bluuebunny/crossref_metadata_2025 huggingface dataset:
Distributed charge/discharge control of energy storages in a renewable‐energy‐based DC micro‐grid
Authors: Eghtedarpour Navid , Farjah Ebrahim
Published: August 2013

This paper proposes a control strategy for the stable operation of the micro‐grid dluring different operating modes while providing the DC voltage control and well quality DC‐Ioads supply. The proposed method adapts the battery energy storage system (BESS) to employ the same control architecture for grid‐connected mode as well as the islanded operation with no need for knowing the micro‐grid operating mode or switching between the corresponding control architectures. Furthermore, the control system presents effective charging of the battery in the micro‐grid. When the system is grid connected and during normal operation, AC grid converter balances active power to ensure a constant DC voltage while the battery has the option to store energy for necessary usage. In order to achieve the system operation under islanding conditions, a coordinated strategy for the BESS, RES and load management including load shedding and considering battery state‐of‐charge (SoC) and battery power limitation is proposed. Seamless transition of the battery converter between charging and discharging, and that of grid side converter between rectification and inversion are ensured for different grid operating modes by the proposed control method. MATLAB/SIMULINK simulations and experimental results are provided to validate the effectiveness of the proposed battery control system.
Key issues of wind capacity integration in congested areas of the Taiwan power system
Authors: Chen Chun‐Lung
Published: August 2013

As wind power penetrations increase in isolated power systems, it is very important to understand how variations in wind plant outputs affect the operation of the multi‐area isolated system on a day‐to‐day basis and what the associated costs are. Production cost models need to be further advanced to adequately simulate utility operations and unit commitment (UC) of generation in response to higher wind penetrations. In this study, the dynamic programming (DP) algorithm is extended to facilitate economic sharing of generation and reserve across areas and to coordinate wind and thermal generation scheduling in isolated power systems with large integration of wind capacity. Five heuristic strategies are incorporated in the DP algorithm to improve solution quality and performance. Four important issues of wind capacity integration in congested areas of the Taiwan power system are also investigated and discussed by using the developed UC software. Numerical experiments are included to understand wind generator capacity in production cost analysis and to illustrate the effect of transmission capacity limits on wind power penetration level in each area.
An Expedient Process for the Synthesis of 2-(N-arylamino)benzaldehydes from 2-Hydroxybenzaldehydes via Smiles Rearrangement
Authors: Saeidian Hamid , Mirjafary Zohreh , Abdolmaleki Ilnaz , Moradnia Farzaneh
Published: August 2013

This paper describes an efficient Smiles rearrangement process for the synthesis of 2-(N-arylamino)benzaldehyde derivatives with reasonable yields. A mechanism is proposed for the reaction course.
Improved interfacial and electrical properties of GaAs metal-oxide-semiconductor capacitors with HfTiON as gate dielectric and TaON as passivation interlayer
Authors: Wang L. S. , Xu J. P. , Zhu S. Y. , Huang Y. , Lai P. T.
Published: August 2013

The interfacial and electrical properties of sputtered HfTiON on sulfur-passivated GaAs with or without TaON as interfacial passivation layer (IPL) are investigated. Experimental results show that the GaAs metal-oxide-semiconductor capacitor with HfTiON/TaON stacked gate dielectric annealed at 600 °C exhibits low interface-state density (1.0 × 1012 cm−2 eV−1), small gate leakage current (7.3 × 10−5 A cm−2 at Vg = Vfb + 1 V), small capacitance equivalent thickness (1.65 nm), and large equivalent dielectric constant (26.2). The involved mechanisms lie in the fact that the TaON IPL can effectively block the diffusions of Hf, Ti, and O towards GaAs surface and suppress the formation of interfacial As-As bonds, Ga-/As-oxides, thus unpinning the Femi level at the TaON/GaAs interface and improving the interface quality and electrical properties of the device.
Mimicking photoisomerisation of azo-materials by a force field switch derived from nonadiabatic ab initio simulations: Application to photoswitchable helical foldamers in solution
Authors: Böckmann Marcus , Braun Sebastian , Doltsinis Nikos L. , Marx Dominik
Published: August 2013

A force field to induce isomerisation of photoswitchable azobenzene groups embedded in molecular materials has been developed in the framework of force field molecular dynamics simulations. A molecular mechanics switching potential has been tuned so as to reproduce both the correct photoisomerisation timescale and mechanism that has been generated by reference nonadiabatic ab initio molecular dynamics. As a first application, we present a force field molecular dynamics study of a prototype photoswitchable foldamer in acetonitrile as solvent. Our analyses reveal that the photoisomerisation of the azobenzene unit embedded in the foldamer occurs via the so-called NN-twist mechanism, and that there exist several distinct unfolding channels for the helix that could be exploited in novel applications of photoresponsive materials.
Rotational diffusion in concentrated platelet systems measured with X-ray photon correlation spectroscopy
Authors: Holmqvist P. , Meester V. , Westermeier F. , Kleshchanok D.
Published: August 2013

Using X-ray photon correlation spectroscopy we have measured the rotational modes of concentrated charged gibbsite platelets in the isotropic regime. This has been done by analyzing the data qualitatively using available theories for non-interacting systems. The relaxation spectra do not follow the same pattern as for spherical particles at larger wave vectors. It will be shown that this deviation from the behavior of spherical systems arises from the influence of the rotational modes. In addition, in the isotropic state a pre-transitional peak in the static q-dependent intensity at large q values is discussed. We suggest that this peak originates from a strong local alignment between platelets before the actual phase transition takes place.
Magnetic state of the manganite nanocompound La0.8Mn1.04O3.5
Authors: Sirenko V. A. , Rykova A. I. , Eremenko A. V.
Published: August 2013

Published data on the temperature dependences M(T) of the magnetization of different manganites and the compound La0.8Mn1.04O3.5 are compared. The results of measurements with cooling in a magnetic field and for zero field are the same only above the splitting temperature T*. This temperature depends on the magnetic field strength at which the M(T) curves are measured. The relative change in T*, which is described by a power-law function with an exponent less than 1, as is typical of spin glass, is compared for all the ceramic samples. La0.8Mn1.04O3.5, which consists of particles with sizes of about 70 nm, is an exception. The behavior of [T*(H)-T*(0)]/T*(H) for this manganite is similar to that for a supermagnet with weak interactions.
Planar elliptical solid immersion lens based on a Cartesian oval
Authors: McCloskey D. , Donegan J. F.
Published: August 2013

We report on the design of a single element planar solid immersion lens which is theoretically capable of confining light to a focal spot with full width half maximum of 0.29 λ (154 nm at λ = 532 nm) and achieving an effective numerical aperture of 1.732. Devices are fabricated and initial optical characterization is performed using a far-field imaging technique providing a lower bound on the numerical aperture of 0.7. Experimental results compare well with two dimensional finite element method simulations. Devices can be mass produced using ultraviolet lithography and produce focal volumes lower than expensive microscope objectives.
Attainable superheating of liquefied gases and their solutions (Review Article)
Authors: Baidakov V. G.
Published: August 2013

This review addresses the kinetics of spontaneous boiling-up of liquefied gases and their solutions. It discusses the theories of thermal and quantum nucleation in metastable liquids. The experimental methods for studying the nucleation kinetics are outlined. The experimental data on the attainable superheating temperature for cryogenic liquids and solutions of liquefied gases are presented in a wide range of pressures, including negative ones. The properties of new-phase nuclei near the boundary of attainable superheating are discussed. The kinetics of initiated and heterogeneous nucleation is considered. The experimental data on detection of quantum tunneling of nuclei are presented. The experimental data are compared with the theories of thermal and quantum nucleation.
Strain evolution in GaN nanowires: From free-surface objects to coalesced templates
Authors: Hugues M. , Shields P. A. , Sacconi F. , Mexis M. , Auf der Maur M. , Cooke M. , Dineen M. , Di Carlo A. , Allsopp D. W. E. , Zúñiga-Pérez J.
Published: August 2013

Top-down fabricated GaN nanowires, 250 nm in diameter and with various heights, have been used to experimentally determine the evolution of strain along the vertical direction of 1-dimensional objects. X-ray diffraction and photoluminescence techniques have been used to obtain the strain profile inside the nanowires from their base to their top facet for both initial compressive and tensile strains. The relaxation behaviors derived from optical and structural characterizations perfectly match the numerical results of calculations based on a continuous media approach. By monitoring the elastic relaxation enabled by the lateral free-surfaces, the height from which the nanowires can be considered strain-free has been estimated. Based on this result, NWs sufficiently high to be strain-free have been coalesced to form a continuous GaN layer. X-ray diffraction, photoluminescence, and cathodoluminescence clearly show that despite the initial strain-free nanowires template, the final GaN layer is strained.
Piezoelectric bimorph-based scanner in the tip-scan mode for high speed atomic force microscope
Authors: Zhao Jianyong , Gong Weitao , Cai Wei , Shang Guangyi
Published: August 2013

A piezoelectric bimorph-based scanner operating in tip-scan mode for high speed atomic force microscope (AFM) is first presented. The free end of the bimorph is used for fixing an AFM cantilever probe and the other one is mounted on the AFM head. The sample is placed on the top of a piezoelectric tube scanner. High speed scan is performed with the bimorph that vibrates at the resonant frequency, while slow scanning is carried out by the tube scanner. The design and performance of the scanner is discussed and given in detailed. Combined with a commercially available data acquisition system, a high speed AFM has been built successfully. By real-time observing the deformation of the pores on the surface of a commercial piezoelectric lead zirconate titanate (PZT-5) ceramics under electric field, the dynamic imaging capability of the AFM is demonstrated. The results show that the notable advantage of the AFM is that dynamic process of the sample with large dimensions can be easily investigated. In addition, this design could provide a way to study a sample in real time under the given experimental condition, such as under an external electric field, on a heating stage, or in a liquid cell.
Non-Markovian near-infrared Q branch of HCl diluted in liquid Ar
Authors: Padilla Antonio , Pérez Justo
Published: August 2013

By using a non-Markovian spectral theory based in the Kubo cumulant expansion technique, we have qualitatively studied the infrared Q branch observed in the fundamental absorption band of HCl diluted in liquid Ar. The statistical parameters of the anisotropic interaction present in this spectral theory were calculated by means of molecular dynamics techniques, and found that the values of the anisotropic correlation times are significantly greater (by a factor of two) than those previously obtained by fitting procedures or microscopic cell models. This fact is decisive for the observation in the theoretical spectral band of a central Q resonance which is absent in the abundant previous researches carried out with the usual theories based in Kubo cumulant expansion techniques. Although the theory used in this work only allows a qualitative study of the Q branch, we can employ it to study the unknown characteristics of the Q resonance which are difficult to obtain with the quantum simulation techniques recently developed. For example, in this study we have found that the Q branch is basically a non-Markovian (or memory) effect produced by the spectral line interferences, where the PR interferential profile basically determines the Q branch spectral shape. Furthermore, we have found that the Q resonance is principally generated by the first rotational states of the first two vibrational levels, those more affected by the action of the dissolvent.
Tuning the ferromagnetic transition temperature in La0.5Sr0.5CoO3 thin films
Authors: Manna Kaustuv , Samal D. , Elizabeth Suja , Anil kumar P. S.
Published: August 2013

Epitaxial La0.5Sr0.5CoO3 (LSCO) thin films are grown on LaAlO3 (100) and SrTiO3 (100) substrates by pulsed laser ablation. By tuning the growth parameters, we are able to enhance the ferromagnetic transition temperature (TC) up to 262 K as evident from ac susceptibility, dc magnetization, and resistivity measurements. The magnitude of TC is the same as that for the bulk stoichiometric LSCO illustrating the high quality of the grown films. Detailed structural analysis clearly reveals that the induced strain in the LSCO film has no role behind this enhancement; in fact, the determining factor is the oxygen stoichiometry. The films also exhibit ageing effect as the TC decreases with time. This is considered in terms of gradual change in the oxygen stoichiometry through diffusion process as the time progresses.
Fluorescent light source with continuously tunable polarization via modification of molecular orientation
Authors: Joo Suk-Hwan , Kim Jang-Kyum , Song Jang-Kun
Published: August 2013

We demonstrate that the polarization of emitted light from a photoluminescent cholesteric liquid crystals (PL-CLC) cell with well-designed electrodes can be electrically switchable among the linearly polarized, circularly polarized, and un-polarized states. Moreover, the degree of polarization can be continuously tunable from zero to the maximum degree of polarization of emitted light from the cell, that is, from 0 to 0.8 and 0 to 0.45 for circularly and linearly polarized light, respectively. The degrees of circular and linear polarizations are mainly governed by the perfectness of the CLC photonic bandgap, and the Sμ order parameter of the PL molecules, respectively. By continuously electrically manipulating the molecular ordering between the planar helicoidal state with a perfect photonic bandgap, the focal conic state with a macroscopic random ordering, and the unwound state with a highly uniaxial ordering, one can selectively produce those types of polarized emitted light with any degree of polarization. The wavelength dependency of the degree of polarization significantly varies depending on the types of polarization and LC alignment states.
Modeling fibril fragmentation in real-time
Authors: Tan Pengzhen , Hong Liu
Published: August 2013

During the application of the mass-action-equation models to the study of amyloid fiber formation, time-consuming numerical calculations constitute a major bottleneck. To conquer this difficulty, here an alternative efficient method is introduced for the fragmentation-only model. It includes two basic steps: (1) simulate close-formed time-evolutionary equations for the number concentration P(t) derived from the moment-closure method; (2) reconstruct the detailed fiber length distribution based on the knowledge of moments obtained in the first step. Compared to direct calculation, our method speeds up the performance by at least 10 000 times (from days to seconds). The accuracy is also satisfactory if suitable functions for the approximate fibril length distribution are taken. Further application to the sonication studies on PI264-b-PFS48 micelles performed by Guerin et al. confirms our method is very promising for the real-time analysis of the experiments on fibril fragmentation.
The effect of weak collisionality on damped modes and its contribution to linear mode coupling in gyrokinetic simulation
Authors: Hilscher P. P. , Imadera K. , Li J. Q. , Kishimoto Y.
Published: August 2013

We revisit the characteristics of stable, damped modes originating from the Landau damping by employing a discretized gyrokinetic Vlasov simulation and also eigenvalue analysis in an unsheared slab geometry. By comparing results between gyrokinetic simulation and an eigenvalue analysis, we found that there exists a critical collisionality βc⋆ at which the Case-van Kampen (CvK) modes are damped down to the analytically estimated Landau damping rate and an eigenmode consistent with Landau's theory emerges. Consequently, the recurrence phenomenon disappears so that the Landau damping can be properly reproduced. The critical collisionality βc⋆ depends on the resolution in velocity space; i.e., a higher (lower) resolution requires a lower (higher) collisionality, while tends to zero (βc⋆→0) as Δv→0. It is found through a reduced model that even in the collisionless case with marginally stable CvK modes, the linear mode coupling between unstable and stable/damped components through a tertiary mode and the resultant energy transfer can be properly calculated such that the stable/damped mode persists as an eigenstate.
Increased photo-stability of quantum dots in segregated bilayer films
Authors: Shcherbatyuk G. V. , Talbot P. , Mandal J. , Krejci A. J. , Dickerson J. H. , Ghosh S.
Published: August 2013

We report a comparative study of photo-stability of CdSe/ZnS quantum dots (QDs) in a variety of thin film samples. These include electrophoretically deposited single and differently sized segregated bilayer films and self-assembled mixed-sized films. Our studies follow static and dynamic QD photoluminescence over prolonged periods of photo-excitation and find that compared to both single-sized and mixed-sized films, the segregated bilayer samples exhibit highest photo-stability. These films show a QD emission quench rate of ∼2.5 times slower than the others and have almost negligible spectral shifts (<2 nm). Time-resolved measurements indicate very short inter-layer energy transfer (ET) time for the acceptor QDs in the bilayer, coupled with low ET efficiency for the donor dots. Further analysis reveals a complex interplay of intra- and inter-ensemble ET, with ET rates that have disparate spectral dependence between the mixed and bilayer films, and we conclude that this leads to the enhanced photo stability in the latter. Our findings provide a vital clue to the optimal design of QD based energy-harvesting structures.
Boron-oxygen defect imaging in p-type Czochralski silicon
Authors: Lim S. Y. , Rougieux F. E. , Macdonald D.
Published: August 2013

In this work, we demonstrate an accurate method for determining the effective boron-oxygen (BO) related defect density on Czochralski-grown silicon wafers using photoluminescence imaging. Furthermore, by combining a recently developed dopant density imaging technique and microscopic Fourier transform infrared spectroscopy measurements of the local interstitial oxygen concentration [Oi], the BO-related defect density, [Oi], and the boron dopant density from the same wafer were determined, all with a spatial resolution of 160 μm. The results clearly confirm the established dependencies of the BO-related defect density on [Oi] and the boron dopant density and demonstrate a powerful technique for studying this important defect.
Computational studies of water exchange around aqueous Li+ with polarizable potential models
Authors: Dang Liem X. , Annapureddy Harsha V. R.
Published: August 2013

To enhance our understanding of the mechanism of water-exchange around aqueous Li+, we carried out a systematic study on this system using molecular dynamics simulations with polarizable potential models. The mechanistic properties associated with the water-exchange process, such as potentials of mean force, time dependent transmission coefficients, and the corresponding rate constants, were examined using transition rate theory, the reactive flux method, and Grote-Hynes treatments of the dynamic response of the solvent. We compared the computed rate theory results with results from previous corresponding studies in which classical non-polarizable force fields were used. Our computed barrier heights for water exchange are significantly larger than those obtained using classical non-polarizable force fields. We also studied the effect of pressure on water-exchange rates and the corresponding activation volume. Our computed rate results for water exchange increase with pressure; therefore, a small negative activation volume is observed.
Stability and bifurcation diagram of Boussinesq thermal convection in a moderately rotating spherical shell allowing rotation of the inner sphere
Authors: Kimura Keiji , Takehiro Shin-ichi , Yamada Michio
Published: August 2013

We investigate the stability and bifurcation of Boussinesq thermal convection in a moderately rotating spherical shell, with the inner sphere free to rotate as a solid body due to the viscous torque of the fluid. The ratio of the inner and outer radii of the spheres and the Prandtl number are fixed to 0.4 and 1, respectively. The Taylor number is varied from 522 to 5002 and the Rayleigh number from 1500 to 10 000. In this parameter range, the finite-amplitude traveling wave solutions, which have four-fold symmetry in the azimuthal direction, bifurcate supercritically at the critical points. The inner sphere rotates in the prograde direction due to the viscous torque of the fluid when the rotation rate is small while it rotates in the retrograde direction when the rotation rate is large. However, the stable region of these traveling wave solutions is quantitatively similar to that in the co-rotating system where the inner and outer spheres rotate with the same angular velocity. The structures of convective motions of these solutions such as the radial component of velocity are quantitatively similar to those in the co-rotating system, but the structure of mean zonal flows is effectively changed by the inner sphere rotation.
A hybrid subgrid-scale model constrained by Reynolds stress
Authors: Verma Aman , Park Noma , Mahesh Krishnan
Published: August 2013

A novel constrained formulation for the dynamic subgrid-scale model for large eddy simulation (LES) is proposed. An externally prescribed Reynolds stress is used as the constraint and is imposed in the near-wall region of wall-bounded flows. However, unlike conventional zonal approaches, Reynolds stress is not imposed as the solution, but used as a constraint on the subgrid-scale stress so that the computed Reynolds stress closely matches the prescribed one only in the mean sense. In the absence of an ideal wall model or adequate near-wall resolution, a LES solution at coarse resolution is expected to be erroneous very near the wall while giving reasonable predictions away from the wall. The Reynolds stress constraint is limited to the region where the LES solution is expected to be erroneous. The Germano-identity error is used as an indicator of LES quality such that the Reynolds stress constraint is activated only where the Germano-identity error exceeds a certain threshold. The proposed model is applied to LES of turbulent channel flow at various Reynolds numbers and grid resolutions to obtain significant improvement over the dynamic Smagorinsky model, especially at coarse resolutions. This constrained formulation can be extended to incorporate constraints on the mean of other flow quantities.
Universal fractional map and cascade of bifurcations type attractors
Authors: Edelman M.
Published: August 2013

We modified the way in which the Universal Map is obtained in the regular dynamics to derive the Universal α-Family of Maps depending on a single parameter α>0, which is the order of the fractional derivative in the nonlinear fractional differential equation describing a system experiencing periodic kicks. We consider two particular α-families corresponding to the Standard and Logistic Maps. For fractional α<2 in the area of parameter values of the transition through the period doubling cascade of bifurcations from regular to chaotic motion in regular dynamics corresponding fractional systems demonstrate a new type of attractors—cascade of bifurcations type trajectories.
A multichannel acoustically driven microfluidic chip to study particle-cell interactions
Authors: Wang Xue-Yan , Fillafer Christian , Pichl Clara , Deinhammer Stephanie , Hofer-Warbinek Renate , Wirth Michael , Gabor Franz
Published: August 2013

Microfluidic devices have emerged as important tools for experimental physiology. They allow to study the effects of hydrodynamic flow on physiological and pathophysiological processes, e.g., in the circulatory system of the body. Such dynamic in vitro test systems are essential in order to address fundamental problems in drug delivery and targeted imaging, such as the binding of particles to cells under flow. In the present work an acoustically driven microfluidic platform is presented in which four miniature flow channels can be operated in parallel at distinct flow velocities with only slight inter-experimental variations. The device can accommodate various channel architectures and is fully compatible with cell culture as well as microscopy. Moreover, the flow channels can be readily separated from the surface acoustic wave pumps and subsequently channel-associated luminescence, absorbance, and/or fluorescence can be determined with a standard microplate reader. In order to create artificial blood vessels, different coatings were evaluated for the cultivation of endothelial cells in the microchannels. It was found that 0.01% fibronectin is the most suitable coating for growth of endothelial monolayers. Finally, the microfluidic system was used to study the binding of 1 μm polystyrene microspheres to three different types of endothelial cell monolayers (HUVEC, HUVECtert, HMEC-1) at different average shear rates. It demonstrated that average shear rates between 0.5 s−1 and 2.25 s−1 exert no significant effect on cytoadhesion of particles to all three types of endothelial monolayers. In conclusion, the multichannel microfluidic platform is a promising device to study the impact of hydrodynamic forces on cell physiology and binding of drug carriers to endothelium.
Microfluidic fabrication of polymeric core-shell microspheres for controlled release applications
Authors: Kong Tiantian , Wu Jun , Yeung Kelvin Wai Kwok , To Michael Kai Tsun , Shum Ho Cheung , Wang Liqiu
Published: August 2013

We report a facile and robust microfluidic method to fabricate polymeric core-shell microspheres as delivery vehicles for biomedical applications. The characteristics of core-shell microspheres can be precisely and easily tuned by manipulating the microfluidic double emulsion templates. The addition of a shell can significantly improve the versatility as well as functionality of these microspheres as delivery vehicles. We demonstrate that the nature of the shell material plays an important role in the properties of the core-shell delivery vehicles. The release kinetics is significantly influenced by the material of the shell and other characteristics such as the thickness. For example, by adding a poly(lactic-co-glycolic acid) (PLGA) shell to an alginate core, the encapsulation efficiency is enhanced and undesired leakage of hydrophilic actives is prevented. By contrast, adding an alginate shell to PLGA core can lead to a reduction of the initial release rate, thus extending the release period of hydrophobic actives. Microfluidic fabrication enables the generation of precisely controlled core-shell microspheres with a narrow size distribution, which enables the investigation of the relationship between the release kinetics of these microspheres and their characteristics. The approach of using core-shell particles as delivery vehicles creates new opportunities to customize the release kinetics of active ingredients.
High-bandwidth polarimeter for a high density, accelerated spheromak
Authors: Carle Patrick J. F. , Howard Stephen , Morelli Jordan
Published: August 2013

A three-beam heterodyne polarimeter has been built to diagnose the PI-1 plasma injector at General Fusion, Inc. The polarimeter measures plasma density and Faraday rotation, which can provide estimates of magnetic field magnitude and direction. Two important calibration steps are required for the polarimeter to produce reasonable Faraday rotation signals. Beam polarization ellipticity must be measured to ensure there is a linear Faraday rotation response. In addition, the two beams travelling through the plasma must be collinear to reduce error due to differences in plasma density. Once calibrated, the Faraday rotation signals are in much better agreement with other diagnostics. For a null signal, the Faraday rotation measurement noise floor is 0.1° at 0.5 MHz bandwidth. Comparing preliminary spheromak Faraday rotation measurements to a model, the maximum error is about 0.3° at 0.5 MHz bandwidth, which is primarily due to electrical noise during the injector's capacitor discharge and limitations of the model. At a bandwidth of 0.5 MHz, the polarimeter has an axial resolution between 6 cm and 30 cm depending on the speed of the spheromak, which varies between 30 km/s and 150 km/s. The spheromak length ranges from 0.75 m to 2 m. Additional polarimeter chords will be added in future upgrades.
Sequential color change on copper surfaces via micro/nano structure modification induced by a picosecond laser
Authors: Fan Peixun , Zhong Minlin , Li Lin , Schmitz Patrick , Lin Cheng , Long Jiangyou , Zhang Hongjun
Published: August 2013

A surface micro/nano structuring technique was demonstrated for colorizing metal surfaces with a picosecond laser. Sequential color change from black to pink was realized on copper surfaces by simply changing the ps laser scanning speeds. Systematic analyses on the spectral response and microstructure characteristics were reported. The spectrum shifting effect corresponding to color change was explained through the surface plasmon resonance mechanism. The current research shows that a high power and high repetition rate ps laser is capable of structuring metal surfaces with a speed up to several meters per second, presenting an efficient and affordable candidate for practical industrial applications.
Response of copper to shock-wave loading at temperatures up to the melting point
Authors: Zaretsky E. B. , Kanel G. I.
Published: August 2013

The evolution of elastic-plastic shock waves as a function of the propagation distance has been studied in 99.999% purity polycrystalline copper over the 300 to 1353 K temperature range. The free surface velocity histories of shock-loaded samples 0.1 to 2.0 mm in thickness have been recorded using the velocity interferometer. The measured decay of the elastic precursor waves has been converted into relationships between the shear stress at Hugoniot elastic limit and the initial plastic strain rate. Independently of the temperature, the initial densities of mobile dislocations in a range of 2.5×106 cm−2 to 5×108 cm−2 are required to provide observed initial strain rates varied from 2.3×103 s−1 to 2×106 s−1. Above 1100 K, the shape of the elastic precursor wave changes with the appearance of a sharp spike at its front part. This change is treated in terms of nucleation and multiplication of mobile dislocations. An analysis of the rise times of the plastic shock waves has shown that for the same level of shear stress, the plastic strain rates after a 2% compressive strain increase with respect to those just behind the elastic precursor front by a factor of 300 at 300 K and by a factor of 30 at 1353 K.
Orientation and position of cylindrical-shaped gold nanoparticles at liquid-liquid interfaces
Authors: Lee Chiwon , Lee Won Bo , Kang Taewook
Published: August 2013

The equilibrium orientation and position of cylindrical-shaped gold nanoparticles (GNPs) at an oil/water interface is studied by varying its geometry and surface property and the oil/water interfacial tension. Numerical calculation reveals that most of the particles studied prefer one of two states of orientation at the interface: either 0° or 90° irrespective of the geometry, the surface property, and the oil/water interfacial tension. In the case of cylindrical-shaped GNPs having a weakly hydrophobic side surface, an increase in oil/water interfacial tension leads to a remarkable change in the orientation and position of the particles depending on the geometry.
Microstructure and ferroelectric properties of epitaxial cation ordered PbSc0.5Ta0.5O3 thin films grown on electroded and buffered Si(100)
Authors: Chopra Anuj , Pantel Daniel , Kim Yunseok , Alexe Marin , Hesse Dietrich
Published: August 2013

Epitaxial PbSc0.5Ta0.5O3 (001) films with an epitaxial LaNiO3 bottom electrode were deposited on CeO2/yttria-stabilized zirconia-buffered Si (100) substrates. Crystal orientation, in-plane and out-of-plane lattice parameters, surface morphology, and microstructure were analyzed by X-ray diffraction, X-ray reciprocal lattice mapping measurements, atomic force microscopy, and transmission electron microscopy, respectively. XRD superstructure reflections indicate that the films are cation ordered. Polarization-field and switching current-voltage hysteresis curves were measured at room temperature. The measured spontaneous polarization Ps, remnant polarization Pr, and coercive voltage Vc were found to be 14 μC/cm2, 4 μC/cm2, and 1.1 V, respectively, at room temperature. Furthermore, field as well as frequency dependence of the dielectric constant were measured at room temperature. Piezoelectric measurements performed on these PST films showed a sharp non-linearity, which is attributed to the possibility of field induced phase transition and/or percolation of polar nano regions.
Retention and entrainment effects: Experiments and theory for porous spheres settling in sharply stratified fluids
Authors: Camassa R. , Khatri S. , McLaughlin R. M. , Prairie J. C. , White B. L. , Yu S.
Published: August 2013

We present an experimental study of single porous spheres settling in a near two-layer ambient density fluid. Data are compared with a first-principle model based on diffusive processes. The model correctly predicts accelerations of the sphere but does not capture the retention time at the density transition quantitatively. Entrainment of lighter fluid through a shell encapsulating the sphere is included in this model empirically. With this parametrization, which exhibits a power law dependence on Reynolds numbers, retention times are accurately captured. Extrapolating from our experimental data, model predictions are presented.
Highly efficient, dual state emission from an organic semiconductor
Authors: Reineke Sebastian , Seidler Nico , Yost Shane R. , Prins Ferry , Tisdale William A. , Baldo Marc A.
Published: August 2013

We report highly efficient, simultaneous fluorescence and phosphorescence (74% yield) at room temperature from a single molecule ensemble of (BzP)PB [N,N′-bis(4-benzoyl-phenyl)-N,N′-diphenyl-benzidine] dispersed into a polymer host. The slow phosphorescence (208 ms lifetime) is very efficient (50%) at room temperature and only possible because the non-radiative rate for the triplet state is extremely low (2.4 × 100 s−1). The ability of an organic molecule to function as an efficient dual state emitter at room temperature is unusual and enables a wide range of applications including the use as broadband down-conversion emitters, optical sensors and attenuators, exciton probes, and spin-independent intermediates for Förster resonant energy transfer.
Time-resolved measurement of free carrier absorption, diffusivity, and internal quantum efficiency in silicon
Authors: Meitzner Jet , Moore Frederick G. , Tillotson Brock M. , Kevan Stephen D. , Richmond Geraldine L.
Published: August 2013

We demonstrate an innovative pump-probe technique for the determination of free carrier absorption, diffusivity, and internal quantum efficiency in Si. The internal quantum efficiencies for excitation by 800 nm, 400 nm, and 267 nm light are found to be 1.00, 1.00, and 1.25, respectively. The free carrier absorption cross section at 1510 nm is determined to be σFCA = 1.69 × 10−17 cm2 and an increased value is observed for high carrier concentrations. A model for free carrier diffusion and absorption is used to extract the relationship between σFCA and carrier concentration.
Parallel array of YBa2Cu3O7−δ superconducting Josephson vortex-flow transistors with high current gains
Authors: Chesca Boris , John Daniel , Kemp Matthew , Brown Jeffrey , Mellor Christopher
Published: August 2013

We have developed a Josephson vortex-flow transistor based on a parallel array of 440 YBa2Cu3O7−δ bicrystal grain boundary Josephson junctions. The array's critical current Ic was measured as a function of the control current Ictrl through a control line that is inductively coupled to the array. The device has a highly asymmetric Ic(Ictrl) curve with several regions where a switching behaviour is observed characterized by a maximum current gain gmax = ∂Ic/∂Ictrl of 19 and a significant dynamic range of 20 μA at 77 K. In the range 4.7–92 K gmax versus temperature is non-monotonic with a maximum recorded at 77 K.
Magnetoelectric effect at thickness shear mode in ferrite-piezoelectric bilayer
Authors: Bichurin M. I. , Petrov R. V. , Petrov V. M.
Published: August 2013

This manuscript discusses first observation of magnetoelectric (ME) coupling at thickness shear modes in a magnetostrictive-piezoelectric bilayer. The measured value of magnetoelectric voltage coefficient is optimized by adjusting the geometry of layers. Theoretical estimates for the bilayer of Y-cut langatate and yttrium iron garnet are in satisfactory agreement with data. The obtained results are expected to facilitate observation of enhanced ME coupling at overlapping of electromechanical and magnetic resonance due to energy transfer between spin waves and phonons.
Numerical simulation of torus breakdown to chaos in an atmospheric-pressure dielectric barrier discharge
Authors: Zhang J. , Wang Y. H. , Wang D. Z.
Published: August 2013

Understanding the routes to chaos occurring in atmospheric-pressure dielectric barrier discharge systems by changing controlling parameters is very important to predict and control the dynamical behaviors. In this paper, a route of a quasiperiodic torus to chaos via the strange nonchaotic attractor is observed in an atmospheric-pressure dielectric barrier discharge driven by triangle-wave voltage. By increasing the driving frequency, the discharge system first bifurcates to a quasiperiodic torus from a stable single periodic state, and then torus and phase-locking periodic state appear and disappear alternately. In the meantime, the torus becomes increasingly wrinkling and stretching, and gradually approaches a fractal structure with the nonpositive largest Lyapunov exponent, i.e., a strange nonchaotic attractor. After that, the discharge system enters into chaotic state. If the driving frequency is further increased, another well known route of period-doubling bifurcation to chaos is also observed.
Structured-illumination photoacoustic Doppler flowmetry of axial flow in homogeneous scattering media
Authors: Zhang Ruiying , Yao Junjie , Maslov Konstantin I. , Wang Lihong V.
Published: August 2013

We propose a method for photoacoustic flow measurement based on the Doppler effect from a flowing homogeneous medium. Excited by spatially modulated laser pulses, the flowing medium induces a Doppler frequency shift in the received photoacoustic signals. The frequency shift is proportional to the component of the flow speed projected onto the acoustic beam axis, and the sign of the shift reflects the flow direction. Unlike conventional flowmetry, this method does not rely on particle heterogeneity in the medium; thus, it can tolerate extremely high particle density. A red-ink phantom flowing in a tube immersed in water was used to validate the method in both the frequency and time domains. The phantom flow immersed in an intralipid solution was also measured.
The formation of double-row oxide stripes during the initial oxidation of NiAl(100)
Authors: Qin Hailang , Zhou Guangwen
Published: August 2013

The initial growth of ultrathin aluminum oxide film during the oxidation of NiAl(100) was studied with scanning tunneling microscopy. Our observations reveal that the oxide film grows initially as pairs of a double-row stripe structure with a lateral size equal to the unit cell of θ-Al2O3. These double-row stripes serve as the very basic stable building units of the ordered oxide phase for growing thicker bulk-oxide-like thin films. It is shown that the electronic properties of these ultrathin double-row stripes do not differ significantly from that of the clean NiAl surface; however, the thicker oxide stripes show a decreased conductivity.
Apparent Sharpness of 3D Video When One Eye's View is More Blurry
Authors: Robinson Alan , Jain Ankit , Scott Mathew , MacLeod Don , Nguyen Truong
Published: August 2013

When the images presented to each eye differ in sharpness, the fused percept remains relatively sharp. Here, we measure this effect by showing stereoscopic videos that have been blurred for one eye, or both eyes, and psychophysically determining when they appear equally sharp. For a range of blur magnitudes, the fused percept always appeared significantly sharper than the blurrier view. From these data, we investigate to what extent discarding high spatial frequencies from just one eye's view reduces the bandwidth necessary to transmit perceptually sharp 3D content. We conclude that relatively high-resolution video transmission has the most potential benefit from this method.
On the Müller-Lyer Illusion in the Carpentered World
Authors: Deręgowski Jan B
Published: August 2013

Implications of the little noticed fact that projective geometry restricts the range of interfin angles of the Müller-Lyer illusion, which are congruent with retinal projections cast by carpentered objects, are presented and tested. Experimental results support the theoretical restrictions. This implies that only Müller-Lyer figures with interfin angles within the 90° to 180° range are appropriate for investigation of the Carpentered World hypothesis.
Holistic Face Processing is Induced by Shape and Texture
Authors: Meinhardt-Injac Bozana , Persike Malte , Meinhardt Günter
Published: August 2013

There is increasing evidence that shape and texture are integral parts of face identity. However, it is less clear whether face-specific processing mechanisms are triggered by face shape alone, or if texture might play an important role. We address this question by studying mechanisms involved in holistic face processing. Face stimuli were either full-color pictures of real faces (shape and texture) or line drawings of the same faces (shape without texture). In a change detection task subjects judged whether eyes and eyebrows in two otherwise identical, sequentially presented faces were different in size or not. Afterwards, subjects had to identify the just presented face among two distractor faces (forced-choice identification task). The results obtained from the two tasks give rise to the conclusion that face identification and change detection tasks engage different processing strategies, which capture different aspects of holistic processing. Real faces were processed holistically, irrespective of task requirements, whereas line drawings were processed holistically only if face identification was required. On the basis of the data we conclude that face shape is relevant for the initial processing stage and feature binding, whereas face texture seems to be involved in processing of face configuration more specifically. Moreover, results demonstrate considerable flexibility of the face processing systems allowing for goal-directed and task-specific recall of face information.
Developmental Changes in the Balance of Disparity, Blur, and Looming/Proximity Cues to Drive Ocular Alignment and Focus
Authors: Horwood Anna M , Riddell Patricia M
Published: August 2013

Accurate coordination of accommodation and convergence is necessary to view near objects and develop fine motor coordination. We used a remote haploscopic videorefraction paradigm to measure longitudinal changes in simultaneous ocular accommodation and vergence to targets at different depths, and to all combinations of blur, binocular disparity, and change-in-size (‘proximity’) cues. Infants were followed longitudinally and compared with older children and young adults, with the prediction that sensitivity to different cues would change during development. Mean infant responses to the most naturalistic condition were similar to those of adults from 6–7 weeks (accommodation) and 8–9 weeks (vergence). Proximity cues influenced responses most in infants of less than 14 weeks of age, but sensitivity declined thereafter. Between 12 and 28 weeks of age infants were equally responsive to all three cues, while in older children and adults manipulation of disparity resulted in the greatest changes in response. Despite rapid development of visual acuity (thus increasing availability of blur cues), responses to blur were stable throughout development. Our results suggest that, during much of infancy, vergence and accommodation responses are not dependent on the development of specific depth cues, but make use of any cues available to drive appropriate changes in response.
Inhibition of SMG-8, a subunit of SMG-1 kinase, ameliorates nonsense-mediated mRNA decay-exacerbated mutant phenotypes without cytotoxicity
Authors: Usuki Fusako , Yamashita Akio , Shiraishi Tadafumi , Shiga Atsushi , Onodera Osamu , Higuchi Itsuro , Ohno Shigeo
Published: August 2013

Nonsense-mediated mRNA decay (NMD) is an mRNA surveillance mechanism that eliminates aberrant mRNAs containing premature termination codons (PTCs). NMD inhibits the production of aberrant proteins that still retain, at least in part, wild-type function as well as dominant-negative peptides. Therefore, the selective inhibition of NMD has the potential to ameliorate NMD-exacerbated mutant phenotypes. However, we do not have sufficient knowledge of how to effectively suppress NMD with minimum cytotoxic effects. In this study, we aimed to identify NMD-related factors that can be targeted to efficiently inhibit NMD without causing significant cytotoxicity to restore the levels of truncated but partially functional proteins. We evaluated the knockdown of 15 NMD components in Ullrich congenital muscular dystrophy fibroblasts, which have a homozygous frameshift mutation causing a PTC in the collagen type VI α 2 gene. Of the 15 NMD factors tested, knockdown of SMG-8 produced the best effect for restoring defective mRNA and protein levels without affecting cell growth, cell-cycle progression, or endoplasmic reticulum stress. The efficacy of SMG-8 knockdown to improve the mutant phenotype was confirmed using another cell line, from a cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy patient who carries a PTC-containing mutation in HtrA serine peptidase 1. Our results suggest that SMG-8 is an appropriate target for inhibiting NMD to improve NMD-exacerbated mutant phenotypes. NMD inhibition by knockdown of SMG-8 may also be useful to induce synergy in combining the use of read-through drugs for patients with nonsense mutation-associated diseases.