bluuebunny/crossref_metadata_2025 huggingface dataset:
Cellulose–spin crossover particle composite papers with reverse printing performance: a proof of concept
Authors: Nagy V. , Suleimanov I. , Molnár G. , Salmon L. , Bousseksou A. , Csóka L.
Published: May 2015

We report on a thermochromic paper with reverse printing performance.
Phase rotation‐based precoding for spatial modulation systems
Authors: Yang Ping , Xiao Yue , Zhang Bo , El‐Hajjar Mohammed , Li Shaoqian , Hanzo Lajos
Published: May 2015

In this study, the authors investigate the benefits of phase‐rotation‐assisted precoding (PRP) technique in spatial modulation (SM) systems, which are based on maximum free distance dmin. First, a closed‐form solution of the maximum‐dmin PRP matrix is derived for the scenario of having two transmit antennas (Nt = 2). Moreover, two numerical methods are proposed for dealing with the case of Nt > 2. The complexity of the proposed algorithms is presented. The authors simulation results show that the proposed PRP algorithms provide beneficial bit error ratio performance improvements compared with both the conventional SM and with the existing adaptive SM.
Joint optimal power allocation and relay selection scheme in energy harvesting asymmetric two‐way relaying system
Authors: Men Jinjin , Ge Jianhua , Zhang Chensi , Li Juan
Published: May 2015

Energy harvesting, which is an emerging technology to prolong the lifetime of energy‐constrained wireless networks, has received significant attention. In this study, the authors consider an amplify‐and‐forward‐based asymmetric two‐way relaying system, where two source nodes exchange information through an energy‐constrained relay node. The relay node scavenges energy from the received signals and uses the harvested energy to forward the received signals to the two terminal nodes. The signal power splitting ratio, depicting the trade‐off between the harvesting energy and the forward signals’ power, is a crucial factor for the system outage probability. Therefore, an optimal power allocation (OPA) scheme, which jointly takes into consideration the optimisation of signal power splitting ratio and the transmission power allocation, is proposed to minimise the outage probability. In addition, a close‐form solution for the OPA scheme is obtained. Finally, a joint OPA and relay selection schemes are presented to further improve the system performance. Simulation results highlight the superiority of the author's proposed scheme.
Blind continuous hidden Markov model‐based spectrum sensing and recognition for primary user with multiple power levels
Authors: Liu Boyang , Li Zan , Si Jiangbo , Zhou Fuhui
Published: May 2015

Spectrum sensing has been well studied because of its significance in cognitive radio. Different from the existing works which a primary user (PU) is assumed to have only one constant transmit power, a more practical scenario that the PU transmitting with multiple power levels is considered. A continuous hidden Markov model (CHMM)‐based blind algorithm for not only detecting the presence of PU but also recognising the transmit power level of the PU is proposed. The training problem of CHMM is solved by combining the wavelet singularity detection with k‐means clustering algorithm. An effective method for estimation of the number of power levels is proposed. Two different strategies are designed to perform spectrum sensing. Simulation results show the efficiency of the proposed algorithm.
Learning a non‐linear combination of Mahalanobis distances using statistical inference for similarity measure
Authors: Mostafa Eslam , Ali Asem M. , Farag Aly A.
Published: May 2015

In this study, the authors learn a similarity measure that discriminates between inter‐class and intra‐class samples based on a statistical inference perspective. A non‐linear combination of Mahalanobis is proposed to reflect the properties of a likelihood ratio test. Since an object's appearance is influenced by the identity of the object and variations in the capturing process, the authors represent the feature vector, which is the difference between two samples in the differences space, as a sample that is drawn from a mixture of many distributions. This mixture consists of the identities distribution and other distributions of the variations in the capturing process, in case of dissimilar samples. However, in the case of similar samples, the mixture consists of the variations in the capturing process distributions only. Using this representation, the proposed similarity measure accurately discriminates between inter‐class and intra‐class samples. To highlight the good performance of the proposed similarity measure, it is tested on different computer vision applications: face verification and person re‐identification. To illustrate how the proposed learning method can easily be used on large scale datasets, experiments are conducted on different challenging datasets: labelled faces in the wild (LFW), public figures face database, ETHZ and VIPeR. Moreover, in these experiments, the authors evaluate different stages, for example, features detector, descriptor type and descriptor dimension, which constitute the face verification pipeline. The experimental results confirm that the learning method outperforms the state‐of‐the‐art.
High‐speed implementation of rate‐distortion optimised quantisation for H.265/HEVC
Authors: He Jing , Yang Fuzheng , Zhou Yicong
Published: May 2015

Rate‐distortion optimised quantisation (RDOQ) is generally utilised in video coding for achieving higher coding efficiency. To determine the optimal quantised level for each transform coefficient, it requires considerable complexity in practice to calculate rate‐distortion (RD) costs from multiple candidates of quantised levels. This study proposes a fast RDOQ algorithm with low computational complexity for the latest video coding standard, the high‐efficiency video coding. Instead of calculating the RD costs from two candidates of quantised levels separately, their RD cost differences were derived. A bit‐rate estimation method is then used to accurately calculate the length of coding bits in the RD cost function, avoiding the high‐computation‐cost process of context‐adaptive binary arithmetic coding. Experimental results show that, with a negligible degradation of coding performance, the proposed algorithm is faster than RDOQ by 74.6% in average.
Performance evaluation of asynchronous multi‐carrier code division multiple access for next‐generation long‐reach fibre optic access networks
Authors: Shoreh Morteza H. , Beyranvand Hamzeh , Salehi Jawad A.
Published: May 2015

In this study, the authors evaluate the performance of asynchronous optical multi‐carrier code division multiple access (MC‐CDMA) for intensity modulated/direct detection systems to be used in next‐generation optical access networks. The proposed system employs Gold sequence in frequency‐domain to provide asynchronous resource sharing. In long‐reach passive optical networks, fibre impairments degradation to the performance of ordinary optical CDMA can be avoided by frequency‐domain digital compensation methods in the proposed MC‐CDMA. In comparison with orthogonal frequency division multiple access, peak‐to‐average power ratio in the proposed MC‐CDMA is reduced and asynchronous resource sharing is achieved. The performance of the proposed optical MC‐CDMA system is analytically evaluated by driving closed‐form equations for signal‐to‐interference plus noise ratio and bit error rate (BER) performances. Furthermore, the simulation results are provided in terms of BER against signal‐to‐noise ratio in one case and the number of users in another, conditioned on the modulation levels. Finally, the analytical formulation of BER is verified with the help of simulation results.
Revisiting topological properties and models of protein–protein interaction networks from the perspective of dataset evolution
Authors: Shao Mingyu , Zhou Shuigeng , Guan Jihong
Published: May 2015

Protein–protein interaction (PPI) networks are crucial for organisms. Many research efforts have thus been devoted to the study on the topological properties and models of PPI networks. However, existing studies did not always report consistent results on the topological properties of PPI networks. Although a number of PPI network models have been introduced, yet in the literature there is no convincing conclusion on which model is best for describing PPI networks. This situation is primarily caused by the incompleteness of current PPI datasets. To solve this problem, in this study, the authors propose to revisit the topological properties and models of PPI networks from the perspective of PPI dataset evolution. Concretely, they used 12 PPI datasets of Arabidopsis thaliana and 10 PPI datasets of Saccharomyces cerevisiae from different Biological General Repository for Interaction Datasets (BioGRID) database versions, and compared the topological properties of these datasets and the fitting capabilities of five typical PPI network models over these datasets.
Three-dimensional convection-driven fronts of the exothermic chlorite-tetrathionate reaction
Authors: Schuszter Gábor , Pótári Gábor , Horváth Dezső , Tóth Ágota
Published: May 2015

Horizontally propagating autocatalytic reaction fronts in fluids are often accompanied by convective motion in the presence of gravity. We experimentally and numerically investigate the stable complex three-dimensional pattern arising in the exothermic chlorite–tetrathionate reaction as a result of the antagonistic thermal and solutal contribution to the density change. By particle image velocimetry measurements, we construct the flow field that stabilizes the front structure. The calculations applied for incompressible fluids using the empirical rate-law model reproduce the experimental observations with good agreement.
Nested arithmetic progressions of oscillatory phases in Olsen's enzyme reaction model
Authors: Gallas Marcia R. , Gallas Jason A. C.
Published: May 2015

We report some regular organizations of stability phases discovered among self-sustained oscillations of a biochemical oscillator. The signature of such organizations is a nested arithmetic progression in the number of spikes of consecutive windows of periodic oscillations. In one of them, there is a main progression of windows whose consecutive number of spikes differs by one unit. Such windows are separated by a secondary progression of smaller windows whose number of spikes differs by two units. Another more complex progression involves a fan-like nested alternation of stability phases whose number of spikes seems to grow indefinitely and to accumulate methodically in cycles. Arithmetic progressions exist abundantly in several control parameter planes and can be observed by tuning just one among several possible rate constants governing the enzyme reaction.
Compatible mechanism to characterize three independent but cross-coupled reactions of chlorite ion
Authors: Nagypál István , Horváth Attila K.
Published: May 2015

Individually proposed kinetic models of the key subsystems of the chlorite–thiosulfate reaction, such as the hypochlorous acid–chlorite, tetrathionate–chlorite, and tetrathionate–chlorine dioxide reactions, have been unified to be able to describe all the main characteristics of these systems simultaneously. A complex 38-step kinetic model is composed in which the subsystems are coupled by the necessary short-lived intermediates and such species that is products or reactants in one system but transients in the other. Such a cross-coupling between the individual systems as well as the sound agreement between the measured and calculated absorbance–time profiles in 367 experimental curves strongly validates the proposed kinetic model.
Application of multireference equation of motion coupled-cluster theory to transition metal complexes and an orbital selection scheme for the efficient calculation of excitation energies
Authors: Huntington Lee M. J. , Nooijen Marcel
Published: May 2015

This paper presents the first application of the multireference equation of motion coupled-cluster (MR-EOMCC) approach to the calculation and characterization of excitation energies of transition metal complexes. The calculated MR-EOM excitation energies are compared with experimental UV/Vis. band maxima, Brueckner based similarity transformed equation of motion (STEOM) calculations and Brueckner based equation of motion coupled cluster (EOM-CCSD(T)) calculations, as well as results calculated with other methods from the literature. The agreement of the excitation energies with experiment is found to be reasonable, and suitable rationalization is given for the discrepancies. An orbital selection scheme is introduced, which can be employed to extend the applicability of the MR-EOMCC methodology to considerably larger systems.
Regular and irregular patterns of self-localized excitation in arrays of coupled phase oscillators
Authors: Wolfrum Matthias , Omel'chenko Oleh E. , Sieber Jan
Published: May 2015

We study a system of phase oscillators with nonlocal coupling in a ring that supports self-organized patterns of coherence and incoherence, called chimera states. Introducing a global feedback loop, connecting the phase lag to the order parameter, we can observe chimera states also for systems with a small number of oscillators. Numerical simulations show a huge variety of regular and irregular patterns composed of localized phase slipping events of single oscillators. Using methods of classical finite dimensional chaos and bifurcation theory, we can identify the emergence of chaotic chimera states as a result of transitions to chaos via period doubling cascades, torus breakup, and intermittency. We can explain the observed phenomena by a mechanism of self-modulated excitability in a discrete excitable medium.
Communication: Ion mobility of the radical cation dimers: (Naphthalene)2+• and naphthalene+•-benzene: Evidence for stacked sandwich and T-shape structures
Authors: Platt Sean P. , Attah Isaac K. , Aziz Saadullah , El-Shall M. Samy
Published: May 2015

Dimer radical cations of aromatic and polycyclic aromatic molecules are good model systems for a fundamental understanding of photoconductivity and ferromagnetism in organic materials which depend on the degree of charge delocalization. The structures of the dimer radical cations are difficult to determine theoretically since the potential energy surface is often very flat with multiple shallow minima representing two major classes of isomers adopting the stacked parallel or the T-shape structure. We present experimental results, based on mass-selected ion mobility measurements, on the gas phase structures of the naphthalene+⋅ ⋅ naphthalene homodimer and the naphthalene+⋅ ⋅ benzene heterodimer radical cations at different temperatures. Ion mobility studies reveal a persistence of the stacked parallel structure of the naphthalene+⋅ ⋅ naphthalene homodimer in the temperature range 230-300 K. On the other hand, the results reveal that the naphthalene+⋅ ⋅ benzene heterodimer is able to exhibit both the stacked parallel and T-shape structural isomers depending on the experimental conditions. Exploitation of the unique structural motifs among charged homo- and heteroaromatic–aromatic interactions may lead to new opportunities for molecular design and recognition involving charged aromatic systems.
Mickelsson-Rajeev cocycle corresponding to dimension five
Authors: Lipponen Henri
Published: May 2015

We construct a Mickelsson-Rajeev-type cocycle corresponding to five space dimensions. In the three dimensional case, this cocycle is shown to be equivalent to the original cocycle proposed by Mickelsson and Rajeev. Furthermore, we construct a local representative for this cocycle and evaluate it explicitly on a five dimensional torus.
Entropic stochastic resonance without external force in oscillatory confined space
Authors: Ding Huai , Jiang Huijun , Hou Zhonghuai
Published: May 2015

We have studied the dynamics of Brownian particles in a confined geometry of dumbbell-shape with periodically oscillating walls. Entropic stochastic resonance (ESR) behavior, characterizing by a maximum value of the coherent factor Q at some optimal level of noise, is observed even without external periodic force in the horizontal direction, which is necessary for conventional ESR where the wall is static and the particle is subjected to the force. Interestingly, the ESR can be remarkably enhanced by the particle gravity G, in contrast to the conventional case. In addition, Q decreases (increases) with G in the small (large) noise limit, respectively, while it non-monotonically changes with G for moderate noise levels. We have applied an effective 1D coarsening description to illustrate such a nontrivial dependence on G, by investigating the property of the 1D effective potential of entropic nature and paying special attention to the excess part resulting from the boundary oscillation. Dependences of the ESR strength with other related parameters are also discussed.
Onsager’s reciprocal relations for electroacoustic and sedimentation: Application to (concentrated) colloidal suspensions
Authors: Gourdin-Bertin S. , Chassagne C.
Published: May 2015

In this article, the relations for electroacoustic phenomena, such as sedimentation potential, sedimentation intensity, colloid vibration potential, colloid vibration intensity/current, or electric sonic amplitude, are given, on the basis of irreversible thermodynamics. This formalism allows in particular to discuss the different expressions for concentrated suspensions found by various authors, which are of great practical interest. It was found that some existing expressions have to be corrected. Relations between the electrophoretic mobilities assessed by the different experiments are derived.
Inertial effects of the semi-passive flapping foil on its energy extraction efficiency
Authors: Deng Jian , Teng Lubao , Pan Dingyi , Shao Xueming
Published: May 2015

The inertia plays a significant role in the response of a system undergoing flow-induced vibrations, which has been extensively investigated by previous researchers. However, the inertial effects of an energy harvester employing the mechanism of flow-induced vibrations have attracted little attention. This paper concentrates on a semi-passive energy extraction system considering its inertial effects. The incompressible Navier-Stokes equations are solved using a finite-volume based numerical solver with a moving grid technique. A partitioned method is used to couple the fluid and structure motions with the sub-iteration technique and an Aitken relaxation, which guarantees a strong fluid-structure coupling. In addition, a fictitious mass is added to resolve the numerical instability aroused by low density ratios. First, at a fixed mass ratio of r = 1, we identify an optimal set of parameters, at which a maximum efficiency of η = 34% is achieved. Further studies with r ranging from 0.125 to 100 are performed around the optimal parameters. The results show that for the semi-passive flapping energy harvester, the energy harvesting efficiency decreases monotonically with increasing mass ratio. We also notice that the total power extraction stays at a high level with little variation for r < 10; therefore, if we concern more about the amount of power extraction rather than its efficiency, the inertial effects can be neglectable for r < 10. Moreover, since one degree of freedom is released for the semi-passive system, it is possible for the system to automatically determine its optimal operational parameters. We note that the optimal phase difference ϕ = 82° has been well determined, which leads to a good timing of vortex-foil interactions. We note two different trends on phase difference for the effects of reduced frequency and mass ratio, respectively. By varying the reduced frequency f∗, an optimal f∗ is identified, at which the minimum phase difference is achieved. While the relationship between phase difference and mass ratio is monotonic, a maximum phase difference is achieved at the nearly zero mass ratio. Nevertheless, both trends point to the same optimal phase difference, i.e., ϕ = 82° at θ0 = 75°. Furthermore, the relationship between the leading edge vortex and the phase difference is systematically investigated, accounting for the physical reason of existence of the optimal phase difference.
White-blue electroluminescence from a Si quantum dot hybrid light-emitting diode
Authors: Xin Yunzi , Nishio Kazuyuki , Saitow Ken-ichi
Published: May 2015

A silicon (Si) quantum dot (QD)-based hybrid inorganic/organic light-emitting diode (LED) was fabricated via solution processing. This device exhibited white-blue electroluminescence at a low applied voltage of 6 V, with 78% of the effective emission obtained from the Si QDs. This hybrid LED produced current and optical power densities 280 and 350 times greater than those previously reported for such device. The superior performance of this hybrid device was obtained by both the prepared Si QDs and the optimized layer structure and thereby improving carrier migration through the hybrid LED and carrier recombination in the homogeneous Si QD layer.
Room temperature ferromagnetism in epitaxial Cr2O3 thin films grown on r-sapphire
Authors: Punugupati Sandhyarani , Narayan Jagdish , Hunte Frank
Published: May 2015

We report on the epitaxial growth and magnetic properties of Cr2O3 thin films grown on r-sapphire substrate using pulsed laser deposition. The X-ray diffraction (XRD) (2θ and Φ) and TEM characterization confirm that the films are grown epitaxially. The r-plane (011¯2) of Cr2O3 grows on r-plane of sapphire. The epitaxial relations can be written as [011¯2] Cr2O3 ‖ [011¯2] Al2O3 (out-of-plane) and [1¯1¯20] Cr2O3 ‖ [1¯1¯20] Al2O3 (in-plane). The as-deposited films showed ferromagnetic behavior up to 400 K but ferromagnetism almost vanishes with oxygen annealing. The Raman spectroscopy data together with strain measurements using high resolution XRD indicate that ferromagnetism in r-Cr2O3 thin films is due to the strain caused by defects, such as oxygen vacancies.
Oxide 2D electron gases as a route for high carrier densities on (001) Si
Authors: Kornblum Lior , Jin Eric N. , Kumah Divine P. , Ernst Alexis T. , Broadbridge Christine C. , Ahn Charles H. , Walker Fred J.
Published: May 2015

Two dimensional electron gases (2DEGs) formed at the interfaces of oxide heterostructures draw considerable interest owing to their unique physics and potential applications. Growing such heterostructures on conventional semiconductors has the potential to integrate their functionality with semiconductor device technology. We demonstrate 2DEGs on a conventional semiconductor by growing GdTiO3-SrTiO3 on silicon. Structural analysis confirms the epitaxial growth of heterostructures with abrupt interfaces and a high degree of crystallinity. Transport measurements show the conduction to be an interface effect, ∼9 × 1013 cm−2 electrons per interface. Good agreement is demonstrated between the electronic behavior of structures grown on Si and on an oxide substrate, validating the robustness of this approach to bridge between lab-scale samples to a scalable, technologically relevant materials system.
Robust fluidic connections to freestanding microfluidic hydrogels
Authors: Faley Shannon L. , Baer Bradly B. , Larsen Taylor S. H. , Bellan Leon M.
Published: May 2015

Biomimetic scaffolds approaching physiological scale, whose size and large cellular load far exceed the limits of diffusion, require incorporation of a fluidic means to achieve adequate nutrient/metabolite exchange. This need has driven the extension of microfluidic technologies into the area of biomaterials. While construction of perfusable scaffolds is essentially a problem of microfluidic device fabrication, functional implementation of free-standing, thick-tissue constructs depends upon successful integration of external pumping mechanisms through optimized connective assemblies. However, a critical analysis to identify optimal materials/assembly components for hydrogel substrates has received little focus to date. This investigation addresses this issue directly by evaluating the efficacy of a range of adhesive and mechanical fluidic connection methods to gelatin hydrogel constructs based upon both mechanical property analysis and cell compatibility. Results identify a novel bioadhesive, comprised of two enzymatically modified gelatin compounds, for connecting tubing to hydrogel constructs that is both structurally robust and non-cytotoxic. Furthermore, outcomes from this study provide clear evidence that fluidic interconnect success varies with substrate composition (specifically hydrogel versus polydimethylsiloxane), highlighting not only the importance of selecting the appropriately tailored components for fluidic hydrogel systems but also that of encouraging ongoing, targeted exploration of this issue. The optimization of such interconnect systems will ultimately promote exciting scientific and therapeutic developments provided by microfluidic, cell-laden scaffolds.
Magnetism switching and band-gap narrowing in Ni-doped PbTiO3 thin films
Authors: Zhou Wenliang , Deng Hongmei , Yu Lu , Yang Pingxiong , Chu Junhao
Published: May 2015

Ions doping-driven structural phase transition accompanied by magnetism switching and band-gap narrowing effects has been observed in PbTi1−xNixO3−δ (xPTNO, x = 0.00, 0.06, and 0.33) thin films. With the increase of x, the xPTNO thin films exhibit not only a phase transition from the pseudotetragonal structure to a centrosymmetric cubic structure but also a drastic decrease of grain size. Moreover, the as-grown Ni-doped PbTiO3 (PTO) thin films show obvious room-temperature ferromagnetism and an increased saturation magnetization with increasing the Ni content, in contrast to undoped PTO, which shows diamagnetism. A bound magnetic polaron model was proposed to understand the observed ferromagnetic behavior of PTO-derived perovskite thin films. Furthermore, the 0.33PTNO thin film presents a narrowed band-gap, much smaller than that of PTO, which is attributed to new states of both the highest occupied molecular orbital and the lowest unoccupied molecular orbital in an electronic structure with the presence of Ni. These findings may open up a route to explore promising perovskite oxides as candidate materials for use in multiferroics and solar-energy devices.
Short-wave infrared barriode detectors using InGaAsSb absorption material lattice matched to GaSb
Authors: Craig A. P. , Jain M. , Wicks G. , Golding T. , Hossain K. , McEwan K. , Howle C. , Percy B. , Marshall A. R. J.
Published: May 2015

Short-wave infrared barriode detectors were grown by molecular beam epitaxy. An absorption layer composition of In0.28Ga0.72As0.25Sb0.75 allowed for lattice matching to GaSb and cut-off wavelengths of 2.9 μm at 250 K and 3.0 μm at room temperature. Arrhenius plots of the dark current density showed diffusion limited dark currents approaching those expected for optimized HgCdTe-based detectors. Specific detectivity figures of around 7×1010 Jones and 1×1010 Jones were calculated, for 240 K and room temperature, respectively. Significantly, these devices could support focal plane arrays working at higher operating temperatures.
Magnetic and nonlinear optical properties of BaTiO3 nanoparticles
Authors: Ramakanth S. , Hamad Syed , Venugopal Rao S. , James Raju K. C.
Published: May 2015

In our earlier studies the BaTiO3 samples were processed at higher temperatures like 1000oC and explained the observed magnetism in it. It is found that the charge transfer effects are playing crucial role in explaining the observed ferromagnetism in it. In the present work the samples were processed at lower temperatures like 650oC-800oC. The carrier densities in these particles were estimated to be ∼ 1019-1020/cm3 range. The band gap is in the range of 2.53eV to 3.2eV. It is observed that magnetization increased with band gap narrowing. The higher band gap narrowed particles exhibited increased magnetization with a higher carrier density of 1.23×1020/cm3 near to the Mott critical density. This hint the exchange interactions between the carriers play a dominant role in deciding the magnetic properties of these particles. The increase in charge carrier density in this undoped BaTiO3 is because of oxygen defects only. The oxygen vacancy will introduce electrons in the system and hence more charge carriers means more oxygen defects in the system and increases the exchange interactions between Ti3+, Ti4+, hence high magnetic moment. The coercivity is increased from 23 nm to 31 nm and then decreased again for higher particle size of 54 nm. These particles do not show photoluminescence property and hence it hints the absence of uniformly distributed distorted [TiO5]-[TiO6] clusters formation and charge transfer between them. Whereas these charge transfer effects are vital in explaining the observed magnetism in high temperature processed samples. Thus the variation of magnetic properties like magnetization, coercivity with band gap narrowing, particle size and charge carrier density reveals the super paramagnetic nature of BaTiO3 nanoparticles. The nonlinear optical coefficients extracted from Z-scan studies suggest that these are potential candidates for optical imaging and signal processing applications.
Perspective: Emergent magnetic phenomena at interfaces
Authors: Suzuki Yuri
Published: May 2015

The discovery of emergent magnetic phenomena is of fundamental and technological interest. This perspective highlights recent promising examples of emergent ferromagnetism at complex oxide interfaces in the context of spin based electronics.
Large magnetoelectric response in modified BNT based ternary piezoelectric [72.5(Bi1/2Na1/2TiO3)-22.5(Bi1/2K1/2TiO3)-5(BiMg1/2Ti1/2O3)]-magnetostrictive (NiFe2O4) particulate (0-3) composites
Authors: Tyagi Mintu , Kumari Mukesh , Chatterjee Ratnamala , Sharma Puneet
Published: May 2015

Lead free ternary solid solution 72.5(Bi1/2Na1/2TiO3)-22.5(Bi1/2K1/2TiO3)-5(BiMg1/2Ti1/2O3) with effective piezoelectric coefficient (d33) of 180 pC/N has been prepared. Further, particulate composites consisting of (1−x)[72.5(BNT)-22.5(BKT)-5(BMgT)]−xNiFe2O4 (NFO) (x = 0, 0.1, 0.2, 0.3) were synthesized, and its structural, magnetoelectric (ME), magnetostrictive, magnetic, and ferroelectric properties were studied. Large ME voltage coefficient, (αE) ∼ 73 mV/cmOe accompanied by high d33 ∼ 125 pC/N, and magnetostrictive strains, (λ11) ∼ −18 × 10−6, were obtained for x = 0.2 composite. The present study demonstrates an environmental-friendly ME particulate composite for future applications.
Investigation of meshing strategies and turbulence models of computational fluid dynamics simulations of vertical axis wind turbines
Authors: Song Chenguang , Zheng Yuan , Zhao Zhenzhou , Zhang Yuquan , Li Chong , Jiang Hao
Published: May 2015

Making good use of vertical axis wind turbines (VAWTs) is an attractive and potential way to deal with the energy and environmental issues due to the unique superiorities of it. Computational Fluid Dynamics (CFD) technology is a useful tool for the design process of VAWTs. Various turbulence models have been developed and available for turbulent flow simulations. Currently, there have been few researchers studying on meshing strategies and turbulence model selections of VAWT simulations. In this paper, 2D unsteady models under 4 meshing strategies and 6 turbulence models were established and simulated to investigate the effect of the above two aspects on numerical simulations of VAWTs. The numerical results were compared with the experimental data of Oler et al. (“Dynamic stall regulation of the Darrieus Turbine,” SAND Report No. 83–7029, Sandia National Laboratories, Albuquerque, 1983, pp. 67–96) and the analytical solution of Deglaire et al. (Eur. J. Mech., B: Fluids 28(4), 506–520 (2009)). The results reveal that a mesh of 213 656 grids is sufficient to meet the requirements of grid independence with the help of boundary layer and size function techniques. Besides, the realizable k-ε model enables the closest CFD simulation of the experimental data and shows better prediction performance than the analytical model of Deglaire et al. and other turbulence models.
Up-gradient particle flux in a drift wave-zonal flow system
Authors: Cui L. , Tynan G. R. , Diamond P. H. , Thakur S. C. , Brandt C.
Published: May 2015

We report a net inward, up-gradient turbulent particle flux in a cylindrical plasma when collisional drift waves generate a sufficiently strong sheared azimuthal flow that drives positive (negative) density fluctuations up (down) the background density gradient, resulting in a steepening of the mean density gradient. The results show the existence of a saturation mechanism for drift-turbulence driven sheared flows that can cause up-gradient particle transport and density profile steepening.
Spectral response of multilayer optical structures to dynamic mechanical loading
Authors: Scripka David , LeCroy Garrett , Summers Christopher J. , Thadhani Naresh N.
Published: May 2015

A computational study of Distributed Bragg Reflectors (DBR) and Optical Microcavities (OMC) was conducted to ascertain their potential as time-resolved mesoscale sensors due to their unique structure-driven spectral characteristics. Shock wave propagation simulations of polymer-based DBRs and glass/ceramic-based OMCs were coupled with spectral response calculations to demonstrate the combined dynamic mechanical and spectral response of the structures. Clear spectral shifts in both structures are predicted as a function of dynamic loading magnitude. Potential applications of the structures include high spatial and temporal resolution surface maps of material states, and in-situ probing of material interfaces during dynamic loading.
Model tests on sinking technique of composite bucket foundations for offshore wind turbines in silty clay
Authors: Zhang Puyang , Guo Yaohua , Liu Yonggang , Ding Hongyan , Le Conghuan
Published: May 2015

The composite bucket foundation (CBF) is a new type of for offshore wind turbines, which can be adapted to the loading characteristics and development needs of offshore wind farms due its special structural form. The composite bucket foundation in the large-scale tests has an outer diameter of 3.5 m and a clear wall height of 0.9 m. There are seven rooms divided inside the CBF by steel bulkheads, which are arranged in a honeycomb structure. The six peripheral rooms with the skirt have the same proportions while the middle orthohexagonal one is a little larger. With the seven-room structure, the CBF has reasonable motion characteristics and towing reliability during the wet-tow construction process. Moreover, the pressure inside the compartments can control the levelness of the CBF during suction installation. Several large-scale model tests on suction installation and adjusting levelness of CBF were carried out in saturated silty clay off the coast of Jiangsu in China. During the sinking process under negative pressure, the tubes valves of all the compartments were controlled to level the foundation in a timely operation. When the foundation started to tilt, the feasibility of the bucket tilt adjusting technique was explored by applying suction/positive pressure and intermittent pumping among the seven rooms. When the required levelness of the foundation was achieved by suction-assisted lowering the high compartments and/or positive pressures raising the low compartments, all of the valves were opened so that the entire foundation could sink. Test results show that the reciprocating adjustment process can be repeated until the CBF is completely penetrated into a designed depth.
Effect of fluctuating oxygen concentration on iron oxidation at the pelagic ferrocline of a meromictic lake
Authors: Bravidor Jenny , Kreling Julika , Lorke Andreas , Koschorreck Matthias
Published: May 2015

Environmental context
The cycling of iron plays an important role in pelagic boundary zones such as the oxic–anoxic interface where physical and chemical gradients occur. The turnover of iron in this zone depends on oxygen fluctuation and the duration of the fluctuation event. This study increases the understanding of biogeochemical iron transformation in such hotspots.

Abstract
In stratified iron-rich lakes, the interface between oxic and anoxic water bodies, the oxycline, is accompanied by a steep gradient of dissolved iron, the ferrocline. It is a hotspot of biogeochemical transformations, namely the cycling of iron (Fe). The rate of iron oxidation, both chemical and microbial, depends on pH, iron and oxygen concentration, and microbial activity. We investigated the ferrocline of the meromictic Lake Waldsee to find out how the ferrocline is influenced by fluctuating oxygen concentrations. We measured diurnal fluctuations of Fe2+, O2 and pH along vertical profiles during two campaigns in July and September 2011 as well as rates of iron oxidation in laboratory incubations. The oxygen content of the water column varied both between the campaigns and diurnally. We observed a diurnal intrusion of O2 into the ferrocline. The diurnal signal was visible in the iron profile in July but not in September. Iron oxidation rates determined in the laboratory demonstrate the importance of microbial iron reduction and the strong pH dependency. We related the reaction timescales for iron oxidation to the characteristic timescale of oxygen fluctuations by calculating non-dimensional numbers. This analysis showed that an oxygenation event had to last at least 10h in order to affect the depth and vertical extent of the ferrocline, which was the case in July but not in September. Our results show that the duration of events can be an important parameter regulating biogeochemical interactions in pelagic redoxclines.
Avian sarcoma leukosis virus receptor-envelope system for simultaneous dissection of multiple neural circuits in mammalian brain
Authors: Matsuyama Makoto , Ohashi Yohei , Tsubota Tadashi , Yaguchi Masae , Kato Shigeki , Kobayashi Kazuto , Miyashita Yasushi
Published: May 2015

Significance

Genetic dissection of multiple neural pathways remains challenging because of the limited number of genetic methods that can be used simultaneously. To overcome this limitation, we used modified avian sarcoma and leukosis virus envelopes and receptors to develop highly orthogonal genetic tools that can achieve expression of different genes in different target cells. From in vitro and in vivo screens, we identified tools that can specifically transfer genes of interest into mammalian neurons via engineered receptors, with minimal unintended interactions. Using this approach, we achieved pathway-specific, differential fluorescent labeling of three thalamic neuronal populations, each projecting into different cortical regions. Thus, our approach provides independent, simultaneous, and specific genetic tools for manipulating intermingled neural pathways in vivo.
Regulation of age-related macular degeneration-like pathology by complement factor H
Authors: Toomey Christopher B. , Kelly Una , Saban Daniel R. , Bowes Rickman Catherine
Published: May 2015

Significance

Age-related macular degeneration (AMD) affects approximately one-third of Americans over 70 and is characterized by lipoprotein-rich sub-retinal pigmented epithelium (sub-RPE) deposits. Substantial evidence has emerged that implicates complement factor H (CFH) in the pathogenesis of AMD. Here, we conduct an in vivo analysis to elucidate the role of CFH in AMD pathology. We show that (
i
) CFH and lipoproteins compete for binding in the sub-RPE extracellular matrix such that decreasing CFH leads to lipoprotein accumulation and sub-RPE deposit formation; and (
ii
) detrimental complement activation within sub-RPE deposits leads to RPE damage and vision loss. This new understanding of the complicated interactions of CFH in development of AMD-like pathology paves the way for identifying more targeted therapeutic strategies for AMD.
Optimal plant growth-promoting concentration of Azospirillum brasilense inoculated to cucumber, lettuce and tomato seeds varies between bacterial strains
Authors: Mangmang Jonathan S. , Deaker Rosalind , Rogers Gordon
Published: May 2015

Azospirillum brasilenseis a well-known plant growth-promoting rhizobacteria (PGPR) that can have positive impact on plant growth when present in sufficient density. The production of phytohormones byAzospirillumhas been proposed as one of the major mechanisms responsible for the observed plant growth effects. In particular, this plant growth-promoting effect could be mediated by IAA (indole-3-acetic acid), a phytohormone produced byAzospirillumin substantial amount, because the effect of inoculation with higher inoculum density on root morphology mimicked the increasing concentration of exogenous IAA applied to the seed. This study evaluated the effect of inoculation with different bacterial concentrations of threeA. brasilensestrains (Sp7, Sp7-S and Sp245) on the early seedling growth and endogenous plant IAA of cucumber, lettuce and tomato. Seeds were inoculated with 8, 7 and 6 log cfu ml−1of each strain before germinating in Petri dishes. The early seedling growth of vegetables was affected by the inoculation with theA. brasilensestrains. In cucumber, seeds inoculated with Sp7 at log 8 and 6 cfu ml−1, Sp7-S and Sp245 at log 8 and 7 increased seedling growth, vigor index and endogenous plant IAA by up to 55%. In lettuce, the inoculation with log 6 of Sp7, log 7 and 6 of Sp7-S, and log 8 and 7 of Sp245 yielded superior seedling growth with improved seedling vigor. In addition, log 7 and 8 of Sp7 and Sp7-S, respectively, increased IAA concentration by more than 20%. In tomato, Sp7 at log 6, Sp7-S and Sp245 at log 7 exerted more positive effects on root biomass. IAA concentrations increased up to 171% by inoculation with all concentrations of Sp7 and Sp7-S and more than 300% by Sp245 at log 8. The bacteria-elicited promotion of plant IAA production might improve plant function via effects on metabolism and morphology. These results demonstrate that seed inoculation with the strains at the studied range of cell concentrations stimulated early seedling development. However, the optimal promoting concentration varied between strains. Strain Sp7 appeared to be more beneficial at log 6 cfu ml−1while Sp7-S and Sp245 were more beneficial at log 7 or higher.
NUMERICAL SIMULATIONS OF HELICITY CONDENSATION IN THE SOLAR CORONA
Authors: Zhao L. , DeVore C. R. , Antiochos S. K. , Zurbuchen T. H.
Published: May 2015

The helicity condensation model has been proposed by Antiochos to explain the observed smoothness of coronal loops and the observed buildup of magnetic shear at filament channels. The basic hypothesis of the model is that magnetic reconnection in the corona causes the magnetic stress injected by photospheric motions to collect only at those special locations where prominences are observed to form. In this work we present the first detailed quantitative MHD simulations of the reconnection evolution proposed by the helicity condensation model. We use the well-known ansatz of modeling the closed corona as an initially uniform field between two horizontal photospheric plates. The system is driven by applying photospheric rotational flows that inject magnetic helicity into the corona. The flows are confined to a finite region on the photosphere so as to mimic the finite flux system of a bipolar active region, for example. The calculations demonstrate that, contrary to common belief, opposite helicity twists do not lead to significant reconnection in such a coronal system, whereas twists with the same sense of helicity do produce substantial reconnection. Furthermore, we find that for a given amount of helicity injected into the corona, the evolution of the magnetic shear is insensitive to whether the pattern of driving photospheric motions is fixed or quasi-random. In all cases, the shear propagates via reconnection to the boundary of the flow region while the total magnetic helicity is conserved, as predicted by the model. We discuss the implications of our results for solar observations and for future, more realistic simulations of the helicity condensation process.
Existence and uniqueness of global classical solutions of a gradient flow of the Landau-de Gennes energy
Authors: Chen Xinfu , Xu Xiang
Published: May 2015

In this paper we establish the existence and uniqueness of global classical solutions to a gradient flow in

R

d

\mathbb {R}^d

,

d
≥
2

d\geq 2

. This gradient flow is generated by the Laudau-de Gennes energy functional that involves four elastic-constant terms describing nematic liquid crystal configurations in the space of

Q
Q

-tensors. We work in Hölder spaces, and deal with

d
=
2

d=2

and

d
≥
3

d\geq 3

separately.
On compositions with 𝑥²/(1-𝑥)
Authors: Herbig Hans-Christian , Herden Daniel , Seaton Christopher
Published: May 2015

In the past, empirical evidence has been presented that Hilbert series of symplectic quotients of unitary representations obey a certain universal system of infinitely many constraints. Formal series with this property have been called symplectic. Here we show that a formal power series is symplectic if and only if it is a formal composite with the formal power series

x
2

/

(
1
−
x
)

x^2/(1-x)

. Hence the set of symplectic power series forms a subalgebra of the algebra of formal power series. The subalgebra property is translated into an identity for the coefficients of the even Euler polynomials, which can be interpreted as a cubic identity for the Bernoulli numbers. Furthermore we show that a rational power series is symplectic if and only if it is invariant under the idempotent Möbius transformation

x
↦
x

/

(
x
−
1
)

x\mapsto x/(x-1)

. It follows that the Hilbert series of a graded Cohen-Macaulay algebra

A
A

is symplectic if and only if

A
A

is Gorenstein with its a-invariant and its Krull dimension adding up to zero. It is shown that this is the case for algebras of regular functions on symplectic quotients of unitary representations of tori.
Persistence and failure of complete spreading in delayed reaction-diffusion equations
Authors: Lin Guo , Ruan Shigui
Published: May 2015

This paper deals with the long time behavior in terms of complete spreading for a population model described by a reaction-diffusion equation with delay, of which the corresponding reaction equation is bistable. When a complete spreading occurs in the corresponding undelayed equation with initial value admitting compact support, it is proved that the invasion can also be successful in the delayed equation if the time delay is small. To spur on a complete spreading, the choice of the initial value would be very technical due to the combination of delay and Allee effects. In addition, we show the possible failure of complete spreading in a quasimonotone delayed equation to illustrate the complexity of the problem.
On the radius in Cayley–Dickson algebras
Authors: Goldberg Moshe , Laffey Thomas
Published: May 2015

In the first two sections of this paper we provide a brief account of the Cayley–Dickson algebras and prove that the radius on these algebras is given by the Euclidean norm. With this observation we resort to three related topics: a variant of the Gelfand formula, stability of subnorms, and the functional power equation.
Cellular automorphisms and self-duality
Authors: Abrams Lowell , Slilaty Daniel
Published: May 2015

We catalog up to a type of reducibility all cellular automorphisms of the sphere, projective plane, torus, Klein bottle, and three-crosscaps (Dyck’s) surface. We also show how one can obtain all self-dual embeddings in a surface

S
S

given a catalog of all irreducible cellular automorphisms in

S
S

.
Accesses to infinity from Fatou components
Authors: Barański Krzysztof , Fagella Núria , Jarque Xavier , Karpińska Bogusława
Published: May 2015

We study the boundary behaviour of a meromorphic map

f
:

C

→

C

^

f: \mathbb {C} \to \widehat {\mathbb {C}}

on its simply connected invariant Fatou component

U
U

. To this aim, we develop the theory of accesses to boundary points of

U
U

and their relation to the dynamics of

f
f

. In particular, we establish a correspondence between invariant accesses from

U
U

to infinity or weakly repelling fixed points of

f
f

and boundary fixed points of the associated inner function on the unit disc. We apply our results to describe the accesses to infinity from invariant Fatou components of the Newton maps.