bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity of the photophysical properties of organometallic complexes to small chemical changes
Authors: Jacko A. C. , Powell B. J. , McKenzie Ross H.
Published: September 2010

We investigate an effective model Hamiltonian for organometallic complexes that are widely used in optoelectronic devices. The two most important parameters in the model are J, the effective exchange interaction between the π and π∗ orbitals of the ligands, and ε∗, the renormalized energy gap between the highest occupied orbitals on the metal and on the ligand. We find that the degree of metal-to-ligand charge transfer character of the lowest triplet state is strongly dependent on the ratio ε∗/J. ε∗ is purely a property of the complex and can be changed significantly by even small variations in the complex’s chemistry, such as replacing substituents on the ligands. We find that small changes in ε∗/J can cause large changes in the properties of the complex, including the lifetime of the triplet state and the probability of injected charges (electrons and holes) forming triplet excitations. These results give some insight into the observed large changes in the photophysical properties of organometallic complexes caused by small changes in the ligands.
Time-resolved x-ray diffraction study of the piezoelectric crystal response to a fast change of an applied electric field
Authors: Gorfman Semen , Schmidt Oleg , Ziolkowski Michael , von Kozierowski Marc , Pietsch Ullrich
Published: September 2010

Time-resolved measurements of the macroscopic and microscopic strains in piezoelectric crystals were performed with a novel data acquisition technique implemented on the basis of a field programmed gate array system. Both types of strains were induced in a crystal by an applied periodic high voltage with fast (within 100 ns) switches between opposite polarities and measured simultaneously by respective angular shifts and integrated intensities of synchrotron x-ray diffraction rocking curves. The time resolution achieved with the developed data acquisition system was 100 ns. The paper demonstrates the particular application of this technique for the investigations of time dynamics of lattice constants and atomic positions in a unit cell for piezoelectric BiB3O6 and Li2SO4⋅H2O crystals. It has been found that 100 ns fast rising time of an applied external electric field induces oscillations of the crystal lattice constants, visible as oscillations of Bragg peak angular positions. At the same time, these oscillations are not observed for the Bragg intensities, i.e., for fractional positions of atoms in the unit cell and correspondingly for bond lengths. The results allow suggesting a model for the mutual interconnection between the deformation of bond lengths and lattice constants in piezoelectric crystals.
A comprehensive study of the influence of the stoichiometry on the physical properties of TiOx films prepared by ion beam deposition
Authors: Marchi M. Claudia , Bilmes Sara A. , Ribeiro C. T. M. , Ochoa E. A. , Kleinke M. , Alvarez F.
Published: September 2010

A comprehensive study of nonstoichiometry titanium oxide thin films (TiOx, 0.3≤x≤2) prepared by ion beam deposition technique is reported. The physical properties of the material are studied by ultraviolet and x-ray photoelectron, Raman, and Fourier transform infrared spectroscopies, and atomic force microscopy. An abrupt transition from metallic characteristics to a wide gap semiconductor is observed in a very narrow range of oxygen variation. Concomitantly with this change the crystal structure and morphology suffer remarkable physical properties modifications. This transformation is ascribed to surface-volume energy minimization due to the influence of oxygen determining the size of the TiO2 particles during coalescence.
Low-temperature adsorption of H2S on Ag(111)
Authors: Russell Selena M. , Liu Da-Jiang , Kawai Maki , Kim Yousoo , Thiel P. A.
Published: September 2010

H 2 S forms a rich variety of structures on Ag(111) at low temperature and submonolayer coverage. The molecules decorate step edges, exist as isolated entities on terraces, and aggregate into clusters and islands, under various conditions. One type of island exhibits a (37×37)R25.3° unit cell. Typically, molecules in the clusters and islands are separated by about 0.4 nm, the same as the S–S separation in crystalline H2S. Density functional theory indicates that hydrogen-bonded clusters contain two types of molecules. One is very similar to an isolated adsorbed H2S molecule, with both S–H bonds nearly parallel to the surface. The other has a S–H bond pointed toward the surface. The potential energy surface for adsorption and diffusion is very smooth.
On vortex dust structures in magnetized dusty plasmas
Authors: Nebbat E. , Annou R.
Published: September 2010

To explain the generation of vortex patterns of dust grains in a magnetized dusty plasma [Huang et al., Plasma Sci. Technol. 9, 1 (2007)], a time dependent nonlinear model that describes vortices as a result of an instability is proposed. Grain-grain as well as grain-ion interactions, particle attachment, and grains drift and diffusion are key elements in the present model. It is found that the latter reproduces the experimental results quite well, whereas the stability analysis shows that the vortex core is grain size dependent.
The direct and inverse problems of an air-saturated porous cylinder submitted to acoustic radiation
Authors: Ogam Erick , Depollier Claude , Fellah Z. E. A.
Published: September 2010

Gas-saturated porous skeleton materials such as geomaterials, polymeric and metallic foams, or biomaterials are fundamental in a diverse range of applications, from structural materials to energy technologies. Most polymeric foams are used for noise control applications and knowledge of the manner in which the energy of sound waves is dissipated with respect to the intrinsic acoustic properties is important for the design of sound packages. Foams are often employed in the audible, low frequency range where modeling and measurement techniques for the recovery of physical parameters responsible for energy loss are still few. Accurate acoustic methods of characterization of porous media are based on the measurement of the transmitted and/or reflected acoustic waves by platelike specimens at ultrasonic frequencies. In this study we develop an acoustic method for the recovery of the material parameters of a rigid-frame, air-saturated polymeric foam cylinder. A dispersion relation for sound wave propagation in the porous medium is derived from the propagation equations and a model solution is sought based on plane-wave decomposition using orthogonal cylindrical functions. The explicit analytical solution equation of the scattered field shows that it is also dependent on the intrinsic acoustic parameters of the porous cylinder, namely, porosity, tortuosity, and flow resistivity (permeability). The inverse problem of the recovery of the flow resistivity and porosity is solved by seeking the minima of the objective functions consisting of the sum of squared residuals of the differences between the experimental and theoretical scattered field data.
Magnetohydrodynamic waves in the presence of relative motion between two populations of a plasma system
Authors: Kumar Subhash , Singh Harinder P.
Published: September 2010

The paper investigates the role of relative motion between the fluid components of a plasma model, which is simulated by concatenation of two anisotropic magnetohydrodynamic (MHD) fluids, on the propagation of low-frequency waves and instabilities. The gyrotropic pressure of both the MHD components is given by generalized polytropic laws that allow the system to reduce to a variety of states. The linearized analysis is carried out and dispersion relation is derived using the normal mode technique. The dispersion relation, which gives numerous earlier results as special cases, is discussed both analytically as well as numerically for parameters appropriate for the space plasma. It is found that the relative motion between the two components, besides modifying the condition for fire-hose instability, causes the concatenated system to exhibit different kinds of relative ordering of the magnitudes of phase speeds of the various MHD modes in the directions parallel and antiparallel to the magnetic field. The relative motion between the components also influences the phase relationship between density and magnetic field fluctuations for the various compressive modes in the background ambient plasma.
Plasma dynamics of a confined extreme ultraviolet light source
Authors: Yeates P. , Kennedy E. T.
Published: September 2010

Laser plasmas were generated by ablation of aluminum targets via a Nd:YAG glass laser, of pulse energy 0.8 J, and duration 15 ns (full width at half maximum) at the fundamental wavelength (1.064 μm). Emission lines in the wavelength range of 27–32 nm (45–37.8 eV) were mapped over a spatial range extending out 1.8 mm from the target surface and for a temporal range of 42 ns after the termination of the laser pulse. Two targets were utilized: a planar surface and a rectangular cavity. The latter was composed of a rectangular shaped cavity of depth 3 mm and height 1.2 mm, cut into an aluminum massive. An irradiance of Ip∼1011 W/cm2 was delivered to both targets and the confining influence of the rectangular cavity upon plasma formation and expansion was studied. Diagnostics of the emitted spectra reveal the unique dynamics of restricted plasma plume expansion, which results in plasma-surface collisions and subsequent plasma rebound within the cavity. These effects give rise to strong enhancement of both continuum and line emission in the contained plasma plume. These enhancements are especially evident for the more highly charged ions. Superior emission from plasma-surface collisions are associated with “forced recombination” during early time scales, while enhanced emission at later stages are associated with plasma plume component rebound and collision.
The properties of tris (8-hydroxyquinoline) aluminum organic light emitting diode with undoped zinc oxide anode layer
Authors: Luka G. , Stakhira P. , Cherpak V. , Volynyuk D. , Hotra Z. , Godlewski M. , Guziewicz E. , Witkowski B. , Paszkowicz W. , Kostruba A.
Published: September 2010

Transparent and conductive undoped zinc oxide films were prepared by atomic layer deposition method for use in tris (8-hydroxyquinoline) aluminum (Alq3)-based organic light emitting diodes. The properties of the ZnO layers were investigated. The ZnO/CuI/Alq3/poly(ethylene glycol) dimethyl ether/Al device turned on at 7.9 V and demonstrated external quantum efficiency of 1.5% which is better comparing to the same structure but with indium tin oxide as anode layer.
Turbulent transport of fast ions in the Large Plasma Device
Authors: Zhou Shu , Heidbrink W. W. , Boehmer H. , McWilliams R. , Carter T. , Vincena S. , Tripathi S. K. P. , Popovich P. , Friedman B. , Jenko F.
Published: September 2010

Strong drift wave turbulence is observed in the Large Plasma Device [H. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] on density gradients produced by a plate limiter. Energetic lithium ions orbit through the turbulent region. Scans with a collimated ion analyzer and with Langmuir probes give detailed profiles of the fast ion spatial distribution and the fluctuating fields. The fast ion transport decreases rapidly with increasing fast ion gyroradius. Unlike the diffusive transport caused by Coulomb collisions, in this case the turbulent transport is nondiffusive. Analysis and simulation suggest that such nondiffusive transport is due to the interaction of the fast ions with stationary two-dimensional electrostatic turbulence.
Effect of dynamical friction on nonlinear energetic particle modes
Authors: Lilley M. K. , Breizman B. N. , Sharapov S. E.
Published: September 2010

A fully nonlinear model is developed for the bump-on-tail instability including the effects of dynamical friction (drag) and velocity space diffusion on the energetic particles driving the wave. The results show that drag provides a destabilizing effect on the nonlinear evolution of waves. Specifically, in the early nonlinear phase of the instability, the drag facilitates the explosive scenario of the wave evolution, leading to the creation of phase space holes and clumps that move away from the original eigenfrequency. Later in time, the electric field associated with a hole is found to be enhanced by the drag, whereas for a clump it is reduced. This leads to an asymmetry of the frequency evolution between holes and clumps. The combined effect of drag and diffusion produces a diverse range of nonlinear behaviors including hooked frequency chirping, undulating, and steady state regimes. An analytical model is presented, which explains the aforementioned diversity. A continuous production of hole-clump pairs in the absence of collisions is also observed.
Distribution and regulation of stochasticity and plasticity in Saccharomyces cerevisiae
Authors: Dar R. D. , Karig D. K. , Cooke J. F. , Cox C. D. , Simpson M. L.
Published: September 2010

Stochasticity is an inherent feature of complex systems with nanoscale structure. In such systems information is represented by small collections of elements (e.g., a few electrons on a quantum dot), and small variations in the populations of these elements may lead to big uncertainties in the information. Unfortunately, little is known about how to work within this inherently noisy environment to design robust functionality into complex nanoscale systems. Here, we look to the biological cell as an intriguing model system where evolution has mediated the trade-offs between fluctuations and function, and in particular we look at the relationships and trade-offs between stochastic and deterministic responses in the gene expression of budding yeast (Saccharomyces cerevisiae). We find gene regulatory arrangements that control the stochastic and deterministic components of expression, and show that genes that have evolved to respond to stimuli (stress) in the most strongly deterministic way exhibit the most noise in the absence of the stimuli. We show that this relationship is consistent with a bursty two-state model of gene expression, and demonstrate that this regulatory motif generates the most uncertainty in gene expression when there is the greatest uncertainty in the optimal level of gene expression.
Information modification and particle collisions in distributed computation
Authors: Lizier Joseph T. , Prokopenko Mikhail , Zomaya Albert Y.
Published: September 2010

Distributed computation can be described in terms of the fundamental operations of information storage, transfer, and modification. To describe the dynamics of information in computation, we need to quantify these operations on a local scale in space and time. In this paper we extend previous work regarding the local quantification of information storage and transfer, to explore how information modification can be quantified at each spatiotemporal point in a system. We introduce the separable information, a measure which locally identifies information modification events where separate inspection of the sources to a computation is misleading about its outcome. We apply this measure to cellular automata, where it is shown to be the first direct quantitative measure to provide evidence for the long-held conjecture that collisions between emergent particles therein are the dominant information modification events.
The complexity of proving chaoticity and the Church–Turing thesis
Authors: Calude Cristian S. , Calude Elena , Svozil Karl
Published: September 2010

Proving the chaoticity of some dynamical systems is equivalent to solving the hardest problems in mathematics. Conversely, classical physical systems may “compute the hard or even the incomputable” by measuring observables which correspond to computationally hard or even incomputable problems.
Discrete analog computing with rotor-routers
Authors: Propp James
Published: September 2010

Rotor-routing is a procedure for routing tokens through a network that can implement certain kinds of computation. These computations are inherently asynchronous (the order in which tokens are routed makes no difference) and distributed (information is spread throughout the system). It is also possible to efficiently check that a computation has been carried out correctly in less time than the computation itself required, provided one has a certificate that can itself be computed by the rotor-router network. Rotor-router networks can be viewed as both discrete analogs of continuous linear systems and deterministic analogs of stochastic processes.
Self-diffusion in two-dimensional hard ellipsoid suspensions
Authors: Zheng Zhongyu , Han Yilong
Published: September 2010

We studied the self-diffusion of colloidal ellipsoids in a monolayer near a flat wall by video microscopy. The image processing algorithm can track the positions and orientations of ellipsoids with subpixel resolution. The translational and rotational diffusions were measured in both the laboratory frame and the body frame along the long and short axes. The long-time and short-time diffusion coefficients of translational and rotational motions were measured as functions of the particle concentration. We observed the nondiffusive crossover region in the intermediate time regime due to the caging of neighboring particles. Both the beginning and the ending times of the intermediate regime exhibit power-law dependence on concentration. The long-time and short-time diffusion anisotropies change nonmonotonically with concentration and reach minima in the semidilute regime because the motions along long axes are caged at lower concentrations than the motions along short axes. The time derivatives of mean-square displacements change linearly with the inverse of time in the intermediate time regimes at various particle densities. This indicates that their relaxation functions decay as 1/t which provides new challenges in theory. The effects of coupling between rotational and translational Brownian motions were demonstrated and the two time scales corresponding to anisotropic particle shape and anisotropic neighboring environment were measured.
Effective strategy of adding nodes and links for maximizing the traffic capacity of scale-free network
Authors: Huang Wei , Chow Tommy W. S.
Published: September 2010

In this paper, we propose an efficient strategy to enhance traffic capacity via the process of nodes and links increment. We show that by adding shortcut links to the existing networks, packets are avoided flowing through hub nodes. We investigate the performances of our proposed strategy under the shortest path routing strategy and the local routing strategy. Our obtained results show that using the proposed strategy, the traffic capacity can be effectively enhanced under the shortest path routing strategy. Under the local routing strategy, the obtained results show that the proposed strategy is efficient only when packets are more likely to be forwarded to low-degree nodes in their routing paths. Compared with other strategies, the obtained results indicate that our proposed strategy of adding nodes and links is the most effective in enhancing the traffic capacity, i.e., the traffic capacity can be maximally enhanced with the least number of additional nodes and links.
Nonlinear semiconductor lasers and amplifiers for all-optical information processing
Authors: Adams M. J. , Hurtado A. , Labukhin D. , Henning I. D.
Published: September 2010

The nonlinear properties of semiconductor lasers and laser amplifiers when subject to optical injection are reviewed and new results are presented for multisection lasers, vertical cavity semiconductor optical amplifiers, and surface-emitting lasers. The main underlying material parameters are outlined and the key design approaches are discussed for both edge-emitting and vertical cavity devices. An overview of theoretical modeling approaches is discussed and a summary of key experimental results is presented. The practical use of optically injected edge-emitting and vertical cavity semiconductor lasers and laser amplifiers is illustrated with examples of applications including, among others, optical logic and chaotic communication.
Neuronal integration of dynamic sources: Bayesian learning and Bayesian inference
Authors: Siegelmann Hava T. , Holzman Lars E.
Published: September 2010

One of the brain’s most basic functions is integrating sensory data from diverse sources. This ability causes us to question whether the neural system is computationally capable of intelligently integrating data, not only when sources have known, fixed relative dependencies but also when it must determine such relative weightings based on dynamic conditions, and then use these learned weightings to accurately infer information about the world. We suggest that the brain is, in fact, fully capable of computing this parallel task in a single network and describe a neural inspired circuit with this property. Our implementation suggests the possibility that evidence learning requires a more complex organization of the network than was previously assumed, where neurons have different specialties, whose emergence brings the desired adaptivity seen in human online inference.
Nature computes: Information processing in quantum dynamical systems
Authors: Wiesner Karoline
Published: September 2010

Nature intrinsically computes. It has been suggested that the entire universe is a computer, in particular, a quantum computer. To corroborate this idea we require tools to quantify the information processing. Here we review a theoretical framework for quantifying information processing in a quantum dynamical system. So-called intrinsic quantum computation combines tools from dynamical systems theory, information theory, quantum mechanics, and computation theory. We will review how far the framework has been developed and what some of the main open questions are. On the basis of this framework we discuss upper and lower bounds for intrinsic information storage in a quantum dynamical system.
Tuning the thermal conductivity of graphene nanoribbons by edge passivation and isotope engineering: A molecular dynamics study
Authors: Hu Jiuning , Schiffli Stephen , Vallabhaneni Ajit , Ruan Xiulin , Chen Yong P.
Published: September 2010

Using classical molecular dynamics simulation, we have studied the effect of edge-passivation by hydrogen (H-passivation) and isotope mixture (with random or superlattice distributions) on the thermal conductivity of rectangular graphene nanoribbons (GNRs) (of several nanometers in size). We find that the thermal conductivity is considerably reduced by the edge H-passivation. We also find that the isotope mixing can reduce the thermal conductivities, with the superlattice distribution giving rise to more reduction than the random distribution. These results can be useful in nanoscale engineering of thermal transport and heat management using GNRs.
Microfabricated deflection tensiometers for insoluble surfactants
Authors: Zell Zachary A. , Choi SiYoung Q. , Leal L. Gary , Squires Todd M.
Published: September 2010

We describe a technique that enables sensitive surface pressure measurements of insoluble surfactants with small quantities in enclosed systems. We microfabricate free-floating microtensiometers that rest at liquid interfaces. Our devices isolate clean interfaces from surfactant-laden ones and deform in response to the surface pressure difference. Elastic beam theory enables straightforward interpretation of the measurements and the deliberate engineering of the sensitivity and dynamic range of the device. Surface pressure isotherms for model surfactant monolayers measured using our microtensiometer show excellent agreement with a conventional Wilhelmy plate.
Introduction to Focus Issue: Intrinsic and Designed Computation: Information Processing in Dynamical Systems—Beyond the Digital Hegemony
Authors: Crutchfield James P. , Ditto William L. , Sinha Sudeshna
Published: September 2010

How dynamical systems store and process information is a fundamental question that touches a remarkably wide set of contemporary issues: from the breakdown of Moore’s scaling laws—that predicted the inexorable improvement in digital circuitry—to basic philosophical problems of pattern in the natural world. It is a question that also returns one to the earliest days of the foundations of dynamical systems theory, probability theory, mathematical logic, communication theory, and theoretical computer science. We introduce the broad and rather eclectic set of articles in this Focus Issue that highlights a range of current challenges in computing and dynamical systems.
Large low-frequency resistance noise in chemical vapor deposited graphene
Authors: Pal Atindra Nath , Bol Ageeth A. , Ghosh Arindam
Published: September 2010

We report a detailed investigation of resistance noise in single layer graphene films on Si/SiO2 substrates obtained by chemical vapor deposition (CVD) on copper foils. We find that noise in these systems to be rather large, and when expressed in the form of phenomenological Hooge equation, it corresponds to Hooge parameter as large as 0.1–0.5. We also find the variation in the noise magnitude with the gate voltage (or carrier density) and temperature to be surprisingly weak, which is also unlike the behavior of noise in other forms of graphene, in particular those from exfoliation.
Au nanoparticles on graphitic petal arrays for surface-enhanced Raman spectroscopy
Authors: Rout Chandra Sekhar , Kumar Anurag , Xiong Guoping , Irudayaraj Joseph , Fisher Timothy S.
Published: September 2010

We report a unique substrate for surface-enhanced Raman scattering (SERS) based on Au nanoparticle-decorated, thin graphitic petals. The petals were grown on Si substrates by microwave plasma chemical vapor deposition without catalyst, followed by Au nanoparticle decoration on the oxygen plasma-treated petals by electrodeposition. The substrates possess high surface area and sharp nanoscale features that enable high SERS sensitivity to detect 1×10−7 M rhodamine 6G in methanol solution. The obtained SERS enhancement is comparable to the best values reported in the literature and is determined to result from high surface area and increased density of Au nanoparticles on the petal surfaces.
Microscaled and nanoscaled platinum sensors
Authors: Rajagopal Aditya , Walavalkar Sameer , Chen Samson , Guo Luke , Gwinn Tom , Scherer Axel
Published: September 2010

We show small and robust platinum resistive heaters and thermometers that are defined by microlithography on silicon substrates. These devices can be used for a wide range of applications, including thermal sensor arrays, programmable thermal sources, and even incandescent light emitters. To explore the miniaturization of such devices, we have developed microscaled and nanoscaled platinum resistor arrays with wire widths as small as 75 nm, fabricated lithographically to provide highly localized heating and accurate resistance (and hence temperature) measurements. We present some of these potential applications of microfabricated platinum resistors in sensing and spectroscopy.
Nanoscale resistive switching and filamentary conduction in NiO thin films
Authors: Ye J. Y. , Li Y. Q. , Gao J. , Peng H. Y. , Wu S. X. , Wu T.
Published: September 2010

We fabricate regular arrays of nanoelectrodes on NiO thin films via nanosphere lithography and directly probe the nanoscale resistive switching using a conductive atomic force microscope. The unipolar resistive switching is consistent with the conducting filament formation/rupture mechanism, and the switching power is as low as 10−9 W. We find that only about half of devices are switchable, and the Monte Carlo simulation suggests strong correlations between the switching reliability, the electrode size, and the filament dimension and density.
Independent individual addressing of multiple neutral atom qubits with a micromirror-based beam steering system
Authors: Knoernschild C. , Zhang X. L. , Isenhower L. , Gill A. T. , Lu F. P. , Saffman M. , Kim J.
Published: September 2010

We demonstrate a scalable approach to addressing multiple atomic qubits for use in quantum information processing. Individually trapped R87b atoms in a linear array are selectively manipulated with a single laser guided by a microelectromechanical beam steering system. Single qubit oscillations are shown on multiple sites at frequencies of ≃3.5 MHz with negligible crosstalk to neighboring sites. Switching times between the central atom and its closest neighbor were measured to be 6–7 μs while moving between the central atom and an atom two trap sites away took 10–14 μs.
Revisit of the Vögel–Fulcher freezing in lead magnesium niobate relaxors
Authors: Ke Shanming , Fan Huiqing , Huang Haitao
Published: September 2010

The Vögel–Fulcher (VF) equation ω=ω0 exp[−Ea/kB(Tm−Tf)] was frequently used to describe the dielectric relaxation of relaxor ferroelectrics where ω is the probe frequency at the peak temperature Tm of either the real or imaginary parts of the dielectric constant. We revisited this relation in a typical relaxor lead magnesium niobate and found that the parameters obtained were not physically meaningful. Meaningful results can only be obtained by fitting the VF relation on the characteristic relaxation time τc, whose temperature dependence can be obtained from the Cole–Cole model. The freezing temperature we obtained is 230 K, below which τc becomes temperature independent.
Spin excitation frequencies in magnetostatically coupled arrays of vortex state circular Permalloy dots
Authors: Awad A. A. , Aranda G. R. , Dieleman D. , Guslienko K. Y. , Kakazei G. N. , Ivanov B. A. , Aliev F. G.
Published: September 2010

Broadband ferromagnetic resonance in square arrays of Permalloy circular dots with different interdot separations was measured in the vortex ground state. The detected spin excitations show a complicated dependence of their frequencies on the interdot coupling strength. A considerable influence of the interdot separation on the gyrotropic vortex frequency and splitting of the azimuthal spin wave frequencies was detected. The gyrotropic frequency and the first azimuthal doublet frequency splitting depend nonmonotonously on the interdot spacing, whereas the dependence of the second doublet frequency splitting on this parameter is monotonous. The observed effects are explained by the influence of both the dipolar and quadrupolar contributions to the dynamic magnetostatic interactions.
Reduction of native oxides on InAs by atomic layer deposited Al2O3 and HfO2
Authors: Timm R. , Fian A. , Hjort M. , Thelander C. , Lind E. , Andersen J. N. , Wernersson L.-E. , Mikkelsen A.
Published: September 2010

Thin high-κ oxide films on InAs, formed by atomic layer deposition, are the key to achieve high-speed metal-oxide-semiconductor devices. We have studied the native oxide and the interface between InAs and 2 nm thick Al2O3 or HfO2 layers using synchrotron x-ray photoemission spectroscopy. Both films lead to a strong oxide reduction, obtaining less than 10% of the native As-oxides and between 10% and 50% of the native In-oxides, depending on the deposition temperature. The ratio of native In- to As-oxides is determined to be 2:1. The exact composition and the influence of different oxidation states and suboxides is discussed in detail.
Slowing surface plasmon polaritons on plasmonic coupled cavities by tuning grating grooves
Authors: Balci Sinan , Kocabas Askin , Kocabas Coskun , Aydinli Atilla
Published: September 2010

We investigate slow surface plasmon polaritons (SPPs) in plasmonic waveguiding bands formed by coupled plasmonic cavities on Moiré surfaces. We demonstrate controlling the group velocity and dispersion of the SPPs by varying the depth of the plasmonic Bragg grating groove. Changing the grating depth results in modification of coupling coefficients between the cavities and hence the SPPs group velocity is altered. Variation in the group velocity and dispersion of SPPs can be measured with polarization dependent spectroscopic reflection measurements. Dispersion of SPPs has been calculated by finite-difference time-domain method in agreement with the experimental data.
Communication: The phoretic drift of a charged particle animated by a direct ionic current
Authors: Yariv Ehud
Published: September 2010

A charged colloidal particle which is suspended in an electrolyte solution drifts due to an external voltage application. For direct currents, particle motion is affected by two separate mechanisms: electro-osmotic slip associated with the electric field and chemi-osmotic slip associated with the inherent salt concentration gradient in the solution. These two mechanisms are interrelated and are of comparable magnitude. Their combined effect is demonstrated for cation-exchange electrodes using a weak-current approximation. The linkage between the two mechanisms results in an effectively modified mobility, whose dependence on the particle zeta potential is nonlinear. At small potentials, the electro-osmotic mechanism dominates and the particle migrates according to the familiar Smoluchowski mobility, linear in the electric field. At large zeta potentials, chemiosmosis becomes dominant: for positively charged particles, it tends to arrest motion, leading to mobility saturation; for negatively charged particles, it enhances the drift, effectively leading to a shifted linear dependence of the mobility on the zeta potential, with twice the Smoluchowski slope.
Influence of nutritional and socio-sexual cues upon reproductive efficiency of goats exposed to the male effect under extensive conditions
Authors: Flores-Najera M. J. , Meza-Herrera C. A. , Echavarría F. G. , Villagomez E. , Iñiguez L. , Salinas H. , Gonzalez-Bulnes A.
Published: September 2010

This study evaluated the effect of nutritional supplementation and socio-sexual cues upon reproductive efficiency of goats exposed to the male effect under rangeland grazing conditions (22°N). Criollo goats (n = 73) were distributed in four experimental groups: (1) continuous males (CM, n = 19) in which males (n = 2) remained together with females from 7 March to 28 July; (2) supplemented males (SM, n = 16) in which males (n = 2) were kept separately and were individually supplemented with 18% crude protein and 2.77 Mcal ME kg–1 DM, during a 30-day period; (3) supplemented males exposed to the female effect (SM + FE, n = 19), in which supplemented males (n = 2) were maintained with females induced to oestrus before being used for male effect; and (4) supplemented males and supplemented females (SM + SF, n = 19) in which males (n = 2) were supplemented as in group SM, and females received the same supplementation as males 30 days before and 30 days after male introduction. Grazing was performed from 0900 to 1900 hours; liveweight (LW) was registered weekly before grazing and (or) supplementation. Ovarian activity was evaluated (serum P4 concentrations) in the four groups before and after male introduction. At the beginning of the study and supplementation, female LW did not differ among treatments (P > 0.01). However, during the supplementation phase, LW increased in a different fashion among groups (P < 0.002), favouring the SM, SM + FE and SM + SF groups. A positive correlation between female LW at the beginning of the rainy season and the onset of ovulatory activity was observed (r = +0.90; P < 0.01). The average date for the onset of ovarian activity differed (P < 0.001) among groups, being earlier in the SM + SF group (9 May ± 4.3 days), which also depicted the shortest interval between the introduction of males until the onset of ovulatory activity (P < 0.001). Results of the present study indicate that nutritional signalling of the reproductive activity of both female and male Criollo goats reared under marginal conditions surmounts the inhibitory effects of long-day photoperiods during the non-reproductive season. An increased level of nutrition during the anestrous season may be used to increase reproductive function of both male and female goats reared in harsh nutritional conditions and applied as a green, clean, and ethical reproductive tool at these latitudes.
Estimation of net carbon sequestration potential with farmland application of bagasse charcoal: life cycle inventory analysis through a pilot sugarcane bagasse carbonisation plant
Authors: Kameyama Koji , Shinogi Yoshiyuki , Miyamoto Teruhito , Agarie Koyu
Published: September 2010

Enriching soil carbon storage is regarded as a viable option for mitigating greenhouse gas (GHG) emissions in the agricultural sector. Carbon sequestration by applying biomass into the soil can be an effective sequestration pathway for agriculture. Biochar, charcoal produced from biomass pyrolysis, is highly stable against microbial decomposition, and applying this to farmland has the potential to mitigate GHG emissions. However, CO2 is emitted throughout the biochar life cycle, including pyrolysis, transportation, and farmland application. Therefore, estimating the net carbon sequestration potential by considering these CO2 emissions is important. To this end, operational data from a pilot sugarcane bagasse carbonisation plant were collected, and the net carbon sequestration potential with farmland application of bagasse charcoal was calculated using inventory data from the pilot plant. The results were as follows: (i) kerosene consumption during the carbonisation process was the greatest contributor to CO2 emissions within the life cycle of applying bagasse charcoal to farmland; (ii) the initial dryness of the feedstock was an important factor in estimating net carbon sequestration potentials; (iii) the CO2 mitigation potential with farmland application of bagasse charcoal on Miyako Island would be 1200–1800 t CO2/year.
Chemical and structural properties of carbonaceous products obtained by pyrolysis and hydrothermal carbonisation of corn stover
Authors: Fuertes A. B. , Arbestain M. Camps , Sevilla M. , Maciá-Agulló J. A. , Fiol S. , López R. , Smernik R. J. , Aitkenhead W. P. , Arce F. , Macías F.
Published: September 2010

The main properties of chars produced from corn stover, either by pyrolysis at 550°C (to produce biochar) or by hydrothermal carbonisation (to produce hydrochar), were studied. Carbonaceous materials were characterised by: SEM imaging, solid-state 13C NMR, FT-IR, Raman spectroscopy, and XPS. The following parameters were determined: elemental composition, cation exchange capacity, acid groups contents, BET, and yield. The hydrochar had a low ash content and low pH (4.7); recovery of C was high (57%), although only about half of the C was aromatic. Atomic O/C and H/C ratios in the hydrochar were higher than in the biochar. The same pattern was observed for the estimated concentration of carboxylic functional groups (0.07 compared with 0.04 mol/kg). The biochar had higher ash content than the hydrochar, and also higher pH (~10) (lime equivalence ~40 kg CaCO3/t). The C recovery (46%) was lower than in the hydrochar, although most of the C recovered was aromatic. Both chars could be used as soil amendments, for very different requirements. Soil responses and the residence times of the chars (especially the hydrochar) must be studied in detail to pursue long-term C sequestration.
Effect of banded biochar on dryland wheat production and fertiliser use in south-western Australia: an agronomic and economic perspective
Authors: Blackwell Paul , Krull Evelyn , Butler Greg , Herbert Allan , Solaiman Zakaria
Published: September 2010

Effects of banded biochar application on dryland wheat production and fertiliser use in 4 experiments in Western Australia and South Australia suggest that biochar has the potential to reduce fertiliser requirement while crop productivity is maintained, and biochar additions can increase crop yields at lower rates of fertiliser use. Banding was used to minimise wind erosion risk and place biochar close to crop roots. The biochars/metallurgical chars used in this study were made at relatively high temperatures from woody materials, forming stable, low-nutrient chars. The results suggest that a low biochar application rate (~1 t/ha) by banding may provide significant positive effects on yield and fertiliser requirement. Benefits are likely to result from improved crop nutrient and water uptake and crop water supply from increased arbuscular mycorrhizal fungal colonisation during dry seasons and in low P soils, rather than through direct nutrient or water supply from biochars. Financial analysis using farm cash flow over 12 years suggests that a break-even total cost of initial biochar use can range from AU$40 to 190/ha if the benefits decline linearly to nil over 12 years, taking into account a P fertiliser saving of 50% or a yield increase of 10%, or both, assuming long-term soil fertility is not compromised. Accreditation of biochar for carbon trading may assist cost reduction.
Stability and stabilisation of biochar and green manure in soil with different organic carbon contents
Authors: Kimetu Joseph M. , Lehmann Johannes
Published: September 2010

Due to its recalcitrance against microbial degradation, biochar is very stable in soil compared to other organic matter additions, making its application to soils a suitable approach for the build-up of soil organic carbon (SOC). The net effects of such biochar addition also depend on its interactions with existing organic matter in soils. A study was established to investigate how the status of pre-existing soil organic matter influences biochar stabilisation in soil in comparison to labile organic additions. Carbon loss was greater in the C-rich sites (C content 58.0 g C/kg) than C-poor soils (C content 21.0–24.0 g C/kg), regardless of the quality of the applied organic resource. Biochar-applied, C-rich soil showed greater C losses, by >0.5 kg/m2.year, than biochar-applied C-poor soil, whereas the difference was only 0.1 kg/m2.year with Tithonia diversifolia green manure. Biochar application reduced the rate of CO2-C loss by 27%, and T. diversifolia increased CO2-C losses by 22% in the C-poor soils. With biochar application, a greater proportion of C (6.8 times) was found in the intra-aggregate fraction per unit C respired than with green manure, indicating a more efficient stabilisation in addition to the chemical recalcitrance of biochar. In SOC-poor soils, biochar application enriched aromatic-C, carboxyl-C, and traces of ketones and esters mainly in unprotected organic matter and within aggregates, as determined by Fourier-transform infrared spectroscopy. In contrast, additions of T. diversifolia biomass enriched conjugated carbonyl-C such as ketones and quinones, as well as CH deformations of aliphatic-C mainly in the intra-aggregate fraction. The data indicate that not only the stability but also the stabilisation of biochar exceeds that of a labile organic matter addition such as green manure.
Influence of biochar application to soil on the availability of As, Cd, Cu, Pb, and Zn to maize (Zea mays L.)
Authors: Namgay Tshewang , Singh Balwant , Singh Bhupinder Pal
Published: September 2010

Biochar has gained importance due to its ability to increase the long-term soil carbon pool and improve crop productivity. However, little research has been done to evaluate the influence of biochar application to soil on the bioavailability of trace elements to plants. A pot experiment was conducted to investigate the influence of biochar on the availability of As, Cd, Cu, Pb, and Zn to maize (Zea mays L.). An activated wood biochar, pyrolysed at 550°C, was applied at 3 rates (0, 5, and 15 g/kg) in factorial combinations with 3 rates (0, 10, and 50 mg/kg) each of As, Cd, Cu, Pb, and Zn separately to a sandy soil. After 10 weeks of growth, plants were harvested, shoot dry matter yield was measured, and concentration of trace elements in shoots was analysed. The soil in pots was analysed for extractable trace elements. The results showed that the addition of wood biochar to soil did not have any significant effect on the dry matter yield of maize plants, even at the highest rate of application. However, trace element application significantly reduced the dry matter yield from 10 to 93% depending on the type of trace element. Biochar application decreased the concentration of As, Cd, and Cu in maize shoots, especially at the highest rate of trace element application, whereas the effects were inconsistent on Pb and Zn concentrations in the shoots. The concentrations of extractable As and Zn in soil increased with biochar application, whereas extractable Cu did not change, Pb decreased, and Cd showed an inconsistent trend. Sorption of trace elements on biochar with initial loadings up to 200 µmol at pH 7 occurred in the order: Pb > Cu > Cd > Zn > As. The results show that biochar application can significantly reduce the availability of trace elements to plants and suggest that biochar application may have potential for the management of soils contaminated by trace elements.
Characterisation and evaluation of biochars for their application as a soil amendment
Authors: Singh Balwant , Singh Bhupinder Pal , Cowie Annette L.
Published: September 2010

Biochar properties can be significantly influenced by feedstock source and pyrolysis conditions; this warrants detailed characterisation of biochars for their application to improve soil fertility and sequester carbon. We characterised 11 biochars, made from 5 feedstocks [Eucalyptus saligna wood (at 400°C and 550°C both with and without steam activation); E. saligna leaves (at 400°C and 550°C with activation); papermill sludge (at 550°C with activation); poultry litter and cow manure (each at 400°C without activation and at 550°C with activation)] using standard or modified soil chemical procedures. Biochar pH values varied from near neutral to highly alkaline. In general, wood biochars had higher total C, lower ash content, lower total N, P, K, S, Ca, Mg, Al, Na, and Cu contents, and lower potential cation exchange capacity (CEC) and exchangeable cations than the manure-based biochars, and the leaf biochars were generally in-between. Papermill sludge biochar had the highest total and exchangeable Ca, CaCO3 equivalence, total Cu, and potential CEC, and the lowest total and exchangeable K. Water-soluble salts were higher in the manure-based biochars, followed by leaf, papermill sludge, and wood biochars. Total As, Cd, Pb, and polycyclic aromatic hydrocarbons in the biochars were either very low or below detection limits. In general, increase in pyrolysis temperature increased the ash content, pH, and surface basicity and decreased surface acidity. The activation treatment had a little effect on most of the biochar properties. X-ray diffraction analysis showed the presence of whewellite in E. saligna biochars produced at 400°C, and the whewellite was converted to calcite in biochars formed at 550°C. Papermill sludge biochar contained the largest amount of calcite. Water-soluble salts and calcite interfered with surface charge measurements and should be removed before the surface charge measurements of biochar. The biochars used in the study ranged from C-rich to nutrient-rich to lime-rich soil amendment, and these properties could be optimised through feedstock formulation and pyrolysis temperature for tailored soil application.