cssi/SciSciGPT-SciSciNet huggingface dataset:
Plastid osmotic stress influences cell differentiation at the plant shoot apex

The balance between proliferation and differentiation in the plant shoot apical meristem is controlled by regulatory loops involving the phytohormone cytokinin and stem cell identity genes. Concurrently, cellular differentiation in the developing shoot is coordinated with the environmental and developmental status of plastids within those cells. Here, we employ an Arabidopsis thaliana mutant exhibiting constitutive plastid osmotic stress to investigate the molecular and genetic pathways connecting plastid osmotic stress with cell differentiation at the shoot apex. msl2 msl3 mutants exhibit dramatically enlarged and deformed plastids in the shoot apical meristem, and develop a mass of callus tissue at the shoot apex. Callus production in this mutant requires the cytokinin receptor AHK2 and is characterized by increased cytokinin levels, downregulation of cytokinin signaling inhibitors ARR7 and ARR15, and induction of the stem cell identity gene WUSCHEL. Furthermore, plastid stress-induced apical callus production requires elevated plastidic reactive oxygen species, ABA biosynthesis, the retrograde signaling protein GUN1, and ABI4. These results are consistent with a model wherein the cytokinin/WUS pathway and retrograde signaling control cell differentiation at the shoot apex.
First-Principles Study of Defective and Nonstoichiometric Sr2FeMoO6

The influence of disorder and stoichiometry-breaking point defects on the structural and magnetic properties of Sr2FeMoO6 have been investigated with the help of electronic structure calculations within the spin-polarized GGA+U approach. Defining the chemical potentials of the constituent elements from constitutional defects, we calculate the energetics of the possible point defects in nonstoichiometric Sr2FeMoO6 and find transition-metal-ion antisites and oxygen vacancies to be dominant. In nonstoichiometric Sr2Fe1+xMo1−xO6 with −0.75 ≤ x ≤ 0.25, both FeMo antisites (for Fe-rich samples or x > 0) and MoFe antisites (for Mo-rich samples or x < 0) lead to a systematic decrease in saturation magnetization. Only MoFe antisites destroy the half-metallic character of the electronic structure, since their t2g band crosses the Fermi level for x ≤ −0.125. This leads to a decrease of spin polarization from 100% for x ≥ −0.125 to 0 at x ≈ −0.75. Oxygen vacancies also reduce the saturation magnetization, but the hal...
Reduction of diaryl alkenes by hypophosphorous acid–iodine in acetic acid

Abstract A mixture of 50% aqueous H 3 PO 2 and I 2 (in catalytic amount) in HOAc efficiently reduces aryl alkenes to the corresponding alkanes in high yield. Addition of acetic anhydride to the medium results in ring-acetylation (or N -acetylation in the case of amines). H 3 PO 2 costs only one-fifth as much as hydriodic acid on a mole basis and one mole of H 3 PO 2 produces four moles of HI, resulting in a 20-fold cost advantage for H 3 PO 2 /I 2 over aqueous HI as a source of HI.
Double ring expansions: A new method for making medium and large cyclic ketones

Abstract A method for making medium and large cyclic ketones by free radical ring expansion of cyclobutanones with sequential Grob fragmentation is described.
The role of isoforms in the evolution of cryptic coloration in Peromyscus mice

A central goal of evolutionary biology is to understand the molecular mechanisms underlying phenotypic adaptation. While the contribution of protein-coding and cis-regulatory mutations to adaptive traits has been well documented, additional sources of variation - such as the production of alternative RNA transcripts from a single gene, or isoforms - have been understudied. Here, we focus on the pigmentation gene Agouti, known to express multiple alternative transcripts, to investigate the role of isoform usage in the evolution of cryptic colour phenotypes in deer mice (genus Peromyscus). We first characterize the Agouti isoforms expressed in the Peromyscus skin and find two novel isoforms not previously identified in Mus. Next, we show that a locally adapted light-coloured population of P. maniculatus living on the Nebraska Sand Hills shows an upregulation of a single Agouti isoform, termed 1C, compared with their ancestral dark-coloured conspecifics. Using in vitro assays, we show that this preference for isoform 1C may be driven by isoform-specific differences in translation. In addition, using an admixed population of wild-caught mice, we find that variation in overall Agouti expression maps to a region near exon 1C, which also has patterns of nucleotide variation consistent with strong positive selection. Finally, we show that the independent evolution of cryptic light pigmentation in a different species, P. polionotus, has been driven by a preference for the same Agouti isoform. Together, these findings present an example of the role of alternative transcript processing in adaptation and demonstrate molecular convergence at the level of isoform regulation.
Biosynthetic inspirations: cationic approaches to cyclopropane formation

The cyclopropyl group has played and continues to play a prominent role in organic chemistry. Its strained structure, interesting bonding characteristics, and value as an internal mechanistic probe have drawn the attention of the physical organic community. More recently, functionally rich cyclopropanes have been targeted due to their ability to control local conformation and project functionality in three dimensions. The prevalence of cyclopropane containing compounds with biological activity, whether isolated from natural sources or rationally designed pharmaceutical agents, has inspired chemists to find novel and diverse approaches to their synthesis. In fact, natural products often inspire and challenge synthetic chemists to consider mimicking the elegance and efficiency of biosynthesis. This review will focus on synthetic methods for the construction of cyclopropanes through cationic pathways and their corresponding inspirations from the biosynthesis of cyclopropane-containing natural products.
Asymmetric synthesis of 4,4-disubstituted-2-cyclohexen-1-ones from a chiral 2-(trimethylsilyl)benzamide

Abstract Birch reduction-alkylation of the chiral 2-(trimethylsilyl)benzamide 4 provides 1,4-cyclohexadienes 5b-5e with diastereomer ratios of >100:1. The conversions of 5b-5e to the 4,4-disubstituted-2-cyclohexen-1-ones 8b-8e are described.
Efficient one-step aldol-type reaction of ketones with acetals and ketals mediated by dibutylboron triflate/diisopropylethyl amine.

A highly efficient one-step Mukaiyama aldol-type reaction has been developed for the synthesis of β-alkoxy carbonyl compounds starting from ketones and acetals/ketals. The reaction is mediated by a combination of Bu2BOTf and i-Pr2NEt affording the products in high yields. Formation of the two possible diastereoisomers of the β-alkoxy ketones from the chiral acetals shows that the condensation takes place by an SN1 mechanism, involving prior opening of the acetal to an oxonium ion.
Delegating Capabilities in Predicate Encryption Systems.

In predicate encryption systems, given a capability, one can evaluate one or more predicates on the encrypted data, while all other information about the plaintext remains hidden. We consider the first such systems to permit delegation of capabilities. In a system that supports delegation, a user Alice who has a capability can delegate to Bob a more restrictive capability, which allows him to learn less about encrypted data than she did. We formally define delegation in predicate encryption systems, and propose a new security definition for delegation. In addition, we present an efficient construction supporting conjunctive queries. The security of our construction can be reduced to the general 3-party Bilinear DiffieHellman assumption, and the Bilinear Decisional Diffie-Hellman assumption in composite-order bilinear groups.
Cross Coupling of Phenyl Groups with Alkyl Iodides on Copper Surfaces: A Radical Mechanism?

The cross coupling of phenyl groups (C6H5) with alkyl iodides in adsorbed monolayers on single-crystal Cu(110) and Cu(100) surfaces under ultrahigh-vacuum conditions has been studied by a combination of temperature-programmed reaction techniques and isotope labeling. In these experiments, phenyl groups were generated on the surface by the dissociative adsorption of iodobenzene. Detailed studies in the case of the CH3I + phenyl reaction to form toluene show that there are two mechanisms for the process: a low-temperature pathway (<160 K; activation energy <10 kcal/mol), in which phenyl groups react directly with CH3I, and a much higher temperature pathway (∼400 K, activation energy ∼27 kcal/mol), in which adsorbed methyl groups produced by C−I bond scission couple with coadsorbed phenyl groups. The mechanism of the low-temperature reaction has yet to be fully resolved, but experimental evidence for a radical mechanism is presented. The relevant observations in this regard include the following: (1) when ...
Cross Talk with the GAR-3 Receptor Contributes to Feeding Defects in Caenorhabditis elegans eat-2 Mutants

Precise signaling at the neuromuscular junction (NMJ) is essential for proper muscle contraction. In the Caenorhabditis elegans pharynx, acetylcholine (ACh) released from the MC and M4 motor neurons stimulates two different types of contractions in adjacent muscle cells, termed pumping and isthmus peristalsis. MC stimulates rapid pumping through the nicotinic ACh receptor EAT-2, which is tightly localized at the MC NMJ, and eat-2 mutants exhibit a slow pump rate. Surprisingly, we found that eat-2 mutants also hyperstimulated peristaltic contractions, and that they were characterized by increased and prolonged Ca2+ transients in the isthmus muscles. This hyperstimulation depends on cross talk with the GAR-3 muscarinic ACh receptor as gar-3 mutation specifically suppressed the prolonged contraction and increased Ca2+ observed in eat-2 mutant peristalses. Similar GAR-3-dependent hyperstimulation was also observed in mutants lacking the ace-3 acetylcholinesterase, and we suggest that NMJ defects in eat-2 and ace-3 mutants result in ACh stimulation of extrasynaptic GAR-3 receptors in isthmus muscles. gar-3 mutation also suppressed slow larval growth and prolonged life span phenotypes that result from dietary restriction in eat-2 mutants, indicating that cross talk with the GAR-3 receptor has a long-term impact on feeding behavior and eat-2 mutant phenotypes.
Syntheses of Fjord Region Bis-dihydrodiol and Bis-anti-diol Epoxide Metabolites of Benzo[s]picene

Efficient syntheses of the trans-3,4-trans-9,10-tetrahydroxy-3,4,9,10-tetrahydro derivatives of benzo[s]picene and the corresponding bis-anti-diol epoxide derivatives in which the epoxide rings lie in the sterically crowded fjord regions are reported. Bis-dihydrodiols and bis-anti-diol epoxides of this type are suspected as proximate and ultimate carcinogenic metabolites, respectively, of several polycyclic aromatic hydrocarbons. These are the first examples of this class of molecules to be synthesized. The syntheses entail in the key step double oxidative photocyclization of a tetramethoxy-2,3-distyrylnaphthalene obtained from double Wittig reaction of naphthalene-2,3-dialdehyde. The bis-dihydrodiols were obtained as a mixture of meso and racemic diastereomers separable by HPLC on a reversed-phase ZORBAX ODS column. The bis-anti-diol epoxide enantiomers derived from the latter were resolved by HPLC on a chiral column.
A transition from SoxB1 to SoxE transcription factors is essential for progression from pluripotent blastula cells to neural crest cells.

Abstract The neural crest is a stem cell population unique to vertebrate embryos that gives rise to derivatives from multiple embryonic germ layers. The molecular underpinnings of potency that govern neural crest potential are highly conserved with that of pluripotent blastula stem cells, suggesting that neural crest cells may have evolved through retention of aspects of the pluripotency gene regulatory network (GRN). A striking difference in the regulatory factors utilized in pluripotent blastula cells and neural crest cells is the deployment of different sub-families of Sox transcription factors; SoxB1 factors play central roles in the pluripotency of naive blastula and ES cells, whereas neural crest cells require SoxE function. Here we explore the shared and distinct activities of these factors to shed light on the role that this molecular hand-off of Sox factor activity plays in the genesis of neural crest and the lineages derived from it. Our findings provide evidence that SoxB1 and SoxE factors have both overlapping and distinct activities in regulating pluripotency and lineage restriction in the embryo. We hypothesize that SoxE factors may transiently replace SoxB1 factors to control pluripotency in neural crest cells, and then poise these cells to contribute to glial, chondrogenic and melanocyte lineages at stages when SoxB1 factors promote neuronal progenitor formation.
Dihalodiazirines and the photochemical generation of dihalocarbenes: new light on old problems

The Graham oxidation of amidines to halodiazirines, coupled with the diazirine exchange reaction, makes available many new diazirine precursors of carbenes. Nitration of the phenoxy moieties of phenoxychloro- or phenoxyfluorodiazirine converts them to leaving groups, ultimately permitting the preparations of CCl2, CClF, and CF2. Absolute rate constants and activation parameters are measured for the additions of these carbenes to several alkenes. The comparative contributions of ΔH‡ and ΔS‡ to ΔG‡ are assessed for these reactions, as are the dependences of ΔH‡ and ΔS‡ on the structures and reactivities of the carbenes and alkenes. Copyright © 2009 John Wiley & Sons, Ltd.
De-singularization by rotation

We consider certain BPS supergravity solutions of string theory which have singularities and we show that the singularity goes away when we add angular momentum. These smooth solutions enable us to obtain global AdS3 as the near horizon geometry of a BPS brane system in an asymptotically flat space.
Lu8Te and Lu7Te. Novel substitutional derivatives of lutetium metal.

Monocrystals of Lu8Te are synthesized by disproportionation of Lu7Te at 1000−1200 °C or by direct reaction of Lu plus Lu2Te3 at 1000 °C for 2 weeks. Lu7Te is produced by arc-melting of a suitable Lu−Lu2Te3 mixture, with good crystals being formed by subsequent annealing at 1300 °C. The structures of Lu8Te (P62m, Z = 1) and Lu7Te (Cmcm, Z = 4) exhibit simple AB··· packing of distorted, not close-packed, layers along one short axis (c, a, respectively). Puckered Lu, Te layers are stacked normal to (010) or (001) in six- or eight-layer repeat sequences, with Te substituting for every third or every other Lu in every third or fourth layer, respectively. Strong Lu−Te bonding is indicated. Both Te substitutions decrease the volume per atom from that in hcp. Lu and also decrease the coordination number of all atoms from 12 to 9−11.
Patterns of shared signatures of recent positive selection across human populations.

Signatures of recent positive selection often overlap across human populations, but the question of how often these overlaps represent a single ancestral event remains unresolved. If a single selective event spread across many populations, the same sweeping haplotype should appear in each population and the selective pressure could be common across populations and environments. Identifying such shared selective events could identify genomic loci and human traits important in recent history across the globe. In addition, genomic annotations that recently became available could help attach these signatures to a potential gene and molecular phenotype selected across populations. Here, we present a catalogue of selective sweeps in humans, and identify those that overlap and share a sweeping haplotype. We connect these sweep overlaps with potential biological mechanisms at several loci, including potential new sites of adaptive introgression, the glycophorin locus associated with malarial resistance and the alcohol dehydrogenase cluster associated with alcohol dependency. Detecting selection events shared across human populations is challenging. Here, the authors identify overlapping and shared signatures of positive selection across human populations and connect shared targets of selection with potential biological mechanisms.
Chiral acetylenic sulfoxides in organic synthesis: Secondary amine cyclization and total synthesis of (S)-(−)-carnegine

Abstract Michael addition of secondary amines 1b–1g onto chiral acetylenic sulfoxides 2 followed by acid induced cyclization afforded structures of tetrahydroisoquinoline skeleton in high to moderate diastereoselectivity. Optical pure (S)-(−)-carnegine has been synthesized.
Synthesis of bicyclic ketals related to zaragozic acid by a novel photoannulation

Abstract The 2,8-dioxabicyclo[3.2.1]octane ring system of the zaragozic acids was synthesized by a Norrish Type II photochemical reaction. This reaction occured through an unusual 1,6-hydrogen abstraction to generate a 1,5-biradical. A solvent study found that using benzene provides the best yield of the desired cyclized product.
An improved method for the N‐alkylation of benzotriazole and 1,2,4‐triazole

The N-alkylation of benzotriazole and 1,2,4-triazole with alkyl halides proceeds efficiently in the presence of sodium hydroxide in N,N-dimethylformamide (DMF).
Redox-switched molecular aggregates: the first example of vesicle formation from hydrophobic ferrocene derivatives

We report here a novel class of ferrocenyl steroids and present the first evidence for aggregation of these systems and particularly for vesicle formation controlled by redox-switched ferrocene amphiphiles
Aging in a Relativistic Biological Space-Time

Here we present a theoretical and mathematical perspective on the process of aging. We extend the concepts of physical space and time to an abstract, mathematically-defined space, which we associate with a concept of ``biological space-time'' in which biological clocks operate. We hypothesize that biological dynamics, represented as trajectories in biological space-time, may be used to model and study different rates of biological aging. As a consequence of this hypothesis, we show how the dilation or contraction of time resulting from accelerated or decelerated biological dynamics may be used to study precipitous or protracted aging. We show specific examples of how these principles may be used to model different rates of aging, with an emphasis on cancer in aging. We discuss the implications of this theory, including novel concepts that may improve our interpretation of biological aging.
Pediatric Sarcoma Data Forms a Unique Cluster Measured via the Earth Mover’s Distance

In this note, we combined pediatric sarcoma data from Columbia University with adult sarcoma data collected from TCGA, in order to see if one can automatically discern a unique pediatric cluster in the combined data set. Using a novel clustering pipeline based on optimal transport theory, this turned out to be the case. The overall methodology may find uses for the classification of data from other biological networking problems.
Transition-Metal-Mediated Dihydropyran Syntheses. Exo Selective Hetero Diels−Alder Reactions of Cobaloxime Dienyl Complexes with Aldehydes

Cobaloxime 1,3-dienyl complex, 2-pyridine bis(dimethylglyoximato)cobalt(III)−(3E)-1,3-pentadiene, participates in exo selective hetero Diels−Alder reactions with a variety of alkyl and aryl aldehyd...
Generation of (E)-silylketene acetals in a Rhodium-DuPhos catalyzed two-step reductive aldol reaction.

Mechanistic studies employing in situ NMR analysis implicate intermediate silicon enolates as reactive intermediates in the Rh-DuPhos catalyzed two-step reductive aldol reaction with Cl2MeSiH. These enolates undergo noncatalyzed reaction with a variety of aldehydes to give the derived syn-aldol adduct in high yields and diastereoselection.
C–H amination/cyclocarbonylation of allene carbamates: a versatile platform for the synthesis of α,β-unsaturated γ-lactams

Abstract Despite their utility as building blocks for the construction of a variety of nitrogen-containing heterocyclic scaffolds, the preparation of allenic amines 2 via the direct C–H amination of allenes of the general structure 1 has not been well-explored. In this report, we describe our preliminary studies on the factors that control the chemoselectivity of Rh-catalyzed aminations of allenes to give either bicyclic methylene aziridines or the desired allenic amines 2. Additionally, the conversion of selected allenic amines to α,β-unsaturated γ-lactam scaffolds via a facile Ru3(CO)12 catalyzed cyclocarbonylation is described.
S-2-Naphthylmethyl thioacetimidate hydrobromide: A new odorless reagent for the mild synthesis of substituted acetamidines

Abstract The development, synthesis and use of S-2-naphthylmethyl thioacetimidate hydrobromide 7 as a highly reactive reagent for the mild conversion of amines to substituted acetamidines in a nonodorous process is described.
The Synthesis of D,L-15-Acetoxypallescensin-A: An Intramolecular Oxidative Free-Radical Approach

Abstract The synthesis of d,l-15-acetoxypallescensin-A 3 is reported. An intramolecular oxidative radical cyclization was used as a stereoselective entry to trans-decalin 12 which was converted in two steps to the pallescensin-A skeleton 14 by modification of Hagiwara's furan procedure.
Gas-Phase Hydrolysis of SOCl2 at 297 and 309 K: Implications for Its Atmospheric Fate

The gas-phase hydrolysis of thionyl chloride (SOCl2) has been investigated at 297 and 309 K in a mixing chamber using FTIR spectroscopy. Reagent concentrations of ∼80 ppmv SOCl2 at relative humidities (RH) of 1−63% were studied at 309 K, while humidities of 1−85% were used in the 297 K studies, all at a total pressure of ∼1 atm in synthetic air. In each experiment, an aliquot of SOCl2(g) was rapidly introduced into a chamber at fixed RH, quickly reaching a maximum and then decreasing exponentially, as monitored by time-resolved infrared spectroscopy. The only observed reaction products were HCl(g) and SO2(g), which were formed in a molar ratio of ∼2:1. The SOCl2 decay data are consistent with, but do not prove, the reaction being a gas-phase hydrolysis that is first order in both SOCl2 and H2O, with the RH-dependent decay data indirectly suggesting the first-order dependence on H2O(g). The 297 K rate constant was measured as (6.3 ± 3.5) × 10-21 cm3/molecule-s. Confirming previous results, SOCl2 absorbed o...
The Endocyclic Restriction Test: Investigation of the Geometries of Nucleophilic Substitution at Phosphorus(III) and Phosphorus(V)

Double labeling has been used under the endocyclic restriction test to show that transfers of phosphorus from oxygen to carbon in the conversions of lithio phosphinite 1 to alkoxy phosphine 8, of lithio phosphinite 2 to alkoxy phosphine 9, of lithio phosphinate 3 to alkoxy phosphine oxide 10, and of lithio phosphinite borane 4 to alkoxy phosphine borane 11 proceed in an intramolecular fashion. The transfers of stereogenic phosphorus in the conversions of lithio phosphinite (R)-5 to alkoxy phosphine (R)-12, of lithio phosphinate (S)-6 to alkoxy phosphine oxide (S)-13, and of lithio phosphinite borane (R)-7 to alkoxy phosphine borane (R)-14 proceed with retention of stereochemistry at phosphorus. These results rule out the classic in-line SN2 pathway and the geometrically equivalent in-line addition−elimination pathway for these endocyclic transfers of phosphorus. The most likely pathway for these nucleophilic substitutions at phosphorus is initial apical nucleophilic attack followed by pseudorotation and e...
Four diterpenoid inhibitors of Cdc25B phosphatase from a marine anemone

Abstract Three new diterpenoids and one known diterpenoid have been isolated from a sea anemone of the order Actiniara, and the structures of the new compounds, actiniarins A–C ( 1 – 3 ) were established on the basis of extensive 1D and 2D NMR spectroscopic data interpretation. Compound 1 has a six-membered ring hemiacetal ring, and the equilibrium of this ring is discussed. All the isolates were evaluated for their inhibition of Cdc25B and for cytotoxicity against the A2780 ovarian cancer cell line.
Towards Diversity-Oriented, Stereoselective Syntheses of Biaryl- or Bis(aryl)metal-Containing Medium Rings

Experimental Techniques and Apparatus Except as otherwise indicated, reactions were carried out under argon with dry, freshly distilled solvents. Tetrahydrofuran was distilled from sodium/benzophenone ketyl. Anhydrous 2-methyltetrahydrofuran (Aldrich, racemic) was stored over activated molecular sieves. Dichloromethane was distilled from calcium hydride. n-BuLi in hexane (Aldrich) and t-BuLi in pentane (Aldrich) were titrated with 1,10phenanthroline and anhydrous 2-butanol before use. All other reagents were purif ied in accordance with the instructions in “Purif ication of Laboratory Chemicals” or used as obtained from commercial sources. Yields refer to chromatographically and spectroscopically pure compounds. All reactions were monitored by thin layer chromatography (TLC) using glass plates precoated with E. Merck silica gel 60 F254 or aluminium oxide 60 F254. Visualization was by the quenching of UV f luorescence (λmax=254nm) or by staining with ceric ammonium molybdate or Dragendorff ’ s reagent (0.08% w/v bismuth subnitrate and 2% w/v KI in 3M aq. AcOH). Retention factors (Rf) are quoted to 0.01. Melting points were obtained using a Mel-Temp II melting point apparatus and are uncorrected. Infrared spectra were recorded either as a thin f ilm between NaCl plates or as a KBr disc on a Nicolet 5PC FT-IR spectrometer with internal referencing. Absorption maxima (νmax) are reported in wavenumbers (cm) and the following abbreviations are used: w, weak; m, medium; s, strong; br, broad. Proton magnetic resonance spectra were recorded on Varian Mercury400 (400MHz), Bruker Avance DMX500 (500MHz), and Varian Unity/Inova500 (500MHz) spectrometers. Proton assignments are supported by H-H COSY, HMQC, NOESY and GOESY spectra where necessary. Chemical shifts (δH) are quoted in ppm and are referenced to tetramethylsilane (internal). Coupling constants (J) are reported in Hertz to the nearest 0.5Hz. Data are reported as follows: chemical shift, integration, multiplicity [br, broad; s, singlet; d, doublet; t, triplet; q, quartet; qui, quintet; sept, septet; m, multiplet; or as a combination of these (e.g. dd, dt, etc.)], coupling constant(s) and assignment. Diastereotopic protons are assigned as X and X', where the ' indicates the lower f ield proton. Carbon magnetic resonance spectra were recorded on Varian Mercury400 (100MHz) and Varian Unity/Inova500 (125MHz) spectrometers. Carbon spectra assignments are supported by DEPT editing and where necessary C-H (HMQC) correlations. Chemical shifts (δC) are quoted in ppm to the nearest 0.01ppm, and are referenced to tetramethylsilane (internal). Fluorine magnetic resonance spectra (F) were recorded on a Varian Mercury300 (282MHz) spectrometer. Chemical shifts (δF) are quoted in ppm to the nearest 0.01ppm and are referenced to CF3CH2OH (external). 4
Magnetism and colossal magnetoresistance of the pseudo-ternary rare-earth transition-metal compounds, Eu14-xCaxMnSb11 (x < 3)

The compounds, Eu14-xCaxMnSb11 (x < 3), have been prepared by heating the mixture of stoichiometric amounts of the elements, sealed in a quartz-jacketed Ta tube, in a two-zone furnace with Thigh = ...
Resilience of Atlantic Slippersnail Crepidula fornicata Larvae in the Face of Severe Coastal Acidification

Globally, average oceanic pH is dropping, and it will continue to decline into the foreseeable future. This ocean acidification (OA) will exacerbate the natural fluctuations in pH that nearshore ecosystems currently experience daily, potentially pushing marine organisms to their physiological limits. Adults of Crepidula fornicata (the Atlantic slippersnail) have proven remarkably resilient to many environmental changes, which is perhaps not surprising considering that they are common intertidally, have a geographically large native range, and have been extremely successful at invading coastal water in many other parts of the world. However, the larvae of C. fornicata have been shown to be somewhat more vulnerable than adults to the effects of reduced pH. Research to date has focused on the physiological impacts of OA on C. fornicata larvae; few studies have explored shifts in gene expression resulting from changes in pH. In the present study, we examined the response of young (4-day old) C. fornicata larvae to two extreme OA treatments (pH 7.5 and 7.6) relative to pH 8.0, documenting both phenotypic and genome-wide gene expression responses. We found that rearing larvae at reduced pH had subtle influences on gene expression, predominantly involving downregulation of genes related to growth and metabolism, accompanied by significantly reduced shell growth rates only for larvae reared at pH 7.5. Additionally, 10-day old larvae that had been reared at the two lower pH levels were far less likely to metamorphose within six hours when exposed to inducer. However, all larvae eventually reached similarly high levels of metamorphosis 24 hours after settlement induction. Finally, there were no observed impacts of OA on larval mortality. Taken together, our results indicate that far future OA levels have observable, but not severe, impacts on C. fornicata larvae, which is consistent with the resilience of this invasive snail across rapidly changing nearshore ecosystems. We propose that future work should delve further into the physiological and transcriptomic responses of all life history stages to gain a more comprehensive understanding of how OA impacts the littoral gastropod C. fornicata.
Short-term Variability of Evolved Massive Stars with TESS

We present the first results from a study of TESS Sector 1 and 2 light curves for eight evolved massive stars in the LMC: six yellow supergiants (YSGs) and two luminous blue variables (LBVs), including S Doradus. We use an iterative prewhitening procedure to characterize the short-timescale variability in all eight stars. The periodogram of one of the YSGs, HD 269953, displays multiple strong peaks at higher frequencies than its fellows. While the field surrounding HD 269953 is quite crowded, it is the brightest star in the region, and has infrared colors indicating it is dusty. We suggest HD 269953 may be in a post-red supergiant evolutionary phase. We find a signal with a period of $\sim5$ days for the LBV HD 269582. The periodogram of S Doradus shows a complicated structure, with peaks below frequencies of 1.5 cycles per day. We fit the shape of the background noise of all eight light curves, and find a red noise component in all of them. However, the power law slope of the red noise and the timescale over which coherent structures arise changes from star to star. Our results highlight the potential for studying evolved massive stars with TESS.
SLING: using dynamic analysis to infer program invariants in separation logic

We introduce a new dynamic analysis technique to discover invariants in separation logic for heap-manipulating programs. First, we use a debugger to obtain rich program execution traces at locations of interest on sample inputs. These traces consist of heap and stack information of variables that point to dynamically allocated data structures. Next, we iteratively analyze separate memory regions related to each pointer variable and search for a formula over predefined heap predicates in separation logic to model these regions. Finally, we combine the computed formulae into an invariant that describes the shape of explored memory regions. We present SLING, a tool that implements these ideas to automatically generate invariants in separation logic at arbitrary locations in C programs, e.g., program pre and postconditions and loop invariants. Preliminary results on existing benchmarks show that SLING can efficiently generate correct and useful invariants for programs that manipulate a wide variety of complex data structures.
Opioid Prescription Usage after Benign Gynecologic Surgery: A Prospective Cohort Study.

Abstract Study Objective To compare the amount of opioids (tablets and morphine milligram equivalents [MMEs]) prescribed by physicians and used by patients after benign gynecologic surgery. Design Prospective cohort study. Setting Tertiary center: main hospital operating room and outpatient surgery center. Patients Women undergoing benign gynecologic surgery. Interventions Major and minor gynecologic surgeries. Measurements and Main Results The surgery groups were minor laparoscopy (Minor), major minimally invasive (Major), and laparotomy (Laparotomy). Demographic, medical, and surgical data were abstracted from electronic medical records. On postoperative day (POD) 7, women completed a telephone survey describing pain levels, prescription use, and satisfaction with pain control. Patients who continued to use opioids for pain relief were surveyed on POD 14. If use continued, patients were surveyed again on POD 28. The primary outcome was amount of opioid prescribed compared with opioid used. Of 193 screened participants 172 were enrolled (89%), and data were analyzed for 154 (90%): 59 (38%) Major, 71 (56%) Minor, and 24 (16%) Laparotomy. The median number of tablets and MMEs prescribed was lowest for the Minor group (Minor, 24 tablets; Major, 30 tablets; Laparotomy, 30 tablets [p Conclusion In this cohort, gynecologic surgeons prescribed nearly 3 times more opioid tablets and MMEs than was used by patients despite patients reporting similar levels of pain after minor and major surgeries.
Combining prediction intervals in the M4 competition

Abstract The 2018 M4 Forecasting Competition was the first M Competition to elicit prediction intervals in addition to point estimates. We take a closer look at the twenty valid interval submissions by examining the calibration and accuracy of the prediction intervals and evaluating their performances over different time horizons. Overall, the submissions fail to estimate the uncertainty properly. Importantly, we investigate the benefits of interval combination using six recently-proposed heuristics that can be applied prior to learning about the realizations of the quantities. Our results suggest that interval aggregation offers improvements in terms of both calibration and accuracy. While averaging interval endpoints maintains its practical appeal as being simple to implement and performs quite well when data sets are large, the median and the interior trimmed average are found to be robust aggregators for the prediction interval submissions across all 100,000 time series.
The Status of the Search for Low Mass WIMPs: 2012

Using information from a recent dark matter symposium at Marina del Rey, we discuss the most recent evidence and constraints on low mass WIMPs. There are now five separate experimental limits on such WIMPs, including a new paper on the XENON100 225 day exposure. There are very different experimental methods with different backgrounds that comprise this limit. We speculate on the possible sources of the reported low mass WIMP signals and background. We present recent arguments concerning DAMA that show the possible DM claims are likely misleading.
On the completion of the mapping class group of genus two

Abstract In this paper, we will study the Lie algebra of the prounipotent radical of the relative completion of the mapping class group of genus two. In particular, we will partially determine a minimal presentation of the Lie algebra by determining the generators and bounding the degree of the relations of it.
On the Positivity of the Coefficients of a Certain Polynomial Defined by Two Positive Definite Matrices

It is shown that the polynomial p(t) = Tr[(A+tB) m ] has positive coefficients when m = 6 and A and B are any two 3-by-3 complex Hermitian positive definite matrices. This case is the first that is not covered by prior, general results. This problem arises from a conjecture raised by Bessis, Moussa, and Villani in connection with a long-standing problem in theoretical physics. The full conjecture, as shown recently by Lieb and Seiringer, is equivalent to p(t) having positive coefficients for any m and any two n-by-n positive definite matrices. We show that, generally, the question in the real case reduces to that of singular A and B, and this is a key part of our proof.
On the AJ conjecture for cables of twist knots

We study the AJ conjecture that relates the A-polynomial and the colored Jones polynomial of a knot in $S^3$. We confirm the AJ conjecture for $(r,2)$-cables of the $m$-twist knot, for all odd integers $r$ satisfying $\begin{cases} (r+8)(r-8m)>0 &{if~} m> 0, \\ r(r+8m-4)>0 &{if~} m<0.\end{cases} $
Conjugate adaptive optics in widefield microscopy with an extended-source wavefront sensor

Subsurface microscopy is often limited by poor image quality due to sample-induced aberrations. Adaptive optics (AO) can counter such aberrations, though generally over limited fields of view. In most applications, AO is either slow or requires a “guide star” in the sample to serve as a localized reference target. We describe a fast closed-loop feedback implementation of AO that requires no guide stars, where the sample itself serves as the reference. Several features of our implementation are new. First, it is based on a high-resolution, single-shot wavefront sensor that is compatible with extended samples. Second, it is applied to widefield (i.e., nonscanning) microscopy in a conjugate AO configuration that increases field of view. Third, it makes use of a fast algorithm to identify sample-induced aberrations using illumination from an arbitrarily shaped source. We present the principle of our technique and proof-of-concept experimental demonstrations.
Limit order trading with a mean reverting reference price

Optimal control models for limit order trading often assume that the underlying asset price is a Brownian motion since they deal with relatively short time scales. The resulting optimal bid and ask limit order prices tend to track the underlying price as one might expect. This is indeed the case with the model of Avellaneda and Stoikov (2008), which has been studied extensively. We consider here this model under the condition when the underlying price is mean reverting. Our main result is that when time is far from the terminal, the optimal price for bid and ask limit orders is constant, which means that it does not track the underlying price. Numerical simulations confirm this behavior. When the underlying price is mean reverting, then for times sufficiently far from terminal, it is more advantageous to focus on the mean price and ignore fluctuations around it. Mean reversion suggests that limit orders will be executed with some regularity, and this is why they are optimal. We also explore intermediate time regimes where limit order prices are influenced by the inventory of outstanding orders. The duration of this intermediate regime depends on the liquidity of the market as measured by specific parameters in the model.
The Devron property

Abstract We introduce a criterion called the Devron property that a discrete dynamical system can possess. The Devron property is said to occur when a class of highly singular inputs of a mapping F are carried by some iterate of F − 1 to a class of highly singular inputs of F − 1 . The inspiration for this definition is the discovery by R. Schwartz that the pentagram map exhibits this kind of behavior. We investigate occurrences of the Devron property in a number of different dynamical systems.
JSPAM: A restricted three-body code for simulating interacting galaxies

Abstract Restricted three-body codes have a proven ability to recreate much of the disturbed morphology of actual interacting galaxies. As more sophisticated n-body models were developed and computer speed increased, restricted three-body codes fell out of favor. However, their supporting role for performing wide searches of parameter space when fitting orbits to real systems demonstrates a continuing need for their use. Here we present the model and algorithm used in the JSPAM code. A precursor of this code was originally described in 1990, and was called SPAM. We have recently updated the software with an alternate potential and a treatment of dynamical friction to more closely mimic the results from n-body tree codes. The code is released publicly for use under the terms of the Academic Free License (“AFL”) v. 3.0 and has been added to the Astrophysics Source Code Library.
The mean number of 3-torsion elements in the class groups and ideal groups of quadratic orders

We determine the mean number of 3-torsion elements in the class groups of quadratic orders, where the quadratic orders are ordered by their absolute discriminants. Moreover, for a quadratic order O we distinguish between the two groups: Cl3(O), the group of ideal classes of order 3; and I3(O), the group of ideals of order 3. We determine the mean values of both |Cl3(O)| and |I3(O)|, as O ranges over any family of orders defined by finitely many (or in suitable cases, even infinitely many) local conditions. As a consequence, we prove the surprising fact that the mean value of the difference |Cl3(O)|− |I3(O)| is equal to 1, regardless of whether one averages over the maximal orders in complex quadratic fields or over all orders in such fields or, indeed, over any family of complex quadratic orders defined by local conditions. For any family of real quadratic orders defined by local conditions, we prove similarly that the mean value of the difference |Cl3(O)|− 1 3 |I3(O)| is equal to 1, independent of the family.
Selling to a No-Regret Buyer

We consider the problem of a single seller repeatedly selling a single item to a single buyer (specifically, the buyer has a value drawn fresh from known distribution D in every round). Prior work assumes that the buyer is fully rational and will perfectly reason about how their bids today affect the seller's decisions tomorrow. In this work we initiate a different direction: the buyer simply runs a no-regret learning algorithm over possible bids. We provide a fairly complete characterization of optimal auctions for the seller in this domain. Specifically: - If the buyer bids according to EXP3 (or any "mean-based" learning algorithm), then the seller can extract expected revenue arbitrarily close to the expected welfare. This auction is independent of the buyer's valuation D , but somewhat unnatural as it is sometimes in the buyer's interest to overbid. - There exists a learning algorithm A such that if the buyer bids according to A then the optimal strategy for the seller is simply to post the Myerson reserve for D every round. - If the buyer bids according to EXP3 (or any "mean-based" learning algorithm), but the seller is restricted to "natural" auction formats where overbidding is dominated (e.g. Generalized First-Price or Generalized Second-Price), then the optimal strategy for the seller is a pay-your-bid format with decreasing reserves over time. Moreover, the seller's optimal achievable revenue is characterized by a linear program, and can be unboundedly better than the best truthful auction yet simultaneously unboundedly worse than the expected welfare.
Automatic differentiation variational inference

Probabilistic modeling is iterative. A scientist posits a simple model, fits it to her data, refines it according to her analysis, and repeats. However, fitting complex models to large data is a bottleneck in this process. Deriving algorithms for new models can be both mathematically and computationally challenging, which makes it difficult to efficiently cycle through the steps. To this end, we develop automatic differentiation variational inference (ADVI). Using our method, the scientist only provides a probabilistic model and a dataset, nothing else. ADVI automatically derives an efficient variational inference algorithm, freeing the scientist to refine and explore many models. ADVI supports a broad class of models--no conjugacy assumptions are required. We study ADVI across ten modern probabilistic models and apply it to a dataset with millions of observations. We deploy ADVI as part of Stan, a probabilistic programming system.
Sliced Wasserstein Distance for Learning Gaussian Mixture Models

Gaussian mixture models (GMM) are powerful parametric tools with many applications in machine learning and computer vision. Expectation maximization (EM) is the most popular algorithm for estimating the GMM parameters. However, EM guarantees only convergence to a stationary point of the log-likelihood function, which could be arbitrarily worse than the optimal solution. Inspired by the relationship between the negative log-likelihood function and the Kullback-Leibler (KL) divergence, we propose an alternative formulation for estimating the GMM parameters using the sliced Wasserstein distance, which gives rise to a new algorithm. Specifically, we propose minimizing the sliced-Wasserstein distance between the mixture model and the data distribution with respect to the GMM parameters. In contrast to the KL-divergence, the energy landscape for the sliced-Wasserstein distance is more well-behaved and therefore more suitable for a stochastic gradient descent scheme to obtain the optimal GMM parameters. We show that our formulation results in parameter estimates that are more robust to random initializations and demonstrate that it can estimate high-dimensional data distributions more faithfully than the EM algorithm.
Horton self-similarity of Kingman’s coalescent tree

Cet article prouve l’auto-similarite a la Horton pour la representation par arbres du processus de coalescence de Kingman. La preuve est basee sur un systeme d’equations differentielles ordinaires de type Smoluchowski decrivant, dans la limite hydrodynamique, l’evolution du nombre de branches d’un ordre de Horton–Strahler donne dans un arbre representant le $N$-coalescent de Kingman. Nous prouvons aussi un lien etroit entre l’arbre de Kingman combinatoire et l’arbre combinatoire des ensembles de niveaux d’un bruit blanc, ce qui implique l’auto-similarite a la Horton de ce dernier.
On Mixing Properties of Some INAR Models

Strictly stationary INAR(1) processes (“integer-valued autoregressive processes of order 1”) with Poisson innovations are “interlaced ρ-mixing.” Bibliography: 20 titles.
On the Supermodularity of Active Graph-Based Semi-Supervised Learning with Stieltjes Matrix Regularization

Active graph-based semi-supervised learning (AG-SSL) aims to select a small set of labeled examples and utilize their graph-based relation to other unlabeled examples to aid in machine learning tasks. It is also closely related to the sampling theory in graph signal processing. In this paper, we revisit the original formulation of graph-based SSL and prove the supermodularity of an AG-SSL objective function under a broad class of regularization functions parameterized by Stieltjes matrices. Under this setting, supermodularity yields a novel greedy label sampling algorithm with guaranteed performance relative to the optimal sampling set. Compared to three state-of-the-art graph signal sampling and recovery methods on two real-life community detection datasets, the proposed AG-SSL method attains superior classification accuracy given limited sample budgets.
A Conditional Construction of Restricted Isometries

We study the restricted isometry property of a matrix that is built from the discrete Fourier transform matrix by collecting rows indexed by quadratic residues. We find an $\epsilon>0$ such that, conditioned on a folklore conjecture in number theory, this matrix satisfies the restricted isometry property with sparsity parameter $K=\Omega(M^{1/2+\epsilon})$, where $M$ is the number of rows.