bluuebunny/crossref_metadata_2025 huggingface dataset:
High Electron Mobility in Epitaxial Graphene on 4H-SiC(0001) via post-growth annealing under hydrogen
Authors: Pallecchi E. , Lafont F. , Cavaliere V. , Schopfer F. , Mailly D. , Poirier W. , Ouerghi A.
Published: April 2014

We investigate the magneto-transport properties of epitaxial graphene single-layer on 4H-SiC(0001), grown by atmospheric pressure graphitization in Ar, followed by H2 intercalation. We directly demonstrate the importance of saturating the Si dangling bonds at the graphene/SiC(0001) interface to achieve high carrier mobility. Upon successful Si dangling bonds elimination, carrier mobility increases from 3 000 cm2V−1s−1 to >11 000 cm2V−1s−1 at 0.3 K. Additionally, graphene electron concentration tends to decrease from a few 1012 cm−2 to less than 1012 cm−2. For a typical large (30 × 280 μm2) Hall bar, we report the observation of the integer quantum Hall states at 0.3 K with well developed transversal resistance plateaus at Landau level filling factors of ν = 2, 6, 10, 14… 42 and Shubnikov de Haas oscillation of the longitudinal resistivity observed from about 1 T. In such a device, the Hall state quantization at ν = 2, at 19 T and 0.3 K, can be very robust: the dissipation in electronic transport can stay very low, with the longitudinal resistivity lower than 5 mΩ, for measurement currents as high as 250 μA. This is very promising in the view of an application in metrology.
Conformation-dependent DNA attraction
Authors: Li Weifeng , Nordenskiöld Lars , Zhou Ruhong , Mu Yuguang
Published: April 2014

The highlighted hydrophobic property of Z-DNA in DNA attraction may help us to understand the biological function of Z-DNA in gene transcription.
Cascade nitrosation and addition–elimination of nitroacetanilides for the highly efficient synthesis of 1,4,2,5-dioxadiazine derivatives
Authors: Mo Shanyan , Huang Peipei , Xu Jiaxi
Published: April 2014

An efficient synthesis of 1,4,2,5-dioxadiazine-3,6-dicarboxamidesviacascade nitrosation and addition–elimination of nitroacetanilides.
The protein recognition ability of zeolites: complete separation of cytochrome c from a ternary protein mixture by zeolite L
Authors: Matsui Masayoshi , Iijima Hiroshi , Kiyozumi Yoshimichi , Mizushina Yoshiyuki , Sakaguchi Kengo , Mizukami Fujio
Published: April 2014

Zeolite L can recognize cytochromecin a model ternary protein mixture and completely separate it with 100% recovery.
H2 production through electro-oxidation of SO2: identifying the fundamental limitations
Authors: Kriek Roelof J. , Rossmeisl Jan , Siahrostami Samira , Björketun Mårten E.
Published: April 2014

The physical and chemical relations controlling the electro-catalytic oxidation of SO2, a known industrial pollutant and pulmonary irritant, are disclosed.
Oxygen vacancy formation and the ion migration mechanism in layered perovskite (Sr,La)3Fe2O7−δ
Authors: Kagomiya Isao , Jimbo Keigo , Kakimoto Ken-ichi , Nakayama Masanobu , Masson Olivier
Published: April 2014

The characteristic ion migration mechanism for Sr2.46La0.54Fe2O7−δ was investigated by combination of experiments [X-ray diffraction, enthalpy investigations of vacancy formation] and computations [bond valence sum, ab initio density functional theory].
Acylation of cellulose in reversible ionic liquids
Authors: Yang Yunlong , Xie Haibo , Liu Enhui
Published: April 2014

1,8-Diazabicyclo[5.4.0]undec-7-ene, in conjunction with methanol after CO2 capture in DMSO created a new solvent capable of dissolving up to 8 wt% of cellulose, which could be applied as a highly efficient reaction media for the synthesis of cellulose esters under mild conditions.
A one-pot biosynthesis of reduced graphene oxide (RGO)/bacterial cellulose (BC) nanocomposites
Authors: Nandgaonkar Avinav G. , Wang Qingqing , Fu Kun , Krause Wendy E. , Wei Qufu , Gorga Russel , A. Lucia Lucian
Published: April 2014

Graphene oxide was successfully reduced to graphene using a bacterial cellulose culture medium that was further processed to fabricate in situ composites of bacterial cellulose/reduced graphene oxide gelatinous hybrids, aerogels, and membranes.
Differential simulated annealing: a robust and efficient global optimization algorithm for parameter estimation of biological networks
Authors: Dai Ziwei , Lai Luhua
Published: April 2014

DSA outperformed five other algorithms in parameter estimation of 95 biological networks and showed significant advantage in large networks.
Analysis of cellular responses of macrophages to zinc ions and zinc oxide nanoparticles: a combined targeted and proteomic approach
Authors: Triboulet Sarah , Aude-Garcia Catherine , Armand Lucie , Gerdil Adèle , Diemer Hélène , Proamer Fabienne , Collin-Faure Véronique , Habert Aurélie , Strub Jean-Marc , Hanau Daniel , Herlin Nathalie , Carrière Marie , Van Dorsselaer Alain , Rabilloud Thierry
Published: April 2014

A combined proteomics and targeted approach has been used to better understand the cellular responses to zinc oxide nanoparticles.
Stiff chains inhibit and flexible chains promote protein adsorption to polyelectrolyte multilayers
Authors: Wu Bo , Liu Guangming , Zhang Guangzhao , Craig Vincent S. J.
Published: April 2014

The relative stiffness of polymers used to form polyelectrolyte multilayers can be used to control protein adsorption. Flexible chains promote protein adsorption whereas inflexible chains can produce antifouling surfaces, even if the constituent chains have no antifouling properties on their own.
Template-directed synthesis of pyrite (FeS2) nanorod arrays with an enhanced photoresponse
Authors: Wang Mudan , Xing Chengcheng , Cao Ke , Zhang Lei , Liu Jiabin , Meng Liang
Published: April 2014

Well-aligned ZnO nanorod arrays were used as templates to produce Fe(OH)3nanotube arrays. The as-grown Fe(OH)3nanotube arrays were then used as templates to obtain an FeS2nanorod array. The FeS2nanorod arrays had much better photovoltaic properties than the FeS2nanoparticles due to the high specific area, direct transport pathways and enhanced light harvesting of the nanorod array structure.
Remarkable improvement in visible-light induced hydrogen generation by ZnO/Pt/Cd1−yZnyS heterostructures through substitution of N and F in ZnO
Authors: Lingampalli S. R. , Rao C. N. R.
Published: April 2014

Co-substitution of N and F brings about remarkable changes in the electronic structure of ZnO, resulting in an improved yield of hydrogen by visible light irradiation of ZnO/Pt/CdS heterostructures.
An electrochemically deposited film as an interface layer to improve the performance of polymer light-emitting diodes
Authors: Yu Tiancheng , Wu Xiaoyan , Lv Ying , Liu Linlin , Du Luyang , Zhou Jiadong , Xie Zengqi , Ma Yuguang
Published: April 2014

An insoluble electrochemically cross-linked thin film is successfully applied as an interface layer between PEDOT:PSS and the light emitting layer in solution-processed polymer light-emitting diodes for enhanced device performance.
Patient-Centered Outcomes Research in Voice
Authors: Francis David O.
Published: April 2014

Patient-centered outcomes research is critically important to improving the management of patients with voice disorders. Currently, wide variation in outcome definitions and treatment decisions exist. It is the responsibility of voice clinicians and researchers to improve the quality of and access to care for patients with voice disorders through the conduct of collaborative and rigorous patient-centered outcomes and comparative effectiveness research. Patients are the ultimate arbiter of their treatment, but need reliable and valid information to make informed decisions. Improving outcomes research will require collaborations among clinicians and study design experts in epidemiology, biostatistics, and data analysis. Moreover, researchers should be encouraged to compare the effectiveness of current treatments, which, to date, are implemented with little systematic, rigorous reinforcing evidence. Patient-reported outcomes research is increasingly emphasized by funding sources and in health care regulation. Oversight is inevitable and the voice community must ensure that it can justify those treatments that we know are beneficial to patients through compelling and patient-centered outcomes research.
Use of Administrative and National Survey Databases in Health Services Research
Authors: Cohen Seth M.
Published: April 2014

Administrative and national survey databases have an important role in the field of health services research. In this article, the concept of health services research will be presented. The types of research questions that can be answered with administrative and national survey databases are discussed, and examples from the literature are provided. The MarketScan®databases and experience using this administrative claims database are described. Precautions and limitations involved in using administrative and national survey databases are presented.
An Example of the Role of Basic Science Research to Inform the Treatment of Unilateral Vocal Fold Paralysis
Authors: Khosla Sid , Oren Liran , Gutmark Ephraim
Published: April 2014

An alternative and complementary approach to randomized trials or other clinical research in unilateral vocal fold paralysis is to use basic science research in animal models to answer the following two questions: (1) how and why do asymmetries affect voice production?, and (2) how do various surgical procedures affect these asymmetries? In this article, we will discuss some of our approaches to the first question. All experiments discussed center around the presence and effects of vortices, or areas of rotational motion, between the folds due to a phenomenon known as flow separation. Therefore, the formation and properties of intraglottal flow separation vortices will be briefly discussed. Then, we will describe experiments that look at the effects of the flow separation vortices on three measures of laryngeal physiology important to voice production: flow skewing, acoustic intensity, and glottal efficiency. Finally, we will explore the effects of some asymmetries on the flow separation vortices and discuss implications for the treatment of unilateral vocal fold paralysis. Our work is early and has some clear limitations. Therefore, the goal of this article is not to fully answer any question, but to show an example of the type of information that can be addressed by research in excised canine larynges.
Detection of spin-resolved electronic structures from a buried ferromagnetic layer utilizing forward Mott scattering
Authors: Ueda S. , Mizuguchi M. , Kojima T. , Ishimaru S. , Tsujikawa M. , Shirai M. , Takanashi K.
Published: April 2014

We report ultrahigh-resolution spin-resolved hard X-ray photoemission (HAXPES) for a buried FeNi alloy film. By utilizing the forward Mott scattering in a Au layer on FeNi, our spin-resolved HAXPES method does not require a standard spin detector and allows us to use the multi-channel electron detection system for the high-efficient electron detection as used in conventional photoemission spectroscopy. A combination of the forward Mott scattering and multi-channel detection leads us to measure a clear spin polarization as well as spin-resolved majority and minority states in the Fe 2p core-level spectra without using the standard spin detector. This method enables us to measure spin-resolved core-level spectra for buried ferromagnetic materials.
Influence of Ga content on the structure and anomalous Hall effect of Fe1−xGax thin films on GaSb(100)
Authors: Anh Tuan Duong , Shin Yooleemi , Phan The-Long , Viet Cuong Tran , Cho Sunglae
Published: April 2014

The Fe1−xGax thin films (x = 0.4, 0.5) have been grown on GaSb(100) substrate using molecular beam epitaxy. An epitaxial film with bcc α-Fe crystal structure (A2) is observed in Fe0.6Ga0.4 film, while an impure Fe3Ga phase with DO3 structure is appeared in Fe0.5Ga0.5 film. The saturated magnetizations at room temperature are observed to be 570 emu/cm3 and 180 emu/cm3 and the coercivities to be 170 and 364 Oe for Fe0.6Ga0.4 and Fe0.5Ga0.5, respectively. A hysteresis trend in Hall resistance vs. magnetic field is observed for Fe0.5Ga0.5 film. However, there is a weak hysteresis noticed in Fe0.4Ga0.6 thin film.
Laboratory experiments on mass transport by large amplitude mode-2 internal solitary waves
Authors: Brandt A. , Shipley K. R.
Published: April 2014

The existence of internal solitary waves (ISWs) in the coastal ocean is well established. Numerous observations of large amplitude (both mode-1 and mode-2) solitary waves have facilitated the identification of their unique properties; in particular they contain regions of internal recirculation (trapped cores) that enable mass transport over large distances. However, the basic physics of mode-2 ISWs is as yet not well understood. The present experiments and the associated numerical simulations are focused on providing the first quantitative measure of the extent of mass transported by mode-2 ISWs and insight into the potential effects of mass transport on coastal mixing and the distribution of biochemical material. The ISWs were generated by the release of fluid from an initially mixed volume. It was found that the amplitude and amount of mass transported by the leading and second, following ISW, was proportional to the level of forcing and was attenuated at an approximately uniform rate as the ISW propagated downstream. At the highest level of ISW forcing, over 40% of the mixed fluid was transported within the leading ISW. Excellent agreement was found with the numerical simulations of Salloum, Knio, and Brandt [“Numerical simulation of mass transport in internal solitary waves,” Phys. Fluids 24, 016602 (2012)] that were designed to replicate the present experimental configuration. In addition, evidence of a new ISW regime was identified, termed very-large amplitude ISW, which exhibited strong internal recirculation, a smooth front face, and local mixing at the aft end. The present data extend to larger amplitudes than prior studies and exhibit a second order dependence of wave speed and wavelength on amplitude.
Dynamic structural disorder in supported nanoscale catalysts
Authors: Rehr J. J. , Vila F. D.
Published: April 2014

We investigate the origin and physical effects of “dynamic structural disorder” (DSD) in supported nano-scale catalysts. DSD refers to the intrinsic fluctuating, inhomogeneous structure of such nano-scale systems. In contrast to bulk materials, nano-scale systems exhibit substantial fluctuations in structure, charge, temperature, and other quantities, as well as large surface effects. The DSD is driven largely by the stochastic librational motion of the center of mass and fluxional bonding at the nanoparticle surface due to thermal coupling with the substrate. Our approach for calculating and understanding DSD is based on a combination of real-time density functional theory/molecular dynamics simulations, transient coupled-oscillator models, and statistical mechanics. This approach treats thermal and dynamic effects over multiple time-scales, and includes bond-stretching and -bending vibrations, and transient tethering to the substrate at longer ps time-scales. Potential effects on the catalytic properties of these clusters are briefly explored. Model calculations of molecule-cluster interactions and molecular dissociation reaction paths are presented in which the reactant molecules are adsorbed on the surface of dynamically sampled clusters. This model suggests that DSD can affect both the prefactors and distribution of energy barriers in reaction rates, and thus can significantly affect catalytic activity at the nano-scale.
Role of solution conductivity in reaction induced charge auto-electrophoresis
Authors: Moran Jeffrey L. , Posner Jonathan D.
Published: April 2014

Catalytic bimetallic Janus particles swim by a bipolar electrochemical propulsion mechanism that results from electroosmotic fluid slip around the particle surface. The flow is driven by electrical body forces which are generated from a coupling of a reaction-induced electric field and net charge in the diffuse layer surrounding the particle. This paper presents simulations, scaling, and physical descriptions of the experimentally observed trend that the swimming speed decays rapidly with increasing solution conductivity. The simulations solve the full Poisson-Nernst-Planck-Stokes equations with multiple ionic species, a cylindrical particle in an infinite fluid, and nonlinear Butler-Volmer boundary conditions to represent the electrochemical surface reactions. The speed of bimetallic particles is reduced in high-conductivity solutions because of reductions in the induced electric field in the diffuse layer near the rod, the total reaction rate, and the magnitude of the rod zeta potential. This work suggests that the auto-electrophoretic mechanism is inherently susceptible to speed reductions in higher ionic strength solutions.
Laboratory-based micro-X-ray fluorescence setup using a von Hamos crystal spectrometer and a focused beam X-ray tube
Authors: Kayser Y. , Błachucki W. , Dousse J.-Cl. , Hoszowska J. , Neff M. , Romano V.
Published: April 2014

The high-resolution von Hamos bent crystal spectrometer of the University of Fribourg was upgraded with a focused X-ray beam source with the aim of performing micro-sized X-ray fluorescence (XRF) measurements in the laboratory. The focused X-ray beam source integrates a collimating optics mounted on a low-power micro-spot X-ray tube and a focusing polycapillary half-lens placed in front of the sample. The performances of the setup were probed in terms of spatial and energy resolution. In particular, the fluorescence intensity and energy resolution of the von Hamos spectrometer equipped with the novel micro-focused X-ray source and a standard high-power water-cooled X-ray tube were compared. The XRF analysis capability of the new setup was assessed by measuring the dopant distribution within the core of Er-doped SiO2 optical fibers.
Three-dimensional surface figure measurement of high-accuracy spherical mirror with nanoprofiler using normal vector tracing method
Authors: Kudo R. , Okuda K. , Usuki K. , Nakano M. , Yamamura K. , Endo K.
Published: April 2014

Processing technology using an extreme ultraviolet light source, e.g., next-generation lithography, requires next-generation high-accuracy mirrors. As it will be difficult to attain the degree of precision required by next-generation high-accuracy mirrors such as aspherical mirrors through conventional processing methods, rapid progress in nanomeasurement technologies will be needed to produce such mirrors. Because the measuring methods used for the surface figure measurement of next-generation mirrors will require high precision, we have developed a novel nanoprofiler that can measure the figures of high-accuracy mirrors without the use of a reference surface. Because the accuracy of the proposed method is not limited by the accuracy of a reference surface, the measurement of free-form mirrors is expected to be realized. By using an algorithm to process normal vectors and their coordinate values at the measurement point obtained by a nanoprofiler, our measurement method can reconstruct three-dimensional shapes. First, we measured the surface of a concave spherical mirror with a 1000-mm radius of curvature using the proposed method, and the measurement repeatability is evaluated as 0.6 nm. Sub-nanometer repeatability is realized, and an increase in the repeatability would be expected by improving the dynamic stiffness of the nanoprofiler. The uncertainty of the measurement using the present apparatus is estimated to be approximately 10 nm by numerical simulation. Further, the uncertainty of a Fizeau interferometer is also approximately 10 nm. The results obtained using the proposed method are compared with those obtained using a Fizeau interferometer. The resulting profiles are consistent within the range of each uncertainty over the middle portions of the mirror.
Model independent x-ray standing wave analysis of periodic multilayer structures
Authors: Yakunin S. N. , Makhotkin I. A. , van de Kruijs R. W. E. , Chuev M. A. , Pashaev E. M. , Zoethout E. , Louis E. , Seregin S. Yu. , Subbotin I. A. , Novikov D. V. , Bijkerk F. , Kovalchuk M. V.
Published: April 2014

We present a model independent approach for the analysis of X-ray fluorescence yield modulated by an X-ray standing wave (XSW), that allow a fast reconstruction of the atomic distribution function inside a sample without fitting procedure. The approach is based on the direct regularized solution of the system of linear equations that characterizes the fluorescence yield. The suggested technique was optimized for, but not limited to, the analysis of periodic layered structures where the XSW is formed under Bragg conditions. The developed approach was applied to the reconstruction of the atomic distribution function for LaN/BN multilayers with 50 periods of 43 Å thick layers. The object is especially difficult to analyze with traditional methods, as the estimated thickness of the interface region between the constituent materials is comparable to the individual layer thicknesses. However, using the suggested technique, it was possible to reconstruct width of the La atomic distribution showing that the La atoms stay localized within the LaN layers and interfaces and do not diffuse into the BN layer. The analysis of the reconstructed profiles showed that the positions of the center of the atomic distribution function can be estimated with an accuracy of 1 Å.
Large eddy simulation studies of the effects of alignment and wind farm length
Authors: Stevens Richard J. A. M. , Gayme Dennice F. , Meneveau Charles
Published: April 2014

Large eddy simulations of wind farms are performed to study the effects of wind turbine row alignment with respect to the incoming flow direction. Various wind farms with fixed stream-wise spacing (7.85 rotor diameters) and varying lateral displacements and span-wise turbine spacings are considered, for a fixed inflow direction. Simulations show that, contrary to common belief, a perfectly staggered (checker-board) configuration does not necessarily give the highest average power output. Instead, the highest mean wind farm power output is found to depend on several factors, the most important one being the alignment that leads to minimization of wake effects from turbines in several upstream rows. This alignment typically occurs at significantly smaller angles than those corresponding to perfect staggering. The observed trends have implications for wind farm designs, especially in sites with a well-defined prevailing wind direction.
Velocity relaxation of a porous sphere immersed in a viscous incompressible fluid
Authors: Felderhof B. U.
Published: April 2014

Velocity relaxation of a spherically symmetric polymer, immersed in a viscous incompressible fluid, and after a sudden small impulse or a sudden twist from a state of rest, is studied on the basis of the linearized Navier-Stokes equations with an added Darcy type drag term. Explicit expressions for the translational and rotational velocity relaxation functions of the polymer and for the flow pattern of the fluid are derived for a uniform permeable sphere. Surprisingly, it is found that the added mass vanishes. For fairly large values of the ratio of sphere radius to the screening length characterizing the permeability, the velocity relaxation functions in the short and intermediate time regime differ significantly from that of a sphere with no-slip boundary condition. At long times, both relaxation functions show universal power law behavior.
Nanostructure evolution in joining of Al and Fe nanoparticles with femtosecond laser irradiation
Authors: Jiao Z. , Huang H. , Liu L. , Hu A. , Duley W. , He P. , Zhou Y.
Published: April 2014

The joining of Al-Fe nanoparticles (NPs) by femtosecond (fs) laser irradiation is reported in this paper. Fe and Al NPs were deposited on a carbon film in vacuum via fs laser ablation. Particles were then exposed to multiple fs laser pulses at fluences between 0.5 and 1.3 mJ/cm2. Transmission Electron Microscopy (TEM) and Electron Diffraction X-ray observations indicate that Al and Fe NPs bond to each other under these conditions. For comparison, bonding of Al to Al and Fe to Fe NPs was also investigated. The nanostructure, as observed using TEM, showed that individual Al NPs were monocrystalline while individual Fe NPs were polycrystalline prior to joining and that these structures are retained after the formation of Al-Al and Fe-Fe NPs. Al-Fe NPs produced by fs laser joining exhibited a mixed amorphous and crystalline phase at the interface. Bonding is suggested to originate from intermixing within a region of high field intensity between particles.
The Taylor-vortex dynamo
Authors: Gissinger Christophe
Published: April 2014

The generation of a magnetic field by dynamo action in a Taylor-vortex flow is investigated numerically. We first discuss how the Taylor vortices generate a spatially subharmonic dynamo, for which the axial wavelength of the magnetic field is twice the one of the flow pattern. Then, we investigate the influence of the Reynolds number and the turbulent fluctuations on the structure and the onset of the Taylor-Couette dynamo. Finally, based on the subharmonic nature of this dynamo, we propose new configurations which could be relevant for laboratory experiments.
Solar energy conversion via hot electron internal photoemission in metallic nanostructures: Efficiency estimates
Authors: Leenheer Andrew J. , Narang Prineha , Lewis Nathan S. , Atwater Harry A.
Published: April 2014

Collection of hot electrons generated by the efficient absorption of light in metallic nanostructures, in contact with semiconductor substrates can provide a basis for the construction of solar energy-conversion devices. Herein, we evaluate theoretically the energy-conversion efficiency of systems that rely on internal photoemission processes at metal-semiconductor Schottky-barrier diodes. In this theory, the current-voltage characteristics are given by the internal photoemission yield as well as by the thermionic dark current over a varied-energy barrier height. The Fowler model, in all cases, predicts solar energy-conversion efficiencies of <1% for such systems. However, relaxation of the assumptions regarding constraints on the escape cone and momentum conservation at the interface yields solar energy-conversion efficiencies as high as 1%–10%, under some assumed (albeit optimistic) operating conditions. Under these conditions, the energy-conversion efficiency is mainly limited by the thermionic dark current, the distribution of hot electron energies, and hot-electron momentum considerations.
Scandium resonant impurity level in PbTe
Authors: Skipetrov E. P. , Skipetrova L. A. , Knotko A. V. , Slynko E. I. , Slynko V. E.
Published: April 2014

We synthesize a scandium-doped PbTe single-crystal ingot and investigate the phase and the elemental composition as well as galvanomagnetic properties of Pb1-yScyTe alloys in weak magnetic fields (4.2 K ≤ T ≤ 300 K, B ≤ 0.07 T) upon varying the scandium content (y ≤ 0.02). We find that all investigated samples are single-phase and n-type. The distribution of scandium impurities along the axis of the ingot is estimated to be exponential. An increase of scandium impurity content leads to a monotonous growth of the free electron concentration by four orders of magnitude (approximately from 1016 cm−3 to 1020 cm−3). In heavily doped alloys (y > 0.01), the free electron concentration at the liquid-helium temperature tends to saturation, indicating the pinning of the Fermi energy by the scandium resonant impurity level located on the background of the conduction band. Using the two-band Kane and six-band Dimmock dispersion relations for IV-VI semiconductors, dependences of the Fermi energy measured from the bottom of the conduction band Ec on the scandium impurity content are calculated and the energy of the resonant scandium level is estimated to be ESc ≈ Ec + 280 meV. Diagrams of electronic structure rearrangement of Pb1-yScyTe alloys upon doping are proposed.
Electronic transitions and dielectric functions of relaxor ferroelectric Pb(In1∕2Nb1∕2)O3-Pb(Mg1∕3Nb2∕3)O3-PbTiO3 single crystals: Temperature dependent spectroscopic study
Authors: Zhu J. J. , Zhang J. Z. , Xu G. S. , Zhang X. L. , Hu Z. G. , Chu J. H.
Published: April 2014

Optical properties and phase transitions of Pb(In1∕2Nb1∕2)O3-Pb(Mg1∕3Nb2∕3)O3-PbTiO3 (PIN-PMN-PT) crystals near morphotropic phase boundary (MPB) have been investigated by temperature dependent transmittance and reflectance spectra. Three critical point energies Eg = 3.17–3.18 eV, Ea = 3.41–3.61 eV, and Eb = 4.74–4.81 eV can be assigned to the transitions from oxygen 2p to titanium d, niobium d, and lead 6p states, respectively. They show narrowing trends with increasing temperature, which can be caused by thermal expansion of the lattice and electron-phonon interaction. Deviation from the linear behaviors can be observed from Ea and Eb versus PT concentration, indicating a complex multiphase structure near MPB region.
Impacts of crystal orientation of GaAs on the interfacial structures and electrical properties of Hf0.6La0.4Ox films
Authors: Jia Tingting , Kimura Hideo , Zhao Hongyang , Yao Qiwen , Cheng Zhenxiang , Cheng Xinghong , Yu Yuehui
Published: April 2014

One of the major challenges in realizing the GaAs channel in the metal oxide semiconductor field effect transistor is the degrading in electron transport properties at the interface between GaAs and the gate oxide. In this study, Hf0.6La0.4Ox gate oxide films were deposited at a low temperature (200 °C) on GaAs(111)A and GaAs(100) substrates by plasma enhanced atomic layer deposition. Microstructure analysis indicates that residuals of gallium oxide, arsenic oxide, and As element remained at the interface of Hf0.6La0.4Ox/GaAs(100). On contrast, a smoother interface is observed between Hf0.6La0.4Ox thin film and GaAs(111)A substrate. Furthermore, a reduction of interfacial layer is observed in Hf0.6La0.4Ox/GaAs(111)A. Electrical characterization of the metal-insulator-semiconductor Pt/Hf0.6La0.4Ox/n-GaAs(111)A capacitor indicated a reduction of Dit and leakage current compared with the capacitor fabricated on GaAs(100).
Electronic structure, molecular orientation, charge transfer dynamics and solar cells performance in donor/acceptor copolymers and fullerene: Experimental and theoretical approaches
Authors: Garcia-Basabe Y. , Marchiori C. F. N. , Borges B. G. A. L. , Yamamoto N. A. D. , Macedo A. G. , Koehler M. , Roman L. S. , Rocco M. L. M.
Published: April 2014

By combining experimental and theoretical approaches, the electronic structure, molecular orientation, charge transfer dynamics and solar cell performance in donor/acceptor copolymer poly[2,7-(9,9-bis(2-ethylhexyl)-dibenzosilole)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PSiF-DBT) films and blended with 6,6.-phenyl-C 61-butyric acid methyl ester (PSiF-DBT:PCBM) were investigated. Good agreement between experimental and theoretical PSiF-DBT UV-Vis absorption spectrum is observed and the main molecular orbitals contributing to the spectrum were determined using DFT single point calculations. Non-coplanar configuration was determined by geometric optimization calculation in isolated PSiF-DBT pentamer and corroborated by angular variation of the sulphur 1s near-edge X-ray absorption fine structure (NEXAFS) spectra. Edge-on and plane-on molecular orientations were obtained for thiophene and benzothiadiazole units, respectively. A power conversion efficiency up to 1.58%, open circuit voltage of 0.51 V, short circuit current of 8.71 mA/cm2 and a fill factor of 35% was obtained using blended PSiF-DBT:PCBM as active layer in a bulk heterojunction solar cell. Ultrafast electron dynamics in the low-femtosecond regime was evaluated by resonant Auger spectroscopy using the core-hole clock methodology around sulphur 1s absorption edge. Electron delocalization times for PSiF-DBT and PSiF-DBT:PCBM polymeric films were derived for selected excitation energies corresponding to the main transitions in the sulphur 1s NEXAFS spectra. The mixture of PSiF-DBT with PCBM improves the charge transfer process involving the π* molecular orbital of the thiophene units.
Camel-back band-induced power factor enhancement of thermoelectric lead-tellurium from Boltzmann transport calculations
Authors: Wang X. G. , Wang L. , Liu J. , Peng L. M.
Published: April 2014

Band structures of PbTe can be abnormally bended via dual-doping on both the cationic and anionic sites to form camel-back multivalley energy band structures near the band edge. As a result, additional carrier pockets and strong intervalley scattering of carriers are introduced. Boltzmann transport calculations indicate that their contradictory effects yield remarkably enhanced power factor due to the improved thermopower and almost unchanged electrical conductivity in low temperature and high carrier concentration ranges. These findings prove dual-doping-induced band bending as an effective approach to improve the thermoelectric properties of PbTe and other similar materials.
Plasma effect on weld pool surface reconstruction by shape-from-polarization analysis
Authors: Coniglio N. , Mathieu A. , Aubreton O. , Stolz C.
Published: April 2014

The polarimetric state of the thermal radiations emitted by the weld metal contains geometric information about the emitting surface. Even though the analysed thermal radiation has a wavelength corresponding to a blind spectral window of the arc plasma, the physical presence of the arc plasma itself interferes with the rays radiated by the weld pool surface before attaining the polarimeter, thus modifying the geometric information transported by the ray. In the present work, the effect of the arc plasma-surrounding zone on the polarimetric state and propagation direction of the radiated ray is analyzed. The interaction with the arc plasma zone induces a drop in ray intensity and a refraction of ray optical path.
Partial root zone drying exerts different physiological responses on field-grown grapevine (Vitis vinifera cv. Monastrell) in comparison to regulated deficit irrigation
Authors: Romero Pascual , Pérez-Pérez Juan Gabriel , del Amor Francisco M. , Martinez-Cutillas Adrián , Dodd Ian C. , Botía Pablo
Published: April 2014

Regulated deficit irrigation (RDI) and partial root zone irrigation (PRI) were compared for 4 years at two irrigation volumes (110 mm year–1 (1) and 78 mm year–1 (2)) in field-grown grafted Monastrell grapevines (Vitis vitifera L.) to distinguish the effects of deficit irrigation from specific PRI effects. PRI-1 and RDI-1 vines received ~30% of the crop evapotranspiration (ETc) from budburst to fruit set, 13–15% from fruit set to veraison and 20% from veraison to harvest. RDI-2 and PRI-2 vines received around 20% of ETc from budburst to fruit set, no irrigation from fruit set to veraison, and recovery (21–24% ETc) thereafter. Compared with RDI-1, PRI-1 increased irrigation depth and total soil water (θv) availability in the root zone, and stimulated greater fine root growth and water uptake. Increased soil volume exploration supported greater canopy water use, vegetative development, biomass accumulation and internal water storage capacity. PRI-1 vines had higher stomatal conductance, lower leaf-level water use efficiency and increased leaf xylem sap concentration ([X-ABA]leaf) following reirrigation. Compared with RDI-2, PRI-2 decreased total θv availability, fine root growth and water uptake, gas exchange, leaf water status, [X-ABA]leaf, biomass accumulation and storage capacity. Xylem ABA decreased with total θv availability in PRI-2, probably from limited sap flow when θv in drying soil was low (≈20%). For this rootstock–scion combination, high irrigation volumes applied to the wet part of the roots (θv > 30%) are critical for increasing root-to-shoot ABA signalling and growth, and improving performance under semiarid conditions.
Model averaging to streamline the stock assessment process
Authors: Millar Colin P. , Jardim Ernesto , Scott Finlay , Osio Giacomo Chato , Mosqueira Iago , Alzorriz Nekane
Published: April 2014

The current fish stock assessment process in Europe can be very resource- and time-intensive. The scientists involved require a very particular set of skills, acquired over their career, drawing from biology, ecology, statistics, mathematical modelling, oceanography, fishery policy, and computing. There is a particular focus on producing a single “best” stock assessment model, but as fishery science advances, there are clear needs to address a range of hypotheses and uncertainties, from large-scale issues such as climate change to specific ones, such as high observation error on young hake. Key to our discussion is the use of the assessment for all frameworks to translate hypotheses into models. We propose a change to the current stock assessment procedure, driven by the use of model averaging to address a range of plausible hypotheses, where increased collaboration between the varied disciplines within fishery science will result in more robust advice.
Simulation of synthetic gecko arrays shearing on rough surfaces
Authors: Gillies Andrew G. , Fearing Ronald S.
Published: April 2014

To better understand the role of surface roughness and tip geometry in the adhesion of gecko synthetic adhesives, a model is developed that attempts to uncover the relationship between surface feature size and the adhesive terminal feature shape. This model is the first to predict the adhesive behaviour of a plurality of hairs acting in shear on simulated rough surfaces using analytically derived contact models. The models showed that the nanoscale geometry of the tip shape alters the macroscale adhesion of the array of fibres by nearly an order of magnitude, and that on sinusoidal surfaces with amplitudes much larger than the nanoscale features, spatula-shaped features can increase adhesive forces by 2.5 times on smooth surfaces and 10 times on rough surfaces. Interestingly, the summation of the fibres acting in concert shows behaviour much more complex that what could be predicted with the pull-off model of a single fibre. Both the Johnson–Kendall–Roberts and Kendall peel models can explain the experimentally observed frictional adhesion effect previously described in the literature. Similar to experimental results recently reported on the macroscale features of the gecko adhesive system, adhesion drops dramatically when surface roughness exceeds the size and spacing of the adhesive fibrillar features.
Generalization of the Schwarz–Christoffel mapping to multiply connected polygonal domains
Authors: Vasconcelos Giovani L.
Published: April 2014

A generalization of the Schwarz–Christoffel mapping to multiply connected polygonal domains is obtained by making a combined use of two preimage domains, namely, a rectilinear slit domain and a bounded circular domain. The conformal mapping from the circular domain to the polygonal region is written as an indefinite integral whose integrand consists of a product of powers of the Schottky-Klein prime functions, which is the same irrespective of the preimage slit domain, and a prefactor function that depends on the choice of the rectilinear slit domain. A detailed derivation of the mapping formula is given for the case where the preimage slit domain is the upper half-plane with radial slits. Representation formulae for other canonical slit domains are also obtained but they are more cumbersome in that the prefactor function contains arbitrary parameters in the interior of the circular domain.
Supra-molecular assembly of aromatic proton sponges to direct the crystallization of extra-large-pore zeotypes
Authors: Martínez-Franco Raquel , Sun Junliang , Sastre German , Yun Yifeng , Zou Xiaodong , Moliner Manuel , Corma Avelino
Published: April 2014

The combination of different experimental techniques, such as solid13C and1H magic-angle spinning NMR spectroscopy, fluorescence spectroscopy and powder X-ray diffraction, together with theoretical calculations allows the determination of the unique structure directing the role of the bulky aromatic proton sponge 1,8-bis(dimethylamino)naphthalene (DMAN) towards the extra-large-pore ITQ-51 zeolite through supra-molecular assemblies of those organic molecules.
Widespread methanotrophic primary production in lowland chalk rivers
Authors: Shelley Felicity , Grey Jonathan , Trimmer Mark
Published: April 2014

Methane is oversaturated relative to the atmosphere in many rivers, yet its cycling and fate is poorly understood. While photosynthesis is the dominant source of autotrophic carbon to rivers, chemosynthesis and particularly methane oxidation could provide alternative sources of primary production where the riverbed is heavily shaded or at depth beneath the sediment surface. Here, we highlight geographically widespread methanotrophic carbon fixation within the gravel riverbeds of over 30 chalk rivers. In 15 of these, the potential for methane oxidation (methanotrophy) was also compared with photosynthesis. In addition, we performed detailed concurrent measurements of photosynthesis and methanotrophy in one large chalk river over a complete annual cycle, where we found methanotrophy to be active to at least 15 cm into the riverbed and to be strongly substrate limited. The seasonal trend in methanotrophic activity reflected that of the riverine methane concentrations, and thus the highest rates were measured in mid-summer. At the sediment surface, photosynthesis was limited by light for most of the year with heavy shading induced by dense beds of aquatic macrophytes. Across 15 rivers, in late summer, we conservatively calculated that net methanotrophy was equivalent to between 1% and 46% of benthic net photosynthetic production within the gravel riverbed, with a median value of 4%. Hence, riverbed chemosynthesis, coupled to the oxidation of methane, is widespread and significant in English chalk rivers.
Unique expression patterns of multiple key genes associated with the evolution of mammalian flight
Authors: Wang Zhe , Dai Mengyao , Wang Yao , Cooper Kimberly L. , Zhu Tengteng , Dong Dong , Zhang Junpeng , Zhang Shuyi
Published: April 2014

Bats are the only mammals capable of true flight. Critical adaptations for flight include a pair of dramatically elongated hands with broad wing membranes. To study the molecular mechanisms of bat wing evolution, we perform genomewide mRNA sequencing andin situhybridization for embryonic bat limbs. We identify seven key genes that display unique expression patterns in embryonic bat wings and feet, compared with mouse fore- and hindlimbs. The expression of all 5′HoxD genes (Hoxd9–13) andTbx3, six known crucial transcription factors for limb and digit development, is extremely high and prolonged in the elongating wing area. The expression ofFam5c, a tumour suppressor, in bat limbs is bat-specific and significantly high in all short digit regions (the thumb and foot digits). These results suggest multiple genetic changes occurred independently during the evolution of bat wings to elongate the hand digits, promote membrane growth and keep other digits short. Our findings also indicate that the evolution of limb morphology depends on the complex integration of multiple gene regulatory networks and biological processes that control digit formation and identity, chondrogenesis, and interdigital regression or retention.
Does polyandry control population sex ratio via regulation of a selfish gene?
Authors: Price Tom A. R. , Bretman Amanda , Gradilla Ana C. , Reger Julia , Taylor Michelle L. , Giraldo-Perez Paulina , Campbell Amy , Hurst Gregory D. D. , Wedell Nina
Published: April 2014

The extent of female multiple mating (polyandry) can strongly impact on the intensity of sexual selection, sexual conflict, and the evolution of cooperation and sociality. More subtly, polyandry may protect populations against intragenomic conflicts that result from the invasion of deleterious selfish genetic elements (SGEs). SGEs commonly impair sperm production, and so are likely to be unsuccessful in sperm competition, potentially reducing their transmission in polyandrous populations. Here, we test this prediction in nature. We demonstrate a heritable latitudinal cline in the degree of polyandry in the fruitflyDrosophila pseudoobscuraacross the USA, with northern population females remating more frequently in both the field and the laboratory. High remating was associated with low frequency of a sex-ratio-distorting meiotic driver in natural populations. In the laboratory, polyandry directly controls the frequency of the driver by undermining its transmission. Hence we suggest that the cline in polyandry represents an important contributor to the cline insex ratioin nature. Furthermore, as the meiotic driver causes sex ratio bias, variation in polyandry may ultimately determine population sex ratio across the USA, a dramatic impact of female mating decisions. As SGEs are ubiquitous it is likely that the reduction of intragenomic conflict by polyandry is widespread.
Two waves of colonization straddling the K–Pg boundary formed the modern reef fish fauna
Authors: Price S. A. , Schmitz L. , Oufiero C. E. , Eytan R. I. , Dornburg A. , Smith W. L. , Friedman M. , Near T. J. , Wainwright P. C.
Published: April 2014

Living reef fishes are one of the most diverse vertebrate assemblages on Earth. Despite its prominence and ecological importance, the origins and assembly of the reef fish fauna is poorly described. A patchy fossil record suggests that the major colonization of reef habitats must have occurred in the Late Cretaceous and early Palaeogene, with the earliest known modern fossil coral reef fish assemblage dated to 50 Ma. Using a phylogenetic approach, we analysed the early evolutionary dynamics of modern reef fishes. We find that reef lineages successively colonized reef habitats throughout the Late Cretaceous and early Palaeogene. Two waves of invasion were accompanied by increasing morphological convergence: one in the Late Cretaceous from 90 to 72 Ma and the other immediately following the end-Cretaceous mass extinction. The surge in reef invasions after the Cretaceous–Palaeogene boundary continued for 10 Myr, after which the pace of transitions to reef habitats slowed. Combined, these patterns match a classic niche-filling scenario: early transitions to reefs were made rapidly by morphologically distinct lineages and were followed by a decrease in the rate of invasions and eventual saturation of morphospace. Major alterations in reef composition, distribution and abundance, along with shifts in climate and oceanic currents, occurred during the Late Cretaceous and early Palaeogene interval. A causal mechanism between these changes and concurrent episodes of reef invasion remains obscure, but what is clear is that the broad framework of the modern reef fish fauna was in place within 10 Myr of the end-Cretaceous extinction.