cssi/SciSciGPT-SciSciNet huggingface dataset:
Three-dimensional simulations of oblique asteroid impacts into water

Abstract Waves generated by impacts into oceans may represent the most significant danger from near-earth asteroids and comets. For impacts near populated shores, the crown splash and subsequent waves, accompanied by sediment lofting and high winds, are more damaging than storm surges from the strongest hurricanes. Asteroids less than 500 m in diameter, impacting deep water far from shores, produce waves that may be detectable over large distances, but are probably not significantly dangerous. We present new three-dimensional simulations of oblique impacts into deep water, with trajectory angles ranging from 27° to 60° (where 90° is vertical). These simulations are performed with the Los Alamos Rage hydrocode, and include atmospheric effects including ablation and airbursts. These oblique impact simulations are specifically performed in order to help determine whether there are additional dangers from the obliquity of impact not covered by previous two-dimensional studies. Water surface elevation profiles, surface pressures, and depth-averaged mass fluxes within the water are prepared for use in propagation studies.
C57BL/6 substrain differences in inflammatory and neuropathic nociception and genetic mapping of a major quantitative trait locus underlying acute thermal nociception.

Sensitivity to different pain modalities has a genetic basis that remains largely unknown. Employing closely related inbred mouse substrains can facilitate gene mapping of nociceptive behaviors in ...
Allergy to Surgical Implants

Surgical implants are essential elements of repair procedures to correct worn out joints, damaged spinal components, heart and vascular disease, and chronic pain. However, many of the materials that provide stability, flexibility, and durability to the implants are also immunogenic. Fortunately, allergic responses to surgical implants are infrequent. When they do occur, however, the associated pain, swelling, inflammation, and decreased range of motion can significantly impair the implant function. Given the high numbers of joint replacements performed in the developed world, allergic reactions to orthopedic implants form the largest category of allergic responses. The most important allergens in this category include nickel, cobalt, chromium, and bone cement. These allergens are also the most important in reactions to spinal surgeries. Multiple cardiac and neurostimulatory devices are constructed of metals and adhesives that can be sensitizing in some individuals. Implantable pulse generators, important in cardiac pacemakers, gastric stimulators, and neurostimulators, may include components made of stainless steel, titanium alloy, platinum and iridium, epoxy resins, poly methyl methacrylates, and isocyanates, all of which are immunogenic in some patients. Cardiac stents and patches are often made of Nitinol, a composite of nickel and titanium. More surgical procedures are closed using skin glues, which are also capable of triggering a blistering contact dermatitis. Patch testing is the gold standard to determine sensitization, and this review provides a list of standard allergens to test for different implants. The patients most appropriate for testing include (1) pre-operative joint replacement patients with a prior history of skin reactions to metal jewelry, jean snaps, watch bands, metal glass frames, artificial nails, or skin glue; (2) post-operative joint replacement failure patients needing revision without an obvious cause such as infection or mechanical incompatibility; and (3) post-operative cardiac or neurological patients with localized rash, pain, swelling, or inflammation near or over the implant.
Associations between Body Mass Index and Urban “Green” Streetscape in Cleveland, Ohio, USA

Public health researchers are increasingly interested in assessing the impact of neighborhood environment on physical activities and chronic health issues among humans. Walkable streets and proximity to green space have long been believed to promote active lifestyles in cities, which contribute to positive health outcomes among residents. Traditionally, urban environmental metrics were calculated at the area level to describe the physical environment of neighborhoods. However, considering the fact that streets are the basic unit for human activities in cities, it is important to understand how the streetscape environment can influence human health conditions. In this study, we investigated the influence of street greenery and walkability on body mass index in Cleveland, Ohio, USA. Different from the area level and overhead view greenery metrics, we used the green view index calculated from the Google Street View to represent the amount of street greenery. The Walk Score was used to indicate the walkability of neighborhoods also at the street level. Statistical analysis results show that the Walk Score has a more significant association with decreased BMI for males than females and the street greenery has a more significant association with decreased BMI for females than males in Cleveland, Ohio. The results of this study would provide a reference for designing gender-specific healthy cities.
Geocoding Without Geotags: A Text-based Approach for reddit

In this paper, we introduce the first geolocation inference approach for reddit, a social media platform where user pseudonymity has thus far made supervised demographic inference difficult to implement and validate. In particular, we design a text-based heuristic schema to generate ground truth location labels for reddit users in the absence of explicitly geotagged data. After evaluating the accuracy of our labeling procedure, we train and test several geolocation inference models across our reddit data set and three benchmark Twitter geolocation data sets. Ultimately, we show that geolocation models trained and applied on the same domain substantially outperform models attempting to transfer training data across domains, even more so on reddit where platform-specific interest-group metadata can be used to improve inferences.
Inferring Demography and Selection in Organisms Characterized by Skewed Offspring Distributions

The recent increase in time-series population genomic data from experimental, natural, and ancient populations has been accompanied by a promising growth in methodologies for inferring demographic and selective parameters from such data. However, these methods have largely presumed that the populations of interest are well-described by the Kingman coalescent. In reality, many groups of organisms, including viruses, marine organisms, and some plants, protists, and fungi, typified by high variance in progeny number, may be best characterized by multiple-merger coalescent models. Estimation of population genetic parameters under Wright-Fisher assumptions for these organisms may thus be prone to serious mis-inference. We propose a novel method for the joint inference of demography and selection under the Ψ-coalescent model, termed Multiple-Merger Coalescent Approximate Bayesian Computation, or MMC-ABC. We first demonstrate mis-inference under the Kingman, and then exhibit the superior performance of MMC-ABC under conditions of skewed offspring distributions. In order to highlight the utility of this approach, we reanalyzed previously published drug-selection lines of influenza A virus. We jointly inferred the extent of progeny-skew inherent to viral replication and identified putative drug-resistance mutations.
Performance Improvement in Noisy Linear Consensus Networks With Time-Delay

We analyze performance of a class of time-delay first-order consensus networks from a graph topological perspective and present methods to improve it. Performance is measured by network's square of $\mathcal {H}_2$ norm and it is derived in closed form. Moreover, we prove that performance is a convex function of the coupling weights of the underlying graph. We demonstrate that the effect of time-delay reincarnates itself in the form of non-monotonicity, leading to counter-intuitive behaviors of the performance as a function of graph topology. For the network design problem, we propose a tight but simple approximation of the performance measure in order to achieve lower complexity in our problems by eliminating the computationally expensive need for eigendecomposition. More specifically, we discuss three $\mathcal {H}_2$ -based optimal design methods to enhance performance. The proposed algorithms provide near-optimal solutions with improved computational complexity as opposed to existing methods in the literature.
Towards a theory of platform dynamics

I introduce a dynamic framework to analyze platforms. The (single) platform owner sets prices at the beginning of each period. Agents (buyers, sellers, readers, consumers, merchants, etc.) make platform membership decisions occasionally. I show that an optimal platform pricing addresses two externalities: across sides and across time periods. This results in optimal prices which depend on platform size in a nontrivial way. By means of numerical simulations, I examine the determinants of equilibrium platform size, showing that the stationary distribution of platform size may be bimodal, that is, with some probability the platform remains very low or takes very long to increase in size. I also contrast the dynamics of proprietary versus nonproprietary (i.e., zero‐priced) platforms, and consider the specific case of asymmetric platforms (one side cares about the other but not vice versa).
Dynamical System Segmentation for Information Measures in Motion

Motions carry information about the underlying task being executed. Previous studies on human motion analysis suggest that complex motions may result from the composition of fundamental submovements called movemes. The existence of finite structure in motion motivates information-theoretic approaches to motion analysis and robotic assistance. We define task embodiment as the amount of task information encoded in an agent's motions. By decoding task-specific information embedded in motion, we can use task embodiment to create detailed performance assessments. We extract an alphabet of behaviors comprising a motion without a priori knowledge using a novel algorithm, which we call dynamical system segmentation. For a given task, we specify an optimal agent, and compute an alphabet of behaviors representative of the task. We identify these behaviors in data from agent executions, and compare their relative frequencies against that of the optimal agent using the Kullback–Leibler divergence. We validate this approach using a dataset of human subjects ( $\mathbf {n=53}$ ) performing a dynamic task, and under this measure find that individuals receiving assistance better embody the task. Moreover, we find that task embodiment is a better predictor of assistance than integrated mean-squared error.
Note on Lagrangian–Eulerian methods for uniqueness in hydrodynamic systems

Abstract We discuss the Lagrangian–Eulerian framework for hydrodynamic models and provide a proof of Lipschitz dependence of solutions on initial data in path space. The paper presents a corrected version of the result in [1] .
The Fundamental Theorem of Algebra in ACL2.

We report on a verification of the Fundamental Theorem of Algebra in ACL2(r). The proof consists of four parts. First, continuity for both complex-valued and real-valued functions of complex numbers is defined, and it is shown that continuous functions from the complex to the real numbers achieve a minimum value over a closed square region. An important case of continuous real-valued, complex functions results from taking the traditional complex norm of a continuous complex function. We think of these continuous functions as having only one (complex) argument, but in ACL2(r) they appear as functions of two arguments. The extra argument is a "context", which is uninterpreted. For example, it could be other arguments that are held fixed, as in an exponential function which has a base and an exponent, either of which could be held fixed. Second, it is shown that complex polynomials are continuous, so the norm of a complex polynomial is a continuous real-valued function and it achieves its minimum over an arbitrary square region centered at the origin. This part of the proof benefits from the introduction of the "context" argument, and it illustrates an innovation that simplifies the proofs of classical properties with unbound parameters. Third, we derive lower and upper bounds on the norm of non-constant polynomials for inputs that are sufficiently far away from the origin. This means that a sufficiently large square can be found to guarantee that it contains the global minimum of the norm of the polynomial. Fourth, it is shown that if a given number is not a root of a non-constant polynomial, then it cannot be the global minimum. Finally, these results are combined to show that the global minimum must be a root of the polynomial. This result is part of a larger effort in the formalization of complex polynomials in ACL2(r).
Generative predecessor models for sample-efficient imitation learning

We propose Generative Predecessor Models for Imitation Learning (GPRIL), a novel imitation learning algorithm that matches the state-action distribution to the distribution observed in expert demonstrations, using generative models to reason probabilistically about alternative histories of demonstrated states. We show that this approach allows an agent to learn robust policies using only a small number of expert demonstrations and self-supervised interactions with the environment. We derive this approach from first principles and compare it empirically to a state-of-the-art imitation learning method, showing that it outperforms or matches its performance on two simulated robot manipulation tasks and demonstrate significantly higher sample efficiency by applying the algorithm on a real robot.
Mode hunting through active information

We propose a new method to find modes based on active information. We develop an algorithm called active information mode hunting (AIMH) that, when applied to the whole space, will say whether there are any modes present and where they are. We show AIMH is consistent and, given that information increases where probability decreases, it helps to overcome issues with the curse of dimensionality. The AIMH also reduces the dimensionality with no resource to principal components. We illustrate the method in three ways: with a theoretical example (showing how it performs better than other mode hunting strategies), a real dataset business application, and a simulation.
Sampling With and Without Replacement

Sampling with replacement is a class of sampling procedures in which the selected elements are replaced in the selection pool following each “draw” and may be reselected on subsequent draws. In contrast, sampling without replacement is a class of procedures in which the already selected elements are not replaced in the pool and cannot be selected again. Keywords: sampling; finite population
Near-Optimal Control Strategy in Leader-Follower Networks: A Case Study for Linear Quadratic Mean-Field Teams

In this paper, a decentralized stochastic control system consisting of one leader and many homogeneous followers is studied. The leader and followers are coupled in both dynamics and cost, where the dynamics are linear and the cost function is quadratic in the states and actions of the leader and followers. The objective of the leader and followers is to reach consensus while minimizing their communication and energy costs. The leader knows its local state and each follower knows its local state and the state of the leader. The number of required links to implement this decentralized information structure is equal to the number of followers, which is the minimum number of links for a communication graph to be connected. In the special case of a leaderless network, no link is required among followers, i.e., the communication graph is not even connected. We propose a near-optimal control strategy that converges to the optimal solution as the number of followers increases. One of the salient features of the proposed solution is that it provides a design scheme, where the convergence rate as well as the collective behavior of the followers can be designed by choosing appropriate cost functions. In addition, the computational complexity of the proposed solution does not depend on the number of followers. Furthermore, the proposed strategy can be computed in a distributed manner, where the leader solves one Riccati equation and each follower solves two Riccati equations to calculate their strategies. Two numerical examples are provided to demonstrate the effectiveness of the results in the control of multi-agent systems.
The volatility of mutual fund performance

Abstract Previous research has shown that fund performance is reduced by higher expense ratios but improved by more active management. Using data for equity mutual funds from 1991 to 2012, we show that prior studies has overlooked the fact that a high degree of active management magnifies the extremes of performance. In addition, funds with higher expense ratios and turnover ratio have had greater volatility of performance as well as lower mean performance, a doubly adverse pattern. Thus, mutual funds with more active management, higher expense ratios and turnover ratios are riskier.
The effect of charter schools on districts’ student composition, costs, and efficiency: The case of New York state

Abstract Charter schools can influence a school district's costs by reducing economies of scale and by changing the share of high cost students a district serves, but might also increase the district's efficiency through competition. Utilizing data for New York State school districts from 1998/99 to 2013/14, we estimate difference-in-differences models to assess the effect of charter schools on enrollment and student composition. Then, we estimate an expenditure function, using data prior to the charter school program, to measure the costs associated with reaching a given performance standard for students in various need categories and different enrollments. Next, using the entire data set, we run a second expenditure function to determine changes in efficiency associated with charter school entry. We find that charter schools increase the cost of providing education, and that these cost increases are larger than short-run efficiency gains, but are offset by efficiency gains in the long term.
Chapter 6 – Windowing

This chapter throws light on the windowing, aiming to optimize finite impulse response (FIR) filter frequency response with a finite number of coefficients. The chapter explains the process of truncating of infinite number of coefficients through windowing that generate a desirable response. This is further elaborated through tapering of coefficients, which holds importance for designers to manage passband and stopband ripple with a trade-off of increasing the transition band. Lastly, with some relevant examples of coefficient windows, aspect of Windowing is supported in all FIR-related filter design software programs.
Changes in the constitution and microstructure of andalusite, cyanite, and sillimanite at high temperatures, and their significance in industrial practice

Owing to their growing commercial importance in the manufacture of refractories and porcelain, the minerals of the sillimanite group (andalusite, cyanite, and sillimanite) were investigated as to their decomposition products and volume changes between cones 10 and 15. Petrographic-microscopic examinations showed that andalusite breaks down at cone 13 into mullite and glass, while cyanite also breaks down into the same components but at cone 12. Sillimanite is not decomposed up to cone 15. The composition of the mullite was checked by chemical analysis. Andalusite shows almost no volume change at dissociation; sillimanite shows a slight expansion up to cone 15; cyanite shows a great expansion and disintegration at dissociation. The practical significance of the behavior of the minerals is discussed as well as their possibilities of use in ceramic ware., Andalusite could be used in the raw state; cyanite would require calcination before use, so that andalusite appears to be best suited for most bodies.
Learning Representations and Generative Models for 3D Point Clouds.

Three-dimensional geometric data offer an excellent domain for studying representation learning and generative modeling. In this paper, we look at geometric data represented as point clouds. We introduce a deep AutoEncoder (AE) network with state-of-the-art reconstruction quality and generalization ability. The learned representations outperform existing methods on 3D recognition tasks and enable shape editing via simple algebraic manipulations, such as semantic part editing, shape analogies and shape interpolation, as well as shape completion. We perform a thorough study of different generative models including GANs operating on the raw point clouds, significantly improved GANs trained in the fixed latent space of our AEs, and Gaussian Mixture Models (GMMs). To quantitatively evaluate generative models we introduce measures of sample fidelity and diversity based on matchings between sets of point clouds. Interestingly, our evaluation of generalization, fidelity and diversity reveals that GMMs trained in the latent space of our AEs yield the best results overall.
Methods to Estimate Surface Roughness Length for Offshore Wind Energy

The northeastern coast of the U.S. is projected to expand its offshore wind capacity from the existing 30 MW to over 22 GW in the next decade. Yet, only a few wind measurements are available in the region and none at hub height, thus extrapolations are needed to estimate wind speed as a function of height. A common method is the log-law, which is based on surface roughness length (z0). No reliable estimates of z0 for the region have been presented in the literature. Here, we fill this knowledge gap using two field campaigns that were conducted in the Nantucket Sound at the Cape Wind (CW) platform. We tested three different methods to calculate z0: 1) analytical, dependent on friction velocity u* and a stability function psi; 2) the Charnock relationship between z0 and u*; and 3) a statistical method based on wind speed observed at the three levels. The first two methods are physical, whereas the statistical method is purely mathematical. Comparing mean and median of z0, we find that the median is a more robust statistics. In general, the median z0 exhibits little seasonal variability and a weak dependency on atmospheric stability, which was predominantly unstable (54-67%). The statistical method, despite delivering unrealistic z0 values at times, gives the best estimates of 60-m winds. The unrealistic z0 values are caused by non-monotonic wind speed profiles, occurring about 41% of the time, and should not be rejected because they produce realistic fits. In summary, if wind speed data from multiple levels are available, the statistical method is recommended. If multi-level wind speeds are not available but advanced sonic anemometry is available at one level, the analytical method is recommended over the Charnock's. If a constant value of z0 is sought after to characterize the region, we recommend the median from the statistical method, i.e., 6.09*10^(-3) m.
Does an interactive trust-enhanced electronic consent improve patient experiences when asked to share their health records for research? A randomized trial.

Objective In the context of patient broad consent for future research uses of their identifiable health record data, we compare the effectiveness of interactive trust-enhanced e-consent, interactive-only e-consent, and standard e-consent (no interactivity, no trust enhancement). Materials and methods A randomized trial was conducted involving adult participants making a scheduled primary care visit. Participants were randomized into 1 of the 3 e-consent conditions. Primary outcomes were patient-reported satisfaction with and subjective understanding of the e-consent. Secondary outcomes were objective knowledge, perceived voluntariness, trust in medical researchers, consent decision, and time spent using the application. Outcomes were assessed immediately after use of the e-consent and at 1-week follow-up. Results Across all conditions, participants (N = 734) reported moderate-to-high satisfaction with consent (mean 4.3 of 5) and subjective understanding (79.1 of 100). Over 94% agreed to share their health record data. No statistically significant differences in outcomes were observed between conditions. Irrespective of condition, black participants and those with lower education reported lower satisfaction, subjective understanding, knowledge, perceived voluntariness, and trust in medical researchers, as well as spent more time consenting. Conclusions A large majority of patients were willing to share their identifiable health records for research, and they reported positive consent experiences. However, incorporating optional additional information and messages designed to enhance trust in the research process did not improve consent experiences. To improve poorer consent experiences of racial and ethnic minority participants and those with lower education, other novel consent technologies and processes may be valuable. (An Interactive Patient-Centered Consent for Research Using Medical Records; NCT03063268).
In situ quasi-elastic neutron scattering study on the water dynamics and reaction mechanisms in alkali-activated slags.

In this study, in situ quasi-elastic neutron scattering (QENS) has been employed to probe the water dynamics and reaction mechanisms occurring during the formation of NaOH- and Na2SiO3-activated slags, an important class of low-CO2 cements, in conjunction with isothermal conduction calorimetry (ICC), Fourier transform infrared spectroscopy (FTIR) analysis and N2 sorption measurements. We show that the single ICC reaction peak in the NaOH-activated slag is accompanied with a transformation of free water to bound water (from QENS analysis), which directly signals formation of a sodium-containing aluminum-substituted calcium–silicate–hydrate (C–(N)–A–S–H) gel, as confirmed by FTIR. In contrast, the Na2SiO3-activated slag sample exhibits two distinct reaction peaks in the ICC data, where the first reaction peak is associated with conversion of constrained water to bound and free water, and the second peak is accompanied by conversion of free water to bound and constrained water (from QENS analysis). The second conversion is attributed to formation of the main reaction product (i.e., C–(N)–A–S–H gel) as confirmed by FTIR and N2 sorption data. Analysis of the QENS, FTIR and N2 sorption data together with thermodynamic information from the literature explicitly shows that the first reaction peak is associated with the formation of an initial gel (similar to C–(N)–A–S–H gel) that is governed by the Na+ ions and silicate species in Na2SiO3 solution and the dissolved Ca/Al species from slag. Hence, this study exemplifies the power of in situ QENS, when combined with laboratory-based characterization techniques, in elucidating the water dynamics and associated chemical mechanisms occurring in complex materials, and has provided important mechanistic insight on the early-age reactions occurring during formation of two alkali-activated slags.
Influence of employing laminated isogrid configuration on mechanical behavior of grid structures

For a long time, a single grid layer, such as isogrid, have been utilized to strengthen a shell or plate or as an independent structural member for various applications. Laminated grid structures c...
Protocol-Aware Recovery for Consensus-Based Storage.

We introduce protocol-aware recovery (PAR), a new approach that exploits protocol-specific knowledge to correctly recover from storage faults in distributed systems. We demonstrate the efficacy of PAR through the design and implementation of corruption-tolerant replication (CTRL), a PAR mechanism specific to replicated state machine (RSM) systems. We experimentally show that the CTRL versions of two systems, LogCabin and ZooKeeper, safely recover from storage faults and provide high availability, while the unmodified versions can lose data or become unavailable. We also show that the CTRL versions have little performance overhead.
Evaluating Quality of Service Traffic Classes on the Megafly Network

An emerging trend in High Performance Computing (HPC) systems that use hierarchical topologies (such as dragonfly) is that the applications are increasingly exhibiting high run-to-run performance variability. This poses a significant challenge for application developers, job schedulers, and system maintainers. One approach to address the performance variability is to use newly proposed network topologies such as megafly (or dragonfly+) that offer increased path diversity compared to a traditional fully connected dragonfly. Yet another approach is to use quality of service (QoS) traffic classes that ensure bandwidth guarantees. In this work, we select HPC application workloads that have exhibited performance variability on current 2-D dragonfly systems. We evaluate the baseline performance expectations of these workloads on megafly and 1-D dragonfly network models with comparably similar network configurations. Our results show that the megafly network, despite using fewer virtual channels (VCs) for deadlock avoidance than a dragonfly, performs as well as a fully connected 1-D dragonfly network. We then exploit the fact that megafly networks require fewer VCs to incorporate QoS traffic classes. We use bandwidth capping and traffic differentiation techniques to introduce multiple traffic classes in megafly networks. In some cases, our results show that QoS can completely mitigate application performance variability while causing minimal slowdown to the background network traffic.
Kinematics of Supernova Remnants: Status of X-Ray Observations

A supernova (SN) explosion drives stellar debris into the circumstellar material (CSM) filling a region on a scale of parsecs with X-ray emitting plasma. The velocities involved in supernova remnants (SNRs), thousands of km s−1, can be directly measured with medium and high-resolution X-ray spectrometers and add an important dimension to our understanding of the last stages of the progenitor, the explosion mechanism, and the physics of strong shocks. After touching on the ingredients of SNR kinematics, I present a summary of the still-growing measurement results from SNR X-ray observations. Given the advances in 2D/3D hydrodynamics, data analysis techniques, and especially X-ray instrumentation, it is clear that our view of SNRs will continue to deepen in the decades ahead.
Triolborates: water-soluble complexes of arylboronic acids as precursors to iodoarenes

Abstract A facile synthesis of aryl and heteroaryl iodides from water-soluble complexes of aryl- and heteroarylboronic acids has been developed.
Using “Idealized Peers” for Automated Evaluation of Student Understanding in an Introductory Psychology Course

Teachers may wish to use open-ended learning activities and tests, but they are burdensome to assess compared to forced-choice instruments. At the same time, forced-choice assessments suffer from issues of guessing (when used as tests) and may not encourage valuable behaviors of construction and generation of understanding (when used as learning activities). Previous work demonstrates that automated scoring of constructed responses such as summaries and essays using latent semantic analysis (LSA) can successfully predict human scoring. The goal for this study was to test whether LSA can be used to generate predictive indices when students are learning from social science texts that describe theories and provide evidence for them. The corpus consisted of written responses generated while reading textbook excerpts about a psychological theory. Automated scoring indices based in response length, lexical diversity of the response, the LSA match of the response to the original text, and LSA match to an idealized peer were all predictive of human scoring. In addition, student understanding (as measured by a posttest) was predicted uniquely by the LSA match to an idealized peer.
Scope and Stereochemistry of [2+2] Photocycloadditions Between Cyclopentenones and 1,2-Dichlorocycloalkenes

Abstract Cyclopentenone and dichlorocycloalkenes give [2+2] adducts whose stereochemistry (from modern NMR) is mostly cis, anti, cis; cis, syn, cis minor adducts are also found. Cophotolysis of dichlorocyclohexene and cycloheptanocyclopentenone does not give any adduct.
[Ta6Cl12(PrCN)6][(Ta6Cl12)Cl6]·2PrCN, A Compound with Homonuclear Mixed-Charge Cluster Units [Ta6Cl12]2+ and [Ta6Cl12]4+

In transition metal cluster chemistry, compounds consisting of both a cluster cation and a cluster anion are not very common. The first members of this type of compound of the composition [M{sub 6}X{sub 12}(EtOH){sub 6}][(Mo{sub 6}Cl{sub 8})Cl{sub 4}X{sub 2}]{center{underscore}dot}mEtOH{center{underscore}dot}nEt{sub 2}O (M = Nb, Ta; X = Cl, Br) have been recently prepared. Crystal structure determinations for [Nb{sub 6}Cl{sub 12}(EtOH){sub 6}][(Mo{sub 6}Cl{sub 8})Cl{sub 6}]{center{underscore}dot}3EtOH{center{underscore}dot}3Et{sub 2}O and [Ta{sub 6}Cl{sub 12}(EtOH){sub 6}][(Mo{sub 6}Cl{sub 8})Cl{sub 6}]{center{underscore}dot}6EtOH revealed the presence of two different hexanuclear cluster cores; namely, the [M{sub 6}X{sub 12}(EtOH){sub 6}]{sup 2+} cluster cations and the [(Mo{sub 6}Cl{sub 8})Cl{sub 4}X{sub 2}]{sup 2{minus}} cluster anions. In fact, these compounds consist of two different heteronuclear cluster units with different charges: [M{sub 6}X{sub 12}]{sup 2+} in the cation and [Mo{sub 6}Cl{sub 8}]{sup 4+} in the anion. The preparation of cation-anion pairs with homonuclear mixed-charge cluster units is also possible. In the present study, the synthesis and crystal structure of the cluster pair [Ta{sub 6}Cl{sub 12}(PrCN){sub 6}][(Ta{sub 6}Cl{sub 12})Cl{sub 6}]{center{underscore}dot}2PrCN is reported. The compound is built of two octahedral homonuclear mixed-charge cluster units: [Ta{sub 6}Cl{sub 12}]{sup 2+} in the [Ta{sub 6}Cl{sub 12}(PrCN){sub 6}]{sup 2+} cluster cation and [Ta{sub 6}Cl{sub 12}]{sup 4+} in the [(Ta{sub 6}Cl{sub 12})Cl{sub 6}]{sup 2{minus}}more » cluster anion.« less
Compact E-Cash.

This paper presents efficient off-line anonymous e-cash schemes where a user can withdraw a wallet containing 2 coins each of which she can spend unlinkably. Our first result is a scheme, secure under the strong RSA and the y-DDHI assumptions, where the complexity of the withdrawal and spend operations is O(` + k) and the user’s wallet can be stored using O(` + k) bits, where k is a security parameter. The best previously known schemes require at least one of these complexities to be O(2 · k). In fact, compared to previous e-cash schemes, our whole wallet of 2 coins has about the same size as one coin in these schemes. Our scheme also offers exculpability of users, that is, the bank can prove to third parties that a user has double-spent. We then extend our scheme to our second result, the first e-cash scheme that provides traceable coins without a trusted third party. That is, once a user has double spent one of the 2 coins in her wallet, all her spendings of these coins can be traced. We present two alternate constructions. One construction shares the same complexities with our first result but requires a strong bilinear map assumption that is only conjectured to hold on MNT curves. The second construction works on more general types of elliptic curves, but the price for this is that the complexity of the spending and of the withdrawal protocols becomes O(` · k) and O(` · k + k) bits, respectively, and wallets take O(` · k) bits of storage. All our schemes are secure in the random oracle model.
Iodine-catalyzed cycloalkenylation of dihydroquinolines and arylamines through a reaction with cyclic ketones under neat conditions

Abstract An iodine-catalyzed direct cycloalkenylation of dihydroquinolines and arylamines has been developed. This method consists of a Friedel–Crafts reaction between dihydroquinolines (or arylamines) and cyclic ketones in which the double bond is selectively generated throughout the course of the reaction resulting in a direct cycloalkenylation, under neat conditions.
Conjugate allylation reactions of alkylidene malononitriles mediated by NHC-ligated palladium catalysts

Conjugate allylation of malononitriles is reported using catalytic N-heterocyclic carbene-ligated palladium complexes. This conjugate allylation reaction yields a variety of monoallylated products. These results contrast the bis-allylation of malononitriles using other palladium-based catalysts. This reaction tolerates a wide variety of functional groups including aryl groups, heteroaromatics, and aliphatic substituents to provide the desired products in good to excellent yields. Derivativation of the monoallylation products to form a triamino pyrimidine is demonstrated.
Differential roles of sleep spindles and sleep slow oscillations in memory consolidation

Sleep plays an important role in the consolidation of recent memories. However, the cellular and synaptic mechanisms of consolidation during sleep remain poorly understood. In this study, using a realistic computational model of the thalamocortical network, we tested the role of Non-Rapid Eye Movement (NREM) sleep in memory consolidation. We found that sleep spindles (the hallmark of N2 stage sleep) and slow oscillations (the hallmark of N3 stage sleep) both promote replay of the spike sequences learned in the awake state and replay was localized at the trained network locations. Memory performance improved after a period of NREM sleep but not after the same time period in awake. When multiple memories were trained, the local nature of the spike sequence replay during spindles allowed replay of the distinct memory traces independently, while slow oscillations promoted competition that could prevent replay of the weak memories in a presence of the stronger memory traces. This could lead to extinction of the weak memories unless when sleep spindles (N2 sleep) preceded slow oscillations (N3 sleep), as observed during the natural sleep cycle. Our study presents a mechanistic explanation for the role of sleep rhythms in memory consolidation and proposes a testable hypothesis how the natural structure of sleep stages provides an optimal environment to consolidate memories.
Functionalization of α,β-Unsaturated Esters and Ketones: A Facile and Highly Stereoselective One-Pot Approach to N-Protected α,β-Dehydroamino Acid Derivatives

A new, facile, and highly stereoselective protocol toward α,β-dehydroamino acid derivatives has been developed. The one-pot synthesis was very convenient to perform by using the aminohalogenation reaction of α,β-unsaturated esters and ketones followed by treatment with specific bases. Only two [2.2.2] bicyclic organic bases were found to be effective for this transformation. Good yields (58−68%) and excellent Z-selectivity were obtained for 12 examples.
Metal-Catalyzed Di-tert-butylsilylene Transfer: Synthesis and Reactivity of Silacyclopropanes

Metal-catalyzed di-tert-butylsilylene transfer was developed as a mild, operationally simple, functional-group-tolerant method for silacyclopropane formation. Di-tert-butylsilylene was transferred from cyclohexene silacyclopropane 1 to an alkene through the use of a metal salt. Silacyclopropanation occurred at temperatures as low as −27 °C when AgOTf or AgOC(O)CF3 were used as catalysts. Complex silacyclopropanes were formed stereospecifically and diastereoselectively from functionalized alkenes. Silacyclopropanes reacted with various carbonyl compounds, including aldehydes, ketones, formate esters, and formamides, in an overall process that efficiently converts alkenes into oxasilacyclopentanes with defined stereochemistry.
Stereoselective synthesis of penaresidin A and related azetidine alkaloids

Several sphingosine-like azetidine alkaloids have been synthesized from the Garner aldehyde 5, including the ATPase activator penaresidin A (1a), its side chain isomer 1b, and the 16-nor analogue (3b) of the protein kinase C inhibitor penazetidine A 3a.
1,4‐Dihydropyridines (DHPs) – a class of very potent drugs: syntheses of isotopically labeled DHP derivatives during the last four decades

1,4-Dihydropyridines (DHPs) belonging to the group of calcium antagonists or calcium channel blockers' are among the most important drugs used in the treatment of cardiovascular diseases. During the development processes all candidates on the market have to be labeled with isotopes. Since the discovery of 1,4-dihydropyridines (DHP) as cardiovascular drugs, the published syntheses for the labeling with radioactive isotopes like tritium, carbon-11, carbon-14, iodine-125 and stable isotopes like deuterium and carbon-13 are reviewed in the present report. The different synthetic routes are depicted and the synthesis details will be discussed with respect to the yields referred to labeled starting materials, specific activities and labeling degrees. Copyright © 2007 John Wiley & Sons, Ltd.
New multi-component reaction accessing 3-aminoimidazo[1,2-a]pyridines

Abstract The novel one step solution phase synthesis of an array of 3-aminoimidazo[1,2-a]pyridines is reported. Reactions were performed in methanol by mixing a α-amino-pyridine, aldehyde and trimethylsilylcyanide (TMSCN) to give the desired product. Mediated by microwave irradiation and catalyzed by scandium triflate, the methodology represents the first one pot preparation of 3-aminoimidazo[1,2-a]pyridines that avoids the use of an isonitrile and subsequent de-protection strategy. The reaction is an example of a formal three-centre-three-component multi-component reaction.
Species Designations Belie Phenotypic and Genotypic Heterogeneity in Oral Streptococci.

ABSTRACT Health-associated oral Streptococcus species are promising probiotic candidates to protect against dental caries. Ammonia production through the arginine deiminase system (ADS), which can increase the pH of oral biofilms, and direct antagonism of caries-associated bacterial species are desirable properties for oral probiotic strains. ADS and antagonistic activities can vary dramatically among individuals, but the genetic basis for these differences is unknown. We sequenced whole genomes of a diverse set of clinical oral Streptococcus isolates and examined the genetic basis of variability in ADS and antagonistic activities. A total of 113 isolates were included and represented 10 species: Streptococcus australis, A12-like, S. cristatus, S. gordonii, S. intermedius, S. mitis, S. oralis including S. oralis subsp. dentisani, S. parasanguinis, S. salivarius, and S. sanguinis. Mean ADS activity and antagonism on Streptococcus mutans UA159 were measured for each isolate, and each isolate was whole genome shotgun sequenced on an Illumina MiSeq. Phylogenies were built of genes known to be involved in ADS activity and antagonism. Several approaches to correlate the pan-genome with phenotypes were performed. Phylogenies of genes previously identified in ADS activity and antagonism grouped isolates by species, but not by phenotype. A genome-wide association study (GWAS) identified additional genes potentially involved in ADS activity or antagonism across all the isolates we sequenced as well as within several species. Phenotypic heterogeneity in oral streptococci is not necessarily reflected by genotype and is not species specific. Probiotic strains must be carefully selected based on characterization of each strain and not based on inclusion within a certain species. IMPORTANCE Representative type strains are commonly used to characterize bacterial species, yet species are phenotypically and genotypically heterogeneous. Conclusions about strain physiology and activity based on a single strain therefore may be inappropriate and misleading. When selecting strains for probiotic use, the assumption that all strains within a species share the same desired probiotic characteristics may result in selection of a strain that lacks the desired traits, and therefore makes a minimally effective or ineffective probiotic. Health-associated oral streptococci are promising candidates for anticaries probiotics, but strains need to be carefully selected based on observed phenotypes. We characterized the genotypes and anticaries phenotypes of strains from 10 species of oral streptococci and demonstrate poor correlation between genotype and phenotype across all species.
The Structural Basis of IKs Ion-Channel Activation: Mechanistic Insights from Molecular Simulations

Abstract Relating ion channel (iCh) structural dynamics to physiological function remains a challenge. Current experimental and computational techniques have limited ability to explore this relationship in atomistic detail over physiological timescales. A framework associating iCh structure to function is necessary for elucidating normal and disease mechanisms. We formulated a modeling schema that overcomes the limitations of current methods through applications of artificial intelligence machine learning. Using this approach, we studied molecular processes that underlie human IKs voltage-mediated gating. IKs malfunction underlies many debilitating and life-threatening diseases. Molecular components of IKs that underlie its electrophysiological function include KCNQ1 (a pore-forming tetramer) and KCNE1 (an auxiliary subunit). Simulations, using the IKs structure-function model, reproduced experimentally recorded saturation of gating-charge displacement at positive membrane voltages, two-step voltage sensor (VS) movement shown by fluorescence, iCh gating statistics, and current-voltage relationship. Mechanistic insights include the following: 1) pore energy profile determines iCh subconductance; 2) the entire protein structure, not limited to the pore, contributes to pore energy and channel subconductance; 3) interactions with KCNE1 result in two distinct VS movements, causing gating-charge saturation at positive membrane voltages and current activation delay; and 4) flexible coupling between VS and pore permits pore opening at lower VS positions, resulting in sequential gating. The new modeling approach is applicable to atomistic scale studies of other proteins on timescales of physiological function.
Novel [1,5] Sigmatropic Rearrangements of Cyclohexadienones Generated from Fischer Carbene Complexes. A New Strategy for Installing the C-20 Angular Ethyl Group in Aspidospermidine Alkaloids

We report here the first examples of a [1,5] sigmatropic rearrangement in a 4a-alkyl-4a-hydrocarbazol-4-one to yield a 3-alkylcarbazol-4-one with a re-aromatized indole nucleus. The reaction of 1-methyl-3-substituted-indole-2-carbene complexes 1 with terminal alkynes yields 3,4a-dialkyl-1-methoxy-9-methylcarbazol-4-ones 2. These 4a-substituted carbazolones thermally rearrange to cleanly give the more highly aromatic 3,3-dialkyl-1-methoxy-9-methylcarbazol-4-ones 3. This reaction provides a convenient entry to the Aspidosperma family of alkaloids, which contain a 3,3-disubstituted carbazole nucleus.
Diastereotopic differentiation on phosphorus templates via the ring-closing metathesis reaction.

A strategy is described in which the ring-closing metathesis reaction is utilized to desymmetrize a number of pseudo-C2-symmetric phosphorus templates 1−3. These reactions give excellent levels of selectivity (12−15:1) with vinyl phosphonamides containing a (E)-Ph group on the diastereotopic olefins. This approach is being developed as an effective method of obtaining P-chiral phosphonamides and phosphonates.