cssi/SciSciGPT-SciSciNet huggingface dataset:
The Chemistry of Trichlorosilyl Enolates. Aldol Addition Reactions of Methyl Ketones

Investigations on the aldol addition chemistry of trichlorosilyl enolates derived from methyl ketones are presented in full. These trichlorosilyl enolates are competent aldol reagents in the absence of additives, reacting with aldehydes at ambient temperature to provide high yields of aldol adducts. When either enol or aldehyde partner bears a stereogenic center, low diastereoselectivity is observed in this uncatalyzed aldol process. The aldol additions are dramatically accelerated by the addition of catalytic quantities of chiral phosphoramides, particularly one derived from N,N‘-dimethylstilbene-1,2-diamine. In this catalyzed mode, good to high enantioselectivities are obtained with a variety of achiral trichlorosilyl enolates and aldehydes. When either partner bears a stereogenic center, high diastereoselectivities are obtained with one enantiomer of the catalyst (matched case), while the other enantiomer provides low diastereoselectivity (mismatched case). The reaction scope, optimization of condition...
Evidence and Role for Bacterial Mucin Degradation in Cystic Fibrosis Airway Disease

Chronic lung infections in cystic fibrosis (CF) patients are composed of complex microbial communities that incite persistent inflammation and airway damage. Despite the high density of bacteria that colonize the lower airways, nutrient sources that sustain bacterial growth in vivo, and how those nutrients are derived, are not well characterized. In this study, we examined the possibility that mucins serve as an important carbon reservoir for the CF lung microbiota. While Pseudomonas aeruginosa was unable to efficiently utilize mucins in isolation, we found that anaerobic, mucin-fermenting bacteria could stimulate the robust growth of CF pathogens when provided intact mucins as a sole carbon source. 16S rRNA sequencing and enrichment culturing of sputum also identified that mucin-degrading anaerobes are ubiquitous in the airways of CF patients. The collective fermentative metabolism of these mucin-degrading communities in vitro generated amino acids and short chain fatty acids (propionate and acetate) during growth on mucin, and the same metabolites were also found in abundance within expectorated sputum. The significance of these findings was supported by in vivo P. aeruginosa gene expression, which revealed a heightened expression of genes required for the catabolism of propionate. Given that propionate is exclusively derived from bacterial fermentation, these data provide evidence for an important role of mucin fermenting bacteria in the carbon flux of the lower airways. More specifically, microorganisms typically defined as commensals may contribute to airway disease by degrading mucins, in turn providing nutrients for pathogens otherwise unable to efficiently obtain carbon in the lung.
An improved amide coupling procedure for the synthesis of N-(pyridin-2-yl)amides

Dehydrative amide couplings with 2-pyridylamines suffer from variable yields. A mild and high-yielding synthesis of N-(pyridin-2-yl)amides employing 2-aminopyridine-N-oxides is presented as a solution.
One-pot synthesis of chalcone epoxides—A green chemistry strategy

Abstract Waste minimization is a very important aspect of an environmentally benign protocol. A one-pot consecutive process has been developed for chalcone epoxide synthesis that allows compounds to be prepared without having to isolate and purify the intermediates. The strategy utilizes consecutive Claisen Schmidt condensation and epoxidation reactions to prepare chalcone epoxides from substituted benzaldehydes and acetophenones in good yields.
Synthetic route to 4-(2-aminoethyl)-5-hydroxyindole derivatives

In synthetic studies leading to the title compounds, application of the Claisen rearrangement of 5-allyloxyindole was investigated. Almost quantitative yields of Claisen rearrangement product were realized, and a strategy for oxidative cleavage of the allyl double bond to an indole-4-acetaldehyde derivative was developed. A new method for conversion of 2,3-dihydroindoles into indoles was utilized: air oxidation in a strongly basic environment. The Claisen rearrangement of allyloxyindoles is presented as a method having considerable potential utility in synthesis of a variety of polysubstituted indoles.
Learning to see again: biological constraints on cortical plasticity and the implications for sight restoration technologies

The 'bionic eye'-so long a dream of the future-is finally becoming a reality with retinal prostheses available to patients in both the US and Europe. However, clinical experience with these implants has made it apparent that the visual information provided by these devices differs substantially from normal sight. Consequently, the ability of patients to learn to make use of this abnormal retinal input plays a critical role in whether or not some functional vision is successfully regained. The goal of the present review is to summarize the vast basic science literature on developmental and adult cortical plasticity with an emphasis on how this literature might relate to the field of prosthetic vision. We begin with describing the distortion and information loss likely to be experienced by visual prosthesis users. We then define cortical plasticity and perceptual learning, and describe what is known, and what is unknown, about visual plasticity across the hierarchy of brain regions involved in visual processing, and across different stages of life. We close by discussing what is known about brain plasticity in sight restoration patients and discuss biological mechanisms that might eventually be harnessed to improve visual learning in these patients.
Synthesis of photo- and electroactive stilbenoid dendrimers carrying dibutylamino peripheral groups.

A novel convergent synthetic route for the preparation of functionalized and fluorescent stilbenoid dendrons built on the 1,3,5-benzene core and endowed with a periphery of dibutylamino groups has been developed. Long alkyl chains have been incorporated on the peripheral amino moieties to increase the solubility of the final products. Good donor ability of the new dendrimers has been observed by cyclic voltammetry measurements as a result of the presence of the peripheral dibutylaniline moieties.
Chemistry on the rim of buckybowls: derivatization of 1,2,5,6-tetrabromocorannulene

Abstract Synthesis of a number of substituted corannulenes and dibenzo[a,g]corannulenes starting from 1,2,5,6-tetrabromocorannulene 3 is described. Since 3 is conveniently obtained by a large scale, non-pyrolytic route, it may serve as a synthon for the further elaboration of this bowl-shaped system.
Application of the intramolecular aza-Wittig reaction to the synthesis of pyrido[2,3-d]pyrimidines

Pyrido[2,3-d]pyrimidines are synthesized in a two-step procedure from amides and tetrazolo[1,5-a]pyridine-8-carbonyl chloride. Reaction of the crude imides with triphenylphosphine effects an intramolecular aza-Wittig reaction to afford a variety of substituted pyrido[2,3-d]pyrimidines in good to moderate yields (30–76%).
Efficient syntheses of thiochromans via cationic cycloadditions.

α-(Benzotriazolyl)methyl thioethers 1a−e reacted with styrenes under Lewis acid catalysis to give novel polysubstituted thiochromans (3,4-dihydro-2H-1-benzothiopyrans) 3−14 and 16−20 in generally high yields. Most thiochromans were isolated as one diastereomer following recrystallization. The configuration and conformation of the products are predicted on the basis of their NMR data. A stepwise reaction, proceeding via a [4+ + 2] cationic polar cycloaddition mechanism, is proposed.
Modeling the mechanism of CLN025 beta-hairpin formation

Beta-hairpins are substructures found in proteins that can lend insight into more complex systems. Furthermore, the folding of beta-hairpins is a valuable test case for benchmarking experimental and theoretical methods. Here, we simulate the folding of CLN025, a miniprotein with a beta-hairpin structure, at its experimental melting temperature using a range of state-of-the-art protein force fields. We construct Markov state models in order to examine the thermodynamics, kinetics, mechanism, and rate-determining step of folding. Mechanistically, we find the folding process is rate-limited by the formation of the turn region hydrogen bonds, which occurs following the downhill hydrophobic collapse of the extended denatured protein. These results are presented in the context of established and contradictory theories of the beta-hairpin folding process. Furthermore, our analysis suggests that the AMBER-FB15 force field, at this temperature, best describes the characteristics of the full experimental CLN025 conformational ensemble, while the AMBER ff99SB-ILDN and CHARMM22* force fields display a tendency to overstabilize the native state.
Dehydroaromatization with V2O5

Vanadium pentoxide is evaluated as a dehydroaromatization reagent. Tetrahydrocarbazole is readily aromatized by V2O5 in refluxing acetic acid under both stoichiometric and catalytic conditions. Indoline, tetrahydroquinoline, and tetrahydroquinoxaline are effectively aromatized by V2O5/silica in refluxing toluene.
Stereoselective N-Glycosylation by Staudinger Ligation

Stereoselective methods for the chemical synthesis of beta-N-glycosyl amides are needed to generate glycopeptides and glycoproteins. Here, we report that the Staudinger ligation can be used to form glycosylated asparagine derivatives. The reaction proceeds with high stereoselectivity, and a variety of glycosyl azides can function as substrates. Our results provide precedence for the use of this powerful amide-bond-forming reaction for N-glycopeptide synthesis. [reaction: see text]
Total synthesis and structural confirmation of brevisamide, a new marine cyclic ether alkaloid from the dinoflagellate Karenia brevis.

The first total synthesis of brevisamide (1) has been accomplished in 21 linear steps starting from cis-but-2-ene-1,4-diol. A synthetic highlight is the Suzuki−Miyaura coupling between an ether ring fragment and a dienol side chain. This result confirmed the structure of 1 isolated from the dinoflagellate Karenia brevis.
Crystal growth, structure, and physical properties of SmCu4Ga8.

Single crystals of SmCu4Ga8 have been grown using Ga flux and characterized by single-crystal X-ray diffraction. SmCu4Ga8, isostructural to SmZn11, crystallizes in the hexagonal P6/mmm (No. 191) sp...
VINYL GROUP PROTECTION IN PORPHYRINS AND CHLORINS : ORGANOSELENIUM DERIVATIVES

Abstract The o-nitrophenylselenoethyl functionality is a useful protected vinyl group in porphyrins and chlorins, and its use is demonstrated in the Vilsmeier formylation reaction which has been shown to adversely affect unmodified vinyl groups in tetrapyrrole systems. The X-ray crystal structure for 3-(2-o-nitro-phenylselenoethyl)-3-devinylchlorin-e6 trimethyl ester 14 is reported.
Cord blood buffy coat DNA methylation is comparable to whole cord blood methylation

Cord blood DNA methylation is associated with numerous health outcomes and environmental exposures. Whole cord blood DNA reflects all nucleated blood cell types, while centrifuging whole blood sepa...
SECOND CANCER INCIDENCE IN CLL PATIENTS RECEIVING BTK INHIBITORS

7511Background: Patients (pts) with chronic lymphocytic leukemia (CLL) suffer morbidity and mortality from CLL and increased risk for second primary neoplasia (SPN). BTK inhibitors (BTKi) are highl...
Trait paranoia shapes inter-subject synchrony in brain activity during an ambiguous social narrative

Individuals often interpret the same event in different ways. How do personality traits modulate brain activity evoked by a complex stimulus? Here we report results from a naturalistic paradigm designed to draw out both neural and behavioral variation along a specific dimension of interest, namely paranoia. Participants listen to a narrative during functional MRI describing an ambiguous social scenario, written such that some individuals would find it highly suspicious, while others less so. Using inter-subject correlation analysis, we identify several brain areas that are differentially synchronized during listening between participants with high and low trait-level paranoia, including theory-of-mind regions. Follow-up analyses indicate that these regions are more active to mentalizing events in high-paranoia individuals. Analyzing participants’ speech as they freely recall the narrative reveals semantic and syntactic features that also scale with paranoia. Results indicate that a personality trait can act as an intrinsic “prime,” yielding different neural and behavioral responses to the same stimulus across individuals.
Stereoselective aldol-type cyclization reaction mediated by dibutylboron triflate/diisopropylethylamine.

Dibutylboron triflate/diisopropylethylamine mediated aldol-type cyclization provides an expedient route for the stereoselective synthesis of cyclic ethers in a single step. The method is highly efficient for the stereoselective synthesis of 4-cis-tetrahydropyranones. The reaction is proposed to proceed via an SN1-type mechanism through a chair-like transition state, in which both substituents occupy equatorial positions.
Preparation and Structural Characterization of an Enantiomerically Pure, C2-Symmetric, Single-Component Ziegler−Natta α-Olefin Polymerization Catalyst

A new linked bis(cyclopentadienyl) ligand, {(C5H3-2-SiMe3-4-CMe3)2Si(OC10H6C10H6O)} (BnBpH2), has been designed to coordinate to transition metals to afford a single enantiomeric C2-symmetric ansa-metallocene. The syntheses of its dipotassium salt and (BnBp)YCl(THF) are described. Steric interactions between the 3- and 3‘-methine positions of the 1,1‘-binaphth-2,2‘-diolate rings of the chiral linker with the α-trimethylsilyl substituents on the cyclopentadienyl rings force enantioselective metalation of this ligand. Thus, coordination to yttrium occurs in an entirely diastereoselective manner: the ligand prepared from (R)-(+)-1,1‘-bi-2-naphthol directs formation of the (S)-yttrocene, (R,S)-(BnBp)YCl(THF), while that from (S)-(−)-1,1‘-bi-2-naphthol directs formation of the (R)-yttrocene, (S,R)-(BnBp)YCl(THF). Removal of coordinated tetrahydrofuran allows the preparation of (BnBp)YCH(SiMe3)2. Treatment of rac-(BnBp)YCH(SiMe3)2 with H2 yields a kinetic mixture of both heterochiral and homochiral dimers (e.g...
Synthesis of the C1-C13 fragment of leucascandrolide A.

The synthesis of the C1−C13 fragment 3 of leucascandrolide A has been completed utilizing a stereoselective and regioselective reductive cleavage of a highly functionalized spiroketal to incorporate the cis-2,6-disubstituted tetrahydropyan. The spiroketal was constructed by addition of a lithiated pyrone 5 to aldehyde 6.
One-pot preparation of ternary and quaternary iminium salts from aldehydes and ketones

A facile, high-yielding, one-step procedure is described for the preparation of a wide range of stable iminium salts by direct combination of an aldehyde or a ketone with a secondary free amine in ...
Reactivity of γ-Hydroxy-α,β-acetylenic Esters with Amines: Facile Synthesis of the Optically Active 4-Amino-2(5H)-furanones

A convenient synthesis of the optically active 4-amino-2(5H)-furanones is discovered by combining an asymmetric alkyne addition to aldehydes and a subsequent aliphatic amine addition. Both steps can be conducted at room temperature and the products are obtained with high enantioselectivity (84-90% ee). The 4-amino-2(5H)-furanones are also found to undergo very facile electrophilic substitution reactions.
The stereoselective construction of fluoroalkenoates via the Peterson olefination reaction using tert-butyl α-fluoro-α-(trialkylsilyl)acetates

Abstract A new version of the Peterson fluoroolefination reaction employing tert-butyl α-fluoro-α-(trialkylsilyl)acetates was developed to construct various fluoro-alkenoates.
Room temperature hydroamination of N-alkenyl ureas catalyzed by a gold(i) N-heterocyclic carbene complex.

Treatment of an N-4-pentenyl or N-5-hexenyl urea with a catalytic 1:1 mixture of a gold(I) N,N-diaryl imidazol-2-ylidine complex and AgOTf at or near room temperature leads to intramolecular exo-hydroamination to form the corresponding nitrogen heterocycle in excellent yield.
Human macrophages survive and adopt activated genotypes in living zebrafish

The inflammatory response, modulated both by tissue resident macrophages and recruited monocytes from peripheral blood, plays a critical role in human diseases such as cancer and neurodegenerative disorders. Here, we sought a model to interrogate human immune behavior in vivo. We determined that primary human monocytes and macrophages survive in zebrafish for up to two weeks. Flow cytometry revealed that human monocytes cultured at the physiological temperature of the zebrafish survive and differentiate comparable to cohorts cultured at human physiological temperature. Moreover, key genes that encode for proteins that play a role in tissue remodeling were also expressed. Human cells migrated within multiple tissues at speeds comparable to zebrafish macrophages. Analysis of gene expression of in vivo educated human macrophages confirmed expression of activated macrophage phenotypes. Here, human cells adopted phenotypes relevant to cancer progression, suggesting that we can define the real time immune modulation of human tumor cells during the establishment of a metastatic lesion in zebrafish.
The stereochemical requirements of the novel δ-opioid selective dipeptide antagonist TMT-Tic

Abstract Five conformationally constrained dipeptide TMT- L -Tic analogues have been synthesized and evaluated for their bioactivity using in vitro bioassays. The most potent and selective analogue (2 S ,3 R )-TMT- L -Tic showed 9 nM binding affinity and 4000-fold selectivity for the δ vs μ opioid receptor. The lowest-energy conformation of (2 S ,3 R )-TMT- L -Tic is suggested to be bioactive one in which the χ 1 torsional angle is trans for TMT and gauche (+) for Tic.
Modeling and quantifying frequency‐dependent fitness in microbial populations with cross‐feeding interactions

Coexistence of two or more populations by frequency-dependent selection is common in nature, and it often arises even in well-mixed experiments with microbes. If ecology is to be incorporated into models of population genetics, then it is important to represent accurately the functional form of frequency-dependent interactions. However, measuring this functional form is problematic for traditional fitness assays, which assume a constant fitness difference between competitors over the course of an assay. Here, we present a theoretical framework for measuring the functional form of frequency-dependent fitness by accounting for changes in abundance and relative fitness during a competition assay. Using two examples of ecological coexistence that arose in a long-term evolution experiment with Escherichia coli, we illustrate accurate quantification of the functional form of frequency-dependent relative fitness. Using a Monod-type model of growth dynamics, we show that two ecotypes in a typical cross-feeding interaction-such as when one bacterial population uses a byproduct generated by another-yields relative fitness that is linear with relative frequency.
Evolutionarily Conserved Alternative Splicing Across Monocots

One difficulty when identifying alternative splicing (AS) events in plants is distinguishing functional AS from splicing noise. One way to add confidence to the validity of a splice isoform is to observe that it is conserved across evolutionarily related species. We use a high throughput method to identify junction-based conserved AS events from RNA-Seq data across nine plant species, including five grass monocots (maize, sorghum, rice, Brachpodium, and foxtail millet), plus two nongrass monocots (banana and African oil palm), the eudicot Arabidopsis, and the basal angiosperm Amborella. In total, 9804 AS events were found to be conserved between two or more species studied. In grasses containing large regions of conserved synteny, the frequency of conserved AS events is twice that observed for genes outside of conserved synteny blocks. In plant-specific RS and RS2Z subfamilies of the serine/arginine (SR) splice-factor proteins, we observe both conservation and divergence of AS events after the whole genome duplication in maize. In addition, plant-specific RS and RS2Z splice-factor subfamilies are highly connected with R2R3-MYB in STRING functional protein association networks built using genes exhibiting conserved AS. Furthermore, we discovered that functional protein association networks constructed around genes harboring conserved AS events are enriched for phosphatases, kinases, and ubiquitylation genes, which suggests that AS may participate in regulating signaling pathways. These data lay the foundation for identifying and studying conserved AS events in the monocots, particularly across grass species, and this conserved AS resource identifies an additional layer between genotype to phenotype that may impact future crop improvement efforts.
NMR observation of the conformations and motions of polymers confined to the narrow channels of their inclusion compounds

When polymers are guests in crystalline inclusion compounds (ICs) formed with small-molecule hosts, they occupy a unique environment. In a cocrystallization process the small-molecule host forms a crystalline lattice containing long narrow channels where the guest polymer chains are included. Because of the narrow channel diameter and because neighboring channels are separated by walls formed exclusively from the small-molecule host lattice, the included polymer chains are highly extended and separated from polymer chains in other IC channels. As a consequence, polymer-IC crystals provide a unique solid state environment for the included polymer chains and serve as models useful for assessing the contributions made by the inherent behavior of individual polymer chains to the properties of ordered, bulk polymers, which can be obscured by pervasive interactions between their tightly packed polymer chains. In this paper we describe the conformations and motions of polymer chains confined to the narrow channels of the following polymer-ICs: i. polyethylene and trans-1, 4-polybutadiene in their ICs with perhydrotriphenylene, ii. poly-epsilon caprolactone and its diblock and triblock copolymers with polybutadiene and poly (ethylene oxide) in their ICs with urea, and iii. nylon-6 in its ICs with alpha-, beta-, and gamma-cyclodextrins. High resolution, solid state NMR serves as both the conformational (C-13 chemical shifts) and motional (relaxation times and line shapes) probe. Comparison with identical NMR measurements performed on the bulk homo- and copolymer samples permits us to draw several conclusions regarding the relationships between the conformations and motions of polymers and their dependence on their ordered solid state environments.
Products and Mechanisms in the Oxidation of Phosphorus by Sulfur at Low Temperature

The oxidation of phosphorus by sulfur at low temperatures (<100 °C) has been shown to produce complex mixtures that include 12 of the 17 known binary phosphorus sulfides. Two of these 17 sulfides have been observed in these mixtures for the first time. The rate-determining and first step in the reaction appears to be the formation of the S8 diradical. This proposal is supported by the observed rate at which the sulfides are formed and the distribution of the sulfide product stoichiometries. Photoinitiation of this oxidation at 0 °C produces a similar array of sulfides. The differences in the product distributions between the thermal and photochemical processes facilitate the understanding of the mother−daughter relationships between the products. The effects of oxidation by sulfur and reduction by phosphorus have been determined for several of the known phosphorus sulfides. The characterizations of phosphorus compounds in molten mixtures of phosphorus and sulfur were performed by 31P NMR and Raman spectro...
A novel series of materials composed of arrays of vanadium oxide container molecules, [V18O42(X)] (X = H2O, Cl-, Br-): synthesis and characterization of [M2(H2N(CH2)2NH2)5][(M(H2N(CH2)2NH2)2]2V18O42(X)]. 9H2O (M = Zn, Cd).

The synthesis and characterization of the novel systems [Zn 2 (H 2 N(CH 2 ) 2 NH 2 ) 5 ][Zn(H 2 N(CH 2 ) 2 NH 2 ) 2 } 2 V 1 8 O 4 2 (H 2 O). 9H 2 O (1), [Cd 2 (H 2 N(CH 2 ) 2 NH 2 ) 5 ][{Cd(H 2 N(CH 2 ) 2 NH 2 ) 2 } 2 V 1 8 O 4 2 (Br)].9H 2 O (2), and [Zn 2 (H 2 N(CH 2 ) 2 NH 2 ) 5 ][{Zn(H 2 N(CH 2 ) 2 -NH 2 ) 2 } 2 V 1 8 O 4 2 (Cl)].9H 2 O (3) have been described. These materials represent a new class of solids that have been prepared by combining conventional coordination compounds with spherical polyoxovanadate clusters. The isomorphous structures of these hybrid solids consist of two-dimensional arrays of container cluster molecules {V 1 8 O 4 2 (X)) (X = H 2 O, Br - , Cl - ) interlinked by the transition metal complex moieties {M(H 2 N(CH 2 ) 2 NH 2 ) 2 } (M = Zn, Cd). These compounds contain an unprecedented complex cation, [M2(H2N(CH2) 2 NH 2 ) 5 ] 4 + . Crystal data for 1: C 9 H 4 6 N 9 O 2 6 V 9 Zn 2 , monoclinic space group P2 1 /m (No. 11), a = 12.3723(7) A, b = 20.9837(11) A, c = 15.8379(8) A, β = 97.3320(10)°, Z = 4.
One-Step Thermo-Chemical Synthetic Method for Nanoscale One-Dimensional Heterostructures

1-D heterostructures represent important nanocale building blocks with substantial potential for exploring and realizing novel device applications at the nanometer scale. Herein, a simple and general one-step thermo-chemical synthetic method has been developed for the synthesis of a variety of 1-D semiconducting heterostructures, including both hierarchical and core/shell structures.
Asymmetric Rh-Catalyzed Hydrogenation of Enamides with a Chiral 1,4-Bisphosphine Bearing Diphenylphosphino Groups

Much effort has been devoted to the development of efficient asymmetric synthetic methods for the preparation of enantiomerically enriched compounds.1,2 Among various methods for the enantiomerically selective synthesis of chiral organic compounds from prochiral precursors, enantioselective catalytic hydrogenation of dehydro precursors has been extensively developed.3 In fact, asymmetric hydrogenation is one of the most practical methods in asymmetric synthesis, accounting for 70% of all procedures used on a commercial scale.4 However, most asymmetric catalytic hydrogenation systems only hydrogenate electron-deficient olefins with high enantioselectivity and high reactivity. In contrast, electronrich olefins, such as simple enamides5 and enolates,6 are generally poor substrates for asymmetric hydrogenation with most known systems. Since enamides and enolates upon asymmetric hydrogenation can be converted to enantiomerically pure amines and alcohols,7 it would be extremely desirable to have a general and efficient method for this transformation. Recently, Burk and coworkers have reported that Rh complexes bearing the electron-rich DuPhosand BPE-type ligands were efficient catalysts for the asymmetric hydrogenation of enamides8 and enolates.9 They reported that analogous Rh-chiral bisphosphines bearing diphenylphosphino groups (e.g., BINAP, DIOP, and CHIRAPHOS) led to significantly lower enantioselectivities in the reduction of enamides (<60% ee).8 We have been interested in elucidating the steric and electronic effects10 of various diphenylphosphino-bearing chiral ligands in asymmetric hydrogenation processes. Recently a new chiral 1,4-bisphosphine, 2(R),2′(R)-bis(diphenylphosphino)-1(R),1′(R)-dicyclopentane ((R,R)BICP, Figure 1), was reported from our laboratory as an excellent ligand for the Rh-catalyzed asymmetric hydrogenation of dehydroamino acids.11 The key feature of this new ligand is that four stereogenic centers are introduced in a conformationally rigid bicyclic backbone, which is fundamentally different from either axially dissymmetric BINAP or bisphosphines with two stereogenic centers. Herein, we describe the highly enantioselective Rhcatalyzed hydrogenation of enamides using the BICP ligand. Among the known chiral bisphosphines with diphenylphosphino groups, the BICP ligand gives the highest enantioselectivity for the rhodium-catalyzed asymmetric hydrogenation of simple enamides.
Electron affinities of selected hydrogenated silicon clusters (SixHy, x=1-7, y=0-15) from density functional theory calculations

Adiabatic electron affinities for 72 hydrogenated silicon compounds containing up to seven silicon atoms are presented. These were computed using density functional theory at the B3LYP/6-311+G(3df,2p)//B3LYP/ 6-31G(d) level and are expected to be accurate to within about 0.15 eV. The electron affinities for acyclic silyl radicals, silylenes, and silenes were all found to increase smoothly with increasing molecular size. Electron affinities of the silyl radicals were greater than those of the silylenes, which were, in turn, greater than those of the silenes. The electron affinity increased with silyl substitution for hydrogen at the unsaturated site for all three of these classes of compounds. Some cyclic and polycyclic clusters had electron affinities that deviated significantly from the trends observed for the acyclic compounds. These deviations could be rationalized (a) in terms of differences in ring strain between the neutral and anionic species and (b) in terms of differences in the interactions between nonbonding electrons and other atoms between the neutral and anionic species.
A Bracketing Relationship between Difference-in-Differences and Lagged-Dependent-Variable Adjustment

Difference-in-differences is a widely used evaluation strategy that draws causal inference from observational panel data. Its causal identification relies on the assumption of parallel trends, which is scale-dependent and may be questionable in some applications. A common alternative is a regression model that adjusts for the lagged dependent variable, which rests on the assumption of ignorability conditional on past outcomes. In the context of linear models, Angrist and Pischke (2009) show that the difference-in-differences and lagged-dependent-variable regression estimates have a bracketing relationship. Namely, for a true positive effect, if ignorability is correct, then mistakenly assuming parallel trends will overestimate the effect; in contrast, if the parallel trends assumption is correct, then mistakenly assuming ignorability will underestimate the effect. We show that the same bracketing relationship holds in general nonparametric (model-free) settings. We also extend the result to semiparametric estimation based on inverse probability weighting. We provide three examples to illustrate the theoretical results with replication files in Ding and Li (2019).
The number of ramified primes in number fields of small degree

In this paper we investigate the distribution of the number of primes which ramify in number fields of degree d ≤ 5. In analogy with the classical Erdős-Kac theorem, we prove for Sd-extensions that the number of such primes is normally distributed with mean and variance log log X.
Endogenizing Epistemic Actions.

Through a series of examples, we illustrate some important drawbacks that the action logic framework suffers from in its ability to represent the dynamics of information updates. We argue that these problems stem from the fact that the action model, a central construct designed to encode agents' uncertainty about actions, is itself effectively common knowledge amongst the agents. In response to these difficulties, we motivate and propose an alternative semantics that avoids them by (roughly speaking) endogenizing the action model. We discuss the relationship to action logic, and provide a sound and complete axiomatization.
Understanding the Impact of Label Granularity on CNN-Based Image Classification

In recent years, supervised learning using Convolutional Neural Networks (CNNs) has achieved great success in image classification tasks, and large scale labeled datasets have contributed significantly to this achievement. However, the definition of a label is often application dependent. For example, an image of a cat can be labeled as "cat" or perhaps more specifically "Persian cat." We refer to this as label granularity. In this paper, we conduct extensive experiments using various datasets to demonstrate and analyze how and why training based on fine-grain labeling, such as "Persian cat" can improve CNN accuracy on classifying coarse-grain classes, in this case "cat." The experimental results show that training CNNs with fine-grain labels improves both network's optimization and generalization capabilities, as intuitively it encourages the network to learn more features, and hence increases classification accuracy on coarse-grain classes under all datasets considered. Moreover, fine-grain labels enhance data efficiency in CNN training. For example, a CNN trained with fine-grain labels and only 40% of the total training data can achieve higher accuracy than a CNN trained with the full training dataset and coarse-grain labels. These results point to two possible applications of this work: (i) with sufficient human resources, one can improve CNN performance by re-labeling the dataset with fine-grain labels, and (ii) with limited human resources, to improve CNN performance, rather than collecting more training data, one may instead use fine-grain labels for the dataset. We also observe that the improvement brought by fine-grain labeling varies from dataset to dataset, therefore we further propose a metric called Average Confusion Ratio to characterize the effectiveness of fine-grain labeling, and show its use through extensive experimentation. Code is available at https://github.com/cmu-enyac/Label-Granularity.
THE BIG CHERN CLASSES AND THE CHERN CHARACTER

Let X be a smooth scheme over a field of characteristic 0. The Atiyah class of the tangent bundle TX of X equips TX[-1] with the structure of a Lie algebra object in the derived category D+(X) of bounded below complexes of modules with coherent cohomology [6]. We lift this structure to that of a Lie algebra object in the category of bounded below complexes of modules in Theorem 2. The "almost free" Lie algebra is equipped with Hochschild coboundary. There is a symmetrization map where is the complex of polydifferential operators with Hochschild coboundary. We prove a theorem (Theorem 1) that measures how I fails to commute with multiplication. Further, we show that is the universal enveloping algebra of in D+(X). This is used to interpret the Chern character of a vector bundle E on X as the "character of a representation" (Theorem 4). Theorems 4 and 1 are then exploited to give a formula for the big Chern classes in terms of the components of the Chern character.
Testing Sparsity-Inducing Penalties

Many penalized maximum likelihood estimators correspond to posterior mode estimators under specific prior distributions. Appropriateness of a particular class of penalty functions can therefore be ...
Statistical Convergence Analysis of Gradient EM on General Gaussian Mixture Models

In this paper, we study convergence properties of the gradient Expectation-Maximization algorithm~\cite{lange1995gradient} for Gaussian Mixture Models for general number of clusters and mixing coefficients. We derive the convergence rate depending on the mixing coefficients, minimum and maximum pairwise distances between the true centers and dimensionality and number of components; and obtain a near-optimal local contraction radius. While there have been some recent notable works that derive local convergence rates for EM in the two equal mixture symmetric GMM, in the more general case, the derivations need structurally different and non-trivial arguments. We use recent tools from learning theory and empirical processes to achieve our theoretical results.
A random dynamical systems approach to filtering in large-scale networks

The paper studies the problem of filtering a discrete-time linear system observed by a network of sensors. The sensors share a common communication medium to the estimator and transmission is bit and power budgeted. Under the assumption of conditional Gaussianity of the signal process at the estimator (which may be ensured by observation packet acknowledgements), the conditional prediction error covariance of the optimum mean-squared error filter is shown to evolve according to a random dynamical system (RDS) on the space of non-negative definite matrices. Our RDS formalism does not depend on the particular medium access protocol (randomized) and, under a minimal distributed observability assumption, we show that the sequence of random conditional prediction error covariance matrices converges in distribution to a unique invariant distribution (independent of the initial filter state), i.e., the conditional error process is shown to be ergodic. Under broad assumptions on the medium access protocol, we show that the conditional error covariance sequence satisfies a Markov- Feller property, leading to an explicit characterization of the support of its invariant measure. The methodology adopted in this work is sufficiently general to envision this application to sample path analysis of more general hybrid or switched systems, where existing analysis is mostly moment-based.
Positivity and lifts of the Frobenius

We show that a smooth scheme over a ring of Witt vectors cannot have a lift of the Frobenius if it has positive Kodaira dimension.
Contextual Outlier Interpretation

Outlier detection plays an essential role in many data-driven applications to identify isolated instances that are different from the majority. While many statistical learning and data mining techniques have been used for developing more effective outlier detection algorithms, the interpretation of detected outliers does not receive much attention. Interpretation is becoming increasingly important to help people trust and evaluate the developed models through providing intrinsic reasons why the certain outliers are chosen. It is difficult, if not impossible, to simply apply feature selection for explaining outliers due to the distinct characteristics of various detection models, complicated structures of data in certain applications, and imbalanced distribution of outliers and normal instances. In addition, the role of contrastive contexts where outliers locate, as well as the relation between outliers and contexts, are usually overlooked in interpretation. To tackle the issues above, in this paper, we propose a novel Contextual Outlier INterpretation (COIN) method to explain the abnormality of existing outliers spotted by detectors. The interpretability for an outlier is achieved from three aspects: outlierness score, attributes that contribute to the abnormality, and contextual description of its neighborhoods. Experimental results on various types of datasets demonstrate the flexibility and effectiveness of the proposed framework compared with existing interpretation approaches.
An energy-conserving ultra-weak discontinuous Galerkin method for the generalized Korteweg–de Vries equation

Abstract We propose an energy-conserving ultra-weak discontinuous Galerkin (DG) method for the generalized Korteweg– de Vries (KdV) equation in one dimension. Optimal a priori error estimate of order k + 1 is obtained for the semi-discrete scheme for the KdV equation without the convection term on general nonuniform meshes when polynomials of degree k ≥ 2 are used. We also numerically observe optimal convergence of the method for the KdV equation with linear or nonlinear convection terms. It is numerically observed for the new method to have a superior performance for long-time simulations over existing DG methods.
Exact Post Model Selection Inference for Marginal Screening

We develop a framework for post model selection inference, via marginal screening, in linear regression. At the core of this framework is a result that characterizes the exact distribution of linear functions of the response y, conditional on the model being selected ("condition on selection" framework). This allows us to construct valid confidence intervals and hypothesis tests for regression coefficients that account for the selection procedure. In contrast to recent work in high-dimensional statistics, our results are exact (non-asymptotic) and require no eigenvalue-like assumptions on the design matrix X. Furthermore, the computational cost of marginal regression, constructing confidence intervals and hypothesis testing is negligible compared to the cost of linear regression, thus making our methods particularly suitable for extremely large datasets. Although we focus on marginal screening to illustrate the applicability of the condition on selection framework, this framework is much more broadly applicable. We show how to apply the proposed framework to several other selection procedures including orthogonal matching pursuit and marginal screening+Lasso.
Ultraviolet regularity for QED in d = 3

We study the ultraviolet problem for quantum electrodynamics in d = 3 using Balaban’s formulation of the renormalization group. The model is defined on a fine toroidal lattice and we seek control as the lattice spacing goes to zero. As a first step, we take a bounded field approximation and solve the renormalization problem. Namely, we show that the bare energy density and the bare fermion mass can be chosen to depend on the lattice spacing, so that under the renormalization group flow they take preassigned values on a macroscopic scale. This is accomplished by a nonperturbative technique which is insensitive to whether the renormalizations are finite or infinite.
On Robust Tie-Line Scheduling in Multi-Area Power Systems

The tie-line scheduling problem in a multi-area power system seeks to optimize tie-line power flows across areas that are independently operated by different system operators (SOs). In this paper, we leverage the theory of multi-parametric linear programming to propose algorithms for optimal tie-line scheduling, respectively, within a deterministic and a robust optimization framework. Aided by a coordinator, the proposed methods are proved to converge to the optimal schedule within a finite number of iterations. A key feature of the proposed algorithms, besides their finite step convergence, is that SOs do not reveal their dispatch cost structures, network constraints, or natures of uncertainty sets to the coordinator. The performance of the algorithms is evaluated using several power system examples.
Parameterizations of the Chazy Equation

The Chazy equation y''' = 2yy '' - 3y'2 is derived from the automorphic properties of Schwarz triangle functions S(alpha, beta, gamma; z). It is shown that solutions y which are analytic in the fundamental domain of these triangle functions, only correspond to certain values of alpha, beta, gamma. The solutions are then systematically constructed. These analytic solutions provide all known and one new parameterization of the Eisenstein series P, Q, R introduced by Ramanujan in his modular theories of signature 2, 3, 4, and 6.
Distributed Fault Detection and Accommodation in Dynamic Average Consensus

This paper presents the formulation of fault detection and accommodation schemes for a network of autonomous agents running internal model-based dynamic average consensus algorithms. We focus on two types of consensus algorithms, one that is internally stable but non-robust to initial conditions and one that is robust to initial conditions but not internally stable. For each consensus algorithm, a fault detection filter based on the unknown input observer scheme is developed for precisely estimating the communication faults that occur on the network edges. We then propose a fault remediation scheme so that the agents could reach average consensus even in the presence of communication faults.
Unit Dependency Graph and Its Application to Arithmetic Word Problem Solving

Math word problems provide a natural abstraction to a range of natural language understanding problems that involve reasoning about quantities, such as interpreting election results, news about casualties, and the financial section of a newspaper. Units associated with the quantities often provide information that is essential to support this reasoning. This paper proposes a principled way to capture and reason about units and shows how it can benefit an arithmetic word problem solver. This paper presents the concept of Unit Dependency Graphs (UDGs), which provides a compact representation of the dependencies between units of numbers mentioned in a given problem. Inducing the UDG alleviates the brittleness of the unit extraction system and allows for a natural way to leverage domain knowledge about unit compatibility, for word problem solving. We introduce a decomposed model for inducing UDGs with minimal additional annotations, and use it to augment the expressions used in the arithmetic word problem solver of (Roy and Roth 2015) via a constrained inference framework. We show that introduction of UDGs reduces the error of the solver by over 10 %, surpassing all existing systems for solving arithmetic word problems. In addition, it also makes the system more robust to adaptation to new vocabulary and equation forms .
Persuasive Faces: Generating Faces in Advertisements.

In this paper, we examine the visual variability of objects across different ad categories, i.e. what causes an advertisement to be visually persuasive. We focus on modeling and generating faces which appear to come from different types of ads. For example, if faces in beauty ads tend to be women wearing lipstick, a generative model should portray this distinct visual appearance. Training generative models which capture such category-specific differences is challenging because of the highly diverse appearance of faces in ads and the relatively limited amount of available training data. To address these problems, we propose a conditional variational autoencoder which makes use of predicted semantic attributes and facial expressions as a supervisory signal when training. We show how our model can be used to produce visually distinct faces which appear to be from a fixed ad topic category. Our human studies and quantitative and qualitative experiments confirm that our method greatly outperforms a variety of baselines, including two variations of a state-of-the-art generative adversarial network, for transforming faces to be more ad-category appropriate. Finally, we show preliminary generation results for other types of objects, conditioned on an ad topic.
Winning strategies for aperiodic subtraction games

We provide a winning strategy for sums of games of Mark-t, an impartial game played on nonnegative integers where each move consists of subtraction by an integer between 1 and t-1 inclusive, or division by t, rounding down when necessary. Our algorithm computes the Sprague-Grundy values for arbitrary n in quadratic time. This addresses one of the directions of further study proposed by Aviezri Fraenkel. In addition, we characterize the P-positions and N-positions for the game in misere play.
Growth and homogeneity of matchbox manifolds

Abstract A matchbox manifold with one-dimensional leaves which has equicontinuous holonomy dynamics must be a homogeneous space, and so must be homeomorphic to a classical Vietoris solenoid. In this work, we consider the problem, what can be said about a matchbox manifold with equicontinuous holonomy dynamics, and all of whose leaves have at most polynomial growth type? We show that such a space must have a finite covering for which the global holonomy group of its foliation is nilpotent. As a consequence, we show that if the growth type of the leaves is polynomial of degree at most 3, then there exists a finite covering which is homogeneous. If the growth type of the leaves is polynomial of degree at least 4, then there are additional obstructions to homogeneity, which arise from the structure of nilpotent groups.