cssi/SciSciGPT-SciSciNet huggingface dataset:
Masked 2-Arylacroleins: Versatile Three-Carbon Units for Organic Synthesis

2-Arylpropenals H2CdC(Ar)CHO are of considerable synthetic value for the preparation of tryptophans,1 vinylic peroxyketals,2 2,2′-bipyridines,3 and functionalized cycloheptenes.4 Accordingly, a variety of methods have been developed for the preparation of 2-arylpropenals based on transformations of various styrenes as follows: (i) reaction of Grignards derived from R-bromo styrenes with ethyl orthoformate;5 (ii) oxidation with selenium dioxide,6 or bromination followed by hydrolysis,7 of R-methylstyrenes; and (iii) three-step cyclopropanation, ring opening, and hydrolysis of styrenes.8 Further routes use 2-arylethanols9 and R-chloroacetals as starting materials.10 However, the application of 2-arylpropenals in synthesis is accompanied by several problems. The compounds are highly toxic.11 The double bond in H2CdC(Ar)CHO, activated by both the aryl and the carbonyl group, is highly reactive; consequently, these molecules are claimed to be unstable above -6 °C,8 although 2-(4-methoxycarbonylphenyl)propenal was isolated apparently at room temperature12 and although 2-phenylpropenal can be distilled at 79-82 °C at reduced pressure.6 At room temperature, atropaldehyde (2-phenylpropenal) undergoes a spontaneous hetero Diels-Alder dimerization to give the corresponding dihydropyran.6 Furthermore, while conjugate additions occur readily, to our best knowledge, the only 1,2-additions of carbon nucleophiles to 2-arylpropenals are allylmagnesium chloride, propynyl bromide in the presence of aluminum amalgam to 2-phenylpropenal,13 and 1-bromo-2-phenylpropene in the presence of zinc and ammonium chloride to 2-(4-methoxycarbonylphenyl)propenal.14 Hence, the development of a route to masked 2-arylpropenals is considerably attractive. We now describe such substrates in which the double bond is masked, allowing for clean 1,2-addition to the aldehyde moiety. Deprotection of the double bond regenerates the unsaturation and renders a formal 1,2addition to 2-arylpropenals.
Summary of experimental results : photons, leptons and heavy quarks

This is a summary of experimental results on photons, leptons and heavyquarks presented at Quark Matter 2008. A first measurement of the bottom to charm contribution to the lepton spectrum has given experimental indication for the suppression of charm and bottom. Excess dileptons have been observed and studied by both NA60 and PHENIX, which may arise from the early production of thermal dileptons and/or the modification of mesons.
An enantioselective synthesis of cryptocarya diacetate.

The enantioselective synthesis of cryptocarya diacetate has been achieved in 10 steps from ethyl sorbate. The route relies upon an enantio- and regioselective Sharpless dihydroxylation and a palladium-catalyzed reduction to form a δ-hydroxy-1-enoate, which was subsequently converted into a benzylidene-protected 3,5-dihydroxy carboxylic ester. This ester was converted into cryptocarya diacetate in 14% overall yield via an allylation and methathesis ring closure reaction sequence.
Allyldimethyltritylsilane. Synthesis of Cyclopentanols, Oxetanes, and Tetrahydrofurans by Reaction with Electron Deficient Olefins

Allyldimethyltritylsilane (ADTS, 1) has been employed to access a variety of cyclopentanols via Lewis acid mediated annulation to electron deficient olefins. The intermediate silylcyclopentanes were converted to their respective cyclopentanols under mild, nonepimerizing oxidative conditions. In addition, ADTS undergoes efficient annulation onto aldehydes to provide oxetanes and tetrahydrofurans. Some preliminary investigations of this annulation to chiral nonracemic bicyclic lactams are presented.
Metallo-aldehyde enolates via enal hydrogenation: catalytic cross aldolization with glyoxal partners as applied to the synthesis of 3,5-disubstituted pyridazines.

Aldehyde enolates generated through rhodium-catalyzed enal hydrogenation are subject to electrophilic trapping by exogenous glyoxal partners to afford β-hydroxy-γ-keto-aldehyde products, which upon exposure to hydrazine afford 3,5-disubstituted pyridazines in moderate yield in a two-step, one-pot sequence.
M(bipyridine)V4O10 (M ) Cu, Ag): Hybrid Analogues of Low-Dimensional Reduced Vanadates

New hybrid layered vanadates, M(bpy)V4O10 (I, M = Cu+; II, M = Ag+; bpy = 4,4‘-bipyridine), were prepared from hydrothermal reactions at 220−230 °C, and their structures were characterized by singl...
Addition of Aryl and Fluoroalkyl Radicals to Fullerene C70: ESR Detection of Five Regioisomeric Adducts and Density Functional Calculations†

The addition of several photochemically generated aryl and fluoroalkyl radicals to fullerene C70 was studied by electron spin resonance and the results were compared with those obtained with C60. While simple alkyl radicals afford only three of the five expected RC70• regioisomers, the more reactive aryl and fluoroalkyl radicals give rise to four, except for the trifluoromethyl radical which yielded for the first time the ESR spectra of all five expected isomers. Semiempirical MO calculations and density functional theory calculations were carried out for HC60• and for the five HC70• regioisomers as models for the corresponding alkyl, aryl, and fluoroalkyl analogs in order to describe the unpaired electron distribution in these radical species and as an aid in the assignment of the observed spectra to specific RC70• regioisomers.
IFNγ induces epigenetic programming of human T-bethi B cells and promotes TLR7/8 and IL-21 induced differentiation.

Although B cells expressing the IFNγR or the IFNγ-inducible transcription factor T-bet promote autoimmunity in Systemic Lupus Erythematosus (SLE)-prone mouse models, the role for IFNγ signaling in human antibody responses is unknown. We show that elevated levels of IFNγ in SLE patients correlate with expansion of the T-bet expressing IgDnegCD27negCD11c+CXCR5neg (DN2) pre-antibody secreting cell (pre-ASC) subset. We demonstrate that naive B cells form T-bethi pre-ASCs following stimulation with either Th1 cells or with IFNγ, IL-2, anti-Ig and TLR7/8 ligand and that IL-21 dependent ASC formation is significantly enhanced by IFNγ or IFNγ-producing T cells. IFNγ promotes ASC development by synergizing with IL-2 and TLR7/8 ligands to induce genome-wide epigenetic reprogramming of B cells, which results in increased chromatin accessibility surrounding IRF4 and BLIMP1 binding motifs and epigenetic remodeling of IL21R and PRDM1 loci. Finally, we show that IFNγ signals poise B cells to differentiate by increasing their responsiveness to IL-21.
Isolated ∞1[ZnPn2]4− Chains in the Zintl Phases Ba2ZnPn2 (Pn = As, Sb, Bi)—Synthesis, Structure, and Bonding

Reported are the synthesis of three new Zintl phases, Ba2ZnAs2 (I), Ba2ZnSb2 (II), Ba2ZnBi2 (III) and their structural characterization by single-crystal X-ray diffraction. They are isoelectronic a...
Synthesis and structural characterization of RE7Zn21Tt2 (RE = La-Nd; Tt = Ge, Sn, and Pb): new structure type among the polar intermetallic phases.

Reported are 11 new ternary phases with the general formula RE7Zn21Tt2 (RE = La–Nd; Tt = Ge, Sn, and Pb), synthesized from the respective elements by reactions at high temperature. Their structures, established on the basis of single-crystal and powder X-ray diffraction work, are shown to be a new structure type with the orthorhombic space group Pbam (No. 55, Pearson symbol oP60). This complex atomic arrangement features condensed polyhedra made up of Zn atoms, interspersed by Ge, Sn, or Pb atoms in trigonal-planar coordination. The structure bears resemblance with the La3Al11 and the LaRhSn2 structure types, which are compared and discussed. Temperature dependent dc magnetization measurements confirm RE3+ ground states for all rare-earth elements, and the expected local-moment magnetism due to the partial filling of their 4f states for RE3+ = Ce3+, Pr3+, and Nd3+. Theoretical considerations of the electronic structure based on the tight-binding linear muffin-tin orbital (TB-LMTO-ASA) method are also pres...
A double-blind pilot dosing study of low field magnetic stimulation (LFMS) for treatment-resistant depression (TRD).

Abstract Background Low field magnetic stimulation is a potentially rapid-acting treatment for depression with mood-enhancing effects in as little as one 20-min session. The most convincing data for LFMS has come from treating bipolar depression. We examined whether LFMS also has rapid mood-enhancing effects in treatment-resistant major depressive disorder, and whether these effects are dose-dependent. Objective/Hypothesis We hypothesized that a single 20-min session of LFMS would reduce depressive symptom severity and that the magnitude of this change would be greater after three 20-min sessions than after a single 20-min session. Methods In a double-blind randomized controlled trial, 30 participants (age 21–65) with treatment-resistant depression were randomized to three 20-min active or sham LFMS treatments with 48 h between treatments. Response was assessed immediately following LFMS treatment using the 6-item Hamilton Depression Rating Scale (HAMD-6), the Positive and Negative Affect Scale (PANAS) and the Visual Analog Scale. Results Following the 3rd session of LFMS, the effect of LFMS on VAS and HAMD-6 was superior to sham (F (1, 24) = 7.45, p = 0.03, Bonferroni–Holm corrected; F (1, 22) = 6.92, p = 0.03, Bonferroni–Holm corrected, respectively). There were no differences between sham and LFMS following the initial or second session with the effect not becoming significant until after the third session. Conclusions Three 20-min LFMS sessions were required for active LFMS to have a mood-enhancing effect for individuals with treatment-resistant depression. As this effect may be transient, future work should address dosing schedules of longer treatment courses as well as biomarker-based targeting of LFMS to optimize patient selection and treatment outcomes.
Intramolecular Hydride Addition to Pyridinium Salts: New Routes to Enantiopure Dihydropyridones

The transformation of a simple disubstituted pyridine into a pyridinium ion bearing an exocyclic hydroxyl group, protected as a silane, enabled an intramolecular hydride transfer reaction to take place when fluoride was used as a nucleophile. The addition was both regio- and stereoselective and enabled the formation of enantiopure dihydropyridones when enantiopure pyridine derivatives were used in this sequence. The heterocyclic products contain ample functionality for further elaboration reactions and subsequent derivatization.
Generative Adversarial Networks Conditioned on Brain Activity Reconstruct Seen Images

We consider the inference problem of reconstructing a visual stimulus from brain activity measurements (e.g. fMRI) that encode this stimulus. Recovering a complete image is complicated by the fact that neural representations are noisy, high-dimensional, and contain incomplete information about image details. Thus, reconstructions of complex images from brain activity require a strong prior. Here we propose to train generative adversarial networks (GANs) to learn a generative model of images that is conditioned on measurements of brain activity. We consider two challenges of this approach: First, given that GANs require far more data to train than is typically collected in an fMRI experiment, how do we obtain enough samples to train a GAN that is conditioned on brain activity? Secondly, how do we ensure that our generated samples are robust against noise present in fMRI data? Our strategy to surmount both of these problems centers around the creation of surrogate brain activity samples that are generated by an encoding model. We find that the generative model thus trained generalizes to real fRMI data measured during perception of images and is able to reconstruct the basic outline of the stimuli.
“For Whom the Bell Tolls” in the Legal System: Access to Justice and Conflict Engagement

Remarks adapted from presentation: Disrupting Law, Reclaiming Justice, a Conversation on Gillian Hadfield’s Rule for a Flat World on October 8, 2018 at Creighton University. Despite the advancement in the ADR movement, there is much work to be done for justice to be accessible to “All.” The legal profession continues to lack diversity among its members and a uniform way of thinking impedes a transformative change to the legal infrastructure. Conflict as an interdisciplinary field draws upon a more diverse group of professionals and theoretical frameworks. I propose that conflict processes, not the legal system, should be the overarching umbrella under which all conflict resolution/engagement processes fall.
Synthesis and Unusual Physical Behavior of a Photorefractive Polymer Containing Tris(bipyridyl)ruthenium(II) Complexes as a Photosensitizer and Exhibiting a Low Glass-Transition Temperature

This paper reports the synthesis and characterization of a low-Tg photorefractive (PR) polymer which contains ionic ruthenium complexes as the photogenerator of charge carriers. It was expected that a combination of the highly efficient photocharge generation of the Ru complex, the efficient charge transporting of the conjugated backbone, and the orientational enhancement associated with low-Tg materials would lead to further improvement of PR performances. However, it was very interesting to find that the PR performance of this polymer was limited by the local internal field formed in response to the external electric field by the alignment of ion pairs around the photocharge generation sites. The effects of such a local field on photocharge generation and photorefractivity were investigated through the analyses of the dependence of photocurrent, photorefractive gain, diffraction efficiency, electrooptic activity, and birefringence on the applied field. The dynamic behavior of the PR grating formation wa...
Synthesis and Chemistry of Highly Fluorinated Oxepane-2,7-diols

Reduction of dimethyl perfluoroadipate with Vitride yielded the title compounds, which were also prepared by dehydration of 1H,6H-perfluorohexane-1,1,6,6-tetrol. The configurations of the oxepanediols were assigned based on the crystal structure of the bis(tert-butyldiphenylsilyl) ether of the cis stereoisomer. Treatment with ethanolic HCl ring-opened the diols to 1H,6H-1,6-diethoxyperfluorohexane-1,6-diol, and dehydration with P 4 O 1 0 gave perfluorohexanedial.
Exact Length Distribution of Filamentous Structures Assembled from a Finite Pool of Subunits

Self-assembling filamentous structures made of protein subunits are ubiquitous in cell biology. These structures are often highly dynamic, with subunits in a continuous state of flux, binding to and falling off of filaments. In spite of this constant turnover of their molecular parts, many cellular structures seem to maintain a well-defined size over time, which is often required for their proper functioning. One widely discussed mechanism of size regulation involves the cell maintaining a finite pool of protein subunits available for assembly. This finite pool mechanism can control the length of a single filament by having assembly proceed until the pool of free subunits is depleted to the point when assembly and disassembly are balanced. Still, this leaves open the question of whether the same mechanism can provide size control for multiple filamentous structures that are assembled from a common pool of protein subunits, as is often the case in cells. We address this question by solving the steady-state...
Aromatic Substituted Group 4 Metallocene Catalysts for the Polymerization of α-Olefins

Six new group 4 metallocene complexes were synthesized as precursors for the polymerization of α-olefins. The phenyl-substituted precursors 2b−4b when activated by methylaluminoxane (MAO) were highly active for the polymerization of ethylene but exhibited no activity for the polymerization of propylene. Bis(2-methylbenz[e]indenyl)zirconium dichloride (5b) was activated with both MAO and triphenylcarbenium tetrakis(pentafluorophenyl)borate (trityl)/triisobutylaluminum producing polypropylene with varying molecular weight depending on polymerization temperature. The titanium precursor 6b had lower activity for ethylene as compared to the zirconium analog 5b and virtually no activity for propylene when activated with either MAO or trityl.
Low-Dimensional Sulfoantimonates with Metal Complexes as Counterions. Hydrothermal Synthesis and Properties of [M(en)3]Sb2S4 (M = Co, Ni) and [M(en)3]Sb4S7 (M = Fe, Ni)

[M(en)3]Sb2S4 (M = Co, Ni) and [M(en)3]Sb4S7 (M = Fe, Ni) were prepared from the MX2/Na3SbS3/en system (X = Cl, Br; en = ethylenediamine) under hydrothermal conditions. Orange-yellow [Ni(en)3]Sb2S4...
Synthesis of brasilibactin A and confirmation of absolute configuration of β-hydroxy acid fragment

Abstract A synthesis of brasilibactin A, a cytotoxic siderophore from the actinomycete of Nocardia brasiliensis, and three unnatural diastereomers of the natural product is described. Four possible diastereomers of the β-hydroxy acid fragment were prepared via asymmetric aldol reactions and used to synthesize brasilibactin A and its diastereomers. Careful analysis of 1H NMR data confirmed that brasilibactin A possesses the 17S,18R absolute stereochemistry.
2,6‐Diarylhexahydro‐4‐pyridazinols by acid‐catalyzed cyclization of benzaldehyde aryl‐2‐(2‐propenyl)hydrazones

Treatment of benzaldehyde l-(2-propenyl)-4-methylsulfonylphenylhydrazone (1f) with 45% sulfuric acid gave 2-(4-methylsulfonylphenyl)-6-phenylhexahydro-4-pyridazinol (2f) in 35% yield rather than the expected 1-(4-methylsulfonylphenyl)-1-(2-propenyl)hydrazine. The halogen-substituted hydrazones 1c-1e and benzaldehyde 1-(2-methyl-2-propenyl)phenylhydrazone (1b) gave similar results.
Oxidative ring opening of 2,5-diarylfurans by Selectfluor®

Abstract Attempted fluorination of some 2,5-diarylfurans with the N–F reagent Selectfluor® has led instead to oxidative ring opening of the furan ring to give the cis-enedione, along with traces of the trans isomer, in good isolated yield.
Relic Neutrinos and Z-Resonance Mechanism for Highest Energy Cosmic Rays

The origin of the highest energy cosmic rays remains elusive. The decay of a superheavy particle (X) into an ultraenergetic neutrino which scatters from a relic neutrino or antineutrino at the Z-resonance has attractive features. Given the necessary X mass of 1014-1015 GeV, the required lifetime, 1015-1016 yr, renders model building a serious challenge, but three logical possibilities are considered: (1) X is a Higgs scalar in SU(15) belonging to high-rank representation, leading to power-enhanced lifetime; (2) a global X quantum number has exponentially suppressed symmetry breaking by instantons; and (3) with additional space dimension(s), localization of X within the real-world brane leads to Gaussian decay suppression, the most efficient of the suppression mechanisms considered.
A new route to heterocyclic compounds by the mercuric acetate oxidation of N-alkyl substituted 4-piperidones

N-Alkyl substituted 4-piperidones readily undergo oxidation in high yield upon reaction with mercuric acetate. Application of the oxidation to the synthesis of the skeletal framework of several alkaloids is described.
The application of organic bases in microwave-promoted Suzuki coupling reactions in water

Traditionally, mineral bases are used in Suzuki coupling protocols. The use of DBU or DABCO as alternative bases for the reaction is reported and the application discussed.
Novel and convenient routes to substituted pyrroles and imidazoles

Abstract S-Melhyl N-(benzotriazol-1-ylmethyl)thioimidate 6 is obtained by lithiation of the corresponding N-(benzotriazol-1-ylmelhyl) thioamide 5 and subsequent reaction with methyl iodide. Derivative 6 undergoes [2 + 3] cycloaddition reactions with α,β-unsaturated -esters, -ketones and -nitriles, and vinylpyridines which are followed by elimination of benzotriazole and the thioalkoxy group, to give 2,3,4-trisubstituted pyrroles. Lithiaiion of 6 followed by reactions with imines gives cyclized 4,5-dihydroimidazoles 14 which upon further treatment with ZnBr2 or direct refluxing in toluene yield the 1,25-trisubstituted imidazoles 15 in good yields.
Germanium nanowire synthesis: An example of solid-phase seeded growth with nickel nanocrystals

Germanium nanowires were synthesized by thermal decomposition of diphenyl germane in the presence of nickel (Ni) nanocrystals in supercritical toluene at 27.8 MPa and temperatures ranging from 410 to 460 °C. The growth temperature is well below the lowest Ni−Ge eutectic temperature (762 °C), and nanowire crystallization appears to occur by solid-phase alloying of the seed particle. We call this nanowire growth mechanism supercritical fluid−solid−solid (SFSS) synthesis.
Acidities of Radical Anions (pKHA−•) Derived from Nitro-Substituted Aromatic Weak Acids and the Formation of Radical Dianions

A simple method has been devised for measuring the equilibrium acidities in DMSO of radical anions by using the equation pKHA−• = pKHA + 16.8[Erd(HA) − Erd(A-) ], which is based on a thermodynamic cycle. The acidities of 24 nitro-substituted aromatic radical anions have been measured in this way. The reversible reduction potentials to form the radical anions and those of their conjugate bases to form the radical dianions were obtained by cyclic voltammetry. The points for the irreversible Erd(HA) values for 6 nitroaromatic compounds were found to fit on or close to the line of a plot of Erd(HA) vs σp- for the reversible Erd(HA) values for 11 nitroaromatic compounds. The σp- value for p-NH2 was estimated to be about −1.0 from this plot. Relative radical dianion stabilization energies have been derived from the equilibrium acidities of the radical anions and the reduction potentials of the parent acids to provide an estimate of the stabilities of the radical dianions, relative to that of the p--OC6H4NO2-• r...
Total Synthesis of Crenulatan Diterpenes: Strategy and stereocontrolled construction of a bicyclic keto‐lactone building block

The bicyclic keto lactone 26 was synthesized for the purpose of developing a viable route to marine diterpenes of the crenulatan type. Following the efficient conversion of (S)-citronellol (5) to the allylated alcohol 9a (Scheme 2), the αβ-unsaturated lactone 12 was efficiently accessed in preparation for stereocontrolled conjugate addition. The hydroxymethyl equivalent most suited to this task was (i-PrO)Me2SiCH2MgCl, which gave 13 predominantly in the presence of CuI and Me3SiCl. Once the OH group was deprotected ( 14), it proved an easy matter to implement acid-catalyzed isomerization to lactone 15, oxidation of which gave the pivotal aldehyde 16. Condensation of 16 with PhSeCH2Li led via21 to 22 (Scheme 3). Once the OH group was protected ( 22b), it proved possible to effect aldolization with crotonaldehyde ( 23). Exposure of 23 to acid gave the sub-target compound 25. Its subsequent oxidation and thermal activation resulted in sequential selenoxide elimination with Claisen rearrangement ( 26). The structural features of 26 require that a chair-like transition state be adopted during the [3.3]sigmatropic event. With the clarification of these issues, a highly serviceable and more advanced assault on the crenulatans should prove capable of being mounted.
Total Synthesis of (+)-Lactacystin

A double stereodifferentiating crotylation between aldehyde 1 and silane (S)-2 to afford homoallylic alcohol 3 is the key diastereoselective step (anti:syn >30:1) in an efficient asymmetric synthesis of (+)-lactacystin. This compound is a metabolite isolated from Streptomyces sp. OM-6519 that exhibits significant neurotrophic activity. An additional important step in the synthesis is a catalytic asymmetric aminohydroxylation used as the key step in the synthesis of the (2R,3S)-hydroxyleucine synthon.
Bicyclic diazasugars. Part 3: β-d-Mannose and 6-deoxy-β-l-gulose analogues

Abstract A bicyclic analogue of β- d -mannopyranose with nitrogen atoms replacing the ring and glycosidic oxygen atoms has been prepared in a single step from 5-O-mesyl- d -mannofuranose by a process that likely involves double displacement and an epoxide intermediate. A similar but protected bicyclic analogue of 6-deoxy-β- l -gulopyranose has been prepared by an electrophilic cyclization reaction.
Manganese(III)-mediated oxidative radical addition of malonates to 2-cyanoindoles

Abstract 2-Cyanoindole and N-methyl-2-cyanoindole undergo manganese(III)-mediated radical addition with activated methylene and methine compounds. Products of the methylene addition underwent additional oxidation during the course of the reaction to furnish the corresponding acetoxy compounds. Several structures were confirmed by X-ray crystallography.
Convenient Synthesis of Julolidines Using Benzotriazole Methodology.

Reaction of N,N-bis[(benzotriazol-1-yl)methyl]aniline (2) with 1-vinylpyrrolidin-2-one gives a mixture of diastereomeric 1,7-bis(2-oxopyrrolidin-1-yl)julolidines 3. After reduction of 3 with LAH, the predominant trans diastereomer of 1,7-di(pyrrolidin-1-yl)julolidine (4) is separated. Reaction of 2 with ethyl vinyl ether yields predominantly trans-1,7-di(benzotriazol-1-yl)julolidine (11). Stepwise synthesis from tetrahydroquinoline 15 gives access to julolidines with two different substituents on C-1 and C-7. Reaction of 1-[(benzotriazol-1-yl)methyl]-1,2,3,4-tetrahydroquinoline (25) with enolizable aldehydes gives a mixture of tetrahydroquinolines 26−29 which are converted into single julolidine products upon treatment with sodium hydride, LAH, or phenylmagnesium bromide. Reactions of 1,2,3,4-tetrahydroquinolines with benzotriazole and 2 molar equiv of enolizable aldehydes gives 1,2,3-trisubstituted julolidines 38−41, which with lithium aluminum hydride, sodium hydride, or a Grignard reagent produce singl...
Ring-Enlarging Cyclohexane Annulations

A Prins−pinacol rearrangement is the key step in a new method for synthesizing cis-bicyclo[n.4.0]alkanones. The alkenyl acetal rearrangement substrates 1 are assembled from cycloalkanone precursors...
Ta5+ Displacements in CsTaQ3 (Q = S, Se, and Te): New One-Dimensional Materials with the BaVS3 Structure

The new compounds CsTaQ3 (Q = S, Se, and Te) have been synthesized through stoichiometric reactions of the elements with Cs2Qn reactive fluxes at 923 K. Their crystal structures have been determined by single-crystal X-ray methods. CsTaQ3 crystallize in the hexagonal space group −P63/mmc with two formula units per cell. Crystal data: CsTaS3, a = 7.266(2) A, c = 5.961(2) A, V = 272.55(10) A3 (T = 115 K), Rw(F2) = 0.072 (NO = 114, NV = 11), R1 = 0.034; CsTaSe3, a = 7.500(1) A, c = 6.182(1) A, V = 301.15(7) A3 (T = 115 K), Rw(F2) = 0.106 (NO = 112, NV = 11), R1 = 0.036; CsTaTe3, a = 7.992(4) A, c = 6.496(4) A, V = 359.3(4) A3 (T = 115 K), Rw(F2) = 0.131 (NO = 111, NV = 10), R1 = 0.038. The compounds adopt the BaVS3 structure type and feature chains of face-sharing octahedra. The Ta5+ centers are displaced from the centers of the Q6 octahedra along the direction of the chains in a centrosymmetric fashion. Geometrical considerations and band structure calculations at the extended Huckel and density functional...
A unified approach to the enantioselective synthesis of 2,6-cis and trans disubstituted tetrahydropyranones

A stereoselective construction of cis- and trans-2,6-disubstituted tetrahydropyranones, based on strategy which combines an asymmetric alkylation and ring closing metathesis for the formation of a cyclic enol ether, is reported.
Synthesis of tetrahydrofuran lignans

This brief review details the racemic and enantioselective syntheses of naturally occuring tetrahydrofuran lignans burseran, dehydroxycubebin,braslignan, and several analogs of the natural products. The key bond-forming strategies employed in these syntheses includes Diels-Alder and nitrile-oxide cycloadditions, stereoselective aikylation, Michael additions, and radical cyclizations.
Adversarial Mahalanobis Distance-based Attentive Song Recommender for Automatic Playlist Continuation

In this paper, we aim to solve the automatic playlist continuation (APC) problem by modeling complex interactions among users, playlists, and songs using only their interaction data. Prior methods mainly rely on dot product to account for similarities, which is not ideal as dot product is not metric learning, so it does not convey the important inequality property. Based on this observation, we propose three novel deep learning approaches that utilize Mahalanobis distance. Our first approach uses user-playlist-song interactions, and combines Mahalanobis distance scores between (i) a target user and a target song, and (ii) between a target playlist and the target song to account for both the user's preference and the playlist's theme. Our second approach measures song-song similarities by considering Mahalanobis distance scores between the target song and each member song (i.e., existing song) in the target playlist. The contribution of each distance score is measured by our proposed memory metric-based attention mechanism. In the third approach, we fuse the two previous models into a unified model to further enhance their performance. In addition, we adopt and customize Adversarial Personalized Ranking (APR) for our three approaches to further improve their robustness and predictive capabilities. Through extensive experiments, we show that our proposed models outperform eight state-of-the-art models in two large-scale real-world datasets.
Mathematical Analysis of Chemical Reaction Systems

The use of mathematical methods for the analysis of chemical reaction systems has a very long history, and involves many types of models: deterministic versus stochastic, continuous versus discrete, and homogeneous versus spatially distributed. Here we focus on mathematical models based on deterministic mass-action kinetics. These models are systems of coupled nonlinear differential equations on the positive orthant. We explain how mathematical properties of the solutions of mass-action systems are strongly related to key properties of the networks of chemical reactions that generate them, such as specific versions of reversibility and feedback interactions.
Open ASEP in the Weakly Asymmetric Regime

We consider ASEP on a bounded interval and on a half-line with sources and sinks. On the full line, Bertini and Giacomin in 1997 proved convergence under weakly asymmetric scaling of the height function to the solution of the KPZ equation. We prove here that under similar weakly asymmetric scaling of the sources and sinks as well, the bounded interval ASEP height function converges to the KPZ equation on the unit interval with Neumann boundary conditions on both sides (different parameter for each side), and likewise for the half-line ASEP to KPZ on a half-line. This result can be interpreted as showing that the KPZ equation arises at the triple critical point (maximal current / high density / low density) of the open ASEP.© 2018 Wiley Periodicals, Inc.
Current Status of the Microlensing Surveys

The ongoing microlensing searches have generated more photometric measurements of pulsating stars than all previous observing projects combined. In particular, OGLE has made ~ 340,000 B, V, and I-band measurements of ~ 1,300 Cepheids in the Large Magellanic Clouds accessible over Internet. Microlensing searches contributed to the development of very efficient image subtraction software which works best in crowded fields. This suggests the use of a period - flux amplitude rather than period - luminosity relation for the Cepheids for distance determination, as the flux amplitude is directly measurable with the image subtraction, and it is not biased by crowding. Future projects will dramatically increase the data rate, will provide all-sky coverage and a complete census of variables, including pulsating stars, to the ever fainter limits. Time will show which approach, a small number of large teams or a large number of small teams, will be more productive.
The Group of Symmetries of the Tower of Hanoi Graph

(2010). The Group of Symmetries of the Tower of Hanoi Graph. The American Mathematical Monthly: Vol. 117, No. 4, pp. 353-360.
Presentation of hyperbolic Kac-Moody groups over rings

Abstract Tits has defined Kac–Moody and Steinberg groups over commutative rings, providing infinite dimensional analogues of the Chevalley–Demazure group schemes. Here we establish simple explicit presentations for all Steinberg and Kac–Moody groups whose Dynkin diagrams are hyperbolic and simply laced. Our presentations are analogues of the Curtis–Tits presentation of the finite groups of Lie type. When the ground ring is finitely generated, we derive the finite presentability of the Steinberg group, and similarly for the Kac–Moody group when the ground ring is a Dedekind domain of arithmetic type. These finite-presentation results need slightly stronger hypotheses when the rank is smallest possible, namely 4. The presentations simplify considerably when the ground ring is Z , a case of special interest because of the conjectured role of the Kac–Moody group E 10 ( Z ) in superstring theory.
First-order Methods for Geodesically Convex Optimization

Geodesic convexity generalizes the notion of (vector space) convexity to nonlinear metric spaces. But unlike convex optimization, geodesically convex (g-convex) optimization is much less developed. In this paper we contribute to the understanding of g-convex optimization by developing iteration complexity analysis for several first-order algorithms on Hadamard manifolds. Specifically, we prove upper bounds for the global complexity of deterministic and stochastic (sub)gradient methods for optimizing smooth and nonsmooth g-convex functions, both with and without strong g-convexity. Our analysis also reveals how the manifold geometry, especially sectional curvature, impacts convergence rates. To the best of our knowledge, our work is the first to provide global complexity analysis for first-order algorithms for general g-convex optimization.
OP2 bundles in M-theory

Ramond has observed that the massless multiplet of eleven-dimensional supergravity can be generated from the decomposition of certain representation of the exceptional Lie group F4 into those of its maximal compact subgroup Spin(9). The possibility of a topological origin for this observation is investigated by studying Cayley plane, OP2, bundles over eleven-manifolds Y. The lift of the topological terms gives constraints on the cohomology of Y which are derived. Topological structures and genera on Y are related to the corresponding ones on the total space M. The latter, being 27-dimensional, might provide a candidate for `bosonic M-theory'. The discussion leads to a connection with an octonionic version of Kreck-Stolz elliptic homology theory.
Scene Memory Transformer for Embodied Agents in Long-Horizon Tasks

Many robotic applications require the agent to perform long-horizon tasks in partially observable environments. In such applications, decision making at any step can depend on observations received far in the past. Hence, being able to properly memorize and utilize the long-term history is crucial. In this work, we propose a novel memory-based policy, named Scene Memory Transformer (SMT). The proposed policy embeds and adds each observation to a memory and uses the attention mechanism to exploit spatio-temporal dependencies. This model is generic and can be efficiently trained with reinforcement learning over long episodes. On a range of visual navigation tasks, SMT demonstrates superior performance to existing reactive and memory-based policies by a margin.
A dynamical polynomial chaos approach for long-time evolution of SPDEs

Abstract We propose a Dynamical generalized Polynomial Chaos (DgPC) method to solve time-dependent stochastic partial differential equations (SPDEs) with white noise forcing. The long-time simulation of SPDE solutions by Polynomial Chaos (PC) methods is notoriously difficult as the dimension of the stochastic variables increases linearly with time. Exploiting the Markovian property of white noise, DgPC [1] implements a restart procedure that allows us to expand solutions at future times in terms of orthogonal polynomials of the measure describing the solution at a given time and the future white noise. The dimension of the representation is kept minimal by application of a Karhunen–Loeve (KL) expansion. Using frequent restarts and low degree polynomials on sparse multi-index sets, the method allows us to perform long time simulations, including the calculation of invariant measures for systems which possess one. We apply the method to the numerical simulation of stochastic Burgers and Navier–Stokes equations with white noise forcing. Our method also allows us to incorporate time-independent random coefficients such as a random viscosity. We propose several numerical simulations and show that the algorithm compares favorably with standard Monte Carlo methods.
Medoids in Almost-Linear Time via Multi-Armed Bandits.

Computing the medoid of a large number of points in high-dimensional space is an increasingly common operation in many data science problems. We present an algorithm Med-dit which uses O(n log n) distance evaluations to compute the medoid with high probability. Med-dit is based on a connection with the multi-armed bandit problem. We evaluate the performance of Med-dit empirically on the Netflix-prize and the single-cell RNA-Seq datasets, containing hundreds of thousands of points living in tens of thousands of dimensions, and observe a 5-10x improvement in performance over the current state of the art. Med-dit is available at this https URL
Mobility improvement and temperature dependence in MoSe2 field-effect transistors on parylene-C substrate

We report low-temperature scanning tunneling microscopy characterization of MoSe2 crystals and the fabrication and electrical characterization of MoSe2 field-effect transistors on both SiO2 and parylene-C substrates. We find that the multilayer MoSe2 devices on parylene-C show a room-temperature mobility close to the mobility of bulk MoSe2 (100–160 cm2 V–1 s–1), which is significantly higher than that on SiO2 substrates (≈50 cm2 V–1 s–1). The room-temperature mobility on both types of substrates are nearly thickness-independent. Our variable-temperature transport measurements reveal a metal–insulator transition at a characteristic conductivity of e2/h. The mobility of MoSe2 devices extracted from the metallic region on both SiO2 and parylene-C increases up to ≈500 cm2 V–1 s–1 as the temperature decreases to ≈100 K, with the mobility of MoSe2 on SiO2 increasing more rapidly. In spite of the notable variation of charged impurities as indicated by the strongly sample-dependent low-temperature mobility, the m...
Statistical Mechanics of Specular Reflections from Fluctuating Membranes and Interfaces

We study the density of specular reflection points in the geometrical optics limit when light scatters off fluctuating interfaces and membranes in thermodynamic equilibrium. We focus on the statistical mechanics of both capillary-gravity interfaces (characterized by a surface tension) and fluid membranes (controlled by a bending rigidity) in thermodynamic equilibrium in two dimensions. Building on work by Berry et al. we show that the statistics of specular points is fully characterized by three fundamental length scales, namely, a correlation length $$\xi $$ , a microscopic length scale $$\ell $$ and the overall size L of the interface or membrane. By combining a scaling analysis with numerical simulations, we confirm the existence of a scaling law for the density of specular reflection points, $$n_{spec}$$ , in two dimensions, given by $$n_{spec}\propto \ell ^{-1}$$ in the limit of thin fluctuating interfaces with the interfacial thickness $$\ell \ll \xi _I$$ . The density of specular reflections thus diverges for fluctuating interfaces in the limit of vanishing thickness and shows no dependance on the interfacial capillary-gravity correlation length $$\xi _I$$ . Although fluid membranes under tension also exhibit a divergence in $$n_{spec}\propto \left( \xi _M\ell \right) ^{-1/2}$$ , the number of specular reflections in this case can grow by decreasing the membrane correlation length $$\xi _{M}$$ .
Algorithmic Information, Plane Kakeya Sets, and Conditional Dimension

We formulate the conditional Kolmogorov complexity of xgiveny at precisionr, where x and y are points in Euclidean spaces and r is a natural number. We demonstrate the utility of this notion in two ways;(1) We prove a point-to-set principle that enables one to use the (relativized, constructive) dimension of a single point in a set E in a Euclidean space to establish a lower bound on the (classical) Hausdorff dimension of E. We then use this principle, together with conditional Kolmogorov complexity in Euclidean spaces, to give a new proof of the known, two-dimensional case of the Kakeya conjecture. This theorem of geometric measure theory, proved by Davies in 1971, says that every plane set containing a unit line segment in every direction has Hausdorff dimension 2.(2)We use conditional Kolmogorov complexity in Euclidean spaces to develop the lower and upper conditional dimensions dim(xvy) and Dim(xvy) of x given y, where x and y are points in Euclidean spaces. Intuitively, these are the lower and upper asymptotic algorithmic information densities of x conditioned on the information in y. We prove that these conditional dimensions are robust and that they have the correct information-theoretic relationships with the well-studied dimensions dim(x) and Dim(x) and the mutual dimensions mdim(x : y) and Mdim(x : y).
On maximum conservative extensions

We investigate the set of Π2 sentences which are Π 1 1 conservative over theories of second order arithmetic. We exhibit new elements of these sets and conclude that the sets are Π2 complete. Along the way, we show that, over the theory RCA0, induction for Σn formulas has essentially no consequences for Δn+1 formulas.
The phone walkers: a study of human dependence on inactive mobile devices

The development of mobile phones has largely increased human interactions. Whilst the use of these devices for communication has received significant attention, there has been little analysis of more passive interactions. Through census data on casual social groups, this work suggests a clear pattern of mobile phones being carried in people’s hands, without the person using it (that is, not looking at it). Moreover, this study suggests that when individuals join members of the opposite sex there is a clear tendency to stop holding mobile phones whilst walking. Although it is not clear why people hold their phones whilst walking in such large proportions (38% of solitary women, and 31% of solitary men), we highlight several possible explanation for holding the device, including the need to advertise status and affluence, to maintain immediate connection with friends and family, and to mitigate feelings related to anxiety and security.
The weight function for monomial crystals of affine type

In this work, an expression for the affine weight is calculated for Nakajima monomial crystals in affine types An(1) and B3(1).
Fast algorithms for distributed optimization and hypothesis testing: A tutorial

We consider several problems in the field of distributed optimization and hypothesis testing. We show how to obtain convergence times for these problems that scale linearly with the total number of nodes in the network by using a recent linear-time algorithm for the average consensus problem.
A Symbolic Approach to Explaining Bayesian Network Classifiers.

We propose an approach for explaining Bayesian network classifiers, which is based on compiling such classifiers into decision functions that have a tractable and symbolic form. We introduce two types of explanations for why a classifier may have classified an instance positively or negatively and suggest algorithms for computing these explanations. The first type of explanation identifies a minimal set of the currently active features that is responsible for the current classification, while the second type of explanation identifies a minimal set of features whose current state (active or not) is sufficient for the classification. We consider in particular the compilation of Naive and Latent-Tree Bayesian network classifiers into Ordered Decision Diagrams (ODDs), providing a context for evaluating our proposal using case studies and experiments based on classifiers from the literature.
IoT-enabled distributed cyber-attacks on transmission and distribution grids

The Internet of things (IoT) will make it possible to interconnect and simultaneously control distributed electrical loads. Various technical and regulatory concerns have been raised that IoT-operated loads are being deployed without appropriately considering and systematically addressing potential cyber-security challenges. Hence, one can envision a hypothetical scenario when an ensemble of IoT-controlled loads can be hacked with malicious intentions of compromising operations of the electrical grid. Under this scenario, the attacker would use geographically distributed IoT-controlled loads to alternate their net power injections into the electrical grid in such a way that may disrupt normal grid operations. This paper presents a modeling framework to analyze grid impacts of distributed cyber-attacks on IoT-controlled loads. This framework is used to demonstrate how a hypothetical distributed cyber-attack propagates from the distribution electrical grid, where IoT-controlled loads are expected to be installed, to the transmission electrical grid. The techno-economic interactions between the distribution and transmission electrical grids are accounted for by means of bilevel optimization. The case study is carried out on the modified versions of the 3-area IEEE Reliability Test System (RTS) and the IEEE 13-bus distribution feeder. Our numerical results demonstrate that the severity of such attacks depends on the penetration level of IoT-controlled loads and the strategy of the attacker.
Wavelength-resolved Neutron Tomography for Crystalline Materials

Wavelength-resolved (WR) neutron transmission tomography is an emerging technique to characterize engineering materials. While tomographic reconstruction for amorphous samples is straightforward, it is challenging to reconstruct samples with single-crystal domains because the attenuation of the sample varies as a function of its orientation with respect to the incident beam due to Bragg scattering. In this paper, we present an algorithm that can reconstruct samples with single-crystal domains from WR neutron tomographic measurements. In particular, we use a model-based iterative reconstruction (MBIR) technique that reconstructs the volume by identifying and leaving out the regions of the measurement that are affected by Bragg scatter. We combine the output of the MBIR method with an algorithm that matches the reconstruction to the identified Bragg scatter to reconstruct a feature that corresponds to the local crystallography of the sample being measured. Using simulated data, we demonstrate how our algorithm can reconstruct materials with single-crystal domains, thereby adding a powerful new capability for WR neutron imaging instruments.