bluuebunny/crossref_metadata_2025 huggingface dataset:
Ferromagnetic nanocomposites as spintronic materials with controlled magnetic structure
Authors: Lashkarev G. V. , Radchenko M. V. , Bugaiova M. E. , Dmitriev A. I. , Lazorenko V. I. , Sichkovskyi V. I. , Knoff W. , Story T. , Stelmakh Y. A. , Krushynskaya L. A.
Published: January 2013

The physical properties of ferromagnetic dilute magnetic semiconductors and nanocomposites are considered in a wide range of temperatures from 5 to 300 K. The latter have several advantages as spintronic materials with a controlled magnetic structure for weak magnetic field sensors. A characteristic feature of ferromagnetic nanocomposites is the spin-dependent tunneling conductance, which is responsible for the negative and positive magnetoresistance. The magnetoresistive effects have a wide range of applications. In particular, materials with such effects may be used in the development of magnetoresistive memory devices, weak magnetic field sensors, medical diagnostic devices, and other items of electronic equipment.
Electroluminescence from spatially confined exciton polaritons in a textured microcavity
Authors: Winkler K. , Schneider C. , Fischer J. , Rahimi-Iman A. , Amthor M. , Forchel A. , Reitzenstein S. , Höfling S. , Kamp M.
Published: January 2013

We report on the formation of spatially confined exciton-polaritons under electrical injection in a textured microcavity. The trapping of polaritons in the diode sample is achieved through a locally elongated GaAs microcavity with a quality factor exceeding 6000. The polaritonic resonances of traps with diameters of 10 μm and 2 μm are studied by angular-resolved electroluminescence spectroscopy, revealing their hybrid light-matter nature.
Melting and superheating in solids with volume shrinkage at melting: A molecular dynamics study of silicon
Authors: Zhang Qi , Li Qikai , Li Mo
Published: January 2013

The thermodynamics of homogeneous melting in superheated crystalline solids with volume shrinkage at melting is investigated using extensive molecular dynamics simulation in conjunction with a classical nucleation theory. A liquid-solid co-existing model is established to overcome the difficult in observing liquid phase formation in a superheated Si crystal. We found that melting is governed by two major factors, the volume change induced strain energy and the curvature of the interface between the liquid and the solid phases. The driving force for melting in superheating regime is lowered by the additional strain energy that restricts homogeneous nucleation of a liquid phase till temperature rises above the normal melting point, thus causing superheating. However, due to the abnormal behavior in the compressibility of the silicon liquid in the superheating regime, the degree of superheating in terms of the liquid nucleation gap becomes significantly reduced. More potential complications caused by the change of the atomic bonding in Si at melting are discussed.
Electronic structure of Fe- vs. Ru-based dye molecules
Authors: Johnson Phillip S. , Cook Peter L. , Zegkinoglou Ioannis , García-Lastra J. M. , Rubio Angel , Ruther Rose E. , Hamers Robert J. , Himpsel F. J.
Published: January 2013

In order to explore whether Ru can be replaced by inexpensive Fe in dye molecules for solar cells, the differences in the electronic structure of Fe- and Ru-based dyes are investigated by X-ray absorption spectroscopy and first-principles calculations. Molecules with the metal in a sixfold, octahedral N cage, such as tris(bipyridines) and tris(phenanthrolines), exhibit a systematic downward shift of the N 1s-to-π* transition when Ru is replaced by Fe. This shift is explained by an extra transfer of negative charge from the metal to the N ligands in the case of Fe, which reduces the binding energy of the N 1s core level. The C 1s-to-π* transitions show the opposite trend, with an increase in the transition energy when replacing Ru by Fe. Molecules with the metal in a fourfold, planar N cage (porphyrins) exhibit a more complex behavior due to a subtle competition between the crystal field, axial ligands, and the 2+ vs. 3+ oxidation states.
The early events in the OH radical oxidation of dimethyl sulfide in water
Authors: Janik Ireneusz , Tripathi G. N. R.
Published: January 2013

The time-resolved Raman observation of a prototype of the hetero-atom three electron bonds (-X-OH) that often form on encounter of the OH radical with chemical species in water is reported. In spite of their wide chemical and biochemical importance, no experimental structural information exists, thus far, on any such bond in solution or in the gas phase. The nature of the >S–O bond formed on the reaction of the OH radical with dimethyl sulfide in water, investigated in the present work, would necessitate a reexamination of the existing reaction mechanisms in related biological systems and development of the appropriate computational methods.
Manipulation of instabilities in core-annular flows using a deformable solid layer
Authors: Gaurav  , Shankar V.
Published: January 2013

The stability of core-annular flow (CAF) of two immiscible fluids surrounded by a soft, deformable solid layer is analyzed to examine the role of solid deformability on the interfacial instabilities in the CAF, using both low-wavenumber asymptotic analysis and numerical solutions by considering axisymmetric perturbations. For CAF in a rigid tube, two qualitatively distinct mechanisms due to capillary forces and viscosity stratification destabilize the interface between the two fluids. We show using a low-wavenumber analysis that the deformability of the solid layer has a stabilizing effect when the more viscous liquid is in the annular region, while it is destabilizing when the less viscous fluid is in the annular region. When the more viscous fluid is in the annulus, our numerical results demonstrate that by tuning the shear modulus of the solid layer, it is possible to maintain a stable core-annular flow (otherwise unstable in a rigid tube), where perturbations with all wavelengths are stable. For the same configuration, when the radius of the core fluid becomes small, we also find that it is possible to restrict the length scale of the instability to a small band of wavelengths. When the less viscous fluid is in the annulus, we show that the CAF (otherwise stable in a rigid tube) could be destabilized by solid deformability. Both these predictions, viz., suppression or enhancement of instability of the liquid-liquid interface by wall deformability could be potentially exploited in microfluidic drop formation applications that seek to control and manipulate the instability of the interface.
Interferometric hard x-ray phase contrast imaging at 204 nm grating period
Authors: Wen Han , Wolfe Douglas E. , Gomella Andrew A. , Miao Houxun , Xiao Xianghui , Liu Chian , Lynch Susanna K. , Morgan Nicole
Published: January 2013

We report on hard x-ray phase contrast imaging experiments using a grating interferometer of approximately 1/10th the grating period achieved in previous studies. We designed the gratings as a staircase array of multilayer stacks which are fabricated in a single thin film deposition process. We performed the experiments at 19 keV x-ray energy and 0.8 μm pixel resolution. The small grating period resulted in clear separation of different diffraction orders and multiple images on the detector. A slitted beam was used to remove overlap of the images from the different diffraction orders. The phase contrast images showed detailed features as small as 10 μm, and demonstrated the feasibility of high resolution x-ray phase contrast imaging with nanometer scale gratings.
Designing an optical set-up of differential laser triangulation for oil film thickness measurement on water
Authors: Baozhen Ge , Jingbin Sun , Pengcheng Liu , Qieni Lü , Di Wu
Published: January 2013

Based on the differential laser triangulation principle, an optical system configuration for measuring the oil film thickness on water is designed and developed. A semiconductor laser of 650 nm wavelength with the maximum power of 5 mW is used as a light source, the magnification of the imaging system is 1.4; the range of the measurement is 0.1 mm–10 mm; the resolution is 2.3 μm and the measurement accuracy is 10 μm theoretically. Experiments are conducted with block gauges and feeler gauges, and the experimental results, with absolute error less than ±25 μm and the maximal measurable thickness 12 mm, indicate that this system presented in this paper can fulfill high accuracy.
Simulation on the translocation of polymer through compound channels
Authors: Wang Chao , Chen Ying-Cai , Sun Li-Zhen , Luo Meng-Bo
Published: January 2013

The translocation of a polymer through compound channels under external electrical field was investigated by Monte Carlo simulation on a three-dimensional simple cubic lattice. The compound channel is composed of two parts: part α with length Lpα and part β with length Lpβ. The two parts have different polymer-channel interactions: a strong attractive interaction with strength ɛα for part α and a variable interaction with strength ɛβ for part β. Results show that the translocation process is remarkably affected by both ɛβ and Lpα, and the fastest translocation can be achieved with a proper choice of ɛβ and Lpα. When ɛβ is large, the translocation is dominated by the last escaping process as it is difficult for the polymer chain to leave the channel. Whereas when Lpα is small and ɛβ ≪ ɛα, the translocation is determined by the initial filling process. For this case, there is a free-energy well at the interface between the part α and the part β, which not only influences the filling dynamics but also affects the translocation probability.
Coat thickness dependent adsorption of hydrophobic molecules at polymer brushes
Authors: Smiatek Jens , Heuer Andreas , Wagner Hendrik , Studer Armido , Hentschel Carsten , Chi Lifeng
Published: January 2013

We study the adsorption properties of hydrophobic test particles at polymer brushes with different coat thicknesses via mesoscopic dissipative particle dynamics simulations. Our findings indicate stronger free energies of adsorption at thin polymer brushes. The reason for this difference is mainly given by entropic contributions due to different elastic deformations of the coatings. The numerical findings are supported by analytical calculations and are in good qualitative agreement to experimental fluorescence intensity results.
Microstrip filters for measurement and control of superconducting qubits
Authors: Longobardi Luigi , Bennett Douglas A. , Patel Vijay , Chen Wei , Lukens James E.
Published: January 2013

Careful filtering is necessary for observations of quantum phenomena in superconducting circuits at low temperatures. Measurements of coherence between quantum states require extensive filtering to protect against noise coupled from room temperature electronics. We demonstrate distributed transmission line filters which cut off exponentially at GHz frequencies and can be anchored at the base temperature of a dilution refrigerator. The compact design makes them suitable to filter many different bias lines in the same setup, necessary for the control and measurement of superconducting qubits.
Large-field high-contrast hard x-ray Zernike phase-contrast nano-imaging beamline at Pohang Light Source
Authors: Lim Jun , Park So Yeong , Huang Jung Yun , Han Sung Mi , Kim Hong-Tae
Published: January 2013

We developed an off-axis-illuminated zone-plate-based hard x-ray Zernike phase-contrast microscope beamline at Pohang Light Source. Owing to condenser optics-free and off-axis illumination, a large field of view was achieved. The pinhole-type Zernike phase plate affords high-contrast images of a cell with minimal artifacts such as the shade-off and halo effects. The setup, including the optics and the alignment, is simple and easy, and allows faster and easier imaging of large bio-samples.
Interfacial study and energy-band alignment of annealed Al2O3 films prepared by atomic layer deposition on 4H-SiC
Authors: Zhang Feng , Sun Guosheng , Zheng Liu , Liu Shengbei , Liu Bin , Dong Lin , Wang Lei , Zhao Wanshun , Liu Xingfang , Yan Guoguo , Tian Lixin , Zeng Yiping
Published: January 2013

Al2O3 films were prepared by atomic layer deposition using trimethylaluminum and H2O at 250 °C on 4H-SiC substrates and annealed at 1000 °C in N2. The as-deposited and annealed Al2O3 films were measured and analyzed near the Al2O3/SiC interfaces by using an X-ray photoelectron spectroscopy (XPS) with etching processing. The XPS results showed that as-deposited Al2O3 films were O-rich and converted to anhydride Al2O3 films after annealed at 1000 °C in N2. Si suboxides were found both at as-deposited and annealed Al2O3/SiC interfaces. Energy band shift between Al2O3 and 4H-SiC was found after annealing. The conduction band offsets of as-grown and annealed Al2O3/SiC were 1.90 and 1.53 eV, respectively. These results demonstrated that Al2O3 can be a good candidate to be applied in SiC metal-oxide-semiconductor devices.
Interaction effects and transport properties of Pt capped Co nanoparticles
Authors: Ludwig A. , Agudo L. , Eggeler G. , Ludwig A. , Wieck A. D. , Petracic O.
Published: January 2013

We studied the magnetic and transport properties of Co nanoparticles (NPs) being capped with varying amounts of Pt. Beside field and temperature dependent magnetization measurements, we performed δΜ measurements to study the magnetic interactions between the Co NPs. We observe a transition from demagnetizing towards magnetizing interactions between the particles for an increasing amount of Pt capping. Resistivity measurements show a crossover from giant magnetoresistance towards anisotropic magnetoresistance.
Hybrid piezoelectric-inductive flow energy harvesting and dimensionless electroaeroelastic analysis for scaling
Authors: Dias J. A. C. , De Marqui C. , Erturk A.
Published: January 2013

Piezoelectric and electromagnetic transduction techniques have peculiar advantages to leverage in the growing field of flow energy harvesting from aeroelastic vibrations. This letter presents the concept of hybrid piezoelectric-inductive power generation with electroaeroelastic modeling and simulations. Dimensionless analysis of the coupled system dynamics is indispensable to proper geometric scaling and optimization of aeroelastic energy harvesters. The governing electroaeroelastic equations are given in dimensionless form, and the effects of aeroelastic and electrical properties are investigated in detail toward understanding the dependence of the cut-in speed (flutter speed) and the maximum power output of the harvester on the system parameters.
Pressure driven tearing and interchange modes in the reversed field pinch
Authors: Paccagnella R.
Published: January 2013

In this work, the magneto-hydro-dynamic stability of pressure driven modes in the reversed field pinch has been analyzed. It is shown that at low and intermediate β's, i.e., typically for values below 20-25%, the tearing parity is dominant, while only at very high β, well above the achieved experimental values, at least part of the modes are converted to ideal interchange instabilities. Before their transition to ideal instabilities, according to their Lundquist number scaling, they can be classified as resistive-g modes.
Hydrogen transport diagnostics by atomic and molecular emission line profiles simultaneously measured for large helical device
Authors: Fujii K. , Shikama T. , Goto M. , Morita S. , Hasuo M.
Published: January 2013

We observe the Balmer-α, -β, and -γ lines of hydrogen atoms and Q branches of the Fulcher-α band of hydrogen molecules simultaneously with their polarization resolved for large helical device. From the fit including the line splits and the polarization dependences by the Zeeman effect, the emission locations, intensities, and the temperatures of the atoms and molecules are determined. The emission locations of the hydrogen atoms are determined outside but close to the last closed flux surface (LCFS). The results are consistent with a previous work (Phys. Plasmas 12, 042501 (2005)). On the other hand, the emission locations of the molecules are determined to be in the divertor legs, which is farer from those of the atoms. The kinetic energy of the atoms is 1 ∼ 20 eV, while the rotational temperature of molecules is ∼0.04 eV. Additionally, substantial wings, which originate from high velocity atoms and are not reproduced by the conventional spectral analysis, are observed in the Balmer line profiles. We develop a one-dimensional model to simulate the transport of the atoms and molecules. The model reproduces the differences of the emission locations of the atoms and molecules when their initial temperatures are assumed to be 3 eV and 0.04 eV, respectively. From the model, the wings of the Balmer-α line is attributed to the high velocity atoms exist deep inside the LCFS, which are generated by the charge exchange collisions with hot protons there.
Charged particle density distributions in multi-component plasmas with two species of warm positive ions
Authors: Hatami M. M.
Published: January 2013

The behavior of charged particle density distributions and the electrostatic potential in the sheath region of a multi-component plasma consisting of electrons and two species of positive ions are investigated by using a fluid description. It is assumed that the ion species are singly charged and have different masses and temperatures. To determine the ion species velocities at the plasma-sheath boundary, we used the recent work of Baalrud et al. [S. Baalrud and C. Hegna, Phys. Plasmas 18, 023505 (2011)]. It is shown that the density distributions of electrons and lighter ion species increase in the sheath region by increasing the temperature of ion species while the density distribution of the heavier ion species decreases. The results also show that by increasing the temperature of the ion species, the electrostatic potential in the sheath region decreases and at the same time the sheath thickness increases.
High mobility half-metallicity in the (LaMnO3)2/(SrTiO3)8 superlattice
Authors: Cossu F. , Singh N. , Schwingenschlögl U.
Published: January 2013

First principles calculations have been performed to investigate the LaMnO3/SrTiO3 superlattice. Structural relaxation within the generalized gradient approximation results in no significant tiltings or rotations of oxygen octahedra, but in distinct distortions in the SrTiO3 region. Taking into account the onsite Coulomb interaction, we find that the Mn spins order ferromagnetically, in contrast to the antiferromagnetic state of bulk LaMnO3. Most importantly, the interface strain combined with charge transfer across the interface induces half-metallicity within the MnO2 layers. The superlattice is particulary interesting for spintronics applications because the half-metallic states are characterized by an extraordinary high mobility.
Laser directly written junctionless in-plane-gate neuron thin film transistors with AND logic function
Authors: Qiang Zhu Li , Dong Wu Guo , Mei Zhou Ju , Dou Wei , Liang Zhang Hong , Wan Qing
Published: January 2013

Junctionless oxide-based neuron thin-film transistors with in-plane-gate structure are fabricated at room temperature by a laser scribing process. The neuron transistors are composed of a bottom indium-tin-oxide floating gate and multiples of in-plane control gates. The control gates, coupling with the floating gate, control the “on” and “off” of the transistor. Effective field-effect modulation of the drain current has been realized. AND logic is demonstrated on a dual in-plane gate neuron transistor. The developed laser scribing technology is highly desirable in terms of the fabrication of high performance neuron transistors with low-cost.
Lifetime of sub-THz coherent acoustic phonons in a GaAs-AlAs superlattice
Authors: Maznev A. A. , Hofmann Felix , Jandl Adam , Esfarjani Keivan , Bulsara Mayank T. , Fitzgerald Eugene A. , Chen Gang , Nelson Keith A.
Published: January 2013

We measure the lifetime of the zone-center 340 GHz longitudinal phonon mode in a GaAs-AlAs superlattice excited and probed with femtosecond laser pulses. By comparing measurements conducted at room temperature and liquid nitrogen temperature, we separate the intrinsic (phonon-phonon scattering) and extrinsic contributions to phonon relaxation. The estimated room temperature intrinsic lifetime of 0.95 ns is compared to available calculations and experimental data for bulk GaAs. We conclude that ∼0.3 THz phonons are in the transition zone between Akhiezer and Landau-Rumer regimes of phonon-phonon relaxation at room temperature.
Effects of anode materials on resistive characteristics of NiO thin films
Authors: Jia Ze , Wang Linkai , Zhang Naiwen , Ren Tianling , Liou Juin J.
Published: January 2013

This letter shows that the NiO-based structure with different anodes has different resistive switching properties. A conical conductive filament (CF) model is proposed for oxygen vacancies distributed in NiO films. Modeling analysis reveals much larger dissolution velocity of CF near anodes than near cathodes during the reset process. Different interfaces shown in Auger electron spectroscopy can be bound with the model to reveal that CF is dissolved in the structure with Pt or Au as anodes, while CF remains constant if the anode material is Ti or Al, which can explain whether switching properties occur in the specific NiO-based structures.
Thermal conductivity measurement of individual Bi2Se3 nano-ribbon by self-heating three-ω method
Authors: Li Guodong , Liang Dong , Qiu Richard L. J. , Gao Xuan P. A.
Published: January 2013

We report thermal conductivity measurements of individual single crystalline Bi2Se3 nano-ribbon (NR) synthesized via the gold nanoparticle catalyzed vapor-liquid-solid mechanism. By using the four-probe third harmonic method, thermal conductivity of Bi2Se3 NRs was obtained in the temperature range of 10 K to 300 K. It is found that the measured thermal conductivities are nearly two orders of magnitude smaller than the bulk value and have a maximum thermal conductivity at temperature (around 200 K) greater than the bulk. The significant reduced thermal conductivity of NRs is attributed to enhanced phonon boundary scattering in nanostructured material.
Light-emitting properties of a strain-tuned microtube containing coupled quantum wells
Authors: Zhen H. L. , Huang G. S. , Kiravittaya S. , Li S. L. , Deneke Ch. , Thurmer Dominic J. , Mei Y. F. , Schmidt O. G. , Lu W.
Published: January 2013

Pre-stressed multi-layer nanomembranes are rolled-up into a microtube in order to tune the strain applied to the contained coupled GaAs quantum wells. Additional GaAs/AlAs adjusting layers were deposited on the top of the nanomembrane to alter the thickness/stiffness of the to-be-rolled nanomembrane. In this way, microtubes with an adjustable diameter and strain are possible from a single initial grown sample. The internal strain state in the microtube affects the energy levels of the quantum wells and their coupling, which can be probed sensitively by photoluminescence. We measure different strain relaxation in rolled-up nanomembranes which we explain using a gradual change of the longitudinal relaxation as the distance of the nanomembrane from the etching front varies.
Ion pseudoheating by low-frequency Alfvén waves revisited
Authors: Dong Chuanfei , Singh Nagendra
Published: January 2013

Pseudoheating of ions in the presence of Alfvén waves is studied. We show that this process can be explained by E × B drift, indicating that the pseudoheating is a consequence of equilibrium MHD system. The analytic solution obtained in this paper is quantitatively in accordance with previous results. Our simulation results show that the Maxwellian distribution is broadened during the pseudoheating; however, the shape of the broadening distribution function depends on the number of wave modes (i.e., a wave spectrum or a monochromatic dispersionless wave) and the initial thermal speed of ions (vp). It is of particular interests to find that the Maxwellian shape is more likely to maintain during the pseudoheating under a wave spectrum compared with a monochromatic wave. It significantly improves our understanding of heating processes in interplanetary space where Alfvénic turbulences exist pervasively. Compared with a monochromatic Alfvén wave, E × B drift produces more energetic particles in a broad spectrum of Alfvén waves, especially when the Alfvénic turbulence with phase coherent wave modes is given. Such particles may escape from the region of interaction with the Alfvén waves and can contribute to fast particle population in astrophysical and space plasmas.
Absorption measurements on silver bromide crystals and fibers in the infrared
Authors: Israeli S. , Katzir A.
Published: January 2013

The absorption coefficients of single crystals of silver bromide, deformed crystals and polycrystalline fibers, extruded from single crystals, were measured by laser calorimetry. The measurements were carried out at three wavelengths in the near-infrared and middle-infrared ranges. The absorption coefficients of the fibers were higher than the coefficients of the crystals and deformed crystals, over the entire spectral range. We suggest that this absorption is due to the weak absorption tail.
Graphdiyne: A promising anode material for lithium ion batteries with high capacity and rate capability
Authors: Zhang Hongyu , Xia Yueyuan , Bu Hongxia , Wang Xiaopeng , Zhang Meng , Luo Youhua , Zhao Mingwen
Published: January 2013

We have carried out first-principles calculations to explore the energetics and dynamics of Li in graphdiyne monolayers. The porous structure of graphdiyne enables both in-plane and out-plane diffusion of Li ions with moderate barriers, 0.35–0.52 eV. A unique Li occupation pattern named as a triangular pattern is identified, with Li atoms occupying three symmetric sites in the triangular-like pores. Based on this occupation pattern, the Li storage capacity of single-layer graphdiyne can be as high as LiC3, which is twice the capacity of commonly used graphite (LiC6). With high Li mobility and high storage capacity, this experimentally available porous carbon material is expected to find applications in efficient lithium storage.
Barrier tunneling time of an electron in graphene
Authors: Li Zhi-Jian , Zhao Haiyan , Nie Yi-Hang , Liang J.-Q.
Published: January 2013

With the help of electron spin-coherent-state, we theoretically investigate the quantum tunneling time of a Dirac electron through a rectangular potential-barrier in monolayer graphene. It is shown that the tunneling time, which is measured in terms of the electron-spin precession in the magnetic field confined in the barrier region, is equal to the dwell time. Moreover, when the wave function in barrier is an oscillating mode, the curve of tunneling-time against the barrier-width oscillates around an increasing average-line. While for the wave function of an evanescent mode, the tunneling time is independent of the barrier width. In particular, the tunneling time just equals the potential width divided by the Fermi velocity in the Klein tunneling.
Non-planar ion-acoustic solitary waves and their head-on collision in a plasma with nonthermal electrons and warm adiabatic ions
Authors: Han Jiu-Ning , He Yong-Lin , Chen Yan , Zhang Ke-Zhi , Ma Bao-Hong
Published: January 2013

By using the model of Cairns et al. [Geophys. Rev. Lett. 22, 2709 (1995)], the head-on collision of cylindrical/spherical ion-acoustic solitary waves in an unmagnetized non-planar plasma consisting of warm adiabatic ions and nonthermally distributed electrons is investigated. The extended Poincaré-Lighthill-Kuo perturbation method is used to derive the modified Korteweg-de Vries equations for ion-acoustic solitary waves in this plasma system. The effects of the plasma geometry m, the ion to electron temperature ratio σ, and the nonthermality of the electron distribution α on the interaction of the colliding solitary waves are studied. It is found that the plasma geometries have a big impact on the phase shifts of solitary waves. Also it is important to note that the phase shifts induced by the collision of compressive and rarefactive solitary waves are very different. We point out that this study is useful to the investigations about the observations of electrostatic solitary structures in astrophysical as well as in experimental plasmas with nonthermal energetic electrons.
Probing ferromagnetic/ferroelectric interfaces via spin wave resonance
Authors: Zhao Y.-L. , Sun Y. , Pan L.-Q. , Li K.-S. , Yu D.-B.
Published: January 2013

The interfacial properties of the ferromagnetic (FM)/ferroelectric (FE) heterostructure La0.7Sr0.3MnO3/BaTiO3 (LSMO/BTO) have been investigated by employing spin wave resonance technique. In addition to the uniform ferromagnetic resonance, spin wave resonances with both body and surface wave modes are observed. The analysis on the spin wave spectrum in comparison with that of a La0.7Sr0.3MnO3 thin film suggests that the ferroelectric BaTiO3 layer not only modifies the in-plane bulk magnetic anisotropy of La0.7Sr0.3MnO3 but also induces surface spin pinning both in plane and out of plane. Moreover, a quantitative determination of spin wave exchange constant D is obtained from the spin wave spectrum at low temperature. Our study proves that spin wave resonance is a powerful tool to investigate the buried interfaces in ferromagnetic/ferroelectric heterostructures.
Investigation of electrical transport in anodized single TiO2 nanotubes
Authors: Hattori Masashi , Noda Kei , Nishi Tatsuya , Kobayashi Kei , Yamada Hirofumi , Matsushige Kazumi
Published: January 2013

Electrical transport in anodized single titania nanotube (TNT) free from any structural effects of titania nanotube array (TNA) was investigated. An anodized TNA was disassembled into single TNTs with two-step anodization technique. Then, single TNT bridges between gold electrodes with a gap of 500 nm were prepared by dielectrophoretic alignment. Quantitative assessment of electron mobility inside single anatase and rutile TNT was carried out by 2-probe current-voltage measurement and analysis based on a metal-semiconductor-metal circuit model with Schottky barriers. Our approach to intrinsic electrical transport of single nanotube is quite effective for understanding the electronic and optical properties of TNA.
High-power THz wave generation in plasma induced by polarization adjusted two-color laser pulses
Authors: Minami Yasuo , Kurihara Takayuki , Yamaguchi Keita , Nakajima Makoto , Suemoto Tohru
Published: January 2013

We introduce a simple and efficient method of enhancing the terahertz field in an air plasma produced by two-color laser pulses, by inserting a specially designed dual-wavelength wave plate between the non-linear optical crystal and the plasma. Adjusting the polarization of the two laser pulses yielded an electric field of 1.4 MV/cm, which was 1.7 times as intense as that obtained from the unmodified system. Additionally, taking a dispersion of the group velocities of the two-color laser pulses into account, we discussed the validity of the enhancement factor.
Biaxially stretchable silver nanowire transparent conductors
Authors: Ho Xinning , Nie Tey Ju , Liu Wenjun , Kweng Cheng Chek , Wei Jun
Published: January 2013

Biaxially stretchable silver nanowire transparent conductors are demonstrated. The silver nanowire film retains its electrical conductivity up to 10% applied strain. We examine the factors limiting stretchability and compare the mechanics of biaxially and uniaxially stretchable systems, which will be useful for exploring biaxially stretchable systems in future.
Improved cathode buffer layer to decrease exciton recombination in organic planar heterojunction solar cells
Authors: Verreet Bregt , Malinowski Pawel E. , Niesen Bjoern , Cheyns David , Heremans Paul , Stesmans Andre , Rand Barry P.
Published: January 2013

We show that an advanced cathode buffer design, consisting of bathocuproine/3,4,9,10-perylenetetracarboxylic bis-benzimidazole/Ag, increases the short-circuit current of organic planar heterojunction cells and reduces the J-V slope at reverse voltages. We study the physical origin of these effects by measuring reflectivity, voltage dependent external quantum efficiency, and voltage dependent photoluminescence. Our findings suggest that the observed effects are mainly associated with a voltage dependent polaron-induced exciton quenching in the C60 layer. Finally, this improved cathode buffer design is applied to a diindeno[1,2,3-cd:1′,2′,3′-lm]perylene/C70 based cell, leading to a considerable planar heterojunction efficiency of 5.7%.
Simulation of multilevel cell spin transfer switching in a full-Heusler alloy spin-valve nanopillar
Authors: Huang H. B. , Ma X. Q. , Liu Z. H. , Zhao C. P. , Shi S. Q. , Chen L. Q.
Published: January 2013

A multilevel cell spin transfer switching process in a full-Heusler Co2FeAl0.5Si0.5 alloy spin-valve nanopillar was investigated using micromagnetic simulations. An intermediate state of two-step spin transfer magnetization switching was reported due to the four-fold magnetocrystalline anisotropy; however, we discovered the intermediate state has two possible directions of −90° and +90°, which could not be detected in the experiments due to the same resistance of the −90° state and the +90° state. The domain structures were analyzed to determine the mechanism of domain wall motion and magnetization switching under a large current. Based on two intermediate states, we reported a multilevel bit spin transfer multi-step magnetization switching by changing the magnetic anisotropy in a full-Heusler alloy nanopillar.
Direct ab-initio molecular dynamic study of ultrafast phase change in Ag-alloyed Ge2Sb2Te5
Authors: Prasai B. , Chen G. , Drabold D. A.
Published: January 2013

We employed ab-initio molecular dynamics to directly simulate the effects of Ag alloying (less than 5% Ag concentration) on the phase change properties of Ge2Sb2Te5. The short range order is preserved, whereas a slight improvement in the chemical order is observed. A slight decrease in the fraction of tetrahedral Ge (sp3 bonding) is reflected in the reduction of the optical band gap and in the increased dielectric constant. Simulations of the amorphous to crystalline phase change cycle revealed the fact that the crystallization speed in Ag0.5Ge2Sb2Te5 is not less than that in Ge2Sb2Te5. Moreover, the smaller density difference and the larger energy difference between the two phases of Ag0.5Ge2Sb2Te5 (compared to Ge2Sb2Te5) suggest a smaller residual stress in devices due to phase transition and improved thermal stability for Ag0.5Ge2Sb2Te5. The potential viability of this material suggests the need for a wide exploration of alternative phase change memory materials.
Surface plasmon coupled light-emitting diode with metal protrusions into p-GaN
Authors: Chen Horng-Shyang , Chen Chia-Feng , Kuo Yang , Chou Wang-Hsien , Shen Chen-Hung , Jung Yu-Lung , Kiang Yean-Woei , Yang C. C.
Published: January 2013

An Ag protrusion array is fabricated on the p-GaN layer of an InGaN/GaN quantum-well (QW) light-emitting diode (LED) for generating surface plasmon coupling with the radiating dipoles in the QWs and hence LED emission enhancement. The tips of the Ag protrusions penetrating into the p-GaN layer are close to the QWs such that the induced near field around the tips can strongly interact with the dipoles in the QWs. With the Ag protrusions, the fabricated flip-chip LED shows a 74.6% enhancement in output intensity at 100 mA in injection current, when compared with a control sample of no Ag protrusion. The simulation results of Ag protrusion absorption agree reasonably well with the experimental data of protrusion reflectance. The simulation also shows a strong near field distribution around the tip of an Ag protrusion for coupling with the radiating dipoles in the QWs.
Esophageal cancer detection based on tissue surface-enhanced Raman spectroscopy and multivariate analysis
Authors: Feng Shangyuan , Lin Juqiang , Huang Zufang , Chen Guannan , Chen Weisheng , Wang Yue , Chen Rong , Zeng Haishan
Published: January 2013

The capability of using silver nanoparticle based near-infrared surface enhanced Raman scattering (SERS) spectroscopy combined with principal component analysis (PCA) and linear discriminate analysis (LDA) to differentiate esophageal cancer tissue from normal tissue was presented. Significant differences in Raman intensities of prominent SERS bands were observed between normal and cancer tissues. PCA-LDA multivariate analysis of the measured tissue SERS spectra achieved diagnostic sensitivity of 90.9% and specificity of 97.8%. This exploratory study demonstrated great potential for developing label-free tissue SERS analysis into a clinical tool for esophageal cancer detection.
Ferrimagnetic transition in the compound Sr0.9La0.1Ti0.9Co0.1O3
Authors: Yang J. , Shao D. F. , Zhu X. B. , Yang Z. R. , Sun Y. P. , Lee Y. P.
Published: January 2013

We have investigated the structural and magnetic properties of Sr0.9La0.1TiO3 and Sr0.9La0.1Ti0.9Co0.1O3. Both samples can be indexed by a cubic lattice with the space group Pm3m at room temperature. The measurements of x-ray photoelectron spectroscopy and electron paramagnetic resonance confirmed the presence of Ti3+ ions in the samples. The sample Sr0.9La0.1TiO3 exhibits a strongly enhanced Pauli-paramagnetism behavior, whereas Sr0.9La0.1Ti0.9Co0.1O3 undergoes a ferrimagnetic transition at 127 K confirmed by a small λ anomaly at 128 K in the curve of specific heat. This transition may originate from a local charge transfer that creates some Co3+-Ti3+ antiferromagnetic pairings.
Electron mobility enhancement in ZnO thin films via surface modification by carboxylic acids
Authors: Spalenka Josef W. , Gopalan Padma , Katz Howard E. , Evans Paul G.
Published: January 2013

Modifying the surface of polycrystalline ZnO films using a monolayer of organic molecules with carboxylic acid attachment groups increases the field-effect electron mobility and zero-bias conductivity, resulting in improved transistors and transparent conductors. The improvement is consistent with the passivation of defects via covalent bonding of the carboxylic acid and is reversible by exposure to a UV-ozone lamp. The properties of the solvent used for the attachment are crucial because solvents with high acid dissociation constants (Ka) for carboxylic acids lead to high proton activities and etching of the nanometers-thick ZnO films, masking the electronic effect.
Soft 2D Layer Porous Coordination Polymers with 1,2-Di(4-pyridyl)ethane
Authors: Kishida Keisuke , Horike Satoshi , Kongpatpanich Kanokwan , Kitagawa Susumu
Published: January 2013

Porous coordination polymer compounds consisting of Zn2+, 1,2-di(4-pyridyl)ethane, and dicarboxylates were synthesised and their crystal structures were determined. These are doubly interpenetrated 2D layer structures, and the flexibility of porous structures is dependent on the substituent group of the dicarboxylate. From gas adsorption studies, distinct adsorption isotherms were observed for CO2, CH4, C2H4, and C2H6 at 195 K and 273 K, respectively.
Genotype and fetal size affect maternal­–fetal amino acid status and fetal endocrinology in Large White×Landrace and Meishan pigs
Authors: Ashworth Cheryl J. , Nwagwu Margaret O. , McArdle Harry J.
Published: January 2013

This study compared maternal plasma amino acid concentrations, placental protein secretion in vitro and fetal body composition and plasma amino acid and hormone concentrations in feto–placental units from the smallest and a normally-sized fetus carried by Large White × Landrace or Meishan gilts on Day 100 of pregnancy. Compared with Large White × Landrace, Meishan placental tissue secreted more protein and Meishan fetuses contained relatively more fat and protein, but less moisture. Fetal plasma concentrations of insulin, triiodothryonine, thyroxine and insulin-like growth factor (IGF)-II were higher in Meishan than Large White × Landrace fetuses. In both breeds, fetal cortisol concentrations were inversely related to fetal size, whereas concentrations of IGF-I were higher in average-sized fetuses. Concentrations of 10 amino acids were higher in Large White × Landrace than Meishan gilts, while glutamine concentrations were higher in Meishan gilts. Concentrations of alanine, aspartic acid, glutamic acid and threonine were higher in Meishan than Large White × Landrace fetuses. Average-sized fetuses had higher concentrations of asparagine, leucine, lysine, phenylalanine, threonine, tyrosine and valine than the smallest fetus. This study revealed novel genotype and fetal size differences in porcine maternal–fetal amino acid status and fetal hormone and metabolite concentrations.
Status of human germ cell differentiation from pluripotent stem cells
Authors: Pera Renee A. Reijo
Published: January 2013

Historically, the quality of life of infertile couples has been greatly diminished by the loss of opportunity to conceive. However, beginning with the advent of IVF in the late 1970s, novel clinical interventions have greatly changed the outlook for those with severe forms of infertility. Yet, in cases in which the quality and quantity of germ cells are most compromised, there are few options. In the present paper, the current status of germ cell development from stem cells is reviewed in light of potential utility for basic science and clinical applications.
Fuel properties and fire behaviour characteristics of prescribed fire in pine-dominated forests at Nam Nao National Park, Thailand
Authors: Wanthongchai K. , Tarusadamrongdet V. , Chinnawong K. , Sooksawat K.
Published: January 2013

Anthropogenic burning has become a common phenomenon throughout Thailand’s pine-dominated ecosystems. This study investigated fuel loads and experimental fire behaviour characteristics in a degraded pine forest (PF) and a pine–oak forest (O-PF), at Nam Nao National Park, Thailand in three replicate 50 × 50-m plots of each forest type. Pre-burn fuel loads, fire behaviour descriptors, fire and soil temperature, the residues left after burning and post-burn fuel recovery for 1 year were investigated. The aboveground fuel load in PF (1.29 kg m–2) was significantly higher than in O-PF (0.87 kg m–2). The main fuel components in the PF stand were grass (45%) and litter (44%), whereas leaf litter was the predominant fuel in the O-PF stand (55%). The fire behaviour characteristics in the PF stand were significantly greater than those in the O-PF stand. Burning at the O-PF and the PF was respectively classified as low (48 kW m–1) and medium intensity (627 kW m–1). During the burning experiment, the surface soil temperatures at all sites were higher than 250°C. However, fire did not cause temperature changes in the deeper soil layers. In the pine forest the post-burn fuel loads 1 year after the fire remained lower than the pre-burn level. These results may imply that a pine forest at Nam Nao National Park requires more than 1 year of fire-free period to recover back to the pre-burn conditions.
Regulation of Hippo pathway by mitogenic growth factors via phosphoinositide 3-kinase and phosphoinositide-dependent kinase-1
Authors: Fan Run , Kim Nam-Gyun , Gumbiner Barry M.
Published: January 2013

The Hippo signaling pathway inhibits cell growth and regulates organ size through a kinase cascade that leads to the phosphorylation and nuclear exclusion of the growth-promoting transcriptional coactivator Yes-associated protein (YAP)/Yorkie. It mediates contact inhibition of cell growth downstream of cadherin adhesion molecules and other cell surface proteins. Contact inhibition is often antagonized by mitogenic growth factor signaling. We report an important mechanism for this antagonism, inhibition of Hippo pathway signaling by mitogenic growth factors. EGF treatment of immortalized mammary cells triggers the rapid translocation of YAP into the nucleus along with YAP dephosphorylation, both of which depend on Lats, the terminal kinase in the Hippo pathway. A small-molecule inhibitor screen of downstream effector pathways shows that EGF receptor inhibits the Hippo pathway through activation of PI3-kinase (PI3K) and phosphoinositide-dependent kinase (PDK1), but independent of AKT activity. The PI3K-PDK1 pathway also mediates YAP nuclear translocation downstream of lysophosphatidic acid and serum as a result of constitutive oncogenic activation of PI3K. PDK1 associates with the core Hippo pathway-kinase complex through the scaffold protein Salvador. The entire Hippo core complex dissociates in response to EGF signaling in a PI3K-PDK1–dependent manner, leading to inactivation of Lats, dephosphorylation of YAP, and YAP nuclear accumulation and transcriptional activation of its target gene,
CTGF
. These findings show that an important activity of mitogenic signaling pathways is to inactivate the growth-inhibitory Hippo pathway and provide a mechanism for antagonism between contact inhibition and growth factor action.
Iron induces bimodal population development by
Escherichia coli
Authors: DePas William H. , Hufnagel David A. , Lee John S. , Blanco Luz P. , Bernstein Hans C. , Fisher Steve T. , James Garth A. , Stewart Philip S. , Chapman Matthew R.
Published: January 2013

Bacterial biofilm formation is a complex developmental process involving cellular differentiation and the formation of intricate 3D structures. Here we demonstrate that exposure to ferric chloride triggers rugose biofilm formation by the uropathogenic
Escherichia coli
strain UTI89 and by enteric bacteria
Citrobacter koseri
and
Salmonella enterica
serovar
typhimurium
. Two unique and separable cellular populations emerge in iron-triggered, rugose biofilms. Bacteria at the air–biofilm interface express high levels of the biofilm regulator
csgD
, the cellulose activator
adrA
, and the curli subunit operon
csgBAC
. Bacteria in the interior of rugose biofilms express low levels of
csgD
and undetectable levels of matrix components curli and cellulose. Iron activation of rugose biofilms is linked to oxidative stress. Superoxide generation, either through addition of phenazine methosulfate or by deletion of
sodA
and
sodB
, stimulates rugose biofilm formation in the absence of high iron. Additionally, overexpression of Mn-superoxide dismutase, which can mitigate iron-derived reactive oxygen stress, decreases biofilm formation in a WT strain upon iron exposure. Not only does reactive oxygen stress promote rugose biofilm formation, but bacteria in the rugose biofilms display increased resistance to H
2
O
2
toxicity. Altogether, we demonstrate that iron and superoxide stress trigger rugose biofilm formation in UTI89. Rugose biofilm development involves the elaboration of two distinct bacterial populations and increased resistance to oxidative stress.