Sample records for anisotropic transport properties

  1. Anisotropic diffusive transport: connecting microscopic scattering and macroscopic transport properties.

    PubMed

    Alerstam, Erik

    2014-06-01

    This work concerns the modeling of radiative transfer in anisotropic turbid media using diffusion theory. A theory for the relationship between microscopic scattering properties (i.e., an arbitrary differential scattering cross-section) and the macroscopic diffusion tensor, in the limit of independent scatterers, is presented. The theory is accompanied by a numerical method capable of performing the calculations. In addition, a boundary condition appropriate for modeling systems with anisotropic radiance is derived. It is shown that anisotropic diffusion theory, when based on these developments, indeed can describe radiative transfer in anisotropic turbid media. More specifically, it is reported that solutions to the anisotropic diffusion equation are in excellent agreement with Monte Carlo simulations, both in steady-state and time-domain. This stands in contrast to previous work on the topic, where inadequate boundary conditions and/or incorrect relations between microscopic scattering properties and the diffusion tensor have caused disagreement between simulations and diffusion theory. The present work thus falsify previous claims that anisotropic diffusion theory cannot describe anisotropic radiative transfer, and instead open for accurate quantitative diffusion-based modeling of anisotropic turbid materials. PMID:25019904

  2. Exceptional and Anisotropic Transport Properties of Photocarriers in Black Phosphorus.

    PubMed

    He, Jiaqi; He, Dawei; Wang, Yongsheng; Cui, Qiannan; Bellus, Matthew Z; Chiu, Hsin-Ying; Zhao, Hui

    2015-06-23

    One key challenge in developing postsilicon electronic technology is to find ultrathin channel materials with high charge mobilities and sizable energy band gaps. Graphene can offer extremely high charge mobilities; however, the lack of a band gap presents a significant barrier. Transition metal dichalcogenides possess sizable and thickness-tunable band gaps; however, their charge mobilities are relatively low. Here we show that black phosphorus has room-temperature charge mobilities on the order of 10(4) cm(2) V(-1) s(-1), which are about 1 order of magnitude larger than silicon. We also demonstrate strong anisotropic transport in black phosphorus, where the mobilities along the armchair direction are about 1 order of magnitude larger than in the zigzag direction. A photocarrier lifetime as long as 100 ps is also determined. These results illustrate that black phosphorus is a promising candidate for future electronic and optoelectronic applications. PMID:25961945

  3. Anisotropic transport properties of ferromagnetic-superconducting bilayers 

    E-print Network

    Kayali, MA; Pokrovsky, Valery L.

    2004-01-01

    V r a Phys bilaye perpendicula y S PHYSICAL REVIEW B 69, 132501 ~2004! ated with the driving force acting on the vortex lattice from an external electric current. We show that the FSB exhibits strong anisotropy of the transport properties... to the expo- nential factor x which is small if b!l . The anisotropy is pronounced when dm is large which can be achieved by us- ing thicker FM layers and decreasing the density of the su- perconducting electrons. dm is temperature dependent...

  4. Anisotropic transport properties of ferromagnetic-superconducting bilayers

    E-print Network

    Kayali, MA; Pokrovsky, Valery L.

    2004-01-01

    vortices increases when approaching the domain walls and can be expressed as nv(x)5(pm? /Lf0)@1/sin(px/L)#, where m?5m2(ev0 /f0) is the renormalized magnetization of the FM stripe. The vorti- ces spontaneously appear in the superconductor. We assume.... Amin Kayali1 and 1Department of Physics, Texas A & M Universit 2Landau Institute for Theoretica ~Received 12 December 2003 We study the transport properties of vortex matte insulator layer from a ferromagnetic layer. We assume conducting ~SC...

  5. Scalable Directed Self-Assembly and Anisotropic Transport Properties of Soft Mesophases for Membrane Applications

    NASA Astrophysics Data System (ADS)

    Osuji, Chinedum

    2013-03-01

    Self-assembly of block copolymers and surfactant mesophases can be can be utilized in creating composite materials with very fine periodic structures. Easy access to nm-scale features coupled with compositional variety and thus tunable physical properties makes these nanoscale heterogeneous materials excellent candidates for selective transport applications including ion-conduction, ultrafiltration and desalination. A critical limitation in their performance however arises from the tortuosity of randomly oriented self-assembled structures. We show that in appropriately engineered systems, magnetic fields provide a viable route for scalable control of morphology, producing well aligned materials over large length scales. Here we discuss this approach for the fabrication of ion conduction membranes, aligned carbon nanotube membranes and nanoporous films. We quantitatively assess the anisotropic transport properties of one such system and confront the data with models based on effective medium theory and composite conductivity calculations. The results demonstrate that directed self-assembly can provide non-trivial enhancement of the transport properties in these applications. Self-assembly of block copolymers and surfactant mesophases can be can be utilized in creating composite materials with very fine periodic structures. Easy access to nm-scale features coupled with compositional variety and thus tunable physical properties makes these nanoscale heterogeneous materials excellent candidates for selective transport applications including ion-conduction, ultrafiltration and desalination. A critical limitation in their performance however arises from the tortuosity of randomly oriented self-assembled structures. We show that in appropriately engineered systems, magnetic fields provide a viable route for scalable control of morphology, producing well aligned materials over large length scales. Here we discuss this approach for the fabrication of ion conduction membranes, aligned carbon nanotube membranes and nanoporous films. We quantitatively assess the anisotropic transport properties of one such system and confront the data with models based on effective medium theory and composite conductivity calculations. The results demonstrate that directed self-assembly can provide non-trivial enhancement of the transport properties in these applications. NSF support is gratefully acknowledged (DMR-0847534, CBET-1133484, CMMI-1246804).

  6. Anisotropic transport properties of zinc-blend ZnTe/CrTe heterogeneous junction nanodevices

    SciTech Connect

    Yao Wei; Gao, G. Y.; Zhu, S. C.; Fu, H. H. [School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); Yao, K. L. [School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074 (China); International Center of Materials Physics, Chinese Academy of Science, Shenyang 110015 (China)

    2012-11-15

    Motivated by the molecular-beam epitaxial growth of zinc-blend-type CrTe thin films on ZnTe, we present a theoretical study on the spin-polarized transport properties of ZnTe/CrTe p-n junction as spin diode and CrTe/ZnTe/CrTe magnetic tunnel junction for (001) and (011) surfaces. Both ZnTe(001)/CrTe(001) and ZnTe(011)/CrTe(011) p-n junctions show excellent spin diode effect, the majority spin current of positive voltage is much larger than that of negative voltage and the minority spin current is absolutely inhibited. The ZnTe(001)/CrTe(001) p-n junction has lower 'turn off' current and higher rectification ratio (about 10{sup 5}) than the ZnTe(011)/CrTe(011) which shows obvious anisotropy. We also find that the tunneling magneto resistance ratio of the CrTe/ZnTe/CrTe magnetic tunnel junction is up to about 4 Multiplication-Sign 10{sup 9}%.

  7. Electron transport properties in m-plane and c-plane AlN/GaN heterostructures with interface roughness and anisotropic in-plane strain scatterings

    NASA Astrophysics Data System (ADS)

    Thongnum, Anusit; Pinsook, Udomsilp

    2015-03-01

    Anisotropic transport properties of a two-dimensional electron gas in nonpolar m-plane AlN/GaN heterostructures with the interface roughness coupled anisotropic in-plane strain scattering were investigated theoretically using a path-integral framework. The scattering potential was composed of the interface roughness and the effective field from the electron charge and the net piezoelectric polarization. We showed that the anisotropic biaxial strains generate only the net piezoelectric polarization along the [0?0?0?1]-direction and cause anisotropy in electron mobility with a magnitude lower than the ?ft[11\\bar{2}0\\right] -direction. We also showed that the anisotropy in electron mobility reduced with increasing electron density. Moreover, the anisotropic electron mobility disappeared when the anisotropic in-plane strain scattering was removed, and the relation for pure interface roughness scattering was reestablished. This formulation with existing roughness parameters gave a good description for the experimental results of polar c-plane AlN/GaN heterostructures.

  8. Anisotropic transport properties of charge-ordered La5/8?yPryCa3/8MnO3 (y = 0.43) film

    NASA Astrophysics Data System (ADS)

    Liu, Yuan-Bo; Wang, Shuan-Hu; Sun, Ji-Rong; Shen, Bao-Gen

    2015-05-01

    The anisotropic resistances along [001] and [1-10] axes are investigated for an La5/8?yPryCa3/8MnO3 (y = 0.43) (LPCMO) film grown on (110)-oriented LaAlO3 substrate. It is found that the charge order (CO) transition is much stronger and the resistance is larger along the [001] direction than that along the [1-10] direction. Special attention has been paid to the different effects of a magnetic field on the resistances of the two axes. The resistance is more susceptible to the magnetic field along the [001] direction compared with that along the [1-10] direction. Our results demonstrate that the anisotropic transport properties can be ascribed to the intrinsic anisotropic strain field in the film, which changes the shape of metallic domains for the phase separation manganite film. We also provide a feasible method to rule out the Joule heat effect from the electric current effect. This could be useful for future construction and application of materials and devices. Project supported by the Knowledge Innovation Project of the Chinese Academy of Sciences and the National Basic Research Program of China.

  9. Anisotropic transport and magnetic properties and magnetic-field tuned states of CeZn11 single crystals

    NASA Astrophysics Data System (ADS)

    Hodovanets, H.; Bud'ko, S. L.; Lin, X.; Taufour, V.; Kim, M. G.; Pratt, D. K.; Kreyssig, A.; Canfield, P. C.

    2013-08-01

    We present detailed temperature- and field-dependent data obtained from magnetization, resistivity, heat capacity, Hall resistivity and thermoelectric power measurements performed on single crystals of CeZn11. The compound orders antiferromagnetically at ˜2 K. The zero-field resistivity and thermoelectric power data show features characteristic of a Ce-based intermetallic with crystal-electric-field splitting and possible Kondo lattice effects. We constructed the T-H phase diagram for the magnetic field applied along the easy [110] direction, which shows that the magnetic field required to suppress TN below 0.4 K is in the range of 45-47.5 kOe. A linear behavior of the ?(T) data, H? [110], was observed only for H=45 kOe for 0.46 K ?T? 1.96 K followed by the Landau-Fermi-liquid regime for a limited range of fields 47.5 kOe ?H? 60 kOe. From the analysis of our data, it appears that CeZn11 is a local moment compound with little or no electronic correlations arising from the Ce 4f shell. The thermoelectric and transport properties of CeZn11 are mostly governed by the crystal-electric-field effects. Given the very high quality of our single crystals, quantum oscillations are found for both CeZn11 and its nonmagnetic analog LaZn11.

  10. Structural and anisotropic transport properties of (Hg,Re)Ba2CaCu2Oy vicinal films

    NASA Astrophysics Data System (ADS)

    Ogawa, A.; Sugano, T.; Wakana, H.; Kamitani, A.; Adachi, S.; Tarutani, Y.; Tanabe, K.

    2005-01-01

    Approximately 160-nm-thick (Hg0.9Re0.1)Ba2CaCu2Oy [(Hg,Re)-1212] epitaxial thin films were fabricated on 2°-18.4°-tilt SrTiO3 vicinal substrates with thin buffer layers. The vicinal films had superior crystallinity and superconducting properties comparable to those for conventional films with no tilt. X-ray diffraction measurements revealed that the tilt angles of the c axes of the (Hg,Re)-1212 are slightly larger by 0.5°-1.5° than the substrate tilt angles, which is attributed to deformation of crystal structure due to lattice mismatch in the c-axis direction. The resistivity and critical current density along the c-axis direction (?c and Jc-c) were estimated to be ?c=500m?cm at room temperature and Jc-c=(1.0-1.4)×105A /cm2 at 10K from transport measurements for different in-plane directions of the vicinal films. The ?c clearly exhibited semiconductor-like temperature dependence below 180K. The temperature dependence of Jc-c almost agreed with the theoretical relationship for superconductor-insulator-superconductor junctions. The current-voltage characteristics in the directions across their a -b planes exhibited a multiple branch structure of intrinsic Josephson junctions with voltage jumps at intervals of approximately 20mV at 4-40K.

  11. Investigation of anisotropic thermal transport in polymers using infrared thermography

    NASA Astrophysics Data System (ADS)

    Nieto Simavilla, David; Venerus, David; Schieber, Jay

    2014-03-01

    During manufacturing, the anisotropic nature of thermal transport in flowing polymers plays an important role in the final properties of materials. In our laboratory, we have investigated anisotropic thermal conductivity in polymers subjected to deformation using an optical technique based on Forced Rayleigh Scattering (FRS). For over a decade, our setup has been the only one capable of testing the linear relationship between anisotropy in thermal conductivity and stress, known as the stress-thermal rule. In order to overcome some of the limitations in the optical properties of materials inherent to FRS, we have recently developed a complementary technique based on infrared thermography (IRT). We validate IRT technique by comparing measurements of anisotropy in thermal conductivity on crosslinked networks against those obtained with FRS. The main advantage of IRT method is that, it allows us to study optically thick materials, including polymers that are prone to strain induced crystallization. Additionally, examination of IRT transient state experiments enables us to study the effect of deformation on other properties such as specific heat capacity.

  12. Anisotropic heat transport in rigid solids

    NASA Astrophysics Data System (ADS)

    Triani, Vita; Cimmelli, Vito A.

    2012-12-01

    A nonlinear model of anisotropic rigid heat conductor is developed in the framework of weakly nonlocal Extended Irreversible Thermodynamics.The restrictions placed on the constitutive functions by the principles of dissipation and material frame indifference are investigated. Nonlinear anisotropic Guyer-Krumhansl and Maxwell-Cattaneo equations are derived. Comparison is made with some other models existing in the literature.

  13. Comparison of transport equations based on Maxwellian and bi-Maxwellian distributions for anisotropic plasmas

    NASA Technical Reports Server (NTRS)

    Barakat, A. R.; Schunk, R. W.

    1982-01-01

    A wide variety of plasma flow conditions is found in aeronomy and space plasma physics. Transport equations based on an isotropic Maxwellian vilecity distribution function can be used to describe plasma flows which contain 'small' temperature anisotropies. However, for plasma flows characterized by large temperature anisotropies, transport equations based on an anisotropic bi-Maxwellian (or two-temperature) velocity distribution function are expected to provide a much better description of the plasma transport properties. The present investigation is concerned with the extent to which transport equations based on both Maxwellian and bi-Maxwellian series expansions can describe plasma flows characterized by non-Maxwellian velocity distributions, giving particular attention to a modelling of the anisotropic character of the distribution function. The obtained results should provide clues as to the extent to which a given series expansion can account for the anisotropic character of a plasma.

  14. Uncluttering Graph Layouts Using Anisotropic Diffusion and Mass Transport

    E-print Network

    Tal, Ayellet

    1 Uncluttering Graph Layouts Using Anisotropic Diffusion and Mass Transport Yaniv Frishman and Ayellet Tal Abstract-- Many graph layouts include very dense areas, mak- ing the layout difficult optimal mass transport problems, a warp to the improved density image is computed. The graph nodes

  15. Anisotropic thermal transport in phosphorene: effects of crystal orientation.

    PubMed

    Liu, Te-Huan; Chang, Chien-Cheng

    2015-06-28

    As an intrinsic thermally anisotropic material, the thermal properties of phosphorene must vary with respect to the crystal chirality. Nevertheless, previous studies of heat transfer in phosphorene have been limited to the 0.0° (zigzag, ZZ) and 90.0° (armchair, AC) chiralities. In this study, we investigate the orientation-dependent thermal transport in phosphorene sheets with a complete set of crystal chirality ranging from 0.0° to 90.0° using the Boltzmann transport equation (BTE) associated with the first-principles calculations. It was found that in the phosphorene sheets, the intrinsic thermal conductivity is a smooth monotonic decreasing function of the crystal chirality, which exhibits sinusoidal behavior bounded by the two terminated values 48.9 (0.0°) and 27.8 (90.0°) W m(-1) K(-1). The optical modes have unusually large contributions to heat transfer, which account for almost 30% of the total thermal conductivity of phosphorene sheets. This is because the optical phonons have comparable group velocities and relaxation times to the acoustic phonons. PMID:26024364

  16. Anisotropic thermal transport in phosphorene: effects of crystal orientation

    NASA Astrophysics Data System (ADS)

    Liu, Te-Huan; Chang, Chien-Cheng

    2015-06-01

    As an intrinsic thermally anisotropic material, the thermal properties of phosphorene must vary with respect to the crystal chirality. Nevertheless, previous studies of heat transfer in phosphorene have been limited to the 0.0° (zigzag, ZZ) and 90.0° (armchair, AC) chiralities. In this study, we investigate the orientation-dependent thermal transport in phosphorene sheets with a complete set of crystal chirality ranging from 0.0° to 90.0° using the Boltzmann transport equation (BTE) associated with the first-principles calculations. It was found that in the phosphorene sheets, the intrinsic thermal conductivity is a smooth monotonic decreasing function of the crystal chirality, which exhibits sinusoidal behavior bounded by the two terminated values 48.9 (0.0°) and 27.8 (90.0°) W m-1 K-1. The optical modes have unusually large contributions to heat transfer, which account for almost 30% of the total thermal conductivity of phosphorene sheets. This is because the optical phonons have comparable group velocities and relaxation times to the acoustic phonons.

  17. The transport coefficient $\\hat{q}$ in an anisotropic plasma

    E-print Network

    Yacine Mehtar-Tani

    2009-09-15

    We investigate the jet quenching parameter in the case of a fast moving quark in an anisotropic plasma. In the leading log approximation, strong indications are found that the transport coefficient increases with increasing anisotropy. Implications for the phenomenology at RHIC are discussed.

  18. Transport and Anisotropic Diffusion Models for Movement in Oriented Habitats

    E-print Network

    Hillen, Thomas

    Transport and Anisotropic Diffusion Models for Movement in Oriented Habitats Thomas Hillen on the specific case of animal movement in oriented habitats. The orientations can be given by magnetic cues features, and the diffusion is given by the variance-covariance matrix of the underlying oriented habitat

  19. Anisotropic transport rates in heterogeneous porous media

    Microsoft Academic Search

    Nicholas B. Engdahl; Gary S. Weissmann

    2010-01-01

    We applied a recently developed method of aquifer characterization, which combines geophysics and geostatistics to create several heterogeneous realizations of a shallow fluvial aquifer that contain representations of sedimentary bounding surfaces. The influence of such small-scale (several centimeters) features on subsurface transport was investigated using high-resolution groundwater models of each of the subsurface realizations. Flow and transport through the models

  20. Anisotropic magnetization and transport properties of RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm)

    SciTech Connect

    Myers, Kenneth D.

    1999-11-08

    This study of the RAgSb{sub 2} series of compounds arose as part of an investigation of rare earth intermetallic compounds containing antimony with the rare earth in a position with tetragonal point symmetry. Materials with the rare earth in a position with tetragonal point symmetry frequently manifest strong anisotropies and rich complexity in the magnetic properties, and yet are simple enough to analyze. Antimony containing intermetallic compounds commonly possess low carrier densities and have only recently been the subject of study. Large single grain crystals were grown of the RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm) series of compounds out of a high temperature solution. This method of crystal growth, commonly known as flux growth is a versatile method which takes advantage of the decreasing solubility of the target compound with decreasing temperature. Overall, the results of the crystal growth were impressive with the synthesis of single crystals of LaAgSb{sub 2} approaching one gram. However, the sample yield diminishes as the rare earth elements become smaller and heavier. Consequently, no crystals could be grown with R=Yb or Lu. Furthermore, EuAgSb{sub 2} could not be synthesized, likely due to the divalency of the Eu ion. For most of the RAgSb{sub 2} compounds, strong magnetic anisotropies are created by the crystal electric field splitting of the Hund's rule ground state. This splitting confines the local moments to lie in the basal plane (easy plane) for the majority of the members of the series. Exceptions to this include ErAgSb{sub 2} and TmAgSb{sub 2}, which have moments along the c-axis (easy axis) and CeAgSb{sub 2}, which at intermediate temperatures has an easy plane, but exchange coupling at low temperatures is anisotropic with an easy axis. Additional anisotropy is also observed within the basal plane of DyAgSb{sub 2}, where the moments are restricted to align along one of the {l_angle}110{r_angle} axes. Most of the RAgSb{sub 2} compounds containing magnetic rare earths, antiferromagnetically ordered at low temperatures. The ordering temperatures of these compounds are approximately proportional to the de Gennes factor, which suggests that the RKKY interaction is the dominant exchange interaction between local moments. Although metamagnetic transitions were observed in many members of the series, the series of sharp step-like transitions in DyAgSb{sub 2} are impressive. In this compound, up to 11 different magnetic states are stable depending on the magnitude and direction of the applied field. The saturated magnetization of these states and the critical fields needed to induce a phase transition vary with the direction of the applied field. Through detailed study of the angular dependence of the magnetization and critical fields, the net distribution of magnetic moments was determined for most, of the metamagnetic states. In DyAgSb{sub 2}, the crystal electric field (CEF) splitting of the Hund's rule ground state creates a strong anisotropy where the local Dy{sup 3+} magnetic moments are constrained to one of the equivalent {l_angle}110{r_angle} directions within the basal plane. The four position clock model was introduced to account for this rich metamagnetic system. Within this model, the magnetic moments are constrained to one of four equivalent orientations within the basal plane and interactions are calculated for up third nearest neighbors. The theoretical phase diagram, generated from the coupling constants is in excellent agreement with the experimental phase diagram. Further investigation of this compound using magnetic X-ray or neutron diffraction would be extremely useful to verify the net distributions of moments and determine the wave vectors of each of the ordered states.

  1. Anisotropic properties in Fe-Pt thick film magnets

    SciTech Connect

    Nakano, M.; Shibata, S.; Yanai, T.; Fukunaga, H. [Department of Electrical and Electronic Engineering, Nagasaki University, Nagasaki 852-8521 (Japan)

    2009-04-01

    As-deposited Fe-Pt thick films prepared by a pulsed laser deposition method with the laser power higher than 5 W had L1{sub 0} ordered phase without a substrate heating system. As the laser power increased, the properties of the obtained films changed from isotropic to anisotropic ones. It was also confirmed that x-ray diffraction analysis agrees with the anisotropic phenomenon in crystalline structure with increasing laser power.

  2. Transport properties of Dirac ferromagnet

    NASA Astrophysics Data System (ADS)

    Fujimoto, Junji; Kohno, Hiroshi

    2014-12-01

    We propose a model ferromagnet based on the Dirac Hamiltonian in three spatial dimensions, and study its transport properties which include anisotropic magnetoresistance (AMR) and anomalous Hall (AH) effect. This relativistic extension allows two kinds of ferromagnetic order parameters, denoted by M and S , which are distinguished by the relative sign between the positive- and negative-energy states (at zero momentum) and become degenerate in the nonrelativistic limit. Because of the relativistic coupling between the spin and the orbital motion, both M and S induce anisotropic deformations of the energy dispersion (and the Fermi surfaces) but in mutually opposite ways. The AMR is determined primarily by the anisotropy of the Fermi surface (group velocity), and secondarily by the anisotropy of the damping; the latter becomes important for M =±S , where the Fermi surfaces are isotropic. Even when the chemical potential lies in the gap, the AH conductivity is found to take a finite nonquantized value ?i j=-(? /3 ?2? ) ?i j kSk , where ? is the (effective) fine structure constant. This offers an example of Hall insulator in three spatial dimensions.

  3. Anisotropic nanomaterials: Synthesis, optical and magnetic properties, and applications

    Microsoft Academic Search

    Matthew John Banholzer

    2010-01-01

    As nanoscience and nanotechnology mature, anisotropic metal nanostructures are emerging in a variety of contexts as valuable class of nanostructures due to their distinctive attributes. With unique properties ranging from optical to magnetic and beyond, these structures are useful in many new applications. Chapter two discusses the nanodisk code: a linear array of metal disk pairs that serve as surface-enhanced

  4. Laser Generated Anisotropic Drives for Radiation Transport Validation

    NASA Astrophysics Data System (ADS)

    Lanier, N. E.; Kline, J. K.; Hager, J. D.

    2013-10-01

    Many astrophysical phenomena are studied in the laboratory by developing a scaled platform whose energy drive is produced via a laser or pulsed power facility. The push to reach more energetic regimes often results in radiation drives that diverge from well-behaved Lambertian Planckian sources. In these cases, typical diffusive radiation flow models can break down. A new platform, that deliberately generates a well-characterized non-Planckian, anisotropic source, has been developed for the OMEGA laser. The resulting data will help validate more complex computational transport schemes like Sn or implicit Monte-Carlo (IMC) models. The platform contains a SiO2 foam mounted on a half-hohlraum. Anisotropy is achieved by inserting an obstruction of either a singular round aperture or annular ring between the foam and hohlraum. In addition, a thin beryllium layer delays the thermal component of the drive while the higher energy M-shell radiation propagates unhindered. The result is a highly non-Planckian, anisotropic, supersonic drive that eventually transitions to sub-sonic. Spectroscopic measurements constrain the source anisotropy, magnitude, and spectral content. Moreover, the Marshak position coupled with spectroscopic absorption measurements quantify the foam's internal energy.

  5. The FN method for anisotropic scattering in neutron transport theory: the critical slab problem.

    NASA Astrophysics Data System (ADS)

    Gülecyüz, M. C.; Tezcan, C.

    1996-08-01

    The FN method which has been applied to many physical problems for isotropic and anisotropic scattering in neutron transport theory is extended for problems for extremely anisotropic scattering. This method depends on the Placzek lemma and the use of the infinite medium Green's function. Here the Green's function for extremely anisotropic scattering which was expressed as a combination of the Green's functions for isotropic scattering is used to solve the critical slab problem. It is shown that the criticality condition is in agreement with the one obtained previously by reducing the transport equation for anisotropic scattering to isotropic scattering and solving using the FN method.

  6. Oxygen-driven anisotropic transport in ultra-thin manganite films

    PubMed Central

    Wang, Baomin; You, Lu; Ren, Peng; Yin, Xinmao; Peng, Yuan; Xia, Bin; Wang, Lan; Yu, Xiaojiang; Mui Poh, Sock; Yang, Ping; Yuan, Guoliang; Chen, Lang; Rusydi, Andrivo; Wang, Junling

    2013-01-01

    Transition metal oxides have a range of unique properties due to coupling of charge, spin, orbital and lattice degrees of freedom and nearly degenerate multiple ground states. These properties make them interesting for applications and for fundamental investigations. Here we report a new phase with abnormal transport anisotropy in La0.7Sr0.3MnO3 ultra-thin films under large tensile strain. This anisotropy is absent in films under smaller tensile strain or compressive strain. Furthermore, thickness and magnetic-field-dependent experiments suggest that the tensile-strain-induced two-dimensional character is crucial for the observed phenomena. X-ray absorption spectroscopy results indicate that this anisotropy is likely driven by O 2p orbital, which hybridizes with Mn 3d. Ab initio calculations confirm this result. Our results may help to understand the anisotropic transport behaviour observed in other systems. PMID:24219875

  7. Preliminary investigation results on fabrics and related physical properties of an anisotropic gneiss

    E-print Network

    Fritz, Harald

    Preliminary investigation results on fabrics and related physical properties of an anisotropic is attributed primarily to a highly anisotropic microcrack pattern, the distinct gneissose banding orientation of minerals (LPO, SPO) has been extensively investigated (Wenk, 1985; Wenk and Christie, 1991

  8. Anisotropic and dynamic mesh adaptation for discontinuous Galerkin methods applied to reactive transport

    Microsoft Academic Search

    Shuyu Sun; Mary F. Wheeler

    2006-01-01

    Mesh adaptation strategies are proposed for discontinuous Galerkin methods applied to reactive transport problems, with emphasis on dynamic and anisotropic adaptation. They include an anisotropic mesh adaptation scheme and two isotropic methods using an L2(L2) norm error estimator and a hierarchic error indicator. These dynamic mesh adaptation approaches are investigated using benchmark cases. Numerical results demonstrate that the three approaches

  9. Anisotropic optical properties of doped poly(3,4-ethylenedioxythiophene)

    Microsoft Academic Search

    L. A. A. Pettersson; T. Johansson; F. Carlsson; H. Arwin; O. Inganäs

    1999-01-01

    Anisotropic optical properties of doped poly(3,4-ethylenedioxythiophene) (PEDOT) thin films have been determined by using variable-angle spectroscopic ellipsometry together with intensity reflectance and transmission spectrophotometry. The optical anisotropy of the PEDOT films are of uniaxial character with the optic axis normal to the film surface. The (ordinary) index of refraction in the plane shows a metallic state behavior while the out

  10. Conformational properties of polymers in anisotropic environments

    E-print Network

    K. Haydukivska; V. Blavatska

    2014-07-11

    We analyze the conformational properties of polymer macromolecules in solutions in presence of extended structural obstacles of (fractal) dimension $\\varepsilon_d$ causing the anisotropy of environment. Applying the pruned-enriched Rosenbluth method (PERM), we obtain numerical estimates for scaling exponents and universal shape parameters of polymers in such environments for a wide range $0parallel and perpendicular to the extended defects.

  11. Direct Imaging of Anisotropic Material Properties using Photorefractive Laser Ultrasound

    SciTech Connect

    Telschow, Kenneth Louis; Deason, Vance Albert; Schley, Robert Scott; Watson, Scott Marshall

    1999-07-01

    Anisotropic properties of materials can be determined by measuring the propagation of elastic waves in different directions. A laser imaging approach is presented that utilizes the adaptive property of photorefractive materials to produce a real-time measurement of the antisymmetric Lamb or flexural traveling wave mode displacement and phase. Continuous excitation is employed and the data is recorded and displayed in all directions simultaneously at video camera frame rates. Fourier transform of the data produces an image of the wave slowness in all planar directions. The results demonstrate imaging of microstructural isotropy and anisotropy and stress induced ansiotropy in plates.

  12. Direct Imaging of Anisotropic Material Properties using Photorefractive Laser Ultrasound

    SciTech Connect

    K.L. Telschow; R.S. Schley; S.M. Watson; V.A. Deason

    1999-06-01

    Anisotropic properties of materials can be determined by measuring the propagation of elastic waves in different directions. A laser imaging approach is presented that utilizes the adaptive property of photorefractive materials to produce a real-time measurement of the antisymmetric Lamb or flexural traveling wave mode displacement and phase. Continuous excitation is employed and the data is recorded and displayed in all directions simultaneously at video camera frame rates. Fourier transform of the data produces an image of the wave slowness in all planar directions. The results demonstrate imaging of microstructural isotropy and anisotropy and stress induced ansiotropy in plates.

  13. Anisotropic wetting properties on various shape of parallel grooved microstructure.

    PubMed

    Tie, Lu; Guo, Zhiguang; Liu, Weimin

    2015-09-01

    It has been revealed experimentally that some superhydrophobic surfaces in nature, such as rice leaf, show strong anisotropic wetting behavior. In this work, based on a thermodynamic approach, the effects of profile shape of parallel grooved microstructure on free energy (FE) with its barrier (FEB) and equilibrium contact angle (ECA) with its hysteresis (CAH) for various orientations of different parallel micro texture surface have been systematically investigated in detail. The results indicated that the anisotropy of wetting properties strongly depended on the specific topographical features and wetting state. In particular, a paraboloidal profile of parallel micro-texture surface is used as an important example to theoretically establish the relationship between surface geometry and anisotropic wetting behavior for optimal design, showing that the wetting behavior of the composite state is similar to that of the non-composite state and the anisotropy will possibly be appeared with the decrease of height or intrinsic contact angle of paraboloidal profile of micro texture. PMID:25982937

  14. Anisotropic mechanical properties of graphene: a molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Yu, Ming; Zeng, Anna; Zeng, Kevin

    2014-03-01

    The anisotropic mechanical properties of monolayer graphene with different shapes have been studied using an efficient quantum mechanics molecular dynamics scheme based on a semi-empirical Hamiltonian (refereed as SCED-LCAO) [PRB 74, 15540; PHYSE 42, 1]. We have found the anisotropic nature of the membrane stress. The stresses along the armchair direction are slightly stronger than that along the zigzag direction, showing strong direction selectivity. The graphene with the rectangular shape could sustain strong load (i . e ., 20%) in both armchair and zigzag directions. The graphene with the rhombus shape show large difference in the strain direction: it will quickly crack after 18 % of strain in armchair the direction, but slowly destroyed after 20% in the zigzag direction. The obtained 2D Young's modulus at infinitesimal strain and the third-order (effective nonlinear) elastic modulus are in good consistent with the experimental observation.

  15. Anisotropic Radiation Transport Experiments on the OMEGA Laser

    NASA Astrophysics Data System (ADS)

    Hager, Jonathan; Lanier, Nick; Kline, John; Flippo, Kirk; Workman, Jonathan; Bruns, H. C.; Schneider, M.; Saculla, M.; McCarville, T.

    2014-10-01

    A new experimental platform is being developed at the OMEGA laser to generate an anisotropic radiation source to provide data that will challenge our implementation of Implicit Monte Carlo (IMC) radiation transport models. A low density silica aerogel foam physics package is mounted to a laser driven half-hohlraum. The x-ray drive from the hohlraum is modified by a filter and aperture to decrease the optical thickness of the foam and increase the source anisotropy, respectively. Point projection backlighting is used to measure the hydrodynamic response to the Marshak wave once it goes subsonic. The temperature of the driven foam can also be inferred using absorption spectroscopy when a titanium dopant is introduced. Experimental results using a Ti doped foam will be presented with analytic calculations and 2-D radiation hydrodynamic simulations demonstrating the impact of the source anisotropy on the measurable parameters in the foam. This work performed under the auspices of the U.S. Department of Energy by LANL under Contract DE-AC52-06NA25396.

  16. Spin-orbit interaction induced anisotropic property in interacting quantum wires

    PubMed Central

    2011-01-01

    We investigate theoretically the ground state and transport property of electrons in interacting quantum wires (QWs) oriented along different crystallographic directions in (001) and (110) planes in the presence of the Rashba spin-orbit interaction (RSOI) and Dresselhaus SOI (DSOI). The electron ground state can cross over different phases, e.g., spin density wave, charge density wave, singlet superconductivity, and metamagnetism, by changing the strengths of the SOIs and the crystallographic orientation of the QW. The interplay between the SOIs and Coulomb interaction leads to the anisotropic dc transport property of QW which provides us a possible way to detect the strengths of the RSOI and DSOI. PACS numbers: 73.63.Nm, 71.10.Pm, 73.23.-b, 71.70.Ej PMID:21711717

  17. Anisotropic MRI contrast reveals enhanced ionic transport in plastic crystals.

    PubMed

    Romanenko, Konstantin; Jin, Liyu; Madsen, Louis A; Pringle, Jennifer M; O'Dell, Luke A; Forsyth, Maria

    2014-11-01

    Organic ionic plastic crystals (OIPCs) are attractive as solid-state electrolytes for electrochemical devices such as lithium-ion batteries and solar and fuel cells. OIPCs offer high ionic conductivity, nonflammability, and versatility of molecular design. Nevertheless, intrinsic ion transport behavior of OIPCs is not fully understood, and their measured properties depend heavily on thermal history. Solid-state magnetic resonance imaging experiments reveal a striking image contrast anisotropy sensitive to the orientation of grain boundaries in polycrystalline OIPCs. Probing triethyl(methyl)phosphonium bis(fluorosulfonyl)imide (P1222FSI) samples with different thermal history demonstrates vast variations in microcrystallite alignment. Upon slow cooling from the melt, microcrystallites exhibit a preferred orientation throughout the entire sample, leading to an order of magnitude increase in conductivity as probed using impedance spectroscopy. This investigation describes both a new conceptual window and a new characterization method for understanding polycrystalline domain structure and transport in plastic crystals and other solid-state conductors. PMID:25312993

  18. Anisotropic Structure and Transport in Self-Assembled Layered Polymer-Clay Nanocomposites

    E-print Network

    Sadoway, Donald Robert

    Anisotropic Structure and Transport in Self-Assembled Layered Polymer-Clay Nanocomposites Jodie L a polymer-clay structure from a unique combination of LbL materials: poly(ethylene imine), Laponite clay transport in LbL assemblies and its correlation to structural anisotropy. Introduction Synthetic clays

  19. Anisotropic magnetic properties of EuAl2Si2

    NASA Astrophysics Data System (ADS)

    Maurya, Arvind; Kulkarni, Ruta; Thamizhavel, A.; Bonville, P.; Dhar, S. K.

    2015-03-01

    EuAl2Si2 is known to crystallize in the CaAl2Si2-type trigonal structure. We have grown single crystals of EuAl2Si2 by flux method, using Al-Si eutectic (87.8% Al) as self-flux, and investigated their anisotropic magnetic properties by means of magnetization, electrical resistivity and heat capacity in zero and applied magnetic fields, and 151Eu Mössbauer spectroscopy. Magnetic susceptibility data show an antiferromagnetic transition at TN = 33.3 K in agreement with the previously reported value on polycrystalline sample. The isothermal magnetization at 2 K measured along and perpendicular to the c-axis shows anisotropic behaviour, which is rather unexpected as Eu2+ is an S-state ion. The spin flip fields along the two directions are 2.8 and 4.8 T, respectively, while two closely spaced spin-flop transitions in the ab-plane are observed near 1.4 and 1.6 T. The electrical resistivity shows an upturn between TN and 60 K as the temperature is lowered below ~ 60 K, suggesting the presence of antiferromagnetic correlations in the paramagnetic state. Magnetoresistivity at 2 K in 14 T is nearly 1070 % for H // [0001]. The results of heat capacity and 151Eu Mössbauer spectroscopy are in conformity with a bulk transition at 33.3 K.

  20. Local and nonlocal anisotropic transport in reversed shear magnetic fields: shearless Cantori and nondiffusive transport.

    PubMed

    Blazevski, Daniel; del-Castillo-Negrete, Diego

    2013-06-01

    A study of anisotropic heat transport in reversed shear (nonmonotonic q-profile) magnetic fields is presented. The approach is based on a recently proposed Lagrangian-Green's function method that allows an efficient and accurate integration of the parallel (i.e., along the magnetic field) heat transport equation. The magnetic field lines are described by a nontwist Hamiltonian system, known to exhibit separatrix reconnection and robust shearless (dq/dr=0) transport barriers. The changes in the magnetic field topology due to separatrix reconnection lead to bifurcations in the equilibrium temperature distribution. For perturbations of moderate amplitudes, magnetic chaos is restricted to bands flanking the shearless region. As a result, the temperature flattens in the chaotic bands and develops a very sharp radial gradient at the shearless region. For perturbations with larger amplitude, shearless Cantori (i.e., critical magnetic surfaces located at the minimum of the q profile) give rise to anomalous temperature relaxation involving widely different time scales. The first stage consists of the relatively fast flattening of the radial temperature profile in the chaotic bands with negligible flux across the shearless region that, for practical purposes, on a short time scale acts as an effective transport barrier despite the lack of magnetic flux surfaces. In the long-time scale, heat starts to flow across the shearless region, albeit at a comparatively low rate. The transport of a narrow temperature pulse centered at the reversed shear region exhibits weak self-similar scaling with non-Gaussian scaling functions indicating that transport at this scale cannot be modeled as a diffusive process with a constant diffusivity. Evidence of nonlocal effective radial transport is provided by the existence of regions with nonzero heat flux and zero temperature gradient. Parametric flux-gradient plots exhibit multivalued loops that question the applicability of the Fourier-Fick's prescription even in the presence of a finite pinch velocity. PMID:23848788

  1. Matter wave transport and Anderson localization in anisotropic three-dimensional disorder

    NASA Astrophysics Data System (ADS)

    Piraud, Marie; Pezzé, Luca; Sanchez-Palencia, Laurent

    2012-09-01

    We study quantum transport of matter waves in anisotropic three-dimensional disorder. First, we show that structured correlations can induce rich effects, such as anisotropic suppression of the white-noise limit and inversion of the transport anisotropy. Second, we show that the localization threshold (mobility edge) is strongly affected by a disorder-induced shift of the energy states, which we calculate. Our work is directly relevant to ultracold-matter waves in optical disorder, and implications on recent experiments are discussed. It also offers scope for further studies of anisotropy effects in other systems with controlled disorder, where counterparts of the discussed effects can be expected.

  2. Structural properties of anisotropically confined binary Coulomb balls.

    PubMed

    Silva, F C O; Apolinario, S W S

    2014-06-01

    We investigate the structural properties of a small binary system of dusty plasma subjected to an anisotropic external confinement. We have found that the ground state can form various symmetrical configurations, which generally correspond to variations of a multiple-ring structure. The presence of such structures is given through a detailed phase diagram constructed for the systems with N=18 and 24 particles. Furthermore, we show that the configurations of multiple rings can present a persistent behavior for the case in which the number of less-charged particles is equal to a multiple of the number of particles per ring. Finally, we discuss the main characteristics of the transitions of first and second orders since these are related to the main configurational changes of the ground states. PMID:25019787

  3. Holographic transports and stability in anisotropic linear axion model

    E-print Network

    Xian-Hui Ge; Yi Ling; Chao Niu; Sang-Jin Sin

    2015-01-15

    We study thermoelectric conductivities and shear viscosities in a holographically anisotropic model. Momentum relaxation is realized through perturbing the linear axion field. AC conductivity exhibits a conherent/incoherent metal transition. The longitudinal shear viscosity for prolate anisotropy violates the bound conjectured by Kovtun-Son-Starinets. We also find that thermodynamic and dynamical instabilities are not always equivalent, which provides a counter example of the Gubser-Mitra conjecture.

  4. TRANSPORT PROPERTIES OF CARTILAGINOUS TISSUES

    PubMed Central

    Jackson, AR; Gu, WY

    2009-01-01

    Cartilaginous tissues, such as articular cartilage and intervertebral disc, are avascular tissues which rely on transport for cellular nutrition. Comprehensive knowledge of transport properties in such tissues is therefore necessary in the understanding of nutritional supply to cells. Furthermore, poor cellular nutrition in cartilaginous tissues is believed to be a primary source of tissue degeneration, which may result in osteoarthritis (OA) or disc degeneration. In this mini-review, we present an overview of the current status of the study of transport properties and behavior in cartilaginous tissues. The mechanisms of transport in these tissues, as well as experimental approaches to measuring transport properties and results obtained are discussed. The current status of bioreactors used in cartilage tissue engineering is also presented. PMID:20126303

  5. Anisotropic transport in unidirectional lateral superlattice around half filling of the second Landau level

    E-print Network

    Iye, Yasuhiro

    Anisotropic transport in unidirectional lateral superlattice around half filling of the second maxima.16,17 The role played by B in the drastic transition of the 5/2 and 7/2 states is not exactly established yet. The most probable picture however, seems to be alteration by B of Haldane's pseudopotential

  6. Spin amplification, reading, and writing in transport through anisotropic magnetic molecules Carsten Timm1,2,

    E-print Network

    von Oppen, Felix

    Spin amplification, reading, and writing in transport through anisotropic magnetic molecules, and reading spin information in molecular memory devices. Magnetic anisotropy is found to be crucial for slow of a magnetic field. We propose schemes for reading and writing spin information based on our findings. DOI: 10

  7. Anisotropic vanadium dioxide sculptured thin films with superior thermochromic properties.

    PubMed

    Sun, Yaoming; Xiao, Xiudi; Xu, Gang; Dong, Guoping; Chai, Guanqi; Zhang, Hua; Liu, Pengyi; Zhu, Hanmin; Zhan, Yongjun

    2013-01-01

    VO2 (M) STF through reduction of V2O5 STF was prepared. The results illustrate that V2O5 STF can be successfully obtained by oblique angle thermal evaporation technique. After annealing at 550 °C/3 min, the V2O5 STF deposited at 85° can be easily transformed into VO2 STF with slanted columnar structure and superior thermochromic properties. After deposition SiO2 antireflective layer, Tlum of VO2 STF is enhanced 26% and ?Tsol increases 60% compared with that of normal VO2 thin films. Due to the anisotropic microstructure of VO2 STF, angular selectivity transmission of VO2 STF is observed and the solar modulation ability is further improved from 7.2% to 8.7% when light is along columnar direction. Moreover, the phase transition temperature of VO2 STF can be depressed into 54.5 °C without doping. Considering the oblique incidence of sunlight on windows, VO2 STF is more beneficial for practical application as smart windows compared with normal homogenous VO2 thin films. PMID:24067743

  8. Computing Thermodynamic And Transport Properties

    NASA Technical Reports Server (NTRS)

    Mcbride, B.; Gordon, Sanford

    1993-01-01

    CET89 calculates compositions in chemical equilibrium and properties of mixtures of any chemical system for which thermodynamic data available. Provides following options: obtains chemical-equilibrium compositions and corresponding thermodynamic mixture properties for assigned thermodynamic states; calculates dilute-gas transport properties of complex chemical mixtures; obtains Chapman-Jouguet detonation properties for gaseous mixtures; calculates properties of incident and reflected shocks in terms of assigned velocities; and calculates theoretical performance of rocket for both equilibrium and frozen compositions during expansion. Rocket performance based on optional models of finite or infinite area combustor.

  9. Transport properties in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Biolsi, L., Jr.

    1979-01-01

    The computer program used to obtain transport properties for the Hulburt-Hirschfelder potential was tested. Transport properties for the C-C interaction were calculated. Rough estimates for transport properties for the important ablation species were obtained as well as estimates of transport properties for some of the species associated with photochemical smog. The results are discussed.

  10. Investigation of Scattering Property for An Anisotropic Dielectric Circular Cylinder

    E-print Network

    Li, Y-L

    2010-01-01

    Utilizing the scales theory of electromagnetic theory, the anisotropic dielectric material is reconstructed into an isotropic medium. The analytic expressions of scattering field and the scattering breadth for an anisotropic material cylinder are first presented. Their validities are checked theoretically. The influences induced by the dielectric constant tensor etc. on the scattering breadth are simulated. The results show that the scatterings both in the forward direction and vertical direction to the incident direction are strong. The dielectric constant in the polarizing direction has a biggish effect on scattering field. The mechanism of results is presented

  11. A new multiscale air quality transport model (Fluidity, 4.1.9) using fully unstructured anisotropic adaptive mesh technology

    NASA Astrophysics Data System (ADS)

    Zheng, J.; Zhu, J.; Wang, Z.; Fang, F.; Pain, C. C.; Xiang, J.

    2015-06-01

    A new anisotropic hr-adaptive mesh technique has been applied to modelling of multiscale transport phenomena, which is based on a discontinuous Galerkin/control volume discretization on unstructured meshes. Over existing air quality models typically based on static-structured grids using a locally nesting technique, the advantage of the anisotropic hr-adaptive model has the ability to adapt the mesh according to the evolving pollutant distribution and flow features. That is, the mesh resolution can be adjusted dynamically to simulate the pollutant transport process accurately and effectively. To illustrate the capability of the anisotropic adaptive unstructured mesh model, three benchmark numerical experiments have been setup for two-dimensional (2-D) transport phenomena. Comparisons have been made between the results obtained using uniform resolution meshes and anisotropic adaptive resolution meshes.

  12. Transport Properties for Combustion Modeling

    SciTech Connect

    Brown, N.J.; Bastein, L.; Price, P.N.

    2010-02-19

    This review examines current approximations and approaches that underlie the evaluation of transport properties for combustion modeling applications. Discussed in the review are: the intermolecular potential and its descriptive molecular parameters; various approaches to evaluating collision integrals; supporting data required for the evaluation of transport properties; commonly used computer programs for predicting transport properties; the quality of experimental measurements and their importance for validating or rejecting approximations to property estimation; the interpretation of corresponding states; combination rules that yield pair molecular potential parameters for unlike species from like species parameters; and mixture approximations. The insensitivity of transport properties to intermolecular forces is noted, especially the non-uniqueness of the supporting potential parameters. Viscosity experiments of pure substances and binary mixtures measured post 1970 are used to evaluate a number of approximations; the intermediate temperature range 1 < T* < 10, where T* is kT/{var_epsilon}, is emphasized since this is where rich data sets are available. When suitable potential parameters are used, errors in transport property predictions for pure substances and binary mixtures are less than 5 %, when they are calculated using the approaches of Kee et al.; Mason, Kestin, and Uribe; Paul and Warnatz; or Ern and Giovangigli. Recommendations stemming from the review include (1) revisiting the supporting data required by the various computational approaches, and updating the data sets with accurate potential parameters, dipole moments, and polarizabilities; (2) characterizing the range of parameter space over which the fit to experimental data is good, rather than the current practice of reporting only the parameter set that best fits the data; (3) looking for improved combining rules, since existing rules were found to under-predict the viscosity in most cases; (4) performing more transport property measurements for mixtures that include radical species, an important but neglected area; (5) using the TRANLIB approach for treating polar molecules and (6) performing more accurate measurements of the molecular parameters used to evaluate the molecular heat capacity, since it affects thermal conductivity, which is important in predicting flame development.

  13. The effect of anisotropic reflectance on imaging spectroscopy of snow properties

    E-print Network

    California at Santa Barbara, University of

    The effect of anisotropic reflectance on imaging spectroscopy of snow properties Thomas H. Paintera directional reflectance affect the mapping of snow properties from imaging spectrometer data? This sensitivity­directional reflectance factor (HDRF) with prescribed snow-covered area and snow grain size. The MEMSCAG model determines

  14. Transport properties in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Biolsi, L., Jr.

    1978-01-01

    The calculation of transport properties near the surface of a probe entering the atmosphere of Jupiter is discussed for (1) transport properties in the pure Jovian atmosphere, (2) transport properties for collisions between monatomic carbon atoms, including the effect of excited electronic states, (3) transport properties at the boundaries for mixing of the pure Jovian atmosphere and the atmosphere due to the injection of gaseous ablation products, and (4) transport properties for interactions involving some of the molecular ablation products. The transport properties were calculated using the kinetic theory of gases. Transport collision integrals were calculated for only a limited set of empirical and semiempirical interaction potentials. Since the accuracy of the fit of these empirical potentials to the true potential usually determines the accuracy of the calculation of the transport properties, the various interaction potentials used in these calculations are discussed.

  15. An asymptotic-preserving Lagrangian algorithm for the time-dependent anisotropic heat transport equation

    SciTech Connect

    Chacon, Luis [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); del-Castillo-Negrete, Diego [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Hauck, Cory D. [Univ. of Tennessee, Knoxville, TN (United States)

    2014-09-01

    We propose a Lagrangian numerical algorithm for a time-dependent, anisotropic temperature transport equation in magnetized plasmas in the large guide field regime. The approach is based on an analytical integral formal solution of the parallel (i.e., along the magnetic field) transport equation with sources, and it is able to accommodate both local and non-local parallel heat flux closures. The numerical implementation is based on an operator-split formulation, with two straightforward steps: a perpendicular transport step (including sources), and a Lagrangian (field-line integral) parallel transport step. Algorithmically, the first step is amenable to the use of modern iterative methods, while the second step has a fixed cost per degree of freedom (and is therefore scalable). Accuracy-wise, the approach is free from the numerical pollution introduced by the discrete parallel transport term when the perpendicular to parallel transport coefficient ratio X? /X? becomes arbitrarily small, and is shown to capture the correct limiting solution when ? = X?L2?/X1L2? ? 0 (with L?? L? , the parallel and perpendicular diffusion length scales, respectively). Therefore, the approach is asymptotic-preserving. We demonstrate the capabilities of the scheme with several numerical experiments with varying magnetic field complexity in two dimensions, including the case of transport across a magnetic island.

  16. Properties of solid and gaseous hydrogen, based upon anisotropic pair interactions

    NASA Technical Reports Server (NTRS)

    Etters, R. D.; Danilowicz, R.; England, W.

    1975-01-01

    Properties of H2 are studied on the basis of an analytic anisotropic potential deduced from atomic orbital and perturbation calculations. The low-pressure solid results are based on a spherical average of the anisotropic potential. The ground state energy and the pressure-volume relation are calculated. The metal-insulator phase transition pressure is predicted. Second virial coefficients are calculated for H2 and D2, as is the difference in second virial coefficients between ortho and para H2 and D2.

  17. Landau levels and magneto-transport property of monolayer phosphorene.

    PubMed

    Zhou, X Y; Zhang, R; Sun, J P; Zou, Y L; Zhang, D; Lou, W K; Cheng, F; Zhou, G H; Zhai, F; Chang, Kai

    2015-01-01

    We investigate theoretically the Landau levels (LLs) and magneto-transport properties of phosphorene under a perpendicular magnetic field within the framework of the effective k·p Hamiltonian and tight-binding (TB) model. At low field regime, we find that the LLs linearly depend both on the LL index n and magnetic field B, which is similar with that of conventional semiconductor two-dimensional electron gas. The Landau splittings of conduction and valence band are different and the wavefunctions corresponding to the LLs are strongly anisotropic due to the different anisotropic effective masses. An analytical expression for the LLs in low energy regime is obtained via solving the decoupled Hamiltonian, which agrees well with the numerical calculations. At high magnetic regime, a self-similar Hofstadter butterfly (HB) spectrum is obtained by using the TB model. The HB spectrum is consistent with the LL fan calculated from the effective k·p theory in a wide regime of magnetic fields. We find the LLs of phosphorene nanoribbon depend strongly on the ribbon orientation due to the anisotropic hopping parameters. The Hall and the longitudinal conductances (resistances) clearly reveal the structure of LLs. PMID:26159856

  18. Landau levels and magneto-transport property of monolayer phosphorene

    PubMed Central

    Zhou, X. Y.; Zhang, R.; Sun, J. P.; Zou, Y. L.; Zhang, D.; Lou, W. K.; Cheng, F.; Zhou, G. H.; Zhai, F.; Chang, Kai

    2015-01-01

    We investigate theoretically the Landau levels (LLs) and magneto-transport properties of phosphorene under a perpendicular magnetic field within the framework of the effective k·p Hamiltonian and tight-binding (TB) model. At low field regime, we find that the LLs linearly depend both on the LL index n and magnetic field B, which is similar with that of conventional semiconductor two-dimensional electron gas. The Landau splittings of conduction and valence band are different and the wavefunctions corresponding to the LLs are strongly anisotropic due to the different anisotropic effective masses. An analytical expression for the LLs in low energy regime is obtained via solving the decoupled Hamiltonian, which agrees well with the numerical calculations. At high magnetic regime, a self-similar Hofstadter butterfly (HB) spectrum is obtained by using the TB model. The HB spectrum is consistent with the LL fan calculated from the effective k·p theory in a wide regime of magnetic fields. We find the LLs of phosphorene nanoribbon depend strongly on the ribbon orientation due to the anisotropic hopping parameters. The Hall and the longitudinal conductances (resistances) clearly reveal the structure of LLs. PMID:26159856

  19. Anisotropic effective-medium modeling of the elastic properties of shales

    SciTech Connect

    Hornby, B.E. (Schlumberger Cambridge Research Ltd. (United Kingdom) Bullard Labs., Cambridge (United Kingdom). Dept. of Earth Sciences); Schwartz, L.M. (Schlumberger-Doll Research, Ridgefield, CT (United States)); Hudson, J.A. (Dept. of Applied Maths and Theoretical Physics, Cambridge (United Kingdom))

    1994-10-01

    Shales are complex porous materials, normally consisting of percolating and interpenetrating fluid and solid phases. The solid phase is generally comprised of several mineral components and forms an intricate and anisotropic microstructure. The shape, orientation, and connection of the two phases control the anisotropic elastic properties of the composite solid. The authors develop a theoretical framework that allows one to predict the effective elastic properties of shales. Its usefulness is demonstrated with numerical modeling and by comparison with established ultrasonic laboratory experiments. The theory is based on a combination of anisotropic formulations of the self-consistent (SCA) and differential effective-medium (DEM) approximations. This combination guarantees that both the fluid and solid phases percolate at all porosities. The modeling of the elastic properties of shales proceeds in four steps. First, the authors consider the case of an aligned biconnected clay-fluid composite composed of ellipsoidal inclusions. Anisotropic elastic constants are estimated for a clay-fluid composite as a function of the fluid-filled porosity and the aspect ratio of the inclusions. Second, a new processing technique is developed to estimate the distribution of clay platelet orientations from digitized scanning electron microphotographs (SEM). Third, the derived clay platelet distribution is employed to estimate the effective elastic parameters of a solid comprising clay-fluid composites oriented at different angles. Finally, silt minerals are included in the calculations as isolated spherical inclusions.

  20. Synthesis and optical properties of anisotropic metal nanoparticles.

    PubMed

    Hao, Encai; Schatz, George C; Hupp, Joseph T

    2004-07-01

    In this paper we overview our recent studies of anisotropic noble metal (e.g. gold and silver) nanoparticles, in which a combination of theory and experiment has been used to elucidate the extinction spectra of the particles, as well as information related to their surface enhanced Raman spectroscopy. We used wet-chemical methods to generate several structurally well-defined nanostructures other than solid spheres, including silver nanodisks and triangular nanoprisms, and gold nanoshells and multipods. When solid spheres are transformed into one of these shapes, the surface plasmon resonances in these particles are strongly affected, typically red-shifting and even splitting into distinctive dipole and quadrupole plasmon modes. In parallel, we have developed computational electrodynamics methods based on the discrete dipole approximation (DDA) method to determine the origins of these intriguing optical features. This has resulted in considerable insight concerning the variation of plasmon wavelength with nanoparticle size, shape and dielectric environment, as well as the use of these particles for optical sensing applications. PMID:15617376

  1. Evolution, Interaction, and Intrinsic Properties of Dislocations in Intermetallics: Anisotropic 3D Dislocation Dynamics Approach

    SciTech Connect

    Qian Chen

    2008-08-18

    The generation, motion, and interaction of dislocations play key roles during the plastic deformation process of crystalline solids. 3D Dislocation Dynamics has been employed as a mesoscale simulation algorithm to investigate the collective and cooperative behavior of dislocations. Most current research on 3D Dislocation Dynamics is based on the solutions available in the framework of classical isotropic elasticity. However, due to some degree of elastic anisotropy in almost all crystalline solids, it is very necessary to extend 3D Dislocation Dynamics into anisotropic elasticity. In this study, first, the details of efficient and accurate incorporation of the fully anisotropic elasticity into 3D discrete Dislocation Dynamics by numerically evaluating the derivatives of Green's functions are described. Then the intrinsic properties of perfect dislocations, including their stability, their core properties and disassociation characteristics, in newly discovered rare earth-based intermetallics and in conventional intermetallics are investigated, within the framework of fully anisotropic elasticity supplemented with the atomistic information obtained from the ab initio calculations. Moreover, the evolution and interaction of dislocations in these intermetallics as well as the role of solute segregation are presented by utilizing fully anisotropic 3D dislocation dynamics. The results from this work clearly indicate the role and the importance of elastic anisotropy on the evolution of dislocation microstructures, the overall ductility and the hardening behavior in these systems.

  2. Anisotropic magnetic properties of the KMo4O6

    NASA Astrophysics Data System (ADS)

    Andrade, M.; Maffei, M. L.; Dos Santos, C. A. M.; Ferreira, B.; Sartori, A. F.

    2012-02-01

    Electrical resistivity measurements in the tetragonal KMo4O6 single crystals show a metal-insulator transition (MIT) near 100K. Magnetization measurements as a function of temperature show no evidence of magnetic ordering at this MIT [1]. Single crystals of KMo4O6 were obtained by electrolysis of a melt with a molar ratio of K2MoO4:MoO3 = 6:1. The process were carried out at 930 C with a current of 20-25mA for 52h in argon atmosphere. After that, electrodes were removed from the melt alloying the crystals to cool down to room temperature rapidly. Scanning Electron Microscopy (SEM) showed that the black single crystals were grown on the platinum cathode. Typical dimensions of the single crystals are 1x0.2x0.2mm^3. X-ray diffractometry confirmed that the single crystals have KMo4O6 tetragonal crystalline structure with space group P4. Magnetization measurements were performed parallel and perpendicular to the c-axis from 2 to 300K. The results show anisotropic behavior between both directions. Furthermore, the temperature independence of the magnetization at high temperature and the upturn at low temperature are observed in agreement with previous results [1]. MxH curves measured at several temperatures show nonlinear behavior and a small magnetic ordering. The magnetic ordering seems to be related to the MIT near 100K. This material is based upon support by FAPESP (2009/14524-6 and 2009/54001-6) and CNPq/NSF (490182/2009-7). M. Andrade is CAPES fellow and C.A.M. dos Santos is CNPq fellow. [4pt] [1] K. V. Ramanujachary et al., J. Sol. State Chem.102 (1993) 69.

  3. The effect of anisotropic heat transport on magnetic islands in 3-D configurations

    SciTech Connect

    Schlutt, M. G.; Hegna, C. C. [University of Wisconsin-Madison, 1500 Engineering Drive, 510 ERB, Madison, Wisconsin 53706 (United States)

    2012-08-15

    An analytic theory of nonlinear pressure-induced magnetic island formation using a boundary layer analysis is presented. This theory extends previous work by including the effects of finite parallel heat transport and is applicable to general three dimensional magnetic configurations. In this work, particular attention is paid to the role of finite parallel heat conduction in the context of pressure-induced island physics. It is found that localized currents that require self-consistent deformation of the pressure profile, such as resistive interchange and bootstrap currents, are attenuated by finite parallel heat conduction when the magnetic islands are sufficiently small. However, these anisotropic effects do not change saturated island widths caused by Pfirsch-Schlueter current effects. Implications for finite pressure-induced island healing are discussed.

  4. TRANSPORT PROPERTY MEASUREMENTS OF HFC-236EA

    EPA Science Inventory

    The report gives results of an evaluation of transport properties of 1,1,1,2,3,3,-hexafluoropropane (HFC-236ea), with liquid viscosity and thermal conductivity being the two main transport properties of interest. In addition, the specific heat and density of refrigerant/lubrican...

  5. TRANSPORT PROPERTY MEASUREMENTS OF HFC-236EA

    EPA Science Inventory

    The report gives results of an evaluation of transport properties of 1, 1, 1, 2, 3, 3-hexafluoropropane (HFC-236ea), with liquid viscosity and thermal conductivity being the two main transport properties of interest. In addition, the specific heat and density of refrigerant/lubri...

  6. The transport properties of activated carbon fibers

    SciTech Connect

    di Vittorio, S.L. (Massachusetts Inst. of Tech., Cambridge, MA (USA). Dept. of Materials Science and Engineering); Dresselhaus, M.S. (Massachusetts Inst. of Tech., Cambridge, MA (USA). Dept. of Electrical Engineering and Computer Science Massachusetts Inst. of Tech., Cambridge, MA (USA). Dept. of Physics); Endo, M. (Shinshu Univ., Nagano (Japan). Dept. of Electrical Engineering); Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons. 19 refs., 4 figs.

  7. Transport properties in unconventional superconductors

    NASA Astrophysics Data System (ADS)

    Cui, Qinghong

    2007-12-01

    This dissertation investigates the transport properties of unconventional superconductors which differ from the conventional superconductors on two aspects, one is the pairing symmetry of the order parameter, the other is the net momentum of the Cooper pair. The former ones are discovered in high- Tc cuprates, heavy-fermion, Sr2RuO4 and so on. The latter ones can be realized by splitting the Fermi surfaces of spin-up and -down electrons under Zeeman field and are known as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states. This work is consisted of two parts. In the first part, we present results of numerical studies of spin quantum Hall transitions in disordered superconductors, in which the pairing order parameter breaks time-reversal symmetry. We focus mainly on p-wave superconductors in which one of the spin components is conserved. The transport properties of the system are studied by numerically diagonalizing pairing Hamiltonians on a lattice, and by calculating the Chern and Thouless numbers of the quasiparticle states. We find that in the presence of disorder, (spin-)current carrying states exist only at discrete critical energies in the thermodynamic limit, and the spin-quantum Hall transition driven by an external Zeeman field has the same critical behavior as the usual integer quantum Hall transition of non-interacting electrons. These critical energies merge and disappear as disorder strength increases, in a manner similar to those in lattice models for integer quantum Hall transition. The second part is a proposal of identifying the FFLO state based on its transport properties in the normal metal/superconductor junction (NSJ). The FFLO state has received renewed interest recently due to the experimental indication of its presence in CeCoIn5, a quasi 2-dimensional (2D) d-wave superconductor. However direct evidence of the spatial variation of the superconducting order parameter, which is the hallmark of the FFLO state, does not yet exist. In this work we examine the possibility of detecting the phase structure of the order parameter directly using conductance spectroscopy through NSJ, which probes the phase sensitive surface Andreev bound states of d-wave superconductors. We employ the Blonder-Tinkham-Klapwijk formalism to calculate the conductance characteristics between a normal metal and a 2D s- or dx2-y2 -wave superconductor in the Fulde-Ferrell state, for all barrier parameter z from the point contact limit (z = 0) to the tunneling limit (z " 1). We find that the zero-bias conductance peak due to these surface Andreev bound states observed in the uniform d-wave superconductor is split and shifted in the Fulde-Ferrell state. We also clarify what weighted bulk density of states is measured by the conductance in the limit of large z.

  8. Magnetic Properties of Isotropic and Anisotropic Linear Chains.

    NASA Astrophysics Data System (ADS)

    Greeney, Robert Edgar

    1988-12-01

    The magnetic susceptibilities and magnetizations of three quasi one-dimensional magnetic systems have been studied at temperatures ranging between room temperature and 1.4 K, with a Vibrating Sample Magnetometer (VSM). X -ray diffraction at room temperature has been carried out to determine the crystal structures of the two new compounds. Mossbauer spectroscopy at temperatures ranging from room temperature to 0.4 K have been performed on the two iron compounds studied. The design and performance of a custom cryostat used in conjunction with the VSM is described in detail. An inner enclosure (hangdown tube) has been used to reduce temperature fluctuations and thermal gradients. Methods for eliminating rubbing-induced background signals, and field-induced errors in thermometry are discussed. The crystal structure of ((CH_3) _3NH) FeCl_3cdot2H _2O, FeTAC, consists of chains of Fe^{2+} ions extending along the b axis of the orthorhombic unit cell (space group Pnma). The low temperature magnetic susceptibilities are highly anisotropic, and can be fit to the 1-d Ising model with a small molecular field correction giving a ferromagnetic intrachain exchange (J_{rm b }/k = 17.4 K). The total interchain exchange is negative and small (Z^'J ^'/ZJ ~ 2 times 10^{-3}). Evidence of long range magnetic order is observed near 3.12 K. Low field magnetization data show metamagnetic transitions when small fields are applied along the b axis. The metamagnetic phase diagram indicates the critical field is 90 Oe at T = 0 K. High field magnetization data up to 150 kOe show the presence of spin canting. X-ray studies show (CH_3)_3 NHFeBr_3cdot2H _2O, FeTAB, to be isostructural with FeTAC. Low temperature powder susceptibility data agree with the predicted susceptibility for a ferromagnetic 1-d Ising magnet with an exchange constant of 4.0(1.0) K. Mossbauer spectroscopy has shown the ordering temperature to be near 1.3(1) K. Copper chloride bis(DMSO) (DMSO is dimethyl sulfoxide) consists of linear chains of antiferromagnetically coupled S = 1over2 ions. The single-crystal dc magnetic susceptibilities have been measured. The data were compared to the predictions of Bucher and Honerkamp for the susceptibilities of XXZ linear chains. Good agreement was found for an exchange strength of J/k = -8.25 K and an anisotropy parameter Delta = 1.1, slightly Ising-like.

  9. The effect of anisotropic reflectance on imaging spectroscopy of snow properties

    Microsoft Academic Search

    Thomas H. Painter; Jeff Dozier

    2004-01-01

    How does snow's anisotropic directional reflectance affect the mapping of snow properties from imaging spectrometer data? This sensitivity study applies two spectroscopy models to synthetic images of the spectral hemispherical–directional reflectance factor (HDRF) with prescribed snow-covered area and snow grain size. The MEMSCAG model determines both sub-pixel snow-covered area and the grain size of the fractional snow cover. The Nolin\\/Dozier

  10. A new method for calculation of elastic properties of anisotropic material by constant pressure molecular dynamics

    Microsoft Academic Search

    Kailiang Yin; Dinghui Zou; Jing Zhong; Duanjun Xu

    2007-01-01

    A new method based on constant pressure molecular dynamics (MD) with the software package Materials Studio (MS) was developed to calculate the anisotropic elastic properties of 1,3,5-tri-amino-2,4,6-tri-nitrobenzene (TATB) which is a typical and widely studied explosive molecular and its single crystal is a typical triclinic lattice. Key points of the method are introduced. Firstly, a P1 periodic super cell of

  11. Physical Properties of Anisotropically Swelling Hydrogen-Bonded Liquid Crystal Polymer Actuators

    Microsoft Academic Search

    Kenneth D. Harris; Cees W. M. Bastiaansen; D. J. Broer

    2007-01-01

    Glassy polymeric actuators are described which reversibly deform in response to changes in pH and\\/or the presence of water. Hydrogen-bonded liquid crystalline monomers act as precursors, and these materials are photopolymerized (without mechanical drawing) into monodomain nematic networks. We discuss the influence of film composition, polymerization conditions, and chemical treatments on the properties of these anisotropic networks. We show that

  12. Magnetic properties of anisotropic Sr-La-system ferrite magnets

    SciTech Connect

    Yamamoto, H.; Nagakura, M. (School of Science and Technology, Meiji Univ., 1-1-1 Higashi-mita, Tama-ku, Kawasaki 214 (JP)); Terada, H. (College of Engineering, Chubu Univ., 1200 Matsumoto-cho, Kasugai 487 (JP))

    1990-05-01

    This paper presents an experiment carried out to investigate the effect of La{sub 2}O{sub 3} addition to the magnetic and physical properties of strontium ferrite magnets. It was found that the La{sub 2}O{sub 3} addition to SrO {center dot} 6Fe{sub 2}O{sub 3} (stoichiometric composition) was very useful in stabilizing the magnetoplumbite structure and that these Sr-La-system ferrites had excellent properties as a permanenent magnet. Compositions were chosen according to the formula ((SrO){sub 1/n+1}(Fe{sub 2}O{sub 3}){sub n/n+1}){sub 100{minus}x}(La{sub 2}O{sub 3}){sub x}, where n was varied between 5.0 and 6.5, and x between 0 and 5.0. The optimum conditions for making magnets and some properties of typical specimens are discussed.

  13. Anisotropic magnetic properties and crystal electric field studies on CePd2Ge2 single crystal.

    PubMed

    Maurya, Arvind; Kulkarni, R; Dhar, S K; Thamizhavel, A

    2013-10-30

    The anisotropic magnetic properties of the antiferromagnetic compound CePd2Ge2, crystallizing in the tetragonal crystal structure have been investigated in detail on a single crystal grown by the Czochralski method. From the electrical transport, magnetization and heat capacity data, the Néel temperature is confirmed to be 5.1 K. Anisotropic behaviour of the magnetization and resistivity is observed along the two principal crystallographic directions-namely, [100] and [001]. The isothermal magnetization measured in the magnetically ordered state at 2 K exhibits a spin reorientation at 13.5 T for the field applied along the [100] direction, whereas the magnetization is linear along the [001] direction attaining a value of 0.94 ?(B)/Ce at 14 T. The reduced value of the magnetization is attributed to the crystalline electric field (CEF) effects. A sharp jump in the specific heat at the magnetic ordering temperature is observed. After subtracting the phononic contribution, the jump in the heat capacity amounts to 12.5 J K(-1)mol(-1) which is the expected value for a spin ½ system. From the CEF analysis of the magnetization data the excited crystal field split energy levels were estimated to be at 120 K and 230 K respectively, which quantitatively explains the observed Schottky anomaly in the heat capacity. A magnetic phase diagram has been constructed based on the field dependence of magnetic susceptibility and the heat capacity data. PMID:24097258

  14. Strain induced anisotropic properties of shape memory polymer

    Microsoft Academic Search

    Richard Beblo; Lisa Mauck Weiland

    2008-01-01

    Heat activated shape memory polymers (SMPs) are increasingly being utilized in ambitious, large deformation designs. These designs may display unexpected or even undesirable performance if the evolution of the SMP's mechanical properties as a function of deformation is neglected. Yet, despite the broadening use of SMPs in complex load bearing structures, there has been little research completed to characterize how

  15. A Numerical Model of Anisotropic Mass Transport Through Grain Boundary Networks

    NASA Astrophysics Data System (ADS)

    Wang, Yibo

    Tin (Sn) thin films are commonly used in electronic circuit applications as coatings on contacts and solders for joining components. It is widely observed, for some such system, that whiskers---long, thin crystalline structures---emerge and grow from the film. The Sn whisker phenomenon has become a highly active research area since Sn whiskers have caused a large amount of damage and loss in manufacturing, military, medical and power industries. Though lead (Pb) addition to Sn has been used to solve this problem for over five decades, the adverse environmental and health effects of Pb have motivated legislation to severely constrain Pb use in society. People are researching and seeking the reasons which cause whiskers and corresponding methods to solve the problem. The contributing factors to cause a Sn whisker are potentially many and much still remains unknown. Better understanding of fundamental driving forces should point toward strategies to improve (a) the accuracy with which we can predict whisker formation, and (b) our ability to mitigate the phenomenon. This thesis summarizes recent important research achievements in understanding Sn whisker formation and growth, both experimentally and theoretically. Focus is then placed on examining the role that anisotropy in grain boundary diffusivity plays in determining whisker characteristics (specifically, whether they form and, if so, where on a surface). To study this aspect of the problem and to enable future studies on stress driven grain boundary diffusion, this thesis presents a numerical anisotropic mass transport model. In addition to presenting details of the model and implementation, model predictions for a set of increasingly complex grain boundary networks are discussed. Preliminary results from the model provide evidence that anisotropic grain boundary diffusion may be a primary driving mechanism in whisker formation.

  16. Direct method for calculating temperature-dependent transport properties

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Yuan, Zhe; Wesselink, R. J. H.; Starikov, Anton A.; van Schilfgaarde, Mark; Kelly, Paul J.

    2015-06-01

    We show how temperature-induced disorder can be combined in a direct way with first-principles scattering theory to study diffusive transport in real materials. Excellent (good) agreement with experiment is found for the resistivity of Cu, Pd, Pt (and Fe) when lattice (and spin) disorder are calculated from first principles. For Fe, the agreement with experiment is limited by how well the magnetization (of itinerant ferromagnets) can be calculated as a function of temperature. By introducing a simple Debye-like model of spin disorder parameterized to reproduce the experimental magnetization, the temperature dependence of the average resistivity, the anisotropic magnetoresistance, and the spin polarization of a Ni80Fe20 alloy are calculated and found to be in good agreement with existing data. Extension of the method to complex, inhomogeneous materials as well as to the calculation of other finite-temperature physical properties within the adiabatic approximation is straightforward.

  17. Synthesis and colloidal properties of anisotropic hydrothermal barium titanate

    NASA Astrophysics Data System (ADS)

    Yosenick, Timothy James

    2005-11-01

    Nanoparticles of high dielectric constant materials, especially BaTiO3, are required to achieve decreased layer thickness in multilayer ceramic capacitors (MLCCs). Tabular metal nanoparticles can produce thin metal layers with low surface roughness via electrophoretic deposition (EPD). To achieve similar results with dielectric layers requires the synthesis and dispersion of tabular BaTiO3 nanoparticles. The goal of this study was to investigate the deposition of thin BaTiO3 layers using a colloidal process. The synthesis, interfacial chemistry and colloidal properties of hydrothermal BaTiO3 a model particle system, was investigated. After characterization of the material system particulates were deposited to form thin layers using EPD. In the current study, the synthesis of BaTiO3 has been investigated using a hydrothermal route. TEM and AFM analyses show that the synthesized particles are single crystal with a majority of the particle having a <111> zone axis and {111} large face. The particles have a median thickness of 5.8 +/- 3.1 nm and face diameter of 27.1 +/- 12.3 nm. Particle growth was likely controlled by the formation of {111} twins and the synthesis pH which stabilizes the {111} face during growth. With limited growth in the <111> direction, the particles developed a plate-like morphology. Physical property characterization shows the powder was suitable for further processing with high purity, low hydrothermal defect concentration, and controlled stoichiometry. TEM observations of thermally treated powders indicate that the particles begin to loose the plate-like morphology by 900 °C. The aqueous passivation, dispersion, and doping of nanoscale BaTiO 3 powders was investigated. Passivation BaTiO3 was achieved through the addition of oxalic acid. The oxalic acid selectively adsorbs onto the particle surface and forms a chemically stable 2-3 nm layer of barium oxalate. The negative surface charge of the oxalate effectively passivated the BaTiO3 providing a surface suitable for the use of a cationic dispersant, polyethylenimine (PEI). Rheological properties indicate the presence of an oxalate-PEI interaction which can be detrimental to dispersion. With a better understanding of the aqueous surface chemistry of BaTiO3 the surface chemistry was manipulated to control the adsorption of aqueous soluble complexes of Co, Nb, and Bi, three common dopants in the processing of BaTiO3 Surface charge, TEM, and EDS analysis showed that while in suspension the dopants selectively absorbed onto the particle surface forming an engineered coating. (Abstract shortened by UMI.)

  18. Optical Properties of Anisotropic Polycrystalline Ce(+3) activated LSO.

    PubMed

    Roy, Sudesna; Lingertat, Helmut; Brecher, Charles; Sarin, Vinod

    2013-03-01

    Polycrystalline cerium activated lutetium oxyorthosilicate (LSO:Ce) is highly desirable technique to make cost effective and highly reproducible radiation detectors for medical imaging. In this article methods to improve transparency in polycrystalline LSO:Ce were explored. Two commercially available powders of different particulate sizes (average particle size 30 and 1500 nm) were evaluated for producing dense LSO:Ce by pressure assisted densification routes, such as hot pressing and hot isostatic pressing. Consolidation of the powders at optimum conditions produced three polycrystalline ceramics with average grain sizes of 500 nm, 700 and 2000 nm. Microstructural evolution studies showed that for grain sizes larger than 1 µm, anisotropy in thermal expansion coefficient and elastic constants of LSO, resulted in residual stress at grain boundaries and triple points that led to intragranular microcracking. However, reducing the grain size below 1 µm effectively avoids microcracking, leading to more favorable optical properties. The optical scattering profiles generated by a Stover scatterometer, measured by a He-Ne laser of wavelength 633 nm, showed that by reducing the grain size from 2 µm to 500 nm, the in-line transmission increased by a factor of 10(3). Although these values were encouraging and showed that small changes in grain size could increase transmission by almost 3 orders of magnitude, even smaller grain sizes need to be achieved in order to get truly transparent material with high in-line transmission. PMID:23505329

  19. Optical properties of anisotropic polycrystalline Ce3+ activated LSO

    NASA Astrophysics Data System (ADS)

    Roy, Sudesna; Lingertat, Helmut; Brecher, Charles; Sarin, Vinod

    2013-03-01

    Polycrystalline cerium activated lutetium oxyorthosilicate (LSO:Ce) is highly desirable technique to make cost effective and highly reproducible radiation detectors for medical imaging. In this article methods to improve transparency in polycrystalline LSO:Ce were explored. Two commercially available powders of different particulate sizes (average particle size 30 and 1500 nm) were evaluated for producing dense LSO:Ce by pressure assisted densification routes, such as hot pressing and hot isostatic pressing. Consolidation of the powders at optimum conditions produced three polycrystalline ceramics with average grain sizes of 500 nm, 700 nm and 2000 nm. Microstructural evolution studies showed that for grain sizes larger than 1 ?m, anisotropy in thermal expansion coefficient and elastic constants of LSO, resulted in residual stress at grain boundaries and triple points that led to intragranular microcracking. However, reducing the grain size below 1 ?m effectively avoids microcracking, leading to more favorable optical properties. The optical scattering profiles generated by a Stover scatterometer, measured by a He-Ne laser of wavelength 633 nm, showed that by reducing the grain size from 2 ?m to 500 nm, the in-line transmission increased by a factor of 103. Although these values were encouraging and showed that small changes in grain size could increase transmission by almost three orders of magnitude, even smaller grain sizes need to be achieved in order to get truly transparent material with high in-line transmission.

  20. Optical Properties of Anisotropic Polycrystalline Ce+3 activated LSO

    PubMed Central

    Roy, Sudesna; Lingertat, Helmut; Brecher, Charles; Sarin, Vinod

    2012-01-01

    Polycrystalline cerium activated lutetium oxyorthosilicate (LSO:Ce) is highly desirable technique to make cost effective and highly reproducible radiation detectors for medical imaging. In this article methods to improve transparency in polycrystalline LSO:Ce were explored. Two commercially available powders of different particulate sizes (average particle size 30 and 1500 nm) were evaluated for producing dense LSO:Ce by pressure assisted densification routes, such as hot pressing and hot isostatic pressing. Consolidation of the powders at optimum conditions produced three polycrystalline ceramics with average grain sizes of 500 nm, 700 and 2000 nm. Microstructural evolution studies showed that for grain sizes larger than 1 µm, anisotropy in thermal expansion coefficient and elastic constants of LSO, resulted in residual stress at grain boundaries and triple points that led to intragranular microcracking. However, reducing the grain size below 1 µm effectively avoids microcracking, leading to more favorable optical properties. The optical scattering profiles generated by a Stover scatterometer, measured by a He-Ne laser of wavelength 633 nm, showed that by reducing the grain size from 2 µm to 500 nm, the in-line transmission increased by a factor of 103. Although these values were encouraging and showed that small changes in grain size could increase transmission by almost 3 orders of magnitude, even smaller grain sizes need to be achieved in order to get truly transparent material with high in-line transmission. PMID:23505329

  1. Direct Observation of Anisotropic Carrier Transport in Organic Semiconductor by Time-Resolved Microscopic Optical Second-Harmonic Imaging

    NASA Astrophysics Data System (ADS)

    Manaka, Takaaki; Matsubara, Kohei; Abe, Kentaro; Iwamoto, Mitsumasa

    2013-10-01

    In-plane anisotropic carrier transport in single-crystalline grains of the dip-coated 6,13-bis(triisopropylsilylethynyl) (TIPS) pentacene film is studied by using the time-resolved microscopic optical second-harmonic generation (TRM-SHG). The TRM-SHG imaging directly visualizes the directional dependence of the carrier velocity, indicating the anisotropic carrier mobility of the TIPS pentacene single crystal. Results showed that the mobility anisotropy is smaller than that obtained from the current-voltage (I-V) characteristics. Overestimation of the mobility anisotropy using the I-V characteristics, compared with that obtained from the TRM-SHG measurement, is ascribed to the effect of the grain boundary on the carrier transport.

  2. Anisotropic magnetic properties and giant magnetocaloric effect of single-crystal PrSi

    NASA Astrophysics Data System (ADS)

    Das, Pranab Kumar; Bhattacharyya, Amitava; Kulkarni, Ruta; Dhar, S. K.; Thamizhavel, A.

    2014-04-01

    A single crystal of PrSi was grown by the Czochralski method in a tetra-arc furnace. Powder x-ray diffraction of the as-grown crystal revealed that PrSi crystallizes in an FeB-type structure with space group Pnma (No. 62). The anisotropic magnetic properties were investigated by means of magnetic susceptibility, isothermal magnetization, electrical transport, and heat capacity measurements. Magnetic susceptibility data clearly indicate the ferromagnetic transition in PrSi with a TC of 52 K. The relative easy axis of magnetization was found to be the [010] direction. Heat capacity data confirm the bulk nature of the transition at 52 K and exhibit a huge anomaly at the transition. A sharp rise in the low-temperature heat capacity has been observed (below 5 K) which is attributed to the 141Pr nuclear Schottky heat capacity arising from the hyperfine field of the Pr moment. The estimated Pr magnetic moment 2.88 ?B/Pr from the hyperfine splitting is in agreement with the saturation magnetization value obtained from the magnetization data measured at 2 K. From the crystal electric field analysis of the magnetic susceptibility, magnetization, and heat capacity data it is found that the degenerate J =4 Hund's rule derived state of the Pr3+ ion splits into nine singlets with an overall splitting of 284 K, the first excited singlet state separated by just 9 K from the ground state. The magnetic ordering in PrGe appears to be due to the exchange-generated admixture of low-lying crystal field levels. The magnetocaloric effect (MCE) has been investigated from magnetization data along all three principal crystallographic directions. The large magnetic entropy change, -?SM=22.2 J/kg K, and the relative cooling power, RCP = 460 J/kg, characteristic of the giant magnetocaloric effect are achieved near the transition temperature (TC = 52 K) for H = 70 kOe along [010]. Furthermore, the PrSi single crystal exhibits a giant MCE anisotropy.

  3. Rotational properties of dipolar Bose-Einstein condensates confined in anisotropic harmonic potentials

    SciTech Connect

    Malet, F.; Reimann, S. M. [Mathematical Physics, Lund Institute of Technology, P.O. Box 118, SE-22100 Lund (Sweden); Kristensen, T. [Ecole Normale Superieure de Cachan, Cachan cedex, F-94230 Cachan (France); Kavoulakis, G. M. [Technological Educational Institute of Crete, P.O. Box 1939, GR-71004 Heraklion (Greece)

    2011-03-15

    We study the rotational properties of a dipolar Bose-Einstein condensate confined in a quasi-two-dimensional anisotropic trap for an arbitrary orientation of the dipoles with respect to their plane of motion. Within the mean-field approximation, we find that the lowest-energy state of the system depends strongly on the relative strength between the dipolar and the contact interactions, as well as on the size and the orientation of the dipoles and the size and the orientation of the deformation of the trapping potential.

  4. Water transport properties of fuel cell ionomers

    SciTech Connect

    Zawodzinski, T.A. Jr.; Springer, T.E.; Davey, J.; Valerio, J.; Gottesfeld, S.

    1991-01-01

    We will report transport parameters measured for several available perfluorosulfonate membranes. The water sorption characteristics, diffusion coefficient of water, electroosmotic drag, and conductivity will be compared for these materials. The intrinsic properties of the membranes will be the basis of our comparison. An objective look at transport parameters should enable us to compare membranes without the skewing effects of extensive features such as membrane thickness. 8 refs., 4 figs., 2 tabs.

  5. Anisotropic mechanical properties of the MA956 ODS steel characterized by the small punch testing technique

    NASA Astrophysics Data System (ADS)

    Turba, K.; Hurst, R. C.; Hähner, P.

    2012-09-01

    The small punch testing technique was used to assess both creep and fracture properties of the MA956 oxide dispersion strengthened ferritic steel. The anisotropy in mechanical properties was addressed, as well as the alloy's susceptibility to thermal embrittlement. Strong anisotropy was found in the material's creep resistance at 725 °C for longer rupture times. Anisotropic behavior was also observed for the ductile-brittle transition temperature (DBTT). The origin of the anisotropy can be related to the strongly directional microstructure which enables a large amount of intergranular cracking during straining at both high and low temperatures. The DBTT of the alloy is very high, and can be further increased by at least 200 °C after 1000 h of ageing at 475 °C, due to the formation of the Cr-rich ?' phase. The particularly high susceptibility of the MA956 to thermal embrittlement is mainly a consequence of its high chromium content.

  6. Low temperature transport properties and heat capacity of single-crystal Na8Si46.

    PubMed

    Stefanoski, S; Martin, J; Nolas, G S

    2010-12-01

    The low temperature thermal conductivity, resistivity, and Seebeck coefficient of single-crystal Na(8)Si(46) are investigated revealing the intrinsic low temperature transport properties of this material. Metallic conduction is observed, with a higher residual resistance ratio than any other known type I clathrate. Heat capacity together with thermal conductivity provide insight into the Na disorder inside the polyhedra formed by the Si framework. Single-crystal structural refinement and thermal property analyses reveal anisotropic disorder for Na inside the tetrakaidecahedra due to a reduction in the symmetry inside these polyhedra, unlike that for Na inside the dodecahedra. PMID:21406746

  7. Crystal growth and anisotropic magnetic properties of V{sub 3}O{sub 7}

    SciTech Connect

    Li, C. [Materials Design and Characterization Laboratory (MDCL), Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Isobe, M., E-mail: isobe@issp.u-tokyo.ac.j [Materials Design and Characterization Laboratory (MDCL), Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Ueda, H.; Matsushita, Y.; Ueda, Y. [Materials Design and Characterization Laboratory (MDCL), Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)

    2009-12-15

    Needle-like crystals of V{sub 3}O{sub 7} up to 2 mm in length were grown by a chemical vapor transport method using NH{sub 4}Cl as a transport agent. The anisotropic magnetic susceptibility was measured for the first time. At 2 K, a spin-flop transition occurs under a magnetic field of 0.1 T. V{sub 3}O{sub 7} is proved to be a uniaxial antiferromagnet with its easy axis parallel to the b-axis of monoclinic structure. A spin structure with antiferromagnetic interaction between (101-bar) layers and ferromagnetic interaction in the layers below the Neel temperature (5.2 K) is suggested. - Graphical abstract: The temperature dependence of the magnetic susceptibility of V{sub 3}O{sub 7} for (H-parallel b) and (H-perpendicular b), respectively, at 0.1 T. The inset shows crystals of V{sub 3}O{sub 7} grown by using NH{sub 4}Cl as the transport agent.

  8. Oriented Morphology and Anisotropic Transport in Uniaxially Stretched Perfluorosulfonate Ionomer Membranes

    SciTech Connect

    J Park; J Li; G Divoux; L Madsen; R Moore

    2011-12-31

    Relations between morphology and transport sensitively govern proton conductivity in perfluorsulfonate ionomers (PFSIs) and thus determine useful properties of these technologically important materials. In order to understand such relations, we have conducted a broad systematic study of H{sup +}-form PFSI membranes over a range of uniaxial extensions and water uptakes. On the basis of small-angle X-ray scattering (SAXS) and {sup 2}H NMR spectroscopy, uniaxial deformation induces a strong alignment of ionic domains along the stretching direction. We correlate ionic domain orientation to transport using pulsed-field-gradient {sup 1}H NMR measurements of water diffusion coefficients along the three orthogonal membrane directions. Intriguingly, we observe that uniaxial deformation enhances water transport in one direction (parallel-to-draw direction) while reducing it in the other two directions (two orthogonal directions relative to the stretching direction). We evaluate another important transport parameter, proton conductivity, along two orthogonal in-plane directions. In agreement with water diffusion experiments, orientation of ionic channels increases proton conduction along the stretching direction while decreasing it in the perpendicular direction. These findings provide valuable fodder for optimal application of PFSI membranes as well as for the design of next generation polymer electrolyte membranes.

  9. Strong in-plane anisotropic optical properties of monolayer, few-layer and bulk ReSe2

    NASA Astrophysics Data System (ADS)

    Zhao, Huan; Guo, Qiushi; Wang, Luhao; Xia, Fengnian; Wang, Han

    2015-03-01

    Recently, there has been growing interest in the anisotropic properties of certain two-dimensional (2D) materials with reduced lattice symmetry, such as black phosphorus, for developing novel applications in nanoelectronics and infrared optoelectronics. In this work, we report the strong anisotropic optical and electronic properties of monolayer, few-layer and bulk ReSe2, an emerging member of the 2D transition metal dichalcogenides (TMDCs) family. With its bulk bandgap around 1.1 eV and potentially tunable with layer number and strain, ReSe2 may complement black phosphorus for optoelectronic applications utilizing its anisotropic properties in the near-infrared and visible range. Through careful investigations of the polarization-resolved Raman spectroscopy, photoluminescence (PL), polarization-resolved optical extinction spectrum, angle-resolved DC conductance and first principles calculations, we observed and explained the consistent dependence of phonon, optical and electrical properties of ReSe2 on its in-plane crystal orientation. Our results reveal the interesting anisotropic properties of 2D ReSe2 and shed light on its potential applications in electronics and optoelectronics. This work was supported by the Army Research Laboratory.

  10. Study of the Anisotropic Properties of Argillite Under Moisture and Mechanical Loads

    NASA Astrophysics Data System (ADS)

    Yang, Diansen; Chanchole, Serge; Valli, Pierre; Chen, Liufeng

    2013-03-01

    Due to various factors, such as sedimentation, layered morphology of clay minerals, in situ stress, etc., argillite rocks often exhibit anisotropic behavior. In order to study the anisotropic properties of the Callovo-Oxfordian (COx) argillite of the Meuse-Haute-Marne site in France considered as a possible host rock for high-level radioactive nuclear waste repository, a series of tests including uniaxial compression and dehydration and hydration at different constant applied stress levels are carried out. In this study, a specific setup combining moisture and mechanical loading with optical observation is used and it allows to continuously capture surface images from which the full-field strains are determined by using Digital Image Correlation techniques. The results show evidence of the mechanical and hydric anisotropy of the material. The anisotropy parameters are identified, assuming the studied argillite as transversely isotropic. The shrinkage and swelling depend on the applied stress and the angle with respect to the vertical direction of the mechanical load and the stratification plane, and this dependence is quantified. The non-linearity and the hysteresis observed during dehydration and hydration cycles are discussed.

  11. Probing anisotropic surface properties and interaction forces of chrysotile rods by atomic force microscopy and rheology.

    PubMed

    Yang, Dingzheng; Xie, Lei; Bobicki, Erin; Xu, Zhenghe; Liu, Qingxia; Zeng, Hongbo

    2014-09-16

    Understanding the surface properties and interactions of nonspherical particles is of both fundamental and practical importance in the rheology of complex fluids in various engineering applications. In this work, natural chrysotile, a phyllosilicate composed of 1:1 stacked silica and brucite layers which coil into cylindrical structure, was chosen as a model rod-shaped particle. The interactions of chrysotile brucite-like basal or bilayered edge planes and a silicon nitride tip were measured using an atomic force microscope (AFM). The force-distance profiles were fitted using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which demonstrates anisotropic and pH-dependent surface charge properties of brucite-like basal plane and bilayered edge surface. The points of zero charge (PZC) of the basal and edge planes were estimated to be around pH 10-11 and 6-7, respectively. Rheology measurements of 7 vol % chrysotile (with an aspect ratio of 14.5) in 10 mM NaCl solution showed pH-dependent yield stress with a local maximum around pH 7-9, which falls between the two PZC values of the edge and basal planes of the rod particles. On the basis of the surface potentials of the edge and basal planes obtained from AFM measurements, theoretical analysis of the surface interactions of edge-edge, basal-edge, and basal-basal planes of the chrysotile rods suggests the yield stress maximum observed could be mainly attributed to the basal-edge attractions. Our results indicate that the anisotropic surface properties (e.g., charges) of chrysotile rods play an important role in the particle-particle interaction and rheological behavior, which also provides insight into the basic understanding of the colloidal interactions and rheology of nonspherical particles. PMID:25115179

  12. Transport properties of graphene quantum dots

    Microsoft Academic Search

    J. W. González; M. Pacheco; L. Rosales; P. A. Orellana

    2011-01-01

    In this work we present a theoretical study of transport properties of a double crossbar junction composed of segments of graphene ribbons with different widths forming a graphene quantum dot structure. The systems are described by a single-band tight binding Hamiltonian and the Green's function formalism using real space renormalization techniques. We show calculations of the local density of states,

  13. High-field transport properties of graphene

    Microsoft Academic Search

    H. M. Dong; W. Xu; F. M. Peeters

    2011-01-01

    We present a theoretical investigation on the transport properties of graphene in the presence of high dc driving fields. Considering electron interactions with impurities and acoustic and optical phonons in graphene, we employ the momentum- and energy-balance equations derived from the Boltzmann equation to self-consistently evaluate the drift velocity and temperature of electrons in graphene in the linear and nonlinear

  14. A note on conservative transport in anisotropic, heterogeneous porous media in the presence of small-amplitude transients

    USGS Publications Warehouse

    Naff, R.L.

    1998-01-01

    The late-time macrodispersion coefficients are obtained for the case of flow in the presence of a small-scale deterministic transient in a three-dimensional anisotropic, heterogeneous medium. The transient is assumed to affect only the velocity component transverse to the mean flow direction and to take the form of a periodic function. For the case of a highly stratified medium, these late-time macrodispersion coefficients behave largely as the standard coefficients used in the transport equation. Only in the event that the medium is isotropic is it probable that significant deviations from the standard coefficients would occur.

  15. Estimation of the distributions of anisotropic, elastic properties and wall stresses of saccular cerebral aneurysms by inverse analysis

    Microsoft Academic Search

    Martin Kroon; Gerhard A. Holzapfel

    2008-01-01

    A new method is proposed for estimating the elastic properties of the inhomogeneous and anisotropic structure of saccular cerebral aneurysms by inverse analysis. The aneurysm is modelled as a membrane and the constitutive response of each individual layer of the passive tissue is characterized by a transversely isotropic strain energy function of exponential type. The collagen fibres in the aneurysm

  16. Anisotropic transport in single-crystal molybdenum bronze, Li0.33MoO3

    NASA Astrophysics Data System (ADS)

    Moshfeghyeganeh, Saeed; Cohn, Joshua L.; Neumeier, John J.

    2015-03-01

    We present transport measurements (resistivity, thermopower, thermal conductivity) on single crystals of the quasi-one-dimensional semiconductor Li0.33MoO3 in the temperature range 200-500 K. First synthesized and studied long ago, the thermal and thermoelectric properties for this compound have not been previously reported. We find extreme anisotropy in the Seebeck coefficient within the a - c planes, with Sc -Sa ~= 300 ? V/K near room temperature. The thermal conductivity at room temperature in the a - c planes was ~ 1 . 5 - 2 W/mK and 7-8 times smaller along b*. We also report x-ray studies of the out-of-plane (b*) lattice constants indicating a small structural transition at T ~ 350 K that coincides with anomalies in the transport properties. This material is based upon work supported by the U.S. Department of Energy Office of Basic Energy Sciences Grant DE-FG02-12ER46888 (Univ. Miami) and the National Science Foundation under Grant DMR-0907036 (Mont. St. Univ.).

  17. Transport properties of ?-FeSi2

    NASA Astrophysics Data System (ADS)

    Arushanov, Ernest; Lisunov, Konstantin G.

    2015-07-01

    The aim of this paper is to summarize considerable experimental efforts undertaken within the last decades in the investigations of transport properties of ?-FeSi2. The ?-FeSi2 compound is the most investigated among a family of semiconducting silicides. This material has received considerable attention as an attractive material for optoelectronic, photonics, photovoltaics and thermoelectric applications. Previous reviews of the transport properties of ?-FeSi2 have been given by Lange and Ivanenko et al. about 15 years ago. The Hall effect, the conductivity, the mobility and the magnetoresistance data are presented. Main attention is paid to the discussion of the impurity (defect) band conductivity, the anomalous Hall effect, the scattering mechanisms of charge carriers, as well as to the hopping conduction and the magnetoresistance.

  18. Diffusive Transport Properties Across Coupling Regimes

    NASA Astrophysics Data System (ADS)

    Dharuman, G.; Murillo, M. S.; Verboncoeur, J.; Christlieb, A.

    2014-10-01

    Transport properties are poorly known across coupling regimes, therefore understanding them is of importance for theoretical and practical reasons. A useful tool is an ultracold plasma system because of the experimental capability to tune the system to attain Coulomb coupling ? ranging from 0.1 to 1 to 10 with the screening parameter ? ranging from 0 to 4 to 8, spanning the regions of the phase diagram from weak to moderate to strongly coupled and screened systems. Strong coupling is possible if Disorder Induced Heating is mitigated which requires a correlated initial ion state. Of particular interest is Rydberg blockaded gas of ultracold atoms where the local blockade effect results in correlations. Predictions of higher coupling in ultracold plasma created from a Rydberg blockaded gas have been reported. In this work we examine the diffusive transport properties of ultracold plasma system using molecular dynamics simulations for experimentally realizable values of ? and ? as discussed above.

  19. Anisotropic properties of molecular beam epitaxy-grown colossal magnetoresistance manganite thin films

    SciTech Connect

    ODonnell, J.; Onellion, M.; Rzchowski, M.S. [Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706 (United States)] [Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706 (United States); Eckstein, J.N.; Bozovic, I. [Varian Research Center, 3075 Hansen Way, Palo Alto, California 94304 (United States)] [Varian Research Center, 3075 Hansen Way, Palo Alto, California 94304 (United States)

    1997-04-01

    We show that both the magnetoresistance and magnetism in tetragonal MBE-grown films of La{sub 1{minus}x}Ca{sub x}MnO{sub 3} show anisotropic effects that depend on both temperature and magnetic field. We show that the {open_quotes}colossal{close_quotes} magnetoresistance depends on the angle between the magnetization and the transport current and that the size of this effect is temperature-dependent. Below the Curie temperature this results in an unusual upturn in the magnetoresistance for small magnetic fields normal to the plane of the film as the magnetization rotates out of the plane. Low-field hysteresis of the in-plane magnetoresistance is also observed, and also shows an anisotropy with respect to the current and magnetization directions. We also find an in-plane biaxial magnetocrystalline anisotropy with easy axes along the {l_brace}100{r_brace} (Mn{endash}O) crystal directions, and evidence for {ital c}-axis magnetocrystalline anisotropy. {copyright} {ital 1997 American Institute of Physics.}

  20. Thermodynamic properties of solid helium using an anharmonic anisotropic continuum model

    SciTech Connect

    Berker, Terrell Dunlap

    1980-01-01

    An anharmonic anisotropic continuum model is used to describe the thermodynamic properties of solid helium for all three structures (hcp, fcc, and bcc) and both isotopes. Using a 6-n potential with the de Boer value for the attractive parameter, the two repulsive parameters b/sub n/ and n are varied to obtain a best fit to experimental hcp /sup 4/He data. The n = 11 potential gives good volume dependence over the entire experimentally accessible volume range, but too large an isotope effect. The n = 10 potential gives a better mass dependence, but a less satisfactory volume dependence. A detailed comparison of the calculations with experimental data shows that while it is possible to fit the volume dependence of the pressure, bulk modulus, and Debye temperature over a very wide range, the model overestimates the zero-point contribution to the free energy. The conclusion is reached that the major discrepancies obtained result from the failure of the continuum model to take account of dispersion. This failure can be remedied by artificially endowing the continuum with dispersion. A program for the further development of the model is outlined. It appears that the approach should be a practical one for realistic calculations of thermodynamic properties over wide volume ranges and useful for the estimation of interatomic potentials from solid state data.

  1. Improvements to the Diffusion Synthetic Acceleration method in neutron transport with highly anisotropic scattering

    SciTech Connect

    Colombo, V. [Universita degli Studi di Bologna (Italy); Coppa, G.G.M.; Melisurgo, V.; Ravetto, P. [Politecnico di Torino (Italy)

    1995-12-31

    Some modifications of the Diffusion Synthetic Acceleration (DSA) technique are proposed to face its loss of effectiveness when dealing with highly anisotropic scattering. A model case convergence analysis of the proposed techniques is performed; an extensive set of comparisons with results obtained by means of already assessed DSA modification techniques is reported for various scattering cross-section configurations. The importance of non asymptotic convergence velocity as a theoretical means to characterize and optimize different acceleration methods is also discussed.

  2. Electronic and transport properties of kinked graphene

    PubMed Central

    Rasmussen, Jesper Toft; Gunst, Tue; Bøggild, Peter; Jauho, Antti-Pekka

    2013-01-01

    Summary Local curvature, or bending, of a graphene sheet is known to increase the chemical reactivity presenting an opportunity for templated chemical functionalisation. Using first-principles calculations based on density functional theory (DFT), we investigate the reaction barrier reduction for the adsorption of atomic hydrogen at linear bends in graphene. We find a significant barrier lowering (?15%) for realistic radii of curvature (?20 Å) and that adsorption along the linear bend leads to a stable linear kink. We compute the electronic transport properties of individual and multiple kink lines, and demonstrate how these act as efficient barriers for electron transport. In particular, two parallel kink lines form a graphene pseudo-nanoribbon structure with a semimetallic/semiconducting electronic structure closely related to the corresponding isolated ribbons; the ribbon band gap translates into a transport gap for electronic transport across the kink lines. We finally consider pseudo-ribbon-based heterostructures and propose that such structures present a novel approach for band gap engineering in nanostructured graphene. PMID:23503656

  3. Investigation of low field dielectric properties of anisotropic porous Pb(Zr,Ti)O3 ceramics: Experiment and modeling

    NASA Astrophysics Data System (ADS)

    Olariu, C. S.; Padurariu, L.; Stanculescu, R.; Baldisserri, C.; Galassi, C.; Mitoseriu, L.

    2013-12-01

    Anisotropic porous Pb(Zr,Ti)O3 ceramics with various porosity degrees have been studied in order to determine the role of the pore shape and orientation on the low-field dielectric properties. Ceramic samples with formula Pb(Zr0.52Ti0.48)0.976Nb0.024O3 with different porosity degrees (dense, 10%, 20%, 40% vol.) have been prepared by solid state reaction. Taking into consideration the shape and orientation of the pore inclusions, the dielectric properties of porous ceramics have been described by using adapted mixing rules models. Rigorous bounds, derived on the basis on Variational Principle, were used to frame dielectric properties of porous composites. The finite element method (FEM) was additionally used to simulate the dielectric response of the porous composites under various applied fields. Among the few effective medium approximation models adapted for anisotropic oriented inclusions, the best results were obtained in case of needle-like shape inclusions (which do not correspond to the real shape of microstructure inclusions). The general case of Wiener bounds limited well the dielectric properties of anisotropic porous composites in case of parallel orientation. Among the theoretical approaches, FEM technique allowed to simulate the distribution of potential and electric field inside composites and provided a very good agreement between the computed permittivity values and experimental ones.

  4. Transport properties of chemically functionalized graphene nanoribbon

    NASA Astrophysics Data System (ADS)

    Qu, C. Q.; Wang, C. Y.; Qiao, L.; Yu, S. S.; Li, H. B.

    2013-07-01

    We perform a theoretical calculation in chemically functionalized zigzag graphene nanoribbons, which are terminated with different single atoms or groups, using density functional theory and nonequilibrium Green’s function techniques. The calculation results reveal that these different species of atoms and groups have a significant impact on the edge states near Fermi level as well as the spin-dependent electronic transport properties. The calculated I-V curves exhibit negative differential resistance, which can be used for application in molecular spin electronic device.

  5. Monolayer-protected silver nano-particle-based anisotropic conductive adhesives: Enhancement of electrical and thermal properties

    Microsoft Academic Search

    Yi Li; Kyoung-Sik Moon; C. P. Wong

    2005-01-01

    Two types of self-assembled monolayers (SAMs), dicarboxylic acid and dithiol, were used to treat the silver nanoparticles.\\u000a Thermogravimetric analyzer (TGA), differential scanning calorimeter (DSC), and contact angle results indicated that the SAMs\\u000a were well coated on the silver nanoparticles and thermally stable below 150°C. By introducing the monolayer-coated silver\\u000a nanoparticles into the anisotropic conductive adhesives (ACAs), the electrical properties and

  6. Fe-nanoparticle coated anisotropic magnet powders for composite permanent magnets with enhanced properties

    NASA Astrophysics Data System (ADS)

    Marinescu, M.; Liu, J. F.; Bonder, M. J.; Hadjipanayis, G. C.

    2008-04-01

    Utilizing the chemical reduction of FeCl2 with NaBH4 in the presence of 2:17 Sm-Co powders, we synthesized composite Sm(Co0.699Fe0.213Cu0.064Zr0.024)7.4/nano-Fe anisotropic hard magnetic powders. The average particle size of the hard magnetic core powder was 21?m while the soft magnetic Fe nanoparticles deposited uniformly on the core powder had a particle size smaller than 100nm. Different reaction protocols, such as immersion of the hard magnetic core powder in each reagent, the use of microemulsion (micelle) technique, or doubling the weight ratio of FeCl2 to core powder, led to different degrees of magnetic coupling of the hard and soft magnetic components of the composite powder. A reaction time of 180s led to deposition of 3.5wt% Fe nanoparticles and improved magnetic properties of the composite powder compared to the uncoated Sm(Co0.699Fe0.213Cu0.064Zr0.024)7.4 powder. The respective magnetic hysteresis parameters were 4?M18kOe=11.3kG, 4?Mr=11kG, and Hci>20kOe with a smooth demagnetization curve.

  7. Magnetic properties of the anisotropic MnBi/Sm2Fe17Nx hybrid magnet

    NASA Astrophysics Data System (ADS)

    Yang, Y. B.; Wei, J. Z.; Peng, X. L.; Xia, Y. H.; Chen, X. G.; Wu, R.; Du, H. L.; Han, J. Z.; Wang, C. S.; Yang, Y. C.; Yang, J. B.

    2014-05-01

    In order to improve the magnetic properties of MnBi compound, anisotropic MnBi/Sm2Fe17Nx hybrid magnet was prepared by grinding of high purity MnBi ribbons and Sm2Fe17Nx particles together. The smooth hysteresis loops of the hybrid magnets indicated that the mixture of the hard/hard phase magnetic components was well exchange coupled. As compared to the single MnBi phase magnet, the remanent magnetization and maximum energy product (BH)max of the composited magnets were improved. As an optimized result, the exchange coupled magnet of MnBi/Sm2Fe17Nx = 3/7 yielded both high remanence and coercivity from 250 K to 380 K. A maximum energy product (BH)max of 18 MGOe was achieved at 300 K, and remained 10 MGOe at 380 K, implying the MnBi/Sm2Fe17Nx magnets can be specially utilized in the high temperature environment.

  8. Length-dependence of flexural rigidity as a result of anisotropic elastic properties of microtubules

    SciTech Connect

    Li, C. [Department of Mechanical Engineering, University of Alberta, Edmonton, T6G 2G8 (Canada); Ru, C.Q. [Department of Mechanical Engineering, University of Alberta, Edmonton, T6G 2G8 (Canada)]. E-mail: c.ru@ualberta.ca; Mioduchowski, A. [Department of Mechanical Engineering, University of Alberta, Edmonton, T6G 2G8 (Canada)

    2006-10-27

    Unexplained length-dependence of flexural rigidity and Young's modulus of microtubules is studied using an orthotropic elastic shell model. It is showed that vibration frequencies and buckling load predicted by the accurate orthotropic shell model are much lower than that given by the approximate isotropic beam model for shorter microtubules, although the two models give almost identical results for sufficiently long microtubules. It is this inaccuracy of the isotropic beam model used by all previous researchers that leads to reported lower flexural rigidity and Young's modulus for shorter microtubules. In particular, much lower shear modulus and circumferential Young's modulus, which only weaken flexural rigidity of shorter microtubules, are responsible for the observed length-dependence of the flexural rigidity. These results confirm that longitudinal Young's modulus of microtubules is length-independent, and the observed length-dependence of the flexural rigidity and Young's modulus is a result of strongly anisotropic elastic properties of microtubules which have a length-dependent weakening effect on flexural rigidity of shorter microtubules.

  9. Anisotropic strain in SmSe and SmTe: Implications for electronic transport

    NASA Astrophysics Data System (ADS)

    Kuroda, Marcelo A.; Jiang, Zhengping; Povolotskyi, Michael; Klimeck, Gerhard; Newns, Dennis M.; Martyna, Glenn J.

    2014-12-01

    Mixed valence rare-earth samarium compounds Sm X (X =Se,Te ) have been recently proposed as candidate materials for use in high-speed, low-power digital switches driven by stress induced changes of resistivity. At room temperature these materials exhibit a pressure driven insulator-to-metal transition with resistivity decreasing by up to seven orders of magnitude over a small pressure range. Thus, the application of only a few GPa's to the piezoresistor (Sm X ) allows the switching device to perform complex logic. Here we study from first principles the electronic properties of these compounds under uniaxial strain and discuss the implications for carrier transport. Based on changes in the band structure and a model we show that the piezoresistive response is mostly governed by the reduction of band gap with strain. Furthermore, the piezoresistive reponse becomes optimal when the Fermi level is pinned near the localized valence band. The piezoresistive effect under uniaxial strain, which must be taken into account in thin films and other systems with reduced dimensionality, is also studied. Under uniaxial strain we find that the piezoresistive response can be substantially larger than in the isotropic case. Analysis of the complex band structure of SmSe yields a tunneling length of the order of 1 nm. This suggest that the conduction mechanism governing the piezoresistive effect in bulk, i.e., thermal promotion of electrons, should still be dominant in few-nanometer-thick films.

  10. Upscaling of Thermal Transport Properties in Enhanced Geothermal Systems

    NASA Astrophysics Data System (ADS)

    Johnson, S.; Hao, Y.; Chiaramonte, L.

    2010-12-01

    : Engineered Geothermal Systems (EGS) have garnered significant attention as a possible source of geographically disperse, carbon-free energy without the environmental impact of many other renewable energy sources. However, a significant barrier to the adoption of EGS is the uncertainty in whether a specific site is amenable to engineering and how fluid injection rates can affect, either through stimulation of the fracture network or through deleterious channeling of the thermal fluid, the heat extraction rate possible in a specific reservoir. Because of the uncertainties involved in determining the exact fracture network topology extant in any particular reservoir, it is desirable to have a stochastic description (distribution) of the possible heat extraction rates that could be achieved. This work provides both an approach and application of the approach for simulating several synthetic fracture networks. The approach uses a coupled geomechanics and discrete fracture network (DFN) solver coupled uni-directionally with a reservoir scale, hydro-thermal transport code, the Non-isothermal Unsaturated-Saturated Flow and Transport simulation code (NUFT), to capture the coupled hydro-thermo-mechanical behavior of these synthetic networks. Particular attention is paid to the upscaling approach used to determine effective permeability and thermal transfer coefficients that are used in the dual porosity/permeability (DKM) model employed in NUFT. This upscaling is based on a multi-scale treatment of the domain, starting with the upscaling of permeability from explicitly represented fractures in the DFN model, which considers the fracture-scale effects of fluid injection, to a finely resolved, unstructured mesh representation of the subdomain. Effective properties of this subdomain are then determined for a variety of sub-sampled discrete fracture network topologies. The result catalog of spatially correlated thermal and fluid properties are then used to populate the properties of an anisotropic regular grid representation of the reservoir. The resultant reservoir-scale system considering the fully-coupled hydro-thermo-mechanical problem is then simulated to determine the resultant heat transfer rate for each synthetic fracture network realization. To complete the parametric study, several fractally spatially distributed systems are realized for each fractal dimension value. The resultant distributions of heat transfer rate and the trends emergent from this study will be presented. Auspices: This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  11. Conductivities and curing properties of electron-beam-irradiated anisotropic conductive films

    NASA Astrophysics Data System (ADS)

    Shin, Tae Gyu; Lee, Inhyuk; Kim, Jae yong

    2012-07-01

    Radiation-curable acrylated epoxy oligomer was irradiated by using an electron beam (E-beam) with dosages of 5, 10, 20, 40, 80, 200, 400, and 550 kGy to investigate the electrical and the physical properties of anisotropic conductive films (ACFs) and to evaluate the potential application of radiation technology to flip-chip package processing. An ACF is an insulating epoxy matrix containing conducting particles that keep the electrical conductivity along the out-of-plane direction and the insulation property along the in-plane direction. The contact resistance between ACF joints cured by using an E-beam irradiation of 80 kGy was measured under a constant bonding pressure of 2 kgf/cm2 to demonstrate the effects of pad pitch size and the number of added conductive particles in the epoxy resin. Three types of PCBs, 1000-, 500-, and 100-µm pad pitches, were employed while the E-beam curable epoxy resin was mixed with conductive particles in a weight ratio of 10:1. The measured average contact resistance was 0.24 ? with a minimum of 0.06 ? for the samples prepared with a 100-µm pad pitch size, which is compatible with or lower than the values obtained from thermally-cured commercial ACFs. Our results demonstrate that an E-beam is an effective radiation method for curing epoxy resins at low temperatures in a short time and can be employed as a new technique for bonding circuits in high-density electric devices.

  12. Effect of Transmural Transport Properties on Atheroma Plaque Formation and Development.

    PubMed

    Cilla, M; Martínez, M A; Peña, E

    2015-07-01

    We propose a mathematical model of atheroma plaque initiation and early development in coronary arteries using anisotropic transmural diffusion properties. Our current approach is on the process on plaque initiation and intimal thickening rather than in severe plaque progression and rupture phenomena. The effect of transport properties, in particular the anisotropy of diffusion properties of the artery, on plaque formation and development is investigated using the proposed mathematical model. There is not a strong influence of the anisotropic transmural properties on LDL, SMCs and collagen distribution and concentrations along the artery. On the contrary, foam cells distribution strongly depends on the value of the radial diffusion coefficient of the substances [Formula: see text] and the ratio [Formula: see text]. Decreasing [Formula: see text] or diffusion coefficients ratio means a higher concentration of the foam cells close to the intima. Due to the fact that foam cells concentration is associated to the necrotic core formation, the final distribution of foam cells is critical to evolve into a vulnerable or fibrotic plaque. PMID:25814436

  13. Analytical modeling of pressure transient behavior for coalbed methane transport in anisotropic media

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Wang, Xiaodong

    2014-06-01

    Resulting from the nature of anisotropy of coal media, it is a meaningful work to evaluate pressure transient behavior and flow characteristics within coals. In this article, a complete analytical model called the elliptical flow model is established by combining the theory of elliptical flow in anisotropic media and Fick's laws about the diffusion of coalbed methane. To investigate pressure transient behavior, analytical solutions were first obtained through introducing a series of special functions (Mathieu functions), which are extremely complex and are hard to calculate. Thus, a computer program was developed to establish type curves, on which the effects of the parameters, including anisotropy coefficient, storage coefficient, transfer coefficient and rate constant, were analyzed in detail. Calculative results show that the existence of anisotropy would cause great pressure depletion. To validate new analytical solutions, previous results were used to compare with the new results. It is found that a better agreement between the solutions obtained in this work and the literature was achieved. Finally, a case study is used to explain the effects of the parameters, including rock total compressibility coefficient, coal medium porosity and anisotropic permeability, sorption time constant, Langmuir volume and fluid viscosity, on bottom-hole pressure behavior. It is necessary to coordinate these parameters so as to reduce the pressure depletion.

  14. Survey of Concrete Transport Properties and their Measurement

    E-print Network

    Bentz, Dale P.

    materials, building technology, capillary flow, cement, chloride ions, concentration profiles, concrete. . . Survey of Concrete Transport Properties and their Measurement NicosS. Martys U of concrete. The basic theory and measurement methods are discussed. Emphasis is placed on transport

  15. An analytical model of anisotropic low-field electron mobility in wurtzite indium nitride

    NASA Astrophysics Data System (ADS)

    Wang, Shulong; Liu, Hongxia; Song, Xin; Guo, Yulong; Yang, Zhaonian

    2014-03-01

    This paper presents a theoretical analysis of anisotropic transport properties and develops an anisotropic low-field electron analytical mobility model for wurtzite indium nitride (InN). For the different effective masses in the ?-A and ?-M directions of the lowest valley, both the transient and steady state transport behaviors of wurtzite InN show different transport characteristics in the two directions. From the relationship between velocity and electric field, the difference is more obvious when the electric field is low in the two directions. To make an accurate description of the anisotropic transport properties under low field, for the first time, we present an analytical model of anisotropic low-field electron mobility in wurtzite InN. The effects of different ionized impurity scattering models on the low-field mobility calculated by Monte Carlo method (Conwell-Weisskopf and Brooks-Herring method) are also considered.

  16. Anisotropic seismic properties of the upper mantle beneath the Torre Alfina area (Northern Apennines, Central Italy)

    NASA Astrophysics Data System (ADS)

    Pera, Emanuela; Mainprice, David; Burlini, Luigi

    2003-07-01

    Central Italy is an active tectonic area that has been recently studied by several regional mantle, Pn and SKS, studies which revealed the presence of a strong regional anisotropy. In this paper, we present the first petrophysical results on the only mantle xenoliths from Central Italy, which place new constraints on the upper mantle structures of this region. The Torre Alfina mantle xenoliths are very small in size, from few millimetres to about 1.5 cm. They are mainly dunites and harzburgites, with subordinate lherzolites and wehrlites. Since olivine and spinel are always present, they should have crystallised in the spinel-bearing lherzolite field. Their mineralogical composition is ol+spl±opx±cpx. Both olivines and pyroxenes are present as porphyroclasts and as neoblasts. The xenoliths show different degrees of recrystallization. Geothermobarometry on these xenoliths give a temperature range of 1040±40 °C and a pressure estimate of about 1.5 GPa, corresponding to 50 to 60 km depth. Previous seismic studies have estimated the Moho to be at 20 to 25 km in this region, hence the xenoliths come from a hot mantle, probably asthenospheric, below a lithosphere of about 25 to 40 km in thickness below the Moho. We measure the crystallographic preferred orientation (CPO) of olivines and pyroxenes using a SEM and the Electron Back Scattered Diffraction (EBSD) technique. The CPO shows all three axes of olivine are tightly clustered: [100] axis is typically more tightly clustered than [010] and [001] is the most widely distributed axis. The fabric strength expressed by the integral J index, varies from 4.5 to 25.9, and decreases with the degree of recrystallization. We use CPO data to calculate anisotropic seismic properties of the xenoliths. They are very homogenous and probably statistically representative of the mantle below the Torre Alfina area. Vp ranges from 8.4 to 9.1 km/s, Vs 1 from 4.8 to 5.0 km/s. The seismic anisotropy is more variable; AVp ranges from 9.8% to 19.3% and AVs from 7.3% to 13.4%. The majority of the xenoliths display an orthorhombic seismic symmetry, but xenoliths with a transverse isotropic behaviour have also been observed. We consider four geodynamic models for the source region of the xenoliths (extension, shear, upwelling, slab tilted), defined by different orientations of the structural reference frame, and we calculated for each model the variation of the seismic properties with temperature, pressure and volume fraction of orthopyroxene. After comparing this variation of calculated seismic parameters with seismic observations from the region, we form the hypothesis that the xenoliths come from either an extensional tectonic zone (lineation X and foliation plane XY horizontal) or transcurrent shear zone (lineation X horizontal and foliation plane XY vertical) and that the mantle beneath Torre Alfina is composed by 70% olivine and 30% orthopyroxene forming an anisotropic layer of about 160 or 110 km in thickness, respectively.

  17. Transport properties of quark and gluon plasmas

    SciTech Connect

    Heiselberg, H.

    1993-12-01

    The kinetic properties of relativistic quark-gluon and electron-photon plasmas are described in the weak coupling limit. The troublesome Rutherford divergence at small scattering angles is screened by Debye screening for the longitudinal or electric part of the interactions. The transverse or magnetic part of the interactions is effectively screened by Landau damping of the virtual photons and gluons transferred in the QED and QCD interactions respectively. Including screening a number of transport coefficients for QCD and QED plasmas can be calculated to leading order in the interaction strength, including rates of momentum and thermal relaxation, electrical conductivity, viscosities, flavor and spin diffusion of both high temperature and degenerate plasmas. Damping of quarks and gluons as well as color diffusion in quark-gluon plasmas is, however, shown not to be sufficiently screened and the rates depends on an infrared cut-off of order the ``magnetic mass,`` m{sub mag} {approximately} g{sup 2}T.

  18. Temperature-dependent Transport Properties of Graphene

    NASA Astrophysics Data System (ADS)

    Zhong, Bochen; Singh, Amol; Uddin, Ahsan; Koley, Goutam; Webb, Richard

    2014-03-01

    Temperature-dependent transport properties of graphene synthesized by chemical vapor deposition (CVD) on a Cu thin sheet have been investigated. Raman spectra of our samples show good quality of the CVD graphene. We have measured the temperature dependence of conductivity, charge-carrier density and Hall mobility of graphene by patterning them into micrometer-sized Hall bars. Quantum Hall effect has been observed when the temperature is about 60 Kelvin, which is the evidence for single-layer graphene. Furthermore, the results of temperature dependence of Hall mobility indicate that impurity and defect scattering is the primary scattering mechanism at low temperature, while substrate surface polar phonon scattering is dominant at high temperature.

  19. Fast and highly anisotropic thermal transport through vertically aligned carbon nanotube arrays

    E-print Network

    Geohegan, David B.

    to date to assemble short nanotubes into macroscopic fibers,4 papers,5,6 or nanotube composites7­9 have, and 3 with few defects and high graphitic order for long-range phonon transport. However, attempts

  20. Transport properties of dense matter. II

    Microsoft Academic Search

    E. Flowers; N. Itoh

    1979-01-01

    Exact solutions for the transport coefficients of a multicomponent system of several interacting Fermi liquids are given in the low temperature limit. The transport coefficients are found by solving a set of coupled Boltzmann transport equations. These solutions for the transport coefficients are used to evaluate the thermal conductivity and viscosity of neutron star matter in the density regime where

  1. A review of some charge transport properties of silicon

    Microsoft Academic Search

    C. Jacoboni; C. Canali; G. Ottaviani; A. Alberigi Quaranta

    1977-01-01

    Basic bulk transport properties of charge carriers in silicon are reviewed, with particular reference to their use in designing solid-state components. The current theoretical model for transport in silicon is outlined, along with experimental techniques for determining most important transport parameters such as the drift velocity and diffusion coefficient. Phenomenological expressions are presented, which are in good agreement with experimental

  2. THERMODYNAMIC AND TRANSPORT PROPERTIES OF SODIUM LIQUID AND VAPOR

    E-print Network

    Kemner, Ken

    THERMODYNAMIC AND TRANSPORT PROPERTIES OF SODIUM LIQUID AND VAPOR ANL/RE-95/2 Reactor Engineering;Thermodynamic and Transport Properties of Sodium Liquid and Vapor ANL/RE-95/2 by J. K. Fink and L. Leibowitz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Vapor

  3. Molecular Simulation of Phase Equilibria and Transport Properties

    Microsoft Academic Search

    Peter James Bereolos

    1995-01-01

    Molecular simulations are used to test models and theories through comparison with experimental results and theoretical predictions. Three areas are covered: transport properties, free energy measurement, and phase diagram calculation. Transport properties of isotropic fluids composed of hard ellipsoids of revolution are studied using molecular dynamics simulation. The self diffusion coefficient, the shear viscosity, and the thermal conductivity are evaluated

  4. Solvothermal synthesis, growth mechanism, and photoluminescence property of sub-micrometer PbS anisotropic structures

    PubMed Central

    2012-01-01

    The sub-micrometer PbS with anisotropic microstructures including fishbone-like dendrites, multipods, cubes, corallines, and hopper cubes were successfully prepared by the solvothermal process. Different morphologies can be obtained by adjusting the reaction temperatures or using the nontoxic controlled reagents which can tune the relative growth rate in the <100> direction and the <111> direction of PbS nuclei. Based on the viewpoint of crystallography about face-centered cubic crystal structure, the possible formation mechanism for sub-micrometer anisotropic structures has been discussed. The difference between the enhanced growth rates on the {100} and {111} planes induced the change of ratio between the growth rates in the <100> and <111> directions, which resulted in the formation of the different PbS anisotropic microstructures. The PbS anisotropic structures exhibited the different visible emission with a peak in the red regions mainly attributed to the variation of shape, size, and the trap state of as-obtained PbS. PMID:23216819

  5. Solvothermal synthesis, growth mechanism, and photoluminescence property of sub-micrometer PbS anisotropic structures.

    PubMed

    Cao, Yali; Hu, Pengfei; Jia, Dianzeng

    2012-01-01

    The sub-micrometer PbS with anisotropic microstructures including fishbone-like dendrites, multipods, cubes, corallines, and hopper cubes were successfully prepared by the solvothermal process. Different morphologies can be obtained by adjusting the reaction temperatures or using the nontoxic controlled reagents which can tune the relative growth rate in the <100> direction and the <111> direction of PbS nuclei. Based on the viewpoint of crystallography about face-centered cubic crystal structure, the possible formation mechanism for sub-micrometer anisotropic structures has been discussed. The difference between the enhanced growth rates on the {100} and {111} planes induced the change of ratio between the growth rates in the <100> and <111> directions, which resulted in the formation of the different PbS anisotropic microstructures. The PbS anisotropic structures exhibited the different visible emission with a peak in the red regions mainly attributed to the variation of shape, size, and the trap state of as-obtained PbS. PMID:23216819

  6. Solvothermal synthesis, growth mechanism, and photoluminescence property of sub-micrometer PbS anisotropic structures

    NASA Astrophysics Data System (ADS)

    Cao, Yali; Hu, Pengfei; Jia, Dianzeng

    2012-12-01

    The sub-micrometer PbS with anisotropic microstructures including fishbone-like dendrites, multipods, cubes, corallines, and hopper cubes were successfully prepared by the solvothermal process. Different morphologies can be obtained by adjusting the reaction temperatures or using the nontoxic controlled reagents which can tune the relative growth rate in the <100> direction and the <111> direction of PbS nuclei. Based on the viewpoint of crystallography about face-centered cubic crystal structure, the possible formation mechanism for sub-micrometer anisotropic structures has been discussed. The difference between the enhanced growth rates on the {100} and {111} planes induced the change of ratio between the growth rates in the <100> and <111> directions, which resulted in the formation of the different PbS anisotropic microstructures. The PbS anisotropic structures exhibited the different visible emission with a peak in the red regions mainly attributed to the variation of shape, size, and the trap state of as-obtained PbS.

  7. Characteristics of immiscible fluid transport in porous media with anisotropic phase permeabilities

    Microsoft Academic Search

    Ro D. Kanevskaya; M. I. Shviller

    1992-01-01

    An average description of the transport of nonuniform fluids in porous media nonuniform with respect to their permeability leads to a system of equations of multiphase flow with tensor absolute and phase permeability functions [1], The solution of problems of flow through porous media when the relative phase permeabilities are tensor functions involves considerable difficulties and requires special analysis. Below,

  8. Transport and Deformation-Potential Theory for Many-Valley Semiconductors with Anisotropic Scattering

    Microsoft Academic Search

    Conyers Herring; Erich Vogt

    1956-01-01

    A transport theory which allows for anisotropy in the scattering processes is developed for semiconductors with multiple nondegenerate band edge points. It is found that the main effects of scattering on the distribution function over each ellipsoidal constant-energy surface can be described by a set of three relaxation times, one for each principal direction; these are the principal components of

  9. Correlations among magnetic, electrical and magneto-transport properties of NiFe nanohole arrays

    NASA Astrophysics Data System (ADS)

    Leitao, D. C.; Ventura, J.; Teixeira, J. M.; Sousa, C. T.; Pinto, S.; Sousa, J. B.; Michalik, J. M.; De Teresa, J. M.; Vazquez, M.; Araujo, J. P.

    2013-02-01

    In this work, we use anodic aluminum oxide (AAO) templates to build NiFe magnetic nanohole arrays. We perform a thorough study of their magnetic, electrical and magneto-transport properties (including the resistance R(T), and magnetoresistance MR(T)), enabling us to infer the nanohole film morphology, and the evolution from granular to continuous film with increasing thickness. In fact, different physical behaviors were observed to occur in the thickness range of the study (2 nm < t < 100 nm). For t < 10 nm, an insulator-to-metallic crossover was visible in R(T), pointing to a granular film morphology, and thus being consistent with the presence of electron tunneling mechanisms in the magnetoresistance. Then, for 10 nm < t < 50 nm a metallic R(T) allied with a larger anisotropic magnetoresistance suggests the onset of morphological percolation of the granular film. Finally, for t > 50 nm, a metallic R(T) and only anisotropic magnetoresistance behavior were obtained, characteristic of a continuous thin film. Therefore, by combining simple low-cost bottom-up (templates) and top-down (sputtering deposition) techniques, we are able to obtain customized magnetic nanostructures with well-controlled physical properties, showing nanohole diameters smaller than 35 nm.

  10. High-field transport properties of graphene

    NASA Astrophysics Data System (ADS)

    Dong, H. M.; Xu, W.; Peeters, F. M.

    2011-09-01

    We present a theoretical investigation on the transport properties of graphene in the presence of high dc driving fields. Considering electron interactions with impurities and acoustic and optical phonons in graphene, we employ the momentum- and energy-balance equations derived from the Boltzmann equation to self-consistently evaluate the drift velocity and temperature of electrons in graphene in the linear and nonlinear response regimes. We find that the current-voltage relation exhibits distinctly nonlinear behavior, especially in the high electric field regime. Under the action of high-fields the large source-drain (sd) current density can be achieved and the current saturation in graphene is incomplete with increasing the sd voltage Vsd up to 3 V. Moreover, for high fields, Vsd>0.1 V, the heating of electrons in graphene occurs. It is shown that the sd current and electron temperature are sensitive to electron density and lattice temperature in the graphene device. This study is relevant to the application of graphene as high-field nano-electronic devices such as graphene field-effect transistors.

  11. Transport properties of mechanically deformed polymer networks

    NASA Astrophysics Data System (ADS)

    Masoud, Hassan; Alexeev, Alexander

    2011-03-01

    We develop a hybrid computational method to probe how the permeation and hindered diffusion change when an isotropic polymer network is deformed by an externally applied force. We use a bond-bending lattice spring model to capture the micromechanics of random networks of interconnected elastic filaments coupled with the dissipative particle dynamics to explicitly model the viscous fluid and diffusive solutes. Our simulations reveal that the network transport properties are defined by the network porosity and by the degree of network anisotropy due to network mechanical deformations. We also show that the internal network structure does not affect the permeation and diffusion of stressed and unstressed networks. Furthermore, our results indicate that permeability of mechanically deformed networks can be predicted based on the alignment of network filaments that is characterized by a second order orientation tensor. Our findings have implications for designing drug delivery agents, tissue engineering, and understanding the function of certain biological systems. Financial support from the Donors of the PetroleumResearchFund, administered by theACS, is gratefully acknowledged.

  12. Effects of multiple reflection in the process of inelastic electron transport through an anisotropic magnetic atom

    NASA Astrophysics Data System (ADS)

    Val'kov, V. V.; Aksenov, S. V.; Ulanov, E. A.

    2013-12-01

    The effect of multiple reflection in the process of electron transport on the current-voltage characteristics of an adsorbed magnetic atom with single-ion anisotropy has been investigated. All orders of the perturbation theory with respect to the parameter of coupling between the contacts and the multilevel impurity have been taken into account by the Keldysh diagram technique with the use of Hubbard operators. It has been shown that the current-voltage characteristics of the system in a strongly nonequilibrium regime contains regions of negative differential conductance. The ways of enhancing this effect are discussed.

  13. Influence of van der Waals corrected xc-functionals on the anisotropic mechanical properties of coinage metals

    NASA Astrophysics Data System (ADS)

    Lee, Ji-Hwan; Park, Jong-Hun; Jung, Young-Kwang; Soon, Aloysius

    2015-03-01

    Current materials-related calculations employ the density-functional theory (DFT), commonly using the (semi-)local-density approximations for the exchange-correlation (xc) functional. The accuracy to studying the electronic structure depends not only on the employed approximation to the xc potential but also upon the system which is being investigated. The difficulties in arriving at a reasonable description of van der Waals (vdW) interactions by DFT-based models, is to date a big challenge. This stems from the well-known fact that vdW interaction is a non-local correlation effect which is not captured in the deployed (semi-)local xc functionals. In this work, using various flavours of vdW-corrected DFT xc functionals, we study the lattice and mechanical properties (including the elastic constants and anisotropic stress-strain curves) of the coinage metals (copper, silver, and gold), and critically assess the reliability of the different vdW-corrected DFT methods in describing their anisotropic mechanical properties which are less reported on in the literature.

  14. Applications of asymmetric nanotextured parylene surface using its wetting and transport properties

    NASA Astrophysics Data System (ADS)

    Sekeroglu, Koray

    In this thesis, basic digital fluidics devices were introduced using polymeric nanorods (nano-PPX) inspired from nature. Natural inspiration ignited this research by observing butterfly wings, water strider legs, rye grass leaves, and their asymmetric functions. Nano-PPX rods, manufactured by an oblique angle polymerization (OAP) method, are asymmetrically aligned structures that have unidirectional wetting properties. Nano-PPX demonstrates similar functions to the directional textured surfaces of animals and plants in terms of wetting, adhesion, and transport. The water pin-release mechanism on the asymmetric nano-PPX surface with adhesion function provides a great transport property. How the asymmetry causes transport is discussed in terms of hysteresis and interface contact of water droplets. In this study, the transport property of nano-PPX rods is used to guide droplets as well as transporting cargo such as microgels. With the addition of tracks on the nano-PPX rods, the surfaces were transformed into basic digital fluidics devices. The track-assisted nano-PPX has been employed to applications (i.e. sorting, mixing, and carrying cargo particles). Thus, digital fluidics devices fabricated on nano-PPX surface is a promising pathway to assemble microgels in the field of bioengineering. The characterization of the nano textured surface was completed using methods such as Scanning Electron Microscopy, Atomic Force Microscopy, Contact Angle Goniometry, and Fourier Transform Infra-Red Spectroscopy. These methods helped to understand the physical and chemical properties of nano-PPX. Parameters such as advancing and receding contact angles, nanorod tilt angle, and critical drop volumes were utilized to investigate the anisotropic wetting properties of nano-PPX surface. This investigation explained the directional wetting behavior of the surface as well as approaching new design parameters for adjusting surface properties. The nanorod tilt angle was a key parameter, thus changing the angle provided the surface with essential wetting properties. This adjustment on the nano-PPX surface exhibited excellent control on water droplet transport as well as guided the droplets from desired points to targets. The results demonstrated that it is possible to create railroad-like paths to manipulate the droplet movements by deforming the nano-PPX surface. Controlling physical properties of the surface granted the inspiration for fabricating basic fluidic devices to sort and mix droplets. These devices are promising for assembly purposes in terms of using microgels in engineering applications (i.e. building blocks for bioengineering). The surface has potential for further development to achieve the directed assembly of microgels into close proximity.

  15. Anisotropic radiation elds: causality and quantum statistics

    E-print Network

    Honingh, Aline

    radiation transport 5 2.1 Radiation transport equation . . . . . . . . . . . . . . . . . . 5 2.2 Closures The transport of radiation through a medium is described by the radiation transport equation for the radiativeAnisotropic radiation #12;elds: causality and quantum statistics A.K. Honingh #12; #12; Anisotropic

  16. Near-field investigations of the anisotropic properties of supported lipid bilayers

    Microsoft Academic Search

    Merrell A Johnson

    2011-01-01

    The details of Polarization Modulation Near-Field Scanning Optical Microscopy (PM-NSOM) are presented. How to properly calibrate and align the system is also introduced. A measurement of Muscovite crystal is used to display the capabilities of the setup. Measurements of supported gel state 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayers are presented, emphasizing how it was tooled in exploiting the anisotropic nature of the

  17. Neoclassical Transport Properties of Tokamak Plasmas

    SciTech Connect

    Weyssow, B. [Universite Libre de Bruxelles (Belgium)

    2004-03-15

    The classical transport theory is strictly valid for a plasma in a homogeneous and stationary magnetic field. In the '60, experiments have shown that this theory does not apply as a local theory of transport in Tokamaks. It was shown that global geometric characteristics of the confining elements have a strong influence on the transport. Three regimes of collisionality are characteristic of the neoclassical transport theory: the banana regime (the electronic diffusion coefficient increases starting from zero), the plateau regime (the diffusion coefficient is almost independent of the collisionality) and the Pfirsch-Schlueter regime (the electronic diffusion coefficient again increases with the collisionality)

  18. Magneto-transport properties of gapped graphene.

    PubMed

    Jiang, Liwei; Zheng, Yisong; Li, Haidong; Shen, Honghai

    2010-04-01

    Based on the Kubo formula, we have studied the electron transport properties of a gapped graphene in the presence of a strong magnetic field. By solving the Dirac equation, we find that the Landau level spectra in two valleys differ from each other in that the n = 0 level in the K valley is located at top of the valence band, whereas it is at the bottom of the conduction band in the K' valley. Thus, in an individual valley, the symmetry between conduction and valence bands is broken by the presence of a magnetic field. By using the self-consistent Born approximation to treat the long range potential scattering, we formulate the diagonal and the Hall conductivities in terms of the Green function. To perform the numerical calculation, we find that a large bandgap can suppress the quantum Hall effect, owing to the enhancement of the bandgap squeezing the spacing between the low-lying Landau levels. On the other hand, if the bandgap is not very large, the odd integer quantum Hall effect experimentally, observed in the gapless graphene, remains in the gapped one. However, such a result does not indicate the half integer quantum Hall effect in an individual valley of the gapped graphene. This is because the heights of the Hall plateaux in either valley can be continuously tuned by the variation of the bandgap. More interestingly, we find that the height of the diagonal conductivity peak corresponding to the n = 0 Landau level is independent of the bandgap if the scattering is not very strong. In the weak scattering limit, we demonstrate analytically that such a peak takes a universal value e(2)/(hpi), regardless of the bandgap. PMID:20220217

  19. Inelastic tunnel transport of electrons through an anisotropic magnetic structure in an external magnetic field

    NASA Astrophysics Data System (ADS)

    Val'kov, V. V.; Aksenov, S. V.; Ulanov, E. A.

    2014-07-01

    Quantum transport of electrons through a magnetic impurity located in an external magnetic field and affected by a substrate is considered using the Keldysh diagram technique for the Fermi and Hubbard operators. It is shown that in a strongly nonequilibrium state induced by multiple reflections of electrons from the impurity, the current-voltage ( I-V) characteristic of the system contains segments with a negative conductivity. This effect can be controlled by varying the anisotropy parameter of the impurity center as well as the parameters of coupling between the magnetic impurity and metal contacts. The application of the magnetic field is accompanied by an increase in the number of Coulomb steps in the I-V curve of the impurity. The effect of appreciable magnetoresistance appears in this case. We demonstrate the possibility of switching between magnetic impurity states with different total spin projection values in the regime of asymmetric coupling of this impurity with the contacts.

  20. Diameter dependence of the transport properties of antimony telluride nanowires.

    PubMed

    Zuev, Yuri M; Lee, Jin Seok; Galloy, Clément; Park, Hongkun; Kim, Philip

    2010-08-11

    We report measurements of electronic, thermoelectric, and galvanomagnetic properties of individual single crystal antimony telluride (Sb(2)Te(3)) nanowires with diameters in the range of 20-100 nm. Temperature-dependent resistivity and thermoelectric power (TEP) measurements indicate hole dominant diffusive thermoelectric generation with an enhancement of the TEP for smaller diameter wires up to 110 microV/K at T = 300 K. We measure the magnetoresistance in magnetic fields both parallel and perpendicular to the nanowire [110] axis, where strong anisotropic positive magnetoresistance behavior was observed. PMID:20698617

  1. Molecular Properties of Bacterial Multidrug Transporters

    PubMed Central

    Putman, Monique; van Veen, Hendrik W.; Konings, Wil N.

    2000-01-01

    One of the mechanisms that bacteria utilize to evade the toxic effects of antibiotics is the active extrusion of structurally unrelated drugs from the cell. Both intrinsic and acquired multidrug transporters play an important role in antibiotic resistance of several pathogens, including Neisseria gonorrhoeae, Mycobacterium tuberculosis, Staphylococcus aureus, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Vibrio cholerae. Detailed knowledge of the molecular basis of drug recognition and transport by multidrug transport systems is required for the development of new antibiotics that are not extruded or of inhibitors which block the multidrug transporter and allow traditional antibiotics to be effective. This review gives an extensive overview of the currently known multidrug transporters in bacteria. Based on energetics and structural characteristics, the bacterial multidrug transporters can be classified into five distinct families. Functional reconstitution in liposomes of purified multidrug transport proteins from four families revealed that these proteins are capable of mediating the export of structurally unrelated drugs independent of accessory proteins or cytoplasmic components. On the basis of (i) mutations that affect the activity or the substrate specificity of multidrug transporters and (ii) the three-dimensional structure of the drug-binding domain of the regulatory protein BmrR, the substrate-binding site for cationic drugs is predicted to consist of a hydrophobic pocket with a buried negatively charged residue that interacts electrostatically with the positively charged substrate. The aromatic and hydrophobic amino acid residues which form the drug-binding pocket impose restrictions on the shape and size of the substrates. Kinetic analysis of drug transport by multidrug transporters provided evidence that these proteins may contain multiple substrate-binding sites. PMID:11104814

  2. Anisotropic flows and the shear viscosity of the QGP within an event by event transport approach

    E-print Network

    Plumari, Salvatore; Scardina, Francesco; Greco, Vincenzo

    2015-01-01

    We have developed a relativistic kinetic transport approach that incorporates initial state fluctuations allowing to study the build up of elliptic flow $v_2$ and high order harmonics $v_3$, $v_4$ and $v_5$ for a fluid at fixed $\\eta/s(T)$. We study the effect of the $\\eta/s$ ratio and its T dependence on the build up of the $v_n(p_T)$ for two different beam energies: RHIC for Au+Au at $\\sqrt{s}=200 \\,GeV$ and LHC for $Pb+Pb$ at $\\sqrt{s}=2.76 \\,TeV$. We find that for the two different beam energies considered the suppression of the $v_n(p_T)$ due to the viscosity of the medium have different contributions coming from the cross over or QGP phase. Our study reveals that only in ultra-central collisions ($0 - 0.2 \\%$) the $v_n(p_T)$ have a stronger sensitivity to the T dependence of $\\eta/s$ in the QGP phase and this sensitivity increases with the order of the harmonic n. Moreover, the study of the correlations between the initial spatial anisotropies $\\epsilon_n$ and the final flow coefficients $v_n$ shows tha...

  3. Analytic Solutions for Current Sheet Structure Determined by Self-consistent, Anisotropic Transport Processes in a Gravitational Field

    NASA Astrophysics Data System (ADS)

    Goodman, Michael L.

    2011-04-01

    A Harris sheet magnetic field with maximum magnitude B 0 and length scale L is combined with the anisotropic electrical conductivity, viscosity, and thermoelectric tensors for an electron-proton plasma to define a magnetohydrodynamic model that determines the steady state of the plasma. The transport tensors are functions of temperature, density, and magnetic field strength, and are computed self-consistently as functions of position x normal to the current sheet. The flow velocity, magnetic field, and gravitational force lie along the z-axis. The plasma is supported against gravity by the viscous force. Analytic solutions are obtained for temperature, density, and velocity. They are valid over a broad range of temperature, density, and magnetic field strength, and so may be generally useful in astrophysical applications. Numerical examples of solutions in the parameter range of the solar atmosphere are presented. The objective is to compare Joule and viscous heating rates, determine the velocity shear that generates viscous forces that support the plasma and are self-consistent with a mean outward mass flux comparable to the solar wind mass flux, and compare the thermoelectric and conduction current contributions to the Joule heating rate. The ratio of the viscous to Joule heating rates per unit mass can exceed unity by orders of magnitude, and increases rapidly with L. The viscous heating rate can be concentrated outside the region where the current density is localized, corresponding to a resistively heated layer of plasma bounded by viscously heated plasma. The temperature gradient drives a thermoelectric current density that can have a magnitude greater than that of the electric-field-driven conduction current density, so thermoelectric effects are important in determining the Joule heating rate.

  4. Anisotropic Thermal and Electrical Properties of Thin Thermal Interface Layers of Graphite Nanoplatelet-Based Composites

    PubMed Central

    Tian, Xiaojuan; Itkis, Mikhail E.; Bekyarova, Elena B.; Haddon, Robert C.

    2013-01-01

    Thermal interface materials (TIMs) are crucial components of high density electronics and the high thermal conductivity of graphite makes this material an attractive candidate for such applications. We report an investigation of the in-plane and through-plane electrical and thermal conductivities of thin thermal interface layers of graphite nanoplatelet (GNP) based composites. The in-plane electrical conductivity exceeds its through-plane counterpart by three orders of magnitude, whereas the ratio of the thermal conductivities is about 5. Scanning electron microscopy reveals that the anisotropy in the transport properties is due to the in-plane alignment of the GNPs which occurs during the formation of the thermal interface layer. Because the alignment in the thermal interface layer suppresses the through-plane component of the thermal conductivity, the anisotropy strongly degrades the performance of GNP-based composites in the geometry required for typical thermal management applications and must be taken into account in the development of GNP-based TIMs.

  5. Atomistic Study of Transport Properties at the Nanoscale 

    E-print Network

    Haskins, Justin

    2013-01-11

    in terms of atomistic properties, three case studies of transport in important, nanosized systems are investigated, including confined water systems, silicon-germanium nanos- tructures, and carbon nanostructures. In the first study of confined water systems...

  6. Properties of the zeroth-, first-, and higher-order approximations of attributes of elastic waves in weakly anisotropic media

    E-print Network

    Cerveny, Vlastislav

    of the perturbation theory on the accuracy of the determination of the acoustical axes in weakly anisotropic media. We in weakly anisotropic media Ve´ronique Farraa) and Ivan Psenci´kb) De´partement de Sismologie, Institut de of elastic waves propagating in weakly anisotropic media leads to approximate but transparent and simple

  7. Quantifying magnetic anisotropy dispersion: Theoretical and experimental study of the magnetic properties of anisotropic FeCuNbSiB ferromagnetic films

    E-print Network

    T. M. L. Alves; C. G. Bezerra; A. D. C. Viegas; S. Nicolodi; M. A. Corrêa; F. Bohn

    2014-12-01

    The Stoner-Wohlfarth model is a traditional and efficient tool to calculate magnetization curves and it can provides further insights on the fundamental physics associated to the magnetic properties and magnetization dynamics. Here, we perform a theoretical and experimental investigation of the quasi-static magnetic properties of anisotropic systems. We consider a theoretical approach which corresponds to a modified version of the Stoner-Wohlfarth model to describe anisotropic systems and a distribution function to express the magnetic anistropy dispersion. We propose a procedure to calculate the magnetic properties for the anisotropic case of the SW model from experimental results of the quadrature of magnetization curves, thus quantifying the magnetic anisotropy dispersion. To test the robustness of the approach, we apply the theoretical model to describe the quasi-static magnetic properties of amorphous FeCuNbSiB ferromagnetic films. We perform calculations and directly compare theoretical results with longitudinal and transverse magnetization curves measured for the films. Thus, our results provide experimental evidence to confirm the validity of the theoretical approach to describe the magnetic properties of anisotropic amorphous ferromagnetic films, revealed by the excellent agreement between numerical calculation and experimental results.

  8. Multiglass properties and magnetoelectric coupling in the uniaxial anisotropic spin-cluster-glass Fe2Ti O5

    NASA Astrophysics Data System (ADS)

    Sharma, Shivani; Basu, Tathamay; Shahee, Aga; Singh, K.; Lalla, N. P.; Sampathkumaran, E. V.

    2014-10-01

    The compound Fe2Ti O5 (FTO) is a well-known uniaxial anisotropic spin-glass insulator with two successive glassy freezing temperatures, i.e., transverse (TT F= 9 K ) and longitudinal (TL F= 55 K ) . In this article, we present the results of measurements of complex dielectric behavior, electric polarization as a function of temperature (T ), in addition to characterization by magnetic susceptibility and heat capacity, primarily to explore magnetoelectric (ME) coupling and multiglass properties in uniaxial anisotropic spin-cluster-glass FTO. The existence of two magnetic transitions is reflected in the isothermal magnetodielectric (MD) behavior in the sense that the sign of MD is different in the T regime T TT F . The data in addition provide evidence for the glassy dynamics of electric dipoles; interestingly, this occurs at much higher temperature (˜100-150 K) than TL F, with high remnant polarization at 10 K (˜4000 ? C /m2) attributable to short-range magnetic correlations, thereby offering a route to attain ME coupling above 77 K.

  9. Anisotropic properties of ultrafast laser-driven microexplosions in lithium niobate crystal

    NASA Astrophysics Data System (ADS)

    Zhou, Guangyong; Gu, Min

    2005-12-01

    Smooth voids are achieved in an anisotropic Fe :LiNbO3 crystal with a high refractive index by use of a femtosecond laser-driven microexplosion method. Due to the anisotropy of the crystal, the maximum fabrication depth and the fabrication power threshold are different in different crystal directions, indicating that the direction perpendicular to the crystal axis is more suitable for thick three-dimensional structure fabrication. The dependence of the threshold power on the illumination wavelength shows that the microexplosion mechanism is caused by a two-photon absorption process. As a result, a near threshold fabrication method can be used to generate quasispherical voids.

  10. Theoretical investigation of thermoelectric transport properties of cylindrical Bi nanowires

    Microsoft Academic Search

    Yu-Ming Lin; Xiangzhong Sun; M. S. Dresselhaus

    2000-01-01

    We report here a theoretical model for the transport properties of cylindrical Bi nanowires. Based on the band structure of Bi nanowires and the semiclassical transport model, the thermoelectric figure of merit Z1DT is calculated for Bi nanowires with various wire diameters and wire orientations. The results show the trigonal axis is the most favorable wire orientation for thermoelectric applications,

  11. Angular momentum transport in a multicomponent solar wind with differentially flowing, thermally anisotropic ions

    E-print Network

    Bo Li; Xing Li

    2008-12-09

    The Helios measurements of the angular momentum flux $L$ for the fast solar wind show that the individual ion contributions, $L_p$ and $L_\\alpha$, tend to be negative (i.e., in the sense of counter-rotation with the Sun). However, the opposite holds for the slow wind, and the overall particle contribution $L_P = L_p + L_\\alpha$ tends to exceed the magnetic one $L_M$. These aspects are at variance with previous models. We examine whether introducing realistic ion temperature anisotropies can resolve this discrepancy. From the general multifluid transport equations with gyrotropic species pressure tensors, we derive the equations governing both the meridional and azimuthal dynamics of general axisymmetrical, rotating stellar winds that include two major ion species. The azimuthal dynamics are examined in detail, using the empirically constructed meridional flow profiles for the solar wind. We find that $L$ is determined by requiring that the solution to the total angular momentum conservation law is unique and smooth close to the Alfven point, where the combined Alfvenic Mach number $M_T=1$. Introducing realistic ion temperature anisotropies may introduce a change of up to 10% in $L$ and up to 1.8 km/s in azimuthal speeds of individual ions between 0.3 and 1 AU, compared with the isotropic case. The latter has strong consequences on the relative importance of $L_P$ and $L_M$. However, introducing ion temperature anisotropies cannot resolve the discrepancy between measurements and models. For the fast-wind solutions, while in extreme cases $L_P$ becomes negative, $L_p$ never does. On the other hand, for the slow-wind solutions, $L_P$ never exceeds $L_M$, even though $L_M$ may be less than the individual ion contribution, since $L_p$ and $L_\\alpha$ always have opposite signs for the slow and fast wind alike.

  12. Transport properties of Dirac semimetal Cd3As2

    NASA Astrophysics Data System (ADS)

    Liang, Tian; Gibson, Quinn; Xiong, Jun; Liu, Minhao; Hirschberger, Maximilian; Cava, Robert; Ong, Nai Phuan

    2014-03-01

    The semimetal Cd3As2 has emerged as an attractive candidate for a Dirac semimetal. A recent LDA calculation reveals that, at the Fermi energy, it has two bulk Dirac nodes which straddle the ? point along the kz axis. The Dirac nodes were recently observed by ARPES. We have made extensive transport measurements of Cd3As2. Because of possible Cd vacancy disorder in the very large unit cell (160 atoms), the SdH oscillations reveal a quantum lifetime that is moderately damped. Despite the disorder, the observed resistivity ? in some crystals displays a RRR of 1000. At 4 K, the residual resistivity is anomalously low (30 n ? cm). We estimate that the mobility exceeds 106 cm2V-1s-1. A magnetic field H strongly increases ? by factors of 100 to 1000 at 10 Tesla. This giant magnetoresistance (MR) is highly anisotropic. The MR is largest when H is perpendicular to the axis (110) and minimal when H is ?(110). We will discuss possible origins of this unusual anisotropic giant MR. We also discuss the possibility of detecting an enhanced longitudinal MR associated with charge pumping between Weyl nodes (the chiral anomaly). Supported by Army Research Office (ARO W911NF-11-1-0379) and NSF-MRSEC Grant DMR 0819860.

  13. Anisotropic charge transport in large single crystals of ?-conjugated organic molecules.

    PubMed

    Hourani, Wael; Rahimi, Khosrow; Botiz, Ioan; Koch, Felix Peter Vinzenz; Reiter, Günter; Lienerth, Peter; Heiser, Thomas; Bubendorff, Jean-Luc; Simon, Laurent

    2014-05-01

    The electronic properties of organic semiconductors depend strongly on the nature of the molecules, their conjugation and conformation, their mutual distance and the orientation between adjacent molecules. Variations of intramolecular distances and conformation disturb the conjugation and perturb the delocalization of charges. As a result, the mobility considerably decreases compared to that of a covalently well-organized crystal. Here, we present electrical characterization of large single crystals made of the regioregular octamer of 3-hexyl-thiophene (3HT)8 using a conductive-atomic force microscope (C-AFM) in air. We find a large anisotropy in the conduction with charge mobility values depending on the crystallographic orientation of the single crystal. The smaller conduction is in the direction of ?-? stacking (along the long axis of the single crystal) with a mobility value in the order of 10(-3) cm(2) V(-1) s(-1), and the larger one is along the molecular axis (in the direction normal to the single crystal surface) with a mobility value in the order of 0.5 cm(2) V(-1) s(-1). The measured current-voltage (I-V) curves showed that along the molecular axis, the current followed an exponential dependence corresponding to an injection mode. In the ?-? stacking direction, the current exhibits a space charge limited current (SCLC) behavior, which allows us to estimate the charge carrier mobility. PMID:24658783

  14. Blind inversion method using Lamb waves for the complete elastic property characterization of anisotropic plates.

    PubMed

    Vishnuvardhan, J; Krishnamurthy, C V; Balasubramaniam, Krishnan

    2009-02-01

    A novel blind inversion method using Lamb wave S(0) and A(0) mode velocities is proposed for the complete determination of elastic moduli, material symmetries, as well as principal plane orientations of anisotropic plates. The approach takes advantage of genetic algorithm, introduces the notion of "statistically significant" elastic moduli, and utilizes their sensitivities to velocity data to reconstruct the elastic moduli. The unknown material symmetry and the principal planes are then evaluated using the method proposed by Cowin and Mehrabadi [Q. J. Mech. Appl. Math. 40, 451-476 (1987)]. The blind inversion procedure was verified using simulated ultrasonic velocity data sets on materials with transversely isotropic, orthotropic, and monoclinic symmetries. A modified double ring configuration of the single transmitter and multiple receiver compact array was developed to experimentally validate the blind inversion approach on a quasi-isotropic graphite-epoxy composite plate. This technique finds application in the area of material characterization and structural health monitoring of anisotropic platelike structures. PMID:19206853

  15. P(VDF-TrFE) nanorod assemblies with anisotropic piezoelectric properties investigated by piezoelectric response microscopy

    NASA Astrophysics Data System (ADS)

    Chen, Xiaosui; Wang, Yunli; Cai, Kai; Bai, Yang; Bo, Shuhui; Guo, Dong

    2014-08-01

    Highly ordered assemblies of the copolymer of vinylidene fluoride and trifluoroethylene P(VDF-TrFE) nanorods with anisotropic piezoelectric response were fabricated on different substrates by using a template-free self-organization method. The significant difference in vertical and lateral piezoelectric responses of the nanorods in piezoresponse force microscopy (PFM) revealed that their molecular dipoles were preferentially oriented parallel to the substrate plane. In addition, dipole orientation distribution map in the nanorods was derived by analyzing the vertical and lateral PFM amplitude and phase images. Infrared reflection spectra further showed that the macromolecular backbones were oriented perpendicularly relative to the substrate. A flat-on lamellar structure and a confined crystallization of dewetted melt phase nanorod formation mechanism were proposed. The highly anisotropic piezoelectric response of the assemblies of nanorods may be promising for nanoscale devices for application in energy harvesting, etc. More importantly, the results demonstrated that self organization could be used for fabricating P(VDF-TrFE) nanostructures by controlling the surface energy of the substrates.

  16. Anisotropic magnetic, magnetoresistance, and electrotransport properties of GdBaCo2O5.5 single crystals

    NASA Astrophysics Data System (ADS)

    Khalyavin, D. D.; Barilo, S. N.; Shiryaev, S. V.; Bychkov, G. L.; Troyanchuk, I. O.; Furrer, A.; Allenspach, P.; Szymczak, H.; Szymczak, R.

    2003-06-01

    Single crystals of GdBaCo2O5.5 layered perovskites have been grown from a flux melt of Gd2O3-BaO-CoO oxides. Magnetic data showed that the GdBaCo2O5.5 single crystals exhibit a magnetic phase transition from an antiferromagnetic state to a ferromagnetic one with spontaneous magnetization around 0.41 ?B per Co ion at Ti˜160 K. Direction of spontaneous magnetic moment coincides with either the a or b axis. It is assumed that Co3+ ions adopt low- and intermediate-spin states in the ratio of 1:1. The giant magnetoresistance effect connected closely with a spontaneous magnetization appearance shows a strong anisotropic that is behavior consistent with the anisotropy of magnetic properties. On the basis of electrical resistivity data the quasi-two-dimensional character of conductivity, above the metal-insulator transition temperature TMI˜370 K, was assumed.

  17. Complex polarization ratio to determine polarization properties of anisotropic tissue using polarization-sensitive optical coherence tomography.

    PubMed

    Park, Jesung; Kemp, Nate J; Rylander, H Grady; Milner, Thomas E

    2009-08-01

    Complex polarization ratio (CPR) in materials with birefringence and biattenuance is shown as a logarithmic spiral in the complex plane. A multi-state Levenberg-Marquardt nonlinear fitting algorithm using the CPR trajectory collected by polarization sensitive optical coherence tomography (PS-OCT) was developed to determine polarization properties of an anisotropic scattering medium. The Levenberg-Marquardt nonlinear fitting algorithm using the CPR trajectory is verified using simulated PS-OCT data with speckle noise. Birefringence and biattenuance of a birefringent film, ex-vivo rodent tail tendon and in-vivo primate retinal nerve fiber layer were determined using measured CPR trajectories and the Levenberg-Marquardt nonlinear fitting algorithm. PMID:19654746

  18. Ellipsometric characterization and density-functional theory analysis of anisotropic optical properties of single-crystal ?-SnS

    SciTech Connect

    Banai, R. E.; Brownson, J. R. S. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Burton, L. A.; Walsh, A. [Centre for Sustainable Chemical Technologies and Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Choi, S. G., E-mail: sukgeun.choi@nrel.gov; To, B. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Hofherr, F.; Sorgenfrei, T.; Cröll, A. [Crystallography—Institute of Earth and Environmental Sciences, University of Freiburg, 79104 Freiburg (Germany)

    2014-07-07

    We report on the anisotropic optical properties of single-crystal tin monosulfide (SnS). The components ?{sub a}, ?{sub b}, and ?{sub c} of the pseudodielectric-function tensor (?)=(??)+i(??) spectra are taken from 0.73 to 6.45 eV by spectroscopic ellipsometry. The measured (?) spectra are in a good agreement with the results of the calculated dielectric response from hybrid density functional theory. The (?) spectra show the direct band-gap onset and a total of eight above-band-gap optical structures that are associated with the interband-transition critical points (CPs). We obtain accurate CP energies by fitting analytic CP expressions to second-energy-derivatives of the (?) data. Their probable electronic origins and implications for photovoltaic applications are discussed.

  19. Magnetism and transport properties of transition metal oxides and nanoparticles

    Microsoft Academic Search

    Dane Thomas Gillaspie

    2006-01-01

    This dissertation is devoted to the study of the properties of transition metal oxides in both thin film and nanocrystalline forms. The first section is devoted to the transport properties of manganese oxide thin film samples. The colossal magnetoresistance in these materials is usually explained using double-exchange, but this explanation is only partially correct. Recent theoretical and experimental work has

  20. THERMODYNAMIC AND TRANSPORT PROPERTIES OF SILICATE MELTS AND MAGMA

    E-print Network

    Spera, Frank J.

    PROPERTIES5 Density and Equation of State6 Enthalpy, Entropy and Heat Capacity7 VI. MAGMA TRANSPORT the temperature of a substance to its internal38 energy. These properties include the enthalpy, entropy and heat diverging plate boundaries. The density, specific heat, viscosity and thermal conductivity of a58 typical

  1. FIELD DETERMINATION OF SOIL HYDRAULIC AND CHEMICAL TRANSPORT PROPERTIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hydraulic and chemical transport properties are the major inputs in predictive models that simulate the movement of water and chemicals through the vadose zone. However, there is a lack of field measurements of such properties to verify models describing water and chemical movement through the soil...

  2. PROPERTIES OF INTERFACES AND TRANSPORT ACROSS THEM

    EPA Science Inventory

    Much of the biological activity in cell cytoplasm occurs in compartments which are thought to form by phase separation, and many of the functions of these compartments occur by the transport or exchange of molecules across interfaces. Thus, a fundamentally based discussion of th...

  3. Effect of mechanical boundary conditions on the dynamic and static properties of a strongly anisotropic ferromagnet

    SciTech Connect

    Gorelikov, G. A.; Fridman, Yu. A., E-mail: frid@crimea.edu [Vernadskii Tavria National University (Ukraine)

    2013-07-15

    The spectra of coupled magnetoelastic waves in a semi-infinite strongly anisotropic easy-plane ferromagnet with a rigidly fixed face are analyzed for two variants of fixation (in the basal plane and perpendicularly to it). The phase states of the system are determined. Differences in the phase diagrams and elementary excitation spectra depending on the choice of the sample fixation plane are considered. When rotational invariance is taken into account, the nonreciprocity effect for the velocities of sound in a crystal appears. It is shown that the velocity of sound in the sample considerably depends on the symmetry of the imposed mechanical boundary conditions. The phase diagrams of the system under investigation are presented.

  4. Anisotropic optical properties of semipolar AlGaN layers grown on m-plane sapphire

    NASA Astrophysics Data System (ADS)

    Feneberg, Martin; Winkler, Michael; Klamser, Juliane; Stellmach, Joachim; Frentrup, Martin; Ploch, Simon; Mehnke, Frank; Wernicke, Tim; Kneissl, Michael; Goldhahn, Rüdiger

    2015-05-01

    The valence band order of AlxGa 1 -x N is investigated experimentally by analyzing the anisotropic dielectric functions of semipolar (11 2 ¯ 2 ) AlGaN thin films grown on m-plane Al2O3. Point-by-point fitted dielectric functions are obtained by spectroscopic ellipsometry and corresponding inter-band transition energies are extracted. The known strain situation of the sample layers is used to correct for the small strain-induced energy shifts within k . p perturbation theory. It also is used to identify transitions related to the three valence bands. Transitions with E ? c from the ?9 valence band verify an inter-band bowing parameter of b =0.9 eV . The transitions with E || c allow determining the crystal field splitting energy which can be described by a linear interpolation between the values for GaN and AlN satisfactorily.

  5. Documentation and verification of VST2D; a model for simulating transient, Variably Saturated, coupled water-heat-solute Transport in heterogeneous, anisotropic 2-Dimensional, ground-water systems with variable fluid density

    USGS Publications Warehouse

    Friedel, Michael J.

    2001-01-01

    This report describes a model for simulating transient, Variably Saturated, coupled water-heatsolute Transport in heterogeneous, anisotropic, 2-Dimensional, ground-water systems with variable fluid density (VST2D). VST2D was developed to help understand the effects of natural and anthropogenic factors on quantity and quality of variably saturated ground-water systems. The model solves simultaneously for one or more dependent variables (pressure, temperature, and concentration) at nodes in a horizontal or vertical mesh using a quasi-linearized general minimum residual method. This approach enhances computational speed beyond the speed of a sequential approach. Heterogeneous and anisotropic conditions are implemented locally using individual element property descriptions. This implementation allows local principal directions to differ among elements and from the global solution domain coordinates. Boundary conditions can include time-varying pressure head (or moisture content), heat, and/or concentration; fluxes distributed along domain boundaries and/or at internal node points; and/or convective moisture, heat, and solute fluxes along the domain boundaries; and/or unit hydraulic gradient along domain boundaries. Other model features include temperature and concentration dependent density (liquid and vapor) and viscosity, sorption and/or decay of a solute, and capability to determine moisture content beyond residual to zero. These features are described in the documentation together with development of the governing equations, application of the finite-element formulation (using the Galerkin approach), solution procedure, mass and energy balance considerations, input requirements, and output options. The VST2D model was verified, and results included solutions for problems of water transport under isohaline and isothermal conditions, heat transport under isobaric and isohaline conditions, solute transport under isobaric and isothermal conditions, and coupled water-heat-solute transport. The first three problems considered in model verification were compared to either analytical or numerical solutions, whereas the coupled problem was compared to measured laboratory results for which no known analytic solutions or numerical models are available. The test results indicate the model is accurate and applicable for a wide range of conditions, including when water (liquid and vapor), heat (sensible and latent), and solute are coupled in ground-water systems. The cumulative residual errors for the coupled problem tested was less than 10-8 cubic centimeter per cubic centimeter, 10-5 moles per kilogram, and 102 calories per cubic meter for liquid water content, solute concentration and heat content, respectively. This model should be useful to hydrologists, engineers, and researchers interested in studying coupled processes associated with variably saturated transport in ground-water systems.

  6. CET89 - CHEMICAL EQUILIBRIUM WITH TRANSPORT PROPERTIES, 1989

    NASA Technical Reports Server (NTRS)

    Mcbride, B.

    1994-01-01

    Scientists and engineers need chemical equilibrium composition data to calculate the theoretical thermodynamic properties of a chemical system. This information is essential in the design and analysis of equipment such as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical processing equipment. The substantial amount of numerical computation required to obtain equilibrium compositions and transport properties for complex chemical systems led scientists at NASA's Lewis Research Center to develop CET89, a program designed to calculate the thermodynamic and transport properties of these systems. CET89 is a general program which will calculate chemical equilibrium compositions and mixture properties for any chemical system with available thermodynamic data. Generally, mixtures may include condensed and gaseous products. CET89 performs the following operations: it 1) obtains chemical equilibrium compositions for assigned thermodynamic states, 2) calculates dilute-gas transport properties of complex chemical mixtures, 3) obtains Chapman-Jouguet detonation properties for gaseous species, 4) calculates incident and reflected shock properties in terms of assigned velocities, and 5) calculates theoretical rocket performance for both equilibrium and frozen compositions during expansion. The rocket performance function allows the option of assuming either a finite area or an infinite area combustor. CET89 accommodates problems involving up to 24 reactants, 20 elements, and 600 products (400 of which may be condensed). The program includes a library of thermodynamic and transport properties in the form of least squares coefficients for possible reaction products. It includes thermodynamic data for over 1300 gaseous and condensed species and transport data for 151 gases. The subroutines UTHERM and UTRAN convert thermodynamic and transport data to unformatted form for faster processing. The program conforms to the FORTRAN 77 standard, except for some input in NAMELIST format. It requires about 423 KB memory, and is designed to be used on mainframe, workstation, and mini computers. Due to its memory requirements, this program does not readily lend itself to implementation on MS-DOS based machines.

  7. Thermodynamic and transport properties of sodium liquid and vapor

    SciTech Connect

    Fink, J.K.; Leibowitz, L.

    1995-01-01

    Data have been reviewed to obtain thermodynamically consistent equations for thermodynamic and transport properties of saturated sodium liquid and vapor. Recently published Russian recommendations and results of equation of state calculations on thermophysical properties of sodium have been included in this critical assessment. Thermodynamic properties of sodium liquid and vapor that have been assessed include: enthalpy, heat capacity at constant pressure, heat capacity at constant volume, vapor pressure, boiling point, enthalpy of vaporization, density, thermal expansion, adiabatic and isothermal compressibility, speed of sound, critical parameters, and surface tension. Transport properties of liquid sodium that have been assessed include: viscosity and thermal conductivity. For each property, recommended values and their uncertainties are graphed and tabulated as functions of temperature. Detailed discussions of the analyses and determinations of the recommended equations include comparisons with recommendations given in other assessments and explanations of consistency requirements. The rationale and methods used in determining the uncertainties in the recommended values are also discussed.

  8. Enhancement of wall jet transport properties

    DOEpatents

    Claunch, Scott D. (Broomfield, CO); Farrington, Robert B. (Golden, CO)

    1997-01-01

    By enhancing the natural instabilities in the boundary layer and in the free shear layer of a wall jet, the boundary is minimized thereby increasing the transport of heat and mass. Enhancing the natural instabilities is accomplished by pulsing the flow of air that creates the wall jet. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct.

  9. An experimental study of transport properties of porous rock salt

    NASA Astrophysics Data System (ADS)

    Spangenberg, E.; Spangenberg, U.; Heindorf, C.

    The influence of porosity on the transport properties of rock salt was investigated on a set of artificial porous rock salt samples. The porosities of the samples range from 5% to 42%. To study the influence of compaction on the pore space structure, five samples representing the investigated porosity range were used to produce thin sections for the analysis of the pore geometry. Permeabilities and electrical formation resistivity factors were measured with a saturated salt solution as pore fluid at room temperature and room pressure. Both properties show a strong correlation to porosity. Permabilities and formation resistivity factors were used in conjunction with the microscopical observations of the mean pore sizes to derive a parameter describing the influence of the constrictions of the transport paths. It is shown that the influence of increasing constrictivity on the transport properties is much stronger than that of decreasing porosity for the mechanically compacted samples.

  10. Multidimensional field and theoretical investigation of solute transport from an injection well into a homogeneous and anisotropic aquifer. Technical completion report

    SciTech Connect

    Chen, C.S.; Holmes, C.; Li, W.; Chace, D.; Fort, M.

    1993-05-01

    The purpose of this project is not so much to compare different methods in analyzing the solute transport problems as to evaluate whether the dispersivity involved in the Advection-Dispersion Equation (ADE) can be relatively intrinsic to aquifers when more detailed groundwater flow fields are taken into account in the mathematical model. Here, the 'more detailed groundwater flow field' means that (1) it is anisotropic and three-dimensional, and (2) it is estimated from three-dimensional depth-specific drawdown data. Of course, the solute transport phenomenon is accordingly considered to be three-dimensional and under the influence of aquifer anisotropy, and is analyzed using three-dimensional depth-specific tracer test data.

  11. Transport properties of interacting magnetic islands in tokamak plasmas

    SciTech Connect

    Gianakon, T.A.; Callen, J.D.; Hegna, C.C.

    1993-10-01

    This paper explores the equilibrium and transient transport properties of a mixed magnetic topology model for tokamak equilibria. The magnetic topology is composed of a discrete set of mostly non-overlapping magnetic islands centered on the low-order rational surfaces. Transport across the island regions is fast due to parallel transport along the stochastic magnetic field lines about the separatrix of each island. Transport between island regions is assumed to be slow due to a low residual cross-field transport. In equilibrium, such a model leads to: a nonlinear dependence of the heat flux on the pressure gradient; a power balance diffusion coefficient which increases from core to edge; and profile resiliency. Transiently, such a model also exhibits a heat pulse diffusion coefficient larger than the power balance diffusion coefficient.

  12. Transport properties of a discrete helical electrostatic quadrupole

    SciTech Connect

    Meitzler, C.R.; Antes, K.; Datte, P.; Huson, F.R. (Texas Accelerator Center, The Woodlands, TX (United States)); Xiu, L. (Houston Univ., TX (United States). Inst. for Beam Particle Dynamics)

    1991-01-01

    The helical electrostatic quadrupole (HESQ) lens has been proposed as a low energy beam transport system which permits intense H{sup {minus}} beams to be focused into an RFQ without seriously increasing the beam's emittance. A stepwise continuous HESQ lens has been constructed, and preliminary tests have shown that the structure does provide focusing. In order to understand the transport properties of this device, further detailed studies have been performed. Emittances were measured 3.5 cm from the end of the HESQ at two different voltages on the HESQ electrodes. A comparison of these experimental results with a linear model of the HESQ beam transport is made. 4 refs., 5 figs.

  13. Transport properties in nontwist area-preserving maps

    SciTech Connect

    Szezech, J. D. Jr.; Caldas, I. L. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo, 05315-970 Sao Paulo (Brazil); Lopes, S. R.; Viana, R. L. [Departamento de Fisica, Universidade Federal do Parana, Caixa Postal 19044, Curitiba, 81531-990 Parana (Brazil); Morrison, P. J. [Department of Physics and Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States)

    2009-12-15

    Nontwist systems, common in the dynamical descriptions of fluids and plasmas, possess a shearless curve with a concomitant transport barrier that eliminates or reduces chaotic transport, even after its breakdown. In order to investigate the transport properties of nontwist systems, we analyze the barrier escape time and barrier transmissivity for the standard nontwist map, a paradigm of such systems. We interpret the sensitive dependence of these quantities upon map parameters by investigating chaotic orbit stickiness and the associated role played by the dominant crossing of stable and unstable manifolds.

  14. Transport properties of water at functionalized molecular interfaces

    PubMed Central

    Feng, Jun; Wong, Ka-Yiu; Dyer, Kippi; Pettitt, B. Montgomery

    2009-01-01

    Understanding transport properties of solvent such as diffusion and viscosity at interfaces with biomacromolecules and hard materials is of fundamental importance to both biology and biotechnology. Our study utilizes equilibrium molecular dynamics simulations to calculate solvent transport properties at a model peptide and microarray surface. Both diffusion and selected components of viscosity are considered. Solvent diffusion is found to be affected near the peptide and surface. The stress-stress correlation function of solvent near the hard surface exhibits long time memory. Both diffusion and viscosity are shown to be closely correlated with the density distribution function of water along the microarray surface. PMID:19791920

  15. Theoretical consistency test of steam transport properties

    NASA Technical Reports Server (NTRS)

    Thoen-Hellemans, J.; Mason, E. A.

    1973-01-01

    The kinetic theory of polyatomic gases is used to test the mutual consistency of the thermal conductivity, viscosity, and specific heat of low-pressure steam from 100 to 700 C. No inconsistency exists within the cited tolerances of the skeleton tables recommended by the Sixth International Conference on the Properties of Steam, but there is some basis for suspecting that the high-temperature thermal conductivity values are slightly low. Methods for tightening the consistency bounds are suggested.

  16. Crystal structure and transport properties of nickel containing germanium clathrates

    Microsoft Academic Search

    Simon Johnsen; Anders Bentien; Georg K. H. Madsen; Mats Nygren; Bo B. Iversen

    2007-01-01

    Four Ba8Ni6-xGe40+x clathrate samples with x=0-0.6 were synthesized and characterized using conventional and synchrotron x-ray powder diffraction. Thermopower, resistivity, thermal conductivity, Hall effect, and magnetic susceptibility were measured between 2 and 400K . To support the interpretation of the physical property data, density functional theory calculations were used to obtain band structures and theoretical transport properties for a wide range

  17. Quantifying magnetic anisotropy dispersion: Theoretical and experimental study of the magnetic properties of anisotropic FeCuNbSiB ferromagnetic films

    NASA Astrophysics Data System (ADS)

    Alves, T. M. L.; Bezerra, C. G.; Viegas, A. D. C.; Nicolodi, S.; Corrêa, M. A.; Bohn, F.

    2015-02-01

    We performed a theoretical and experimental investigation of the quasi-static magnetic properties of anisotropic systems. We considered a modified Stoner-Wohlfarth model to describe anisotropic systems, and a distribution function to express the magnetic anisotropy dispersion. We also proposed a procedure to calculate the magnetic properties from experimental results of the quadrature of magnetization curves, thus quantifying the magnetic anisotropy dispersion. To test the robustness of the approach, we applied the theoretical model to describe the quasi-static magnetic properties of amorphous FeCuNbSiB ferromagnetic films, and directly compared the theoretical results with longitudinal and transverse magnetization curves measured for the films. Our films are characterized by anisotropy fields between 7 and 10.5 Oe, values compatible with that obtained for several amorphous magnetic materials, as well as by anisotropy dispersions expressed by exponents n between 14 and 30. Thus, the excellent agreement between numerical calculation and experimental results provides support to confirm the validity of our theoretical approach to describe the magnetic properties of anisotropic amorphous ferromagnetic films.

  18. Anisotropic Fermi surface from holography

    NASA Astrophysics Data System (ADS)

    Fang, Li Qing; Ge, Xian-hui; Wu, Jian-Pin; Leng, Hong-Qiang

    2015-06-01

    We investigate the probe holographic fermions by using an anisotropic charged black brane solution. We derive the equation of motion of probe bulk fermions with one Fermi momentum along the anisotropic and one along the isotropic directions. We then numerically solve the equation and analyze the properties of Green function with these two momentums. We find in this case the shape of Fermi surface is anisotropic. However, for both Fermi momentums perpendicular to the anisotropic direction, the Fermi surface is isotropic. We verify that our system obeys the recently conjectured bound for thermoelectric diffusion constants for the stable branch of the black brane solutions.

  19. Calculating anisotropic physical properties from texture data using the MTEX open source package

    E-print Network

    Hielscher, Ralf

    available MATLAB toolbox13 that covers a wide range of problems in quantitative texture analysis, e the classical work of Voigt24 (1928) and Reuss (1929). Such an approach is only feasible if the bulk properties

  20. Cosmic Strings and Anisotropic Universe

    E-print Network

    K. L. Mahanta; S. K. Tripathy

    2014-10-04

    Plane symmetric bulk viscous string cosmological models with strange quark matter are investigated. We have incorporated bulk viscous pressure to study its affect on the properties of the model. Assuming an anisotropic relationship among the metric potentials, we have tried to put some constraints on the anisotropic parameter.

  1. Optical nanotomography of anisotropic fluids

    E-print Network

    Loss, Daniel

    LETTERS Optical nanotomography of anisotropic fluids ANTONIO DE LUCA1 *, VALENTIN BARNA2 *, TIMOTHY September 2008; doi:10.1038/nphys1077 The physical properties of anisotropic fluids can be manipulated,2 . This facilitates the use of ordered fluids in a variety of scientific endeavours and applications. Although future

  2. Tuning transport properties of nanofluidic devices with local charge inversion

    PubMed Central

    He, Yan; Gillespie, Dirk; Boda, Dezs?; Vlassiouk, Ivan; Eisenberg, Robert S.; Siwy, Zuzanna S.

    2009-01-01

    Nanotubes can selectively conduct ions across membranes to make ionic devices with transport characteristics similar to biological ion channels and semiconductor electron devices. Depending on the surface charge profile of the nanopore, ohmic resistors, rectifiers, and diodes can be made. Here we show that a uniformly charged conical nanopore can have all these transport properties by changing the ion species and their concentrations on each side of the membrane. Moreover, the cation vs. anion selectivity of the pores can be changed. We find that polyvalent cations like Ca2+ and the trivalent cobalt sepulchrate produce localized charge inversion to change the effective pore surface charge profile from negative to positive. These effects are reversible so that the transport and selectivity characteristics of ionic devices can be tuned, much as the gate voltage tunes the properties of a semiconductor. PMID:19317490

  3. Magneto-transport Properties in Suspended Graphene Devices

    NASA Astrophysics Data System (ADS)

    Jung, Suyong; Klimov, Nikolai; Newell, David; Stroscio, Joseph; Zhitenev, Nikolai

    2010-03-01

    High carrier mobility and long coherence lengths are the main attributes which have attracted so much attention to graphene as a new electronic material. Recent studies have shown that electronic properties of graphene are extremely sensitive to disorder, particularly those induced by substrate interactions. By simply isolating graphene devices from the substrate by suspending them, however, they have shown interesting charge transport behaviors such as ballistic transport [1] and the fractional quantum Hall effects[2,3], which can be attributed to the intrinsic electronic properties of graphene. In this talk, we present results on magneto-transport measurements of suspended graphene devices with different geometries and degrees of disorder as a function of temperature. Two- and four-probe measurements of devices with different aspect ratios are compared and discussed. [1] X. Du et al., Nature Nanotechnology 3, 491 (2008). [2] X. Du et al., Nature 462, 192 (2009). [3] K. Bolotin et al., Nature 462, 196 (2009).

  4. Effects of nanosized constriction on thermal transport properties of graphene

    NASA Astrophysics Data System (ADS)

    Yao, Wen-Jun; Cao, Bing-Yang; Yun, He-Ming; Chen, Bao-Ming

    2014-08-01

    Thermal transport properties of graphene with nanosized constrictions are investigated using nonequilibrium molecular dynamics simulations. The results show that the nanosized constrictions have a significant influence on the thermal transport properties of graphene. The thermal resistance of the nanosized constrictions is on the order of 107 to 109 K/W at 150 K, which reduces the thermal conductivity by 7.7% to 90.4%. It is also found that the constriction resistance is inversely proportional to the width of the constriction and independent of the heat current. Moreover, we developed an analytical model for the ballistic thermal resistance of the nanosized constrictions in two-dimensional nanosystems. The theoretical prediction agrees well with the simulation results in this paper, which suggests that the thermal transport across the nanosized constrictions in two-dimensional nanosystems is ballistic in nature.

  5. Reference Fluid Thermodynamic and Transport Properties Database (REFPROP)

    National Institute of Standards and Technology Data Gateway

    SRD 23 NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP) (PC database for purchase)   NIST 23 contains revised data in a Windows version of the database, including 105 pure fluids and allowing mixtures of up to 20 components. The fluids include the environmentally acceptable HFCs, traditional HFCs and CFCs and 'natural' refrigerants like ammonia

  6. Morphologic and transport properties of natural organic floc

    Microsoft Academic Search

    Laurel G. Larsen; Judson W. Harvey; John P. Crimaldi

    2009-01-01

    The morphology, entrainment, and settling of suspended aggregates (“floc”) significantly impact fluxes of organic carbon, nutrients, and contaminants in aquatic environments. However, transport properties of highly organic floc remain poorly understood. In this study detrital floc was collected in the Florida Everglades from two sites with different abundances of periphyton for use in a settling column and in racetrack flume

  7. Transport properties in metakaolin blended concrete M. Shekarchi a

    E-print Network

    Mobasher, Barzin

    characteristics of concrete containing different levels of metakaolin. Water penetration, gas permeability, waterTransport properties in metakaolin blended concrete M. Shekarchi a , A. Bonakdar b , M. Bakhshi b of the approaches in improving the durability of concrete is to use blended cement materials such as fly ash, silica

  8. Investigation of mass transport properties of microfibrillated cellulose (MFC) films

    Microsoft Academic Search

    Matteo Minelli; Marco Giacinti Baschetti; Ferruccio Doghieri; Mikael Ankerfors; Tom Lindström; István Siró; David Plackett

    2010-01-01

    The structure and transport properties of a four different films based on two different generations of microfibrillated cellulose (MFC), alone or in combination with glycerol as plasticizer, were investigated through FE-SEM analysis and sorption or permeation experiments. FE-SEM revealed the existence of complex structures in the different samples. A porous, closely packed fiber network, more homogeneous in the samples containing

  9. Thermoelectric Transport Properties of Individual Bismuth Nanowires Stephen B. Cronina

    E-print Network

    Cronin, Steve

    Thermoelectric Transport Properties of Individual Bismuth Nanowires Stephen B. Cronina , Yu bismuth is a poor thermoelectric material because, as a semimetal, the coexistence of holes and electrons that if the overlap of the conduction and valence bands (38meV at 77K) could be removed, Bi could then have a ZT

  10. Transport properties of annealed CdSe colloidal nanocrystal solids

    Microsoft Academic Search

    M. Drndic; M. V. Jarosz; N. Y. Morgan; M. A. Kastner; M. G. Bawendi

    2002-01-01

    Transport properties of artificial solids composed of colloidal CdSe nanocrystals (NCs) are studied from 6 to 250 K, before and after annealing. After the solids are annealed, three changes are observed. First, transmission electron micrographs show that the separation between NCs decreases with annealing. Second, the optical absorption spectrum changes: the excitonic peaks of the NC solids shift to lower

  11. Measurement of gas transport properties for chemical vapor infiltration

    SciTech Connect

    Starr, T.L.; Hablutzel, N. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Engineering

    1996-12-01

    In the chemical vapor infiltration (CVI) process for fabricating ceramic matrix composites (CMCs), transport of gas phase reactant into the fiber preform is a critical step. The transport can be driven by pressure or by concentration. This report describes methods for measuring this for CVI preforms and partially infiltrated composites. Results are presented for Nicalon fiber cloth layup preforms and composites, Nextel fiber braid preforms and composites, and a Nicalon fiber 3-D weave composite. The results are consistent with a percolating network model for gas transport in CVI preforms and composites. This model predicts inherent variability in local pore characteristics and transport properties, and therefore, in local densification during processing; this may lead to production of gastight composites.

  12. Transport properties in semiconducting NbS{sub 2} nanoflakes

    SciTech Connect

    Huang, Y. H.; Chen, R. S., E-mail: rsc@mail.ntust.edu.tw; Ho, C. H. [Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Peng, C. C.; Huang, Y. S. [Department of Electronic Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China)

    2014-09-01

    The electronic transport properties in individual niobium disulphide (NbS{sub 2}) nanoflakes mechanically exfoliated from the bulk crystal with three rhombohedral (3R) structure grown by chemical vapor transport were investigated. It is found that the conductivity values of the single-crystalline nanoflakes are approximately two orders of magnitude lower than that of their bulk counterparts. Temperature-dependent conductivity measurements show that the 3R-NbS{sub 2} nanoflakes exhibit semiconducting transport behavior, which is also different from the metallic character in the bulk crystals. In addition, the noncontinuous conductivity variations were observed at the temperature below 180?K for both the nanoflakes and the bulks, which is attributed to the probable charge density wave transition. The photoconductivities in the semiconducting nanoflakes were also observed under the excitation at 532?nm wavelength. The probable mechanisms resulting in the different transport behaviors between the NbS{sub 2} nanostructure and bulk were discussed.

  13. Influence of anisotropic strain on the dielectric and ferroelectric properties of SrTiO3 thin films on DyScO3 substrates

    Microsoft Academic Search

    Michael D Biegalski; E. Vlahos; G. Sheng; Y. L. Li; M. Bernhagen; P. Reiche; R. Uecker; S. K. Streiffer; L. Q. Chen; Venkatraman Gopalan; D. G. Schlom; S. Trolier-McKinstry

    2009-01-01

    The in-plane dielectric and ferroelectric properties of coherent anisotropically strained SrTiO3 thin films grown on orthorhombic (101) DyScO3 substrates were examined as a function of the angle between the applied electric field and the principal directions of the substrate. The dielectric permittivity revealed two distinct maxima as a function of temperature along the [100]p and [010]p SrTiO3 pseudocubic directions. These

  14. Transport properties of self-consolidating concrete

    SciTech Connect

    Sonebi, M.; Nanukuttan, S. [Queens University Belfast, Belfast (United Kingdom). School of Planning Architecture & Civil Engineering

    2009-03-15

    This study reports the findings from an investigation carried out to study the effect of the mixture variations on the durability of medium- and high-strength self-consolidating concrete (SCC). The mixture variations studied include the type of mineral admixtures, such as limestone powder (LSP) and pulverized fuel ash (PFA), and viscosity-modifying admixtures (VMA) for both medium- and high-strength SCC. Air permeability, water permeability, capillary absorption, and chloride diffusivity were used to assess the durability of SCC mixtures in comparison with normal, vibrated concretes. The results showed that SCC mixtures, for medium- and high-strength grades using PFA followed by LSP give lower permeability, properties compared with normal concretes. SCC made with VMA had a higher sorptivity, air permeability, and water permeability compared with other SCC mixtures, which can be attributed to higher water-cement ratio (w/c) and lack of pore filling effect. An in-place migration coefficient was obtained using the in-place ion migration test. This was used to compare the potential diffusivity of different concretes. The results indicated that SCC, for both grades of strength, made with PFA showed much lower diffusivity values in comparison with other mixtures, whereas the SCC mixtures with VMA showed higher diffusivity.

  15. SIMULATIONS OF TRANSPORT AND FIELD-EMISSION PROPERTIES OF MULTI-WALL CARBON NANOTUBES

    E-print Network

    Mayer, Alexandre

    SIMULATIONS OF TRANSPORT AND FIELD-EMISSION PROPERTIES OF MULTI-WALL CARBON NANOTUBES Alexandre- emission properties of multi-wall carbon nanotubes. The structure considered for the transport properties of electronic transport in a multi-wall structure with an overview of their essential field-emission properties

  16. Wentzel-Bardeen singularity in coupled Luttinger liquids: Transport properties

    SciTech Connect

    Martin, T.

    1994-08-26

    The recent progress on 1 D interacting electrons systems and their applications to study the transport properties of quasi one dimensional wires is reviewed. We focus on strongly correlated elections coupled to low energy acoustic phonons in one dimension. The exponents of various response functions are calculated, and their striking sensitivity to the Wentzel-Bardeen singularity is discussed. For the Hubbard model coupled to phonons the equivalent of a phase diagram is established. By increasing the filling factor towards half filling the WB singularity is approached. This in turn suppresses antiferromagnetic fluctuations and drives the system towards the superconducting regime, via a new intermediate (metallic) phase. The implications of this phenomenon on the transport properties of an ideal wire as well as the properties of a wire with weak or strong scattering are analyzed in a perturbative renormalization group calculation. This allows to recover the three regimes predicted from the divergence criteria of the response functions.

  17. Abnormal percolative transport and colossal electroresistance induced by anisotropic strain in (011)-Pr(0.7)(Ca(0.6)Sr(0.4))(0.3)MnO?/PMN-PT heterostructure.

    PubMed

    Zhao, Ying-Ying; Wang, Jing; Kuang, Hao; Hu, Feng-Xia; Zhang, Hong-Rui; Liu, Yao; Zhang, Ying; Wang, Shuan-Hu; Wu, Rong-Rong; Zhang, Ming; Bao, Li-Fu; Sun, Ji-Rong; Shen, Bao-Gen

    2014-01-01

    Abnormal percolative transport in inhomogeneous systems has drawn increasing interests due to its deviation from the conventional percolation picture. However, its nature is still ambiguous partly due to the difficulty in obtaining controllable abnormal percolative transport behaviors. Here, we report the first observation of electric-field-controlled abnormal percolative transport in (011)-Pr(0.7)(Ca(0.6)Sr(0.4))(0.3)MnO3/0.7Pb(Mg(1/3)Nb(2/3))O3-0.3PbTiO3 heterostructure. By introducing an electric-field-induced in-plane anisotropic strain-field in a phase separated PCSMO film, we stimulate a significant inverse thermal hysteresis (~ -17.5?K) and positive colossal electroresistance (~11460%), which is found to be crucially orientation-dependent and completely inconsistent with the well accepted conventional percolation picture. Further investigations reveal that such abnormal inverse hysteresis is strongly related to the preferential formation of ferromagnetic metallic domains caused by in-plane anisotropic strain-field. Meanwhile, it is found that the positive colossal electroresistance should be ascribed to the coactions between the anisotropic strain and the polarization effect from the poling of the substrate which leads to orientation and bias-polarity dependencies for the colossal electroresistance. This work unambiguously evidences the indispensable role of the anisotropic strain-field in driving the abnormal percolative transport and provides a new perspective for well understanding the percolation mechanism in inhomogeneous systems. PMID:25399635

  18. Investigating linkages between atmospheric and terrain properties and spatial anisotropic multiscaling in orographic convective precipitation

    NASA Astrophysics Data System (ADS)

    Nogueira, M.; Barros, A. P.; Miranda, P. M.

    2011-12-01

    The solutions of idealized fully nonlinear cloud resolving numerical simulations of orographic convective precipitation display statistical multiscaling, similar to what is commonly found in observations in the atmosphere. This result is verified even in the absence of scaling in the initial conditions or terrain forcing, suggesting that this scaling behavior should be a general property of the nonlinear solutions of the Navier-Stokes like equations governing the atmospheric dynamics. By taking advantage of this scale invariance property, statistical downscaling methods can be constructed which can be used as sub-grid scale parameterizations and provide a way to bridge between coarser resolution numerical simulations and the high resolution needs of hydrological applications. However, the horizontal scaling exponent function (and respective multifractal parameters) varies with atmospheric and terrain properties, particularly small scale terrain spectra, atmospheric stability and mean wind speed. This result qualitatively agrees with the predictions of linear stability analysis that suggests the governing role of these parameters in embedded convective structures. Hence multiscaling statistical parameters should be computed for each particular geographical location and atmospheric conditions, bringing the necessity of development of relationships to predict them from coarse grid atmospheric data and terrain spectra. The spatial anisotropy (both vertical and horizontal) of the scaling exponent function for rain, cloud and velocity fields is also investigated. Based on the computed statistical multifractal exponents, multifractal simulations are performed to test the ability of these cascade models in reproducing the statistical properties of the atmospheric fields and the sensitivity of the statistical properties of the fields to variations in the multifractal parameters. Finally, simulations with scaling terrain forcing are created and the relationship between scaling of rain, cloud and wind fields and topography is explored.

  19. Transport processes in partially saturate concrete: Testing and liquid properties

    NASA Astrophysics Data System (ADS)

    Villani, Chiara

    The measurement of transport properties of concrete is considered by many to have the potential to serve as a performance criterion that can be related to concrete durability. However, the sensitivity of transport tests to several parameters combined with the low permeability of concrete complicates the testing. Gas permeability and diffusivity test methods are attractive due to the ease of testing, their non-destructive nature and their potential to correlate to in-field carbonation of reinforced concrete structures. This work was aimed at investigating the potential of existing gas transport tests as a way to reliably quantify transport properties in concrete. In this study gas permeability and diffusivity test methods were analyzed comparing their performance in terms of repeatability and variability. The influence of several parameters was investigated such as moisture content, mixture proportions and gas flow. A closer look to the influence of pressure revealed an anomalous trend of permeability with respect to pressure. An alternative calculation is proposed in an effort to move towards the determination of intrinsic material properties that can serve as an input for service life prediction models. The impact of deicing salts exposure was also analyzed with respect to their alteration of the degree of saturation as this may affect gas transport in cementitious materials. Limited information were previously available on liquid properties over a wide range of concentrations. To overcome this limitation, this study quantified surface tension, viscosity in presence of deicing salts in a broad concentration range and at different temperatures. Existing models were applied to predict the change of fluid properties during drying. Vapor desorption isotherms were obtained to investigate the influence of deicing salts presence on the non-linear moisture diffusion coefficient. Semi-empirical models were used to quantify the initiation and the rate of drying using liquid properties and pore structure information as inputs. Concrete exposed to deicing salts resulted to have a reduced gas transport due to the higher degree of saturation (DOS). The higher DOS is believed to contribute to the premature deterioration observed in concrete pavements exposed to deicing salts. Moisture diffusion and moisture profiles in concrete are known to directly relate with the stresses generated during shrinkage and creep mechanisms. The alteration due to the presence of shrinkage reducing admixtures on drying was also investigated in this work. Liquid properties were used to predict the diffusion coefficient in presence of SRA. Moisture profiles obtained using Fick's second law for diffusion were compared to relative humidity profiles measured on concrete slabs. Results confirm that a qualitative prediction of drying in concrete elements is realistic when using this type of approach.

  20. Modelling of the transport properties of topologically protected edge states

    NASA Astrophysics Data System (ADS)

    Dang, Xiaoqian; Burton, J. D.; Tsymbal, Evgeny

    2014-03-01

    One of the great successes of modern condensed matter physics is the discovery of topological insulators (TI). A thorough investigation of their transport properties, along with proposed device geometries, could bring such materials from fundamental research to potential applications. Here we report on theoretical investigations of transport properties of simple systems which incorporate TIs and their protected edge states. We utilize the tight-binding form of the Bernevig-Hughes-Zhang model as a prototype for generic topological insulators. Transport properties are investigated theoretically by constructing the Green's functions and employing the Landauer-Büttiker formalism. We study the limitations to scattering-free transport around defects/impurities through topologically protected edge states, as well as the prospect of metal-TI-metal tunnel junctions where the protected edge states reside between the metal electrode and the insulating bulk of the TI. Elucidating the fundamental physical effects that occur in these (and other) systems will be an integral step in establishing TIs as a building block for potential electronic device applications.

  1. Charge carrier transport properties in layer structured hexagonal boron nitride

    SciTech Connect

    Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X., E-mail: hx.jiang@ttu.edu [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

    2014-10-15

    Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (~ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700?°K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of ? ? (T/T{sub 0}){sup ??} with ? = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ?? = 192 meV (or 1546 cm{sup -1}), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

  2. Charge carrier transport properties in layer structured hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2014-10-01

    Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of ? ? (T/T0)-? with ? = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ?? = 192 meV (or 1546 cm-1), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.

  3. Anisotropic Magnetic Property of Single-Grained Al68Pd23Mn9 Icosahedral Quasicrystals

    Microsoft Academic Search

    Susumu Matsuo; Hiroshi Nakano; Tsutomu Ishimasa; Masahiro Mori

    1993-01-01

    Magnetic properties were studied for single-grained Al68Pd23Mn9 icosahedral quasicrystals which had high degree of structural perfections. An anisotropy associated with the directional order in the icosahedral phase was found for the first time in the nonlinear region of the magnetization-vs-magnetic-field curve of the single-grained quasicrystal along 5-, 3-, and 2-fold axes below 40 K. No anisotropy was found in the

  4. Osmotic compression of anisotropic proteins: interaction properties and associated structures in wheat gliadin dispersions.

    PubMed

    Boire, Adeline; Menut, Paul; Morel, Marie-Hélène; Sanchez, Christian

    2015-04-30

    In this Article, we investigated the interaction properties of wheat gliadins, properties that are at the basis of their functionality in wheat grain and in food matrixes. We established the equation of state of our isolate by osmotic compression and characterized the concentration-induced structural transitions, from the secondary structure of proteins to the rheological properties. We evidenced three thermodynamical regimes corresponding to several structuring regimes. First, for ? < 0.03, gliadins behave as repulsive colloids, with a positive second virial coefficient, arising presumably from their surface charge density and/or their steric repulsion. No intermolecular interaction was detected by FT-IR, suggesting that proteins form a stable dispersion. In the second regime, the system becomes more easily compressible, i.e., less repulsive and/or more attractive. It is associated with the disappearance of ?-sheet intramolecular structures of the proteins in favor of random coils/?-helix and intermolecular ?-sheet interactions. This coincides with the appearance of elasticity and the increase of the apparent viscosity. Finally, in the last regime, for ? > 0.16, FT-IR spectra show that proteins are strongly interacting via intermolecular interactions. A correlation peak develops in SAXS, revealing a global order in the dispersion. Interestingly, the osmotic pressure applied to extract the solvent is higher than expected from a hard-sphere-like protein and we highlighted a liquid-like state at very high concentration (>450 g L(-1)) which is in contrast with most proteins that form gel or glass at such concentration. In the discussion, we questioned the existence of supramolecular assemblies and the role of the solvation that would lead to this specific behavior. PMID:25839358

  5. An Immersed Boundary Method for Computing Anisotropic Permeability of

    E-print Network

    Al Hanbali, Ahmad

    = - k µf · pf (k: permeability tensor) k: measure of flAn Immersed Boundary Method for Computing Anisotropic Permeability of Structured Porous Media David for Computing Anisotropic Permeability of Structured Porous Media #12;Outline 1 Averaged transport in porous

  6. Using moisture transport properties of rice seed components for identifying fissure resistance 

    E-print Network

    Thomas, Audrey Elizabeth

    2002-01-01

    Fissure resistance was related to the moisture transport properties of Cypress, Lemont, LaGrue, and Teqing rice varieties. The moisture transport properties, moisture diffusivity and resistance, were calculated using a three-dimensional moisture...

  7. Universal Multifractal Properties of the Small Scale Intermittency in Anisotropic and Inhomogeneous Turbulence

    E-print Network

    M. Alber; S. Lueck; C. Renner; J. Peinke

    2000-07-12

    The notion of self-similar energy cascades and multifractality has long since been connected with fully developed, homogeneous and isotropic turbulence. We introduce a number of amendments to the standard methods for analysing the multifractal properties of the energy dissipation field of a turbulent flow. We conjecture that the scaling assumption for the moments of the energy dissipation rate is valid within the transition range to dissipation introduced by Castaing et al.(Physica D (46), 177 (1990)). The multifractal spectral functions appear to be universal well within the error margins and exhibit some as yet undiscussed features. Furthermore, this universality is also present in the neither homogeneous nor isotropic flows in the wake very close to a cylinder or the off-centre region of a free jet.

  8. Effective Hydraulic Properties Determined from Transient Unsaturated Flow in Anisotropic Soils

    SciTech Connect

    Ward, Andy L.; Zhang, Z. F.

    2007-11-01

    Hydraulic parameters including the pore connectivity/tortuosity tensor (L_i) were inversely estimated using the STOMP numerical simulator coupled with the parameter estimation code, UCODE. Results show that six of eight parameters required for a modified van Genuchten-Mualem model could be inversely estimated using water content measured during transient infiltration from a surface line source and approximated prior information. Soils showed evidence of saturation-dependent anisotropy that was well described with the connectivity tensor. Variability of the vertical saturated hydraulic conductivity was larger than the horizontal. The autocorrelation ranges for the horizonatal and vertical Ks; the inverse of the air-entry value, and the horizontal connectivity were between 2.4 and 4.6 m whereas the van Genuchten shape parameter, n, and saturated water content showed no autocorrelation. Accurate upscaling of hydraulic properties requires the correct assessment of the connectivity of facies.

  9. Structure, Transport Properties, and Magnetism of Artificially-Structured Materials

    Microsoft Academic Search

    John Q. Xiao

    1993-01-01

    Structural, magnetic, and magneto-transport properties of three different classes of artificially structured materials: (1) multilayers (Fe(110)\\/Ag(111) and Fe(110)\\/W(110)), (2) Fe-nitrides, and (3) metallic granular solids (Co\\/Ag, Co\\/Cu Fe\\/Ag and (Ni-Fe)\\/Ag), prepared by magnetron sputtering are presented. In the multilayers, the structure has been characterized using both low-angle and high-angle x-ray diffraction together with theoretical modeling. The magnetic properties of the

  10. Engineered microstructures and transport properties in YBCO coated conductors.

    SciTech Connect

    Holesinger, T. G. (Terry G.); Gibbons, B. J. (Brady J.); Coulter, J. Y. (James Y.); Foltyn, S. R. (Stephen R.); Arendt, P. N. (Paul N.)

    2001-01-01

    Each process used to deposit or make the bi-axially textured template, buffer layer(s), and the superconductor in a coated conductor creates interfaces along which defects or interfacial reactions may result. These defects can be additive and propagate through the entire film structure to affect the growth and properties of the superconducting film. Defects within the films and their corresponding transport properties have been correlated with the differences in the thickness of the underlying buffer layer material. This knowledge can be used to control and engineer the structure of the coated conductor to maximize critical current densities.

  11. Electrical and thermal transport properties of CdO ceramics

    NASA Astrophysics Data System (ADS)

    Lü, Qing; Wang, ShuFang; Li, LongJiang; Wang, JiangLong; Dai, ShouYu; Yu, Wei; Fu, GuangSheng

    2014-09-01

    High temperature electrical and thermal transport properties, that is, electrical conductivity, Seebeck coefficient and thermal conductivity, of CdO ceramics have been investigated. Because of the good electrical properties and low thermal conductivity, the dimensionless figure-of-merit ZT of the CdO ceramics reaches 0.34 at 1023 K. This value is comparable to the best reported ZT for the n-type oxide ceramic thermoelectric materials and remains as potential to be further improved by porosity controlling or nanostructuring.

  12. Coefficients for calculating thermodynamic and transport properties of individual species

    Microsoft Academic Search

    Bonnie J. McBride; Sanford Gordon; Martin A. Reno

    1993-01-01

    Libraries of thermodynamic data and transport properties are given for individual species in the form of least-squares coefficients. Values of C(sup 0)(sub p)(T), H(sup 0)(T), and S(sup 0)(T) are available for 1130 solid, liquid, and gaseous species. Viscosity and thermal conductivity data are given for 155 gases. The original C(sup 0)(sub p)(T) values were fit to a fourth-order polynomial with

  13. Thermodynamic and Transport Properties of Two-temperature Oxygen Plasmas

    Microsoft Academic Search

    S. Ghorui; Joachim V. R. Heberlein; E. Pfender

    2007-01-01

    Thermodynamic and transport properties of two-temperature oxygen plasmas are presented. Variation of species densities, mass\\u000a densities, specific heat, enthalpy, viscosity, thermal conductivity, collision frequency and electrical conductivity as a\\u000a function of temperature, pressure and different degree of temperature non-equilibrium are computed. Reactional, electronic\\u000a and heavy particle components of the total thermal conductivity are discussed. To meet practical needs of fluid-dynamic

  14. Transport properties of polyaniline-cellulose-acetate blends

    Microsoft Academic Search

    Jérôme Planès; Andreas Wolter; Yasmina Cheguettine; Adam Pron; Françoise Genoud; Maxime Nechtschein

    1998-01-01

    Transport properties of polyaniline (PANI)-cellulose acetate (CA) conducting blends have been investigated at various length scales and temperatures. We report on the results of dc and ac conductivity measurements, magnetoresistance and electron-spin resonance (ESR) performed on composite films with PANI weight fraction p ranging from the percolation threshold-pc~=0.1%-to a few percent. Three different PANI doping agents have been tested, namely,

  15. Magnetic and transport properties of MnBi\\/Bi nanocomposites

    Microsoft Academic Search

    Kyongha Kang; L. H. Lewis; Y. F. Hu; Qiang Li; A. R. Moodenbaugh; Young-Suk Choi

    2006-01-01

    The magnetic and transport properties of a nanostructured Mn-Bi eutectic composition (~Mn5Bi95) produced by melt spinning and low-temperature\\/short time vacuum annealing were studied. A hysteretic magnetostructural transformation from low-temperature phase to high-temperature phase MnBi is confirmed at 520 K. The fact that the transition temperature is lower than that reported for bulk MnBi (633 K), is tentatively attributed to interfacial

  16. Magnetic and magneto-transport properties in nanostructured materials

    Microsoft Academic Search

    Fengyuan Yang

    2001-01-01

    Magneto-transport, magnetic and structural properties of three nanostructured systems: (1) single-crystal bismuth films with and without antidot arrays made by electrodeposition, (2) epitaxial half-metallic CrO2 films made by chemical vapor deposition (CVD), and (3) exchange-coupled Co\\/FeMn\\/permalloy trilayers prepared by magnetron sputtering are presented. Single-crystal Bi thin films have been made by electrodeposition followed by suitable annealing. X-ray diffraction verifies that

  17. Transport and magnetic properties of BaVSe3

    Microsoft Academic Search

    Ana Akrap; Vladan Stevanovic; Mirta Herak; Marko Miljak; Neven Barisic; Helmuth Berger; László Forró

    2008-01-01

    We report a comprehensive study of transport, magnetotransport, and magnetic properties of single crystals of BaVSe3 . The paramagnetic metal-ferromagnetic metal transition at 43 K was followed as a function of pressure by measuring the electrical resistivity and the thermoelectric power. The exponent of the low-temperature power-law dependence of the resistivity increases with pressure. The effective magnetic moment obtained from

  18. Thermoelectric transport properties of PbTe under pressure

    Microsoft Academic Search

    Lanqing Xu; Yongping Zheng; Jin-Cheng Zheng

    2010-01-01

    In this work, we present a comprehensive picture of structural, dynamical, electronic, and transport properties of PbTe at ambient and high pressures. The first-principles linear-response calculations show that there exists an anharmonic instability of the optical branch phonon at the Brillouin-zone (BZ) center and soft phonons at the BZ boundary X point. The k -dependent soft modes may lead to

  19. Transport and Superconducting Properties of Rare Earth Magnetic Superconductors

    Microsoft Academic Search

    Hu. Zhou

    1988-01-01

    An investigation of transport and magnetic properties of two groups of magnetic superconductors, tetragonal {cal R}Rh_4 B_4 and orthorhombic high -T_{rm c} oxides {cal R}Ba_2 Cu_3O_{7 -delta}, where {cal R} represents rare earth elements and Y, was carried out by means of electrical resistance and magnetic measurements. Single crystals of {cal R} Rh_4B_4 were successfully synthesized using a copper flux

  20. Anisotropic metamaterial optical fibers.

    PubMed

    Pratap, Dheeraj; Anantha Ramakrishna, S; Pollock, Justin G; Iyer, Ashwin K

    2015-04-01

    Internal physical structure can drastically modify the properties of waveguides: photonic crystal fibers are able to confine light inside a hollow air core by Bragg scattering from a periodic array of holes, while metamaterial loaded waveguides for microwaves can support propagation at frequencies well below cutoff. Anisotropic metamaterials assembled into cylindrically symmetric geometries constitute light-guiding structures that support new kinds of exotic modes. A microtube of anodized nanoporous alumina, with nanopores radially emanating from the inner wall to the outer surface, is a manifestation of such an anisotropic metamaterial optical fiber. The nanopores, when filled with a plasmonic metal such as silver or gold, greatly increase the electromagnetic anisotropy. The modal solutions in such anisotropic circular waveguides can be uncommon Bessel functions with imaginary orders. PMID:25968741

  1. Viscoelastic properties of actin networks influence material transport

    NASA Astrophysics Data System (ADS)

    Stam, Samantha; Weirich, Kimberly; Gardel, Margaret

    2015-03-01

    Directed flows of cytoplasmic material are important in a variety of biological processes including assembly of a mitotic spindle, retraction of the cell rear during migration, and asymmetric cell division. Networks of cytoskeletal polymers and molecular motors are known to be involved in these events, but how the network mechanical properties are tuned to perform such functions is not understood. Here, we construct networks of either semiflexible actin filaments or rigid bundles with varying connectivity. We find that solutions of rigid rods, where unimpeded sliding of filaments may enhance transport in comparison to unmoving tracks, are the fastest at transporting network components. Entangled solutions of semiflexible actin filaments also transport material, but the entanglements provide resistance. Increasing the elasticity of the actin networks with crosslinking proteins slows network deformation further. However, the length scale of correlated transport in these networks is increased. Our results reveal how the rigidity and connectivity of biopolymers allows material transport to occur over time and length scales required for physiological processes. This work was supported by the U. Chicago MRSEC

  2. Properties of an affine transport equation and its generalized holonomy

    E-print Network

    Justin Vines; David A. Nichols

    2014-12-12

    We investigate properties of a transport equation that was recently used to study the observer dependence of angular momentum in general relativity. The associated map between the tangent spaces at two points on a curve is affine, and for this reason, the operation was called "affine transport". The map consists of a homogeneous (linear) part given by the parallel transport map along the curve, plus an inhomogeneous part which is related to the development of a curve in a manifold into an affine tangent space (also described as the rolling of a manifold along a tangent space without slipping or twisting). For closed curves, the affine transport equation defines a "generalized holonomy". We use covariant bitensor calculus to compute the generalized holonomy around geodesic polygon loops, specifically for triangles and "parallelogramoids" with sides formed from geodesic segments. For small loops, we recover the well-known result for the leading-order holonomy of parallel transport ($\\sim$ Riemann $\\times$ area), and we derive the leading-order inhomogeneous part of the generalized holonomy ($\\sim$ Riemann $\\times$ area$^{3/2}$), as well as corrections to both results through order area squared.

  3. Modulating electronic transport properties of carbon nanotubes to improve the thermoelectric power factor via nanoparticle decoration.

    PubMed

    Yu, Choongho; Ryu, Yeontack; Yin, Liang; Yang, Hongjoo

    2011-02-22

    Nanoparticle decoration on carbon nanotubes was employed to modulate their electrical conductance and thermopower and thereby improved the thermoelectric power factor. Nanotubes were made into films by spraying nanotube solutions on glass substrates, and then the films were immersed in different concentrations of CuSO(4) or HAuCl(4) solutions for various time periods. Copper ions in the solutions were reduced on nanotubes by obtaining electrons from zinc electrodes, whose reduction potential is lower than that of copper (galvanic displacement). Gold ions were reduced on nanotubes by both silver counter electrodes and spontaneous reaction due to larger reduction potentials than those of nanotubes. These reactions made electrons donated to (copper incorporation) or withdrawn from (gold incorporation) nanotubes depending on the difference in their work functions and reduction potentials, resulting in considerable changes in electron transport. In this paper, a series of experiments at different ion concentrations and reaction time periods were systematically performed in order to find optimum nanoparticle formation conditions and corresponding electronic transport changes for better thermoelectric power factor. Transport measurement results show that electronic properties can be considerably altered and modulated, resulting in 2-fold improvement in the thermoelectric power factor with 1 mM/30 min reaction. Reactions with solutions of a low metal ion concentration, such as 1 mM, yielded well-distributed small particles over large surface areas, which strongly affected electron transfer between nanoparticles and nanotubes. Successive copper and gold decorations on nanotubes made electrical conductance (or thermopower) serially decreased and increased (or increased and decreased) upon precipitating different metal particles. This transport behavior is believed to be from the changes in the Fermi level as a result of electron exchanges between reduced metals and nanotubes. Thermopower improvement after copper decoration can be attributed to the enlarged gap between the Fermi level and the mean of differential electrical conductivity. Such behaviors often appear when the Fermi level is shifted toward the spike-shape density of states in nanotubes due to anisotropic differential electrical conductivity. Finally, this study demonstrates that the thermoelectric power factor can be considerably increased by properly locating the Fermi level of carbon nanotubes with nanoparticles, providing promising opportunities of developing efficient organic thermoelectric materials as well as various electronic materials of desired properties. PMID:21222461

  4. Rotationally anisotropic second-harmonic generation studies of the structure and electronic properties of bimetallic interfaces, Ag on Cu(110)

    SciTech Connect

    Hoffbauer, M.A.; McVeigh, V.J.

    1990-01-01

    Rotationally anisotropic surface second-harmonic generation (SHG) has been measured from a clean, well-ordered Cu(110) single-crystal surface as a function of both surface temperature and Ag coverage. For the clean Cu(110) surface, the temperature dependence of the SH response at a fixed azimuthal angle can be correlated with a surface phase transformation. A large decrease in the rotationally anisotropic SH response as a function of surface temperature can be related to changes in the surface disorder. The results are compared with other studies of Cu(110) surface structure using both x-ray and He-atom scattering. The rotationally anisotropic SH response has also been measured as a function of Ag coverage with the Cu(110) surface temperature fixed at 300 K. The results closely follow the formation of an ordered Ag(111)-like overlayer, the nucleation of three-dimensional Ag nanoclusters (<20 {angstrom} thick) that enhance the anisotropic SH response, and the subsequent growth of a {approximately}10 monolayer thick Ag film. Variations in the rotationally anisotropic SH response as a function of Ag coverage are used to separate the resonant surface electronic contributions to the nonlinear susceptibility of the interface. 22 refs., 4 figs.

  5. Interface disorder and transport properties in HTC/CMR superlattices

    NASA Astrophysics Data System (ADS)

    Haberkorn, N.; Guimpel, J.; Sirena, M.; Steren, L. B.; Campillo, G.; Saldarriaga, W.; Gómez, M. E.

    2004-08-01

    The physical properties of superlattices are affected by interface disorder, like roughness and interdiffusion. X-ray diffraction allows its measurement through modeling and structure refinement. The high- Tc RBa 2Cu 3O 7 (RBCO) and colossal magnetoresistance La xA 1-xMnO 3 (LAMO) perovskites are interesting superlattice partners given their similar lattice parameters and because the combination of magnetic and superconducting properties is interesting for both basic and applied research. We have investigated the structural and transport properties of YBCO/La 2/3Ca 1/3MnO 3 and GdBCO/La 0.6Sr 0.04MnO 3 superlattices grown by sputtering on (1 0 0)MgO. We find a roughness of 1 RBCO unit cell and a 30% interdiffusion in the same length from the interfaces for all samples. The superconducting behavior is found strongly dependent on the LAMO layer thickness.

  6. Linear elastic properties derivation from microstructures representative of transport parameters.

    PubMed

    Hoang, Minh Tan; Bonnet, Guy; Tuan Luu, Hoang; Perrot, Camille

    2014-06-01

    It is shown that three-dimensional periodic unit cells (3D PUC) representative of transport parameters involved in the description of long wavelength acoustic wave propagation and dissipation through real foam samples may also be used as a standpoint to estimate their macroscopic linear elastic properties. Application of the model yields quantitative agreement between numerical homogenization results, available literature data, and experiments. Key contributions of this work include recognizing the importance of membranes and properties of the base material for the physics of elasticity. The results of this paper demonstrate that a 3D PUC may be used to understand and predict not only the sound absorbing properties of porous materials but also their transmission loss, which is critical for sound insulation problems. PMID:24907783

  7. Numerical evaluation of apparent transport parameters from forced-gradient tracer tests in statistically anisotropic heterogeneous formations

    NASA Astrophysics Data System (ADS)

    Pedretti, D.; Fernandez-Garcia, D.; Bolster, D.; Sanchez-Vila, X.; Benson, D.

    2012-04-01

    For risk assessment and adequate decision making regarding remediation strategies in contaminated aquifers, solute fate in the subsurface must be modeled correctly. In practical situations, hydrodynamic transport parameters are obtained by fitting procedures, that aim to mathematically reproduce solute breakthrough (BTC) observed in the field during tracer tests. In recent years, several methods have been proposed (curve-types, moments, nonlocal formulations) but none of them combine the two main characteristic effects of convergent flow tracer tests (which are the most used tests in the practice): the intrinsic non-stationarity of the convergent flow to a well and the ubiquitous multiscale hydraulic heterogeneity of geological formations. These two effects separately have been accounted for by a lot of methods that appear to work well. Here, we investigate both effects at the same time via numerical analysis. We focus on the influence that measurable statistical properties of the aquifers (such as the variance and the statistical geometry of correlation scales) have on the shape of BTCs measured at the pumping well during convergent flow tracer tests. We built synthetic multigaussian 3D fields of heterogeneous hydraulic conductivity fields with variable statistics. A well is located in the center of the domain to reproduce a forced gradient towards it. Constant-head values are imposed on the boundaries of the domains, which have 251x251x100 cells. Injections of solutes take place by releasing particles at different distances from the well and using a random walk particle tracking scheme with constant local coefficient of dispersivity. The results show that BTCs partially display the typical anomalous behavior that has been commonly referred to as the effect of heterogeneity and connectivity (early and late arrival times of solute differ from the one predicted by local formulations). Among the most salient features, the behaviors of BTCs after the peak (the slope of the BTCs in log-log scales, which is the diagnostic plot to infer power-law type nonlocal distribution parameters due to hydraulic heterogeneity) indicate that anisotropy generates apparent higher capacity coefficients in certain directions. At very late times, however, the slopes display similar values, indicating that at these spatial scales (injection distances comparable with the integral scales), particles are stacked in low K areas for much longer than the advection times in higher K zones.

  8. Upscaling flow and transport properties in synthetic porous media

    NASA Astrophysics Data System (ADS)

    Jasinski, Lukasz; Dabrowski, Marcin

    2015-04-01

    Flow and transport through the porous media has instances in nature and industry: contaminant migration in geological formations, gas/oil extraction from proppant filled hydraulic fractures and surrounding porous matrix, underground carbon dioxide sequestration and many others. We would like to understand the behavior of propagating solute front in such medium, mainly flow preferential pathways and the solute dispersion due to the porous medium geometry. The motivation of our investigation is to find connection between the effective flow and transport properties and porous media geometry in 2D and 3D for large system sizes. The challenge is to discover a good way of upscaling flow and transport processes to obtain results comparable to these calculated on pore-scale in much faster way. We study synthetic porous media made of densely packed poly-disperse disk-or spherical-shaped grains in 2D and 3D, respectively. We use various protocols such as the random sequential addition (RSA) algorithm to generate densely packed grains. Imposed macroscopic pressure gradient invokes fluid flow through the pore space of generated porous medium samples. As the flow is considered in the low Reynolds number regime, a stationary velocity field is obtained by solving the Stokes equations by means of finite element method. Void space between the grains is accurately discretized by using body-fitting triangular or tetrahedral mesh. Finally, pure advection of a front carried by the velocity field is studied. Periodicity in all directions is applied to microstructure, flow and transport processes. Effective permeability of the media can be calculated by integrating the velocity field on cross sections, whereas effective dispersion coefficient is deduced by application of centered moment methods on the concentration field of transported solute in time. The effective parameters are investigated as a function of geometrical parameters of the media, such as porosity, specific surface area and fractal dimension of the pore space geometry. Discretization effects are taken into account. Furthermore, as we aim to simulate transport processes in complex and large systems in 3D, following upscaling technique is checked against the original calculations. The pore space of the media is approximated in the form of a capillary network by converting the pore space throats between the grains into lines in 2D and polygons in 3D. Effective flow and transport properties are calculated on such network models and compared with the results obtained for original geometry.

  9. Transport properties of transition metal impurities on gold nanowires

    NASA Astrophysics Data System (ADS)

    Pontes, Renato B.; da Silva, Edison Z.; Fazzio, Adalberto; da Silva, Antônio J. R.

    2009-03-01

    Performing first principles density functional theory (DFT) we calculated the electronic and transport properties of a Au thin nanowire with transition metal atoms (Mn, Fe, Ni or Co) bridging the two sides of the Au nanowire. We will show that these systems have strong spin dependent transport properties and that the local symmetry can dramatically change them, leading to a significant spin polarized conductance. This spin dependent transport is also associated with the transition metal in the nanowire, in particular with the d-level positioning. Using Co, for example [1], when the symmetry permits the mixing between the wire s-orbitals with the transition metal d-states, there are interference effects that resemble Fano-like resonances with an anisotropy of 0.07 at the Fermi level. On the other hand, if this symmetry decouples such states, we simply have a sum of independent transmission channels and the calculated anisotropy was 0.23. The anisotropies for the other transition metals, as well as calculated transmittances for two Co impurities will also be presented [1] R. B. Pontes, E. Z. da Silva, A. Fazzio and Antônio J. R. da Silva, J. Am. Chem. Soc. 130 (30), 9897-903, 2008

  10. Morphologic and transport properties of natural organic floc

    NASA Astrophysics Data System (ADS)

    Larsen, Laurel G.; Harvey, Judson W.; Crimaldi, John P.

    2009-01-01

    The morphology, entrainment, and settling of suspended aggregates ("floc") significantly impact fluxes of organic carbon, nutrients, and contaminants in aquatic environments. However, transport properties of highly organic floc remain poorly understood. In this study detrital floc was collected in the Florida Everglades from two sites with different abundances of periphyton for use in a settling column and in racetrack flume entrainment experiments. Although Everglades flocs are similar to other organic aggregates in terms of morphology and settling rates, they tend to be larger and more porous than typical mineral flocs because of biostabilization processes and relatively low prevailing shear stresses typical of wetlands. Flume experiments documented that Everglades floc was entrained at a low bed shear stress of 1.0 × 10-2 Pa, which is considerably smaller than the typical entrainment threshold of mineral floc. Because of similarities between Everglades floc and other organic floc populations, floc transport characteristics in the Everglades typify the behavior of floc in other organic-rich shallow-water environments. Highly organic floc is more mobile than less organic floc, but because bed shear stresses in wetlands are commonly near the entrainment threshold, wetland floc dynamics are often transport-limited rather than supply limited. Organic floc transport in these environments is therefore governed by the balance between entrainment and settling fluxes, which has implications for ecosystem metabolism, materials cycling, and even landscape evolution.

  11. Rhamnolipid surface thermodynamic properties and transport in agricultural soil.

    PubMed

    Renfro, Tyler Dillard; Xie, Weijie; Yang, Guang; Chen, Gang

    2014-03-01

    Rhamnolipid is a biosurfactant produced by several Pseudomonas species, which can wet hydrophobic soils by lowering the cohesive and/or adhesive surface tension. Because of its biodegradability, rhamnolipid applications bring minimal adverse impact on the soil and groundwater as compared with that of chemical wetting agents. Subsequently, rhamnolipid applications have more advantages when used to improve irrigation in the agricultural soil, especially under draught conditions. In the presence of rhamnolipid, water surface tension dropped linearly with the increase of rhamnolipid concentration until the rhamnolipid critical micelle concentration (CMC) of 30 mg/L was reached. Below the CMC, rhamnolipid had linear adsorption isotherms on the soil with a partition coefficient of 0.126 L/kg. Rhamnolipid transport breakthrough curves had a broad and diffuse infiltration front, indicating retention of rhamnolipid on the soil increased with time. Rhamnolipid transport was found to be well represented by the advection-dispersion equation based on a local equilibrium assumption. When applied at concentrations above the CMC, the formed rhamnolipid micelles prevented rhamnolipid adsorption (both equilibrium adsorption and kinetic adsorption) in the soil. It was discovered in this research that rhamnolipid surface thermodynamic properties played the key role in controlling rhamnolipid transport. The attractive forces between rhamnolipid molecules contributed to micelle formation and facilitated rhamnolipid transport. PMID:24394947

  12. Strain induced peculiarities in transport properties of Bi nanowires.

    PubMed

    Condrea, E; Gilewski, A; Nicorici, A

    2013-05-22

    We report results on the effect of strain on the thermopower and electrical resistance of glass-coated individual Bi nanowires. Here, we show that there is a critical diameter of wires below which the contribution of holes to the charge transport in pure Bi nanowires is more significant than that of electrons. The properties of Bi nanowires are examined in the light of a strain induced electronic topological transition. At low temperatures, the thermopower dependences on strain exhibit a non-monotonic behavior inherent in thinner wires, where the thermopower is dominated by the diffusion transport mechanism of holes. The hole-dominated transport can be transformed into electron-dominated transport through a smooth manipulation with the phonon spectrum and Fermi surface by applying a uniaxial strain. A fairly high value of the thermoelectric power factor (S(2)/? = 89 ?W cm(-1) K(-2)) was found in the temperature range of 80-300 K, where the dominant mechanism contributing to the thermopower is diffusive thermoelectric generation with electrons as the majority carrier. PMID:23615862

  13. Low temperature carrier transport properties in isotopically controlled germanium

    SciTech Connect

    Itoh, K.

    1994-12-01

    Investigations of electronic and optical properties of semiconductors often require specimens with extremely homogeneous dopant distributions and precisely controlled net-carrier concentrations and compensation ratios. The previous difficulties in fabricating such samples are overcome as reported in this thesis by growing high-purity Ge single crystals of controlled {sup 75}Ge and {sup 70}Ge isotopic compositions, and doping these crystals by the neutron transmutation doping (NTD) technique. The resulting net-impurity concentrations and the compensation ratios are precisely determined by the thermal neutron fluence and the [{sup 74}Ge]/[{sup 70}Ge] ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples the authors have conducted four types of electron (hole) transport studies probing the nature of (1) free carrier scattering by neutral impurities, (2) free carrier scattering by ionized impurities, (3) low temperature hopping conduction, and (4) free carrier transport in samples close to the metal-insulator transition.

  14. Transport properties of zigzag graphene nanoribbon decorated with copper clusters

    NASA Astrophysics Data System (ADS)

    Berahman, M.; Sheikhi, M. H.

    2014-09-01

    Using non-equilibrium green function with density functional theory, the present study investigates the transport properties of decorated zigzag graphene nanoribbon with a copper cluster. We have represented the decoration of zigzag graphene nanoribbon with single copper atom and cluster containing two and three copper atoms. In all the cases, copper atoms tend to occupy the edge state. In addition, we have shown that copper can alter the current-voltage characteristic of zigzag graphene nanoribbon and create new fluctuations and negative differential resistance. These alternations are made due to discontinuity in the combination of orbitals along the graphene nanoribbon. Decoration alters these discontinuities and creates more visible fluctuations. However, in low bias voltages, the changes are similar in all the cases. The study demonstrates that in the decorated zigzag graphene nanoribbon, the edge states are the main states for transporting electron from one electrode to another.

  15. Transport properties of zigzag graphene nanoribbon decorated with copper clusters

    SciTech Connect

    Berahman, M.; Sheikhi, M. H., E-mail: msheikhi@shirazu.ac.ir [School of Electrical and Computer Eng, Shiraz University, Shiraz (Iran, Islamic Republic of); Nanotechnology Research Institute, Shiraz University, Shiraz (Iran, Islamic Republic of)

    2014-09-07

    Using non-equilibrium green function with density functional theory, the present study investigates the transport properties of decorated zigzag graphene nanoribbon with a copper cluster. We have represented the decoration of zigzag graphene nanoribbon with single copper atom and cluster containing two and three copper atoms. In all the cases, copper atoms tend to occupy the edge state. In addition, we have shown that copper can alter the current-voltage characteristic of zigzag graphene nanoribbon and create new fluctuations and negative differential resistance. These alternations are made due to discontinuity in the combination of orbitals along the graphene nanoribbon. Decoration alters these discontinuities and creates more visible fluctuations. However, in low bias voltages, the changes are similar in all the cases. The study demonstrates that in the decorated zigzag graphene nanoribbon, the edge states are the main states for transporting electron from one electrode to another.

  16. Transport and magnetic properties of BaVSe3

    NASA Astrophysics Data System (ADS)

    Akrap, Ana; Stevanovi?, Vladan; Herak, Mirta; Miljak, Marko; Bariši?, Neven; Berger, Helmuth; Forró, László

    2008-12-01

    We report a comprehensive study of transport, magnetotransport, and magnetic properties of single crystals of BaVSe3 . The paramagnetic metal-ferromagnetic metal transition at 43 K was followed as a function of pressure by measuring the electrical resistivity and the thermoelectric power. The exponent of the low-temperature power-law dependence of the resistivity increases with pressure. The effective magnetic moment obtained from magnetic susceptibility in the paramagnetic regime is ?eff=1.40?B . The study was completed by band-structure calculations based on density-functional theory both at ambient and high pressures. Transport coefficients of BaVSe3 resemble the high-pressure phase of BaVS3 , which suggest that the replacement of sulfur with selenium can be viewed as chemical pressure.

  17. Transport properties of the hot and dense sQGP

    NASA Astrophysics Data System (ADS)

    Berrehrah, H.; Bratkovskaya, E.; Cassing, W.; Marty, R.

    2015-05-01

    The transport properties of the quark gluon plasma (QGP) are studied in a QCD medium at finite temperature and chemical potential. We calculate the shear viscosity ?(T,?q) and the electric conductivity ?e(T, ?q) for a system of interacting massive and broad quasi-particles as described by the dynamical quasi-particle model “DQPM” at finite temperature T and quark chemical potential ?q within the relaxation time approximation. Our results are in a good agreement with lattice QCD at finite temperature and show clearly the increase of the transport coefficients with increasing T and ?q. Our results provide the basic ingredients for the study of the hot and dense matter in the Beam Energy Scan (BES) at RHIC and CBM at FAIR.

  18. Transport properties of ultrathin black phosphorus on hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Doganov, Rostislav A.; Koenig, Steven P.; Yeo, Yuting; Watanabe, Kenji; Taniguchi, Takashi; Özyilmaz, Barbaros

    2015-02-01

    Ultrathin black phosphorus, or phosphorene, is a two-dimensional material that allows both high carrier mobility and large on/off ratios. Similar to other atomic crystals, like graphene or layered transition metal dichalcogenides, the transport behavior of few-layer black phosphorus is expected to be affected by the underlying substrate. The properties of black phosphorus have so far been studied on the widely utilized SiO2 substrate. Here, we characterize few-layer black phosphorus field effect transistors on hexagonal boron nitride—an atomically smooth and charge trap-free substrate. We measure the temperature dependence of the field effect mobility for both holes and electrons and explain the observed behavior in terms of charged impurity limited transport. We find that in-situ vacuum annealing at 400 K removes the p-doping of few-layer black phosphorus on both boron nitride and SiO2 substrates and reduces the hysteresis at room temperature.

  19. Transport Properties of operational gas mixtures used at LHC

    E-print Network

    Yasser Assran; Archana Sharma

    2011-10-31

    This report summarizes some useful data on the transport characteristics of gas mixtures which are required for detection of charged particles in gas detectors. We try to replace Freon used for RPC detector in the CMS experiment with another gas while maintaining the good properties of the Freon gas mixture unchanged. We try to switch to freonless gas mixture because Freon is not a green gas, it is very expensive and its availability is decreasing. Noble gases like Ar, He, Ne and Xe (with some quenchers like carbon dioxide, methane, ethane and isobutene) are investigated. Transport parameters like drift velocity, diffusion, Townsend coefficient, attachment coefficient and Lorentz angle are computed using Garfield software for different gas mixtures and compared with experimental data.

  20. Transport properties of individual C{sub 60}-molecules

    SciTech Connect

    Géranton, G. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany)] [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany); Seiler, C.; Evers, F. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany) [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany); Center for Functional Nanostructures, Karlsruhe Institute of Technology, Campus South, D-76131 Karlsruhe (Germany); Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, Campus South, D-76128 Karlsruhe (Germany); Bagrets, A. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany) [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany); Steinbuch Center for Supercomputing, Karlsruhe Institute of Technology, D-76128 Karlsruhe (Germany); Venkataraman, L. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)] [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

    2013-12-21

    Electrical and thermal transport properties of C{sub 60} molecules are investigated with density-functional-theory based calculations. These calculations suggest that the optimum contact geometry for an electrode terminated with a single-Au atom is through binding to one or two C-atoms of C{sub 60} with a tendency to promote the ?sp{sup 2}-hybridization into an ?sp{sup 3}-type one. Transport in these junctions is primarily through an unoccupied molecular orbital that is partly hybridized with the Au, which results in splitting the degeneracy of the lowest unoccupied molecular orbital triplet. The transmission through these junctions, however, cannot be modeled by a single Lorentzian resonance, as our results show evidence of quantum interference between an occupied and an unoccupied orbital. The interference results in a suppression of conductance around the Fermi energy. Our numerical findings are readily analyzed analytically within a simple two-level model.

  1. Proton transport properties in zwitterion blends with Brønsted acids.

    PubMed

    Yoshizawa-Fujita, Masahiro; Byrne, Nolene; Forsyth, Maria; MacFarlane, Douglas R; Ohno, Hiroyuki

    2010-12-16

    We describe zwitterion, 3-(1-butyl-1H-imidazol-3-ium-3-yl)propane-1-sulfonate (Bimps), mixtures with 1,1,1-trifluoro-N-(trifluoromethylsulfonyl)methanesulfoneamide (HN(Tf)(2)) as new proton transport electrolytes. We report proton transport mechanisms in the mixtures based on results from several methods including thermal analyses, the complex-impedance method, and the pulsed field gradient spin echo NMR (pfg-NMR) method. The glass transition temperature (Tg) of the mixtures decreased with increasing HN(Tf)(2) concentration up to 50 mol %. The Tg remained constant at -55 °C with further acid doping. The ionic conductivity of HN(Tf)(2) mixtures increased with the HN(Tf)(2) content up to 50 mol %. Beyond that ratio, the mixtures showed no increase in ionic conductivity (10(-4) S cm(-1) at room temperature). This tendency agrees well with that of Tg. However, the self-diffusion coefficients obtained from the pfg-NMR method increased with HN(Tf)(2) content even above 50 mol % for all component ions. At HN(Tf)(2) 50 mol %, the proton diffusion of HN(Tf)(2) was the fastest in the mixture. These results suggest that Bimps cannot dissociate excess HN(Tf)(2), that is, the excess HN(Tf)(2) exists as molecular HN(Tf)(2) in the mixtures. The zwitterion, Bimps, forms a 1:1 complex with HN(Tf)(2) and the proton transport property in this mixture is superior to those of other mixing ratios. Furthermore, CH(3)SO(3)H and CF(3)SO(3)H were mixed with Bimps for comparison. Both systems showed a similar tendency, which differed from that of the HN(Tf)(2) system. The Tg decreased linearly with increasing acid content for every mixing ratio, while the ionic conductivity increased linearly. Proton transport properties in zwitterion/acid mixtures were strongly affected by the acid species added. PMID:21087027

  2. Transport properties of Fibonacci heterostructures: a nonparabolic approach

    NASA Astrophysics Data System (ADS)

    Palomino-Ovando, M.; Cocoletzi, G. H.

    1998-07-01

    A fourth order hamiltonian is used to explore transport properties of semiconductor Fibonacci heterostructures. The tunneling current and time delay are obtained for different Fibonacci sequences constructed withGaAsandAlxGa1 - xAs. Energy minibands are calculated to study the fractal dimension and critical electronic states in quasi-periodic arrays. Results show that nonparabolic corrections produce changes in the tunneling current, time delay and fractal dimension, and a low voltage shift of the current peaks compared with the parabolic theory. The electronic states preserve their critical nature in the presence of nonparabolic effects.

  3. Electronic structures and transport properties of fluorinated boron nitride nanoribbons.

    PubMed

    Zeng, Jing; Chen, Ke-Qiu; Sun, Chang Q

    2012-06-14

    By applying the nonequilibrium Green's functions and the density-functional theory, we investigate the electronic structures and transport properties of fluorinated zigzag-edged boron nitride nanoribbons. The results show that the transition between half-metal and semiconductor in zigzag-edged boron nitride nanoribbons can be realized by fluorination at different sites or by the change of the fluorination level. Moreover, the negative differential resistance and varistor-type behaviors can also be observed in such fluorinated zigzag-edged boron nitride nanoribbon devices. Therefore, the fluorination of zigzag-edged boron nitride nanoribbons will provide the possibilities for a multifunctional molecular device design. PMID:22555657

  4. Study of electronic transport properties of doped 8AGNR

    SciTech Connect

    Sharma, Uma Shankar, E-mail: umashankar-rjit@yahoo.co.in [Rustamji Institute of Technology, BSF Academy Tekanpur, Gwalior-475005 (India); Srivastava, Anurag [Advanced Materials Research Group, Computational Nanoscience and Technology Lab, ABV-Indian Institute of Information Technology and Management Gwalior-474015 (India); Verma, U. P. [School of Studies in Physics, Jiwaji University, Gwalior-474011 (India)

    2014-04-24

    The electronic and transport properties of 8-armchair graphene nanoribbon (8AGNR) with defect at different sites are investigated by performing first-principles calculations based on density functional theory (DFT). The calculated results show that the 8AGNR are semiconductor. The introduction of 3d transition metals, creates the nondegenerate states in the conduction band, makes 8AGNR metallic. The computed transmission spectrum confirms that AGNR are semiconducting in nature and their band gap remain unchanged and localized states appear when there is vacancy in their structures, and the conductance decreases due to defects compared with the pristine nanoribbon.

  5. Transport and magnetic properties of CMR manganites with antidot arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Du, Kai; Niu, Jiebin; Wei, Wengang; Chen, Jinjie; Yin, Lifeng; Shen, Jian

    2014-03-01

    We fabricated and characterized a series of manganites thin film samples with different densities of antidots. With increasing antidot density, the samples show higher MIT temperature and lower resistivity under zero and low magnetic fields. These differences become smaller and finally vanished when the magnetic field is large enough to melt the charge ordered phase in the system, which is expected in our theoretical explanations. We believe that emerging edge states at the ring of antidotes play a significant role for observed metal-insulator transition and electrical transport properties, which are of great importance of real storage and sensor device design. Magnetic property measurements and theoretical simulation also support the conclusion. These results open up new ways to control and tune the strongly correlated oxides without introduce any new material or field.

  6. Electronic and transport properties of LiCoO2.

    PubMed

    Andriyevsky, Bohdan; Doll, Klaus; Jacob, Timo

    2014-11-14

    Using first principles density functional theory (DFT), the electronic and magnetic properties as well as the Li-ion migration in LiCoO2 have been studied with a gradient corrected functional. The magnetic properties were also investigated in addition using a gradient corrected functional in combination with an on-site repulsion U and a hybrid functional. We find LiCoO2 to be non-magnetic under ambient conditions. A magnetic ground state can be obtained by a volume expansion corresponding to a negative pressure of -8 GPa due to a competition between Hund's rules favoring magnetism on the Co(3+) ions and the crystal field splitting, which suppresses magnetism at zero pressure. The barrier for lithium transport is determined to be 0.44 eV from nudged elastic band (NEB) calculations on the Li0.917CoO2 system. PMID:25264622

  7. Thermal and transport properties of the neutron star inner crust

    E-print Network

    Dany Page; Sanjay Reddy

    2012-01-26

    We review the nuclear and condensed matter physics underlying the thermal and transport properties of the neutron star inner crust. These properties play a key role in interpreting transient phenomena such as thermal relaxation in accreting neutron stars, superbursts, and magnetar flares. We emphasize simplifications that occur at low temperature where the inner crust can be described in terms of electrons and collective excitations. The heat conductivity and heat capacity of the solid and superfluid phase of matter is discussed in detail and we emphasize its role in interpreting observations of neutron stars in soft X-ray transients. We highlight recent theoretical and observational results, and identify future work needed to better understand a host of transient phenomena in neutron stars.

  8. RELATIONSHIP BETWEEN SOLUTE TRANSPORT PROPERTIES AND TISSUE MORPHOLOGY IN HUMAN ANNULUS FIBROSUS

    PubMed Central

    Travascio, Francesco; Jackson, Alicia R.; Brown, Mark D.; Gu, Wei Yong

    2009-01-01

    Poor nutritional supply to the intervertebral disc is believed to be an important factor leading to disc degeneration. However, little is known regarding anisotropic and inhomogeneous transport in human annulus fibrosus (AF) and its relation to tissue morphology. We hypothesized that solute diffusivity in human AF is anisotropic and inhomogeneous and that transport behaviors are associated with tissue composition and structure. To test these hypotheses, we measured the direction-dependent diffusivity of a fluorescent molecule (fluorescein, 332Da) in three regions of AF using a fluorescence recovery after photobleaching (FRAP) technique, and associated transport results to the regional variation in water content and collagen architecture in the tissue. It was found that diffusivity in AF was anisotropic, with higher values in the axial direction than in the radial direction for all regions investigated. The values of the diffusion coefficient ranged from 0.38±0.25×10?6 cm2/s (radial diffusivity in outer AF) to 2.68±0.84×10?6 cm2/s (axial diffusivity in inner AF). In both directions, diffusivity decreased moving from inner to outer AF. Tissue structure was investigated using both Scanning Electron Microscopy (SEM) and Environmental Scanning Electron Microscopy (ESEM) imaging. A unique arrangement of microtubes was found in human AF. Furthermore, we also found that the density of these microtubes varied moving from inner to outer AF. A similar trend of regional variation was found for water content, with the highest value also measured in inner AF. Therefore, we concluded that a relationship exists among the anisotropic and inhomogeneous diffusion in human AF and the structure and composition of the tissue. PMID:19489044

  9. Controlling the Electrical Transport Properties of Nanocontacts to Nanowires.

    PubMed

    Lord, Alex M; Maffeis, Thierry G; Kryvchenkova, Olga; Cobley, Richard J; Kalna, Karol; Kepaptsoglou, Despoina M; Ramasse, Quentin M; Walton, Alex S; Ward, Michael B; Köble, Jürgen; Wilks, Steve P

    2015-07-01

    The ability to control the properties of electrical contacts to nanostructures is essential to realize operational nanodevices. Here, we show that the electrical behavior of the nanocontacts between free-standing ZnO nanowires and the catalytic Au particle used for their growth can switch from Schottky to Ohmic depending on the size of the Au particles in relation to the cross-sectional width of the ZnO nanowires. We observe a distinct Schottky to Ohmic transition in transport behavior at an Au to nanowire diameter ratio of 0.6. The current-voltage electrical measurements performed with a multiprobe instrument are explained using 3-D self-consistent electrostatic and transport simulations revealing that tunneling at the contact edge is the dominant carrier transport mechanism for these nanoscale contacts. The results are applicable to other nanowire materials such as Si, GaAs, and InAs when the effects of surface charge and contact size are considered. PMID:26042356

  10. Quantum Molecular Dynamics calculation of electrical and thermal transport properties

    NASA Astrophysics Data System (ADS)

    Desjarlais, Michael

    2011-10-01

    Dense, strongly-coupled plasmas, with degenerate or partially degenerate electrons--ubiquitous in high energy density physics, inertial fusion, planetary science, and warm dense matter--are very difficult to describe accurately with traditional theoretical approaches. Over the last decade, density functional based molecular dynamics, also know as quantum molecular dynamics (QMD), has emerged as a powerful tool for the study of dense quantum plasmas, providing accurate equation of state, structural, and transport properties. This talk will focus on the QMD calculation of electrical and thermal conductivities with a much higher degree of accuracy than was possible with earlier methods. Within the density functional approach, electrical and thermal conductivities are extracted directly from the electronic orbitals using the Kubo-Greenwood and Chester-Thellung formalisms, circumventing the need to define the ionization states and collision cross sections. These transport calculations have now been used to generate several wide-range transport models for use in large-scale simulation codes, allowing unprecedented simulations of complex experiments. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  11. Magnetic and transport properties of some manganites with colossal magnetoresistance

    NASA Astrophysics Data System (ADS)

    Zhao, Junhui

    The magnetic and electrical transport properties of the manganese perovskites are investigated through measurements of the field and temperature dependent ac susceptibility and resistivity respectively. Magnetic critical behaviour and the underlying physics are studied in detail using an approach based on scaling theory. The resistivity data are analyzed in terms of the double exchange and (bi)polaron theories. Also, measurements of the spontaneous resistive anisotropy (SRA) are presented and discussed based on the localized and itinerant models. The experimental data on La1-xCa xMnO3 (x = 0.33) indicate that the critical phase transition (from a paramagnetic to ferromagnetic state) is of the second order/continuous type, critical exponent values found are consistent with those predicted by the near-neighbor 3-dimensional Heisenberg model despite uncertainties introduced at both lower and higher field which arise from the effect of both a mixed inhomogeneous state and possible single ion anisotropy. Measurements of temperature and field-dependent resistivity on sample La0.67Ca0.33MnO3 indicate that the transport behaviour can be generally categorized into three regimes: a ferromagnetic metal dominated by double exchange at temperatures lower than T c; a metal insulator transition near Tc with the coexistence of double exchange and polaron formation; and a paramagnetic insulator characterized by small polaronic hopping at high temperature. Systematic measurements on the series La1- xMgxMnO3 (0.05 ? x ? 0.6) are presented with emphasis on the effect of the small average A-site radius on magnetic and transport properties. The experimental data show all samples undergo a paramagnetic to ferromagnetic transition with decreasing temperature. The Curie temperature, Tc, decreases with increasing doping level, x, beyond the 0.1 level. The study of the series (La1-xNd x)0.67Pb0.33MnO3 (0 ? x ? 1) shows the influence of the substitution of Nd3+ ions at the A-site on the magnetic and transport properties under the condition of a fixed ratio of Mn3+/Mn4+. With increases in x, the transition temperature Tc decreases; whereas resistivity and magnetoresistance increase. All of the compounds display a phase transition from a paramagnetic insulator to ferromagnetic metal, a typical characteristic of double-exchange systems. (Abstract shortened by UMI.)

  12. Asymmetric nanopore membranes: Single molecule detection and unique transport properties

    NASA Astrophysics Data System (ADS)

    Bishop, Gregory William

    Biological systems rely on the transport properties of transmembrane channels. Such pores can display selective transport by allowing the passage of certain ions or molecules while rejecting others. Recent advances in nanoscale fabrication have allowed the production of synthetic analogs of such channels. Synthetic nanopores (pores with a limiting dimension of 1--100 nm) can be produced in a variety of materials by several different methods. In the Martin group, we have been exploring the track-etch method to produce asymmetric nanopores in thin films of polymeric or crystalline materials. Asymmetric nanopores are of particular interest due to their ability to serve as ion-current rectifiers. This means that when a membrane that contains such a pore or collection of pores is used to separate identical portions of electrolyte solution, the magnitude of the ionic current will depend not only on the magnitude of the applied potential (as expected) but also the polarity. Ion-current rectification is characterized by an asymmetric current--potential response. Here, the interesting transport properties of asymmetric nanopores (ion-current rectification and the related phenomenon of electroosmotic flow rectification) are explored. The effects of pore shape and pore density on these phenomena are investigated. Membranes that contain a single nanopore can serve as platforms for the single-molecule sensing technique known as resistive pulse sensing. The resistive-pulse sensing method is based on the Coulter principle. Thus, the selectivity of the technique is based largely upon size, making the analysis of mixtures by this method difficult in many cases. Here, the surface of a single nanopore membrane is modified with a molecular recognition agent in an attempt to obtain a more selective resistive-pulse sensor for a specific analyte.

  13. TASK 7 DEMONSTRATION OF THAMES FOR MICROSTRUCTURE AND TRANSPORT PROPERTIES

    SciTech Connect

    Langton, C.; Bullard, J.; Stutzman, P.; Snyder, K.; Garboczi, E.

    2010-03-29

    The goal of the Cementitious Barriers Partnership (CBP) is to develop a reasonable and realible set of tools to reduce the uncertainty in predicting the structural, hydraulic and chemical performance of cement barriers used in nuclear applications that are exposed to dynamic environmental conditions over extended time frames. One of these tools, the responsibility of NIST, is THAMES (Thermodynamic Hydration and Microstructure Evolution Simulator), which is being developed to describe cementitious binder microstructures and calculate important engineering properties during hydration and degradation. THAMES is designed to be a 'micro-probe', used to evaluate changes in microstructure and properties occurring over time because of hydration or degradation reactions in a volume of about 0.001 mm{sup 3}. It will be used to map out microstructural and property changes across reaction fronts, for example, with spatial resolution adequate to be input into other models (e.g., STADIUM{reg_sign}, LeachSX{trademark}) in the integrated CBP package. THAMES leverages thermodynamic predictions of equilibrium phase assemblages in aqueous geochemical systems to estimate 3-D virtual microstructures of a cementitious binder at different times during the hydration process or potentially during degradation phenomena. These virtual microstructures can then be used to calculate important engineering properties of a concrete made from that binder at prescribed times. In this way, the THAMES model provides a way to calculate the time evolution of important material properties such as elastic stiffness, compressive strength, diffusivity, and permeability. Without this model, there would be no way to update microstructure and properties for the barrier materials considered as they are exposed to the environment, thus greatly increasing the uncertainty of long-term transport predictions. This Task 7 report demonstrates the current capabilities of THAMES. At the start of the CBP project, THAMES did not exist, so that it is in the early stages of development. However, extensive experience with 3-D microstructure models at NIST is making possible a timely development process.

  14. A Kinetic Theory for Nonanalog Monte Carlo Particle Transport Algorithms: Exponential Transform with Angular Biasing in Planar-Geometry Anisotropically Scattering Media

    NASA Astrophysics Data System (ADS)

    Ueki, Taro; Larsen, Edward W.

    1998-09-01

    We show that Monte Carlo simulations of neutral particle transport in planar-geometry anisotropically scattering media, using the exponential transform with angular biasing as a variance reduction device, are governed by a new "Boltzmann Monte Carlo" (BMC) equation, which includes particle weight as an extra independent variable. The weight moments of the solution of the BMC equation determine the moments of the score and the mean number of collisions per history in the nonanalog Monte Carlo simulations. Therefore, the solution of the BMC equation predicts the variance of the score and the figure of merit in the simulation. Also, by (i) using an angular biasing function that is closely related to the "asymptotic" solution of the linear Boltzmann equation and (ii) requiring isotropic weight changes at collisions, we derive a new angular biasing scheme. Using the BMC equation, we propose a universal "safe" upper limit of the transform parameter, valid for any type of exponential transform. In numerical calculations, we demonstrate that the behavior of the Monte Carlo simulations and the performance predicted by deterministically solving the BMC equation agree well, and that the new angular biasing scheme is always advantageous.

  15. Propagation properties of a partially polarized electromagnetic twist anisotropic Gaussian Schell-model beam in turbulent atmosphere

    Microsoft Academic Search

    Haiyan Wang; Xiangyin Li

    2010-01-01

    Based on the extended Huygens–Fresnel integral formula, analytical formulae for the elements of cross-spectral density matrix of partially polarized electromagnetic twist anisotropic Gaussian Schell-model (TAGSM) beam propagating in turbulent atmosphere can been derived by a tensor method. Our main attention was focus on the effect of the atmospheric turbulence, twist parameters and partial coherence on the spectral degree of polarization,

  16. Existence of anti-plane shear surface waves in anisotropic elastic half-space with depth-dependent material properties

    Microsoft Academic Search

    T. C. T. Ting

    2010-01-01

    It is known that an anti-plane shear surface wave does not exist in anisotropic elastic half-space x2?0 when the material is homogeneous. For a functionally graded material for which the elastic stiffness C44, C45, C55 and the mass density ? depend on the depth x2 of the half-space, an anti-plane shear surface wave may exist. Exact solutions for four cases

  17. Transport properties of ribbon-shaped carbon fibers: Property-structure relationship

    NASA Astrophysics Data System (ADS)

    Gallego, Nidia Constanza

    Mesophase pitch-based carbon fibers are an ideal material for applications in which high rates of heat dissipation and low mass are required. Unfortunately, the high cost of current commercial high thermal conductivity mesophase pitch-based carbon fibers has limited their use in high volume applications. Understanding how the structure develops during the fiber formation process and how this structure relates to the final fiber properties is the way to optimizing the fiber properties while reducing the processing costs. Ribbon-shaped fibers have been developed at Clemson University and are being evaluated as a low-cost high thermal conductivity alternative fiber to traditional round-shaped fibers. However, the characterization of the thermal transport properties of carbon fibers is a difficult and time-consuming process. The objectives of this study were to evaluate the transport (both thermal and electronic) properties of ribbon-shaped fibers produced from an AR mesophase at different processing conditions, to characterize the structure of these fibers, to study their structure-property relationships, and to develop a model capable of estimating the thermal conductivity of carbon fibers based upon their structural parameters. For this purpose, several sets of ribbon fibers were produced from an AR mesophase at different spinning temperatures and shear rates and heat treated at a final temperature of 2400°C. The electrical resistivities, magnetoresistances and thermal conductivities of these fibers were measured and the structural parameters were determined with x-ray techniques. Two approaches (a short-fiber composite, and a periodic composite) were utilized to model the relationship between the structure of the fiber and its thermal conductivity. The results of this study confirmed that ribbon-shaped fibers develop excellent transport properties at lower graphitization temperatures than those used commercially for round-shaped fibers. Additionally, for the first time, two models that directly relate the structure of the carbon fiber to its thermal conductivity were developed.

  18. Electrical transport properties of single-layer WS2.

    PubMed

    Ovchinnikov, Dmitry; Allain, Adrien; Huang, Ying-Sheng; Dumcenco, Dumitru; Kis, Andras

    2014-08-26

    We report on the fabrication of field-effect transistors based on single layers and bilayers of the semiconductor WS2 and the investigation of their electronic transport properties. We find that the doping level strongly depends on the device environment and that long in situ annealing drastically improves the contact transparency, allowing four-terminal measurements to be performed and the pristine properties of the material to be recovered. Our devices show n-type behavior with a high room-temperature on/off current ratio of ?10(6). They show clear metallic behavior at high charge carrier densities and mobilities as high as ?140 cm(2)/(V s) at low temperatures (above 300 cm(2)/(V s) in the case of bilayers). In the insulating regime, the devices exhibit variable-range hopping, with a localization length of about 2 nm that starts to increase as the Fermi level enters the conduction band. The promising electronic properties of WS2, comparable to those of single-layer MoS2 and WSe2, together with its strong spin-orbit coupling, make it interesting for future applications in electronic, optical, and valleytronic devices. PMID:25069042

  19. Anisotropic hydrodynamics

    NASA Astrophysics Data System (ADS)

    Florkowski, W.; Martinez, M.; Ryblewski, R.; Strickland, M.

    2013-05-01

    The recently formulated framework of anisotropic hydrodynamics is used in 3+1 dimensions to study behavior of matter created in relativistic heavy-ion collisions. The model predictions for various hadronic observables show that the effects of the initial anisotropy of pressure may be compensated by appropriate adjustment of the initial energy density. In this way, the final hadronic observables become insensitive to the early stage dynamics and the early thermalization/isotropization puzzle may be circumvented.

  20. Anisotropic branes

    NASA Astrophysics Data System (ADS)

    Banerjee, Souvik; Bhowmick, Samrat; Mukherji, Sudipta

    2013-10-01

    We present a class of anisotropic brane configurations which shows BKL oscillations near their cosmological singularities. Near horizon limits of these solutions represent Kasner space embedded in AdS background. Dynamical probe branes in these geometries inherit anisotropies from the background. Amusingly, for a probe M5 brane, we find that there exists a parameter region where three of its world-volume directions expand while the rest contract.

  1. Simulating liquid water for determining its structural and transport properties.

    PubMed

    Arismendi-Arrieta, Daniel; Medina, Juan S; Fanourgakis, George S; Prosmiti, Rita; Delgado-Barrio, Gerardo

    2014-01-01

    Molecular dynamics simulations are carried out for calculating structural and transport properties of pure liquid water, such as radial distribution functions and self-diffusion and viscosity coefficients, respectively. We employed reparameterized versions of the ab initio water potential by Niesar, Clementi and Corongiu (NCC). In order to investigate the role of the electrostatic contribution, the partial charges of the NCC model are adjusted so that to reproduce the dipole moment values of the SPC/E, SPC/Fw and TIP4P/2005 water models. The single and collective transport coefficients are obtained by employing the Green-Kubo relations at various temperatures. Additionally, in order to overcome convergence difficulties arising from the long correlation times of the stress-tensor autocorrelation functions, a previously reported fitting scheme was employed. The present results indicate that there is a significant relationship between the dipole moment value of the model, and the calculated transport coefficients. We found that by adjusting the molecular dipole moment of the NCC to the value of the TIP4P/2005, the obtained values for the self-diffusion and viscosity coefficients are in better agreement with experiment, compared to the values obtained with the original NCC model. Even though the predictions of the present model exhibits an overall correct behavior, we conclude that further improvements are still required. In order to achieve that, a careful reparameterization of the repulsion-dispersion terms of the potential model is proposed. Also, the effect of the inclusion of many-body effects such as polarizability, should also be investigated. PMID:23415103

  2. Electron-neutron scattering and transport properties of neutron stars

    E-print Network

    Bridget Bertoni; Sanjay Reddy; Ermal Rrapaj

    2014-09-27

    We show that electrons can couple to the neutron excitations in neutron stars and find that this can limit their contribution to the transport properties of dense matter, especially the shear viscosity. The coupling between electrons and neutrons is induced by protons in the core, and by ions in the crust. We calculate the effective electron-neutron interaction for the kinematics of relevance to the scattering of degenerate electrons at high density. We use this interaction to calculate the electron thermal conductivity, electrical conductivity, and shear viscosity in the neutron star inner crust, and in the core where we consider both normal and superfluid phases of neutron-rich matter. In some cases, particularly when protons are superconducting and neutrons are in their normal phase, we find that electron-neutron scattering can be more important than the other scattering mechanisms considered previously.

  3. Magnetic and transport properties of MnBi/Bi nanocomposites

    NASA Astrophysics Data System (ADS)

    Kang, Kyongha; Lewis, L. H.; Hu, Y. F.; Li, Qiang; Moodenbaugh, A. R.; Choi, Young-Suk

    2006-04-01

    The magnetic and transport properties of a nanostructured Mn-Bi eutectic composition (~Mn5Bi95) produced by melt spinning and low-temperature/short time vacuum annealing were studied. A hysteretic magnetostructural transformation from low-temperature phase to high-temperature phase MnBi is confirmed at 520 K. The fact that the transition temperature is lower than that reported for bulk MnBi (633 K), is tentatively attributed to interfacial strain between MnBi and the Bi matrix. A positive temperature coefficient of coercivity is confirmed in the nanocomposites, with a maximum coercivity value of 36 kOe at 500 K. Magnetic field annealing the as-spun composites (525 K at 10 kOe) produces nanoparticle alignment. Annealed MnBi/Bi composites have a very large ordinary magnetoresistance (MR) ratio normal to the ribbon at 5 T, 275% at room temperature and 10 000% at 5 K.

  4. Transport properties of hadronic matter in magnetic field

    E-print Network

    Guru Kadam

    2015-03-06

    We study the effect of magnetic field on the transport properties like shear and bulk viscosities of hot and dense hadronic matter within hadron resonance gas model. We estimate the bulk viscosity using low energy theorems for bilocal correlators of the energy momentum tensor generalized to finite temperature, density and magnetic field. We use Gaussian ansatz for the spectral function at low frequency. We estimate shear viscosity coefficient using molecular kinetic theory. We find that vacuum contribution due to finite magnetic field dominates the bulk viscosity ({\\zeta}) for the temperatures up to 0.1GeV and increases with magnetic field while ratio {\\zeta}/s decreases with magnetic field. We also find that shear viscosity coefficient of hadronic matter decreases with magnetic field.

  5. Dynamical and transport properties of liquid gallium at high pressures

    NASA Astrophysics Data System (ADS)

    Sheppard, D.; Mazevet, S.; Cherne, F. J.; Albers, R. C.; Kadau, K.; Germann, T. C.; Kress, J. D.; Collins, L. A.

    2015-06-01

    Quantum molecular dynamics (QMD) simulations are used to calculate the equation of state, structure, and transport properties of liquid gallium along the principal shock Hugoniot. The calculated Hugoniot is in very good agreement with experimental data up to a pressure of 150 GPa as well as with our earlier classical molecular dynamics calculations using a modified embedded atom method (MEAM) potential. The self-diffusion and viscosity calculated using QMD agree with experimental measurements better than the MEAM results, which we attribute to capturing the complexity of the electronic structure at elevated temperatures. Calculations of the DC conductivity were performed around the Hugoniot. Above a density of 7.5 g/cm3, the temperature increases rapidly along the Hugoniot, and the optical conductivity decreases, indicating simple liquid metal behavior.

  6. Optical and transport properties of dense liquid silica

    NASA Astrophysics Data System (ADS)

    Qi, Tingting; Millot, Marius; Kraus, Richard G.; Root, Seth; Hamel, Sebastien

    2015-06-01

    Using density-functional-theory based molecular dynamics and the Kubo-Greenwood linear response theory, we evaluated the high-pressure equation of state and the optical and transport properties of quartz and fused silica shock-compressed to 2000 GPa. The computed Hugoniots and corresponding optical reflectivity values are in very good agreement with published data for quartz, and new data that we obtained on fused silica using magnetically launched flyer plate experiments. The rise of optical reflectivity upon shock compression appears to be primarily a temperature-driven mechanism, which is relatively insensitive to small density variation. We observed that the electrical conductivity does not display Drude-like frequency dependence, especially at lower temperatures. In addition, the Wiedemann-Franz relation between electrical and thermal conductivities was found to be invalid. It suggests that even at three-fold compression, warm dense liquid silica on the Hugoniot curve is still far away from the degenerate limit.

  7. The electrical transport properties of liquid Rb using pseudopotential theory

    SciTech Connect

    Patel, A. B., E-mail: amit07patel@gmail.com; Bhatt, N. K., E-mail: amit07patel@gmail.com; Thakore, B. Y., E-mail: amit07patel@gmail.com; Jani, A. R. [Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388120, Gujarat (India); Vyas, P. R. [Department of Physics, School of Sciences, Gujarat University, Ahmedabad-380009, Gujarat (India)

    2014-04-24

    Certain electric transport properties of liquid Rb are reported. The electrical resistivity is calculated by using the self-consistent approximation as suggested by Ferraz and March. The pseudopotential due to Hasegawa et al for full electron-ion interaction, which is valid for all electrons and contains the repulsive delta function due to achieve the necessary s-pseudisation was used for the calculation. Temperature dependence of structure factor is considered through temperature dependent potential parameter in the pair potential. Finally, thermo-electric power and thermal conductivity are obtained. The outcome of the present study is discussed in light of other such results, and confirms the applicability of pseudopotential at very high temperature via temperature dependent pair potential.

  8. Dark matter transport properties and rapidly rotating neutron stars

    E-print Network

    Horowitz, C J

    2012-01-01

    Neutron stars are attractive places to look for dark matter because their high densities allow repeated interactions. Weakly interacting massive particles (WIMPs) may scatter efficiently in the core or in the crust of a neutron star. In this paper we focus on WIMP contributions to transport properties, such as shear viscosity or thermal conductivity, because these can be greatly enhanced by long mean free paths. We speculate that WIMPs increase the shear viscosity of neutron star matter and help stabilize r-mode oscillations. These are collective oscillations where the restoring force is the Coriolis force. At present r-modes are thought to be unstable in many observed rapidly rotating stars. If WIMPs stabilize the r-modes, this would allow neutron stars to spin rapidly. This likely requires WIMP-nucleon cross sections near present experimental limits and an appropriate density of WIMPs in neutron stars.

  9. Transport properties of doped GeSn alloys

    NASA Astrophysics Data System (ADS)

    D'Costa, Vijay R.; Tolle, John; Xie, Junqi; Menéndez, José; Kouvetakis, John

    2010-01-01

    We present a systematic study of the transport properties of n- and p-type Ge0.98Sn0.02 alloys using infrared spectroscopic ellipsometry and electrical measurements. We measure the dielectric function of our samples in the infrared range where the response is mainly due to free carrier absorption. In the case of p-type material, we observe, in addition to the free carrier response, optical transitions between split-off (SO), light (LH), and heavy-hole (HH) bands. The electron and hole mobilities for Ge0.98Sn0.02 alloys with carrier concentrations >1018 cm-3 are comparable to those found in Ge samples with similar doping concentrations. The electron and hole effective masses of Ge0.98Sn0.02 alloys are close to that of n-doped and p-doped Ge respectively.

  10. Transport properties of polyaniline-cellulose-acetate blends

    NASA Astrophysics Data System (ADS)

    Planès, Jérôme; Wolter, Andreas; Cheguettine, Yasmina; Pro?, Adam; Genoud, Françoise; Nechtschein, Maxime

    1998-09-01

    Transport properties of polyaniline (PANI)-cellulose acetate (CA) conducting blends have been investigated at various length scales and temperatures. We report on the results of dc and ac conductivity measurements, magnetoresistance and electron-spin resonance (ESR) performed on composite films with PANI weight fraction p ranging from the percolation threshold-pc~=0.1%-to a few percent. Three different PANI doping agents have been tested, namely, camphor sulfonic acid (CSA), di(i-octyl phosphate) (DiOP) and phenyl phosphonic acid (PPA). The percolative behavior of ?dc resembles that of published results on PANI/PMMA blends. The onset frequency ?? of the dispersion in ?ac appears to follow the scaling law: ??~?zdc with z~=1. The temperature dependence is of the form of ln?(T)~-(T0/T)? the exponent decreasing from 0.75 to 0.5 with increasing p. The microscopic metallic character of transport is found in ESR and microwave measurements. Spin-dependent conductivity is inferred from the (B/T)2 universal behavior of magnetoresistance. Those results are discussed in conjunction with the ongoing debate on the nature of disorder in conducting polymers-homogeneous versus heterogeneous.

  11. Transport properties of liquid metal hydrogen under high pressures

    NASA Technical Reports Server (NTRS)

    Brown, R. C.; March, N. H.

    1972-01-01

    A theory is developed for the compressibility and transport properties of liquid metallic hydrogen, near to its melting point and under high pressure. The interionic force law is assumed to be of the screened Coulomb type, because hydrogen has no core electrons. The random phase approximation is used to obtain the structure factor S(k) of the system in terms of the Fourier transform of this force law. The long wavelenth limit of the structure factor S(o) is related to the compressibility, which is much lower than that of alkali metals at their melting points. The diffusion constant at the melting point is obtained in terms of the Debye frequency, using a frequency spectrum analogous with the phonon spectrum of a solid. A similar argument is used to obtain the combined shear and bulk viscosities, but these depend also on S(o). The transport coefficients are found to be about the same size as those of alkali metals at their melting points.

  12. Electron Transport Materials: Synthesis, Properties and Device Performance

    SciTech Connect

    Cosimbescu, Lelia; Wang, Liang; Helm, Monte L.; Polikarpov, Evgueni; Swensen, James S.; Padmaperuma, Asanga B.

    2012-06-01

    We report the design, synthesis and characterization, thermal and photophysical properties of two silane based electron transport materials, dibenzo[b,d]thiophen-2-yltriphenylsilane (Si{phi}87) and (dibenzo[b,d]thiophen-2-yl)diphenylsilane (Si{phi}88) and their performance in blue organic light emitting devices (OLEDs). The utility of these materials in blue OLEDs with iridium (III) bis[(4,6-difluorophenyl)-pyridinato-N,C']picolinate (Firpic) as the phosphorescent emitter was demonstrated. Using the silane Si{phi}87 as the electron transport material (ETm) an EQE of 18.2% was obtained, with a power efficiency of 24.3 lm/W (5.8V at 1mA/cm{sup 2}), in a heterostructure. When Si{phi}88 is used, the EQE is 18.5% with a power efficiency of 26.0 lm/W (5.5V at 1mA/cm{sup 2}).

  13. Updated Chemical, Radiative, and Transport Properties of Thermospheric Odd Nitrogen

    NASA Astrophysics Data System (ADS)

    Yonker, J. D.; Venkataramani, K.; Bailey, S. M.; Wang, W.; Solomon, S. C.; Randall, C. E.

    2014-12-01

    In the past decade many laboratory and quantum chemical results relevant to the chemical, transport, and radiative properties of thermospheric odd nitrogen have appeared. The impact of these updates on the odd nitrogen abundances, fluxes, and neutral temperature are assessed by inclusion into the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) and comparison with data from the Student Nitric Oxide Explorer (SNOE) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) experiments. Regarding chemistry, electronically and vibrationally excited molecular nitrogen (N2(A)) has been found to be an important source of nitric oxide (NO) and electronically excited atomic nitrogen (N(2D)) [Campbell et al, 2007] while many key branching ratios and temperature dependences have been revised [Hellberg et al, 2003; Galvao et al, 2013]. The yields of vibrationally excited NO(v) from the N(2D)+O2 and N(4S)+O2 reactions have been determined [Miquel et al, 2003; Sultanov et al, 2006]; radiative cascade from NO(v) results in enhanced cooling near 5.3 ?m which contributes roughly 20% of that due to collisions with hot atomic oxygen. Collision integrals for the He-NO and He-N(4S) interactions are known [Partridge et al, 2001; Haghighi et al, 2003] and the resulting transport coefficients are calculated and input to TIE-GCM v2.0, wherein He is treated as a major species.

  14. The Influence of Anisotropic Strain on the Dielectric and Ferroelectric Properties of SrTiO3 Thin Films on DyScO3 Substrates

    SciTech Connect

    Biegalski, Michael D [ORNL; Trolier-McKinstry, Susan [Pennsylvania State University; Schlom, Darrell [Pennsylvania State University; Kumar, Amit [Pennsylvania State University; Sheng, Guang [Pennsylvania State University, University Park, PA; Vlahos, Eftihia [Pennsylvania State University, University Park, PA; Chen, Long-Qing [Pennsylvania State University; Uecker, Rinhold [Institute for Crystal Growth, Berlin, Germany; Streiffer, Stephen [Argonne National Laboratory (ANL); Gopalan, Venkatraman [ORNL

    2009-01-01

    The in-plane dielectric and ferroelectric properties of coherent anisotropically strained SrTiO{sub 3} thin films grown on orthorhombic (101) DyScO{sub 3} substrates were examined as a function of the angle between the applied electric field and the principal directions of the substrate. The dielectric permittivity revealed two distinct maxima as a function of temperature along the [100]{sub p} and [010]{sub p} SrTiO{sub 3} pseudocubic directions. These data, in conjunction with optical second-harmonic generation, show that the switchable ferroelectric polarization develops first predominantly along the in-plane axis with the larger tensile strain before developing a polarization component along the perpendicular direction with smaller strain as well, leading to domain twinning at the lower temperature. Finally, weak signatures in the dielectric and second-harmonic generation response were detected at the SrTiO{sub 3} tilt transition close to 165 K. These studies indicate that anisotropic biaxial strain can lead to new ferroelectric domain reorientation transitions that are not observed in isotropically strained films.

  15. A general methodology for inverse estimation of the elastic and anelastic properties of anisotropic open-cell porous materials—with application to a melamine foam

    NASA Astrophysics Data System (ADS)

    Cuenca, Jacques; Van der Kelen, Christophe; Göransson, Peter

    2014-02-01

    This paper proposes an inverse estimation method for the characterisation of the elastic and anelastic properties of the frame of anisotropic open-cell foams used for sound absorption. A model of viscoelasticity based on a fractional differential constitutive equation is used, leading to an augmented Hooke's law in the frequency domain, where the elastic and anelastic phenomena appear as distinctive terms in the stiffness matrix. The parameters of the model are nine orthotropic elastic moduli, three angles of orientation of the material principal directions and three parameters governing the anelastic frequency dependence. The inverse estimation consists in numerically fitting the model on a set of transfer functions extracted from a sample of material. The setup uses a seismic-mass measurement repeated in the three directions of space and is placed in a vacuum chamber in order to remove the air from the pores of the sample. The method allows to reconstruct the full frequency-dependent complex stiffness matrix of the frame of an anisotropic open-cell foam and in particular it provides the frequency of maximum energy dissipation by viscoelastic effects. The characterisation of a melamine foam sample is performed and the relation between the fractional-derivative model and other types of parameterisations of the augmented Hooke's law is discussed.

  16. Multiple-pumped-well aquifer test to determine the anisotropic properties of a karst limestone aquifer in Pasco County, Florida, USA

    NASA Astrophysics Data System (ADS)

    Motz, Louis H.

    2009-06-01

    Groundwater-level data from an aquifer test utilizing four pumped wells conducted in the South Pasco wellfield in Pasco County, Florida, USA, were analyzed to determine the anisotropic transmissivity tensor, storativity, and leakance in the vicinity of the wellfield. A weighted least-squares procedure was used to analyze drawdowns measured at eight observation wells, and it was determined that the major axis of transmissivity extends approximately from north to south and the minor axis extends approximately from west to east with an angle of anisotropy equal to N4.54°W. The transmissivity along the major axis {( {T_{{? ? }} } )} is 14,019 m2 day-1, and the transmissivity along the minor axis {( {T_{{? ? }} } )} is 4,303 m2 day-1. The equivalent transmissivity Te = {( {T_{{? ? }} T_{{? ? }} } )}^{1/2} = 7,767{{m}2 } day^{-1}, and the ratio of anisotropy is 3.26. The storativity of the aquifer is 7.52 × 10-4, and the leakance of the overlying confining unit is 1.37 × 10-4 day-1. The anisotropic properties determined for the South Pasco wellfield in this investigation confirm the results of previous aquifer tests conducted in the wellfield and help to quantify the NW-SE to NE-SW trends for regional fracture patterns and inferred solution-enhanced flow zones in west-central Florida.

  17. Anisotropic magnetic properties of Dy{sub 6}Cr{sub 4}Al{sub 43} single crystal

    SciTech Connect

    Maurya, Arvind, E-mail: arvindmaurya@tifr.res.in; Thamizhavel, A., E-mail: arvindmaurya@tifr.res.in; Dhar, S. K., E-mail: arvindmaurya@tifr.res.in [Department of Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Mumbai-400005 (India)

    2014-04-24

    We have studied the anisotropic magnetic behavior of the rare earth intermetallic compound Dy{sub 6}Cr{sub 4}Al{sub 43}. This compound crystallizes in the hexagonal symmetry and orders ferromagnetically at 8.3 K as confirmed by the magnetic susceptibility and heat capacity measurements. A significant anisotropy in the magnetization is observed between the c axis and the ab-plane. The easy axis liesin theab-plane at low temperatures; however it orients itselfalong the c-axis above 170 K as inferred from the susceptibility data.

  18. Magnetic and transport properties of magnetite thin films

    NASA Astrophysics Data System (ADS)

    Zhang, Guomin; Fan, Chongfei; Pan, Liqing; Wang, Fengping; Wu, Ping; Qiu, Hong; Gu, Yousong; Zhang, Yue

    2005-05-01

    Magnetite (Fe 3O 4) films were prepared by DC reactive magnetron sputtering at various oxygen partial pressures with the ratio ? of oxygen to argon changing from 0.50:50 to 0.70:50 at room temperature, and then the Fe 3O 4 films were annealed at 480 °C for 80 min. The properties of the films were studied by X-ray diffraction, scanning electron microscopy, magnetic hysteresis loops, magnetoresistance (MR), etc. The results showed when ? increased, resistivity of magnetite films were increased exponentially, and only these magnetite films of ?>0.60:50 showed MR effects. After annealing, the resistivity decreased about one order; and all magnetite films showed MR effects. The Verwey transition of the magnetite films was confirmed by MR- T curves. XRD and SEM showed that the films were composed of Fe 3O 4 nanoparticles with highly preferential orientation and the best conditions for high-quality magnetite films were ?=0.65:50 and 0.675:50. The magnetic transport properties of the films infer that strong coupling between Fe 3O 4 nanoparticles originated from RKKY exchange interaction and dipolar interaction, this made the films differ from metallic granular ones and higher-order terms of (M/M s) 2, such as (M/M s) 4 and (M/M s) 6, should be added to the fitting functions of the MR-(M/M s) curves.

  19. Dependence of dynamic magnetization and magneto-transport properties of FeAlSi films with oblique sputtering studied via spin rectification effect

    NASA Astrophysics Data System (ADS)

    Soh, Wee Tee; Zhong, Xiaoxi; Ong, C. K.

    2014-09-01

    FeAlSi (Sendust) is known to possess excellent soft magnetic properties comparable to traditional soft magnetic alloys such as NiFe (Permalloy), while having a relatively higher resistance for lower eddy current losses. However, their dynamic magnetic and magneto-transport properties are not well-studied. Via the spin rectification effect, we electrically characterize a series of obliquely sputtered FeAlSi films at ferromagnetic resonance. The variations of the anisotropy fields and damping with oblique angle are extracted and discussed. In particular, two-magnon scattering is found to dominate the damping behavior at high oblique angles. An analysis of the results shows large anomalous Hall effect and anisotropic magneto-resistance across all samples, which decreases sharply with increasing oblique incidence.

  20. A two-step hybrid technique for accurately localizing acoustic source in anisotropic structures without knowing their material properties.

    PubMed

    Kundu, T; Yang, X; Nakatani, H; Takeda, N

    2015-02-01

    Acoustic source localization techniques generally assume straight line propagation of waves from the acoustic source to the sensor. However, it is well-known that in anisotropic plates the acoustic energy does not always propagate in straight lines. Even for isotropic plates containing a cavity or an inclusion between the acoustic source and the sensor the straight line propagation assumption is violated. In such cases only options available in localizing acoustic source is to use relatively expensive distributed sensor systems, or to follow time reversal techniques based on the impulse response functions which is labor intensive and computationally demanding. A two-step hybrid technique is proposed in this paper for predicting acoustic source in anisotropic plates. During the first step it was assumed that the waves propagated along straight lines from the acoustic source to the sensor. The source was localized with this simplifying assumption. Then this first prediction was improved in the second step by solving an optimization problem. Experimental results showed that the second step always moved the estimates towards the actual source location. Thus it always reduced the prediction error irrespective of whether the final prediction coincided with the actual source location or not. PMID:25245206

  1. Characterization of fluid transport properties of reservoirs using induced microseismicity

    Microsoft Academic Search

    Serge A. Shapiro; Elmar Rothert; Volker Rath; Jan Rindschwentner

    2002-01-01

    We systematically describe an approach to estimate the large-scale permeability of reservoirs using seismic emission (microseismicity) induced by fluid injection. We call this approach seismicity-based reservoir char- acterization (SBRC). A simple variant of the approach is based on the hypothesis that the triggering front of hydraulically-induced microseismicity propagates like a diffusive process (pore pressure relaxation) in an effective homogeneous anisotropic

  2. Methods for the anisotropic wavelet packet transform

    Microsoft Academic Search

    Rade Kutil; Dominik Engel

    2008-01-01

    Anisotropic wavelet packets present a flexible transform with interesting properties and applications. While certain aspects of this transform have been investigated in conjunction with applications, this paper aims at providing a basic theoretical framework for working with anisotropic wavelet packets. Random decompositions are developed which have distributions with different average decomposition depths and degrees of anisotropy. They can be used

  3. VAPOUR PHASE CHEMICAL TRANSPORT PROPERTIES OF THE CADMIUM TELLURIDE-IODINE SYSTEM

    E-print Network

    Boyer, Edmond

    155 VAPOUR PHASE CHEMICAL TRANSPORT PROPERTIES OF THE CADMIUM TELLURIDE-IODINE SYSTEM C. PAORICI, it was shown that no iodine chemical transport is possible in closed tubes in the hot-cold direction, but only was explained in terms of a reverse (cold-hot) iodine transport associated with a reduced sublimation tendency

  4. Effect of Mn substitution on the transport properties of co-sputtered Fe3-xMnxSi epilayers

    NASA Astrophysics Data System (ADS)

    Tang, M.; Jin, C.; Bai, H. L.

    2014-11-01

    Motivated by the theoretical calculations that Fe3-xMnxSi can simultaneously exhibit a high spin polarization with a high Curie temperature to be applied in spintronic devices, and in order to further study the effect of Mn contents on the physical properties of Fe3-xMnxSi, we have investigated the effect of Mn substitution on the transport properties of epitaxial Fe3-xMnxSi ( 0 ?x ?1 ) films systematically. The Fe3-xMnxSi films were epitaxially grown on MgO(001) plane with 45° rotation. The magnetization for various x shows enhanced irreversibility, implying the antiferromagnetic ordering induced by the substitution of Mn. A metal-semiconductor crossover was observed due to the enhanced disorders of interactions and the local lowering of symmetry induced by the substitution of Mn. The single-domain state in the Fe3-xMnxSi films leads to twofold symmetric curves of the anisotropic magnetoresistance and planar Hall resistivity.

  5. Avalanche properties in a transport model based on critical-gradient fluctuation dynamics

    SciTech Connect

    Garcia, L.; Carreras, B.A. [Universidad Carlos III, 28911 Leganes, Madrid (Spain); Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 (United States)

    2005-09-15

    A simple one-dimensional transport model based on critical-gradient fluctuation dynamics is applied to describe some of the properties of plasma-turbulence-induced transport. This model combines avalanche-like transport with diffusion. The particle flux is self-regulated by the stability properties of the fluctuations. A high-gradient edge region emerges where transport dynamics is close to marginal stability. In steady state, the core remains at the subcritical gradient. The avalanches change from quasiperiodic events triggered mostly near the edge region to intermittent transport events depending on the noise level of the particle source.

  6. Influence of Si Co-doping on electrical transport properties of magnesium-doped boron nanoswords

    E-print Network

    Gao, Hongjun

    Influence of Si Co-doping on electrical transport properties of magnesium- doped boron nanoswords://apl.aip.org/about/rights_and_permissions #12;Influence of Si Co-doping on electrical transport properties of magnesium-doped boron nanoswords; published online 9 March 2012) Magnesium-doped boron nanoswords were synthesized via a thermoreduction

  7. Avalanche properties in a transport model based on critical-gradient fluctuation dynamics

    E-print Network

    Martín-Solís, José Ramón

    Avalanche properties in a transport model based on critical-gradient fluctuation dynamics L avalanche-like transport with diffusion. The particle flux is self-regulated by the stability properties. In steady state, the core remains at the subcritical gradient. The avalanches change from quasiperiodic

  8. Effect of hydrochloric acid on the transport properties of tin through ion-exchange membranes

    Microsoft Academic Search

    M. García-Gabaldón; V. Pérez-Herranz; J. García-Antón; J. L. Guiñón

    2009-01-01

    This work presents a study of the transport properties of two ion-exchange membranes present in an electrochemical reactor used to process the wasted and rinse baths of the electroless plating of polymers industry. The influence of the hydrochloric acid on the transport properties of tin through both cation- and anion-exchange membranes has been evaluated by chronopotentiometry. The shape of the

  9. Anisotropic Adaptive Meshes Black-Box Anisotropic

    E-print Network

    Kurien, Susan

    Anisotropic Adaptive Meshes LV Black-Box Anisotropic Mesh Generators for Engineering Applications Konstantin Lipnikov, lipnikov@lanl.gov Yuri Vassilevski, vasilevs@dodo.inm.ras.ru The adaptive mesh methods for generating adaptive anisotropic meshes were proposed (see [4, 3] and references therein). The theoretical

  10. Molecular Simulation of Phase Equilibria and Transport Properties

    NASA Astrophysics Data System (ADS)

    Bereolos, Peter James

    1995-01-01

    Molecular simulations are used to test models and theories through comparison with experimental results and theoretical predictions. Three areas are covered: transport properties, free energy measurement, and phase diagram calculation. Transport properties of isotropic fluids composed of hard ellipsoids of revolution are studied using molecular dynamics simulation. The self diffusion coefficient, the shear viscosity, and the thermal conductivity are evaluated for a range of densities and elongations and are compared to the predictions of an Enskog kinetic theory for nonspherical bodies. The simulation and the kinetic theory values for the shear viscosity and the thermal conductivity show the same qualitative behavior, that is, increasing with density and with particle nonsphericity. Quantitatively, there is good agreement at low densities (up to 30% of closest packing); at higher densities (60% of closest packing) deviations from Enskog theory are larger than, and in the opposite direction to those seen for hard spheres. The Stokes-Einstein and Debye relations are tested, and indicate a transition from a kinetic theory region towards the hydrodynamic limit as density increases. A new Monte Carlo method of free energy calculation, which does not rely on particle insertion is analyzed. The justification for the use of the method in the NVT ensemble is shown. The method is extended into the isothermal-isobaric ensemble where it is successfully applied to a variety of hard molecules. Analysis shows that the single particle sampling portion of the method should not be extended to the NPT ensemble. Isothermal phase diagrams for a variety of mixtures are determined by a combination of semi-grand ensemble simulation and orthogonal collocation integration. The semi-grand ensemble avoids problems of particle insertion that are encountered in some other widely used techniques. Orthogonal collocation allows the simulations to be run in parallel as opposed to stepwise integration techniques. The orthogonal collocation method is first studied numerically on an ideal system to demonstrate its superiority in suppressing error propagation. Next, Lennard-Jones mixtures, including some which form azeotropes, are examined and compared with prior works. Finally, three systems of real molecules, Krypton-Argon Methane-Ethane, and Ethane -Carbon Dioxide are simulated and compared with experimental results.

  11. Interfacial and transport properties of nanoconstrained inorganic and organic materials

    NASA Astrophysics Data System (ADS)

    Kocherlakota, Lakshmi Suhasini

    Nanoscale constraints impact the material properties of both organic and inorganic systems. The systems specifically studied here are (i) nanoconstrained polymeric systems, poly(l-trimethylsilyl-1-propyne) (PTMSP) and poly(ethylene oxide) (PEO) relevant to gas separation membranes (ii) Zwitterionic polymers poly(sulfobetaine methacrylate)(pSBMA), poly(carboxybetaine acrylamide) (pCBAA), and poly(oligo(ethylene glycol) methyl methacrylate) (PEGMA) brushes critical for reducing bio-fouling (iii) Surface properties of N-layer graphene sheets. Interfacial constraints in ultrathin poly(l-trimethylsilyl-1-propyne) (PTMSP) membranes yielded gas permeabilities and CO2/helium selectivities that exceed bulk PTMSP membrane transport properties by up to three-fold for membranes of submicrometer thickness. Indicative of a free volume increase, a molecular energetic mobility analysis (involving intrinsic friction analysis) revealed enhanced methyl side group mobilities in thin PTMSP membranes with maximum permeation, compared to bulk films. Aging studies conducted over the timescales relevant to the conducted experiments signify that the free volume states in the thin film membranes are highly unstable in the presence of sorbing gases such as CO2. To maintain this high free volume configuration of polymer while improving the temporal stability an "inverse" architecture to conventional polymer nanocomposites was investigated, in which the polymer phase of PTMSP and PEO were interfacially and dimensionally constrained in nanoporous anodic aluminum oxide (AAO) membranes. While with this architecture the benefits of nanocomposite and ultrathin film membranes of PTMSP could be reproduced and improved upon, also the temporal stability could be enhanced substantially. The PEO-AAO nanocomposite membranes also revealed improved gas selectivity properties of CO2 over helium. In the thermal transition studies of zwitterionic pSBMA brushes a reversible critical transition temperature of 60 °C in 27 nm films was evidenced, indicating changes in molecular conformations with respect to the temperature. pCBAA and pEGMA brushes displayed no thermal transitions, suggesting that the molecular conformations of these systems were insensitive to temperature in the investigated regime. The surface energy of a dimensionally constrained inorganic system, graphene is studied via local Hamaker constant determination from a single graphene layer to bulk graphite. Intrinsic friction scattering analysis of dipolar fluctuations of the Van der Waals interactions between an atomic force microscopy tip and graphene layers revealed a four-fold reduction in the surface energy from bulk HOPG to graphene. A numerical analysis based on electron energy loss spectroscopy confirms quantitatively the results.

  12. Scattering polarization by anisotropic biomolecules.

    PubMed

    Nee, Tsu-Wei; Nee, Soe-Mie F; Yang, De-Ming; Huang, Yu-Shan

    2008-05-01

    The full polarization properties of anisotropic biomolecule optical scattering are investigated theoretically. By using a simple ellipsoid model of a single biomolecule, the scattering fields and Mueller matrices are derived from fundamental electromagnetism theory. The energy of scattered photons is not necessarily equal to that of the incident laser beam. This theory can be generally applied to the experiments of fluorescence, Raman scattering, and second-harmonic generation. Fitting of a single tetramethylrhodamine-labeled lipid molecule's anisotropic imaging experiment is demonstrated. This theory has provided a fundamental simulation analysis tool of understanding and developing the optical polarimetric sensing science and technology of the anisotropic biomolecules and biomedium. The medium dielectric constant of the model ellipsoid provides a theoretic background for correlating the optical polarization properties of a biomolecule to its microscopic electronic structure. PMID:18451909

  13. Oxygen nonstoichiometry and transport properties of strontium substituted lanthanum ferrite

    SciTech Connect

    Sogaard, Martin [Fuel Cells and Solid State Chemistry Department, Riso National Laboratory, Frederiksborgvej 399, DK-4000 Roskilde (Denmark)], E-mail: martin.soegaard@risoe.dk; Vang Hendriksen, Peter [Fuel Cells and Solid State Chemistry Department, Riso National Laboratory, Frederiksborgvej 399, DK-4000 Roskilde (Denmark); Mogensen, Mogens [Fuel Cells and Solid State Chemistry Department, Riso National Laboratory, Frederiksborgvej 399, DK-4000 Roskilde (Denmark)

    2007-04-15

    This study presents an investigation of the properties of (La{sub 0.6}Sr{sub 0.4}){sub 0.99}FeO{sub 3-{delta}} (LSF40) covering thermomechanical properties, oxygen nonstoichiometry and electronic and ionic conductivity. Finally, oxygen permeation experiments have been carried out and the oxygen flux has been determined as a function of temperature and driving force. The electrical conductivity was measured using a 4 probe method. It is shown that the electrical conductivity is a function of the charge carrier concentration only. The electron hole mobility is found to decrease with increasing charge carrier concentration in agreement with recent literature. Values of the chemical diffusion coefficient, D{sub Chem}, and the surface exchange coefficient, k{sub Ex}, have been determined using electrical conductivity relaxation. At 800 deg. CD{sub Chem} is determined to be 6.2x10{sup -6}cm{sup 2}s{sup -1} with an activation energy of 137kJmol{sup -1}. The surface exchange coefficient is found to decrease with decreasing oxygen partial pressure. Oxygen permeation experiments were carried out. The flux through a membrane placed between air and wet hydrogen/nitrogen was J{sub O{sub 2}}{approx}1.8x10{sup -6}molcm{sup -2}s{sup -1} (corresponding to an equivalent electrical current density of 670mAcm{sup -2}). The oxygen permeation measurements are successfully interpreted based on the oxygen nonstoichiometry data and the determined transport parameters.

  14. Experimental investigation of electron transport properties of gallium nitride nanowires

    NASA Astrophysics Data System (ADS)

    Motayed, Abhishek; Davydov, Albert V.; Mohammad, S. N.; Melngailis, John

    2008-07-01

    We report transport properties of gallium nitride (GaN) nanowires grown using direct reaction of ammonia and gallium vapor. Reliable devices, such as four-terminal resistivity measuring structures and field-effect transistors, were realized by dielectrophoretically aligning the nanowires on an oxidized silicon substrate and subsequently applying standard microfabrication techniques. Room-temperature resistivity in the range of (1.0-6.2)×10-2 ? cm was obtained for the nanowires with diameters ranging from 200 to 90 nm. Temperature-dependent resistivity and mobility measurements indicated the possible sources for the n-type conductivity and high background charge carrier concentration in these nanowires. Specific contact resistance in the range of 5.0×10-5 ? cm2 was extracted for Ti/Al/Ti/Au metal contacts to GaN nanowires. Significant reduction in the activation energy of the dopants at low temperatures (<200 K) was observed in the temperature-dependent resistivity measurement of these nanowires, which is linked to the onset of degeneracy. Temperature-dependent field-effect mobility measurements indicated that the ionized impurity scattering is the dominant mechanism in these nanowires at all temperatures.

  15. Magnetic and transport properties of PrRhSi3.

    PubMed

    Anand, V K; Adroja, D T; Hillier, A D

    2013-05-15

    We have investigated the magnetic and transport properties of a noncentrosymmetric compound PrRhSi3 by dc magnetic susceptibility ?(T), isothermal magnetization M(H), thermoremanent magnetization M(t), specific heat Cp(T), electrical resistivity ?(T,H) and muon spin relaxation (?SR) measurements. At low fields ?(T) shows two anomalies near 15 and 7 K with an irreversibility between ZFC and FC data below 15 K. In contrast, no anomaly is observed in Cp(T) or ?(T) data. M(H) data at 2 K exhibit very sharp increase below 0.5 T and a weak hysteresis. M(t) exhibits very slow relaxation, typical for a spin-glass system. Even though the absence of any anomaly in Cp(T) is consistent with the spin-glass type behavior, there is no obvious origin of spin-glass behavior in this structurally well ordered compound. The crystal electric field (CEF) analysis of Cp(T) data indicates a CEF-split singlet ground state lying below a doublet at 81(1) K and a quasi-triplet at 152(2) K. The ?(T) data indicate a metallic behavior, and ?(H) exhibits a very high positive magnetoresistance, as high as ~300% in 9 T at 2 K. No long range magnetic order or spin-glass behavior was detected in a ?SR experiment down to 1.2 K. PMID:23604428

  16. Valuation of utility and transportation property: a classified annotated bibliography

    SciTech Connect

    Clatanoff, R.M.

    1983-01-01

    A selected, classified, annotated bibliography is presented with 270 references to published works on the appraisal and assessment of utilities and transportation companies. It does not include works on the taxation of these enterprises unless material on valuation is included, and it does not include works on valuation unless material on these enterprises is included. The bibliography does not include references to articles on current events; for these the reader should consult such publications as Engineering News-Record; Public Utilities Fortnightly; Commerce Clearing House's State Tax Review (for news of statutory law and regulations), and the Assessment and Valuation Legal Reporter (for news of case law). Works selected for inclusion were chosen primarily from those published since 1970. Charles F. Conlon's 1971 paper, The Unitary Approach to the Appraisal of Public Utility Property for Tax Purposes, concludes with a classified bibliography of publications up to 1970. Certain major pre-1970 works, which readers would expecte to find in a bibliography on this topic, are listed here, as are all the references from an earlier IAAO bibliography (which this one supersedes).

  17. Strain dependence of the heat transport properties of graphene nanoribbons.

    PubMed

    Yeo, Pei Shan Emmeline; Loh, Kian Ping; Gan, Chee Kwan

    2012-12-14

    Using a combination of accurate density-functional theory and a nonequilibrium Green's function method, we calculate the ballistic thermal conductance characteristics of tensile-strained armchair (AGNR) and zigzag (ZGNR) edge graphene nanoribbons, with widths between 3 and 50 ?. The optimized lateral lattice constants for AGNRs of different widths display a three-family behavior when the ribbons are grouped according to N modulo 3, where N represents the number of carbon atoms across the width of the ribbon. Two lowest-frequency out-of-plane acoustic modes play a decisive role in increasing the thermal conductance of AGNR-N at low temperatures. At high temperatures the effect of tensile strain is to reduce the thermal conductance of AGNR-N and ZGNR-N. These results could be explained by the changes in force constants in the in-plane and out-of-plane directions with the application of strain. This fundamental atomistic understanding of the heat transport in graphene nanoribbons paves a way to effect changes in their thermal properties via strain at various temperatures. PMID:23149343

  18. Anisotropic Electrical Properties of Epitaxial Hf-doped Bi4Ti3O12 Thin Films on (100)- and (111)-oriented SrTiO3 Substrates

    NASA Astrophysics Data System (ADS)

    Zhu, J.; Wang, X. P.; Luo, W. B.; Li, Y. R.

    Epitaxial thin films of (00l)- and (104)-oriented Bi4Ti3-xHfxO12(BTH) have been fabricated on (100)- and (111)-oriented SrTiO3 substrates with SrRuO3 bottom electrodes by pulsed laser deposition, respectively. X-ray diffraction scans revealed that a unique epitaxial relationship between film and substrate: BTH (001)//SrTiO3 (001); BTH [1-10]////SrTiO3 [100] is valid for both orientations, irrespective of their orientation. The strong dependences of ferroelectric properties on the film orientation were observed. The remanent polarization 2Pr is 45.6 ?C/cm2 for (104)-oriented BTH film, while 2Pr is 4.5 ?C/cm2 for (00l)-oriented BTH film. The anisotropic properties of BTH are similar to that of pure Bi4Ti3O12(BIT): the polarization vector of BTH films is close to the a axis, indicating that Hf substitution does not change the orientation dependence of electric properties in BIT.

  19. Mechanical identification of layer-specific properties of mouse carotid arteries using 3D-DIC and a hyperelastic anisotropic

    E-print Network

    Paris-Sud XI, Université de

    1 Mechanical identification of layer-specific properties of mouse carotid arteries using 3D;2 Mechanical identification of layer-specific properties of mouse carotid arteries using 3D arterial diseases; however determining mechanical properties of arteries remains a challenge. This paper

  20. Anisotropic magnetohydrodynamic spectral transfer in the diffusion approximation W. H. Matthaeus,1

    E-print Network

    Oughton, Sean

    Anisotropic magnetohydrodynamic spectral transfer in the diffusion approximation W. H. Matthaeus,1 2009 A theoretical model of spectral transfer for anisotropic magnetohydrodynamic MHD turbulence spectral transport closure to magnetohydrodynamics MHD in which anisotropy is in- duced by a large

  1. Enhancement of Red Electroluminescence from Device with Tetraphenylchlorin Doped into Hole-Transporting Material by Improving Electron Transporting Property

    Microsoft Academic Search

    Raghu Nath Bera; Youichi Sakakibara; Madoka Tokumoto; Kazuhiro Saito

    2002-01-01

    We have improved the performance of red-emitting organic electroluminescent devices in which tetraphenylchlorin (TPC) was doped into a hole-transporting material, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) by increasing the electron-transporting property of the device with optimized thicknesses of the hole-blocking layer of 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ) and the electron-transporting layer of tris(8-hydroxyquinoline) aluminum (Alq3). These devices emitted a good red band with a peak at approximately

  2. Evaluation of Baltic Sea transport properties using particle tracking

    NASA Astrophysics Data System (ADS)

    Dargahi, Bijan; Cvetkovic, Vladimir

    2014-05-01

    Particle tracking model (PTM) is an effective tool for quantifying transport properties of large water bodies such as the Baltic Sea. We have applied PTM to our fully calibrated and validated Baltic Sea 3D hydrodynamic model for a 10-years period (2000-9). One hundred particles were released at a constant rate during an initial 10-days period from all the Baltic Sea sub-basins, the major rivers, and the open boundary in the Arkona Basin. In each basin, the particles were released at two different depths corresponding to the deep water and middle water layers. The objectives of the PTM simulations were to analyse the intra-exchange processes between the Baltic Sea basins and to estimate the arrival times and the paths of particles released from the rivers. The novel contribution of this study is determining the paths and arrival times of deeper water masses rather than the surface masses. Advective and diffusive transport processes in the Bornholm and Arkona basins are both driven by the interacting flows of the northern basins of the Baltic Sea and the North Sea. Particles released from Arkona basin flows northwards along the Stople Channel. The Gotland basins are the major contributors to the exchange process in the Baltic Sea. We find high values of the advection ratio, indicative of a forced advective transport process. The Bay of Gdansk is probably the most vulnerable region in the Baltic Sea. This is despite the fact that the main exchanging basins are the Bornholm Sea and the Easter Gotland Basin. The main reason is the intensive supply of the particles from the northern basins that normally take about 3000 days to reach the Bay of Gdansk. The process maintains a high level of particle concentration (90%) along its coastlines even after the 10-years period. Comparing the particle paths in the Western and Eastern Gotland basins two interesting features were found. Particles travelled in all four directions in the former basin and the middle layer particles reached the surface flow in the eastern most part of the Gulf of Finland. This implies mixing of deeper waters of the Western Gotland Basin with the sub-surface waters of the Gulf of Finland. We believe strong density current and upwelling processes drive the process. Surprisingly, the two rivers Narva and Venta have the highest spreading in comparison to other rivers. This is despite the relatively low flow discharge values that rules out a correlation between high moment flows and the extent of spreading. We found the flow discharge to be correlated with the advection lengths. The lack of any correlation for the other rivers, signifies different hydrodynamic characteristics among the basins. The results of our PTM study may be used for a general environmental assessment in terms of sensitivity of the various coastlines and rick to the release of contaminants in the Baltic Sea.

  3. EquilTheTA: Thermodynamic and transport properties of complex equilibrium plasmas

    SciTech Connect

    Colonna, G.; D'Angola, A. [CNR-IMIP Bari, via Amendola 122/D - 70126 Bari (Italy); DIFA, Universita della Basilicata, via dell'Ateneo Lucano, 1085100 Potenza (Italy)

    2012-11-27

    EquilTheTA (EQUILibrium for plasma THErmodynamics and Transport Applications) is a web-based software which calculates chemical equilibrium product concentrations from any set of reactants and determines thermodynamic and transport properties for the product mixture in wide temperature and pressure ranges. The program calculates chemical equilibrium by using a hierarchical approach, thermodynamic properties and transport coefficients starting from recent and accurate databases of atomic and molecular energy levels and collision integrals. In the calculations, Debye length and cut-off are consistently updated and virial corrections (up to third order) can be considered. Transport coefficients are calculated by using high order approximations of the Chapman-Enskog method.

  4. Temperature-dependent thermal transport properties of Archean rocks

    NASA Astrophysics Data System (ADS)

    Merriman, J. D.; Hofmeister, A.; Nabelek, P. I.; Whittington, A. G.; Benn, K.

    2010-12-01

    Heat transfer controls the rates and styles of fundamental planetary processes including the formation and differentiation of planetary crust, the rheological behavior of the lithosphere and asthenosphere, and the secular cooling of the Earth following its accretion. The Earth's first few hundred million years were characterized by much higher radiogenic heat production and heat flow out of the mantle than seen today, and early continental crust was comprised of rock associations such as granite-greenstone belts and intrusions of tonalite-trondhjemite-granodiorite (TTG). The composition of Archean crustal rocks, and likely variations in radiogenic heat production, have been well documented in past studies. However, the thermal transport properties of these rocks, thermal diffusivity D and thermal conductivity (k=D?CP, where ? is density and CP is isobaric heat capacity), are less well constrained, especially at high temperatures. High temperature measurements of D and k are few, and contact methods may suffer from a combination of imperfect physical contacts and unwanted direct radiative transfer. Using the laser flash analysis (LFA) technique, we determined D of a suite of 14 granite-greenstone and TTG rocks including samples from the Abitibi and Barberton greenstone belts, over a range of crustal temperatures at atmospheric pressure. Dehydration and devolatilization of amphiboles and biotite prevented direct measurement of D for most samples above ~750K, however previous studies of T-dependent D have shown that values of bulk rock diffusivity asymptotically approach a constant value above the ?-? quartz transition (846K). Our measurements yielded a range of D at room temperature from ~3.8 mm2 s-1 for banded iron to ~1 mm2 s-1 for granodiorite. D for all samples decreases with increasing T, and the range of D for the suite narrows to ~0.45 and 0.70 mm2 s-1 for granodiorite and tholeiite basalt respectively by ~1000K. Density of each sample was measured using the Archimedean method and was assumed ~constant over crustal P and T. The T-dependence of CP was calculated from modal mineralogy and published CP data for mineral end-members. Calculated values of k ranged from ~5.7 Wm-1k-1 for a quartz-rich (~38%) tonalite to ~1.7 Wm-1k-1 for a quartz-free syenite at 280K. The range of k at higher temperatures is less restricted than D, as a result of the general increase in CP at higher temperatures and varied between ~2.5 Wm-1k-1 for amphibolite and ~1.5 Wm-1k-1 for syenite. These results show that the T-dependence of D and k cannot be ignored, and variations in thermal transport properties between different rock types, and for a single rock type at different temperatures, may be more important than differences in their radiogenic heat production. This has important implications for the geothermal gradient of Archean crust, its rheological behavior and potential for partial melting.

  5. Decoupling Mechanical and Ion Transport Properties in Polymer Electrolyte Membranes

    NASA Astrophysics Data System (ADS)

    McIntosh, Lucas D.

    Polymer electrolytes are mixtures of a polar polymer and salt, in which the polymer replaces small molecule solvents and provides a dielectric medium so that ions can dissociate and migrate under the influence of an external electric field. Beginning in the 1970s, research in polymer electrolytes has been primarily motivated by their promise to advance electrochemical energy storage and conversion devices, such as lithium ion batteries, flexible organic solar cells, and anhydrous fuel cells. In particular, polymer electrolyte membranes (PEMs) can improve both safety and energy density by eliminating small molecule, volatile solvents and enabling an all-solid-state design of electrochemical cells. The outstanding challenge in the field of polymer electrolytes is to maximize ionic conductivity while simultaneously addressing orthogonal mechanical properties, such as modulus, fracture toughness, or high temperature creep resistance. The crux of the challenge is that flexible, polar polymers best-suited for polymer electrolytes (e.g., poly(ethylene oxide)) offer little in the way of mechanical robustness. Similarly, polymers typically associated with superior mechanical performance (e.g., poly(methyl methacrylate)) slow ion transport due to their glassy polymer matrix. The design strategy is therefore to employ structured electrolytes that exhibit distinct conducting and mechanically robust phases on length scales of tens of nanometers. This thesis reports a remarkably simple, yet versatile synthetic strategy---termed polymerization-induced phase separation, or PIPS---to prepare PEMs exhibiting an unprecedented combination of both high conductivity and high modulus. This performance is enabled by co-continuous, isotropic networks of poly(ethylene oxide)/ionic liquid and highly crosslinked polystyrene. A suite of in situ, time-resolved experiments were performed to investigate the mechanism by which this network morphology forms, and it appears to be tied to the disordered structure observed in diblock polymer melts near the order-disorder transition. In the resulting solid PEMs, the conductivity and modulus are both high, exceeding the 1 mS/cm and approaching the 1 GPa metrics, respectively, often cited for lithium-metal batteries. In the final chapter, an alternative synthetic route to generate nanostructured PEMs is presented. This strategy relies on the formation of a thermodynamically stable network morphology exhibited by a triblock terpolymer prepared with crosslinking moieties along the backbone. Although the mechanical properties of the resulting PEM are excellent, the conductivity is found to be somewhat limited by network defects that result from the solvent-casting procedure.

  6. High field transport properties of a bilayer graphene

    NASA Astrophysics Data System (ADS)

    Bhargavi, K. S.; Kubakaddi, S. S.

    2014-02-01

    The high electric field transport properties namely, hot electron energy loss rate P, momentum loss rate Q, electron temperature Te and drift velocity Vd are studied theoretically in a bilayer graphene (BLG) by employing the momentum and energy balance technique. P and Q are investigated as a function of Te by considering the electron interaction with the acoustic phonons (APs) and the surface polar phonons (SPPs). In the Bloch-Grüneisen regime P (Q) due to APs is ~Te4 (Te2.5), with a new feature of a kink appearing due to the chiral nature of the electrons. The predicted Te4 is consistent with the recent experimental observation of heat resistance (Yan et al. Nature Nanotechnology 3 (2012) 472 [35]). Hot phonon effect is taken into account for SPPs. A dip has been observed in the hot phonon distribution of SPPs, a new feature, which is not found in conventional two-dimensional electron gas, and this can be attributed to the chiral nature of the electrons. P (Q) due to SPPs is found to be dominant at about Te>150 (180) K for a lattice temperature T=4.2 K. It is observed that the hot phonon effect is found to reduce P and Q due to SPPs significantly. Te and Vd are calculated as a function of the electric field E by taking into account the additional channels for momentum relaxation due to Coulomb impurity (CI) and short-range disorder (SD). Te is found to increase with the increasing electric field and is significantly enhanced by the hot phonon effect. Low field Vd is found to be limited by CI, SD and APs and in the high field region it reaches a near saturation value. The hot phonon effect tends to reduce the value of Vd. The presence of disorders CI and SD reduces Vd significantly and in clean samples larger saturation velocity can be achieved at a relatively smaller E.

  7. Magnetic and magneto-transport properties in nanostructured materials

    NASA Astrophysics Data System (ADS)

    Yang, Fengyuan

    2001-08-01

    Magneto-transport, magnetic and structural properties of three nanostructured systems: (1) single-crystal bismuth films with and without antidot arrays made by electrodeposition, (2) epitaxial half-metallic CrO2 films made by chemical vapor deposition (CVD), and (3) exchange-coupled Co/FeMn/permalloy trilayers prepared by magnetron sputtering are presented. Single-crystal Bi thin films have been made by electrodeposition followed by suitable annealing. X-ray diffraction verifies that the films are trigonal axis oriented single-crystal films. High resolution transmission electron microscope reveals the expected six-fold symmetry of the atomic structure of Bi(001) films. These films exhibit very large magnetoresistance (MR) at both low temperature and room temperature, as well as strong anisotropy among the perpendicular, transverse, and longitudinal geometries. At very low temperature, the MR of Bi films shows Shubnikov-de Haas oscillations, further confirming the high quality of the films. Bi films with ordered antidot arrays patterned by optical lithography exhibit pronounced angular dependence in magnetoresistance, in agreement with theoretical calculations. X-ray diffraction studies of epitaxial CrO2 films, made by CVD on TiO2(100) substrates demonstrate single-crystal quality of the films. These films exhibit a strong uniaxial magnetocrystalline anisotropy with a unique switching behavior, which can be described by a simple model. Critical behavior of the CrO2 films, determined by magnetometry with the magnetic field along the uniaxial anisotropy axis, indicates that CrO2 is a Heisenberg ferromagnet with long-range interaction. Trilayers of permalloy/FeMn/Co with various thicknesses t AF of the antiferromagnetic FeMn layer prepared by magnetron sputtering have been designed to reveal the spin structure within FeMn. A spiraling spin structure has been observed in such trilayers.

  8. Spectral and transport properties of quantum wires with bond disorder

    NASA Astrophysics Data System (ADS)

    Altland, Alexander; Merkt, Rainer

    2001-07-01

    Systems with bond disorder are defined through lattice Hamiltonians that are of pure nearest neighbour hopping type, i.e., do not contain on-site contributions. They stand representative for the general family of disordered systems with chiral symmetries. Application of the Dorokhov-Mello-Pereyra-Kumar transfer matrix technique P.W. Brouwer et al. [Phys. Rev. Lett 81 (1998) 862; Phys. Rev. Lett. 84 (2000) 1913] has shown that both spectral and transport properties of quasi one-dimensional systems belonging to this category are highly unusual. Most notably, regimes with absence of exponential Anderson localization are observed, the single particle density of states exhibits singular structure in the vicinity of the band centre, and the manifestation of these phenomena depends in an apparently topological manner on the even- or oddness of the channel number. In this paper we re-consider the problem from the complementary perspective of the nonlinear ?-model. Relying on the standard analogy between one-dimensional statistical field theories and zero-dimensional quantum mechanics, we will relate the problem to the behaviour of a quantum point particle subject to an Aharonov-Bohm flux. We will build on this analogy to re-derive earlier DMPK results, identify a new class of even/odd staggering phenomena (now dependent on the total number of sites in the system) and trace back the anomalous behaviour of the bond disordered system to a simple physical mechanism, viz. the flux periodicity of the quantum Aharonov-Bohm system. We will also touch upon connections to the low energy physics of other lattice systems, notably disordered chiral systems in 0 and 2 dimensions and antiferromagnetic spin chains.

  9. Anisotropic evaluation of synthetic surgical meshes

    Microsoft Academic Search

    E. R. SaberskiS; S. B. Orenstein; Y. W. Novitsky

    2011-01-01

    Introduction  The material properties of meshes used in hernia repair contribute to the overall mechanical behavior of the repair. The anisotropic\\u000a potential of synthetic meshes, representing a difference in material properties (e.g., elasticity) in different material axes,\\u000a is not well defined to date. Haphazard orientation of anisotropic mesh material can contribute to inconsistent surgical outcomes.\\u000a We aimed to characterize and compare

  10. Effects of interlayer coupling on the magnetic and transport properties of superconducting multilayers and high-temperature superconductors

    SciTech Connect

    Gray, K.E.; Hettinger, J.D.; Kim, D.H.

    1994-06-01

    The effect of interlayer coupling on the transport properties and dissipation in a magnetic field is reviewed for superconducting multilayers including highly-anisotropic high-temperature superconductors (HTS). For the applied field parallel to the superconducting layers the absence of any Lorentz-force dependence of the dissipation leads to an explanation other than flux motion. This is consistent with a Josephson junction dissipation which dominates flux motion of the insulating regions between layers. However, in is seen to cross over from phase slips at Josephson junctions to depinning of vortices from the external field at high fields and temperatures. For fields perpendicular to the superconducting layers the much greater resistive broadening in HTS is due to dissipation by thermally-activated flux motion, consistent with a lack of intrinsic pinning. We show experimental evidence that the associated flux motion occurs as a result of a crossover from three dimensional (3D) vortex lines to 2D independent pancake-like vortices, residing in the Cu-O layers. This 3D to 2D crossover occurs after k{sub B}T exceeds the Josephson coupling energy.

  11. Effects of proximity to an electronic topological transition on normal-state transport properties of the high-Tc superconductors

    NASA Astrophysics Data System (ADS)

    Angilella, G. G.; Pucci, R.; Varlamov, A. A.; Onufrieva, F.

    2003-04-01

    Within the time-dependent Ginzburg-Landau theory, the effects of the superconducting fluctuations on the transport properties above the critical temperature are characterized by a nonzero imaginary part of the relaxation rate ? of the order parameter. Here, we evaluate Im ? for an anisotropic dispersion relation typical of the high-Tc cuprate superconductors (HTS’s), characterized by a proximity to an electronic topological transition (ETT). We find that Im ? abruptly changes sign at the ETT as a function of doping, in agreement with the universal behavior of the HTS’s. We also find that an increase of the in-plane anisotropy, as is given by a nonzero value of the next-nearest to nearest hopping ratio r=t'/t, increases the value of |Im ?| close to the ETT, as well as its singular behavior at low temperature, therefore enhancing the effect of superconducting fluctuations. Such a result is in qualitative agreement with the available data for the excess Hall conductivity for several cuprates and cuprate superlattices.

  12. Structure and Anisotropic Properties of BaFe2-xNixAs2 (x = 0, 1, and 2) Single Crystals

    SciTech Connect

    Safa-Sefat, Athena [ORNL; Jin, Rongying [ORNL; McGuire, Michael A [ORNL; Sales, Brian C [ORNL; Mandrus, David [ORNL; Ronning, F. [Los Alamos National Laboratory (LANL); Bauer, E D [Los Alamos National Laboratory (LANL); Mozharivskyj, Yurij [McMaster University

    2009-01-01

    The crystal structure, anisotropic electrical resistivity and magnetic susceptibility, as well as specific heat results from single crystals of BaFe2As2, BaNi2As2, and BaFeNiAs2 are surveyed. BaFe2As2 properties demonstrate the equivalence of C(T), Fisher s d(?T)/dT, and d?/dT results in determining the antiferromagnetic transition at TN = 132(1) K. BaNi2As2 shows a structural phase transition from a high-temperature tetragonal phase to a low-temperature triclinic (P?) phase at T0 = 131 K. The superconducting critical temperature for BaNi2As2 is well below T0 and at Tc = 0.69 K. BaFeNiAs2 does not show any sign of superconductivity to 0.4 K and exhibits properties similar to BaCo2As2, a renormalized paramagnetic metal.

  13. Effect of antiphase boundaries on electrical transport properties of Fe3O4 nanostructures

    NASA Astrophysics Data System (ADS)

    Li, Hongliang; Wu, Yihong; Guo, Zaibing; Wang, Shijie; Teo, Kie Leong; Veres, Teodor

    2005-06-01

    Fe3O4 nanowires have been fabricated based on Fe3O4 thin films grown on ?-Al2O3 (0001) substrates using the hard mask and ion milling technique. Compared with thin films, the Fe3O4 nanowire exhibits a slightly sharper Verwey transition but pronounced anisotropic magnetoresistance properties in the film plane at low magnetic field. Detailed bias-dependence study of both the conductance and magnetoresistance curves for both the thin films and nanowires suggests that the electrical conduction in magnetite near and above the Verwey transition temperature is dominated by a tunneling mechanism across antiphase boundaries.

  14. Hydraulic Conductivity Distributions for Anisotropic Systems and Application to Tc Transport at the U.S. Department of Energy Hanford Site

    SciTech Connect

    Hunt, A. G.

    2006-01-06

    Abstract: At the United States Department of Energy Hanford Site a spill of radioactive Technetium has been migrating horizontally in the vadose zone rather than flowing vertically to the water table. This result has been interpreted as being due to horizontal anisotropy in the hydraulic conductivity, K, (a tendency for fluids to migrate more easily in the horizontal direction) due to high horizontal connectivity of sedimentary deposits with a tendency for larger values of K. Such layers have larger components of silt and clay than the predominantly sandy soils at the Hanford site. It is generally accepted that effects of such anisotropy tend to be greater at smaller length scales, probably because of the lack of perfect correlations at large length scales. It has also been suggested that this anisotropy in K is maximized under relatively dry conditions when finer soils (with smaller pores) trap moisture more effectively than sands and gravels. The random component of the distribution of the Hanford flood deposits requires a probabilistic framework for the calculation of K. The work on this project had two main components: 1) to use continuum percolation theory applied to random fractal models to produce a general framework for calculating distributions of K under anisotropic conditions and as a function of system scale, 2) to apply the scheme for calculation to the Hanford site. The results of the general calculation (submitted for publication in Philosophical Magazine) are that the mean horizontal and vertical K values become equal in the limit of large system size (in agreement with general perception above) while the distributions of K values cause significant overlap of expected experimental values of K in the vertical and horizontal directions already at intermediate length scales. In order to make these calculation specific to the Hanford site, however, values of the appropriate length scales to describe the Hanford subsurface as well as to describe the maximum anisotropy in K (largest ratio of horizontal to vertical values) must be provided. The data analyzed so far (received from Pacific Northwest National Laboratory Researchers, Dr. Glendon Gee and Dr. Mark Rockhold) has suggested that the majority of the finer soils in the Hanford subsurface have particularly low values of K at low moisture contents rather than particularly large values as expected by most researchers. Preliminary results suggest that about 50% of the Hanford Site subsurface may contain soils which preferentially retain water under dry conditions, however, only about 20% of these appear to be highly conductive as well. Thus only about 10% of the Hanford subsurface may actually contain soil which not only retains water preferentially under generally dry conditions, but which also has unusually high hydraulic conductivity. If this is the case, then the argument that such highly conductive regions may tend to be connected, even for short distances in the horizontal direction, may fall apart. So several alternate hypotheses have to be considered: 1) that the very small proportion (ca. 10%) of soils which retain water and are highly conductive is sufficient to percolate, even though typical percolation probabilities tend to be 15% or higher, 2) the subset of soils analyzed (from the DOE sponsored Vadose Zone Transport Study Site) is not a representative sample, 3) the horizontal transport is occurring at higher moisture contents. Further research on this particular aspect is thus required, and will be performed in the summer of 2006.

  15. Anisotropically structured magnetic aerogel monoliths

    NASA Astrophysics Data System (ADS)

    Heiligtag, Florian J.; Airaghi Leccardi, Marta J. I.; Erdem, Derya; Süess, Martin J.; Niederberger, Markus

    2014-10-01

    Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. Electronic supplementary information (ESI) available: Digital photographs of dispersions and gels with different water-to-ethanol ratios; magnetic measurements of an anatase aerogel containing 0.25 mol% Fe3O4 nanoparticles; XRD patterns of the iron oxide and titania nanoparticles. See DOI: 10.1039/c4nr04694c

  16. Anisotropic Transport of Electrons in a Novel FET Channel with Chains of InGaAs Nano-Islands Embedded along Quasi-Periodic Multi-Atomic Steps on Vicinal (111)B GaAs

    SciTech Connect

    Akiyama, Y.; Kawazu, T. [National Institute for Materials Science, Tsukuba-shi, Ibaraki 305-0047 (Japan); IIS, University of Tokyo, Meguro-ku, Tokyo 153-8505 (Japan); Noda, T. [National Institute for Materials Science, Tsukuba-shi, Ibaraki 305-0047 (Japan); Sakaki, H. [National Institute for Materials Science, Tsukuba-shi, Ibaraki 305-0047 (Japan); IIS, University of Tokyo, Meguro-ku, Tokyo 153-8505 (Japan); Toyota Technological Institute, Tempaku-ku, Nagoya 468-8511 (Japan)

    2010-01-04

    We have studied electron transport in n-AlGaAs/GaAs heterojunction FET channels, in which chains of InGaAs nano-islands are embedded along quasi-periodic steps. By using two samples, conductance G{sub para}(V{sub g}) parallel to the steps and G{sub perp}(V{sub g}) perpendicular to them were measured at 80 K as functions of gate voltage V{sub g}. At sufficiently high V{sub g}, G{sub para} at 80 K is several times as high as G{sub perp}, which manifests the anisotropic two-dimensional transport of electrons. When V{sub g} is reduced to -0.7 V, G{sub perp} almost vanishes, while {sub Gpara} stays sizable unless V{sub g} is set below -0.8 V. These results indicate that 'inter-chain' barriers play stronger roles than 'intra-chain' barriers.

  17. The statistical properties of the city transport in Cuernavaca (Mexico) and Random matrix ensembles

    E-print Network

    M. Krbalek; P. Seba

    2000-01-11

    We analyze statistical properties of the city bus transport in Cuernavaca (Mexico) and show that the bus arrivals display probability distributions conforming those given by the Unitary Ensemble of random matrices.

  18. Transport properties of high-temperature air in a magnetic field

    SciTech Connect

    Bruno, D. [Institute of Inorganic Methodologies and Plasmas, CNR, 70126 Bari (Italy); Capitelli, M.; Catalfamo, C. [Department of Chemistry, University of Bari, 70126 Bari (Italy); Giordano, D. [Aerothermodynamics Section, ESA-ESTEC, 2200 AG Noordwijk (Netherlands)

    2011-01-15

    Transport properties of equilibrium air plasmas in a magnetic field are calculated with the Chapman-Enskog method. The range considered for the temperature is [50-50 000] K and for the magnetic induction is [0-300] T.

  19. Free approximation of transport properties in organic system using Stochastic Random Matrix Theory

    E-print Network

    Xie, Wanqin, S.M. Massachusetts Institute of Technology

    2014-01-01

    The proposed research is a study and application of Stochastic analysis- Random Matrix Theory(RMT) to fast calculate the transport properties of large static systems with relatively large disorder in mesoscopic size. As a ...

  20. Transport and optical properties of low-dimensional complex systems

    NASA Astrophysics Data System (ADS)

    Iurov, Andrii

    Over the last five years of my research work, I, my research was mainly concerned with certain crucial tunneling, transport and optical properties of novel low-dimensional graphitic and carbon-based materials as well as topological insulators. Both single-electron and many-body problems were addressed. We investigated the Dirac electrons transmission through a potential barrier in the presence of circularly polarized light. An anomalous photon-assisted enhanced transmission is predicted and explained in a comparison with the well-known Klein paradox. It is demonstrated that the perfect transmission for nearly-head-on collision in an infinite graphene is suppressed in gapped dressed states of electrons, which is further accompanied by shift of peaks as a function of the incident angle away from the head-on collision. We calculate the energy bands for graphene monolayers when electrons move through a periodic electrostatic potential in the presence of a uniform perpendicular magnetic field. We clearly demonstrate the quantum fractal nature of the energy bands at reasonably low magnetic fields. We present results for the energy bands as functions of both wave number and magnetic flux through the unit cells of the resulting moi?e superlattice. This feature is also observed at extremely high magnetic fields. We have discovered a novel feature in the plasmon excitations for a pair of Coulomb-coupled non-concentric spherical two-dimensional electron gases (S2DEGs). Our results show that the plasmon excitations for such pairs depend on the orientation with respect to the external electromagnetic probe field. The origin of this anisotropy of the inter-sphere Coulomb interaction is due to the directional asymmetry of the electrostatic coupling of electrons in excited states which depend on both the angular momentum quantum number L and its projection M on the axis of quantization taken as the probe E-field direction. Such an effect from the plasmon spatial correlation is expected to be experimentally observable by employing circularly-polarized light or a helical light beam for incidence. The S2DEG serves as a simple model for fullerenes as well as metallic dimers, when the energy bands are far apart. Magnetoplasmons in gapped graphene have been investigated and the exchange energy dependence on magnetic field is presented.

  1. Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes*

    E-print Network

    Brand, Paul H.

    Transport and Pharmacological Properties of Nine Different Human Na,K-ATPase Isozymes* (Received and is the pharmacological receptor for digitalis in man. Nine different human Na,K-ATPase isozymes, composed of 3 and isoforms, were expressed in Xe- nopus oocytes and were analyzed for their transport and pharmacological

  2. Molecular dynamics studies of transport properties and equation of state of supercritical fluids

    Microsoft Academic Search

    Obika C. Nwobi

    1998-01-01

    Many chemical propulsion systems operate with one or more of the reactants above the critical point in order to enhance their performance. Most of the computational fluid dynamics (CFD) methods used to predict these flows require accurate information on the transport properties and equation of state at these supercritical conditions. This work involves the determination of transport coefficients and equation

  3. Surface and Subsurface Solute Transport Properties at Row and Inter-Row Positions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although numerous studies have investigated the effects of crop production practices on soil water dynamics, not much information is available on the impact of row position on solute transport. A field experiment was carried out to evaluate surface and subsurface solute transport properties in plant...

  4. Characterisation and modelling of the transport properties in lithium battery gel electrolytes

    Microsoft Academic Search

    Peter Georén; Göran Lindbergh

    2004-01-01

    A recent development trend for rechargeable lithium batteries is the use of ternary gel electrolytes. The main advantage of the gels is the mechanical rigidity, which improves as the polymer content is increased. However, the transport properties deteriorate with increasing polymer amount. This dualistic optimisation problem has caused an increased interest in understanding the transport processes in gels, however no

  5. Mesoscale transport properties induced by near critical resistive pressure-gradient-driven turbulence in toroidal geometry

    E-print Network

    Martín-Solís, José Ramón

    Mesoscale transport properties induced by near critical resistive pressure diffusive equation for mesoscale tracer-particle transport. The indices of the fractional derivates a mesoscale regime. That is, for time scales above the fluctuation scales reaching to the trans- port scales

  6. Electrolytes: transport properties and non-equilibrium thermodynamics

    SciTech Connect

    Miller, D.G.

    1980-12-01

    This paper presents a review on the application of non-equilibrium thermodynamics to transport in electrolyte solutions, and some recent experimental work and results for mutual diffusion in electrolyte solutions.

  7. The phase diagram and transport properties for hydrogen-helium fluid planets

    NASA Technical Reports Server (NTRS)

    Stevenson, D. J.; Salpeter, E. E.

    1977-01-01

    The properties of pure hydrogen and helium are examined, taking into account metallic hydrogen, molecular hydrogen, and the molecular-metallic transition. Metallic hydrogen-helium mixtures are considered along with molecular hydrogen-helium mixtures, the total phase diagram, and minor constituents, including deuterium. The transport properties of the metallic and the molecular phase are also discussed, giving attention to electrical conductivity, thermal conductivity, viscosity, self-diffusion, interdiffusion, radiative opacity, and second-order transport coefficients.

  8. Modeling the transport and optical properties of smoke plumes from South American biomass burning

    Microsoft Academic Search

    R. I. Matichuk; P. R. Colarco; J. A. Smith; O. B. Toon

    2008-01-01

    This study investigates the transport and optical properties of smoke plumes from South American biomass burning by using an aerosol transport and microphysical model. In general, the model can reproduce the smoke aerosol optical properties observed by satellite and ground-based instruments during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) campaign. The simulated spatial

  9. Using a Flume to Demonstrate Fluid Properties and Sediment Transport

    NSDL National Science Digital Library

    Jill Singer

    A 20-foot long recirculating flume is used for a series of demonstrations designed to help students explore the principles of fluid dynamics and sediment transport. The design and construction of the flume and four demonstrations are described in the attached activity. The demonstrations build upon each other so that students have a chance to develop an understanding of sedimentary transport processes and the deposits they produce.

  10. Thermodynamic and transport properties of air/water mixtures

    NASA Technical Reports Server (NTRS)

    Fessler, T. E.

    1981-01-01

    Subroutine WETAIR calculates properties at nearly 1,500 K and 4,500 atmospheres. Necessary inputs are assigned values of combinations of density, pressure, temperature, and entropy. Interpolation of property tables obtains dry air and water (steam) properties, and simple mixing laws calculate properties of air/water mixture. WETAIR is used to test gas turbine engines and components operating in relatively humid air. Program is written in SFTRAN and FORTRAN.

  11. Properties of yeast Saccharomyces cerevisiae plasma membrane dicarboxylate transporter.

    PubMed

    Aliverdieva, D A; Mamaev, D V; Bondarenko, D I; Sholtz, K F

    2006-10-01

    Transport of succinate into Saccharomyces cerevisiae cells was determined using the endogenous coupled mitochondrial succinate oxidase system. The dependence of succinate oxidation rate on the substrate concentration was a curve with saturation. At neutral pH the K(m) value of the mitochondrial "succinate oxidase" was fivefold less than that of the cellular "succinate oxidase". O-Palmitoyl-L-malate, not penetrating across the plasma membrane, completely inhibited cell respiration in the presence of succinate but not glucose or pyruvate. The linear inhibition in Dixon plots indicates that the rate of succinate oxidation is limited by its transport across the plasmalemma. O-Palmitoyl-L-malate and L-malate were competitive inhibitors (the K(i) values were 6.6 +/- 1.3 microM and 17.5 +/- 1.1 mM, respectively). The rate of succinate transport was also competitively inhibited by the malonate derivative 2-undecyl malonate (K(i) = 7.8 +/- 1.2 microM) but not phosphate. Succinate transport across the plasma membrane of S. cerevisiae is not coupled with proton transport, but sodium ions are necessary. The plasma membrane of S. cerevisiae is established to have a carrier catalyzing the transport of dicarboxylates (succinate and possibly L-malate and malonate). PMID:17125465

  12. Colloquium: Structural, electronic, and transport properties of silicon nanowires

    E-print Network

    Wu, Zhigang

    429 C. Passivated nanowires 431 D. Mechanical properties of nanowires 433 III. Electronic Properties of carbon nanotubes CNTs reported in the beginning of the 1990s Iijima, 1991 . The reason is twofold structure of graphene Castro Neto et al., 2009 are such that the properties of the CNT depends critically

  13. Grooved organogel surfaces towards anisotropic sliding of water droplets.

    PubMed

    Zhang, Pengchao; Liu, Hongliang; Meng, Jingxin; Yang, Gao; Liu, Xueli; Wang, Shutao; Jiang, Lei

    2014-05-21

    Periodic micro-grooved organogel surfaces can easily realize the anisotropic sliding of water droplets attributing to the formed slippery water/oil/solid interface. Different from the existing anisotropic surfaces, this novel surface provides a versatile candidate for the anisotropic sliding of water droplets and might present a promising way for the easy manipulation of liquid droplets for water collection, liquid-directional transportation, and microfluidics. PMID:24610716

  14. Procedures for construction of anisotropic elastic plastic property closures for face-centered cubic polycrystals using first-order bounding relations

    NASA Astrophysics Data System (ADS)

    Proust, Gwénaëlle; Kalidindi, Surya R.

    2006-08-01

    Microstructure-sensitive design (MSD) is a novel mathematical framework that facilitates a rigorous consideration of the material microstructure as a continuous design variable in the engineering design enterprise [Adams, B.L., Henrie, A., Henrie, B., Lyon, M., Kalidindi, S.R., Garmestani, H., 2001. Microstructure-sensitive design of a compliant beam. J. Mech. Phys. Solids 49(8), 1639-1663; Adams, B.L., Lyon, M., Henrie, B., 2004. Microstructures by design: linear problems in elastic-plastic design. Int. J. Plasticity 20(8-9), 1577-1602; Kalidindi, S.R., Houskamp, J.R., Lyons, M., Adams, B.L., 2004. Microstructure sensitive design of an orthotropic plate subjected to tensile load. Int. J. Plasticity 20(8-9), 1561-1575]. MSD employs spectral representations of the local state distribution functions in describing the microstructure quantitatively, and these in turn enable development of invertible linkages between microstructure and effective properties using established homogenization (composite) theories. As a natural extension of the recent publications in MSD, we provide in this paper a detailed account of the methods that can be readily used by mechanical designers to construct first-order elastic-plastic property closures. The main focus in this paper is on the crystallographic texture (also called Orientation Distribution Function or ODF) as the main microstructural parameter controlling the elastic and yield properties of cubic (fcc and bcc) polycrystalline metals. The following specific advances are described in this paper: (i) derivation of rigorous first-order bounds for the off-diagonal terms of the effective elastic stiffness tensor and their incorporation in the MSD framework, (ii) delineation of the union of the property closures corresponding to both the upper and lower bound theories resulting in comprehensive first-order closures, (iii) development of generalized and readily usable expressions for effective anisotropic elastic-plastic properties that could be applied to all cubic polycrystals, and (iv) identification of the locations of readily available or easily processable ODFs (e.g. textures that are produced by rolling, drawing, etc.) on the property closures. It is anticipated that the advances communicated in this paper will make the mathematical framework of MSD highly accessible to the mechanical designers.

  15. Geochemical & Physical Aquifer Property Heterogeneity: A Multiscale Sedimentologic Approach to Reactive Solute Transport

    SciTech Connect

    Murray, Chris; Allen-King, Richelle; Weissmann, Gary

    2006-06-01

    This project is testing the hypothesis that sedimentary lithofacies determine the geochemical and physical hydrologic properties that control reactive solute transport (Figure 1). We are testing that hypothesis for one site, a portion of the saturated zone at the Hanford Site (Ringold Formation), and for a model solute, carbon tetrachloride (CT). The representative geochemical and physical aquifer properties selected for quantification in the proposed project are the properties that control CT transport: hydraulic conductivity (K) and reactivity (sorption distribution coefficient, Kd, and anaerobic transformation rate constant, kn). We are combining observations at outcrop analog sites (to measure lithofacies dimensions and statistical relations) with measurements from archived and fresh core samples (for geochemical experiments and to provide additional constraint to the stratigraphic model) from the Ringold Formation to place local-scale lithofacies successions, and their distinct hydrologic property distributions, into the basinal context, thus allowing us to estimate the spatial distributions of properties that control reactive solute transport in the subsurface.

  16. Pauli paramagnetic effects on mixed-state properties in a strongly anisotropic superconductor: Application to Sr2RuO4

    NASA Astrophysics Data System (ADS)

    Amano, Yuujirou; Ishihara, Masahiro; Ichioka, Masanori; Nakai, Noriyuki; Machida, Kazushige

    2015-04-01

    We study theoretically the mixed-state properties of a strong uniaxially anisotropic type-II superconductor with the Pauli paramagnetic effect, focusing on their behaviors when the magnetic field orientation is tilted from the conduction layer a b plane. On the basis of Eilenberger theory, we quantitatively estimate significant contributions of the Pauli paramagnetic effects on a variety of physical observables, including transverse and longitudinal components of the flux-line lattice form factors, magnetization curves, Sommerfeld coefficient, field distributions, and magnetic torques. We apply these studies to Sr2RuO4 and quantitatively explain several seemingly curious behaviors, including the Hc 2 suppression for the a b -plane direction, the larger anisotropy ratio and intensity found by the spin-flip small-angle neutron scattering, and the first-order transition observed recently in magnetocaloric, specific-heat, and magnetization measurements in a coherent and consistent manner. Those lead us to conclude that Sr2RuO4 is either a spin-singlet or a spin-triplet pairing with the d -vector components in the a b plane.

  17. The effect of electron induced hydrogenation of graphene on its electrical transport properties

    SciTech Connect

    Woo, Sung Oh [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States)] [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States); Teizer, Winfried [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States) [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States); WPI-Advanced Institute for Materials Research, Tohoku University, Sendai (Japan)

    2013-07-22

    We report a deterioration of the electrical transport properties of a graphene field effect transistor due to energetic electron irradiation on a stack of Poly Methyl Methacrylate (PMMA) on graphene (PMMA/graphene bilayer). Prior to electron irradiation, we observed that the PMMA layer on graphene does not deteriorate the carrier transport of graphene but improves its electrical properties instead. As a result of the electron irradiation on the PMMA/graphene bilayer, the Raman “D” band appears after removal of PMMA. We argue that the degradation of the transport behavior originates from the binding of hydrogen generated during the PMMA backbone secession process.

  18. Transport properties of novel molybdenum bronze oxide materials

    NASA Astrophysics Data System (ADS)

    Hagmann, Joseph; Le, Son; Schneemeyer, Lynn; Olsen, Patti; Siegrist, Theo; Richter, Curt; Seiler, David

    2015-03-01

    Reduced ternary molybdenum oxides, or bronzes, offer an attractive materials platform to study a wide variety of remarkable physical phenomena, including charge density waves and superconductivity, in a system with highly varied structural chemistry. Interesting electronic behaviors in these materials arise from the strong hybridization of the 4d states of high-valent Mo with O p orbitals (conditions amenable to itinerancy) and reduced dimensionality arising from ordered O vacancies. This study aims to demonstrate the transport phenomena in a series of novel molybdenum bronze materials, including the new electrochemically-grown molybdenum bronzes, K3Li3Mo15O47, and the rare earth molybdenum bronze, HoMo16O44, and relate these behaviors to their experimentally-characterized structures. Dependence of the transport behavior on numerous experimental parameters, including temperature, magnetic field, drive voltage and drive current, and gate voltage, is presented to fully reveal charge carrier transport in these materials.

  19. Functional properties of ion channels and transporters in tumour vascularization

    PubMed Central

    Fiorio Pla, Alessandra; Munaron, Luca

    2014-01-01

    Vascularization is crucial for solid tumour growth and invasion, providing metabolic support and sustaining metastatic dissemination. It is now accepted that ion channels and transporters play a significant role in driving the cancer growth at all stages. They may represent novel therapeutic, diagnostic and prognostic targets for anti-cancer therapies. On the other hand, although the expression and role of ion channels and transporters in the vascular endothelium is well recognized and subject of recent reviews, only recently has their involvement in tumour vascularization been recognized. Here, we review the current literature on ion channels and transporters directly involved in the angiogenic process. Particular interest will be focused on tumour angiogenesis in vivo as well as in the different steps that drive this process in vitro, such as endothelial cell proliferation, migration, adhesion and tubulogenesis. Moreover, we compare the ‘transportome’ system of tumour vascular network with the physiological one. PMID:24493751

  20. Transport properties of dense deuterium-tritium plasmas.

    PubMed

    Wang, Cong; Long, Yao; He, Xian-Tu; Wu, Jun-Feng; Ye, Wen-Hua; Zhang, Ping

    2013-07-01

    Consistent descriptions of the equation of states and information about the transport coefficients of the deuterium-tritium mixture are demonstrated through quantum molecular dynamic (QMD) simulations (up to a density of 600 g/cm(3) and a temperature of 10(4) eV). Diffusion coefficients and viscosity are compared to the one-component plasma model in different regimes from the strong coupled to the kinetic one. Electronic and radiative transport coefficients, which are compared to models currently used in hydrodynamic simulations of inertial confinement fusion, are evaluated up to 800 eV. The Lorentz number is discussed from the highly degenerate to the intermediate region. One-dimensional hydrodynamic simulation results indicate that different temperature and density distributions are observed during the target implosion process by using the Spitzer model and ab initio transport coefficients. PMID:23944567

  1. Electronic and transport properties in geometrically disordered graphene antidot lattices

    NASA Astrophysics Data System (ADS)

    Fan, Zheyong; Uppstu, Andreas; Harju, Ari

    2015-03-01

    A graphene antidot lattice, created by a regular perforation of a graphene sheet, can exhibit a considerable band gap required by many electronics devices. However, deviations from perfect periodicity are always present in real experimental setups and can destroy the band gap. Our numerical simulations, using an efficient linear-scaling quantum transport simulation method implemented on graphics processing units, show that disorder that destroys the band gap can give rise to a transport gap caused by Anderson localization. The size of the defect-induced transport gap is found to be proportional to the radius of the antidots and inversely proportional to the square of the lattice periodicity. Furthermore, randomness in the positions of the antidots is found to be more detrimental than randomness in the antidot radius. The charge carrier mobilities are found to be very small compared to values found in pristine graphene, in accordance with recent experiments.

  2. Magnetic and transport properties of Sm7Rh3 single crystal

    NASA Astrophysics Data System (ADS)

    Tsutaoka, Takanori; Noguchi, Daisuke; Nakamori, Yuko; Nakamoto, Go; Kurisu, Makio

    2013-10-01

    A Sm7Rh3 single crystal with Th7Fe3-type hexagonal structure was grown by the Czochralski method. The magnetic and transport measurements revealed a uniaxial magnetocrystalline anisotropy in the magnetic susceptibility, magnetization and electrical resistivity. Sm7Rh3 was found to exhibit antiferromagnetic transition at TN=54.0 K and another magnetic transition at Tt=25.0 K. The specific heat data clearly showed the bulk nature of paramagnetic to ordered magnetic phase transition by the presence of a sharp peak at TN and a small anomaly at Tt. The paramagnetic susceptibility does not obey the Curie-Weiss law, attributing to the temperature independent Van Vleck contribution and Pauli paramagnetism of conduction electrons. Metamagnetic phase transitions were observed along the c-axis in the ordered states. The magnetic field H-temperature T phase diagram was constructed. Anisotropic paramagnetic electrical resistivity showed the small negative temperature coefficients.

  3. Thermodynamical and microscopic properties of turbulent transport in the edge plasma

    NASA Astrophysics Data System (ADS)

    Ghendrih, Ph; Norscini, C.; Hasenbeck, F.; Dif-Pradalier, G.; Abiteboul, J.; Cartier-Michaud, T.; Garbet, X.; Grandgirard, V.; Marandet, Y.; Sarazin, Y.; Tamain, P.; Zarzoso, D.

    2012-12-01

    Edge plasma turbulence modelled with 2D interchange is shown to exhibit convective transport at the microscale level. This transport property is related to avalanche like transport in such a flux-driven system. Correlation functions and source modulation are used to analyse the transport properties but do not allow one to recover the Fick law that must characterise the system at large scales. Coarse graining is then introduced to average out the small scales in order to recover the Fick law. One finds that the required space averaging is comparable to the system size while the time averaging is comparable to the confinement time. The system is then reduced to a single reservoir such that transport is characterised by a single scalar, either the diffusion coefficient of the Fick law or a characteristic evolution time constant.

  4. Anisotropic optical film embedded with cellulose nanowhisker.

    PubMed

    Kim, Dah Hee; Song, Young Seok

    2015-10-01

    We investigated anisotropic optical behaviors of composite films embedded with CNWs. To control the orientation of CNWs, elongation was applied to the composite film. Morphological and mechanical analyses of the specimens were carried out to examine the influence of the applied extension. The CNWs were found to be aligned in the elongated direction, yielding remarkable anisotropic microstructure and optical properties. As the applied elongation and CNW loading increased, the resulting degree of polarization and birefringence increased due to increased interactions between the embedded particles. This study suggests a way to prepare an anisotropic optical component with nanoparticles of which the microstructures, such as orientation and filler content, can be controlled. PMID:26076646

  5. Transport and Superconducting Properties of Rare Earth Magnetic Superconductors.

    NASA Astrophysics Data System (ADS)

    Zhou, Hu.

    An investigation of transport and magnetic properties of two groups of magnetic superconductors, tetragonal {cal R}Rh_4 B_4 and orthorhombic high -T_{rm c} oxides {cal R}Ba_2 Cu_3O_{7 -delta}, where {cal R} represents rare earth elements and Y, was carried out by means of electrical resistance and magnetic measurements. Single crystals of {cal R} Rh_4B_4 were successfully synthesized using a copper flux method for {cal R} = Y, Sm, Gd, Tb, Dy, Ho, Er, Tm, and Lu. Strong magnetic anisotropy was observed, with the easy magnetization direction along the c-axis for {cal R} = Tb, Dy, and Ho, and along the a-axis for { cal R} = Er and Tm. Theoretical calculations based on the crystalline electric field (CEF) effect gave excellent fits to the experimental data. Significant influence of the magnetic anisotropy on the upper critical magnetic field H_{rm C2} of the superconducting state was observed in { cal R}Rh_4B _4 with {cal R} = Y, Er, and Tm. Lower H_{rm C2} values were observed for these compounds in the easy directions. Electrical resistance and magnetic measurements on polycrystalline {cal R}Ba _2Cu_3O _{7-delta} samples for {cal R} = Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu established almost identical superconducting transition temperatures T_ {rm c} = 90 to 94 K for all these compounds (except for {cal R} = La which has T_{rm c} = 56 K), revealing apparent decoupling of the conduction electrons and the {cal R} magnetic ions. The upper critical magnetic fields H _{rm C2} of these high-T _{rm c} oxides are estimated by the WHHM theory to be of the order of megaoersteds at 0 Kelvin. In the normal state, the susceptibility of these compounds can be fitted to the sum of a Curie-Weiss term and a temperature independent term. The temperature and magnetic field dependences of J_{ rm c} obtained by this model are consistent with those obtained from direct current-voltage measurements. Fine powders of {cal R}Ba _2Cu_3O_ {7-delta} can be aligned in nonmagnetic epoxy by an applied magnetic field at room temperature due to the magnetic anisotropy of these compounds. The directions of the easy axes of {cal R}Ba_2Cu_3 O_{7-delta} are the same as those of {cal R} Rh_4B_4 for the same rare earth {cal R} , and there exists a good correspondence between the sign of the Stevens alpha_{ rm J} factor and the directions of the easy axes of both families of compounds. A preliminary analysis suggests this correlation reflects the similarity of the symmetries of the crystal structure at the rare earth site. (Abstract shortened with permission of author.).

  6. Temperature dependence of electronic transport property in ferroelectric polymer films

    NASA Astrophysics Data System (ADS)

    Zhao, X. L.; Wang, J. L.; Tian, B. B.; Liu, B. L.; Zou, Y. H.; Wang, X. D.; Sun, S.; Sun, J. L.; Meng, X. J.; Chu, J. H.

    2014-10-01

    The leakage current mechanism of ferroelectric copolymer of polyvinylidene fluoride with trifluoroethylene prepared by Langmuir-Blodgett was investigated in the temperature range from 100 K to 350 K. The electron as the dominant injected carrier was observed in the ferroelectric copolymer films. The transport mechanisms in copolymer strongly depend on the temperature and applied voltage. From 100 K to 200 K, Schottky emission dominates the conduction. With temperature increasing, the Frenkel-Poole emission instead of the Schottky emission to conduct the carrier transport. When the temperature gets to 260 K, the leakage current becomes independent of temperature, and the space charge limited current conduction was observed.

  7. Transport properties of dense deuterium-tritium plasmas

    E-print Network

    Wang, Cong; He, Xian-Tu; Zhang, Ping

    2012-01-01

    Consistent descriptions of the equation of states, and information about transport coefficients of deuterium-tritium mixture are demonstrated through quantum molecular dynamic (QMD) simulations (up to a density of 600 g/cm$^{3}$ and a temperature of $10^{4}$ eV). Diffusion coefficients and viscosity are compared with one component plasma model in different regimes from the strong coupled to the kinetic one. Electronic and radiative transport coefficients, which are compared with models currently used in hydrodynamic simulations of inertial confinement fusion, are evaluated up to 800 eV. The Lorentz number is also discussed from the highly degenerate to the intermediate region.

  8. Metal Vapors in Gas Tungsten Arcs: Part II. Theoretical Calculations of Transport Properties

    E-print Network

    Eagar, Thomas W.

    ( ( Metal Vapors in Gas Tungsten Arcs: Part II. Theoretical Calculations of Transport Properties G, if the presence of other metal vapors such as iron or manganese is also considered. It is therefore concluded, the effects of vapors emitted by the tungsten electrode may have a great effect on arc properties

  9. Calorimetric and transport properties of Zircalloy 2, Zircalloy 4, and Inconel 625

    Microsoft Academic Search

    K. D. Magli?; N. Lj. Perovi?; A. M. Stanimirovi?

    1994-01-01

    This paper presents the measurements and the results on thermal and electrical transport properties of three nuclear reactor cladding materials: Zircalloy 2, Zircalloy 4, and Inconel 625. Study of these materials constituted a part of the IAEA coordinated research program aimed at the generation and establishment of a reliable and complete database of the thermal properties of reactor materials. Measured

  10. Crystallinity and oxygen transport properties of PET bottle walls

    Microsoft Academic Search

    R. Y. F. Liu; Y. S. Hu; D. A. Schiraldi; A. Hiltner; E. Baer

    2004-01-01

    Oxygen transport was coupled with other methods to study the relationship of gas barrier to solid state structure in the PET blown bottle wall. Commercial 2-L carbonated soft drink bottles blown under different process conditions were studied. Crystallinity determinations from heat of melting, density, glycol trans fraction, and oxygen solubility were compared. The reasons for lack of correlation between conventional

  11. Transport Properties of the Dust Components in Weakly Ionized Plasma

    NASA Astrophysics Data System (ADS)

    Vaulina, O. S.; Adamovich, X. G.; Petrov, O. F.; Fortov, V. E.

    2008-09-01

    The experimental study of transport processes are presented for the dusty plasma in radio-frequency (RF-) capacitive discharge. Validity of the Langevin and Green-Kubo equations for the description of dynamics of dusty grains is verified. Experimental examination of the Einstein-Stokes relation between the viscosity and diffusion constants is carried out.

  12. Transport, vertical structure and radiative properties of dust events in southeast China determined from ground and space sensors

    E-print Network

    Li, Zhanqing

    Transport, vertical structure and radiative properties of dust events in southeast China determined March 2011 Accepted 11 April 2011 Keywords: Dust Transport Vertical structure Radiative properties March 14e17 and April 25e26 in 2009 where such dust events are uncommon. The transport behavior, spatio

  13. Basic knowledge on radiative and transport properties to begin in thermal plasmas modelling

    NASA Astrophysics Data System (ADS)

    Cressault, Y.

    2015-05-01

    This paper has for objectives to present the radiative and the transport properties for people beginning in thermal plasmas. The first section will briefly recall the equations defined in numerical models applied to thermal plasmas; the second section will particularly deal with the estimation of radiative losses; the third part will quickly present the thermodynamics properties; and the last part will concern the transport coefficients (thermal conductivity, viscosity and electrical conductivity of the gas or mixtures of gases). We shall conclude the paper with a discussion about the validity of these results the lack of data for some specific applications, and some perspectives concerning these properties for non-equilibrium thermal plasmas.

  14. Electronic transport properties of one dimensional lithium nanowire using density functional theory

    NASA Astrophysics Data System (ADS)

    Thakur, Anil; Kumar, Arun; Chandel, Surjeet; Ahluwalia, P. K.

    2015-05-01

    Single nanowire electrode devices are a unique platform for studying as energy storage devices. Lithium nanowire is of much importance in lithium ion batteries and therefore has received a great deal of attention in past few years. In this paper we investigated structural and electronic transport properties of Li nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Li nanowire are investigated theoretically. The calculations are performed in two steps: first an optimized geometry for Li nanowire is obtained using DFT calculations, and then the transport relations are obtained using NEGF approach. SIESTA and TranSIESTA simulation codes are used in the calculations correspondingly. The electrodes are chosen to be the same as the central region where transport is studied, eliminating current quantization effects due to contacts and focusing the electronic transport study to the intrinsic structure of the material. By varying chemical potential in the electrode regions, an I-V curve is traced which is in agreement with the predicted behavior. Agreement of bulk properties of Li with experimental values make the study of electronic and transport properties in lithium nanowires interesting because they are promising candidates as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Li nano wire indicates that Li nanowire can be used as an electrode device.

  15. Opto-electronic transport properties of graphene oxide based devices

    NASA Astrophysics Data System (ADS)

    Das, Poulomi; Ibrahim, Sk; Chakraborty, Koushik; Ghosh, Surajit; Pal, Tanusri

    2015-06-01

    Large area, solution-processed, graphene oxide (GO)nanocomposite based photo FET has been successfully fabricated. The device exhibits p-type charge transport characteristics in dark condition. Our measurements indicate that the transport characteristics are gate dependent and extremely sensitive to solar light. Photo current decay mechanism of GO is well explained and is associated with two phenomena: a) fast response process and b) slow response process. Slow response photo decay can be considered as the intrinsic phenomena which are present for both GO and reduced GO (r-GO), whereas the first response photo decay is controlled by the surface defect states. Demonstration of photo FET performance of GO thin film is a significant step forward in integrating these devices in various optoelectronic circuits.

  16. Thermodynamic and transport property modeling in super critical water

    E-print Network

    Kutney, Michael C. (Michael Charles)

    2005-01-01

    Supercritical water oxidation (SCWO) is a thermally-based, remediation and waste-treatment process that relies on unique property changes of water when water is heated and pressurized above its critical point. Above its ...

  17. Transport and mechanical properties of PET\\/ Rodrun 3000 blown films

    Microsoft Academic Search

    L. Di Maio; L. Incarnato; D. Acierno

    1996-01-01

    Blends of different ratios of poly(ethylene terephthalate) (PET) and a thermotropic liquid crystalline polymer (TLCP) composed of 40 mol% of polyethyleneterephthalate and 60 mol% of p-hydroxybenzoic acid (Rodrun 3000) have been processed in a laboratory-based film-blowing extrusion apparatus. Gas permeability measurements have been performed on the films in order to evaluate the effect of the mesophase on the transport behaviour

  18. Electron transport and emission properties of C(100)

    Microsoft Academic Search

    J. E. Yater; A. Shih; R. Abrams

    1997-01-01

    Secondary-electron-emission spectroscopy is used to probe the transport and emission of impact-ionized electrons in single-crystal diamond. By studying the emission from a cesiated C(100) surface having a negative electron affinity (NEA), the full energy spectrum of the internal electrons is revealed in the measured energy distribution data. The kinetic energy of the electrons and the height of the surface energy

  19. Transport properties of high temperature air in local thermodynamic equilibrium

    Microsoft Academic Search

    M. Capitelli; G. Colonna; C. Gorse

    2000-01-01

    :   In the paper new calculated transport coefficients of air in the temperature range 50-100 000 K are presented. The results\\u000a have been obtained by means of the perturbative Chapman-Enskog method, assuming that the plasma is in local thermodynamic\\u000a equilibrium (LTE). The calculations include viscosity, thermal conductivity, electric conductivity and multicomponent diffusion\\u000a coefficients. For the calculation, a recent compilation of

  20. Properties of yeast Saccharomyces cerevisiae plasma membrane dicarboxylate transporter

    Microsoft Academic Search

    D. A. Aliverdieva; D. V. Mamaev; D. I. Bondarenko; K. F. Sholtz

    2006-01-01

    Transport of succinate into Saccharomyces cerevisiae cells was determined using the endogenous coupled mitochondrial succinate oxidase system. The dependence of succinate oxidation\\u000a rate on the substrate concentration was a curve with saturation. At neutral pH the K\\u000a m value of the mitochondrial “succinate oxidase” was fivefold less than that of the cellular “succinate oxidase”. O-Palmitoyl-L-malate,\\u000a not penetrating across the plasma

  1. Non-linear transport equations : Properties deduced through transformation groups

    Microsoft Academic Search

    J. Gutierrez; A. Munier; J. Burgan; M. Feix

    Transport equations in configuration space (linear and non-linear heat equations) and in phase space (Vlasov-Poisson systems for plasmas, beams and gravitating gases) are considered in the frame of transformation group techniques. Both self-similar and more qeneral groups are introduced to find specially interesting solutions. Two kinds of results are obtained time evolution of given initial situations and systematic derivation of

  2. Oxygen nonstoichiometry and transport properties of strontium substituted lanthanum ferrite

    Microsoft Academic Search

    Martin Søgaard; Peter Vang Hendriksen; Mogens Mogensen

    2007-01-01

    This study presents an investigation of the properties of (La0.6Sr0.4)0.99FeO3-? (LSF40) covering thermomechanical properties, oxygen nonstoichiometry and electronic and ionic conductivity. Finally, oxygen permeation experiments have been carried out and the oxygen flux has been determined as a function of temperature and driving force.The electrical conductivity was measured using a 4 probe method. It is shown that the electrical conductivity

  3. Interface transport properties in ion-gated nano-sheets

    NASA Astrophysics Data System (ADS)

    Ye, J. T.; Zhang, Y. J.; Kasahara, Y.; Iwasa, Y.

    2013-07-01

    Recent advances in atomic-scale preparation of ultrathin nano-sheets and efficient field-effect gating mediated by movement of ions have provided a prolific paradigm for creating exotic states at interfaces of a new-type of device called electric-double layer transistors (EDLTs). We present a short review on these liquid/solid interfaces formed on nano-sheets prepared by micro cleaving a bulk layered single crystal, which can be electrostatically doped to a high carrier density of ˜1014 cm-2. Atomically flat surfaces prepared on various layered materials allowed ideal transport when they acted as transistor channels after accumulating dense carriers. The unique system combining these two advantages enabled observations of novel transport phenomena showing quantum phase transition of charge and spin states controlled by electric field. Examples include gate-induced metal-insulator transition, opening of new transport channels, and field-induced interface superconductivity, which present a rapidly growing field with emerging opportunities for science and technology.

  4. Coalescence of water films on carbon-based substrates: the role of the interfacial properties and anisotropic surface topography.

    PubMed

    Ren, Hongru; Li, Xiongying; Li, Hui; Zhang, Leining; Wu, Weikang

    2015-05-01

    Molecular dynamics (MD) simulations are carried out to study the coalescence of identical adjacent and nonadjacent water films on graphene (G), vertically or horizontally stacked carbon nanotube arrays (VCNTA and HCNTA respectively). We highlight the key importance of carbon-based substrates in the growth of the liquid bridge connecting the two water films. This simulation provides reliable evidence to confirm a linear increase of the liquid bridge height, which is sensitive to the surface properties and the geometric structure. In the case of nonadjacent water films, the meniscus liquid bridge occurs solely on the VCNTA, which is attributed to the spreading of water films driven by the capillary force. Our results provide an available method to tune the coalescence of adjacent or nonadjacent films with alteration of topographically patterned surfaces, which has important implications in the design of condensation, ink-jet printing and drop manipulation on a substrate. PMID:25839066

  5. Anisotropic colloidal crystal particles from microfluidics.

    PubMed

    Cheng, Yao; Zhu, Cun; Xie, Zhuoying; Gu, Hongcheng; Tian, Tian; Zhao, Yuanjin; Gu, Zhongze

    2014-05-01

    Anisotropic colloidal crystal particles (CCPs) have showed their great potential in biotechnology and structural materials due to their anisotropic shapes and tunable optical property. However, their controllable generation is still a challenge. Here, a novel microfluidic approach is developed to generate anisotropic CCPs. The microfluidic device is composed of an injection capillary and a collection capillary with available size and shape. Based on the device, the anisotropic particles with non-close-packed colloidal crystal structures are achieved by photo-polymerizing droplet templates in a confined collection capillary with different shapes and sizes. Moreover, anisotropic close-packed CCPs can be made from non-close-packed CCPs through a thermal process. It is demonstrated that the anisotropic CCPs in different sizes, structural colors and shapes (rods, cuboids and disks) can be generated. These distinguishable features of resultant particles make them ideal barcodes for high-throughput bioassays. In order to prove it, DNA multiplex detection is carried out. The experimental results indicate that achieved particles have a great encoding capacity and are highly practical for multiplex coding bioassays. Therefore, we believe that the anisotropic CCPs would be highly promising barcodes in biomedical applications, including high-throughput bioassays and cell culture research where multiplexing is needed. PMID:24594033

  6. Anisotropic Model Colloids

    NASA Astrophysics Data System (ADS)

    van Kats, C. M.

    2008-10-01

    The driving forces for fundamental research in colloid science are the ability to manage the material properties of colloids and to unravel the forces that play a role between colloids to be able to control and understand the processes where colloids play an important role. Therefore we are searching for colloidal materials with specific physical properties to better understand our surrounding world.Until recently research in colloid science was mainly focused on spherical (isotropic) particles. Monodisperse spherical colloids serve as a model system as they exhibit similar phase behaviour as molecular and atomic systems. Nevertheless, in many cases the spherical shape is not sufficient to reach the desired research goals. Recently the more complex synthesis methods of anisotropic model colloids has strongly developed. This thesis should be regarded as a contribution to this research area. Anisotropic colloids can be used as a building block for complex structures and are expected not only to lead to the construction of full photonic band gap materials. They will also serve as new, more realistic, models systems for their molecular analogues. Therefore the term ‘molecular colloids” is sometimes used to qualify these anisotropic colloidal particles. In the introduction of this thesis, we give an overview of the main synthesis techniques for anisotropic colloids. Chapter 2 describes the method of etching silicon wafers to construct monodisperse silicon rods. They subsequently were oxidized and labeled (coated) with a fluorescent silica layer. The first explorative phase behaviour of these silica rods was studied. The particles showed a nematic ordering in charge stabilized suspensions. Chapter 3 describes the synthesis of colloidal gold rods and the (mesoporous) silica coating of gold rods. Chapter 4 describes the physical and optical properties of these particles when thermal energy is added. This is compared to the case where the particles are irradiated with femtosecond laserpulses of variable wavelengths. We show that we can grow a silica layer on the gold rods with controllable thickness. In future this can be used to control the alignment of the gold rods a 3D crystal in an electric field. The silica coated gold rods can be used in optical switches. In chapter 4 we show to have a very local control of changing the aspect ratio of gold rods by irradiation with femtosecond laserpulses of 82 MHz with a threshold of ~ 2 picojoules to deform the particles. In chapter 5 and 6 we show how, starting from spherical particles, dimers (dumbbells), trimers and multimers can be formed by controlled aggregation. Chapter 7 finally shows an overview of syntheses where the pores of (mainly) silica particles is decreased. We show that the pores of the given particles could be decreased from macroporous to (ultra)microporous. Through a full control of pore size particles can selectively be filled with materials (for instance a drug) and be controllably closed. This opens a route for synthesis of particles that can be used as molecular filters or in biomedical applications such as smart drug delivery.

  7. Pesticide Transport with Runoff from Creeping Bentgrass Turf: Relationship of Pesticide Properties to Mass Transport

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The off-site transport of pesticides with runoff is both an agronomic and environmental concern resulting from reduced control of target pests in the area of application and contamination of surrounding ecosystems. Experiments were designed to measure the quantity of pesticides in runoff from creepi...

  8. Influence of raw materials and milling technological process on magnetic properties of sintered anisotropic Sr-ferrite magnet

    SciTech Connect

    Teng, Y.; Lu, B.; Yao, J. [Beijing General Research Institute of Mining and Metallurgy, Research Center for Magnetic Materials, Beijing, 100054 (China)] [Beijing General Research Institute of Mining and Metallurgy, Research Center for Magnetic Materials, Beijing, 100054 (China)

    1997-04-01

    It is necessary to reduce the Sr-ferrite grain size below 1 {mu}m for high coercivity, besides a high degree of density and orientation for high residual induction. However, submicron Sr-ferrite particles are difficult to orient in a magnetic field at pressing stage because of their cohesion. For preventing this cohesion, treatments with dispersants and reducing coercive force of S-ferrite particles are very effective. In this research, a study was done correlating purity and aggregation state of raw materials with intrinsic coercive force and microstructure of presintered Sr-ferrite sample, and a presintered sample with uniform grain size distribution and lower coercivity was gained. The classical pulverizing process is composed of coarse dry milling and fine wet milling. The results confirm that compared with wet milling, a long dry milling time promotes the development of crystal deformation and reduces the coercive force of the powders effectively; hence the viscosity is also lowered. By enhancing dry-milling time to control average particle size under 1.8 {mu}m and fine wet milling up to 0.75 {mu}m with optimum amount of dispersant, a well dispersed Sr-ferrite slurry is prepared. By these methods, a remarkable improvement of magnetic properties was achieved. {copyright} {ital 1997 American Institute of Physics.}

  9. Direct measurements of transport and water properties through the Bering Strait

    Microsoft Academic Search

    A. T. Roach; K. Aagaard; C. H. Pease; S. A. Salo; T. Weingartner; V. Pavlov; M. Kulakov

    1995-01-01

    Four years of temperature, salinity, and velocity data enable a direct computation of volume transport and a temporal description of water properties exchanged through the Bering Strait. The mean volume transport over the 4-year period (September 1990 through September 1994) is 0.83 Sv northward with a weekly standard deviation of 0.66 Sv. The maximum error in this mean estimate is

  10. Transport and magnetic properties of epitaxial and polycrystalline magnetite thin films

    Microsoft Academic Search

    X. W. Li; A. Gupta; Gang Xiao; G. Q. Gong

    1998-01-01

    The transport and magnetic properties of magnetite (Fe3O4) thin films grown epitaxially on single crystal MgO(100) and SrTiO3(100) substrates, and with multiple grain orientations on polycrystalline SrTiO3 substrates, have been investigated. The films are grown using pulsed laser deposition and their epitaxial quality determined using ion channeling measurements. Transport and magnetic studies of Fe3O4 films as a function of thickness

  11. Laser probing of transport properties and rotational alignment of N(2)(+) drifted in He

    NASA Astrophysics Data System (ADS)

    Anthony, Eric Baxley

    1998-09-01

    Results of transport property and rotational alignment experiments of the atmospherically important molecule N2+ are presented, as measured in a flow-drift apparatus using the technique of single-frequency laser- induced fluorescence (LIF). A trace amount of N2+ is drifted in helium as a buffer gas; the external axial electric field of the drift tube varies the center-of-mass collision energy of the ion-neutral pair. The net effect over hundreds of buffer gas collisions is to establish a steady-state anisotropic ion velocity distribution, the precise character of which is determined by the ion-neutral interaction potential, mass ratio, and field strength. A single-frequency ring dye laser is used to probe Doppler profiles of various rotational lines of the (/nu/sp/prime,?/prime') = (0,0) band in the B/ [2?u+] - X/ [2?g+] system at 390 nm. The single-frequency cw laser technique allows one to measure the velocity component distribution function (VCDF) along the laser propagation direction k; the VCDF is a projection of the complete ion velocity distribution function. Additionally, the rotational alignment of the ions as a function of one component of sub-Doppler laboratory velocity is probed by polarized LIF. Drift velocities and ion mobilities are determined from the shift of the first moments of the coaxial LIF Doppler profiles, while perpendicular and parallel translational temperatures are determined from the widths or second central moments of the profiles in the direction probed. Drift velocities measured up to a field strength of 16 Td appear to be in good agreement with data derived from earlier arrival-time measurements. A small but definite increase in mobility with increasing rotational state from J = 13.5 to J = 22.5 is observed. A significant difference of over 100 K between the parallel and perpendicular temperatures is measured at the highest field strength employed (16 Td). A small degree of positive skewness or third central moment is observed as well in the parallel VCDF's, which is of particular interest since a high-velocity tail has not been previously reported for any molecular ion system. Additionally, by probing with linearly polarized light and measuring the degree of polarization of the resultant LIF, the collision-induced quadrupole rotational alignment parameter A0(2) is determined as a function of field strength and velocity subgroup. A strong correlation is found between the degree of rotational alignment and the velocity subgroup when probed parallel to the field direction, with the alignment parameters generally increasing monotonically across the distribution. A dramatic difference in velocity-selected alignment as a function of rotational state is observed as well, for experiments conducted on various rotational lines at a fixed field strength of 12 Td. For sufficiently low rotational state (J about 9), it appears that A0(2) changes sign across the Doppler profile.

  12. Ab-initio transport properties of nanostructures from maximally-localized Wannier functions

    E-print Network

    Arrigo Calzolari; Nicola Marzari; Ivo Souza; Marco Buongiorno Nardelli

    2003-11-02

    We present a comprehensive first-principles study of the ballistic transport properties of low dimensional nanostructures such as linear chains of atoms (Al, C) and carbon nanotubes in presence of defects. A novel approach is introduced where quantum conductance is computed from the combination of accurate plane-wave electronic structure calculations, the evaluation of the corresponding maximally-localized Wannier functions, and the calculation of transport properties by a real-space Green's function method based on the Landauer formalism. This approach is computationally very efficient, can be straightforwardly implemented as a post-processing step in a standard electronic-structure calculation, and allows to directly link the electronic transport properties of a device to the nature of the chemical bonds, providing insight onto the mechanisms that govern electron flow at the nanoscale.

  13. Studies of Transport Properties of Fractures: Final Report

    SciTech Connect

    Stephen R. Brown

    2006-06-30

    We proposed to study several key factors controlling the character and evolution of fracture system permeability and transport processes. We suggest that due to surface roughness and the consequent channeling in single fractures and in fracture intersections, the tendency of a fracture system to plug up, remain permeable, or for permeability to increase due to chemical dissolution/precipitation conditions will depend strongly on the instantaneous flow channel geometry. This geometry will change as chemical interaction occurs, thus changing the permeability through time. To test this hypothesis and advance further understanding toward a predictive capability, we endeavored to physically model and analyze several configurations of flow and transport of inert and chemically active fluids through channels in single fractures and through fracture intersections. This was an integrated program utilizing quantitative observations of fractures and veins in drill core, quantitative and visual observations of flow and chemical dissolution and precipitation within replicas of real rough-walled fractures and fracture intersections, and numerical modeling via lattice Boltzmann methods.

  14. Low-field carrier transport properties in biased bilayer graphene

    NASA Astrophysics Data System (ADS)

    Hu, Bo

    2014-07-01

    Based on a semiclassical Boltzmann transport equation in random phase approximation, we develop a theoretical model to understand low-field carrier transport in biased bilayer graphene, which takes into account the charged impurity scattering, acoustic phonon scattering, and surface polar phonon scattering as three main scattering mechanisms. The surface polar optical phonon scattering of carriers in supported bilayer graphene is thoroughly studied using the Rode iteration method. By considering the metal-BLG contact resistance as the only one free fitting parameter, we find that the carrier density dependence of the calculated total conductivity agrees well with that observed in experiment under different temperatures. The conductivity results also suggest that in high carrier density range, the metal-BLG contact resistance can be a significant factor in determining the BLG conductivity at low temperature, and both acoustic phonon scattering and surface polar phonon scattering play important roles at higher temperature, especially for BLG samples with a low doping concentration, which can compete with charged impurity scattering.

  15. The influence of Ni-rich nanoclusters on the anisotropic magnetic properties of CdSb doped with Ni

    NASA Astrophysics Data System (ADS)

    Laiho, R.; Lashkul, A. V.; Lisunov, K. G.; Lähderanta, E.; Ojala, I.; Zakhvalinskii, V. S.

    2006-03-01

    The magnetic properties of oriented CdSb single crystals doped with 2 at% of Ni are investigated. From measurements of magnetic irreversibility defined by deviation of the zero-field-cooled (ZFC) susceptibility from the field-cooled (FC) susceptibility, the value of the mean anisotropy field BK ~ 4 kG is obtained. The ZFC susceptibility displays a broad maximum at a blocking temperature, Tb, depending on B according to the law [Tb(B)/Tb(0)]1/2 = 1 - B/BK with Tb(0) ~ 100 K. The field dependence of the magnetization exhibits saturation above ~20-30 kG with values of Ms different for B along the [1 0 0], [0 1 0] and [0 0 1] axes. The temperature dependence of Ms is weak, increasing slightly upon cooling the sample below ~100 K. The temperature dependence of the coercive field, Bc(T), is weak above Tb but is enhanced strongly with decreasing temperature below Tb. The anisotropy of Bc is inverted with respect to the anisotropy of Ms. Such behaviour can be attributed to spheroidal Ni-rich Ni1-xSbx nanoparticles with a high aspect ratio, broad size distribution and distribution of the orientation of the major axis around a preferred direction. The relation Bc Lt BK and the anisotropies of Ms and Bc are consistent with reversal of the magnetization by the curling mode, whereas the Tb(B) dependence is typical of the coherent rotation mode. This difference is connected to the proximity of the average transversal cluster radius to a critical value for transition between the two magnetization reversal modes within a wide crossover interval, due to broad distribution of the cluster sizes.

  16. Magnetic and transport properties of epitaxial stepped Fe3O4(100) thin films

    NASA Astrophysics Data System (ADS)

    Wu, Han-Chun; Syrlybekov, Askar; Mauit, Ozhet; Mouti, Anas; Coileáin, Cormac Ó.; Abid, Mourad; Abid, Mohamed; Shvets, Igor V.

    2014-09-01

    We investigate the magnetic and transport properties of epitaxial stepped Fe3O4 thin films grown with different thicknesses. Magnetization measurements suggest that the steps induce additional anisotropy, which has an easy axis perpendicular to steps and the hard axis along the steps. Separate local transport measurements, with nano-gap contacts along a single step and perpendicular to a single step, suggest the formation of a high density of anti-phase boundaries (APBs) at the step edges are responsible for the step induced anisotropy. Our local transport measurements also indicate that APBs distort the long range charge-ordering of magnetite.

  17. Controlling anisotropic nanoparticle growth through plasmon excitation

    Microsoft Academic Search

    Rongchao Jin; Y. Charles Cao; Encai Hao; Gabriella S. Métraux; George C. Schatz; Chad A. Mirkin

    2003-01-01

    Inorganic nanoparticles exhibit size-dependent properties that are of interest for applications ranging from biosensing and catalysis to optics and data storage. They are readily available in a wide variety of discrete compositions and sizes. Shape-selective synthesis strategies now also yield shapes other than nanospheres, such as anisotropic metal nanostructures with interesting optical properties. Here we demonstrate that the previously described

  18. Properties of the S(N)-equivalent integral transport operator and the iterative acceleration of neutral particle transport methods

    NASA Astrophysics Data System (ADS)

    Rosa, Massimiliano

    We have derived expressions for the elements of the matrix representing a certain angular (SN) and spatial discretized form of the neutron integral transport operator. This is the transport operator that if directly inverted on the once-collided fixed particle source produces, without the need for an iterative procedure, the converged limit of the scalar fluxes for the iterative procedure. The asymptotic properties of this operator's elements have then been investigated in homogeneous and periodically heterogeneous limits in one-dimensional and two-dimensional geometries. The thesis covers the results obtained from this asymptotic study of the matrix structure of the discrete integral transport operator and illustrates how they relate to the iterative acceleration of neutral particle transport methods. Specifically, it will be shown that in one-dimensional problems (both homogeneous and periodically heterogeneous) and homogeneous two-dimensional problems, containing optically thick cells, the discrete integral transport operator acquires a sparse matrix structure, implying a strong local coupling of a cell-averaged scalar flux only with its nearest Cartesian neighbors. These results provide further insight into the excellent convergence properties of diffusion-based acceleration schemes for this broad class of transport problems. In contrast, the results of the asymptotic analysis for two-dimensional periodically heterogeneous problems point to a sparse but non-local matrix structure due to long-range coupling of a cell's average flux with its neighboring cells, independent of the distance between the cells in the spatial mesh. The latter results indicate that cross-derivative coupling, namely coupling of a cell's average flux to its diagonal neighbors, is of the same order as self-coupling and coupling with its first Cartesian neighbors. Hence they substantiate the conjecture that the loss of robustness of diffusion-based acceleration schemes, in particular of the Adjacent-cell Preconditioner (AP) considered in this work, in the presence of sharp material discontinuities in periodically heterogeneous multi-dimensional problems, is due to a structural deficiency of such low-order operators since they ignore cross-derivative coupling. This conjecture has been successfully verified by amending the AP formalism to account for cross-derivative coupling by the inclusion of matrix elements that account for the coupling of a cell's average flux to its first diagonal neighbors. Preliminary results of the Fourier analysis for the novel acceleration scheme indicate that robustness of the accelerated iterations can be recovered by accounting for cross-derivative coupling. The new acceleration scheme has also been implemented in a two-dimensional transport code and numerical results from the code have successfully verified the predictions of the Fourier analysis.

  19. Density Functional Study of the Transport and Electronic Properties of Waved Graphene Nanoribbons

    NASA Astrophysics Data System (ADS)

    Hammouri, Mahmoud; Vasiliev, Igor

    2015-03-01

    First principles ab initio calculations are employed to study the electronic and transport properties of waved graphene nanoribbons. Our calculations are performed using the SIESTA and TRANSIESTA density functional electronic structure codes. We find that the band gaps of graphene nanoribbons with symmetrical edges change very slightly with the increasing compression, whereas the band gaps of nanoribbons with asymmetrical edges change significantly. The computed IV-characteristics of the waved graphene nanoribbons with different compression ratios reveal the effect of compression on the transport properties of graphene nanoribbons. Supported by NMSU GREG Award and by NSF CHE-1112388.

  20. Design and control of electron transport properties of single molecules

    PubMed Central

    Pan, Shuan; Fu, Qiang; Huang, Tian; Zhao, Aidi; Wang, Bing; Luo, Yi; Yang, Jinlong; Hou, Jianguo

    2009-01-01

    We demonstrate in this joint experimental and theoretical study how one can alter electron transport behavior of a single melamine molecule adsorbed on a Cu (100) surface by performing a sequence of elegantly devised and well-controlled single molecular chemical processes. It is found that with a dehydrogenation reaction, the melamine molecule becomes firmly bonded onto the Cu surface and acts as a normal conductor controlled by elastic electron tunneling. A current-induced hydrogen tautomerization process results in an asymmetric melamine tautomer, which in turn leads to a significant rectifying effect. Furthermore, by switching on inelastic multielectron scattering processes, mechanical oscillations of an N-H bond between two configurations of the asymmetric tautomer can be triggered with tuneable frequency. Collectively, this designed molecule exhibits rectifying and switching functions simultaneously over a wide range of external voltage. PMID:19706435

  1. Electrical transport properties of CaB6

    NASA Astrophysics Data System (ADS)

    Stankiewicz, Jolanta; Sesé, Javier; Balakrishnan, Geetha; Fisk, Zachary

    2014-10-01

    We report results from a systematic electron-transport study in a broad temperature range on 12 CaB6 single crystals. None of the crystals were intentionally doped. The different carrier densities observed presumably arise from slight variations in the Ca:B stoichiometry. In these crystals, the variation of the electrical resistivity and of the Hall effect with temperature can be consistently accounted for by the model we propose, in which B-antisite defects (B atom replacing Ca atom) are "amphoteric." The magnetotransport measurements reveal that most of the samples we have studied are close to a metal-insulator transition at low temperatures. The magnetoresistance changes smoothly from negative—for weakly metallic samples—to positive values—for samples in a localized regime.

  2. Collective Transport Properties of Driven Skyrmions with Random Disorder.

    PubMed

    Reichhardt, C; Ray, D; Reichhardt, C J Olson

    2015-05-29

    We use particle-based simulations to examine the static and driven collective phases of Skyrmions interacting with random quenched disorder. We show that nondissipative effects due to the Magnus term reduce the depinning threshold and strongly affect the Skyrmion motion and the nature of the dynamic phases. The quenched disorder causes the Hall angle to become drive dependent in the moving Skyrmion phase, while different flow regimes produce distinct signatures in the transport curves. For weak disorder, the Skyrmions form a pinned crystal and depin elastically, while for strong disorder the system forms a pinned amorphous state that depins plastically. At high drives the Skyrmions can dynamically reorder into a moving crystal, with the onset of reordering determined by the strength of the Magnus term. PMID:26066455

  3. Collective Transport Properties of Driven Skyrmions with Random Disorder

    NASA Astrophysics Data System (ADS)

    Reichhardt, C.; Ray, D.; Reichhardt, C. J. Olson

    2015-05-01

    We use particle-based simulations to examine the static and driven collective phases of Skyrmions interacting with random quenched disorder. We show that nondissipative effects due to the Magnus term reduce the depinning threshold and strongly affect the Skyrmion motion and the nature of the dynamic phases. The quenched disorder causes the Hall angle to become drive dependent in the moving Skyrmion phase, while different flow regimes produce distinct signatures in the transport curves. For weak disorder, the Skyrmions form a pinned crystal and depin elastically, while for strong disorder the system forms a pinned amorphous state that depins plastically. At high drives the Skyrmions can dynamically reorder into a moving crystal, with the onset of reordering determined by the strength of the Magnus term.

  4. Scaling properties of charge transport in polycrystalline graphene.

    PubMed

    Van Tuan, Dinh; Kotakoski, Jani; Louvet, Thibaud; Ortmann, Frank; Meyer, Jannik C; Roche, Stephan

    2013-04-10

    Polycrystalline graphene is a patchwork of coalescing graphene grains of varying lattice orientations and size, resulting from the chemical vapor deposition (CVD) growth at random nucleation sites on metallic substrates. The morphology of grain boundaries has become an important topic given its fundamental role in limiting the mobility of charge carriers in polycrystalline graphene, as compared to mechanically exfoliated samples. Here we report new insights to the current understanding of charge transport in polycrystalline geometries. We created realistic models of large CVD-grown graphene samples and then computed the corresponding charge carrier mobilities as a function of the average grain size and the coalescence quality between the grains. Our results reveal a remarkably simple scaling law for the mean free path and conductivity, correlated to atomic-scale charge density fluctuations along grain boundaries. PMID:23448361

  5. Al-based systems with unusual mechanical and transport properties

    NASA Astrophysics Data System (ADS)

    Müllerová, K.; Kovácik, J.; Simancík, F.; Vec, P.

    2005-03-01

    Addition of selected transition-metal elements into aluminum matrix is known to yield systems that exhibit unique structural arrangements and mechanical properties, especially high yield strength obtained after suitable heat treatment. These lightweight systems are known to be compactable from ribbon shape prepared by rapid quenching of the melt into bulk form, yielding physically and technically attractive materials. The combination of knowledge about formation of aluminum-based foams with the physics of rapid quenching and compaction is shown as a possible route for approaching the preparation of lightweight materials with potentially auxetic behavior. Enhancement of this property is discussed briefly in terms of tailoring the network or cell-pore structure of different dimensions, ranging from millimeters down to nanoscale and sub-nanoscale atomic ordering.

  6. Transport properties of graphene under periodic and quasiperiodic magnetic superlattices

    NASA Astrophysics Data System (ADS)

    Lu, Wei-Tao; Wang, Shun-Jin; Wang, Yong-Long; Jiang, Hua; Li, Wen

    2013-08-01

    We study the transmission of Dirac electrons through the one-dimensional periodic, Fibonacci, and Thue-Morse magnetic superlattices (MS), which can be realized by two different magnetic blocks arranged in certain sequences in graphene. The numerical results show that the transmission as a function of incident energy presents regular resonance splitting effect in periodic MS due to the split energy spectrum. For the quasiperiodic MS with more layers, they exhibit rich transmission patterns. In particular, the transmission in Fibonacci MS presents scaling property and fragmented behavior with self-similarity, while the transmission in Thue-Morse MS presents more perfect resonant peaks which are related to the completely transparent states. Furthermore, these interesting properties are robust against the profile of MS, but dependent on the magnetic structure parameters and the transverse wave vector.

  7. Transport Properties of Graphene with Nanoscale Lateral Resolution

    Microsoft Academic Search

    Filippo Giannazzo; Vito Raineri; Emanuele Rimini

    \\u000a Graphene, a two-dimensional sheet of C atoms, is the object of many scientific studies, especially due to the outstanding\\u000a electronic properties. The behavior of graphene based nano-devices or mesoscopic devices is ultimately influenced by the lateral\\u000a homogeneity of the carrier density, electron mean free path, and mobility on the layer. This chapter reviews the main applications\\u000a of scanning probe methods

  8. Magnetic and transport properties of magnetite thin films

    Microsoft Academic Search

    Guomin Zhang; Chongfei Fan; Liqing Pan; Fengping Wang; Ping Wu; Hong Qiu; Yousong Gu; Yue Zhang

    2005-01-01

    Magnetite (Fe3O4) films were prepared by DC reactive magnetron sputtering at various oxygen partial pressures with the ratio ? of oxygen to argon changing from 0.50:50 to 0.70:50 at room temperature, and then the Fe3O4 films were annealed at 480°C for 80min. The properties of the films were studied by X-ray diffraction, scanning electron microscopy, magnetic hysteresis loops, magnetoresistance (MR),

  9. Designing chromonic mesogens for the fabrication of anisotropic optical materials

    NASA Astrophysics Data System (ADS)

    Tam-Chang, Suk-Wah; Huang, Liming; Gyan, Aryal; Seo, Wonewoo; Mahinay, Delfin; Iverson, Isaac K.

    2008-02-01

    Perylene monoimides and diimides have applications as luminescent materials and in organic photovoltaic devices as chromophores and conducting materials. Materials in which these compounds are oriented in a preferred direction will possess useful anisotropic properties that are not attainable from materials in which the compounds are randomly oriented. Anisotropic materials of these compounds can be prepared by taking advantage of the unique properties of chromonic liquid crystals. In this paper we describe the principles for designing perylene monoimides and diimides with desired optical properties and chromonic liquid-crystalline properties. In addition, we demonstrate the fabrication of anisotropic optical materials via organization of these compounds into a lyotropic chromonic liquidcrystalline phase.

  10. Anisotropic nanomaterials: structure, growth, assembly, and functions

    PubMed Central

    Sajanlal, Panikkanvalappil R.; Sreeprasad, Theruvakkattil S.; Samal, Akshaya K.; Pradeep, Thalappil

    2011-01-01

    Comprehensive knowledge over the shape of nanomaterials is a critical factor in designing devices with desired functions. Due to this reason, systematic efforts have been made to synthesize materials of diverse shape in the nanoscale regime. Anisotropic nanomaterials are a class of materials in which their properties are direction-dependent and more than one structural parameter is needed to describe them. Their unique and fine-tuned physical and chemical properties make them ideal candidates for devising new applications. In addition, the assembly of ordered one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) arrays of anisotropic nanoparticles brings novel properties into the resulting system, which would be entirely different from the properties of individual nanoparticles. This review presents an overview of current research in the area of anisotropic nanomaterials in general and noble metal nanoparticles in particular. We begin with an introduction to the advancements in this area followed by general aspects of the growth of anisotropic nanoparticles. Then we describe several important synthetic protocols for making anisotropic nanomaterials, followed by a summary of their assemblies, and conclude with major applications. PMID:22110867

  11. WETAIR: A computer code for calculating thermodynamic and transport properties of air-water mixtures

    NASA Technical Reports Server (NTRS)

    Fessler, T. E.

    1979-01-01

    A computer program subroutine, WETAIR, was developed to calculate the thermodynamic and transport properties of air water mixtures. It determines the thermodynamic state from assigned values of temperature and density, pressure and density, temperature and pressure, pressure and entropy, or pressure and enthalpy. The WETAIR calculates the properties of dry air and water (steam) by interpolating to obtain values from property tables. Then it uses simple mixing laws to calculate the properties of air water mixtures. Properties of mixtures with water contents below 40 percent (by mass) can be calculated at temperatures from 273.2 to 1497 K and pressures to 450 MN/sq m. Dry air properties can be calculated at temperatures as low as 150 K. Water properties can be calculated at temperatures to 1747 K and pressures to 100 MN/sq m. The WETAIR is available in both SFTRAN and FORTRAN.

  12. Oligomers Modulate Interfibril Branching and Mass Transport Properties of Collagen Matrices

    PubMed Central

    Whittington, Catherine F.; Brandner, Eric; Teo, Ka Yaw; Han, Bumsoo; Nauman, Eric; Voytik-Harbin, Sherry L.

    2013-01-01

    Mass transport within collagen-based matrices is critical to tissue development, repair, and pathogenesis as well as the design of next generation tissue engineering strategies. This work shows how collagen precursors, specified by intermolecular cross-link composition, provide independent control of collagen matrix mechanical and transport properties. Collagen matrices were prepared from tissue-extracted monomers or oligomers. Viscoelastic behavior was measured in oscillatory shear and unconfined compression. Matrix permeability and diffusivity were measured using gravity-driven permeametry and integrated optical imaging, respectively. Both collagen types showed an increase in stiffness and permeability hindrance with increasing collagen concentration (fibril density); however, different physical property-concentration relationships were noted. Diffusivity wasn’t affected by concentration for either collagen type over the range tested. In general, oligomer matrices exhibited a substantial increase in stiffness and only a modest decrease in transport properties when compared to monomer matrices prepared at the same concentration. The observed differences in viscoelastic and transport properties were largely attributed to increased levels of interfibril branching within oligomer matrices. The ability to relate physical properties to relevant microstructure parameters, including fibril density and interfibril branching, is expected to advance the understanding of cell-matrix signaling as well as facilitate model-based prediction and design of matrix-based therapeutic strategies. PMID:23842082

  13. Transport Properties of Bi2212 Round Wires Grown in High Magnetic Fields

    Microsoft Academic Search

    Ken-ichiro Takahashi; Takushi Inoue; Gen Nishijima; Satoshi Awaji; Kazuo Watanabe

    2007-01-01

    The transport critical current density Jc is one of the most important properties for practical applications of high-Tc superconductors. The Jc properties of high-Tc superconductors are highly dependent on the microstructural texturing of the superconducting phase. In order to improve the grain alignment of the superconducting phase melt-processing in high magnetic fields is a very effective method based on the

  14. Review and assessment of thermodynamic and transport properties for the CONTAIN Code

    Microsoft Academic Search

    Valdez

    1988-01-01

    A study was carried out to review available data and correlations on the thermodynamic and transport properties of materials applicable to the CONTAIN computer code. CONTAIN is the NRC's best-estimate, mechanistic computer code for modeling containment response to a severe accident. Where appropriate, recommendations have been made for suitable approximations for material properties of interests. Based on a modified Benedict-Webb-Rubin

  15. Transport and Thermoelectric Properties of Semi-Heusler Alloys based on (Zr,Hf)NiSn

    Microsoft Academic Search

    V. Ponnambalam; Y. Xia; S. Bhattacharya; A. L. Pope; T. M. Tritt; S. J. Poon

    1999-01-01

    The electronic transport properties of substituted narrow-gap semiconducting (Zr,Hf)NiSn alloys are measured in order to investigate carrier conduction and bandgap features and thermoelectric properties. The undoped alloys exhibit a very large resistivity ratio r(4.2K)\\/r(295K) of 100-300, low carrier densities 1016- 1018 cm-3, and thermally activated conduction at T>50K. The roles of band overlapping and heavy electron mass are discussed. The

  16. Two-dimensional arrays of tunnel junctions: transport properties and phase transitions

    Microsoft Academic Search

    Ian Wooldridge; Per Delsing

    2000-01-01

    We describe the transport properties of 2d arrays of aluminium–aluminium oxide–aluminium tunnel junctions. The dependence of these properties on temperature and external magnetic field is examined. The arrays have been fabricated on oxidized silicon substrates using e-beam lithography and shadow evaporation. By altering the fabrication parameters used we are able to control the ratio between the charging energy and the

  17. Electrical transport properties of CaB6

    NASA Astrophysics Data System (ADS)

    Stankiewicz, Jolanta; Sesé, Javier; Balakrishnan, Geetha; Fisk, Zachary

    2015-03-01

    We report results from a systematic electron-transport study in a broad temperature range on twelve CaB6 single crystals. None of the crystals were intentionally doped. The different carrier densities observed presumably arise from slight variations in the Ca:B stoichiometry. In these crystals, the variation of the electrical resistivity and of the Hall effect with temperature can be consistently explained by a variable charge state of intrinsic defects, most likely B-antisites (B atom replacing Ca atom). Our model is also consistent with the presence of a narrow, defect related, impurity band close to the Fermi level. Thus it may indicate the validity of defect-driven intrinsic ferromagnetism in alkaline-earth hexaborides. The magnetotransport measurements reveal that most of the samples we have studied are close to a metal-insulator transition at low temperatures. The magnetoresistance changes smoothly from negative--for weakly metallic samples--to positive values--for samples in a localized regime. We acknowledge support from Grant MAT2012-38213-C02-01 of MEC, Spain and EP/I007210/1 from EPSRC, UK.

  18. Spin transport properties in lower n-acene-graphene nanojunctions.

    PubMed

    Zou, Dongqing; Cui, Bin; Kong, Xiangru; Zhao, Wenkai; Zhao, Jingfen; Liu, Desheng

    2015-05-01

    A series of n-acene-graphene (n = 3, 4, 5, 6) devices, in which n-acene molecules are sandwiched between two zigzag graphene nanoribbon (ZGNR) electrodes, are modeled through the spin polarized density functional theory combined with the non-equilibrium Green's function technique. Our theoretical results show that for n-acene molecules ranging from anthracene to hexacene, the spin-polarized electronic states near the Fermi level can be induced by the spin-polarized ZGNR electrodes, which strengthen gradually to facilitate the electronic transport. A nearly 100% spin filtering ratio and a dual-orientation spin-rectifying effect are observed in a wide range of bias voltage. Importantly, an over 8000% giant magnetoresistance is obtained in the low bias range from -0.1 V to +0.1 V. Moreover, negative differential resistance behaviors are detected in these devices. The potential mechanisms of these intriguing phenomena are proposed and these findings would be instructive for the design and synthesis of high-performance graphene-based spin-related devices. PMID:25835485

  19. Transport and magnetic properties of GdNiBC

    NASA Astrophysics Data System (ADS)

    Zhou, X. Z.; Kunkel, H. P.; Cowen, J. A.; Williams, Gwyn

    1998-05-01

    The borocarbide series (RC) m(NiB) n (R=rare earth, Y; m, n=1 or 2) has attracted much interest since the R=Lu, m=1, n=2 compound was found to display superconductivity near 16.5 K. While the m=1, n=2 systems display not only superconductivity, but also heavy electron behaviour (Yb) and various forms of magnetic order, the series with m= n=1 has not been investigated as extensively. Here we summarise the results of transport and magnetic measurements on GdNiBC from which we infer the presence of two transitions (as in GdNi 2B 2C) rather than a single anomaly found in earlier studies. However, susceptibility data on a powdered specimen display a single peaked structure reminiscent of that reported previously, suggesting that the present arc-melted materials may develop orientational texture. Furthermore, magnetoresistance measurements on the latter reveal an enhanced response with ( ?(0)- ?( H))/ ?(0) exceeding 33% near 10 K in fields of 8 T.

  20. Transport properties of a single-molecule diode.

    PubMed

    Lörtscher, Emanuel; Gotsmann, Bernd; Lee, Youngu; Yu, Luping; Rettner, Charles; Riel, Heike

    2012-06-26

    Charge transport through single diblock dipyrimidinyl diphenyl molecules consisting of a donor and acceptor moiety was measured in the low-bias regime and as a function of bias at different temperatures using the mechanically controllable break-junction technique. Conductance histograms acquired at 10 mV reveal two distinct peaks, separated by a factor of 1.5, representing the two orientations of the single molecule with respect to the applied bias. The current-voltage characteristics exhibit a temperature-independent rectification of up to a factor of 10 in the temperature range between 300 and 50 K with single-molecule currents of 45-70 nA at ±1.5 V. The current-voltage characteristics are discussed using a semiempirical model assuming a variable coupling of the molecular energy levels as well as a nonsymmetric voltage drop across the molecular junction, thus shifting the energy levels accordingly. The excellent agreement of the data with the proposed model suggests that the rectification originates from an asymmetric Coulomb blockade in combination with an electric-field-induced level shifting. PMID:22582743

  1. Hard-wall potential function for transport properties of alkali metal vapors.

    PubMed

    Ghatee, Mohammad Hadi; Niroomand-Hosseini, Fatemeh

    2007-01-01

    This study demonstrates that the transport properties of alkali metals are determined principally by the repulsive wall of the pair interaction potential function. The (hard-wall) Lennard-Jones (LJ) (15-6) effective pair potential function is used to calculate the transport collision integrals. Accordingly, reduced collision integrals of K, Rb, and Cs metal vapors are obtained from the Chapman-Enskog solution of the Boltzmann equation. The law of corresponding states based on the experimental transport reduced collision integral is used to verify the validity of a LJ(15-6) hybrid potential in describing the transport properties. LJ(8.5-4) potential function and a simple thermodynamic argument with the input PVT data of liquid metals provide the required molecular potential parameters. Values of the predicted viscosity of monatomic alkali metal vapor are in agreement with typical experimental data with average absolute deviations of 2.97% for K in the range of 700-1500 K, 1.69% for Rb, and 1.75% for Cs in the range of 700-2000 K. In the same way, the values of predicted thermal conductivity are in agreement with experiment within 2.78%, 3.25%, and 3.63% for K, Rb, and Cs, respectively. The LJ(15-6) hybrid potential with a hard-wall repulsion character conclusively predicts the best transport properties of the three alkali metal vapors. PMID:17212493

  2. Computer codes for the evaluation of thermodynamic properties, transport properties, and equilibrium constants of an 11-species air model

    NASA Technical Reports Server (NTRS)

    Thompson, Richard A.; Lee, Kam-Pui; Gupta, Roop N.

    1990-01-01

    The computer codes developed provide data to 30000 K for the thermodynamic and transport properties of individual species and reaction rates for the prominent reactions occurring in an 11-species nonequilibrium air model. These properties and the reaction-rate data are computed through the use of curve-fit relations which are functions of temperature (and number density for the equilibrium constant). The curve fits were made using the most accurate data believed available. A detailed review and discussion of the sources and accuracy of the curve-fitted data used herein are given in NASA RP 1232.

  3. On uniqueness and non-degeneracy of anisotropic polarons

    E-print Network

    Julien Ricaud

    2014-12-03

    We study the anisotropic Choquard--Pekar equation which de-scribes a polaron in an anisotropic medium. We prove the uniqueness and non-degeneracy of minimizers in a weakly anisotropic medium. In addition, for a wide range of anisotropic media, we derive the symmetry properties of minimizers and prove that the kernel of the associated linearized operator is reduced, apart from three functions coming from the translation invariance, to the kernel on the subspace of functions that are even in each of the three principal directions of the medium.

  4. Anisotropic thermal conduction in galaxy clusters with MHD in Gadget

    E-print Network

    Arth, Alexander; Beck, Alexander M; Petkova, Margarita; Lesch, Harald

    2014-01-01

    We present an implementation of thermal conduction including the anisotropic effects of magnetic fields for SPH. The anisotropic thermal conduction is mainly proceeding parallel to magnetic fields and suppressed perpendicular to the fields. We derive the SPH formalism for the anisotropic heat transport and solve the corresponding equation with an implicit conjugate gradient scheme. We discuss several issues of unphysical heat transport in the cases of extreme ansiotropies or unmagnetized regions and present possible numerical workarounds. We implement our algorithm into the GADGET code and study its behaviour in several test cases. In general, we reproduce the analytical solutions of our idealised test problems, and obtain good results in cosmological simulations of galaxy cluster formations. Within galaxy clusters, the anisotropic conduction produces a net heat transport similar to an isotropic Spitzer conduction model with an efficiency of one per cent. In contrast to isotropic conduction our new formalism ...

  5. From transport to disorder: Thermodynamic properties of finite dust clouds

    NASA Astrophysics Data System (ADS)

    Schella, André; Mulsow, Matthias; Melzer, André; Schablinski, Jan; Block, Dietmar

    2013-06-01

    The quantities entropy and diffusion are measured for two- and three-dimensional (3D) dust clusters in the fluid state. Entropy and diffusion are predicted to be closely linked via unstable modes. The method of instantaneous normal modes is applied for various laser-heated clusters to determine these unstable modes and the corresponding diffusive properties. The configurational entropy is measured for 2D and 3D clusters from structural rearrangements. The entropy shows a threshold behavior at a critical temperature for the 2D clusters, allowing us to estimate a configurational melting temperature. Further, the entropic disorder increases for larger clusters. Finally, the predicted relation between entropy and unstable modes has been confirmed from our experiments for 2D systems, whereas 3D systems do not show such a clear correlation.

  6. Multiple-pumped-well aquifer test to determine the anisotropic properties of a karst limestone aquifer in Pasco County, Florida, USA

    Microsoft Academic Search

    Louis H. Motz

    2009-01-01

    Groundwater-level data from an aquifer test utilizing four pumped wells conducted in the South Pasco wellfield in Pasco County, Florida, USA, were analyzed to determine the anisotropic transmissivity tensor, storativity, and leakance in the vicinity of the wellfield. A weighted least-squares procedure was used to analyze drawdowns measured at eight observation wells, and it was determined that the major axis

  7. The transport properties of the molecular-scale B2C and BC3 electronic devices

    NASA Astrophysics Data System (ADS)

    Li, Guiqin; Li, Runqin

    2012-09-01

    The transport properties of the molecular-scale B2C and BC3 electronic devices are investigated with an ab initio method combined with a nonequilibrium Green function technique. The effects of different BC graphenes and ribbon lengths on the transport properties of the devices are significant. The results show that the devices with different BC graphenes and sizes have unusual transmission coefficients, which leads to special current transport mechanisms for the devices. Notably, the current strength of the device with the shortest ribbon length is the largest in three B2C devices, but the current strength of the device with the shortest ribbon length is the smallest for BC3 device.

  8. Carrier Transport Properties of p-Type Silicon-Metal Silicide Nanocrystal Composite Films

    NASA Astrophysics Data System (ADS)

    Ohishi, Yuji; Miyazaki, Yoshinobu; Muta, Hiroaki; Kurosaki, Ken; Yamanaka, Shinsuke; Uchida, Noriyuki; Tada, Tetsuya

    2015-06-01

    In this study, we synthesized p-type nanocomposite films consisting of Si-nickel silicide and Si-molybdenum silicide nanocrystals and measured the temperature dependence of their electrical properties. To evaluate grain boundary potential barrier height, we developed a theoretical model taking into account the effect of ionized impurities, acoustic phonons, and grain boundaries. The potential barrier height was sufficiently low not to substantially affect carrier transport in the Si-nickel silicide composite film. Carrier transport in the Si-molybdenum silicide composite film was found to be affected by a scattering mechanism not included in this model. Thus, the transition metal significantly affects carrier transport and the thermoelectric properties of Si-metal silicide nanocomposite films.

  9. Effect of stabilizer on dynamic thermal transport property of ZnO nanofluid.

    PubMed

    Neogy, Rajesh Kumar; Raychaudhuri, Arup Kumar

    2013-01-01

    In this paper, we investigate the effect of adding a stabilizer on the dynamic thermal properties of ZnO nanofluid (containing 5 to 10 nm diameter of ZnO nanocrystals) measured using a 3? method. Addition of the stabilizer leads to the stabilization of the nanofluid and also substantial reduction of the enhancement of thermal transport compared to that seen in the bare ZnO nanofluid. This also alters the frequency dependence of the thermal transport and the characteristic time scale associated with it. It is suggested that the addition of the stabilizer inhibits the thermodiffusion-assisted local aggregation thus leading to substantial reduction of the enhancement of thermal transport properties of the bare nanofluid as proposed in some recent models, and this also alters the characteristic time scales by altering the scale of aggregation. PMID:23497347

  10. Transport and infrared photoresponse properties of InN nanorods/Si heterojunction

    PubMed Central

    2011-01-01

    The present work explores the electrical transport and infrared (IR) photoresponse properties of InN nanorods (NRs)/n-Si heterojunction grown by plasma-assisted molecular beam epitaxy. Single-crystalline wurtzite structure of InN NRs is verified by the X-ray diffraction and transmission electron microscopy. Raman measurements show that these wurtzite InN NRs have sharp peaks E2(high) at 490.2 cm-1 and A1(LO) at 591 cm-1. The current transport mechanism of the NRs is limited by three types of mechanisms depending on applied bias voltages. The electrical transport properties of the device were studied in the range of 80 to 450 K. The faster rise and decay time indicate that the InN NRs/n-Si heterojunction is highly sensitive to IR light. PMID:22122843

  11. Orientation effect on the electronic transport properties of C24 fullerene molecule

    NASA Astrophysics Data System (ADS)

    Zhao, Wen-Kai; Yang, Chuan-Lu; Zhao, Jing-Fen; Wang, Mei-Shan; Ma, Xiao-Guang

    2012-06-01

    The transport properties of the cage-like molecule depend on its orientation between the electrodes, but the investigation on the mechanism has not been found. Using first-principle density-functional theory (DFT) and non-equilibrium Green’s function (NEGF) formalism for quantum transport calculation, we study the electronic transport properties of C24 fullerene molecule with different orientations in Au-C24-Au two-probe system. The effects of k-point sampling on the Brillouin zone are explored. Our results show that the negative differential resistance of C24 molecule is found in such a system and can be tuned by the molecule's orientation in the two-probe system. We also proposed a mechanism for it. The I-V characteristic under bias voltage is determined. The present findings could be helpful for the application of the C24 molecule in the field of single molecular devices or nanometer electronics.

  12. Human nongastric H -K -ATPase: transport properties of ATP1al1 assembled with different -subunits

    E-print Network

    Brand, Paul H.

    Human nongastric H -K -ATPase: transport properties of ATP1al1 assembled with different -subunits March 2002 Crambert, Gilles, Jean-Daniel Horisberger, Nikolai N. Modyanov, and Ka¨thi Geering. Human of human nongastric H -K -ATPase, ATP1al1 (AL1), and of the Na -K -ATPase 1-subunit ( 1) expressed

  13. Thermoelectric Transport Properties of Single Bismuth Nanowires S. B. Cronin1

    E-print Network

    Cronin, Steve

    Thermoelectric Transport Properties of Single Bismuth Nanowires S. B. Cronin1 , Y.-M. Lin3 , M thermoelectric material. Bi nanowires, however, have been predicted to have a high thermoelectric efficiency [1,2]. The thermoelectric enhancement is based on the sharp features in the one-dimensional density of states

  14. Transport Properties of Bi-related Nanowire Systems Y. M. Lin,1

    E-print Network

    Cronin, Steve

    , MA 02139 4 Delphi Research Labs, Delphi Automotive Systems, Warren, MI 48090 * On leave fromTransport Properties of Bi-related Nanowire Systems Y. M. Lin,1 S. B. Cronin,2 J. Y. Ying,3 J. Heremans,4 and M. S. Dresselhaus1,2,* 1 Department of Electrical Engineering and Computer Science, 2

  15. Magnetic and transport properties of the ferromagnetic semiconductor heterostructures ,,In,Mn...As/,,Ga,Al...Sb

    E-print Network

    Iye, Yasuhiro

    Magnetic and transport properties of the ferromagnetic semiconductor heterostructures ,,In developments in crystal growth of the III-V com- pound based magnetic semiconductor have offered great op ferromagnetic ordering at low temperatures.2­9 Previous work on a series of In0.94Mn0.06As/GaSb heterostructures

  16. Nonasymptotic properties of transport and mixing G. Boffetta and A. Celani

    E-print Network

    Cencini, Massimo

    Nonasymptotic properties of transport and mixing G. Boffetta and A. Celani Dipartimento di Fisica Generale and Istituto Nazionale Fisica della Materia, Universita` di Torino, Via Pietro Giuria 1, 10125 Torino, Italy M. Cencini Dipartimento di Fisica and Istituto Nazionale Fisica della Materia, Universita

  17. Deformationally dependent fluid transport properties of porcine coronary arteries based on location in the coronary vasculature

    PubMed Central

    Keyes, Joseph T.; Lockwood, Danielle R.; Simon, Bruce R.; Vande Geest, Jonathan P.

    2013-01-01

    Objective Understanding coronary artery mass transport allows researchers to better comprehend how drugs or proteins move through, and deposit into, the arterial wall. Characterizing how the convective component of transport changes based on arterial location could be useful to better understand how molecules distribute in different locations in the coronary vasculature. Methods and results We measured the mechanical properties and wall fluid flux transport properties of de-endothelialized (similar to post-stenting or angioplasty) left anterior descending (LADC) and right (RC) porcine coronary arteries along their arterial lengths. Multiphoton microscopy was used to determine microstructural differences. Proximal LADC regions had a higher circumferential stiffness than all other regions. Permeability decreased by 198% in the LADC distal region compared to other LADC regions. The RC artery showed a decrease of 46.9% from the proximal to middle region, and 51.7% from the middle to distal regions. The porosity increased in the intima between pressure states, without differences through the remainder of the arterial thickness. Conclusions We showed that the permeabilities and mechanical properties do vary in the coronary vasculature. With variations in mechanical properties, overexpansion of stents can occur more easily while variations in permeability may lead to altered transport based on location. PMID:23127633

  18. Ab initio study of deuterium in the dissociating regime: Sound speed and transport properties

    Microsoft Academic Search

    J. Clérouin; J.-F. Dufrêche

    2001-01-01

    The sound speed and the transport properties of dense hydrogen (deuterium) are computed from local spin-density approximation molecular-dynamics simulations in the dissociating regime. The sound speed cs is evaluated from the thermodynamical differentiation of the equation of state in the molecular phase and is in very good agreement with recent experiments. The diffusion constant D and the viscosity eta are

  19. 2,3-Dihydroxypropyl methacrylate and 2-hydroxyethyl methacrylate hydrogels: gel structure and transport properties

    E-print Network

    Harmon, Julie P.

    in their use as contact lens materials and in other biomedical applications. To date research characterizing transport properties in these polymers. This is important, for example, in contact lens applications because significant for contact lens applications. For the initial drying phase, time ! 0, the loss of penetrant

  20. Transport Properties for Aqueous Sodium Sulfonate Surfactants 2. Intradiffusion Measurements: Influence of the Obstruction Effect

    E-print Network

    Annunziata, Onofrio

    Transport Properties for Aqueous Sodium Sulfonate Surfactants 2. Intradiffusion Measurements@chemna.dichi.unina.it Received July 24, 1998; accepted April 14, 1999 Intradiffusion coefficients of sodium alkylsulfonates [CH3 the computation of the Gouy­Chapman layer thickness from the experimental coefficients has been proposed

  1. INVITED FEATURE PAPERS Growth and transport properties of p-type GaNBi alloys

    E-print Network

    Wu, Junqiao

    INVITED FEATURE PAPERS Growth and transport properties of p-type GaNBi alloys Alejandro X. Levander 2011) Thin films of GaNBi alloys with up to 12.5 at.% Bi were grown on sapphire using low to the midgap position of GaN, whereas the conduction band edge shifted more gradually. I. INTRODUCTION Alloying

  2. Hole transporting properties of tris,,8-hydroxyquinoline... aluminum ,,Alq3... H. H. Fonga

    E-print Network

    So, Shu K.

    3 is one of the most commonly used materials used in organic light-emitting diodes OLEDs . Alq3 recombination of electrons and holes inside an organic light-emitting material. This process is restrictedHole transporting properties of tris,,8-hydroxyquinoline... aluminum ,,Alq3... H. H. Fonga and S. K

  3. Frequency distribution of water and solute transport properties derived from pan sampler data

    E-print Network

    Walter, M.Todd

    Frequency distribution of water and solute transport properties derived from pan sampler data Jan Boll,1 John S. Selker,2 Gil Shalit,3 and Tammo S. Steenhuis4 Abstract. Modeling of water and solute samplers. Spatial distributions of solute velocity, dispersion coefficient, water flux, and solute

  4. Examining injection properties of boreal forest fires using surface and satellite measurements of CO transport

    Microsoft Academic Search

    Edward J. Hyer; Dale J. Allen; Eric S. Kasischke

    2007-01-01

    Boreal forest fires are highly variable in space and time and also have variable vertical injection properties. We compared a University of Maryland Chemistry and Transport Model (UMD-CTM) simulation of boreal forest fire CO in the summer of 2000 to surface observations from the NOAA Cooperative Air Sampling Network and satellite observations of CO from the Measurement of Pollutants in

  5. Transport Properties of the Quark-Gluon Plasma -- A Lattice QCD Perspective

    E-print Network

    Harvey B. Meyer

    2011-06-09

    Transport properties of a thermal medium determine how its conserved charge densities (for instance the electric charge, energy or momentum) evolve as a function of time and eventually relax back to their equilibrium values. Here the transport properties of the quark-gluon plasma are reviewed from a theoretical perspective. The latter play a key role in the description of heavy-ion collisions, and are an important ingredient in constraining particle production processes in the early universe. We place particular emphasis on lattice QCD calculations of conserved current correlators. These Euclidean correlators are related by an integral transform to spectral functions, whose small-frequency form determines the transport properties via Kubo formulae. The universal hydrodynamic predictions for the small-frequency pole structure of spectral functions are summarized. The viability of a quasiparticle description implies the presence of additional characteristic features in the spectral functions. These features are in stark contrast with the functional form that is found in strongly coupled plasmas via the gauge/gravity duality. A central goal is therefore to determine which of these dynamical regimes the quark-gluon plasma is qualitatively closer to as a function of temperature. We review the analysis of lattice correlators in relation to transport properties, and tentatively estimate what computational effort is required to make decisive progress in this field.

  6. Transport and Phase Equilibria Properties for Steam Flooding of Heavy Oils

    SciTech Connect

    Gabitto, Jorge; Barufet, Maria

    2002-11-20

    The objectives of this research included experimental determination and rigorous modeling and computation of phase equilibrium diagrams, volumetric, and transport properties of hydrocarbon/CO2/water mixtures at pressures and temperatures typical of steam injection processes for thermal recovery of heavy oils.

  7. Nuclear microprobe studies of the electronic transport properties of cadmium zinc telluride (CZT) radiation detectors

    Microsoft Academic Search

    Gyorgy Vizkelethy; Barney L. Doyle; David S. Walsh; Ralph B. James

    2000-01-01

    Ion Beam Induced Charge Collection (IBICC) is a proven albeit relatively new method to measure the electronic transport properties of room temperature radiation detectors. Using an ion microbeam, the charge collection efficiency of CZT detectors can be mapped with submicron resolution and maps of the electron mobility and lifetime can be calculated. The nuclear microprobe can be used not only

  8. Optical and transport properties of ultrathin NbN films and nanostructures

    Microsoft Academic Search

    A. Semenov; B. Günther; U. Böttger; H.-W. Hübers; H. Bartolf; A. Engel; A. Schilling; K. Ilin; M. Siegel; R. Schneider; D. Gerthsen; N. A. Gippius

    2009-01-01

    Optical and transport properties of a series of ultrathin NbN films with different thickness grown on sapphire have been evaluated by means of spectral ellipsometry and dc measurements of superconducting critical parameters. The growth process and thus the nitrogen content have been optimized for each film in the series to achieve the highest superconducting transition temperature, which however increases with

  9. Magnetic, transport, and optical properties of monolayer copper oxides M. A. Kastner and R. J. Birgeneau

    E-print Network

    Wilczek, Frank

    as a function of carrier density beginning with the antiferromagnetic in- sulator and working oMagnetic, transport, and optical properties of monolayer copper oxides M. A. Kastner and R. J insulator-to-metal transitions as a function of pressure or temperature; oth- ers that transform from

  10. Surface and volume charge transport properties of polyimide revealed by surface potential decay with genetic algorithm

    Microsoft Academic Search

    Daomin Min; Mengu Cho; Arifur R. Khan; Shengtao Li

    2012-01-01

    It is very important to understand the surface and volume charge transportation properties of high insulating materials, such as polyimide, in order to find suitable method to mitigate the electrostatic discharge (ESD) of certain sensitive components on spacecraft. An isothermal surface potential decay (ISPD) experiment is performed inside a ground based vacuum chamber on polyimide under a simulated space environment.

  11. Investigating the Transport Properties of Silicate Liquids at Mantle Pressures

    NASA Astrophysics Data System (ADS)

    Reid, J. E.; Suzuki, A.; Poe, B. T.; Funakoshi, K.; Rubie, D. C.

    2001-12-01

    Understanding the effects of high pressure on silicate liquid properties, such as viscosity, ionic diffusion and thermal diffusivity, is critical for modeling magmatic processes in the mantle. Until recently, measurements of such properties were restricted to pressures of less that 2.5 GPa. However, with the development of multianvil systems together with experimental techniques utilizing synchrotron radiation, the pressures of such measurements have now been extended to 13 GPa in the case of viscosity measurements and 17 GPa for ionic diffusion experiments. The use of multianvil presses on synchrotron beamlines together with the recent development of a new cell for in-situ falling sphere viscometry has facilitated viscosity measurements up to 13 GPa at temperatures greater than 2000 oC. This method allows accurate and precise determinations for even very low-viscosity depolymerised liquids such as diopside and komatiite. Ionic self-diffusion in depolymerised silicate liquids has also been investigated at pressures up to 17 GPa using a large volume 5000-ton multianvil system at the Bayerisches Geoinstitut. The ability to compare direct viscosity determinations and oxygen or silicon self-diffusion coefficients for diopside liquid at high pressure has proved the Eyring relation to be valid. Thus, diffusion experiments provide a valuable means of estimating viscosity at considerably higher pressures than are currently attainable in falling sphere experiments. Compared to more polymerized silicate and alumino-silicate compositions, diopside and komatiite liquids show only a small effect of pressure on viscosity up to 17 and 7 GPa respectively. Prospects for the future include extending diffusivity measurements to 24 GPa and making direct viscosity determinations of very low viscosity silicate liquids over a large pressure range. Measurements on peridotitic liquids, in particular, will enable better constraints to be placed on the dynamics and crystallization behavior of a deep magma ocean during the early history of the Earth.

  12. Transport properties of Dirac fermions in two dimensions

    NASA Astrophysics Data System (ADS)

    DaSilva, Ashley M.

    The Dirac equation in particle physics is used to describe spin 1/2 fermions (such as electrons) moving at relativistic speeds. In condensed matter physics, this is usually not relevant, since particles in matter move slowly compared to the speed of light. However, recent progress has revealed two-dimensional realizations of Dirac fermions in condensed matter systems with zero mass and a redefined "speed of light." One of these systems, graphene, has been studied theoretically for decades as a building block of graphite. The other, the topological insulator, is quite new; this state of matter was predicted less than 10 years ago. Graphene was first isolated in 2004, and since then there has been an explosion of graphene research in the physics community. Much of the recent excitement has to do with the potential applications of graphene in devices. In this dissertation, I will discuss two problems related to graphene devices, and in particular how to use the strong interaction of graphene with its surroundings as an asset. I will show that a Boltzmann transport theory with all scattering mechanisms describes the current vs voltage of a graphene sheet extremely well using no adjustable parameters. One crucial element of this model is the transfer of energy from electrons directly to the substrate via scattering with optical phonons at the interface. The interaction is due to an electric field that is set up by these optical phonons, which is so strongly interacting in part due to the two dimensionality of the graphene. I will also discuss the adsorption of He atoms on a graphene sheet. This causes a change in the graphene conductivity which is large enough to be measurable. Work in this direction could provide a route to graphene sensors. The topological insulator is a recently predicted state of matter which is nominally an insulator but has metallic surface states which are topologically protected. This topological protection arises from the symmetry of the system, which requires a two-fold degeneracy at any time reversal symmetric momentum, and a band inversion, which provides a swapping of the conduction and valance band at a surface. These two conditions imply that an odd number of states will cross the gap even in the presence of disorder (as long as that disorder is time reversal symmetric). This manifests as a Dirac cone at the surface of insulators such as Bi2Se3 and Bi2Te 3. To be a true topological insulator, one must have a bulk insulator; experimentally however, most samples are bulk conductors. While rapid improvement is being made through techniques such as doping, one of the goals of the research presented in this thesis is to work towards a transport signal which is unique to the surface state even in the presence of a conducting bulk. In this direction, quantum corrections to the magnetoresistance have been shown to fail, as both bulk and surface have similar experimental signals. However work in this dissertation shows that we can still gain some insight by modeling the experimental data with the theory of quantum corrections. I will show evidence that electron-electron interactions are necessary to understand the low temperature conductivity of Bi2Se3 thin films. One unambiguous transport signal is the quantum Hall response; the energy of Dirac fermions in a strong magnetic field is quite different than their parabolic counterparts. Given this, a question that arises is the nature of the fractional quantum Hall effect in topological insulator surface states. I will predict the conditions under which the fractional quantum Hall effect is stable. Finally, one of the reasons topological insulators have gained so much enthusiasm is the potential application to topological quantum computation. This may be made possible if the theoretical predictions of particles called Majorana fermions could be realized experimentally. I discuss evidence that two necessary (although not sufficient) conditions are met: topological insulators can be made superconducting and there is evidence for the formation of vo

  13. Anisotropic Laplace-Beltrami Operators for Shape Analysis

    E-print Network

    Anisotropic Laplace-Beltrami Operators for Shape Analysis Mathieu Andreux1,2 , Emanuele Rodol`a2 an anisotropic Laplace-Beltrami op- erator for shape analysis. While keeping useful properties of the stan- dard Laplace-Beltrami operator, it introduces variability in the directions of principal curvature, giving rise

  14. Analysis of Data from Pumping Tests in Anisotropic Aquifers

    Microsoft Academic Search

    MAHDI S. HANTUSH

    1966-01-01

    In conventional methods of aquifer tests homogeneous and isotropic aquifers are assumed. In many instances, however, the aquifers tested are anisotropic. Procedures are outlined for determining the principal directions of anisotropy and the hydraulic properties of homogeneous anisotropic aquifers. Data from pumping tests in leaky or nonleaky aquifers are used. The aquifers are uniform in thickness, and the flow therein

  15. Flow and transport in unsaturated fractured rock: Effects of multiscale heterogeneity of hydrogeologic properties

    SciTech Connect

    Zhou, Quanlin; Liu, Hui-Hai; Bodvarsson, Gudmundur S.; Oldenburg, Curtis M.

    2002-07-09

    The heterogeneity of hydrogeologic properties at different scales may have different effects on flow and transport processes in a subsurface system. A model for the unsaturated zone of Yucca Mountain, Nevada, is developed to represent complex heterogeneity at two different scales: (1) layer scale corresponding to geologic layering and (2) local scale. The layer-scale hydrogeologic properties are obtained using inverse modeling, based on the available measurements collected from the Yucca Mountain site. Calibration results show a significant lateral and vertical variability in matrix and fracture properties. Hydrogeologic property distributions in a two-dimensional, vertical cross section of the site are generated by combining the average layer-scale matrix and fracture properties with local-scale perturbations generated using a stochastic simulation method. The unsaturated water flow and conservative (nonsorbing) tracer transport through the cross section are simulated for different sets of matrix and fracture property fields. Comparison of simulation results indicates that the local-scale heterogeneity of matrix and fracture properties has a considerable effect on unsaturated flow processes, leading to fast flow paths in fractures and the matrix. These paths shorten the travel time of a conservative tracer from the source (repository) horizon in the unsaturated zone to the water table for small fractions of total released tracer mass. As a result, the local-scale heterogeneity also has a noticeable effect on global tracer transport processes, characterized by an average breakthrough curve at the water table, especially at the early arrival time of tracer mass. However, the effect is not significant at the later time after 20 percent tracer mass reaches the water table. The simulation results also verify that matrix diffusion plays an important role in overall solute transport processes in the unsaturated zone at Yucca Mountain.

  16. Effects of age and zinc supplementation on transport properties in the jejunum of piglets.

    PubMed

    Gefeller, E M; Martens, H; Aschenbach, J R; Klingspor, S; Twardziok, S; Wrede, P; Pieper, R; Lodemann, U

    2015-06-01

    Zinc is effective in the prevention and treatment of post-weaning diarrhoea and in promoting piglet growth. Its effects on the absorption of nutrients and the secretory capacity of the intestinal epithelium are controversial. We investigated the effects of age, dietary pharmacological zinc supplementation and acute zinc exposure in vitro on small-intestinal transport properties of weaned piglets. We further examined whether the effect of zinc on secretory responses depended on the pathway by which chloride secretion is activated. A total of 96 piglets were weaned at 26 days of age and allocated to diets containing three different levels of zinc oxide (50, 150 and 2500 ppm). At the age of 32, 39, 46 and 53 days, piglets were killed, and isolated epithelia from the mid-jejunum were used for intestinal transport studies in conventional Ussing chambers, with 23 ?m ZnSO4 being added to the serosal side for testing acute effects. Absorptive transport was stimulated by mucosal addition of d-glucose or l-glutamine. Secretion was activated by serosal addition of prostaglandin E2 , carbachol or by mucosal application of Escherichia coli heat-stable enterotoxin (Stp ). Jejunal transport properties showed significant age-dependent alterations (p < 0.03). Both absorptive and secretory responses were highest in the youngest piglets (32 d). The dietary zinc supplementation had no significant influence on jejunal absorptive and secretory responses. However, the pre-treatment of epithelia with ZnSO4 in vitro led to a small but significant decrease in both absorptive and secretory capacities (p < 0.05), with an exception for carbachol (p = 0.07). The results showed that, in piglets, chronic supplementation with zinc did not sustainably influence the jejunal transport properties in the post-weaning phase. Because transport properties are influenced by the addition of zinc in vitro, we suggest that possible epithelial effects of zinc depend on the acute presence of this ion. PMID:25039419

  17. Influence of substrate type on transport properties of superconducting FeSe0.5Te0.5 thin films

    NASA Astrophysics Data System (ADS)

    Yuan, Feifei; Iida, Kazumasa; Langer, Marco; Hänisch, Jens; Ichinose, Ataru; Tsukada, Ichiro; Sala, Alberto; Putti, Marina; Hühne, Ruben; Schultz, Ludwig; Shi, Zhixiang

    2015-06-01

    FeSe0.5Te0.5 thin films were grown by pulsed laser deposition on CaF2, LaAlO3 and MgO substrates and structurally and electro-magnetically characterized in order to study the influence of the substrate on their transport properties. The in-plane lattice mismatch between FeSe0.5Te0.5 bulk and the substrate shows no influence on the lattice parameters of the films, whereas the type of substrate affects the crystalline quality of the films and, therefore, the superconducting properties. The film on MgO showed an extra peak in the angular dependence of critical current density Jc(?) at ? = 180° (H||c), which arises from c-axis defects as confirmed by transmission electron microscopy. In contrast, no Jc(?) peaks for H||c were observed in films on CaF2 and LaAlO3. Jc(?) can be scaled successfully for both films without c-axis correlated defects by the anisotropic Ginzburg–Landau approach with appropriate anisotropy ratio ?J. The scaling parameter ?J is decreasing with decreasing temperature, which is different from what we observed in FeSe0.5Te0.5 films on Fe-buffered MgO substrates.

  18. Robust anisotropic diffusion

    Microsoft Academic Search

    Michael J. Black; Guillermo Sapiro; David H. Marimont; David Heeger

    1998-01-01

    Relations between anisotropic diffusion and robust statis tics are described in this pa- per. Specifically, we show that anisotropic diffusion can be seen as a robust estimation procedure that estimates a piecewise smooth image from a noi sy input image. The \\

  19. Anisotropic pressure and hyperons in neutron stars

    E-print Network

    A. Sulaksono

    2014-12-23

    We study the effects of anisotropic pressure on properties of the neutron stars with hyperons inside its core within the framework of extended relativistic mean field. It is found that the main effects of anisotropic pressure on neutron star matter is to increase the stiffness of the equation of state, which compensates for the softening of the EOS due to the hyperons. The maximum mass and redshift predictions of anisotropic neutron star with hyperonic core are quite compatible with the result of recent observational constraints if we use the parameter of anisotropic pressure model $h \\le 0.8$[1] and $\\Lambda \\le -1.15$ [2]. The radius of the corresponding neutron star at $M$=1.4 $M_\\odot$ is more than 13 km, while the effect of anisotropic pressure on the minimum mass of neutron star is insignificant. Furthermore, due to the anisotropic pressure in the neutron star, the maximum mass limit of higher than 2.1 $M_\\odot$ cannot rule out the presence of hyperons in the neutron star core.

  20. Transport properties of two-dimensional electron gases containing linear ordering InAs self-assembled quantum dots

    SciTech Connect

    Kim, Gil-Ho; Ritchie, D. A.; Liang, C.-T.; Lian, G. D.; Yuan, J.; Pepper, M.; Brown, L. M.

    2001-06-11

    We present a study of the anisotropic properties of two-dimensional electron gases formed in GaAs/AlGaAs heterostructures in which InAs self-assembled quantum dots have been inserted into the center of a GaAs quantum well. We observe an anisotropic mobility for the orthogonal [{bar 1}10] and [110] directions. The mobility in the [{bar 1}10] direction was found to be up to approximately twice that in the [110] direction. It is suggested that the interface roughness scattering due to the inserted InAs material could be a cause for the large anisotropies in mobility. {copyright} 2001 American Institute of Physics.

  1. Charge Transport Properties in TiO2 Network with Different Particle Sizes for Dye Sensitized Solar Cells

    E-print Network

    Cao, Guozhong

    the large improvement in performance of dye sensitized solar cells (DSCs) achieved in 1991, mesoporousCharge Transport Properties in TiO2 Network with Different Particle Sizes for Dye Sensitized Solar sensitized solar cells, nanoparticle size, impedance, charge transport properties INTRODUCTION Since

  2. High-field thermal transports properties of REBCO coated conductors

    E-print Network

    Bonura, M

    2014-01-01

    The use of REBCO coated conductors is envisaged for many applications, extending from power cables to high-?eld magnets. Whatever the case, thermal properties of REBCO tapes play a key role for the stability of superconducting devices. In this work, we present the ?rst study on the longitudinal thermal conductivity (k) of REBCO coated conductors in magnetic ?elds up to 19 T applied both parallelly and perpendicularly to the thermal-current direction. Copper-stabilized tapes from six industrial manufacturers have been investigated. We show that zero-?eld k of coated conductors can be calculated with an accuracy of ‡ 15% from the residual resistivity ratio of the stabilizer and the Cu/non-Cu ratio. Measurements performed at high ?elds have allowed us to evaluate the consistency of the procedures generally used for estimating in-?eld k in the framework of the Wiedemann-Franz law from an electrical characterization of the materials. In-?eld data are intended to provide primary ingredients for the ...

  3. Transport properties of silver-calcium doped lanthanum manganite

    NASA Astrophysics Data System (ADS)

    Cherif, B.; Rahmouni, H.; Smari, M.; Dhahri, E.; Moutia, N.; Khirouni, K.

    2015-01-01

    Electrical properties of silver-calcium doped lanthanum manganite (La0.5Ca0.5-xAgxMnO3 with 0.0

  4. Structure and transport properties of Ge quantum dots in a SiO2 matrix

    NASA Astrophysics Data System (ADS)

    Slunjski, R.; Dub?ek, P.; Radi?, N.; Bernstorff, S.; Pivac, B.

    2015-06-01

    Germanium (Ge) nanoparticles or quantum dots (QDs) embedded in a transparent dielectric matrix have properties radically different from the bulk semiconductor and present a great potential for application in electronic and optoelectronic devices. Due to quantum confinement properties, the optical bandgap of QD-based materials can be tuned by varying the nanoparticle size. These properties may be exploited for the fabrication of nanoscale electronic devices or advanced solar cells. In this work we explored structural and transport properties of QD based superstructures for advanced solar cells. Magnetron cosputtering was used for deposition and upon suitable thermal treatment a superstructure of QDs was formed. Transport properties were explored by I–V measurement in the dark together with a C–V characterization. The obtained results were modeled with the known transport mechanisms for QDs containing materials. A special emphasis is given to trap controlled space charge limited current and hopping conductivity mechanism. We have shown that in our samples a significant charge is stored in the SiO2 layers with embedded Ge QDs. That charge is predominantly stored into traps at or close to the Ge(QDs)/SiO2 interface.

  5. Transport Properties of Sodium Silicate Glasses with High Water Contents

    NASA Astrophysics Data System (ADS)

    Molinelli, Joyce E.

    Sodium disilicate and sodium tetrasilicate glasses with water contents ranging up to approximately eleven weight percent water were prepared by a hydrothermal method. They contain water as hydroxyls bonded to the silica network and molecular water located within the glass structure in non-network sites. Conduction and diffusion measurements were performed on these glasses to see the effects of the sample compositions on such properties as ionic conductivity, dielectric relaxation and sodium diffusion. Water hydration measurements were performed on sodium trisilicate glasses as well. It was found that ionic conductivity is due mainly to the motion of sodium ions. The conductivity, static dielectric constant, and sodium diffusion coefficient go through a minimum with increasing water content. This is attributed to the predominance of each of the two "types" of water in a part of the range of water contents studied. For any given water content, the conductivity and diffusion coefficient increase with increasing sodium oxide content. From the water hydration measurements, the diffusion coefficient of molecular water in the glass was estimated and was found to increase with increasing water content in the glasses studied. The hydration was found to be controlled by either of two mechanisms, the usual Fickian diffusion of molecular water due to the chemical potential gradient or Case II diffusion due to the stress gradient. Most compositions studied were predominantly controlled by one of these types, although there are expected to be compositions in which both types contribute significantly. It is believed that the hydroxyl content prevents ionic motion in these glasses. On the other hand, it is believed that the molecular water content contributes to the motion by a general loosening of the network, increasng conductivity and diffusion.

  6. Static and transport properties of alkyltrimethylammonium cation-based room-temperature ionic liquids.

    PubMed

    Seki, Shiro; Tsuzuki, Seiji; Hayamizu, Kikuko; Serizawa, Nobuyuki; Ono, Shimpei; Takei, Katsuhito; Doi, Hiroyuki; Umebayashi, Yasuhiro

    2014-05-01

    We have measured physicochemical properties of five alkyltrimethylammonium cation-based room-temperature ionic liquids and compared them with those obtained from computational methods. We have found that static properties (density and refractive index) and transport properties (ionic conductivity, self-diffusion coefficient, and viscosity) of these ionic liquids show close relations with the length of the alkyl chain. In particular, static properties obtained by experimental methods exhibit a trend complementary to that by computational methods (refractive index ? [polarizability/molar volume]). Moreover, the self-diffusion coefficient obtained by molecular dynamics (MD) simulation was consistent with the data obtained by the pulsed-gradient spin-echo nuclear magnetic resonance technique, which suggests that computational methods can be supplemental tools to predict physicochemical properties of room-temperature ionic liquids. PMID:24702446

  7. Charge transport and memristive properties of graphene quantum dots embedded in poly(3-hexylthiophene) matrix

    NASA Astrophysics Data System (ADS)

    Cosmin Obreja, Alexandru; Cristea, Dana; Mihalache, Iuliana; Radoi, Antonio; Gavrila, Raluca; Comanescu, Florin; Kusko, Cristian

    2014-08-01

    We show that graphene quantum dots (GQD) embedded in a semiconducting poly(3-hexylthiophene) polymeric matrix act as charge trapping nanomaterials. In plane current-voltage (I-V) measurements of thin films realized from this nanocomposite deposited on gold interdigitated electrodes revealed that the GQD enhanced dramatically the hole transport. I-V characteristics exhibited a strong nonlinear behavior and a pinched hysteresis loop, a signature of a memristive response. The transport properties of this nanocomposite were explained in terms of a trap controlled space charge limited current mechanism.

  8. Accessing the transport properties of graphene and its multilayers at high carrier density

    PubMed Central

    Ye, Jianting; Craciun, Monica F.; Koshino, Mikito; Russo, Saverio; Inoue, Seiji; Yuan, Hongtao; Shimotani, Hidekazu; Morpurgo, Alberto F.; Iwasa, Yoshihiro

    2011-01-01

    We present a comparative study of high carrier density transport in mono-, bi-, and trilayer graphene using electric double-layer transistors to continuously tune the carrier density up to values exceeding 1014 cm-2. Whereas in monolayer the conductivity saturates, in bi- and trilayer filling of the higher-energy bands is observed to cause a nonmonotonic behavior of the conductivity and a large increase in the quantum capacitance. These systematic trends not only show how the intrinsic high-density transport properties of graphene can be accessed by field effect, but also demonstrate the robustness of ion-gated graphene, which is crucial for possible future applications. PMID:21828007

  9. Transport Properties of CVD Grown TMDs on Flat and Patterned Substrates

    NASA Astrophysics Data System (ADS)

    Martinez, Joseph; Nguyen, Ariana; Scott, Thomas; Preciado, Edwin; Klee, Velveth; Sun, Dezheng; Sharma, Pankaj; Lu, I.-Hsi; Barroso, David; Kim, Sukhyun; Shur, V. Ya.; Gruverman, Alexei; Dowben, Peter A.; Bartels, Ludwig

    2015-03-01

    Transition Metal Dichalcogenides (TMDs), MX2 (M =Mo, W, etc., X =S, Se, Te), have shown great promise for applications as electronic, spintronic and photonic materials. We show growth of MX2 materials under UHV (ultrahigh vacuum) and via CVD (chemical vapor deposition) on both flat and patterned substrates. Deposition on periodically-poled ferroelectric substrates reveals the impact of poling domains and the ability to reversibly invert the transport characteristics from n- to p-doped. 3D geometric patterning of substrates permits the growth across trenches and at angles to the substrate plane leading to modifications of the commonly-addressed in-plane transport properties.

  10. Improving charge transport property and energy transfer with carbon quantum dots in inverted polymer solar cells

    SciTech Connect

    Liu, Chunyu; Chang, Kaiwen; Guo, Wenbin, E-mail: guowb@jlu.edu.cn, E-mail: chenwy@jlu.edu.cn, E-mail: dawei.yan@hotmail.com; Li, Hao; Shen, Liang [State Key Laboratory on Integrated Optoelectronics, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Chen, Weiyou, E-mail: guowb@jlu.edu.cn, E-mail: chenwy@jlu.edu.cn, E-mail: dawei.yan@hotmail.com [College of Electronic Science and Engineering, Jilin University, 2699 Qianjin Street, Changchun 130012 (China); Yan, Dawei, E-mail: guowb@jlu.edu.cn, E-mail: chenwy@jlu.edu.cn, E-mail: dawei.yan@hotmail.com [Research Center of Laser Fusion, CAEP, P.O. Box 919-983, Mianyang 621900 (China)

    2014-08-18

    Carbon quantum dots (Cdots) are synthesized by a simple method and introduced into active layer of polymer solar cells (PSCs). The performance of doped devices was apparently improved, and the highest power conversion efficiency of 7.05% was obtained, corresponding to a 28.2% enhancement compared with that of the contrast device. The charge transport properties, resistance, impedance, and transient absorption spectrum are systematically investigated to explore how the Cdots affect on PSCs performance. This study reveals the importance of Cdots in enhancing the efficiency of PSCs and gives insight into the mechanism of charge transport improvement.

  11. Magnetically Controlled Electronic Transport Properties of a Ferromagnetic Junction on the Surface of a Topological Insulator

    NASA Astrophysics Data System (ADS)

    Liu, Zheng-Qin; Wang, Rui-Qiang; Deng, Ming-Xun; Hu, Liang-Bin

    2015-06-01

    We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topological insulator. The current-voltage characteristic curve and the tunneling conductance are calculated theoretically. Two interesting transport features are predicted: observable negative differential conductances and linear conductances tunable from unit to nearly zero. These features can be magnetically manipulated simply by changing the spacial orientation of the magnetization. Our results may contribute to the development of high-speed switching and functional applications or electrically controlled magnetization switching. Supported by National Natural Science Foundation of China under Grant Nos. 11174088, 11175067, 11274124

  12. Synthesis and Quantum Transport Properties of Bi2Se3 Topological Insulator Nanostructures

    PubMed Central

    Yan, Yuan; Liao, Zhi-Min; Zhou, Yang-Bo; Wu, Han-Chun; Bie, Ya-Qing; Chen, Jing-Jing; Meng, Jie; Wu, Xiao-Song; Yu, Da-Peng

    2013-01-01

    Bi2Se3 nanocrystals with various morphologies, including nanotower, nanoplate, nanoflake, nanobeam and nanowire, have been synthesized. Well-distinguished Shubnikov-de Haas (SdH) oscillations were observed in Bi2Se3 nanoplates and nanobeams. Careful analysis of the SdH oscillations suggests the existence of Berry's phase ?, which confirms the quantum transport of the surface Dirac fermions in both Bi2Se3 nanoplates and nanobeams without intended doping. The observation of the singular quantum transport of the topological surface states implies that the high-quality Bi2Se3 nanostructures have superiorities for investigating the novel physical properties and developing the potential applications. PMID:23405278

  13. Properties of transported African mineral dust aerosols in the Mediterranean region

    NASA Astrophysics Data System (ADS)

    Denjean, Cyrielle; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Triquet, Sylvain; Zapf, Pascal; Loisil, Rodrigue; Bourrianne, Thierry; Freney, Evelyn; Dupuy, Regis; Sellegri, Karine; Schwarzenbock, Alfons; Torres, Benjamin; Mallet, Marc; Cassola, Federico; Prati, Paolo; Formenti, Paola

    2015-04-01

    The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), one intensive airborne campaign (ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) has been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 µm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to the dust origin and transport. Case studies of dust transport from known but differing origins (source regions in Tunisia, Algeria, and Mauritania) and at different times after transport, will be presented. Results will be compared to equivalent measurements over source regions interpreted in terms of the evolution of the particle size distribution, chemical composition and optical properties.

  14. Multiple-pumped-well aquifer test to determine the anisotropic properties of a karst limestone aquifer in Pasco County, Florida, USA

    Microsoft Academic Search

    Louis H. Motz

    2009-01-01

    Groundwater-level data from an aquifer test utilizing four pumped wells conducted in the South Pasco wellfield in Pasco County,\\u000a Florida, USA, were analyzed to determine the anisotropic transmissivity tensor, storativity, and leakance in the vicinity\\u000a of the wellfield. A weighted least-squares procedure was used to analyze drawdowns measured at eight observation wells, and\\u000a it was determined that the major axis

  15. A new approach to the pseudo-orthogonal properties of eigenfunction expansion form of the crack-tip complex potential function in anisotropic and piezoelectric fracture mechanics

    Microsoft Academic Search

    Zhuo-Cheng Ou; Yi-Heng Chen

    2006-01-01

    Over the past twenty years, the well-known weight function theory based on the Bueckner work conjugate integral has been widely used to calculate crack tip fracture dominant parameter such as the stress intensity factor, the energy release rate (or the J-integral) and the T-stress in various kinds of cracked materials (e.g. isotropic materials, anisotropic materials and piezoelectric materials). Meanwhile, the

  16. Correlation of microstructure and thermo-mechanical properties of a novel hydrogen transport membrane

    NASA Astrophysics Data System (ADS)

    Zhang, Yongjun

    A key part of the FutureGen concept is to support the production of hydrogen to fuel a "hydrogen economy," with the use of clean burning hydrogen in power-producing fuel cells, as well as for use as a transportation fuel. One of the key technical barriers to FutureGen deployment is reliable and efficient hydrogen separation technology. Most Hydrogen Transport Membrane (HTM) research currently focuses on separation technology and hydrogen flux characterization. No significant work has been performed on thermo-mechanical properties of HTMs. The objective of the thesis is to understand the structure-property correlation of HTM and to characterize (1) thermo mechanical properties under different reducing environments and thermal cycles (thermal shock), and (2) evaluate the stability of the novel HTM material. A novel HTM cermet bulk sample was characterized for its physical and mechanical properties at both room temperature and at elevated temperature up to 1000°C. Micro-structural properties and residual stresses were evaluated in order to understand the changing mechanism of the microstructure and its effects on the mechanical properties of materials. A correlation of the microstructural and thermo mechanical properties of the HTM system was established for both HTM and the substrate material. Mechanical properties of both selected structural ceramics and the novel HTM cermet bulk sample are affected mainly by porosity and microstructural features, such as grain size and pore size-distribution. The Young's Modulus (E-value) is positively correlated to the flexural strength for materials with similar crystallographic structure. However, for different crystallographic materials, physical properties are independent of mechanical properties. Microstructural properties, particularly, grain size and crystallographic structure, and thermodynamic properties are the main factors affecting the mechanical properties at both room and high temperatures. The HTM cermet behaves more like an elastic material at room temperature and as a ductile material at temperature above 850°C. The oxidation and the plasticity of Pd phase mainly affected the mechanical properties of HTM cermet at high temperature, also as a result of thermal cycling. Residual stress induced in the HTM by thermo cycles also plays a very critical role in defining the thermo-mechanical properties.

  17. Conformally flat polytropes for anisotropic matter

    E-print Network

    L. Herrera; A. Di Prisco; W. Barreto; J. Ospino

    2014-11-05

    We analyze in detail conformally flat spherically symmetric fluid distributions, satisfying a polytropic equation of state. Among the two possible families of relativistic polytropes, only one contains models which satisfy all the required physical conditions. The ensuing configurations are necessarily anisotropic and show interesting physical properties. Prospective applications of the presented models to the study of super-Chandrasekhar white dwarfs, are discussed.

  18. Anisotropic magnetoresistance effect in sub-micron nickel disks

    NASA Astrophysics Data System (ADS)

    Wren, T.; Kazakova, O.

    2015-05-01

    The hysteretic transport properties of vortex states in sub-micron nickel disks are measured using the anisotropic magnetoresistance (AMR) effect and correlated with the magnetization state of the disks using in-situ magnetic force microscopy and micromagnetic modelling. The magnetoresistance behavior is described by a simple AMR model; however, the nucleation and annihilation fields of the vortex state differ when the magnetic field is applied parallel (0°) or perpendicular (90°) to the applied current within the sample plane. In the 0° orientation, the vortex magnetoresistance behaves similar to that reported in the literature. However, in the 90° orientation, the vortex nucleates and annihilates at lower applied fields than in the 0° orientation. Moreover, in the latter orientation, the annihilation process occurs in a two-step transition. This difference is attributed to the effect of the inhomogeneous current distribution within the magnetic disk.

  19. 41 CFR 102-36.400 - Who pays for the transportation costs when foreign excess personal property is returned to the...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...the transportation costs when foreign excess personal property is returned to the United States...Continued) FEDERAL MANAGEMENT REGULATION PERSONAL PROPERTY 36-DISPOSITION OF EXCESS PERSONAL PROPERTY Personal Property Whose...

  20. 41 CFR 102-36.400 - Who pays for the transportation costs when foreign excess personal property is returned to the...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...the transportation costs when foreign excess personal property is returned to the United States...Continued) FEDERAL MANAGEMENT REGULATION PERSONAL PROPERTY 36-DISPOSITION OF EXCESS PERSONAL PROPERTY Personal Property Whose...

  1. Study of transport properties with relativistic ponderomotive effect in two-electron temperature plasma

    NASA Astrophysics Data System (ADS)

    Sen, Sonu; Varshney, Meenu Asthana; Dubey, A.; Varshney, Dinesh

    2014-04-01

    In the present paper we make an analytical investigation to study transport properties with relativistic ponderomotive effect in two-electron temperature plasma. Using fluid model the two-electron temperature are introduced through relativistic ponderomotive force for the transportation of two species of electrons. Applying WKB and paraxial ray approximation the nonlinear dielectric constant and self-focusing equation is evaluated and analyzed with experimental relevance. Numerical calculations are made for different concentration of electron density (1019-1021 per cm3) at arbitrary values of laser intensity in the range 1018-1021 W/cm2. For a minimum radius depending on the initial conditions it is oscillating between a minimum and maximum value. The hot electrons leading to the increase of the on-axis transportation and favorable effect on relativistic self-focusing.

  2. Study of transport properties with relativistic ponderomotive effect in two-electron temperature plasma

    SciTech Connect

    Sen, Sonu, E-mail: ssen.plasma@gmail.com; Dubey, A. [Department of Engineering Physics, Indore Institute of Science and Technology, Indore-453331 (India); Varshney, Meenu Asthana [Department of Physics, M. B. Khalsa College, Indore?452002 (India); Varshney, Dinesh [School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa road Campus, Indore-452001 (India)

    2014-04-24

    In the present paper we make an analytical investigation to study transport properties with relativistic ponderomotive effect in two-electron temperature plasma. Using fluid model the two-electron temperature are introduced through relativistic ponderomotive force for the transportation of two species of electrons. Applying WKB and paraxial ray approximation the nonlinear dielectric constant and self-focusing equation is evaluated and analyzed with experimental relevance. Numerical calculations are made for different concentration of electron density (10{sup 19}?10{sup 21} per cm{sup 3}) at arbitrary values of laser intensity in the range 10{sup 18}?10{sup 21} W/cm{sup 2}. For a minimum radius depending on the initial conditions it is oscillating between a minimum and maximum value. The hot electrons leading to the increase of the on-axis transportation and favorable effect on relativistic self-focusing.

  3. Transport properties of Nd1-xFexOF polycrystalline films

    NASA Astrophysics Data System (ADS)

    Corrales-Mendoza, I.; Rangel-Kuoppa, Victor-Tapio; Conde-Gallardo, A.

    2013-12-01

    The transport properties of Nd1-xFexOF films with 0.2transport properties are not governed by a typical band conduction mechanism but by a variable range hopping process.

  4. Impacts of Transport Properties of Porous Corrosion Product Layer on Effective Corrosion Rate

    NASA Astrophysics Data System (ADS)

    Li, Xiaobai; Cook, David

    2012-11-01

    Condensing exhaust gases containing H2O, SO3 and NOx cause serious corrosion failure in various industry processes. For example, in modern compact heat cells, corrosion products deposit on top of the heat exchanger cooling fins, blocking the flow passages and drastically decreasing system performance. The transport properties of porous corrosion product layers play important role in determining the corrosion tendency and observed corrosion rate. To understand the corrosion mechanism for Aluminum alloy in sulfuric acid environment, impacts of transport properties of corrosion residual layers are investigated with different numerical models for porous layer diffusivity. The effective corrosion rates resulted from these models are compared to corresponding experimental measurements. A multilayer diffusivity model in which diffusivity depends both on porous layer structure and composition shows excellent agreements with experimental data. This model is currently being used in a multi-scale flow simulation framework to predict corrosion phenomena in heat cells.

  5. Atomistic force field for pyridinium-based ionic liquids: reliable transport properties.

    PubMed

    Voroshylova, Iuliia V; Chaban, Vitaly V

    2014-09-11

    Reliable force field (FF) is a central issue in successful prediction of physical chemical properties via computer simulations. This work introduces refined FF parameters for six popular ionic liquids (ILs) of the pyridinium family (butylpyridinium tetrafluoroborate, bis(trifluoromethanesulfonyl)imide, dicyanamide, hexafluorophosphate, triflate, chloride). We elaborate a systematic procedure, which allows accounting for specific cation-anion interactions in the liquid phase. Once these interactions are described accurately, all experimentally determined transport properties can be reproduced. We prove that three parameters per interaction site (atom diameter, depth of potential well, point electrostatic charge) provide a sufficient basis to predict thermodynamics (heat of vaporization, density), structure (radial distributions), and transport (diffusion, viscosity, conductivity) of ILs at room conditions and elevated temperature. The developed atomistic models provide a systematic refinement upon the well-known Canongia Lopes-Pádua (CL&P) FF. Together with the original CL&P parameters the present models foster a computational investigation of ionic liquids. PMID:25144141

  6. Standards and conventions for the TOPS (Transportation Operational Personal Property Standard System) user interface

    SciTech Connect

    Truett, T.; Diegel, S.; Kraemer, K.; Loftis, J.; Meszaros, P.; Singley, P.; Spears, M.; Stevens, M.; Stevens, S.; Wilkinson-Singley, E.; Yow, T.

    1988-08-01

    The Transportation Operational Personal Property Standard System (TOPS) is an automated information management system to help administer the personal property transportation program for the Department of Defense. Prototype testing at four field sites is planned for the late summer of 1988. These standards are written to ensure that the user interface for TOPS is consistent among modules, easy for the user to understand, and efficient to use. The standards provide guidance to TOPS analysts in the design of screens, the programming of function keys, and the implementation of user instructions, error messages, and help files. In cases where flexibility is more important than consistency, optional conventions are suggested. 14 refs., 12 figs., 2 tabs.

  7. Magnetism and transport properties of zigzag graphene nanoribbons/hexagonal boron nitride heterostructures

    NASA Astrophysics Data System (ADS)

    Ilyasov, V. V.; Meshi, B. C.; Nguyen, V. C.; Ershov, I. V.; Nguyen, D. C.

    2014-02-01

    Results of ab initio study of magnetism and transport properties of charge carriers in zigzag graphene nanoribbons (ZGNR) on hexagonal boron nitride (h-BN(0001)) substrate are presented within the density functional theory framework. Peculiarities of the interface band structure and its role in the formation of magnetism and transport properties of the ZGNR/h-BN(0001) heterostructure have been studied using two different density functional approximations. The effect of the substrate and graphene nanoribbons width on the low-energy spectrum of ?-electrons, local magnetic moments on atoms of interface, and charge carriers mobility in the ZGNR/h-BN(0001) heterostructures have been established for the first time. The regularity consisting in the charge carrier mobility growth with decrease of dimers number in nanoribbon was also established. It is found that the charge carriers mobility in the N-ZGNR/h-BN(0001) (N—number of carbon (C) dimers) heterostructures is 5% higher than in freestanding ZGNR.

  8. Theoretical study of electronic transport properties of a graphene-silicene bilayer

    NASA Astrophysics Data System (ADS)

    Berdiyorov, G. R.; Bahlouli, H.; Peeters, F. M.

    2015-06-01

    Electronic transport properties of a graphene-silicene bilayer system are studied using density-functional theory in combination with the nonequilibrium Green's function formalism. Depending on the energy of the electrons, the transmission can be larger in this system as compared to the sum of the transmissions of separated graphene and silicene monolayers. This effect is related to the increased electron density of states in the bilayer sample. At some energies, the electronic states become localized in one of the layers, resulting in the suppression of the electron transmission. The effect of an applied voltage on the transmission becomes more pronounced in the layered sample as compared to graphene due to the larger variation of the electrostatic potential profile. Our findings will be useful when creating hybrid nanoscale devices where enhanced transport properties will be desirable.

  9. Irradiation response of commercial, high-Tc superconducting tapes: Electromagnetic transport properties

    NASA Astrophysics Data System (ADS)

    Gapud, A. A.; Greenwood, N. T.; Alexander, J. A.; Khan, A.; Leonard, K. J.; Aytug, T.; List, F. A.; Rupich, M. W.; Zhang, Y.

    2015-07-01

    Effects of low dose ion irradiation on the electrical transport current properties of commercially available high-temperature superconducting, coated-conductor tapes were investigated, in view of potential applications in irradiative environments. Three different tapes, each with unique and tailored as-grown flux-pinning structures, were irradiated with Au and Ni ions at energies that provide a range of damage effects, with accumulated damage levels near that expected for conductors in, for example, a fusion reactor environment. Measurements using transport current determined the pre- and post-irradiation resistivity, critical current density, and pinning force density, yielding critical temperatures, irreversibility lines, and inferred vortex creep rates. Results show that, at the irradiation damage levels tested, any detriment to as-grown pre-irradiation properties is modest; indeed in one case already-superior pinning forces are enhanced, leading to higher critical currents.

  10. Quantum path integral molecular dynamics simulations on transport properties of dense liquid helium

    E-print Network

    Kang, Dongdong; Sun, Huayang; Yuan, Jianmin

    2015-01-01

    Transport properties of dense liquid helium under the conditions of planet's core and cool atmosphere of white dwarfs have been investigated by using the improved centroid path-integral simulations combined with density functional theory. The self-diffusion is largely higher and the shear viscosity is notably lower predicted with the quantum mechanical description of the nuclear motion compared with the description by Newton equation. The results show that nuclear quantum effects (NQEs), which depends on the temperature and density of the matter via the thermal de Broglie wavelength and the ionization of electrons, are essential for the transport properties of dense liquid helium at certain astrophysical conditions. The Stokes-Einstein relation between diffusion and viscosity in strongly coupled regime is also examined to display the influences of NQEs.

  11. Transport and AC loss properties of the repaired multifilamentary REBCO superconducting tapes

    NASA Astrophysics Data System (ADS)

    Yamasaki, S.; Iwakuma, M.; Funaki, K.; Kato, J.; Chikumoto, T.; Tanabe, K.; Nakao, K.; Izumi, T.; Yamada, Y.; Shiohara, Y.; Saito, T.

    2010-11-01

    For near-future applications of REBa 2Cu 3O 7 (REBCO) coated conductors to electric power cables, transformers and Superconducting Magnetic Energy Storage (SMES), the long taped wires with high performance in the transport properties have been designed and fabricated. Moreover, in order to drastically reduce AC losses in perpendicular field configuration, advanced multifilament YBCO coated conductors (MFYCCs) fabricated with technique of a laser scribing process have been also developed. In the present study, from engineering viewpoints to utilize such advanced conductors, we evaluated the transport and AC loss properties of short MFYCCs with a repaired part or a joint by a diffusion joint technique with the saddle-shaped pickup coil method.

  12. Magnetism and transport properties of zigzag graphene nanoribbons/hexagonal boron nitride heterostructures

    SciTech Connect

    Ilyasov, V. V., E-mail: viily@mail.ru, E-mail: chuongnguyen11@gmail.com; Meshi, B. C.; Nguyen, V. C., E-mail: viily@mail.ru, E-mail: chuongnguyen11@gmail.com; Ershov, I. V. [Don State Technical University, 1 Gagarin Sq, 344000 Rostov on Don (Russian Federation); Nguyen, D. C. [Department of Electronic Materials, School of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet Rd, 10000 Hanoi (Viet Nam)

    2014-02-07

    Results of ab initio study of magnetism and transport properties of charge carriers in zigzag graphene nanoribbons (ZGNR) on hexagonal boron nitride (h-BN(0001)) substrate are presented within the density functional theory framework. Peculiarities of the interface band structure and its role in the formation of magnetism and transport properties of the ZGNR/h-BN(0001) heterostructure have been studied using two different density functional approximations. The effect of the substrate and graphene nanoribbons width on the low-energy spectrum of ?-electrons, local magnetic moments on atoms of interface, and charge carriers mobility in the ZGNR/h-BN(0001) heterostructures have been established for the first time. The regularity consisting in the charge carrier mobility growth with decrease of dimers number in nanoribbon was also established. It is found that the charge carriers mobility in the N-ZGNR/h-BN(0001) (N—number of carbon (C) dimers) heterostructures is 5% higher than in freestanding ZGNR.

  13. Electronic and transport properties of a molecular junction with asymmetric contacts

    NASA Astrophysics Data System (ADS)

    Tsai, M.-H.; Lu, T.-H.

    2010-02-01

    Asymmetric molecular junctions have been shown experimentally to exhibit a dual-conductance transport property with a pulse-like current-voltage characteristic, by Reed and co-workers. Using a recently developed first-principles integrated piecewise thermal equilibrium current calculation method and a gold-benzene-1-olate-4-thiolate-gold model molecular junction, this unusual transport property has been reproduced. Analysis of the electrostatics and the electronic structure reveals that the high-current state results from subtle bias induced charge transfer at the electrode-molecule contacts that raises molecular orbital energies and enhances the current-contributing molecular density of states and the probabilities of resonance tunneling of conduction electrons from one electrode to another.

  14. Irradiation of commercial, high-Tc superconducting tape for potential fusion applications: electromagnetic transport properties

    SciTech Connect

    Aytug, Tolga [ORNL; Gapud, Albert A. [University of South Alabama, Mobile; List III, Frederick Alyious [ORNL; Leonard, Keith J [ORNL; Rupich, Marty [American Superconductor Corporation, Westborough, MA; Zhang, Yanwen [ORNL; Greenwood, N T [University of South Alabama, Mobile; Alexander, J A [University of South Alabama, Mobile; Khan, A [University of South Alabama, Mobile

    2015-01-01

    Effects of low dose irradiation on the electrical transport current properties of commercially available high-temperature superconducting, coated-conductor tapes were investigated, in view of potential applications in the irradiative environment of fusion reactors. Three different tapes, each with unique as-grown flux-pinning structures, were irradiated with Au and Ni ions at energies that provide a range of damage effects, with accumulated damage levels near that expected for conductors in a fusion reactor environment. Measurements using transport current determined the pre- and post-irradiation resistivity, critical current density, and pinning force density, yielding critical temperatures, irreversibility lines, and inferred vortex creep rates. Results show that at the irradiation damage levels tested, any detriment to as-grown pre-irradiation properties is modest; indeed in one case already-superior pinning forces are enhanced, leading to higher critical currents.

  15. Nanofiber connectors Flexible Carbon-Nanofiber Connectors with Anisotropic

    E-print Network

    Javey, Ali

    Nanofiber connectors Flexible Carbon-Nanofiber Connectors with Anisotropic Adhesion Properties to design self-selective connectors to bind morphologically self-similar components together. Specifically, we recently reported self- selective connectors based on inorganic/organic nanowire (NW) arrays

  16. Interactive FORTRAN IV computer programs for the thermodynamic and transport properties of selected cryogens (fluids pack)

    NASA Technical Reports Server (NTRS)

    Mccarty, R. D.

    1980-01-01

    The thermodynamic and transport properties of selected cryogens had programmed into a series of computer routines. Input variables are any two of P, rho or T in the single phase regions and either P or T for the saturated liquid or vapor state. The output is pressure, density, temperature, entropy, enthalpy for all of the fluids and in most cases specific heat capacity and speed of sound. Viscosity and thermal conductivity are also given for most of the fluids. The programs are designed for access by remote terminal; however, they have been written in a modular form to allow the user to select either specific fluids or specific properties for particular needs. The program includes properties for hydrogen, helium, neon, nitrogen, oxygen, argon, and methane. The programs include properties for gaseous and liquid states usually from the triple point to some upper limit of pressure and temperature which varies from fluid to fluid.

  17. Calorimetric and transport properties of Zircalloy 2, Zircalloy 4, and Inconel 625

    SciTech Connect

    Maglic, K.D.; Perovic, N.Lj.; Stanimirovic, A.M. [Institute of Nuclear Sciences, Belgrade (Yugoslavia)

    1994-07-01

    This paper presents the measurements and the results on thermal and electrical transport properties of three nuclear reactor cladding materials: Zircalloy 2, Zircalloy 4, and Inconel 625. Study of these materials constituted a part of the IAEA coordinated research program aimed at the generation and establishment of a reliable and complete database of the thermal properties of reactor materials. Measured properties include thermal diffusivity, specific heat, and electrical resistivity. Thermal diffusivity was measured by the laser pulse technique. Specific heat and electrical resistivity were measured using a millisecond-resolution direct electrical pulse heating technique. Thermal conductivity was computed from the experimentally determined thermal diffusivity and specific heat functions and the room temperature density values. Measurements were performed in the 20 to 1500{degrees}C temperature range, depending on the material and property concerned.

  18. Calorimetric and transport properties of Zircalloy 2, Zircalloy 4, and Inconel 625

    NASA Astrophysics Data System (ADS)

    Magli?, K. D.; Perovi?, N. Lj.; Stanimirovi?, A. M.

    1994-07-01

    This paper presents the measurements and the results on thermal and electrical transport properties of three nuclear reactor cladding materials: Zircalloy 2, Zircalloy 4, and Inconel 625. Study of these materials constituted a part of the IAEA coordinated research program aimed at the generation and establishment of a reliable and complete database of the thermal properties of reactor materials. Measured properties include thermal diffusivity, specific heat, and electrical resistivity. Thermal diffusivity was measured by the laser pulse technique. Specific heat and electrical resistivity were measured using a millisecond-resolution direct electrical pulse heating technique. Thermal conductivity was computed from the experimentally determined thermal difusivity and specific heat functions and the room temperature density values. Measurements were performed in the 20 to 1500°C temperature range, depending on the material and property concerned.

  19. Numerical estimation of transport properties of cementitious materials using 3D digital images

    NASA Astrophysics Data System (ADS)

    Ukrainczyk, N.; Koenders, E. A. B.; van Breugel, K.

    2013-07-01

    A multi-scale characterisation of the transport process within cementitious microstructure possesses a great challenge in terms of modelling and schematization. In this paper a numerical method is proposed to mitigate the resolution problems in numerical methods for calculating effective transport properties of porous materials using 3D digital images. The method up-scales sub-voxel information from the fractional occupancy level of the interface voxels, i.e. voxels containing phaseboundary, to increase the accuracy of the pore schematization and hence the accuracy of the numerical transport calculation as well. The numerical identification of the subvoxels that is associated with their level of occupancy by each phase is obtained by increasing the pre-processing resolution. The proposed method is presented and employed for hydrated cement paste microstructures obtained from Hymostruc, a numerical model for cement hydration and microstructure simulation. The new method significantly reduces computational efforts, is relatively easy to implement, and improves the accuracy of the estimation of the effective transport property.

  20. Point Mutations Effects on Charge Transport Properties of the Tumor-Suppressor Gene p53

    E-print Network

    Chi-Tin Shih; Stephan Roche; Rudolf A. Römer

    2007-08-23

    We report on a theoretical study of point mutations effects on charge transfer properties in the DNA sequence of the tumor-suppressor p53 gene. On the basis of effective single-strand or double-strand tight-binding models which simulate hole propagation along the DNA, a statistical analysis of charge transmission modulations associated with all possible point mutations is performed. We find that in contrast to non-cancerous mutations, mutation hotspots tend to result in significantly weaker {\\em changes of transmission properties}. This suggests that charge transport could play a significant role for DNA-repairing deficiency yielding carcinogenesis.

  1. Electronic Transport Properties of Pentacene Single Crystals upon Exposure to Air

    E-print Network

    Oana D. Jurchescu; Jacob Baas; Thomas T. M. Palstra

    2005-01-24

    We report the effect of air exposure on the electronic properties of pentacene single crystals. Air can diffuse reversibly in and out of the crystals and controls the physical properties. We discern two competing mechanisms that modulate the electronic transport. The presence of oxygen increases the hole conduction, as in dark four O2 molecules introduce one charge carrier. This effect is enhanced by the presence of visible light. Contrarily, water, present in ambient air, is incorporated in the crystal lattice and forms trapping sites for injected charges.

  2. Boundary states and transport properties between d-wave superconductors and ferromagnets

    NASA Astrophysics Data System (ADS)

    Kashiwaya, Satoshi; Sawa, Akihito; Koyanagi, Masao; Kashiwaya, Hiromi; Kurosawa, Itaru; Tanaka, Yukio; Yoshida, Nobukatsu

    2000-03-01

    The transport properties between ferromagnets and d-wave superconductors have been investigated experimentally. Layered structures of YBCO/LSMO have been fabricated by laser sputtering methods and patterned by chemical etching processes. Temperature dependences and magnetic responses of the junctions showed several anomalous properties, i.e., asymmetric peak splitting and background increment. By comparing theoretical formula [1] with experimental spectra, the presence of native ferromagnetic insulator between YBCO and LSMO has been suggested. The possibility for the formation of broken time-reversal symmetry states is discussed. [1] S. Kashiwaya, et. al, Phys. Rev. B 60, 3572 (1999).

  3. Local transport properties, morphology and microstructure of ZnO decorated SiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Van Nostrand, Joseph E.; Cortez, Rebecca; Rice, Zachary P.; Cady, Nathaniel C.; Bergkvist, Magnus

    2010-10-01

    We report on a novel, surfactant free method for achieving nanocrystalline ZnO decoration of an SiO2 nanoparticle at ambient temperature. The size distributions of the naked and decorated SiO2 nanoparticles are measured by means of dynamic light scattering, and a monodisperse distribution is observed for each. The morphology and microstructure of the nanoparticles are explored using atomic force microscopy and high resolution transmission electron microscopy. Investigation of the optical properties of the ZnO decorated SiO2 nanoparticles shows absorption at 350 nm. This blue shift in absorption as compared to bulk ZnO is shown to be consistent with quantum confinement effects due to the small size of the ZnO nanocrystals. Finally, the local electronic transport properties of the nanoparticles are explored by scanning conductance atomic force microscopy. A memristive hysteresis in the transport properties of the individual ZnO decorated SiO2 nanoparticles is observed. Optical absorption measurements suggest the presence of oxygen vacancies, whose migration and annihilation appear to contribute to the dynamic conduction properties of the ZnO decorated nanoparticles. We believe this to be the first demonstration of a ZnO decorated SiO2 nanoparticle, and this represents a simple yet powerful way of achieving the optical and electrical properties of ZnO in combination with the simplicity of SiO2 synthesis.

  4. Some thermal transport properties of the FPU model with quadratic pinning

    E-print Network

    Kenichiro Aoki

    2008-01-02

    Thermal transport properties of the FPU $\\beta$ model with a quadratic pinning term are investigated for various couplings and temperatures. In particular, the size dependence of the thermal conductivity, $\\kappa\\propto L^\\alpha$, is studied. $\\alpha$ agrees with that of the FPU $\\beta$ model (with no pinning) at high temperatures but decreases at low temperatures. This crossover behavior occurs at a temperature depending on the strength of the quadratic pinning.

  5. Noise and electrical transport properties of polycrystalline InSb thin films

    Microsoft Academic Search

    Junji Shigeta; Nobuo Kotera; Tetsu Oi

    1976-01-01

    Both noise and electrical transport properties of polycrystalline InSb thin films are measured and analyzed for the same potential model. Films are prepared by evaporation upon sputtered SiO2 glass and annealed in an Ar atmosphere. Films are inhomogeneously compensated and show what appears to be p- and n-type conduction at low temperatures. It is found that the n-type films actually

  6. Critical behavior of superconductors and electrical transport properties of carbon nanotube thin films

    Microsoft Academic Search

    Hua Xu

    2007-01-01

    With AC microwave measurements from 10 MHz up to 50 GHz and DC nanovolt level measurements we have investigated the superconducting phase transition of YBa2Cu3O7-delta films in zero magnetic field and electrical transport properties of single walled carbon nanotube networks. We studied the microwave conductivity of YBa2Cu3O 7-delta thin films around Tc for different incident microwave power and observed that

  7. Magnetic and transport properties of the ferromagnetic semiconductor heterostructures (In,Mn)As\\/(Ga,Al)Sb

    Microsoft Academic Search

    A. Oiwa; A. Endo; S. Katsumoto; Y. Iye; H. Ohno; H. Munekata

    1999-01-01

    We have investigated the magnetic and transport properties of (In,Mn)As thin films grown on a (Ga,Al)Sb layer. Strong perpendicular magnetic anisotropy is observed for the (In,Mn)As layer, the thickness of which is less than the critical value required for relaxation of lattice-mismatch-induced strain. The anomalous Hall coefficient is found to be approximately proportional to the square of resistivity in the

  8. Real-space transfer and hot-electron transport properties in III-V semiconductor heterostructures

    Microsoft Academic Search

    Ryoji Sakamoto; Kiyoyasu Akai; Masataka Inoue

    1989-01-01

    Real-space transfer (RST) of hot electrons in heterostructures was studied using Monte Carlo simulations. Hot-electron distributions in real space were determined self-consistently by taking into account the space-charge field across the heterointerface. Using the analysis of hot-electron distributions in heterostructures, high-field transport properties are discussed from the viewpoint of heterostructure engineering. The simulations indicate that the effects of real-space transfer

  9. An extension of the group contribution model for thermodynamic and transport properties of dilute gases

    Microsoft Academic Search

    Seung-Kyo Oh; Chol-Ho Sim

    2002-01-01

    Earlier work of the group contribution method presented by Oh and Campbell [Oh and Campbell, 1997] for prediction of second\\u000a virial coefficients and dilute gas transport properties has been repeated with a new set of normal alkane second virial coefficient\\u000a data (methane, ethane, propane, and normal pentane critically compiled by Dymond and Smith [1980], normal hexane recommended\\u000a by Dymond et

  10. Chemical and Transport Properties of Carbon–Oxygen–Hydrogen Plasmas in Isochoric Conditions

    Microsoft Academic Search

    Bernard Pateyron; Guy Delluc; Pierre Fauchais

    2005-01-01

    The composition and transport properties of CO2, CO, CH4, CO + Ar (50 vol%), CO + Fe (50 vol%) have been calculated at constant volume assuming local thermodynamic equilibrium (LTE). Except at low temperature (T 4 starting at 0.1 MPa and 298 K the pressure can reach 40 MPa at 20,000 K. The consequence is a shift to higher temperatures of dissociation

  11. Transport properties of CO2-expanded acetonitrile from molecular dynamics simulations

    E-print Network

    Houndonougbo, Yao; Laird, Brian Bostian; Kuczera, Krzysztof

    2007-02-21

    rates. CXLs are a compromise between organic liquids and super- critical CO2. From the processing standpoint, catalyst and reactant solubilities are sufficient to yield relatively high re- action rates. Replacement of part of the organic liquid... our results with those of Li and Maroncelli, who recently reported simulations of transport properties for CO2-acetonitrile mixtures using a different potential for CH3CN and different simulation conditions.11 The molecular models and computational...

  12. Ab initio transport properties of nanostructures from maximally localized Wannier functions

    Microsoft Academic Search

    Arrigo Calzolari; Nicola Marzari; Ivo Souza; Marco Buongiorno Nardelli

    2004-01-01

    We present a comprehensive first-principles study of the ballistic transport properties of low-dimensional nanostructures such as linear chains of atoms (Al, C) and carbon nanotubes in the presence of defects. An approach is introduced where quantum conductance is computed from the combination of accurate plane-wave electronic structure calculations, the evaluation of the corresponding maximally localized Wannier functions, and the calculation

  13. A computational study of the quantum transport properties of a Cu-CNT composite.

    PubMed

    Ghorbani-Asl, Mahdi; Bristowe, Paul D; Koziol, Krzysztof

    2015-07-01

    The quantum transport properties of a Cu-CNT composite are studied using a non-equilibrium Green's function approach combined with the self-consistent-charge density-functional tight-binding method. The results show that the electrical conductance of the composite depends strongly on CNT density and alignment but more weakly on chirality. Alignment with the applied bias is preferred and the conductance of the composite increases as its mass density increases. PMID:26120607

  14. A planarized triphenylborane mesogen: discotic liquid crystals with ambipolar charge-carrier transport properties.

    PubMed

    Kushida, Tomokatsu; Shuto, Ayumi; Yoshio, Masafumi; Kato, Takashi; Yamaguchi, Shigehiro

    2015-06-01

    A discotic liquid-crystalline (LC) material, consisting of a planarized triphenylborane mesogen, was synthesized. X-ray diffraction analysis confirmed that this compound forms a hexagonal columnar LC phase with an interfacial distance of 3.57?Å between the discs. At ambient temperature, this boron-centered discotic liquid crystal exhibited ambipolar carrier transport properties with electron and hole mobility values of approximately 10(-3) and 3×10(-5) ?cm(2) ?V(-1) ?s(-1) , respectively. PMID:25907576

  15. Transport properties of separating membranes MF4SK during alkaline electrolysis of water

    Microsoft Academic Search

    A. N. Ponomarev; Yu. L. Moskvin; S. D. Babenko

    2007-01-01

    The transport properties of separating membranes MF-4SK are studied during electrolysis of H2O in solutions of KOH. The effective diffusion coefficients of molecules of KOH and H2O and the transfer coefficients of ions K+ and OH? and molecules of H2O are measured at KOH concentrations reaching 11 M, currents reaching 0.31 A cm?2, at ambient temperature and at 80°C. In

  16. CPP transport properties of polycrystalline Fe3O4 thin films sputtered on Cu underlayers

    Microsoft Academic Search

    F. Qin; Y. Nozaki; K. Matsuyama

    2005-01-01

    Transport properties of sputtered Fe3O4 thin films have been studied with the current perpendicular to plane (CPP) configuration. Fabricated polycrystalline Fe3O4 films exhibit superior CPP conductivity of 12 kOmega-1.m-1. In addition to the Verwey transition (VT), observed at 114 K, another type of drastic conductivity change [field induced transition (FT)] was observed at lower temperature (T<70 K) and higher bias

  17. Transport properties of strongly correlated metals: crossover from Fermi liquid to bad metal

    Microsoft Academic Search

    Ross H. McKenzie; Jaime Merino

    2000-01-01

    The temperature dependence of the transport properties of the metallic phase of a frustrated Hubbard model on the hypercubic lattice at half-filling are calculated. Dynamical mean-field theory, which maps the Hubbard model onto a single impurity Anderson model that is solved self-consistently, and becomes exact in the limit of large dimensionality, is used. As the temperature increases there is a

  18. Geochemical and transport properties of dissolved organic carbon in a clay-rich aquitard

    Microsoft Academic Search

    M. Jim Hendry; J. R. Ranville; B. E. J. Boldt-Leppin; L. I. Wassenaar

    2003-01-01

    The properties and controls on the diffusive transport of dissolved organic carbon (DOC) in a thick clay-rich till aquitard were investigated. DOC was measured in 14 piezometers ranging in depth from 1.2 to 43 m below ground (BG). The DOC data showed a decrease in concentration with depth from 168 mg\\/L in the surficial, fractured, and oxidized zone (1.2 m

  19. Geochemical and transport properties of dissolved organic carbon in a clay-rich aquitard

    Microsoft Academic Search

    M. Jim Hendry; J. R. Ranville; B. E. J. Boldt-Leppin; L. I. Wassenaar

    2003-01-01

    [1] The properties and controls on the diffusive transport of dissolved organic carbon (DOC) in a thick clay-rich till aquitard were investigated. DOC was measured in 14 piezometers ranging in depth from 1.2 to 43 m below ground ( BG). The DOC data showed a decrease in concentration with depth from 168 mg\\/L in the surficial, fractured, and oxidized zone

  20. The influence of magnetic ordering on the transport properties of Cr–Fe–Mn alloys

    Microsoft Academic Search

    K. Perzynska; M. Biernacka; L. Dobrzynski; D. Satula; K. Szymanski; J. Waliszewski; P. Zaleski

    2002-01-01

    In order to understand conditions in which magnetic ordering affects the electric transport properties in magnetically disordered Cr–Fe–Mn alloys, GMR was investigated in two series of samples: Cr75+xFe16+xMn9?x and Cr75+yFe16?yMn9. Magnetic structure of these alloys turned out to be very complex. The observed magnetoresistivity is shown to be particularly sensitive to the FM ordering.