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During human brain development through infancy and childhood, microstructural and macrostructural changes take place to reshape the brain's structural networks and better adapt them to sophisticated functional and cognitive requirements. However, structural topological configuration of the human brain during this specific development period is not well understood. In this study, diffusion magnetic resonance image (dMRI) of 25 neonates, 13 toddlers, and 25 preadolescents were acquired to characterize network dynamics at these 3 landmark cross-sectional ages during early childhood. dMRI tractography was used to construct human brain structural networks, and the underlying topological properties were quantified by graph-theory approaches. Modular organization and small-world attributes are evident at birth with several important topological metrics increasing monotonically during development. Most significant increases of regional nodes occur in the posterior cingulate cortex, which plays a pivotal role in the functional default mode network. Positive correlations exist between nodal efficiencies and fractional anisotropy of the white matter traced from these nodes, while correlation slopes vary among the brain regions. These results reveal substantial topological reorganization of human brain structural networks through infancy and childhood, which is likely to be the outcome of both heterogeneous strengthening of the major white matter tracts and pruning of other axonal fibers., (© The Author 2013. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

We investigate the influence of foliation orientation and fine-scale folding on the static and dynamic elastic properties and unconfined strength of the Poorman schist. Measurements from triaxial and uniaxial laboratory experiments reveal a significant amount of variability in the static and dynamic Young’s modulus depending on the sample orientation relative to the foliation plane. Dynamic P-wave modulus and S-wave modulus are stiffer in the direction parallel to the foliation plane as expected for transversely isotropic mediums with average Thomsen parameters values 0.133 and 0.119 for epsilon and gamma, respectively. Static Young’s modulus varies significantly between 21 and 117 GPa, and a peculiar trend is observed where some foliated sample groups show an anomalous decrease in the static Young’s modulus when the symmetry axis (x3-axis) is oriented obliquely to the direction of loading. Utilizing stress and strain relationships for transversely isotropic medium, we derive the analytical expression for Young’s modulus as a function of the elastic moduli E1, E3, ν31, and G13 and sample orientation to fit the static Young’s modulus measurements. Regression of the equation to the Young’s modulus data reveals that the decrease in static Young’s modulus at oblique symmetry axis orientations is directly influenced by a low shear modulus, G13, which we attribute to shear sliding along foliation planes during static deformation that occurs as soon as the foliation is subject to shear stress. We argue that such difference between dynamic and static anisotropy is a characteristic of near-zero porosity anisotropic rocks. The uniaxial compressive strength also shows significant variability ranging from 21.9 to 194.6 MPa across the five sample locations and is the lowest when the symmetry axis is oriented 45° or 60° from the direction of loading, also a result of shear sliding along foliation planes during static deformation.

The state with effective total moment Jeff = 1/2 stabilized by the spin-orbit coupling is known to suppress Jahn-Teller distortions and may induce a strong exchange anisotropy. This in turn may lead to the formation of an elusive spin-liquid state in real materials. While recent studies have demonstrated that such a situation can be realized in 3d transition-metal compounds such as those based on Co2+ and Cu2+, diagnosis of Jeff = 1/2 state remains challenging. We show that resonant inelastic X-ray scattering is an effective tool to probe this state and apply it to CuAl2O4, material where Cu2+ ions were previously proposed to be in the Jeff = 1/2 state. Our results unambiguously demonstrate that, contrary to previous expectations, a competitive (to Jeff = 1/2) Jahn-Teller state realizes in this compound. [ABSTRACT FROM AUTHOR]

We investigated the current-induced magnetization switching in a Heusler alloy Co2FeAl-based spin-valve nanopillar by using micromagnetic simulations. We demonstrated that the elimination of the intermediate state is originally resulted from the decease of effective magnetic anisotropy constant. The magnetization switching can be achieved at a small current density of 1.0×104 A/cm2 by increasing the demagnetization factors of x and y axes. Based on our simulation, we found magnetic anisotropy and demagnetization energies have different contributions to the magnetization switching. © 2014 AIP Publishing LLC. [ABSTRACT FROM AUTHOR]

We investigated the spin-transfer switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin-valve nanopillar through micromagnetic simulation. A two-step switching hysteresis loop due to the fourfold in-plane magnetocrystalline anisotropy of Co2FeAl0.5Si0.5 layers was obtained. The simulation explains the experimental result of the resistance versus current hysteresis loop and yields good agreement with the measured critical current. Furthermore, the magnetization trajectory and magnetization distribution were shown and analyzed to elucidate the different characters of two-step switching. [ABSTRACT FROM AUTHOR]

This work investigates the effect of the polarization anisotropy on the linewidth enhancement factor and the reflection sensitivity of InAs/InP quantum dash semiconductor lasers. The results show that the small linewidth enhancement factor and high stability against external optical feedback are obtained for nanostructures oriented perpendicular to the cavity axis as opposed to those oriented parallel to the cavity axis. Effective simulations on the critical feedback level of these two lasers are also in agreement with experimental results. Such anisotropy is attributed to the polarization dependence of the transition matrix element in these quantum nanostructures. [ABSTRACT FROM AUTHOR]

Fluid identification in fractured reservoirs is a challenging issue and has drawn increasing attentions. As aligned fractures in subsurface formations can induce anisotropy, we must choose parameters independent with azimuths to characterize fractures and fluid effects such as anisotropy parameters for fractured reservoirs. Anisotropy is often frequency dependent due to wave-induced fluid flow between pores and fractures. This property is conducive for identifying fluid type using azimuthal seismic data in fractured reservoirs. Through the numerical simulation based on Chapman model, we choose the P-wave anisotropy parameter dispersion gradient (PADG) as the new fluid factor. PADG is dependent both on average fracture radius and fluid type but independent on azimuths. When the aligned fractures in the reservoir are meter-scaled, gas-bearing layer could be accurately identified using PADG attribute. The reflection coefficient formula for horizontal transverse isotropy media by Rüger is reformulated and simplified according to frequency and the target function for inverting PADG based on frequency-dependent amplitude versus azimuth is derived. A spectral decomposition method combining Orthogonal Matching Pursuit and Wigner-Ville distribution is used to prepare the frequency-division data. Through application to synthetic data and real seismic data, the results suggest that the method is useful for gas identification in reservoirs with meter-scaled fractures using high-qualified seismic data. [ABSTRACT FROM AUTHOR]

Ordered L10 FePt films with magnetic perpendicular anisotropy were fabricated with a Pt/Cr bilayer. The squareness of the L10 FePt film with a Cr underlayer and a Pt buffer was close to one when a magnetic field was applied perpendicular to the film’s plane, because a semicoherent epitaxial growth was initiated from the Cr (002) underlayer; continued through the Pt buffer layer, and extended into the L10 FePt (001) magnetic layer. Without the Pt buffer layer, the Cr atoms may diffuse directly into the FePt magnetic layer. Consequently, an epitaxial barrier of the Cr-rich FePtCr alloy formed between the Cr underlayer and the FePt magnetic layer, degrading the magnetic performance and epitaxial growth of the latter. [ABSTRACT FROM AUTHOR]

Presents an equation for the damped dynamics of magnetization in ferromagnets. Information on a ferromagnet mathematical model with uniaxial anisotropy; Discussion on the relaxation of the modulus of magnetization; Derivation of the equation for the damped dynamics of magnetization in ferromagnets.

Presents information on a study on the anisotropy and Faraday effect of cobalt ferrite films made by radio frequency sputtering and annealed at different temperatures. Experimental procedure; Results and discussion; Conclusion.

Abstract: Cu6Sn5 is an important intermetallic compound (IMC) commonly formed during lead-free soldering. It is known that Cu6Sn5 exhibits significantly different thermo-mechanical deformation behaviour compared to both bulk solder alloys and their substrates. In high-density 3-D electrical packages individual solder joints may contain only a few grains of Cu6Sn5. The knowledge of the mechanical properties, creep and crack behaviour of Cu6Sn5 on different crystal planes is therefore essential to understanding the deformation of lead-free solder joints in service. In this research, the mechanical properties, creep and crack patterns on diverse crystal planes of hexagonal Cu6Sn5 and (Cu,Ni)6Sn5 were investigated using electron back scattered diffraction (EBSD), scanning electron microscopy (SEM) and nanoindentation. It was found that the mechanical properties, creep and crack patterns of hexagonal Cu6Sn5 were strongly related to the crystal orientation. The addition of Ni was found to reduce the anisotropy in hardness and the creep of Cu6Sn5 and had a significant effect on the crack patterns of Cu6Sn5. [Copyright &y& Elsevier]

Abstract: The mechanical reliability of solder joints is influenced by a layer of Cu6Sn5 intermetallics (IMC) present at the interface of tin-based solders/Cu substrates. We have discovered that the mechanical properties of hexagonal Cu6Sn5 are strongly related to the crystal orientation, using Electron Back Scattered Diffraction (EBSD) and nanoindentation on unidirectionally solidified Sn–4wt% Cu with/without 0.05wt% Ni. This fundamental discovery on the anisotropic mechanical properties of Cu6Sn5 may find practical applications in designing soldering processes to obtain preferred IMC orientations. [Copyright &y& Elsevier]

Tadpole-shaped (Ni, Al)/AlN nanoparticles were synthesized via evaporating Ni-Al alloy in a mixed atmosphere of N2 and H2. As a counterpart, the spherical-shaped (Ni, Al)/Al2O3 nanoparticles were also prepared from the same target alloy while in a mixture of Ar and H2. The electromagnetic parameters of as-made nanoparticles/paraffin composites were then investigated in the frequency range of 2-18 GHz. Excellent microwave absorption can be obtained for the tadpole-shaped (Ni, Al)/AlN-paraffin composite at high frequencies and in a thin layer, which is thought to be the result of the enhanced polarization in the anisotropic tadpole-shaped nanoparticles. With the increasing of the composite thickness, the frequency of effective reflection loss shifts towards lower frequencies due to an improved impedance match and absorption. [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) lattice model with anisotropic resonant microstructures is found to provide an anisotropic band gap structure. A 2D continuum with anisotropic effective mass density is introduced to represent this lattice system. Two methods are proposed to derive the equivalent continuum. In the first method, the effective mass density of the equivalent continuum is obtained by matching the dispersion relations for harmonic waves propagating in the principal directions. The second approach employs an approximate estimation of the effective mass density by volume-averaging an effective mass that represents the resonant microstructure. For both equivalent continuum models, the effective mass density is frequency-dependent and may become negative in certain frequency ranges. Subsequently, the effective mass density of the equivalent continuum assumes the form of a second-order tensor. Thus, it suffices to determine the effective mass density tensor with respect to the principle directions. It is shown numerically that the local-resonance effect is accurately described by the equivalent continuum model. In addition, the effect of anisotropic mass density on wave propagation is numerically illustrated and discussed. [ABSTRACT FROM AUTHOR]

In this paper we study multiphase models for simultaneous heat and mass transfer processes during bread baking. Our main objective is to provide an explanation and a remedy to the observed erroneous and/or divergent results associated with an instantaneous phase change model used in the literature. We propose a reaction-diffusion model based on the Hertz-Knudsen equation, where phase change is not instantaneous but determined by an evaporation/condensation rate. A splitting scheme is designed for the reaction-diffusion model so that a link between these two models can be established and the nonintuitive numerical instability associated with the instantaneous phase change model can be identified and eliminated. The evaporation/condensation rate is estimated by comparing results of the reaction-diffusion model with experimental observations reported in the literature. For evaporation/condensation rate beyond the estimated value, oscillatory solution with multiple regions of dry and two-phase zones is observed. We show that these are caused by an instability intrinsic to the model (which we call diffusive instability) using linear stability analysis and numerical tests. [ABSTRACT FROM AUTHOR]

The propagation process and the anisotropy of the indentation cracks of poled PZT-5H ferroelectric ceramics in air and water under sustained load were investigated using Vickers indentation equipment. It is found that the length of the indentation cracks increased with increasing time to keep indentation load in air and water, thus, sub-critical crack growth or stress corrosion cracking (SCC) under sustained load occurred. For the cracks parallel to the poling direction, the threshold stress intensity factor for cracks arrest, K ISCC , is larger, whereas the crack propagation rate, da/dt, is smaller than those for the cracks perpendicular to the poling direction. The anisotropy of susceptibility to SCC is related to the anisotropy of fracture toughness. The larger the fracture toughness is, the more susceptibility to SCC is, that is, the smaller the K ISCC is, the larger the da/dt is. [ABSTRACT FROM AUTHOR]

A dislocation-based boundary-element method (BEM) is presented to provide solutions to the crack problems in anisotropic half-planes. The boundary of the half-plane is first modeled by a dislocation array, which is then discretized into boundary elements. Each element is simulated as a continuous dislocation array with linear distribution between the two element nodes. As a result, the singular integral equations derived from the continuous dislocation method for each element can be solved analytically. After the dislocation densities at the element nodes are determined from the prescribed traction forces along the half-plane boundary, the elastic solution of the halfplane can be calculated. Two basic solutions for an anisotropic half plane, that is, traction boundary solution and dislocation solution, are derived and compared with the analytical solutions. These solutions are then applied to solve crack problems in the half-plane subjected to different loading. The results from the dislocation-based BEM are compared with those from the analytical solutions to verify the described BEM. Excellent agreements are achieved for all of the cases. [ABSTRACT FROM AUTHOR]

The effect of WO3 on mullite formation and mullite whisker morphology, in oxide mixtures activated by a high-energy ball milling process, was investigated. Differential thermal analysis (DTA) measurement indicated that WO3 enhanced the mullite phase formation, with mullitization temperature of 951 °C, 921 °C and 835 °C for the samples doped with 5, 10 and 20 mol% WO3, respectively. However, the presence of WO3 had an undesired effect on the whisker morphology. A decrease in the length of mullite whisker was observed with increasing WO3 content. The effect of WO3 on the mullite phase formation temperature, as well as the whisker morphology, was explained using a dissolution-precipitation mechanism. [Copyright &y& Elsevier]

Exact solutions for interfacial edge dislocations in an anisotropic bicrystal under plane strain are derived in elementary closed-form by the method of image dislocations. The stresses in the two adjoining crystals, which may have dissimilar elastic constants and/or dissimilar material axis orientations, are shown to be given by the sum of three rational functions of first to second order degree polynomials. Numerical results for an interfacial glide edge dislocation in several bicrystals of hexagonal ceramics show complex dependence on the material and orientational inhomogeneities. In particular, the interfacial stresses when plotted against the c-axis orientations of the two crystals are shown to possess extrema, saddle points, and a center of symmetry/antisymmetry. [Copyright &y& Elsevier]

This article cites a study to measure local cell stiffness, local contraction force and the elasticity of the mechanical coupling between the cytoskeleton and the extracellular matrix. The highly organized cytoskeletal structure of adult cardiac myocytes immediately suggests an anisotropic material behavior, but most current techniques fail to provide accurate measurements of anisotropic mechanical properties. This method allows independent measurement of the cytoskeletal stiffness in arbitrary directions and thus can quantify the cytoskeletal properties more accurately.

Initial stress (σi) of a room-temperature deposited FePt films was manipulated to study the order-disorder transformation. We observed that, while σi was increased from -1.01 (compressive) to 0.18 GPa (tensile), the phase transformation activation energy decreased from 0.387 to 0.23 eV/atom. This causes a reduction in ordering temperature of about 100 °C. We also found that densification induces an increase in tensile stress of about 1 GPa before ordering. In the films with small σi, strong tension facilitates the nucleation of L10 FePt; however, if highly compressive σi cancels the densification tension, ordering is retarded causing higher ordering temperature. [ABSTRACT FROM AUTHOR]

Polycrystalline magnetostrictive alloys Pr(Fe1-xCox)1.9 (0≤x≤0.5) with cubic Laves phase were synthesized by high-pressure annealing. Measurements of Curie temperature, easy magnetic direction (EMD), and magnetostriction were made on these alloys. The EMD of the alloys rotates continuously from <111> for x=0.0 to <110> for x=0.3 and then shows a tendency to <111> with further increasing x. Two magnetostriction peaks at low fields are observed around x=0.2 and x=0.4 due to the lower anisotropy of these two alloys, which is consistent with the variation of EMD. This work demonstrates that the composition anisotropy compensation can be realized in Pr(Fe1-xCox)1.9 system [ABSTRACT FROM AUTHOR]

The carbon-coated Ni(C) nanocapsules were prepared by a modified arc-discharge method in methane atmosphere. Its electromagnetic parameters were measured at 2–18 GHz. It is observed that the natural resonance which appeared at 5.5 GHz is dominant among microwave absorption properties of Ni(C) nanocapsules, as the consequence of the increased surface anisotropic energy for nanosized particles. The measured relative complex permittivity indicates that a high resistivity existed in Ni(C) nanocapsules samples. The maximum reflection loss of Ni(C) nanocomposites can reach 32 dB at 13 GHz with 2 mm in thickness. The microwave absorptive mechanisms of Ni(C) nanocapsule absorbent were discussed. [ABSTRACT FROM AUTHOR]

A multilevel cell spin transfer switching process in a full-Heusler Co2FeAl0.5Si0.5 alloy spin-valve nanopillar was investigated using micromagnetic simulations. An intermediate state of two-step spin transfer magnetization switching was reported due to the four-fold magnetocrystalline anisotropy; however, we discovered the intermediate state has two possible directions of -90° and +90°, which could not be detected in the experiments due to the same resistance of the -90° state and the +90° state. The domain structures were analyzed to determine the mechanism of domain wall motion and magnetization switching under a large current. Based on two intermediate states, we reported a multilevel bit spin transfer multi-step magnetization switching by changing the magnetic anisotropy in a full-Heusler alloy nanopillar. [ABSTRACT FROM AUTHOR]

Mullite phase formation and grain growth, in a CuO-doped Al2O3 and silica mixture, has been investigated. The oxide mixture was activated with both stainless steel and tungsten carbide milling media. The milled powders demonstrated a much lower mullite formation temperature when compared to the conventional solid-state reaction process. Anisotropic grain growth was observed in the powders milled with stainless steel media, while well-shaped mullite whiskers were produced in the WC milled samples. The lowered mullitization temperature together with the anisotropic grain growth behavior was attributed to the refined microstructure of the powders as a result of the high-energy ball milling process. [Copyright &y& Elsevier]

The Landsat satellites have been providing spectacular imagery of the Earth's surface for over 40 years. However, they acquire images at view angles ± 7.5° from nadir that cause small directional effects in the surface reflectance. There are also variations with solar zenith angle over the year that can cause apparent change in reflectance even if the surface properties remain constant. When Landsat data from adjoining paths, or from long time series are used, a model of the surface anisotropy is required to adjust all Landsat observations to a uniform nadir view (primarily for visual consistency, vegetation monitoring, or detection of subtle surface changes). Here a generalized approach is developed to provide consistent view angle corrections across the Landsat archive. While this approach is not applicable for generation of Landsat surface albedo, which requires a full characterization of the surface bidirectional reflectance distribution function (BRDF), or for correction to a constant solar illumination angle across a wide range of sun angles, it provides Landsat nadir BRDF-adjusted reflectance (NBAR) for a range of terrestrial monitoring applications. The Landsat NBAR is derived as the product of the observed Landsat reflectance and the ratio of the reflectances modeled using MODIS BRDF spectral model parameters for the observed Landsat and for a nadir view and fixed solar zenith geometry. In this study, a total of 567 conterminous United States (CONUS) January and July 2010 Landsat 5 Thematic Mapper (TM) and Landsat 7 Enhanced Thematic Mapper (ETM +) images that have swath edge overlapping paths sensed in alternating backscatter and forward scattering orientations were used. The average difference between Landsat 5 TM and Landsat 7 ETM + surface reflectance in the forward and backward scatter directions at the overlapping Landsat scan edges was quantified. The CONUS July view zenith BRDF effects were about 0.02 in the Landsat visible bands, and about 0.03, 0.05 and 0.06, in the 2.1 μm, 1.6 μm and near-infrared bands respectively. Comparisons of Landsat 5 TM and Landsat 7 ETM + NBAR derived using MODIS BRDF spectral model parameters defined with respect to different spatial and temporal scales, and defined with respect to different land cover types, were undertaken. The results suggest that, because the BRDF shapes of different terrestrial surfaces are sufficiently similar over the narrow 15° Landsat field of view, a fixed set of MODIS BRDF spectral model parameters may be adequate for Landsat NBAR derivation with little sensitivity to the land cover type, condition, or surface disturbance. A fixed set of BRDF spectral model parameters, derived from a global year of highest quality snow-free MODIS BRDF product values, are provided so users may implement the described Landsat NBAR generation method. [ABSTRACT FROM AUTHOR]

High-energy ball milling had a great influence on phase formation and morphology development of mullite derived from oxide precursors. Mullite phase was formed at 1300 °C in an oxide mixture of Al2O3 and quartz without high-energy ball milling and the mullitization was not complete up to 1500 °C. After milling for 5 h, the mullitization temperature was reduced by about 200 °C. At the same time, mullite whiskers were obtained. Based on these results, microstructural composite mullite ceramics were proposed to be made from the mixtures of the oxide precursors with and without the high-energy ball milling. The unmilled precursor was sintered to equiaxed grains while the milled one resulted in anisotropic grains. The relative proportion of the equiaxed and anisotropic grains could be readily adjusted by the precursor mixtures. Moreover, the mullite crystallites coming from the milled precursor powder at low temperature acted as seeds to enhance the mullite phase formation of the composites. It is believed that the mullite whiskers produced in this way can also be used as reinforcing components to design structural composites of others materials. [Copyright &y& Elsevier]