bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling of Polypyrrole Actuators
Authors: Samani Mehrdad Bahrami , Whitten Philip G. , Spinks Geoffrey M. , Cook Christopher D. 
Published: April 2011

ABSTRACTConducting polymers (CP) are a promising area in the field of micro actuators, and have potential applications in micro robotics. Their properties are modelled as having an electro-chemical active component and a passive viscoelastic component. Methods exist to model the passive component as a configuration of springs and dashpots and the electro-active effects as a strain generator. Typically, the strain is assumed to be proportional to the charge transferred, and the two components are assumed to be independent. We show that there is a significant interaction between the two components for polypyrrole actuators, by observing the dynamic elastic modulus whilst varying the electric potential. The elastic modulus was measured in-situ by applying a high frequency rectangular isotonic stress input and recording the corresponding strain output. Two separate potential control inputs, vs. a reference electrode, were used. In the first experiment, a triangular voltage signal with variable frequency was applied to the PPy helix tube actuator and in the second experiment; a step voltage signal was applied to the actuator. The value of total real modulus was calculated during both experiments to evaluate the effect of actuation on the mechanical properties of PPy actuator. The performance of the mentioned method was confirmed by comparing its results to that of a sinusoidal stress input during a temperature ramp through the glass transition of polyethylene terephthalate (PET). We show that polypyrrole actuators show a complex change in stiffness with contractile state, which mimic skeletal muscle [1].
High Conductivity Ionic Liquid- Nafion Mat Composites for High Speed Ionic Polymer Transducers
Authors: Akle Barbar , Leo Donald J. , Nah Changwoon , Kader Abdul M. 
Published: April 2011

ABSTRACTIonomeric polymer transducers consist of an ion-exchange membrane plated with conductive metal layers on the outer surfaces. Such materials are known to generate large bending strain (> 9% is possible) at low applied voltages (typically less than 5 V). The main disadvantage of ionomer–ionic liquid transducers is the slow speed of response. The speed of response in such actuators has been correlated to the ionic liquid content and the conductivity of the membrane. To increase the conductivity of the transducers a Nafion™ mat is hydrated with 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI-Tf) ionic liquids and high surface area RuO2 electrodes are attached using the Direct Assembly Process (DAP). The Nafion™ mat is prepared from homogenous solution electrospinning. The solution is prepared by mixing 1 wt % of polyethylene oxide solution in methanol (PEO, Mol. wt 3×106) to 5 wt % Nafion 1100 solution.. The syringe needle is connected to a 15kV power supply and is placed 15cm away from the collecting drum. The measured conductivities of water hydrated Nafion electro-spun fibers are 16.8 mS/cm, which are lower than the nominal 110 mS/cm that of H+ Nafion membranes. The uptake is measured to be around 250 %wt compared to 58 %wt obtained in Nafion films. The ionic conductivity of 110 %wt swollen ionic liquids-Nafion mat composite is computed to be 0.9 mS/cm compared to 0.3 mS/cm in ionic liquid-Nafion membrane composite. The speed of response in actuators with an ionic liquid- Nafion™ mat is 1.34 %/s compared to 0.88 %/s for that in ionic liquid Nafion™ film transducers.
Space Charge Modelling in Solid Dielectrics under High Electric Field Based on Double Charge Injection Model
Authors: Chen George , Loi Su Han 
Published: April 2011

ABSTRACTPresent study aims to develop a clear insight on factors that influence space charge dynamics in solid dielectrics through a numerical simulation. The model used for the simulation is proposed by Alison and Hill [1] which describes charge dynamics as a result of bipolar transport with single level trapping. In this model, a constant mobility and no detrapping have been assumed. The simulation results show that carrier mobility, trapping coefficient and Schottky barrier have a significant effect on the space charge dynamics. Many features of space charge profiles observed by experiments have been revealed in despite of over simplistic model. More importantly, the simulation allows us to study the role of each individual parameter in the formation of space charge in solid dielectrics, so that the experimental results can be better understood.
The growth of epitaxial uranium oxide observed by micro-Raman spectroscopy
Authors: Caculitan Niña , Siekhaus Wigbert J. 
Published: April 2011

AbstractRaman spectroscopy can be performed with micrometer resolution and can thus be used to determine the dependence of oxide thickness on the substrate’s grain structure or local impurity inclusions. The Raman signal amplitude emitted from an epitaxial uranium oxide layer as a function of oxide thickness has been modeled for light of 632.8 nm wavelength incident on the oxide and reflected from the uranium substrate using the optical properties determined by spectrophotometry. The model shows that the Raman signal increases with oxide thickness and saturates at about 150 nm thickness. The model was compared with the measured Raman signal amplitude of an epitaxial uranium oxide layer growing in air with a known time dependence of oxide growth.
Murataite Ceramics Doped with Lanthanides and Uranium
Authors: Stefanovsky Sergey , Yudintsev S.V. , Nikonov B.S. , Stefanovsky O.I. 
Published: April 2011

AbstractPhase composition of the murataite-based ceramics containing 10 wt.% of mixed oxides simulating rare earth/actinide (REE/An) and actinide (An) fractions of high level waste (HLW) was studied. The ceramics were prepared by melting of oxide mixtures in Pt ampoules in air at ∼1500 °C. Ceramics with REE/An and An fractions surrogates are composed of predominant murataite-type phases and minor extra phases: perovskite and crichtonite. Three murataite-related phases with five- (5C), eight- (8C), and three-fold (3C) elementary fluorite unit cell are present in these ceramics. These phases form core, intermediate zone, and rim of the murataite grains, respectively. They are predominant host phases for the rare earth elements and uranium whose concentrations are reduced in a row: M-5C>M-8C>M-3C. Appreciate fraction of Ce, Nd, and Pu may enter the perovskite phase. In the An-Gd ceramic perovskite and murataite were found to be predominant and secondary in abundance phases respectively.
Structural Investigation of δ-stabilized Plutonium Alloys Under Pressure
Authors: Faure Philippe , Klosek Vincent , Genestier Claudine , Baclet Nathalie , Heathman Steve , Normile Peter , Haire Richard 
Published: April 2011

AbstractThe mechanism responsible for the stability of the delta-phase in plutonium alloys remains poorly understood despite previous extensive studies. In the present experiments, three alloys (Pu-8at%Am, Pu-15at%Am and Pu-2at%Ga) were studied under pressure by X-ray diffraction in diamond anvil cells and revealed i) a pressure-induced softening in the compressibility of the delta-phase and ii) the presence of an intermediate γ’-phase across the δ → α’ phase transition. The softening, an anomalous behaviour, is shown to be coherent with other known unusual properties found for these alloys like NTE (Negative Thermal Expansion). Furthermore, it has been observed that the cell volume for the α’-phase formed under pressure depends on the rate of the pressure increase. This behaviour may be related to the diffusion of solute atoms to specific sites within the α’-phase unit cell. Such diffusion may also explain the α’-phase unit cell’s volume shrinkage versus time in a Pu-2at%Ga sample kept at a constant pressure.These XRD results, obtained under pressure, may be used to test first-principle calculations or other general modelling which aim at predicting the solute’s diffusion and/or self-irradiation effects in plutonium alloys.
Structural investigation of Neptunium(IV) in toxicological processes
Authors: Den Auwer Christophe , Moisy Philippe , Guillaumont Dominique , Vidaud Claude , Funke Harald , Hennig Christoph 
Published: April 2011

AbstractGeneral understanding of intramolecular interactions engaged in molecular actinide species, in other words physical chemical mechanisms that drive the affinity of chelating ligands for actinide cations still needs to be deepened. In this field, X ray Absorption Spectroscopy has been extensively used as a structural and electronic metal cation probe. Combination with more traditional spectroscopic techniques as spectrophotometry is an ideal tool for the understanding of the chelation mechanism. Metallobiomolecules are considered as elaborate inorganic complexes with well-designed metal active sites. Although the various interaction processes between essential cations to biology and proteins are widely studied, focus on the actinide family is more seldom. Actinide impact to biological cycles has been motivated by risk assessments related to the wide use of nuclear fuel sources and industrial or military applications. In particular, the interactions of these cations with the biologically active complexation sites are only partially understood.
Combinatorial Fabrication and Screening of Organic Light-Emitting Device Arrays
Authors: Shinar Joseph , Shinar Ruth 
Published: April 2011

AbstractStudies of combinatorial fabrication and screening of organic light-emitting devices (OLEDs) are reviewed. These studies include screening of luminescent materials, electron and hole transport layers, lower-gap emitting guest dopants in small molecular emitters, and electronically doped polymeric anodes. The review focuses on screening of 2-dimensional (2-d) small molecular UV/violet arrays, 1-d blue-to-red arrays, and 1-d intense white OLED libraries, and briefly describes arrays fabricated to study Förster energy transfer in guest-host OLEDs. It demonstrates that combinatorial fabrication of OLEDs has become a powerful tool for screening OLED materials and configurations, and for studying their basic properties.
Knowledge Discovery Applications in High-Throughput Polymer Characterization
Authors: Su Jing , Zapata Pedro , Meredith Carson 
Published: April 2011

AbstractThe use of combinatorial libraries for screening cell-material interactions presents a significant need for robust informatics methods capable of extracting knowledge from large, combinatorial datasets. We describe the development of local quantitative metrics based on distributions of other cells and microstructures about each individual cell. The local metrics are shown to be superior to global, summary statistics in detecting sensitive effects of surface microstructure on proliferation of MC3T3-E1 osteoblasts.
Wireless sensor array system for combinatorial screening of sensor materials
Authors: Morris William , Potyrailo Radislav 
Published: April 2011

AbstractScreening of materials arrays for their viscoelastic, gas-sorbing, and electrical properties is important for a variety of practical applications ranging from sensor to protective coatings. Complex impedance analysis of the materials arrays is an attractive approach to analyze these materials properties. We developed a wireless proximity sensor array system for combinatorial screening of these types of materials and demonstrated its applicability for sensor materials. In the developed system, sensor materials are applied onto an array of resonators and arranged for performance testing in a test chamber. Each resonator is coupled to a receiver antenna. An array of these antennas is read with a single scanning transmitter antenna or an array of transmitter antennas. Such high-throughput screening approach of sensor materials permits their evaluation in complex environments where additional wiring is not desirable or adds a prohibitively complex design.
Global Optimization of Atomic Cluster Structures Using Parallel Genetic Algorithms
Authors: Oña Ofelia , Bazterra Victor E. , Caputo María C. , Ferraro Marta B. , Facelli Julio 
Published: April 2011

AbstractThe study of the structure and physical properties of atomic clusters is an extremely active area of research due to their importance, both in fundamental science and in applied technology. For medium size atomic clusters most of the structures reported today have been obtained by local optimizations of plausible structures using DFT (Density Functional Theory) methods and/or by global optimizations in which much more approximate methods are used to calculate the cluster’s energetics. Our previous work shows that these approaches can not be reliably used to study atomic cluster structures and that approaches based on global optimization schemes are needed. In this paper, we report the implementation and application of a parallel Genetic Algorithm (GA) to predict the structure of medium size atomic clusters.
Dynamics of Director Fluctuations in Confined Liquid Crystals
Authors: Basu Sarmistha , Arroyo Edwin , Aliev Fouad 
Published: April 2011

AbstractDynamic light scattering was applied to study the influence of randomness, boundary conditions (planar-axial and homeotropic-radial) and layer thickness (at nanoscale) of 5CB and 8CB confined to cylindrical pores and filled with Aerosil particles on relaxation of director orientational fluctuations. For confined 8CB in the nematic phase two well-defined relaxation processes were observed for both axial and radial orientations of the liquid crystal. The first process is qualitatively associated with bulk-like nematic director fluctuations. The second relaxation process (with slower relaxation time than the first one) is most likely due to the fluctuations in layers nearest the wall surface. The separation between the first and the second (slow) processes is clearer for thinner layers and the amplitude of the slow process is greater for thinner layers. This suggests that the slow process is surface related relaxation. The mode due to relaxation of fluctuations of director orientation in the vicinity of the surface of Aerosil particles was observed in filled liquid crystals as well.
The Encounter Probability for Random Walkers in a Confined Space
Authors: Lavine James P. 
Published: April 2011

AbstractParticles diffusing in a confined space should encounter one another with a probability that depends on the size and dimension of the space. The present work uses pairs of random walkers on a lattice to investigate the encounter probability in one, two, and three spatial dimensions. There is an initial rapid decay of the survival-time distribution that is followed by an exponential decay in time. The characteristic time for this latter decay is strongly dependent on the model space size and scales as a power law in the size. The exponent of the power law depends on the number of spatial dimensions. For a fixed L, the exponential tail of the survival-time distribution has a similar slope when the initial separation of the two walkers is varied. The spacing between the exponential decay curves scales with the initial separation in 1-D, but not in 2-D or 3-D. In addition, the mapping of two random walkers to an equivalent single walker is explored.
Site-specific Labeling of Active Proteins with Gold Nanoparticles
Authors: Aubin-Tam Marie-Eve , Hamad-Schifferli Kimberly 
Published: April 2011

ABSTRACTCovalent conjugation of nanoparticles to proteins is challenging as proteins have numerous residues to which the nanoparticle can non-specifically adsorb. This is problematic as non-specific adsorption is known to denature the protein, altering its structure and thus compromising protein activity. We study site specific gold nanoparticle labeling of two enzymes, Ribonuclease S and Cytochrome c, with the goal of understanding conditions that minimize non-specific adsorption and optimize protein structure and activity. Ribonuclease S is a two-piece protein made of S-peptide and S-protein. 3nm gold nanoparticle is attached to a mutated cysteine residue on the S-peptide. The altered enzymatic activity of gold labeled Ribonuclease S is determined using RNA substrate with a fluorophore-quencher couple. Cytochrome c is linked to 1.5nm nanoparticles with ligands having neutral, negatively, or positively charged endgroups, through covalent attachment of gold with a specific surface cysteine residue. The labeled protein is characterized by circular dichroism spectroscopy and UV-visible absorption. For both proteins, agarose gel electrophoresis was used to determine optimal reaction stoichiometry and also probe non-specific adsorption between the nanoparticle and protein.
The Aspect Ratio Dependence of the Fluorescence of Gold Nanorods: An Experimental and Theoretical Study
Authors: Eustis Susie , El-Sayed Mostafa A. 
Published: April 2011

ABSTRACTExperimental observations and theoretical treatments are carried out for the band shape and relative intensity of the emission from gold nanorods of various aspect ratios in the range between 2.6 (1.5 theory) and 6.3 (9 theory). The calculation of the fluorescence spectra requires knowledge of the nanorod size distribution, the enhancement factors and the shape of the un-enhanced fluorescence spectrum. The comparison between the observed and calculated fluorescence band shapes is found to be good. The calculated changes in the relative intensities with aspect ratios are found to be much greater than that observed experimentally. This is due to the fact that for the observed emission of all the rods studied, nonradiative processes dominate the relaxation mechanism of the excited state, a fact that was not included in the theoretical treatments. Experimental results and theoretical treatments will be presented.
A Computational Study on CO Adsorption onto SnO2 Small Grains
Authors: Mazzone Anna M. , Morandi V. 
Published: April 2011

ABSTRACTThe focus of this study is on the adsorption properties of the nanocrystalline materials and SnO2 has been chosen as the appropriate example. Therefore model structures consisting on SnO2 grains with a rutile lattice and a size comparable with the experimental ones have been considered and the adsorbed system is generated by depositing a CO molecule above a tin or oxygen atom on the grain	surface. The calculations, based on semi-empirical Hartree-Fock and scattering theories, illustrate the dependence of the binding and adsorption energies of grains on their size and shape and show the effects of these energies on the grain conductance.
Iron Oxide Composite Nanoparticles and Sensing Properties
Authors: Wang Lingyan , Shi Xiajing , Mahs Sakienah , Choi Jeongku , Sarup Karan , Wang Guannan Roger , Luo Jin , Lu Susan , Zhong Chuan-Jian 
Published: April 2011

ABSTRACTThis paper reports findings of an investigation of the synthesis of monolayer-capped iron oxide and core (iron oxide)-shell (gold) nanocomposite and their assembly towards thin films as sensing materials. Pre-synthesized and size-defined iron oxide nanoparticles were used as seeding materials for the reduction of gold precursors, which was shown to be effective for coating the iron oxide cores with gold shells (Fe oxide@Au). The unique aspect of our synthesis is the formation of Fe oxide@Au core-shell nanoparticles with controllable surface properties. By controlling the reaction temperatures and manipulating the capping agent properties and solution compositions, the size, shape, composition, and monodispersity can be tailored. The core-shell nanoparticles were shown to form molecularly-mediated thin film assemblies using molecular mediators. The sensing properties of the nanostructures on piezoelectric devices were examined for the detection of volatile organic compounds. The preliminary results have provided important insights into the design of core-shell nanocomposites as sensing materials.
Analytical TEM Observation of Gold Nano-Particles on Cerium Oxide
Authors: Akita Tomoki , Tanaka Koji , Kohyama Masanori , Haruta Masatake 
Published: April 2011

ABSTRACTThe structure of Au nano-particles supported on CeO2 was investigated by using an analytical transmission electron microscope (TEM). The shape change of Au particles was observed during TEM observation, such as shrinking down to a mono-atomic layer on the CeO2 substrate. The electron beam irradiation experiment revealed that the shape change of Au particles is concerning with the oxidation state or the density of oxygen vacancies of CeO2 substrate where the rapid desorption and adsorption of oxygen occurs. It was also found that the reduction by strong electron beam irradiation and subsequent oxidation generate the decoration of Au particles by cerium oxide.
Electrosynthesis of Magnetostrictive Nanosensor Array
Authors: Li Suiqiong , Orona Lisa , Fu Liling , Cheng Z.-Y. 
Published: April 2011

ABSTRACTMagnetostrictive nanobars as sensor platform were induced. Based on the resonance behavior of strips made from thin films, it is identified that the amorphous Fe-B alloy is a good candidate for fabricating high performance sensor platform. The fabrication process of amorphous Fe-B nanobars using electrochemical deposition is reported. The magnetization hysteresis loop of Fe-B nanobars with the diameters of 50, 100 and 200 nm, respectively, was characterized. It is found that, for all nanobars, the coercive field measured along length direction is smaller than the coercive field measured perpendicular to length direction. The physics behind the phenomena is discussed.
Preparation and Characterization of Thin Films by Pulsed Laser Deposition for NOx gas Sensor
Authors: Bhuiyan Md. Mosharraf Hossain , Ueda Tsuyoshi , Shinguu Hiroshi , Ikegami Tomoaki , Ebihara Kenji 
Published: April 2011

ABSTRACTGas sensors based on WO3 thin films doped with platinum (Pt) or palladium (Pd) were prepared by KrF excimer pulsed laser deposition method combined with dc sputtering. The films were deposited on silicon, quartz and Al2O3 sensor substrate with Pt interdigital electrodes at various substrate temperatures from 300°C to 500 °C, and oxygen pressures from 100 mTorr to 300 m Torr, respectively during the deposition. The morphology and structure of the films were examined by AFM and XRD. The sensor property of the WO3−x thin films was measured by the two terminal resistance method at operating temperatures of 25 °C to 400 °C. The sensitivity of the WO3 thin film gas sensors with doping (platinum or palladium) was found to be higher than that of undoped WO3 thin films gas sensors. The sensitivity of the pt doped WO3 films to different concentration of NO gas was examined and the sensitivity was found to be increased with increasing NO gas concentration.