bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of adsorbed chain rigidity in reinforcement of polymer nanocomposites
Authors: Yang Siyang , Hassan Mohammed , Akcora Pinar 
Published: October 2018

ABSTRACTThe thermomechanical behavior of polymer nanocomposites is mostly governed by interfacial properties which rely on particle–polymer interactions, particle loading, and dispersion state. We recently showed that poly(methyl methacrylate) (PMMA) adsorbed nanoparticles in poly(ethylene oxide) (PEO) matrices displayed an unusual thermal stiffening response. The molecular origin of this unique stiffening behavior resulted from the enhanced PEO mobility within glassy PMMA chains adsorbed on nanoparticles. In addition, dynamic asymmetry and chemical heterogeneities existing in the interfacial layers around particles were shown to improve the reinforcement of composites as a result of good interchain mixing. Here, the role of chain rigidity in this interfacially controlled reinforcement in PEO composites is investigated. We show that particles adsorbed with less rigid polymers improve the mechanical properties of composites. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2019,57, 9–14
Formations of belonging inAustralia: The role of nostalgia in experiences of time and place
Authors: Cuervo Hernán , Cook Julia 
Published: October 2018

AbstractAlthough residential mobility has been studied at length, residentialimmobilityhas been addressed comparatively rarely. In this article, we draw on interviews conducted with 35 participants aged 38–39 in 2012 in Victoria, Australia, in which they were asked to reflect on their lives over the previous 20 years, focusing specifically on those who have remained in or returned to the areas in which they grew up. We focus on the role of nostalgia in the participants' experiences of and relationships with place, finding that far from signifying a purely, or even predominantly, melancholic experience their expressions of nostalgia held the power to enliven the present, even while anchoring them to the past. We contend that nostalgia can form an integral part of practices that reconcile continuity and change and produce feelings of familiarity and comfort, which buffer individuals against the uncertainties associated with wider contexts shaped by rapid social change.
GPUs as boosters to analyze scalar and vector fields in quantum chemistry
Authors: Hernández‐Esparza Raymundo , Vázquez‐Mayagoitia Álvaro , Soriano‐Agueda Luis‐Antonio , Vargas Rubicelia , Garza Jorge 
Published: October 2018

AbstractThe analysis of scalar and vector fields in quantum chemistry is an essential task for the computational chemistry community, where such quantities must be evaluated rapidly to perform a particular study. For example, the atoms in molecules approach proposed by Bader has become popular; however, this method demands significant computational resources to compute the involved tasks in short times. In this article, we discuss the importance of graphics processing units (GPU) to analyze electron density, and related fields, implementing several scalar, and vector fields within the graphics processing units for atoms and molecules (GPUAM) code developed by a group of the Universidad Autónoma Metropolitana in México City. With this application, the quantum chemistry community can perform demanding computational tasks on a desktop, where CPUs and GPUs are used to their maximum capabilities. The performance of GPUAM is tested in several systems and over different GPUs, where a GPU installed in a workstation converts it to a robust high‐performance computing system.
Solvation thermodynamics of neutral and charged solutes using the solvation‐layer interface condition continuum dielectric model
Authors: Mehdizadeh Rahimi Ali , Molavi Tabrizi Amirhossein , Goossens Spencer , Knepley Matthew G. , Bardhan Jaydeep P. 
Published: October 2018

AbstractWe demonstrate that the solvation‐layer interface condition (SLIC) continuum dielectric model for molecular electrostatics, combined with a simple solvent‐accessible‐surface‐area (SASA)‐proportional model for nonpolar solvent effects, accurately predicts solvation entropies of neutral and charged small molecules. The SLIC/SASA model has only seven fitting parameters in total and achieves this accuracy using a training set with only 20 compounds. Despite this simplicity, solvation free energies and entropies are nearly as accurate as those predicted by the more sophisticated Langevin dipoles solvation model. Surprisingly, the model automatically reproduces the negligible contribution of electrostatics to the solvation of hydrophobic compounds. Opportunities for improvement include nonpolar solvation, anion solvation entropies, and heat capacities. More molecular realism may be needed for these quantities. To enable a future, explicit‐solvent‐based assessment of the SLIC/SASA implicit‐solvent model, we predict solvation entropies for the Mobley test set, which are available as Supporting Information.
Charged‐cell periodic DFT simulations via an impurity model based on density embedding: Application to the ionization potential of liquid water
Authors: Tölle Johannes , Severo Pereira Gomes André , Ramos Pablo , Pavanello Michele 
Published: October 2018

AbstractCalculations of charged systems in periodic boundary conditions (PBC) are problematic because there are spurious interactions between the charges in different periodic images that can affect the physical picture. In addition, the intuitive limit of Coulomb interactions decaying to zero as the interacting charges are placed at infinite separation no longer applies, and for example total energies become undefined. Leveraging subsystem density functional theory (also known as density embedding) we define an impurity model that embeds a finite neutral or charged subsystem within an extended (infinite) surrounding subsystem. The combination of the impurity model and a consistent choice of the Coulomb reference provides us with an algorithm for evaluating the ionization potential (IP) in extended systems. We demonstrate our approach in a pilot calculation of the IP of liquid water, based on a configuration from a prior ab initio molecular dynamics (AIMD) simulation of liquid water (Genova et al., J. Chem. Phys. 2016, 144, 234105). The calculations with the impurity model capture the broadening on the ionization energies introduced by the interactions between the water molecules. Furthermore, the calculated average IP value (10.5 eV) compare favorably to experiments (9.9‐10.06 eV) and very recent simulations based on the GW approximation (10.55 eV), while at the same time outperforming density embedding calculations carried out with a naïve handling of the electrostatic interactions (about 7 eV).
Partition potential for hydrogen bonding in formic acid dimers
Authors: Gómez Sara , Oueis Yan , Restrepo Albeiro , Wasserman Adam 
Published: October 2018

AbstractThe ground‐state energy and density of 4 low‐energy conformations of the formic acid dimer were calculated via partition density functional theory (PDFT). The differences between isolated and PDFT monomer densities display similar deformation patterns for primary and secondary hydrogen bonds (HBs) among all 4 dimers. In contrast, the partition potential shows no transferable features in the bonding regions. These observations highlight the global character of the partition potential and the cooperative effect that occurs when a dimer is bound via more than 1 HB. We also provide numerical confirmation of the intuitive (but unproven) observation that fragment deformation energies are larger for systems with larger binding energies.
Multireference exciplex binding energies: Basis set convergence and error
Authors: Krueger Rachel A. , Blanquart Guillaume 
Published: October 2018

AbstractIn multichromophore systems, characterization of electronic structure requires characterization of exciplexes, electron‐hole pairs delocalized over multiple molecules. Computing exciplex binding energy requires an accurate description of both the noncovalent interactions between the chromophores and their excited electronic states. The critical role of basis set selection for accurate description of noncovalent interactions is well known, but for some of the most accurate excited‐state methods, basis set dependence is incompletely understood. In this work, the impact of basis set size and diffuseness on CASSCF/NEVPT2 binding energies is determined for three systems in their lowest singlet excited states: the benzene excimer, the cis‐butadiene‐benzene exciplex, and the benzene‐naphthalene exciplex. We demonstrate that excellent CBS binding energies may be obtained using the moderately‐sized jun‐cc‐pV(D + d)Z and jun‐cc‐pV(T + d)Z basis sets and a simple N−3 model. Repeating this procedure with the N = 3, 4 basis sets from the most diffuse basis set family applied to each system yields a binding energy of 56.6 ± 1.2 kJ/mol for the benzene excimer and binding energies of 11.1 ± 0.5 kJ/mol and 19.2 ± 1.7 kJ/mol for the cis‐butadiene‐benzene exciplex and the benzene‐naphthalene exciplex, respectively.
Controlling the Charge Density Wave Transition in Monolayer TiSe2: Substrate and Doping Effects
Authors: Kolekar Sadhu , Bonilla Manuel , Diaz Horacio Coy , Hashimoto Makato , Lu Donghui , Batzill Matthias 
Published: October 2018

AbstractTiSe2 is an exciting material because it can be tuned between superconducting and charge density wave (CDW) transitions. In the monolayer limit, TiSe2 exhibits a sizable energy gap in the CDW phase that makes it a promising quantum material. It is shown that interfacing a single layer of TiSe2 with dissimilar van der Waals materials enables control of its properties. Using angle‐resolved photoemission spectroscopy, the energy gap opening is analyzed as a function of temperature for TiSe2 monolayers supported on different van der Waals substrates. A substantial increase in the CDW transition temperature of ≈45 K is observed on MoS2 compared to graphite (highly oriented pyrolytic graphite) substrates. This control of the CDW in monolayer TiSe2 is suggested to arise from varying charge screening of the unconventional CDW of TiSe2 by the substrate. In addition, the suppression of CDW order and a complete closing of the energy gap by electron doping of monolayer TiSe2 is demonstrated. Regulating the many‐body physics phenomena in monolayer TiSe2 lays the foundation of modifying TiSe2 in, for example, artificial van der Waals heterostructures and thus creates a new approach for utilizing the quantum states of TiSe2 in device applications.
Cooperative autonomous search, grasping, and delivering in a treasure hunt scenario by a team of unmanned aerial vehicles
Authors: Spurný Vojtěch , Báča Tomáš , Saska Martin , Pěnička Robert , Krajník Tomáš , Thomas Justin , Thakur Dinesh , Loianno Giuseppe , Kumar Vijay 
Published: October 2018

AbstractThis paper addresses the problem of autonomous cooperative localization, grasping and delivering of colored ferrous objects by a team of unmanned aerial vehicles (UAVs). In the proposed scenario, a team of UAVs is required to maximize the reward by collecting colored objects and delivering them to a predefined location. This task consists of several subtasks such as cooperative coverage path planning, object detection and state estimation, UAV self‐localization, precise motion control, trajectory tracking, aerial grasping and dropping, and decentralized team coordination. The failure recovery and synchronization job manager is used to integrate all the presented subtasks together and also to decrease the vulnerability to individual subtask failures in real‐world conditions. The whole system was developed for the Mohamed Bin Zayed International Robotics Challenge (MBZIRC) 2017, where it achieved the highest score and won Challenge No. 3—Treasure Hunt. This paper does not only contain results from the MBZIRC 2017 competition but it also evaluates the system performance in simulations and field tests that were conducted throughout the year‐long development and preparations for the competition.
Data‐driven mobility risk prediction for planetary rovers
Authors: Skonieczny Krzysztof , Shukla Dhara K. , Faragalli Michele , Cole Matthew , Iagnemma Karl D. 
Published: October 2018

AbstractMobility assessment and prediction continues to be an important and active area of research for planetary rovers, with the need illustrated by multiple examples of high slip events experienced by rovers on Mars. Despite slip versus slope being one of the strongest and most broadly used relationships in mobility prediction, this relationship is nonetheless far from precisely predictable. Although the literature has made significant advances in the predictability of average mobility, the other key related aspect of the problem is the risk caused by edge cases. A key contribution of this study is a metric for explicitly assessing mobility risk based on data‐driven nonparametric slip versus slope relationships. The data‐driven approach is meant to address limitations of past model‐based approaches. The metric is informed by past work in terramechanics relating drawbar pull (i.e., net traction) to slip: High slip fraction (HSF), defined as the proportion of slip data points above 20%. Another contribution is a low complexity mobility prediction framework, the autonomous soil assessment system. Field tests demonstrate that, for sand and gravel, rover trafficability becomes nonlinear and highly variable above the 20% slip threshold. HSF is shown to be a useful metric for categorizing rover‐terrain interactions into low, medium, or high risk, correctly and consistently. Furthermore, the metric is shown to be useful for early detection of potentially hazardous changes in rover‐terrain conditions. The combination of HSF with an appropriately sized queue structure for modeling slip versus slope enables an appropriate balance between responsiveness and stability.
Shared autonomy for low‐cost underwater vehicles
Authors: Lawrance Nicholas , DeBortoli Robert , Jones Dylan , McCammon Seth , Milliken Lauren , Nicolai Austin , Somers Thane , Hollinger Geoffrey 
Published: October 2018

AbstractThis field report presents an overview of the development and testing of a semi‐autonomous underwater vehicle (sAUV). The work presented here is aimed at bridging the gap between current remotely operated vehicles and autonomous research platforms by developing shared autonomy capabilities for low‐cost underwater vehicles. We use commercially available components and open‐source software interfaces to provide a wider range of capabilities for underwater autonomy research at a lower cost than previously available systems. We describe the overall structure of the system, discuss its capabilities, and provide results demonstrating system performance. We place particular emphasis on shared autonomy, where a human operator is assisted in controlling an underwater tethered vehicle. We present three capabilities developed for the sAUV: (a) an assisted control mode that provides a variable level of assistance using an on‐line estimate of user skill level, (b) a planner to generate paths that avoid tether entanglement, and (c) a sonar processing algorithm that identifies informative sonar images for selecting features for 3D scene reconstruction. The vehicle has been deployed on five off‐shore and near‐shore marine field deployments since 2015, and this report includes selected results from four of those trials to demonstrate the capabilities and limitations of the sAUV system.
Evaluating flow management as a strategy to recover an endangered sturgeon species in the Upper Missouri River, USA
Authors: Erwin Susannah O. , Bulliner Edward A. , Fischenich J. Craig , Jacobson Robert B. , Braaten Patrick J. , DeLonay Aaron J. 
Published: October 2018

AbstractIn the Upper Missouri River, Fort Peck and Garrison Dams limit the length of free‐flowing river available to the endangered pallid sturgeon. These barriers restrict the upstream migration of adults and downstream larval dispersal. A one‐dimensional (1D) modelling framework is currently in use to evaluate reservoir operation alternatives and to simulate drift of dispersing free embryos for different flow regimes and reservoir stages. This paper presents the results of a large‐scale tracer experiment conducted in 2016 and associated modelling performed to evaluate flow management scenarios that might aid species recovery. Breakthrough curves from the tracer experiment were used to infer the 1D longitudinal dispersion coefficient from a parameter optimization procedure. Simulations generated using the calibrated 1D advection–dispersion model were compared with field observations of the passive tracer and with larval fish collected during a previous experiment in 2007. When used with the appropriate range of dispersion coefficients, the 1D modelling framework agrees well with the available direct measurements of larval drift distances. Although we cannot unequivocally state whether insufficient length of free‐flowing river alone is causing recruitment failure, given the current thermal regime and our understanding of pallid sturgeon development, the time required for pallid sturgeon to transition to the benthos and initiate feeding might exceed the duration of drift available given constraints of reservoir operations.
Simulating the effect of environmental flow duration on seedling emergence from riparian seed banks of the Upper Hunter River, New South Wales
Authors: Stone Luke , Fryirs Kirstie , Leishman Michelle 
Published: October 2018

AbstractPassive riparian revegetation techniques are important tools in river rehabilitation. However, the utility of the sediment seed bank as a passive riparian regeneration option is poorly understood. After modelling a range of flows for field‐surveyed cross sections, a glasshouse seedling emergence experiment was undertaken to compare the effects of simulated flow duration on seedling emergence of desirable riparian species that occur on benches of the gravel‐bedded Hunter River near Muswellbrook, New South Wales. The duration of inundation did have an effect (although not always significant) on seed germination for most species. The most successful simulated flood conditions differed among species, with the control treatment (no inundation) resulting in the most germination for only two of the 10 species examined. These findings suggest that although environmental flows for the sole purpose of stimulating the riparian seed bank in order to facilitate regeneration of desirable riparian species would be largely ineffective and complicated by differing inundation responses among species, seed bank stimulation using environmental flows could be a value‐added benefit from flows allocated for other purposes. As such, consideration of flow duration is worthy of inclusion in environmental flow allocation planning.
Counting Hamilton cycles in sparse random directed graphs
Authors: Ferber Asaf , Kwan Matthew , Sudakov Benny 
Published: October 2018

AbstractLet be the random directed graph on n vertices where each of the possible arcs is present independently with probability p. A celebrated result of Frieze shows that if then typically has a directed Hamilton cycle, and this is best possible. In this paper, we obtain a strengthening of this result, showing that under the same condition, the number of directed Hamilton cycles in is typically . We also prove a hitting‐time version of this statement, showing that in the random directed graph process, as soon as every vertex has in‐/out‐degrees at least 1, there are typically directed Hamilton cycles.
Spanning universality in random graphs
Authors: Ferber Asaf , Nenadov Rajko 
Published: October 2018

AbstractA graph is said to be ‐universal if it contains every graph with n vertices and maximum degree at most Δ as a subgraph. Dellamonica, Kohayakawa, Rödl and Ruciński used a “matching‐based” embedding technique introduced by Alon and Füredi to show that the random graph is asymptotically almost surely ‐universal for , a threshold for the property that every subset of Δ vertices has a common neighbor. This bound has become a benchmark in the field and many subsequent results on embedding spanning graphs of maximum degree Δ in random graphs are proven only up to this threshold. We take a step towards overcoming limitations of former techniques by showing that is almost surely ‐universal for .
Using classroom observations to evaluate science teaching: Implications of lesson sampling for measuring science teaching effectiveness across lesson types
Authors: Mikeska Jamie N. , Holtzman Steven , McCaffrey Daniel F. , Liu Shuangshuang , Shattuck Tamara 
Published: October 2018

AbstractDespite the prevalent use of observational measures in teacher evaluation systems, research has only recently begun to take into account how aspects of the instructional environment and lesson sampling design may interact with teachers’ scores on these measures. Instead, one assumption guiding current evaluation systems is that the variation in teachers’ instructional practices captured by the lessons sampled is a valid measure of their teaching quality. Our study investigates this assumption by examining whether scores from observational measures of science teachers’ instructional practices vary depending on lesson type. Results show that science teachers’ scores on certain observational measures vary across lab and nonlab lessons, suggesting that the claims one can make about science teaching effectiveness are dependent on the particular types of lessons observed. Given the increasing prominence and use of observational measures within evaluation systems, it is imperative to ensure that the observed lessons adequately represent variation in a teacher’s practice and are not subject to undue instability from the types of lessons included in the sample, especially in science where there are clear distinctions in the instructional practices teachers employ across lab and nonlab lessons. Implications for measuring science teaching quality are discussed.
What is engineering? Elaborating the nature of engineering for K‐12 education
Authors: Pleasants Jacob , Olson Joanne K. 
Published: October 2018

AbstractWhat is engineering? What do engineers do? How is engineering related to, but distinct from, science? These questions all relate to the nature of engineering (NOE), and as engineering is incorporated into K‐12 education across the United States, the NOE is becoming increasingly important for students and teachers. While many policy documents call for students to learn more about the structure of the engineering discipline, little has been done to define the NOE construct. This paper presents key dimensions of the NOE via a framework synthesized from studies of the engineering discipline from philosophical, historical, and sociological perspectives, as well as perspectives from within the engineering field. The framework identifies and elaborates nine features of engineering, each of which capture an important aspect of the NOE. For teachers, these features serve as points of entry for discussing NOE ideas with students. For researchers, the features provide a set of constructs to guide future inquiries into teachers’ and students’ NOE knowledge.