and the kinetic part of the system describes the evolution of the density function of the thermal cloud. An existence and uniqueness result for the system is supplied. We also prove the convergence to equilibrium of the density function of the thermal cloud and a scattering theory for the wave function of the condensate.
Corrosion of Si, C, and SiC in molten salt

Abstract Corrosion of Si, C, and SiC in fluoride salt has been studied byab initio molecular dynamics. The standard dissolution potential for Si is found to be smaller (easier to corrode) than that of C. The dissolved Si attracts F−ions and forms SiF62-, whereas the dissolved C species forms neutral CF4molecules. A swapping mechanism is identified for the initial corrosion stage, where Si first comes to the surface and then is dissolved, leaving behind chain- and ring-like C structures. A strategy to suppress SiC corrosion is also discussed based on Be doping, including avoiding Be2C formation.
A notion of minor-based matroid connectivity

Abstract For a matroid N, a matroid M is N-connected if every two elements of M are in an N-minor together. Thus a matroid is connected if and only if it is U 1 , 2 -connected. This paper proves that U 1 , 2 is the only connected matroid N such that if M is N-connected with | E ( M ) | > | E ( N ) | , then M \ e or M / e is N-connected for all elements e. Moreover, we show that U 1 , 2 and M ( W 2 ) are the only matroids N such that, whenever a matroid has an N-minor using { e , f } and an N-minor using { f , g } , it also has an N-minor using { e , g } . Finally, we show that M is U 0 , 1 ⊕ U 1 , 1 -connected if and only if every clonal class of M is trivial.
ANOMALIES AND THE EULER CHARACTERISTIC OF ELLIPTIC CALABI-YAU THREEFOLDS

We investigate the delicate interplay between the types of singular fibers in elliptic fibrations of Calabi-Yau threefolds (used to formulate F-theory) and the "matter" representation of the associated Lie algebra. The main tool is the analysis and the appropriate interpretation of the anomaly formula for six-dimensional supersymmetric theories. We find that this anomaly formula is geometrically captured by a relation among codimension two cycles on the base of the elliptic fibration, and that this relation holds for elliptic fibrations of any dimension. We introduce a "Tate cycle" which efficiently describes thisrelation- ship, and which is remarkably easy to calculate explicitly from the Weierstrass equation of the fibration. We check the anomaly cancellation formula in a num- ber of situations and show how this formula constrains the geometry (and in particular the Euler characteristic) of the Calabi-Yau threefold.
Approximation of points on low-dimensional manifolds via random linear projections

This paper considers the approximate reconstruction of points x ∈RD which are close to a given compact d-dimensional submanifold M of RD using a small number of linear measurements of x. In particular, it is shown that a number of measurements of x, which is independent of the extrinsic dimension D suffices for a highly accurate reconstruction of x. Furthermore, it is also proved that all vectors x which are sufficiently close to M can be reconstructed with uniform approximation guarantees when the number of linear measurements of x depends logarithmically on D. Finally, the proofs of these facts are constructive: a practical algorithm for manifold-based signal recovery is presented in the process of proving the two main results mentioned above.
Classification of Reductive Monoid Spaces Over an Arbitrary Field

In this semi-expository paper, we review the notion of a spherical space. In particular, we present some recent results of Wedhorn on the classification of spherical spaces over arbitrary fields. As an application, we introduce and classify reductive monoid spaces over an arbitrary field.
Playing games against nature: optimal policies for renewable resource allocation

In this paper we introduce a class of Markov decision processes that arise as a natural model for many renewable resource allocation problems. Upon extending results from the inventory control literature, we prove that they admit a closed form solution and we show how to exploit this structure to speed up its computation. We consider the application of the proposed framework to several problems arising in very different domains, and as part of the ongoing effort in the emerging field of Computational Sustainability we discuss in detail its application to the Northern Pacific Halibut marine fishery. Our approach is applied to a model based on real world data, obtaining a policy with a guaranteed lower bound on the utility function that is structurally very different from the one currently employed.
A proposed gravitodynamic theory

This paper proposes a gravitodynamic theory because there are similarities between gravitational theory and electrodynamics. Based on Einstein's principle of equivalence, two coordinate conditions are proposed into the four-dimensional line element and transformations. As a consequence,the equation of motion for gravitational force or inertial force has a form similar to the equation of Lorentz force on a charge in electrodynamics. The inertial forces in auniformly rotating system are calculated, which show that the Coriolis force is produced by a magnetic-type gravitational field. We have also calculated the Sagnac effect due to the rotation. These experimental facts strongly support our proposed coordinate conditions. In addition, the gravitodynamic field equations are briefly discussed. Since only four gravitational potentials (3 + 1 split) enter the metric tensor, the gravitodynamic field equations in ``3+1 split" form would be analogous to Maxwell's equations.
Combinatorics of linked systems of quartet trees

We apply classical quartet techniques to the problem of phylogenetic decisiveness and find a value $k$ such that all collections of at least $k$ quartets are decisive. Moreover, we prove that this bound is optimal and give a lower-bound on the probability that a collection of quartets is decisive.