cssi/SciSciGPT-SciSciNet huggingface dataset:
Anomalous Late Jurassic motion of the Pacific Plate with implications for true polar wander

Abstract True polar wander, or TPW, is the rotation of the entire mantle–crust system about an equatorial axis that results in a coherent velocity contribution for all lithospheric plates. One of the most recent candidate TPW events consists of a ∼30° rotation during Late Jurassic time (160–145 Ma). However, existing paleomagnetic documentation of this event derives exclusively from continents, which compose less than 50% of the Earth's surface area and may not reflect motion of the entire mantle–crust system. Additional paleopositional information from the Pacific Basin would significantly enhance coverage of the Earth's surface and allow more rigorous testing for the occurrence of TPW. We perform paleomagnetic analyses on core samples from Ocean Drilling Program (ODP) Site 801B, which were taken from the oldest available Pacific crust, to determine its paleolatitude during the Late Jurassic and Early Cretaceous (167–133 Ma). We find that the Pacific Plate underwent a steady southward drift of 0.49°–0.74° My−1 except for an interval between Kimmeridgian and Tithonian time (157–147 Ma), during which it underwent northward motion at 1.45° ± 0.76° My−1 (1σ). This trajectory indicates that the plates of the Pacific Basin participated in the same large-amplitude (∼30°) rotation as continental lithosphere in the 160–145 Ma interval. Such coherent motion of a large majority of the Earth's surface strongly supports the occurrence of TPW, suggesting that a combination of subducting slabs and rising mantle plumes was sufficient to significantly perturb the Earth's inertia tensor in the Late Jurassic.
A General Theory of Sample Complexity for Multi-Item Profit Maximization

One of the most tantalizing and long-standing open problems in mechanism design is profit maximization in multi-item, multi-buyer settings. Much of the literature surrounding this problem rests on the strong assumption that the mechanism designer knows the distribution over buyers' values. In reality, this information is rarely available. The support of the distribution alone is often doubly exponential, so obtaining and storing the distribution is impractical. We relax this assumption and instead assume that the mechanism designer only has a set of samples from the distribution. We develop learning-theoretic foundations of sample-based mechanism design. In particular, we provide generalization guarantees which bound the difference between the empirical profit of a mechanism over a set of samples and its expected profit on the unknown distribution.In this paper, we present a general theory for deriving worst-case generalization bounds in multi-item settings, as well as data-dependent guarantees when the distribution over buyers' values is well-behaved. We analyze mechanism classes that have not yet been studied in the sample-based mechanism design literature and match or improve over the best-known guarantees for many of the special classes that have been studied. The classes we study include randomized mechanisms, pricing mechanisms, multi-part tariffs, and generalized VCG auctions such as affine maximizer auctions.
Probing Soot Formation and Chemical Evolution During Combustion

There are gaps in the understanding of soot formation during combustion, which are largely attributable to a limited ability to probe relevant particle parameters during formation. This talk will describe approaches to developing appropriate diagnostics.
Concentration-dependent swelling and structure of ionic microgels: simulation and theory of a coarse-grained model

We study swelling and structural properties of ionic microgel suspensions within a comprehensive coarse-grained model that combines the polymeric and colloidal natures of microgels as permeable, compressible, charged spheres governed by effective interparticle interactions. The model synthesizes the Flory-Rehner theory of cross-linked polymer gels, the Hertz continuum theory of effective elastic interactions, and a theory of density-dependent effective electrostatic interactions. Implementing the model using Monte Carlo simulation and thermodynamic perturbation theory, we compute equilibrium particle size distributions, swelling ratios, volume fractions, net valences, radial distribution functions, and static structure factors as functions of concentration. Trial Monte Carlo moves comprising particle displacements and size variations are accepted or rejected based on the total change in elastic and electrostatic energies. The theory combines first-order thermodynamic perturbation and variational free energy approximations. For illustrative system parameters, theory and simulation agree closely at concentrations ranging from dilute to beyond particle overlap. With increasing concentration, as microgels deswell, we predict a decrease in the net valence and an unusual saturation of pair correlations. Comparison with experimental data for deionized, aqueous suspensions of PNIPAM particles demonstrates the capacity of the coarse-grained model to predict and interpret measured swelling behavior.
What teachers believe : mental models about accountability, absenteeism, and student learning

The time teachers spend teaching is low in several developing countries. However, improving teacher effort has proven difficult. Why is it so difficult to increase teacher effort? One possibility is that teachers are resistant to increasing effort because they do not believe their effort is suboptimal. Such beliefs may be based on their mental models on absenteeism, accountability, and student learning. This paper explores this idea using data from 16,000 teachers across eight developing countries, spanning five regions. It finds that, on average, teachers support test-based accountability and believe that they are in fact held accountable for student learning. In several countries, many teachers tend to normalize two types of suboptimal behaviors. These are (i) certain types of absenteeism, and (ii) paying extra attention to well-performing and well-resourced students. Finally, the paper shows that ideas of accountability and absenteeism are strongly framed by context in two direct ways. The first is whether teachers favor exclusively reward-based forms of accountability. The second is the degree to which they support absenteeism linked to community tasks. These results provide actionable insights on how changing teacher behavior sustainably might require reshaping underlying mental models.
Organocatalytic Highly Enantioselective Synthesis of Secondary α-Hydroxyphosphonates

[reaction: see text] The first organocatalytic cross aldol reaction of ketones and diethyl formylphosphonate hydrate has been realized by using readily available l-prolinamide as the catalyst. Secondary alpha-hydroxyphosphonates have been synthesized in high enantioselective (up to >99% ee) and good diastereoselectivity.
Photon-mediated interactions between quantum emitters in a diamond nanocavity

Photon-mediated interactions between quantum systems are essential for realizing quantum networks and scalable quantum information processing. We demonstrate such interactions between pairs of silicon-vacancy (SiV) color centers coupled to a diamond nanophotonic cavity. When the optical transitions of the two color centers are tuned into resonance, the coupling to the common cavity mode results in a coherent interaction between them, leading to spectrally resolved superradiant and subradiant states. We use the electronic spin degrees of freedom of the SiV centers to control these optically mediated interactions. Such controlled interactions will be crucial in developing cavity-mediated quantum gates between spin qubits and for realizing scalable quantum network nodes.
Designing an Adaptive Web Navigation Interface for Users with Variable Pointing Performance

Many online services and products require users to point and interact with user interface elements. For individuals who experience variable pointing ability due to physical impairments, environmental issues or age, using an input device (e.g., a computer mouse) to select elements on a website can be difficult. Adaptive user interfaces dynamically change their functionality in response to user behavior. They can support individuals with variable pointing abilities by 1) adapting dynamically to make element selection easier when a user is experiencing pointing difficulties, and 2) informing users about these pointing errors. While adaptive interfaces are increasingly prevalent on the Web, little is known about the preferences and expectations of users with variable pointing abilities and how to design systems that dynamically support them given these preferences. We conducted an investigation with 27 individuals who intermittently experience pointing problems to inform the design of an adaptive interface for web navigation. We used a functional high-fidelity prototype as a probe to gather information about user preferences and expectations. Our participants expected the system to recognize and integrate their preferences for how pointing tasks were carried out, preferred to receive information about system functionality and wanted to be in control of the interaction. We used findings from the study to inform the design of an adaptive Web navigation interface, PINATA that tracks user pointing performance over time and provides dynamic notifications and assistance tailored to their specifications. Our work contributes to a better understanding of users' preferences and expectations of the design of an adaptive pointing system.
N6-Methyladenosine–binding proteins suppress HIV-1 infectivity and viral production

The internal N6-methyladenosine (m6A) modification of cellular mRNA regulates post-transcriptional gene expression. The YTH domain family proteins (YTHDF1–3 or Y1–3) bind to m6A-modified cellular mRNAs and modulate their metabolism and processing, thereby affecting cellular protein translation. We previously reported that HIV-1 RNA contains the m6A modification and that Y1–3 proteins inhibit HIV-1 infection by decreasing HIV-1 reverse transcription activity. Here, we investigated the mechanisms of Y1–3–mediated inhibition of HIV-1 infection in target cells and the effect of Y1–3 on viral production levels in virus-producing cells. We found that Y1–3 protein overexpression in HIV-1 target cells decreases viral genomic RNA (gRNA) levels and inhibits both early and late reverse transcription. Purified recombinant Y1–3 proteins preferentially bound to the m6A-modified 5′ leader sequence of gRNA compared with its unmodified RNA counterpart, consistent with the strong binding of Y1–3 proteins to HIV-1 gRNA in infected cells. HIV-1 mutants with two altered m6A modification sites in the 5′ leader sequence of gRNA exhibited significantly lower infectivity than WT, replication-competent HIV-1, confirming that these sites alter viral infection. HIV-1 produced from cells in which endogenous Y1, Y3, or Y1–3 proteins were knocked down singly or together had increased viral infectivity compared with HIV-1 produced in control cells. Interestingly, we found that Y1–3 proteins and HIV-1 Gag protein formed a complex with RNA in HIV-1–producing cells. Overall, these results indicate that Y1–3 proteins inhibit HIV-1 infection and provide new insights into the mechanisms by which the m6A modification of HIV-1 RNA affects viral replication.
Developing Robot Driver Etiquette Based on Naturalistic Human Driving Behavior

Automated vehicles can change the society by improved safety, mobility, and fuel efficiency. However, due to the higher cost and change in business model, over the coming decades, the highly automated vehicles likely will continue to interact with many human-driven vehicles. In the past, the control/design of the highly automated (robotic) vehicles mainly considers safety and efficiency but failed to address the “driving culture” of surrounding human-driven vehicles. Thus, the robotic vehicles may demonstrate behaviors very different from other vehicles. We study this “driving etiquette” problem in this paper. As the first step, we report the key behavior parameters of human driven vehicles derived from a large naturalistic driving database. The results can be used to guide future algorithm design of highly automated vehicles or to develop realistic human-driven vehicle behavior model in simulations.
Cost-Sensitive Active Learning for Intracranial Hemorrhage Detection

Deep learning for clinical applications is subject to stringent performance requirements, which raises a need for large labeled datasets. However, the enormous cost of labeling medical data makes this challenging. In this paper, we build a cost-sensitive active learning system for the problem of intracranial hemorrhage detection and segmentation on head computed tomography (CT). We show that our ensemble method compares favorably with the state-of-the-art, while running faster and using less memory. Moreover, our experiments are done using a substantially larger dataset than earlier papers on this topic. Since the labeling time could vary tremendously across examples, we model the labeling time and optimize the return on investment. We validate this idea by core-set selection on our large labeled dataset and by growing it with data from the wild.
Prime Residue Class of Uniform Charges on the Integers

There is a probability charge on the power set of the integers that gives probability 1 / p to every residue class modulo a prime p. There exists such a charge that gives probability w to the set of prime numbers iff $$w \in [0,1/2]$$. Similarly, there is such a charge that gives probability x to a residue class modulo c, where c is composite, iff $$x \in [0,1/y]$$, where y is the largest prime factor of c.
Transparency and Explanation in Deep Reinforcement Learning Neural Networks

Autonomous AI systems will be entering human society in the near future to provide services and work alongside humans. For those systems to be accepted and trusted, the users should be able to understand the reasoning process of the system, i.e. the system should be transparent. System transparency enables humans to form coherent explanations of the system's decisions and actions. Transparency is important not only for user trust, but also for software debugging and certification. In recent years, Deep Neural Networks have made great advances in multiple application areas. However, deep neural networks are opaque. In this paper, we report on work in transparency in Deep Reinforcement Learning Networks (DRLN). Such networks have been extremely successful in accurately learning action control in image input domains, such as Atari games. In this paper, we propose a novel and general method that (a) incorporates explicit object recognition processing into deep reinforcement learning models, (b) forms the basis for the development of "object saliency maps", to provide visualization of internal states of DRLNs, thus enabling the formation of explanations and (c) can be incorporated in any existing deep reinforcement learning framework. We present computational results and human experiments to evaluate our approach.
Simple, Efficient, and Neural Algorithms for Sparse Coding

Sparse coding is a basic task in many fields including signal processing, neuroscience and machine learning where the goal is to learn a basis that enables a sparse representation of a given set of data, if one exists. Its standard formulation is as a non-convex optimization problem which is solved in practice by heuristics based on alternating minimization. Recent work has resulted in several algorithms for sparse coding with provable guarantees, but somewhat surprisingly these are outperformed by the simple alternating minimization heuristics. Here we give a general framework for understanding alternating minimization which we leverage to analyze existing heuristics and to design new ones also with provable guarantees. Some of these algorithms seem implementable on simple neural architectures, which was the original motivation of Olshausen and Field (1997a) in introducing sparse coding. We also give the first efficient algorithm for sparse coding that works almost up to the information theoretic limit for sparse recovery on incoherent dictionaries. All previous algorithms that approached or surpassed this limit run in time exponential in some natural parameter. Finally, our algorithms improve upon the sample complexity of existing approaches. We believe that our analysis framework will have applications in other settings where simple iterative algorithms are used.
News coverage, digital activism, and geographical saliency: A case study of refugee camps and volunteered geographical information.

The last several decades have witnessed a shift in the way in which news is delivered and consumed by users. With the growth and advancements in mobile technologies, the Internet, and Web 2.0 technologies users are not only consumers of news, but also producers of online content. This has resulted in a novel and highly participatory cyber-physical news awareness ecosystem that fosters digital activism, in which volunteers contribute content to online communities. While studies have examined the various components of this news awareness ecosystem, little is still known about how news media coverage (and in particular digital media) impacts digital activism. In order to address this challenge and develop a greater understanding of it, this paper focuses on a specific form of digital activism, that of the production of digital geographical content through crowdsourcing efforts. Using refugee camps from around the world as a case study, we examine the relationship between news coverage (via Google news), search trends (via Google trends) and user edit contribution patterns in OpenStreetMap, a prominent geospatial data crowdsourcing platform. In addition, we compare and contrast these patterns with user edit patterns in Wikipedia, a well-known non-geospatial crowdsourcing platform. Using Google news and Google trends to derive a measure of thematic public awareness, our findings indicate that digital activism bursts tend to take place during periods of sustained build-up of public awareness deficit or surplus. These findings are in line with two prominent mass communication theories: agenda setting and corrective action, and suggest the emergence of a novel stimulus-awareness-activism framework in today’s participatory digital age. Moreover, these findings further complement existing research examining the motivational factors that drive users to contribute to online collaborative communities. This paper brings us one step closer to understanding the underlying mechanisms that drive digital activism in particular in the geospatial domain.
Multigrid treatment of implicit continuum diffusion

Abstract Implicit treatment of diffusive terms of various differential orders common in continuum mechanics modeling, such as computational fluid dynamics, is investigated with spectral and multigrid algorithms in non-periodic 2D domains. In doubly periodic time dependent problems these terms are handled efficiently by spectral methods , but in non-periodic systems solved with distributed memory parallel computing and 2D domain decomposition , this efficiency is lost for a large number of processors. We built and present here a multigrid algorithm for these types of problems that outperforms a spectral solution employing the highly optimized FFTW library. This solver is suitable for high performance computing and may be able to efficiently treat implicit diffusion of arbitrary order by introducing auxiliary equations of lower order. We test these solvers for fourth and sixth order diffusion with harmonic test functions as well as turbulent 2D magnetohydrodynamic simulations. It is also shown that an anisotropic operator without mixed-derivative terms improves model accuracy and speed, and we examine the impact that the various diffusion operators have on the energy, the enstrophy, and the qualitative aspect of a simulation.
Competitive Dynamics in the Sharing Economy: An Analysis in the Context of Airbnb and Hotels

This paper studies how the sharing economy fundamentally changes the way the industry accommodates demand fluctuations and how incumbent firms should strategically respond in the context of Airbnb ...
Asymmetry and Spillover Effects in the North American Equity Markets

In this paper we examine the issue of asymmetry in the return and volatility spillover effects from the US equity market into the Canadian and Mexican equity markets. We model the conditional volatility of the returns in each of the three markets using the asymmetric power model of Ding, Granger and Engle (1993). The empirical findings indicate that the US market has a significant impact on the returns in the Canadian and Mexican markets. However, the findings for Canada vary considerably from those for Mexico. In particular, the empirical results indicate that volatility spillover effects, but not return spillover effects, exhibit an asymmetric behavior, with negative shocks from the US equity market impacting on the conditional volatility of the Canadian and Mexican equity markets more deeply than positive shocks. Moreover, while the impact of positive shocks from the US equity market is not much different between the two markets, this is not the case with negative shocks, which affect the volatility of the Mexican market more intensely than the volatility of the Canadian market.
Spanish null complement anaphora at the grammar-discourse interface

El estudio de la anafora de complemento nulo ( null complement anaphora , NCA, en ingles) es relevante en el estudio de la interfaz gramatica-discurso, dado que parece materializar algunos de los procesos centrales de otros fenomenos como, por ejemplo, la referencia, la anafora, la elipsis, la inferencia, la prominencia o la acomodacion. A pesar de que la NCA ha sidomuy estudiada, todavia esta vivo el debate sobre si se trata de un proceso de elipsis o anaforico. Este articulo contribuye a la consideracion de la NCA como una anafora profunda a partir de evidencias discursivas en espanol. Defendemos que la NCA es una anafora que selecciona el antecedente mas prominente en estructuras discursivas jerarquicas muy definidas. Nuestro analisis se basa, principalmente, en la comparacion entre los pronombres neutros y la NCA en espanol, y en la similitud del comportamiento manifestado por la NCA y los pronombres en condiciones de insercion discursiva. Revisamos explicaciones anteriores de la NCA (Depiante 2000, 2001; Williamson 2012), y tratamos de aplicar a la NCA en espanol una propuesta de analisis de la elipsis de SV basada en relaciones discursivas (Hardt & Romero 2004).
Hilbert’s ‘Monkey Saddle’ and Other Curiosities in the Equilibrium Problem of Three Point Particles on a Circle for Repulsive Power Law Forces

This article determines all possible (proper as well as pseudo) equilibrium arrangements under a repulsive power law force of three point particles on the unit circle. These are the critical points of the sum over the three (standardized) Riesz pair interaction terms, each given by $$V_s(r)= s^{-1}\left( r^{-s}-1 \right) $$ when the real parameter $$s \ne 0$$, and by $$V_0(r) := \lim _{s\rightarrow 0}V_s(r) = -\ln r$$; here, r is the chordal distance between the particles in the pair. The bifurcation diagram which exhibits all these equilibrium arrangements together as functions of s features three obvious “universal” equilibria, which do not depend on s, and two not-so-obvious continuous families of s-dependent non-universal isosceles triangular equilibria. The two continuous families of non-universal equilibria are disconnected, yet they bifurcate off of a common universal limiting equilibrium (the equilateral triangular configuration), at $$s=-4$$, where the graph of the total Riesz energy of the 3-particle configurations has the shape of a “monkey saddle.” In addition, one of the families of non-universal equilibria also bifurcates off of another universal equilibrium (the antipodal arrangement), at $$s=-2$$. While the bifurcation at $$s=-4$$ is analytical, the one at $$s=-2$$ is not. The bifurcation analysis presented here is intended to serve as template for the treatment of similar N-point equilibrium problems on $${\mathbb {S}}^d$$ for small N.
Growth Uncertainty and Risksharing

Abstract We propose a new methodology to evaluate the gains from global risksharing that is closely connected to the empirical growth literature. We obtain estimates of diversifiable growth uncertainty at various horizons from regressions of country-specific deviations from world growth on a wide set of variables in the information set. This is used to obtain a measure of the welfare gain from risksharing for a representative country. We find large benefits from risksharing. The gain for a 35-year horizon, corresponding to a welfare equivalent permanent increase in consumption, is 6.6% when based on a set of 49 countries, and 1.5% when based on 21 OECD countries.
Attenuating Bias in Word vectors

Word vector representations are well developed tools for various NLP and Machine Learning tasks and are known to retain significant semantic and syntactic structure of languages. But they are prone to carrying and amplifying bias which can perpetrate discrimination in various applications. In this work, we explore new simple ways to detect the most stereotypically gendered words in an embedding and remove the bias from them. We verify how names are masked carriers of gender bias and then use that as a tool to attenuate bias in embeddings. Further, we extend this property of names to show how names can be used to detect other types of bias in the embeddings such as bias based on race, ethnicity, and age.
Decision flexibility

The development of new methods and representations for temporal decision-making requires a principled basis for characterizing and measuring the flexibility of decision strategies in the face of uncertainty. Our goal in this paper is to provide a framework -- not a theory -- for observing how decision policies behave in the face of informational perturbations, to gain clues as to how they might behave in the face of unanticipated, possibly unarticulated uncertainties. To this end, we find it beneficial to distinguish between two types of uncertainty: "Small World" uncertainty and "Large World" uncertainty. The first type can be resolved by posing an unambiguous question to a "clairvoyant," and is anchored on some well-defined aspect of a decision frame. The second type is more troublesome, yet it is often of greater interest when we address the issue of flexibility; this type of uncertainty can be resolved only by consulting a "psychic". We next observe that one approach to flexibility frequently used in the economics literature is already implicitly accounted for in the Maximum Expected Utility (MEU) principle from decision theory. Though simple, the observation establishes the context for a more illuminating notion of flexibility, what we term flexibility with respect to information revelation. We show how to perform flexibility analysis of a static (i.e., single period) decision problem using a simple example, and we observe that the most flexible alternative thus identified is not necessarily the MEU alternative. We extend our analysis for a dynamic (i.e., multi-period) model, and we demonstrate how to calculate the value of flexibility for decision strategies that allow downstream revision of an upstream commitment decision.
International propagation of shocks: A dynamic factor model using survey forecasts

Abstract This paper studies the pathways for the propagation of shocks across the G7 and major Asia-Pacific countries using multi-horizon forecasts of real GDP growth from 1995 to 2017. We show that if the forecasts are efficient in the long run, the results obtained using these forecasts are comparable to those obtained from the actual outturns. We measure global business cycle connectedness and study the impacts of both country-specific shocks and common international shocks using a panel factor structural VAR model. Our results suggest that there is a strong convergence of business cycles within the group of industrialized countries, as well as within the group of developing economies during non-recessionary periods. In particular, we find an increased decoupling between the industrialized and developing economies after the 2008 recession. However, the direction of shock spillovers during recessions and other crisis periods varies, depending on the nature and origin of the episode.
A sensitive HPLC-MS/MS method for the determination of dolutegravir in human plasma.

A sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) assay was developed and validated to facilitate the assessment of clinical pharmacokinetics of dolutegravir (DTG) in plasma samples. This work describes an assay system requiring only a 20 µL aliquot of human plasma that is subjected to a simple acetonitrile protein precipitation containing a stably labeled isotope of DTG used as an internal standard. Chromatography was performed on an XBridge C18, 2.1 mm × 50 mm, reversed phase analytical column, using a 60:40 acetonitrile/water mobile phase containing 0.1% formic acid. Detection of the analyte and internal standard was achieved by ESI positive ionization tandem mass spectrometry. The precursor/product transitions (m/z) monitored were 420.1/136.0 and 428.1/283.1 for DTG and DTG-IS, respectively. The dynamic range of this assay extends from 5 to 10,000 ng/mL, with a mean coefficient of determination (r, mean ± SD) of 0.9996 ± 0.0003. The mean precision values for calibration standards ranged from 0.7 to 4.1%, while accuracy values were 98.3 to 102.0%. Validation results demonstrated high accuracy ( ≤ 6.5% deviation) and high precision ( ≤ 9.1% CV) for the quality control samples. This assay system provides an accurate, precise, and sensitive method for DTG quantitation and was successfully applied to clinical research samples as part of a phase I/II pediatric clinical trial.
Draft Aphaenogaster genomes expand our view of ant genome size variation across climate gradients

Given the abundance, broad distribution, and diversity of roles that ants play in many ecosystems, they are an ideal group to serve as ecosystem indicators of climatic change. At present, only a few whole-genome sequences of ants are available (19 of >16,000 species), mostly from tropical and sub-tropical species. To address this limited sampling, we sequenced genomes of temperate-latitude species from the genus Aphaenogaster, a genus with important seed dispersers. In total, we sampled seven colonies of six species: Aphaenogaster ashmeadi, Aphaenogaster floridana, Aphaenogaster fulva, Aphaenogaster miamiana, Aphaenogaster picea, and Aphaenogaster rudis. The geographic ranges of these species collectively span eastern North America from southern Florida to southern Canada, which encompasses a latitudinal gradient in which many climatic variables are changing rapidly. For the six genomes, we assembled an average of 271,039 contigs into 47,337 scaffolds. The Aphaenogaster genomes displayed high levels of completeness with 96.1% to 97.6% of Hymenoptera BUSCOs completely represented, relative to currently sequenced ant genomes which ranged from 88.2% to 98.5%. Additionally, the mean genome size was 370.5 Mb, ranging from 310.3 to 429.7, which is comparable to that of other sequenced ant genomes (212.8-396.0 Mb) and flow cytometry estimates (210.7-690.4 Mb). In an analysis of currently sequenced ant genomes and the new Aphaenogaster sequences, we found that after controlling for both spatial autocorrelation and phylogenetics ant genome size was marginally correlated with sample site climate similarity. Of all examined climate variables, minimum temperature, and annual precipitation had the strongest correlations with genome size, with ants from locations with colder minimum temperatures and higher levels of precipitation having larger genomes. These results suggest that climate extremes could be a selective force acting on ant genomes and point to the need for more extensive sequencing of ant genomes.
Unraveling the dislocation core structure at a van der Waals gap in bismuth telluride.

Tetradymite-structured chalcogenides such as bismuth telluride (Bi2Te3) are of significant interest for thermoelectric energy conversion and as topological insulators. Dislocations play a critical role during synthesis and processing of such materials and can strongly affect their functional properties. The dislocations between quintuple layers present special interest since their core structure is controlled by the van der Waals interactions between the layers. In this work, using atomic-resolution electron microscopy, we resolve the basal dislocation core structure in Bi2Te3, quantifying the disregistry of the atomic planes across the core. We show that, despite the existence of a stable stacking fault in the basal plane gamma surface, the dislocation core spreading is mainly due to the weak bonding between the layers, which leads to a small energy penalty for layer sliding parallel to the van der Waals gap. Calculations within a semidiscrete variational Peierls-Nabarro model informed by first-principles calculations support our experimental findings. The atomic level core structure of dislocations in non-metallic materials such as chalcogenides remains elusive. Here, the authors combine atomic-resolution electron microscopy and simulations to image a dislocation core in bismuth telluride and show it spreads because of weak bonding between atomic layers.
Three Dimensional Time Domain Simulation of the Quantum Magnetic Susceptibility

A way of using the Finite Difference Time Domain method is described to simulate the magnetic susceptibility of a quantum toroid. This simulation is based on the direct implementation of the time-dependent Schrodinger equation in three dimensions. First, the ground state eigenenergy and eigenstate are found. Next, the expectation value of the quantum magnetic dipole operator is calculated as a function of the applied magnetic field strength with a static magnetic field, and the results are compared with classical results. Then the magnetic dipole moment is calculated with a time-oscillating magnetic field applied. These expectation values are used to calculate the linear and nonlinear magnetic susceptibility of a torus, both without a grating and with a grating to increase irregularities in the shape, by repeating the calculations at various frequencies. The results are consistent with the expected results. This method can be used to calculate the quantum magnetic susceptibility of any structure in order to search for structures with better nonlinear properties.
Reaction–Transport Coupling in a Nanostructured Porous Electrode

Author(s): Houle, FA | Abstract: The function of nanoporous electrodes involves chemical reactions coupled to transport of reactants and products into and out of the solid matrix. To understand how this coupling can depend on electrode structure and chemistry, a general multiscale, molecular-level computational framework is introduced and applied to a model system containing a nanoporous photoanode, the dye-sensitized solar cell. The pore structure and electrolyte composition are systematically varied to probe this coupling, revealing that in most cases the photocurrent density depends on dye coverage within the anode matrix, the specific architecture of an individual pore, and electrolyte gradients in between the anode and cathode. The large electrolyte gradients that develop in the anode are not kinetically controlling. The computational framework demonstrated is general and can be applied to other electrochemical, photochemical, and thermally driven nanoporous systems to evaluate the fundamental characteristics of their function.
Application of P-chirogenic bisphospholane ligands to rhodium catalyzed asymmetric hydrogenation of α- and β-acetamido dehydroamino acid derivatives

Two previously reported P-chirogenic bisphospholane rhodium catalysts have been applied to the asymmetric hydrogenation of α- and β-acetamido dehydroamino acid derivatives. For α-acetamido dehydroamino acid derivatives, catalyst 4 produced very high enantiomeric excesses. These are contrasted with the previously reported enantiomeric excesses using catalyst 2. Both catalysts provide excellent enantioselectivity (96%) for the β-acetamido dehydroamino acid derivative, (E)-methyl 3-acetamido-2-butenoate. However, catalyst 2 produces higher enantioselectivity (89%) for the (Z)-isomer when compared to catalyst 4 (83%).
Stereo- and Regioselective Pt(DVDS)/P(iBuNCH2CH2)3N-Catalyzed Hydrosilylation of Terminal Alkynes

The catalyst system Pt(DVDS)/P(iBuNCH2CH2)3N (DVDS = [(H2CCH)Me2Si]2O), containing a bulky aminophosphine ligand, catalyzes the hydrosilylation of terminal alkynes possessing a variety of functional groups using Ph3SiH or Et3SiH. These reactions occur stereo- and regioselectively to give β-(E)-vinylsilanes with 97−99% selectivity in 76−98% yield. Using Pt2(DVDS)3, this selectivity ranged from 63 to 93%, except in one case, where the selectivities were the same for both catalyst systems.
TiCl4-Mediated Baylis–Hillman and aldol reactions without the direct use of a Lewis base

Abstract TiCl4-Mediated Baylis–Hillman and aldol reactions were developed without the direct use of a Lewis base. These processes involve the conjugate addition of TiCl4 to α,β-unsaturated substrates followed by carbonyl coupling. Baylis–Hillman olefins were obtained when α,β-unsaturated ketones were employed as the substrates, whereas β-halogenated aldol products were generated with an α,β-unsaturated N-acyl benzoxalinone as the Michael-type acceptor.
Tetracyanomanganate(II) and its salts of divalent first-row transition metal ions.

The first known paramagnetic, tetrahedral cyanide complex, [MnII(CN)4]2-, is formed by the photoinduced decomposition of [MnIV(CN)6]2- in nonaqueous solutions or by thermal decomposition in the solid state. In acetonitrile or dichloromethane, photoexcitation into the ligand-to-metal charge transfer band (λmax = 25 700 cm-1, e = 3700 cm-1 M-1) causes the homolytic cleavage of cyanide radicals and reduction of MnIV. Free cyanide in dichloromethane leads to the isolation of polycyanide oligomers such as [C12N12]2- and [C4N4]-, which was crystallographically characterized as the PPN+ salt C40H30N5P2: monoclinic space group = I2/a, a = 18.6314(2) A, b = 9.1926(1) A, c = 20.8006(1), β =106.176(2)°, Z = 4]. In the solid state MnIV−CN bond homolysis is thermally activated above 122 °C, according to differential scanning calorimetry measurements, leading to the reductive elimination of cyanogen. The [MnII(CN)4]2- ion has a dynamic solution behavior, as evidenced by its concentration-dependent electronic and elect...
Cutoff dependence of the Casimir effect

The problem of calculating the Casimir force on two conducting planes by means of the stress tensor is examined. The evaluation of this quantity is carried out using an explicit regularization procedure which has its origin in the underlying (2+1) dimensional Poincare invariance of the system. The force between the planes is found to depend on the ratio of two independent cutoff parameters, thereby rendering any prediction for the Casimir effect an explicit function of the particular calculational scheme employed. Similar results are shown to obtain in the case of the conducting sphere.
Synthesis of an Isostere of an O-Linked Glycopeptide

[reaction: see text] A route for the synthesis of an electrophilic, carbocyclic galactose equivalent from D-galactose is described. The strategy utilizes ring-closing metathesis with Grubbs's second-generation catalyst as the key step. The galactose-derived electrophile reacted in an S(N)2 fashion with N-Boc-cysteine methyl ester to provide an alpha-galactosylserine isostere. The method was extended to the synthesis of a glycopeptide isostere.
RADICAL CYCLIZATIONS OF ACYLGERMANE OXIME ETHERS AND HYDRAZONES : DIRECT ROUTES TO CYCLIC HYDRAZONES AND OXIMES

Efficient syntheses of ω-halo-, phenylseleno-, and vinylacylgermane hydrazones and oxime ethers have been developed, and the radical cyclizations of these substrates have been studied. The preparation of substituted triphenylacylgermanes has been improved through a copper-mediated coupling of acid chlorides and LiGePh3. Condensation of various acylgermanes with O-benzyl hydroxylamine or N,N-dimethylhydrazine efficiently generates the new acceptor systems, which undergo 5-exo cyclizations in good yields. The acylgermane hydrazone and -oxime ether radicals have cyclization rate constants of about 107 s-1 and are thus better acceptors than the parent acylgermanes.
An Aza-Achmatowicz Approach toward the Hydroxylated Piperidine Alkaloids (±)-Azimic Acid and (±)-Deoxocassine

The synthesis of several cis-2,3,6-trisubstituted piperidines has been developed employing the aza-Achmatowicz oxidation as the key reaction step. Its usage is illustrated by the facile synthesis of the piperidin-3-ol alkaloids (±)-deoxocassine and (±)-azimic acid.
An improved preparation and a new application of trichloromethylcarbinols from enolizable ketones

Abstract We report an improved method for the preparation of trichloromethylcarbinols from enolizable ketones. Trichloromethylcarbinols were obtained in good to excellent yields by using of a combination of CHCl3, n-BuLi, and chlorotitanium (IV) triisopropoxide. Hydrolysis of the trichloromethylcarbinol to an α,β-unsaturated ester was also explored.
Reverse selectivity in m-CPBA oxidation of oligothiophenes to sulfones.

Oligothiophene sulfones of up to six rings can be conveniently prepared by the direct oxidation of butyl-substituted thiophene oligomers with m-CPBA in dichloromethane. Reverse selectivity of oxidi...
Synthesis of new mixed ring zirconocenes and evidence of ring loss

Abstract The synthesis of the substituted silyl cyclopentadiene ligand [C 5 H 5 –Si(CH 3 ) 2 ( p -C 6 H 4 Br)] (Cp Si H) ( 1 ) is described. Deprotonation of ( 1 ) gives (Cp Si Li) ( 2 ) which reacts with 1/2 ZrCl 4 to produce the bent, sandwich complex Zr(Cp Si ) 2 Cl 2 ( 3 ). Compound ( 3 ) can be alkylated to give Zr(Cp Si ) 2 (CH 3 ) 2 ( 4 ). Reaction of Cp*ZrCl 3 ·(Et 2 O) 1/2 with ( 2 ) in ether produces ( 3 ) and Zr(Cp Si )(C 5 Me 5 )Cl 2 ( 5 ) as the minor and major products, respectively, whereas reaction in toluene produces only 5 . Et 2 O and THF are found to catalyze the observed ring loss during the synthesis of 5 . Alkylation of 5 produces Zr(Cp Si )(C 5 Me 5 )(CH 3 ) 2 ( 6 ).
Extreme Star Formation

Extreme star formation includes star formation in starbursts and regions forming super star clusters.We survey the current problems in our understanding of the star formation process in starbursts and super star clusters—initial mass functions, cluster mass functions, star formation efficiencies, and radiative feedback into molecular clouds—that are critical to our understanding of the formation and survival of large star clusters, topics that will be the drivers of the observations of the next decade.
Total Synthesis of (±)-Scopadulcic Acid B

The first total synthesis of a scopadulan diterpene is described. The key step is a double Heck cyclization of dienyl aryl iodide 8 to form tetracyclic enones 24 and 25 in 80−85% combined yield.
Synthetic, Biologically Active Amphiphilic Peptides

Amphiphilic peptides typically consist of a peptide portion that may be 5-25 (or more) amino acids in length. The hydrophobic portion may be a single fatty acid residue, but can also be more elaborate. The main focus of this article lies on the family of synthetic anion binders (SATs) of the general structure (R(1))(2)N-COCH(2)OCH(2)CO-(Aaa)(n)-OR(3). The most-common R(1) group is the octadecyl (C(18)H(37)) group. The most studied peptide sequence in this family is (Gly)(3)-Pro-(Gly)(3), although different sequences (and longer and shorter peptides) have been prepared as well. The C-terminal ester residue providing the most effective anion release from liposomes is heptyl (C(7)H(15)), although many others have been examined. The compound (C(18)H(37))(2)N-COCH(2)OCH(2)CO-(Gly)(3)-Pro-(Gly)(3)-OBn (Bn=benzyl) was found to mediate Cl(-) transport in mouse epithelial cells.
Synthesis of Homoallyl Ethers via Allylation of Acetals in Ionic Liquids Catalyzed by Trimethylsilyl Trifluoromethanesulfonate

The chemoselective allylation of acetals using allyltrimethylsilane in ionic liquids is catalyzed by TMS triflate (5.0−20.0 mol %). The reaction proceeds smoothly at room temperature to afford the corresponding homoallyl ether in good yield. Since the ionic liquids are easily recovered and recycled, they are a useful alternative to dichloromethane, which is the commonly used solvent for allylations.
Infrared spectroscopy of water cluster anions, (H2O)n=3-24-)in the HOH bending region: persistence of the double H-bond acceptor (AA) water molecule in the excess electron binding site of the class I isomers.

We report vibrational predissociation spectra of water cluster anions, (H2O)n=3-24- in the HOH bending region to explore whether the characteristic red-shifted feature associated with electron bind...
6-bromopurine nucleosides as reagents for nucleoside analogue synthesis.

Surprisingly facile direct substitution reactions with acetyl-protected 6-bromopurine nucleosides are described. Included in the series of bromonucleosides studied is the guanosine derivative N2-2‘,3‘,5‘-tetraacetyl-6-bromopurine ribonucleoside, the synthesis of which is reported here for the first time. Brominated nucleosides had not previously been considered optimal substrates for SNAr reactions given the general reactivity trend for halogenated aromatic systems (i.e. F > Cl > Br > I). However, even weakly nucleophilic aromatic amines give high yields of the substitution products in polar solvents with these 6-bromopurine nucleosides. For primary aromatic amines, secondary aliphatic amines, and imidazole, reaction takes place only at C6, with no effect on the acetyl-protected ribose. In addition, we report the first synthesis of 3‘,5‘-di-O-acetyl-6-bromopurine-2‘-deoxyribonucleoside and its reaction with an arylamine in MeOH in the absence of added metal catalyst. Thus, C6-arylamine derivatives of both...
Quantifying Nucleation In Vivo Reveals the Physical Basis of Prion-like Phase Behavior

Protein self-assemblies modulate protein activities over biological timescales that can exceed the lifetimes of the proteins or even the cells that harbor them. We hypothesized that these timescales relate to kinetic barriers inherent to the nucleation of ordered phases. To investigate nucleation barriers in living cells, we developed distributed amphifluoric FRET (DAmFRET). DAmFRET exploits a photoconvertible fluorophore, heterogeneous expression, and large cell numbers to quantify via flow cytometry the extent of a protein's self-assembly as a function of cellular concentration. We show that kinetic barriers limit the nucleation of ordered self-assemblies and that the persistence of the barriers with respect to concentration relates to structure. Supersaturation resulting from sequence-encoded nucleation barriers gave rise to prion behavior and enabled a prion-forming protein, Sup35 PrD, to partition into dynamic intracellular condensates or to form toxic aggregates. Our results suggest that nucleation barriers govern cytoplasmic inheritance, subcellular organization, and proteotoxicity.