bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increasing Precision and Confidence Level in Fracture Energy Measurement by Optimizing the Number of Test Replicates for Disk-Shaped Compact Tension Fracture Test (ASTM D7313)
Authors: Oshone Mirkat , Dave Eshan V. , Sias Jo E. , Voels Joseph M. , Ghosh Debaroti , Dai Shongtao 
Published: June 2019

Abstract
Different fracture-based tests and parameters have been developed in recent years to assess thermal cracking performance of asphalt mixtures. Agencies have adopted some of these tests, established threshold values, and incorporated them into their specifications to evaluate mixes during design and production. Because of the heterogeneous nature of asphalt mixtures, there can be a substantial amount of variability associated with mechanical test results obtained from fracture-based tests. To obtain unbiased properties with variabilities only inherent to the material itself and not caused by mixture production, specimen fabrication, or testing related factors, an appropriate number of replicate specimens need to be tested. This article provides the results of a study to establish a practical number of replicate tests that are required to obtain accurate and representative asphalt mixture fracture energy from the disk-shaped compact tension (DCT) fracture test for routine use by producers and agencies. Statistical analyses were performed to determine the precision and accuracy associated with the use of 4, 8, and 12 replicates. A total of 368 fracture energy measurements (16 replicates for 23 mixtures) were used for the analysis. The statistical analysis consistently indicated that 12 replicates results in higher confidence in the estimate of the mean. The maximum difference between measurements when 4 replicates are used ranges from 3 to 25 % but reduces to 1 to 9 % for 12 replicates. For 4 replicates, the data set used in this study indicated that 41 % of the time, it was not possible to confidently distinguish whether mixtures met a minimum threshold value or not. However, this error margin drops to 12 % when using 12 replicates. Based on these results, 12-replicate specimens are recommended to ensure necessary accuracy and repeatability for performance-based specifications using DCT fracture energy.
Reward Expectation Modulates Local Field Potentials, Spiking Activity and Spike-Field Coherence in the Primary Motor Cortex
Authors: An Junmo , Yadav Taruna , Hessburg John P. , Francis Joseph T. 
Published: June 2019

AbstractReward modulation (M1) could be exploited in developing an autonomously updating brain-computer interface (BCI) based on a reinforcement learning (RL) architecture. For an autonomously updating RL-based BCI system, we would need a reward prediction error, or a state-value representation from the user’s neural activity, which the RL-BCI agent could use to update its BCI decoder. In order to understand the multifaceted effects of reward on M1 activity, we investigated how neural spiking, oscillatory activities and their functional interactions are modulated by conditioned stimuli related reward expectation. To do so, local field potentials (LFPs) and single/multi-unit activities were recorded simultaneously and bilaterally from M1 cortices while four non-human primates (NHPs) performed cued center-out reaching or grip force tasks either manually using their right arm/hand or observed passively. We found that reward expectation influenced the strength of α (8–14 Hz) power, α-γ comodulation, α spike-field coherence (SFC), and firing rates (FRs) in general in M1. Furthermore, we found that an increase in α-band power was correlated with a decrease in neural spiking activity, that FRs were highest at the trough of the α-band cycle and lowest at the peak of its cycle. These findings imply that α oscillations modulated by reward expectation have an influence on spike FR and spike timing during both reaching and grasping tasks in M1. These LFP, spike, and spike-field interactions could be used to follow the M1 neural state in order to enhance BCI decoding (An et al., 2018; Zhao et al., 2018).
Computational study of Mg insertion into amorphous silicon: advantageous energetics over crystalline silicon for Mg storage
Authors: Legrain Fleur , Malyi Oleksandr I. , Tan Teck L. , Manzhos Sergei 
Published: June 2019

ABSTRACTWe show in a theoretical density functional theory study that amorphous Si (a-Si) has more favorable energetics for Mg storage compared to crystalline Si (c-Si). Specifically, Mg and Li insertion is compared in a model a-Si simulation cell. Multiple sites for Mg insertion with a wide range of binding energies are identified. For many sites, Mg defect formation energies are negative, whereas they are positive in c-Si. Moreover, while clustering in c-Si destabilizes the insertion sites (by about 0.1/0.2 eV per atom for nearest-neighbor Li/Mg), it is found to stabilize some of the insertion sites for both Li (by up to 0.27 eV) and Mg (by up to 0.35 eV) in a-Si. This could have significant implications on the performance of Si anodes in Mg batteries.
Beyond “Train-the-Trainer:” A Preliminary Report on a New Scaffolding Strategy for Science Communication Workshop Dissemination
Authors: Alpert Carol Lynn 
Published: June 2019

ABSTRACTThis paper reports on the development and results to date of a new strategy to disseminate a well-validated, successful science communication workshop program to multiple campuses hosting National Science Foundation (NSF) Research Experience for Undergraduates or REU-like research programs. The REU Science Communication Workshop program (REU SCW) is based on the premise that the most effective pedagogy for science communication skills development is one in which students practice iteratively using their own research material, with expert coaching and facilitated peer feedback. After testing several models for widespread dissemination, the most promising capacity-building strategy is one that scaffolds the traditional “train-the-trainer” approach with a new “piggyback” professional development model.
Proliferation and Osteogenic Differentiation of Mesenchymal Stem Cells on Biodegradable Calcium-deficient Hydroxyapatite Tubular Bacterial Cellulose Composites
Authors: Favi Pelagie , Dhar Madhu , Neilsen Nancy , Benson Roberto 
Published: June 2019

ABSTRACTAdvanced biomaterials that mimic the structure and function of native tissues and permit stem cells to adhere and differentiate is of paramount importance in the development of stem cell therapies for bone defects. Successful bone repair approaches may include an osteoconductive scaffold that permits excellent cell adhesion and proliferation, and cells with an osteogenic potential. The objective of this study was to evaluate the cell proliferation, viability and osteocyte differentiation of equine-derived bone marrow mesenchymal stem cells (EqMSCs) when seeded onto biocompatible and biodegradable calcium-deficient hydroxyapatite (CdHA) tubular-shaped bacterial cellulose scaffolds (BC-TS) of various sizes. The biocompatible gel-like BC-TS was synthesized using the bacterium Gluconacetobacter sucrofermentans under static culture in oxygen-permeable silicone tubes. The BC-TS scaffolds were modified using a periodate oxidation to yield biodegradable scaffolds. Additionally, CdHA was deposited in the scaffolds to mimic native bone tissues. The morphological properties of the resulting BC-TS and its composites were characterized using scanning electron microscopy. The ability of the BC-TS and its composites to support and maintain EqMSCs growth, proliferation and osteogenic differentiation in vitro was also assessed. BC-TS and its composites exhibited aligned nanofibril structures. MTS assay demonstrated increasing proliferation and viability with time (days 1, 2 and 3). Cell-scaffold constructs were cultured for 8 days under osteogenic conditions and the resulting osteocytes were positive for alizarin red. In summary, biocompatible and biodegradable CdHA BC-TS composites support the proliferation, viability and osteogenic differentiation of EqMSCs cultured onto its surface in vitro, allowing for future potential use for tissue engineering therapies.
Nanostructured Ceramic and Ceramic-Polymer Composites as Dual Functional Interface for Bioresorbable Metallic Implants
Authors: Johnson Ian , Tian Qiaomu , Liu Huinan 
Published: June 2019

ABSTRACTMillions of medical implants and devices (e.g., screws, plates, and pins) are used each year worldwide in surgery, and traditionally the components have been limited to permanent metals (e.g., stainless steel, titanium alloys) and polyester-based absorbable polymers. Because of clinical problems associated with these traditional materials, a novel class of biodegradable metallic materials, i.e., magnesium-based alloys, attracted great attention and clinical interests. Magnesium (Mg) is particularly attractive for load-bearing orthopedic applications because it has comparable modulus and strength to cortical bone. Controlling the interface of Mg with the biological environment, however, is the key challenge that currently limits this biodegradable metal for broad applications in medical devices and implants. This paper will particularly focus on creating nanostructured interface between the biodegradable metallic implant and surrounding tissue for the dual purposes of (1) mediating the degradation of the metallic implants and (2) simultaneously enhancing bone tissue regeneration and integration. Nanophase hydroxyapatite (nHA) is an excellent candidate as a coating material due to its osteoconductivity that has been widely reported. Applying nHA coatings or nHA containing composite coatings on Mg alloys is therefore promising in serving the needed dual functions. The composite of nHA and poly(lactic-co-glycolic acid) (PLGA) as a dual functional interface provides additional benefits for medical implant applications. Specifically, the polymer phase promotes interfacial adhesion between the nHA and Mg, and the degradation products of PLGA and Mg neutralize each other. Our results indicate that nHA and nHA/PLGA coatings slow down Mg degradation rate and enhance adhesion of bone marrow stromal cells, thus promising as the next-generation multifunctional implant materials. Further optimization of the coatings and their interfacial properties are still needed to bring them into clinical applications.
Correlation of Stress Relaxation and Microstructure Change in Polycrystalline Thin Films on Substrates: Au on Si <100> at RT
Authors: Vermeulen A. C. , Delhez R. , Mittemeijer E. J. 
Published: June 2019

AbstractStress relaxation in polycrystalline layers can be explained by processes, in which the microstructure plays a dominant role. The microstructure itself may also be subjected to changes. With X-ray diffraction information about both the stress and the microstructure can be obtained without destroying the specimen and without disturbing the stress relaxation process.In this paper a model system is studied: Au on Si<100>. The specimens showed a simultaneous decrease of macrostress and dislocation density with time at room temperature. This could be interpreted on the basis of a model founded on thermally activated dislocation motion. It followed that the grain size is an important parameter for the change of the dislocation density.
The Modified Gibbs-Wulff Construction and Critical Nucleus Morphology at an Interface
Authors: Lee J. K. , Choy J. H. , Choi Y. 
Published: June 2019

AbstractThe conditions for the equilibrium shape of a second-phase particle nucleating either at a planar interface or at a spherically curved interface are reviewed under the assumption that the interfacial structure of the nucleation site has a torque of an appropriate strength. The results are then incorporated into the modified Gibbs-Wulff construction in order to demonstrate a graphical representation of both the equilibrium shape and the free energy barrier for heterogeneous nucleation.
Initial Evolution of Cobalt Silicides in The Cobalt/Amorphous-Silicon Thin Film System
Authors: Miura Hideo , Ma En , Thompson Carl V. 
Published: June 2019

AbstractThe initial phase formation sequence for reactions in cobalt/ amorphous-silicon multi-layer thin films has been investigated using a combination of differential scanning calorimetry, thin film X-ray diffraction, and transmission electron microscopy. Multilayer thin films with various overall atomic concentration ratios and various bilayer thicknesses were used in this study. It was found that crystalline CoSi is always the first phase to nucleate in the interdiffused amorphous layer which preexisted at the as-deposited coba It/amorphous-si licon interface. The CoSi nucleates at temperatures as low as about 530 K, but does not grow until the next phase, which is Co2 Si when excess Co is available, starts to nucleate and grow. The activation energy of the CoSi nucleation was found to be 1.-6±0.1 eV.
On the Diffusion Behaviour in Stressed Ni-Zr Couples
Authors: Mazzone G. , Montone A. , Antisari M. Vittori 
Published: June 2019

AbstractSolid state reactions at the interface of bulk Ni-Zr couples have been induced at several temperatures by compressive plastic deformation. The reaction product is an amorphous phase whose thickness increases with applied load and sample temperature. In addition, similar samples have been thermally reacted in order to measure the thermal interdiffusion coefficent in the same conditions. Measurements on stressed couples show that the interdiffusion coefficent (several orders of magnitude larger than the corresponding thermal value) follows a dual regime Arrhenius behaviour. The activation energy is independent of load and of the order of 0.2 eV in the low temperature regime extending up to 550 K. A different behaviour characterized by a single value of the activation energy in the whole temperature range has been observed in thermally treated samples.
Molecular Dynamics Simulation of the Effect of Interfaces in Melting and Solid-State Amorphization
Authors: Wolf Dieter , Yip Sidney 
Published: June 2019

AbstractA newly developed molecular dynamics code was used to study the effect of free surfaces, grain boundaries and voids in the process of melting. It was found that conventional “thermodynamic melting” occurs via nucleation of the liquid at the extended defects with subsequent growth into the crystal. In the absence of interfaces, or when this transition is kinetically hindered, however, a second type of melting transition can be triggered by an elastic instability first described by Born (“mechanical melting”). It is suggested that the distinct characteristic features associated with the two types of melting are actually observed in solid-state amorphization experiments. A unified thermodynamics-based description, in the form of an extended phase diagram, of melting and solid-state amorphization is proposed which brings out the parallels between these two phenomena and suggests that their underlying causes are apparently the same. By investigating the effect of surface stresses on the structure and elastic behavior of free-standing thin films, we discuss how these concepts need to be modified in thin-film and small-grained materials.
Effect of Annealing on the Dielectric Properties and Microstructure of Tantalum Oxide T14in Films
Authors: Chun Chang Hwan , Kim Geun Hong , Yi Kyoung-Soo 
Published: June 2019

AbstractEffects of heat treatments on the dielectric properties of tantalum oxide thin films(250Å) deposited on the p-Si substrates by RF reactive sputtering were investigated. The leakage current density was considerably reduced from 10-9 to 10-12A/μm2 at an electric field of 2MV/cm after rapid thermal annealing in O2 at 1000°C, while little leakage reduction was observed after annealing at 500°C.The structural changes of tantalum oxide thin film after annealing were examined using high resolution transmission electron microscopy. The leakage reduction after annealing can be attributed to crystallization and reoxidation of the amorphous tantalum oxide thin film.
Phase Transformations in Sputtered Ni-Ti Film: Effects of Heat Treatment and Precipitates
Authors: Busch J. D. , Berkson Mitchell H. , Johnson A. D. 
Published: June 2019

AbstractThis research investigated the influence of heat treatment and precipitation on the phase transformation temperatures of sputter-deposited nickel-titanium films. Films 5 to 10 microns thick were subjected to isochronal and isothermal heat treatments in vacuum. Four-point resistance measutements were made and the TP, TR, Ma, and Mc temperatures identified. The correlation between transformation temperatures and the film's microstructure was studied using transmission electron microscopy. Existence of Ti2Ni and Ti11Ni14 precipitates was seen to adversely influence the phase transformation temperatures. It was concluded that precipitate-free film is preferable for mechanical actuator applications.
Structural and Electrical Properties of Titanium-Nickel Films Deposited Onto Silicon Substrates
Authors: Collen Kathleen R. , Ellis Arthur B. , Busch J. D. , Johnson A. D. 
Published: June 2019

AbstractThin films of the shape memory alloy NiTi have been sputter-deposited onto ptype silicon substrates. Films that are initially amorphous may be crystallized by vacuum annealing. The crystalline films exhibit the B2->B19′ phase change associated with the shape memory effect while remaining in contact with the silicon substrate. Transition temperatures were determined by resistance measurements and x-ray diffraction. The NiTi - Si contacts are diodes, as evidenced by their current-voltage characteristics; however, the effect of the phase change on the barrier height could not be determined.
How Strong is the Electron Correlation in Conjugated Polymers
Authors: Wu C. Q. 
Published: June 2019

ABSTRACTCorrelation effects on the band gap are studied to get the strength of electron interactions in conjugated polymers. In the presence of an additional electron or hole, the correlation induces a polarization cloud around the additional particle, which forms a polaron. For the excitation energy of a polaron, there is a competition between a loss of correlation energy in the ground state and a gain of polarization energy due to the scattering through the additional particle. The calculation has been done both for the Hubbard Model and long-range interactions. For polyacetylene, we obtain the on-site repulsion U = 4.4 eV and the nearest-neighbor interaction V = 0.8 eV. The polarization effect of Σ electrons and theoretical results on the effective interaction are discussed. The strength of effective interactions should depends on physical processes.
Energetics of Epitaxial Monolayers Deposited on a (111) Surface of an FCC Crystal: Application to a Cu Monolayer on Au(111)
Authors: Zypman F. R. , Fonseca L. F. , Blum L. 
Published: June 2019

ABSTRACTWe study a system in which a monolayer of atoms of one kind are deposited epitaxialy onto a (111) surface of an FCC crystal using the Tight Binding approximation. First, we obtain an analytical expression for the energy spectrum of the system. This turns out to be an interesting result from the mathematical standpoint due to its simplicity, and to the fact that no artificial boundary conditions (like periodic or vanishing) were imposed on the wave functions. All the spectral information is shown to be contained in the roots of a quadratic polynomial. Then, for Cu on Au, we study the density of states and wave function decay out from the outer layer. This is done at zero and finite voltage applied between an electrode and bulk Gold, immersed in an electrolyte. This problem is of interest in electrochemistry.
Electrochemical Heteroepitaxial Growth of Molecular Films on Ordered Substrates
Authors: Last Julie A. , Hooks Daniel E. , Yip Christopher M. , Ward Michael D. 
Published: June 2019

ABSTRACTElectrocrystallization of the organic superconductor bis(ethylenedithio)tetrathiafulvalene triiodide, (ET)2I3, on a highly ordered pyrolytic graphite (HOPG) substrate has been visualized using in situ atomic force microscopy (AFM). Previous studies have revealed the formation of a coincident epitaxial monolayer with a structure identical to that of a (001) layer of the superconducting beta phase of this material prior to bulk crystal growth. However, the symmetry of the HOPG substrate leads to domain boundary defects during self assembly of the separately growing domains. The number of defects is significantly reduced after an electrochemical annealing process in which the potential is cycled about the monolayer deposition potential. Annealing of these films is important if they are to be used in electronic devices as the defects may serve as barriers to electron transport in the two-dimensional layers.In addition to (ET)2I3, monolayer growth also has been visualized during electrocrystallization of (ET)2ReO4 on HOPG. The role of coincident epitaxy with HOPG in the monolayer formation and molecular orientation will be discussed.Structurally modified substrates have also been investigated. Studies of the electrocrystallization of (ET)2I3 on HOPG, thermally treated to produce well-defined monolayer depth pit structures, have demonstrated that (ET)2I3 monolayer growth can occur inside the pit structures. The presence of monolayer domain boundaries within large pits indicates that multiple, independent nucleation events can occur in the pits, providing an opportunity to determine critical nucleation sizes by varying the pit dimensions. Recently we have discovered that MoS2 substrates can be electrochemically etched, giving rise to monolayer deep triangular pits.
Electrolyte Electroreflectance of Boron Phosphide (BP)
Authors: Schroten E. , Goossens A. , Schoonman J. 
Published: June 2019

ABSTRACTAn electrolyte electroreflectance study has been performed on boron phosphide thin films epitaxially grown on silicon (100) substrates. To our knowledge, this paper is the first report on the electrolyte electroreflectance spectrum of BP. All our boron phosphide of 1.5 μm thick films show a pronounced peak at the energy 4.25 eV, indicating a critical point in the valence or conduction band of the semiconductor. Photoreflectance measurements confirm these results. The 4.25 eV energy level is much lower than previously reported direct bandgap values of BP. The electrolyte electroreflectance spectrum of much thinner layers shows, besides the 4.25 eV peak, some other features at still lower incident photon energies caused by interference effects.
Electrochemical Deposition of Metals on Semiconductors
Authors: Oskam Gerko , Long John G. , Nikolova Maria , Searson Peter C. 
Published: June 2019

ABSTRACTThe general concepts governing the electrochemical deposition of metal films on semiconductors are discussed, and recent results on the fabrication of Schottky junctions consisting of silicon electrodeposited with platinum, copper and gold are presented. In order to obtain good adherent metal films, the density of nuclei should be high and the films should be grown at low current densities where the charge transfer process is rate limiting. This situation can be realized using potential controlled electrochemical deposition. For metal deposition on silicon, the surface should be pretreated in HF to dissolve the oxide layer. Furthermore, the surface should be stable during deposition which can be achieved by tailoring the deposition solutions and by using electrochemical deposition at negative potentials. It is shown that by using this approach, n-type silicon / Pt, Au, and Cu Schottky junctions can be fabricated of a quality comparable to that of junctions prepared by sputter and vapor deposition techniques.