bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Ambjorn-Olesen electroweak condensates
Authors: Bartolucci Daniele , De Marchis Francesca
Published: July 2012

We obtain sufficient conditions for the existence of the Ambjorn-Olesen [“On electroweak magnetism,” Nucl. Phys. B315, 606–614 (1989)10.1016/0550-3213(89)90004-7] electroweak N-vortices in case N ⩾ 1 and therefore generalize earlier results [D. Bartolucci and G. Tarantello, “Liouville type equations with singular data and their applications to periodic multivortices for the electroweak theory,” Commun. Math. Phys. 229, 3–47 (2002)10.1007/s002200200664; J. Spruck and Y. Yang, “On multivortices in the electroweak theory I: Existence of periodic solutions,” Commun. Math. Phys. 144, 1–16 (1992)10.1007/BF02099188] which handled the cases N ∈ {1, 2, 3, 4}. The variational argument provided here has its own independent interest as it generalizes the one adopted by Ding et al. [“Existence results for mean field equations,” Ann. Inst. Henri Poincare, Anal. Non Lineaire 16, 653–666 (1999)10.1016/S0294-1449(99)80031-6] to obtain solutions for Liouville-type equations on closed 2-manifolds. In fact, we obtain at once a second proof of the existence of supercritical conformal metrics on surfaces with conical singularities and prescribed Gaussian curvature recently established by Bartolucci, De Marchis and Malchiodi [Int. Math. Res. Not. 24, 5625–5643 (2011)10.1093/imrn/rnq285].
Time-resolved hyperspectral fluorescence spectroscopy using frequency-modulated excitation
Authors: DiBenedetto John , Capelle Gene A. , O’Neill Mary
Published: July 2012

An intensity-modulated excitation light source is used together with a micro-channel plate intensified CCD detector gated at a slightly different frequency to generate a beat frequency from a fluorescent sample. The addition of a spectrograph produces a hyperspectral time-resolved data product where the resulting beat frequency is detected with a low frame rate camera. Measuring the beat frequency of the spectrum as a function of time allows separation of the excited fluorescence from ambient constant light sources. The excitation and detector repetition rates are varied over a range of discrete frequencies, and the phase shift of the beat wave maps out the emission decay rate(s).
Ab Initio studies of the interaction potential for the Xe–NO(X 2Π) van der Waals complex: Bound states and fully quantum and quasi-classical scattering
Authors: Kłos J. , Aoiz F. J. , Menéndez M. , Brouard M. , Chadwick H. , Eyles C. J.
Published: July 2012

Adiabatic potential energy surfaces for the ground electronic state of the Xe⋅⋅⋅NO(X2Π) van der Waals complex have been calculated using the spin-restricted coupled cluster method with single, double, and non-iterative triple excitations (RCCSD(T)). The scalar relativistic effects present in the Xe atom were included by an effective core potential and we extended the basis with bond functions to improve the description of the dispersion interaction. It has been found that the global minimum on the A′ adiabatic surface occurs at a T-shaped geometry with γe = 94° and Re = 7.46 a0, and with well depth of De = 148.68 cm−1. There is also an additional local minimum for the collinear geometry Xe–NO with a well depth of 104.5 cm−1. The adiabat of A′′ symmetry exhibits a single minimum at a distance Re = 7.68 a0 and has a skewed geometry with γe = 64° and a well depth of 148.23 cm−1. Several Cnl van der Waals dispersion coefficients are also estimated, of which C6, 0 and C6, 2 are in a reasonable agreement with previous theoretical results obtained by Nielson et al. [J. Chem. Phys. 64, 2055 (1976)]10.1063/1.432428. The new potential energy surfaces were used to calculate bound states of the complex for total angular momentum quantum numbers up to J = 7/2. The ground state energy of Xe⋅⋅⋅NO(X2Π) is D0 = 117 cm−1, which matches the experimental value very accurately (within 3.3%). Scattering calculations of integral and differential cross sections have also been performed using fully quantum close coupling calculations and quasi-classical trajectory method at a collision energy of 63 meV. These calculations reveal the important role played by L-type rainbows in the scattering dynamics of the heavier Rg–NO(X) systems.
Frequency-stabilized cavity ring-down spectroscopy measurements of line mixing and collision-induced absorption in the O2 A-band
Authors: Long D. A. , Robichaud D. J. , Hodges J. T.
Published: July 2012

Frequency-stabilized cavity ring-down spectroscopy measurements were performed in the P-branch of the O2 A-band [b1Σg+ ← X 3Σg−(0,0)] near atmospheric pressure. Line mixing parameters and collision-induced absorption were quantified and reported. These measurements show qualitative differences with those taken at relatively high pressure (2 MPa–20 MPa). We also assess the implications of these measurements on atmospheric retrievals.
Sc2@C70 rather than Sc2C2@C68: Density functional theory characterization of metallofullerene Sc2C70
Authors: Zheng Hong , Zhao Xiang , Wang Wei-Wei , Yang Tao , Nagase Shigeru
Published: July 2012

Detailed study on Sc2C70 series has been performed based on fully screening for C70 tetra- and hexa- anions. With a combined methodology of quantum chemistry and statistical mechanics, our calculation results reveal that the Sc2C70, which was proposed as the first metal-carbide endohedral metallofullerene with a non-isolated pentagon rule (non-IPR) cage (Sc2C2@C68:6073_C2v), is in fact a C70 non-IPR metallofullerene structure (Sc2@C70:7854_C2v) with three pair of pentagon adjacency thanks to its significant thermodynamic and kinetic stability. According to the natural bond analysis and orbital interaction diagram, each scandium atom should only transfer two 4s electrons to the carbon cages and the valence state of Sc2@C70 is (Sc2+)2@C704−. In addition, the simulation of UV-Vis-NIR spectrum for Sc2@C70:7854_C2v shows good accordance to the experimental spectrum.
Up to fourth virial coefficients from simple and efficient internal-coordinate sampling: Application to neon
Authors: Wiebke Jonas , Pahl Elke , Schwerdtfeger Peter
Published: July 2012

A simple and efficient internal-coordinate importance sampling protocol for the Monte Carlo computation of (up to fourth-order) virial coefficients \documentclass[12pt]{minimal}\begin{document}$\bar{B}_n$\end{document}B¯n of atomic systems is proposed. The key feature is a multivariate sampling distribution that mimics the product structure of the dominating pairwise-additive parts of the \documentclass[12pt]{minimal}\begin{document}$\bar{B}_n$\end{document}B¯n. This scheme is shown to be competitive over routine numerical methods and, as a proof of principle, applied to neon: The second, third, and fourth virial coefficients of neon as well as equation-of-state data are computed from ab initio two- and three-body potentials; four-body contributions are found to be insignificant. Kirkwood–Wigner quantum corrections to first order are found to be crucial to the observed agreement with recent ab initio and experimental reference data sets but are likely inadequate at very low temperatures.
On calculation of thermal conductivity from Einstein relation in equilibrium molecular dynamics
Authors: Kinaci A. , Haskins J. B. , Çağın T.
Published: July 2012

In equilibrium molecular dynamics, Einstein relation can be used to calculate the thermal conductivity. This method is equivalent to Green-Kubo relation and it does not require a derivation of an analytical form for the heat current. However, it is not as commonly used as Green-Kubo relationship. Its wide use is hindered by the lack of a proper definition for integrated heat current (energy moment) under periodic boundary conditions. In this paper, we developed an appropriate definition for integrated heat current to calculate thermal conductivity of solids under periodic conditions. We applied this method to solid argon and silicon based systems; compared and contrasted with the Green-Kubo approach.
Orbitally invariant internally contracted multireference unitary coupled cluster theory and its perturbative approximation: Theory and test calculations of second order approximation
Authors: Chen Zhenhua , Hoffmann Mark R.
Published: July 2012

A unitary wave operator, exp (G), G+ = −G, is considered to transform a multiconfigurational reference wave function Φ to the potentially exact, within basis set limit, wave function Ψ = exp (G)Φ. To obtain a useful approximation, the Hausdorff expansion of the similarity transformed effective Hamiltonian, exp (−G)Hexp (G), is truncated at second order and the excitation manifold is limited; an additional separate perturbation approximation can also be made. In the perturbation approximation, which we refer to as multireference unitary second-order perturbation theory (MRUPT2), the Hamiltonian operator in the highest order commutator is approximated by a Møller-Plesset-type one-body zero-order Hamiltonian. If a complete active space self-consistent field wave function is used as reference, then the energy is invariant under orbital rotations within the inactive, active, and virtual orbital subspaces for both the second-order unitary coupled cluster method and its perturbative approximation. Furthermore, the redundancies of the excitation operators are addressed in a novel way, which is potentially more efficient compared to the usual full diagonalization of the metric of the excited configurations. Despite the loss of rigorous size-extensivity possibly due to the use of a variational approach rather than a projective one in the solution of the amplitudes, test calculations show that the size-extensivity errors are very small. Compared to other internally contracted multireference perturbation theories, MRUPT2 only needs reduced density matrices up to three-body even with a non-complete active space reference wave function when two-body excitations within the active orbital subspace are involved in the wave operator, exp (G). Both the coupled cluster and perturbation theory variants are amenable to large, incomplete model spaces. Applications to some widely studied model systems that can be problematic because of geometry dependent quasidegeneracy, H4, P4, and BeH2, are performed in order to test the new methods on problems where full configuration interaction results are available.
Electronically excited-state properties and predissociation mechanisms of phosphorus monofluoride: A theoretical study including spin–orbit coupling
Authors: Yu Le , Bian Wensheng
Published: July 2012

The 51 Ω states generated from the 22 Λ − S states of phosphors monofluoride have been investigated using the valence internally contracted multireference configuration interaction method with the Davidson correction and the entirely uncontracted aug-cc-pV5Z basis set. The spin–orbit coupling is computed using the state interaction approach with the Breit–Pauli Hamiltonian. Based on the calculated potential energy curves, the spectroscopic constants of the bound and quasibound Λ − S and Ω states are obtained, and very good agreement with experiment is achieved. Several quasibound states caused by avoided crossings are found. Various curve crossings and avoided crossings are revealed, and with the help of our computed spin–orbit coupling matrix elements, the predissociation mechanisms of the a1Δ, b1Σ+, e3Π, g1Π, and (3)3Π states are analyzed. The intricate couplings among different electronic states are investigated. We propose that the avoided crossing between the A3Π0 + and ${\rm b}^{\rm 1} {\rm \Sigma }_{{\rm 0 + }}^{\rm + }$b1Σ0++ states may be responsible for the fact that the A3Π ν′ ⩾ 12 vibrational levels can not be observed in experiment. The transition properties of the A3Π − X3Σ− transition are studied, and our computed Franck–Condon factors and radiative lifetimes match the experimental results very well.
A microcontroller-based lock-in amplifier for sub-milliohm resistance measurements
Authors: Bengtsson Lars E.
Published: July 2012

This paper presents a novel approach to the design of a digital ohmmeter with a resolution of <60 μΩ based on a general-purpose microcontroller and a high-impedance instrumentation amplifier only. The design uses two digital I/O-pins to alternate the current through the sample resistor and combined with a proper firmware routine, the design is a lock-in detector that discriminates any signal that is out of phase/frequency with the reference signal. This makes it possible to selectively detect the μV drop across sample resistors down to 55.6 μΩ using only the current that can be supplied by the digital output pins of a microcontroller. This is achieved without the need for an external reference signal generator and does not rely on the computing processing power of a digital signal processor.
The vibrational structure of the oxygen K-shell spectra in acenaphthenequinones: An ab initio study
Authors: Duflot Denis , Flament Jean-Pierre
Published: July 2012

The vibrational structure of the K-shell O1s → π* of acenaphthenequinone C12H6O2 and its halogenated compound C12H2Br2Cl2O2 has been simulated using an entirely ab initio approach. For both molecules, analysis of the calculated Franck-Condon factors confirm without ambiguity that, contrary to initial claims, the C–H stretching modes are not modified in the core states and are not excited. For C12H6O2, the vibrational fine structure appears to be mainly due to three modes, involving C=O* asymmetric stretch and in-plane ring deformation modes, due to the symmetry breaking of the core state. For C12H2Br2Cl2O2, the vibrational excitation arises essentially from the C=O* asymmetric stretch, with numerous secondary peaks arising from hot and combination bands. For both molecules, these bands are probably responsible for the asymmetry deduced in the experimental fits using a unique Morse potential and initially assigned to anharmonic effects.
Effects of rapid thermal annealing on GaAs1-xBix alloys
Authors: Mohmad A. R. , Bastiman F. , Hunter C. J. , Richards R. , Sweeney S. J. , Ng J. S. , David J. P. R.
Published: July 2012

The effects of rapid thermal annealing on the optical and structural properties of GaAs1-xBix alloys for x ranging from 0.022 to 0.065 were investigated. At room temperature, the annealed GaAs1-xBix showed modest improvement (∼3 times) in photoluminescence (PL) while the PL peak wavelength remained relatively unchanged. It was found that bismuth related defects are not easily removed by annealing and the PL improvement may be dominated by the reduction of other types of defects including arsenic and gallium related defects. Also, the optimum annealing temperature is Bi composition dependent. For samples with x < 0.048, the optimum annealing temperature is 700 °C but reduces to 600 °C for higher compositions.
Estimating the largest Lyapunov exponent and noise level from chaotic time series
Authors: Yao Tian-Liang , Liu Hai-Feng , Xu Jian-Liang , Li Wei-Feng
Published: July 2012

A novel method for estimating simultaneously the largest Lyapunov exponent (LLE) and noise level (NL) from a noisy chaotic time series is presented in this paper. We research the influence of noise on the average distance of different pairs of points in an embedding phase space and provide a rescaled formula for calculating the LLE when the time series is contaminated with noise. Our algorithm is proposed based on this formula and the invariant of the LLE in different dimensional embedding phase spaces. With numerical simulation, we find that the proposed method provides a reasonable estimate of the LLE and NL when the NL is less than 10% of the signal content. The comparison with Kantz algorithm shows that our method gives more accurate results of the LLE for the noisy time series. Furthermore, our method is not sensitive to the distribution of the noise.
Origin of synergistic effect over Ni-based bimetallic surfaces: A density functional theory study
Authors: Fan Chen , Zhu Yi-An , Xu Yue , Zhou Yan , Zhou Xing-Gui , Chen De
Published: July 2012

Density functional theory calculations have been conducted to explore the physical origin of the synergistic effect over Ni-based surface alloys using methane dissociation as a probe reaction. Some late transition metal atoms (M = Cu, Ru, Rh, Pd, Ag, Pt, and Au) are substituted for surface Ni atoms to examine the variation in electronic structure and adsorption property of Ni(111). Two types of threefold hollow sites, namely, the Ni2M and Ni3 sites, are taken into account. The calculated results indicate that the variation in the CHx adsorption energy at the Ni2M and Ni3 sites is dominated by the ensemble and ligand effect, respectively, and the other factors such as surface and adsorbate distortion and electrostatic interaction affect the catalytic properties of the bimetallic surfaces to a smaller extent. Both the Brønsted–Evans–Polanyi relationship and the scaling correlation hold true on the Ni-based bimetallic surfaces. With the combination of these two linear energy relations, the corrected binding energy of atomic C is found to be a good descriptor for representing the catalytic activity of the alloyed surfaces. Considering the compromise between the catalytic activity and catalyst stability, we suggest that the Rh/Ni catalyst is a good candidate for methane dissociation.
Ring polymer dynamics in curved spaces
Authors: Wolf S. , Curotto E.
Published: July 2012

We formulate an extension of the ring polymer dynamics approach to curved spaces using stereographic projection coordinates. We test the theory by simulating the particle in a ring, \documentclass[12pt]{minimal}\begin{document}${\mathbb T}^1$\end{document}T1, mapped by a stereographic projection using three potentials. Two of these are quadratic, and one is a nonconfining sinusoidal model. We propose a new class of algorithms for the integration of the ring polymer Hamilton equations in curved spaces. These are designed to improve the energy conservation of symplectic integrators based on the split operator approach. For manifolds, the position-position autocorrelation function can be formulated in numerous ways. We find that the position-position autocorrelation function computed from configurations in the Euclidean space \documentclass[12pt]{minimal}\begin{document}${\mathbb R}^2$\end{document}R2 that contains \documentclass[12pt]{minimal}\begin{document}${\mathbb T}^1$\end{document}T1 as a submanifold has the best statistical properties. The agreement with exact results obtained with vector space methods is excellent for all three potentials, for all values of time in the interval simulated, and for a relatively broad range of temperatures.
Resistivity in rough metallic thin films: A Monte Carlo study
Authors: Rickman J. M. , Barmak K.
Published: July 2012

The impact of interfacial roughness on the resistivity of thin copper films is examined using Monte Carlo simulation. In particular, after comparing the results of the Fuchs-Sondheimer model with those obtained from the simulation of a film bounded by flat surfaces, we highlight the role of collisions with two rough surfaces on electron trajectories. We then calculate the resistivity as a function of the amplitude of interfacial roughness and provide an interpretation of our results in terms of a simple trapping model in which conduction electrons are temporarily localized in surface indentations.
Mesoporous silicon photonic structures with thousands of periods
Authors: Svyakhovskiy Sergey E. , Maydykovsky Anton I. , Murzina Tatiana V.
Published: July 2012

In this work, we present the results on the fabrication and characterization of the structural and optical properties of thick mesoporous silicon-based 1D photonic crystals (PC) containing up to 2500 periods (400 μm thick) made by electrochemical etching in the hydrofluoric acid solution. The composition of multilayered structures with good spatial periodicity up to thousands of layers and with good reproducibility of porosity of alternate layers is demonstrated that is proven by SEM measurements. Comparative studies of the reflectivity spectra from the front and back sides of a thick free-standing PC also testify a good periodicity of the multilayer structure which manifests itself by the appearance of the photonic band gaps. We demonstrate that the main mechanism that restricts the fabrication of thick porous silicon-based photonic crystals is the local decreasing of the HF concentration in pores.
Photocurrent of lead-free (K0.5Na0.5)(Mn0.005Nb0.995)O3 ferroelectric nanotubes
Authors: Park Jungmin , Won Ahn Chang , Won Kim Ill
Published: July 2012

We fabricated (K0.5Na0.5)(Mn0.005Nb0.995)O3 (KNMN) nanotubes using (K0.5Na0.5)(Mn0.005 Nb0.995)O3 sol on an anodic aluminum oxide (AAO) template. The highly ordered AAO template was fabricated by a two-step anodization process. Lead-free (K0.5Na0.5)(Mn0.005Nb0.995)O3 ferroelectric nanotubes were fabricated by infiltration with KNMN sol inside the AAO template by a sol-gel process. The outer diameter and thickness of the wall in the KNMN nanotube were about 70 nm and 5 nm, respectively. The crystalline structure, surface morphology, and ferroelectric and photocurrent properties were investigated. The maximum power conversion efficiencies (η) of KNMN nanotubes were higher than that of KNMN film due to the greater effective area (KNMN nanotubes: η = 0.02%, KNMN film: η = 0.008%).
Identification of unavoided crossings in nonadiabatic photoexcited dynamics involving multiple electronic states in polyatomic conjugated molecules
Authors: Fernandez-Alberti Sebastian , Roitberg Adrian E. , Nelson Tammie , Tretiak Sergei
Published: July 2012

Radiationless transitions between electronic excited states in polyatomic molecules take place through unavoided crossings of the potential energy surfaces with substantial non-adiabatic coupling between the respective adiabatic states. While the extent in time of these couplings are large enough, these transitions can be reasonably well simulated through quantum transitions using trajectory surface hopping-like methods. In addition, complex molecular systems may have multiple “trivial” unavoided crossings between noninteracting states. In these cases, the non-adiabatic couplings are described as sharp peaks strongly localized in time. Therefore, their modeling is commonly subjected to the identification of regions close to the particular instantaneous nuclear configurations for which the energy surfaces actually cross each other. Here, we present a novel procedure to identify and treat these regions of unavoided crossings between non-interacting states using the so-called Min-Cost algorithm. The method differentiates between unavoided crossings between interacting states (simulated by quantum hops), and trivial unavoided crossings between non-interacting states (detected by tracking the states in time with Min-Cost procedure). We discuss its implementation within our recently developed non-adiabatic excited state molecular dynamics framework. Fragments of two- and four-ring linear polyphenylene ethynylene chromophore units at various separations have been used as a representative molecular system to test the algorithm. Our results enable us to distinguish and analyze the main features of these different types of radiationless transitions the molecular system undertakes during internal conversion.
Note: Tesla transformer damping
Authors: Reed J. L.
Published: July 2012

Unexpected heavy damping in the two winding Tesla pulse transformer is shown to be due to small primary inductances. A small primary inductance is a necessary condition of operability, but is also a refractory inefficiency. A 30% performance loss is demonstrated using a typical “spiral strip” transformer. The loss is investigated by examining damping terms added to the transformer's governing equations. A significant alteration of the transformer's architecture is suggested to mitigate these losses. Experimental and simulated data comparing the 2 and 3 winding transformers are cited to support the suggestion.
ZnO light-emitting devices with a lifetime of 6.8 hours
Authors: Liu J. S. , Shan C. X. , Shen H. , Li B. H. , Zhang Z. Z. , Liu L. , Zhang L. G. , Shen D. Z.
Published: July 2012

Lithium-nitrogen doped p-type Mg0.25Zn0.75O films have been realized, and p-Mg0.25Zn0.75O/n-ZnO single-heterostructured light-emitting devices (LEDs) have been constructed. Obvious emission at around 392 nm has been observed from the LEDs under the injection of continuous current, which can be attributed to the near-band-edge emission of ZnO. The LED can work continuously for 6.8 h under a continuous current of 20 mA, revealing the good reliability of the LED. The results reported in this letter reveal that reliable ZnO-based LEDs can be realized, thus high-performance ZnO-based LEDs may be promised in the future.
A model of an artificial one-dimensional quasicrystal composed of semiconductor quantum dots
Authors: Ma Wen-Long , Li Shu-Shen
Published: July 2012

A model is presented of an artificial one-dimensional quasicrystal composed of semiconductor quantum dots (QDs) arranged in a Fibonacci sequence. Compared to the typical one-dimensional quasicrystal, the major advantage of this artificial system is that its electronic properties can be tuned by controlling the number of dots in the system. A self-similar hierarchy of energy gaps is found in the energy spectra of this system just as in the one-dimensional quasicrystal and the localized states may appear quite symmetrically in the two main energy gaps of the energy spectra. Numerical calculations show that whether the localized states exist or not, but depends on the number of dots in a way quite similar to the generation of a Fibonacci sequence. Such an artificial structure may offer new research directions in semiconductor QD devices.
Fabrication and characterization of fibers with built-in liquid crystal channels and electrodes for transverse incident-light modulation
Authors: Stolyarov Alexander M. , Wei Lei , Sorin Fabien , Lestoquoy Guillaume , Joannopoulos John D. , Fink Yoel
Published: July 2012

We report on an all-in-fiber liquid crystal (LC) structure designed for the modulation of light incident transverse to the fiber axis. A hollow cavity flanked by viscous conductors is introduced into a polymer matrix, and the structure is thermally drawn into meters of fiber containing the geometrically scaled microfluidic channel and electrodes. The channel is filled with LCs, whose director orientation is modulated by an electric field generated between the built-in electrodes. Light transmission through the LC-channel at a particular location can be tuned by the driving frequency of the applied field, which directly controls the potential profile along the fiber.
Domain-related origin of magnetic relaxation in compressively strained manganite thin films
Authors: Bakaul S. R. , Miao B. F. , Lin W. , Hu W. , David A. , Ding H. F. , Wu T.
Published: July 2012

Magnetic relaxation is ubiquitous in magnetic materials, and elucidation of the underlying mechanisms is important for achieving reliable device operations. Here, we systematically investigate the magnetic relaxation in compressively strained La0.7Sr0.3MnO3 thin films. Upon the removal of external magnetic field, the slow time-dependent increase of in-plane magnetization is correlated with the break-up of magnetic domains and the emergence of additional domain walls, whereas a reduction of magnetization for the initial short period dominates the magnetic relaxation at lower temperatures in thinner films. These relaxation effects underline the importance of domain dynamics in the properties of magnetic thin films.
Magnetic properties of Co2C and Co3C nanoparticles and their assemblies
Authors: Carroll Kyler J. , Huba Zachary J. , Spurgeon Steven R. , Qian Meichun , Khanna Shiv N. , Hudgins Daniel M. , Taheri Mitra L. , Carpenter Everett E.
Published: July 2012

Nano-composite material consisting of Co2C and Co3C nanoparticles has recently been shown to exhibit unusually large coercivities and energy products. Experimental studies that can delineate the properties of individual phases have been undertaken and provide information on how the coercivities and the energy product change with the size and composition of the nanoparticles. The studies indicate that while both phases are magnetic, the Co3C has higher magnetization and coercivity compared to Co2C. Through first principles electronic structure studies using a GGA+U functional, we provide insight on the role of C intercalation on enhancing the magnetic anisotropy of the individual phases.
Anisotropic electrical properties in bismuth layer structured dielectrics with natural super lattice structure
Authors: Kojima Takashi , Kimura Junichi , Suzuki Muneyasu , Takahashi Kenji , Oikawa Takahiro , Sakashita Yukio , Kato Kazumi , Watanabe Takayuki , Takenaka Tadashi , Yamada Tomoaki , Funakubo Hiroshi
Published: July 2012

Dielectric property of epitaxial SrBi4Ti4O15 thin films with (001)-, (1110)-, (105)/(015)-, and (100)/(010)-orientations was investigated as a function of film thickness. As the tilting angle of c-axis from the surface normal is smaller, the relative dielectric constant begins to degrade at thinner thickness; eventually, the (001)-oriented films for which the c-axis is vertical to the substrate do not show noticeable degradation. The leakage current density also strongly depends of the tilting angle of the c-axis. The results indicate that the layer structure of SrBi4Ti4O15 exhibits a small size effect with high insulation performance.
Exchange bias and its thermal stability in ferromagnetic/antiferromagnetic antidot arrays
Authors: Gong W. J. , Yu W. J. , Liu W. , Guo S. , Ma S. , Feng J. N. , Li B. , Zhang Z. D.
Published: July 2012

The exchange bias (EB) effect and its thermal stability in nanoscale Co/NiO antidot arrays and sheet films have been investigated. The EB field HE increases with increasing Co thickness (tCo) and reaches a maximum at tCo = 8 nm in the antidot arrays, whereas HE decreases with tCo in the sheet films. Compared with the sheet films, HE in the antidot arrays is either enhanced or decreased, depending on the thickness of the ferromagnetic Co layer, which is due to the three-dimensional effects in the antiferromagnetic NiO and ferromagnetic Co layers caused by the nanopores. A higher thermal stability is observed in the antidot arrays due to the out-of-plane anisotropy constant K1 of the misaligned antiferromagnetic magnetization component.
Resonance magnetoelectric effects in a layered composite under magnetic and electrical excitations
Authors: Fetisov L. Y. , Chashin D. V. , Fetisov Y. K. , Segalla A. G. , Srinivasan G.
Published: July 2012

A novel three-layer composite consisting of a lead zirconate titanate (PZT) substrate, a PZT film on one side, and a film of ferromagnetic alloy on the other side is fabricated and used for studies on the nature of magneto-electric (ME) interactions. The strain mediated ME voltage under an ac magnetic excitation is compared with the voltage produced by pure piezoelectric response of the sample to an ac electric field. The ME voltage response measured across PZT substrate or PZT film under an ac magnetic field shows peaks at bending modes and longitudinal acoustic modes, with a higher voltage at bending mode than for the longitudinal acoustic mode. A variation in the bending mode frequency with bias magnetic field or electric field is observed and is attributed to variation in the Young’s modulus of the magnetic or piezoelectric layers. Estimates of resonance frequencies and ME coefficients are in agreement with the data. Under an ac electric excitation, piezoelectric effects result in a resonance in the voltage measured across the PZT substrate and film. A quantitative agreement is inferred between the measured ME voltage and the voltage produced under an ac electric field.
Quantitative coherent scattering spectra in apertureless terahertz pulse near-field microscopes
Authors: Moon Kiwon , Do Youngwoong , Lim Meehyun , Lee Gyuseok , Kang Hyeona , Park Kee-Su , Han Haewook
Published: July 2012

We present quantitative coherent measurements of scattering pulses and spectra in terahertz apertureless near-field microscopes. Broadband near-field image contrasts for both amplitude and phase spectra are measured directly from time-domain scattering signals with an unprecedentedly high single-scan signal-to-noise ratio (∼48 dB), with approach curves for both short (<200 nm) and long (up to 82 μm) ranges. By using the line dipole image method, we obtain quantitative broadband THz imaging contrasts with nanoscale resolution.
Influences of annealing temperature on structural characterization and magnetic properties of Mn-doped BaTiO3 ceramics
Authors: Phan The-Long , Zhang P. , Grinting D. , Yu S. C. , Nghia N. X. , Dang N. V. , Lam V. D.
Published: July 2012

Polycrystalline samples of BaTiO3 doped with 2.0 at. % Mn were prepared by solid-state reaction at various temperatures (Tan) ranging from 500 to 1350 °C, used high-pure powders of BaCO3, TiO2, and MnCO3 as precursors. Experimental results obtained from x-ray diffraction patterns and Raman scattering spectra reveal that tetragonal Mn-doped BaTiO3 starts constituting as Tan ≈ 500 °C. The Tan increase leads to the development of this phase. Interestingly, there is the tetragonal-hexagonal transformation in the crystal structure of BaTiO3 as Tan ≈ 1100 °C. Such the variations influence directly magnetic properties of the samples. Besides paramagnetic contributions of Mn2+ centers traced to electron spin resonance, the room-temperature ferromagnetism found in the samples is assigned to exchange interactions taking place between Mn3+ and Mn4+ ions located in tetragonal BaTiO3 crystals.
Crystalline silicon surface passivation by intrinsic silicon thin films deposited by low-frequency inductively coupled plasma
Authors: Zhou H. P. , Wei D. Y. , Xu S. , Xiao S. Q. , Xu L. X. , Huang S. Y. , Guo Y. N. , Khan S. , Xu M.
Published: July 2012

Amorphous and microcrystal hydrogenated intrinsic silicon (a-Si:H/μc-Si:H) thin films with good silicon surface passivation effect were deposited using a precursor gases of silane and hydrogen, which were discharged by low frequency inductively coupled high density plasma source. With regard to silicon surface passivation, the effect of discharge power on thin films properties, including the optical band gap, the crystal fraction, and bond configuration, as well as the deposition rate were thoroughly investigated. It was found that the best passivation effect was obtained at the region near the transition regime from a-Si:H to μc-Si:H with a minimized incubation layer between the passivation layer and substrate. Cz-silicon wafer passivated by as-deposited μc-Si:H thin films without any post-deposition thermal annealing possesses minority carrier lifetime of about 234 μs. This is attributed to the chemical annealing from the high-density hydrogen plasma during the deposition process. Subsequent thermal annealing in hydrogen flow increased the lifetime to 524 μs with a suppressed maximum surface recombination velocity of as low as 60 cm/s. Throughout the process flow covering the pre-deposition H plasma treatment, the film deposition from H2 diluted feedstock gases and the post-deposition annealing, hydrogen plays a vital role to enhance the minority carrier lifetime by improving the interface properties. The injection level dependent surface recombination velocity was also extracted from the lifetime measurement. The effectivity of the a-Si:H/μc-Si:H for silicon surface passivation in a practical heterojunction solar cell was further validated by the excellent photovoltaic performance.
Matrix role in Ge nanoclusters embedded in Si3N4 or SiO2
Authors: Mirabella S. , Cosentino S. , Gentile A. , Nicotra G. , Piluso N. , Mercaldo L. V. , Simone F. , Spinella C. , Terrasi A.
Published: July 2012

Ge nanoclusters (NCs), synthesized by ion implantation and annealing up to 900 °C, result small (∼2 nm) and amorphous in Si3N4, crystalline and much larger in SiO2. The NCs ripening and crystallization kinetics in Si3N4 is retarded by larger interfacial energy and lower diffusivity of Ge in comparison to SiO2. Ge NCs absorb light more efficiently when embedded in Si3N4 than in SiO2. A significant effect of the barrier height on absorption was evidenced, in agreement with effective mass theory predictions. The smaller bandgap of Ge NCs embedded in Si3N4 and their closeness is promising features for light harvesting applications.
Perception While Watching Movies: Effects of Physical Screen Size and Scene Type
Authors: Troscianko Tom , Meese Timothy S. , Hinde Stephen
Published: July 2012

Over the last decade, television screens and display monitors have increased in size considerably, but has this improved our televisual experience? Our working hypothesis was that the audiences adopt a general strategy that “bigger is better.” However, as our visual perceptions do not tap directly into basic retinal image properties such as retinal image size (C. A. Burbeck, 1987), we wondered whether object size itself might be an important factor. To test this, we needed a task that would tap into the subjective experiences of participants watching a movie on different-sized displays with the same retinal subtense. Our participants used a line bisection task to self-report their level of “presence” (i.e., their involvement with the movie) at several target locations that were probed in a 45-min section of the movie “ The Good, The Bad, and The Ugly.” Measures of pupil dilation and reaction time to the probes were also obtained. In Experiment 1, we found that subjective ratings of presence increased with physical screen size, supporting our hypothesis. Face scenes also produced higher presence scores than landscape scenes for both screen sizes. In Experiment 2, reaction time and pupil dilation results showed the same trends as the presence ratings and pupil dilation correlated with presence ratings, providing some validation of the method. Overall, the results suggest that real-time measures of subjective presence might be a valuable tool for measuring audience experience for different types of (i) display and (ii) audiovisual material.
Short-term effects of a prolonged blackwater event on aquatic fauna in the Murray River, Australia: considerations for future events
Authors: King A. J. , Tonkin Z. , Lieshcke J.
Published: July 2012

Blackwater contains high levels of dissolved organic carbon that can be rapidly consumed by microbes, sometimes leading to extremely low levels of dissolved oxygen (hypoxia) and drastic consequences for aquatic life, including fish kills. Drought-breaking rains in late 2010 inundated large areas of the Barmah–Millewa Forest, southern Murray–Darling Basin, Australia, and resulted in a prolonged hypoxic blackwater event within the forest and the Murray River downstream. This study investigated the short-term effects of the blackwater event on fish and crayfish. Compared with non-affected sites, blackwater affected sites had: significantly higher abundances of emerged Murray crayfish (Euastacus armatus) that were vulnerable to desiccation, predation and exploitation; large numbers of dead or dying shrimp and yabbies; significantly reduced abundances of native fish; but contained similar abundances of alien fish species (particularly common carp, Cyprinus carpio). The nature of the mechanisms that caused these changes and the longer term significance of the event on the river system remains an important area for future research. We also propose a range of management considerations for reducing the blackwater impacts, such as the timing of environmental water delivery after prolonged drought and the importance of maintaining river–floodplain connectivity during flood periods.
Practical uses of non-parametric methods in fisheries assessment modelling
Authors: Hillary R. M.
Published: July 2012

The vast majority of fisheries stock assessment modelling is parametric, where specific models are assumed and fitted to data, the results of which are used to assess stock status and provide scientific advice. Often, the assumed models may not acceptably explain the data, or the data are not informative enough to estimate the parameters of even the most simple models. Using a fully inferential statistical framework, artificial neural networks were fitted to example data sets (stock-recruit, catch and relative abundance) and key assessment quantities such as maximum sustainable yield and relative biomass depletion were estimated. The combination of flexibility and statistical rigor suggests there is an as yet under-utilised role for such approaches in stock assessment, and not just in data-poor scenarios.
A phytochrome–phototropin light signaling complex at the plasma membrane
Authors: Jaedicke Katharina , Lichtenthäler Anna Lena , Meyberg Rabea , Zeidler Mathias , Hughes Jon
Published: July 2012

Phytochromes are red/far-red photochromic photoreceptors central to regulating plant development. Although they are known to enter the nucleus upon light activation and, once there, regulate transcription, this is not the complete picture. Various phytochrome effects are manifested much too rapidly to derive from changes in gene expression, whereas others seem to occur without phytochrome entering the nucleus. Phytochromes also guide directional responses to light, excluding a genetic signaling route and implying instead plasma membrane association and a direct cytoplasmic signal. However, to date, no such association has been demonstrated. Here we report that a phytochrome subpopulation indeed associates physically with another photoreceptor, phototropin, at the plasma membrane. Yeast two-hybrid methods using functional photoreceptor molecules showed that the phytochrome steering growth direction in
Physcomitrella
protonemata binds several phototropins specifically in the photoactivated Pfr state. Split-YFP studies
in planta
showed that the interaction occurs exclusively at the plasma membrane. Coimmunoprecipitation experiments provided independent confirmation of in vivo phy-phot binding. Consistent with this interaction being associated with a cellular signal, we found that phytochrome-mediated tropic responses are impaired in

Physcomitrella phot
−

mutants. Split-YFP revealed a similar interaction between
Arabidopsis
phytochrome A and phototropin 1 at the plasma membrane. These associations additionally provide a functional explanation for the evolution of neochrome photoreceptors. Our results imply that the elusive phytochrome cytoplasmic signal arises through binding and coaction with phototropin at the plasma membrane.
Defect in regulatory B-cell function and development of systemic autoimmunity in T-cell Ig mucin 1 (Tim-1) mucin domain-mutant mice
Authors: Xiao Sheng , Brooks Craig R. , Zhu Chen , Wu Chuan , Sweere Johanna M. , Petecka Sonia , Yeste Ada , Quintana Francisco J. , Ichimura Takaharu , Sobel Raymond A. , Bonventre Joseph V. , Kuchroo Vijay K.
Published: July 2012

Tim-1, a type I transmembrane glycoprotein, consists of an IgV domain and a mucin domain. The IgV domain is essential for binding Tim-1 to its ligands, but little is known about the role of the mucin domain, even though genetic association of TIM-1 with atopy/asthma has been linked to the length of mucin domain. We generated a Tim-1–mutant mouse (Tim-1Δmucin) in which the mucin domain was deleted genetically. The mutant mice showed a profound defect in IL-10 production from regulatory B cells (Bregs). Associated with the loss of IL-10 production in B cells, older Tim-1Δmucinmice developed spontaneous autoimmunity associated with hyperactive T cells, with increased production of IFN-γ and elevated serum levels of Ig and autoantibodies. However, Tim-1Δmucinmice did not develop frank systemic autoimmune disease unless they were crossed onto the Fas-mutant lpr mice on a C57BL/6 background. Tim-1Δmucinlpr mice developed accelerated and fulminant systemic autoimmunity with accumulation of abnormal double-negative T cells and autoantibodies to a number of lupus-associated autoantigens. Thus, Tim-1 plays a critical role in maintaining suppressive Breg function, and our data also demonstrate an unexpected role of the Tim-1 mucin domain in regulating Breg function and maintaining self-tolerance.
Potential of GLMM in modelling invasive spread.
Authors: Thiele J. , Markussen B.
Published: July 2012

Utilization of generalized linear mixed models (GLMM) in invasion biology has increased exponentially during the last 5-10 years. GLMM are useful tools that can handle data with various distributions as well as spatial or temporal dependence, which are involved in many study designs. We review the current state-of-the-art of GLMM with special focus on applications in invasion biology. This review covers all steps of data analysis with GLMM. We address frequently encountered practical problems, such as failure of convergence, and put some emphasis on validation of model assumptions. Further, we point towards possibilities of analysing zero-heavy data using combined GLMM. More detailed insight into practical applications of GLMM is provided in three worked examples in the supplementary material. Regarding applications of GLMM in invasion biology, a literature analysis showed that random effects are mostly used to account for non-independence of observations through study design, but rarely for estimation of random variation. There may be some potential in using random-effect estimation more consciously, as in some recent studies of genetic variation of invasive species. Often, invasion biologists have to deal with count data or proportions. In such cases, several methods of parameter estimation are available, but their suitability depends on characteristics of the data at hand and, hence, they should be chosen carefully. Also, repeated measures are common in invasion biology. In GLMM frameworks, the auto-correlation of such data can be modelled by structured co-variance matrices. This opportunity, however, has seldom been used.
Analysing time series data of phenotypic measurements - trade-off in sexual reproduction and vegetative growth of perennial ryegrass (
Lolium perenne
)?
Authors: Thiele J. , Markussen B.
Published: July 2012

In this example, we analyse repeated phenotypic measurements of perennial ryegrass (
Lolium perenne
) from a greenhouse experiment. We hypothesize that there is a trade-off between sexual reproduction (flower stems) and vegetative propagation (tillers) within polycormons of this species. This is not directly a study of biological invasions; however, we want to find out, if fewer flowering plants (cultivars, in this case) would be more competitive and could invade seminatural grasslands. Similar repeated measures are quite often used in invasion biology. Sexual reproduction or, more precisely, the degree of flowering of the plants, was modified by cold treatments (vernalization). Cold temperature (<6°C) is a prerequisite for flowering of perennial ryegrass. The shorter the cold period, the lower the number of flowering stems that emerge afterwards. In this way, plants (polycormons) of perennial ryegrass with varying numbers of flowering stems were produced, species This forms Supplement D to Thiele J, Markussen B. Potential of GLMM in modelling invasive spread.