bluuebunny/crossref_metadata_2025 huggingface dataset:
An X-ray absorption spectroscopy study of the inversion degree in zinc ferrite nanocrystals dispersed on a highly porous silica aerogel matrix
Authors: Carta D. , Marras C. , Loche D. , Mountjoy G. , Ahmed S. I. , Corrias A.
Published: February 2013

The structural properties of zinc ferrite nanoparticles with spinel structure dispersed in a highly porous SiO2 aerogel matrix were compared with a bulk zinc ferrite sample. In particular, the details of the cation distribution between the octahedral (B) and tetrahedral (A) sites of the spinel structure were determined using X-ray absorption spectroscopy. The analysis of both the X-ray absorption near edge structure and the extended X-ray absorption fine structure indicates that the degree of inversion of the zinc ferrite spinel structures varies with particle size. In particular, in the bulk microcrystalline sample, Zn2+ ions are at the tetrahedral sites and trivalent Fe3+ ions occupy octahedral sites (normal spinel). When particle size decreases, Zn2+ ions are transferred to octahedral sites and the degree of inversion is found to increase as the nanoparticle size decreases. This is the first time that a variation of the degree of inversion with particle size is observed in ferrite nanoparticles grown within an aerogel matrix.
Orientation correlation of p-nitroaniline molecules in acetone solution observed by hyper-Rayleigh scattering
Authors: Shelton David P.
Published: February 2013

Measurements of the polarization dependence of hyper-Rayleigh scattering (HRS) by solutions of p-nitroaniline (PNA) in acetone-d6 were used to study molecular orientation correlations. The HRS observations were analyzed in terms of short range direct dipole-dipole correlations between the PNA molecules, a long range transverse polar mode for the PNA molecules, and a long range ion-induced longitudinal polar mode. The conclusion that long range correlations are present is opposite to that in previous work, due to previous neglect of the ion-induced contribution. Depolarized HRS not explained by local correlations appears above 0.1 M PNA concentration, and analysis of the HRS observations indicates strong orientation correlations with a range of 10 nm for the PNA molecules.
Shape of a large drop on a rough hydrophobic surface
Authors: Park Joonsik , Park Jaebum , Lim Hyuneui , Kim Ho-Young
Published: February 2013

Large drops on solid surfaces tend to flatten due to gravitational effect. Their shapes can be predicted by solving the Young-Laplace equation when their apparent contact angles are precisely given. However, for large drops sitting on rough surfaces, the apparent contact angles are often unavailable a priori and hard to define. Here we develop a model to predict the shape of a given volume of large drop placed on a rough hydrophobic surface using an overlapping geometry of double spheroids and the free energy minimization principle. The drop shape depends on the wetting state, thus our model can be used not only to predict the shape of a drop but also to infer the wetting state of a large drop through the comparison of theory and experiment. The experimental measurements of the shape of large water drops on various micropillar arrays agree well with the model predictions. Our theoretical model is particularly useful in predicting and controlling shapes of large drops on surfaces artificially patterned in microscopic scales, which are frequently used in microfluidics and lab-on-a-chip technology.
Supertransvectants, cohomology, and deformations
Authors: Ben Fraj Nizar , Laraiedh Ismail , Omri Salem
Published: February 2013

Over the (1, N)-dimensional real superspace, N = 2, 3, we classify \documentclass[12pt]{minimal}\begin{document}$\mathfrak {osp}(N|2)$\end{document}osp(N|2)-invariant binary differential operators acting on the superspaces of weighted densities, where \documentclass[12pt]{minimal}\begin{document}$\mathfrak {osp}(N|2)$\end{document}osp(N|2) is the orthosymplectic Lie superalgebra. This result allows us to compute the first differential \documentclass[12pt]{minimal}\begin{document}$\mathfrak {osp}(N|2)$\end{document}osp(N|2)-relative cohomology of the Lie superalgebra \documentclass[12pt]{minimal}\begin{document}$\mathcal {K}(N)$\end{document}K(N) of contact vector fields with coefficients in the superspace of linear differential operators acting on the superspaces of weighted densities. We classify generic formal \documentclass[12pt]{minimal}\begin{document}$\mathfrak {osp}(3|2)$\end{document}osp(3|2)-trivial deformations of the \documentclass[12pt]{minimal}\begin{document}$\mathcal {K}(3)$\end{document}K(3)-module structure on the superspaces of symbols of differential operators. We prove that any generic formal \documentclass[12pt]{minimal}\begin{document}$\mathfrak {osp}(3|2)$\end{document}osp(3|2)-trivial deformation of this \documentclass[12pt]{minimal}\begin{document}$\mathcal {K}(3)$\end{document}K(3)-module is equivalent to its infinitesimal part. This work is the simplest generalization of a result by the first author et al. [Basdouri, I., Ben Ammar, M., Ben Fraj, N., Boujelbene, M., and Kammoun, K., “Cohomology of the Lie superalgebra of contact vector fields on \documentclass[12pt]{minimal}\begin{document}$\mathbb {K}^{1|1}$\end{document}K1|1 and deformations of the superspace of symbols,” J. Nonlinear Math. Phys. 16, 373 (2009)10.1142/S1402925109000431].
Self-organized circular flow of classical point particles
Authors: Malyshev V. A.
Published: February 2013

We consider Newtonian dynamics of N charged particles on the circle with nearest neighbour interaction with Coulomb repulsive potential r−1. Also there is an external accelerating force which is non-zero only on a small part of the circle. We construct homogeneous solutions where the velocities of all particles are approximately equal and their density is approximately uniform. This gives a qualitative mathematical model for some features of the direct electric current, in agreement with a suggestion by R. Feynman.
A semi-phenomenological model to predict the acoustic behavior of fully and partially reticulated polyurethane foams
Authors: Doutres Olivier , Atalla Noureddine , Dong Kevin
Published: February 2013

This paper proposes simple semi-phenomenological models to predict the sound absorption efficiency of highly porous polyurethane foams from microstructure characterization. In a previous paper [J. Appl. Phys. 110, 064901 (2011)], the authors presented a 3-parameter semi-phenomenological model linking the microstructure properties of fully and partially reticulated isotropic polyurethane foams (i.e., strut length l, strut thickness t, and reticulation rate Rw) to the macroscopic non-acoustic parameters involved in the classical Johnson-Champoux-Allard model (i.e., porosity ϕ, airflow resistivity σ, tortuosity α∝, viscous Λ, and thermal Λ′ characteristic lengths). The model was based on existing scaling laws, validated for fully reticulated polyurethane foams, and improved using both geometrical and empirical approaches to account for the presence of membrane closing the pores. This 3-parameter model is applied to six polyurethane foams in this paper and is found highly sensitive to the microstructure characterization; particularly to strut's dimensions. A simplified micro-/macro model is then presented. It is based on the cell size Cs and reticulation rate Rw only, assuming that the geometric ratio between strut length l and strut thickness t is known. This simplified model, called the 2-parameter model, considerably simplifies the microstructure characterization procedure. A comparison of the two proposed semi-phenomenological models is presented using six polyurethane foams being either fully or partially reticulated, isotropic or anisotropic. It is shown that the 2-parameter model is less sensitive to measurement uncertainties compared to the original model and allows a better estimation of polyurethane foams sound absorption behavior.
The effect of defects and their passivation on the density of states of the 4H-silicon-carbide/silicon-dioxide interface
Authors: Salemi S. , Goldsman N. , Ettisserry D. P. , Akturk A. , Lelis A.
Published: February 2013

The 4H-SiC(0001)/SiO2 interface has a variety of likely defects as reported in the literature. We investigate the defects at the SiC side of the interface using density functional theory. We also investigate the effects of passivating these states. The defects studied include a single carbon interstitial, a carbon pair interstitial, and a silicon vacancy at the interface. Density functional theory has been employed to calculate the total and projected density of states (pDOS) and the energy levels of the defects. The results of our calculations indicate that a carbon interstitial and a pair of carbons give rise to traps near the conduction band and valence band. The silicon vacancy gives rise to traps that are closer to the valence band. The effects of hydrogen and nitrogen passivation on the defect energy levels have been investigated. Our studies indicate that hydrogen and nitrogen passivation can eliminate states near the conduction and valence bands, although in some cases they may introduce levels in the midgap.
Plasma electron source for the generation of wide-aperture pulsed beam at forevacuum pressures
Authors: Oks E. , Burdovitsin V. , Medovnik A. , Yushkov Yu.
Published: February 2013

This article reports on design and application of wide-aperture pulsed beam source, based on hollow cathode discharge. The source is intended for electron beam generation in pressure range 2–15 Pa. Multi-aperture extraction system, used in a source, provided beam cross-section uniformity of 10% on diameter 40 mm. The limiting values of the current density, pulse duration, and accelerating voltage are 350 mA/cm2, 250 μs, and 10 kV, respectively. These parameters are sufficient for surface modification of various materials, including non-conducting matters.
Electrical conductance across self-assembled lipid bilayers
Authors: Guha Ingrid , Kedzierski Jakub , Abedian Behrouz
Published: February 2013

This study investigates electrical conduction across lipid bilayers that self-assemble in oil between a water drop and a hafnium oxide surface. Morphology and electrical properties of two bilayers formed from equal molar concentrations of sorbitan monooleate (Span 80) and sorbitan trioleate (Span 85) in dodecane are quantified and compared. The molecular structures of the two surfactants are quite similar, except that sorbitan monooleate contains one unsaturated lipid tail per molecule, whereas sorbitan trioleate contains three. We find that the leakage current density across both bilayers increases exponentially with electric field. The relative leakage current densities across the two bilayers scale with the packing density of lipid tails in the bilayers. This correlation provides evidence that the lipid tail interactions through thermal fluctuations provide a pathway of electrical conduction across the membrane.
Direct evidence of mismatching effect on H emission in laser-induced atmospheric helium gas plasma
Authors: Sukra Lie Zener , On Tjia May , Hedwig Rinda , Margaretha Suliyanti Maria , Nur Abdulmadjid Syahrun , Idris Nasrullah , Mangasi Marpaung Alion , Pardede Marincan , Jobiliong Eric , Ramli Muliadi , Suyanto Heri , Fukumoto Kenichi , Kagawa Kiichiro , Hendrik Kurniawan Koo
Published: February 2013

A time-resolved orthogonal double pulse laser-induced breakdown spectroscopy (LIBS) with helium surrounding gas is developed for the explicit demonstration of time mismatch between the passage of fast moving impurity hydrogen atoms and the formation of thermal shock wave plasma generated by the relatively slow moving major host atoms of much greater masses ablated from the same sample. Although this so-called “mismatching effect” has been consistently shown to be responsible for the gas pressure induced intensity diminution of hydrogen emission in a number of LIBS measurements using different ambient gases, its explicit demonstration has yet to be reported. The previously reported helium assisted excitation process has made possible the use of surrounding helium gas in our experimental set-up for showing that the ablated hydrogen atoms indeed move faster than the simultaneously ablated much heavier major host atoms as signaled by the earlier H emission in the helium plasma generated by a separate laser prior to the laser ablation. This conclusion is further substantiated by the observed dominant distribution of H atoms in the forward cone-shaped target plasma.
Voltage-controlled surface plasmon-polaritons in double graphene layer structures
Authors: Svintsov D. , Vyurkov V. , Ryzhii V. , Otsuji T.
Published: February 2013

The spectra and damping of surface plasmon-polaritons (SPPs) in double graphene layer structures are studied. It is proved that SPPs in those structures exhibit an outstanding voltage tunability of velocity and damping, inherent to gated graphene, and a pronounced low-frequency coupling with photons inherent to non-gated structures. It is also shown that the spatial dispersion of conductivity significantly augments the free path and cutoff frequency of SPPs, which is of great importance for practical applications.
Simultaneous optical and photoacoustic measurement of nonlinear absorption
Authors: Chantharasupawong Panit , Philip Reji , Thomas Jayan
Published: February 2013

A measurement technique to perform optical Z-scan and photoacoustic Z-scan simultaneously called OPAZ-scan is demonstrated. It is found that the simultaneous measurement of the optical and photoacoustic Z-scan signals provides substantially better insight into the mechanism of optical nonlinearity. The system is able to identify mixed nonlinear processes within a mixture of nonlinear scattering species and nonlinear absorbers.
Unified understanding of both thermally assisted and precessional spin-transfer switching in perpendicularly magnetized giant magnetoresistive nanopillars
Authors: Tomita H. , Miwa S. , Nozaki T. , Yamashita S. , Nagase T. , Nishiyama K. , Kitagawa E. , Yoshikawa M. , Daibou T. , Nagamine M. , Kishi T. , Ikegawa S. , Shimomura N. , Yoda H. , Suzuki Y.
Published: February 2013

We report on the spin-transfer magnetization switching properties of CoFe/Pd-based perpendicularly magnetized giant magnetoresistive cells over a wide current pulse duration time range. Analytic expressions without empirical parameters like attempt frequency are tested experimentally for the thermally assisted and precessional regimes. Good agreement with the experiment data is obtained using a common parameter set in both regimes, which leads to a comprehensive understanding of the switching properties including the origin of the attempt frequency.
An in situ diffraction study of domain wall motion contributions to the frequency dispersion of the piezoelectric coefficient in lead zirconate titanate
Authors: Seshadri Shruti B. , Prewitt Anderson D. , Studer Andrew J. , Damjanovic Dragan , Jones Jacob L.
Published: February 2013

The contribution of non-180° domain wall displacement to the frequency dependence of the longitudinal piezoelectric coefficient has been determined experimentally in lead zirconate titanate using time-resolved, in situ neutron diffraction. Under subcoercive electric fields of low frequencies, approximately 3% to 4% of the volume fraction of non-180° domains parallel to the field experienced polarization reorientation. This subtle non-180° domain wall motion directly contributes to 64% to 75% of the magnitude of the piezoelectric coefficient. Moreover, part of the 33 pm/V decrease in piezoelectric coefficient across 2 orders of magnitude in frequency is quantitatively attributed to non-180° domain wall motion effects.
Ab initio atomistic thermodynamics calculations of the initial deposition of epitaxial MgO film on GaAs(001)-β2(2 × 4)
Authors: Tamarany Rizcky , Kim Hyung-Jun , Choi Jung-Hae , Lee Seung-Cheol
Published: February 2013

Ab initio calculations were performed to investigate the initial deposition of epitaxial MgO on GaAs(001)-β2(2 × 4). The differences between the chemical bonding of Mg-As and O-As were characterized by the adsorption energies of atomic O and Mg at several symmetrically distinct sites, and O bonding was substantially stronger than that of Mg. Thermodynamics were analyzed through the introduction of environmental chemical potentials simulating in situ growth conditions by the sputtering of a stoichiometric MgO target. A surface phase diagram was generated under Mg and O environments with constrained equilibrium, and the results explained the initial formation of an epitaxial MgO phase on GaAs(001)-β2(2 × 4).
Giant enhancement of phonon-assisted one-photon excited frequency upconversion in a Nd3+-doped tellurite glass
Authors: Marques M. S. , Menezes L. de S. , Lozano B. W. , Kassab L. R. P. , de Araújo C. B.
Published: February 2013

Changing the sample's temperature from 200 K to 535 K, we observed 670-fold enhancement of a phonon-assisted upconversion emission at ≈754 nm obtained from a Nd3+-doped tellurite glass excited by 5 ns laser pulses at 805 nm. A rate-equation model, including the relevant energy levels and temperature dependent transition rates, is proposed to describe the process. The results fit well with the data when one considers the nonradiative transitions contributing for the 754 nm luminescence are promoted by an effective phonon mode with energy of 700 cm−1.
Anisotropic magnetoresistance and planar Hall effect in La2∕3Ca1∕3MnO3 thin films with misfit strain
Authors: Li J. , Wang S. G. , Zhang Y. , Cui L. M. , Jin Y. R. , Deng H. , Zheng D. N. , Zimmers A. , Aubin H. , Lang P. L.
Published: February 2013

In our previous study anisotropic magnetoresistance (AMR) and planar Hall effect (PHE) of epitaxial La2∕3Ca1∕3MnO3 (LCMO) thin films grown on SrTiO3(001) (STO) substrates were studied, and a phenomenological model in the high field limit was developed based on the 4/mmm point group. The derived longitudinal resistivity includes a four-fold as well as a two-fold symmetry term of the in-plane field angle, which can fit the experimental results well. In this study, to highlight the effects of misfit strain, AMR and PHE of LCMO thin films epitaxially grown on LaAlO3(001) substrates were studied, along either the [110] or the [100] direction. Both values are around a few percent, comparable to those measured in films on STO. Nevertheless, only tiny four-fold oscillations appear below the metal-insulator transition temperature Tp along the [110] direction, in contrast to the case of STO, where the four-fold term is prominent. The relationship between this four-fold symmetry and the misfit strain is then discussed in terms of the partial recovery of orbital magnetic moment. The mechanism for AMR and PHE in manganites then can be understood as an anisotropic percolation at metal-insulator transition resulting in the peak, and the spin-orbital coupling effect that accounts for the remnant far below Tp.
“Water window” sources: Selection based on the interplay of spectral properties and multilayer reflection bandwidth
Authors: Li Bowen , Higashiguchi Takeshi , Otsuka Takamitsu , Jiang Weihua , Endo Akira , Dunne Padraig , O'Sullivan Gerry
Published: February 2013

Development of laser-produced plasma “water window” sources poses a major challenge in x-ray research and most effort has focused on line sources for use with zone plate optics. Here, a comparison of carbon and nitrogen line emission with that from both 3d – 4f and 4d – 4f unresolved transition arrays shows that, at power densities available from “table-top” solid-state lasers, 3d – 4f emission from zirconium plasmas is most intense, and calculations show that in an imaging system based on multilayer mirrors, for reflectance bandwidths >1% has superior performance than either line or broader-band sources. For bandwidths <1%, line sources are preferable.
The change of electrical transport characterizations in Ga doped ZnO films with various thicknesses
Authors: Li Ying , Huang Qin , Bi Xiaofang
Published: February 2013

GZO films with different thicknesses were prepared at room temperature by magnetron sputtering and the structure is characterized using two-dimensional X-ray diffraction along with transmission electron microscope and X-ray photoelectron spectroscopy. The films show a textured orientation along the c-axis and an average transmittance of over 90%. The films of 100 and 200 nm are characterized by a semiconductor behavior in the temperature range of 80–320 K, while the conduction behavior turns into a metallic transport at 160 K as the film thickness increases to 400 nm. Temperature dependence of the conductivity manifests a weak localization effect dominated in the semiconductor behavior. The transition between semiconductor and metallic behavior with increasing the thickness is shown to be associated to crystallinity of the films which is improved with decreasing defects and lattice distortion. It is suggested that the improvement of crystallinity should be favored by reduction of the weak localization effect and in turn enhance the semiconductor-to-metal transition.
Random analysis on controlled buckling structure for energy harvesting
Authors: Wang Yong , Ma Teng , Yu Hongyu , Jiang Hanqing
Published: February 2013

The controlled buckling piezoelectric structures can be used for stretchable energy harvesting due to the stretchability and piezoelectricity. In this paper, the ambient environmental excitation is modeled as a bound-limited white noise, and the random analysis is conducted to study the system response of controlled buckling structures. The spatial distribution of the harvestable energy is revealed, and the optimal locations of electrodes for maximal energy output are indicated. The optimal locations of electrodes are robust to the upper bound of environment excitation and the applied strain. This work provides a theoretical basis for stretchable energy harvesting using controlled buckling structures.
Two dimensional ferroelectric domain patterns in Yb3+ optically active LiNbO3 fabricated by direct electron beam writing
Authors: Mateos L. , Bausá L. E. , Ramírez M. O
Published: February 2013

We report on highly controllable ferroelectric domain inversion in Yb3+ doped LiNbO3 laser crystal. The ferroelectric domain patterns are fabricated by direct electron beam writing without any previous masking process. Square lattices of inverted domains with diameters and distance between domains as low as 1 μm are demonstrated. The lateral growth of the inverted domains is analyzed as a function of the applied charge and the threshold values for domains in the 1–10 μm length scale are determined. Spatially resolved low temperature fluorescence spectroscopy and non-collinear second harmonic generation experiments are also employed to evaluate the optical properties of the system.
A simple criterion for filament break-up in drop-on-demand inkjet printing
Authors: Hoath S. D. , Jung S. , Hutchings I. M.
Published: February 2013

Jets from drop-on-demand inkjet print-heads consist of a main drop with a trailing filament, which either condenses into the main drop, or breaks up into satellite drops. Filament behaviour is quantitatively similar to that of larger, free symmetrical filaments, and can be predicted from the aspect ratio and Ohnesorge number. Symmetrical filaments generated from inkjet print-heads show the same behaviour. A simple model, based on competition between the processes of axial shortening and radial necking, predicts the critical aspect ratio below which the jet condenses into a single drop. The success of this simple criterion supports the underlying physical model.
Influence of molybdenum doping on the switching characteristic in silicon oxide-based resistive switching memory
Authors: Chen Yu-Ting , Chang Ting-Chang , Huang Jheng-Jie , Tseng Hsueh-Chih , Yang Po-Chun , Chu Ann-Kuo , Yang Jyun-Bao , Huang Hui-Chun , Gan Der-Shin , Tsai Ming-Jinn , Sze Simon M.
Published: February 2013

This report compares Mo-doped and undoped SiO2 thin films of a similar thickness as well as MoOx. The Mo-doped SiO2 film exhibited switching behavior after the forming process, unlike the undoped SiO2 film. Through material analyses, a self-assembled layer is observed in the Mo-doped SiO2 film. Due to the formation of this layer, the thickness required to be broken down is effectively reduced. Subsequently, the occurrence of the switching behavior in the thinner SiO2 film further confirmed the supposition. A comparison of the two switching behaviors shows that SiO2 dominates the switching characteristic of the Mo-doped SiO2.
Detecting p-type conduction in Ba-doped InN
Authors: Xie Q. Y. , Xie W. M. , Wang J. L. , Zhu H. P. , Yang J. H. , Sun L. , Wu X. S.
Published: February 2013

The buried p-type conduction is demonstrated in InN with Ba ion implantation dose increases up to 1 × 1015 ions/cm−2. The in-plane lattice parameter increases by about 1.2% deep in the film due to larger Ba replacing smaller indium (In). The n-type conductivity is also detected at the surface, which may results from the N-deficiency. First-principles calculations show that holes at the surface, induced by Ba ion implantation, are compensated by extra electrons from the In adlayer. The p-type carriers dominate in the bulk layers, which is in good agreement with the experimental results.
Strong heavy-to-light hole intersubband absorption in the valence band of carbon-doped GaAs/AlAs superlattices
Authors: Hossain M. I. , Ikonic Z. , Watson J. , Shao J. , Harrison P. , Manfra M. J. , Malis O.
Published: February 2013

We report strong mid-infrared absorption of in-plane polarized light due to heavy-to-light hole intersubband transitions in the valence band of C-doped GaAs quantum wells with AlAs barriers. The transition energies are well reproduced by theoretical calculations including layer inter-diffusion. The inter-diffusion length was estimated to be 8 ± 2 Å, a value that is consistent with electron microscopy measurements. These results highlight the importance of modeling the nanoscale structure of the semiconductors for accurately reproducing intra-band transition energies of heavy carriers such as the holes.
On the hydrophobicity of modified Ga-polar GaN surfaces
Authors: Dzięcielewski I. , Weyher J. L. , Dzwolak W.
Published: February 2013

In this communication, we show that chemical modifications of etched GaN (with different morphological features) through treatment with trichlorododecylsilane or sputtering nano-Au films followed by covalent binding of 1-dodecanethiol strongly affect surface water repellency characteristics. Binding of 1-dodecanethiol to Au-coated whiskers results in GaN crystals becoming superhydrophobic with the contact angles approaching 150°. For a single type of surface morphology, a pairwise comparison of contact angle values of trichlorododecylsilane- and Au/1-dodecanethiol-modified surfaces provides an insight into relative abundance of –OH groups on GaN's Ga-polar side, which mediate and control binding of the hydrophobic silane compound, but not of thiols.
Rational design of Nb-based alloys for hydrogen separation: A first principles study
Authors: Ryu Byungki , Park Hyeon Cheol , Cho Eunseog , Kim Kwanghee , Lee Jaeho , Liu Meilin
Published: February 2013

We have investigated the effect of alloying metal elements on hydrogen solubility and mechanical integrity of Nb-based alloys, Nb15M1 (where M = Ca–Zn, Ge), using first principles-based calculations. In general, the chemical interaction between the interstitial H and metal is weakened as the alloying element is changed from an early to a late transition metal, leading to lower H solubility and higher resistance to H embrittlement. This effect becomes more pronounced when a smaller alloying element is used due to stronger elastic interaction between interstitial H and metal atoms. These finding may provide scientific basis for rational design of Nb-based hydrogen separation membranes with tailored H solubility to effectively suppress H embrittlement while maintaining excellent hydrogen permeation rate.
Theory of magnetoelectric effect in multilayer nanocomposites on a substrate: Static bending-mode response
Authors: Krantz Matthias C. , Gerken Martina
Published: February 2013

Magnetoelectric (ME) coefficients for bending excitation in static magnetic fields and the bending response of multilayer composites with alternating magnetostrictive (MS) and piezoelectric (PE) layers on a substrate are investigated systematically. Theory and closed-form analytic solutions for the static magnetoelectric and the bending response coefficients are presented. Results of systematic variation of layer numbers, layer sequences, PE volume fractions, substrate thicknesses, and four different material systems (employing FeCoBSi, Terfenol-D, AlN, PZT, and Si) are given for a fixed total composite thickness of 5μm. Among more than 105 structures investigated the greatest static ME coefficient of 62.3 V/cmOe is predicted for all odd layer number FeCoBSi-AlN multilayer composites on a Si substrate at vanishing substrate thickness and a PE material fraction of 38%. Varying the substrate thickness from 0μm to 20μm and the PE fraction from 0% to 100%, broad parameter regions of high ME coefficients are found for odd and large layer number nanocomposites. These regions are further enhanced to narrow maxima at vanishing substrate thickness, which correspond to structures of vanishing static bending response. For bilayers and even layer number cases broad maxima of the ME coefficient are observed at nonzero substrates and bending response. The optimal layer sequence and PE fraction depend on the material system. Bending response maxima occur at zero Si substrate thickness and nonzero PE fractions for bilayers. For multilayers nonzero Si substrates and zero PE fractions are found to be optimal. Structures of even ME layer numbers of PE-MS...Sub layer sequence display regions of vanishing bending response with large ME coefficients, i.e., produced by longitudinal excitation.
One-dimensional broadband phononic crystal filter with unit cells made of two non-uniform impedance-mirrored elements
Authors: Lee Il Kyu , Kim Yoon Jae , Oh Joo Hwan , Kim Yoon Young
Published: February 2013

A one-dimensional finite-sized phononic crystal(PC) made of a specially-configured unit cell is proposed to realize broad bandpass, high-performance filtering. The unit cell is specially-configured with two elements having mirrored impedance distributions of each other. One element has a non-uniform impedance distribution that is so engineered as to maximize wave transmission in the pass band and to minimize transmission in the adjacent stop band while the other, exactly the mirrored distribution. The mirroring approach naturally yields the overall impedance contrast within the resulting unit cell, necessary to form stop bands in a PC of the unit cells. More importantly, the good transmission performance of the orginally-engineered element can be preserved by the approach because no additional impedance mismatch is introduced along the interface of the two impedance-mirrored elements. Extraordinary performance of the PC filter made of the proposed unit cell, such as high transmission, large bandwidth and sharp roll-off, is demonstrated by using one-dimensional longitudinal elastic wave problems.
Synthesis and characterization of MoS2/Ti composite coatings on Ti6Al4V prepared by laser cladding
Authors: Yang Rongjuan , Liu Zongde , Wang Yongtian , Yang Guang , Li Hongchuan
Published: February 2013

The MoS2/Ti composite coating with sub-micron grade structure has been prepared on Ti6Al4V by laser method under argon protection. The morphology, microstructure, microhardness and friction coefficient of the coating were examined. The results indicated that the molybdenum disulfide was decomposed during melting and resolidification. The phase organization of composite coating mainly consisted of ternary element sulfides, molybdenum sulfides and titanium sulfides. The friction coefficient of and the surface roughness the MoS2/Ti coating were lower than those of Ti6Al4V. The composite coating exhibits excellent adhesion to the substrates, less surface roughness, good wear resistance and harder surface.
Assessing the role of cladogenesis in macroevolution by integrating fossil and molecular evidence
Authors: Strotz Luke C. , Allen Andrew P.
Published: February 2013

Assessing the extent to which population subdivision during cladogenesis is necessary for long-term phenotypic evolution is of fundamental importance in a broad range of biological disciplines. Differentiating cladogenesis from anagenesis, defined as evolution within a species, has generally been hampered by dating precision, insufficient fossil data, and difficulties in establishing a direct link between morphological changes detectable in the fossil record and biological species. Here we quantify the relative frequencies of cladogenesis and anagenesis for macroperforate planktic Foraminifera, which arguably have the most complete fossil record currently available, to address this question. Analyzing this record in light of molecular evidence, while taking into account the precision of fossil dating techniques, we estimate that the fraction of speciation events attributable to anagenesis is <19% during the Cenozoic era (last 65 Myr) and <10% during the Neogene period (last 23 Myr). Our central conclusion—that cladogenesis is the predominant mode by which new planktic Foraminifera taxa become established at macroevolutionary time scales—differs markedly from the conclusion reached in a recent study based solely on fossil data. These disparate findings demonstrate that interpretations of macroevolutionary dynamics in the fossil record can be fundamentally altered in light of genetic evidence.
A generalized G-SFED continuum solvation free energy calculation model
Authors: Lee Sehan , Cho Kwang-Hwi , Kang Young-Mook , Scheraga Harold A. , No Kyoung Tai
Published: February 2013

Significance

This paper deals with a long-standing problem in biophysics, which is resolved here. The model has a strong physical background and will have a wide range of applications to physical and biological problems. The model proposed in this article, GSFED model, can be used for the solvation free energy calculation of most organic solutes in most organic solvents. Since the computing time depends linearly on the size of the molecule, the model can be applied easily to large molecules, for example proteins. The model can provide reliable salvation free energies of experimentally unavailable solute-solvent pairs.
Identification of CDCP1 as a hypoxia-inducible factor 2α (HIF-2α) target gene that is associated with survival in clear cell renal cell carcinoma patients
Authors: Emerling Brooke M. , Benes Cyril H. , Poulogiannis George , Bell Eric L. , Courtney Kevin , Liu Hui , Choo-Wing Rayman , Bellinger Gary , Tsukazawa Kazumi S. , Brown Victoria , Signoretti Sabina , Soltoff Stephen P. , Cantley Lewis C.
Published: February 2013

CUB domain-containing protein 1 (CDCP1) is a transmembrane protein that is highly expressed in stem cells and frequently overexpressed and tyrosine-phosphorylated in cancer. CDCP1 promotes cancer cell metastasis. However, the mechanisms that regulate CDCP1 are not well-defined. Here we show that hypoxia induces CDCP1 expression and tyrosine phosphorylation in hypoxia-inducible factor (HIF)-2α–, but not HIF-1α–, dependent fashion. shRNA knockdown of CDCP1 impairs cancer cell migration under hypoxic conditions, whereas overexpression of HIF-2α promotes the growth of tumor xenografts in association with enhanced CDCP1 expression and tyrosine phosphorylation. Immunohistochemistry analysis of tissue microarray samples from tumors of patients with clear cell renal cell carcinoma shows that increased CDCP1 expression correlates with decreased overall survival. Together, these data support a critical role for CDCP1 as a unique HIF-2α target gene involved in the regulation of cancer metastasis, and suggest that CDCP1 is a biomarker and potential therapeutic target for metastatic cancers.
Plenary Rhetoric in Indian Country: TheLone Wolf v. HitchcockCase and the Codification of a Weakened Native Character
Authors: Black Jason Edward
Published: February 2013

The U.S. Congress passed the General Allotment (Dawes) Act of 1887 as a part of its assimilationist plan to remake American Indians in the image of the U.S. nation. The act helped constitute a changed Native identity as it contracted reservation lines and forced an agricultural economy onto Native reservations. The Supreme Court case Lone Wolf v. Hitchcock (1903) resulted from American Indian protests of the Dawes Act, including the argument that the assimilationist plan had been implemented against Natives' will. The resulting decision granted Congress the ultimate “plenary” power to abrogate treaties without any limits because American Indians were wards. Through an analysis of the case and Indian Commissioner reports addressing plenary power, I argue that the Lone Wolf holding served as an imperial discourse that maligned American Indian identities through a parent-child relationship. This denigration manifested through Lone Wolf's construction of American Indians as cultural wards, its reduction of Native property to commodity through a westernized economic plan, and its assimilation of Native communities into dominant U.S. culture. In addition, I contend that the Lone Wolf case solidified a wider U.S. nationalism by emboldening federal power over indigenous communities through a familial rhetorical strategy.
A “Literary Approach to Speech Work”: Oral Reading and Speech at San Jose State Teachers College, 1862–1930
Authors: Bordelon Suzanne
Published: February 2013

This essay investigates the ways that some teachers colleges not typically considered in traditional histories of the Speech field reconfigured aspects of elocution or the performance arts through their teaching practices. Focusing on San Jose State Teachers College in the early decades of the twentieth century when Speech was emerging as a discipline, this analysis demonstrates how some speech teachers refashioned and democratized the teaching of oral reading, particularly the oral reading of poetry. In so doing, this study reveals the gendered nature of our standard histories while broadening our understanding of how teachers colleges fit into the disciplinary split between Speech and English.
After the Revolution: Cuban Women's Healing Practices and Knowledge Spaces
Authors: Corrigan Lisa M.
Published: February 2013

In Blessed by Thunder: Memoir of a Cuban Girlhood, Flor Fernandez Barrios examines the consequences of Castro's Revolution and its silencing, censoring, and prohibitions on the writing, speaking, thinking, and performance of public rituals of communities and families. Barrios is able to use the history of storytelling and orality to integrate her roles as a daughter, granddaughter, and healer into a larger history of Cuban women who have preserved knowledge practices that exist outside of the state's masculine identity and its sanctioned social and medical institutions. As Barrios rewrites the Cuban Revolution through the collective memories of three generations of women in her family, she articulates her own Cuban-ness as well as her relationship to Afro-Cuban culture, an often-overlooked connection that tells us as much about upper-class culture on the island during this period in the early 1960s as it does about Afro-Cuban life practices such as Santería.
Collocutio: Transformational Speeches
Authors: Ornatowski Cezar M. , Marin Noemi
Published: February 2013

Transformational speeches represent the relationship between rhetoric and history, particularly attempts to exert control at moments of change in the life of a political community. Such speeches re-imagine the definition, principles, or motivation of a community. They also enlarge the scope and vocabulary of political speech. Finally, they interpret or constitute situations at the boundary between past and future. Collected in this Collocutio are fresh translations of historically significant transformational speeches from Bulgaria, Cuba, Mexico, Poland, and Romania.
Comparative study of RNA-seq- and Microarray-derived coexpression networks in Arabidopsis thaliana
Authors: Giorgi Federico M. , Del Fabbro Cristian , Licausi Francesco
Published: February 2013

Motivation: Coexpression networks are data-derived representations of genes behaving in a similar way across tissues and experimental conditions. They have been used for hypothesis generation and guilt-by-association approaches for inferring functions of previously unknown genes. So far, the main platform for expression data has been DNA microarrays; however, the recent development of RNA-seq allows for higher accuracy and coverage of transcript populations. It is therefore important to assess the potential for biological investigation of coexpression networks derived from this novel technique in a condition-independent dataset.

Results: We collected 65 publicly available Illumina RNA-seq high quality Arabidopsis thaliana samples and generated Pearson correlation coexpression networks. These networks were then compared with those derived from analogous microarray data. We show how Variance-Stabilizing Transformed (VST) RNA-seq data samples are the most similar to microarray ones, with respect to inter-sample variation, correlation coefficient distribution and network topological architecture. Microarray networks show a slightly higher score in biology-derived quality assessments such as overlap with the known protein–protein interaction network and edge ontological agreement. Different coexpression network centralities are investigated; in particular, we show how betweenness centrality is generally a positive marker for essential genes in A.thaliana, regardless of the platform originating the data. In the end, we focus on a specific gene network case, showing that although microarray data seem more suited for gene network reverse engineering, RNA-seq offers the great advantage of extending coexpression analyses to the entire transcriptome.

Contact:  fgiorgi@appliedgenomics.org

Supplementary information:  Supplementary data are available at Bioinformatics online.
RepeatExplorer: a Galaxy-based web server for genome-wide characterization of eukaryotic repetitive elements from next-generation sequence reads
Authors: Novák Petr , Neumann Pavel , Pech Jiří , Steinhaisl Jaroslav , Macas Jiří
Published: February 2013

Motivation: Repetitive DNA makes up large portions of plant and animal nuclear genomes, yet it remains the least-characterized genome component in most species studied so far. Although the recent availability of high-throughput sequencing data provides necessary resources for in-depth investigation of genomic repeats, its utility is hampered by the lack of specialized bioinformatics tools and appropriate computational resources that would enable large-scale repeat analysis to be run by biologically oriented researchers.

Results: Here we present RepeatExplorer, a collection of software tools for characterization of repetitive elements, which is accessible via web interface. A key component of the server is the computational pipeline using a graph-based sequence clustering algorithm to facilitate de novo repeat identification without the need for reference databases of known elements. Because the algorithm uses short sequences randomly sampled from the genome as input, it is ideal for analyzing next-generation sequence reads. Additional tools are provided to aid in classification of identified repeats, investigate phylogenetic relationships of retroelements and perform comparative analysis of repeat composition between multiple species. The server allows to analyze several million sequence reads, which typically results in identification of most high and medium copy repeats in higher plant genomes.

Implementation and availability: RepeatExplorer was implemented within the Galaxy environment and set up on a public server at http://repeatexplorer.umbr.cas.cz/. Source code and instructions for local installation are available at http://w3lamc.umbr.cas.cz/lamc/resources.php.

Contact:  macas@umbr.cas.cz
Do Labor Market Policies have Displacement Effects? Evidence from a Clustered Randomized Experiment *
Authors: Crépon Bruno , Duflo Esther , Gurgand Marc , Rathelot Roland , Zamora Philippe
Published: February 2013

This article reports the results from a randomized experiment designed to evaluate the direct and indirect (displacement) impacts of job placement assistance on the labor market outcomes of young, educated job seekers in France. We use a two-step design. In the first step, the proportions of job seekers to be assigned to treatment (0%, 25%, 50%, 75%, or 100%) were randomly drawn for each of the 235 labor markets (e.g., cities) participating in the experiment. Then, in each labor market, eligible job seekers were randomly assigned to the treatment, following this proportion. After eight months, eligible, unemployed youths who were assigned to the program were significantly more likely to have found a stable job than those who were not. But these gains are transitory, and they appear to have come partly at the expense of eligible workers who did not benefit from the program, particularly in labor markets where they compete mainly with other educated workers, and in weak labor markets. Overall, the program seems to have had very little net benefits.
Identification of Tobacco streak virus Associated With a Virus-like Mottle Symptom on Hosta
Authors: Fisher John R.
Published: February 2013

In this brief, the authors describe the identification of Tobacco streak virus associated with a virus-like leaf symptom on Hosta spp. The identity of the virus was confirmed by ELISA and PCR using cDNAs synthesized from dsRNA template and immuncaptured virions and primers to amplify the movement protein and capsid protein genes. This is the first report of TSV infecting Hosta in Ohio, and to our knowledge in the United States.

Accepted for publication 17 December 2012. Published 22 January 2013.
Fluoroscopic Radiation Exposure in Spinal Surgery
Authors: Mulconrey Daniel S.
Published: February 2013

Study Design:

Prospective in vivo investigation of fluoroscopic radiation exposure during spinal surgery.

Objective:

To quantify the total amount of radiation dosage and identify techniques to maintain safe levels of fluoroscopic exposure in the operating room.

Summary of Background Data:

No previous study has performed an in vivo examination of fluoroscopic radiation exposure to the spinal surgeon and operating room personnel. Previous similar studies were in vitro, used older versions of fluoroscopy, and increased fluoro times associated with pedicle screw placement.

Methods:

Thirty-five surgeries were evaluated in 18 males and 17 females (mean age 52.4 y; range, 26.0–79.4). Surgeries included 37 lumbar levels fused, 45 lumbar decompressions, 8 anterior cervical fusions, and 19 transforaminal lumbar interbody fusion procedures. Spinal instrumentation was implemented in all fusion procedures (104 lumbar pedicle screws, 14 iliac, 22 anterior cervical). Radiation dosimetry was obtained through unprotected badges placed on surgeon’s chest, first assistant chest, cranial and caudal end of operating table.

Results:

Total fluoroscopic time was 37.01 minutes. Mean fluoroscopic time with lumbar spine instrumentation was greater than decompression alone (1.74 vs. 0.22 min). Total fluoroscopic radiation exposure was obtained for surgeon (1225 mrem), first assistant (369 mrem), cranial table (92 mrem), and caudal table (150 mrem). Mean dose/min (mrem/min) was calculated for surgeon (33.1), first assistant (9.97), cranial table (2.48), and caudal table (4.05). To remain below the maximum yearly permissible level of radiation, the estimated total number of minutes for the surgeon would be 453.

Conclusions:

The results of this in vivo study indicate fluoroscopic dosage to the spine surgeon remains below the annual maximum limit of radiation exposure. Increasing distance from radiation source led to a significantly diminished in vivo dosimetry reading. Monitoring fluoroscopic time and maintaining a distance from the beam source, radiation exposure to the spine surgeon may be kept within current safety standards.