bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical properties of pSi/[6,6] phenyl-C61 butyric acid methyl ester/Al hybrid heterojunctions: Experimental and theoretical evaluation of diode operation
Authors: Bednorz Mateusz , Fromherz Thomas , Matt Gebhard J. , Brabec Christoph J. , Scharber Markus , Serdar Sariciftci N.
Published: December 2012

In this work, we analyze electrically the Al/p-Si/[6,6] phenyl-C61 butyric acid methyl ester/Al hybrid heterojunction. The barrier height at the p-Si/PCBM interface corresponding to the difference between Si valence band edge and the lowest unoccupied molecular orbital energy level of PCBM is studied with current-voltage (J-V) and capacitance-voltage (C-V) methods and determined to be ≃0.55 eV. This value is in agreement with the onset energy of spectrally resolved photocurrent measurements presented in a previous publication [Matt et al., Adv. Mater. 22, 647 (2010)]. For the J-V characteristics, a thorough model based on an interface generation-recombination current is proposed. All relevant energy levels for this model are obtained experimentally. As origin of the large reverse current, the thermal generation of charge carriers throughout the Si depletion region is identified by the thermal activation measurements.
Structures of mixed argon-nitrogen clusters
Authors: Nagasaka Masanari , Serdaroglu Ertugrul , Flesch Roman , Rühl Eckart , Kosugi Nobuhiro
Published: December 2012

The structures of mixed argon-nitrogen clusters of different compositions are investigated by analyzing core level shifts and relative intensities of surface and bulk sites in the Ar 2p3/2 regime in soft X-ray photoelectron spectroscopy. These structures are confirmed by core level shift calculations taking induced dipole interactions into account, in which several model structures of the mixed clusters are considered by Monte Carlo simulations. These results suggest that the mixed argon-nitrogen clusters show partial core-shell structures, where an argon core is partially covered by nitrogen molecules.
BX90: A new diamond anvil cell design for X-ray diffraction and optical measurements
Authors: Kantor I. , Prakapenka V. , Kantor A. , Dera P. , Kurnosov A. , Sinogeikin S. , Dubrovinskaia N. , Dubrovinsky L.
Published: December 2012

We present a new design of a universal diamond anvil cell, suitable for different kinds of experimental studies under high pressures. Main features of the cell are an ultimate 90-degrees symmetrical axial opening and high stability, making the presented cell design suitable for a whole range of techniques from optical absorption to single-crystal X-ray diffraction studies, also in combination with external resistive or double-side laser heating. Three examples of the cell applications are provided: a Brillouin scattering of neon, single-crystal X-ray diffraction of α-Cr2O3, and resistivity measurements on the (Mg0.60Fe0.40)(Si0.63Al0.37)O3 silicate perovskite.
Analytical continuation approaches to electronic transport: The resonant level model
Authors: Wilner Eli Y. , Levy Tal J. , Rabani Eran
Published: December 2012

The analytical continuation average spectrum method (ASM) and maximum entropy (MaxEnt) method are applied to the dynamic response of a noninteracting resonant level model within the framework of the Kubo formula for electric conductivity. The frequency dependent conductivity is inferred from the imaginary time current-current correlation function for a wide range of temperatures, gate voltages, and spectral densities representing the leads, and compared with exact results. We find that the MaxEnt provides more accurate results compared to the ASM over the full spectral range.
Central configurations and homographic solutions for the quasihomogeneous N-body problem
Authors: Paraschiv Victor
Published: December 2012

For the N-body problem given by quasihomogeneous force functions of the form C1/ra + C2/rb (C1, C2 real, and 0 < a ⩽ b), we prove that the simultaneous and extraneous central configurations are the only types of central configurations. Then we focus on attractive-attractive force functions (C1 and C2 positive) and analyze the connection between central configurations and homographic solutions. Namely, we extend the classical Lagrange's theorem (a solution is homographicif and only if the bodies form equivalent central configurations for all times) to attractive-attractive quasihomogeneous problems, and give sufficient conditions for the construction of homographic solutions.
Optimization of power generation from a set of low-temperature abandoned gas wells, using organic Rankine cycle
Authors: Ebrahimi Mahyar , Torshizi Seyed Ebrahim Moussavi
Published: December 2012

This research article deals with the employment of organic Rankine cycle (ORC) to generate electricity from a set of low-temperature abandoned gas wells in Iran. At first, a thermodynamic analysis was performed to select an appropriate power cycle; consequently organic Rankine cycle was chosen. Then, a comprehensive investigation was carried out to find a typical low-temperature abandoned gas reservoir, so an abandoned gas reservoir in the central part of Iran was considered. The next step was selecting the working fluid; in this regard, a vast range of common organic fluids were studied and R125 was chosen. Finally, the gas well and the power plant were simulated, and then a parametric optimization of the ORC plant was performed in order to achieve optimum power generation, and also to compute generated power at different operational parameters of gas wells and power cycle.
Subdiffusion in hair bundle dynamics: The role of protein conformational fluctuations
Authors: Sharma Rati , Cherayil Binny J.
Published: December 2012

The detection of sound signals in vertebrates involves a complex network of different mechano-sensory elements in the inner ear. An especially important element in this network is the hair bundle, an antenna-like array of stereocilia containing gated ion channels that operate under the control of one or more adaptation motors. Deflections of the hair bundle by sound vibrations or thermal fluctuations transiently open the ion channels, allowing the flow of ions through them, and producing an electrical signal in the process, eventually causing the sensation of hearing. Recent high frequency (0.1–10 kHz) measurements by Kozlov et al. [Proc. Natl. Acad. Sci. U.S.A. 109, 2896 (2012)]10.1073/pnas.1121389109 of the power spectrum and the mean square displacement of the thermal fluctuations of the hair bundle suggest that in this regime the dynamics of the hair bundle are subdiffusive. This finding has been explained in terms of the simple Brownian motion of a filament connecting neighboring stereocilia (the tip link), which is modeled as a viscoelastic spring. In the present paper, the diffusive anomalies of the hair bundle are ascribed to tip link fluctuations that evolve by fractional Brownian motion, which originates in fractional Gaussian noise and is characterized by a power law memory. The predictions of this model for the power spectrum of the hair bundle and its mean square displacement are consistent with the experimental data and the known properties of the tip link.
Competing nonlinearities with metamaterials
Authors: Kapitanova Polina V. , Slobozhnanyuk Alexey P. , Shadrivov Ilya V. , Belov Pavel A. , Kivshar Yuri S.
Published: December 2012

We suggest an approach for creating metamaterials with sign-varying nonlinear response. We demonstrate that microwave metamaterials with such competing nonlinearities can be created by loading split-ring resonators (“meta-atoms” of the structure) with pairs of varactor diodes and photodiodes exhibiting nonmonotonic resonance frequency shift with changing incident microwave power. Additionally, the nonlinear response of such metamaterials can be controlled by illuminating the meta-atoms by light.
An electrically switchable surface free energy on a liquid crystal and polymer composite film
Authors: Lin Yi-Hsin , Chu Ting-Yu , Tsou Yu-Shih , Chang Kai-Han , Chiu Ya-Ping
Published: December 2012

An electrically switchable surface free energy on a liquid crystal and polymer composite film (LCPCF) resulting from the orientations of liquid crystal molecules is investigated. By modification of Cassie’s model and the measurement based on the Chibowski’s film pressure model (E. Chibowski, Adv. Colloid Interface Sci. 103, 149 (2003)), the surface free energy of LCPCF is electrically switchable from 36×10−3J/m2 to 51×10−3J/m2 while the average tilt angle of LC molecules changes from 0° to 32° with the applied pulsed voltage. The switchable surface free energy of LCPCF can help us to design biosensors and photonics devices, such as electro-optical switches, blood sensors, and sperm testers.
Manipulation of giant Faraday rotation in graphene metasurfaces
Authors: Fallahi Arya , Perruisseau-Carrier Julien
Published: December 2012

Faraday rotation is a fundamental magneto-optical phenomenon used in various optical control and magnetic field sensing techniques. Recently, it was shown that a giant Faraday rotation can be achieved in the low-THz regime by a single monoatomic graphene layer. Here, we demonstrate that this exceptional property can be manipulated through adequate nano-patterning, notably achieving giant rotation up to 6THz with features no smaller than 100 nm. The effect of the periodic patterning on the Faraday rotation is predicted by a simple physical model, which is then verified and refined through accurate full-wave simulations.
Reverse mass transport during capping of In0.5Ga0.5As/GaAs quantum dots
Authors: Eisele H. , Ebert Ph. , Liu N. , Holmes A. L. , Shih C.-K.
Published: December 2012

The rates of indium mass transport between the wetting layer, the quantum dots, and the capping layer are derived from the indium distributions probed by cross-sectional scanning tunneling microscopy of the In0.5Ga0.5As/GaAs quantum dot system. During capping, a lateral back-segregation from the quantum dots toward the wetting layer is found, reversing the Stranski-Krastanov growth mode during quantum dot formation. This lateral back-segregation critically affects the resulting indium distribution in the wetting layer, the apparent segregation coefficients as well as the quantum dot shape. Furthermore, the strain effect on the segregation coefficient is quantified.
Falling plumes of point particles in viscous fluid
Authors: Crosby Andrew , Lister John R.
Published: December 2012

The growth of radial bulges on the conduit of a falling viscous plume of particles, reported by Pignatel et al. for a finite starting plume [F. Pignatel, M. Nicolas, É. Guazzelli, and D. Saintillan, “Falling jets of particles in viscous fluids,” Phys. Fluids 21, 123303 (2009)10.1063/1.3276235], is investigated both numerically and analytically. As a model for the plume conduit, an infinite vertical cylinder of identical non-Brownian point particles falling under gravity in Stokes flow is considered. Numerically, this is implemented with periodic boundary conditions of a large, but finite, period. The quasi-periodic numerical simulations exhibit qualitatively similar behaviour to that previously observed for the finite plume, demonstrating that neither the plume head nor the plume source play a role in the growth of the radial bulges. This growth is instead shown to be due to fluctuations in the average number density of particles along the plume about its mean value n, which leads to an initial growth rate proportional to n−1/2. The typical length scale of the bulges, which is of the order of 10 plume radii, results from the particle plume responding most strongly to density fluctuations in the axial direction on this scale. Large radial bulges undergo a nonlinear wave-breaking mechanism, which entrains ambient fluid and reduces the magnitude of perturbations on the plume surface. This contributes towards an outwards diffusion of the plume in which the increase in radius, at sufficiently large times, is proportional to t2/3.
The c-axis thermal conductivity of graphite film of nanometer thickness measured by time resolved X-ray diffraction
Authors: Harb M. , von Korff Schmising C. , Enquist H. , Jurgilaitis A. , Maximov I. , Shvets P. V. , Obraztsov A. N. , Khakhulin D. , Wulff M. , Larsson J.
Published: December 2012

We report on the use of time resolved X-ray diffraction to measure the dynamics of strain in laser-excited graphite film of nanometer thickness, obtained by chemical vapour deposition (CVD). Heat transport in the CVD film is simulated with a 1-dimensional heat diffusion model. We find the experimental data to be consistent with a c-axis thermal conductivity of ∼0.7 W m−1 K−1. This value is four orders of magnitude lower than the thermal conductivity in-plane, confirming recent theoretical calculations of the thermal conductivity of multilayer graphene.
Electrically active Er doping in InAs, In0.53Ga0.47As, and GaAs
Authors: Burke Peter G. , Ismer Lars , Lu Hong , Frantz Elan , Janotti Anderson , Van de Walle Chris G. , Bowers John E. , Gossard Arthur C.
Published: December 2012

The electron concentration in dilute alloys of Er in GaAs, In0.53Ga0.47As, and InAs grown by molecular beam epitaxy is studied as a function of Er concentration and In content. Using first-principles calculations based on hybrid density functional theory, we attribute an observed increase in conduction electron concentration to Er incorporation on interstitial sites. Er also incorporates on substitutional sites where it is isovalent and electrically inactive. The formation energy of interstitial Er in InAs is significantly smaller than in GaAs, allowing for more electrically active Er in InAs. The results provide insight into characteristics of rare-earth elements as dopants in semiconductors.
Surface doping in T6/PDI-8CN2 heterostructures investigated by transport and photoemission measurements
Authors: Aversa L. , Verucchi R. , Tatti R. , Di Girolamo F. V. , Barra M. , Ciccullo F. , Cassinese A. , Iannotta S.
Published: December 2012

In this paper, we discuss the surface doping in sexithiophene (T6) organic field-effect transistors by N,N′-bis (n-octyl)-dicyanoperylenediimide (PDI-8CN2). We show that an accumulation heterojunction is formed at the interface between the organic semiconductors and that the consequent band bending in T6 caused by PDI-8CN2 deposition can be addressed as the cause of the surface doping in T6 transistors. Several evidences of this phenomenon have been furnished both by electrical transport and photoemission measurements, namely, the increase in the conductivity, the shift of the threshold voltage, and the shift of the T6 highest occupied molecular orbital peak towards higher binding energies.
Intrinsically tunable 0.67BiFeO3-0.33BaTiO3 thin film bulk acoustic wave resonators
Authors: Vorobiev A. , Gevorgian S. , Martirosyan N. , Löffler M. , Olsson E.
Published: December 2012

Intrinsically tunable 0.67BiFeO3−0.33BaTiO3 (BF–BT) thin film bulk acoustic wave resonators with record high tunability of 4.4% and effective electromechanical coupling coefficient of 10% are fabricated and analyzed. The analysis, based on the theory of the dc field induced piezoelectric effect with the mechanical loading by the electrodes taken into account, reveals that the enhanced parameters are associated with the inherently high BF–BT electrostriction coefficient, which is found to be 5.9 × 1010 m/F. The Q-factor of the BF–BT resonators is up to 220 at 4.1 GHz and is limited mainly by acoustic wave scattering at reflection from a relatively rough top interface.
Asymmetric hysteresis loops and its dependence on magnetic anisotropy in exchange biased Co/CoO core-shell nanoparticles
Authors: Chandra Sayan , Khurshid Hafsa , Phan Manh-Huong , Srikanth Hariharan
Published: December 2012

The origin of asymmetry in field cooled (FC) hysteresis loops exhibiting exchange bias (EB) is investigated by studying the static and dynamic magnetic properties of core-shell Co/CoO nanoparticles. Two distinct freezing temperatures coresponding to the core (Tf-cr ∼ 190 K) and the shell moments (Tf-sh ∼ 95 K) are obtained from the energy barrier distribution. The FC loops are symmetric in the temperature range Tf-sh ≤ T ≤ Tf-cr, however, asymmetry in hysteresis is observed immediately below Tf-sh. These intriguing features are also probed by radio frequency transverse susceptibility (TS) experiments. We show that the first anisotropy fields obtained from the demagnetization and return curves of field cooled TS measurement, shift along the negative field axis and strikingly resemble the temperature dependence of EB. Field cooled TS measurements reveal the effect of competing Zeeman and anisotropy energy above and below Tf-sh to account for the development of asymmetry. Our study indicates that asymmetry in FC hysteresis loops is intrinsic to core-shell nanoparticles and develops only below the freezing temperature of the shell due to enhanced magnetic anisotropy.
Electric field-induced tetragonal to orthorhombic phase transitions in [110]c-oriented BaTiO3 single crystals
Authors: Franzbach D. J. , Gu Y. J. , Chen L. Q. , Webber K. G.
Published: December 2012

Electric field-induced phase transitions in [110]c-oriented BaTiO3 single crystals were studied by macroscopic electrical measurements in the temperature range from 20 °C to 50 °C. Discontinuous, hysteretic jumps in the polarization and strain were observed, indicating a tetragonal ↔ orthorhombic phase transition. The critical electric field to induce the transition was found to shift to higher values with increasing temperature. The Landau-Devonshire theory was used to analyze the observed electric field-induced T ↔ O phase transitions.
Correlated evolution of barrier capacitance charging, generation, and drift currents and of carrier lifetime in Si structures during 25 MeV neutrons irradiation
Authors: Gaubas E. , Ceponis T. , Jasiunas A. , Uleckas A. , Vaitkus J. , Cortina E. , Militaru O.
Published: December 2012

The in situ examination of barrier capacitance charging, of generation and drift currents, and of carrier lifetime in Si structures during 25 MeV neutrons irradiation has been implemented to correlate radiation induced changes in carrier recombination, thermal release, and drift characteristics and to clarify their impact on detector performance. It has been shown that microwave probed photo-conductivity technique implemented in contact-less and distant manner can be a powerful tool for examination in wide dynamic range of carrier lifetime modified by radiation defects and for rather precise prediction of detector performance.
Dynamic axial mode tuning in a rolled-up optical microcavity
Authors: Li Shilong , Ma Libo , Zhen Honglou , Jorgensen Matthew R. , Kiravittaya Suwit , Schmidt Oliver G.
Published: December 2012

We demonstrate a dynamic axial mode tuning method by means of near-field probe in a rolled-up optical microcavity. The spatially selective nature of the tuning has been explored through both the lateral and transversal probing processes. A series of perturbation calculations based on the axial confinement model are performed to prove and improve the understanding of experimental results.
Interplay of polarization fields and Auger recombination in the efficiency droop of nitride light-emitting diodes
Authors: Kioupakis Emmanouil , Yan Qimin , Van de Walle Chris G.
Published: December 2012

We use theoretical modeling to investigate the effect of polarization fields and non-radiative Auger recombination on the efficiency-droop and green-gap problems of polar and nonpolar nitride light-emitting diodes. The dependence of radiative and nonradiative recombination rates on electron-hole wave-function overlap is analyzed. Device designs that minimize the polarization fields lead to higher efficiency, not because the internal quantum efficiency is improved at a given carrier density but because they can be operated at a lower carrier density for a given current density.
Microstructure and martensitic transformation in the Fe-Mn-Al-Ni shape memory alloy with B2-type coherent fine particles
Authors: Omori T. , Nagasako M. , Okano M. , Endo K. , Kainuma R.
Published: December 2012

Microstructure and martensitic transformation yielding a magnetic change were investigated for Fe43.5Mn34Al15Ni7.5 alloy with B2-type fine precipitates. Thermoelastic martensitic transformation from the ferromagnetic parent phase to the weak magnetic martensite with a nano-twinned fcc structure was confirmed. High-angle annular dark-field scanning transmission electron microscopic observation revealed that a β particle of about 10 nm maintains coherency with the matrix martensite phase, even though distorted due to the martensitic transformation. The martensitic transformation temperatures decreased about 75 K by application of a magnetic field of 70 kOe and magnetic field-induced reverse martensitic transformation was confirmed.
Power losses in bilayer inverted small molecule organic solar cells
Authors: Trinh Cong , Bakke Jonathan R. , Brennan Thomas P. , Bent Stacey F. , Navarro Francisco , Bartynski Andrew , Thompson Mark E.
Published: December 2012

Inverted bilayer organic solar cells using copper phthalocyanine (CuPc) as a donor and C60 as an acceptor with the structure: glass/indium tin oxide (ITO)/ZnO/C60/CuPc/MoO3/Al, in which the zinc oxide (ZnO) was deposited by atomic layer deposition, are compared with a conventional device: glass/ITO/CuPc/C60/bathocuproine/Al. These inverted and conventional devices give short circuit currents of 3.7 and 4.8 mA/cm2, respectively. However, the inverted device gives a reduced photoresponse from the CuPc donor compared to that of the conventional device. Optical field models show that the arrangement of organic layers in the inverted devices leads to lower absorption of long wavelengths by the CuPc donor; the low energy portion of the spectrum is concentrated near the metal oxide electrode in both devices.
Toward terahertz heterodyne detection with superconducting Josephson junctions
Authors: Malnou M. , Luo A. , Wolf T. , Wang Y. , Feuillet-Palma C. , Ulysse C. , Faini G. , Febvre P. , Sirena M. , Lesueur J. , Bergeal N.
Published: December 2012

We report on the high-frequency mixing properties of ion irradiated YBa2Cu3O7 Josephson junctions. The frequency range, spanning above and below the characteristic frequencies fc of the junctions, permits a clear observation of the transition between two mixing regimes. The experimental conversion gain was found to be in good agreement with the prediction of the three-port model. Finally, we discuss the potential of the junctions to build a Josephson mixer operating in the terahertz frequency range.
Formation of arsenolite crystals at room temperature after very high dose arsenic implantation in silicon
Authors: Meirer Florian , Giubertoni Damiano , Demenev Evgeny , Vanzetti Lia , Gennaro Salvatore , Fedrizzi Michele , Pepponi Giancarlo , Mehta Apurva , Pianetta Piero , Steinhauser Georg , Vishwanath Vinayak , Foad Majeed , Bersani Massimo
Published: December 2012

Spontaneous growth of arsenolite micro-crystals at room temperature after high fluence, low energy arsenic trihydride implantation in silicon was observed on the wafer surface after exposure to air. The crystals have been identified unambiguously by x-ray absorption and fluorescence spectroscopy. Thermal treatment easily sublimates the crystals at temperatures as low as 200 °C without any relevant in-diffusion of As into the substrate. The deposition of a thin As-rich layer under high fluence implantation conditions is suggested as possible precursor for crystal formation. The same layer can explain the anomalous retained dose increase often observed after annealing.
Infrared imagery of streak formation in a breaking wave
Authors: Handler Robert A. , Savelyev Ivan , Lindsey Michael
Published: December 2012

High resolution infrared imagery of breaking waves in a wave-tank free of wind shear or current reveals the production of a “streaky,” quasi-periodic thermal pattern produced during the breaking process. The streaks, or elongated patterns of warm and cold fluid, are found to form only when surface turbulence is present before wave breaking occurs. This suggests that wave-turbulence interaction is one mechanism that can lead to streak formation in breaking wave systems. More specifically, the streaky structures observed in these experiments may be caused by an intense, rapid tilting, and stretching of pre-existing vertical vorticity by the Stokes drift generated at or near the breaking wave crests, thereby generating a coherent system of counter-rotating vortices. We attempt to relate our observations to the recent theory of Teixeira and Belcher [J. Fluid Mech. 458, 229–267 (2002)10.1017/S0022112002007838]. Some properties of the streaks, such as the dependence of their lifetimes and spanwise scale on wave amplitude, are presented.
Precise relationship between voltage and frequency at the appearance of negative capacitance in InGaN diodes
Authors: Feng L. F. , Li Y. , Li D. , Hu X. D. , Yang W. , Wang C. D. , Xing Q. Y.
Published: December 2012

The exact relationship between voltage and frequency when negative capacitance (NC) appears in light-emitting diodes containing InGaN was determined both experimentally and by solving the physical equations for the complete equivalent circuit of a symmetrical p-n junction combined with its boundary condition. Results from the calculation revealed that NC depends on the recombination lifetime of carriers; therefore, we can accurately determine recombination lifetime from the appearance of NC.
Significant increase in conduction band discontinuity due to solid phase epitaxy of Al2O3 gate insulator films on GaN semiconductor
Authors: Toyoda S. , Shinohara T. , Kumigashira H. , Oshima M. , Kato Y.
Published: December 2012

We have investigated band discontinuities and chemical structures of Al2O3 gate insulator films on n-type GaN semiconductor by photoemission and x-ray absorption spectroscopy. It is found that the solid phase epitaxy at the GaN crystal during annealing procedures at 800 °C leads to phase transformation of Al2O3 films from amorphous to crystalline. Changes in crystallographic structures closely correlate with the significant increase in conduction band discontinuity at the Al2O3/GaN interface, which suggests that epitaxial Al2O3 films on GaN semiconductor, free from grain boundaries of Al2O3 polycrystalline, hold the potential for high insulation performance.
4-fold enhancement in the critical current density of YBa2Cu3O7 films by practical ion irradiation
Authors: Matsui H. , Ogiso H. , Yamasaki H. , Kumagai T. , Sohma M. , Yamaguchi I. , Manabe T.
Published: December 2012

We report an up-to-4-fold enhancement in the in-magnetic-field critical current density at 77 K of epitaxial YBa2Cu3O7 films on CeO2-buffered SrTiO3 substrates by 3-MeV Au2+ irradiation. This indicates that irradiation using an industrially practical ion beam, which generally has kinetic energy less than 5 MeV, can provide a substantial increase in the in-field current performance of high-temperature superconductor films. Transmission electron microscopy results show that point-like defects smaller than 6 nm in diameter were created in the films by the irradiation.
Integrating magnetoresistive sensors with microelectromechanical systems for noise reduction
Authors: Hu Jiafei , Pan Mengchun , Tian Wugang , Chen Dixiang , Luo Feilu
Published: December 2012

1/f noise is the dominant detection limit of magnetoresistive (MR) sensors at low frequency. The vertical motion flux modulation (VMFM) integrating with microelectromechanical systems (MEMS) can reduce 1/f noise by tens or hundreds of times, although thermal-mechanical noise possibly has strong impact on the detection ability of VMFM sensors like common MEMS sensors. Surprisingly, the voltage noise originated from thermal-mechanical noise is actually far less than the noise base of MR sensors, which indicates a great perspective for the integration of MEMS and MR sensors.
Dynamical topology and statistical properties of spatiotemporal chaos
Authors: Zhuang Quntao , Gao Xun , Ouyang Qi , Wang Hongli
Published: December 2012

For spatiotemporal chaos described by partial differential equations, there are generally locations where the dynamical variable achieves its local extremum or where the time partial derivative of the variable vanishes instantaneously. To a large extent, the location and movement of these topologically special points determine the qualitative structure of the disordered states. We analyze numerically statistical properties of the topologically special points in one-dimensional spatiotemporal chaos. The probability distribution functions for the number of point, the lifespan, and the distance covered during their lifetime are obtained from numerical simulations. Mathematically, we establish a probabilistic model to describe the dynamics of these topologically special points. In spite of the different definitions in different spatiotemporal chaos, the dynamics of these special points can be described in a uniform approach.
High frequency conductivity in carbon nanotubes
Authors: Abukari S. S. , Mensah S. Y. , Mensah N. G. , Adu K. A. , Rabiu M. , Twum A.
Published: December 2012

We report on theoretical analysis of high frequency conductivity in carbon nanotubes. Using the kinetic equation with constant relaxation time, an analytical expression for the complex conductivity is obtained. The real part of the complex conductivity is initially negative at zero frequency and become more negative with increasing frequency, until it reaches a resonance minimum at ω ∼ ωB for metallic zigzag CNs and ω < ωB for armchair CNs. This resonance enhancement is indicative for terahertz gain without the formation of current instabilities induced by negative dc conductivity. We noted that due to the high density of states of conduction electrons in metallic zigzag carbon nanotubes and the specific dispersion law inherent in hexagonal crystalline structure result in a uniquely high frequency conductivity than the corresponding values for metallic armchair carbon nanotubes. We suggest that this phenomenon can be used to suppress current instabilities that are normally associated with a negative dc differential conductivity.
Growth of ∼5 cm2V−1s−1 mobility, p-type Copper(I) oxide (Cu2O) films by fast atmospheric atomic layer deposition (AALD) at 225°C and below
Authors: Muñoz-Rojas D. , Jordan M. , Yeoh C. , Marin A. T. , Kursumovic A. , Dunlop L. A. , Iza D. C. , Chen A. , Wang H. , MacManus Driscoll J. L.
Published: December 2012

Phase pure, dense Cu2O thin films were grown on glass and polymer substrates at 225°C by rapid atmospheric atomic layer deposition (AALD). Carrier mobilities of 5 cm2V−1s−1 and carrier concentrations of ∼1016 cm−3 were achieved in films of thickness 50 - 120 nm, over a >10 cm2 area. Growth rates were ∼1 nm·min−1 which is two orders of magnitude faster than conventional ALD.. The high mobilities achieved using the atmospheric, low temperature method represent a significant advance for flextronics and flexible solar cells which require growth on plastic substrates.
Direct imaging of phase relation in a pair of coupled vortex oscillators
Authors: Vogel Andreas , Drews André , Weigand Markus , Meier Guido
Published: December 2012

We study the magnetization dynamics in a stray-field coupled pair of ferromagnetic squares in the vortex state. Micromagnetic simulations give an idea of the mediating stray field during vortex gyration. The frequency-dependent phase relation between the vortices in the spatially separated squares is studied using time-resolved scanning transmission x-ray microscopy while one element is harmonically excited via an alternating magnetic field. It is shown that the normal modes of coupled vortex-core motion can be understood as an attractive (low-frequency) and a repulsive (high-frequency) mode of the effective magnetic moments of the microstructures.
RASGRF2
regulates alcohol-induced reinforcement by influencing mesolimbic dopamine neuron activity and dopamine release
Authors: Stacey David , Bilbao Ainhoa , Maroteaux Matthieu , Jia Tianye , Easton Alanna C. , Longueville Sophie , Nymberg Charlotte , Banaschewski Tobias , Barker Gareth J. , Büchel Christian , Carvalho Fabiana , Conrod Patricia J. , Desrivières Sylvane , Fauth-Bühler Mira , Fernandez-Medarde Alberto , Flor Herta , Gallinat Jürgen , Garavan Hugh , Bokde Arun L. W. , Heinz Andreas , Ittermann Bernd , Lathrop Mark , Lawrence Claire , Loth Eva , Lourdusamy Anbarasu , Mann Karl F. , Martinot Jean-Luc , Nees Frauke , Palkovits Miklós , Paus Tomas , Pausova Zdenka , Rietschel Marcella , Ruggeri Barbara , Santos Eugenio , Smolka Michael N. , Staehlin Oliver , Jarvelin Marjo-Riitta , Elliott Paul , Sommer Wolfgang H. , Mameli Manuel , Müller Christian P. , Spanagel Rainer , Girault Jean-Antoine , Schumann Gunter ,   the IMAGEN Consortium
Published: December 2012

The firing of mesolimbic dopamine neurons is important for drug-induced reinforcement, although underlying genetic factors remain poorly understood. In a recent genome-wide association metaanalysis of alcohol intake, we identified a suggestive association of SNP rs26907 in the
ras-specific guanine-nucleotide releasing factor 2
(
RASGRF2
) gene, encoding a protein that mediates Ca
2+
-dependent activation of the ERK pathway. We performed functional characterization of this gene in relation to alcohol-related phenotypes and mesolimbic dopamine function in both mice and adolescent humans. Ethanol intake and preference were decreased in
Rasgrf2
−/−
mice relative to WT controls. Accordingly, ethanol-induced dopamine release in the ventral striatum was blunted in
Rasgrf2
−/−
mice. Recording of dopamine neurons in the ventral tegmental area revealed reduced excitability in the absence of Ras-GRF2, likely because of lack of inhibition of the
I

A

potassium current by ERK. This deficit provided an explanation for the altered dopamine release, presumably linked to impaired activation of dopamine neurons firing. Functional neuroimaging analysis of a monetary incentive–delay task in 663 adolescent boys revealed significant association of ventral striatal activity during reward anticipation with a
RASGRF2
haplotype containing rs26907, the SNP associated with alcohol intake in our previous metaanalysis. This finding suggests a link between the
RASGRF2
haplotype and reward sensitivity, a known risk factor for alcohol and drug addiction. Indeed, follow-up of these same boys at age 16 y revealed an association between this haplotype and number of drinking episodes. Together, these combined animal and human data indicate a role for
RASGRF2
in the regulation of mesolimbic dopamine neuron activity, reward response, and alcohol use and abuse.
RETRACTED: Mutant surfactant A2 proteins associated with familial pulmonary fibrosis and lung cancer induce TGF-β1 secretion
Authors: Maitra Meenakshi , Cano Christopher A. , Garcia Christine Kim
Published: December 2012

Mutations in the genes encoding the lung surfactant proteins are found in patients with interstitial lung disease and lung cancer, but their pathologic mechanism is poorly understood. Here we show that bronchoalveolar lavage fluid from humans heterozygous for a missense mutation in the gene encoding surfactant protein (SP)-A2 (
SFTPA2
) contains more TGF-β1 than control samples. Expression of mutant SP-A2 in lung epithelial cells leads to secretion of latent TGF-β1, which is capable of autocrine and paracrine signaling. TGF-β1 secretion is not observed in lung epithelial cells expressing the common SP-A2 variants or other misfolded proteins capable of increasing cellular endoplasmic reticulum stress. Activation of the unfolded protein response is necessary for maximal TGF-β1 secretion because gene silencing of the unfolded protein response transducers leads to an ∼50% decrease in mutant SP-A2–mediated TGF-β1 secretion. Expression of the mutant SP-A2 proteins leads to the coordinated increase in gene expression of TGF-β1 and two TGF-β1–binding proteins, LTBP-1 and LTBP-4; expression of the latter is necessary for secretion of this cytokine. Inhibition of the TGF-β autocrine positive feedback loop by a pan–TGF-β–neutralizing antibody, a TGF-β receptor antagonist, or LTBP gene silencing results in the reversal of TGF-β–mediated epithelial-to-mesenchymal transition and cell death. Because secretion of latent TGF-β1 is induced specifically by mutant SP-A2 proteins, therapeutics targeted to block this pathway may be especially beneficial for this molecularly defined subgroup of patients.
The Exotic Portrayal of Women in Isabella Bird Bishop'sJourneys in Persia and Kurdistan
Authors: Roselezam Wan , Yahya Wan , Ghaderi Farah , Jusoff Kamaruzaman
Published: December 2012

Isabella Bird Bishop'sJourneys in Persia and Kurdistanis presented as an objective picture of Persia, purportedly reflecting eye-witness accounts. Setting the narrative in its historical context and employing the concept of exoticism, this paper aims to unearth its subtle imperialist underpinnings. It argues that Bird's portrayal of Persian women and their mores and manners as exotic is an effect of a mode of representation which depicts and constructs difference based on a British-oriented system of evaluation, in line with its imperialist interest in Persia. As such, the exotic representation of Persian women in need of British benign tutelage and a chivalric mission could be interpreted as lending implicit support to Britain's colonial intervention in and imposition on Persia.
Şeref Xan'sSharafnama: Kurdish Ethno-Politics in the Early Modern World, Its Meaning and Its Legacy
Authors: Bajalan Djene Rhys
Published: December 2012

This paper critically analyzes theSharafnama, a history of the Kurds, written by the late sixteenth century ruler of Bitlis, Şeref Xan. Given the politically sensitive nature of the Middle East's “Kurdish Question,” theSharafnamahas become an extremely important resource through which Kurdish nationalists have sought to construct a coherent “national narrative.” This is due to the fact that Şeref Xan's book constitutes one of the few systematic histories of the Kurds written before the twentieth century. This paper moves away from nationalist inspired interpretations of theSharafnama, which see the work as a “national(ist)” history. Instead, it posits that, although the piece can be regarded as a manifestation of Kurdish “ethno-politics,” it is necessary to look at it within the context of the relationship between the Kurdish tribal princes who ruled large areas of “Kurdistan,” on one hand, and the Ottoman and Safavid empires who competed for control of this region, on the other. In particular, it brings to the fore an often forgotten and/or ignored aspect of Şeref Xan's history, namely its pro-Ottoman bias. In this way, the article makes broader points relating to the nature of the Kurdish identity in the early modern period, and the influence of such conceptions on the later construction of the modern Kurdish identity.
Case study of trainee teachers' responses to the impact on engagement and motivation in learning through a model of cross‐curricular context‐based learning: ‘keeping fit and healthy'
Authors: Birchinall Liz
Published: December 2012

This article examines whether models of cross‐curricular, context‐based learning are more effective in engaging learners through generating conditions which interest, motivate, engage and inspire pupils through a variety of effective pedagogies. This article reports on a case study of two cohorts of primary PGCE trainee teachers (292) over two years who participated in a model of context‐based learning. Trainee teachers commented on the models with regard to their impact on engagement and motivation. Analyses of their responses were made during the period of the course. Experiences of trainees thus far had been predominantly a discrete subject model of teacher training, developing subject and pedagogical skills and knowledge within the core subjects, closely aligned to the focus on the core subjects in English state primary schools. In contrast, the holistic approach to the context‐based learning model predominantly encompassed constructivist and enquiry‐based pedagogies with learning placed within a context, also known as situated learning.
Does Children's Age Impact the Division of Housework?
Authors: Zabel Cordula , Heintz-Martin Valerie K.
Published: December 2012

In this study, we investigate couples' division of household tasks by the age of the youngest child, comparing France, eastern Germany, and western Germany. For our analyses, we draw on Generations and Gender Survey (GGS) data. As expected, our findings are that the division of housework is less egalitarian for couples with preschool age children than for childless couples, and these differences are greatest in western Germany. However, we had also expected the division of housework to be more egalitarian again for couples with older children, among whom maternal employment rates are higher than among those with younger children. Our findings confirmed this expectation for western Germany. Surprisingly though, we found that in both eastern Germany and France, the division of housework was actually continuously less egalitarian the older couples' children. An explanation may be that the traditionalizing impact of parenthood unfolds slowly with parenthood duration as couples increasingly yield to societal expectations regarding parental roles. In western Germany, where women reduce their employment most significantly when becoming mothers, employment status effects appear to dominate any other trends associated with the age of the youngest child.
Formation of core–shell micro/nano particles through pulsed-laser deposition in liquid
Authors: Jo Young Kyong , Wen Sy-Bor
Published: December 2012

A new methodology for generating core–shell micro/nanoparticle (CSPs) based on laser ablation in liquid is developed. This new method showed no observable restriction for generating core and shell materials of different combinations. However, to form a high-quality shell with the new method, the adhesion energy between the core and the shell material should be as high as possible. The obtained thickness and smoothness of the shell are also affected by amount of ablation time and the applied laser energy. Based on the test, smoother (i.e. with less condensed island growth) and thicker shell can be achieved with longer ablation time and lower ablation energy. The developed new methodology can be directly extended to the generation of multiple layered core–shell micro/nanoparticles with different configurations through introducing more ablation targets in the liquid.
X-band EMI shielding mechanisms and shielding effectiveness of high structure carbon black/polypropylene composites
Authors: Al-Saleh Mohammed H , Sundararaj Uttandaraman
Published: December 2012

The electromagnetic interference (EMI) shielding effectiveness (SE) and EMI shielding mechanisms of high structure carbon black (HS-CB)/polypropylene (PP) composites in the X-band frequency range were studied. Composite plates with three different thicknesses and five different electrical conductivities were studied. The reflection loss and absorption loss of the composites were quantified based on the electromagnetic radiation power balance. The results showed that for HS-CB/PP composites, absorption loss contribution to the overall attenuation is more than the contribution of the reflection loss. The ability of the theoretical model to predict the EMI shielding by reflection and absorption was found to be a function of the shielding plate thickness and conductivity.
A dominant mutation inmec-7/β-tubulinaffects axon development and regeneration inCaenorhabditis elegansneurons
Authors: Kirszenblat Leonie , Neumann Brent , Coakley Sean , Hilliard Massimo A.
Published: December 2012

Microtubules have been known for decades to be basic elements of the cytoskeleton. They form long, dynamic, rope-like structures within the cell that are essential for mitosis, maintenance of cell shape, and intracellular transport. More recently, in vitro studies have implicated microtubules as signaling molecules that, through changes in their stability, have the potential to trigger growth of axons and dendrites in developing neurons. In this study, we show that specific mutations in the Caenorhabditis elegans mec-7/β-tubulin gene cause ectopic axon formation in mechanosensory neurons in vivo. In mec-7 mutants, the ALM mechanosensory neuron forms a long ectopic neurite that extends posteriorly, a phenotype that can be mimicked in wild-type worms with a microtubule-stabilizing drug (paclitaxel), and suppressed by mutations in unc-33/CRMP2 and the kinesin-related gene, vab-8. Our results also reveal that these ectopic neurites contain RAB-3, a marker for presynaptic loci, suggesting that they have axon-like properties. Interestingly, in contrast with the excessive axonal growth observed during development, mec-7 mutants are inhibited in axonal regrowth and remodeling following axonal injury. Together our results suggest that MEC-7/β-tubulin integrity is necessary for the correct number of neurites a neuron generates in vivo and for the capacity of an axon to regenerate.
Epidemiology of Puccinia graminis f.sp. tritici-Ug99 in the Rift Valley “Flyway” from Uganda-Kenya to Yemen
Authors: Nagarajan Subrahmaniam , Kogel Hans J. , Zadoks Jan C.
Published: December 2012

Dispersal of a new virulence of Puccinia graminis tritici (Pgt)-Ug99 from Uganda-Kenya to Yemen, over >1000 km, happened in four years. Geo-agro-ecology of wheat cultivation and the epidemiology of Pgt indicate that the Rift Valley is a natural conduit “flyway.” The widely prevalent “green bridges” favor survival and spread of Pgt. This part of the Rift Valley is one single epidemiological zone, and the annual Pgt build-up is from the endogenous inoculum.

Accepted for publication 18 October 2012. Published 14 November 2012.
Anti‐TNF, Infliximab, and Adalimumab Can Be Effective in Eosinophilic Bowel Disease
Authors: Turner Dan , Wolters Victorien M. , Russell Richard K. , Shakhnovich Valentina , Muise Aleixo M. , Ledder Oren , Ngan Bo , Friesen Craig
Published: December 2012

Background:

Eosinophilic enterocolitis (EEC) is an emerging distinct inflammatory bowel disease of unknown etiology. There are no published data on the effect of infliximab (IFX) or adalimumab (ADA) for the treatment of refractory cases.

Methods:

A report of all pediatric cases with EEC treated with anti‐tumor necrosis factor, identified after an open international call.

Results:

We describe here the first 8 children with refractory EEC who were treated with IFX (75% boys; mean age at diagnosis 8.6 ± 4.03 [range 1.6–14 years]; mean age at IFX treatment 11.7 ± 4.4 [range 4.2–16 years]). Allergic and infectious causes of EEC were excluded in all cases. Rapid and complete clinical remission was documented in 6 (75%) children following the induction infusions: 3 (38%) with endoscopic remission, 2 (25%) with endoscopic improvement, and 1 unknown. Four of the 6 responders had secondary loss of response and were switched to ADA, 3 of whom with sustained remission using high doses. Overall, the 6 responders were followed for a median of 7 years (range 4–12; interquartile range 6.4–8.8 years) without evidence of developing Crohn disease or ulcerative colitis. The only case with macroscopic findings on endoscopy was a primary nonresponder.

Conclusions:

IFX and ADA may be effective in cases of refractory idiopathic EEC; however, because this is an uncontrolled report, further prospective studies are warranted.