Anisotropic bias dependent transport property of defective phosphorene layer
Umar Farooq, M.; Hashmi, Arqum; Hong, Jisang
2015-01-01
Phosphorene is receiving great research interests because of its peculiar physical properties. Nonetheless, no systematic studies on the transport properties modified due to defects have been performed. Here, we present the electronic band structure, defect formation energy and bias dependent transport property of various defective systems. We found that the defect formation energy is much less than that in graphene. The defect configuration strongly affects the electronic structure. The band gap vanishes in single vacancy layers, but the band gap reappears in divacancy layers. Interestingly, a single vacancy defect behaves like a p-type impurity for transport property. Unlike the common belief, we observe that the vacancy defect can contribute to greatly increasing the current. Along the zigzag direction, the current in the most stable single vacancy structure was significantly increased as compared with that found in the pristine layer. In addition, the current along the armchair direction was always greater than along the zigzag direction and we observed a strong anisotropic current ratio of armchair to zigzag direction. PMID:26198318
Anisotropic transport properties of ferromagnetic-superconducting bilayers
Kayali, MA; Pokrovsky, Valery L.
2004-01-01
We study the transport properties of vortex matter in a superconducting thin film separated by a thin insulator layer from a ferromagnetic layer. We assume an alternating stripe structure for both FM and superconducting (SC) layers as found in S...
Transport properties of the two-dimensional interacting anisotropic electron gas at zero temperature
NASA Astrophysics Data System (ADS)
Khrapai, V. S.; Gold, A.
2010-02-01
At zero temperature we calculate the transport properties of the two-dimensional interacting electron gas in (110) AlAs quantum wells and (110) Si metal-oxide-semiconductor field-effect transistor structures. In these structures the effective mass is anisotropic, which gives rise to anisotropic transport properties. We use the theoretical approach developed by Tokura [Phys. Rev. B 58, 7151 (1998)], where the conductivity tensor is calculated using the Boltzmann equation. The density dependence of the anisotropic mobility for impurity scattering and for interface-roughness scattering is studied. The predictive power of the theory is demonstrated and we compare with experimental results. For (110) AlAs quantum wells with a mass ratio mx/my=5.5 we find mobility anisotropies in the range 1.5
Anisotropic transport properties in tilted c-axis MgB2 thin films
NASA Astrophysics Data System (ADS)
Orgiani, P.; Chen, Ke; Cui, Yi; Li, Qi; Ferrando, V.; Putti, M.; Iavarone, M.; Di Capua, R.; Ciancio, R.; Vaglio, R.; Maritato, L.; Xi, X. X.
2010-02-01
We report on superconducting magnesium diboride MgB2 thin films grown on both YSZ and MgO substrates, with two different orientations, namely [110] and [211]. MgB2 off-axis growth mode (namely, with the c-axis tilted with respect to the film surface's normal) is achievable on these substrates. Depending on the type and orientation of the substrate, tilting angle can be varied. As a consequence of tilted growth, anisotropic transport properties are observed. In very thin films, resistance measurements provide an estimate of the resistivity anisotropic ratio ?c/?ab, where ?c is the resistivity along the c axis and ?ab is the in-plane resistivity. All these findings clearly demonstrate that tilted MgB2 films offer new exciting possibilities to both investigate intrinsic fundamental properties of MgB2 and to explore possible applications in planar superconducting devices.
Strain-induced anisotropic transport properties of LaBaCo?O?.?+? thin films on NdGaO? substrates.
Liu, Ming; Zou, Qiang; Ma, Chunrui; Collins, Greg; Mi, Shao-Bo; Jia, Chun-Lin; Guo, Haiming; Gao, Hongjun; Chen, Chonglin
2014-06-11
Thin films of double-perovskite structural LaBaCo2O5.5+? were epitaxially grown on (110) NdGaO3 substrates by pulsed laser deposition. Microstructural studies by high-resolution X-ray diffraction and transmission electron microscopy revealed that the films have an excellent quality epitaxial structure. In addition, strong in-plane anisotropic strains were measured. Electrical transport properties of the films were characterized by an ultra-high-vacuum four-probe scanning tunneling microscopy system at different temperatures. It was found that the anisotropic in-plane strain can significantly tune the values of film resistance up to 590%. PMID:24824560
NASA Astrophysics Data System (ADS)
Thongnum, Anusit; Pinsook, Udomsilp
2015-03-01
Anisotropic transport properties of a two-dimensional electron gas in nonpolar m-plane AlN/GaN heterostructures with the interface roughness coupled anisotropic in-plane strain scattering were investigated theoretically using a path-integral framework. The scattering potential was composed of the interface roughness and the effective field from the electron charge and the net piezoelectric polarization. We showed that the anisotropic biaxial strains generate only the net piezoelectric polarization along the [0?0?0?1]-direction and cause anisotropy in electron mobility with a magnitude lower than the ?ft[11\\bar{2}0\\right] -direction. We also showed that the anisotropy in electron mobility reduced with increasing electron density. Moreover, the anisotropic electron mobility disappeared when the anisotropic in-plane strain scattering was removed, and the relation for pure interface roughness scattering was reestablished. This formulation with existing roughness parameters gave a good description for the experimental results of polar c-plane AlN/GaN heterostructures.
Zou, Q; Liu, M; Wang, G Q; Lu, H L; Yang, T Z; Guo, H M; Ma, C R; Xu, X; Zhang, M H; Jiang, J C; Meletis, E I; Lin, Y; Gao, H J; Chen, C L
2014-05-14
Highly epitaxial LaBaCo2O5.5+? (LBCO) thin films were grown on different miscut (001) SrTiO3 substrates (miscut angle of 0.5°, 3.0°, and 5.0°) to study the substrate surface step terrace effect on the in-plane electrical transport properties. The microstructure studies by X-ray diffraction and transmission electron microscopy indicate that the as-grown films are A-site disordered cubic perovskite structures with the c-axis highly oriented along the film growth direction. The four-probe scanning tunneling microscopy (STM) studies show that the LBCO thin films grown on the vicinal SrTiO3 substrates have a typical semiconductor behavior with the substrate surface terrace step inducing anisotropic electronic transport properties. These results indicate that in highly epitaxial thin films the surface terrace step induced local strains can play an important role in controlling the electronic transport properties and the anisotropic nature. PMID:24716582
Phase diagram and anisotropic transport properties of Nd{sub 1{minus}x}Sr{sub x}MnO{sub 3} crystals
Kuwahara, H.; Okuda, T.; Tomioka, Y.; Kimura, T.; Asamitsu, A. [Joint Research Center for Atom Technology, Tsukuba, Ibaraki (Japan); Tokura, Y. [Joint Research Center for Atom Technology, Tsukuba, Ibaraki (Japan); [Univ. of Tokyo (Japan)
1998-12-31
The authors have investigated electronic transport and magnetic properties of perovskite-type Nd{sub 1{minus}x}Sr{sub x}MnO{sub 3} crystals with change of controlled hole-doping level (0.30 {le} x {le} 0.80). The electronic phase diagram of Nd{sub 1{minus}x}Sr{sub x}MnO{sub 3} was obtained by systematic measurements of magnetization (magnetic structure), resistivity, and lattice parameter. The authors have also studied the anisotropic transport properties of x = 0.50 and 0.55 crystals with different magnetic structures: CE-type antiferromagnetic (AF) structure for x = 0.50 and A-type layered AF one for x = 0.55. In the case of the x = 0.55 crystal, the metallic behavior was observed within the ferromagnetic (F) layers, while along the AF-coupling direction the crystal remains insulating over the whole temperature region. The observed large anisotropy is due to the magnetic as well as orbital-ordering induced confinement of the spin-polarized carriers within the F sheets. The nearly isotropic transport behavior has been confirmed for the CE-type AF charge-ordered state in the x = 0.50 crystal.
Ma, Y; Gustavsson, J S; Haglund, A; Gustavsson, M; Gustafsson, S E
2014-04-01
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
Theoretical studies of anisotropic energy transport in TATB crystals
NASA Astrophysics Data System (ADS)
Kroonblawd, Matthew; Sewell, Thomas
2015-06-01
Anisotropic thermal transport properties were determined theoretically for single crystals of the insensitive explosive 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) using molecular dynamics. TATB exhibits a graphitic-like layered packing structure with a two-dimensional hydrogen-bonding network within, but not between, the molecule-thick layers that comprise the crystal. Anisotropic thermal conductivity coefficients were determined for initially defect-free and defective TATB crystals at various temperatures and pressures, and direction-dependent relaxation of idealized hot spots was studied. The room temperature, atmospheric pressure thermal conductivity for TATB is predicted to be generally greater and more anisotropic than the thermal conductivities of other molecular explosives; conduction within the layers is at least 68% greater than conduction between them. The phonon mean free path length is predicted to be less than 1 nm. Decreases in thermal conductivity induced by molecular vacancy defects are also anisotropic and exhibit a linear dependence on defect density. Results from the hot-spot relaxation simulations were compared with and fit to an analytical solution for the one-dimensional continuum heat equation by treating the thermal diffusivity as a parameter. Validity of the continuum heat equation predictions for TATB is assessed for length scales below 20 nm.
NASA Astrophysics Data System (ADS)
Guo, Ruiqiang; Wang, Xinjiang; Kuang, Youdi; Huang, Baoling
2015-09-01
Tin selenide (SnSe) and tin sulfide (SnS) have recently attracted particular interest due to their great potential for large-scale thermoelectric applications. A complete prediction of the thermoelectric performance and the understanding of underlying heat and charge transport details are the key to further improvement of their thermoelectric efficiency. We conduct comprehensive investigations of both thermal and electrical transport properties of SnSe and SnS using first-principles calculations combined with the Boltzmann transport theory. Due to the distinct layered lattice structure, SnSe and SnS exhibit similarly anisotropic thermal and electrical behaviors. The cross-plane lattice thermal conductivity ?L is 40 -60 % lower than the in-plane values. Extremely low ?L is found for both materials because of high anharmonicity, while the average ?L of SnS is ˜8 % higher than that of SnSe from 300 to 750 K. It is suggested that nanostructuring would be difficult to further decrease ?L because of the short mean free paths of dominant phonon modes (1-30 nm at 300 K), while alloying would be efficient in reducing ?L considering that the relative ?L contribution (˜65 %) of optical phonons is remarkably large. On the electrical side, the anisotropic electrical conductivities are mainly due to the different effective masses of holes and electrons along the a , b , and c axes. This leads to the highest optimal ZT values along the b axis and lowest ones along the a axis in both p -type materials. However, the n -type ones exhibit the highest ZT s along the a axis due to the enhancement of power factor when the chemical potential gradually approaches the secondary conduction band valley that causes significant increase in electron mobility and density of states. Owing to the larger mobility and smaller ?L along the given direction, SnSe exhibits larger optimal ZTs compared with SnS in both p - and n -type materials. For both materials, the peak ZT s of n -type materials are much higher than those of p -type ones along the same direction. The predicted highest ZT values at 750 K are 1.0 in SnSe and 0.6 in SnS along the b axis for the p -type doping, while those for the n -type doping reach 2.7 in SnSe and 1.5 in SnS along the a axis, rendering them among the best bulk thermoelectric materials for large-scale applications. Our calculations show reasonable agreements with the experimental results and quantitatively predict the great potential in further enhancing the thermoelectric performance of SnSe and SnS, especially for the n -type materials.
Numerical investigation of nanoparticles transport in anisotropic porous media.
Salama, Amgad; Negara, Ardiansyah; El Amin, Mohamed; Sun, Shuyu
2015-10-01
In this work the problem related to the transport of nanoparticles in anisotropic porous media is investigated numerically using the multipoint flux approximation. Anisotropy of porous media properties is an essential feature that exists almost everywhere in subsurface formations. In anisotropic media, the flux and the pressure gradient vectors are no longer collinear and therefore interesting patterns emerge. The transport of nanoparticles in subsurface formations is affected by several complex processes including surface charges, heterogeneity of nanoparticles and soil grain collectors, interfacial dynamics of double-layer and many others. We use the framework of the theory of filtration in this investigation. Processes like particles deposition, entrapment, as well as detachment are accounted for. From the numerical methods point of view, traditional two-point flux finite difference approximation cannot handle anisotropy of media properties. Therefore, in this work we use the multipoint flux approximation (MPFA). In this technique, the flux components are affected by more neighboring points as opposed to the mere two points that are usually used in traditional finite volume methods. We also use the experimenting pressure field approach which automatically constructs the global system of equations by solving multitude of local problems. This approach facilitates to a large extent the construction of the global system. A set of numerical examples is considered involving two-dimensional rectangular domain. A source of nanoparticles is inserted in the middle of the anisotropic layer. We investigate the effects of both anisotropy angle and anisotropy ratio on the transport of nanoparticles in saturated porous media. It is found that the concentration plume and porosity contours follow closely the principal direction of anisotropy of permeability of the central domain. PMID:26212784
Anisotropic transport in modulation doped quantum well structures
NASA Technical Reports Server (NTRS)
Radulescu, D. C.; Wicks, G. W.; Schaff, W. J.; Calawa, A. R.; Eastman, L. F.
1987-01-01
The degree of anisotropy in the anisotropic electron transport that has been observed in GaAs modulation-doped quantum wells grown by MBE on Al(0.3)Ga(0.7)As is related to the thickness and growth parameters of this substrate, which is grown just prior to the inverted interface. It is presently observed that the inverted interface has an anisotropic roughness which affects the 77 K low field electron transport parallel to the interface, and gives rise to anisotropic electron scattering in the GaAs modulation-doped quantum well.
NASA Technical Reports Server (NTRS)
Barakat, A. R.; Schunk, R. W.
1982-01-01
A wide variety of plasma flow conditions is found in aeronomy and space plasma physics. Transport equations based on an isotropic Maxwellian vilecity distribution function can be used to describe plasma flows which contain 'small' temperature anisotropies. However, for plasma flows characterized by large temperature anisotropies, transport equations based on an anisotropic bi-Maxwellian (or two-temperature) velocity distribution function are expected to provide a much better description of the plasma transport properties. The present investigation is concerned with the extent to which transport equations based on both Maxwellian and bi-Maxwellian series expansions can describe plasma flows characterized by non-Maxwellian velocity distributions, giving particular attention to a modelling of the anisotropic character of the distribution function. The obtained results should provide clues as to the extent to which a given series expansion can account for the anisotropic character of a plasma.
Thermodynamic properties of magneto-anisotropic nanoparticles.
Bandyopadhyay, Malay
2009-06-10
The purpose of this paper is to study the thermodynamic equilibrium properties of a collection of non-interacting three-dimensional (3D) magnetically anisotropic nanoparticles in the light of classical statistical physics. Pertaining to the angular dependence (?) of the magnetic field with the anisotropy axis, energy landscape plots are obtained which reveal a continuous transition from a double well to a single well for [Formula: see text] and show an asymmetric bistable shape for other values of ?. The present analysis is related to the interpretation of equilibrium magnetization and static susceptibility of a nanomagnetic system as a function of external magnetic field, B, and temperature, T. The magnetization and susceptibility confirm the non-Langevin behaviour of magneto-anisotropic monodomain particles. The susceptibility analysis establishes the ferromagnetic-, antiferromagnetic- and paramagnetic-like coupling for various ?. This study reveals the essential role of magneto-anisotropic energy in the interpretation of the magnetic behaviour of a collection of non-interacting single-domain nanoparticles. PMID:21825600
Low-temperature properties of anisotropic superconductors with Kondo impurities
Borkowski, L.S.; Hirschfeld, P.J. (Univ. of Florida, Gainesville, FL (United States))
1994-08-01
The authors present a self-consistent theory of superconductors in the presence of Kondo impurities, using large-N slave-boson methods to treat the impurity dynamics. The technique is tested on the s-wave case and shown to give good results compared to other methods for T[sub K] > [Tc]. They calculate low temperature thermodynamic and transport properties for various superconducting states, including isotropic s-wave and representative anisotropic model states with line and point nodes on the Fermi surface.
Transport equations for multicomponent anisotropic space plasmas - A review
NASA Technical Reports Server (NTRS)
Barakat, A. R.; Schunk, R. W.
1982-01-01
An attempt is made to present a unified approach to the study of transport phenomena in multicomponent anisotropic space plasmas. In particular, a system of generalized transport equations is presented that can be applied to widely different plasma flow conditions. The generalized transport equations can describe subsonic and supersonic flows, collision-dominated and collisionless flows, plasma flows in rapidly changing magnetic field configurations, multicomponent plasma flows with large temperature differences between the interacting species, and plasma flows that contain anisotropic temperature distributions. In addition, if Maxwell's equations of electricity and magnetism are added to the system of transport equations, they can be used to model electrostatic shocks, double layers, and magnetic merging processes. These transport equations also contain terms which act to regulate both the heat flow and temperature anisotropy, processes which appear to be operating in the solar wind.
Anisotropic thermal transport in phosphorene: effects of crystal orientation.
Liu, Te-Huan; Chang, Chien-Cheng
2015-06-28
As an intrinsic thermally anisotropic material, the thermal properties of phosphorene must vary with respect to the crystal chirality. Nevertheless, previous studies of heat transfer in phosphorene have been limited to the 0.0° (zigzag, ZZ) and 90.0° (armchair, AC) chiralities. In this study, we investigate the orientation-dependent thermal transport in phosphorene sheets with a complete set of crystal chirality ranging from 0.0° to 90.0° using the Boltzmann transport equation (BTE) associated with the first-principles calculations. It was found that in the phosphorene sheets, the intrinsic thermal conductivity is a smooth monotonic decreasing function of the crystal chirality, which exhibits sinusoidal behavior bounded by the two terminated values 48.9 (0.0°) and 27.8 (90.0°) W m(-1) K(-1). The optical modes have unusually large contributions to heat transfer, which account for almost 30% of the total thermal conductivity of phosphorene sheets. This is because the optical phonons have comparable group velocities and relaxation times to the acoustic phonons. PMID:26024364
Anisotropic flow in transport+hydrodynamics hybrid approaches
Hannah Petersen
2014-11-26
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 RHIC and LHC energies, existing hybrid caluclations for collective flow observables at lower beam energies are discussed and remaining challenges outlined.
Investigation of anisotropic thermal transport in cross-linked polymers
NASA Astrophysics Data System (ADS)
Simavilla, David Nieto
Thermal transport in lightly cross-linked polyisoprene and polybutadine subjected to uniaxial elongation is investigated experimentally. We employ two experimental techniques to assess the effect that deformation has on this class of materials. The first technique, which is based on Forced Rayleigh Scattering (FRS), allows us to measure the two independent components of the thermal diffusivity tensor as a function of deformation. These measurements along with independent measurements of the tensile stress and birefringence are used to evaluate the stress-thermal and stress-optic rules. The stress-thermal rule is found to be valid for the entire range of elongations applied. In contrast, the stress-optic rule fails for moderate to large stretch ratios. This suggests that the degree of anisotropy in thermal conductivity depends on both orientation and tension in polymer chain segments. The second technique, which is based on infrared thermography (IRT), allows us to measure anisotropy in thermal conductivity and strain induced changes in heat capacity. We validate this method measurements of anisotropic thermal conductivity by comparing them with those obtained using FRS. We find excellent agreement between the two techniques. Uncertainty in the infrared thermography method measurements is estimated to be about 2-5 %. The accuracy of the method and its potential application to non-transparent materials makes it a good alternative to extend current research on anisotropic thermal transport in polymeric materials. A second IRT application allows us to investigate the dependence of heat capacity on deformation. We find that heat capacity increases with stretch ratio in polyisoprene specimens under uniaxial extension. The deviation from the equilibrium value of heat capacity is consistent with an independent set of experiments comparing anisotropy in thermal diffusivity and conductivity employing FRS and IRT techniques. We identify finite extensibility and strain-induced crystallization as the possible causes explaining our observations and evaluate their contribution making use of classical rubber elasticity results. Finally, we study of the role of evaporation-induced thermal effects in the well-know phenomena of the tears of wine. We develop a transport model and support its predictions by experimentally measuring the temperature gradient present in wine and cognac films using IRT. Our results demonstrate that the Marangoni flow responsible for wine tears results from both composition and temperature gradients, whose relative contribution strongly depends on the thermodynamic properties of ethanol-water mixtures. The methods developed here can be used to obtain a deeper understanding of Marangoni flows, which are ubiquitous in nature and modern technology.
Importance of anisotropic flow components for oceanic eddy-induced transport
NASA Astrophysics Data System (ADS)
Kamenkovich, I. V.; Berloff, P. S.; Rypina, I. I.
2012-12-01
This study explores the properties and origins of the oceanic eddy-induced material transport, using numerically simulated Lagrangian particle trajectories. This transport is strongly anisotropic, with the spreading rate in one direction ("major" direction) significantly exceeding the spreading rate in the across direction ("minor" direction), and is controlled by transient eddies with long length scales. In this regard, two types of spectral modes are critical for setting the anisotropic properties of the material transport: one corresponding to zonally-elongated Fourier modes (ZEMs), and the other - to meridionally-elongated Fourier modes (MEMs). In particular, ZEM-part of the spectrum dominates the zonal velocity variance and zonal material transport, and the MEM-part - the meridional velocity variance and meridional material transport. The velocity variance in the zonal and meridional directions are similar, but the Lagrangian decorrelation time scales are significantly longer in the major direction than in the minor one, and the anisotropy of the material transport cannot be derived from the velocity variance alone.; Anisotropic spectrum of transient eddies. Spectral power is shown as a function of zonal (x-axis) and meridional (y-axis) wavenumbers, nonimensionalized by the Rossby deformation radius. Note peaks corresponding to zonally- and meridionally elongated modes (ZEMs and MEMs).
Anisotropic transport rates in heterogeneous porous media
Nicholas B. Engdahl; Gary S. Weissmann
2010-01-01
We applied a recently developed method of aquifer characterization, which combines geophysics and geostatistics to create several heterogeneous realizations of a shallow fluvial aquifer that contain representations of sedimentary bounding surfaces. The influence of such small-scale (several centimeters) features on subsurface transport was investigated using high-resolution groundwater models of each of the subsurface realizations. Flow and transport through the models
Anisotropic magnetization and transport properties of RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm)
Myers, Kenneth D.
1999-11-08
This study of the RAgSb{sub 2} series of compounds arose as part of an investigation of rare earth intermetallic compounds containing antimony with the rare earth in a position with tetragonal point symmetry. Materials with the rare earth in a position with tetragonal point symmetry frequently manifest strong anisotropies and rich complexity in the magnetic properties, and yet are simple enough to analyze. Antimony containing intermetallic compounds commonly possess low carrier densities and have only recently been the subject of study. Large single grain crystals were grown of the RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm) series of compounds out of a high temperature solution. This method of crystal growth, commonly known as flux growth is a versatile method which takes advantage of the decreasing solubility of the target compound with decreasing temperature. Overall, the results of the crystal growth were impressive with the synthesis of single crystals of LaAgSb{sub 2} approaching one gram. However, the sample yield diminishes as the rare earth elements become smaller and heavier. Consequently, no crystals could be grown with R=Yb or Lu. Furthermore, EuAgSb{sub 2} could not be synthesized, likely due to the divalency of the Eu ion. For most of the RAgSb{sub 2} compounds, strong magnetic anisotropies are created by the crystal electric field splitting of the Hund's rule ground state. This splitting confines the local moments to lie in the basal plane (easy plane) for the majority of the members of the series. Exceptions to this include ErAgSb{sub 2} and TmAgSb{sub 2}, which have moments along the c-axis (easy axis) and CeAgSb{sub 2}, which at intermediate temperatures has an easy plane, but exchange coupling at low temperatures is anisotropic with an easy axis. Additional anisotropy is also observed within the basal plane of DyAgSb{sub 2}, where the moments are restricted to align along one of the {l_angle}110{r_angle} axes. Most of the RAgSb{sub 2} compounds containing magnetic rare earths, antiferromagnetically ordered at low temperatures. The ordering temperatures of these compounds are approximately proportional to the de Gennes factor, which suggests that the RKKY interaction is the dominant exchange interaction between local moments. Although metamagnetic transitions were observed in many members of the series, the series of sharp step-like transitions in DyAgSb{sub 2} are impressive. In this compound, up to 11 different magnetic states are stable depending on the magnitude and direction of the applied field. The saturated magnetization of these states and the critical fields needed to induce a phase transition vary with the direction of the applied field. Through detailed study of the angular dependence of the magnetization and critical fields, the net distribution of magnetic moments was determined for most, of the metamagnetic states. In DyAgSb{sub 2}, the crystal electric field (CEF) splitting of the Hund's rule ground state creates a strong anisotropy where the local Dy{sup 3+} magnetic moments are constrained to one of the equivalent {l_angle}110{r_angle} directions within the basal plane. The four position clock model was introduced to account for this rich metamagnetic system. Within this model, the magnetic moments are constrained to one of four equivalent orientations within the basal plane and interactions are calculated for up third nearest neighbors. The theoretical phase diagram, generated from the coupling constants is in excellent agreement with the experimental phase diagram. Further investigation of this compound using magnetic X-ray or neutron diffraction would be extremely useful to verify the net distributions of moments and determine the wave vectors of each of the ordered states.
Anisotropic properties in Fe-Pt thick film magnets
Nakano, M.; Shibata, S.; Yanai, T.; Fukunaga, H. [Department of Electrical and Electronic Engineering, Nagasaki University, Nagasaki 852-8521 (Japan)
2009-04-01
As-deposited Fe-Pt thick films prepared by a pulsed laser deposition method with the laser power higher than 5 W had L1{sub 0} ordered phase without a substrate heating system. As the laser power increased, the properties of the obtained films changed from isotropic to anisotropic ones. It was also confirmed that x-ray diffraction analysis agrees with the anisotropic phenomenon in crystalline structure with increasing laser power.
Anisotropic magnetic properties of TbNi2B2C single crystals
C. V. Tomy; L. A. Afalfiz; M. R. Lees; J. M. Martin; D. Mck. Paul; D. T. Adroja
1996-01-01
Magnetic and transport properties of single crystals of TbNi2B2C have been investigated by ac susceptibility, dc magnetization, specific heat, and resistance measurements. The compound shows highly anisotropic magnetic properties which come about as a result of the Tb magnetic moments lying predominantly in the ab plane. The ac susceptibility and low-field dc magnetization measurements indicate the presence of two magnetic
Theory for propulsion and transport in an anisotropic fluid
NASA Astrophysics Data System (ADS)
Powers, Thomas; Krieger, Madison; Spagnolie, Saverio
2013-11-01
Swimming microorganisms are typically found in complex fluids, which are full of polymers. When these polymers align, the fluid becomes anisotropic. We seek to understand how anisotropy affects swimming when the stroke is prescribed. We model the anisotropic fluid with a nematic liquid crystal. The swimmer is a two-dimensional sheet deforming via propagating transverse or longitudinal waves. We find that the nature of anchoring conditions for the nematic degrees of freedom plays a critical role in determining the swimming speed. Furthermore, we study the fluid transport induced by the swimmers motion by calculating the flux of fluid in the laboratory frame. Finally, we elucidate the various limits of the nematic theory, such as the six-fold symmetric hexatic case and Ericksen's transversely isotropic fluid.
NASA Technical Reports Server (NTRS)
Biolsi, Louis; Biolsi, David
1987-01-01
The strong long-range interactions between (among) charged species require the inclusion of higher order contributions to the transport properties (viscosity, thermal conductivity, diffusion) of ionized gases than are required for neutral gases. These higher order contributions have been rewritten so that they are given in terms of universal functions which can be tabulated. Tables which provide for the rapid calculation of some higher order contributions to the transport properties of both ions and electrons are given. Some results which are useful for calculating the higher order contributions to the transport properties of mixtures of ions are also given. These results are applied to the ionic species in air at high temperatures.
Anisometric transport of ions and particles in anisotropic tissue spaces.
Grover, N B
1966-01-01
The results of time-lapse measurements and electron microscopic observations on the diffusion of histological dyes, colloidal particles, and heavy metal salts in excised chicken breast tendon are reported. In all cases, the transport was found to be anisometric, the extent of the spreading being much greater parallel than perpendicular to the collagen fibers. The diffusion of colloidal gold was shown to be governed by a random diffusion process, with coefficients of 3 to 5 x 10(-7) and 1 to 2 x 10(-7) cm(2)/sec for the parallel and perpendicular directions, respectively; the anisotropy was attributed to steric hindrance. In the diffusion of uranyl nitrate, a sharp boundary appeared at the leading edge of the diffusate and advanced at a rate proportional to the square root of time. Electron micrographs showed uranyl nitrate clusters localized in space on the surface of the collagen fibrils and tightly bound to the polar amino acid regions of the macromolecule. A model was proposed involving diffusion with attrition, and predicted a sharp boundary advancing proportionally to the square root of time and to the 0.65 power of the initial diffusate concentration. Application of the model to the experimental results for uranyl nitrate gave a diffusion coefficient of 10 x 10(-7) and 4 x 10(-7) cm(2)/sec for the parallel and perpendicular directions, respectively, and a possible explanation of this large difference was advanced. The importance of anisometric transport in anisotropic tissues was indicated. PMID:5903153
Anisotropic wetting properties on various shape of parallel grooved microstructure.
Tie, Lu; Guo, Zhiguang; Liu, Weimin
2015-09-01
It has been revealed experimentally that some superhydrophobic surfaces in nature, such as rice leaf, show strong anisotropic wetting behavior. In this work, based on a thermodynamic approach, the effects of profile shape of parallel grooved microstructure on free energy (FE) with its barrier (FEB) and equilibrium contact angle (ECA) with its hysteresis (CAH) for various orientations of different parallel micro texture surface have been systematically investigated in detail. The results indicated that the anisotropy of wetting properties strongly depended on the specific topographical features and wetting state. In particular, a paraboloidal profile of parallel micro-texture surface is used as an important example to theoretically establish the relationship between surface geometry and anisotropic wetting behavior for optimal design, showing that the wetting behavior of the composite state is similar to that of the non-composite state and the anisotropy will possibly be appeared with the decrease of height or intrinsic contact angle of paraboloidal profile of micro texture. PMID:25982937
Anisotropic transport in modulation-doped quantum-well structures
NASA Technical Reports Server (NTRS)
Radulescu, D. C.; Wicks, G. W.; Schaff, W. J.; Calawa, A.R.; Eastman, L. F.
1987-01-01
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.
Anisometric Transport of Ions and Particles in Anisotropic Tissue Spaces
Grover, N. B.
1966-01-01
The results of time-lapse measurements and electron microscopic observations on the diffusion of histological dyes, colloidal particles, and heavy metal salts in excised chicken breast tendon are reported. In all cases, the transport was found to be anisometric, the extent of the spreading being much greater parallel than perpendicular to the collagen fibers. The diffusion of colloidal gold was shown to be governed by a random diffusion process, with coefficients of 3 to 5 × 10-7 and 1 to 2 × 10-7 cm2/sec for the parallel and perpendicular directions, respectively; the anisotropy was attributed to steric hindrance. In the diffusion of uranyl nitrate, a sharp boundary appeared at the leading edge of the diffusate and advanced at a rate proportional to the square root of time. Electron micrographs showed uranyl nitrate clusters localized in space on the surface of the collagen fibrils and tightly bound to the polar amino acid regions of the macromolecule. A model was proposed involving diffusion with attrition, and predicted a sharp boundary advancing proportionally to the square root of time and to the 0.65 power of the initial diffusate concentration. Application of the model to the experimental results for uranyl nitrate gave a diffusion coefficient of 10 × 10-7 and 4 × 10-7 cm2/sec for the parallel and perpendicular directions, respectively, and a possible explanation of this large difference was advanced. The importance of anisometric transport in anisotropic tissues was indicated. ImagesFigure 1Figure 4Figure 5Figure 6 PMID:5903153
Anisotropic MRI contrast reveals enhanced ionic transport in plastic crystals.
Romanenko, Konstantin; Jin, Liyu; Madsen, Louis A; Pringle, Jennifer M; O'Dell, Luke A; Forsyth, Maria
2014-11-01
Organic ionic plastic crystals (OIPCs) are attractive as solid-state electrolytes for electrochemical devices such as lithium-ion batteries and solar and fuel cells. OIPCs offer high ionic conductivity, nonflammability, and versatility of molecular design. Nevertheless, intrinsic ion transport behavior of OIPCs is not fully understood, and their measured properties depend heavily on thermal history. Solid-state magnetic resonance imaging experiments reveal a striking image contrast anisotropy sensitive to the orientation of grain boundaries in polycrystalline OIPCs. Probing triethyl(methyl)phosphonium bis(fluorosulfonyl)imide (P1222FSI) samples with different thermal history demonstrates vast variations in microcrystallite alignment. Upon slow cooling from the melt, microcrystallites exhibit a preferred orientation throughout the entire sample, leading to an order of magnitude increase in conductivity as probed using impedance spectroscopy. This investigation describes both a new conceptual window and a new characterization method for understanding polycrystalline domain structure and transport in plastic crystals and other solid-state conductors. PMID:25312993
Anisotropic Structure and Transport in Self-Assembled Layered Polymer-Clay Nanocomposites
Sadoway, Donald Robert
Anisotropic Structure and Transport in Self-Assembled Layered Polymer-Clay Nanocomposites Jodie L a polymer-clay structure from a unique combination of LbL materials: poly(ethylene imine), Laponite clay transport in LbL assemblies and its correlation to structural anisotropy. Introduction Synthetic clays
Effective Transport Properties
NASA Astrophysics Data System (ADS)
Mauri, Roberto
In this chapter we study a particular case of multiphase systems, namely two-phase materials in which one of the phases is randomly dispersed in the other, so that the composite can be viewed on a macroscale as an effective continuum, with well defined properties. In general, the theoretical determination of the parameter for an effective medium requires, as a rule, the solution of a corresponding transport problem at the microscale, which takes into account the morphology of the system and its evolution. As the mathematical problem is well-posed on a microscale, this can be accomplished using, for example, the multiple scale approach shown in Chap.
The effect of anisotropic reflectance on imaging spectroscopy of snow properties
Dozier, Jeff
The effect of anisotropic reflectance on imaging spectroscopy of snow properties Thomas H. Paintera in revised form 19 September 2003; accepted 30 September 2003 Abstract How does snow's anisotropic directional reflectance affect the mapping of snow properties from imaging spectrometer data? This sensitivity
Blazevski, Daniel; del-Castillo-Negrete, Diego
2013-06-01
A study of anisotropic heat transport in reversed shear (nonmonotonic q-profile) magnetic fields is presented. The approach is based on a recently proposed Lagrangian-Green's function method that allows an efficient and accurate integration of the parallel (i.e., along the magnetic field) heat transport equation. The magnetic field lines are described by a nontwist Hamiltonian system, known to exhibit separatrix reconnection and robust shearless (dq/dr=0) transport barriers. The changes in the magnetic field topology due to separatrix reconnection lead to bifurcations in the equilibrium temperature distribution. For perturbations of moderate amplitudes, magnetic chaos is restricted to bands flanking the shearless region. As a result, the temperature flattens in the chaotic bands and develops a very sharp radial gradient at the shearless region. For perturbations with larger amplitude, shearless Cantori (i.e., critical magnetic surfaces located at the minimum of the q profile) give rise to anomalous temperature relaxation involving widely different time scales. The first stage consists of the relatively fast flattening of the radial temperature profile in the chaotic bands with negligible flux across the shearless region that, for practical purposes, on a short time scale acts as an effective transport barrier despite the lack of magnetic flux surfaces. In the long-time scale, heat starts to flow across the shearless region, albeit at a comparatively low rate. The transport of a narrow temperature pulse centered at the reversed shear region exhibits weak self-similar scaling with non-Gaussian scaling functions indicating that transport at this scale cannot be modeled as a diffusive process with a constant diffusivity. Evidence of nonlocal effective radial transport is provided by the existence of regions with nonzero heat flux and zero temperature gradient. Parametric flux-gradient plots exhibit multivalued loops that question the applicability of the Fourier-Fick's prescription even in the presence of a finite pinch velocity. PMID:23848788
Anisotropic Elastic Resonance Scattering model for the Neutron Transport equation
Mohamed Ouisloumen; Abderrafi M. Ougouag; Shadi Z. Ghrayeb
2014-11-24
The resonance scattering transfer cross-section has been reformulated to account for anisotropic scattering in the center-of-mass of the neutron-nucleus system. The main innovation over previous implementations is the relaxation of the ubiquitous assumption of isotropic scattering in the center-of-mass and the actual effective use of scattering angle distributions from evaluated nuclear data files in the computation of the angular moments of the resonant scattering kernels. The formulas for the high order anisotropic moments in the laboratory system are also derived. A multi-group numerical formulation is derived and implemented into a module incorporated within the NJOY nuclear data processing code. An ultra-fine energy mesh cross section library was generated using these new theoretical models and then was used for fuel assembly calculations with the PARAGON lattice physics code. The results obtained indicate a strong effect of this new model on reactivity, multi-group fluxes and isotopic inventory during depletion.
Holographic transports and stability in anisotropic linear axion model
Ge, Xian-Hui; Niu, Chao; Sin, Sang-Jin
2014-01-01
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.
Time-dependent macrodispersion for solute transport in anisotropic heterogeneous aquifers
Gedeon Dagan
1988-01-01
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
Time-independent one-speed neutron transport equation with anisotropic scattering in absorbing media
Hangelbroek, R. J.
1980-06-01
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.
Reentrant Quantum Hall Effect and Anisotropic Transport in a Bilayer System at High Filling Factors
Gusev, Guennady
Reentrant Quantum Hall Effect and Anisotropic Transport in a Bilayer System at High Filling Factors 17 May 2007; published 20 September 2007) We report on the measurements of the quantum Hall effect is the Landau index number, in the presence of the in-plane magnetic field. The quantum Hall states
Anisotropic vanadium dioxide sculptured thin films with superior thermochromic properties
Sun, Yaoming; Xiao, Xiudi; Xu, Gang; Dong, Guoping; Chai, Guanqi; Zhang, Hua; Liu, Pengyi; Zhu, Hanmin; Zhan, Yongjun
2013-01-01
VO2 (M) STF through reduction of V2O5 STF was prepared. The results illustrate that V2O5 STF can be successfully obtained by oblique angle thermal evaporation technique. After annealing at 550°C/3?min, the V2O5 STF deposited at 85° can be easily transformed into VO2 STF with slanted columnar structure and superior thermochromic properties. After deposition SiO2 antireflective layer, Tlum of VO2 STF is enhanced 26% and ?Tsol increases 60% compared with that of normal VO2 thin films. Due to the anisotropic microstructure of VO2 STF, angular selectivity transmission of VO2 STF is observed and the solar modulation ability is further improved from 7.2% to 8.7% when light is along columnar direction. Moreover, the phase transition temperature of VO2 STF can be depressed into 54.5°C without doping. Considering the oblique incidence of sunlight on windows, VO2 STF is more beneficial for practical application as smart windows compared with normal homogenous VO2 thin films. PMID:24067743
Viscous corrections to anisotropic flow and transverse momentum spectra from transport theory
Plumari, Salvatore; Greco, Vincenzo; Ollitrault, Jean-Yves
2015-01-01
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...
Ultrasonic evaluation of interfacial properties in imperfect anisotropic layered substrates
Ko, R.T.
1993-01-01
Interface conditions in layered substrates are critical to the performance of these materials. Most studies of interface conditions in layered substrates are confined to the extreme cases and give no details about the intermediate cases. In this study the lowest order mode of the generalized Lamb wave was used to examine the interfacial properties of imperfect layered substrates. Anisotropic specimens of various configurations with controlled interface conditions were made with a meshed intervening layer technique. It was noted that at very low and very high frequencies the effect of anisotropy of the dispersion curve in a silicon layered substrate was significant. The results also showed that the position of the turning point in the dispersion curve was sensitive to bond quality variation. As the quality of bonding decreased, this turning point shifted toward low velocities and frequencies and finally resembled that of the completely misbonded case. Furthermore, empirical formula which relate the stiffness constant and the position of the turning point for a partially bonded material were also obtained. It is noteworthy that the position of the turning point does not vary significantly with orientation. By incorporating an effective interface layer into a multiple layer formulation and comparing the calculated results with the experimental data, the interfacial properties of the layered substrate were evaluated. Moreover, the shape of the dispersion curve of this lowest order mode was found to be dependent on the bond quality and anisotropy, but the dominating factor was the bond quality. Therefore, the turning point in the dispersion curve of the lowest order mode may be used to assess bond quality in an anistropic layered substrate.
Electric field activated nonlinear anisotropic charge transport in doped polypyrrole
NASA Astrophysics Data System (ADS)
Varade, Vaibhav; Anjaneyulu, P.; Suchand Sangeeth, C. S.; Ramesh, K. P.; Menon, R.
2013-12-01
Electric field activated nonlinear transport is investigated in polypyrrole thin film in both in-plane and out-of-plane geometries down to 5 K and strong anisotropy is observed. A morphological model is suggested to explain the anisotropy through inter-chain and intra-chain transport. The deviation from the variable range hopping at low temperature is accounted by fluctuation assisted transport. From Zabrodaskii plots, it is found that electric field can tune the transport from insulating to metallic regime. Glazman-Matveev model is used to describe the nonlinear conduction. Field scaling analysis shows that conductance data at different temperature falls on to a single curve. Nonlinearity exponent, mT and characteristic length, LE are estimated to characterize the transport in both the geometries.
An engineered anisotropic nanofilm with unidirectional wetting properties
Niranjan A. Malvadkar; Matthew J. Hancock; Koray Sekeroglu; Walter J. Dressick; Melik C. Demirel
2010-01-01
Anisotropic textured surfaces allow water striders to walk on water, butterflies to shed water from their wings and plants to trap insects and pollen. Capturing these natural features in biomimetic surfaces is an active area of research. Here, we report an engineered nanofilm, composed of an array of poly(p-xylylene) nanorods, which demonstrates anisotropic wetting behaviour by means of a pin-release
Transport properties of uranium dioxide
Fink, J.K.; Chasanov, M.G.; Leibowitz, L.
1981-04-01
In order to provide reliable and consistent data on the thermophysical properties of reactor materials for reactor safety studies, this revision is prepared for the transport properties of the uranium dioxide portion of the fuel property section of the report Properties for LMFBR Safety Analysis. Since the original report was issued in 1976, measurements of thermal diffusivity and emissivity have been made. In addition to incorporating this new data, new equations have been derived to fit the thermal diffusivity and thermal conductivity data. This analysis is consistent with the analysis of enthalpy and heat capacity. A new form of equation for the emissivity is also given. The present report comprises the transport part of the UO/sub 2/ portion of section A of the planned complete revision of Properties for LMFBR Safety Analysis.
Anisotropic heat transport in integrable and chaotic 3-D magnetic fields
Del-Castillo-Negrete, Diego B [ORNL] [ORNL; Blazevski, D. [University of Texas, Austin] [University of Texas, Austin; Chacon, Luis [ORNL] [ORNL
2012-01-01
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.
Spatial frequency analysis of anisotropic drug transport in tumor samples
NASA Astrophysics Data System (ADS)
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
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.
Uncluttering Graph Layouts Using Anisotropic Diffusion and Mass Transport
Tal, Ayellet
optimal mass transport problems, a warp to the improved density image is computed. The graph nodes are displaced according to the warp. The warp maintains the overall structure of the graph, thus limiting of graphs [1], [2]. It has applications in a variety of areas, including software engineering, software
Transport in anisotropic model systems analyzed by a correlated projection superoperator technique
Hendrik Weimer; Mathias Michel; Jochen Gemmer; Günter Mahler
2008-01-17
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.
Transport in anisotropic model systems analyzed by a correlated projection superoperator technique.
Weimer, Hendrik; Michel, Mathias; Gemmer, Jochen; Mahler, Günter
2008-01-01
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 Schrödinger equation. PMID:18351829
Zhang, Rujing; Chen, Qiao; Zhen, Zhen; Jiang, Xin; Zhong, Minlin; Zhu, Hongwei
2015-09-01
Assembling particular building blocks into composites with diverse targeted structures has attracted considerable interest for understanding its new properties and expanding the potential applications. Anisotropic organization is considered as a frequently used targeted architecture and possesses many peculiar properties because of its unusual shapes. Here, we show that anisotropic graphene monoliths (AGMs), three-dimensional architectures of well-aligned graphene sheets obtained by a dip-coating method using cellulose acetate fibers as templates show thermal-insulating, fire-retardant, and anisotropic properties. They exhibit a feature of higher mechanical strength and thermal/electrical conductivities in the axial direction than in the radial direction. Elastic polymer resins are then introduced into the pores of the AGMs to form conductive and flexible composites. The composites, as AGMs, retain the unique anisotropic properties, revealing opposite resistance change under compressions in different directions. The outstanding anisotropic properties of AGMs make them possible to be applied in the fields of thermal insulation, integrated circuits, and electromechanical devices. PMID:26284380
NASA Astrophysics Data System (ADS)
Kaleta, Jerzy; Królewicz, Micha?; Lewandowski, Daniel
2011-08-01
In this paper the magnetomechanical properties of magnetorheological (MR) elastomers with isotropic and anisotropic structure are examined. A method for manufacturing magnetorheological elastomers (MRE) with thermoplastic elastomer matrix and 60 µm iron particles is presented. The influence of various chemical compositions on the material parameters is investigated. The properties of isotropic and anisotropic MR elastomers are examined in a wide range of mechanical and magnetic stimulations. Test samples are subjected to cyclic shearing with a constant frequency of 1 Hz. The change in magnetomechanical properties is expressed by the relative change of hysteresis loop area ?W and stress amplitude ??.
NASA Astrophysics Data System (ADS)
Zheng, J.; Zhu, J.; Wang, Z.; Fang, F.; Pain, C. C.; Xiang, J.
2015-06-01
A new anisotropic hr-adaptive mesh technique has been applied to modelling of multiscale transport phenomena, which is based on a discontinuous Galerkin/control volume discretization on unstructured meshes. Over existing air quality models typically based on static-structured grids using a locally nesting technique, the advantage of the anisotropic hr-adaptive model has the ability to adapt the mesh according to the evolving pollutant distribution and flow features. That is, the mesh resolution can be adjusted dynamically to simulate the pollutant transport process accurately and effectively. To illustrate the capability of the anisotropic adaptive unstructured mesh model, three benchmark numerical experiments have been setup for two-dimensional (2-D) transport phenomena. Comparisons have been made between the results obtained using uniform resolution meshes and anisotropic adaptive resolution meshes.
Transport Properties for Combustion Modeling
Brown, N.J.; Bastein, L.; Price, P.N.
2010-02-19
This review examines current approximations and approaches that underlie the evaluation of transport properties for combustion modeling applications. Discussed in the review are: the intermolecular potential and its descriptive molecular parameters; various approaches to evaluating collision integrals; supporting data required for the evaluation of transport properties; commonly used computer programs for predicting transport properties; the quality of experimental measurements and their importance for validating or rejecting approximations to property estimation; the interpretation of corresponding states; combination rules that yield pair molecular potential parameters for unlike species from like species parameters; and mixture approximations. The insensitivity of transport properties to intermolecular forces is noted, especially the non-uniqueness of the supporting potential parameters. Viscosity experiments of pure substances and binary mixtures measured post 1970 are used to evaluate a number of approximations; the intermediate temperature range 1 < T* < 10, where T* is kT/{var_epsilon}, is emphasized since this is where rich data sets are available. When suitable potential parameters are used, errors in transport property predictions for pure substances and binary mixtures are less than 5 %, when they are calculated using the approaches of Kee et al.; Mason, Kestin, and Uribe; Paul and Warnatz; or Ern and Giovangigli. Recommendations stemming from the review include (1) revisiting the supporting data required by the various computational approaches, and updating the data sets with accurate potential parameters, dipole moments, and polarizabilities; (2) characterizing the range of parameter space over which the fit to experimental data is good, rather than the current practice of reporting only the parameter set that best fits the data; (3) looking for improved combining rules, since existing rules were found to under-predict the viscosity in most cases; (4) performing more transport property measurements for mixtures that include radical species, an important but neglected area; (5) using the TRANLIB approach for treating polar molecules and (6) performing more accurate measurements of the molecular parameters used to evaluate the molecular heat capacity, since it affects thermal conductivity, which is important in predicting flame development.
An Algorithm for the Transport of Anisotropic Neutrons
NASA Technical Reports Server (NTRS)
Tweed, J.
2005-01-01
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.
NASA Astrophysics Data System (ADS)
Kunz, Matthew W.
2011-10-01
In weakly collisional plasmas such as the intracluster medium (ICM), heat and momentum transport become anisotropic with respect to the local magnetic field direction. Anisotropic heat conduction causes the slow magnetosonic wave to become buoyantly unstable to the magnetothermal instability (MTI) when the temperature increases in the direction of gravity and to the heat-flux-driven buoyancy instability (HBI) when the temperature decreases in the direction of gravity. The local changes in magnetic field strength that attend these instabilities cause pressure anisotropies that viscously damp motions parallel to the magnetic field. In this paper we employ a linear stability analysis to elucidate the effects of anisotropic viscosity (i.e. Braginskii pressure anisotropy) on the MTI and HBI. By stifling the convergence/divergence of magnetic field lines, pressure anisotropy significantly affects how the ICM interacts with the temperature gradient. Instabilities which depend upon the convergence/divergence of magnetic field lines to generate unstable buoyant motions (the HBI) are suppressed over much of the wavenumber space, whereas those which are otherwise impeded by field-line convergence/divergence (the MTI) are strengthened. As a result, the wavenumbers at which the HBI survives largely unsuppressed in the ICM have parallel components too small to rigorously be considered local. This is particularly true as the magnetic field becomes more and more orthogonal to the temperature gradient. The field-line insulation found by recent numerical simulations to be a non-linear consequence of the standard HBI might therefore be attenuated. In contrast, the fastest growing MTI modes are unaffected by anisotropic viscosity. However, we find that anisotropic viscosity couples slow and Alfvén waves in such a way as to buoyantly destabilize Alfvénic fluctuations when the temperature increases in the direction of gravity. Consequently, many wavenumbers previously considered MTI stable or slow growing are in fact maximally unstable. We discuss the physical interpretation of these instabilities in detail.
Mechanical transport and porous media equivalence in anisotropic fracture networks
Endo, H.K.; Witherspoon, P.A.
1985-01-01
The objective of this work is to investigate the directional characteristics of hydraulic effective porosity in an effort to understand porous medium equivalence for continuous and discontinuous fracture systems. Continuous systems contain infinitely long fractures. Discontinuous systems consist of fractures with finite lengths. The distribution of apertures (heterogeneity) has a major influence on the degree of porous medium equivalence for distributed continuous and discontinuous systems. When the aperture distribution is narrow, the hydraulic effective porosity is slightly less than the total porosity for continuous systems, and greater than the rock effective porosity for discontinuous systems. However, when heterogeneity is significant, the hydraulic effective porosity is directionally dependent and greater than total porosity for both systems. Non-porous medium behavior ws found to differ for distributed continuous systems and for continuous systems with parallel sets. For the latter systems, hydraulic effective porosity abruptly decreases below total porosity in those particular directions where the hydraulic gradient and the orientation of a fracture set are orthogonal. The results for the continuous systems with parallel sets also demonstrate that a system that behaves like a continuum for fluid flux may not behave like a continuum for mechanical transport. 3 references, 13 figures.
Transport properties in the atmosphere of Jupiter
NASA Technical Reports Server (NTRS)
Biolsi, L., Jr.
1979-01-01
Activities reported include: (1) testing of the computer program used to obtain transport properties for the Hulburt-Hirschfelder potential; (2) calculation of transport properties for the C2-C interaction; (3) preliminary calculations for the C2-C2 interaction; (4) calculation of transport properties for the C2H-He interaction; (5) consideration of the effect of inelastic collisions on the transport properties; and (6) the use of the Hulburt-Hirschfelder potential to model ion-atom interactions.
Transport properties in the atmosphere of Jupiter
NASA Technical Reports Server (NTRS)
Biolsi, L., Jr.
1978-01-01
The calculation of transport properties near the surface of a probe entering the atmosphere of Jupiter is discussed for (1) transport properties in the pure Jovian atmosphere, (2) transport properties for collisions between monatomic carbon atoms, including the effect of excited electronic states, (3) transport properties at the boundaries for mixing of the pure Jovian atmosphere and the atmosphere due to the injection of gaseous ablation products, and (4) transport properties for interactions involving some of the molecular ablation products. The transport properties were calculated using the kinetic theory of gases. Transport collision integrals were calculated for only a limited set of empirical and semiempirical interaction potentials. Since the accuracy of the fit of these empirical potentials to the true potential usually determines the accuracy of the calculation of the transport properties, the various interaction potentials used in these calculations are discussed.
The Isotropy Problem of Ultra-High Energy Cosmic Rays: The Effects of Anisotropic Transport
NASA Astrophysics Data System (ADS)
Kumar, Rahul; Eichler, David
2013-04-01
Time dependent anisotropic transport of ultra-high energy cosmic rays (UHECRs) from point-like sources in the Galaxy is calculated in various ways. To fully account for the discreteness of UHECR sources in space and time, the Monte Carlo method is used to randomly place sources in the Galaxy and calculate the anisotropy of UHECR flux, given specific realisations of source distribution. We show that reduction in the rate of cross-field transport reduces the anisotropy. However, if the crossfield transport is very small, drift of UHECRs in the Galactic magnetic field (GMF) becomes the dominant contributor to the anisotropy. Test particle simulations further illustrate the effect of drift and verify our analytical calculation. The surprisingly low anisotropy measured by Auger can be interpreted as intermittency of UHECR sources, without invoking a flat source distribution and/or a high source rate. Frequent events that follow star formation, such as hypernovae, imply an anisotropy that exceeds the Auger limit.
Scaling Properties of Fidelity in Spin-one Anisotropic Model
Yu-Chin Tzeng; Min-Fong Yang
2008-01-14
By means of the density matrix renormalization group technique, the scaling relation of the fidelity susceptibility proposed recently is verified for the spin-one XXZ spin chain with an on-site anisotropic term. Moreover, from the results of both the fidelity susceptibility and the entanglement entropy, the critical points and some of the corresponding critical exponents are determined through a proper finite-size scaling analysis, and these values agree with the findings in the literature. Thus our work provides a numerical support of the use of the fidelity in detecting quantum phase transitions.
Viscous corrections to anisotropic flow and transverse momentum spectra from transport theory
Salvatore Plumari; Giovanni Luca Guardo; Vincenzo Greco; Jean-Yves Ollitrault
2015-07-10
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 in viscous hydrodynamic calculations. In particular, it is too slow to explain the observed maximum of $v_n$ at $p_T\\sim 3$ GeV/c.
Chacon, Luis [Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); del-Castillo-Negrete, Diego [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Hauck, Cory D. [Univ. of Tennessee, Knoxville, TN (United States)
2014-09-01
We propose a Lagrangian numerical algorithm for a time-dependent, anisotropic temperature transport equation in magnetized plasmas in the large guide field regime. The approach is based on an analytical integral formal solution of the parallel (i.e., along the magnetic field) transport equation with sources, and it is able to accommodate both local and non-local parallel heat flux closures. The numerical implementation is based on an operator-split formulation, with two straightforward steps: a perpendicular transport step (including sources), and a Lagrangian (field-line integral) parallel transport step. Algorithmically, the first step is amenable to the use of modern iterative methods, while the second step has a fixed cost per degree of freedom (and is therefore scalable). Accuracy-wise, the approach is free from the numerical pollution introduced by the discrete parallel transport term when the perpendicular to parallel transport coefficient ratio X_{?} /X_{?} becomes arbitrarily small, and is shown to capture the correct limiting solution when ? = X?L^{2}_{?}/X1L^{2}_{?} ? 0 (with L?? L? , the parallel and perpendicular diffusion length scales, respectively). Therefore, the approach is asymptotic-preserving. We demonstrate the capabilities of the scheme with several numerical experiments with varying magnetic field complexity in two dimensions, including the case of transport across a magnetic island.
Fritz, Harald
Preliminary investigation results on fabrics and related physical properties of an anisotropic June 2000 Abstract In order to evaluate the fabric-dependent anisotropy of a particular gneiss type, we; Siegesmund, 1996; PrÏikryl, 1998) has remained a rewarding task and several attempts from the engineering
Magneto-transport properties in layered manganite crystals
Kimura, T.; Tomioka, Y.; Okuda, T.; Kuwahara, H.; Asamitsu, A. [Joint Research Center for Atom Technology, Tsukuba, Ibaraki (Japan); Tokura, Y. [Univ. of Tokyo (Japan). Dept. of Applied Physics
1998-12-31
Anisotropic charge transport and magnetic properties have been investigated for single crystals of the layered manganite, La{sub 2{minus}2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7} (0.3 {le} x {le} 0.5). Remarkable variations in the magnetic structure as well as in the charge-transport properties are observed with changing doping-level x. A crystal with x = 0.3 behaves like a 2-dimensional ferromagnetic metal in the temperature region between {approximately} 90 K and {approximately} 270 K, and shows the interplane tunneling magnetoresistance at lower temperatures. These characteristic charge-transport properties are attributed to the interplane magnetic coupling between the adjacent MnO{sub 2} bilayers, and are strongly affected by the application of pressure as well as low magnetic fields through the change in magnetic structure. With increase of the carrier concentration toward x = 0.5, the charge-ordered phase is stabilized and dominates the charge transport and magnetic properties.
Anisotropic effective-medium modeling of the elastic properties of shales
Hornby, B.E. (Schlumberger Cambridge Research Ltd. (United Kingdom) Bullard Labs., Cambridge (United Kingdom). Dept. of Earth Sciences); Schwartz, L.M. (Schlumberger-Doll Research, Ridgefield, CT (United States)); Hudson, J.A. (Dept. of Applied Maths and Theoretical Physics, Cambridge (United Kingdom))
1994-10-01
Shales are complex porous materials, normally consisting of percolating and interpenetrating fluid and solid phases. The solid phase is generally comprised of several mineral components and forms an intricate and anisotropic microstructure. The shape, orientation, and connection of the two phases control the anisotropic elastic properties of the composite solid. The authors develop a theoretical framework that allows one to predict the effective elastic properties of shales. Its usefulness is demonstrated with numerical modeling and by comparison with established ultrasonic laboratory experiments. The theory is based on a combination of anisotropic formulations of the self-consistent (SCA) and differential effective-medium (DEM) approximations. This combination guarantees that both the fluid and solid phases percolate at all porosities. The modeling of the elastic properties of shales proceeds in four steps. First, the authors consider the case of an aligned biconnected clay-fluid composite composed of ellipsoidal inclusions. Anisotropic elastic constants are estimated for a clay-fluid composite as a function of the fluid-filled porosity and the aspect ratio of the inclusions. Second, a new processing technique is developed to estimate the distribution of clay platelet orientations from digitized scanning electron microphotographs (SEM). Third, the derived clay platelet distribution is employed to estimate the effective elastic parameters of a solid comprising clay-fluid composites oriented at different angles. Finally, silt minerals are included in the calculations as isolated spherical inclusions.
Landau levels and magneto-transport property of monolayer phosphorene
NASA Astrophysics Data System (ADS)
Zhou, X. Y.; Zhang, R.; Sun, J. P.; Zou, Y. L.; Zhang, D.; Lou, W. K.; Cheng, F.; Zhou, G. H.; Zhai, F.; Chang, Kai
2015-07-01
We investigate theoretically the Landau levels (LLs) and magneto-transport properties of phosphorene under a perpendicular magnetic field within the framework of the effective k·p Hamiltonian and tight-binding (TB) model. At low field regime, we find that the LLs linearly depend both on the LL index n and magnetic field B, which is similar with that of conventional semiconductor two-dimensional electron gas. The Landau splittings of conduction and valence band are different and the wavefunctions corresponding to the LLs are strongly anisotropic due to the different anisotropic effective masses. An analytical expression for the LLs in low energy regime is obtained via solving the decoupled Hamiltonian, which agrees well with the numerical calculations. At high magnetic regime, a self-similar Hofstadter butterfly (HB) spectrum is obtained by using the TB model. The HB spectrum is consistent with the LL fan calculated from the effective k·p theory in a wide regime of magnetic fields. We find the LLs of phosphorene nanoribbon depend strongly on the ribbon orientation due to the anisotropic hopping parameters. The Hall and the longitudinal conductances (resistances) clearly reveal the structure of LLs.
Landau levels and magneto-transport property of monolayer phosphorene
Zhou, X. Y.; Zhang, R.; Sun, J. P.; Zou, Y. L.; Zhang, D.; Lou, W. K.; Cheng, F.; Zhou, G. H.; Zhai, F.; Chang, Kai
2015-01-01
We investigate theoretically the Landau levels (LLs) and magneto-transport properties of phosphorene under a perpendicular magnetic field within the framework of the effective k·p Hamiltonian and tight-binding (TB) model. At low field regime, we find that the LLs linearly depend both on the LL index n and magnetic field B, which is similar with that of conventional semiconductor two-dimensional electron gas. The Landau splittings of conduction and valence band are different and the wavefunctions corresponding to the LLs are strongly anisotropic due to the different anisotropic effective masses. An analytical expression for the LLs in low energy regime is obtained via solving the decoupled Hamiltonian, which agrees well with the numerical calculations. At high magnetic regime, a self-similar Hofstadter butterfly (HB) spectrum is obtained by using the TB model. The HB spectrum is consistent with the LL fan calculated from the effective k·p theory in a wide regime of magnetic fields. We find the LLs of phosphorene nanoribbon depend strongly on the ribbon orientation due to the anisotropic hopping parameters. The Hall and the longitudinal conductances (resistances) clearly reveal the structure of LLs. PMID:26159856
Multimodel analysis of anisotropic diffusive tracer-gas transport in a deep arid unsaturated zone
Green, Christopher T.; Walvoord, Michelle Ann; Andraski, Brian J.; Striegl, Rob; Stonestrom, David A.
2015-01-01
Gas transport in the unsaturated zone affects contaminant flux and remediation, interpretation of groundwater travel times from atmospheric tracers, and mass budgets of environmentally important gases. Although unsaturated zone transport of gases is commonly treated as dominated by diffusion, the characteristics of transport in deep layered sediments remain uncertain. In this study, we use a multimodel approach to analyze results of a gas-tracer (SF6) test to clarify characteristics of gas transport in deep unsaturated alluvium. Thirty-five separate models with distinct diffusivity structures were calibrated to the tracer-test data and were compared on the basis of Akaike Information Criteria estimates of posterior model probability. Models included analytical and numerical solutions. Analytical models provided estimates of bulk-scale apparent diffusivities at the scale of tens of meters. Numerical models provided information on local-scale diffusivities and feasible lithological features producing the observed tracer breakthrough curves. The combined approaches indicate significant anisotropy of bulk-scale diffusivity, likely associated with high-diffusivity layers. Both approaches indicated that diffusivities in some intervals were greater than expected from standard models relating porosity to diffusivity. High apparent diffusivities and anisotropic diffusivity structures were consistent with previous observations at the study site of rapid lateral transport and limited vertical spreading of gas-phase contaminants. Additional processes such as advective oscillations may be involved. These results indicate that gases in deep, layered unsaturated zone sediments can spread laterally more quickly, and produce higher peak concentrations, than predicted by homogeneous, isotropic diffusion models.
Multimodel analysis of anisotropic diffusive tracer-gas transport in a deep arid unsaturated zone
NASA Astrophysics Data System (ADS)
Green, Christopher T.; Walvoord, Michelle A.; Andraski, Brian J.; Striegl, Robert G.; Stonestrom, David A.
2015-08-01
Gas transport in the unsaturated zone affects contaminant flux and remediation, interpretation of groundwater travel times from atmospheric tracers, and mass budgets of environmentally important gases. Although unsaturated zone transport of gases is commonly treated as dominated by diffusion, the characteristics of transport in deep layered sediments remain uncertain. In this study, we use a multimodel approach to analyze results of a gas-tracer (SF6) test to clarify characteristics of gas transport in deep unsaturated alluvium. Thirty-five separate models with distinct diffusivity structures were calibrated to the tracer-test data and were compared on the basis of Akaike Information Criteria estimates of posterior model probability. Models included analytical and numerical solutions. Analytical models provided estimates of bulk-scale apparent diffusivities at the scale of tens of meters. Numerical models provided information on local-scale diffusivities and feasible lithological features producing the observed tracer breakthrough curves. The combined approaches indicate significant anisotropy of bulk-scale diffusivity, likely associated with high-diffusivity layers. Both approaches indicated that diffusivities in some intervals were greater than expected from standard models relating porosity to diffusivity. High apparent diffusivities and anisotropic diffusivity structures were consistent with previous observations at the study site of rapid lateral transport and limited vertical spreading of gas-phase contaminants. Additional processes such as advective oscillations may be involved. These results indicate that gases in deep, layered unsaturated zone sediments can spread laterally more quickly, and produce higher peak concentrations, than predicted by homogeneous, isotropic diffusion models.
Identifying the complete space of feasible anisotropic properties in polycrystalline microstructures
NASA Astrophysics Data System (ADS)
Proust, Gwenaelle
Current engineering design focuses mainly on the geometrical optimization of a component, while the material selection is often limited to picking a material based on a set of properties reported in handbooks. The inherent anisotropic behavior of materials is often ignored in the design process, and is usually assumed to be addressed by the safety factor employed. This simple treatment of material selection in the design and optimization process often leads to inefficient design. In this study, we present a rigorous and a comprehensive procedure that facilitates the treatment of material microstructure as a continuous design variable in the elastic-plastic design of structural components made from anisotropic polycrystalline metals. The mechanical behavior of a metal is influenced by several details of its microstructure, including chemical composition, grain size distribution, crystallographic texture, among others. Here, we focus on the crystallographic texture (also called Orientation Distribution Function or ODF) as the main microstructural parameter controlling the anisotropic elastic-plastic properties of interest. The property closures that we have delineated describe the complete set of feasible property combinations for a given polycrystalline material system, while accounting for all possible textures. The property closures are obtained here using a spectral representation of ODF and its relationship with rigorous first order bounds on the effective properties of interest in design. Using the proposed methodology, we successfully developed a few examples of property closures for face centered cubic (fcc) and hexagonal close-packed (hcp) metals. The mechanical anisotropic behavior at the single crystal level for face centered cubic metals has been characterized using the nanoindentation technique along with orientation imaging mapping. This methodology shows promising possibilities to extract fundamental elastic and plastic parameters. However, the methods proposed in the literature to extract data from the load-displacement curves cause discrepancy between the experimental and expected values. The discrepancy could be attributed to the induced plastic deformation among other factors.
Phonon heat conduction in layered anisotropic crystals
NASA Astrophysics Data System (ADS)
Minnich, A. J.
2015-02-01
The thermal properties of anisotropic crystals are of both fundamental and practical interest, but transport phenomena in anisotropic materials such as graphite remain poorly understood because solutions of the Boltzmann equation often assume isotropy. Here, we extend an analytic solution of the transient, frequency-dependent Boltzmann equation to highly anisotropic solids and examine its predictions for graphite. We show that this simple model predicts key results, such as long c -axis phonon mean free paths and a negative correlation of cross-plane thermal conductivity with in-plane group velocity, that were previously observed with computationally expensive molecular-dynamics simulations. Further, using our analytic solution, we demonstrate a method to reconstruct the anisotropic mean free path spectrum of crystals with arbitrary dispersion relations without any prior knowledge of their harmonic or anharmonic properties using observations of quasiballistic heat conduction. These results provide a useful analytic framework to understand thermal transport in anisotropic crystals.
Anisotropic Thermoelectric Properties of MnSi? Film Prepared on R-Sapphire
NASA Astrophysics Data System (ADS)
Takeda, Komei; Kikuchi, Yuta; Hayashi, Kei; Miyazaki, Yuzuru; Kajitani, Tsuyoshi
2012-05-01
We attempted to obtain an epitaxial MnSi? (?˜1.7) film on R-sapphire, i.e., Sapphire(1102), substrate by pulsed laser deposition. We prepared MnSi? films by changing the substrate temperature gradient. It was found that the MnSi? film, whose temperature gradient in a substrate is parallel to Sapphire[1120], could be grown epitaxially on the substrate. The epitaxial relationship was MnSi?(1000)[0010] ? Sapphire(1102)[1120]. The thermoelectric properties of the epitaxial MnSi? film were different in the a- and c-axes, reflecting the anisotropic MnSi? crystal structure. The anisotropic thermoelectric properties are discussed in terms of the electronic structure.
The effect of anisotropic heat transport on magnetic islands in 3-D configurations
Schlutt, M. G.; Hegna, C. C.
2012-08-15
An analytic theory of nonlinear pressure-induced magnetic island formation using a boundary layer analysis is presented. This theory extends previous work by including the effects of finite parallel heat transport and is applicable to general three dimensional magnetic configurations. In this work, particular attention is paid to the role of finite parallel heat conduction in the context of pressure-induced island physics. It is found that localized currents that require self-consistent deformation of the pressure profile, such as resistive interchange and bootstrap currents, are attenuated by finite parallel heat conduction when the magnetic islands are sufficiently small. However, these anisotropic effects do not change saturated island widths caused by Pfirsch-Schlueter current effects. Implications for finite pressure-induced island healing are discussed.
Anisotropic parton escape is the dominant source of azimuthal anisotropy in transport models
Liang He; Terrence Edmonds; Zi-Wei Lin; Feng Liu; Denes Molnar; Fuqiang Wang
2015-07-02
We trace the development of elliptic anisotropy ($v_2$) via parton-parton collision history in two transport models. The parton $v_2$ is studied as a function of the number of collisions of each parton in Au+Au and $d$+Au collisions at $\\sqrt{s_{_{\\rm NN}}}=200$~GeV. It is found that the majority of $v_2$ comes from the anisotropic escape probability of partons, with no fundamental difference at low and high transverse momenta. The contribution to $v_2$ from hydrodynamic-type collective flow is found to be small. Only when the parton-parton cross-section is set unrealistically large does this contribution start to take over. Our findings challenge the current paradigm emerged from hydrodynamic comparisons to anisotropy data.
Interventional nerve visualization via the intrinsic anisotropic optical properties of the nerves
NASA Astrophysics Data System (ADS)
Chin, Kenneth W.; Meijerink, Andries; Chin, Patrick T. K.
2015-07-01
We present an optical concept to visualize nerves during surgical interventions. The concept relies on the anisotropic optical properties of the nerves which allows for specific switching of the optical reflection by the nervous tissue. Using a low magnification polarized imaging system we are able to visualize the on and off switching of the optical reflection of the nervous tissue, enabling a non-invasive nerve specific real-time nerve visualization during surgery.
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...
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...
The transport properties of activated carbon fibers
di Vittorio, S.L. . Dept. of Materials Science and Engineering); Dresselhaus, M.S. . Dept. of Electrical Engineering and Computer Science Massachusetts Inst. of Tech., Cambridge, MA . Dept. of Physics); Endo, M. . Dept. of Electrical Engineering); Issi, J-P.; Piraux, L.
1990-07-01
The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons. 19 refs., 4 figs.
Characterising the Anisotropic Mechanical Properties of Excised Human Skin
Aisling Ni Annaidh; Karine Bruyere; Michel Destrade; Michael D. Gilchrist; Melanie Ottenio
2013-02-13
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 0.012s$^{-1}$ on skin from the back. Digital Image Correlation was used for 2D strain measurement and a histological examination of the dermis was also performed. The mean ultimate tensile strength (UTS) was 21.6$\\pm$8.4MPa, the mean failure strain 54$\\pm$17%, the mean initial slope 1.18$\\pm$0.88MPa, the mean elastic modulus 83.3$\\pm$34.9MPa and the mean strain energy was 3.6$\\pm$1.6MJ/m$^3$. A multivariate analysis of variance has shown that these mechanical properties of skin are dependent upon the orientation of Langer lines (P$skin using a structural constitutive model.
Anisotropic magnetic properties and domain structure in Fe-3%Si (110) steel sheet
NASA Astrophysics Data System (ADS)
Shin, Sunmi; Schaefer, Rudolf; DeCooman, B. C.
2011-04-01
The understanding of the anisotropic magnetization mechanism in 3%Si steel is relevant to both the design of the electrotechnical applications of 3%Si steel and the fundamental materials science of soft magnetic materials. In the present study, the relation between the anisotropic magnetic properties and the magnetization curves of 3%Si-Fe (110) steel sheet for various directions of axial magnetization was studied taking into account the domain structure. The magnetic loss of the (110) steel sheet were measured in an applied field at an angle ? to the [001] axis. The angle ? was varied from 0° to 90°, in steps of 15°. In off-[001] directions, the magnetization resulted in a highly structured domain pattern and domain wall displacements, which could be related to the shape of the magnetization curves. The magnetization curves could be divided in four segments, with each segment related to a specific domain structure.
Symmetry-adapted bases for the parametrization of anisotropic properties
van de Walle, Axel; Demers, Steve; Hong, Qijun; Kowalski, Adam; Miljacic, Ljubomir; Pomrehn, Gregory; Tiwary, Pratyush
2013-01-01
We present a simple and general method to generate a set of basis functions suitable for parametrizing the anisotropy of a given physical property in the presence of symmetry constraints. This mathematical tool has direct applications in various fields, for instance, to parametrize the orientation-dependence of interface energies or to represent the so-called constituent strain elastic energy of superlattice structures in the long wavelength limit. The proposed method can be easily implemented using generic linear algebra operations without having consider many different subcases that depend on the point group symmetry considered. The method exploits a direct correspondence between spherical harmonics and polynomial functions of a unit vectors expressed in tensor notation. The method has been implemented in the "gencs" code of the Alloy Theoretic Automated Toolkit (ATAT).
Turbulent anomalous transport and anisotropic electron heating in a return current system
Lee, Kuang Wu; Buechner, Joerg [Max-Planck-Institut fuer Sonnensystemforschung, 37191 Katlenburg-Lindau (Germany)
2011-02-15
Anisotropic electron heating due to self-generated electromagnetic turbulences is observed in collisionless return current plasmas. The corresponding energy conversion, electron heating, and associated anomalous momentum transport are investigated by means of a two-dimensional electromagnetic particle-in-cell simulation code. The return current model consists of two counterstreaming electron beams with different temperatures and a stationary ion background. First, a general multifluid dispersion analyzer is presented in a clear matrix form that allows to study electron streaming instabilities. The numerical simulation confirms the predicted electrostatic electron-electron acoustic instability. Generating electromagnetic waves, the system evolves into a nonlinear stage. As a result, the electron drifts are slowed down due to turbulence-induced anomalous momentum exchange. Localized electric and magnetic field fluctuations play major roles in the energy conversion. Perpendicular electron heating follows the growth of magnetic field perturbations and the slowing of the electron drifts. Parallel and perpendicular electron heating occurs at different time scales. It is shown that the longer lasting perpendicular electron heating is caused by preheated parallel electron flows. The deflection of the preheated parallel electron flows in the localized turbulences, which is essentially a two-dimensional effect, leads to perpendicular electron heating even after the saturation of parallel electron heating. We conclude that the self-generated magnetic turbulence dominates the anomalous transport process in the late stage of return current system evolution.
Optical Properties of Anisotropic Polycrystalline Ce+3 activated LSO
Roy, Sudesna; Lingertat, Helmut; Brecher, Charles; Sarin, Vinod
2012-01-01
Polycrystalline cerium activated lutetium oxyorthosilicate (LSO:Ce) is highly desirable technique to make cost effective and highly reproducible radiation detectors for medical imaging. In this article methods to improve transparency in polycrystalline LSO:Ce were explored. Two commercially available powders of different particulate sizes (average particle size 30 and 1500 nm) were evaluated for producing dense LSO:Ce by pressure assisted densification routes, such as hot pressing and hot isostatic pressing. Consolidation of the powders at optimum conditions produced three polycrystalline ceramics with average grain sizes of 500 nm, 700 and 2000 nm. Microstructural evolution studies showed that for grain sizes larger than 1 µm, anisotropy in thermal expansion coefficient and elastic constants of LSO, resulted in residual stress at grain boundaries and triple points that led to intragranular microcracking. However, reducing the grain size below 1 µm effectively avoids microcracking, leading to more favorable optical properties. The optical scattering profiles generated by a Stover scatterometer, measured by a He-Ne laser of wavelength 633 nm, showed that by reducing the grain size from 2 µm to 500 nm, the in-line transmission increased by a factor of 103. Although these values were encouraging and showed that small changes in grain size could increase transmission by almost 3 orders of magnitude, even smaller grain sizes need to be achieved in order to get truly transparent material with high in-line transmission. PMID:23505329
Monte Carlo inversion of ultrasonic array data to map anisotropic weld properties.
Zhang, Jie; Hunter, Alan; Drinkwater, Bruce W; Wilcox, Paul D
2012-11-01
The quality of an ultrasonic array image depends on accurate information about its acoustic properties. Inaccurate acoustic properties can cause image degradation such as blurring, mislocation of reflectors, and the introduction of artifacts. In this paper, for the specific case of an inhomogeneous and anisotropic austenitic steel weld, Monte Carlo Markov Chain (MCMC) inversion is used to estimate unknown acoustic properties from array data. The approach uses active beacons that transmit ultrasound through the anisotropic weld; the ultrasound is then captured by a receiving array. A forward model of the ultrasonic array data is then optimized with respect to the experimental data using an MCMC inversion. The result of this process is the extraction of a material property map that describes the anisotropy distribution within the weld region. These extracted material properties are then used within an imaging algorithm-the total focusing method in this paper-to produce autofocused images. This MCMC inversion approach is first applied to simulated data to test the convergence, robustness, and accuracy of the method and its implementation. The extracted weld map is used to show improved imaging of defects within the weld, relative to an image formed assuming a constant velocity. Finally, the MCMC inversion approach is used on experimental data from a 110-mm-thick steel plate containing an austenitic weld. Here the extracted weld map is used to show that defect location errors of greater than 5 mm are reduced to around 2 mm when the extracted weld map is used. PMID:23192812
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
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.
Anisotropic Spin Transport and Strong Visible-Light Absorbance in Few-Layer SnSe and GeSe.
Shi, Guangsha; Kioupakis, Emmanouil
2015-10-14
SnSe and GeSe are layered compound semiconductors that can be exfoliated to form two-dimensional materials. In this work, we use predictive calculations based on density functional and many-body perturbation theory to study the electronic and optical properties of single-layer, double-layer, and bulk SnSe and GeSe. The fundamental band gap is direct in single-layer and double-layer GeSe, but indirect in single-layer and double-layer SnSe. Moreover, the interplay of spin-orbit coupling and lack of inversion symmetry in the monolayer structures results in anisotropic spin splitting of the energy bands, with potential applications in directionally dependent spin transport. We also show that single-layer and double-layer SnSe and GeSe exhibit unusually strong optical absorbance in the visible range. Our results suggest that single-layer and double-layer SnSe and GeSe are promising materials for ultrathin-film photovoltaic applications with theoretical upper bounds to the conversion efficiency that approach the efficiency records realized in organic and dye-sensitized solar cells. PMID:26393677
Direct method for calculating temperature-dependent transport properties
NASA Astrophysics Data System (ADS)
Liu, Yi; Yuan, Zhe; Wesselink, R. J. H.; Starikov, Anton A.; van Schilfgaarde, Mark; Kelly, Paul J.
2015-06-01
We show how temperature-induced disorder can be combined in a direct way with first-principles scattering theory to study diffusive transport in real materials. Excellent (good) agreement with experiment is found for the resistivity of Cu, Pd, Pt (and Fe) when lattice (and spin) disorder are calculated from first principles. For Fe, the agreement with experiment is limited by how well the magnetization (of itinerant ferromagnets) can be calculated as a function of temperature. By introducing a simple Debye-like model of spin disorder parameterized to reproduce the experimental magnetization, the temperature dependence of the average resistivity, the anisotropic magnetoresistance, and the spin polarization of a Ni80Fe20 alloy are calculated and found to be in good agreement with existing data. Extension of the method to complex, inhomogeneous materials as well as to the calculation of other finite-temperature physical properties within the adiabatic approximation is straightforward.
NASA Astrophysics Data System (ADS)
Baldwin, Steven L.
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.
Gillman, A; Matouš, K; Atkinson, S
2013-02-01
In this paper, a systematic method is presented for developing microstructure-statistics-property relations of anisotropic polydisperse particulate composites using microcomputer tomography (micro-CT). Micro-CT is used to obtain a detailed three-dimensional representation of polydisperse microstructures, and an image processing pipeline is developed for identifying particles. In this work, particles are modeled as idealized shapes in order to guide the image processing steps and to provide a description of the discrete micro-CT data set in continuous Euclidean space. n-point probability functions used to describe the morphology of mixtures are calculated directly from real microstructures. The statistical descriptors are employed in the Hashin-Shtrikman variational principle to compute overall anisotropic bounds and self-consistent estimates of the thermal-conductivity tensor. We make no assumptions of statistical isotropy nor ellipsoidal symmetry, and the statistical description is obtained directly from micro-CT data. Various mixtures consisting of polydisperse ellipsoidal and spherical particles are prepared and studied to show how the morphology impacts the overall anisotropic thermal-conductivity tensor. PMID:23496506
Simulation of charge transport in ion channels and nanopores with anisotropic permittivity.
Toghraee, Reza; Mashl, R Jay; Lee, Kyu Il; Jakobsson, Eric; Ravaioli, Umberto
2009-06-01
Ion channels are part of nature's solution for regulating biological environments. Every ion channel consists of a chain of amino acids carrying a strong and sharply varying permanent charge, folded in such a way that it creates a nanoscopic aqueous pore spanning the otherwise mostly impermeable membranes of biological cells. These naturally occurring proteins are particularly interesting to device engineers seeking to understand how such nanoscale systems realize device-like functions. Availability of high-resolution structural information from X-ray crystallography, as well as large-scale computational resources, makes it possible to conduct realistic ion channel simulations. In general, a hierarchy of simulation methodologies is needed to study different aspects of a biological system like ion channels. Biology Monte Carlo (BioMOCA), a three-dimensional coarse-grained particle ion channel simulator, offers a powerful and general approach to study ion channel permeation. BioMOCA is based on the Boltzmann Transport Monte Carlo (BTMC) and Particle-Particle-Particle-Mesh (P(3)M) methodologies developed at the University of Illinois at Urbana-Champaign. In this paper we briefly discuss the various approaches to simulating ion flow in channel systems that are currently being pursued by the biophysics and engineering communities, and present the effect of having anisotropic dielectric constants on ion flow through a number of nanopores with different effective diameters. PMID:20445807
Transport properties of ground state oxygen atoms
NASA Technical Reports Server (NTRS)
Holland, Paul M.; Biolsi, Louis
1988-01-01
The transport properties of dilute monatomic gases depend on the two-body interactions between like atoms. When two ground-state oxygen atoms interact, they can follow any of 18 potential energy curves corresponding to O2, all of which contribute to the transport properties of the ground-state atoms. Transport collision integrals have been calculated for those interactions with an attractive minimum in the potential, and repulsive ab initio potential-energy curves have been accurately represented. Results are given for viscosity, thermal conductivity, and diffusion and they are compared with previous theoretical calculations.
NASA Astrophysics Data System (ADS)
Sun, Hong-xiang; Zhang, Shu-yi; Xia, Jian-ping
2015-06-01
The propagation characteristics of laser-generated Rayleigh waves in coating-substrate structures with anisotropic and viscoelastic properties have been investigated quantitatively. Based on the plane strain theory, finite element models for simulating laser-generated Rayleigh waves in coating-substrate structures are established, in which the carbon fiber-reinforced epoxy matrix composite and aluminum are used as the coating and/or the substrate alternately. The numerical results exhibit that the characteristics of the laser-generated Rayleigh waves, including attenuation, velocity, and dispersion, are mainly and closely related to the anisotropic and viscoelastic properties of the composite in the coating-substrate structures.
NASA Astrophysics Data System (ADS)
Turba, K.; Hurst, R. C.; Hähner, P.
2012-09-01
The small punch testing technique was used to assess both creep and fracture properties of the MA956 oxide dispersion strengthened ferritic steel. The anisotropy in mechanical properties was addressed, as well as the alloy's susceptibility to thermal embrittlement. Strong anisotropy was found in the material's creep resistance at 725 °C for longer rupture times. Anisotropic behavior was also observed for the ductile-brittle transition temperature (DBTT). The origin of the anisotropy can be related to the strongly directional microstructure which enables a large amount of intergranular cracking during straining at both high and low temperatures. The DBTT of the alloy is very high, and can be further increased by at least 200 °C after 1000 h of ageing at 475 °C, due to the formation of the Cr-rich ?' phase. The particularly high susceptibility of the MA956 to thermal embrittlement is mainly a consequence of its high chromium content.
NASA Astrophysics Data System (ADS)
Hudson, Stephen; Hutter, Jeffrey; Millon, Leonardo; Wan, Wankei; Nieh, Mu-Ping
2009-03-01
Poly(vinyl alcohol) (PVA) hydrogels are formed from PVA solution by creation of physical cross-links during freeze/thaw cycling. By choosing a suitable freeze/thaw protocol and applying a strain during thermal processing, gels with permanent, anisotropic bulk mechanical properties matching those of cardiovascular tissues can be made, making them useful for applications ranging from artificial heart valves to vascular grafts. We have performed small- and ultra small-angle neutron scattering (SANS and USANS) measurements covering length scales from 2 nm to 10 ?m, and modeled the structure as interconnected PVA blobs of size 20 to 50 nm arranged in fractal aggregates extending to at least 10 ?m. Here, we discuss the relationship between the microstructure and bulk mechanical properties. Strength increases with the number of thermal cycles due to reinforcement of the small-scale gel phase, while anisotropy is due to elongation of the much larger fractal aggregates.
Impact of magnetic properties on the Casimir torque between anisotropic metamaterial plates
Deng Gang; Liu Zhongzhu; Luo Jun [Department of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)
2009-12-15
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.
NASA Astrophysics Data System (ADS)
Lu, Wanglin; Ma, Xiaomeng; Fei, Zhen; Zhou, Jianguang; Zhang, Zhiyong; Jin, Chuanhong; Zhang, Ze
2015-07-01
In this study, we correlated the angular dependence of the Raman response of black phosphorus to its crystallographic orientation by using transmission electron microscopy and Raman spectroscopy. It was found that the intensity of the Ag 2 mode reached a maximum when the polarization direction of the incident light was parallel to the zigzag crystallographic orientation. Notably, it was further confirmed that the zigzag crystallographic direction exhibited superior conductance and carrier mobility. Because of the lattice extension along the armchair direction, an intensification of the anisotropic Raman response was observed. This work provides direct evidence of the correlation between anisotropic properties and crystallographic direction and represents a turning point in the discussion of the angular-dependent electronic properties of black phosphorus.
The effects of anisotropic viscosity on turbulence and heat transport in the intracluster medium
NASA Astrophysics Data System (ADS)
Parrish, Ian J.; McCourt, Michael; Quataert, Eliot; Sharma, Prateek
2012-05-01
In the intracluster medium (ICM) of galaxy clusters, heat and momentum are transported almost entirely along (but not across) magnetic field lines. We perform the first fully self-consistent Braginskii magnetohydrodynamics (MHD) simulations of galaxy clusters including both of these effects. Specifically, we perform local and global simulations of the magnetothermal instability (MTI) and the heat-flux-driven buoyancy instability (HBI) and assess the effects of viscosity on their saturation and astrophysical implications. We find that viscosity has only a modest effect on the saturation of the MTI. As in previous calculations, we find that the MTI can generate nearly sonic turbulent velocities in the outer parts of galaxy clusters, although viscosity somewhat suppresses the magnetic field amplification. At smaller radii in cool-core clusters, viscosity can decrease the linear growth rates of the HBI. However, it has less of an effect on the HBI's non-linear saturation, in part because three-dimensional interchange motions (magnetic flux tubes slipping past each other) are not damped by anisotropic viscosity. In global simulations of cool-core clusters, we show that the HBI robustly inhibits radial thermal conduction and thus precipitates a cooling catastrophe. The effects of viscosity are, however, more important for higher entropy clusters. We argue that viscosity can contribute to the global transition of cluster cores from cool-core to non-cool-core states: additional sources of intracluster turbulence, such as can be produced by active galactic nuclei feedback or galactic wakes, suppress the HBI, heating the cluster core by thermal conduction; this makes the ICM more viscous, which slows the growth of the HBI, allowing further conductive heating of the cluster core and a transition to a non-cool-core state.
Crystal growth and anisotropic magnetic properties of V{sub 3}O{sub 7}
Li, C.; Isobe, M.; Ueda, H.; Matsushita, Y.; Ueda, Y.
2009-12-15
Needle-like crystals of V{sub 3}O{sub 7} up to 2 mm in length were grown by a chemical vapor transport method using NH{sub 4}Cl as a transport agent. The anisotropic magnetic susceptibility was measured for the first time. At 2 K, a spin-flop transition occurs under a magnetic field of 0.1 T. V{sub 3}O{sub 7} is proved to be a uniaxial antiferromagnet with its easy axis parallel to the b-axis of monoclinic structure. A spin structure with antiferromagnetic interaction between (101-bar) layers and ferromagnetic interaction in the layers below the Neel temperature (5.2 K) is suggested. - Graphical abstract: The temperature dependence of the magnetic susceptibility of V{sub 3}O{sub 7} for (H-parallel b) and (H-perpendicular b), respectively, at 0.1 T. The inset shows crystals of V{sub 3}O{sub 7} grown by using NH{sub 4}Cl as the transport agent.
Strong in-plane anisotropic optical properties of monolayer, few-layer and bulk ReSe2
NASA Astrophysics Data System (ADS)
Zhao, Huan; Guo, Qiushi; Wang, Luhao; Xia, Fengnian; Wang, Han
2015-03-01
Recently, there has been growing interest in the anisotropic properties of certain two-dimensional (2D) materials with reduced lattice symmetry, such as black phosphorus, for developing novel applications in nanoelectronics and infrared optoelectronics. In this work, we report the strong anisotropic optical and electronic properties of monolayer, few-layer and bulk ReSe2, an emerging member of the 2D transition metal dichalcogenides (TMDCs) family. With its bulk bandgap around 1.1 eV and potentially tunable with layer number and strain, ReSe2 may complement black phosphorus for optoelectronic applications utilizing its anisotropic properties in the near-infrared and visible range. Through careful investigations of the polarization-resolved Raman spectroscopy, photoluminescence (PL), polarization-resolved optical extinction spectrum, angle-resolved DC conductance and first principles calculations, we observed and explained the consistent dependence of phonon, optical and electrical properties of ReSe2 on its in-plane crystal orientation. Our results reveal the interesting anisotropic properties of 2D ReSe2 and shed light on its potential applications in electronics and optoelectronics. This work was supported by the Army Research Laboratory.
Yang, Dingzheng; Xie, Lei; Bobicki, Erin; Xu, Zhenghe; Liu, Qingxia; Zeng, Hongbo
2014-09-16
Understanding the surface properties and interactions of nonspherical particles is of both fundamental and practical importance in the rheology of complex fluids in various engineering applications. In this work, natural chrysotile, a phyllosilicate composed of 1:1 stacked silica and brucite layers which coil into cylindrical structure, was chosen as a model rod-shaped particle. The interactions of chrysotile brucite-like basal or bilayered edge planes and a silicon nitride tip were measured using an atomic force microscope (AFM). The force-distance profiles were fitted using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which demonstrates anisotropic and pH-dependent surface charge properties of brucite-like basal plane and bilayered edge surface. The points of zero charge (PZC) of the basal and edge planes were estimated to be around pH 10-11 and 6-7, respectively. Rheology measurements of 7 vol % chrysotile (with an aspect ratio of 14.5) in 10 mM NaCl solution showed pH-dependent yield stress with a local maximum around pH 7-9, which falls between the two PZC values of the edge and basal planes of the rod particles. On the basis of the surface potentials of the edge and basal planes obtained from AFM measurements, theoretical analysis of the surface interactions of edge-edge, basal-edge, and basal-basal planes of the chrysotile rods suggests the yield stress maximum observed could be mainly attributed to the basal-edge attractions. Our results indicate that the anisotropic surface properties (e.g., charges) of chrysotile rods play an important role in the particle-particle interaction and rheological behavior, which also provides insight into the basic understanding of the colloidal interactions and rheology of nonspherical particles. PMID:25115179
J Park; J Li; G Divoux; L Madsen; R Moore
2011-12-31
Relations between morphology and transport sensitively govern proton conductivity in perfluorsulfonate ionomers (PFSIs) and thus determine useful properties of these technologically important materials. In order to understand such relations, we have conducted a broad systematic study of H{sup +}-form PFSI membranes over a range of uniaxial extensions and water uptakes. On the basis of small-angle X-ray scattering (SAXS) and {sup 2}H NMR spectroscopy, uniaxial deformation induces a strong alignment of ionic domains along the stretching direction. We correlate ionic domain orientation to transport using pulsed-field-gradient {sup 1}H NMR measurements of water diffusion coefficients along the three orthogonal membrane directions. Intriguingly, we observe that uniaxial deformation enhances water transport in one direction (parallel-to-draw direction) while reducing it in the other two directions (two orthogonal directions relative to the stretching direction). We evaluate another important transport parameter, proton conductivity, along two orthogonal in-plane directions. In agreement with water diffusion experiments, orientation of ionic channels increases proton conduction along the stretching direction while decreasing it in the perpendicular direction. These findings provide valuable fodder for optimal application of PFSI membranes as well as for the design of next generation polymer electrolyte membranes.
Against the grain: The physical properties of anisotropic partially molten rocks
NASA Astrophysics Data System (ADS)
Ghanbarzadeh, S.; Hesse, M. A.; Prodanovic, M.
2014-12-01
Partially molten rocks commonly develop textures that appear close to textural equilibrium, where the melt network evolves to minimize the energy of the melt-solid interfaces, while maintaining the dihedral angle ? at solid-solid-melt contact lines. Textural equilibrium provides a powerful model for the melt distribution that controls the petro-physical properties of partially molten rocks, e.g., permeability, elastic moduli, and electrical resistivity. We present the first level-set computations of three-dimensional texturally equilibrated melt networks in rocks with an anisotropic fabric. Our results show that anisotropy induces wetting of smaller grain boundary faces for ? > 0 at realistic porosities ? < 3%. This was previously not thought to be possible at textural equilibrium and reconciles the theory with experimental observations. Wetting of the grain boundary faces leads to a dramatic redistribution of the melt from the edges to the faces that introduces strong anisotropy in the petro-physical properties such as permeability, effective electrical conductivity and mechanical properties. Figure, on left, shows that smaller grain boundaries become wetted at relatively low melt fractions of 3% in stretched polyhedral grains with elongation factor 1.5. Right plot represents the ratio of melt electrical conductivity to effective conductivity of medium (known as formation factor) as an example of anisotropy in physical properties. The plot shows that even slight anisotropy in grains induces considerable anisotropy in electrical properties.
Coupled light transport-heat diffusion model for laser dosimetry with dynamic optical properties
London, R.A.; Glinsky, M.E.; Zimmerman, G.B.; Eder, D.C.; Jacques, S.L.
1995-03-01
The effect of dynamic optical properties on the spatial distribution of light in laser therapy is studied via numerical simulations. A two-dimensional, time dependent computer program called LATIS is used. Laser light transport is simulated with a Monte Carlo technique including anisotropic scattering and absorption. Thermal heat transport is calculated with a finite difference algorithm. Material properties are specified on a 2-D mesh and can be arbitrary functions of space and time. Arrhenius rate equations are solved for tissue damage caused by elevated temperatures. Optical properties are functions of tissue damage, as determined by previous measurements. Results are presented for the time variation of the light distribution and damage within the tissue as the optical properties of the tissue are altered.
Properties and an anisotropic model of cancellous bone from the proximal tibial epiphysis.
Williams, J L; Lewis, J L
1982-02-01
An investigation has been made of the source and magnitude of anisotropic material properties of cancellous bone in the proximal epiphysis of the human tibia. Results are reported for stiffness measurements made in three orthogonal directions on 21 cubes of cancellous bone before testing to failure along one of the three principal axes. The structure is approximately transversely isotropic. Strength and stiffness are linear with area fraction for loading along the isotropic axis. Strength is proportional to stiffness for all directions. A finite element model is proposed, based on experimental observations, which enables one to predict the elastic constants of cylindrically structured cancellous bone in the tibia from morphological measurements in the transverse plane. PMID:7078118
Exact analysis of the spectral properties of the anisotropic two-bosons Rabi model
Shuai Cui; Jun-Peng Cao; Luigi Amico; Heng Fan
2015-06-22
We introduce the anisotropic two-photon Rabi model in which the rotating and counter rotating terms enters along with two different coupling constants. Eigenvalues and eigenvectors are studied with exact means. We employ a variation of the Braak method based on Bogolubov rotation of the underlying $su(1,1)$ Lie algebra. Accordingly, the spectrum is provided by the analytical properties of a suitable meromorphic function. Our formalism applies to the two-modes Rabi model as well, sharing the same algebraic structure of the two-photon model. Through the analysis of the spectrum, we discover that the model displays a first order and a parity symmetry breaking quantum phase transitions as the spin-boson coupling strength is varied.
Effect of mechanical stresses on the magnetic properties of anisotropic electrical steel
NASA Astrophysics Data System (ADS)
Korzunin, G. S.; Puzhevich, R. B.; Tsyrlin, M. B.
2007-02-01
It has been shown that mechanical stresses arising in anisotropic electrical-sheet steel during both sheet making (residual stresses) and fabrication of magnetic conductors from the sheet parts (applied stresses) have a strong effect on its magnetic properties. It is shown that the principal cause of this effect is the high stress sensitivity of the magnetic texture of the metal. The main varieties of the applied stresses which are mostly responsible for the deterioration of the magnetic characteristics of the steel have been examined. Basically, these are the stretching of the band during straightening annealing and the effect of bending of the specimens while cutting them with guillotine shears during the preparation of the specimens for tests. The technique of the determination of residual stresses by measuring the flexure of the specimen after the insulating coating is removed from its one side is discussed.
Graphene aerogel/epoxy composites with exceptional anisotropic structure and properties.
Wang, Zhenyu; Shen, Xi; Akbari Garakani, Mohammad; Lin, Xiuyi; Wu, Ying; Liu, Xu; Sun, Xinying; Kim, Jang-Kyo
2015-03-11
3D interconnected graphene aerogels (GAs) are prepared through one-step chemical reduction and rational assembly of graphene oxide (GO) sheets, so that the difficulties to uniformly disperse the individual graphene sheets in the polymer matrixes are avoided. Apart from ultralow density, high porosity, high electrical conductivity, and excellent compressibility, the resulting GAs possess a cellular architecture with a high degree of alignment when the graphene content is above a threshold, ?0.5 wt %. The composites prepared by infiltrating GA with epoxy resin present excellent electrical conductivities, together with high mechanical properties and fracture toughness. The unusual anisotropic structure gives rise to ?67% and ?113% higher electrical conductivity and fracture toughness of the composites, respectively, in the alignment direction than that transverse to it. PMID:25691257
Electronic transport properties in graphene oxide frameworks
NASA Astrophysics Data System (ADS)
Zhu, P.; Cruz-Silva, E.; Meunier, V.
2014-02-01
The electronic transport properties in multiterminal graphene oxide framework (GOF) materials are investigated using a combination of theoretical and computational methods. GOFs make up four-terminal [origin=c]90H-shaped GNR-L-GNR junctions where sandwiched boronic acid molecules (L) are covalently linked to two graphene nanoribbons (GNRs) of different edge chiralities. The transport properties are governed by both tunneling and quasiresonant regimes. We determine how the presence of linker molecules affects the transport properties and establish that the through-molecule transport properties can be tuned by varying the chemical composition of the pillar molecules but are not significantly modified when changing the type of electrodes from zigzag GNRs to armchair GNRs. In addition, we find that in multilinker systems containing two parallel molecules in the device area, the coupling between the molecules can lead to both constructive and destructive quantum interferences. We also examine the inability of the classical Kirchhoff's superposition law to account for electron flow in multilinker GOF nanonetworks.
Electronic and transport properties of phosphorene nanoribbons
NASA Astrophysics Data System (ADS)
Wu, Qingyun; Shen, Lei; Yang, Ming; Cai, Yongqing; Huang, Zhigao; Feng, Yuan Ping
2015-07-01
By combining density functional theory and nonequilibrium Green's function, we study the electronic and transport properties of monolayer black phosphorus nanoribbons (PNRs). First, we investigate the band gap of PNRs and its modulation by the ribbon width and an external transverse electric field. Our calculations indicate a giant Stark effect in PNRs, which can switch on transport channels of semiconducting PNRs under low bias, inducing an insulator-metal transition. Next, we study the transport channels in PNRs via the calculations of the current density and local electron transmission pathway. In contrast to graphene and MoS2 nanoribbons, the carrier transport channels under low bias are mainly located in the interior of both armchair and zigzag PNRs, and immune to a small amount of edge defects. Last, a device of the PNR-based dual-gate field-effect transistor, with high on/off ratio of 103, is proposed based on the giant electric-field tuning effect.
Mechanical properties of cancellous bone in the human mandibular condyle are anisotropic.
Giesen, E B; Ding, M; Dalstra, M; van Eijden, T M
2001-06-01
The objective of the present study was (1) to test the hypothesis that the elastic and failure properties of the cancellous bone of the mandibular condyle depend on the loading direction, and (2) to relate these properties to bone density parameters. Uniaxial compression tests were performed on cylindrical specimens (n=47) obtained from the condyles of 24 embalmed cadavers. Two loading directions were examined, i.e., a direction coinciding with the predominant orientation of the plate-like trabeculae (axial loading) and a direction perpendicular to the plate-like trabeculae (transverse loading). Archimedes' principle was applied to determine bone density parameters. The cancellous bone was in axial loading 3.4 times stiffer and 2.8 times stronger upon failure than in transverse loading. High coefficients of correlation were found among the various mechanical properties and between them and the apparent density and volume fraction. The anisotropic mechanical properties can possibly be considered as a mechanical adaptation to the loading of the condyle in vivo. PMID:11470118
Transport and Magnetization Studies of the Highly Anisotropic Synthetic Organic Materials of the bis
NASA Astrophysics Data System (ADS)
Swanson, Alka Garg
The synthetic organic compounds (BEDT-TTF) _2X (based on bis(ethylene-dithio)tetrathiafulvalene) are highly anisotropic metals and superconductors which exhibit anomalous magnetic and electrical properties. In order to understand these anomalous properties it is important to map out the Fermi surface for each compound. Theoretically, such Fermi surfaces have been mapped out for many of the (BEDT-TTF)_2X compounds and their respective de Haas van Alphen (dHvA) or Shubnikov de Haas (SdH) frequencies have been predicted. This thesis reports the measurements of the de Haas van Alphen and Shubnikov de Haas frequencies at low temperatures (T <=q 4.2 K) in magnetic fields up to 23 tesla for X = I_3, AuBr_2, Cu(NCS)_2 and KHg(NCS)_4. It is found that the experimental frequencies are at odds with the predicted frequencies. These measurements show that these organics are defect free crystals with the electronic relaxation time, tau approaching 8 times 10^{-12} seconds. The results of each measured compound are summarized as follows: (1) In theta(BEDT-TTF) _2I_3, the SdH and dHvA frequencies of 730 and 4170 tesla are observed. The magnetization measurements reveal 'saw-tooth' jumps in the 170th Landau tube, evidence for a defect and impurity free two dimensional system. (2) In beta ^{''}(BEDT -TTF)_2AuBr_2 the SdH and dHvA frequencies of 47, 168, 218 and 269 tesla are observed with evidence for one and three dimensional Fermi surfaces coexisting. (3) In kappa (BEDT-TTF)_2Cu(NCS) _2, the dHvA frequency is determined to be 622 tesla and the magnetization studies reveal flux jump phenomena in the superconducting state of the sample similar to that observed in the ceramic high temperature superconductors. (4) In (BEDT-TTF)_2KHg(NCS) _4, the SdH frequencies of 674 and 1352 tesla are determined and evidence for direct observation of spin splitting in the 30th Landau tube is reported.
Anisotropic transport in single-crystal molybdenum bronze, Li0.33MoO3
NASA Astrophysics Data System (ADS)
Moshfeghyeganeh, Saeed; Cohn, Joshua L.; Neumeier, John J.
2015-03-01
We present transport measurements (resistivity, thermopower, thermal conductivity) on single crystals of the quasi-one-dimensional semiconductor Li0.33MoO3 in the temperature range 200-500 K. First synthesized and studied long ago, the thermal and thermoelectric properties for this compound have not been previously reported. We find extreme anisotropy in the Seebeck coefficient within the a - c planes, with Sc -Sa ~= 300 ? V/K near room temperature. The thermal conductivity at room temperature in the a - c planes was ~ 1 . 5 - 2 W/mK and 7-8 times smaller along b*. We also report x-ray studies of the out-of-plane (b*) lattice constants indicating a small structural transition at T ~ 350 K that coincides with anomalies in the transport properties. This material is based upon work supported by the U.S. Department of Energy Office of Basic Energy Sciences Grant DE-FG02-12ER46888 (Univ. Miami) and the National Science Foundation under Grant DMR-0907036 (Mont. St. Univ.).
Effects of nanofiber on the electrical properties of anisotropic conductive adhesives (ACAs).
Suk, Kyoung-Lim; Chung, Chang-Kyu; Paik, Kyung-Wook
2013-01-01
The effects of nanofiber on the electrical properties of anisotropic conductive films (ACFs) were investigated from the perspectives of the joint and insulation resistances. To obtain stable electrical properties for fine-pitch chip-on-film (COF) packages, two kinds of nanofiber ACFs were demonstrated: (1) polystyrene (PS) and polyacrylonitrile (PAN) nanofiber ACFs, which were formed by laminating ACFs on the top and bottom sides of PS and PAN nanofibers, and (2) PAN nanofiber coupled with conductive particle (PAN/Cp nanofiber) ACF, which was made by laminating non conductive films (NCFs) on both sides of a PAN/Cp nanofiber. The effects of the nanofiber thickness, melting, and structure on the electrical properties of the nanofiber ACFs were analyzed. Among the two different nanofiber ACFs, the PAN/Cp nanofiber ACF showed the most stable joint resistance (below 4 mOmega) and insulation resistance (above 10(8) Omega (between 7 microm bump space) due to the thin insulation layer. PMID:23646737
Transport properties in the Jovian atmosphere
NASA Technical Reports Server (NTRS)
Biolsi, L.
1978-01-01
Transport properties in a Jupiter-like atmosphere (89 mol % hydrogen and 11 mol % helium) are obtained by using the method of the kinetic theory of gases. The transport collision integrals are calculated by fitting various two-body semiempirical interaction potentials for which the collision integrals are tabulated to ab initio quantum mechanical calculations of the two-body interactions. The collision integrals are used to calculate the binary diffusion coefficients, viscosity, and 'total' thermal conductivity of the pure gases and the gas mixtures at 1-atm pressure from 1000 K to 25,000 K.
NASA Astrophysics Data System (ADS)
Zhubayev, Alimzhan; Houben, Maartje; Smeulders, David; Barnhoorn, Auke
2014-05-01
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.
Directional effects during ion implantation: Lateral mass transport and anisotropic growth
M. Chicoine; S. Roorda; L. Cliche; R. A. Masut
1997-01-01
In this paper we present experiments aimed at understanding three different phenomena that deform the surface of solids during irradiation by 24-MeV heavy ions. These phenomena are (1) density changes; (2) anisotropic growth, which describes the thinning of a solid along the normal to the surface and its growth in the surface plane without density changes; and (3) lateral mass
Transport properties of ?-FeSi2
NASA Astrophysics Data System (ADS)
Arushanov, Ernest; Lisunov, Konstantin G.
2015-07-01
The aim of this paper is to summarize considerable experimental efforts undertaken within the last decades in the investigations of transport properties of ?-FeSi2. The ?-FeSi2 compound is the most investigated among a family of semiconducting silicides. This material has received considerable attention as an attractive material for optoelectronic, photonics, photovoltaics and thermoelectric applications. Previous reviews of the transport properties of ?-FeSi2 have been given by Lange and Ivanenko et al. about 15 years ago. The Hall effect, the conductivity, the mobility and the magnetoresistance data are presented. Main attention is paid to the discussion of the impurity (defect) band conductivity, the anomalous Hall effect, the scattering mechanisms of charge carriers, as well as to the hopping conduction and the magnetoresistance.
Transport properties of partially equilibrated quantum wires.
Micklitz, T.; Rech, J.; Matveev, K. A.; Materials Science Division; Ludwig-Maximilians-Univ.
2010-01-01
We study the effect of thermal equilibration on the transport properties of a weakly interacting one-dimensional electron system. Although equilibration is severely suppressed due to phase-space restrictions and conservation laws, it can lead to intriguing signatures in partially equilibrated quantum wires. We consider an ideal homogeneous quantum wire. At finite temperature we find a correction to the quantized conductance, which for a short wire scales with its length, but saturates in the limit of an infinitely long wire. We also discuss thermoelectric properties of long quantum wires. We show that the uniform quantum wire is a perfect thermoelectric refrigerator, approaching Carnot efficiency with increasing wire length.
Xie, Xiao Lu; Li, Chun Hua; Yang, Yong Xiao; Jin, Lu; Tan, Jian Jun; Zhang, Xiao Yi; Su, Ji Guo; Wang, Cun Xin
2015-09-01
The transporter MsbA is a kind of multidrug resistance ATP-binding cassette transporter that can transport lipid A, lipopolysaccharides, and some amphipathic drugs from the cytoplasmic to the periplasmic side of the inner membrane. In this work, we explored the allosteric pathway of MsbA from the inward- to outward-facing states during the substrate transport process with the adaptive anisotropic network model. The results suggest that the allosteric transitions proceed in a coupled way. The large-scale closing motions of the nucleotide-binding domains occur first, accompanied with a twisting motion at the same time, which becomes more obvious in middle and later stages, especially for the later. This twisting motion plays an important role for the rearrangement of transmembrane helices and the opening of transmembrane domains on the periplasmic side that mainly take place in middle and later stages respectively. The topological structure plays an important role in the motion correlations above. The conformational changes of nucleotide-binding domains are propagated to the transmembrane domains via the intracellular helices IH1 and IH2. Additionally, the movement of the transmembrane domains proceeds in a nonrigid body, and the two monomers move in a symmetrical way, which is consistent with the symmetrical structure of MsbA. These results are helpful for understanding the transport mechanism of the ATP-binding cassette exporters. Proteins 2015; 83:1643-1653. © 2015 Wiley Periodicals, Inc. PMID:26148303
Anisotropic optical properties of arrays of gold nanorods embedded in alumina
NASA Astrophysics Data System (ADS)
Atkinson, Ron; Hendren, William R.; Wurtz, Gregory A.; Dickson, Wayne; Zayats, Anatoly V.; Evans, Paul; Pollard, Robert J.
2006-06-01
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 to a Maxwell-Garnett based theory modified to take into account the strongly anisotropic nature of the medium. Transverse and longitudinal plasmon resonances are observed. The interaction between the nanorods leads to the splitting of the longitudinal resonance with the longer-wavelength resonance being forbidden for direct optical observations. The shorter-wavelength resonance related to the symmetric coupling between longitudinal plasma excitations in the nanorods depends on rod length, polarization state, and angle of incidence of the probing light. The impact of electron confinement on the optical properties of the gold rods is also seen and may be incorporated into the Maxwell-Garnett theory by restricting the mean free path of the conduction electrons to produce excellent agreement between observations and the complete theory. Annealing experiments that modify the physical structure of the gold confirm this conclusion.
Cvetkovic, A; Straathof, A J J; Hanlon, D N; van der Zwaag, S; Krishna, R; van der Wielen, L A M
2004-05-20
The diffusion of a solute, fluorescein into lysozyme protein crystals has been studied by confocal laser scanning microscopy (CLSM). Confocal laser scanning microscopy makes it possible to non-invasively obtain high-resolution three-dimensional (3-D) images of spatial distribution of fluorescein in lysozyme crystals at various time steps. Confocal laser scanning microscopy gives the fluorescence intensity profiles across horizontal planes at several depths of the crystal representing the concentration profiles during diffusion into the crystal. These intensity profiles were fitted with an anisotropic model to determine the diffusivity tensor. Effective diffusion coefficients obtained range from 6.2 x 10(-15) to 120 x 10(-15) m2/s depending on the lysozyme crystal morphology. The diffusion process is found to be anisotropic, and the level of anisotropy depends on the crystal morphology. The packing of the protein molecules in the crystal seems to be the major factor that determines the anisotropy. PMID:15112291
Directional drop transport achieved on high-temperature anisotropic wetting surfaces.
Liu, Chengcheng; Ju, Jie; Ma, Jie; Zheng, Yongmei; Jiang, Lei
2014-09-17
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
Hirschfeld, P.J.; Woelfle, P.; Einzel, D.
1988-01-01
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.
Anisotropic Magnetic Properties of a Pressure-induced Superconductor Ce2Ni3Ge5
NASA Astrophysics Data System (ADS)
Thamizhavel, Arumugam; Nakashima, Hiroshi; Obiraki, Yoshiko; Nakashima, Miho; Matsuda, Tatsuma D; Haga, Yoshinori; Sugiyama, Kiyohiro; Takeuchi, Tetsuya; Settai, Rikio; Hagiwara, Masayuki; Kindo, Koichi; ?nuki, Yoshichika
2005-10-01
Single crystals of a pressure-induced superconductor Ce2Ni3Ge5 have been successfully grown by the flux method. The anisotropic magnetic properties due to the orthorhombic crystal structure have been studied precisely by the electrical resistivity, specific heat, magnetic susceptibility, and high-field magnetization measurements. The results of these measurements confirmed two antiferromagnetic transitions at TN1=5.0 K and TN2=4.3 K. The electronic specific heat coefficient obtained from the low-temperature specific heat data amounts to 90 mJ/K2\\cdotmol Ce. The high-field magnetization for H \\parallel [100] shows four magnetic transitions at 11.8, 12.9, 17.5 and 23.9 T with a saturation moment of 0.73 ?B/Ce at 1.3 K. On the other hand, two magnetic transitions are observed for H \\parallel [010] and [001], with saturation moments of 0.43 and 1.1 ?B/Ce, respectively. We have also performed the crystalline electric field (CEF) analysis on the magnetic susceptibility and magnetization to understand the magnetocrystalline anisotropy, where the splitting energies of two excited doublets in the CEF scheme are estimated to be 140 and 576 K, respectively.
Structure and anisotropic properties of single crystals nickel doped barium iron arsenide
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
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.
NASA Astrophysics Data System (ADS)
Hou, Yongqiang; Qi, Hongji; Li, Xu; He, Kai; Fang, Ming; Yi, Kui; Shao, Jianda
2013-07-01
On the basis of theoretical analysis of biaxial birefringent thin films, this study investigates the optical properties of phase shift on reflection and/or transmission through slanted columnar TiO2 sculptured anisotropic thin film (ATF) deposited with glancing angle deposition (GLAD) technique via reactive electron-beam evaporation. The tilted nanocolumn microstructures of thin film induce the optical anisotropy. The optical constants dispersion equations of TiO2 ATF are determined from fitting the transmittance spectra for s- and p-polarized waves measured at normal and oblique incidence within 400-1200nm. With the extracted structure parameters, the phase shifts of polarized light are analyzed with the characteristic matrix and then measured with spectroscopic ellipsometry in the deposition plane. A reasonably good agreement between the theoretical studies and experimental measurements is obtained. In addition, the dependence of the phase shift on oblique incidence angle is also discussed. The results show a greater generality and superiority of the characteristic matrix method. Birefringence of the biaxial ATF performed a sophisticated phase modulation with varied incidence angles over a broad range to have a wide-angle phase shift.
Transport properties of ground state nitrogen atoms
NASA Technical Reports Server (NTRS)
Rainwater, J. C.; Biolsi, L.; Biolsi, K. J.; Holland, P. M.
1983-01-01
In view of the dependence of the transport properties of dilute monatomic gases on the two-body, atom-atom interaction potential, any one of four potential energy curves corresponding to the N2 molecule can be followed when two ground state N atoms interact. Transport collision integrals for the 1Sigma(+)g and 3Sigma(+)u states have been calculated by representing their potentials with the Hulburt-Hirschfelder (1941, 1961) potential. The 5Sigma(+)g state has a large local maximum requiring changes in a previously used computational procedure, and its potential has also been represented by a Hulburt-Hirschfelder potential. Collision integrals for the 7Sigma(+)u state have been obtained through the direct use of a recently proposed theoretical potential for this state. The collision integrals are compared with results gathered from previous studies.
Transport properties of individual C60-molecules.
Géranton, G; Seiler, C; Bagrets, A; Venkataraman, L; Evers, F
2013-12-21
Electrical and thermal transport properties of C60 molecules are investigated with density-functional-theory based calculations. These calculations suggest that the optimum contact geometry for an electrode terminated with a single-Au atom is through binding to one or two C-atoms of C60 with a tendency to promote the sp(2)-hybridization into an sp(3)-type one. Transport in these junctions is primarily through an unoccupied molecular orbital that is partly hybridized with the Au, which results in splitting the degeneracy of the lowest unoccupied molecular orbital triplet. The transmission through these junctions, however, cannot be modeled by a single Lorentzian resonance, as our results show evidence of quantum interference between an occupied and an unoccupied orbital. The interference results in a suppression of conductance around the Fermi energy. Our numerical findings are readily analyzed analytically within a simple two-level model. PMID:24359380
Electronic and transport properties of nanotubes Jean-Christophe Charlier*
Podgornik, Rudolf
the electronic and transport properties of carbon nanotubes. The focus is mainly theoretical, but when Nanotubes 679 III. Electronic Properties of Carbon Nanotubes 681 A. From graphite to nanotubes 682 B. Tight-Wales, etc. 697 I. Optical properties and excitonic effects 698 IV. Transport Properties of Carbon Nanotubes
Elastic properties of the Abrikosov flux-line lattice in anisotropic superconductors
NASA Astrophysics Data System (ADS)
Schönenberger, A. M.; Geshkenbein, V. B.; Blatter, G.
1993-12-01
The elastic moduli of the vortex lattice in uniaxial strong type-II superconductors are calculated for magnetic inductions Hc1<anisotropic situation is based on the mapping of the anisotropic problem to the corresponding isotropic situation. In performing this transformation we use the scaling rules connecting the anisotropic quantities with their known isotropic counterparts. The scaling approach is valid in the dispersive region which accounts for the major part of the Brillouin zone for fields B>>Hc1. The advantage of this method lies in its simplicity and in its general applicability. The resulting moduli agree with the elastic moduli derived previously by means of the traditional approach based on the expansion of the anisotropic London functional. In addition to the usual moduli, we obtain a new mixed shear-tilt modulus.
Transport properties of epitaxial lift off films
NASA Technical Reports Server (NTRS)
Mena, R. A.; Schacham, S. E.; Young, P. G.; Haugland, E. J.; Alterovitz, S. A.
1993-01-01
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.
Magnetic anisotropic properties in Fe 3O 4 and CoFe 2O 4 ferrite epitaxy thin films
NASA Astrophysics Data System (ADS)
Horng, Lance; Chern, G.; Chen, M. C.; Kang, P. C.; Lee, D. S.
2004-04-01
Epitaxial thin films of Fe 3O 4 and CoFe 2O 4 on MgO (0 0 1) substrates were grown by molecular beam epitaxy at low temperature growth process. Magnetization and hysteresis loop of both films were measured to investigate magnetic anisotropic properties at various temperatures. Anomalous magnetic properties are found to be correlated with crystalline, shape, and stress anisotropies. The Fe 3O 4 film below Verwey structural transition has a change in crystal structure, thus causing many anomalous magnetic properties. Crystalline anisotropy and anomalous magnetic properties are affected substantially by Co ions. The saturation magnetization of Co-ferrite film becomes much lower than that of Fe 3O 4 film, being very different from the bulks. It indicates that the low temperature growth process could not provide enough energy to have the lowest energy state.
Eslami, Hossein; Mohammadzadeh, Laila; Mehdipour, Nargess
2012-03-14
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
NASA Astrophysics Data System (ADS)
Muthinti, Gangadhara R.; Medikonda, Manasa; Fronheiser, Jody; Kamineni, Vimal K.; Peterson, Brennan; Race, Joseph; Diebold, Alain C.
2013-04-01
The uses of strained channel became prevalent at the 65 nm node and have continued to be a large part of logic device performance improvements in every technology generation. These material and integration innovations will continue to be important in sub-22nm devices, and are already being applied in finFET devices where total available in-channel strains are potentially higher. The measurement of structures containing these materials is complicated by the intrinsic correlation of the measured optical thickness and variation of optical properties with strain, as well as the dramatic reduction in total volume of the device. Optical scatterometry has enabled characterization of the feature shape and dimensions of complex 3D structures, including non-planar transistors and memory structures. Ellipsometric methods have been successfully applied to the measurement of thin films of SiGe and related strained structures. A direction for research is validating that the thin film stress results can be extended into the much more physically complex 3D shape. There are clear challenges in this: the stress in a SiGe fin is constrained to match the underlying Si along one axis, but the sides and top are free, leading to very large strain gradients both along the fin width and height. Practical utilization of optical techniques as a development tool is often limited by the complexity of the scatterometry model and setup, and this added material complexity presents a new challenge. In this study, generalized spectroscopic ellipsometric measurements of strained grating was undertaken, in parallel with reference cross sectional and top down SEM data. The measurements were modeled for both anisotropy calculations, as well as full scatterometry calculations, fitting the strain and structure. The degree to which strain and CD can be quickly quantified in an optical model is discussed. Sum decomposition method has been implemented to extract the effective anisotropic coefficients and a discussion on the effect of anisotropy toward modeling is presented. Finally, errors in the scatterometry measurement are analyzed, and the relative strengths and limitations of these optical measurements compared.
REGULAR ARTICLE Transport properties of chrysazine-type molecules
Gross, E.K.U.
REGULAR ARTICLE Transport properties of chrysazine-type molecules Angelica G. Zacarias · E. K. U(s) 2009. This article is published with open access at Springerlink.com Abstract Electronic transport and its connection to the leads can be identified by its transport characteristics. The calculated
Transport properties of supercooled confined water
NASA Astrophysics Data System (ADS)
Mallamace, F.; Branca, C.; Broccio, M.; Corsaro, C.; Gonzalez-Segredo, N.; Spooren, J.; Stanley, H. E.; Chen, S.-H.
2008-07-01
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.
Cuenca, Jacques; Göransson, Peter
2012-08-01
This paper presents a method for simultaneously identifying both the elastic and anelastic properties of the porous frame of anisotropic open-cell foams. The approach is based on an inverse estimation procedure of the complex stiffness matrix of the frame by performing a model fit of a set of transfer functions of a sample of material subjected to compression excitation in vacuo. The material elastic properties are assumed to have orthotropic symmetry and the anelastic properties are described using a fractional-derivative model within the framework of an augmented Hooke's law. The inverse estimation problem is formulated as a numerical optimization procedure and solved using the globally convergent method of moving asymptotes. To show the feasibility of the approach a numerically generated target material is used here as a benchmark. It is shown that the method provides the full frequency-dependent orthotropic complex stiffness matrix within a reasonable degree of accuracy. PMID:22894184
Kovalev, Alexey A.; Tserkovnyak, Yaroslav; Vyborny, Karel; Sinova, Jairo.
2009-01-01
We present a study of transport in multiple-band noninteracting Fermi metallic systems based on the Keldysh formalism and the self-consistent T-matrix approximation (TMA) taking into account the effects of Berry curvature due to spin-orbit coupling...
Nunner, Tamara
2012-01-01
realized and experimental control over such systems is rapidly improving.1 A prime difference between responsible for transport to few well-defined collective modes of the molecule, with recent research focusing been discussed in molecular spin valves, which have been realized in setups with C60,14 and more
Fluid transport properties by equilibrium molecular dynamics. II. Multicomponent systems
Dysthe, Dag Kristian
Fluid transport properties by equilibrium molecular dynamics. II. Multicomponent systems D. K than 25 years molecular dynamics has been used to study fluid transport properties. Such MD studies dynamics has been applied to multicomponent mixtures of flexible, multicenter models of linear and branched
Observation of an even-odd anisotropic transport of two-dimensional electrons in high Landau levels
NASA Astrophysics Data System (ADS)
Liu, Guangtong; Yang, Changli; Lu, Li; Du, Rui-Rui; Pfeiffer, Loren; West, Ken; Institute of Physics, Chinese Academy of Sciences Team; International Center for Quantum Materials, Peking University Collaboration; Department of Electrical Engineering, Princeton University Collaboration
2015-03-01
Recently a rich variety of collective phases1 have been reported by low-temperature magnetotransport experiments in ultrahigh mobility (? >= 1000 m2/Vs) two-dimensional electron gases (2DEGs). These novel phases, characterized by highly anisotropy in the longitudinal resistance and reentrant integer quantum Hall effect (RIQHE) in the Hall resistance, have stimulated strong interest in high (N >= 2) Landau levels (LLs). In this study, ultrahigh mobility L-shaped Hall-bar samples were constructed on a 20-nm GaAs/AlGaAs quantum well (QW). After a brief red light-emitting diode (LED) illumination at low temperatures, the specimen attained a mobility of ? ~ 17 (12) × 106 cm2/Vs and an electron density of ne = 3.37 (3.38) × 1011/cm2 along the <110>(<110>) direction. The low-temperature magnetoresistance (Rxx) data in tilted fields demonstrate that an even-odd anisotropic transport behavior exists in high Landau levels (N >= 2) along the <110>direction, which is very robust and can persist up to a 100 mK temperature and 66° tilt-field. The possible origins will be discussed.
Transport properties of alkali metal doped fullerides
NASA Astrophysics Data System (ADS)
Yadav, Daluram; Yadav, Nishchhal
2015-07-01
We have studied the intercage interactions between the adjacent C60 cages and expansion of lattice due to the intercalation of alkali atoms based on the spring model to estimate phonon frequencies from the dynamical matrix for the intermolecular alkali-C60 phonons. We considered a two-peak model for the phonon density of states to investigate the nature of electron pairing mechanism for superconducting state in fullerides. Coulomb repulsive parameter and the electron phonon coupling strength are obtained within the random phase approximation. Transition temperature, Tc, is obtained in a situation when the free electrons in lowest molecular orbital are coupled with alkali-C60 phonons as 5 K, which is much lower as compared to reported Tc (20 K). The superconducting pairing is mainly driven by the high frequency intramolecular phonons and their effects enhance it to 22 K. The importance of the present study, the pressure effect and normal state transport properties are calculated within the same model leading superconductivity.
Equilibrium and transport properties of constrained systems
Debasish Chaudhuri
2006-10-16
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.
Transport properties of isospin effective mass splitting
J. Rizzo; M. Colonna; M. Di Toro; V. Greco
2003-09-12
We investigate in detail the momentum dependence ($MD$) of the effective in medium Nucleon-Nucleon ($NN$) interaction in the isovector channel. We focus the discussion on transport properties of the expected neutron-proton ($n/p$) effective mass splitting at high isospin density. We look at observable effects from collective flows in Heavy Ion Collisions ($HIC$) of charge asymmetric nuclei at intermediate energies. Using microscopic kinetic equation simulations nucleon transverse and elliptic collective flows in $Au+Au$ collisions are evaluated. In spite of the reduced charge asymmetry of the interacting system interesting $isospin-MD$ effects are revealed. Good observables, particularly sensitive to the $n/p$-mass splitting, appear to be the differences between neutron and proton flows. The importance of more exclusive measurements, with a selection of different bins of the transverse momenta ($p_t$) of the emitted particles, is stressed. In more inclusive data a compensation can be expected from different $p_t$-contributions, due to the microscopic $isospin-MD$ structure of the nuclear mean field in asymmetric matter.
Transport Properties and Thermal Expansion of Sr
Kharton, V. V.; Kovalevsky, A. V.; Viskup, A. P.; Jurado, J. R.; Figueiredo, F. M.; Naumovich, E. N.; Frade, J. R.
2001-02-01
Increasing iron concentration in perovskite-type solid solutions Sr{sub 0.97}Ti{sub 1-x}Fe{sub x}O{sub 3-{delta}} (x=0.2-0.8) was found to decrease the unit cell volume and to increase the partial ionic and electronic conductivities as well as the thermal expansion. The oxygen permeation through Sr{sub 0.97}(Ti,Fe)O{sub 3-{delta}} membranes is limited by both bulk ionic conduction and surface exchange rates. Prolonged stabilization under oxygen chemical potential gradients suggests formation of ordered microdomains in the perovskite lattice. The activation energy for the ionic conductivity, evaluated from oxygen permeation and Faradaic efficiency data, is nearly independent of iron content, varying in the range 97-104 kJ/mol. Thermal expansion coefficients of Sr{sub 0.97}Ti{sub 1-x}Fe{sub x}O{sub 3-{delta}} (x=0.4-0.8) vary from (11.7-13.8) x 10{sup {minus}6} K{sup {minus}1} at temperatures of 300-720 K to (16.6-27.0) x 10{sup {minus}6} K{sup {minus}1} at higher temperatures. In comparison with the Sr(Ti, Co)O{sub 3-{delta}} system, strontium titanates ferrites possess somewhat poorer transport properties, but lower thermal expansion.
NASA Astrophysics Data System (ADS)
Lee, Ji-Hwan; Park, Jong-Hun; Jung, Young-Kwang; Soon, Aloysius
2015-03-01
Current materials-related calculations employ the density-functional theory (DFT), commonly using the (semi-)local-density approximations for the exchange-correlation (xc) functional. The accuracy to studying the electronic structure depends not only on the employed approximation to the xc potential but also upon the system which is being investigated. The difficulties in arriving at a reasonable description of van der Waals (vdW) interactions by DFT-based models, is to date a big challenge. This stems from the well-known fact that vdW interaction is a non-local correlation effect which is not captured in the deployed (semi-)local xc functionals. In this work, using various flavours of vdW-corrected DFT xc functionals, we study the lattice and mechanical properties (including the elastic constants and anisotropic stress-strain curves) of the coinage metals (copper, silver, and gold), and critically assess the reliability of the different vdW-corrected DFT methods in describing their anisotropic mechanical properties which are less reported on in the literature.
Reentrant Quantum Hall Effect and Anisotropic Transport in a Bilayer System at High Filling Factors
NASA Astrophysics Data System (ADS)
Gusev, G. M.; Bakarov, A. K.; Lamas, T. E.; Portal, J. C.
2007-09-01
We report on the measurements of the quantum Hall effect states in double quantum well structures at the filling factors ?=4N+1 and ?=4N+3, where N is the Landau index number, in the presence of the in-plane magnetic field. The quantum Hall states at these filling factors vanish and reappear several times and exhibit anisotropy. Repeated reentrance of the transport gap occurs due to the periodic vanishing of the tunneling amplitude in the presence of the in-plane field. Anisotropy demonstrates the existence of the stripes in the ground states.
Applications of asymmetric nanotextured parylene surface using its wetting and transport properties
NASA Astrophysics Data System (ADS)
Sekeroglu, Koray
In this thesis, basic digital fluidics devices were introduced using polymeric nanorods (nano-PPX) inspired from nature. Natural inspiration ignited this research by observing butterfly wings, water strider legs, rye grass leaves, and their asymmetric functions. Nano-PPX rods, manufactured by an oblique angle polymerization (OAP) method, are asymmetrically aligned structures that have unidirectional wetting properties. Nano-PPX demonstrates similar functions to the directional textured surfaces of animals and plants in terms of wetting, adhesion, and transport. The water pin-release mechanism on the asymmetric nano-PPX surface with adhesion function provides a great transport property. How the asymmetry causes transport is discussed in terms of hysteresis and interface contact of water droplets. In this study, the transport property of nano-PPX rods is used to guide droplets as well as transporting cargo such as microgels. With the addition of tracks on the nano-PPX rods, the surfaces were transformed into basic digital fluidics devices. The track-assisted nano-PPX has been employed to applications (i.e. sorting, mixing, and carrying cargo particles). Thus, digital fluidics devices fabricated on nano-PPX surface is a promising pathway to assemble microgels in the field of bioengineering. The characterization of the nano textured surface was completed using methods such as Scanning Electron Microscopy, Atomic Force Microscopy, Contact Angle Goniometry, and Fourier Transform Infra-Red Spectroscopy. These methods helped to understand the physical and chemical properties of nano-PPX. Parameters such as advancing and receding contact angles, nanorod tilt angle, and critical drop volumes were utilized to investigate the anisotropic wetting properties of nano-PPX surface. This investigation explained the directional wetting behavior of the surface as well as approaching new design parameters for adjusting surface properties. The nanorod tilt angle was a key parameter, thus changing the angle provided the surface with essential wetting properties. This adjustment on the nano-PPX surface exhibited excellent control on water droplet transport as well as guided the droplets from desired points to targets. The results demonstrated that it is possible to create railroad-like paths to manipulate the droplet movements by deforming the nano-PPX surface. Controlling physical properties of the surface granted the inspiration for fabricating basic fluidic devices to sort and mix droplets. These devices are promising for assembly purposes in terms of using microgels in engineering applications (i.e. building blocks for bioengineering). The surface has potential for further development to achieve the directed assembly of microgels into close proximity.
Neoclassical Transport Properties of Tokamak Plasmas
Weyssow, B.
2004-03-15
The classical transport theory is strictly valid for a plasma in a homogeneous and stationary magnetic field. In the '60, experiments have shown that this theory does not apply as a local theory of transport in Tokamaks. It was shown that global geometric characteristics of the confining elements have a strong influence on the transport. Three regimes of collisionality are characteristic of the neoclassical transport theory: the banana regime (the electronic diffusion coefficient increases starting from zero), the plateau regime (the diffusion coefficient is almost independent of the collisionality) and the Pfirsch-Schlueter regime (the electronic diffusion coefficient again increases with the collisionality)
Transport and thermodynamic properties of iron-based superconductors
NASA Astrophysics Data System (ADS)
Kuzmanovski, Dushko
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.
Diameter dependence of the transport properties of antimony telluride nanowires.
Zuev, Yuri M; Lee, Jin Seok; Galloy, Clément; Park, Hongkun; Kim, Philip
2010-08-11
We report measurements of electronic, thermoelectric, and galvanomagnetic properties of individual single crystal antimony telluride (Sb(2)Te(3)) nanowires with diameters in the range of 20-100 nm. Temperature-dependent resistivity and thermoelectric power (TEP) measurements indicate hole dominant diffusive thermoelectric generation with an enhancement of the TEP for smaller diameter wires up to 110 microV/K at T = 300 K. We measure the magnetoresistance in magnetic fields both parallel and perpendicular to the nanowire [110] axis, where strong anisotropic positive magnetoresistance behavior was observed. PMID:20698617
Carbone, G; Lorenz, B; Persson, B N J; Wohlers, A
2009-07-01
In this paper we extend the theory of contact mechanics and rubber friction developed by one of us (B.N.J. Persson, J. Chem. Phys. 115, 3840 (2001)) to the case of surfaces with anisotropic surface roughness. As an application we calculate the viscoelastic contribution to the rubber friction. We show that the friction coefficient may depend significantly on the sliding direction, while the area of contact depends weakly on the sliding direction. We have carried out experiments for rubber blocks sliding on unidirectionally polished steel surfaces. The experimental data are in a good qualitative agreement with the theory. PMID:19578912
26 CFR 49.4271-1 - Tax on transportation of property by air.
Code of Federal Regulations, 2010 CFR
2010-04-01
...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)...
Souza, W.R.; Voss, C.I.
1987-01-01
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.
Anisotropic flows and the shear viscosity of the QGP within an event by event transport approach
Plumari, Salvatore; Scardina, Francesco; Greco, Vincenzo
2015-01-01
We have developed a relativistic kinetic transport approach that incorporates initial state fluctuations allowing to study the build up of elliptic flow $v_2$ and high order harmonics $v_3$, $v_4$ and $v_5$ for a fluid at fixed $\\eta/s(T)$. We study the effect of the $\\eta/s$ ratio and its T dependence on the build up of the $v_n(p_T)$ for two different beam energies: RHIC for Au+Au at $\\sqrt{s}=200 \\,GeV$ and LHC for $Pb+Pb$ at $\\sqrt{s}=2.76 \\,TeV$. We find that for the two different beam energies considered the suppression of the $v_n(p_T)$ due to the viscosity of the medium have different contributions coming from the cross over or QGP phase. Our study reveals that only in ultra-central collisions ($0 - 0.2 \\%$) the $v_n(p_T)$ have a stronger sensitivity to the T dependence of $\\eta/s$ in the QGP phase and this sensitivity increases with the order of the harmonic n. Moreover, the study of the correlations between the initial spatial anisotropies $\\epsilon_n$ and the final flow coefficients $v_n$ shows tha...
Anisotropic colloidal transport and periodic stick-slip motion in cholesteric finger textures.
Chen, Kui; Metcalf, Linnea P; Rivas, David P; Reich, Daniel H; Leheny, Robert L
2015-06-01
We have investigated the mobility of discoidal colloidal particles sedimenting within cholesteric finger textures formed by mixtures of the nematic liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) and the chiral dopant 4-(2-methylbutyl)-4'-cyanobiphenyl (CB15) with cholesteric pitch p between 24 and 114 ?m. The nickel disks, with radius 17 ?m and thickness 300 nm, displayed varied transport behavior that depended on the size of the pitch and the orientation of the gravitational force with respect to the cholesteric axis. In textures with small pitch (p < 40 ?m), the disks moved perpendicular to the axis irrespective of the orientation of gravity as a result of an elastic retarding force that prevented motion along the axis. In textures with larger pitch, the disks similarly moved perpendicular to the axis when the angle between the force and axis was large. When the angle was small, the disks displayed stick-slip motion caused by periodic yielding of the finger texture. A model considering viscous drag on the particles and the elastic energy cost of deforming the finger texture describes the stick-slip motion accurately. The effective drag viscosities obtained from the disk motion are anomalously large compared with those of pure nematic 5CB indicating a large contribution to the dissipation from the motion of disclinations in the texture in the vicinity of the translating disks. PMID:25875803
Goodman, Michael L.
2011-04-10
A Harris sheet magnetic field with maximum magnitude B{sub 0} and length scale L is combined with the anisotropic electrical conductivity, viscosity, and thermoelectric tensors for an electron-proton plasma to define a magnetohydrodynamic model that determines the steady state of the plasma. The transport tensors are functions of temperature, density, and magnetic field strength, and are computed self-consistently as functions of position x normal to the current sheet. The flow velocity, magnetic field, and gravitational force lie along the z-axis. The plasma is supported against gravity by the viscous force. Analytic solutions are obtained for temperature, density, and velocity. They are valid over a broad range of temperature, density, and magnetic field strength, and so may be generally useful in astrophysical applications. Numerical examples of solutions in the parameter range of the solar atmosphere are presented. The objective is to compare Joule and viscous heating rates, determine the velocity shear that generates viscous forces that support the plasma and are self-consistent with a mean outward mass flux comparable to the solar wind mass flux, and compare the thermoelectric and conduction current contributions to the Joule heating rate. The ratio of the viscous to Joule heating rates per unit mass can exceed unity by orders of magnitude, and increases rapidly with L. The viscous heating rate can be concentrated outside the region where the current density is localized, corresponding to a resistively heated layer of plasma bounded by viscously heated plasma. The temperature gradient drives a thermoelectric current density that can have a magnitude greater than that of the electric-field-driven conduction current density, so thermoelectric effects are important in determining the Joule heating rate.
Computer program for calculating thermodynamic and transport properties of fluids
NASA Technical Reports Server (NTRS)
Hendricks, R. C.; Braon, A. K.; Peller, I. C.
1975-01-01
Computer code has been developed to provide thermodynamic and transport properties of liquid argon, carbon dioxide, carbon monoxide, fluorine, helium, methane, neon, nitrogen, oxygen, and parahydrogen. Equation of state and transport coefficients are updated and other fluids added as new material becomes available.
a Theory of Transport Properties of Random Alloys
David Grave Resendes
1986-01-01
A theory of the low temperature transport properties of a random substitutional binary alloy is presented that formulates the single site approximations (SSA)--both the average t-matrix (ATA) and the coherent potential (CPA) approximations--along lines entirely parallel to those introdued by P. N. Argyres for the equilibrium properties. An energy-dependent statistical density operator is introduced, in terms of which many transport
Park, Jesung; Kemp, Nate J; Rylander, H Grady; Milner, Thomas E
2009-08-01
Complex polarization ratio (CPR) in materials with birefringence and biattenuance is shown as a logarithmic spiral in the complex plane. A multi-state Levenberg-Marquardt nonlinear fitting algorithm using the CPR trajectory collected by polarization sensitive optical coherence tomography (PS-OCT) was developed to determine polarization properties of an anisotropic scattering medium. The Levenberg-Marquardt nonlinear fitting algorithm using the CPR trajectory is verified using simulated PS-OCT data with speckle noise. Birefringence and biattenuance of a birefringent film, ex-vivo rodent tail tendon and in-vivo primate retinal nerve fiber layer were determined using measured CPR trajectories and the Levenberg-Marquardt nonlinear fitting algorithm. PMID:19654746
NASA Astrophysics Data System (ADS)
Ozyar, U. F.; Deligoz, E.; Colakoglu, K.
2015-02-01
The anisotropic elastic properties of XYSb (X = Ti, Zr, Hf; Y = Si, Ge) compounds have been investigated by using first-principles calculations based on density functional theory. The calculated lattice parameters are in excellent agreement with the available experimental data. The computed elastic constants indicate that all compounds are mechanically stable according to the elastic stability criteria under pressure. We have calculated the bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Debye temperature, and anisotropy value from the obtained elastic constants according to the Voigt-Reuss-Hill approximation. Additionally, the ductility and brittleness are characterized with the estimation from Pugh's rule (B/G) and Poisson's ratio. Furthermore, the elastic anisotropy have been visualized in detail by plotting the directional dependence of compressibility, Young's and shear moduli.
NASA Astrophysics Data System (ADS)
Liu, W. Q.; Zuo, J. H.; Yue, M.; Cui, Z. Z.; Zhang, D. T.; Zhang, J. X.; Zhang, P. Y.; Ge, H. L.; Guo, Z. H.; Li, W.
2011-04-01
Chemical coating, hot compaction, and hot deformation techniques have been applied to prepare bulk anisotropic SmCo5/?-Fe nanocomposite magnets. The effects of ?-Fe content on the structure and magnetic properties of the magnets were studied. With the increase of the ?-Fe content, both the saturation magnetization (Ms) and remanence (Mr) of the magnets rise first, peak at 10 vol. % ?-Fe content and then fall while the coercivity (Hci) of the magnets drops simultaneously. Crystal structure analysis shows that the magnets exhibit a strong c-axis crystal texture of the SmCo5 phase, which, however, weakens gradually as the ?-Fe content increases. Microstructure observation also shows that there are many SmCo5 equiaxial grains even after hot deformation in the magnets with 15 vol. % ?-Fe.
Gorelikov, G. A.; Fridman, Yu. A.
2013-07-15
The spectra of coupled magnetoelastic waves in a semi-infinite strongly anisotropic easy-plane ferromagnet with a rigidly fixed face are analyzed for two variants of fixation (in the basal plane and perpendicularly to it). The phase states of the system are determined. Differences in the phase diagrams and elementary excitation spectra depending on the choice of the sample fixation plane are considered. When rotational invariance is taken into account, the nonreciprocity effect for the velocities of sound in a crystal appears. It is shown that the velocity of sound in the sample considerably depends on the symmetry of the imposed mechanical boundary conditions. The phase diagrams of the system under investigation are presented.
Anisotropic optical properties of semipolar AlGaN layers grown on m-plane sapphire
NASA Astrophysics Data System (ADS)
Feneberg, Martin; Winkler, Michael; Klamser, Juliane; Stellmach, Joachim; Frentrup, Martin; Ploch, Simon; Mehnke, Frank; Wernicke, Tim; Kneissl, Michael; Goldhahn, Rüdiger
2015-05-01
The valence band order of AlxGa 1 -x N is investigated experimentally by analyzing the anisotropic dielectric functions of semipolar (11 2 ¯ 2 ) AlGaN thin films grown on m-plane Al2O3. Point-by-point fitted dielectric functions are obtained by spectroscopic ellipsometry and corresponding inter-band transition energies are extracted. The known strain situation of the sample layers is used to correct for the small strain-induced energy shifts within k . p perturbation theory. It also is used to identify transitions related to the three valence bands. Transitions with E ? c from the ?9 valence band verify an inter-band bowing parameter of b =0.9 eV . The transitions with E || c allow determining the crystal field splitting energy which can be described by a linear interpolation between the values for GaN and AlN satisfactorily.
Thermodynamics and magnetic properties of the anisotropic 3D Hubbard model.
Imriška, Jakub; Iazzi, Mauro; Wang, Lei; Gull, Emanuel; Greif, Daniel; Uehlinger, Thomas; Jotzu, Gregor; Tarruell, Leticia; Esslinger, Tilman; Troyer, Matthias
2014-03-21
We study the anisotropic 3D Hubbard model with increased nearest-neighbor tunneling amplitudes along one direction using the dynamical cluster approximation and compare the results to a quantum simulation experiment of ultracold fermions in an optical lattice. We find that the short-range spin correlations are significantly enhanced in the direction with stronger tunneling amplitudes. Our results agree with the experimental observations and show that the experimental temperature is lower than the strong tunneling amplitude. We characterize the system by examining the spin correlations beyond neighboring sites and determine the distribution of density, entropy, and spin correlation in the trapped system. We furthermore investigate the dependence of the critical entropy at the Néel transition on anisotropy. PMID:24702384
Ortiz, Aurélie U; Fuchs, Alain H; Coudert, François-Xavier
2012-01-01
We performed ab initio calculations of the elastic constants of five flexible metal-organic frameworks: MIL-53(Al), MIL-53(Ga), MIL-47 and the square and lozenge structures of DMOF-1. Tensorial analysis of the elastic constants reveal a highly anisotropic elastic behavior, some deformation directions exhibiting very low Young's modulus and shear modulus. This anisotropy can reach a 400:1 ratio between the most rigid and weakest directions, in stark contrast with the case of non-flexible MOFs such as MOF-5 and ZIF-8. In addition, we show that flexible MOFs can display extremely large negative linear compressibility (NLC). These results uncover the microscopic roots of stimuli-induced structural transitions in flexible MOFs, by linking the local elastic behavior of the material and its multistability.
Ortiz, Aurélie U; Boutin, Anne; Fuchs, Alain H; Coudert, François-Xavier
2012-11-01
We performed ab initio calculations of the elastic constants of five flexible metal-organic frameworks (MOFs): MIL-53(Al), MIL-53(Ga), MIL-47, and the square and lozenge structures of DMOF-1. Tensorial analysis of the elastic constants reveals a highly anisotropic elastic behavior, some deformation directions exhibiting very low Young's modulus and shear modulus. This anisotropy can reach a 400:1 ratio between the most rigid and weakest directions, in stark contrast to the case of nonflexible MOFs such as MOF-5 and ZIF-8. In addition, we show that flexible MOFs can display extremely large negative linear compressibility. These results uncover the microscopic roots of stimuli-induced structural transitions in flexible MOFs, by linking the local elastic behavior of the material and its multistability. PMID:23215398
NASA Astrophysics Data System (ADS)
Ortiz, Aurélie U.; Boutin, Anne; Fuchs, Alain H.; Coudert, François-Xavier
2012-11-01
We performed ab initio calculations of the elastic constants of five flexible metal-organic frameworks (MOFs): MIL-53(Al), MIL-53(Ga), MIL-47, and the square and lozenge structures of DMOF-1. Tensorial analysis of the elastic constants reveals a highly anisotropic elastic behavior, some deformation directions exhibiting very low Young’s modulus and shear modulus. This anisotropy can reach a 400?1 ratio between the most rigid and weakest directions, in stark contrast to the case of nonflexible MOFs such as MOF-5 and ZIF-8. In addition, we show that flexible MOFs can display extremely large negative linear compressibility. These results uncover the microscopic roots of stimuli-induced structural transitions in flexible MOFs, by linking the local elastic behavior of the material and its multistability.
NASA Astrophysics Data System (ADS)
Haas, Stephan
1993-05-01
We consider an isolated missing link in an anisotropic Heisenberg antiferromagnet of spin S and coupling constants Jz?Jxy on a square lattice. The interplay between longitudinal terms, involving Sz , and transverse terms, representing the quantum fluctuations, of the Hamiltonian is investigated. Within the linearized spin-wave approximation (LSWA), we find that the local magnetic moment is slightly enhanced at the sites adjacent to the impurity link. It is also shown that quantum fluctuations on neighboring sites are drastically reduced in the vicinity of the impurity. Using perturbation theory we argue that the longitudinal zero-temperature susceptibility (??) vanishes up to O(hz4). The static transversal susceptibility [?? (T=0)] is obtained within the LSWA, and is shown to be enhanced due to the defect.
Transport properties of pancreatic cancer describe gemcitabine delivery and response
Koay, Eugene J.; Truty, Mark J.; Cristini, Vittorio; Thomas, Ryan M.; Chen, Rong; Chatterjee, Deyali; Kang, Ya’an; Bhosale, Priya R.; Tamm, Eric P.; Crane, Christopher H.; Javle, Milind; Katz, Matthew H.; Gottumukkala, Vijaya N.; Rozner, Marc A.; Shen, Haifa; Lee, Jeffery E.; Wang, Huamin; Chen, Yuling; Plunkett, William; Abbruzzese, James L.; Wolff, Robert A.; Varadhachary, Gauri R.; Ferrari, Mauro; Fleming, Jason B.
2014-01-01
Background. The therapeutic resistance of pancreatic ductal adenocarcinoma (PDAC) is partly ascribed to ineffective delivery of chemotherapy to cancer cells. We hypothesized that physical properties at vascular, extracellular, and cellular scales influence delivery of and response to gemcitabine-based therapy. Methods. We developed a method to measure mass transport properties during routine contrast-enhanced CT scans of individual human PDAC tumors. Additionally, we evaluated gemcitabine infusion during PDAC resection in 12 patients, measuring gemcitabine incorporation into tumor DNA and correlating its uptake with human equilibrative nucleoside transporter (hENT1) levels, stromal reaction, and CT-derived mass transport properties. We also studied associations between CT-derived transport properties and clinical outcomes in patients who received preoperative gemcitabine-based chemoradiotherapy for resectable PDAC. Results. Transport modeling of 176 CT scans illustrated striking differences in transport properties between normal pancreas and tumor, with a wide array of enhancement profiles. Reflecting the interpatient differences in contrast enhancement, resected tumors exhibited dramatic differences in gemcitabine DNA incorporation, despite similar intravascular pharmacokinetics. Gemcitabine incorporation into tumor DNA was inversely related to CT-derived transport parameters and PDAC stromal score, after accounting for hENT1 levels. Moreover, stromal score directly correlated with CT-derived parameters. Among 110 patients who received preoperative gemcitabine-based chemoradiotherapy, CT-derived parameters correlated with pathological response and survival. Conclusion. Gemcitabine incorporation into tumor DNA is highly variable and correlates with multiscale transport properties that can be derived from routine CT scans. Furthermore, pretherapy CT-derived properties correlate with clinically relevant endpoints. Trial registration. Clinicaltrials.gov NCT01276613. Funding. Lustgarten Foundation (989161), Department of Defense (W81XWH-09-1-0212), NIH (U54CA151668, KCA088084). PMID:24614108
PROPERTIES OF INTERFACES AND TRANSPORT ACROSS THEM
Much of the biological activity in cell cytoplasm occurs in compartments which are thought to form by phase separation, and many of the functions of these compartments occur by the transport or exchange of molecules across interfaces. Thus, a fundamentally based discussion of th...
Determination of Transport Properties in Chromium Disilicide Nanowires via
Shi, Li
Determination of Transport Properties in Chromium Disilicide Nanowires via Combined Thermoelectric The Seebeck coefficient, electrical conductivity, and thermal conductivity of individual chromium disilicide to characterize the TE properties of single-crystal chromium disilicide (CrSi2) NWs and correlate them
Thermodynamic and transport properties of dense quantum Coulomb systems
Bonitz, Michael
Thermodynamic and transport properties of dense quantum Coulomb systems M. Bonitz and V including path integral Monte Carlo simulations of the equi- librium behavior of dense hydrogen and electron-hole plasmas and molecular dynamics and quantum kinetic theory simulations of the nonequilibrium properties
NASA Astrophysics Data System (ADS)
Lai, K. H.; Chen, J. S.; Liu, C. W.
2014-12-01
The formation of dissolution-induced finger patterns in geologic media is an important issue in a range of geologic settings and industrial applications. A considerable amount of research has been conducted into the morphological evolution of chemical dissolution fronts within an isotropic fluid-saturated porous medium. Although real geologic media are never perfectly isotropic, previous studies often assume they are. This study investigates temporal porosity evolution in an anisotropic fluid-saturated porous medium. A series of numerical simulations are performed to evaluate the morphological evolution of chemical dissolution front. Simulation results indicate that morphological evolution of chemical dissolution fronts not only depends on the spacing of two local non-uniformities and the upstream pressure gradient but also the medium anisotropic permeability ratio. However, the effect of the medium anisotropic permeability ratio decreases with increasing upstream pressure gradient.
Anisotropic electronic properties of the bronze, CsP8W8O40
E. Wang; M. Greenblatt
1988-01-01
Cesium tungsten phosphate oxide, CsP8W8O40, bronze single crystals were grown by chemical vapor transport with KBr as the transporting agent. Electrical resistivity measurements on oriented crystals with varrhoa (RT) = 5.9 × 10-2 Omega cm, varrhob (RT) = 4.5 × 10-2 Omega cm, and varrhoc (RT) = 5.7 × 10-3 Omega cm indicate quasi-one-dimensional behavior. A broad transition observed at
Friedel, Michael J.
2001-01-01
This report describes a model for simulating transient, Variably Saturated, coupled water-heatsolute Transport in heterogeneous, anisotropic, 2-Dimensional, ground-water systems with variable fluid density (VST2D). VST2D was developed to help understand the effects of natural and anthropogenic factors on quantity and quality of variably saturated ground-water systems. The model solves simultaneously for one or more dependent variables (pressure, temperature, and concentration) at nodes in a horizontal or vertical mesh using a quasi-linearized general minimum residual method. This approach enhances computational speed beyond the speed of a sequential approach. Heterogeneous and anisotropic conditions are implemented locally using individual element property descriptions. This implementation allows local principal directions to differ among elements and from the global solution domain coordinates. Boundary conditions can include time-varying pressure head (or moisture content), heat, and/or concentration; fluxes distributed along domain boundaries and/or at internal node points; and/or convective moisture, heat, and solute fluxes along the domain boundaries; and/or unit hydraulic gradient along domain boundaries. Other model features include temperature and concentration dependent density (liquid and vapor) and viscosity, sorption and/or decay of a solute, and capability to determine moisture content beyond residual to zero. These features are described in the documentation together with development of the governing equations, application of the finite-element formulation (using the Galerkin approach), solution procedure, mass and energy balance considerations, input requirements, and output options. The VST2D model was verified, and results included solutions for problems of water transport under isohaline and isothermal conditions, heat transport under isobaric and isohaline conditions, solute transport under isobaric and isothermal conditions, and coupled water-heat-solute transport. The first three problems considered in model verification were compared to either analytical or numerical solutions, whereas the coupled problem was compared to measured laboratory results for which no known analytic solutions or numerical models are available. The test results indicate the model is accurate and applicable for a wide range of conditions, including when water (liquid and vapor), heat (sensible and latent), and solute are coupled in ground-water systems. The cumulative residual errors for the coupled problem tested was less than 10-8 cubic centimeter per cubic centimeter, 10-5 moles per kilogram, and 102 calories per cubic meter for liquid water content, solute concentration and heat content, respectively. This model should be useful to hydrologists, engineers, and researchers interested in studying coupled processes associated with variably saturated transport in ground-water systems.
NASA Astrophysics Data System (ADS)
Lee, K.; Gibson, R. L.
2002-12-01
The wavefront construction method is an efficient way to model wave propagation in anisotropic media. This method is based on asymptotic ray theory, and it explicitly tracks the propagation of wavefronts through the earth model. The first step is to trace a fan of rays through the earth model, initializing the wavefront by constructing a mesh from the set of all ray points at a specified travel time. The wavefront is thus a mesh composed of quadrilateral cells defined by four neighboring rays. Rays are computed by kinematic ray tracing using Runge-Kutta methods. The basic geometry, or coordinate system, used to select the rays comprising the initial mesh has significant affects on the precision and performance of the numerical calculation. A common approach is to trace rays with regular increments in the azimuthal and declination takeoff angles. These two angles, along with travel time, define a ray coordinate system that is commonly used for implementations of conventional ray tracing for wavefront construction schemes. While the ray coordinate system is straightforward to implement and has been used extensively, it has some drawbacks (Gibson et al., 2002). The most important is that the derivatives of Cartesian coordinates on the ray with respect to the azimuthal takeoff angle vanish near the poles of the coordinate system, leading to potential numerical errors. Our implementation applies paraxial methods, and the poor estimates of derivatives can seriously degrade the performance of the algorithm. Also, specifying an initial ray field with even increments in takeoff angles leads to large concentrations of rays near the poles, which is numerically inefficient. To overcome these important limitations of the ray coordinate system, we apply a new mesh generation algorithm that utilizes a cubic gnomonic mesh. A cubic gnomonic mesh maps points chosen at regular intervals on the surface of a cube surrounding the source point to the focal sphere. In essence, the initial directions of the rays are defined by drawing a line segment from the source point through each initial mesh point on the cubic surface. Then all of the calculations of derivatives for the paraxial method are performed on the geometry defined by this new set of ray coordinates. The ray density is uniform in all directions, and the derivatives never vanish since there are no poles in the new ray coordinate system. We will compare the numerical results of ray coordinate and cubic gnomonic coordinate systems to illustrate the advantages of the new system. We will also describe the implementation of the new scheme and show examples of applications to anisotropic earth models.
Transport properties of a meson gas
D. Fernandez-Fraile; A. Gomez Nicola
2007-07-09
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.
Unsaturated Zone and Saturated Zone Transport Properties (U0100)
J. Conca
2000-12-20
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.
Properties of intracellular transport: the role of cytoskeleton topology
NASA Astrophysics Data System (ADS)
Korabel, Nickolay; Huang, Kerwyn C.; Gopinathan, Ajay
2013-03-01
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.
Enhancement of wall jet transport properties
Claunch, S.D.; Farrington, R.B.
1997-02-04
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. 17 figs.
Enhancement of wall jet transport properties
Claunch, Scott D. (Broomfield, CO); Farrington, Robert B. (Golden, CO)
1997-01-01
By enhancing the natural instabilities in the boundary layer and in the free shear layer of a wall jet, the boundary is minimized thereby increasing the transport of heat and mass. Enhancing the natural instabilities is accomplished by pulsing the flow of air that creates the wall jet. Such pulsing of the flow of air can be accomplished by sequentially occluding and opening a duct that confines and directs the flow of air, such as by rotating a disk on an axis transverse to the flow of air in the duct.
Electron-Transport Properties of Few-Layer Black Phosphorus.
Xu, Yuehua; Dai, Jun; Zeng, Xiao Cheng
2015-06-01
We perform the first-principles computational study of the effect of number of stacking layers and stacking style of the few-layer black phosphorus (BPs) on the electronic properties, including transport gap, current-voltage (i-v) relation, and differential conductance. Our computation is based on the nonequilibrium Green's function approach combined with density functional theory calculations. Specifically, we compute electron-transport properties of monolayer BP, bilayer BP, and trilayer BP as well as bilayer BPs with AB-, AA-, or AC-stacking. We find that the stacking number has greater influence on the transport gap than the stacking type. Conversely, the stacking type has greater influence on i-v curve and differential conductance than on the transport gap. This study offers useful guidance for determining the number of stacking layers and the stacking style of few-layer BP sheets in future experimental measurements and for potential applications in nanoelectronic devices. PMID:26266491
Thermodynamic and transport properties of sodium liquid and vapor
Fink, J.K.; Leibowitz, L.
1995-01-01
Data have been reviewed to obtain thermodynamically consistent equations for thermodynamic and transport properties of saturated sodium liquid and vapor. Recently published Russian recommendations and results of equation of state calculations on thermophysical properties of sodium have been included in this critical assessment. Thermodynamic properties of sodium liquid and vapor that have been assessed include: enthalpy, heat capacity at constant pressure, heat capacity at constant volume, vapor pressure, boiling point, enthalpy of vaporization, density, thermal expansion, adiabatic and isothermal compressibility, speed of sound, critical parameters, and surface tension. Transport properties of liquid sodium that have been assessed include: viscosity and thermal conductivity. For each property, recommended values and their uncertainties are graphed and tabulated as functions of temperature. Detailed discussions of the analyses and determinations of the recommended equations include comparisons with recommendations given in other assessments and explanations of consistency requirements. The rationale and methods used in determining the uncertainties in the recommended values are also discussed.
Transport Properties of Semiconducting Phosphate Glasses
M. Sayer; A. Mansingh
1972-01-01
The temperature and frequency dependence of conductivity, dielectric properties, infrared absorption, and electron-paramagnetic-resonance data are presented for semiconducting phosphate glasses based on oxides of Ti, V, Mn, Fe, Co, Ni, Cu, Mo, and W. The vanadate system is examined in a range of compositions, most of the others in the composition 50 mol% oxide. A polaronic model is shown to
Middle Atmosphere Transport Properties of Assimilated Datasets
NASA Technical Reports Server (NTRS)
Pawson, Steven; Rood, Richard
1999-01-01
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.
Middle Atmospheric Transport Properties of Assimilated Datasets
NASA Technical Reports Server (NTRS)
Pawson, Steven; Rood, Richard
1999-01-01
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.
NASA Astrophysics Data System (ADS)
Lam, Wai Sze Tiffany
Optical components made of anisotropic materials, such as crystal polarizers and crystal waveplates, are widely used in many complex optical system, such as display systems, microlithography, biomedical imaging and many other optical systems, and induce more complex aberrations than optical components made of isotropic materials. The goal of this dissertation is to accurately simulate the performance of optical systems with anisotropic materials using polarization ray trace. This work extends the polarization ray tracing calculus to incorporate ray tracing through anisotropic materials, including uniaxial, biaxial and optically active materials. The 3D polarization ray tracing calculus is an invaluable tool for analyzing polarization properties of an optical system. The 3x3 polarization ray tracing P matrix developed for anisotropic ray trace assists tracking the 3D polarization transformations along a ray path with series of surfaces in an optical system. To better represent the anisotropic light-matter interactions, the definition of the P matrix is generalized to incorporate not only the polarization change at a refraction/reflection interface, but also the induced optical phase accumulation as light propagates through the anisotropic medium. This enables realistic modeling of crystalline polarization elements, such as crystal waveplates and crystal polarizers. The wavefront and polarization aberrations of these anisotropic components are more complex than those of isotropic optical components and can be evaluated from the resultant P matrix for each eigen-wavefront as well as for the overall image. One incident ray refracting or reflecting into an anisotropic medium produces two eigenpolarizations or eigenmodes propagating in different directions. The associated ray parameters of these modes necessary for the anisotropic ray trace are described in Chapter 2. The algorithms to calculate the P matrix from these ray parameters are described in Chapter 3 for anisotropic ray tracing. x. Chapter 4 presents the data reduction of the P matrix of a crystal waveplate. The diattenuation is embedded in the singular values of P. The retardance is divided into two parts: (A) The physical retardance induced by OPLs and surface interactions, and (B) the geometrical transformation induced by geometry of a ray path, which is calculated by the geometrical transform Q matrix. The Q matrix of an anisotropic intercept is derived from the generalization of s- and p-bases at the anisotropic intercept; the p basis is not confined to the plane of incidence due to the anisotropic refraction or reflection. Chapter 5 shows how the multiple P matrices associated with the eigenmodes resulting from propagation through multiple anisotropic surfaces can be combined into one P matrix when the multiple modes interfere in their overlapping regions. The resultant P matrix contains diattenuation induced at each surface interaction as well as the retardance due to ray propagation and total internal reflections. The polarization aberrations of crystal waveplates and crystal polarizers are studied in Chapter 6 and Chapter 7. A wavefront simulated by a grid of rays is traced through the anisotropic system and the resultant grid of rays is analyzed. The analysis is complicated by the ray doubling effects and the partially overlapping eigen-wavefronts propagating in various directions. The wavefront and polarization aberrations of each eigenmode can be evaluated from the electric field distributions. The overall polarization at the plane of interest or the image quality at the image plane are affected by each of these eigen-wavefronts. Isotropic materials become anisotropic due to stress, strain, or applied electric or magnetic fields. In Chapter 8, the P matrix for anisotropic materials is extended to ray tracing in stress birefringent materials which are treated as spatially varying anisotropic materials. Such simulations can predict the spatial retardance variation throughout the stressed optical component and its effects on the point spread function and mod
Transport properties of high-temperature Jupiter atmosphere components
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
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.
Frelek, Jadwiga; Szczepek, Wojciech J; Neubrech, Stephan; Schultheis, Bernd; Brechtel, Joachim; Kuball, Hans-Georg
2002-04-15
Substituted cisoid 4-en-6-one steroids with isotropically distributed and partially oriented molecules were analyzed by circular dichroism (CD) and anisotropic circular dichroism (ACD) spectroscopy, respectively. CD and ACD data supplement their respective phenomenological information. For a series of C3-substituted enones 1 to 7, the difference of CD (Delta epsilon) and ACD (Delta epsilon(A)) values, that is, Delta epsilon -Delta epsilon(A), vary in the n-* transition region in the same direction, independently of the nature and position (3 alpha or 3 beta) of the substituent. For 7-bromo-substituted enones 5 and 6 the sign of the n-pi* CD band is opposite to that predicted by the enone helicity rule. The ACD data indicate that this behavior is a consequence of the effect of vibronic coupling caused by the 7-bromo substituent. In contrast to the results obtained for the series of C7-unsubstituted compounds 1 to 4, the intensity of the CD bands for 5 and 6 is determined by the vibrational progressions of a different symmetry. Therefore, the helicity rule must fail in both cases because the rule can only be applied to those vibrational transitions for which the rule was developed. The sign of the coordinates Delta epsilon(*)(II), estimated from the ACD data, yields additional stereochemical information that cannot be obtained from the CD data alone. The CD and ACD spectra in the region of the pi-pi* transition vary for enones 1 to 4 in a different fashion and indicate dependence upon spatial orientation (3 alpha or 3 beta) of substituents. This dependence may lead to the possibility of extracting additional stereochemical information from the ACD spectra. Furthermore, the experimental findings indicate that the second CD band located at about 220 nm belongs to a forbidden transition and not to an allowed pi-pi* transition. PMID:12007100
Transport properties of interacting magnetic islands in tokamak plasmas
Gianakon, T.A.; Callen, J.D.; Hegna, C.C.
1993-10-01
This paper explores the equilibrium and transient transport properties of a mixed magnetic topology model for tokamak equilibria. The magnetic topology is composed of a discrete set of mostly non-overlapping magnetic islands centered on the low-order rational surfaces. Transport across the island regions is fast due to parallel transport along the stochastic magnetic field lines about the separatrix of each island. Transport between island regions is assumed to be slow due to a low residual cross-field transport. In equilibrium, such a model leads to: a nonlinear dependence of the heat flux on the pressure gradient; a power balance diffusion coefficient which increases from core to edge; and profile resiliency. Transiently, such a model also exhibits a heat pulse diffusion coefficient larger than the power balance diffusion coefficient.
Transport properties in nontwist area-preserving maps
Szezech Jr., J. D.; Caldas, I. L.; Lopes, S. R.; Viana, R. L.; Morrison, P. J.
2009-01-01
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.
Transport properties in nontwist area-preserving maps
Szezech Jr., J. D.; Caldas, I. L.; Lopes, S. R.; Viana, R. L.; Morrison, P. J.
2009-10-23
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.
Theoretical consistency test of steam transport properties
NASA Technical Reports Server (NTRS)
Thoen-Hellemans, J.; Mason, E. A.
1973-01-01
The kinetic theory of polyatomic gases is used to test the mutual consistency of the thermal conductivity, viscosity, and specific heat of low-pressure steam from 100 to 700 C. No inconsistency exists within the cited tolerances of the skeleton tables recommended by the Sixth International Conference on the Properties of Steam, but there is some basis for suspecting that the high-temperature thermal conductivity values are slightly low. Methods for tightening the consistency bounds are suggested.
NASA Astrophysics Data System (ADS)
Alves, T. M. L.; Bezerra, C. G.; Viegas, A. D. C.; Nicolodi, S.; Corrêa, M. A.; Bohn, F.
2015-02-01
We performed a theoretical and experimental investigation of the quasi-static magnetic properties of anisotropic systems. We considered a modified Stoner-Wohlfarth model to describe anisotropic systems, and a distribution function to express the magnetic anisotropy dispersion. We also proposed a procedure to calculate the magnetic properties from experimental results of the quadrature of magnetization curves, thus quantifying the magnetic anisotropy dispersion. To test the robustness of the approach, we applied the theoretical model to describe the quasi-static magnetic properties of amorphous FeCuNbSiB ferromagnetic films, and directly compared the theoretical results with longitudinal and transverse magnetization curves measured for the films. Our films are characterized by anisotropy fields between 7 and 10.5 Oe, values compatible with that obtained for several amorphous magnetic materials, as well as by anisotropy dispersions expressed by exponents n between 14 and 30. Thus, the excellent agreement between numerical calculation and experimental results provides support to confirm the validity of our theoretical approach to describe the magnetic properties of anisotropic amorphous ferromagnetic films.
Determination of the anisotropic elastic properties of Ge1Sb2Te4
NASA Astrophysics Data System (ADS)
Marmier, Arnaud; Kohary, Krisztian; Wright, C. David
2011-06-01
The elastic properties of Ge-Sb-Te (GST) alloys are important for phase-change devices (such as CD-RW, DVD-RW, Blu-ray, or phase-change random access memory) because the transition between the crystalline and amorphous phases involves a volume change accommodated by a strain estimated to be between 150 MPa and 10 GPa. However, the elastic properties of GST alloys are poorly characterized and the experimental and theoretical values show large discrepancies. We carry out a careful analysis of the elastic properties of a model system, crystalline Ge1Sb2Te4, using density functional theory and elastic anisotropy considerations. We show that Ge1Sb2Te4 exhibits significant anisotropy in its elastic properties.
Anisotropic Fermi surface from holography
Li Qing Fang; Xian-Hui Ge; Jian-Pin Wu; Hong-Qiang Leng
2015-06-13
We investigate the probe holographic fermions by using an anisotropic charged black brane solution. We derive the equation of motion of probe bulk fermions with one Fermi momentum along the anisotropic and one along the isotropic directions. We then numerically solve the equation and analyze the properties of Green function with these two momentums. We find in this case the shape of Fermi surface is anisotropic. However, for both Fermi momentums perpendicular to the anisotropic direction, the Fermi surface is isotropic. We verify that our system obeys the recently conjectured bound for thermoelectric diffusion constants for the stable branch of the black brane solutions.
Near-field investigations of the anisotropic properties of supported lipid bilayers
NASA Astrophysics Data System (ADS)
Johnson, Merrell A.
2011-12-01
The details of Polarization Modulation Near-Field Scanning Optical Microscopy (PM-NSOM) are presented. How to properly calibrate and align the system is also introduced. A measurement of Muscovite crystal is used to display the capabilities of the setup. Measurements of supported gel state 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayers are presented, emphasizing how it was tooled in exploiting the anisotropic nature of the acyl chains. A discussion of how the effective retardance (DeltaS = 2 pi (ne-no) t /lambda) and the direction of the projection of the acyl chains (?) are measured simultaneously is given, (where t is the thickness of the bilayer and lambda is the wavelength of light used). It is shown from DeltaS the birefringence (ne-n o) of the bilayer is determined, by assuming the acyl chain tilt with respect to the membrane's normal to be approximately ? ? 32 degrees. Time varying experiments show lateral diffusions of ˜ 2x10 -12 (cm2)/s. Temperature controlled PM-NSOM is shown to be a viable way to determine the main phase transition temperature (Tm) for going from the gel to liquid disorder state of supported DPPC bilayers. A change DeltaS ˜ (3.8+/-0.3 mrad) at the main phase transition temperature Tm (? 41°C) is observed. This agrees well with previous values of ( ne-no) and translates to an assumed ? ˜ 32 degrees, when T < Tm and 0 when T > Tm. Evidence of supper heating and supper cooling will be presented, along with a discussion of the fluctuations that occur around Tm. Finally it is shown how physical parameters such as the polarizability are extracted from the data. Values of the transverse (alpha t) and longitudinal (alphal) polarizabilites of the acyl chains are shown to be, alphat = 44.2A3 and alphal = 94.4 A3, which correspond well with the theoretical values of a single palmitic acid (C16) alpha t = 25.14 A3 and alpha l = 45.8 A3.
Optical nanotomography of anisotropic fluids
Loss, Daniel
LETTERS Optical nanotomography of anisotropic fluids ANTONIO DE LUCA1 *, VALENTIN BARNA2 *, TIMOTHY September 2008; doi:10.1038/nphys1077 The physical properties of anisotropic fluids can be manipulated,2 . This facilitates the use of ordered fluids in a variety of scientific endeavours and applications. Although future
Cornelius, A. L.; Arko, A. J.; Sarrao, J. L.; Hundley, M. F.; Fisk, Z.
2000-12-01
We have used high pulsed magnetic fields to 50 T to observe de Haas--van Alphen oscillations in the tetragonal antiferromagnet CeRhIn{sub 5}, which has an enhanced value of the electronic specific heat coefficient {gamma}{approx}>420 mJ/molK{sup 2}. For T
Hybrid silica-polyimide composite membranes: gas transport properties
Chris J. Cornelius; Eva Marand
2002-01-01
The gas permeability, diffusivity, and selectivity properties of gases such as He, O2, N2, CH4, and CO2 were evaluated for a series of hybrid inorganic–organic composites based on 6FDA-6FpDA and 6FDA-6FpDA-DABA polyimides and various organo-silica structures. The organo-silica domains were introduced into the polymer matrix via sol–gel reactions. The gas transport properties of these hybrid membranes were dependent on the
NASA Astrophysics Data System (ADS)
Min, Byunghoon; An, Chan-Yong; Kim, Chang-Bae; Lee, Gun Bok
2015-04-01
Fluxes of both the vorticity and the plasma density due to the nonlinear E × B convective derivatives are divided into two parts. One part, which is almost isotropic, is well known to engage in the transfer of energies from the energy-producing scale where the phase mismatch between the density and the electric potential is large. The other part, in the Fourier space , is found to be highly anisotropic. If it is summed over k y , the result is nearly random around zero in k x while the sum over k x is approximately proportional to k y . In Fourier space, such anisotropic fluxes are found to be closely related to the gradients of the squares of the vorticity and the electric potential, respectively. We argue that the advecting velocities in Fourier space may be predicted on dimensional grounds.
Anisotropic Artificial Impedance Surfaces
NASA Astrophysics Data System (ADS)
Quarfoth, Ryan Gordon
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.
Hua Yu; Wang Xingguo; Li Zhengneng
1998-01-01
The study on property degradation of damaged composite laminates is extended to anisotropic laminates with matrix cracking.\\u000a In (I) of the paper, an idea of “stiffness patition” is proposed to deal with the puzzle that the in-plane normal response is coupled\\u000a with the shear response of the laminates. For (?\\u000a m\\u000a \\/90\\u000a n\\u000a ), laminates containing transversely cracked layers under
NASA Astrophysics Data System (ADS)
Hallberg, Håkan
2014-12-01
The present study elaborates on a 2D level set model of polycrystal microstructures that was recently established by adding the influence of anisotropic grain boundary energy and mobility on microstructure evolution. The new model is used to trace the evolution of grain boundary character distribution during grain growth. The employed level set formulation conveniently allows the grain boundary characteristics to be quantified in terms of coincidence site lattice (CSL) type per unit of grain boundary length, providing a measure of the distribution of such boundaries. In the model, both the mobility and energy of the grain boundaries are allowed to vary with misorientation. In addition, the influence of initial polycrystal texture is studied by comparing results obtained from a polycrystal with random initial texture against results from a polycrystal that initially has a cube texture. It is shown that the proposed level set formulation can readily incorporate anisotropic grain boundary properties and the simulation results further show that anisotropic grain boundary properties only have a minor influence on the evolution of CSL boundary distribution during grain growth. As anisotropic boundary properties are considered, the most prominent changes in the CSL distributions are an increase of general low-angle ?1 boundaries as well as a more stable presence of ?3 boundaries. The observations also hold for the case of an initially cube-textured polycrystal. The presence of this kind of texture has little influence over the evolution of the CSL distribution. Taking into consideration the anisotropy of grain boundary properties, grain growth alone does not seem to be sufficient to promote any significantly increased overall presence of CSL boundaries.
Architecture and properties of anisotropic polymer composite scaffolds for bone tissue engineering.
Mathieu, Laurence Marcelle; Mueller, Thomas L; Bourban, Pierre-Etienne; Pioletti, Dominique P; Müller, Ralph; Månson, Jan-Anders E
2006-02-01
Bone is a complex porous composite structure with specific characteristics such as viscoelasticity and anisotropy, both in morphology and mechanical properties. Bone defects are regularly filled with artificial tissue grafts, which should ideally have properties similar to those of natural bone. Open cell composite foams made of bioresorbable poly(L-lactic acid) (PLA) and ceramic fillers, hydroxyapatite (HA) or beta-tricalcium phosphate (beta-TCP), were processed by supercritical CO2 foaming. Their internal 3D-structure was then analysed by micro-computed tomography (microCT), which evidenced anisotropy in morphology with pores oriented in the foaming direction. Furthermore compressive tests demonstrated anisotropy in mechanical behaviour, with an axial modulus up to 1.5 times greater than the transverse modulus. Composite scaffolds also showed viscoelastic behaviour with increased modulus for higher strain rates. Such scaffolds prepared by gas foaming of polymer composite materials therefore possess suitable architecture and properties for bone tissue engineering applications. PMID:16051346
Structure and transport properties of nanostructured materials.
Sonwane, C G; Li, Q
2005-03-31
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
Effects of nanosized constriction on thermal transport properties of graphene
2014-01-01
Thermal transport properties of graphene with nanosized constrictions are investigated using nonequilibrium molecular dynamics simulations. The results show that the nanosized constrictions have a significant influence on the thermal transport properties of graphene. The thermal resistance of the nanosized constrictions is on the order of 107 to 109 K/W at 150 K, which reduces the thermal conductivity by 7.7% to 90.4%. It is also found that the constriction resistance is inversely proportional to the width of the constriction and independent of the heat current. Moreover, we developed an analytical model for the ballistic thermal resistance of the nanosized constrictions in two-dimensional nanosystems. The theoretical prediction agrees well with the simulation results in this paper, which suggests that the thermal transport across the nanosized constrictions in two-dimensional nanosystems is ballistic in nature. PACS 65.80.CK; 61.48.Gh; 63.20.kp; 31.15.xv PMID:25232292
Tuning transport properties of nanofluidic devices with local charge inversion
He, Yan; Gillespie, Dirk; Boda, Dezs?; Vlassiouk, Ivan; Eisenberg, Robert S.; Siwy, Zuzanna S.
2009-01-01
Nanotubes can selectively conduct ions across membranes to make ionic devices with transport characteristics similar to biological ion channels and semiconductor electron devices. Depending on the surface charge profile of the nanopore, ohmic resistors, rectifiers, and diodes can be made. Here we show that a uniformly charged conical nanopore can have all these transport properties by changing the ion species and their concentrations on each side of the membrane. Moreover, the cation vs. anion selectivity of the pores can be changed. We find that polyvalent cations like Ca2+ and the trivalent cobalt sepulchrate produce localized charge inversion to change the effective pore surface charge profile from negative to positive. These effects are reversible so that the transport and selectivity characteristics of ionic devices can be tuned, much as the gate voltage tunes the properties of a semiconductor. PMID:19317490
Transport properties at nano scales via first principles studies
Chun Zhang
2004-01-01
There are two main difficulties for the first principles study of transport properties at the nano scale. The first is that many-body interactions need to be taken into account for the infinite system without periodic boundary conditions. The other is that the system is usually in a non-equilibrium state. Both of these two difficulties are beyond the ability of conventional
Oxygen transport properties estimation by DSMC-CT simulations
NASA Astrophysics Data System (ADS)
Bruno, Domenico; Frezzotti, Aldo; Ghiroldi, Gian Pietro
2014-12-01
Coupling DSMC simulations with classical trajectories calculations is emerging as a powerful tool to improve predictive capabilities of computational rarefied gas dynamics. The considerable increase of computational effort outlined in the early application of the method (Koura,1997) can be compensated by running simulations on massively parallel computers. In particular, GPU acceleration has been found quite effective in reducing computing time (Ferrigni,2012; Norman et al.,2013) of DSMC-CT simulations. The aim of the present work is to study rarefied Oxygen flows by modeling binary collisions through an accurate potential energy surface, obtained by molecular beams scattering (Aquilanti, et al.,1999). The accuracy of the method is assessed by calculating molecular Oxygen shear viscosity and heat conductivity following three different DSMC-CT simulation methods. In the first one, transport properties are obtained from DSMC-CT simulations of spontaneous fluctuation of an equilibrium state (Bruno et al, Phys. Fluids, 23, 093104, 2011). In the second method, the collision trajectory calculation is incorporated in a Monte Carlo integration procedure to evaluate the Taxman's expressions for the transport properties of polyatomic gases (Taxman,1959). In the third, non-equilibrium zero and one-dimensional rarefied gas dynamic simulations are adopted and the transport properties are computed from the non-equilibrium fluxes of momentum and energy. The three methods provide close values of the transport properties, their estimated statistical error not exceeding 3%. The experimental values are slightly underestimated, the percentage deviation being, again, few percent.
Computer programs for thermodynamic and transport properties of hydrogen
NASA Technical Reports Server (NTRS)
Hall, W. J.; Mc Carty, R. D.; Roder, H. M.
1968-01-01
Computer program subroutines provide the thermodynamic and transport properties of hydrogen in tabular form. The programs provide 18 combinations of input and output variables. This program is written in FORTRAN 4 for use on the IBM 7044 or CDC 3600 computers.
Transport properties of a Bentheim sandstone under deformation
NASA Astrophysics Data System (ADS)
Jasinski, L.; Sangaré, D.; Adler, P. M.; Mourzenko, V. V.; Thovert, J.-F.; Gland, N.; Békri, S.
2015-01-01
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.
Reference Fluid Thermodynamic and Transport Properties Database (REFPROP)
National Institute of Standards and Technology Data Gateway
SRD 23 NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP) (PC database for purchase) NIST 23 contains revised data in a Windows version of the database, including 105 pure fluids and allowing mixtures of up to 20 components. The fluids include the environmentally acceptable HFCs, traditional HFCs and CFCs and 'natural' refrigerants like ammonia
Elastic properties of anisotropic synthetic calcitemuscovite Bjarne S. G. Almqvist,1
Cattin, Rodolphe
. Their elastic properties have been measured using compressional and shear waves in confining hydrostatic compressional waves, indicating that waves propagating by shearing are less affected by sample porosity velocities. Shear waves display less of a difference between calculated and measured values, than do
d Original Contribution VISCOELASTIC AND ANISOTROPIC MECHANICAL PROPERTIES OF IN VIVO
Paris 7 - Denis Diderot, Université
and dynamic medium. In this article, these mechanical properties are characterized for the brachialis muscle muscular fibers direction. Finally, the dispersion of the shear waves is studied for these different is a complex active and passive tissue. The skeletal muscle is composed of muscular fibers running parallel
Measurement of anisotropic thermophysical properties of cylindrical Li-ion cells
Texas at Arlington, University of
high energy content in Li-ion batteries, thermal phenomena play an important role in performance Naval Surface Warfare Center, Carderock Division, U.S. Navy, 1000 Kitty Hawk Ave., Building 77L, Philadelphia, PA 19112, USA h i g h l i g h t s Presents a new method for measuring thermal properties
Anisotropic Flow from RHIC to the LHC
Raimond Snellings
2006-10-05
Anisotropic flow is recognized as one of the main observables providing information on the early stage of a heavy-ion collision. At RHIC the large observed anisotropic flow and its successful description by ideal hydrodynamics is considered evidence for an early onset of thermalization and almost ideal fluid properties of the produced strongly coupled Quark Gluon Plasma. This write-up discusses some key RHIC anisotropic flow measurements and for anisotropic flow at the LHC some predictions.
Exact quantum scattering calculations of transport properties: CH2(X?3B1, a?1A1)-helium.
Dagdigian, Paul J; Alexander, Millard H
2013-04-28
Transport properties for collisions of methylene, in both its ground X?(3)B1 and low-lying a?(1)A1 electronic states, with helium have been computed using recently computed high-quality ab initio potential energy surfaces (PESs). Because of the difference in the orbital occupancy of the two electronic states, the anisotropies of the PESs are quite different. The CH2(a?)-He PES is very anisotropic because of the strong interaction of the electrons on the helium atom with the unoccupied CH2 orbital perpendicular to the molecular plane, while the anisotropy of the CH2(X?)-He PES is significantly less since this orbital is singly occupied in this case. To investigate the importance of the anisotropy on the transport properties, calculations were performed with the full potential and with the spherical average of the potential for both electronic states. Significant differences (over 20% for the a? state at the highest temperatures considered) in the computed transport properties were found. PMID:23635136
Transport properties of silicate melts at high pressure
NASA Astrophysics Data System (ADS)
Lesher, C. E.; Gaudio, S. J.; Clark, A. N.; O'Dwyer-Brown, L.
2012-12-01
It is well appreciated that the transport properties (e.g., diffusion, viscosity) of silicate melts are intimately linked by melt structure and the time scales of structural relaxation. These linkages have been explored exten-sively at low pressure, but our understanding is more limited for high-pressure conditions relevant to the Earth's deep interior. Transport property models based on free-volume, activation energy and/or configurational entropy have merits, but their validity in extrapolation is uncertain. Moreover, the structural implications at high pressure are conflicting and lack experimental support. We examine these issues and review theoretical efforts to model transport properties at high pressure, as well as, those constraints provided by laboratory experiments and simulations. We emphasis the need to consider the properties of melt not only for high-pressure superheated conditions, but also for supercooled conditions in the vicinity of the glass transition. For example, the time scales for density relaxation traversing the glass transition at high pressure can be monitored using in situ X-ray miroctomography/absorption and ex vivo by the Archimedes' method combined with spectroscopy. These approaches are amenable to both strong and fragile liquids. Taken together with superliquidus data, we can greatly improve the interpolation of melt properties within the melting interval for refractory mantle compositions.
Review on measurement techniques of transport properties of nanowires.
Rojo, Miguel Muñoz; Calero, Olga Caballero; Lopeandia, A F; Rodriguez-Viejo, J; Martín-Gonzalez, Marisol
2013-12-01
Physical properties at the nanoscale are novel and different from those in bulk materials. Over the last few decades, there has been an ever growing interest in the fabrication of nanowire structures for a wide variety of applications including energy generation purposes. Nevertheless, the study of their transport properties, such as thermal conductivity, electrical conductivity or Seebeck coefficient, remains an experimental challenge. For instance, in the particular case of nanostructured thermoelectrics, theoretical calculations have shown that nanowires offer a promising way of enhancing the hitherto low efficiency of these materials in the conversion of temperature differences into electricity. Therefore, within the thermoelectrical community there has been a great experimental effort in the measurement of these quantities in actual nanowires. The measurements of these properties at the nanoscale are also of interest in fields other than energy, such as electrical components for microchips, field effect transistors, sensors, and other low scale devices. For all these applications, knowing the transport properties is mandatory. This review deals with the latest techniques developed to perform the measurement of these transport properties in nanowires. A thorough overview of the most important and modern techniques used for the characterization of different kinds of nanowires will be shown. PMID:24113712
Review on measurement techniques of transport properties of nanowires
NASA Astrophysics Data System (ADS)
Rojo, Miguel Muñoz; Calero, Olga Caballero; Lopeandia, A. F.; Rodriguez-Viejo, J.; Martín-Gonzalez, Marisol
2013-11-01
Physical properties at the nanoscale are novel and different from those in bulk materials. Over the last few decades, there has been an ever growing interest in the fabrication of nanowire structures for a wide variety of applications including energy generation purposes. Nevertheless, the study of their transport properties, such as thermal conductivity, electrical conductivity or Seebeck coefficient, remains an experimental challenge. For instance, in the particular case of nanostructured thermoelectrics, theoretical calculations have shown that nanowires offer a promising way of enhancing the hitherto low efficiency of these materials in the conversion of temperature differences into electricity. Therefore, within the thermoelectrical community there has been a great experimental effort in the measurement of these quantities in actual nanowires. The measurements of these properties at the nanoscale are also of interest in fields other than energy, such as electrical components for microchips, field effect transistors, sensors, and other low scale devices. For all these applications, knowing the transport properties is mandatory. This review deals with the latest techniques developed to perform the measurement of these transport properties in nanowires. A thorough overview of the most important and modern techniques used for the characterization of different kinds of nanowires will be shown.
Boire, Adeline; Menut, Paul; Morel, Marie-Hélène; Sanchez, Christian
2015-04-30
In this Article, we investigated the interaction properties of wheat gliadins, properties that are at the basis of their functionality in wheat grain and in food matrixes. We established the equation of state of our isolate by osmotic compression and characterized the concentration-induced structural transitions, from the secondary structure of proteins to the rheological properties. We evidenced three thermodynamical regimes corresponding to several structuring regimes. First, for ? < 0.03, gliadins behave as repulsive colloids, with a positive second virial coefficient, arising presumably from their surface charge density and/or their steric repulsion. No intermolecular interaction was detected by FT-IR, suggesting that proteins form a stable dispersion. In the second regime, the system becomes more easily compressible, i.e., less repulsive and/or more attractive. It is associated with the disappearance of ?-sheet intramolecular structures of the proteins in favor of random coils/?-helix and intermolecular ?-sheet interactions. This coincides with the appearance of elasticity and the increase of the apparent viscosity. Finally, in the last regime, for ? > 0.16, FT-IR spectra show that proteins are strongly interacting via intermolecular interactions. A correlation peak develops in SAXS, revealing a global order in the dispersion. Interestingly, the osmotic pressure applied to extract the solvent is higher than expected from a hard-sphere-like protein and we highlighted a liquid-like state at very high concentration (>450 g L(-1)) which is in contrast with most proteins that form gel or glass at such concentration. In the discussion, we questioned the existence of supramolecular assemblies and the role of the solvation that would lead to this specific behavior. PMID:25839358
Transport processes in partially saturate concrete: Testing and liquid properties
NASA Astrophysics Data System (ADS)
Villani, Chiara
The measurement of transport properties of concrete is considered by many to have the potential to serve as a performance criterion that can be related to concrete durability. However, the sensitivity of transport tests to several parameters combined with the low permeability of concrete complicates the testing. Gas permeability and diffusivity test methods are attractive due to the ease of testing, their non-destructive nature and their potential to correlate to in-field carbonation of reinforced concrete structures. This work was aimed at investigating the potential of existing gas transport tests as a way to reliably quantify transport properties in concrete. In this study gas permeability and diffusivity test methods were analyzed comparing their performance in terms of repeatability and variability. The influence of several parameters was investigated such as moisture content, mixture proportions and gas flow. A closer look to the influence of pressure revealed an anomalous trend of permeability with respect to pressure. An alternative calculation is proposed in an effort to move towards the determination of intrinsic material properties that can serve as an input for service life prediction models. The impact of deicing salts exposure was also analyzed with respect to their alteration of the degree of saturation as this may affect gas transport in cementitious materials. Limited information were previously available on liquid properties over a wide range of concentrations. To overcome this limitation, this study quantified surface tension, viscosity in presence of deicing salts in a broad concentration range and at different temperatures. Existing models were applied to predict the change of fluid properties during drying. Vapor desorption isotherms were obtained to investigate the influence of deicing salts presence on the non-linear moisture diffusion coefficient. Semi-empirical models were used to quantify the initiation and the rate of drying using liquid properties and pore structure information as inputs. Concrete exposed to deicing salts resulted to have a reduced gas transport due to the higher degree of saturation (DOS). The higher DOS is believed to contribute to the premature deterioration observed in concrete pavements exposed to deicing salts. Moisture diffusion and moisture profiles in concrete are known to directly relate with the stresses generated during shrinkage and creep mechanisms. The alteration due to the presence of shrinkage reducing admixtures on drying was also investigated in this work. Liquid properties were used to predict the diffusion coefficient in presence of SRA. Moisture profiles obtained using Fick's second law for diffusion were compared to relative humidity profiles measured on concrete slabs. Results confirm that a qualitative prediction of drying in concrete elements is realistic when using this type of approach.
The direction of maximum spread in anisotropic forest fires and its critical properties
NASA Astrophysics Data System (ADS)
Duarte, J. A. M. S.; Carvalho, João Marques; Ruskin, H. J.
1992-05-01
Some new critical properties related to the spread along the anisotropy axis of directed percolation as a model for wind-biased forest or wild land fire, are introduced and discussed. We show that it is possible to extract the burned mass along the axis, its appropriate exponent, and the gap exponent for successive bulk moments of the total burned mass from Monte Carlo studies at the critical probability. We provide evidence for a new, analogous exponent for the mass burned on the axis and propose a scaling relation for it, based on the numerical evidence.
NASA Astrophysics Data System (ADS)
Ojeda, Oscar; Cagin, Tahir
2011-03-01
Localization of strain and changes under extreme conditions in energetic materials (EM) can cause runaway reactions and unexpected initiation. A clear understanding of the mechanical properties is a perquisite in understanding the interplay between mechanical, chemical and thermodynamic properties that relate sensitivity and EM's before they undergo initiation. We have conducted first principles ground state studies, complemented by atomistic calculations at elevated temperatures and pressures, for energetic commonly used secondary EM's with varying sensitivities. Chemical information found from ab intio methods, and from compression at elevated temperatures show that external conditions relevant to impact and shock behavior can have different effects on the studied systems. These range from changes in local conformation, changes in the hydrogen-bonding network, and more drastically to a full crystallographic transition in which the symmetry of the system undergoes a transformation. Due to the chemical, mechanical and thermodynamic level information that provides, multiscale modeling methods, can then be applied to the understanding of other type of systems and give a clearer understanding of the molecular processes that undergo energetic materials, prior to initiation. Laboratory of Computational Engineering of Nanomaterials.
Charge carrier transport properties in layer structured hexagonal boron nitride
Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X., E-mail: hx.jiang@ttu.edu [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)
2014-10-15
Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (~ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700?°K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of ? ? (T/T{sub 0}){sup ??} with ? = 3.02, satisfying the two-dimensional (2D) carrier transport limit dominated by the polar optical phonon scattering. This behavior is a direct consequence of the fact that hBN is a layer structured material. The optical phonon energy deduced from the temperature dependence of the hole mobility is ?? = 192 meV (or 1546 cm{sup -1}), which is consistent with values previously obtained using other techniques. The present results extend our understanding of the charge carrier transport properties beyond the traditional III-nitride semiconductors.
Electron Transport Materials: Synthesis, Properties and Device Performance
Lelia Cosimbescu; Liang Wang; Monte L. Helm; Evgueni Polikarpov; James S. Swensen; Asanga B. Padmaperuma
2012-01-01
We report the design, synthesis and characterization, thermal and photophysical properties of two silane based electron transport materials, dibenzo[b,d]thiophen-2-yltriphenylsilane (SiÏ87) and (dibenzo[b,d]thiophen-2-yl)diphenylsilane (SiÏ88) 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 SiÏ87 as the electron transport
Thermodynamic properties of anisotropic spin ladder in a longitudinal magnetic field
NASA Astrophysics Data System (ADS)
Rezania, H.
2015-08-01
We address thermodynamic properties of quasi-one dimensional two leg antiferromagnetic ladder in the presence of magnetic field. A generalized bond operator formalism is used to transform the spin model to a hard core bosonic gas. We have implemented Green's function approach to obtain the temperature dependence of spin excitation spectrum in field induced spin polarized phase. The results show energy gap that vanishes at critical magnetic field for fixed values of temperatures. We have also found the temperature dependence of the specific heat and magnetization component in the magnetic field direction for various magnetic field strengths and anisotropies in the Heisenberg interactions on both leg and rung couplings. At low temperatures, the specific heat is found to be monotonically increasing with temperature for magnetic fields in the spin polarized phase region. Furthermore we studied the temperature dependence of the longitudinal magnetization for different magnetic field and anisotropy parameters.
Float zone growth and anisotropic spectral properties of Nd:LaVO4 single crystals
NASA Astrophysics Data System (ADS)
Yomogida, Shohei; Higuchi, Mikio; Ogawa, Takayo; Wada, Satoshi; Takahashi, Junichi
2012-11-01
Nd:LaVO4 single crystals were successfully grown by the floating zone method and their optical properties along each optic elasticity axis were investigated. The crystals grown at 10 mm/h in air did not contain any macroscopic defects for Nd-concentrations upto 5 at%. The optic elasticity axes were determined by the conoscopic figures with a polarizing microscope. The absorption cross-section along the Z-axis was 2.6×10-20 cm2 near 800 nm and the FWHM was 20 nm. The absorption cross-sections along other directions were much the same as that along the Z-axis. The fluorescence lifetime of the 5 at%-doped crystal was approximately 80 ?s. All the polarized fluorescence spectra of the Nd:LaVO4 single crystal had a broadened band around 1060 nm with FWHMs of 7-10 nm, which are wide enough to generate femtosecond order pulses.
NASA Astrophysics Data System (ADS)
Delette, G.
2015-09-01
Models of polycrystalline microstructures, representative for sintered permanent magnets with various grain size distributions and alignment degrees, were generated by the Voronoï tessellation technique. The polycrystalline models were meshed and then a stress/strain analysis was performed with the Finite Element Method (FEM) in order to derive the relation between the homogenized properties (thermal expansion coefficient, elastic constants) and the degree of grain alignment. Residual stresses after sintering were also analyzed and a possible mechanism involved in the decrease in mechanical strength is discussed. It is argued that small sized and poorly aligned grains dispersed in the polycrystalline material are highly stressed after elaboration and could be responsible for the initiation of failure.
Anisotropic superconducting properties of single-crystalline FeSe0.5Te0.5
NASA Astrophysics Data System (ADS)
Bendele, M.; Weyeneth, S.; Puzniak, R.; Maisuradze, A.; Pomjakushina, E.; Conder, K.; Pomjakushin, V.; Luetkens, H.; Katrych, S.; Wisniewski, A.; Khasanov, R.; Keller, H.
2010-06-01
Iron-chalcogenide single crystals with the nominal composition FeSe0.5Te0.5 and a transition temperature of Tc?14.6K were synthesized by the Bridgman method. The structural and anisotropic superconducting properties of those crystals were investigated by means of single crystal x-ray and neutron powder diffraction, superconducting quantum interference device and torque magnetometry, and muon-spin rotation (?SR). Room temperature neutron powder diffraction reveals that 95% of the crystal volume is of the same tetragonal structure as PbO. The structure refinement yields a stoichiometry of Fe1.045Se0.406Te0.594 . Additionally, a minor hexagonal Fe7Se8 impurity phase was identified. The magnetic penetration depth ? at zero temperature obtained by means of ?SR was found to be ?ab(0)=491(8)nm in the ab plane and ?c(0)=1320(14)nm along the c axis. The zero-temperature value of the superfluid density ?s(0)??-2(0) obeys the empirical Uemura relation observed for various unconventional superconductors, including cuprates and iron pnictides. The temperature dependences of both ?ab and ?c are well described by a two-gap s+s -wave model with the zero-temperature gap values of ?S(0)=0.51(3)meV and ?L(0)=2.61(9)meV for the small and the large gap, respectively. The magnetic penetration depth anisotropy parameter ??(T)=?c(T)/?ab(T) increases with decreasing temperature, in agreement with ??(T) observed in the iron-pnictide superconductors.
NASA Astrophysics Data System (ADS)
Song, Dongxing; Jing, Dengwei; Luo, Bing; Geng, Jiafeng; Ren, Yuxun
2015-07-01
Magnetic field can enhance both thermal conductivity and Lorentz force resistance of the magnetic nanofluids (MNFs), in which the former is favored while the latter often leads to pressure drop of the flow. It is assumed that there would exist a balance between the magnetic field induced thermal conductivity and Lorentz force if one can appropriately adjust the angle of the imposing magnetic field with respect to the direction of the flow. In the present study, the effects of direction of magnetic field ( ?) on anisotropic thermodynamic properties of magnetic nanofluids in channel were studied. The effects of direction of magnetic field on thermal conductivity, Nusselt number, global total entropy generation, and other parameters, such as velocity, temperature, and concentration, have been discussed in detail. A greater ? can lead to a larger thermal conductivity normal to the walls of channel and a more uniform temperature field. However, the velocity of magnetic nanofluid tends to decrease. There is a threshold for magnetic intensity (B). When magnetic intensity becomes large than the threshold, its effect on thermal conductivity will tends to be constant. The effect of increase of ? is found to be similar to that of increasing Hartmann number ( H a ) and both can lead to augment of Lorentz resistance force along flow direction. With the increases of ? and H a , both heat transfer efficiency (Nu) and global total entropy generation ( ST ) increase. Here, ST indicates the extent of loss of useful work due to the irreversibility of the process. A comprehensive utility index, Iu , is defined for evaluation of the performance of a practical heat transfer system employing MNFs. For the case where the purpose of heat transfer is to cool an equipment such as electrical device, guaranteeing heat transfer efficiency (Nu) is more important than decreasing useful energy loss ( ST ); thus, we propose a large ? relative to the flow direction. For industrial processes, where energy loss ( ST ) have to be particularly considered, a small ? is recommended.
Anisotropic metamaterial optical fibers.
Pratap, Dheeraj; Anantha Ramakrishna, S; Pollock, Justin G; Iyer, Ashwin K
2015-04-01
Internal physical structure can drastically modify the properties of waveguides: photonic crystal fibers are able to confine light inside a hollow air core by Bragg scattering from a periodic array of holes, while metamaterial loaded waveguides for microwaves can support propagation at frequencies well below cutoff. Anisotropic metamaterials assembled into cylindrically symmetric geometries constitute light-guiding structures that support new kinds of exotic modes. A microtube of anodized nanoporous alumina, with nanopores radially emanating from the inner wall to the outer surface, is a manifestation of such an anisotropic metamaterial optical fiber. The nanopores, when filled with a plasmonic metal such as silver or gold, greatly increase the electromagnetic anisotropy. The modal solutions in such anisotropic circular waveguides can be uncommon Bessel functions with imaginary orders. PMID:25968741
Zhan, Xin, Ph. D. Massachusetts Institute of Technology
2010-01-01
The objective of this thesis is to better understand the transport and seismoelectric (SE) properties of porous permeable rock. Accurate information of rock transport properties, together with pore geometry, can aid us to ...
Using moisture transport properties of rice seed components for identifying fissure resistance
Thomas, Audrey Elizabeth
2002-01-01
Fissure resistance was related to the moisture transport properties of Cypress, Lemont, LaGrue, and Teqing rice varieties. The moisture transport properties, moisture diffusivity and resistance, were calculated using a three-dimensional moisture...
Electrical Transport Properties of Liquid Al-Cu Alloys
NASA Astrophysics Data System (ADS)
Thakore, B. Y.; Khambholja, S. G.; Suthar, P. H.; Jani, A. R.
2010-06-01
Electrical transport properties viz. electrical resistivity, thermoelectric power and thermal conductivity of liquid Al-Cu alloys as a function of Cu concentration have been studied in the present paper. Ashcroft empty core model potential has been used to incorporate the ion-electron interaction. To incorporate the exchange and correlation effects, five different forms of local field correction functions viz. Hartree, Taylor, Ichimaru et al., Farid et al. and Sarkar et al. have been used. The transport properties of binary system have been studied using Faber-Ziman formulation combined with Ashcroft-Langreth (AL) partial structure factor. The computed values of electrical resistivity are compared with experimental data and for low Cu concentration, good agreement has been observed. Further, thermoelectric power and thermal conductivity have also been predicted.
Low temperature transport properties of Ce-Al metallic glasses
Zeng, Q. S. [Zhejiang Univ., Hangzhou (China). International Center for New-Structured Materials; Carnegie Inst. of Washington, Argonne, IL (United States). Geophysical Lab., High Pressure Synergetic Consortium (HPSync); Rotundu, C. R. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division; Mao, W. L. [Zhejiang Univ., Hangzhou (China). International Center for New-Structured Materials; Stanford Univ., CA (United States). Geological and Environmental Sciences; SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES) and Photon Science; Dai, J. H. [Zhejiang Univ., Hangzhou (China). Dept. of Physics; Xiao, Y. M. [Carnegie Inst. of Washington, Argonne, IL (United States). Geophysical Lab. High Pressure Collaborative Access Team (HPCAT); Chow, P. [Carnegie Inst. of Washington, Argonne, IL (United States). Geophysical Lab. High Pressure Collaborative Access Team (HPCAT); Chen, X. J. [Carnegie Inst. of Washington, Washington, DC (United States). Geophysical Lab.; Qin, C. L. [Hebei Univ. of Technology, Tianjing (China). School of Materials Science and Engineering; Mao, H.-k. [Zhejiang Univ., Hangzhou (China). International Center for New-Structured Materials; Carnegie Inst. of Washington, Argonne, IL (United States). Geophysical Lab., High Pressure Synergetic Consortium (HPSync); Carnegie Inst. of Washington, Washington, DC (United States). Geophysical Lab.; Hebei Univ. of Technology, Tianjing (China). School of Materials Science and Engineering; Jiang, J. Z. [Zhejiang Univ., Hangzhou (China). International Center for New-Structured Materials
2011-01-01
The low temperature transport properties of Ce_{75}? x Al_{25+ x} (x?=?0, 10, and 15 at. %) metallic glasses were investigated. Magnetic field and composition tuned magnetoresistances changing from negative to positive values were observed at low temperature. It was suggested that these peculiar phenomena were caused by the tunable competition between the Kondo effect and the Ruderman-Kittel-Kasuya-Yoshida interaction in Ce-Al metallic glass with the variation in Ce content and magnetic field. Further magnetization and Ce-2p3d resonant inelastic x-ray scattering spectroscopy measurements supported this scenario. These Ce-Al metallic glasses could provide an interesting model system for the investigation of 4f electron behaviors in complex condensed matter with tunable transport properties.
Transport properties and microstructural characteristics of a thermally cracked mylonite
NASA Astrophysics Data System (ADS)
Le Ravalec, M.; Darot, M.; Reuschlé, T.; Guéguen, Y.
1996-03-01
An experimental study was carried out on a granitic mylonite (La Bresse, France) to analyze the influence of pore microstructure on transport properties. Different crack networks were obtained by a controlled thermal treatment. Microstructures were analyzed by means of gas adsorption and mercury porosimetry. Transport properties have been investigated by measuring gas permeability and electrical conductivity. The dependence of permeability on confining pressure shows an exponential decrease, characteristic of a porosity made of cracks. Correlations between measured parameters have been analyzed by comparing them with relations deduced from theoretical models. Linking the formation factor to the porosity leads to a rather low tortuosity value (about 2.4), characterizing a medium with a well connected porosity. Correlation between permeability k and formation factor F leads to a power-law relation k ? F -n where n?2.9, which is consistent with a crack model describing the behavior of the thermally treated rock.
Transport properties of polyaniline-cellulose-acetate blends
Jérôme Planès; Andreas Wolter; Yasmina Cheguettine; Adam Pron; Françoise Genoud; Maxime Nechtschein
1998-01-01
Transport properties of polyaniline (PANI)-cellulose acetate (CA) conducting blends have been investigated at various length scales and temperatures. We report on the results of dc and ac conductivity measurements, magnetoresistance and electron-spin resonance (ESR) performed on composite films with PANI weight fraction p ranging from the percolation threshold-pc~=0.1%-to a few percent. Three different PANI doping agents have been tested, namely,
Surface and transport properties of Ag–Cu liquid alloys
R. Novakovic; E. Ricci; D. Giuranno; A. Passerone
2005-01-01
The applicability of quasi-lattice theory (QLT) to describe surface and transport properties of Ag–Cu liquid alloys is substantiated by surface tension experimental data. The surface tension of molten Ag, Cu and Ag–Cu alloys has been measured by the pinned-sessile drop method over a temperature range. The results obtained are in good agreement with other reported measurements on pure elements and
Transport properties of thermo-responsive ion track membranes
N Reber; A Küchel; R Spohr; A Wolf; M Yoshida
2001-01-01
The permeation of orange G (MW 452), methylene blue (MW 319), and bovine albumin (MW 68000), through thermo-responsive ion track membranes was studied. For this purpose, poly-N-isopropylacrylamide (poly-NIPAAm) hydro-gel was chemically grafted onto single\\/multi-pore ion track membranes of poly(ethylene terephthalate) (PET).The local transport properties were studied by measuring the electrical current through single pore membranes. It was found that the
Magneto-optical transport properties of monolayer phosphorene
NASA Astrophysics Data System (ADS)
Tahir, M.; Vasilopoulos, P.; Peeters, F. M.
2015-07-01
The electronic properties of monolayer phosphorene are exotic due to its puckered structure and large intrinsic direct band gap. We derive and discuss its band structure in the presence of a perpendicular magnetic field. Further, we evaluate the magneto-optical Hall and longitudinal optical conductivities as functions of temperature, magnetic field, and Fermi energy, and show that they are strongly influenced by the magnetic field. The imaginary part of the former and the real part of the latter exhibit regular interband oscillations as functions of the frequency ? in the range ? ? ˜1.5 -2 eV . Strong intraband responses in the latter and weak ones in the former occur at much lower frequencies. The magneto-optical response can be tuned in the microwave-to-terahertz and visible frequency ranges in contrast with a conventional two-dimensional electron gas or graphene in which the response is limited to the terahertz regime. This ability to isolate carriers in an anisotropic structure may make phosphorene a promising candidate for new optical devices.
Electronic structure and transport properties of doped PbSe
NASA Astrophysics Data System (ADS)
Peng, Haowei; Song, Jung-Hwan; Kanatzidis, M. G.; Freeman, Arthur J.
2011-09-01
Understanding the electronic structure and transport properties of doped PbSe for its thermoelectric applications is an urgent need. Using a first-principles approach, we first explore the band structures of PbSe doped with a series of impurities, including cation-site substitutional impurities (Na, K, Rb; Mg, Ca, Sr; Cu, Ag, Au; Zn, Cd, Hg; Ga, In, Tl; Ge, Sn; As, Sb, Bi) and anion-site substitutional impurities (P, As, Sb; O, S, Te). Then we calculate the density of states (DOS) difference between the doped samples and pure host sample, which is a useful quantity to recognize the possibility of improving transport properties. The exhibited chemical trends and the nature of the impurity states are well explained with a simplified linear combination of atomic orbitals (LCAO) picture. Finally, we calculate the transport properties of these doped systems within the framework of Boltzmann theory and constant relaxation time approximation. Typical competing behavior between the electrical conductivity and Seebeck coefficient is exhibited, and a significant enhancement of thermoelectric power factor is found in the cation-site Au-doped p-type samples, and cation-site As-doped n-type samples.
Path-Integration Computation of the Transport Properties of Nanoparticles
NASA Astrophysics Data System (ADS)
Douglas, Jack
2014-03-01
There is need for effective computational methods for calculating the transport properties of polymers and complex-shaped particle aggregates arising in materials science and biology as a foundation for rational material design and the design of well-defined measurements assessing the environmental impact of nanoparticles. We focus on the problem of calculating basic solution transport properties (translational diffusion coefficient, intrinsic viscosity) of isolated particles having essentially any geometry using a novel computational method involving path integration developed by Mansfield and Douglas. The basic concepts behind the method are described and the method is validated in cases where exact analytic, or at least highly accurate numerical estimates, are known for comparison. After defining and validating our method, some applications of the program are given to some non-trivial problems illustrating the use of the program for charactering such as nanoparticles with grafted DNA brush layers, DNA orgami, carbon nanotubes, etc. The path-integration method is evidently a powerful tool for computing basic transport properties of complex-shaped objects and should find wide application in polymer science, nanotechnological applications and biology.
Viscoelastic properties of actin networks influence material transport
NASA Astrophysics Data System (ADS)
Stam, Samantha; Weirich, Kimberly; Gardel, Margaret
2015-03-01
Directed flows of cytoplasmic material are important in a variety of biological processes including assembly of a mitotic spindle, retraction of the cell rear during migration, and asymmetric cell division. Networks of cytoskeletal polymers and molecular motors are known to be involved in these events, but how the network mechanical properties are tuned to perform such functions is not understood. Here, we construct networks of either semiflexible actin filaments or rigid bundles with varying connectivity. We find that solutions of rigid rods, where unimpeded sliding of filaments may enhance transport in comparison to unmoving tracks, are the fastest at transporting network components. Entangled solutions of semiflexible actin filaments also transport material, but the entanglements provide resistance. Increasing the elasticity of the actin networks with crosslinking proteins slows network deformation further. However, the length scale of correlated transport in these networks is increased. Our results reveal how the rigidity and connectivity of biopolymers allows material transport to occur over time and length scales required for physiological processes. This work was supported by the U. Chicago MRSEC
Miyamoto, Nobuyoshi; Shintate, Morio; Ikeda, Shogo; Hoshida, Yasutomo; Yamauchi, Yusuke; Motokawa, Ryuhei; Annaka, Masahiko
2013-02-01
Macroscopically anisotropic hydrogels were synthesized by hybridization of poly(N-isopropylacrylamide) with liquid crystalline inorganic nanosheets; their anisotropies in the structure and properties are demonstrated. PMID:23283288
Anisotropically branched metal nanostructures.
Ye, Enyi; Regulacio, Michelle D; Zhang, Shuang-Yuan; Loh, Xian Jun; Han, Ming-Yong
2015-10-01
Metal nanostructures display a multitude of technologically useful properties that can be tailored through fine-tuning of certain parameters, such as size, shape and composition. In many cases, the shape or morphology of metal nanostructures plays the most crucial role in the determination of their properties and their suitability in specific applications. In this tutorial review, we provide a summary of recent research that centers on metal nanostructures having anisotropically branched morphologies. The branched structural features that are exhibited by these materials endow them with unique properties that can be utilized in many important applications. The formation of branched architectures can be achieved in solution through a variety of synthetic strategies, four of which are highlighted in this review and these are: (1) seedless growth, (2) seeded growth, (3) templated growth, and (4) chemical etching. The usefulness of these anisotropically branched metal nanostructures in the areas of plasmonics, catalysis and biomedicine is also presented. PMID:26065370
Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures
NASA Astrophysics Data System (ADS)
Sapkota, Keshab R.
Present computing and communication devices rely on two different classes of technologies; information processing devices are based on electrical charge transport in semiconducting materials while information storage devices are based on orientation of electron spins in magnetic materials. A realization of a hybrid-type device that is based on charge as well as spin properties of electrons would perform both of these actions thereby enhancing computation power to many folds and reducing power consumptions. This dissertation focuses on the fabrication of such spin-devices based on metallic and semiconducting nanostructures which can utilize spin as well as charge properties of electrons. A simplified design of the spin-device consists of a spin injector, a semiconducting or metallic channel, and a spin detector. The channel is the carrier of the spin signal from the injector to the detector and therefore plays a crucial role in the manipulation of spin properties in the device. In this work, nanostructures like nanowires and nanostripes are used to function the channel in the spin-device. Methods like electrospinning, hydrothermal, and wet chemical were used to synthesize nanowires while physical vapor deposition followed by heat treatment in controlled environment was used to synthesis nanostripes. Spin-devices fabrication of the synthesized nanostructures were carried out by electron beam lithography process. The details of synthesis of nanostructures, device fabrication procedures and measurement techniques will be discussed in the thesis. We have successfully fabricated the spin-devices of tellurium nanowire, indium nanostripe, and indium oxide nanostripe and studied their spin transport properties for the first time. These spin-devices show large spin relaxation length compared to normal metals like copper and offer potentials for the future technologies. Further, Heusler alloys nanowires like nanowires of Co 2FeAl were synthesized and studied for electrical transport properties since such systems are halfmetallic in nature and promise the possibilities of spin injection and detection. The study was extended to dilute magnetic semiconducting nanowire system of Cd1-xMnxTe which possess both magnetic and semiconducting properties. In summary, the studies made in this thesis will offer a new understanding of spin transport behavior for future technology.
Radiation Transport Properties of Polyethylene-Fiber Composites
NASA Technical Reports Server (NTRS)
Kaul, Raj K.; Barghouty, A. F.; Dahche, H. M.
2003-01-01
Composite materials that can both serve as 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 piece 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 NASA's Marshall Space Flight Center and tested against 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.
Space radiation transport properties of polyethylene-based composites
NASA Technical Reports Server (NTRS)
Kaul, R. K.; Barghouty, A. F.; Dahche, H. M.
2004-01-01
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.
Space radiation transport properties of polyethylene-based composites.
Kaul, R K; Barghouty, A F; Dahche, H M
2004-11-01
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. PMID:15644352
Upscaling flow and transport properties in synthetic porous media
NASA Astrophysics Data System (ADS)
Jasinski, Lukasz; Dabrowski, Marcin
2015-04-01
Flow and transport through the porous media has instances in nature and industry: contaminant migration in geological formations, gas/oil extraction from proppant filled hydraulic fractures and surrounding porous matrix, underground carbon dioxide sequestration and many others. We would like to understand the behavior of propagating solute front in such medium, mainly flow preferential pathways and the solute dispersion due to the porous medium geometry. The motivation of our investigation is to find connection between the effective flow and transport properties and porous media geometry in 2D and 3D for large system sizes. The challenge is to discover a good way of upscaling flow and transport processes to obtain results comparable to these calculated on pore-scale in much faster way. We study synthetic porous media made of densely packed poly-disperse disk-or spherical-shaped grains in 2D and 3D, respectively. We use various protocols such as the random sequential addition (RSA) algorithm to generate densely packed grains. Imposed macroscopic pressure gradient invokes fluid flow through the pore space of generated porous medium samples. As the flow is considered in the low Reynolds number regime, a stationary velocity field is obtained by solving the Stokes equations by means of finite element method. Void space between the grains is accurately discretized by using body-fitting triangular or tetrahedral mesh. Finally, pure advection of a front carried by the velocity field is studied. Periodicity in all directions is applied to microstructure, flow and transport processes. Effective permeability of the media can be calculated by integrating the velocity field on cross sections, whereas effective dispersion coefficient is deduced by application of centered moment methods on the concentration field of transported solute in time. The effective parameters are investigated as a function of geometrical parameters of the media, such as porosity, specific surface area and fractal dimension of the pore space geometry. Discretization effects are taken into account. Furthermore, as we aim to simulate transport processes in complex and large systems in 3D, following upscaling technique is checked against the original calculations. The pore space of the media is approximated in the form of a capillary network by converting the pore space throats between the grains into lines in 2D and polygons in 3D. Effective flow and transport properties are calculated on such network models and compared with the results obtained for original geometry.
Rhamnolipid surface thermodynamic properties and transport in agricultural soil.
Renfro, Tyler Dillard; Xie, Weijie; Yang, Guang; Chen, Gang
2014-03-01
Rhamnolipid is a biosurfactant produced by several Pseudomonas species, which can wet hydrophobic soils by lowering the cohesive and/or adhesive surface tension. Because of its biodegradability, rhamnolipid applications bring minimal adverse impact on the soil and groundwater as compared with that of chemical wetting agents. Subsequently, rhamnolipid applications have more advantages when used to improve irrigation in the agricultural soil, especially under draught conditions. In the presence of rhamnolipid, water surface tension dropped linearly with the increase of rhamnolipid concentration until the rhamnolipid critical micelle concentration (CMC) of 30 mg/L was reached. Below the CMC, rhamnolipid had linear adsorption isotherms on the soil with a partition coefficient of 0.126 L/kg. Rhamnolipid transport breakthrough curves had a broad and diffuse infiltration front, indicating retention of rhamnolipid on the soil increased with time. Rhamnolipid transport was found to be well represented by the advection-dispersion equation based on a local equilibrium assumption. When applied at concentrations above the CMC, the formed rhamnolipid micelles prevented rhamnolipid adsorption (both equilibrium adsorption and kinetic adsorption) in the soil. It was discovered in this research that rhamnolipid surface thermodynamic properties played the key role in controlling rhamnolipid transport. The attractive forces between rhamnolipid molecules contributed to micelle formation and facilitated rhamnolipid transport. PMID:24394947
Strain induced peculiarities in transport properties of Bi nanowires.
Condrea, E; Gilewski, A; Nicorici, A
2013-05-22
We report results on the effect of strain on the thermopower and electrical resistance of glass-coated individual Bi nanowires. Here, we show that there is a critical diameter of wires below which the contribution of holes to the charge transport in pure Bi nanowires is more significant than that of electrons. The properties of Bi nanowires are examined in the light of a strain induced electronic topological transition. At low temperatures, the thermopower dependences on strain exhibit a non-monotonic behavior inherent in thinner wires, where the thermopower is dominated by the diffusion transport mechanism of holes. The hole-dominated transport can be transformed into electron-dominated transport through a smooth manipulation with the phonon spectrum and Fermi surface by applying a uniaxial strain. A fairly high value of the thermoelectric power factor (S(2)/? = 89 ?W cm(-1) K(-2)) was found in the temperature range of 80-300 K, where the dominant mechanism contributing to the thermopower is diffusive thermoelectric generation with electrons as the majority carrier. PMID:23615862
Reservoir transport and poroelastic properties from oscillating pore pressure experiments
NASA Astrophysics Data System (ADS)
Hasanov, Azar K.
Hydraulic transport properties of reservoir rocks, permeability and storage capacity are traditionally defined as rock properties, responsible for the passage of fluids through the porous rock sample, as well as their storage. The evaluation of both is an important part of any reservoir characterization workflow. Moreover, permeability and storage capacity are main inputs into any reservoir simulation study, routinely performed by reservoir engineers on almost any major oil and gas field in the world. An accurate reservoir simulation is essential for production forecast and economic analysis, hence the transport properties directly control the profitability of the petroleum reservoir and their estimation is vital for oil and gas industry. This thesis is devoted to an integrated study of reservoir rocks' hydraulic, streaming potential and poroelastic properties as measured with the oscillating pore pressure experiment. The oscillating pore pressure method is traditionally used to measure hydraulic transport properties. We modified the method and built an experimental setup, capable of measuring all aforementioned rock properties simultaneously. The measurements were carried out for four conventional reservoir-rock quality samples at a range of oscillation frequencies and effective stresses. An apparent frequency dependence of permeability and streaming potential coupling coefficient was observed. Measured frequency dispersion of drained poroelastic properties indicates an intrinsically inelastic nature of the porous mineral rock frame. Standard Linear Model demonstrated the best fit to the experimental dispersion data. Pore collapse and grain crushing effects took place during hydrostatic loading of the dolomitic sample and were observed in permeability, coupling coefficient and poroelastic measurements simultaneously. I established that hydraulically-measured storage capacities are overestimated by almost one order of magnitude when compared to elastically-derived ones. The fact that the values of storage capacities as estimated from the hydraulic component of the oscillating pore pressure experiment are unreliable was also demonstrated by comparing poroelastic Biot and Skempton coefficients. These coefficients were estimated both from hydraulic and strain measurements and the comparison of two datasets points out ambiguity of hydraulic measurements. I also introduce a novel method, which allowed us to estimate the permeability from the full range of acquired frequency data by utilizing a nonlinear least-squares regression. I additionally performed numerical simulation of oscillatory fluid flow. The simulated frequency-dependent results displayed an excellent agreement with both analytical solution and experimental data. This agreement proves that numerical simulation is a powerful tool in predicting frequency response of a porous rock sample to harmonic pore pressure excitations.
Transport Properties of Negative Ions in HBR Plasmas
NASA Astrophysics Data System (ADS)
Stojanovic, Vladimir; Ivanovic, Nenad; Radmilovic-Radjenovic, Marija; Raspopovic, Zoran; Bojarov, Aleksandar; Petrovic, Zoran
2014-10-01
Low temperature plasma in halogenated gases is standard environment for dry etching of semiconductors. Amount of negative ions in HBr plasmas determines electronegativity so modeling etching devices requires data for anion transport properties. In this work we present cross section set for Br- ions in HBr assembled by using Denpoh-Nanbu theory. The threshold energy values were calculated by known heats of formation. The calculated total cross section accounts for ion-induced-dipole and ion-permanent-dipole interaction by using the local-dipole model. The total cross section was corrected to fit the reduced mobility obtained by SACM (Statistical Adiabatic Channel Model) approximation. Existing cross section measurements were used to scale calculated cross sections. Finally, we used Monte Carlo method to determine transport parameters for Br- as a function of reduced electric fields that can be used in fluid and hybrid plasma models.
Electronic correlation and transport properties of nuclear fuel materials
NASA Astrophysics Data System (ADS)
Yin, Quan; Kutepov, Andrey; Haule, Kristjan; Kotliar, Gabriel; Savrasov, Sergey Y.; Pickett, Warren E.
2011-11-01
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.
Transport properties of individual C{sub 60}-molecules
Géranton, G. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany)] [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany); Seiler, C.; Evers, F. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany) [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany); Center for Functional Nanostructures, Karlsruhe Institute of Technology, Campus South, D-76131 Karlsruhe (Germany); Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, Campus South, D-76128 Karlsruhe (Germany); Bagrets, A. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany) [Institute of Nanotechnology, Karlsruhe Institute of Technology, Campus North, D-76128 Karlsruhe (Germany); Steinbuch Center for Supercomputing, Karlsruhe Institute of Technology, D-76128 Karlsruhe (Germany); Venkataraman, L. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)] [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)
2013-12-21
Electrical and thermal transport properties of C{sub 60} molecules are investigated with density-functional-theory based calculations. These calculations suggest that the optimum contact geometry for an electrode terminated with a single-Au atom is through binding to one or two C-atoms of C{sub 60} with a tendency to promote the ?sp{sup 2}-hybridization into an ?sp{sup 3}-type one. Transport in these junctions is primarily through an unoccupied molecular orbital that is partly hybridized with the Au, which results in splitting the degeneracy of the lowest unoccupied molecular orbital triplet. The transmission through these junctions, however, cannot be modeled by a single Lorentzian resonance, as our results show evidence of quantum interference between an occupied and an unoccupied orbital. The interference results in a suppression of conductance around the Fermi energy. Our numerical findings are readily analyzed analytically within a simple two-level model.
Structural and robustness properties of smart-city transportation networks
NASA Astrophysics Data System (ADS)
Zhang, Zhen-Gang; Ding, Zhuo; Fan, Jing-Fang; Meng, Jun; Ding, Yi-Min; Ye, Fang-Fu; Chen, Xiao-Song
2015-09-01
The concept of smart city gives an excellent resolution to construct and develop modern cities, and also demands infrastructure construction. How to build a safe, stable, and highly efficient public transportation system becomes an important topic in the process of city construction. In this work, we study the structural and robustness properties of transportation networks and their sub-networks. We introduce a complementary network model to study the relevance and complementarity between bus network and subway network. Our numerical results show that the mutual supplement of networks can improve the network robustness. This conclusion provides a theoretical basis for the construction of public traffic networks, and it also supports reasonable operation of managing smart cities. Project supported by the Major Projects of the China National Social Science Fund (Grant No. 11 & ZD154).
Transport properties of zigzag graphene nanoribbon decorated with copper clusters
Berahman, M.; Sheikhi, M. H.
2014-09-07
Using non-equilibrium green function with density functional theory, the present study investigates the transport properties of decorated zigzag graphene nanoribbon with a copper cluster. We have represented the decoration of zigzag graphene nanoribbon with single copper atom and cluster containing two and three copper atoms. In all the cases, copper atoms tend to occupy the edge state. In addition, we have shown that copper can alter the current-voltage characteristic of zigzag graphene nanoribbon and create new fluctuations and negative differential resistance. These alternations are made due to discontinuity in the combination of orbitals along the graphene nanoribbon. Decoration alters these discontinuities and creates more visible fluctuations. However, in low bias voltages, the changes are similar in all the cases. The study demonstrates that in the decorated zigzag graphene nanoribbon, the edge states are the main states for transporting electron from one electrode to another.
Transport properties of ultrathin black phosphorus on hexagonal boron nitride
NASA Astrophysics Data System (ADS)
Doganov, Rostislav A.; Koenig, Steven P.; Yeo, Yuting; Watanabe, Kenji; Taniguchi, Takashi; Özyilmaz, Barbaros
2015-02-01
Ultrathin black phosphorus, or phosphorene, is a two-dimensional material that allows both high carrier mobility and large on/off ratios. Similar to other atomic crystals, like graphene or layered transition metal dichalcogenides, the transport behavior of few-layer black phosphorus is expected to be affected by the underlying substrate. The properties of black phosphorus have so far been studied on the widely utilized SiO2 substrate. Here, we characterize few-layer black phosphorus field effect transistors on hexagonal boron nitride—an atomically smooth and charge trap-free substrate. We measure the temperature dependence of the field effect mobility for both holes and electrons and explain the observed behavior in terms of charged impurity limited transport. We find that in-situ vacuum annealing at 400 K removes the p-doping of few-layer black phosphorus on both boron nitride and SiO2 substrates and reduces the hysteresis at room temperature.
Low temperature carrier transport properties in isotopically controlled germanium
Itoh, K.
1994-12-01
Investigations of electronic and optical properties of semiconductors often require specimens with extremely homogeneous dopant distributions and precisely controlled net-carrier concentrations and compensation ratios. The previous difficulties in fabricating such samples are overcome as reported in this thesis by growing high-purity Ge single crystals of controlled {sup 75}Ge and {sup 70}Ge isotopic compositions, and doping these crystals by the neutron transmutation doping (NTD) technique. The resulting net-impurity concentrations and the compensation ratios are precisely determined by the thermal neutron fluence and the [{sup 74}Ge]/[{sup 70}Ge] ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples the authors have conducted four types of electron (hole) transport studies probing the nature of (1) free carrier scattering by neutral impurities, (2) free carrier scattering by ionized impurities, (3) low temperature hopping conduction, and (4) free carrier transport in samples close to the metal-insulator transition.
Transport Properties of operational gas mixtures used at LHC
Assran, Yasser
2011-01-01
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.
Transport Properties of operational gas mixtures used at LHC
Yasser Assran; Archana Sharma
2011-10-31
This report summarizes some useful data on the transport characteristics of gas mixtures which are required for detection of charged particles in gas detectors. We try to replace Freon used for RPC detector in the CMS experiment with another gas while maintaining the good properties of the Freon gas mixture unchanged. We try to switch to freonless gas mixture because Freon is not a green gas, it is very expensive and its availability is decreasing. Noble gases like Ar, He, Ne and Xe (with some quenchers like carbon dioxide, methane, ethane and isobutene) are investigated. Transport parameters like drift velocity, diffusion, Townsend coefficient, attachment coefficient and Lorentz angle are computed using Garfield software for different gas mixtures and compared with experimental data.
Coefficients for calculating thermodynamic and transport properties of individual species
NASA Technical Reports Server (NTRS)
Mcbride, Bonnie J.; Gordon, Sanford; Reno, Martin A.
1993-01-01
Libraries of thermodynamic data and transport properties are given for individual species in the form of least-squares coefficients. Values of C(sup 0)(sub p)(T), H(sup 0)(T), and S(sup 0)(T) are available for 1130 solid, liquid, and gaseous species. Viscosity and thermal conductivity data are given for 155 gases. The original C(sup 0)(sub p)(T) values were fit to a fourth-order polynomial with 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.
Geophysical and transport properties of reservoir rocks. Summary annual report
Cook, N.G.W.
1990-04-29
Definition of petrophysical properties, such as porosity, permeability and fluid saturation, on the scale of meters, is the key to planning and control of successful Enhanced Oil Recovery techniques for domestic reservoirs. Macroscopic transport properties in reservoir rocks depend critically upon processes at the pore level involving interactions between the pore topology and the physical and chemical properties of the rock minerals and interstitial fluids. Similar interactions at the pore level determine also the macroscopic electrical and seismic properties of reservoir rocks. The objective of this research is to understand, using analysis and experiment, how fluids in pores affect the geophysical and sport properties of reservoir rocks. The goal is to develop equations-relating seismic and electrical properties of rock to the porosity, permeability and fluid saturations so as to invert geophysical images for improved reservoir management. Results from seismic measurements performed so far in this study suggest that even subtle changes in fluid contacts and the in-situ state of effective stress can be detected using geophysical imaging techniques. The experiments using Wood`s metal and wax are revealing the topology and sport properties of the pore space in clastic sedimentary rocks. A deeper understanding of these properties is considered-to be the key to the recovery of much of the mobile oil left in domestic reservoirs and to the effective management of enhanced oil recovery techniques. The results of Wood`s metal percolation tests indicate that most of the permeability of Berea sandstone resides in the critical percolating paths and these paths occupy only a small fraction of the total porosity. This result may have important implications for flooding in terms of override and efficiency as a function of saturation.
NASA Astrophysics Data System (ADS)
Kovalevskiy, Mikhail
2013-04-01
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)
Anisotropic properties of a single superconducting CaCuO2/SrTiO3 interface
NASA Astrophysics Data System (ADS)
Salvato, M.; Tieri, G.; Balestrino, G.; Di Castro, D.
2015-09-01
The transport properties of CaCuO2/SrTiO3 single interfaces are studied by resistance versus temperature measurements in external magnetic fields. The superconducting anisotropy ? ={? }a-b/{? }c, where {? }a-b and {? }c are the superconducting coherence lengths parallel and perpendicular to the interface, respectively, shows values higher than that previously obtained for CaCuO2/SrTiO3 superlattices deposited in the same conditions. The larger anisotropy, observed for the single interfaces, indicates that the charge carriers are confined inside a thin superconducting layer next to the interface rather than spread throughout the whole CaCuO2 block. The activation energy and the irreversibility line confirm this hypothesis, suggesting that quasi two-dimensional transport is dominant in this system. The interpretation of the experimental data in the framework of the Berezinskii–Kosterlitz–Thouless theory confirms that the thickness of the superconducting sheet layer is about 1 nm, corresponding roughly to two CaCuO2 unit cells.
Polymerizable ionic liquid with state of the art transport properties.
Jeremias, Sebastian; Kunze, Miriam; Passerini, Stefano; Schönhoff, Monika
2013-09-12
The physicochemical properties of diallyldimethylammonium-bis(trifluoromethanesulfonyl)imide (DADMATFSI) and its binary mixture with LiTFSI are presented herein, also showing this novel compound as a polymerizable room temperature ionic liquid with excellent transport properties for Li(+) ions. In particular, results of pulsed field gradient (PFG)-NMR diffusion experiments and impedance measurements show that DADMATFSI exhibits state of the art properties of ionic liquids. Similar ionic diffusion coefficients and a similarly high conductivity as seen in the benchmark compound N-butyl-N-methylpyrrolidinium-bis(trifluoromethanesulfonyl)imide (PYR14TFSI) are observed. In accordance, the Li transference number in the binary mixture matches the trend seen for PYR14TFSI-LiTFSI mixtures. In addition to these impressive properties as ionic liquid, DADMATFSI was polymerized by UV treatment. The polymerization is demonstrated and the ion conducting properties of the resulting gel polymer electrolyte are investigated, showing that DADMATFSI can be transformed into an ionogel and may have applications where polymerization is desirable. PMID:23957879
Magnetization and Transport Properties for Particles in Spin Textures
NASA Astrophysics Data System (ADS)
McCormick, Timothy; Trivedi, Nandini
2015-03-01
We use exact-diagonalization and Monte Carlo (ED +MC) to calculate the magnetization M(T) and the spin polarization P(T) for a charged particle moving in a variety of ferromagnetic, spiral and chiral spin textures. We derive an effective spin Hamiltonian by integrating out charged degrees of freedom and compare its magnetization with that of the full Hamiltonian. We then calculate transport properties such as the dynamical conductivity ?sigma(?omega) and the anomalous Hall conductivity using the Chern number. This work has been supported by Grant Number NSF-DMR1309461.
Thermodynamic and transport properties of cryogenic propellants and related fluids
NASA Technical Reports Server (NTRS)
Johnson, V. J.
1973-01-01
Significant advances have been made in recent years in the quality and range of thermophysical data for the cryogenic propellants, pressurants, and inertants. A review of recently completed and current data compilation projects for helium, hydrogen, argon, nitrogen, oxygen, fluorine, and methane is given together with recommended references for thermodynamic and transport property data tables for these fluids. Modern techniques in the plotting of thermodynamic charts from tabular data (or from functions such as the equation of state) have greatly improved their precision and value. A list of such charts is included.
Transport properties of plastic separator for renewable energy applications
NASA Astrophysics Data System (ADS)
Sharma, A. L.; Thakur, A. K.
2013-06-01
We report innovative results on optimization of intercalated polymer-clay nanocomposite endowed with desirable properties; (i) very high ionic conductivity (˜10-3 S cm-1) at room temperature, (ii) tion˜99% and cation transport number (tLi+)˜67%: Intercalation of (PAN)8LiCF3SO3 complex into dodecylamine modified montmorillonite clay (DMMT) nanometric channels has been confirmed by Transmission electron microscopy (TEM) analysis. The optimized polymer film serves dual purpose of electrolyte and separator in energy storage devices.
Transport properties of ZrN superconducting films
Cassinese, A.; Iavarone, M.; Vaglio, R.; Grimsditch, M.; Uran, S.
2000-12-01
Superconductivity in nitrides presents intriguing aspects related to the role of optical phonons. In the present paper we report on high-quality superconducting zirconium nitride film preparation and characterization (including Raman scattering) as well as on both dc and microwave frequency transport properties. The high-temperature dc resistivity shows no evidence of saturation effects, possibly due to the low electron-phonon coupling. Surface impedance data can be well fitted by the standard BCS expressions. The data provide further evidence of the ''conventional'' nature of superconductivity in these compounds.
Effective Potential Energies and Transport Properties for Nitrogen and Oxygen
NASA Technical Reports Server (NTRS)
Stallcop, James R.; Partridge, Harry; Levin, Eugene; Kwak, Dochan (Technical Monitor)
2001-01-01
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.
Li, Yijing; Barbic, Jernej
2015-10-01
The Finite Element Method (FEM) is commonly used to simulate isotropic deformable objects in computer graphics. Several applications (wood, plants, muscles) require modeling the directional dependence of the material elastic properties in three orthogonal directions. We investigate linear orthotropic materials, a special class of linear anisotropic materials where the shear stresses are decoupled from normal stresses, as well as general linear (non-orthotropic) anisotropic materials. Orthotropic materials generalize transversely isotropic materials, by exhibiting different stiffness in three orthogonal directions. Orthotropic materials are, however, parameterized by nine values that are difficult to tune in practice, as poorly adjusted settings easily lead to simulation instabilities. We present a user-friendly approach to setting these parameters that is guaranteed to be stable. Our approach is intuitive as it extends the familiar intuition known from isotropic materials. Similarly to linear orthotropic materials, we also derive a stability condition for a subset of general linear anisotropic materials, and give intuitive approaches to tuning them. In order to simulate large deformations, we augment linear corotational FEM simulations with our orthotropic and general anisotropic materials. PMID:26340037
Electronic and transport properties of LiCoO2.
Andriyevsky, Bohdan; Doll, Klaus; Jacob, Timo
2014-11-14
Using first principles density functional theory (DFT), the electronic and magnetic properties as well as the Li-ion migration in LiCoO2 have been studied with a gradient corrected functional. The magnetic properties were also investigated in addition using a gradient corrected functional in combination with an on-site repulsion U and a hybrid functional. We find LiCoO2 to be non-magnetic under ambient conditions. A magnetic ground state can be obtained by a volume expansion corresponding to a negative pressure of -8 GPa due to a competition between Hund's rules favoring magnetism on the Co(3+) ions and the crystal field splitting, which suppresses magnetism at zero pressure. The barrier for lithium transport is determined to be 0.44 eV from nudged elastic band (NEB) calculations on the Li0.917CoO2 system. PMID:25264622
Predicting the transport properties of sedimentary rocks from microgeometry
Schlueter, E.M.
1995-02-01
The author investigates through analysis and experiment 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. The approach is to measure fluid permeability and electrical conductivity of rock samples using single and multiple fluid phases that can be frozen in place (wetting and nonwetting) over a range of pore pressures. These experiments are analyzed in terms of the microphysics and microchemistry of the processes involved to provide a theoretical basis for the macroscopic constitutive relationships between fluid-flow and geophysical properties that the authors develop. The purpose of these experiments and their analyses is to advance the understanding of the mechanisms and factors that control fluid transport in porous media. This understanding is important in characterizing porous media properties and heterogeneities before simulating and monitoring the progress of complex flow processes at the field scale in permeable media.
Predicting the transport properties of sedimentary rocks from microgeometry
Schlueter, E.M.
1993-01-01
We investigate through analysis and experiment 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. Our approach is to measure fluid permeability and electrical conductivity of rock samples using single and multiple fluid phases that can be frozen in place (wetting and nonwetting) over a range of pore pressures. These experiments are analyzed in terms of the microphysics and microchemistry of the processes involved to provide a theoretical basis for the macroscopic constitutive relationships between fluid-flow and geophysical properties that we develop. The purpose of these experiments and their analyses is to advance the understanding of the mechanisms and factors that control fluid transport in porous media. This understanding is important in characterizing porous media properties and heterogeneities before simulating and monitoring the progress of complex flow processes at the field scale in permeable media.
Thermal and transport properties of the neutron star inner crust
Page, Dany
2012-01-01
We review the nuclear and condensed matter physics underlying the thermal and transport properties of the neutron star inner crust. These properties play a key role in interpreting transient phenomena such as thermal relaxation in accreting neutron stars, superbursts, and magnetar flares. We emphasize simplifications that occur at low temperature where the inner crust can be described in terms of electrons and collective excitations. The heat conductivity and heat capacity of the solid and superfluid phase of matter is discussed in detail and we emphasize its role in interpreting observations of neutron stars in soft X-ray transients. We highlight recent theoretical and observational results, and identify future work needed to better understand a host of transient phenomena in neutron stars.
Thermal and transport properties of the neutron star inner crust
Dany Page; Sanjay Reddy
2012-01-26
We review the nuclear and condensed matter physics underlying the thermal and transport properties of the neutron star inner crust. These properties play a key role in interpreting transient phenomena such as thermal relaxation in accreting neutron stars, superbursts, and magnetar flares. We emphasize simplifications that occur at low temperature where the inner crust can be described in terms of electrons and collective excitations. The heat conductivity and heat capacity of the solid and superfluid phase of matter is discussed in detail and we emphasize its role in interpreting observations of neutron stars in soft X-ray transients. We highlight recent theoretical and observational results, and identify future work needed to better understand a host of transient phenomena in neutron stars.
Quantum Molecular Dynamics calculation of electrical and thermal transport properties
NASA Astrophysics Data System (ADS)
Desjarlais, Michael
2011-10-01
Dense, strongly-coupled plasmas, with degenerate or partially degenerate electrons--ubiquitous in high energy density physics, inertial fusion, planetary science, and warm dense matter--are very difficult to describe accurately with traditional theoretical approaches. Over the last decade, density functional based molecular dynamics, also know as quantum molecular dynamics (QMD), has emerged as a powerful tool for the study of dense quantum plasmas, providing accurate equation of state, structural, and transport properties. This talk will focus on the QMD calculation of electrical and thermal conductivities with a much higher degree of accuracy than was possible with earlier methods. Within the density functional approach, electrical and thermal conductivities are extracted directly from the electronic orbitals using the Kubo-Greenwood and Chester-Thellung formalisms, circumventing the need to define the ionization states and collision cross sections. These transport calculations have now been used to generate several wide-range transport models for use in large-scale simulation codes, allowing unprecedented simulations of complex experiments. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Theory of the electronic and transport properties of epitaxial graphene
NASA Astrophysics Data System (ADS)
Buongiorno Nardelli, Marco
2011-03-01
Advances in the epitaxial growth of graphene films on SiC have the potential to open new classes of device applications that may revolutionize the semiconductor roadmap for future decades. However, this progress will require an in-depth understanding and utilization of the electronic processes that take place at the nanoscale. In this talk I will review our recent results on the electronic and transport properties of epitaxial graphene on SiC. Using calculations from first principles, I will discuss the the role of the interface buffer layer in the tuning of the band alignment and the magnetic doping at the heterojunction; I will describe the effect of electron-phonon interactions in mono- and bi-layer graphene in determining the intrinsic carrier-phonon scattering properties of this material and thus the ultimate limit of any electronic device; finally, I will briefly discuss the thermal properties of the graphene/SiC interface, since understanding of the heat transfer properties is essential for optimal thermal management and heat removal in device applications. Work done in collaboration with K.W. Kim, T. Jayasekera, J. Mullen, K. Borysenko, S. Xu, X. Li and B.D. Kong.
Hydrophobic organic contaminant transport property heterogeneity in the Borden Aquifer
NASA Astrophysics Data System (ADS)
Allen-King, Richelle M.; Kalinovich, Indra; Dominic, David F.; Wang, Guohui; Polmanteer, Reid; Divine, Dana
2015-03-01
We determined that the spatial heterogeneity in aquifer properties governing the reactive transport of volatile organic contaminants is defined by the arrangement of lithofacies. We measured permeability (k) and perchloroethene sorption distribution coefficient (Kd) for lithofacies that we delineated for samples from the Canadian Forces Base Borden Aquifer. We compiled existing data and collected 57 new cores to characterize a 30 m section of the aquifer near the test location of Mackay et al. (1986). The k and Kd were measured for samples taken at six elevations from all cores to create a data set consisting of nearly 400 colocated measurements. Through analysis of variance (corrected for multiple comparisons), we determined that the 12 originally mapped lithofacies could be grouped into five relatively distinct chemohydrofacies that capture the variability of both transport properties. The mean of ln k by lithofacies was related to the grain size and the variance was relatively consistent. In contrast, both the mean and variance of ln Kd were greater for more poorly sorted lithofacies, which were also typically more coarse-grained. Half of the aquifer sorption capacity occurred in the three highest-sorbing lithofacies but comprised only 20% of its volume. The model of the aquifer that emerged is that of discontinuous scour-fill deposits of medium sand, generally characterized by greater Kd and k, within laterally extensive fine-grained to very fine-grained sands of lower Kd and k. Our findings demonstrate the importance of considering source rock composition, transport, and deposition processes when constructing conceptual models of chemohydrofacies.
RELATIONSHIP BETWEEN CELL SURFACE PROPERTIES AND TRANSPORT OF BACTERIA THROUGH SOIL
A study was conducted to relate the properties of Enterobacter, Pseudomonas, Bacillus, Achromobacter, Flavobacterium, and Arthrobacter strains to their transport with water moving through soil. the bacteria differed markedly in their extent of transport; their hydrophobicity, as...
FRONTIERS ARTICLE Fundamentals of energy transport, energy conversion, and thermal properties
Malen, Jonathan A.
FRONTIERS ARTICLE Fundamentals of energy transport, energy conversion, and thermal properties, thermoelectrics, and photovoltaics. However, energy transport and conversion, at the organicinorganic interface and as an energy conversion technology. Aviram and Ratner's revolutionary suggestion that molecules could behave
Quantifying Effective Flow and Transport Properties in Heterogeneous Porous Media
NASA Astrophysics Data System (ADS)
Heidari, P.; Li, L.
2012-12-01
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.
Thermomagnetic Transport in Polycrystalline Samples
NASA Astrophysics Data System (ADS)
Zebarjadi, M.
2015-07-01
Polycrystalline/single-phase nanocomposite samples are used widely for thermoelectrics and many other applications. The presence of many interfaces improves the thermoelectric properties by suppressing phonon transport more than electron transport. When polycrystalline samples are made out of anisotropic crystals, it is not clear how the transport properties are related to those of single crystal. In this paper, we describe a simple process of averaging over different crystallographic directions to calculate the properties of isotropic polycrystalline samples made out of anisotropic crystals. We apply the developed averaging model to (Bi0.2Sb0.8)2Te3 samples for which experimental data are available. We further point out the importance of thermomagnetic measurements in providing additional information on electron relaxation times, compared with what regular thermoelectric measurements reveal.
Thermomagnetic Transport in Polycrystalline Samples
NASA Astrophysics Data System (ADS)
Zebarjadi, M.
2015-10-01
Polycrystalline/single-phase nanocomposite samples are used widely for thermoelectrics and many other applications. The presence of many interfaces improves the thermoelectric properties by suppressing phonon transport more than electron transport. When polycrystalline samples are made out of anisotropic crystals, it is not clear how the transport properties are related to those of single crystal. In this paper, we describe a simple process of averaging over different crystallographic directions to calculate the properties of isotropic polycrystalline samples made out of anisotropic crystals. We apply the developed averaging model to (Bi0.2Sb0.8)2Te3 samples for which experimental data are available. We further point out the importance of thermomagnetic measurements in providing additional information on electron relaxation times, compared with what regular thermoelectric measurements reveal.
The calculation of transport properties in quantum liquids using the maximum entropy numerical
Rabani, Eran
properties in quantum liquids. The method is applied to the case of liquid para-hydrogen at two thermodynamic to study transport properties in fluid para-hydrogen at two thermodynamic state points: a liquid nearThe calculation of transport properties in quantum liquids using the maximum entropy numerical
Modelling Coulomb Collisions in Anisotropic Plasmas
NASA Astrophysics Data System (ADS)
Hellinger, P.; Travnicek, P. M.
2009-12-01
Collisional transport in anisotropic plasmas is investigated comparing the theoretical transport coefficients (Hellinger and Travnicek, 2009) for anisotropic particles with the results of the corresponding Langevin equation, obtained as a generalization of Manheimer et al. (1997). References: Hellinger, P., and P. M. Travnicek (2009), On Coulomb collisions in bi-Maxwellian plasmas, Phys. Plasmas, 16, 054501. Manheimer, W. M., M. Lampe and G. Joyce (1997), Langevin representation of Coulomb collisions in PIC simulations, J. Comput. Phys., 138, 563-584.
Optical and Transport Properties of Organic Molecules: Methods and Applications
NASA Astrophysics Data System (ADS)
Strubbe, David Alan
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
Physicochemical properties determine nanomaterial cellular uptake, transport, and fate.
Zhu, Motao; Nie, Guangjun; Meng, Huan; Xia, Tian; Nel, Andre; Zhao, Yuliang
2013-03-19
Although a growing number of innovations have emerged in the fields of nanobiotechnology and nanomedicine, new engineered nanomaterials (ENMs) with novel physicochemical properties are posing novel challenges to understand the full spectrum of interactions at the nano-bio interface. Because these could include potentially hazardous interactions, researchers need a comprehensive understanding of toxicological properties of nanomaterials and their safer design. In depth research is needed to understand how nanomaterial properties influence bioavailability, transport, fate, cellular uptake, and catalysis of injurious biological responses. Toxicity of ENMs differ with their size and surface properties, and those connections hold true across a spectrum of in vitro to in vivo nano-bio interfaces. In addition, the in vitro results provide a basis for modeling the biokinetics and in vivo behavior of ENMs. Nonetheless, we must use caution in interpreting in vitro toxicity results too literally because of dosimetry differences between in vitro and in vivo systems as well the increased complexity of an in vivo environment. In this Account, we describe the impact of ENM physicochemical properties on cellular bioprocessing based on the research performed in our groups. Organic, inorganic, and hybrid ENMs can be produced in various sizes, shapes and surface modifications and a range of tunable compositions that can be dynamically modified under different biological and environmental conditions. Accordingly, we cover how ENM chemical properties such as hydrophobicity and hydrophilicity, material composition, surface functionalization and charge, dispersal state, and adsorption of proteins on the surface determine ENM cellular uptake, intracellular biotransformation, and bioelimination versus bioaccumulation. We review how physical properties such as size, aspect ratio, and surface area of ENMs influence the interactions of these materials with biological systems, thereby affecting their hazard potential. We discuss our actual experimental findings and show how these properties can be tuned to control the uptake, biotransformation, fate, and hazard of ENMs. This Account provides specific information about ENM biological behavior and safety issues. This research also assists the development of safer nanotherapeutics and guides the design of new materials that can execute novel functions at the nano-bio interface. PMID:22891796
The effect of microporosity on transport properties in porous media
NASA Astrophysics Data System (ADS)
Mehmani, Ayaz; Prodanovi?, Maša
2014-01-01
Sizeable amounts of connected microporosity with various origins can have a profound effect on important petrophysical properties of a porous medium such as (absolute/relative) permeability and capillary pressure relationships. We construct pore-throat networks that incorporate both intergranular porosity and microporosity. The latter originates from two separate mechanisms: partial dissolution of grains and pore fillings (e.g. clay). We then use the reconstructed network models to estimate the medium flow properties. In this work, we develop unique network construction algorithms and simulate capillary pressure-saturation and relative permeability-saturation curves for cases with inhomogeneous distributions of pores and micropores. Furthermore, we provide a modeling framework for variable amounts of cement and connectivity of the intergranular porosity and quantifying the conditions under which microporosity dominates transport properties. In the extreme case of a disconnected inter-granular network due to cementation a range of saturations within which neither fluid phase is capable of flowing emerges. To our knowledge, this is the first flexible pore scale model, from first principles, to successfully approach this behavior observed in tight reservoirs.
Semiconducting carbon nanotube transistors: Electron and spin transport properties
NASA Astrophysics Data System (ADS)
Chen, Yung-Fu
Single-walled carbon nanotubes (SWNTs) have attracted great interest both scientifically and technologically due to their long mean free paths and high carrier velocities at room temperature, and possibly very long spin-scattering lengths. This thesis will describe experiments to probe the charge-and spin-transport properties of long, clean individual SWNTs prepared by chemical vapor deposition and contacted by metal electrodes. A SWNT field-effect transistor (SWNT-FET) has been shown to be sensitive to single electrons in charge traps. A single charge trap near a SWNT-FET is explored here using both electronic and scanned-probe techniques, and a simple model is developed to determine the capacitances of the trap to the SWNT and gate electrode. SWNTs are contacted with ferromagnetic electrodes in order to explore the transport of spin-polarized current through the SWNT. In some cases spin-dependent transport was observed, verifying long spin scattering lengths in SWNT. However, in many cases no spin-dependent effects were observed; these results will be discussed in the context of the present state of results in the literature. Semiconducting SWNTs (s-SWNTs) with Schottky-barrier contacts are measured at high bias. Nearly symmetric ambipolar transport is observed, with electron and hole currents significantly exceeding 25 muA, the reported current limit in m-SWNTs. Four simple models for the field-dependent velocity (ballistic, current saturation, velocity saturation, and constant mobility) are studied in the unipolar regime; the high-bias behavior is best explained by a velocity saturation model with a saturation velocity of 2 x 107 cm/s. A simple Boltzmann equation model for charge transport in s-SWNTs is developed with two adjustable parameters, the elastic and inelastic scattering lengths. The model predicts velocity saturation rather than current saturation in s-SWNTs, in agreement with experiment. Contact effects in s-SWNT-FET are explored by electrically heating the devices. These experiments resolve the origin of nanotube p-type behavior in air by showing that the observed p-type behavior upon air exposure cannot be explained by change in contact work function, but is instead due to doping of the nanotube. Modest doping of the SWNT narrows the Schottky Barriers and provides a high-conductance Ohmic tunnel contact from electrode to SWNT.
Anisotropic magnetic properties of Dy{sub 6}Cr{sub 4}Al{sub 43} single crystal
Maurya, Arvind, E-mail: arvindmaurya@tifr.res.in; Thamizhavel, A., E-mail: arvindmaurya@tifr.res.in; Dhar, S. K., E-mail: arvindmaurya@tifr.res.in [Department of Condensed Matter Physics and Material Science, Tata Institute of Fundamental Research, Mumbai-400005 (India)
2014-04-24
We have studied the anisotropic magnetic behavior of the rare earth intermetallic compound Dy{sub 6}Cr{sub 4}Al{sub 43}. This compound crystallizes in the hexagonal symmetry and orders ferromagnetically at 8.3 K as confirmed by the magnetic susceptibility and heat capacity measurements. A significant anisotropy in the magnetization is observed between the c axis and the ab-plane. The easy axis liesin theab-plane at low temperatures; however it orients itselfalong the c-axis above 170 K as inferred from the susceptibility data.
NASA Astrophysics Data System (ADS)
Cuenca, Jacques; Van der Kelen, Christophe; Göransson, Peter
2014-02-01
This paper proposes an inverse estimation method for the characterisation of the elastic and anelastic properties of the frame of anisotropic open-cell foams used for sound absorption. A model of viscoelasticity based on a fractional differential constitutive equation is used, leading to an augmented Hooke's law in the frequency domain, where the elastic and anelastic phenomena appear as distinctive terms in the stiffness matrix. The parameters of the model are nine orthotropic elastic moduli, three angles of orientation of the material principal directions and three parameters governing the anelastic frequency dependence. The inverse estimation consists in numerically fitting the model on a set of transfer functions extracted from a sample of material. The setup uses a seismic-mass measurement repeated in the three directions of space and is placed in a vacuum chamber in order to remove the air from the pores of the sample. The method allows to reconstruct the full frequency-dependent complex stiffness matrix of the frame of an anisotropic open-cell foam and in particular it provides the frequency of maximum energy dissipation by viscoelastic effects. The characterisation of a melamine foam sample is performed and the relation between the fractional-derivative model and other types of parameterisations of the augmented Hooke's law is discussed.
Cuenca, Jacques Van der Kelen, Christophe; Göransson, Peter
2014-02-28
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.
Anisotropic universe with anisotropic sources
Aluri, Pavan K.; Panda, Sukanta; Sharma, Manabendra; Thakur, Snigdha, E-mail: aluri@iucaa.ernet.in, E-mail: sukanta@iiserb.ac.in, E-mail: manabendra@iiserb.ac.in, E-mail: snigdha@iiserb.ac.in [Department of Physics, IISER Bhopal, Bhopal - 462023 (India)
2013-12-01
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.
Electronic structures and transport properties of sulfurized carbon nanotubes
NASA Astrophysics Data System (ADS)
Xu, B.; Feng, Y. P.
2010-11-01
The electronic and transport properties of side-walled sulfurized (8, 0) zigzag carbon nanotube were investigated by using density functional theory coupled with a non-equilibrium Green function approach. It is found that the adsorption of the sulfur chains largely reduces the bandgap of the semiconducting (8, 0) carbon nanotube, even changing it into a metallic one. More importantly, the transmission eigenstates around the Fermi level are contributed by not only the sulfur chains but also the complex system made of the sulfur chains and the single-walled carbon nanotube. Our results provide a method to improve the conductivity and utilization rate of the surface in the electrodes of supercapacitor which are made of the carbon nanotubes.
Transport properties of hadronic matter in magnetic field
Guru Kadam
2015-03-06
We study the effect of magnetic field on the transport properties like shear and bulk viscosities of hot and dense hadronic matter within hadron resonance gas model. We estimate the bulk viscosity using low energy theorems for bilocal correlators of the energy momentum tensor generalized to finite temperature, density and magnetic field. We use Gaussian ansatz for the spectral function at low frequency. We estimate shear viscosity coefficient using molecular kinetic theory. We find that vacuum contribution due to finite magnetic field dominates the bulk viscosity ({\\zeta}) for the temperatures up to 0.1GeV and increases with magnetic field while ratio {\\zeta}/s decreases with magnetic field. We also find that shear viscosity coefficient of hadronic matter decreases with magnetic field.
Electrical Transport Properties of Liquid Sn-Sb Binary Alloys
NASA Astrophysics Data System (ADS)
Thakore, B. Y.; Suthar, P. H.; Khambholja, S. G.; Jani, A. R.
2010-06-01
The study of electrical transport properties viz. electrical resistivity, thermo electrical power and thermal conductivity of liquid Sn-Sb binary alloys have been made by our well recognized single parametric model potential. In the present work, screening functions due to Hartree, Taylor, Ichimaru et al.. Farid et al.. and Sarkar et al.. have been employed to incorporate the exchange and correlation effects. The liquid alloy is studied as a function of its composition at temperature 823 K according to the Faber-Ziman model. Further, thermoelectric power and thermal conductivity have been predicted. The values of electrical resistivity of binary alloys computed with Ichimaru et al. and Farid et al.. screening function are in good agreement with the experimental data.
Shear strain induced modulation to the transport properties of graphene
NASA Astrophysics Data System (ADS)
He, Xin; Gao, Li; Tang, Ning; Duan, Junxi; Xu, Fujun; Wang, Xinqiang; Yang, Xuelin; Ge, Weikun; Shen, Bo
2014-08-01
Applying shear strain has been considered as a hopeful method to open a band gap of graphene. To study the transport properties of graphene under shear strain, a device was fabricated to apply shear strain, up to 16.7%, to graphene grown by chemical vapor deposition method. A top gate with ionic liquid as the dielectric material was used to tune the carrier density. The conductance of the Dirac point and carrier mobility is found to increase with a comparatively small increasing strain but then decrease with a larger one. Such a behavior might be related to several factors: the wrinkles, the transverse conducting channels, and the grain boundaries of graphene. Our study is helpful to further understand the strain engineering in graphene.
Dynamical and transport properties of liquid gallium at high pressures
NASA Astrophysics Data System (ADS)
Sheppard, D.; Mazevet, S.; Cherne, F. J.; Albers, R. C.; Kadau, K.; Germann, T. C.; Kress, J. D.; Collins, L. A.
2015-06-01
Quantum molecular dynamics (QMD) simulations are used to calculate the equation of state, structure, and transport properties of liquid gallium along the principal shock Hugoniot. The calculated Hugoniot is in very good agreement with experimental data up to a pressure of 150 GPa as well as with our earlier classical molecular dynamics calculations using a modified embedded atom method (MEAM) potential. The self-diffusion and viscosity calculated using QMD agree with experimental measurements better than the MEAM results, which we attribute to capturing the complexity of the electronic structure at elevated temperatures. Calculations of the DC conductivity were performed around the Hugoniot. Above a density of 7.5 g/cm3, the temperature increases rapidly along the Hugoniot, and the optical conductivity decreases, indicating simple liquid metal behavior.
Critical transport properties of random metals in large magnetic fields.
Phillips, J C
1997-09-30
The threshold behavior of the transport properties of a random metal in the critical region near a metal-insulator transition is strongly affected by the measuring electromagnetic fields. In spite of the randomness, the electrical conductivity exhibits striking phase-coherent effects due to broken symmetry, which greatly sharpen the transition compared with the predictions of effective medium theories, as previously explained for electrical conductivities. Here broken symmetry explains the sign reversal of the T --> 0 magnetoconductance of the metal-insulator transition in Si(B,P), also previously not understood by effective medium theories. Finally, the symmetry-breaking features of quantum percolation theory explain the unexpectedly very small electrical conductivity temperature exponent alpha = 0.22(2) recently observed in Ni(S,Se)2 alloys at the antiferromagnetic metal-insulator transition below T = 0.8 K. PMID:11038580
Electron-neutron scattering and transport properties of neutron stars
NASA Astrophysics Data System (ADS)
Bertoni, Bridget; Reddy, Sanjay; Rrapaj, Ermal
2015-02-01
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.
The electrical transport properties of liquid Rb using pseudopotential theory
Patel, A. B., E-mail: amit07patel@gmail.com; Bhatt, N. K., E-mail: amit07patel@gmail.com; Thakore, B. Y., E-mail: amit07patel@gmail.com; Jani, A. R. [Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388120, Gujarat (India); Vyas, P. R. [Department of Physics, School of Sciences, Gujarat University, Ahmedabad-380009, Gujarat (India)
2014-04-24
Certain electric transport properties of liquid Rb are reported. The electrical resistivity is calculated by using the self-consistent approximation as suggested by Ferraz and March. The pseudopotential due to Hasegawa et al for full electron-ion interaction, which is valid for all electrons and contains the repulsive delta function due to achieve the necessary s-pseudisation was used for the calculation. Temperature dependence of structure factor is considered through temperature dependent potential parameter in the pair potential. Finally, thermo-electric power and thermal conductivity are obtained. The outcome of the present study is discussed in light of other such results, and confirms the applicability of pseudopotential at very high temperature via temperature dependent pair potential.
Transport properties of nitrogen in single walled carbon nanotubes
NASA Astrophysics Data System (ADS)
Sokhan, V. P.; Nicholson, D.; Quirke, N.
2004-02-01
Transport properties including collective and tracer diffusivities of nitrogen, modeled as a diatomic molecule, in single walled carbon nanotubes have been studied by equilibrium molecular dynamics at different temperatures and as a function of pressure. It is shown that while the asymptotic decay of the translational and rotational velocity autocorrelation function is algebraic, the collective velocity decays exponentially with the relaxation time related to the interfacial friction. The tracer diffusivity in the nanochannel, which is comparable in magnitude with diffusivity in the equilibrium bulk phase, depends only weakly on the conditions at the fluid-solid interface, whereas the collective diffusivity is a strong function of the hydrodynamic boundary conditions and is found to be three orders of magnitude higher than self-diffusivity in carbon nanotubes and for the comparatively rough surface of the rare-gas tube it is one order of magnitude greater. A relationship between the collective diffusivity and the Maxwell coefficient describing wall collisions is obtained. The transport coefficients appear to be insensitive to the long-range details of the potential function.
Transport properties of tomato fruit tonoplast membrane vesicles
Oleski, N.; Joyce, D.; Osteryoung, K.; Bennett, A.B.
1986-04-01
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.
Transport properties of liquid metal hydrogen under high pressures
NASA Technical Reports Server (NTRS)
Brown, R. C.; March, N. H.
1972-01-01
A theory is developed for the compressibility and transport properties of liquid metallic hydrogen, near to its melting point and under high pressure. The interionic force law is assumed to be of the screened Coulomb type, because hydrogen has no core electrons. The random phase approximation is used to obtain the structure factor S(k) of the system in terms of the Fourier transform of this force law. The long wavelenth limit of the structure factor S(o) is related to the compressibility, which is much lower than that of alkali metals at their melting points. The diffusion constant at the melting point is obtained in terms of the Debye frequency, using a frequency spectrum analogous with the phonon spectrum of a solid. A similar argument is used to obtain the combined shear and bulk viscosities, but these depend also on S(o). The transport coefficients are found to be about the same size as those of alkali metals at their melting points.
Electron Transport Materials: Synthesis, Properties and Device Performance
Cosimbescu, Lelia; Wang, Liang; Helm, Monte L.; Polikarpov, Evgueni; Swensen, James S.; Padmaperuma, Asanga B.
2012-06-01
We report the design, synthesis and characterization, thermal and photophysical properties of two silane based electron transport materials, dibenzo[b,d]thiophen-2-yltriphenylsilane (Si{phi}87) and (dibenzo[b,d]thiophen-2-yl)diphenylsilane (Si{phi}88) and their performance in blue organic light emitting devices (OLEDs). The utility of these materials in blue OLEDs with iridium (III) bis[(4,6-difluorophenyl)-pyridinato-N,C']picolinate (Firpic) as the phosphorescent emitter was demonstrated. Using the silane Si{phi}87 as the electron transport material (ETm) an EQE of 18.2% was obtained, with a power efficiency of 24.3 lm/W (5.8V at 1mA/cm{sup 2}), in a heterostructure. When Si{phi}88 is used, the EQE is 18.5% with a power efficiency of 26.0 lm/W (5.5V at 1mA/cm{sup 2}).
Updated Chemical, Radiative, and Transport Properties of Thermospheric Odd Nitrogen
NASA Astrophysics Data System (ADS)
Yonker, J. D.; Venkataramani, K.; Bailey, S. M.; Wang, W.; Solomon, S. C.; Randall, C. E.
2014-12-01
In the past decade many laboratory and quantum chemical results relevant to the chemical, transport, and radiative properties of thermospheric odd nitrogen have appeared. The impact of these updates on the odd nitrogen abundances, fluxes, and neutral temperature are assessed by inclusion into the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) and comparison with data from the Student Nitric Oxide Explorer (SNOE) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) experiments. Regarding chemistry, electronically and vibrationally excited molecular nitrogen (N2(A)) has been found to be an important source of nitric oxide (NO) and electronically excited atomic nitrogen (N(2D)) [Campbell et al, 2007] while many key branching ratios and temperature dependences have been revised [Hellberg et al, 2003; Galvao et al, 2013]. The yields of vibrationally excited NO(v) from the N(2D)+O2 and N(4S)+O2 reactions have been determined [Miquel et al, 2003; Sultanov et al, 2006]; radiative cascade from NO(v) results in enhanced cooling near 5.3 ?m which contributes roughly 20% of that due to collisions with hot atomic oxygen. Collision integrals for the He-NO and He-N(4S) interactions are known [Partridge et al, 2001; Haghighi et al, 2003] and the resulting transport coefficients are calculated and input to TIE-GCM v2.0, wherein He is treated as a major species.
Dynamical properties and transport coefficients of Kihara linear fluids
NASA Astrophysics Data System (ADS)
MacDowell, L. G.; Garzón, B.; Calero, S.; Lago, S.
1997-03-01
Transport properties of spherical and linear molecules modeled by the Kihara potential are studied by molecular dynamics simulations. Diffusion coefficients, shear viscosities, and thermal conductivities are calculated for a wide range of the fluid region and for several elongations. The corresponding individual and collective correlation functions are discussed along with angular velocity and reorientational correlation functions. Relaxation times and simple models relevant to orientational motion are also studied. The results obtained are discussed in a corresponding states framework, using previous Gibbs ensemble Monte Carlo data for the liquid-vapor equilibria of the models. In this way, the role of elongation can be studied. It is found that in most of the liquid region, the diffusion coefficient is weakly dependent on elongation. On the other hand, both viscosity and thermal conductivity are found to decrease with elongation. The dependence of transport coefficients on density and temperature is also discussed. On testing the Stokes-Einstein relation, it was observed that, unlike previous findings for hard spheres, stick boundary conditions perform just as good as slip boundary conditions for the Lennard-Jones fluid and the low-elongated Kihara fluid.
NASA Astrophysics Data System (ADS)
Wang, Haiyan; Li, Xiangyin
2010-10-01
With the help of the tensor method, the cross-spectral density matrix for the stochastic electromagnetic twist anisotropic Gaussian-Schell model (ETAGSM) beam truncated by a slit aperture propagating in turbulent atmosphere are derived. The spectral properties of this kind of beam are investigated in detail. It is shown by numerical results and analysis that the affection of the slit aperture on the spectral properties of the stochastic ETAGSM beam is obvious in the near field; while in the far field, the atmospheric turbulence plays an important role; the source beam's coherence can weaken the affection of the slit aperture and the atmospheric turbulence on the spectral properties of the stochastic ETAGSM beam truncated by a slit aperture propagating in turbulent atmosphere, while the twist properties of the source beam can strong the affection of the slit aperture on the spectral properties in the near field. Also, the spectral degree of polarization and normalized spectral density distributions and corresponding contour graphs of the stochastic ETAGSM beam truncated by a slit aperture propagating in turbulent atmosphere and free space at different propagation distances are investigated in detail.
Predicting the transport properties of sedimentary rocks from microstructure
Schlueter, E.M.
1995-01-01
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.
Kundu, T; Yang, X; Nakatani, H; Takeda, N
2015-02-01
Acoustic source localization techniques generally assume straight line propagation of waves from the acoustic source to the sensor. However, it is well-known that in anisotropic plates the acoustic energy does not always propagate in straight lines. Even for isotropic plates containing a cavity or an inclusion between the acoustic source and the sensor the straight line propagation assumption is violated. In such cases only options available in localizing acoustic source is to use relatively expensive distributed sensor systems, or to follow time reversal techniques based on the impulse response functions which is labor intensive and computationally demanding. A two-step hybrid technique is proposed in this paper for predicting acoustic source in anisotropic plates. During the first step it was assumed that the waves propagated along straight lines from the acoustic source to the sensor. The source was localized with this simplifying assumption. Then this first prediction was improved in the second step by solving an optimization problem. Experimental results showed that the second step always moved the estimates towards the actual source location. Thus it always reduced the prediction error irrespective of whether the final prediction coincided with the actual source location or not. PMID:25245206
Transport Properties and Diamagnetism of Dirac Electrons in Bismuth
NASA Astrophysics Data System (ADS)
Fuseya, Yuki; Ogata, Masao; Fukuyama, Hidetoshi
2015-01-01
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.
Magnetic and transport properties of magnetite thin films
NASA Astrophysics Data System (ADS)
Zhang, Guomin; Fan, Chongfei; Pan, Liqing; Wang, Fengping; Wu, Ping; Qiu, Hong; Gu, Yousong; Zhang, Yue
2005-05-01
Magnetite (Fe 3O 4) films were prepared by DC reactive magnetron sputtering at various oxygen partial pressures with the ratio ? of oxygen to argon changing from 0.50:50 to 0.70:50 at room temperature, and then the Fe 3O 4 films were annealed at 480 °C for 80 min. The properties of the films were studied by X-ray diffraction, scanning electron microscopy, magnetic hysteresis loops, magnetoresistance (MR), etc. The results showed when ? increased, resistivity of magnetite films were increased exponentially, and only these magnetite films of ?>0.60:50 showed MR effects. After annealing, the resistivity decreased about one order; and all magnetite films showed MR effects. The Verwey transition of the magnetite films was confirmed by MR- T curves. XRD and SEM showed that the films were composed of Fe 3O 4 nanoparticles with highly preferential orientation and the best conditions for high-quality magnetite films were ?=0.65:50 and 0.675:50. The magnetic transport properties of the films infer that strong coupling between Fe 3O 4 nanoparticles originated from RKKY exchange interaction and dipolar interaction, this made the films differ from metallic granular ones and higher-order terms of (M/M s) 2, such as (M/M s) 4 and (M/M s) 6, should be added to the fitting functions of the MR-(M/M s) curves.
Optical and transport properties of an alkali-doped methanofullerene
NASA Astrophysics Data System (ADS)
Saab, A. P.; Stucky, G. D.; Srdanov, V. I.; Hummelen, J. C.; Gonzalez, M.; Wudl, F.
2002-09-01
We examine the effects of monoderivatization on the electronic properties of C60. For this we chose the phenyl-C61-octanoic acid cholesteryl ester, 6,6PCOCr, whose nonlinear optical properties have been investigated in the past. While the optical absorption spectrum of this methano fullerene is similar to that of C60, substantial differences are observed upon doping with potassium. Similarly, the doping-dependent conductivity of the functionalized fullerene shows two maxima as opposed to the single maximum for C60. The experimental observations are consistent with the doping-induced degeneracy removal of the parent C60 LUMO (t1u) orbital, which in potassium-doped methanofullerene splits into two components separated by about 0.5 eV. We provide experimental evidence that the doping of 6,6PCOCr proceeds, as in C60, with six consecutive reduction (electron transfer) steps, yielding K66,6PCOCr stoichiometry at the end. The transport in partially doped 6,6PCOCr thin films occurs by thermally activated hopping of the charge carriers with activation energy Ea[congruent with]0.25 eV and hopping probability proportional to the number of unpaired electrons in the reduced molecule.
NASA Astrophysics Data System (ADS)
Sakakibara, H.; Ando, H.; Kuroki, Y.; Kawai, S.; Ueda, K.; Asano, H.
2015-05-01
Epitaxial bilayers of antiferromagnetic Mn3GaN/ferromagnetic Co3FeN with an antiperovskite structure were grown by reactive magnetron sputtering, and their structural, magnetic, and electrical properties were investigated. Exchange coupling with an exchange field Hex of 0.4 kOe at 4 K was observed for Mn3GaN (20 nm)/Co3FeN (5 nm) bilayers. Negative anisotropic magnetoresistance (AMR) effect in Co3FeN was observed and utilized to detect magnetization reversal in exchange-coupled Mn3GaN/Co3FeN bilayers. The AMR results showed evidence for current-induced spin transfer torque in antiferromagnetic Mn3GaN.
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
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.
Zhao, Ying-Ying; Wang, Jing; Kuang, Hao; Hu, Feng-Xia; Liu, Yao; Wu, Rong-Rong; Zhang, Xi-Xiang; Sun, Ji-Rong; Shen, Bao-Gen
2015-01-01
Memory effect of electric-field control on magnetic behavior in magnetoelectric composite heterostructures has been a topic of interest for a long time. Although the piezostrain and its transfer across the interface of ferroelectric/ferromagnetic films are known to be important in realizing magnetoelectric coupling, the underlying mechanism for nonvolatile modulation of magnetic behaviors remains a challenge. Here, we report on the electric-field control of magnetic properties in wide-band (011)-Pr0.7Sr0.3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 heterostructures. By introducing an electric-field-induced in-plane anisotropic strain field during the cooling process from room temperature, we observe an in-plane anisotropic, nonvolatile modulation of magnetic properties in a wide-band Pr0.7Sr0.3MnO3 film at low temperatures. We attribute this anisotropic memory effect to the preferential seeding and growth of ferromagnetic (FM) domains under the anisotropic strain field. In addition, we find that the anisotropic, nonvolatile modulation of magnetic properties gradually diminishes as the temperature approaches FM transition, indicating that the nonvolatile memory effect is temperature dependent. By taking into account the competition between thermal energy and the potential barrier of the metastable magnetic state induced by the anisotropic strain field, this distinct memory effect is well explained, which provides a promising approach for designing novel electric-writing magnetic memories. PMID:25909177
A Nystrom algorithm for electrostatics of an anisotropic composite
Helsing, Johan
A Nystrom algorithm for electrostatics of an anisotropic composite Johan Helsing Department algorithms for the electrostatics of locally anisotropic composites seems to be a poorly explored area ective properties of lo- cally anisotropic composites is a topic of importance in physics and in physical
Spectroscopic properties of anisotropic absorption in a neodymium-doped YAlO{sub 3} laser crystal
Zhang, X. [Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, People`s Republic of (China)] [Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, People`s Republic of (China); Jiang, B. [Department of Physics, Xiamen University, Xiamen 361005, People`s Republic of (China)] [Department of Physics, Xiamen University, Xiamen 361005, People`s Republic of (China); Yang, Y.; Wang, Z. [Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, People`s Republic of (China)] [Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, People`s Republic of (China)
1997-05-01
Absorption spectra of YAlO{sub 3}:Nd for the three crystallographic axes are investigated at room temperature. The spectral strengths indicate that the absorption coefficient of YAlO{sub 3}:Nd is anisotropic. The anisotropy of the local electric field acting on the rare-earth ion in a laser crystal is considered. An extended Judd{endash}Ofelt theory is applied to calculate the absorption cross sections and oscillator strengths of the electric-dipole transitions in the different principal directions. Three groups of the phenomenological parameters are derived from a least-squares-fitting procedure. We also analyze theoretically the anisotropy of the optical absorption of YAlO{sub 3}:Nd crystal in detail. {copyright} {ital 1997 American Institute of Physics.}
Menaka; Sharma, Soma; Ramanujachary, Kandalam V; Lofland, Samuel E; Ganguli, Ashok K
2011-08-15
Anisotropic nanostructures of nickel borate with controlled size and morphology have been synthesized by a precursor-mediated route. The nickel boron precursor has been synthesized using microemulsions using Tergitol as a surfactant. Microemulsions with various co-surfactants (1-butanol, 1-hexanol and 1-octanol) have been used to obtain uniform nanorods (dia 3-5 nm, length 25 nm) and nanospindles (dia 30 nm, length 400 nm). A higher chain length of the co-surfactant (octanol) leads to more uniform rods rather than spindles (butanol). These nanorods show antiferromagnetic behavior with the Néel temperature ranging from 44 to 47 K. Though there is no marked variation in N?el temperature, the magnetic moment increases drastically with the anisotropy of nanorods (thinner rods). PMID:21605870
Effect of Mn substitution on the transport properties of co-sputtered Fe3-xMnxSi epilayers
NASA Astrophysics Data System (ADS)
Tang, M.; Jin, C.; Bai, H. L.
2014-11-01
Motivated by the theoretical calculations that Fe3-xMnxSi can simultaneously exhibit a high spin polarization with a high Curie temperature to be applied in spintronic devices, and in order to further study the effect of Mn contents on the physical properties of Fe3-xMnxSi, we have investigated the effect of Mn substitution on the transport properties of epitaxial Fe3-xMnxSi ( 0 ?x ?1 ) films systematically. The Fe3-xMnxSi films were epitaxially grown on MgO(001) plane with 45° rotation. The magnetization for various x shows enhanced irreversibility, implying the antiferromagnetic ordering induced by the substitution of Mn. A metal-semiconductor crossover was observed due to the enhanced disorders of interactions and the local lowering of symmetry induced by the substitution of Mn. The single-domain state in the Fe3-xMnxSi films leads to twofold symmetric curves of the anisotropic magnetoresistance and planar Hall resistivity.
Palczewski, Krzysztof
Expression, purification and structural properties of ABC transporter ABCA4 and its individual Keywords: ABCA4 ABCA subfamily ABC transporter Heterologous expression Monodispersity Electron microscopy. Introduction ATP-binding cassette (ABC) transporters comprise one of the largest and most ancient protein
Magnetic and transport properties of diluted granular multilayers
NASA Astrophysics Data System (ADS)
Silva, H. G.; Gomes, H. L.; Pogorelov, Y. G.; Pereira, L. M. C.; Kakazei, G. N.; Sousa, J. B.; Araújo, J. P.; Mariano, J. F. L.; Cardoso, S.; Freitas, P. P.
2009-12-01
The magnetic and transport properties of Co80Fe20(t)/Al2O3(4 nm) multilayers with low nominal thicknesses t =0.7 and 0.9 nm of Co80Fe20 granular layers are studied. Magnetic studies find a superparamagnetic state above the blocking temperature Tb (of field-cooled/zero-field-cooled splitting) that grows with t and decreases with H. The low-voltage Ohmic tunnel transport passes to non-Ohmic I ?V3/2 law for applied fields above ˜500 V/cm. At fixed V, the temperature dependence of conductance reveals an anomalous dip around ˜220 K, which can be attributed to the effect of surface contamination by supercooled water. Current-in-plane tunnel magnetoresistance (MR) ratio tends, at lower t, to higher maximum values (˜8% at room temperature) but to lower field sensitivity. This may indicate growing discorrelation effect (e.g., between shrinking areas of correlated moments) in this regime and corroborates the deficit of granule magnetization estimated from the Inoue-Maekawa MR fit, compared to that from direct magnetization measurements. MR displays a mean-field-like critical behavior when t approaches the point of superparamagnetic/superferromagnetic transition (tc˜1.3 nm at room temperature) from below, different from the formerly reported percolationlike behavior at approaching it from above. With growing temperature, MR reveals, beyond the common decrease, an anomalous plateau from Tb˜30-50 K up to some higher value T?˜150-200 K, not seen at higher t.
NASA Technical Reports Server (NTRS)
Gordon, S.
1982-01-01
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.
Electron transport properties of carbon-based nanostructures
NASA Astrophysics Data System (ADS)
Diaz Pinto, Carlos A.
Grapheme and graphene-related systems have been the focus of intensive research due to their exceptional electronic behavior. Their properties have been studied for decades, from the unique band structure predicted for a single layer of graphite, to the unexpected linear magnetoresistance observed in its bulk form. Since its experimental isolation in 2004, studies on graphene monolayer, bilayer, and few-layer systems garnered an overwhelming amount of attention from the scientific community, with studies focusing on multilayers with nanometer thicknesses paling in comparison. The main motivation of this study is to further the understanding of systems consisting of multilayer graphene and ultrathin graphite (graphitic multilayers) through electron transport experiments. Uniquely designed and fabricated devices based on carbon nanostructures were used to study the transport of charge carriers under high electric and magnetic fields. For short-channel suspended graphitic multilayer devices, the two-terminal differential conductance dI/dV as a function of drain-source bias Vd displays a pronounced dip pinned at Vd=0, explained by the hot electron effect. The dip is attenuated under high magnetic fields, likely due to intra-Landau level cyclotron phonon scattering. Also, distinct high-energy dI/dV anomalies have been observed and shown to be related to intrinsic phonon-emission processes in graphite. The evolution of such dI/dV anomalies under magnetic fields is understood as a consequence of the inter-Landau level cyclotron-phonon resonance scattering. The magnetoresistance (MR) of this system shows Shubnikov-de Haas oscillations on top of a strong positive nearly-linear background. Upon the introduction of a significant amount of short-range disorders through ion implantation, the positive MR transforms into a negative MR. The results for the MR of pure and implanted graphitic multilayers can be understood by considering a recent magneto-transport theory for two-dimensional systems. Four terminal measurements on unique multi-terminal devices with suspended multilayer graphene grown by ambient-pressure chemical vapor deposition also display the dI/dV dip related to the hot electron effect, and its attenuation at high magnetic fields, confirming its intrinsic nature for multilayer graphene systems.
NASA Technical Reports Server (NTRS)
Gordon, S.; Mcbride, B.; Zeleznik, F. J.
1984-01-01
An addition to the computer program of NASA SP-273 is given that permits transport property calculations for the gaseous phase. Approximate mixture formulas are used to obtain viscosity and frozen thermal conductivity. Reaction thermal conductivity is obtained by the same method as in NASA TN D-7056. Transport properties for 154 gaseous species were selected for use with the program.
Influence of Si Co-doping on electrical transport properties of magnesium-doped boron nanoswords
Gao, Hongjun
Influence of Si Co-doping on electrical transport properties of magnesium- doped boron nanoswords://apl.aip.org/about/rights_and_permissions #12;Influence of Si Co-doping on electrical transport properties of magnesium-doped boron nanoswords; published online 9 March 2012) Magnesium-doped boron nanoswords were synthesized via a thermoreduction
The synthesis and transport properties of the complex salt /TMPD/ /TCNQ/2
NASA Technical Reports Server (NTRS)
Somoano, R.; Hadek, V.; Yen, S. P. S.; Rembaum, A.; Deck, R.
1975-01-01
The syntheses and transport properties of the complex salt /TMPD/ /TCNQ/2 are described. At high temperatures, the complex is a magnetic semiconductor with transport properties intermediate between those found in the highly conducting and poorly conducting TCNQ salts. The complex undergoes a transition below 50-60 K to a state exhibiting singlet-triplet behavior with weakly alternating exchange coupling.
Effect of hydrochloric acid on the transport properties of tin through ion-exchange membranes
M. García-Gabaldón; V. Pérez-Herranz; J. García-Antón; J. L. Guiñón
2009-01-01
This work presents a study of the transport properties of two ion-exchange membranes present in an electrochemical reactor used to process the wasted and rinse baths of the electroless plating of polymers industry. The influence of the hydrochloric acid on the transport properties of tin through both cation- and anion-exchange membranes has been evaluated by chronopotentiometry. The shape of the
Microstructure and water vapor transport properties of temperature sensitive polyurethanes
NASA Astrophysics Data System (ADS)
Ding, Xuemei
Temperature sensitive polyurethane (TS-PU) is one novel type of smart polymers. The water vapor permeability (WVP) of its membrane could undergo a significant increase as temperature increases within a predetermined temperature range. Such smart property enables this material to have a broad range of potential applications to textile industry, medicine, environmental fields and so on. However, based on the literature review, contradicting results were found on some TS-PUs. The aims of this project are to synthesize TS-PU with Tm in the broader temperature range including ambient temperature range, and then investigate systematically the relationships between microstructure and water vapor transport properties of TS-PU. For this purpose, in this project, a series of polyurethanes (PU) were synthesized using five different crystalline polyols with approximately similar molecule weight and three different hydrophilic contents, and dense membranes were prepared accordingly. The microstructure and properties of these PUs were investigated using DSC, WAXD, DMA, FTIR, GPC, POM, TEM, SEM and PALS. Their equilibrium water sorption and water vapor permeability were measured accordingly. Results show that crystal melting of these resulting PUs take place in the temperature range from -10--60°C as desired. Storage modulus (E') drops down quickly in the temperature range of crystal melting, suggesting a great transition in the predetermined temperature range. The decreased HSC as well as regular chemical structure of polyols results in the larger spherulites and higher melting end temperature, and the higher crystallinity induces the more obvious incompatibility of soft segment and hard segment in the PUs. These PUs are proved to have good enough tensile properties for textile application. The mean free volume size and fractional free volume increase more significantly in the temperature range of crystal melting than in other temperature intervals. Finally, as expected, the WVP of semi-crystalline PU membranes increases significantly in the temperature range of crystal melting. Equilibrium water sorption keeps approximately constant. The significant increase in WVP of semi-crystalline PU is obviously correlated with the sharp increase in the free volume in the predetermined temperature range.
Transport properties of multicomponent thermal plasmas: Grad method versus Chapman-Enskog method
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
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.
NASA Astrophysics Data System (ADS)
Sahoo, Pranati
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.
Valuation of utility and transportation property: a classified annotated bibliography
Clatanoff, R.M.
1983-01-01
A selected, classified, annotated bibliography is presented with 270 references to published works on the appraisal and assessment of utilities and transportation companies. It does not include works on the taxation of these enterprises unless material on valuation is included, and it does not include works on valuation unless material on these enterprises is included. The bibliography does not include references to articles on current events; for these the reader should consult such publications as Engineering News-Record; Public Utilities Fortnightly; Commerce Clearing House's State Tax Review (for news of statutory law and regulations), and the Assessment and Valuation Legal Reporter (for news of case law). Works selected for inclusion were chosen primarily from those published since 1970. Charles F. Conlon's 1971 paper, The Unitary Approach to the Appraisal of Public Utility Property for Tax Purposes, concludes with a classified bibliography of publications up to 1970. Certain major pre-1970 works, which readers would expecte to find in a bibliography on this topic, are listed here, as are all the references from an earlier IAAO bibliography (which this one supersedes).
Novel Transport Properties of Intercalated Graphite Films Prepared by CVD
NASA Astrophysics Data System (ADS)
Williams, K. A.; Grigorian, L.; Sumanasekera, G. U.; Eklund, P. C.
1998-03-01
With primary focus on possible thermoelectric applications, Se, Te, and Bi were selected for intercalation into graphite via an open-tube CVD approach. Benzene and Ph_2Se_2, Ph_2Te_2, or Ph_3Bi (Ph = phenyl group, C_6H_5) were used for the carbon and intercalant sources. Experiments employing polycrystalline Ni substrates and Ph_2Se2 will be emphasized. Film growth was found to be very sensitive to the orientation of individual grains in the Ni substrate: faces of grains with a poor lattice match to the a-b plane of graphite were generally coated by amorphous material or nickel selenide, while (111) faces readily seeded formation of graphite intercalation compounds, as confirmed by electron microscopy. Due to the experimental geometry, transport properties of our films were measured along c-axis, normal to the substrate surface. The conductivity ?e was two orders of magnitude greater than in pristine graphite at 300 K, while the c-axis Seebeck coefficient Sc exceeded -50 ?V/K, roughly five times greater than in graphite. These two factors in conjunction lead to significantly improved power factors for the intercalated materials as compared to pristine graphite. Whereas graphite has Sc increasing with temperature in the range 100 K to 300 K, our intercalated samples showed more complex behavior over this range, increasing sharply at lower temperatures. This work was supported by ARPA MDA 972-95-1-0021
Transport Properties of Nanoscale Materials by First-principles Calculations
NASA Astrophysics Data System (ADS)
Mizuseki, Hiroshi; Belosludov, Rodion V.; Lee, S.-U.; Kawazoe, Yoshiyuki
2009-03-01
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.
NASA Technical Reports Server (NTRS)
Hansen, C Frederick; Heims, Steve P
1958-01-01
Thermodynamic and transport properties of high temperature air, and the reaction rates for the important chemical processes which occur in air, are reviewed. Semiempirical, analytic expressions are presented for thermodynamic and transport properties of air. Examples are given illustrating the use of these properties to evaluate (1) equilibrium conditions following shock waves, (2) stagnation region heat flux to a blunt high-speed body, and (3) some chemical relaxation lengths in stagnation region flow.
Transport properties of correlated electron systems in the nanoscale
NASA Astrophysics Data System (ADS)
Wu, Tail-Lung
The goal of this dissertation is to understand the microscopic origin of metal-insulator transition (MIT) in strongly correlated electron systems. Two such systems, VO2 and V2O5 in their nanoscale form are investigated. Results from experimental studies of electrical transport properties and of Raman spectroscopic measurements from single nanowires of these systems across the MIT are presented. In the VO2 system, the doping and confinement effects of MIT on the individual W-doped VO2 nanowires are studied. The hysteretic and abrupt transitions in the temperature or in the electrical driven MIT are observed and studied. While increasing the W content, the pronouncedly decreasing rate (- (48-56) K/at. % W) of the MIT transition temperature (Tc) and low activation energy (Ea<100 meV) suggest a more complex phase domain nucleation in this quasi-1D system. Also, while driving MIT by applying voltage across sample, the temperature dependence of threshold voltages (VTH ) suggests the charge ordering and Joule heating in these nanowires, respectively. To understand the role of structural phase during the MITs, the simultaneous electrical transport and Raman spectroscopic measurements across temperature- and voltage-driven phase transitions are performed. Our results indicate no intermediate structural phases are required to mediate the structural phase transition. Moreover, both MITs show the coexistence of monoclinic (M1) and rutile (R) during the transitions. The implications of these results are discussed. In the V2O5 system, two single-crystal vanadium oxide bronzes in their nanowire form, beta'-CuxV2O 5 and delta-KxV2O5, were studied. The hysteretic temperature driven MIT ranging up to almost 5 orders of magnitude in both nanowires has not been previously seen in their bulk form. Furthermore, the above room temperature transition (Tc=360-390 K) is also in strong contrast with the typical sub 200 K values in bulk bronzes, indicating the importance of matrix confinement and of ion intercalation in the vanadium oxide bronzes. Our results from the studies of temperature- and of electrical-driven MIT suggest that the intrinsic electronic instability in single nanowire are the result of approaching single domain limits.
NASA Astrophysics Data System (ADS)
Kosaka, Masataka; Monde, Masanori
2015-09-01
For safe and fast fueling of hydrogen in a fuel cell electric vehicle at hydrogen fueling stations, an understanding of the heat transferred from the gas into the tank wall (carbon fiber reinforced plastic (CFRP) material) during hydrogen fueling is necessary. Its thermal properties are needed in estimating heat loss accurately during hydrogen fueling. The CFRP has anisotropic thermal properties, because it consists of an adhesive agent and layers of the CFRP which is wound with a carbon fiber. In this paper, the thermal diffusivity and thermal conductivity of the tank wall material were measured by an inverse solution for one-dimensional unsteady heat conduction. As a result, the thermal diffusivity and thermal conductivity were 2.09 × 10^{-6}{ m}2{\\cdot }{s}^{-1} and 3.06{ W}{\\cdot }{m}{\\cdot }^{-1}{K}^{-1} for the axial direction, while they were 6.03 × 10^{-7} {m}2{\\cdot }{s}^{-1} and 0.93 {W}{\\cdot }{m}^{-1}{\\cdot }{K}^{-1} for the radial direction. The thermal conductivity for the axial direction was about three times higher than that for the radial direction. The thermal diffusivity shows the same trend in both directions because the thermal capacity, ? c , is independent of direction, where ? is the density and c is the heat capacity.
Temperature-dependent thermal transport properties of Archean rocks
NASA Astrophysics Data System (ADS)
Merriman, J. D.; Hofmeister, A.; Nabelek, P. I.; Whittington, A. G.; Benn, K.
2010-12-01
Heat transfer controls the rates and styles of fundamental planetary processes including the formation and differentiation of planetary crust, the rheological behavior of the lithosphere and asthenosphere, and the secular cooling of the Earth following its accretion. The Earth's first few hundred million years were characterized by much higher radiogenic heat production and heat flow out of the mantle than seen today, and early continental crust was comprised of rock associations such as granite-greenstone belts and intrusions of tonalite-trondhjemite-granodiorite (TTG). The composition of Archean crustal rocks, and likely variations in radiogenic heat production, have been well documented in past studies. However, the thermal transport properties of these rocks, thermal diffusivity D and thermal conductivity (k=D?CP, where ? is density and CP is isobaric heat capacity), are less well constrained, especially at high temperatures. High temperature measurements of D and k are few, and contact methods may suffer from a combination of imperfect physical contacts and unwanted direct radiative transfer. Using the laser flash analysis (LFA) technique, we determined D of a suite of 14 granite-greenstone and TTG rocks including samples from the Abitibi and Barberton greenstone belts, over a range of crustal temperatures at atmospheric pressure. Dehydration and devolatilization of amphiboles and biotite prevented direct measurement of D for most samples above ~750K, however previous studies of T-dependent D have shown that values of bulk rock diffusivity asymptotically approach a constant value above the ?-? quartz transition (846K). Our measurements yielded a range of D at room temperature from ~3.8 mm2 s-1 for banded iron to ~1 mm2 s-1 for granodiorite. D for all samples decreases with increasing T, and the range of D for the suite narrows to ~0.45 and 0.70 mm2 s-1 for granodiorite and tholeiite basalt respectively by ~1000K. Density of each sample was measured using the Archimedean method and was assumed ~constant over crustal P and T. The T-dependence of CP was calculated from modal mineralogy and published CP data for mineral end-members. Calculated values of k ranged from ~5.7 Wm-1k-1 for a quartz-rich (~38%) tonalite to ~1.7 Wm-1k-1 for a quartz-free syenite at 280K. The range of k at higher temperatures is less restricted than D, as a result of the general increase in CP at higher temperatures and varied between ~2.5 Wm-1k-1 for amphibolite and ~1.5 Wm-1k-1 for syenite. These results show that the T-dependence of D and k cannot be ignored, and variations in thermal transport properties between different rock types, and for a single rock type at different temperatures, may be more important than differences in their radiogenic heat production. This has important implications for the geothermal gradient of Archean crust, its rheological behavior and potential for partial melting.
Decoupling Mechanical and Ion Transport Properties in Polymer Electrolyte Membranes
NASA Astrophysics Data System (ADS)
McIntosh, Lucas D.
Polymer electrolytes are mixtures of a polar polymer and salt, in which the polymer replaces small molecule solvents and provides a dielectric medium so that ions can dissociate and migrate under the influence of an external electric field. Beginning in the 1970s, research in polymer electrolytes has been primarily motivated by their promise to advance electrochemical energy storage and conversion devices, such as lithium ion batteries, flexible organic solar cells, and anhydrous fuel cells. In particular, polymer electrolyte membranes (PEMs) can improve both safety and energy density by eliminating small molecule, volatile solvents and enabling an all-solid-state design of electrochemical cells. The outstanding challenge in the field of polymer electrolytes is to maximize ionic conductivity while simultaneously addressing orthogonal mechanical properties, such as modulus, fracture toughness, or high temperature creep resistance. The crux of the challenge is that flexible, polar polymers best-suited for polymer electrolytes (e.g., poly(ethylene oxide)) offer little in the way of mechanical robustness. Similarly, polymers typically associated with superior mechanical performance (e.g., poly(methyl methacrylate)) slow ion transport due to their glassy polymer matrix. The design strategy is therefore to employ structured electrolytes that exhibit distinct conducting and mechanically robust phases on length scales of tens of nanometers. This thesis reports a remarkably simple, yet versatile synthetic strategy---termed polymerization-induced phase separation, or PIPS---to prepare PEMs exhibiting an unprecedented combination of both high conductivity and high modulus. This performance is enabled by co-continuous, isotropic networks of poly(ethylene oxide)/ionic liquid and highly crosslinked polystyrene. A suite of in situ, time-resolved experiments were performed to investigate the mechanism by which this network morphology forms, and it appears to be tied to the disordered structure observed in diblock polymer melts near the order-disorder transition. In the resulting solid PEMs, the conductivity and modulus are both high, exceeding the 1 mS/cm and approaching the 1 GPa metrics, respectively, often cited for lithium-metal batteries. In the final chapter, an alternative synthetic route to generate nanostructured PEMs is presented. This strategy relies on the formation of a thermodynamically stable network morphology exhibited by a triblock terpolymer prepared with crosslinking moieties along the backbone. Although the mechanical properties of the resulting PEM are excellent, the conductivity is found to be somewhat limited by network defects that result from the solvent-casting procedure.
Electronic and Transport Properties of Substitutionally and Structurally Disordered Systems.
NASA Astrophysics Data System (ADS)
Hwang, Miaogy
Two problems concerning disordered systems are addressed in this work: the electronic and transport properties of substitutionally disordered systems; and the band tail behavior of structually disordered systems. Two simulation methods, the position space renormalization group approach and the recursive method, along with sample results for the exact calculation of the densities of states of materials in a tight-binding description are presented. Exact computer simulations for the zero temperature ac conductivity of one-dimensional substitutionally disordered alloys are also conducted. The results are obtained by directly diagonalizing the Hamiltonian of a disordered chain and then evaluating the Kubo-Greenwood formula for the ac conductivity. Convergence was obtained and confirmed by another independent simulation method. We used the simulation results to calibrate analytic theories calculating the ac conductivity of substitutionally disordered systems and found that the extensions of both the coherent potential approximation (CPA) and the formalism of Blackman, Esterling and Berk fail to pick out the sharp peaks and dips in the exact spectra. Thus, we generalized the embedded cluster method and were able to capture the peaks and dips for moderate cluster sizes. To unify various analytic theories, we formulated a cluster field theory. It encompasses Hamiltonians of muffin-tin and tight-binding characters and it also provides a general framework to deal with any cluster calculation. Finally the problem concerning the tails in the DOS spectra of a structurally disordered system was investigated in the context of a one dimensional Lorentz model by using the path integral approach. The band tail behavior is determined by the ensemble averaged Green function at long time. A Monte-Carlo (Metropolis) method was developed to evaluate the Green function numerically. Although yielding correct asymptotic behavior, previous methods by Friedberg and Luttinger, and Luttinger and Tao were found to have underestimated the averaged Green function by an order of magnitude. In addition, our Monte-Carlo method can be applied to systems with higher dimensions or with more realistic potentials.
EquilTheTA: Thermodynamic and transport properties of complex equilibrium plasmas
Colonna, G.; D'Angola, A.
2012-11-27
EquilTheTA (EQUILibrium for plasma THErmodynamics and Transport Applications) is a web-based software which calculates chemical equilibrium product concentrations from any set of reactants and determines thermodynamic and transport properties for the product mixture in wide temperature and pressure ranges. The program calculates chemical equilibrium by using a hierarchical approach, thermodynamic properties and transport coefficients starting from recent and accurate databases of atomic and molecular energy levels and collision integrals. In the calculations, Debye length and cut-off are consistently updated and virial corrections (up to third order) can be considered. Transport coefficients are calculated by using high order approximations of the Chapman-Enskog method.
Equations of state and transport properties of mixtures in the warm dense regime
NASA Astrophysics Data System (ADS)
Hou, Yong; Dai, Jiayu; Kang, Dongdong; Ma, Wen; Yuan, Jianmin
2015-02-01
We have performed average-atom molecular dynamics to simulate the CH and LiH mixtures in the warm dense regime, and obtained equations of state and the ionic transport properties. The electronic structures are calculated by using the modified average-atom model, which have included the broadening of energy levels, and the ion-ion pair potentials of mixtures are constructed based on the temperature-dependent density functional theory. The ionic transport properties, such as ionic diffusion and shear viscosity, are obtained through the ionic velocity correlation functions. The equations of state and transport properties for carbon, hydrogen and lithium, hydrogen mixtures in a wide region of density and temperature are calculated. Through our computing the average ionization degree, average ion-sphere diameter and transition properties in the mixture, it is shown that transport properties depend not only on the ionic mass but also on the average ionization degree.
Effect of antiphase boundaries on electrical transport properties of Fe3O4 nanostructures
NASA Astrophysics Data System (ADS)
Li, Hongliang; Wu, Yihong; Guo, Zaibing; Wang, Shijie; Teo, Kie Leong; Veres, Teodor
2005-06-01
Fe3O4 nanowires have been fabricated based on Fe3O4 thin films grown on ?-Al2O3 (0001) substrates using the hard mask and ion milling technique. Compared with thin films, the Fe3O4 nanowire exhibits a slightly sharper Verwey transition but pronounced anisotropic magnetoresistance properties in the film plane at low magnetic field. Detailed bias-dependence study of both the conductance and magnetoresistance curves for both the thin films and nanowires suggests that the electrical conduction in magnetite near and above the Verwey transition temperature is dominated by a tunneling mechanism across antiphase boundaries.
NASA Technical Reports Server (NTRS)
Svehla, R. A.; Mcbride, B. J.
1973-01-01
Program performs calculations such as chemical equilibrium for assigned thermodynamic states, theoretical rocket performance for both equilibrium and frozen compositions during expansion, incident and reflected shock properties, and Chapman-Jouget detonation properties. Features include simplicity of input and storage of all thermodynamic and transport property data on master tape.
Anisotropic Sobolev Capacity with Fractional Order
Jie Xiao; Deping Ye
2014-10-02
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.
Freitas, P.P.; Plaskett, T.S.; Moreira, J.M.; Amaral, V.S.
1988-11-15
We describe the competing magnetic, localization, and phonon effects on the transport properties of amorphous magnetic U/sub x/T/sub 1-//sub x/ films, with T = Fe, Ni, Gd, Tb, and Yb. Amorphous U/sub x/Fe/sub 1-//sub x/ films change from collinear to random ferromagnetism as x increases, and the temperature dependence of the resistivity denotes the competing effects of spin-flip and non-spin-flip exchange scattering processes. The resistivity has a minimum at T/sub f/ rising sharply below this temperature. The sign of the magnetic resistivity and the magnetoresistance indicates >0, while the anisotropic magnetoresistance indicates a local exchange gap. Amorphous U/sub x/Gd/sub 1-//sub x/ and a-U/sub x/Tb/sub 1-//sub x/ are, respectively, spin glasses and random anisotropy dominated systems. The resistivity increases smoothly through T/sub f/ and has a slight upturn at low temperatures that we associate with weak localization. The magnetoresistance is negative in both systems and the anisotropic magnetoresistance is null, although the applied field induces anisotropic behavior in the Tb containing films (asperomagnets). All samples show quadratic and positive field dependence of magnetoresistance well inside the paramagnetic regime, and a linear regime below T/sub f/. At low temperatures and in the a-U/sub x/Gd/sub 1-//sub x/ films, negative (H)/sup 1/2/ and H/sup 2/ regimes occur and are associated with weak localization processes dominated by the inelastic mean free path.
Akiyama, Y.; Kawazu, T. [National Institute for Materials Science, Tsukuba-shi, Ibaraki 305-0047 (Japan); IIS, University of Tokyo, Meguro-ku, Tokyo 153-8505 (Japan); Noda, T. [National Institute for Materials Science, Tsukuba-shi, Ibaraki 305-0047 (Japan); Sakaki, H. [National Institute for Materials Science, Tsukuba-shi, Ibaraki 305-0047 (Japan); IIS, University of Tokyo, Meguro-ku, Tokyo 153-8505 (Japan); Toyota Technological Institute, Tempaku-ku, Nagoya 468-8511 (Japan)
2010-01-04
We have studied electron transport in n-AlGaAs/GaAs heterojunction FET channels, in which chains of InGaAs nano-islands are embedded along quasi-periodic steps. By using two samples, conductance G{sub para}(V{sub g}) parallel to the steps and G{sub perp}(V{sub g}) perpendicular to them were measured at 80 K as functions of gate voltage V{sub g}. At sufficiently high V{sub g}, G{sub para} at 80 K is several times as high as G{sub perp}, which manifests the anisotropic two-dimensional transport of electrons. When V{sub g} is reduced to -0.7 V, G{sub perp} almost vanishes, while {sub Gpara} stays sizable unless V{sub g} is set below -0.8 V. These results indicate that 'inter-chain' barriers play stronger roles than 'intra-chain' barriers.
The transport and quantum capacitance properties of epitaxial graphene
NASA Astrophysics Data System (ADS)
Xia, J. L.; Chen, Fang; Tedesco, J. L.; Gaskill, D. K.; Myers-Ward, R. L.; Eddy, C. R.; Ferry, D. K.; Tao, N. J.
2010-04-01
Epitaxial graphene field effect transistors were fabricated, characterized, and studied. Both the capacitance and transport measurements were performed on the same devices using an electrochemical gate. The quantum capacitance of the epitaxial graphene was extracted, which was similar to that of exfoliated graphene near the Dirac point, but it exhibits a large sublinear behavior at high carrier densities. The recently developed self-consistent theory for charged impurities in graphene is found to provide a reasonable description of the transport data, but a more complete theory is needed to explain both the transport and quantum capacitance data for the epitaxial graphene devices.
NASA Astrophysics Data System (ADS)
Proust, Gwénaëlle; Kalidindi, Surya R.
2006-08-01
Microstructure-sensitive design (MSD) is a novel mathematical framework that facilitates a rigorous consideration of the material microstructure as a continuous design variable in the engineering design enterprise [Adams, B.L., Henrie, A., Henrie, B., Lyon, M., Kalidindi, S.R., Garmestani, H., 2001. Microstructure-sensitive design of a compliant beam. J. Mech. Phys. Solids 49(8), 1639-1663; Adams, B.L., Lyon, M., Henrie, B., 2004. Microstructures by design: linear problems in elastic-plastic design. Int. J. Plasticity 20(8-9), 1577-1602; Kalidindi, S.R., Houskamp, J.R., Lyons, M., Adams, B.L., 2004. Microstructure sensitive design of an orthotropic plate subjected to tensile load. Int. J. Plasticity 20(8-9), 1561-1575]. MSD employs spectral representations of the local state distribution functions in describing the microstructure quantitatively, and these in turn enable development of invertible linkages between microstructure and effective properties using established homogenization (composite) theories. As a natural extension of the recent publications in MSD, we provide in this paper a detailed account of the methods that can be readily used by mechanical designers to construct first-order elastic-plastic property closures. The main focus in this paper is on the crystallographic texture (also called Orientation Distribution Function or ODF) as the main microstructural parameter controlling the elastic and yield properties of cubic (fcc and bcc) polycrystalline metals. The following specific advances are described in this paper: (i) derivation of rigorous first-order bounds for the off-diagonal terms of the effective elastic stiffness tensor and their incorporation in the MSD framework, (ii) delineation of the union of the property closures corresponding to both the upper and lower bound theories resulting in comprehensive first-order closures, (iii) development of generalized and readily usable expressions for effective anisotropic elastic-plastic properties that could be applied to all cubic polycrystals, and (iv) identification of the locations of readily available or easily processable ODFs (e.g. textures that are produced by rolling, drawing, etc.) on the property closures. It is anticipated that the advances communicated in this paper will make the mathematical framework of MSD highly accessible to the mechanical designers.
Free approximation of transport properties in organic system using Stochastic Random Matrix Theory
Xie, Wanqin, S.M. Massachusetts Institute of Technology
2014-01-01
The proposed research is a study and application of Stochastic analysis- Random Matrix Theory(RMT) to fast calculate the transport properties of large static systems with relatively large disorder in mesoscopic size. As a ...
TRANSPORT PROPERTIES OF DENSELY PACKED COMPOSITES. EFFECT OF SHAPES AND SPACINGS OF
Berlyand, Leonid
to manufacture integrated circuit packages by either injection moulding or by capillary-action filling of small spaces. Given the scale of industrial processes impacted by the transport properties of rigid
Transport properties of high-temperature air in a magnetic field
Bruno, D. [Institute of Inorganic Methodologies and Plasmas, CNR, 70126 Bari (Italy); Capitelli, M.; Catalfamo, C. [Department of Chemistry, University of Bari, 70126 Bari (Italy); Giordano, D. [Aerothermodynamics Section, ESA-ESTEC, 2200 AG Noordwijk (Netherlands)
2011-01-15
Transport properties of equilibrium air plasmas in a magnetic field are calculated with the Chapman-Enskog method. The range considered for the temperature is [50-50 000] K and for the magnetic induction is [0-300] T.
Chen, Ying
The effective transport properties and percolation of continuum composites have commonly been studied using discrete models, i.e., by mapping the continuum to a lattice or network. In this study we instead directly solve ...
Optical characterization of complex mechanical and thermal transport properties
Johnson, Jeremy A. (Jeremy Andrew)
2011-01-01
Time-resolved impulsive stimulated light scattering (ISS), also known as transient grating spectroscopy, was used to investigate phonon mediated thermal transport in semiconductors and mechanical degrees of freedom linked ...
Yang, Chun; Geva, Tal; Gaudette, Glenn; del Nido, Pedro J.
2010-01-01
Right and left ventricle (RV/LV) combination models with three different patch materials (Dacron scaffold, treated pericardium, and contracting myocardium), two-layer construction, fiber orientation, and active anisotropic material properties were introduced to evaluate the effects of patch materials on RV function. A material-stiffening approach was used to model active heart contraction. Cardiac magnetic resonance (CMR) imaging was performed to acquire patient-specific ventricular geometries and cardiac motion from a patient with severe RV dilatation due to pulmonary regurgitation needing RV remodeling and pulmonary valve replacement operation. Computational models were constructed and solved to obtain RV stroke volume, ejection fraction, patch area variations, and stress/strain data for patch comparisons. Our results indicate that the patch model with contracting myocardium leads to decreased stress level in the patch area, improved RV function and patch area contractility. Maximum Stress-P1 (maximum principal stress) value at the center of the patch from the Dacron scaffold patch model was 350% higher than that from the other two models. Patch area reduction ratio was 0.3%, 3.1% and 27.4% for Dacron scaffold, pericardium, and contracting myocardium patches, respectively. These findings suggest that the contracting myocardium patch model may lead to improved recovery of RV function in patients with severe chronic pulmonary regurgitation. PMID:21209792
Thermodynamic and transport properties of air/water mixtures
NASA Technical Reports Server (NTRS)
Fessler, T. E.
1981-01-01
Subroutine WETAIR calculates properties at nearly 1,500 K and 4,500 atmospheres. Necessary inputs are assigned values of combinations of density, pressure, temperature, and entropy. Interpolation of property tables obtains dry air and water (steam) properties, and simple mixing laws calculate properties of air/water mixture. WETAIR is used to test gas turbine engines and components operating in relatively humid air. Program is written in SFTRAN and FORTRAN.
Using a Flume to Demonstrate Fluid Properties and Sediment Transport
NSDL National Science Digital Library
Jill Singer
A 20-foot long recirculating flume is used for a series of demonstrations designed to help students explore the principles of fluid dynamics and sediment transport. The design and construction of the flume and four demonstrations are described in the attached activity. The demonstrations build upon each other so that students have a chance to develop an understanding of sedimentary transport processes and the deposits they produce.
Surface and Subsurface Solute Transport Properties at Row and Inter-Row Positions
Technology Transfer Automated Retrieval System (TEKTRAN)
Although numerous studies have investigated the effects of crop production practices on soil water dynamics, not much information is available on the impact of row position on solute transport. A field experiment was carried out to evaluate surface and subsurface solute transport properties in plant...
Walker diffusion method for calculation of transport properties of finite composite systems.
Van Siclen, Clinton DeW
2002-02-01
A heterogeneous medium may be represented by a scalar field of local transport coefficients (e.g., conductivity) or by a "resistor network" derived from that scalar field. In either case the effective (macroscopic) and local (microscopic) transport properties may be calculated by the walker diffusion method. Some sample calculations for disordered systems are presented to demonstrate the method. PMID:11863624
Absorption and transport properties of ultra-fine cellulose webs Gerardo Callegari a,
Muzzio, Fernando J.
Absorption and transport properties of ultra-fine cellulose webs Gerardo Callegari a, , Ilya Electrospinning Cellulose Nanoweb KozenyCarman Washburn a b s t r a c t Characterization of transport for full characterization of the nanowebs. As an example, we used electrospun cellulose acetate nanowebs
Ward, Charles A.
Surface excess properties from energy transport measurements during water evaporation Fei Duan 2004; revised manuscript received 21 March 2005; published 2 November 2005 When water evaporates to evaporate water at the observed rate and that it is perhaps thermocapillary convection that transports
Heat transport properties of clean spin ladders coupled to phonons: Umklapp scattering and drag
Mehta, Pankaj
Heat transport properties of clean spin ladders coupled to phonons: Umklapp scattering and drag E; published 17 December 2007 We study the low-temperature heat transport in clean two-leg spin-ladder compounds coupled to three- dimensional phonons. We argue that the very large heat conductivities observed
Walker Diffusion Method for Calculation of Transport Properties of Finite Composite Systems
Van Siclen, Clinton D
2002-01-01
A heterogeneous medium may be represented by a scalar field of local transport coefficients (e.g., conductivity) or by a “resistor network” derived from that scalar field. In either case the effective (macroscopic) and local (microscopic) transport properties may be calculated by the walker diffusion method. Some sample calculations for disordered systems are presented to demonstrate the method.
The phase diagram and transport properties for hydrogen-helium fluid planets
NASA Technical Reports Server (NTRS)
Stevenson, D. J.; Salpeter, E. E.
1977-01-01
The properties of pure hydrogen and helium are examined, taking into account metallic hydrogen, molecular hydrogen, and the molecular-metallic transition. Metallic hydrogen-helium mixtures are considered along with molecular hydrogen-helium mixtures, the total phase diagram, and minor constituents, including deuterium. The transport properties of the metallic and the molecular phase are also discussed, giving attention to electrical conductivity, thermal conductivity, viscosity, self-diffusion, interdiffusion, radiative opacity, and second-order transport coefficients.
Conformal Anisotropic Quantum Cosmology
Chagoya, J F
2012-01-01
In this paper we apply the ideas put forward by Ho\\v{r}ava, and introduce anisotropic transformations to cosmology. We start with the Kantowski-Sachs cosmological model and impose anisotropic transformation invariance on the minisuperspace variables. We study the symmetries of the anisotropic model and by canonical quantization find a Schr\\"odinger type equation for $z\
Conformal Anisotropic Quantum Cosmology
J. F. Chagoya; M. Sabido
2012-12-14
In this paper we apply the ideas put forward by Ho\\v{r}ava, and introduce anisotropic transformations to cosmology. We start with the Kantowski-Sachs cosmological model and impose anisotropic transformation invariance on the minisuperspace variables. We study the symmetries of the anisotropic model and by canonical quantization find a Schr\\"odinger type equation for $z\
Anisotropic optical film embedded with cellulose nanowhisker.
Kim, Dah Hee; Song, Young Seok
2015-10-01
We investigated anisotropic optical behaviors of composite films embedded with CNWs. To control the orientation of CNWs, elongation was applied to the composite film. Morphological and mechanical analyses of the specimens were carried out to examine the influence of the applied extension. The CNWs were found to be aligned in the elongated direction, yielding remarkable anisotropic microstructure and optical properties. As the applied elongation and CNW loading increased, the resulting degree of polarization and birefringence increased due to increased interactions between the embedded particles. This study suggests a way to prepare an anisotropic optical component with nanoparticles of which the microstructures, such as orientation and filler content, can be controlled. PMID:26076646
Murray, Chris; Allen-King, Richelle; Weissmann, Gary
2006-06-01
This project is testing the hypothesis that sedimentary lithofacies determine the geochemical and physical hydrologic properties that control reactive solute transport (Figure 1). We are testing that hypothesis for one site, a portion of the saturated zone at the Hanford Site (Ringold Formation), and for a model solute, carbon tetrachloride (CT). The representative geochemical and physical aquifer properties selected for quantification in the proposed project are the properties that control CT transport: hydraulic conductivity (K) and reactivity (sorption distribution coefficient, Kd, and anaerobic transformation rate constant, kn). We are combining observations at outcrop analog sites (to measure lithofacies dimensions and statistical relations) with measurements from archived and fresh core samples (for geochemical experiments and to provide additional constraint to the stratigraphic model) from the Ringold Formation to place local-scale lithofacies successions, and their distinct hydrologic property distributions, into the basinal context, thus allowing us to estimate the spatial distributions of properties that control reactive solute transport in the subsurface.
The effect of electron induced hydrogenation of graphene on its electrical transport properties
Woo, Sung Oh; Teizer, Winfried; WPI-Advanced Institute for Materials Research, Tohoku University, Sendai
2013-07-22
We report a deterioration of the electrical transport properties of a graphene field effect transistor due to energetic electron irradiation on a stack of Poly Methyl Methacrylate (PMMA) on graphene (PMMA/graphene bilayer). Prior to electron irradiation, we observed that the PMMA layer on graphene does not deteriorate the carrier transport of graphene but improves its electrical properties instead. As a result of the electron irradiation on the PMMA/graphene bilayer, the Raman “D” band appears after removal of PMMA. We argue that the degradation of the transport behavior originates from the binding of hydrogen generated during the PMMA backbone secession process.
Transport properties of novel molybdenum bronze oxide materials
NASA Astrophysics Data System (ADS)
Hagmann, Joseph; Le, Son; Schneemeyer, Lynn; Olsen, Patti; Siegrist, Theo; Richter, Curt; Seiler, David
2015-03-01
Reduced ternary molybdenum oxides, or bronzes, offer an attractive materials platform to study a wide variety of remarkable physical phenomena, including charge density waves and superconductivity, in a system with highly varied structural chemistry. Interesting electronic behaviors in these materials arise from the strong hybridization of the 4d states of high-valent Mo with O p orbitals (conditions amenable to itinerancy) and reduced dimensionality arising from ordered O vacancies. This study aims to demonstrate the transport phenomena in a series of novel molybdenum bronze materials, including the new electrochemically-grown molybdenum bronzes, K3Li3Mo15O47, and the rare earth molybdenum bronze, HoMo16O44, and relate these behaviors to their experimentally-characterized structures. Dependence of the transport behavior on numerous experimental parameters, including temperature, magnetic field, drive voltage and drive current, and gate voltage, is presented to fully reveal charge carrier transport in these materials.
Transport properties of dense deuterium-tritium plasmas.
Wang, Cong; Long, Yao; He, Xian-Tu; Wu, Jun-Feng; Ye, Wen-Hua; Zhang, Ping
2013-07-01
Consistent descriptions of the equation of states and information about the transport coefficients of the deuterium-tritium mixture are demonstrated through quantum molecular dynamic (QMD) simulations (up to a density of 600 g/cm(3) and a temperature of 10(4) eV). Diffusion coefficients and viscosity are compared to the one-component plasma model in different regimes from the strong coupled to the kinetic one. Electronic and radiative transport coefficients, which are compared to models currently used in hydrodynamic simulations of inertial confinement fusion, are evaluated up to 800 eV. The Lorentz number is discussed from the highly degenerate to the intermediate region. One-dimensional hydrodynamic simulation results indicate that different temperature and density distributions are observed during the target implosion process by using the Spitzer model and ab initio transport coefficients. PMID:23944567
Magnetic and transport properties of Sm7Rh3 single crystal
NASA Astrophysics Data System (ADS)
Tsutaoka, Takanori; Noguchi, Daisuke; Nakamori, Yuko; Nakamoto, Go; Kurisu, Makio
2013-10-01
A Sm7Rh3 single crystal with Th7Fe3-type hexagonal structure was grown by the Czochralski method. The magnetic and transport measurements revealed a uniaxial magnetocrystalline anisotropy in the magnetic susceptibility, magnetization and electrical resistivity. Sm7Rh3 was found to exhibit antiferromagnetic transition at TN=54.0 K and another magnetic transition at Tt=25.0 K. The specific heat data clearly showed the bulk nature of paramagnetic to ordered magnetic phase transition by the presence of a sharp peak at TN and a small anomaly at Tt. The paramagnetic susceptibility does not obey the Curie-Weiss law, attributing to the temperature independent Van Vleck contribution and Pauli paramagnetism of conduction electrons. Metamagnetic phase transitions were observed along the c-axis in the ordered states. The magnetic field H-temperature T phase diagram was constructed. Anisotropic paramagnetic electrical resistivity showed the small negative temperature coefficients.
Temperature dependence of electronic transport property in ferroelectric polymer films
NASA Astrophysics Data System (ADS)
Zhao, X. L.; Wang, J. L.; Tian, B. B.; Liu, B. L.; Zou, Y. H.; Wang, X. D.; Sun, S.; Sun, J. L.; Meng, X. J.; Chu, J. H.
2014-10-01
The leakage current mechanism of ferroelectric copolymer of polyvinylidene fluoride with trifluoroethylene prepared by Langmuir-Blodgett was investigated in the temperature range from 100 K to 350 K. The electron as the dominant injected carrier was observed in the ferroelectric copolymer films. The transport mechanisms in copolymer strongly depend on the temperature and applied voltage. From 100 K to 200 K, Schottky emission dominates the conduction. With temperature increasing, the Frenkel-Poole emission instead of the Schottky emission to conduct the carrier transport. When the temperature gets to 260 K, the leakage current becomes independent of temperature, and the space charge limited current conduction was observed.
Highly anisotropic elements for acoustic pentamode applications.
Layman, Christopher N; Naify, Christina J; Martin, Theodore P; Calvo, David C; Orris, Gregory J
2013-07-12
Pentamode metamaterials are a class of acoustic metafluids that are characterized by a divergence free modified stress tensor. Such materials have an unconventional anisotropic stiffness and isotropic mass density, which allow themselves to mimic other fluid domains. Here we present a pentamode design formed by an oblique honeycomb lattice and producing customizable anisotropic properties. It is shown that anisotropy in the stiffness can exceed 3 orders of magnitude, and that it can be realistically tailored for transformation acoustic applications. PMID:23889408
NASA Technical Reports Server (NTRS)
Lanyi, Janos K.
1977-01-01
Cell envelope vesicles prepared from H. halobium contain bacteriorhodopsin and upon illumination protons are ejected. Coupled to the proton motive force is the efflux of Na(+). Measurements of Na-22 flux, exterior pH change, and membrane potential, Delta(psi) (with the dye 3,3'-dipentyloxadicarbocyanine) indicate that the means of Na(+) transport is sodium/proton exchange. The kinetics of the pH changes and other evidence suggests that the antiport is electrogenic (H(+)/Na(++ greater than 1). The resulting large chemical gradient for Na(+) (outside much greater than inside), as well as the membrane potential, will drive the transport of 18 amino acids. The I9th, glutamate, is unique in that its accumulation is indifferent to Delta(psi): this amino acid is transported only when a chemical gradient for Na(+) is present. Thus, when more and more NaCl is included in the vesicles glutamate transport proceeds with longer and longer lags. After illumination the gradient of H+() collapses within 1 min, while the large Na(+) gradient and glutamate transporting activity persists for 10- 15 min, indicating that proton motive force is not necessary for transport. A chemical gradient of Na(+), arranged by suspending vesicles loaded with KCl in NaCl, drives glutamate transport in the dark without other sources of energy, with V(sub max) and K(sub m) comparable to light-induced transport. These and other lines of evidence suggest that the transport of glutamate is facilitated by symport with Na(+), in an electrically neutral fashion, so that only the chemical component of the Na(+) gradient is a driving force.
NASA Astrophysics Data System (ADS)
Higashi, Takuya; Yamasaki, Naoyuki; Utsumi, Hideyuki; Yoshida, Hiroyuki; Fujii, Akihiko; Ozaki, Masanori
2011-09-01
Uniaxially aligned films of thiophene-based polymers were successfully fabricated by a novel film-forming method using the capillary action of polymer solutions without applying any mechanical or thermal stress to the polymers. Unique optical and electrical anisotropies were studied in the poly(2,5-bis(3-alkylthiophene-2-yl)thieno[3,2-b]thiophene) (pBTTT) and poly(2,5-bis(3-alkylthiophene-2-yl)thieno[2,3-b]thiophene) (pBTCT) films fabricated by the method. Moreover, the improvements of the optical and electrical properties of the aligned polymer films by thermal annealing were also demonstrated.
ELECTRONIC AND TRANSPORT PROPERTIES OF THERMOELECTRIC Ru2Si3
NASA Astrophysics Data System (ADS)
Singh, David J.; Parker, David
2013-10-01
We report calculations of the doping and temperature dependent thermopower of Ru2Si3 based on Boltzmann transport theory and the first principles electronic structure. We find that the performance reported to date can be significantly improved by optimization of the doping level and that ultimately n-type should have higher ZT than p-type.
Andrei, Eva Y.
1 Electronic properties of graphene: a perspective from scanning tunneling microscopy and magneto recent experimental progress in probing the electronic properties of graphene and how they are influenced. The focus is on results obtained using scanning tunneling microscopy, spectroscopy, transport and magneto
NASA Technical Reports Server (NTRS)
Svehla, R. A.; Mcbride, B. J.
1973-01-01
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.
Anisotropic thermal properties of the polar crystal Cs{sub 2}TeMo{sub 3}O{sub 12}
Zhang, Junjie; Zhang, Zhonghan; Sun, Youxuan; Zhang, Chengqian; Tao, Xutang
2012-11-15
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.
NASA Astrophysics Data System (ADS)
Wang, Pei-Pei; Long, Yu-Jia; Zhao, Ling-Xiao; Chen, Dong; Xue, Mian-Qi; Chen, Gen-Fu
2015-08-01
Not Available Supported by the National Basic Research Program of China under Grant No 2015CB921303, and the Strategic Priority Research Program (B) of Chinese Academy of Sciences under Grant No XDB07020100.
NASA Astrophysics Data System (ADS)
Barreto, Lucas; Perkins, Edward; Johannsen, Jens; Ulstrup, Søren; Fromm, Felix; Raidel, Christian; Seyller, Thomas; Hofmann, Philip
2013-01-01
The electronic transport properties of epitaxial monolayer graphene (MLG) and hydrogen-intercalated quasi free-standing bilayer graphene (QFBLG) on SiC(0001) are investigated by micro multi-point probes. Using a probe with 12 contacts, we perform four-point probe measurements with the possibility to effectively vary the contact spacing over more than one order of magnitude, allowing us to establish that the transport is purely two-dimensional. Combined with the carrier density obtained by angle-resolved photoemission spectroscopy, we find the room temperature mobility of MLG to be (870±120) cm2/V s. The transport in QFBLG is also found to be two-dimensional with a mobility of (1600±160) cm2/V s.
Anisotropic colloidal crystal particles from microfluidics.
Cheng, Yao; Zhu, Cun; Xie, Zhuoying; Gu, Hongcheng; Tian, Tian; Zhao, Yuanjin; Gu, Zhongze
2014-05-01
Anisotropic colloidal crystal particles (CCPs) have showed their great potential in biotechnology and structural materials due to their anisotropic shapes and tunable optical property. However, their controllable generation is still a challenge. Here, a novel microfluidic approach is developed to generate anisotropic CCPs. The microfluidic device is composed of an injection capillary and a collection capillary with available size and shape. Based on the device, the anisotropic particles with non-close-packed colloidal crystal structures are achieved by photo-polymerizing droplet templates in a confined collection capillary with different shapes and sizes. Moreover, anisotropic close-packed CCPs can be made from non-close-packed CCPs through a thermal process. It is demonstrated that the anisotropic CCPs in different sizes, structural colors and shapes (rods, cuboids and disks) can be generated. These distinguishable features of resultant particles make them ideal barcodes for high-throughput bioassays. In order to prove it, DNA multiplex detection is carried out. The experimental results indicate that achieved particles have a great encoding capacity and are highly practical for multiplex coding bioassays. Therefore, we believe that the anisotropic CCPs would be highly promising barcodes in biomedical applications, including high-throughput bioassays and cell culture research where multiplexing is needed. PMID:24594033
Thermodynamic and transport property modeling in super critical water
Kutney, Michael C. (Michael Charles)
2005-01-01
Supercritical water oxidation (SCWO) is a thermally-based, remediation and waste-treatment process that relies on unique property changes of water when water is heated and pressurized above its critical point. Above its ...
Understanding hopping transport and thermoelectric properties of conducting polymers
NASA Astrophysics Data System (ADS)
Ihnatsenka, S.; Crispin, X.; Zozoulenko, I. V.
2015-07-01
We calculate the conductivity ? and the Seebeck coefficient S for the phonon-assisted hopping transport in conducting polymers poly(3,4-ethylenedioxythiophene) or PEDOT, experimentally studied by Bubnova et al. [J. Am. Chem. Soc. 134, 16456 (2012)], 10.1021/ja305188r. We use the Monte Carlo technique as well as the semianalytical approach based on the transport energy concept. We demonstrate that both approaches show a good qualitative agreement for the concentration dependence of ? and S . At the same time, we find that the semianalytical approach is not in a position to describe the temperature dependence of the conductivity. We find that both Gaussian and exponential density of states (DOS) reproduce rather well the experimental data for the concentration dependence of ? and S giving similar fitting parameters of the theory. The obtained parameters correspond to a hopping model of localized quasiparticles extending over 2-3 monomer units with typical jumps over a distance of 3-4 units. The energetic disorder (broadening of the DOS) is estimated to be 0.1 eV. Using the Monte Carlo calculation we reproduce the activation behavior of the conductivity with the calculated activation energy close to the experimentally observed one. We find that for a low carrier concentration a number of free carriers contributing to the transport deviates strongly from the measured oxidation level. Possible reasons for this behavior are discussed. We also study the effect of the dimensionality on the charge transport by calculating the Seebeck coefficient and the conductivity for the cases of three-, two-, and one-dimensional motion.
Electron transport properties of single molecular junctions under mechanical modulations
Jianfeng Zhou; Cunlan Guo; Bingqian Xu
2012-01-01
Electron transport behaviors of single molecular junctions are very sensitive to the atomic scale molecule–metal electrode contact interfaces, which have been difficult to control. We used a modified scanning probe microscope-break junction technique (SPM-BJT) to control the dynamics of the contacts and simultaneously monitor both the conductance and force. First, by fitting the measured data into a modified multiple tunneling
Theoretical studies of the transport properties in compound semiconductors
NASA Technical Reports Server (NTRS)
Segall, Benjamin
1994-01-01
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.
NASA Astrophysics Data System (ADS)
van Kats, C. M.
2008-10-01
The driving forces for fundamental research in colloid science are the ability to manage the material properties of colloids and to unravel the forces that play a role between colloids to be able to control and understand the processes where colloids play an important role. Therefore we are searching for colloidal materials with specific physical properties to better understand our surrounding world.Until recently research in colloid science was mainly focused on spherical (isotropic) particles. Monodisperse spherical colloids serve as a model system as they exhibit similar phase behaviour as molecular and atomic systems. Nevertheless, in many cases the spherical shape is not sufficient to reach the desired research goals. Recently the more complex synthesis methods of anisotropic model colloids has strongly developed. This thesis should be regarded as a contribution to this research area. Anisotropic colloids can be used as a building block for complex structures and are expected not only to lead to the construction of full photonic band gap materials. They will also serve as new, more realistic, models systems for their molecular analogues. Therefore the term ‘molecular colloids” is sometimes used to qualify these anisotropic colloidal particles. In the introduction of this thesis, we give an overview of the main synthesis techniques for anisotropic colloids. Chapter 2 describes the method of etching silicon wafers to construct monodisperse silicon rods. They subsequently were oxidized and labeled (coated) with a fluorescent silica layer. The first explorative phase behaviour of these silica rods was studied. The particles showed a nematic ordering in charge stabilized suspensions. Chapter 3 describes the synthesis of colloidal gold rods and the (mesoporous) silica coating of gold rods. Chapter 4 describes the physical and optical properties of these particles when thermal energy is added. This is compared to the case where the particles are irradiated with femtosecond laserpulses of variable wavelengths. We show that we can grow a silica layer on the gold rods with controllable thickness. In future this can be used to control the alignment of the gold rods a 3D crystal in an electric field. The silica coated gold rods can be used in optical switches. In chapter 4 we show to have a very local control of changing the aspect ratio of gold rods by irradiation with femtosecond laserpulses of 82 MHz with a threshold of ~ 2 picojoules to deform the particles. In chapter 5 and 6 we show how, starting from spherical particles, dimers (dumbbells), trimers and multimers can be formed by controlled aggregation. Chapter 7 finally shows an overview of syntheses where the pores of (mainly) silica particles is decreased. We show that the pores of the given particles could be decreased from macroporous to (ultra)microporous. Through a full control of pore size particles can selectively be filled with materials (for instance a drug) and be controllably closed. This opens a route for synthesis of particles that can be used as molecular filters or in biomedical applications such as smart drug delivery.
Electronic transport properties of one dimensional lithium nanowire using density functional theory
NASA Astrophysics Data System (ADS)
Thakur, Anil; Kumar, Arun; Chandel, Surjeet; Ahluwalia, P. K.
2015-05-01
Single nanowire electrode devices are a unique platform for studying as energy storage devices. Lithium nanowire is of much importance in lithium ion batteries and therefore has received a great deal of attention in past few years. In this paper we investigated structural and electronic transport properties of Li nanowire using density functional theory (DFT) with SIESTA code. Electronic transport properties of Li nanowire are investigated theoretically. The calculations are performed in two steps: first an optimized geometry for Li nanowire is obtained using DFT calculations, and then the transport relations are obtained using NEGF approach. SIESTA and TranSIESTA simulation codes are used in the calculations correspondingly. The electrodes are chosen to be the same as the central region where transport is studied, eliminating current quantization effects due to contacts and focusing the electronic transport study to the intrinsic structure of the material. By varying chemical potential in the electrode regions, an I-V curve is traced which is in agreement with the predicted behavior. Agreement of bulk properties of Li with experimental values make the study of electronic and transport properties in lithium nanowires interesting because they are promising candidates as bridging pieces in nanoelectronics. Transmission coefficient and V-I characteristic of Li nano wire indicates that Li nanowire can be used as an electrode device.
Thermal transport properties of organic films for advanced VLSI systems
NASA Astrophysics Data System (ADS)
Kurabayashi, Katsuo
1998-11-01
Polymer films play an important role in the development of fast integrated circuits and novel electronic and optoelectronic devices. A wide variety of polymer films are being developed for application as low-dielectric-constant passivation for multilevel metallization in highly-integrated circuits. A new trend in novel electronic device technologies employs electrically-conducting polymer films as active layers because of the ease with which they can be processed, their low cost, and their high electroluminescence efficiency. However, the low thermal conductivities of polymer films yield large temperature rises and temperature gradient magnitudes in the metallization and in novel devices, which facilitate electromigration-induced interconnect failure and reduce the lifetime of organic devices. The thermal conductivities of these films are expected to be strongly anisotropic and to differ substantially from those of bulk materials due to the partial orientation of molecular strands. This work develops experimental techniques for measuring the thermal conductivity anisotropy. The vertical conductivity is isolated using Joule heating and electrical-resistance thermometry in a microfabricated metal/polymer/metal mesa, which resembles the multilevel interconnection in integrated circuits. The lateral thermal conductivity is measured using harmonic Joule heating in a free-standing polymer membrane on which a metallic heater/thermometer is patterned. The suspended membrane structure is fabricated using the silicon back etch technique, which is widely used for microelectromechanical system (MEMS) fabrications. The obtained data for BTDA-ODA polyimide films of varying thickness show that the anisotropy factor lies between four and eight and favors lateral conduction. The data are used to the development of a model for the anisotropy that accounts for the degree of orientation which is influenced by the processing details. A model is developed for showing a relationship between molecular-level details of the films and their thermal conductivities. The data, theory, and experimental techniques developed in this work are aiding with the thermal design of on-chip interconnection and packaging structures for the IC industry. This work provides the basis for the assessment of a broad variety of new organic materials in electronic systems, including organic optoelectronic devices.
Large-deviation properties of resilience of transportation networks
NASA Astrophysics Data System (ADS)
Hartmann, Alexander K.
2014-05-01
Distributions of the resilience of transport networks are studied numerically, in particular the large-deviation tails. Thus, not only typical quantities like average or variance but the distributions over the (almost) full support can be studied. For a proof of principle, a simple transport model based on the edge-betweenness and three abstract yet widely studied random network ensembles are considered here: Erd?s-Rényi random networks with finite connectivity, small world networks and spatial networks embedded in a two-dimensional plane. Using specific numerical large-deviation techniques, probability densities as small as 10-80 are obtained here. This allows to study typical but also the most and the least resilient networks. The resulting distributions fulfill the mathematical large-deviation principle, i.e., can be well described by rate functions in the thermodynamic limit. The analysis of the limiting rate function reveals that the resilience follows an exponential distribution almost everywhere. An analysis of the structure of the network shows that the most-resilient networks can be obtained, as a rule of thumb, by minimizing the diameter of a network. Also, trivially, by including more links a network can typically be made more resilient. On the other hand, the least-resilient networks are very rare and characterized by one (or few) small core(s) to which all other nodes are connected. In total, the spatial network ensemble turns out to be most suitable for obtaining and studying resilience of real mostly finite-dimensional networks. Studying this ensemble in combination with the presented large-deviation approach for more realistic, in particular dynamic transport networks appears to be very promising.
Synthesis and electrical transport properties of Gd doped nanocrystalline ceria
NASA Astrophysics Data System (ADS)
Anirban, Sk.; Sinha, A.; Dutta, A.
2013-06-01
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.
Transport properties in a superconducting proximity sandwich, Kondo effect
Mori, N.
1981-04-01
Temperature-dependent properties are evaluated in a superconducting Kondo alloy induced by the proximity effect. These include (i) the order parameter, (ii) the dc Josephson current, and (iii) the thermal conductivity and ultrasonic attenuation, in the case when there is reentance of superconductivity. The calculations are based on the theory given by Kaiser, in which the McMillan tunneling model and the Mueller-Hartmann-Zittartz theory are combined. The temperature dependence of pair-breaking is reflected directly in the above properties in much the same way as in an intrinsic Kondo superconductor, indicating that proximity-effect studies may provide detailed information on the Kondo effect in superconductivity.
Microsphere-chain waveguides: Focusing and transport properties
Allen, Kenneth W. Astratov, Vasily N.; Darafsheh, Arash; Abolmaali, Farzaneh; Mojaverian, Neda; Limberopoulos, Nicholaos I.; Lupu, Anatole
2014-07-14
It is shown that the focusing properties of polystyrene microsphere-chain waveguides (MCWs) formed by sufficiently large spheres (D???20?, where D is the sphere diameter and ? is the wavelength of light) scale with the sphere diameter as predicted by geometrical optics. However, this scaling behavior does not hold for mesoscale MCWs with D???10? resulting in a periodical focusing with gradually reducing beam waists and in extremely small propagation losses. The observed effects are related to properties of nanojet-induced and periodically focused modes in such structures. The results can be used for developing focusing microprobes, laser scalpels, and polarization filters.
Microscopic calculations of transport properties of neutron matter
Omar Benhar; Artur Polls; Marco Valli; Isaac Vidana
2009-11-26
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.
Controlling anisotropic nanoparticle growth through plasmon excitation
Rongchao Jin; Y. Charles Cao; Encai Hao; Gabriella S. Métraux; George C. Schatz; Chad A. Mirkin
2003-01-01
Inorganic nanoparticles exhibit size-dependent properties that are of interest for applications ranging from biosensing and catalysis to optics and data storage. They are readily available in a wide variety of discrete compositions and sizes. Shape-selective synthesis strategies now also yield shapes other than nanospheres, such as anisotropic metal nanostructures with interesting optical properties. Here we demonstrate that the previously described
RICE UNIVERSITY Transport Properties of Topological Phases in
Natelson, Douglas
of topologically superconducting phases hosting exotic Majorana modes. #12;Acknowledgments I would like to thank my and superconductors. Surprisingly, edge modes persist in spite of comparable bulk conduction of non-trivial origin of this material system and good interface to superconductors allows us to probe topological properties of helical
Electron transport properties of single molecular junctions under mechanical modulations
NASA Astrophysics Data System (ADS)
Zhou, Jianfeng; Guo, Cunlan; Xu, Bingqian
2012-04-01
Electron transport behaviors of single molecular junctions are very sensitive to the atomic scale molecule-metal electrode contact interfaces, which have been difficult to control. We used a modified scanning probe microscope-break junction technique (SPM-BJT) to control the dynamics of the contacts and simultaneously monitor both the conductance and force. First, by fitting the measured data into a modified multiple tunneling barrier model, the static contact resistances, corresponding to the different contact conformations of single alkanedithiol and alkanediamine molecular junctions, were identified. Second, the changes of contact decay constant were measured under mechanical extensions of the molecular junctions, which helped to classify the different single molecular conductance sets into specific microscopic conformations of the molecule-electrode contacts. Third, by monitoring the changes of force and contact decay constant with the mechanical extensions, the changes of conductance were found to be caused by the changes of contact bond length and by the atomic reorganizations near the contact bond. This study provides a new insight into the understanding of the influences of contact conformations, especially the effect of changes of dynamic contact conformation on electron transport through single molecular junctions.
Differential effects of aging on transport properties of anterior and posterior human sclera
O. A. Boubriak; J. P. G. Urban; A. J. Bron
2003-01-01
The transport properties and composition of 44 pairs of human sclera, 37–91 years were compared. Solute transport, diffusion and partition coefficients of posterior sclera for solutes ranging in mass from 0·023–70kDa were higher than those of anterior sclera; the posterior region was also more hydrated. The differences in partition coefficient between anterior and posterior sclera became more pronounced as solute
NASA Astrophysics Data System (ADS)
Lange, Kyle J.; Sui, Pang-Chieh; Djilali, Ned
2012-06-01
A key challenge in the use of simulations to determine transport properties of PEMFC catalyst layers is the computational reconstruction of the catalyst layer microstructure. In this work, a number of different algorithms incorporating different assumptions are used to computationally reconstruct a large number of catalyst layer microstructures. In particular, the different algorithms use a variety of methods to account for agglomeration and distribution of carbon black spheres and ionomer. A pore scale model is then used to compute effective transport properties for each microstructure. It is found that the choice of the considered reconstruction algorithms does not have a significant effect on effective transport properties in most cases. Finally, the model assumptions which account for Knudsen diffusion are analyzed and modified to account for non-cylindrical pore structures. When cases are run using the Derjaguin correction for Knudsen diffusion, the obtained computational results are much closer to experimental data.
Christoph Junghans; Matej Praprotnik; Kurt Kremer
2007-09-03
We introduce a variation of the dissipative particle dynamics (DPD) thermostat that allows for controlling transport properties of molecular fluids. The standard DPD thermostat acts only on a relative velocity along the interatomic axis. Our extension includes the damping of the perpendicular components of the relative velocity, yet keeping the advantages of conserving Galilei invariance and within our error bar also hydrodynamics. This leads to a second friction parameter for tuning the transport properties of the system. Numerical simulations of a simple Lennard-Jones fluid and liquid water demonstrate a very sensitive behaviour of the transport properties, e.g., viscosity, on the strength of the new friction parameter. We envisage that the new thermostat will be very useful for the coarse-grained and adaptive resolution simulations of soft matter, where the diffusion constants and viscosity of the coarse-grained models are typically too high/low, respectively, compared to all-atom simulations.
Site Dependent Transport Properties of N-Doped Graphene Nanoribbons with Zigzag Edges
NASA Astrophysics Data System (ADS)
Hu, Yang; Gu, Yousong; Sun, Xu; Wang, Xueqiang
2012-08-01
The electronic structures and the electronic transport properties for nitrogen doped (zigzag grapheme nanoribbons) z-GNRs were investigated by first-principles calculations. For the perfect Z-5-8 GNR, the band structure, DOS and transimission spectrum is almost symmetry around the Fermi level, and the I-V curve is almost linear. For the N-doped Z-5-8 GNRs, there exist gaps in the band structures and DOS plots, and conductance is lower than that of the perfect one. As the doping site moves from inner to edge, electrical conductance is decreased. Nitrogen doping at the edge has the greatest impact on the transport properties of Z-5-8 GNR. Therefore, it can be concluded that influences of nitrogen doping on the transport properties for z-GNRs is sites dependent.
A DFT look at transport properties of Graphene nano-ribbons coupled to DNA Base pairs
NASA Astrophysics Data System (ADS)
Gayles, Jacob; Agapito, Luis; Woloweic, Christian; Kioussis, Nicholas
2010-03-01
This study investigates the electronic structure and transport properties of DNA base pairs coupled to reconstructed zigzag edge Graphene Nano-Ribbons (z-GNRs PRL 101, 115502 (2008)^1 ). Ab initio electronic structure calculations show reconstructed z-GNR to be more stable compared to the unreconstructed^1. By cleaving these metallic reconstructed ribbons, we create two graphene electrodes separated by a 5 å wide gap. The DNA base pair is then coupled to the graphene electrodes and relaxed using density functional theory. Transport properties are calculated in the ATK commercial packages (Atomistix ToolKit version 7.0, QuantumWise A/S). We compare tunneling currents for different base pairs, at finite biases. Understanding transport properties of the base pairs will potentially benefit areas such as DNA sensors and DNA sequencing.
Accurate transport properties for H-CO and H-CO2
NASA Astrophysics Data System (ADS)
Dagdigian, Paul J.
2015-08-01
Transport properties for collisions of hydrogen atoms with CO and CO2 have been computed by means of quantum scattering calculations. The carbon oxides are important species in hydrocarbon combustion. The following potential energy surfaces (PES's) for the interaction of the molecule fixed in its equilibrium geometry were employed: for H-CO, the PES was taken from the work of Song et al. [J. Phys. Chem. A 117, 7571 (2013)], while the PES for H-CO2 was computed in this study by a restricted coupled cluster method that included single, double, and (perturbatively) triple excitations. The computed transport properties were found to be significantly different from those computed by the conventional approach that employs isotropic Lennard-Jones (12-6) potentials. The effect of using the presently computed accurate transport properties in 1-dimensional combustion simulations of methane-air flames was investigated.
Zuo, Guangchao; Shen, Rong; Ma, Shaojie; Guo, Wanlin
2010-01-26
The single-file water transport through a biomimic water channel consisting of a (6,6) carbon nanotube (CNT) with different types of external point charges is studied using molecular dynamics simulations. It is demonstrated that, as in the aquaporins, asymmetrically positioned charges cannot generate robust unidirectional water flow in the CNT. Thermal fluctuation in bulk water competes with charge affinity to steer the water transport, resulting in nonmonotonic flow with intermittent reversal of transport direction. The energetic analysis suggests that the water-water interaction, determined by dipole orientation configuration, influences the transport rate significantly. These findings can provide correct biomimic understanding of water transport properties and will benefit the design of efficient functional nanofluidic devices. PMID:20000381
Magnetic and transport properties of epitaxial stepped Fe3O4(100) thin films
NASA Astrophysics Data System (ADS)
Wu, Han-Chun; Syrlybekov, Askar; Mauit, Ozhet; Mouti, Anas; Coileáin, Cormac Ó.; Abid, Mourad; Abid, Mohamed; Shvets, Igor V.
2014-09-01
We investigate the magnetic and transport properties of epitaxial stepped Fe3O4 thin films grown with different thicknesses. Magnetization measurements suggest that the steps induce additional anisotropy, which has an easy axis perpendicular to steps and the hard axis along the steps. Separate local transport measurements, with nano-gap contacts along a single step and perpendicular to a single step, suggest the formation of a high density of anti-phase boundaries (APBs) at the step edges are responsible for the step induced anisotropy. Our local transport measurements also indicate that APBs distort the long range charge-ordering of magnetite.
Squeezing a gel to establish network structure-transport property relationships
NASA Astrophysics Data System (ADS)
Chan, Edwin; Nadermann, Nichole; McLeod, Kelly; Tew, Greg
2015-03-01
Gels are used in many applications, ranging from drug delivery to water purification, where regulating transport of a particular permeant is critical. The structure of the gel determines its transport properties but developing the gel structure-transport property relationships often require multiple measurement techniques. In this work, we demonstrate poroelastic relaxation indentation (PRI) as a single measurement tool to establish the relationships between the polymer network structure and the transport properties of well-defined hydrogel networks synthesized via a thiol-norbornene click reaction of poly(ethylene glycol) (PEG) chains. We use PRI to quantify the mechanical and transport properties of a series of ``click'' hydrogels with different crosslink densities. By applying various thermodynamic network swelling models to the describe the mechanical response of these gels as measured from PRI, we are able to extract thermodynamic parameters of these hydrogels including the Flory chi parameter and the mesh size. We validate our approach by comparing the thermodynamic parameters obtained from PRI with results from neutrons scattering studies of the same series of hydrogels.
Functional Properties of the Retinal Glutamate Transporters GLT-1c and EAAT5*
Schneider, Nicole; Cordeiro, Sönke; Machtens, Jan-Philipp; Braams, Simona; Rauen, Thomas; Fahlke, Christoph
2014-01-01
In the mammalian retina, glutamate uptake is mediated by members of a family of glutamate transporters known as “excitatory amino acid transporters (EAATs).” Here we cloned and functionally characterized two retinal EAATs from mouse, the GLT-1/EAAT2 splice variant GLT-1c, and EAAT5. EAATs are glutamate transporters and anion-selective ion channels, and we used heterologous expression in mammalian cells, patch-clamp recordings and noise analysis to study and compare glutamate transport and anion channel properties of both EAAT isoforms. We found GLT-1c to be an effective glutamate transporter with high affinity for Na+ and glutamate that resembles original GLT-1/EAAT2 in all tested functional aspects. EAAT5 exhibits glutamate transport rates too low to be accurately measured in our experimental system, with significantly lower affinities for Na+ and glutamate than GLT-1c. Non-stationary noise analysis demonstrated that GLT-1c and EAAT5 also differ in single-channel current amplitudes of associated anion channels. Unitary current amplitudes of EAAT5 anion channels turned out to be approximately twice as high as single-channel amplitudes of GLT-1c. Moreover, at negative potentials open probabilities of EAAT5 anion channels were much larger than for GLT-1c. Our data illustrate unique functional properties of EAAT5, being a low-affinity and low-capacity glutamate transport system, with an anion channel optimized for anion conduction in the negative voltage range. PMID:24307171
Transport properties of graphene under periodic and quasiperiodic magnetic superlattices
NASA Astrophysics Data System (ADS)
Lu, Wei-Tao; Wang, Shun-Jin; Wang, Yong-Long; Jiang, Hua; Li, Wen
2013-08-01
We study the transmission of Dirac electrons through the one-dimensional periodic, Fibonacci, and Thue-Morse magnetic superlattices (MS), which can be realized by two different magnetic blocks arranged in certain sequences in graphene. The numerical results show that the transmission as a function of incident energy presents regular resonance splitting effect in periodic MS due to the split energy spectrum. For the quasiperiodic MS with more layers, they exhibit rich transmission patterns. In particular, the transmission in Fibonacci MS presents scaling property and fragmented behavior with self-similarity, while the transmission in Thue-Morse MS presents more perfect resonant peaks which are related to the completely transparent states. Furthermore, these interesting properties are robust against the profile of MS, but dependent on the magnetic structure parameters and the transverse wave vector.
Ballistic transport properties in pristine/doped/pristine graphene junctions
NASA Astrophysics Data System (ADS)
Ardenghi, J. S.; Bechthold, P.; Gonzalez, E.; Jasen, P.; Juan, A.
2014-08-01
We investigate the ballistic electron transport in a monolayer graphene with configurational averaged impurities, located between two clean graphene leads. It is shown that the electron transmission are strongly dependent on the concentration of impurities and the incident energy. In turn, the conductance computed using the Landauer formalism shows a similar behavior to those found in experimental works as a function of the applied voltage for different concentrations of impurities in the limit of low temperatures. In the limit of zero bias voltage, the conductance shows a minimum value which reduces to zero for high concentration of impurities which disentangle graphene sublattices. These results can be very helpful for exploring the tunneling mechanism of electrons through doped thermodynamically stable graphene.
Electronic transport properties through thiophenes on switchable domains
T. Kunze; S. Gemming; V. Pankoke; K. Morawetz; R. Luschtinetz; G. Seifert
2009-11-05
The electronic transport of electrons and holes through stacks of $\\alpha$,$\\ome ga$-dicyano-$\\beta$,$\\beta$'-dibutyl- quaterthiophene (DCNDBQT) as part of a nov el organic ferroic field-effect transistor (OFFET) is investigated. The novel ap plication of a ferroelectric instead of a dielectric substrate provides the poss ibility to switch bit-wise the ferroelectric domains and to employ the polarizat ion of these domains as a gate field in an organic semiconductor. A device conta ining very thin DCNDBQT films of around 20 nm thickness is intended to be suitab le for logical as well as optical applications. We investigate the device proper ties with the help of a phenomenological model called multilayer organic light-e mitting diodes (MOLED), which was extended to transverse fields. The results sho wed, that space charge and image charge effects play a crucial role in these org anic devices.
Collective Transport Properties of Driven Skyrmions with Random Disorder.
Reichhardt, C; Ray, D; Reichhardt, C J Olson
2015-05-29
We use particle-based simulations to examine the static and driven collective phases of Skyrmions interacting with random quenched disorder. We show that nondissipative effects due to the Magnus term reduce the depinning threshold and strongly affect the Skyrmion motion and the nature of the dynamic phases. The quenched disorder causes the Hall angle to become drive dependent in the moving Skyrmion phase, while different flow regimes produce distinct signatures in the transport curves. For weak disorder, the Skyrmions form a pinned crystal and depin elastically, while for strong disorder the system forms a pinned amorphous state that depins plastically. At high drives the Skyrmions can dynamically reorder into a moving crystal, with the onset of reordering determined by the strength of the Magnus term. PMID:26066455
Charge transport properties of CdMnTe radiation detectors
Kim K.; Rafiel, R.; Boardman, M.; Reinhard, I.; Sarbutt, A.; Watt, G.; Watt, C.; Uxa, S.; Prokopovich, D.A.; Belas, E.; Bolotnikov, A.E.; James, R.B.
2012-04-11
Growth, fabrication and characterization of indium-doped cadmium manganese telluride (CdMnTe)radiation detectors have been described. Alpha-particle spectroscopy measurements and time resolved current transient measurements have yielded an average charge collection efficiency approaching 100 %. Spatially resolved charge collection efficiency maps have been produced for a range of detector bias voltages. Inhomogeneities in the charge transport of the CdMnTe crystals have been associated with chains of tellurium inclusions within the detector bulk. Further, it has been shown that the role of tellurium inclusions in degrading chargecollection is reduced with increasing values of bias voltage. The electron transit time was determined from time of flight measurements. From the dependence of drift velocity on applied electric field the electron mobility was found to be n = (718 55) cm2/Vs at room temperature.
Collective Transport Properties of Driven Skyrmions with Random Disorder
NASA Astrophysics Data System (ADS)
Reichhardt, C.; Ray, D.; Reichhardt, C. J. Olson
2015-05-01
We use particle-based simulations to examine the static and driven collective phases of Skyrmions interacting with random quenched disorder. We show that nondissipative effects due to the Magnus term reduce the depinning threshold and strongly affect the Skyrmion motion and the nature of the dynamic phases. The quenched disorder causes the Hall angle to become drive dependent in the moving Skyrmion phase, while different flow regimes produce distinct signatures in the transport curves. For weak disorder, the Skyrmions form a pinned crystal and depin elastically, while for strong disorder the system forms a pinned amorphous state that depins plastically. At high drives the Skyrmions can dynamically reorder into a moving crystal, with the onset of reordering determined by the strength of the Magnus term.
Novel electronic and transport properties of graphene superlattices
NASA Astrophysics Data System (ADS)
Park, Cheol-Hwan
2009-03-01
Charge carriers in graphene show linear and isotropic energy dispersion relation and chiral behavior, like massless neutrinos in particle physics. Because of these novel properties, many interesting and unconventional phenomena occur in graphene. On the other hand, since the 1970's, metallic and semiconducting superlattice structures -- man-made crystals -- have been extensively studied regarding to their fundamental electronic and optical properties as well as many applications. In this talk, I will present calculations on the properties of charge carriers in graphene under an external periodic potential (graphene superlattices) which are found to be greatly different from those of conventional two-dimensional electron gases in similar conditions [1-3]. I will discuss the anisotropies in the group velocity around the Dirac point and in the gap opening at the supercell Brillouin zone boundary [1]. Next, I will focus on the special cases where the group velocity along one direction becomes zero [1,2], emphasizing the phenomena of pseudospin collapse and possible electron beam supercollimation effects in these systems [2]. Finally, I will discuss the properties of a new generation of massless Dirac fermions at the supercell Brillouin zone boundaries and their experimental implications [3]. [4pt] [1] C. -H. Park, L. Yang, Y. -W. Son, M. L. Cohen, and S. G. Louie, Nature Phys. 4, 870 (2008). [0pt] [2] C. -H. Park, Y. -W. Son, L. Yang, M. L. Cohen, and S. G. Louie, Nano Lett. 8, 2920 (2008). [0pt] [3] C. -H. Park, L. Yang, Y. -W. Son, M. L. Cohen, and S. G. Louie, Phys. Rev. Lett. 101, 126804 (2008).
Transport properties and nanosensors of oxide nanowires and nanobelts
Changshi Lao
2007-01-01
ZnO is one of the most important materials for electronics, optoelectronics, piezoelectricity and optics. With a wide band gap of 3.37eV and an exiton binding energy of 60meV, ZnO ID nanostructures exhibit promising properties in a lot of optical device applications. It is also an important piezoelectric material and has applications in a new category of nanodevices, nano-piezotronics. Demonstrated prototype
Anisotropic models for compact stars
NASA Astrophysics Data System (ADS)
Maurya, S. K.; Gupta, Y. K.; Ray, Saibal; Dayanandan, Baiju
2015-05-01
In the present paper we obtain an anisotropic analog of the Durgapal and Fuloria (Gen Relativ Gravit 17:671, 1985) perfect fluid solution. The methodology consists of contraction of the anisotropic factor with the help of both metric potentials and . Here we consider the same as Durgapal and Fuloria (Gen Relativ Gravit 17:671, 1985) did, whereas is as given by Lake (Phys Rev D 67:104015, 2003). The field equations are solved by the change of dependent variable method. The solutions set mathematically thus obtained are compared with the physical properties of some of the compact stars, strange star as well as white dwarf. It is observed that all the expected physical features are available related to the stellar fluid distribution, which clearly indicates the validity of the model.
Pore-scale heterogeneity, energy dissipation and the transport properties of rocks
Bernabe, Y.; Revil, A. [Universite Louis Pasteur, Strasbourg (France)] [Universite Louis Pasteur, Strasbourg (France)
1995-06-15
The authors construct model systems to study pore scale conductivity, by making the models from an array of spheres, tubes, and cracks with different dimensions. They vary the conductivity of this system by changing the sizes and distributions of the different pore elements. To determine the transport properties of this model system, they equated the sum of the energy lost at each pore junction, to the total energy lost in the array, for either fluid or electrical conduction through the array. The authors argue that this model conduction system should be applicable to study conductivity through rock, and allow one to learn more about transport properties of rock.
Electrical Transport Properties of Polyaniline Containing HCl, CuCl2 and Multiwall Carbon Nanotube
NASA Astrophysics Data System (ADS)
Meikap, A. K.
2011-07-01
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.
NASA Astrophysics Data System (ADS)
Yu, Minghao; Kihara, Hisashi; Abe, Ken-ichi; Takahashi, Yusuke
2015-06-01
A relatively simple method for calculating accurately the third-order electron transport properties of nitrogen and air thermal plasmas is presented. The electron transport properties, such as the electrical conductivity and the electron thermal conductivity, were computed with the best and latest available collision cross-section data in the temperature and pressure ranges of T = 300 - 15000 K and p = 0.01 - 1.0 atm, respectively. The results obtained under the atmospheric pressure condition showed good agreements with the experimental and the high-accuracy theoretical results. The presently-introduced method has good application potential in numerical simulations of nitrogen and air inductively-coupled plasmas.
The effect of the transport property models on the shuttle boundary layer
NASA Technical Reports Server (NTRS)
Bertin, J. J.; Neal, D. R.; Stalmach, D. D.
1978-01-01
Theoretical solutions for the nonsimilar, laminar boundary-layer were computed for four points along the shuttle entry trajectory. Since the boundary layer is that region of the flow field where the effects of viscosity and of thermal conductivity are most important, numerical solutions for the boundary layer were generated using different models for the transport properties. These solutions indicate that the displacement thickness and the heat-transfer rates are very sensitive to changes in the models for thermal conductivity and for specific heat. Thus, the solutions are sensitive to the assumed transport-property model.
WETAIR: A computer code for calculating thermodynamic and transport properties of air-water mixtures
NASA Technical Reports Server (NTRS)
Fessler, T. E.
1979-01-01
A computer program subroutine, WETAIR, was developed to calculate the thermodynamic and transport properties of air water mixtures. It determines the thermodynamic state from assigned values of temperature and density, pressure and density, temperature and pressure, pressure and entropy, or pressure and enthalpy. The WETAIR calculates the properties of dry air and water (steam) by interpolating to obtain values from property tables. Then it uses simple mixing laws to calculate the properties of air water mixtures. Properties of mixtures with water contents below 40 percent (by mass) can be calculated at temperatures from 273.2 to 1497 K and pressures to 450 MN/sq m. Dry air properties can be calculated at temperatures as low as 150 K. Water properties can be calculated at temperatures to 1747 K and pressures to 100 MN/sq m. The WETAIR is available in both SFTRAN and FORTRAN.
Structure evolution and electrical transport property of Si nanowire
NASA Astrophysics Data System (ADS)
Wang, Y.; Li, Q. Q.; Dong, J. C.; He, Y. Z.; Li, H.
2015-02-01
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.
The Effects of Atmospheric pH on the Transport Properties of Gallium Nitride
NASA Astrophysics Data System (ADS)
McElroy, Andrew; Dyck, Jeffrey S.; Kash, Kathleen
2011-04-01
It has been theorized that there exists a thin layer of water molecules on the surface of many materials when in air. This layer is predicted to have an effect on the electrochemical properties of the material. GaN is one of these materials. It has been demonstrated that the optical properties of GaN are affected by the pH of the atmosphere around the sample. In this study the effects of pH on transport properties are tested. A system was developed to test the Hall coefficient and resistivity of samples under different ambients to discover the effects of pH on carrier concentration and Hall mobility of GaN. Thus far, the results show that the pH of the ambient water vapor does not have an effect on the transport properties. This project was funded through the National Science Foundation (DMR-1006132) and the Huntington and Codrington Foundations.
Perturbation Hamiltonians in heterogeneous anisotropic weakly
Cerveny, Vlastislav
, for reference anisotropic model, the perturbed medium may be anisotropic perfectly elastic, or anisotropicPerturbation Hamiltonians in heterogeneous anisotropic weakly dissipative media Vlastislav #20, isotropic or anisotropic, weakly dissipative media. In addition to the phase-space coordinates, repre
Magnetic colloid by PLA: Optical, magnetic and thermal transport properties
NASA Astrophysics Data System (ADS)
Pandey, B. K.; Shahi, A. K.; Gopal, Ram
2015-08-01
Ferrofluids of cobalt and cobalt oxide nanoparticles (NPs) have been successfully synthesized using liquid phase-pulse laser ablation (LP-PLA) in ethanol and double distilled water, respectively. The mechanism of laser ablation in liquid media and formation process for Co target in double distilled water (DDW) and ethanol are speculated based on the reactions between laser generated highly nascent cobalt species and vaporized solvent media in a confined high temperature and pressure at the plume-surrounding liquid interface region. Optical absorption, emission, vibrational and rotational properties have been investigated using UV-vis absorption, photoluminescence (PL) and Fourier transform-infra red (FT-IR) spectroscopy, respectively. In this study optical band gap of cobalt oxide ferrofluids has been engineered using different pulse energy of Nd:YAG laser in the range of (2.80-3.60 eV). Vibrating sample magnetometer (VSM) is employed to determine the magnetic properties of ferrofluids of cobalt and cobalt oxide NPs while their thermal conductivities are examined using rotating disc method. Ferrofluids have gained enormous curiosity due to many technological applications, i.e. drug delivery, coolant and heating purposes.
Electrical transport properties of CaB6
NASA Astrophysics Data System (ADS)
Stankiewicz, Jolanta; Sesé, Javier; Balakrishnan, Geetha; Fisk, Zachary
2015-03-01
We report results from a systematic electron-transport study in a broad temperature range on twelve CaB6 single crystals. None of the crystals were intentionally doped. The different carrier densities observed presumably arise from slight variations in the Ca:B stoichiometry. In these crystals, the variation of the electrical resistivity and of the Hall effect with temperature can be consistently explained by a variable charge state of intrinsic defects, most likely B-antisites (B atom replacing Ca atom). Our model is also consistent with the presence of a narrow, defect related, impurity band close to the Fermi level. Thus it may indicate the validity of defect-driven intrinsic ferromagnetism in alkaline-earth hexaborides. The magnetotransport measurements reveal that most of the samples we have studied are close to a metal-insulator transition at low temperatures. The magnetoresistance changes smoothly from negative--for weakly metallic samples--to positive values--for samples in a localized regime. We acknowledge support from Grant MAT2012-38213-C02-01 of MEC, Spain and EP/I007210/1 from EPSRC, UK.
NASA Astrophysics Data System (ADS)
Schwen, Andreas; Backus, Jason; Walton, Riley J.; Wendroth, Ole
2014-05-01
Leaching of solutes below the root zone has been identified as a main source of potential groundwater pollution. In structured soils, preferential flow paths can have a significant influence on rapid leaching of solutes. Dye tracer experiments have been frequently used to map the spatial distribution of macropore structures. However, the relative influence of the macropore network on solute leaching under field conditions and its correlation with physical properties of the matric soil (texture, density, mechanical strength) and land use effects have not been analyzed yet and require innovative sampling techniques. The objectives of the present study were to map the macropore network and analyze the leaching behaviour of a conservative tracer under two contrasting land uses. Ponded infiltration experiments with Potassiumbromide (KBr) and Brilliant Blue (BB) were conducted on a silt loam soil in Lexington, KY. Two land use systems, grassland and cropland (wheat), were tested. At soil water content close to field capacity, a total of 30 mm multi-tracer solution was infiltrated on an area of 1.2 × 0.7 m with a ponding head of 20 mm. The concentrations of KBr and BB were 10 and 5 g/L, respectively. After 24 hours, 10 profile sections (width: 100 cm, depth: 70 cm) were excavated in steps of 5 cm and sampled. Dye stained areas were mapped based on digital image analysis. The relative dye coverage was calculated as a function of depth. Vane shear resistance was measured as a proxy for soil mechanical strength. At every other profile section, the soil was sampled for soil water content at regular intervals along a 10 × 10 cm raster. X-ray fluorescence analysis was used to derive concentrations of Br, SiO2 and Al2O3, the latter two being used as proxy for soil particle size distribution. Anisotropic variance and covariance analysis was applied to derive direction-dependent correlations between physical, mechanical, and hydrological observations and to identify the relative influence of the macropore network and land use regime on solute leaching.
Electromagnetic scattering by a wedge with anisotropic impedance faces
Giuseppe Pelosi; Giuliano Manara; Paolo Nepa
1998-01-01
Electromagnetic scattering from the edge of an anisotropic impedance wedge, illuminated at oblique incidence, is addressed. In particular, the paper provides a review of existing solutions for this important topic in diffraction theory. Both numerical and analytical techniques, suitable to properly account for the scattering properties of the wedge's anisotropic impedance faces, are considered
Travascio, Francesco; Zhao, Weizhao; Gu, Wei Yong
2009-04-01
In this study, a new method for determination of an anisotropic diffusion tensor by a single fluorescence recovery after photobleaching (FRAP) experiment was developed. The method was based on two independent analyses of video-FRAP images: the fast Fourier transform and the Karhunen-Loève transform. Computer-simulated FRAP tests were used to evaluate the sensitivity of the method to experimental parameters, such as the initial size of the bleached spot, the choice of the frequencies used in the Fourier analysis, the orientation of the diffusion tensor, and experimental noise. The new method was also experimentally validated by determining the anisotropic diffusion tensor of fluorescein (332 Da) in bovine annulus fibrosus. The results obtained were in agreement with those reported in a previous study. Finally, the method was used to characterize fluorescein diffusion in bovine meniscus. Our findings indicate that fluorescein diffusion in bovine meniscus is anisotropic. This study provides a new tool for the determination of anisotropic diffusion tensor that could be used to investigate the correlation between the structure of biological tissues and their transport properties. PMID:19224367
Michael J. Black; Guillermo Sapiro; David H. Marimont; David Heeger
1998-01-01
Relations between anisotropic diffusion and robust statis tics are described in this pa- per. Specifically, we show that anisotropic diffusion can be seen as a robust estimation procedure that estimates a piecewise smooth image from a noi sy input image. The \\
NASA Technical Reports Server (NTRS)
Thompson, Richard A.; Lee, Kam-Pui; Gupta, Roop N.
1990-01-01
The computer codes developed provide data to 30000 K for the thermodynamic and transport properties of individual species and reaction rates for the prominent reactions occurring in an 11-species nonequilibrium air model. These properties and the reaction-rate data are computed through the use of curve-fit relations which are functions of temperature (and number density for the equilibrium constant). The curve fits were made using the most accurate data believed available. A detailed review and discussion of the sources and accuracy of the curve-fitted data used herein are given in NASA RP 1232.
A numerical model of non-equilibrium thermal plasmas. I. Transport properties
NASA Astrophysics Data System (ADS)
Zhang, Xiao-Ning; Li, He-Ping; Murphy, Anthony B.; Xia, Wei-Dong
2013-03-01
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 me/mh ? 1, where me and mh 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.
Effect of Alignment on Transport Properties of Carbon Nanotube/Metallic Junctions
NASA Technical Reports Server (NTRS)
Wincheski, Buzz; Namkung, Min; Smits, Jan; Williams, Phillip; Harvey, Robert
2003-01-01
Ballistic and spin coherent transport in single walled carbon nanotubes (SWCNT) are predicted to enable high sensitivity single-nanotube devices for strain and magnetic field sensing. Based upon these phenomena, electron beam lithography procedures have been developed to study the transport properties of purified HiPCO single walled carbon nanotubes for development into sensory materials for nondestructive evaluation. Purified nanotubes are dispersed in solvent suspension and then deposited on the device substrate before metallic contacts are defined and deposited through electron beam lithography. This procedure produces randomly dispersed ropes, typically 2 - 20 nm in diameter, of single walled carbon nanotubes. Transport and scanning probe microscopy studies have shown a good correlation between the junction resistance and tube density, alignment, and contact quality. In order to improve transport properties of the junctions a technique has been developed to align and concentrate nanotubes at specific locations on the substrate surface. Lithographic techniques are used to define local areas where high frequency electric fields are to be concentrated. Application of the fields while the substrate is exposed to nanotube-containing solution results in nanotube arrays aligned with the electric field lines. A second electron beam lithography layer is then used to deposit metallic contacts across the aligned tubes. Experimental measurements are presented showing the increased tube alignment and improvement in the transport properties of the junctions.
Anisotropic pressure and hyperons in neutron stars
A. Sulaksono
2014-12-23
We study the effects of anisotropic pressure on properties of the neutron stars with hyperons inside its core within the framework of extended relativistic mean field. It is found that the main effects of anisotropic pressure on neutron star matter is to increase the stiffness of the equation of state, which compensates for the softening of the EOS due to the hyperons. The maximum mass and redshift predictions of anisotropic neutron star with hyperonic core are quite compatible with the result of recent observational constraints if we use the parameter of anisotropic pressure model $h \\le 0.8$[1] and $\\Lambda \\le -1.15$ [2]. The radius of the corresponding neutron star at $M$=1.4 $M_\\odot$ is more than 13 km, while the effect of anisotropic pressure on the minimum mass of neutron star is insignificant. Furthermore, due to the anisotropic pressure in the neutron star, the maximum mass limit of higher than 2.1 $M_\\odot$ cannot rule out the presence of hyperons in the neutron star core.
The theory of bio-energy transport in the protein molecules and its properties
NASA Astrophysics Data System (ADS)
Pang, Xiao-feng
2011-10-01
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.
NASA Astrophysics Data System (ADS)
Ziemys, Arturas; Milosevic, Miljan; Kojic, Milos; Multiscale transport Team
2014-03-01
Transport theories based on the continuum hypothesis may not be appropriate, especially in case of diffusion, due to surface effects at nanoscale. Our computational and experimental findings, supported by studies elsewhere, revealed the necessity to account for interface and confinement effects. Thermodynamic aspects were established that might be responsible for reduced diffusivity at interface; more specifically - due to entropy-enthalpy compensation and cage-breaking processes. The thickness of liquid with altered diffusivity at solid-liquid interface depends on material and diffusing molecule nature and properties. We have developed a concept and computational model to bridge those molecular effects within nanoconfinement with transport at macro scale for systems where interface dominates over other properties (e.g. nanochannels, nanopores, polymers). The concept was validated against molecular transport through nanochannels and polymers. Novel parameters are introduced that determine diffusion regime and kinetics within the nanoscale confined fluids. New diffusion transport characteristics are established when nanochannel confining dimension approaches sizes of diffusing molecules, determining bounds of the non-Fickian transport regimes. The developed multiscale method could be used to study material transport and optimize nanoporous materials for biomedical and industrial applications.
Transport properties of Dirac fermions in two dimensions
NASA Astrophysics Data System (ADS)
DaSilva, Ashley M.
The Dirac equation in particle physics is used to describe spin 1/2 fermions (such as electrons) moving at relativistic speeds. In condensed matter physics, this is usually not relevant, since particles in matter move slowly compared to the speed of light. However, recent progress has revealed two-dimensional realizations of Dirac fermions in condensed matter systems with zero mass and a redefined "speed of light." One of these systems, graphene, has been studied theoretically for decades as a building block of graphite. The other, the topological insulator, is quite new; this state of matter was predicted less than 10 years ago. Graphene was first isolated in 2004, and since then there has been an explosion of graphene research in the physics community. Much of the recent excitement has to do with the potential applications of graphene in devices. In this dissertation, I will discuss two problems related to graphene devices, and in particular how to use the strong interaction of graphene with its surroundings as an asset. I will show that a Boltzmann transport theory with all scattering mechanisms describes the current vs voltage of a graphene sheet extremely well using no adjustable parameters. One crucial element of this model is the transfer of energy from electrons directly to the substrate via scattering with optical phonons at the interface. The interaction is due to an electric field that is set up by these optical phonons, which is so strongly interacting in part due to the two dimensionality of the graphene. I will also discuss the adsorption of He atoms on a graphene sheet. This causes a change in the graphene conductivity which is large enough to be measurable. Work in this direction could provide a route to graphene sensors. The topological insulator is a recently predicted state of matter which is nominally an insulator but has metallic surface states which are topologically protected. This topological protection arises from the symmetry of the system, which requires a two-fold degeneracy at any time reversal symmetric momentum, and a band inversion, which provides a swapping of the conduction and valance band at a surface. These two conditions imply that an odd number of states will cross the gap even in the presence of disorder (as long as that disorder is time reversal symmetric). This manifests as a Dirac cone at the surface of insulators such as Bi2Se3 and Bi2Te 3. To be a true topological insulator, one must have a bulk insulator; experimentally however, most samples are bulk conductors. While rapid improvement is being made through techniques such as doping, one of the goals of the research presented in this thesis is to work towards a transport signal which is unique to the surface state even in the presence of a conducting bulk. In this direction, quantum corrections to the magnetoresistance have been shown to fail, as both bulk and surface have similar experimental signals. However work in this dissertation shows that we can still gain some insight by modeling the experimental data with the theory of quantum corrections. I will show evidence that electron-electron interactions are necessary to understand the low temperature conductivity of Bi2Se3 thin films. One unambiguous transport signal is the quantum Hall response; the energy of Dirac fermions in a strong magnetic field is quite different than their parabolic counterparts. Given this, a question that arises is the nature of the fractional quantum Hall effect in topological insulator surface states. I will predict the conditions under which the fractional quantum Hall effect is stable. Finally, one of the reasons topological insulators have gained so much enthusiasm is the potential application to topological quantum computation. This may be made possible if the theoretical predictions of particles called Majorana fermions could be realized experimentally. I discuss evidence that two necessary (although not sufficient) conditions are met: topological insulators can be made superconducting and there is evidence for the formation of vo
Effect of stabilizer on dynamic thermal transport property of ZnO nanofluid
2013-01-01
In this paper, we investigate the effect of adding a stabilizer on the dynamic thermal properties of ZnO nanofluid (containing 5 to 10 nm diameter of ZnO nanocrystals) measured using a 3? method. Addition of the stabilizer leads to the stabilization of the nanofluid and also substantial reduction of the enhancement of thermal transport compared to that seen in the bare ZnO nanofluid. This also alters the frequency dependence of the thermal transport and the characteristic time scale associated with it. It is suggested that the addition of the stabilizer inhibits the thermodiffusion-assisted local aggregation thus leading to substantial reduction of the enhancement of thermal transport properties of the bare nanofluid as proposed in some recent models, and this also alters the characteristic time scales by altering the scale of aggregation. PMID:23497347
NASA Astrophysics Data System (ADS)
Lin, Tao; Liu, Xiaojun; Lou, Zhidong; Hou, Yanbing; Teng, Feng
2014-08-01
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.
Modulation of Drug Transport Properties by Multicomponent Diffusion in Surfactant Aqueous Solutions
Annunziata, Onofrio
Modulation of Drug Transport Properties by Multicomponent Diffusion in Surfactant Aqueous Solutions ReceiVed July 1, 2008 Diffusion coefficients of drug compounds are crucial parameters used for modeling diffusion. A multicomponent diffusion study on drug-surfactant-water ternary mixtures is reported here
Satoru Ishizuka; Hiroshi Tsuji
1984-01-01
Abstract-An aerothcrmochemical analysis has been made on the counterflow diffusion flame established in the forward stagnation region of a porous cylinder and the effects of transport properties on the temperature of the flame are investigated. By making the flame sheet approximation and adopting a model in which the fuel and oxygen are treated as trace species while an inert gas
Glass foams: formation, transport properties, and heat, mass, and radiation transfer
Pilon, Laurent
Glass foams: formation, transport properties, and heat, mass, and radiation transfer Andrei G of Technology, Atlanta, GA 30332-0405, USA b Heat Transfer Laboratory, School of Mechanical Engineering, Purdue process. Hence, understanding the mechanisms of foam formation as well as development of theoretical
Nonasymptotic properties of transport and mixing G. Boffetta and A. Celani
Cencini, Massimo
Nonasymptotic properties of transport and mixing G. Boffetta and A. Celani Dipartimento di Fisica Generale and Istituto Nazionale Fisica della Materia, Universita` di Torino, Via Pietro Giuria 1, 10125 Torino, Italy M. Cencini Dipartimento di Fisica and Istituto Nazionale Fisica della Materia, Universita
Harmon, Julie P.
in their use as contact lens materials and in other biomedical applications. To date research characterizing transport properties in these polymers. This is important, for example, in contact lens applications because significant for contact lens applications. For the initial drying phase, time ! 0, the loss of penetrant
Ab initio modeling of quantum transport properties of molecular electronic devices
Jeremy Taylor; Hong Guo; Jian Wang
2001-01-01
We report on a self-consistent ab initio technique for modeling quantum transport properties of atomic and molecular scale nanoelectronic devices under external bias potentials. The technique is based on density functional theory using norm conserving nonlocal pseudopotentials to define the atomic core and nonequilibrium Green's functions (NEGF's) to calculate the charge distribution. The modeling of an open device system is
High pressure apparatus for transport properties study in high magnetic field
Alsmadi, A. M.; Nakotte, H.; Honda, F.; Sechovsky, V.; Mikulina, O.; Kamarad, J.; Lacerda, A. H.
2002-01-01
We have designed a high pressure apparatus for measuring electrical-transport properties at low temperatures, high magnetic field and hydrostatic pressure up to 10 kbar. Details of the high-pressure cell and an exemplary study on UNiAI are described and discussed briefly.
Structural, Optical, and Transport Properties of -and Ag3VO4 K. R. Poeppelmeier,*,
Poeppelmeier, Kenneth R.
Structural, Optical, and Transport Properties of - and Ag3VO4 V. Cloet, A. Raw, K. R. Poeppelmeier Information ABSTRACT: The structures of - and -Ag3VO4 were studied via single- crystal X-ray diffraction (XRD of the single crystals was maintained as Ag3VO4 reversibly transitioned between -Ag3VO4 and -Ag3VO4. The optical
Transport and Phase Equilibria Properties for Steam Flooding of Heavy Oils
Gabitto, Jorge; Barrufet, Maria
2002-11-20
The objectives of this research included experimental determination and rigorous modeling and computation of phase equilibrium diagrams, volumetric, and transport properties of hydrocarbon/CO2/water mixtures at pressures and temperatures typical of steam injection processes for thermal recovery of heavy oils.
S. J. Cabardo; T. A. G. Langrish; R. Dickson; B. Joe
2006-01-01
Variability is a key issue in the processing of many biological materials, in this case the drying of hardwood timber. This article reports the measurements of variability of the diffusion coefficient (a transport property), the initial moisture content, and the basic density that are relevant to the drying of blackbutt, Eucalyptus pilularis Sm, from northern New South Wales in Australia.
Effects of nonmagnetic impurities on the spin transport property of a graphene nanoribbon device
Lee, EokKyun
. Because of the linear dispersion and concomitant topological constraints in the graphene band structureEffects of nonmagnetic impurities on the spin transport property of a graphene nanoribbon device to an edge of a graphene nanoribbon device GND with zigzag edges. A center-located impurity enables both
Helical poly(arginine) mimics with superior cell-penetrating and molecular transporting properties
Cheng, Jianjun
Helical poly(arginine) mimics with superior cell- penetrating and molecular transporting properties Haoyu Tang, Lichen Yin, Kyung Hoon Kim and Jianjun Cheng* Poly(arginine) mimics bearing long hydrophobic the helicities of poly(arginine) mimics. These helical poly(arginine) mimics show superior cell membrane
Electrical Transport Properties of Au-Doped DNA Molecules J. S. Hwang1
Hwang, Sung Woo
,2 , Y. W. Kwon3 , J. I. Jin3 , S. W. Hwang1,2 and D. Ahn1 1 Institute of Quantum Information ProcessingElectrical Transport Properties of Au-Doped DNA Molecules J. S. Hwang1 , S. H. Hong1,2 , H. K. Kim1
Electronic Transport Properties of Ensembles of Perylene-Substituted Poly-isocyanopeptide Arrays
Chris E. Finlayson; Richard H. Friend; Matthijs B. J. Otten; Erik Schwartz; Jeroen J. L. M. Cornelissen; Roeland J. M. Nolte; Alan E. Rowan; P. Samori; Vicenzo Palermo; Andrea Liscio; Kalina Peneva; K. Mullen; Sara Trapani; David Beljonne
2008-01-01
The electronic transport properties of stacks of perylene-bis(dicarboximide) (PDI) chromophores, covalently fixed to the side arms of rigid, helical polyisocyanopeptides, are studied using thin-film transistors. In device architectures where the transistor channel lengths are somewhat greater than the average polymer chain length, carrier mobilities of order 10 ? 3 cm 2 V ? 1 s ? 1 at 350 K
Modeling the water transport properties of casein-based edible coating
G. G Buonocore; M. A Del Nobile; C Di Martino; G Gambacorta; E La Notte; L Nicolais
2003-01-01
A mathematical model able to predict the water transport properties of casein-based edible coating is presented. The model consists of two parts. The first is aimed to describe the water solubilization process into the investigated film, and it was derived taking into account the presence of both “bound water” and “free water”. The second is intended to describe the water
Maruyama, Shigeo
Carrier transport properties in single-walled carbon nanotubes studied by photoluminescence. We have investigated the photoluminescence (PL) of in individual single-walled carbon nanotubes-field dependence of PL intensity. Time-resolved photoluminescence of SWNTs dispersed in surfactant solution has
Influence of Calcium Hydroxide Dissolution on the Transport Properties of Hydrated Cement Systems
Bentz, Dale P.
Influence of Calcium Hydroxide Dissolution on the Transport Properties of Hydrated Cement Systems and Technology Gaithersburg, MD 20899 USA Reprinted from Materials Science of Concrete: Calcium Hydroxide in Concrete, Special Volume, Proceedings. American Ceramic Society. Workshop on the Role of Calcium Hydroxide
Non-equilibrium quantum transport properties of organic molecules on silicon
Wenchang Lu; V. Meunier; J. Bernholc
2005-01-01
Electronic and quantum transport properties of organic molecules on Si surfaces are studied within density functional theory. This system is synthetically accessible and has potential applications in chemical sensors, resonant tunneling devices and molecular logic. Since the bonding of organic molecules on Si is well defined and often well characterized, it constitutes an ideal model system for systematic comparisons with
Zhou, Quanlin; Liu, Hui-Hai; Bodvarsson, Gudmundur S.; Oldenburg, Curtis M.
2002-07-09
The heterogeneity of hydrogeologic properties at different scales may have different effects on flow and transport processes in a subsurface system. A model for the unsaturated zone of Yucca Mountain, Nevada, is developed to represent complex heterogeneity at two different scales: (1) layer scale corresponding to geologic layering and (2) local scale. The layer-scale hydrogeologic properties are obtained using inverse modeling, based on the available measurements collected from the Yucca Mountain site. Calibration results show a significant lateral and vertical variability in matrix and fracture properties. Hydrogeologic property distributions in a two-dimensional, vertical cross section of the site are generated by combining the average layer-scale matrix and fracture properties with local-scale perturbations generated using a stochastic simulation method. The unsaturated water flow and conservative (nonsorbing) tracer transport through the cross section are simulated for different sets of matrix and fracture property fields. Comparison of simulation results indicates that the local-scale heterogeneity of matrix and fracture properties has a considerable effect on unsaturated flow processes, leading to fast flow paths in fractures and the matrix. These paths shorten the travel time of a conservative tracer from the source (repository) horizon in the unsaturated zone to the water table for small fractions of total released tracer mass. As a result, the local-scale heterogeneity also has a noticeable effect on global tracer transport processes, characterized by an average breakthrough curve at the water table, especially at the early arrival time of tracer mass. However, the effect is not significant at the later time after 20 percent tracer mass reaches the water table. The simulation results also verify that matrix diffusion plays an important role in overall solute transport processes in the unsaturated zone at Yucca Mountain.
Zhou, Quanlin; Liu, Hui-Hai; Bodvarsson, Gudmundur S; Oldenburg, Curtis M
2003-01-01
The heterogeneity of hydrogeologic properties at different scales may have different effects on flow and transport processes in a subsurface system. A model for the unsaturated zone of Yucca Mountain, Nevada, is developed to represent complex heterogeneity at two different scales: (1) layer scale corresponding to geologic layering and (2) local scale. The layer-scale hydrogeologic properties are obtained using inverse modeling, based on the available measurements collected from the Yucca Mountain site. Calibration results show a significant lateral and vertical variability in matrix and fracture properties. Hydrogeologic property distributions in a two-dimensional, vertical cross-section of the site are generated by combining the average layer-scale matrix and fracture properties with local-scale perturbations generated using a stochastic simulation method. The unsaturated water flow and conservative (nonsorbing) tracer transport through the cross-section are simulated for different sets of matrix and fracture property fields. Comparison of simulation results indicates that the local-scale heterogeneity of matrix and fracture properties has a considerable effect on unsaturated flow processes, leading to fast flow paths in fractures and the matrix. These paths shorten the travel time of a conservative tracer from the source (repository) horizon in the unsaturated zone to the water table for small fractions of total released tracer mass. As a result, the local-scale heterogeneity also has a noticeable effect on global tracer transport processes, characterized by an average breakthrough curve at the water table, especially at the early arrival time of tracer mass. However, the effect is not significant at the later time after 20% tracer mass reaches the water table. The simulation results also verify that matrix diffusion plays an important role in overall solute transport processes in the unsaturated zone at Yucca Mountain. PMID:12498572
Thermoelectric Transport Properties of Gold-Iron at Millikelvin Temperatures.
NASA Astrophysics Data System (ADS)
Chesire, Daniel Patrick
Measurements of the electrical resistivity, and both static and isoelectric thermopower have been made on a fine Au wire containing 1 ppm Fe over a range of temperatures between 7 K and 24 mK. A shallow minimum at higher temperatures and unitary limit in the resistivity data characteristic of the Kondo effect were observed in the lower temperature ranges. The minimum coincides with that observed by other workers. Both the resistivity and the two thermopowers were measured with a Superconducting Quantum Interference Detector (SQUID) which has extremely high sensitivity and a very good signal-to-noise ratio. The static and isoelectric thermopowers were measured under two different boundary conditions. The static thermopower was measured by keeping the electric current through the sample equal to zero by using a compensating current source. The isoelectric thermopower was measured under the condition that the electric field across the sample was kept equal to zero by using a superconducting short. The static and isoelectric thermopowers both exhibited a broad minimum attributed to the interaction of a dilute concentration of Fe impurities with the Au conduction electrons. The data have been analyzed in terms of linear transport theory, using the Mueller-Hartmann expression for the Kondo contribution. Since the measurements were made at low temperatures, the diffusion and phonon drag thermopowers were small enough that the major contribution to the measured thermopower was from the Kondo effect. The theory was shown to fit the data well down to 0.2 K. Below this temperature, the theoretical expression for the thermopower did not agree well with the measurements in this work. The static thermopower, S, was found to be related to the isoelectric thermopower, (SIGMA)(,E=0), and the resistivity, (rho), by the simple relation S = (rho)(SIGMA)(,E=0). The isoelectric data was found to have a better signal-to-noise ratio than the static thermopower and a large enough signal at low temperatures to make it useful as a small-thermal-mass thermometer. It has been shown that this type of thermometer can be used as a thermocouple, leading to a great improvement over other types of nonmetallic thermometric devices because the AuFe can be directly attached to small metallic samples by spot-welding or soldering. Direct attachment helps eliminate thermal boundary-impedance problems. In addition, it was demonstrated that a sample could be suspended from the thermocouple eliminating extraneous sources of heat leaks due to mechanical support mechanisms.
Thermal-induced changes in Transport Properties of PFSA Ionomers
NASA Astrophysics Data System (ADS)
Kusoglu, Ahmet; Weber, Adam
2014-03-01
Perfluorosulfonic-acid ionomers are widely used as the solid-electrolyte in electrochemical energy applications due to their remarkable conductivity and chemical/mechanical stability. Driven by achieving even higher conductivities, it is of interest to increase ion-exchange capacities without deteriorating the mechanical stability. Heat-treatments are commonly employed to change the balance between chemical and mechanical properties, where the latter can be enhanced by annealing-induced crystallinity at the expense of reduced conductivity. In this talk, we focus on how the annealing time membrane undergoes results in non-monotonic changes in its nanostructure, crystallinity and ion conductivity. Hydrophilic domains and crystallinity of the annealed samples, studied by Small- and Wide-angle X-Ray scattering, are correlated to their swelling and conductivity. Our results suggest that the conductivity can be enhanced by optimizing the annealing procedure for the ionomer. However, over a long period of annealing, conductivity and crystallinity of the ionomer appear to decrease and increase, respectively, although by preserving the overall chemical/mechanical balance. Our findings provide new insights into the thermal treatments in altering the structure/function relationship of ionomers due to their non-equilibrium state. Funded by DOE EERE FCTO under contract number DE-AC02-05CH11231.
High-field thermal transport properties of REBCO coated conductors
NASA Astrophysics Data System (ADS)
Bonura, Marco; Senatore, Carmine
2015-02-01
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.
Transport properties of silver-calcium doped lanthanum manganite
NASA Astrophysics Data System (ADS)
Cherif, B.; Rahmouni, H.; Smari, M.; Dhahri, E.; Moutia, N.; Khirouni, K.
2015-01-01
Electrical properties of silver-calcium doped lanthanum manganite (La0.5Ca0.5-xAgxMnO3 with 0.0
Review of Anisotropic Terahertz Material Response
NASA Astrophysics Data System (ADS)
Arikawa, Takashi; Zhang, Qi; Ren, Lei; Belyanin, Alexey A.; Kono, Junichiro
2013-11-01
Anisotropy is ubiquitous in solids and enhanced in low-dimensional materials. In response to an electromagnetic wave, anisotropic absorptive and refractive properties result in dichroic and birefringent optical phenomena both in the linear and nonlinear optics regimes. Such material properties have led to a diverse array of useful polarization components in the visible and near-infrared, but mature technology is non-existent in the terahertz (THz). Here, we review several novel types of anisotropic material responses observed in the THz frequency range, including both linear and circular anisotropy, which have long-term implications for the development of THz polarization optics. We start with the extreme linear anisotropy of macroscopically aligned carbon nanotubes, arising from their intrinsically anisotropic dynamic conductivity. Magnetically induced anisotropy will then be reviewed, including the giant Faraday effects observed in semiconductors, semimetals, and two-dimensional electron systems.
Meddings, J B; DeSouza, D; Goel, M; Thiesen, S
1990-01-01
Both transport function and microvillus membrane physical properties evolve as the enterocyte matures and migrates up the crypt-villus axis. We isolated enriched fractions of villus tip, mid-villus, and crypt enterocytes from which microvillus membrane vesicles were prepared. Using this material we characterized the alterations that occur in microvillus membrane fluidity as the rabbit enterocyte matures and correlated these with kinetic studies of glucose transport. With increasing maturity the microvillus membrane becomes more rigid due to both an increase in the cholesterol/phospholipid ratio and alterations in individual phospholipid subclasses. Maximal rates of glucose transport were greatest in microvillus membrane vesicles prepared from mature cells. However, the glucose concentration producing half-maximal rates of transport (Km) was significantly lower in crypt microvillus membrane vesicles, suggesting that a distinct glucose transporter existed in crypt enterocytes. This distinction disappeared when differences between membrane lipid environments were removed. By fluidizing villus-tip microvillus membrane vesicles, in vitro, to levels seen in the crypt microvillus membrane, we observed a reduction in the Km of this transport system. These data suggest that the kinetic characteristics of the sodium-dependent glucose transporter are dependent upon its local membrane environment. Images PMID:2318967
NASA Astrophysics Data System (ADS)
Shimizu, Toshihiro; Inaba, Tsuginori
Various studies have been carried out on the particle composition of ionized Argon containing excited atoms in a steady state. In some of these reports, the thermodynamic and transport properties were calculated under conditions of chemical equilibrium and LTE (Local Thermal Equilibrium). However, there have been few reports of the particle composition and thermodynamic and transport properties of ionized Argon under conditions of non-chemical equilibrium in time change. In this study, the time taken for the system to change from a non-equilibrium state to an equilibrium state was elucidated for an Argon plasma arc under changing temperature conditions (from 300K to 10,000K). First, the particle composition of partially ionized Argon plasma changing from a non-equilibrium state to an equilibrium state was calculated using a chemical kinetic method at 3,000K-25,000K, without taking radiation into account. The thermodynamic and transport properties including mass density, enthalpy, specific heat, electrical and thermal conductivity and viscosity were calculated based on a Chapman-Enskog first order approximation using the values obtained for particle composition in the equilibrium state. These results showed that the method is valid. Second, the particle composition and thermodynamic and transport properties were investigated under conditions of changing temperature (from 300K to 10,000K). It was shown that the particle composition changed from a non-equilibrium state to an equilibrium state in the order of ?s. The thermodynamic and transport properties were separated with the changing or not changing category in non-chemical equilibrium in time change.
NASA Astrophysics Data System (ADS)
Zhang, X. Q.; Li, H.; Liew, K. M.
2007-10-01
The structures of Ge nanowires are studied by means of geometry optimization method in this paper. As the radii of carbon nanotubes increase, the structures of the Ge nanowires transform from a monoatomic chain to helical and multishell coaxial cylinders. The physical properties, such as density of states, transmission functions, current-voltage (I-V) characteristics, and conductance spectra (G-V) of optimized nanowires sandwiched between two gold contacts are also obtained. The transport properties of a carbon-coated Ge atomic chain are significantly different from those of Ge single atomic chain. Furthermore, some nonequilibrium properties of Ge nanowires are compared with those of Sn and Si nanowires.
NASA Astrophysics Data System (ADS)
Cui, Liling; Yang, Bingchu; Li, Xinmei; He, Jun; Long, Mengqiu
2014-11-01
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.
1988-01-01
A detailed investigation of hydrologic and transport properties of the shallow aquifer underlying the selenium-contaminated Kesterson Reservoir, Merced County, California has been carried out. The aquifer is composed of a sequence of sands, silts, and clays deposited on the flood plain of the San Joaquin River. Transport properties were evaluated by two multiple well tracer experiments. A new method for
NASA Astrophysics Data System (ADS)
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
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.
NASA Astrophysics Data System (ADS)
Clamagirand, J. M.; Ares, J. R.; Diaz-Chao, P.; Pascual, A.; Ferrer, I. J.; Sánchez, C.
2015-04-01
An experimental system able to simultaneously measure the electrical resistance and the thermopower of metallic and semiconducting thin films (with thicknesses from ~nm to ~µm) under sulfur atmosphere from room temperature up to 400?°C and total pressures >0.5–1?mbar is designed and implemented. Calibration tests of the system were performed with palladium foils and films as well as p-type and n-type sulfide semiconducting films: iron disulfide and palladium monosulfide. Uncertainties of measured thermopower and resistance values are less than 10% and 5%, respectively. To check the capability of the system under sulfur atmosphere, in situ measurements of transport properties during sulfuration of palladium films were carried out. During the process, sulfur partial pressure and film temperature are accurately controlled. Apparatus may be used to determine the evolution of transport properties of different metal sulfides during their formation/decomposition processes, opening new pathways to investigate the thermoelectric properties of more complex thin film sulfides.
Modulation of the electron transport properties in graphene nanoribbons doped with BN chains
Liu, Wu; Zhang, Kaiwang, E-mail: kwzhang@xtu.edu.cn; Zhong, JianXin [Department of Physics, Xiangtan University, Xiangtan 411105 (China); Wang, Ru-Zhi, E-mail: wrz@bjut.edu.cn [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Liu, Li-Min, E-mail: limin.liu@csrc.ac.cn [Beijing Computational Science Research Centre, Beijing, 100084 (China)
2014-06-15
Using density-functional theory and the non-equilibrium Green's function method, the electron transport properties of zigzag graphene nanoribbons (ZGNRs) doped with BN chains are studied by systematically calculating the energy band structure, density of states and the transmission spectra for the systems. The BN chains destroyed the electronic transport properties of the ZGNRs, and an energy gap appeared for the ZGNRs, and displayed variations from a metal to a wide-gap semiconductor. With an increase in the number of BN chains, the band gap increased gradually in the band structure and the transmission coefficient decreased near the Fermi surface. Additionally, the doping position had a significant effect on the electronic properties of the ZGNRs.
Goldman, R.S.; Kavanagh, K.L.; Wieder, H.H.; Robbins, V.M.; Ehrlich, S.N.; Feenstra, R.M.
1996-12-01
We have investigated the effects of buffer strain relaxation on the transport properties of two-dimensional electron gases (2DEGs). The 2DEGs consist of modulation-doped In{sub 0.53}Ga{sub 0.47}As/In{sub 0.52}Al{sub 0.48}As heterostructures grown lattice-mismatched to GaAs via compositionally step-graded In{sub {ital x}}Ga{sub 1{minus}{ital x}}As buffers, with different composition gradients, or lattice-matched to InP. We find a variation in 2DEG electronic properties which occurs simultaneously with large differences in epilayer tilt and mosaic spread in the step-graded buffers. This indicates a correlation between the {ital mechanism} of buffer strain relaxation and the 2DEG transport properties. {copyright} {ital 1996 American Institute of Physics.}
Transport properties of pyroclastic rocks from Montagne Pelée volcano (Martinique, Lesser Antilles)
NASA Astrophysics Data System (ADS)
Bernard, Marie-Lise; Zamora, Maria; GéRaud, Yves; Boudon, Georges
2007-05-01
The hydraulic and electrical properties of pyroclastic rocks have been investigated in laboratory on a representative sampling of Montagne Pelée (Martinique, France) deposits with renewed interest in geophysical applications. This sampling covers all the lithologic units of this volcano: lava dome and lava flows, pumices from ash-and-pumice fall and flow deposits, lava blocks from block-and-ash flow and Peléean "nuées ardentes" deposits, scoriae from scoria flow deposits. The connected porosity varies over a wide range from 3 to 62%. The unconnected porosity is important only on pumices where it can reach 15%. The permeability covers more than 5 orders of magnitude, ranging from 10-16 to 35 × 10-12 m2. The higher values are obtained on lava blocks and the scoriae, even if these rocks are less porous than the pumices. The formation factor ranges from 7 to 1139. The transport properties of these rocks are slightly correlated with porosity. This indicates that these properties are not only controlled by the connected porosity. To connect the transport properties to the textural characteristics of the pore network of pyroclastic rocks, different models, based on geometrical considerations or percolation theory, were tested. The pore access radius distribution and the tortuosity control the transport properties of pyroclastic rocks. Consequently, the models (electric and hydraulic) based on the concept of percolation (e.g., the models of Katz and Thompson), apply better than the equivalent channel model of Kozeny-Carman. In addition, the difference in transport properties observed on lava blocks and pumices confirms that the mechanisms of degassing and vesiculation are different for these two types of rock.
Transport signature of spin gapless semiconducting properties in quaternary Heusler of CoFeCrAl
NASA Astrophysics Data System (ADS)
Xu, Guizhou; Zhang, Xiaoming; Liu, Enke; Wang, Wenhong; Wu, Guangheng; Institute of physics Team
2015-03-01
Spin gapless semiconductors (SGS), since proposed by Wang in 2008, have attracted intensive attention due to its potential application in spintronics. In our previous works, we have predicted some quaternary Heusler alloys are promising to be candidates of SGS. In this presentation, we will report the transport signature of SGS properties for CoFeCrAl, one of SGS candidate. The results show that samples treated in different ways can present distinguished transport properties. On the one hand, the arc-melted bulk samples exhibit a negative temperature dependence of resistivity accompanying with a negative magnetoresistance from 5-300K, revealing a normal transport behavior signifying for a metallic magnetic system. On the other hand, for the melt-spun ribbon samples, a positive temperature dependence of the resistivity as well as positive sign of magnetoresistance were observed, which implies that a semiconducting-like transport mechanism dominate in this sample. Based on our first principles analysis, this difference can be attributed to the occurrence of anti-site occupation between Co/Cr atoms in the compound. Our findings raised the possibility to tune the properties of SGS through proper sample treatments due to its atomic-occupation sensitivity.
Highly anisotropic physics in phosphorene
NASA Astrophysics Data System (ADS)
Ezawa, Motohiko
2015-04-01
Phosphorene, monolayer black phosphorus, is a highly anistropicmaterial, where the band structure is Dirac like in one direction and Schrödinger like in the other direction. We present several analytic formulas to demonstrate the electronic properties. The conductance is highly anisotropic reflecting the anisotropy of the band structure. We also deteminethe cyclotron motion in phosphoreneand Landau level quantization by using the Bohr-Sommerfeldquantization. We show that the Landau-level energy behaves as B2/3 as a function of external magnetic field, which is highly contrasted to the case of graphene where the Landau-level energy behaves as ?B.
Istomin, V. A.; Kustova, E. V.
2012-11-27
The aim of this work is to describe the influence of electronic excitation of electrically neutral particles in chemically non-equilibrium five-component N{sub 2}/N{sub 2}{sup +}/N/N{sup +}/e{sup -} and O{sub 2}/O{sub 2}{sup +}/O/O{sup +}/e{sup -} ionized mixtures without magnetic field. Using the modified Chapman-Enskog method, the transport coefficients are found in the temperature range 500-50000 K for various mixture compositions. The flow conditions, where excitation of electronic degrees of freedom is of importance for the evaluation of transport properties are specified.
Cosmin Obreja, Alexandru; Cristea, Dana; Radoi, Antonio; Gavrila, Raluca; Comanescu, Florin; Kusko, Cristian, E-mail: cristian.kusko@imt.ro [National Institute for R and D in Microtechnologies, 72996, Bucharest (Romania); Mihalache, Iuliana [National Institute for R and D in Microtechnologies, 72996, Bucharest (Romania); Physics Department, University Bucharest, P.O. Box MG-11, 077125 Bucharest (Romania)
2014-08-25
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.
Properties of transported African mineral dust aerosols in the Mediterranean region
NASA Astrophysics Data System (ADS)
Denjean, Cyrielle; Chevaillier, Servanne; Gaimoz, Cécile; Grand, Noel; Triquet, Sylvain; Zapf, Pascal; Loisil, Rodrigue; Bourrianne, Thierry; Freney, Evelyn; Dupuy, Regis; Sellegri, Karine; Schwarzenbock, Alfons; Torres, Benjamin; Mallet, Marc; Cassola, Federico; Prati, Paolo; Formenti, Paola
2015-04-01
The transport of mineral dust aerosols is a global phenomenon with strong climate implications. Depending on the travel distance over source regions, the atmospheric conditions and the residence time in the atmosphere, various transformation processes (size-selective sedimentation, mixing, condensation of gaseous species, and weathering) can modify the physical and chemical properties of mineral dust, which, in turn, can change the dust's optical properties. The model predictions of the radiative effect by mineral dust still suffer of the lack of certainty of these properties, and their temporal evolution with transport time. Within the frame of the ChArMex project (Chemistry-Aerosol Mediterranean experiment, http://charmex.lsce.ipsl.fr/), one intensive airborne campaign (ADRIMED, Aerosol Direct Radiative Impact in the regional climate in the MEDiterranean region, 06 June - 08 July 2013) has been performed over the Central and Western Mediterranean, one of the two major transport pathways of African mineral dust. In this study we have set up a systematic strategy to determine the optical, physical and optical properties of mineral dust to be compared to an equivalent dataset for dust close to source regions in Africa. This study is based on airborne observations onboard the SAFIRE ATR-42 aircraft, equipped with state of the art in situ instrumentation to measure the particle scattering and backscattering coefficients (nephelometer at 450, 550, and 700 nm), the absorption coefficient (PSAP at 467, 530, and 660 nm), the extinction coefficient (CAPS at 530 nm), the aerosol optical depth (PLASMA at 340 to 1640 nm), the size distribution in the extended range 40 nm - 30 µm by the combination of different particle counters (SMPS, USHAS, FSSP, GRIMM) and the chemical composition obtained by filter sampling. The chemistry and transport model CHIMERE-Dust have been used to classify the air masses according to the dust origin and transport. Case studies of dust transport from known but differing origins (source regions in Tunisia, Algeria, and Mauritania) and at different times after transport, will be presented. Results will be compared to equivalent measurements over source regions interpreted in terms of the evolution of the particle size distribution, chemical composition and optical properties.
Relationship between cell surface properties and transport of bacteria through soil
Gannon, J.T.; Manilal, V.B.; Alexander, M. (Cornell Univ., Ithaca, NY (USA))
1991-01-01
One means of bringing about the remediation of underground sites containing polluting chemicals is to inoculate the sites with bacteria able to metabolize those compounds. However, successful bioremediation of such sites requires the movement of the biodegradative bacteria through soil, aquifer solids, or groundwater. A study was conducted to relate the properties of Enterobacter, Pseudomonas, Bacillus, Achromobacter, Flavobacterium, and Arthrobacter strains to their transport with water moving through soil. The bacteria differed markedly in their extent of transport; their hydrophobicity, as measured by adherence to n-octane and by hydrophobic-interaction chromatography; and their net surface electrostatic charge, as determined by electrostatic interaction chromatography and by measurements of the zeta potential. Transport of the 19 strains through Kendaia loam or their retention by this soil was not correlated with hydrophobicities or net surface charges of the cells or the presence of capsules. Among 10 strains tested, the presence of flagella was also not correlated with transport. Retention was statistically related to cell size, with bacteria shorter than 1.0 {mu}m usually showing higher percentages of cells being transported through the soil. We suggest that more than one characteristic of bacterial cells determines whether the organisms are transported through soil with moving water.
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
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.
The surface and transport properties of meconium and reconstituted meconium solutions.
Rubin, B K; Tomkiewicz, R P; Patrinos, M E; Easa, D
1996-12-01
Passage of meconium in utero and subsequent pulmonary aspiration of meconium admixed with amniotic fluid is a major cause of neonatal respiratory distress. Airway clearance is the first defense of the lung, and clearance is dependent on the bulk physical (rheologic) as well as the surface properties of airway material. We therefore evaluated the surface adhesive properties and the transport properties of freshly passed meconium and of two dilutions of reconstituted, blended, meconium as used to mimic the effect of meconium passage into the amniotic fluid in animal models of meconium aspiration syndrome. Reconstituted and fresh meconium had similar physical and transport properties, including an extremely high interfacial (adhesion) tension and very poor transportability by either airflow or cilia. The similarities between the freshly passed and reconstituted meconium suggest that the latter is an adequate substitute for use in animal models of meconium aspiration syndrome. The high adhesiveness of meconium suggests a potential role for surfactant administration as an adhesive to improve airway clearance after meconium aspiration. PMID:8947959
Conformally flat polytropes for anisotropic matter
L. Herrera; A. Di Prisco; W. Barreto; J. Ospino
2014-11-05
We analyze in detail conformally flat spherically symmetric fluid distributions, satisfying a polytropic equation of state. Among the two possible families of relativistic polytropes, only one contains models which satisfy all the required physical conditions. The ensuing configurations are necessarily anisotropic and show interesting physical properties. Prospective applications of the presented models to the study of super-Chandrasekhar white dwarfs, are discussed.
Central Density Dependent Anisotropic Compact Stars
Mehedi Kalam; Farook Rahaman; Sk. Monowar Hossein; Saibal Ray
2012-12-27
Stars can be treated as self-gravitating fluid. In this connection, we propose a model for an anisotropic star under the relativistic framework of Krori-Barua (1975) spacetime. It is shown that the solutions are regular and singularity free. The uniqueness of the model is that interior physical properties of the star solely depend on the central density of the matter distribution.
NASA Astrophysics Data System (ADS)
Guedj, C.; Hung, L.; Zobelli, A.; Blaise, P.; Sottile, F.; Olevano, V.
2014-12-01
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.
Monotonic solution of heterogeneous anisotropic diffusion problems
NASA Astrophysics Data System (ADS)
Aricò, Costanza; Tucciarelli, Tullio
2013-11-01
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.
Transport properties of initially neutral gas disturbed by intense electron beam
NASA Astrophysics Data System (ADS)
Angus, Justin; Swanekamp, Steve; Schumer, Joseph; Mosher, Dave; Ottinger, Paul
2013-10-01
The behavior of intense electron beams (those with current densities on the order of hundreds of kA/cm2 and beam rise times on the order of 100 ns) traveling through gaseous mediums depends strongly on the transport properties of the medium. For example, the conductivity of the medium, which is very sensitive to the ionization state and temperature of the gas, has a strong influence on the beam behavior through the plasma return current. Since the beam is responsible for ionizing and heating the gas, self-consistently solving for the gas transport properties and the beam propagation is essential for an accurate description of the system. An advanced gas chemistry model to describe the transport properties of a strongly disturbed gaseous system is presented in this work. A focal point of this work is an accurate description of the medium's conductivity as the gas progresses from its weakly ionized state, where swarm models are valid, to a strongly ionized state where the Spitzer-Harm model applies. The behavior of intense electron beams (those with current densities on the order of hundreds of kA/cm2 and beam rise times on the order of 100 ns) traveling through gaseous mediums depends strongly on the transport properties of the medium. For example, the conductivity of the medium, which is very sensitive to the ionization state and temperature of the gas, has a strong influence on the beam behavior through the plasma return current. Since the beam is responsible for ionizing and heating the gas, self-consistently solving for the gas transport properties and the beam propagation is essential for an accurate description of the system. An advanced gas chemistry model to describe the transport properties of a strongly disturbed gaseous system is presented in this work. A focal point of this work is an accurate description of the medium's conductivity as the gas progresses from its weakly ionized state, where swarm models are valid, to a strongly ionized state where the Spitzer-Harm model applies. NRL Karle Fellowship
Finslerian grounds for four--directional anisotropic kinematics
G. S. Asanov
2005-10-13
Upon straightforward four--directional extension of the special--relativistic two--dimensional transformations to the four--dimensional case we lead to convenient totally anisotropic kinematic transformations, which prove to reveal many remarkable group and invariance properties. Such a promise is shown to ground the basic manifold with the Finslerian fourth-root metric function to measure length of relativistic four--vectors. Conversion to the framework of relativistic four--momentum is also elucidated. The relativity principle is strictly retained. An interesting particular algebra for subtraction and composition of three-dimensional relative velocities is arisen. The correspondence principle is operative in the sense that at small relative velocities the transformations introduced tend approximately to ordinary Lorentzian precursors. The transport synchronization remains valid. Abbreviation RF will be used for (inertial) reference frames. {\\bf Keywords:} special relativity, invariance, Finsler geometry.
Anisotropic simplicial minisuperspace model
Cristovao Correia da Silva; Ruth M. Williams
1999-06-04
The computation of the simplicial minisuperspace wavefunction in the case of anisotropic universes with a scalar matter field predicts the existence of a large classical Lorentzian universe like our own at late times
Enhancement of non-resonant dielectric cloaks using anisotropic composites
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
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.