bluuebunny/crossref_metadata_2025 huggingface dataset:
A laboratory 8 keV transmission full-field x-ray microscope with a polycapillary as condenser for bright and dark field imaging
Authors: Baumbach S. , Kanngießer B. , Malzer W. , Stiel H. , Wilhein T.
Published: August 2015

This article introduces a laboratory setup of a transmission full-field x-ray microscope at 8 keV photon energy. The microscope operates in bright and dark field imaging mode with a maximum field of view of 50 μm. Since the illumination geometry determines whether the sample is illuminated homogeneously and moreover, if different imaging methods can be applied, the condenser optic is one of the most significant parts. With a new type of x-ray condenser, a polycapillary optic, we realized bright field imaging and for the first time dark field imaging at 8 keV photon energy in a laboratory setup. A detector limited spatial resolution of 210 nm is measured on x-ray images of Siemens star test patterns.
Effect of substrate rotation on domain structure and magnetic relaxation in magnetic antidot lattice arrays
Authors: Mallick Sougata , Mallik Srijani , Bedanta Subhankar
Published: August 2015

Microdimensional triangular magnetic antidot lattice arrays were prepared by varying the speed of substrate rotation. The pre-deposition patterning has been performed using photolithography technique followed by a post-deposition lift-off. Surface morphology taken by atomic force microscopy depicted that the growth mechanism of the grains changes from chain like formation to island structures due to the substrate rotation. Study of magnetization reversal via magneto optic Kerr effect based microscopy revealed reduction of uniaxial anisotropy and increase in domain size with substrate rotation. The relaxation measured under constant magnetic field becomes faster with rotation of the substrate during deposition. The nature of relaxation for the non-rotating sample can be described by a double exponential decay. However, the relaxation for the sample with substrate rotation is well described either by a double exponential or a Fatuzzo-Labrune like single exponential decay, which increases in applied field.
Highly ionized xenon and volumetric weighting in restricted focal geometries
Authors: Strohaber J. , Kolomenskii A. A. , Schuessler H. A.
Published: August 2015

The ionization of xenon atoms subjected to 42 fs, 800 nm pulses of radiation from a Ti:Sapphire laser was investigated. In our experiments, a maximum laser intensity of ∼2×1015W/cm2 was used. Xenon ions were measured using a time-of-flight ion mass spectrometer having an entrance slit with dimensions of 12μm×400μm. The observed yields Xen+(n=1−7) were partially free of spatial averaging. The ion yields showed sequential and nonsequential multiple ionization and dip structures following saturation. To investigate the dip structures and to perform a comparison between experimental and simulated data, with the goal of clarifying the effects of residual spatial averaging, we derived a hybrid analytical-numerical solution for the integration kernel in restricted focal geometries. We simulated xenon ionization using Ammosov-Delone-Krainov and Perelomov-Popov-Terent'ev theories and obtained agreement with the results of observations. Since a large number of experiments suffer from spatial averaging, the results presented are important to correctly interpret experimental data by taking into account spatial averaging.
Stabilization and convergence rate in a chemotaxis system with consumption of chemoattractant
Authors: Zhang Qingshan , Li Yuxiang
Published: August 2015

We consider chemotaxis system with consumption of chemoattractant {vt=Δv−uv,ut=Δu−χ∇⋅(u∇v), under homogeneous Neumann boundary conditions. It is proved that if either n ≤ 2 or 0<χ≤16(n+1)‖v(x,0)‖L∞(Ω), n ≥ 3, the global classical solution (u, v) of this problem converges to (ū0,0) exponentially as t → ∞, where ū0≔1|Ω|∫Ωu(x,0)dx.
Structural instability of the CoO4 tetrahedral chain in SrCoO3−δ thin films
Authors: Glamazda A. , Choi K.-Y. , Lemmens P. , Choi Woo Seok , Jeen Hyoungjeen , Meyer Tricia L. , Lee Ho Nyung
Published: August 2015

Raman scattering experiments together with detailed lattice dynamic calculations are performed to elucidate crystallographic and electronic peculiarities of SrCoO3−δ films. We observe that the 85 cm−1 phonon mode involving the rotation of a CoO4 tetrahedron undergoes a huge hardening by 21 cm−1 with decreasing temperature. In addition, new phonon modes appear at 651.5 and 697.6 cm−1. The latter modes are attributed to the Jahn-Teller activated modes. Upon cooling from room temperature, all phonons exhibit an exponential-like increase of intensity with a characteristic energy of about 103–107 K. We attribute this phenomenon to an instability of the CoO4 tetrahedral chain structure, which constitutes a key ingredient to understand the electronic and structural properties of the brownmillerite SrCoO2.5.
Observation of inverse spin Hall effect in ferromagnetic FePt alloys using spin Seebeck effect
Authors: Seki Takeshi , Uchida Ken-ichi , Kikkawa Takashi , Qiu Zhiyong , Saitoh Eiji , Takanashi Koki
Published: August 2015

We experimentally observed the inverse spin Hall effect (ISHE) of ferromagnetic FePt alloys. Spin Seebeck effect due to the temperature gradient generated the spin current (Js) in the FePt|Y3Fe5O12 (YIG) structure, and Js was injected from YIG to FePt and converted to the charge current through ISHE of FePt. The significant difference in magnetization switching fields for FePt and YIG led to the clear separation of the voltage of ISHE from that of anomalous Nernst effect in FePt. We also investigated the effect of ordering of FePt crystal structure on the magnitude of ISHE voltage in FePt.
Experimental study of the thermal conductivity of sintered tungsten: Evidence of a critical behaviour with porosity
Authors: Gheribi Aïmen E. , Gardarein Jean-Laurent , Autissier Emmanuel , Rigollet Fabrice , Richou Marianne , Chartrand Patrice
Published: August 2015

Rear face flash experiments were performed in order to determine the thermal conductivity of sintered tungsten at room temperature. Ten different samples were synthesized with the spark plasma sintering technique. The microstructure obtained from the sintering is porous and consists of angular grains with medium sphericity. The average grain size (d) and the porosity (P) of the samples lie within the ranges of 2μm≤d≤7μm and 0≤P≤0.35. We show that the dependence of the thermal conductivity of the sintered tungsten samples on the porosity shows a critical behaviour. A theoretical explanation of this behaviour and a predictive model for this porosity dependence are proposed.
Interfacial trapping in an aged discotic liquid crystal semiconductor
Authors: Dawson Nathan J. , Patrick Michael S. , Paul Sanjoy , Ellman Brett , Semyonov Alexander , Twieg Robert J. , Matthews Rachael , Pentzer Emily , Singer Kenneth D.
Published: August 2015

This study reports on time-of-flight (TOF) hole mobility measurements in aged 2,3,6,7,10,11-Hexakis(pentyloxy)triphenylene columnar liquid crystals. In contrast to the original samples reported in 2006, homeotropically aligned samples yielded TOF transients with an extended non-exponential rise. The experimental data were fit to a simple model that accurately reproduces the TOF transients assuming delayed charge release from traps near the optically excited electrode. While interfacial trapping appears only in the aged materials, the bulk mobility is similar to the pristine material. The model addresses dispersive transport in quasi-one-dimensional materials, determines the charge carrier mobility in systems with interfacial traps, and provides a method for characterizing the traps.
THz behavior of indium-tin-oxide films on p-Si substrates
Authors: Brown E. R. , Zhang W-D. , Chen H. , Mearini G. T.
Published: August 2015

This paper reports broadband THz free-space transmission measurements and modeling of indium-tin-oxide (ITO) thin films on p-doped Si substrates. Two such samples having ITO thickness of 50 and 100 nm, and DC sheet conductance 260 and 56 Ω/sq, respectively, were characterized between 0.2 and 1.2 THz using a frequency-domain spectrometer. The 50-nm-film sample displayed very flat transmittance over the 1-THz bandwidth, suggesting it is close to the critical THz sheet conductance that suppresses multi-pass interference in the substrate. An accurate transmission-line-based equivalent circuit is developed to explain the effect, and then used to show that the net reflectivity and absorptivity necessarily oscillate with frequency. This has important implications for the use of thin-film metallic coupling layers on THz components and devices, such as detectors and sources. Consistent with previous reported results, the sheet conductance that best fits the THz transmittance data is roughly 50% higher than the DC values for both samples.
Charge states of the reactants in the hydrogen passivation of interstitial iron in P-type crystalline silicon
Authors: Sun Chang , Liu AnYao , Phang Sieu Pheng , Rougieux Fiacre E. , Macdonald Daniel
Published: August 2015

Significant reductions in interstitial iron (Fei) concentrations occur during annealing Fe-containing silicon wafers with silicon nitride films in the temperature range of 250 °C–700 °C. The silicon nitride films are known to release hydrogen during the annealing step. However, in co-annealed samples with silicon oxide films, which are hydrogen-lean, changes in the Fei concentrations were much less significant. The precipitation of Fei is ruled out as a possible explanation for the significant reductions. The hydrogen passivation of Fei, which is the complexing of monatomic H and isolated Fei forming a recombination-inactive hydride, is proposed as the most probable model to explain the reductions. Under the assumption that the reduction is caused by the hydrogenation of Fei, the reactants' charge states in the hydrogenation reaction are determined by two independent approaches. In the first approach, illumination is found to have a small but detectible impact on the reaction kinetics in the lower temperature range. The dominating reactants' charge states are concluded to be Fe0 + H+ as revealed by modelling the injection-dependent charge states of isolated Fei and monatomic H. In the second approach, the reaction kinetics are fitted with the Arrhenius equation over a large temperature range of 250 °C–700 °C. A reasonable fit is only obtained when assuming the reacting charge states are Fe0 + H+. This supports the conclusion on the reacting charge states and also gives a value of the activation energy of hydrogenation in the 0.7–0.8 eV range.
High frequency transmission to a junction of a scanning tunneling microscope
Authors: Hervé M. , Peter M. , Wulfhekel W.
Published: August 2015

We report on an easy method to calibrate the transmission of radio-frequency (rf) voltages to the tunneling junction of a scanning tunneling microscope. The transmission strongly depends on frequency, as the cabling shows frequency dependent damping and the impedance mismatch between the cable and the tunneling junction induces reflections. To first order, the current-voltage characteristic of the junction induces a rf tunneling current of the same frequency as the rf voltage. Omnipresent non-linearities of the current-voltage characteristic of the junction to second order, however, generate an additional rectified DC. A direct comparison between this current and the second derivative of the current-voltage curve allows to determine the rf transmission to the tunneling junction. The transmission data up to 2 GHz were used to compensate the rf damping such that at every frequency a constant amplitude at the tunneling junction could be realized expanding the bandwidth of the experiment from less then 100 MHz to 2 GHz.
Characterization of a radio frequency hollow electrode discharge at low gas pressures
Authors: Ahadi Amir Mohammad , Trottenberg Thomas , Rehders Stefan , Strunskus Thomas , Kersten Holger , Faupel Franz
Published: August 2015

A radio frequency (RF) hollow discharge configuration is presented, which makes use of a combination of RF plasma generation and the hollow cathode effect. The system was especially designed for the treatment of nanoparticles, plasma polymerization, and nanocomposite fabrication. The process gas streams through the plasma in the inner of the cylindrical electrode system. In the here presented measurements, pure argon and argon with oxygen admixtures are exemplarily used. The discharge is characterized by probe measurements in the effluent, electrical measurements of the discharge parameters, and visual observations of the plasma glow. It is found that the RF fluctuations of the plasma potential are weak. The plasma potential resembles the one of a DC hollow cathode discharge, the RF hollow electrode acts as a cathode due to the self-bias, and a high voltage sheath forms in its inner cylinder.
Nonlinear upper hybrid waves and the induced density irregularities
Authors: Kuo Spencer P.
Published: August 2015

Upper hybrid waves are excited parametrically by the O-mode high-frequency heater waves in the ionospheric heating experiments. These waves grow to large amplitudes and self-induced density perturbations provide nonlinear feedback. The lower hybrid resonance modifies the nonlinear feedback driven by the ponderomotive force; the nonlinear equation governing the envelope of the upper hybrid waves is derived. Solutions in symmetric alternating functions, in non-alternating periodic functions, as well as in solitary functions are shown. The impact of lower hybrid resonance on the envelope of the upper hybrid waves is explored; the results show that both the spatial period and amplitude are enlarged. The average fluctuation level of induced density irregularities is also enhanced. In the soliton form, the induced density cavity is widened considerably.
Exponential yield sensitivity to long-wavelength asymmetries in three-dimensional simulations of inertial confinement fusion capsule implosions
Authors: Haines Brian M.
Published: August 2015

In this paper, we perform a series of high-resolution 3D simulations of an OMEGA-type inertial confinement fusion (ICF) capsule implosion with varying levels of initial long-wavelength asymmetries in order to establish the physical energy loss mechanism for observed yield degradation due to long-wavelength asymmetries in symcap (gas-filled capsule) implosions. These simulations demonstrate that, as the magnitude of the initial asymmetries is increased, shell kinetic energy is increasingly retained in the shell instead of being converted to fuel internal energy. This is caused by the displacement of fuel mass away from and shell material into the center of the implosion due to complex vortical flows seeded by the long-wavelength asymmetries. These flows are not fully turbulent, but demonstrate mode coupling through non-linear instability development during shell stagnation and late-time shock interactions with the shell interface. We quantify this effect by defining a separation lengthscale between the fuel mass and internal energy and show that this is correlated with yield degradation. The yield degradation shows an exponential sensitivity to the RMS magnitude of the long-wavelength asymmetries. This strong dependence may explain the lack of repeatability frequently observed in OMEGA ICF experiments. In contrast to previously reported mechanisms for yield degradation due to turbulent instability growth, yield degradation is not correlated with mixing between shell and fuel material. Indeed, an integrated measure of mixing decreases with increasing initial asymmetry magnitude due to delayed shock interactions caused by growth of the long-wavelength asymmetries without a corresponding delay in disassembly.
Opto-mechano-electrical tripling in ZnO nanowires probed by photocurrent spectroscopy in a high-resolution transmission electron microscope
Authors: Zhang C. , Xu Z. , Kvashnin D. G. , Tang D.-M. , Xue Y. M. , Bando Y. , Sorokin P. B. , Golberg D.
Published: August 2015

Photocurrent spectroscopy of individual free-standing ZnO nanowires inside a high-resolution transmission electron microscope (TEM) is reported. By using specially designed optical in situ TEM system capable of scanning tunneling microscopy probing paired with light illumination, opto-mechano-electrical tripling phenomenon in ZnO nanowires is demonstrated. Splitting of photocurrent spectra at around 3.3 eV under in situ TEM bending of ZnO nanowires directly corresponds to nanowire deformation and appearance of expanded and compressed nanowire sides. Theoretical simulation of a bent ZnO nanowire has an excellent agreement with the experimental data. The splitting effect could be explained by a change in the valence band structure of ZnO nanowires due to a lattice strain. The strain-induced splitting provides important clues for future flexible piezo-phototronics.
Spatial concentration distribution analysis of cells in electrode-multilayered microchannel by dielectric property measurement
Authors: Yao Jiafeng , Kodera Tatsuya , Obara Hiromichi , Sugawara Michiko , Takei Masahiro
Published: August 2015

The spatial concentration distribution of cells in a microchannel is measured by combining the dielectric properties of cells with the specific structure of the electrode-multilayered microchannel. The dielectric properties of cells obtained with the impedance spectroscopy method includes the cell permittivity and dielectric relaxation, which corresponds to the cell concentration and structure. The electrode-multilayered microchannel is constructed by 5 cross-sections, and each cross-section contains 5 electrode-layers embedded with 16 micro electrodes. In the experiment, the dielectric properties of cell suspensions with different volume concentrations are measured with different electrode-combinations corresponding to different electric field distributions. The dielectric relaxations of different cell concentrations are compared and discussed with the Maxwell-Wagner dispersion theory, and the relaxation frequencies are analysed by a cell polarization model established based on the Hanai cell model. Moreover, a significant linear relationship with AC frequency dependency between relative permittivity and cell concentration was found, which provides a promising way to on-line estimate cell concentration in microchannel. Finally, cell distribution in 1 cross-section of the microchannel (X and Y directions) was measured with different electrode-combinations using the dielectric properties of cell suspensions, and cell concentration distribution along the microchannel (Z direction) was visualized at flowing state. The present cell spatial sensing study provides a new approach for 3 dimensional non-invasive online cell sensing for biological industry.
Micromechanical measurement of beating patterns in the quantum oscillatory chemical potential of InGaAs quantum wells due to spin-orbit coupling
Authors: Herzog Florian , Heyn Christian , Hardtdegen Hilde , Schäpers Thomas , Wilde Marc A. , Grundler Dirk
Published: August 2015

The quantum oscillatory magnetization M(B) and chemical potential μ(B) of a two-dimensional (2D) electron system provide important and complementary information about its ground state energy at low temperature T. We developed a technique that provides both quantities in the same cool-down process via a decoupled static operation and resonant excitation of a micromechanical cantilever. On InGaAs/InP heterostructures, we observed beating patterns in both M(B) and μ(B) attributed to spin-orbit interaction. A significantly enhanced sensitivity in μ enabled us to extract Rashba and Dresselhaus parameters with high accuracy. The technique is powerful for detailed investigations on the electronic properties of 2D materials.
Facile chemical synthesis, electromagnetic response, and enhanced microwave absorption of cobalt powders with controllable morphologies
Authors: Wen S. L. , Liu Y. , Zhao X. C.
Published: August 2015

Spherical (sample A), chain-like (sample B), and flake-like (sample C) cobalt powders are synthesized on a large scale through simple chemical liquid reduction method. Based on uniformly dispersing samples into a paraffin matrix, morphology-dependent electromagnetic responses in GHz range, including permittivity and permeability, are investigated for these three cobalt powders in the microwave frequency of 2-18 GHz. The calculated reflection loss (RL) indicates as-prepared samples have potential application as a candidate for microwave absorption. The maximum RL of sample A is −15.28 dB at 12.85 GHz with a matching thickness of 2.5 mm. The maximum RL of sample B is −28.05 dB at 5.74 GHz corresponding to a thickness of 2.0 mm, and the maximum RL of sample C is −41.17 dB at 5.10 GHz with a thickness of 2.5 mm. Mechanism of morphology-dependent electromagnetic response and microwave absorption of the Cobalt powders is also discussed in this paper.
Two-dimensional concentrated-stress low-frequency piezoelectric vibration energy harvesters
Authors: Sharpes Nathan , Abdelkefi Abdessattar , Priya Shashank
Published: August 2015

Vibration-based energy harvesters using piezoelectric materials have long made use of the cantilever beam structure. Surmounting the deficiencies in one-dimensional cantilever-based energy harvesters has been a major focus in the literature. In this work, we demonstrate a strategy of using two-dimensional beam shapes to harvest energy from low frequency excitations. A characteristic Zigzag-shaped beam is created to compare against the two proposed two-dimensional beam shapes, all of which occupy a 25.4 × 25.4 mm2 area. In addition to maintaining the low-resonance bending frequency, the proposed beam shapes are designed with the goal of realizing a concentrated stress structure, whereby stress in the beam is concentrated in a single area where a piezoelectric layer may be placed, rather than being distributed throughout the beam. It is shown analytically, numerically, and experimentally that one of the proposed harvesters is able to provide significant increase in power production, when the base acceleration is set equal to 0.1 g, with only a minimal change in the resonant frequency compared to the current state-of-the-art Zigzag shape. This is accomplished by eliminating torsional effects, producing a more pure bending motion that is necessary for high electromechanical coupling. In addition, the proposed harvesters have a large effective beam tip whereby large tip mass may be placed while retaining a low-profile, resulting in a low volume harvester and subsequently large power density.
Fast transient charging behavior of HfInZnO thin-film transistor
Authors: Kim Taeho , Hur Ji-Hyun , Jeon Sanghun
Published: August 2015

Threshold voltage instabilities and mobility degradation of amorphous oxide-based thin-film transistors (TFTs) are associated with charging phenomena in gate dielectrics, interfaces. The wide range of charge trapping when using DC techniques may mislead to the evaluation of intrinsic device characteristics. In this investigation, we studied the charging behavior in HfInZnO TFTs with the Hf metal content by fast and transient current measurement methods. Since the charge-trapping effect is negligible during fast voltage ramping, the drain current measured by the fast I−V method was higher than that obtained from DC measurement, indicating that conventional DC measurement underestimates the mobility values even for oxide-TFTs. The mobility values of the HfInZnO TFTs with high and low Hf contents were measured by the fast I–V method to be 2.7 and 13.5 cm2/V s, respectively, which were increased by 16–68% after the fast I−V measurement. In addition, trapping time constants of 24 and 17 μs for both devices were estimated by the transient I−V method. According to the fitting model, the charge trapping was governed by multiple processes with two different time constants.
Note: A novel method for generating multichannel quasi-square-wave pulses
Authors: Mao C. , Zou X. , Wang X.
Published: August 2015

A 21-channel quasi-square-wave nanosecond pulse generator was constructed. The generator consists of a high-voltage square-wave pulser and a channel divider. Using an electromagnetic relay as a switch and a 50-Ω polyethylene cable as a pulse forming line, the high-voltage pulser produces a 10-ns square-wave pulse of 1070 V. With a specially designed resistor-cable network, the channel divider divides the high-voltage square-wave pulse into 21 identical 10-ns quasi-square-wave pulses of 51 V, exactly equal to 1070 V/21. The generator can operate not only in a simultaneous mode but also in a delay mode if the cables in the channel divider are different in length.
Shape-adapting thermoacoustic imaging system based on flexible multi-element transducer
Authors: Ji Zhong , Ding Wenzheng , Ye Fanghao , Lou Cunguang , Xing Da
Published: August 2015

Microwave-induced thermoacoustic (TA) imaging is efficient in detecting the anomaly that has difference in microwave absorption with normal tissue, particularly for breast tumor and foreign objects. However, the traditional circular-scanning TA system needs a large operating space for rotation of the transducers and bulk of coupling medium. The linear-scanning system can overcome these problems partially but usually lose some information and cause image distortion. In order to overcome these limitations, a shape-adapting TA imaging system based on flexible multi-element transducer is proposed in this letter. The experimental results show that this system provides obvious advantages, including shape adaptation, information integrity, and efficient transmission, which make it a preferred choice for biomedical applications, especially for breast tumor detection.
Graphene surface plasmon polaritons with opposite in-plane electron oscillations along its two surfaces
Authors: Liang Huawei , Ruan Shuangchen , Zhang Min , Su Hong , Li Irene Ling
Published: August 2015

We predict the existence of a surface plasmon polariton (SPP) mode that can be guided by a graphene monolayer, regardless of the sign of the imaginary part of its conductivity. In this mode, in-plane electron oscillations along two surfaces of graphene are of opposite directions, which is very different from conventional SPPs on graphene. Significantly, coating graphene with dielectric films yields a way to guide the SPPs with both sub-wavelength mode widths and ultra-long propagation distances. In particular, the mode characteristics are very sensitive to the chemical potential of graphene, so the graphene-based waveguide can find applications in many optoelectronic devices.
Scaffold metamaterial and its application as strain sensor
Authors: Wu Wei , Ren Mengxin , Pi Biao , Wu Yang , Cai Wei , Xu Jingjun
Published: August 2015

In this paper, strain sensors based on planar scaffold metamaterial design are demonstrated. The optical properties of such metamaterials are studied, which are proved to be highly dependent on the deformation of the structure. Fabricating such metamaterial on compliant polymeric substrate, the geometric parameters could be tuned with external strain and hence are found to control the reflection resonance condition of the metamaterial. Such mechanical tunability provides the opportunity to realize efficient strain sensors and about 27 nm resonance wavelength shift is observed by applying as much as 37% tensile strain. Furthermore, distinct from most of the previous works, our structures are based on “intaglio” design, which could be manufactured directly by one step fabrication using focused ion beam cutting, hence makes the fabrication process much simpler.
The density and velocity of plasma bullets propagating along one dielectric tube
Authors: Ji Longfei , Xia Yang , Bi Zhenhua , Niu Jinhai , Liu Dongping
Published: August 2015

This study shows that the propagation of plasma bullets along one dielectric tube is strongly affected by many discharge parameters, such as the waveform of applied voltage (AC or pulsed DC), peak voltage, He flow rate, and the frequency of AC voltage. Analysis indicates that the density and velocity of plasma bullets are mainly determined by the electric field at the front of plasma bullets. These discharge parameters may significantly influence the distribution of plasma potential along the tube, thus control the electric field at the front of plasma bullets and their propagation. An increase in the pulsed DC voltage with its rise time of <40-50 ns can lead to an obvious improvement in the electric field at the front of plasma bullets, resulting in generation of a plasma in the high density gas and a fast propagation of plasma bullets. He flowing through the tube can contribute to the surface diffusion of charged species, and greatly increase the electric field at the front of plasma bullets. During the propagation of plasma bullets, their density is decreased due to the surface recombination of charged species, such as electrons and ions.
Ni-coated CaCu3Ti4O12/low density polyethylene composite material with ultra-high dielectric permittivity
Authors: Gao L. , Wang X. , Chen Y. , Chi Q. G. , Lei Q. Q.
Published: August 2015

We report a novel low-density polyethylene (LDPE) composite filled with nickel-coated CaCu3Ti4O12 ceramic (denoted as CCTO@Ni), prepared by a melt mixing technique, and its prominent dielectric characteristics. The effects of magnetic field treatment on the dielectric properties of CCTO@Ni/LDPE composite films with a low filler concentration of 10 vol.% were investigated. Our results show that the dielectric permittivity, loss tangent, and conductivity of the LDPE composite films initially improved and then decreased with increasing treatment time under the applied magnetic field. Magnetic field treatment for 60 min led to an ultra-high dielectric permittivity value of 1.57 × 104, four orders of magnitude higher than that of the pure LDPE material. Our results indicate that the magnetic treatment may have induced a percolation effect and enhanced the interfacial polarization of the CCTO@Ni/LDPE composite, resulting in the observed changes in its dielectric properties.
Tunable superconducting qudit mediated by microwave photons
Authors: Cho Sung Un , Bae Myung-Ho , Kang Kicheon , Kim Nam
Published: August 2015

We have investigated the time-domain characteristics of the Autler-Townes doublet in a superconducting circuit. The transition probabilities between the ground state and the Autler-Townes doublet states are shown to be controlled in a phase-coherent manner using a well-known microwave pulse pattern technique. The experimental results are well explained by a numerical simulation based on the Markovian master equation. Our result indicates that the Autler-Townes doublet states might be useful as a tunable qudit for implementation of quantum information processing, in particular as a multivalued quantum logic element.
Communication: Activation energy of tension-induced pore formation in lipid membranes
Authors: Karal Mohammad Abu Sayem , Yamazaki Masahito
Published: August 2015

Tension plays a vital role in pore formation in biomembranes, but the mechanism of pore formation remains unclear. We investigated the temperature dependence of the rate constant of constant tension (σ)–induced pore formation in giant unilamellar vesicles of lipid membranes using an experimental method we developed. By analyzing this result, we determined the activation energy (Ua) of tension-induced pore formation as a function of tension. A constant (U0) that does not depend on tension was found to contribute significantly to Ua. Analysis of the activation energy clearly indicated that the dependence of Ua on σ in the classical theory is correct, but that the classical theory of pore formation is not entirely correct due to the presence of U0. We can reasonably consider that U0 is a nucleation free energy to form a hydrophilic pre-pore from a hydrophobic pre-pore or a region with lower lateral lipid density. After obtaining U0, the evolution of a pre-pore follows a classical theory. Our data provide valuable information that help explain the mechanism of tension-induced pore formation in biomembranes and lipid membranes.
Growth responses of Baumea juncea (Cyperaceae) plants from inland artesian spring and coastal habitats to salinity and waterlogging treatments
Authors: Gellie Nick , Beaumont Kieren , Mackay Duncan , Whalen Molly , Clarke Laurence
Published: August 2015

Artesian springs of arid inland Australia provide permanent water that supports naturally fragmented wetland communities. Some plant species that occur at springs have more extensive populations in coastal wetland areas of Australia where they may experience quite different environmental conditions. The present study investigated the growth response of one such species, Baumea juncea (R.Br.) Palla (Cyperaceae), to salinity and waterlogging. Plants from each region were subjected to combinations of salinity (freshwater or 20% seawater) and waterlogging (unsaturated or saturated soil), in a factorial design, for a period of 5 months. All plants survived and although the final aboveground biomasses did not differ significantly among the treatment combinations, for spring plants, the relative growth of roots was greater in unsaturated soil than in saturated soil. For the growth parameters of total biomass, culm biomass and rhizome biomass, spring and coastal plants showed contrasting responses to the treatment combinations; for spring plants in fresh water, these parameters were greater in the saturated treatment than in the unsaturated treatment, whereas for spring plants in saline water, these variables were lower in the saturated treatment than in the unsaturated treatment. Coastal plants displayed the reverse pattern. For the remaining parameters of root biomass, root : culm ratio and aboveground : belowground biomass ratio, plants from spring and coastal regions grown under saline conditions displayed contrasting responses to waterlogging. Our findings showed that the growth responses of plants of B. juncea to waterlogging and salinity differ for spring and coastal plants, suggesting potential differential adaptation by populations in these disjunct and distinct environments.
Visible Light-Promoted Metal-Free Reduction of Organohalides by 2-Naphthyl or 2-Hydroxynaphthyl-Substituted 1,3-Dimethylbenzimidazolines
Authors: Hasegawa Eietsu , Mori Kazuma , Tsuji Shiori , Nemoto Kazuki , Ohta Taku , Iwamoto Hajime
Published: August 2015

The visible light-promoted reduction reactions of some organohalides were investigated using 2-aryl-1,3-dimethylbenzimidazolines (Ar-DMBIH) possessing 2-naphthyl or 2-hydroxynaphthyl substituents. In these reduction reactions, single-electron transfer from photo-excited Ar-DMBIH, attained by Xe lamp irradiation through an appropriate glass-filter (λ > 390 nm), to the halide substrates leads to the carbon–halogen bond cleavage, followed by the rearrangements of the formed carbon radicals such as 5-exo hexenyl cyclization and the Dowd–Beckwith ring expansion. Addition of 1,8-diazabicyclo[5.4.0]undec-7-ene was found to enhance the reducing ability of hydroxynaphthyl-substituted DMBIH. A household white light-emitting diode was also used as a light source for these reactions.
Language ideological debates over orthography in European linguistic history
Authors: Villa Laura , Vosters Rik
Published: August 2015

This introductory article to the special issue on the historical sociolinguistics of spelling sketches an overview of the current interest in the field for the sociopolitical nature of the written language. Spelling is understood as a powerful tool for sociopolitical mobilization and thus becomes a recurrent source of conflict. Orthographic debates are the object of study chosen by the authors in this special issue to analyze the non-linguistic dimension of language matters. Approaching them as language ideological debates allows us to carry out a deeper examination of the political projects, social structures, identity issues and cultural practices that are at stake when an orthographic conflict emerges. Adopting such theoretical approach to the study of spelling, the editors of this volume have gathered works that look at the past and present of a number of European languages (Dutch, German, Lithuanian, Macedonian, Portuguese and Spanish) since the Early Modern period until recent times.
Official orthographies, spelling debates and nation-building projects after the fall of the Spanish Empire
Authors: Villa Laura
Published: August 2015

The collapse of the Spanish Empire in the first half of the nineteenth century prompted a need to reorganize the former colonial space in independent countries by creating territorial, political and identity boundaries in Spanish-speaking America. The imposition of a national language – the officialization of grammatical and orthographic norms and their promotion through emerging public education systems – was a key instrument in the nation-building processes developed in Spain and the newly independent American republics. In this socio-political context resistance to official norms and their implementation was frequent. This article studies three language ideological debates over Spanish orthography, occurring in the central decades of the century: the resistance to the officialization of the Royal Spanish Academy’s orthography in Spain (1844), the opposition to Sarmiento’s simplification proposal in Chile (1844) and the reception of the Chilean orthography in Spain (1846). The significance of spelling as an identity marker and a political tool is emphasized.
Proficiency and efficiency
Authors: Voeste Anja
Published: August 2015

In Late Medieval and Early Modern times, the modernization of printing and the increasing proficiency of related crafts had an impact on spelling. The challenges of microtypography, especially of text alignment, led to a bundle of new spelling variants that annoyed early grammatography. Nevertheless, the conflict-ridden working conditions in the printing shops and the needs of the market appear to be the decisive factors, initiating novel spelling strategies that were aimed at accessing new consumer groups. A development was set in motion that supported unskilled readers, applying noun capitalization, punctuation, and syllabic spellings to assist in the process of decoding.
The Portuguese Language Spelling Accord
Authors: Marquilhas Rita
Published: August 2015

The process of adopting an official orthography for the Portuguese language was completed very late in history, only in the twentieth century, and it was independently triggered by the Brazilian Letters Academy (in 1907) and the Portuguese sciences academy (in 1911). The diplomatic negotiations between the nations involved were countless ones along the following decades, and also included, in due time, other former Portuguese colonies. Since 2006, all countries are gradually ratifying a unified orthography decided in 1990, but the process is much debated in the public space. The root of the disagreement has to do with the fact that both the Portuguese and the Brazilian sets of graphematic norms, although aiming at phonological segments, include transcription rules for variant matter: different phonetic realizations that are triggered by phonological processes.
Macedonian orthographic controversies
Authors: Kramer Christina E.
Published: August 2015

The standardization of the Macedonian language and controversies surrounding it have been described in detail by many scholars. This paper seeks to contribute to this discussion in several ways. First, I will provide a brief summary of debates concerning selection of an orthography in the period 1944–1945. Significantly, I will expand that discussion through inclusion of important archival materials from the Koneski archive at the Macedonian Academy of Sciences. Second, I will briefly discuss debates that have arisen with suggestions for orthographic reform since the 1940s. In the final section of the paper I will examine the use of Cyrillic and new debates surrounding the use of different systems of transliteration in the Latin alphabet that compete in the linguistic landscape as well as in on-line fora leading to new proposals for orthographic reform.
Defining ‘Lithuanian’
Authors: Tamošiūnaitė Aurelija
Published: August 2015

After the 1863 uprising, in order to diminish Polish influence over Lithuanians, the authorities of the Russian Empire banned the use of Latin letters for Lithuanian texts and implemented the Cyrillic script. The article discusses the linguistic ideologies that underlay this orthographic reform for Lithuanian. The study provides a discursive analysis of opposing accounts expressed in contemporary administrative and media discourses by the key supporters and opponents of the reform. Competing discourses regarding the use of Cyrillic vs. Latin for Lithuanian contested, shaped, and defined the ideological meanings of these scripts: Cyrillic was symbolically linked to Russification, Russianness, Orthodoxy, and Imperial authority, while the Latin script was associated with Polonization, Polishness, the Catholic Church, and anti-imperial resistance. The competing discourses regarding the alphabet change for Lithuanian, via its differentiation from the imposed Cyrillic as well as from the Latin-Polish writing tradition, helped to shape and define the notion of a modern Lithuanian alphabet.
TTBK2 with EB1/3 regulates microtubule dynamics in migrating cells through KIF2A phosphorylation
Authors: Watanabe Takashi , Kakeno Mai , Matsui Toshinori , Sugiyama Ikuko , Arimura Nariko , Matsuzawa Kenji , Shirahige Aya , Ishidate Fumiyoshi , Nishioka Tomoki , Taya Shinichiro , Hoshino Mikio , Kaibuchi Kozo
Published: August 2015

Microtubules (MTs) play critical roles in various cellular events, including cell migration. End-binding proteins (EBs) accumulate at the ends of growing MTs and regulate MT end dynamics by recruiting other plus end–tracking proteins (+TIPs). However, how EBs contribute to MT dynamics through +TIPs remains elusive. We focused on tau-tubulin kinase 2 (TTBK2) as an EB1/3-binding kinase and confirmed that TTBK2 acted as a +TIP. We identified MT-depolymerizing kinesin KIF2A as a novel substrate of TTBK2. TTBK2 phosphorylated KIF2A at S135 in intact cells in an EB1/3-dependent fashion and inactivated its MT-depolymerizing activity in vitro. TTBK2 depletion reduced MT lifetime (facilitated shrinkage and suppressed rescue) and impaired HeLa cell migration, and these phenotypes were partially restored by KIF2A co-depletion. Expression of nonphosphorylatable KIF2A, but not wild-type KIF2A, reduced MT lifetime and slowed down the cell migration. These findings indicate that TTBK2 with EB1/3 phosphorylates KIF2A and antagonizes KIF2A-induced depolymerization at MT plus ends for cell migration.
Concentrating on the mitotic spindle
Authors: Maddox Paul S. , Ladouceur Anne-Marie
Published: August 2015

In eukaryotes, the microtubule-based spindle drives chromosome segregation. In this issue, Schweizer et al. (2015; J. Cell Biol. http://dx.doi.org/10.1083/jcb.201506107) find that the spindle area is demarcated by a semipermeable organelle barrier. Molecular crowding, which is microtubule independent, causes the enrichment and/or retention of crucial factors in the spindle region. Their results add an important new feature to the models of how this structure assembles and is regulated.
Glutathione release through connexin hemichannels: Implications for chemical modification of pores permeable to large molecules
Authors: Tong Xuhui , Lopez William , Ramachandran Jayalakshmi , Ayad Wafaa A. , Liu Yu , Lopez-Rodriguez Angelica , Harris Andrew L. , Contreras Jorge E.
Published: August 2015

Cysteine-scanning mutagenesis combined with thiol reagent modification is a powerful method with which to define the pore-lining elements of channels and the changes in structure that accompany channel gating. Using the Xenopus laevis oocyte expression system and two-electrode voltage clamp, we performed cysteine-scanning mutagenesis of several pore-lining residues of connexin 26 (Cx26) hemichannels, followed by chemical modification using a methanethiosulfonate (MTS) reagent, to help identify the position of the gate. Unexpectedly, we observed that the effect of MTS modification on the currents was reversed within minutes of washout. Such a reversal should not occur unless reducing agents, which can break the disulfide thiol–MTS linkage, have access to the site of modification. Given the permeability to large metabolites of connexin channels, we tested whether cytosolic glutathione (GSH), the primary cell reducing agent, was reaching the modified sites through the connexin pore. Inhibition of gamma-glutamylcysteine synthetase by buthionine sulfoximine decreased the cytosolic GSH concentration in Xenopus oocytes and reduced reversibility of MTS modification, as did acute treatment with tert-butyl hydroperoxide, which oxidizes GSH. Cysteine modification based on thioether linkages (e.g., maleimides) cannot be reversed by reducing agents and did not reverse with washout. Using reconstituted hemichannels in a liposome-based transport-specific fractionation assay, we confirmed that homomeric Cx26 and Cx32 and heteromeric Cx26/Cx32 are permeable to GSH and other endogenous reductants. These results show that, for wide pores, accessibility of cytosolic reductants can lead to reversal of MTS-based thiol modifications. This potential for reversibility of thiol modification applies to on-cell accessibility studies of connexin channels and other channels that are permeable to large molecules, such as pannexin, CALHM, and VRAC.
The effects of Tmc1 Beethoven mutation on mechanotransducer channel function in cochlear hair cells
Authors: Beurg Maryline , Goldring Adam C. , Fettiplace Robert
Published: August 2015

Sound stimuli are converted into electrical signals via gating of mechano-electrical transducer (MT) channels in the hair cell stereociliary bundle. The molecular composition of the MT channel is still not fully established, although transmembrane channel–like protein isoform 1 (TMC1) may be one component. We found that in outer hair cells of Beethoven mice containing a M412K point mutation in TMC1, MT channels had a similar unitary conductance to that of wild-type channels but a reduced selectivity for Ca2+. The Ca2+-dependent adaptation that adjusts the operating range of the channel was also impaired in Beethoven mutants, with reduced shifts in the relationship between MT current and hair bundle displacement for adapting steps or after lowering extracellular Ca2+; these effects may be attributed to the channel’s reduced Ca2+ permeability. Moreover, the density of stereociliary CaATPase pumps for Ca2+ extrusion was decreased in the mutant. The results suggest that a major component of channel adaptation is regulated by changes in intracellular Ca2+. Consistent with this idea, the adaptive shift in the current–displacement relationship when hair bundles were bathed in endolymph-like Ca2+ saline was usually abolished by raising the intracellular Ca2+ concentration.