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1

NASA Astrophysics Data System (ADS)

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.

Alerstam, Erik

2014-06-01

2

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

Alerstam, Erik

2014-06-01

3

Linking elastic, mechanical and transport properties in anisotropically cracked rocks

NASA Astrophysics Data System (ADS)

Damage and crack porosity can result in a decrease of the mechanical strength of the rock, the development of elastic and mechanical anisotropy and the enhancement of transport properties. Using Non-Interactive Crack Effective Medium (NIC) theory as a fundamental tool, it is possible to calculate dry and wet elastic properties of cracked rocks in terms of a crack density tensor, average crack aspect ratio and mean crack fabric orientation using the solid grains and fluid elastic properties. Using the same tool, we show that the anisotropy, the shear wave splitting and the dispersion of elastic waves can be derived for anisotropic crack fabrics. Mechanically, the existence of embedded microcrack fabrics in rocks also significantly influences the fracture toughness (KIC) of rocks. We show that KIC can show large amounts of anisotropy as well, the degree and orientation of which being largely constrained once again by the microcrack fabric. NIC can predict relatively well KIC at high crack density, by simply using dimensionless crack densities inverted from velocities. A decrease of 50% for crack densities larger than 1, 80% for crack densities larger than 5 is predicted, in close agreement with our observed experimental variation of KIC. At the microscale, this can be interpreted by the fact that the main fracture is strongly interacting with the pre-existing microcrack fabric. Finally, and above the percolation threshold, macroscopic fluid flow also depends on the porosity, crack density and aspect ratio. Using the permeability model of Guéguen and Dienes (1989) and the crack density and aspect ratio recovered from the elastic wave velocity inversion, we successfully predict the evolution of permeability with pressure for direct comparison with the laboratory measurements. These combined experimental and modelling results illustrate the importance of understanding the details of how rock microstructures change in response to an external stimulus in predicting the simultaneous evolution of rock physical properties.

Schubnel, A.; Benson, P.; Nasseri, F.; Gueguen, Y.; Meredith, P.; Young, R.

2007-12-01

4

Numerical modelling of mass transport in an arterial wall with anisotropic transport properties.

Coronary artery disease results in blockages or narrowing of the artery lumen. Drug eluting stents (DES) were developed to replace bare metal stents in an effort to combat re-blocking of the diseased artery following treatment. The numerical models developed within this study focus on representing the changing trends of drug delivery from an idealised DES in an arterial wall with an anisotropic ultra-structure. To reduce the computational burden of solving coupled physics problems, a model reduction strategy was adopted. Particular focus has been placed upon adequately modelling the influence of strut compression as there is a paucity of numerical studies that account for changes in transport properties in compressed regions of the arterial wall due to stent deployment. This study developed an idealised numerical modelling framework to account for the changes in the directionally dependent porosity and tortuosities of the arterial wall as a result of radial strut compression. The results show that depending on the degree of strut compression, trends in therapeutic drug delivery within the arterial wall can be either increased or decreased. The study highlights the importance of incorporating compression into numerical models to better represent transport within the arterial wall and suggests an appropriate numerical modelling framework that could be utilised in more realistic patient specific arterial geometries. PMID:24210470

Denny, William J; Walsh, Michael T

2014-01-01

5

Anisotropic transport properties of ferromagnetic-superconducting bilayers

. Erdin [Phys. Rev. Lett. 88, 017001 (2002)]. We calculate the periodic pinning force in the stripe structure resulting from a highly inhomogeneous distribution of the vortices and antivortices. We show that the transport in SC-FM bilayer is highly...

Kayali, MA; Pokrovsky, Valery L.

2004-01-01

6

NASA Astrophysics Data System (ADS)

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.

Osuji, Chinedum

2013-03-01

7

Anisotropic magnetothermal transport and spin Seebeck effect

NASA Astrophysics Data System (ADS)

The anisotropic properties of thermal transport in insulating or conducting ferromagnets are derived on the basis of the Onsager reciprocity relations applied to a magnetic system. It is shown that the angular dependence of the temperature gradient takes the same form as that of the anisotropic magnetoresistance, including anomalous and planar Hall contributions. The measured thermocouple generated between the extremities of the nonmagnetic electrode in thermal contact to the ferromagnet follows this same angular dependence. The sign and amplitude of the magnetovoltaic signal is controlled by the difference of the Seebeck coefficients of the thermocouple.

Wegrowe, J.-E.; Drouhin, H.-J.; Lacour, D.

2014-03-01

8

NASA Astrophysics Data System (ADS)

We consider the implications of a phenomenological model self-energy for the charge transport properties of the metallic phase of the overdoped cuprate superconductors. The self-energy is the sum of two terms with characteristic dependencies on temperature, frequency, location on the Fermi surface, and doping. The first term is isotropic over the Fermi surface, independent of doping, and has the frequency and temperature dependence characteristic of a Fermi liquid. The second term is anisotropic over the Fermi surface (vanishing at the same points as the superconducting energy gap), strongly varies with doping (scaling roughly with Tc, the superconducting transition temperature), and has the frequency and temperature dependence characteristic of a marginal Fermi liquid. Previously it has been shown this self-energy can describe a range of experimental data including angle-dependent magnetoresistance and quasiparticle renormalizations determined from specific heat, quantum oscillations, and angle-resolved photoemission spectroscopy. Without introducing new parameters and neglecting vertex corrections we show that this model self-energy can give a quantitative description of the temperature and doping dependence of a range of reported transport properties of Tl2Ba2CuO6+? samples. These include the intralayer resistivity, the frequency-dependent optical conductivity, the intralayer magnetoresistance, and the Hall coefficient. The temperature dependence of the latter two are particularly sensitive to the anisotropy of the scattering rate and to the shape of the Fermi surface. In contrast, the temperature dependence of the Hall angle is dominated by the Fermi liquid contribution to the self-energy that determines the scattering rate in the nodal regions of the Fermi surface.

Kokalj, J.; Hussey, N. E.; McKenzie, Ross H.

2012-07-01

9

Anisotropic flow in transport + hydrodynamics hybrid approaches

NASA Astrophysics Data System (ADS)

This contribution to the focus issue covers anisotropic flow in hybrid approaches. The historical development of hybrid approaches and their impact on the interpretation of flow measurements is reviewed. The major ingredients of a hybrid approach and the transition criteria between transport and hydrodynamics are discussed. The results for anisotropic flow in (event-by-event) hybrid approaches are presented. Some hybrid approaches rely on hadronic transport for the late stages for the reaction (so called afterburner) and others employ transport approaches for the early non-equilibrium evolution. In addition, there are ‘full’ hybrid calculations where a fluid evolution is dynamically embedded in a transport simulation. After demonstrating the success of hybrid approaches at high Relativistic Heavy Ion Collider and Large Hadron Collider energies, existing hybrid caluclations for collective flow observables at lower beam energies are discussed and remaining challenges outlined.

Petersen, Hannah

2014-12-01

10

Anisotropic Transport in Energetic Displacement Cascades

NASA Astrophysics Data System (ADS)

Theoretical concepts and experimental investigations of the effect of target species atomic mass, system geometry, and thermodynamic effects on the anisotropic transport in the ion mixing of metallic systems are reported. Atomic transport mechanisms are discussed in terms of ballistic (collision cascades) and thermal spike transport theory. In the collision cascade case the largely isotropic low energy displacements have a small anisotropic component due to preferential inward momentum distributions. This anisotropic component depends on projectile mass, target mass, and energy transfer to the target atom. Lighter mass species are thought to preferentially displace inward, in a bilayer interface mixing case, due to their greater associated range. Furthermore, the preferential transport is thought to compound with increasing irradiation dose. In the thermal spike case atomic transport is described as an isotropic process when both species in a bilayer system have approximately equal cohesive energies, however, thermal spike induced transport becomes anisotropic when the cohesive energy of the bilayer species differ. Under conditions of different cohesive energies on each side of a bilayer interface, it is thought that the cohesive energy material displaces preferentially into the low cohesive energy layer. Experimental systems of bilayer samples with zero heats of mixing and similar cohesive energies, but different atomic masses, such as Ta on top of Nb (Ta/Nb), Nb on top of Ta (Nb/Ta), Hf on top of Zr (Hf/Zr), and Zr on top of Hf (Zr/Hf) were irradiated by 300 keV Kr^ {++} at a dose of 2 times 10^{16}Kr ^{++}/cm^2 at 77 K. The samples were investigated using embedded markers and Rutherford backscattering spectrometry. The experimental results indicate that the anisotropic transport is dominated by a preferential displacement of the top layer species into the bottom layer. In addition, there is a small enhancement of the inward displacement when the lighter species is on top, indicating a small preferential recoil displacement of the lighter species over the heavier one. The effect of a gradient in cohesive energy across a bilayer interface was investigated by ion mixing experiments of W/Pd, Pd/W, Nb/Cu, Cu/Nb, Ag/V, and V/Ag. The results indicate a preferential transport of higher cohesive energy material (W, Nb, and V) into the low cohesive energy material (Pd, Cu, and Ag). This phenomenon is explained in terms of activation energies and energy deposition gradients. The experimental results suggest that the mechanisms responsible for interface mixing during ion irradiation scale with species cohesive energy. High cohesive energy systems are governed largely by collision cascade transport while low cohesive energy systems are governed by thermal spike transport.

Auner, Gregory William

11

Elastic Anisotropy and Anisotropic Transport Properties of Cu3SbSe4 and Cu3SbS4

NASA Astrophysics Data System (ADS)

Copper-based ternary chalcogenide semiconductors with zincblende-related crystal structures have recently emerged as some of the best performing p-type thermoelectric materials. Here, first-principles calculations are used to investigate the structural, elastic, and thermoelectric properties of Cu3SbSe4 and Cu3SbS4. The calculated lattice constants and atomic coordinates are in good agreement with those obtained in the previous experiments, which shows that our method is reliable. We found that the hybridization among atoms forms [SbSe4] and [CuSe4] tetrahedral structures. The spin–orbit (SO) interaction is included in the calculations for electronic structures and thermoelectric properties. It is predicted that Cu3SbSe4 and Cu3SbS4 are mechanically stable, relatively soft materials with high compressibility, and are low small-hardness ionic materials, and with more anisotropy in shear than in compressibility. The results also show that the mechanical stability of these materials is limited by the shear modulus G. Furthermore, Cu3SbSe4 can be classified as a brittle material, whereas Cu3SbS4 can be classified as a ductile material. The semiclassical Boltzmann transport theory was used to calculate the Seebeck coefficients, electrical conductivities, electronic thermal conductivities, power factors, and thermoelectric figures of merit ZeT of Cu3SbSe4 and Cu3SbS4 along two crystallographic directions, and the optimal doping concentrations were estimated on the basis of the predicted thermoelectric properties. The temperature dependences of the thermoelectric transport properties of Cu3SbSe4 and Cu3SbS4 were also estimated and compared with experimental data, with good agreement observed.

Xu, Bin; Zhang, Xiangdan; Sun, Yunzhou; Zhang, Jing; Wang, Yusheng; Yi, Lin

2014-09-01

12

Phase Diagram and Anisotropic Transport Properties of Nd_1-xSr_xMnO3 Crystals

NASA Astrophysics Data System (ADS)

We have investigated electronic transport and magnetic properties of Nd_1-xSr_xMnO3 crystals with controlled band filling (0.30 <= x <= 0.80) grown by the floating zone method. The phase diagram of Nd_1-xSr_xMnO3 was obtained by measurements of magnetization, resistivity, and crystal structure. The electronic and magnetic properties are critically changed depending on x especially near x=0.50, in which CE-type antiferromagnetic (AF) structure with charge-ordered state exits below 155 K. Such a charge-ordered state completely disappears and ferromagnetic (F) metallic state is stabilized when x is decreased below ~0.47. On the other hand, A-type layered AF structure with T_N ~225K shows up when x is increased to x=0.55. For the A-type x=0.55 crystal, the metallic behavior was observed within the F layers, while along the AF coupled direction the crystal remains insulating over the whole temperature region. The anisotropy ratio of resistivity for the AF and F directions is ~10^2 at 4.2K although the multi-domain structures cannot be eliminated in crystal. We have also confirmed the nearly isotropic transport behavior for the CE-type AF charge-ordered state for the x=0.50 crystal. This work was supported by NEDO of Japan.

Kuwahara, H.; Tomioka, Y.; Asamitsu, A.; Tokura, Y.

1997-03-01

13

On the anisotropic elastic properties of hydroxyapatite.

NASA Technical Reports Server (NTRS)

Experimental measurements of the isotropic elastic moduli on polycrystalline specimens of hydroxyapatite and fluorapatite are compared with elastic constants measured directly from single crystals of fluorapatite in order to derive a set of pseudo single crystal elastic constants for hydroxyapatite. The stiffness coefficients thus derived are given. The anisotropic and isotropic elastic properties are then computed and compared with similar properties derived from experimental observations of the anisotropic behavior of bone.

Katz, J. L.; Ukraincik, K.

1971-01-01

14

A new method based on the adaptation of the Pulse Transient Hot Strip technique to slab sample geometry has been developed for studying thermal conductivity and thermal diffusivity of anisotropic thin film materials (<50 ?m) with thermal conductivity in the 0.01-100 W/mK range, deposited on thin substrates (i.e., wafers). Strength of this technique is that it provides a well-controlled thermal probing depth, making it possible to probe a predetermined depth of the sample layer and thereby avoiding the influence from material(s) deeper down in the sample. To verify the technique a series of measurements were conducted on a y-cut single crystal quartz wafer. A Hot Strip sensor (32-?m wide, 3.2-mm long) was deposited along two orthogonal crystallographic (x- and z-) directions and two independent pulse transients were recorded. Thereafter, the data was fitted to our theoretical model, and the anisotropic thermal transport properties were determined. Using a thermal probing depth of only 30 ?m, we obtained a thermal conductivity along the perpendicular (parallel) direction to the z-, i.e., optic axis of 6.48 (11.4) W/mK, and a thermal diffusivity of 3.62 (6.52) mm(2)/s. This yields a volumetric specific heat of 1.79 MJ/mK. These values agree well with tabulated data on bulk crystalline quartz supporting the accuracy of the technique, and the obtained standard deviation of less than 2.7% demonstrates the precision of this new measurement technique. PMID:24784644

Ma, Y; Gustavsson, J S; Haglund, A; Gustavsson, M; Gustafsson, S E

2014-04-01

15

Anisotropic properties of rare earth silver dibismites

NASA Astrophysics Data System (ADS)

We report measurements of structural, magnetic, thermal and transport properties of the newly synthesized rare earth silver dibismite series RAgBi 2 (R=La-Nd, Sm, Gd), grown via self-flux method. All of the compounds are metals, and those with magnetic ions exhibit long-range magnetic order at low temperatures, with the exception of PrAgBi 2. For the lightest rare earths the samples are of extremely high quality. For LaAgBi 2 de Haas van Alphen oscillations are found in remarkably small fields and high temperatures. The magnetic ground states for compounds that order magnetically appear to be antiferromagnetic, but with less local moment anisotropy than that seen in RBi 2. Anisotropic metamagnetism is observed for CeAgBi 2; however, no large magnetoresistance was observed in any of RAgBi 2, as opposed to either the RAgSb 2 or RSb 2 series. Magnetic ordering temperatures scale poorly with de Gennes scaling.

Petrovic, C.; Bud'ko, S. L.; Strand, J. D.; Canfield, P. C.

2003-04-01

16

Symmetry properties of anisotropic dielectric gratings

This paper describes a theoretical analysis of liquid crystal grating structures and their properties based on the symmetry of the constitutive equations. Exact equations derived by using Bloch-Floquet theorem for one-dimensional anisotropic gratings are discussed. Scattering efficiency of the gratings is analyzed using the method of coupled plane waves having well defined parallel components of the wave vector to decompose

P. Galatola; C. Oldano; P. B. Sunilkumar

1994-01-01

17

Anisotropic Properties of High Transition Temperature Superconductors

The anisotropic normal and superconducting properties in high transition temperature superconductors and related compounds, especially, rm Sm_{1.85 }Ce_{0.15}CuO_{4-y},YBa _2Cu_3O_{y} (6 <=q y <=q 7),Y_{1-x}Pr _{x}Ba_2Cu_3O_{7 -delta} (0 <=q x <=q 1), and La_{1.67}M_{0.33 }NiO_4 (M = Ca, Sr, and Ba) are reported. The anisotropic superconducting state thermodynamic parameters of the electron-doped compound rm Sm_{1.85}Ce_{0.15}CuO _{4-y} have been derived from reversible

Seung-Ho. Han

1994-01-01

18

The Anisotropic Transport Effects on Dilute Plasmas

NASA Astrophysics Data System (ADS)

We examine the linear stability analysis of a hot, dilute, and differentially rotating plasma by considering anisotropic transport effects. In dilute plasmas, the ion Larmor radius is small compared with its collisional mean free path. In this case, the transport of heat and momentum along the magnetic field lines becomes important. This paper presents a novel linear instability that may be more powerful and greater than ideal magnetothermal instability and ideal magnetorotational instability in the dilute astrophysical plasmas. This type of plasma is believed to be found in the intracluster medium (ICM) of galaxy clusters and radiatively ineffective accretion flows around black holes. We derive the dispersion relation of this instability and obtain the instability condition. There is at least one unstable mode that is independent of the temperature gradient direction for a helical magnetic field geometry. This novel instability is driven by the gyroviscosity coupled with differential rotation. Therefore, we call it gyroviscous-modified magnetorotational instability (GvMRI). We examine how the instability depends on signs of the temperature gradient and the gyroviscosity and also on the magnitude of the thermal frequency and on the values of the pitch angle. We provide a detailed physical interpretation of the obtained results. The GvMRI is applicable not only to the accretion flows and ICM but also to the transition region between cool dense gas and the hot low-density plasma in stellar coronae, accretion disks, and the multiphase interstellar medium because it is independent of the temperature gradient direction.

Devlen, Ebru

2011-04-01

19

The annulus fibrosus (AF) of the intervertebral disc (IVD) exhibits a fiber-organized structure which is responsible for anisotropic\\u000a and inhomogeneous mechanical and transport properties. Due to its particular morphology, nutrient transport within AF is regulated\\u000a by complex transport kinetics. This work investigates the diffusive transport of a small solute in the posterior and anterior\\u000a regions of AF since diffusion is

Francesco Travascio; Wei Yong Gu

2007-01-01

20

Anisotropic Properties of Stainless Steel—Clad Aluminum Sheet

NASA Astrophysics Data System (ADS)

The production of a stainless steel—clad aluminum sheet by the cold rolling process is a more efficient and economical approach compared with the other types of processes utilized for the production of such sheets. Because both the stainless steel and aluminum sheets show the highly anisotropic behavior, it is necessary to investigate anisotropic properties of clad sheets for the design of process. In this paper, to investigate the anisotropic properties of stainless steel—clad aluminum sheet, two kinds of clad sheets were considered: STS439/AA3003 and STS439/AA1050/STS304 clad sheets. The uni-axial tension tests at 0, 45 and 90 degrees for the rolling direction were performed to obtained yield stresses and R values. The strain ratio at balanced biaxial tension state was measured from compression disk test. In order to describe the anisotropic behavior of the clad sheet, nonquadratic anisotropic yield function Yld2000-2d was utilized.

Kim, Daeyong; Hwang, Bum Kyu; Lee, Young Seon; Kim, Ji Hoon; Kim, Min-Joong

2010-06-01

21

The annulus fibrosus (AF) of the intervertebral disc (IVD) exhibits a fiber-organized structure which is responsible for anisotropic and inhomogeneous mechanical and transport properties. Due to its particular morphology, nutrient transport within AF is regulated by complex transport kinetics. This work investigates the diffusive transport of a small solute in the posterior and anterior regions of AF since diffusion is the major transport mechanism for low molecular weight nutrients (e.g., oxygen and glucose) in IVD. Diffusion coefficient (D) of fluorescein (332 Da) in bovine coccygeal AF was measured in the three major (axial, circumferential and radial) directions of the IVD by means of Fluorescence Recovery After Photobleaching (FRAP) technique. It was found that the diffusion coefficient was anisotropic and inhomogeneous. In both anterior and posterior regions, the diffusion coefficient in the radial direction was found to be lowest. Circumferential and axial diffusion coefficients were not significantly different in both posterior and anterior regions and their values were about 130% and 150% the value of the radial diffusion coefficient, respectively. The values of diffusion coefficients in the anterior region were in general higher than those of corresponding diffusion coefficients in the posterior region. This study represents the first quantitative analysis of anisotropic diffusion transport in AF by means of FRAP technique and provides additional knowledge on understanding the pathways of nutritional supply into IVD. PMID:17605108

Travascio, Francesco; Gu, Wei Yong

2009-01-01

22

Anisotropic properties of rare-earth dibismites

NASA Astrophysics Data System (ADS)

We report measurements of magnetic, thermal and transport properties of single crystals of rare-earth dibismites RBi 2 (R=La-Nd, Sm), grown via self-flux method. All compounds are good metals, and those with magnetic ions order antiferromagnetically at low temperatures. Ce, Pr and Sm members of the series show single magnetic transition whereas NdBi 2 most likely exhibits two magnetic transitions. Significant magnetic anisotropy and a series of metamagnetic transitions in fields up to 55 kG are found in PrBi 2. Ordering temperatures range from 3 K to just above 16 K and they scale well with the de Gennes factor.

Petrovic, C.; Bud'ko, S. L.; Canfield, P. C.

2002-06-01

23

Microstructures and viscoelastic properties of anisotropic magnetorheological elastomers

The microstructures and viscoelastic properties of anisotropic magnetorheological elastomers are investigated. The measurement results show that their mechanical properties are greatly dependent on the magnetic flux density applied during preparation. A finite-column model is proposed to describe the relationships between the microstructures and the viscoelastic properties. The simulation results agree well with the experimental results.

Lin Chen; X L Gong; W H Li

2007-01-01

24

Anisotropic Tribological Properties of Silicon Carbide

NASA Technical Reports Server (NTRS)

The anisotropic friction, deformation and fracture behavior of single crystal silicon carbide surfaces were investigated in two categories. The categories were called adhesive and abrasive wear processes, respectively. In the adhesive wear process, the adhesion, friction and wear of silicon carbide were markedly dependent on crystallographic orientation. The force to reestablish the shearing fracture of adhesive bond at the interface between silicon carbide and metal was the lowest in the preferred orientation of silicon carbide slip system. The fracturing of silicon carbide occurred near the adhesive bond to metal and it was due to primary cleavages of both prismatic (10(-1)0) and basal (0001) planes.

Miyoshi, K.; Buckley, D. H.

1980-01-01

25

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

epl draft Matter wave transport and Anderson localization in anisotropic three-dimensional disorder study quantum transport of matter waves in anisotropic three-dimensional dis- order. First, we show is directly relevant to ultracold-matter waves in optical disorder, and implications on recent experiments

Paris-Sud XI, UniversitÃ© de

26

We trace the development of azimuthal anisotropy ($v_n$) in A Multi-Phase Transport (AMPT) model using parton-parton collision history. The parton $v_n$ is studied as a function of the number of collisions of each parton in Au+Au and d+Au collisions at $\\sqrt{S_{NN}}$=200~GeV. It is found that the majority of $v_n$ comes from the anisotropic escape probability of partons, with no fundamental difference at low and high transverse momenta. The contribution to $v_n$ from the parton collective flow appears small; however, it is this small anisotropy from the collective flow, not that from the anisotropic escape probability, that is most relevant for medium properties in heavy ion collisions.

He, Liang; Lin, Zi-Wei; Liu, Feng; Molnar, Denes; Wang, Fuqiang

2015-01-01

27

Transport properties of Dirac ferromagnet

NASA Astrophysics Data System (ADS)

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.

Fujimoto, Junji; Kohno, Hiroshi

2014-12-01

28

Optical Properties of Anisotropic Core-Shell Pyramidal Particles

This paper describes an approach to fabricate anisotropic core-shell particles by assembling dielectric beads within fabricated noble metal pyramidal structures. Particles with gold (Au) shells and different dielectric cores were generated, and their optical properties were characterized by single particle spectroscopy. Because of their unique geometry, these particles exhibit multiple plasmon resonances from visible to near-IR wavelengths. PMID:19290590

Sweeney, Christina M.; Hasan, Warefta; Nehl, Colleen L.; Odom, Teri W.

2009-01-01

29

Transport Properties of Nanocomposites

Transport Properties of Nanocomposites were studied in this work. A Monte Carlo technique was used to model the percolation behavior of fibers in a nanocomposite. Once the percolation threshold was found, the effect of fiber dimensions...

Narayanunni, Vinay

2010-07-14

30

TOPICAL REVIEW: Textured silicon nitride: processing and anisotropic properties

NASA Astrophysics Data System (ADS)

Textured silicon nitride (Si3N4) has been intensively studied over the past 15 years because of its use for achieving its superthermal and mechanical properties. In this review we present the fundamental aspects of the processing and anisotropic properties of textured Si3N4, with emphasis on the anisotropic and abnormal grain growth of ?-Si3N4, texture structure and texture analysis, processing methods and anisotropic properties. On the basis of the texturing mechanisms, the processing methods described in this article have been classified into two types: hot-working (HW) and templated grain growth (TGG). The HW method includes the hot-pressing, hot-forging and sinter-forging techniques, and the TGG method includes the cold-pressing, extrusion, tape-casting and strong magnetic field alignment techniques for ?-Si3N4 seed crystals. Each processing technique is thoroughly discussed in terms of theoretical models and experimental data, including the texturing mechanisms and the factors affecting texture development. Also, methods of synthesizing the rodlike ?-Si3N4 single crystals are presented. Various anisotropic properties of textured Si3 N4 and their origins are thoroughly described and discussed, such as hardness, elastic modulus, bending strength, fracture toughness, fracture energy, creep behavior, tribological and wear behavior, erosion behavior, contact damage behavior and thermal conductivity. Models are analyzed to determine the thermal anisotropy by considering the intrinsic thermal anisotropy, degree of orientation and various microstructure factors. Textured porous Si3N4 with a unique microstructure composed of oriented elongated ?-Si3N4 and anisotropic pores is also described for the first time, with emphasis on its unique mechanical and thermal-mechanical properties. Moreover, as an important related material, textured ?-Sialon is also reviewed, because the presence of elongated ?-Sialon grains allows the production of textured ?-Sialon using the same methods as those used for textured ?-Si3N4 and ?-Sialon. Corrections were made to this article on 24 September 2008.

Zhu, Xinwen; Sakka, Yoshio

2008-07-01

31

NASA Astrophysics Data System (ADS)

We report on the possibility to generate highly anisotropic quantum conductivity in disordered graphene-based superlattices. Our quantum simulations, based on an efficient real-space implementation of the Kubo-Greenwood formula, show that in disordered graphene superlattices the strength of multiple scattering phenomena can strongly depend on the transport measurement geometry. This eventually yields the coexistence of a ballistic waveguide and a highly resistive channel (Anderson insulator) in the same two-dimensional platform, evidenced by a ?yy/?xx ratio varying over several orders of magnitude, and suggesting the possibility of building graphene electronic circuits based on the unique properties of chiral massless Dirac fermions in graphene.

Pedersen, Jesper Goor; Cummings, Aron W.; Roche, Stephan

2014-04-01

32

Oxygen-driven anisotropic transport in ultra-thin manganite films

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

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

33

Conformational properties of polymers in anisotropic environments

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 $0polymer renormalization scheme. Both numerical and analytical studies qualitatively confirm the existence of two characteristic length scales of polymer chain in directions parallel and perpendicular to the extended defects.

K. Haydukivska; V. Blavatska

2014-07-11

34

Anisotropic transport in modulation-doped quantum-well structures

NASA Technical Reports Server (NTRS)

Anisotropic electron transport has been observed in GaAs modulation-doped quantum wells grown by molecular-beam epitaxy on a thick (001) Al(0.3)Ga(0.7)As buffer grown at 620 C. Thicker quantum wells (150, 200, and 300 A) show progressively less anisotropy, which vanishes for a 300-A quantum well. The degree of anisotropy is also reduced or eliminated by suspending growth of the Al(0.3)Ga(0.7)As for a period of 300 s prior to growing the GaAs quantum well. Growing the Al(0.3)Ga(0.7)As buffer at higher temperatures (680 C) also reduces the degree of anisotropy. Higher two-dimensional electron gas sheet densities result in less anisotropy.The anisotropy is eliminated by replacing the thick Al(0.3)Ga(0.7)As buffer with a periodic multilayer structure comprising 15 A of GaAs and 200 A of Al(0.3)Ga(0.7)As. The degree of anisotropy is related to the thickness and growth parameters of the Al(0.3)Ga(0.7)As layer grown just prior to the growth of the GaAs.

Radulescu, D. C.; Wicks, G. W.; Schaff, W. J.; Calawa, A.R.; Eastman, L. F.

1987-01-01

35

Anisotropic linear elastic properties of fractal-like composites

NASA Astrophysics Data System (ADS)

In this work, the anisotropic linear elastic properties of two-phase composite materials, made up of square inclusions embedded in a matrix, are investigated. The inclusions present a fractal hierarchical distribution and are supposed to have the same Poisson’s ratio as the matrix but a different Young’s modulus. The effective elastic moduli of the medium are computed at each fractal iteration by coupling a position-space renormalization-group technique with a finite element analysis. The study allows to obtain and generalize some fundamental properties of fractal composite materials.

Carpinteri, Alberto; Cornetti, Pietro; Pugno, Nicola; Sapora, Alberto

2010-11-01

36

NASA Astrophysics Data System (ADS)

A solution method for solving particle transport problems has been developed. This solution approach embodies a finite element projection technique and a related equivalent variational Raleigh-Ritz formalism. Particle flux in the transport equation is expressed as a linear and separable sum of odd and even components in the direction variables. Then a classical variational principle is obtained and shown to be equivalent to a Bubnov-Galerkin projected solution. A dual finite element basis of polynomial splines in space and spherical harmonics in angle is used in the Bubnov -Galerkin equations. The general theoretical and numerical problem formalism is carried out in a 3-dimensional geometry with anisotropic scattering and with a piecewise constant energy dependence. This is a seven-dimensional problem with time dependence, three spatial and two angular or directional variables and with a multigroup treatment of the energy dependence. The boundary conditions for most physical problems of interest are dealt with explicitly and rigorously by a classical minimization (variational) principle. The solution method is developed as a complementary alternative to the standard solution techniques of Discrete Ordinates, Monte Carlo and the P(,n) method. The Galerkin projected operator and transport matrix are positive definite, symmetric and self-adjoint. This insures existence, uniqueness, and convergence of the solution. This formalism does not have the inherent properties which have produced the ray effect problem in discrete ordinates. The computational validation of the method was obtained by a computer solution to the air-over-ground problem. This problem is of significant interest in the areas of nuclear weapons effects and radiation physics. It is modeled in cylindrical (r,z) geometry with an exponentially varying atmosphere, anisotropic scattering, anisotropic first scatter sources, and with the air-ground interface included. Results for the air-over-ground problem are presented. These results show that this solution approach mitigates ray effects. They also show the potential of this technique to serve as a viable alternative to Discrete Ordinates and Monte Carlo. However, further work in extending the computer implementation of the method to time and energy dependent problems, and to solving and validating this technique on a larger class of particle transport problems is required.

Wills, Eze Ewart

37

Anisotropic MRI contrast reveals enhanced ionic transport in plastic crystals.

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

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

2014-11-01

38

NASA Astrophysics Data System (ADS)

Rectangular waveguide methods are appealing for measuring isotropic and anisotropic materials because of high signal strength due to field confinement, and the ability to control the polarization of the applied electric field. As a stepping stone to developing methods for characterizing materials with fully-populated anisotropic tensor characteristics, techniques are presented in this dissertation to characterize isotropic, biaxially anisotropic, and gyromagnetic materials. Two characterization techniques are investigated for each material, and thus six different techniques are described. Additionally, a waveguide standard is introduced which may be used to validate the measurement of the permittivity and permeability of materials at microwave frequencies. The first characterization method examined is the Nicolson-Ross-Weir (NRW) technique for the extraction of isotropic parameters of a sample completely filling the cross-section of a rectangular waveguide. A second technique is proposed for the characterization of an isotropic conductor-backed sample filling the cross-section of a waveguide. If the sample is conductor-backed, and occupies the entire cross-section, a transmission measurement is not available, and thus a method must be found for providing two sufficiently different reflection measurements.The technique proposed here is to place a waveguide iris in front of the sample, exposing the sample to a spectrum of evanescent modes. By measuring the reflection coefficient with and without an iris, the necessary two data may be obtained to determine the material parameters. A mode-matching approach is used to determine the theoretical response of a sample placed behind the waveguide iris. This response is used in a root-searching algorithm to determine permittivity and permeability by comparing to measurements of the reflection coefficient. For the characterization of biaxially anisotropic materials, the first method considers an extension of the NRW technique for characterization of a sample filling the cross-section of a waveguide. Due to the rectangular nature of the waveguide, typically three different samples are manufactured from the same material in order to characterize the six complex material parameters. The second technique for measuring the electromagnetic properties of a biaxially anisotropic material sample uses a reduced-aperture waveguide sample holder designed to accommodate a cubical sample. All the tensor material parameters can then be determined by measuring the reflection and transmission coefficients of a single sample placed into several orientations. The parameters are obtained using a root-searching algorithm by comparing theoretically computed and measured reflection and transmission coefficients. The theoretical coefficients are determined using a mode matching technique. The first technique for characterizing the electromagnetic properties of gyromagnetic materials considers requires filling the cross-section of a waveguide. The material parameters are extracted from the measured reflection and transmission coefficients. Since the cross-sectional dimensions of waveguides become prohibitively large at low frequencies, and it is at these frequencies that the gyromagnetic properties are most pronounced, sufficiently large samples may not be available. Therefore, the second technique uses a reduced-aperture sample holder that does not require the sample to fill the entire cross section of the guide. The theoretical reflection and transmission coefficients for both methods are determined using a mode matching technique. A nonlinear least squares method is employed to extract the gyromagnetic material parameters. Finally, this dissertation introduces a waveguide standard that acts as a surrogate material with both electric and magnetic properties and is useful for verifying systems designed to characterize engineered materials using the NRW technique. A genetic algorithm is used to optimize the all-metallic structure to produce a surrogate with both relative permittivity and permeability near s

Crowgey, Benjamin Reid

39

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

Blazevski, Daniel; del-Castillo-Negrete, Diego

2013-06-01

40

Magnetic and transport properties of multilayer nanoscale antidot arrays C. C. Wang and A. O to the interplay of different interlayer coupling mechanisms. The transport properties of the antidot arrays typically show a superposition of anisotropic and giant magnetoresistance effects, and the relative

Adeyeye, Adekunle

41

Holographic transports and stability in anisotropic linear axion model

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.

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

2015-01-15

42

Strain modulated anisotropic geometric, electronic and thermoelectric properties of Black Phosphorus

The anisotropic geometric, electronic, and thermoelectric (TE) properties of bulk black phosphorus (BP) with strain applied have been systematically investigated using first-principles calculations combined with semi-classical Boltzmann transport theory. The layer thickness of one single layer inside bulk BP, exhibiting maximum with a tensile strain of $4\\%$ applied, is slightly larger than that of freestanding phosphorene. The lattice constant $b$ always increase whatever compressive or tensile strain is applied along the $z$ direction, showing an unusual mechanical response with a negative Possion ratio, which may due to the hinge-like structure. The electronic properties are sensitive to strain, as an increasing compressive strain would lead to the band gap transiting from direct to indirect ($0.578 \\mathrm{GPa}$), and then to zero ($1.699 \\mathrm{GPa}$), while the tensile strain would enlarge the band gap almost linearly. When there is no strain applied, the $ZT$ value is found to be maximal along $x$ dir...

Qin, Guangzhao; Yue, Sheng-Ying; Cui, Hui-Juan; Zheng, Qing-Rong; Yan, Qing-Bo; Su, Gang

2014-01-01

43

Time-independent one-speed neutron transport equation with anisotropic scattering in absorbing media

This report treats the time-independent, one-speed neutron transport equation with anisotropic scattering in absorbing media. For nuclear gain operators existence and uniqueness of solutions to the half-space and finite-slab problems are proved in L/sub 2/-space. The formulas needed for explicit calculations are derived by the use of perturbation theory techniques.

Hangelbroek, R. J.

1980-06-01

44

Viscous corrections to anisotropic flow and transverse momentum spectra from transport theory

Viscous hydrodynamics is commonly used to model the evolution of the matter created in an ultra-relativistic heavy-ion collision. It provides a good description of transverse momentum spectra and anisotropic flow. These observables, however, cannot be consistently derived using viscous hydrodynamics alone, because they depend on the microscopic interactions at freeze-out. We derive the ideal hydrodynamic limit and the first-order viscous correction to anisotropic flow ($v_2$, $v_3$ and $v_4$) and momentum spectrum using a transport calculation. The linear response coefficient to the initial anisotropy, $v_n(p_T)/\\varepsilon_n$, depends little on $n$ in the ideal hydrodynamic limit. The viscous correction to the spectrum depends not only on the differential cross section, but also on the initial momentum distribution. This dependence is not captured by standard second-order viscous hydrodynamics. The viscous correction to anisotropic flow increases with $p_T$, but this increase is slower than usually assumed i...

Plumari, Salvatore; Greco, Vincenzo; Ollitrault, Jean-Yves

2015-01-01

45

Anisotropic vanadium dioxide sculptured thin films with superior thermochromic properties

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

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

2013-01-01

46

Anisotropic vanadium dioxide sculptured thin films with superior thermochromic properties.

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

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

2013-01-01

47

Anisotropic quantum transport in a network of vertically aligned graphene sheets.

Novel anisotropic quantum transport was observed in a network of vertically aligned graphene sheets (VAGSs), which can be regarded as composed of plenty of quasi-parallel, nearly intrinsic, freestanding monolayers of graphene. When a magnetic field was perpendicular to most graphene sheets, magnetoresistance (MR) curves showed a weak localization (WL) effect at low field and a maximum value at a critical field ascribed to diffusive boundary scattering. While the magnetic field was parallel to the graphene sheets, the MR maximum disappeared and exhibited a transition from WL to weak antilocalization (WAL) with increasing temperature and magnetic field. Edges as atomically sharp defects are the main elastic and inelastic intervalley scattering sources, and inelastic scattering is ascribed to electron-electron intervalley scattering in the ballistic regime. This is the first time simultaneously observing WL, WAL and diffusive boundary scattering in such a macroscopic three-dimensional graphene system. These indicate the VAGS network is a robust platform for the study of the intrinsic physical properties of graphene. PMID:25090659

Huang, J; Guo, L-W; Li, Z-L; Chen, L-L; Lin, J-J; Jia, Y-P; Lu, W; Guo, Y; Chen, X-L

2014-08-27

48

Spatial frequency analysis of anisotropic drug transport in tumor samples

Abstract. Directional Fourier spatial frequency analysis was used on standard histological sections to identify salient directional bias in the spatial frequencies of stromal and epithelial patterns within tumor tissue. This directional bias is shown to be correlated to the pathway of reduced fluorescent tracer transport. Optical images of tumor specimens contain a complex distribution of randomly oriented aperiodic features used for neoplastic grading that varies with tumor type, size, and morphology. The internal organization of these patterns in frequency space is shown to provide a precise fingerprint of the extracellular matrix complexity, which is well known to be related to the movement of drugs and nanoparticles into the parenchyma, thereby identifying the characteristic spatial frequencies of regions that inhibit drug transport. The innovative computational methodology and tissue validation techniques presented here provide a tool for future investigation of drug and particle transport in tumor tissues, and could potentially be used a priori to identify barriers to transport, and to analyze real-time monitoring of transport with respect to therapeutic intervention. PMID:24395585

Russell, Stewart; Samkoe, Kimberley S.; Gunn, Jason R.; Hoopes, P. Jack; Nguyen, Thienan A.; Russell, Milo J.; Alfano, Robert R.; Pogue, Brian W.

2014-01-01

49

Anisotropic heat transport in integrable and chaotic 3-D magnetic fields

A study of anisotropic heat transport in 3-D chaotic magnetic fields is presented. The approach is based on the recently proposed Lagrangian-Green s function (LG) method in Ref. [1] that allows an efficient and accurate integration of the parallel transport equation applicable to general magnetic fields with local or non-local parallel flux closures. We focus on reversed shear magnetic field configurations known to exhibit separatrix reconnection and shearless transport barriers. The role of reconnection and magnetic field line chaos on temperature transport is studied. Numerical results are presented on the anomalous relaxation of radial temperature gradients in the presence of shearless Cantori partial barri- ers. Also, numerical evidence of non-local effective radial temperature transport in chaotic fields is presented. Going beyond purely parallel transport, the LG method is generalized to include finite perpendicular diffusivity, and the problem of temperature flattening inside a magnetic island is studied.

Del-Castillo-Negrete, Diego B [ORNL] [ORNL; Blazevski, D. [University of Texas, Austin] [University of Texas, Austin; Chacon, Luis [ORNL] [ORNL

2012-01-01

50

Transport theory for disordered multiple-band systems: Anomalous Hall effect and anisotropic magnetoresistance Alexey A. Kovalev,1,2 Yaroslav Tserkovnyak,1 Karel V?born?,3 and Jairo Sinova2,3 1Department of Physics and Astronomy, University... of California, Los Angeles, California 90095, USA 2Department of Physics, Texas A&M University, College Station, Texas 77843-4242, USA 3Institute of Physics, ASCR, Cukrovarnick? 10, 162 53 Praha 6, Czech Republic #1;Received 16 February 2009; revised...

Kovalev, Alexey A.; Tserkovnyak, Yaroslav; Vyborny, Karel; Sinova, Jairo.

2009-01-01

51

Transport properties in the atmosphere of Jupiter

NASA Technical Reports Server (NTRS)

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.

Biolsi, L., Jr.

1979-01-01

52

Transport in anisotropic model systems analyzed by a correlated projection superoperator technique

By using a correlated projection operator, the time-convolutionless (TCL) method to derive a quantum master equation can be utilized to investigate the transport behavior of quantum systems as well. Here, we analyze a three-dimensional anisotropic quantum model system according to this technique. The system consists of Heisenberg coupled two-level systems in one direction and weak random interactions in all other ones. Depending on the partition chosen, we obtain ballistic behavior along the chains and normal transport in the perpendicular direction. These results are perfectly confirmed by the numerical solution of the full time-dependent Schr\\"odinger equation.

Hendrik Weimer; Mathias Michel; Jochen Gemmer; Günter Mahler

2008-01-17

53

Anisotropic Pressure, Transport, and Shielding of Magnetic Perturbations

We compute the effect on a tokamak of applying a nonaxisymmetric magnetic perturbation ??. An equilibrium with scalar pressure p yields zero net radial current, and therefore zero torque. Thus, the usual approach, which assumes scalar pressure, is not self-consistent, and masks the close connection which exists between that radial current and the in-surface currents, which provide shielding or amplification of ??. Here, we analytically compute the pressure anisoptropy, anisoptropy, pll, p? ? p, and from this, both the radial and in-surface currents. The surface-average of the radial current recovers earlier expressions for ripple transport, while the in-surface currents provide an expression for the amount of self-consistent shielding the plasma provides.

H.E. Mynick and A.H. Boozer

2008-05-23

54

An Algorithm for the Transport of Anisotropic Neutrons

NASA Technical Reports Server (NTRS)

One major obstacle to human space exploration is the possible limitations imposed by the adverse effect of long-term exposure to the space environment. Even before human spaceflight began, the potentially brief exposure of astronauts to the very intense random solar particle events (SPE) were of great concern. A new challenge appears in deep space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays (GCR) since the missions are of long duration and the accumulated GCR exposures can be high. Because cancer induction rates increase behind low to rather large thicknesses of aluminum shielding, according to available biological data on mammalian exposures to GCR like ions, the shield requirements for a Mars mission are prohibitively expensive in terms of mission launch costs. Therefore, a critical issue in the Human Exploration and Development of Space enterprise is cost effective mitigation of risk associated with ionizing radiation exposure. In order to estimate astronaut risk to GCR exposure and associated cancer risks and health hazards, it is necessary to do shield material studies. To determine an optimum radiation shield material it is necessary to understand nuclear interaction processes such as fragmentation and secondary particle production which is a function of energy dependent cross sections. This requires knowledge of material transmission characteristics either through laboratory testing or improved theoretical modeling. Here ion beam transport theory is of importance in that testing of materials in the laboratory environment generated by particle accelerators is a necessary step in materials development and evaluation for space use. The approximations used in solving the Boltzmann transport equation for the space setting are often not sufficient for laboratory work and those issues are a major emphasis of the present work.

Tweed, J.

2005-01-01

55

Anisotropic transport and early dynamical impact of Cosmic Rays around Supernova remnants

We present a novel implementation of cosmic rays (CR) in the magneto-hydrodynamic code FLASH. CRs are described as separate fluids with different energies. CR advection, energy dependent anisotropic diffusion with respect to the magnetic field and adiabatic losses to follow the evolution of spectra are taken into account. We present a first study of the transport and immediate (~150 kyr) dynamical impact of CRs on the turbulent magnetised interstellar medium around supernova remnants on scales up to 80 pc. CR diffusion quickly leads to an efficient acceleration of low-density gas (mainly perpendicular to the magnetic field) with accelerations up to two orders of magnitude above the thermal values. Peaked (at 1 GeV) CR injection spectra have a stronger impact on the dynamics than power-law spectra. For realistic magnetic field configurations low energy CRs (with smaller diffusion coefficients) distribute anisotropically with large spatial variations of a factor of ten and more. Adiabatic losses can change the ...

Girichidis, Philipp; Walch, Stefanie; Hanasz, Michal

2014-01-01

56

A simulative study was performed to measure the dielectric properties of anisotropic tissue using several in vivo and in vitro probes. COMSOL Multiphysics was selected to carry out the simulation. Five traditional probes and a newly designed probe were used in this study. One of these probes was an in vitro measurement probe and the other five were in vivo. The simulations were performed in terms of the minimal tissue volume for in vivo measurements, the calibration of a probe constant, the measurement performed on isotropic tissue and the measurement performed on anisotropic tissue. Results showed that the in vitro probe can be used to measure the in-cell dielectric properties of isotropic and anisotropic tissues. When measured with the five in vivo probes, the dielectric properties of isotropic tissue were all measured accurately. For the measurements performed on anisotropic tissue, large errors were observed when the four traditional in vivo probes were used, but only a small error was observed when the new in vivo probe was used. This newly designed five-electrode in vivo probe may indicate the dielectric properties of anisotropic tissue more accurately than these four traditional in vivo probes. PMID:23603795

Huo, Xuyang; Shi, Xuetao; You, Fusheng; Fu, Feng; Liu, Ruigang; Tang, Chi; Lu, Qiang; Dong, Xiuzhen

2013-05-21

57

We propose a Lagrangian numerical algorithm for a time-dependent, anisotropic tem- perature 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 lo- cal and nonlocal 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. Al- gorithmically, 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 par- allel transport term when the perpendicular to parallel transport coefficient ratio / becomes arbitrarily small, and is shown to capture the correct limiting solution when / 0. Therefore, the approach is asymptotic-preserving. We demonstrate the ca- pabilities of the scheme with several numerical experiments with varying magnetic field complexity in two dimensions, including the case of transport across a magnetic island.

Chacon, Luis [ORNL; Del-Castillo-Negrete, Diego B [ORNL; Hauck, C. [Oak Ridge National Laboratory (ORNL)

2014-01-01

58

Magnetic and Transport Properties of FeAs Single Crystals

NASA Astrophysics Data System (ADS)

Magnetic susceptibility and transport properties of an itinerant helimagnet FeAs are studied in single-crystalline samples of this binary compound. A kink due to the magnetic transition is observed in the temperature dependences of both the susceptibility and the resistivity. The Hall coefficient shows a reentrant sign change with temperature, signifying a complicated competition between multiple bands. In the helical ordered state, we found an unexpected formation of some anisotropic antiferromagnetic domains, which is reflected in a spin-glass like behavior observed only in the c-axis magnetic susceptibility.

Segawa, Kouji; Ando, Yoichi

2009-10-01

59

Transport and thermal properties of heavy-fermion superconductors - A unified picture

The transport and thermal properties of heavy-fermion superconductors are explained in terms of: (1) an anisotropic order parameter with a line or lines of nodes and (2) an effective mean free path which, except for the lowest temperatures, is approximately temperature independent and of a similar magnitude as in the nominal state. Such a mean free path is shown to

S. Schmitt-Rink; K. Miyake; C. M. Varma

1986-01-01

60

Transport properties in the atmosphere of Jupiter

NASA Technical Reports Server (NTRS)

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.

Biolsi, L., Jr.

1978-01-01

61

Journal of Fluorescence, Vol. 14, No. 4, July 2004 (Â©2004) Synthesis and Optical Properties of anisotropic noble metal (e.g. gold and silver) nanopar- ticles, in which a combination of theory-defined nanostructures other than solid spheres, including silver nanodisks and triangular nanoprisms, and gold

62

NASA Astrophysics Data System (ADS)

Transmittance and reflectance from spruce wood and bovine ligamentum nuchae as two different fibrous media are examined by time-of-flight spectroscopy for varying source detector separations and several orientations of the fibers in the sample. The anisotropic diffusion theory is used to obtain the absorption coefficient and the diffusion coefficients parallel and perpendicular to the fibers. The results are compared to those obtained with the isotropic diffusion theory. It is shown that for increasing source detector separations, the retrieved optical properties change as expected from Monte Carlo simulations performed in a previous study. This confirms that the anisotropic diffusion theory yields useful results for certain experimental conditions.

Simon, Emanuel; Krauter, Philipp; Kienle, Alwin

2014-07-01

63

Transmittance and reflectance from spruce wood and bovine ligamentum nuchae as two different fibrous media are examined by time-of-flight spectroscopy for varying source detector separations and several orientations of the fibers in the sample. The anisotropic diffusion theory is used to obtain the absorption coefficient and the diffusion coefficients parallel and perpendicular to the fibers. The results are compared to those obtained with the isotropic diffusion theory. It is shown that for increasing source detector separations, the retrieved optical properties change as expected from Monte Carlo simulations performed in a previous study. This confirms that the anisotropic diffusion theory yields useful results for certain experimental conditions. PMID:25055055

Simon, Emanuel; Krauter, Philipp; Kienle, Alwin

2014-07-01

64

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

*, Departments of Chemical Engineering, Materials Science and Engineering, and Electrical Engineering are of interest for tuning bulk properties (rheological, mechanical, transport) at the nanoscale in the design- ion conducting electrolyte owing to recent advances that demonstrate high conductivity

Sadoway, Donald Robert

65

The diverse atomic configurations induce the anisotropic surface properties. For investigating anisotropic phenomena, we developed a rotational positioning system adapted to atomic force microscope (AFM). This rotational positioning system is applied to revolve the measured sample to defined angular direction, and it composed of an inertial rotational stepper and a visual angular measurement. The inertial rotational stepper with diameter 30 mm and height 7.6 mm can be easily attached to the AFM-system built in any general optical microscope. Based on a clearance less bearing and the inertial driving method, its bidirectional angular resolution reaches 0.005 deg. per step. For realizing a close-loop controlled angular positioning function, the visual measurement method is utilized. Through the feedback control, the angular positioning error is less than 0.01 deg. For verifying the system performance, we used it to investigate the anisotropic surface properties of graphite. Through a modified cantilever tip, the atomic-scale stick-slip, and the anisotropic friction phenomena can be distinctly detected.

Liao, H.-S.; Juang, B.-J. [Department of Mechanical Engineering, National Taiwan University, 10617, Taipei, Taiwan (China); Institute of Physics, Academia Sinica, 11529, Taipei, Taiwan (China); Chang, W.-C.; Lai, W.-C.; Chang, C.-S. [Institute of Physics, Academia Sinica, 11529, Taipei, Taiwan (China); Huang, K.-Y. [Department of Mechanical Engineering, National Taiwan University, 10617, Taipei, Taiwan (China)

2011-11-15

66

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.

Qian Chen

2008-08-18

67

Anisotropic magnetic properties of the KMo4O6

NASA Astrophysics Data System (ADS)

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.

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

2012-02-01

68

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

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.

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

2012-08-15

69

Field dependent Anisotropic Micro Rheological and Microstructrual properties of Ferrofluids

We have measured micro-rheological and micro-structural properties of a super paramagnetic ferrofluid made of Mn$_{0.75}$Zn$_{0.25}$Fe$_2$O$_4$ (MZF) nanoparticles, using passive microrheology in a home built inverted microscope. Thermal motion of a probe microsphere was measured for different values of an applied external magnetic field and analysed. The analysis shows anisotropy in magnetoviscous effect. Additional microrheological properties, such as storage modulus and loss modulus and their transition is seen. Following the analysis given in \\cite{Oliver Muller, Stefan Mahle}, we have obtained microstructural properties such as elongational flow coefficient $\\lambda_2$, relaxation time constant $\\tau$, coefficient of dissipative magnetization $\\alpha$ etc. From a single set of viscosity data, all the above parameters could be obtained. Our values for the above parameters are in agreement with earlier theoretical calculations and macro-rheological experimental measurements.

Balaji Yendeti; G. Thirupathi; Ashok Vudaygiri; R. Singh

2014-02-20

70

Picosecond Acoustic Measurement of Anisotropic Properties of Thin Films

NASA Astrophysics Data System (ADS)

Properties of thin metallic films have been studied extensively by means of laser-picosecond ultrasonics. Generation of longitudinal and shear waves via thermoelastic mechanism and large source has been only demonstrated for waves vectors along the normal to the interface. However, such measurements cannot provide complete information about elastic properties of films. As it has been already shown for nanosecond ultrasonics, the knowledge of group or phase velocities in several directions for sources with small lateral size allows determining the stiffness tensor coefficients of a sample. The experimental set-up was prepared to obtain the thinnest size for the source to achieve acoustic diffraction. The identification of the stiffness tensor components, based on the inversion of the bulk waves phase velocities, is applied to signals simulated and experimentally recorded for a material with hexagonal properties. First estimation of stiffness tensor coefficients for thin metallic film 2.1 ?m has been performed.

Perton, M.; Rossignol, C.; Chigarev, N.; Audoin, B.

2007-03-01

71

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

Kailiang Yin; Dinghui Zou; Jing Zhong; Duanjun Xu

2007-01-01

72

Anisotropic electronic properties of Ni nanowires in oriented mesoporous silica film

NASA Astrophysics Data System (ADS)

The electronic behavior of Ni nanowires in an oriented mesoporous silica thin film was reported. The hybrid film was prepared using a facile method of airflow-induced mesopore orientation from silica sol solution containing Ni2+ cation, followed by H2 reduction. Because of the confinement effect, the Ni nanowires were aligned in the oriented mesochannels, which resulted in anisotropic electronic responses. Such a property would be of great importance in the design of nanodevices for advanced photoelectric applications.

Cui, Wei; Lu, Xuemin; Su, Bin; Lu, Qinghua; Wei, Yen

2009-10-01

73

Characterization of the anisotropic mechanical properties of excised human skin

The mechanical properties of skin are important for a number of applications including surgery, dermatology, impact biomechanics and forensic science. In this study, we have investigated the influence of location and orientation on the deformation characteristics of 56 samples of excised human skin. Uniaxial tensile tests were carried out at a strain rate of 0.012 s?1 on skin from the back.

Aisling Ní Annaidh; Karine Bruyère; Michel Destrade; Michael D. Gilchrist; Mélanie Otténio

74

Strain induced anisotropic properties of shape memory polymer

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

Richard Beblo; Lisa Mauck Weiland

2008-01-01

75

Time-dependent macrodispersion for solute transport in anisotropic heterogeneous aquifers

NASA Astrophysics Data System (ADS)

The expected values of the spatial second-order moments of a solute body transported by groundwater are derived for flow through heterogeneous formations of a stationary random anisotropic structure. They are based on a general formulation, which reduces to most existing results in the literature as particular cases. Detailed results are given for the spatial variance as a function of time in the case of axisymmetric anisotropy, average flow parallel to the plane of isotropy, first-order approximation in the log conductivity variance ?Y2, and high Peclet numbers. These results fill the gap existing between the studies of Dagan (1982, 1984), on one hand, and those of Gelhar and Axness (1983) and Neuman et al. (1987), on the other. A preliminary investigation of the higher-order effects in ?Y2 suggests that the use of the first-order approximations is warranted, at present, only for ?Y2 ? 1. The impact of the errors of estimation of the parameters on which transport depends is briefly analyzed.

Dagan, Gedeon

1988-09-01

76

A Numerical Model of Anisotropic Mass Transport Through Grain Boundary Networks

NASA Astrophysics Data System (ADS)

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.

Wang, Yibo

77

TRANSPORT PROPERTY MEASUREMENTS OF HFC-236EA

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...

78

TRANSPORT PROPERTY MEASUREMENTS OF HFC-236EA

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...

79

Anisotropic compressive properties of passive porcine muscle tissue.

The body has approximately 434 muscles, which makes up 40-50% of the body by weight. Muscle is hierarchical in nature and organized in progressively larger units encased in connective tissue. Like many soft tissues, muscle has nonlinear visco-elastic behavior, but muscle also has unique characteristics of excitability and contractibility. Mechanical testing of muscle has been done for crash models, pressure sore models, back pain, and other disease models. The majority of previous biomechanical studies on muscle have been associated with tensile properties in the longitudinal direction as this is muscle's primary mode of operation under normal physiological conditions. Injury conditions, particularly high rate injuries, can expose muscle to multiple stress states. Compressive stresses can lead to tissue damage, which may not be reversible. In this study, we evaluate the structure-property relationships of porcine muscle tissue under compression, in both the transverse and longitudinal orientations at 0.1?s-1, 0.01?s-1, or 0.001?s-1. Our results show an initial toe region followed by an increase in stress for muscle in both the longitudinal and transverse directions tested to 50% strain. Strain rate dependency was also observed with the higher strain rates showing significantly more stress at 50% strain. Muscle in the transverse orientation was significantly stiffer than in the longitudinal orientation indicating anisotropy. The mean area of fibers in the longitudinal orientation shows an increasing mean fiber area and a decreasing mean fiber area in the transverse orientation. Data obtained in this study can help provide insight on how muscle injuries are caused, ranging from low energy strains to high rate blast events, and can also be used in developing computational injury models. PMID:25068816

Pietsch, Renee; Wheatley, Benjamin B; Haut Donahue, Tammy L; Gilbrech, Ryan; Prabhu, Rajkumar; Liao, Jun; Williams, Lakiesha N

2014-11-01

80

A macroscopic model of the Hall effects and magnetoresistance in anisotropic semiconductor wafers is developed. The results obtained by solving the electrodynamic boundary problem allow the potential and eddy currents in anisotropic semiconductors to be calculated at different current-contact locations, depending on the parameters of the sample material's anisotropy. The results of this study are of great practical importance for investigating the physical properties of anisotropic semiconductors and simulating the electron-transport phenomena in devices based on anisotropic semiconductors.

Filippov, V. V., E-mail: wwfilippow@mail.ru [Lipetsk State Pedagogical University (Russian Federation); Bormontov, E. N. [Voronezh State University (Russian Federation)

2013-07-15

81

NASA Astrophysics Data System (ADS)

The goal of elucidating the physical mechanisms underlying the propagation of ultrasonic waves in anisotropic soft tissue such as myocardium has posed an interesting and largely unsolved problem in the field of physics for the past 30 years. In part because of the vast complexity of the system being studied, progress towards understanding and modeling the mechanisms that underlie observed acoustic parameters may first require the guidance of careful experiment. Knowledge of the causes of observed ultrasonic properties in soft tissue including attenuation, speed of sound, and backscatter, and how those properties are altered with specific pathophysiologies, may lead to new noninvasive approaches to the diagnosis of disease. The primary aim of this Dissertation is to contribute to an understanding of the physics that underlies the mechanisms responsible for the observed interaction of ultrasound with myocardium. To this end, through-transmission and backscatter measurements were performed by varying acoustic properties as a function of angle of insonification relative to the predominant myofiber direction and by altering the material properties of myocardium by increased protein cross-linking induced by chemical fixation as an extreme form of changes that may occur in certain pathologies such as diabetes. Techniques to estimate acoustic parameters from backscatter were broadened and challenges to implementing these techniques in vivo were addressed. Provided that specific challenges identified in this Dissertation can be overcome, techniques to estimate attenuation from ultrasonic backscatter show promise as a means to investigate the physical interaction of ultrasound with anisotropic biological media in vivo. This Dissertation represents a step towards understanding the physics of the interaction of ultrasonic waves with anisotropic biological media.

Baldwin, Steven L.

82

Spin transport in the two-dimensional quantum disordered anisotropic Heisenberg model

NASA Astrophysics Data System (ADS)

We use the self consistent harmonic approximation together with the Linear Response Theory to study the effect of nonmagnetic disorder on spin transport in the quantum diluted two-dimensional anisotropic Heisenberg model with spin S=1 in a square lattice. The model has a BKT transition at zero dilution. We calculate the regular part of the spin conductivity ?reg(?) and the Drude weight DS(T) as a function of the non-magnetic concentration, x. Our calculations show that the spin conductivity drops abruptly to zero at xcSCHA?0.5 indicating that the system changes from an ideal spin conductor state to an insulator. This value is far above the site percolation threshold xcsite?0.41. Although the SCHA fails in determining precisely the percolation threshold, both the spin conductivity and the Drude weight show a quite regular behavior inside 0?x?xcSCHA indicating that the transition stays in the same universality class all along the interval.

Lima, L. S.; Pires, A. S. T.; Costa, B. V.

2014-12-01

83

NASA Astrophysics Data System (ADS)

Based on the electro-elastic surface/interface theory, the size-dependent effective piezoelectric and dielectric coefficients of anisotropic piezoelectric composites that consist of spherically piezoelectric inclusions under a uniform electric field are investigated, and the analytical solutions for the elastic displacement and electric potentials are derived. With consideration of the coupling effects of elasticity, permittivity and piezoelectricity, the effective field method is introduced to derive the effective dielectric and piezoelectric responses in the dilute limit. The numerical examples show that the effective dielectric constant exhibits a significant variation due to the surface/interface effect. The dielectric property of the surface/interface displays greater effect than the piezoelectric property, and the elastic property shows little effect. A comparison with the existing results validates the present approach.

Huang, Ming-Juan; Fang, Xue-Qian; Liu, Jin-Xi; Feng, Wen-Jie; Zhao, Yong-Mao

2015-01-01

84

Transport properties of alumina nanofluids.

Recent studies have showed that nanofluids have significantly greater thermal conductivity compared to their base fluids. Large surface area to volume ratio and certain effects of Brownian motion of nanoparticles are believed to be the main factors for the significant increase in the thermal conductivity of nanofluids. In this paper all three transport properties, namely thermal conductivity, electrical conductivity and viscosity, were studied for alumina nanofluid (aluminum oxide nanoparticles in water). Experiments were performed both as a function of volumetric concentration (3-8%) and temperature (2-50?°C). Alumina nanoparticles with a mean diameter of 36 nm were dispersed in water. The effect of particle size was not studied. The transient hot wire method as described by Nagaska and Nagashima for electrically conducting fluids was used to test the thermal conductivity. In this work, an insulated platinum wire of 0.003 inch diameter was used. Initial calibration was performed using de-ionized water and the resulting data was within 2.5% of standard thermal conductivity values for water. The thermal conductivity of alumina nanofluid increased with both increase in temperature and concentration. A maximum thermal conductivity of 0.7351 W m(-1) K(-1) was recorded for an 8.47% volume concentration of alumina nanoparticles at 46.6?°C. The effective thermal conductivity at this concentration and temperature was observed to be 1.1501, which translates to an increase in thermal conductivity by 22% when compared to water at room temperature. Alumina being a good conductor of electricity, alumina nanofluid displays an increasing trend in electrical conductivity as volumetric concentration increases. A microprocessor-based conductivity/TDS meter was used to perform the electrical conductivity experiments. After carefully calibrating the conductivity meter's glass probe with platinum tip, using a standard potassium chloride solution, readings were taken at various volumetric concentrations. A 3457.1% increase in the electrical conductivity was measured for a small 1.44% volumetric concentration of alumina nanoparticles in water. The highest value of electrical conductivity, 314 µS cm(-1), was recorded for a volumetric concentration of 8.47%. In the determination of the kinematic viscosity of alumina nanofluid, a standard kinematic viscometer with constant temperature bath was used. Calibrated capillary viscometers were used to measure flow under gravity at precisely controlled temperatures. The capillary viscometers were calibrated with de-ionized water at different temperatures, and the resulting kinematic viscosity values were found to be within 3% of the standard published values. An increase of 35.5% in the kinematic viscosity was observed for an 8.47% volumetric concentration of alumina nanoparticles in water. The maximum kinematic viscosity of alumina nanofluid, 2.901?42 mm(2) s(-1), was obtained at 0?°C for an 8.47% volumetric concentration of alumina nanoparticles. The experimental results of the present work will help researchers arrive at better theoretical models. PMID:21730657

Wong, Kau-Fui Vincent; Kurma, Tarun

2008-08-27

85

; revised manuscript received 3 March 2012; published 27 March 2012) Anisotropic single-molecule magnets may rates. As a by-product, we also derive S-matrix expressions for the various torques entering- electromechanics and molecular spintronics, assumes tha

Nunner, Tamara

86

Impact of magnetic properties on the Casimir torque between anisotropic metamaterial plates

The quantized surface mode technique is used to calculate the Casimir torque between two parallel anisotropic metamaterial plates with in-plane optical axes, and our main concern is focused on the impact of the magnetic properties of the plates on the Casimir torque. Our result shows that at small separation, the Casimir torque between the two plates with frequency dependent permeabilities is larger than that between two nonmagnetic plates, while at large separation it is smaller. This can be explained as a result of the impact of both magnetic properties and material dispersion of the plates. The impact of the Drude background in connected metallic metamaterial is also discussed. These phenomena provide us with new understanding about the Casimir effect and show great potential in application.

Deng Gang; Liu Zhongzhu; Luo Jun [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

2009-12-15

87

NASA Astrophysics Data System (ADS)

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.

Turba, K.; Hurst, R. C.; Hähner, P.

2012-09-01

88

A differential effective medium (DEM) model is used to predict elastic properties for a set of porous and anisotropic aggregates, comprised of mixtures of calcite and muscovite. The DEM takes into consideration an anisotropic background medium with triclinic or higher symmetry, in which inclusions of idealized ellipsoidal shape are added incrementally. In general, the calculated elastic properties of a solid

Bjarne S. G. Almqvist; David Mainprice; Claudio Madonna; Luigi Burlini; Ann M. Hirt

2011-01-01

89

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

90

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

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

2014-09-16

91

NASA Astrophysics Data System (ADS)

This thesis seeks to contribute to a better understanding of the physics of interaction of ultrasonic waves with inhomogeneous and anisotropic media, one example of which is the human heart. The clinical success of echocardiography has generated a considerable interest in the development of ultrasonic techniques to measure the elastic properties of heart tissue. It is hypothesized that the elastic properties of myocardium are influenced by the interstitial content and organization of collagen. Collagen, which is the main component of tendon, interconnects the muscle cells of the heart to form locally unidirectional myofibers. This thesis therefore employs ultrasonic techniques to characterize the linear elastic properties of both heart and tendon. The linear elastic properties of tissues possessing a unidirectional arrangement of fibers may be described in terms of five independent elastic stiffness coefficients. Three of these coefficients were determined for formalin fixed specimens of bovine Achilles tendon and human myocardium by measuring the velocity of longitudinal mode ultrasonic pulses as a function of angle of propagation relative to the fiber axis of the tissue. The remaining two coefficients were determined by measuring the velocity of transverse mode ultrasonic waves through these tissues. To overcome technical difficulties associated with the extremely high attenuation of transverse mode waves at low megahertz frequencies, a novel measurement system was developed based on the sampled continuous wave technique. Results of these measurements were used to assess the influence of interstitial collagen, and to model the mechanical properties of heart wall.

Hoffmeister, Brentley Keith

1995-01-01

92

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.

Naff, R.L.

1998-01-01

93

Electronic transport properties of SWGaNNTs

NASA Astrophysics Data System (ADS)

In the present study, the electronic transport properties of single wall gallium nitride nanotubes (SWGaNNTs) were theoretically studied by using ab-initio calculations under density functional theory (DFT) with TranSIESTA code employing norm-conserving pseudopotential. The curvature has prominent effect on the band structure of SWGaNNTs, the energy bandgap decreases as the decrease the diameter. the calculated bandgap of (9,0) is 1.8126 eV are good experiment with the previous reported by theoretical studies. It is also observed that, there is a corresponding relation between the electronic transport properties and the valley of state density of GaNNT.

Sharma, U. S.; Shah, R.; Pathak, C.; Sharma, M.

2013-06-01

94

Modeling materials with optimized transport properties

Following demands for materials with peculiar transport properties, e.g. in magnetoelectronics or thermoelectrics, there is a need for materials modeling at the quantum-mechanical level. We combine density-functional with various scale-bridging tools to establish correlations between the macroscopic properties and the atomic structure of materials. For examples, magnetic memory devices exploiting the tunneling magneto-resistance (TMR) effect depend crucially on the spin

Peter Kratzer; Vladimir M. Fomin; B. Hülsen; M. Scheffler

2010-01-01

95

Electrical transport properties of small sodium clusters

NASA Astrophysics Data System (ADS)

We present calculations on electric transport properties of small sodium clusters NaN (N<=9), based on the Landauer formalism combined with an approximate density-functional approach. For a given cluster size N, the resistance depends sensitively on the cluster geometry (isomers). As a function of cluster size, an even-odd oscillation of the minimal resistance is found.

Gutiérrez, R.; Grossmann, F.; Knospe, O.; Schmidt, R.

2001-07-01

96

Modifying electronic transport properties of graphene by electron beam irradiation.

??In this thesis, electron beam irradiation effects on the electronic transport properties ofgraphene have been systematically studied. In situ electron beam irradiation and simultaneous transport… (more)

He, Yuheng

2011-01-01

97

NASA Astrophysics Data System (ADS)

The Posidonia Shale Formation (PSF) is one of the possible resource shales for unconventional gas in Northern Europe and currently is of great interest to hydrocarbon exploration and production. Due to low permeability of shales, economically viable production requires hydraulic fracturing of the reservoir. The design of hydrofractures requires an estimate of stress state within the reservoir and geomechanical properties such as Young's modulus and Poisson's ratio. Shales are often highly anisotropic and the models which neglect shale anisotropy may fail to predict the behaviour of hydrofractures. Seismic attenuation anisotropy, on the other hand, can play a key role in quantitative rock characterization. Where the attenuation anisotropy can potentially be linked to anisotropic permeability of shales, its fluid/gas saturation and preferred development of anisotropic fracture orientations. In this research, by utilizing the so-called Thomsen's notations, the elastic anisotropy of our (fractured and unfractured) shales has been investigated using a pulse transmission technique in the ultrasonic frequency range (0.3-1 MHz). Assuming transverse isotropy of the shales, and taking the axis x3 as the axis of rotational symmetry, directional Young's moduli and Poisson's ratios were obtained. The Young's modulus measured parallel to bedding (E1) is found to be larger than the Young's modulus measured orthogonal to bedding (E3). In case of the Poisson's ratios, we found that ?31 is larger than ?12, where ?ijrelates elastic strain in xj direction to stress applied in xi direction. Finally, attenuation anisotropy in dry and layer-parallel fractured Posidonia shale samples has been studied in the same frequency range. The attenuation of compressional (QP-1) and shear (QS-1) waves increases substantially with a macro (or wavelength) fracture introduction, especially for P and S waves propagating orthogonal to the bedding. In non-fractured and fractured dry shales, QP-1 is always larger than QS-1. This inequality was also found for the fractured shale using different fluids (water, oil) on the fracture surface. A high-viscosity fluid decreases QP-1 and QS-1 in both (orthogonal and parallel to the bedding) directions, and the QP-1 to QS-1 ratio decreases with the increase of fluid viscosity.

Zhubayev, Alimzhan; Houben, Maartje; Smeulders, David; Barnhoorn, Auke

2014-05-01

98

Directional drop transport achieved on high-temperature anisotropic wetting surfaces.

The surfaces of ambient-temperature superhydrophilic tilting silicon nanowires (TSNWs) exhibit an anisotropic wetting performance at high temperature and a deposited drop moves directionally on this surface. A vapor film forming beneath the drop after spreading reduces the surface friction and the heat transfer efficiency between the drop and the surface, so the drop moves with a constant speed and little mass loss. PMID:25066230

Liu, Chengcheng; Ju, Jie; Ma, Jie; Zheng, Yongmei; Jiang, Lei

2014-09-17

99

NASA Astrophysics Data System (ADS)

There has been a steady accumulation of observational evidence that the solar wind may be thought of as spaghetti: a network of individual magnetic flux tubes each with its own magnetic and plasma characteristics. As early as 1963, Parker referred to these tubes as magnetic and plasma ``filaments,'' and the picture has undergone several refinements since then [Bartley et al. 1966, Marliani et al. 1973, Tu and Marsch 1990, Bruno et al. 2001], culminating in the recent work of Borovsky [2008] who has suggested that these are fossil structures that originate at the solar surface. We use the weakly compressible MHD turbulence model [Bhattacharjee et al., 1998], which incorporates the effect of background spatial inhomogeneities, to describe such structures. We revisit the model equations, showing their relation to recent work by Hunana and Zank [2010]. For a model of interchange-instability driven turbulence, we then use the 1998 model equations to make predictions for the beta scaling of the anisotropic magnetic fluctuation spectra (the so-called variance anisotropy) observed by ACE, and show that the predictions bracket the observations well. We also predict the scaling of the anisotropic transport coefficients for particles and thermal energy.

Bhattacharjee, A.; Smith, C.; Vasquez, B.

2010-11-01

100

ac electrical transport properties of magnetite (abstract)

Electrical transport properties of synthetic magnetite (Fe3(1??)O4) single crystals of controlled stoichiometry have been characterized by ac impedance measurements between 5 Hz and 10 MHz, as a function of temperature (77 K

R. J. Rasmussen; J. M. Honig

1988-01-01

101

Electrical transport properties of ultrathin disordered films

We report an experimental study of quench condensed (2K?T?15K) disordered ultrathin films of Bi where localization effects and superconductivity compete. Experiments are done with different substrates and\\/or different underlayers. Quasi-free-standing films of Bi, prepared by quenching Bi vapours onto solid Xe, are also studied. The results show a dependence of the transport properties both on the dielectric constant of the

G. Sambandamurthy; K. Das Gupta; N. Chandrasekhar

2000-01-01

102

Using conducting probe atomic force microscopy (CAFM) we have investigated the electrical conduction properties of monolayer films of a pentathiophene derivative on a SiO(2)/Si-p+ substrate. By a combination of current-voltage spectroscopy and current imaging we show that lateral charge transport takes place in the plane of the monolayer via hole injection into the highest occupied molecular orbitals of the pentathiophene unit. Our CAFM data suggest that the conductivity is anisotropic relative to the crystalline directions of the molecular lattice. PMID:21848283

Hendriksen, Bas L M; Martin, Florent; Qi, Yabing; Mauldin, Clayton; Vukmirovic, Nenad; Ren, Junfeng; Wormeester, Herbert; Katan, Allard J; Altoe, Virginia; Aloni, Shaul; Fréchet, Jean M J; Wang, Lin-Wang; Salmeron, Miquel

2011-10-12

103

The discrete ordinates method is the most powerful and generally used deterministic method to obtain approximate solutions of the Boltzmann transport equation. A finite element formulation, utilizing a canonical form of the transport equation, is here developed to obtain both integral and pointwise solutions to neutron transport problems. The formulation is based on the use of linear triangles. A general

R. A. Lillie; J. C. Robinson

1976-01-01

104

Anisotropic strain in SmSe and SmTe: Implications for electronic transport

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

105

NASA Astrophysics Data System (ADS)

Temperature dependence of the dispersion properties of liquid crystal core photonic crystal fibers with large air fraction in clads between 300 and 2000 nm for different core diameters have been calculated by a multipole method, which is modified to treat anisotropic inclusions rigorously. In calculations, air holes are assumed to be arranged in a regular hexagonal array in fused silica and a central hole is filled with liquid crystal to create a core. Below the clearing point temperature, the liquid crystal molecules are assumed to be oriented parallel to the cylindrical axis of the holes, where the liquid crystal is highly anisotropic. The large changes of the dispersion properties are found at the clearing point temperature, where the liquid crystal becomes isotropic.

Karasawa, Naoki

2015-03-01

106

The interaction of superconductivity with magnetism has been one of the most interesting and important phenomena in solid state physics since the 1950`s when small amounts of magnetic impurities were incorporated in superconductors. The discovery of the magnetic superconductors RNi{sub 2}B{sub 2}C (R = rare earth, Y) offers a new system to study this interaction. The wide ranges of superconducting transition (T{sub c}) and antiferromagnetic (AF) ordering temperatures (T{sub N}) (0 K {le} T{sub c} {le} 16 K, 0 K {le} T{sub N} {le} 20 K) give a good opportunity to observe a variety of interesting phenomena. Single crystals of high quality with appropriate size and mass are crucial in examining the anisotropic intrinsic properties. Single crystals have been grown successfully by an unusual high temperature flux method and characterized thoroughly by X-ray, electrical transport, magnetization, neutron scattering, scanning electron microscopy, and other measurements.

Cho, B.

1995-11-01

107

Structure and anisotropic properties of single crystals nickel doped barium iron arsenide

The crystal structure, anisotropic electrical resistivity and magnetic susceptibility, as well as specific heat results of the pure single crystals of BaFe{sub 2}As{sub 2}, BaFeNiAs{sub 2}, and BaNi{sub 2}As{sub 2} are surveyed. BaFe{sub 2}As{sub 2} properties demonstrate the equivalence of C(T), Fisher's d({chi}T)/dT and d{rho}/dT results in determining the antiferromagnetic transition at T{sub N} = 132(1) K. BaNi{sub 2}As{sub 2} shows a structural phase transition from a high-temperature tetragonal phase to a low-temperature triclinic pol symmetry at T{sub 0} 131 K, with superconducting critical temperature well below at {Tc} 0.69 K. BaFeNiAs{sub 2} does not show any sign of superconductivity and gives behavioral similarity to BaCo{sub 2}As{sub 2}, a renomalized paramagnetic metal.

Ronning, Filip [Los Alamos National Laboratory; Bauer, Eric D [Los Alamos National Laboratory; Sefat, A S [ORNL; Jin, R [ORNL; Mcguire, M A [ORNL; Sales, B C [ORNL; Mandrus, D [ORNL

2009-01-01

108

Anisotropic effective medium properties from interacting Ag nanoparticles in silicon dioxide.

Films containing a layer of Ag nanoparticles embedded in silicon dioxide were produced by RF magnetron sputtering. Optical transmittance measurements at several angles of incidence (from normal to 75°) revealed two surface plasmon resonance (SPR) peaks, which depend on electric field direction: one in the ultraviolet and another red-shifted from the dilute Ag/SiO? system resonance at 410 nm. In order to investigate the origin of this anisotropic behavior, the structural properties were determined by transmission electron microscopy, revealing the bidimensional plane distribution of Ag nanoparticles with nearly spherical shape as well as the filling factor of metal in the composite. A simple model linked to these experimental parameters allowed description of the most relevant features of the SPR positions, which, depending on the field direction, were distinctly affected by the coupling of oscillations between close nanoparticles, as described by a modified Drude-Lorentz dielectric function introduced into the Maxwell-Garnett relation. This approach allowed prediction of the resonance for light at 75° incidence from the SPR position for light at normal incidence, in good agreement with experimental observation. PMID:24921871

Menegotto, Thiago; Horowitz, Flavio

2014-05-01

109

We present a systematic discussion of the effect of resonant impurity scattering on anisotropic model states of heavy-fermion superconductors. The impurity scattering is treated in the self-consistent T-matrix approximation including a renormalization of the frequency ..omega.. and the quasiparticle energy xi/sub k/. Model states considered include the axial and polar states familiar from superfluid /sup 3/He as well as two states, termed hexial and hybrid, occurring in the group-theoretical classification of singlet states in hexagonal symmetry. We calculate the density of states, the critical temperature and the order parameter, the specific heat, the thermal conductivity, and the spin-lattice relaxation rate. Vertex corrections are included in the calculations of two-particle quantities. The observed properties of the prototype Fermi-liquid material UPt/sub 3/ show many qualitative features in common with our model. However, it turns out to be difficult to identify any given state with certainty. An experimental test of our predictions on the behavior as a function of impurity concentration, particularly in the gapless regime at low temperatures, would allow for a more definitive characterization of the superconducting state.

Hirschfeld, P.J.; Woelfle, P.; Einzel, D.

1988-01-01

110

Magnetic properties of the anisotropic MnBi/Sm2Fe17Nx hybrid magnet

NASA Astrophysics Data System (ADS)

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.

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

111

NASA Astrophysics Data System (ADS)

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.

Wang, Lei; Wang, Xiaodong

2014-06-01

112

Cortical bone is a multiscale composite material. Its elastic properties are anisotropic and heterogeneous across its cross-section, due to endosteal bone resorption which might affect bone strength. The aim of this paper was to describe a homogenization method leading to the estimation of the variation of the elastic coefficients across the bone cross-section and along the bone longitudinal axis. The method uses the spatial variations of bone porosity and of the degree of mineralization of the bone matrix (DMB) obtained from the analysis of 3-D synchrotron micro-computed tomography images. For all three scales considered (the foam (100 nm), the ultrastructure (5 microm) and the mesoscale (500 microm)), the elastic coefficients were determined using the Eshelby's inclusion problem. DMB values were used at the scale of the foam. Collagen was introduced at the scale of the ultrastructure and bone porosity was introduced at the mesoscale. The pores were considered as parallel cylinders oriented along the bone axis. Each elastic coefficient was computed for different regions of interest, allowing an estimation of its variations across the bone cross-section and along the bone longitudinal axis. The method was applied to a human femoral neck bone specimen, which is a site of osteoporotic fracture. The computed elastic coefficients for cortical bone were in good agreement with experimental results, but some discrepancies were obtained in the endosteal part (trabecular bone). These results highlight the importance of accounting for the heterogeneity of cortical bone properties across bone cross-section and along bone longitudinal axis. PMID:20392446

Sansalone, V; Naili, S; Bousson, V; Bergot, C; Peyrin, F; Zarka, J; Laredo, J D; Haïat, G

2010-07-20

113

Electronic and transport properties of kinked graphene.

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

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

2013-01-01

114

A solution method for solving particle transport problems has been developed. This solution approach embodies a finite element projection technique and a related equivalent variational Raleigh-Ritz formalism. Particle flux in the transport equation is expressed as a linear and separable sum of odd and even components in the direction variables. Then a classical variational principle is obtained and shown to

Eze Ewart Wills

1984-01-01

115

Biomechanical models have the potential to predict failure of atherosclerotic plaques and to improve the risk assessment of plaque rupture. The applicability of these models depends strongly on the used material models. Current biomechanical models employ isotropic material models, although it is generally accepted that plaque tissue behaves highly anisotropic. The aim of the present study is to determine the local anisotropic mechanical properties of human atherosclerotic plaque tissue by means of micro-indentation tests. The indentation was performed on top of an inverted confocal microscope allowing the visualisation and quantification of the collagen fibre deformations perpendicular to the indentation direction of the plaque. Based on this, the anisotropic properties of plaque tissue perpendicular to the indentation direction (middle of the fibrous cap, shoulder of the cap, remaining intima tissue) were derived. There were no significant differences between the different indentation locations for the fibre stiffness (total median 80.6kPa, 25th-75th percentile 17.7-157.0kPa), and fibre dispersion. PMID:25553556

Chai, Chen-Ket; Akyildiz, Ali C; Speelman, Lambert; Gijsen, Frank J H; Oomens, Cees W J; van Sambeek, Marc R H M; Lugt, Aad van der; Baaijens, Frank P T

2015-03-01

116

Anisotropy of the electrical transport properties in a Ni2MnGa single crystal: Experiment and theory

NASA Astrophysics Data System (ADS)

Electrical transport properties in ferromagnetic shape memory Ni-Mn-Ga single crystal have been investigated both in experiment and theory by analyzing electrical resistivity along different crystallographic directions during heating. The experimental results show a clear first-order martensitic transformation and a large anisotropic resistivity (AR) of 23.7% at the tetragonal martensitic phase. The theoretical conductivity (? =1/?), estimated using first-principles calculations combined with classical Boltzman transport theory, proves essential crystallographic anisotropic resistivity (AR=31%) in the martensitic phase and agrees well with experimental results. The AR in the martensitic phase is reveled to mainly originate from the splitting of the minority-spin Ni 3d and Ga 4p states near the Fermi level and hence reconstruction of the minority-spin Fermi surface upon martensitic transformation.

Zeng, Min; Cai, Meng-Qiu; Or, Siu Wing; Chan, Helen Lai Wa

2010-04-01

117

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

118

While polymers are known as thermal insulators, recent studies show that stretched single chains of polymers have a very high thermal conductivity. In this work, our new simulation scheme for simulation of heat flow in nanoconfined fluids [H. Eslami, L. Mohammadzadeh, and N. Mehdipour, J. Chem. Phys. 135, 064703 (2011)] is employed to study the effect of chain ordering (stretching) on the rate of heat transfer in polyamide-6,6 nanoconfined between graphene surfaces. Our results for the heat flow in the parallel direction (the plane of surfaces) show that the coefficient of thermal conductivity depends on the intersurface distance and is much higher than that of the bulk polymer. A comparison of results in this work with our former findings on the heat flow in the perpendicular direction, with the coefficient of heat conductivity less than the bulk sample, reveal that well-organized polymer layers between the confining surfaces show an anisotropic heat conduction; the heat conduction in the direction parallel to the surfaces is much higher than that in the perpendicular direction. The origin of such anisotropy in nanometric heat flow is shown to be the dramatic anisotropy in chain conformations (chain stretching) beside the confining surfaces. The results indicate that the coefficients of heat conductivity in both directions, normal and parallel to the surfaces, depend on the degree of polymer layering between the surfaces and the pore width. PMID:22423855

Eslami, Hossein; Mohammadzadeh, Laila; Mehdipour, Nargess

2012-03-14

119

NASA Astrophysics Data System (ADS)

Giant transverse magnetoelectric voltage coefficients |?˜E| = 751 and 305 V/cmOe at two electromechanical antiresonance frequencies are found in the symmetric metglas/[011]-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 crystal/metglas laminate. Unique torsional and diagonal vibration modes are identified to be responsible for those giant |?˜E| values. Moreover, ?˜E is found to be anisotropic depending on the in-plane magnetic field directions, making the piezoelectrics with anisotropic planar piezoelectricity potentially useful base materials for multi-frequency, phase-sensitive magnetoelectric devices.

Rajaram Patil, Deepak; Chai, Yisheng; Kambale, Rahul C.; Jeon, Byung-Gu; Yoo, Kyongjun; Ryu, Jungho; Yoon, Woon-Ha; Park, Dong-Soo; Jeong, Dae-Yong; Lee, Sang-Goo; Lee, Jeongho; Nam, Joong-Hee; Cho, Jeong-Ho; Kim, Byung-Ik; Hoon Kim, Kee

2013-02-01

120

Modeling graphene: Magnetic, transport and optical properties

NASA Astrophysics Data System (ADS)

Graphene, with its unique linear dispersion near the Fermi energy, has attracted great attention since its successful isolation from highly oriented pyrolytic graphite in 2004. Many important properties have been identified in graphene, including a remarkably high mobility at room temperature, an unusual quantum hall effect, and an ambipolar electric field effect. It has been proposed as a candidate for many applications, such as optical modulators, spintronic devices, and solar cells. Understanding the fundamental properties of graphene is therefore important. In this dissertation, I present a study of transport, magnetism and optical properties of graphene. In the first chapter, I introduce the electronic properties of mono layer and few layer graphene. In the second chapter, I present low temperature transport measurements in few layer graphene. An electric-field induced semimetal-to-metal transition is observed based on the temperature dependence of the resistance for different applied gate voltages. At small gate voltages the resistance decreases with increasing temperature due to the increase in carrier concentration resulting from thermal excitation of electron-hole pairs, as it is characteristic of a semimetal. At large gate, voltages excitations of electron-hole pairs are suppressed, and the resistance increases with increasing temperature because of the decrease in mean free path due to electron-phonon scattering, as is characteristic of a metal. The electron and hole mobilities are almost equal, so there is approximate electron-hole symmetry. The data are analyzed according to two different theoretical models for few-layer graphene. A simple two band (STB) model, two overlapping bands with quadratic energy-versus-momentum dispersion relations, is used to explain the experimental observations. The best fitting parameter for the overlap energy is found to be 16 meV. However, at low temperatures, the STB suggests that the conductivity is gate independent in the small gate voltage regime, which is not observed in the data. By considering frustration of the electronic potential due to impurities from the substrate, a Gaussian-distribution puddle model can successfully describe the observed transport behavior in the low temperature, small gate voltage regime. In the third chapter, I investigate the effects of point and line defects in monolayer graphene within the framework of the Hubbard model, using a self-consistent mean field theory. These defects are found to induce characteristic patterns into the electronic density of states and cause non-uniform distributions of magnetic moments in the vicinity of the impurity sites. Specifically, defect induced resonances in the local density of states are observed at energies close to the Dirac points. The magnitudes of the frequencies of these resonance states are shown to decrease with the strength of the scattering potential, whereas their amplitudes decay algebraically with increasing distance from the defect. For the case of defect clusters, we observe that with increasing defect cluster size the local magnetic moments in the vicinity of the cluster center are strongly enhanced. Furthermore, non-trivial impurity induced magnetic patterns are observed in the presence of line defects: zigzag line defects are found to introduce stronger-amplitude magnetic patterns than armchair line defects. When the scattering strength of these topological defects is increased, the induced patterns of magnetic moments become more strongly localized. In the fourth chapter, I theoretically study the electronic properties properties in graphene dots under mechanical deformation, using both tight binding lattice model and effective Dirac model. We observed an edge state, which is tunned by an effective quantum well originating from a strain-induced gauge field. Applying a uniaxial strain along the zigzag or armchair directions enhances or dampens the edge state due to the development of edge quantum wells. When an arc bending deformation is applied, the inner and outer edges of graphene dot

Chang, Yi Chen

121

Anisotropic Fermi surface from holography

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 analysis 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.

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

2014-01-01

122

Transport properties of epitaxial lift off films

NASA Technical Reports Server (NTRS)

Transport properties of epitaxially lifted-off (ELO) films were characterized using conductivity, Hall, and Shubnikov-de Haas measurements. A 10-15 percent increase in the 2D electron gas concentration was observed in these films as compared with adjacent conventional samples. We believe this result to be caused by a backgating effect produced by a charge build up at the interface of the ELO film and the quartz substrate. This increase results in a substantial decrease in the quantum lifetime in the ELO samples, by 17-30 percent, but without a degradation in carrier mobility. Under persistent photoconductivity, only one subband was populated in the conventional structure, while in the ELO films the population of the second subband was clearly visible. However, the increase of the second subband concentration with increasing excitation is substantially smaller than anticipated due to screening of the backgating effect.

Mena, R. A.; Schacham, S. E.; Young, P. G.; Haugland, E. J.; Alterovitz, S. A.

1993-01-01

123

Calculation of Thermoelectric Transport Properties in Heterostructures

NASA Astrophysics Data System (ADS)

We present a model that can predict the Seebeck coefficient of different interfaces. Within this model we solve the Poisson equation and Schrödinger equation self-consistently to obtain the potential profile across the interface. Then we use the nonequilibrium Green's function (NEGF) method to calculate the transport properties across the interface. We apply our model to a ZnO grain boundary, describing the boundary as a back-to-back Schottky barrier. The potential profile in the considered system is similar to a rigid-shift potential, and thus the Seebeck coefficient obtained from the rigid-shift potential shows no deviation in comparison with the Seebeck coefficient obtained from the self-consistent potential.

Bachmann, M.; Czerner, M.; Heiliger, C.

2011-05-01

124

Transport properties of polycrystalline boron doped diamond

NASA Astrophysics Data System (ADS)

The influence of doping level in the electronic conductivity and resistivity properties of synthetic diamond films grown by hot filament chemical vapor deposition (HFCVD) was investigated. Eight different doping level concentrations varied from 500 to 30,000 ppm were considered. The polycrystalline morphology observed by scanning electron microscopy and Raman spectra was strongly affected by the addition of boron. The electric characterization by Hall effect as a function of temperature and magnetic field showed that at sufficiently low temperatures, electrical conduction is dominated by variable range hopping (VRH) conducting process. The resistivity was also investigated by temperature-dependent transport measurements in order to investigate the conduction mechanism in the doped samples. The samples exhibited the VRH (m = 1/4) mechanism in the temperature range from 77 to 300 K. The interface between metal, and our HFCVD diamond was also investigated for the lower doped samples.

de Oliveira, J. R.; Berengue, O. M.; Moro, J.; Ferreira, N. G.; Chiquito, A. J.; Baldan, M. R.

2014-08-01

125

Anisotropic thermal transport in double-pancake coil wound with DI-BSCCO® tape

NASA Astrophysics Data System (ADS)

We have measured the temperature dependence of the thermal resistances Rr( T) and Rz( T) of the parallelepiped samples cut from a double-pancake coil along the radial ( r) and the thickness ( z) directions, respectively. The double-pancake coil was wound with DI-BSCCO® tape fabricated by Sumitomo Electric Industries, Ltd. DI-BSCCO is a (Bi, Pb) 2Sr 2Ca 2Cu 3O 10+ x tape sheathed with silver. Both Rr( T) and Rz( T) increase monotonically with decreasing temperature. We analyze the thermal transport in the coil by use of the parallel and series heat current circuit of DI-BSCCO tapes and insulators.

Naito, T.; Fujishiro, H.; Yamada, Y.

2010-11-01

126

A review of some charge transport properties of silicon

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

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

1977-01-01

127

Transport properties of supercooled confined water

NASA Astrophysics Data System (ADS)

This article presents an overview of recent experiments performed on transport properties of water in the deeply supercooled region, a temperature region of fundamental importance in the science of water. We report data of nuclear magnetic resonance, quasi-elastic neutron scattering, Fourier-transform infrared spectroscopy, and Raman spectroscopy, studying water confined in nanometer-scale environments. When contained within small pores, water does not crystallise, and can be supercooled well below its homogeneous nucleation temperature Th. On this basis it is possible to carry out a careful analysis of the well known thermodynamical anomalies of water. Studying the temperature and pressure dependencies of water dynamics, we show that the liquid-liquid phase transition (LLPT) hypothesis represents a reliable model for describing liquid water. In this model, water in the liquid state is a mixture of two different local structures, characterised by different densities, namely the low density liquid (LDL) and the high-density liquid (HDL). The LLPT line should terminate at a special transition point: a low-T liquid-liquid critical point. We discuss the following experimental findings on liquid water: (i) a crossover from non-Arrhenius behaviour at high T to Arrhenius behaviour at low T in transport parameters; (ii) a breakdown of the Stokes-Einstein relation; (iii) the existence of a Widom line, which is the locus of points corresponding to maximum correlation length in the p-T phase diagram and which ends in the liquid-liquid critical point; (iv) the direct observation of the LDL phase; (v) a minimum in the density at approximately 70 K below the temperature of the density maximum. In our opinion these results represent the experimental proofs of the validity of the LLPT hypothesis.

Mallamace, F.; Branca, C.; Broccio, M.; Corsaro, C.; Gonzalez-Segredo, N.; Spooren, J.; Stanley, H. E.; Chen, S.-H.

2008-07-01

128

Statistical properties of fractal dendrites and anisotropic diffusion-limited aggregates

Crystalline dendrites, growing in a two-dimensional diffusion field at small Péclet numbers, are investigated. It is shown that, far from the tip, the distribution in size of the side branches gives them a fractal structure of dimension df~=1.58+\\/-0.03. In spite of the fluctuations, their overall area is the same as the underlying stable parabola observed at the tip. Similarly, anisotropic

Y. Couder; F. Argoul; A. Arnéodo; J. Maurer; M. Rabaud

1990-01-01

129

Transport properties of hybrid graphene/graphane nanoribbons

NASA Astrophysics Data System (ADS)

The transport properties of hybrid nanoribbons constructed by substituting zigzag graphane nanoribbons into zigzag graphene nanoribbons are investigated using the first-principles calculations and non-equilibrium Green's function. The transport properties of the hybrid systems are improved due to the appearance of transport platform with nontrivial conductance around the Fermi level. This enhancement attributes to the extra bands induced by the substituted graphane nanoribbons. Moreover, this enhancement is sensitive to the position and concentration of the substituted graphane nanoribbons in the system. Our results indicate that such hybrid system is an effective approach to modulate the transport properties of zigzag graphene nanoribbons.

Zou, Wei; Yu, Zhizhou; Zhang, C. X.; Zhong, J. X.; Sun, L. Z.

2012-03-01

130

Transport properties of silver selenomolybdate glassy ionic conductors

NASA Astrophysics Data System (ADS)

Transport properties of silver selenomolybdate glassy ionic conductors have been reported for wide composition and temperature ranges. It has been observed that the transport properties of these glasses depend strongly on the modifier content as well as on the glass formers ratio. A direct correlation between the ion transport and the modification of the glass structure has been predicted. Transport properties of these glasses are also strongly influenced by the existence of dual character of SeO2 as a glass former and a glass modifier. Structural models for different compositions have also been proposed.

Deb, B.; Ghosh, A.

2012-11-01

131

Optical and electrical transport properties of semicontinuous metallic films

Semicontinuous metallic films posses unique optical and electrical transport properties. The strong localization and large enhancement of electric fields demonstrated by these films make them interesting in terms of a fundamental understanding of these phenomena as well as potentially useful in a large variety of applications. The field distributions and electrical transport properties of these films depend on the structural

Katyayani Seal

2003-01-01

132

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

NASA Astrophysics Data System (ADS)

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.

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

133

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

134

High-field transport properties of graphene

NASA Astrophysics Data System (ADS)

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.

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

2011-09-01

135

Transport properties of fully screened Kondo models

NASA Astrophysics Data System (ADS)

We study the nonequilibrium transport properties of fully (exactly) screened Kondo quantum dots subject to a finite bias voltage or a finite temperature. First, we calculate the Fermi-liquid coefficients of the conductance for models with arbitrary spin, i.e., its leading behavior for small bias voltages or temperatures. Second, we determine the low-temperature behavior of the static susceptibility from the exactly known Bethe ansatz results for the magnetization. Third, we study the crossover from strong to weak coupling in the spin-1/2 and the spin-1 models coupled to one or two screening channels, respectively. Using a real-time renormalization group method we calculate the static and dynamical spin-spin correlation functions for the spin-1/2 model as well as the linear and differential conductance and the static susceptibility for the spin-1 model. We define various Kondo scales and discuss their relations. We assess the validity of the renormalization-group treatment by comparing with known results for the temperature dependence of the linear conductance and static susceptibility as well as the Fermi-liquid behavior at low energies.

Hörig, Christoph B. M.; Mora, Christophe; Schuricht, Dirk

2014-04-01

136

Equilibrium and transport properties of constrained systems

NASA Astrophysics Data System (ADS)

Systems under external confinement and constraints often show interesting properties. In this thesis, we study some systems under external confinement. We begin by finding out the probability distribution of end-to-end separation of a Worm Like Chain (WLC) polymer whose ends are positionally (and orientationally) constrained. We use Monte-Carlo simulations (MC) and a theoretical mapping of the WLC to a quantum particle moving on the surface of an unit sphere to find multimodality in Helmholtz ensemble as a generic signature of semi-flexibility. Secondly, we study Laser Induced Freezing using a Kosterlitz-Thouless type renormalization group calculation and a restricted MC simulation to obtain phase diagrams for Hard Disk, Soft Disk and DLVO potentials. They show very good agreement with phase diagrams simulated by other groups. Lastly, we study the strain response and failure mechanism of a two-dimensional solid confined within a hard wall channel using MC and molecular dynamics simulations. We find a reversible plastic failure through solid-smectic coexistence and observe layering transitions. Mean field calculations can capture some of these features. We study the heat transport in this system thorugh nonequilibrium molecular dynamics simulations and find strong signatures of the transitions. We propose a simple free volume calculation that reproduces some qualitative features of the strain response of heat current for small strains.

Chaudhuri, Debasish

2006-10-01

137

Anisotropic flows and the shear viscosity of the QGP within a transport approach

NASA Astrophysics Data System (ADS)

We study the build up of elliptic flow v2 and high order harmonics vn within a transport approach at fixed shear viscosity to entropy density ratio ?/s and with initial state fluctuations. In particular we study the effect of a temperature dependent ?/s for two different beam energies: RHIC for Au+Au at = 200 GeV and LHC for Pb + Pb at = 2.76 TeV. We find that for the two different beam energies considered the suppression of the elliptic flow and of higher harmonics v3(pT) and v4(pT) due to the viscosity of the medium have different contributions coming from the cross over or QGP phase. Moreover, we discuss the correlation between the initial spatial anisotropies epsilonn and flow coefficients vn. We observe that the elliptic flow v2 is strongly correlated with initial eccentricity epsilon2. While higher harmonics v3 and v4 are weakly correlated to their asymmetry measure in coordinate space epsilon3 and epsilon4.

Plumari, S.; Guardo, G. L.; Puglisi, A.; Scardina, F.; Greco, V.

2014-09-01

138

The groundwater system in southern Oahu, Hawaii consists of a thick, areally extensive freshwater lens overlying a zone of transition to a thick saltwater body. This system is analyzed in cross section with a variable-density groundwater flow and solute transport model on a regional scale. The simulation is difficult, because the coastal aquifer system has a saltwater transition zone that is broadly dispersed near the discharge area, but is very sharply defined inland. Steady-state simulation analysis of the transition zone in the layered basalt aquifer of southern Oahu indicates that a small transverse dispersivity is characteristic of horizontal regional flow. Further, in this system flow is generally parallel to isochlors and steady-state behavior is insensitive to the longitudinal dispersivity. Parameter analysis identifies that only six parameters control the complex hydraulics of the system: horizontal and vertical hydraulic conductivity of the basalt aquifer; hydraulic conductivity of the confining "caprock" layer; leakance below the caprock; specific yield; and aquifer matrix compressibility. The best-fitting models indicate the horizontal hydraulic conductivity is significantly greater than the vertical hydraulic conductivity. These models give values for specific yield and aquifer compressibility which imply a considerable degree of compressive storage in the water table aquifer. ?? 1987.

Souza, W.R.; Voss, C.I.

1987-01-01

139

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.

Bo Li; Xing Li

2008-12-09

140

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.

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

2013-01-01

141

Anisotropic magnetic properties of Dy6Cr4Al43 single crystal

NASA Astrophysics Data System (ADS)

We have studied the anisotropic magnetic behavior of the rare earth intermetallic compound Dy6Cr4Al43. 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.

Maurya, Arvind; Thamizhavel, A.; Dhar, S. K.

2014-04-01

142

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

Smooth voids are achieved in an anisotropic Fe:LiNbO{sub 3} 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.

Zhou Guangyong; Gu Min [center for Micro-Photonics and center for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, PO Box 218, Hawthorn, Victoria 3122 (Australia)

2005-12-12

143

NASA Astrophysics Data System (ADS)

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.`

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

2014-10-01

144

Magneto-transport properties of gapped graphene.

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

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

2010-04-01

145

Transport and thermodynamic properties of iron-based superconductors

NASA Astrophysics Data System (ADS)

Iron-based superconductors (FeSCs) are a novel family of high-temperature superconductors. The rich phase diagrams exhibited by these compounds under various doping regimes, their multi-band electronic structure, the high superconducting critical temperature with exotic realization of order parameters, all contribute to this system being of considerable theoretical interest. In this Thesis, we report on our past work aimed at addressing possible signatures of the exotic superconducting (SC) order parameters (OPs), the coexistence with spin-density wave (SDW) phase, and fluctuations effects, as reflected in various transport or thermodynamic properties of these materials. We present a theoretical description of the differential conductance of point contacts between a normal metal and a multi-band superconductor with s+/--wave symmetry. We demonstrate that the interband impurity scattering broadens the coherent peak near the superconducting gap and significantly reduces its height even at relatively low scattering rates for an extended s+/--wave gap. Our mean-field treatment of the zero-temperature London penetration depth of a clean multi-band superconductor in the case when both SC and SDW orders coexist shows that the supefluid density closely follows the evolution of the superconducting order parameter as doping is increased, saturating to a BCS value in the pure superconducting state. Furthermore, a strong anisotropic in-pane penetration depth is shown to be induced by the SDW order. Beyond mean-field level, however, the monotonic behavior of both penetration depth, and specific heat jump is modified into a sharp peak near the tetracritical point - a point of intersection of four phase transition lines. We show that in the case of specific heat jump, this effect originates from thermal fluctuations of the SDW OP near the tetracritical point. Thermal fluctuations result in a power-law dependence of the specific heat jump fluctuation correction that is stronger than the contribution of mass renormalization due to quantum fluctuations of SDW in the vicinity of the putative critical point beneath the superconducting dome.

Kuzmanovski, Dushko

146

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

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

2009-02-01

147

Functional Properties and Genomics of Glucose Transporters

Glucose is the major energy source for mammalian cells as well as an important substrate for protein and lipid synthesis. Mammalian cells take up glucose from extracellular fluid into the cell through two families of structurallyrelated glucose transporters. The facilitative glucose transporter family (solute carriers SLC2A, protein symbol GLUT) mediates a bidirectional and energy-independent process of glucose transport in most tissues and cells, while the NaM+/glucose cotransporter family (solute carriers SLC5A, protein symbol SGLT) mediates an active, Na+-linked transport process against an electrochemical gradient. The GLUT family consists of thirteen members (GLUT1-12 and HMIT). Phylogenetically, the members of the GLUT family are split into three classes based on protein similarities. Up to now, at least six members of the SGLT family have been cloned (SGLT1-6). In this review, we report both the genomic structure and function of each transporter as well as intra-species comparative genomic analysis of some of these transporters. The affinity for glucose and transport kinetics of each transporter differs and ranges from 0.2 to 17mM. The ability of each protein to transport alternative substrates also differs and includes substrates such as fructose and galactose. In addition, the tissue distribution pattern varies between species. There are different regulation mechanisms of these transporters. Characterization of transcriptional control of some of the gene promoters has been investigated and alternative promoter usage to generate different protein isoforms has been demonstrated. We also introduce some pathophysiological roles of these transporters in human. PMID:18660845

Zhao, Feng-Qi; Keating, Aileen F

2007-01-01

148

26 CFR 49.4271-1 - Tax on transportation of property by air.

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 true Tax on transportation of property by air. 49.4271-1...FACILITIES AND SERVICES EXCISE TAXES Transportation of Property § 49.4271-1 Tax on transportation of property by air. (a)...

2010-04-01

149

NASA Astrophysics Data System (ADS)

We investigate the magnetic properties and Mott transition in the Hubbard model for weakly coupled chains on the anisotropic triangular lattice. Taking into account 120? Néel and collinear orderings, the magnetic phase diagram is studied at zero temperature and half-filling by the variational cluster approximation. We found that, when the on-site Coulomb repulsion U is relatively large, the nonmagnetic insulator, which is a candidate of the spin liquid state, is realized for a wide range of interchain hopping from the quasi-two-dimensional to the almost one-dimensional regime. When the interchain hopping is relatively large, this nonmagnetic insulator becomes a magnetic state as U decreases. For rather small interchain hopping, this nonmagnetic insulator changes to a paramagnetic metal as U decreases, thus purely paramagnetic metal-insulator transition (Mott transition) takes place. Implications of our results for Cs2CuBr4 and Cs2CuCl4 are discussed.

Yamada, A.

2014-12-01

150

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 ????=???{sub 1}??+?i??{sub 2}? 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.

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

151

NASA Astrophysics Data System (ADS)

The effect of sputtering anisotropic ejection on the optical properties and internal stress of niobium pentoxide (Nb2O5) films prepared by ion-beam sputtering deposition (IBSD) was investigated experimentally. Thin films were deposited on unheated BK7 glass substrates and silicon wafers at different ejection angles surrounding a metal target. The ejection angles varied from 0° to 75° in increments of 15° for each substrate. It was found that the optical constants of the Nb2O5 films were significantly influenced by the sputtering ejection angle. The surface roughness and residual stress in the Nb2O5 thin films were also found to vary with the ejection angle. In this work, Nb2O5 films had a higher refractive index, lower absorption, lower stress and lower roughness when films deposited at an ejection angle of 30°.

Tien, Chuen-Lin

2010-11-01

152

Theoretical investigation of thermoelectric transport properties of cylindrical Bi nanowires

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,

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

2000-01-01

153

Electronic and Transport Properties of Ferrocene: Theoretical Study

The transport properties of a single ferrocene molecule have been investigated using the nonequilibrium Green's function formalism for quantum transport and the density functional theory (DFT) of electronic structures using local orbital basis sets. The conductance of a single ferrocenedithiolate molecule depends on the position of the sulfur atoms. The current-voltage characteristics show that the iron atom enhances the conductivity

Tomoki Uehara; Rodion V. Belosludov; Amir A. Farajian; Hiroshi Mizuseki; Yoshiyuki Kawazoe

2006-01-01

154

The microgeometry and transport properties of sedimentary rock

This monograph describes recent progress in modelling the transport properties of sedimentary rock. Statistical descriptions are applied to the pore-space geometry and to the transport processes involving pore fluids. Fractals are used to quantify the pore geometry at length scales shorter than grain size. Percolation theory is applied to fluid flow. The permeability can be expressed in terms of a

A. H. Thompson; A. J. Katz; C. E. Krohn

1987-01-01

155

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.

Friedel, Michael J.

2001-01-01

156

This study highlights the synthesis of shape-controlled La2NiO(4+?) nanostructures using a reverse microemulsion method. We report that surfactant to water mass ratio plays a key role in controlling the shape of the nanostructures. These nanostructures show a strong dependence of their oxygen transport properties on their geometries. PMID:25385161

Ma, X; Wang, B; Xhafa, E; Sun, K; Nikolla, E

2015-01-01

157

Diameter Dependence of the Transport Properties of Antimony Telluride Nanowires

Diameter Dependence of the Transport Properties of Antimony Telluride Nanowires Yuri M. Zuev, Jin properties of individual single crystal antimony telluride (Sb2Te3) nanowires with diameters in the range figure of merit in single crystal chalcogenide Sb2Te3 NWs. Antimony telluride (Sb2Te3) is a small bandgap

Heller, Eric

158

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...

159

Transport properties of a meson gas

We present recent results on a systematic method to calculate transport coefficients for a meson gas (in particular, we analyze a pion gas) at low temperatures in the context of Chiral Perturbation Theory. Our method is based on the study of Feynman diagrams with a power counting which takes into account collisions in the plasma by means of a non-zero particle width. In this way, we obtain results compatible with analysis of Kinetic Theory with just the leading order diagram. We show the behavior with temperature of electrical and thermal conductivities and shear and bulk viscosities, and we discuss the fundamental role played by unitarity. We obtain that bulk viscosity is negligible against shear viscosity near the chiral phase transition. Relations between the different transport coefficients and bounds on them based on different theoretical approximations are also discussed. We also comment on some applications to heavy-ion collisions.

D. Fernandez-Fraile; A. Gomez Nicola

2007-07-09

160

Magnetic and transport properties of the ? alloys

Magnetization and transport measurements have been performed to study the martensitic and pre-martensitic transitions for a series of ferromagnetic Heusler 0953-8984\\/11\\/13\\/016\\/img10 alloys. Both magnetization and resistivity measurements show a clear jump at the martensitic transition and a discontinuous slope change at the pre-martensitic transition. The characteristic temperatures correspond well with those derived from previous direct structural results from neutron scattering,

F. Zuo; X. Su; P. Zhang; G. C. Alexandrakis; F. Yang; K. H. Wu

1999-01-01

161

Unsaturated Zone and Saturated Zone Transport Properties (U0100)

This Analysis/Model Report (AMR) summarizes transport properties for the lower unsaturated zone hydrogeologic units and the saturated zone at Yucca Mountain and provides a summary of data from the Busted Butte Unsaturated Zone Transport Test (UZTT). The purpose of this report is to summarize the sorption and transport knowledge relevant to flow and transport in the units below Yucca Mountain and to provide backup documentation for the sorption parameters decided upon for each rock type. Because of the complexity of processes such as sorption, and because of the lack of direct data for many conditions that may be relevant for Yucca Mountain, data from systems outside of Yucca Mountain are also included. The data reported in this AMR will be used in Total System Performance Assessment (TSPA) calculations and as general scientific support for various Process Model Reports (PMRs) requiring knowledge of the transport properties of different materials. This report provides, but is not limited to, sorption coefficients and other relevant thermodynamic and transport properties for the radioisotopes of concern, especially neptunium (Np), plutonium (Pu), Uranium (U), technetium (Tc), iodine (I), and selenium (Se). The unsaturated-zone (UZ) transport properties in the vitric Calico Hills (CHv) are discussed, as are colloidal transport data based on the Busted Butte UZTT, the saturated tuff, and alluvium. These values were determined through expert elicitation, direct measurements, and data analysis. The transport parameters include information on interactions of the fractures and matrix. In addition, core matrix permeability data from the Busted Butte UZTT are summarized by both percent alteration and dispersion.

J. Conca

2000-12-20

162

Barrier properties of gastrointestinal mucus to nanoparticle transport.

Gastrointestinal mucus, a complex network of highly branched glycoproteins and macromolecules, is the first barrier through which orally delivered drug and gene vectors must traverse. The diffusion of such vectors can be restricted by the high adhesivity and viscoelasticity of mucus. In this investigation, the barrier properties of gastrointestinal mucus to particle transport were explored using real-time multiple particle tracking. The influence of surface chemistry on particle transport rates was examined using amine-, carboxylate-, and sulfate-modified polystyrene nanoparticles. A strong dependence of particle mobility in gastrointestinal mucus on surface charge was observed, with anionic particles diffusing 20-30 times faster than cationic particles. Comparison of diffusion coefficients calculated for gastrointestinal mucus with significantly varying values previously reported in the literature for other mucus sources, including cervicovaginal mucus and cystic fibrosis sputum, highlight the dependence of mucus barrier properties on the anatomical source. A significant degree of transport rate heterogeneity was also observed in native gastrointestinal mucus, suggesting a highly heterogeneous distribution of pore sizes. Furthermore, the suitability of purified mucin as a model system for transport studies was assessed by comparing particle transport rates between native intestinal mucus and purified porcine gastric mucin. Particle transport rates were approximately threefold lower in native mucus compared to purified mucin for anionic particles, yet comparable for cationic particles. Differences between barrier properties of the purified mucin preparation and native mucus depended on specific carrier properties, indicating that the purified mucin preparation does not provide an accurate model system for native mucus. PMID:20857389

Crater, Jason S; Carrier, Rebecca L

2010-12-01

163

Magnetic and Transport Properties of RBi2 and RAgBi2

NASA Astrophysics Data System (ADS)

038

RBi2 (R=La-Nd, Sm) and RAgBi2 (R=La-Nd, Sm, Gd) rare earth series crystallize in orthorhombic LaBi2 and tetragonal ZrCuSi2 structure. Whereas some RBi2 alloys have been reported before without space group and crystal structure determination, here we report for the first time existence or new ternary RAgBi2 series. 038

All RBi2 with incomplete 4f shell exhibit long range antiferromagnetic order. CeBi2 and SmBi2 show single magnetic transitions. PrBi2 and NdBi2 show double transitions with substantial metamagnetism and magnetic anisotropy created by crystalline electric field splitting of the Hund's rule multiplet. 038

RAgBi2 crystals are far less air sensitive than RBi_2, more ordered, and have bigger RRR. Magnetic ground states for these compounds appear to be antiferromagnetic, but with less local moment anisotropy than one seen in RBi_2. Anisotropic metamagnetism is observed for Ce and Pr members of the series, however no big magnetoresistance was observed in RAgBi_2, as opposed to RAgSb2 and RSb_2. 038

Magnetic ordering temperatures scale well with deGennes scaling in case of RBi2 whereas there is poorer agreement for RAgBi_2. The anisotropic magnetic and transport properties will be discussed and comparison with physical properties of rare earth diantimonide and silver diantimonide series will be given.

Petrovic, Cedomir; Bud'Ko, Sergey; Canfield, Paul; Choe, Wonyoung; Miller, Gordon

2002-03-01

164

Properties of intracellular transport: the role of cytoskeleton topology

NASA Astrophysics Data System (ADS)

The eukaryotic cytoskeleton is composed of polarized filaments forming a complex, intertwined network. Various motor proteins such as kinesins or myosins convert ATP into mechanical work and are able to walk processively or even diffuse along the cytoskeleton. Large organelles such as vesicles or mitochondria can randomly bind and unbind to one or several motors and their transport in the cell can be described as alternating phases of diffusion in the cytoplasm and phases of directed or diffusive transport along the cytoskeletal network. Intracellular transport has been the focus of extensive studies both experimentally and theoretically. However, the impact of the cytoskeleton network structure on transport properties, which is expected to be significant, is not fully understood. We develop a computational model of intracellular transport, and explore the impact of the cytoskeletal structure on transport properties. We show that transport can be enhanced even by diffusional motion along the cytoskeleton after memory effects due to cytoskeletal structure are taken into account. We also explore the influence of the network structure on the first passage time distributions for a cargo to reach the cell membrane after being exported from the nucleus and for transport from the membrane to the nucleus.

Korabel, Nickolay; Huang, Kerwyn C.; Gopinathan, Ajay

2013-03-01

165

A finite element space-angle synthesis (FESAS) solution of the steady state anisotropic Boltzmann equation in a two-dimensional cylindrical geometry was developed. Starting from a variational principle the Bubnov-Galerkin solution method was applied to the second order even parity form of the Boltzmann equation. A trial function flux expansion in bicubic splines and spherical (surface) harmonics was used. A first scatter

Wills

1981-01-01

166

Physical transport properties of marine microplastic pollution

NASA Astrophysics Data System (ADS)

Given the complexity of quantitative collection, knowledge of the distribution of microplastic pollution in many regions of the world ocean is patchy, both spatially and temporally, especially for the subsurface environment. However, with knowledge of typical hydrodynamic behavior of waste plastic material, models predicting the dispersal of pelagic and benthic plastics from land sources into the ocean are possible. Here we investigate three aspects of plastic distribution and transport in European waters. Firstly, we assess patterns in the distribution of plastics found in fluvial strandlines of the North Sea and how distribution may be related to flow velocities and distance from source. Second, we model transport of non-buoyant preproduction pellets in the Nazaré Canyon of Portugal using the MOHID system after assessing the density, settling velocity, critical and depositional shear stress characteristics of such waste plastics. Thirdly, we investigate the effect of surface turbulences and high pressures on a range of marine plastic debris categories (various densities, degradation states and shapes tested) in an experimental water column simulator tank and pressure laboratory. Plastics deposited on North Sea strandlines varied greatly spatially, as a function of material composition and distance from source. Model outputs indicated that such dense production pellets are likely transported up and down canyon as a function of tidal forces, with only very minor net down canyon movement. Behaviour of plastic fragments under turbulence varied greatly, with the dimensions of the material, as well as density, playing major determining roles. Pressure was shown to affect hydrodynamic behaviours of only low density foam plastics at pressures ? 60 bar.

Ballent, A.; Purser, A.; Mendes, P. de Jesus; Pando, S.; Thomsen, L.

2012-12-01

167

Anisotropic Artificial Impedance Surfaces

NASA Astrophysics Data System (ADS)

Anisotropic artificial impedance surfaces are a group of planar materials that can be modeled by the tensor impedance boundary condition. This boundary condition relates the electric and magnetic field components on a surface using a 2x2 tensor. The advantage of using the tensor impedance boundary condition, and by extension anisotropic artificial impedance surfaces, is that the method allows large and complex structures to be modeled quickly and accurately using a planar boundary condition. This thesis presents the theory of anisotropic impedance surfaces and multiple applications. Anisotropic impedance surfaces are a generalization of scalar impedance surfaces. Unlike the scalar version, anisotropic impedance surfaces have material properties that are dependent on the polarization and wave vector of electromagnetic radiation that interacts with the surface. This allows anisotropic impedance surfaces to be used for applications that scalar surfaces cannot achieve. Three of these applications are presented in this thesis. The first is an anisotropic surface wave waveguide which allows propagation in one direction, but passes radiation in the orthogonal direction without reflection. The second application is a surface wave beam shifter which splits a surface wave beam in two directions and reduces the scattering from an object placed on the surface. The third application is a patterned surface which can alter the scattered radiation pattern of a rectangular shape. For each application, anisotropic impedance surfaces are constructed using periodic unit cells. These unit cells are designed to give the desired surface impedance characteristics by modifying a patterned metallic patch on a grounded dielectric substrate. Multiple unit cell geometries are analyzed in order to find the setup with the best performance in terms of impedance characteristics and frequency bandwidth.

Quarfoth, Ryan Gordon

168

Enhancement of wall jet transport properties

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.

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

1997-01-01

169

Transport properties of high-temperature Jupiter atmosphere components

Transport properties of high-temperature helium and hydrogen plasmas as well as Jupiter atmosphere have been calculated for equilibrium and nonequilibrium conditions using higher approximations of the Chapman-Enskog method. A complete database of transport cross sections for relevant interactions has been derived, including minority species, by using both ab initio and phenomenological potentials. Inelastic collision integrals terms, due to resonant charge-exchange channels, have been also considered.

Bruno, D.; Colonna, G.; De Pascale, O.; Laricchiuta, A. [Department of Chemistry, University of Bari, via Orabona 4 Bari 70125 (Italy); Catalfamo, C.; Diomede, P. [CNR-IMIP Bari, via Orabona 4 Bari 70125 (Italy); Capitelli, M.; Gorse, C.; Longo, S. [Department of Chemistry, University of Bari, via Orabona 4 Bari 70125 (Italy); CNR-IMIP Bari, via Orabona 4 Bari 70125 (Italy); Giordano, D. [Aerothermodynamics Section, ESA-ESTEC, Keplerlaan 1 2200 AG Noordwijk (Netherlands); Pirani, F. [Department of Chemistry, University of Perugia, via Elce di Sotto 8 Perugia 06123 (Italy)

2010-11-15

170

High temperature transport properties of air

NASA Technical Reports Server (NTRS)

A general computer code was developed to allow calculation of atom-atom and ion-atom transport collision integrals from accurate potential energy curves described by a set of discrete data points for a broad range of scattering conditions. This code is based upon semiclassical approximations that properly account for quantum mechanical behavior such as tunneling effects near a barrier maximum, resonance charge exchange, and nuclear symmetry effects. Transport collision integrals were determined for N-N, O-O, N(+)-N, and O(+)-O interactions from complete sets of accurate potential functions derived from combined experimental and ab initio structure calculations. For the O-O case, this includes results for excited states. The calculated values of the N(+)-N and O(+)-O resonance charge exchange cross section Q(ex) agree well with measurements from beam experiment that are available at high energies where the diffusion cross section Q(d) satisfies Q(d) approximately equal to 2Q(ex).

Levin, E.; Partridge, Harry; Stallcop, J. R.

1987-01-01

171

Middle Atmosphere Transport Properties of Assimilated Datasets

NASA Technical Reports Server (NTRS)

One of the most compelling reasons for performing data assimilation in the middle atmosphere is to obtain global, balanced datasets for studies of trace gas transport and chemistry. This is a major motivation behind the Goddard Earth observation System-Data Assimilation System (GEOS-DAS). Previous studies have shown that while this and other data assimilation systems can generally obtain good estimates of the extratropical rotational velocity field, the divergent part of the dynamical field is deficient; this impacts the "residual circulation" and leads to spurious trace gas transport on seasonal and interannual timescales. These problems are impacted by the quality and the method of use of the observational data and by deficiencies in the atmospheric general circulation model. Whichever the cause at any place and time, the "solution" is to introduce non-physical forcing terms into the system (the so-called incremental analysis updates); these can directly (thermal) or indirectly (mechanical) affect the residual circulation. This paper will illustrate how the divergent circulation is affected by deficiencies in both observations and models. Theoretical considerations will be illustrated with examples from the GEOS-DAS and from simplified numerical experiments. These are designed to isolate known problems, such as the inability of models to sustain a quasi-biennial oscillation and sparse observational constraints on tropical dynamics, or radiative inconsistencies in the presence of volcanic aerosols.

Pawson, Steven; Rood, Richard

1999-01-01

172

Middle Atmospheric Transport Properties of Assimilated Datasets

NASA Technical Reports Server (NTRS)

One of the most compelling reasons for performing data assimilation in the middle atmosphere is to obtain global, balanced datasets for studies of trace gas transport and chemistry. This is a major motivation behind the Goddard Earth observation System-Data Assimilation System (GEOS-DAS). Previous studies have shown that while this and other data assimilation systems can generally obtain good estimates of the extratropical rotational velocity field, the divergent part of the dynamical field is deficient; this impacts the "residual circulation" and leads to spurious trace gas transport on seasonal and interannual timescales. These problems are impacted by the quality and the method of use of the observational data and by deficiencies in the atmospheric general circulation model. Whichever the cause at any place and time, the "solution" is to introduce non-physical forcing terms into the system (the so-called incremental analysis updates); these can directly (thermal) or indirectly (mechanical) affect the residual circulation. This paper will illustrate how the divergent circulation is affected by deficiencies in both observations and models. Theoretical considerations will be illustrated with examples from the GEOS-DAS and from simplified numerical experiments. These are designed to isolate known problems, such as the inability of models to sustain a quasi-biennial oscillation and sparse observational constraints on tropical dynamics, or radiative inconsistencies in the presence of volcanic aerosols.

Pawson, Steven; Rood, Richard

1999-01-01

173

Transport properties in nontwist area-preserving maps

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.

Szezech Jr., J. D. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo (Brazil); Caldas, I. L. [Instituto de Fisica, Universidade de Sao Paulo, Sao Paulo (Brazil); Lopes, S. R. [Departamento de Fisica, Universidade Federal do Parana, Curitiba (Brazil); Viana, R. L. [Departamento de Fisica, Universidade Federal do Parana, Curitiba (Brazil); Morrison, P. J. [Univ. of Texas at Austin (United States)

2009-10-23

174

Electronic transport properties of coupled quantum dots on carbon nanotubes.

We investigate the electronic transport properties of coupled quantum dots, controlled by local gates on carbon nanotubes. The inter-dot coupling can be tuned from weak to strong by changing gate voltages, and oscillates in short and long period with the distance between two gates. We introduce a one-dimensional scattering model to describe the mechanism of the electron transport through the carbon nanotube quantum dots. We show that pi and PI* channels contribute differently to the inter-dot coupling and the transport phase plays a key role in the oscillations of the coupling. PMID:21125895

Qian, Haiyun; Lu, Jun-Qiang

2010-08-01

175

NASA Astrophysics Data System (ADS)

The complex microstructures of thermally sprayed coatings are very sensitive to processing conditions and have a significant influence on the properties. The thermal transport property is a very important design parameter for thermally sprayed coatings. Despite considerable progress in this area, there is continued need to clarify the interrelationships among processing, microstructure and thermal transport properties. This has been enabled through continued advancements in processing science and control, enhancements in microstructural characterization and new methods of property characterization. The purpose of this research is to seek a successive pathway to prior efforts in understanding the effect of microstructural defects on the thermal transport property of thermally sprayed coatings. Relationship between microstructure and thermal conductivity is investigated for three sets of plasma sprayed yttria stabilized zirconia (YSZ) coating systems made using different morphology powders, different particle size distribution and controlled modification of particle states via plasma torch parameters. By integrating the results, maps of the thermal conductivity-porosity relationship have been established. Such maps highlight the role of splat thickness and interfaces in thermal conductivity. Furthermore, a new microstructural parameter termed "effective porosity" is proposed which considers the dominating role of interlamellar pores on through thickness thermal transport in thermally sprayed coatings. This effective porosity is rationalized based on the heat transport mechanism and enables better understanding of microstructure-thermal transport property correlation. An inverse linear model and a percolation model are established which can serve as predictive tools for understanding microstructure-thermal conductivity relationships. In addition, a systematic assessment of thermal conductivity anisotropy has been carried out for YSZ, Al2O 3 and several metallic coatings. These results are analyzed from the point of view of modified percolation theory which considers the effect of anisotropic microstructural defects of sprayed coatings on the thermal transport property. In the case of the ceramic coatings (YSZ, Al2O3), the temperature dependent thermal conductivity is also examined for various starting microstructures in collaboration with the Oak Ridge National Laboratory (ORNL). The decisive role of starting microstructure on temperature dependent thermal conductivity is presented. In addition, sintering effects resulting from thermal cycling and isothermal exposure on both room temperature and temperature dependent thermal conductivity have been carefully examined in an effort to assess the relationship to effective starting microstructure and provide quantitative information for life prediction. This dissertation also extends to an investigation of thermal conductivity of metal and alloy thermal spray coatings. A range of metallic materials have been considered and the variation of thermal conductivity is interpreted from the point of view of intrinsic attributes (atomic structure, electronic structure and phase structure) as well as extrinsic effects (as a consequence of oxidation and defected microstructure). Finally, in order to achieve precise and reliable measurement of thermal transport property, the applicability and repeatability of both the laser and xenon flash techniques have been examined through the measurements on these coating systems: ceramics, semiconductors, metals, alloys and composites.

Chi, Weiguang

176

NASA Astrophysics Data System (ADS)

Magnetic properties of nanogranular ferromagnetic Co/Al2O3 films with 74.5 at% Co, which is above the percolation limit, are investigated. It is established that the films have perpendicular magnetic anisotropy and a weaker in-plane anisotropy. The magnetization curves show that the film consists of two magnetic components: a dominating contribution from magneto-anisotropic isolated grains with the anisotropy axis perpendicular to the film plane and a weaker contribution from the percolated part of the film. This two-component magnetic composition of the films, with the dominating contribution from the nanograins, is confirmed by transmission electron microscopy as well as by ferromagnetic resonance spectroscopy. It is further established that the coercive field of the film is almost entirely determined by the percolated part of the film. In this, the angular dependence of the coercive force, Hc (?H), is essentially proportional to sin-1?H, where ?H is the angle between the applied field and the film's normal. However, for ?H ? 0, Hc (?H) there is a narrow minimum with Hc approaching zero. Such non-linear dependence agrees well with our modelling results for a two-component magnetic system of the film, where the non-percolated nanograins have a distinct perpendicular anisotropy. The reported results should be important for in-depth characterization and understanding the magnetism and anisotropy in inhomogeneous systems as well as for applications, specifically in perpendicular magnetic recording.

Kulyk, M. M.; Kalita, V. M.; Lozenko, A. F.; Ryabchenko, S. M.; Stognei, O. V.; Sitnikov, A. V.; Korenivski, V.

2014-08-01

177

Single tube electric transport properties of synthesized Titania nanotubes

NASA Astrophysics Data System (ADS)

Titania nanotube arrays fabricated by means of electrochemical anodization is currently the main interest of several research groups due to its promising applications. The high aspect ratio, durability, cheap and scalable fabrication technique make it highly attractive material for efficient solar cell. In this regard extensive research work is being carried out to investigate its properties. In our previous work we were able to find a mechanism for separating a single titania nanotube from the titania nanotube arrays and to measure its electric transport properties using e-beam lithography technique, In this work we investigated the effect of thermal annealing on the transport properties, we studied the effect of different annealing temperatures, heating and cooling rates, and in different gases. As a result, we were able to find the optimal annealing conditions to enhance the transport properties in blank titania nanotube. Under these optimal conditions, we were able to study the effect of coating TNTs with N719 dye and gold nanoparticles on the transport properties. As a result of our work we were able to optimize the treatments for more efficient solar cell fabrication.

Abdelmoula, Mohamed; Menon, Latika

2011-03-01

178

NASA Astrophysics Data System (ADS)

The infrared (ir) optical properties and vibrational behavior of anisotropic absorbing crystals in spectral regions including strong resonances are considered. In particular, the optical parameters, namely the complex dielectric tensor and refractive indexes, of barium nitroprusside trihydrate (BNP), Ba[Fe(CN)5NO].3H2O (orthorhombic, space group C52v), in the range 1500-2300 cm-1, which includes the strongly polar NO stretching mode, are determined. To this purpose, transversal electric (TE) reflectance data on (001) planes of BNP in the spectral range 250-4000 cm-1 were analyzed by the Kramers-Kronig method. The values obtained for the optical parameters were employed to get transversal (TO) and longitudinal (LO) frequencies of the NO optic stretching mode of symmetry species B1 (polarized along the crystal a axis) and to show the impossibility of obtaining sharp peaks for accurate frequency measurement of the TO mode by transmission spectroscopy because too-thin crystals films (less than 1 ?m thick) would be required. The dielectric tensor was employed to predict correctly the position and shape of the NO reststrahlen band due to the LO mode B1 in the reflectance spectrum from the (100) face. This band occurs only for oblique incidence and transversal-magnetic (TM) polarization of the ir beam. The computed TM-polarized, off-axis transmittance spectra through bc crystal plates of BNP in the NO stretching region are in good agreement with spectroscopic data and exhibit a sharp, strong absorption band at 1982 cm-1 which is due to the coupling of the LO mode B1 with the ir radiation. Our results show that strongly absorbing LO modes polarized perpendicularly to the plate can be easily identified and their frequencies measured accurately in relatively thick samples of an anisotropic substance. Finally, a least-squares fit to reflection data of the calculated TE reflectance on a (001) plane of BNP, derived from a damped harmonic-oscillator model for the dielectric constant along a, leads to a value for the transition strength of the NO stretching which is in accordance with values obtained by independent spectroscopic measurements.

Piro, O. E.; González, S. R.; Aymonino, P. J.; Castellano, E. E.

1987-08-01

179

Anisotropic optical properties of arrays of gold nanorods embedded in alumina

A series of thin films comprising gold nanorods embedded in an alumina matrix have been fabricated with lengths ranging from 75 to 330nm . Their optical properties, expressed in terms of extinction -ln(T) , where T is optical transmittance, have been measured as a function of wavelength, rod length, angle of incidence, and incident polarization state. The results are compared

Ron Atkinson; William R. Hendren; Gregory A. Wurtz; Wayne Dickson; Anatoly V. Zayats; Paul Evans; Robert J. Pollard

2006-01-01

180

FROM 3D IMAGING OF STRUCTURES TO DIFFUSIVE PROPERTIES OF ANISOTROPIC CELLULAR MATERIALS

morphological tool to extract geometrical characteristics of the media from X-ray images. The anisotropy of the geometry of each phase is observed and the relationship between microstructure and effective properties. The conductive heat transfers are computed on a vertex-edge network to determine directional effective

Boyer, Edmond

181

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)-Pr0.7(Ca0.6Sr0.4)0.3MnO3/0.7Pb(Mg1/3Nb2/3)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

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

182

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

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

183

Engineering of micro- and nanostructured surfaces with anisotropic geometries and properties.

Widespread approaches to fabricate surfaces with robust micro- and nanostructured topographies have been stimulated by opportunities to enhance interface performance by combining physical and chemical effects. In particular, arrays of asymmetric surface features, such as arrays of grooves, inclined pillars, and helical protrusions, have been shown to impart unique anisotropy in properties including wetting, adhesion, thermal and/or electrical conductivity, optical activity, and capability to direct cell growth. These properties are of wide interest for applications including energy conversion, microelectronics, chemical and biological sensing, and bioengineering. However, fabrication of asymmetric surface features often pushes the limits of traditional etching and deposition techniques, making it challenging to produce the desired surfaces in a scalable and cost-effective manner. We review and classify approaches to fabricate arrays of asymmetric 2D and 3D surface features, in polymers, metals, and ceramics. Analytical and empirical relationships among geometries, materials, and surface properties are discussed, especially in the context of the applications mentioned above. Further, opportunities for new fabrication methods that combine lithography with principles of self-assembly are identified, aiming to establish design principles for fabrication of arbitrary 3D surface textures over large areas. PMID:22396318

Tawfick, Sameh; De Volder, Michael; Copic, Davor; Park, Sei Jin; Oliver, C Ryan; Polsen, Erik S; Roberts, Megan J; Hart, A John

2012-04-01

184

ElAM: A computer program for the analysis and representation of anisotropic elastic properties

NASA Astrophysics Data System (ADS)

The continuum theory of elasticity has been used for more than a century and has applications in many fields of science and engineering. It is very robust, well understood and mathematically elegant. In the isotropic case elastic properties are easily represented, but for non-isotropic materials, even in the simple cubic symmetry, it can be difficult to visualise how properties such as Young's modulus or Poisson's ratio vary with stress/strain orientation. The ElAM ( Elastic Anisotropy Measures) code carries out the required tensorial operations (inversion, rotation, diagonalisation) and creates 3D models of an elastic property's anisotropy. It can also produce 2D cuts in any given plane, compute averages following diverse schemes and query a database of elastic constants to support meta-analyses. Program summaryProgram title: ElAM1.0 Catalogue identifier: AEHB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 43 848 No. of bytes in distributed program, including test data, etc.: 2 498 882 Distribution format: tar.gz Programming language: Fortran90 Computer: Any Operating system: Linux, Windows (XP, Vista) RAM: Depends chiefly on the size of the arrays representing elastic properties in 3D Classification: 7.7 Nature of problem: Representation of elastic moduli and ratios, and of wave velocities, in 3D; automatic discovery of unusual elastic properties. Solution method: Stiffness matrix (6×6) inversion and conversion to compliance tensor (3×3×3×3), tensor rotation, dynamic matrix diagonalisation, simple optimisation, postscript and VRML output preparation. Running time: Dependent on angular accuracy and size of elastic constant database (from a few seconds to a few hours). The tests provided take from a few seconds for test0 to approximately 1 hour for test4.

Marmier, Arnaud; Lethbridge, Zoe A. D.; Walton, Richard I.; Smith, Christopher W.; Parker, Stephen C.; Evans, Kenneth E.

2010-12-01

185

Transport properties of pristine and doped graphene

NASA Astrophysics Data System (ADS)

Graphene has attracted a lot of attention for various applications recently. Chemically exfoliated graphene is one of the best methods to prepare good quality and large amount of few-layer graphene sheets. We prepared pristine and doped graphene using chemical exfoliation through high energy tip sonication technique. The exfoliated graphene was later sintered for studying thermoelectric properties. The thermopower of these samples exhibits valleys, tentatively assigned to phonon drag, which shift towards higher temperature upon vacuum annealing and electron doping. Such a similar behavior was previously observed in doped carbon nanotubes. The effects of vaccum annealing and doping upon the fundamental behavior of thermoelectric power and thermal conduction of graphene will be presented.

Puneet, Pooja; Podila, Ramakrishna; Oliveira, Luciana; Tritt, Terry; Rao, Apparao

2012-02-01

186

Structure and transport properties of nanostructured materials.

In the present manuscript, we have presented the simulation of nanoporous aluminum oxide using a molecular-dynamics approach with recently developed dynamic charge transfer potential using serial/parallel programming techniques (Streitz and Mintmire Phys. Rev. B 1994, 50, 11996). The structures resembling recently invented ordered nanoporous crystalline material, MCM-41/SBA-15 (Kresge et al. Nature 1992, 359, 710), and inverted porous solids (hollow nanospheres) with up to 10 000 atoms were fabricated and studied in the present work. These materials have been used for separation of gases and catalysis. On several occasions including the design of the reactor, the knowledge of surface diffusion is necessary. In the present work, a new method for estimating surface transport of gases based on a hybrid Monte Carlo method with unbiased random walk of tracer atom on the pore surface has been introduced. The nonoverlapping packings used in the present work were fabricated using an algorithm of very slowly settling rigid spheres from a dilute suspension into a randomly packed bed. The algorithm was modified to obtain unimodal, homogeneous Gaussian and segregated bimodal porous solids. The porosity of these solids was varied by densification using an arbitrary function or by coarsening from a highly densified pellet. The surface tortuosity for the densified solids indicated an inverted bell shape curve consistent with the fact that at very high porosities there is a reduction in the connectivity while at low porosities the pores become inaccessible or dead-end. The first passage time distribution approach was found to be more efficient in terms of computation time (fewer tracer atoms needed for the linearity of Einstein's plot). Results by hybrid discrete-continuum simulations were close to the discrete simulations for a boundary layer thickness of 5lambda. PMID:16851615

Sonwane, C G; Li, Q

2005-03-31

187

Exceptional charge transport properties of graphene on germanium.

The excellent charge transport properties of graphene suggest a wide range of application in analog electronics. While most practical devices will require that graphene be bonded to a substrate, such bonding generally degrades these transport properties. In contrast, when graphene is transferred to Ge(001) its conductivity is extremely high and the charge carrier mobility derived from the relevant transport measurements is, under some circumstances, higher than that of freestanding, edge-supported graphene. We measure a mobility of ? 5 × 10(5) cm(2) V(-1) s(-1) at 20 K, and ? 10(3) cm(2) V(-1) s(-1) at 300 K. These values are close to the theoretical limit for doped graphene. Carrier densities in the graphene are as high as 10(14) cm(-2) at 300 K. PMID:25203974

Cavallo, Francesca; Rojas Delgado, Richard; Kelly, Michelle M; Sánchez Pérez, José R; Schroeder, Daniel P; Xing, Huili Grace; Eriksson, Mark A; Lagally, Max G

2014-10-28

188

Tuning transport properties of nanofluidic devices with local charge inversion

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

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

2009-01-01

189

Transport properties of Ni-WS2 photoconductive thin films

It is shown that the annealing under Ar of sputtered WSx amorphous films deposited on Ni coated substrates gives bidimensional polycrystalline 2H–WS2 films. Ni enhances the formation of large crystallites. The temperature dependence of the mobility and its dependence versus the Ni content clearly show that transport properties are governed by grain boundaries. A basic grain boundary model like the

O. Lignier; G. Couturier; J. Salardenne

1997-01-01

190

Magnetic and Transport Properties of FeAs Single Crystals

Magnetic susceptibility and transport properties of an itinerant helimagnet FeAs are studied in single-crystalline samples of this binary compound. A kink due to the magnetic transition is observed in the temperature dependences of both the susceptibility and the resistivity. The Hall coefficient shows a reentrant sign change with temperature, signifying a complicated competition between multiple bands. In the helical ordered

Kouji Segawa; Yoichi Ando

2009-01-01

191

An experimental study of transport properties of porous rock salt

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

E. Spangenberg; U. Spangenberg; C. Heindorf

1998-01-01

192

Atomistic Study of Transport Properties at the Nanoscale

on the nanostructure. Quantum dot superlattices are shown to be effective structures for controlling the thermal transport properties, the available range of thermal conductivity using these structures being 0.1-160 W/mK. The final study concerns graphene...

Haskins, Justin

2013-01-11

193

Electrical transport properties of insulating quench condensed Bi films

We have studied the low temperature electrical transport properties of mesoscopic structures of ultrathin short Bi films. Films were prepared in situ by quench deposition in a ^3He cryostat. Our current effort is primarily focused on insulating films obtained in the initial stage of film growth. Extremely high sheet resistance characterizes these films. Resistance measurements were made possible by preparing

M. M. Rosario; Y. Liu

2000-01-01

194

Electrical transport properties of ultrathin superconducting Pb films

We present electrical transport properties of metallic ultra thin epitaxially grown Pb (111) films on Si (111) substrate. We observed a reduced superconducting transition temperature from bulk Pb using electrical resistivity measurements and deduced the temperature dependence of out-of-plane critical magnetic fields from the sheet resistance R as a function of the applied magnetic field. These results are consistent with

R. P. Panguluri; M. M. Ozer; J. R. Thompson; H. H. Weitering; B. E. Nadgorny

2007-01-01

195

Transport properties of a Bentheim sandstone under deformation

NASA Astrophysics Data System (ADS)

The mechanical and transport properties of a Bentheim sandstone are studied both experimentally and numerically. Three classical classes of loads are applied to a sample whose permeability is measured. The elasticity and the Stokes equations are discretized on unstructured tetrahedral meshes which precisely follow the deformations of the sample. Numerical results are presented, discussed, and compared to the available experimental data.

Jasinski, L.; Sangaré, D.; Adler, P. M.; Mourzenko, V. V.; Thovert, J.-F.; Gland, N.; Békri, S.

2015-01-01

196

Transport properties in semiconducting NbS2 nanoflakes

NASA Astrophysics Data System (ADS)

The electronic transport properties in individual niobium disulphide (NbS2) 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-NbS2 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 NbS2 nanostructure and bulk were discussed.

Huang, Y. H.; Peng, C. C.; Chen, R. S.; Huang, Y. S.; Ho, C. H.

2014-09-01

197

Transport properties of self-consolidating concrete

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.

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

2009-03-15

198

Anisotropic Metamaterial Optical Fibers

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 anisotropic circular waveguides can be uncommon Bessel functions with imaginary orders.

Pratap, Dheeraj; Pollock, Justin G; Iyer, Ashwin K

2014-01-01

199

Models of two level systems for anisotropic glassy materials

NASA Astrophysics Data System (ADS)

We use an extended version of the standard tunneling model to explain the sound absorption in anisotropic glassy materials and heat transport in mesoscopic slabs and bridges. The glassy properties are determined by an ensemble of two level systems (TLS). In our model a TLS is characterized by a 3x3 symmetric tensor, [T], which couples to the strain field, [S], through a 3x3x3x3 tensor of coupling constants, [[R

Anghel, Dragos-Victor; Dumitru, Irina Mihaela; Nemnes, Alexandru George; Churochkin, Dmitrii

2013-03-01

200

Evaluating anisotropic properties in the porcine temporomandibular joint disc using nanoindentation.

The objective of this study was to determine the viscoelastic properties present within the intermediate zone of the porcine temporomandibular joint (TMJ) disc using nanoindentation. A 50-microm conospherical indenter tip using a displacement-controlled ramp function with a 600 nm/s loading and unloading rate, a 3000-nm peak displacement with a holding period of 30 s was used to indent the samples. Experimental load-relaxation tests were performed on the TMJ disc to determine the response in three different directions; the mediolateral, anteroposterior, and articular surface directions. The experimental data were analyzed using a generalized Maxwell model to obtain values for short- and long-time relaxation modulus and of material time constants. The short time relaxation modulus E ( I ) values were 180.92, 64.99, and 487.77 kPa for testing done on the articular surface, mediolateral, and anteroposterior directions, respectively. Corresponding values for the long-time relaxation modulus E (infinity) were 45.9, 14.97, and 133.5 kPa. The method confirmed anisotropy present within the central intermediate zone of the porcine TMJ disc due to the directional orientation of the collagen fibers. PMID:20195763

Yuya, P A; Amborn, E K; Beatty, M W; Turner, J A

2010-07-01

201

Charge carrier transport properties in layer structured hexagonal boron nitride

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.

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

202

Transport properties of single TiO2 nanotubes

NASA Astrophysics Data System (ADS)

We investigated the electric transport properties of single TiO2 nanotubes separated from an anodic titania nanotube array. The temperature dependence of the resistance measured with the conventional four point method of all investigated samples show a Mott variable range hopping behavior. The results obtained with two contacts indicate the existence of a potential barrier between the Cr/Au contacts and samples surfaces, which influence is clearly observable at temperatures <150 K. Impedance spectroscopy in the frequency range of 40 Hz to 1 MHz carried out at room temperature indicates that the electronic transport of these polycrystalline tubes is dominated by the grain cores.

Stiller, Markus; Barzola-Quiquia, José; Lorite, Israel; Esquinazi, Pablo; Kirchgeorg, Robin; Albu, Sergiu P.; Schmuki, Patrik

2013-10-01

203

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.

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

1990-01-01

204

NASA Astrophysics Data System (ADS)

A new method for approximating anisotropic, multi-group scatter cross sections for use in discretized and Monte Carlo multi-group neutron transport is presented. The new method eliminates unphysical artifacts such as negative group scatter cross sections and falsely positive cross sections. Additionally, when combined with the discrete elements angular quadrature method, the new cross sections eliminate the lack of angular support in the discrete ordinates quadrature method. The new method generates piecewise-average group-to-group scatter cross sections. The accuracy and efficiency for calculating the discrete elements cross sections has improved by many orders of magnitude compared to DelGrande and Mathews previous implementation. The new cross sections have extended the discrete elements method to all neutron-producing representations in the Evaluated Nuclear Data Files. The new cross section method has been validated and tested with the cross section generation code, NJOY. Results of transport calculations using discrete elements, discrete ordinates, and Monte Carlo methods for two, one-dimensional slab geometry problems are compared.

Gerts, David Walter

205

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

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...

Thomas, Audrey Elizabeth

2012-06-07

206

Transport properties of two finite armchair graphene nanoribbons

In this work, we present a theoretical study of the transport properties of two finite and parallel armchair graphene nanoribbons connected to two semi-infinite leads of the same material. Using a single ?-band tight binding Hamiltonian and based on Green’s function formalisms within a real space renormalization techniques, we have calculated the density of states and the conductance of these systems considering the effects of the geometric confinement and the presence of a uniform magnetic field applied perpendicularly to the heterostructure. Our results exhibit a resonant tunneling behaviour and periodic modulations of the transport properties as a function of the geometry of the considered conductors and as a function of the magnetic flux that crosses the heterostructure. We have observed Aharonov-Bohm type of interference representing by periodic metal-semiconductor transitions in the DOS and conductance curves of the nanostructures. PMID:23279756

2013-01-01

207

Generalized thermodynamic and transport properties. I. Simple liquids

NASA Astrophysics Data System (ADS)

We propose a method by which the generalized transport properties and coefficients at all wavelengths and frequencies can be obtained by inversion of an exact kinetic equation. The necessary data are the density-density, energy-energy, and density-energy time correlation functions, which can be obtained by molecular-dynamics simulation. In addition, also the coupling between viscous stress tensor and energy flux vector can be obtained without approximation. This allows one to check the validity of the Markov assumption in a straightforward way. As a first test case, the theory is applied to liquid argon in two thermodynamic states. For this system, we calculate and discuss generalized thermodynamic (enthalpy, specific heats, and thermal expansion) and transport properties (longitudinal viscosity, thermal conductivity).

Bertolini, D.; Tani, A.

2011-03-01

208

TOPICAL REVIEW: Nanoscale transport properties at silicon carbide interfaces

NASA Astrophysics Data System (ADS)

Wide bandgap semiconductors promise devices with performances not achievable using silicon technology. Among them, silicon carbide (SiC) is considered the top-notch material for a new generation of power electronic devices, ensuring the improved energy efficiency required in modern society. In spite of the significant progress achieved in the last decade in the material quality, there are still several scientific open issues related to the basic transport properties at SiC interfaces and ion-doped regions that can affect the devices' performances, keeping them still far from their theoretical limits. Hence, significant efforts in fundamental research at the nanoscale have become mandatory to better understand the carrier transport phenomena, both at surfaces and interfaces. In this paper, the most recent experiences on nanoscale transport properties will be addressed, reviewing the relevant key points for the basic devices' building blocks. The selected topics include the major concerns related to the electronic transport at metal/SiC interfaces, to the carrier concentration and mobility in ion-doped regions and to channel mobility in metal/oxide/SiC systems. Some aspects related to interfaces between different SiC polytypes are also presented. All these issues will be discussed considering the current status and the drawbacks of SiC devices.

Roccaforte, F.; Giannazzo, F.; Raineri, V.

2010-06-01

209

Electrical and thermal transport properties of CdO ceramics

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

210

Reply to comment on “liquid metal transport properties”

The method used to determine energy parameters with which to correlate liquid metal transport properties yields relative and not absolute values for these parameters. The choice of a reference substance and its value of E\\/k is arbitrary. Professor Collings' point is well taken that one might as well use an up-to-date value of E\\/k for the energy parameter of the

Alan D. Pasternak

1974-01-01

211

Electrical transport properties of tungsten silicide thin films

The electrical transport properties of cosputtered tungsten silicide films were investigated. The microstructure of the annealed film was determined by x-ray diffraction. Both resistivity and Hall coefficients for the WSi2 films were measured in the temperature range 80–300 K. The current carriers in tungsten disilicide were found to be positive holes. The carrier concentration determined from this experiment is ?1×1022

B. Z. Li; R. G. Aitken

1985-01-01

212

Electrical transport properties of undoped CVD diamond films

Polycrystalline diamond films synthesized by microwave-assisted chemical vapor deposition (MACVD) were examined with transient photoconductivity, and two fundamental electrical transport properties, the carrier mobility and lifetime, were measured. The highest mobility measured is 50 sq cm\\/V per sec at low initial carrier densities (less than 10 exp 15\\/cu cm). Electron-hole scattering causes the carrier mobility to decrease at higher densities.

L. S. Pan; D. R. Kania; S. Han; J. W. Ager III; M. Landstrass; O. L. Landen; P. Pianetta

1992-01-01

213

Electrical Transport Properties of Polydiacetylene Films during Thermochromic Process

Using the top-contact field-effect transistor (FET) model, the electrical transport properties of polymerized 10,12-tricosadiynoic acid (PTDA) films in the blue and red phases were investigated in detail. The current-voltage (I-V) characteristics of the PTDA films during thermochromic transition were examined. The typical FET characteristics were observed for the PTDA films in the blue phase, but not in the red phase.

Gang Zou; Eunju Lim; Norifumi Kajimoto; Hideki Kohn; Yuki Ohshima; Takaaki Manaka; Mitsumasa Iwamoto

2007-01-01

214

Electrical transport properties of crystalline silicon carbide\\/silicon heterojunctions

The electrical transport properties of ?-SiC\\/Si heterojunctions were investigated using current-voltage (I-V) and capacitance-voltage (C-V) characteristics. The heterojunctions were fabricated by growing n-type crystalline ?-SiC films on p-type Si substrates by chemical vapor deposition (CVD). The I-V data measured at various temperatures indicate that at relatively high current, the heterojunction forward current is dominated by thermionic emission of carriers and

Muhammad I. Chaudhry

1991-01-01

215

Properties of an affine transport equation and its generalized holonomy

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.

Justin Vines; David A. Nichols

2014-12-12

216

Semiconducting black phosphorus: synthesis, transport properties and electronic applications.

Phosphorus is one of the most abundant elements preserved in earth, and it comprises a fraction of ?0.1% of the earth crust. In general, phosphorus has several allotropes, and the two most commonly seen allotropes, i.e. white and red phosphorus, are widely used in explosives and safety matches. In addition, black phosphorus, though rarely mentioned, is a layered semiconductor and has great potential in optical and electronic applications. Remarkably, this layered material can be reduced to one single atomic layer in the vertical direction owing to the van der Waals structure, and is known as phosphorene, in which the physical properties can be tremendously different from its bulk counterpart. In this review article, we trace back to the research history on black phosphorus of over 100 years from the synthesis to material properties, and extend the topic from black phosphorus to phosphorene. The physical and transport properties are highlighted for further applications in electronic and optoelectronics devices. PMID:25307017

Liu, Han; Du, Yuchen; Deng, Yexin; Ye, Peide D

2014-10-13

217

Space radiation transport properties of polyethylene-based composites

NASA Technical Reports Server (NTRS)

Composite materials that can serve as both effective shielding materials against cosmic-ray and energetic solar particles in deep space, as well as structural materials for habitat and spacecraft, remain a critical and mission enabling component in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density, coupled with high hydrogen content. Polyethylene-fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at the NASA Marshall Space Flight Center and tested against a 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples.

Kaul, R. K.; Barghouty, A. F.; Dahche, H. M.

2004-01-01

218

NASA Astrophysics Data System (ADS)

An anisotropic tunnel microporous crystal was prepared. Active transportation of anthracene as a guest molecule in the anisotropic tunnels was observed. The direction of anthracene movement implies that the anisotropic tunnel did not work as a flap-check valve. The direction of the movement was consistent with that caused by a Brownian ratchet.An anisotropic tunnel microporous crystal was prepared. Active transportation of anthracene as a guest molecule in the anisotropic tunnels was observed. The direction of anthracene movement implies that the anisotropic tunnel did not work as a flap-check valve. The direction of the movement was consistent with that caused by a Brownian ratchet. Electronic supplementary information (ESI) available. CCDC reference numbers 837539 and 837540. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2nr30880k

Kataoka, Keisuke; Yasumoto, Tetsuaki; Manabe, Yousuke; Sato, Hiroyasu; Yamano, Akihito; Katagiri, Toshimasa

2013-01-01

219

NASA Astrophysics Data System (ADS)

The KTB German Superdeep Well (Germany, Windischeschenbach) has limiting depth of 9101 m. It is one of the world deepest well among the continental boreholes. A study of physical parameters including elastic ones of the massif intersected by the well allowed to represent a real pattern of changing properties and the state of crystalline rocks in upper and middle part of the Earth crust. Such a deep section enables performing analyses of large spectrum of geological and geophysical objects, such as minerals, crystalline rocks, geological strata, formation complexes et al. Recently obtained results permit to get a general idea of elastic-anisotropic properties of crystalline rocks extracted from great depths. A study of properties and state of rocks along the KTB section will make it possible to most precisely determine regular changes of the Earth's rock properties within a large range of depths. Below are the results of investigation of elastic-anisotropic properties for 13 core samples of the KTB rocks in the range of 4.1 to 7.1 km. In this interval the well has penetrated metamorphosed rocks [1]. The measurements have been done by an acoustopolarization method with recent improvements and with devices for determination of sample elastic properties [2 3]. The data obtained are the result of extended study into the KTB rock samples by the method [4]. Study of rock samples from the KTB Superdeep Well in the 4100-7100 m depth range showed that they all are elastic anisotropic and pertain to a orthorhombic symmetry type. Virtually the degree of linear acoustic anisotropic absorption (LAAA) effect has been detected in all samples. Its appearance is likely related to directional orientation of mineral grains as well as to the generation of microcracks during drilling and lithostatic stress release. The several samples showed an angular unconformity between the LAAA orientation and elastic symmetry elements. The shear waves depolarization (DSW) effect was detected in garnet amphibolites samples. There was observed a tendency to persistence in propagation rate of compression and shear wave velocities. The pattern of change in anisotropy factors for compression and shear waves in depth shows itself in a similar way. There is an inverse correlation between density and anisotropy. R E F E R E N C E S 1. Emmermann R., Althaus E., Giese P., Stockhert B.. KTB Hauptbohrung. Results of Geoscientific Investigation in the KTB Field Laboratory. Final Report: 0-9101m. KTB Report 95-2. Hannover. 1995. 2. Gorbatsevich F.F. Acoustopolariscopy of rock forming minerals and crystalline rocks. Apatity, Kola Science Centre RAS, 2002, p. 140. (In Russian) 3. Kovalevskiy M.V. Automated hardware-software complex Acoustpol: Tutorial: Apatity, «K & M» Publ., 2009. 54p. (In Russian). 4. Kovalevsky M.V., Gorbatsevich F.F., Harms U., Dahlheim H.-A. Ultrasonic polarization measurements of elastic-anisotropic properties of metamorphized rocks on the slit of German KTB Superdeep Well // Geophysical magazine.- Geophysics Institute of NAS of Ukraine. -2012.- Issue 34.-#2.-P. 36-48. (In Russian)

Kovalevskiy, Mikhail

2013-04-01

220

Morphologic and transport properties of natural organic floc

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. Copyright 2009 by the American Geophysical Union.

Larsen, L.G.; Harvey, J.W.; Crimaldi, J.P.

2009-01-01

221

Morphologic and transport properties of natural organic floc

NASA Astrophysics Data System (ADS)

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.

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

2009-01-01

222

Electronic correlation and transport properties of nuclear fuel materials

NASA Astrophysics Data System (ADS)

The electronic structures and transport properties of a series of actinide monocarbides, mononitrides, and dioxides are studied systematically using a combination of density-functional theory and dynamical mean-field theory. The studied materials present different electronic correlation strength and degree of localization of 5f electrons, where a metal-insulator boundary naturally lies within. In the spectral function of Mott-insulating uranium oxide, a resonance peak is observed in both theory and experiment and may be understood as a generalized Zhang-Rice state. We also investigate the interplay between electron-electron and electron-phonon interactions, both of which are responsible for the transport in the metallic compounds. Our findings allow us to gain insight in the roles played by different scattering mechanisms, and suggest how to improve their thermal conductivities.

Yin, Quan; Kutepov, Andrey; Haule, Kristjan; Kotliar, Gabriel; Savrasov, Sergey Y.; Pickett, Warren E.

2011-11-01

223

Structure and transport properties of isomer-separated C82

NASA Astrophysics Data System (ADS)

Structure of isomer-separated crystalline C82 has been studied by powder x-ray diffraction with synchrotron radiation. The Rietveld refinement was achieved by assuming a simple cubic lattice (space group Pa3¯). The C2(a) symmetry for the C82 molecule was supported in this analysis. Transport properties of thin film of C82 have been studied by resistivity measurement. The thin film showed a narrow-gap semiconductorlike behavior with gap energy of 0.43 eV. The field effect transistor (FET) of a C82 thin film showed an n-channel normally-on depletion-type behavior, and the mobility was 1.9×10-3 cm2 V-1 s-1 whose value was one of the largest ? among normally-on FETs with fullerenes. A hopping transport was found as channel conduction for the C82 FET above 150 K.

Kubozono, Y.; Rikiishi, Y.; Shibata, K.; Hosokawa, T.; Fujiki, S.; Kitagawa, H.

2004-04-01

224

Transport Properties of operational gas mixtures used at LHC

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.

Yasser Assran; Archana Sharma

2011-10-31

225

Transport properties of ZnFe2O4-? thin films

NASA Astrophysics Data System (ADS)

This study presents an experimental investigation on the transport properties of ZnFe2O4-? (ZFO) thin films to clarify the ambient atmosphere effects on the transport properties by varying the oxygen pressure and the substrate temperature. Previous investigations have demonstrated the significant role of Fe2+ ion concentration due to oxygen vacancies on the transport properties of ZFO. Our systematic investigation suggests that the electrical transport of ZFO thin films is also strongly influenced by structural disorders and vacancies.

Marcu, Aurelian; Yanagida, Takeshi; Nagashima, Kazuki; Tanaka, Hidekazu; Kawai, Tomoji

2007-07-01

226

Coefficients for calculating thermodynamic and transport properties of individual species

NASA Technical Reports Server (NTRS)

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 integration constants for H(sup 0)(T) and S(sup 0)(T). For each species the integration constant for H(sup 0)(T) includes the heat of formation. Transport properties have a different functional form. The temperature range for most of the data is 300 to 5000 K, although some of the newer thermodynamic data have a range of 200 to 6000 K. Because the species are mainly possible products of reaction, the data are useful for chemical equilibrium and kinetics computer codes. Much of the data has been distributed for several years with the NASA Lewis equilibrium program CET89. The thermodynamic properties of the reference elements were updated along with about 175 species that involve the elements carbon, hydrogen, oxygen, and nitrogen. These sets of data will be distributed with the NASA Lewis personal computer program for calculating chemical equilibria, CETPC.

Mcbride, Bonnie J.; Gordon, Sanford; Reno, Martin A.

1993-01-01

227

Coefficients for calculating thermodynamic and transport properties of individual species

NASA Astrophysics Data System (ADS)

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 integration constants for H(sup 0)(T) and S(sup 0)(T). For each species the integration constant for H(sup 0)(T) includes the heat of formation. Transport properties have a different functional form. The temperature range for most of the data is 300 to 5000 K, although some of the newer thermodynamic data have a range of 200 to 6000 K. Because the species are mainly possible products of reaction, the data are useful for chemical equilibrium and kinetics computer codes. Much of the data has been distributed for several years with the NASA Lewis equilibrium program CET89. The thermodynamic properties of the reference elements were updated along with about 175 species that involve the elements carbon, hydrogen, oxygen, and nitrogen. These sets of data will be distributed with the NASA Lewis personal computer program for calculating chemical equilibria, CETPC.

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

1993-10-01

228

Proton transport properties in zwitterion blends with Brønsted acids.

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

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

2010-12-16

229

43Tc99 is spreading mostly laterally through the U.S. Department of Energy Hanford site sediments. At higher tensions in the unsaturated zone, the hydraulic conductivity may be strongly anisotropic as a consequence of finer soils to retain more water than coarser ones, and for these soils to have been deposited primarily in horizontal structures. We have tried to develop a consistent modeling procedure that could predict the behavior of Tc plumes. Our procedure consists of: (1) Adapting existing numerical recipes based on critical path analysis to calculate the hydraulic conductivity, K, as a function of tension, h, (2) Statistically correlating the predicted K at various values of the tension with fine content, (3) Seeking a tension value, for which the anisotropy and the horizontal K values are both sufficiently large to accommodate multi-kilometer spreading, (4) Predicting the distribution of K values for vertical flow as a function of system support volume, (5) Comparing the largest likely K value in the vertical direction with the expected K in the horizontal direction, (6) Finding the length scale at which the two K values are roughly equal, (7) Comparing that length scale with the horizontal spreading of the plume. We find that our predictions of the value of the tension at which the principle spreading is likely occurring compares very well with experiment. However, we seem to underestimate the physical length scale at which the predominantly horizontal spreading begins to take on significant vertical characteristics. Our data and predictions would seem to indicate that this should happen after horizontal transport of somewhat over a km, but the chiefly horizontal transport appears to continue out to scales of 10km or so.

Allen G Hunt

2008-06-09

230

NASA Astrophysics Data System (ADS)

It is demonstrated by numerical simulation that the anisotropic material properties of 6H-SiC can have an important effect on the forward voltage drop of 10 kV 6H-SiC power diodes. A pronounced difference in the carrier distribution was seen for substrates with the surface normal parallel or orthogonal to the c-axis. In fact, it is found that current conduction along the low-mobility c-axis in 6H-SiC (i.e. when the normal to the substrate surface is parallel to the c-axis) can lead to a lower forward voltage drop than if the main current conduction is in the high-mobility direction (orthogonal to the c-axis). Depending on the device geometry the c-axis orientation can be used in the optimization of the forward voltage drop. The effect of anisotropy is expected to be of importance also for on-state losses in other bipolar 6H-SiC devices (e.g. IGBTs). For the design of 4H-SiC bipolar power devices the effect of anisotropic conduction properties is not likely to be critical.

Tornblad, O.; Östling, M.; Lindefelt, U.; Breitholtz, B.

1999-02-01

231

Transport properties of diluted inverted micelles and microemulsions

Experimental results concerning 3 transport properties are discussed: viscosity, mass diffusion, and heat transfer in the ternary system sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/water/CCl4. Thermal conductivity has been investigated by a thermal lens technique using a single laser pulse in the microsecond range. The results are discussed and compared by using a model based upon the kinetic theory of fluids. The study shows how such investigations can lead to an original determination of the intermicellar potential in microemulsions. 99 references.

Lalanne, J.R.; Pouligny, B.; Sein, E.

1983-02-17

232

Effective Potential Energies and Transport Properties for Nitrogen and Oxygen

NASA Technical Reports Server (NTRS)

The results of recent theoretical studies for N--N2, O--O2, N2--N2 interactions are applied to the transport properties of nitrogen and oxygen gases. The theoretical results are used to select suitable oxygen interaction energies from previous work for determining the diffusion and viscosity coefficients at high temperatures. A universal formulation is applied to determine the collision integrals for O2--O2 interactions at high temperatures and to calculate certain ratios for determining higher-order collision integrals.

Stallcop, James R.; Partridge, Harry; Levin, Eugene; Kwak, Dochan (Technical Monitor)

2001-01-01

233

Simplified curve fits for the transport properties of equilibrium air

NASA Technical Reports Server (NTRS)

New, improved curve fits for the transport properties of equilibruim air have been developed. The curve fits are for viscosity and Prandtl number as functions of temperature and density, and viscosity and thermal conductivity as functions of internal energy and density. The curve fits were constructed using grabau-type transition functions to model the tranport properties of Peng and Pindroh. The resulting curve fits are sufficiently accurate and self-contained so that they can be readily incorporated into new or existing computational fluid dynamics codes. The range of validity of the new curve fits are temperatures up to 15,000 K densities from 10 to the -5 to 10 amagats (rho/rho sub o).

Srinivasan, S.; Tannehill, J. C.

1987-01-01

234

The electrical transport properties of high quality Bi-2223 crystal

NASA Astrophysics Data System (ADS)

We have studied electrical transport properties of a high quality Bi2Sr2Ca2Cu3O10 + x crystal below a superconducting critical temperature, Tc. In magnetic fields B parallel to the c axis just above a voltage response onset resistance versus temperature data are well fitted to the vortex-glass model. Obtained from the vortex-glass analysis, a melting transition boundary for Bi-2223 crystal is shifted towards lower temperatures compared to previously reported data for a (Bi, Pb)-2223 single crystal. The critical current density, Jc, of Bi-2223 crystals is close to Jc values presented elsewhere for Bi-2223 tapes, suggesting a principal role of weak intrinsic pinning properties of Bi-2223 as a main limiting factor of Jc of Bi-2223 conductors.

Eltsev, Yuri; Lee, Sergey; Nakao, Koichi; Tajima, Setsuko

2010-05-01

235

Electronic and transport properties of LiCoO2.

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

Andriyevsky, Bohdan; Doll, Klaus; Jacob, Timo

2014-11-14

236

Anisotropic universe with anisotropic sources

NASA Astrophysics Data System (ADS)

We analyze the state space of a Bianchi-I universe with anisotropic sources. Here we consider an extended state space which includes null geodesics in this background. The evolution equations for all the state observables are derived. Dynamical systems approach is used to study the evolution of these equations. The asymptotic stable fixed points for all the evolution equations are found. We also check our analytic results with numerical analysis of these dynamical equations. The evolution of the state observables are studied both in cosmic time and using a dimensionless time variable. Then we repeat the same analysis with a more realistic scenario, adding the isotropic (dust like dark) matter and a cosmological constant (dark energy) to our anisotropic sources, to study their co-evolution. The universe now approaches a de Sitter space asymptotically dominated by the cosmological constant. The cosmic microwave background anisotropy maps due to shear are also generated in this scenario, assuming that the universe contains anisotropic matter along with the usual (dark) matter and vacuum (dark) energy since decoupling. We find that they contribute dominantly to the CMB quadrupole. We also constrain the current level of anisotropy and also search for any cosmic preferred axis present in the data. We use the Union 2 Supernovae data to this extent. An anisotropy axis close to the mirror symmetry axis seen in the cosmic microwave background data from Planck probe is found.

Aluri, Pavan K.; Panda, Sukanta; Sharma, Manabendra; Thakur, Snigdha

2013-12-01

237

ECOLE POLYTECHNIQUE Anisotropic Magnetoresistance

ECOLE POLYTECHNIQUE Anisotropic Magnetoresistance Magnetometer for inertial navigation systems, anisotropic magnetoresistance magnetometer, cross-field error, flipping, magnetometer calibration, indoor Mohamadabadi This work addresses the relevant errors of the anisotropic magnetoresistance sensor for inertial

Paris-Sud XI, UniversitÃ© de

238

Electronic structures and transport properties of silicene on Ag surface

NASA Astrophysics Data System (ADS)

It has been predicted from first-principle that ``silicene'', a two-dimensional buckled honeycomb structure of silicon, is thermally stable and has a graphene-like band structure. In experiments, epitaxial silicene were observed to form at hexagonal Ag(111) and ZrB2(0001) surfaces. However, electronic structure and transport properties related to silicene have not been thoroughly studied. In this work, we have studied band structures of silicene on top of Ag surface using density-functional theory. The effective band structure mapped onto 1x1 unit cell of monolayer silicene on Ag(111) surface could be compared directly with Angle-Resolved Photoemission Spectra (ARPES). We have also studied electronic transport property across monolayer and bilayer silicene sheets using the Non-Equilibrium Green's Function (NEGF) method. The transmission curve shows a maximum at Fermi energy for the monolayer silicene case, but shows a minimum for the bilayer silicene case, which can be explained by their band structures.

Wang, Yun-Peng; Cheng, Hai-Ping

2013-03-01

239

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.

Cuenca, Jacques, E-mail: jcuenca@kth.se; Van der Kelen, Christophe; Göransson, Peter [Marcus Wallenberg Laboratory for Sound and Vibration Research, Royal Institute of Technology (KTH), Teknikringen 8, SE-10044 Stockholm (Sweden)

2014-02-28

240

Quantifying Effective Flow and Transport Properties in Heterogeneous Porous Media

NASA Astrophysics Data System (ADS)

Spatial heterogeneity, the spatial variation in physical and chemical properties, exists at almost all scales and is an intrinsic property of natural porous media. It is important to understand and quantify how small-scale spatial variations determine large-scale "effective" properties in order to predict fluid flow and transport behavior in the natural subsurface. In this work, we aim to systematically understand and quantify the role of the spatial distribution of sand grains of different sizes in determining effective dispersivity and effective permeability using quasi-2D flow-cell experiments and numerical simulations. Two dimensional flow cells (20 cm by 20 cm) were packed with the same total amount of fine and coarse sands however with different spatial patterns. The homogeneous case has the completely mixed fine and coarse sands. The four zone case distributes the fine sand in four identical square zones within the coarse sand matrix. The one square case has all the fine sands in one square block. With the one square case pattern, two more experiments were designed in order to examine the effect of grain size contrast on effective permeability and dispersivity. Effective permeability was calculated based on both experimental and modeling results. Tracer tests were run for all cases. Advection dispersion equations were solved to match breakthrough data and to obtain average dispersivity. We also used Continuous Time Random Walk (CTRW) to quantify the non-Fickian transport behavior for each case. For the three cases with the same grain size contrast, the results show that the effective permeability does not differ significantly. The effective dispersion coefficient is the smallest for the homogeneous case (0.05 cm) and largest for the four zone case (0.27 cm). With the same pattern, the dispersivity value is the largest with the highest size contrast (0.28 cm), which is higher than the one with the lowest case by a factor of 2. The non-Fickian behavior was quantified by the ? value within the CTRW framework. Fickian transport will result in ? values larger than 2 while its deviation from 2 indicates the extent of non-Fickian behavior. Among the three cases with the same grain size contrast, the ? value is closest to 2 in the homogeneous case (1.95), while smallest in the four zone case (1.89). In the one square case, with the highest size contrast, the ? value was 1.57, indicating increasing extent of non-Fickian behavior with higher size contrast. This study is one step toward understanding how small-scale spatial variation in physical properties affect large-scale flow and transport behavior. This step is important in predicting subsurface transport processes that are relevant to earth sciences, environmental engineering, and petroleum engineering.

Heidari, P.; Li, L.

2012-12-01

241

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

( ( Metal Vapors in Gas Tungsten Arcs: Part II. Theoretical Calculations of Transport Properties G. J. DUNN and T. W. EAGAR Theoretical calculations of gas tungsten arc transport properties have, the effects of vapors emitted by the tungsten electrode may have a great effect on arc properties

Eagar, Thomas W.

242

Optical and Transport Properties of Organic Molecules: Methods and Applications

NASA Astrophysics Data System (ADS)

Organic molecules are versatile and tunable building blocks for technology, in nanoscale and bulk devices. In this dissertation, I will consider some important applications for organic molecules involving optical and transport properties, and develop methods and software appropriate for theoretical calculations of these properties. Specifically, we will consider second-harmonic generation, a nonlinear optical process; photoisomerization, in which absorption of light leads to mechanical motion; charge transport in junctions formed of single molecules; and optical excitations in pentacene, an organic semiconductor with applications in photovoltaics, optoelectronics, and flexible electronics. In the Introduction (Chapter 1), I will give an overview of some phenomenology about organic molecules and these application areas, and discuss the basics of the theoretical methodology I will use: density-functional theory (DFT), time-dependent density-functional theory (TDDFT), and many-body perturbation theory based on the GW approximation. In the subsequent chapters, I will further discuss, develop, and apply this methodology. 2. I will give a pedagogical derivation of the methods for calculating response properties in TDDFT, with particular focus on the Sternheimer equation, as will be used in subsequent chapters. I will review the many different response properties that can be calculated (dynamic and static) and the appropriate perturbations used to calculate them. 3. Standard techniques for calculating response use either integer occupations (as appropriate for a system with an energy gap) or fractional occupations due to a smearing function, used to improve convergence for metallic systems. I will present a generalization which can be used to compute response for a system with arbitrary fractional occupations. 4. Chloroform (CHCl3) is a small molecule commonly used as a solvent in measurements of nonlinear optics. I computed its hyperpolarizability for second-harmonic generation with TDDFT with a real-space grid, finding good agreement with calculations using localized bases and with experimental measurements, and that the response is very long-ranged in space. 5. N C 60 is an endohedral fullerene, a sphere of carbon containing a single N atom inside, which is weakly coupled electronically. I show with TDDFT calculations that a laser pulse can excite the vibrational mode of this N atom, transiently turning on and off the system's ability to undergo second-harmonic generation. The calculated susceptibility is as large as some commercially used frequency-doubling materials. 6. A crucial question in understanding experimental measurements of nonlinear optics and their relation to device performance is the effect of the solution environment on the properties of the isolated molecules. I will consider possible explanations for the large enhancement of the hyperpolarizability of chloroform in solution, demonstrate an ab initio method of calculating electrostatic effects with local-field factors, and derive the equations necessary for a full calculation of liquid chloroform. 7. Many-body perturbation theory, in the GW approximation for quasiparticle band-structure and Bethe-Salpeter equation for optical properties, is a powerful method for calculations in solids, nanostructures, and molecules. The BerkeleyGW code is a freely available implementation of this methodology which has been extensively tested and efficiently parallelized for use on large systems. 8. Molecular junctions, in which a single molecule is contacted to two metallic leads, are interesting systems for studying nanoscale transport. I will present a method called DFT+Sigma which approximates many-body perturbation theory to enable accurate and efficient calculations of the conductance of these systems. 9. Azobenzene is a molecule with the unusual property that it can switch reversible between two different geometries, cis and trans, upon absorption of light. I have calculated the structures of these two forms when absorbed on the Au(111) surface, to understand scanning

Strubbe, David Alan

243

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

NASA Astrophysics Data System (ADS)

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.

Gallego, Nidia Constanza

244

Epitaxial growth and electrical transport properties of Cr{sub 2}GeC thin films

Cr{sub 2}GeC thin films were grown by magnetron sputtering from elemental targets. Phase-pure Cr{sub 2}GeC was grown directly onto Al{sub 2}O{sub 3}(0001) at temperatures of 700-800 deg. C. These films have an epitaxial component with the well-known epitaxial relationship Cr{sub 2}GeC(0001)//Al{sub 2}O{sub 3}(0001) and Cr{sub 2}GeC(1120)//Al{sub 2}O{sub 3}(1100) or Cr{sub 2}GeC(1120)//Al{sub 2}O{sub 3}(1210). There is also a large secondary grain population with (1013) orientation. Deposition onto Al{sub 2}O{sub 3}(0001) with a TiN(111) seed layer and onto MgO(111) yielded growth of globally epitaxial Cr{sub 2}GeC(0001) with a virtually negligible (1013) contribution. In contrast to the films deposited at 700-800 deg. C, the ones grown at 500-600 deg. C are polycrystalline Cr{sub 2}GeC with (1010)-dominated orientation; they also exhibit surface segregations of Ge as a consequence of fast Ge diffusion rates along the basal planes. The room-temperature resistivity of our samples is 53-66 {mu}{Omega}cm. Temperature-dependent resistivity measurements from 15-295 K show that electron-phonon coupling is important and likely anisotropic, which emphasizes that the electrical transport properties cannot be understood in terms of ground state electronic structure calculations only.

Eklund, Per [Institut Pprime, UPR 3346, Universite de Poitiers, SP2MI-Boulevard 3, Teleport 2-BP 30179, 86962 Futuroscope Chasseneuil Cedex (France); Thin Film Physics Division, Linkoeping University, IFM, 581 83 Linkoeping (Sweden); Bugnet, Matthieu; Mauchamp, Vincent; Dubois, Sylvain; Tromas, Christophe; Jaouen, Michel; Cabioc'h, Thierry [Institut Pprime, UPR 3346, Universite de Poitiers, SP2MI-Boulevard 3, Teleport 2-BP 30179, 86962 Futuroscope Chasseneuil Cedex (France); Jensen, Jens [Thin Film Physics Division, Linkoeping University, IFM, 581 83 Linkoeping (Sweden); Piraux, Luc; Gence, Loiek [Institute of Condensed Matter and Nanosciences, Universite Catholique de Louvain, B-1348 Louvain la Neuve (Belgium)

2011-08-15

245

Neutrons for fuel cell membranes: Structure, sorption and transport properties

NASA Astrophysics Data System (ADS)

A molecular level understanding of structure and transport properties in fuel cell ionomer membranes is essential for designing new electrolytes with improved performance. Scattering techniques are suited tools for this purpose. In particular, neutron scattering, which has been extensively used in hydrogen-containing systems, is well adapted to investigate water-dependent complex polymeric morphologies. We report Small-Angle Neutron Scattering (SANS) studies on different types of fuel cell polymers: perfluorinated, radiation-grafted and sulfonated polyphosphazene membranes. We show that contrast variation methods can be efficiently employed to provide new insights on membrane microstructure and reveal ionic condensation effects. Neutrons have been used also as non-intrusive diagnosis tool to probe water properties and distribution inside membranes. Recently, in-situ neutronography and SANS experiments on operating fuel cells have been reported. In-plane cartography of water distribution at the surface of bipolar plates and water profiles across membrane thickness have been obtained and studied as a function of operating conditions. The last section of the article is devoted to the use of Quasi-Elastic Neutron Scattering to study water dynamics at molecular scale. We show that analysis with an appropriate sophisticated diffusion model allows to extract diffusion coefficients, characteristic times and length-scales of molecular motions. This quantitative information is fruitfully integrated in multi-scale modelling and usefully compared with numerical simulations. QENS also permits to compare alternative polymers and relate dynamical properties to chemical composition and membrane nanostructure.

Lyonnard, S.; Gebel, G.

2012-11-01

246

Effect of antiphase boundaries on electrical transport properties of Fe3O4 nanostructures

Fe3O4 nanowires have been fabricated based on Fe3O4 thin films grown on alpha-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

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

2005-01-01

247

Dark matter transport properties and rapidly rotating neutron stars

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.

C. J. Horowitz

2012-05-16

248

Vacancy effects on electronic and transport properties of graphene nanoribbons

NASA Astrophysics Data System (ADS)

We analytically study vacancy effects on electronic and transport properties of graphene nanoribbons and nanodots using Green's function approach. For semiconducting systems, the presence of a vacancy induces a zero-energy midgap state. The spatial pattern of the wave functions critically depends on the atomistic edge structures and can be used as an unambiguous probe of the edge structure. For metallic systems, the midgap vacancy state does not exist. In these systems, the vacancy mainly works as a source of electronic scattering and modifies electronic transmission. We derive that the electronic transmission coefficient can be written as T =cos2(? ) , where ? denotes the phase angle of the on-site Green's function at the vacancy site of the ideal systems. At small energies, T exhibits distinctly different functional form depending on edge structures.

Deng, Hai-Yao; Wakabayashi, Katsunori

2015-01-01

249

Electron-neutron scattering and transport properties of neutron stars

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.

Bridget Bertoni; Sanjay Reddy; Ermal Rrapaj

2014-09-27

250

Spin transport properties of triarylamine-based nanowires.

Triarylamine-derivatives can self-assemble upon light irradiation in one-dimensional nanowires with remarkable hole transport properties. We use a combination of density functional theory and Monte Carlo simulations to predict the nanowires spin-diffusion length. The orbital nature of the nanowires valence band, namely a singlet ?-like band localised on N, suggests that hyperfine coupling may be weak and that spin-orbit interaction is the primary source of intrinsic spin relaxation. Thus, we construct a model where the spin-orbit interaction mixes the spins of the valence band with that of three degenerate lower valence bands of sp(2) nature. The model includes also electron-phonon interaction with a single longitudinal mode. We find a room temperature spin-diffusion length of the order of 100 nm, which increases to 300 nm at 200 K. Our results indicate that triarylamine-based nanowires are attractive organic semiconductors for spintronics applications. PMID:24825819

Bhattacharya, Sandip; Akande, Akinlolu; Sanvito, Stefano

2014-06-25

251

The electrical transport properties of liquid Rb using pseudopotential theory

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.

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

252

Electronic and Transport Properties of DNA-based Nanowires

NASA Astrophysics Data System (ADS)

We study theoretically the transport properties through the quasi-one-dimensional (Q1D) one-channel DNA model and two-dimensional (2D) four-channel DNA model. We use a tight-binding (TB) technique to investigate the transmission, current-voltage characteristics, the differential conductance, and localization length as a function of incoming electron energy and magnetic flux. We find that the behavior of the transmission coefficients varies depending on the parameters of the backbone onsite energy, hopping integral from bases to backbone, and hydrogen bonds. Further, the fluctuations in the twisting angle from the temperature effects and the Aharonov-Bohm (AB) magnetic flux effect cause suppression and oscillations in the transmission.

Joe, Yong S.; Lee, Sun H.; Hedin, Eric R.

2011-12-01

253

Transport Properties through Nanomaterials by First-principles Calculations

NASA Astrophysics Data System (ADS)

Nanoscale molecular devices are potential candidates for this next step, and they would make it possible to realize the most advantageous devices. Our group has covered a wide range of nanoscale materials[1] such as self-assembled nanowires on Si(001) [2, 3], quantum length dependence of conductance in oligomers [4] and single-molecule rotation switch [5] and so on. In this presentation, we will present our recent study on the transport properties of these nanoscale materials using the nonequilibrium Green's function formalism for quantum transport and the density functional theory (DFT) of electronic structures using local orbital basis sets. References 1. http://www-lab.imr.edu/˜mizuseki/nanowire.html 2. J.-T. Wang, C. Chen, E. G. Wang, D.-S. Wang, H. Mizuseki, and Y. Kawazoe, Phys. Rev. Lett., 97 (2006) 046103. 3. R. V. Belosludov, A. A. Farajian, H. Mizuseki, K. Miki, and Y. Kawazoe, Phys. Rev. B, 75 (2007) 113411. 4. Y. X. Zhou, F. Jiang, H. Chen, R. Note, H. Mizuseki, and Y. Kawazoe, Phys. Rev. B, 75 (2007) 245407. 5. Y. Y. Liang, F. Jiang, Y. X. Zhou, H. Chen, R. Note, H. Mizuseki, and Y. Kawazoe, J. Chem. Phys. 127 (2007) 084107.

Mizuseki, Hiroshi; Belosludov, Rodion; Uck Lee, Sang; Kawazoe, Yoshiyuki

2008-03-01

254

Electron Transport Materials: Synthesis, Properties and Device Performance

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}).

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

2012-06-01

255

Transport properties of tomato fruit tonoplast membrane vesicles

To study the role of the tonoplast in tomato fruit development, methods were developed to isolate sealed tonoplast membrane vesicles. Low density (approx. 1.23 g/cc) membrane vesicles they found to possess a NO/sub 3//sup -/-sensitive H/sup +/-translocating ATPase. The properties of this H/sup +/-ATPase are similar to those described for other tonoplast H/sup +/-ATPases. ATP-dependent Ca/sup + +/ transport into the vesicles proceeded by two mechanisms, one operative at low Ca/sup + +/ concentrations (1 ..mu..M) and inhibited by vanadate, and the other operative at high Ca/sup + +/ concentrations (10 ..mu..M) and inhibited by NO/sub 3//sup -/. Their present results indicate that the high affinity (vanadate-sensitive) Ca/sup + +/ transporter resides in E.R. membrane that contaminates the tonoplast preparation. Citrate uptake in tonoplast vesicles is stimulated by ATP and inhibited by NO/sub 3//sup -/ suggesting that citrate uptake is driven indirectly by the H/sup +/-ATPase. The substrate for sugar uptake is UDP-glucose resulting in the appearance of sucrose inside the tonoplast vesicle. No evidence for ATP stimulation of glucose, fructose, or sucrose uptake was observed.

Oleski, N.; Joyce, D.; Osteryoung, K.; Bennett, A.B.

1986-04-01

256

Transport properties of graphene devices transferred to STO substrates

NASA Astrophysics Data System (ADS)

The effect of substrate on graphene transport properties can help us understand the scattering mechanisms relevant to its carrier mobility. Single-layer graphene is easily located on the surface of Silicon with 300nm SiO2 using optical microscopy. We have developed a technique for wet-etching the SiO2, peeling the device with metallic leads from the surface, and transferring it to any substrate. This technique eliminates the need to locate the graphene flake on the target substrate for aligning and patterning. A direct comparison can be made between the transport properties of graphene on SiO2 and the target substrate. A device has been transferred to 500um and 200um thick Strontium Titanate (STO) substrates as well as 250nm thick layer of STO that has been grown epitaxially on Nb-doped STO via Pulsed Laser Deposition. The STO layer, with a higher dielectric constant than SiO2, has a higher capacitance and produces a more effective graphene FET. A higher mobility is expected for a device on the surface of a material with a higher dielectric constant if charged impurity scattering is a primary limiting factor. The devices transferred to STO display a gate voltage dependent hysteresis in both the longitudinal and Hall resistances. However, the mobility obtained from these measurements remains the same as that of the device on SiO2. Possible reasons for the absence of the high dielectric substrate effect on graphene carrier mobility and hysteretic behavior will be discussed.

Sachs, Raymond; Odenthal, Patrick; Kawakami, Roland; Shi, Jing

2013-03-01

257

Predicting the transport properties of sedimentary rocks from microstructure

Understanding transport properties of sedimentary rocks, including permeability, relative permeability, and electrical conductivity, is of great importance for petroleum engineering, waste isolation, environmental restoration, and other applications. These transport properties axe controlled to a great extent by the pore structure. How pore geometry, topology, and the physics and chemistry of mineral-fluid and fluid-fluid interactions affect the flow of fluids through consolidated/partially consolidated porous media are investigated analytically and experimentally. Hydraulic and electrical conductivity of sedimentary rocks are predicted from the microscopic geometry of the pore space. Cross-sectional areas and perimeters of individual pores are estimated from two-dimensional scanning electron microscope (SEM) photomicrographs of rock sections. Results, using Berea, Boise, Massilon, and Saint-Gilles sandstones show close agreement between the predicted and measured permeabilities. Good to fair agreement is found in the case of electrical conductivity. In particular, good agreement is found for a poorly cemented rock such as Saint-Gilles sandstone, whereas the agreement is not very good for well-cemented rocks. The possible reasons for this are investigated. The surface conductance contribution of clay minerals to the overall electrical conductivity is assessed. The effect of partial hydrocarbon saturation on overall rock conductivity, and on the Archie saturation exponent, is discussed. The region of validity of the well-known Kozeny-Carman permeability formulae for consolidated porous media and their relationship to the microscopic spatial variations of channel dimensions are established. It is found that the permeabilities predicted by the Kozeny-Carman equations are valid within a factor of three of the observed values methods.

Schlueter, E.M.

1995-01-01

258

NASA Astrophysics Data System (ADS)

Molecular simulations in the isothermal statistical ensembles require that the macroscopic thermal and mechanical equilibriums are respected and that the local values of these properties are constant at every point in the system. The thermal equilibrium in Monte Carlo simulations can be checked through the calculation of the configurational temperature, {k_BT_{conf}={< |nabla _r U({r}^N)|2>}/{< nabla _r{^2} U({r}^N) >}}, where nabla _r is the nabla operator of position vector r. As far as we know, T_{conf} was never calculated with the anisotropic Gay-Berne potential, whereas the calculation of T_{conf} is much more widespread with more common potentials (Lennard Jones, electrostatic, …). We establish here an operational expression of the macroscopic and local configurational temperatures, and we investigate locally the isotropic liquid phase, the liquid / vapor interface, and the isotropic-nematic transition by Monte Carlo simulations.

Ghoufi, Aziz; Morineau, Denis; Lefort, Ronan; Malfreyt, Patrice

2011-01-01

259

41 CFR 302-7.10 - Is property acquired en route eligible for transportation at Government expense?

Code of Federal Regulations, 2011 CFR

...2011-07-01 false Is property acquired en route eligible for transportation at Government... § 302-7.10 Is property acquired en route eligible for transportation at Government expense? No, property acquired en route will not be eligible for...

2011-07-01

260

41 CFR 302-7.10 - Is property acquired en route eligible for transportation at Government expense?

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Is property acquired en route eligible for transportation at Government... § 302-7.10 Is property acquired en route eligible for transportation at Government expense? No, property acquired en route will not be eligible for...

2010-07-01

261

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.

Soh, Wee Tee; Ong, C. K. [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore); Zhong, Xiaoxi, E-mail: xiaoxi.zhong@gmail.com [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore); School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China)

2014-09-15

262

Transport Properties and Diamagnetism of Dirac Electrons in Bismuth

NASA Astrophysics Data System (ADS)

Bismuth crystal is known for its noteworthy properties resulting from particular electronic states, e.g., the Shubnikov–de Haas effect and the de Haas–van Alphen effect. Above all, the large diamagnetism of bismuth had been a long-standing puzzle since soon after the establishment of quantum mechanics, which was resolved eventually in 1970, on the basis of the effective Hamiltonian derived by Wolff, as being due to the interband effects of a magnetic field in the presence of a large spin–orbit interaction. This Hamiltonian is essentially the same as the Dirac Hamiltonian but with spatial anisotropy and an effective velocity much smaller than the light velocity. This paper reviews recent progress in the theoretical understanding of transport and optical properties, such as the weak-field Hall effect together with the spin Hall effect, and the magneto-optic effect, of a system described by the Wolff Hamiltonian and its isotropic version with a special focus on exploring the possible relationship with orbital magnetism. It is shown that there is a fundamental relationship between the spin Hall conductivity and orbital susceptibility in the insulating state, and the possibility of a fully spin-polarized electric current in magneto-optics. Experimental tests of these interesting features have been proposed.

Fuseya, Yuki; Ogata, Masao; Fukuyama, Hidetoshi

2015-01-01

263

NASA Astrophysics Data System (ADS)

Transport property in fault zone will change by shear deformation during and after earthquakes, and the change in transport property may lead to the fault strength transition as well. Previous study by Tanikawa et al. (2012) revealed that, for permeable rocks, shear induced permeability in medium to high slip velocity is mainly controlled by the fluid viscosity that changes due to frictional heating. However, impermeable fault rocks may show different evolution process for the fluid transport property compared to permeable fault rock. In this study, rock-to-rock friction tests was conducted on granite samples to see a shear induced transport property in impermeable fault rocks. We measured flow rate during and after friction test using a rotary shear apparatus. Two 20-mm-long hollow cylindrical specimens (outer and inner diameters of 25 and 9.5 mm, respectively) of low permeable Aji Granite (permeability of 10^-19 m^2) were used in all tests. One cylindrical specimen was fixed and the other rotated under a fixed axial stress of 2 MPa. We applied the total slip displacements of 1.5 and 3 m at various constant slip rates from 0.076 to 150 mm/s. To measure shear-induced fluid transport property, radial flow from the inner wall to the outer wall of the specimen was induced by applying a differential pore pressure between the inner and outer walls. Nitrogen gas was used as a pore fluid. Friction coefficient typically decreased from 0.9 to 0.5 with an increase of slip velocity. At the same slip rate, friction coefficient increased with an increase in apparent permeability of specimen. Apparent permeability during and after friction test were over one order of magnitude larger than that of intact granite. At slower slip rate below 0.01 m/s, permeability decreased soon after sliding ceased, though at high slip rate, permeability increased after sliding. By comparing initial permeability and permeability after 10 minutes of friction tests, results show a reduction in permeability that occurred when initial permeability is high. In contrast, permeability increases with sliding when initial permeability is low. This transition transport property is (intrinsic) transmissivity of ~2*10^-21 m3 that is equivalent to fracture aperture of ~0.3 ?m assuming that threshold aperture is equivalent to hydraulic aperture evaluated by cubic law. We assume that the permeability change during sliding is caused by the production of gouge and smoothing of slip surface that changes aperture size and real contact area of specimens. The change of surface property resulted in change of friction property as well. The reduction of permeability immediately after sliding is probably caused by the thermo-elastic effect on aperture due to frictional heating.

Tanikawa, Wataru; Tadai, Osamu; Mukoyoshi, Hideki; Hirose, Takehiro

2013-04-01

264

Some arguments of Bristow (1960) concerning the effects of cracks on elastic and transport (i.e., electrical or thermal conduction) properties of cold-worked metals are reexamined. The discussion is posed in terms of a modern understanding of bounds and estimates for physical properties of polycrystals--in contrast to Bristow's approach using simple mixture theory. One type of specialized result emphasized here is the cross-property estimates and bounds that can be obtained using the methods presented. Our results ultimately agree with those of Bristow, i.e., confirming that microcracking is not likely to be the main cause of the observed elastic behavior of cold-worked metals. However, it also becomes clear that the mixture theory approach to the analysis is too simple and that crack-crack interactions are necessary for proper quantitative study of Bristow's problem.

Berryman, J.G.

2007-10-02

265

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

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.

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

266

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

Paris-Sud XI, UniversitÃ© de

267

Effect of transport properties of fiber types on steel reinforcement corrosion

This study investigated the transport properties of fiber types in concrete to evaluate their effect on the corrosion of steel reinforcement. The fibers used in this research are polypropylene (PP), polyvinyl alcohol (PVA), and hooked-end steel fiber (Steel). The addition of PVA fibers having relatively good resistance to transport properties indicated the best resistance to the initiation time of corrosion.

B. Kim; A. J. Boyd; J.-Y. Lee

2011-01-01

268

Electric transport properties of epitaxial Fe and Cr films with very low intralayer scattering

The low-temperature transport properties of epitaxial Fe and Cr films grown on MgO(1 0 0) substrates by molecular beam epitaxy are characterised by extremely low intralayer resistivities, indicating a very small concentration of defects. This makes such films particularly suitable for studies of the influence of the interface scattering on the transport properties of Fe\\/Cr superlattices.

R. Schad; P. Beliën; G. Verbanck; C. D. Potter; K. Temst; V. V. Moshchalkov; Y. Bruynseraede

1998-01-01

269

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

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

Gao, Hongjun

270

Interfacial and transport properties of nanoconstrained inorganic and organic materials

NASA Astrophysics Data System (ADS)

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.

Kocherlakota, Lakshmi Suhasini

271

NASA Technical Reports Server (NTRS)

Thermodynamic and transport combustion properties were calculated for a wide range of conditions for the reaction of hydrocarbons with air. Three hydrogen-carbon atom ratios (H/C = 1.7, 2.0, 2.1) were selected to represent the range of aircraft fuels. For each of these H/C ratios, combustion properties were calculated for the following conditions: Equivalence ratio: 0, 0.25, 0.5, 0.75, 1.0, 1.25 Water - dry air mass ratio: 0, 0.03 Pressure, kPa: 1.01325, 10.1325, 101.325, 1013.25, 5066.25 (or in atm: 0.01, 0.1, 1, 10, 50) Temperature, K: every 10 degrees from 200 to 900 K; every 50 degrees from 900 to 3000 K Temperature, R: every 20 degrees from 360 to 1600 R; very 100 degrees from 1600 to 5400 R. The properties presented are composition, density, molecular weight, enthalphy, entropy, specific heat at constant pressure, volume derivatives, isentropic exponent, velocity of sound, viscosity, thermal conductivity, and Prandtl number. Property tables are based on composites that were calculated by assuming both: (1) chemical equilibrium (for both homogeneous and heterogeneous phases) and (2) constant compositions for all temperatures. Properties in SI units are presented in this report for the Kelvin temperature schedules.

Gordon, S.

1982-01-01

272

Transport properties of pure and doped MNiSn (M=Zr, Hf)

We have studied the transport properties in a family of pure and doped intermetallics of the form MNiSi (M=Zr, Hf), the structures known as the half-Heusler alloys. We have shown that the transport is very sensitive to structural arrangements of the constituent atoms, and this can be manipulated by annealing, isostructural alloying, and doping. The unusual transport properties are viewed

C. Uher; J. Yang; S. Hu; D. T. Morelli; G. P. Meisner

1999-01-01

273

Transport properties of multicomponent thermal plasmas: Grad method versus Chapman-Enskog method

Transport properties (thermal conductivity, viscosity, and electrical conductivity) for multicomponent Ar-Fe thermal plasmas at atmospheric pressure have been determined by means of two different methods. The transport coefficients set based on Grad's method is compared with the data obtained when using the Chapman-Enskog's method. Results from both applied methods are in good agreement. It is shown that the Grad method is suitable for the determination of transport properties of the thermal plasmas.

Porytsky, P. [Institute for Nuclear Research, 03680 Kyiv (Ukraine); Krivtsun, I.; Demchenko, V. [Paton Welding Institute, 03680 Kyiv (Ukraine); Reisgen, U.; Mokrov, O.; Zabirov, A. [RWTH Aachen University, ISF-Welding and Joining Institute, 52062 Aachen (Germany); Gorchakov, S.; Timofeev, A.; Uhrlandt, D. [Leibniz Institute for Plasma Science and Technology (INP Greifswald), 17489 Greifswald (Germany)

2013-02-15

274

NASA Astrophysics Data System (ADS)

Increasing energy demands and decreasing natural energy resources have sparked search for alternative clean and renewable energy sources. For instance, currently there is a tremendous interest in thermoelectric and photovoltaic solar energy production technologies. Half-Heusler (HH) alloys are among the most popular material systems presently under widespread investigations for high temperature thermoelectric energy conversion. Approaches to increase the thermoelectric figure of merit (ZT) of HH range from (1) chemical substitution of atoms with different masses within the same atomic position in the crystal structure to optimize carrier concentration and enhance phonon scattering via mass fluctuation and (2) embedding secondary phonon scattering centers in the matrix (nanostructuring) to further reduce thermal conductivity. This work focuses on three material systems. The first part describes the synthesis and properties (thermal conductivity, electrical conductivity, magnetic) of various oxide nanostructures (NiO, Co3O4) which were subsequently used as inclusion phases in a HH matrix to reduce the thermal conductivity. Detailed reviews of the past efforts along with the current effort to optimize synthetic routes are presented. The effects of the synthesis conditions on the thermoelectric properties of compacted pellets of NiO and Co3O4 are also discussed. The second part of the work discusses the development of synthetic strategies for the fabrication of p-type and n-type bulk nanostructured thermoelectric materials made of a half-Heusler matrix based on (Ti,Hf)CoSb, containing nanostructures with full-Heusler (FH) compositions and structures coherently embedded inside the half-Heusler matrix. The role of the nanostructures in the regulation of phonon and charge carrier transports within the half-heusler matrix is extensively discussed by combining transport data and electron microscopy images. It was found that the FH nanoinclusions form staggered heterojunctions with a valence band (VB) offset energy at the HH/FH phase boundaries. The resulting energy barrier discriminates existing holes with respect to their energy by trapping low energy holes, while promoting the transport of high energy holes through the VB of the FH-quantum dots. This "carrier culling" results in surprisingly large increase in the mobility and the effective mass of high energy holes contributing to electronic conduction. The simultaneous reduction in the density and the increase in the effective mass of holes resulted in large enhancements of the thermopower, whereas the increase in the mobility minimizes the drop in the electrical conductivity. In the third part, the application of this concept of nanostructuring on the Copper Selenide material system is described. Various synthetic approaches such as liquid assisted solid-state reaction and mechanical alloying are utilized for the fabrication of copper selenide compositions. We found that the mechanical alloying clearly decreases the thermal conductivity of the composition as well increases the Seebeck due to decrease in carrier concentrations.

Sahoo, Pranati

275

Transport Properties of Nanoscale Materials by First-principles Calculations

NASA Astrophysics Data System (ADS)

Molecular devices are potential candidates for the next step towards nanoelectronic technology. Our group has covered a wide range of nanoscale wires, which have potential application in molecular electronics using first-principles calculations and nonequilibrium Green's function formalism [1]. Our target materials are supramolecular enamel wires (covered wires) [2], connection between organic molecules and metal electrodes, self-assembled nanowires on silicon surface [3], porphyrin [4], phthalocyanine, metallocene [5], fused-ring thiophene molecules, length dependence of conductance in alkanedithiols and so on. Namely, we have investigated a relationship of the energy levels of delocalized frontier orbitals (HOMO and LUMO) and Fermi level of metal electrodes and estimate the electronic transport properties through atomic and molecular wires using Green's function approach. References [1] http://www-lab.imr.edu/˜mizuseki/nanowire.html [2] R. V. Belosludov, A. A. Farajian, H. Baba, H. Mizuseki, and Y. Kawazoe, Jpn. J. Appl. Phys., 44, 2823 (2005). [3] R. V. Belosludov, A. A. Farajian, H. Mizuseki, K. Miki, and Y. Kawazoe, Phys. Rev. B, 75, 113411 (2007). [4] S.-U. Lee, R. V. Belosludov, H. Mizuseki, and Y. Kawazoe, Small 4 (2008) 962. [5] S.-U Lee, R. V. Belosludov, H. Mizuseki, and Y. Kawazoe, J. Phys. Chem. C. 111 (2007) 15397.

Mizuseki, Hiroshi; Belosludov, Rodion V.; Lee, S.-U.; Kawazoe, Yoshiyuki

2009-03-01

276

Prediction of transport properties related to heat transfer

NASA Astrophysics Data System (ADS)

The lecture defines the problems which are encountered in the creation of data banks for use in computer-aided design in modern industry. In addition to the obvious requirements of accuracy, the lecture discusses the problem of internal and external consistency and places great emphasis on the less quantifiable characteristics which good data must possess, notably reliability. The lecture briefly characterizes the degree of accuracy with which it is necessary to know the transport properties of fluids in order to design heat-transfer equipment with success. The second part of the lecture describes the extended law of corresponding states for gases, emphasizing its roots in statistical thermodynamics. Taking low-density noble gases and their mixtures as one extreme, the lecture analyzes the progress that has been made during the last twenty-five years from the point of view of calculation. Extensions of the extended law of corresponding states to higher densities and more complex molecules are mentioned at the end.

Kestin, J.

277

Transport properties of high-quality reduced graphene oxide

NASA Astrophysics Data System (ADS)

Chemical production of graphene, especially reducing graphene oxide has gained a lot of interest in recent years. Yet the transport properties of such materials are usually not compatable to those of graphene. We have found a way to overcome this problem using a modification of the standard Hummer's method. Single flakes of reduced graphene oxide have been investigated. The graphene oxide was deposited onto a SiO2/Si substrate and subsequently reduced using hydrogen iodine. The resulting reduced graphene oxide samples were patterned by electron beam lithography. We have characterized the quality of the samples by combining Raman spectroscopy and Hall mobility measurements in magnetic fields up to 14 T and temperatures down to 0.3 K. High-quality samples had a Raman D/G ratio of better than 1 and showed Hall mobilities exceeding 1000 cm^2/Vs. This is nearly two orders of magnitude higher than what is known for standard reduced graphene oxide. The best samples even show Shubnikov-de Haas oscillations and Hall plateaus. S. Eigler, Christoph Dotzer, Andreas Hirsch, Michael Enzelberger, Paul M"uller, Chem. Mater., 24 1276 (2012)

Enzelberger, M.; Eigler, S.; Hoffmann, P.; Grimm, S.; Hirsch, A.; M&üLler, P.

2013-03-01

278

NASA Technical Reports Server (NTRS)

Accurate numerical prediction of high-temperature, chemically reacting flowfields requires a knowledge of the physical properties and reaction kinetics for the species involved in the reacting gas mixture. Assuming an 11-species air model at temperatures below 30,000 degrees Kelvin, SPECIES (Computer Codes for the Evaluation of Thermodynamic Properties, Transport Properties, and Equilibrium Constants of an 11-Species Air Model) computes values for the species thermodynamic and transport properties, diffusion coefficients and collision cross sections for any combination of the eleven species, and reaction rates for the twenty reactions normally occurring. The species represented in the model are diatomic nitrogen, diatomic oxygen, atomic nitrogen, atomic oxygen, nitric oxide, ionized nitric oxide, the free electron, ionized atomic nitrogen, ionized atomic oxygen, ionized diatomic nitrogen, and ionized diatomic oxygen. Sixteen subroutines compute the following properties for both a single species, interaction pair, or reaction, and an array of all species, pairs, or reactions: species specific heat and static enthalpy, species viscosity, species frozen thermal conductivity, diffusion coefficient, collision cross section (OMEGA 1,1), collision cross section (OMEGA 2,2), collision cross section ratio, and equilibrium constant. The program uses least squares polynomial curve-fits of the most accurate data believed available to provide the requested values more quickly than is possible with table look-up methods. The subroutines for computing transport coefficients and collision cross sections use additional code to correct for any electron pressure when working with ionic species. SPECIES was developed on a SUN 3/280 computer running the SunOS 3.5 operating system. It is written in standard FORTRAN 77 for use on any machine, and requires roughly 92K memory. The standard distribution medium for SPECIES is a 5.25 inch 360K MS-DOS format diskette. The contents of the diskettes are compressed using the PKWARE archiving tools. The utility to unarchive the files, PKUNZIP.EXE, is included. This program was last updated in 1991. SUN and SunOS are registered trademarks of Sun Microsystems, Inc.

Thompson, R. A.

1994-01-01

279

Anisotropic Sobolev Capacity with Fractional Order

In this paper, we introduce the anisotropic Sobolev capacity with fractional order and develop some basic properties for this new object. Applications to the theory of anisotropic fractional Sobolev spaces are provided. In particular, we give geometric characterizations for a nonnegative Radon measure $\\mu$ that naturally induces an embedding of the anisotropic fractional Sobolev class $\\dot{\\Lambda}_{\\alpha,K}^{1,1}$ into the $\\mu$-based-Lebesgue-space $L^{n/\\beta}_\\mu$ with $0<\\beta\\le n$. Also, we investigate the anisotropic fractional $\\alpha$-perimeter. Such a geometric quantity can be used to approximate the anisotropic Sobolev capacity with fractional order. Estimation on the constant in the related Minkowski inequality, which is asymptotically optimal as $\\alpha\\rightarrow 0^+$, will be provided.

Jie Xiao; Deping Ye

2014-10-02

280

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.

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

281

Anisotropic etching of silicon

Anisotropic etching of silicon has become an important technology in silicon semiconductor processing during the past ten years. It will continue to gain stature and acceptance as standard processing technology in the next few years. Anisotropic etching of

K. E. Bean

1978-01-01

282

Transport Properties at Different Scales Using Digital Rocks

NASA Astrophysics Data System (ADS)

In this paper we explore how rock heterogeneity translates into scale-dependent permeability and formation factor, as well as the relation between them. We used a detailed 3-D representation of pore structure of unconsolidated sand obtained from X-ray CT scan. For the samples, loose sand grains were collected from Pomponio Beach and Ano Nuevo costal dune (eolian). These loose sand grains were mixed with epoxy, packed and 3D images were digitized by High-resolution X-ray tomography (CT- scanning). Fluid flow and electrical current were computationally simulated through subsets of the microstructure at different scales. The autocorrelation lengths, a, of the entire sample were calculated in three different directions. The autocorrelation lengths show slight anisotropy in Z-direction in both samples. Since the anisotropy wasn't large so it wasn't considered further in the current analysis. Further, the anisotropy in Z-direction can be attributed to change in the resolution in Z-direction as the artifact of the 3D CT scans. The average autocorrelation, however, was used to calculate the Representative Elementary Volume (REV). Keehm (2003) suggested for single phase fluid flow the REV should be approximately ten times the autocorrelation length, a. Hence for the current analysis a REV of 200 x 200 x 200 pixels for the Pomponio Beach sands (a = 20 pixels) while a REV of 120 x 120 x 120 pixels for Año Nuevo costal dune sands (a = 12 pixels) were considered. The size of the subsets randomly selected from the microstructure varied from 200 x 200 x 200 pixels (= 10a x 10a x 10a) to 25 x 25 x 25 pixels (= 1.25a x 1.25a x 1.25a) for Pomponio Beach sands where as the size of the subsets for Año Nuevo costal dune sands altered from 175 x 175 x 175 pixels (= 14.5a x 14.5a x 14.5a) to 25 x 25 x 25 pixels (= 2.1a x 2.1a x 2.1a). The number of subsets selected for the analysis increased as the size of subset decreased in order to obtain statistically meaningful results. As can be observed the maximum size of subsets chosen was approximately equal to or greater than the REV of the sample. The size of subsets was significantly reduced from the REV sizes in order to study the effect of scales on the transport properties as well as the relationships between these transport properties. Electrical conductivity and single-phase permeability simulations were carried out for the subsets thus obtained. As the size of subsets decreased, the scatter in the computed permeability and resistivity increased although they still followed the expected trends of effective medium relations in each case. Different effective medium relations used to compare with the simulated data in current paper were: (a) For porosity-permeability relation: Kozeny- Carman relation (Carman, 1961), (b) For porosity-formation factor relation: Archie's equation (Archie, 1942) and (c) For permeability-formation factor: Katz and Thompson (Katz and Thompson, 1987). The clouds of the simulated data of different size subsets as well as their corresponding means tended towards a higher value as the size of subsets was decreased though they still fell on the effective medium trend line. However, the computational time required for calculating the bigger subset sizes was far greater than for smaller subset sizes.

Richa, R.; Mukerji, T.; Mavko, G.

2007-12-01

283

Temperature-dependent thermal transport properties of Archean rocks

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

284

EquilTheTA: Thermodynamic and transport properties of complex equilibrium plasmas

NASA Astrophysics Data System (ADS)

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.

Colonna, G.; D'Angola, A.

2012-11-01

285

Decoupling Mechanical and Ion Transport Properties in Polymer Electrolyte Membranes

NASA Astrophysics Data System (ADS)

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.

McIntosh, Lucas D.

286

High field transport properties of a bilayer graphene

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

287

Effect of antiphase boundaries on electrical transport properties of Fe3O4 nanostructures

NASA Astrophysics Data System (ADS)

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.

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

2005-06-01

288

Nature and properties of hexitol transport systems in Escherichia coli.

In Escherichia coli K-12 the naturally occurring hexitols D-mannitol, D-glucitol, and galactitol are taken up and phosphorylated via three distinct transport systems by a mechanism called either group translocation or vectorial phosphorylation. For every system, a membrane-bound enzyme II-complex of the phosphoenolpyruvate-dependent phosphotransferase system has been found, each requiring phosphoenolpyruvate, enzyme I, and HPr or alternatively P-HPr as the phosphate donor. Cells with a constitutive synthesis of all hexitol transport systems but with low P-HPr levels have very low transport and phosphorylating activities in vivo, although 40 to 90% of the enzyme II-complex activities are detected in cell extracts of such mutants. No indications for additional hexitol transport systems, especially for systems able to transport and accumulate free hexitols as in Klebsiella aerogenes, have been found. Substrate Km, and Vmax of the three transport systems for several hexitols and hexitol analogues have been determined by growth rates, transport activities, and in vitro phosphorylating activities. Each system was found to take up several hexitols, but only one hexitol serves as the inducer. This inducer invariably is the substrate with the highest affinity. Since bacterial transport systems, as a general rule, seem to have a relatively broad substrate specificity, in contrast to a more restricted inducer specificity, we propose to name the system inducible by D-mannitol and coded by the gene mtlA the D-mannitol transport system, the system inducible by D-glucitol and coded by gutA the D-glucitol transport system, and the system inducible by galactitol and coded by gatA the galactitol transport system. PMID:1100608

Lengeler, J

1975-10-01

289

Properties of Mutants in Galactose Taxis and Transport

?-Methylgalactoside (mgl) permease mutants of Escherichia coli, which are defective in three genes, mglA, mglB, and mglC, were assayed for galactose taxis and galactose transport. The mglB product is the galactose-binding protein. Previous evidence, supported by our new findings, shows that the galactose-binding protein is the recognition component for galactose taxis as well as for galactose transport. Most mutants defective in mglB showed strong effects on both chemotaxis and transport; however, a couple showed effects chiefly on one process or the other, thus allowing a separation of chemotaxis and transport. The mglA and mglC products have not yet been identified, but they must be components of the galactose transport machinery since mutants defective in mglA or mglC, or both, showed strongly reduced transport. Although some of these mutants showed little chemotaxis, most gave close to wild-type chemotactic responses. Thus, transport is not required for galactose taxis. The bacteria detect changes in the fraction of binding protein associated with galactose, not changes in the rate of transport. PMID:4359648

Ordal, George W.; Adler, Julius

1974-01-01

290

Use of a genetic variant to study the hexose transport properties of human skin fibroblasts.

Human skin fibroblasts from 'normal' subjects were found to possess at least two hexose transport systems. One system was responsible for the uptake of 2-deoxy-D-glucose (dGlc), D-glucose and D-galactose, whereas the other was responsible primarily for the uptake of 3-O-methyl-D-glucose (MeGlc). The transport of dGlc was the rate-limiting step in the uptake process; over 97% of the internalized dGlc was phosphorylated and the specific activity of hexokinase was several times higher than that for dGlc transport. The dGlc transport system was activated by glucose starvation, and was very sensitive to inhibition by cytochalasin B and energy uncouplers. Fibroblasts isolated from a patient with symptoms of hypoglycaemia were found to differ from their normal counterparts in the dGlc transport system. They exhibited a much higher transport affinity for dGlc, D-glucose and D-galactose, with no change in the respective transport capacity. Transport was not the rate-limiting step in dGlc uptake by these cells. Moreover, the patient's dGlc transport system was no longer sensitive to inhibition by cytochalasin B and energy uncouplers. This suggested that the intrinsic properties of the patient's dGlc transport system were altered. It should be noted that the patient's dGlc transport system could still be activated by glucose starvation. Despite the changes in the dGlc transport system, the MeGlc transport system in the patient's fibroblasts remained unaltered. The observed difference in the properties of the two hexose transport systems in the 'normal' and the patient's fibroblasts strongly suggests that the two transport systems may be coded or regulated by different genes. The present finding provides the first genetic evidence from naturally occurring fibroblasts indicating the presence of two different hexose transport systems. PMID:2306216

Mesmer, O T; Gordon, B A; Rupar, C A; Lo, T C

1990-01-01

291

Following the same philosophy of our previous force field for primary amines (J. Phys. Chem. B2011, 115, 14617), we present an extension for secondary and tertiary amines using the anisotropic united atom (AUA4) approach. The force field is developed to predict the phase equilibrium and transport properties of secondary and tertiary amines. The transferability was studied for an important set of molecules including as secondary amines dimethylamine, diethylamine, di-n-propylamine, di-iso-propylamine, and di-iso-butylamine. We have also tested diethylenetriamine, a multifunctional molecule which includes two primary and one secondary amino groups. For tertiary amines, we have included simulations for trimethylamine, triethylamine, tri-n-propylamine, and methyldiethylamine. Monte Carlo simulations in the Gibbs ensemble were carried out to study thermodynamic properties such as equilibrium densities, vaporization enthalpies, and vapor pressures. Critical coordinates (critical density and critical temperature) and normal boiling points were also calculated. The shear viscosity coefficients were studied for dimethyl, diethyl, di-n-propyl, trimethyl, triethyl, and tri-n-propylamine at different temperatures using molecular dynamics in the isothermal isobaric ensemble. Our results show a very good agreement with experimental values for all the studied molecules for both thermodynamic and transport properties, demonstrating the transferability of our force field. PMID:22551443

Orozco, Gustavo A; Nieto-Draghi, Carlos; Mackie, Allan D; Lachet, Véronique

2012-05-31

292

Quantum chaos and electron transport properties in a quantum waveguide

NASA Astrophysics Data System (ADS)

We numerically investigate electron transport properties in an electron waveguide which can be constructed in 2DEG of the heterostructure of GaAs and AlGaAs. We apply R-matrix theory to solve a Schrodinger equation and construct a S-matrix, and we then calculate conductance of an electron waveguide. We study single impurity scattering in a waveguide. A delta-function model as a single impurity is very attractive, but it has been known that delta-function potential does not give a convergent result in two or higher space dimensions. However, we find that it can be used as a single impurity in a waveguide with the truncation of the number of modes. We also compute conductance for a finite size impurity by using R-matrix theory. We propose an appropriate criteria for determining the cut-off mode for a delta-function impurity that reproduces the conductance of a waveguide when a finite impurity presents. We find quantum scattering echoes in a ripple waveguide. A ripple waveguide (or cavity) is widely used for quantum chaos studies because it is easy to control a particle's dynamics. Moreover we can obtain an exact expression of Hamiltonian matrix with for the waveguide using a simple coordinate transformation. Having an exact Hamiltonian matrix reduces computation time significantly. It saves a lot of computational needs. We identify three families of resonance which correspond to three different classical phase space structures. Quasi bound states of one of those resonances reside on a hetero-clinic tangle formed by unstable manifolds and stable manifolds in the phase space of a corresponding classical system. Resonances due to these states appear in the conductance in a nearly periodic manner as a function of energy. Period from energy frequency gives a good agreement with a prediction of the classical theory. We also demonstrate wavepacket dynamics in a ripple waveguide. We find quantum echoes in the transmitted probability of a wavepacket. The period of echoes also agrees with the classical predictions. We also compute the electron transmission probability through a multi-ripple electron waveguide. We find an effect analogous to the Dicke effect in the multi-ripple electron waveguide. We show that one of the S-matrix poles, that of the super-radiant resonance state, withdraws further from the real axis as each ripple is added. The lifetime of the super-radiant state, for N quantum dots, decreases as 1N . This behavior of the lifetime of the super-radiant state is a signature of the Dicke effect.

Lee, Hoshik

293

Oscillatory Behavior in the Transport Properties of Transition Metal Superlattices

NASA Astrophysics Data System (ADS)

Oscillations in the low temperature electrical resistivity, as a function of the individual layer thickness and/or superlattice period, have been recently observed in Co/Ni superlattices. This was believed to be a superlattice effect because the oscillations disappeared with decreasing number of bilayers. In this thesis, systematic studies have been made to understand the origin of this unusual behavior in the electrical transport of Co/Ni superlattices. First, Co/Ni was investigated extensively because Co and Ni have very similar material properties. They are both ferromagnetic, have fcc lattices in thin film form, and have almost identical electronic band structure. Superlattice films were grown by molecular beam epitaxy (MBE) and these structure was characterized by reflection high energy electron diffraction (RHEED), low energy electron diffraction (LEED), Auger electron spectroscopy (AES), and X-ray diffraction (XRD). The measured residual resistivity, usually caused by impurity atoms, lattice defects, interfaces, or grain boundaries, is very small in Co/Ni superlattice films. Due to this small background resistivity, unusual intrinsic resistivity oscillations have been clearly observed in these films. The oscillation amplitude does not change with temperature. However, a small amount of random fluctuation in the superlattice period, artificially introduced during film growth, significantly increases the oscillation amplitude. The resistivity at a minimum rm( rho_{min}) and maximum rm(rho_{max}) of oscillations was also measured as a function of film thickness in order to study the evolution of this effect. rho_{min} increases monotonically with decreasing thickness due to surface scattering, which is well described by the quantum size effect theory. However, rho_{max} becomes nonmonotonic by proper choice of superlattice period, indicating the presence of an additional scattering mechanism associated with the superlattice structure. Similar resistivity oscillations have also been observed in Cu/Ni superlattices, but not in Pd/Ag. The absence of oscillations in Pd/Ag suggests d-electrons may play a key role in this effect. We propose a model based on electron localization. A one-dimensional tight-binding Hamiltonian showed that d -electrons can be localized under slightly broken superlattice symmetry. A resonance scattering between these localized d-electrons and the conduction s-electrons may contribute to the residual resistivity. The scattering cross-section is strongly dependent upon the energy of the electrons involved. Therefore, if such localized states lie at the Fermi level, enhanced resistivity is expected. A model calculation shows that localized states appear close to superlattice periods for which the resistivity exhibits maxima.

Kim, Sihong

294

Transport properties of high-temperature air in a magnetic field

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.

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

295

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

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 ...

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

2014-01-01

296

Electron Irradiation Induced Changes of the Electrical Transport Properties of Graphene

This research investigates the effect of electron irradiation on transport properties in graphene Field Effect Transistor (FET) devices. Upon irradiation, graphene is doped with electrons and adsorbs molecules by transfer of accumulated electrons...

Woo, Sung Oh

2014-08-06

297

Transport properties of antimony nanowires J. Heremans and C. M. Thrush

Transport properties of antimony nanowires J. Heremans and C. M. Thrush Delphi Research Labs of the resistivity and the longitudinal and transverse mag- netoresistance of antimony quantum wires with diameters to nanowire arrays of another group-V semimetal: antimony Sb . As in Bi, electronic transport phenomena in Sb

Cronin, Steve

298

Modulation of Drug Transport Properties by Multicomponent Diffusion in Surfactant Aqueous Solutions

Modulation of Drug Transport Properties by Multicomponent Diffusion in Surfactant Aqueous Solutions to the modulation of diffusion-based drug transport. Introduction Diffusion occurs in a large number of biological concentra- tion-gradients of additives may be used to modulate the rate of drug diffusion. Among all

Annunziata, Onofrio

299

FRONTIERS ARTICLE Fundamentals of energy transport, energy conversion, and thermal properties

FRONTIERS ARTICLE Fundamentals of energy transport, energy conversion, and thermal properties, thermoelectrics, and photovoltaics. However, energy transport and conversion, at the organicÂinorganic interface and as an energy conversion technology. Aviram and Ratner's revolutionary suggestion that molecules could behave

Malen, Jonathan A.

300

Using a Flume to Demonstrate Fluid Properties and Sediment Transport

NSDL National Science Digital Library

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.

Jill Singer

301

Thermodynamic and transport properties of air/water mixtures

NASA Technical Reports Server (NTRS)

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.

Fessler, T. E.

1981-01-01

302

Mechanical and Transport Properties of Nafion: Effects of Temperature and Water Activity

\\u000a Recent studies have shown that water absorption changes the mechanical and transport properties of Nafion by orders of magnitude.\\u000a The unusually large changes in properties are indicative of microstructural changes induced by water absorption. The experimental\\u000a findings of changes in proton conduction, water transport, elastic modulus, and stress relaxation are highlighted and explained\\u000a by microphase segregation of hydrophilic domains resulting

Jay Benziger; Andrew Bocarsly; May Cheah; Paul Majsztrik; Barclay Satterfield; Qiao Zhao

303

Superconducting transport properties of grain boundaries in YBa2Cu3O7 bicrystals

Previous work on the superconducting transport properties of individual grain boundaries in thin-film bicrystals of YBa2Cu3O7 has been extended to provide a more comprehensive picture of their weak-link characteristics. Grain boundaries with three different geometries have been studied; the transport properties of all three types of boundaries are essentially identical, which implies that the poor superconducting coupling between grains is

D. Dimos; P. Chaudhari; J. Mannhart

1990-01-01

304

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

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

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

2008-01-01

305

We have investigated the electrical transport properties of several low-dimensional or small-structured systems, including high-T_{rm c} superconductors, mesoscopic superconductor -normal metal junctions, and nanostructured magnetic granular solids. A number of anomalous transport properties due to the unique dimensionality and structures are systematically studied against structural, temperature, and magnetic field variations. The results are compared with various theoretical models. The normal

Peng Xiong

1994-01-01

306

Magnetic and electrical-transport property variations of epitaxially grown MnAs thin films

We have studied the magnetic and electrical-transport property variations of epitaxial MnAs thin films grown on Si(001) and GaAs(001) substrates by molecular beam epitaxy as a function of the growth temperature and film thickness. All samples show a ferromagnetic behavior with the exception of MnAs?Si(001) deposited at low growth temperatures. Interestingly, the electrical-transport properties change from metallic to semiconducting on

J. H. Song; J. J. Lee; Y. Cui; J. B. Ketterson

2005-01-01

307

Magnetic and electrical-transport property variations of epitaxially grown MnAs thin films

We have studied the magnetic and electrical-transport property variations of epitaxial MnAs thin films grown on Si(001) and GaAs(001) substrates by molecular beam epitaxy as a function of the growth temperature and film thickness. All samples show a ferromagnetic behavior with the exception of MnAs\\/Si(001) deposited at low growth temperatures. Interestingly, the electrical-transport properties change from metallic to semiconducting on

J. H. Song; J. J. Lee; Y. Cui; J. B. Ketterson

2005-01-01

308

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.

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

2006-06-01

309

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

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.

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

310

Anisotropic thermal properties of the polar crystal Cs{sub 2}TeMo{sub 3}O{sub 12}

A Cs{sub 2}TeMo{sub 3}O{sub 12} single crystal with dimensions of 17 mm Multiplication-Sign 17 mm Multiplication-Sign 18 mm was grown using the top-seeded solution growth method. Thermal properties, including thermal expansion, specific heat, thermal diffusivity and thermal conductivity, were investigated as a function of temperature. The average linear thermal expansion coefficients along different crystallographic directions were measured to be {alpha}{sub a}=7.34 Multiplication-Sign 10{sup -6} K{sup -1} and {alpha}{sub c}=32.02 Multiplication-Sign 10{sup -6} K{sup -1} over the temperature range of 30-430 Degree-Sign C. The specific heat was measured to be 0.400-0.506 J g{sup -1} K{sup -1} from 22 Degree-Sign C to 440 Degree-Sign C. The thermal conductivity was calculated to be 1.86 and 0.76 W m{sup -1} K{sup -1} at 22 Degree-Sign C along the a and c axes, respectively. With increasing temperature from 22 to 430 Degree-Sign C, the thermal conductivity decreases by 33.0% along the a axis, while it decreases by 18.5% below 200 Degree-Sign C and then remains unchanged along the c axis. The relationship between structure and the thermal properties is also discussed. - Graphical Abstract: Centimeter-sized crystals of polar Cs{sub 2}TeMo{sub 3}O{sub 12} were grown using the top-seeded solution growth method. The relative large anisotropy in thermal expansion and thermal conductivity of Cs{sub 2}TeMo{sub 3}O{sub 12} is attributable to its layered structure. Highlights: Black-Right-Pointing-Pointer Cs{sub 2}TeMo{sub 3}O{sub 12} single crystals with dimensions of 17 Multiplication-Sign 17 Multiplication-Sign 18 mm{sup 3} were grown. Black-Right-Pointing-Pointer Thermal properties of Cs{sub 2}TeMo{sub 3}O{sub 12} were studied as a function of temperature. Black-Right-Pointing-Pointer The thermal expansion anisotropy of Cs{sub 2}TeMo{sub 3}O{sub 12} is explained using its structure. Black-Right-Pointing-Pointer To protect Cs{sub 2}TeMo{sub 3}O{sub 12} crystal, a small cooling rate should be used during growth. Black-Right-Pointing-Pointer A large temperature gradient should be avoided during processing and application.

Zhang, Junjie; Zhang, Zhonghan; Sun, Youxuan; Zhang, Chengqian [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, Shandong (China)] [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, Shandong (China); Tao, Xutang, E-mail: txt@icm.sdu.edu.cn [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, Shandong (China)] [State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, Shandong (China)

2012-11-15

311

Transport Properties of the Dust Components in Weakly Ionized Plasma

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.

Vaulina, O. S.; Adamovich, X. G.; Petrov, O. F.; Fortov, V. E. [Institute for High Temperatures, RAS, Moscow (Russian Federation)

2008-09-07

312

Hole transporting properties of tris,,8-hydroxyquinoline... aluminum ,,Alq3... H. H. Fonga

Hole transporting properties of tris,,8-hydroxyquinoline... aluminum ,,Alq3... H. H. Fonga and S. K of tris 8-hydroxyquinoline aluminum Alq3 were investigated by time-of-flight TOF technique between 278 be desirable to understand the electrical properties of the slow carriers. Tris 8-hydroxyquinoline aluminum Alq

So, Shu K.

313

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

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

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

1994-01-01

314

Correlation of structural and electrical transport properties in hydrogenated silicon films

In this work we report on the correlation between the structural properties, i.e., crystalline\\/amorphous phase ratio and grain size, and the electrical transport properties of hydrogenated silicon thin films. The samples were deposited by means of pulsed laser ablation of a high purity silicon target in presence of hydrogen gas. Infrared spectroscopy measurements showed a monohydride preferential incorporation at the

F. Barreca; E. Fazio; F. Neri; S. Trusso; C. Vasi

2000-01-01

315

Thermoelectric Transport Properties of Single Bismuth Nanowires S. B. Cronin1

Thermoelectric Transport Properties of Single Bismuth Nanowires S. B. Cronin1 , Y.-M. Lin3 , M be made n and p type, thus eliminating this cancellation. Bismuth, as a one- carrier type material, has is based on the unique properties of bulk bismuth. Bi has the smallest effective mass of all known

Cronin, Steve

316

Transport properties of Ag-Y123 fibers prepared using the polymer-metal precursor technique

NASA Astrophysics Data System (ADS)

We report on the fabrication and superconducting transport properties of superconducting fibers with typical cross-sectional areas of 10 2 to 10 3 ?m 2 made using the polymer-metal precursor (PMC) technique. These samples show superconducting properties similar to good quality bulk polycrystalline pellets, with J c(77K) ~ 10 3A/cm 2 and J c(4K) ~ 10 4A/cm 2. Magnetic field measurements show that the fiber’s superconducting transport properties are dominated by weak links between grains, as in bulk polycrystalline materials.

Tiernan, W. M.; Hallock, R. B.; Chien, James C. W.; Gong, B. M.; Dong, S. H.; Yang, Y. S.

1990-08-01

317

NASA Technical Reports Server (NTRS)

A FORTRAN IV computer program for the calculation of the thermodynamic and transport properties of complex mixtures is described. The program has the capability of performing calculations such as:(1) chemical equilibrium for assigned thermodynamic states, (2) theoretical rocket performance for both equilibrium and frozen compositions during expansion, (3) incident and reflected shock properties, and (4) Chapman-Jouguet detonation properties. Condensed species, as well as gaseous species, are considered in the thermodynamic calculation; but only the gaseous species are considered in the transport calculations.

Svehla, R. A.; Mcbride, B. J.

1973-01-01

318

NASA Astrophysics Data System (ADS)

The effects of the electric and magnetic field variation on multiferroic heterostructure were studied in this work. Thin films of polycrystalline Fe50Pt50 (FePt) were grown by dc-sputtering on top of the commercial slabs of lead magnesium niobate-lead titanate (PMN-PT). The sample was a (011)-cut single crystal and had one side polished. In this condition, the PMN-PT/FePt operates in the L-T (longitudinal magnetized-transverse polarized) mode. A FePt thin film of 20 nm was used in this study to avoid the characteristic broad microwave absorption line associated with these films above thicknesses of 40 nm. For the in-plane easy magnetization axis (01-1), a microwave magnetoelectric (ME) coupling of 28 Oe cm kV -1 was estimated, whereas a value of 42 Oe cm kV -1 was obtained through the hard magnetization axis (100). Insight into the effects of the in-plane strain anisotropy on the ME coupling is obtained from the dc-magnetization loops. It was observed that the trend was opposite along the easy and hard magnetic directions. In particular, along the easy-magnetic axis (01-1), a square and narrow loop with a factor of Mr/MS of 0.96 was measured at 10 kV/cm. Along the hard-magnetic axis, a factor of 0.16 at 10 kV/cm was obtained. Using electric tuning via microwave absorption at X-band (9.78 GHz), we observe completely different trends along the easy and hard magnetic directions; Multiple absorption lines along the latter axis compared to a single and narrower absorption line along the former. In spite of its intrinsic complexity, we propose a model which gives good agreement both for static and microwave properties. These observations are of fundamental interest for future ME microwave components, such as filters, phase-shifters, and resonators.

Vargas, Jose M.; Gómez, Javier

2014-10-01

319

Thermodynamic and transport property modeling in super critical water

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 ...

Kutney, Michael C. (Michael Charles)

2005-01-01

320

Growth, magnetic, and transport properties of magnetic superlattices.

??Three series of epitaxial magnetic superlattices are grown on GaAs substrates: cobalt-gold, cobalt-copper, and cobalt-chromium. The interrelationship between crystal microstructure, magnetic, and magnetotransport properties is… (more)

Vavra, William Paul

1992-01-01

321

Anisotropic nanomaterials: structure, growth, assembly, and functions

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

Sajanlal, Panikkanvalappil R.; Sreeprasad, Theruvakkattil S.; Samal, Akshaya K.; Pradeep, Thalappil

2011-01-01

322

Perovskite solid electrolytes: Structure, transport properties and fuel cell applications

Doped barium cerate perovskites, first investigated by Iwahara and co-workers, have ionic conductivities of the order of 20 mS\\/cm at 800 °C making them attractive as fuel cell electrolytes for this temperature region. They have been used to construct laboratory scale fuel cells, which, in addition to performance data, have provided an unexpected insight into the transport processes operating in

N. Bonanos; K. S. Knight; B. Ellis

1995-01-01

323

Theoretical studies of the transport properties in compound semiconductors

NASA Technical Reports Server (NTRS)

This final report is an overview of the work done on Cooperative Agreement NCC 3-55 with the Solid State Technology Branch of the NASA-Lewis Research Center (LeRC). Over the period of time that the agreement was in effect, the principal investigator and, in the last three years, the co-principal investigator worked on a significant number of projects and interacted with members of the Solid State Technology (SST) branch in a number of different ways. For the purpose of this report, these efforts will be divided into five categories: 1) work directly with experimental electrical transport studies conducted by members of the SST branch; 2) theoretical work on electrical transport in compound semiconductors; 3) electronic structure calculations which are relevant to the electrical transport in polytypes of SiC and SiC-AlN alloys; 4) the electronic structure calculations of polar interfaces; and 5) consultative and supportive activities related to experiments and other studies carried out by SST branch members. Work in these categories is briefly discussed.

Segall, Benjamin

1994-01-01

324

Theoretical studies of the transport properties in compound semiconductors

NASA Astrophysics Data System (ADS)

This final report is an overview of the work done on Cooperative Agreement NCC 3-55 with the Solid State Technology Branch of the NASA-Lewis Research Center (LeRC). Over the period of time that the agreement was in effect, the principal investigator and, in the last three years, the co-principal investigator worked on a significant number of projects and interacted with members of the Solid State Technology (SST) branch in a number of different ways. For the purpose of this report, these efforts will be divided into five categories: 1) work directly with experimental electrical transport studies conducted by members of the SST branch; 2) theoretical work on electrical transport in compound semiconductors; 3) electronic structure calculations which are relevant to the electrical transport in polytypes of SiC and SiC-AlN alloys; 4) the electronic structure calculations of polar interfaces; and 5) consultative and supportive activities related to experiments and other studies carried out by SST branch members. Work in these categories is briefly discussed.

Segall, Benjamin

1994-06-01

325

properties of polycrystalline zeolite LTA films Abraham Greenstein,1 Yeny Hudiono,2 Samuel Graham,1 of phonon scattering mechanisms on the thermal transport properties of zeolite LTA, via experiment measurements and mechanistic understanding of the thermal transport properties of zeolite materials

Nair, Sankar

326

Tuning the electronic transport properties of grapheme through functionalisation with fluorine

We demonstrate the possibility to tune the electronic transport properties of graphene mono-layers and multi-layers by functionalisation with fluorine. For mono-layer samples, with increasing the fluorine content, we observe a transition from electronic transport through Mott variable range hopping (VRH) in two dimensions to Efros-Shklovskii VRH. Multi-layer fluorinated graphene with high concentration of fluorine show two-dimensional Mott VRH transport, whereas CF0.28 multi-layer flakes exhibit thermally activated transport through near neighbour hopping. Our experimental findings demonstrate that the ability to control the degree of functionalisation of graphene is instrumental to engineer different electronic properties in graphene materials. PMID:21910905

2011-01-01

327

Metal nanowires: atomic arrangement and electrical transport properties

NASA Astrophysics Data System (ADS)

We have studied the atomic arrangement and defect formation in metal nanowires (NWs) generated by mechanical elongation using in situ high resolution transmission electron microscopy. It has been observed that the narrowest constriction of gold and platinum NWs is crystalline and defect-free; in particular, gold NWs adopt only three kinds of atomic arrangement. A model correlating these gold structures and the quantum conductance behaviour is proposed, which showed a remarkable agreement with ultrahigh-vacuum mechanically controllable break junction electrical transport measurements.

Rodrigues, Varlei; Ugarte, Daniel

2002-06-01

328

Microscopic calculations of transport properties of neutron matter

We discuss the results of calculations of the shear viscosity and thermal conductivity of pure neutron matter, carried out within the Landau-Abrikosov-Khalatnikov formalism. The probability of neutron-neutron collisions in the nuclear medium has been obtained from a realistic potential, using both the correlated basis function and the G-matrix approach. The results of our work indicate that medium modifications of nucleon-nucleon scattering are large, their inclusion leading to a dramatic enhancement of the transport coefficients. On the other hand, the results obtained from the two theoretical schemes appear to be in fairly good agreement.

Benhar, Omar; Valli, Marco [INFN, Sezione di Roma, I-00185 Roma (Italy); Dipartimento di Fisica, Universita 'La Sapienza', I-00185 Roma (Italy); Polls, Artur [Departament d'Estructura i Constituents de la Materia, E-08028 Barcelona (Spain); Vidana, Isaac [Centro de Fisica Computacional, Department of Physics, University of Coimbra, P-3004-516 Coimbra (Portugal)

2010-02-15

329

Synthesis and electrical transport properties of Gd doped nanocrystalline ceria

NASA Astrophysics Data System (ADS)

In this paper we report synthesis and electrical properties of Ce1-xGdxO2-? (x=0.05-0.2) materials. The materials were prepared using the citrate auto ignition method. The XRD patterns indicate the single phase of the prepared materials. The electrical properties were studied using impedance spectroscopy in a temperature range 250°C to 550°C. It has been observed that the total ionic conductivity increases with the increase in Gd concentration. The electrical data analysis was done using the conductivity formalism.

Anirban, Sk.; Sinha, A.; Dutta, A.

2013-06-01

330

Effect of Temperature on Thermal Transport and Mechanical Properties of Trans-polyisoprene

NASA Astrophysics Data System (ADS)

Thick and thin films of trans-polyisoprene (TPI) have been prepared using solution casting method by dissolving TPI in toluene. Thick films of TPI have been used to determine thermal transport properties at different temperatures through Thermal Constant Analyzer (TCA). The results show that thermal conductivity, thermal diffusivity and volumetric heat capacity increase with respect to temperature. Thin films of TPI on the other hand have been utilized for the measurement of mechanical properties such as Young's modulus, tensile strength and toughness. The effect of temperature on the mechanical properties of thin films of TPI has been investigated using Dynamic Mechanical analyzer (DMA) and it was found that the mechanical properties decrease with increasing temperature. Above said behavior of the thermal transport and mechanical properties as a function of temperatures is attributed to the increase in free volume of molecules in chains with temperature.

Baboo, Mahesh; Dixit, Manasvi; Sharma, Kananbala; Saxena, N. S.

2010-06-01

331

Unusual electronic transport properties in doped TiCoSb Half-Heusler Alloys

The sublattices of semiconducting TiCoSb Half-Heusler alloys are systematically doped and the resulting electrical transport properties are investigated. While all three sites can be doped to result in semimetallic behavior, transport behavior that can be ascribed to the presence of mobility edge and impurity band are observed in the vanadium- and manganese- doped alloys. Resistivity values reaching several W-cm and

Y. Xia; S. Bhattacharya; V. Ponnambalam; S. J. Poon; A. L. Pope; T. M. Tritt

1999-01-01

332

Magnetism and transport properties of melt-spun ribbon Cu 2MnAl Heusler alloy

The magnetism and transport characterizations of the melt-spun ribbon Cu2MnAl alloy are presented. The temperature dependence of magnetization agrees well with the spin-wave theory. A qualitative interpretation has been given for the transport properties and led to information about the microscopic scattering mechanisms involved. A negative GMR for Cu2MnAl ribbons up to 3.5% at high field is reported. The maximal

Ming Zhang; Guodong Liu; Yuting Cui; Haining Hu; Zhuhong Liu; Jinglan Chen; Guangheng Wu; Yu Sui; Zhengnan Qian; Xixiang Zhang

2004-01-01

333

Direct measurements of transport and water properties through the Bering Strait

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

A. T. Roach; K. Aagaard; C. H. Pease; S. A. Salo; T. Weingartner; V. Pavlov; M. Kulakov

1995-01-01

334

Transport properties of double quantum dots with electron-phonon coupling

NASA Astrophysics Data System (ADS)

We study transport through a double quantum dot system in which each quantum dot is coupled to a phonon mode. Such a system can be realized, e.g., using a suspended carbon nanotube. We find that the interplay between strong electron-phonon coupling and interdot tunneling can lead to a negative differential conductance at bias voltages exceeding the phonon frequency. Various transport properties are discussed, and we explain the physics of the occurrence of negative differential conductance in this system.

Walter, Stefan; Trauzettel, Björn; Schmidt, Thomas L.

2013-11-01

335

Transport and magnetic properties of epitaxial and polycrystalline magnetite thin films

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

X. W. Li; A. Gupta; Gang Xiao; G. Q. Gong

1998-01-01

336

Magnetic and electric transport properties in Fe3O4 thin films and nanowires

The transport properties of both epitaxial Fe3O4 thin films and nanowires grown on ?-Al2O3 (0001) substrates using molecular beam epitaxy were investigated. The latter allows one to confine the APBs or tunnel junctions in a one-dimensional nanowire, which reduces substantially the number of boundaries, or junctions. The bias-dependence of conductance and magnetoresistance suggests that the electron transport of Fe3O4 nanowires

Hongliang Li; Yihong Wu; Kie Leong Teo; Zaibing Guo; Shijie Wang; T. Veres

2005-01-01

337

Directional wetting in anisotropic inverse opals.

Porous materials display interesting transport phenomena due to restricted motion of fluids within the nano- to microscale voids. Here, we investigate how liquid wetting in highly ordered inverse opals is affected by anisotropy in pore geometry. We compare samples with different degrees of pore asphericity and find different wetting patterns depending on the pore shape. Highly anisotropic structures are infiltrated more easily than their isotropic counterparts. Further, the wetting of anisotropic inverse opals is directional, with liquids filling from the side more easily. This effect is supported by percolation simulations as well as direct observations of wetting using time-resolved optical microscopy. PMID:24941308

Phillips, Katherine R; Vogel, Nicolas; Burgess, Ian B; Perry, Carole C; Aizenberg, Joanna

2014-07-01

338

Low-field carrier transport properties in biased bilayer graphene

NASA Astrophysics Data System (ADS)

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.

Hu, Bo

2014-07-01

339

Studies of Transport Properties of Fractures: Final Report

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.

Stephen R. Brown

2006-06-30

340

Exact quantum scattering calculations of transport properties for the H2O-H system.

Transport properties for collisions of water with hydrogen atoms are computed by means of exact quantum scattering calculations. For this purpose, a potential energy surface (PES) was computed for the interaction of rigid H2O, frozen at its equilibrium geometry, with a hydrogen atom, using a coupled-cluster method that includes all singles and doubles excitations, as well as perturbative contributions of connected triple excitations. To investigate the importance of the anisotropy of the PES on transport properties, calculations were performed with the full potential and with the spherical average of the PES. We also explored the determination of the spherical average of the PES from radial cuts in six directions parallel and perpendicular to the C2 axis of the molecule. Finally, the computed transport properties were compared with those computed with a Lennard-Jones 12-6 potential. PMID:24320328

Dagdigian, Paul J; Alexander, Millard H

2013-11-21

341

Exact quantum scattering calculations of transport properties for the H2O-H system

NASA Astrophysics Data System (ADS)

Transport properties for collisions of water with hydrogen atoms are computed by means of exact quantum scattering calculations. For this purpose, a potential energy surface (PES) was computed for the interaction of rigid H2O, frozen at its equilibrium geometry, with a hydrogen atom, using a coupled-cluster method that includes all singles and doubles excitations, as well as perturbative contributions of connected triple excitations. To investigate the importance of the anisotropy of the PES on transport properties, calculations were performed with the full potential and with the spherical average of the PES. We also explored the determination of the spherical average of the PES from radial cuts in six directions parallel and perpendicular to the C2 axis of the molecule. Finally, the computed transport properties were compared with those computed with a Lennard-Jones 12-6 potential.

Dagdigian, Paul J.; Alexander, Millard H.

2013-11-01

342

Electronic, magnetic and transport properties of graphene ribbons terminated by nanotubes

NASA Astrophysics Data System (ADS)

We study, by density functional and large-scale tight-binding transport calculations, the electronic structure, magnetism and transport properties of the recently proposed graphene ribbons with edges rolled to form nanotubes. Edges with armchair nanotubes present magnetic moments localized either in the tube or the ribbon and of metallic or half-metallic character, depending on the symmetry of the junction. These properties have potential for spin valve and spin filter devices with advantages over other proposed systems. Edges with zigzag nanotubes are either metallic or semiconducting without affecting the intrinsic mobility of the ribbon. Varying the type and size of the nanotubes and ribbons offers the possibility to tailor the magnetic and transport properties, making these systems very promising for applications.

Akhukov, M. A.; Yuan, Shengjun; Fasolino, A.; Katsnelson, M. I.

2012-12-01

343

Magnetic and transport properties of epitaxial stepped Fe3O4(100) thin films

NASA Astrophysics Data System (ADS)

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.

Wu, Han-Chun; Syrlybekov, Askar; Mauit, Ozhet; Mouti, Anas; Coileáin, Cormac Ó.; Abid, Mourad; Abid, Mohamed; Shvets, Igor V.

2014-09-01

344

Anisotropic pressure and hyperons in neutron stars

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.

A. Sulaksono

2014-12-23

345

Saccharomyces cerevisiae Bpt1p is an ATP-binding cassette (ABC) protein that belongs to the MRP subfamily and is a close homologue of the glutathione conjugate (GS conjugate) transporter Ycf1p. The function of Bpt1p has previously been evaluated only in vitro, by using nonphysiological substrates. In the present study we examined the localization, regulation, and transport properties of Bpt1p in vivo, as well as its capacity to transport a set of prototypical MRP substrates in vitro. Our results show that Bpt1p, like Ycf1p, localizes to the yeast vacuolar membrane, plays a role in cadmium detoxification and ade2 pigmentation in vivo, and can participate in the transport of GS conjugates and glucuronate conjugates, as well as free glutathione, in vitro. However, in all of these cases the contribution of Bpt1p is substantially less than that of Ycf1p. In addition, the expression patterns of YCF1 and BPT1 differ significantly. Whereas YCF1 expression is markedly increased by cadmium, adenine limitation in an ade2 strain, or overexpression of the stress-responsive transcription factor Yap1p, BPT1 expression is only modestly affected under these conditions. Thus, although the functional capabilities of Bpt1p and Ycf1p overlap, their differences in regulation and substrate preference imply that they contribute to cellular detoxification processes in different ways. PMID:12455987

Sharma, Kailash Gulshan; Mason, Deborah L.; Liu, Guosheng; Rea, Philip A.; Bachhawat, Anand K.; Michaelis, Susan

2002-01-01

346

Direct measurements of transport properties are essential for site characterization

Direct measurements of transport parameters on subsurface sediments using, the UFA method provided detailed hydrostratigraphic mapping, and subsurface flux distributions at a mixed-waste disposal site at Hanford. Seven hundred unsaturated conductivity measurements on fifty samples were obtained in only six months total of UFA run time. These data are used to provide realistic information to conceptual models, predictive models and restoration strategies. The UFA instrument consists of an ultracentrifuge with a constant, ultralow flow pump that provides fluid to the sample surface through a rotating seal assembly and microdispersal system. Effluent from the sample is collected in a transparent, volumetrically-calibrated chamber at the bottom of the sample assembly. Using a strobe light, an observer can check the chamber while the sample is being centrifuged. Materials can be run in the UFA as recomposited samples or in situ samples can be subcored directly into the sample UFA chamber.

Wright, J. [Pacific Northwest Lab., Richland, WA (United States); Conca, J.L. [Washington State Univ. Tri-Cities, Richland, WA (United States). Environmental Sciences

1994-08-01

347

Spin-polarized transport properties of GdN nanocontacts

NASA Astrophysics Data System (ADS)

Gadolinium nitride (GdN) nanocontacts were recently experimentally shown to be efficient spin filters. Our study is aimed at identifying and analyzing the physical processes responsible for the high spin polarization of the tunneling current in GdN nanostructures. By the example of planar contacts and atomic chains attached to Cu electrodes we assert, using first principle techniques, that a 100% spin-filtering effect can be indeed achieved in GdN nanocontacts. Our analysis shows that the spin filtering is due to the predominant role of nitrogen majority p states in the electron transport, while minority conductance decays exponentially with contact size due to the presence of a minority band gap at the Fermi level. Additionally, GdN zigzag infinite chains are found to be as efficient spin filters as their planar contact counterparts, also exhibiting a 100% spin-filtering effect, which is robust against chain geometry changes.

Sivkov, Ilia N.; Brovko, Oleg O.; Stepanyuk, Valeri S.

2014-05-01

348

Magneto-transport properties of a random distribution of few-layer graphene patches

NASA Astrophysics Data System (ADS)

In this study, we address the electronic properties of conducting films constituted of an array of randomly distributed few layer graphene patches and investigate on their most salient galvanometric features in the moderate and extreme disordered limit. We demonstrate that, in annealed devices, the ambipolar behaviour and the onset of Landau level quantization in high magnetic field constitute robust hallmarks of few-layer graphene films. In the strong disorder limit, however, the magneto-transport properties are best described by a variable-range hopping behaviour. A large negative magneto-conductance is observed at the charge neutrality point, in consistency with localized transport regime.

Iacovella, Fabrice; Trinsoutrot, Pierre; Mitioglu, Anatolie; Conédéra, Véronique; Pierre, Mathieu; Raquet, Bertrand; Goiran, Michel; Vergnes, Hugues; Caussat, Brigitte; Plochocka, Paulina; Escoffier, Walter

2014-11-01

349

Electrical Transport Properties of Polyaniline Containing HCl, CuCl2 and Multiwall Carbon Nanotube

NASA Astrophysics Data System (ADS)

Electrical transport properties of hydrochloric acid (HCl) doped polyaniline (PANI) and composite of PANI with Copper Chloride (CuCl2) and multiwall Carbon Nanotube (MWNT) was measured within a temperature range 77?T?300 K in presence and in absence of a magnetic field up to 1Tesla. The electrical transport properties can be explained by the variable range hopping (VRH) theory. All the samples have shown negative d.c magnetoconductivity at the room temperature but PANI-HCl sample has shown a transition from positive to negative magnetoconductivity as the temperature is increased.

Meikap, A. K.

2011-07-01

350

Selectively Permeable Polymers and Gas-separation Membranes: Structure and Transport Properties

NASA Astrophysics Data System (ADS)

The relationship between the permeability coefficients and the sorption and diffusion properties of highly elastic and vitreous polymers has been examined. The concept of free volume can be used to interpret the characteristics of transport not only in highly elastic but also in vitreous polymers. The properties are discussed of the basic polymeric materials of gas-separation membranes; heterophase polymeric systems such as block copolymers and polymers with liquid-crystalline additives and additives undergoing specific interaction, and also quasi-liquid membranes with components facilitating the transport of gases. The bibliography contains 84 references.

Durgar'yan, S. G.; Yampol'skii, Yu P.; Plate, Nikolai A.

1988-06-01

351

Transport properties of graphene under periodic and quasiperiodic magnetic superlattices

NASA Astrophysics Data System (ADS)

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.

Lu, Wei-Tao; Wang, Shun-Jin; Wang, Yong-Long; Jiang, Hua; Li, Wen

2013-08-01

352

Magnetic and transport properties of magnetite thin films

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),

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

2005-01-01

353

NASA Astrophysics Data System (ADS)

Micro-characterized variables are proposed to precisely characterize a micro-V-grooved Si surface through the 3D measured topography rather than the designed one. In this study, level and gradient micro-grooved surfaces with depth of 25-80 µm were precisely and smoothly fabricated using a new micro-grinding process rather than laser machining and chemical etching. The objective is to investigate how these accurate micro-characterized variables systematically influence anisotropic wetting and droplet self-movement on such regular micro-structured surfaces without surface chemical modification. First, the anisotropic wetting, droplet sliding, pinning effect and droplet impact were experimentally investigated; then, theoretical anisotropic wetting models were constructed to predict and design the anisotropic wetting. The experiments show that the level micro-V-grooved surface produces the anisotropic wetting and pinning effects. It not only approximates superhydrophobicity but also produces high surface free energy. Moreover, the gradient micro-V-grooved surface with large pitch may lead to much easier droplet sliding than the level one along the micro-groove. The droplet self-movement trend increases with increasing the micro-groove gradient and micro-V-groove ratio. The micro-groove pitch and depth also influence the droplet impact. Theoretical analyses show that the wetting anisotropy and the droplet anisotropy both reach their largest value and disappear for a sharp micro-groove top when the micro-V-groove ratio is equal to 0.70 and 2.58, respectively, which may change the wetting between the composite state and the non-composite state. It is confirmed that the wetting behavior may be designed and predicted by the accurate micro-characterized variables of a regular micro-structured surface.

Li, P.; Xie, J.; Cheng, J.; Wu, K. K.

2014-07-01

354

WETAIR: A computer code for calculating thermodynamic and transport properties of air-water mixtures

NASA Technical Reports Server (NTRS)

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.

Fessler, T. E.

1979-01-01

355

Oligomers Modulate Interfibril Branching and Mass Transport Properties of Collagen Matrices

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

Whittington, Catherine F.; Brandner, Eric; Teo, Ka Yaw; Han, Bumsoo; Nauman, Eric; Voytik-Harbin, Sherry L.

2013-01-01

356

Anisotropic magnetoresistance in an antiferromagnetic semiconductor

NASA Astrophysics Data System (ADS)

Recent studies in devices comprising metal antiferromagnets have demonstrated the feasibility of a novel spintronic concept in which spin-dependent phenomena are governed by an antiferromagnet instead of a ferromagnet. Here we report experimental observation of the anisotropic magnetoresistance in an antiferromagnetic semiconductor Sr2IrO4. Based on ab initio calculations, we associate the origin of the phenomenon with large anisotropies in the relativistic electronic structure. The antiferromagnet film is exchange coupled to a ferromagnet, which allows us to reorient the antiferromagnet spin-axis in applied magnetic fields via the exchange spring effect. We demonstrate that the semiconducting nature of our AFM electrode allows us to perform anisotropic magnetoresistance measurements in the current-perpendicular-to-plane geometry without introducing a tunnel barrier into the stack. Temperature-dependent measurements of the resistance and anisotropic magnetoresistance highlight the large, entangled tunabilities of the ordinary charge and spin-dependent transport in a spintronic device utilizing the antiferromagnet semiconductor.

Fina, I.; Marti, X.; Yi, D.; Liu, J.; Chu, J. H.; Rayan-Serrao, C.; Suresha, S.; Shick, A. B.; Železný, J.; Jungwirth, T.; Fontcuberta, J.; Ramesh, R.

2014-09-01

357

Structure evolution and electrical transport property of Si nanowire

NASA Astrophysics Data System (ADS)

Various optimized Si and its alloy nanowires, from a monoatomic chain to helical and multishell coaxial cylinder, have been obtained. Results reveal that the structure of the Si nanowires transforms as the radii of the carbon nanotubes increase, despite of the chirality of the CNTs. We also calculate the physical properties, such as density of states, transmission functions, current-voltage (I-V) characteristics, and conductance spectra (G-V) of optimized nanowires and alloy nanowires sandwiched between two gold contacts. Interestingly, compared with the pure Si nanowires, the conductance of the alloy nanowires is even lower.

Wang, Y.; Li, Q. Q.; Dong, J. C.; He, Y. Z.; Li, H.

2015-02-01

358

Mechanical and thermal transport properties of graphene with defects

NASA Astrophysics Data System (ADS)

The roles of defects including monatomic vacancies and Stone-Wales dislocations in the mechanical and thermal properties of graphene are investigated here through molecular dynamics (MD) simulations. The results show that Young's modulus of a defected graphene sheet has a gentle dependence with the concentration of defects, while the thermal conductivity is much more sensitive. Analysis based on the effective medium theory (EMT) indicates that this sensitivity originates from the scattering of phonons by defects and delocalized interaction between them, which leads to a transition from propagating to diffusive mode as the concentration increases.

Hao, Feng; Fang, Daining; Xu, Zhiping

2011-07-01

359

Transport properties of stripe-ordered high Tc cuprates

Transport measurements provide important characterizations of the nature of stripe order in the cuprates. Initial studies of systems such as La{sub 1.6?x}Nd{sub 0.4}Sr{sub x}CuO{sub 4} demonstrated the strong anisotropy between in-plane and c-axis resistivities, but also suggested that stripe order results in a tendency towards insulating behavior within the planes at low temperature. More recent work on La{sub 2?x}Ba{sub x}CuO{sub 4} with x = 1/8 has revealed the occurrence of quasi-two-dimensional superconductivity that onsets with spin-stripe order. The suppression of three-dimensional superconductivity indicates a frustration of the interlayer Josephson coupling, motivating a proposal that superconductivity and stripe order are intertwined in a pair-density-wave state. Complementary characterizations of the low-energy states near the Fermi level are provided by measurements of the Hall and Nernst effects, each revealing intriguing signatures of stripe correlations and ordering. We review and discuss this work.

Jie, Q.; Han, S.J.; Dimitrov, I.; Tranquada, J.M.; Li, Q.

2012-01-01

360

Transport properties of overheated electrons trapped on a helium surface

NASA Astrophysics Data System (ADS)

An ultra-strong photovoltaic effect has recently been reported for electrons trapped on a liquid helium surface under a microwave excitation tuned at intersubband resonance [D. Konstantinov, A.D. Chepelianskii, K. Kono, J. Phys. Soc. Jpn 81, 093601 (2012)]. In this article, we analyze theoretically the redistribution of the electron density induced by an overheating of the surface electrons under irradiation, and obtain quantitative predictions for the photocurrent dependence on the effective electron temperature and confinement voltages. We show that the photo-current can change sign as a function of the parameters of the electrostatic confinement potential on the surface, while the photocurrent measurements reported so far have been performed only at a fixed confinement potential. The experimental observation of this sign reversal could provide a reliable estimation of the electron effective temperature in this new out of equilibrium state. Finally, we have also considered the effect of the temperature on the outcome of capacitive transport measurement techniques. These investigations led us to develop, numerical and analytical methods for solving the Poisson-Boltzmann equation in the limit of very low temperatures which could be useful for other systems.

Closa, Fabien; Raphäel, Elie; Chepelianskii, Alexei D.

2014-08-01

361

Transport and Magnetic Properties of MgFeVO4

NASA Astrophysics Data System (ADS)

A new spinel compound, MgFeVO4, was prepared by solid-state reactions. On the basis of the Mössbauer spectrum, it can be deduced that both Fe and V in MgFeVO4 are trivalent. Structure refinements based on X-ray and neutron diffraction data indicated that V3+ ions are likely to occupy the octahedral site, whereas Fe3+ and Mg2+ ions take both octahedral and tetrahedral sites. The formula of the compound can be represented as (Mg1-xFex)[MgxFe1-xV]O4 (x=0.638). The transport measurements indicate that MgFeVO4 is an n-type semiconductor with the hopping mechanism below 170 K and thermally activated mechanism at high temperatures. The DC and AC magnetic data show the antiferromagnetic interactions and spin glass behavior in MgFeVO4. The time-dependent magnetic relaxation and the exchange bias effect related to the spin glass phase are also analyzed. The curve fittings give long flipping times and large n values, indicating that strongly interacting clusters rather than individual spins are the predominant spin glass features.

Zhang, Xue; Kuang, Xiao-Jun; Wang, Yong-Gang; Wang, Xiao-Ming; Wang, Chun-Hai; Zhang, Yan; Chen, Chinping; Jing, Xi-Ping

2013-02-01

362

Transport Properties of ZnSe- ITO Hetero Junction

NASA Astrophysics Data System (ADS)

In this report, ITO(Indium Tin Oxide) was used on the glass substrates as the transparent electrode, and ZnSe layer was prepared by the vacuum deposition on this ITO. Then, the electrical characteristics of this sample were investigated by mans of the electric current transport analysis. The sample that ZnSe was prepared as 3.4 ?m in case of ITO-ZnSe sample, has high density level at the junction surface. The ITO-ZnSe junction has two type of diffusion current. However, the ITO-ZnSe sample that ZnSe layer was prepared as 0.1 ?m can be assumed as the ohmic contact, and ITO-ZnSe(0.1?m) -CdTe sample shows the avalanche breakdown, and it is considered that the avalanche breakdown occurs in CdTe layer. It is difficult to occur the avalanche breakdown, if ZnSe-CdTe junction has high-density level and CdTe layer has high-density defect. Hence, the ZnSe-CdTe sample that CdTe layer was prepared on ITO-ZnSe(0.1?m) substrate has not high-density level at the junction surface, and the CdTe layer with little lattice imperfection can be prepared. It found that ITO-ZnSe(0.1?m) substrate is available for the II-VI compounds semiconductor device through above analysis result.

Ichibakase, Tsuyoshi

363

Role of Local and Global Transport Properties in Ignition Regimes

NASA Astrophysics Data System (ADS)

Recent experiments by the FTU machine with high poloidal fields and peaked density profiles have produced advanced regimes such as Alcator A and C. Extrapolation of the Alcator C results for nearly equal plasma densities and magnetic fields, leads to relatively long confinement times ?E in Ignitor(B. Coppi, A. Airoldi, F. Bombarda, et al., MIT RLE Report) PTP 99/06 (1999)., based on a diffusion coefficient involving the profile consistency constraint and on the fact that the loop voltage of ohmic heated plasmas is in a narrow range (~= 1.5V). Simulations by different transport codes indicate that the optimal ignition conditions in Ignitor correspond to a minimum central pressure p_0~= 3.3 MPa, with peak ion temperatures T_0~= 10.5 keV, when the total ?_E~= 0.6 sec. The ?-particle power is ~= 19 MW. The igniting pressure profile does not change appreciably when the values of the peak temperature, and to a lesser extent that of the density, are increased for ?E < 0.6 sec. A peaked density profile may be crucial to achieving ignition, if the confinement is degraded significantly. Supported in part by ENEA and the US DoE.

Cenacchi, G.; Coppi, B.; Airoldi, A.; Bombarda, F.; Detragiache, P.; Sugiyama, L. E.

2000-10-01

364

Transport and Thermoelectric Properties of Semi-Heusler Alloys based on (Zr,Hf)NiSn

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

V. Ponnambalam; Y. Xia; S. Bhattacharya; A. L. Pope; T. M. Tritt; S. J. Poon

1999-01-01

365

Comparison of the Water Transporting Properties of MIP and AQP1

. In this paper we compare the water-transport properties of Aquaporin (AQP1), a known water channel, and those of the 28 kD\\u000a Major Intrinsic Protein of Lens (MIP), a protein with an undefined physiological role. To make the comparison as direct as\\u000a possible we measured functional properties in Xenopus laevis oocytes injected with cRNAs coding for the appropriate protein. We

G. Chandy; G. A. Zampighi; M. Kreman; J. E. Hall

1997-01-01

366

A study of transport properties in Cu and P doped ZnSb

NASA Astrophysics Data System (ADS)

ZnSb samples have been doped with copper and phosphorus and sintered at 798 K. Electronic transport properties are interpreted as being influenced by an impurity band close to the valence band. At low Cu dopant concentrations, this impurity band degrades the thermoelectric properties as the Seebeck coefficient and effective mass are reduced. At carrier concentrations above 1 × 1019 cm-3, the Seebeck coefficient in Cu doped samples can be described by a single parabolic band.

Valset, K.; Song, X.; Finstad, T. G.

2015-01-01

367

The structural and electrical properties of undoped microcrystalline silicon-carbon films deposited by plasma-enhanced chemical vapour deposition are analysed. Raman spectroscopy and high-resolution transmission electron micro-scopy suggest that the films are constituted of silicon microcrystals, surrounded by a grain-boundary region, or interconnected or separated by a hydrogenated amorph-ous silicon carbide channel. The dependences of the electrical transport properties upon the structure

F. Demtchelis; C. F. Pirri; E. Tresso

1993-01-01

368

Electrical transport properties of Ti-doped Fe2O3(0001) epitaxial films

The electrical transport properties for compositionally and structurally well-defined epitaxial -(TiFe{sub 1-x})O(0001) films have been investigated for x {<=} 0.09. All films were grown by oxygen plasma-assisted molecular beam epitaxy using two different growth rates: 0.05-0.06 \\/s and 0.22-0.24 \\/s. Despite no detectable difference in cation valence and structural properties, films grown at the lower rate were highly resistive whereas

Bo Zhao; Tiffany C. Kaspar; Timothy Droubay; John S. McCloy; Mark E. Bowden; V. Shutthanandan; Steve M. Heald; Scott A. Chambers

2011-01-01

369

Monte Carlo Calculations of Single-Phase Effective Permeability in 2-D Anisotropic Porous Media

NASA Astrophysics Data System (ADS)

Effective parameters determine the upscaled flow and transport properties in heterogeneous porous media under ergodic conditions. Explicit expressions have been proposed for the single phase effective fluid permeability of media with short-range correlations, based on a first-order perturbation expansion of the disorder and the Landau-Lifshitz conjecture (L. W. Gelhar and C. L. Axness, Water Resour. Res., 19(1), 161 (1983).). These estimates have been recently verified to higher orders in the isotropic case by means of a one-loop renormalization calculation (D. T. Hristopulos and G. Christakos, Stoch. Envir. Res. & Risk Asses., 13, 131 (1999).). However, most natural porous media are anisotropic. We investigate flow in 2-D anisotropic media using Monte Carlo simulations. We find that the effective permeability for strong heterogeneity deviates considerably from the perturbation-based conjecture. We discuss these results in connection with second order perturbation calculations.

Hristopulos, Dionissios; Christakos, George

1999-11-01

370

The theory of bio-energy transport in the protein molecules and its properties

NASA Astrophysics Data System (ADS)

The bio-energy transport is a basic problem in life science and related to many biological processes. Therefore to establish the mechanism of bio-energy transport and its theory have an important significance. Based on different properties of structure of ?-helical protein molecules some theories of bio-energy transport along the molecular chains have been proposed and established, where the energy is released by hydrolysis of adenosine triphosphate (ATP). A brief survey of past researches on different models and theories of bio-energy, including Davydov's, Takeno's, Yomosa's, Brown et al.'s, Schweitzer's, Cruzeiro-Hansson's, Forner's and Pang's models were first stated in this paper. Subsequently we studied and reviewed mainly and systematically the properties, thermal stability and lifetimes of the carriers (solitons) transporting the bio-energy at physiological temperature 300 K in Pang's and Davydov's theories. From these investigations we know that the carrier (soliton) of bio-energy transport in the ?-helical protein molecules in Pang's model has a higher binding energy, higher thermal stability and larger lifetime at 300 K relative to those of Davydov's model, in which the lifetime of the new soliton at 300 K is enough large and belongs to the order of 10 -10 s or ?/??700. Thus we can conclude that the soliton in Pang's model is exactly the carrier of the bio-energy transport, Pang's theory is appropriate to ?-helical protein molecules.

Pang, Xiao-feng

2011-10-01

371

Growth, magnetic, and transport properties of magnetic superlattices

Three series of epitaxial magnetic superlattices are grown on GaAs substrates: cobalt-gold, cobalt-copper, and cobalt-chromium. The interrelationship between crystal microstructure, magnetic, and magnetotransport properties is explored with reflection high-energy electron diffraction (RHEED), magnetometry, Hall effect, and magnetoresistance. Perpendicular anisotropy is observed in the cobalt-gold and cobalt-copper superlattices with cobalt thickness less than 18[angstrom] and 9[angstrom], respectively. This anisotropy is found to significantly enhance magnetoresistance at cryogenic temperatures. A calculation of the magnetoelastic anisotropy due to epitaxial strain is presented, and when added to the magnetocrystalline and shape anisotropies, quantitatively accounts for the experimental data. In the cobalt-chromium superlattices a structural transition in the chromium layers from close-packed to body centered cubic in the Kurdjumov-Sachs and Nishiyama-Wasserman orientations is observed in real-time with a charge coupled device RHEED detection system.

Vavra, W.P.

1992-01-01

372

NASA Technical Reports Server (NTRS)

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.

Thompson, Richard A.; Lee, Kam-Pui; Gupta, Roop N.

1990-01-01

373

NASA Astrophysics Data System (ADS)

The charge injection and transport properties of six organic light-emitting molecules with push-pull structures were studied by theoretical calculations. The ground-state geometries for the neutral, cationic and anionic states were optimized using density functional theory. Subsequently, the ionization potentials and electron affinities were calculated. We computed the reorganization energies and the transfer integrals based on the Marcus electron transfer theory. It was found that in addition to being emitters the six compounds are multifunctional materials being capable of transport for both holes and electrons. Moreover, the double-branched compound DCDPC2 was found to have higher charge injection ability and better balanced charge transport properties than single-branched compounds.

Lin, Tao; Liu, Xiaojun; Lou, Zhidong; Hou, Yanbing; Teng, Feng

2014-08-01

374

Transport and infrared photoresponse properties of InN nanorods/Si heterojunction

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

2011-01-01

375

The use of Impedance Spectroscopy (IS) as a tool to evaluate the electrical and transport properties of cement-based materials was critically evaluated. Emphasis was placed on determining the efficacy of IS by applying it as a tool to investigate several families of cement-based materials. Also, the functional aspects of electroding and null corrections were also addressed. The technique was found

John David Shane

2000-01-01

376

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

Edward J. Hyer; Dale J. Allen; Eric S. Kasischke

2007-01-01

377

Magnetic And Transport Properties Of Fe2VB Heusler Alloy: A New Report

The transport and magnetic properties of the Fe2VB Heusler alloy have been studied for the first time. The temperature dependence of electrical resistivity (upto 100 K) follows conventional ferromagnetic metallic nature. The M-H curves at 5 and 300 K exhibit ferromagnetism. However, the curie-temperature is not yet known.

M. Vasundhara; V. Srinivas; V. V. Rao; T. V. Chandrashekhar Rao

2008-01-01

378

Electronic, magnetic and transport properties of (Fe1-xVx)3Al alloys

We report electronic, magnetic and transport properties of (Fe1-x Vx )3 Al alloys with x = 0 - 0.38 and analyse the results on the basis of the measured electronic specific-heat coefficient, the Debye temperature and the magnetic stiffness constant. As the V composition increases, the electrical resistivity increases rapidly at low temperatures and the magnetization decreases significantly in parallel

M. Kato; Y. Nishino; U. Mizutani; S. Asano

2000-01-01

379

Transport properties of yttrium-doped zirconia-Influence of kinetic demixing

Transmission electron microscopy, XPS analysis, electrical conductivity and diffusion measurements were used to characterize the transport properties and grain boundary segregation phenomena in 9 mol% yttria-stabilized zirconia (YSZ). The highest grain boundary electrical conductivity (?gb) and oxygen diffusion coefficient (DO) values are shown by samples with a cleaner microstructure, sintered at 1600 °C and rapidly cooled at the end of sintering. XPS

A. Rizea; G. Petot-Ervas; C. Petot; M. Abrudeanu; M. J. Graham; G. I. Sproule

2007-01-01

380

Microstructure and transport properties of ZnO:Mn diluted magnetic semiconductor thin films

Microstructure and transport properties of ZnO:Mn diluted magnetic semiconductor thin films Z. Yang Microstructural studies using transmission electron microscopy were performed on a ZnO:Mn diluted magnetic.1063/1.3087473 I. INTRODUCTION In recent years, ZnO-based diluted magnetic semicon- ductor DMS materials have been

Yang, Zheng

381

Transport Properties of the Quark-Gluon Plasma -- A Lattice QCD Perspective

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.

Harvey B. Meyer

2011-06-09

382

Frequency distribution of water and solute transport properties derived from pan sampler data

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

Walter, M.Todd

383

Influence of Interface Barrier on Lateral Transport Properties for Metal\\/Semiconductor Systems

This work reports on an investigation of the transport properties of metal semiconductor systems in the direction parallel to the interface. Anomalies caused by the shunting effect for resistivity and Hall coefficient measurement on metal semiconductor systems were analyzed in detail. It is found that the above-mentioned anomalies are closely related with the Schottky barrier height as well as the

Sekika Yamamoto; Tyuzi Ohyama; Eizo Otsuka; Syouichi Yamauchi; Motohiro Iwami

1994-01-01

384

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

Keyes, Joseph T.; Lockwood, Danielle R.; Simon, Bruce R.; Vande Geest, Jonathan P.

2013-01-01

385

Nonasymptotic properties of transport and mixing G. Boffetta and A. Celani

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

Cencini, Massimo

386

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

is applied to describe some of the properties of plasma-turbulence-induced transport. This model combines of numerical results from three- dimensional plasma turbulence models also show the existence of a nondiffusive mostly inward and creating a wake of low-level stationary fluctuations. These low-level fluctuations

MartÃn-SolÃs, JosÃ© RamÃ³n

387

26 CFR 49.4271-1 - Tax on transportation of property by air.

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Tax on transportation of property...CONTINUED) MISCELLANEOUS EXCISE TAXES FACILITIES AND SERVICES EXCISE...making the payment subject to tax. Such person shall retain...district in which is located the principal place of business...

2011-04-01

388

Bismuth thin films were prepared on glass substrates with RF magnetron sputtering and the effects of deposition temperature on surface morphology and their electrical transport properties were investigated. Grain growth of bismuth and the coalescence of grains were observed above 393K with field emission secondary electron microscopy. Continuous thin films could not be obtained above 448K because of the segregation

Dong-Ho Kim; Sung-Hun Lee; Jong-Kuk Kim; Gun-Hwan Lee

2006-01-01

389

Electrical transport properties of semiconducting rhenium silicide thin films on silicon(111)

Electrical transport properties of semiconducting rhenium silicide thin films are investigated. This silicide, which shows a commensurable fit with the (111) surface of silicon, has been epitaxially grown on such substrates by reactive deposition at 650 °C. A first kind of sample has been annealed at 750 °C under ultra-high vacuum. A second kind of sample has been annealed at

I. Ali; P. Muret; A. Haydar

2001-01-01

390

Carbon nanotubes have been synthesised with high density on a large area of platinum pre patterned layer of silicon nitride solid substrate by means of chemical vapour deposition of acetylene at 500 °C in ammonia ambient. The effect of the microwave induced thermal annealing, in atmospheric air, on the morphology and electrical transport properties of nanotubes films has been evaluated.

F. Bussolotti; V. Grossi; S. Santucci; L. Lozzi; M. Passacantando

2008-01-01

391

Low temperature electrical transport properties of B-doped ZnO films

Low temperature electrical transport properties of boron-doped zinc oxide thin films prepared by metal-organic chemical vapor deposition technique were investigated. The temperature coefficient of resistivities is negative at low temperatures and becomes positive at relatively high temperatures. The magnetic field dependence of resistivity was measured at different temperatures from 2 to 30 K. The samples exhibit negative magnetoresistivity at all

X. D. Liu; E. Y. Jiang; Z. Q. Li

2007-01-01

392

Study of electrical transport properties in polycrystalline CdTe thin films

Polycrystalline CdTe thin films deposited by the Close Space Sublimation method (CSS) were characterized through measurements of thermoelectric power (?) and resistivity (?) in order to determine the scattering mechanism which mainly affect their electrical transport properties. The results were interpreted with the help of theoretical calculations of ? vs. T, carried out using a theoretical model developed specially for

C. E. Jácome; J. M. Flórez; G. Gordillo

2001-01-01

393

On the transport properties of a dense fully-ionized hydrogen plasma. II. Quantum analysis

1161 On the transport properties of a dense fully-ionized hydrogen plasma. II. Quantum analysis B of a fully ionized hydrogen plasma within the context of the classical kinetic theory. Quantum effects were plasma from a quantum kinetic equation [4-6]. However, the quantum correlations of the electron subsystem

Paris-Sud XI, UniversitÃ© de

394

NIST Standard Reference Database 23 NIST Reference Fluid Thermodynamic and Transport Properties--

#12;NIST Standard Reference Database 23 NIST Reference Fluid Thermodynamic and Transport Properties (NIST) uses its best efforts to deliver a high quality copy of the Database and to verify that the data or omissions in the Database. Â©2007 copyright by the U.S. Secretary of Commerce on behalf of the United States

Magee, Joseph W.

395

. Positioning gra- phene in proximity to hexagonal boron nitride (h-BN), which has a lattice constant similarElectronic structure and quantum transport properties of trilayers formed from graphene and boron nitride Xiaoliang Zhong,a Rodrigo G. Amorim,a Ralph H. Scheicher,b Ravindra Pandey*a and Shashi P. Karnac

Pandey, Ravi

396

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.

Kim, Gil-Ho; Ritchie, D. A.; Liang, C.-T.; Lian, G. D.; Yuan, J.; Pepper, M.; Brown, L. M.

2001-06-11

397

Clay and pillard clay membranes: Synthesis, characterization and transport properties

NASA Astrophysics Data System (ADS)

In this work, the preparation and characterization of ceramic multilayer membranes with an Alsb2Osb3-pillared montmorillonite (Al-PILC) and a Laponite separating layer have been studied. Al-PILC is a pillared clay prepared by intercalation of polyoxo cations of aluminium between the montmorillonite clay sheets, followed by a thermal treatment (400sp°C) to obtain rigid oxide pillars. The free spacing between the clay plates is about 0.8 nm. Laponite is a synthetic clay with a pore structure formed by the stacking of very small clay plates. To deposit an Al-PILC top layer on a macro- or mesoporous aluminiumoxide support membrane, two preparation routes were considered. According to the standard preparation route of a pillared clay, the easiest way is to use a suspension of clay mixed with the pillaring solution in which the support membrane is dipped. However, it is not possible to deposit uniform and crack-free top layers in this way because of the formation of unstable suspensions. A second preparation route is based on an indirect pillaring procedure. By dipping a support membrane in a stable clay suspension, a thin clay film is deposited in a first step. Pillaring is achieved via immersion of the supported clay film in the pillaring solution in a second step. After a washing procedure, the membrane is dried and calcined at 400sp°C. Laponite membranes were simply prepared by dipping a support membrane in a suspension of this synthetic clay in water. Afterwards a drying at room temperature and a calcination at 400 ar 500sp°C is performed. Both membrane types were tested for gas separation and pervaporation purposes. Transport of permanent gases (He, N2) occurs by means of Knudsen diffusion. Diffusion is kinetically controlled and for a binary mixture, the maximum separation factor is determined by the difference in molecular weight of both components. From pervaporation experiments with water/alcohol mixtures it was found that Al-PILC membranes can be used for dehydration of water/ethanol, water/2-propanol and water/1-butanol mixtures.

Vercauteren, Sven

398

Transport and magnetic properties of RTX and related compounds

NASA Astrophysics Data System (ADS)

Physical properties of RTX compounds (R = Rare earth, T = Transition metal and X = main group element from B, C or N group) compounds have been studied by means of electrical resistivity, heat capacity, dc magnetization and NMR. Searching for new magnetic materials is always an interesting topic from both a technological and basic research prospective; it is even more interesting when unusual magnetic phases are observed. Ternary intermetallic plumbides are interesting because of their unconventional magnetic ordering and variety of multiple magnetic transitions. Crystalline electric fields (CEF) also strongly effect the magnetic properties of these intermetallics. To understand the phase transitions, CEF effects, and magnetic interactions, a systematic study of the RNiPb, R 2Ni2Pb, R5NiPb3 and RCuGe systems were conducted. Among the results for NdNiPb a single antiferromagnetic transition was found at 3.5K, while the superconductivity found in some ingots of this material was shown not to correspond to a bulk behavior for this phase. Nd2Ni 2Pb was shown to have a canted zero field magnetic structure with a low temperature metamagnetic transition 3 T. In NdCuGe, a 3K AF transition was found along with a corresponding magnon contribution to the specific heat and magnetic and thermodynamic behavior from which the detailed CEF configuration was obtained. In a series of measurements on recently-synthesized R 5NiPb3 (R=Ce, Nd, Gd), for Ce5NiPb 3 a transition at 48 K was found, which was confirmed to be ferromagnetic character from field dependent heat capacity and Curie-Weiss susceptibility. Nd5NiPb3 exhibits two transitions, an antiferromagnetic transition at 42 K and an apparently weak ferromagnetic canting transition at 8 K. For Gd5NiPb3, a ferro- or ferrimagnetic transition was found at 68 K. For the Ce and Nd materials metamagnetism was also observed at low temperatures. In addition, very large metallic type gamma terms were found in the specific heat, as well as a reduced value of the magnetic entropy, for all three systems. These results imply a lack of ordering for one of the two in-equivalent chains in these materials. This is discussed in terms of possible geometrical frustration on one of the spin chains.

Goruganti, Venkateshwarlu

399

Monotonic solution of heterogeneous anisotropic diffusion problems

NASA Astrophysics Data System (ADS)

Anisotropic problems arise in various areas of science and engineering, for example groundwater transport and petroleum reservoir simulations. The pure diffusive anisotropic time-dependent transport problem is solved on a finite number of nodes, that are selected inside and on the boundary of the given domain, along with possible internal boundaries connecting some of the nodes. An unstructured triangular mesh, that attains the Generalized Anisotropic Delaunay condition for all the triangle sides, is automatically generated by properly connecting all the nodes, starting from an arbitrary initial one. The control volume of each node is the closed polygon given by the union of the midpoint of each side with the “anisotropic” circumcentre of each final triangle. A structure of the flux across the control volume sides similar to the standard Galerkin Finite Element scheme is derived. A special treatment of the flux computation, mainly based on edge swaps of the initial mesh triangles, is proposed in order to obtain a stiffness M-matrix system that guarantees the monotonicity of the solution. The proposed scheme is tested using several literature tests and the results are compared with analytical solutions, as well as with the results of other algorithms, in terms of convergence order. Computational costs are also investigated.

Aricò, Costanza; Tucciarelli, Tullio

2013-11-01

400

Structural, magnetic, and transport properties of Permalloy for spintronic experiments

Permalloy (Ni{sub 80}Fe{sub 20}) is broadly used to prepare magnetic nanostructures for high-frequency experiments where the magnetization is either excited by electrical currents or magnetic fields. Detailed knowledge of the material properties is mandatory for thorough understanding its magnetization dynamics. In this work, thin Permalloy films are grown by dc-magnetron sputtering on heated substrates and by thermal evaporation with subsequent annealing. The specific resistance is determined by van der Pauw methods. Point-contact Andreev reflection is employed to determine the spin polarization of the films. The topography is imaged by atomic-force microscopy, and the magnetic microstructure by magnetic-force microscopy. Transmission-electron microscopy and transmission-electron diffraction are performed to determine atomic composition, crystal structure, and morphology. From ferromagnetic resonance absorption spectra the saturation magnetization, the anisotropy, and the Gilbert damping parameter are determined. Coercive fields and anisotropy are measured by magneto-optical Kerr magnetometry. The sum of the findings enables optimization of Permalloy for spintronic experiments.

Nahrwold, Gesche; Scholtyssek, Jan M.; Motl-Ziegler, Sandra; Albrecht, Ole; Merkt, Ulrich; Meier, Guido [Institut fuer Angewandte Physik und Zentrum fuer Mikrostrukturforschung, Universitaet Hamburg, Jungiusstrasse 11, 20355 Hamburg (Germany)

2010-07-15

401

High-field thermal transports properties of REBCO coated conductors

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 ...

Bonura, M

2014-01-01

402

Transport properties of silver-calcium doped lanthanum manganite

NASA Astrophysics Data System (ADS)

Electrical properties of silver-calcium doped lanthanum manganite (La0.5Ca0.5-xAgxMnO3 with 0.0

Cherif, B.; Rahmouni, H.; Smari, M.; Dhahri, E.; Moutia, N.; Khirouni, K.

2015-01-01

403

High-field thermal transport properties of REBCO coated conductors

NASA Astrophysics Data System (ADS)

The use of REBCO coated conductors (CCs) is envisaged for many applications, extending from power cables to high-field 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 first study on the longitudinal thermal conductivity (?) of REBCO CCs in magnetic fields up to 19 T applied both parallel and perpendicularly to the thermal-current direction. Copper-stabilized tapes from six industrial manufacturers have been investigated. We show that zero-field ? of CCs 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 fields have allowed us to evaluate the consistency of the procedures generally used for estimating in-field ? in the framework of the Wiedemann–Franz law from an electrical characterization of the materials. In-field data are intended to provide primary ingredients for the thermal stability analysis of high-temperature superconductor-based magnets.

Bonura, Marco; Senatore, Carmine

2015-02-01

404

Extending anisotropic operators to recover smooth shapes

Anisotropic differential operators are widely used in image enhancement processes. Recently, their property of smoothly extending functions to the whole image domain has begun to be exploited. Strong ellipticity of differential operators is a requirement that ensures existence of a unique solution. This condition is too restrictive for operators designed to extend image level sets: their own functionality implies that

Debora Gil; Petia Radeva

2005-01-01

405

Conformally flat polytropes for anisotropic matter

NASA Astrophysics Data System (ADS)

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.

Herrera, L.; Di Prisco, A.; Barreto, W.; Ospino, J.

2014-12-01

406

NASA Astrophysics Data System (ADS)

Using nonequlilibrium Green's functions in combination with the density-functional theory, we investigate the spin transport properties of molecular junction based on metal (Cu, Fe) phthalocyanines between V-shaped zigzag-edged graphene nanorribons. The results show that the electronic transport properties mainly depend on the center transition metal. The negative differential resistance behaviors and spin splitting phenomenon can be observed.

Cui, Liling; Yang, Bingchu; Li, Xinmei; He, Jun; Long, Mengqiu

2014-11-01

407

NASA Astrophysics Data System (ADS)

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/), two intensive airborne campaigns (TRAQA, TRansport and Air QuAlity, 18 June - 11 July 2012, and ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) have 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.

Denjean, Cyrielle; Di Biagio, Claudia; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Loisil, Rodrigue; Triquet, Sylvain; Zapf, Pascal; Roberts, Greg; Bourrianne, Thierry; Torres, Benjamin; Blarel, Luc; Sellegri, Karine; Freney, Evelyn; Schwarzenbock, Alfons; Ravetta, François; Laurent, Benoit; Mallet, Marc; Formenti, Paola

2014-05-01

408

NASA Astrophysics Data System (ADS)

Accumulated pollen in stratified fossil reservoirs is used to infer temporal changes in vegetation composition. Transport and dispersal by winds are known to introduce large biases in the interpretation of polynic records. In order to calibrate the models used to infer information about past species distributions, human activities and climate, contemporary time series of polynic records are assessed and modelled. In this study we analyse measurements collected hourly in Bariloche, Argentina (41° 10' S, 71° 15' W, 850 masl) of the species Weinmannia trichosperma, a characteristic forest tree which grows only the western (Chilean) slopes of the Andes, but not on the eastern (Argentinian) slopes where the measurements were collected. Instead of the simplistic Gaussian plume mixing model that is usually employed by the palynological community, we apply a full 3D Lagrangian dispersion model to interpret the observations and assess the impact of long-range transport over the Andean mountain range. The Lagrangian calculation of the origins of the air masses (the "backward footprint") is consistent not only with the Chilean Weinmania pollen measurements but also with a set of species only found on the dryer steppe located to the east of the measurement site in Argentina. The agreement of the modelling results indicates that significant interpretation mistakes may arise from inconsistent transport treatment. We also discuss the further application of inverse trajectory modelling to the estimation of source intensity.

Pérez, Claudio; Bianchi, María Martha; Gassmann, Marisa; Pisso, Ignacio

2014-05-01

409

Enhancement of non-resonant dielectric cloaks using anisotropic composites

Cloaking techniques conceal objects by controlling the flow of electromagnetic waves to minimize scattering. Herein, the effectiveness of homogenized anisotropic materials in non-resonant dielectric multilayer cloaking is studied. Because existing multilayer cloaking by isotropic materials can be regarded as homogenous anisotropic cloaking from a macroscopic view, anisotropic materials can be efficiently designed through optimization of their physical properties. Anisotropic properties can be realized in two-phase composites if the physical properties of the material are within appropriate bounds. The optimized anisotropic physical properties are identified by a numerical optimization technique based on a full-wave simulation using the finite element method. The cloaking performance measured by the total scattering width is improved by about 2.8% and 25% in eight- and three-layer cylindrical cloaking materials, respectively, compared with multilayer cloaking by isotropic materials. In all cloaking examples, the optimized microstructures of the two-phase composites are identified as the simple lamination of two materials, which maximizes the anisotropy. The same performance as published for eight-layer cloaking by isotropic materials is achieved by three-layer cloaking using the anisotropic material. Cloaking with an approximately 50% reduction of total scattering width is achieved even in an octagonal object. Since the cloaking effect can be realized using just a few layers of the laminated anisotropic dielectric composite, this may have an advantage in the mass production of cloaking devices.

Takezawa, Akihiro, E-mail: akihiro@hiroshima-u.ac.jp; Kitamura, Mitsuru [Division of Mechanical Systems and Applied Mechanics, Institute of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima (Japan)] [Division of Mechanical Systems and Applied Mechanics, Institute of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima (Japan)

2014-01-15

410

NASA Astrophysics Data System (ADS)

The effect of nanocrystal orientation on the energy loss spectra of monoclinic hafnia (m-HfO2) is measured by high resolution transmission electron microscopy (HRTEM) and valence energy loss spectroscopy (VEELS) on high quality samples. For the same momentum-transfer directions, the dielectric properties are also calculated ab initio by time-dependent density-functional theory (TDDFT). Experiments and simulations evidence anisotropy in the dielectric properties of m-HfO2, most notably with the direction-dependent oscillator strength of the main bulk plasmon. The anisotropic nature of m-HfO2 may contribute to the differences among VEELS spectra reported in literature. The good agreement between the complex dielectric permittivity extracted from VEELS with nanometer spatial resolution, TDDFT modeling, and past literature demonstrates that the present HRTEM-VEELS device-oriented methodology is a possible solution to the difficult nanocharacterization challenges given in the International Technology Roadmap for Semiconductors.

Guedj, C.; Hung, L.; Zobelli, A.; Blaise, P.; Sottile, F.; Olevano, V.

2014-12-01

411

Cellular distribution and kinetic properties of high-affinity glutamate transporters.

L-glutamic acid is a key chemical transmitter of excitatory signals in the nervous system. The termination of glutamatergic transmission occurs via uptake of glutamate by a family of high-affinity glutamate transporters that utilize the Na+/K+ electrochemical gradient as a driving force. The stoichiometry of a single translocation cycle is still debatable, although all proposed models stipulate an inward movement of a net positive charge. This electrogenic mechanism is capable of translocating the neurotransmitter against its several thousand-fold concentration gradient, therefore, keeping the resting glutamate concentration below the treshold levels. The five cloned transporters (GLAST/EAAT1, GLT1/EAAT2, EAAC1/EAAT3, EAAT4, and EAAT5) exhibit distinct distribution patterns and kinetic properties in different brain regions, cell types, and reconstitution systems. Moreover, distinct pharmacological profiles were revealed among the species homologues. GLAST and GLT1, the predominant glutamate transporters in the brain, are coexpressed in astroglial processes, whereas neuronal carriers are mainly located in the dendrosomatic compartment. Some of these carrier proteins may possess signal transducing properties, distinct from their transporter activity. Some experimental conditions and several naturally occurring and synthetic compounds are capable of regulating the expression of glutamate transporters. However, selective pharmacological tools interfering with the individual glutamate carriers have yet to be developed. PMID:9510415

Gegelashvili, G; Schousboe, A

1998-01-01

412

NASA Astrophysics Data System (ADS)

We have used the non-equilibrium Green's function in combination with the density functional theory to investigate the quantum transport properties of the molecular junctions including a terminated benzene ring directly coupled to surface of metal electrodes (physisorption). The other side of molecule was connected to electrode via thiolate bond (chemisorption). Two different electrodes have been studied, namely Cu and Al. Rectification and negative differential resistance behavior have been observed. We found that the electron transport mechanism is affected by the nature of benzene-electrode coupling. In other words, the transport mechanism depends on the nature of metallic electrode. Changing from sp- to sd-metallic electrode, the molecular junction changes from the Schottky to p-n junction-like diode. The transmission spectra, projected density of state, molecular projected self-consistent Hamiltonian, transmission eigenchannel, and Muliken population have been analyzed for explanation of electronic transport properties. Understanding the transport mechanism in junction having direct coupling of ?-conjugate to electrode will be useful to design the future molecular devices.

Lan, Tran Nguyen

2014-01-01

413

Structure-dependent optical and electrical transport properties of nanostructured Al-doped ZnO.

The structure-property relation of nanostructured Al-doped ZnO thin films has been investigated in detail through a systematic variation of structure and morphology, with particular emphasis on how they affect optical and electrical properties. A variety of structures, ranging from compact polycrystalline films to mesoporous, hierarchically organized cluster assemblies, are grown by pulsed laser deposition at room temperature at different oxygen pressures. We investigate the dependence of functional properties on structure and morphology and show how the correlation between electrical and optical properties can be studied to evaluate energy gap, conduction band effective mass and transport mechanisms. Understanding these properties opens up opportunities for specific applications in photovoltaic devices, where optimized combinations of conductivity, transparency and light scattering are required. PMID:22914557

Gondoni, P; Ghidelli, M; Di Fonzo, F; Carminati, M; Russo, V; Li Bassi, A; Casari, C S

2012-09-14

414

DRFM: A new package for the evaluation of gas-phase transport properties

This report describes a complete and modernized procedure to evaluate pure species, binary and mixture transport properties of gases in the low density limit. This includes a description of the relationships used to calculate these quantities and the means used to obtain the necessary input data. The purpose of this work is to rectify certain limitations of previous transport packages, specifically: to employ collision integrals suitable for high temperatures, to modernize the mixture formula, and to modernize the input data base. This report includes a set of input parameters for: the species involved in H{sub 2}-, CO - air combustion, the noble gases, methane and the oxides of nitrogen.

Paul, P.H.

1997-11-01

415

NASA Astrophysics Data System (ADS)

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.

Liu, Chunyu; Chang, Kaiwen; Guo, Wenbin; Li, Hao; Shen, Liang; Chen, Weiyou; Yan, Dawei

2014-08-01

416

NASA Astrophysics Data System (ADS)

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.

Cosmin Obreja, Alexandru; Cristea, Dana; Mihalache, Iuliana; Radoi, Antonio; Gavrila, Raluca; Comanescu, Florin; Kusko, Cristian

2014-08-01

417

Synthesis and Quantum Transport Properties of Bi2Se3 Topological Insulator Nanostructures

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

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

418

Anisotropic power-law k-inflation

NASA Astrophysics Data System (ADS)

It is known that power-law k-inflation can be realized for the Lagrangian P=Xg(Y), where X=-(??)2/2 is the kinetic energy of a scalar field ? and g is an arbitrary function in terms of Y=Xe??/Mpl (? is a constant and Mpl is the reduced Planck mass). In the presence of a vector field coupled to the inflaton with an exponential coupling f(?)?e??/Mpl, we show that the models with the Lagrangian P=Xg(Y) generally give rise to anisotropic inflationary solutions with ?/H=constant, where ? is an anisotropic shear and H is an isotropic expansion rate. Provided these anisotropic solutions exist in the regime where the ratio ?/H is much smaller than 1, they are stable attractors irrespective of the forms of g(Y). We apply our results to concrete models of k-inflation such as the generalized dilatonic ghost condensate and the Dirac-Born-Infeld model and we numerically show that the solutions with different initial conditions converge to the anisotropic power-law inflationary attractors. Even in the de Sitter limit (??0) such solutions can exist, but in this case the null energy condition is generally violated. The latter property is consistent with the Wald’s cosmic conjecture stating that the anisotropic hair does not survive on the de Sitter background in the presence of matter respecting the dominant/strong energy conditions.

Ohashi, Junko; Soda, Jiro; Tsujikawa, Shinji

2013-11-01

419

NASA Astrophysics Data System (ADS)

The discovery of fullerenes and carbon nanotubes has been very significant to the field of nanotechnology by providing an abundance of stable, highly symmetric, non-reactive, and relatively large molecules that can, in principle, be manipulated one at a time. At the present stage, a theoretical effort should be carried out in order to find and understand novel phenomena in molecule-based nanostructures which could serve as a basis for fabricating useful molecular devices. In this thesis we investigate from first-principles the transport properties of molecular devices: fullerene and carbon nanotube systems. We begin with charge transport in carbon nanotubes with oxygen, and find that the interaction between oxygen molecules and carbon nanotubes significantly modifies the electronic structure near the Fermi level for both zigzag and armchair tubes. The subtle difference of the adsorption sites of oxygen and the distance between oxygen and nanotubes can cause totally different results of their transport properties. Then we investigate current flow from the point of view of current density distribution in molecular devices, for current density gives local information of nonequilibrium transport, thereby providing useful and vivid insight to transport properties of molecular electronics. It has been found when an intrinsic carbon nanotube is doped with either a boron or a nitrogen atoms through a replacement of a carbon atom, the local physical properties around the impurity atoms (boron or nitrogen) undergo a significant change, resulting in a dramatic change of the local current distribution. It is suggested that there appears a chiral current flow in the B- and N-doped armchair nanotubes near the impurity. As for a gated C 60 molecular device, the current distribution and the total current flow are both obviously affected by the gate voltage, which indicates the importance of the gate voltage in such a molecular device. Finally, we discuss the contact effects on transport properties of the molecular devices. We study the effects of the contact geometry as well as the electrode material and find that different orientations of C 60 connected to Au(111) leads can cause significant changes in the current-voltage (I-V) characteristics of such C60 molecular devices. On the other hand, the electrode material is crucial to obtain low resistance ohmic contacts. Our first-principles calculations of transport suggest that Ti has higher affinity for carbide formation. So the choice of proper electrode materials will play an important role in the design of nanoscale devices.

Liu, Yi

420

We investigate with state of the art density functional theory the structural, electronic, and transport properties of a class of recently synthesized nanostructures based on triarylamine derivatives. First, we consider the single molecule precursors in the gas phase and calculate their static properties, namely (i) the geometrical structure of the neutral and cationic ions, (ii) the electronic structure of the frontier molecular orbitals, and (iii) the ionization potential, hole extraction potential, and internal reorganization energy. This initial study does not evidence any direct correlation between the properties of the individual molecules and their tendency to self-assembly. Subsequently, we investigate the charge transport characteristics of the triarylamine derivatives nanowires, by using Marcus theory. For one derivative we further construct an effective Hamiltonian including intermolecular vibrations and evaluate the mobility from the Kubo formula implemented with Monte Carlo sampling. These two methods, valid respectively in the sequential hopping and polaronic band limit, give us values for the room-temperature mobility in the range 0.1–12 cm{sup 2}/Vs. Such estimate confirms the superior transport properties of triarylamine-based nanowires, and make them an attracting materials platform for organic electronics.

Akande, Akinlolu, E-mail: akandea@tcd.ie; Bhattacharya, Sandip; Cathcart, Thomas; Sanvito, Stefano [School of Physics, AMBER and CRANN Institute, Trinity College Dublin, Dublin 2 (Ireland)] [School of Physics, AMBER and CRANN Institute, Trinity College Dublin, Dublin 2 (Ireland)

2014-02-21

421

NASA Astrophysics Data System (ADS)

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.

Zhang, Yongjun

422

The kinetic coefficients of high-quality single crystals of ternary layered n-PbBi{sub 4}Te{sub 7} compounds have been measured in the temperature range of 77-400 K. These crystals, doped with electroactive Cd and Ag impurities, were grown by Czochralski pulling with melt supply through a floating crucible. A significant anisotropy of the thermoelectric properties is found. The means of incorporation of electroactive impurities into the ternary compound lattice is established. The experimental values of the Nernst-Ettingshausen coefficient have been analyzed together with the Seebeck, Hall, and conductivity data. The features of transport phenomena in PbBi{sub 4}Te{sub 7} can be explained within the single-band model of nonparabolic energy spectrum and mixed mechanism of electron scattering from acoustic phonons and the Coulomb potential of impurities. It is suggested that acoustic phonon scattering is dominant along the cleavage plane, whereas the impurity scattering dominates along the trigonal axis.

Zhitinskaya, M. K., E-mail: m_zhitinskaya@mail.ru; Nemov, S. A.; Muhtarova, A. A. [St. Petersburg State Politechnical University (Russian Federation); Shelimova, L. E.; Svechnikova, T. E. [Russian Academy of Sciences, Baikov Institute of Metallurgy and Materials Science (Russian Federation); Konstantinov, P. P. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2010-06-15

423

Properties of thiamine transport in isolated perfused hearts of chronically alcoholic guinea pigs.

The aim of this study was to determine the mechanism of transport of (14)C-thiamine in the hearts of healthy (nonalcoholic) and chronically alcoholic guinea pigs. We used the single-pass, paired-tracer dilution method on isolated and retrogradely perfused guinea pig hearts. The maximal cellular uptake (U(max)) and total cellular uptake (U(tot)) of (14)C-thiamine were determined under control conditions and under influence of possible modifiers. We tested how the presence of unlabeled thiamine, metabolic inhibitors, or absence of sodium ions influence the transport of (14)C-thiamine. The results of our experiments show that the transport of (14)C-thiamine is specific and energy-dependent and that its properties are significantly changed under the influence of chronic alcoholism. The latter effect occurs by increase in both U(max) and U(tot), as a manifestation of a compensatory mechanism in thiamine deficiency. PMID:18418424

Petrovic, Milos M; Scepanovic, Ljiljana; Rosic, Gvozden; Mitrovic, Dusan M

2008-04-01

424

In this work the effect of zinc concentration, pH, and boric acid concentration on the zinc transport properties through an IONICS 67-HMR-412 cation-exchange membrane was evaluated. The limiting current density and the transport numbers were determined by means of chronopotentiometry. A model between the limiting current density and the bulk zinc concentration was established, assuming a potential relationship between the zinc transport number through the membrane and the bulk zinc concentration together with the Levich equation for the DBL thickness. A decrease in the initial pH value of the solutions causes considerable modifications both in the plateau region and in the overlimiting current density region of the current-membrane potential curves. The results show that the presence of boric acid produces the precipitation of zinc metaborate on the anodic layer of the cation-exchange membrane. PMID:19878955

Herraiz-Cardona, I; Ortega, E; Pérez-Herranz, V

2010-01-15

425

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.

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

426

NASA Astrophysics Data System (ADS)

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.

Sen, Sonu; Varshney, Meenu Asthana; Dubey, A.; Varshney, Dinesh

2014-04-01

427

A numerical model of non-equilibrium thermal plasmas. I. Transport properties

A self-consistent and complete numerical model for investigating the fundamental processes in a non-equilibrium thermal plasma system consists of the governing equations and the corresponding physical properties of the plasmas. In this paper, a new kinetic theory of the transport properties of two-temperature (2-T) plasmas, based on the solution of the Boltzmann equation using a modified Chapman-Enskog method, is presented. This work is motivated by the large discrepancies between the theories for the calculation of the transport properties of 2-T plasmas proposed by different authors in previous publications. In the present paper, the coupling between electrons and heavy species is taken into account, but reasonable simplifications are adopted, based on the physical fact that m{sub e}/m{sub h} Much-Less-Than 1, where m{sub e} and m{sub h} are, respectively, the masses of electrons and heavy species. A new set of formulas for the transport coefficients of 2-T plasmas is obtained. The new theory has important physical and practical advantages over previous approaches. In particular, the diffusion coefficients are complete and satisfy the mass conversation law due to the consideration of the coupling between electrons and heavy species. Moreover, this essential requirement is satisfied without increasing the complexity of the transport coefficient formulas. Expressions for the 2-T combined diffusion coefficients are obtained. The expressions for the transport coefficients can be reduced to the corresponding well-established expressions for plasmas in local thermodynamic equilibrium for the case in which the electron and heavy-species temperatures are equal.

Zhang XiaoNing; Xia WeiDong [Department of Thermal Science and Energy Engineering, University of Science and Technology of China, Hefei, Anhui Province 230026 (China); Li HePing [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China); Murphy, Anthony B. [CSIRO Materials Science and Engineering, PO Box 218, Lindfield NSW 2070 (Australia)

2013-03-15

428

High-density carbon nanotube buckypapers with superior transport and mechanical properties.

High-density buckypapers were obtained by using well-aligned carbon nanotube arrays. The density of the buckypapers was as high as 1.39 g cm(-3), which is close to the ultimate density of ideal buckypapers. Then we measured the transport and mechanical properties of the buckypapers. Our results demonstrated that its electrical and thermal conductivities could be almost linearly improved by increasing its density. In particular, its superior thermal conductivity is nearly twice that of common metals, which enables it a lightweight and more efficient heat-transfer materials. The Young's modulus of the buckypapers could reach a magnitude over 2 GPa, which is greatly improved compared with previous reported results. In view of this, our work provided a simple and convenient method to prepare high-density buckypapers with excellent transport and mechanical properties. PMID:22925031

Zhang, Ling; Zhang, Guang; Liu, Changhong; Fan, Shoushan

2012-09-12

429

Transport properties of Nd1-xFexOF polycrystalline films

NASA Astrophysics Data System (ADS)

The transport properties of Nd1-xFexOF films with 0.2

Corrales-Mendoza, I.; Rangel-Kuoppa, Victor-Tapio; Conde-Gallardo, A.

2013-12-01

430

The combined effect of bulk and interface electron-phonon couplings on the transport properties is investigated in a model for organic semiconductors gated with polarizable dielectrics. While the bulk electron-phonon interaction affects the behavior of mobility in the coherent regime below room temperature, the interface coupling is dominant for the activated high $T$ contribution of localized polarons. In order to improve the description of the transport properties, the presence of disorder is needed in addition to electron-phonon couplings. The effects of a weak disorder largely enhance the activation energies of mobility and induce the small polaron formation at lower values of electron-phonon couplings in the experimentally relevant window $150 K

C. A. Perroni; V. Cataudella

2011-09-28

431

Electronic transport properties of BN sheet on adsorption of ammonia (NH3) gas.

We report the detection of ammonia gas through electronic and transport properties analysis of boron nitride sheet. The density functional theory (DFT) based ab initio approach has been used to calculate the electronic and transport properties of BN sheet in presence of ammonia gas. Analysis confirms that the band gap of the sheet increases due to presence of ammonia. Out of different positions, the bridge site is the most favorable position for adsorption of ammonia and the mechanism of interaction falls between weak electrostatic interaction and chemisorption. On relaxation, change in the bond angles of the ammonia molecule in various configurations has been reported with the distance between NH3 and the sheet. An increase in the transmission of electrons has been observed on increasing the bias voltage and I-V relationship. This confirms that, the current increases on applying the bias when ammonia is introduced while a very small current flows for pure BN sheet. PMID:25666919

Srivastava, Anurag; Bhat, Chetan; Jain, Sumit Kumar; Mishra, Pankaj Kumar; Brajpuriya, Ranjeet

2015-03-01

432

Transport properties of boron-doped single-walled silicon carbide nanotubes

NASA Astrophysics Data System (ADS)

The doped boron (B) atom in silicon carbide nanotube (SiCNT) can substitute car