Science.gov

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. PMID:24976360

  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. 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

  5. Bench-to-bedside review: Microvascular dysfunction in sepsis –hemodynamics, oxygen transport, and nitric oxide

    PubMed Central

    Bateman, Ryon M; Sharpe, Michael D; Ellis, Christopher G

    2003-01-01

    The microcirculation is a complex and integrated system that supplies and distributes oxygen throughout the tissues. The red blood cell (RBC) facilitates convective oxygen transport via co-operative binding with hemoglobin. In the microcirculation oxygen diffuses from the RBC into neighboring tissues, where it is consumed by mitochondria. Evidence suggests that the RBC acts as deliverer of oxygen and 'sensor' of local oxygen gradients. Within vascular beds RBCs are distributed actively by arteriolar tone and passively by rheologic factors, including vessel geometry and RBC deformability. Microvascular oxygen transport is determined by microvascular geometry, hemodynamics, and RBC hemoglobin oxygen saturation. Sepsis causes abnormal microvascular oxygen transport as significant numbers of capillaries stop flowing and the microcirculation fails to compensate for decreased functional capillary density. The resulting maldistribution of RBC flow results in a mismatch of oxygen delivery with oxygen demand that affects both critical oxygen delivery and oxygen extraction ratio. Nitric oxide (NO) maintains microvascular homeostasis by regulating arteriolar tone, RBC deformability, leukocyte and platelet adhesion to endothelial cells, and blood volume. NO also regulates mitochondrial respiration. During sepsis, NO over-production mediates systemic hypotension and microvascular reactivity, and is seemingly protective of microvascular blood flow. PMID:12974969

  6. Nucleoside transporter subtype expression and function in rat skeletal muscle microvascular endothelial cells.

    PubMed

    Archer, Richard G E; Pitelka, Václav; Hammond, James R

    2004-09-01

    1. Microvascular endothelial cells (MVECs) form a barrier between circulating metabolites, such as adenosine, and the surrounding tissue. We hypothesize that MVECs have a high capacity for the accumulation of nucleosides, such that inhibition of the endothelial nucleoside transporters (NT) would profoundly affect the actions of adenosine in the microvasculature. 2. We assessed the binding of [(3)H]nitrobenzylmercaptopurine riboside (NBMPR), a specific probe for the inhibitor-sensitive subtype of equilibrative NT (es), and the uptake of [(3)H]formycin B (FB), by MVECs isolated from rat skeletal muscle. The cellular expression of equilibrative (ENT1, ENT2, ENT3) and concentrative (CNT1, CNT2, CNT3) NT subtypes was also determined using both qualitative and quantitative polymerase chain reaction techniques. 3. In the absence of Na(+), MVECs accumulated [(3)H]FB with a V(max) of 21+/-1 pmol microl(-1) s(-1). This uptake was mediated equally by es (K(m) 260+/-70 microm) and ei (equilibrative inhibitor-insensitive; K(m) 130+/-20 microm) NTs. 4. A minor component of Na(+)-dependent cif (concentrative inhibitor-insensitive FB transporter)/CNT2-mediated [(3)H]FB uptake (V(i) 0.008+/-0.005 pmol microl(-1) s(-1) at 10 microm) was also observed at room temperature upon inhibition of ENTs with dipyridamole (2,6-bis(diethanolamino)-4,8-dipiperidinopyrimido-[5,4-d]pyrimidine)/NBMPR. 5. MVECs had 122,000 high-affinity (K(d) 0.10 nm) [(3)H]NBMPR binding sites (representing es transporters) per cell. A lower-affinity [(3)H]NBMPR binding component (K(d) 4.8 nm) was also observed that may be related to intracellular es-like proteins. 6. Rat skeletal muscle MVECs express es/ENT1, ei/ENT2, and cif/CNT2 transporters with characteristics typical of rat tissues. This primary cell culture model will enable future studies on factors influencing NT subtype expression, and the consequent effect on adenosine bioactivity, in the microvasculature. PMID:15289294

  7. Nucleoside transporter subtype expression and function in rat skeletal muscle microvascular endothelial cells

    PubMed Central

    Archer, Richard G E; Pitelka, Václav; Hammond, James R

    2004-01-01

    Microvascular endothelial cells (MVECs) form a barrier between circulating metabolites, such as adenosine, and the surrounding tissue. We hypothesize that MVECs have a high capacity for the accumulation of nucleosides, such that inhibition of the endothelial nucleoside transporters (NT) would profoundly affect the actions of adenosine in the microvasculature. We assessed the binding of [3H]nitrobenzylmercaptopurine riboside (NBMPR), a specific probe for the inhibitor-sensitive subtype of equilibrative NT (es), and the uptake of [3H]formycin B (FB), by MVECs isolated from rat skeletal muscle. The cellular expression of equilibrative (ENT1, ENT2, ENT3) and concentrative (CNT1, CNT2, CNT3) NT subtypes was also determined using both qualitative and quantitative polymerase chain reaction techniques. In the absence of Na+, MVECs accumulated [3H]FB with a Vmax of 21±1 pmol μl−1 s−1. This uptake was mediated equally by es (Km 260±70 μM) and ei (equilibrative inhibitor-insensitive; Km 130±20 μM) NTs. A minor component of Na+-dependent cif (concentrative inhibitor-insensitive FB transporter)/CNT2-mediated [3H]FB uptake (Vi 0.008±0.005 pmol μl−1 s−1 at 10 μM) was also observed at room temperature upon inhibition of ENTs with dipyridamole (2,6-bis(diethanolamino)-4,8-dipiperidinopyrimido-[5,4-d]pyrimidine)/NBMPR. MVECs had 122,000 high-affinity (Kd 0.10 nM) [3H]NBMPR binding sites (representing es transporters) per cell. A lower-affinity [3H]NBMPR binding component (Kd 4.8 nM) was also observed that may be related to intracellular es-like proteins. Rat skeletal muscle MVECs express es/ENT1, ei/ENT2, and cif/CNT2 transporters with characteristics typical of rat tissues. This primary cell culture model will enable future studies on factors influencing NT subtype expression, and the consequent effect on adenosine bioactivity, in the microvasculature. PMID:15289294

  8. Modulation of bovine microvascular endothelial cell proteolytic properties by inhibitors of angiogenesis.

    PubMed

    Pepper, M S; Vassalli, J D; Wilks, J W; Schweigerer, L; Orci, L; Montesano, R

    1994-08-01

    A tightly controlled increase in extracellular proteolysis, restricted both in time and space, is an important component of the angiogenic process, while anti-proteolysis is effective in inhibiting angiogenesis. By focussing on the plasminogen activator (PA)-plasmin system, the objective of the present studies was to assess whether previously described inhibitors of angiogenesis modify bovine microvascular endothelial cell proteolytic properties. We demonstrate that although synthetic angiostatic steroids (U-24067 and U-42129), heparin, suramin, interferon alpha-2a, and retinoic acid are all inhibitors of in vitro angiogenesis, each of these agents has distinct effects on the plasminogen-dependent proteolytic system. Specifically, angiostatic steroids and interferon alpha-2a reduce urokinase-type PA (u-PA) and PA inhibitor-1 activity, while heparin and retinoic acid increase u-PA activity. Suramin reduces cell-associated u-PA activity and greatly increases PAI-1 production at doses which induce monolayer disruption. These findings demonstrate that a spectrum of alterations in extracellular proteolysis is associated with anti-angiogenesis, and that anti-angiogenesis and anti-proteolysis are not necessarily correlated. A reduction in extracellular proteolysis would be expected to reduce invasion, whereas an increase in proteolysis might modulate the activity of inhibitory cytokines, which in turn could reduce endothelial cell proliferation and migration and inhibit angiogenesis. The spectrum of effects on different elements of the PA system observed in response to the agents assessed suggests that the role of modulations in extracellular proteolytic activity in anti-angiogenesis is likely to be varied and complex. PMID:7525617

  9. 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.

  10. Optical imaging measurements of oxygen transport fluctuations and gradients in tumor microvascular networks

    NASA Astrophysics Data System (ADS)

    Sorg, Brian S.; Hardee, Matthew E.; Moeller, Benjamin J.; Dewhirst, Mark W.

    2006-02-01

    It is well established that hypoxia can influence tumor biology and physiology, gene expression, metastatic potential, treatment efficacy, and patient survival. Most human solid tumors have been shown to have some hypoxic regions, thus there is a strong motivation to understand the various causes of hypoxia. One key to understanding tumor hypoxia involves the study of oxygen transport to tumors, and the connection between hypoxia, tumor microvasculature, and the tumor microenvironment. Recent research has suggested that the causes of tumor hypoxia are much more complex than indicated by the classical paradigms ("chronic" and "acute" hypoxia), and several potential factors have been identified. Two such factors are temporal fluctuations in tissue pO II and longitudinal gradients in oxygen transport. Research has shown the existence of low frequency (<2 cycles per minute) fluctuations in tumor pO II without cessation of blood flow that can lead to transient hypoxia. In addition, longitudinal gradients in tumor pO II along the arteriolar afferent direction have been documented in window chamber tumors. However, the causes of the pO II temporal fluctuations and longitudinal gradients are not exactly known, and the clinical significance of these observations is not well understood. In this preliminary study, we demonstrate the potential of optical imaging measurements of hemoglobin saturation to add new information in these areas. Slow temporal fluctuations of hemoglobin saturation (HbSat) and gradients in the average HbSat were observed in some 4T1 mouse mammary carcinoma microvessels. With additional research, the mechanisms behind these phenomena and insights into their clinical significance may be revealed.

  11. Computing Thermodynamic And Transport Properties

    NASA Technical Reports Server (NTRS)

    Mcbride, B.; Gordon, Sanford

    1993-01-01

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

  12. 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.

  13. Transport properties in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Biolsi, L., Jr.

    1979-01-01

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

  14. 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

  15. 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.

  16. Hypoxanthine uptake by skeletal muscle microvascular endothelial cells from equilibrative nucleoside transporter 1 (ENT1)-null mice: effect of oxidative stress.

    PubMed

    Bone, D B J; Antic, M; Quinonez, D; Hammond, J R

    2015-03-01

    Adenosine is an endogenous regulator of vascular tone. This activity of adenosine is terminated by its uptake and metabolism by microvascular endothelial cells (MVEC). The predominant transporter involved is ENT1 (equilibrative nucleoside transporter subtype 1). MVEC also express the nucleobase transporter (ENBT1) which is involved in the cellular flux of adenosine metabolites such as hypoxanthine. Changes in either of these transport systems would impact the bioactivity of adenosine and its metabolism, including the formation of oxygen free radicals. MVEC isolated from skeletal muscle of ENT1(+/+) and ENT1(-/-) mice were subjected to oxidative stress induced by simulated ischemia/reperfusion or menadione. The functional activities of ENT1 and ENBT1 were assessed based on zero-trans influx kinetics of radiolabeled substrates. There was a reduction in the rate of ENBT1-mediated hypoxanthine uptake by ENT1(+/+) MVEC treated with menadione or after exposure to conditions that simulate ischemia/reperfusion. In both cases, the superoxide dismutase mimetic MnTMPyP attenuated the loss of ENBT1 activity, implicating superoxide radicals in the response. In contrast, MVEC isolated from ENT1(-/-) mice showed no reduction in ENBT1 activity upon treatment with menadione or simulated ischemia/reperfusion, but they did have a significantly higher level of catalase activity relative to ENT1(+/+) MVEC. These data suggest that ENBT1 activity is decreased in MVEC in response to the increased superoxide radical that is associated with ischemia/reperfusion injury. MVEC isolated from ENT1(-/-) mice do not show this reduction in ENBT1, possibly due to increased catalase activity. PMID:25448155

  17. Transport properties in the atmosphere of Jupiter

    NASA Technical Reports Server (NTRS)

    Biolsi, L., Jr.

    1978-01-01

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

  18. 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

  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. 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

  1. TRANSPORT PROPERTY MEASUREMENTS OF HFC-236EA

    EPA Science Inventory

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

  2. 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.

  3. 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.

  4. TRANSPORT PROPERTY MEASUREMENTS OF HFC-236EA

    EPA Science Inventory

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

  5. Transport properties of fission product vapors

    SciTech Connect

    Im, K.H.; Ahluwalia, R.K.

    1983-07-01

    Kinetic theory of gases is used to calculate the transport properties of fission product vapors in a steam and hydrogen environment. Provided in tabular form is diffusivity of steam and hydrogen, viscosity and thermal conductivity of the gaseous mixture, and diffusivity of cesium iodide, cesium hydroxide, diatomic tellurium and tellurium dioxide. These transport properties are required in determining the thermal-hydraulics of and fission product transport in light water reactors.

  6. 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 ...

  7. 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

  8. Autologous Microvascular Breast Reconstruction

    PubMed Central

    Ramakrishnan, Venkat

    2013-01-01

    Autologous microvascular breast reconstruction is widely accepted as a key component of breast cancer treatment. There are two basic donor sites; the anterior abdominal wall and the thigh/buttock region. Each of these regions provides for a number of flaps that are successfully utilised in breast reconstruction. Refinement of surgical technique and the drive towards minimising donor site morbidity whilst maximising flap vascularity in breast reconstruction has seen an evolution towards perforator based flap reconstructions, however myocutaneous flaps are still commonly practiced. We review herein the current methods of autologous microvascular breast reconstruction. PMID:23362474

  9. 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

  10. Calculating Theromodynamic And Transport Properties Of Fluids

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.; Klem, Mark D.

    1987-01-01

    Computer program incorporates van der Waals equation and correction tables. FLUID program developed to calculate thermodynamic and transport properties of pure fluids in both liquid and gas phases. Properties calculated by use of simple gas model, empirical corrections, and efficient numerical interpolation scheme. Produces results that agree very well with measured values. Much faster than older, more complex programs developed for same purpose.

  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. Applications of microvascular surgery.

    PubMed

    Miller, C W; Fowler, J D

    1990-09-01

    The advent of microvascular surgery has radically changed the discipline of human reconstructive surgery over the last decade. The ability to anastomose vessels less than 1 mm in diameter allows the distant transfer of tissues with a known blood supply from one area of the body to another. These tissues can be detached from their local blood supply and reperfused by anastomosing vessels supplying the tissue transfer to vessels near the recipient site. This technique has been used to transfer a variety of tissues and combinations of tissues including skin, muscle, bone, and bowel to solve a variety of difficult reconstructive problems. Applications, potential applications, and problems associated with microvascular free tissue transfer will be discussed in this chapter. PMID:2134600

  13. 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.

  14. Thermodynamic and transport properties of fluids

    NASA Technical Reports Server (NTRS)

    Fessler, T. E.

    1980-01-01

    Computer program subroutine FLUID calculates thermodynamic and transport properties of pure fluids in liquid, gas, or two-phase (liquid/gas) conditions. Program determines thermodynamic state from assigned values for temperature and density, pressure and density, temperature and pressure, pressure and entropy, or pressure and enthalpy.

  15. Electronic transport properties in graphene oxide frameworks

    NASA Astrophysics Data System (ADS)

    Zhu, P.; Cruz-Silva, E.; Meunier, V.

    2014-02-01

    The electronic transport properties in multiterminal graphene oxide framework (GOF) materials are investigated using a combination of theoretical and computational methods. GOFs make up four-terminal [origin=c]90H-shaped GNR-L-GNR junctions where sandwiched boronic acid molecules (L) are covalently linked to two graphene nanoribbons (GNRs) of different edge chiralities. The transport properties are governed by both tunneling and quasiresonant regimes. We determine how the presence of linker molecules affects the transport properties and establish that the through-molecule transport properties can be tuned by varying the chemical composition of the pillar molecules but are not significantly modified when changing the type of electrodes from zigzag GNRs to armchair GNRs. In addition, we find that in multilinker systems containing two parallel molecules in the device area, the coupling between the molecules can lead to both constructive and destructive quantum interferences. We also examine the inability of the classical Kirchhoff's superposition law to account for electron flow in multilinker GOF nanonetworks.

  16. Properties of interfaces and transport across them.

    PubMed

    Cabezas, H

    2000-01-01

    Much of the biological activity in cell cytoplasm occurs in compartments some of which may be formed, as suggested in this book, by phase separation, and many of the functions of such compartments depend on the transport or exchange of molecules across interfaces. Thus a fundamentally based discussion of the properties of phases, interfaces, and diffusive transport across interfaces has been given to further elucidate these phenomena. An operational criterion for the width of interfaces is given in terms of molecular and physical arguments, and the properties of molecules inside phases and interfaces are discussed in terms of molecular arguments. In general, the properties of the interface become important when the molecules diffusing across are smaller than the width of the interface. Equilibrium partitioning, Donnan phenomena, and electrochemical potentials at interfaces are also discussed in detail. The mathematical expressions for modeling transport across interfaces are discussed in detail. These describe a practical and detailed model for transport across interfaces. For molecules smaller than the width of the interface, this includes a detailed model for diffusion inside the interface. Last, the question of the time scale for phase formation and equilibration in biological systems is discussed. PMID:10610364

  17. Transport properties in the Jovian atmosphere

    NASA Technical Reports Server (NTRS)

    Biolsi, L.

    1978-01-01

    Transport properties in a Jupiter-like atmosphere (89 mol % hydrogen and 11 mol % helium) are obtained by using the method of the kinetic theory of gases. The transport collision integrals are calculated by fitting various two-body semiempirical interaction potentials for which the collision integrals are tabulated to ab initio quantum mechanical calculations of the two-body interactions. The collision integrals are used to calculate the binary diffusion coefficients, viscosity, and 'total' thermal conductivity of the pure gases and the gas mixtures at 1-atm pressure from 1000 K to 25,000 K.

  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. Charge Transport Properties in Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Moog, Mark; Tsui, Frank; Vonwald, Ian; You, Wei

    Electrical transport properties in poly(3-methyl)thiophene (P3MT) brushes have been studied. The P3MT brushes correspond to a new type of surface-tethered, vertically oriented conjugated molecular wires, sandwiched between two metallic electrodes to form the electrode-molecule-electrode (EME) devices. P3MT is a highly conjugated polymer, a ''workhorse'' material for organic electronics and photonics. The P3MT brushes were grown on ITO surfaces with controlled length (between 2 and 100 nm). The top electrodes were transfer-printed Au films with lateral dimensions between 200 nm and 50 μm. I-V and differential conductance measurements were performed using conductive AFM and 4-terminal techniques. Tunneling and field-emission measurements in EME devices with molecular lengths < 5 nm show HOMO mediated direct hole tunneling with energy barriers of 0.3 and 0.5 eV at the respective interfaces with ITO and Au. The transport properties in longer brushes are indicative of the two quasi-Ohmic interfaces with a characteristic offset in the conductance minimum of 0.12 V biased toward the ITO. Temperature dependent parameters have been examined at various molecular lengths. The drift mobility and the interplay between intra- and intermolecular transport have been investigated.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Transport properties of strontium titanate niobates

    SciTech Connect

    Podkorytov, A.L.; Pantyukhina, M.I.; Zhukovskii, V.M.

    1995-08-01

    In this work the authors studied transport properties of Sr{sub 3}NiNb{sub 2}O{sub 10} and Sr{sub 6-x}Ti{sub x}Nb{sub 2}O{sub 11+x} in order to develop views concerning their high-temperature behavior and mechanisms of disordering in their structures. The authors measured the electrical conductivity (f+1 kHz, RLC meter, 500-1300{degrees}C) and the effective self-diffusion coefficients of radionuclides {sup 90}Sr, {sup 44}Ti, and {sup 95}Nb using radiometric depth profiling (RKB-4IeM {beta}-radiometer) of ceramic samples (porosity no greater than 10%), as described. The samples with radionuclides applied to their faces were annealed in the range 1270-1470 K for 24-100 h. The error in the diffusion coefficients thus measured did not exceed 20%.

  5. Transport properties of epitaxial lift off films

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. Transport properties of alkali metal doped fullerides

    NASA Astrophysics Data System (ADS)

    Yadav, Daluram; Yadav, Nishchhal

    2015-07-01

    We have studied the intercage interactions between the adjacent C60 cages and expansion of lattice due to the intercalation of alkali atoms based on the spring model to estimate phonon frequencies from the dynamical matrix for the intermolecular alkali-C60 phonons. We considered a two-peak model for the phonon density of states to investigate the nature of electron pairing mechanism for superconducting state in fullerides. Coulomb repulsive parameter and the electron phonon coupling strength are obtained within the random phase approximation. Transition temperature, Tc, is obtained in a situation when the free electrons in lowest molecular orbital are coupled with alkali-C60 phonons as 5 K, which is much lower as compared to reported Tc (20 K). The superconducting pairing is mainly driven by the high frequency intramolecular phonons and their effects enhance it to 22 K. The importance of the present study, the pressure effect and normal state transport properties are calculated within the same model leading superconductivity.

  11. 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

  12. 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)

  13. Multiple Functions of Glutamate Uptake via Meningococcal GltT-GltM l-Glutamate ABC Transporter in Neisseria meningitidis Internalization into Human Brain Microvascular Endothelial Cells

    PubMed Central

    Yanagisawa, Tatsuo; Kim, Kwang Sik; Yokoyama, Shigeyuki; Ohnishi, Makoto

    2015-01-01

    We previously reported that Neisseria meningitidis internalization into human brain microvasocular endothelial cells (HBMEC) was triggered by the influx of extracellular l-glutamate via the GltT-GltM l-glutamate ABC transporter, but the underlying mechanism remained unclear. We found that the ΔgltT ΔgltM invasion defect in assay medium (AM) was alleviated in AM without 10% fetal bovine serum (FBS) [AM(−S)]. The alleviation disappeared again in AM(−S) supplemented with 500 μM glutamate. Glutamate uptake by the ΔgltT ΔgltM mutant was less efficient than that by the wild-type strain, but only upon HBMEC infection. We also observed that both GltT-GltM-dependent invasion and accumulation of ezrin, a key membrane-cytoskeleton linker, were more pronounced when N. meningitidis formed larger colonies on HBMEC under physiological glutamate conditions. These results suggested that GltT-GltM-dependent meningococcal internalization into HBMEC might be induced by the reduced environmental glutamate concentration upon infection. Furthermore, we found that the amount of glutathione within the ΔgltT ΔgltM mutant was much lower than that within the wild-type N. meningitidis strain only upon HBMEC infection and was correlated with intracellular survival. Considering that the l-glutamate obtained via GltT-GltM is utilized as a nutrient in host cells, l-glutamate uptake via GltT-GltM plays multiple roles in N. meningitidis internalization into HBMEC. PMID:26099588

  14. Transport properties of finite-beta microturbulence

    SciTech Connect

    Pueschel, M. J.; Jenko, F.

    2010-06-15

    Via nonlinear gyrokinetic simulations, microturbulent transport is investigated for electromagnetic trapped electron mode (TEM) and ion temperature gradient (ITG) tokamak core turbulence with beta up to and beyond the kinetic ballooning mode threshold. Deviations from linear expectations are explained by zonal flow activity in the TEM case. For the ITG scenario, beta-induced changes are observed in the nonlinear critical gradient upshift--from a certain beta, a strong increase is observed in the Dimits shift. Additionally, a Rechester-Rosenbluth-type model for magnetic transport is applied, and the amplitudes of magnetic field fluctuations are quantified for different types of turbulence.

  15. 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.

  16. 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...

  17. 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

  18. Endoscopic and Microscopic Microvascular Decompression.

    PubMed

    Piazza, Matthew; Lee, John Y K

    2016-07-01

    The introduction of the endoscope into the neurosurgeon's armamentarium has revolutionized ventral and anterior skull-base surgery and, more recently, has been used in the surgical treatment of cerebellopontine angle (CPA) pathology. The utilization of the endoscope in microvascular decompression (MVD) for trigeminal neuralgia and other associated cranial nerve hyperactivity syndromes allows for unparalleled panoramic views and illumination of the neurovascular structures within the CPA and identification of vessel-nerve contact traditionally unseen using the microscope. In this article, the technical advantages and challenges of using the endoscope for MVD, operative technique, and patient outcomes of endoscopic MVD are discussed. PMID:27324997

  19. 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

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. Middle Atmosphere Transport Properties of Assimilated Datasets

    NASA Technical Reports Server (NTRS)

    Pawson, Steven; Rood, Richard

    1999-01-01

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

  6. Middle Atmospheric Transport Properties of Assimilated Datasets

    NASA Technical Reports Server (NTRS)

    Pawson, Steven; Rood, Richard

    1999-01-01

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

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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. PMID:26266491

  13. Transport properties of high-temperature Jupiter atmosphere components

    SciTech Connect

    Bruno, D.; Colonna, G.; De Pascale, O.; Laricchiuta, A.; Catalfamo, C.; Diomede, P.; Capitelli, M.; Gorse, C.; Longo, S.; Giordano, D.; Pirani, F.

    2010-11-15

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

  14. 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.

  15. 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.

  16. Transport properties of a discrete helical electrostatic quadrupole

    SciTech Connect

    Meitzler, C.R.; Antes, K.; Datte, P.; Huson, F.R. ); Xiu, L. . Inst. for Beam Particle Dynamics)

    1991-01-01

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

  17. Coronary microvascular dysfunction: an update

    PubMed Central

    Crea, Filippo; Camici, Paolo G.; Bairey Merz, Cathleen Noel

    2014-01-01

    Many patients undergoing coronary angiography because of chest pain syndromes, believed to be indicative of obstructive atherosclerosis of the epicardial coronary arteries, are found to have normal angiograms. In the past two decades, a number of studies have reported that abnormalities in the function and structure of the coronary microcirculation may occur in patients without obstructive atherosclerosis, but with risk factors or with myocardial diseases as well as in patients with obstructive atherosclerosis; furthermore, coronary microvascular dysfunction (CMD) can be iatrogenic. In some instances, CMD represents an epiphenomenon, whereas in others it is an important marker of risk or may even contribute to the pathogenesis of cardiovascular and myocardial diseases, thus becoming a therapeutic target. This review article provides an update on the clinical relevance of CMD in different clinical settings and also the implications for therapy. PMID:24366916

  18. 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.

  19. Transport properties of water at functionalized molecular interfaces

    PubMed Central

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

    2009-01-01

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

  20. 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.

  1. 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

  2. Reducing Microvascular Dysfunction in Revascularized Patients with ST-Elevation Myocardial Infarction by Off-Target Properties of Ticagrelor versus Prasugrel. Rationale and Design of the REDUCE-MVI Study.

    PubMed

    Janssens, Gladys N; van Leeuwen, Maarten A H; van der Hoeven, Nina W; de Waard, Guus A; Nijveldt, Robin; Diletti, Roberto; Zijlstra, Felix; von Birgelen, Clemens; Escaned, Javier; Valgimigli, Marco; van Royen, Niels

    2016-06-01

    Microvascular injury is present in a large proportion of patients with ST-elevation myocardial infarction (STEMI) despite successful revascularization. Ticagrelor potentially mitigates this process by exerting additional adenosine-mediated effects. This study aims to determine whether ticagrelor is associated with a better microvascular function compared to prasugrel as maintenance therapy after STEMI. A total of 110 patients presenting with STEMI and additional intermediate stenosis in another coronary artery will be studied after successful percutaneous coronary intervention (PCI) of the infarct-related artery. Patients will be randomized to treatment with ticagrelor or prasugrel for 1 year. FFR-guided PCI of the non-infarct-related artery will be performed at 1 month. Microvascular function will be assessed by measurement of the index of microcirculatory resistance (IMR) in the infarct-related artery and non-infarct-related artery, immediately after primary PCI and after 1 month. The REDUCE-MVI study will establish whether ticagrelor as a maintenance therapy may improve microvascular function in patients after revascularized STEMI. PMID:27102290

  3. 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.

  4. Computer programs for thermodynamic and transport properties of hydrogen

    NASA Technical Reports Server (NTRS)

    Hall, W. J.; Mc Carty, R. D.; Roder, H. M.

    1968-01-01

    Computer program subroutines provide the thermodynamic and transport properties of hydrogen in tabular form. The programs provide 18 combinations of input and output variables. This program is written in FORTRAN 4 for use on the IBM 7044 or CDC 3600 computers.

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

    National Institute of Standards and Technology Data Gateway

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

  6. Properties and Transport Behavior among 12 Different Environmental Escherichia coli

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Escherichia coli is a commonly used indicator organism for detecting the presence of fecal-borne pathogenic microorganisms in water supplies. The importance of E. coli as an indicator organism has led to numerous studies looking at cell properties and transport behavior of this microorganism. In man...

  7. 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.

  8. 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.

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

    PubMed Central

    2014-01-01

    Thermal transport properties of graphene with nanosized constrictions are investigated using nonequilibrium molecular dynamics simulations. The results show that the nanosized constrictions have a significant influence on the thermal transport properties of graphene. The thermal resistance of the nanosized constrictions is on the order of 107 to 109 K/W at 150 K, which reduces the thermal conductivity by 7.7% to 90.4%. It is also found that the constriction resistance is inversely proportional to the width of the constriction and independent of the heat current. Moreover, we developed an analytical model for the ballistic thermal resistance of the nanosized constrictions in two-dimensional nanosystems. The theoretical prediction agrees well with the simulation results in this paper, which suggests that the thermal transport across the nanosized constrictions in two-dimensional nanosystems is ballistic in nature. PACS 65.80.CK; 61.48.Gh; 63.20.kp; 31.15.xv PMID:25232292

  10. 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

  11. Mass-Transport Properties In Growth Of Crystals From Vapors

    NASA Technical Reports Server (NTRS)

    Wiedemeier, H.

    1992-01-01

    Brief report summarizes results of experimental and theoretical studies of mass-transport properties of GeSe/Gel4 and Hg0.8Cd0.2Te systems in connection with growth of crystals in closed ampoules. Primary emphasis in studies was on thermochemical analyses, on development of mathematical models to predict diffusion-limited mass transport, and on comparison of theoretically predicted with experimental fluxes. Results applied to design, preparation, performance, and analysis of crystal-growth experiments of semiconducting materials on Earth and in outer space. Model extended to predict mass flux and overall composition of transport products of Hg0.8Cd0.2Te transport system.

  12. 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.

  13. A computational model of oxygen delivery by hemoglobin-based oxygen carriers in three-dimensional microvascular networks

    PubMed Central

    Tsoukias, Nikolaos M.; Goldman, Daniel; Vadapalli, Arjun; Pittman, Roland N.; Popel, Aleksander S.

    2009-01-01

    A detailed computational model is developed to simulate oxygen transport from a three-dimensional microvascular network to surrounding tissue in the presence of hemoglobin-based oxygen carriers. The model accounts for nonlinear O2 consumption, myoglobin facilitated diffusion and nonlinear oxyhemoglobin dissociation in the RBCs and plasma. It also includes a detailed description of intravascular resistance to O2 transport and is capable of incorporating realistic three-dimensional microvascular network geometries. Simulations in this study were performed using a computer-generated microvascular architecture that mimics morphometric parameters for the hamster cheek pouch retractor muscle. Theoretical results are presented next to corresponding experimental data. Phosphoresence quenching microscopy provided PO2 measurements at the arteriolar and venular ends of capillaries in the hamster retractor muscle before and after isovolemic hemodilution with three different hemodilutents; a non-oxygen-carrying plasma expander and two hemoglobin solutions with different oxygen affinities. Sample results in a microvascular network show an enhancement of diffusive shunting between arterioles, venules and capillaries and a decrease in hemoglobin’s effectiveness for tissue oxygenation when its affinity for O2 is decreased. Model simulations suggest that microvascular network anatomy can affect the optimal hemoglobin affinity for reducing tissue hypoxia. O2 transport simulations in realistic representations of microvascular networks should provide a theoretical framework for choosing optimal parameter values in the development of hemoglobin-based blood-substitutes. PMID:17686494

  14. Coronary microvascular dysfunction, microvascular angina, and treatment strategies.

    PubMed

    Marinescu, Mark A; Löffler, Adrián I; Ouellette, Michelle; Smith, Lavone; Kramer, Christopher M; Bourque, Jamieson M

    2015-02-01

    Angina without coronary artery disease (CAD) has substantial morbidity and is present in 10% to 30% of patients undergoing angiography. Coronary microvascular dysfunction (CMD) is present in 50% to 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 or myocardial perfusion reserve <2.5 by positron emission tomography, cardiac magnetic resonance imaging, dilution methods, or intracoronary Doppler in the absence of coronary artery stenosis ≥50% or structural heart disease. Only 8 papers met the strict inclusion criteria. The papers were heterogeneous, using different treatments, endpoints, and definitions of CMD. The 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 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 published data. 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

  15. 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

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

    SciTech Connect

    Martin, T.

    1994-08-26

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

  17. 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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    Due to its large in-plane thermal conductivity, high temperature and chemical stability, large energy band gap (˜ 6.4 eV), hexagonal boron nitride (hBN) has emerged as an important material for applications in deep ultraviolet photonic devices. Among the members of the III-nitride material system, hBN is the least studied and understood. The study of the electrical transport properties of hBN is of utmost importance with a view to realizing practical device applications. Wafer-scale hBN epilayers have been successfully synthesized by metal organic chemical deposition and their electrical transport properties have been probed by variable temperature Hall effect measurements. The results demonstrate that undoped hBN is a semiconductor exhibiting weak p-type at high temperatures (> 700 °K). The measured acceptor energy level is about 0.68 eV above the valence band. In contrast to the electrical transport properties of traditional III-nitride wide bandgap semiconductors, the temperature dependence of the hole mobility in hBN can be described by the form of μ ∝ (T/T0)-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-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.

  19. 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

  20. Intrinsic electronic and transport properties of graphyne sheets and nanoribbons.

    PubMed

    Wu, Wenzhi; Guo, Wanlin; Zeng, Xiao Cheng

    2013-10-01

    Graphyne, a two-dimensional carbon allotrope like graphene but containing doubly and triply bonded carbon atoms, has been proven to possess amazing electronic properties as graphene. Although the electronic, optical, and mechanical properties of graphyne and graphyne nanoribbons (NRs) have been previously studied, their electron transport behaviors have not been understood. Here we report a comprehensive study of the intrinsic electronic and transport properties of four distinct polymorphs of graphyne (α, β, γ, and 6,6,12-graphynes) and their nanoribbons (GyNRs) using density functional theory coupled with the non-equilibrium Green's function (NEGF) method. Among the four graphyne sheets, 6,6,12-graphyne displays notable directional anisotropy in the transport properties. Among the GyNRs, those with armchair edges are nonmagnetic semiconductors whereas those with zigzag edges can be either antiferromagnetic or nonmagnetic semiconductors. Among the armchair GyNRs, the α-GyNRs and 6,6,12-GyNRs exhibit distinctive negative differential resistance (NDR) behavior. On the other hand, the zigzag α-GyNRs and zigzag 6,6,12-GyNRs exhibit symmetry-dependent transport properties, that is, asymmetric zigzag GyNRs behave as conductors with nearly linear current-voltage dependence, whereas symmetric GyNRs produce very weak currents due to the presence of a conductance gap around the Fermi level under finite bias voltages. Such symmetry-dependent behavior stems from different coupling between π* and π subbands. Unlike α- and 6,6,12-GyNRs, both zigzag β-GyNRs and zigzag γ-GyNRs exhibit NDR behavior regardless of the symmetry. PMID:23949158

  1. Transport properties of the calcium ionophore ETH-129.

    PubMed

    Wang, E; Erdahl, W L; Hamidinia, S A; Chapman, C J; Taylor, R W; Pfeiffer, D R

    2001-12-01

    The transport mechanism and specificities of ionophore ETH-29 have been investigated in a highly defined phospholipid vesicle system, with the goal of facilitating the application of this compound to biological problems. ETH-129 transports Ca(2+) via an electrogenic mechanism, in contrast to A23187 and ionomycin, which function in a charge neutral manner. The rate of transport is a function of membrane potential, increasing by 3.9-fold per 59 mV over a broad range of that parameter. Rate is independent of the transmembrane pH gradient and strongly stimulated by the uncoupler carbonyl cyanide m-chlorophenylhydrazone when no external potential has been applied. The effect of uncoupler reflects the collapse of an opposing potential arising during Ca(2+) transport, but also reflects the formation of a mixed complex between the uncoupler, ETH-129, and Ca(2+) that readily permeates the vesicle membrane. Oleate does not substitute for the uncoupler in either regard. ETH-129 transports polyvalent cations according to the selectivity sequence La(3+) > Ca(2+) > Zn(2+) approximately equal to Sr(2+) > Co(2+) approximately equal to Ni(2+) approximately equal to Mn(2+), with the magnitude of the selectivity coefficients reflecting the cation concentration range considered. There is little or no activity for the transport of Na(+), K(+), and Mg(2+). These properties suggest that ETH-129 will be useful for investigating the consequences of a mitochondrial Ca(2+) overload in mammalian cells, which is difficult to pursue through the application of electroneutral ionophores. PMID:11720991

  2. 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.

  3. Electrical Transport Properties of Liquid Al-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Thakore, B. Y.; Khambholja, S. G.; Suthar, P. H.; Jani, A. R.

    2010-06-01

    Electrical transport properties viz. electrical resistivity, thermoelectric power and thermal conductivity of liquid Al-Cu alloys as a function of Cu concentration have been studied in the present paper. Ashcroft empty core model potential has been used to incorporate the ion-electron interaction. To incorporate the exchange and correlation effects, five different forms of local field correction functions viz. Hartree, Taylor, Ichimaru et al., Farid et al. and Sarkar et al. have been used. The transport properties of binary system have been studied using Faber-Ziman formulation combined with Ashcroft-Langreth (AL) partial structure factor. The computed values of electrical resistivity are compared with experimental data and for low Cu concentration, good agreement has been observed. Further, thermoelectric power and thermal conductivity have also been predicted.

  4. Electrical transport properties of manganite powders under pressure

    NASA Astrophysics Data System (ADS)

    Rodríguez, M. G.; Leyva, A. G.; Acha, C.

    2012-08-01

    We have measured the electrical resistance of micrometric to nanometric powders of the LaPryCaMnO3 (LPCMO with y=0.3) manganite for hydrostatic pressures up to 4 kbar. By applying different final thermal treatments to samples synthesized by a microwave assisted denitration process, we obtained two particular grain characteristic dimensions (40 nm and 1000 nm) which allowed us to analyze the grain size sensitivity of the electrical conduction properties of both the metal electrode interface with manganite (Pt/LPCMO) and the intrinsic intergranular interfaces formed by the LPCMO powder, conglomerate under the only effect of external pressure. We also analyzed the effects of pressure on the phase diagram of these powders. Our results indicate that different magnetic phases coexist at low temperatures and that the electrical transport properties are related to the intrinsic interfaces, as we observe evidences of a granular behavior and an electronic transport dominated by the Space Charge limited Current mechanism.

  5. Transport properties of two finite armchair graphene nanoribbons.

    PubMed

    Rosales, Luis; González, Jhon W

    2013-01-01

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

  6. Transport properties of two finite armchair graphene nanoribbons

    PubMed Central

    2013-01-01

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

  7. 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.

  8. 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.

  9. Volume transport and property distributions of the Mozambique Channel

    NASA Astrophysics Data System (ADS)

    DiMarco, Steven F.; Chapman, Piers; Nowlin, Worth D.; Hacker, Peter; Donohue, Kathleen; Luther, Mark; Johnson, Gregory C.; Toole, John

    We summarize previous estimates of volume transport and property distributions through the Mozambique Channel and offer additional estimates and measurements based on recently acquired hydrographic and float data. Previously published property distributions are consistent with southward spreading through the Channel. Waters of the Mozambique Channel are characterized by shallow and intermediate oxygen minima separated by a relative maximum. Based on hydrographic sections, the intermediate maximum in dissolved oxygen is seen to decrease in value as it spreads southward. The highest values are found in the westward flow of the South Equatorial Current just north of Madagascar and within the western 200 km of the Channel. Similarly, oxygen concentrations at the intermediate oxygen minimum, which derives from the Arabian Sea, increase southwards, while its depth increases from 900 to 1100 m, supporting previous studies and indicating southward spreading and mixing along the Mozambique Channel. Historical transports based on hydrographic data in the Channel vary from 5 Sv northward to 26 Sv southward depending on reference level and time of the year. Balancing transport below 2500 m (the sill depth in the Channel), we estimate the net southward transports above this depth to be 29.1 and 5.9 Sv for the northern and southern sections, respectively—the difference is presumably related to seasonality and eddy variability superimposed on the mean flow. Individual deep float trajectories show the presence of many eddies, but the overall flow in the channel is southward, and broadly consistent with hydrography. Model outputs also show mean southward transport with considerable seasonal variability. Satellite data show high variability in sea surface height anomalies and high eddy kinetic energy associated with eddy activity. Although the geostrophic transport values are consistent with the historical limits, the lowered ADCP measurements suggest a substantial barotropic

  10. TOPICAL REVIEW: Nanoscale transport properties at silicon carbide interfaces

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

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

  11. 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.

  12. Thermoelectric transport properties of In2Se3 single crystal

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi Huong; Duong, Van Thiet; Nguyen, Van Quang; Duong, Anh Tuan; Cho, Sunglae; Song, Jae Yong; Park, Hyun-Min

    In recent years the discovery and development of green energy source are one of the top concerns in science. The enormous efforts have been devoted to search for thermoelectric materials. Enhancement of thermoelectric figure of merit (ZT = (S2 σ / κ) T) is currently research goal of scientists. In2Se3 is one of semiconductors with layered structure, which is good for thermoelectric applications. In this study, we report on the transport and thermoelectric properties of In2Se3 single crystal. The layered crystal structure of In2Se3 was determined by XRD and FE-SEM measurements. Ellipsometry measurement illustrated the indirect band gap of In2Se3, about 1.61 eV. Transport properties have been studied in the temperature range from 20 to 400 K along axis which is parallel to the layers direction. Interestingly, Seebeck coefficient was n-type and increased with temperature and the electrical conductivity increased with temperature. Therefore, power factor increased up to 2.69 µWcm-1K-2at 400 K. In this talk, we will discuss more on transport properties.

  13. 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.

  14. Viscoelastic properties of actin networks influence material transport

    NASA Astrophysics Data System (ADS)

    Stam, Samantha; Weirich, Kimberly; Gardel, Margaret

    2015-03-01

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

  15. Who Is at Risk for Coronary Microvascular Disease?

    MedlinePlus

    ... Stumble. Share this page from the NHLBI on Tumblr. Share this page from the NHLBI on Twitter. Who Is at Risk for Coronary Microvascular Disease? Coronary microvascular disease can affect both men and ...

  16. Neutrophils, nitric oxide, and microvascular permeability in severe sepsis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    STUDY OBJECTIVES: Alterations in microvascular permeability are prevalent in patients with sepsis; a recent study reported that patients with septic shock had increased capillary filtration coefficient (Kf), a noninvasive index of microvascular permeability. We aimed to determine whether patients wi...

  17. 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. PMID:26364289

  18. 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

  19. 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

  20. Space radiation transport properties of polyethylene-based composites.

    PubMed

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

    2004-11-01

    Composite materials that can serve as both effective shielding materials against cosmic-ray and energetic solar particles in deep space, as well as structural materials for habitat and spacecraft, remain a critical and mission enabling component in mission planning and exploration. Polyethylene is known to have excellent shielding properties due to its low density, coupled with high hydrogen content. Polyethylene-fiber reinforced composites promise to combine this shielding effectiveness with the required mechanical properties of structural materials. Samples of polyethylene-fiber reinforced epoxy matrix composite 1-5 cm thick were prepared at the NASA Marshall Space Flight Center and tested against a 500 MeV/nucleon Fe beam at the HIMAC facility of NIRS in Chiba, Japan. This paper presents measured and calculated results for the radiation transport properties of these samples. PMID:15644352

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. Transport properties of transition metal impurities on gold nanowires

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

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

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. Thermal transport and thermoelectric properties of beta-graphyne nanostructures.

    PubMed

    Ouyang, Tao; Hu, Ming

    2014-06-20

    Graphyne, an allotrope of graphene, is currently a hot topic in the carbon-based nanomaterials research community. Taking beta-graphyne as an example, we performed a comprehensive study of thermal transport and related thermoelectric properties by means of nonequilibrium Green's function (NEGF). Our simulation demonstrated that thermal conductance of beta-graphyne is only approximately 26% of that of the graphene counterpart and also shows evident anisotropy. Meanwhile, thermal conductance of armchair beta-graphyne nanoribbons (A-BGYNRs) presents abnormal stepwise width dependence. As for the thermoelectric property, we found that zigzag beta-graphyne nanoribbons (Z-BGYNRs) possess superior thermoelectric performance with figure of merit value achieving 0.5 at room temperature, as compared with graphene nanoribbons (~0.05). Aiming at obtaining a better thermoelectric coefficient, we also investigated Z-BGYNRs with geometric modulations. The results show that the thermoelectric performance can be enhanced dramatically (figure of merit exceeding 1.5 at room temperature), and such enhancement strongly depends on the width of the nanoribbons and location and quantity of geometric modulation. Our findings shed light on transport properties of beta-graphyne as high efficiency thermoelectrics. We anticipate that our simulation results could offer useful guidance for the design and fabrication of future thermoelectric devices. PMID:24859889

  15. Multi-scale mechanical and transport properties of a hydrogel.

    PubMed

    Salahshoor, Hossein; Rahbar, Nima

    2014-09-01

    In this paper, molecular dynamic simulation was used to study the effect of water on the equilibrated structure and mechanical properties of cross-linked hydrogel at multiple scales. The hydrogel consisted of Polyethylene glycol diglycidyl ether (PEGDGE) as epoxy and the Jeffamine, poly-oxy-alkylene-amines, as curing agent. The results for systems with various water contents indicated that the cross-links were more hydrophilic within the hydrogel structure. Effects of cross-linking on the transport properties were also investigated by computing diffusion coefficients of water molecules. A new Coarse-Grained (CG) scheme for hydrogels is proposed, and validated by comparing the transport properties with the all-atom method, demonstrating the capability of the model to capture the correct dynamic evolution of the system. The all-atom model of the hydrogel was mapped to the CG model using the MARTINI force field. This method resulted in a more realistic representation of the stiffness of the system, compared to the previous experimental studies in the literature. The variation of the stiffness of the hydrogel as a function of the water content showed that 40% water content is the optimal value for mechanical performance of the hydrogel. PMID:24967978

  16. Electronic correlation and transport properties of nuclear fuel materials

    SciTech Connect

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

    2011-11-15

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

  17. 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.

  18. 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.

  19. 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).

  20. Thermoelectric transport properties of molybdenum from abinitio simulations

    NASA Astrophysics Data System (ADS)

    French, Martin; Mattsson, Thomas R.

    2014-10-01

    We employ abinitio simulations based on density functional theory (DFT) to calculate the electronic transport coefficients (electrical conductivity, thermal conductivity, and thermopower) of molybdenum over a broad range of thermodynamic states. By comparing to available experimental data, we show that DFT is able to describe the desired transport properties of this refractory metal with high accuracy. Most noteworthy, both the positive sign and the quantitative values of the thermopower of solid molybdenum are reproduced very well. We calculate the electrical and thermal conductivity in the solid and the fluid phase between 1000 and 20 000 K and a wide span in density and develop empirical fit formulas for direct use in practical applications, such as magneto-hydrodynamics simulations. The influence of thermal expansion in conductivity measurements at constant pressure is also discussed in some detail.

  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 in Superconducting Wires Coupled to Ferromagnetic Leads

    NASA Astrophysics Data System (ADS)

    Chen, Qiao; Zhang, Ya-Min; Xu, H. Q.; Xu, Ning

    2016-02-01

    We investigate the transport properties of a pair of Majorana bound states in both serial configuration and T-shape configuration with ferromagnetic leads. By using a non-equilibrium Green's function method, the formula of current and shot noise are obtained. The numerical results show that the coupling between the Majorana bounds states at the ends of a wire can be tuned by the polarization P and polarization angle θ intimately in serial configuration. However, this coupling in T-shape configuration is only affected by ferromagnetic leads faintly. In addition, the Fano factor in both configurations is influenced by the polarization P and polarization angle θ intimately at low bias region. Because of the different transport mechanisms, the serial configuration and T-shape configuration show sub-Poissonian and super-Poissonian shot noise at low bias, respectively.

  3. Electronic correlation and transport properties of nuclear fuel materials

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  4. Transport properties of the hot and dense sQGP

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  5. 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

  6. Thermodynamic and transport properties of cryogenic propellants and related fluids

    NASA Technical Reports Server (NTRS)

    Johnson, V. J.

    1973-01-01

    Significant advances have been made in recent years in the quality and range of thermophysical data for the cryogenic propellants, pressurants, and inertants. A review of recently completed and current data compilation projects for helium, hydrogen, argon, nitrogen, oxygen, fluorine, and methane is given together with recommended references for thermodynamic and transport property data tables for these fluids. Modern techniques in the plotting of thermodynamic charts from tabular data (or from functions such as the equation of state) have greatly improved their precision and value. A list of such charts is included.

  7. Transport properties in periodically modulated zigzag silicene nanoribbon

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Shuang; Shen, Man; An, Xing-Tao; Liu, Jian-Jun

    2016-04-01

    We study theoretically the electronic transport properties of zigzag silicene nanoribbon superlattices subject to a periodic electric field perpendicular to the surface of silicene. Our results show that the conductivity of the system depends on the superlattice structural parameters and show effects analogous to those found with two-dimensional semiconductor superlattices. For a superlattice with Nb barriers, a series of resonant peaks, each of which is split into (Nb - 1) subpeaks, and transmission blockade regions appear in the conductance spectrum, which indicates the formation of minibands and minigaps. These silicene-based quantum structures can provide concepts for the design nanodevices.

  8. Synthesis and electrical transport properties of SnS nanoparticles

    NASA Astrophysics Data System (ADS)

    Chaki, S. H.; Deshpande, M. P.; Chaudhary, M. D.; Tailor, J. P.; Mahato, K. S.

    2013-02-01

    The SnS nanoparticles were synthesized at ambient temperature by simple wet chemical method. The stoichiometric and structural characterization was done by EDAX and XRD techniques respectively. The crystallite size was determined using Scherrer's formula and Hall-Williamson plot using XRD data. The electrical transport properties studies were carried out on pellets prepared by hydraulic pressing of SnS nanoparticles. The thermoelectric power and dc resistivity variation with temperature was studied on the pellets. Room temperature Hall effect measurement was made on the pellet. The obtained results are discussed in details.

  9. 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.

  10. 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

  11. Study of electronic transport properties of doped 8AGNR

    SciTech Connect

    Sharma, Uma Shankar; Srivastava, Anurag; Verma, U. P.

    2014-04-24

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

  12. How to assess microvascular structure in humans.

    PubMed

    Rizzoni, Damiano; Aalkjaer, Christian; De Ciuceis, Carolina; Porteri, Enzo; Rossini, Claudia; Rosei, Claudia Agabiti; Sarkar, Annamaria; Rosei, Enrico Agabiti

    2011-12-01

    Structural alterations of subcutaneous small resistance arteries, as indicated by an increased media to lumen ratio, are frequently present in hypertensive and/or diabetic patients. However, the evaluation of microvascular structure is not an easy task. Among the methods that may be applied to humans, plethysmographic evaluation of small arteries and wire or pressure micromyography were extensively used in the last decades. Media to lumen ratio of small arteries evaluated by micromyography was demonstrated to possess a strong prognostic significance; however, its extensive evaluation is limited by the invasiveness of the assessment, since a biopsy of subcutaneous fat is needed. Non-invasive approaches were then proposed, including capillaroscopy, which provides information about microvascular rarefaction. Recently, the interest of investigators has focused on the retinal microvascular bed. In particular, a non-invasive measurement of wall thickness to internal lumen ratio of retinal arterioles using scanning laser Doppler flowmetry has been recently introduced. Preliminary data suggest a fairly good agreement between this approach and micromyographic measurements, generally considered the gold standard approach. Therefore, the evaluation of microvascular structure is progressively moving from bench to bedside, and it could represent, in the immediate future, an evaluation to be performed in all hypertensive patients, in order to obtain a better stratification of cardiovascular risk. PMID:22283671

  13. 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

  14. Electronic and transport properties of LiCoO2.

    PubMed

    Andriyevsky, Bohdan; Doll, Klaus; Jacob, Timo

    2014-11-14

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

  15. 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.

  16. 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).

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. Graphene on graphene antidot lattices: Electronic and transport properties

    NASA Astrophysics Data System (ADS)

    Gregersen, Søren Schou; Pedersen, Jesper Goor; Power, Stephen R.; Jauho, Antti-Pekka

    2015-03-01

    Graphene bilayer systems are known to exhibit a band gap when the layer symmetry is broken by applying a perpendicular electric field. The resulting band structure resembles that of a conventional semiconductor with a parabolic dispersion. Here, we introduce a bilayer graphene heterostructure, where single-layer graphene is placed on top of another layer of graphene with a regular lattice of antidots. We dub this class of graphene systems GOAL: graphene on graphene antidot lattice. By varying the structure geometry, band-structure engineering can be performed to obtain linearly dispersing bands (with a high concomitant mobility), which nevertheless can be made gapped with a perpendicular field. We analyze the electronic structure and transport properties of various types of GOALs, and draw general conclusions about their properties to aid their design in experiments.

  3. 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.

  4. 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.

  5. 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.

  6. Soil properties and preferential solute transport at the field scale

    NASA Astrophysics Data System (ADS)

    Koestel, J. K.; Luong, N. M.; Nørgaard, T.; Vendelboe, A. L.; Moldrup, P.; Jarvis, N. J.; Lamandé, M.; Iversen, B. V.; Wollesen de Jonge, L.

    2012-04-01

    An important fraction of water flow and solute transport through soil takes place through preferential flow paths. Although this had been already observed in the nineteenth century, it had been forgotten by the scientific community until it was rediscovered during the 1970s. The awareness of the relevance of preferential flow was broadly re-established in the community by the early 1990s. However, since then, the notion remains widespread among soil scientists that the occurrence and strength of preferential flow cannot be predicted from measurable proxy variables such as soil properties or land management practices (e.g. Beven, K., 1991, Modeling preferential flow - an uncertain future, Preferential Flow, 1-11). In our study, we present evidence that disproves this notion. We evaluated breakthrough curve experiments under a constant irrigation rate of 1 cm/h conducted on 65 soil columns (20 cm diameter and 20 height) which had been sampled from an approximately 1 ha large loamy field-site in Silstrup, Denmark. We show that the holdback factor, which is an indicator for the strength of preferential transport, is strongly correlated to the bulk density, which in turn is correlated to the organic matter content. By applying multiple linear regression in a bootstrapping framework, we could estimate the holdback factor from the bulk density and the very fine sand fraction with a coefficient of determination of 0.65. Our results raise hopes that it is indeed possible to establish pedotransfer functions for soil susceptibility to preferential flow and transport.

  7. Bipolar Charge Transport Properties of Poly(imide-thienyl(thienylenevinylene))

    NASA Astrophysics Data System (ADS)

    Lafalce, Evan; Jiang, Xiaomei; Zhang, Cheng

    2014-03-01

    The charge transport properties of π-conjugated polymers are of interest from a fundamental perspective and also because they are a limiting factor for many optoelectronic device applications. In this work, we study the charge carrier mobility and recombination in Poly(imide-thienyl(thienylenevinylene)) (imide-PTV), a novel PTV derivative with imide side group. The electron and hole mobility are determined separately through the Space Charge Limited Current (SCLC) analysis of single carrier diodes. These devices are fabricated using interfacial layers that provide carrier selective contacts. A mobility asymmetry factor of approximately 20 that favors hole transport is observed, with the hole mobility of the order of 10-5 [cm2/V*s]. Similar results are obtained from the analysis of the intensity dependence of photoconductivity. Complimentary analysis of the ambipolar carrier mobility through carrier extraction under linearly increasing voltage (CELIV) and double injection transient techniques are also presented. The effects of carrier recombination and trapping are discussed. We conclude that the hole transport is not the limiting factor for power conversion efficiency of photovoltaic device based on imide-PTV and PCBM.

  8. 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

  9. 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.

  10. Ionic transport properties of template-synthesized gold nanotube membranes

    NASA Astrophysics Data System (ADS)

    Gao, Peng

    Ionic transport in nanotubes exhibits unique properties due to the strong interactions between ions and the nanotube surface. The main objective of my research is to explore and regulate the ionic transport in gold nanotube membranes. Chapter 1 overviews a versatile method of fabricating nanostructured materials, called the template synthesis. Important parameters of the template synthesis are introduced such as templates and deposition methods. The template synthesis method is used to prepare membranes used in this dissertation. Chapter 2 describes a method to increase the ionic conductivity in membranes containing gold nanotubes with small diameter (4 nm). The gold nanotube membrane is prepared by the electroless plating of gold in a commercially available polycarbonate membrane. Voltages are applied to the gold nanotube membrane and fixed charges are injected on the gold nanotube walls. We show that ionic conductivity of the gold nanotube membrane can be enhanced in aqueous potassium chloride (KCl) solution at negative applied voltages. When the most negative voltage (-0.8 V vs. Ag/AgCl) is applied to the membrane, the ionic conductivity of the solution inside the gold nanotube (94 mS.cm-1) is comparable to that of 1 M aqueous KCl, over two orders of magnitude higher than that of the 0.01 M KCl contacting the membrane. Chapter 3 explores another important transport property of the gold nanotube membrane -- ion permselectivity. When the permselective membrane separates two electrolyte solutions at different concentrations, a membrane potential is developed and measured by the potentiometric method. Surface charge density and the ion mobilities are estimated by fitting the experimental data with a pre-existing model. The surface charge density of the gold nanotube membrane in this research is estimated to be 2 muC/cm2. Chapter 4 describes voltage-controlled ionic transport in a gold/polypyrrole membrane doped with sodium dodecylbenzene sulfonate (DBS). Polypyrrole

  11. Electrical transport properties of single-layer WS2.

    PubMed

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

    2014-08-26

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

  12. Physicochemical properties determine nanomaterial cellular uptake, transport and fate

    PubMed Central

    Zhu, Motao; Nie, Guangjun; Meng, Huan; Xia, Tian; Nel, Andre; Zhao, Yuliang

    2015-01-01

    CONSPECTUS There are a growing range of innovations in the field of nanobiotechnology and nanomedicine. However, the increased number of engineered nanomaterials (ENMs) and their novel physicochemical properties pose a new challenge of understanding the full spectrum of their interactions at the nano/bio interface, including the potential to engage in hazardous interactions. A comprehensive understanding of these interactions is required, including the physicochemical properties that control bioavailability and how this knowledge could be used for safer nanomaterial design. To this end, considerable knowledge generation and exploration is required to understand how material properties influence ENM uptake, transport and fate, as well as the biological consequences of these interactions at cellular level. The toxicity mechanisms of different ENMs differ with nanosize/nanosurface which directly correlates to the physicochemical activities of ENMs in vivo. So, to explore their underlying physicochemical processes of ENMs in cells will be essentially helpful for definitely understanding the toxicity of ENMs. In addition, the in vitro results are indispensable for modeling the biokinetics of ENMs. Nevertheless, we need to proceed such extrapolation with due caution, because the dosage relevance between the in vitro and in vivo exposure largely influences outcomes of the toxic response. In this Account, we delineate our view of the impact of ENM physicochemical properties on cellular bioprocessing based on the research performed in our laboratories. Because organic, inorganic, and hybrid ENMs can be produced in various sizes, shapes, surface modifications and compositions, and their widely tunable compositions and structures that can be dynamically modified under different biological and environmental use conditions. Therefore, a description of how ENM chemical properties such as (1) hydrophobicity and hydropholicity, (2) material composition, (3) surface

  13. Transport properties of highly asymmetric hard-sphere mixtures.

    PubMed

    Bannerman, Marcus N; Lue, Leo

    2009-04-28

    The static and dynamic properties of binary mixtures of hard spheres with a diameter ratio of sigma(B)/sigma(A)=0.1 and a mass ratio of m(B)/m(A)=0.001 are investigated using event driven molecular dynamics. The contact values of the pair correlation functions are found to compare favorably with recently proposed theoretical expressions. The transport coefficients of the mixture, determined from simulation, are compared to the predictions of the revised Enskog theory using both a third-order Sonine expansion and direct simulation Monte Carlo. Overall, the Enskog theory provides a fairly good description of the simulation data, with the exception of systems at the smallest mole fraction of larger spheres (x(A)=0.01) examined. A "fines effect" was observed at higher packing fractions, where adding smaller spheres to a system of large spheres decreases the viscosity of the mixture; this effect is not captured by the Enskog theory. PMID:19405594

  14. Transport properties of highly asymmetric hard-sphere mixtures

    NASA Astrophysics Data System (ADS)

    Bannerman, Marcus N.; Lue, Leo

    2009-04-01

    The static and dynamic properties of binary mixtures of hard spheres with a diameter ratio of σB/σA=0.1 and a mass ratio of mB/mA=0.001 are investigated using event driven molecular dynamics. The contact values of the pair correlation functions are found to compare favorably with recently proposed theoretical expressions. The transport coefficients of the mixture, determined from simulation, are compared to the predictions of the revised Enskog theory using both a third-order Sonine expansion and direct simulation Monte Carlo. Overall, the Enskog theory provides a fairly good description of the simulation data, with the exception of systems at the smallest mole fraction of larger spheres (xA=0.01) examined. A "fines effect" was observed at higher packing fractions, where adding smaller spheres to a system of large spheres decreases the viscosity of the mixture; this effect is not captured by the Enskog theory.

  15. 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.

  16. Electrical Transport Properties of Liquid Sn-Sb Binary Alloys

    NASA Astrophysics Data System (ADS)

    Thakore, B. Y.; Suthar, P. H.; Khambholja, S. G.; Jani, A. R.

    2010-06-01

    The study of electrical transport properties viz. electrical resistivity, thermo electrical power and thermal conductivity of liquid Sn-Sb binary alloys have been made by our well recognized single parametric model potential. In the present work, screening functions due to Hartree, Taylor, Ichimaru et al.. Farid et al.. and Sarkar et al.. have been employed to incorporate the exchange and correlation effects. The liquid alloy is studied as a function of its composition at temperature 823 K according to the Faber-Ziman model. Further, thermoelectric power and thermal conductivity have been predicted. The values of electrical resistivity of binary alloys computed with Ichimaru et al. and Farid et al.. screening function are in good agreement with the experimental data.

  17. 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.

  18. 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.

  19. Transport Properties of n-POLYANILINE/p-POROUS Silicon Heterojunctions

    NASA Astrophysics Data System (ADS)

    Farag, A. A. M.; Ashery, A.; Yahia Abed, M.; Shenashen, M. A.; Hindia, T. A.

    The donor/acceptor heterojunction devices having configuration n-PANI/p-PSi were fabricated by in-situ chemical oxidative polymerization method of aniline on p-type porous silicon. The structure of n-PANI/p-PSi junctions was examined by scanning electron microscopy and X-ray diffraction spectroscopy. The dark current-voltage measurements were performed in the temperature range of 303-393 K to determine the electrical transport mechanisms of these devices. Rectifying properties were obtained and capacitance-voltage at 1 MHz behavior indicates an abrupt interface. At low forward bias, the current was found to be limited by thermionic emission of holes from p-PSi over the PANI/PSi barrier in the PANI thin film. For relatively higher voltage, the conduction was dominated by a space charge limited current mechanism, with an exponential distribution of traps. Also, various electrical parameters were determined from the I-V and C-V analysis.

  20. Structural and Transport Properties of Dielectrophoretically Assembled Interconnects

    NASA Astrophysics Data System (ADS)

    Ozturk, Birol; Talukdar, Ishan; Thapa, Prem; Blackledge, Charles; Grischkowsky, Daniel; Flanders, Bret

    2006-03-01

    Dielectrophoresis was used to form ˜140nm diameter interconnects composed of gold nanorods between targeted points in a circuit. Cleanroom-based lithographic procedures were used to produce identical arrays of electrodes, improving the sample-to-sample reproducibility of the interconnect-conductances to ˜10%. Transmission electron microscopy and low temperature conductivity analyses indicate that the Coulomb Blockade associated with the individual nanorods is the primary conductance-limiting feature. To further improve the reproducibility of the structural and transport properties of dielectrophoretic interconnects, we investigate submicron wire formation in aqueous solutions of indium acetate. Our preliminary data show that single crystal wires with submicron diameters may be fabricated from such solutions.

  1. Optical and transport properties of dense liquid silica

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  2. 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.

  3. Spin transport properties of triarylamine-based nanowires.

    PubMed

    Bhattacharya, Sandip; Akande, Akinlolu; Sanvito, Stefano

    2014-06-25

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

  4. Transport timescales and tracer properties in the extratropical UTLS

    NASA Astrophysics Data System (ADS)

    Hoor, P.; Wernli, H.; Hegglin, M. I.; Bönisch, H.

    2010-08-01

    A comprehensive evaluation of seasonal backward trajectories initialized in the northern hemisphere lowermost stratosphere (LMS) has been performed to investigate the factors that determine the temporal and spatial structure of troposphere-to-stratosphere-transport (TST) and it's impact on the LMS. In particular we explain the fundamental role of the transit time since last TST (tTST) for the chemical composition of the LMS. According to our results the structure of the LMS can be characterized by a layer with tTST<40 days forming a narrow band around the local tropopause. This layer extends about 30 K above the local dynamical tropopause, corresponding to the extratropical tropopause transition layer (ExTL) as identified by CO. The LMS beyond this layer shows a relatively well defined separation as marked by an aprupt transition to longer tTST indicating less frequent mixing and a smaller fraction of tropospheric air. Thus the LMS constitutes a region of two well defined regimes of tropospheric influence. These can be characterized mainly by different transport times from the troposphere and different fractions of tropospheric air. Carbon monoxide (CO) mirrors this structure of tTST due to it's finite lifetime on the order of three months. Water vapour isopleths, on the other hand, do not uniquely indicate TST and are independent of tTST, but are determined by the Lagrangian Cold Point (LCP) of air parcels. Most of the backward trajectories from the LMS experienced their LCP in the tropics and sub-tropics, and TST often occurs 20 days after trajectories have encountered their LCP. Therefore, ExTL properties deduced from CO and H2O provide totally different informations on transport and particular TST for the LMS.

  5. Magnetocaloric-transport properties correlation in doped manganites

    NASA Astrophysics Data System (ADS)

    Mohamed, Abd El-Moez A.; Hernando, B.; Ahmed, A. M.

    2016-05-01

    This investigation is interested in studying the relation between magnetocaloric effect and transport properties in La0.7Ba0.3MnO3 manganite compound. The resistivity shows a metal-semiconductor transition at Tms temperature near to its reported Curie temperature (Tc). Magnetic field application decreases resistivity and increases Tms towards higher temperatures. The magnetoresistance shows a peak around Tc and increases in value with the applied magnetic field. A similar behavior has been observed between magnetic entropy change (ΔS), resistivity and magnetoresistance around Tc, this is attributed to the spin order/disorder feature that plays a main role in the magnetocaloric-transport correlation. In spite of this similarity, the correspondence among the experimental ΔS and ΔS based resistivity calculations is missing because of lattice polarons effect on resistivity as a result of the electron-phonon interaction. The magnetocaloric-magnetoresistance relation is also studied and results show the contribution of additional factors in the magnetoresistance mechanism other than spin disorder suppression as Jahn-Teller effect and electronic phase separation.

  6. 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}).

  7. Transport properties of elastically coupled fractional Brownian motors

    NASA Astrophysics Data System (ADS)

    Lv, Wangyong; Wang, Huiqi; Lin, Lifeng; Wang, Fei; Zhong, Suchuan

    2015-11-01

    Under the background of anomalous diffusion, which is characterized by the sub-linear or super-linear mean-square displacement in time, we proposed the coupled fractional Brownian motors, in which the asymmetrical periodic potential as ratchet is coupled mutually with elastic springs, and the driving source is the external harmonic force and internal thermal fluctuations. The transport mechanism of coupled particles in the overdamped limit is investigated as the function of the temperature of baths, coupling constant and natural length of the spring, the amplitude and frequency of driving force, and the asymmetry of ratchet potential by numerical stimulations. The results indicate that the damping force involving the information of historical velocity leads to the nonlocal memory property and blocks the traditional dissipative motion behaviors, and it even plays a cooperative role of driving force in drift motion of the coupled particles. Thus, we observe various non-monotonic resonance-like behaviors of collective directed transport in the mediums with different diffusion exponents.

  8. Transport properties of polyaniline-cellulose-acetate blends

    NASA Astrophysics Data System (ADS)

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

    1998-09-01

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

  9. 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.

  10. Tuning transport properties on graphene multiterminal structures by mechanical deformations

    NASA Astrophysics Data System (ADS)

    Latge, Andrea; Torres, Vanessa; Faria, Daiara

    The realization of mechanical strain on graphene structures is viewed as a promise route to tune electronic and transport properties such as changing energy band-gaps and promoting localization of states. Using continuum models, mechanical deformations are described by effective gauge fields, mirrored as pseudomagnetic fields that may reach quite high values. Interesting symmetry features are developed due to out of plane deformations on graphene; lift sublattice symmetry was predicted and observed in centrosymmetric bumps and strained nanobubbles. Here we discuss the effects of Gaussian-like strain on a hexagonal graphene flake connected to three leads, modeled as perfect graphene nanoribbons. The Green function formalism is used within a tight-binding approximation. For this particular deformation sharp resonant states are achieved depending on the strained structure details. We also study a fold-strained structure in which the three leads are deformed extending up to the very center of the hexagonal flake. We show that conductance suppressions can be controlled by the strain intensity and important transport features are modeled by the electronic band structure of the leads.

  11. 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.

  12. Sex-Specific Factors in Microvascular Angina

    PubMed Central

    Humphries, Karin H.; Bairey Merz, C. Noel

    2014-01-01

    Among women presenting for evaluation of suspected ischemic symptoms, a diagnosis of normal coronary arteries is five times more common, as compared to men. These women are often labeled as cardiac syndrome X (CSX), a subset of which have microvascular angina (MA) due to microvascular coronary dysfunction (MCD). MCD is not benign and is associated with an annual 2.5% cardiac event rate. Non-invasive testing for MCD remains insensitive although newer imaging modalities such as adenosine cardiac magnetic resonance imaging (CMRI) appear promising. The gold standard for diagnosis of MCD is coronary reactivity testing (CRT), an invasive technique which is not available in many countries. With regard to treatment, large scale trials are lacking. While research is ongoing, the current platform of therapy consists of anti-anginal, anti-platelet and endothelial modifying agents (primarily angiotensin converting enzyme inhibitors and statins). PMID:24582724

  13. 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

  14. 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...

  15. Retinal microvascular network attenuation in Alzheimer's disease

    PubMed Central

    Williams, Michael A.; McGowan, Amy J.; Cardwell, Chris R.; Cheung, Carol Y.; Craig, David; Passmore, Peter; Silvestri, Giuliana; Maxwell, Alexander P.; McKay, Gareth J.

    2015-01-01

    Introduction Cerebral small-vessel disease has been implicated in the development of Alzheimer's disease (AD). The retinal microvasculature enables the noninvasive visualization and evaluation of the systemic microcirculation. We evaluated retinal microvascular parameters in a case-control study of AD patients and cognitively normal controls. Methods Retinal images were computationally analyzed and quantitative retinal parameters (caliber, fractal dimension, tortuosity, and bifurcation) measured. Regression models were used to compute odds ratios (OR) and confidence intervals (CI) for AD with adjustment for confounders. Results Retinal images were available in 213 AD participants and 294 cognitively normal controls. Persons with lower venular fractal dimension (OR per standard deviation [SD] increase, 0.77 [CI: 0.62–0.97]) and lower arteriolar tortuosity (OR per SD increase, 0.78 [CI: 0.63–0.97]) were more likely to have AD after appropriate adjustment. Discussion Patients with AD have a sparser retinal microvascular network and retinal microvascular variation may represent similar pathophysiological events within the cerebral microvasculature of patients with AD. PMID:26634224

  16. Transport Properties of Gate Tunable Graphene-Based Tunnel Diodes

    NASA Astrophysics Data System (ADS)

    Farmer, Damon; Perebeinos, Vasili; Avouris, Phaedon

    2012-02-01

    Due to its linear dispersion relation and unique physical properties, graphene has become a material of intense experimental and theoretical investigation. There has been rapid progress in the fabrication and understanding of graphene devices, particularly those based on the field effect transistor (FET) configuration. These three-terminal switches rely on a gate field to control electronic transport (diffusive or quasi-ballistic) in the graphene channel, where the field is perpendicular to the current flow. Here, a different type of three-terminal graphene device is demonstrated, one based on quantum tunneling. These devices build upon the convention two-terminal metal-insulator-metal (MIM) tunnel diode configuration by replacing one of the metal electrodes with graphene. Incorporation of a third (gate) electrode allows for modulation of the accessible density of states in the graphene electrode, thereby tuning the threshold voltage for tunneling in the diode. This tunable diode concept, where the gate field is parallel to the tunneling direction, is novel for a purely solid-state system. The device characteristics owing to the unique properties of graphene will be discussed, as will the underlying physics of device operation.

  17. 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

  18. Optical and Transport Properties of Organic Molecules: Methods and Applications

    NASA Astrophysics Data System (ADS)

    Strubbe, David Alan

    Organic molecules are versatile and tunable building blocks for technology, in nanoscale and bulk devices. In this dissertation, I will consider some important applications for organic molecules involving optical and transport properties, and develop methods and software appropriate for theoretical calculations of these properties. Specifically, we will consider second-harmonic generation, a nonlinear optical process; photoisomerization, in which absorption of light leads to mechanical motion; charge transport in junctions formed of single molecules; and optical excitations in pentacene, an organic semiconductor with applications in photovoltaics, optoelectronics, and flexible electronics. In the Introduction (Chapter 1), I will give an overview of some phenomenology about organic molecules and these application areas, and discuss the basics of the theoretical methodology I will use: density-functional theory (DFT), time-dependent density-functional theory (TDDFT), and many-body perturbation theory based on the GW approximation. In the subsequent chapters, I will further discuss, develop, and apply this methodology. 2. I will give a pedagogical derivation of the methods for calculating response properties in TDDFT, with particular focus on the Sternheimer equation, as will be used in subsequent chapters. I will review the many different response properties that can be calculated (dynamic and static) and the appropriate perturbations used to calculate them. 3. Standard techniques for calculating response use either integer occupations (as appropriate for a system with an energy gap) or fractional occupations due to a smearing function, used to improve convergence for metallic systems. I will present a generalization which can be used to compute response for a system with arbitrary fractional occupations. 4. Chloroform (CHCl3) is a small molecule commonly used as a solvent in measurements of nonlinear optics. I computed its hyperpolarizability for second

  19. 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

  20. 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

  1. 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

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

    SciTech Connect

    Sogaard, Martin Vang Hendriksen, Peter; Mogensen, Mogens

    2007-04-15

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

  3. 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.

  4. 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.

  5. 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

  6. Transport Properties of Nanoscale Materials by First-principles Calculations

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

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

  7. 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. PMID:23604428

  8. 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.

  9. 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

  10. 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

  11. 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

  12. 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

  13. Microvascular transplantation of the rat submandibular gland.

    PubMed

    Spiegel, J H; Zhang, F; Levin, D E; Singer, M I; Buncke, H J

    2000-11-01

    Xerostomia results from salivary gland irradiation during treatment of head and neck malignancies. In addition to having difficulty with speech and swallowing, these patients experience loss of taste, dental caries, and chronic fungal infections. The paired submandibular glands provide 70 percent of the normal salivary flow and are difficult to shield during radiation therapy. Another sicca condition, xerophthalmia, may result from facial nerve injury or other medical disorders and results in pain, corneal ulceration, and possible vision loss. Treatment options for xerostomia are limited, and management of xerophthalmia usually focuses on the eyelids, rather than the fundamental problem of inadequate secretory protection. In this study, a rat model for submandibular gland microvascular transplantation was developed to assess the feasibility of salivary tissue transfer. Sixteen rats underwent submandibular gland transplantation from the neck to the groin. Fourteen of these rats underwent microvascular anastomosis of the vascular pedicle. Ten glands were assessed for viability at 4 days after transplantation, and four glands were examined after 7, 10, 14, or 21 days. By gross and histologic examination, 93 percent of transplanted glands showed expected long-term viability after at least 4 postoperative days. Microvascular techniques were shown to be applicable to the transplantation of submandibular gland salivary tissue. This has not previously been shown in a rat model. It is possible that submandibular glands could be transplanted to the eye for treatment of xerophthalmia and out of the neck during irradiation of the head and neck, with subsequent replantation after treatment as a means of preventing permanent xerostomia. PMID:11083564

  14. 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.

  15. Correlating Transport Behavior with Cell Properties for Eight Porcine Escherichia coli Isolates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study we investigate how growth stage and depositional environment affect variability of cell properties and transport behavior of eight porcine E. coli isolates. We compared the surface properties and transport behavior for cells harvested at two different growth stages (exponential and sta...

  16. 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.

  17. 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.

  18. Influenza Infects Lung Microvascular Endothelium Leading to Microvascular Leak: Role of Apoptosis and Claudin-5

    PubMed Central

    Armstrong, Susan M.; Wang, Changsen; Tigdi, Jayesh; Si, Xiaoe; Dumpit, Carlo; Charles, Steffany; Gamage, Asela; Moraes, Theo J.; Lee, Warren L.

    2012-01-01

    Severe influenza infections are complicated by acute lung injury, a syndrome of pulmonary microvascular leak. The pathogenesis of this complication is unclear. We hypothesized that human influenza could directly infect the lung microvascular endothelium, leading to loss of endothelial barrier function. We infected human lung microvascular endothelium with both clinical and laboratory strains of human influenza. Permeability of endothelial monolayers was assessed by spectrofluorimetry and by measurement of the transendothelial electrical resistance. We determined the molecular mechanisms of flu-induced endothelial permeability and developed a mouse model of severe influenza. We found that both clinical and laboratory strains of human influenza can infect and replicate in human pulmonary microvascular endothelium, leading to a marked increase in permeability. This was caused by apoptosis of the lung endothelium, since inhibition of caspases greatly attenuated influenza-induced endothelial leak. Remarkably, replication-deficient virus also caused a significant degree of endothelial permeability, despite displaying no cytotoxic effects to the endothelium. Instead, replication-deficient virus induced degradation of the tight junction protein claudin-5; the adherens junction protein VE-cadherin and the actin cytoskeleton were unaffected. Over-expression of claudin-5 was sufficient to prevent replication-deficient virus-induced permeability. The barrier-protective agent formoterol was able to markedly attenuate flu-induced leak in association with dose-dependent induction of claudin-5. Finally, mice infected with human influenza developed pulmonary edema that was abrogated by parenteral treatment with formoterol. Thus, we describe two distinct mechanisms by which human influenza can induce pulmonary microvascular leak. Our findings have implications for the pathogenesis and treatment of acute lung injury from severe influenza. PMID:23115643

  19. Effects of macrophage-activating lipopeptide-2 (MALP-2) on the vascularisation of implanted polyurethane scaffolds seeded with microvascular fragments.

    PubMed

    Grässer, C; Scheuer, C; Parakenings, J; Tschernig, T; Eglin, D; Menger, M D; Laschke, M W

    2016-01-01

    The seeding of scaffolds with adipose tissue-derived microvascular fragments represents a promising strategy to establish a sufficient blood supply in tissue constructs. Herein, we analysed whether a single application of macrophage-activating lipopeptide-2 (MALP-2) at the implantation site further improves the early vascularisation of such microvessel-seeded constructs. Microvascular fragments were isolated from epididymal fat pads of C57BL/6 mice. The fragments were seeded on polyurethane scaffolds, which were implanted into mouse dorsal skinfold chambers exposed to MALP-2 or vehicle (control). The inflammatory host tissue response and the vascularisation of the scaffolds were analysed using intravital fluorescence microscopy, histology and immunohistochemistry. We found that the numbers of microvascular adherent leukocytes were significantly increased in MALP-2-treated chambers during the first 3 days after scaffold implantation when compared to controls. This temporary inflammation resulted in an improved vascularisation of the host tissue surrounding the implants, as indicated by a higher density of CD31-positive microvessels at day 14. However, the MALP-2-exposed scaffolds themselves presented with a lower functional microvessel density in their centre. In addition, in vitro analyses revealed that MALP-2 promotes apoptotic cell death of endothelial and perivascular cells in isolated microvascular fragments. Hence, despite the beneficial pro-angiogenic properties of MALP-2 at the implantation site, the herein evaluated approach may not be recommended to improve the vascularisation capacity of microvascular fragments in tissue engineering applications. PMID:27386841

  20. 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...

  1. Isolation of Primary Murine Brain Microvascular Endothelial Cells

    PubMed Central

    Ruck, Tobias; Bittner, Stefan; Epping, Lisa; Herrmann, Alexander M.; Meuth, Sven G.

    2014-01-01

    The blood-brain-barrier is ultrastructurally assembled by a monolayer of brain microvascular endothelial cells (BMEC) interconnected by a junctional complex of tight and adherens junctions. Together with other cell-types such as astrocytes or pericytes, they form the neurovascular unit (NVU), which specifically regulates the interchange of fluids, molecules and cells between the peripheral blood and the CNS. Through this complex and dynamic system BMECs are involved in various processes maintaining the homeostasis of the CNS. A dysfunction of the BBB is observed as an essential step in the pathogenesis of many severe CNS diseases. However, specific and targeted therapies are very limited, as the underlying mechanisms are still far from being understood. Animal and in vitro models have been extensively used to gain in-depth understanding of complex physiological and pathophysiological processes. By reduction and simplification it is possible to focus the investigation on the subject of interest and to exclude a variety of confounding factors. However, comparability and transferability are also reduced in model systems, which have to be taken into account for evaluation. The most common animal models are based on mice, among other reasons, mainly due to the constantly increasing possibilities of methodology. In vitro studies of isolated murine BMECs might enable an in-depth analysis of their properties and of the blood-brain-barrier under physiological and pathophysiological conditions. Further insights into the complex mechanisms at the BBB potentially provide the basis for new therapeutic strategies. This protocol describes a method to isolate primary murine microvascular endothelial cells by a sequence of physical and chemical purification steps. Special considerations for purity and cultivation of MBMECs as well as quality control, potential applications and limitations are discussed. PMID:25489873

  2. Evaluation of Baltic Sea transport properties using particle tracking

    NASA Astrophysics Data System (ADS)

    Dargahi, Bijan; Cvetkovic, Vladimir

    2014-05-01

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

  3. 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

  4. 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

  5. Single and Few Layer Silicene: Structural, Electronic and Transport Properties

    NASA Astrophysics Data System (ADS)

    Carey, J. David; Roome, Nathanael

    Single layer silicene has weaker π bonding that graphene resulting in buckling of the Si atoms in different sub-lattices. Despite the loss of planarity, a linear bandstructure emerges where we find a Fermi velocity of about 5.3 x 105 m/s. Determination of the phonon dispersion characteristics reveals a Γ point optical phonon with an energy of 69 meV and a K point optical phonon with an energy of 62 meV. In graphene these phonons play important role in scattering electrons, and in Raman spectroscopy, but have larger energies of 194 and 166 meV, respectively. The lower phonon energies in silicene, arising from the higher atomic masses, would be expected to scatter carriers efficiently and limit carrier mobility. We have calculated, however, that the electron-optical phonon coupling matrix elements are about a factor of 25 times smaller than in graphene and this important result will help with the further development of silicene based devices due to reduced phonon scattering. The two stable stacking configurations of bilayer silicene, AA and AB, now have to account of the position of the atomic buckling in the two layers, leading to four possible atomic configurations with the buckling between the layers being in- or out-of-phase with each other. We find that in contrast to graphene, the two stable configurations are based on AA type stacking being about 70 meV per atom more stable than AB stacking. The potential for elemental layered materials beyond graphene for device applications will also be discussed. Single and Few Layer Silicene: Structural, Electronic and Transport Properties.

  6. Fabrication transport properties of QMG current limiting elements

    NASA Astrophysics Data System (ADS)

    Morita, Mitsuru; Hirano, H.; Hayashi, H.; Terazono, K.; Kajikawa, K.; Funaki, K.; Hamajima, T.

    2004-10-01

    A high durability design for QMG current limiting elements was developed by reinforcement using metal bypasses. Metal bypasses with high specific resistivity were bonded to both surfaces of QMG bulk superconductor using solder. I-shaped short QMG current limiting elements with cross-sections of 2.2 × 0.8 mm and an effective length of 20 mm were reinforced by I-shaped NiCr or SUS bypasses. Meander-shaped QMG with cross-sections of 2.2 × 0.8 mm and an effective length of 180 mm was reinforced by meander-shaped NiCr bypasses. These elements were molded by resin and GFRP. The external bypass was jointed to the element in parallel electrically. The current limiting elements have a current capacity of 1 kA class in 77 K. In order to measure transport properties in fault conditions, a half cycle of sinusoidal current up to about 4 kA was applied to the elements. I-shaped short samples with 0.5 mm thick NiCr showed an endurance voltage of 13 V(electric field strength of 6.5 V/cm) without damage, when the peak value of applied current was 4.2 kA. For the meander-shaped samples, endurance voltage of 92 V was observed through one element, when the peak value of applied current was 4.0 kA. This voltage is about four times higher than that tolerated by conventional meander-shaped elements that have no NiCr bypass reinforcement. In the case of metal bypassing both sides of a superconductor in fault conditions, fault current flows through the metal bypasses. Then, both the superconductor and metal bypass expand by Joule heating. Therefore, the mechanical stress on a superconductor is reduced relative to the presence of metal bypasses. It is considered that metal bypasses lead to high durability against thermal shock.

  7. Pulmonary particulate matter and systemic microvascular dysfunction.

    PubMed

    Nurkiewicz, Timothy R; Porter, Dale W; Hubbs, Ann F; Stone, Samuel; Moseley, Amy M; Cumpston, Jared L; Goodwill, Adam G; Frisbee, Stephanie J; Perrotta, Peter L; Brock, Robert W; Frisbee, Jefferson C; Boegehold, Matthew A; Frazer, David G; Chen, Bean T; Castranova, Vincent

    2011-12-01

    Pulmonary particulate matter (PM) exposure has been epidemiologically associated with an increased risk of cardiovascular morbidity and mortality, but the mechanistic foundations for this association are unclear. Exposure to certain types of PM causes changes in the vascular reactivity of several macrovascular segments. However, no studies have focused upon the systemic microcirculation, which is the primary site for the development of peripheral resistance and, typically, the site of origin for numerous pathologies. Ultrafine PM--also referred to as nanoparticles, which are defined as ambient and engineered particles with at least one physical dimension less than 100 nm (Oberdorster et al. 2005)--has been suggested to be more toxic than its larger counterparts by virtue of a larger surface area per unit mass. The purpose of this study was fourfold: (1) determine whether particle size affects the severity of postexposure microvascular dysfunction; (2) characterize alterations in microvascular nitric oxide (NO) production after PM exposure; (3) determine whether alterations in microvascular oxidative stress are associated with NO production, arteriolar dysfunction, or both; and (4) determine whether circulating inflammatory mediators, leukocytes, neurologic mechanisms, or a combination of these play a fundamental role in mediating pulmonary PM exposure and peripheral microvascular dysfunction. To achieve these goals, we created an inhalation chamber that generates stable titanium dioxide (TiO2) aerosols at concentrations up to 20 mg/m3. TiO2 is a well-characterized particle devoid of soluble metals. Sprague Dawley and Fischer 344 (F-344) rats were exposed to fine or nano-TiO2 PM (primary count modes of approximately 710 nm and approximately 100 nm in diameter, respectively) at concentrations of 1.5 to 16 mg/m3 for 4 to 12 hours to produce pulmonary loads of 7 to 150 microg in each rat. Twenty-four hours after pulmonary exposure, the following procedures were

  8. 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

  9. 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

  10. Heterogeneous ageing of skeletal muscle microvascular function.

    PubMed

    Muller-Delp, Judy M

    2016-04-15

    The distribution of blood flow to skeletal muscle during exercise is altered with advancing age. Changes in arteriolar function that are muscle specific underlie age-induced changes in blood flow distribution. With advancing age, functional adaptations that occur in resistance arterioles from oxidative muscles differ from those that occur in glycolytic muscles. Age-related adaptations of morphology, as well as changes in both endothelial and vascular smooth muscle signalling, differ in muscle of diverse fibre type. Age-induced endothelial dysfunction has been reported in most skeletal muscle arterioles; however, unique alterations in signalling contribute to the dysfunction in arterioles from oxidative muscles as compared with those from glycolytic muscles. In resistance arterioles from oxidative muscle, loss of nitric oxide signalling contributes significantly to endothelial dysfunction, whereas in resistance arterioles from glycolytic muscle, alterations in both nitric oxide and prostanoid signalling underlie endothelial dysfunction. Similarly, adaptations of the vascular smooth muscle that occur with advancing age are heterogeneous between arterioles from oxidative and glycolytic muscles. In both oxidative and glycolytic muscle, late-life exercise training reverses age-related microvascular dysfunction, and exercise training appears to be particularly effective in reversing endothelial dysfunction. Patterns of microvascular ageing that develop among muscles of diverse fibre type and function may be attributable to changing patterns of physical activity with ageing. Importantly, aerobic exercise training, initiated even at an advanced age, restores muscle blood flow distribution patterns and vascular function in old animals to those seen in their young counterparts. PMID:26575597

  11. 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.

  12. Myocardial perfusion echocardiography and coronary microvascular dysfunction.

    PubMed

    Barletta, Giuseppe; Del Bene, Maria Riccarda

    2015-12-26

    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. 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.

  14. 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

  15. 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

  16. 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

  17. 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.

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

    SciTech Connect

    Colonna, G.; D'Angola, A.

    2012-11-27

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

  19. 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.

  20. [Transport properties of disordered porous media from the microstructure

    SciTech Connect

    Not Available

    1993-01-01

    Progress was made in 4 general areas: quantitative characterization of microstructure via n-point distribution functions; determination of bounds on effective properties that depend on these n-point functions (conductivity, NMR, permeability); derivation of cross- property relations; and development of efficient first-passage time algorithms (Brownian-motion simulations) to compute effective diffusion properties.

  1. 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

    Program performs calculations such as chemical equilibrium for assigned thermodynamic states, theoretical rocket performance for both equilibrium and frozen compositions during expansion, incident and reflected shock properties, and Chapman-Jouget detonation properties. Features include simplicity of input and storage of all thermodynamic and transport property data on master tape.

  2. 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

  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. 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.

  5. 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

  6. 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.

  7. Globular adiponectin ameliorates metabolic insulin resistance via AMPK-mediated restoration of microvascular insulin responses.

    PubMed

    Zhao, Lina; Fu, Zhuo; Wu, Jing; Aylor, Kevin W; Barrett, Eugene J; Cao, Wenhong; Liu, Zhenqi

    2015-09-01

    Adiponectin is an adipokine with anti-inflammatory and anti-diabetic properties. Hypoadiponectinaemia is closely associated with endothelial dysfunction and insulin resistance in obesity and diabetes. Insulin resistance is present in muscle microvasculature and this may contribute to decreased insulin delivery to, and action in, muscle. In this study we examined whether adiponectin ameliorates metabolic insulin resistance by affecting muscle microvascular recruitment. We demonstrated that a high-fat diet induces vascular adiponectin and insulin resistance but globular adiponectin administration can restore vascular insulin responses and improve insulin's metabolic action via an AMPK- and nitric oxide-dependent mechanism. This suggests that globular adiponectin might have a therapeutic potential for improving insulin resistance and preventing cardiovascular complications in patients with diabetes via modulation of microvascular insulin responses. Hypoadiponectinaemia is closely associated with endothelial dysfunction and insulin resistance, and microvasculature plays a critical role in the regulation of insulin action in muscle. Here we tested whether adiponectin replenishment could improve metabolic insulin sensitivity in male rats fed a high-fat diet (HFD) via the modulation of microvascular insulin responses. Male Sprague-Dawley rats were fed either a HFD or low-fat diet (LFD) for 4 weeks. Small resistance artery myograph changes in tension, muscle microvascular recruitment and metabolic response to insulin were determined. Compared with rats fed a LFD, HFD feeding abolished the vasodilatory actions of globular adiponectin (gAd) and insulin on pre-constricted distal saphenous arteries. Pretreatment with gAd improved insulin responses in arterioles isolated from HFD rats, which was blocked by AMP-activated protein kinase (AMPK) inhibition. Similarly, HFD abolished microvascular responses to either gAd or insulin and decreased insulin-stimulated glucose disposal by

  8. 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.

  9. Diagnosis of coronary microvascular dysfunction - Present status.

    PubMed

    Mittal, S R

    2015-01-01

    Definite clinical diagnosis of microvascular angina is not possible with the existing knowledge. Resting electrocardiogram may be normal, and exercise electrocardiogram may be unremarkable. Echocardiography usually does not show regional wall motion abnormalities. Transthoracic Doppler echocardiography can satisfactorily evaluate only left anterior descending coronary artery and that too in some patients. Radio-isotope imaging can detect only severe localized disease. Noninvasive diagnosis needs high index of suspicion. At present, definite diagnosis is based on documentation of normal epicardial coronaries, coronary flow reserve less than 2.5 on adenosine induced hyperemia, and absence of spasm of epicardial coronaries on acetylcholine provocation. Invasive evaluation is costly, needs sophisticated equipments and expertise. Therapeutic and prognostic implications of various parameters remains to be evaluated. At present invasive evaluation is recommended only for patients with intractable symptoms with unconfirmed diagnosis, requiring repeated hospitalization and evaluation with failure of empirical therapy. PMID:26702685

  10. 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