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Sample records for microvascular transport properties

  1. Microvascular Transport and Tumor Cell Adhesion in the Microcirculation

    PubMed Central

    Fu, Bingmei M.; Liu, Yang

    2016-01-01

    One critical step in tumor metastasis is tumor cell adhesion to the endothelium forming the microvessel wall. Understanding this step may lead to new therapeutic concepts for tumor metastasis. Vascular endothelium forming the microvessel wall and the glycocalyx layer at its surface are the principal barriers to, and regulators of the material exchange between circulating blood and body tissues. The cleft between adjacent ECs (interendothelial cleft) is the principal pathway for water and solutes transport through the microvessel wall in health. It is also suggested to be the pathway for high molecular weight plasma proteins, leukocytes and tumor cells across microvessel walls in disease. Thus the first part of the review introduced the mathematical models for water and solutes transport through the interendothelial cleft. These models, combined with the experimental results from in vivo animal studies and electron microscopic observations, are used to evaluate the role of the endothelial surface glycocalyx, the junction strand geometry in the interendothelial cleft, and the surrounding extracellular matrix and tissue cells, as the determinants of microvascular transport. The second part of the review demonstrated how the microvascular permeability, hydrodynamic factors, microvascular geometry and cell adhesion molecules affect tumor cell adhesion in the microcirculation. PMID:22476895

  2. Oxidative stress modulates nucleobase transport in microvascular endothelial cells.

    PubMed

    Bone, Derek B J; Antic, Milica; Vilas, Gonzalo; Hammond, James R

    2014-09-01

    Purine nucleosides and nucleobases play key roles in the physiological response to vascular ischemia/reperfusion events. The intra- and extracellular concentrations of these compounds are controlled, in part, by equilibrative nucleoside transporter subtype 1 (ENT1; SLC29A1) and by equilibrative nucleobase transporter subtype 1 (ENBT1). These transporters are expressed at the membranes of numerous cell types including microvascular endothelial cells. We studied the impact of reactive oxygen species on the function of ENT1 and ENBT1 in primary (CMVEC) and immortalized (HMEC-1) human microvascular endothelial cells. Both cell types displayed similar transporter expression profiles, with the majority (>90%) of 2-chloro[(3)H]adenosine (nucleoside) uptake mediated by ENT1 and [(3)H]hypoxanthine (nucleobase) uptake mediated by ENBT1. An in vitro mineral oil-overlay model of ischemia/reperfusion had no effect on ENT1 function, but significantly reduced ENBT1 Vmax in both cell types. This decrease in transport function was mimicked by the intracellular superoxide generator menadione and could be reversed by the superoxide dismutase mimetic MnTMPyP. In contrast, neither the extracellular peroxide donor TBHP nor the extracellular peroxynitrite donor 3-morpholinosydnonimine (SIN-1) affected ENBT1-mediated [(3)H]hypoxanthine uptake. SIN-1 did, however, enhance ENT1-mediated 2-chloro[(3)H]adenosine uptake. Our data establish HMEC-1 as an appropriate model for study of purine transport in CMVEC. Additionally, these data suggest that the generation of intracellular superoxide in ischemia/reperfusion leads to the down-regulation of ENBT1 function. Modification of purine transport by oxidant stress may contribute to ischemia/reperfusion induced vascular damage and should be considered in the development of therapeutic strategies.

  3. Modeling of Cerebral Oxygen Transport Based on In vivo Microscopic Imaging of Microvascular Network Structure, Blood Flow, and Oxygenation

    PubMed Central

    Gagnon, Louis; Smith, Amy F.; Boas, David A.; Devor, Anna; Secomb, Timothy W.; Sakadžić, Sava

    2016-01-01

    Oxygen is delivered to brain tissue by a dense network of microvessels, which actively control cerebral blood flow (CBF) through vasodilation and contraction in response to changing levels of neural activity. Understanding these network-level processes is immediately relevant for (1) interpretation of functional Magnetic Resonance Imaging (fMRI) signals, and (2) investigation of neurological diseases in which a deterioration of neurovascular and neuro-metabolic physiology contributes to motor and cognitive decline. Experimental data on the structure, flow and oxygen levels of microvascular networks are needed, together with theoretical methods to integrate this information and predict physiologically relevant properties that are not directly measurable. Recent progress in optical imaging technologies for high-resolution in vivo measurement of the cerebral microvascular architecture, blood flow, and oxygenation enables construction of detailed computational models of cerebral hemodynamics and oxygen transport based on realistic three-dimensional microvascular networks. In this article, we review state-of-the-art optical microscopy technologies for quantitative in vivo imaging of cerebral microvascular structure, blood flow and oxygenation, and theoretical methods that utilize such data to generate spatially resolved models for blood flow and oxygen transport. These “bottom-up” models are essential for the understanding of the processes governing brain oxygenation in normal and disease states and for eventual translation of the lessons learned from animal studies to humans.

  4. Modeling of Cerebral Oxygen Transport Based on In vivo Microscopic Imaging of Microvascular Network Structure, Blood Flow, and Oxygenation

    PubMed Central

    Gagnon, Louis; Smith, Amy F.; Boas, David A.; Devor, Anna; Secomb, Timothy W.; Sakadžić, Sava

    2016-01-01

    Oxygen is delivered to brain tissue by a dense network of microvessels, which actively control cerebral blood flow (CBF) through vasodilation and contraction in response to changing levels of neural activity. Understanding these network-level processes is immediately relevant for (1) interpretation of functional Magnetic Resonance Imaging (fMRI) signals, and (2) investigation of neurological diseases in which a deterioration of neurovascular and neuro-metabolic physiology contributes to motor and cognitive decline. Experimental data on the structure, flow and oxygen levels of microvascular networks are needed, together with theoretical methods to integrate this information and predict physiologically relevant properties that are not directly measurable. Recent progress in optical imaging technologies for high-resolution in vivo measurement of the cerebral microvascular architecture, blood flow, and oxygenation enables construction of detailed computational models of cerebral hemodynamics and oxygen transport based on realistic three-dimensional microvascular networks. In this article, we review state-of-the-art optical microscopy technologies for quantitative in vivo imaging of cerebral microvascular structure, blood flow and oxygenation, and theoretical methods that utilize such data to generate spatially resolved models for blood flow and oxygen transport. These “bottom-up” models are essential for the understanding of the processes governing brain oxygenation in normal and disease states and for eventual translation of the lessons learned from animal studies to humans. PMID:27630556

  5. Modeling of Cerebral Oxygen Transport Based on In vivo Microscopic Imaging of Microvascular Network Structure, Blood Flow, and Oxygenation.

    PubMed

    Gagnon, Louis; Smith, Amy F; Boas, David A; Devor, Anna; Secomb, Timothy W; Sakadžić, Sava

    2016-01-01

    Oxygen is delivered to brain tissue by a dense network of microvessels, which actively control cerebral blood flow (CBF) through vasodilation and contraction in response to changing levels of neural activity. Understanding these network-level processes is immediately relevant for (1) interpretation of functional Magnetic Resonance Imaging (fMRI) signals, and (2) investigation of neurological diseases in which a deterioration of neurovascular and neuro-metabolic physiology contributes to motor and cognitive decline. Experimental data on the structure, flow and oxygen levels of microvascular networks are needed, together with theoretical methods to integrate this information and predict physiologically relevant properties that are not directly measurable. Recent progress in optical imaging technologies for high-resolution in vivo measurement of the cerebral microvascular architecture, blood flow, and oxygenation enables construction of detailed computational models of cerebral hemodynamics and oxygen transport based on realistic three-dimensional microvascular networks. In this article, we review state-of-the-art optical microscopy technologies for quantitative in vivo imaging of cerebral microvascular structure, blood flow and oxygenation, and theoretical methods that utilize such data to generate spatially resolved models for blood flow and oxygen transport. These "bottom-up" models are essential for the understanding of the processes governing brain oxygenation in normal and disease states and for eventual translation of the lessons learned from animal studies to humans. PMID:27630556

  6. Quantifying uncertainties in the microvascular transport of nanoparticles

    PubMed Central

    Lee, Tae-Rin; Greene, M. Steven; Jiang, Zhen; Kopacz, Adrian M.; Decuzzi, Paolo; Wing, Wei Chen; Liu, Wing Kam

    2014-01-01

    The character of nanoparticle dispersion in the microvasculature is a driving factor in nanoparticle-based therapeutics and bio-sensing. It is difficult, with current experimental and engineering capability, to understand dispersion of nanoparticles because their vascular system is more complex than mouse models and because nanoparticle dispersion is so sensitive to in vivo environments. Furthermore, uncertainty can not be ignored due to the high variation of location-specific vessel characteristics as well as variation across patients. In this paper, a computational method that considers uncertainty is developed to predict nanoparticle dispersion and transport characteristics in the microvasculature with a three step process. First, a computer simulation method is developed to predict blood flow and the dispersion of nanoparticles in the microvessels. Second, experiments for nanoparticle dispersion coefficients are combined with results from the computer model to suggest the true values of its unknown and unmeasurable parameters – red blood cell deformability and red blood cell interaction – using the Bayesian statistical framework. Third, quantitative predictions for nanoparticle tranpsort in the tumor microvasculature are made that consider uncertainty in the vessel diameter, flow velocity, and hematocrit. Our results show that nanoparticle transport is highly sensitive to the microvasculature. PMID:23872851

  7. Gestational Diabetes Reduces Adenosine Transport in Human Placental Microvascular Endothelium, an Effect Reversed by Insulin

    PubMed Central

    Salomón, Carlos; Westermeier, Francisco; Puebla, Carlos; Arroyo, Pablo; Guzmán-Gutiérrez, Enrique; Pardo, Fabián; Leiva, Andrea; Casanello, Paola; Sobrevia, Luis

    2012-01-01

    Gestational diabetes mellitus (GDM) courses with increased fetal plasma adenosine concentration and reduced adenosine transport in placental macrovascular endothelium. Since insulin modulates human equilibrative nucleoside transporters (hENTs) expression/activity, we hypothesize that GDM will alter hENT2-mediated transport in human placental microvascular endothelium (hPMEC), and that insulin will restore GDM to a normal phenotype involving insulin receptors A (IR-A) and B (IR-B). GDM effect on hENTs expression and transport activity, and IR-A/IR-B expression and associated cell signalling cascades (p42/44 mitogen-activated protein kinases (p42/44mapk) and Akt) role in hPMEC primary cultures was assayed. GDM associates with elevated umbilical whole and vein, but not arteries blood adenosine, and reduced hENTs adenosine transport and expression. IR-A/IR-B mRNA expression and p42/44mapk/Akt ratios (‘metabolic phenotype’) were lower in GDM. Insulin reversed GDM-reduced hENT2 expression/activity, IR-A/IR-B mRNA expression and p42/44mapk/Akt ratios to normal pregnancies (‘mitogenic phenotype’). It is suggested that insulin effects required IR-A and IR-B expression leading to differential modulation of signalling pathways restoring GDM-metabolic to a normal-mitogenic like phenotype. Insulin could be acting as protecting factor for placental microvascular endothelial dysfunction in GDM. PMID:22808198

  8. Characterization of cationic amino acid transporters and expression of endothelial nitric oxide synthase in human placental microvascular endothelial cells.

    PubMed

    Dye, J F; Vause, S; Johnston, T; Clark, P; Firth, J A; D'Souza, S W; Sibley, C P; Glazier, J D

    2004-01-01

    We investigated the expression and activity of arginine transporters and endothelial nitric oxide synthase (eNOS) in human placental microvascular endothelial cells (HPMEC). Using RT-PCR amplification products for eNOS, CAT1, CAT2A, CAT2B, CAT4, 4F2hc (CD98), rBAT and the light chains y+LAT1, y+LAT2, and b0+T1 were detected in HPMEC, but not B0+. Immunohistochemistry and Western blotting confirmed the presence of 4F2hc and CAT1 protein in HPMEC. 4F2hc-light chain dimers were indicated by a shift in molecular mass detected under nonreducing conditions. L-Arginine transport into HPMEC was independent of Na+ or Cl- and was inhibited by the neutral amino acid glutamine, but not by cystine. The Ki for glutamine inhibition was greater in the absence of Na+. Kinetic analysis supported a two-transporter model attributed to system y+L and system y+. Expression of eNOS in HPMEC was detectable by immunohistochemistry and ELISA but not by Western blotting. Activity of eNOS in HPMEC, measured over 48 h, either as the basal production of nitric oxide (NO) or as the accumulation of intracellular cGMP was not detectable. We conclude that HPMEC transport cationic amino acids by systems y+ and y+L and that basal eNOS expression and activity in these cells is low. PMID:14597568

  9. Regulation of monocarboxylic acid transporter-1 by cAMP dependent vesicular trafficking in brain microvascular endothelial cells.

    PubMed

    Uhernik, Amy L; Li, Lun; LaVoy, Nathan; Velasquez, Micah J; Smith, Jeffrey P

    2014-01-01

    In this study, a detailed characterization of Monocarboxylic Acid Transporter-1 (Mct1) in cytoplasmic vesicles of cultured rat brain microvascular endothelial cells shows them to be a diverse population of endosomes intrinsic to the regulation of the transporter by a brief 25 to 30 minute exposure to the membrane permeant cAMP analog, 8Br-cAMP. The vesicles are heterogeneous in size, mobility, internal pH, and co-localize with discreet markers of particular types of endosomes including early endosomes, clathrin coated vesicles, caveolar vesicles, trans-golgi, and lysosomes. The vesicular localization of Mct1 was not dependent on its N or C termini, however, the size and pH of Mct1 vesicles was increased by deletion of either terminus demonstrating a role for the termini in vesicular trafficking of Mct1. Using a novel BCECF-AM based assay developed in this study, 8Br-cAMP was shown to decrease the pH of Mct1 vesicles after 25 minutes. This result and method were confirmed in experiments with a ratiometric pH-sensitive EGFP-mCherry dual tagged Mct1 construct. Overall, the results indicate that cAMP signaling reduces the functionality of Mct1 in cerebrovascular endothelial cells by facilitating its entry into a highly dynamic vesicular trafficking pathway that appears to lead to the transporter's trafficking to autophagosomes and lysosomes.

  10. Regulation of Monocarboxylic Acid Transporter-1 by cAMP Dependent Vesicular Trafficking in Brain Microvascular Endothelial Cells

    PubMed Central

    Uhernik, Amy L.; Li, Lun; LaVoy, Nathan; Velasquez, Micah J.; Smith, Jeffrey P.

    2014-01-01

    In this study, a detailed characterization of Monocarboxylic Acid Transporter-1 (Mct1) in cytoplasmic vesicles of cultured rat brain microvascular endothelial cells shows them to be a diverse population of endosomes intrinsic to the regulation of the transporter by a brief 25 to 30 minute exposure to the membrane permeant cAMP analog, 8Br-cAMP. The vesicles are heterogeneous in size, mobility, internal pH, and co-localize with discreet markers of particular types of endosomes including early endosomes, clathrin coated vesicles, caveolar vesicles, trans-golgi, and lysosomes. The vesicular localization of Mct1 was not dependent on its N or C termini, however, the size and pH of Mct1 vesicles was increased by deletion of either terminus demonstrating a role for the termini in vesicular trafficking of Mct1. Using a novel BCECF-AM based assay developed in this study, 8Br-cAMP was shown to decrease the pH of Mct1 vesicles after 25 minutes. This result and method were confirmed in experiments with a ratiometric pH-sensitive EGFP-mCherry dual tagged Mct1 construct. Overall, the results indicate that cAMP signaling reduces the functionality of Mct1 in cerebrovascular endothelial cells by facilitating its entry into a highly dynamic vesicular trafficking pathway that appears to lead to the transporter's trafficking to autophagosomes and lysosomes. PMID:24454947

  11. 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. 11 ; however, the task requires massive computations and is therefore difficult to implement from the practical standpoint. Here, instead, we focus on a deterministic approach to the problem, where the geometry and spatial configuration of the particles comprising the included phase are given and the solution to the microscale problem is therefore sought analytically. As examples, we study the effective thermal conductivity of solid reinforced materials (Sect. 10.1), the effective viscosity of non-colloidal suspensions (Sect. 10.2), the effective permeability of porous materials (10.3) and the effective self- and gradient diffusivities of colloidal suspensions (Sect. 10.4). Then, in Sect. 10.5, an alternative dynamic definition of the transport coefficients is considered, which can also serve as a basis to determine the effective properties of complex systems.

  12. Microvascular rarefaction

    PubMed Central

    2010-01-01

    The goals of this presentation are twofold: (1) to briefly sketch the field of vascular rarefaction as a key component of various fibrotic diseases and (2) to illustrate it with four vignettes depicting diverse mechanisms of microvascular rarefaction. Specifically, I shall describe migratory and angiogenic incompetence of endothelial cells under conditions of reduced bioavailability of nitric oxide, role of endothelial-to-mesenchymal cell and mesenchymal stem cell-to-endothelial reprogramming, and potential role of antiangiogenic peptides in the development of graft vascular disease as exemplified by chronic allograft nephropathy PMID:20592859

  13. Transport properties of uranium dioxide

    SciTech Connect

    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.

  14. Effects of the physicochemical properties of titanium dioxide nanoparticles, commonly used as sun protection agents, on microvascular endothelial cells.

    PubMed

    Strobel, Claudia; Torrano, Adriano A; Herrmann, Rudolf; Malissek, Marcelina; Bräuchle, Christoph; Reller, Armin; Treuel, Lennart; Hilger, Ingrid

    2014-01-01

    Until now, the potential effects of titanium dioxide (TiO2) nanoparticles on endothelial cells are not well understood, despite their already wide usage. Therefore, the present work characterizes six TiO2 nanoparticle samples in the size range of 19 × 17 to 87 × 13 nm, which are commonly present in sun protection agents with respect to their physicochemical properties (size, shape, ζ-potential, agglomeration, sedimentation, surface coating, and surface area), their interactions with serum proteins and biological impact on human microvascular endothelial cells (relative cellular dehydrogenase activity, adenosine triphosphate content, and monocyte chemoattractant protein-1 release). We observed no association of nanoparticle morphology with the agglomeration and sedimentation behavior and no variations of the ζ-potential (-14 to -19 mV) in dependence on the surface coating. In general, the impact on endothelial cells was low and only detectable at concentrations of 100 μg/ml. Particles containing a rutile core and having rod-like shape had a stronger effect on cell metabolism than those with anatase core and elliptical shape (relative cellular dehydrogenase activity after 72 h: 60 vs. 90 %). Besides the morphology, the nanoparticle shell constitution was found to influence the metabolic activity of the cells. Upon cellular uptake, the nanoparticles were localized perinuclearly. Considering that in the in vivo situation endothelial cells would come in contact with considerably lower nanoparticle amounts than the lowest-observable adverse effects level (100 μg/ml), TiO2 nanoparticles can be considered as rather harmless to humans under the investigated conditions.

  15. Transport Properties for Combustion Modeling

    SciTech Connect

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

    2010-02-19

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

  16. Oxygen transport in a three-dimensional microvascular network incorporated with early tumour growth and preexisting vessel cooption: numerical simulation study.

    PubMed

    Cai, Yan; Zhang, Jie; Wu, Jie; Li, Zhi-yong

    2015-01-01

    We propose a dynamic mathematical model of tissue oxygen transport by a preexisting three-dimensional microvascular network which provides nutrients for an in situ cancer at the very early stage of primary microtumour growth. The expanding tumour consumes oxygen during its invasion to the surrounding tissues and cooption of host vessels. The preexisting vessel cooption, remodelling and collapse are modelled by the changes of haemodynamic conditions due to the growing tumour. A detailed computational model of oxygen transport in tumour tissue is developed by considering (a) the time-varying oxygen advection diffusion equation within the microvessel segments, (b) the oxygen flux across the vessel walls, and (c) the oxygen diffusion and consumption within the tumour and surrounding healthy tissue. The results show the oxygen concentration distribution at different time points of early tumour growth. In addition, the influence of preexisting vessel density on the oxygen transport has been discussed. The proposed model not only provides a quantitative approach for investigating the interactions between tumour growth and oxygen delivery, but also is extendable to model other molecules or chemotherapeutic drug transport in the future study.

  17. Transport properties of ceramic composites

    SciTech Connect

    Starr, T.L.; Hablutzel, N.

    1996-08-01

    Instrumentation and procedures have been completed for measurement of gas permeability and mass diffusivity of fiber preforms and porous materials. Results are reported for composites reinforced with Nicalon fiber in cloth lay-up and 3-D weave and with Nextel fiber in multi-layer braid. Measured permeability values range from near 100 to less than 0.1 darcies. Mass diffusivity is reported as a structure factor relating the diffusion through the porous material to that in free space. This measure is independent of the diffusing species and depends only on the pore structure of the material. Measurements are compared to predictions of a node-bond model for gas transport. Model parameters adjusted to match measured transport properties relate to physical microstructure features of the different architectures. Combination of this transport model with the CVI process model offers a predictive method to evaluate the densification behavior of various fiber preforms.

  18. 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.

  19. Transport properties of ceramic composites

    SciTech Connect

    Starr, T.L.

    1995-08-01

    This project involves experimental and modeling investigation of the transport properties of chemical vapor infiltration (CVI) preforms and densified composites, with particular emphasis on gas permeability and mass diffusivity. The results of this work will be useful both for on-going CVI process development and for evaluation and optimization of composite materials for fossil energy applications. With preforms made with 500 filaments/tow Nicalon at 40 vol% fiber loading, permeability values are similar for square-weave cloth layup and 3-D weave at low density. At greater densification the 3-D weave permeability is lower and approaches zero with significantly more closed porosity than the cloth layup. For filament wound preforms we were unable to make reliable measurements with the available materials. A model for gas transport in these materials utilizes percolation theory concepts. The ultimate achievable density is related to the closing of a continuous gas path through the preform. As the density approaches this limit the gas permeability and diffusivity vanish exponentially. The value of this limit is controlled primarily by the preform fiber architecture. The observed difference between the cloth layup and 3-D weave materials is due to the larger pores at tow crossing points found in the 3-D weave.

  20. Integration of Self-Assembled Microvascular Networks with Microfabricated PEG-Based Hydrogels

    PubMed Central

    Cuchiara, Michael P.; Gould, Daniel J.; McHale, Melissa K.; Dickinson, Mary E.

    2013-01-01

    Despite tremendous efforts, tissue engineered constructs are restricted to thin, simple tissues sustained only by diffusion. The most significant barrier in tissue engineering is insufficient vascularization to deliver nutrients and metabolites during development in vitro and to facilitate rapid vascular integration in vivo. Tissue engineered constructs can be greatly improved by developing perfusable microvascular networks in vitro in order to provide transport that mimics native vascular organization and function. Here a microfluidic hydrogel is integrated with a self-assembling pro-vasculogenic co-culture in a strategy to perfuse microvascular networks in vitro. This approach allows for control over microvascular network self-assembly and employs an anastomotic interface for integration of self-assembled micro-vascular networks with fabricated microchannels. As a result, transport within the system shifts from simple diffusion to vessel supported convective transport and extra-vessel diffusion, thus improving overall mass transport properties. This work impacts the development of perfusable prevascularized tissues in vitro and ultimately tissue engineering applications in vivo. PMID:23536744

  1. Transport properties of rippled graphene.

    PubMed

    Zwierzycki, Maciej

    2014-04-01

    The exceptionally high mobility of carriers in graphene is one of its defining characteristics, especially in view of potential applications. Therefore it is of both practical and fundamental importance to understand the mechanisms responsible for limiting the values of the mobility. The aim of the paper is to study theoretically one such mechanism, i.e. scattering on ripples. The transport properties of rippled graphene are studied using the single-band tight-binding model. Both the bond-length variation, corresponding to the vector potential in the effective mass picture, and the fluctuating scalar potential are included in the formalism. The samples are modeled as self-similar surfaces characterized by the roughness exponent, with values ranging from those typical for graphene on SiO2 to those seen for suspended samples. The range of calculated resistivities and mobilities overlaps with those from experiments. The results presented in this paper support the notion of rippling as one of the important factors limiting the mobility of carriers in graphene.

  2. The transport properties of activated carbon fibers

    SciTech Connect

    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.

  3. TRANSPORT PROPERTY MEASUREMENTS OF HFC-236EA

    EPA Science Inventory

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

  4. The Transport Properties of Activated Carbon Fibers

    DOE R&D Accomplishments Database

    di Vittorio, S. L.; Dresselhaus, M. S.; Endo, M.; 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.

  5. Immortalized human cerebral microvascular endothelial cells maintain the properties of primary cells in an in vitro model of immune migration across the blood brain barrier

    PubMed Central

    Daniels, Brian P.; Cruz-Orengo, Lillian; Pasieka, Tracy Jo; Couraud, Pierre-Olivier; Romero, Ignacio A.; Weksler, Babette; Cooper, John A.; Doering, Tamara L.; Klein, Robyn S.

    2012-01-01

    The immortalized human cerebral microvascular endothelial cell line HCMEC/D3 presents a less expensive and more logistically feasible alternative to primary human brain microvascular endothelial cells (HBMEC’s) for use in constructing in vitro models of the blood brain barrier (BBB). However, the fidelity of the HCMEC/D3 cell line to primary HBMEC’s in studies of immune transmigration has yet to be established. Flow cytometric analysis of primary human leukocyte migration across in vitro BBB’s generated with either HCMEC/D3 or primary HBMEC’s revealed that HCMEC/D3 maintains the immune barrier properties of primary HBMEC’s. Leukocyte migration responses and inflammatory cytokine production were statistically indistinguishable between both endothelial cell types, and both cell types responded similarly to astrocyte coculture, stimulation of leukocytes with phorbol myristate acetate (PMA) and ionomycin, and inflammatory cytokine treatment. This report is the first to validate the HCMEC/D3 cell line in a neuroimmunological experimental system via direct comparison to primary HBMEC’s, demonstrating remarkable fidelity in terms of barrier resistance, immune migration profiles, and responsiveness to inflammatory cytokines. Moreover, we report novel findings demonstrating that interaction effects between immune cells and resident CNS cells are preserved in HCMEC/D3, suggesting that important characteristics of neuroimmune interactions during CNS inflammation are preserved in systems utilizing this cell line. Together, these findings demonstrate that HCMEC/D3 is a valid and powerful tool for less expensive and higher throughput in vitro investigations of immune migration at the BBB. PMID:23068604

  6. Hemorheology and Microvascular Disorders

    PubMed Central

    Cho, Daniel J

    2011-01-01

    The present review presents basic concepts of blood rheology related to vascular diseases. Blood flow in large arteries is dominated by inertial forces exhibited at high flow velocities, while viscous forces (i.e., blood rheology) play an almost negligible role. When high flow velocity is compromised by sudden deceleration as at a bifurcation, endothelial cell dysfunction can occur along the outer wall of the bifurcation, initiating inflammatory gene expression and, through mechanotransduction, the cascade of events associated with atherosclerosis. In sharp contrast, the flow of blood in microvessels is dominated by viscous shear forces since the inertial forces are negligible due to low flow velocities. Shear stress is a critical parameter in microvascular flow, and a force-balance approach is proposed for determining microvascular shear stress, accounting for the low Reynolds numbers and the dominance of viscous forces over inertial forces. Accordingly, when the attractive forces between erythrocytes (represented by the yield stress of blood) are greater than the shear force produced by microvascular flow, tissue perfusion itself cannot be sustained, leading to capillary loss. The yield stress parameter is presented as a diagnostic candidate for future clinical research, specifically, as a fluid dynamic biomarker for microvascular disorders. The relation between the yield stress and diastolic blood viscosity (DBV) is described using the Casson model for viscosity, from which one may be able determine thresholds of DBV where the risk of microvascular disorders is high. PMID:21779279

  7. What Causes Coronary Microvascular Disease?

    MedlinePlus

    ... Living With Clinical Trials Links Related Topics Angina Atherosclerosis Coronary Heart Disease Coronary Heart Disease Risk Factors ... Microvascular Disease? The same risk factors that cause atherosclerosis may cause coronary microvascular disease. Atherosclerosis is a ...

  8. 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.

  9. Microvascular invasion in hepatocellular carcinoma

    PubMed Central

    Ünal, Emre; İdilman, İlkay Sedakat; Akata, Deniz; Özmen, Mustafa Nasuh; Karçaaltıncaba, Muşturay

    2016-01-01

    Microvascular invasion is a crucial histopathologic prognostic factor for hepatocellular carcinoma. We reviewed the literature and aimed to draw attention to clinicopathologic and imaging findings that may predict the presence of microvascular invasion in hepatocellular carcinoma. Imaging findings suggesting microvascular invasion are disruption of capsule, irregular tumor margin, peritumoral enhancement, multifocal tumor, increased tumor size, and increased glucose metabolism on positron emission tomography-computed tomography. In the presence of typical findings, microvascular invasion may be predicted. PMID:26782155

  10. Targeting brain microvascular endothelial cells: a therapeutic approach to neuroprotection against stroke

    PubMed Central

    Yu, Qi-jin; Tao, Hong; Wang, Xin; Li, Ming-chang

    2015-01-01

    Brain microvascular endothelial cells form the interface between nervous tissue and circulating blood, and regulate central nervous system homeostasis. Brain microvascular endothelial cells differ from peripheral endothelial cells with regards expression of specific ion transporters and receptors, and contain fewer fenestrations and pinocytotic vesicles. Brain microvascular endothelial cells also synthesize several factors that influence blood vessel function. This review describes the morphological characteristics and functions of brain microvascular endothelial cells, and summarizes current knowledge regarding changes in brain microvascular endothelial cells during stroke progression and therapies. Future studies should focus on identifying mechanisms underlying such changes and developing possible neuroprotective therapeutic interventions. PMID:26807131

  11. Transport Properties and Transport Phenomena in Casting Nickel Superalloys

    NASA Astrophysics Data System (ADS)

    Felicelli, S. D.; Sung, P. K.; Poirier, D. R.; Heinrich, J. C.

    1998-11-01

    Nickel superalloys that are used in the high-temperature regions of gas-turbine engines are cast by directional solidification (DS). In the DS processes, the castings are cooled from below, and three zones exist during solidification: (1) an all-solid zone at the bottom, (2) a "mushy zone" that is comprised of solid and liquid material, and (3) an overlying all-liquid zone. Computer simulations can be useful in predicting the complex transport phenomena that occur during solidification, but realistic simulations require accurate values of the transport properties. In addition to transport properties, the thermodynamic equilibria between the solid and liquid during solidification must also be known with reasonable accuracy. The importance of using reasonably accurate estimations of the transport properties is illustrated by two-dimensional simulations of the convection during solidification and the coincidental macrosegregation in the DS castings of multicomponent Ni-base alloys. In these simulations, we examine the sensitivity of the calculated results to measured partition ratios, thermal expansion coefficients, and viscosities that are estimated by regression analyses and correlations of existing property data.

  12. Computing Thermodynamic And Transport Properties Of Air

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    EQAIRS computer program is set of FORTRAN 77 routines for computing thermodynamic and transport properties of equilibrium air for temperatures from 100 to 30,000 K. Computes properties from 11-species, curve-fit mathematical model. Successfully implemented on DEC VAX-series computer running VMS, Sun4-series computer running SunOS, and IBM PC-compatible computer running MS-DOS.

  13. Reduction in cardiolipin decreases mitochondrial spare respiratory capacity and increases glucose transport into and across human brain cerebral microvascular endothelial cells.

    PubMed

    Nguyen, Hieu M; Mejia, Edgard M; Chang, Wenguang; Wang, Ying; Watson, Emily; On, Ngoc; Miller, Donald W; Hatch, Grant M

    2016-10-01

    Microvessel endothelial cells form part of the blood-brain barrier, a restrictively permeable interface that allows transport of only specific compounds into the brain. Cardiolipin is a mitochondrial phospholipid required for function of the electron transport chain and ATP generation. We examined the role of cardiolipin in maintaining mitochondrial function necessary to support barrier properties of brain microvessel endothelial cells. Knockdown of the terminal enzyme of cardiolipin synthesis, cardiolipin synthase, in hCMEC/D3 cells resulted in decreased cellular cardiolipin levels compared to controls. The reduction in cardiolipin resulted in decreased mitochondrial spare respiratory capacity, increased pyruvate kinase activity, and increased 2-deoxy-[(3) H]glucose uptake and glucose transporter-1 expression and localization to membranes in hCMEC/D3 cells compared to controls. The mechanism for the increase in glucose uptake was an increase in adenosine-5'-monophosphate kinase and protein kinase B activity and decreased glycogen synthase kinase 3 beta activity. Knockdown of cardiolipin synthase did not affect permeability of fluorescent dextran across confluent hCMEC/D3 monolayers grown on Transwell(®) inserts. In contrast, knockdown of cardiolipin synthase resulted in an increase in 2-deoxy-[(3) H]glucose transport across these monolayers compared to controls. The data indicate that in hCMEC/D3 cells, spare respiratory capacity is dependent on cardiolipin. In addition, reduction in cardiolipin in these cells alters their cellular energy status and this results in increased glucose transport into and across hCMEC/D3 monolayers. Microvessel endothelial cells form part of the blood-brain barrier, a restrictively permeable interface that allows transport of only specific compounds into the brain. In human adult brain endothelial cell hCMEC/D3 monolayers cultured on Transwell(®) plates, knockdown of cardiolipin synthase results in decrease in mitochondrial

  14. Transmural variation and anisotropy of microvascular flow conductivity in the rat myocardium

    PubMed Central

    Smith, Amy F.; Shipley, Rebecca J.; Lee, Jack; Sands, Gregory B.; LeGrice, Ian J.; Smith, Nicolas P.

    2015-01-01

    Transmural variations in the relationship between structural and fluid transport properties of myocardial capillary networks are determined via continuum modelling approaches using recent three-dimensional (3D) data on the microvascular structure. Specifically, the permeability tensor, which quantifies the inverse of the blood flow resistivity of the capillary network, is computed by volume-averaging flow solutions in synthetic networks with geometrical and topological properties derived from an anatomically-detailed microvascular data set extracted from the rat myocardium. Results show that the permeability is approximately ten times higher in the principal direction of capillary alignment (the ‘longitudinal’ direction) than perpendicular to this direction, reflecting the strong anisotropy of the microvascular network. Additionally, a 30% increase in capillary diameter from subepicardium to subendocardium is shown to translate to a 130% transmural rise in permeability in the longitudinal capillary direction. This result supports the hypothesis that perfusion is preferentially facilitated during diastole in the subendocardial microvasculature to compensate for the severely-reduced systolic perfusion in the subendocardium. PMID:24866569

  15. Thermodynamic and transport properties of gaseous tetrafluoromethane in chemical equilibrium

    NASA Technical Reports Server (NTRS)

    Hunt, J. L.; Boney, L. R.

    1973-01-01

    Equations and in computer code are presented for the thermodynamic and transport properties of gaseous, undissociated tetrafluoromethane (CF4) in chemical equilibrium. The computer code calculates the thermodynamic and transport properties of CF4 when given any two of five thermodynamic variables (entropy, temperature, volume, pressure, and enthalpy). Equilibrium thermodynamic and transport property data are tabulated and pressure-enthalpy diagrams are presented.

  16. Transport properties of individual C60-molecules

    NASA Astrophysics Data System (ADS)

    Géranton, G.; Seiler, C.; Bagrets, A.; Venkataraman, L.; Evers, F.

    2013-12-01

    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 sp2-hybridization into an sp3-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.

  17. Electronic transport properties of silicon clusters

    NASA Astrophysics Data System (ADS)

    Matsuura, Yukihito

    2016-02-01

    The electronic transport properties of silicon clusters were examined via theoretical calculations using the first-principles method. Additionally, p-type doping and n-type doping were analyzed by calculating conductance and current of boron- and phosphorus-doped silicon clusters. The p-type doping and n-type doping provided a new transmission peak at an energy level around the Fermi level to increase conductance. Furthermore, simultaneous boron and phosphorus doping resulted in noticeable rectifying characteristics, with the current drive in forward bias being three times higher than that in the reverse bias. A p-n junction was achieved even on a molecular scale.

  18. Microvascular decompression for intractable singultus.

    PubMed

    Saito, Atsushi; Hatayama, Toru; Kon, Hiroyuki; Nakamura, Taigen; Sasaki, Tatsuya

    2016-10-01

    Intractable singultus due to cerebrovascular disease is very rare. We report a case of intractable singultus that improved after microvascular decompression and present a literature review. The patient was a 58-year-old man with a 30-year history of persistent singultus. Its frequency and duration gradually increased and it was resistant to multiple medical treatments. Microvascular decompression to relieve pressure on the anterolateral surface of the lower medulla oblongata from the vertebral artery resulted in the resolution of singultus. Patients with intractable idiopathic singultus who fail to respond to medical therapy need to be considered for the evaluation of cerebrovascular diseases and microvascular decompression. PMID:27335312

  19. Electronic transport properties of (fluorinated) metal phthalocyanine

    NASA Astrophysics Data System (ADS)

    Fadlallah, M. M.; Eckern, U.; Romero, A. H.; Schwingenschlögl, U.

    2016-01-01

    The magnetic and transport properties of the metal phthalocyanine (MPc) and F16MPc (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn and Ag) families of molecules in contact with S-Au wires are investigated by density functional theory within the local density approximation, including local electronic correlations on the central metal atom. The magnetic moments are found to be considerably modified under fluorination. In addition, they do not depend exclusively on the configuration of the outer electronic shell of the central metal atom (as in isolated MPc and F16MPc) but also on the interaction with the leads. Good agreement between the calculated conductance and experimental results is obtained. For M = Ag, a high spin filter efficiency and conductance is observed, giving rise to a potentially high sensitivity for chemical sensor applications.

  20. Transport properties of quark and gluon plasmas

    SciTech Connect

    Heiselberg, H.

    1993-12-01

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

  1. Electrical transport properties of silicon surfaces

    NASA Astrophysics Data System (ADS)

    Yoo, Kwonjae

    The understanding and utilization of electronic transport phenomena in low-dimensional, quantum-confined structures is of enormous scientific and technological interest. We have studied the electrical transport properties of systems that are quantum confined in one dimension but periodic in the other two dimensions, namely surfaces and ultrathin film materials. The electrical conductance of atomically clean, reconstructed silicon surfaces and interfaces was measured as a function of temperature in ultrahigh vacuum using the classical four-point probe technique. We employed Silicon on Insulator (SOI) technology to enhance the surface sensitivity of the four-point probe measurements. High-quality ohmic contacts were fabricated using ion-implantation. The Si(100)2 x 1 surface reconstruction consists of a two-dimensional, anti-ferromagnetic c(4 x 2) array of buckled silicon dimers. The surface undergoes a c(4 x 2) → 2 x 1 order-disorder transition near T = 200 K. Above 200 K, dimers fluctuate rapidly and the long-range c(4 x 2) ordering is destroyed. The conductance of this two-dimensional system has a temperature-dependence that is characteristic of a metal. The surface conductance appears closely correlated with the order parameter of the low-temperature c(4 x 2) structure. Thermally activated flip-flop motion of the Si dimers thus appears to be the dominant scattering mechanism. Recent high-resolution photoemission experiments indicate that the Si(111)7 x 7 surface reconstruction is a two-dimensional, correlated metal. The surface electrical conductivity decreases with increasing temperature, thus confirming metallic transport. However, conductivity measurements on ultrathin SOI indicate insulating behavior. The origin of this discrepancy is not understood and requires further investigation of the sheet conductance as a function of the SOI layer thickness. The Ga/Si(112) interface consists of a self-assembled, mesoscopic array of atomic Ga wires on a high-index Si

  2. 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.

  3. Transport properties of alkali metal doped fullerides

    SciTech Connect

    Yadav, Daluram Yadav, Nishchhal

    2015-07-31

    We have studied the intercage interactions between the adjacent C{sub 60} 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-C{sub 60} 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, T{sub c}, is obtained in a situation when the free electrons in lowest molecular orbital are coupled with alkali-C{sub 60} phonons as 5 K, which is much lower as compared to reported T{sub c} (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.

  4. Tuning anisotropic electronic transport properties of phosphorene via substitutional doping.

    PubMed

    Guo, Caixia; Xia, Congxin; Fang, Lizhen; Wang, Tianxing; Liu, Yufang

    2016-10-01

    Using first-principles calculations, we studied the anisotropic electronic transport properties of pristine and X-doped phosphorene (X = B, Al, Ga, C, Si, Ge, N, As, O, S, and Se atoms). The results show that doping different elements can induce obviously different electronic transport characteristics. Moreover, isovalent doping maintains semiconducting characteristics and anisotropic transport properties, while group IV and VI atoms doping can induce metal properties. Meanwhile, Al and Ga substituting P decrease the anisotropic behaviors of transport, and other atom doping still preserves anisotropic characteristics. Interestingly, obvious negative differential resistance behaviors can be observed in C, Si, Ge, O, S, and Se-doped phosphorene.

  5. Globular Adiponectin Enhances Muscle Insulin Action via Microvascular Recruitment and Increased Insulin Delivery

    PubMed Central

    Zhao, Lina; Chai, Weidong; Fu, Zhuo; Dong, Zhenhua; Aylor, Kevin W.; Barrett, Eugene J.; Cao, Wenhong; Liu, Zhenqi

    2014-01-01

    Rationale Adiponectin enhances insulin action and induces nitric oxide–dependent vasodilatation. Insulin delivery to muscle microcirculation and transendothelial transport are 2 discrete steps that limit insulin's action. We have shown that expansion of muscle microvascular surface area increases muscle insulin delivery and action. Objective To examine whether adiponectin modulates muscle microvascular recruitment thus insulin delivery and action in vivo. Methods and Results Overnight fasted adult male rats were studied. We determined the effects of adiponectin on muscle microvascular recruitment, using contrast-enhanced ultrasound, on insulin-mediated microvascular recruitment and whole-body glucose disposal, using contrast-enhanced ultrasound and insulin clamp, and on muscle insulin clearance and uptake with 125I-insulin. Globular adiponectin potently increased muscle microvascular blood volume without altering microvascular blood flow velocity, leading to a significantly increased microvascular blood flow. This was paralleled by a ≈30% to 40% increase in muscle insulin uptake and clearance, and ≈30% increase in insulin-stimulated whole-body glucose disposal. Inhibition of endothelial nitric oxide synthase abolished globular adiponectin-mediated muscle microvascular recruitment and insulin uptake. In cultured endothelial cells, globular adiponectin dose-dependently increased endothelial nitric oxide synthase phosphorylation but had no effect on endothelial cell internalization of insulin. Conclusions Globular adiponectin increases muscle insulin uptake by recruiting muscle microvasculature, which contributes to its insulin-sensitizing action. PMID:23459195

  6. Transport properties of graphene and its application

    NASA Astrophysics Data System (ADS)

    Lu, Jianming

    This thesis focuses on the transport properties of graphene, a new emerging atomically thin, two-dimensional material, with and without the application of a magnetic field. Because of its high mobility, graphene is a promising candidate for Extraordinary Magnetoresistance (EMR) devices. The magnetoresistance of an EMR device arises mainly from its geometry rather than the intrinsic response of the material itself to an applied magnetic field. As a result, the geometric parameters play an important role in its performance. Experiments employing various combinations of geometric parameters and graphene of different quality levels were conducted to determine the optimal results. We found that the optimized parameters vary for different applied magnetic fields. In a magnetic field of 9 Tesla, magnetoresistance up to 55,000% was observed. In addition, Finite Element Analysis (FEA) simulations are used to complement the experiments and explain the measured magnetoresistance. The excellent agreement between the simulations and experimental results indicates that theoretical simulation can be used as a convenient method to explore EMR devices with alternative geometries or materials. The anomalous quantum Hall effect is one of the most exciting properties of graphene. The observation of the v=0 state above a critical magnetic field is closely related to the quality of the graphene, where a higher quality reduces the critical field needed. With our high quality graphene sample, the critical field is reduced to 6.75 Tesla. Moreover, from 6.75 T to 9T, the resistance at the cross point of the metal-insulator transition (MIT) is very close to h/2e2, which resembles the case of a disordered two-dimensional electron gas (2DEG) and may indicate a similar physical mechanism. In addition to the magnetotransport measurements, the current saturation of graphene in a high electric field is studied both theoretically and experimentally. This thesis focuses primarily on bilayer graphene

  7. Neoclassical Transport Properties of Tokamak Plasmas

    SciTech Connect

    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)

  8. Direct ink writing of microvascular networks

    NASA Astrophysics Data System (ADS)

    Wu, Willie

    Nature is replete with examples of embedded microvascular systems that enable efficient fluid flow and distribution for autonomic healing, cooling, and energy harvesting. The ability to incorporate microvascular networks in functional materials systems is therefore both scientifically and technologically important. In this PhD thesis, the direct-write assembly of planar and 3D biomimetic microvascular networks within polymer and hydrogel matrices is demonstrated. In addition, the influence of network design of fluid transport efficiency is characterized. Planar microvascular networks composed of periodic lattices of uniformal microchannels and hierarchical, branching architectures are constructed by direct-write assembly of a fugitive organic ink. Several advancements are required to facilitate their patterning, including pressure valving, dual ink printing, and dynamic pressure variation to allow tunable control of ink deposition. The hydraulic conductance is measured using a high pressure flow meter as a function of network design. For a constant vascular volume and areal coverage, 2- and 4-generation branched architectures that obey Murray's Law exhibited the highest hydraulic conductivity. These experimental observations are in good agreement with predictions made by analytic models. 3D microvascular networks are fabricated by omnidirectional printing a fugitive organic ink into a photopolymerizable hydrogel matrix that is capped with fluid filler of nearly identical composition. Using this approach, 3D networks of arbitrary design can be patterned. After ink deposition is complete, the matrix and fluid filler are chemically cross-linked via UV irradiation, and the ink is removed by liquefication. Aqueous solutions composed of a triblock copolymer of polyethylene oxide (PEO)-polypropylene oxide (PPO)-PEO constitute the materials system of choice due to their thermal- and concentration-dependent phase behavior. Specifically, the fugitive ink consists of a 23 w

  9. New technique to quantitate regional pulmonary microvascular transit times from dynamic x-ray CT images

    NASA Astrophysics Data System (ADS)

    Tajik, Jehangir K.; Tran, Binh Q.; Hoffman, Eric A.

    1998-07-01

    Microvascular red blood cell mean transit time is a crucial parameter underlying basic pulmonary physiology. Dynamic x-ray CT imaging during bolus radiopaque tracer injection offers the ability to make functional measurements throughout the lungs, but is not able to resolve individual microvascular beds. We have implemented a model-free Fast Fourier Transform deconvolution algorithm to extract the microvascular transport characteristics from the acquired time-intensity data. The deconvolved feeding arterial bolus input curves and corresponding regional pulmonary parenchymal 'response' functions provide measures of regional pulmonary tracer residence times, allowing calculation of microvascular transit times for different spatial regions of the pulmonary system. The acquired feeding (main) pulmonary artery and regional pulmonary parenchyma time-intensity curves were fit to gamma variate functions which were then sampled with a temporal resolution of 0.1 seconds. Deconvolution of the feeding arterial and regional parenchymal curves consistently results in bimodal regional residue functions. The two modes consist of a relatively large, sharp, narrow peak approximating a delta function followed by a smaller more dispersed curve. The sharp, narrow peak appears to be due to small artery inclusion in the sampled parenchymal region (partial volume effects). The magnitude of the dominant arterial peak decreases as sampling locations are moved from the less expanded dependent to the more expanded non-dependent lung regions of supine dogs. Mathematical separation of the two modes allowed isolation of the arterial and microvascular components. The shape and transit times of the putative microvascular components agree well with results from similar measurements via microfocal angiography and in vivo microscopy. Reconvolving the microvascular component with the input curve results in a corrected parenchymal curve representing the regional microvascular transport characteristics

  10. 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.

  11. PROPERTIES OF INTERFACES AND TRANSPORT ACROSS THEM

    EPA Science Inventory

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

  12. Transport properties of pancreatic cancer describe gemcitabine delivery and response

    PubMed Central

    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

  13. Lagrangian transport properties of pulmonary interfacial flows.

    PubMed

    Smith, Bradford J; Lukens, Sarah; Yamaguchi, Eiichiro; Gaver, Donald P

    2011-11-01

    Disease states characterized by airway fluid occlusion and pulmonary surfactant insufficiency, such as respiratory distress syndrome, have a high mortality rate. Understanding the mechanics of airway reopening, particularly involving surfactant transport, may provide an avenue to increase patient survival via optimized mechanical ventilation waveforms. We model the occluded airway as a liquid-filled rigid tube with the fluid phase displaced by a finger of air that propagates with both mean and sinusoidal velocity components. Finite-time Lyapunov exponent (FTLE) fields are employed to analyse the convective transport characteristics, taking note of Lagrangian coherent structures (LCSs) and their effects on transport. The Lagrangian perspective of these techniques reveals flow characteristics that are not readily apparent by observing Eulerian measures. These analysis techniques are applied to surfactant-free velocity fields determined computationally, with the boundary element method, and measured experimentally with micro particle image velocimetry (μ-PIV). We find that the LCS divides the fluid into two regimes, one advected upstream (into the thin residual film) and the other downstream ahead of the advancing bubble. At higher oscillatory frequencies particles originating immediately inside the LCS experience long residence times at the air-liquid interface, which may be conducive to surfactant transport. At high frequencies a well-mixed attractor region is identified; this volume of fluid cyclically travels along the interface and into the bulk fluid. The Lagrangian analysis is applied to velocity data measured with 0.01 mg ml(-1) of the clinical pulmonary surfactant Infasurf in the bulk fluid, demonstrating flow field modifications with respect to the surfactant-free system that were not visible in the Eulerian frame.

  14. Lagrangian transport properties of pulmonary interfacial flows

    PubMed Central

    Smith, Bradford J.; Lukens, Sarah; Yamaguchi, Eiichiro; Gaver, Donald P.

    2012-01-01

    Disease states characterized by airway fluid occlusion and pulmonary surfactant insufficiency, such as respiratory distress syndrome, have a high mortality rate. Understanding the mechanics of airway reopening, particularly involving surfactant transport, may provide an avenue to increase patient survival via optimized mechanical ventilation waveforms. We model the occluded airway as a liquid-filled rigid tube with the fluid phase displaced by a finger of air that propagates with both mean and sinusoidal velocity components. Finite-time Lyapunov exponent (FTLE) fields are employed to analyse the convective transport characteristics, taking note of Lagrangian coherent structures (LCSs) and their effects on transport. The Lagrangian perspective of these techniques reveals flow characteristics that are not readily apparent by observing Eulerian measures. These analysis techniques are applied to surfactant-free velocity fields determined computationally, with the boundary element method, and measured experimentally with micro particle image velocimetry (μ-PIV). We find that the LCS divides the fluid into two regimes, one advected upstream (into the thin residual film) and the other downstream ahead of the advancing bubble. At higher oscillatory frequencies particles originating immediately inside the LCS experience long residence times at the air–liquid interface, which may be conducive to surfactant transport. At high frequencies a well-mixed attractor region is identified; this volume of fluid cyclically travels along the interface and into the bulk fluid. The Lagrangian analysis is applied to velocity data measured with 0.01 mg ml−1 of the clinical pulmonary surfactant Infasurf in the bulk fluid, demonstrating flow field modifications with respect to the surfactant-free system that were not visible in the Eulerian frame. PMID:23049141

  15. Magnetic and Transport Properties of Mn-ion implanted Si

    NASA Astrophysics Data System (ADS)

    Preisler, V.; Ogawa, M.; Han, X.; Wang, K. L.

    2010-01-01

    We investigate the magnetic and transport properties of Mn-ion implanted Si. Both temperature dependent and field dependent measurements of the samples using a SQUID magnometer reveal ferromagnetic properties at room temperature. Magnetotransport measurements show a large positive magnetoresistance up to 4.5 T with no signs of saturation.

  16. Physical transport properties of marine microplastic pollution

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  17. Enhancement of wall jet transport properties

    DOEpatents

    Claunch, Scott D.; Farrington, Robert B.

    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.

  18. Enhancement of wall jet transport properties

    DOEpatents

    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.

  19. Transport properties of porous media from the microstructure

    SciTech Connect

    Torquato, S.

    1995-12-31

    The determination of the effective transport properties of a random porous medium remains a challenging area of research because the properties depend on the microstructure in a highly complex fashion. This paper reviews recent theoretical and experimental progress that we have made on various aspects of this problem. A unified approach is taken to characterize the microstructure and the seemingly disparate properties of the medium.

  20. CET89 - CHEMICAL EQUILIBRIUM WITH TRANSPORT PROPERTIES, 1989

    NASA Technical Reports Server (NTRS)

    Mcbride, B.

    1994-01-01

    Scientists and engineers need chemical equilibrium composition data to calculate the theoretical thermodynamic properties of a chemical system. This information is essential in the design and analysis of equipment such as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical processing equipment. The substantial amount of numerical computation required to obtain equilibrium compositions and transport properties for complex chemical systems led scientists at NASA's Lewis Research Center to develop CET89, a program designed to calculate the thermodynamic and transport properties of these systems. CET89 is a general program which will calculate chemical equilibrium compositions and mixture properties for any chemical system with available thermodynamic data. Generally, mixtures may include condensed and gaseous products. CET89 performs the following operations: it 1) obtains chemical equilibrium compositions for assigned thermodynamic states, 2) calculates dilute-gas transport properties of complex chemical mixtures, 3) obtains Chapman-Jouguet detonation properties for gaseous species, 4) calculates incident and reflected shock properties in terms of assigned velocities, and 5) calculates theoretical rocket performance for both equilibrium and frozen compositions during expansion. The rocket performance function allows the option of assuming either a finite area or an infinite area combustor. CET89 accommodates problems involving up to 24 reactants, 20 elements, and 600 products (400 of which may be condensed). The program includes a library of thermodynamic and transport properties in the form of least squares coefficients for possible reaction products. It includes thermodynamic data for over 1300 gaseous and condensed species and transport data for 151 gases. The subroutines UTHERM and UTRAN convert thermodynamic and transport data to unformatted form for faster processing. The program conforms to the FORTRAN 77 standard, except for

  1. Unsaturated Zone and Saturated Zone Transport Properties (U0100)

    SciTech Connect

    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.

  2. Magnetothermoelectric transport properties of multiterminal graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Wei, Miao-Miao; Zhang, Ying-Tao; Guo, Ai-Min; Liu, Jian-Jun; Xing, Yanxia; Sun, Qing-Feng

    2016-06-01

    The Peltier effect and the Ettingshausen effect are investigated in graphene nanoribbons, where charge current produces heat current along the longitudinal direction in the former case, and longitudinal charge current generates transverse heat current in the latter case. With the aid of the nonequilibrium Green's function and the Landauer-Büttiker formalism, the Peltier coefficient Πc and the Ettingshausen coefficient Ec are obtained. We found that the Kelvin relation is always valid for the longitudinal thermoelectric transport, i.e., Πc=T Sc , with T the temperature and Sc the Seebeck coefficient. In contrast, for transverse magnetothermoelectric transport, the Kelvin relation breaks down and Ec≠T Nc usually, with Nc the Nernst coefficient. In the region of weak magnetic field, the Ettingshausen effect depends strongly on device parameters. When the Fermi energy EF is close to the Dirac point, the Ettingshausen effect of the semiconducting armchair graphene nanoribbon is much stronger than that of the metallic one. When EF is far away from the Dirac point, the Ettingshausen coefficient Ec oscillates around zero. When under a strong magnetic field, Ec is independent of the device parameters and swells only near the Dirac point. Further, the dependence of Ec on EF can be scaled by EF/kBT , with a peak value of (2 ln2 ) kBT /e for the three-terminal system and (4/3 ln2 ) kBT /e for the four-terminal system. We also study the impact of disorder on the Ettingshausen effect. Regardless of the magnetic field strength, Ec is robust against moderate disorder scattering. In addition, in the strong magnetic field, Ec with additional regular oscillating structure can be caused by disorder.

  3. Thermodynamic and transport properties of sodium liquid and vapor

    SciTech Connect

    Fink, J.K.; Leibowitz, L.

    1995-01-01

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

  4. Electron-Transport Properties of Few-Layer Black Phosphorus.

    PubMed

    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.

  5. Dielectric and electrical transport properties of biopolymers

    NASA Astrophysics Data System (ADS)

    Bartsch, Carrie M.; Subramanyam, Guru; Grote, James G.; Hopkins, F. Kenneth; Brott, Lawrence L.; Naik, Rajesh R.

    2007-02-01

    A new capacitive test structure is used to characterize biopolymers at microwave frequencies. The new test structure is comprised of a parallel plate capacitor, combined with coplanar waveguide-based input and output feed lines. This allows electrical measurements to be taken easily under an applied DC electric field and at various temperatures. The dielectric properties are characterized for two biopolymer thin films: a deoxyribonucleic acid (DNA)-based film and a bovine serum albumin (BSA)-based film. These bio-dielectric thin films are compared with a standard commercial polymer thin film, poly[Bisphenol A carbonate-co-4,4'(3,3,5-trimethyl cyclohexylidene) diphenol], also known as amorphous polycarbonate (APC).

  6. Transport properties of interacting magnetic islands in tokamak plasmas

    SciTech Connect

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

    1993-10-01

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

  7. Transport properties in nontwist area-preserving maps

    SciTech Connect

    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.

  8. A history of vascular and microvascular surgery.

    PubMed

    Rickard, Rory F; Hudson, Donald A

    2014-10-01

    The history of microvascular surgery is intimately linked to that of vascular surgery. Microvascular techniques, developed mainly in China, Japan, Australia, and the United States of America, built on the principles of vascular anastomosis established by pioneers in France, Germany, Italy, and the United States of America. We present a history of the technique here.

  9. Transport properties associated with carbon-phenolic ablators

    NASA Technical Reports Server (NTRS)

    Biolsi, L.

    1982-01-01

    Entry vehicle heat shields designed for entry into the atmosphere of the outer planets are usually made of carbonaceous material such as carbon-phenolic ablator. Ablative injection of this material is an important mechanism for reducing the heat at the surface of the entry vehicle. Conductive transport properties in the shock layer are important for some entry conditions. The kinetic theory of gases has been used to calculate the transport properties for 17 gaseous species obtained from the ablation of carbon-phenolic heat shields. Results are presented for the pure species and for the gas mixture.

  10. Measurement of the radiative transport properties of reticulated alumina foams

    SciTech Connect

    Hale, M.J.; Bohn, M.S.

    1992-12-01

    This paper presents a method for determining radiative transport properties of reticulated materials. The method has both experimental and analytical components. A polar nephelometer is used to measure the scattering profile of a sample of the reticulated material. The results of a Monte Carlo simulation of the experiment are then combined with the experimental results to give the scatter albedo and extinction coefficient. This paper presents the results of using this method to determine the radiative transport properties of four different porosities (10, 20, 30, 65 pores per inch) of cylindrical reticulated alumina samples ranging in thickness form 0.5 inches to 2. 5 inches.

  11. Transport properties of water at functionalized molecular interfaces

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

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

  12. Transport properties of self-consolidating concrete

    SciTech Connect

    Sonebi, M.; Nanukuttan, S.

    2009-03-15

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

  13. Magnetic particle spectroscopy allows precise quantification of nanoparticles after passage through human brain microvascular endothelial cells

    NASA Astrophysics Data System (ADS)

    Gräfe, C.; Slabu, I.; Wiekhorst, F.; Bergemann, C.; von Eggeling, F.; Hochhaus, A.; Trahms, L.; Clement, J. H.

    2016-06-01

    Crossing the blood-brain barrier is an urgent requirement for the treatment of brain disorders. Superparamagnetic iron oxide nanoparticles (SPIONs) are a promising tool as carriers for therapeutics because of their physical properties, biocompatibility, and their biodegradability. In order to investigate the interaction of nanoparticles with endothelial cell layers in detail, in vitro systems are of great importance. Human brain microvascular endothelial cells are a well-suited blood-brain barrier model. Apart from generating optimal conditions for the barrier-forming cell units, the accurate detection and quantification of SPIONs is a major challenge. For that purpose we use magnetic particle spectroscopy to sensitively and directly quantify the SPION-specific iron content. We could show that SPION concentration depends on incubation time, nanoparticle concentration and location. This model system allows for further investigations on particle uptake and transport at cellular barriers with regard to parameters including particles’ shape, material, size, and coating.

  14. Magnetic particle spectroscopy allows precise quantification of nanoparticles after passage through human brain microvascular endothelial cells

    NASA Astrophysics Data System (ADS)

    Gräfe, C.; Slabu, I.; Wiekhorst, F.; Bergemann, C.; von Eggeling, F.; Hochhaus, A.; Trahms, L.; Clement, J. H.

    2016-06-01

    Crossing the blood–brain barrier is an urgent requirement for the treatment of brain disorders. Superparamagnetic iron oxide nanoparticles (SPIONs) are a promising tool as carriers for therapeutics because of their physical properties, biocompatibility, and their biodegradability. In order to investigate the interaction of nanoparticles with endothelial cell layers in detail, in vitro systems are of great importance. Human brain microvascular endothelial cells are a well-suited blood–brain barrier model. Apart from generating optimal conditions for the barrier-forming cell units, the accurate detection and quantification of SPIONs is a major challenge. For that purpose we use magnetic particle spectroscopy to sensitively and directly quantify the SPION-specific iron content. We could show that SPION concentration depends on incubation time, nanoparticle concentration and location. This model system allows for further investigations on particle uptake and transport at cellular barriers with regard to parameters including particles’ shape, material, size, and coating.

  15. Magnetic particle spectroscopy allows precise quantification of nanoparticles after passage through human brain microvascular endothelial cells.

    PubMed

    Gräfe, C; Slabu, I; Wiekhorst, F; Bergemann, C; von Eggeling, F; Hochhaus, A; Trahms, L; Clement, J H

    2016-06-01

    Crossing the blood-brain barrier is an urgent requirement for the treatment of brain disorders. Superparamagnetic iron oxide nanoparticles (SPIONs) are a promising tool as carriers for therapeutics because of their physical properties, biocompatibility, and their biodegradability. In order to investigate the interaction of nanoparticles with endothelial cell layers in detail, in vitro systems are of great importance. Human brain microvascular endothelial cells are a well-suited blood-brain barrier model. Apart from generating optimal conditions for the barrier-forming cell units, the accurate detection and quantification of SPIONs is a major challenge. For that purpose we use magnetic particle spectroscopy to sensitively and directly quantify the SPION-specific iron content. We could show that SPION concentration depends on incubation time, nanoparticle concentration and location. This model system allows for further investigations on particle uptake and transport at cellular barriers with regard to parameters including particles' shape, material, size, and coating. PMID:27163489

  16. Single tube electric transport properties of synthesized Titania nanotubes

    NASA Astrophysics Data System (ADS)

    Abdelmoula, Mohamed; Menon, Latika

    2011-03-01

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

  17. Properties of an affine transport equation and its holonomy

    NASA Astrophysics Data System (ADS)

    Vines, Justin; Nichols, David A.

    2016-10-01

    An affine transport equation was used recently to study properties of angular momentum and gravitational-wave memory effects in general relativity. In this paper, we investigate local properties of this transport equation in greater detail. Associated with this transport equation is a map between the tangent spaces at two points on a curve. This map consists of a homogeneous (linear) part given by the parallel transport map along the curve plus an inhomogeneous part, which is related to the development of a curve in a manifold into an affine tangent space. For closed curves, the affine transport equation defines a "generalized holonomy" that takes the form of an affine map on the tangent space. We explore the local properties of this generalized holonomy by using covariant bitensor methods to compute the generalized holonomy around geodesic polygon loops. We focus on triangles and "parallelogramoids" with sides formed from geodesic segments. For small loops, we recover the well-known result for the leading-order linear holonomy (˜ Riemann × area), and we derive the leading-order inhomogeneous part of the generalized holonomy (˜ Riemann × area^{3/2}). Our bitensor methods let us naturally compute higher-order corrections to these leading results. These corrections reveal the form of the finite-size effects that enter into the holonomy for larger loops; they could also provide quantitative errors on the leading-order results for finite loops.

  18. 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

  19. Magneto-transport properties in layered manganite crystals

    SciTech Connect

    Kimura, T.; Tomioka, Y.; Okuda, T.; Kuwahara, H.; Asamitsu, A.; Tokura, Y.

    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.

  20. Transport properties of a Bentheim sandstone under deformation.

    PubMed

    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.

  1. Oxygen transport properties estimation by DSMC-CT simulations

    SciTech Connect

    Bruno, Domenico; Frezzotti, Aldo; Ghiroldi, Gian Pietro

    2014-12-09

    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.

  2. Transport Properties of Metallic Ruthenates: A DFT+DMFT Investigation.

    PubMed

    Deng, Xiaoyu; Haule, Kristjan; Kotliar, Gabriel

    2016-06-24

    We present a systematical theoretical study on the transport properties of an archetypal family of Hund's metals, Sr_{2}RuO_{4}, Sr_{3}Ru_{2}O_{7}, SrRuO_{3}, and CaRuO_{3}, within the combination of first principles density functional theory and dynamical mean field theory. The agreement between theory and experiments for optical conductivity and resistivity is good, which indicates that electron-electron scattering dominates the transport of ruthenates. We demonstrate that in the single-site dynamical mean field approach the transport properties of Hund's metals fall into the scenario of "resilient quasiparticles." We explain why the single layered compound Sr_{2}RuO_{4} has a relative weak correlation with respect to its siblings, which corroborates its good metallicity. PMID:27391734

  3. Transport Properties of Metallic Ruthenates: A DFT +DMFT Investigation

    NASA Astrophysics Data System (ADS)

    Deng, Xiaoyu; Haule, Kristjan; Kotliar, Gabriel

    2016-06-01

    We present a systematical theoretical study on the transport properties of an archetypal family of Hund's metals, Sr2RuO4 , Sr3 Ru2 O7 , SrRuO3 , and CaRuO3 , within the combination of first principles density functional theory and dynamical mean field theory. The agreement between theory and experiments for optical conductivity and resistivity is good, which indicates that electron-electron scattering dominates the transport of ruthenates. We demonstrate that in the single-site dynamical mean field approach the transport properties of Hund's metals fall into the scenario of "resilient quasiparticles." We explain why the single layered compound Sr2 RuO4 has a relative weak correlation with respect to its siblings, which corroborates its good metallicity.

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

    SciTech Connect

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

    2014-09-01

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

  5. Transport properties of hierarchical micro-mesoporous materials.

    PubMed

    Schneider, Daniel; Mehlhorn, Dirk; Zeigermann, Philipp; Kärger, Jörg; Valiullin, Rustem

    2016-06-13

    Adding mesopore networks in microporous materials using the principles of hierarchical structure design is recognized as a promising route for eliminating their transport limitations and, therefore, for improving their value in technological applications. Depending on the routes of physico-chemical procedures or post-synthesis treatments used, very different geometries of the intentionally-added transport mesopores can be obtained. Understanding the structure-dynamics relationships in these complex materials with multiple porosities under different thermodynamical conditions remains a challenging task. In this review, we summarize the results obtained so far on experimental and theoretical studies of diffusion in micro-mesoporous materials. By considering four common classes of bi-porous materials, which are differing by the inter-connectivities of their sup-spaces as one of the most important parameter determining the transport rates, we discuss their generic transport properties and correlate the results delivered by the equilibrium and non-equilibrium techniques of diffusion measurements.

  6. Review on measurement techniques of transport properties of nanowires.

    PubMed

    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

  7. Review on measurement techniques of transport properties of nanowires.

    PubMed

    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.

  8. Transport properties and electronic structure of epitaxial tunnel junctions

    NASA Astrophysics Data System (ADS)

    Freyss, M.; Papanikolaou, N.; Bellini, V.; Zeller, R.; Dederichs, P. H.; Turek, I.

    2002-02-01

    We present ab initio calculations for the electronic ground-state and transport properties of epitaxial Fe/semiconductor/Fe (0 0 1) tunnel junctions. The ground state properties are determined by the ab initio Screened KKR Green's function method and the transport properties by a Green's function formulation of the Landauer-Büttiker formalism. We focus on tunnel junctions with a semiconducting ZnSe barrier and compare them to results for junctions with Si and GaAs barriers. We comment on the presence of metal-induced gap states (MIGS) in the semiconductor, the spin polarization of which strongly depends on the nature of the barrier. We investigate furthermore the influence of one atomic layer at the interface of a non-magnetic metal (Cu, Ag, Al) and of a magnetic 3d transition metal.

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

    SciTech Connect

    Martin, T.

    1994-08-26

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

  10. 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

  11. Kinetic theory of transport processes in partially ionized reactive plasma, II: Electron transport properties

    NASA Astrophysics Data System (ADS)

    Zhdanov, V. M.; Stepanenko, A. A.

    2016-11-01

    The previously obtained in (Zhdanov and Stepanenko, 2016) general transport equations for partially ionized reactive plasma are employed for analysis of electron transport properties in molecular and atomic plasmas. We account for both elastic and inelastic interaction channels of electrons with atoms and molecules of plasma and also the processes of electron impact ionization of neutral particles and three-body ion-electron recombination. The system of scalar transport equations for electrons is discussed and the expressions for non-equilibrium corrections to electron ionization and recombination rates and the diagonal part of the electron pressure tensor are derived. Special attention is paid to analysis of electron energy relaxation during collisions with plasma particles having internal degrees of freedom and the expression for the electron coefficient of inelastic energy losses is deduced. We also derive the expressions for electron vector and tensorial transport fluxes and the corresponding transport coefficients for partially ionized reactive plasma, which represent a generalization of the well-known results obtained by Devoto (1967). The results of numerical evaluation of contribution from electron inelastic collisions with neutral particles to electron transport properties are presented for a series of molecular and atomic gases.

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

    SciTech Connect

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

    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 μ ∝ (T/T{sub 0}){sup −α} with α = 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 ħω = 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.

  13. Deeper Penetration of Erythrocytes into the Endothelial Glycocalyx Is Associated with Impaired Microvascular Perfusion

    PubMed Central

    Lee, Dae Hyun; Dane, Martijn J. C.; van den Berg, Bernard M.; Boels, Margien G. S.; van Teeffelen, Jurgen W.; de Mutsert, Renée; den Heijer, Martin; Rosendaal, Frits R.; van der Vlag, Johan; van Zonneveld, Anton Jan; Vink, Hans; Rabelink, Ton J.

    2014-01-01

    Changes in endothelial glycocalyx are one of the earliest changes in development of cardiovascular disease. The endothelial glycocalyx is both an important biological modifier of interactions between flowing blood and the vessel wall, and a determinant of organ perfusion. We hypothesize that deeper penetration of erythrocytes into the glycocalyx is associated with reduced microvascular perfusion. The population-based prospective cohort study (the Netherlands Epidemiology of Obesity [NEO] study) includes 6,673 middle-aged individuals (oversampling of overweight and obese individuals). Within this cohort, we have imaged the sublingual microvasculature of 915 participants using sidestream darkfield (SDF) imaging together with a recently developed automated acquisition and analysis approach. Presence of RBC (as a marker of microvascular perfusion) and perfused boundary region (PBR), a marker for endothelial glycocalyx barrier properties for RBC accessibility, were assessed in vessels between 5 and 25 µm RBC column width. A wide range of variability in PBR measurements, with a mean PBR of 2.14 µm (range: 1.43–2.86 µm), was observed. Linear regression analysis showed a marked association between PBR and microvascular perfusion, reflected by RBC filling percentage (regression coefficient β: −0.034; 95% confidence interval: −0.037 to −0.031). We conclude that microvascular beds with a thick (“healthy”) glycocalyx (low PBR), reflects efficient perfusion of the microvascular bed. In contrast, a thin (“risk”) glycocalyx (high PBR) is associated with a less efficient and defective microvascular perfusion. PMID:24816787

  14. Drag-Reducing Polymer Enhances Microvascular Perfusion in the Traumatized Brain with Intracranial Hypertension.

    PubMed

    Bragin, Denis E; Thomson, Susan; Bragina, Olga; Statom, Gloria; Kameneva, Marina V; Nemoto, Edwin M

    2016-01-01

    Current treatments for traumatic brain injury (TBI) have not focused on improving microvascular perfusion. Drag-reducing polymers (DRP), linear, long-chain, blood-soluble, nontoxic macromolecules, may offer a new approach to improving cerebral perfusion by primary alteration of the fluid dynamic properties of blood. Nanomolar concentrations of DRP have been shown to improve hemodynamics in animal models of ischemic myocardium and ischemic limb, but have not yet been studied in the brain. We recently demonstrated that DRP improved microvascular perfusion and tissue oxygenation in a normal rat brain. We hypothesized that DRP could restore microvascular perfusion in hypertensive brain after TBI. Using in vivo two-photon laser scanning microscopy we examined the effect of DRP on microvascular blood flow and tissue oxygenation in hypertensive rat brains with and without TBI. DRP enhanced and restored capillary flow, decreased microvascular shunt flow, and, as a result, reduced tissue hypoxia in both nontraumatized and traumatized rat brains at high intracranial pressure. Our study suggests that DRP could constitute an effective treatment for improving microvascular flow in brain ischemia caused by high intracranial pressure after TBI. PMID:27165871

  15. Deeper penetration of erythrocytes into the endothelial glycocalyx is associated with impaired microvascular perfusion.

    PubMed

    Lee, Dae Hyun; Dane, Martijn J C; van den Berg, Bernard M; Boels, Margien G S; van Teeffelen, Jurgen W; de Mutsert, Renée; den Heijer, Martin; Rosendaal, Frits R; van der Vlag, Johan; van Zonneveld, Anton Jan; Vink, Hans; Rabelink, Ton J

    2014-01-01

    Changes in endothelial glycocalyx are one of the earliest changes in development of cardiovascular disease. The endothelial glycocalyx is both an important biological modifier of interactions between flowing blood and the vessel wall, and a determinant of organ perfusion. We hypothesize that deeper penetration of erythrocytes into the glycocalyx is associated with reduced microvascular perfusion. The population-based prospective cohort study (the Netherlands Epidemiology of Obesity [NEO] study) includes 6,673 middle-aged individuals (oversampling of overweight and obese individuals). Within this cohort, we have imaged the sublingual microvasculature of 915 participants using sidestream darkfield (SDF) imaging together with a recently developed automated acquisition and analysis approach. Presence of RBC (as a marker of microvascular perfusion) and perfused boundary region (PBR), a marker for endothelial glycocalyx barrier properties for RBC accessibility, were assessed in vessels between 5 and 25 µm RBC column width. A wide range of variability in PBR measurements, with a mean PBR of 2.14 µm (range: 1.43-2.86 µm), was observed. Linear regression analysis showed a marked association between PBR and microvascular perfusion, reflected by RBC filling percentage (regression coefficient β: -0.034; 95% confidence interval: -0.037 to -0.031). We conclude that microvascular beds with a thick ("healthy") glycocalyx (low PBR), reflects efficient perfusion of the microvascular bed. In contrast, a thin ("risk") glycocalyx (high PBR) is associated with a less efficient and defective microvascular perfusion.

  16. Drag-Reducing Polymer Enhances Microvascular Perfusion in the Traumatized Brain with Intracranial Hypertension.

    PubMed

    Bragin, Denis E; Thomson, Susan; Bragina, Olga; Statom, Gloria; Kameneva, Marina V; Nemoto, Edwin M

    2016-01-01

    Current treatments for traumatic brain injury (TBI) have not focused on improving microvascular perfusion. Drag-reducing polymers (DRP), linear, long-chain, blood-soluble, nontoxic macromolecules, may offer a new approach to improving cerebral perfusion by primary alteration of the fluid dynamic properties of blood. Nanomolar concentrations of DRP have been shown to improve hemodynamics in animal models of ischemic myocardium and ischemic limb, but have not yet been studied in the brain. We recently demonstrated that DRP improved microvascular perfusion and tissue oxygenation in a normal rat brain. We hypothesized that DRP could restore microvascular perfusion in hypertensive brain after TBI. Using in vivo two-photon laser scanning microscopy we examined the effect of DRP on microvascular blood flow and tissue oxygenation in hypertensive rat brains with and without TBI. DRP enhanced and restored capillary flow, decreased microvascular shunt flow, and, as a result, reduced tissue hypoxia in both nontraumatized and traumatized rat brains at high intracranial pressure. Our study suggests that DRP could constitute an effective treatment for improving microvascular flow in brain ischemia caused by high intracranial pressure after TBI.

  17. Anisotropic bias dependent transport property of defective phosphorene layer

    PubMed Central

    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

  18. Work functions and transport properties of finite metallic hexaboride nanorods

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Luo, Guangfu; Sabirianov, Renat F.; Mei, Wai-Ning; Valencia, Daniel; Sierra Llavina, Carlos H.; Lu, Jun-Qiang; Cheung, Chin Li

    2014-03-01

    We performed density functional theory calculations of finite metallic hexaboride LaB6 nanorods, which are regarded as good thermoelectric materials for their low work functions. Our purpose is to facilitate the research and manufacture of metal hexaboride probes, thus we study extensively the work functions and electron transport properties of these finite nanorods. The work functions were deducted from the calculated electrostatic potential and the Fermi energy. We found that these finite LaB6 nanorods have low work functions similar to their infinite counterpart. To further investigate the electron transport properties, we adopted the combined Landauer-Buttiker formalism and non-equilibrium Green's function technique to compute the transmission coefficients near the Fermi level and found that the finite LaB6 nanorods can be converted from metallic to semiconducting by applying a gate voltage larger than 10 V.

  19. Modeling transport properties of inhomogeneous superconductor-metal composites

    SciTech Connect

    Borroto, A.; Altshuler, E.; Del Río, L.; Arronte, M.; Johansen, T. H.

    2014-11-17

    We propose a model for a superconductor-metal composite that allows to derive intrinsic transport properties of the superconducting phase based on 2D images of its cross section, and a minimal set of parameters. The method is tested experimentally by using, as model composite, a “transversal bridge” made on a Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} (BSCCO)-Ag multi-filamentary tape. It is shown that the approach allows to predict the measured I−〈E〉 curves of the filaments. In addition, one can determine the critical current anisotropy between the longitudinal and transverse directions of the Ag-BSCCO tape, and also of its superconducting filaments separately, which emphasizes the role of the morphology of the composite in the transport properties.

  20. 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.

  1. Relaxation and transport properties of liquid n-triacontane

    NASA Astrophysics Data System (ADS)

    Kondratyuk, N. D.; Lankin, A. V.; Norman, G. E.; Stegailov, V. V.

    2015-11-01

    Molecular modelling is used to calculate transport properties and to study relaxation of liquid n-triacontane (C30H62). The problem is important in connection with the behavior of liquid isolators in a pre-breakdown state. Two all-atom models and a united-atom model are used. Shear viscosity is calculated using the Green-Kubo formula. The force fields are compared with each other using the following criteria: the required time for one molecular dynamics step, the compliance of the main physical and transport properties with experimental values. The problem of the system equilibration is considered. The united-atom potential is used to model the n-triacontane liquid with an initial directional orientation. The time of relaxation to the disordered state, when all molecules orientations are randomized, are obtained. The influence of the molecules orientations on the shear viscosity value and the shear viscosity relaxation are treated.

  2. Low temperature transport properties of Ce-Al metallic glasses

    SciTech Connect

    Zeng, Q. S.; Rotundu, C. R.; Mao, W. L.; Dai, J. H.; Xiao, Y. M.; Chow, P.; Chen, X. J.; Qin, C. L.; Mao, H.-k.; Jiang, J. Z.

    2011-01-01

    The low temperature transport properties of Ce75- x Al25+ 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.

  3. CALIPSO observations of changes in dust properties during transatlantic transport

    NASA Astrophysics Data System (ADS)

    Marshak, A.; Yang, W.; Varnai, T.; Kostinski, A. B.

    2015-12-01

    The vertical distribution of dust shape and size is highly important for understanding and estimating dust radiative forcing. We used CALIPSO nighttime datasets to examine the vertical structure and evolution of Saharan dust during transatlantic transport. The results show that most Saharan dust is lifted to high altitude and descends after traveling thousands of km-s. Initially, the depolarization ratio and color ratio of Saharan dust are uniformly distributed along altitude, suggesting vertically constant particle size and shape distributions. During transport, the depolarization ratio of Saharan dust drops at lower altitudes, suggesting that particle shapes become less irregular; while at relatively high altitudes, the depolarization ratio of dust increases during transport. The changes observed during transport likely come from the effects of gravitational sorting caused by variations in particle shape and size. A simple model with only two shapes qualitatively captures these features and confirms that shape-induced differential settling contribute significantly to the observed vertical stratification of dust properties. In addition, the effect of clouds on dust properties will be also discussed.

  4. 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.

  5. Thermomagnetic transport properties of ferromagnetic MnBi

    NASA Astrophysics Data System (ADS)

    Boona, Stephen; Heremans, Joseph

    Spin-dependent transport phenomena such as the spin Seebeck effect and magnon drag offer intriguing new possibilities for tuning the thermoelectric properties of magnetically ordered materials. One particularly interesting approach is to examine magnetic materials that are expected to display large intrinsic spin orbit coupling, such as MnBi. In spite of this material's popularity as a candidate for rare-earth free permanent magnets, no studies have been published so far concerning its Seebeck or Nernst coefficients. This talk will discuss our recent measurements of the thermomagnetic properties of high purity polycrystalline MnBi between 2K and 385K and in magnetic fields up to 7T. Our measurements reveal the existence of a substantial anomalous Nernst effect (ANE) from 382K down to the spin reorientation temperature of 90K, while the other transport phenomena show relatively weak magnetic field dependence at all temperatures. We also observe that the Seebeck and ANE coefficients display strikingly similar temperature dependence, with the former peaking at approximately -10 μV/K and the latter at approximately -2.5 μV/K/T, hinting at the important role of spin-dependent processes in determining the transport properties of this material.

  6. Modeling Saharan dust emissions, transport, deposition, and optical properties

    NASA Astrophysics Data System (ADS)

    Colarco, Peter Richard

    We simulate Saharan dust emissions, transport, and removal with a three-dimensional aerosol transport model driven by assimilated meteorology. We explore dust distributions and optical properties for model runs over the tropical North Atlantic for time periods covering the ACE-2 (summer 1997, Canary Islands) and PRIDE (summer 2000, Puerto Rico) field experiments. Modeled dust fields are compared to ground-based, in situ, and satellite observations. Dust imaginary refractive index and single scatter albedo at UV wavelengths are inferred near source regions by computing the TOMS Aerosol Index from modeled dust fields. Our results indicate a dust aerosol that is considerably less absorbing than previous estimates. The timing of downwind dust events is generally uncorrelated with the details of the dust source process, indicating the dust exists in a persistent reservoir over source regions and the timing of its transport to remote regions is most strongly controlled by the transporting dynamics. Our model simulates the complicated vertical distributions of dust observed over Puerto Rico. The dust vertical distribution is controlled by sedimentation of dust particles and a general descending air motion over the tropical North Atlantic. Low-level dust can be transported directly from source regions, but the majority of it is efficiently eroded away in transit by wet removal processes. Our computed estimates of iron deposition fluxes into the North Atlantic are in reasonable agreement with estimates based on station data.

  7. 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

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

    PubMed

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

    2014-06-01

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

  9. 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.

  10. 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.

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

    PubMed

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

    2015-05-01

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

  12. Small molecules with ambipolar transporting properties for efficient OLEDs

    NASA Astrophysics Data System (ADS)

    Duan, Lian; Wei, Peng; Qiu, Yong

    2007-11-01

    For stable and efficienct organic light-emitting diodes, it is essential to find molecules with high photoluminescent efficiency, little self-quenching and balanced charge transporting properties. Recently, we've designed and synthesized some highly emissive naphtho[2,3-c][1,2,5]thiadiazole (NTD) derivatives and naphtho[2,3-c][1,2,5]selenadiazole (NSeD) derivatives with unusual ambipolar transporting properties. The ambipolar transporting properties of the NTDs were explained by Marcus theory with carrier reorganization energies and charge-transfer integrals. We obtained high quality single crystals of 4,9-di(biphenyl-4-yl)-naphtho[2,3-c][1,2,5]thiadiazole (NTD02) and 4,9-bis(4-(2,2-diphenylvinyl)phenyl)-naphtho[2,3-c][1,2,5]thiadiazole (NTD05). They have disordered NTD rings' orientation with the opposite directions in the center of the molecule because of NTD's planar configuration and the single-bond connection with the phenyl substituents. The packing structure of NTD02 shows the planar arrangement of NTD rings, forming a "charge transporting channel". Quantum calculation also confirms that the π-π stacking interaction in NTD derivatives benefits the charge transporting via intermolecular hopping on NTD rings. The hole and electron mobilities of NTD05 are 7.16×10 -4 cm2/VÂ.s and 6.19×10 -4 cm2/V•s at an electronic field E = 2.0×10 5 V/cm, respectively. The hole mobility of NTD05 is close to that of N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'-biphenyl)-4,4'-diamine (NPB) and the electron mobility of NTD05 is two orders-of-magnitude higher than that of tris(8-hydroxyquinoline) aluminum (Alq 3). For the NTD derivatives, NTD05 also shows the best performance in non-doped OLEDs. CIE coordinates of (0.65, 0.35) and a peak efficiency of 2.4% are achieved for a double layer OLED with NPB as the hole transporting layer and NTD05 as the emitting layer. Moreover, we get ultimate red emission with CIE coordinates of (0.71, 0.29) for some of the NSeD based non

  13. Red Cell Properties after Different Modes of Blood Transportation

    PubMed Central

    Makhro, Asya; Huisjes, Rick; Verhagen, Liesbeth P.; Mañú-Pereira, María del Mar; Llaudet-Planas, Esther; Petkova-Kirova, Polina; Wang, Jue; Eichler, Hermann; Bogdanova, Anna; van Wijk, Richard; Vives-Corrons, Joan-Lluís; Kaestner, Lars

    2016-01-01

    Transportation of blood samples is unavoidable for assessment of specific parameters in blood of patients with rare anemias, blood doping testing, or for research purposes. Despite the awareness that shipment may substantially alter multiple parameters, no study of that extent has been performed to assess these changes and optimize shipment conditions to reduce transportation-related artifacts. Here we investigate the changes in multiple parameters in blood of healthy donors over 72 h of simulated shipment conditions. Three different anticoagulants (K3EDTA, Sodium Heparin, and citrate-based CPDA) for two temperatures (4°C and room temperature) were tested to define the optimal transportation conditions. Parameters measured cover common cytology and biochemistry parameters (complete blood count, hematocrit, morphological examination), red blood cell (RBC) volume, ion content and density, membrane properties and stability (hemolysis, osmotic fragility, membrane heat stability, patch-clamp investigations, and formation of micro vesicles), Ca2+ handling, RBC metabolism, activity of numerous enzymes, and O2 transport capacity. Our findings indicate that individual sets of parameters may require different shipment settings (anticoagulants, temperature). Most of the parameters except for ion (Na+, K+, Ca2+) handling and, possibly, reticulocytes counts, tend to favor transportation at 4°C. Whereas plasma and intraerythrocytic Ca2+ cannot be accurately measured in the presence of chelators such as citrate and EDTA, the majority of Ca2+-dependent parameters are stabilized in CPDA samples. Even in blood samples from healthy donors transported using an optimized shipment protocol, the majority of parameters were stable within 24 h, a condition that may not hold for the samples of patients with rare anemias. This implies for as short as possible shipping using fast courier services to the closest expert laboratory at reach. Mobile laboratories or the travel of the patients to

  14. Red Cell Properties after Different Modes of Blood Transportation.

    PubMed

    Makhro, Asya; Huisjes, Rick; Verhagen, Liesbeth P; Mañú-Pereira, María Del Mar; Llaudet-Planas, Esther; Petkova-Kirova, Polina; Wang, Jue; Eichler, Hermann; Bogdanova, Anna; van Wijk, Richard; Vives-Corrons, Joan-Lluís; Kaestner, Lars

    2016-01-01

    Transportation of blood samples is unavoidable for assessment of specific parameters in blood of patients with rare anemias, blood doping testing, or for research purposes. Despite the awareness that shipment may substantially alter multiple parameters, no study of that extent has been performed to assess these changes and optimize shipment conditions to reduce transportation-related artifacts. Here we investigate the changes in multiple parameters in blood of healthy donors over 72 h of simulated shipment conditions. Three different anticoagulants (K3EDTA, Sodium Heparin, and citrate-based CPDA) for two temperatures (4°C and room temperature) were tested to define the optimal transportation conditions. Parameters measured cover common cytology and biochemistry parameters (complete blood count, hematocrit, morphological examination), red blood cell (RBC) volume, ion content and density, membrane properties and stability (hemolysis, osmotic fragility, membrane heat stability, patch-clamp investigations, and formation of micro vesicles), Ca(2+) handling, RBC metabolism, activity of numerous enzymes, and O2 transport capacity. Our findings indicate that individual sets of parameters may require different shipment settings (anticoagulants, temperature). Most of the parameters except for ion (Na(+), K(+), Ca(2+)) handling and, possibly, reticulocytes counts, tend to favor transportation at 4°C. Whereas plasma and intraerythrocytic Ca(2+) cannot be accurately measured in the presence of chelators such as citrate and EDTA, the majority of Ca(2+)-dependent parameters are stabilized in CPDA samples. Even in blood samples from healthy donors transported using an optimized shipment protocol, the majority of parameters were stable within 24 h, a condition that may not hold for the samples of patients with rare anemias. This implies for as short as possible shipping using fast courier services to the closest expert laboratory at reach. Mobile laboratories or the travel of the

  15. Red Cell Properties after Different Modes of Blood Transportation.

    PubMed

    Makhro, Asya; Huisjes, Rick; Verhagen, Liesbeth P; Mañú-Pereira, María Del Mar; Llaudet-Planas, Esther; Petkova-Kirova, Polina; Wang, Jue; Eichler, Hermann; Bogdanova, Anna; van Wijk, Richard; Vives-Corrons, Joan-Lluís; Kaestner, Lars

    2016-01-01

    Transportation of blood samples is unavoidable for assessment of specific parameters in blood of patients with rare anemias, blood doping testing, or for research purposes. Despite the awareness that shipment may substantially alter multiple parameters, no study of that extent has been performed to assess these changes and optimize shipment conditions to reduce transportation-related artifacts. Here we investigate the changes in multiple parameters in blood of healthy donors over 72 h of simulated shipment conditions. Three different anticoagulants (K3EDTA, Sodium Heparin, and citrate-based CPDA) for two temperatures (4°C and room temperature) were tested to define the optimal transportation conditions. Parameters measured cover common cytology and biochemistry parameters (complete blood count, hematocrit, morphological examination), red blood cell (RBC) volume, ion content and density, membrane properties and stability (hemolysis, osmotic fragility, membrane heat stability, patch-clamp investigations, and formation of micro vesicles), Ca(2+) handling, RBC metabolism, activity of numerous enzymes, and O2 transport capacity. Our findings indicate that individual sets of parameters may require different shipment settings (anticoagulants, temperature). Most of the parameters except for ion (Na(+), K(+), Ca(2+)) handling and, possibly, reticulocytes counts, tend to favor transportation at 4°C. Whereas plasma and intraerythrocytic Ca(2+) cannot be accurately measured in the presence of chelators such as citrate and EDTA, the majority of Ca(2+)-dependent parameters are stabilized in CPDA samples. Even in blood samples from healthy donors transported using an optimized shipment protocol, the majority of parameters were stable within 24 h, a condition that may not hold for the samples of patients with rare anemias. This implies for as short as possible shipping using fast courier services to the closest expert laboratory at reach. Mobile laboratories or the travel of the

  16. Predicting radiative transport properties of plasma sprayed porous ceramics

    NASA Astrophysics Data System (ADS)

    Wang, B. X.; Zhao, C. Y.

    2016-03-01

    The typical yttria-stabilized zirconia material for making the thermal barrier coatings (TBCs) is intrinsically semitransparent to thermal radiation, and the unique disordered microstructures in TBCs make them surprisingly highly scattering. To quantitatively understand the influence of disordered microstructures, this paper presents a quantitative prediction on the radiative properties, especially the transport scattering coefficient of plasma sprayed TBC based on microstructure analysis and rigorous electromagnetic theory. The impact of the porosity, shape, size, and orientation of different types of voids on transport scattering coefficient is comprehensively investigated under the discrete dipole approximation. An inverse model integrating these factors together is then proposed to quantitatively connect transport scattering coefficient with microstructural information, which is also validated by available experimental data. Afterwards, an optimization procedure is carried out based on this model to obtain the optimal size and orientation distribution of the microscale voids to achieve the maximal radiation insulation performance at different operating temperatures, providing guidelines for practical coating design and fabrication. This work suggests that the current model is effective and also efficient for connecting scattering properties to microstructures and can be implemented as a quantitative tool for further studies like non-destructive infrared imaging as well as micro/nanoscale thermal design of TBCs.

  17. Influence of biofilms on transport properties in porous media

    NASA Astrophysics Data System (ADS)

    Davit, Y.

    2015-12-01

    Microbial activity and biofilm growth in porous media can drastically modify transport properties such as permeability, longitudinal and transverse dispersion or effective reaction rates. Understanding these effects has proven to be a considerable challenge. Advances in this field have been hindered by the difficulty of modeling and visualizing these multi-phase non-linear effects across a broad range of spatial and temporal scales. To address these issues, we are developing a strategy that combines imaging techniques based on x-ray micro-tomography with homogenization of pore-scale transport equations. Here, we review recent progress in x-ray imaging of biofilms in porous media, with a particular focus on the contrast agents that are used to differentiate between the fluid and biofilm phases. We further show how the 3D distribution of the different phases can be used to extract specific information about the biofilm and how effective properties can be calculated via the resolution of closure problems. These closure problems are obtained using the method of volume averaging and must be adapted to the problem of interest. In hydrological systems, we show that a generic formulation for reactive solute transport is based on a domain decomposition approach at the micro-scale yielding macro-scale models reminiscent of multi-rate mass transfer approaches.

  18. 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

  19. 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

  20. Morphologic and transport properties of natural organic floc

    USGS Publications Warehouse

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

    2009-01-01

    The morphology, entrainment, and settling of suspended aggregates ("floc") significantly impact fluxes of organic carbon, nutrients, and contaminants in aquatic environments. However, transport properties of highly organic floc remain poorly understood. In this study detrital floc was collected in the Florida Everglades from two sites with different abundances of periphyton for use in a settling column and in racetrack flume entrainment experiments. Although Everglades flocs are similar to other organic aggregates in terms of morphology and settling rates, they tend to be larger and more porous than typical mineral flocs because of biostabilization processes and relatively low prevailing shear stresses typical of wetlands. Flume experiments documented that Everglades floc was entrained at a low bed shear stress of 1.0 ?? 10-2 Pa, which is considerably smaller than the typical entrainment threshold of mineral floc. Because of similarities between Everglades floc and other organic floc populations, floc transport characteristics in the Everglades typify the behavior of floc in other organic-rich shallow-water environments. Highly organic floc is more mobile than less organic floc, but because bed shear stresses in wetlands are commonly near the entrainment threshold, wetland floc dynamics are often transport-limited rather than supply limited. Organic floc transport in these environments is therefore governed by the balance between entrainment and settling fluxes, which has implications for ecosystem metabolism, materials cycling, and even landscape evolution. Copyright 2009 by the American Geophysical Union.

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

    SciTech Connect

    Géranton, G.; Seiler, C.; Evers, F.; Bagrets, A.; Venkataraman, L.

    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.

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

    NASA Astrophysics Data System (ADS)

    Berahman, M.; Sheikhi, M. H.

    2014-09-01

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

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

    SciTech Connect

    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.

  4. 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.

  5. 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).

  6. 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.

  7. Low temperature carrier transport properties in isotopically controlled germanium

    SciTech Connect

    Itoh, K.

    1994-12-01

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

  8. Geophysical and transport properties of reservoir rocks. Summary annual report

    SciTech Connect

    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.

  9. 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.

  10. Polymerizable ionic liquid with state of the art transport properties.

    PubMed

    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.

  11. Transport properties of pseudospin-1 photons (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Chan, Che Ting; Fang, Anan; Zhang, Zhao-Qing; Louie, Steven G.

    2015-09-01

    Pseudospin is of central importance in governing many unusual transport properties of graphene and other artificial systems which have pseudospins of 1/2. These unconventional transport properties are manifested in phenomena such as Klein tunneling, and collimation of electron beams in one-dimensional external potentials. Here we show that in certain photonic crystals (PCs) exhibiting conical dispersions at the center of Brillouin zone, the eigenstates near the "Dirac-like point" can be described by an effective spin-orbit Hamiltonian with a pseudospin of 1. This effective Hamiltonian describes within a unified framework the wave propagations in both positive and negative refractive index media which correspond to the upper and lower conical bands respectively. Different from a Berry phase of π for the Dirac cone of pseudospin-1/2 systems, the Berry phase for the Dirac-like cone turns out to be zero from this pseudospin-1 Hamiltonian. In addition, we found that a change of length scale of the PC can shift the Dirac-like cone rigidly up or down in frequency with its group velocity unchanged, hence mimicking a gate voltage in graphene and allowing for a simple mechanism to control the flow of pseudospin-1 photons. As a photonic analogue of electron potential, the length-scale induced Dirac-like point shift is effectively a photonic potential within the effective pseudospin-1 Hamiltonian description. At the interface of two different potentials, the 3-component spinor gives rise to distinct boundary conditions which do not require each component of the wave function to be continuous, leading to new wave transport behaviors as shown in Klein tunneling and supercollimation. For examples, the Klein tunneling of pseudospin-1 photons is much less anisotropic with reference to the incident angle than that of pseudospin-1/2 electrons, and collimation can be more robust with pseudospin-1 than pseudospin-1/2. The special wave transport properties of pseudospin-1 photons

  12. Electrical tuning of transport properties of topological insulator ultrathin films.

    PubMed

    Li, H; Shao, J M; Zhang, H B; Yang, G W

    2014-03-21

    Considering that topological insulator (TI) ultrathin films (UTFs) provide an ideal platform for the transport measurement of topologically protected surface states, we have investigated the transport properties of the three-dimensional (3D) TI UTFs through an array of potential barriers. The 3D TI UTF was considered to be thin enough (5 nm) that the top and bottom surface states of the UTF can hybridize to create an energy gap at the Dirac point, which results in a hyperbola-like energy dispersion. It was found that the Klein tunneling effect disappears due to the interaction between the top and bottom surface states. By tuning the barrier strength or the incident energy, three kinds of transport processes can be realized, and the conditions of the transport processes were determined. The oscillatory characters of the transmission (conductance) spectra without a decaying envelope are due to the novel surface states of TIs, which are quite different from that observed for a conventional two-dimensional electron gas. For the structure consisting of two anti-parallel potential barriers, the conductance spectra exhibit a perfect on/off switching effect by tuning the barrier strength, which is favorable for electrically controllable device applications. In the case of a superlattice (SL) structure, due to the mini-gaps induced by the SL geometry, some additional resonant peaks and valleys can be observed in the transmission spectra, and similar characters are also reflected in the conductance spectra. Owing to the Dirac characters of the charge carriers therein, the transmission (conductance) spectra never decay with increasing barrier strength, which is distinguished from that observed for semiconductor SLs. These findings were not only meaningful for understanding the basic physical processes in the transport of TIs, but also useful for developing nanoscaled TI-based devices.

  13. Directed evolution reveals hidden properties of VMAT, a neurotransmitter transporter.

    PubMed

    Gros, Yael; Schuldiner, Shimon

    2010-02-12

    The vesicular neurotransmitter transporter VMAT2 is responsible for the transport of monoamines into synaptic and storage vesicles. VMAT2 is the target of many psychoactive drugs and is essential for proper neurotransmission and survival. Here we describe a new expression system in Saccharomyces cerevisiae that takes advantage of the polyspecificity of VMAT2. Expression of rVMAT2 confers resistance to acriflavine and to the parkinsonian toxin 1-methyl-4-phenylpyridinium (MPP(+)) by their removal into the yeast vacuole. This expression system allowed identification of a new substrate, acriflavine, and isolation of mutants with modified affinity to tetrabenazine (TBZ), a non-competitive inhibitor of VMAT2 that is used in the treatment of various movement disorders including Tourette syndrome and Huntington chorea. Whereas one type of mutant obtained displayed decreased affinity to TBZ, a second type showed only a slight decrease in the affinity to TBZ, displayed a higher K(m) to the neurotransmitter serotonin, but conferred increased resistance to acriflavine and MPP(+). A protein where both types of mutations were combined (with only three amino acid replacements) lost most of the properties of the neurotransmitter transporter (TBZ-insensitive, no transport of neurotransmitter) but displayed enhanced resistance to the above toxicants. The work described here shows that in the case of rVMAT2, loss of traits acquired in evolution of function (such as serotonin transport and TBZ binding) bring about an improvement in older functions such as resistance to toxic compounds. A process that has taken millions of years of evolution can be reversed by three mutations. PMID:20007701

  14. A dynamic opto-physiological model to effectively interpret retinal microvascular circulation

    NASA Astrophysics Data System (ADS)

    Hassan, Harnani; Hu, Sijung; Dwyer, Vincent M.

    2015-03-01

    The demand of non-invasive ocular screening is rapidly growing due to an increase of age related eye diseases worldwide. An indeed in-depth understanding of optical properties is required to elucidate nature of retinal tissue. The research aims to investigate an effective biomedical engineering approach to allow process region of interests (ROIs) in eyes to reveal physiological status. A dynamic opto-physiological model (DOPM) representing retinal microvascular circulation underlying a diffusion approximation to solve radiative transport theorem (RTT) has being developed to interpret patho-physiological phenomena. DOPM is being applied in imaging photoplethysmography (iPPG) to extract PPG signals from a series of 2D matrix images to access blood perfusion and oxygen saturation distributions. A variation of microvascular circulation could be mapped for an effectively diagnostic screening. The work presents mathematical modelling based ten layers of ocular tissue tested with four set of controlled parameters demontrated detection ratio between normal tissue damage or abnormal tissue and significant change of AC signal amplitude in these tissues. The result shows signicant change of AC signal amplitude in abnormal tissue. The preliminary results show extractable PPG signals from eye fundus video; experimented at five ROIs: whole fundus, optical disk, main vein vessel, lesion area and affected area. The outcome shows optical disk region gave a better performance compared to whole fundus region and main vein vessel. The robustness, miniaturization and artefact reduction capability of DOPM to discriminate oxygenation levels in retina could offer a new insight to access retinal patho-physiological status.

  15. Transport properties of diluted inverted micelles and microemulsions

    SciTech Connect

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

    1983-02-17

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

  16. The Effect of Microstructure On Transport Properties of Porous Electrodes

    NASA Astrophysics Data System (ADS)

    Peterson, Serena W.

    The goal of this work is to further understand the relationships between porous electrode microstructure and mass transport properties. This understanding allows us to predict and improve cell performance from fundamental principles. The investigated battery systems are the widely used rechargeable Li-ion battery and the non-rechargeable alkaline battery. This work includes three main contributions in the battery field listed below. Direct Measurement of Effective Electronic Transport in Porous Li-ion Electrodes. An accurate assessment of the electronic conductivity of electrodes is necessary for understanding and optimizing battery performance. The bulk electronic conductivity of porous LiCoO2-based cathodes was measured as a function of porosity, pressure, carbon fraction, and the presence of an electrolyte. The measurements were performed by delamination of thin-film electrodes from their aluminum current collectors and by use of a four-line probe. Imaging and Correlating Microstructure To Conductivity. Transport properties of porous electrodes are strongly related to microstructure. An experimental 3D microstructure is needed not only for computation of direct transport properties, but also for a detailed electrode microstructure characterization. This work utilized X-ray tomography and focused ion beam (FIB)/scanning electron microscopy (SEM) to obtain the 3D structures of alkaline battery cathodes. FIB/SEM has the advantage of detecting carbon additives; thus, it was the main tomography tool employed. Additionally, protocols and techniques for acquiring, processing and segmenting series of FIB/SEM images were developed as part of this work. FIB/SEM images were also used to correlate electrodes' microstructure to their respective conductivities for both Li-ion and alkaline batteries. Electrode Microstructure Metrics and the 3D Stochastic Grid Model. A detailed characterization of microstructure was conducted in this work, including characterization of the

  17. 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.

  18. Stacking dependence of carrier transport properties in multilayered black phosphorous.

    PubMed

    Sengupta, A; Audiffred, M; Heine, T; Niehaus, T A

    2016-02-24

    We present the effect of different stacking orders on carrier transport properties of multi-layer black phosphorous. We consider three different stacking orders AAA, ABA and ACA, with increasing number of layers (from 2 to 6 layers). We employ a hierarchical approach in density functional theory (DFT), with structural simulations performed with generalized gradient approximation (GGA) and the bandstructure, carrier effective masses and optical properties evaluated with the meta-generalized gradient approximation (MGGA). The carrier transmission in the various black phosphorous sheets was carried out with the non-equilibrium green's function (NEGF) approach. The results show that ACA stacking has the highest electron and hole transmission probabilities. The results show tunability for a wide range of band-gaps, carrier effective masses and transmission with a great promise for lattice engineering (stacking order and layers) in black phosphorous. PMID:26809017

  19. Generalized thermodynamic and transport properties. II. Molecular liquids.

    PubMed

    Bertolini, D; Tani, A

    2011-03-01

    In the present paper, we extend the method described in paper I [D. Bertolini and A. Tani, preceding paper, Phys. Rev. E 83, 031201 (2011)] to molecular liquids, which allows us to solve the exact kinetic equation proposed by de Schepper et al. [Phys. Rev. A 38, 271 (1988)] without approximations. In particular, generalized thermodynamic properties (enthalpy, specific heat, and thermal expansion coefficient) and transport properties (longitudinal viscosity, thermal conductivity) have been calculated for three liquids of increasing complexity, namely dimethyl sulfoxide, hydrogen fluoride, and SPC/E water. All results have been obtained by the molecular formalism as well as the atomic one, corrected for intramolecular correlations that are due to the models adopted. As done for simple liquids, the coupling between the viscous stress tensor and the energy flux vector has been calculated exactly. We also show that the Markov assumption for the dynamics related to thermal conductivity can only be adopted with caution.

  20. Diameter Dependence of the Transport Properties of Antimony Telluride Nanowires

    NASA Astrophysics Data System (ADS)

    Zuev, Yuri; Lee, Jin Sook; Park, Hongkun; Kim, Philip

    2010-03-01

    We report measurements of electronic, thermoelectric, and galvanometric properties of individual semimetallic single crystal antimony telluride (Sb2Te3) nanowires. Microfabricated heater and thermometer electrodes were used to probe the transport properties of the nanowires with diameters in the range of 22 - 95nm and temperatures in the range of 2 - 300K. Temperature dependent resistivity varies depending on nanowire diameter. Thermoelectric power (TEP) measurements indicate hole dominant diffusive thermoelectric generation, with an enhancement of the TEP for smaller diameter wires. The large surface-to-volume ratio of Sb2Te3 nanowires makes them an excellent platform to explore novel phenomena in this predicted topological insulator. We investigate mesoscopic magnetoresistance effects in magnetic fields both parallel and perpendicular to the nanowire axis.

  1. Predicting the transport properties of sedimentary rocks from microgeometry

    SciTech Connect

    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.

  2. Predicting the transport properties of sedimentary rocks from microgeometry

    SciTech Connect

    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.

  3. Simplified curve fits for the transport properties of equilibrium air

    NASA Technical Reports Server (NTRS)

    Srinivasan, S.; Tannehill, J. C.

    1987-01-01

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

  4. Stacking dependence of carrier transport properties in multilayered black phosphorous

    NASA Astrophysics Data System (ADS)

    Sengupta, A.; Audiffred, M.; Heine, T.; Niehaus, T. A.

    2016-02-01

    We present the effect of different stacking orders on carrier transport properties of multi-layer black phosphorous. We consider three different stacking orders AAA, ABA and ACA, with increasing number of layers (from 2 to 6 layers). We employ a hierarchical approach in density functional theory (DFT), with structural simulations performed with generalized gradient approximation (GGA) and the bandstructure, carrier effective masses and optical properties evaluated with the meta-generalized gradient approximation (MGGA). The carrier transmission in the various black phosphorous sheets was carried out with the non-equilibrium green’s function (NEGF) approach. The results show that ACA stacking has the highest electron and hole transmission probabilities. The results show tunability for a wide range of band-gaps, carrier effective masses and transmission with a great promise for lattice engineering (stacking order and layers) in black phosphorous.

  5. Control of photon transport properties in nanocomposite nanowires

    NASA Astrophysics Data System (ADS)

    Moffa, M.; Fasano, V.; Camposeo, A.; Persano, L.; Pisignano, D.

    2016-02-01

    Active nanowires and nanofibers can be realized by the electric-field induced stretching of polymer solutions with sufficient molecular entanglements. The resulting nanomaterials are attracting an increasing attention in view of their application in a wide variety of fields, including optoelectronics, photonics, energy harvesting, nanoelectronics, and microelectromechanical systems. Realizing nanocomposite nanofibers is especially interesting in this respect. In particular, methods suitable for embedding inorganic nanocrystals in electrified jets and then in active fiber systems allow for controlling light-scattering and refractive index properties in the realized fibrous materials. We here report on the design, realization, and morphological and spectroscopic characterization of new species of active, composite nanowires and nanofibers for nanophotonics. We focus on the properties of light-confinement and photon transport along the nanowire longitudinal axis, and on how these depend on nanoparticle incorporation. Optical losses mechanisms and their influence on device design and performances are also presented and discussed.

  6. Stacking dependence of carrier transport properties in multilayered black phosphorous.

    PubMed

    Sengupta, A; Audiffred, M; Heine, T; Niehaus, T A

    2016-02-24

    We present the effect of different stacking orders on carrier transport properties of multi-layer black phosphorous. We consider three different stacking orders AAA, ABA and ACA, with increasing number of layers (from 2 to 6 layers). We employ a hierarchical approach in density functional theory (DFT), with structural simulations performed with generalized gradient approximation (GGA) and the bandstructure, carrier effective masses and optical properties evaluated with the meta-generalized gradient approximation (MGGA). The carrier transmission in the various black phosphorous sheets was carried out with the non-equilibrium green's function (NEGF) approach. The results show that ACA stacking has the highest electron and hole transmission probabilities. The results show tunability for a wide range of band-gaps, carrier effective masses and transmission with a great promise for lattice engineering (stacking order and layers) in black phosphorous.

  7. Optical and electrical transport properties of semicontinuous metallic films

    NASA Astrophysics Data System (ADS)

    Seal, Katyayani

    Semicontinuous metallic films posses unique optical and electrical transport properties. The strong localization and large enhancement of electric fields demonstrated by these films make them interesting in terms of a fundamental understanding of these phenomena as well as potentially useful in a large variety of applications. The field distributions and electrical transport properties of these films depend on the structural geometry and morphology of the samples and therefore also on the metal concentration, with distinctive properties near the percolation threshold where an insulator-to-metal transition occurs. This dissertation focuses on an experimental investigation of the optical, electrical transport and structural properties of semicontinuous silver-glass composites near the percolation threshold. Particular emphasis is placed on the optical enhancement observed in these films in terms of their near-field optical intensity distribution. The samples were synthesized by pulsed laser ablation and the percolation threshold was identified in terms of structural properties using transmission electron microscopy as well as electrical resistivity and optical transmission through in-situ measurements during sample synthesis. The optical intensity distributions were measured using near-field optical microscopy (NSOM) and found to depend strongly on metal concentration and wavelength. The degree of localization was found to increase as metal concentrations was varied above and below the percolation threshold and also found to increase with increase in wavelength. Comparisons of the experimental results with theoretical calculations of the local field distributions obtained using the block elimination method showed good agreement. In addition, composite systems involving the coupling of enhancement from semicontinuous films with two other resonance phenomena are also studied viz. semicontinuous films (1) with random subwavelength apertures and (2) deposited on

  8. FLUID- THERMODYNAMIC AND TRANSPORT PROPERTIES OF FLUIDS (IBM PC VERSION)

    NASA Technical Reports Server (NTRS)

    Fessler, T. E.

    1994-01-01

    The accurate computation of the thermodynamic and transport properties of fluids is a necessity for many engineering calculations. The FLUID program was developed to calculate the thermodynamic and transport properties of pure fluids in both the liquid and gas phases. Fluid properties are calculated using a simple gas model, empirical corrections, and an efficient numerical interpolation scheme. FLUID produces results that are in very good agreement with measured values, while being much faster than older more complex programs developed for the same purpose. A Van der Waals equation of state model is used to obtain approximate state values. These values are corrected for real-gas effects by model correction factors obtained from tables based on experimental data. These tables also accurately compensate for the special circumstances which arise whenever phase conditions occur. Viscosity and thermal conductivity values are computed directly from tables. Interpolation within tables is based on Lagrange's three point formula. A set of tables must be generated for each fluid implemented. FLUID currently contains tables for nine fluids including dry air and steam. The user can add tables for any fluid for which adequate thermal property data is available. The FLUID routine is structured so that it may easily be incorporated into engineering programs. The IBM 360 version of FLUID was developed in 1977. It is written in FORTRAN IV and has been implemented on an IBM 360 with a central memory requirement of approximately 222K of 8 bit bytes. The IBM PC version of FLUID is written in Microsoft FORTRAN 77 and has been implemented on an IBM PC with a memory requirement of 128K of 8 bit bytes. The IBM PC version of FLUID was developed in 1986.

  9. FLUID- THERMODYNAMIC AND TRANSPORT PROPERTIES OF FLUIDS (IBM VERSION)

    NASA Technical Reports Server (NTRS)

    Fessler, T. E.

    1994-01-01

    The accurate computation of the thermodynamic and transport properties of fluids is a necessity for many engineering calculations. The FLUID program was developed to calculate the thermodynamic and transport properties of pure fluids in both the liquid and gas phases. Fluid properties are calculated using a simple gas model, empirical corrections, and an efficient numerical interpolation scheme. FLUID produces results that are in very good agreement with measured values, while being much faster than older more complex programs developed for the same purpose. A Van der Waals equation of state model is used to obtain approximate state values. These values are corrected for real-gas effects by model correction factors obtained from tables based on experimental data. These tables also accurately compensate for the special circumstances which arise whenever phase conditions occur. Viscosity and thermal conductivity values are computed directly from tables. Interpolation within tables is based on Lagrange's three point formula. A set of tables must be generated for each fluid implemented. FLUID currently contains tables for nine fluids including dry air and steam. The user can add tables for any fluid for which adequate thermal property data is available. The FLUID routine is structured so that it may easily be incorporated into engineering programs. The IBM 360 version of FLUID was developed in 1977. It is written in FORTRAN IV and has been implemented on an IBM 360 with a central memory requirement of approximately 222K of 8 bit bytes. The IBM PC version of FLUID is written in Microsoft FORTRAN 77 and has been implemented on an IBM PC with a memory requirement of 128K of 8 bit bytes. The IBM PC version of FLUID was developed in 1986.

  10. Coronary microvascular obstruction in acute myocardial infarction.

    PubMed

    Niccoli, Giampaolo; Scalone, Giancarla; Lerman, Amir; Crea, Filippo

    2016-04-01

    The success of a primary percutaneous intervention (PCI) in the setting of ST elevation myocardial infarction depends on the functional and structural integrity of coronary microcirculation. Coronary microvascular dysfunction and obstruction (CMVO) occurs in up to half of patients submitted to apparently successful primary PCI and is associated to a much worse outcome. The current review summarizes the complex mechanisms responsible for CMVO, including pre-existing coronary microvascular dysfunction, and highlights the current limitations in the assessment of microvascular function. More importantly, at the light of the substantial failure of trials hitherto published on the treatment of CMVO, this review proposes a novel integrated therapeutic approach, which should overcome the limitations of previous studies.

  11. Nonlinear Transport and Noise Properties of Acoustic Phonons

    NASA Astrophysics Data System (ADS)

    Walczak, Kamil

    We examine heat transport carried by acoustic phonons in molecular junctions composed of organic molecules coupled to two thermal baths of different temperatures. The phononic heat flux and its dynamical noise properties are analyzed within the scattering (Landauer) formalism with transmission probability function for acoustic phonons calculated within the method of atomistic Green's functions (AGF technique). The perturbative computational scheme is used to determine nonlinear corrections to phononic heat flux and its noise power spectral density with up to the second order terms with respect to temperature difference. Our results show the limited applicability of ballistic Fourier's law and fluctuation-dissipation theorem to heat transport in quantum systems. We also derive several noise-signal relations applicable to nanoscale heat flow carried by phonons, but valid for electrons as well. We also discuss the extension of the perturbative transport theory to higher order terms in order to address a huge variety of problems related to nonlinear thermal effects which may occur at nanoscale and at strongly non-equilibrium conditions with high-intensity heat fluxes. This work was supported by Pace University Start-up Grant.

  12. Transport properties of highly ordered heterogeneous ion-exchange membranes.

    PubMed

    Shapiro, V; Freger, V; Linder, C; Oren, Y

    2008-08-01

    Model "ordered" heterogeneous ion exchange membranes are made with ion exchange particles heaving ion exchange capacity in the range 3 to 2.5 meq/gr (dry basis) and diameters ranging from 37 to 7 microm and 2 component room-temperature vulcanizing silicon rubber as a polymeric matrix, by applying an electric field normal to the membrane surface during preparation. These membranes were shown to have an improved ionic conductivity compared with "nonordered" membranes based on the same ion exchange content (for instance, at 10% resin content "nonordered" membranes show <10(-5) mS/cm while "ordered" membranes have conductivity of 1 mS/cm). The transport properties of ordered membranes were compared with those of nonordered membranes, through the current-voltage characteristics. Limiting currents measured for the ordered membranes were significantly higher than those of the nonordered membranes with the same resin concentration. In addition, higher limiting currents were observed in ordered membranes as the resin particles became smaller. Energy dispersion spectrometry analyses revealed that the concentration of cation exchange groups on the membrane surface was higher for ordered membrane as compared to that of nonordered membranes. This implies that the local current density for the conducting domains at the surface of the nonordered membranes is higher, leading to higher concentration polarization and, eventually, to lower average limiting current densities. The effect of ordering the particles on the membrane conductivity and transport properties was studied, and the advantages of the ordered membranes are discussed.

  13. Topological phases and transport properties of screened interacting quantum wires

    NASA Astrophysics Data System (ADS)

    Xu, Hengyi; Xiong, Ye; Wang, Jun

    2016-10-01

    We study theoretically the effects of long-range and on-site Coulomb interactions on the topological phases and transport properties of spin-orbit-coupled quasi-one-dimensional quantum wires imposed on a s-wave superconductor. The distributions of the electrostatic potential and charge density are calculated self-consistently within the Hartree approximation. Due to the finite width of the wires and charge repulsion, the potential and density distribute inhomogeneously in the transverse direction and tend to accumulate along the lateral edges where the hard-wall confinement is assumed. This result has profound effects on the topological phases and the differential conductance of the interacting quantum wires and their hybrid junctions with superconductors. Coulomb interactions renormalize the gate voltage and alter the topological phases strongly by enhancing the topological regimes and producing jagged boundaries. Moreover, the multicritical points connecting different topological phases are modified remarkably in striking contrast to the predictions of the two-band model. We further suggest the possible non-magnetic topological phase transitions manipulated externally with the aid of long-range interactions. Finally, the transport properties of normal-superconductor junctions are further examined, in particular, the impacts of Coulomb interactions on the zero-bias peaks related to the Majorana fermions and near zero-energy peaks.

  14. Transport and divertor properties of the dynamic ergodic divertor

    NASA Astrophysics Data System (ADS)

    Lehnen, M.; Abdullaev, S.; Biel, W.; de Bock, M. F. M.; Brezinsek, S.; Busch, C.; Classen, I.; Finken, K. H.; von Hellermann, M.; Jachmich, S.; Jakubowski, M.; Jaspers, R.; Koslowski, H. R.; Krämer-Flecken, A.; Kikuchi, Y.; Liang, Y.; Nicolai, A.; Pospieszczyk, A.; Van Rompuy, T.; Samm, U.; Schmitz, O.; Sergienko, G.; Unterberg, B.; Wolf, R.; Zimmermann, O.; TEXTOR Team

    2005-12-01

    The concept of the dynamic ergodic divertor (DED) is based on plasma edge ergodization by a resonant perturbation. Such a divertor concept is closely related to helical or island divertors in stellerators. The base mode of the DED perturbation field can be m/n = 12/4, 6/2 or 3/1. The 3/1 base mode with its deep penetration of the perturbation field provides the excitation of tearing modes. This topic was presented elsewhere. In this contribution we concentrate on the divertor properties of the DED. We report on the characterization of the topology, transport properties in ergodic fields, impurity transport and density limit behaviour. The 12/4 base where the perturbation is restricted to the plasma edge is suitable for divertor operation. With increasing perturbation field island chains are built up at the resonance layers. Overlapping islands lead to ergodization. The plasma is guided in the laminar region via open field lines of short connection length to the divertor target. The magnetic topology is not only controlled by the coil current but especially by the edge safety factor. For appropriate edge safety factor we observe a strong temperature drop in the plasma edge, indicating an expansion of the laminar region, which is necessary to decouple the divertor plasma from the core plasma. The modifications of the magnetic topology can be directly seen, for example, from carbon emission lines. The magnetic structure is calculated by the ATLAS code and shows good agreement with the experimental findings.

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

    SciTech Connect

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

    2010-03-29

    The goal of the Cementitious Barriers Partnership (CBP) is to develop a reasonable and realible set of tools to reduce the uncertainty in predicting the structural, hydraulic and chemical performance of cement barriers used in nuclear applications that are exposed to dynamic environmental conditions over extended time frames. One of these tools, the responsibility of NIST, is THAMES (Thermodynamic Hydration and Microstructure Evolution Simulator), which is being developed to describe cementitious binder microstructures and calculate important engineering properties during hydration and degradation. THAMES is designed to be a 'micro-probe', used to evaluate changes in microstructure and properties occurring over time because of hydration or degradation reactions in a volume of about 0.001 mm{sup 3}. It will be used to map out microstructural and property changes across reaction fronts, for example, with spatial resolution adequate to be input into other models (e.g., STADIUM{reg_sign}, LeachSX{trademark}) in the integrated CBP package. THAMES leverages thermodynamic predictions of equilibrium phase assemblages in aqueous geochemical systems to estimate 3-D virtual microstructures of a cementitious binder at different times during the hydration process or potentially during degradation phenomena. These virtual microstructures can then be used to calculate important engineering properties of a concrete made from that binder at prescribed times. In this way, the THAMES model provides a way to calculate the time evolution of important material properties such as elastic stiffness, compressive strength, diffusivity, and permeability. Without this model, there would be no way to update microstructure and properties for the barrier materials considered as they are exposed to the environment, thus greatly increasing the uncertainty of long-term transport predictions. This Task 7 report demonstrates the current capabilities of THAMES. At the start of the CBP project, THAMES

  16. 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.

  17. Thrombin stimulates albumin transcytosis in lung microvascular endothelial cells via activation of acid sphingomyelinase.

    PubMed

    Kuebler, Wolfgang M; Wittenberg, Claudia; Lee, Warren L; Reppien, Eike; Goldenberg, Neil M; Lindner, Karsten; Gao, Yizhuo; Winoto-Morbach, Supandi; Drab, Marek; Mühlfeld, Christian; Dombrowsky, Heike; Ochs, Matthias; Schütze, Stefan; Uhlig, Stefan

    2016-04-15

    Transcellular albumin transport occurs via caveolae that are abundant in lung microvascular endothelial cells. Stimulation of albumin transcytosis by proinflammatory mediators may contribute to alveolar protein leak in lung injury, yet the regulation of albumin transport and its underlying molecular mechanisms are so far incompletely understood. Here we tested the hypothesis that thrombin may stimulate transcellular albumin transport across lung microvascular endothelial cells in an acid-sphingomyelinase dependent manner. Thrombin increased the transport of fluorescently labeled albumin across confluent human lung microvascular endothelial cell (HMVEC-L) monolayers to an extent that markedly exceeds the rate of passive diffusion. Thrombin activated acid sphingomyelinase (ASM) and increased ceramide production in HMVEC-L, but not in bovine pulmonary artery cells, which showed little albumin transport in response to thrombin. Thrombin increased total caveolin-1 (cav-1) content in both whole cell lysates and lipid rafts from HMVEC-L, and this effect was blocked by inhibition of ASM or de novo protein biosynthesis. Thrombin-induced uptake of albumin into lung microvascular endothelial cells was confirmed in isolated-perfused lungs by real-time fluorescence imaging and electron microscopy of gold-labeled albumin. Inhibition of ASM attenuated thrombin-induced albumin transport both in confluent HMVEC-L and in intact lungs, whereas HMVEC-L treatment with exogenous ASM increased albumin transport and enriched lipid rafts in cav-1. Our findings indicate that thrombin stimulates transcellular albumin transport in an acid sphingomyelinase-dependent manner by inducing de novo synthesis of cav-1 and its recruitment to membrane lipid rafts. PMID:26851257

  18. 41 CFR 302-7.10 - Is property acquired en route eligible for transportation at Government expense?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Property Management Federal Travel Regulation System RELOCATION ALLOWANCES TRANSPORTATION AND STORAGE OF PROPERTY 7-TRANSPORTATION AND TEMPORARY STORAGE OF HOUSEHOLD GOODS AND PROFESSIONAL BOOKS, PAPERS,...

  19. Dietary nitrite prevents hypercholesterolemic microvascular inflammation and reverses endothelial dysfunction.

    PubMed

    Stokes, Karen Y; Dugas, Tammy R; Tang, Yaoping; Garg, Harsha; Guidry, Eric; Bryan, Nathan S

    2009-05-01

    The nitrite anion is an endogenous product of mammalian nitric oxide (NO) metabolism, a key intermediate in the nitrogen cycle in plants, and a constituent of many foods. Research over the past 6 years has revealed surprising biological and cytoprotective activity of this anion. Hypercholesterolemia causes a proinflammatory phenotype in the microcirculation. This phenotype appears to result from a decline in NO bioavailability that results from a reduction in NO biosynthesis, inactivation of NO by superoxide, or both. Since nitrite has been shown to be potently cytoprotective and restore NO biochemical homeostasis, we investigated if supplemental nitrite could attenuate microvascular inflammation caused by a high cholesterol diet. C57Bl/6J mice were fed either a normal diet or a high cholesterol diet for 3 wk to induce microvascular inflammation. Mice on the high cholesterol diet received either nitrite-free drinking water or supplemental nitrite at 33 or 99 mg/l ad libitum in their drinking water. The results from this investigation reveal that mice fed a cholesterol-enriched diet exhibited significantly elevated leukocyte adhesion to and emigration through the venular endothelium as well as impaired endothelium-dependent relaxation in arterioles. Administration of nitrite in the drinking water inhibited the leukocyte adhesion and emigration and prevented the arteriolar dysfunction. This was associated with sparing of reduced tetrahydrobiopterin and decreased levels of C-reactive protein. These data reveal novel anti-inflammatory properties of nitrite and implicate the use of nitrite as a new natural therapy for microvascular inflammation and endothelial dysfunction associated with hypercholesterolemia.

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

    NASA Astrophysics Data System (ADS)

    Xiao, John Q.

    Structural, magnetic, and magneto-transport properties of three different classes of artificially structured materials: (1) multilayers (Fe(110)/Ag(111) and Fe(110)/W(110)), (2) Fe-nitrides, and (3) metallic granular solids (Co/Ag, Co/Cu Fe/Ag and (Ni-Fe)/Ag), prepared by magnetron sputtering are presented. In the multilayers, the structure has been characterized using both low-angle and high-angle x-ray diffraction together with theoretical modeling. The magnetic properties of the Fe/Ag and Fe/W multilayers have been studied when the layer thickness of Fe and the intervening Ag or W layers are systematically varied. In the case of Fe/Ag multilayers, the interfaces are sharp. The Fe magnetic moment slightly increases with decreasing Fe layer thickness. The magnetization shows a B T^{3/2} dependence with very large values of B. In the Fe/W multilayers, there are small intermixed regions of one or two monolayers at the interfaces. The Fe moments within this region are deteriorated, whereas the rest of the Fe moments maintain their bulk values. With reactive sputtering using a mixture of argon and ammonia gases, all stable Fe-nitrides (gamma ^'-Fe_4N, varepsilon-Fe_{2 -3}N, and zeta-Fe _2N) of single phase can be fabricated. The phase diagram of Fe-nitride composition as a function of pressure of NH_3 has been determined. The magnetic properties and the Mossbauer parameters are in excellent agreement with those from the bulk samples. The magneto-transport properties in metallic granular solids, related metastable alloys and in samples with mixed phases, have been extensively studied. We have investigated the magneto-transport properties as a function of the annealing temperature, temperatures, and the magnetic concentration. For the first time, giant magnetoresistance (GMR) has been observed in non-layered but granular solids. We have shown that the GMR is isotropic and is the extra resistivity due to scattering from the non-aligned ferromagnetic entities. This extra

  1. Roles of LOX-1 in microvascular dysfunction.

    PubMed

    Lubrano, Valter; Balzan, Silvana

    2016-05-01

    Studies from human and animal models with metabolic disease and hypertension highlight atrophic remodeling, reduced lumen size and thinner vascular walls of microvessels with profound density reduction. This impaired vascular response limits the perfusion of peripheral tissues inducing organ damage. These conditions are strongly associated with oxidative stress and in particular with the up-regulation of lectin-like oxidized low density lipoprotein receptor-1 (LOX-1). Several factors such as cytokines, shear stress, and advanced glycation end-products, especially oxLDL, can up-regulate LOX-1. The activation of this receptor induces the production of adhesion molecules, cytokines and the release of reactive oxygen species via NADPH oxidase. LOX-1 is considered a potent mediator of endothelial dysfunction and it is significantly associated with reduced microvascular endothelium NO-dependent vasodilation in hypercholesterolemia and hypertension. Microvascular endothelial cells increased the expression of IL-6 in association with the increased concentration of LDL and its degree of oxidation. Moreover, increased IL-6 levels are associated with up-regulation of LOX-1 in a dose-dependent manner. Another consequence of microvascular inflammation is the generation of small amounts of ROS, similar to those induced by low concentration of oxLDL (<5 μg/mL) which induces capillary tube formation of endothelial cells, through LOX-1 up-regulation. In light of its central role, LOX-1 represents an attractive therapeutic target for the treatment of human atherosclerotic diseases and microvascular disorders. PMID:26907636

  2. 1D-transport properties of single superconducting lead nanowires

    NASA Astrophysics Data System (ADS)

    Michotte, S.; Mátéfi-Tempfli, S.; Piraux, L.

    2003-09-01

    We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have uniform diameter of ∼40 nm and a very large aspect ratio (∼500). The diameter of the nanowire is small enough to ensure a 1D superconducting regime in a wide temperature range below Tc. The non-zero resistance in the superconducting state and its variation caused by fluctuations of the superconducting order parameter were measured versus temperature, magnetic field, and applied DC current (or voltage). The current induced breakdowns in the V- I characteristics may be explained by the formation of phase slip centers. Moreover, DC voltage driven measurements reveal the existence of a new S-shape behavior near the formation of these phase slip centers.

  3. Research on transport properties of HFC-227ea

    NASA Astrophysics Data System (ADS)

    Shi, Lin; Liu, Xiaojun; Duan, Yuanyuan; Han, Lizhong; Zhu, Mingshan

    2001-10-01

    HFC-227ea(1,1,1,2,3,3,3-heptafluoropropane) is considered as a promising refrigerant alternative, especially as a component in mixtures, to replace to CFC-12, HCFC-22 and R502. But reliable transport properties data for HFC-227ea are very limited. In this paper, experimental data of viscosity along the saturation line and gaseous thermal conductivity of HFC-227ea are given. The viscosity of HFC-227ea was measured with a capillary viscometer at temperatures between 263.15 K and 333.15 K along the saturation line and its uncertainty of the results is estimated to be no more than ±3%. The thermal conductivity of gaseous HFC-227ea was also measured with a transient hot-wire instrument at temperatures between 259.28 K and 341.75 K and pressures up to 1.289MPa, and its uncertainty of the results is estimated to be less than ±1%.

  4. Improved Carrier-Transport Properties of Passivated Cdmnte Crystals

    SciTech Connect

    Kim, K.; Camarda, G; Bolotnikov, A; James, R; Hong, J; Kim, S

    2009-01-01

    By analyzing photoconductive decay curves, we compared the surface recombination velocities of semi-insulating CdMnTe:In crystals grown by the vertical Bridgman method with or without surface passivation. Sulfur passivation effectively prevents the formation of a conductive Te oxide layer on the CdMnTe surface and reduces the surface recombination velocities by about one third. We demonstrated, from IR observations of the distribution maps of Te precipitates, that their configuration affects the anomalous photoconductive decay curves and the gamma-ray spectrum in some areas of the CdMnTe crystal. Notably, not only the size but also the spatial configuration of the Te precipitates modulates the carrier-transport properties.

  5. Coarse grained modeling of transport properties in monoclonal antibody solution

    NASA Astrophysics Data System (ADS)

    Swan, James; Wang, Gang

    Monoclonal antibodies and their derivatives represent the fastest growing segment of the bio pharmaceutical industry. For many applications such as novel cancer therapies, high concentration, sub-cutaneous injections of these protein solutions are desired. However, depending on the peptide sequence within the antibody, such high concentration formulations can be too viscous to inject via human derived force alone. Understanding how heterogenous charge distribution and hydrophobicity within the antibodies leads to high viscosities is crucial to their future application. In this talk, we explore a coarse grained computational model of therapeutically relevant monoclonal antibodies that accounts for electrostatic, dispersion and hydrodynamic interactions between suspended antibodies to predict assembly and transport properties in concentrated antibody solutions. We explain the high viscosities observed in many experimental studies of the same biologics.

  6. Electrical Transport Properties of Au-Doped Deoxyribonucleic Acid Molecules

    NASA Astrophysics Data System (ADS)

    Hwang, Jong Seung; Hong, Su Heon; Kim, Hyung Kwon; Kwon, Young Whan; Jin, Jung Il; Hwang, Sung Woo; Ahn, Doyeol

    2005-04-01

    Deoxyribonucleic acid (DNA) molecules were doped with Au atoms and their electrical transport properties were measured. The Au doping was carried out by incubating a mixture of HAuCl4\\cdot3H2O and DNA solutions. The binding of Au atoms to DNA bases was identified using Fourier transform infrared spectroscopy and X-ray photoemission spectroscopy. The Au-doped DNA molecules were deposited on nanoelectrodes and the presence of the molecules between the electrodes was determined by both scanning electron microscopy and atomic force microscopy. Measurement of the current-voltage characteristics showed that the Au-doped DNA molecules exhibited a higher conductivity than undoped DNA molecules. Detailed analysis of the chemical composition shows that there is a strong possibility of reliably controlling the conductivity of DNA molecules using this method.

  7. Electronic transport properties of a quinone-based molecular switch

    NASA Astrophysics Data System (ADS)

    Zheng, Ya-Peng; Bian, Bao-An; Yuan, Pei-Pei

    2016-09-01

    In this paper, we carried out first-principles calculations based on density functional theory and non-equilibrium Green's function to investigate the electronic transport properties of a quinone-based molecule sandwiched between two Au electrodes. The molecular switch can be reversibly switched between the reduced hydroquinone (HQ) and oxidized quinone (Q) states via redox reactions. The switching behavior of two forms is analyzed through their I- V curves, transmission spectra and molecular projected self-consistent Hamiltonian at zero bias. Then we discuss the transmission spectra of the HQ and Q forms at different bias, and explain the oscillation of current according to the transmission eigenstates of LUMO energy level for Q form. The results suggest that this kind of a quinone-based molecule is usable as one of the good candidates for redox-controlled molecular switches.

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

    PubMed

    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/cm(3), the temperature increases rapidly along the Hugoniot, and the optical conductivity decreases, indicating simple liquid metal behavior.

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

    NASA Astrophysics Data System (ADS)

    Patel, A. B.; Bhatt, N. K.; Thakore, B. Y.; Vyas, P. R.; Jani, A. R.

    2014-04-01

    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.

  10. Optical and transport properties of dense liquid silica

    SciTech Connect

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

    2015-06-15

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

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

    SciTech Connect

    Patel, A. B. Bhatt, N. K. Thakore, B. Y. Jani, A. R.; Vyas, P. R.

    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.

  12. Microvascular dysfunction in the context of diabetic neuropathy.

    PubMed

    Stirban, Alin

    2014-01-01

    Microvascular dysfunction in diabetes plays a crucial role in the development of diabetic complications. The skin, as one of the most accessible organs, serves as a model for the investigation of microvascular dysfunction. Several non-invasive, mostly laser-Doppler-based methods have been developed lately to assess microvascular function in the skin. Microvascular functional changes occur even in the prediabetic state and become more complex with overt diabetes, being exacerbated by the presence of peripheral and/or autonomic diabetic neuropathy. The present article aims at shedding light on the implication of endothelial and neurovascular dysfunction in microvascular changes in diabetes, highlighting the contribution of different forms of diabetic neuropathy.

  13. Compaction and transport properties of newly replicated Caulobacter crescentus DNA.

    PubMed

    Hong, Sun-Hae; McAdams, Harley H

    2011-12-01

    Upon initiating replication of the Caulobacter chromosome, one copy of the parS centromere remains at the stalked pole; the other moves to the distal pole. We identified the segregation dynamics and compaction characteristics of newly replicated Caulobacter DNA during transport (highly variable from cell to cell) using time-lapse fluorescence microscopy. The parS centromere and a length (also highly variable) of parS proximal DNA on each arm of the chromosome are segregated with the same relatively slow transport pattern as the parS locus. Newly replicated DNA further than about 100 kb from parS segregates with a different and faster pattern, while loci at 48 kb from parS segregate with the slow pattern in some cells and the fast pattern in others. The observed parS-proximal DNA compaction characteristics have scaling properties that suggest the DNA is branched. HU2-deletion strains exhibited a reduced compaction phenotype except near the parS site where only the ΔHU1ΔHU2 double mutant had a compaction phenotype. The chromosome shows speed-dependent extension during translocation suggesting the DNA polymer is under tension. While DNA segregation is highly reliable and succeeds in virtually all wild-type cells, the high degree of cell to cell variation in the segregation process is noteworthy.

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

    SciTech Connect

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

    2015-02-23

    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 SiO{sub 2} 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 SiO{sub 2} substrates and reduces the hysteresis at room temperature.

  15. Transport properties of nanoconstrictions in armchair graphene ribbons

    NASA Astrophysics Data System (ADS)

    Romanovsky, Igor; Yannouleas, Constantine; Landman, Uzi

    2014-03-01

    The transport properties of nanoconstrictions and quantum-point contacts formed in atomically precise segmented armchair graphene nanoribbons (SaGRs) are investigated using a tight-binding non-equilibrium Green's function (TB-NEGF) approach and relativistic quantum-field theory modeling.[2] The TB behavior is accounted for by a one-dimensional Dirac-transfer-matrix (DTM) model using variable-mass (scalar-field) barriers assigned to the junctions between the nanoribbon segments. It is shown that the topology of the junctions (sharp versus smooth) and the ratio of length over width of the constriction are the principal factors influencing the height of the mass barriers, and thus they control the extent of trapping and confinement by the constriction of graphene's relativistic carriers, even in the case of all-metallic SaGRs. A rich variety of transport patterns ensues, ranging from ballistic quantized conductance to resonant tunneling associated with Coulomb blockade. Supported by the U.S. D.O.E. (FG05-86ER-45234).

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

    SciTech Connect

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

    2012-06-01

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

  17. 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.

  18. Predicting the transport properties of sedimentary rocks from microstructure

    SciTech Connect

    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.

  19. RELATIONSHIP BETWEEN CELL SURFACE PROPERTIES AND TRANSPORT OF BACTERIA THROUGH SOIL

    EPA Science Inventory

    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...

  20. Elastic and transport properties in polycrystals of crackedgrains: Cross-property relations and microstructure

    SciTech Connect

    Berryman, J.G.

    2007-10-02

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

  1. The mechanisms of gastric mucosal injury: focus on microvascular endothelium as a key target.

    PubMed

    Tarnawski, A S; Ahluwalia, A; Jones, M K

    2012-01-01

    This paper reviews and updates current views on gastric mucosal injury with a focus on the microvascular endothelium as the key target and the role of the anti-apoptosis protein survivin. Under normal conditions, mucosal integrity is maintained by well structured and mutually amplifying defense mechanisms, which include pre-epithelial "barrier"--the first line of defense; and, an epithelial "barrier". Other important defense mechanisms of gastric mucosa include: continuous epithelial cell renewal, blood flow through mucosal microvessels (providing oxygen and nutrients), an endothelial microvascular "barrier," sensory innervation, and generation of PGs, nitric oxide and hydrogen sulfide. The microvascular endothelium lining gastric mucosal blood microvessels severs not only as a barrier but is a biologically active tissue involved in many synthetic and metabolic functions. It allows transport of oxygen and nutrients, and produces prostaglandins and leukotriens, procoagulant factors, nitric oxide, endothelin, ghrelin, HSP, growth factors such VEGF, bFGF, angiopoietin 2 and others, specific types of collagen, plasminogen activator, and can also actively contract. Accumulating evidence indicates that the gastric microvascular endothelium is a critical target for injury by ethanol, NSAIDs, free radicals, ischemia-reperfusion and other damaging factors. The injury--microvessel rupture, plasma and erythrocyte extravasation, platelet aggregation and fibrin deposition caused by these damaging factors--occurs early (1-5 min), precedes glandular epithelial cell injury and results in cessation of blood flow, ischemia, hypoxia and impaired oxygen and nutrient transport. As a consequence, mucosal necrosis develops. One of the main reasons for the increased susceptibility of gastric microvascular endothelial (vs. epithelial) cells to injury is reduced expression levels of survivin, an anti-apoptosis protein, which is a regulator of both proliferation and cell survival. PMID

  2. Theoretical study on transport properties of topological states of matter

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiu-Chuan

    In condensed matter physics, states of matter are usually classified by symmetry. Topological states of matter describe new quantum states of matter that cannot adiabatically connect to conventional states of matter even though they share the same symmetry. Thus, the discovery of topological states of matter has opened a new research era and attracted intensive research interests in recent years. This dissertation is devoted to the theoretical and numerical study of transport properties of topological states of matter, mainly focusing on two topological systems, time reversal invariant topological insulator nano-structures and the quantum anomalous Hall insulators. The first system studied in this dissertation is time reversal invariant topological insulator, which is an insulating material behaving as an insulator in its interior but with conducting channels on its surface. The conducting surface states of a topological insulator are known as "helical states" due to the spin texture in the momentum space and protected by time reversal symmetry. Helical surface states have been observed in surface sensitive experiments, such as angular-resolved photon emission spectroscopy and scanning tunneling microscopy. However, signatures of topological surface states in transport measurements are complicated by the dominating conduction from bulk channels and strong disorder effect. Therefore, in this dissertation, we numerically study transport in disordered topological insulator nano-structures, e.g. nanowires and nanotubes, which possess a larger surfaceto-volume ratio compared to bulk systems. For a topological insulator nanowire, it is found that a gapless mode with linear dispersion, which is refered to as a topological state in the main text, arises when a half-integer magnetic flux quantum is inserted along the nanowire. We find that topological states possess a longer localization length than other non-topological states. Thus, for a long nanowire or nanotube, a

  3. Low Temperature Carrier Transport Properties in Isotopically Controlled Germanium

    NASA Astrophysics Data System (ADS)

    Itoh, Kohei

    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 ^{74}Ge and ^{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 (^{74 }Ge) / (^{70}Ge) ratios of the starting Ge materials, respectively. This method also guarantees unprecedented doping uniformity. Using such samples we 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. We have also performed infrared absorption spectroscopy studies of compensated Ge samples, investigating the line broadening mechanism due to random electric fields arising from ionized impurity centers. In the study of neutral impurity scattering, we find excellent agreement between the low temperature experimental mobility and phase shift calculations for the hydrogen atom scaled to shallow impurities in semiconductors. In the ionized impurity scattering study, none of the theories we have tested so far explains our low temperature experimental mobilities in highly compensated Ge (K>0.3). We discuss possible problems associated with the theories, in particular, the treatment of the screening mechanism. In the study of low temperature hopping conduction, we show results of temperature dependent resistivity measurements as a function of both the net-carrier concentration and the compensation

  4. 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

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

    NASA Astrophysics Data System (ADS)

    Kocherlakota, Lakshmi Suhasini

    Nanoscale constraints impact the material properties of both organic and inorganic systems. The systems specifically studied here are (i) nanoconstrained polymeric systems, poly(l-trimethylsilyl-1-propyne) (PTMSP) and poly(ethylene oxide) (PEO) relevant to gas separation membranes (ii) Zwitterionic polymers poly(sulfobetaine methacrylate)(pSBMA), poly(carboxybetaine acrylamide) (pCBAA), and poly(oligo(ethylene glycol) methyl methacrylate) (PEGMA) brushes critical for reducing bio-fouling (iii) Surface properties of N-layer graphene sheets. Interfacial constraints in ultrathin poly(l-trimethylsilyl-1-propyne) (PTMSP) membranes yielded gas permeabilities and CO2/helium selectivities that exceed bulk PTMSP membrane transport properties by up to three-fold for membranes of submicrometer thickness. Indicative of a free volume increase, a molecular energetic mobility analysis (involving intrinsic friction analysis) revealed enhanced methyl side group mobilities in thin PTMSP membranes with maximum permeation, compared to bulk films. Aging studies conducted over the timescales relevant to the conducted experiments signify that the free volume states in the thin film membranes are highly unstable in the presence of sorbing gases such as CO2. To maintain this high free volume configuration of polymer while improving the temporal stability an "inverse" architecture to conventional polymer nanocomposites was investigated, in which the polymer phase of PTMSP and PEO were interfacially and dimensionally constrained in nanoporous anodic aluminum oxide (AAO) membranes. While with this architecture the benefits of nanocomposite and ultrathin film membranes of PTMSP could be reproduced and improved upon, also the temporal stability could be enhanced substantially. The PEO-AAO nanocomposite membranes also revealed improved gas selectivity properties of CO2 over helium. In the thermal transition studies of zwitterionic pSBMA brushes a reversible critical transition temperature of 60

  6. Transport properties of damaged materials. Cementitious barriers partnership

    SciTech Connect

    Langton, C.

    2014-11-01

    The objective of the Cementitious Barriers Partnership (CBP) project is to develop tools to improve understanding and prediction of the long-term structural, hydraulic, and chemical performance of cementitious barriers used in low-level waste storage applications. One key concern for the long-term durability of concrete is the degradation of the cementitious matrix, which occurs as a result of aggressive chemical species entering the material or leaching out in the environment, depending on the exposure conditions. The objective of the experimental study described in this report is to provide experimental data relating damage in cementitious materials to changes in transport properties, which can eventually be used to support predictive model development. In order to get results within a reasonable timeframe and to induce as much as possible uniform damage level in materials, concrete samples were exposed to freezing and thawing (F/T) cycles. The methodology consisted in exposing samples to F/T cycles and monitoring damage level with ultrasonic pulse velocity measurements. Upon reaching pre-selected damage levels, samples were tested to evaluate changes in transport properties. Material selection for the study was motivated by the need to get results rapidly, in order to assess the relevance of the methodology. Consequently, samples already available at SIMCO from past studies were used. They consisted in three different concrete mixtures cured for five years in wet conditions. The mixtures had water-to-cement ratios of 0.5, 0.65 and 0.75 and were prepared with ASTM Type I cement only. The results showed that porosity is not a good indicator for damage caused by the formation of microcracks. Some materials exhibited little variations in porosity even for high damage levels. On the other hand, significant variations in tortuosity were measured in all materials. This implies that damage caused by internal pressure does not necessarily create additional pore space in

  7. Geometrical and transport properties of Bentheimer sandstone under deformation

    NASA Astrophysics Data System (ADS)

    Jasinski, Lukasz; Thovert, Jean Francois; Mourzenko, Valeri; Gland, Nicolas; Youssef, Souhail; Vizika, Olga; Adler, Pierre

    2010-05-01

    During industrial, geoscientific or environmental drilling campaigns, rock samples are often extracted few km below surface under large pressures p and their in situ properties may significantly differ from the ones measured in the lab close to atmospheric pressure p_a. Our first objective is to derive from measurements made at pa the geometric and transport properties at p. In petroleum industry, during production, the vertical effective stress in the reservoir increases as the pore pressure decreases from few hundreds to few tens bar; in average the horizontal effective stress increases as well, but at a lower rate along an oedometric path, favoring shear stress and reservoir depletion; a complex geology induces locally a variety of stress paths between the two extreme hydrostatic and uniaxial paths. For storage, CO2 might be injected into deep geological formations; such a re-injection will decrease the effective stress. Therefore, our second objective is to test numerically the sensitivity of transport properties to stress path. The methodology can be summarized as follows. First, the rock geometry on the pore scale is obtained by microtomography. The major geometric characteristics are derived by extracting the pore skeleton. Second, the sample is submitted to hydrostatic, oedometric or uniaxial deformations. Then, the permeability K is derived by routines based on finite volume discretization operating on cubic or on unstructured tetrahedral elements. This methodology is applied to a real Bentheimer sandstone of porosity E close to 0.23-0.24. It is binarized with 5003 and 10003 voxels equal to 6 and 3 microns. E, the correlation function, the specific area, the hydraulic radius, the skeleton and the percolation properties of the pore space are calculated. The influence of various boundary conditions on K in the uncompressed sample is studied; K is slightly anisotropic. Then, the sample is submitted to the overall deformations and the influence of the loading

  8. Geometrical and transport properties of Bentheimer sandstone under deformation

    NASA Astrophysics Data System (ADS)

    Jasinski, L.; Mourzenko, V.; Thovert, J.; Gland, N.; Youssef, S.; Vizika, O.; Adler, P. M.

    2009-12-01

    During industrial, geoscientific or environmental drilling campaigns, rock samples are often extracted few km below surface under large pressures p and their in situ properties may significantly differ from the ones measured in the lab close to atmospheric pressure p_a. Our first objective is to derive from measurements made at p_a the geometric and transport properties at p. In petroleum industry, during production, the vertical effective stress in the reservoir increases as the pore pressure decreases from few hundreds to few tens bar; in average the horizontal effective stress increases as well, but at a lower rate along an oedometric path, favoring shear stress and reservoir depletion; a complex geology induces locally a variety of stress paths between the two extreme hydrostatic and uniaxial paths. For storage, CO2 might be injected into deep geological formations; such a re-injection will decrease the effective stress. Therefore, our second objective is to test numerically the sensitivity of transport properties to stress path. The methodology can be summarized as follows. First, the rock geometry on the pore scale is obtained by microtomography. The major geometric characteristics are derived by extracting the pore skeleton. Second, the sample is submitted to hydrostatic, oedometric or uniaxial deformations. Then, the permeability K is derived by routines based on finite volume discretization operating on cubic or on unstructured tetrahedral elements. This methodology is applied to a real Bentheimer sandstone of porosity E close to 0.23-0.24. It is binarized with 500^3 and 1000^3 voxels equal to 6 and 3 microns. E, the correlation function, the specific area, the hydraulic radius, the skeleton and the percolation properties of the pore space are calculated. The influence of various boundary conditions on K in the uncompressed sample is studied; K is slightly anisotropic. Then, the sample is submitted to the overall deformations and the influence of the

  9. Thermodynamic and transport combustion properties of hydrocarbons with air. Part 1: Properties in SI units

    NASA Astrophysics Data System (ADS)

    Gordon, S.

    1982-07-01

    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.

  10. Thermodynamic and transport combustion properties of hydrocarbons with air. Part 1: Properties in SI units

    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.

  11. Treatment of hemimasticatory spasm with microvascular decompression.

    PubMed

    Wang, Yong-Nan; Dou, Ning-Ning; Zhou, Qiu-Meng; Jiao, Wei; Zhu, Jin; Zhong, Jun; Li, Shi-Ting

    2013-01-01

    Hemimasticatory spasm is a rare disorder characterized by paroxysmal involuntary contraction of the jaw-closing muscles. As the ideology and pathogenesis of the disease are still unclear, there has been no treatment that could give rise to a good outcome so far. Herein, we tried to use surgical management to cure the disease. Six patients with the disease were included in this study. These patients underwent microvascular decompression of the motor fibers of the trigeminal root. After the operation, all faces of the patients felt relaxed at varied degrees, except for 1 patient. Our study showed that microvascular decompression of the trigeminal nerve could lead to a better outcome. However, a control study with a large sample is needed before this technique is widely used.

  12. The unusual properties of effective blood substitutes.

    PubMed

    Tsai, Amy G; Intaglietta, Marcos

    2002-03-01

    Blood substitutes or oxygen carrying plasma expanders were originally formulated to simulate the transport properties of blood, particularly oxygen carrying capacity, viscosity, p50, and colloid osmotic pressure, under the hypothesis that blood is the most desirable fluid in volume restitution. However, changes introduced into the organism during hemorrhage adversely affect microvascular function due to reflex vasoconstriction which causes the fall of functional capillary density, and lowers tissue oxygenation, conditions that are not universally reversed with retransfusion of blood. The restoration of microvascular function is seldom complete upon retransfusion of blood. New formulations of hemoglobin molecules in solutions whose oncotic pressure is in the range of 60-100 mmHg, p50 is about 5 mmHg, viscosity 3-4 cP, and oxygen carrying capacity in the range of 4-7 g/dl equivalent hemoglobin deliver better microvascular function after resuscitation when compared to whole blood and oxygen carrying plasma expanders with transport properties similar to those of blood. The improved performance is in part due to the increased plasma viscosity which increases capillary transmural pressure which reverses capillary collapse induced during low perfusion pressures. High oncotic pressure reinforces this effect, since it brings more fluid into the circulation. Microvascular transport studies of the effects of resuscitation in shock show that functional capillary density is the primary determinant of survival, thus maintenance of an open and fully perfused microcirculation is more critical than insuring oxygen supply, since closed capillaries lead to the accumulation of slowly diffusing byproducts of metabolism which ultimately become toxic. The required combination of properties can be achieved by conjugating hemoglobin and polyethylene glycol. Resuscitation fluids based on hemoglobin containing vesicles may provide the next level of functional improvement in the formulation

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

    PubMed Central

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

    2015-01-01

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

  14. Magnetic and transport properties of PrRhSi3.

    PubMed

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

    2013-05-15

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

  15. Transport properties of bismuth nano-wire systems.

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Dresselhaus, M. S.; Ying, J. Y.; Heremans, J.

    1998-03-01

    Ultra-fine Bi nano-wires (10--120 nm diameter) with packing density as high as 7×10^10/cm^2 were fabricated by pressure injecting molten Bi into the evacuated channels of an anodic alumina template. The resulting Bi nano-wires are shown to be single crystals (with the same structure as bulk Bi) and all the nano-wires are similarly oriented. The small effective mass of Bi, high anisotropy of its Fermi surface, and the high aspect ratio (length/diameter) of Bi nano-wires make this an excellent system for studying quantum confinement effects in a one-dimensional (1D) electron gas. Transport properties, such as electrical conductivity, magnetoresistance and thermoelectric power, are investigated for both Bi nano-wire arrays and free-standing Bi nano-wires with various wire diameters (10-120 nm) and Te doping concentrations (0.025-0.5 at.%), and at various temperatures and magnetic fields. A theoretical model based on the basic band structure of bulk Bi, suitably modified for the 1D situation, explains the many unusual effects that are observed. Strong evidence is provided for an interesting quantum confinement-induced semimetal to semiconductor transition in such Bi nano-wires.

  16. Thermodynamic and transport properties of aqueous and molten electrolytes

    SciTech Connect

    Conway, B.E.; Bockris, J.O.M.; Yeager, E.

    1983-01-01

    This book examines the physical chemistry of electrolytes in solution and in the molten state. Topics considered include ionic solvation (solvents, thermodynamic and transport properties, spectroscopic and diffraction methods, theoretical aspects of solvation), ionic interactions and activity behavior of electrolyte solutions (the Debye-Hueckel evaluation of the activity coefficient of an electrolyte in solution, statistical-mechanical treatments of ionic interactions in solution, ion-solvent interactions in the activity behavior of electrolytes, short-range ionic interactions), the conductance of electrolyte solutions (the basis of the Onsager approach, the boundary conditions, differential equations for two-particle distribution functions, recent developments in conductance, transference numbers, ionic limiting mobilities, the conductance of mixtures of electrolytes, optimization in measurements and data processing), proton solvation and proton transfer in chemical and electrochemical processes (proton solvation and characterization of the H/sub 3/O/sup +/ ion, proton transfer in chemical ionization processes in solution, continuous proton transfer in conductance processes, proton transfer in electrode processes), and the structure and thermodynamics of molten salts (molten salts as liquids, single salts, salt mixtures). Nonaqueous solutions are not covered in this volume.

  17. Prediction of transport properties related to heat transfer

    NASA Astrophysics Data System (ADS)

    Kestin, J.

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-07-01

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

  19. Nanostructured semiconductors for thermoelectric energy conversion: Synthesis and transport properties

    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

  20. Understanding electronic structure and transport properties in nanoscale junctions

    NASA Astrophysics Data System (ADS)

    Dhungana, Kamal B.

    Understanding the electronic structure and the transport properties of nanoscale materials are pivotal for designing future nano-scale electronic devices. Nanoscale materials could be individual or groups of molecules, nanotubes, semiconducting quantum dots, and biomolecules. Among these several alternatives, organic molecules are very promising and the field of molecular electronics has progressed significantly over the past few decades. Despite these progresses, it has not yet been possible to achieve atomic level control at the metal-molecule interface during a conductance measurement, which hinders the progress in this field. The lack of atomic level information of the interface also makes it much harder for theorist to interpret the experimental results. To identify the junction configuration that possibly exists during the experimental measurement of conductance in molecular junction, we created an ensemble of Ruthanium-bis(terpyridine) molecular devices, and studied the transport behavior in these molecular junctions. This helps us identifying the junction geometry that yields the experimentally measured current-voltage characteristics. Today's electronic devices mostly ignore the spin effect of an electron. The inclusion of spin effect of an electron on solid-state transistor allows us to build more efficient electronic devices; this also alleviates the problem of huge heat dissipation in the nanoscale electronic devices. Different materials have been utilized to build three terminals spin transistor since its inception in 1950. In search of suitable candidates for the molecular spin transistor, we have recently designed a spin-valve transistor based on an organometallic molecule; a large amplification (320 %) in tunnel magneto-resistance (TMR) is found to occur at an experimentally accessible gate field. This suggests that the organic molecules can be utilized for making the next generation three terminal spintronic devices. Similarly, we have designed a

  1. Predictors of Microvascular Invasion in Hepatocellular Carcinoma.

    PubMed

    Yamashita, Yo-Ichi; Shirabe, Ken; Aishima, Shinichi; Maehara, Yoshihiko

    2015-09-01

    This chapter covers a range of important topics in the evaluation of the microvascular invasion (MVI) in hepatocellular carcinoma (HCC) before treatment. The malignant potential of HCC is reflected by the types of MVI such as portal venous (vp), hepatic vein (vv) or bile duct (b) infiltration. The identification of the type of MVI in HCC has a key role in decisions regarding the effective treatment of HCC. Here, we describe the possible and important predictors of MVI in HCC. PMID:26398341

  2. Fabrication of 3-dimensional multicellular microvascular structures

    PubMed Central

    Barreto-Ortiz, Sebastian F.; Fradkin, Jamie; Eoh, Joon; Trivero, Jacqueline; Davenport, Matthew; Ginn, Brian; Mao, Hai-Quan; Gerecht, Sharon

    2015-01-01

    Despite current advances in engineering blood vessels over 1 mm in diameter and the existing wealth of knowledge regarding capillary bed formation, studies for the development of microvasculature, the connecting bridge between them, have been extremely limited so far. Here, we evaluate the use of 3-dimensional (3D) microfibers fabricated by hydrogel electrospinning as templates for microvascular structure formation. We hypothesize that 3D microfibers improve extracellular matrix (ECM) deposition from vascular cells, enabling the formation of freestanding luminal multicellular microvasculature. Compared to 2-dimensional cultures, we demonstrate with confocal microscopy and RT-PCR that fibrin microfibers induce an increased ECM protein deposition by vascular cells, specifically endothelial colony-forming cells, pericytes, and vascular smooth muscle cells. These ECM proteins comprise different layers of the vascular wall including collagen types I, III, and IV, as well as elastin, fibronectin, and laminin. We further demonstrate the achievement of multicellular microvascular structures with an organized endothelium and a robust multicellular perivascular tunica media. This, along with the increased ECM deposition, allowed for the creation of self-supporting multilayered microvasculature with a distinct circular lumen following fibrin microfiber core removal. This approach presents an advancement toward the development of human microvasculature for basic and translational studies.—Barreto-Ortiz, S. F., Fradkin, J., Eoh, J., Trivero, J., Davenport, M., Ginn, B., Mao, H.-Q., Gerecht, S. Fabrication of 3-dimensional multicellular microvascular structures. PMID:25900808

  3. SPECIES - EVALUATING THERMODYNAMIC PROPERTIES, TRANSPORT PROPERTIES & EQUILIBRIUM CONSTANTS OF AN 11-SPECIES AIR MODEL

    NASA Technical Reports Server (NTRS)

    Thompson, R. A.

    1994-01-01

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

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

    SciTech Connect

    Garcia, L.; Carreras, B.A.

    2005-09-15

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

  5. Hypertension Management and Microvascular Insulin Resistance in Diabetes

    PubMed Central

    Ko, Seung-Hyun; Cao, Wenhong; Liu, Zhenqi

    2011-01-01

    Type 2 diabetes is in essence a vascular disease and is frequently associated with hypertension, macrovascular events, and microvascular complications. Microvascular dysfunction, including impaired recruitment and capillary rarefaction, has been implicated in the pathogenesis of diabetic complications. Microvascular insulin resistance and renin-angiotensin system upregulation are present in diabetes, and each contributes to the development of hypertension and microvascular dysfunction. In the insulin-sensitive state, insulin increases microvascular perfusion by increasing endothelial nitric oxide production, but this effect is abolished by insulin resistance. Angiotensin II, acting via the type 1 receptors, induces inflammation and oxidative stress, leading to impaired insulin signaling, reduced nitric oxide availability, and vasoconstriction. Conversely, it acts on the type 2 receptors to cause vasodilatation. Because substrate and hormonal exchanges occur in the microvasculature, antihypertensive agents targeted to improve microvascular insulin sensitivity and function may have beneficial effects beyond their capacity to lower blood pressure in patients with diabetes. PMID:20582734

  6. 26 CFR 49.4271-1 - Tax on transportation of property by air.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... transportation from Chicago to New York if the property is in the course of exportation, by continuous movement, by boat from New York to Europe and in due course is so exported. Delays caused by circumstances... 26 Internal Revenue 16 2010-04-01 2010-04-01 true Tax on transportation of property by air....

  7. 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.

  8. Computer program for calculation of complex chemical equilibrium compositions and applications. Supplement 1: Transport properties

    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.

  9. Skin microvascular endothelial function as a biomarker in cardiovascular diseases?

    PubMed

    Hellmann, Marcin; Roustit, Matthieu; Cracowski, Jean-Luc

    2015-08-01

    Skin microvascular endothelial function is impaired in many cardiovascular diseases, and could be therefore considered as a representative vascular bed. However, today, available evidence allows considering skin microvascular endothelial function neither as a diagnostic biomarker nor as a prognostic biomarker in cardiovascular diseases. Large follow-up studies using standardized methods should now be conducted to assess the potential predictive value of skin microvascular function in cardiovascular diseases.

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

    SciTech Connect

    Porytsky, P.; Krivtsun, I.; Demchenko, V.; Reisgen, U.; Mokrov, O.; Zabirov, A.; Gorchakov, S.; Timofeev, A.; Uhrlandt, D.

    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.

  11. Evaluation of Baltic Sea transport properties using particle tracking

    NASA Astrophysics Data System (ADS)

    Dargahi, Bijan; Cvetkovic, Vladimir

    2014-05-01

    Particle tracking model (PTM) is an effective tool for quantifying transport properties of large water bodies such as the Baltic Sea. We have applied PTM to our fully calibrated and validated Baltic Sea 3D hydrodynamic model for a 10-years period (2000-9). One hundred particles were released at a constant rate during an initial 10-days period from all the Baltic Sea sub-basins, the major rivers, and the open boundary in the Arkona Basin. In each basin, the particles were released at two different depths corresponding to the deep water and middle water layers. The objectives of the PTM simulations were to analyse the intra-exchange processes between the Baltic Sea basins and to estimate the arrival times and the paths of particles released from the rivers. The novel contribution of this study is determining the paths and arrival times of deeper water masses rather than the surface masses. Advective and diffusive transport processes in the Bornholm and Arkona basins are both driven by the interacting flows of the northern basins of the Baltic Sea and the North Sea. Particles released from Arkona basin flows northwards along the Stople Channel. The Gotland basins are the major contributors to the exchange process in the Baltic Sea. We find high values of the advection ratio, indicative of a forced advective transport process. The Bay of Gdansk is probably the most vulnerable region in the Baltic Sea. This is despite the fact that the main exchanging basins are the Bornholm Sea and the Easter Gotland Basin. The main reason is the intensive supply of the particles from the northern basins that normally take about 3000 days to reach the Bay of Gdansk. The process maintains a high level of particle concentration (90%) along its coastlines even after the 10-years period. Comparing the particle paths in the Western and Eastern Gotland basins two interesting features were found. Particles travelled in all four directions in the former basin and the middle layer particles

  12. 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

  13. Xiang-Qi-Tang and its active components exhibit anti-inflammatory and anticoagulant properties by inhibiting MAPK and NF-κB signaling pathways in LPS-treated rat cardiac microvascular endothelial cells.

    PubMed

    He, Chang-Liang; Yi, Peng-Fei; Fan, Qiao-Jia; Shen, Hai-Qing; Jiang, Xiao-Lin; Qin, Qian-Qian; Song, Zhou; Zhang, Cui; Wu, Shuai-Cheng; Wei, Xu-Bin; Li, Ying-Lun; Fu, Ben-Dong

    2013-04-01

    Xiang-Qi-Tang (XQT) is a Chinese herbal formula containing Cyperus rotundus, Astragalus membranaceus and Andrographis paniculata. Alpha-Cyperone (CYP), astragaloside IV (AS-IV) and andrographolide (AND) are the three major active components in this formula. XQT may modulate the inflammatory or coagulant responses. We therefore assessed the effects of XQT on lipopolysaccharide (LPS)-induced inflammatory model of rat cardiac microvascular endothelial cells (RCMECs). XQT, CYP, AS-IV and AND inhibited the production of tumor necrosis factor alpha (TNF-α), intercellular cell adhesion molecule-1 (ICAM-1) and plasminogen activator inhibitor-1 (PAI-1), and up-regulated the mRNA expression of Kruppel-like factor 2 (KLF2). XQT and CYP inhibited the secretion of tissue factor (TF). To further explore the mechanism, we found that XQT, or its active components CYP, AS-IV and AND significantly inhibited extracellular signal-regulated kinase (ERK), c-jun NH2-terminal kinase (JNK) and p38 phosphorylation protein expression as well as decreased the phosphorylation levels of nuclear factor κB (NF-κB) p65 proteins in LPS-stimulated RCMECs. These results suggested that XQT and its active components inhibited the expression of inflammatory and coagulant mediators via mitogen-activated protein kinase (MAPKs) and NF-κB signaling pathways. These findings may contribute to future research on the action mechanisms of this formula, as well as therapy for inflammation- or coagulation-related diseases. PMID:23171279

  14. A Review of the Thermodynamic, Transport, and Chemical Reaction Rate Properties of High-temperature Air

    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.

  15. Structural Properties of the Brazilian Air Transportation Network.

    PubMed

    Couto, Guilherme S; da Silva, Ana Paula Couto; Ruiz, Linnyer B; Benevenuto, Fabrício

    2015-09-01

    The air transportation network in a country has a great impact on the local, national and global economy. In this paper, we analyze the air transportation network in Brazil with complex network features to better understand its characteristics. In our analysis, we built networks composed either by national or by international flights. We also consider the network when both types of flights are put together. Interesting conclusions emerge from our analysis. For instance, Viracopos Airport (Campinas City) is the most central and connected airport on the national flights network. Any operational problem in this airport separates the Brazilian national network into six distinct subnetworks. Moreover, the Brazilian air transportation network exhibits small world characteristics and national connections network follows a power law distribution. Therefore, our analysis sheds light on the current Brazilian air transportation infrastructure, bringing a novel understanding that may help face the recent fast growth in the usage of the Brazilian transport network.

  16. Structural Properties of the Brazilian Air Transportation Network.

    PubMed

    Couto, Guilherme S; da Silva, Ana Paula Couto; Ruiz, Linnyer B; Benevenuto, Fabrício

    2015-09-01

    The air transportation network in a country has a great impact on the local, national and global economy. In this paper, we analyze the air transportation network in Brazil with complex network features to better understand its characteristics. In our analysis, we built networks composed either by national or by international flights. We also consider the network when both types of flights are put together. Interesting conclusions emerge from our analysis. For instance, Viracopos Airport (Campinas City) is the most central and connected airport on the national flights network. Any operational problem in this airport separates the Brazilian national network into six distinct subnetworks. Moreover, the Brazilian air transportation network exhibits small world characteristics and national connections network follows a power law distribution. Therefore, our analysis sheds light on the current Brazilian air transportation infrastructure, bringing a novel understanding that may help face the recent fast growth in the usage of the Brazilian transport network. PMID:26312421

  17. Properties of the stochastic energization-relaxation channel model for vectorial ion transport.

    PubMed Central

    Muneyuki, E; Fukami, T A

    2000-01-01

    A model for the primary active transport by an ion pump protein is proposed. The model, the "energization-relaxation channel model," describes an ion pump as a multiion channel that undergoes stochastic transitions between two conformational states by external energy supply. When the potential profile along ion transport pathway is asymmetrical, a net ion flux is induced by the transitions. In this model, the coupling of the conformational change and ion transport is stochastic and loose. The model qualitatively reproduces known properties of active transport such as the effect of ion concentration gradient and membrane potential on the rate of transport and the inhibition of ion transport at high ion concentration. We further examined the effect of various parameters on the ion transport properties of this model. The efficiency of the coupling was almost 100% under some conditions. PMID:10692306

  18. Directed assembly of three-dimensional microvascular networks

    NASA Astrophysics Data System (ADS)

    Therriault, Daniel

    Three-dimensional (3-D) microvascular networks with pervasive, interconnected channels less than 300 mum in diameter may find widespread application in microfluidic devices, biotechnology, sensors, and autonomic healing materials. Although microchannel arrays are readily constructed in two-dimensions by photolithographic or soft lithographic techniques, their construction in three-dimensions remains a challenging problem. The development of a microfabrication method to build 3-D microvascular networks based on direct-write assembly is described is this thesis. The method is based on the robotic deposition of a fugitive organic ink to form a free-standing scaffold structure. Secondary infiltration of a structural resin followed by setting of the matrix and removal of the scaffold yields an embedded pervasive network of smooth cylindrical channels (˜10--500 mum) with defined connectivity. Rheological and other material properties studies of fugitive organic ink were performed in order to identify the critical characteristics required for successful deposition of 3-D scaffolds by direct-write assembly. Guided by the results of these studies, several new ink formulations were screened for improved deposition performance. The most successful of these inks (40wt% microcrystalline wax, 60wt% petroleum jelly) showed excellent deposition and had an equilibrium modulus at room temperature (G 'eq ˜ 7.70 kPa 1 Hz) nearly two orders of magnitude higher than the original ink. The optimized ink was used to successfully build thick (i.e., ˜100 layers) scaffold structures at room temperature with negligible time-dependent deformation post-deposition. Secondary infiltration of the resin was accomplished at room temperature while maintaining the scaffold architecture. The optimized ink was also successfully extruded through small micronozzles (1 mum). The construction of 3-D microvascular networks enables microfluidic devices with unparallel geometric complexity. In one example, a

  19. Oscillatory Behavior in the Transport Properties of Transition Metal Superlattices

    NASA Astrophysics Data System (ADS)

    Kim, Sihong

    Oscillations in the low temperature electrical resistivity, as a function of the individual layer thickness and/or superlattice period, have been recently observed in Co/Ni superlattices. This was believed to be a superlattice effect because the oscillations disappeared with decreasing number of bilayers. In this thesis, systematic studies have been made to understand the origin of this unusual behavior in the electrical transport of Co/Ni superlattices. First, Co/Ni was investigated extensively because Co and Ni have very similar material properties. They are both ferromagnetic, have fcc lattices in thin film form, and have almost identical electronic band structure. Superlattice films were grown by molecular beam epitaxy (MBE) and these structure was characterized by reflection high energy electron diffraction (RHEED), low energy electron diffraction (LEED), Auger electron spectroscopy (AES), and X-ray diffraction (XRD). The measured residual resistivity, usually caused by impurity atoms, lattice defects, interfaces, or grain boundaries, is very small in Co/Ni superlattice films. Due to this small background resistivity, unusual intrinsic resistivity oscillations have been clearly observed in these films. The oscillation amplitude does not change with temperature. However, a small amount of random fluctuation in the superlattice period, artificially introduced during film growth, significantly increases the oscillation amplitude. The resistivity at a minimum rm( rho_{min}) and maximum rm(rho_{max}) of oscillations was also measured as a function of film thickness in order to study the evolution of this effect. rho_{min} increases monotonically with decreasing thickness due to surface scattering, which is well described by the quantum size effect theory. However, rho_{max} becomes nonmonotonic by proper choice of superlattice period, indicating the presence of an additional scattering mechanism associated with the superlattice structure. Similar resistivity

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

    NASA Astrophysics Data System (ADS)

    Iurov, Andrii

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

  1. 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.

  2. Equations of state and transport properties of mixtures in the warm dense regime

    SciTech Connect

    Hou, Yong; Dai, Jiayu; Kang, Dongdong; Ma, Wen; Yuan, Jianmin

    2015-02-15

    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.

  3. Electrolytes: transport properties and non-equilibrium thermodynamics

    SciTech Connect

    Miller, D.G.

    1980-12-01

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

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

    PubMed

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

    2006-10-01

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

  5. Analysis Of Transport Properties of Mechanically Alloyed Lead Tin Telluride

    NASA Astrophysics Data System (ADS)

    Krishna, Rajalakshmi

    these inclusions would not be less than that expected in alloys without these inclusions while the portion of the thermal conductivity that is not due to charge carriers (the lattice thermal conductivity) would be less than what would be expected from alloys that do not have these inclusions. Furthermore, it would be possible to approximate the observed changes in the electrical and thermal transport properties using existing physical models for the scattering of electrons and phonons by small inclusions. The approach taken to investigate this hypothesis was to first experimentally characterize the mobile carrier concentration at room temperature along with the extent and type of secondary phase inclusions present in a series of three mechanically alloyed Pb1-xSnxTe alloys with different Sn content. Second, the physically based computational model was developed. This model was used to determine what the electronic conductivity, Seebeck coefficient, total thermal conductivity, and the portion of the thermal conductivity not due to mobile charge carriers would be in these particular Pb1-x SnxTe alloys if there were to be no secondary phase inclusions. Third, the electronic conductivity, Seebeck coecient and total thermal conductivity was experimentally measured for these three alloys with inclusions present at elevated temperatures. The model predictions for electrical conductivity and Seebeck coefficient were directly compared to the experimental elevated temperature electrical transport measurements. The computational model was then used to extract the lattice thermal conductivity from the experimentally measured total thermal conductivity. This lattice thermal conductivity was then compared to what would be expected from the alloys in the absence of secondary phase inclusions. Secondary phase inclusions were determined by X-ray diraction analysis to be present in all three alloys to a varying extent. The inclusions were found not to significantly degrade electrical

  6. Listeriolysin O mediates cytotoxicity against human brain microvascular

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Penetration of the brain microvascular endothelial layer is one of the routes L. monocytogenes use to breach the blood-brain barrier. Because host factors in the blood severely limit direct invasion of human brain microvascular endothelial cells (HBMECs) by L. monocytogenes, alternative mechanisms m...

  7. Rapid homogeneous endothelialization of high aspect ratio microvascular networks.

    PubMed

    Naik, Nisarga; Hanjaya-Putra, Donny; Haller, Carolyn A; Allen, Mark G; Chaikof, Elliot L

    2015-08-01

    Microvascularization of an engineered tissue construct is necessary to ensure the nourishment and viability of the hosted cells. Microvascular constructs can be created by seeding the luminal surfaces of microfluidic channel arrays with endothelial cells. However, in a conventional flow-based system, the uniformity of endothelialization of such an engineered microvascular network is constrained by mass transfer of the cells through high length-to-diameter (L/D) aspect ratio microchannels. Moreover, given the inherent limitations of the initial seeding process to generate a uniform cell coating, the large surface-area-to-volume ratio of microfluidic systems demands long culture periods for the formation of confluent cellular microconduits. In this report, we describe the design of polydimethylsiloxane (PDMS) and poly(glycerol sebacate) (PGS) microvascular constructs with reentrant microchannels that facilitates rapid, spatially homogeneous endothelial cell seeding of a high L/D (2 cm/35 μm; > 550:1) aspect ratio microchannels. MEMS technology was employed for the fabrication of a monolithic, elastomeric, reentrant microvascular construct. Isotropic etching and PDMS micromolding yielded a near-cylindrical microvascular channel array. A 'stretch - seed - seal' operation was implemented for uniform incorporation of endothelial cells along the entire microvascular area of the construct yielding endothelialized microvascular networks in less than 24 h. The feasibility of this endothelialization strategy and the uniformity of cellularization were established using confocal microscope imaging. PMID:26227213

  8. Rapid homogeneous endothelialization of high aspect ratio microvascular networks.

    PubMed

    Naik, Nisarga; Hanjaya-Putra, Donny; Haller, Carolyn A; Allen, Mark G; Chaikof, Elliot L

    2015-08-01

    Microvascularization of an engineered tissue construct is necessary to ensure the nourishment and viability of the hosted cells. Microvascular constructs can be created by seeding the luminal surfaces of microfluidic channel arrays with endothelial cells. However, in a conventional flow-based system, the uniformity of endothelialization of such an engineered microvascular network is constrained by mass transfer of the cells through high length-to-diameter (L/D) aspect ratio microchannels. Moreover, given the inherent limitations of the initial seeding process to generate a uniform cell coating, the large surface-area-to-volume ratio of microfluidic systems demands long culture periods for the formation of confluent cellular microconduits. In this report, we describe the design of polydimethylsiloxane (PDMS) and poly(glycerol sebacate) (PGS) microvascular constructs with reentrant microchannels that facilitates rapid, spatially homogeneous endothelial cell seeding of a high L/D (2 cm/35 μm; > 550:1) aspect ratio microchannels. MEMS technology was employed for the fabrication of a monolithic, elastomeric, reentrant microvascular construct. Isotropic etching and PDMS micromolding yielded a near-cylindrical microvascular channel array. A 'stretch - seed - seal' operation was implemented for uniform incorporation of endothelial cells along the entire microvascular area of the construct yielding endothelialized microvascular networks in less than 24 h. The feasibility of this endothelialization strategy and the uniformity of cellularization were established using confocal microscope imaging.

  9. First-principles calculations of thermal, electrical, and thermoelectric transport properties of semiconductors

    NASA Astrophysics Data System (ADS)

    Zhou, Jiawei; Liao, Bolin; Chen, Gang

    2016-04-01

    The transport properties of semiconductors are key to the performance of many solid-state devices (transistors, data storage, thermoelectric cooling and power generation devices, etc). An understanding of the transport details can lead to material designs with better performances. In recent years simulation tools based on first-principles calculations have been greatly improved, being able to obtain the fundamental ground-state properties of materials (such as band structure and phonon dispersion) accurately. Accordingly, methods have been developed to calculate the transport properties based on an ab initio approach. In this review we focus on the thermal, electrical, and thermoelectric transport properties of semiconductors, which represent the basic transport characteristics of the two degrees of freedom in solids—electronic and lattice degrees of freedom. Starting from the coupled electron-phonon Boltzmann transport equations, we illustrate different scattering mechanisms that change the transport features and review the first-principles approaches that solve the transport equations. We then present the first-principles results on the thermal and electrical transport properties of semiconductors. The discussions are grouped based on different scattering mechanisms including phonon-phonon scattering, phonon scattering by equilibrium electrons, carrier scattering by equilibrium phonons, carrier scattering by polar optical phonons, scatterings due to impurities, alloying and doping, and the phonon drag effect. We show how the first-principles methods allow one to investigate transport properties with unprecedented detail and also offer new insights into the electron and phonon transport. The current status of the simulation is mentioned when appropriate and some of the future directions are also discussed.

  10. Analysis of community properties and node properties to understand the structure of the bus transport network

    NASA Astrophysics Data System (ADS)

    Sun, Yeran; Mburu, Lucy; Wang, Shaohua

    2016-05-01

    Akin to most infrastructures, intraurban bus networks are large and highly complex. Understanding the composition of such networks requires an intricate decomposition of the network into modules, taking into account the manner in which network links are distributed among the nodes. There exists for each set of highly interlinked nodes little connectivity with the next set of highly interlinked nodes. This inherent property of nodes makes community detection a popular approach for analyzing the structure of complex networks. In this study, we attempt to understand the structure of the intraurban bus network of Ireland's capital city, Dublin in a two-step approach. We first analyze the modular structure of the network by identifying potential communities. Secondly, we assess the prominence of each network node by examining the module-based topological properties of the nodes. Results of this empirical study reveal a clear pattern of independent communities, indicating thus, an implicit multi-community structure of the intraurban bus network. Examination of the geographic characteristics of the identified communities shows a degree of socio-economic divisions of the Dublin city. Furthermore, a large majority of the important nodes (vital transportation hubs) are located at the city center, implying that most of the bus lines in Dublin city tend to intersect the city's core.

  11. Current Diagnostic and Therapeutic Strategies in Microvascular Angina

    PubMed Central

    Mumma, Bryn; Flacke, Nathalie

    2014-01-01

    Microvascular angina is common among patients with signs and symptoms of acute coronary syndrome and is associated with an increased risk of cardiovascular and cerebrovascular events. Unfortunately, microvascular is often under-recognized in clinical settings. The diagnosis of microvascular angina relies on assessment of the functional status of the coronary microvasculature. Invasive strategies include acetylcholine provocation, intracoronary Doppler ultrasound, and intracoronary thermodilution; noninvasive strategies include cardiac positron emission tomography (PET), cardiac magnetic resonance, and Doppler echocardiography. Once the diagnosis of microvascular angina is established, treatment is focused on improving symptoms and reducing future risk of cardiovascular and cerebrovascular events. Pharmacologic options and lifestyle modifications for patients with microvascular angina are similar to those for patients with coronary artery disease. PMID:25685641

  12. Myocardial perfusion echocardiography and coronary microvascular dysfunction

    PubMed Central

    Barletta, Giuseppe; Del Bene, Maria Riccarda

    2015-01-01

    Our understanding of coronary syndromes has evolved in the last two decades out of the obstructive atherosclerosis of epicardial coronary arteries paradigm to include anatomo-functional abnormalities of coronary microcirculation. No current diagnostic technique allows direct visualization of coronary microcirculation, but functional assessments of this circulation are possible. This represents a challenge in cardiology. Myocardial contrast echocardiography (MCE) was a breakthrough in echocardiography several years ago that claimed the capability to detect myocardial perfusion abnormalities and quantify coronary blood flow. Research demonstrated that the integration of quantitative MCE and fractional flow reserve improved the definition of ischemic burden and the relative contribution of collaterals in non-critical coronary stenosis. MCE identified no-reflow and low-flow within and around myocardial infarction, respectively, and predicted the potential functional recovery of stunned myocardium using appropriate interventions. MCE exhibited diagnostic performances that were comparable to positron emission tomography in microvascular reserve and microvascular dysfunction in angina patients. Overall, MCE improved echocardiographic evaluations of ischemic heart disease in daily clinical practice, but the approval of regulatory authorities is lacking. PMID:26730291

  13. Microvascular Repair: Post-Angiogenesis Vascular Dynamics

    PubMed Central

    LeBlanc, Amanda J.; Krishnan, Laxminarayanan; Sullivan, Christopher J.; Williams, Stuart K.; Hoying, James B.

    2013-01-01

    Vascular compromise and the accompanying perfusion deficits cause or complicate a large array of disease conditions and treatment failures. This has prompted the exploration of therapeutic strategies to repair or regenerate vasculatures thereby establishing more competent microcirculatory beds. Growing evidence indicates that an increase in vessel numbers within a tissue does not necessarily promote an increase in tissue perfusion. Effective regeneration of a microcirculation entails the integration of new stable microvessel segments into the network via neovascularization. Beginning with angiogenesis, neovascularization entails an integrated series of vascular activities leading to the formation of a new mature microcirculation and includes vascular guidance and inosculation, vessel maturation, pruning, arterio-venous specification, network patterning, structural adaptation, intussusception, and microvascular stabilization. While the generation of new vessel segments is necessary to expand a network, without the concomitant neovessel remodeling and adaptation processes intrinsic to microvascular network formation, these additional vessel segments give rise to a dysfunctional microcirculation. While many of the mechanisms regulating angiogenesis have been detailed, a thorough understanding of the mechanisms driving post-angiogenesis activities specific to neovascularization has yet to be fully realized, but is necessary in order to develop effective therapeutic strategies for repairing compromised microcirculations as a means to treat disease. PMID:22734666

  14. Effects of radiation therapy in microvascular anastomoses

    SciTech Connect

    Fried, M.P.

    1985-07-01

    The otolaryngologist, as a head and neck surgeon, commonly cares for patients with upper aerodigestive tract malignancies. Therapy of these neoplasms often requires wide excision. One standard reconstructive procedure utilizes pedicled regional flaps, both dermal and myodermal which have some disadvantages. The shortcomings of these pedicled regional flaps have led to the use of the vascularized free flap in certain cases. The occasional case may lead to catastrophe if microanastomoses fail when combined with radiation. Notwithstanding, many surgical series have reported success when radiation has been given. The present investigation was undertaken to assess the effects of radiation therapy on microvascular anastomoses when radiation is administered pre- or postoperatively or when nonradiated tissue is transferred to an irradiated recipient site. These effects were observed serially in an experimental rat model using a tubed superficial epigastric flap that adequately reflected tissue viability and vascular patency. The histologic changes were then noted over a three month period after completion of both radiation and surgery. This study adds credence to the observation of the lack of deleterious effects of radiation on experimental microvascular anastomotic patency whether the radiation is given before or after surgery or if radiated tissue is approximated to nonradiated vessels.

  15. Transport in Halobacterium Halobium: Light-Induced Cation-Gradients, Amino Acid Transport Kinetics, and Properties of Transport Carriers

    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.

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

    PubMed Central

    Fiorio Pla, Alessandra; Munaron, Luca

    2014-01-01

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

  17. 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.

  18. The spin-dependent transport properties of zigzag α-graphyne nanoribbons and new device design

    NASA Astrophysics Data System (ADS)

    Ni, Yun; Wang, Xia; Tao, Wei; Zhu, Si-Cong; Yao, Kai-Lun

    2016-05-01

    By performing first-principle quantum transport calculations, we studied the electronic and transport properties of zigzag α-graphyne nanoribbons in different magnetic configurations. We designed the device based on zigzag α-graphyne nanoribbon and studied the spin-dependent transport properties, whose current-voltage curves show obvious spin-polarization and conductance plateaus. The interesting transport behaviours can be explained by the transport spectra under different magnetic configurations, which basically depends on the symmetry matching of the electrodes’ bandstructures. Simultaneously, spin Seebeck effect is also found in the device. Thus, according to the transport behaviours, zigzag α-graphyne nanoribbons can be used as a dual spin filter diode, a molecule signal converter and a spin caloritronics device, which indicates that α-graphyne is a promising candidate for the future application in spintronics.

  19. The spin-dependent transport properties of zigzag α-graphyne nanoribbons and new device design.

    PubMed

    Ni, Yun; Wang, Xia; Tao, Wei; Zhu, Si-Cong; Yao, Kai-Lun

    2016-01-01

    By performing first-principle quantum transport calculations, we studied the electronic and transport properties of zigzag α-graphyne nanoribbons in different magnetic configurations. We designed the device based on zigzag α-graphyne nanoribbon and studied the spin-dependent transport properties, whose current-voltage curves show obvious spin-polarization and conductance plateaus. The interesting transport behaviours can be explained by the transport spectra under different magnetic configurations, which basically depends on the symmetry matching of the electrodes' bandstructures. Simultaneously, spin Seebeck effect is also found in the device. Thus, according to the transport behaviours, zigzag α-graphyne nanoribbons can be used as a dual spin filter diode, a molecule signal converter and a spin caloritronics device, which indicates that α-graphyne is a promising candidate for the future application in spintronics. PMID:27180808

  20. The spin-dependent transport properties of zigzag α-graphyne nanoribbons and new device design

    PubMed Central

    Ni, Yun; Wang, Xia; Tao, Wei; Zhu, Si-Cong; Yao, Kai-Lun

    2016-01-01

    By performing first-principle quantum transport calculations, we studied the electronic and transport properties of zigzag α-graphyne nanoribbons in different magnetic configurations. We designed the device based on zigzag α-graphyne nanoribbon and studied the spin-dependent transport properties, whose current-voltage curves show obvious spin-polarization and conductance plateaus. The interesting transport behaviours can be explained by the transport spectra under different magnetic configurations, which basically depends on the symmetry matching of the electrodes’ bandstructures. Simultaneously, spin Seebeck effect is also found in the device. Thus, according to the transport behaviours, zigzag α-graphyne nanoribbons can be used as a dual spin filter diode, a molecule signal converter and a spin caloritronics device, which indicates that α-graphyne is a promising candidate for the future application in spintronics. PMID:27180808

  1. Walker Diffusion Method for Calculation of Transport Properties of Finite Composite Systems

    SciTech Connect

    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.

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

    SciTech Connect

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

    2008-09-07

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

  3. 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.

  4. Monte Carlo Simulations on the Thermoelectric Transport Properties of Width-Modulated Nanowires

    NASA Astrophysics Data System (ADS)

    Zianni, X.

    2016-03-01

    We performed Monte Carlo simulations on the electron and phonon transport properties of Si nanowires with constant widths and of nanowires modulated by a constriction. We discuss and compare the transport properties and the thermoelectric efficiency in the nanowires. An overall figure of merit ( ZT) enhancement is predicted compared to the corresponding non-modulated nanowires. The ZT enhancement in thick, modulated nanowires has been found comparable to that in thin, non-modulated nanowires.

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

    SciTech Connect

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

    2006-06-01

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

  6. Comparison on thermal transport properties of graphene and phosphorene nanoribbons

    PubMed Central

    Peng, Xiao-Fang; Chen, Ke-Qiu

    2015-01-01

    We investigate ballistic thermal transport at low temperatures in graphene and phosphorene nanoribbons (PNRS) modulated with a double-cavity quantum structure. A comparative analysis for thermal transport in these two kinds of nanomaterials is made. The results show that the thermal conductance in PNRS is greater than that in graphene nanoribbons (GNRS). The ratio kG/kP (kG is the thermal conductivity in GNRS and kP is the thermal conductivity in PNRS) decreases with lower temperature or for narrower nanoribbons, and increases with higher temperature or for wider nanoribbons. The greater thermal conductance and thermal conductivity in PNRS originate from the lower cutoff frequencies of the acoustic modes. PMID:26577958

  7. Acute Alcohol Intoxication-Induced Microvascular Leakage

    PubMed Central

    Doggett, Travis M.; Breslin, Jerome W.

    2014-01-01

    Background Alcohol intoxication can increase inflammation and worsen injury, yet the mechanisms involved are not clear. We investigated whether acute alcohol intoxication elevates microvascular permeability, and investigated potential signaling mechanisms in endothelial cells that may be involved. Methods Conscious rats received a 2.5 g/kg alcohol bolus via gastric catheters to produce acute intoxication. Microvascular leakage of intravenously administered FITC-albumin from the mesenteric microcirculation was assessed by intravital microscopy. Endothelial-specific mechanisms were studied using cultured endothelial cell monolayers. Transendothelial electrical resistance (TER) served as an index of barrier function, before and after treatment with alcohol or its metabolite acetaldehyde. Pharmacologic agents were used to test the roles of alcohol metabolism, oxidative stress, p38 mitogen-activated protein (MAP) kinase, myosin light chain kinase (MLCK), rho kinase (ROCK), and exchange protein activated by cAMP (Epac). VE-cadherin localization was investigated to assess junctional integrity. Rac1 and RhoA activation were assessed by ELISA assays. Results Alcohol significantly increased FITC-albumin extravasation from the mesenteric microcirculation. Alcohol also significantly decreased TER and disrupted VE-cadherin organization at junctions. Acetaldehyde significantly decreased TER, but inhibition of ADH or application of a superoxide dismutase mimetic failed to prevent alcohol-induced decreases in TER. Inhibition of p38 MAP kinase, but not MLCK or ROCK, significantly attenuated the alcohol-induced barrier dysfunction. Alcohol rapidly decreased GTP-bound Rac1 but not RhoA during the drop in TER. Activation of Epac increased TER, but did not prevent alcohol from decreasing TER. However, activation of Epac after initiation of alcohol-induced barrier dysfunction quickly resolved TER to baseline levels. Conclusions Our results suggest that alcohol intoxication increases

  8. 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 σ 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 σ 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 σ 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.

  9. Atrial natriuretic peptide increases microvascular blood flow and macromolecular escape during renin infusion in the hamster

    SciTech Connect

    Boric, M.P.; Albertini, R. )

    1990-02-01

    The effects of Atrial Natriuretic Peptide (ANP) on microvascular hemodynamics and macromolecular permselectivity were studied in the hamster cheek pouch under resting conditions and during intravenous renin infusion. Fluorescent intravital microscopy was used to observe arteriolar diameters and to detect escape of fluorescent dextran of 150 K-Daltons (FITC-Dx-150). Microvascular plasma flow was estimated by clearance of 51Cr-EDTA and net macromolecular transport by clearance of FITC-Dx-150. At rest, topical ANP (2-250 ng/ml) had no effect on arteriolar diameter, 51Cr-EDTA clearance, relative vascular conductance (RVC) or FITC-Dx-150 clearance. Infusion of renin (10 mU/Kg/Hr, iv) elevated systemic arterial pressure by 30% and reduced cheek pouch RVC by 26%. During renin infusion, topical ANP (50 ng/ml) produced transient arteriolar vasodilation, and increased 51Cr-EDTA clearance (+35%), RVC (+58%) and FITC-Dx-150 clearance (+54%), without affecting systemic pressure. ANP did not induce venular leakage sites under any condition, but changes in FITC-Dx-150 clearance were highly correlated with changes in 51Cr-EDTA clearance, suggesting that the larger macromolecular escape was due to increases in microvascular blood flow and capillary/post-capillary hydrostatic pressure.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Woo, Sung Oh; Teizer, Winfried

    2013-07-01

    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.

  12. Differentiation state determines neural effects on microvascular endothelial cells

    SciTech Connect

    Muffley, Lara A.; Pan, Shin-Chen; Smith, Andria N.; Ga, Maricar; Hocking, Anne M.; Gibran, Nicole S.

    2012-10-01

    Growing evidence indicates that nerves and capillaries interact paracrinely in uninjured skin and cutaneous wounds. Although mature neurons are the predominant neural cell in the skin, neural progenitor cells have also been detected in uninjured adult skin. The aim of this study was to characterize differential paracrine effects of neural progenitor cells and mature sensory neurons on dermal microvascular endothelial cells. Our results suggest that neural progenitor cells and mature sensory neurons have unique secretory profiles and distinct effects on dermal microvascular endothelial cell proliferation, migration, and nitric oxide production. Neural progenitor cells and dorsal root ganglion neurons secrete different proteins related to angiogenesis. Specific to neural progenitor cells were dipeptidyl peptidase-4, IGFBP-2, pentraxin-3, serpin f1, TIMP-1, TIMP-4 and VEGF. In contrast, endostatin, FGF-1, MCP-1 and thrombospondin-2 were specific to dorsal root ganglion neurons. Microvascular endothelial cell proliferation was inhibited by dorsal root ganglion neurons but unaffected by neural progenitor cells. In contrast, microvascular endothelial cell migration in a scratch wound assay was inhibited by neural progenitor cells and unaffected by dorsal root ganglion neurons. In addition, nitric oxide production by microvascular endothelial cells was increased by dorsal root ganglion neurons but unaffected by neural progenitor cells. -- Highlights: Black-Right-Pointing-Pointer Dorsal root ganglion neurons, not neural progenitor cells, regulate microvascular endothelial cell proliferation. Black-Right-Pointing-Pointer Neural progenitor cells, not dorsal root ganglion neurons, regulate microvascular endothelial cell migration. Black-Right-Pointing-Pointer Neural progenitor cells and dorsal root ganglion neurons do not effect microvascular endothelial tube formation. Black-Right-Pointing-Pointer Dorsal root ganglion neurons, not neural progenitor cells, regulate

  13. Microvascularization on collared peccary placenta: a microvascular cast study [corrected] in late pregnancy.

    PubMed

    Santos, Tatiana Carlesso; Oliveira, Moacir Franco; Dantzer, Vibeke; Miglino, Maria Angélica

    2012-07-01

    The microvascularization of the collared peccary (Tayassu tajacu) placenta was studied by vascular casts and immunolocalization of α-smooth muscle actin and vimentin, to identify the three dimensional organization and vascular flow interrelation in the microvasculature between the maternal and fetal compartments of the placentae. The immunolocalization of vimentin in the vascular endothelium and in the smooth muscle cells of blood vessels showed indented capillaries along the uterine epithelium and the trophoblast at the sides of complementary maternal and fetal microfolds, or rugae. This confers the three-dimensional structure observed in vascular casts. On the maternal side, casts demonstrated uterine folds coated by with primary and secondary ridges, and by areolae dispersed between these ridges. The arteriole runs through the center/middle of ridges, branching at the top into a microvascular network wall in a basket-like fashion. At the base of these baskets venules were formed. On the fetal side, arterioles branched centrally in the fetal rugae into a capillary network in a bulbous form, complementary to the opposite maternal depressions forming the baskets. At the base of the bulbous protrusions, the fetal venules arise. The blood vessel orientation in the materno-fetal interface of the placentae of collared peccaries suggests a blood flow pattern of the type countercurrent to cross current. The same pattern has been reported in domestic swine demonstrating that, even after 38 million years, the Tayassuidae and Suidae families exhibit similar placental morphology, which is here characterized at the microvascular level.

  14. Detecting the local transport properties and the dimensionality of transport of epitaxial graphene by a multi-point probe approach

    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.

  15. Electronic and transport properties of PSi@MoS2 nanocables.

    PubMed

    Sun, Cuicui; Zhang, Guiling; Shang, Yan; Yang, Zhao-Di; Sun, Xiaojun

    2016-02-14

    Electronic structures and transport properties of prototype MoS2 nanotube (15, 0) nanocables, including undoped PSi@MoS2 and B- and P-doped PSi@MoS2 (where PSi refers to polysilane), are investigated using the density functional theory (DFT) and the non-equilibrium Green's function (NEGF) methods. It is found that transport properties of two-probe systems by sandwiching finite long nanocables between two Au electrodes are basically in agreement with the electronic structures of their corresponding infinitely long systems. Encapsulating undoped and doped PSi nanowires inside the MoS2 nanotubes could not significantly affect the electronic and transport properties. B-doping and P-doping upon PSi play different roles in the electronic and transport properties. B-doping may exert constructive and destructive effects on electron transport depending on its position and applied bias direction, while P-doping displays a negligible effect. In addition, we found that bi-doping by two adjacent B atoms could slightly enhance the conductivity. These results could offer some clues for conducting experiments to achieve nanoelectronic devices with intrinsic transport properties of MoS2 nanotubes.

  16. [Study of transport properties of the polymeric membranous dressing with silver ions].

    PubMed

    Slezak, Andrzej; Kucharzewski, Marek; Grzegorczyn, Sławomir; Slezak, Izabella H

    2005-01-01

    The transport properties of polymeric membraneous dresing silver ion containing Textus Bioactive were studied. This dressing is made of three types of theromoplastic polymeric fibers, formed into two-layers membrane. In first layer occure the polymeric fiber, which the core is hydrophobic and hydrophilic surfaces contain a silver zeolite. These fibers neighborours with hydrophilic super absorbing polymers. Third type of polymeric fibers occur in the second layer of membrane and is arranged parallel to surface's skin, creating a net preventing stick of membraneous dressing to treated wound. Using of the Kedem-Katchalsky equations the transport model of this membrane and the temporal and concentration characteristics of transport parameters (hydraulic permeability, refection and solute permeability) were determined. Experimental results show that the polymeric membranous dressing contain the silver ions posses non-linear transport properties, which are consequence of structure and physicochemical properties of polymeric membranes.

  17. The effect of mucolytic agents on the rheologic and transport properties of canine tracheal mucus.

    PubMed

    Martin, R; Litt, M; Marriott, C

    1980-03-01

    The effect of several sulfhydryl and other agents on the rheologic and mucociliary transport properties of a model secretion, reconstituted canine tracheal mucus, was investigated. The mucus was obtained via the canine tracheal pouch. Rheologic properties were determined by mirorheometry, and the ciliary transport rate was determined using the frog palate technique. It was found that N-acetyl cysteine decreased the elastic modulus, leading to improved mucociliary transport at concentrations such that the mucin did not precipitate. S-carboxymethyl cysteine had no effect on either mucus properties or mucociliary transport rate, and its reported effectiveness in vivo must be due to some mechanism other than solubilization of mucin. Similar results were found with other blocked sulfhydryl compounds. Urea and potassium iodide to decrease mucus elasticity, but are harmful to cilia at the concentrations needed.

  18. Self-healing materials with microvascular networks.

    PubMed

    Toohey, Kathleen S; Sottos, Nancy R; Lewis, Jennifer A; Moore, Jeffrey S; White, Scott R

    2007-08-01

    Self-healing polymers composed of microencapsulated healing agents exhibit remarkable mechanical performance and regenerative ability, but are limited to autonomic repair of a single damage event in a given location. Self-healing is triggered by crack-induced rupture of the embedded capsules; thus, once a localized region is depleted of healing agent, further repair is precluded. Re-mendable polymers can achieve multiple healing cycles, but require external intervention in the form of heat treatment and applied pressure. Here, we report a self-healing system capable of autonomously repairing repeated damage events. Our bio-inspired coating-substrate design delivers healing agent to cracks in a polymer coating via a three-dimensional microvascular network embedded in the substrate. Crack damage in the epoxy coating is healed repeatedly. This approach opens new avenues for continuous delivery of healing agents for self-repair as well as other active species for additional functionality.

  19. Electronic, magnetic and transport properties of rare-earth monopnictides.

    PubMed

    Duan, Chun-Gang; Sabirianov, R F; Mei, W N; Dowben, P A; Jaswal, S S; Tsymbal, E Y

    2007-08-01

    The electronic structures and magnetic properties of many rare-earth monopnictides are reviewed in this article. Possible candidate materials for spintronics devices from the rare-earth monopnictide family, i.e. high polarization (nominally half-metallic) ferromagnets and antiferromagnets, are identified. We attempt to provide a unified picture of the electronic properties of these strongly correlated systems. The relative merits of several ab initio theoretical methods, useful in the study of the rare-earth monopnictides, are discussed. We present our current understanding of the possible half-metallicity, semiconductor-metal transitions, and magnetic orderings in the rare-earth monopnictides. Finally, we propose some potential strategies to improve the magnetic and electronic properties of these candidate materials for spintronics devices. PMID:21694120

  20. Transport properties of Nb/InAs(2DEG)/Nb Josephson field-effect transistors

    NASA Astrophysics Data System (ADS)

    Richter, A.; Koch, M.; Matsuyama, T.; Merkt, U.

    1999-11-01

    We investigate transport properties of mesoscopic semiconductor-superconductor weak links. The superconducting Nb electrodes of our junctions are coupled by the two-dimensional electron gas of an InAs heterostructure grown on a GaAs substrate. We report on the properties of Josephson field-effect transistors utilizing these junctions.

  1. Phase transition of the microvascular network architecture in human pathologies.

    PubMed

    Bianciardi, Giorgio; Traversi, Claudio; Cattaneo, Ruggero; De Felice, Claudia; Monaco, Annalisa; Tosi, Gianmarco; Parrini, Stefano; Latini, Giuseppe

    2012-01-01

    We have investigated the microvascular pattern in acquired or genetic diseases in humans. The lower gingival and vestibular oral mucosa, as well as the optic nerve head, was chosen to characterize the vascular pattern complexity due to the simple accessibility and visibility Local fractal dimensions, fractal dimension of the minimum path and Lempel-Ziv complexity have been used as operational numerical tools to characterize the microvascular networks. In the normal healthy subjects microvascular networks show nonlinear values corresponding to the complexity of a diffusion limited aggregation (DLA) model, while in several acquired or genetic diseases they are approaching the ones of an invasion percolation model. PMID:23193796

  2. Microsphere-chain waveguides: Focusing and transport properties

    SciTech Connect

    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 ≥ 20λ, where D is the sphere diameter and λ 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 ≤ 10λ 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.

  3. Transport Properties of III-N Hot Electron Transistors

    NASA Astrophysics Data System (ADS)

    Suntrup, Donald J., III

    Unipolar hot electron transistors (HETs) represent a tantalizing alternative to established bipolar transistor technologies. During device operation electrons are injected over a large emitter barrier into the base where they travel along the device axis with very high velocity. Upon arrival at the collector barrier, high-energy electrons pass over the barrier and contribute to collector current while low-energy electrons are quantum mechanically reflected back into the base. Designing the base with thickness equal to or less than the hot electron mean free path serves to minimize scattering events and thus enable quasi-ballistic operation. Large current gain is achieved by increasing the ratio of transmitted to reflected electrons. Although III-N HETs have undergone substantial development in recent years, there remain ample opportunities to improve key device metrics. In order to engineer improved device performance, a deeper understanding of the operative transport physics is needed. Fortunately, the HET provides fertile ground for studying several prominent electron transport phenomena. In this thesis we present results from several studies that use the III-N HET as both emitter and analyzer of hot electron momentum states. The first provides a measurement of the hot electron mean free path and the momentum relaxation rate in GaN; the second relies on a new technique called electron injection spectroscopy to investigate the effects of barrier height inhomogeneity in the emitter. To supplement our analysis we develop a comprehensive theory of coherent electron transport that allows us to model the transfer characteristics of complex heterojunctions. Such a model provides a theoretical touchstone with which to compare our experimental results. While these studies are of potential interest in their own right, we interpret the results with an eye toward improving next-generation device performance.

  4. FORTRAN 4 computer program for calculation of thermodynamic and transport properties of complex chemical systems

    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.

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

    SciTech Connect

    Cressault, Y.

    2015-05-15

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

  6. Direct pore-scale computation of material and transport properties for North Sea reservoir rocks

    NASA Astrophysics Data System (ADS)

    Øren, P.-E.; Bakke, S.; Held, R.

    2007-12-01

    This work investigates two complex, heterogeneous sandstone lithofacies in a North Sea petroleum reservoir field. We compare samples acquired by X-ray microtomography with numerically reconstructed lithofacies, obtained from a geological process based reconstruction technique. Effective material and transport properties of these digitized rocks, such as electrical resistivity, elastic moduli, fluid permeability, and magnetic resonance (NMR), are computed. The comparison largely reveals an excellent agreement of calculated effective properties between the actual and reconstructed pore structures. A dependence of the effective properties on the specific mineralogy could be investigated in case of the reconstructed rocks. Our results allow for an interpretation of trends in effective medium properties and facilitate the construction of cross-property relations for the investigated lithofacies. The present study demonstrates the potential and feasibility of combining computer generated rocks with numerical calculations to derive material and transport properties for reservoir rocks.

  7. Electrical Transport Properties of Polymorphic MoS2.

    PubMed

    Kim, Jun Suk; Kim, Jaesu; Zhao, Jiong; Kim, Sungho; Lee, Jin Hee; Jin, Youngjo; Choi, Homin; Moon, Byoung Hee; Bae, Jung Jun; Lee, Young Hee; Lim, Seong Chu

    2016-08-23

    The engineering of polymorphs in two-dimensional layered materials has recently attracted significant interest. Although the semiconducting (2H) and metallic (1T) phases are known to be stable in thin-film MoTe2, semiconducting 2H-MoS2 is locally converted into metallic 1T-MoS2 through chemical lithiation. In this paper, we describe the observation of the 2H, 1T, and 1T' phases coexisting in Li-treated MoS2, which result in unusual transport phenomena. Although multiphase MoS2 shows no transistor-gating response, the channel resistance decreases in proportion to the temperature, similar to the behavior of a typical semiconductor. Transmission electron microscopy images clearly show that the 1T and 1T' phases are randomly distributed and intervened with 2H-MoS2, which is referred to as the 1T and 1T' puddling phenomenon. The resistance curve fits well with 2D-variable range-hopping transport behavior, where electrons hop over 1T domains that are bounded by semiconducting 2H phases. However, near 30 K, electrons hop over charge puddles. The large temperature coefficient of resistance (TCR) of multiphase MoS2, -2.0 × 10(-2) K(-1) at 300 K, allows for efficient IR detection at room temperature by means of the photothermal effect. PMID:27399325

  8. Electrical Transport Properties of Polymorphic MoS2.

    PubMed

    Kim, Jun Suk; Kim, Jaesu; Zhao, Jiong; Kim, Sungho; Lee, Jin Hee; Jin, Youngjo; Choi, Homin; Moon, Byoung Hee; Bae, Jung Jun; Lee, Young Hee; Lim, Seong Chu

    2016-08-23

    The engineering of polymorphs in two-dimensional layered materials has recently attracted significant interest. Although the semiconducting (2H) and metallic (1T) phases are known to be stable in thin-film MoTe2, semiconducting 2H-MoS2 is locally converted into metallic 1T-MoS2 through chemical lithiation. In this paper, we describe the observation of the 2H, 1T, and 1T' phases coexisting in Li-treated MoS2, which result in unusual transport phenomena. Although multiphase MoS2 shows no transistor-gating response, the channel resistance decreases in proportion to the temperature, similar to the behavior of a typical semiconductor. Transmission electron microscopy images clearly show that the 1T and 1T' phases are randomly distributed and intervened with 2H-MoS2, which is referred to as the 1T and 1T' puddling phenomenon. The resistance curve fits well with 2D-variable range-hopping transport behavior, where electrons hop over 1T domains that are bounded by semiconducting 2H phases. However, near 30 K, electrons hop over charge puddles. The large temperature coefficient of resistance (TCR) of multiphase MoS2, -2.0 × 10(-2) K(-1) at 300 K, allows for efficient IR detection at room temperature by means of the photothermal effect.

  9. Studies of Transport Properties of Fractures: Final Report

    SciTech Connect

    Stephen R. Brown

    2006-06-30

    We proposed to study several key factors controlling the character and evolution of fracture system permeability and transport processes. We suggest that due to surface roughness and the consequent channeling in single fractures and in fracture intersections, the tendency of a fracture system to plug up, remain permeable, or for permeability to increase due to chemical dissolution/precipitation conditions will depend strongly on the instantaneous flow channel geometry. This geometry will change as chemical interaction occurs, thus changing the permeability through time. To test this hypothesis and advance further understanding toward a predictive capability, we endeavored to physically model and analyze several configurations of flow and transport of inert and chemically active fluids through channels in single fractures and through fracture intersections. This was an integrated program utilizing quantitative observations of fractures and veins in drill core, quantitative and visual observations of flow and chemical dissolution and precipitation within replicas of real rough-walled fractures and fracture intersections, and numerical modeling via lattice Boltzmann methods.

  10. 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.

  11. Impact of carbonation on the durability of cementitious materials: water transport properties characterization

    NASA Astrophysics Data System (ADS)

    Auroy, M.; Poyet, S.; Le Bescop, P.; Torrenti, J.-M.

    2013-07-01

    Within the context of long-lived intermediate level radioactive waste geological disposal, reinforced concrete would be used. In service life conditions, the concrete structures would be subjected to drying and carbonation. Carbonation relates to the reaction between carbon dioxide (CO2) and the main hydrates of the cement paste (portlandite and C-S-H). Beyond the fall of the pore solution pH, indicative of steel depassivation, carbonation induces mineralogical and microstructural changes (due to portlandite and C-S-H dissolution and calcium carbonate precipitation). This results in the modification of the transport properties, which can impact the structure durability. Because concrete durability depends on water transport, this study focuses on the influence of carbonation on water transport properties. In fact, the transport properties of sound materials are known but they still remain to be assessed for carbonated ones. An experimental program has been designed to investigate the transport properties in carbonated materials. Four hardened cement pastes, differing in mineralogy, are carbonated in an accelerated carbonation device (in controlled environmental conditions) at CO2 partial pressure of about 3%. Once fully carbonated, all the data needed to describe water transport, using a simplified approach, will be evaluated.

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

    SciTech Connect

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

    2015-05-15

    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.

  13. Charge transport properties of CdMnTe radiation detectors

    SciTech Connect

    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.

  14. 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.

  15. Direct measurements of transport properties are essential for site characterization

    SciTech Connect

    Wright, J.; Conca, J.L.

    1994-08-01

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

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

    PubMed

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

    2015-06-23

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

  17. Lithologic melt partitioning and transport properties of partially molten harzburgite

    NASA Astrophysics Data System (ADS)

    Miller, K. J.; Zhu, W.; Montesi, L.; Gaetani, G. A.; Le Roux, V.; Xiao, X.

    2015-12-01

    Quantitative constraints on melt transport in upper mantle are critical to understanding various dynamic processes at ocean ridges. In this study, we propose that thermodynamic gradients, resulting from spatial variations in mineralogy, can unevenly partition melt between olivine and orthopyroxene (opx), the two most abundant minerals in the upper mantle. The lithologic melt partitioning leads to higher melt fraction in olivine-rich regions compared to opx-rich regions, which may have important implications for melt transport. Lithologic partitioning has been experimentally confirmed in analogue systems, such as quartz/fluorite-H2O (Watson, 1999), but has never been observed in olivine/opx-melt samples. We synthesized olivine/opx-melt (harzburgite) samples by isostatically pressing oxide-high alumina basalt mixtures at 1350 °C and 1.5 GPa in a piston-cylinder apparatus. Nominal melt fractions of 0.02 to 0.20 and a constant 3 to 2 (olivine to opx) volume ratio were tested. Experimental charges were quenched, cored, and imaged using synchrotron X-ray microtomography. The resulting 3-D images constitute digital rock samples on which local melt fraction distributions, permeabilities, and electrical conductivities were numerically quantified. Our results are strong evidence for melt partitioning between olivine and opx: local melt fractions are 10 to 50% higher around olivine than opx grains. At the same melt fraction, permeabilities of whole harzburgite samples are lower compared to monomineralic olivine-melt samples (Miller et al., 2014). However, the presence of opx negligibly affects the permeability-porosity relation unless the abundance of opx is more than 40 vol. %. In contrast, electrical conductivities of harzburgites are systematically lower than those of olivine-melt samples. Lithological melt partitioning could be another mechanism responsible for forming high-porosity melt pathways in addition to reaction infiltration instability and deformation melt bands.

  18. Microvascular temporalis fascia transfer for penile girth enhancement.

    PubMed

    Küçükçelebi, A; Ertaş, N M; Aydin, A; Eroğlu, A; Ozmen, E; Velidedeoğlu, H

    2001-07-01

    The authors report a 44-year-old man with inadequate penile girth that caused psychological problems. Using microvascular temporalis fascia transfer, they achieved satisfactory penile girth enhancement based on reliable vascularity in a single stage. PMID:11756810

  19. Protein osmotic pressure gradients and microvascular reflection coefficients.

    PubMed

    Drake, R E; Dhother, S; Teague, R A; Gabel, J C

    1997-08-01

    Microvascular membranes are heteroporous, so the mean osmotic reflection coefficient for a microvascular membrane (sigma d) is a function of the reflection coefficient for each pore. Investigators have derived equations for sigma d based on the assumption that the protein osmotic pressure gradient across the membrane (delta II) does not vary from pore to pore. However, for most microvascular membranes, delta II probably does vary from pore to pore. In this study, we derived a new equation for sigma d. According to our equation, pore-to-pore differences in delta II increase the effect of small pores and decrease the effect of large pores on the overall membrane osmotic reflection coefficient. Thus sigma d for a heteroporous membrane may be much higher than previously derived equations indicate. Furthermore, pore-to-pore delta II differences increase the effect of plasma protein osmotic pressure to oppose microvascular fluid filtration. PMID:9277520

  20. Bottom-up processing and low temperature transport properties of polycrystalline SnSe

    SciTech Connect

    Ge, Zhen-Hua; Wei, Kaya; Lewis, Hutton; Martin, Joshua; Nolas, George S.

    2015-05-15

    A hydrothermal approach was employed to efficiently synthesize SnSe nanorods. The nanorods were consolidated into polycrystalline SnSe by spark plasma sintering for low temperature electrical and thermal properties characterization. The low temperature transport properties indicate semiconducting behavior with a typical dielectric temperature dependence of the thermal conductivity. The transport properties are discussed in light of the recent interest in this material for thermoelectric applications. The nanorod growth mechanism is also discussed in detail. - Graphical abstract: SnSe nanorods were synthesized by a simple hydrothermal method through a bottom-up approach. Micron sized flower-like crystals changed to nanorods with increasing hydrothermal temperature. Low temperature transport properties of polycrystalline SnSe, after SPS densification, were reported for the first time. This bottom-up synthetic approach can be used to produce phase-pure dense polycrystalline materials for thermoelectrics applications. - Highlights: • SnSe nanorods were synthesized by a simple and efficient hydrothermal approach. • The role of temperature, time and NaOH content was investigated. • SPS densification allowed for low temperature transport properties measurements. • Transport measurements indicate semiconducting behavior.

  1. Microvascular Plasticity: Angiogenesis in Health and Disease--Preface.

    PubMed

    Secomb, Timothy W; Pries, Axel R

    2016-02-01

    This Special Topic Issue is concerned with the mechanisms that determine the structure of microvascular networks. The vast number of vessels and the highly plastic character of the microcirculation give evidence that microvascular network structures emerge as a result of responses of individual vessels and cells to the local stimuli that they experience, through a combination of angiogenesis, remodeling and pruning. The articles in this issue of Microcirculation address a range of cellular and molecular mechanisms involved in these processes. PMID:26639099

  2. Microvascular complications and diabetic retinopathy: recent advances and future implications.

    PubMed

    Barot, Megha; Gokulgandhi, Mitan R; Patel, Sulabh; Mitra, Ashim K

    2013-03-01

    Retinal microvascular alterations have been observed during diabetic retinopathy (DR) due to the retinal susceptibility towards subtle pathological alterations. Therefore, retinal microvascular pathology is essential to understand the nature of retinal degenerations during DR. In this review, the role of retinal microvasculature complications during progression of DR, along with recent efforts to normalize such alterations for better therapeutic outcome, will be underlined. In addition, current therapeutics and future directions for advancement of standard treatment for DR patients will be discussed. PMID:23464520

  3. Investigation of boron modified graphene nanostructures; optoelectronic properties of graphene nanoparticles and transport properties of graphene nanosheets

    NASA Astrophysics Data System (ADS)

    Armaković, Stevan; Armaković, Sanja J.

    2016-11-01

    In this work we investigated optoelectronic properties of graphene nanoparticles and transport properties of graphene nanosheets and the consequences on these properties after modifications with boron atoms. Within the framework of density functional theory (DFT) several important optoelectronic quantities have been calculated for graphene nanoparticles: oxidation and reduction potentials, hole and electron reorganization energies, while thermally activated delayed fluorescence was assessed by calculations of energy separation between the lowest excited singlet (S1) and triplet (T1) state, Δ E (S1 -T1) . Obtained results show that optoelectronic properties of graphene nanoparticles are significantly improved by the modification with boron atoms and that investigated structures can be considered as a promising organic light emitting diode (OLED) materials. Influence of boron atoms to charge and heat transport properties of graphene nanosheets was investigated as well, employing the self-consistent non-equilibrium Green's functions with DFT. On the other side it is shown that charge transport of graphene nanosheets is not influenced by the introduction of boron atoms, while influence to the phonon subsystem is minimal.

  4. 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.

  5. Spin-polarized quantum transport properties through flexible phosphorene

    NASA Astrophysics Data System (ADS)

    Chen, Mingyan; Yu, Zhizhou; Xie, Yiqun; Wang, Yin

    2016-10-01

    We report a first-principles study on the tunnel magnetoresistance (TMR) and spin-injection efficiency (SIE) through phosphorene with nickel electrodes under the mechanical tension and bending on the phosphorene region. Both the TMR and SIE are largely improved under these mechanical deformations. For the uniaxial tension (ɛy) varying from 0% to 15% applied along the armchair transport (y-)direction of the phosphorene, the TMR ratio is enhanced with a maximum of 107% at ɛy = 10%, while the SIE increases monotonously from 8% up to 43% with the increasing of the strain. Under the out-of-plane bending, the TMR overall increases from 7% to 50% within the bending ratio of 0%-3.9%, and meanwhile the SIE is largely improved to around 70%, as compared to that (30%) of the flat phosphorene. Such behaviors of the TMR and SIE are mainly affected by the transmission of spin-up electrons in the parallel configuration, which is highly dependent on the applied mechanical tension and bending. Our results indicate that the phosphorene based tunnel junctions have promising applications in flexible electronics.

  6. Cross Sections and Transport Properties of BR- Ions in AR

    NASA Astrophysics Data System (ADS)

    Jovanovic, Jasmina; Stojanovic, Vladimir; Raspopovic, Zoran; Petrovic, Zoran

    2014-10-01

    We have used a combination of a simple semi-analytic theory - Momentum Transfer Theory (MTT) and exact Monte Carlo (MC) simulations to develop Br- in Ar momentum transfer cross section based on the available data for reduced mobility at the temperature T = 300 K over the range 10 Td <= E / N <= 300 Td. At very low energies, we have extrapolated obtained cross sections towards Langevin's cross section. Also, we have extrapolated data to somewhat higher energies based on behavior of similar ions in similar gases and by the addition of the total detachment cross section that was used from the threshold around 7.7 eV. Relatively complete set was derived which can be used in modeling of plasmas by both hybrid, particle in cell (PIC) and fluid codes. A good agreement between calculated and measured ion mobilities and longitudinal diffusion coefficients is an independent proof of the validity of the cross sections that were derived for the negative ion mobility data. In addition to transport coefficients we have also calculated the net rate coefficients of elastic scattering and detachment. Author acknowledge Ministry of Education, Science and Technology, Proj. Nos. 171037 and 410011.

  7. Properties of the S(N)-equivalent integral transport operator and the iterative acceleration of neutral particle transport methods

    NASA Astrophysics Data System (ADS)

    Rosa, Massimiliano

    We have derived expressions for the elements of the matrix representing a certain angular (SN) and spatial discretized form of the neutron integral transport operator. This is the transport operator that if directly inverted on the once-collided fixed particle source produces, without the need for an iterative procedure, the converged limit of the scalar fluxes for the iterative procedure. The asymptotic properties of this operator's elements have then been investigated in homogeneous and periodically heterogeneous limits in one-dimensional and two-dimensional geometries. The thesis covers the results obtained from this asymptotic study of the matrix structure of the discrete integral transport operator and illustrates how they relate to the iterative acceleration of neutral particle transport methods. Specifically, it will be shown that in one-dimensional problems (both homogeneous and periodically heterogeneous) and homogeneous two-dimensional problems, containing optically thick cells, the discrete integral transport operator acquires a sparse matrix structure, implying a strong local coupling of a cell-averaged scalar flux only with its nearest Cartesian neighbors. These results provide further insight into the excellent convergence properties of diffusion-based acceleration schemes for this broad class of transport problems. In contrast, the results of the asymptotic analysis for two-dimensional periodically heterogeneous problems point to a sparse but non-local matrix structure due to long-range coupling of a cell's average flux with its neighboring cells, independent of the distance between the cells in the spatial mesh. The latter results indicate that cross-derivative coupling, namely coupling of a cell's average flux to its diagonal neighbors, is of the same order as self-coupling and coupling with its first Cartesian neighbors. Hence they substantiate the conjecture that the loss of robustness of diffusion-based acceleration schemes, in particular of the

  8. 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.

  9. Accurate transport properties for H–CO and H–CO{sub 2}

    SciTech Connect

    Dagdigian, Paul J.

    2015-08-07

    Transport properties for collisions of hydrogen atoms with CO and CO{sub 2} 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–CO{sub 2} 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.

  10. The MIDAS data-bank system for the transport properties of fluids/sup 1/

    SciTech Connect

    Laesecke, A.; Krauss, R.; Stephan, K.; Hanley, H.J.M.; Cezairliyan, A.

    1986-07-01

    The development of the MIDAS Data-Bank System from its origin as part of the first DECHEMA properties data project in 1977 is described. The system concentrates the rapidly increasing amount of data for the viscosity and thermal conductivity for pure fluids and fluid mixtures by evaluation of the most reliable data sets. The data sets are represented by density-temperature correlations which are the customary method to correlate transport properties. To allow for a direct calculation of the transport properties from given pressures and temperatures, a new type of equation has been developed. As an example, the simultaneous representation of the viscosity and thermal conductivity of oxygen by one transport equation of state is discussed.

  11. Transport properties and Stokes-Einstein relation in Al-rich liquid alloys

    NASA Astrophysics Data System (ADS)

    Jakse, N.; Pasturel, A.

    2016-06-01

    We use ab initio molecular dynamics simulations to study the transport properties and the validity of the Stokes-Einstein relation in Al-rich liquid alloys with Ni, Cu, and Zn as alloying elements. First, we show that the composition and temperature dependence of their transport properties present different behaviors, which can be related to their local structural ordering. Then, we evidence that the competition between the local icosahedral ordering and the local chemical ordering may cause the breakdown of the Stokes-Einstein relation even in the liquid phase. We demonstrate that this breakdown can be captured by entropy-scaling relationships developed by Rosenfeld and using the two-body excess entropy. Our findings provide a unique framework to study the relation between structure, thermodynamics, and dynamics in metallic melts and pave the way towards the explanation of various complex transport properties in metallic melts.

  12. Symmetry-dependent transport properties and magnetoresistance in zigzag silicene nanoribbons

    NASA Astrophysics Data System (ADS)

    Kang, Jun; Wu, Fengmin; Li, Jingbo

    2012-06-01

    First principles calculations are performed to study the transport properties of zigzag silicene nanoribbons (ZSiNRs). ZSiNRs show symmetry-dependent transport properties similar to those of zigzag graphene nanoribbons, although the σ mirror plane is absent. Even-N and odd-N ZSiNRs have very different current-voltage relationships, which can be attributed to the different parity of their π and π* bands under c2 symmetry operation with respect to the center axis. Moreover, magnetoresistance effect is observed in even-N ZSiNRs, and the order can reach 1 000 000%. On the basis of these interesting transport properties, ZSiNR-based logic devices, such as not, and, and or gates, are proposed.

  13. Transport properties and Stokes-Einstein relation in Al-rich liquid alloys.

    PubMed

    Jakse, N; Pasturel, A

    2016-06-28

    We use ab initio molecular dynamics simulations to study the transport properties and the validity of the Stokes-Einstein relation in Al-rich liquid alloys with Ni, Cu, and Zn as alloying elements. First, we show that the composition and temperature dependence of their transport properties present different behaviors, which can be related to their local structural ordering. Then, we evidence that the competition between the local icosahedral ordering and the local chemical ordering may cause the breakdown of the Stokes-Einstein relation even in the liquid phase. We demonstrate that this breakdown can be captured by entropy-scaling relationships developed by Rosenfeld and using the two-body excess entropy. Our findings provide a unique framework to study the relation between structure, thermodynamics, and dynamics in metallic melts and pave the way towards the explanation of various complex transport properties in metallic melts. PMID:27369522

  14. Transport properties and Stokes-Einstein relation in Al-rich liquid alloys.

    PubMed

    Jakse, N; Pasturel, A

    2016-06-28

    We use ab initio molecular dynamics simulations to study the transport properties and the validity of the Stokes-Einstein relation in Al-rich liquid alloys with Ni, Cu, and Zn as alloying elements. First, we show that the composition and temperature dependence of their transport properties present different behaviors, which can be related to their local structural ordering. Then, we evidence that the competition between the local icosahedral ordering and the local chemical ordering may cause the breakdown of the Stokes-Einstein relation even in the liquid phase. We demonstrate that this breakdown can be captured by entropy-scaling relationships developed by Rosenfeld and using the two-body excess entropy. Our findings provide a unique framework to study the relation between structure, thermodynamics, and dynamics in metallic melts and pave the way towards the explanation of various complex transport properties in metallic melts.

  15. SmB6 thin films synthesis and transport properties

    NASA Astrophysics Data System (ADS)

    Li, Yufan; Huang, Sunxiang; Chien, C.-L.

    2015-03-01

    SmB6, the candidate of the newly proposed topological Kondo insulator, has attracted great research interest in its physical properties. Evidences supporting the presence of the topologically protected surface state were gathered from various experimental studies, however mainly focusing on bulk specimens. In this work, (100) textured SmB6 thin films with dominant epitaxy were synthesized by DC magnetron sputtering. The resistivity saturates below 10 K and forms a plateau, while at higher temperatures the insulating behavior manifests a band gap ~3 meV consistent with the reported value of bulk samples. A sign change of the normal Hall coefficient may indicate the formation of the hybridization energy gap. Now at University of Miami.

  16. From transport to disorder: thermodynamic properties of finite dust clouds.

    PubMed

    Schella, André; Mulsow, Matthias; Melzer, André; Schablinski, Jan; Block, Dietmar

    2013-06-01

    The quantities entropy and diffusion are measured for two- and three-dimensional (3D) dust clusters in the fluid state. Entropy and diffusion are predicted to be closely linked via unstable modes. The method of instantaneous normal modes is applied for various laser-heated clusters to determine these unstable modes and the corresponding diffusive properties. The configurational entropy is measured for 2D and 3D clusters from structural rearrangements. The entropy shows a threshold behavior at a critical temperature for the 2D clusters, allowing us to estimate a configurational melting temperature. Further, the entropic disorder increases for larger clusters. Finally, the predicted relation between entropy and unstable modes has been confirmed from our experiments for 2D systems, whereas 3D systems do not show such a clear correlation.

  17. Electronic transport properties of Ir-decorated graphene.

    PubMed

    Wang, Yilin; Xiao, Shudong; Cai, Xinghan; Bao, Wenzhong; Reutt-Robey, Janice; Fuhrer, Michael S

    2015-10-28

    Graphene decorated with 5d transitional metal atoms is predicted to exhibit many intriguing properties; for example iridium adatoms are proposed to induce a substantial topological gap in graphene. We extensively investigated the conductivity of single-layer graphene decorated with iridium deposited in ultra-high vacuum at low temperature (7 K) as a function of Ir concentration, carrier density, temperature, and annealing conditions. Our results are consistent with the formation of Ir clusters of ~100 atoms at low temperature, with each cluster donating a single electronic charge to graphene. Annealing graphene increases the cluster size, reducing the doping and increasing the mobility. We do not observe any sign of an energy gap induced by spin-orbit coupling, possibly due to the clustering of Ir.

  18. Respiratory and calcium transport properties of spiny lobster hepatopancreas mitochondria.

    PubMed

    Tsokos, J; Kreisberg, R; Michaels, A; Komm, B; Linton, J

    1983-07-15

    Mitochondria were isolated from the hepatopancreas of the Florida spiny lobster Panulirus argus using a high osmolarity medium containing 600 mM mannitol, 83 mM sucrose, 5 mM 4-morpholinepropanesulfonic acid, pH 7.6, 0.5% bovine serum albumin (BSA), and 1 mM EDTA. O2 uptake and Ca2+ transport were measured by electrode methods in similar media (plus 4 mM KPi, 3.3 mM MgCl2, and 0.67 mg/ml BSA, with 80 mM KCl replacing a portion of the osmotic support). Substrate-supported respiration was observed to be coupled to phosphorylation of ADP or uptake of Ca2+ ions. State 3 rates (nanogram atoms O X minute-1 X milligram protein-1 +/- SEM (N)) were: 49.2 +/- 3.9 (19), succinate; 30.9 +/- 3.9 (6), DL-palmitoyl carnitine; 29.0 +/- 2.7(9), L-malate; 40.0 +/- 2.3(3), L-glutamate; 27.7 +/- 2.2(5), D-3-hydroxybutyrate; and 26.4 +/- 2.4 (18), L-proline +/- pyruvate. alpha-Glycerol phosphate was not oxidized. Ca2+ uptake driven by succinate oxidation proceeded with Ca:O ratios of 4.0 +/- 0.2 (SEM). Hepatopancreas mitochondria were not uncoupled by Ca2+ uptake in excess of 1100 ng atoms X mg protein-1. Ca2+ efflux could be induced by ruthenium red, indicating the presence of an active Ca2+ cycle. These mitochondria may provide a favorable model system in which to study regulation of the Ca2+ cycle. PMID:6870285

  19. 41 CFR 302-7.10 - Is property acquired en route eligible for transportation at Government expense?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 41 Public Contracts and Property Management 4 2011-07-01 2011-07-01 false Is property acquired en route eligible for transportation at Government expense? 302-7.10 Section 302-7.10 Public Contracts and... PROPERTY 7-TRANSPORTATION AND TEMPORARY STORAGE OF HOUSEHOLD GOODS AND PROFESSIONAL BOOKS, PAPERS,...

  20. Thermal transport in bismuth telluride quintuple layer: mode-resolved phonon properties and substrate effects

    PubMed Central

    Shao, Cheng; Bao, Hua

    2016-01-01

    The successful exfoliation of atomically-thin bismuth telluride (Bi2Te3) quintuple layer (QL) attracts tremendous research interest in this strongly anharmonic quasi-two-dimensional material. The thermal transport properties of this material are not well understood, especially the mode-wise properties and when it is coupled with a substrate. In this work, we have performed molecular dynamics simulations and normal mode analysis to study the mode-resolved thermal transport in freestanding and supported Bi2Te3 QL. The detailed mode-wise phonon properties are calculated and the accumulated thermal conductivities with respect to phonon mean free path (MFP) are constructed. It is shown that 60% of the thermal transport is contributed by phonons with MFP longer than 20 nm. Coupling with a-SiO2 substrate leads to about 60% reduction of thermal conductivity. Through varying the interfacial coupling strength and the atomic mass of substrate, we also find that phonon in Bi2Te3 QL is more strongly scattered by interfacial potential and its transport process is less affected by the dynamics of substrate. Our study provides an in-depth understanding of heat transport in Bi2Te3 QL and is helpful in further tailoring its thermal property through nanostructuring. PMID:27263656

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  2. Effects of partial hydrogenation on electronic transport properties in C60 molecular devices

    NASA Astrophysics Data System (ADS)

    Chen, L. N.; Cao, C.; Wu, X. Z.; Ma, S. S.; Huang, W. R.; Xu, H.

    2012-12-01

    By using nonequilibrium Green's functions in combination with the density-function theory, we investigate electronic transport properties of molecular devices with pristine and partial hydrogenation. The calculated results show that the electronic transport properties of molecular devices can be modulated by partial hydrogenation. Interestingly, our results exhibit negative differential resistance behavior in the case of the imbalance H-adsorption in C60 molecular devices under low bias. However, negative differential resistance behavior cannot be observed in the case of the balance H-adsorption. A mechanism is proposed for the hydrogenation and negative differential resistance behavior.

  3. Spintronic and transport properties of linear atomic strings of transition metals (Fe, Co, Ni)

    NASA Astrophysics Data System (ADS)

    Tyagi, Neha; Jaiswal, Neeraj K.; Srivastava, Pankaj

    2016-05-01

    In the present work, first-principles investigations have been performed to study the spintronic and transport properties of linear atomic strings of Fe, Co and Ni. The structural stabilities of the considered strings were compared on the basis of binding energies which revealed that all the strings are energetically feasible to be achieved. Further, all the considered strings are found to be ferromagnetic and the observed magnetic moment ranges from 1.38 to 1.71 μB. The observed transport properties and high spin polarization points towards their potential for nano interconnects and spintronic applications.

  4. Transport properties of coupled one-dimensional interacting electron systems with impurities

    NASA Astrophysics Data System (ADS)

    Kimura, Takashi; Kuroki, Kazuhiko; Aoki, Hideo

    1995-05-01

    We consider two one-dimensional interacting electron systems that are coupled via interchain tunneling to calculate transport properties in the presence of impurities or a single barrier by using the bosonization formalisms for the non-Luttinger-liquid phases on the phase diagram obtained by Fabrizio [Phys. Rev. B 48, 15 838 (1993)]. We find for the weak- and strong-interaction phases, where the superconducting correlation dominates in the ground state, that the interchain transfer enhances the conductivity and the Anderson localization is suppressed. This shows that multichain systems can have unique transport properties.

  5. Pore-scale heterogeneity, energy dissipation and the transport properties of rocks

    SciTech Connect

    Bernabe, Y.; Revil, A.

    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.

  6. Transport properties of armchair graphene nanoribbons under uniaxial strain: A first principles study

    NASA Astrophysics Data System (ADS)

    Van Nguyen, Chuong; Ilyasov, Victor V.; Van Hieu, Nguyen; Ngoc Hieu, Nguyen

    2016-07-01

    In this work, transport properties of armchair graphene nanoribbons (AGNRs) under uniaxial strain are considered using density functional theory. We found that carrier mobility of AGNRs depends strongly on uniaxial strain. The electron mobility of 5-AGNR is up to 38.5 ×104cm2 / V s at an elongation of 6%. However, the dependence of the effective mass of electrons and holes of AGNR on uniaxial strain can almost be described by the same function and their effective masses coincide at an elongation of 10%. The sensitivity to strain of the transport properties of AGNRs opens many ways for applications in nanoelectromechanical devices.

  7. 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.

  8. Calculated transport and magnetic properties of some perovskite metallic oxides AMO{sub 3}

    SciTech Connect

    Santi, G.; Jarlborg, T.

    1998-12-31

    The authors study some compounds of the perovskite (or pseudo-cubic perovskite) series AMO{sub 3}, where M is a transition metal and A is Ca, Sr, or Nd, by LSDA self-consistent electronic structure calculations with the LMTO method. Transport and magnetic properties, as well as Fermi surfaces are calculated. These materials exhibit sharp density of states features in the vicinity of the Fermi level that strongly affect their transport and magnetic properties and make them very sensitive to structural deformation and stoichiometry. Calculated total energies are very close for anti-ferromagnetic and ferromagnetic solutions. This explains qualitatively the magnetoresistive anomalies shown by this family of compounds.

  9. Impact of point defects on the electronic and transport properties of silicene nanoribbons

    NASA Astrophysics Data System (ADS)

    Iordanidou, K.; Houssa, M.; van den Broek, B.; Pourtois, G.; Afanas'ev, V. V.; Stesmans, A.

    2016-01-01

    We study the impact of various point defects on the structural, electronic and ballistic transport properties of armchair silicene nanoribbons, using the density functional theory and the non equilibrium Green’s function method. The effect of a Stone-Wales defect, an interior/edge vacancy and an edge dangling bond is examined. Our results show that structural imperfections can alter the electronic structure (energy band structure and density of states) of the nanoribbons and can either increase or decrease the ballistic current. The dependence of the transport properties on the position of the defects (sublattice A or B) and on their distance from the contact is also investigated.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Vercauteren, Sven

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

  12. Magneto-optical transport properties of monolayer WSe2

    NASA Astrophysics Data System (ADS)

    Tahir, M.; Vasilopoulos, P.

    2016-07-01

    The recent experimental realization of a high quality WSe2 leads to the possibility of magneto-optical measurements and the manipulation of the spin and valley degrees of freedom. We study the influence of the very strong spin-orbit coupling and of the anisotropic lifting of the valley pseudospin degeneracy on its magnetotransport properties. The energy spectrum of WSe2 is derived and discussed in the presence of a perpendicular magnetic field B . Correspondingly we evaluate the magneto-optical Hall conductivity and the optical longitudinal conductivity as functions of the frequency, magnetic field, and Fermi energy. They are strongly influenced by the field B and the strong spin splitting. The former exhibits valley polarization and the latter beatings of oscillations. The magneto-optical responses can be tuned in two different regimes: the microwave-to-terahertz regime and the visible-frequency one. The absorption peaks involving the n =0 LL appear in between these two regimes and show a magnetic control of the spin and valley splittings. We also evaluate the power absorption spectrum.

  13. Modifying zirconia solid electrolyte surface property to enhance oxide transport

    SciTech Connect

    Liaw, B.Y.; Song, S.Y.

    1996-12-31

    Bismuth-strontium-calcium-copper oxide (Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}, BSCCO) is known for its high T{sub c} superconducting behavior and mixed conducting property. The applicability of similar high T{sub c} cuprates for intermediate-temperature solid oxide fuel cell (SOFC) application has been studied recently. We investigated the electrochemical behavior of several Ag{vert_bar}BSCCO{vert_bar}10 mol% yttria-stabilized zirconia (YSZ){vert_bar}Ag and Ag{vert_bar}YSZ{vert_bar}Ag cells using complex impedance spectroscopy. A highly uniform and porous microstructure was observed at the interface of the YSZ and BSCCO. The ionic conductivity determined from the Nyquest plots in the temperature range of 200-700{degrees}C agrees with the values reported in the literature. The specific resistance of the BSCCO{vert_bar}YSZ interface was also determined to be lower than those of the conventional manganite electrode, suggesting that BSCCO seems attractive for cathode applications in SOFC.

  14. Oligomers Modulate Interfibril Branching and Mass Transport Properties of Collagen Matrices

    PubMed Central

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

    2013-01-01

    Mass transport within collagen-based matrices is critical to tissue development, repair, and pathogenesis as well as the design of next generation tissue engineering strategies. This work shows how collagen precursors, specified by intermolecular cross-link composition, provide independent control of collagen matrix mechanical and transport properties. Collagen matrices were prepared from tissue-extracted monomers or oligomers. Viscoelastic behavior was measured in oscillatory shear and unconfined compression. Matrix permeability and diffusivity were measured using gravity-driven permeametry and integrated optical imaging, respectively. Both collagen types showed an increase in stiffness and permeability hindrance with increasing collagen concentration (fibril density); however, different physical property-concentration relationships were noted. Diffusivity wasn’t affected by concentration for either collagen type over the range tested. In general, oligomer matrices exhibited a substantial increase in stiffness and only a modest decrease in transport properties when compared to monomer matrices prepared at the same concentration. The observed differences in viscoelastic and transport properties were largely attributed to increased levels of interfibril branching within oligomer matrices. The ability to relate physical properties to relevant microstructure parameters, including fibril density and interfibril branching, is expected to advance the understanding of cell-matrix signaling as well as facilitate model-based prediction and design of matrix-based therapeutic strategies. PMID:23842082

  15. Scalp reconstruction by microvascular free tissue transfer

    SciTech Connect

    Furnas, H.; Lineaweaver, W.C.; Alpert, B.S. )

    1990-05-01

    We report on a series of patients with scalp defects who have been treated with a variety of free flaps, spanning the era of microvascular free tissue transfer from its incipient stages to the present. Between 1971 and 1987, 18 patients underwent scalp reconstruction with 21 free flaps: 11 latissimus dorsi, 3 scalp transfers between identical twins, 3 groin, one combined latissimus dorsi and serratus anterior, two serratus anterior, and one omentum. These flaps were used to cover scalp defects resulting from burns, trauma, radiation, and tumors in patients ranging from 7 to 79 years of age. Follow-up has ranged from 3 weeks to 7 years. All of our flaps survived and covered complex defects, many of which had failed more conservative attempts at cover. One patient received radiation therapy to his flap without unfavorable sequelae. This experience began with a pioneering omental flap and includes cutaneous and muscle flaps. The latissimus dorsi is our first choice for free flap reconstruction of extensive, complicated scalp wounds because of its large size, predictable blood supply, ease of harvesting, and provision of excellent vascularity to compromised beds.

  16. Influence of silicone sheets on microvascular anastomosis.

    PubMed

    Hoang Nguyen, The; Kloeppel, Marcus; Hoehnke, Christoph; Staudenmaier, Rainer

    2008-12-01

    The use of silicone products combined with free flap transfer is well established in reconstructive surgery. We determined the risk of thrombosis as a result of direct contact between the silicone sheet and the point of microanastomosis. We performed microvascular surgery in 24 female Chinchilla Bastard rabbits weighing 3500 to 4000 g using two groups: Group 1 (n = 12), microanastomosis directly in contact with silicone sheets; and Group 2 (n = 12), microanastomosis protected by a 2 x 3 x 1-cm muscle cuff before being placed in contact with the silicone. We assessed flow-through of the microanastomosis by selective microangiography and histology at 1 and 3 weeks. All microanastomoses in Group 1 were occluded by postoperative thromboses, whereas all microanastomoses in Group 2 had adequate flow-through. Histologic analysis revealed thromboses in Group 1 formed from collagenous bundles of fiber securely attached to the intraluminal wall of the vessel. Three weeks after the procedure, these thromboses were canalized by varying small vessels. In Group 2, a slight luminal stenosis with evidence of infiltration of inflammatory cells at the microanastomosis line was observed histologically in all cases. Prefabricated flaps using silicone sheets and muscular cuffs placed around the anastomoses appear to reduce the risk of thrombosis and enhance neovascularization. PMID:18636304

  17. Investigations of electrical transport properties of individual carbon nanotubes with nanoprober

    NASA Astrophysics Data System (ADS)

    Feng, Wei; Hayama, Kazumi; Akinaga, Hiroyuki

    2016-06-01

    We investigated and discussed quantitatively the transport properties of individual multiwalled (MW) carbon nanotubes (CNTs) by four-terminal measurement using a nanoprobing system. The homogeneity of the CNT was visibly examined using the electron beam absorbed current function of the nanoprober. The observed ohmic properties of the current-voltage characteristics and metallic transport properties of the CNTs proved that reliable contact of four probes was achieved on the outermost shell of MWCNTs. The experimental methodology was validated for the intrinsic properties of individual CNTs. Lower resistance per unit length was evaluated for thicker CNT. The measured resistance per unit length was lower than those reported by other researchers, but higher than ideally expected.

  18. 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.

  19. Coupled light transport-heat diffusion model for laser dosimetry with dynamic optical properties

    SciTech Connect

    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.

  20. Investigations of electrical transport properties of individual carbon nanotubes with nanoprober

    NASA Astrophysics Data System (ADS)

    Feng, Wei; Hayama, Kazumi; Akinaga, Hiroyuki

    2016-06-01

    We investigated and discussed quantitatively the transport properties of individual multiwalled (MW) carbon nanotubes (CNTs) by four-terminal measurement using a nanoprobing system. The homogeneity of the CNT was visibly examined using the electron beam absorbed current function of the nanoprober. The observed ohmic properties of the current–voltage characteristics and metallic transport properties of the CNTs proved that reliable contact of four probes was achieved on the outermost shell of MWCNTs. The experimental methodology was validated for the intrinsic properties of individual CNTs. Lower resistance per unit length was evaluated for thicker CNT. The measured resistance per unit length was lower than those reported by other researchers, but higher than ideally expected.

  1. Computer codes for the evaluation of thermodynamic properties, transport properties, and equilibrium constants of an 11-species air model

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    The computer codes developed provide data to 30000 K for the thermodynamic and transport properties of individual species and reaction rates for the prominent reactions occurring in an 11-species nonequilibrium air model. These properties and the reaction-rate data are computed through the use of curve-fit relations which are functions of temperature (and number density for the equilibrium constant). The curve fits were made using the most accurate data believed available. A detailed review and discussion of the sources and accuracy of the curve-fitted data used herein are given in NASA RP 1232.

  2. Structure and transport properties of ethylcellulose membranes with different types and granulation of magnetic powder

    NASA Astrophysics Data System (ADS)

    Krasowska, Monika; Strzelewicz, Anna; Rybak, Aleksandra; Dudek, Gabriela; Cieśla, Michał

    2016-06-01

    Structure and transport properties of ethylcellulose membranes with dispersed magnetic powder were investigated. The study mainly focused on diffusion, which is one of the transport mechanisms. The transport properties depend on many parameters like: polymeric matrix used, type of powder, its amount and granulation. The structure of the pattern formed by magnetic particles in the membrane matrix was studied. Description of the system was based on the phenomenological and molecular (random walk on a fractal lattice) approaches. Two parameters were calculated: the fractal dimension of random walk dw, and the fractal dimension of membrane structure df. The knowledge of both parameters made it possible to use the generalized equation of diffusion on the fractal structure obtained by Metzler et al. The research was carried out to determine the influence of magnetic powder granulation on the transport properties. The results showed that the random walk within the membranes of the smallest magnetic powder granulation was of the most subdiffusive character. Detailed investigation and quantitative description of gas transport through the membranes enables designing the membranes to be used in air oxygen enrichment.

  3. Electrical and thermal transport property studies of high-temperature thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Bates, J. L.; Garnier, J. E.; Olsen, L. C.; Griffin, C. W.

    1984-07-01

    The first year of this research emphasized the study of electronically conducting oxides with varied transport characteristics, an evaluation of theoretical models, and the determination of a high-temperature transport property data base. Oxide systems based on SnO2-In2O3, (La, Y) (Mg,Ca,Sr) CrO3, HfO2-RxOy-In3O3 and La(Sr)MnO3 were selected for initial studies and represent different crystallographic/defect structures and transport characteristics. The electrical conductivity, Seeback coefficient and thermal conductivity for these oxides are being measured and have provided a preliminary data base for evaluating transport properties and the figure of merit. The purpose of this report is to describe the technical results obtained during the first year's study of high-temperature thermoelectric materials. The scope of the research is (1) to develop theoretical models for electrical, thermal, and thermoelectric behavior of refractory oxide materials, (2) to determine electrical transport properties necessary to develop and test these models, (3) to determine methods for increasing the figure of merit in refractory oxide systems by varying composition, defect structure. microstructure, etc., and (4) to use these models to establish theoretical and empirical limits of the figure of merit for these oxides and other refractory materials.

  4. 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.

  5. 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 α-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 α-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 τ/τ⩾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 α-helical protein molecules.

  6. High pressure apparatus for transport properties study in high magnetic field

    SciTech Connect

    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.

  7. Transport and Phase Equilibria Properties for Steam Flooding of Heavy Oils

    SciTech Connect

    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.

  8. Transport and Phase Equilibria Properties for Steam Flooding of Heavy Oils

    SciTech Connect

    Gabitto, Jorge; Barrufet, Maria

    2001-12-18

    The objectives of this research included experimental determination and rigorous modeling and computation of phase equilibria, volumetric, and transport properties of hydrocarbon/CO2/water mixtures at pressures and temperatures typical of steam injection processes for thermal recovery of heavy oils.

  9. Interplay between the magnetic and magneto-transport properties of 3D interconnected nanowire networks

    NASA Astrophysics Data System (ADS)

    da Câmara Santa Clara Gomes, Tristan; De La Torre Medina, Joaquín; Velázquez-Galván, Yenni G.; Martínez-Huerta, Juan Manuel; Encinas, Armando; Piraux, Luc

    2016-07-01

    We have explored the interplay between the magnetic and magneto-transport properties of 3D interconnected nanowire networks made of various magnetic metals by electrodeposition into nanoporous membranes with crossed channels and controlled topology. The close relationship between their magnetic and structural properties has a direct impact on their magneto-transport behavior. In order to accurately and reliably describe the effective magnetic anisotropy and anisotropic magnetoresistance, an analytical model inherent to the topology of 3D nanowire networks is proposed and validated. The feasibility to obtain magneto-transport responses in nanowire network films based on interconnected nanowires makes them very attractive for the development of mechanically stable superstructures that are suitable for potential technological applications.

  10. Transport properties of an asymmetric mixture in the dense plasma regime.

    PubMed

    Ticknor, Christopher; Kress, Joel D; Collins, Lee A; Clérouin, Jean; Arnault, Philippe; Decoster, Alain

    2016-06-01

    We study how concentration changes ionic transport properties along isobars-isotherms for a mixture of hydrogen and silver, representative of turbulent layers relevant to inertial confinement fusion and astrophysics. Hydrogen will typically be fully ionized while silver will be only partially ionized but can have a large effective charge. This will lead to very different physical conditions for the H and Ag. Large first principles orbital free molecular dynamics simulations are performed and the resulting transport properties are analyzed. Comparisons are made with transport theory in the kinetic regime and in the coupled regime. The addition of a small amount of heavy element in a light material has a dramatic effect on viscosity and diffusion of the mixture. This effect is explained through kinetic theory as a manifestation of a crossover between classical diffusion and Lorentz diffusion. PMID:27415378

  11. Surface transport properties of reticulopodia: do intracellular and extracellular motility share a common mechanism?

    PubMed

    Bowser, S S; Israel, H A; McGee-Russell, S M; Rieder, C L

    1984-12-01

    The reticulopodial networks of the foraminiferan protozoans Allogromia sp., strain NF, and A. laticollaris display rapid (up to 11 microns/second) and bidirectional saltatory transport of membrane surface markers (polystyrene microspheres). Electron microscopy shows that microspheres adhere directly to the reticulopodial surface glycocalyx. A videomicroscopic analysis of this phenomenon reveals that microsphere movement is typically independent of pseudopod extension/withdrawal and that particles of different sizes and surface properties display similar motile characteristics. The motile properties of surface-associated microspheres appear identical to those of saltating intracellular organelles. Indeed, in some instances the surface-attached microspheres appear transiently linked in motion to these underlying organelles. Our observations suggest that, in reticulopodia, surface transport of microspheres and intracellular transport of organelles are driven by a common mechanism.

  12. The transport properties of the molecular-scale B2C and BC3 electronic devices

    NASA Astrophysics Data System (ADS)

    Li, Guiqin; Li, Runqin

    2012-09-01

    The transport properties of the molecular-scale B2C and BC3 electronic devices are investigated with an ab initio method combined with a nonequilibrium Green function technique. The effects of different BC graphenes and ribbon lengths on the transport properties of the devices are significant. The results show that the devices with different BC graphenes and sizes have unusual transmission coefficients, which leads to special current transport mechanisms for the devices. Notably, the current strength of the device with the shortest ribbon length is the largest in three B2C devices, but the current strength of the device with the shortest ribbon length is the smallest for BC3 device.

  13. Systemic Microvascular Dysfunction and Inflammation after Pulmonary Particulate Matter Exposure

    PubMed Central

    Nurkiewicz, Timothy R.; Porter, Dale W.; Barger, Mark; Millecchia, Lyndell; Rao, K. Murali K.; Marvar, Paul J.; Hubbs, Ann F.; Castranova, Vincent; Boegehold, Matthew A.

    2006-01-01

    The epidemiologic association between pulmonary exposure to ambient particulate matter (PM) and cardiovascular dysfunction is well known, but the systemic mechanisms that drive this effect remain unclear. We have previously shown that acute pulmonary exposure to PM impairs or abolishes endothelium-dependent arteriolar dilation in the rat spinotrapezius muscle. The purpose of this study was to further characterize the effect of pulmonary PM exposure on systemic microvascular function and to identify local inflammatory events that may contribute to these effects. Rats were intratracheally instilled with residual oil fly ash (ROFA) or titanium dioxide at 0.1 or 0.25 mg/rat 24 hr before measurement of pulmonary and systemic microvascular responses. In vivo microscopy of the spinotrapezius muscle was used to study systemic arteriolar responses to intraluminal infusion of the Ca2+ ionophore A23187 or iontophoretic abluminal application of the adrenergic agonist phenylephrine (PHE). Leukocyte rolling and adhesion were quantified in venules paired with the studied arterioles. Histologic techniques were used to assess pulmonary inflammation, characterize the adherence of leukocytes to systemic venules, verify the presence of myeloperoxidase (MPO) in the systemic microvascular wall, and quantify systemic microvascular oxidative stress. In the lungs of rats exposed to ROFA or TiO2, changes in some bronchoalveolar lavage markers of inflammation were noted, but an indication of cellular damage was not found. In rats exposed to 0.1 mg ROFA, focal alveolitis was evident, particularly at sites of particle deposition. Exposure to either ROFA or TiO2 caused a dose-dependent impairment of endothelium-dependent arteriolar dilation. However, exposure to these particles did not affect microvascular constriction in response to PHE. ROFA and TiO2 exposure significantly increased leukocyte rolling and adhesion in paired venules, and these cells were positively identified as

  14. Systemic microvascular dysfunction and inflammation after pulmonary particulate matter exposure.

    PubMed

    Nurkiewicz, Timothy R; Porter, Dale W; Barger, Mark; Millecchia, Lyndell; Rao, K Murali K; Marvar, Paul J; Hubbs, Ann F; Castranova, Vincent; Boegehold, Matthew A

    2006-03-01

    The epidemiologic association between pulmonary exposure to ambient particulate matter (PM) and cardiovascular dysfunction is well known, but the systemic mechanisms that drive this effect remain unclear. We have previously shown that acute pulmonary exposure to PM impairs or abolishes endothelium-dependent arteriolar dilation in the rat spinotrapezius muscle. The purpose of this study was to further characterize the effect of pulmonary PM exposure on systemic microvascular function and to identify local inflammatory events that may contribute to these effects. Rats were intratracheally instilled with residual oil fly ash (ROFA) or titanium dioxide at 0.1 or 0.25 mg/rat 24 hr before measurement of pulmonary and systemic microvascular responses. In vivo microscopy of the spinotrapezius muscle was used to study systemic arteriolar responses to intraluminal infusion of the Ca2+ ionophore A23187 or iontophoretic abluminal application of the adrenergic agonist phenylephrine (PHE). Leukocyte rolling and adhesion were quantified in venules paired with the studied arterioles. Histologic techniques were used to assess pulmonary inflammation, characterize the adherence of leukocytes to systemic venules, verify the presence of myeloperoxidase (MPO) in the systemic microvascular wall, and quantify systemic microvascular oxidative stress. In the lungs of rats exposed to ROFA or TiO2, changes in some bronchoalveolar lavage markers of inflammation were noted, but an indication of cellular damage was not found. In rats exposed to 0.1 mg ROFA, focal alveolitis was evident, particularly at sites of particle deposition. Exposure to either ROFA or TiO2 caused a dose-dependent impairment of endothelium-dependent arteriolar dilation. However, exposure to these particles did not affect microvascular constriction in response to PHE. ROFA and TiO2 exposure significantly increased leukocyte rolling and adhesion in paired venules, and these cells were positively identified as

  15. Electronic structure and transport properties of CrAs/GaAs/CrAs trilayersfrom first principles theory

    NASA Astrophysics Data System (ADS)

    Bengone, O.; Eriksson, O.; Fransson, J.; Turek, I.; Kudrnovský, J.; Drchal, V.

    2004-07-01

    We present a theoretical study of the transport properties of a CrAs/GaAs/CrAs trilayer. The theory was based on a first principles method for calculating the electronic structure, in combination with a Kubo-Landauer approach for calculating the transport properties in a current perpendicular to the plane geometry. We have also investigated the electronic structure and the magnetic properties of this trilayer, with special focus on electronic and magnetic properties at the CrAs/GaAs interface. Finally, we have studied the effects of chemical disorder on the transport properties, in particular the influence of As antisites at both the Cr and Ga sites.

  16. Computational design of microvascular biomimetic materials

    NASA Astrophysics Data System (ADS)

    Aragon, Alejandro Marcos

    Biomimetic microvascular materials are increasingly considered for a variety of autonomic healing, cooling and sensing applications. The microvascular material of interest in this work consists of a network of hollow microchannels, with diameters as small as 10 mum, embedded in a polymeric matrix. Recent advances in the manufacturing of this new class of materials have allowed for the creation of very complex 2D and 3D structures. The computational design of such network structures, which is the focus of this work, involves a set of particular challenges, including a large number of design variables (e.g., topology of the network, number of diameters to consider and their sizes) that define the network, and a large number of multidisciplinary objective functions and constraints that drive the optimization process. The computational design tool to be developed must be capable of capturing the trade-off between the different objective and constraint functions, as, for example, networks designed for flow efficiency are likely to have a topology that is very different from those designed for structural integrity or thermal control. In this work, we propose to design these materials using Genetic Algorithms (GAs), the most common methodology within a broader category of Evolutionary Algorithms (EAs). GAs can be combined with a Pareto-selection mechanism to create Multi-Objective Genetic Algorithms (MOGAs), which enable the optimization of an arbitrary number of objective functions. As a result, a Pareto-optimal front is obtained, where all candidates are optimal solutions to the optimization problem. Adding a procedure to deal with constraints results in a powerful tool for multi-objective constrained optimization. The method allows the use of discrete variable problems and it does not require any a priori knowledge of the optimal solution. Furthermore, GAs search the entire decision space so the optimal solutions found are likely to be global. The

  17. Bariatric surgery and microvascular complications of type 2 diabetes mellitus.

    PubMed

    Jackson, Sabrina; le Roux, Carel W; Docherty, Neil G

    2014-11-01

    Metabolic dysregulation is the defining characteristic of type 2 diabetes mellitus (T2DM) and can give rise to microvascular complications, specifically retinopathy, nephropathy and neuropathy. Pharmacological targeting of risk factors for microvascular complications can yield therapeutic gains, particularly in relation to retinopathy and nephropathy. Bariatric surgery is superior to intensified pharmacotherapy in relation to glycaemic control and can remediate dyslipidaemia and hypertension. Consequently, evidence of the effect of bariatric surgery on microvascular complications is now emerging in the literature. Examination of the recent published evidence base (covering the period 2011-2014) on the effects of bariatric surgery on microvascular complications reveals further evidence supportive of the efficacy of bariatric surgery in preventing the incidence and progression of albuminuria and arresting renal functional decline. Data on retinopathy are more ambivalent potentially representing the potential in some cases for a degree of surgery associated reactive hypoglycaemia to detract from the benefits of amelioration of hyperglycaemia. A significant gap in the literature remains in relation to the effects of surgery on diabetic neuropathy. Overall, there is a pressing need for prospective randomised controlled trials examining long-term microvascular outcomes following bariatric surgery in patients with T2DM.

  18. Brain microvascular function during cardiopulmonary bypass

    SciTech Connect

    Sorensen, H.R.; Husum, B.; Waaben, J.; Andersen, K.; Andersen, L.I.; Gefke, K.; Kaarsen, A.L.; Gjedde, A.

    1987-11-01

    Emboli in the brain microvasculature may inhibit brain activity during cardiopulmonary bypass. Such hypothetical blockade, if confirmed, may be responsible for the reduction of cerebral metabolic rate for glucose observed in animals subjected to cardiopulmonary bypass. In previous studies of cerebral blood flow during bypass, brain microcirculation was not evaluated. In the present study in animals (pigs), reduction of the number of perfused capillaries was estimated by measurements of the capillary diffusion capacity for hydrophilic tracers of low permeability. Capillary diffusion capacity, cerebral blood flow, and cerebral metabolic rate for glucose were measured simultaneously by the integral method, different tracers being used with different circulation times. In eight animals subjected to normothermic cardiopulmonary bypass, and seven subjected to hypothermic bypass, cerebral blood flow, cerebral metabolic rate for glucose, and capillary diffusion capacity decreased significantly: cerebral blood flow from 63 to 43 ml/100 gm/min in normothermia and to 34 ml/100 gm/min in hypothermia and cerebral metabolic rate for glucose from 43.0 to 23.0 mumol/100 gm/min in normothermia and to 14.1 mumol/100 gm/min in hypothermia. The capillary diffusion capacity declined markedly from 0.15 to 0.03 ml/100 gm/min in normothermia but only to 0.08 ml/100 gm/min in hypothermia. We conclude that the decrease of cerebral metabolic rate for glucose during normothermic cardiopulmonary bypass is caused by interruption of blood flow through a part of the capillary bed, possibly by microemboli, and that cerebral blood flow is an inadequate indicator of capillary blood flow. Further studies must clarify why normal microvascular function appears to be preserved during hypothermic cardiopulmonary bypass.

  19. Hypercholesterolemia and microvascular dysfunction: interventional strategies.

    PubMed

    Stapleton, Phoebe A; Goodwill, Adam G; James, Milinda E; Brock, Robert W; Frisbee, Jefferson C

    2010-01-01

    Hypercholesterolemia is defined as excessively high plasma cholesterol levels, and is a strong risk factor for many negative cardiovascular events. Total cholesterol levels above 200 mg/dl have repeatedly been correlated as an independent risk factor for development of peripheral vascular (PVD) and coronary artery disease (CAD), and considerable attention has been directed toward evaluating mechanisms by which hypercholesterolemia may impact vascular outcomes; these include both results of direct cholesterol lowering therapies and alternative interventions for improving vascular function. With specific relevance to the microcirculation, it has been clearly demonstrated that evolution of hypercholesterolemia is associated with endothelial cell dysfunction, a near-complete abrogation in vascular nitric oxide bioavailability, elevated oxidant stress, and the creation of a strongly pro-inflammatory condition; symptoms which can culminate in profound impairments/alterations to vascular reactivity. Effective interventional treatments can be challenging as certain genetic risk factors simply cannot be ignored. However, some hypercholesterolemia treatment options that have become widely used, including pharmaceutical therapies which can decrease circulating cholesterol by preventing either its formation in the liver or its absorption in the intestine, also have pleiotropic effects with can directly improve peripheral vascular outcomes. While physical activity is known to decrease PVD/CAD risk factors, including obesity, psychological stress, impaired glycemic control, and hypertension, this will also increase circulating levels of high density lipoprotein and improving both cardiac and vascular function. This review will provide an overview of the mechanistic consequences of the predominant pharmaceutical interventions and chronic exercise to treat hypercholesterolemia through their impacts on chronic sub-acute inflammation, oxidative stress, and microvascular structure

  20. 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

  1. On statistical properties of transport barriers in magnetospheric and laboratory boundary layers

    NASA Astrophysics Data System (ADS)

    Savin, Sergey; Budaev, Viacheslav; Zeleniy, Lev; Amata, Ermanno; Kozak, Lyudmila; Buechner, Joerg; Romanov, Stanislav; Blecki, Jan; Balikhin, Michael A.; Lezhen, Liudmila

    Transport barriers at outer magnetospheric boundaries have a dualistic feature: being effec-tive in limitation of the momentum transfer and serving as an effective obstacle, they display the super-diffusive statistical properties and provide partial exchange of plasmas. In tokamaks namely the statistical properties of transport barriers look to control the high and low heating modes, while small size of the barriers prevents their detailed studies. We tend to use magne-tospheric multi-spacecraft data to improve understanding of common physics in the transport barriers. We show examples from Interball-1 and Cluster with quiet solar wind. The inherently turbulent crossings in this equilibrium cases demonstrate ion heating namely in the transport barrier. It agrees with the kinetic energy transformation into the thermal one inside the barrier -the turbulent dissipation of the magnetosheath kinetic energy -as simultaneously with the ion temperature rise, the general velocity component drops from its model prediction. In sense of the momentum transfer the transport turbulent barriers effectively isolate the high-alti-tude cusp from fast-flowing magnetosheath. Contrary to that, several examples from different missions and different plasma parameters demonstrate the super-diffusive transport character. The individual coherent structures inside the barriers, which we call Alfvenic 'collapsons', have similar scale chains to that of high kinetic plasma pressure jets, showing mutual interaction features. We think that the interacting jets and barriers, accompanying by classic and/ or micro-reconnection, have rather general importance for the plasma physics, and for understanding of turbulence and mechanisms of magnetic field generation. These coherent, nonlinear interacting structures, most probably, provide intermittency a long-range correlations inside the transport barriers (c.f. blobs and flow spikes in fusion devices). We recall that very high-amplitude turbulence in

  2. Glucose transport and microvillus membrane physical properties along the crypt-villus axis of the rabbit.

    PubMed Central

    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

  3. Electronic transport and mechanical properties of phosphorus and phosphorus-nitrogen doped carbon nanotubes

    SciTech Connect

    Sumpter, Bobby G; Charlier, Jean Christophe; Terrones Maldonado, Mauricio; Meunier, Vincent; Terrones Maldonado, Humberto; Cruz Silva, Eduardo; Lopez, Florentino; Munoz-Sandoval, Emilio

    2009-01-01

    We present a density functional theory study of the electronic structure, quantum transport and mechanical properties of recently synthesized phosphorus (P) and phosphorus-nitrogen (PN) doped single-walled carbon nanotubes. The results demonstrate that substitutional P and PN doping creates localized electronic states that modify the electron transport properties by acting as scattering centers. For low doping concentrations (1 doping site per ~200 atoms), the quantum conductance for metallic nanotubes is found to be only slightly reduced. The substitutional doping also alters the mechanical strength, leading to a 50% reduction in the elongation upon fracture, while Young s modulus remains approximately unchanged. Overall, the PN- and P-doped nanotubes display promising properties for components in composite materials and, in particular, for fast response and ultra sensitive sensors operating at the molecular level.

  4. Quantifying the transport properties of lipid mesophases by theoretical modelling of diffusion experiments

    NASA Astrophysics Data System (ADS)

    Antognini, Luca M.; Assenza, Salvatore; Speziale, Chiara; Mezzenga, Raffaele

    2016-08-01

    Lyotropic Liquid Crystals (LLCs) are a class of lipid-based membranes with a strong potential for drug-delivery employment. The characterization and control of their transport properties is a central issue in this regard, and has recently prompted a notable volume of research on the topic. A promising experimental approach is provided by the so-called diffusion setup, where the drug molecules diffuse from a feeding chamber filled with water to a receiving one passing through a LLC. In the present work we provide a theoretical framework for the proper description of this setup, and validate it by means of targeted experiments. Due to the inhomogeneity of the system, a rich palette of different diffusion dynamics emerges from the interplay of the different time- and lengthscales thereby present. Our work paves the way to the employment of diffusion experiments to quantitatively characterize the transport properties of LLCs, and provides the basic tools for device diffusion setups with controlled kinetic properties.

  5. Correlation of buffer strain relaxation modes with transport properties of two-dimensional electron gases

    SciTech Connect

    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.}

  6. Optical, physical and chemical properties of transported African mineral dust aerosols in the Mediterranean region

    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

  7. Effects of Ordered Stacking Faults on Electrical Transport Properties in Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Collette, Marc; Moutanabbir, Oussama; Champagne, Alexandre

    Lattice defects in silicon nanowires (SiNWs) allow the exploration of the fundamental physics governing transport mechanisms. We study charge transport in SiNW transistors with stacking faults in the 3C sequence, producing local hexagonal ordering. This structure leads to polytype SiNWs with distinct properties for novel applications in thermoelectronics. Since charge carrier and phonon behavior depend on crystal structure, these planar defects affect the transport properties of the nanowire. We grow our SiNWs using a VLS method, with stacking faults induced during growth. Structural characterization of each SiNW is done with Raman spectroscopy to quantify hexagonality. Individual nanowires are located and contacted using different metals to understand the Schottky barrier of the contacts at the SiNWs. We suspend 2 μm-long SiNW devices using a wet oxide etch to uncouple the SiNW from the substrate. We study the electrical properties by I-V measurements across the FET device while modulating the applied back gate voltage. Our initial data show that the presence of stacking faults causes an increase in resistivity by two orders of magnitude, thus greatly hindering charge transport through the SiNW.

  8. Influence of the dynamic ergodic divertor on transport properties in TEXTOR

    NASA Astrophysics Data System (ADS)

    Finken, K. H.; Unterberg, B.; Xu, Y.; Abdullaev, S. S.; Jakubowski, M.; Lehnen, M.; de Bock, M. F. M.; Bozhenkov, S.; Brezinsek, S.; Busch, C.; Classen, I. G. J.; Coenen, J. W.; Harting, D.; von Hellermann, M.; Jachmich, S.; Jaspers, R. J. E.; Kikuchi, Y.; Krämer-Flecken, A.; Liang, Y.; Mitri, M.; Peleman, P.; Pospieszczyk, A.; Reiser, D.; Reiter, D.; Samm, U.; Schega, D.; Schmitz, O.; Soldatov, S.; Van Schoor, M.; Vergote, M.; Weynants, R. R.; Wolf, R.; Zimmermann, O.; TEXTOR Team

    2007-07-01

    Experiments to investigate transport properties under the influence of the dynamic ergodic divertor (DED) on TEXTOR are discussed. Relativistic runaway electrons are applied for studying transport properties of ergodization such as enhanced runaway loss. The ergodization causes an enhanced loss rate; this loss is higher for low relativistic electrons than for highly relativistic ones, in good agreement with particle orbit mapping. Edge transport can be controlled by the DED perturbation: in limiter H-mode plasmas ELM-like particle and heat bursts associated with the formation of enhanced edge pressure gradients are mitigated in the 6/2 configuration on the expense of a reduced pedestal height. Finally, the plasma is driven back to L-mode under the influence of the magnetic perturbation. In the 3/1 configuration the onset of tearing modes limits the possibility to affect edge transport. A mode of spontaneous density built-up has been found for the TEXTOR-DED as well. This mode is in particular strong for an inward shifted plasma; the built-up has a resonant character with respect to q(a). Langmuir probe measurements with two probe arrays show a strong influence of the magnetic ergodization on both the edge plasma equilibrium and fluctuation parameters. In particular, in the ergodic zone the turbulence properties and turbulence-driven flux are profoundly modified.

  9. Free and microvascular bone grafting in the irradiated dog mandible

    SciTech Connect

    Altobelli, D.E.; Lorente, C.A.; Handren, J.H. Jr.; Young, J.; Donoff, R.B.; May, J.W. Jr.

    1987-01-01

    Microvascular and free rib grafts were placed in 4.5 cm defects in an edentate mandibular body defect 18 to 28 days after completion of 50 Gy of irradiation from a /sup 60/Co source. The animals were sacrificed from two to forty weeks postoperatively and evaluated clinically, radiographically, and histologically. There was a marked difference in the alveolar mucosal viability with the two grafts. Mucosal dehiscence was not observed over any of the microvascular grafts, but was present in seven-eighths of the free grafts. Union of the microvascular bone graft to the host bone occurred within six weeks. In contrast, after six weeks the free graft was sequestered in all the animals. An unexpected finding with both types of graft was the marked subperiosteal bone formation. This bone appeared to be derived from the host bed, stabilizing and bridging the defects bilaterally. The results suggest that radiated periosteum may play an important role in osteogenesis.

  10. Regional cutaneous microvascular flow responses during gravitational and LBNP stresses

    NASA Technical Reports Server (NTRS)

    Breit, Gregory A.; Watenpaugh, Donald E.; Ballard, Richard E.; Murthy, Gita; Hargens, Alan R.

    1993-01-01

    Due to the regional variability of local hydrostatic pressures, microvascular flow responses to gravitational stress probably vary along the length of the body. Although these differences in local autoregulation have been observed previously during whole-body tilting, they have not been investigated during application of artificial gravitational stresses, such as lower body negative pressure or high gravity centrifugation. Although these stresses can create equivalent G-levels at the feet, they result in distinct distributions of vascular transmural pressure along the length of the body, and should consequently elicit different magnitudes and distributions of microvascular response. In the present study, the effects of whole-body tilting and lower body negative pressure on the level and distribution of microvascular flows within skin along the length of the body were compared.

  11. Vascular grafts in microvascular surgery. An experimental study

    SciTech Connect

    Marrangoni, A.G.; Marcelli, G.; Culig, M.; Simone, S.T.

    1988-02-01

    The patency of microvascular grafts depends on the luminal diameter, which is determined by the amount of fibrin and platelets deposited on the intraluminal surface and the anastomotic site, and the extent of pseudointimal formation. An experimental microvascular model in rats has been developed in our laboratory using Indium-111-labeled platelets to measure the amount of deposition on grafts inserted into the infrarenal aorta. This study was designed to assess the patency rates in these grafts and the pathologic maturation as determined by light and electron microscopy. Our study suggests that substantial patency rates can be achieved in aspirin-treated rats, although there was little influence on the pathologic maturation. Indium-111 oxine-labeled platelets can be used to document platelet aggregation, and the technique can be a valuable adjunct in the study of microvascular grafts.

  12. Charge transport and memristive properties of graphene quantum dots embedded in poly(3-hexylthiophene) matrix

    SciTech Connect

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

    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.

  13. Magnetically Controlled Electronic Transport Properties of a Ferromagnetic Junction on the Surface of a Topological Insulator

    NASA Astrophysics Data System (ADS)

    Liu, Zheng-Qin; Wang, Rui-Qiang; Deng, Ming-Xun; Hu, Liang-Bin

    2015-06-01

    We have investigated the transport properties of the Dirac fermions through a ferromagnetic barrier junction on the surface of a strong topological insulator. The current-voltage characteristic curve and the tunneling conductance are calculated theoretically. Two interesting transport features are predicted: observable negative differential conductances and linear conductances tunable from unit to nearly zero. These features can be magnetically manipulated simply by changing the spacial orientation of the magnetization. Our results may contribute to the development of high-speed switching and functional applications or electrically controlled magnetization switching. Supported by National Natural Science Foundation of China under Grant Nos. 11174088, 11175067, 11274124

  14. Electrical transport properties of electrodeposited polypyrrole/single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kim, Ji Hun; Oh, Je Seung; Chang, Young Wook; Yoo, Seung Hwan; Choi, Hyang Hee; Yoo, Kyung-Hwa

    2007-03-01

    Single-walled carbon nanotubes (CNT) coated by conducting polypyrrole (PPy) have been synthesized by electrochemical polymerization of pyrrole on CNTs. In order to study the influence of PPy on the electrical transport properties of CNTs, the temperature dependences of the conductivity have been measured on bare CNTs and CNT/PPy. At room temperatures, the conductivity of CNT/PPy was reduced with thin PPy layers, whereas it was enhanced with thick PPy layers. In addition, depending on the PPy thickness, different temperature dependences of conductivity have been observed. Possible electrical transport mechanisms are discussed.

  15. Third-order transport properties of ion-swarms from mobility and diffusion coefficients

    NASA Astrophysics Data System (ADS)

    Koutselos, Andreas D.

    2005-08-01

    A method is presented for the calculation of third order transport properties of ions drifting in gases under the action of an electrostatic field with the use of mobility and ion-diffusion coefficients. The approach is based on a three-temperature treatment of the Boltzmann equation for the ion transport and follows the development of generalized Einstein relations (GER), between diffusion coefficients and mobility. The whole procedure is tested by comparison with numerical and molecular dynamics simulation results for three available alkali ion-noble gas systems. Extension to systems involving internal degrees of freedom and inelastic collisions is shown to follow the development of molecular GER.

  16. Improving charge transport property and energy transfer with carbon quantum dots in inverted polymer solar cells

    SciTech Connect

    Liu, Chunyu; Chang, Kaiwen; Guo, Wenbin E-mail: chenwy@jlu.edu.cn Li, Hao; Shen, Liang; Chen, Weiyou E-mail: chenwy@jlu.edu.cn; Yan, Dawei E-mail: chenwy@jlu.edu.cn

    2014-08-18

    Carbon quantum dots (Cdots) are synthesized by a simple method and introduced into active layer of polymer solar cells (PSCs). The performance of doped devices was apparently improved, and the highest power conversion efficiency of 7.05% was obtained, corresponding to a 28.2% enhancement compared with that of the contrast device. The charge transport properties, resistance, impedance, and transient absorption spectrum are systematically investigated to explore how the Cdots affect on PSCs performance. This study reveals the importance of Cdots in enhancing the efficiency of PSCs and gives insight into the mechanism of charge transport improvement.

  17. 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

  18. Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Denjean, C.; Cassola, F.; Mazzino, A.; Triquet, S.; Chevaillier, S.; Grand, N.; Bourrianne, T.; Momboisse, G.; Sellegri, K.; Schwarzenbock, A.; Freney, E.; Mallet, M.; Formenti, P.

    2016-02-01

    This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June-July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of transport (1-5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried a higher concentration of pollution particles below 3 km above sea level (a.s.l.) than above 3 km a.s.l., resulting in a scattering Ångström exponent up to 2.2 below 3 km a.s.l. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate absorption of light by the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assumed similar to those of native dust in radiative transfer simulations, modelling studies and satellite retrievals

  19. Development of the REFPROP database and transport properties of refrigerants. Final report

    SciTech Connect

    McLinden, M.O.

    1998-07-01

    This task consisted of developing Version 6.0 of the NIST Thermodynamic and Transport Properties of Refrigerants and Refrigerant Mixtures Database (REFPROP), entailing a complete revision of this database. This program is based on the most accurate pure fluid and mixture models currently available. The database development is further divided into the development of a graphical user interface and the development of Fortran subroutines which implement the property models. Three models are used for the thermodynamic properties of pure components, depending on the availability of data. The first is the modified Benedict-Webb-Rubin (MBWR) equation of state. It is capable of accurately representing the properties of a fluid over wide ranges of temperature, pressure, and density. The MBWR equation is the basis for the current international standard for the properties of R123. The second high-accuracy pure-fluid equation of state is written in terms of reduced molar Helmholtz free energy. This Helmholtz energy model is the basis for the international standard formulation for R134a. The third pure-fluid model is the extended corresponding states (ECS) model of Huber and Ely (1994). It is used for fluids with limited experimental data. The database calculates seventeen thermodynamic and transport properties, including surface tensions of pure fluids and mixtures. Commercialized blends, such as R407C and R410A, are predefined in the interface and are listed in a table.

  20. First principles study of the structural, electronic, and transport properties of triarylamine-based nanowires

    NASA Astrophysics Data System (ADS)

    Akande, Akinlolu; Bhattacharya, Sandip; Cathcart, Thomas; Sanvito, Stefano

    2014-02-01

    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 cm2/Vs. Such estimate confirms the superior transport properties of triarylamine-based nanowires, and make them an attracting materials platform for organic electronics.

  1. Relationship between cell surface properties and transport of bacteria through soil

    SciTech Connect

    Gannon, J.T.; Manilal, V.B.; Alexander, M. )

    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.

  2. Correlation of microstructure and thermo-mechanical properties of a novel hydrogen transport membrane

    NASA Astrophysics Data System (ADS)

    Zhang, Yongjun

    A key part of the FutureGen concept is to support the production of hydrogen to fuel a "hydrogen economy," with the use of clean burning hydrogen in power-producing fuel cells, as well as for use as a transportation fuel. One of the key technical barriers to FutureGen deployment is reliable and efficient hydrogen separation technology. Most Hydrogen Transport Membrane (HTM) research currently focuses on separation technology and hydrogen flux characterization. No significant work has been performed on thermo-mechanical properties of HTMs. The objective of the thesis is to understand the structure-property correlation of HTM and to characterize (1) thermo mechanical properties under different reducing environments and thermal cycles (thermal shock), and (2) evaluate the stability of the novel HTM material. A novel HTM cermet bulk sample was characterized for its physical and mechanical properties at both room temperature and at elevated temperature up to 1000°C. Micro-structural properties and residual stresses were evaluated in order to understand the changing mechanism of the microstructure and its effects on the mechanical properties of materials. A correlation of the microstructural and thermo mechanical properties of the HTM system was established for both HTM and the substrate material. Mechanical properties of both selected structural ceramics and the novel HTM cermet bulk sample are affected mainly by porosity and microstructural features, such as grain size and pore size-distribution. The Young's Modulus (E-value) is positively correlated to the flexural strength for materials with similar crystallographic structure. However, for different crystallographic materials, physical properties are independent of mechanical properties. Microstructural properties, particularly, grain size and crystallographic structure, and thermodynamic properties are the main factors affecting the mechanical properties at both room and high temperatures. The HTM cermet behaves

  3. Disorder effect on the transport properties of graphene quantum well structures.

    PubMed

    Xu, G J; Wu, B H; Xu, X G; Cao, J C

    2010-11-01

    We study the disorder effect on the transport properties of graphene quantum well structures using a phenomenological statistical model. By adopting the transfer matrix method combined with a Monte Carlo averaging procedure, we observe transitions from ballistic transport to the diffusive limit. It is found that the transmission probability of incident electrons is sensitive to the disorder effect. The significance of the disorder effect depends on the incident angle of the electrons. For normal incidence, the perfect transmission due to the Klein tunneling remains robust against the disorder effect. For tilted incidence, the transmission possibility can be suppressed. In particular, we found that the transmission probability for electrons with a very small angle, i.e. the wavevector along the transport direction is zero in the barrier, can be greatly suppressed. As a result, abrupt dips at these wavevectors emerge in the transmission spectrum. PMID:21403324

  4. Interactive FORTRAN IV computer programs for the thermodynamic and transport properties of selected cryogens (fluids pack)

    NASA Technical Reports Server (NTRS)

    Mccarty, R. D.

    1980-01-01

    The thermodynamic and transport properties of selected cryogens had programmed into a series of computer routines. Input variables are any two of P, rho or T in the single phase regions and either P or T for the saturated liquid or vapor state. The output is pressure, density, temperature, entropy, enthalpy for all of the fluids and in most cases specific heat capacity and speed of sound. Viscosity and thermal conductivity are also given for most of the fluids. The programs are designed for access by remote terminal; however, they have been written in a modular form to allow the user to select either specific fluids or specific properties for particular needs. The program includes properties for hydrogen, helium, neon, nitrogen, oxygen, argon, and methane. The programs include properties for gaseous and liquid states usually from the triple point to some upper limit of pressure and temperature which varies from fluid to fluid.

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

    NASA Astrophysics Data System (ADS)

    Maglić, K. D.; Perović, N. Lj.; Stanimirović, A. M.

    1994-07-01

    This paper presents the measurements and the results on thermal and electrical transport properties of three nuclear reactor cladding materials: Zircalloy 2, Zircalloy 4, and Inconel 625. Study of these materials constituted a part of the IAEA coordinated research program aimed at the generation and establishment of a reliable and complete database of the thermal properties of reactor materials. Measured properties include thermal diffusivity, specific heat, and electrical resistivity. Thermal diffusivity was measured by the laser pulse technique. Specific heat and electrical resistivity were measured using a millisecond-resolution direct electrical pulse heating technique. Thermal conductivity was computed from the experimentally determined thermal difusivity and specific heat functions and the room temperature density values. Measurements were performed in the 20 to 1500°C temperature range, depending on the material and property concerned.

  6. Transport, Structural and Mechanical Properties of Quaternary FeVTiAl Alloy

    NASA Astrophysics Data System (ADS)

    Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

    2016-08-01

    The electronic, structural, magnetic and transport properties of FeVTiAl quaternary alloy have been investigated within the framework of density functional theory. The material is a completely spin-polarized half-metallic ferromagnet in its ground state with F-43m structure. The structural stability was further confirmed by elastic constants in the cubic phase with high Young's modulus and brittle nature. The present study predicts an energy band gap of 0.72 eV in a localized minority spin channel at equilibrium lattice parameter of 6.00 Å. The transport properties of the material are discussed based on the Seebeck coefficient, and electrical and thermal conductivity coefficients. The alloy presents large values of Seebeck coefficients, ~39 μV K-1 at room temperature (300 K), and has an excellent thermoelectric performance with ZT = ~0.8.

  7. On the statistical and transport properties of a non-dissipative Fermi-Ulam model.

    PubMed

    Livorati, André L P; Dettmann, Carl P; Caldas, Iberê L; Leonel, Edson D

    2015-10-01

    The transport and diffusion properties for the velocity of a Fermi-Ulam model were characterized using the decay rate of the survival probability. The system consists of an ensemble of non-interacting particles confined to move along and experience elastic collisions with two infinitely heavy walls. One is fixed, working as a returning mechanism of the colliding particles, while the other one moves periodically in time. The diffusion equation is solved, and the diffusion coefficient is numerically estimated by means of the averaged square velocity. Our results show remarkably good agreement of the theory and simulation for the chaotic sea below the first elliptic island in the phase space. From the decay rates of the survival probability, we obtained transport properties that can be extended to other nonlinear mappings, as well to billiard problems. PMID:26520073

  8. Nonlinear thermoelectric response due to energy-dependent transport properties of a quantum dot

    NASA Astrophysics Data System (ADS)

    Svilans, Artis; Burke, Adam M.; Svensson, Sofia Fahlvik; Leijnse, Martin; Linke, Heiner

    2016-08-01

    Quantum dots are useful model systems for studying quantum thermoelectric behavior because of their highly energy-dependent electron transport properties, which are tunable by electrostatic gating. As a result of this strong energy dependence, the thermoelectric response of quantum dots is expected to be nonlinear with respect to an applied thermal bias. However, until now this effect has been challenging to observe because, first, it is experimentally difficult to apply a sufficiently large thermal bias at the nanoscale and, second, it is difficult to distinguish thermal bias effects from purely temperature-dependent effects due to overall heating of a device. Here we take advantage of a novel thermal biasing technique and demonstrate a nonlinear thermoelectric response in a quantum dot which is defined in a heterostructured semiconductor nanowire. We also show that a theoretical model based on the Master equations fully explains the observed nonlinear thermoelectric response given the energy-dependent transport properties of the quantum dot.

  9. Unusual electronic transport properties in doped TiCoSb Half-Heusler Alloys*

    NASA Astrophysics Data System (ADS)

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

    1999-11-01

    The sublattices of semiconducting TiCoSb Half-Heusler alloys are systematically doped and the resulting electrical transport properties are investigated. While all three sites can be doped to result in semimetallic behavior, transport behavior that can be ascribed to the presence of mobility edge and impurity band are observed in the vanadium- and manganese- doped alloys. Resistivity values reaching several W-cm and several hundred W-cm at 295K and 4.2K, respectively, are observed. Properties such as these have not been reported previously for a metal-rich bandgap compound. Specific heat measurements also indicate anomalous results at low temperature. Hall effect and thermopower measurements will be discussed.

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

    PubMed

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

    2015-03-01

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

  11. Numerical evaluation of the light transport properties of alternative He-3 neutron detectors using ceramic scintillators

    NASA Astrophysics Data System (ADS)

    Ohzu, A.; Takase, M.; Haruyama, M.; Kurata, N.; Kobayashi, N.; Kureta, M.; Nakamura, T.; Toh, K.; Sakasai, K.; Suzuki, H.; Soyama, K.; Seya, M.

    2015-10-01

    The light transport properties of scintillator light inside alternative He-3 neutron detectors using scintillator sheets have been investigated by a ray-tracing simulation code. The detector consists of a light-reflecting tube, a thin rectangular ceramic scintillator sheet laminated on a glass plate, and two photo-multiplier tubes (PMTs) mounted at both ends of the detector tube. The flashes of light induced on the surface of the scintillator sheet via nuclear interaction between the scintillator and neutrons are detected by the two PMTs. The light output at both ends of various detectors in which the scintillator sheets are installed with several different arrangements were examined and evaluated in comparison with experimental results. The results derived from the simulation reveal that the light transport property is strongly dependent on the arrangement of the scintillator sheet inside the tube and the shape of the tube.

  12. Transport Properties of Amine/Carbon Dioxide Reactive Mixtures and Implications to Carbon Capture Technologies.

    PubMed

    Turgman-Cohen, Salomon; Giannelis, Emmanuel P; Escobedo, Fernando A

    2015-08-19

    The structure and transport properties of physisorbed and chemisorbed CO2 in model polyamine liquids (hexamethylenediamine and diethylenetriamine) are studied via molecular dynamics simulations. Such systems are relevant to CO2 absorption processes where nonaqueous amines are used as absorbents (e.g., when impregnated or grafted onto mesoporous media or misted in the gas phase). It is shown that accounting for the ionic speciation resulting from CO2 chemisorption enabled us to capture the qualitative changes in extent of absorption and fluidity with time that are observed in thermogravimetric experiments. Simulations reveal that high enough concentration of reacted CO2 leads to strong intermolecular ionic interactions and the arrest of molecular translations. The transport properties obtained from the simulations of the ionic speciated mixtures are also used to construct an approximate continuum-level model for the CO2 absorption process that mimics thermogravimetric experiments.

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

    PubMed

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

    2015-03-01

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

  14. Irradiation response of commercial, high-Tc superconducting tapes: Electromagnetic transport properties

    SciTech Connect

    Gapud, A. A.; Greenwood, N. T.; Alexander, J. A.; Khan, A.; Leonard, K. J.; Aytug, T.; List III, F. A.; Rupich, M. W.; Zhang, Y.

    2015-07-01

    Effects of low dose irradiation on the electrical transport current properties of commercially available high-temperature superconducting, coated-conductor tapes were investigated, in view of potential applications in the irradiative environment of fusion reactors. Three different tapes, each with unique as-grown flux-pinning structures, were irradiated with Au and Ni ions at energies that provide a range of damage effects, with accumulated damage levels near that expected for conductors in a fusion reactor environment. Measurements using transport current determined the pre- and post-irradiation resistivity, critical current density, and pinning force density, yielding critical temperatures, irreversibility lines, and inferred vortex creep rates. Results show that at the irradiation damage levels tested, any detriment to as-grown pre-irradiation properties is modest; indeed in one case already-superior pinning forces are enhanced, leading to higher critical currents.

  15. Irradiation response of commercial, high-Tc superconducting tapes: Electromagnetic transport properties

    DOE PAGES

    Gapud, A. A.; Greenwood, N. T.; Alexander, J. A.; Khan, A.; Leonard, K. J.; Aytug, T.; List III, F. A.; Rupich, M. W.; Zhang, Y.

    2015-07-01

    Effects of low dose irradiation on the electrical transport current properties of commercially available high-temperature superconducting, coated-conductor tapes were investigated, in view of potential applications in the irradiative environment of fusion reactors. Three different tapes, each with unique as-grown flux-pinning structures, were irradiated with Au and Ni ions at energies that provide a range of damage effects, with accumulated damage levels near that expected for conductors in a fusion reactor environment. Measurements using transport current determined the pre- and post-irradiation resistivity, critical current density, and pinning force density, yielding critical temperatures, irreversibility lines, and inferred vortex creep rates. Results showmore » that at the irradiation damage levels tested, any detriment to as-grown pre-irradiation properties is modest; indeed in one case already-superior pinning forces are enhanced, leading to higher critical currents.« less

  16. Impacts of Transport Properties of Porous Corrosion Product Layer on Effective Corrosion Rate

    NASA Astrophysics Data System (ADS)

    Li, Xiaobai; Cook, David

    2012-11-01

    Condensing exhaust gases containing H2O, SO3 and NOx cause serious corrosion failure in various industry processes. For example, in modern compact heat cells, corrosion products deposit on top of the heat exchanger cooling fins, blocking the flow passages and drastically decreasing system performance. The transport properties of porous corrosion product layers play important role in determining the corrosion tendency and observed corrosion rate. To understand the corrosion mechanism for Aluminum alloy in sulfuric acid environment, impacts of transport properties of corrosion residual layers are investigated with different numerical models for porous layer diffusivity. The effective corrosion rates resulted from these models are compared to corresponding experimental measurements. A multilayer diffusivity model in which diffusivity depends both on porous layer structure and composition shows excellent agreements with experimental data. This model is currently being used in a multi-scale flow simulation framework to predict corrosion phenomena in heat cells.

  17. Measuring the electronic transport properties of individual nano-objects under high pressures

    NASA Astrophysics Data System (ADS)

    Caillier, C.; Ayari, A.; Le Floch, S.; Féret, H.; Guiraud, G.; San-Miguel, A.

    2011-09-01

    We describe a setup to carry out electronic transport measurements under high pressures on individual nano-objects. It is based on a home-automated three-stage gas compressor working with argon or helium up to 1 GPa. The setup was successfully tested on contacted individual nanotubes, for which we evidence strong evolutions of the transport properties. These evolutions are related to fundamental issues such as the modification of the nano-object contact resistance, the pressure-induced modification of the nano-object geometry or pressure-induced changes in the intrinsic electronic properties of the nanosystem. A cryostat has also been adapted to the pressure cell, allowing combined pressure and temperature experiments down to 12 K.

  18. Irradiation response of commercial, high-Tc superconducting tapes: Electromagnetic transport properties

    NASA Astrophysics Data System (ADS)

    Gapud, A. A.; Greenwood, N. T.; Alexander, J. A.; Khan, A.; Leonard, K. J.; Aytug, T.; List, F. A.; Rupich, M. W.; Zhang, Y.

    2015-07-01

    Effects of low dose ion irradiation on the electrical transport current properties of commercially available high-temperature superconducting, coated-conductor tapes were investigated, in view of potential applications in irradiative environments. Three different tapes, each with unique and tailored as-grown flux-pinning structures, were irradiated with Au and Ni ions at energies that provide a range of damage effects, with accumulated damage levels near that expected for conductors in, for example, a fusion reactor environment. Measurements using transport current determined the pre- and post-irradiation resistivity, critical current density, and pinning force density, yielding critical temperatures, irreversibility lines, and inferred vortex creep rates. Results show that, at the irradiation damage levels tested, any detriment to as-grown pre-irradiation properties is modest; indeed in one case already-superior pinning forces are enhanced, leading to higher critical currents.

  19. First-Principles Investigation of Structural, Thermal and Transport Properties of Anatase TiO2

    NASA Astrophysics Data System (ADS)

    Naffouti, Wafa; Ben Nasr, Tarek; Meradji, Hocine; Kamoun-Turki, Najoua

    2016-10-01

    A theoretical calculation of the structural, thermal and transport properties of anatase titanium dioxide (TiO2) was investigated with the help of density functional theory and Boltzmann theory. The fully optimized structure was obtained by minimizing the total energy. The variations of the volume ( V), bulk modulus ( B), Debye temperature (Θ), heat capacities at constant volume ( C v ) and constant pressure ( C p ), entropy ( S), Grüneisen parameter ( γ) and thermal expansion coefficient ( α) as a function of the pressure ( P) and temperature ( T) were all obtained and analyzed in detail. Boltzmann theory calculations have been used to evaluate important transport properties such as Seebeck coefficient ( S), electrical conductivity ( σ), electronic thermal conductivity ( K el ) and power factor ( S 2 σ) with respect to scattering time ( τ) as a function of chemical potential ( μ).

  20. Transport Properties of Amine/Carbon Dioxide Reactive Mixtures and Implications to Carbon Capture Technologies.

    PubMed

    Turgman-Cohen, Salomon; Giannelis, Emmanuel P; Escobedo, Fernando A

    2015-08-19

    The structure and transport properties of physisorbed and chemisorbed CO2 in model polyamine liquids (hexamethylenediamine and diethylenetriamine) are studied via molecular dynamics simulations. Such systems are relevant to CO2 absorption processes where nonaqueous amines are used as absorbents (e.g., when impregnated or grafted onto mesoporous media or misted in the gas phase). It is shown that accounting for the ionic speciation resulting from CO2 chemisorption enabled us to capture the qualitative changes in extent of absorption and fluidity with time that are observed in thermogravimetric experiments. Simulations reveal that high enough concentration of reacted CO2 leads to strong intermolecular ionic interactions and the arrest of molecular translations. The transport properties obtained from the simulations of the ionic speciated mixtures are also used to construct an approximate continuum-level model for the CO2 absorption process that mimics thermogravimetric experiments. PMID:26200117

  1. First-Principles Investigation of Structural, Thermal and Transport Properties of Anatase TiO2

    NASA Astrophysics Data System (ADS)

    Naffouti, Wafa; Ben Nasr, Tarek; Meradji, Hocine; Kamoun-Turki, Najoua

    2016-06-01

    A theoretical calculation of the structural, thermal and transport properties of anatase titanium dioxide (TiO2) was investigated with the help of density functional theory and Boltzmann theory. The fully optimized structure was obtained by minimizing the total energy. The variations of the volume (V), bulk modulus (B), Debye temperature (Θ), heat capacities at constant volume (C v ) and constant pressure (C p ), entropy (S), Grüneisen parameter (γ) and thermal expansion coefficient (α) as a function of the pressure (P) and temperature (T) were all obtained and analyzed in detail. Boltzmann theory calculations have been used to evaluate important transport properties such as Seebeck coefficient (S), electrical conductivity (σ), electronic thermal conductivity (K el ) and power factor (S 2 σ) with respect to scattering time (τ) as a function of chemical potential (μ).

  2. Magnetization and electric transport properties of single-crystal MgB2 nanowires.

    PubMed

    Wu, Cen-Shawn; Chang, Yu-Cheng; Chen, Weimeng; Chen, Chinping; Feng, Qingrong

    2012-11-23

    High quality single-crystal magnesium diboride (MgB(2)) nanowires with lengths exceeding 10 μm were successfully synthesized by hybrid physical chemical vapor deposition. The magnetization and electrical transport properties of single-crystal MgB(2) nanowires (NWs) were measured. The superconducting transition temperature of the NWs was 37 K, as confirmed by magnetization measurements. The disordered behavior of the nanowires was observed by four-terminal current-voltage characteristic measurements of an individual NW from T = 10 to 300 K. The temperature-dependent resistivity curves for seven NWs collapsed into a universal curve described by the variable range hopping model, showing intrinsic nonmetallic transport properties. This implies that the granular superconducting defect states are critical to the superconductivity of the individual MgB(2) NWs.

  3. Magnon excitation and temperature dependent transport properties in magnetic tunnel junctions with Heusler compound electrodes

    NASA Astrophysics Data System (ADS)

    Drewello, Volker; Ebke, Daniel; Schäfers, Markus; Kugler, Zoë; Reiss, Günter; Thomas, Andy

    2012-04-01

    Magnetic tunnel junctions were prepared with the Heusler compounds Co2FeAl, Co2FeSi, and Co2MnSi as the soft magnetic electrode. The Co2MnSi electrodes had a multilayer design that used either the Co2FeAl or the Co2FeSi compound as a buffer material. Pinned Co-Fe was used as the hard reference electrode. The electronic transport characteristics were analyzed by tunneling spectroscopy. The dependence of sample properties on the buffer material was of interest, especially the gap in the minority density of states of the Heusler electrode. The temperature dependence of the transport properties was also investigated.

  4. Transport properties of hybrid topological superconductor devices in contact with an environment

    NASA Astrophysics Data System (ADS)

    Komnik, A.

    2016-03-01

    We investigate the transport properties of different realizations of one-dimensional quantum wires coupled to a number of external electrodes in terms of the full counting statistics. Focusing on the setups in which edge states of Majorana type are realizable, we analyze the effects of the exchange of charge carriers with the environment. We find a very strong suppression of the nonlocal current correlations, which decay exponentially with the coupling strength and the wire length. Local properties such as transport currents and current correlations measured at individual contacts between the wire and external electrodes turn out to develop an asymmetry when they are energy resolved. We provide a number of exact analytical solutions and discuss experimental implications of our findings.

  5. The influence of inner hydrophobisation on water transport properties of modified lime plasters

    NASA Astrophysics Data System (ADS)

    Pavlíková, Milena; Pavlík, Zbyšek; Pernicová, Radka; Černý, Robert

    2016-06-01

    The effect of hydrophobic agent admixture on water vapour and liquid water transport properties of newly designed lime plasters is analysed in the paper. The major part of physico - chemical building deterioration is related to the penetration of moisture and soluble salts into the building structure. For that reason, the modified lime plasters were in the broad range of basic material properties tested. From the quantitative point of view, the measured results clearly demonstrate the big differences in the behaviour of studied materials depending on applied modifying admixtures. From the practical point of view, plaster made of lime hydrate, metakaolin, zinc stearate and air-entraining agent can be recommended for renovation purposes. The accessed material parameters will be used as input data for computational modelling of moisture transport in this type of porous building materials and will be stored in material database.

  6. Superior transport properties of InGaN channel heterostructure with high channel electron mobility

    NASA Astrophysics Data System (ADS)

    Zhang, Yachao; Zhou, Xiaowei; Xu, Shengrui; Zhang, Jinfeng; Zhang, Jincheng; Hao, Yue

    2016-06-01

    A high-quality AlGaN/InGaN heterostructure is grown by pulsed metal organic chemical vapor deposition on a sapphire substrate. A two-step AlN interlayer is adopted to improve the interface morphology and protect the high-quality InGaN channel. Temperature-dependent Hall measurement shows superior transport properties compared with the traditional GaN channel heterostructure at elevated temperatures. Further, a record highest channel electron mobility of 1681 cm2/(V·s) at room temperature for an InGaN channel heterostructure is obtained. We attribute the excellent transport properties to the improvement in the material quality, as well as the rationally designed epitaxial structure and well-controlled growth condition.

  7. On the statistical and transport properties of a non-dissipative Fermi-Ulam model

    SciTech Connect

    Livorati, André L. P.; Dettmann, Carl P.; Caldas, Iberê L.; Leonel, Edson D.

    2015-10-15

    The transport and diffusion properties for the velocity of a Fermi-Ulam model were characterized using the decay rate of the survival probability. The system consists of an ensemble of non-interacting particles confined to move along and experience elastic collisions with two infinitely heavy walls. One is fixed, working as a returning mechanism of the colliding particles, while the other one moves periodically in time. The diffusion equation is solved, and the diffusion coefficient is numerically estimated by means of the averaged square velocity. Our results show remarkably good agreement of the theory and simulation for the chaotic sea below the first elliptic island in the phase space. From the decay rates of the survival probability, we obtained transport properties that can be extended to other nonlinear mappings, as well to billiard problems.

  8. Theoretical study of electronic transport properties of a graphene-silicene bilayer

    NASA Astrophysics Data System (ADS)

    Berdiyorov, G. R.; Bahlouli, H.; Peeters, F. M.

    2015-06-01

    Electronic transport properties of a graphene-silicene bilayer system are studied using density-functional theory in combination with the nonequilibrium Green's function formalism. Depending on the energy of the electrons, the transmission can be larger in this system as compared to the sum of the transmissions of separated graphene and silicene monolayers. This effect is related to the increased electron density of states in the bilayer sample. At some energies, the electronic states become localized in one of the layers, resulting in the suppression of the electron transmission. The effect of an applied voltage on the transmission becomes more pronounced in the layered sample as compared to graphene due to the larger variation of the electrostatic potential profile. Our findings will be useful when creating hybrid nanoscale devices where enhanced transport properties will be desirable.

  9. Transport, Structural and Mechanical Properties of Quaternary FeVTiAl Alloy

    NASA Astrophysics Data System (ADS)

    Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

    2016-11-01

    The electronic, structural, magnetic and transport properties of FeVTiAl quaternary alloy have been investigated within the framework of density functional theory. The material is a completely spin-polarized half-metallic ferromagnet in its ground state with F-43m structure. The structural stability was further confirmed by elastic constants in the cubic phase with high Young's modulus and brittle nature. The present study predicts an energy band gap of 0.72 eV in a localized minority spin channel at equilibrium lattice parameter of 6.00 Å. The transport properties of the material are discussed based on the Seebeck coefficient, and electrical and thermal conductivity coefficients. The alloy presents large values of Seebeck coefficients, ~39 μV K-1 at room temperature (300 K), and has an excellent thermoelectric performance with ZT = ~0.8.

  10. Transport and AC loss properties of the repaired multifilamentary REBCO superconducting tapes

    NASA Astrophysics Data System (ADS)

    Yamasaki, S.; Iwakuma, M.; Funaki, K.; Kato, J.; Chikumoto, T.; Tanabe, K.; Nakao, K.; Izumi, T.; Yamada, Y.; Shiohara, Y.; Saito, T.

    2010-11-01

    For near-future applications of REBa 2Cu 3O 7 (REBCO) coated conductors to electric power cables, transformers and Superconducting Magnetic Energy Storage (SMES), the long taped wires with high performance in the transport properties have been designed and fabricated. Moreover, in order to drastically reduce AC losses in perpendicular field configuration, advanced multifilament YBCO coated conductors (MFYCCs) fabricated with technique of a laser scribing process have been also developed. In the present study, from engineering viewpoints to utilize such advanced conductors, we evaluated the transport and AC loss properties of short MFYCCs with a repaired part or a joint by a diffusion joint technique with the saddle-shaped pickup coil method.

  11. Transport properties of gases and binary liquids near the critical point

    NASA Technical Reports Server (NTRS)

    Sengers, J. V.

    1972-01-01

    A status report is presented on the anomalies observed in the behavior of transport properties near the critical point of gases and binary liquids. The shear viscosity exhibits a weak singularity near the critical point. An analysis is made of the experimental data for those transport properties, thermal conductivity and thermal diffusivity near the gas-liquid critical point and binary diffusion coefficient near the critical mixing point, that determine the critical slowing down of the thermodynamic fluctuations in the order parameter. The asymptotic behavior of the thermal conductivity appears to be closely related to the asymptotic behavior of the correlation length. The experimental data for the thermal conductivity and diffusivity are shown to be in substantial agreement with current theoretical predictions.

  12. Tailoring the Transport Properties of Zeolitic Imidazolate Frameworks by Post-Synthetic Thermal Modification.

    PubMed

    Zhang, Chen; Koros, William J

    2015-10-28

    Understanding how to control transport properties of zeolitic imidazolate frameworks (ZIFs) is critical to extend ZIF-based membranes and adsorbents to a wide spectrum of gas and vapor separations. In this work, we report a facile post-synthetic thermal modification (PSTM) technique to tailor ZIFs' transport properties by balancing diffusivity and diffusion selectivity. With controllable dissociation of framework methyl groups from a precursor ZIF (ZIF-8), we have prepared thermally modified ZIFs showing substantially increased n-butane diffusivity and attractive n/iso-butane diffusion selectivity. Hybrid ZIF/polymer mixed-matrix membranes formed using these thermally modified ZIFs are expected to deliver attractive butane isomer separation performance. Membranes based on such materials can potentially be used to retrofit refinery alkylation units for producing premium gasoline blending stocks. PMID:26451850

  13. Theoretical study of electronic transport properties of a graphene-silicene bilayer

    SciTech Connect

    Berdiyorov, G. R.; Bahlouli, H.; Peeters, F. M.

    2015-06-14

    Electronic transport properties of a graphene-silicene bilayer system are studied using density-functional theory in combination with the nonequilibrium Green's function formalism. Depending on the energy of the electrons, the transmission can be larger in this system as compared to the sum of the transmissions of separated graphene and silicene monolayers. This effect is related to the increased electron density of states in the bilayer sample. At some energies, the electronic states become localized in one of the layers, resulting in the suppression of the electron transmission. The effect of an applied voltage on the transmission becomes more pronounced in the layered sample as compared to graphene due to the larger variation of the electrostatic potential profile. Our findings will be useful when creating hybrid nanoscale devices where enhanced transport properties will be desirable.

  14. Point Mutations Effects on Charge Transport Properties of the Tumor-Suppressor Gene p53

    NASA Astrophysics Data System (ADS)

    Roemer, Rudolf A.; Shih, Chi-Tin; Roche, Stephan

    2008-03-01

    We report on a theoretical study of point mutations effects on charge transfer properties in the DNA sequence of the tumor-suppressor p53 gene. On the basis of effective tight-binding models which simulate hole propagation along the DNA, a statistical analysis of mutation-induced charge transfer modifications is performed. In contrast to non-cancerous mutations, mutation hotspots tend to result in significantly weaker changes of transmission properties. This suggests that charge transport could play a significant role for DNA-repairing deficiency yielding carcinogenesis.

  15. A study of transport properties in Cu and P doped ZnSb

    SciTech Connect

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

    2015-01-28

    ZnSb samples have been doped with copper and phosphorus and sintered at 798 K. Electronic transport properties are interpreted as being influenced by an impurity band close to the valence band. At low Cu dopant concentrations, this impurity band degrades the thermoelectric properties as the Seebeck coefficient and effective mass are reduced. At carrier concentrations above 1 × 10{sup 19 }cm{sup −3}, the Seebeck coefficient in Cu doped samples can be described by a single parabolic band.

  16. Magnetic and transport properties of Mn{sub 2}CoAl oriented films

    SciTech Connect

    Jamer, Michelle E.; Assaf, Badih A.; Devakul, Trithep; Heiman, Don

    2013-09-30

    The structure, magnetic, and transport properties of thin films of the Heusler ferrimagnet Mn{sub 2}CoAl have been investigated for properties related to spin gapless semiconductors. Oriented films were grown by molecular beam epitaxy on GaAs substrates and the structure was found to transform from tetragonal to cubic for increasing annealing temperature. The anomalous Hall resistivity is found to be proportional to the square of the longitudinal resistivity and magnetization expected for a topological Berry curvature origin. A delicate balance of the spin-polarized carrier type when coupled with voltage gate-tuning could significantly impact advanced electronic devices.

  17. Effect of Li2O on the microstructure, magnetic and transport properties of Tl-2223 superconductor

    NASA Astrophysics Data System (ADS)

    Shipra, R.; Sefat, A. S.

    2015-12-01

    The present study gives an account of the effect of addition of Li2O on the ease of phase formation and superconducting properties of Tl2Ba2Ca2Cu3O10 + δ (Tl-2223) material. Li2O slightly decreases the superconducting transition temperature, while an optimal concentration of 20% Li2O improves the critical current density (Jc) by about two fold. We also found substantial effects on the synthesis temperature, microstructure and normal state transport properties of Tl-2223 with Li2O addition. Short-time annealing under flowing Ar + 4%H2 (1 h) further improves the superconducting volume fractions, as well as Jc.

  18. Influence of molecular chain orientation on optical and carrier transport properties of polymer blends

    NASA Astrophysics Data System (ADS)

    Kažukauskas, Vaidotas; Čyras, Valius; Pranaitis, Mindaugas; Apostoluk, Aleksandra; Rocha, Licinio; Sicot, Lionel; Raimond, Paul; Sentein, Carole

    2007-02-01

    We have investigated properties of poly(9-vinylcarbazole) (PVK) doped with 30% wt 4-dibutylamino-4'-nitrostilbene (DBANS), depending on orientation of the polar DBANS molecules. Appearance of the orientation-induced built-in electric field was proven optically by the solid electric field induced second harmonic generation and electrically by the current-voltage characterization. Modification of optical properties was evidenced by the spectral dependencies of the absorption coefficient. The thermally stimulated current spectra had demonstrated that carrier transport and trapping are affected, too.

  19. Effect of the molecular chain orientation on carrier transport and optical properties of polymer blends

    NASA Astrophysics Data System (ADS)

    Kažukauskas, V.; Čyras, V.; Pranaitis, M.; Apostoluk, A.; Rocha, L.; Sicot, L.; Raimond, P.; Sentein, C.

    2007-03-01

    We have investigated properties of poly(9-vinylcarbazole) (PVK) doped with 30% wt 4-dibutylamino-4'-nitrostilbene (DBANS), depending on the orientation of the polar DBANS molecules. Appearance of the orientation-induced built-in electrical field was proven optically by the Solid Electric Field Induced Second Harmonic Generation and electrically by Current-Voltage characterization. Modification of optical properties was evidenced by the spectral dependencies of absorption coefficient. The Thermally Stimulated Currents spectra demonstrated that carrier transport and trapping are affected, too. This paper has been presented at “ECHOS06”, Paris, 28 30 juin 2006.

  20. Numerical estimation of transport properties of cementitious materials using 3D digital images

    NASA Astrophysics Data System (ADS)

    Ukrainczyk, N.; Koenders, E. A. B.; van Breugel, K.

    2013-07-01

    A multi-scale characterisation of the transport process within cementitious microstructure possesses a great challenge in terms of modelling and schematization. In this paper a numerical method is proposed to mitigate the resolution problems in numerical methods for calculating effective transport properties of porous materials using 3D digital images. The method up-scales sub-voxel information from the fractional occupancy level of the interface voxels, i.e. voxels containing phaseboundary, to increase the accuracy of the pore schematization and hence the accuracy of the numerical transport calculation as well. The numerical identification of the subvoxels that is associated with their level of occupancy by each phase is obtained by increasing the pre-processing resolution. The proposed method is presented and employed for hydrated cement paste microstructures obtained from Hymostruc, a numerical model for cement hydration and microstructure simulation. The new method significantly reduces computational efforts, is relatively easy to implement, and improves the accuracy of the estimation of the effective transport property.

  1. Transport properties through graphene grain boundaries: strain effects versus lattice symmetry

    NASA Astrophysics Data System (ADS)

    Hung Nguyen, V.; Hoang, Trinh X.; Dollfus, P.; Charlier, J.-C.

    2016-06-01

    As most materials available at the macroscopic scale, graphene samples usually appear in a polycrystalline form and thus contain grain boundaries. In the present work, the effect of uniaxial strain on the electronic transport properties through graphene grain boundaries is investigated using atomistic simulations. A systematic picture of transport properties with respect to the strain and lattice symmetry of graphene domains on both sides of the boundary is provided. In particular, it is shown that strain engineering can be used to open a finite transport gap in all graphene systems where the two domains are arranged in different orientations. This gap value is found to depend on the strain magnitude, on the strain direction and on the lattice symmetry of graphene domains. By choosing appropriately the strain direction, a large transport gap of a few hundred meV can be achieved when applying a small strain of only a few percents. For a specific class of graphene grain boundary systems, strain engineering can also be used to reduce the scattering on defects and thus to significantly enhance the conductance. With a large strain-induced gap, these graphene heterostructures are proposed to be promising candidates for highly sensitive strain sensors, flexible electronic devices and p-n junctions with non-linear I-V characteristics.

  2. Hydrostatic pressure effect on charge transport properties of phenacene organic semiconductors.

    PubMed

    Nguyen, Thao P; Shim, Ji Hoon

    2016-05-18

    We investigate the charge transport properties of phenacene organic semiconductors including phenanthrene, chrysene and picene using density functional theory (DFT) calculations under hydrostatic pressure. Under compression, the crystal structures of the three materials are altered and thus, a decrease in the intermolecular distances gives changes in charge transport properties while the molecular structures remain stable. As a result of the applied pressure, the mobilities of these materials increase dramatically. Chrysene shows a transition from a p-type semiconductor to an ambipolar semiconductor at around 2.0 GPa. Interestingly, chrysene favors electron transport at above 3.0 GPa. On the other hand, both phenanthrene and picene exhibit hole transport characteristics under high pressure. Between 3.1 and 4.3 GPa, the picene crystal is found to transform from an anisotropic mobility to an isotropic mobility in the ab plane. We also found that, the bulk modulus representing the resistance of the material under pressure compression follows a linear relationship with molecular length. PMID:27146786

  3. Size distribution and optical properties of African mineral dust after intercontinental transport

    NASA Astrophysics Data System (ADS)

    Denjean, Cyrielle; Formenti, Paola; Desboeufs, Karine; Chevaillier, Servanne; Triquet, Sylvain; Maillé, Michel; Cazaunau, Mathieu; Laurent, Benoit; Mayol-Bracero, Olga L.; Vallejo, Pamela; Quiñones, Mariana; Gutierrez-Molina, Ian E.; Cassola, Federico; Prati, Paolo; Andrews, Elisabeth; Ogren, John

    2016-06-01

    The transatlantic transport of mineral dust from Africa is a persistent atmospheric phenomenon, clue for understanding the impacts of dust at the global scale. As part of the DUST Aging and Transport from Africa to the Caribbean (Dust-ATTACk) intensive field campaign, the size distribution and optical properties of mineral dust were measured in June-July 2012 on the east coast of Puerto Rico, more than 5000 km from the west coast of Africa. During the recorded dust events, the PM10 (particulate matter 10 micrometers or less in diameter) concentrations increased from 20 to 70 µg m-3. Remote sensing observations and modeling analysis were used to identify the main source regions, which were found in the Western Sahara, Mauritania, Algeria, Niger, and Mali. The microphysical and optical properties of the dust plumes were almost independent of origin. The size distribution of mineral dust after long-range transport may have modal diameters similar to those on the eastern side of the Atlantic short time after emission, possibly depending on height of transport. Additional submicron particles of anthropogenic absorbing aerosols (likely from regional marine traffic activities) can be mixed within the dust plumes, without affecting in a significant way the PM10 absorption properties of dust observed in Puerto Rico. The Dust-ATTACk experimental data set may be useful for modeling the direct radiative effect of dust. For accurate representation of dust optical properties over the Atlantic remote marine region, we recommend mass extinction efficiency (MEE) and single-scattering albedo values in the range 1.1-1.5 m2 g-1 and 0.97-0.98, respectively, for visible wavelengths.

  4. Electronic conduction properties of indium tin oxide: single-particle and many-body transport.

    PubMed

    Lin, Juhn-Jong; Li, Zhi-Qing

    2014-08-27

    Indium tin oxide (Sn-doped In2O3-δ or ITO) is a very interesting and technologically important transparent conducting oxide. This class of material has been extensively investigated for decades, with research efforts mostly focusing on the application aspects. The fundamental issues of the electronic conduction properties of ITO from room temperature down to liquid-helium temperatures have rarely been addressed thus far. Studies of the electrical-transport properties over a wide range of temperature are essential to unravelling the underlying electronic dynamics and microscopic electronic parameters. In this topical review, we show that one can learn rich physics in ITO material, including the semi-classical Boltzmann transport, the quantum-interference electron transport, as well as the many-body Coulomb electron-electron interaction effects in the presence of disorder and inhomogeneity (granularity). To fully reveal the numerous avenues and unique opportunities that the ITO material has provided for fundamental condensed matter physics research, we demonstrate a variety of charge transport properties in different forms of ITO structures, including homogeneous polycrystalline thin and thick films, homogeneous single-crystalline nanowires and inhomogeneous ultrathin films. In this manner, we not only address new physics phenomena that can arise in ITO but also illustrate the versatility of the stable ITO material forms for potential technological applications. We emphasize that, microscopically, the novel and rich electronic conduction properties of ITO originate from the inherited robust free-electron-like energy bandstructure and low-carrier concentration (as compared with that in typical metals) characteristics of this class of material. Furthermore, a low carrier concentration leads to slow electron-phonon relaxation, which in turn causes the experimentally observed (i) a small residual resistance ratio, (ii) a linear electron diffusion thermoelectric power in

  5. Mass transport properties of Pu/DT mixtures from orbital free molecular dynamics simulations

    SciTech Connect

    Kress, Joel David; Ticknor, Christopher; Collins, Lee A.

    2015-09-16

    Mass transport properties (shear viscosity and diffusion coefficients) for Pu/DT mixtures were calculated with Orbital Free Molecular Dynamics (OFMD). The results were fitted to simple functions of mass density (for ρ=10.4 to 62.4 g/cm3) and temperature (for T=100 up to 3,000 eV) for Pu/DT mixtures consisting of 100/0, 25/75, 50/50, and 75/25 by number.

  6. Influence of the electronic structure on the transport properties of some iron pnictides

    NASA Astrophysics Data System (ADS)

    Rullier-Albenque, Florence

    2016-01-01

    An important feature of the iron-based pnictides is their multi-band electronic structure with both electron and hole bands at the Fermi level. The size of these pockets can be changed by different types of substitution, resulting in a variety of original magnetic and electronic properties. The contributions of both types of carriers will thus have important consequences on the evolution of the transport properties versus temperature and doping. It has been pointed out that Hund's rule interaction plays a prominent role in the physics of these compounds by allowing a strong orbital differentiation between the 3d Fe orbitals. As a result, a description in terms of more or less correlated electrons was proposed and may have important consequences on the scattering lifetimes of the different carriers. Finally, the presence of very flat bands at the Fermi level may induce a semiconductor-like behavior, with a change in carrier concentration with temperature. In this paper, we will review the evolution of transport properties with chemical doping/substitution in iron pnictides. We will more particularly focus on the 122 family (Ba(Sr,Ca)Fe2As2) and the 111 LiFeAs compound for which sizeable single crystals required for transport measurements are available. The combined resistivity, Hall effect and magnetoresistance data will be analyzed in association with electronic structure calculations, angle-resolved photoemission measurements and quantum oscillations. In spite of the strong interplay between antiferromagnetism and superconductivity in most part of their phase diagram, direct signatures of spin fluctuations are difficult to identify in the transport properties of iron pnictides. We will show that measurements of the longitudinal magnetoresistance provide a powerful tool for studying the coupling between the charge carriers and the spin degrees of freedom.

  7. The relationship between red blood cell deformability metrics and perfusion of an artificial microvascular network

    PubMed Central

    Sosa, Jose M.; Nielsen, Nathan D.; Vignes, Seth M.; Chen, Tanya G.; Shevkoplyas, Sergey S.

    2013-01-01

    The ability of red blood cells (RBC) to undergo a wide range of deformations while traversing the microvasculature is crucial for adequate perfusion. Interpretation of RBC deformability measurements performed in vitro in the context of microvascular perfusion has been notoriously difficult. This study compares the measurements of RBC deformability performed using micropore filtration and ektacytometry with the RBC ability to perfuse an artificial microvascular network (AMVN). Human RBCs were collected from healthy consenting volunteers, leukoreduced, washed and exposed to graded concentrations (0% – 0.08%) of glutaraldehyde (a non-specific protein cross-linker) and diamide (a spectrin-specific protein cross-linker) to impair the deformability of RBCs. Samples comprising cells with two different levels of deformability were created by adding non-deformable RBCs (hardened by exposure to 0.08% glutaraldehyde) to the sample of normal healthy RBCs. Ektacytometry indicated a nearly linear decline in RBC deformability with increasing glutaraldehyde concentration. Micropore filtration showed a significant reduction only for concentrations of glutaraldehyde higher than 0.04%. Neither micropore filtration nor ektacytometry measurements could accurately predict the AMVN perfusion. Treatment with diamide reduced RBC deformability as indicated by ektacytometry, but had no significant effect on either micropore filtration or the AMVN perfusion. Both micropore filtration and ektacytometry showed a linear decline in effective RBC deformability with increasing fraction of non-deformable RBCs in the sample. The corresponding decline in the AMVN perfusion plateaued above 50%, reflecting the innate ability of blood flow in the microvasculature to bypass occluded capillaries. Our results suggest that in vitro measurements of RBC deformability performed using either micropore filtration or ektacytometry may not represent the ability of same RBCs to perfuse microvascular networks

  8. Zingiber officinale attenuates retinal microvascular changes in diabetic rats via anti-inflammatory and antiangiogenic mechanisms

    PubMed Central

    Dongare, Shirish; Mathur, Rajani; Saxena, Rohit; Mathur, Sandeep; Agarwal, Renu; Nag, Tapas C.; Srivastava, Sushma; Kumar, Pankaj

    2016-01-01

    Purpose Diabetic retinopathy is a common microvascular complication of long-standing diabetes. Several complex interconnecting biochemical pathways are activated in response to hyperglycemia. These pathways culminate into proinflammatory and angiogenic effects that bring about structural and functional damage to the retinal vasculature. Since Zingiber officinale (ginger) is known for its anti-inflammatory and antiangiogenic properties, we investigated the effects of its extract standardized to 5% 6-gingerol, the major active constituent of ginger, in attenuating retinal microvascular changes in rats with streptozotocin-induced diabetes. Methods Diabetic rats were treated orally with the vehicle or the ginger extract (75 mg/kg/day) over a period of 24 weeks along with regular monitoring of bodyweight and blood glucose and weekly fundus photography. At the end of the 24-week treatment, the retinas were isolated for histopathological examination under a light microscope, transmission electron microscopy, and determination of the retinal tumor necrosis factor-α (TNF-α), nuclear factor-kappa B (NF-κB), and vascular endothelial growth factor (VEGF) levels. Results Oral administration of the ginger extract resulted in significant reduction of hyperglycemia, the diameter of the retinal vessels, and vascular basement membrane thickness. Improvement in the architecture of the retinal vasculature was associated with significantly reduced expression of NF-κB and reduced activity of TNF-α and VEGF in the retinal tissue in the ginger extract–treated group compared to the vehicle-treated group. Conclusions The current study showed that ginger extract containing 5% of 6-gingerol attenuates the retinal microvascular changes in rats with streptozotocin-induced diabetes through anti-inflammatory and antiangiogenic actions. Although precise molecular targets remain to be determined, 6-gingerol seems to be a potential candidate for further investigation. PMID:27293376

  9. Calculation of transport properties of liquid metals and their alloys via molecular dynamics

    NASA Astrophysics Data System (ADS)

    Cherne, Frank Joseph, III

    The advanced casting modeler requires accurate viscosity and diffusivity data of liquid metals and their alloys. The present work discusses the use of equilibrium and non-equilibrium molecular dynamics techniques to obtain such data without having to rely on oversimplified phenomenological expressions or difficult and expensive experiments. Utilizing the embedded atom method (EAM), the viscosities and diffusivities for a series of equilibrium and non-equilibrium molecular dynamics simulations of nickel, aluminum, and nickel-aluminum alloys are presented. A critical comparison between the equilibrium and non-equilibrium methods is presented. Besides the transport properties, structural data for the liquids are also evaluated. EAM does a poor job of describing the transport properties of nickel-aluminum alloys, particularly near the equiatomic concentration. It has been suggested that charge transfer between nickel and aluminum atoms is responsible for the discrepancy between numerical calculations and available experimental data. A modified electronic distribution function has been developed to simulate the charge transfer associated with compound formation. The effects of such a "charge transfer" modification to the embedded atom method are evaluated. The results of these simulations indicate that the embedded atom method combined with molecular dynamics may be used as a method to predict reasonably the transport properties.

  10. Transport properties of the topological Kondo insulator SmB6 under the irradiation of light

    NASA Astrophysics Data System (ADS)

    Zhu, Guo-Bao; Yang, Hui-Min

    2016-10-01

    In this paper, we study transport properties of the X point in the Brillouin zone of the topological Kondo insulator SmB6 under the application of a circularly polarized light. The transport properties at high-frequency regime and low-frequency regime as a function of the ratio (κ) of the Dresselhaus-like and Rashba-like spin-orbit parameter are studied based on the Floquet theory and Boltzmann equation respectively. The sign of Hall conductivity at high-frequency regime can be reversed by the ratio κ and the amplitude of the light. The amplitude of the current can be enhanced by the ratio κ. Our findings provide a way to control the transport properties of the Dirac materials at low-frequency regime. Project supported by the National Natural Science Foundation of China (Grant Nos. 11504095 and 11447145), the Foundation of Heze University (Grant Nos. XY14B002 and XYPY01), and the Project funded by the Higher Educational Science and Technology Program of Shandong Province, China (Grant No. J15LJ55).

  11. User interface techniques in the counseling module of TOPS (Transportation Operational Personal Property Standard)

    SciTech Connect

    Yow, T.G.

    1989-10-01

    The Transportation Operational Personal Property Standard System (TOPS) is an automated information management system to help administer the personal property transporation program for the Department of Defense (DOD). TOPS was fielded at four prototype sites in the late summer of 1988. Prototype testing is currently underway, with system deployment scheduled for 1989. When fully deployed, TOPS will save DOD both time and money and help ensure that all shipments made by armed services personnel are handled quickly and efficiently. The success of the TOPS system depends upon several key factors. Of course, TOPS must give transportation clerks at military personal property shipping offices a tool with which they can perform their jobs with greater ease, speed, and correctness. However, before TOPS can achieve success in the field, it must first find acceptance from the transportation clerks themselves. The purpose of this document is to examine the user interface techniques used in the Counseling module of TOPS to ensure user acceptance and data base integrity, both key elements in the ultimate success of TOPS. 6 refs., 12 figs.

  12. Origin of electrochemical, structural and transport properties in non-aqueous zinc electrolytes

    DOE PAGES

    Han, Sang -Don; Rajput, Nav Nidhi; Qu, Xiaohui; Pan, Baofei; He, Meinan; Ferrandon, Magali S.; Liao, Chen; Persson, Kristin A.; Burrell, Anthony K.

    2016-01-14

    Through coupled experimental analysis and computational techniques, we uncover the origin of anodic stability for a range of nonaqueous zinc electrolytes. By examination of electrochemical, structural, and transport properties of nonaqueous zinc electrolytes with varying concentrations, it is demonstrated that the acetonitrile Zn(TFSI)2, acetonitrile Zn(CF3SO3)2, and propylene carbonate Zn(TFSI)2 electrolytes can not only support highly reversible Zn deposition behavior on a Zn metal anode (≥99% of Coulombic efficiency), but also provide high anodic stability (up to ~3.8 V). The predicted anodic stability from DFT calculations is well in accordance with experimental results, and elucidates that the solvents play an importantmore » role in anodic stability of most electrolytes. Molecular dynamics (MD) simulations were used to understand the solvation structure (e.g., ion solvation and ionic association) and its effect on dynamics and transport properties (e.g., diffusion coefficient and ionic conductivity) of the electrolytes. Lastly, the combination of these techniques provides unprecedented insight into the origin of the electrochemical, structural, and transport properties in nonaqueous zinc electrolytes« less

  13. Thermodynamic Properties and Transport Coefficients of Nitrogen, Hydrogen and Helium Plasma Mixed with Silver Vapor

    NASA Astrophysics Data System (ADS)

    Zhou, Xue; Cui, Xinglei; Chen, Mo; Zhai, Guofu

    2016-05-01

    Species composites of Ag-N2, Ag-H2 and Ag-He plasmas in the temperature range of 3,000-20,000 K and at 1 atmospheric pressure were calculated by using the minimization of Gibbs free energy. Thermodynamic properties and transport coefficients of nitrogen, hydrogen and helium plasmas mixed with a variety of silver vapor were then calculated based on the equilibrium composites and collision integral data. The calculation procedure was verified by comparing the results obtained in this paper with the published transport coefficients on the case of pure nitrogen plasma. The influences of the silver vapor concentration on composites, thermodynamic properties and transport coefficients were finally analyzed and summarized for all the three types of plasmas. Those physical properties were important for theoretical study and numerical calculation on arc plasma generated by silver-based electrodes in those gases in sealed electromagnetic relays and contacts. supported by National Natural Science Foundation of China (Nos. 51277038 and 51307030)

  14. a universal regulation for the angle resolved transport properties of Dirac cones and beyond

    NASA Astrophysics Data System (ADS)

    Li, Zhenzhu; Liu, Zhirong

    A universal regulation for the angle resolved transport properties of two-dimensional (2D) Dirac cones, such as graphene, graphynes or even beyond, was established for the first time. The anisotropy and isotropy properties of 2D Dirac cones were investigated theoretically combining with first-principles calculation. It was found the moving direction of Dirac cones (θmove) varies with the strain orientation (θq) can be approximately described by a linear law. Moreover, θmove is related the hopping (S12) between two bases with respective to the strain. The coefficients, ax, ay, aγ in the taylor expansion formula of S12 and strain were determined with DFT calculations. Graphene and graphynes were calculated to check the universality of the theory, which turns out to be working well. This new regulation could also be recommended into semiconductive systems to predict their transport behaviors, such as phosphorene or MoS2, whose angle resolved transport properties have been widely investigated experimentally for comparison.

  15. Dispersion stability and electrokinetic properties of intrinsic plutonium colloids: implications for subsurface transport.

    PubMed

    Abdel-Fattah, Amr I; Zhou, Dongxu; Boukhalfa, Hakim; Tarimala, Sowmitri; Ware, S Doug; Keller, Arturo A

    2013-06-01

    Subsurface transport of plutonium (Pu) may be facilitated by the formation of intrinsic Pu colloids. While this colloid-facilitated transport is largely governed by the electrokinetic properties and dispersion stability (resistance to aggregation) of the colloids, reported experimental data is scarce. Here, we quantify the dependence of ζ-potential of intrinsic Pu(IV) colloids on pH and their aggregation rate on ionic strength. Results indicate an isoelectric point of pH 8.6 and a critical coagulation concentration of 0.1 M of 1:1 electrolyte at pH 11.4. The ζ-potential/pH dependence of the Pu(IV) colloids is similar to that of goethite and hematite colloids. Colloid interaction energy calculations using these values reveal an effective Hamaker constant of the intrinsic Pu(IV) colloids in water of 1.85 × 10(-19) J, corresponding to a relative permittivity of 6.21 and refractive index of 2.33, in agreement with first principles calculations. This relatively high Hamaker constant combined with the positive charge of Pu(IV) colloids under typical groundwater aquifer conditions led to two contradicting hypotheses: (a) the Pu(IV) colloids will exhibit significant aggregation and deposition, leading to a negligible subsurface transport or (b) the Pu(IV) colloids will associate with the relatively stable native groundwater colloids, leading to a considerable subsurface transport. Packed column transport experiments supported the second hypothesis.

  16. Transport properties of track-etched membranes having variable effective pore-lengths

    NASA Astrophysics Data System (ADS)

    Nguyen, Quoc Hung; Ali, Mubarak; Nasir, Saima; Ensinger, Wolfgang

    2015-12-01

    The transport rate of molecules through polymeric membranes is normally limited because of their micrometer-scale thickness which restricts their suitability for more practical application. To study the effect of effective pore length on the transport behavior, polymer membranes containing cylindrical and asymmetric-shaped nanopores were prepared through a two-step ion track-etching technique. Permeation experiments were performed separately to investigate the transport properties (molecular flux and selectivity) of these track-etched membranes. The permeation data shows that the molecular flux across membranes containing asymmetric nanopores is higher compared to those having cylindrical pores. On the other hand, the cylindrical pore membranes exhibit higher selectivity than asymmetric pores for the permeation of charged molecules across the membrane. Current-voltage (I-V) measurements of single-pore membranes further verify that asymmetric pores exhibit lower resistance for the flow of ions and therefore show higher currents than cylindrical pores. Moreover, unmodified and polyethyleneimine (PEI) modified asymmetric-shaped pore membranes were successfully used for the separation of cationic and anionic analyte molecules from their mixture, respectively. In this study, two distinct effects (pore geometry and pore density, i.e. number of pores cm-2), which mainly influence membrane selectivity and molecular transport rates, were thoroughly investigated in order to optimize the membrane performance. In this context, we believe that membranes with high molecular transport rates could readily find their application in molecular separation and controlled drug delivery processes.

  17. [Effects of Cultivation Soil Properties on the Transport of Genetically Engineered Microorganism in Huabei Plain].

    PubMed

    Zhang, Jing; Liu, Ping; Liu, Chun; Chen, Xiao-xuan; Zhang, Lei

    2015-12-01

    The transport of genetically engineered microorganism (GEM) in the soil is considered to be the important factor influencing the enhanced bioremediation of polluted soil. The transport of an atrazine-degrading GEM and its influencing factors were investigated in the saturated cultivation soil of Huabei Plain. The results showed that horizontal infiltration was the main mechanism of GEM transport in the saturated cultivation soil. The transport process could be simulated using the filtration model. Soil properties showed significant effects on pore water flow and GEM transport in saturated soil. When particle size, porosity and sand component of the soil increased, the hydraulic conductivity constant increased and filtration coefficient of GEM decreased in saturated soil, indicating the reduced retention of GEM in the soil. An increase in infiltration flow also increased hydraulic conductivity constant in saturated soil and consequently decreased filtration coefficient of GEM. When hydraulic conductivity constants ranged from 5.02 m · d⁻¹ to 6.70 m · d⁻¹ in the saturated soil, the filtration coefficients of GEM varied from 0.105 to 0.274. There was a significantly negative correlation between them. PMID:27012008

  18. [Effects of Cultivation Soil Properties on the Transport of Genetically Engineered Microorganism in Huabei Plain].

    PubMed

    Zhang, Jing; Liu, Ping; Liu, Chun; Chen, Xiao-xuan; Zhang, Lei

    2015-12-01

    The transport of genetically engineered microorganism (GEM) in the soil is considered to be the important factor influencing the enhanced bioremediation of polluted soil. The transport of an atrazine-degrading GEM and its influencing factors were investigated in the saturated cultivation soil of Huabei Plain. The results showed that horizontal infiltration was the main mechanism of GEM transport in the saturated cultivation soil. The transport process could be simulated using the filtration model. Soil properties showed significant effects on pore water flow and GEM transport in saturated soil. When particle size, porosity and sand component of the soil increased, the hydraulic conductivity constant increased and filtration coefficient of GEM decreased in saturated soil, indicating the reduced retention of GEM in the soil. An increase in infiltration flow also increased hydraulic conductivity constant in saturated soil and consequently decreased filtration coefficient of GEM. When hydraulic conductivity constants ranged from 5.02 m · d⁻¹ to 6.70 m · d⁻¹ in the saturated soil, the filtration coefficients of GEM varied from 0.105 to 0.274. There was a significantly negative correlation between them.

  19. Properties and transport of Asian dust from 10 years of MISR data

    NASA Astrophysics Data System (ADS)

    Kalashnikova, O. V.; Sokolik, I. N.; Garay, M. J.; Wu, D. L.

    2009-12-01

    We use the 10-year aerosol data record from the Multi-angle Imaging SpectroRadiometer (MISR) aboard the Terra satellite to investigate climatological linkages between the dust source activities, mid-range, and long-range transport of Asian dust. The inter-annual and seasonal variability of Asian dust loadings and properties as retrieved by MISR at selected regions along the transport routes was investigated. In particular, we examine the Taklamakan and East and Central Gobi regions (dust sources), South Korea and Japan regions (mid-range transport), and the North Pacific region along the northwestern U.S. coast (long-range transport). To avoid the gridding and averaging effects in Level 3 products, we use the Level 2 MISR swath data. Within each selected region, the analysis was performed to examine the multi-annual mean and variability of the aerosol optical depth and particle nonsphericity as well as time-lag correlation between the regions, taking into account the effects of MISR sampling and cloud screening. The results will be presented and interpreted in the context of atmospheric dynamics variability, including variability of meteorological regimes in dust sources and the large-scale atmospheric circulation features controlling the trans-Pacific transport of Asian dust.

  20. Thermal provocation to evaluate microvascular reactivity in human skin

    PubMed Central

    2010-01-01

    With increased interest in predictive medicine, development of a relatively noninvasive technique that can improve prediction of major clinical outcomes has gained considerable attention. Current tests that are the target of critical evaluation, such as flow-mediated vasodilation of the brachial artery and pulse-wave velocity, are specific to the larger conduit vessels. However, evidence is mounting that functional changes in the microcirculation may be an early sign of globalized microvascular dysfunction. Thus development of a test of microvascular reactivity that could be used to evaluate cardiovascular risk or response to treatment is an exciting area of innovation. This mini-review is focused on tests of microvascular reactivity to thermal stimuli in the cutaneous circulation. The skin may prove to be an ideal site for evaluation of microvascular dysfunction due to its ease of access and growing evidence that changes in skin vascular reactivity may precede overt clinical signs of disease. Evaluation of the skin blood flow response to locally applied heat has already demonstrated prognostic utility, and the response to local cooling holds promise in patients in whom cutaneous disorders are present. Whether either of these tests can be used to predict cardiovascular morbidity or mortality in a clinical setting requires further evaluation. PMID:20507974

  1. Xenobiotic Particle Exposure and Microvascular Endpoints: A Call to Arms

    PubMed Central

    Stapleton, Phoebe A.; Minarchick, Valerie C.; McCawley, Michael; Knuckles, Travis L.; Nurkiewicz, Timothy R.

    2011-01-01

    Xenobiotic particles can be considered in two genres: air pollution particulate matter and engineered nanoparticles. Particle exposures can occur in the greater environment, the workplace, and our homes. The majority of research in this field has, justifiably, focused on pulmonary reactions and outcomes. More recent investigations indicate that cardiovascular effects are capable of correlating with established mortality and morbidity epidemiological data following particle exposures. While the preliminary and general cardiovascular toxicology has been defined, the mechanisms behind these effects, specifically within the microcirculation, are largely unexplored. Therefore, the purpose of this review is several fold: first, a historical background on toxicological aspects of particle research is presented. Second, essential definitions, terminology, and techniques that may be unfamiliar to the microvascular scientist will be discussed. Third, the most current concepts and hypotheses driving cardiovascular research in this field will be reviewed. Lastly, potential future directions for the microvascular scientist will be suggested. Collectively speaking, microvascular research in the particle exposure field represents far more than a “niche”. The immediate demand for basic, translational, and clinical studies is high and diverse. Microvascular scientists at all career stages are strongly encouraged to expand their research interests to include investigations associated with particle exposures. PMID:21951337

  2. Functional Properties of the Arabidopsis Peptide Transporters AtPTR1 and AtPTR5*

    PubMed Central

    Hammes, Ulrich Z.; Meier, Stefan; Dietrich, Daniela; Ward, John M.; Rentsch, Doris

    2010-01-01

    The Arabidopsis di- and tripeptide transporters AtPTR1 and AtPTR5 were expressed in Xenopus laevis oocytes, and their selectivity and kinetic properties were determined by voltage clamping and by radioactive uptake. Dipeptide transport by AtPTR1 and AtPTR5 was found to be electrogenic and dependent on protons but not sodium. In the absence of dipeptides, both transporters showed proton-dependent leak currents that were inhibited by Phe-Ala (AtPTR5) and Phe-Ala, Trp-Ala, and Phe-Phe (AtPTR1). Phe-Ala was shown to reduce leak currents by binding to the substrate-binding site with a high apparent affinity. Inhibition of leak currents was only observed when the aromatic amino acids were present at the N-terminal position. AtPTR1 and AtPTR5 transport activity was voltage-dependent, and currents increased supralinearly with more negative membrane potentials and did not saturate. The voltage dependence of the apparent affinities differed between Ala-Ala, Ala-Lys, and Ala-Asp and was not conserved between the two transporters. The apparent affinity of AtPTR1 for these dipeptides was pH-dependent and decreased with decreasing proton concentration. In contrast to most proton-coupled transporters characterized so far, −Imax increased at high pH, indicating that regulation of the transporter by pH overrides the importance of protons as co-substrate. PMID:20937801

  3. Transportation.

    ERIC Educational Resources Information Center

    Crank, Ron

    This instructional unit is one of 10 developed by students on various energy-related areas that deals specifically with transportation and energy use. Its objective is for the student to be able to discuss the implication of energy usage as it applies to the area of transportation. Some topics covered are efficiencies of various transportation…

  4. Crystal Phase- and Orientation-Dependent Electrical Transport Properties of InAs Nanowires.

    PubMed

    Fu, Mengqi; Tang, Zhiqiang; Li, Xing; Ning, Zhiyuan; Pan, Dong; Zhao, Jianhua; Wei, Xianlong; Chen, Qing

    2016-04-13

    We report a systematic study on the correlation of the electrical transport properties with the crystal phase and orientation of single-crystal InAs nanowires (NWs) grown by molecular-beam epitaxy. A new method is developed to allow the same InAs NW to be used for both the electrical measurements and transmission electron microscopy characterization. We find both the crystal phase, wurtzite (WZ) or zinc-blende (ZB), and the orientation of the InAs NWs remarkably affect the electronic properties of the field-effect transistors based on these NWs, such as the threshold voltage (VT), ON-OFF ratio, subthreshold swing (SS) and effective barrier height at the off-state (ΦOFF). The SS increases while VT, ON-OFF ratio, and ΦOFF decrease one by one in the sequence of WZ ⟨0001⟩, ZB ⟨131⟩, ZB ⟨332⟩, ZB ⟨121⟩, and ZB ⟨011⟩. The WZ InAs NWs have obvious smaller field-effect mobility, conductivities, and electron concentration at VBG = 0 V than the ZB InAs NWs, while these parameters are not sensitive to the orientation of the ZB InAs NWs. We also find the diameter ranging from 12 to 33 nm shows much less effect than the crystal phase and orientation on the electrical transport properties of the InAs NWs. The good ohmic contact between InAs NWs and metal remains regardless of the variation of the crystal phase and orientation through temperature-dependent measurements. Our work deepens the understanding of the structure-dependent electrical transport properties of InAs NWs and provides a potential way to tailor the device properties by controlling the crystal phase and orientation of the NWs.

  5. REPRESENTING AEROSOL DYNAMICS AND PROPERTIES IN CHEMICAL TRANSPORT MODELS BY THE METHOD OF MOMENTS.

    SciTech Connect

    SCHWARTZ, S.E.; MCGRAW, R.; BENKOVITZ, C.M.; WRIGHT, D.L.

    2001-04-01

    Atmospheric aerosols, suspensions of solid or liquid particles, are an important multi-phase system. Aerosols scatter and absorb shortwave (solar) radiation, affecting climate (Charlson et al., 1992; Schwartz, 1996) and visibility; nucleate cloud droplet formation, modifying the reflectivity of clouds (Twomey et al., 1984; Schwartz and Slingo, 1996) as well as contributing to composition of cloudwater and to wet deposition (Seinfeld and Pandis, 1998); and affect human health through inhalation (NRC, 1998). Existing and prospective air quality regulations impose standards on concentrations of atmospheric aerosols to protect human health and welfare (EPA, 1998). Chemical transport and transformation models representing the loading and geographical distribution of aerosols and precursor gases are needed to permit development of effective and efficient strategies for meeting air quality standards, and for examining aerosol effects on climate retrospectively and prospectively for different emissions scenarios. Important aerosol properties and processes depend on their size distribution: light scattering, cloud nucleating properties, dry deposition, and penetration into airways of lungs. The evolution of the mass loading itself depends on particle size because of the size dependence of growth and removal processes. For these reasons it is increasingly recognized that chemical transport and transformation models must represent not just the mass loading of atmospheric particulate matter but also the aerosol microphysical properties and the evolution of these properties if aerosols are to be accurately represented in these models. If the size distribution of the aerosol is known, a given property can be evaluated as the integral of the appropriate kernel function over the size distribution. This has motivated the approach of determining aerosol size distribution, and of explicitly representing this distribution and its evolution in chemical transport models.

  6. Crystal Phase- and Orientation-Dependent Electrical Transport Properties of InAs Nanowires.

    PubMed

    Fu, Mengqi; Tang, Zhiqiang; Li, Xing; Ning, Zhiyuan; Pan, Dong; Zhao, Jianhua; Wei, Xianlong; Chen, Qing

    2016-04-13

    We report a systematic study on the correlation of the electrical transport properties with the crystal phase and orientation of single-crystal InAs nanowires (NWs) grown by molecular-beam epitaxy. A new method is developed to allow the same InAs NW to be used for both the electrical measurements and transmission electron microscopy characterization. We find both the crystal phase, wurtzite (WZ) or zinc-blende (ZB), and the orientation of the InAs NWs remarkably affect the electronic properties of the field-effect transistors based on these NWs, such as the threshold voltage (VT), ON-OFF ratio, subthreshold swing (SS) and effective barrier height at the off-state (ΦOFF). The SS increases while VT, ON-OFF ratio, and ΦOFF decrease one by one in the sequence of WZ ⟨0001⟩, ZB ⟨131⟩, ZB ⟨332⟩, ZB ⟨121⟩, and ZB ⟨011⟩. The WZ InAs NWs have obvious smaller field-effect mobility, conductivities, and electron concentration at VBG = 0 V than the ZB InAs NWs, while these parameters are not sensitive to the orientation of the ZB InAs NWs. We also find the diameter ranging from 12 to 33 nm shows much less effect than the crystal phase and orientation on the electrical transport properties of the InAs NWs. The good ohmic contact between InAs NWs and metal remains regardless of the variation of the crystal phase and orientation through temperature-dependent measurements. Our work deepens the understanding of the structure-dependent electrical transport properties of InAs NWs and provides a potential way to tailor the device properties by controlling the crystal phase and orientation of the NWs. PMID:27002386

  7. Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Denjean, C.; Cassola, F.; Mazzino, A.; Triquet, S.; Chevaillier, S.; Grand, N.; Bourrianne, T.; Momboisse, G.; Sellegri, K.; Schwarzenbock, A.; Freney, E.; Mallet, M.; Formenti, P.

    2015-08-01

    This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June-July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of tranport (1-5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried higher concentration of pollution particles at intermediate altitude (1-3 km) than at elevated altitude (> 3 km), resulting in scattering Angstrom exponent up to 2.2 within the intermediate altitude. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate light absorption of the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00 ± 0.04. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assimilated to those of native dust in radiative transfer simulations, modeling studies and

  8. Representative equations for the thermodynamic and transport properties of fluids near the gas-liquid critical point

    NASA Technical Reports Server (NTRS)

    Sengers, J. V.; Basu, R. S.; Sengers, J. M. H. L.

    1981-01-01

    A survey is presented of representative equations for various thermophysical properties of fluids in the critical region. Representative equations for the transport properties are included. Semi-empirical modifications of the theoretically predicted asymtotic critical behavior that yield simple and practical representations of the fluid properties in the critical region are emphasized.

  9. A Novel Microvascular Flow Technique: Initial Results in Thyroids.

    PubMed

    Machado, Priscilla; Segal, Sharon; Lyshchik, Andrej; Forsberg, Flemming

    2016-03-01

    To evaluate the flow imaging capabilities of a new prototype ultrasound (US) image processing technique (superb micro-vascular imaging [SMI]; Toshiba Medical Systems, Tokyo, Japan) for depiction of microvascular flow in normal thyroid tissue and thyroid nodules compared with standard color and power Doppler US imaging.Ten healthy volunteers and 22 patients, with a total of 25 thyroid nodules, scheduled for US-guided fine needle aspiration were enrolled in this prospective study. Subjects underwent US examination consisting of grayscale, color and power Doppler imaging (CDI and PDI) followed by color and monochrome SMI and pulsed Doppler. SMI is a novel, microvascular flow imaging mode implemented on the Aplio 500 US system (Toshiba). SMI uses advanced clutter suppression to extract flow signals from large to small vessels and depicts this information at high frame rates as a color overlay image or as a monochrome map of flow. Two radiologists independently scored still images and digital clips for overall flow detection, vessel branching details and noise on a visual-analog scale of 1 (worst) to 10 (best).For the volunteers SMI visualized microvasculature with significantly lower velocity than CDI and PDI (P < 0.012). In all thyroid nodules, SMI demonstrated microvascular flow with significantly higher image scores and provided better depiction of the vessel branching details compared with CDI and PDI (P < 0.0001). Clutter noise was significantly higher in monochrome SMI mode than in the other modes, including color SMI (P < 0.001).The novel SMI mode consistently improved the depiction of thyroid microvascular flow compared with standard CDI and PDI.

  10. A Novel Microvascular Flow Technique: Initial Results in Thyroids.

    PubMed

    Machado, Priscilla; Segal, Sharon; Lyshchik, Andrej; Forsberg, Flemming

    2016-03-01

    To evaluate the flow imaging capabilities of a new prototype ultrasound (US) image processing technique (superb micro-vascular imaging [SMI]; Toshiba Medical Systems, Tokyo, Japan) for depiction of microvascular flow in normal thyroid tissue and thyroid nodules compared with standard color and power Doppler US imaging.Ten healthy volunteers and 22 patients, with a total of 25 thyroid nodules, scheduled for US-guided fine needle aspiration were enrolled in this prospective study. Subjects underwent US examination consisting of grayscale, color and power Doppler imaging (CDI and PDI) followed by color and monochrome SMI and pulsed Doppler. SMI is a novel, microvascular flow imaging mode implemented on the Aplio 500 US system (Toshiba). SMI uses advanced clutter suppression to extract flow signals from large to small vessels and depicts this information at high frame rates as a color overlay image or as a monochrome map of flow. Two radiologists independently scored still images and digital clips for overall flow detection, vessel branching details and noise on a visual-analog scale of 1 (worst) to 10 (best).For the volunteers SMI visualized microvasculature with significantly lower velocity than CDI and PDI (P < 0.012). In all thyroid nodules, SMI demonstrated microvascular flow with significantly higher image scores and provided better depiction of the vessel branching details compared with CDI and PDI (P < 0.0001). Clutter noise was significantly higher in monochrome SMI mode than in the other modes, including color SMI (P < 0.001).The novel SMI mode consistently improved the depiction of thyroid microvascular flow compared with standard CDI and PDI. PMID:25900162

  11. Graphene transport properties upon exposure to PMMA processing and heat treatments

    NASA Astrophysics Data System (ADS)

    Gammelgaard, Lene; Caridad, José M.; Cagliani, Alberto; Mackenzie, David M. A.; Petersen, Dirch H.; Booth, Timothy J.; Bøggild, Peter

    2014-12-01

    The evolution of graphene's electrical transport properties due to processing with the polymer polymethyl methacrylate (PMMA) and heat are examined in this study. The use of stencil (shadow mask) lithography enables fabrication of graphene devices without the usage of polymers, chemicals or heat, allowing us to measure the evolution of the electrical transport properties during individual processing steps from the initial as-exfoliated to the PMMA-processed graphene. Heating generally promotes the conformation of graphene to SiO2 and is found to play a major role for the electrical properties of graphene while PMMA residues are found to be surprisingly benign. In accordance with this picture, graphene devices with initially high carrier mobility tend to suffer a decrease in carrier mobility, while in contrast an improvement is observed for low carrier mobility devices. We explain this by noting that flakes conforming poorly to the substrate will have a higher carrier mobility which will however be reduced as heat treatment enhance the conformation. We finally show the electrical properties of graphene to be reversible upon heat treatments in air up to 200 °C.

  12. Transport and Thermoelectric Properties of Ca3Co4O9 Thin Films

    NASA Astrophysics Data System (ADS)

    Hu, Yufeng; Si, Weidong; Sutter, Eli; Sabatini, Robert

    2005-03-01

    It has been discovered recently that cobaltates have very large thermoelectric power, which shows that cobaltates hold great promise to be potential integrated heating spreading solution, such as thermal management of microprocessors. Among the cobaltates, Ca3Co4O9 and Ca2Co2O5 are exhibiting best thermoelectric properties. The ZT value for these calcium-cobaltates reaches as high as 2.7 at T >= 873 K, which clearly challenges the best conventional thermoelectric materials found in intermetallic compounds, such as Bi2Te3/Sb2Te3 alloys. The purpose of this work is to study the transport and thermoelectric properties of Ca3Co4O9 thin films. We have successfully grown the Ca3Co4O9 c-axis orientated thin films using Pulsed Laser Deposition (PLD) technique on various substrates, including Si, LaAlO3, Al2O3. The resistivity and thermoelectric power measurements show that these films have superior thermoelectric properties, similar to that found in the bulk samples. The detailed transport and thermoelectric properties of Ca3Co4O9 thin films will be discussed. This work was supported by the U. S. Dept. of Energy, Office of Basic Energy Science, under contract No. DE-AC-02-98CH10886.

  13. Computational Study of the Thermal and Electronic Transport Properties of Rigidly-Interconnected Carbon Nano Foam

    NASA Astrophysics Data System (ADS)

    Park, Sora; Kwon, Young-Kyun; Tománek, David

    2012-02-01

    We study the thermal and electronic transport properties of rigidly-interconnected structures having sp^2 carbon minimal surface called schwarzites. The system consists of core parts composed of schwarzite and interconnection parts with (4,4) carbon nanotube segments [1]. Using direct molecular dynamics simulations with the Tersoff potential, we compute the thermal conductivity of various configurations to explore the dependence on the number of core parts and on the length of interconnection parts. Our calculations show that each core part plays as a scattering center, which reduces the phonon mean free path and thus the thermal conductivity. We also investigate the electronic transport properties of the system by applying the non-equilibrium Green function approach in combination with density functional theory. We explore the effects of different core connectivity and structural defects introduced near the core parts on the electrical conductance. These thermal and electonic properties may be connected to the thermoelectric properties of the schwarzite system.[1] S. Park, K. Kittimanapun, J. S. Ahn, Y.-K. Kwon and D. Tom'anek, J. Phys.: Condens. Matter 22, 334220 (2010).

  14. Radiation Transport Properties of Potential In Situ-Developed Regolith-Epoxy Materials for Martian Habitats

    NASA Technical Reports Server (NTRS)

    Miller, J.; Heilbronn, L.; Singleterry, R. C., Jr.; Thibeault, S. A.; Wilson, J. W.; Zeitlin, C. J.

    2001-01-01

    We will evaluate the radiation transport properties of epoxy-martian regolith composites. Such composites, which would use both in situ materials and chemicals fabricated from elements found in the martian atmosphere, are candidates for use in habitats on Mars. The principal objective is to evaluate the transmission properties of these materials with respect to the protons and heavy charged particles in the galactic cosmic rays which bombard the martian surface. The secondary objective is to evaluate fabrication methods which could lead to technologies for in situ fabrication. The composites will be prepared by NASA Langley Research Center using simulated martian regolith. Initial evaluation of the radiation shielding properties will be made using transport models developed at NASA-LaRC and the results of these calculations will be used to select the composites with the most favorable radiation transmission properties. These candidates will then be empirically evaluated at particle accelerators which produce beams of protons and heavy charged particles comparable in energy to the radiation at the surface of Mars.

  15. Effects of the proximity of Au nanoparticles on magnetic and transport properties of LSMO ultrathin layers

    SciTech Connect

    Brivio, S.; Magen Dominguez, Cesar; Sidorenko, A; Petti, D.; Cantoni, M.; Finazzi, M; Ciccacci, F; Renzi, R; Varela del Arco, Maria; Picozzi, S.; Bertacco, R.

    2010-01-01

    The effect of the proximity of Au nanoparticles on the transport and magnetic properties of ultrathin La2/3Sr1/3MnO3 (LSMO) films has been investigated. We find a huge increase of the resistivity of the manganite (by four orders of magnitude for a Au nominal thickness of 2 nm), which is accompanied by a strong decrease of the Curie temperature. A combined scanning transmission electron microscopy and electron energy loss spectroscopy (STEM-EELS) analysis shows that interfaces are coherent and atomically sharp, and that the structural quality is very high. On the other end, a strong reduction of the Mn oxidation state is seen upon Au capping. NMR data show a strong attenuation of the double exchange signal upon formation of Au nanoparticles. Ab-initio calculations indicate a negligible influence of Au on LSMO at an ideal interface, with the LSMO surface magnetic and electronic properties essentially unchanged upon creation of the Au/LSMO interface. In view of these calculations, the experimental results cannot be explained in terms of purely electrostatic effects induced by the proximity of a noble metal. Here we propose that the main driving force underlying the observed change in physical properties is the high reactivity of Au nanoparticles which can locally pump oxygen from the manganite, thus favouring a phase separation ensuing from O inhomogeneity which deteriorates the transport and electrical properties.

  16. Performance assessment of several equations of state and second virial coefficients in modified Enskog theory: Results for transport properties

    NASA Astrophysics Data System (ADS)

    Kiani, M.; Alavianmehr, M. M.; Otoofat, M.; Mohsenipour, A. A.; Ghatee, A.

    2015-11-01

    In this work, we identify a simple method for predicting transport properties of fluids over wide ranges of temperatures and pressure. In this respect, the capability of several equations of state (EOS) and second virial coefficient correlations to predict transport properties of fluids including carbon dioxide, methane and argon using modified Enskog theory (MET) is investigated. The transport properties in question are viscosity and thermal conductivity. The results indicate that the SRK EOS employed in the modified Enskog theory outperforms other equations of state. The average absolute deviation was found to be 12.2 and 18.5% for, respectively, the calculated thermal conductivity and viscosity using the MET.

  17. Tuning The Optical, Charge Injection, and Charge Transport Properties of Organic Electronic Devices

    NASA Astrophysics Data System (ADS)

    Zalar, Peter

    Since the early 1900's, synthetic insulating polymers (plastics) have slowly taken over the role that traditional materials like wood or metal have had as basic components for construction, manufactured goods, and parts. Plastics allow for high throughput, low temperature processing, and control of bulk properties through molecular modifications. In the same way, pi-conjugated organic molecules are emerging as a possible substitute for inorganic materials due to their electronic properties. The semiconductive nature of pi-conjugated materials make them an attractive candidate to replace inorganic materials, primarily due to their promise for low cost and large-scale production of basic semiconducting devices such as light-emitting diodes, solar cells, and field-effect transistors. Before organic semiconductors can be realized as a commercial product, several hurdles must be cleared. The purpose of this dissertation is to address three distinct properties that dominate the functionality of devices harnessing these materials: (1) optical properties, (2) charge injection, and (3) charge transport. First, it is shown that the electron injection barrier in the emissive layer of polymer light-emitting diodes can be significantly reduced by processing of novel conjugated oligoelectrolytes or deoxyribonucleic acid atop the emissive layer. Next, the charge transport properties of several polymers could be modified by processing them from solvents containing small amounts of additives or by using regioregular and enantiopure chemical structures. It is then demonstrated that the optical and electronic properties of Lewis basic polymer structures can be readily modified by interactions with strongly electron-withdrawing Lewis acids. Through red-shifted absorption, photoluminescence, and electroluminescence, a single pi-conjugated backbone can be polychromatic. In addition, interaction with Lewis acids can remarkably p-dope the hole transport of the parent polymer, leading to a

  18. Computer codes for the evaluation of thermodynamic and transport properties for equilibrium air to 30000 K

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    The computer codes developed here provide self-consistent thermodynamic and transport properties for equilibrium air for temperatures from 500 to 30000 K over a temperature range of 10 (exp -4) to 10 (exp -2) atm. These properties are computed through the use of temperature dependent curve fits for discrete values of pressure. Interpolation is employed for intermediate values of pressure. The curve fits are based on mixture values calculated from an 11-species air model. Individual species properties used in the mixture relations are obtained from a recent study by the present authors. A review and discussion of the sources and accuracy of the curve fitted data used herein are given in NASA RP 1260.

  19. Computer programs for thermodynamic and transport properties of hydrogen (tabcode-II)

    NASA Technical Reports Server (NTRS)

    Roder, H. M.; Mccarty, R. D.; Hall, W. J.

    1972-01-01

    The thermodynamic and transport properties of para and equilibrium hydrogen have been programmed into a series of computer routines. Input variables are the pair's pressure-temperature and pressure-enthalpy. The programs cover the range from 1 to 5000 psia with temperatures from the triple point to 6000 R or enthalpies from minus 130 BTU/lb to 25,000 BTU/lb. Output variables are enthalpy or temperature, density, entropy, thermal conductivity, viscosity, at constant volume, the heat capacity ratio, and a heat transfer parameter. Property values on the liquid and vapor boundaries are conveniently obtained through two small routines. The programs achieve high speed by using linear interpolation in a grid of precomputed points which define the surface of the property returned.

  20. Mechanical and transport properties of IBAD/EDDC-SmBCO coated conductor tapes during fatigue loading

    NASA Astrophysics Data System (ADS)

    Shin, Hyung-Seop; Dedicatoria, Marlon J.

    2011-06-01

    In electrical devices like superconducting motor, generator and SMES, HTS coated conductor (CC) tapes will be subjected to alternating stress or strain during manufacturing and operation. The repeated loading will affect the mechanical integrity and eventually the electrical transport property of CC tapes. Therefore in such applications, electro-mechanical property of CC tapes should be evaluated. In this study, the endurance of an IBAD/EDDC-SmBCO CC tape under high-cycle fatigue loading has been evaluated. Applied maximum stress and fatigue life ( S-N) relation was obtained at 77 K. The mechanical properties and the critical current, I c, of the sample under fatigue loading were investigated at 77 K. Considering the practical operating environment, the effect of the stress ratio R, on the degradation behavior of I c under fatigue loading was also examined.

  1. Strain-modulated electronic and thermal transport properties of two-dimensional O-silica

    NASA Astrophysics Data System (ADS)

    Han, Yang; Qin, Guangzhao; Jungemann, Christoph; Hu, Ming

    2016-07-01

    Silica is one of the most abundant materials in the Earth’s crust and is a remarkably versatile and important engineering material in various modern science and technology. Recently, freestanding and well-ordered two-dimensional (2D) silica monolayers with octahedral (O-silica) building blocks were found to be theoretically stable by (Wang G et al 2015 J. Phys. Chem. C 119 15654-60). In this paper, by performing first-principles calculations, we systematically investigated the electronic and thermal transport properties of 2D O-silica and also studied how these properties can be tuned by simple mechanical stretching. Unstrained 2D O-silica is an insulator with an indirect band gap of 6.536 eV. The band gap decreases considerably with bilateral strain up to 29%, at which point a semiconductor-metal transition occurs. More importantly, the in-plane thermal conductivity of freestanding 2D O-silica is found to be unusually high, which is around 40 to 50 times higher than that of bulk α-quartz and more than two orders of magnitude higher than that of amorphous silica. The thermal conductivity of O-silica decreases by almost two orders of magnitude when the bilateral stretching strain reaches 10%. By analyzing the mode-dependent phonon properties and phonon-scattering channel, the phonon lifetime is found to be the dominant factor that leads to the dramatic decrease of the lattice thermal conductivity under strain. The very sensitive response of both band gap and phonon transport properties to the external mechanical strain will enable 2D O-silica to easily adapt to the different environment of realistic applications. Our study is expected to stimulate experimental exploration of further physical and chemical properties of 2D silica systems, and offers perspectives on modulating the electronic and thermal properties of related low-dimensional structures for applications such as thermoelectric, photovoltaic, and optoelectronic devices.

  2. Strain-modulated electronic and thermal transport properties of two-dimensional O-silica.

    PubMed

    Han, Yang; Qin, Guangzhao; Jungemann, Christoph; Hu, Ming

    2016-07-01

    Silica is one of the most abundant materials in the Earth's crust and is a remarkably versatile and important engineering material in various modern science and technology. Recently, freestanding and well-ordered two-dimensional (2D) silica monolayers with octahedral (O-silica) building blocks were found to be theoretically stable by (Wang G et al 2015 J. Phys. Chem. C 119 15654-60). In this paper, by performing first-principles calculations, we systematically investigated the electronic and thermal transport properties of 2D O-silica and also studied how these properties can be tuned by simple mechanical stretching. Unstrained 2D O-silica is an insulator with an indirect band gap of 6.536 eV. The band gap decreases considerably with bilateral strain up to 29%, at which point a semiconductor-metal transition occurs. More importantly, the in-plane thermal conductivity of freestanding 2D O-silica is found to be unusually high, which is around 40 to 50 times higher than that of bulk α-quartz and more than two orders of magnitude higher than that of amorphous silica. The thermal conductivity of O-silica decreases by almost two orders of magnitude when the bilateral stretching strain reaches 10%. By analyzing the mode-dependent phonon properties and phonon-scattering channel, the phonon lifetime is found to be the dominant factor that leads to the dramatic decrease of the lattice thermal conductivity under strain. The very sensitive response of both band gap and phonon transport properties to the external mechanical strain will enable 2D O-silica to easily adapt to the different environment of realistic applications. Our study is expected to stimulate experimental exploration of further physical and chemical properties of 2D silica systems, and offers perspectives on modulating the electronic and thermal properties of related low-dimensional structures for applications such as thermoelectric, photovoltaic, and optoelectronic devices. PMID:27199352

  3. Strain-modulated electronic and thermal transport properties of two-dimensional O-silica

    NASA Astrophysics Data System (ADS)

    Han, Yang; Qin, Guangzhao; Jungemann, Christoph; Hu, Ming

    2016-07-01

    Silica is one of the most abundant materials in the Earth’s crust and is a remarkably versatile and important engineering material in various modern science and technology. Recently, freestanding and well-ordered two-dimensional (2D) silica monolayers with octahedral (O-silica) building blocks were found to be theoretically stable by (Wang G et al 2015 J. Phys. Chem. C 119 15654–60). In this paper, by performing first-principles calculations, we systematically investigated the electronic and thermal transport properties of 2D O-silica and also studied how these properties can be tuned by simple mechanical stretching. Unstrained 2D O-silica is an insulator with an indirect band gap of 6.536 eV. The band gap decreases considerably with bilateral strain up to 29%, at which point a semiconductor–metal transition occurs. More importantly, the in-plane thermal conductivity of freestanding 2D O-silica is found to be unusually high, which is around 40 to 50 times higher than that of bulk α-quartz and more than two orders of magnitude higher than that of amorphous silica. The thermal conductivity of O-silica decreases by almost two orders of magnitude when the bilateral stretching strain reaches 10%. By analyzing the mode-dependent phonon properties and phonon-scattering channel, the phonon lifetime is found to be the dominant factor that leads to the dramatic decrease of the lattice thermal conductivity under strain. The very sensitive response of both band gap and phonon transport properties to the external mechanical strain will enable 2D O-silica to easily adapt to the different environment of realistic applications. Our study is expected to stimulate experimental exploration of further physical and chemical properties of 2D silica systems, and offers perspectives on modulating the electronic and thermal properties of related low-dimensional structures for applications such as thermoelectric, photovoltaic, and optoelectronic devices.

  4. Dynamic Evolution of Cement Composition and Transport Properties under Conditions Relevant to Geological Carbon Sequestration

    SciTech Connect

    Brunet, Jean-Patrick Leopold; Li, Li; Karpyn, Zuleima T; Strazisar, Brian; Grant, Bromhal

    2013-08-01

    Assessing the possibility of CO{sub 2} leakage is one of the major challenges for geological carbon sequestration. Injected CO{sub 2} can react with wellbore cement, which can potentially change cement composition and transport properties. In this work, we develop a reactive transport model based on experimental observations to understand and predict the property evolution of cement in direct contact with CO{sub 2}-saturated brine under diffusion-controlled conditions. The model reproduced the observed zones of portlandite depletion and calcite formation. Cement alteration is initially fast and slows down at later times. This work also quantified the role of initial cement properties, in particular the ratio of the initial portlandite content to porosity (defined here as φ), in determining the evolution of cement properties. Portlandite-rich cement with large φ values results in a localized “sharp” reactive diffusive front characterized by calcite precipitation, leading to significant porosity reduction, which eventually clogs the pore space and prevents further acid penetration. Severe degradation occurs at the cement–brine interface with large φ values. This alteration increases effective permeability by orders of magnitude for fluids that preferentially flow through the degraded zone. The significant porosity decrease in the calcite zone also leads to orders of magnitude decrease in effective permeability, where fluids flow through the low-permeability calcite zone. The developed reactive transport model provides a valuable tool to link cement–CO{sub 2} reactions with the evolution of porosity and permeability. It can be used to quantify and predict long-term wellbore cement behavior and can facilitate the risk assessment associated with geological CO{sub 2} sequestration.

  5. Electrical and thermal transport properties of layered Bi2YO4Cu2Se2

    NASA Astrophysics Data System (ADS)

    Xiao, Yu; Pei, Yanling; Chang, Cheng; Zhang, Xiao; Tan, Xing; Ye, Xinxin; Gong, Shengkai; Lin, Yuanhua; He, Jiaqing; Zhao, Li-Dong

    2016-07-01

    Bi2YO4Cu2Se2 possesses a low thermal conductivity and high electrical conductivity at room temperature, which was considered as a potential thermoelectric material. In this work, we have investigated the electrical and thermal transport properties of Bi2YO4Cu2Se2 system in the temperature range from 300 K to 873 K. We found that the total thermal conductivity decreases from ~1.8 W m-1 K-1 to ~0.9 W m-1 K-1, and the electrical conductivity decreases from ~850 S/cm to ~163 S/cm in the measured temperature range. To investigate how potential of Bi2YO4Cu2Se2 system, we prepared the heavily Iodine doped samples to counter-dope intrinsically high carrier concentration and improve the electrical transport properties. Interestingly, the Seebeck coefficient could be enhanced to ~+80 μV/K at 873 K, meanwhile, we found that a low thermal conductivity of ~0.7 W m-1 K-1 could be achieved. The intrinsically low thermal conductivity in this system is related to the low elastic properties, such as Young's modulus of 70-72 GPa, and Grüneisen parameters of 1.55-1.71. The low thermal conductivity makes Bi2YO4Cu2Se2 system to be a potential thermoelectric material, the ZT value ~0.06 at 873 K was obtained, a higher performance is expected by optimizing electrical transport properties through selecting suitable dopants, modifying band structures or by further reducing thermal conductivity through nanostructuring etc.

  6. Mixing rules for optical and transport properties of warm, dense matter

    SciTech Connect

    Kress, Joel D; Horner, Daniel A; Collins, Lee A

    2009-01-01

    The warm, dense matter (WDM) regime requires a sophisticated treatment since neither ideal gas laws or fully ionized plasma models apply. Mixtures represent the predominant form of matter throughout the universe and the ability to predict the properties of a mixture, though direct simulation or from convolution of the properties of the constituents is both a challenging prospect and an important goal. Through quantum molecular dynamics (QMD), we accurately simulate WDM and compute equations of state, transport, and optical properties of such materials, including mixtures, in a self-consistent manner from a single simulation. With the ability to directly compute the mixture properties, we are able to validate mixing rules for combining the optical and dynamical properties of Li and H separately to predict the properties of lithium hydride (LiH). We have examined two such mixing rules and extend them to morphologies beyond a simple liquid alloy. We have also studied a mixture of polyethylene and aluminum at T = 1 eV.

  7. Mixing Rules for Optical and Transport Properties of Warm, Dense Matter

    NASA Astrophysics Data System (ADS)

    Kress, J. D.; Horner, D. A.; Collins, L. A.

    2009-12-01

    The warm, dense matter (WDM) regime requires a sophisticated treatment, since neither ideal gas laws or fully ionized plasma models apply. Mixtures represent the predominant form of matter throughout the universe and the ability to predict the properties of a mixture, through direct simulation or from convolution of the properties of the constituents is both a challenging prospect and an important goal. Through quantum molecular dynamics, we accurately simulate WDM and compute equations of state, transport, and optical properties of such materials, including mixtures, in a self-consistent manner from a single simulation. With the ability to directly compute the mixture properties, we are able to validate mixing rules for combining the optical and dynamical properties of Li and H separately to predict the properties of lithium hydride (LiH). We have examined two such mixing rules and extend them to morphologies beyond a simple liquid alloy. We have also studied a mixture of polyethylene and aluminum at T = 1 eV.

  8. Mixing Rules for Optical and Transport Properties of Warm, Dense Matter

    NASA Astrophysics Data System (ADS)

    Kress, Joel; Horner, Daniel; Collins, Lee

    2009-06-01

    Warm, dense matter (WDM) is a regime that requires sophisticated treatment; it is not well described by ideal gas laws or plasma models. A myriad of physical systems fall under the WDM umbrella, from the element ratios in large gas planets and the cooling of white dwarf stars to energy transfer in inertial confinement fusion plasmas and materials under shock compression. Mixtures represent the predominant form of matter throughout the universe and the ability to predict the properties of a mixture, through direct simulation or from convolution of the properties of the constituents is both a challenging prospect and an important goal. Through quantum molecular dynamics (QMD), we can accurately simulate WDM and compute equation of state, transport, and optical properties of such materials, including mixtures, in a self-consistent way from a single simulation. With the ability to directly compute the full mixture properties, we are able to validate mixing rules for combining the optical and dynamical properties of Li and H separately to predict the properties of lithium hydride (LiH). We have looked at two such mixing rules and extend them to morphologies beyond a simple liquid alloy. We have also studied shock compressed methane and polyethylene, where we have looked at the effect of impurities.

  9. Transport properties of WSe2 nanotube heterojunctions: A first-principles study

    NASA Astrophysics Data System (ADS)

    Yu, Zhizhou; Wang, Jian

    2015-05-01

    Using the nonequilibrium Green's function method within the framework of density functional theory, we investigate various transport properties, such as I -V characteristics, shot noise, thermopower, dynamical conductance, of Au- and Na-encapsulated WSe2 nanotube heterojunctions. First-principles transport calculations show that from I -V curves large rectification ratio is found in the (8,0) heterojunction and for shot noise it exhibits sub-Poissonian behaviors under positive biases (on Au-encapsulated tubes) while Poissonian behaviors are found under negative biases. For thermopower, it is found that as one sweeps the Fermi energy, the thermopower can change its sign. For dynamic conductance, the (5,5) heterojunction exhibits capacitivelike behavior. We find that the spin-orbit interaction (SOI) is very important for WSe2 nanotubes. Due to the band splitting originated from SOI, the intrinsic band gap of Au-doped (5,5) nanotube is reduced by about 58% and that of the Na-doped system vanishes, while that of the doped (8,0) nanotubes decreases by about 40%. The reduction of band gap has an important impact on the transport properties. For instance, the transmission gap is decreased by about 48% and 16% in the transmission spectrum of the (5,5) and (8,0) heterojunctions, respectively. The current of the (5,5) heterojunction under small bias is almost doubled and the rectification ratio of the (8,0) heterojunction is enhanced by more than 120% due to SOI.

  10. Research Update: Structural and transport properties of (Ca,La)FeAs2 single crystal

    NASA Astrophysics Data System (ADS)

    Caglieris, F.; Sala, A.; Fujioka, M.; Hummel, F.; Pallecchi, I.; Lamura, G.; Johrendt, D.; Takano, Y.; Ishida, S.; Iyo, A.; Eisaki, H.; Ogino, H.; Yakita, H.; Shimoyama, J.; Putti, M.

    2016-02-01

    Structural and transport properties in the normal and superconducting states are investigated in a Ca0.8La0.2FeAs2 single crystal with Tc = 27 K, belonging to the newly discovered 112 family of iron based superconductors. The transport critical current density Jc for both field directions measured in a focused ion beam patterned microbridge reveals a weakly field dependent and low anisotropic behaviour with a low temperature value as high as Jc(B = 0) ˜ 105 A/cm2. This demonstrates not only bulk superconductivity but also the potential of 112 superconductors towards applications. Interestingly, this superconducting compound undergoes a structural transition below 100 K which is evidenced by temperature-dependent X-ray diffraction measurements. Data analysis of Hall resistance and magnetoresistivity indicate that magnetotransport properties are largely dominated by an electron band, with a change of regime observed in correspondence of the onset of a structural transition. In the low temperature regime, the contribution of a hole band to transport is suggested, possibly playing a role in determining the superconducting state.

  11. Literature Survey of Crude Oil Properties Relevant to Handling and Fire Safety in Transport.

    SciTech Connect

    Lord, David; Luketa, Anay; Wocken, Chad; Schlasner, Steve; Aulich, Ted; Allen, Ray; Rudeen, David Keith

    2015-03-01

    Several fiery rail accidents in 2013-2015 in the U.S. and Canada carrying crude oil produced from the Bakken region of North Dakota have raised questions at many levels on the safety of transporting this, and other types of crude oil, by rail. Sandia National Laboratories was commissioned by the U.S. Department of Energy to investigate the material properties of crude oils, and in particular the so-called "tight oils" like Bakken that comprise the majority of crude oil rail shipments in the U.S. at the current time. The current report is a literature survey of public sources of information on crude oil properties that have some bearing on the likelihood or severity of combustion events that may occur around spills associated with rail transport. The report also contains background information including a review of the notional "tight oil" field operating environment, as well a basic description of crude oils and potential combustion events in rail transport. This page intentionally blank

  12. A comparative investigation of trap-limited hole transport properties in organic bulk heterojunctions

    NASA Astrophysics Data System (ADS)

    Li, Bixin; Chen, Jiangshan; Yang, Dezhi; Ma, Dongge

    2011-11-01

    We have investigated the bulk hole transport properties of copper phthalocyanine (CuPc):fullerene (C60) and zinc phthalocyanine (ZnPc):C60 bulk heterojunctions by analyzing thickness- and temperature-dependent current density-voltage (J-V) characteristics in hole-only device configurations, i.e. indium-tin-oxide (ITO)/poly(ethylene-dioxythiophene):polystyrenesulphonate (PEDOT:PSS)/CuPc: C60 or ZnPc:C60/molybdenum oxide (MoO3)/Al. It has been found that the hole transport is governed by a space-charge-limited current (SCLC) model in the presence of exponentially distributed traps within the bandgap. The hole mobility of CuPc:C60 mixture (1 × 10-5 cm2 V-1 s-1) is higher than that of ZnPc:C60 mixture (6.2 × 10-6 cm2 V-1 s-1), which can be ascribed to the differences of the characteristic trap energy and the total density of traps in both bulk heterojunctions. These results indicate that the SCLC method is applicable for studying the transport properties in organic bulk heterojunction.

  13. Transport properties for an electroneutral Yukawa-type fluid in the MSA

    NASA Astrophysics Data System (ADS)

    Montes-Perez, J.; Herrera, J. N.

    2014-01-01

    In the framework of a linear response theory, in which Onsager’s continuity equations are combined with the Mean Spherical Approximation (MSA) from the theory of correlation functions in equilibrium, and using a Green’s function formalism, we consider the transport properties of electrolytes. The interaction between the ions in the electrolyte is represented by an intermolecular Yukawa potential which satisfies the electroneutrality condition. The model contains an adjustable parameter z which takes into account the effects of the solvent. Transport processes in an ionic solution are determined by two dominant forces: the relaxation and the electrophoretic forces; their contributions to the transport properties are calculated using the Fuoss-Onsager theory. We find the conductivity and the self-diffusion coefficient for a family of electrolytes using the linear response theory. The predictions of our model can be adjusted by means of the parameter z. The electrophoretic effect, due to the hydrodynamic interaction between the ions, is calculated using the Rotne-Prager tensor. Our theoretical results are in good agreement with experimental data for electrolytes 1-1, even for high concentrations. We applied this theory also to two unsymmetrical electrolytes, namely the aqueous solutions of MgCl2 and CaCl2, with results in good accord with experimental data.

  14. Empirical investigation of topological and weighted properties of a bus transport network from China

    NASA Astrophysics Data System (ADS)

    Shu-Min, Feng; Bao-Yu, Hu; Cen, Nie; Xiang-Hao, Shen; Yu-Sheng, Ci

    2016-03-01

    Many bus transport networks (BTNs) have evolved into directed networks. A new representation model for BTNs is proposed, called directed-space P. The bus transport network of Harbin (BTN-H) is described as a directed and weighted complex network by the proposed representation model and by giving each node weights. The topological and weighted properties are revealed in detail. In-degree and out-degree distributions, in-weight and out-weight distributions are presented as an exponential law, respectively. There is a strong relation between in-weight and in-degree (also between out-weight and out-degree), which can be fitted by a power function. Degree-degree and weight-weight correlations are investigated to reveal that BTN-H has a disassortative behavior as the nodes have relatively high degree (or weight). The disparity distributions of out-degree and in-degree follow an approximate power-law. Besides, the node degree shows a near linear increase with the number of routes that connect to the corresponding station. These properties revealed in this paper can help public transport planners to analyze the status quo of the BTN in nature. Project supported by the National High Technology Research and Development Program of China (Grant No. 2014AA110304).

  15. Fabrication of self-supporting porous silicon membranes and tuning transport properties by surface functionalization

    NASA Astrophysics Data System (ADS)

    Velleman, Leonora; Shearer, Cameron James; Ellis, Amanda Vera; Losic, Dusan; Voelcker, Nicolas Hans; Shapter, Joseph George

    2010-09-01

    This study presents a simple approach to perform selective mass transport through freestanding porous silicon (pSi) membranes. pSi membranes were fabricated by the electrochemical etching of silicon to produce membranes with controlled structure and pore sizes close to molecular dimensions (~12 nm in diameter). While these membranes are capable of size-exclusion based separations, chemically specific filtration remains a great challenge especially in the biomedical field. Herein, we investigate the transport properties of chemically functionalized pSi membranes. The membranes were functionalized using silanes (heptadecafluoro-1,1,2,2-tetrahydrodecyl)dimethylchlorosilane (PFDS) and N-(triethoxysilylpropyl)-o-polyethylene oxide urethane (PEGS) to give membranes hydrophobic (PFDS) and hydrophilic (PEGS) properties. The transport of probe dyes tris(2,2'-bipyridyl)dichlororuthenium(ii) hexahydrate (Rubpy) and Rose Bengal (RB) through these functionalized membranes was examined to determine the effect surface functionalization has on the selectivity and separation ability of pSi membranes. This study provides the basis for further investigation into more sophisticated surface functionalization and coupled with the biocompatibility of pSi will lead to new advances in membrane based bio-separations.

  16. Highly Anisotropic intrinsic electronic transport properties of monolayer and bilayer phosphorene from first principles1

    NASA Astrophysics Data System (ADS)

    Jin, Zhenghe; Mullen, Jeffrey; Kim, Ki Wook

    We present an analysis of the electron(hole)-phonon scattering in monolayer and bilayer phosphorene using first principles. Density Functional Theory (DFT) and Density Functional Perturbation Theory (DFPT) are used to calculate the scattering matrix elements and full band Monte Carlo carrier transport simulation is employed to obtain the intrinsic electron/hole mobility. Room temperature mobility and saturation velocity in monolayer and bilayer phosphorene are extracted and significant layer number dependence in the mobility is revealed which results from the carrier-phonon interaction matrix elements. The transport properties are also varied with the crystal orientation with anisotropy mobility mostly attributed to the anisotropic band structure and effective masses. Our calculation reveals monolayer phosphorene has anisotropic hole transport property with the room temperature mobility in the armchair direction (458 cm2/Vs) about five times larger than in the zigzag direction (90 cm2/Vs). For bilayer phosphorene, the mobility on both directions increases to 1610 cm2/Vs and 760 cm2/Vs along armchair and zigzag direction respectively. The increased mobility in bilayer is consistent with the experiments which revealed low field mobility of over one thousand in multiple layer phosphorene structure, which provides optimal material for channel in field-effect transistor and a good opportunity for high-performance p-type device. 1This work was supported, in part, by SRC/NRI SWAN.

  17. Theory of Band Warping and its Effects on Thermoelectronic Transport Properties

    NASA Astrophysics Data System (ADS)

    Mecholsky, Nicholas; Resca, Lorenzo; Pegg, Ian; Fornari, Marco

    2015-03-01

    Transport properties of materials depend upon features of band structures near extrema in the BZ. Such features are generally described in terms of quadratic expansions and effective masses. Such expansions, however, are permissible only under strict conditions that are sometimes violated by materials. Suggestive terms such as ``band warping'' have been used to refer to such situations and ad hoc methods have been developed to treat them. We develop a generally applicable theory, based on radial expansions, and a corresponding definition of angular effective mass which also accounts for effects of band non-parabolicity and anisotropy. Further, we develop precise procedures to evaluate band warping quantitatively and as an example we analyze the warping features of valence bands in silicon using first-principles calculations and we compare those with semi-empirical models. We use our theory to generalize derivations of transport coefficients for cases of either single or multiple electronic bands, with either quadratically expansible or warped energy surfaces. We introduce the transport-equivalent ellipsoid and illustrate the drastic effects that band warping can induce on thermoelectric properties using multi-band models. Vitreous State Laboratory and Samsung's GRO program.

  18. Hopping Conduction and Bacteria: Transport Properties of Disordered Reaction-Diffusion Systems

    NASA Astrophysics Data System (ADS)

    Missel, Andrew; Dahmen, Karin

    2008-03-01

    Reaction-diffusion (RD) systems are used to model everything from the formation of animal coat patterns to the spread of genes in a population to the seasonal variation of plankton density in the ocean. In all of these problems, disorder plays a large role, but determining its effects on transport properties in RD systems has been a challenge. We present here both analytical and numerical studies of a particular disordered RD system consisting of particles which are allowed to diffuse and compete for resources (2A->A) with spatially homogeneous rates, reproduce (A->2A) in certain areas (``oases''), and die (A->0) everywhere else (the ``desert''). In the low oasis density regime, transport is mediated through rare ``hopping events'' in which a small number of particles diffuse through the desert from one oasis to another; the situation is mathematically analogous to hopping conduction in doped semiconductors, and this analogy, along with some ideas from first passage percolation theory, allows us to make some quantitative predictions about the transport properties of the system on a large scale.

  19. Coronary Microvascular Dysfunction and Microvascular Angina: A Systematic Review of Therapies

    PubMed Central

    Marinescu, Mark A; Löffler, Adrián I.; Ouellette, Michelle; Smith, Lavone; Kramer, Christopher M.; Bourque, Jamieson

    2015-01-01

    Angina without coronary artery disease (CAD) has substantial morbidity and is present in 10–30% of patients undergoing angiography. Coronary microvascular dysfunction (CMD) is present in 50–65% of these patients. The optimal treatment of this cohort is undefined. We performed a systematic review to evaluate treatment strategies for objectively defined CMD in the absence of CAD. We included studies assessing therapy in human subjects with angina and coronary flow reserve (CFR) or myocardial perfusion reserve (MPR) <2.5 by positron emission tomography (PET), cardiac magnetic resonance imaging (CMR), dilution methods, or intracoronary Doppler in the absence of coronary artery stenosis ≥50% or structural heart disease. Only 8 articles met strict inclusion criteria. The articles were heterogeneous, using different treatments, end-points, and definitions of CMD. Small sample sizes severely limit the power of these studies, with an average of 11 patients per analysis. Studies evaluating, sildenafil, quinapril, estrogen, and transcutaneous electrical nerve stimulation (TENS) application demonstrated benefits in their respective endpoints. No benefit was found with L-arginine, doxazosin, pravastatin, and diltiazem. Our systematic review highlights that there is little data to support therapies for CMD. We assess the data meeting rigorous inclusion criteria and review the related but excluded literature. We additionally describe the next steps needed to address this research gap, including a standardized definition of CMD, routine assessment of CMD in studies of chest pain without obstructive CAD, and specific therapy assessment in the population with confirmed CMD. PMID:25677893

  20. Transport mechanism and regulatory properties of the human amino acid transporter ASCT2 (SLC1A5).

    PubMed

    Scalise, Mariafrancesca; Pochini, Lorena; Panni, Simona; Pingitore, Piero; Hedfalk, Kristina; Indiveri, Cesare

    2014-11-01

    The kinetic mechanism of the transport catalyzed by the human glutamine/neutral amino acid transporter hASCT2 over-expressed in P. pastoris was determined in proteoliposomes by pseudo-bi-substrate kinetic analysis of the Na(+)-glutamineex/glutaminein transport reaction. A random simultaneous mechanism resulted from the experimental analysis. Purified functional hASCT2 was chemically cross-linked to a stable dimeric form. The oligomeric structure correlated well with the kinetic mechanism of transport. Half-saturation constants (Km) of the transporter for the other substrates Ala, Ser, Asn and Thr were measured both on the external and internal side. External Km were much lower than the internal ones confirming the asymmetry of the transporter. The electric nature of the transport reaction was determined imposing a negative inside membrane potential generated by K(+) gradients in the presence of valinomycin. The transport reaction resulted to be electrogenic and the electrogenicity originated from external Na(+). Internal Na(+) exerted a stimulatory effect on the transport activity which could be explained by a regulatory, not a counter-transport, effect. Native and deglycosylated hASCT2 extracted from HeLa showed the same transport features demonstrating that the glycosyl moiety has no role in transport function. Both in vitro and in vivo interactions of hASCT2 with the scaffold protein PDZK1 were revealed.

  1. Charge transport properties of bulk Ta3N5 from first principles

    NASA Astrophysics Data System (ADS)

    Morbec, Juliana M.; Galli, Giulia

    2016-01-01

    Tantalum nitride is considered a promising material for photoelectrochemical water splitting, however, its charge transport properties remain poorly understood. We investigated polaronic and band transport in Ta3N5 using first-principles calculations. We first studied the formation of small polarons using density-functional theory (DFT) including DFT +U and hybrid functionals. We found that electron small polarons may occur but hole polarons are not energetically favorable. The estimated polaronic mobility for electrons is at least three orders of magnitude smaller than that measured in Ta3N5 films, suggesting that the main transport mechanism for both electrons and holes is bandlike. Since band transport is strongly affected by the carrier effective masses, and Ta3N5 is known to have large electron and hole effective masses, we also investigated whether substitutional impurities or strain may help lower the effective masses. We found a significant reduction in both electron and hole effective masses (up to 17% for electrons and 39% for holes) under applied strain, which may lead to a substantial improvement (up to 30% for electrons and 15% for holes) in the carrier mobilities.

  2. Property Valuation and Radioactive Materials Transportation: A Legal, Economic and Public Perception Analysis

    SciTech Connect

    Holm, J. A.; Thrower, A. W.; Widmayer, D. A.; Portner, W.

    2003-02-26

    The shipment of transuranic (TRU) radioactive waste to the Waste Isolation Pilot Plant (WIPP) in New Mexico raised a serious socioeconomic issue - the potential devaluation of property values due to the transportation of TRU waste from generator sites to the disposal facility. In 1992, the New Mexico Supreme Court held in City of Santa Fe v. Komis that a loss in value from public perception of risk was compensable. This issue has become an extremely important one for the development of the Yucca Mountain repository in Nevada for disposal of spent nuclear fuel and high-level radioactive waste. Much research has been conducted about the potential impacts of transportation of spent fuel and radioactive waste. This paper examines the pertinent studies conducted since the Komis case. It examines how the public debate on radioactive materials transportation continues and is now focused on transportation of high-level waste and spent nuclear fuel to the proposed Yucca Mountain repository. Finally, the paper suggests a path forward DOE can take to address this issue.

  3. Intrinsic non-ohmic electronic transport properties of the transparent In-Zn-O compound nanobelts under ohmic contact and out of the space charge limited transport region.

    PubMed

    Wen, Jing; Zhang, Xitian; Gao, Hong

    2016-02-19

    It is generally accepted that the nonlinear I-V characteristics for semiconductor nanostructures are mainly induced by the Schottky contacts or by the space charge limited transport mechanism. We perform I-V measurements on undoped and doped In-Zn-O compound nanobelts and confirm that their intrinsic non-ohmic transport behaviors are not caused by these mechanisms. A model based on the hopping assisted trap state electrons transport process is introduced to explain the nonlinear I-V characteristics and to extract their electrical parameters. An understanding of this trap-state influenced carrier transport can advance the progress of nanomaterials applications and enable us to distinguish their intrinsic transport behaviors from contact effects. The results also indicate that the material has good electrical properties and can be used as a potential substitute for In2O3.

  4. Mechanical Properties of the Assembly Welded Joint of the Oil Transportation Tank After a Long-Term Service

    NASA Astrophysics Data System (ADS)

    Pimnev, A. L.; Zemenkova, M. Yu; Zemenkov, Yu D.; Iljyashchenko, D. P.

    2016-04-01

    The paper provides results of studying a change in mechanical properties of the design elements metal and assembly welded joints of a vertical steel tank after a long-term service in oil transport facilities.

  5. Thermodynamic and transport combustion properties of hydrocarbons with air. Part 4: Compositions corresponding to Rankine temperature schedules in part 3

    NASA Technical Reports Server (NTRS)

    Gordon, S.

    1982-01-01

    The equilibrium compositions corresponding to the thermodynamic and transport combustion properties for a wide range of conditions for the reaction of hydrocarbons with air are presented. The compositions presented correspond to Rankine temperature schedules.

  6. Thermal transport properties of metal/MoS{sub 2} interfaces from first principles

    SciTech Connect

    Mao, Rui; Kong, Byoung Don; Kim, Ki Wook

    2014-07-21

    Thermal transport properties at the metal/MoS{sub 2} interfaces are analyzed by using an atomistic phonon transport model based on the Landauer formalism and first-principles calculations. The considered structures include chemisorbed Sc(0001)/MoS{sub 2} and Ru(0001)/MoS{sub 2}, physisorbed Au(111)/MoS{sub 2}, as well as Pd(111)/MoS{sub 2} with intermediate characteristics. Calculated results illustrate a distinctive dependence of thermal transfer on the details of interfacial microstructures. More specifically, the chemisorbed case with a stronger bonding exhibits a generally smaller interfacial thermal resistance than the physisorbed. Comparison between metal/MoS{sub 2} and metal/graphene systems suggests that metal/MoS{sub 2} is significantly more resistive. Further examination of lattice dynamics identifies the presence of multiple distinct atomic planes and bonding patterns at the interface as the key origins of the observed large thermal resistance.

  7. Calculated transport properties of CdO: Thermal conductivity and thermoelectric power factor

    NASA Astrophysics Data System (ADS)

    Lindsay, L.; Parker, D. S.

    2015-10-01

    We present first-principles calculations of the thermal and electronic transport properties of the oxide semiconductor CdO. In particular, we find from theory that the accepted thermal conductivity κ value of 0.7 W m-1K-1 is approximately one order of magnitude too small; our calculations of κ of CdO are in good agreement with recent measurements. We also find that alloying of MgO with CdO is an effective means to reduce the lattice contribution to κ , despite MgO having a much larger thermal conductivity. We further consider the electronic structure of CdO in relation to thermoelectric performance, finding that large thermoelectric power factors may occur if the material can be heavily doped p type. This work develops insight into the nature of thermal and electronic transport in an important oxide semiconductor.

  8. Light-Emitting Organic Materials with Variable Charge Injection and Transport Properties

    SciTech Connect

    Chen, A. C.-A.; Wallace, J. U.; Wei, S. K.-H.; Zeng, L.; Shen, S. H.; Blenton, T. N.

    2006-01-01

    Novel light-emitting organic materials comprising conjugated oligomers chemically attached via a flexible spacer to an electron- or hole-conducting core were designed for tunable charge injection and transport properties. Representative glassy-isentropic and glassy-liquid-crystalline (i.e., noncrystaline solid) materials were synthesized and characterized; they were found to exhibit a glass transition temperature and a clearing point close to 140 and 250 C, respectively; an orientational order parameter of 0.75; a photoluminescence quantum yield up to 51%; and HOMO and LUMO energy levels intermediate between those of blue-emitting oligofluorenes and the ITO and Mg/Ag electrodes commonly used in organic light-emitting diodes, OLEDs. This class of materials will help to balance charge injection and transport and to spread out the charge recombination zone, thereby significantly improving the device efficiency and lifetime of unpolarized and polarized OLEDs.

  9. Effect of substitutional impurities on the electronic transport properties of graphene

    NASA Astrophysics Data System (ADS)

    Berdiyorov, G. R.; Bahlouli, H.; Peeters, F. M.

    2016-10-01

    Density-functional theory in combination with the nonequilibrium Green's function formalism is used to study the effect of substitutional doping on the electronic transport properties of hydrogen passivated zig-zag graphene nanoribbon devices. B, N and Si atoms are used to substitute carbon atoms located at the center or at the edge of the sample. We found that Si-doping results in better electronic transport as compared to the other substitutions. The transmission spectrum also depends on the location of the substitutional dopants: for single atom doping the largest transmission is obtained for edge substitutions, whereas substitutions in the middle of the sample give larger transmission for double carbon substitutions. The obtained results are explained in terms of electron localization in the system due to the presence of impurities.

  10. Molecular-Flow Properties of RIB Type Vapor-Transport Systems Using a Fast-Valve

    SciTech Connect

    Alton, Gerald D; Bilheux, Hassina Z; Zhang, Y.; Liu, Yuan

    2014-01-01

    The advent of the fast-valve device, described previously, permits measurement of molecular-flow times of chemically active or inactive gaseous species through radioactive ion beam (RIB) target ion source systems, independent of size, geometry and materials of construction. Thus, decay losses of short-half-life RIBs can be determined for a given target/vapor-transport system in advance of on-line operation, thereby ascertaining the feasibility of the system design for successful processing of a given isotope. In this article, molecular-flow-time theory and experimentally measured molecular-flow time data are given for serial- and parallel-coupled Ta metal RIB vapor-transport systems similar to those used at ISOL based RIB facilities. In addition, the effect of source type on the molecular-flow time properties of a given system is addressed, and a chemical passivation method for negating surface adsorption enthalpies for chemically active gaseous species on Ta surfaces is demonstrated.

  11. Calculated transport properties of CdO: thermal conductivity and thermoelectric power factor

    DOE PAGES

    Lindsay, Lucas R.; Parker, David S.

    2015-10-01

    We present first principles calculations of the thermal and electronic transport properties of the oxide semiconductor CdO. In particular, we find from theory that the accepted thermal conductivity κ value of 0.7 Wm-1K-1 is approximately one order of magnitude too small; our calculations of κ of CdO are in good agreement with recent measurements. We also find that alloying of MgO with CdO is an effective means to reduce the lattice contribution to κ, despite MgO having a much larger thermal conductivity. We further consider the electronic structure of CdO in relation to thermoelectric performance, finding that large thermoelectric powermore » factors may occur if the material can be heavily doped p-type. This work develops insight into the nature of thermal and electronic transport in an important oxide semiconductor.« less

  12. Electronic and Quantum Transport Properties of Atomically Identified Si Point Defects in Graphene.

    PubMed

    Lopez-Bezanilla, Alejandro; Zhou, Wu; Idrobo, Juan-Carlos

    2014-05-15

    We report high-resolution scanning transmission electron microscopy images displaying a range of inclusions of isolated silicon atoms at the edges and inner zones of graphene layers. Whereas the incorporation of Si atoms to a graphene armchair edge involves no reconstruction of the neighboring carbon atoms, the inclusion of a Si atom to a zigzag graphene edge entails the formation of five-membered carbon rings. In all the observed atomic edge terminations, a Si atom is found bridging two C atoms in a 2-fold coordinated configuration. The atomic-scale observations are underpinned by first-principles calculations of the electronic and quantum transport properties of the structural anomalies. Experimental estimations of Si-doped graphene band gaps realized by means of transport measurements may be affected by a low doping rate of 2-fold coordinated Si atoms at the graphene edges, and 4-fold coordinated at inner zones due to the apparition of mobility gaps. PMID:26270371

  13. A theoretical study of charge transport properties of trifluoromethyl (-CF3) substituted naphthalene (TFMNA) molecule

    NASA Astrophysics Data System (ADS)

    Sahoo, S. R.; Parida, S. K.; Sahu, S.

    2016-09-01

    We present a density functional (DFT) study of the charge transport properties of CF3-naphthalene. Nature of charge transport is investigated using parameters such as reorganization energy (X), transfer integral (t), ionization potential (IP), electron affinity (EA), and carrier mobility (μ) computed through electronic structure calculations. We observe a decrease in X and IP from 2,6-DTFMNA to 1,5-DTFMNA, whereas, the EA is found to be enhanced, as a result p-type characteristics, with mild n-type signature, in the organic semiconductor gets increased. In addition, the HOMO-LUMO gap also gets reduced inferring more charge injection through the potential barrier. The maximum hole and electron mobility values for the substituted compound are obtained to be 2.17 cm2/ Vsec & 0.20 cm2/ Vsec, respectively.

  14. Microstructure and thermo-electrical transport properties of Cd-Sn alloys

    SciTech Connect

    Ari, M. Saatci, B.; Guenduez, M.; Meydaneri, F.; Bozoklu, M.

    2008-05-15

    The thermophysical transport properties of Cd-Sn alloys have been investigated for six samples. The electrical resistivity measurements were obtained by using a standard dc four-point probe technique in the temperature range of 300 K-550 K. The resistivity of samples increases linearly with temperature and the electrical current mainly flows through the Sn phase channel. The electrical conductivity of samples is inversely proportional to temperature. Also, thermal conductivity of the Cd-Sn alloys was determined. The phonon component contribution of thermal conductivity dominates the thermal conduction processes at T < 500 K. The electronic component contribution of thermal conductivity affects the thermal transport process at T > 500 K. The thermal conductivity of the Cd-Sn alloys also depends on the grain size and grain boundary of the pure Cd and the pure Sn phases in the matrix. The temperature coefficient of resistivity was also determined, which is independent with the alloying elements.

  15. Low Band Gap Thiophene-Perylene Diimide Systems with Tunable Charge Transport Properties

    SciTech Connect

    Balaji, Ganapathy; Kale, Tejaswini S.; Keerthi, Ashok; Della Pelle, Andrea M.; Thayumanavan, S.; Vallyaveettil, Surech

    2010-11-30

    Perylenediimide-pentathiophene systems with varied architecture of thiophene units were synthesized. The photophysical, electrochemical, and charge transport behavior of the synthesized compounds were studied. Both molecules showed a low band gap of ~1.4 eV. Surprisingly, the molecule with pentathiophene attached via β-position to the PDI unit upon annealing showed a predominant hole mobility of 1 × 10-4 cm2 V-1 s-1 whereas the compound with branched pentathiophene attached via β-position showed an electron mobility of 9.8 × 10-7 cm2 V-1 s-1. This suggests that charge transport properties can be tuned by simply varying the architecture of pentathiophene units.

  16. Calculated transport properties of CdO: thermal conductivity and thermoelectric power factor

    SciTech Connect

    Lindsay, Lucas R.; Parker, David S.

    2015-10-01

    We present first principles calculations of the thermal and electronic transport properties of the oxide semiconductor CdO. In particular, we find from theory that the accepted thermal conductivity κ value of 0.7 Wm-1K-1 is approximately one order of magnitude too small; our calculations of κ of CdO are in good agreement with recent measurements. We also find that alloying of MgO with CdO is an effective means to reduce the lattice contribution to κ, despite MgO having a much larger thermal conductivity. We further consider the electronic structure of CdO in relation to thermoelectric performance, finding that large thermoelectric power factors may occur if the material can be heavily doped p-type. This work develops insight into the nature of thermal and electronic transport in an important oxide semiconductor.

  17. Magnon-drag and thermomagnetic transport properties of Ca doped YIG

    NASA Astrophysics Data System (ADS)

    Zheng, Yuanhua; He, Bin; Chen, Xi; Zhou, Jianshi; Shi, Li; Myers, Roberto; Heremans, Joseph

    Yttrium-iron garnet (YIG) is an insulating ferromagnet commonly used to study various spin transport phenomena: in conjunction with a Pt film, it generates the well-known spin-Seebeck effect. Because of the close relationship between the spin-Seebeck effect and the magnon-drag charge Seebeck effect, we investigate the thermoelectric transport properties of an electrically conducting bulk YIG crystal doped p-type with Ca. A large and sharp change in the thermopower of Ca:YIG near the Curie temperature has been observed, which is potentially explained by the magnon-drag model. We present the temperature dependence of electrical conductivity, magneto-thermopower, and Hall coefficient of Ca:YIG. Photo-excitation of the carriers from the valence band into the Ca level results in photoconductivity and photo-Seebeck effects as well. Acknowledgement: ARO MURI W911NF-14-1-0016.

  18. Effects of intervalley scattering on the transport properties in one−dimensional valleytronic devices

    PubMed Central

    Zhou, Jiaojiao; Cheng, Shuguang; You, Wen-Long; Jiang, Hua

    2016-01-01

    Based on a one-dimensional valley junction model, the effects of intervalley scattering on the valley transport properties are studied. We analytically investigate the valley transport phenomena in three typical junctions with both intervalley and intravalley scattering included. For the tunneling between two gapless valley materials, different from conventional Klein tunneling theory, the transmission probability of the carrier is less than 100% while the pure valley polarization feature still holds. If the junction is composed of at least one gapped valley material, the valley polarization of the carrier is generally imperfect during the tunneling process. Interestingly, in such circumstance, we discover a resonance of valley polarization that can be tuned by the junction potential. The extension of our results to realistic valley materials are also discussed. PMID:26980163

  19. Thermodynamic and transport properties of two-temperature SF{sub 6} plasmas

    SciTech Connect

    Wang Weizong; Rong Mingzhe; Wu Yi; Spencer, Joseph W.; Yan, Joseph D.; Mei, DanHua

    2012-08-15

    This paper deals with thermodynamic and transport properties of SF{sub 6} plasmas in a two-temperature model for both thermal equilibrium and non-equilibrium conditions. The species composition and thermodynamic properties are numerically determined using the two-temperature Saha equation and Guldberg-Waage equation according to deviation of van de Sanden et al. Transport properties including diffusion coefficient, viscosity, thermal conductivity, and electrical conductivity are calculated with most recent collision interaction potentials by adopting Devoto's electron and heavy particle decoupling approach but expanded to the third-order approximation (second-order for viscosity) in the frame of Chapman-Enskog method. The results are computed for various values of pressures from 0.1 atm to 10 atm and ratios of the electron temperature to the heavy particle temperature from 1 to 20 with electron temperature range from 300 to 40 000 K. In the local thermodynamic equilibrium regime, results are compared with available results of previously published studies.

  20. Quantifying the transport properties of lipid mesophases by theoretical modelling of diffusion experiments.

    PubMed

    Antognini, Luca M; Assenza, Salvatore; Speziale, Chiara; Mezzenga, Raffaele

    2016-08-28

    Lyotropic Liquid Crystals (LLCs) are a class of lipid-based membranes with a strong potential for drug-delivery employment. The characterization and control of their transport properties is a central issue in this regard, and has recently prompted a notable volume of research on the topic. A promising experimental approach is provided by the so-called diffusion setup, where the drug molecules diffuse from a feeding chamber filled with water to a receiving one passing through a LLC. In the present work we provide a theoretical framework for the proper description of this setup, and validate it by means of targeted experiments. Due to the inhomogeneity of the system, a rich palette of different diffusion dynamics emerges from the interplay of the different time- and lengthscales thereby present. Our work paves the way to the employment of diffusion experiments to quantitatively characterize the transport properties of LLCs, and provides the basic tools for device diffusion setups with controlled kinetic properties. PMID:27586942

  1. The optimization of mechanical properties for nuclear transportation casks in ASTM A350 LF5

    SciTech Connect

    Price, S.; Honeyman, G.A.

    1997-12-31

    Transport flasks are required for the movement of spent nuclear fuel. Due to their nature of operation, it is necessary that these flasks are produced from forged steels with exceptional toughness properties. The material specification generally cited for flask manufacture is ASTM A350 Grade LF5 Class 1, a carbon-manganese-nickel alloy. The range of chemical analysis permitted by this specification is very broad and it is the responsibility of the material manufacturer to select a composition within this range which will satisfy all the mechanical properties requirements, and to ensure safe and reliable performance. Forgemasters Steel and Engineering Limited have experience in the manufacture of large high integrity fuel element flask forgings which extend over several decades. This experience and involvement in international standards in US, Europe and Japan has facilitated the development of an optimized analysis with a low carbon content, nickel levels towards the top end of the allowed range, a deliberate aluminum addition to control grain size and strictly controlled residual element levels. The resultant steel has excellent low temperature impact properties which greatly exceed the requirements of the specification. This analysis is now being adopted for the manufacture of all current transport flasks.

  2. Dielectric properties of water under extreme conditions and transport of carbonates in the deep Earth.

    PubMed

    Pan, Ding; Spanu, Leonardo; Harrison, Brandon; Sverjensky, Dimitri A; Galli, Giulia

    2013-04-23

    Water is a major component of fluids in the Earth's mantle, where its properties are substantially different from those at ambient conditions. At the pressures and temperatures of the mantle, experiments on aqueous fluids are challenging, and several fundamental properties of water are poorly known; e.g., its dielectric constant has not been measured. This lack of knowledge of water dielectric properties greatly limits our ability to model water-rock interactions and, in general, our understanding of aqueous fluids below the Earth's crust. Using ab initio molecular dynamics, we computed the dielectric constant of water under the conditions of the Earth's upper mantle, and we predicted the solubility products of carbonate minerals. We found that MgCO3 (magnesite)--insoluble in water under ambient conditions--becomes at least slightly soluble at the bottom of the upper mantle, suggesting that water may transport significant quantities of oxidized carbon. Our results suggest that aqueous carbonates could leave the subducting lithosphere during dehydration reactions and could be injected into the overlying lithosphere. The Earth's deep carbon could possibly be recycled through aqueous transport on a large scale through subduction zones.

  3. Fundamental investigation of the transport properties of superacids in aqueous and non-aqueous media

    NASA Astrophysics Data System (ADS)

    Suarez, Sophia

    In the quest to develop more efficient energy providers one of the main focus of research has been on the improvement of ion transport. In lithium battery research this has led to the incorporation of various lithium salts, ceramics and plasticizers into the poly(ethylene)oxide (PEO) matrix, the polymer most used In Proton Conduction Membrane (PCM) fuel cell research this has led to the development of new membranes, which are designed with to replicate Nafion's ((c)DuPont) proton transport but also improve upon its deficiency of transporting intact fuel molecules and its dependence upon the presence of solvating water molecules. To better understand the process of ion transport, NMR was used to investigate dynamic properties such as D (self-diffusion coefficient) and T1 (spin-lattice relaxation time) of various proton and lithium ion-conducting systems. Ionic conductivity and viscosity measurements were also performed. The systems studied includes aqueous superacid solutions (trifluoromethanesulfonic (TFSA), para-toluenesulfonic (PTSA) and bis(trifluoromethanesulfonyl)imide (TFSI)); nano-porous (NP-) PCM's incorporating various ceramics and 3M fuel/2M H2SO4 solutions; and P(EO)20LiBETI (LiN(SO 2CF2CF3)2 composite incorporating SiO 2 ceramic nano particles. The objective of the study of the superacid solutions was to determine the effect of concentration on the transport. It was found that beyond the ionic conductivity maximum, fluctuations in both D and T1 supports the existence of local ordering in the ionic network, caused by the reduced solvent dielectric coefficient and increasing viscosity. Of the three superacids TFSA was the most conductive and most affected by reduced solvent concentration. For the P(EO)20LiBETI composite the aim was to determine the effect of the ceramic on the ion transport of the composite in a solvent free environment. Results show that the ceramic causes only modest increase in the lithium transport below 90°C. The objective in the

  4. Regional cutaneous microvascular flow responses during gravitational and LBNP stresses.

    PubMed

    Breit, G A; Watenpaugh, D E; Ballard, R E; Murthy, G; Hargens, A R

    1993-01-01

    The most significant cardiovascular event during the transition to microgravity is the redistribution of vascular transmural pressures that results from the loss of hydrostatic gradients along the length of the body. The well-documented effects of this redistribution include facial venous engorgement, headache, and a significant decrease in leg volume. These effects predominantly represent bulk fluid volume shifts, especially in the venous macro- and microcirculation, where volume is a direct function of pressure, related by the mechanical compliance of the vascular compartment. When considering the effect of gravitational pressure alterations on microcirculatory blood flow and volume, however, this direct monotonic relationship no longer applies. Regional microvascular perfusion is largely a function of local arteriolar tone, which is subject to a variety of central and local controls. Lower body venous pooling during application of footward gravitational stress unloads arterial and cardiopulmonary baroreceptors, increasing sympathetic arteriolar tone to elicit vasoconstriction and a general decrease in microvascular perfusion. The same stimulus also triggers an increase in the levels of circulating vasoactive hormones, such as norepinephrine and angiotensin II, further augmenting arteriolar tone. Vasomotor tone is also mediated by local mechanisms such as myogenic autoregulation and veno-arteriolar reflexes, which enhance microvascular tone in response to elevated local arteriolar and venular pressure, respectively. Due to the regional variability of local hydrostatic pressures, microvascular flow responses to gravitational stress probably vary along the length of the body. Although these differences in local autoregulation have been observed previously during whole-body tilting, they have not been investigated during application of artificial gravitational stresses, such as lower body negative pressure (LBNP) or +Gz centrifugation. Although these stresses can

  5. Electrical Transport of Topological Insulator-bismuth selenide and Thermoelectric Properties of Graphene

    NASA Astrophysics Data System (ADS)

    Wei, Peng

    2011-12-01

    This thesis summarizes our work in the past four years in the field of transport studies of the topological insulator materials and thermoelectric properties of graphene. The first half of the thesis is focused on the transport properties of topological insulator material-Bi2Se3. In our research, we systematically tune the position of the chemical potential in p-type Ca-doped Bi2Se3 thin devices first by eliminating excess holes with controlled post-fabrication electron beam irradiation that results in an insulating bulk state. In spite of the fact that the energetic electron beam creates defects to localize the bulk carriers and inevitably to cause additional scattering, we find a tenfold increase in carrier mobility associated with the extended states in the band gap. In addition, the resistance undergoes a fivefold increase and passes the maximum as the chemical potential is further tuned by electrostatic gating. A cusp-like low-field magnetoresistance feature also emerges which is indicative of strong spin-orbit interaction. The observed gate-tunable high-mobility is a signature of massless Dirac fermions in the band gap of Bi2Se3. The second half of this thesis is focused on graphene. Our work first reported the thermoelectric study of graphene and demonstrated the anomalous thermoelectric transport of massless Dirac fermions. As a direct consequence of the linear dispersion of massless particles, we find that the Seebeck coefficient Sxx diverges with 1/n2D , where n2D is the carrier density. We observe a very large Nernst signal Sxy (˜ 50 muV/K at 8 T) at the Dirac point, and an oscillatory dependence of both Sxx and Sxy on n 2D at low temperatures. Our results underscore the anomalous thermoelectric transport in graphene, which may be used as a highly sensitive probe for impurity bands near the Dirac point.

  6. Prediction of Shale Transport Properties Using the Lattice Boltzmann Method: Permeability and Effective Knudsen Diffusivity

    NASA Astrophysics Data System (ADS)

    Kang, Q.; Chen, L.

    2014-12-01

    Although short-term production of unconventional gas depends on the area of contact created by hydraulic fracturing and connections with pre-existing natural fracture networks, sustainable recovery is limited by transfer of gas from nanoporous matrix into the fractures, because the permeability of hydraulic fractures is orders of magnitude higher than that of the shale matrix. Therefore, a fundamental understanding of hydrocarbon mobility in shale matrix is urgently needed for improving recovery efficiencies. Shale transport properties (diffusivity, permeability, and electronic conductivity), which are critical for understanding the fundamental transport mechanisms, are still poorly understood. There have been some studies using experimental techniques such as scanning electron microscopy (SEM) to visualize the nanoscale structures of shale. Due to the ultra-low porosity and permeability, it is difficult to experimentally investigate the fundamental transport processes inside the shale or accurately measure the transport properties. Advanced pore-scale numerical methods, e.g., the lattice Boltzman method (LBM) may provide an alternative approach. In the present study, three-dimensional nanoscale porous structures of shale are reconstructed based on SEM images of shale samples. Characterization analysis of the nanoscale reconstructed shale is performed, including determination of porosity, pore size distribution, specific surface area, and pore connectivity. The LBM flow model and diffusion model are adopted to simulate fluid flow and Knudsen diffusion in the reconstructed shale, respectively. Tortuosity, intrinsic permeability, and effective Knudsen diffusivity are numerically predicted. The tortuosity is much higher than what is commonly employed in Bruggeman equation. Correction of the intrinsic permeability by taking into consideration the contribution of Knudsen diffusion, which leads to the apparent permeability, is performed. The correction factor under

  7. Linking aquifer spatial properties and non-Fickian transport in mobile-immobile like alluvial settings

    USGS Publications Warehouse

    Zhang, Yong; Green, Christopher T.; Baeumer, Boris

    2014-01-01

    Time-nonlocal transport models can describe non-Fickian diffusion observed in geological media, but the physical meaning of parameters can be ambiguous, and most applications are limited to curve-fitting. This study explores methods for predicting the parameters of a temporally tempered Lévy motion (TTLM) model for transient sub-diffusion in mobile–immobile like alluvial settings represented by high-resolution hydrofacies models. The TTLM model is a concise multi-rate mass transfer (MRMT) model that describes a linear mass transfer process where the transfer kinetics and late-time transport behavior are controlled by properties of the host medium, especially the immobile domain. The intrinsic connection between the MRMT and TTLM models helps to estimate the main time-nonlocal parameters in the TTLM model (which are the time scale index, the capacity coefficient, and the truncation parameter) either semi-analytically or empirically from the measurable aquifer properties. Further applications show that the TTLM model captures the observed solute snapshots, the breakthrough curves, and the spatial moments of plumes up to the fourth order. Most importantly, the a priori estimation of the time-nonlocal parameters outside of any breakthrough fitting procedure provides a reliable “blind” prediction of the late-time dynamics of subdiffusion observed in a spectrum of alluvial settings. Predictability of the time-nonlocal parameters may be due to the fact that the late-time subdiffusion is not affected by the exact location of each immobile zone, but rather is controlled by the time spent in immobile blocks surrounding the pathway of solute particles. Results also show that the effective dispersion coefficient has to be fitted due to the scale effect of transport, and the mean velocity can differ from local measurements or volume averages. The link between medium heterogeneity and time-nonlocal parameters will help to improve model predictability for non

  8. ROLE OF ATP IN REGULATING RENAL MICROVASCULAR FUNCTION AND IN HYPERTENSION

    PubMed Central

    Guan, Zhengrong; Inscho, Edward W.

    2011-01-01

    Adenosine triphosphate (ATP) is an essential energy substrate for cellular metabolism but it can also influence many biological processes when released into the extracellular milieu. Research has established that extracellular ATP acts as an autocrine/paracrine factor that regulates many physiological functions. Alternatively, excessive extracellular ATP levels contribute to pathophysiological processes such as inflammation, cell proliferation and apoptosis, and atherosclerosis. Renal P2 receptors are widely distributed throughout glomeruli, vasculature and tubular segments, and participate in controlling renal vascular resistance, mediating renal autoregulation, and regulating tubular transport function. This review will focus on the role of ATP-P2 receptor signaling in regulating renal microvascular function and autoregulation, recent advances on the role of ATP-P2 signaling in hypertension-associated renal vascular injury, and emerging new directions. PMID:21768526

  9. In vivo microstructural and microvascular imaging of the human corneo-scleral limbus using optical coherence tomography

    PubMed Central

    Li, Peng; An, Lin; Reif, Roberto; Shen, Tueng T.; Johnstone, Murray; Wang, Ruikang K

    2011-01-01

    The corneo-scleral limbus contains several biological components, which are important constituents for understanding, diagnosing and managing several ocular pathologies, such as glaucoma and corneal abnormalities. An anterior segment optical coherence tomography (AS-OCT) system integrated with optical microangiography (OMAG) is used in this study to non-invasively visualize the three-dimensional microstructural and microvascular properties of the limbal region. Advantages include first the ability to correct optical distortion of microstructural images enabling quantification of relationships in the anterior chamber angle. Second, microvascular images enable the visualization of the microcirculation in the limbal area without the use of exogenous contrast agents. Third, by combining the microstructural and microvascular information, the aqueous outflow pathway can be identified. The proposed AS-OCT can serve as a useful tool for ophthalmological research to determine normal and pathologic changes in the outflow system. As a clinical tool it has the potential to detect early aqueous outflow system abnormalities that lead to the pressure elevation in glaucoma. Recent surgical innovations and their implementations also rely on an assessment of outflow system structure and function, which can be revealed by AS-OCT. PMID:22076271

  10. On the Transport and Radiative Properties of Plasmas with Small-Scale Electromagnetic Fluctuations

    NASA Astrophysics Data System (ADS)

    Keenan, Brett D.

    Plasmas with sub-Larmor-scale ("small-scale") electromagnetic fluctuations are a feature of a wide variety of high-energy-density environments, and are essential to the description of many astrophysical/laboratory plasma phenomena. Radiation from particles, whether they be relativistic or non-relativistic, moving through small-scale electromagnetic turbulence has spectral characteristics distinct from both synchrotron and cyclotron radiation. The radiation, carrying information on the statistical properties of the turbulence, is also intimately related to the particle diffusive transport. We investigate, both theoretically and numerically, the transport of non-relativistic and transrelativistic particles in plasmas with high-amplitude isotropic sub-Larmor-scale magnetic turbulence---both with and without a mean field component---and its relation to the spectra of radiation simultaneously produced by these particles. Furthermore, the transport of particles through small-scale electromagnetic turbulence---under certain conditions---resembles the random transport of particles---via Coulomb collisions---in collisional plasmas. The pitch-angle diffusion coefficient, which acts as an effective "collision" frequency, may be substantial in these, otherwise, collisionless environments. We show that this effect, colloquially referred to as the plasma "quasi-collisionality", may radically alter the expected radiative transport properties of candidate plasmas. We argue that the modified magneto-optic effects in these plasmas provide an attractive, novel, diagnostic tool for the exploration and characterization of small-scale electromagnetic turbulence. Lastly, we speculate upon the manner in which quasi-collisions may affect inertial confinement fusion (ICF), and other laser-plasma experiments. Finally, we show that mildly relativistic jitter radiation, from laser-produced plasmas, may offer insight into the underlying electromagnetic turbulence. Here we investigate the

  11. The phase diagram and transport properties of MgO from theory and experiment

    NASA Astrophysics Data System (ADS)

    Shulenburger, Luke

    2013-06-01

    Planetary structure and the formation of terrestrial planets have received tremendous interest due to the discovery of so called super-earth exoplanets. MgO is a major constituent of Earth's mantle, the rocky cores of gas giants and is a likely component of the interiors of many of these exoplanets. The high pressure - high temperature behavior of MgO directly affects equation of state models for planetary structure and formation. In this work, we examine MgO under extreme conditions using experimental and theoretical methods to determine its phase diagram and transport properties. Using plate impact experiments on Sandia's Z facility the solid-solid phase transition from B1 to B2 is clearly determined. The melting transition, on the other hand, is subtle, involving little to no signal in us-up space. Theoretical work utilizing density functional theory (DFT) provides a complementary picture of the phase diagram. The solid-solid phase transition is identified through a series of quasi-harmonic phonon calculations and thermodynamic integration, while the melt boundary is found using phase coexistence calculations. One issue of particular import is the calculation of reflectivity along the Hugoniot and the influence of the ionic structure on the transport properties. Particular care is necessary because of the underestimation of the band gap and attendant overestimation of transport properties due to the use of semi-local density functional theory. We will explore the impact of this theoretical challenge and its potential solutions in this talk. The integrated use of DFT simulations and high-accuracy shock experiments together provide a comprehensive understanding of MgO under extreme conditions. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  12. Citrulline does not enhance blood flow, microvascular circulation, or myofibrillar protein synthesis in elderly men at rest or following exercise.

    PubMed

    Churchward-Venne, Tyler A; Cotie, Lisa M; MacDonald, Maureen J; Mitchell, Cameron J; Prior, Todd; Baker, Steven K; Phillips, Stuart M

    2014-07-01

    Aging is associated with anabolic resistance, a reduced sensitivity of myofibrillar protein synthesis (MPS) to postprandial hyperaminoacidemia, particularly with low protein doses. Impairments in postprandial skeletal muscle blood flow and/or microvascular perfusion with hyperaminoacidemia and hyperinsulinemia may contribute to anabolic resistance. We examined whether providing citrulline, a precursor for arginine and nitric oxide synthesis, would increase arterial blood flow, skeletal muscle microvascular perfusion, MPS, and signaling through mTORC1. Twenty-one elderly males (65-80 yr) completed acute unilateral resistance exercise prior to being assigned to ingest a high dose (45 g) of whey protein (WHEY) or a low dose (15 g) of whey protein with 10 g of citrulline (WHEY + CIT) or with 10 g of nonessential amino acids (WHEY + NEAA). A primed, continuous infusion of L-[ring-(13)C6] phenylalanine with serial muscle biopsies was used to measure MPS and protein phosphorylation, whereas ultrasound was used to measure microvascular circulation under basal and postprandial conditions in both a rested (FED) and exercised (EX-FED) leg. Argininemia was greater in WHEY + CIT vs. WHEY and WHEY + NEAA from 30 to 300 min postexercise (P < 0.001), but there were no treatment differences in blood flow or microvascular perfusion (all P > 0.05). Phosphorylation of p70S6K-Thr(389) was greater in WHEY vs. WHEY + NEAA (P = 0.02). Postprandial MPS was greater in WHEY vs. WHEY + CIT and WHEY + NEAA under both FED (WHEY: ~128%; WHEY + CIT: ~56%; WHEY + NEAA: ~38%) and EX-FED (WHEY: ~251%; WHEY + CIT: ~124%; WHEY + NEAA: ~108%) conditions (P = 0.003). Citrulline coingestion with a low quantity of protein was ineffective in augmenting the anabolic properties of protein compared with nonessential amino acids.

  13. Synthesis, crystal packing, and ambipolar carrier transport property of twisted dibenzo[g,p]chrysenes.

    PubMed

    Ueda, Yasuyuki; Tsuji, Hayato; Tanaka, Hideyuki; Nakamura, Eiichi

    2014-06-01

    A versatile method for the synthesis of dibenzo[g,p]chrysene (DBC) derivatives based on regio- and stereoselective stannyllithiation to diarylacetylenes is described. This method affords a variety of DBCs possessing both electron-donating and electron-withdrawing functional groups. These twisted molecules take brickwork packing structures in single crystals. Thus, ambipolar carrier transport properties with mobility values of up to 10(-3)  cm(2)  V(-1)  s(-1) in the amorphous state were achieved. Functional groups on DBC frameworks are considered to increase carrier mobility through the enhancement of intermolecular interactions in the brickwork packing structures.

  14. About the TVD property for the flux-corrected transport techniques

    NASA Astrophysics Data System (ADS)

    Gascón, Ll.; García, J. A.

    The flux-corrected transport techniques (FCT) are widely used in many calculation codes to simulate problems governed by hyperbolic conservation laws. The aim of this paper is to obtain the optimum values of the parameters which appear in the definition of the FCT techniques in order to satisfy the total variation diminishing (TVD) property introduced by Harten in [4]. Numerical results involving linear advection of a square wave and for the Sod test case have been presented to compare the various types of the FCT techniques.

  15. Temperature dependent spin transport properties of platinum inferred from spin Hall magnetoresistance measurements

    SciTech Connect

    Meyer, Sibylle Althammer, Matthias; Geprägs, Stephan; Opel, Matthias; Goennenwein, Sebastian T. B.; Gross, Rudolf

    2014-06-16

    We study the temperature dependence of the spin Hall magnetoresistance (SMR) in yttrium iron garnet/platinum hybrid structures via magnetization orientation dependent magnetoresistance measurements. Our experiments show a decrease of the SMR magnitude with decreasing temperature. Using the sensitivity of the SMR to the spin transport properties of the normal metal, we interpret our data in terms of a decrease of the spin Hall angle in platinum from 0.11 at room temperature to 0.075 at 10 K, while the spin diffusion length and the spin mixing conductance of the ferrimagnetic insulator/normal metal interface remain almost constant.

  16. Fast preparation and thermal transport property of TiCoSb-based half-Heusler compounds

    NASA Astrophysics Data System (ADS)

    Xie, Wen-Jie; Tang, Xin-Feng; Zhang, Qing-Jie

    2007-11-01

    TiCoSb-based half-Heusler compounds with the substitution of Zr for Ti have been prepared quickly by combining high-energy ball milling method with spark plasma sintering technique, and their thermal transport properties have been investigated. With the increase of the concentration of Zr, the thermal conductivity of Ti1-xZrxCoSb compounds decreases significantly. Compared with the thermal conductivity of TiCoSb compound, that of Ti0.5Zr0.5CoSb decreases by 200% at 1000 K.

  17. Electron transport property of cobalt-centered porphyrin-armchair graphene nanoribbon (AGNR) junction

    SciTech Connect

    Mondal, Rajkumar; Sarkar, Utpal

    2015-06-24

    We have investigated the electron transport properties of Cobalt-centered (Co-centered) porphyrin molecule using the density functional theory and non-equilibrium greens function method. Here we have reported transmission coefficient as well as current voltage characteristics of Co-centered porphyrine molecule connected between armchair graphene nanoribbons. It has been found that at low bias region i.e., 0 V to 0.3 V it does not contribute any current. Gradual increase of bias voltage results different order of magnitude of current in different bias region.

  18. Study of Transport Properties in Armchair Graphyne Nanoribbons: A Density Functional Approach

    NASA Astrophysics Data System (ADS)

    Golafrooz Shahri, S.; Roknabadi, M. R.; Shahtahmasebi, N.; Behdani, M.

    2016-07-01

    In present paper, the non-equilibrium Green function (NEGF) method along with the density functional theory (DFT) are used to investigate the effect of width on transport and electronic properties of armchair graphyne (γ-graphyne) nanoribbons. The results show that all the studied nanoribbons are semiconductor and their band gaps decrease as the widths of nanoribbons increase, which will result in increasing current at a certain voltage. Also our results show the promising application of armchair graphyne nanoribbons in nano-electrical devices.

  19. Modelling the optical properties of aerosols in a chemical transport model

    NASA Astrophysics Data System (ADS)

    Andersson, E.; Kahnert, M.

    2015-12-01

    According to the IPCC fifth assessment report (2013), clouds and aerosols still contribute to the largest uncertainty when estimating and interpreting changes to the Earth's energy budget. Therefore, understanding the interaction between radiation and aerosols is both crucial for remote sensing observations and modelling the climate forcing arising from aerosols. Carbon particles are the largest contributor to the aerosol absorption of solar radiation, thereby enhancing the warming of the planet. Modelling the radiative properties of carbon particles is a hard task and involves many uncertainties arising from the difficulties of accounting for the morphologies and heterogeneous chemical composition of the particles. This study aims to compare two ways of modelling the optical properties of aerosols simulated by a chemical transport model. The first method models particle optical properties as homogeneous spheres and are externally mixed. This is a simple model that is particularly easy to use in data assimilation methods, since the optics model is linear. The second method involves a core-shell internal mixture of soot, where sulphate, nitrate, ammonia, organic carbon, sea salt, and water are contained in the shell. However, by contrast to previously used core-shell models, only part of the carbon is concentrated in the core, while the remaining part is homogeneously mixed with the shell. The chemical transport model (CTM) simulations are done regionally over Europe with the Multiple-scale Atmospheric Transport and CHemistry (MATCH) model, developed by the Swedish Meteorological and Hydrological Institute (SMHI). The MATCH model was run with both an aerosol dynamics module, called SALSA, and with a regular "bulk" approach, i.e., a mass transport model without aerosol dynamics. Two events from 2007 are used in the analysis, one with high (22/12-2007) and one with low (22/6-2007) levels of elemental carbon (EC) over Europe. The results of the study help to assess the

  20. Transport properties for the oxygen system - O2, O, O(+), and e

    NASA Technical Reports Server (NTRS)

    Biolsi, Louis

    1988-01-01

    The transport properties of the oxygen system, O2, O, O(+), and the electron, e, are calculated and their applications are discussed. The possible two-body interactions in the oxygen system are examined and the exponential repulsive potential is used to determine collision integrals for these interactions. Values are presented for the viscosity of the pure gases, the self-diffusion coefficient of the pure gases at 1 atm pressure, the translational thermal conductivity of the pure gases, and the internal thermal conductivity of O2.