cssi/SciSciGPT-SciSciNet huggingface dataset:
The neural architecture of executive functions is established by middle childhood

Executive functions (EFs) are regulatory cognitive processes that support goal-directed thoughts and behaviors and that involve two primary networks of functional brain activity in adulthood: the fronto-parietal and cingulo-opercular networks. The current study assessed whether the same networks identified in adulthood underlie child EFs. Using task-based fMRI data from a diverse sample of N = 117 children and early adolescents (M age = 10.17 years), we assessed the extent to which neural activity was shared across switching, updating, and inhibition domains, and whether these patterns were qualitatively consistent with adult EF-related activity. Brain regions that were consistently engaged across switching, updating, and inhibition tasks closely corresponded to the cingulo-opercular and fronto-parietal networks identified in studies of adults. Isolating brain activity during more demanding task periods highlighted contributions of the dorsal anterior cingulate and anterior insular regions of the cingulo-opercular network. Results were independent of age and time-on-task effects. These results indicate that the two core brain networks that support EFs are in place by middle childhood, in agreement with resting-state findings of adultlike brain network organization. Improvement in EFs from middle childhood to adulthood, therefore, are likely due to quantitative changes in activity within these networks, rather than qualitative changes in the organization of the networks themselves. Improved knowledge of how the brain's functional organization supports EF in childhood has critical implications for understanding the maturation of cognitive abilities.
Rearrangement reactions of lithiated oxiranes.

The first computational study of the rearrangement reactions of oxiranes initiated by lithium dialkylamides is presented. Aside from the well-known carbenoid insertion pathways, both β-elimination and α-lithiation have been suggested as the exclusive mechanism by which oxiranes react in the presence of organolithium bases. The products of the former are allyl alcohols (and, in some cases, dienes) and are ketones in the case of the latter. The computational studies reported in this work indicate that both mechanisms could be simultaneously operational. In particular, our work shows that the allyl alcohols from β-elimination are unlikely to undergo 1,3-hydrogen transfer to the vinyl alcohols and thus to the ketones, suggesting that ketones are formed through the opening of the oxirane ring after α-substitution. Elimination of LiOH from the lithiated allyl alcohol is found to result in the diene product. Low activation barriers for β-elimination are offered as the explanation for the few special cases where ...
Aerodigestive sampling reveals altered microbial exchange between lung, oropharyngeal, and gastric microbiomes in children with impaired swallow function

Background Children with oropharyngeal dysphagia have impaired airway protection mechanisms and are at higher risk for pneumonia and other pulmonary complications. Aspiration of gastric contents is often implicated as a cause for these pulmonary complications, despite being supported by little evidence. The goal of this study is to determine the relative contribution of oropharyngeal and gastric microbial communities to perturbations in the lung microbiome of children with and without oropharyngeal dysphagia and aspiration. Methods We conducted a prospective cohort study of 220 patients consecutively recruited from a tertiary aerodigestive center undergoing simultaneous esophagogastroduodenoscopy and flexible bronchoscopy. Bronchoalveolar lavage, gastric and oropharyngeal samples were collected from all recruited patients and 16S sequencing was performed. A subset of 104 patients also underwent video fluoroscopic swallow studies to assess swallow function and were categorized as aspiration/no aspiration. To ensure the validity of the results, we compared the microbiome of these aerodigestive patients to the microbiome of pediatric patients recruited to a longitudinal cohort study of children with suspected GERD; patients recruited to this study had oropharyngeal, gastric and/or stool samples available. The relationships between microbial communities across the aerodigestive tract were described by analyzing within- and between-patient beta diversities and identifying taxa which are exchanged between aerodigestive sites within patients. These relationships were then compared in patients with and without aspiration to evaluate the effect of aspiration on the aerodigestive microbiome. Results Within all patients, lung, oropharyngeal and gastric microbiomes overlap. The degree of similarity is the lowest between the oropharynx and lungs (median Jensen-Shannon distance (JSD) = 0.90), and as high between the stomach and lungs as between the oropharynx and stomach (median JSD = 0.56 for both; p = 0.6). Unlike the oropharyngeal microbiome, lung and gastric communities are highly variable across people and driven primarily by person rather than body site. In patients with aspiration, the lung microbiome more closely resembles oropharyngeal rather than gastric communities and there is greater prevalence of microbial exchange between the lung and oropharynx than between gastric and lung sites (p = 0.04 and 4x10−5, respectively). Conclusions The gastric and lung microbiomes display significant overlap in patients with intact airway protective mechanisms while the lung and oropharynx remain distinct. In patients with impaired swallow function and aspiration, the lung microbiome shifts towards oropharyngeal rather than gastric communities. This finding may explain why antireflux surgeries fail to show benefit in pediatric pulmonary outcomes.
A novel hydrogen transfer hydroalumination of alkenes with triisobutylaluminum catalyzed by Pd and other late transition metal complexes

Abstract Hydrogen transfer hydroalumination of terminal alkenes and dienes can be achieved with 1.1 equiv. of ( i -Bu) 3 Al and catalytic amounts of Cl 2 Pd(PPh 3 ) 2 and other late transition metal complexes containing Co, Rh, Ni, and Pt at ambient temperature in high yields.
Facile synthesis of novel spiro[azetidine‐2,4′(1′H)‐isoquinoline‐1′,3′,4(2′H)‐triones]

A convenient general method for the synthesis of a new heterocycle, spiro[azetidine-2,4′(1′H)-iso-quinoline-1′,3′,4(2′H)-trione] is described. The key intermediate 2 was prepared by direct halogenation of position-4 of acid 3 with thionyl chloride, and subsequent treatment of the generated 4-Cl, 4-acetyl chloride 11 with a THF/NH3 solution at low temperature.
Enantioselective addition of vinylzinc reagents to 3,4-dihydroisoquinoline N-oxide.

Ligand 2a promotes the enantioselective addition of vinylzinc reagents to 3,4-dihydroisoquinoline N-oxide to yield chiral allylic hydroxylamines. With 0.1 equiv of the ligand, the product is obtained in up to 84% ee, whereas with 1.2 equiv of the ligand, the ee is increased to the 90−95% range with a variety of aliphatic, cyclic, and aromatic vinylzinc reagents. This method was used to synthesize the protected unnatural amino acid N-Cbz-d-1,2,3,4-tetrahydroisoquinoline-1-carboxylic acid in three steps from the allylic hydroxylamine.
Cleavage of ethers and geminal diacetates using the boron triiodide-N,N-diethylaniline complex

Abstract The boron triiodide-N,N-diethylaniline complex, generated in situ from borane:N,N-diethylaniline and iodine cleaves ethers and regenerates carbox-aldehydes from the corresponding geminal diacetate derivatives under mild conditions in good yields. Recently a simple procedure for the preparation of alkyl and alkenyl iodides in good yields using boron triiodide-N,N-diethylaniline complex and acetic acid was reported.1 This prompted us to report our results on the cleavage of ethers and regeneration of aldehydes from geminal diacetates using the boron triiodide-N,N-diethylaniline reagent.
Protein Glycosylation: The Clash of the Titans

Enzymes catalyze a variety of transformations with spectacular rate enhancements while demonstrating exquisite selectivities. Information from complementary structural and mechanistic studies has yielded insight into the inner workings of many enzyme-catalyzed reactions. In particular, studies of transformations that involve the interaction of one or more small-molecule substrates with soluble enzymes have met with notable success. There remain, however, a number of reactions, including those involving the covalent modification of macromolecular substrates, that confound us by their complexity. One such transformation, asparagine-linked glycosylation, involves the enzyme-catalyzed modification of an asparagine side chain in a nascent polypeptide with a triantennary tetradecasaccharide (GlcNAc_2Man_9Glc_3) moiety. This first committed step in the biosynthesis of N-linked glycoproteins is catalyzed by oligosaccharyl transferase (OT), a heteromeric membrane-associated enzyme complex, found in the lumen of the endoplasmic reticulum (ER) of eukaryotic cells. Glycosyl transfer to the nitrogen of the carboxamide side chain of an asparagine occurs through the intermediacy of a dolichol-linked pyrophosphate donor as illustrated in Figure 1. The primary peptide sequence requirements for the glycosylation process include a minimum -Asn-Xaa-Ser/Thr- tripeptide recognition motif where Xaa can be any of the 20 natural amino acids except proline. Thus, while OT exhibits rather simple substrate requirements, the enzyme catalyzes an unusual and specific reaction wherein the nucleophilicity of the asparagine side chain must be greatly enhanced to form a covalent linkage with the oligosaccharide. After transfer of the initial tetradecasaccharide, subsequent diversification of the primary glycoprotein conjugates arises from enzyme-catalyzed processing steps that occur in both the ER and the Golgi apparatus. Specifically, the core oligosaccharide structures are subject to the action of an elaborate array of glycosyl hydrolase and glycosyl transferase enzymes. The latter class of enzymes catalyzes the incorporation of a broader diversity of carbohydrate units including fucose, sialic acid, and galactose. The collective action of these enzymes generates the structural diversity associated with mature N-linked glycoproteins in eukaryotic cells.
A computational model of perceptual and mnemonic deficits in medial temporal lobe amnesia

Damage to the medial temporal lobe (MTL) has long been known to impair declarative memory, and recent evidence suggests that it also impairs visual perception. A theory termed the representational-hierarchical account explains such impairments by assuming that MTL stores conjunctive representations of items and events, and that individuals with MTL damage must rely upon representations of simple visual features in posterior visual cortex, which are inadequate to support memory and perception under certain circumstances. One recent study of visual discrimination behavior revealed a surprising antiperceptual learning effect in MTL-damaged individuals: With exposure to a set of visual stimuli, discrimination performance worsened rather than improved [Barense, M. D., Groen, I. I. A., Lee, A. C. H., Yeung, L. K., Brady, S. M., Gregori, M., et al. Intact memory for irrelevant information impairs perception in amnesia. Neuron, 75, 157-167, 2012]. We extend the representational-hierarchical account to explain this paradox by assuming that difficult visual discriminations are performed by comparing the relative "representational tunedness"-or familiarity-of the to-be-discriminated items. Exposure to a set of highly similar stimuli entails repeated presentation of simple visual features, eventually rendering all feature representations maximally and, thus, equally familiar; hence, they are inutile for solving the task. Discrimination performance in patients with MTL lesions is therefore impaired by stimulus exposure. Because the unique conjunctions represented in MTL do not occur repeatedly, healthy individuals are shielded from this perceptual interference. We simulate this mechanism with a neural network previously used to explain recognition memory, thereby providing a model that accounts for both mnemonic and perceptual deficits caused by MTL damage with a unified architecture and mechanism.
Conjugative Interaction in Styrenes

Conjugative interactions of the carbon−carbon double bond are fundamental in organic chemistry. In this work, equilibria are established among conjugated and unconjugated isomers of two β-substitut...
Steroids labeled with 18F for imaging tumors by positron emission tomography

Abstract The chemistry to label radiopharmaceuticals for imaging with positron emission tomography (PET) with the 2 h half life positron-emitting radionuclide fluorine-18 ( 18 F) requires ease, efficiency, and speed. Furthermore, when high specific activities are needed, as in imaging high affinity, low capacity receptors, reactions need to work well at the tracer level scale. This review covers 18 F synthetic methods and their application to the preparation of [ 18 F]-labeled steroids for imaging hormone-responsive cancers. The methods exemplified are fluoride ion displacement of sulfonates and opening of cyclic sulfates, nucleophilic aromatic substitution, and halogen fluoride addition to alkenes.
Synthesis of linearly-fused benzodehydro[12]annulenes

Abstract This communication describes the preparation of the first linearly-fused benzodehydro[12]annulene systems, which we have called acediynes. These stable antiaromatic materials exhibit absorption properties that closely resemble the spectra of the corresponding acenes.
[n + 1] Annulation Route to Highly Substituted Cyclic Ketones with Pendant Ketone, Nitrile, and Ester Functionality

Two carbon acids connected by a tether containing a ketone undergo two Michael reactions to 3-butyn-2-one to afford highly substituted and functionalized cyclic ketones with pendant ketone, nitrile, and ester functionality. The stereochemical courses of the double Michael reactions vary remarkably with the structure of the starting material. Double Michael adducts with equatorially disposed cyano groups can be hydrogenated to afford trans-fused bicyclic amines.
Regioselectivity Control in a Ruthenium-Catalyzed Cycloisomerization of Diyne-ols

The ruthenium-catalyzed cycloisomerization of diynes containing one silyl alkyne and one propargyl alcohol yields 2-silyl-[6H]-pyrans instead of the expected unsaturated acylsilanes except when additional conjugation of a aromatic ring is present at the δ-position. Under certain conditions, a facile ruthenium-catalyzed isomerization of the product takes place as well. This regioselectivity of the cyclization can be controlled by the choice of solvent system. DFT calculations confirm the expected greater stability of the silyl-pyrans relative to the acylsilanes.
Syntheses of pyrrolo- and indoloisoquinolinones by intramolecular cyclizations of 1-(2-arylethyl)-5-benzotriazolylpyrrolidin-2-ones and 3-benzotriazolyl-2-(2-arylethyl)-1-isoindolinones.

1,5,6,10b-Tetrahydropyrrolo[2,1-a]isoquinolin-3(2H)-ones 17a,b, 17d,e, and 5,12b-dihydroisoindolo[1,2-a]isoquinolin-8(6H)-ones 22a−e were prepared by intramolecular cyclizations of 1-(2-arylethyl)-5-benzotriazolyl-pyrrolidin-2-ones 15a,b, 15d,e, and 3-benzotriazolyl-2-(2-arylethyl)-1-isoindolinones 20a−e, respectively, in the presence of titanium chloride. Products from chiral amines were obtained with stereoselectivities of ≥94%.
Dopamine Modulation of Prefrontal Cortex Activity Is Manifold and Operates at Multiple Temporal and Spatial Scales.

Summary Although the function of dopamine in subcortical structures is largely limited to reward and movement, dopamine neurotransmission in the prefrontal cortex (PFC) is critical to a multitude of temporally and functionally diverse processes, such as attention, working memory, behavioral flexibility, action planning, and sustained motivational and affective states. How does dopamine influence computation of these temporally complex functions? We find causative links between sustained and burst patterns of phasic dopamine neuron activation and modulation of medial PFC neuronal activity at multiple spatiotemporal scales. These include a multidirectional and weak impact on individual neuron rate activity but a robust influence on coordinated ensemble activity, gamma oscillations, and gamma-theta coupling that persisted for minutes. In addition, PFC network responses to burst pattern of dopamine firing were selectively strengthened in behaviorally active states. This multiplex mode of modulation by dopamine input may enable PFC to compute and generate spatiotemporally diverse and specialized outputs.
The crystal and electronic band structure of the diamond-like semiconductor Ag2ZnSiS4

Abstract Single crystals of the new diamond-like semiconductor Ag 2 ZnSiS 4 have been synthesized using high-temperature, solid state synthesis at 800 °C. The compound crystallizes in the monoclinic, noncentrosymmetric space group Pn with a = 6.4052(1) A, b = 6.5484(1) A, c = 7.9340(1) A, β = 90.455(1)° and R 1 (for all data) = 2.42%. The electronic band structure and density of states were calculated using density functional theory (DFT) and the full potential linearized augmented plane wave (LAPW) method within the Wien2k program suite. The calculated band structure suggests that Ag 2 ZnSiS 4 is a direct band gap semiconductor with a calculated band gap of 1.88 eV at the Γ-point. The calculated density of states of Ag 2 ZnSiS 4 is compared with that of AgGaS 2 . The band gap of Ag 2 ZnSiS 4 was also determined experimentally as 3.28 eV via optical diffuse reflectance spectroscopy.
Isotope Effects on the Ring Inversion of Cyclooctatetraene

1H NMR studies (400 MHz) on isopropoxycyclooctatetraene (C8H7-O-C3H7) and its ring-d7 analogue (C8D7-O-C3H7) show that there is an inverse isotope effect on the rate of ring inversion of kH/kD = 0.68−0.57 in the temperature range from −10 to −50 °C. These experiments confirm the validity of previously published DFT calculations on cyclooctatetraene/cyclooctatetraene-d8, which predict an inverse isotope effect of about this size on the rate of ring inversion in this temperature range. The large inverse isotope effect upon ring inversion explains why the similarly large normal equilibrium isotope effect, found in the reduction of benzene to its corresponding anion radical, is not observed in the analogous reduction of cyclooctatetraene.
Sex differences in gene regulation in the dorsal root ganglion after nerve injury.

Pain is a subjective experience derived from complex interactions among biological, environmental, and psychosocial pathways. Sex differences in pain sensitivity and chronic pain prevalence are well established. However, the molecular basis underlying these sex dimorphisms are poorly understood particularly with regard to the role of the peripheral nervous system. Here we sought to identify shared and distinct gene networks functioning in the peripheral nervous systems that may contribute to sex differences of pain in rats after nerve injury. We performed RNA-seq on dorsal root ganglia following chronic constriction injury of the sciatic nerve in male and female rats. Analysis from paired naive and injured tissues showed that 1513 genes were differentially expressed between sexes. Genes which facilitated synaptic transmission in naive and injured females did not show increased expression in males. Appreciating sex-related gene expression differences and similarities in neuropathic pain models may help to improve the translational relevance to clinical populations and efficacy of clinical trials of this major health issue.
Synthesis of ladder polyaromatics as new molecular device candidates

In order to investigate one of the proposed molecular electronics switching mechanisms, we synthesized several molecules whose cores are unable to undergo conformational rotation. Preparation of these molecules, all of which are terminated with the thioacetyl moiety, takes advantage of an improved synthesis of 2,7-dibromophenanthrene, use of the reduced form of phenanthrenequinone as a protecting group, and various Sonogashira and halogen to Li to S conversions.
α-Nitrogen activating effect in the room temperature copper-promoted N-arylation of heteroarylcarboxamides with phenyl siloxane or p-toluylboronic acid

Abstract Heteroarylcarboxamides containing α-nitrogens undergo copper-promoted N -phenylation with hypervalent phenyl trimethylsiloxane at room temperature, in the absence of base and in air . Arylboronic acid can substitute for phenyl trimethylsiloxane as the organometalloid. The α-heteroatom chelating effect is in the decreasing order of N>O, S. This discovery opens up the possibility of using other α-nitrogen functional groups to direct the N -arylation of peptides and simple amides under conditions as mild as that of amide bond formation.
A Counterselectable Sucrose Sensitivity Marker Permits Efficient and Flexible Mutagenesis in Streptococcus agalactiae

Streptococcus agalactiae (group B Streptococcus [GBS]) is a cause of severe infections, particularly during the newborn period. While methods exist for generating chromosomal mutations in GBS, they are cumbersome and inefficient and present significant challenges if the goal is to study subtle mutations, such as single-base-pair polymorphisms. To address this problem, we have developed an efficient and flexible GBS mutagenesis protocol based on sucrose counterselection against levansucrase (SacB) expressed from a temperature-selective shuttle vector. GBS containing the SacB expression cassette demonstrates lethal sensitivity to supplemental sucrose whether the plasmid DNA is replicating outside of the chromosome or has been integrated during a crossover event. Transmission electron microscopy shows that SacB-mediated lethal sucrose sensitivity results from the accumulation of inclusion bodies that eventually lead to complete degradation of normal cellular architecture and subsequent lysis. We used this new mutagenesis technique to generate an in-frame, allelic exchange knockout of the GBS sortase gene srtA, demonstrating that >99% of colonies that emerge from our protocol had the expected knockout phenotype and that among a subset tested by sequencing, 100% had the correct genotype. We also generated barcoded nonsense mutations in the cylE gene in two GBS strains, showing that the approach can be used to make small, precise chromosomal mutations.IMPORTANCE The ability to generate chromosomal mutations is fundamental to microbiology. Historically, however, GBS pathogenesis research has been made challenging by the relative genetic intractability of the organism. Generating a single knockout in GBS using traditional techniques can take many months, with highly variable success rates. Furthermore, traditional methods do not offer a straightforward way to generate single-base-pair polymorphisms or other subtle changes, especially to noncoding regions of the chromosome. We have developed a new sucrose counterselection-based method that permits rapid, efficient, and flexible GBS mutagenesis. Our technique requires no additional equipment beyond what is needed for traditional approaches. We believe that it will catalyze rapid advances in GBS genetics research by significantly easing the path to generating mutants.
Synthesis of (E)-2-(4,7-dichloroquinolin-2-yl)-3-dimethylamino-2-propene-1-al and its use as a synthetic intermediate

Abstract A novel synthesis is described for (E)-2-(4,7-dichloroquinolin-2-yl)-3-dimethylamino-2-propene-1-al (4), which reacts with nucleophiles to yield heterocycle-substituted 4,7-dichloroquinolines (5–7).
Stereoselective Synthesis of Highly Functionalized Trisubstituted Olefins via the Aldol Reaction of Allenoxyborinates with Carbonyl Compounds

Allenoxyborinates, generated via the reaction of dicyclohexylborane with α,β-acetylenic ketones, react in situ with excess starting ketone to afford stereodefined, functionalized, trisubstituted olefins in good yields. The allenoxyborinates, (RCHCC(R‘)OB(c-C6H11)2, can also be trapped by aldehydes and ketones when R‘ is a tert-butyl group.
Photochemistry and reaction intermediates of the bimetallic Group VIII cyclopentadienyl metal carbonyl compounds, (η5-C5H5)2M2(CO)4 and their derivatives

Abstract The bonding, structures and photochemistry of the Group VIII metal cyclopentadienyl carbonyl derivatives of the form, (η 5 -C 5 H 5 ) 2 M 2 (CO) 4 , where M=Fe, Ru and Os, are reviewed. The primary emphasis of the review is to bring together the somewhat complex literature in this field, to critically examine the evidence and interpretations and to identify areas for future research opportunities.
The CGC and the Glasma: Two lectures at the Yukawa Institute

These lectures present the theory of the Color Glass Condensate (CGC) and the Glasma in an elementary and intuitive manner. This matter controls the high energy limit of QCD. The CGC is the universal limit for the components of a hadron wavefunction important for high energy scattering processes. It is a highly coherent, extremely high energy density ensemble of gluon states. The Glasma is matter produced in the collision of CGCs of two hadrons. It has properties much different from those of the CGC, and is produced in a very short time after the collision. It eventually evolves from the the Color Glass Condensate initial conditions into a Quark Gluon Plasma. We can visualize the collision of two high energy hadrons as shown in Fig. 1. Before the collision, two hadrons appear as Lorentz contracted sheets approaching one another at near light speed. These we will later describe as two sheets of Colored Glass. In a very short time, the sheets of Color Glass interpenetrate one another. This we think of as the initial singularity for the collision. This is of course not a real singularity for finite collision energy, but we will see it becomes one in the limitmore » of infinite energy. After the initial singularity, a Glasma is formed. This is composed of highly coherent gluon fields of very high energy density. If we imagine that the sheets of Colored Glass have passed through one another largely intact, the Glasma forms in the region between the receding sheets. As time goes on, the Glasma evolves into a Quark Gluon Plasma, and eventually into a gas of ordinary hadrons. These lectures are about the earliest stages of these collisions, and will describe neither the Quark Gluon Plasma nor the Hadron Gas. I will motivate the CGC and Glasma from simple physical considerations, and provide a sketchy derivation from QCD. There will be some discussion of experimental tests of these ideas.« less
The Supply and Demand Effects of Review Platforms

Review platforms such as Yelp and TripAdvisor aggregate crowd-sourced information about users' experiences with products and services. We analyze their impact on the hotel industry using a panel of hotel prices, sales and reviews from five US states over a 10-year period from 2005--2014. Both hotel demand and prices are positively correlated with their average ratings on TripAdvisor, Expedia and Hotels.com, and such correlations have grown over our sample period from a statistical zero in the base year to a substantial level today: a hotel rated one star higher on all the platforms on average has 25% higher demand, and charges 9% more. We argue that the price increases are due to a combination of revenue management and re-pricing: increased demand from higher ratings shifts hotels along an upward sloping supply curve, and also causes small but significant changes in the supply curve itself. A natural experiment in our data that caused abrupt changes in the ratings of some hotels but not others, suggests that these associations are causal. Building on this causal interpretation, we estimate heterogenous treatment effects, showing that the impact of review platforms on hotels varies by organization form and hotel class. Specifically, we show that independent hotels that had little outside reputation prior to the entry of review platforms stand to gain more than chains.
Good tutors are not dear enemies in song sparrows

Birdsong is the most widely studied example of vocal learning outside human language and shares important parallels with it, including the importance of social factors during development. Our understanding of how social factors affect song learning, however, remains surprisingly incomplete. Here we examine the possible role of aggressive interactions in determining song ‘tutor’ choice in song sparrows, Melospiza melodia, a songbird in which individuals display song learning strategies ranging from learning primarily from one tutor, to learning a few songs each from a number of tutors. We test two hypotheses: the competition hypothesis suggests that young birds learn more from tutors with whom they compete especially intensely and predicts that tutees will respond with high aggression to tutor songs. In contrast, the cooperation hypothesis suggests that song learning reflects a cooperative relationship between the tutor and the tutee and predicts that tutees will respond with low aggression to tutor songs. In a playback experiment we found that birds responded more aggressively to songs of their tutors than they did to songs of strangers and that the strength of aggressive response correlated positively with how much they had learned from that tutor. These results provide the first field evidence for the hypothesis that young males preferentially learn their songs from adult males with whom they compete most intensely during the song-learning phase, and perhaps afterwards.
An Efficient Multigram Synthesis of Monomers for the Preparation of Novel Oligonucleotides Containing Isosteric Non-Phosphorous Backbones

Abstract The facile preparation of two novel classes of nucleoside analogs for the inclusion as dimeric non-phosphorous containing subunits in chimeric backbones has been accomplished. The concise preparation of 3′-formylnucleosides and 5′-O-(N-methylhydroxylamino)-nucleosides is reported.
Repeated losses of PRDM9-directed recombination despite the conservation of PRDM9 across vertebrates

The genetic information of Eukaryotic organisms (animals, plants and fungi) is encoded on strands of DNA called chromosomes. In animals that sexually reproduce, most cells carry two copies of each chromosome, with one inherited from each of their parents. Sex cells such as sperm and egg cells are the exception, and contain only a paternal or maternal set respectively. These chromosomes are not exact copies of the parental chromosomes, but are instead combinations of both of them, generated by a process called meiotic recombination. Meiotic recombination begins by breaking the chromosomes, and the repair of those breaks shuffles DNA segments between the two chromosomes. This shuffling is known as a “recombination event”. In humans, apes and mice, the location of recombination events depends on where a protein called PRDM9 binds to the DNA. Over the course of evolution, this binding location has changed relatively rapidly so that even closely related species such as humans and chimpanzees localize recombination events to different DNA regions. In contrast, closely related species that do not produce PRDM9 tend to direct recombination events to similar DNA regions. It remains unclear when PRDM9 first evolved its role in recombination, or why different methods of directing recombination have developed. To begin answering these questions, Baker, Schumer et al. investigated whether 225 species of vertebrates (backboned animals) have a gene that encodes PRDM9. This analysis revealed that even distantly related animals have genes that produce equivalents of the complete PRDM9 protein. However, several species have independently lost the ability to produce PRDM9. In certain other species, particular regions of the gene have been removed or shortened. Notably, only species that carry genes that contain regions called the KRAB and SSXRD domains show relatively rapid evolution of where PRDM9 binds in the DNA. To investigate this phenomenon further, Baker, Schumer et al. constructed a map of recombination events in swordtail fish, which carry a version of the gene that lacks the KRAB and SSXRD domains. The PRDM9 protein produced by this gene does not direct where recombination events occur. Overall, it appears that the KRAB and SSXRD domains are necessary for PRDM9 to direct meiotic recombination. Furthermore, Baker, Schumer et al. predict that those species that have complete versions of PRDM9 use this protein to localize recombination events. Knowing which species use PRDM9 in this way is the first step towards understanding why recombination mechanisms change in evolution, and with what consequences.
spe-43 is required for sperm activation in C. elegans.

Abstract Successful fertilization requires that sperm are activated prior to contacting an oocyte. In C. elegans, this activation process, called spermiogenesis, transforms round immobile spermatids into motile, fertilization-competent spermatozoa. We describe the phenotypic and genetic characterization of spe-43, a new component of the spe-8 pathway, which is required for spermiogenesis in hermaphrodites; spe-43 hermaphrodites are self-sterile, while spe-43 males show wild-type fertility. When exposed to Pronase to activate sperm in vitro, spe-43 spermatids form long rigid spikes radiating outward from the cell periphery instead of forming a motile pseudopod, indicating that spermiogenesis initiates but is not completed. Using a combination of recombinant and deletion mapping and whole genome sequencing, we identified F09E8.1 as spe-43. SPE-43 is predicted to exist in two isoforms; one isoform appears to be a single-pass transmembrane protein while the other is predicted to be a secreted protein. SPE-43 can bind to other known sperm proteins, including SPE-4 and SPE-29, which are known to impact spermiogenesis. In summary, we have identified a membrane protein that is present in C. elegans sperm and is required for sperm activation via the hermaphrodite activation signal.
A New Palladium(II)-Catalyzed Asymmetric Chlorohydrin Synthesis

The Pd(II)-catalyzed oxidation of ethene in aqueous solution (Wacker reaction) gives exclusively acetaldehyde at low [Cl-] (1.0 M). At high [Cl-] (>2.5 M) and high [CuCl2] (>3 M), formation of ethylene chlorohydrin occurs to an appreciable extent (Scheme 1).1,2 Previous studies in these laboratories have shown that substitution of chloride by pyridine in the coordination sphere of PdCl4 to give PdCl3(pyridine) resulted in the formation of chlorohydrin at [Cl-] as low as 0.2 M.3,4 At this low [Cl-], PdCl4 gives only acetaldehyde at any [CuCl2]. This finding opens up the possibility of an asymmetric chlorohydrin synthesis with R-olefins. Pd(II) catalysts containing chiral auxiliaries should produce optically active products. The logical starting point is the replacement of pyridine with a chiral amine L*. Scheme 2 outlines the general reaction scheme with monodentate chiral amines such as (CH3)2C*NH(CH3)Ph. As shown, the two positional isomers, 2 and 3, arise from the two possible modes of hydroxypalladation. The ratio 2/3 of about 4 for propene and 1-pentene is typical for a number of catalysts. As expected, the optical purity of 2 was low, with ee’s of 10-15%. Catalysts with chiral chelating diphosphines should give much higher optical purities. However, the monometallic Pd(II) complex containing a diphosphine ligand is a neutral species and thus insoluble in the reaction media. The solution to this problem involved two different approaches. One approach used sulfonated chiral ligands while the other involved bimetallic complexes with a bridging diphosphine ligand.6 The structures of the two catalytic systems are shown below. Synthesis of the tetrasulfonated ligand involved treatment of Tol-BINAP with H2SO4 containing 20% SO3 at room temperature for 24 h followed by neutralization with NaOH.7 Recrystallization from methanol provided pure samples. Reaction with K2PdCl4 or PdCl2(PhCN)2 provided the chiral catalyst. 31P NMR measurements confirmed that all the tolyl rings were sulfonated. In these catalysts X ) Cl. Treatment of a solution of [Pd(CH3CN)4]BF4 in CH3CN with 1,3,5-pentanetriones gave the bimetallic triketone complexes. Addition of the chiral diphosphine ligand provided the chiral bimetallic complex. After purification, the products were characterized by elemental analysis and 1H13C and 31P NMR. As initially prepared, X is the CH3CN ligand. However, in the actual reaction mixtures, CH3CN is almost certainly replaced by Cl-. Gas uptake measurements using gas burets monitored the progress of the reactions.8,9 Propene oxidation was monitored by propene consumption. With the other nongaseous olefins the gas was dioxygen. This is possible because the CuCl formed in the first oxidation step to form chlorohydrin readily reacts with dioxygen to give CuCl2. Thus, as with the Wacker reaction, the chlorohydrin synthesis is a net air oxidation.
On the estimation errors of KM and V from time-course experiments using the Michaelis-Menten equation.

Abstract The conditions under which the Michaelis–Menten equation accurately captures the steady-state kinetics of a simple enzyme-catalyzed reaction is contrasted with the conditions under which the same equation can be used to estimate parameters, KM and V, from progress curve data. Validity of the underlying assumptions leading to the Michaelis–Menten equation are shown to be necessary, but not sufficient to guarantee accurate estimation of KM and V. Detailed error analysis and numerical “experiments” show the required experimental conditions for the independent estimation of both KM and V from progress curves. A timescale, tQ, measuring the portion of the time course over which the progress curve exhibits substantial curvature provides a novel criterion for accurate estimation of KM and V from a progress curve experiment. It is found that, if the initial substrate concentration is of the same order of magnitude as KM, the estimated values of the KM and V will correspond to their true values calculated from the microscopic rate constants of the corresponding mass-action system, only so long as the initial enzyme concentration is less than KM.
Low-Temperature Solution-Mediated Synthesis of Polycrystalline Intermetallic Compounds from Bulk Metal Powders

A variety of binary intermetallic compounds of late transition metals with low-melting post-transition metals have been synthesized in bulk quantities by reacting molten metal dispersions with fine...
Open Framework and Microporous Transition Metal Silicates

A family of microporous and open-framework microporous transition metal silicates have been prepared by hydrothermal synthesis at T ≤ 240 °C. The structures of the compound are based on a common principle in which anionic silicate components (layers, chains, or cluster anions) are connected by isolated transition metal polyhedra by sharing four corners in a square arrangement. Known examples of this class of compounds are reviewed and some recent progress on extending the syntheses to include organic templates are discussed.
N-sulfonylbenzotriazoles as advantageous reagents for C-sulfonylation.

Reactions of readily available N-(alkyl-, aryl-, and heteroarylsulfonyl)benzotriazoles 3a−h with diverse nitriles, reactive heteroaromatics, alkylheteroaromatics, sulfones, and esters produced α-cy...
Metabolic marker gene mining provides insight in global mcrA diversity and, coupled with targeted genome reconstruction, sheds further light on metabolic potential of the Methanomassiliicoccales

Over the past years, metagenomics has revolutionized our view of microbial diversity. Moreover, extracting near-complete genomes from metagenomes has led to the discovery of known metabolic traits in unsuspected lineages. Genome-resolved metagenomics relies on assembly of the sequencing reads and subsequent binning of assembled contigs, which might be hampered by strain heterogeneity or low abundance of a target organism. Here we present a complementary approach, metagenome marker gene mining, and use it to assess the global diversity of archaeal methane metabolism through the mcrA gene. To this end, we have screened 18,465 metagenomes for the presence of reads matching a database representative of all known mcrA proteins and reconstructed gene sequences from the matching reads. We use our mcrA dataset to assess the environmental distribution of the Methanomassiliicoccales and reconstruct and analyze a draft genome belonging to the 'Lake Pavin cluster', an uncultivated environmental clade of the Methanomassiliicoccales. Analysis of the 'Lake Pavin cluster' draft genome suggests that this organism has a more restricted capacity for hydrogenotrophic methylotrophic methanogenesis than previously studied Methanomassiliicoccales, with only genes for growth on methanol present. However, the presence of the soluble subunits of methyltetrahydromethanopterin:CoM methyltransferase (mtrAH) provide hypothetical pathways for methanol fermentation, and aceticlastic methanogenesis that await experimental verification. Thus, we show that marker gene mining can enhance the discovery power of metagenomics, by identifying novel lineages and aiding selection of targets for in-depth analyses. Marker gene mining is less sensitive to strain heterogeneity and has a lower abundance threshold than genome-resolved metagenomics, as it only requires short contigs and there is no binning step. Additionally, it is computationally cheaper than genome resolved metagenomics, since only a small subset of reads needs to be assembled. It is therefore a suitable approach to extract knowledge from the many publicly available sequencing projects.
Taming of superacids: PVP-triflic acid as an effective solid triflic acid equivalent for Friedel–Crafts hydroxyalkylation and acylation

Abstract The application of poly(4-vinylpyridine) supported trifluoromethanesulfonic acid (PVP-TfOH, 1:10) as a convenient solid superacid catalyst system in Friedel–Crafts reactions is described. In the presence of PVP-TfOH, one pot solvent-free synthesis of a wide variety of diarylacetic acid derivatives was achieved by Friedel–Crafts hydroxyalkylation reaction of glyoxylic acid with arenes under mild conditions. Acylation of both activated and deactivated aromatic compounds with acetyl chloride was also achieved using PVP-TfOH complex under solvent-free conditions at room temperature. As the polymer supported triflic acid was found to be a very efficient and an easy-to-handle solid acid, it can be a useful addition to environmentally more adaptable strong acid catalyst systems.
Stabilization of glycosyl sulfonium ions for stereoselective O-glycosylation

Abstract Bis(trifluoroacetoxy)iodobenzene can be used for studying the stereoselectivity of O-glycosylation from thioglycosides and the use of reagent-stabilized sulfonium ions to prohibit the formation of oxonium ions is also discussed.
PCIF1 Catalyzes m6Am mRNA Methylation to Regulate Gene Expression.

Summary mRNA modifications play important roles in regulating gene expression. One of the most abundant mRNA modifications is N6,2-O-dimethyladenosine (m6Am). Here, we demonstrate that m6Am is an evolutionarily conserved mRNA modification mediated by the Phosphorylated CTD Interacting Factor 1 (PCIF1), which catalyzes m6A methylation on 2-O-methylated adenine located at the 5′ ends of mRNAs. Furthermore, PCIF1 catalyzes only 5′ m6Am methylation of capped mRNAs but not internal m6A methylation in vitro and in vivo . To study the biological role of m6Am, we developed a robust methodology (m6Am-Exo-Seq) to map its transcriptome-wide distribution, which revealed no global crosstalk between m6Am and m6A under assayed conditions, suggesting that m6Am is functionally distinct from m6A. Importantly, we find that m6Am does not alter mRNA transcription or stability but negatively impacts cap-dependent translation of methylated mRNAs. Together, we identify the only human mRNA m6Am methyltransferase and demonstrate a mechanism of gene expression regulation through PCIF1-mediated m6Am mRNA methylation.
How Might a Disorderly Resolution of Global Imbalances Affect Global Wealth

Partly reflecting structural advantages such a liquidity and strong investor protection, foreigners have built up extremely large positions in U.S. (as well as other dollar-denominated) financial assets. This paper describes the impact on global wealth of an unanticipated shock to U.S. financial markets. For every 10 percent decline in the dollar, U.S. equity markets, and U.S. bond markets, total wealth losses to foreigners could amount to about 5 percentage points of foreign GDP. Four stylized facts emerge: (i) foreign countries, particularly emerging markets, are more exposed to U.S. bonds than U.S. equities; (ii) U.S. exposure has increased for most countries; (iii) on average, U.S. asset holdings of developed countries and emerging markets (scaled by GDP) are very similar; and (iv) based on their reserve positions, wealth losses of emerging market governments could, on average, amount to about 2¾ percentage points of their GDP.
Solving lubrication problems at the nanometer scale

Lubrication problems at lengthscales for which the traditional Navier–Stokes description fails can be solved using a modified Reynolds lubrication equation that is based on the following two observations: first, classical Reynolds equation failure at small lengthscales is a result of the failure of the Poiseuille flowrate closure (the Reynolds equation is derived from a statement of mass conservation, which is valid at all scales); second, averaging across the film thickness eliminates the need for a constitutive relation providing spatial resolution of flow profiles in this direction. In other words, the constitutive information required to extend the classical Reynolds lubrication equation to small lengthscales is limited to knowledge of the flowrate as a function of the gap height, which is significantly less complex than a general constitutive relation, and can be obtained by experiments and/or offline molecular simulations of pressure-driven flow under fully developed conditions. The proposed methodology, which is an extension of the generalized lubrication equation of Fukui and Kaneko to dense fluids, is demonstrated and validated via comparison to molecular dynamics simulations of a model lubrication problem.
Search versus Decision for Election Manipulation Problems

Most theoretical definitions about the complexity of manipulating elections focus on the decision problem of recognizing which instances can be successfully manipulated rather than the search problem of finding the successful manipulative actions. Since the latter is a far more natural goal for manipulators, that definitional focus may be misguided if these two complexities can differ. Our main result is that they probably do differ: If P ≠ NP ∩ coNP (which itself is well known to hold if integer factoring is hard), then for election manipulation, election bribery, and some types of election control, there are election systems for which the problem of recognizing which instances can be successfully manipulated is polynomial-time solvable, yet the task of producing the successful manipulations cannot be done in polynomial time.