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Sample records for transient enhanced diffusion

  1. Transient enhanced diffusion from decaborane molecular ion implantation

    NASA Astrophysics Data System (ADS)

    Agarwal, Aditya; Gossmann, H.-J.; Jacobson, D. C.; Eaglesham, D. J.; Sosnowski, M.; Poate, J. M.; Yamada, I.; Matsuo, J.; Haynes, T. E.

    1998-10-01

    Transient enhanced diffusion (TED) from implantation of 5 keV B10H14 and 0.5 keV B ions has been quantified and compared for nominal boron doses of 1014 and 1015cm-2. Boron diffusivity during annealing was extracted from secondary ion mass spectroscopy depth profiles of diffused marker layers in boron doping-superlattices and the actual implanted B dose was independently measured by nuclear reaction analysis. Comparable enhancements were observed from both ions. Transmission electron microscopy analysis revealed that both boron- and decaborane-implanted samples were amorphized at a nominal 1015cm-2 B dose. A comparison with data from low energy Si implants revealed a similar dependence of diffusivity enhancement on implant dose. These findings are consistent with the understanding that TED is caused by the interstitial supersaturation resulting from a number of excess interstitials approximately equal to the number of implanted atoms which can become substitutional in the silicon lattice. Accordingly, no contribution to TED is expected from the hydrogen in the B10H14 ions and none is observed. Furthermore, there is no detectable effect in the diffusion profiles which can be attributed to a difference in the ion damage produced by the decaborane molecule and the boron atom. In both cases the reduction in diffusivity enhancement is due only to proximity of the implantation-induced excess interstitials to the wafer surface.

  2. Transient enhanced diffusion from decaborane molecular ion implantation

    SciTech Connect

    Agarwal, A.; Gossmann, H.; Jacobson, D.C.; Eaglesham, D.J.; Sosnowski, M.; Poate, J.M.; Yamada, I.; Matsuo, J.; Haynes, T.E.

    1998-10-01

    Transient enhanced diffusion (TED) from implantation of 5thinspkeVthinspB{sub 10}H{sub 14} and 0.5 keV B ions has been quantified and compared for nominal boron doses of 10{sup 14} and 10{sup 15}thinspcm{sup {minus}2}. Boron diffusivity during annealing was extracted from secondary ion mass spectroscopy depth profiles of diffused marker layers in boron doping-superlattices and the actual implanted B dose was independently measured by nuclear reaction analysis. Comparable enhancements were observed from both ions. Transmission electron microscopy analysis revealed that both boron- and decaborane-implanted samples were amorphized at a nominal 10{sup 15}thinspcm{sup {minus}2}thinspB dose. A comparison with data from low energy Si implants revealed a similar dependence of diffusivity enhancement on implant dose. These findings are consistent with the understanding that TED is caused by the interstitial supersaturation resulting from a number of excess interstitials approximately equal to the number of implanted atoms which can become substitutional in the silicon lattice. Accordingly, no contribution to TED is expected from the hydrogen in the B{sub 10}H{sub 14} ions and none is observed. Furthermore, there is no detectable effect in the diffusion profiles which can be attributed to a difference in the ion damage produced by the decaborane molecule and the boron atom. In both cases the reduction in diffusivity enhancement is due only to proximity of the implantation-induced excess interstitials to the wafer surface. {copyright} {ital 1998 American Institute of Physics.}

  3. Transient enhanced diffusion of dopants in preamorphized Si layers

    SciTech Connect

    Claverie, A.; Bonafos, C.; Omri, M.; Mauduit, B. de; Ben Assayag, G.; Martinez, A.; Alquier, D.; Mathiot, D.

    1997-11-01

    Transient Enhanced Diffusion (TED) of dopants in Si is the consequence of the evolution, upon annealing, of a large supersaturation of Si self-interstitial atoms left after ion bombardment. In the case of amorphizing implants, this supersaturation is located just beneath the c/a interface and evolves through the nucleation and growth of End-Of-Range (EOR) defects. For this reason, the authors discuss here the relation between TED and EOR defects. Modelling of the behavior of these defects upon annealing allows one to understand why and how they affect dopant diffusion. This is possible through the development of the Ostwald ripening theory applied to extrinsic dislocation loops. This theory is shown to be readily able to quantitatively describe the evolution of the defect population (density, size) upon annealing and gives access to the variations of the mean supersaturation of Si self-interstitial atoms between the loops and responsible for TED. This initial supersaturation is, before annealing, at least 5 decades larger than the equilibrium value and exponentially decays with time upon annealing with activation energies that are the same than the ones observed for TED. It is shown that this time decay is precisely at the origin of the transient enhancement of boron diffusivity through the interstitial component of boron diffusion. Side experiments shed light on the effect of the proximity of a free surface on the thermal behavior of EOR defects and allow us to quantitatively describe the space and time evolutions of boron diffusivity upon annealing of preamorphized Si layers.

  4. Control of Phosphorus Transient Enhanced Diffusion using Co-implantation

    NASA Astrophysics Data System (ADS)

    Vanderpool, Aaron; Budrevich, Andre; Taylor, Mitch

    2006-11-01

    The production of Ultra Shallow Junctions (USJ) in silicon devices requires controlling the Transient Enhanced Diffusion (TED) of electrical dopants. USJ development has focused on boron because hole mobility is lower than electron mobility in silicon and because arsenic has such excellent diffusion properties. However, the advent of strain enhanced mobility in P-type silicon has created the need to study higher solubility N-type dopants like phosphorus and find methods to control their diffusion. Co-implants have proven effective in controlling the interstitial diffusion mechanisms of boron TED. In this work the effectiveness of some co-implants on phosphorus to form high performance USJ is reported. It has been found that carbon and fluorine co-implants reduce phosphorus diffusion. As work with boron has shown, this is due to the carbon Kick-out mechanism and Fluorine-Vacancy clusters, both of which consume the interstitials driving TED. It has also been found that record levels of phosphorus diffusion control can be obtained if boron and carbon are co-implanted. In this junction diffusion control increases as the boron implant energy decreases; even as low as 0.5 KeV. However, this may be activating Uphill diffusion. The data also shows that the carbon implant energy has very little effect on phosphorus diffusion. The boron and carbon co-implants also produce the steepest phosphorus USJ yet reported at 2.5nm/decade with a solubility >1.0E21 atoms/cm3. Counter intuitively it has been found that the boron and carbon USJ is shallower with a higher solubility if the phosphorus implant energy is increased from 2 to 3 KeV. These boron and carbon co-implant findings are quite novel even if they are not technologically useful. They strongly support the widely held model that phosphorus TED occurs via an interstitial diffusion mechanism and that techniques to block this mechanism can control it. The boron implanted below the phosphorus is probably consuming interstitials very efficiently in Boron Interstitialcy clusters (BI+) causing boron TED rather than phosphorus TED. The electrical characteristics of a phosphorus USJ with high doses of boron below it may be undesirable; but, it does demonstrate that phosphorus diffusion can be well controlled if the right co-implants are found.

  5. Phosphorous transient enhanced diffusion suppression and activation enhancement with cluster carbon co-implantation

    SciTech Connect

    Nakashima, Yoshiki; Hamamoto, Nariaki; Nagayama, Tsutomu; Koga, Yuji; Umisedo, Sei; Kawamura, Yasunori; Hashimoto, Masahiro; Onoda, Hiroshi

    2012-11-06

    Carbon co-implantation is well known as an effective method for suppressing boron/phosphorous transient enhanced diffusion (TED). Germanium pre-amorphization implantation (PAI) is usually applied prior to carbon co-implantation for suppressing channeling tail of dopants. In this study, cluster carbon was applied instead of the combination of germanium PAI and monomer carbon co-implantation prior to phosphorous implantation. Dependence of phosphorous activation and TED on amorphous layer thickness, carbon dose, carbon distribution and substrate temperature have been investigated. Cluster carbon implantation enables thick amorphous layer formation and TED suppression at the same time and low temperature implantation enhances the ability of amorphous layer formation so that shallow junction and low Rs can be achieved without Ge implantation.

  6. Transient enhanced diffusion of Sb and B due to MeV silicon implants

    SciTech Connect

    Eaglesham, D.J.; Haynes, T.E.; Gossmann, H.; Jacobson, D.C.; Stolk, P.A.; Poate, J.M.

    1997-06-01

    We measure the transient enhanced diffusion of shallow molecular-beam-epitaxy grown marker layers of Sb and B due to deep MeV Si{sup +} ion implants at very high doses ({approx}10{sup 16}cm{sup {minus}2}). We expect the near-surface region of these implants to be vacancy rich, and we observe transient enhanced diffusion of Sb (the classic vacancy diffuser). The large enhancements imply a significant vacancy supersaturation ({approx}700 at 740{degree}C). Double implantation of the high-dose MeV Si followed by a shallow (40 keV) Si implant and annealing produces a greatly reduced number of {l_brace}311{r_brace} defects compared to a 40 keV implant into virgin Si, again consistent with a vacancy-rich region in the near-surface region of an MeV implant. However, the shallow B marker layers also show transient enhanced diffusion for the same MeV implant under similar annealing conditions, implying that an interstitial supersaturation is present at the same time. We discuss possible mechanisms for a simultaneous supersaturation of both types of point defects. {copyright} {ital 1997 American Institute of Physics.}

  7. Transient enhanced diffusion of B at low temperatures under extrinsic conditions

    NASA Astrophysics Data System (ADS)

    Giles, L. F.; Colombeau, B.; Cowern, N.; Molzer, W.; Schaefer, H.; Bach, K. H.; Haibach, P.; Roozeboom, F.

    2005-04-01

    Transient enhanced diffusion of B in silicon is modelled at temperatures down to 500 °C, using a simplified model of self-interstitial clusters to describe the time evolution of the self-interstitial supersaturation, S. The model is highly predictive, providing an accurate description of diffusion both in the peak and tail regions of B marker layers, over a wide range of annealing conditions. The model is well adapted for implementation into existing 2D commercial simulation tools. Fundamental parameters of atomic-scale B diffusion were extracted for the first time at T = 500 °C, under both intrinsic and extrinsic conditions.

  8. Suppression of transient enhanced diffusion in sub-micron patterned silicon template by dislocation loops formation

    NASA Astrophysics Data System (ADS)

    Hu, Kuan-Kan; Chang, Ruey-Dar; Woon, Wei Yen

    2015-10-01

    We investigate the evolution of two dimensional transient enhanced diffusion (TED) of phosphorus in sub-micron scale patterned silicon template. Samples doped with low dose phosphorus with and without high dose silicon self-implantation, were annealed for various durations. Dopant diffusion is probed with plane-view scanning capacitance microscopy. The measurement revealed two phases of TED. Significant suppression in the second phase TED is observed for samples with high dose self-implantation. Transmission electron microscopy suggests the suppressed TED is related to the evolution of end of range defect formed around ion implantation sidewalls.

  9. The effect of boron implant energy on transient enhanced diffusion in silicon

    SciTech Connect

    Liu, J.; Krishnamoorthy, V.; Gossman, H.; Rubin, L.; Law, M.E.; Jones, K.S.

    1997-02-01

    Transient enhanced diffusion (TED) of boron in silica after low energy boron implantation and annealing was investigated using boron-doping superlattices (DSLs) grown by low temperature molecular beam epitaxy. Boron ions were implanted at 5, 10, 20, and 40 keV at a constant dose of 2{times}10{sup 14}/cm{sup 2}. Subsequent annealing was performed at 750{degree}C for times of 3 min, 15 min, and 2 h in a nitrogen ambient. The broadening of the boron spikes was measured by secondary ion mass spectroscopy and simulated. Boron diffusivity enhancement was quantified as a function of implant energy. Transmission electron microscopy results show that {l_angle}311{r_angle} defects are only seen for implant energies {ge}10 keV at this dose and that the density increases with energy. DSL studies indicate the point defect concentration in the background decays much slower when {l_angle}311{r_angle} defects are present. These results imply there are at least two sources of TED for boron implants (B-I): short time component that decays rapidly consistent with nonvisible B-I pairs and a longer time component consistent with interstitial release from the {l_angle}311{r_angle} defects. {copyright} {ital 1997 American Institute of Physics.}

  10. Modeling and simulation of transient enhanced diffusion based on interactions of point and extended defects

    NASA Astrophysics Data System (ADS)

    Gencer, Alp H.

    As device sizes in VLSI technology get smaller, the importance of predictive process modeling increases. One of the biggest challenges in predictive process modeling today lies in modeling of Transient Enhanced Diffusion (TED). TED is the greatly enhanced diffusion of dopants in silicon seen during annealing of the damage created by the ion implantation of the dopants. As one moves to smaller thermal budgets, TED is often the primary source of diffusion and thus determines the final junction depth. It is known that TED is caused by the excess interstitial concentration that persists due to ion implantation. But how this excess interstitial concentration evolves over time and affects the diffusion of dopants remains unclear. Our work attempts to understand the physical processes occurring during ion implant annealing, express them in a mathematical model, integrate this model into a diffusion equation solver and quantitatively match the experimental observations. To this end, we have developed a solid physical model (KPM) for the evolution of extended defects ({311} defects and dislocation loops) which are observed under TED conditions. We have also developed different versions of KPM that have applicability under different circumstances, and have different levels of computational efficiency. We believe that the range of models developed will give the user the ability to make a compromise between accuracy and computational time. We have applied KPM to {311} defects that are observed under non-amorphizing implant conditions and we were able to get a good agreement. We have then used this model to predict TED behavior based on marker layer experiments and we found a good match. To extend the model to dislocation loops, we assumed that dislocation loops form by unfaulting of {311} defects as observed experimentally. We accounted for this transformation in our model and we were able to obtain a good match to the experimental data without any modifications in the {311} defect model. Our work also involved in developing a computer software that is capable of solving the models that we have postulated. To this end, we have developed DOPDEES, a one-dimensional multi purpose partial differential equation initial value solver. To enable faster technology transfer, we have also developed Process Modeling Modules (PMM) which consists a set of scripts that encapsulate the models that we have developed in a ready to use form.

  11. Nonlinear Diffusion and Transient Osmosis

    NASA Astrophysics Data System (ADS)

    Akira, Igarashi; Lamberto, Rondoni; Antonio, Botrugno; Marco, Pizzi

    2011-08-01

    We investigate both analytically and numerically the concentration dynamics of a solution in two containers connected by a narrow and short channel, in which diffusion obeys a porous medium equation. We also consider the variation of the pressure in the containers due to the flow of matter in the channel. In particular, we identify a phenomenon, which depends on the transport of matter across nano-porous membranes, which we call transient osmosis". We find that nonlinear diffusion of the porous medium equation type allows numerous different osmotic-like phenomena, which are not present in the case of ordinary Fickian diffusion. Experimental results suggest one possible candidate for transiently osmotic processes.

  12. Quenched disorder enhances chaotic diffusion

    NASA Astrophysics Data System (ADS)

    Popescu, M. N.; Braiman, Y.; Family, F.; Hentschel, H. G. E.

    1998-10-01

    We show that chaotic diffusion of a single particle moving on a one-dimensional rough surface is enhanced by a small amount of spatial quenched disorder. In addition to enhanced diffusion we also find that there is a crossover from expanding to bounded motion. The crossover time to bounded motion decreases with increasing disorder, and there exists a threshold value of disorder above which chaotic motion is completely suppressed.

  13. Enhanced diffusion welding

    NASA Technical Reports Server (NTRS)

    Holko, K. H.; Moore, T. J. (inventors)

    1973-01-01

    Surfaces of unrecrystallized alloys are sanded and polished. This is followed by a two-step welding process by which the strength of the parent metal is retained at the weld joint. The first step forces the surfaces into intimate contact at a temperature where the metal still has good ductility. The second step causes diffusion, recrystallization, and grain growth across the original weld interface.

  14. Ultrasonic enhancement of battery diffusion.

    PubMed

    Hilton, R; Dornbusch, D; Branson, K; Tekeei, A; Suppes, G J

    2014-03-01

    It has been demonstrated that sonic energy can be harnessed to enhance convection in Galvanic cells during cyclic voltammetry; however, the practical value of this approach is limited due to the lack of open volumes for convection patterns to develop in most batteries. This study evaluates the ability of ultrasonic waves to enhance diffusion in membrane separators commonly used in sandwich-architecture batteries. Studies include the measuring of open-circuit performance curves to interpret performances in terms of reductions in concentration overpotentials. The use of a 40 kHz sonicator bath can consistently increase the voltage of the battery and reduce overpotential losses up to 30%. This work demonstrates and quantifies battery enhancement due to enhanced diffusion made possible with ultrasonic energy. PMID:24210813

  15. Thermal Diffusivity Measurements in Edible Oils using Transient Thermal Lens

    NASA Astrophysics Data System (ADS)

    Valdez, R. Carbajal.; Pérez, J. L. Jiménez.; Cruz-Orea, A.; Martín-Martínez, E. San.

    2006-11-01

    Time resolved thermal lens (TL) spectrometry is applied to the study of the thermal diffusivity of edible oils such as olive, and refined and thermally treated avocado oils. A two laser mismatched-mode experimental configuration was used, with a He Ne laser as a probe beam and an Ar+ laser as the excitation one. The characteristic time constant of the transient thermal lens was obtained by fitting the experimental data to the theoretical expression for a transient thermal lens. The results showed that virgin olive oil has a higher thermal diffusivity than for refined and thermally treated avocado oils. This measured thermal property may contribute to a better understanding of the quality of edible oils, which is very important in the food industry. The thermal diffusivity results for virgin olive oil, obtained from this technique, agree with those reported in the literature.

  16. Cavity Enhanced Ultrafast Transient Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Allison, Thomas K.; Reber, Melanie Roberts; Chen, Yuning

    2015-06-01

    Ultrafast spectroscopy on gas phase systems is typically restricted to techniques involving photoionization, whereas solution phase experiments utilize the detection of light. At Stony Brook, we are developing new techniques for performing femtosecond time-resolved spectroscopy using frequency combs and high-finesse optical resonators. A large detection sensitivity enhancement over traditional methods enables the extension of all-optical ultrafast spectroscopies, such as broad-band transient absorption spectroscopy (TAS) and 2D spectroscopy, to dilute gas phase samples produced in molecular beams. Here, gas phase data can be directly compared to solution phase data. Initial demonstration experiments are focusing on the photodissociation of iodine in small neutral argon clusters, where cluster size strongly influences the effects solvent-caging and geminate recombination. I will discuss these initial results, our high power home-built Yb:fiber laser systems, and also extensions of the methods to the mid-IR to study the vibrational dynamics of hydrogen bonded clusters.

  17. Shearrate diffusion and constitutive relations during transients in simple shear

    NASA Astrophysics Data System (ADS)

    Ries, Alexander; Brendel, Lothar; Wolf, Dietrich E.

    2015-07-01

    Granular matter, consisting of hard, frictional, cohesionless spheres, sheared in a simple shear geometry with smooth walls undergoes a velocity driven transition from a jammed or creeping state (low wall velocity) to a flow state with a finite shear rate in the bulk (high wall velocity). In the flow state, the state variables volume fraction ? , inertial number I and the macroscopic friction ? of the bulk follow an exponential transient. The characteristic time of this progression grows with the wall velocity and the system size and is typically large compared to the inverse shear rate. It is shown that I, first being stationary in the shear zones, spreads diffusively into the bulk. The other state variables follow according to the constitutive laws, well known from the steady state.

  18. Enhancing Rotational Diffusion Using Oscillatory Shear

    NASA Astrophysics Data System (ADS)

    Leahy, Brian D.; Cheng, Xiang; Ong, Desmond C.; Liddell-Watson, Chekesha; Cohen, Itai

    2013-05-01

    Taylor dispersion—shear-induced enhancement of translational diffusion—is an important phenomenon with applications ranging from pharmacology to geology. Through experiments and simulations, we show that rotational diffusion is also enhanced for anisotropic particles in oscillatory shear. This enhancement arises from variations in the particle’s rotation (Jeffery orbit) and depends on the strain amplitude, rate, and particle aspect ratio in a manner that is distinct from the translational diffusion. This separate tunability of translational and rotational diffusion opens the door to new techniques for controlling positions and orientations of suspended anisotropic colloids.

  19. Enhanced diffusion of phosphorus at grain boundaries

    NASA Technical Reports Server (NTRS)

    Cheng, L. J.; Shyu, C. M.; Stika, K. M.; Daud, T.; Crotty, G. T.

    1982-01-01

    Enhanced diffusion of phosphorus at grain boundaries in cast polycrystalline photovoltaic materials (Wacker, HEM, and Semix) was studied. It was found that the enhancements for the three materials were the same, indicating that the properties of boundaries are similar, even though they were grown by different techniques. In addition, it was observed that grain boundaries capable of enhancing the diffusion always have strong recombination activities. Both phenomena could be related to dangling bonds existing at the boundaries. The present study gives the first evidence that incoherent second order twins of 111/115-plane type are diffusion-active.

  20. Anomalous diffusion with transient subordinators: a link to compound relaxation laws.

    PubMed

    Stanislavsky, Aleksander; Weron, Karina; Weron, Aleksander

    2014-02-01

    This paper deals with a problem of transient anomalous diffusion which is currently found to emerge from a wide range of complex processes. The nonscaling behavior of such phenomena reflects changes in time-scaling exponents of the mean-squared displacement through time domain - a more general picture of the anomalous diffusion observed in nature. Our study is based on the identification of some transient subordinators responsible for transient anomalous diffusion. We derive the corresponding fractional diffusion equation and provide links to the corresponding compound relaxation laws supported by this case generalizing many empirical dependencies well-known in relaxation investigations. PMID:24511928

  1. Research on Transient Liquid Phase Diffusion Bonding of Steel Sandwich Panels Under Small Plastic Deformation

    NASA Astrophysics Data System (ADS)

    Li, H.; Li, Z. X.

    2008-12-01

    Plastic deformation was newly introduced in transient liquid phase (TLP) diffusion bonding of steel sandwich panels. The effect of plastic deformation on bonding strength was investigated through lab experiments. It was assumed that three factors, including newly generated metal surface area, deformation heat, and lattice distortion, contribute to the acceleration of interface atoms diffusion and increase of diffusion coefficients. A numerical model of isothermal solidification time was developed for TLP bonding process under plastic deformation and applied to carbon steel sandwich panels bonding with copper interlayer. A reasonable isothermal solidification time was obtained when an effective diffusion coefficient was used. Based on lab experiments, the effects of plastic deformation on interlayer film thickness and isothermal solidification time were studied through theoretical calculation with the new model. The evolution of interlayer film thickness indicates a good agreement between the calculation and experimental measurement. The results show that the isothermal solidification time is obviously reduced due to the effect of plastic deformation. Furthermore, a new steel sandwich cooling panel for heat exchanger was fabricated by TLP diffusion bonding under 13.1% plastic deformation. The test results suggest that a steel sandwich panel of inequidistant fin structure can provide enhanced heat transfer efficiency.

  2. Enhancing photocurrent transient spectroscopy by electromagnetic modeling.

    PubMed

    Diesinger, H; Panahandeh-Fard, M; Wang, Z; Baillargeat, D; Soci, C

    2012-05-01

    The shape and duration of photocurrent transients generated by a photoconductive switch depend on both the intrinsic response of the active material and the geometry of the transmission line structure. The present electromagnetic model decouples both shape forming contributions. In contrast to previously published work, it accounts for the particular operating mode of transient spectroscopy. The objective is to increase the time resolution by two approaches, by optimizing structural response and by deconvolving it from experimental data. The switch structure is represented by an effective transimpedance onto which the active material acts as current generator. As proof of concept, the response of a standard microstrip switch is modeled and deconvolved from experimental data acquired in GaAs, yielding a single exponential material response and hence supporting the validity of the approach. Beyond compensating for the response deterioration by the structure, switch architectures can be a priori optimized with respect to frequency response. As an example, it is shown that a microstrip gap that can be deposited on materials incompatible with standard lithography reduces pulse broadening by an order of magnitude if it is provided with transitions to coplanar access lines. PMID:22667598

  3. A comparison of implicit numerical methods for solving the transient spherical diffusion equation

    NASA Technical Reports Server (NTRS)

    Curry, D. M.

    1977-01-01

    Comparative numerical temperature results obtained by using two implicit finite difference procedures for the solution of the transient diffusion equation in spherical coordinates are presented. The validity and accuracy of these solutions are demonstrated by comparison with exact analytical solutions.

  4. Contrast Enhancement by Nonlinear Diffusion Filtering.

    PubMed

    Liang, Zhetong; Liu, Weijian; Yao, Ruohe

    2016-02-01

    To enhance the visual quality of an image that is degraded by uneven light, an effective method is to estimate the illumination component and compress it. Some previous methods have either defects of halo artifacts or contrast loss in the enhanced image due to incorrect estimation. In this paper, we discuss this problem and propose a novel method to estimate the illumination. The illumination is obtained by iteratively solving a nonlinear diffusion equation. During the diffusion process, surround suppression is embedded in the conductance function to specially enhance the diffusive strength in textural areas of the image. The proposed estimation method has the following two merits: 1) the boundary areas are preserved in the illumination, and thus halo artifacts are prevented and 2) the textural details are preserved in the reflectance to not suffer from illumination compression, which contributes to the contrast enhancement in the result. Experimental results show that the proposed algorithm achieves excellent performance in artifact removal and local contrast enhancement. PMID:26685234

  5. Enhanced Nanorod Diffusion in Polymer Melts

    NASA Astrophysics Data System (ADS)

    Composto, Russell J.; Clarke, Nigel; Winey, Karen I.; Choi, Jihoon

    2014-03-01

    Using Rutherford backscattering spectroscopy (RBS), the translational diffusion of titanium oxide (TiO2) nanorods (l = 43.1 nm and d = 4.6 nm) is measured in entangled and unentangled polymer melts, polystyrene (PS; Mn = 9-2000 kg/mol). Nanorods in entangled systems (Mn = 160, 650, and 2000 kg/mol) are found to diffuse up to two orders of magnitude faster than predicted by classical theory. However, diffusion of nanorods in unentangled systems (Mn = 9 and 65 kg/mol) is captured by this continuum theory. Below or near the entanglement limitation, Mn <=Me (Me: entanglement molecular weight), unentangled polymer melts described by Rouse dynamics can be modeled as a continuum matrix against nanoscale inclusions. However, in highly entangled systems (Mn >>Me) the standard continuum models are no longer valid and lead to local non-hydrodynamic friction at the length scale of the tube diameter (i.e., dt = 8 nm for PS). Thus, enhanced diffusion of nanorods parallel to the tubes may be responsible for the faster than expected translational diffusion in entangled polymer melts. These experiments provide new insight into the relevant parameters that govern the diffusion of anisotropic nanoparticles in complex fluids.

  6. Can Disorder Enhance Incoherent Exciton Diffusion?

    PubMed

    Lee, Elizabeth M Y; Tisdale, William A; Willard, Adam P

    2015-07-30

    Recent experiments aimed at probing the dynamics of excitons have revealed that semiconducting films composed of disordered molecular subunits, unlike expectations for their perfectly ordered counterparts, can exhibit a time-dependent diffusivity in which the effective early time diffusion constant is larger than that of the steady state. This observation has led to speculation about what role, if any, microscopic disorder may play in enhancing exciton transport properties. In this article, we present the results of a model study aimed at addressing this point. Specifically, we introduce a general model, based upon Frster theory, for incoherent exciton diffusion in a material composed of independent molecular subunits with static energetic disorder. Energetic disorder leads to heterogeneity in molecule-to-molecule transition rates, which we demonstrate has two important consequences related to exciton transport. First, the distribution of local site-specific hopping rates is broadened in a manner that results in a decrease in average exciton diffusivity relative to that in a perfectly ordered film. Second, since excitons prefer to make transitions that are downhill in energy, the steady state distribution of exciton energies is biased toward low-energy molecular subunits, those that exhibit reduced diffusivity relative to a perfectly ordered film. These effects combine to reduce the net diffusivity in a manner that is time dependent and grows more pronounced as disorder is increased. Notably, however, we demonstrate that the presence of energetic disorder can give rise to a population of molecular subunits with exciton transfer rates exceeding those of subunits in an energetically uniform material. Such enhancements may play an important role in processes that are sensitive to molecular-scale fluctuations in exciton density field. PMID:26106811

  7. Review of enhanced vapor diffusion in porous media

    SciTech Connect

    Webb, S.W.; Ho, C.K.

    1998-08-01

    Vapor diffusion in porous media in the presence of its own liquid has often been treated similar to gas diffusion. The gas diffusion rate in porous media is much lower than in free space due to the presence of the porous medium and any liquid present. However, enhanced vapor diffusion has also been postulated such that the diffusion rate may approach free-space values. Existing data and models for enhanced vapor diffusion, including those in TOUGH2, are reviewed in this paper.

  8. Anisotropic enhanced backscattering induced by anisotropic diffusion

    NASA Astrophysics Data System (ADS)

    Bret, B. P. J.; Lagendijk, A.

    2004-09-01

    The enhanced backscattering cone displaying a strong anisotropy from a material with anisotropic diffusion is reported. The constructive interference of the wave is preserved in the helicity preserving polarization channel and completely lost in the nonpreserving one. The internal reflectivity at the interface modifies the width of the backscatter cone. The reflectivity coefficient is measured by angular-resolved transmission. This interface property is found to be isotropic, simplifying the backscatter cone analysis. The material used is a macroporous semiconductor, gallium phosphide, in which pores are etched in a disordered position but with a preferential direction.

  9. Transient spatiotemporal chaos in a diffusively and synaptically coupled Morris-Lecar neuronal network

    NASA Astrophysics Data System (ADS)

    Lafranceschina, Jacopo

    Transient spatiotemporal chaos was reported in models for chemical reactions and in experiments for turbulence in shear flow. This study shows that transient spatiotemporal chaos also exists in a diffusively coupled Morris-Lecar (ML) neuronal network, with a collapse to either a global rest state or to a state of pulse propagation. Adding synaptic coupling to this network reduces the average lifetime of spatiotemporal chaos for small to intermediate coupling strengths and almost all numbers of synapses. For large coupling strengths, close to the threshold of excitation, the average lifetime increases beyond the value for only diffusive coupling, and the collapse to the rest state dominates over the collapse to a traveling pulse state. The regime of spatiotemporal chaos is characterized by a slightly increasing Lyapunov exponent and degree of phase coherence as the number of synaptic links increases. In contrast to the diffusive network, the pulse solution must not be asymptotic in the presence of synapses. The fact that chaos could be transient in higher dimensional systems, such as the one being explored in this study, point to its presence in every day life. Transient spatiotemporal chaos in a network of coupled neurons and the associated chaotic saddle provide a possibility for switching between metastable states observed in information processing and brain function. Such transient dynamics have been observed experimentally by Mazor, when stimulating projection neurons in the locust antennal lobe with different odors.

  10. Fracture-Flow-Enhanced Solute Diffusion into Fractured Rock

    SciTech Connect

    Wu, Yu-Shu; Ye, Ming; Sudicky, E.A.

    2007-12-15

    We propose a new conceptual model of fracture-flow-enhanced matrix diffusion, which correlates with fracture-flow velocity, i.e., matrix diffusion enhancement induced by rapid fluid flow within fractures. According to the boundary-layer or film theory, fracture flow enhanced matrix diffusion may dominate mass-transfer processes at fracture-matrix interfaces, because rapid flow along fractures results in large velocity and concentration gradients at and near fracture-matrix interfaces, enhancing matrix diffusion at matrix surfaces. In this paper, we present a new formulation of the conceptual model for enhanced fracture-matrix diffusion, and its implementation is discussed using existing analytical solutions and numerical models. In addition, we use the enhanced matrix diffusion concept to analyze laboratory experimental results from nonreactive and reactive tracer breakthrough tests, in an effort to validate the new conceptual model.

  11. Resonant enhanced diffusion in time-dependent flow

    NASA Astrophysics Data System (ADS)

    Castiglione, P.; Crisanti, A.; Mazzino, A.; Vergassola, M.; Vulpiani, A.

    1998-09-01

    Explicit examples of scalar enhanced diffusion due to resonances between different transport mechanisms are presented. Their signature is provided by the sharp and narrow peaks observed in the effective diffusivity coefficients and, in the absence of molecular diffusion, by anomalous transport. For the time-dependent flow considered here, resonances arise between their oscillations in time and either molecular diffusion or a mean flow. The effective diffusivities are calculated using multiscale techniques.

  12. Elucidating transient macromolecular interactions using paramagnetic relaxation enhancement

    PubMed Central

    Clore, G. Marius; Tang, Chun; Iwahara, Junji

    2007-01-01

    Recent advances in the use of paramagnetic relaxation enhancement (PRE) in structure refinement and in the analysis of transient dynamic processes involved in macromolecular complex formation are presented. In the slow exchange regime, we show, using the SRY/DNA complex as an example, that the PRE provides a powerful tool that can lead to significant increases in the reliability and accuracy of NMR structure determinations. Refinement necessitates the use of an ensemble representation of the paramagnetic center and a model free extension of the Solomon-Bloembergen equations. In the fast exchange regime, the PRE provides insight into dynamic processes and the existence of transient, low population intermediate species. The PRE allows one to characterize dynamic non-specific binding of a protein to DNA; to directly demonstrate that the search process whereby a transcription factor locates its specific DNA target site involves both intramolecular (sliding) and intermolecular (hopping and intersegment transfer) translocation; and to detect and visualize the distribution of an ensemble of transient encounter complexes in protein-protein association. PMID:17913493

  13. ENHANCED SEVERE TRANSIENT ANALYSIS FOR PREVENTION TECHNICAL PROGRAM PLAN

    SciTech Connect

    Gougar, Hans

    2014-09-01

    This document outlines the development of a high fidelity, best estimate nuclear power plant severe transient simulation capability that will complement or enhance the integral system codes historically used for licensing and analysis of severe accidents. As with other tools in the Risk Informed Safety Margin Characterization (RISMC) Toolkit, the ultimate user of Enhanced Severe Transient Analysis and Prevention (ESTAP) capability is the plant decision-maker; the deliverable to that customer is a modern, simulation-based safety analysis capability, applicable to a much broader class of safety issues than is traditional Light Water Reactor (LWR) licensing analysis. Currently, the RISMC pathway’s major emphasis is placed on developing RELAP-7, a next-generation safety analysis code, and on showing how to use RELAP-7 to analyze margin from a modern point of view: that is, by characterizing margin in terms of the probabilistic spectra of the “loads” applied to systems, structures, and components (SSCs), and the “capacity” of those SSCs to resist those loads without failing. The first objective of the ESTAP task, and the focus of one task of this effort, is to augment RELAP-7 analyses with user-selected multi-dimensional, multi-phase models of specific plant components to simulate complex phenomena that may lead to, or exacerbate, severe transients and core damage. Such phenomena include: coolant crossflow between PWR assemblies during a severe reactivity transient, stratified single or two-phase coolant flow in primary coolant piping, inhomogeneous mixing of emergency coolant water or boric acid with hot primary coolant, and water hammer. These are well-documented phenomena associated with plant transients but that are generally not captured in system codes. They are, however, generally limited to specific components, structures, and operating conditions. The second ESTAP task is to similarly augment a severe (post-core damage) accident integral analyses code with high fidelity simulations that would allow investigation of multi-dimensional, multi-phase containment phenomena that are only treated approximately in established codes.

  14. Boron-enhanced-diffusion of boron: The limiting factor for ultra-shallow junctions

    SciTech Connect

    Agarwal, A. |; Eaglesham, D.J.; Gossmann, H.J.; Pelaz, L.; Herner, S.B.; Jacobson, D.C.; Haynes, T.E.; Erokhin, Y.; Simonton, R.

    1997-12-01

    Reducing implant energy is an effective way to eliminate transient enhanced diffusion (TED) due to excess interstitials from the implant. It is shown that TED from a fixed Si dose implanted at energies from 0.5 to 20 keV into boron doping-superlattices decreases linearly with decreasing Si ion range, virtually disappearing at sub-keV energies. However, for sub-keV B implants diffusion remains enhanced and x{sub j} is limited to {ge} 100 nm at 1,050 C. The authors term this enhancement, which arises in the presence of B atomic concentrations at the surface of {approx} 6%, Boron-Enhanced-Diffusion (BED).

  15. Observation of silicon self-diffusion enhanced by the strain originated from end-of-range defects using isotope multilayers

    NASA Astrophysics Data System (ADS)

    Isoda, Taiga; Uematsu, Masashi; Itoh, Kohei M.

    2015-09-01

    Si self-diffusion in the presence of end-of-range (EOR) defects is investigated using natSi/28Si isotope multilayers. The isotope multilayers were amorphized by Ge ion implantation, and then annealed at 800-950 C. The behavior of Si self-interstitials is investigated through the 30Si self-diffusion. The experimental 30Si profiles show further enhancement of Si self-diffusion at the EOR defect region, in addition to the transient enhanced diffusion via excess Si self-interstitials by EOR defects. To explain this additional enhanced diffusion, we propose a model which takes into account enhanced diffusion by tensile strain originated from EOR defects. The calculation results based on this model have well reproduced the experimental 30Si profiles.

  16. Measurements of the transient velocity field in a strongly curved diffusing bend with periodic inflow unsteadiness

    NASA Astrophysics Data System (ADS)

    Yaras, M. I.; Orsi, P.

    This study examined the effects of periodic inflow unsteadiness on the flow development through fishtail-shaped diffusers utilized on small gas turbine engines. The periodic unsteadiness is due to the distortion of the flow in the peripheral direction at the exit of the centrifugal compressor impeller, caused by the jet-wake type of flow discharging from each impeller passage. Measurements of the transient velocity field were performed throughout the diffuser using a miniature 4-wire probe, at frequencies of inflow unsteadiness corresponding to design and off-design operating conditions in gas turbine installations. At the low end of the tested inflow unsteadiness frequencies, significant effects of inflow unsteadiness were observed on the time-averaged flow distortion throughout the diffuser. At these frequencies, the time variation of flow distortion was found to remain at comparable magnitudes throughout the diffuser.

  17. Monte Carlo study of non-diffusive relaxation of a transient thermal grating in thin membranes

    NASA Astrophysics Data System (ADS)

    Zeng, Lingping; Chiloyan, Vazrik; Huberman, Samuel; Maznev, Alex A.; Peraud, Jean-Philippe M.; Hadjiconstantinou, Nicolas G.; Nelson, Keith A.; Chen, Gang

    2016-02-01

    The impact of boundary scattering on non-diffusive thermal relaxation of a transient grating in thin membranes is rigorously analyzed using the multidimensional phonon Boltzmann equation. The gray Boltzmann simulation results indicate that approximating models derived from previously reported one-dimensional relaxation model and Fuchs-Sondheimer model fail to describe the thermal relaxation of membranes with thickness comparable with phonon mean free path. Effective thermal conductivities from spectral Boltzmann simulations free of any fitting parameters are shown to agree reasonably well with experimental results. These findings are important for improving our fundamental understanding of non-diffusive thermal transport in membranes and other nanostructures.

  18. Transient decrease in water diffusion observed in human occipital cortex during visual stimulation

    PubMed Central

    Darquié, Anne; Poline, Jean-Baptiste; Poupon, Cyril; Saint-Jalmes, Hervé; Le Bihan, Denis

    2001-01-01

    Using MRI, we report the observation of a transient decrease of the apparent diffusion coefficient (ADC) of water in the human brain visual cortex during activation by a black and white 8-Hz-flickering checkerboard. The ADC decrease was small (<1%), but significant and reproducible, and closely followed the time course of the activation paradigm. Based on the known sensitivity of diffusion MRI to cell size in tissues and on optical imaging studies that have revealed changes in the shape of neurons and glial cells during activation, the observed ADC findings have been tentatively ascribed to a transient swelling of cortical cells. These preliminary results suggest a new approach to produce images of brain activation with MRI from signals directly associated with neuronal activation, and not through changes in local blood flow. PMID:11459931

  19. Frequency-resolved Raman for transient thermal probing and thermal diffusivity measurement.

    PubMed

    Wang, Tianyu; Xu, Shen; Hurley, David H; Yue, Yanan; Wang, Xinwei

    2016-01-01

    A new transient Raman thermal probing technique, frequency-resolved Raman (FR-Raman), is developed for probing the transient thermal response of materials and measuring their thermal diffusivity. The FR-Raman uses an amplitude-modulated square-wave laser for simultaneous material heating and Raman excitation. The evolution profile of Raman properties: intensity, Raman wavenumber, and emission, against frequency are reconstructed and used for fitting to determine the thermal diffusivity. A microscale silicon (Si) cantilever is used to investigate the capacity of this new technique. The thermal diffusivity is determined as 9.5710-5??m2/s, 11.0010-5??m2/s, and 9.0210-5??m2/s via fitting Raman intensity, wavenumber, and total Raman emission, respectively. The results agree well with literature data. The FR-Raman provides a novel way for transient thermal probing with very high temporal resolution and micrometer-scale spatial resolution. PMID:26696163

  20. Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquifer-aquitard complexes

    USGS Publications Warehouse

    Zhang, Yong; Green, Christopher T.; Tick, Geoffrey R.

    2015-01-01

    This study evaluates the role of the Peclet number as affected by molecular diffusion in transient anomalous transport, which is one of the major knowledge gaps in anomalous transport, by combining Monte Carlo simulations and stochastic model analysis. Two alluvial settings containing either short- or long-connected hydrofacies are generated and used as media for flow and transport modeling. Numerical experiments show that 1) the Peclet number affects both the duration of the power-law segment of tracer breakthrough curves (BTCs) and the transition rate from anomalous to Fickian transport by determining the solute residence time for a given low-permeability layer, 2) mechanical dispersion has a limited contribution to the anomalous characteristics of late-time transport as compared to molecular diffusion due to an almost negligible velocity in floodplain deposits, and 3) the initial source dimensions only enhance the power-law tail of the BTCs at short travel distances. A tempered stable stochastic (TSS) model is then applied to analyze the modeled transport. Applications show that the time-nonlocal parameters in the TSS model relate to the Peclet number,Pe. In particular, the truncation parameter in the TSS model increases nonlinearly with a decrease inPedue to the decrease of the mean residence time, and the capacity coefficient increases with an increase in molecular diffusion which is probably due to the increase in the number of immobile particles. The above numerical experiments and stochastic analysis therefore reveal that the Peclet number as affected by molecular diffusion controls transient anomalous transport in alluvial aquiferaquitard complexes.

  1. Diffuse-charge effects on the transient response of electrochemical cells.

    PubMed

    van Soestbergen, M; Biesheuvel, P M; Bazant, M Z

    2010-02-01

    We present theoretical models for the time-dependent voltage of an electrochemical cell in response to a current step, including effects of diffuse charge (or "space charge") near the electrodes on Faradaic reaction kinetics. The full model is based on the classical Poisson-Nernst-Planck equations with generalized Frumkin-Butler-Volmer boundary conditions to describe electron-transfer reactions across the Stern layer at the electrode surface. In practical situations, diffuse charge is confined to thin diffuse layers (DLs), which poses numerical difficulties for the full model but allows simplification by asymptotic analysis. For a thin quasi-equilibrium DL, we derive effective boundary conditions on the quasi-neutral bulk electrolyte at the diffusion time scale, valid up to the transition time, where the bulk concentration vanishes due to diffusion limitation. We integrate the thin-DL problem analytically to obtain a set of algebraic equations, whose (numerical) solution compares favorably to the full model. In the Gouy-Chapman and Helmholtz limits, where the Stern layer is thin or thick compared to the DL, respectively, we derive simple analytical formulas for the cell voltage versus time. The full model also describes the fast initial capacitive charging of the DLs and superlimiting currents beyond the transition time, where the DL expands to a transient non-equilibrium structure. We extend the well-known Sand equation for the transition time to include all values of the superlimiting current beyond the diffusion-limiting current. PMID:20365567

  2. Anomalous diffusion process applied to magnetic resonance image enhancement

    NASA Astrophysics Data System (ADS)

    Senra Filho, A. C. da S.; Garrido Salmon, C. E.; Murta Junior, L. O.

    2015-03-01

    Diffusion process is widely applied to digital image enhancement both directly introducing diffusion equation as in anisotropic diffusion (AD) filter, and indirectly by convolution as in Gaussian filter. Anomalous diffusion process (ADP), given by a nonlinear relationship in diffusion equation and characterized by an anomalous parameters q, is supposed to be consistent with inhomogeneous media. Although classic diffusion process is widely studied and effective in various image settings, the effectiveness of ADP as an image enhancement is still unknown. In this paper we proposed the anomalous diffusion filters in both isotropic (IAD) and anisotropic (AAD) forms for magnetic resonance imaging (MRI) enhancement. Filters based on discrete implementation of anomalous diffusion were applied to noisy MRI T2w images (brain, chest and abdominal) in order to quantify SNR gains estimating the performance for the proposed anomalous filter when realistic noise is added to those images. Results show that for images containing complex structures, e.g. brain structures, anomalous diffusion presents the highest enhancements when compared to classical diffusion approach. Furthermore, ADP presented a more effective enhancement for images containing Rayleigh and Gaussian noise. Anomalous filters showed an ability to preserve anatomic edges and a SNR improvement of 26% for brain images, compared to classical filter. In addition, AAD and IAD filters showed optimum results for noise distributions that appear on extreme situations on MRI, i.e. in low SNR images with approximate Rayleigh noise distribution, and for high SNR images with Gaussian or non central χ noise distributions. AAD and IAD filter showed the best results for the parametric range 1.2 < q < 1.6, suggesting that the anomalous diffusion regime is more suitable for MRI. This study indicates the proposed anomalous filters as promising approaches in qualitative and quantitative MRI enhancement.

  3. Boron-enhanced diffusion of boron from ultralow-energy ion implantation

    SciTech Connect

    Agarwal, A.; Gossmann, H.; Eaglesham, D.J.; Herner, S.B.; Fiory, A.T.; Haynes, T.E.

    1999-04-01

    We have investigated the diffusion enhancement mechanism of boron-enhanced diffusion (BED), wherein boron diffusivity is enhanced four to five times over the equilibrium diffusivity at 1050&hthinsp;{degree}C in the proximity of a silicon layer containing a high boron concentration. It is demonstrated that BED is driven by excess interstitials injected from the high boron concentration layer during annealing. For evaporated layers, BED is observed above a threshold boron concentration between 1{percent} and 10{percent}, though it appears to be closer to 1{percent} for B-implanted layers. For sub-keV B implants above the threshold, BED dominates over the contribution from transient-enhanced diffusion to junction depth. For 0.5 keV B, this threshold implantation dose lies between 3{times}10{sup 14} and 1{times}10{sup 15} cm{sup {minus}2}. It is proposed that the excess interstitials responsible for BED are produced during the formation of a silicon boride phase in the high B concentration layers. {copyright} {ital 1999 American Institute of Physics.}

  4. Transient and periodic spatiotemporal structures in a reaction-diffusion-mechanics system

    NASA Astrophysics Data System (ADS)

    Kostin, V. A.; Osipov, G. V.

    2016-01-01

    We study transient spatiotemporal structures induced by a weak space-time localized stimulus in an excitable contractile fiber within a two-component globally coupled reaction-diffusion model. The model which we develop allows us to analyze various regimes of excitation spreading and determine origin of the induced structures for various contraction types (defined by the fiber fixation) and global coupling strengths. One of the most notable effects we observed is the after-excitation effect. It leads to emergence of multiple excitation pulses excited by a single external stimulus and can result in long-lasting transient activity and appearance of new oscillatory attractor regimes, including the ones with multiple phase clusters.

  5. Transient liquid phase diffusion bonding of Udimet 720 for Stirling power converter applications

    NASA Technical Reports Server (NTRS)

    Mittendorf, Donald L.; Baggenstoss, William G.

    1992-01-01

    Udimet 720 has been selected for use on Stirling power converters for space applications. Because Udimet 720 is generally considered susceptible to strain age cracking if traditional fusion welding is used, other joining methods are being considered. A process for transient liquid phase diffusion bonding of Udimet 720 has been theoretically developed in an effort to eliminate the strain age crack concern. This development has taken into account such variables as final grain size, joint homogenization, joint efficiency related to bonding aid material, bonding aid material application method, and thermal cycle.

  6. Color Histogram Diffusion for Image Enhancement

    NASA Technical Reports Server (NTRS)

    Kim, Taemin

    2011-01-01

    Various color histogram equalization (CHE) methods have been proposed to extend grayscale histogram equalization (GHE) for color images. In this paper a new method called histogram diffusion that extends the GHE method to arbitrary dimensions is proposed. Ranges in a histogram are specified as overlapping bars of uniform heights and variable widths which are proportional to their frequencies. This diagram is called the vistogram. As an alternative approach to GHE, the squared error of the vistogram from the uniform distribution is minimized. Each bar in the vistogram is approximated by a Gaussian function. Gaussian particles in the vistoram diffuse as a nonlinear autonomous system of ordinary differential equations. CHE results of color images showed that the approach is effective.

  7. {l_brace}311{r_brace} Defects in ion-implanted silicon: The cause of transient diffusion, and a mechanism for dislocation formation

    SciTech Connect

    Eaglesham, D.J.; Stolk, P.A.; Cheng, J.Y.; Gossmann, H.J.; Poate, J.M.; Haynes, T.E.

    1995-04-01

    Ion implantation is used at several critical stages of Si integrated circuit manufacturing. The authors show how {l_brace}311{r_brace} defects arising after implantation are responsible for both enhanced dopant diffusion during annealing, and stable dislocations post-anneal. They observe {l_brace}311{r_brace} defects in the earliest stages of an anneal. They subsequently undergo rapid Ostwald ripening and evaporation. At low implant doses evaporation dominates, and they can quantitatively relate the interstitials emitted from these defects to the transient enhancement in diffusivity of dopants such as B and P. At higher doses Ostwald ripening is significant, and they observe the defects to undergo a series of unfaulting reactions to form both Frank loops and perfect dislocations. They demonstrate the ability to control both diffusion and dislocations by the addition of small amounts of carbon impurities.

  8. Hole diffusivity in GaAsBi alloys measured by a picosecond transient grating technique

    NASA Astrophysics Data System (ADS)

    Nargelas, S.; Jaraiunas, K.; Bertulis, K.; Pa?ebutas, V.

    2011-02-01

    We applied a time-resolved transient grating technique for investigation of nonequilibrium carrier dynamics in GaAs1-xBix alloys with x =0.025-0.063. The observed decrease in carrier bipolar diffusivity with lowering temperature and its saturation below 80 K revealed a strong localization of nonequilibrium holes. Thermal activation energy ?Ea=46 meV of diffusivity and low hole mobility value ?h=10-20 cm2/V s at room temperature confirmed the hybridization model of the localized Bi states with the valence band of GaAs. Nonlinear increase in carrier recombination rate with the Bi content, 1/?R?Bi(x )3.2 indicated an increasing structural disorder in the alloy.

  9. Parareal in time 3D numerical solver for the LWR Benchmark neutron diffusion transient model

    NASA Astrophysics Data System (ADS)

    Baudron, Anne-Marie; Lautard, Jean-Jacques; Maday, Yvon; Riahi, Mohamed Kamel; Salomon, Julien

    2014-12-01

    In this paper we present a time-parallel algorithm for the 3D neutrons calculation of a transient model in a nuclear reactor core. The neutrons calculation consists in numerically solving the time dependent diffusion approximation equation, which is a simplified transport equation. The numerical resolution is done with finite elements method based on a tetrahedral meshing of the computational domain, representing the reactor core, and time discretization is achieved using a ?-scheme. The transient model presents moving control rods during the time of the reaction. Therefore, cross-sections (piecewise constants) are taken into account by interpolations with respect to the velocity of the control rods. The parallelism across the time is achieved by an adequate use of the parareal in time algorithm to the handled problem. This parallel method is a predictor corrector scheme that iteratively combines the use of two kinds of numerical propagators, one coarse and one fine. Our method is made efficient by means of a coarse solver defined with large time step and fixed position control rods model, while the fine propagator is assumed to be a high order numerical approximation of the full model. The parallel implementation of our method provides a good scalability of the algorithm. Numerical results show the efficiency of the parareal method on large light water reactor transient model corresponding to the Langenbuch-Maurer-Werner benchmark.

  10. Parareal in time 3D numerical solver for the LWR Benchmark neutron diffusion transient model

    SciTech Connect

    Baudron, Anne-Marie; Riahi, Mohamed Kamel; Salomon, Julien

    2014-12-15

    In this paper we present a time-parallel algorithm for the 3D neutrons calculation of a transient model in a nuclear reactor core. The neutrons calculation consists in numerically solving the time dependent diffusion approximation equation, which is a simplified transport equation. The numerical resolution is done with finite elements method based on a tetrahedral meshing of the computational domain, representing the reactor core, and time discretization is achieved using a θ-scheme. The transient model presents moving control rods during the time of the reaction. Therefore, cross-sections (piecewise constants) are taken into account by interpolations with respect to the velocity of the control rods. The parallelism across the time is achieved by an adequate use of the parareal in time algorithm to the handled problem. This parallel method is a predictor corrector scheme that iteratively combines the use of two kinds of numerical propagators, one coarse and one fine. Our method is made efficient by means of a coarse solver defined with large time step and fixed position control rods model, while the fine propagator is assumed to be a high order numerical approximation of the full model. The parallel implementation of our method provides a good scalability of the algorithm. Numerical results show the efficiency of the parareal method on large light water reactor transient model corresponding to the Langenbuch–Maurer–Werner benchmark.

  11. Sodium channels in transient retinal bipolar cells enhance visual responses in ganglion cells.

    PubMed

    Ichinose, Tomomi; Shields, Colleen R; Lukasiewicz, Peter D

    2005-02-16

    Retinal bipolar cells are slow potential neurons that respond to photoreceptor inputs with graded potentials and do not fire action potentials. We found that transient ON bipolar cells recorded in retinal slices possess voltage-gated sodium channels located on either their dendrites or somas. The sodium currents in these neurons did not generate spikes but enhanced voltage responses evoked by visual stimulation, which selectively boosted transmission to transient ganglion cells. In contrast, sodium currents were not found in sustained ON bipolar cells, and light responses in sustained bipolar cells and ganglion cells were not affected by TTX. The presence of sodium channels in transient ON bipolar cells contributed to the separation of transient and sustained signals by selectively enhancing the responses of ON transient ganglion cells to light. Our results suggest that bipolar cell sodium channels augment transient signals and contribute to the temporal segregation of visual information. PMID:15716422

  12. Partial transient liquid phase diffusion bonding of Zircaloy-4 to stabilized austenitic stainless steel 321

    SciTech Connect

    Atabaki, M. Mazar; Hanzaei, A. Talebi

    2010-10-15

    An innovative method was applied for bonding Zircaloy-4 to stabilized austenitic stainless steel 321 using an active titanium interlayer. Specimens were joined by a partial transient liquid phase diffusion bonding method in a vacuum furnace at different temperatures under 1 MPa dynamic pressure of contact. The influence of different bonding temperatures on the microstructure, microindentation hardness, joint strength and interlayer thickness has been studied. The diffusion of Fe, Cr, Ni and Zr has been investigated by scanning electron microscopy and energy dispersive spectroscopy elemental analyses. Results showed that control of the heating and cooling rate and 20 min soaking at 1223 K produces a perfect joint. However, solid-state diffusion of the melting point depressant elements into the joint metal causes the solid/liquid interface to advance until the joint is solidified. The tensile strength of all the bonded specimens was found around 480-670 MPa. Energy dispersive spectroscopy studies indicated that the melting occurred along the interface of the bonded specimens as a result of the transfer of atoms between the interlayer and the matrix during bonding. This technique provides a reliable method of bonding zirconium alloy to stainless steel.

  13. Non-diffusive relaxation of a transient thermal grating analyzed with the Boltzmann transport equation

    NASA Astrophysics Data System (ADS)

    Collins, Kimberlee C.; Maznev, Alexei A.; Tian, Zhiting; Esfarjani, Keivan; Nelson, Keith A.; Chen, Gang

    2013-09-01

    The relaxation of an one-dimensional transient thermal grating (TTG) in a medium with phonon-mediated thermal transport is analyzed within the framework of the Boltzmann transport equation (BTE), with the goal of extracting phonon mean free path (MFP) information from TTG measurements of non-diffusive phonon transport. Both gray-medium (constant MFP) and spectrally dependent MFP models are considered. In the gray-medium approximation, an analytical solution is derived. For large TTG periods compared to the MFP, the model yields an exponential decay of grating amplitude with time in agreement with Fourier's heat diffusion equation, and at shorter periods, phonon transport transitions to the ballistic regime, with the decay becoming strongly non-exponential. Spectral solutions are obtained for Si and PbSe at 300 K using phonon dispersion and lifetime data from density functional theory calculations. The spectral decay behaviors are compared to several approximate models: a single MFP solution, a frequency-integrated gray-medium model, and a "two-fluid" BTE solution. We investigate the utility of using the approximate models for the reconstruction of phonon MFP distributions from non-diffusive TTG measurements.

  14. Moderate MAS enhances local 1H spin exchange and spin diffusion

    NASA Astrophysics Data System (ADS)

    Roos, Matthias; Micke, Peter; Saalwchter, Kay; Hempel, Gnter

    2015-11-01

    Proton NMR spin-diffusion experiments are often combined with magic-angle spinning (MAS) to achieve higher spectral resolution of solid samples. Here we show that local proton spin diffusion can indeed become faster at low (<10 kHz) spinning rates as compared to static conditions. Spin diffusion under static conditions can thus be slower than the often referred value of 0.8 nm2/ms, which was determined using slow MAS (Clauss et al., 1993). The enhancement of spin diffusion by slow MAS relies on the modulation of the orientation-dependent dipolar couplings during sample rotation and goes along with transient level crossings in combination with dipolar truncation. The experimental finding and its explanation is supported by density matrix simulations, and also emphasizes the sensitivity of spin diffusion to the local coupling topology. The amplification of spin diffusion by slow MAS cannot be explained by any model based on independent spin pairs; at least three spins have to be considered.

  15. Enhancing the Sensitivity of HAWC to sub-Tev Transients

    NASA Astrophysics Data System (ADS)

    Wisher, Ian

    2013-04-01

    The High Altitude Water Cherenkov (HAWC) Observatory, currently being built 4100 meters above sea level near Pico de Orizaba, Mexico, is well-suited for observing transient phenomena above 1 TeV due to its large field of view (2 sr) and high uptime (˜100%). However, sub-TeV transient events are also of physical interest due to the overlap in energy with satellite experiments such as the Fermi gamma-ray space telescope. This presents a challenge since the sub-TeV primary particles observed with HAWC tend to be difficult to distinguish from noise. To address this problem, we propose a method in which particle arrival directions are fit to triplets of triggered PMTs in a short sliding trigger window (100 ns). The resulting arrival directions are then summed in a coarsely binned significance map of the sky with a time window of one to several seconds. This algorithm is simple enough to be applied online, and can localize the positions of transient sources to within 8 degrees. We run the method over HAWC30 detector data to estimate the noise rate and use simulated events to calculate the sensitivity to transients.

  16. Enhanced diffusion welding of TD-NiCr sheet.

    NASA Technical Reports Server (NTRS)

    Holko, K. H.; Moore, T. J.

    1972-01-01

    A method termed 'enhanced diffusion welding' has been developed to produce solid-state welds in TD-NiCr (Ni-20Cr-2ThO2) alloy sheet with weld strengths of 100% of the parent metal strength. Diffusion welded joints were made in specially processed TD-NiCr that equaled the tensile-shear and creep-rupture shear strengths of the parent material at 1090 deg C. The following observations have been made: specially processed TD-NiCr is preferred over commercial TD-NiCr for diffusion welding; the weld line can be eliminated when joining specially processed TD-NiCr by 600-grit sanding and electropolishing the faying surfaces prior to welding; and, a two-step weld cycle is preferred for diffusion welding of this alloy.

  17. Levy dynamics of enhanced diffusion - Application to turbulence

    NASA Astrophysics Data System (ADS)

    Shlesinger, M. F.; West, B. J.; Klafter, J.

    1987-03-01

    A stochastic process called a Levy (1937) walk is introduced, which is a random walk with a nonlocal memory coupled in space and in time in a scaling fashion. Levy walks result in enhanced diffusion, i.e., diffusion that grows as t exp a, where a is greater than 1. When applied to the description of a passive scalar diffusing in a fluctuating fluid flow, the model generalizes Taylor's (1921) correlated-walk approach. It yields Richardson's t exp 3 law for the turbulent diffusion of a passive scalar in a Kolmogorov (1941) -5/3 homogeneous turbulent flow and also gives the deviations from the 5/3 exponent resulting from Mandelbrot's (1976) intermittency. The model can be extended to studies of chemical reactions in turbulent flow.

  18. Improved Diffusion Imaging through SNR-Enhancing Joint Reconstruction

    PubMed Central

    Haldar, Justin P.; Wedeen, Van J.; Nezamzadeh, Marzieh; Dai, Guangping; Weiner, Michael W.; Schuff, Norbert; Liang, Zhi-Pei

    2012-01-01

    Quantitative diffusion imaging is a powerful technique for the characterization of complex tissue microarchitecture. However, long acquisition times and limited signal-to-noise ratio (SNR) represent significant hurdles for many in vivo applications. This paper presents a new approach to reduce noise while largely maintaining resolution in diffusion weighted images, using a statistical reconstruction method that takes advantage of the high level of structural correlation observed in typical datasets. Compared to existing denoising methods, the proposed method performs reconstruction directly from the measured complex k-space data, allowing for Gaussian noise modeling and theoretical characterizations of the resolution and SNR of the reconstructed images. In addition, the proposed method is compatible with many different models of the diffusion signal (e.g., diffusion tensor modeling, q-space modeling, etc.). The joint reconstruction method can provide significant improvements in SNR relative to conventional reconstruction techniques, with a relatively minor corresponding loss in image resolution. Results are shown in the context of diffusion spectrum imaging tractography and diffusion tensor imaging, illustrating the potential of this SNR-enhancing joint reconstruction approach for a range of different diffusion imaging experiments. PMID:22392528

  19. Modeling ballistic effects in frequency-dependent transient thermal transport using diffusion equations

    NASA Astrophysics Data System (ADS)

    Maassen, Jesse; Lundstrom, Mark

    2016-03-01

    Understanding ballistic phonon transport effects in transient thermoreflectance experiments and explaining the observed deviations from classical theory remains a challenge. Diffusion equations are simple and computationally efficient but are widely believed to break down when the characteristic length scale is similar or less than the phonon mean-free-path. Building on our prior work, we demonstrate how well-known diffusion equations, namely, the hyperbolic heat equation and the Cattaneo equation, can be used to model ballistic phonon effects in frequency-dependent periodic steady-state thermal transport. Our analytical solutions are found to compare excellently to rigorous numerical results of the phonon Boltzmann transport equation. The correct physical boundary conditions can be different from those traditionally used and are paramount for accurately capturing ballistic effects. To illustrate the technique, we consider a simple model problem using two different, commonly used heating conditions. We demonstrate how this framework can easily handle detailed material properties, by considering the case of bulk silicon using a full phonon dispersion and mean-free-path distribution. This physically transparent approach provides clear insights into the nonequilibrium physics of quasi-ballistic phonon transport and its impact on thermal transport properties.

  20. Temperature dependent normal and anomalous electron diffusion in porous Ti O2 studied by transient surface photovoltage

    NASA Astrophysics Data System (ADS)

    Dittrich, Thomas; Mora-Ser, Ivn; Garca-Belmonte, Germ; Bisquert, Juan

    2006-01-01

    A model system of nanoporous TiO2 sensitized with dye molecules at the outer surface is investigated by time resolved surface photovoltage (SPV) at temperatures between -120C and 270C to get information about electron diffusion over more than 10 orders of magnitude in time. The SPV transients increase in time due to independent electron diffusion and reach a maximum at a certain peak time due to reaching the screening length. The increasing parts of the SPV transients are characterized by a power law while the SPV power coefficient amounts to half of the dispersion parameter of anomalous diffusion. Anomalous diffusion is observed for times down to the duration time of the laser pulse (150ps) . With increasing temperature, the SPV power coefficient increases to its saturation value of 0.5 corresponding to normal diffusion. At lower temperatures, the SPV power coefficients decrease with increasing intensity of the exciting laser pulses. The decay of the SPV transients is determined by thermally activated normal diffusion. The minimal charge transfer time of an electron back to the positively charged dye molecule amounts to 2ps which is obtained from thermally activated logarithmic decays.

  1. Bifurcation analysis and transient spatio-temporal dynamics for a diffusive plant-herbivore system with Dirichlet boundary conditions.

    PubMed

    Wang, Lin; Watmough, James; Yu, Fang

    2015-08-01

    In this paper, we study a diffusive plant-herbivore system with homogeneous and nonhomogeneous Dirichlet boundary conditions. Stability of spatially homogeneous steady states is established. We also derive conditions ensuring the occurrence of Hopf bifurcation and steady state bifurcation. Interesting transient spatio-temporal behaviors including oscillations in one or both of space and time are observed through numerical simulations. PMID:25974343

  2. Simultaneous Determination of Thermal Conductivity and Thermal Diffusivity of Food and Agricultural Materials Using a Transient Plane-Source Method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Thermal conductivity and thermal diffusivity are two important physical properties essential for designing any food engineering processes. Recently a new transient plane-source method was developed to measure a variety of materials, but its application in foods has not been documented. Therefore, ...

  3. Strong enhancement of surface diffusion by nonlinear surface acoustic waves

    NASA Astrophysics Data System (ADS)

    Shugaev, Maxim V.; Manzo, Anthony J.; Wu, Chengping; Zaitsev, Vladimir Yu.; Helvajian, Henry; Zhigilei, Leonid V.

    2015-06-01

    The phenomenon of acoustic activation of surface diffusion is investigated in a combined computational and experimental study. The ability of pulsed laser-generated surface acoustic waves (SAWs) to enhance the mobility of small atomic clusters is demonstrated by directly tracking, with fluorescence microscopy, individual A u8 clusters moving on a (111) silicon substrate. A 19-fold increase in the effective diffusion coefficient is measured in room temperature experiments in the presence of SAWs generated by nanosecond pulse laser irradiation at a 100 Hz repetition rate. A strong enhancement of cluster mobility by SAWs is also observed in large-scale molecular dynamics simulations of surface diffusion of small atomic clusters. The analysis of the computational results demonstrates that the nonlinear sharpening of SAWs and the corresponding enrichment of the SAW spectra by high frequency harmonics which are capable of dynamic coupling to the cluster vibrations are responsible for the efficient acoustic activation of surface mobility in the simulations. The increase in the effective diffusion coefficient is proportional to the number of the SAW pulses passing through the diffusion region per unit time and a dramatic 4500-fold diffusion enhancement (corresponds to an equivalent temperature increase by 103K ) is predicted in the simulations for 15 GHz SAWs. The ability of SAWs to affect atomic-level surface processes has far-reaching implications for the design of new techniques where the acoustic energy serves as an effective substitution for thermal activation in applications where heating must be avoided or rapid switching of surface conditions is required.

  4. Time-independent hybrid enrichment for finite element solution of transient conduction–radiation in diffusive grey media

    SciTech Connect

    Mohamed, M. Shadi; Seaid, Mohammed; Trevelyan, Jon; Laghrouche, Omar

    2013-10-15

    We investigate the effectiveness of the partition-of-unity finite element method for transient conduction–radiation problems in diffusive grey media. The governing equations consist of a semi-linear transient heat equation for the temperature field and a stationary diffusion approximation to the radiation in grey media. The coupled equations are integrated in time using a semi-implicit method in the finite element framework. We show that for the considered problems, a combination of hyperbolic and exponential enrichment functions based on an approximation of the boundary layer leads to improved accuracy compared to the conventional finite element method. It is illustrated that this approach can be more efficient than using h adaptivity to increase the accuracy of the finite element method near the boundary walls. The performance of the proposed partition-of-unity method is analyzed on several test examples for transient conduction–radiation problems in two space dimensions.

  5. Superplastic deformation enhanced diffusion bonding of aluminum alloy 7475

    SciTech Connect

    Sunwoo, A.; Lum, R.

    1995-08-15

    The purpose of this work is to determine the feasibility of concurrent solid-state diffusion bonding and superplastic forming of Al alloy 7475. The authors used the concept of superplastic deformation to study the diffusion bonding of superplastic Al alloy 7475. Superplastic alloys attain large plastic elongation through grain-boundary sliding -- i.e., very fine internal grains slide and rotate, allowing neighboring grains to switch. Similarly, if grains on the surface are also sliding and rotating, then the oxide film should be disrupted by new grains coming to the surface. A surface that contains these nonoxidized grains should be able to bond with a minimum of applied contact pressure. Thus, the bonds can be produced easily by applying gas pressure during superplastic forming. This is the hypothesis the authors are attempting to prove in this study. It is difficult to make a direct comparison with other reported data, since the diffusion bonding conditions vary significantly. However, it can be concluded that, for a given 7475 composition, prior thermomechanical processing can influence its diffusion-bonding characteristics. Beginning with this preprocessed material, they used a unique method, never before reported, to obtain diffusion bonding concurrently with superplastic forming to achieve ductile, oxide-free bonds at significantly lower pressures in an argon atmosphere. This work clearly proves that superplastic deformation enhances solid state diffusion bonding of aluminum alloy.

  6. The Effect of Velocity on the Extinction Behavior of a Diffusion Flame during Transient Depressurization

    NASA Technical Reports Server (NTRS)

    Goldmeer, Jeffrey S.; Urban, David L.; Tien, James

    1999-01-01

    Current fire suppression plans for the International Space Station include the use of venting (depressurization) as a method for extinguishing a fire. Until recently this process had only been examined as part of a material flammability experiment performed on Skylab in the early 1970's. Due to the low initial pressure (0.35 Atm) and high oxygen concentration (65%), the Skylab experimental results are not applicable for understanding the effects of venting on a fire in a space station environment (21%O2, 1 Atm). Recent research examined the extinction behavior of a diffusion flame over a polymethyl methacrylate (PMMA) cylinder during a transient depressurization in low-gravity. The numerical model was used to examine extinction limits as a function of depressurization rate, forced flow velocity, and initial solid phase temperature. The experimental and numerically predicted extinction data indicated that as the solid phase temperature increased the pressure required to extinguish the flame decreased. The numerical model was also used to examine conditions not obtainable in the low-gravity experiments. From these simulations, a series of extinction boundaries were generated that showed a region of increased flammability existed at a forced flow of 10 cm/s. Analysis of these extinction boundaries indicated that they were quasi-steady in nature, and that the final extinction conditions were independent of the transient process. The velocity range in the previous study was limited and thus the results did not examine the effects of velocities less than 1 cm/s or greater than 20 cm/s. This study utilized low-gravity experiments performed on NASA's Reduced-gravity Research Aircraft Laboratory and numerical simulations to examine conditions applicable to the Space Station environment. This paper extends the analysis of the previous study to a comprehensive examination of the effect of increased velocity on extinction behavior and extinction limits during a transient depressurization in low-gravity. This is achieved by examining extinction data from buoyant (normal-gravity) and low-buoyant (low-gravity) depressurization. experiments, as well as from numerical predictions of flame behavior during depressurization in a non-buoyant (zero-gravity) environment.

  7. Enhanced Methanol Diffusion in Homogeneous Isotropic and Anisotropic Silica Aerogels

    NASA Astrophysics Data System (ADS)

    Lee, Jeongseop; Mounce, A. M.; Oh, Sangwon; Zimmerman, A. M.; Halperin, W. P.

    2014-03-01

    It has recently been shown that chiral superfluid 3He states can be stabilized using stretched, anisotropic, high porosity silica aerogel.[2] We present a novel approach to characterize the aerogel structure using nuclear magnetic resonance measurement of the enhanced diffusion of methanol vapor, similar to previous reports of diffusion of water in partially filled porous glass.[3] The diffusion coefficient is determined by the molecular motion in the vapor phase in fast exchange with adsorbed phase. Consequently, the diffusion is enhanced by two orders of magnitude beyond that of the bulk fluid but is limited by the elastic mean free path λ for ballistic molecular motion in the aerogel. The mean free paths in the presence of global anisotropy in a stretched (radially shrunken) aerogel, were found to be larger in the direction of strain by an amount consistent with the strain amplitude measured independently. This work was supported by the DOE BES under grants No. DE-FG02-05ER46248.

  8. Enhanced photocoagulation with catheter-based diffusing optical device

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook; Kim, Jeehyun; Oh, Jungwhan

    2012-11-01

    A novel balloon catheter-based diffusing optical device was designed and evaluated to assist in treating excessive menstrual bleeding. A synthetic fused-silica fiber was micro-machined precisely to create scattering segments on a 25 mm long fiber tip for uniform light distribution. A visible wavelength (λ=532 nm) was used to specifically target the endometrium due to the high vascularity of the uterine wall. Optical simulation presented 30% wider distribution of photons along with approximately 40% higher irradiance induced by addition of a glass cap to the diffuser tip. Incorporation of the optical diffuser with a polyurethane balloon catheter considerably enhanced coagulation depth and area (i.e., 3.5 mm and 18.9 cm2 at 1 min irradiation) in tissue in vitro. The prototype device demonstrated the coagulation necrosis of 2.8±1.2 mm (n=18) and no thermal damage to myometrium in in vivo caprine models. A prototype 5 cm long balloon catheter-assisted optical diffuser was also evaluated with a cadaveric human uterus to confirm the coagulative response of the uterine tissue as well as to identify the further design improvement and clinical applicability. The proposed catheter-based diffusing optical device can be a feasible therapeutic tool to photocoagulate endometrial cell layers in an efficient and safe manner.

  9. Enhanced photocoagulation with catheter-based diffusing optical device.

    PubMed

    Kang, Hyun Wook; Kim, Jeehyun; Oh, Jungwhan

    2012-11-01

    A novel balloon catheter-based diffusing optical device was designed and evaluated to assist in treating excessive menstrual bleeding. A synthetic fused-silica fiber was micro-machined precisely to create scattering segments on a 25 mm long fiber tip for uniform light distribution. A visible wavelength (?=532??nm) was used to specifically target the endometrium due to the high vascularity of the uterine wall. Optical simulation presented 30% wider distribution of photons along with approximately 40% higher irradiance induced by addition of a glass cap to the diffuser tip. Incorporation of the optical diffuser with a polyurethane balloon catheter considerably enhanced coagulation depth and area (i.e., 3.5 mm and 18.9??cm2 at 1 min irradiation) in tissue in vitro. The prototype device demonstrated the coagulation necrosis of 2.81.2??mm (n=18) and no thermal damage to myometrium in in vivo caprine models. A prototype 5 cm long balloon catheter-assisted optical diffuser was also evaluated with a cadaveric human uterus to confirm the coagulative response of the uterine tissue as well as to identify the further design improvement and clinical applicability. The proposed catheter-based diffusing optical device can be a feasible therapeutic tool to photocoagulate endometrial cell layers in an efficient and safe manner. PMID:23154817

  10. Enhancing chemical identification efficiency by SAW sensor transients through a data enrichment and information fusion strategya simulation study

    NASA Astrophysics Data System (ADS)

    Singh, Prashant; Yadava, R. D. S.

    2013-05-01

    The paper proposes a new approach for improving the odor recognition efficiency of a surface acoustic wave (SAW) transient sensor system based on a single polymer coating. The vapor identity information is hidden in transient response shapes through dependences on specific vapor solvation and diffusion parameters in the polymer coating. The variations in the vapor exposure and purge durations and the sensor operating frequency have been used to create diversity in transient shapes via termination of the vapor-polymer equilibration process up to different stages. The transient signals were analyzed by the discrete wavelet transform using Daubechies-4 mother wavelet basis. The wavelet approximation coefficients were then processed by principal component analysis for creating feature space. The set of principal components define the vapor identity information. In an attempt to enhance vapor class separability we analyze two types of information fusion methods. In one, the sensor operation frequency is fixed and the sensing and purge durations are varied, and in the second, the sensing and purge durations are fixed and the sensor operating frequency is varied. The fusion is achieved by concatenation of discrete wavelet coefficients corresponding to various transients prior to the principal component analysis. The simulation experiments with polyisobutylene SAW sensor coating for operation frequencies over [55-160] MHz and sensing durations over [5-60] s were analyzed. The target vapors are seven volatile organics: chloroform, chlorobenzene, o-dichlorobenzene, n-heptane, toluene, n-hexane and n-octane whose concentrations were varied over [10-100] ppm. The simulation data were generated using a SAW sensor transient response model that incorporates the viscoelastic effects due to polymer coating and an additive noise source in the output. The analysis reveals that: (i) in single transient analysis the class separability increases with sensing duration for a given frequency of operation, and also with frequency for a given sensing duration, and (ii) the information fusion based on both the multiple sensing cycles and the multiple sensing frequencies enhances the class separability by nearly an order of magnitude.

  11. Transient electron heat diffusivity obtained from trace impurity injection on TFTR

    SciTech Connect

    Kissick, M. W.; Fredrickson, E. D.; Callen, J. D.; Bush, C. E.; Chang, Z. Y.; Efthimion, P. C.; Hulse, R. A.; Mansfield, D. K.; Park, H. K.; Schivell, J.; Scott, S. D.; Synakowski, E. J.; Taylor, G.; Zarnstorff, M. C.

    1993-08-01

    A new method for obtaining a transient (``pulse``) electron heat diffusivity (χep) in the radial region 0.38 < r/a < 0.56 in TFTR L-mode discharges is presented. Small electron temperature perturbations were caused by single bursts of injected impurities which radiated and cooled the plasma edge. An iron injection case by laser ablation was found to be more definitive than a supporting helium gas puff case. In this new ``cold pulse`` method, we concentrate on modeling just the electron temperature perturbations, tracked with ECE (electron cyclotron emission) diagnostics and on being able to justify separation in space and time from the cooling source. This χep is obtained for these two cases to be χep = (6.0m²/s ± 35%) ~ 4χe(power balance) which is consistent with, but more definitive than, results from other studies that are more susceptible to ambiguities in the source profile.

  12. Nanostructure Particle-Reinforced Transient Liquid Phase Diffusion Bonding: a Comparative Study

    NASA Astrophysics Data System (ADS)

    Cooke, Kavian O.; Khan, Tahir I.; Oliver, Gossett D.

    2011-08-01

    Particle-reinforced aluminum-metal matrix composites (Al-MMCs) are used in many engineering applications, because they provide significant advantages when compared to monolithic aluminum alloys. However, there still exists the need to identify a suitable joining process for these materials, which minimizes particulate disruption and retains the strength of the MMC within the joint region. This study presents a comparison between joint qualities achieved when a monolithic interlayer is used vs when a nanoparticle-reinforced composite interlayer is used during transient liquid phase diffusion bonding of Al-6061 alloy containing 15 vol pct of Al2O3 particles. Examination of the joint region using scanning electron microscopy (SEM), wavelength dispersive spectroscopy (WDS), and X-ray diffraction (XRD) showed the formation of eutectic phases such as Al3Ni, Al9FeNi, and Ni3Si within the joint zone. The results indicate that the addition of nanoparticle reinforcements into the interlayer can be used to improve joint strength and minimize particle segregation.

  13. Reduction of transient diffusion from 1{endash}5 keV Si{sup +} ion implantation due to surface annihilation of interstitials

    SciTech Connect

    Agarwal, A.; Gossmann, H.-.; Eaglesham, D.J.; Pelaz, L.; Jacobson, D.C.; Haynes, T.E.; Erokhin, Y.E.

    1997-11-01

    The reduction of transient enhanced diffusion (TED) with reduced implantation energy has been investigated and quantified. A fixed dose of 1{times}10{sup 14} cm{sup {minus}2} Si{sup +} was implanted at energies ranging from 0.5 to 20 keV into boron doping superlattices and enhanced diffusion of the buried boron marker layers was measured for anneals at 810, 950, and 1050{degree}C. A linearly decreasing dependence of diffusivity enhancement on decreasing Si{sup +} ion range is observed at all temperatures, extrapolating to {approximately}1 for 0 keV. This is consistent with our expectation that at zero implantation energy there would be no excess interstitials from the implantation and hence no TED. Monte Carlo modeling and continuum simulations are used to fit the experimental data. The results are consistent with a surface recombination length for interstitials of {lt}10 nm. The data presented here demonstrate that in the range of annealing temperatures of interest for p-n junction formation, TED is reduced at smaller ion implantation energies and that this is due to increased interstitial annihilation at the surface. {copyright} {ital 1997 American Institute of Physics.}

  14. The heat released during catalytic turnover enhances the diffusion of an enzyme.

    PubMed

    Riedel, Clement; Gabizon, Ronen; Wilson, Christian A M; Hamadani, Kambiz; Tsekouras, Konstantinos; Marqusee, Susan; Press, Steve; Bustamante, Carlos

    2015-01-01

    Recent studies have shown that the diffusivity of enzymes increases in a substrate-dependent manner during catalysis. Although this observation has been reported and characterized for several different systems, the precise origin of this phenomenon is unknown. Calorimetric methods are often used to determine enthalpies from enzyme-catalysed reactions and can therefore provide important insight into their reaction mechanisms. The ensemble averages involved in traditional bulk calorimetry cannot probe the transient effects that the energy exchanged in a reaction may have on the catalyst. Here we obtain single-molecule fluorescence correlation spectroscopy data and analyse them within the framework of a stochastic theory to demonstrate a mechanistic link between the enhanced diffusion of a single enzyme molecule and the heat released in the reaction. We propose that the heat released during catalysis generates an asymmetric pressure wave that results in a differential stress at the protein-solvent interface that transiently displaces the centre-of-mass of the enzyme (chemoacoustic effect). This novel perspective on how enzymes respond to the energy released during catalysis suggests a possible effect of the heat of reaction on the structural integrity and internal degrees of freedom of the enzyme. PMID:25487146

  15. The heat released during catalytic turnover enhances the diffusion of an enzyme

    PubMed Central

    Riedel, Clement; Gabizon, Ronen; Wilson, Christian A. M.; Hamadani, Kambiz; Tsekouras, Konstantinos; Marqusee, Susan; Pressé, Steve; Bustamante, Carlos

    2015-01-01

    Recent studies have shown that the diffusivity of enzymes increases in a substrate-dependent manner during catalysis1,2. Although this observation has been reported and characterized for several different systems3–10, the precise origin of this phenomenon is unknown. Calorimetric methods are often used to determine enthalpies from enzyme-catalysed reactions and can therefore provide important insight into their reaction mechanisms11,12. The ensemble averages involved in traditional bulk calorimetry cannot probe the transient effects that the energy exchanged in a reaction may have on the catalyst. Here we obtain single-molecule fluorescence correlation spectroscopy data and analyse them within the framework of a stochastic theory to demonstrate a mechanistic link between the enhanced diffusion of a single enzyme molecule and the heat released in the reaction. We propose that the heat released during catalysis generates an asymmetric pressure wave that results in a differential stress at the protein–solvent interface that transiently displaces the centre-of-mass of the enzyme (chemoacoustic effect). This novel perspective on how enzymes respond to the energy released during catalysis suggests a possible effect of the heat of reaction on the structural integrity and internal degrees of freedom of the enzyme. PMID:25487146

  16. Radiation enhanced diffusion of Nd in UO2

    NASA Astrophysics Data System (ADS)

    Han, Xiaochun; Heuser, Brent J.

    2015-11-01

    Single crystal UO2 thin films with Nd as tracer elements in the film mid-plane have been grown on yttria-stabilized zirconia (YSZ) substrates. The films were irradiated with 1.8 MeV Kr+ ions in the temperature range from 400 °C to 1113 °C, where an evident enhanced diffusion was found in UO2. The temperature dependent measurements have shown an activation energy of 0.56 ± 0.04 eV below 800 °C, and 1.9 ± 0.3 eV above 900 °C. The rate-dependent measurements have shown a linear dependence on the radiation flux, which indicates radiation enhanced diffusion (RED) is in the sink limited kinetics regime. Comparison of the RED results between UO2 and CeO2 has shown significant differences, which indicates that CeO2 used as UO2 surrogate may be questioned in terms of cation diffusion.

  17. Transient Density Enhancements of the Martian Orbiting Dust Torus

    NASA Astrophysics Data System (ADS)

    Juhasz, A.; Horanyi, M.

    2014-12-01

    The moons Phobos and Deimos have been suggested to be responsible for sustaining a permanently present dust cloud around Mars. The equilibrium size and spatial distribution of this dust torus has been the subject of numerous theoretical studies. However, no observational evidence has been found as of yet. Because of the renewed interest in Phobos and Deimos as potential targets for human precursor mission to Mars, there is a new opportunity for the detection of the putative Martian dust clouds using in situ measurements. Both Phobos and Deimos, as all airless bodies in the solar system, are continually bombarded by interplanetary dust grains, generating secondary ejecta particles. The surface gravity escape of these objects are low, hence most secondary particles escapethem, but remain in orbit about Mars. Subsequent perturbations by solar radiation pressure, electromagnetic forces acting on charged grains, and collisions with the moons or Mars itself limit the lifetime of the produced particles. The size dependent production rates and lifetimes set the most abundant particle size range of 10 - 30 micron in radius. Large, but short-lived, dust density enhancements can be predicted during periods of meteor showers. Also, comet Siding Spring will flyby Mars in October, 2014. Its dust tail can 'sand-blast' both Phobos and Deimos, dramatically increasing their dust production for a few hours. We present the results of our numerical studies on the temporal and spatial evolution of the dust clouds raised during highly enhanced production rates that last only hours-to-days.

  18. Small quantum absorption refrigerator in the transient regime: Time scales, enhanced cooling, and entanglement

    NASA Astrophysics Data System (ADS)

    Brask, Jonatan Bohr; Brunner, Nicolas

    2015-12-01

    A small quantum absorption refrigerator, consisting of three qubits, is discussed in the transient regime. We discuss time scales for coherent dynamics, damping, and approach to the steady state, and we study cooling and entanglement. We observe that cooling can be enhanced in the transient regime, in the sense that lower temperatures can be achieved compared to the steady-state regime. This is a consequence of coherent dynamics but can occur even when this dynamics is strongly damped by the dissipative thermal environment, and we note that precise control over couplings or timing is not needed to achieve enhanced cooling. We also show that the amount of entanglement present in the refrigerator can be much larger in the transient regime compared to the steady state. These results are of relevance to future implementations of quantum thermal machines.

  19. Enhancing the ABAQUS Thermomechanics Code to Simulate Steady and Transient Fuel Rod Behavior

    SciTech Connect

    R. L. Williamson; D. A. Knoll

    2009-09-01

    A powerful multidimensional fuels performance capability, applicable to both steady and transient fuel behavior, is developed based on enhancements to the commercially available ABAQUS general-purpose thermomechanics code. Enhanced capabilities are described, including: UO2 temperature and burnup dependent thermal properties, solid and gaseous fission product swelling, fuel densification, fission gas release, cladding thermal and irradiation creep, cladding irradiation growth , gap heat transfer, and gap/plenum gas behavior during irradiation. The various modeling capabilities are demonstrated using a 2D axisymmetric analysis of the upper section of a simplified multi-pellet fuel rod, during both steady and transient operation. Computational results demonstrate the importance of a multidimensional fully-coupled thermomechanics treatment. Interestingly, many of the inherent deficiencies in existing fuel performance codes (e.g., 1D thermomechanics, loose thermo-mechanical coupling, separate steady and transient analysis, cumbersome pre- and post-processing) are, in fact, ABAQUS strengths.

  20. Enhancing the ABAQUS thermomechanics code to simulate multipellet steady and transient LWR fuel rod behavior

    SciTech Connect

    R. L. Williamson

    2011-08-01

    A powerful multidimensional fuels performance analysis capability, applicable to both steady and transient fuel behavior, is developed based on enhancements to the commercially available ABAQUS general-purpose thermomechanics code. Enhanced capabilities are described, including: UO2 temperature and burnup dependent thermal properties, solid and gaseous fission product swelling, fuel densification, fission gas release, cladding thermal and irradiation creep, cladding irradiation growth, gap heat transfer, and gap/plenum gas behavior during irradiation. This new capability is demonstrated using a 2D axisymmetric analysis of the upper section of a simplified multipellet fuel rod, during both steady and transient operation. Comparisons are made between discrete and smeared-pellet simulations. Computational results demonstrate the importance of a multidimensional, multipellet, fully-coupled thermomechanical approach. Interestingly, many of the inherent deficiencies in existing fuel performance codes (e.g., 1D thermomechanics, loose thermomechanical coupling, separate steady and transient analysis, cumbersome pre- and post-processing) are, in fact, ABAQUS strengths.

  1. Enhanced self-diffusion of adsorbed methanol in silica aerogel

    NASA Astrophysics Data System (ADS)

    Lee, Jeongseop A.; Mounce, A. M.; Oh, Sangwon; Zimmerman, A. M.; Halperin, W. P.

    2014-11-01

    Molecular transport of a two-component system of liquid and vapor in a porous medium can be anomalously increased owing to fast exchange between the two phases [Phys. Rev. Lett. 63, 43 (1989), 10.1103/PhysRevLett.63.43]. We have investigated this phenomenon measuring the self-diffusion coefficient of methanol adsorbed in a 98% porosity aerogel using nuclear magnetic resonance field gradient techniques. We found enhancement of several orders of magnitude from which we determined the ballistic mean-free path in the vapor phase. We have grown globally uniform anisotropic aerogels and applied the diffusion measurements to characterize the anisotropy. Our results are important for understanding the novel properties of superfluid 3He confined within an aerogel framework and for application to other physical systems.

  2. A review of porous media enhanced vapor-phase diffusion mechanisms, models, and data: Does enhanced vapor-phase diffusion exist?

    SciTech Connect

    Ho, C.K.; Webb, S.W.

    1996-05-01

    A review of mechanisms, models, and data relevant to the postulated phenomenon of enhanced vapor-phase diffusion in porous media is presented. Information is obtained from literature spanning two different disciplines (soil science and engineering) to gain a diverse perspective on this topic. Findings indicate that while enhanced vapor diffusion tends to correct the discrepancies observed between past theory and experiments, no direct evidence exists to support the postulated processes causing enhanced vapor diffusion. Numerical modeling analyses of experiments representative of the two disciplines are presented in this paper to assess the sensitivity of different systems to enhanced vapor diffusion. Pore-scale modeling is also performed to evaluate the relative significance of enhanced vapor diffusion mechanisms when compared to Fickian diffusion. The results demonstrate the need for additional experiments so that more discerning analyses can be performed.

  3. Sharpening of neurite morphology using complex coherence enhanced diffusion.

    PubMed

    Mustaffa, Izadora; Trenado, Carlos; Rahim, Hazli Rafis Abd; Schafer, Karl-Herbert; Strauss, Daniel J

    2009-01-01

    The study of the molecular mechanisms involved in neurite outgrowth and differentiation, requires essential accurate and reproducible segmentation and quantification of neuronal processes. The common method used in this study is to detect and trace individual neurites, i.e. neurite tracing. The challenge comes mainly from the morphological problem in which these images contains ambiguities such as neurites discontinuities and intensity differences. In our work, we encounter a bigger challenge as the neurites in our images have a higher density of neurites. In this paper, we present a hybrid complex coherence-enhanced method for sharpening the morphology of neurons from such images. Coherence-enhanced diffusion (CED) is used to enhance the flowlike structures of the neurites, while the imaginary part of the complex nonlinear diffusion of the image cancels the appearance of 'clouds'. We also describe an elementary method for estimating the density of neuritis based on the obtained images. Our preliminary results show that the proposed methodology is a step ahead toward an effective neuronal morphology algorithm. PMID:19964080

  4. Enhanced Diffusion of Enzymes that Catalyze Exothermic Reactions

    NASA Astrophysics Data System (ADS)

    Golestanian, Ramin

    2015-09-01

    Enzymes have been recently found to exhibit enhanced diffusion due to their catalytic activities. A recent experiment [C. Riedel et al., Nature (London) 517, 227 (2015)] has found evidence that suggests this phenomenon might be controlled by the degree of exothermicity of the catalytic reaction involved. Four mechanisms that can lead to this effect, namely, self-thermophoresis, boost in kinetic energy, stochastic swimming, and collective heating are critically discussed, and it is shown that only the last two can be strong enough to account for the observations. The resulting quantitative description is used to examine the biological significance of the effect.

  5. Enhanced Diffusion of Enzymes that Catalyze Exothermic Reactions.

    PubMed

    Golestanian, Ramin

    2015-09-01

    Enzymes have been recently found to exhibit enhanced diffusion due to their catalytic activities. A recent experiment [C. Riedel etal., Nature (London) 517, 227 (2015)] has found evidence that suggests this phenomenon might be controlled by the degree of exothermicity of the catalytic reaction involved. Four mechanisms that can lead to this effect, namely, self-thermophoresis, boost in kinetic energy, stochastic swimming, and collective heating are critically discussed, and it is shown that only the last two can be strong enough to account for the observations. The resulting quantitative description is used to examine the biological significance of the effect. PMID:26382704

  6. Enhanced diffusion of dopants in vacancy supersaturation produced by MeV implantation

    SciTech Connect

    Venezia, V.C. |; Haynes, T.E.; Agarwal, A. |; Gossmann, H.J.; Eaglesham, D.J.

    1997-04-01

    The diffusion of Sb and B markers has been studied in vacancy supersaturations produced by MeV Si implantation in float zone (FZ) silicon and bonded etch-back silicon-on-insulator (BESOI) substrates. MeV Si implantation produces a vacancy supersaturated near-surface region and an interstitial-rich region at the projected ion range. Transient enhanced diffusion (TED) of Sb in the near surface layer was observed as a result of a 2 MeV Si{sup +}, 1 {times} 10{sup 16}/cm{sup 2}, implant. A 4{times} larger TED of Sb was observed in BESOI than in FZ silicon, demonstrating that the vacancy supersaturation persists longer in BESOI than in FZ. B markers in samples with MeV Si implant showed a factor of 10{times} smaller diffusion relative to markers without the MeV Si{sup +} implant. This data demonstrates that a 2 MeV Si{sup +} implant injects vacancies into the near surface region.

  7. An enhanced finite element technique for diffuse phase transition

    NASA Astrophysics Data System (ADS)

    Mnch, I.; Krau, M.

    2015-10-01

    We propose a finite element technique to enhance phase-field simulations. As adaptive p-method it and can be generally applied to finite element formulations. However, diffuse interfaces have non-linear gradients within regions typically smaller compared to the size of the overall model. Thus, enhanced field interpolation with higher polynomial functions on demand allows for coarser meshing or lower regularization length for the phase transition. Our method preserves continuity of finite elements and is particularly advantageous in the context of parallelized computing. An analytical solution for the evolution of a phase-field variable governed by the Allen-Cahn equation is used to define an error measure and to investigate the proposed method. Several examples demonstrate the capability of this finite element technique.

  8. Intermolecular Paramagnetic Relaxation Enhancement (PRE) Studies of Transient Complexes in Intrinsically Disordered Proteins.

    PubMed

    Janowska, Maria K; Baum, Jean

    2016-01-01

    NMR interchain paramagnetic relaxation enhancement (PRE) techniques are a very powerful approach for detecting transient interchain interactions between intrinsically disordered proteins. These experiments, requiring a mixed sample containing a 1:1 ratio of isotope-labeled (15)N protein and natural abundance (14)N protein with a paramagnetic spin label, provide data that is limited to interchain interactions only. Application of these experiments to weakly associated transient species such as those that are present in the very early stages of self-assembly processes will aid our understanding of protein aggregation or fibril formation processes. PMID:26453204

  9. Ion-beam-induced enhanced diffusion from gold thin films in silicon

    NASA Astrophysics Data System (ADS)

    Ghatak, J.; Sundaravel, B.; Nair, K. G. M.; Satyam, P. V.

    2008-12-01

    We report enhanced diffusion of gold atoms from gold films of various thicknesses (that are deposited on Si) due to 1.5 MeV Au2+ ion impacts under high flux conditions. The maximum depths of mass transport have been found to be 95, 160 and 13 nm for the cases of 5.3, 10.9 and 27.5 nm thick gold films, respectively, at a fluence of 1 1014 ions cm-2. Interestingly, at a higher fluence of 1 1015 ions cm-2, gold atoms from the 27.5 thick films are transported to a maximum depth of 265 nm in the substrate. The enhanced diffusion for various film thicknesses is consistent with the recoil profiles of Au atoms into Si, which are obtained using Monte Carlo simulations (TRIM). These results have been explained on the basis of the ion-beam-induced flux-dependent amorphous nature of the substrate, and transient beam-induced temperature effects. This work also confirms the absence of ion-induced spike confinement effects that might arise from the morphological nature of the isolated nanostructures.

  10. ATC Enhancement Considering Transient Stability by Optimal Power Flow Control Using UPFC

    NASA Astrophysics Data System (ADS)

    Masuta, Taisuke; Motoki, Hiroaki; Yokoyama, Akihiko

    With recent development of power electronics technology, power system stability enhancement and optimal power flow control by using Flexible AC Transmission System (FACTS) devices have so far been studied. The FACTS devices to relieve multiple constraints can also make it possible to enhance Available Transfer Capability (ATC) without construction of new transmission lines. In this paper, a new method for improving transient stability by Unified Power Flow Controller (UPFC) is proposed. Then the proposed method is applied to an OPF control method by using UPFC for relieving multiple constraints. The new OPF method is used for enhancement of ATC taking into account Transient stability constraints as well as overload and steady-state stability constraints. The OPF problem is formulated to minimize total capacity of inverters of UPFC. Effectiveness of the proposed method is shown by numerical examples for IEEJ East-10-machine test system.

  11. A Nonlinear Excitation Controller Design Method for Terminal Voltage Regulation and Transient Stability Enhancement

    NASA Astrophysics Data System (ADS)

    Huang, Chongxin; Zhang, Kaifeng; Dai, Xianzhong; Zang, Qiang

    2014-06-01

    This paper proposes a cascade control method to design a nonlinear excitation controller to guarantee the terminal voltage regulation and the transient stability. Firstly, a nonlinear automatic voltage regulator (NAVR) in the inner loop is designed to control the terminal voltage exactly. Secondly, the generator model including the NAVR is transformed to be a reduced one. Subsequently, based on the reduced generator model, the nonlinear power system stabilizer in the external loop is designed to enhance the transient stability of the power systems. Furthermore, a coordination strategy is presented to improve the performances of the terminal voltage regulation in the steady state and the stability in the transient state. Finally, the proposed method is verified by numerous simulation results.

  12. Persistent order due to transiently enhanced nesting in an electronically excited charge density wave.

    PubMed

    Rettig, L; Cortés, R; Chu, J-H; Fisher, I R; Schmitt, F; Moore, R G; Shen, Z-X; Kirchmann, P S; Wolf, M; Bovensiepen, U

    2016-01-01

    Non-equilibrium conditions may lead to novel properties of materials with broken symmetry ground states not accessible in equilibrium as vividly demonstrated by non-linearly driven mid-infrared active phonon excitation. Potential energy surfaces of electronically excited states also allow to direct nuclear motion, but relaxation of the excess energy typically excites fluctuations leading to a reduced or even vanishing order parameter as characterized by an electronic energy gap. Here, using femtosecond time- and angle-resolved photoemission spectroscopy, we demonstrate a tendency towards transient stabilization of a charge density wave after near-infrared excitation, counteracting the suppression of order in the non-equilibrium state. Analysis of the dynamic electronic structure reveals a remaining energy gap in a highly excited transient state. Our observation can be explained by a competition between fluctuations in the electronically excited state, which tend to reduce order, and transiently enhanced Fermi surface nesting stabilizing the order. PMID:26804717

  13. Persistent order due to transiently enhanced nesting in an electronically excited charge density wave

    PubMed Central

    Rettig, L.; Cortés, R.; Chu, J.-H.; Fisher, I. R.; Schmitt, F.; Moore, R. G.; Shen, Z.-X.; Kirchmann, P. S.; Wolf, M.; Bovensiepen, U.

    2016-01-01

    Non-equilibrium conditions may lead to novel properties of materials with broken symmetry ground states not accessible in equilibrium as vividly demonstrated by non-linearly driven mid-infrared active phonon excitation. Potential energy surfaces of electronically excited states also allow to direct nuclear motion, but relaxation of the excess energy typically excites fluctuations leading to a reduced or even vanishing order parameter as characterized by an electronic energy gap. Here, using femtosecond time- and angle-resolved photoemission spectroscopy, we demonstrate a tendency towards transient stabilization of a charge density wave after near-infrared excitation, counteracting the suppression of order in the non-equilibrium state. Analysis of the dynamic electronic structure reveals a remaining energy gap in a highly excited transient state. Our observation can be explained by a competition between fluctuations in the electronically excited state, which tend to reduce order, and transiently enhanced Fermi surface nesting stabilizing the order. PMID:26804717

  14. Transient stability enhancement of electric power generating systems by 120-degree phase rotation

    DOEpatents

    Cresap, Richard L. (Portland, OR); Taylor, Carson W. (Portland, OR); Kreipe, Michael J. (Portland, OR)

    1982-01-01

    A method and system for enhancing the transient stability of an intertied three-phase electric power generating system. A set of power exporting generators (10) is connected to a set of power importing generators (20). When a transient cannot be controlled by conventional stability controls, and imminent loss of synchronism is detected (such as when the equivalent rotor angle difference between the two generator sets exceeds a predetermined value, such as 150 degrees), the intertie is disconnected by circuit breakers. Then a switch (30) having a 120-degree phase rotation, or a circuit breaker having a 120-degree phase rotation is placed in the intertie. The intertie is then reconnected. This results in a 120-degree reduction in the equivalent rotor angle difference between the two generator sets, making the system more stable and allowing more time for the conventional controls to stabilize the transient.

  15. Persistent order due to transiently enhanced nesting in an electronically excited charge density wave

    NASA Astrophysics Data System (ADS)

    Rettig, L.; Corts, R.; Chu, J.-H.; Fisher, I. R.; Schmitt, F.; Moore, R. G.; Shen, Z.-X.; Kirchmann, P. S.; Wolf, M.; Bovensiepen, U.

    2016-01-01

    Non-equilibrium conditions may lead to novel properties of materials with broken symmetry ground states not accessible in equilibrium as vividly demonstrated by non-linearly driven mid-infrared active phonon excitation. Potential energy surfaces of electronically excited states also allow to direct nuclear motion, but relaxation of the excess energy typically excites fluctuations leading to a reduced or even vanishing order parameter as characterized by an electronic energy gap. Here, using femtosecond time- and angle-resolved photoemission spectroscopy, we demonstrate a tendency towards transient stabilization of a charge density wave after near-infrared excitation, counteracting the suppression of order in the non-equilibrium state. Analysis of the dynamic electronic structure reveals a remaining energy gap in a highly excited transient state. Our observation can be explained by a competition between fluctuations in the electronically excited state, which tend to reduce order, and transiently enhanced Fermi surface nesting stabilizing the order.

  16. Diffuse dispersive delay and the time convolution/attenuation of transients

    NASA Technical Reports Server (NTRS)

    Bittner, Burt J.

    1991-01-01

    Test data and analytic evaluations are presented to show that relatively poor 100 KHz shielding of 12 Db can effectively provide an electromagnetic pulse transient reduction of 100 Db. More importantly, several techniques are shown for lightning surge attenuation as an alternative to crowbar, spark gap, or power zener type clipping which simply reflects the surge. A time delay test method is shown which allows CW testing, along with a convolution program to define transient shielding effectivity where the Fourier phase characteristics of the transient are known or can be broadly estimated.

  17. Experiments on Transient Oscillations in a Circuit of Diffusively Coupled Inverting Amplifiers

    NASA Astrophysics Data System (ADS)

    Horikawa, Yo; Kitajima, Hiroyuki

    2007-07-01

    Transient oscillations in a ring neuron network with inhibitory coupling are observed in an analog circuit made with operating amplifiers experimentally. The transient oscillations last more than 10sec in the circuit of 40 amplifiers with the time constant 1 ms. The duration of the oscillations increases exponentially as the number of the amplifiers. Computer simulation shows that the transient oscillations are traveling waves in which the nodes in the circuit are separated into two blocks and their boundaries are moving. The mechanism of the oscillations and the exponential dependence of the duration on the system size are explained qualitatively.

  18. Improved antibiotic-free plasmid vector design by incorporation of transient expression enhancers.

    PubMed

    Luke, J M; Vincent, J M; Du, S X; Gerdemann, U; Leen, A M; Whalen, R G; Hodgson, C P; Williams, J A

    2011-04-01

    Methods to improve plasmid-mediated transgene expression are needed for gene medicine and gene vaccination applications. To maintain a low risk of insertional mutagenesis-mediated gene activation, expression-augmenting sequences would ideally function to improve transgene expression from transiently transfected intact plasmid, but not from spurious genomically integrated vectors. We report herein the development of potent minimal, antibiotic-free, high-manufacturing-yield mammalian expression vectors incorporating rationally designed additive combinations of expression enhancers. The SV40 72?bp enhancer incorporated upstream of the cytomegalovirus (CMV) enhancer selectively improved extrachromosomal transgene expression. The human T-lymphotropic virus type I (HTLV-I) R region, incorporated downstream of the CMV promoter, dramatically increased mRNA translation efficiency, but not overall mRNA levels, after transient transfection. A similar mRNA translation efficiency increase was observed with plasmid vectors incorporating and expressing the protein kinase R-inhibiting adenoviral viral associated (VA)1 RNA. Strikingly, HTLV-I R and VA1 did not increase transgene expression or mRNA translation efficiency from plasmid DNA after genomic integration. The vector platform, when combined with electroporation delivery, further increased transgene expression and improved HIV-1 gp120 DNA vaccine-induced neutralizing antibody titers in rabbits. These antibiotic-free vectors incorporating transient expression enhancers are safer, more potent alternatives to improve transgene expression for DNA therapy or vaccination. PMID:21107439

  19. Transient Liquid Phase Diffusion Bonding of Magnesium Alloy (Mg-AZ31) to Titanium Alloy (Ti-6Al-4V)

    NASA Astrophysics Data System (ADS)

    Atieh, Anas Mahmoud

    The magnesium alloy Mg-AZ31 and titanium alloy Ti-6Al-4V have physical characteristics and mechanical properties that makes it attractive for a wide range of engineering applications in the aerospace and automotive industries. However, the differences in melting temperature and coefficient of thermal expansion hinder the use of traditional fusion welding techniques. Transient liquid phase (TLP) bonding of magnesium alloy Mg-AZ31 and titanium alloy Ti-6Al- 4V was performed and different interlayer types and configurations were used to facilitate joint formation. The joining of these alloys using Ni foils was successful at a bonding temperature of 515C, bonding pressure 0.2 MPa, for bonding time of 5 minutes. At the Ni/Mg-AZ31 bond interface, the formation of a eutectic liquid between Mg and Ni was observed. The formation of Mg2Ni and Mg3AlNi2 were identified along the bond interface resulting in an isothermally solidified joint. At the Ni/Ti-6Al-4V interface, the solid-state diffusion process results in joint formation. The use of double Ni-Cu sandwich joint resulted in further enhancement in joint formation and this produced joints with greater shear strength values. The configuration of Mg-AZ31/Cu- Ni/Ti-6Al-4V or Mg-AZ31/Ni-Cu/Ti-6Al-4V influence the mechanism of bonding and the type of intermetallics formed within the joint. The application of thin Ni electrodeposited coatings resulted in further enhancements of joint quality due to better surface-to-surface contact and a reduction in the formation of intermetallics at the joint. The effect of Cu nano-particles in the coatings was found to decrease the eutectic zone width and this resulted in an increase the shear strength of the joints. The highest shear strength of 69 MPa was possible with bonds made using coatings containing Cu nano-particle dispersion.

  20. A transient-enhanced NMOS low dropout voltage regulator with parallel feedback compensation

    NASA Astrophysics Data System (ADS)

    Han, Wang; Lin, Tan

    2016-02-01

    This paper presents a transient-enhanced NMOS low-dropout regulator (LDO) for portable applications with parallel feedback compensation. The parallel feedback structure adds a dynamic zero to get an adequate phase margin with a load current variation from 0 to 1 A. A class-AB error amplifier and a fast charging/discharging unit are adopted to enhance the transient performance. The proposed LDO has been implemented in a 0.35 μm BCD process. From experimental results, the regulator can operate with a minimum dropout voltage of 150 mV at a maximum 1 A load and IQ of 165 μA. Under the full range load current step, the voltage undershoot and overshoot of the proposed LDO are reduced to 38 mV and 27 mV respectively.

  1. Fluorine-enhanced boron diffusion in germanium-preamorphized silicon

    SciTech Connect

    Jacques, J.M.; Jones, K.S.; Robertson, L.S.; Li-Fatou, A.; Hazelton, C.M.; Napolitani, E.; Rubin, L.M.

    2005-10-01

    Silicon wafers were preamorphized with 60 keV Ge{sup +} or 70 keV Si{sup +} at a dose of 1x10{sup 15} atoms/cm{sup 2}. F{sup +} was then implanted into some samples at 6 keV at doses ranging from 1x10{sup 14} to 5x10{sup 15} atoms/cm{sup 2}, followed by {sup 11}B{sup +} implants at 500 eV, 1x10{sup 15} atoms/cm{sup 2}. Secondary-ion-mass spectrometry confirmed that fluorine enhances boron motion in germanium-preamorphized materials in the absence of annealing. The magnitude of boron diffusion scales with increasing fluorine dose. Boron motion in as-implanted samples occurs when fluorine is concentrated above 1x10{sup 20} atoms/cm{sup 3}. Boron atoms are mobile in as-implanted, amorphous material at concentrations up to 1x10{sup 19} atoms/cm{sup 3}. Fluorine directly influences boron motion only prior to activation annealing. During the solid-phase epitaxial regrowth process, fluorine does not directly influence boron motion, it simply alters the recrystallization rate of the silicon substrate. Boron atoms can diffuse in germanium-amorphized silicon during recrystallization at elevated temperatures without the assistance of additional dopants. Mobile boron concentrations up to 1x10{sup 20} atoms/cm{sup 3} are observed during annealing of germanium-preamorphized wafers.

  2. Stress enhanced diffusion of krypton ions in polycrystalline titanium

    SciTech Connect

    Nsengiyumva, S.; Raji, A. T.; Rivière, J. P.; Britton, D. T.; Härting, M.

    2014-07-14

    An experimental investigation on the mutual influence of pre-existing residual stress and point defect following ion implantation is presented. The study has been carried out using polycrystalline titanium samples energetically implanted with krypton ions at different fluences. Ion beam analysis was used to determine the concentration profile of the injected krypton ions, while synchrotron X-ray diffraction has been used for stress determination. Ion beam analysis and synchrotron X-ray diffraction stress profile measurements of the implanted titanium samples show a clear evidence of stress-enhanced diffusion of krypton ions in titanium. It is further observed that for the titanium samples implanted at low fluence, ion implantation modifies the pre-existing residual stress through the introduction of point and open volume defects. The stress fields resulting from the ion implantation act to drift the krypton inclusions towards the surface of titanium.

  3. Distributed Multi-Agent-Based Protection Scheme for Transient Stability Enhancement in Power Systems

    NASA Astrophysics Data System (ADS)

    Rahman, M. S.; Mahmud, M. A.; Pota, H. R.; Hossain, M. J.; Orchi, T. F.

    2015-04-01

    This paper presents a new distributed agent-based scheme to enhance the transient stability of power systems by maintaining phase angle cohesiveness of interconnected generators through proper relay coordination with critical clearing time (CCT) information. In this distributed multi-agent infrastructure, intelligent agents represent various physical device models to provide dynamic information and energy flow among different physical processes of power systems. The agents can communicate with each other in a distributed manner with a final aim to control circuit breakers (CBs) with CCT information as this is the key issue for maintaining and enhancing the transient stability of power systems. The performance of the proposed scheme is evaluated on a standard IEEE 39-bus New England benchmark system under different large disturbances such as three-phase short-circuit faults and changes in loads within the systems. From the simulation results, it is found that the proposed scheme significantly enhances the transient stability of power systems as compared to a conventional scheme of static CB operation.

  4. Optical Transient-Grating Measurements of Spin Diffusion andRelaxation in a Two-Dimensional Electron Gas

    SciTech Connect

    Weber, Christopher P.

    2005-12-15

    Spin diffusion in n-GaAs quantum wells, as measured by our optical transient-grating technique, is strongly suppressed relative to that of charge. Over a broad range of temperatures and dopings, the suppression of Ds relative to Dc agrees quantitatively with the prediction of ''spin Coulomb dra'' theory, which takes into account the exchange of spin in electron-electron collisions. Moreover, the spin-diffusion length, Ls, is a nearly constant 1 micrometer over the same range of T and n, despite Ds's varying by nearly two orders of magnitude. This constancy supports the D'yakonov-Perel'-Kachorovskii model of spin relaxation through interrupted precessional dephasing in the spin-orbit field.

  5. Unilateral temporal lobe stroke causing ischemic transient global amnesia: role for diffusion-weighted imaging in the initial evaluation.

    PubMed

    Greer, D M; Schaefer, P W; Schwamm, L H

    2001-07-01

    Ischemia has been proposed as a cause of transient global amnesia (TGA), but proof has been lacking. The authors performed magnetic resonance imaging on a 77-year-old woman with classic TGA at 4 hours and at 6 days after the onset of symptoms. Her initial diffusion-weighted imaging (DWI) and apparent diffusion coefficient imaging suggested an acute infarct in the left mesial temporal lobe. Follow-up T2-weighted imaging at 6 days confirmed the lesion as an ischemic infarct, despite resolution of her symptoms. DWI permits early detection of small ischemic lesions and may identify patients with ischemic TGA who should be evaluated for potential sources of emboli. PMID:11462302

  6. Experimental observations of Soret-driven convection in the transient diffusive boundary layer

    NASA Astrophysics Data System (ADS)

    Messlinger, Stephan; Kramer, Christoph; Schmied, Jrgen J.; Winkel, Florian; Schpf, Wolfgang; Rehberg, Ingo

    2013-11-01

    The onset of transient Soret-driven convection is investigated experimentally in a colloidal suspension of thermosensitive nanoparticles by the shadowgraph technique and by particle tracking observations. From the shadowgraph images, the concentration profile is reconstructed, giving evidence of a convective motion inside the transient boundary layer. Furthermore, the latency times for the convection onset are extracted from the measurements. The results point out that particle tracking is superior to the shadowgraph method for detecting the onset of convection. The onset latency times obtained from these experiments obey scaling laws which are in accordance with the predictions from theoretical treatments.

  7. Transmission-grating-photomasked transient spin grating and its application to measurement of electron-spin ambipolar diffusion in (110) GaAs quantum wells.

    PubMed

    Chen, Ke; Wang, Wenfang; Wu, Jingda; Schuh, D; Wegscheider, W; Korn, T; Lai, Tianshu

    2012-03-26

    A circular dichromatic transient absorption difference spectroscopy of transmission-grating-photomasked transient spin grating is developed and formularized. It is very simple in experimental setup and operation, and has high detection sensitivity. It is applied to measure spin diffusion dynamics and excited electron density dependence of spin ambipolar diffusion coefficient in (110) GaAs quantum wells. It is found that the spin ambipolar diffusion coefficient of (110) and (001) GaAs quantum wells is close to each other, but has an opposite dependence tendency on excited electron density. This spectroscopy is expected to have extensive applicability in the measurement of spin transport. PMID:22453489

  8. Comparison of homogenized and enhanced diffusion solutions of model PWR problems

    SciTech Connect

    Lewis, E. E.; Smith, M. A.

    2012-07-01

    Model problem comparisons in slab geometry are made between two forms of homogenized diffusion theory and enhanced diffusion theory. The pin-cell discontinuity factors for homogenized diffusion calculations are derived from homogenized variational nodal P1 response matrices and from standard finite differencing. Enhanced diffusion theory consists of applying quasi-reflected interface conditions to reduce variational nodal Pn response matrices to one degree of freedom per interface, without homogenization within the cell. As expected both homogenized diffusion methods preserve reaction rates exactly if the discontinuity factors are derived from the P 11 reference solutions. If no reference lattice solution is available, discontinuity factors may be approximated from single cells with reflected boundary conditions; the computational effort is then comparable to calculating the enhanced diffusion response matrices. In this situation enhanced diffusion theory gives the most accurate results and finite difference discontinuity factors the least accurate. (authors)

  9. Influence of Chemically Enhanced Diffusion on Cap Dolostones?

    NASA Astrophysics Data System (ADS)

    Bristow, T.

    2014-12-01

    Cap dolostones, a globally distributed layer of carbonate rock that sits directly on terminal glacial deposits of the severe Cryogenian ice-age, contain important records of the conditions during the early stage of climatic recovery. Negative carbon isotope signals preserved in the cap are central to discussions of the mechanisms, drivers and time-scale of this interval of extreme climate change. These signals have been attributed to the rapid rise in temperature and acidic ocean conditions predicted to result from huge amounts of CO2 in the atmosphere, which bumped the Earth out of the Snowball state. Questions remain however, because detailed investigations of cap dolostone isotopic variability within individual sedimentary basins show systematic variations that are difficult to explain by temperature effects alone. Furthermore, other influences on cap isotopes have been hypothesized including, the release of massive amounts of methane trapped by the ice and upwelling of deep ocean water with negative signals. This contribution will explore the potential impact of chemically enhanced diffusion (CED) on the carbon isotopic compositions of cap dolostones using a box model. CED is a process by which CO2 gas is transferred to solution via reaction with hydroxide anions. In the modern ocean, rates of CED are thought to be insignificant and CO2 gas transfer is accomplished primarily by diffusion and dissolution, with minimal isotopic fraction. However, in various highly productive lakes, the strong negative isotope fraction of -27 associated CED impacts the isotopic composition of dissolved inorganic carbon. Post-glacial oceans may have been chemically similar to highly productive lakes and initial modeling results indicate that CED could have influenced the carbon isotopic composition of seawater and thus the cap dolostone. Implications for post-glacial oceanic conditions will be discussed.

  10. A nonlinear, transient finite element method for coupled solvent diffusion and large deformation of hydrogels

    NASA Astrophysics Data System (ADS)

    Bouklas, Nikolaos; Landis, Chad M.; Huang, Rui

    2015-06-01

    Hydrogels are capable of coupled mass transport and large deformation in response to external stimuli. In this paper, a nonlinear, transient finite element formulation is presented for initial boundary value problems associated with swelling and deformation of hydrogels, based on a nonlinear continuum theory that is consistent with classical theory of linear poroelasticity. A mixed finite element method is implemented with implicit time integration. The incompressible or nearly incompressible behavior at the initial stage imposes a constraint to the finite element discretization in order to satisfy the Ladyzhenskaya-Babuska-Brezzi (LBB) condition for stability of the mixed method, similar to linear poroelasticity as well as incompressible elasticity and Stokes flow; failure to choose an appropriate discretization would result in locking and numerical oscillations in transient analysis. To demonstrate the numerical method, two problems of practical interests are considered: constrained swelling and flat-punch indentation of hydrogel layers. Constrained swelling may lead to instantaneous surface instability for a soft hydrogel in a good solvent, which can be regulated by assuming a stiff surface layer. Indentation relaxation of hydrogels is simulated beyond the linear regime under plane strain conditions, in comparison with two elastic limits for the instantaneous and equilibrium states. The effects of Poisson's ratio and loading rate are discussed. It is concluded that the present finite element method is robust and can be extended to study other transient phenomena in hydrogels.

  11. Diffusion in mesoporous materials and polymers swelling: a transient calorimetric approach.

    PubMed

    Nedelec, Jean-Marie; Grolier, Jean Pierre E; Baba, Mohamed

    2008-09-01

    The diffusion of water and benzene has been followed by DSC using the thermoporosimetry (TPM) approach. The diffusion of water has been observed during the drying of a water impregnated mesoporous silica gel at 40 degrees C under dry air. It was found that the confinement affects the evaporation rate of water. The diffusion of benzene has been observed during the drying and the swelling of a cross linked PDMS sample. The mesh size distributions (MSD) of the elastomer, during swelling and drying, have been calculated at various times using the TPM formalism. Extrapolating the mean mesh size of the polymeric network, it was found that the dry polymer has an average mesh of about 2.5 nm. PMID:18701958

  12. Molecular dynamics simulation study on the transient response of solvation structure during the translational diffusion of solute.

    PubMed

    Yamaguchi, T; Matsuoka, T; Koda, S

    2005-01-01

    The transient response function of the density profile of the solvent around a solute during the translational diffusion of the solute is formulated based on the generalized Langevin formalism. The resultant theory is applied to both neat Lennard-Jones fluids and cations in liquid water, and the response functions are obtained from the analysis of the molecular dynamics simulations. In the case of the self-diffusion of Lennard-Jones fluids, the responses of the solvation structures are in harmony with conventional pictures based on the mode-coupling theory, that is, the binary collision in the low-density fluids, the backflow effect from medium to high density fluids, and the backscatter effect in the liquids near the triple point. In the case of cations in water, the qualitative behavior is strongly dependent on the size of cations. The pictures similar to simple dense liquids are obtained for the large ion and the neutral molecule, while the solvent waters within the first solvation shell of small ions show an oscillatory response in the short-time region. In particular, the oscillation is remarkably underdumped for lithium ion. The origin of the oscillation is discussed in relation to the theoretical treatment of the translational diffusion of ions in water. PMID:15638679

  13. Molecular dynamics simulation study on the transient response of solvation structure during the translational diffusion of solute

    NASA Astrophysics Data System (ADS)

    Yamaguchi, T.; Matsuoka, T.; Koda, S.

    2005-01-01

    The transient response function of the density profile of the solvent around a solute during the translational diffusion of the solute is formulated based on the generalized Langevin formalism. The resultant theory is applied to both neat Lennard-Jones fluids and cations in liquid water, and the response functions are obtained from the analysis of the molecular dynamics simulations. In the case of the self-diffusion of Lennard-Jones fluids, the responses of the solvation structures are in harmony with conventional pictures based on the mode-coupling theory, that is, the binary collision in the low-density fluids, the backflow effect from medium to high density fluids, and the backscatter effect in the liquids near the triple point. In the case of cations in water, the qualitative behavior is strongly dependent on the size of cations. The pictures similar to simple dense liquids are obtained for the large ion and the neutral molecule, while the solvent waters within the first solvation shell of small ions show an oscillatory response in the short-time region. In particular, the oscillation is remarkably underdumped for lithium ion. The origin of the oscillation is discussed in relation to the theoretical treatment of the translational diffusion of ions in water.

  14. Effects of arsenic deactivation on arsenic-implant induced enhanced diffusion in silicon

    SciTech Connect

    Dokumaci, O.; Law, M.E.; Krishnamoorthy, V.; Jones, K.S.

    1996-12-31

    The enhanced diffusion of boron due to high dose arsenic implantation into silicon is studied as a function of arsenic dose. The behavior of both the type-V and end-of-range loops is investigated by transmission electron microscopy (TEM). The role of arsenic deactivation induced interstitials and type-V loops on enhanced diffusion is assessed. Reduction of the boron diffusivity is observed with increasing arsenic dose at three different temperatures. The possible explanations for this reduction are discussed.

  15. Persistent order due to transiently enhanced nesting in an electronically excited charge density wave

    DOE PAGESBeta

    Rettig, L.; Cortés, R.; Chu, J. -H.; Fisher, I. R.; Schmitt, F.; Moore, R. G.; Shen, Z. -X.; Kirchmann, P. S.; Wolf, M.; Bovensiepen, U.

    2016-01-25

    Non-equilibrium conditions may lead to novel properties of materials with broken symmetry ground states not accessible in equilibrium as vividly demonstrated by non-linearly driven mid-infrared active phonon excitation. Potential energy surfaces of electronically excited states also allow to direct nuclear motion, but relaxation of the excess energy typically excites fluctuations leading to a reduced or even vanishing order parameter as characterized by an electronic energy gap. Here, using femtosecond time-and angle-resolved photoemission spectroscopy, we demonstrate a tendency towards transient stabilization of a charge density wave after near-infrared excitation, counteracting the suppression of order in the non-equilibrium state. Analysis of themore » dynamic electronic structure reveals a remaining energy gap in a highly excited transient state. In conclusion, our observation can be explained by a competition between fluctuations in the electronically excited state, which tend to reduce order, and transiently enhanced Fermi surface nesting stabilizing the order.« less

  16. A multigroup diffusion solver using pseudo transient continuation for a radiation-hydrodynamic code with patch-based AMR

    NASA Astrophysics Data System (ADS)

    Shestakov, Aleksei I.; Offner, Stella S. R.

    2008-01-01

    We present a scheme to solve the nonlinear multigroup radiation diffusion (MGD) equations. The method is incorporated into a massively parallel, multidimensional, Eulerian radiation-hydrodynamic code with Adaptive Mesh Refinement (AMR). The patch-based AMR algorithm refines in both space and time creating a hierarchy of levels, coarsest to finest. The physics modules are time-advanced using operator splitting. On each level, separate "level-solve" packages advance the modules. Our multigroup level-solve adapts an implicit procedure which leads to a two-step iterative scheme that alternates between elliptic solves for each group with intra-cell group coupling. For robustness, we introduce pseudo transient continuation (?tc). We analyze the magnitude of the ?tc parameter to ensure positivity of the resulting linear system, diagonal dominance and convergence of the two-step scheme. For AMR, a level defines a subdomain for refinement. For diffusive processes such as MGD, the refined level uses Dirichlet boundary data at the coarse-fine interface and the data is derived from the coarse level solution. After advancing on the fine level, an additional procedure, the sync-solve (SS), is required in order to enforce conservation. The MGD SS reduces to an elliptic solve on a combined grid for a system of G equations, where G is the number of groups. We adapt the "partial temperature" scheme for the SS; hence, we reuse the infrastructure developed for scalar equations. Results are presented. We consider a multigroup test problem with a known analytic solution. We demonstrate utility of ?tc by running with increasingly larger timesteps. Lastly, we simulate the sudden release of energy Y inside an Al sphere (r = 15 cm) suspended in air at STP. For Y = 11 kT, we find that gray radiation diffusion and MGD produce similar results. However, if Y = 1 MT, the two packages yield different results. Our large Y simulation contradicts a long-standing theory and demonstrates the inadequacy of gray diffusion.

  17. Transient Evolution of a Planar Diffusion Flame Aft of a Translating Flat Plate

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.

    2003-01-01

    The high degree of spatial symmetry of a planar diffusion flame affords great simplifications for experimental and modeling studies of gaseous fuel combustion. Particularly, in a microgravity environment, where buoyancy effects are negligible, an effectively strain-rate-free, vigorous flame may be obtained. Such a flame can also provide long residence times and large length scales for practical probing of flame structures and soot processes. This 2-D numerical study explores the feasibility of establishing such a planar diffusion flame in an enclosed container utilizing a realistic test protocol for a microgravity experiment. Fuel and oxygen mixtures, initially segregated into two half-volumes of a squat rectangular container by a thin separator, are ignited as soon as a flammable mixture is formed in the wake of the separator withdrawn in the centerplane. A triple-flame ensues that propagates behind the trailing edge of the separator. The results of calculations show that the mechanically- and thermally-induced convection decays in about two seconds. The establishment of a planar diffusion flame after this period seems feasible in the central region of the container with sufficient quantities of reactants left over for subsequent studies. An analysis of the flame initiation and formation process suggests how the feasibility of creating such a flame can be further improved.

  18. SPECIAL ISSUE DEVOTED TO THE 80TH BIRTHDAY OF S.A. AKHMANOV: Transient coherent anti-Stokes Raman scattering spectroscopy as a tool for measuring the diffusion coefficient and size of gas molecules

    NASA Astrophysics Data System (ADS)

    Nikitin, Sergei Yu

    2009-07-01

    Formulas are derived for evaluating the diffusion coefficient and size of gas molecules from transient coherent anti-Stokes Raman scattering measurements. Numerical estimates are presented for hydrogen.

  19. Power Supply Reliability Assessment in UPFC-installed Transmission System for ATC Enhancement Considering Transient Stability

    NASA Astrophysics Data System (ADS)

    Masuta, Taisuke; Yokoyama, Akihiko

    With recent development of power electronics technology, power system stability enhancement and optimal power flow control by using Flexible AC Transmission System (FACTS) devices have so far been studied. The FACTS devices to relieve multiple constraints can also make it possible to enhance Available Transfer Capability (ATC) without construction of new transmission lines. The previous research revealed that ATC is expanded by avoiding multiple constraints in OPF using Unified Power Flow Controller (UPFC). For long-term operation of such ATC-expanded power system, it is necessary to evaluate power system reliability. In this paper, the evaluation method of supply reliability for UPFC-installed power system is proposed. Both thermal capacity and transient stability constraints are considered. The effectiveness of the proposed method is shown by numerical examples for IEEJ East10-machine test system.

  20. Enhanced diffusion of oxygen depending on Fermi level position in heavily boron-doped silicon

    SciTech Connect

    Torigoe, Kazuhisa Fujise, Jun; Ono, Toshiaki; Nakamura, Kozo

    2014-11-21

    The enhanced diffusivity of oxygen in heavily boron doped silicon was obtained by analyzing oxygen out-diffusion profile changes found at the interface between a lightly boron-doped silicon epitaxial layer and a heavily boron-doped silicon substrate by secondary ion mass spectrometry. It was found that the diffusivity is proportional to the square root of boron concentration in the range of 10{sup 18 }cm{sup −3}–10{sup 19 }cm{sup −3} at temperatures from 750 °C to 950 °C. The model based on the diffusion of oxygen dimers in double positive charge state could explain the enhanced diffusion. We have concluded that oxygen diffusion enhanced in heavily boron-doped silicon is attributed to oxygen dimers ionized depending on Fermi level position.

  1. Experimental correlations for transient soot measurement in diesel exhaust aerosol with light extinction, electrical mobility and diffusion charger sensor techniques

    NASA Astrophysics Data System (ADS)

    Bermdez, Vicente; Pastor, Jos V.; Lpez, J. Javier; Campos, Daniel

    2014-06-01

    A study of soot measurement deviation using a diffusion charger sensor with three dilution ratios was conducted in order to obtain an optimum setting that can be used to obtain accurate measurements in terms of soot mass emitted by a light-duty diesel engine under transient operating conditions. The paper includes three experimental phases: an experimental validation of the measurement settings in steady-state operating conditions; evaluation of the proposed setting under the New European Driving Cycle; and a study of correlations for different measurement techniques. These correlations provide a reliable tool for estimating soot emission from light extinction measurement or from accumulation particle mode concentration. There are several methods and correlations to estimate soot concentration in the literature but most of them were assessed for steady-state operating points. In this case, the correlations are obtained by more than 4000 points measured in transient conditions. The results of the new two correlations, with less than 4% deviation from the reference measurement, are presented in this paper.

  2. Surface-diffusion enhanced Ga incorporation in ZnO nanowires by oxygen vacancies

    NASA Astrophysics Data System (ADS)

    Wang, Jianyu; Sun, Huabin; Sheng, Yun; Yang, Lijun; Gao, Fan; Yin, Yao; Hu, Zheng; Wan, Qin; Zhang, Rong; Zheng, Youdou; Shi, Yi

    2016-01-01

    The surface diffusion process substantially influences the epitaxial growth of semiconductor nanowires. The spontaneous incorporation of Ga and the uniform axial-distribution over long ZnO nanowires are experimentally observed, which is attributed to the surface diffusion on ZnO sidewalls. The existence of abundant oxygen vacancies on the nanowire sidewalls greatly enhances the surface diffusion. Simulation on the diffusion dynamics is performed, and the strong bond energy between Ga and O atoms is verified. With the assistance of an oxygen vacancy, the diffusion barrier for Ga atoms decreased from 1.26 to 0.85 eV, resulting in a two orders of magnitude increase in the surface diffusion coefficient. The present work demonstrates the key role of surface diffusion process in the enhanced impurity incorporation during the growth of nanostructured semiconductors.

  3. Opto-Thermal Transient Emission Radiometry (OTTER) to image diffusion in nails in vivo.

    PubMed

    Xiao, P; Zheng, X; Imhof, R E; Hirata, K; McAuley, W J; Mateus, R; Hadgraft, J; Lane, M E

    2011-03-15

    This work describes the first application of Opto-Thermal Transient Emission Radiometry (OTTER), an infrared remote sensing technique, to probe the extent to which solvents permeate the human nail in vivo. Decanol, glycerol and butyl acetate were selected as model solvents. After application of the solvents, individually, to human volunteers, OTTER was used to depth profile the solvents. The permeation rate of the solvents was ranked as glycerol>decanol>butyl acetate. It is possible that some of the butyl acetate may have evaporated during the experiment. The ability of decanol to extract lipids from biological tissue is also considered. These preliminary results demonstrate the potential of OTTER as a tool to identify optimal excipients with which to target drugs to the nail. PMID:21251961

  4. Ultrasound speckle suppression and edge enhancement using multiscale nonlinear wavelet diffusion.

    PubMed

    Yue, Yong; Croitoru, Mihai M; Bidani, Akhil; Zwischenberger, Joseph B; Clark, John W

    2005-01-01

    This paper introduces a novel multiscale nonlinear wavelet diffusion (MNWD) method for ultrasound speckle suppression and edge enhancement. It considers wavelet diffusion as an approximation to nonlinear diffusion within the framework of the dyadic wavelet transform. Consequently, this knowledge is exploited in the design of a speckle suppression filter with an edge enhancement feature. MNWD takes advantage of the sparsity and multiresolution properties of wavelet, and the iterative edge enhancement feature of nonlinear diffusion. In our algorithm, speckle is suppressed by employing the iterative multiscale diffusion on the wavelet coefficients, while the edges of the image are enhanced by using an iterative signal compensation process. We validate the proposed method using synthetic and real echocardiographic images. Performance improvement over other traditional denoising filters is quantified in terms of noise suppression and structural preservation indices. The application of the proposed method is demonstrated by the segmentation of the echocardiographic image using the active contour. PMID:17281740

  5. WEE1 kinase inhibition enhances the radiation response of diffuse intrinsic pontine gliomas.

    PubMed

    Caretti, Viola; Hiddingh, Lotte; Lagerweij, Tonny; Schellen, Pepijn; Koken, Phil W; Hulleman, Esther; van Vuurden, Dannis G; Vandertop, W Peter; Kaspers, Gertjan J L; Noske, David P; Wurdinger, Thomas

    2013-02-01

    Diffuse intrinsic pontine glioma (DIPG) is a fatal pediatric disease. Thus far, no therapeutic agent has proven beneficial in the treatment of this malignancy. Therefore, conventional DNA-damaging radiotherapy remains the standard treatment, providing transient neurologic improvement without improving the probability of overall survival. During radiotherapy, WEE1 kinase controls the G(2) cell-cycle checkpoint, allowing for repair of irradiation (IR)-induced DNA damage. Here, we show that WEE1 kinase is one of the highest overexpressed kinases in primary DIPG tissues compared with matching non-neoplastic brain tissues. Inhibition of WEE1 by MK-1775 treatment of DIPG cells inhibited the IR-induced WEE1-mediated phosphorylation of CDC2, resulting in reduced G(2)-M arrest and decreased cell viability. Finally, we show that MK-1775 enhances the radiation response of E98-Fluc-mCherry DIPG mouse xenografts. Altogether, these results show that inhibition of WEE1 kinase in conjunction with radiotherapy holds potential as a therapeutic approach for the treatment of DIPG. PMID:23270927

  6. Enhanced paracellular transport of insulin can be achieved via transient induction of myosin light chain phosphorylation

    PubMed Central

    Taverner, Alistair; Dondi, Ruggero; Almansour, Khaled; Laurent, Floriane; Owens, Siân-Eleri; Eggleston, Ian M.; Fotaki, Nikoletta; Mrsny, Randall J.

    2015-01-01

    The intestinal epithelium functions to effectively restrict the causal uptake of luminal contents but has been demonstrated to transiently increase paracellular permeability properties to provide an additional entry route for dietary macromolecules. We have examined a method to emulate this endogenous mechanism as a means of enhancing the oral uptake of insulin. Two sets of stable Permeant Inhibitor of Phosphatase (PIP) peptides were rationally designed to stimulate phosphorylation of intracellular epithelial myosin light chain (MLC) and screened using Caco-2 monolayers in vitro. Apical application of PIP peptide 640, designed to disrupt protein–protein interactions between protein phosphatase 1 (PP1) and its regulator CPI-17, resulted in a reversible and non-toxic transient reduction in Caco-2 monolayer trans-epithelial electric resistance (TEER) and opening of the paracellular route to 4 kDa fluorescent dextran but not 70 kDa dextran in vitro. Apical application of PIP peptide 250, designed to impede MYPT1-mediated regulation of PP1, also decreased TEER in a reversible and non-toxic manner but transiently opened the paracellular route to both 4 and 70 kDa fluorescent dextrans. Direct injection of PIP peptides 640 or 250 with human insulin into the lumen of rat jejunum caused a decrease in blood glucose levels that was PIP peptide and insulin dose-dependent and correlated with increased pMLC levels. Systemic levels of insulin suggested approximately 3–4% of the dose injected into the intestinal lumen was absorbed, relative to a subcutaneous injection. Measurement of insulin levels in the portal vein showed a time window of absorption that was consistent with systemic concentration-time profiles and approximately 50% first-pass clearance by the liver. Monitoring the uptake of a fluorescent form of insulin suggested its uptake occurred via the paracellular route. Together, these studies add validation to the presence of an endogenous mechanism used by the intestinal epithelium to dynamically regulate its paracellular permeability properties and better define the potential to enhance the oral delivery of biopharmaceuticals via a transient regulation of an endogenous mechanism controlling the intestinal paracellular barrier. PMID:25980620

  7. Interface- and diffusion-limited capillary rise of reactive melts with a transient contact angle

    NASA Astrophysics Data System (ADS)

    Asthana, Rajiv

    2002-07-01

    The kinetics of unidirectional capillary penetration by a reactive fluid under the limiting cases of diffusion control and interface control has been derived for the reactive infiltration phenomenon characterized by a shrinking capillary radius due to interphase formation and an exponentially decaying contact angle. The computational outcomes for the reactive penetration of Si3N4 capillaries by AgCuTi brazes and of carbon capillaries by Si show that greater lengths are attained at lower values of the parabolic rate constant (under diffusion control), and the limiting length is reached earlier at larger values of the linear rate constant (under interface control). A capillary-driven flow analysis (Washburn equation) overestimates the infiltration kinetics, whereas an analysis that considers pore shrinkage but assumes the contact angle and the capillary pressure to be constant during flow underestimates the kinetics. The penetration lengths predicted by the analysis at pore closure due to reaction choking exhibit a slightly better agreement with the recent measurements in the Si/C system than the models of reactive flows currently in vogue.

  8. Oscillatory behavior of finite difference methods for the solution of the two dimensional transient heat (Diffusion) equation

    NASA Astrophysics Data System (ADS)

    Cuthrell, Joseph E.

    1986-03-01

    The two dimensional transient heat (diffusion) equation with Dirichlet boundary conditions was solved using the Dufort-Frankel, Saul'ev, and Exponential (Power-law) finite difference schemes. All methods were investigated for oscillatory behavior and comparisons of accuracy made. To predict the time step at which oscillatory behavior would occur, the coefficient, matrix, and probabilistic methods of stability analysis were utilized. At time steps greater than the square of the mesh divided by the thermal diffusivity, oscillatory solutions were apparent in both the Dufort-Frankel and Saul'ev schems. The exponential method, as predicted, did not oscillate for any size time step. Although the exponential scheme was the most accurate at large time steps, the solution still contained enough error to be unusable in many engineering applications. At small time steps, all methods were more accurate than the fully implicit formulation. The exponential method was found to be the slowest computationally. The Saul'ev scheme proved to be the fastest while still achieving the required degree of accuracy.

  9. Transient Liquid-Phase Diffusion Bonding of Aluminum Metal Matrix Composite Using a Mixed Cu-Ni Powder Interlayer

    NASA Astrophysics Data System (ADS)

    Maity, Joydeep; Pal, Tapan Kumar

    2012-07-01

    In the present study, the transient liquid-phase diffusion bonding of an aluminum metal matrix composite (6061-15 wt.% SiCp) has been investigated for the first time using a mixed Cu-Ni powder interlayer at 560 C, 0.2 MPa, for different holding times up to 6 h. The microstructure of the isothermally solidified zone contains equilibrium precipitate CuAl2, metastable precipitate Al9Ni2 in the matrix of ?-solid solution along with the reinforcement particles (SiC). On the other hand, the microstructure of the central bond zone consists of equilibrium phases such as NiAl3, Al7Cu4Ni and ?-solid solution along with SiC particles (without any segregation) and the presence of microporosities. During shear test, the crack originates from microporosities and propagates along the interphase interfaces resulting in poor bond strength for lower holding times. As the bonding time increases, with continual diffusion, the structural heterogeneity is diminished, and the microporosities are eliminated at the central bond zone. Accordingly, after 6-h holding, the microstructure of the central bond zone mainly consists of NiAl3 without any visible microporosity. This provides a joint efficiency of 84% with failure primarily occurring through decohesion at the SiC particle/matrix interface.

  10. Transient gamma-secretase inhibition accelerates and enhances fracture repair likely via Notch signaling modulation.

    PubMed

    Wang, Cuicui; Shen, Jie; Yukata, Kiminori; Inzana, Jason A; O'Keefe, Regis J; Awad, Hani A; Hilton, Matthew J

    2015-04-01

    Approximately 10% of skeletal fractures result in healing complications and non-union, while most fractures repair with appropriate stabilization and without pharmacologic intervention. It is the latter injuries that cannot be underestimated as the expenses associated with their treatment and subsequent lost productivity are predicted to increase to over $74 billion by 2015. During fracture repair, local mesenchymal stem/progenitor cells (MSCs) differentiate to form new cartilage and bone, reminiscent of events during skeletal development. We previously demonstrated that permanent loss of gamma-secretase activity and Notch signaling accelerates bone and cartilage formation from MSC progenitors during skeletal development, leading to pathologic acquisition of bone and depletion of bone marrow derived MSCs. Here, we investigated whether transient and systemic gamma-secretase and Notch inhibition is capable of accelerating and enhancing fracture repair by promoting controlled MSC differentiation near the fracture site. Our radiographic, microCT, histological, cell and molecular analyses reveal that single and intermittent gamma-secretase inhibitor (GSI) treatments significantly enhance cartilage and bone callus formation via the promotion of MSC differentiation, resulting in only a moderate reduction of local MSCs. Biomechanical testing further demonstrates that GSI treated fractures exhibit superior strength earlier in the healing process, with single dose GSI treated fractures exhibiting bone strength approaching that of un-fractured tibiae. These data further establish that transient inhibition of gamma-secretase activity and Notch signaling temporarily increases osteoclastogenesis and accelerates bone remodeling, which coupled with the effects on MSCs likely explains the accelerated and enhanced fracture repair. Therefore, we propose that the Notch pathway serves as an important therapeutic target during skeletal fracture repair. PMID:25527421

  11. A simple Boltzmann transport equation for ballistic to diffusive transient heat transport

    NASA Astrophysics Data System (ADS)

    Maassen, Jesse; Lundstrom, Mark

    2015-04-01

    Developing simplified, but accurate, theoretical approaches to treat heat transport on all length and time scales is needed to further enable scientific insight and technology innovation. Using a simplified form of the Boltzmann transport equation (BTE), originally developed for electron transport, we demonstrate how ballistic phonon effects and finite-velocity propagation are easily and naturally captured. We show how this approach compares well to the phonon BTE, and readily handles a full phonon dispersion and energy-dependent mean-free-path. This study of transient heat transport shows (i) how fundamental temperature jumps at the contacts depend simply on the ballistic thermal resistance, (ii) that phonon transport at early times approach the ballistic limit in samples of any length, and (iii) perceived reductions in heat conduction, when ballistic effects are present, originate from reductions in temperature gradient. Importantly, this framework can be recast exactly as the Cattaneo and hyperbolic heat equations, and we discuss how the key to capturing ballistic heat effects is to use the correct physical boundary conditions.

  12. A simple Boltzmann transport equation for ballistic to diffusive transient heat transport

    SciTech Connect

    Maassen, Jesse Lundstrom, Mark

    2015-04-07

    Developing simplified, but accurate, theoretical approaches to treat heat transport on all length and time scales is needed to further enable scientific insight and technology innovation. Using a simplified form of the Boltzmann transport equation (BTE), originally developed for electron transport, we demonstrate how ballistic phonon effects and finite-velocity propagation are easily and naturally captured. We show how this approach compares well to the phonon BTE, and readily handles a full phonon dispersion and energy-dependent mean-free-path. This study of transient heat transport shows (i) how fundamental temperature jumps at the contacts depend simply on the ballistic thermal resistance, (ii) that phonon transport at early times approach the ballistic limit in samples of any length, and (iii) perceived reductions in heat conduction, when ballistic effects are present, originate from reductions in temperature gradient. Importantly, this framework can be recast exactly as the Cattaneo and hyperbolic heat equations, and we discuss how the key to capturing ballistic heat effects is to use the correct physical boundary conditions.

  13. Diffuse dural gadolinium MRI enhancement associated with bilateral chronic subdural hematomas.

    PubMed

    Blitshteyn, Svetlana; Mechtler, Laszlo L; Bakshi, Rohit

    2004-01-01

    Chronic subdural hematomas (CSDHs) typically present with cognitive dysfunction and a history of trauma. Localized dural enhancement on postcontrast MRI scans associated with the surrounding membrane has been described in CSDH. We present an 83-year-old man with rapidly progressing cognitive dysfunction 4 weeks after head trauma related to a fall. MRI showed CSDHs, which in addition to localized dural gadolinium enhancement, showed a marked diffuse, symmetric, contiguous pachymeningeal enhancement of the supratentorial and infratentorial intracranial dural mater. Meningeal biopsy failed to disclose an infectious or neoplastic cause of the enhancement and instead showed fibrocollagenous change. We conclude that diffuse dural enhancement on MRI scans associated with CSDH cause does not necessarily indicate a superimposed process such as infection or malignancy. CSDH should be considered in the differential diagnosis of diffuse dural enhancement, especially when supported by appropriate clinical findings. PMID:15050219

  14. A Diffusible Signal from Arbuscular Mycorrhizal Fungi Elicits a Transient Cytosolic Calcium Elevation in Host Plant Cells1[W

    PubMed Central

    Navazio, Lorella; Moscatiello, Roberto; Genre, Andrea; Novero, Mara; Baldan, Barbara; Bonfante, Paola; Mariani, Paola

    2007-01-01

    The implication of calcium as intracellular messenger in the arbuscular mycorrhizal (AM) symbiosis has not yet been directly demonstrated, although often envisaged. We used soybean (Glycine max) cell cultures stably expressing the bioluminescent Ca2+ indicator aequorin to detect intracellular Ca2+ changes in response to the culture medium of spores of Gigaspora margarita germinating in the absence of the plant partner. Rapid and transient elevations in cytosolic free Ca2+ were recorded, indicating that diffusible molecules released by the mycorrhizal fungus are perceived by host plant cells through a Ca2+-mediated signaling. Similar responses were also triggered by two Glomus isolates. The fungal molecules active in generating the Ca2+ transient were constitutively released in the medium, and the induced Ca2+ signature was not modified by the coculture of germinating spores with plant cells. Even ungerminated spores were able to generate the signaling molecules, as proven when the germination was blocked by a low temperature. The fungal molecules were found to be stable to heat treatment, of small molecular mass (<3 kD), and, on the basis of extraction with an organic solvent, partially lipophilic. Evidence for the specificity of such an early fungal signal to the AM symbiosis is suggested by the lack of a Ca2+ response in cultured cells of the nonhost plant Arabidopsis (Arabidopsis thaliana) and by the up-regulation in soybean cells of genes related to Medicago truncatula DMI1, DMI2, and DMI3 and considered essential for the establishment of the AM symbiosis. PMID:17142489

  15. A Multigroup diffusion solver using pseudo transient continuation for a radiation-hydrodynamic code with patch-based AMR

    SciTech Connect

    Shestakov, A I; Offner, S R

    2006-09-21

    We present a scheme to solve the nonlinear multigroup radiation diffusion (MGD) equations. The method is incorporated into a massively parallel, multidimensional, Eulerian radiation-hydrodynamic code with adaptive mesh refinement (AMR). The patch-based AMR algorithm refines in both space and time creating a hierarchy of levels, coarsest to finest. The physics modules are time-advanced using operator splitting. On each level, separate 'level-solve' packages advance the modules. Our multigroup level-solve adapts an implicit procedure which leads to a two-step iterative scheme that alternates between elliptic solves for each group with intra-cell group coupling. For robustness, we introduce pseudo transient continuation ({Psi}tc). We analyze the magnitude of the {Psi}tc parameter to ensure positivity of the resulting linear system, diagonal dominance and convergence of the two-step scheme. For AMR, a level defines a subdomain for refinement. For diffusive processes such as MGD, the refined level uses Dirichet boundary data at the coarse-fine interface and the data is derived from the coarse level solution. After advancing on the fine level, an additional procedure, the sync-solve (SS), is required in order to enforce conservation. The MGD SS reduces to an elliptic solve on a combined grid for a system of G equations, where G is the number of groups. We adapt the 'partial temperature' scheme for the SS; hence, we reuse the infrastructure developed for scalar equations. Results are presented. We consider a multigroup test problem with a known analytic solution. We demonstrate utility of {Psi}tc by running with increasingly larger timesteps. Lastly, we simulate the sudden release of energy Y inside an Al sphere (r = 15 cm) suspended in air at STP. For Y = 11 kT, we find that gray radiation diffusion and MGD produce similar results. However, if Y = 1 MT, the two packages yield different results. Our large Y simulation contradicts a long-standing theory and demonstrates the inadequacy of gray diffusion.

  16. A Multigroup diffusion Solver Using Pseudo Transient Continuation for a Radiaiton-Hydrodynamic Code with Patch-Based AMR

    SciTech Connect

    Shestakov, A I; Offner, S R

    2007-03-02

    We present a scheme to solve the nonlinear multigroup radiation diffusion (MGD) equations. The method is incorporated into a massively parallel, multidimensional, Eulerian radiation-hydrodynamic code with adaptive mesh refinement (AMR). The patch-based AMR algorithm refines in both space and time creating a hierarchy of levels, coarsest to finest. The physics modules are time-advanced using operator splitting. On each level, separate 'level-solve' packages advance the modules. Our multigroup level-solve adapts an implicit procedure which leads to a two-step iterative scheme that alternates between elliptic solves for each group with intra-cell group coupling. For robustness, we introduce pseudo transient continuation ({Psi}tc). We analyze the magnitude of the {Psi}tc parameter to ensure positivity of the resulting linear system, diagonal dominance and convergence of the two-step scheme. For AMR, a level defines a subdomain for refinement. For diffusive processes such as MGD, the refined level uses Dirichet boundary data at the coarse-fine interface and the data is derived from the coarse level solution. After advancing on the fine level, an additional procedure, the sync-solve (SS), is required in order to enforce conservation. The MGD SS reduces to an elliptic solve on a combined grid for a system of G equations, where G is the number of groups. We adapt the 'partial temperature' scheme for the SS; hence, we reuse the infrastructure developed for scalar equations. Results are presented. We consider a multigroup test problem with a known analytic solution. We demonstrate utility of {Psi}tc by running with increasingly larger timesteps. Lastly, we simulate the sudden release of energy Y inside an Al sphere (r = 15 cm) suspended in air at STP. For Y = 11 kT, we find that gray radiation diffusion and MGD produce similar results. However, if Y = 1 MT, the two packages yield different results. Our large Y simulation contradicts a long-standing theory and demonstrates the inadequacy of gray diffusion.

  17. Temperature-dependent radiation-enhanced diffusion in ion-bombarded solids

    SciTech Connect

    Marton, D.; Fine, J.; Chambers, G.P.

    1988-12-05

    Temperature-dependent radiation-enhanced-diffusion rates for Ag in Ni have been found to decrease at elevated temperatures. The observed narrowing of interface interdiffusion regions with increasing temperature depends on both defect concentration and migration processes which occur in ion-bombarded solids. These findings can be interpreted in terms of a general model of radiation-enhanced diffusion that involves long-lived complex defects which can migrate for large distances and which are themselves subject to annealing.

  18. Cannabidiol enhances microglial phagocytosis via transient receptor potential (TRP) channel activation

    PubMed Central

    Hassan, Samia; Eldeeb, Khalil; Millns, Paul J; Bennett, Andrew J; Alexander, Stephen P H; Kendall, David A

    2014-01-01

    Background and Purpose Microglial cells are important mediators of the immune response in the CNS. The phytocannabinoid, cannabidiol (CBD), has been shown to have central anti-inflammatory properties, and the purpose of the present study was to investigate the effects of CBD and other phytocannabinoids on microglial phagocytosis. Experimental Approach Phagocytosis was assessed by measuring ingestion of fluorescently labelled latex beads by cultured microglial cells. Drug effects were probed using single-cell Ca2+ imaging and expression of mediator proteins by immunoblotting and immunocytochemistry. Key Results CBD (10??M) enhanced bead phagocytosis to 175 7% control. Other phytocannabinoids, synthetic and endogenous cannabinoids were without effect. The enhancement was dependent upon Ca2+ influx and was abolished in the presence of EGTA, the Ca2+ channel inhibitor SKF96365, the transient receptor potential (TRP) channel blocker ruthenium red, and the TRPV1 antagonists capsazepine and AMG9810. CBD produced a sustained increase in intracellular Ca2+ concentration in BV-2 microglia and this was abolished by ruthenium red. CBD rapidly increased the expression of TRPV2 and TRPV1 proteins and caused a translocation of TRPV2 to the cell membrane. Wortmannin blocked CBD enhancement of BV-2 cell phagocytosis, suggesting that it is mediated by PI3K signalling downstream of the Ca2+ influx. Conclusions and Implications The TRPV-dependent phagocytosis-enhancing effect of CBD suggests that pharmacological modification of TRPV channel activity could be a rational approach to treating neuroinflammatory disorders involving changes in microglial function and that CBD is a potential starting point for future development of novel therapeutics acting on the TRPV receptor family. PMID:24641282

  19. Transiently enhanced LPS-induced fever following hyperthermic stress in rabbits

    NASA Astrophysics Data System (ADS)

    Shibata, Masaaki; Uno, Tadashi; Riedel, Walter; Nishimaki, Michiyo; Watanabe, Kaori

    2005-11-01

    Hyperthermia has been shown to induce an enhanced febrile response to the bacterial-derived endotoxin lipopolysaccharide (LPS). The aim of the present study was to test the hypothesis that the enhanced LPS-induced fever seen in heat stressed (HS) animals is caused by leakage of intestinal bacterial LPS into the circulation. Male rabbits were rendered transiently hyperthermic (a maximum rectal temperature of 43C) and divided into three groups. They were then allowed to recover in a room at 24C for 1, 2 or 3 days post-HS. One day after injection with LPS, the post-HS rabbits exhibited significantly higher fevers than the controls, though this was not seen in rabbits at either 2 or 3 days post-HS. The plasma levels of endogenous LPS were significantly increased during the HS as compared to those seen in normothermic rabbits prior to HS. LPS fevers were not induced in these animals. One day post-HS, rabbits that had been pretreated with oral antibiotics exhibited significantly attenuated LPS levels. When challenged with human recombinant interleukin-1? instead of LPS, the 1-day post-HS rabbits did not respond with enhanced fevers. The plasma levels of TNF? increased similarly during LPS-induced fevers in both the control and 1-day post-HS rabbits, while the plasma levels of corticosterone and the osmolality of the 1-day post-HS rabbits showed no significant differences to those seen prior to the HS. These results suggest that the enhanced fever in the 1-day post-HS rabbits is LPS specific, and may be caused by increased leakage of intestinal endotoxin into blood circulation.

  20. Coupled glide-climb diffusion-enhanced crystal plasticity

    NASA Astrophysics Data System (ADS)

    Geers, M. G. D.; Cottura, M.; Appolaire, B.; Busso, E. P.; Forest, S.; Villani, A.

    2014-10-01

    This paper presents a fully coupled glide-climb crystal plasticity model, whereby climb is controlled by the diffusion of vacancies. An extended strain gradient crystal plasticity model is therefore proposed, which incorporates the climbing of dislocations in the governing transport equations. A global-local approach is adopted to separate the scales and assess the influence of local diffusion on the global plasticity problem. The kinematics of the crystal plasticity model is enriched by incorporating the climb kinematics in the crystallographic split of the plastic strain rate tensor. The potential of the fully coupled theory is illustrated by means of two single slip examples that illustrate the interaction between glide and climb in either bypassing a precipitate or destroying a dislocation pile-up.

  1. Cholesterol enhances surface water diffusion of phospholipid bilayers

    SciTech Connect

    Cheng, Chi-Yuan; Kausik, Ravinath; Han, Songi; Olijve, Luuk L. C.

    2014-12-14

    Elucidating the physical effect of cholesterol (Chol) on biological membranes is necessary towards rationalizing their structural and functional role in cell membranes. One of the debated questions is the role of hydration water in Chol-embedding lipid membranes, for which only little direct experimental data are available. Here, we study the hydration dynamics in a series of Chol-rich and depleted bilayer systems using an approach termed {sup 1}H Overhauser dynamic nuclear polarization (ODNP) NMR relaxometry that enables the sensitive and selective determination of water diffusion within 5–10 Å of a nitroxide-based spin label, positioned off the surface of the polar headgroups or within the nonpolar core of lipid membranes. The Chol-rich membrane systems were prepared from mixtures of Chol, dipalmitoyl phosphatidylcholine and/or dioctadecyl phosphatidylcholine lipid that are known to form liquid-ordered, raft-like, domains. Our data reveal that the translational diffusion of local water on the surface and within the hydrocarbon volume of the bilayer is significantly altered, but in opposite directions: accelerated on the membrane surface and dramatically slowed in the bilayer interior with increasing Chol content. Electron paramagnetic resonance (EPR) lineshape analysis shows looser packing of lipid headgroups and concurrently tighter packing in the bilayer core with increasing Chol content, with the effects peaking at lipid compositions reported to form lipid rafts. The complementary capability of ODNP and EPR to site-specifically probe the hydration dynamics and lipid ordering in lipid membrane systems extends the current understanding of how Chol may regulate biological processes. One possible role of Chol is the facilitation of interactions between biological constituents and the lipid membrane through the weakening or disruption of strong hydrogen-bond networks of the surface hydration layers that otherwise exert stronger repulsive forces, as reflected in faster surface water diffusivity. Another is the concurrent tightening of lipid packing that reduces passive, possibly unwanted, diffusion of ions and water across the bilayer.

  2. Experimental investigation of the elastic enhancement factor in a transient region between regular and chaotic dynamics

    NASA Astrophysics Data System (ADS)

    ?awniczak, Micha?; Bia?ous, Ma?gorzata; Yunko, Vitalii; Bauch, Szymon; Sirko, Leszek

    2015-03-01

    We present the results of an experimental study of the elastic enhancement factor W for a microwave rectangular cavity simulating a two-dimensional quantum billiard in a transient region between regular and chaotic dynamics. The cavity was coupled to a vector network analyzer via two microwave antennas. The departure of the system from an integrable one due to the presence of antennas acting as scatterers is characterized by the parameter of chaoticity ? =2.8 . The experimental results for the rectangular cavity are compared with those obtained for a microwave rough cavity simulating a chaotic quantum billiard. The experimental results were obtained for the frequency range ? =16 -18.5 GHz and moderate absorption strength ? =5.2 -7.4 . We show that the elastic enhancement factor for the rectangular cavity lies below the theoretical value W =3 predicted for integrable systems, and it is significantly higher than that obtained for the rough cavity. The results obtained for the microwave rough cavity are smaller than those obtained within the framework of random matrix theory, and they lie between them and those predicted within a recently introduced model of the two-channel coupling [V. V. Sokolov and O. V. Zhirov, arXiv:1411.6211 [nucl-th

  3. Transient inhibition of ATM kinase is sufficient to enhance cellular sensitivity to Ionizing Radiation

    PubMed Central

    Rainey, Michael D.; Charlton, Maura E.; Stanton, Robert V.; Kastan, Michael B.

    2008-01-01

    In response to DNA damage, the ATM protein kinase activates signal transduction pathways essential for coordinating cell cycle progression with DNA repair. In the human disease ataxia-telangiectasia, mutation of the ATM gene results in multiple cellular defects, including enhanced sensitivity to ionizing radiation. This phenotype highlights ATM as a potential target for novel inhibitors that could be used to enhance tumor cell sensitivity to radiotherapy. A targeted compound library was screened for potential inhibitors of the ATM kinase and CP466722 was identified. The compound is non-toxic and does not inhibit PI3K or PI3K-like protein kinase family members in cells. CP466722 inhibited cellular ATM-dependent phosphorylation events and disruption of ATM function resulted in characteristic cell cycle checkpoint defects. Inhibition of cellular ATM kinase activity was rapidly and completely reversed by removing CP466722. Interestingly, clonogenic survival assays demonstrated that transient inhibition of ATM is sufficient to sensitize cells to ionizing radiation and suggests that therapeutic radiosensitization may only require ATM inhibition for short periods of time. The ability of CP466722 to rapidly and reversibly regulate ATM activity provides a new tool to ask questions about ATM function that could not easily be addressed using genetic models or RNA interference technologies. PMID:18794134

  4. Discrimination Enhancement with Transient Feature Analysis of a Graphene Chemical Sensor.

    PubMed

    Nallon, Eric C; Schnee, Vincent P; Bright, Collin J; Polcha, Michael P; Li, Qiliang

    2016-01-19

    A graphene chemical sensor is subjected to a set of structurally and chemically similar hydrocarbon compounds consisting of toluene, o-xylene, p-xylene, and mesitylene. The fractional change in resistance of the sensor upon exposure to these compounds exhibits a similar response magnitude among compounds, whereas large variation is observed within repetitions for each compound, causing a response overlap. Therefore, traditional features depending on maximum response change will cause confusion during further discrimination and classification analysis. More robust features that are less sensitive to concentration, sampling, and drift variability would provide higher quality information. In this work, we have explored the advantage of using transient-based exponential fitting coefficients to enhance the discrimination of similar compounds. The advantages of such feature analysis to discriminate each compound is evaluated using principle component analysis (PCA). In addition, machine learning-based classification algorithms were used to compare the prediction accuracies when using fitting coefficients as features. The additional features greatly enhanced the discrimination between compounds while performing PCA and also improved the prediction accuracy by 34% when using linear discrimination analysis. PMID:26674670

  5. Study of the translational diffusion of the benzophenone ketyl radical in comparison with stable molecules in room temperature ionic liquids by transient grating spectroscopy

    SciTech Connect

    Nishiyama, Y.; Fukuda, M.; Terazima, M.; Kimura, Y.

    2008-04-28

    Transient grating (TG) spectroscopy has been applied to the photoinduced hydrogen-abstraction reaction of benzophenone (BP) in various kinds of room temperature ionic liquids (RTILs). After the photoexcitation of BP in RTILs, the formation of a benzophenone ketyl radical (BPK) was confirmed by the transient absorption method, and the TG signal was analyzed to determine the diffusion coefficients of BPK and BP. For comparison, diffusion coefficients of carbon monoxide (CO), diphenylacetylene (DPA), and diphenylcyclopropenone (DPCP) in various RTILs were determined by the TG method using the photodissociation reaction of DPCP. While the diffusion coefficients of the stable molecules BP, DPA, and DPCP were always larger than those predicted by the Stokes-Einstein (SE) relation in RTILs, that of BPK was much smaller than those of the stable molecules and relatively close to that predicted by the SE relation in all solvents. For the smallest molecule CO, the deviation from the SE relation was evident. The diffusion coefficients of stable molecules are better represented by a power law of the inverse of the viscosity when the exponent was less than unity. The ratios of the diffusion coefficient of BP to that of BPK were larger in RTILs (2.7-4.0) than those (1.4-2.3) in conventional organic solvents. The slow diffusion of BPK in RTILs was discussed in terms of the fluctuation of the local electric field produced by the surrounding solvent ions.

  6. Revisiting Taylor Dispersion: Differential enhancement of rotational and translational diffusion under oscillatory shear

    NASA Astrophysics Data System (ADS)

    Leahy, Brian; Ong, Desmond; Cheng, Xiang; Cohen, Itai

    2013-03-01

    The idea of Taylor dispersion - enhancement of translational diffusion under shear - has found applications in fields from pharmacology to chemical engineering. Here, in a combination of experiment and simulations, we study the translational and rotational diffusion of colloidal dimers under triangle-wave oscillatory shear. We find that the rotational diffusion is enhanced, in addition to the enhanced translational diffusion. This ``rotational Taylor dispersion'' depends strongly on the strain rate (Peclet number), aspect ratio, and the shear strain, in contradistinction to translational Taylor dispersion in a shear flow, which depends only weakly on strain rate and aspect ratio. This separate tunability of translations and orientations promises important applications in mixing and self-assembly of solutions of anisometric colloids. We discuss the corresponding effect on the structure and rheology of denser suspensions of rod-like particles. B. L. acknowledges supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

  7. Boron-enhanced diffusion of boron from ultralow-energy boron implantation

    SciTech Connect

    Agarwal, A.; Eaglesham, D.J.; Gossmann, H.J.; Pelaz, L.; Herner, S.B.; Jacobson, D.C.; Haynes, T.E.; Erokhin, Y.E.

    1998-05-03

    The authors have investigated the diffusion enhancement mechanism of BED (boron enhanced diffusion), wherein the boron diffusivity is enhanced three to four times over the equilibrium diffusivity at 1,050 C in the proximity of a silicon layer containing a high boron concentration. It is shown that BED is associated with the formation of a fine-grain polycrystalline silicon boride phase within an initially amorphous Si layer having a high B concentration. For 0.5 keV B{sup +}, the threshold implantation dose which leads to BED lies between 3 {times} 10{sup 14} and of 1 {times} 10{sup 15}/cm{sup {minus}2}. Formation of the shallowest possible junctions by 0.5 keV B{sup +} requires that the implant dose be kept lower than this threshold.

  8. Rapid acquisition of high-affinity DNA aptamer motifs recognizing microbial cell surfaces using polymer-enhanced capillary transient isotachophoresis.

    PubMed

    Saito, Shingo; Hirose, Kazuki; Tsuchida, Maho; Wakui, Koji; Yoshimoto, Keitaro; Nishiyama, Yoshitaka; Shibukawa, Masami

    2016-01-11

    We present a polymer-enhanced capillary transient isotachophoresis (PectI) selection methodology for acquisition of high-affinity (kinetically inert) DNA aptamers capable of recognizing distinct microbial cell surfaces, which requires only a single electrophoretic separation between particles (free cells and cells bound with aptamers) and molecules (unbound or dissociated DNA) in free solution. PMID:26525483

  9. Diffuse Infantile Hepatic Hemangioendothelioma With Early Central Enhancement in an Adult

    PubMed Central

    Dong, Aisheng; Dong, Hui; Zuo, Changjing; He, Tianlin

    2015-01-01

    Abstract Infantile hepatic hemangioendothelioma (IHH) is the most common vascular tumor of the liver in infancy. Adult with IHH is extremely rare. We presented a diffuse IHH in an adult patient with computed tomography (CT) and magnetic resonance image (MRI) findings. A 39-year-old man was admitted to our hospital because of a 2-year history of abnormal liver function tests and a 7-day history of jaundice. Physical examination revealed enlarged liver. Unenhanced abdominal CT showed enlargement of the liver with diffuse hypodensity. Enhanced CT on the arterial phase revealed multiple centrally enhanced lesions diffusely involved the enlarged liver. The enhanced areas of the lesions became larger on the portal phase and all the lesions became homogeneous enhanced on the delayed phase. These lesions showed heterogeneously hyperintense on T2-weighted image, hypointense on T1-weighted image, and early centrally enhanced on dynamic gadolinium-enhanced MRI, with complete tumor enhancement after 180?s. The patient underwent orthotopic liver transplantation. IHH type 2 was confirmed by pathology. The patient died of tumor recurrence in the liver 4 months after transplantation. Unlike the previously described imaging appearances of IHH, this case showed diffuse nodules with early central enhancement on CT and MRI. Considering the importance of the ability to differentiate IHH from other hepatic tumors, radiologists should be aware of these imaging appearances to establish knowledge of the entire spectrum of IHH. PMID:26705232

  10. M3B2 and M5B3 Formation in Diffusion-Affected Zone During Transient Liquid Phase Bonding Single-Crystal Superalloys

    NASA Astrophysics Data System (ADS)

    Sheng, Naicheng; Hu, Xiaobing; Liu, Jide; Jin, Tao; Sun, Xiaofeng; Hu, Zhuangqi

    2015-04-01

    Precipitates in the diffusion-affected zone (DAZ) during transient liquid phase bonding (TLP) single-crystal superalloys were observed and investigated. Small size and dendritic-shaped precipitates were identified to be M3B2 borides and intergrowth of M3B2/M5B3 borides. The orientation relationships among M3B2, M5B3, and matrix were determined using transmission electron microscope (TEM). Composition characteristics of these borides were also analyzed by TEM energy-dispersive spectrometer. Because this precipitating phenomenon deviates from the traditional parabolic transient liquid phase bonding model which assumed a precipitates free DAZ during TLP bonding, some correlations between the deviation of the isothermal solidification kinetics and these newly observed precipitating behaviors were discussed and rationalized when bonding the interlayer containing the high diffusivity melting point depressant elements and substrates of low solubility.

  11. Enhancement of Low Energy Electron-Ion Recombination in a Magnetic Field: Influence of Transient Field Effects

    SciTech Connect

    Hoerndl, Maria; Yoshida, Shuhei; Burgdoerfer, Joachim; Wolf, Andreas; Gwinner, Gerald

    2005-12-09

    Electron-ion recombination observed in storage ring experiments shows a strong enhancement relative to what standard radiative recombination rates predict. We simulate the effect of a transient motional electric field induced by the merging of an electron and an ion beam in the electron cooler which opens an additional pathway for free-bound transitions of electrons. We show that the measured rate contains a significant contribution from radiative stabilization of Rydberg states formed by this transient motional electric field. The absolute excess recombination rates obtained are in good agreement with the experimental data. The scaling of the rate with the ion charge and the magnetic guiding field is analyzed.

  12. Enhancement of crop photosynthesis by diffuse light: quantifying the contributing factors

    PubMed Central

    Li, T.; Heuvelink, E.; Dueck, T. A.; Janse, J.; Gort, G.; Marcelis, L. F. M.

    2014-01-01

    Background and Aims Plants use diffuse light more efficiently than direct light. However, experimental comparisons between diffuse and direct light have been obscured by co-occurring differences in environmental conditions (e.g. light intensity). This study aims to analyse the factors that contribute to an increase in crop photosynthesis in diffuse light and to quantify their relative contribution under different levels of diffuseness at similar light intensities. The hypothesis is that the enhancement of crop photosynthesis in diffuse light results not only from the direct effects of more uniform vertical and horizontal light distribution in the crop canopy, but also from crop physiological and morphological acclimation. Methods Tomato (Solanum lycopersicum) crops were grown in three greenhouse compartments that were covered by glass with different degrees of light diffuseness (0, 45 and 71 % of the direct light being converted into diffuse light) while maintaining similar light transmission. Measurements of horizontal and vertical photosynthetic photon flux density (PPFD) distribution in the crop, leaf photosynthesis light response curves and leaf area index (LAI) were used to quantify each factor's contribution to an increase in crop photosynthesis in diffuse light. In addition, leaf temperature, photoinhibition, and leaf biochemical and anatomical properties were studied. Key Results The highest degree of light diffuseness (71 %) increased the calculated crop photosynthesis by 7·2 %. This effect was mainly attributed to a more uniform horizontal (33 % of the total effect) and vertical PPFD distribution (21 %) in the crop. In addition, plants acclimated to the high level of diffuseness by gaining a higher photosynthetic capacity of leaves in the middle of the crop and a higher LAI, which contributed 23 and 13 %, respectively, to the total increase in crop photosynthesis in diffuse light. Moreover, diffuse light resulted in lower leaf temperatures and less photoinhibition at the top of the canopy when global irradiance was high. Conclusions Diffuse light enhanced crop photosynthesis. A more uniform horizontal PPFD distribution played the most important role in this enhancement, and a more uniform vertical PPFD distribution and higher leaf photosynthetic capacity contributed more to the enhancement of crop photosynthesis than did higher values of LAI. PMID:24782436

  13. Canonical Wnt signaling transiently stimulates proliferation and enhances neurogenesis in neonatal neural progenitor cultures

    SciTech Connect

    Hirsch, Cordula; Campano, Louise M.; Woehrle, Simon; Hecht, Andreas . E-mail: andreas.hecht@mol-med.uni-freiburg.de

    2007-02-01

    Canonical Wnt signaling triggers the formation of heterodimeric transcription factor complexes consisting of {beta}-catenin and T cell factors, and thereby controls the execution of specific genetic programs. During the expansion and neurogenic phases of embryonic neural development canonical Wnt signaling initially controls proliferation of neural progenitor cells, and later neuronal differentiation. Whether Wnt growth factors affect neural progenitor cells postnatally is not known. Therefore, we have analyzed the impact of Wnt signaling on neural progenitors isolated from cerebral cortices of newborn mice. Expression profiling of pathway components revealed that these cells are fully equipped to respond to Wnt signals. However, Wnt pathway activation affected only a subset of neonatal progenitors and elicited a limited increase in proliferation and neuronal differentiation in distinct subsets of cells. Moreover, Wnt pathway activation only transiently stimulated S-phase entry but did not support long-term proliferation of progenitor cultures. The dampened nature of the Wnt response correlates with the predominant expression of inhibitory pathway components and the rapid actuation of negative feedback mechanisms. Interestingly, in differentiating cell cultures activation of canonical Wnt signaling reduced Hes1 and Hes5 expression suggesting that during postnatal neural development, Wnt/{beta}-catenin signaling enhances neurogenesis from progenitor cells by interfering with Notch pathway activity.

  14. Transient Stability Enhancement of Power Systems by Lyapunov-Based Recurrent Neural Networks UPFC Controllers

    NASA Astrophysics Data System (ADS)

    Chu, Chia-Chi; Tsai, Hung-Chi; Chang, Wei-Neng

    A Lyapunov-based recurrent neural networks unified power flow controller (UPFC) is developed for improving transient stability of power systems. First, a simple UPFC dynamical model, composed of a controllable shunt susceptance on the shunt side and an ideal complex transformer on the series side, is utilized to analyze UPFC dynamical characteristics. Secondly, we study the control configuration of the UPFC with two major blocks: the primary control, and the supplementary control. The primary control is implemented by standard PI techniques when the power system is operated in a normal condition. The supplementary control will be effective only when the power system is subjected by large disturbances. We propose a new Lyapunov-based UPFC controller of the classical single-machine-infinite-bus system for damping enhancement. In order to consider more complicated detailed generator models, we also propose a Lyapunov-based adaptive recurrent neural network controller to deal with such model uncertainties. This controller can be treated as neural network approximations of Lyapunov control actions. In addition, this controller also provides online learning ability to adjust the corresponding weights with the back propagation algorithm built in the hidden layer. The proposed control scheme has been tested on two simple power systems. Simulation results demonstrate that the proposed control strategy is very effective for suppressing power swing even under severe system conditions.

  15. Development of a Fully Coupled Transient Double-Diffusive Convective Model: Application to a Salinity-Gradient Solar Pond

    NASA Astrophysics Data System (ADS)

    Suarez, F.; Tyler, S. W.; Childress, A. E.

    2008-12-01

    A solar pond is a water body which is heated by absorption of solar radiation and which can provide long- term thermal storage for collected energy. To avoid large heat losses, convection must be suppressed close to the top of the pond. A salinity-gradient solar pond (SGSP) is an artificially stratified solar pond consisting of three thermally distinctive layers: the upper convective zone (UCZ), the non-convective zone (NCZ), and the lower convective zone (LCZ). The UCZ is a relatively thin layer of "cold" and "fresh" water. In the NCZ, the salt gradient suppresses convection within the pond, and thus, the NCZ acts as insulation for the LCZ. The LCZ is the layer where the salt concentration and temperature are the highest. The solar radiation that penetrates the pond's upper layers reaches the LCZ, which can approach temperatures greater than 90C. Modeling the fluid dynamics of this system is difficult because it requires solution of a set of three second- order non-linear partial differential equations. In order to evaluate the thermal performance and stability of an SGSP, numerical simulation of both heat and mass are required but challenging as double-diffusive convection is likely to occur. Previous approaches have typically assumed no convective transport of solutes, which led to static salinity boundaries of the layers within the SGSP. A 2-D fully coupled numerical model that evaluates the transient performance of an SGSP is introduced. The model simulates the coupled momentum, heat, and mass transfer within the pond. The model can evaluate the influence of meteorological conditions on pond performance by properly describing the heat fluxes through the surface and the solar radiation absorption within the pond, which are typically not well included. Preliminary results show that in a one-week period, for a 1.0 m depth SGSP under summer conditions and without heat extraction, the thicknesses of the UCZ and LCZ increases from 0.1 to 0.2 m, and from 0.5 to 0.6 m, respectively; while the NCZ decreases from 0.4 to 0.2 m, showing that the assumption of static salinity boundaries within the pond is not correct. Double-diffusive processes were successfully simulated during this time period, in which the temperature of the LCZ increased from 20C to more than 50C, showing that an SGSP is a promising technology for renewable energy.

  16. Nonlinear multiscale wavelet diffusion for speckle suppression and edge enhancement in ultrasound images.

    PubMed

    Yue, Yong; Croitoru, Mihai M; Bidani, Akhil; Zwischenberger, Joseph B; Clark, John W

    2006-03-01

    This paper introduces a novel nonlinear multiscale wavelet diffusion method for ultrasound speckle suppression and edge enhancement. This method is designed to utilize the favorable denoising properties of two frequently used techniques: the sparsity and multiresolution properties of the wavelet, and the iterative edge enhancement feature of nonlinear diffusion. With fully exploited knowledge of speckle image models, the edges of images are detected using normalized wavelet modulus. Relying on this feature, both the envelope-detected speckle image and the log-compressed ultrasonic image can be directly processed by the algorithm without need for additional preprocessing. Speckle is suppressed by employing the iterative multiscale diffusion on the wavelet coefficients. With a tuning diffusion threshold strategy, the proposed method can improve the image quality for both visualization and auto-segmentation applications. We validate our method using synthetic speckle images and real ultrasonic images. Performance improvement over other despeckling filters is quantified in terms of noise suppression and edge preservation indices. PMID:16524086

  17. Efficient text segmentation and adaptive color error diffusion for text enhancement

    NASA Astrophysics Data System (ADS)

    Kwon, Jae-Hyun; Park, Tae-Yong; Kim, Yun-Tae; Cho, Yang-Ho; Ha, Yeong-Ho

    2004-12-01

    This paper proposes an adaptive error diffusion algorithm for text enhancement followed by an efficient text segmentation that uses the maximum gradient difference (MGD). The gradients are calculated along with scan lines, then the MGD values are filled within a local window to merge text segments. If the value is above a threshold, the pixel is considered as potential text. Isolated segments are then eliminated in a non-text region filtering process. After the text segmentation, a conventional error diffusion method is applied to the background, while edge enhancement error diffusion is used for the text. Since it is inevitable that visually objectionable artifacts are generated when using two different halftoning algorithms, gradual dilation is proposed to minimize the boundary artifacts in the segmented text blocks before halftoning. Sharpening based on the gradually dilated text region (GDTR) then prevents the printing of successive dots around the text region boundaries. The method is extended to halftone color images to sharpen the text regions. The proposed adaptive error diffusion algorithm involves color halftoning that controls the amount of edge enhancement using a general error filter. However, edge enhancement unfortunately produces color distortion, as edge enhancement and color difference are trade-offs. The multiplicative edge enhancement parameters are selected based on the amount of edge sharpening and color difference. Plus, an additional error factor is introduced to reduce the dot elimination artifact generated by the edge enhancement error diffusion. In experiments, the text of a scanned image was sharper when using the proposed algorithm than with conventional error diffusion without changing the background.

  18. Efficient text segmentation and adaptive color error diffusion for text enhancement

    NASA Astrophysics Data System (ADS)

    Kwon, Jae-Hyun; Park, Tae-Yong; Kim, Yun-Tae; Cho, Yang-Ho; Ha, Yeong-Ho

    2005-01-01

    This paper proposes an adaptive error diffusion algorithm for text enhancement followed by an efficient text segmentation that uses the maximum gradient difference (MGD). The gradients are calculated along with scan lines, then the MGD values are filled within a local window to merge text segments. If the value is above a threshold, the pixel is considered as potential text. Isolated segments are then eliminated in a non-text region filtering process. After the text segmentation, a conventional error diffusion method is applied to the background, while edge enhancement error diffusion is used for the text. Since it is inevitable that visually objectionable artifacts are generated when using two different halftoning algorithms, gradual dilation is proposed to minimize the boundary artifacts in the segmented text blocks before halftoning. Sharpening based on the gradually dilated text region (GDTR) then prevents the printing of successive dots around the text region boundaries. The method is extended to halftone color images to sharpen the text regions. The proposed adaptive error diffusion algorithm involves color halftoning that controls the amount of edge enhancement using a general error filter. However, edge enhancement unfortunately produces color distortion, as edge enhancement and color difference are trade-offs. The multiplicative edge enhancement parameters are selected based on the amount of edge sharpening and color difference. Plus, an additional error factor is introduced to reduce the dot elimination artifact generated by the edge enhancement error diffusion. In experiments, the text of a scanned image was sharper when using the proposed algorithm than with conventional error diffusion without changing the background.

  19. Cladding oxidation model development based on diffusion equations and a simulation of the monoclinic-tetragonal phase transformation of zirconia during transient oxidation

    NASA Astrophysics Data System (ADS)

    He, Xiaoqiang; Yu, Hongxing; Jiang, Guangming; Dang, Gaojian; Wu, Dan; Zhang, Yu

    2014-08-01

    Zircaloy cladding oxidation is mostly represented by parabolic rate correlation. But the correlation approach is not suitable for long-term isothermal oxidation [4] or oxidation occurs under steam starvation conditions [5] and cannot obtain the detailed oxygen distribution which impacts the detailed mechanical behavior. To obtain the detailed oxygen distribution, a multi-phase diffusion problem with moving boundaries was introduced to simulate the cladding oxidation [9,10]. However, the hysteresis phenomenon related to the coexistence of monoclinic-tetragonal phases of zirconia which are very important to model the cladding oxidation during a LOCA, is not analyzed. In this study, a cladding oxidation model based on diffusion equations in the temperature range from 923 K to 2098 K which contains ?-Zr, ?-Zr, monoclinic-ZrO2, tetragonal-ZrO2, and cubic-ZrO2 is developed and the detailed oxygen distribution in the cladding could be obtained. It showed that the simulations of short-term and long-term isothermal oxidation, transient oxidation, and oxidation under steam starvation conditions were reasonable through comparing with the experimental data. We found that our model can give a reasonable simulation of the hysteresis phenomenon of monoclinic-tetragonal phase transformation during transient oxidation as well as a much better simulation of the hypothetical LOCA transient oxidation experiments [11] in ORNL than that by the code based on the parabolic rate correlation. This indicates that the developed model can accurately simulate the cladding oxidation during a LOCA transient.

  20. Enhanced ionic diffusion in ionomer-filled nanopores.

    PubMed

    Allahyarov, Elshad; Taylor, Philip L; Löwen, Hartmut

    2015-12-28

    Coarse-grained simulations in the united-atom-model approximation are used to investigate confinement-induced morphological changes in Nafion-like ionomers. The system we study models a cylindrical pore in a hydrophobic matrix of supporting material with pore diameters that vary from 0.7 to 3.96 nm. Simulation results indicate a strong dependence of the equilibrium ionomer structures both on the pore diameter and on the sulfonate concentration in the pore. In the case of larger pores, the ionic clustering has the shape of a branched wire-like network oriented parallel to the pore axis. In the case of narrow pores, the ionic clusters occupy the pore center and exhibit strong density modulations both along the pore axis and across the pore diameter. The calculated diffusion coefficients for the ions indicate a sharp increase within the narrow pores. This finding is explained by ballistic-type ionic motion at shorter times and by the collective motion of ions in hydrophilic clusters. The influence of the hydrophobic walls on the distribution of ions and solvent molecules is discussed. PMID:26723611

  1. Enhanced ionic diffusion in ionomer-filled nanopores

    NASA Astrophysics Data System (ADS)

    Allahyarov, Elshad; Taylor, Philip L.; Lwen, Hartmut

    2015-12-01

    Coarse-grained simulations in the united-atom-model approximation are used to investigate confinement-induced morphological changes in Nafion-like ionomers. The system we study models a cylindrical pore in a hydrophobic matrix of supporting material with pore diameters that vary from 0.7 to 3.96 nm. Simulation results indicate a strong dependence of the equilibrium ionomer structures both on the pore diameter and on the sulfonate concentration in the pore. In the case of larger pores, the ionic clustering has the shape of a branched wire-like network oriented parallel to the pore axis. In the case of narrow pores, the ionic clusters occupy the pore center and exhibit strong density modulations both along the pore axis and across the pore diameter. The calculated diffusion coefficients for the ions indicate a sharp increase within the narrow pores. This finding is explained by ballistic-type ionic motion at shorter times and by the collective motion of ions in hydrophilic clusters. The influence of the hydrophobic walls on the distribution of ions and solvent molecules is discussed.

  2. The self-irradiation driven enhancement of diffusion processes in nuclear-safe ceramics

    NASA Astrophysics Data System (ADS)

    Smirnov, E. A.; Timofeeva, L. F.

    2000-07-01

    The problem of long-term storage of nuclear-safe ceramics (NSC) supposedly containing plutonium, transition and rare-earth metals oxides is connected first with the necessity of the plutonium isotope enhanced diffusional release prognostication at storage temperatures. For lack of experimental features on diffusion processes in NSC, our estimations are based on the literature data for thermal-activated and radiation-enhanced diffusion (TAD and RED, respectively) of U and Pu in UO2 and (U, Pu)O2 oxides.

  3. Wrinkles enhance the diffuse reflection from the dragonfly Rhyothemis resplendens

    PubMed Central

    Nixon, M. R.; Orr, A. G.; Vukusic, P.

    2015-01-01

    The dorsal surfaces of the hindwings of the dragonfly Rhyothemis resplendens (Odonata: Libellulidae) reflect a deep blue from the multilayer structure in its wing membrane. The layers within this structure are not flat, but distinctly wrinkled, with a thickness of several hundred nanometres and interwrinkle crest distances of 5 m and greater. A comparison between the backscattered light from R. resplendens and a similar, but un-wrinkled multilayer in the damselfly Matronoides cyaneipennis (Odonata: Calopterygidae) shows that the angle over which incident light is backscattered is increased by the wrinkling in the R. resplendens structure. Whereas the reflection from the flat multilayer of M. cyaneipennis is effectively specular, the reflection from the wrinkled R. resplendens multilayer spans 1.47 steradians (equivalent to 40 for all azimuthal angles). This property enhances the visibility of the static wing over a broader angle range than is normally associated with a smooth multilayer, thereby markedly increasing its conspicuousness. PMID:25540236

  4. Buffer scheme with battery energy storage capability for enhancement of network transient stability and load ride-through

    NASA Astrophysics Data System (ADS)

    Wang, X. Y.; Vilathgamuwa, D. M.; Choi, S. S.

    2008-05-01

    This paper examines a buffer scheme to mitigate the negative impacts of power-conditioned loads on network voltage and transient stabilities. The scheme is based on the use of battery energy-storage systems in the buffers. The storage systems ensure that protected loads downstream of the buffers can ride through upstream voltage sags and swells. Also, by controlling the buffers to operate in either constant impedance or constant power modes, power is absorbed or injected by the storage systems. The scheme thereby regulates the rotor-angle deviations of generators and enhances network transient stability. A computational method is described in which the capacity of the storage systems is determined to achieve simultaneously the above dual objectives of load ride-through and stability enhancement. The efficacy of the resulting scheme is demonstrated through numerical examples.

  5. The role of diffusion in ferritin-induced relaxation enhancement of protons.

    PubMed

    Boss, Michael A; Chris Hammel, P

    2012-04-01

    The influence of proton diffusion on nuclear magnetic resonance (NMR) relaxation was investigated in the presence of horse spleen ferritin at 7 T. Binary mixtures of water and glycerol were used to control diffusion within the range of 0.6-2.0 × 10(-9)m(2)/s, which was confirmed by pulsed gradient techniques. The effect of chemical exchange by hydrolysis between water and glycerol on relaxation was characterized with Carr-Purcell-Meiboom-Gill (CPMG) dispersion experiments. The relaxation rate enhancement of the protons due to ferritin was found to be inversely proportional to the diffusion coefficient. The enhancement increased by a factor of 3.6 over the range of diffusion coefficients, while the hydroxyl proton concentration decreased by a factor of 1.3. This result is in disagreement with the proton exchange dephasing model, which is independent of diffusion but predicts an inverse dependence on the hydroxyl concentration. Our data indicate that the role of diffusion dominates and must be considered when relaxation rates are used to determine iron concentration in vivo. PMID:22410189

  6. Note: Using fast digitizer acquisition and flexible resolution to enhance noise cancellation for high performance nanosecond transient absorbance spectroscopy

    NASA Astrophysics Data System (ADS)

    Rimshaw, A.; Grieco, C.; Asbury, J. B.

    2015-06-01

    We demonstrate a nanosecond transient absorbance spectrometer that utilizes flexible resolution and rapid data acquisition triggering modes. The instrument features signal-to-noise (S/N) levels enhanced by an order of magnitude especially within the first 100 ns. The primary gain in S/N comes from our sequential subtraction method, which requires a fast digitizer trigger rearm time to detect every laser trigger event.

  7. A scale-based forward-and-backward diffusion process for adaptive image enhancement and denoising

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Niu, Ruiqing; Zhang, Liangpei; Wu, Ke; Sahli, Hichem

    2011-12-01

    This work presents a scale-based forward-and-backward diffusion (SFABD) scheme. The main idea of this scheme is to perform local adaptive diffusion using local scale information. To this end, we propose a diffusivity function based on the Minimum Reliable Scale (MRS) of Elder and Zucker (IEEE Trans. Pattern Anal. Mach. Intell. 20(7), 699-716, 1998) to detect the details of local structures. The magnitude of the diffusion coefficient at each pixel is determined by taking into account the local property of the image through the scales. A scale-based variable weight is incorporated into the diffusivity function for balancing the forward and backward diffusion. Furthermore, as numerical scheme, we propose a modification of the Perona-Malik scheme (IEEE Trans. Pattern Anal. Mach. Intell. 12(7), 629-639, 1990) by incorporating edge orientations. The article describes the main principles of our method and illustrates image enhancement results on a set of standard images as well as simulated medical images, together with qualitative and quantitative comparisons with a variety of anisotropic diffusion schemes.

  8. NESTLE: Few-group neutron diffusion equation solver utilizing the nodal expansion method for eigenvalue, adjoint, fixed-source steady-state and transient problems

    SciTech Connect

    Turinsky, P.J.; Al-Chalabi, R.M.K.; Engrand, P.; Sarsour, H.N.; Faure, F.X.; Guo, W.

    1994-06-01

    NESTLE is a FORTRAN77 code that solves the few-group neutron diffusion equation utilizing the Nodal Expansion Method (NEM). NESTLE can solve the eigenvalue (criticality); eigenvalue adjoint; external fixed-source steady-state; or external fixed-source. or eigenvalue initiated transient problems. The code name NESTLE originates from the multi-problem solution capability, abbreviating Nodal Eigenvalue, Steady-state, Transient, Le core Evaluator. The eigenvalue problem allows criticality searches to be completed, and the external fixed-source steady-state problem can search to achieve a specified power level. Transient problems model delayed neutrons via precursor groups. Several core properties can be input as time dependent. Two or four energy groups can be utilized, with all energy groups being thermal groups (i.e. upscatter exits) if desired. Core geometries modelled include Cartesian and Hexagonal. Three, two and one dimensional models can be utilized with various symmetries. The non-linear iterative strategy associated with the NEM method is employed. An advantage of the non-linear iterative strategy is that NSTLE can be utilized to solve either the nodal or Finite Difference Method representation of the few-group neutron diffusion equation.

  9. Short-Term Increases in Transient Receptor Potential Vanilloid-1 Mediate Stress-Induced Enhancement of Neuronal Excitation

    PubMed Central

    Weitlauf, Carl; Ward, Nicholas J.; Lambert, Wendi S.; Sidorova, Tatiana N.; Ho, Karen W.; Sappington, Rebecca M.

    2014-01-01

    Progression of neurodegeneration in disease and injury is influenced by the response of individual neurons to stressful stimuli and whether this response includes mechanisms to counter declining function. Transient receptor potential (TRP) cation channels transduce a variety of disease-relevant stimuli and can mediate diverse stress-dependent changes in physiology, both presynaptic and postsynaptic. Recently, we demonstrated that knock-out or pharmacological inhibition of the TRP vanilloid-1 (TRPV1) capsaicin-sensitive subunit accelerates degeneration of retinal ganglion cell neurons and their axons with elevated ocular pressure, the critical stressor in the most common optic neuropathy, glaucoma. Here we probed the mechanism of the influence of TRPV1 on ganglion cell survival in mouse models of glaucoma. We found that induced elevations of ocular pressure increased TRPV1 in ganglion cells and its colocalization at excitatory synapses to their dendrites, whereas chronic elevation progressively increased ganglion cell Trpv1 mRNA. Enhanced TRPV1 expression in ganglion cells was transient and supported a reversal of the effect of TRPV1 on ganglion cells from hyperpolarizing to depolarizing, which was also transient. Short-term enhancement of TRPV1-mediated activity led to a delayed increase in axonal spontaneous excitation that was absent in ganglion cells from Trpv1−/− retina. In isolated ganglion cells, pharmacologically activated TRPV1 mobilized to discrete nodes along ganglion cell dendrites that corresponded to sites of elevated Ca2+. These results suggest that TRPV1 may promote retinal ganglion cell survival through transient enhancement of local excitation and axonal activity in response to ocular stress. PMID:25392504

  10. Short-term increases in transient receptor potential vanilloid-1 mediate stress-induced enhancement of neuronal excitation.

    PubMed

    Weitlauf, Carl; Ward, Nicholas J; Lambert, Wendi S; Sidorova, Tatiana N; Ho, Karen W; Sappington, Rebecca M; Calkins, David J

    2014-11-12

    Progression of neurodegeneration in disease and injury is influenced by the response of individual neurons to stressful stimuli and whether this response includes mechanisms to counter declining function. Transient receptor potential (TRP) cation channels transduce a variety of disease-relevant stimuli and can mediate diverse stress-dependent changes in physiology, both presynaptic and postsynaptic. Recently, we demonstrated that knock-out or pharmacological inhibition of the TRP vanilloid-1 (TRPV1) capsaicin-sensitive subunit accelerates degeneration of retinal ganglion cell neurons and their axons with elevated ocular pressure, the critical stressor in the most common optic neuropathy, glaucoma. Here we probed the mechanism of the influence of TRPV1 on ganglion cell survival in mouse models of glaucoma. We found that induced elevations of ocular pressure increased TRPV1 in ganglion cells and its colocalization at excitatory synapses to their dendrites, whereas chronic elevation progressively increased ganglion cell Trpv1 mRNA. Enhanced TRPV1 expression in ganglion cells was transient and supported a reversal of the effect of TRPV1 on ganglion cells from hyperpolarizing to depolarizing, which was also transient. Short-term enhancement of TRPV1-mediated activity led to a delayed increase in axonal spontaneous excitation that was absent in ganglion cells from Trpv1(-/-) retina. In isolated ganglion cells, pharmacologically activated TRPV1 mobilized to discrete nodes along ganglion cell dendrites that corresponded to sites of elevated Ca(2+). These results suggest that TRPV1 may promote retinal ganglion cell survival through transient enhancement of local excitation and axonal activity in response to ocular stress. PMID:25392504

  11. A New Transient Two-Wire Method for Measuring the Thermal Diffusivity of Electrically Conducting and Highly Corrosive Liquids Using Small Samples

    NASA Astrophysics Data System (ADS)

    Kadjo, A.; Garnier, J.-P.; Maye, J. P.; Martemianov, S.

    2008-08-01

    The transient hot-wire (THW) technique is widely used for measurements of the thermal conductivity of most fluids, and some attempts have also been carried out for simultaneous measurements of the thermal diffusivity with the same hot wire. However, for some particular liquids like concentrated nitric acid solutions or similar nitric mixtures, for which the thermal properties are important for industrial or security applications, this technique may be difficult to use, because of possible technological incompatibilities between measurement probe materials and highly electrically conducting and corrosive liquids. Moreover, the possible highly energetic (explosive) character of these liquids requires minimum volume liquid samples and safety measurement devices and processes. It is the purpose of this paper to report on a modified THW technique (previously used for thermal-diffusivity measurements in soils), which is associated with a specific patented double-wire probe and is shown to be valid for direct thermal-diffusivity measurements in liquids. This method responds to the previous requirements and allows automatic and quasi-simultaneous thermal-conductivity and thermal-diffusivity measurements to be made safely on liquids compatible with the tantalum technology, with liquid sample volumes < 2 cm3. Low uncertainties are found for the thermal-diffusivity data when relative measurements are carried out with reference liquids like water or toluene.

  12. POZylation: a new approach to enhance nanoparticle diffusion through mucosal barriers

    NASA Astrophysics Data System (ADS)

    Mansfield, Edward D. H.; Sillence, Katy; Hole, Patrick; Williams, Adrian C.; Khutoryanskiy, Vitaliy V.

    2015-08-01

    The increasing use of nanoparticles in the pharmaceutical industry is generating concomitant interest in developing nanomaterials that can rapidly penetrate into, and permeate through, biological membranes to facilitate drug delivery and improve the bioavailability of active pharmaceutical ingredients. Here, we demonstrate that the permeation of thiolated silica nanoparticles through porcine gastric mucosa can be significantly enhanced by their functionalization with either 5 kDa poly(2-ethyl-2-oxazoline) or poly(ethylene glycol). Nanoparticle diffusion was assessed using two independent techniques; Nanoparticle Tracking Analysis, and fluorescence microscopy. Our results show that poly(2-ethyl-2-oxazoline) and poly(ethylene glycol) have comparable abilities to enhance diffusion of silica nanoparticles in mucin dispersions and through the gastric mucosa. These findings provide a new strategy in the design of nanomedicines, by surface modification or nanoparticle core construction, for enhanced transmucosal drug delivery.The increasing use of nanoparticles in the pharmaceutical industry is generating concomitant interest in developing nanomaterials that can rapidly penetrate into, and permeate through, biological membranes to facilitate drug delivery and improve the bioavailability of active pharmaceutical ingredients. Here, we demonstrate that the permeation of thiolated silica nanoparticles through porcine gastric mucosa can be significantly enhanced by their functionalization with either 5 kDa poly(2-ethyl-2-oxazoline) or poly(ethylene glycol). Nanoparticle diffusion was assessed using two independent techniques; Nanoparticle Tracking Analysis, and fluorescence microscopy. Our results show that poly(2-ethyl-2-oxazoline) and poly(ethylene glycol) have comparable abilities to enhance diffusion of silica nanoparticles in mucin dispersions and through the gastric mucosa. These findings provide a new strategy in the design of nanomedicines, by surface modification or nanoparticle core construction, for enhanced transmucosal drug delivery. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03178h

  13. Application of a combined superconducting fault current limiter and STATCOM to enhancement of power system transient stability

    NASA Astrophysics Data System (ADS)

    Mahdad, Belkacem; Srairi, K.

    2013-12-01

    Stable and reliable operation of the power system network is dependent on the dynamic equilibrium between energy production and power demand under large disturbance such as short circuit or important line tripping. This paper investigates the use of combined model based superconducting fault current limiter (SFCL) and shunt FACTS Controller (STATCOM) for assessing the transient stability of a power system considering the automatic voltage regulator. The combined model located at a specified branch based on voltage stability index using continuation power flow. The main role of the proposed combined model is to achieve simultaneously a flexible control of reactive power using STATCOM Controller and to reduce fault current using superconducting technology based SFCL. The proposed combined model has been successfully adapted within the transient stability program and applied to enhance the transient power system stability of the WSCC9-Bus system. Critical clearing time (CCT) has been used as an index to evaluate and validate the contribution of the proposed coordinated Controller. Simulation results confirm the effectiveness and perspective of this combined Controller to enhance the dynamic power system performances.

  14. Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase IV enhances CO2 fluxes across Xenopus oocyte plasma membranes

    PubMed Central

    Occhipinti, Rossana; Boron, Walter F.

    2014-01-01

    Human carbonic anhydrase IV (CA IV) is GPI-anchored to the outer membrane surface, catalyzing CO2/HCO3? hydration-dehydration. We examined effects of heterologously expressed CA IV on intracellular-pH (pHi) and surface-pH (pHS) transients caused by exposing oocytes to CO2/HCO3?/pH 7.50. CO2 influx causes a sustained pHi fall and a transient pHS rise; CO2 efflux does the opposite. Both during CO2 addition and removal, CA IV increases magnitudes of maximal rate of pHi change (dpHi/dt)max, and maximal pHS change (?pHS) and decreases time constants for pHi changes (?pHi) and pHS relaxations (?pHS). Decreases in time constants indicate that CA IV enhances CO2 fluxes. Extracellular acetazolamide blocks all CA IV effects, but not those of injected CA II. Injected acetazolamide partially reduces CA IV effects. Thus, extracellular CA is required for, and the equivalent of cytosol-accessible CA augments, the effects of CA IV. Increasing the concentration of the extracellular non-CO2/HCO3? buffer (i.e., HEPES), in the presence of extracellular CA or at high [CO2], accelerates CO2 influx. Simultaneous measurements with two pHS electrodes, one on the oocyte meridian perpendicular to the axis of flow and one downstream from the direction of extracellular-solution flow, reveal that the downstream electrode has a larger (i.e., slower) ?pHS, indicating [CO2] asymmetry over the oocyte surface. A reaction-diffusion mathematical model (third paper in series) accounts for the above general features, and supports the conclusion that extracellular CA, which replenishes entering CO2 or consumes exiting CO2 at the extracellular surface, enhances the gradient driving CO2 influx across the cell membrane. PMID:24965590

  15. Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase IV enhances CO2 fluxes across Xenopus oocyte plasma membranes.

    PubMed

    Musa-Aziz, Raif; Occhipinti, Rossana; Boron, Walter F

    2014-11-01

    Human carbonic anhydrase IV (CA IV) is GPI-anchored to the outer membrane surface, catalyzing CO2/HCO3 (-) hydration-dehydration. We examined effects of heterologously expressed CA IV on intracellular-pH (pHi) and surface-pH (pHS) transients caused by exposing oocytes to CO2/HCO3 (-)/pH 7.50. CO2 influx causes a sustained pHi fall and a transient pHS rise; CO2 efflux does the opposite. Both during CO2 addition and removal, CA IV increases magnitudes of maximal rate of pHi change (dpHi/dt)max, and maximal pHS change (?pHS) and decreases time constants for pHi changes (?pHi ) and pHS relaxations (?pHS ). Decreases in time constants indicate that CA IV enhances CO2 fluxes. Extracellular acetazolamide blocks all CA IV effects, but not those of injected CA II. Injected acetazolamide partially reduces CA IV effects. Thus, extracellular CA is required for, and the equivalent of cytosol-accessible CA augments, the effects of CA IV. Increasing the concentration of the extracellular non-CO2/HCO3 (-) buffer (i.e., HEPES), in the presence of extracellular CA or at high [CO2], accelerates CO2 influx. Simultaneous measurements with two pHS electrodes, one on the oocyte meridian perpendicular to the axis of flow and one downstream from the direction of extracellular-solution flow, reveal that the downstream electrode has a larger (i.e., slower) ?pHS , indicating [CO2] asymmetry over the oocyte surface. A reaction-diffusion mathematical model (third paper in series) accounts for the above general features, and supports the conclusion that extracellular CA, which replenishes entering CO2 or consumes exiting CO2 at the extracellular surface, enhances the gradient driving CO2 influx across the cell membrane. PMID:24965590

  16. Differentiation of Reactive and Tumor Metastatic Lymph Nodes with Diffusion-weighted and SPIO Enhanced MRI

    PubMed Central

    Zhang, Fan; Zhu, Lei; Huang, Xinglu; Niu, Gang; Chen, Siouan

    2012-01-01

    Objectives Determination of lymphatic metastasis is of great importance for both treatment planning and patient prognosis. We aim to distinguish tumor metastatic lymph nodes (TLNs) and reactive lymph nodes (RLNs) with diffusion-weighted and superparamagnetic iron oxide (SPIO) enhanced magnetic resonance imaging (MRI). Materials and methods Ipsilateral popliteal lymph node metastasis or lymphadenitis model was established by hock injection of either luciferase-expressing 4T1 murine breast cancer cells or Complete Freund Adjuvant (CFA) in male Balb/C mice. At different time points after inoculation, bioluminescence imaging, T2-weighted, diffusion-weighted and SPIO enhanced MRI were performed. Imaging findings were confirmed by histopathological staining. Results Size enlargement was observed in both TLNs and RLNs. At day 28, TLNs showed strong bioluminescence signal and bigger size than RLNs (p < 0.01). At early stages up to day 21, both TLNs and RLNs appeared homogeneous on diffusion-weighted imaging (DWI). At day 28, TLNs showed heterogeneous apparent diffusion coefficient (ADC) map with significantly higher average ADC value of 0.41 ± 0.03 × 10−3 mm2/s than that of RLNs (0.34 ± 0.02 10−3 mm2/s, p < 0.05). On SPIO enhanced MRI, both TLNs and RLNs showed distinct T2 signal reduction at day 21 after inoculation. At day 28, TLNs demonstrated partial uptake of the iron oxide particles, which was confirmed by Prussian blue staining. Conclusions Both diffusion-weighted and SPIO enhanced MRI can distinguish tumor metastatic lymph nodes from reactive lymph nodes. However, neither method is able to detect tumor metastasis to the draining lymph nodes at early stages. PMID:22588595

  17. Effects of Pulse Current on Transient Liquid Phase (TLP) Diffusion Bonding of SiCp/2024Al Composites Sheet Using Mixed Al, Cu, and Ti Powder Interlayer

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Jiang, Shaosong; Zhang, Kaifeng

    2012-09-01

    The effects of pulse current on transient liquid phase (TLP) diffusion bonding of SiCp/2024Al composites sheet were investigated at 853 K (580 C) using a mixed slurry of Al, Cu, and Ti powder interlayer. The process parameters were as follows: the pulse current density of 1.15 102 A/mm2, the original pressure of 0.5 MPa, the vacuum of 1.3 10-3 Pa, and the bonding time from 15 to 60 minutes. Moreover, the bonding mechanism in correlation with the microstructural and mechanical properties variation was analyzed.

  18. Long-Term Monitoring of Post-Stroke Plasticity After Transient Cerebral Ischemia in Mice Using In Vivo and Ex Vivo Diffusion Tensor MRI

    PubMed Central

    Granziera, C; DArceuil, H; Zai, L; Magistretti, P.J; Sorensen, A.G; de Crespigny, A.J

    2007-01-01

    We used a murine model of transient focal cerebral ischemia to study: 1) in vivo DTI long-term temporal evolution of the apparent diffusion coefficient (ADC) and diffusion fractional anisotropy (FA) at days 4, 10, 15 and 21 after stroke 2) ex vivo distribution of a plasticity-related protein (GAP-43) and its relationship with the ex vivo DTI characteristics of the striato-thalamic pathway (21 days). All animals recovered motor function. In vivo ADC within the infarct was significantly increased after stroke. In the stroke group, GAP-43 expression and FA values were significantly higher in the ipsilateral (IL) striatum and contralateral (CL) hippocampus compared to the shams. DTI tractography showed fiber trajectories connecting the CL striatum to the stroke region, where increased GAP43 and FA were observed and fiber tracts from the CL striatum terminating in the IL hippocampus. Our data demonstrate that DTI changes parallel histological remodeling and recovery of function. PMID:19018310

  19. Cooperative enhancement of TPA in cruciform double-chain DSB derivation: a femtosecond transient absorption spectra study

    NASA Astrophysics Data System (ADS)

    He, X.; Wang, Y.; Yang, Z.; Ma, Y.; Yang, Y.

    2010-09-01

    Femtosecond time-resolved transient absorption (TA) spectra study was adopted to study the mechanism of the cooperative enhancement of two-photon absorption (TPA) cross section from the linear structure 1,4-di(4'-N,N-diphenylaminostyryl)benzene (DPA-DSB) to its cruciform double-chain dimer DPA-TSB. The results suggested that a non-emissive intramolecular charge-transfer (ICT) state, ICT, was present upon excitation in the dimer, which was absent in the monomer. The existence of this non-emissive state, indicating the enhancement of the intramolecular charge-transfer of the dimer, should be the reason for the cooperative enhancement of the TPA cross section of the dimer compared to the monomer.

  20. Assessing the accuracy of 1-D analytical heat tracing for estimating near-surface sediment thermal diffusivity and water flux under transient conditions

    NASA Astrophysics Data System (ADS)

    Rau, Gabriel C.; Cuthbert, Mark O.; McCallum, Andrew M.; Halloran, Landon J. S.; Andersen, Martin S.

    2015-08-01

    Amplitude decay and phase delay of oscillating temperature records measured at two vertical locations in near-surface sediments can be used to infer water fluxes, thermal diffusivity, and sediment scour/deposition. While methods that rely on the harmonics-based analytical heat transport solution assume a steady state water flux, many applications have reported transient fluxes but ignored the possible violation of this assumption in the method. Here we use natural heat tracing as an example to investigate the extent to which changes in the water flux, and associated temperature signal nonstationarity, can be separated from other influences. We systematically scrutinize the assumption of steady state flow in analytical heat tracing and test the capabilities of the method to detect the timing and magnitude of flux transients. A numerical model was used to synthesize the temperature response to different step and ramp changes in advective thermal velocity magnitude and direction for both a single-frequency and multifrequency temperature boundary. Time-variable temperature amplitude and phase information were extracted from the model output with different signal-processing methods. We show that a worst-case transient flux induces a temperature nonstationarity, the duration of which is less than 1 cycle for realistic sediment thermal diffusivities between 0.02 and 0.13 m2/d. However, common signal-processing methods introduce erroneous temporal spreading of advective thermal velocities and significant anomalies in thermal diffusivities or sensor spacing, which is used as an analogue for streambed scour/deposition. The most time-variant spectral filter can introduce errors of up to 57% in velocity and 33% in thermal diffusivity values with artifacts spanning 2 days around the occurrence of rapid changes in flux. Further, our results show that analytical heat tracing is unable to accurately resolve highly time-variant fluxes and thermal diffusivities and does not allow for the inference of scour/depositional processes due to the limitations of signal processing in disentangling flux-related signal nonstationarities from those stemming from other sources. To prevent erroneous interpretations, hydrometric data should always be acquired in combination with temperature records.

  1. Biogeochemical Processes Responsible for the Enhanced Transport of Plutonium Under transient Unsaturated Ground Water Conditions

    SciTech Connect

    Fred J. Molz, III

    2010-05-28

    To better understand longer-term vadose zone transport in southeastern soils, field lysimeter experiments were conducted at the Savannah River Site (SRS) near Aiken, SC, in the 1980s. Each of the three lysimeters analyzed herein contained a filter paper spiked with different Pu solutions, and they were left exposed to natural environmental conditions (including the growth of annual weed grasses) for 11 years. The resulting Pu activity measurements from each lysimeter core showed anomalous activity distributions below the source, with significant migration of Pu above the source. Such results are not explainable by adsorption phenomena alone. A transient variably saturated flow model with root water uptake was developed and coupled to a soil reactive transport model. Somewhat surprisingly, the fully transient analysis showed results nearly identical to those of a much simpler steady flow analysis performed previously. However, all phenomena studied were unable to produce the upward Pu transport observed in the data. This result suggests another transport mechanism such as Pu uptake by roots and upward transport due to transpiration. Thus, the variably saturated flow and reactive transport model was extended to include uptake and transport of Pu within the root xylem, along with computational methodology and results. In the extended model, flow velocity in the soil was driven by precipitation input along with transpiration and drainage. Water uptake by the roots determined the flow velocity in the root xylem, and this along with uptake of Pu in the transpiration stream drove advection and dispersion of the two Pu species in the xylem. During wet periods with high potential evapotranspiration, maximum flow velocities through the xylem would approached 600 cm/hr, orders of magnitude larger that flow velocities in the soil. Values for parameters and the correct conceptual viewpoint for Pu transport in plant xylem was uncertain. This motivated further experiments devoted to Pu uptake by corn roots and xylem transport. Plants were started in wet paper wrapped around each corn seed. When the tap roots were sufficiently long, the seedlings were transplanted to a soil container with the tap root extending out the container bottom. The soil container was then placed over a nutrient solution container, and the solution served as an additional medium for root growth. To conduct an uptake study, a radioactive substance, such as Pu complexed with the bacterial siderophore DFOB, was added to the nutrient solution. After a suitable elapsed time, the corn plant was sacrificed, cut into 10 cm lengths, and the activity distribution measured. Experimental results clarified the basic nature of Pu uptake and transport in corn plants, and resulting simulations suggested that each growing season Pu in the SRS lysimeters would move into the plant shoots and be deposited on the soil surface during the Fall dieback. Subsequent isotope ratio analyses showed that this did happen. OVERALL RESULTS AND CONCLUSIONS - (1) Pu transport downward from the source is controlled by advection, dispersion and adsorption, along with surface-mediated REDOX reactions. (2) Hysteresis, extreme root distribution functions, air-content dependent oxidation rate constants, and large evaporation rates from the soil surface were not able to explain the observed upward migration of Pu. (3) Small amounts of Pu uptake by plant roots and translocation in the transpiration stream creates a realistic mechanism for upward Pu migration (4) Realistic xylem cross-sectional areas imply high flow velocities under hot, wet conditions. Such flow velocities produce the correct shape for the observed activity distributions in the top 20 cm of the lysimeter soil. (5) Simulations imply that Pu should have moved into the above-ground grass tissue each year during the duration of the experiments, resulting in an activity residual accumulating on the soil surface. An isotope ratio analysis showed that the observed surface Pu residue was from the buried sources, not atmospheric fallout. (6) The plant experiments indicate a Pu-DFOB velocity in the corn xylem of at least 174 cm/hr, much higher than ionic Pu in soil. Thus, Pu complexation with chelating agents is probably what led to the observed enhanced uptake and mobility in grasses. (7) Plant experiments show that the uptake of Fe-DFOB, Pu-DFOB and the resulting distributions are very similar. This supports the hypothesis that plant and bacterial iron-seeking chemistry mistakes Pu for Fe.

  2. Integral solutions to transient nonlinear heat (mass) diffusion with a power-law diffusivity: a semi-infinite medium with fixed boundary conditions

    NASA Astrophysics Data System (ADS)

    Hristov, Jordan

    2016-03-01

    Closed form approximate solutions to nonlinear heat (mass) diffusion equation with power-law nonlinearity of the thermal (mass) diffusivity have been developed by the integral-balance method avoiding the commonly used linearization by the Kirchhoff transformation. The main improvement of the solution is based on the double-integration technique and a new approach to the space derivative. Solutions to Dirichlet and Neumann boundary condition problems have been developed and benchmarked against exact numerical and approximate analytical solutions available in the literature.

  3. Enhanced diffusion of high-temperature implanted aluminum in silicon carbide

    SciTech Connect

    Suvorov, A.V.; Usov, I.O.; Sokolov, V.V.; Suvorova, A.A.

    1996-12-31

    The diffusion of aluminum in silicon carbide during high-temperature Al{sup +} ion implantation was studied using secondary ion mass spectrometry (SIMS). Transmission electron microscopy (TEM) has been used to determine the microstructure of the implanted sample. A 6H-SiC wafer was implanted at a temperature of 1,800 C with 40 keV Al ions to a dose of 2 {times} 10{sup 16} cm{sup {minus}2}. It was established that an Al step-like profile starts at the interface between the crystal region and the damaged layer. The radiation enhanced diffusion coefficient of Al at the interface was determined to be D{sub i} = 2.8 {times} 10{sup {minus}12} cm{sup 2}/s, about two orders of magnitude higher than the thermally activated diffusion coefficient. The Si vacancy-rich near-surface layer formed by this implantation condition is believed to play a significant role in enhanced Al diffusion.

  4. Enhancement of hyperspectral imagery using spectrally weighted tensor anisotropic nonlinear diffusion for classification

    NASA Astrophysics Data System (ADS)

    Marin-Mcgee, Maider J.; Velez-Reyes, Miguel

    2013-05-01

    Tensor Anisotropic Nonlinear Diffusion (TAND) is a divergence PDE-based diffusion technique that is "guided" by an edge descriptor, such as the structure tensor, to stir the diffusion. The structure tensor for vector valued images such as HSI is most often defined as the average of the scalar structure tensors for each band. The problem with this definition is the assumption that all bands provide the same amount of edge information giving them the same weights. As a result non-edge pixels can be reinforced and edges can be weakened resulting in poor performance by processes that depend on the structure tensor. Iterative processes such as TAND, in particular, are vulnerable to this phenomenon. Recently a weighted structure tensor based on the heat operator has been proposed [1]. The weights are based on the heat operator. This tensor takes advantage of the fact that, in HSI, neighboring spectral bands are highly correlated, as are the bands of its gradient. By taking advantage of local spectral information, the proposed scheme gives higher weighting to local spectral features that could be related to edge information allowing the diffusion process to better enhance edges while smoothing out uniform regions facilitating the process of classification. This article present how classification results are affected by using TAND based on the heat weighted structure tensor as an image enhancement step in a classification system.

  5. Evidence of enhanced double-diffusive convection below the main stream of the Kuroshio Extension

    NASA Astrophysics Data System (ADS)

    Nagai, Takeyoshi; Inoue, Ryuichiro; Tandon, Amit; Yamazaki, Hidekatsu

    2015-12-01

    In this study, a Navis-MicroRider microstructure float and an EM-APEX float were deployed along the Kuroshio Extension Front. The observations deeper than 150 m reveal widespread interleaving thermohaline structures for at least 900 km along the front, presumably generated through mesoscale stirring and near-inertial oscillations. In these interleaving structures, microscale thermal dissipation rates ? are very high O(>10-7 K2s-1), while turbulent kinetic energy dissipation rates ? are relatively low O(10-10-10-9 Wkg-1), with effective thermal diffusivity K? of O(10-3 m2s-1) consistent with the previous parameterizations for double-diffusion, and, K? is two orders of magnitude larger than the turbulent eddy diffusivity for density K?. The average observed dissipation ratio ? in salt finger and diffusive convection favorable conditions are 1.2 and 4.0, respectively, and are larger than that for turbulence. Our results suggest that mesoscale subduction/obduction and near-inertial motions could catalyze double-diffusive favorable conditions, and thereby enhancing the diapycnal tracer fluxes below the Kuroshio Extension Front.

  6. Enhanced nitrogen removal in single-chamber microbial fuel cells with increased gas diffusion areas.

    PubMed

    Yan, Hengjing; Regan, John M

    2013-03-01

    Single-chamber microbial fuel cells (MFCs) with nitrifiers pre-enriched at the air cathodes have previously been demonstrated as a passive strategy for integrating nitrogen removal into current-generating bioelectrochemical systems. To further define system design parameters for this strategy, we investigated in this study the effects of oxygen diffusion area and COD/N ratio in continuous-flow reactors. Doubling the gas diffusion area by adding an additional air cathode or a diffusion cloth significantly increased the ammonia and COD removal rates (by up to 115% and 39%), ammonia removal efficiency (by up to 134%), the cell voltage and cathode potentials, and the power densities (by a factor of approximately 2). When the COD/N ratio was lowered from 13 to 3, we found up to 244% higher ammonia removal rate but at least 19% lower ammonia removal efficiency. An increase of COD removal rate by up to 27% was also found when the COD/N ratio was lowered from 11 to 3. The Coulombic efficiency was not affected by the additional air cathode, but decreased by an average of 11% with the addition of a diffusion cloth. Ammonia removal by assimilation was also estimated to understand the ammonia removal mechanism in these systems. These results showed that the doubling of gas diffusion area enhanced N and COD removal rates without compromising electrochemical performance. PMID:23097182

  7. Investigation of NO interaction on Rh/doped TiO2-based automotive catalyst using combined transient diffuse reflectance Fourier transform infrared and mass spectrometry

    NASA Astrophysics Data System (ADS)

    Chafik, T.; Ouassini, A.; Verykios, X. E.

    1998-07-01

    The interaction of NO with Rh supported on W+6 doped TiO2 has been investigated by coupling transient diffuse reflectance Fourier transform Infrared spectroscopy and mass spectrometry. The experiments were carried out in dynamic conditions (under reactant flow and at temperature reaction) at atmospheric pressure. By comparing the results obtained with undoped Rh/TiO2 and Rh/TiO2(W6+) catalysts, the analytical approach used permitted to emphasis the effect of carrier doping, with respect to the elementary steps and surface intermediates involved in NO interaction process. It was found that W6+-doping of TiO2 promotes significantly the formation of Rh-NO- species and enhances the thermal stability of Rh-NO+ on Rh/TiO2 (W6+) surfaces. This leads to a drastic increase in the selectivity of NO decomposition reaction towards N2 formation, whereas the N2O yield decreases significantly. L'intéraction de NO sur un catalyseur à base de rhodium supporté sur TiO2 dopé par le tungstène W6+ a été étudiée en régime transitoire par couplage de la spectroscopie Infrarouge Diffuse à Transformée de Fourier (DRIFT) et la spectrométrie de masse. Ces études ont été effectuées dans des conditions dynamiques (sous flux de réactifs gazeux et à la température de la réaction) à la pression atmosphérique. La comparaison des études menées avec des catalyseurs non dopé (Rh/TiO2) et dopé (Rh/TiO2(W6+)) a permis de mettre en évidence l'influence du dopage du support catalytique sur la nature des intermédiaires superficiels et les étapes élémentaires intervenant dans le processus d'interaction de NO avec ces solides. Il a été montré que le dopage de TiO2 par W6+ accroît la formation des espèces Rh-NO- et la stabilité thermique des espèces Rh-NO+ sur Rh/TiO2(W6+). Ceci est à l'origine de l'augmentation de la sélectivité de la conversion de NO en N2 suite à la diminution considérable de la quantité N2O formée.

  8. Chemical modification of catalyst support for enhancement of transient catalytic activity: Nitric oxide reduction by carbon monoxide over rhodium

    SciTech Connect

    Cho, B.K. )

    1991-09-01

    A commercial ceria powder was chemically modified by doping with gadolinia in order to improve its oxygen storage/transport characteristics. The catalytic activity of Rh impregnated on this modified ceria support was measured and compared with those impregnated on conventional ceria or alumina support, using a packed-bed reactor and an isotopic reactant ({sup 13}CO) for the NO + CO reaction under both cycled- and steady-feed conditions. Results of transient pulse experiments indicated that the oxygen uptakes of both ceria and modified ceria are an order of magnitude greater than that of alumina. This work has demonstrated that the chemical modification of the ceria support can significantly enhance the catalytic activity of Rh for the NO + CO reaction under cycled feedstream conditions at high temperatures above 500 C. This enhancement of catalytic activity of Rh supported on the modified ceria is discussed in light of the oxygen storage and transport characteristics of the modified support.

  9. Impact of weak excitatory synapses on chaotic transients in a diffusively coupled Morris-Lecar neuronal network

    SciTech Connect

    Lafranceschina, Jacopo Wackerbauer, Renate

    2015-01-15

    Spatiotemporal chaos collapses to either a rest state or a propagating pulse solution in a ring network of diffusively coupled, excitable Morris-Lecar neurons. Weak excitatory synapses can increase the Lyapunov exponent, expedite the collapse, and promote the collapse to the rest state rather than the pulse state. A single traveling pulse solution may no longer be asymptotic for certain combinations of network topology and (weak) coupling strengths, and initiate spatiotemporal chaos. Multiple pulses can cause chaos initiation due to diffusive and synaptic pulse-pulse interaction. In the presence of chaos initiation, intermittent spatiotemporal chaos exists until typically a collapse to the rest state.

  10. Gradual Diffusion and Punctuated Phase Space Density Enhancements of Highly Relativistic Electrons: Van Allen Probes Observations

    NASA Technical Reports Server (NTRS)

    Baker, D. N.; Jaynes, A. N.; Li, X.; Henderson, M. G.; Kanekal, S. G.; Reeves, G. D.; Spence, H. E.; Claudepierre, S. G.; Fennell, J. F.; Hudson, M. K.

    2014-01-01

    The dual-spacecraft Van Allen Probes mission has provided a new window into mega electron volt (MeV) particle dynamics in the Earth's radiation belts. Observations (up to E (is) approximately 10MeV) show clearly the behavior of the outer electron radiation belt at different timescales: months-long periods of gradual inward radial diffusive transport and weak loss being punctuated by dramatic flux changes driven by strong solar wind transient events. We present analysis of multi-MeV electron flux and phase space density (PSD) changes during March 2013 in the context of the first year of Van Allen Probes operation. This March period demonstrates the classic signatures both of inward radial diffusive energization and abrupt localized acceleration deep within the outer Van Allen zone (L (is) approximately 4.0 +/- 0.5). This reveals graphically that both 'competing' mechanisms of multi-MeV electron energization are at play in the radiation belts, often acting almost concurrently or at least in rapid succession.

  11. Tumor characterization in small animals using magnetic resonance-guided dynamic contrast enhanced diffuse optical tomography

    NASA Astrophysics Data System (ADS)

    Lin, Yuting; Thayer, Dave; Nalcioglu, Orhan; Gulsen, Gultekin

    2011-10-01

    We present a magnetic resonance (MR)-guided near-infrared dynamic contrast enhanced diffuse optical tomography (DCE-DOT) system for characterization of tumors using an optical contrast agent (ICG) and a MR contrast agent [Gd-diethylenetriaminepentaacetic acid (DTPA)] in a rat model. Both ICG and Gd-DTPA are injected and monitored simultaneously using a combined MRI-DOT system, resulting in accurate co-registration between two imaging modalities. Fisher rats bearing R3230 breast tumor are imaged using this hybrid system. For the first time, enhancement kinetics of the exogenous contrast ICG is recovered from the DCE-DOT data using MR anatomical a priori information. As tumors grow, they undergo necrosis and the tissue transforms from viable to necrotic. The results show that the physiological changes between viable and necrotic tissue can be differentiated more accurately based on the ICG enhancement kinetics when MR anatomical information is utilized.

  12. Validation of diffusion tensor magnetic resonance axonal fiber imaging with registered manganese-enhanced optic tracts.

    PubMed

    Lin, C P; Tseng, W Y; Cheng, H C; Chen, J H

    2001-11-01

    Noninvasive mapping of white matter tracts using diffusion tensor magnetic resonance imaging (DTMRI) is potentially useful in revealing anatomical connectivity in the human brain. However, a gold standard for validating DTMRI in defining axonal fiber orientation is still lacking. This study presents the first validation of the principal eigenvector of the diffusion tensor in defining axonal fiber orientation by superimposing DTMRI with manganese-enhanced MRI of optic tracts. A rat model was developed in which optic tracts were enhanced by manganese ions. Manganese ion (Mn(2+)) is a potent T1-shortening agent and can be uptaken and transported actively along the axon. Based on this property, we obtained enhanced optic tracts with a T1-weighted spin-echo sequence 10 h after intravitreal injection of Mn(2+). The images were compared with DTMRI acquired with exact spatial registration. Deviation angles between tangential vectors of the enhanced tracts and the principal eigenvectors of the diffusion tensor were then computed pixel by pixel. We found that under signal-to-noise (SNR) of 30, the variance of deviation angles was (13.27 degrees). In addition, the dependence of this variance on SNR obeys stochastic behavior if SNR is greater than 10. Based on this relation, we estimated that an rms deviation of less than 10 degrees could be achieved with DTMRI when SNR is 40 or greater. In conclusion, our method bypasses technical difficulties in conventional histological approach and provides an in vivo gold standard for validating DTMRI in mapping white matter tracts. PMID:11697935

  13. Enhanced thrust and speed revealed in the forward flight of a butterfly with transient body translation.

    PubMed

    Fei, Yueh-Han John; Yang, Jing-Tang

    2015-09-01

    A butterfly with broad wings, flapping at a small frequency, flies an erratic trajectory at an inconstant speed. A large variation of speed within a cycle is observed in the forward flight of a butterfly. A self-propulsion model to simulate a butterfly is thus created to investigate the transient translation of the body; the results, which are in accordance with experimental data, show that the shape of the variation of the flight speed is similar to a sinusoidal wave with a maximum (J=0.89) at the beginning of the downstroke, and a decrease to a minimum (J=0.17) during a transition from downstroke to upstroke; the difference between the extrema of the flight speed is enormous in a flapping cycle. At a high speed, a clapping motion of the butterfly wings decreases the generation of drag. At a small speed, a butterfly is able to capture the induced wakes generated in a downstroke, and effectively generates a thrust at the beginning of an upstroke. The wing motion of a butterfly skillfully interacts with its speed so as to enable an increased speed with the same motion. Considering a butterfly to fly in a constant inflow leads to either an underestimate of its speed or an overestimate of its generated lift, which yields an inaccurate interpretation of the insect's flight. Our results reveal the effect of transient translation on a butterfly in forward flight, which is especially important for an insect with a small flapping frequency. PMID:26465553

  14. Enhanced thrust and speed revealed in the forward flight of a butterfly with transient body translation

    NASA Astrophysics Data System (ADS)

    Fei, Yueh-Han John; Yang, Jing-Tang

    2015-09-01

    A butterfly with broad wings, flapping at a small frequency, flies an erratic trajectory at an inconstant speed. A large variation of speed within a cycle is observed in the forward flight of a butterfly. A self-propulsion model to simulate a butterfly is thus created to investigate the transient translation of the body; the results, which are in accordance with experimental data, show that the shape of the variation of the flight speed is similar to a sinusoidal wave with a maximum (J =0.89 ) at the beginning of the downstroke, and a decrease to a minimum (J =0.17 ) during a transition from downstroke to upstroke; the difference between the extrema of the flight speed is enormous in a flapping cycle. At a high speed, a clapping motion of the butterfly wings decreases the generation of drag. At a small speed, a butterfly is able to capture the induced wakes generated in a downstroke, and effectively generates a thrust at the beginning of an upstroke. The wing motion of a butterfly skillfully interacts with its speed so as to enable an increased speed with the same motion. Considering a butterfly to fly in a constant inflow leads to either an underestimate of its speed or an overestimate of its generated lift, which yields an inaccurate interpretation of the insect's flight. Our results reveal the effect of transient translation on a butterfly in forward flight, which is especially important for an insect with a small flapping frequency.

  15. Impurity-trapped excitons and electron traps in CaF2:Yb2+ and SrF2:Yb2+ probed by transient photoluminescence enhancement

    NASA Astrophysics Data System (ADS)

    Senanayake, P. S.; Wells, J. P. R.; Reid, M. F.; Berden, G.; Meijerink, A.; Reeves, R. J.

    2013-01-01

    CaF$_2$:Yb$^{2+}$ and SrF$_2$:Yb$^{2+}$ crystals have been investigated by a two-color UV + IR transient photoluminescence enhancement technique. The enhancement gives information about both changes in internal energy levels of the excitons and liberation of electrons from traps in the crystals.

  16. Entropy-Driven Enhanced Self-Diffusion in Confined Reentrant Supernematics

    NASA Astrophysics Data System (ADS)

    Mazza, Marco G.; Greschek, Manuel; Valiullin, Rustem; Krger, Jrg; Schoen, Martin

    2010-11-01

    We present a molecular dynamics study of reentrant nematic phases using the Gay-Berne-Kihara model of a liquid crystal in nanoconfinement. At densities above those characteristic of smectic A phases, reentrant nematic phases form that are characterized by a large value of the nematic order parameter S?1. Along the nematic director these supernematic phases exhibit a remarkably high self-diffusivity, which exceeds that for ordinary, lower-density nematic phases by an order of magnitude. Enhancement of self-diffusivity is attributed to a decrease of rotational configurational entropy in confinement. Recent developments in the pulsed field gradient NMR technique are shown to provide favorable conditions for an experimental confirmation of our simulations.

  17. Quantification and normalization of noise variance with sparsity regularization to enhance diffuse optical tomography

    PubMed Central

    Yao, Jixing; Tian, Fenghua; Rakvongthai, Yothin; Oraintara, Soontorn; Liu, Hanli

    2015-01-01

    Conventional reconstruction of diffuse optical tomography (DOT) is based on the Tikhonov regularization and the white Gaussian noise assumption. Consequently, the reconstructed DOT images usually have a low spatial resolution. In this work, we have derived a novel quantification method for noise variance based on the linear Rytov approximation of the photon diffusion equation. Specifically, we have implemented this quantification of noise variance to normalize the measurement signals from all source-detector channels along with sparsity regularization to provide high-quality DOT images. Multiple experiments from computer simulations and laboratory phantoms were performed to validate and support the newly developed algorithm. The reconstructed images demonstrate that quantification and normalization of noise variance with sparsity regularization (QNNVSR) is an effective reconstruction approach to greatly enhance the spatial resolution and the shape fidelity for DOT images. Since noise variance can be estimated by our derived expression with relatively limited resources available, this approach is practically useful for many DOT applications. PMID:26309760

  18. Enhanced diffusion, chemotaxis, and pumping by active enzymes: progress toward an organizing principle of molecular machines.

    PubMed

    Astumian, R Dean

    2014-12-23

    Active enzymes diffuse more rapidly than inactive enzymes. This phenomenon may be due to catalysis-driven conformational changes that result in "swimming" through the aqueous solution. Recent additional work has demonstrated that active enzymes can undergo chemotaxis toward regions of high substrate concentration, whereas inactive enzymes do not, and, further, that active enzymes immobilized at surfaces can directionally pump liquids. In this Perspective, I will discuss these phenomena in light of Purcell's work on directed motion at low Reynold's number and in the context of microscopic reversibility. The conclusions suggest that a deep understanding of catalytically driven enhanced diffusion of enzymes and related phenomena can lead toward a general organizing principle for the design, characterization, and operation of molecular machines. PMID:25533171

  19. Enhancement in Diffusion of Electrolyte through Membrane Using Ultrasonic Dialysis Equipment with Plane Membrane

    NASA Astrophysics Data System (ADS)

    Li, Hui; Ohdaira, Etsuzo; Ide, Masao

    1995-05-01

    Application of ultrasound to accelerate the dialysis separation of electrolytes through a membrane was studied with ultrasonic dialysis equipment. The experiments were conducted with cellophane membrane and KCl solution, CH3COONa solution, and a mixture of KCl and saponin solutions. It was found that the diffusion velocity of electrolyte through a membrane with ultrasonic irradiation is faster than that without ultrasonic irradiation, and it increases with acoustic pressure. It has become clear that the reasons for enhancement caused by ultrasound are increase in liquid particle velocity and diffusion coefficient due to ultrasonic vibration. It was confirmed that the permeability of the membrane was not degraded by ultrasound in the ranges of acoustic pressure and irradiation time in this study.

  20. Multispecies diffusion models: A study of uranyl species diffusion

    SciTech Connect

    Liu, Chongxuan; Shang, Jianying; Zachara, John M.

    2011-12-14

    Rigorous numerical description of multi-species diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication for imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multi-species diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multi-species diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multi-species U(VI) diffusion under steady-state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that a fully coupled diffusion model can be well approximated by a component-based diffusion model, which considers difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be rigorously enforced, if necessary, by adding an artificial kinetic reaction term induced by the charge separation. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from US Department of Energy's Hanford 300A where intragrain diffusion is a rate-limiting process controlling U(VI) adsorption and desorption. The grain-scale reactive diffusion model was able to describe U(VI) adsorption/desorption kinetics that has been described using a semi-empirical, multi-rate model. Compared with the multi-rate model, the diffusion models have the advantage to provide spatiotemporal speciation evolution within the diffusion domains.

  1. Absorption enhancement and carrier diffusion in single lead sulfide nanowire Schottky solar cells

    NASA Astrophysics Data System (ADS)

    Yang, Yiming; Peng, Xingyue; Hyatt, Steven; Yu, Dong

    2015-08-01

    Semiconductor nanowire (NW) solar cells have promising potentials in solar energy conversion, benefiting from their low fabrication cost and enhanced optical absorption through light confinement. Recently, we have shown that the absorption efficiency can be significantly improved in lead sulfide (PbS) NWs with high refractive indices, by a direct observation of 350% external quantum efficiency (EQE). In this proceeding paper, we further examine the optical resonance mechanism in this promising nanomaterial. Particularly, we will present our recent results on resonance modes calculation, polarization and substrate effects on optical resonance, and intensity dependent minority carrier diffusion lengths in single PbS NW Schottky junction solar cells.

  2. Analytical resolution of the reactive diffusion equation for transient electronics including materials whose porosity value changes in terms of their thickness

    NASA Astrophysics Data System (ADS)

    Vargas Toro, Agustín.

    2014-05-01

    Transient electronic devices are a new technology development whose main characteristic is that its components can disappear in a programmed and controlled way, which means such devices have a pre-engineered service life. Nowadays, transient electronics have a large application field, involving from the reduction of e-waste in the planet until the development of medical instruments and implants that can be discarded when the patients do not need it anymore, avoiding the trouble of having an extra procedure for them. These devices must be made from biocompatible materials avoiding long-term adverse effects in the environment and patients. It is fundamental to develop an analytical model that allows describing the behavior of these materials considering cases which its porosity may be constant or not, in presence of water or any other biofluid. In order to accomplish this analysis was solve the reactive diffusion equation based on Bromwich's integral and the Residue theorem for two material cases, those whose porosity is constant, and those whose porosity increases linearly in terms of its thickness, where was found a general expression. This allows to the analysis of the relation of the electric resistance (per unit length) and the rate of dissolution of the material.

  3. Transient Electrochemical Surface-Enhanced Raman Spectroscopy: A Millisecond Time-Resolved Study of an Electrochemical Redox Process.

    PubMed

    Zong, Cheng; Chen, Chan-Juan; Zhang, Meng; Wu, De-Yin; Ren, Bin

    2015-09-16

    The pursuit of techniques with a high time resolution together with molecular signature information at the electrochemical interfaces has never stopped in order to explicitly monitor and understand the dynamic electrochemical processes. Here, we developed a transient electrochemical surface-enhanced Raman spectroscopy (TEC-SERS) to monitor the structural evolution of surface species at a time resolution that equals the transient electrochemical methods (e.g., cyclic voltammetry and chronoamperometry), so that the Raman signal with the molecular signature information and the electrochemical current signal can be precisely correlated. The technique was employed to study the redox process of nile blue on Ag surfaces. We revealed an interesting two-rate constant process and a peculiar increase of the absolute intensity during the reduction of nile blue on the Ag surface, which both related to the dissociation of nile blue aggregates and the follow-up reduction. Therefore, we were able to uncover the processes that are impossible to observe by conventional steady state SERS methods. The ability to provide a time resolution shorter than the charging time of the double layer capacitance with molecular fingerprint information has unprecedented significance for investigation of both reversible and irreversible electrochemical processes. PMID:26325244

  4. AAV-Mediated Gene Targeting Is Significantly Enhanced by Transient Inhibition of Nonhomologous End Joining or the Proteasome In Vivo

    PubMed Central

    Paulk, Nicole K.; Loza, Laura Marquez; Finegold, Milton J.

    2012-01-01

    Abstract Recombinant adeno-associated virus (rAAV) vectors have clear potential for use in gene targeting but low correction efficiencies remain the primary drawback. One approach to enhancing efficiency is a block of undesired repair pathways like nonhomologous end joining (NHEJ) to promote the use of homologous recombination. The natural product vanillin acts as a potent inhibitor of NHEJ by inhibiting DNA-dependent protein kinase (DNA-PK). Using a homology containing rAAV vector, we previously demonstrated in vivo gene repair frequencies of up to 0.1% in a model of liver disease hereditary tyrosinemia type I. To increase targeting frequencies, we administered vanillin in combination with rAAV. Gene targeting frequencies increased up to 10-fold over AAV alone, approaching 1%. Fah?/?Ku70?/? double knockout mice also had increased gene repair frequencies, genetically confirming the beneficial effects of blocking NHEJ. A second strategy, transient proteasomal inhibition, also increased gene-targeting frequencies but was not additive to NHEJ inhibition. This study establishes the benefit of transient NHEJ inhibition with vanillin, or proteasome blockage with bortezomib, for increasing hepatic gene targeting with rAAV. Functional metabolic correction of a clinically relevant disease model was demonstrated and provided evidence for the feasibility of gene targeting as a therapeutic strategy. PMID:22486314

  5. Transient Enhancement of Spike-Evoked Calcium Signaling by a Serotonergic Interneuron

    PubMed Central

    Hill, Evan S.; Sakurai, Akira; Katz, Paul S.

    2008-01-01

    Enhancement of presynaptic Ca2+ signals is widely recognized as a potential mechanism for heterosynaptic potentiation of neurotransmitter release. Here we show that stimulation of a serotonergic interneuron increased spike-evoked Ca2+ in a manner consistent with its neuromodulatory effect on synaptic transmission. In the gastropod mollusk, Tritonia diomedea, stimulation of a serotonergic dorsal swim interneuron (DSI) at physiological rates heterosynaptically enhances the strength of output synapses made by another swim interneuron, C2, onto neurons in the pedal ganglion. Using intracellular electrophysiological recording combined with real-time confocal imaging of C2 (loaded with Oregon Green Bapta 1), it was determined that DSI stimulation increases the amplitude of spike-evoked Ca2+ signals in C2 without altering basal Ca2+ signals. This neuromodulatory action was restricted to distal neurites of C2 where synapses with pedal neurons are located. The effect of DSI stimulation on C2 spike-evoked Ca2+ signals resembled DSI heterosynaptic enhancement of C2 synapses in several measures: both decayed within 15 s, both were abolished by the serotonin receptor antagonist, methysergide, and both were independent of DSI's depolarizing actions on C2. A brief puff of serotonin could mimic the enhancement of spike-evoked Ca2+ signals in the distal neurites of C2, but larger puffs or bath-applied serotonin elicited nonphysiological effects. These results suggest that DSI heterosynaptic enhancement of C2 synaptic strength may be mediated by a local enhancement of spike-evoked Ca2+ signals in the distal neurites of C2. PMID:18815341

  6. Enhanced soot formation in flickering CH{sub 4}/air diffusion flames

    SciTech Connect

    Shaddix, C.R.; Harrington, J.E.; Smyth, K.C.

    1994-12-31

    Optical methods are used to examine soot production in a co-flowing, axisymmetric CH{sub 4}/air diffusion flame in which the fuel flow rate is acoustically forced to create a time-varying flowfield. For a particular forcing condition in which tip clipping occurs (0.75 V loudspeaker excitation), elastic scattering of vertically polarized light from the soot particles increases by nearly an order of magnitude with respect to that observed for a steady flame with the same mean fuel flow rate. Peak soot volume fractions, as measured by time-resolved laser extinction/tomography at 632.8 and 454.5 run and calibrated laser-induced incandescence (LII), show a factor of 4-5 enhancement in this flickering flame. A Mie analysis suggests that most of the enhanced soot production results from the formation of larger particles in the time-varying flowfield.

  7. Coronary Plaque Boundary Enhancement in IVUS Image by Using a Modified Perona-Malik Diffusion Filter

    PubMed Central

    Anam, S.; Uchino, E.; Suetake, N.

    2014-01-01

    We propose a modified Perona-Malik diffusion (PMD) filter to enhance a coronary plaque boundary by considering the conditions peculiar to an intravascular ultrasound (IVUS) image. The IVUS image is commonly used for a diagnosis of acute coronary syndrome (ACS). The IVUS image is however very grainy due to heavy speckle noise. When the normal PMD filter is applied for speckle noise reduction in the IVUS image, the coronary plaque boundary becomes vague. For this problem, we propose a modified PMD filter which is designed in special reference to the coronary plaque boundary detection. It can then not only reduce the speckle noise but also enhance clearly the coronary plaque boundary. After applying the modified PMD filter to the IVUS image, the coronary plaque boundaries are successfully detected further by applying the Takagi-Sugeno fuzzy model. The accuracy of the proposed method has been confirmed numerically by the experiments. PMID:25506357

  8. Lack of transient receptor potential melastatin 8 activation by phthalate esters that enhance contact hypersensitivity in mice.

    PubMed

    Kurohane, Kohta; Sahara, Yurina; Kimura, Ayako; Narukawa, Masataka; Watanabe, Tatsuo; Daimon, Takashi; Imai, Yasuyuki

    2013-03-13

    We studied the involvement of sensory neurons in skin sensitization to allergens using a mouse model in which the T-helper type 2 response is essential. Skin sensitization to fluorescein isothiocyanate (FITC) has been shown to be enhanced by several phthalate esters, including dibutyl phthalate (DBP). For different types of phthalate esters, we found a correlation between the ability of transient receptor potential (TRP) A1 activation and that of enhancing skin sensitization. A TRPA1-specific antagonist, HC-030031, was shown to suppress skin sensitization in the presence of DBP. However, since phthalate esters also activate TRPV1, phthalate esters could activate other types of TRP channels non-selectively. Furthermore, sensitization to FITC is also enhanced by menthol, which activates TRPA1 and TRPM8. Here we established an in vitro system for measuring TRPM8 activation. The selectivity for TRPM8 was established by the fact that two TRPM8 agonists (menthol and icilin) induced calcium mobilization, whereas agonists of TRPA1 and TRPV1 did not. We demonstrated that phthalate esters do not activate TRPM8. TRPA1-antagonist HC-030031 did not inhibit TRPM8 activation induced by menthol or icilin. These results show that phthalate esters activate TRPA1 and TRPV1 with selectivity. TRPM8 activation is not likely to be involved in the sensitization to FITC. PMID:23296101

  9. Transient Enhancement and Detuning of Laser-Driven Parametric Instabilities by Particle Trapping

    NASA Astrophysics Data System (ADS)

    Vu, Hoanh X.

    2000-10-01

    Results are presented on kinetic regimes of backward stimulated Raman scattering [1] (BSRS) dominated by electron trapping in the primary daughter Langmuir wave (LW). This study is motivated by the need to understand the unexpectedly high BSRS reflectivities observed in experiments emulating the conditions of the National Ignition Facility (NIF) [2,3]. In the case of BSRS, it is found in our study that electron trapping can lead to much larger transient reflectivities than predicted by standard fluid-like Zakharov models (with fixed, linear, Landau damping)in regimes with high Landau damping of the primary Langmuir wave (LW)with large values of k_1?D [4]. It is also found that the LW frequency shift associated with trapped electrons [5] introduces a secular phase shift between the LW and the BSRS ponderomotive force. This phase shift detunes and saturates BSRS and a similar effect, due to ion trapping, is now understood to be the saturation mechanism for stimulated Brillouin scattering. [1] W.L. Kruer, The Physics of Laser-Plasma Interaction (Addison-Wesley, New York, 1988). [2] J.C. Fernandez et al., Observed Insensitivity of Stimulated Raman Scattering on Electron Density, Phys. Plasmas, accepted (2000). [3] D.S. Montgomery, private communication (1999). [4] D.A. Russell, D.F. DuBois, and H.A. Rose, Phys. Plasmas 6, 1294 (1999). [5] G.J. Morales and T.M. O'Neil, Phys. Rev. Lett. 28, 417 (1972).

  10. Dynamic contrast-enhanced diffuse optical tomography (DCE-DOT): experimental validation with a dynamic phantom

    PubMed Central

    Unlu, Mehmet Burcin; Lin, Yuting; Gulsen, Gultekin

    2010-01-01

    Dynamic contrast-enhanced diffuse optical tomography (DCE-DOT) can provide spatially resolved enhancement kinetics of an optical contrast agent. We undertook a systematic phantom study to evaluate the effects of the geometrical parameters such as the depth and size of the inclusion as well as the optical parameters of the background on the recovered enhancement kinetics of the most commonly used optical contrast agent, indocyanine green (ICG). For this purpose a computer-controlled dynamic phantom was constructed. An ICG–intralipid–water mixture was circulated through the inclusions while the DCE-DOT measurements were acquired with a temporal resolution of 16 s. The same dynamic study was repeated using inclusions of different sizes located at different depths. In addition to this, the effect of non-scattering regions was investigated by placing a second inclusion filled with water in the background. The phantom studies confirmed that although the peak enhancement varied substantially for each case, the recovered injection and dilution rates obtained from the percentage enhancement maps agreed within 15% independent of not only the depth and the size of the inclusion but also the presence of a non-scattering region in the background. Although no internal structural information was used in these phantom studies, it may be necessary to use it for small objects buried deep in tissue. However, the different contrast mechanisms of optical and other imaging modalities as well as imperfect co-registration between both modalities may lead to potential errors in the structural a priori. Therefore, the effect of erroneous selection of structural priors was investigated as the final step. Again, the injection and dilution rates obtained from the percentage enhancement maps were also immune to the systematic errors introduced by erroneous selection of the structural priors, e.g. choosing the diameter of the inclusion 20% smaller increased the peak enhancement 60% but changed the injection and dilution rates only less than 10%. PMID:19841515

  11. Multispecies diffusion models: A study of uranyl species diffusion

    NASA Astrophysics Data System (ADS)

    Liu, Chongxuan; Shang, Jianying; Zachara, John M.

    2011-12-01

    Rigorous numerical description of multispecies diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication in imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multispecies diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multispecies diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multispecies U(VI) diffusion under a steady state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that for multispecies U(VI) diffusion under transient chemical conditions, a fully coupled diffusion model could be well approximated by a component-based diffusion model when the diffusion coefficient for each chemical component was properly selected. The component-based diffusion model considers the difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be enforced, if necessary, by adding a secondary migration term resulting from model simplification. The effect of ion activity coefficient gradients on multispecies diffusion is also discussed. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from U.S. Department of Energy's Hanford 300A, where intragranular diffusion is a rate-limiting process controlling U(VI) adsorption and desorption. The grain-scale reactive diffusion model was able to describe U(VI) adsorption/desorption kinetics that had been previously described using a semiempirical, multirate model. Compared with the multirate model, the diffusion models have the advantage to provide spatiotemporal speciation evolution within the diffusion domains.

  12. Microstructural evolution in the partial transient liquid phase diffusion bonding of Zircaloy-4 to stainless steel 321 using active titanium filler metal

    NASA Astrophysics Data System (ADS)

    Atabaki, M. Mazar

    2010-11-01

    Microstructural evolution of the partial transient liquid phase diffusion bonded Zircaloy-4 and stainless steel 321 using an active Ti-base interlayer were studied at different temperatures. Additionally, simple analytical models were developed to predict the evolution of the interlayer and intermetallics during the bonding operation. Bonds were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Precision measurement of the interlayer width was made as a function of the bonding temperature. The liquid film migration occurred as a result of chemical solubility differences between the stable and metastable phases. The formation and growth model of the intermetallic compounds at the interfaces of Zircaloy-4/Ti-base interlayer and stainless steel 321/Ti-base interlayer for controlling the bonding process was studied considering the diffusion kinetics and the thermodynamics. The evolution of the interlayer thickness indicated a good agreement between the calculation and experimental measurement. It was also demonstrated that the low isothermal solidification kinetic was not only due to the enrichment of the liquid phase with the base alloying elements such as Ti and Zr, but also the reduction of solid solubility limit of Cu in the base alloys contributed to the reduction of isothermal solidification kinetic.

  13. Chlorine Diffusion in Uranium Dioxide: Thermal Effects versus Radiation Enhanced Effects

    SciTech Connect

    Pipon, Yves; Moncoffre, Nathalie; Bererd, Nicolas; Jaffrezic, Henri; Raimbault, Louis; Scheidegger, Andre M.; Carlot, Gaelle

    2007-07-01

    Chlorine is present as an impurity in the UO{sub 2} nuclear fuel. {sup 35}Cl is activated into {sup 36}Cl by thermal neutron capture. In case of interim storage or deep geological disposal of the spent fuel, this isotope is known to be able to contribute significantly to the instant release fraction because of its mobile behavior and its long half life (around 300000 years). It is therefore important to understand its migration behavior within the fuel rod. During reactor operation, chlorine diffusion can be due to thermally activated processes or can be favoured by irradiation defects induced by fission fragments or alpha decay. In order to decouple both phenomena, we performed two distinct experiments to study the effects of thermal annealing on the behaviour of chlorine on one hand and the effects of the irradiation with fission products on the other hand. During in reactor processes, part of the {sup 36}Cl may be displaced from its original position, due to recoil or to collisions with fission products. In order to study the behavior of the displaced chlorine, {sup 37}Cl has been implanted into sintered depleted UO{sub 2} pellets (mean grain size around 18 {mu}m). The spatial distribution of the implanted and pristine chlorine has been analyzed by SIMS before and after treatment. Thermal annealing of {sup 37}Cl implanted UO{sub 2} pellets (implantation fluence of 10{sup 13} ions.cm{sup -2}) show that it is mobile from temperatures as low as 1273 K (E{sub a}=4.3 eV). The irradiation with fission products (Iodine, E=63.5 MeV) performed at 300 and 510 K, shows that the diffusion of chlorine is enhanced and that a thermally activated contribution is preserved (E{sub a}=0.1 eV). The diffusion coefficients measured at 1473 K and under fission product irradiation at 510 K are similar (D = 3.10{sup -14} cm{sup 2}.s{sup -1}). Considering in first approximation that the diffusion length L can be expressed as a function of the diffusion coefficient D and time t by : L=(Dt)1/2, the diffusion distance after 3 years is L=17 {mu}m. It results that there is a great probability for the chlorine contained in the UO{sub 2} grains to have reached the grain boundaries after 3 years, in the core of the fuel rod as well as at its periphery. Moreover, diffusion and concentration of chlorine at grain boundaries has been evidenced using SIMS mapping. Our results indicate therefore, that, during reactor operation and after, the majority of {sup 36}Cl is likely to have moved to grain boundaries, rim and gap. This fraction might then significantly contribute to the rapid or instant release of chlorine. This could have important consequences for safety assessment. During reactor operation, chlorine ({sup 35}Cl), an impurity of the nuclear fuel, is activated into {sup 36}Cl, a long lived mobile isotope. Because of its long half life and its mobility, this isotope may contribute significantly to the instant release fraction under disposal conditions. Thermal annealing of Cl implanted UO{sub 2} sintered pellets show that it is mobile from temperatures as low as 1273 K (E{sub a} = 4.3 eV). Chlorine diffusion induced by irradiation with fission products preserves a thermally activated contribution. The radiation induced defects significantly enhance chlorine migration. (authors)

  14. Enhanced mossy fiber sprouting and synapse formation in organotypic hippocampal cultures following transient domoic acid excitotoxicity.

    PubMed

    Prez-Gmez, Anabel; Tasker, R Andrew

    2014-05-01

    We have previously reported evidence of BDNF upregulation and increased neurogenesis in rat organotypic hippocampal slice cultures (OHSC) after a transient excitotoxic injury to the hippocampal CA1 area induced by low concentrations of the AMPA/kainate receptor agonist domoic acid (DOM). The changes observed in OHSC were consistent with observations in vivo, where low concentrations of DOM administered to rats during perinatal development caused increased BDNF and TrkB expression in the resulting adult animals. The in vivo low dose-DOM treatment also results in permanent alterations in hippocampal structure and function, including abnormal formation of dentate granule cell axons projecting to area CA3 (mossy fiber sprouting). Our objective in the current study is to determine if low concentrations of DOM induce mossy fiber sprouting and/or synaptogenesis in OHSC in order to facilitate future studies on the mechanisms of structural hippocampal plasticity induced by DOM. We report herein that application of a low concentration of DOM (2 ?M) for 24 h followed by recovery induced a significant increase in the expression of the mossy fiber marker ZnT3 that progressed over time in culture. The DOM insult (2 ?M, 24 h) also resulted in a significant upregulation of both the presynaptic marker synaptophysin and the postsynaptic marker PSD-95. All of the observed effects were fully antagonized by co-administration of the AMPA/kainate antagonists CNQX or NBQX but only partly by the NMDA antagonist CPP and not by the calcium channel blocker nifedipine. We conclude that exposure of OHSC to concentrations of DOM below those required to induce permanent neurotoxicity can induce a progressive change in hippocampal structure that can effectively model DOM effects in vivo. PMID:24347374

  15. Diffuse Infantile Hepatic Hemangioendothelioma With Early Central Enhancement in an Adult: A Case Report of CT and MRI Findings.

    PubMed

    Dong, Aisheng; Dong, Hui; Zuo, Changjing; He, Tianlin

    2015-12-01

    Infantile hepatic hemangioendothelioma (IHH) is the most common vascular tumor of the liver in infancy. Adult with IHH is extremely rare. We presented a diffuse IHH in an adult patient with computed tomography (CT) and magnetic resonance image (MRI) findings.A 39-year-old man was admitted to our hospital because of a 2-year history of abnormal liver function tests and a 7-day history of jaundice. Physical examination revealed enlarged liver. Unenhanced abdominal CT showed enlargement of the liver with diffuse hypodensity. Enhanced CT on the arterial phase revealed multiple centrally enhanced lesions diffusely involved the enlarged liver. The enhanced areas of the lesions became larger on the portal phase and all the lesions became homogeneous enhanced on the delayed phase. These lesions showed heterogeneously hyperintense on T2-weighted image, hypointense on T1-weighted image, and early centrally enhanced on dynamic gadolinium-enhanced MRI, with complete tumor enhancement after 180?s. The patient underwent orthotopic liver transplantation. IHH type 2 was confirmed by pathology. The patient died of tumor recurrence in the liver 4 months after transplantation.Unlike the previously described imaging appearances of IHH, this case showed diffuse nodules with early central enhancement on CT and MRI. Considering the importance of the ability to differentiate IHH from other hepatic tumors, radiologists should be aware of these imaging appearances to establish knowledge of the entire spectrum of IHH. PMID:26705232

  16. Ultralarge transient optical gain from tensile-strained, n-doped germanium on silicon by spin-on dopant diffusion

    NASA Astrophysics Data System (ADS)

    Xu, Xuejun; Wang, Xiaoxin; Nishida, Keisuke; Takabayashi, Koki; Sawano, Kentarou; Shiraki, Yasuhiro; Li, Haofeng; Liu, Jifeng; Maruizumi, Takuya

    2015-09-01

    The direct band gap optical gain of tensile-strained, highly n-doped germanium on silicon is investigated by femtosecond ultrafast transmittance spectroscopy. A germanium film with 0.22% tensile strain is grown on a silicon substrate by using molecular beam epitaxy. An activated doping concentration up to 4 1019 cm-3 is achieved by phosphorus diffusion from a spin-on dopant source. The transmittance of the germanium film is clearly increased upon increasing the pump power. A peak optical gain of up to 5300 cm-1 around 1.7 m and a gain spectrum broader than 300 nm are obtained. These results show a simple yet promising way to realize gain medium for monolithic-integrated germanium lasers.

  17. 1,25 (OH)2D3 enhances PTH-induced Ca2+ transients in preosteoblasts by activating L-type Ca2+ channels

    NASA Technical Reports Server (NTRS)

    Li, W.; Duncan, R. L.; Karin, N. J.; Farach-Carson, M. C.

    1997-01-01

    We previously demonstrated electrophysiologically that 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] shifts the activation threshold of L-type Ca2+ channels in osteoblasts toward the resting potential and prolongs mean open time. Presently, we used single-cell Ca2+ imaging to study the combined effects of 1,25(OH)2D3 and parathyroid hormone (PTH) during generation of Ca2+ transients in fura 2-loaded MC3T3-E1 cells. Pretreatment with 1,25(OH)2D3 concentrations, which alone did not produce Ca2+ transients, consistently enhanced Ca2+ responses to PTH. Enhancement was dose dependent over the range of 1 to 10 nM and was blocked by pretreatment with 5 microM nitrendipine during pretreatment. A 1,25(OH)2D3 analog that activates L-type channels and shifts their activation threshold also enhanced PTH responses. In contrast, an analog devoid of membrane Ca2+ effects did not enhance PTH-induced Ca2+ transients. The PTH-induced Ca2+ transient involved activation of a dihydropyridine-insensitive cation channel that was inhibited by Gd3+. Together, these data suggest that 1,25(OH)2D3 increases osteoblast responsiveness to PTH through rapid modification of L-type Ca2+ channel gating properties, whose activation enhances Ca2+ entry through other channels such as the PTH-responsive, Gd(3+)-sensitive cation channel.

  18. Application of a modified flux-coupling type superconducting fault current limiter to transient performance enhancement of micro-grid

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Zheng, Feng; Deng, Changhong; Li, Shichun; Li, Miao; Liu, Hui; Zhu, Lin; Guo, Fang

    2015-11-01

    Concerning the application and development of a micro-grid system which is designed to accommodate high penetration of intermittent renewable resources, one of the main issues is related to an increase in the fault-current level. It is crucial to ensure the micro-grid's operational stability and service reliability when a fault occurs in the main network. In this paper, our research group suggests a modified flux-coupling type superconducting fault current limiter (SFCL) to enhance the transient performance of a typical micro-grid system. The SFCL is installed at the point of common coupling (PCC) between the main network and the micro-grid, and it is expected to actively improve the micro-grid's fault ride-through capability. And for some specific faults, the micro-grid should disconnect from the main network, and the SFCL's contribution is to make the micro-grid carry out a smooth transition between its grid-connected and islanded modes. Related theory derivation, technical discussion and simulation analysis are performed. From the demonstrated results, applying the SFCL can effectively limit the fault current, maintain the power balance, and enhance the voltage and frequency stability of the micro-grid.

  19. Measurement of large spiral and target waves in chemical reaction-diffusion-advection systems: turbulent diffusion enhances pattern formation.

    PubMed

    von Kameke, A; Huhn, F; Muuzuri, A P; Prez-Muuzuri, V

    2013-02-22

    In the absence of advection, reaction-diffusion systems are able to organize into spatiotemporal patterns, in particular spiral and target waves. Whenever advection is present that can be parametrized in terms of effective or turbulent diffusion D(*), these patterns should be attainable on a much greater, boosted length scale. However, so far, experimental evidence of these boosted patterns in a turbulent flow was lacking. Here, we report the first experimental observation of boosted target and spiral patterns in an excitable chemical reaction in a quasi-two-dimensional turbulent flow. The wave patterns observed are ~50 times larger than in the case of molecular diffusion only. We vary the turbulent diffusion coefficient D(*) of the flow and find that the fundamental Fisher-Kolmogorov-Petrovsky-Piskunov equation, v(f) proportional sqrt[D(*)], for the asymptotic speed of a reactive wave remains valid. However, not all measures of the boosted wave scale with D(*) as expected from molecular diffusion, since the wave fronts turn out to be highly filamentous. PMID:23473206

  20. A finite element simulation on transient large deformation and mass diffusion in electrodes for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    An, Yonghao; Jiang, Hanqing

    2013-10-01

    Lithium-ion batteries have attracted great deal of attention recently. Silicon is one of the most promising anode materials for high-performance lithium-ion batteries, due to its highest theoretical specific capacity. However, the short lifetime confined by mechanical failure in the silicon anode is now considered to be the biggest challenge in desired applications. High stress induced by the huge volume change due to lithium insertion/extraction is the main reason underlying this problem. Some theoretical models have been developed to address this issue. In order to properly implement these models, we develop a finite element based numerical method using a commercial software package, ABAQUS, as a platform at the continuum level to study fully coupled large deformation and mass diffusion problem. Using this method, large deformation, elasticity-plasticity of the electrodes, various spatial and temporal conditions, arbitrary geometry and dimension could be fulfilled. The interaction between anode and other components of the lithium ion batteries can also be studied as an integrated system. Several specific examples are presented to demonstrate the capability of this numerical platform.

  1. Calcium transient evoked by TRPV1 activators is enhanced by tumor necrosis factor-? in rat pulmonary sensory neurons

    PubMed Central

    Hu, Youmin; Gu, Qihai; Lin, Ruei-Lung; Kryscio, Richard

    2010-01-01

    TNF?, a proinflammatory cytokine known to be involved in the pathogenesis of allergic asthma, has been shown to induce hyperalgesia in somatic tissue via a sensitizing effect on dorsal root ganglion neurons expressing transient receptor potential vanilloid type 1 receptor (TRPV1). Because TRPV1-expressing pulmonary sensory neurons play an important role in regulating airway function, this study was carried out to determine whether TNF? alters the sensitivity of these neurons to chemical activators. Responses of isolated nodose and jugular ganglion neurons innervating the rat lungs were determined by measuring the transient increase in intracellular Ca2+ concentration ([Ca2+]i). Our results showed the following. 1) A pretreatment with TNF? (50 ng/ml) for ?24 h increased significantly the peak ?[Ca2+]i evoked by capsaicin (Cap) in these neurons. A pretreatment with the same concentration of TNF? for a longer duration (?48 h) did not further increase the response, but pretreatment for a shorter duration (1 h) or with a lower concentration (25 ng/ml, 24 h) failed to enhance the Cap sensitivity. 2) The same TNF? pretreatment also induced similar but less pronounced and less uniform increases in the responses to acid (pH 6.55.5), 2-aminoethoxydiphenyl borate (2-APB), a common activator of TRPV1, V2, and V3 channels, and allyl isothiocyanate (AITC), a selective activator of TRPA1 channel. 3) In sharp contrast, the responses to ATP, ACh, and KCl were not affected by TNF?. 4) The TNF?-induced hypersensitivity to Cap was not prevented by pretreatment with indomethacin (30 ?M). 5) The immunoreactivity to both TNF receptor types 1 and 2 were detected in rat vagal pulmonary sensory neurons. In conclusion, prolonged treatment with TNF? induces a pronounced potentiating effect on the responses of isolated pulmonary sensory neurons to TRPV1 activators. This action of TNF? may contribute in part to the airway hyperresponsiveness induced by this cytokine. PMID:20639352

  2. Enhanced-Transient Expression of Hepatitis C Virus Core Protein in Nicotiana tabacum, a Protein With Potential Clinical Applications

    PubMed Central

    Mohammadzadeh, Sara; Khabiri, Alireza; Roohvand, Farzin; Memarnejadian, Arash; Salmanian, Ali Hatef; Ajdary, Soheila; Ehsani, Parastoo

    2014-01-01

    Background: Hepatitis C virus (HCV) is major cause of liver cirrhosis in humans. HCV capsid (core) protein (HCVcp) is a highly demanded antigen for various diagnostic, immunization and pathogenesis studies. Plants are considered as an expression system for producing safe and inexpensive biopharmaceutical proteins. Although invention of transgenic (stable) tobacco plants expressing HCVcp with proper antigenic properties was recently reported, no data for “transient-expression” that is currently the method of choice for rapid, simple and lower-priced protein expression in plants is available for HCVcp. Objectives: The purpose of this study was to design a highly codon-optimized HCVcp gene for construction of an efficient transient-plant expression system for production of HCVcp with proper antigenic properties in a regional tobacco plant (Iranian Jafarabadi-cultivar) by evaluation of different classes of vectors and suppression of gene-silencing in tobacco. Materials and Methods: A codon-optimized gene encoding the Kozak sequence, 6xHis-tag, HCVcp (1-122) and KDEL peptide in tandem (from N- to C-terminal) was designed and inserted into potato virus-X (PVX) and classic pBI121 binary vectors in separate cloning reactions. The resulted recombinant plasmids were transferred into Agrobacterium tumefaciens and vacuum infiltrated into tobacco leaves. The effect of gene silencing suppressor P19 protein derived from tomato bushy stunt virus on the expression yield of HCVcp by each construct was also evaluated by co-infiltration in separate groups. The expressed HCVcp was evaluated by dot and western blotting and ELISA assays. Results: The codon-optimized gene had an increased adaptation index value (from 0.65 to 0.85) and reduced GC content (from 62.62 to 51.05) in tobacco and removed the possible deleterious effect of “GGTAAG” splice site in native HCVcp. Blotting assays via specific antibodies confirmed the expression of the 15 kDa HCVcp. The expression level of HCVcp was enhanced by 4-5 times in P19 co-agroinfiltrated plants with better outcomes for PVX, compared to pBI121 vector (0.022% versus 0.019% of the total soluble protein). The plant-derived HCVcp (pHCVcp) could properly identify the HCVcp antibody in HCV-infected human sera compared to Escherichia coli-derived HCVcp (eHCVcp), indicating its potential for diagnostic/immunization applications. Conclusions: By employment of gene optimization strategies, use of viral-based vectors and suppression of plant-derived gene silencing effect, efficient transient expression of HCVcp in tobacco with proper antigenic properties could be possible. PMID:25598788

  3. Laser imaging of chemistry-flowfield interactions: Enhanced soot formation in time-varying diffusion flames

    SciTech Connect

    Harrington, J.E.; Shaddix, C.R.; Smyth, K.C.

    1994-12-31

    Models of detailed flame chemistry and soot formation are based upon experimental results obtained in steady, laminar flames. For successful application of these descriptions to turbulent combustion, it is instructive to test predictions against measurements in time-varying flowfields. This paper reports the use of optical methods to examine soot production and oxidation processes in a co-flowing, axisymmetric CH{sub 4}/air diffusion flame in which the fuel flow rate is acoustically forced to create a time-varying flowfield. For a particular forcing condition in which tip clipping occurs (0.75 V loudspeaker excitation), elastic scattering of vertically polarized light from the soot particles increases by nearly an order of magnitude with respect to that observed for a steady flame with the same mean fuel flow rate. The visible flame luminosity and laser-induced fluorescence attributed to polycyclic aromatic hydrocarbons (PAH) are also enhanced. Peak soot volume fractions, as measured by time-resolved laser extinction/tomography at 632.8 and 454.5 nm and calibrated laser-induced incandescence (LII), show a factor of 4--5 enhancement in this flickering flame. The LII method is found to track the soot volume fraction closely and to give better signal-to-noise than the extinction measurements in both the steady and time-varying flowfields. A Mie analysis suggests that most of the enhanced soot production results from the formation of larger particles in the time-varying flowfield.

  4. Performance Enhancement of Pharmacokinetic Diffuse Fluorescence Tomography by Use of Adaptive Extended Kalman Filtering

    PubMed Central

    Wang, Xin; Wu, Linhui; Yi, Xi; Zhang, Yanqi; Zhang, Limin; Zhao, Huijuan; Gao, Feng

    2015-01-01

    Due to both the physiological and morphological differences in the vascularization between healthy and diseased tissues, pharmacokinetic diffuse fluorescence tomography (DFT) can provide contrast-enhanced and comprehensive information for tumor diagnosis and staging. In this regime, the extended Kalman filtering (EKF) based method shows numerous advantages including accurate modeling, online estimation of multiparameters, and universal applicability to any optical fluorophore. Nevertheless the performance of the conventional EKF highly hinges on the exact and inaccessible prior knowledge about the initial values. To address the above issues, an adaptive-EKF scheme is proposed based on a two-compartmental model for the enhancement, which utilizes a variable forgetting-factor to compensate the inaccuracy of the initial states and emphasize the effect of the current data. It is demonstrated using two-dimensional simulative investigations on a circular domain that the proposed adaptive-EKF can obtain preferable estimation of the pharmacokinetic-rates to the conventional-EKF and the enhanced-EKF in terms of quantitativeness, noise robustness, and initialization independence. Further three-dimensional numerical experiments on a digital mouse model validate the efficacy of the method as applied in realistic biological systems. PMID:26089975

  5. Dramatic performance enhancement of evanescent-wave multimode fiber fluorometer using non-Lambertian light diffuser.

    PubMed

    Ma, Jianjun; Bock, Wojtek J

    2007-12-10

    To enhance the performance of an evanescent-wave (EW) based sensor, efforts are usually made to modify the sensor architecture rather than the excitation source. In this paper, we theoretically examine the role of meridian and skew rays under total internal reflection (TIR) as well as tunneling rays with the emphasis on sensor performance. Our further investigation indicates that the intensity profile of the light source enormously influences the EW power, and thus the collectable fluorescent emission level as well. A non-Lambertian fiber-optic side-emitting diffuser (FOSED) is proposed and experimentally verified, revealing that a proper alignment of this FOSED can dramatically improve the signal quality and reduce the level of stray excitation light. In particular, the adoption of a FOSED or other light diffusers with similar output profiles will ensure that the excitation power is used more efficiently, suggesting a lower demand on the excitation source power level, and the performance of the stray light filter and detector. The superiority of this innovation is further addressed by comparing it with a long period grating (LPG) fiber-optic sensor, which claims highly efficient core to cladding mode coupling. This study presents a new concept for the construction of a high-performance and cost-effective EW-based sensor system. PMID:19550936

  6. Wavelet-based multiscale anisotropic diffusion for speckle reduction and edge enhancement

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Niu, Ruiqing; Wu, Ke; Yu, Xin

    2009-10-01

    In order to improve signal-to-noise ratio (SNR) and image quality, this paper introduces a wavelet-based multiscale anisotropic diffusion algorithm to remove speckle noise and enhance edges. In our algorithm, we use the tool of wavelet to construct a linear scale-space for the speckle image. Due to the smoothing functionality of the scaling function, the wavelet-based multiscale representation of the speckle image is much more stationary than the raw speckle image. Noise is mostly located in the finest scale and tends to decrease as the scale increases. Furthermore, a robust speckle reduction anisotropic diffusion (SRAD) is to be proposed and we perform the improved SRAD on the stationary scale-space rather than on the rough speckle image domain. Qualitative experiments based on a speckle Synthetic aperture radar (SAR) image show the elegant characteristics of edge-preserving filtering versus the traditional adaptive filters. Quantitative analyses, based on the first order statistics and Equivalent Number of Looks, confirm the validity and effectiveness of the proposed algorithm.

  7. Diffusion coefficients and dissociation constants of enhanced green fluorescent protein binding to free standing membranes.

    PubMed

    Thomas, Franziska A; Visco, Ilaria; Petrek, Zden?k; Heinemann, Fabian; Schwille, Petra

    2015-12-01

    Recently, a new and versatile assay to determine the partitioning coefficient [Formula: see text] as a measure for the affinity of peripheral membrane proteins for lipid bilayers was presented in the research article entitled, "Introducing a fluorescence-based standard to quantify protein partitioning into membranes" [1]. Here, the well-characterized binding of hexahistidine-tag (His6) to NTA(Ni) was utilized. Complementarily, this data article reports the average diffusion coefficient [Formula: see text] of His6-tagged enhanced green fluorescent protein (eGFP-His6) and the fluorescent lipid analog ATTO-647N-DOPE in giant unilamellar vesicles (GUVs) containing different amounts of NTA(Ni) lipids. In addition, dissociation constants [Formula: see text] of the NTA(Ni)/eGFP-His6 system are reported. Further, a conversion between [Formula: see text] and [Formula: see text] is provided. PMID:26587560

  8. Shape-parameterized diffuse optical tomography holds promise for sensitivity enhancement of fluorescence molecular tomography

    PubMed Central

    Wu, Linhui; Wan, Wenbo; Wang, Xin; Zhou, Zhongxing; Li, Jiao; Zhang, Limin; Zhao, Huijuan; Gao, Feng

    2014-01-01

    A fundamental approach to enhancing the sensitivity of the fluorescence molecular tomography (FMT) is to incorporate diffuse optical tomography (DOT) to modify the light propagation modeling. However, the traditional voxel-based DOT has been involving a severely ill-posed inverse problem and cannot retrieve the optical property distributions with the acceptable quantitative accuracy and spatial resolution. Although, with the aid of an anatomical imaging modality, the structural-prior-based DOT method with either the hard- or soft-prior scheme holds promise for in vivo acquiring the optical background of tissues, the low robustness of the hard-prior scheme to the segmentation error and inferior performance of the soft-prior one in the quantitative accuracy limit its further application. We propose in this paper a shape-parameterized DOT method for not only effectively determining the regional optical properties but potentially achieving reasonable structural amelioration, lending itself to FMT for comparably improved recovery of fluorescence distribution. PMID:25360379

  9. {sup 1}H relaxation enhancement induced by nanoparticles in solutions: Influence of magnetic properties and diffusion

    SciTech Connect

    Kruk, D.; Korpała, A.; Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków ; Taheri, S. Mehdizadeh; Förster, S.; Kozłowski, A.; Rössler, E. A.

    2014-05-07

    Magnetic nanoparticles that induce nuclear relaxation are the most promising materials to enhance the sensitivity in Magnetic Resonance Imaging. In order to provide a comprehensive understanding of the magnetic field dependence of the relaxation enhancement in solutions, Nuclear Magnetic Resonance {sup 1}H spin-lattice relaxation for decalin and toluene solutions of various Fe{sub 2}O{sub 3} nanoparticles was investigated. The relaxation experiments were performed in a frequency range of 10 kHz–20 MHz by applying Field Cycling method, and in the temperature range of 257–298 K, using nanoparticles differing in size and shape: spherical – 5 nm diameter, cubic – 6.5 nm diameter, and cubic – 9 nm diameter. The relaxation dispersion data were interpreted in terms of a theory of nuclear relaxation induced by magnetic crystals in solution. The approach was tested with respect to its applicability depending on the magnetic characteristics of the nanocrystals and the time-scale of translational diffusion of the solvent. The role of Curie relaxation and the contributions to the overall {sup 1}H spin-lattice relaxation associated with the electronic spin-lattice and spin-spin relaxation was thoroughly discussed. It was demonstrated that the approach leads to consistent results providing information on the magnetic (electronic) properties of the nanocrystals, i.e., effective electron spin and relaxation times. In addition, features of the {sup 1}H spin-lattice relaxation resulting from the electronic properties of the crystals and the solvent diffusion were explained.

  10. Selective-diffusion regularization for enhancement of microcalcifications in digital breast tomosynthesis reconstruction

    SciTech Connect

    Lu Yao; Chan, Heang-Ping; Wei Jun; Hadjiiski, Lubomir M.

    2010-11-15

    Purpose: Digital breast tomosynthesis (DBT) has been shown to improve mass detection. Detection of microcalcifications is more challenging because of the large breast volume to be searched for subtle signals. The simultaneous algebraic reconstruction technique (SART) was found to provide good image quality for DBT, but the image noise is amplified with an increasing number of iterations. In this study, the authors developed a selective-diffusion (SD) method for noise regularization with SART to improve the contrast-to-noise ratio (CNR) of microcalcifications in the DBT slices for human or machine detection. Methods: The SD method regularizes SART reconstruction during updating with each projection view. Potential microcalcifications are differentiated from the noisy background by estimating the local gradient information. Different degrees of regularization are applied to the signal or noise classes, such that the microcalcifications will be enhanced while the noise is suppressed. The new SD method was compared to several current methods, including the quadratic Laplacian (QL) method, the total variation (TV) method, and the nonconvex total p-variation (TpV) method for noise regularization with SART. A GE GEN2 prototype DBT system with a stationary digital detector was used for the acquisition of DBT scans at 21 angles in 3 deg. increments over a {+-}30 deg. range. The reconstruction image quality without regularization and that with the different regularization methods were compared using the DBT scans of an American College of Radiology phantom and a human subject. The CNR and the full width at half maximum (FWHM) of the line profiles of microcalcifications within the in-focus DBT slices were used as image quality measures. Results: For the comparison of large microcalcifications in the DBT data of the subject, the SD method resulted in comparable CNR to the nonconvex TpV method. Both of them performed better than the other two methods. For subtle microcalcifications, the SD method was superior to other methods in terms of CNR. In both the subject and phantom DBT data, for large microcalcifications, the FWHM of the SD method was comparable to that without regularization, which was wider than that of the TV type methods. For subtle microcalcifications, the SD method had comparable FWHM values to the TV type methods. All three regularization methods were superior to the QL method in terms of FWHM. Conclusions: The SART regularized by the selective-diffusion method enhanced the CNR and preserved the sharpness of microcalcifications. In comparison with three existing regularization methods, the selective-diffusion regularization was superior to the other methods for subtle microcalcifications.

  11. Transient diffusion, desorption, and reaction studies of cyclopropane and propylene with NaX and Eu/NaX zeolites

    SciTech Connect

    Efstathiou, A.M.; Suib, S.L.; Bennett, C.O. )

    1992-05-01

    The exchange of Eu[sup 3+] for Na[sup +] cations into the sodalite cages of X zeolite (Eu[sub 25]Na[sub 11]X) leads selectively to the isomerization reaction of cyclopropane to propylene. The latter reaction is catalyzed by Broensted acid sites with an apparent activation energy of 10.6 kcal/mol. Sorption measurements of cyclopropane and propylene with Eu/NaX and NaX zeolites at 40 C support the view that Na[sup +] cations might be considered as sites for sorption of these molecules. Force fields created by Eu[sub 4]O[sup 10+] present in Eu/NaX zeolite may affect sorption. On the other hand, Broensted acid sites in Eu/NaX enhance sorption of cyclopropane and propylene at 40 C. Chemisorption of propylene on the Broensted acid sites of Eu/NaX is reversible and may occur via a propylene carbenium cation intermediate. Small amounts of hexene are formed during this sorption. The amount of Broensted acid sites in the present Eu/NaX is at least 0.6 mmol/g cat.

  12. Microstructures and Mechanical Properties of Transient Liquid-Phase Diffusion-Bonded Ti3Al/TiAl Joints with TiZrCuNi Interlayer

    NASA Astrophysics Data System (ADS)

    Ren, H. S.; Xiong, H. P.; Pang, S. J.; Chen, B.; Wu, X.; Cheng, Y. Y.; Chen, B. Q.

    2016-04-01

    Transient liquid-phase diffusion bonding of Ti3Al-based alloy to TiAl intermetallics was conducted using Ti-13Zr-21Cu-9Ni (wt pct) interlayer foil. The joint microstructures were examined using a scanning electron microscope (SEM) equipped with an electron probe micro-analyzer (EPMA). The microhardness across the joint was measured and joint strengths were tested. The results show that the Ti3Al/TiAl joint mainly consists of Ti-rich phase, Ti2Al layer, α 2-Ti3Al band, and residual interlayer alloy dissolved with Al. The amount of residual interlayer at the central part of the joint is decreased with the increase of the bonding temperature, and meantime the Ti2Al and α 2-Ti3Al reaction bands close to the joined Ti3Al-based alloy become thickened gradually. Furthermore, the central part of the joint exhibits the maximum microhardness across the whole joint. The joints bonded at 1193 K (920 °C) for 600 seconds with a pressure of 2 MPa presented the maximum shear strength of 417 MPa at room temperature, and the strength of 234 MPa was maintained at 773 K (500 °C).

  13. Microstructures and Mechanical Properties of Transient Liquid-Phase Diffusion-Bonded Ti3Al/TiAl Joints with TiZrCuNi Interlayer

    NASA Astrophysics Data System (ADS)

    Ren, H. S.; Xiong, H. P.; Pang, S. J.; Chen, B.; Wu, X.; Cheng, Y. Y.; Chen, B. Q.

    2016-01-01

    Transient liquid-phase diffusion bonding of Ti3Al-based alloy to TiAl intermetallics was conducted using Ti-13Zr-21Cu-9Ni (wt pct) interlayer foil. The joint microstructures were examined using a scanning electron microscope (SEM) equipped with an electron probe micro-analyzer (EPMA). The microhardness across the joint was measured and joint strengths were tested. The results show that the Ti3Al/TiAl joint mainly consists of Ti-rich phase, Ti2Al layer, ? 2-Ti3Al band, and residual interlayer alloy dissolved with Al. The amount of residual interlayer at the central part of the joint is decreased with the increase of the bonding temperature, and meantime the Ti2Al and ? 2-Ti3Al reaction bands close to the joined Ti3Al-based alloy become thickened gradually. Furthermore, the central part of the joint exhibits the maximum microhardness across the whole joint. The joints bonded at 1193 K (920 C) for 600 seconds with a pressure of 2 MPa presented the maximum shear strength of 417 MPa at room temperature, and the strength of 234 MPa was maintained at 773 K (500 C).

  14. Management of Microbial Communities through Transient Disturbances Enhances the Functional Resilience of Nitrifying Gas-Biofilters to Future Disturbances.

    PubMed

    Cabrol, Léa; Poly, Franck; Malhautier, Luc; Pommier, Thomas; Lerondelle, Catherine; Verstraete, Willy; Lepeuple, Anne-Sophie; Fanlo, Jean-Louis; Roux, Xavier Le

    2016-01-01

    Microbial communities have a key role for the performance of engineered ecosystems such as waste gas biofilters. Maintaining constant performance despite fluctuating environmental conditions is of prime interest, but it is highly challenging because the mechanisms that drive the response of microbial communities to disturbances still have to be disentangled. Here we demonstrate that the bioprocess performance and stability can be improved and reinforced in the face of disturbances, through a rationally predefined strategy of microbial resource management (MRM). This strategy was experimentally validated in replicated pilot-scale nitrifying gas-biofilters, for the two steps of nitrification. The associated biological mechanisms were unraveled through analysis of functions, abundances and community compositions for the major actors of nitrification in these biofilters, that is, ammonia-oxidizing bacteria (AOB) and Nitrobacter-like nitrite-oxidizers (NOB). Our MRM strategy, based on the application of successive, transient perturbations of increasing intensity, enabled to steer the nitrifier community in a favorable way through the selection of more resistant AOB and NOB sharing functional gene sequences close to those of, respectively, Nitrosomonas eutropha and Nitrobacter hamburgensis that are well adapted to high N load. The induced community shifts resulted in significant enhancement of nitrification resilience capacity following the intense perturbation. PMID:26651080

  15. Enhanced plasmid DNA utilization in transiently transfected CHO-DG44 cells in the presence of polar solvents.

    PubMed

    Rajendra, Yashas; Balasubramanian, Sowmya; Kiseljak, Divor; Baldi, Lucia; Wurm, Florian M; Hacker, David L

    2015-11-01

    Although the protein yields from transient gene expression (TGE) with Chinese hamster ovary (CHO) cells have recently improved, the amount of plasmid DNA (pDNA) needed for transfection remains relatively high. We describe a strategy to reduce the pDNA amount by transfecting CHO-DG44 cells with 0.06 ?g pDNA/10(6) cells (10% of the optimal amount) in the presence of nonspecific (filler) DNA and various polar solvents including dimethylsufoxide, dimethyl formamide, acetonitrile, dimethyl acetamide (DMA), and hexamethyl phosphoramide (HMP). All of the polar solvents with the exception of HMP increased the production of a recombinant antibody in comparison to the untreated control transfection. In the presence of 0.25% DMA, the antibody yield in a 7-day batch culture was 500 mg/L. This was fourfold higher than the yield from the untreated control transfection. Mechanistic studies revealed that the polar solvents did not affect polyethylenimine-mediated pDNA delivery into cells or nuclei. The steady-state transgene mRNA level was elevated in the presence of each of the polar solvents tested, while the transgene mRNA half-life remained the same. These results indicated that the polar solvents enhanced transgene transcription. When screening a panel of recombinant antibodies and Fc-fusion proteins for production in the presence of the polar solvents, the highest increase in yield was observed following DMA addition for 11 of the 12 proteins. These results are expected to enhance the applicability of high-yielding TGE processes with CHO-DG44 cells by decreasing the amount of pDNA required for transfection. 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1571-1578, 2015. PMID:26260195

  16. Application of 17% EDTA Enhances Diffusion of (45)Ca-labeled OH(-) and Ca(2+) in Primary Tooth Root Canal.

    PubMed

    Ximenes, Marcos; Cavalcanti Taguchi, Carolina Mayumi; Triches, Thaisa Cezaria; Sartori, Neimar; Pereira Dias, Luis Alberto; de Araujo, Elaine Bortoleti; Cardoso, Mariane

    2016-01-01

    Proper cleaning of the root canal is key to the success of endodontic treatment as it allows more effective diffusion of medication throughout the dentinal tubules. The aim of this in vitro study was to investigate the efficacy of 17% ethylenediaminetetraacetic acid (EDTA) in enhancing diffusion of hydroxyl (OH(-)) and calcium ions (Ca(2+)) throughout the root canal in primary teeth. The canals of 25 primary tooth roots were cleaned with endodontic files and 1% sodium hypochlorite. Three groups (G) were then established: GI, in which final irrigation was performed with 1% sodium hypochlorite; GII, in which 17% EDTA was used; and GIII, in which no irrigation was performed. The roots canals in GI and GII were filled with a calcium hydroxide-based paste labeled with the radioisotope calcium-45. Diffusion of OH(-) was detected with pH strips and Ca(2+) analyzed by measuring radioactivity in counts per min. Group II differed statistically from the other groups in diffusion of OH(-) at 24 hr (p<0.05), but no significant difference among groups was found at the day 7 evaluation; GII also differed statistically from the other groups in diffusion of Ca(2+) at 24 hr (p<0.05). These results suggest that application of 17% EDTA in primary tooth enhances diffusion of OH(-) and Ca(2+). PMID:26961333

  17. Radiation-enhanced diffusion and defect production during ion irradiation of MgO and Al

    NASA Astrophysics Data System (ADS)

    van Sambeek, Andrew I.

    1997-12-01

    Point defect production and radiation enhanced diffusion measurements have been conducted on single crystal oxides MgO and Al2O3. Point defect concentrations are obtained from measurements of the in-plane strain on cantilevered beam samples using bending analysis. The deflection of the sample is proportional to the stress in the irradiated layer, and is measured by the change in capacitance between the free end of the irradiated sample and a reference electrode. Elasticity theory is used to calculate the strain from the measured in-plane stress. Point defect concentrations are obtained by dividing the volumetric strain by the Frenkel pair relaxation volume. Saturation values of 0.8 to 1.2% were obtained for 1.0 MeV Ne, Ar and Kr irradiations of MgO. Defect production efficiencies of 0.26, 0.24, 0.19 and 0.44 were obtained for low fluence Kr, Ar, Ne, and He irradiation of MgO. Defect production efficiencies for low fluence 1.0 MeV Kr and Ne irradiation of Al2O3 were 0.17 and 0.24. Radiation enhanced diffusion of O18, Ca and Zn buried tracer layers in MBE grown MgO was measured following irradiation with either 2.0 MeV Kr or 1.0 MeV Ne, He or H from 30 to 1500oC. This represents the first reported RED measurements on an oxide system. Ion beam mixing at 30oC on both sublattices was approximately 1.0 to 5.0 A5/ev indicating the temperature independent mixing (ballistic mixing) is produced only by direct recoil and cascade events and that thermal spikes are not significant. D red was proportional to the square root of the irradiation flux with an activation enthalpy of 1.2 eV for diffusion on the anion sublattice from 1350 to 1500oC. The flux dependence is characteristic of kinetics in the recombination limited regime; accordingly, the measured activation enthalpy of 1.2 eV is identified as one-half the migration enthalpy of the anion vacancy. This assignment agrees with the predicted anion vacancy migration enthalpy of 2.1 to 2.4 eV. Between 1150oC and 1350oC an apparent activation enthalpy of 4.1 eV was measured. This enthalpy was attributed to vacancy clustering reactions. Measurements on the cation sublattice were conducted at temperatures below 900oC. At higher temperatures excessive thermal diffusion from extrinsic vacancies stemming from trivalent impurities prevented measurements of RED.

  18. A stochastic model for induced seismicity based on non-linear pressure diffusion and irreversible permeability enhancement

    NASA Astrophysics Data System (ADS)

    Gischig, Valentin S.; Wiemer, Stefan

    2013-08-01

    During deep reservoir engineering projects, in which permeability is enhanced by high-pressure fluid injection, seismicity is invariably induced, posing nuisance to the local population and a potential hazard for structures. Hazard and risk assessment tools that can operate in real-time during reservoir stimulation depend on the ability to efficiently model induced seismicity. We here propose a novel modelling approach based on a combination of physical considerations and stochastic elements. It can model a large number of synthetic event catalogues, and at the same time is constrained by observations of hydraulic behaviour in the injection well. We model fluid flow using non-linear pressure diffusion equations, in which permeability increases irreversibly above a prescribed pressure threshold. The transient pressure field is used to trigger events at so-called `seed points' that are distributed randomly in space and represent potential earthquake hypocentres. We assign to each seed point a differential stress based on the mean estimates of the in situ stress field and add a normal distributed random value. Assuming a fault orientation with respect to the stress field and a Mohr-Coulomb failure criterion, we evaluate at each time step, if a seed point is triggered through a pressure increase. A negative proportional relationship between differential stress and b values is further assumed as observed from tectonic earthquakes and in laboratory experiments. As soon as an event is triggered, we draw a random magnitude from a power-law distribution with a b value corresponding to the differential stress at the triggered seed point. We thus obtain time-dependent catalogues of seismic events including magnitude. The strategy of modelling flow and seismicity in a decoupled manner ensures efficiency and flexibility of the model. The model parameters are calibrated using observations from the Basel deep geothermal experiment in 2006. We are able to reproduce the hydraulic behaviour, the space-time evolution of the seismicity and its frequency-magnitude distribution. A large number of simulations of the calibrated model are then used to capture the variability of the process, an important input to compute probabilistic seismic hazard. We also use the calibrated model to explore alternative injection scenarios by varying injection volume, pressure as well as depth, and show the possible effect of those parameters on seismic hazard.

  19. The heat released in single catalytic events locally enhances enzyme diffusion

    NASA Astrophysics Data System (ADS)

    Tsekouras, Konstantinos; Riedel, Clement; Wilson, Christian; Hamadani, Kambiz; Marqusee, Susan; Presse, Steve; Bustamante, Carlos

    2014-03-01

    Recent experiments have shown that some enzymes catalyzing highly exothermic reactions exhibit increased diffusion with rising substrate concentration. We present a stochastic theory linking increased enzyme diffusion to reaction rate, discuss other possible origins for diffusion coefficient increases and finally provide a mechanistic interpretation showing how the heat released by the reaction perturbs the enzyme.

  20. An asixymmetric diffusion experiment for the determination of diffusion and sorption coefficients of rock samples

    SciTech Connect

    Takeda, M.; Hiratsuka, T.; Ito, K.; Finsterle, S.

    2011-02-01

    Diffusion anisotropy is a critical property in predicting migration of substances in sedimentary formations with very low permeability. The diffusion anisotropy of sedimentary rocks has been evaluated mainly from laboratory diffusion experiments, in which the directional diffusivities are separately estimated by through-diffusion experiments using different rock samples, or concurrently by in-diffusion experiments in which only the tracer profile in a rock block is measured. To estimate the diffusion anisotropy from a single rock sample, this study proposes an axisymmetric diffusion test, in which tracer diffuses between a cylindrical rock sample and a surrounding solution reservoir. The tracer diffusion between the sample and reservoir can be monitored from the reservoir tracer concentrations, and the tracer profile could also be obtained after dismantling the sample. Semi-analytical solutions are derived for tracer concentrations in both the reservoir and sample, accounting for an anisotropic diffusion tensor of rank two as well as the dilution effects from sampling and replacement of reservoir solution. The transient and steady-state analyses were examined experimentally and numerically for different experimental configurations, but without the need for tracer profiling. These experimental configurations are tested for in- and out-diffusion experiments using Koetoi and Wakkanai mudstones and Shirahama sandstone, and are scrutinized by a numerical approach to identify favorable conditions for parameter estimation. The analysis reveals the difficulty in estimating diffusion anisotropy; test configurations are proposed for enhanced identifiability of diffusion anisotropy. Moreover, it is demonstrated that the axisymmetric diffusion test is efficient in obtaining the sorption parameter from both steady-state and transient data, and in determining the effective diffusion coefficient if isotropic diffusion is assumed. Moreover, measuring reservoir concentrations in an axisymmetric diffusion experiment coupled with tracer profiling may be a promising approach to estimate of diffusion anisotropy of sedimentary rocks.

  1. Evaluation of Cranial and Cervical Arteries and Brain Tissue in Transient Ischemic Attack Patients with Magnetic Resonance Angiography and Diffusion-Weighted Imaging

    PubMed Central

    Li, Jian-Long; Li, Chang-Shan; Fu, Jun-Hua; Zhang, Ke; Xu, Rui; Xu, Wen-Jian

    2015-01-01

    Background Magnetic resonance angiography (MRA) and diffusion-weighted imaging (DWI) have been widely used in the prediction of ischemic stroke; however, the differences of the 2 methods in detection the artery lesion differences between transient ischemic attack (TIA) and infarction patients have been long neglected. We performed the present study to investigate the differences between vessel characteristics detected by MRA and DWI in acute stroke and TIA patients. Material/Methods We classified 110 subjects into 2 groups and all the patients underwent both MRA and DWI. The degree of stenosis of cranial and cervical arteries, the distribution of the stenosis, the development and changes of the vessels, and the DWI scanning results of the brain tissue were all analyzed. Results We detected a significant difference in the number and the degree of stenosis of cranial and cervical arteries among the 3 groups (P=0.006). Compared with health controls, patients with TIA and cerebral infraction had much more severe stenosis and occlusive arteries (P<0.05). However, no significant difference was detected between TIA and cerebral infraction patients (P=0.148). Moreover, a higher rate of unilateral vertebral artery dysplasia was found in the vertebrobasilar TIA patients. Higher lesion signals were also observed by DWI in TIA patients of internal carotid artery system (4/8, 50%). Conclusions Vessel characteristics were not significantly different between TIA and infarction patients. Unilateral vertebral artery hypoplasia was a predisposing factor for vertebrobasilar TIA and ischemic focus in DWI detection was always caused by severe artery lesions. PMID:26073092

  2. Levy diffusion in a force field, Huber relaxation kinetics, and nonequilibrium thermodynamics: H theorem for enhanced diffusion with Levy white noise

    SciTech Connect

    Vlad, Marcel O.; Center of Mathematical Statistics, Casa Academiei Romane, Calea Septembrie 13, Bucharest 5, ; Ross, John; Schneider, Friedemann W.

    2000-08-01

    A characteristic functional approach is suggested for Levy diffusion in disordered systems with external force fields. We study the overdamped motion of an ensemble of independent particles and assume that the force acting upon one particle is made up of two additive components: a linear term generated by a harmonic potential and a second term generated by the interaction with the disordered system. The stochastic properties of the second term are evaluated by using Huber's approach to complex relaxation [Phys. Rev. B 31, 6070 (1985)]. We assume that the interaction between a moving particle and the environment can be expressed by the contribution of a large number of relaxation channels, each channel having a very small probability of being open and obeying Poisson statistics. Two types of processes are investigated: (a) Levy diffusion with static disorder for which the fluctuations of the random force are frozen and last forever and (b) diffusion with strong dynamic disorder and independent Levy fluctuations (Levy white noise). In both cases we show that the probability distribution of the position of a diffusing particle tends towards a stationary nonequilibrium form. The characteristic functional of concentration fluctuations is evaluated in both cases by using the theory of random point processes. For large times the fluctuations of the concentration field are stationary and the corresponding probability density functional can be evaluated analytically. In this limit the fluctuations depend on the distribution of the total number of particles but are independent of the initial positions of the particles. We show that the logarithm of the stationary probability functional plays the role of a nonequilibrium thermodynamic potential, which has a structure similar to the Helmholtz free energy in equilibrium thermodynamics: it is made up of the sum of an energetic component, depending on the external mechanical potential, and of an entropic component, depending on the concentration field. We show that the conditions for the existence and stability of the nonequilibrium steady state, which emerges for large times, can be expressed in terms of the stochastic potential. For Levy white noise the average concentration field can be expressed as the solution of a fractional Fokker-Planck equation. We show that the stochastic potential is a Lyapunov function of the fractional Fokker-Planck equation, which ensures that all transient solutions for the average concentration field tend towards a unique stationary form. (c) 2000 The American Physical Society.

  3. Enhanced diffusion of uranium and thorium linked to crystal plasticity in zircon.

    PubMed

    Timms, Nicholas E; Kinny, Peter D; Reddy, Steven M

    2006-01-01

    The effects of crystal-plasticity on the U-Th-Pb system in zircon is studied by quantitative microstructural and microchemical analysis of a large zircon grain collected from pyroxenite of the Lewisian Complex, Scotland. Electron backscatter diffraction (EBSD) mapping reveals a c.18 degree variation in crystallographic orientation that comprises both a gradual change in orientation and a series of discrete low-angle (<4 degrees) boundaries. These microstructural data are consistent with crystal-plastic deformation of zircon associated with the formation and migration of dislocations. A heterogeneous pattern of dark cathodoluminescence, with the darkest domains coinciding with low-angle boundaries, mimics the deformation microstructure identified by EBSD. Geochemical data collected using the Sensitive High Resolution Ion MicroProbe (SHRIMP) shows a positive correlation between concentrations of the elements U, Th and Pb (ranging from 20-60 ppm, 30-110 ppm, and 14-36 ppm, respectively) and Th/U ratio (1.13-1.8) with the deformation microstructure. The highest measured concentrations and Th/U coincide with low-angle boundaries. This enrichment is interpreted to reflect enhanced bulk diffusion of U and Th due to the formation and migration of high-diffusivity dislocations. 207Pb/206Pb ages for individual analyses show no significant variation across the grain, and define a concordant, combined mean age of 2451 +/- 14 Ma. This indicates that the grain was deformed shortly after initial crystallization, most probably during retrograde Inverian metamorphism at amphibolite facies conditions. The elevated Th over U and consistent 207Pb/206Pb ages indicates that deformation most likely occurred in the presence of a late-stage magmatic fluid that drove an increase in the Th/U during deformation. The relative enrichment of Th over U implies that Th/U ratio may not always be a robust indicator of crystallization environment. This study provides the first evidence of deformation-related modification of the U-Th system in zircon and has fundamental implications for the application and interpretation of zircon trace element data. PMID:17181855

  4. Enhanced diffusion of Uranium and Thorium linked to crystal plasticity in zircon

    PubMed Central

    Timms, Nicholas E; Kinny, Peter D; Reddy, Steven M

    2006-01-01

    The effects of crystal-plasticity on the U-Th-Pb system in zircon is studied by quantitative microstructural and microchemical analysis of a large zircon grain collected from pyroxenite of the Lewisian Complex, Scotland. Electron backscatter diffraction (EBSD) mapping reveals a c.18° variation in crystallographic orientation that comprises both a gradual change in orientation and a series of discrete low-angle (<4°) boundaries. These microstructural data are consistent with crystal-plastic deformation of zircon associated with the formation and migration of dislocations. A heterogeneous pattern of dark cathodoluminescence, with the darkest domains coinciding with low-angle boundaries, mimics the deformation microstructure identified by EBSD. Geochemical data collected using the Sensitive High Resolution Ion MicroProbe (SHRIMP) shows a positive correlation between concentrations of the elements U, Th and Pb (ranging from 20–60 ppm, 30–110 ppm, and 14–36 ppm, respectively) and Th/U ratio (1.13 – 1.8) with the deformation microstructure. The highest measured concentrations and Th/U coincide with low-angle boundaries. This enrichment is interpreted to reflect enhanced bulk diffusion of U and Th due to the formation and migration of high-diffusivity dislocations. 207Pb/206Pb ages for individual analyses show no significant variation across the grain, and define a concordant, combined mean age of 2451 ± 14 Ma. This indicates that the grain was deformed shortly after initial crystallization, most probably during retrograde Inverian metamorphism at amphibolite facies conditions. The elevated Th over U and consistent 207Pb/206Pb ages indicates that deformation most likely occurred in the presence of a late-stage magmatic fluid that drove an increase in the Th/U during deformation. The relative enrichment of Th over U implies that Th/U ratio may not always be a robust indicator of crystallization environment. This study provides the first evidence of deformation-related modification of the U-Th system in zircon and has fundamental implications for the application and interpretation of zircon trace element data. PMID:17181855

  5. Enhancing weak transient signals in SEVIRI false colour imagery: application to dust source detection in southern Africa

    NASA Astrophysics Data System (ADS)

    Murray, Jon E.; Brindley, Helen E.; Bryant, Robert G.; Russell, Jacqui E.; Jenkins, Katherine F.

    2013-04-01

    Understanding the processes governing the availability and entrainment of mineral dust into the atmosphere requires dust sources to be identified and the evolution of dust events to be monitored. To achieve this aim a wide range of approaches have been developed utilising observations from a variety of different satellite sensors. Global maps of source regions and their relative strengths have been derived from instruments in low Earth orbit (e.g. Total Ozone Monitoring Spectrometer (TOMS) (Prospero et al., 2002), MODerate resolution Imaging Spectrometer (MODIS) (Ginoux et al., 2012)). Instruments such as MODIS can also be used to improve precise source location (Baddock et al., 2009) but the information available is restricted to the satellite overpass times which may not be coincident with active dust emission from the source. Hence, at a regional scale, some of the more successful approaches used to characterise the activity of different sources use high temporal resolution data available from instruments in geostationary orbit. For example, the widely used red-green-blue (RGB) dust scheme developed by Lensky and Rosenfeld (2008) (hereafter LR2008) makes use of observations from selected thermal channels of the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) in a false colour rendering scheme in which dust appears pink. This scheme has provided the basis for numerous studies of north African dust sources and factors governing their activation (e.g. Schepanski et al., 2007, 2009, 2012). However, the LR2008 imagery can fail to identify dust events due to the effects of atmospheric moisture, variations in dust layer height and optical properties, and surface conditions (Brindley et al., 2012). Here we introduce a new method designed to circumvent some of these issues and enhance the signature of dust events using observations from SEVIRI. The approach involves the derivation of a composite clear-sky signal for selected channels on an individual time-step and pixel basis. These composite signals are subtracted from each observation in the relevant channels to enhance weak transient signals associated with low levels of dust emission. Different channel combinations are then rendered in false colour imagery to better identify dust source locations and activity. We have applied this new clear-sky difference (CSD) algorithm over three key source regions in southern Africa: the Makgadikgadi Basin, Etosha Pan, and the Namibian and western South African coast. Case studies indicate that advantages associated with the CSD approach include an improved ability to detect dust and distinguish multiple sources, the observation of source activation earlier in the diurnal cycle, and an improved ability to pinpoint dust source locations. These advantages are confirmed by a survey of four-years of data, comparing the results obtained using the CSD technique with those derived from LR2008 dust imagery. On average the new algorithm more than doubles the number of dust events identified, with the greatest improvement for the Makgadigkadi Basin and coastal regions. We anticipate exploiting this new activation record derived using the CSD approach to better understand the surface and meteorological conditions controlling dust uplift and subsequent atmospheric transport.

  6. Diffusion of innovation: enhancing the dissemination of the Ponseti method in Latin America through virtual forums.

    PubMed

    Jayawardena, Asitha; Boardman, Allison; Cook, Thomas; Oprescu, Florin; Morcuende, Jose A

    2011-01-01

    This ethnographic study evaluated the use of low-bandwidth web-conferencing to enhance diffusion of a specific best practice, the Ponseti method to treat clubfoot, in three economically diverse countries in Latin America. A "Ponseti Virtual Forum" (PVF) was organized in Guatemala, Peru and Chile to examine the influences of economic level and telecommunication infrastructure on the effectiveness of tins approach. Across the three countries, a total of 14 different sites participated in the PVFs. Thirty-three Ponseti-trained practitioners were interviewed before and after each PVF, which included interactions with a Spanish-speaking Ponseti method expert. Semi-structured interviews, observations, and IP address data were triangulated and analyzed. The results demonstrated that 100% of the practitioners rated the sessions as very useful and that they would use this approach again. The largest obstacles to using PVFs were financial (7 out of 9 practitioners) in Guatemala; a lack of equipment and network access (6 out of 11) in Peru; and the organization and implementation of the conferences themselves (7 out of 9) in Chile. This study illustrates the usefulness of Ponseti Virtual Forums in Latin America. Health officials in Peru are currently developing a large-scale information session for traumatologists about the Ponseti method, while practitioners in Guatemala and Chile are organizing monthly scholarly meetings for physicians in remote areas. This initial feedback suggests that low-bandwidth web-conferencing can be an important vehicle for the dissemination of best practices, such as the Ponseti method, in developing countries. PMID:22096417

  7. Surface enhancement effect on the diffuse reflectance infrared Fourier transform spectra of compounds having a pyridine ring

    NASA Astrophysics Data System (ADS)

    Higuchi, Seiichiro; Takayama, Kazumi; Gohshi, Yohichi; Furuya, Keiichi

    1999-01-01

    A surface enhancement effect was examined for the diffuse reflectance infrared spectra of structurally related compounds having a pyridine ring when a silver colloidal solution was used as the medium which induced the effect. Filter paper, which was considered to provide a favorable state of aggregation of the silver colloidal particles, was used for the preparation of the samples to be measured. It was proved experimentally that when the molecules were dissolved in the silver colloidal solution and the resulting solution was applied dropwise to filter paper, the spectra measured for the filter paper sample exhibited a surface-enhanced infrared absorption (SEIRA) effect for some samples, but not for other samples. It was speculated that the existence of an electron-donating functional group in the molecule was necessary for the realization of SEIRA in the diffuse reflectance infrared spectra. This speculation was confirmed by experiments involving other types of molecules: L-phenylalanine, m-aminophenol and p-chloroaniline.

  8. Major mouse placental compartments revealed by diffusion-weighted MRI, contrast-enhanced MRI, and fluorescence imaging

    PubMed Central

    Solomon, Eddy; Avni, Reut; Hadas, Ron; Raz, Tal; Garbow, Joel Richard; Bendel, Peter; Frydman, Lucio; Neeman, Michal

    2014-01-01

    Mammalian models, and mouse studies in particular, play a central role in our understanding of placental development. Magnetic resonance imaging (MRI) could be a valuable tool to further these studies, providing both structural and functional information. As fluid dynamics throughout the placenta are driven by a variety of flow and diffusion processes, diffusion-weighted MRI could enhance our understanding of the exchange properties of maternal and fetal blood poolsand thereby of placental function. These studies, however, have so far been hindered by the small sizes, the unavoidable motions, and the challenging air/water/fat heterogeneities, associated with mouse placental environments. The present study demonstrates that emerging methods based on the spatiotemporal encoding (SPEN) of the MRI information can robustly overcome these obstacles. Using SPEN MRI in combination with albumin-based contrast agents, we analyzed the diffusion behavior of developing placentas in a cohort of mice. These studies successfully discriminated the maternal from the fetal blood flows; the two orders of magnitude differences measured in these fluids apparent diffusion coefficients suggest a nearly free diffusion behavior for the former and a strong flow-based component for the latter. An intermediate behavior was observed by these methods for a third compartment that, based on maternal albumin endocytosis, was associated with trophoblastic cells in the interphase labyrinth. Structural features associated with these dynamic measurements were consistent with independent intravital and ex vivo fluorescence microscopy studies and are discussed within the context of the anatomy of developing mouse placentas. PMID:24969421

  9. Controlled surface modification with poly(ethylene)glycol enhances diffusion of PLGA nanoparticles in human cervical mucus

    PubMed Central

    Cu, Yen; Saltzman, W. Mark

    2009-01-01

    Drug delivery to mucosal epithelia is severely limited by the mucus gel, which is a physical diffusion barrier as well as an enzymatic barrier in some sites. Loading of drug into polymer particles can protect drugs from degradation and enhance their stability. To improve efficacy of nanoparticulate drug carriers, it has been speculated that polymers such as poly(ethylene)glycol (PEG) incorporated on the particle surface will enhance transport in mucus. In the present study, we demonstrate the direct influence of PEG on surface properties of poly(lactic-co-glycolic)acid (PLGA) nanoparticles (d = 170 ± 57 nm). PEG of various molecular weights (MW = 2, 5, 10 kDa) were incorporated at a range of densities from 5 – 100% on the particle surface. Our results indicate PEG addition improves dispersion, neutralize charge, and enhance particle diffusion in cervical mucus in a manner strongly dependent on polymer MW and density. Diffusion of PEGylated particles was 3 – 10× higher than unmodified PLGA particles. These findings improve the understanding of, and confirm a possible direction for, the rational design of effective carriers for mucosal drug/vaccine delivery. PMID:19053536

  10. Investigation of radiation enhanced diffusion of magnesium in substrates flown on the NASA genesis mission.

    SciTech Connect

    King, B. V.; Pellin, M. J.; Burnett, D. S.

    2008-12-01

    The thermal diffusion of an Mg implant in Si has been measured with SIMS and compared to RIMS (resonant ionisation mass spectrometry) measurements of Mg implantation and diffusion in Si wafers exposed to solar wind irradiation in the NASA Genesis mission. The Genesis samples show much more surface segregation that the samples annealed in the laboratory, due to diffusion and segregation of the implanted Mg to the heavily damaged near surface regions of the Genesis wafers. This Mg transport has been modeled by solving a set of stiff differential equations and found to agree with RIMS measurements for a Mg interstitial migration energy of 0.7 eV.

  11. Transient ischemia elicits a sustained enhancement of thrombus development in the cerebral microvasculature: Effects of anti-thrombotic therapy

    PubMed Central

    Tang, Ya Hui; Vital, Shantel; Russell, Janice; Seifert, Hilary; Senchenkova, Elena; Granger, D. Neil

    2014-01-01

    Objective: While transient ischemic attack (TIA) is a well-known harbinger of ischemic stroke, the mechanisms that link TIA to subsequent strokes remain poorly understood. The overall aim of this study was to determine whether: 1) brief periods of transient cerebral ischemia render this tissue more vulnerable to thrombus development and 2) antiplatelet agents used in TIA patients alter ischemia-induced thrombogenesis. Approach & Results: The middle cerebral artery of C57BL/6 mice was occluded for 2.5 10 minutes, followed by reperfusion periods of 1 28 days. Intravital microscopy was used to monitor thrombus development in cerebral microvessels induced by light/dye photoactivation. Thrombosis was quantified as the time to platelet aggregation on the vessel wall and the time for complete blood flow cessation. While brief periods of cerebral ischemia were not associated with neurological deficits or brain infarction (evaluated after 1 day), it yielded a pronounced and prolonged (up to 28 days) acceleration of thrombus formation, compared to control (sham) mice. This prothrombotic phenotype was not altered by pre- and/or post-treatment of mice with either aspirin (A), clopidogrel (C), dipyridamole (D), or atorvastatin (S), or with A + D + S. Conclusions: The increased vulnerability of the cerebral vasculature to thrombus development after a brief period of transient ischemia can be recapitulated in a murine model. Antiplatelet or antithrombotic agents used in patients with TIA show no benefit in this mouse model of brief transient ischemia. PMID:25058045

  12. Semi-permeable Diffusion Barriers Enhance Patterning Robustness in the C. elegans Germline.

    PubMed

    Cinquin, Amanda; Zheng, Likun; Taylor, Pete H; Paz, Adrian; Zhang, Lei; Chiang, Michael; Snow, Joshua J; Nie, Qing; Cinquin, Olivier

    2015-11-23

    Positional information derived from local morphogen concentration plays an important role in patterning. A key question is how morphogen diffusion and gene expression regulation shape positional information into an appropriate profile with suitably low noise. We address this question using a model system--the C. elegans germline--whose regulatory network has been well characterized genetically but whose spatiotemporal dynamics are poorly understood. We show that diffusion within the germline syncytium is a critical control of stem cell differentiation and that semi-permeable diffusion barriers present at key locations make it possible--in combination with a feedback loop in the germline regulatory network--for mitotic zone size to be robust against spatial noise in Notch signaling. Spatial averaging within compartments defined by diffusion barriers is an advantageous patterning strategy, which attenuates noise while still allowing for sharp transitions between compartments. This strategy could apply to other organs. PMID:26609956

  13. Enhanced oxygen diffusivity in interfaces of nanocrystalline ZrO2?Y2O3

    PubMed Central

    Knner, Gregor; Reimann, Klaus; Rwer, Ralf; Sdervall, Ulf; Schaefer, Hans-Eckhardt

    2003-01-01

    First measurements of oxygen grain boundary diffusion coefficients in nanocrystalline yttria-doped ZrO2 (n-ZrO2?6.9 mol % Y2O3) are presented. The 18O diffusion profiles measured by secondary ion mass spectroscopy are much deeper in the nanocrystalline specimens than in single crystals. An oxygen diffusivity, DB, in the grain boundaries can be deduced, which is ?3 orders of magnitude higher than in single crystals. From the present data the temperature variation of the oxygen grain boundary diffusivity, DB = 2.0 10?5 exp (?0.91 eV/kBT) m2/s, and the oxygen surface exchange coefficient, k = 1.4 10?2 exp (?1.13 eV/kBT) m/s, are derived. PMID:12655074

  14. Multiphoton microscopy guides neurotrophin modification with poly(ethylene glycol) to enhance interstitial diffusion

    NASA Astrophysics Data System (ADS)

    Stroh, Mark; Zipfel, Warren R.; Williams, Rebecca M.; Ma, Shu Chin; Webb, Watt W.; Saltzman, W. Mark

    2004-07-01

    Brain-derived neurotrophic factor (BDNF) is a promising therapeutic agent for the treatment of neurodegenerative diseases. However, the limited distribution of this molecule after administration into the brain tissue considerably hampers its efficacy. Here, we show how multiphoton microscopy of fluorescently tagged BDNF in brain-tissue slices provides a useful and rapid screening method for examining the diffusion of large molecules in tissues, and for studying the effects of chemical modifications-for example, conjugating with polyethylene glycol (PEG)-on the diffusion constant. This single variable, obtained by monitoring short-term diffusion in real time, can be effectively used for rational drug design. In this study on fluorescently tagged BDNF and BDNF-PEG, we identify slow diffusion as a major contributing factor to the limited penetration of BDNF, and demonstrate how chemical modification can be used to overcome this barrier.

  15. A diffusible compound can enhance conjugal transfer of the Ti plasmid in Agrobacterium tumefaciens.

    PubMed

    Zhang, L H; Kerr, A

    1991-03-01

    Several octopine strains of Agrobacterium tumefaciens were tested for Ti plasmid (pTi) transfer after induction by 400 micrograms of octopine per ml for 24 h. The strains could be divided into two groups, transfer efficient (Trae) and transfer inefficient (Traie); the respective rates of transfer were 0.77 x 10(-2) to 1.14 x 10(-2) and 0.33 x 10(-6) to 9.8 x 10(-6) plasmid transconjugant per donor cell. Transfer efficiencies of Traie strains were greatly increased when the time of induction was 72 h. A diffusible conjugation factor (CF) that can enhance conjugal transfer of pTi in A. tumefaciens was discovered when both Trae and Traie donor strains were induced in the same plate. The evidence indicates that CF is a key factor affecting transfer efficiency of pTi but is not sufficient by itself to induce transfer. Trac mutants can produce CF constitutively, and Trae strains can produce it after induction by low octopine concentrations. The transfer efficiency of Traie strains was greatly increased by adding CF to the induction medium. The thermosensitive strain B6S, which normally cannot conjugate at temperatures above 30 degrees C, could transfer pTi efficiently at 32 and 34 degrees C in the presence of CF. Production of CF is dependent on the presence of pTi but appears to be common for different opine strains; it was first detected in octopine strains, but nopaline strains also produced the same or a similar compound. CF is very biologically active, affecting donor but not recipient bacterial cells, but CF does not promote aggregation. Data suggest that CF might be an activator or derepressor in the conjugation system of A. tumefaciens. CF is a dialyzable small molecule and is resistant to DNase, RNase, protease, and heating to 100 degrees C for 10 min, but autoclaving (121 degrees C for 15 min) and alkaline treatment removed all activity. PMID:2001991

  16. A diffusible compound can enhance conjugal transfer of the Ti plasmid in Agrobacterium tumefaciens.

    PubMed Central

    Zhang, L H; Kerr, A

    1991-01-01

    Several octopine strains of Agrobacterium tumefaciens were tested for Ti plasmid (pTi) transfer after induction by 400 micrograms of octopine per ml for 24 h. The strains could be divided into two groups, transfer efficient (Trae) and transfer inefficient (Traie); the respective rates of transfer were 0.77 x 10(-2) to 1.14 x 10(-2) and 0.33 x 10(-6) to 9.8 x 10(-6) plasmid transconjugant per donor cell. Transfer efficiencies of Traie strains were greatly increased when the time of induction was 72 h. A diffusible conjugation factor (CF) that can enhance conjugal transfer of pTi in A. tumefaciens was discovered when both Trae and Traie donor strains were induced in the same plate. The evidence indicates that CF is a key factor affecting transfer efficiency of pTi but is not sufficient by itself to induce transfer. Trac mutants can produce CF constitutively, and Trae strains can produce it after induction by low octopine concentrations. The transfer efficiency of Traie strains was greatly increased by adding CF to the induction medium. The thermosensitive strain B6S, which normally cannot conjugate at temperatures above 30 degrees C, could transfer pTi efficiently at 32 and 34 degrees C in the presence of CF. Production of CF is dependent on the presence of pTi but appears to be common for different opine strains; it was first detected in octopine strains, but nopaline strains also produced the same or a similar compound. CF is very biologically active, affecting donor but not recipient bacterial cells, but CF does not promote aggregation. Data suggest that CF might be an activator or derepressor in the conjugation system of A. tumefaciens. CF is a dialyzable small molecule and is resistant to DNase, RNase, protease, and heating to 100 degrees C for 10 min, but autoclaving (121 degrees C for 15 min) and alkaline treatment removed all activity. Images PMID:2001991

  17. Calcium diffusion enhanced after cleavage of negatively charged components of brain extracellular matrix by chondroitinase ABC

    PubMed Central

    Hrab?tov, Sabina; Masri, Daniel; Tao, Lian; Xiao, Fanrong; Nicholson, Charles

    2009-01-01

    The concentration of extracellular calcium plays a critical role in synaptic transmission and neuronal excitability as well as other physiological processes. The time course and extent of local fluctuations in the concentration of this ion largely depend on its effective diffusion coefficient (D*) and it has been speculated that fixed negative charges on chondroitin sulphate proteoglycans (CSPGs) and other components of the extracellular matrix may influence calcium diffusion because it is a divalent cation. In this study we used ion-selective microelectrodes combined with pressure ejection or iontophoresis of ions from a micropipette to quantify diffusion characteristics of neocortex and hippocampus in rat brain slices. We show that D* for calcium is less than the value predicted from the behaviour of the monovalent cation tetramethylammonium (TMA), a commonly used diffusion probe, but D* for calcium increases in both brain regions after the slices are treated with chondroitinase ABC, an enzyme that predominantly cleaves chondroitin sulphate glycans. These results suggest that CSPGs do play a role in determining the local diffusion properties of calcium in brain tissue, most likely through electrostatic interactions mediating rapid equilibrium binding. In contrast, chondroitinase ABC does not affect either the TMA diffusion or the extracellular volume fraction, indicating that the enzyme does not alter the structure of the extracellular space and that the diffusion of small monovalent cations is not affected by CSPGs in the normal brain ionic milieu. Both calcium and CSPGs are known to have many distinct roles in brain physiology, including brain repair, and our study suggests they may be functionally coupled through calcium diffusion properties. PMID:19546165

  18. Evidence of enhanced self-organized criticality (SOC) dynamics during the radially non-local transient transport in the HL-2A tokamak

    NASA Astrophysics Data System (ADS)

    Pan, O.; Xu, Y.; Hidalgo, C.; Zhong, W. L.; Shi, Z. B.; Ji, X. Q.; Jiang, M.; Feng, B. B.; Zhou, Y.; Cheng, J.; Liu, Y.; Xu, M.; Chen, W.; Ding, X. T.; Yan, L. W.; Yang, Q. W.; Duan, X. R.; Liu, Yong; the HL-2A Team

    2015-09-01

    Self-organized criticality (SOC) dynamics have been investigated in non-local transport regimes induced by the supersonic molecular beam injection in the HL-2A tokamak. Experimental evidence shows that the SOC or avalanche behaviors, such as the Hurst parameter, self-similarity and large-scale radial correlations in turbulence, are remarkably enhanced during the prompt non-local phase, together with an increase of inward propagation of turbulent events. These results highlight the importance of SOC paradigm during the transient non-local thermal transport in magnetically confined plasmas.

  19. Thaumatin Crystallization Aboard the International Space Station Using Liquid-Liquid Diffusion in the Enhanced Gaseous Nitrogen Dewar (EGN)

    NASA Technical Reports Server (NTRS)

    Kundrot, Craig; Barnes, Cindy L.; Snell, Edward H.; Stinson, Thomas N. (Technical Monitor)

    2002-01-01

    This paper reports results from the first biological crystal growth experiment on the International Space Station (ISS). Crystals of thaumatin were grown using liquid-liquid diffusion in Tygon tubing transported in the Enhanced Gaseous Nitrogen Dewar (EGN). Different Volume ratios and concentrations of protein and precipitant were used to test different adaptations of the vapor diffusion crystallization recipe to the liquid-liquid diffusion method. The EGN warmed up from -196 C to 0 C in about four days, about the same time it took to warm from 0 C to 20 C. The temperature within the EGN was 20 - 24 C for the majority of the experiment. Air gaps that blocked liquid-liquid diffusion formed in the tubes. Nonetheless, crystals were grown. Synchrotron diffraction data collected from the best space grown crystal extended to 1.28 Angstroms, comparable to previous studies of space-grown thaumatin crystals. The resolution of the best ground control crystal was only 1.47 Angstroms. It is not clear if the difference in diffraction limit is due to factors other than crystal size. Improvements in temperature control and the elimination of air gaps are needed, but the results show that EGN on the ISS can be used to produce space grown crystals that diffract to high resolution.

  20. LED lamp or bulb with remote phosphor and diffuser configuration with enhanced scattering properties

    SciTech Connect

    Tong, Tao; Le Toquin, Ronan; Keller, Bernd; Tarsa, Eric; Youmans, Mark; Lowes, Theodore; Medendorp, Jr., Nicholas W; Van De Ven, Antony; Negley, Gerald

    2014-11-11

    An LED lamp or bulb is disclosed that comprises a light source, a heat sink structure and an optical cavity. The optical cavity comprises a phosphor carrier having a conversions material and arranged over an opening to the cavity. The phosphor carrier comprises a thermally conductive transparent material and is thermally coupled to the heat sink structure. An LED based light source is mounted in the optical cavity remote to the phosphor carrier with light from the light source passing through the phosphor carrier. A diffuser dome is included that is mounted over the optical cavity, with light from the optical cavity passing through the diffuser dome. The properties of the diffuser, such as geometry, scattering properties of the scattering layer, surface roughness or smoothness, and spatial distribution of the scattering layer properties may be used to control various lamp properties such as color uniformity and light intensity distribution as a function of viewing angle.

  1. Stable isotope-enhanced two- and three-dimensional diffusion ordered 13C-NMR spectroscopy (SIE-DOSY 13C-NMR)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stable Isotope-Enhanced Diffusion Ordered (SIE-DOSY) 13C-NMR has been applied to 13C-enriched carbohydrates and has been used to determine diffusion coefficients for pentose and hexose monosaccharides, a disaccharide and a trisaccharide. These 2D spectra were obtained with as little as 8 min of acq...

  2. A Study of the Effect of Nanosized Particles on Transient Liquid Phase Diffusion Bonding Al6061 Metal-Matrix Composite (MMC) Using Ni/Al2O3 Nanocomposite Interlayer

    NASA Astrophysics Data System (ADS)

    Cooke, Kavian O.

    2012-06-01

    Transient liquid phase (TLP) diffusion bonding of Al-6061 containing 15 vol pct alumina particles was carried out at 873 K (600 C) using electrodeposited nanocomposite coatings as the interlayer. Joint formation was attributed to the solid-state diffusion of Ni into the Al-6061 alloy followed by eutectic formation and isothermal solidification of the joint region. An examination of the joint region using an electron probe microanalyzer (EPMA), transmission electron microscopy (TEM), wavelength-dispersive spectroscopy (WDS), and X-ray diffraction (XRD) showed the formation of intermetallic phases such as Al3Ni, Al9FeNi, and Ni3Si within the joint zone. The result indicated that the incorporation of 50 nm Al2O3 dispersions into the interlayer can be used to improve the joint significantly.

  3. Stroma cell-derived factor-1? signaling enhances calcium transients and beating frequency in rat neonatal cardiomyocytes.

    PubMed

    Hadad, Ielham; Veithen, Alex; Springael, Jean-Yves; Sotiropoulou, Panagiota A; Mendes Da Costa, Agns; Miot, Franoise; Naeije, Robert; De Deken, Xavier; Entee, Kathleen Mc

    2013-01-01

    Stroma cell-derived factor-1? (SDF-1?) is a cardioprotective chemokine, acting through its G-protein coupled receptor CXCR4. In experimental acute myocardial infarction, administration of SDF-1? induces an early improvement of systolic function which is difficult to explain solely by an anti-apoptotic and angiogenic effect. We wondered whether SDF-1? signaling might have direct effects on calcium transients and beating frequency.Primary rat neonatal cardiomyocytes were culture-expanded and characterized by immunofluorescence staining. Calcium sparks were studied by fluorescence microscopy after calcium loading with the Fluo-4 acetoxymethyl ester sensor. The cardiomyocyte enriched cellular suspension expressed troponin I and CXCR4 but was vimentin negative. Addition of SDF-1? in the medium increased cytoplasmic calcium release. The calcium response was completely abolished by using a neutralizing anti-CXCR4 antibody and partially suppressed and delayed by preincubation with an inositol triphosphate receptor (IP3R) blocker, but not with a ryanodine receptor (RyR) antagonist. Calcium fluxes induced by caffeine, a RyR agonist, were decreased by an IP3R blocker. Treatment with forskolin or SDF-1? increased cardiomyocyte beating frequency and their effects were additive. In vivo, treatment with SDF-1? increased left ventricular dP/dtmax.These results suggest that in rat neonatal cardiomyocytes, the SDF-1?/CXCR4 signaling increases calcium transients in an IP3-gated fashion leading to a positive chronotropic and inotropic effect. PMID:23460790

  4. Taylor-Aris dispersion in the presence of shear-enhanced diffusion and variable mean flow

    NASA Astrophysics Data System (ADS)

    Rubinstein, Gregory; Christov, Ivan; Stone, Howard

    2012-11-01

    Controlling the dispersion of colloidal suspensions is important in applications ranging from drug delivery to water purification. Previously, Griffiths and Stone [EPL (2012) 97, 58005] considered the influence of shear-induced diffusion on the Taylor-Aris dispersion of a colloidal suspension flowing in a cylindrical pipe. In this work, we extend their analysis to a radial outflow geometry, which features velocity variations along the flow direction. We found that the shear-induced diffusion due to the hydrodynamic interactions between the colloidal particles tends to decrease dispersion in the flow direction, as does the decrease in the velocity as the fluid flows radially outward. Using the method of multiple time scales, we derived an averaged dispersion equation that demonstrates the impact of these two effects. We also extended our methodology to coupled dispersion problems, in which the suspended particulate phase releases heat into the ambient fluid or the colloidal particles dissolve into the solvent medium.

  5. Flow range enhancement by secondary flow effect in low solidity circular cascade diffusers

    NASA Astrophysics Data System (ADS)

    Sakaguchi, Daisaku; Tun, Min Thaw; Mizokoshi, Kanata; Kishikawa, Daiki

    2014-08-01

    High-pressure ratio and wide operating range are highly required for compressors and blowers. The technical issue of the design is achievement of suppression of flow separation at small flow rate without deteriorating the efficiency at design flow rate. A numerical simulation is very effective in design procedure, however, cost of the numerical simulation is generally high during the practical design process, and it is difficult to confirm the optimal design which is combined with many parameters. A multi-objective optimization technique is the idea that has been proposed for solving the problem in practical design process. In this study, a Low Solidity circular cascade Diffuser (LSD) in a centrifugal blower is successfully designed by means of multi-objective optimization technique. An optimization code with a meta-model assisted evolutionary algorithm is used with a commercial CFD code ANSYS-CFX. The optimization is aiming at improving the static pressure coefficient at design point and at low flow rate condition while constraining the slope of the lift coefficient curve. Moreover, a small tip clearance of the LSD blade was applied in order to activate and to stabilize the secondary flow effect at small flow rate condition. The optimized LSD blade has an extended operating range of 114 % towards smaller flow rate as compared to the baseline design without deteriorating the diffuser pressure recovery at design point. The diffuser pressure rise and operating flow range of the optimized LSD blade are experimentally verified by overall performance test. The detailed flow in the diffuser is also confirmed by means of a Particle Image Velocimeter. Secondary flow is clearly captured by PIV and it spreads to the whole area of LSD blade pitch. It is found that the optimized LSD blade shows good improvement of the blade loading in the whole operating range, while at small flow rate the flow separation on the LSD blade has been successfully suppressed by the secondary flow effect.

  6. Cocrystals of Hydrochlorothiazide: Solubility and Diffusion/Permeability Enhancements through Drug-Coformer Interactions.

    PubMed

    Sanphui, Palash; Devi, V Kusum; Clara, Deepa; Malviya, Nidhi; Ganguly, Somnath; Desiraju, Gautam R

    2015-05-01

    Hydrochlorothiazide (HCT) is a diuretic and a BCS class IV drug with low solubility and low permeability, exhibiting poor oral absorption. The present study attempts to improve the physicochemical properties of the drug using a crystal engineering approach with cocrystals. Such multicomponent crystals of HCT with nicotinic acid (NIC), nicotinamide (NCT), 4-aminobenzoic acid (PABA), succinamide (SAM), and resorcinol (RES) were prepared using liquid-assisted grinding, and their solubilities in pH 7.4 buffer were evaluated. Diffusion and membrane permeability were studied using a Franz diffusion cell. Except for the SAM and NIC cocrystals, all other binary systems exhibited improved solubility. All of the cocrystals showed improved diffusion/membrane permeability compared to that of HCT with the exception of the SAM cocrystal. When the solubility was high, as in the case of PABA, NCT, and RES cocrystals, the flux/permeability dropped slightly. This is in agreement with the expected interplay between solubility and permeability. Improved solubility/permeability is attributed to new drug-coformer interactions. Cocrystals of SAM, however, showed poor solubility and flux. This cocrystal contains a primary sulfonamide dimer synthon similar to that of HCT polymorphs, which may be a reason for its unusual behavior. Hirshfeld surface analysis was carried out in all cases to determine whether a correlation exists between cocrystal permeability and drug-coformer interactions. PMID:25800383

  7. Enhanced Organic Solar Cell Stability through the Effective Blocking of Oxygen Diffusion using a Self-Passivating Metal Electrode.

    PubMed

    Lee, Hansol; Jo, Sae Byeok; Lee, Hyo Chan; Kim, Min; Sin, Dong Hun; Ko, Hyomin; Cho, Kilwon

    2016-03-01

    A new and simple strategy for enhancing the stability of organic solar cells (OSCs) was developed by using self-passivating metal top electrodes. Systematic investigations on O2 permeability of Al top electrodes revealed that the main pathways for oxidation-induced degradation could be greatly suppressed by simply controlling the nanoscale morphology of the Al electrode. The population of nanoscale pinholes among Al grains, which critically decided the diffusion of O2 molecules toward the Al-organic interfaces that are vulnerable to oxidation, was successfully regulated by rapidly depositing Al or promoting lateral growth among the Al grains, accompanied by increasing the deposition thickness. Our observations suggested that the stability of OSCs with conventional architectures might be greatly enhanced simply by controlling the fabrication conditions of the Al top electrode, without the aid of additional secondary treatments. PMID:26791576

  8. Diffuse cauda equina enhancement in a middle aged male with Susac syndrome and symptomatic cauda equina syndrome.

    PubMed

    Allmendinger, Andrew M; Viswanadhan, Narayan; Klufas, Roman A; Hsu, Liangge

    2013-10-15

    Susac syndrome is a rare neurologic disorder first described by Susac et al. in 1979. Clinically, Susac syndrome consists of a triad including encephalopathy, branch retinal artery occlusions and sensorineural hearing loss. All three components of the triad usually do not present at the same time, thus delaying time to diagnosis. MRI studies often show characteristic punched out lesions of the central fibers of the corpus callosum. Intracranial leptomeningeal enhancement may be seen, however, cauda equina involvement has not been described to our knowledge. We present a case of Susac syndrome in a middle-aged male with symptoms of cauda equina syndrome, and spinal MRI showing diffuse enhancement of the nerve roots of the cauda equina. PMID:23845898

  9. Radiation-enhanced diffusion in amorphous Ni-Zr studied by in situ electron irradiation in a transmission electron microscope

    NASA Astrophysics Data System (ADS)

    Bellini, Stefania; Montone, Amelia; Vittori-Antisari, Marco

    1994-10-01

    Radiation-enhanced diffusion (RED) in a Ni-Zr metallic glass has been studied by high-energy electron irradiation performed in situ in a transmission electron microscope. Irradiations have been carried out on thin foil cross-sectional specimens obtained from Ni-Zr bulk diffusion couples. The diffusivity under electron irradiation has been derived from the growth rate of a thin Ni-Zr amorphous film present at the Ni-Zr interface. Experimental results show that the Ni is the most mobile species in these experimental conditions and that radiation damage occurs in glassy metals at a lower electron energy relative to the corresponding crystalline compound. Moreover, the dose-rate sensitivity of RED appears to depend also on the energy of the electron beam. To explain this effect, the process of radiation displacement in metallic glasses has been modeled within the framework of the free-volume theory of the structure of metallic glasses. The results of this simple model can qualitatively explain our results as well as those relative to RED induced by high-energy ion irradiation.

  10. Improving Surface Geostrophic Current from a GOCE-Derived Mean Dynamic Topography Using Edge-Enhancing Diffusion Filtering

    NASA Astrophysics Data System (ADS)

    Sánchez-Reales, J. M.; Andersen, O. B.; Vigo, M. I.

    2015-02-01

    With increased geoid resolution provided by the gravity and steady-state ocean circulation explorer (GOCE) mission, the ocean's mean dynamic topography (MDT) can be now estimated with an accuracy not available prior to using geodetic methods. However, an altimetric-derived MDT still needs filtering in order to remove short wavelength noise unless integrated methods are used in which the three quantities are determined simultaneously using appropriate covariance functions. We studied nonlinear anisotropic diffusive filtering applied to the oceańs MDT and a new approach based on edge-enhancing diffusion (EED) filtering is presented. EED filters enable controlling the direction and magnitude of the filtering, with subsequent enhancement of computations of the associated surface geostrophic currents (SGCs). Applying this method to a smooth MDT and to a noisy MDT, both for a region in the Northwestern Pacific Ocean, we found that EED filtering provides similar estimation of the current velocities in both cases, whereas a non-linear isotropic filter (the Perona and Malik filter) returns results influenced by local residual noise when a difficult case is tested. We found that EED filtering preserves all the advantages that the Perona and Malik filter have over the standard linear isotropic Gaussian filters. Moreover, EED is shown to be more stable and less influenced by outliers. This suggests that the EED filtering strategy would be preferred given its capabilities in controlling/preserving the SGCs.

  11. Proton conduction and hydrogen diffusion in olivine: an attempt to reconcile laboratory and field observations and implications for the role of grain boundary diffusion in enhancing conductivity

    NASA Astrophysics Data System (ADS)

    Jones, Alan G.

    2016-02-01

    Proton conduction in olivine is directly related to the diffusion rate of hydrogen by the Nernst-Einstein equation, but prior attempts to use this relationship have always invoked additional terms to try to reconcile laboratory measurements of proton conduction and hydrogen diffusion data. New diffusion experiments on olivine demonstrate that lattice diffusion associated with vacancies is indeed highly dependent on the defect site where hydrogen is bonded, but from none of the sites is diffusion fast enough to explain the observed laboratory proton conduction experiments. Hydrogen diffusion associated with polarons (redox-exchange) is significantly faster but still cannot explain the low activation energy typical of electrical conductivity measurements. A process of bulk diffusion, which combines lattice diffusion (either associated with redox-exchange or vacancies) with the far faster grain boundary diffusion, explains the laboratory results, but does not explain the field observations with an average grain size of 0.5-2 cm at 100 km below the Jagersfontein kimberlite field on the Kaapvaal craton. Either conduction is dominantly along well-interconnected grain boundaries of very fine-grained (0.01 mm) damp (80 wt ppm) olivine grains or fine-grained (0.05 mm), wet (400 wt ppm) pyroxene grains, or another conduction mechanism must be primarily responsible for the field observations. If diffusion is the correct explanation, the conductivity below the Gibeon kimberlite field in Namibia is too high to be explained by increased thermal state alone of a diffusion process, even for such fine-grained pyroxenes.

  12. Recombinant Modified Vaccinia Virus Ankara Generating Excess Early Double-Stranded RNA Transiently Activates Protein Kinase R and Triggers Enhanced Innate Immune Responses

    PubMed Central

    Wolfersttter, Michael; Schweneker, Marc; Spth, Michaela; Lukassen, Susanne; Klingenberg, Marieken; Brinkmann, Kay; Wielert, Ursula; Lauterbach, Henning; Hochrein, Hubertus; Chaplin, Paul; Suter, Mark

    2014-01-01

    ABSTRACT Double-stranded RNA (dsRNA) is an important molecular pattern associated with viral infection and is detected by various extra- and intracellular recognition molecules. Poxviruses have evolved to avoid producing dsRNA early in infection but generate significant amounts of dsRNA late in infection due to convergent transcription of late genes. Protein kinase R (PKR) is activated by dsRNA and triggers major cellular defenses against viral infection, including protein synthesis shutdown, apoptosis, and type I interferon (IFN-I) production. The poxviral E3 protein binds and sequesters viral dsRNA and is a major antagonist of the PKR pathway. We found that the highly replication-restricted modified vaccinia virus Ankara (MVA) engineered to produce excess amounts of dsRNA early in infection showed enhanced induction of IFN-? in murine and human cells in the presence of an intact E3L gene. IFN-? induction required a minimum overlap length of 300 bp between early complementary transcripts and was strongly PKR dependent. Excess early dsRNA produced by MVA activated PKR early but transiently in murine cells and induced enhanced systemic levels of IFN-?, IFN-?, and other cytokines and chemokines in mice in a largely PKR-dependent manner. Replication-competent chorioallantois vaccinia virus Ankara (CVA) generating excess early dsRNA also enhanced IFN-I production and was apathogenic in mice even at very high doses but showed no in vitro host range defect. Thus, genetically adjuvanting MVA and CVA to generate excess early dsRNA is an effective method to enhance innate immune stimulation by orthopoxvirus vectors and to attenuate replicating vaccinia virus in vivo. IMPORTANCE Efficient cellular sensing of pathogen-specific components, including double-stranded RNA (dsRNA), is an important prerequisite of an effective antiviral immune response. The prototype poxvirus vaccinia virus (VACV) and its derivative modified vaccinia virus Ankara (MVA) produce dsRNA as a by-product of viral transcription. We found that inhibition of cellular dsRNA recognition established by the virus-encoded proteins E3 and K3 can be overcome by directing viral overexpression of dsRNA early in infection without compromising replication of MVA in permissive cells. Early dsRNA induced transient activation of the cellular dsRNA sensor protein kinase R (PKR), resulting in enhanced production of interferons and cytokines in cells and mice. Enhancing the capacity of MVA to activate the innate immune system is an important approach to further improve the immunogenicity of this promising vaccine vector. PMID:25297997

  13. Experimental Assessment and Enhancement of Planar Laser-Induced Fluorescence Measurements of Nitric Oxide in an Inverse Diffusion Flame

    NASA Technical Reports Server (NTRS)

    Partridge, William P.; Laurendeau, Normand M.

    1997-01-01

    We have experimentally assessed the quantitative nature of planar laser-induced fluorescence (PLIF) measurements of NO concentration in a unique atmospheric pressure, laminar, axial inverse diffusion flame (IDF). The PLIF measurements were assessed relative to a two-dimensional array of separate laser saturated fluorescence (LSF) measurements. We demonstrated and evaluated several experimentally-based procedures for enhancing the quantitative nature of PLIF concentration images. Because these experimentally-based PLIF correction schemes require only the ability to make PLIF and LSF measurements, they produce a more broadly applicable PLIF diagnostic compared to numerically-based correction schemes. We experimentally assessed the influence of interferences on both narrow-band and broad-band fluorescence measurements at atmospheric and high pressures. Optimum excitation and detection schemes were determined for the LSF and PLIF measurements. Single-input and multiple-input, experimentally-based PLIF enhancement procedures were developed for application in test environments with both negligible and significant quench-dependent error gradients. Each experimentally-based procedure provides an enhancement of approximately 50% in the quantitative nature of the PLIF measurements, and results in concentration images nominally as quantitative as LSF point measurements. These correction procedures can be applied to other species, including radicals, for which no experimental data are available from which to implement numerically-based PLIF enhancement procedures.

  14. Enhancement in Quality Factor of SRF Niobium Cavities by Material Diffusion

    SciTech Connect

    Dhakal, Pashupati; Ciovati, Gianluigi; Kneisel, Peter K.; Myneni, Ganapati Rao

    2015-06-01

    An increase in the quality factor of superconducting radiofrequency cavities is achieved by minimizing the surface resistance during processing steps. The surface resistance is the sum of temperature independent residual resistance and temperature/material dependent Bardeen-Cooper-Schrieffer (BCS) resistance. High temperature heat treatment usually reduces the impurities concentration from the bulk niobium, lowering the residual resistance. The BCS part can be reduced by selectively doping non-magnetic impurities. The increase in quality factor, termed as Q-rise, was observed in cavities when titanium or nitrogen thermally diffused in the inner cavity surface.

  15. Transient receptor potential ankyrin 1 activation enhances hapten sensitization in a T-helper type 2-driven fluorescein isothiocyanate-induced contact hypersensitivity mouse model

    SciTech Connect

    Shiba, Takahiro; Tamai, Takuma; Sahara, Yurina; Kurohane, Kohta; Watanabe, Tatsuo; Imai, Yasuyuki

    2012-11-01

    Some chemicals contribute to the development of allergies by increasing the immunogenicity of other allergens. We have demonstrated that several phthalate esters, including dibutyl phthalate (DBP), enhance skin sensitization to fluorescein isothiocyanate (FITC) in a mouse contact hypersensitivity model, in which the T-helper type 2 (Th2) response is essential. On the other hand, some phthalate esters were found to activate transient receptor potential ankyrin 1 (TRPA1) cation channels on sensory neurons. We then found a positive correlation between the enhancing effects of several types of phthalate esters on skin sensitization to FITC and their ability to activate TRPA1. Here we examined the involvement of TRPA1 in sensitization to FITC by using TRPA1 agonists other than phthalate esters. During skin sensitization to FITC, the TRPA1 agonists (menthol, carvacrol, cinnamaldehyde and DBP) augmented the ear-swelling response as well as trafficking of FITC-presenting dendritic cells to draining lymph nodes. We confirmed that these TRPA1 agonists induced calcium influx into TRPA1-expressing Chinese hamster ovary (CHO) cells. We also found that TRPA1 antagonist HC-030031 inhibited DBP-induced calcium influx into TRPA1-expressing CHO cells. After pretreatment with this antagonist upon skin sensitization to FITC, the enhancing effect of DBP on sensitization was suppressed. These results suggest that TRPA1 activation will become a useful marker to find chemicals that facilitate sensitization in combination with other immunogenic haptens. -- Highlights: ► Role of TRPA1 activation was revealed in a mouse model of skin sensitization to FITC. ► TRPA1 agonists enhanced skin sensitization as well as dendritic cell trafficking. ► Dibutyl phthalate (DBP) has been shown to enhance skin sensitization to FITC. ► TRPA1 activation by DBP was inhibited by a selective antagonist, HC-030031. ► HC-030031 inhibited the enhancing effect of DBP on skin sensitization to FITC.

  16. Proton conduction and hydrogen diffusion in olivine: Reconciling laboratory and field observations and implications for the role of grain boundary diffusion in enhanced conductivity

    NASA Astrophysics Data System (ADS)

    Jones, Alan G.

    2015-04-01

    Proton conduction is directly related to the diffusion of hydrogen through the Nernst-Einstein equation, but prior attempts to use this relationship have always invoked additional terms to try to reconcile proton conduction and hydrogen diffusion data. However, experimental data on hydrogen diffusion through the mineral lattice only constrain the rate of proton migration coupled with defects (such as vacancies) or coupled to polarons (electron holes mostly associated to ferric iron) and not the diffusion of uncoupled free protons. New diffusion experiments on olivine demonstrate that lattice diffusion associated to vacancies is indeed highly dependent on the defect site where hydrogen is bonded, but in any case is not fast enough to explain the observed laboratory proton conduction experiments. Hydrogen diffusion associated to polarons (redox-exchange) is significantly faster but still cannot explain the low activation energy typical of electrical conductivity measurements. A process of bulk diffusion, which combines lattice diffusion (either associated to redox-exchange or vacancies) with the far faster grain boundary diffusion, explains both the laboratory results and also field observations, and infers an average grain size of 0.5-2 cm at 100 km below the Jagersfontein kimberlite field on the Kaapvaal craton, which is consistent with petrological observations on xenolith material. Beneath the Gibeon kimberlite field on the nearby Rehoboth terrane, the higher conductivity observed cannot solely be explained by elevated temperature; either there is more water in the lithosphere (approx. double), or the average grain size is smaller (approx. half), or a combination of the two.

  17. Hydroxylamine diffusion can enhance N?O emissions in nitrifying biofilms: a modeling study.

    PubMed

    Sabba, Fabrizio; Picioreanu, Cristian; Prez, Julio; Nerenberg, Robert

    2015-02-01

    Wastewater treatment plants can be significant sources of nitrous oxide (N2O), a potent greenhouse gas. However, little is known about N2O emissions from biofilm processes. We adapted an existing suspended-growth mathematical model to explore N2O emissions from nitrifying biofilms. The model included N2O formation by ammonia-oxidizing bacteria (AOB) via the hydroxylamine and the nitrifier denitrification pathways. Our model suggested that N2O emissions from nitrifying biofilms could be significantly greater than from suspended growth systems under similar conditions. The main cause was the formation and diffusion of hydroxylamine, an AOB nitrification intermediate, from the aerobic to the anoxic regions of the biofilm. In the anoxic regions, hydroxylamine oxidation by AOB provided reducing equivalents used solely for nitrite reduction to N2O, since there was no competition with oxygen. For a continuous system, very high and very low dissolved oxygen (DO) concentrations resulted in lower emissions, while intermediate values led to higher emissions. Higher bulk ammonia concentrations and greater biofilm thicknesses increased emissions. The model effectively predicted N2O emissions from an actual pilot-scale granular sludge reactor for sidestream nitritation, but significantly underestimated the emissions when the NH2OH diffusion coefficient was assumed to be minimal. This numerical study suggests an unexpected and important role of hydroxylamine in N2O emission in biofilms. PMID:25539140

  18. Non-random walk diffusion enhances the sink strength of semicoherent interfaces

    PubMed Central

    Vattré, A.; Jourdan, T.; Ding, H.; Marinica, M.-C.; Demkowicz, M. J.

    2016-01-01

    Clean, safe and economical nuclear energy requires new materials capable of withstanding severe radiation damage. One strategy of imparting radiation resistance to solids is to incorporate into them a high density of solid-phase interfaces capable of absorbing and annihilating radiation-induced defects. Here we show that elastic interactions between point defects and semicoherent interfaces lead to a marked enhancement in interface sink strength. Our conclusions stem from simulations that integrate first principles, object kinetic Monte Carlo and anisotropic elasticity calculations. Surprisingly, the enhancement in sink strength is not due primarily to increased thermodynamic driving forces, but rather to reduced defect migration barriers, which induce a preferential drift of defects towards interfaces. The sink strength enhancement is highly sensitive to the detailed character of interfacial stresses, suggesting that ‘super-sink' interfaces may be designed by optimizing interface stress fields. Such interfaces may be used to create materials with unprecedented resistance to radiation-induced damage. PMID:26822632

  19. Non-random walk diffusion enhances the sink strength of semicoherent interfaces

    NASA Astrophysics Data System (ADS)

    Vattré, A.; Jourdan, T.; Ding, H.; Marinica, M.-C.; Demkowicz, M. J.

    2016-01-01

    Clean, safe and economical nuclear energy requires new materials capable of withstanding severe radiation damage. One strategy of imparting radiation resistance to solids is to incorporate into them a high density of solid-phase interfaces capable of absorbing and annihilating radiation-induced defects. Here we show that elastic interactions between point defects and semicoherent interfaces lead to a marked enhancement in interface sink strength. Our conclusions stem from simulations that integrate first principles, object kinetic Monte Carlo and anisotropic elasticity calculations. Surprisingly, the enhancement in sink strength is not due primarily to increased thermodynamic driving forces, but rather to reduced defect migration barriers, which induce a preferential drift of defects towards interfaces. The sink strength enhancement is highly sensitive to the detailed character of interfacial stresses, suggesting that `super-sink' interfaces may be designed by optimizing interface stress fields. Such interfaces may be used to create materials with unprecedented resistance to radiation-induced damage.

  20. Non-random walk diffusion enhances the sink strength of semicoherent interfaces.

    PubMed

    Vattré, A; Jourdan, T; Ding, H; Marinica, M-C; Demkowicz, M J

    2016-01-01

    Clean, safe and economical nuclear energy requires new materials capable of withstanding severe radiation damage. One strategy of imparting radiation resistance to solids is to incorporate into them a high density of solid-phase interfaces capable of absorbing and annihilating radiation-induced defects. Here we show that elastic interactions between point defects and semicoherent interfaces lead to a marked enhancement in interface sink strength. Our conclusions stem from simulations that integrate first principles, object kinetic Monte Carlo and anisotropic elasticity calculations. Surprisingly, the enhancement in sink strength is not due primarily to increased thermodynamic driving forces, but rather to reduced defect migration barriers, which induce a preferential drift of defects towards interfaces. The sink strength enhancement is highly sensitive to the detailed character of interfacial stresses, suggesting that 'super-sink' interfaces may be designed by optimizing interface stress fields. Such interfaces may be used to create materials with unprecedented resistance to radiation-induced damage. PMID:26822632

  1. New multiscale speckle suppression and edge enhancement with nonlinear diffusion and homomorphic filtering for medical ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Kang, Jinbum; Yoo, Yangmo

    2014-03-01

    Speckle, shown as a granular pattern, considerably degrades the image quality of ultrasound B-mode imaging and lowers the performance of image segmentation and registration techniques. Thus, speckle reduction while preserving the tissue structure (e.g., edges and boundaries of lesions) is important for ultrasound B-mode imaging. In this paper, a new approach for speckle reduction and edge enhancement based on laplacian pyramid nonlinear diffusion and homomorphic filtering (LPNDHF) is proposed for ultrasound B-mode imaging. In LPNDHF, nonlinear diffusion with a weighting factor is applied in multi-scale domain (i.e., laplacian pyramid) for effectively suppressing the speckle. In addition, in order to overcome the drawback from the previous LPND method, i.e., blurred edges, homomorphic filtering for edge and contrast enhancement is also applied from a finer scale to a coarser scale. From the simulation study, the proposed LPNDHF method showed the higher edge preservation and structure similarity values compared to the LPND and LPND with shock filtering (LPNDSF). Also, the LPNDHF provided the higher CNR values compared to LPND and LPNDSF, i.e., 5.02 vs. 3.66 and 2.91, respectively. From the tissue mimicking phantom study, the similar improvement in CNR was achieved from the LPNDHF over LPND and LPNDSF, i.e., 2.35 vs. 1.83 and 1.30. Moreover, the consistent results were obtained with the in vivo abdominal study. These preliminary results demonstrate that the proposed LPNDHF can improve the image quality of ultrasound B-mode imaging by increasing contrast and enhancing the specific signal details while effectively suppressing speckle.

  2. Transient receptor potential ankyrin 1 activation enhances hapten sensitization in a T-helper type 2-driven fluorescein isothiocyanate-induced contact hypersensitivity mouse model.

    PubMed

    Shiba, Takahiro; Tamai, Takuma; Sahara, Yurina; Kurohane, Kohta; Watanabe, Tatsuo; Imai, Yasuyuki

    2012-11-01

    Some chemicals contribute to the development of allergies by increasing the immunogenicity of other allergens. We have demonstrated that several phthalate esters, including dibutyl phthalate (DBP), enhance skin sensitization to fluorescein isothiocyanate (FITC) in a mouse contact hypersensitivity model, in which the T-helper type 2 (Th2) response is essential. On the other hand, some phthalate esters were found to activate transient receptor potential ankyrin 1 (TRPA1) cation channels on sensory neurons. We then found a positive correlation between the enhancing effects of several types of phthalate esters on skin sensitization to FITC and their ability to activate TRPA1. Here we examined the involvement of TRPA1 in sensitization to FITC by using TRPA1 agonists other than phthalate esters. During skin sensitization to FITC, the TRPA1 agonists (menthol, carvacrol, cinnamaldehyde and DBP) augmented the ear-swelling response as well as trafficking of FITC-presenting dendritic cells to draining lymph nodes. We confirmed that these TRPA1 agonists induced calcium influx into TRPA1-expressing Chinese hamster ovary (CHO) cells. We also found that TRPA1 antagonist HC-030031 inhibited DBP-induced calcium influx into TRPA1-expressing CHO cells. After pretreatment with this antagonist upon skin sensitization to FITC, the enhancing effect of DBP on sensitization was suppressed. These results suggest that TRPA1 activation will become a useful marker to find chemicals that facilitate sensitization in combination with other immunogenic haptens. PMID:22935519

  3. Increases in reactive oxygen species enhance vascular endothelial cell migration through a mechanism dependent on the transient receptor potential melastatin 4 ion channel.

    PubMed

    Sarmiento, Daniela; Montorfano, Ignacio; Cerda, Oscar; Cceres, Mnica; Becerra, Alvaro; Cabello-Verrugio, Claudio; Elorza, Alvaro A; Riedel, Claudia; Tapia, Pablo; Velsquez, Luis A; Varela, Diego; Simon, Felipe

    2015-03-01

    A hallmark of severe inflammation is reactive oxygen species (ROS) overproduction induced by increased inflammatory mediators secretion. During systemic inflammation, inflammation mediators circulating in the bloodstream interact with endothelial cells (ECs) raising intracellular oxidative stress at the endothelial monolayer. Oxidative stress mediates several pathological functions, including an exacerbated EC migration. Because cell migration critically depends on calcium channel-mediated Ca(2+) influx, the molecular identification of the calcium channel involved in oxidative stress-modulated EC migration has been the subject of intense investigation. The transient receptor potential melastatin 4 (TRPM4) protein is a ROS-modulated non-selective cationic channel that performs several cell functions, including regulating intracellular Ca(2+) overload and Ca(2+) oscillation. This channel is expressed in multiple tissues, including ECs, and contributes to the migration of certain immune cells. However, whether the TRPM4 ion channel participates in oxidative stress-mediated EC migration is not known. Herein, we investigate whether oxidative stress initiates or enhances EC migration and study the role played by the ROS-modulated TRPM4 ion channel in oxidative stress-mediated EC migration. We demonstrate that oxidative stress enhances, but does not initiate, EC migration in a dose-dependent manner. Notably, we demonstrate that the TRPM4 ion channel is critical in promoting H2O2-enhanced EC migration. These results show that TRPM4 is a novel pharmacological target for the possible treatment of severe inflammation and other oxidative stress-mediated inflammatory diseases. PMID:24518820

  4. Dislocation Enhancement of Seismic-Frequency Attenuation: Subgrain Boundary Diffusion and Triggered, Critical Emission of Dislocations

    NASA Astrophysics Data System (ADS)

    Cooper, R. F.; McCarthy, C.

    2012-12-01

    Combined compressional creep and (Young's-modulus) attenuation experiments on polycrystalline ice-I (200 ≤ T[K] ≤ 260; 3 ≤ d[μm] ≤ 500; σmean = 1MPa and Δσ = 0.16MPa applied in a frequency range 10-4 ≤ ν[Hz] ≤ 10-1) demonstrate the attenuation behavior associated with the seismic attenuation band and the "high-temperature background," i.e., a power-law response Q-1 ∝ ν-m with m ~ 0.33. This response has, in general, been associated with grain boundary sliding rate-limited by atomic diffusion [e.g., 1-3], a mechanism that is very sensitive to grain size. In our experiments, however, with a grain size variation ~102, the attenuation response is independent of grain size, to first order. Scrutiny of the physics suggests that the attenuation is effected primarily by diffusive relaxation of subgrain boundaries [4, 5], the size of which, in materials deforming by a dislocation mechanism (as is the ice in our experiments), is set by the deviatoric stress [6, 7]. Applying the diffusion-effected physics to the subgrain size matches the universal scaling [e.g., 3] for materials that are linear-viscoelastic. Our ice specimens, however, demonstrate modest non-linearity, resulting in greater attenuation than that associated with the diffusion process [cf. 8] and yet retain the power-law form for attenuation, including the same slope m. The result is consistent with "self-organized critical" behavior in dislocation emission [9, 10] and the physics overall can be understood via models of self-similar scaling of crystalline (effective) viscosity [e.g., 11]. The potential application to seismic studies is profound: for example, if the upper mantle of Earth is convecting via a dislocation-creep or dislocation-accommodated grain-boundary-sliding mechanism, then the attenuation response is related not to the grain size, but rather to the subgrain structure associated with the creep of the rock. Thus, seismic attenuation measurements may well be useful for interpreting flow behavior in the mantle. [1] T.T. Gribb and R.F. Cooper, J. Geophys. Res. 103, doi:10.1029/98JB02786 (1998). [2] I. Jackson and U.H. Faul, Phys. Earth Planet. Inter. 183, doi:10.1016/j.pepi.2010.09.005 (2010). [3] C. McCarthy et al., J. Geophys. Res. 116, doi:10.1029/2011JB008384 (2011). [4] D.S. Stone et al., J. Geophys. Res. 109, doi:10.1029/2004JB003064 (2004). [5] Y. Gueguen et al., Phys. Earth Planet. Interior. 55, 254-258 (1989). [6] R.J. Twiss, Pure Appl. Geophys. 115, 227-244 (1977). [7] S.V. Raj and G.M. Pharr, Mater. Sci. Engr. 81, 217-237 (1986). [8] R.J.M. Farla et al., Science 336, 332-335 (2012). [9] T. Richeton et al., Nature Mater. 4, 465-469 (2005). [10] J. Puthoff, M.Sc. Thesis, University of Wisconsin-Madison (2005). [11] D.S. Stone, Acta Metall. Mater. 31, 599-608 (1991).

  5. Enhanced anisotropic ionic diffusion in layered electrolyte structures from density functional theory

    NASA Astrophysics Data System (ADS)

    Hirschfeld, J. A.; Lustfeld, H.

    2014-01-01

    Electrolytes with high ionic diffusivity at temperatures distinctively lower than the presently used ones are the prerequisite for the success of, e.g., solid oxide fuel cells. We have found a promising structure having an asymmetric but superior ionic mobility in the direction of the oxygen-ion current. Using a layering of zirconium and yttrium in the fluorite structure of zirconia, a high vacancy concentration and a low migration barrier in two dimensions are obtained, while the mobility in the third direction is basically sacrificed. According to our density functional theory calculations an electrolyte made of this structure could operate at a temperature reduced by ≈200∘C. Thus a window to a different class of electrolytes has been flung open. In our structure the price paid is a more complicated manufacturing method.

  6. Contrast-enhanced diffuse optical tomography of brain perfusion in humans using ICG

    NASA Astrophysics Data System (ADS)

    Habermehl, Christina; Schmitz, Christoph; Steinbrink, Jens

    2012-02-01

    Regular monitoring of brain perfusion at the bedside in neurointensive care is desirable. Currently used imaging modalities are not suited for constant monitoring and often require a transport of the patient. Noninvasive near infrared spectroscopy (NIRS) in combination with an injection of a safe dye (indocyanine green, ICG) could serve as a quasi-continuous brain perfusion monitor. In this work, we evaluate prerequisites for the development of a brain perfusion monitor using continuous wave (cw) NIRS technique. We present results from a high-resolution diffuse optical tomography (HR-DOT) experiment in humans demonstrating the separation of signals from skin from the brain. This technique can help to monitor neurointensive care patients on a regular basis, detecting changes in cortical perfusion in time.

  7. Non-random walk diffusion enhances the sink strength of semicoherent interfaces

    DOE PAGESBeta

    Vattré, A.; Jourdan, T.; Ding, H.; Marinica, M. -C.; Demkowicz, M. J.

    2016-01-29

    Clean, safe and economical nuclear energy requires new materials capable of withstanding severe radiation damage. One strategy of imparting radiation resistance to solids is to incorporate into them a high density of solid-phase interfaces capable of absorbing and annihilating radiation-induced defects. Here we show that elastic interactions between point defects and semicoherent interfaces lead to a marked enhancement in interface sink strength. Our conclusions stem from simulations that integrate first principles, object kinetic Monte Carlo and anisotropic elasticity calculations. Surprisingly, the enhancement in sink strength is not due primarily to increased thermodynamic driving forces, but rather to reduced defect migrationmore » barriers, which induce a preferential drift of defects towards interfaces. The sink strength enhancement is highly sensitive to the detailed character of interfacial stresses, suggesting that ‘super-sink’ interfaces may be designed by optimizing interface stress fields. Lastly, such interfaces may be used to create materials with unprecedented resistance to radiation-induced damage.« less

  8. A comparison of boron and phosphorus diffusion and dislocation loop growth from silicon implants into silicon

    SciTech Connect

    Jingwei Xu; Law, M.E.

    1996-12-31

    Transient Enhanced Diffusion (TED) results from implantation damage creating enhanced diffusion of dopants in silicon. This phenomena has mostly been studied using boron marker layers. We have performed an experiment using boron, phosphorus, and dislocation markers to compare TED effects. This experiment shows that phosphorus is enhanced significantly more than boron during damage annealing. Dislocation growth indicates that a number of interstitials greater than the damage dose is captured during these anneals. The time to saturate the dislocation growth agrees well with phosphorus diffusion saturation, and is greater than the boron saturation.

  9. Loss of the Tectorial Membrane Protein CEACAM16 Enhances Spontaneous, Stimulus-Frequency, and Transiently Evoked Otoacoustic Emissions

    PubMed Central

    Goodyear, Richard J.; Homma, Kazuaki; Legan, P. Kevin; Korchagina, Julia; Naskar, Souvik; Siegel, Jonathan H.; Dallos, Peter; Zheng, Jing

    2014-01-01

    ?-Tectorin (TECTA), ?-tectorin (TECTB), and carcinoembryonic antigen-related cell adhesion molecule 16 (CEACAM) are secreted glycoproteins that are present in the tectorial membrane (TM), an extracellular structure overlying the hearing organ of the inner ear, the organ of Corti. Previous studies have shown that TECTA and TECTB are both required for formation of the striated-sheet matrix within which collagen fibrils of the TM are imbedded and that CEACAM16 interacts with TECTA. To learn more about the structural and functional significance of CEACAM16, we created a Ceacam16-null mutant mouse. In the absence of CEACAM16, TECTB levels are reduced, a clearly defined striated-sheet matrix does not develop, and Hensen's stripe, a prominent feature in the basal two-thirds of the TM in WT mice, is absent. CEACAM16 is also shown to interact with TECTB, indicating that it may stabilize interactions between TECTA and TECTB. Although brain-stem evoked responses and distortion product otoacoustic emissions are, for most frequencies, normal in young mice lacking CEACAM16, stimulus-frequency and transiently evoked emissions are larger. We also observed spontaneous otoacoustic emissions (SOAEs) in 70% of the homozygous mice. This incidence is remarkable considering that <3% of WT controls have SOAEs. The predominance of SOAEs >15 kHz correlates with the loss of Hensen's stripe. Results from mice lacking CEACAM16 are consistent with the idea that the organ of Corti evolved to maximize the gain of the cochlear amplifier while preventing large oscillations. Changes in TM structure appear to influence the balance between energy generation and dissipation such that the system becomes unstable. PMID:25080593

  10. Fabrication and evaluation of enhanced diffusion bonded titanium honeycomb core sandwich panels with titanium aluminide face sheets

    NASA Technical Reports Server (NTRS)

    Hoffmann, E. K.; Bird, R. K.; Bales, T. T.

    1989-01-01

    A joining process was developed for fabricating lightweight, high temperature sandwich panels for aerospace applications using Ti-14Al-21Nb face sheets and Ti-3Al-2.5V honeycomb core. The process, termed Enhanced Diffusion Bonding (EDB), relies on the formation of a eutectic liquid through solid-state diffusion at elevated temperatures and isothermal solidification to produce joints in thin-gage titanium and titanium aluminide structural components. A technique employing a maskant on the honeycomb core was developed which permitted electroplating a controlled amount of EDB material only on the edges of the honeycomb core in order to minimize the structural weight and metallurgical interaction effects. Metallurgical analyses were conducted to determine the interaction effects between the EDB materials and the constituents of the sandwich structure following EDB processing. The initial mechanical evaluation was conducted with butt joint specimens tested at temperatures from 1400 - 1700 F. Further mechanical evaluation was conducted with EDB sandwich specimens using flatwise tension tests at temperatures from 70 - 1100 F and edgewise compression tests at ambient temperature.

  11. High-Rate and Cycling-Stable Nickel-Rich Cathode Materials with Enhanced Li(+) Diffusion Pathway.

    PubMed

    Tian, Jun; Su, Yuefeng; Wu, Feng; Xu, Shaoyu; Chen, Fen; Chen, Renjie; Li, Qing; Li, Jinghui; Sun, Fengchun; Chen, Shi

    2016-01-13

    The nickel-rich LiNi0.7Co0.15Mn0.15O2 material was sintered by Li source with the Ni0.7Co0.15Mn0.15(OH)2 precursor, which was prepared via hydrothermal treatment after coprecipitation. The intensity ratio of I(110)/I(108) obtained from X-ray diffraction patterns and high-resolution transmission electronmicroscopy confirm that the particles have enhanced growth of (110), (100), and (010) surface planes, which supply superior inherent Li(+) deintercalation/intercalation. The electrochemical measurement shows that the LiNi0.7Co0.15Mn0.15O2 material has high cycling stability and rate capability, along with fast charge and discharge ability. Li(+) diffusion coefficient at the oxidation peaks obtained by cyclic voltammogram measurement is as large as 10(-11) (cm(2) s(-1)) orders of magnitude, implying that the nickel-rich material has high Li(+) diffusion capability. PMID:26601895

  12. Control of surface plasmon resonance in out-diffused silver nanoislands for surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Piliugina, E. S.; Heisler, F.; Chervinskii, S. D.; Samusev, A. K.; Lipovskii, A. A.

    2015-12-01

    We present the studies of self-assembled silver nanoislands on the surface of silver ion-exchanged glasses. The nanoislands were formed by out-diffusion of reduced silver atoms from the bulk of the glass to its surface. Control of silver ions distribution in the glass by thermal poling after the ion exchange allowed formation of relatively big, up to 250 nm, isolated silver nanoislands while without the poling an ensemble of silver nanoislands with average size from several to tens of nanometers with random size distribution was formed. The nanoislands were characterized using atomic force microscopy and spectral measurements. We used optical absorption spectroscopy for random nanoislands and dark field scattering spectroscopy for isolated ones, corresponding spectra showed peaks in the vicinity of 450 nm and 600 nm, respectively. The random nanoislands significantly enhanced Raman scattering from Rhodamine 6G, also the modification of Raman signal from deposited on the surface of the samples bacteriorhodopsin in purple membranes was registered.

  13. A Transient Diffusion Model Yields Unitary Gap Junctional Permeabilities from Images of Cell-to-Cell Fluorescent Dye Transfer Between Xenopus Oocytes

    PubMed Central

    Nitsche, Johannes M.; Chang, Hou-Chien; Weber, Paul A.; Nicholson, Bruce J.

    2004-01-01

    As ubiquitous conduits for intercellular transport and communication, gap junctional pores have been the subject of numerous investigations aimed at elucidating the molecular mechanisms underlying permeability and selectivity. Dye transfer studies provide a broadly useful means of detecting coupling and assessing these properties. However, given evidence for selective permeability of gap junctions and some anomalous correlations between junctional electrical conductance and dye permeability by passive diffusion, the need exists to give such studies a more quantitative basis. This article develops a detailed diffusion model describing experiments (reported separately) involving transport of fluorescent dye from a “donor” region to an “acceptor” region within a pair of Xenopus oocytes coupled by gap junctions. Analysis of transport within a single oocyte is used to determine the diffusion and binding characteristics of the cellular cytoplasm. Subsequent double-cell calculations then yield the intercellular junction permeability, which is translated into a single-channel permeability using concomitant measurements of intercellular conductance, and known single-channel conductances of gap junctions made up of specific connexins, to count channels. The preceding strategy, combined with use of a graded size series of Alexa dyes, permits a determination of absolute values of gap junctional permeability as a function of dye size and connexin type. Interpretation of the results in terms of pore theory suggests significant levels of dye-pore affinity consistent with the expected order of magnitude of typical (e.g., van der Waals) intermolecular attractions. PMID:15041648

  14. Identifying knowledge-attitude-practice gaps to enhance HPV vaccine diffusion.

    PubMed

    Cohen, Elisia L; Head, Katharine J

    2013-01-01

    To examine differences in knowledge, attitudes, and related practices among adopters and nonadopters of the human papillomavirus (HPV) vaccine, the researchers conducted 83 in-depth interviews with 18- to 26-year-old women. The study identified knowledge-attitude-practice gaps in the context of the HPV vaccine to explain why diffusion of a preventive innovation (such as the HPV vaccine) requires targeted risk communication strategies in order to increase demand. Salient findings included similarities between vaccinated and unvaccinated women's lack of knowledge and uncertainties about HPV and cervical cancer. Vaccinated women who had no knowledge of HPV or no-risk/low-risk perceptions of HPV reported receiving vaccination, indicating HPV risk protection behavior could precede knowledge acquisition for vaccinated women. These vaccinated women identified an interpersonal network supportive of vaccination and reported supportive social influences. Among unvaccinated women, unsupportive vaccination attitudes included low perceived personal risk of HPV. In contrast, unvaccinated women often cited erroneous beliefs that HPV could be avoided by abstinence, monogamy, and knowledge of their partners' sexual history as reasons that the vaccine was not personally relevant. Unvaccinated women cited interpersonal influences that activated short- and long-term vaccination safety and efficacy concerns. Different levels of fear regarding the HPV vaccine may underlie (a) attitudinal differences between vaccinated and unvaccinated women in perceived vaccination value and (b) attitude-practice gaps. PMID:23767775

  15. Comparison of the enhanced steady-state diffusion of calcium by calbindin-D9K and calmodulin: possible importance in intestinal calcium absorption.

    PubMed

    Feher, J J; Fullmer, C S; Fritzsch, G K

    1989-01-01

    The diffusion of calcium was measured using the unidirectional flux of 45Ca across an aqueous layer. The aqueous layer was bounded by two dialysis membranes and convection was eliminated by gelling the aqueous layer with agarose. The apparent self-diffusion coefficient was determined by the dependence of the tracer flux on the diffusion distance. The apparent self-diffusion coefficient increased linearly with the concentration of calbindin-D9K and calmodulin, but the effect of calmodulin was markedly less than that of calbindin-D9K. This difference is attributed to the lower association constant for calmodulin. The ion-exchange resin Chelex-100 also increased the steady-state of 45Ca, but the effect of Chelex-100 was much less efficient than the effect of calbindin-D9K. The mechanism of enhanced diffusion was attributed to an enhanced gradient of total 45Ca. These results indicate that the steady-state unidirectional calcium flux is a superposition of free calcium diffusion and bound calcium diffusion, with only a small contribution due to a 'bucket brigade' mechanism. We suggest that this phenomenon may be important in calcium absorption across the intestine. PMID:2776187

  16. Indocyanine green enhanced co-registered diffuse optical tomography and photoacoustic tomography

    PubMed Central

    Kumavor, Patrick D.; Alqasemi, Umar; Li, Hai; Xu, Yan; Zanganeh, Saeid; Zhu, Quing

    2013-01-01

    Abstract. To overcome the intensive light scattering in biological tissue, diffuse optical tomography (DOT) in the near-infrared range for breast lesion detection is usually combined with other imaging modalities, such as ultrasound, x-ray, and magnetic resonance imaging, to provide guidance. However, these guiding imaging modalities may depend on different contrast mechanisms compared to the optical contrast in the DOT. As a result, they cannot provide reliable guidance for DOT because some lesions may not be detectable by a nonoptical modality but may have a high optical contrast. An imaging modality that relies on optical contrast to provide guidance is desirable for DOT. We present a system that combines a frequency-domain DOT and real-time photoacoustic tomography (PAT) systems to detect and characterize deeply seated targets embedded in a turbid medium. To further improve the contrast, the exogenous contrast agent, indocyanine green (ICG), is used. Our experimental results show that the combined system can detect a tumor-mimicking phantom, which is immersed in intralipid solution with the concentrations ranging from 100 to 10 μM and with the dimensions of 0.8  cm×0.8  cm×0.6  cm, up to 2.5 cm in depth. Mice experiments also confirmed that the combined system can detect tumors and monitor the ICG uptake and washout in the tumor region. This method can potentially improve the accuracy to detect small breast lesions as well as lesions that are sensitive to background tissue changes, such as the lesions located just above the chest wall. PMID:24343437

  17. Decay of force transients following active stretch is slower in older than young men: support for a structural mechanism contributing to residual force enhancement in old age.

    PubMed

    Power, Geoffrey A; Herzog, Walter; Rice, Charles L

    2014-10-17

    Following active lengthening of muscle, force reaches an isometric steady state above that which would be achieved for a purely isometric contraction at the same muscle length. This fundamental property of muscle, termed "residual force enhancement (RFE)," cannot be predicted by the force-length relationship, and is unexplained by the cross-bridge theory of muscle contraction. Recently, we showed that older adults experience higher RFE than young for the ankle dorsiflexors primarily owing to a greater reliance on passive force enhancement (PFE) and similar RFE for the knee extensors but a greater contribution of PFE to total RFE. Natural adult aging may prove a useful model in exploring mechanisms of RFE which may reside in the dissipation of force transients following stretch. A post-hoc analysis was conducted on previously described RFE experiments in young (~26 years) and old (~77 years) men for the dorsiflexors and knee extensors to fit the force following stretch with a biexponential decay. In both muscle groups the decay half-life of the first exponential was two times slower in the older compared with young men. There were significant associations between PFE and the decay in force, suggesting a greater "non-active" contribution to total RFE across muscles in older compared with young men. The greater "non-active" component of RFE in older adults could be due to structural age-related changes causing increased muscle stiffness during and following stretch. PMID:25242133

  18. Redox Signal-mediated Enhancement of the Temperature Sensitivity of Transient Receptor Potential Melastatin 2 (TRPM2) Elevates Glucose-induced Insulin Secretion from Pancreatic Islets.

    PubMed

    Kashio, Makiko; Tominaga, Makoto

    2015-05-01

    Transient receptor potential melastatin 2 (TRPM2) is a thermosensitive Ca(2+)-permeable cation channel expressed by pancreatic β cells where channel function is constantly affected by body temperature. We focused on the physiological functions of redox signal-mediated TRPM2 activity at body temperature. H2O2, an important molecule in redox signaling, reduced the temperature threshold for TRPM2 activation in pancreatic β cells of WT mice but not in TRPM2KO cells. TRPM2-mediated [Ca(2+)]i increases were likely caused by Ca(2+) influx through the plasma membrane because the responses were abolished in the absence of extracellular Ca(2+). In addition, TRPM2 activation downstream from the redox signal plus glucose stimulation enhanced glucose-induced insulin secretion. H2O2 application at 37 °C induced [Ca(2+)]i increases not only in WT but also in TRPM2KO β cells. This was likely due to the effect of H2O2 on KATP channel activity. However, the N-acetylcysteine-sensitive fraction of insulin secretion by WT islets was increased by temperature elevation, and this temperature-dependent enhancement was diminished significantly in TRPM2KO islets. These data suggest that endogenous redox signals in pancreatic β cells elevate insulin secretion via TRPM2 sensitization and activity at body temperature. The results in this study could provide new therapeutic approaches for the regulation of diabetic conditions by focusing on the physiological function of TRPM2 and redox signals. PMID:25817999

  19. Diffusion Enhancement in FePt Nanoparticles for L1_0 Stability

    NASA Astrophysics Data System (ADS)

    Acet, Mehmet; Spasova, M.; Elsukova, A.

    FePt has a high magnetic anisotropy in the thermodynamically stable L1_0 phase, so that nanoparticles of this material could remain ferromagnetic at small sizes and be used for magnetic storage. However, the stabilization of the L1_0 phase is not straight forward at small particle sizes, and instead, twinned icosahedral structures are formed which are thought to be metastable. In order to enhance the formation of the L1_0 phase, the lattice has to be agitated so that icosahedral structures will destabilize. In addition to thermal annealing we introduce agitation methods related to oxygen reactive sputtering, nitriding-denitriding, and segregation in FePt nanoparticles prepared in the gas phase. We discuss principally the structural properties of the particles obtained prior to and after employing the various agitation techniques.

  20. Diffuse reflectance spectroscopy measurement of substrate temperature and temperature transient during molecular beam epitaxy and implications for low-temperature III-V epitaxy

    NASA Astrophysics Data System (ADS)

    Thompson, P.; Li, Y.; Zhou, J. J.; Sato, D. L.; Flanders, L.; Lee, H. P.

    1997-03-01

    We report diffuse reflectance spectroscopy (DRS) measurement of Knudsen cell induced radiative heating of the sample during molecular beam epitaxy of GaAs at substrate temperatures between 200 and 600 C. The temperature rises, as large as 12 C, were observed for In-bonded samples at a substrate temperature of 200 C. As-grown GaAs layers deposited between 200 and 300 C are characterized using double crystal x-ray diffraction. The onset of a distinct x-ray peak associated with the low-temperature grown GaAs layer is identified, at a DRS measured temperature between 260 and 270 C.

  1. Arctic canopy photosynthetic efficiency enhanced under diffuse light, linked to a reduction in the fraction of the canopy in deep shade.

    PubMed

    Williams, Mathew; Rastetter, Edward B; Van der Pol, Laura; Shaver, Gaius R

    2014-06-01

    We investigated how radiation conditions within a tundra canopy were linked to canopy photosynthesis, and how this linkage explained photosynthetic sensitivity to sky conditions, that is total radiation and its diffuse fraction. We measured within canopy radiation at leaf scales and net CO2 exchanges at canopy scales, under varied total irradiance and diffuse fraction, in Alaskan shrub tundra. Normalised mean radiation profiles within canopies showed no significant differences with varied diffuse fractions. However, radiation density distribution was non-normal, being more unimodal under diffuse conditions and distinctly bimodal under direct sunlight. There was a nearly three-fold increase in the proportion of the canopy in deep shade under direct illumination, compared to diffuse conditions. Under diffuse conditions the canopy had higher light-use efficiency (LUE), resulting in up to 17% greater photosynthesis. The enhancement in LUE under diffuse illumination was not related to differences in the mean light profiles, but instead was due to significant shifts in the density distribution of light at leaf scales, in particular a reduced fraction of the canopy in deep shade under diffuse illumination. These results provide unique information for testing radiative transfer schemes in canopy models, and for better understanding canopy structure and trait variation within plant canopies. PMID:24593320

  2. Transient performance

    NASA Astrophysics Data System (ADS)

    Curnock, Barry

    Gas turbine engine transient behavior, that which is concerned with the changes in engine parameters during acceleration or decceleration of an engine from one steady state point to a different steady state point, is considered. An engine can also experience cyclic aerodynamic phenomena which occur at a nominally steady condition; examples are compressor rotator stall and intake or afterburner buzz. The following are discussed: certification requirements; mechanism of acceleration; compressor working lines and surge; and some important factors (pressure level, moment of inertia, heat soakage, clearances, measurement of transients, thrust reversal, and transient maneuvers which involve significant changes to the shaft speeds of the engine). A set of graphics illustrating transient performance is presented.

  3. Transient Intervals of Hyper-Gravity Enhance Endothelial Barrier Integrity: Impact of Mechanical and Gravitational Forces Measured Electrically

    PubMed Central

    Szulcek, Robert; van Bezu, Jan; Boonstra, Johannes; van Loon, Jack J. W. A.; van Nieuw Amerongen, Geerten P.

    2015-01-01

    Background Endothelial cells (EC) guard vascular functions by forming a dynamic barrier throughout the vascular system that sensitively adapts to ‘classical’ biomechanical forces, such as fluid shear stress and hydrostatic pressure. Alterations in gravitational forces might similarly affect EC integrity, but remain insufficiently studied. Methods In an unique approach, we utilized Electric Cell-substrate Impedance Sensing (ECIS) in the gravity-simulators at the European Space Agency (ESA) to study dynamic responses of human EC to simulated micro- and hyper-gravity as well as to classical forces. Results Short intervals of micro- or hyper-gravity evoked distinct endothelial responses. Stimulated micro-gravity led to decreased endothelial barrier integrity, whereas hyper-gravity caused sustained barrier enhancement by rapid improvement of cell-cell integrity, evidenced by a significant junctional accumulation of VE-cadherin (p = 0.011), significant enforcement of peripheral F-actin (p = 0.008) and accompanied by a slower enhancement of cell-matrix interactions. The hyper-gravity triggered EC responses were force dependent and nitric-oxide (NO) mediated showing a maximal resistance increase of 29.2±4.8 ohms at 2g and 60.9±6.2 ohms at 4g vs. baseline values that was significantly suppressed by NO blockage (p = 0.011). Conclusion In conclusion, short-term application of hyper-gravity caused a sustained improvement of endothelial barrier integrity, whereas simulated micro-gravity weakened the endothelium. In clear contrast, classical forces of shear stress and hydrostatic pressure induced either short-lived or no changes to the EC barrier. Here, ECIS has proven a powerful tool to characterize subtle and distinct EC gravity-responses due to its high temporal resolution, wherefore ECIS has a great potential for the study of gravity-responses such as in real space flights providing quantitative assessment of a variety of cell biological characteristics of any adherent growing cell type in an automated and continuous fashion. PMID:26637177

  4. Magnetofection Mediated Transient NANOG Overexpression Enhances Proliferation and Myogenic Differentiation of Human Hair Follicle Derived Mesenchymal Stem Cells.

    PubMed

    Son, Seoyoung; Liang, Mao-Shih; Lei, Pedro; Xue, Xiaozheng; Furlani, Edward P; Andreadis, Stelios T

    2015-07-15

    We used magnetofection (MF) to achieve high transfection efficiency into human mesenchymal stem cells (MSCs). A custom-made magnet array, matching well-to-well to a 24-well plate, was generated and characterized. Theoretical predictions of magnetic force distribution within each well demonstrated that there was no magnetic field interference among magnets in adjacent wells. An optimized protocol for efficient gene delivery to human hair follicle derived MSCs (hHF-MSCs) was established using an egfp-encoding plasmid, reaching approximately ∼50% transfection efficiency without significant cytotoxicity. Then we applied the optimized MF protocol to express the pluripotency-associated transcription factor NANOG, which was previously shown to reverse the effects of organismal aging on MSC proliferation and myogenic differentiation capacity. Indeed, MF-mediated NANOG delivery increased proliferation and enhanced the differentiation of hHF-MSCs into smooth muscle cells (SMCs). Collectively, our results show that MF can achieve high levels of gene delivery to MSCs and, therefore, may be employed to moderate or reverse the effects of cellular senescence or reprogram cells to the pluripotent state without permanent genetic modification. PMID:25685943

  5. Nuclear Overhauser Enhancement Imaging of Glioblastoma at 7 Tesla: Region Specific Correlation with Apparent Diffusion Coefficient and Histology

    PubMed Central

    Windschuh, Johannes; Meissner, Jan-Eric; Zaiss, Moritz; Eidel, Oliver; Kickingereder, Philipp; Nowosielski, Martha; Wiestler, Benedikt; Sahm, Felix; Floca, Ralf Omar; Neumann, Jan-Oliver; Wick, Wolfgang; Heiland, Sabine; Bendszus, Martin; Schlemmer, Heinz-Peter; Ladd, Mark Edward; Bachert, Peter; Radbruch, Alexander

    2015-01-01

    Objective To explore the correlation between Nuclear Overhauser Enhancement (NOE)-mediated signals and tumor cellularity in glioblastoma utilizing the apparent diffusion coefficient (ADC) and cell density from histologic specimens. NOE is one type of chemical exchange saturation transfer (CEST) that originates from mobile macromolecules such as proteins and might be associated with tumor cellularity via altered protein synthesis in proliferating cells. Patients and Methods For 15 patients with newly diagnosed glioblastoma, NOE-mediated CEST-contrast was acquired at 7 Tesla (asymmetric magnetization transfer ratio (MTRasym) at 3.3ppm, B1 = 0.7 ?T). Contrast enhanced T1 (CE-T1), T2 and diffusion-weighted MRI (DWI) were acquired at 3 Tesla and coregistered. The T2 edema and the CE-T1 tumor were segmented. ADC and MTRasym values within both regions of interest were correlated voxelwise yielding the correlation coefficient rSpearman (rSp). In three patients who underwent stereotactic biopsy, cell density of 12 specimens per patient was correlated with corresponding MTRasym and ADC values of the biopsy site. Results Eight of 15 patients showed a weak or moderate positive correlation of MTRasym and ADC within the T2 edema (0.16?rSp?0.53, p<0.05). Seven correlations were statistically insignificant (p>0.05, n = 4) or yielded rSp?0 (p<0.05, n = 3). No trend towards a correlation between MTRasym and ADC was found in CE-T1 tumor (-0.310.05, n = 6). The biopsy-analysis within CE-T1 tumor revealed a strong positive correlation between tumor cellularity and MTRasym values in two of the three patients (rSppatient3 = 0.69 and rSppatient15 = 0.87, p<0.05), while the correlation of ADC and cellularity was heterogeneous (rSppatient3 = 0.545 (p = 0.067), rSppatient4 = -0.021 (p = 0.948), rSppatient15 = -0.755 (p = 0.005)). Discussion NOE-imaging is a new contrast promising insight into pathophysiologic processes in glioblastoma regarding cell density and protein content, setting itself apart from DWI. Future studies might be based on the assumption that NOE-mediated CEST visualizes cellularity more accurately than ADC, especially in the CE-T1 tumor region. PMID:25789657

  6. Connectivity-based fixel enhancement: Whole-brain statistical analysis of diffusion MRI measures in the presence of crossing fibres.

    PubMed

    Raffelt, David A; Smith, Robert E; Ridgway, Gerard R; Tournier, J-Donald; Vaughan, David N; Rose, Stephen; Henderson, Robert; Connelly, Alan

    2015-08-15

    In brain regions containing crossing fibre bundles, voxel-average diffusion MRI measures such as fractional anisotropy (FA) are difficult to interpret, and lack within-voxel single fibre population specificity. Recent work has focused on the development of more interpretable quantitative measures that can be associated with a specific fibre population within a voxel containing crossing fibres (herein we use fixel to refer to a specific fibre population within a single voxel). Unfortunately, traditional 3D methods for smoothing and cluster-based statistical inference cannot be used for voxel-based analysis of these measures, since the local neighbourhood for smoothing and cluster formation can be ambiguous when adjacent voxels may have different numbers of fixels, or ill-defined when they belong to different tracts. Here we introduce a novel statistical method to perform whole-brain fixel-based analysis called connectivity-based fixel enhancement (CFE). CFE uses probabilistic tractography to identify structurally connected fixels that are likely to share underlying anatomy and pathology. Probabilistic connectivity information is then used for tract-specific smoothing (prior to the statistical analysis) and enhancement of the statistical map (using a threshold-free cluster enhancement-like approach). To investigate the characteristics of the CFE method, we assessed sensitivity and specificity using a large number of combinations of CFE enhancement parameters and smoothing extents, using simulated pathology generated with a range of test-statistic signal-to-noise ratios in five different white matter regions (chosen to cover a broad range of fibre bundle features). The results suggest that CFE input parameters are relatively insensitive to the characteristics of the simulated pathology. We therefore recommend a single set of CFE parameters that should give near optimal results in future studies where the group effect is unknown. We then demonstrate the proposed method by comparing apparent fibre density between motor neurone disease (MND) patients with control subjects. The MND results illustrate the benefit of fixel-specific statistical inference in white matter regions that contain crossing fibres. PMID:26004503

  7. Connectivity-based fixel enhancement: Whole-brain statistical analysis of diffusion MRI measures in the presence of crossing fibres

    PubMed Central

    Raffelt, David A.; Smith, Robert E.; Ridgway, Gerard R.; Tournier, J-Donald; Vaughan, David N.; Rose, Stephen; Henderson, Robert; Connelly, Alan

    2015-01-01

    In brain regions containing crossing fibre bundles, voxel-average diffusion MRI measures such as fractional anisotropy (FA) are difficult to interpret, and lack within-voxel single fibre population specificity. Recent work has focused on the development of more interpretable quantitative measures that can be associated with a specific fibre population within a voxel containing crossing fibres (herein we use fixel to refer to a specific fibre population within a single voxel). Unfortunately, traditional 3D methods for smoothing and cluster-based statistical inference cannot be used for voxel-based analysis of these measures, since the local neighbourhood for smoothing and cluster formation can be ambiguous when adjacent voxels may have different numbers of fixels, or ill-defined when they belong to different tracts. Here we introduce a novel statistical method to perform whole-brain fixel-based analysis called connectivity-based fixel enhancement (CFE). CFE uses probabilistic tractography to identify structurally connected fixels that are likely to share underlying anatomy and pathology. Probabilistic connectivity information is then used for tract-specific smoothing (prior to the statistical analysis) and enhancement of the statistical map (using a threshold-free cluster enhancement-like approach). To investigate the characteristics of the CFE method, we assessed sensitivity and specificity using a large number of combinations of CFE enhancement parameters and smoothing extents, using simulated pathology generated with a range of test-statistic signal-to-noise ratios in five different white matter regions (chosen to cover a broad range of fibre bundle features). The results suggest that CFE input parameters are relatively insensitive to the characteristics of the simulated pathology. We therefore recommend a single set of CFE parameters that should give near optimal results in future studies where the group effect is unknown. We then demonstrate the proposed method by comparing apparent fibre density between motor neurone disease (MND) patients with control subjects. The MND results illustrate the benefit of fixel-specific statistical inference in white matter regions that contain crossing fibres. PMID:26004503

  8. TU-A-9A-11: Gold Nanoparticles Enhanced Diffuse Optical Tomography: A Proof of Concept Study

    SciTech Connect

    Yang, Y; Dogan, N

    2014-06-15

    Purpose: To investigate the feasibility and potential of gold nanoparticles (GNP) enhanced diffuse optical tomography (DOT) as a novel imaging strategy for tumor detection. Methods: Simulation was performed on a digital homogeneous cylindrical phantom of 30mm×30mm. Gold nanorods (GNR) with aspect ratio 3.9 and effective radius 21.86nm were used as contrast agent. The peak light absorption for these GNR occurs at 842nm within the near-infrared region, with the absorption cross-section of 1.97×10{sup -14}m{sup -2} and scatter cross-section of 1.07×10{sup -14}m{sup -2}. A 6mmdiameter sphere of GNR solution was positioned inside the tissue-simulating phantom. Simulations were performed at the GNR concentration level of 1nM, 100pM and 10pM, respectively. The points representing laser sources and light detectors were around the phantom with 30o apart tangentially and 1mm apart axially for 9 rows. As one point being source, all the other points within the current row and nearby four rows become detectors. Hence there are 108 source points in total and 55 detector points corresponding to each source. Forward light transport at 842nm wavelength was run on a three-dimensional mesh of 33186 nodes (∼0.5mm resolution) to acquire the light emission data. Reconstruction was performed on a coarse mesh of 19408 nodes (∼1mm resolution) with ∼20minutes on a 2.4GHz CPU and 8GB RAM computer. Results: The position of the GNR solution at 1nM, 100pM and 10pM concentration was reconstructed, respectively, with <1mm error. The GNR concentration was interpreted from the reconstructed absorption coefficient within the enhanced volume. The reconstructed maximum concentrations were 0.3nM, 120.0pM, and 5.3pM, respectively. Conclusion: To the best of our knowledge, this is the first time to apply GNP to enhance DOT. The simulation results showed the high sensitivity of GNP enhanced DOT, which is in pM concentration level, compared to the μM level for MRI agents and nM level for PET agents.

  9. Transient-mode liquid phase epitaxial growth of GaAs on GaAs-coated Si substrates prepared by migration-enhanced molecular beam epitaxy

    NASA Technical Reports Server (NTRS)

    Nakamura, Shuji; Sakai, Shiro; Chang, Shi S.; Ramaswamy, Ramu V.; Kim, Jae-Hoon; Radhakrishnan, Gouri; Liu, John K.; Katz, Joseph

    1989-01-01

    Planar oxide-maskless growth of GaAs was demonstrated by transient-mode liquid phase epitaxy (TMLPE) on GaAs-coated Si substrates that were prepared by migration-enhanced molecular beam epitaxy (MEMBE). In TMLPE, the cool substrate was brought into contact with hot melts for a short time. A GaAs layer as thick as 30 microns was grown in 10 sec. The etch pits observed in TMLPE-grown layers became longer in one direction and decreased in density with increasing the TMLPE epilayer thickness. The density of etch pits in a 20 micron-thick layer was approximately 5 x 10 the 6th/sq cm. Strong bandgap emission elliptically polarized with a major axis perpendicular to the surface was observed at about 910 nm, while deep-level emission from the TMLPE/MEMBE GaAs interface was detected at 980 nm. The photoluminescence intensity divided by the carrier concentration of the TMLPE-grown layer was about 270 times larger than that of the MEMBE-grown layer used as a substrate.

  10. Evaluation of Transient Elastography, Acoustic Radiation Force Impulse Imaging (ARFI), and Enhanced Liver Function (ELF) Score for Detection of Fibrosis in Morbidly Obese Patients

    PubMed Central

    Karlas, Thomas; Dietrich, Arne; Peter, Veronica; Wittekind, Christian; Lichtinghagen, Ralf; Garnov, Nikita; Linder, Nicolas; Schaudinn, Alexander; Busse, Harald; Prettin, Christiane; Keim, Volker; Trltzsch, Michael; Schtz, Tatjana; Wiegand, Johannes

    2015-01-01

    Background Liver fibrosis induced by non-alcoholic fatty liver disease causes peri-interventional complications in morbidly obese patients. We determined the performance of transient elastography (TE), acoustic radiation force impulse (ARFI) imaging, and enhanced liver fibrosis (ELF) score for fibrosis detection in bariatric patients. Patients and Methods 41 patients (median BMI 47 kg/m2) underwent 14-day low-energy diets to improve conditions prior to bariatric surgery (day 0). TE (M and XL probe), ARFI, and ELF score were performed on days -15 and -1 and compared with intraoperative liver biopsies (NAS staging). Results Valid TE and ARFI results at day -15 and -1 were obtained in 49%/88% and 51%/90% of cases, respectively. High skin-to-liver-capsule distances correlated with invalid TE measurements. Fibrosis of liver biopsies was staged as F1 and F3 in n = 40 and n = 1 individuals. However, variations (median/range at d-15/-1) of TE (4.6/2.675 and 6.7/2.921.3 kPa) and ARFI (2.1/0.73.7 and 2.0/0.73.8 m/s) were high and associated with overestimation of fibrosis. The ELF score correctly classified 87.5% of patients. Conclusion In bariatric patients, performance of TE and ARFI was poor and did not improve after weight loss. The ELF score correctly classified the majority of cases and should be further evaluated. PMID:26528818

  11. Tris-hydroxymethyl-aminomethane enhances capsaicin-induced intracellular Ca(2+) influx through transient receptor potential V1 (TRPV1) channels.

    PubMed

    Murakami, Satoshi; Sudo, Yuka; Miyano, Kanako; Nishimura, Hitomi; Matoba, Motohiro; Shiraishi, Seiji; Konno, Hiroki; Uezono, Yasuhito

    2016-02-01

    Non-selective transient receptor potential vanilloid (TRPV) cation channels are activated by various insults, including exposure to heat, acidity, and the compound capsaicin, resulting in sensations of pain in the skin, visceral organs, and oral cavity. Recently, TRPV1 activation was also demonstrated in response to basic pH elicited by ammonia and intracellular alkalization. Tris-hydroxymethyl aminomethane (THAM) is widely used as an alkalizing agent; however, the effects of THAM on TRPV1 channels have not been defined. In this study, we characterized the effects of THAM-induced TRPV1 channel activation in baby hamster kidney cells expressing human TRPV1 (hTRPV1) and the Ca(2+)-sensitive fluorescent sensor GCaMP2 by real-time confocal microscopy. Notably, both capsaicin (1 μM) and pH 6.5 buffer elicited steep increases in the intracellular Ca(2+) concentration ([Ca(2+)]i), while treatment with THAM (pH 8.5) alone had no effect. However, treatment with THAM (pH 8.5) following capsaicin application elicited a profound, long-lasting increase in [Ca(2+)]i that was completely inhibited by the TRPV1 antagonist capsazepine. Taken together, these results suggest that hTRPV1 pre-activation is required to provoke enhanced, THAM-induced [Ca(2+)]i increases, which could be a mechanism underlying pain induced by basic pH. PMID:26738986

  12. Theory of enhanced proximity effect by midgap Andreev resonant state in diffusive normal-metal/triplet superconductor junctions

    NASA Astrophysics Data System (ADS)

    Tanaka, Y.; Kashiwaya, S.; Yokoyama, T.

    2005-03-01

    Enhanced proximity effect by the midgap Andreev resonant state (MARS) in a diffusive normal-metal/insulator/triplet superconductor (DN/TS) junction is studied based on the Keldysh-Nambu quasiclassical Greens-function formalism. By choosing a p -wave superconductor as a typical example of the TS, conductance of the junction and the spatial variation of the quasiparticle local density of states (LDOS) in the DN are calculated as the function of the magnitudes of the resistance Rd , Thouless energy in the DN, and the transparency of the insulating barrier. The resulting conductance spectrum has a zero-bias conductance peak (ZBCP) and the LDOS has a zero energy peak (ZEP) except for ?=?/2 (0????/2) , where ? denotes the angle between the lobe direction of the p -wave pair potential and the normal to the interface. The widths of the ZBCP and the ZEP are reduced with the increase of Rd while their heights are drastically enhanced. These peaks are revealed to be suppressed by applying a magnetic field. When the magnitude of Rd / R0 is sufficiently large, the total zero voltage resistance of the junction is almost independent of the Rd for ???/2 . The extreme case is ?=0 , where total zero voltage resistance is always R0 /2 . We also studied the charge transport in px +i py -wave junctions, where only the quasiparticles with perpendicular injection feel the MARS. Even in this case, the resulting LDOS in the DN has a ZEP. Thus the existence of the ZEP in the LDOS of the DN region is a remarkable feature for DN/TS junctions which have never been expected for the DN/singlet superconductor junctions where the MARS and proximity effect compete with each other. Based on these results, a crucial test to identify triplet pairing superconductors based on tunneling experiments is proposed.

  13. Diffusion-weighted imaging and dynamic contrast-enhanced MRI in assessing response and recurrent disease in gynaecological malignancies.

    PubMed

    Hameeduddin, Ayshea; Sahdev, Anju

    2015-01-01

    Magnetic resonance imaging (MRI) has an established role in imaging pelvic gynaecological malignancies. It is routinely used in staging endometrial and cervical cancer, characterizing adnexal masses, selecting optimal treatment, monitoring treatment and detecting recurrent disease. MRI has also been shown to have an excellent performance and an evolving role in surveillance of patients after chemoradiotherapy in cervical cancer, post-trachelectomy, detecting early recurrence and planning exenterative surgery in isolated central recurrences in both cervical and endometrial cancer and in young patients on surveillance for medically managed endometrial cancer. However, conventional MRI still has limitations when the morphological appearance of early recurrent or residual disease overlaps with normal pelvic anatomy or treatment effects in the pelvis. In particular, after chemoradiotherapy for cervical cancer, distinguishing between radiotherapy changes and residual or early recurrent disease within the cervix or the vaginal vault can be challenging on conventional MRI alone. Therefore, there is an emerging need for functional imaging to overcome these limitations. The purpose of this paper is to discuss the emerging functional MRI techniques and their applications in predicting treatment response, detecting residual disease and early recurrent disease to optimize the treatment options available using diffusion-weighted imaging and dynamic contrast enhancement particularly in cervical and endometrial cancer. PMID:25889065

  14. Enhanced hydroxyl radical generation in the combined ozonation and electrolysis process using carbon nanotubes containing gas diffusion cathode.

    PubMed

    Wu, Donghai; Lu, Guanghua; Zhang, Ran; Lin, Qiuhong; Yan, Zhenhua; Liu, Jianchao; Li, Yi

    2015-10-01

    Combination of ozone together with electrolysis (ozone-electrolysis) is a promising wastewater treatment technology. This work investigated the potential use of carbon nanotube (CNT)-based gas diffusion cathode (GDC) for ozone-electrolysis process employing hydroxyl radicals (·OH) production as an indicator. Compared with conventional active carbon (AC)-polytetrafluoroethylene (PTFE) and carbon black (CB)-PTFE cathodes, the production of ·OH in the coupled process was improved using CNTs-PTFE GDC. Appropriate addition of acetylene black (AB) and pore-forming agent Na2SO4 could enhance the efficiency of CNTs-PTFE GDC. The optimum GDC composition was obtained by response surface methodology (RSM) analysis and was determined as CNTs 31.2 wt%, PTFE 60.6 wt%, AB 3.5 wt%, and Na2SO4 4.7 wt%. Moreover, the optimized CNT-based GDC exhibited much more effective than traditional Ti and graphite cathodes in Acid Orange 7 (AO7) mineralization and possessed the desirable stability without performance decay after ten times reaction. The comparison tests revealed that peroxone reaction was the main pathway of ·OH production in the present system, and cathodic reduction of ozone could significantly promote ·OH generation. These results suggested that application of CNT-based GDC offers considerable advantages in ozone-electrolysis of organic wastewater. PMID:26036588

  15. Characterization of light transport in scattering media at sub-diffusion length scales with Low-coherence Enhanced Backscattering

    PubMed Central

    Turzhitsky, Vladimir; Rogers, Jeremy D.; Mutyal, Nikhil N.; Roy, Hemant K.; Backman, Vadim

    2009-01-01

    Low-coherence enhanced backscattering (LEBS) is a technique that has recently shown promise for tissue characterization and the detection of early pre-cancer. Although several Monte Carlo models of LEBS have been described, these models have not been accurate enough to predict all of the experimentally observed LEBS features. We present an appropriate Monte Carlo model to simulate LEBS peak properties from polystyrene microsphere suspensions in water. Results show that the choice of the phase function greatly impacts the accuracy of the simulation when the transport mean free path (ls*) is much greater than the spatial coherence length (LSC). When ls* < LSC, a diffusion approximation based model of LEBS is sufficiently accurate. We also use the Monte Carlo model to validate that LEBS can be used to measure the radial scattering probability distribution (radial point spread function), p(r), at small length scales and demonstrate LEBS measurements of p(r) from biological tissue. In particular, we show that pre-cancerous and benign mucosal tissues have different small length scale light transport properties. PMID:21037980

  16. Disrupting NOTCH Slows Diffuse Intrinsic Pontine Glioma Growth, Enhances Radiation Sensitivity, and Shows Combinatorial Efficacy With Bromodomain Inhibition.

    PubMed

    Taylor, Isabella C; Htt-Cabezas, Marianne; Brandt, William D; Kambhampati, Madhuri; Nazarian, Javad; Chang, Howard T; Warren, Katherine E; Eberhart, Charles G; Raabe, Eric H

    2015-08-01

    NOTCH regulates stem cells during normal development and stemlike cells in cancer, but the roles of NOTCH in the lethal pediatric brain tumor diffuse intrinsic pontine glioma (DIPG) remain unknown. Because DIPGs express stem cell factors such as SOX2 and MYCN, we hypothesized that NOTCH activity would be critical for DIPG growth. We determined that primary DIPGs expressed high levels of NOTCH receptors, ligands, and downstream effectors. Treatment of the DIPG cell lines JHH-DIPG1 and SF7761 with the ?-secretase inhibitor MRK003 suppressed the level of the NOTCH effectors HES1, HES4, and HES5; inhibited DIPG growth by 75%; and caused a 3-fold induction of apoptosis. Short hairpin RNAs targeting the canonical NOTCH pathway caused similar effects. Pretreatment of DIPG cells with MRK003 suppressed clonogenic growth by more than 90% and enhanced the efficacy of radiation therapy. The high level of MYCN in DIPG led us to test sequential therapy with the bromodomain inhibitor JQ1 and MRK003, and we found that JQ1 and MRK003 inhibited DIPG growth and induced apoptosis. Together, these results suggest that dual targeting of NOTCH and MYCN in DIPG may be an effective therapeutic strategy in DIPG and that adding a ?-secretase inhibitor during radiation therapy may be efficacious initially or during reirradiation. PMID:26115193

  17. Quantification of fibrosis in infarcted swine hearts by ex vivo late gadolinium-enhancement and diffusion-weighted MRI methods

    NASA Astrophysics Data System (ADS)

    Pop, Mihaela; Ghugre, Nilesh R.; Ramanan, Venkat; Morikawa, Lily; Stanisz, Greg; Dick, Alexander J.; Wright, Graham A.

    2013-08-01

    Many have speculated that MRI signal characteristics can be used to identify regions of heterogeneous infarct associated with an arrhythmogenic substrate; however, direct evidence of this relationship is limited. The aim of this study was to demonstrate the remodelling characteristics of fibrosis by means of histology and high-resolution MR imaging. For this purpose, we performed whole-mount histology in heart samples (n = 9) collected from five swine at six weeks post-infarction and compared the extent of fibrosis in the infarcted areas delineated in these histological images with that obtained ex vivo by MRI using late gadolinium-enhancement (LGE) and diffusion-weighted imaging (DWI) methods. All MR images were obtained at a submillimetre resolution (i.e., voxel size of 0.6×0.6×1.2 mm3). Specifically, in the histology images, we differentiated moderate fibrosis (consisting of a mixture of viable and non-viable myocytes, known as border zone, BZ) from severe fibrosis (i.e., the dense scar). Correspondingly, tissue heterogeneities in the MR images were categorized by a Gaussian mixture model into healthy, BZ and scar. Our results showed that (a) both MRI methods were capable of qualitatively distinguishing sharp edges between dense scar and healthy tissue from regions of heterogeneous BZ; (b) the BZ and dense scar areas had intermediate-to-high increased values of signal intensity in the LGE images and of apparent diffusion coefficient in the DWI, respectively. In addition, as demonstrated by the Picrosirius Red and immunohistochemistry stains, the viable bundles in the BZ were clearly separated by thin collagen strands and had reduced expression of Cx43, whereas the core scar was composed of dense fibrosis. A quantitative analysis demonstrated that the comparison between BZ/scar extent in LGE and DWI to the corresponding areas identified in histology yielded very good correlations (i.e., for the scar identified by LGE, R2 was 0.96 compared to R2 = 0.93 for the scar identified in ADC maps, whereas the BZ had R2 = 0.95 for the correlation between LGE and histology compared to R2 = 0.91 obtained for ADC). This novel study represents an intermediate step in translating such research to the in vivo stages, as well as in establishing the best and most accurate MR method to help identify arrhythmia substrate in patients with structural heart disease.

  18. Atomistic modeling of intrinsic and radiation-enhanced fission gas (Xe) diffusion in UO2 +/- x: Implications for nuclear fuel performance modeling

    SciTech Connect

    Giovanni Pastore; Michael R. Tonks; Derek R. Gaston; Richard L. Williamson; David Andrs; Richard Martineau

    2014-03-01

    Based on density functional theory (DFT) and empirical potential calculations, the diffusivity of fission gas atoms (Xe) in UO2 nuclear fuel has been calculated for a range of non-stoichiometry (i.e. UO2x), under both out-of-pile (no irradiation) and in-pile (irradiation) conditions. This was achieved by first deriving expressions for the activation energy that account for the type of trap site that the fission gas atoms occupy, which includes the corresponding type of mobile cluster, the charge state of these defects and the chemistry acting as boundary condition. In the next step DFT calculations were used to estimate migration barriers and internal energy contributions to the thermodynamic properties and calculations based on empirical potentials were used to estimate defect formation and migration entropies (i.e. pre-exponentials). The diffusivities calculated for out-of-pile conditions as function of the UO2x nonstoichiometrywere used to validate the accuracy of the diffusion models and the DFT calculations against available experimental data. The Xe diffusivity is predicted to depend strongly on the UO2x non-stoichiometry due to a combination of changes in the preferred Xe trap site and in the concentration of uranium vacancies enabling Xe diffusion, which is consistent with experiments. After establishing the validity of the modeling approach, it was used for studying Xe diffusion under in-pile conditions, for which experimental data is very scarce. The radiation-enhanced Xe diffusivity is compared to existing empirical models. Finally, the predicted fission gas diffusion rates were implemented in the BISON fuel performance code and fission gas release from a Risø fuel rod irradiation experiment was simulated. 2014 Elsevier B.V. All rights

  19. Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase II enhances CO2 fluxes across Xenopus oocyte plasma membranes.

    PubMed

    Musa-Aziz, Raif; Occhipinti, Rossana; Boron, Walter F

    2014-11-01

    The ?-carbonic anhydrases (CAs) are zinc-containing enzymes that catalyze the interconversion of CO2 and HCO3 (-). Here, we focus on human CA II (CA II), a ubiquitous cytoplasmic enzyme. In the second paper in this series, we examine CA IV at the extracellular surface. After microinjecting recombinant CA II in a Tris solution (or just Tris) into oocytes, we expose oocytes to 1.5% CO2/10 mM HCO3 (-)/pH 7.50 while using microelectrodes to monitor intracellular pH (pHi) and surface pH (pHS). CO2 influx causes the familiar sustained pHi fall as well as a transient pHS rise; CO2 efflux does the opposite. Both during CO2 addition and removal, CA II increases the magnitudes of the maximal rate of pHi change, (dpHi/dt)max, and the maximal change in pHS, ?pHS. Preincubating oocytes with the inhibitor ethoxzolamide eliminates the effects of CA II. Compared with pHS, pHi begins to change only after a delay of ~9 s and its relaxation has a larger (i.e., slower) time constant (?pHi > ?pHS ). Simultaneous measurements with two pHi electrodes, one superficial and one deep, suggest that impalement depth contributes to pHi delay and higher ?pHi . Using higher CO2/HCO3 (-) levels, i.e., 5%/33 mM HCO3 (-) or 10%/66 mM HCO3 (-), increases (dpHi/dt)max and ?pHS, though not in proportion to the increase in [CO2]. A reaction-diffusion mathematical model (described in the third paper in this series) accounts for the above general features and supports the conclusion that cytosolic CA-consuming entering CO2 or replenishing exiting CO2-increases CO2 fluxes across the cell membrane. PMID:24965587

  20. Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase II enhances CO2 fluxes across Xenopus oocyte plasma membranes

    PubMed Central

    Occhipinti, Rossana; Boron, Walter F.

    2014-01-01

    The ?-carbonic anhydrases (CAs) are zinc-containing enzymes that catalyze the interconversion of CO2 and HCO3?. Here, we focus on human CA II (CA II), a ubiquitous cytoplasmic enzyme. In the second paper in this series, we examine CA IV at the extracellular surface. After microinjecting recombinant CA II in a Tris solution (or just Tris) into oocytes, we expose oocytes to 1.5% CO2/10 mM HCO3?/pH 7.50 while using microelectrodes to monitor intracellular pH (pHi) and surface pH (pHS). CO2 influx causes the familiar sustained pHi fall as well as a transient pHS rise; CO2 efflux does the opposite. Both during CO2 addition and removal, CA II increases the magnitudes of the maximal rate of pHi change, (dpHi/dt)max, and the maximal change in pHS, ?pHS. Preincubating oocytes with the inhibitor ethoxzolamide eliminates the effects of CA II. Compared with pHS, pHi begins to change only after a delay of ?9 s and its relaxation has a larger (i.e., slower) time constant (?pHi > ?pHS). Simultaneous measurements with two pHi electrodes, one superficial and one deep, suggest that impalement depth contributes to pHi delay and higher ?pHi. Using higher CO2/HCO3? levels, i.e., 5%/33 mM HCO3? or 10%/66 mM HCO3?, increases (dpHi/dt)max and ?pHS, though not in proportion to the increase in [CO2]. A reaction-diffusion mathematical model (described in the third paper in this series) accounts for the above general features and supports the conclusion that cytosolic CAconsuming entering CO2 or replenishing exiting CO2increases CO2 fluxes across the cell membrane. PMID:24965587

  1. Oxidative stress increases phosphorylation of IkappaB kinase-alpha by enhancing NF-kappaB-inducing kinase after transient focal cerebral ischemia.

    PubMed

    Song, Yun Seon; Kim, Min-Soo; Kim, Hyun-Ae; Jung, Bo-In; Yang, Jiwon; Narasimhan, Purnima; Kim, Gab Seok; Jung, Joo Eun; Park, Eun-Hee; Chan, Pak H

    2010-07-01

    The IkappaB kinase (IKK) complex is a central component in the classic activation of the nuclear factor-kappaB (NF-kappaB) pathway. It has been reported to function in physiologic responses, including cell death and inflammation. We have shown that IKK is regulated by oxidative status after transient focal cerebral ischemia (tFCI) in mice. However, the mechanism by which oxidative stress influences IKKs after tFCI is largely unknown. Nuclear accumulation and phosphorylation of IKKalpha (pIKKalpha) were observed 1 h after 30 mins of tFCI in mice. In copper/zinc-superoxide dismutase knockout mice, levels of NF-kappaB-inducing kinase (NIK) (an upstream kinase of IKKalpha), pIKKalpha, and phosphorylation of histone H3 (pH3) on Ser10 were increased after tFCI and were higher than in wild-type mice. Immunohistochemistry showed nuclear accumulation and pIKKalpha in mouse brain endothelial cells after tFCI. Nuclear factor-kappaB-inducing kinase was increased, and it enhanced pH3 by inducing pIKKalpha after oxygen-glucose deprivation (OGD) in mouse brain endothelial cells. Both NIK and pH3 interactions with IKKalpha were confirmed by coimmunoprecipitation. Treatment with IKKalpha small interfering RNA significantly reduced cell death after OGD. These results suggest that augmentation of NIK, IKKalpha, and pH3 in response to oxidative stress is involved in cell death after cerebral ischemia (or stroke). PMID:20125184

  2. Enhanced production of secretory glycoprotein VSTM1-v2 with mouse IgG? signal peptide in optimized HEK293F transient transfection.

    PubMed

    Liu, Huihui; Zou, Xiajuan; Li, Ting; Wang, Xiaolin; Yuan, Wanqiong; Chen, Yingyu; Han, Wenling

    2016-02-01

    VSTM1-v2 is a secretory glycoprotein identified by our laboratory. Our previous study revealed that VSTM1-v2 could promote differentiation and activation of Th17 cells. To explore the role of VSTM1-v2 in the immune system further, a source of abundant high-quality recombinant protein is warranted. However, high-level expression of bioactive VSTM1-v2 is difficult due to its weak secretion capacity. To obtain sufficient recombinant VSTM1-v2, we developed an improved expression and purification system by replacing the native signal peptide with a mouse IgG? signal peptide that did not alter the protein cleavage site. We also optimized parameters for a transient gene expression system in HEK293F cells suspended in serum-free media with polyethyleneimine. Finally, 3.6mg/L recombinant VSTM1-v2 protein with N-glycosylation and no less than 95% purity was obtained through one-step purification with Ni affinity chromatography. The final yield after purification was increased by more than 7-fold compared to the yield from our previously reported HEK293T system (from 0.5mg/L to 3.6mg/L). More importantly, VSTM1-v2 protein exhibited excellent bioactivity. In conclusion, the improved system is not only a dependable source of abundant bioactive VSTM1-v2 for functional studies but also demonstrates a highly efficient approach for enhancing the production of proteins in a short time period, especially for secretory proteins with poor yields. PMID:26140918

  3. Sensitivity enhancement in direct coupling of supported liquid membrane extractions to capillary electrophoresis by means of transient isotachophoresis and large electrokinetic injections.

    PubMed

    Pant??kov, Pavla; Kub?, Pavel; Bo?ek, Petr

    2015-04-10

    Enhanced sensitivity for determination of basic drugs in body fluids was achieved by in-line coupling of extraction across supported liquid membrane (SLM) to large electrokinetic injection and transient isotachophoresis-capillary zone electrophoresis (tITP-CZE) in commercial CZE instrument. Twelve cm long tITP plug of 300mM ammonium acetate was formed in the separation capillary just before the electrokinetic injection of acceptor solution containing nortriptyline, haloperidol and loperamide extracted across the SLM. The tITP plug ensured efficient stacking and preconcentration of the injected basic drugs due to the tITP action of ammonium and the drugs were then separated by CZE using 5.2M acetic acid as background electrolyte. No interferences were observed from highly-abundant body fluid species (NaCl and human serum albumin) due to the excellent clean-up properties of SLMs and analytical sensitivity increased up to 340 times compared to SLM extractions coupled in-line to CZE with standard hydrodynamic injections. The SLM-tITP-CZE method was characterized by good repeatability (RSDs of peak areas below 7.8%), linearity over two orders of magnitude (r(2) better than 0.994) and limits of detection (defined as 3S/N) between 3 and 45?g/L. Interfacing of SLM extractions to CZE instrumentation was achieved by low-cost, disposable micro-extraction devices, which can be routinely prepared in every analytical laboratory. These devices eliminated sample carry-over, minimized the need for manual sample handling and ensured fully automated determination (including extraction, injection, preconcentration and separation) of the three basic drugs in 20?L of untreated body fluids. PMID:25747667

  4. Diffusion-Weighted and Gd-EOB-DTPA–Contrast-Enhanced Magnetic Resonance Imaging for Characterization of Tumor Necrosis in an Animal Model

    PubMed Central

    Vossen, Josephina A.; Buijs, Manon; Geschwind, Jean-Francois H.; Liap, Eleni; Ventura, Veronica Prieto; Lee, Kwang Hun; Bluemke, David A; Kamel, Ihab R

    2009-01-01

    Purpose To evaluate the role of diffusion-weighted magnetic resonance imaging (MRI) in determining tumor necrosis and contrast-enhanced MRI using gadoxetic acid disodium (Gd-EOB-DTPA) in determining maximum tumor size measurement and tumor delineation compared with criterion-standard histologic measurements in the rabbit VX2 liver tumor model. Materials and Methods VX2 tumors were implanted in the livers of 13 rabbits. Magnetic resonance imaging was performed using a 1.5-T MRI scanner and an extremity coil. The imaging protocol included T2-weighted fast spin-echo images, 3-dimensional T1-weighted spoiled gradient-echo with and without fat suppression after administration of Gd-EOB-DTPA, and diffusion-weighted echo planar images. Rabbits were killed, and the tumor was harvested and sliced at 4-mm intervals in the axial plane. The MRI parameters evaluated were tumor size, tumor delineation, and tumor apparent diffusion coefficient (ADC) values. Histologic sections were evaluated to quantify tumor necrosis. Results On contrast-enhanced MRI (obtained from 11 rabbits), the mean tumor sizes were 20, 19, and 20 mm in the arterial, portal venous, and delayed phases, respectively. Tumor delineation was most distinguishable in the delayed phase. On diffusion-weighted MRI (acquired in 13 rabbits), the mean tumor ADC value was 1.84 × 10−3 mm2/s. The mean tumor size at pathology was 16 mm. The mean percent necrosis at the tumor’s pathologic condition was 36%. The correlation between ADC value and percent necrosis showed an R value of 0.68. Conclusions Contrast-enhanced MRI using Gd-EOB-DTPA may provide additional information about tumor outline in the liver. More-over, we showed a remarkable correlation between ADC values and tumor necrosis. Thus, diffusion-weighted imaging may be useful to assess tumor necrosis; nevertheless, the search for new modalities remains important. PMID:19638862

  5. Modeling the Effect of Intra-Voxel Diffusion of Contrast Agent on the Quantitative Analysis of Dynamic Contrast Enhanced Magnetic Resonance Imaging

    PubMed Central

    Barnes, Stephanie L.; Quarles, C. Chad; Yankeelov, Thomas E.

    2014-01-01

    Quantitative dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) provides estimates of physiologically relevant parameters related to tissue blood flow, vascular permeability, and tissue volume fractions which can then be used for prognostic and diagnostic reasons. However, standard techniques for DCE-MRI analysis ignore intra-voxel diffusion, which may play an important role in contrast agent distribution and voxel signal intensity and, thus, will affect quantification of the aforementioned parameters. To investigate the effect of intra-voxel diffusion on quantitative DCE-MRI, we developed a finite element model of contrast enhancement at the voxel level. For diffusion in the range of that expected for gadolinium chelates in tissue (i.e., 110?4 to 410?4 mm2/s), parameterization errors range from ?58% to 12% for Ktrans, ?9% to 8% for ve, and ?60% to 213% for vp over the range of Ktrans, ve, vp, and temporal resolutions investigated. Thus the results show that diffusion has a significant effect on parameterization using standard techniques. PMID:25275536

  6. Coercivity enhancement of recycled Nd-Fe-B sintered magnets by grain boundary diffusion with DyH3 nano-particles

    NASA Astrophysics Data System (ADS)

    Ji, Weixiao; Liu, Weiqiang; Yue, Ming; Zhang, Dongtao; Zhang, Jiuxing

    2015-11-01

    The waste VCM magnets were disassembled from hard disk. After removing the coating of nickel by electrochemical method, the waste VCM magnets were recycled by grain boundary diffusion with DyH3 nano-particles. Compared to that of the original magnet, the coercivity of recycled magnets increases by 11.81 kOe, while the remanence keeps almost invariant. Investigation shows that Dy is preferentially enriched as (Nd,Dy)2Fe14B phase in the surface region of the Nd2Fe14B matrix grains indicated by the remarkable enhancement of the magneto-crystalline anisotropy field of the magnet. As a result, the magnet diffused with a small amount of DyH3 nano-particles possesses enhanced coercivity without remarkably sacrificing its magnetization.

  7. Intravoxel Incoherent Motion Diffusion-weighted Imaging of Multiple Myeloma Lesions: Correlation with Whole-Body Dynamic Contrast Agent-enhanced MR Imaging.

    PubMed

    Bourillon, Camille; Rahmouni, Alain; Lin, Chieh; Belhadj, Karim; Beaussart, Pauline; Vignaud, Alexandre; Zerbib, Pierre; Pigneur, Frdric; Cuenod, Charles-Andr; Bessalem, Hocine; Cavet, Madeleine; Boutekadjirt, Amal; Haioun, Corinne; Luciani, Alain

    2015-12-01

    Purpose To correlate intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) parameters with the enhancement patterns of bone marrow and focal lesion obtained on whole-body (WB) dynamic contrast agent-enhanced (DCE) magnetic resonance (MR) images in patients with stage-III multiple myeloma (MM) before and after systemic therapy. Materials and Methods Twenty-seven patients with MM were retrospectively included in this institutional review board-approved study. Requirement for written informed consent was waived. All patients underwent WB DCE MR imaging before treatment and 18 patients underwent repeat MR imaging 3 months after treatment. A transverse IVIM DWI sequence with 10 b values (0, 10, 20, 30, 50, 80, 100, 200, 400, and 800 sec/mm(2)) was acquired within bone marrow and focal lesions. The IVIM parameters (perfusion fraction [f], molecular diffusion coefficient [D], and perfusion-related D [D*]) and apparent diffusion coefficient (ADC) were extracted for both focal lesions and bone marrow and correlated with focal lesions and maximal bone marrow enhancement (BMEmax) (Spearman correlation coefficient) at baseline and at follow-up (Wilcoxon signed-rank test). Results D and ADC values positively correlated with BMEmax (r = 0.7, P < .001; and r = 0.455, P = .0435, respectively). Patients with increased BMEmax showed significantly increased ADC and D within bone marrow versus patients who did not have increased BMEmax (ADC, 0.67 10(-3) mm(2)/sec vs 0.54 10(-3) mm(2)/sec, P = .03; D, 0.58 10(-3) mm(2)/sec vs 0.42 10(-3) mm(2)/sec, P < .001). Within focal lesions, f was the maximum in lesions that showed enhancement followed by washout. After treatment in good responders, the significant decrease in maximal enhancement value of focal lesions (baseline vs after treatment, 213.9% 78.7 [standard deviation] vs 131% 53.6, respectively; P < .001) was accompanied by a significant decrease in f (baseline vs after treatment, 11% 3.8 vs 5.8% 4.7, respectively; P < .001). Conclusion Diffuse bone marrow involvement is associated with increased D. Hypervascular focal lesions with high maximal enhancement value of focal lesions also show high f value. Likewise, the decreased maximal enhancement value of focal lesions after treatment is accompanied by decreased f. () RSNA, 2015 Online supplemental material is available for this article. PMID:26131910

  8. Erratum: The chemistry of transient molecular cloud cores

    NASA Astrophysics Data System (ADS)

    Garrod, R. T.; Williams, D. A.; Hartquist, T. W.; Rawlings, J. M. C.; Viti, S.

    2005-09-01

    We assume that some, but not all, of the structure observed in molecular clouds is associated with transient features which are not bound by self-gravity. We investigate the chemistry of a transient density fluctuation, with properties similar to those of a core within a molecular cloud. We run a multipoint chemical code through a core's condensation from a diffuse medium to its eventual dispersion, over a period of ~1 Myr. The dynamical description adopted for our study is based on an understanding of a particular mechanism, involving slow-mode wave excitation, for transient structure formation which so far has been studied in detail only with plane-parallel models in which self-gravity has not been included. We find a significant enhancement of the chemical composition of the core material on its return to diffuse conditions, whilst the expansion of the core as it disperses moves this material out to large distances from the core centre. This process transports molecular species formed in the high-density regions out into the diffuse medium. Chemical enrichment of the cloud as a whole also occurs, as other cores of various sizes, life-spans and separations evolve throughout. Enrichment is strongly affected by freeze-out on to dust grains, which takes place in high-density, high visual extinction regions. As the core disperses after reaching its peak density and the visual extinction drops below a critical value, grain mantles are evaporated back into the gas phase, initiating more chemistry. The influence of the sizes, masses and cycle periods of cores will be large both for the level of chemical enrichment of a dark cloud and ultimately for the low-mass star formation rate. The cores in which stars form are almost certainly bound by their self-gravity and are not transient in the sense that the cores on which most of our study is focused are transient. Obviously, enrichment of the chemistry of low-density material will not take place if self-gravity prevents the re-expansion of a core. We also consider the case of a self-gravitating core, by holding its peak density conditions for a further 0.4 Myr. We find that the differences near the peak densities between transient and gravitationally bound cores are generally small, and the resultant column densities for objects near the peak densities do not provide definitive criteria for discriminating between transient and bound cores. However, increases in fractional abundances due to reinjection of mantle-borne species may provide a criterion for detection of a non-bound core.

  9. Investigation of starting transients in the thermally choked ram accelerator

    NASA Technical Reports Server (NTRS)

    Burnham, E. A.; Hinkey, J. B.; Bruckner, A. P.

    1992-01-01

    An experimental investigation of the starting transients of the thermally choked ram accelerator is presented in this paper. Construction of a highly instrumented tube section and instrumentation inserts provide high resolution experimental pressure, luminosity, and electromagnetic data of the starting transients. Data obtained prior to and following the entrance diaphragm show detailed development of shock systems in both combustible and inert mixtures. With an evacuated launch tube, starting the diffuser is possible at any Mach number above the Kantrowitz Mach number. The detrimental effects and possible solutions of higher launch tube pressures and excessive obturator leakage (blow-by) are discussed. Ignition of a combustible mixture is demonstrated with both perforated and solid obturators. The relative advantages and disadvantages of each are discussed. Data obtained from these starting experiments enhance the understanding of the ram accelerator, as well as assist in the validation of unsteady, chemically reacting CFD codes.

  10. Self- and dopant diffusion in extrinsic boron doped isotopically controlled silicon multilayer structures

    SciTech Connect

    Sharp, Ian D.; Bracht, Hartmut A.; Silvestri, Hughes H.; Nicols, Samuel P.; Beeman, Jeffrey W.; Hansen, John L.; Nylandsted Larsen, Arne; Haller, Eugene E.

    2002-04-01

    Isotopically controlled silicon multilayer structures were used to measure the enhancement of self- and dopant diffusion in extrinsic boron doped silicon. {sup 30}Si was used as a tracer through a multilayer structure of alternating natural Si and enriched {sup 28}Si layers. Low energy, high resolution secondary ion mass spectrometry (SIMS) allowed for simultaneous measurement of self- and dopant diffusion profiles of samples annealed at temperatures between 850 C and 1100 C. A specially designed ion- implanted amorphous Si surface layer was used as a dopant source to suppress excess defects in the multilayer structure, thereby eliminating transient enhanced diffusion (TED) behavior. Self- and dopant diffusion coefficients, diffusion mechanisms, and native defect charge states were determined from computer-aided modeling, based on differential equations describing the diffusion processes. We present a quantitative description of B diffusion enhanced self-diffusion in silicon and conclude that the diffusion of both B and Si is mainly mediated by neutral and singly positively charged self-interstitials under p-type doping. No significant contribution of vacancies to either B or Si diffusion is observed.

  11. Direct observation of dopant atom diffusion in a bulk semiconductor crystal enhanced by a large size mismatch.

    PubMed

    Ishikawa, Ryo; Mishra, Rohan; Lupini, Andrew R; Findlay, Scott D; Taniguchi, Takashi; Pantelides, Sokrates T; Pennycook, Stephen J

    2014-10-10

    Diffusion is one of the fundamental processes that govern the structure, processing, and properties of materials and it plays a crucial role in determining device lifetimes. However, direct observations of diffusion processes have been elusive and limited only to the surfaces of materials. Here we use an aberration-corrected electron microscope to locally excite and directly image the diffusion of single Ce and Mn dopants inside bulk wurtzite-type AlN single crystals, identifying correlated vacancy-dopant and interstitial-dopant kick-out mechanisms. Using a 200 kV electron beam to supply energy, we observe a higher frequency of dopant jumps for the larger and heavier Ce atoms than the smaller Mn atoms. These observations confirm density-functional-theory-based predictions of a decrease in diffusion barrier for large substitutional atoms. The results show that combining depth sensitive microscopy with theoretical calculations represents a new methodology to investigate diffusion mechanisms, not restricted to surface phenomena, but within bulk materials. PMID:25375721

  12. Glutathionylation-Dependence of Na(+)-K(+)-Pump Currents Can Mimic Reduced Subsarcolemmal Na(+) Diffusion.

    PubMed

    Garcia, Alvaro; Liu, Chia-Chi; Cornelius, Flemming; Clarke, Ronald J; Rasmussen, Helge H

    2016-03-01

    The existence of a subsarcolemmal space with restricted diffusion for Na(+) in cardiac myocytes has been inferred from a transient peak electrogenic Na(+)-K(+) pump current beyond steady state on reexposure of myocytes to K(+) after a period of exposure to K(+)-free extracellular solution. The transient peak current is attributed to enhanced electrogenic pumping of Na(+) that accumulated in the diffusion-restricted space during pump inhibition in K(+)-free extracellular solution. However, there are no known physical barriers that account for such restricted Na(+) diffusion, and we examined if changes of activity of the Na(+)-K(+) pump itself cause the transient peak current. Reexposure to K(+) reproduced a transient current beyond steady state in voltage-clamped ventricular myocytes as reported by others. Persistence of it when the Na(+) concentration in patch pipette solutions perfusing the intracellular compartment was high and elimination of it with K(+)-free pipette solution could not be reconciled with restricted subsarcolemmal Na(+) diffusion. The pattern of the transient current early after pump activation was dependent on transmembrane Na(+)- and K(+) concentration gradients suggesting the currents were related to the conformational poise imposed on the pump. We examined if the currents might be accounted for by changes in glutathionylation of the ?1 Na(+)-K(+) pump subunit, a reversible oxidative modification that inhibits the pump. Susceptibility of the ?1 subunit to glutathionylation depends on the conformational poise of the Na(+)-K(+) pump, and glutathionylation with the pump stabilized in conformations equivalent to those expected to be imposed on voltage-clamped myocytes supported this hypothesis. So did elimination of the transient K(+)-induced peak Na(+)-K(+) pump current when we included glutaredoxin 1 in patch pipette solutions to reverse glutathionylation. We conclude that transient K(+)-induced peak Na(+)-K(+) pump current reflects the effect of conformation-dependent ?1 pump subunit glutathionylation, not restricted subsarcolemmal diffusion of Na(+). PMID:26958887

  13. Step-wise transient method

    NASA Astrophysics Data System (ADS)

    Malinarič, Svetozár

    2016-03-01

    The step-wise transient (SWT) method is an experimental technique for measuring the thermal diffusivity and conductivity of solid materials. A theoretical model, design of the experimental apparatus and sources of error are presented. Methods of experiment optimization and evaluation are illustrated by charts. The experiment is verified for polymethylmethacrylate (PMMA), yielding the thermal diffusivity 0.112 mm2 s‑1 and thermal conductivity 0.197 W.m‑1 K‑1 with the coefficient of variation around 0.7% for various values of input heat power and specimen thicknesses.

  14. Three-Tesla magnetic resonance elastography for hepatic fibrosis: Comparison with diffusion-weighted imaging and gadoxetic acid-enhanced magnetic resonance imaging

    PubMed Central

    Park, Hee Sun; Kim, Young Jun; Yu, Mi Hye; Choe, Won Hyeok; Jung, Sung Il; Jeon, Hae Jeong

    2014-01-01

    AIM: To evaluate the feasibility of 3-Tesla magnetic resonance elastography (MRE) for hepatic fibrosis and to compare that with diffusion-weighted imaging (DWI) and gadoxetic acid-enhanced magnetic resonance (MR) imaging. METHODS: Forty-two patients were included in the study. On MRE, mean stiffness values were measured on the elastograms in kilopascals. The apparent diffusion coefficient (ADC) of the liver was measured using DWI. On gadoxetic acid enhanced MR, the contrast enhancement index (CEI) was calculated as signal intensity (SI)post/SIpre, where SIpost is liver-to-muscle SI ratio on hepatobiliary phase images and SIpre is that on nonenhanced images. Correlation between aspartate aminotransferase to the platelet ratio index (APRI) and three MR parameters was assessed. Each MR parameter was compared between a hepatic fibrosis (HF) group and non-hepatic fibrosis (nHF) group. RESULTS: Liver stiffness showed strong positive correlation with APRI [Spearman correlation coeffiecient (r) = 0.773, P < 0.0001], while ADC and CEI showed weak or prominent negative correlation (r = -0.28 and -0.321, respectively). In the HF group, only liver stiffness showed strong correlation with APRI (r = 0.731, P < 0.0001). Liver stiffness, ADC, and APRI were significantly different between the HF group and nHF group. CONCLUSION: MRE at 3-Tesla could be a feasible method for the assessment of hepatic fibrosis. PMID:25516671

  15. Binary and ternary gas mixtures with temperature enhanced diffuse glow discharge characteristics for use in closing switches

    DOEpatents

    Christophorou, L.G.; Hunter, S.R.

    1988-06-28

    An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc. 11 figs.

  16. Binary and ternary gas mixtures with temperature enhanced diffuse glow discharge characteristics for use in closing switches

    DOEpatents

    Christophorou, L.G.; Hunter, S.R.

    1990-06-26

    An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc. 11 figs.

  17. Binary and ternary gas mixtures with temperature enhanced diffuse glow discharge characteristics for use in closing switches

    DOEpatents

    Christophorou, Loucas G. (Oak Ridge, TN); Hunter, Scott R. (Oak Ridge, TN)

    1990-01-01

    An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc.

  18. Radiologic-Pathologic Analysis of Contrast-enhanced and Diffusion-weighted MR Imaging in Patients with HCC after TACE: Diagnostic Accuracy of 3D Quantitative Image Analysis

    PubMed Central

    Chapiro, Julius; Wood, Laura D.; Lin, MingDe; Duran, Rafael; Cornish, Toby; Lesage, David; Charu, Vivek; Schernthaner, Rdiger; Wang, Zhijun; Tacher, Vania; Savic, Lynn Jeanette; Kamel, Ihab R.

    2014-01-01

    Purpose To evaluate the diagnostic performance of three-dimensional (3Dthree-dimensional) quantitative enhancement-based and diffusion-weighted volumetric magnetic resonance (MR) imaging assessment of hepatocellular carcinoma (HCChepatocellular carcinoma) lesions in determining the extent of pathologic tumor necrosis after transarterial chemoembolization (TACEtransarterial chemoembolization). Materials and Methods This institutional review boardapproved retrospective study included 17 patients with HCChepatocellular carcinoma who underwent TACEtransarterial chemoembolization before surgery. Semiautomatic 3Dthree-dimensional volumetric segmentation of target lesions was performed at the last MR examination before orthotopic liver transplantation or surgical resection. The amount of necrotic tumor tissue on contrast materialenhanced arterial phase MR images and the amount of diffusion-restricted tumor tissue on apparent diffusion coefficient (ADCapparent diffusion coefficient) maps were expressed as a percentage of the total tumor volume. Visual assessment of the extent of tumor necrosis and tumor response according to European Association for the Study of the Liver (EASLEuropean Association for the Study of the Liver) criteria was performed. Pathologic tumor necrosis was quantified by using slide-by-slide segmentation. Correlation analysis was performed to evaluate the predictive values of the radiologic techniques. Results At histopathologic examination, the mean percentage of tumor necrosis was 70% (range, 10%100%). Both 3Dthree-dimensional quantitative techniques demonstrated a strong correlation with tumor necrosis at pathologic examination (R2 = 0.9657 and R2 = 0.9662 for quantitative EASLEuropean Association for the Study of the Liver and quantitative ADCapparent diffusion coefficient, respectively) and a strong intermethod agreement (R2 = 0.9585). Both methods showed a significantly lower discrepancy with pathologically measured necrosis (residual standard error [RSEresidual standard error] = 6.38 and 6.33 for quantitative EASLEuropean Association for the Study of the Liver and quantitative ADCapparent diffusion coefficient, respectively), when compared with non-3Dthree-dimensional techniques (RSEresidual standard error = 12.18 for visual assessment). Conclusion This radiologic-pathologic correlation study demonstrates the diagnostic accuracy of 3Dthree-dimensional quantitative MR imaging techniques in identifying pathologically measured tumor necrosis in HCChepatocellular carcinoma lesions treated with TACEtransarterial chemoembolization. RSNA, 2014 Online supplemental material is available for this article. PMID:25028783

  19. Cation diffusion in the electrical double layer enhances the mass transfer rates for Sr2+, Co2+ and Zn2+ in compacted illite

    NASA Astrophysics Data System (ADS)

    Glaus, M. A.; Aertsens, M.; Appelo, C. A. J.; Kupcik, T.; Maes, N.; Van Laer, L.; Van Loon, L. R.

    2015-09-01

    Enhanced mass transfer rates have been frequently observed in diffusion studies with alkaline and earth alkaline elements in compacted clay minerals and clay rocks. Whether this phenomenon - often termed surface diffusion - is also relevant for more strongly sorbing species is an open question. We therefore investigated the diffusion of Sr2+, Co2+ and Zn2+ in compacted illite with respect to variations of the concentration of the background electrolyte, pH and carbonate. New experimental techniques were developed in order to avoid artefacts stemming from the confinement of the clay sample. A distinct dependence of the effective diffusion coefficients on the concentration of the background electrolyte was observed for all three elements. A similar correlation was found for the sorption distribution ratio (Rd) derived from tracer breakthrough in the case of Sr2+, while this dependence was much weaker for Co2+ and Zn2+. Model calculations using Phreeqc resulted in a good agreement with the experimental data when it was assumed that the cationic species, present in the electrical double layer (EDL) of the charged clay surface, are mobile. Species bound to the specific surface complexation sites at the clay edges were assumed to be immobile. An assessment of the mobility of the type of cationic elements studied here in argillaceous media thus requires an analysis of their distribution among specifically sorbed surface species and species in the EDL. The normal approach of deriving unknown effective diffusion coefficients from reference values of an uncharged water tracer may significantly underestimate the mobility of metal cations in argillaceous media.

  20. Enlarged extracellular space of aquaporin-4-deficient mice does not enhance diffusion of Alexa Fluor 488 or dextran polymers

    PubMed Central

    Xiao, Fanrong; Hrab?tov, Sabina

    2010-01-01

    Aquaporin-4 (AQP4) water channels expressed on glia have been implicated in maintaining the volume of extracellular space (ECS). A previous diffusion study employing small cation tetramethylammonium and real-time iontophoretic (RTI) method demonstrated an increase of about 25% in the ECS volume fraction (?) in the neocortex of AQP4?/? mice compared to AQP4+/+ mice but no change in the hindrance imposed to diffusing molecules (tortuosity ?). In contrast, other diffusion studies employing large molecules (dextran polymers) and fluorescence recovery after photobleaching (FRAP) method measured a decrease of about 1020% in ? in the neocortex of AQP4?/? mice. These conflicting findings on ? would imply that large molecules diffuse more readily in the enlarged ECS of AQP4?/? mice than in wild type but small molecules do not. To test this hypothesis, we used integrative optical imaging (IOI) to measure tortuosity with a small Alexa Fluor 488 (MW 547, ?AF) and two large dextran polymers (MW 3,000, ?dex3 and MW 75,000, ?dex75) in the in vitro neocortex of AQP4+/+ and AQP4?/? mice. We found that ?AF = 1.59, ?dex3 = 1.76 and ?dex75 = 2.30 obtained in AQP4?/? mice were not significantly different from ?AF = 1.61, ?dex3 = 1.76, and ?dex75 = 2.33 in AQP4+/+ mice. These IOI results demonstrate that ? measured with small and large molecules each remain unchanged in the enlarged ECS of AQP4?/? mice compared to values in AQP4+/+ mice. Further analysis suggests that the FRAP method yields diffusion parameters not directly comparable with those obtained by IOI or RTI methods. Our findings have implications for the role of glial AQP4 in maintaining the ECS structure. PMID:19303428

  1. Effects of Lewis Number on Temperatures of Spherical Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Santa, K. J.; Sun, Z.; Chao, B. H.; Sunderland, P. B.; Axelbaum, R. I.; Urban, D. L.; Stocker, D. P.

    2007-01-01

    Spherical diffusion flames supported on a porous sphere were studied numerically and experimentally. Experiments were performed in 2.2 s and 5.2 s microgravity facilities. Numerical results were obtained from a Chemkin-based program. The program simulates flow from a porous sphere into a quiescent environment, yields both steady-state and transient results, and accounts for optically thick gas-phase radiation. The low flow velocities and long residence times in these diffusion flames lead to enhanced radiative and diffusive effects. Despite similar adiabatic flame temperatures, the measured and predicted temperatures varied by as much as 700 K. The temperature reduction correlates with flame size but characteristic flow times and, importantly, Lewis number also influence temperature. The numerical results show that the ambient gas Lewis number would have a strong effect on flame temperature if the flames were steady and nonradiating. For example, a 10% decrease in Lewis number would increase the steady-state flame temperature by 200 K. However, for these transient, radiating flames the effect of Lewis number is small. Transient predictions of flame sizes are larger than those observed in microgravity experiments. Close agreement could not be obtained without either increasing the model s thermal and mass diffusion properties by 30% or reducing mass flow rate by 25%.

  2. Early annihilation and diffuse backgrounds in models of weakly interacting massive particles in which the cross section for pair annihilation is enhanced by 1/upsilon.

    PubMed

    Kamionkowski, Marc; Profumo, Stefano

    2008-12-31

    Recent studies have considered modifications to the standard weakly interacting massive particle scenario in which the pair annihilation cross section (times relative velocity v) is enhanced by a factor 1/upsilon to approximately 10(-3) in the Galaxy, enough to explain several puzzling Galactic radiation signals. We show that in these scenarios a burst of weakly interacting massive particle annihilation occurs in the first collapsed dark-matter halos. We show that severe constraints to the annihilation cross section derive from measurements of the diffuse extragalactic radiation and from ionization and heating of the intergalactic medium. PMID:19437633

  3. Transient thermal imaging of a vertical cavity surface-emitting laser using thermoreflectance microscopy

    NASA Astrophysics Data System (ADS)

    Garcia, V. G.; Farzaneh, M.

    2016-01-01

    Thermal transient response at the surface of a Vertical Cavity Surface-emitting Laser (VCSEL) is measured under operating conditions using a thermoreflectance imaging technique. From the transient curve, a thermal time constant of (9.7 ± 0.5) μs is obtained for the device surface in response to a 40 μs heating pulse. A cross-plane thermal diffusivity of the order of 2 × 10-6 m2/s has been deduced from both the experimental data and heat transfer modeling. This reduced thermal diffusivity compared to the bulk is attributed to the enhanced phonon scattering at the boundaries of the VCSEL's multi-layered structure.

  4. Transient heliosheath modulation

    NASA Astrophysics Data System (ADS)

    Quenby, J. J.; Webber, W. R.

    2015-10-01

    Voyager 1 has explored the solar wind-interstellar medium interaction region between the terminal shock and heliopause, following the intensity distribution of Galactic cosmic ray protons above 200 MeV energy. Before this component reached the expected galactic flux level at 121.7 au from the Sun, four episodes of rapid intensity change occurred with a behaviour similar to that found in Forbush Decreases in the inner Solar system, rather than that expected from a mechanism related to models for the long-term modulation found closer to the Sun. Because the mean solar wind flow is both expected and observed to be perpendicular to the radial direction close to the heliopause, an explanation is suggested in terms of transient radial flows related to possible heliopause boundary flapping. It is necessary that the radial flows are of the order either of the sound speed found for conditions downstream of the terminal shock or of the fluctuations found near the boundary by the Voyager 1 Low Energy Charged Particle detector and that the relevant cosmic ray diffusion perpendicular to the mean field is controlled by `slab' fluctuations accounting for about 20 per cent of the total power in the field variance. However, additional radial drift motion related to possible north to south gradients in the magnetic field may allow the inclusion of some diffusion according to the predictions of a theory based upon the presence of 2D turbulence. The required field gradients may arise due to field variation in the field carried by solar plasma flow deflected away from the solar equatorial plane. Modulation amounting to a total 30 per cent drop in galactic intensity requires explanation by a combination of transient effects.

  5. Enhanced diffusive ion scattering in front of the Earth's quasi-parallel bow shock: a case study

    NASA Astrophysics Data System (ADS)

    Kis, Arpad; Scholer, Manfred; Klecker, Berndt; Lucek, Elisabeth; Dandouras, Iannis; Lemperger, Istvn; Wesztergom, Viktor; Novk, Attila; Szalai, Sndor

    2014-05-01

    In our study we report on observations of energetic ions upstream of the Earth's quasi-parallel bow shock by Cluster at times of large inter-spacecraft separation distance. For the analysis we use the ion data provided by the CIS-HIA in the 10-32 keV energy range and the magnetic data recorded by the FGM instrument. We determine the spatial gradient of partial energetic ion densities at various distances from the bow shock. The gradient in all energy channels decreases exponentially with distance and the e-folding distance of the gradients depends approximately linearly on energy but there is a significant difference in their values obtained at the observed three upstream ion events. We demonstrate for the first time that under specific interplanetary conditions the mechanism of the diffuse ion scattering can change significantly and results in an anomalous diffusive process charactized by an unusually small e-folding distance.

  6. Measurement of radiation-enhanced diffusion of La in single crystal thin film CeO 2

    NASA Astrophysics Data System (ADS)

    Pappas, Harrison K.; Heuser, Brent J.; Strehle, Melissa M.

    2010-10-01

    The diffusion of La, a trivalent cation dopant, actinide surrogate, and high-yield fission product, in CeO 2, a UO 2 nuclear fuel surrogate, during 1.8 MeV Kr + ion bombardment over a temperature range from 673 K to 1206 K has been measured with secondary ion mass spectroscopy. The diffusivity under these irradiation conditions has been analyzed with a model based on a combination of sink-limited and recombination-limited kinetics. This analysis yielded a cation vacancy migration energy of Emv ˜ 0.4 eV below ˜800 K, were recombination-limited kinetics dominated the behavior. The thermal diffusivity of La in the same system was measured over a range of 873-1073 K and was characterized by an activation enthalpy of Ea=Efv+Emv˜1.4 eV. The measurement of both the migration enthalpy and total activation enthalpy separately allows the vacancy formation enthalpy on the cation sublattice to be determined; Efv ˜ 1 eV. The mixing parameter under energetic heavy-ion bombardment at room temperature was measured as well and found to be ˜4 × 10 -5 nm 5/eV.

  7. Stable isotope-enhanced two- and three-dimensional diffusion ordered 13C NMR spectroscopy (SIE-DOSY 13C NMR)

    NASA Astrophysics Data System (ADS)

    Vermillion, Karl; Price, Neil P. J.

    2009-06-01

    The feasibility of obtaining high quality homonuclear or heteronuclear diffusion-ordered 13C NMR data is shown to be greatly improved by using 13C isotopically-enriched samples. Stable isotope-enhanced diffusion ordered (SIE-DOSY) 13C NMR has been applied to 13C-enriched carbohydrates, and has been used to determine diffusion coefficients for pentose and hexose monosaccharides, and a disaccharide and trisaccharide. These 2D spectra were obtained with as little as 8 min of acquisition time. Fully resolved 3D DOSY-HMQC NMR spectra of [U- 13C]xylose, [U- 13C]glucose, and [1- 13C gal]lactose were obtained in 5 h. Sample derivatization with [ carbonyl- 13C]acetate (peracetylation) extends the usefulness of the technique to included non-labeled sugars; the 13C-carbonyl - carbohydrate ring proton 1H- 13C correlations also provide additional structural information, as shown for the 3-D DOSY-HMQC analysis of a mixture of maltotriose and lactose per-[ carbonyl- 13C]acetates.

  8. Gd-EOB-DTPA-Enhanced MR Imaging of the Liver: The Effect on T2 Relaxation Times and Apparent Diffusion Coefficient (ADC)

    PubMed Central

    Cieszanowski, Andrzej; Podgórska, Joanna; Rosiak, Grzegorz; Maj, Edyta; Grudziński, Ireneusz P.; Kaczyński, Bartosz; Szeszkowski, Wojciech; Milczarek, Krzysztof; Rowiński, Olgierd

    2016-01-01

    Summary Background To investigate the effect of gadoxetic acid disodium (Gd-EOB-DTPA) on T2 relaxation times and apparent diffusion coefficient (ADC) values of the liver and focal liver lesions on a 1.5-T system. Material/Methods Magnetic resonance (MR) studies of 50 patients with 35 liver lesions were retrospectively analyzed. All examinations were performed at 1.5T and included T2-weighted turbo spin-echo (TSE) and diffusion-weighted (DW) images acquired before and after intravenous administration of Gd-EOB-DTPA. To assess the effect of this hepatobiliary contrast agent on T2-weighted TSE images and DW images T2 relaxation times and ADC values of the liver and FLLs were calculated and compared pre- and post-injection. Results The mean T2 relaxation times of the liver and focal hepatic lesions were lower on enhanced than on unenhanced T2-weighted TSE images (decrease of 2.7% and 3.6% respectively), although these differences were not statistically significant. The mean ADC values of the liver showed statistically significant decrease (of 4.6%) on contrast-enhanced DW images, compared to unenhanced images (P>0.05). The mean ADC value of liver lesions was lower on enhanced than on unenhanced DW images, but this difference (of 2.9%) did not reach statistical significance. Conclusions The mean T2 relaxation times of the liver and focal liver lesions as well as the mean ADC values of liver lesions were not significantly different before and after administration of Gd-EOB-DTPA. Therefore, acquisition of T2-weighted and DW images between the dynamic contrast-enhanced examination and hepatobiliary phase is feasible and time-saving.

  9. Microgravity Turbulent Gas-Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    1996-01-01

    A gas-jet diffusion flame is similar to the flame on a Bunsen burner, where a gaseous fuel (e.g., propane) flows from a nozzle into an oxygen-containing atmosphere (e.g., air). The difference is that a Bunsen burner allows for (partial) premixing of the fuel and the air, whereas a diffusion flame is not premixed and gets its oxygen (principally) by diffusion from the atmosphere around the flame. Simple gas-jet diffusion flames are often used for combustion studies because they embody the mechanisms operating in accidental fires and in practical combustion systems. However, most practical combustion is turbulent (i.e., with random flow vortices), which enhances the fuel/air mixing. These turbulent flames are not well understood because their random and transient nature complicates analysis. Normal gravity studies of turbulence in gas-jet diffusion flames can be impeded by buoyancy-induced instabilities. These gravitycaused instabilities, which are evident in the flickering of a candle flame in normal gravity, interfere with the study of turbulent gas-jet diffusion flames. By conducting experiments in microgravity, where buoyant instabilities are avoided, we at the NASA Lewis Research Center hope to improve our understanding of turbulent combustion. Ultimately, this could lead to improvements in combustor design, yielding higher efficiency and lower pollutant emissions. Gas-jet diffusion flames are often researched as model flames, because they embody mechanisms operating in both accidental fires and practical combustion systems (see the first figure). In normal gravity laboratory research, buoyant air flows, which are often negligible in practical situations, dominate the heat and mass transfer processes. Microgravity research studies, however, are not constrained by buoyant air flows, and new, unique information on the behavior of gas-jet diffusion flames has been obtained.

  10. Relationship between diffusion parameters derived from intravoxel incoherent motion MRI and perfusion measured by dynamic contrast-enhanced MRI of soft tissue tumors.

    PubMed

    Marzi, Simona; Stefanetti, Linda; Sperati, Francesca; Anelli, Vincenzo

    2016-01-01

    Our aim was to evaluate the link between diffusion parameters measured by intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) and the perfusion metrics obtained with dynamic contrast-enhanced (DCE) MRI in soft tissue tumors (STTs). Twenty-eight patients affected by histopathologically confirmed STT were included in a prospective study. All patients underwent both DCE MRI and IVIM DWI. The perfusion fraction f, diffusion coefficient D and perfusion-related diffusion coefficient D* were estimated using a bi-exponential function to fit the DWI data. DCE MRI was acquired with a temporal resolution of 3-5?s. Maps of the initial area under the gadolinium concentration curve (IAUGC), time to peak (TTP) and maximum slope of increase (MSI) were derived using commercial software. The relationships between the DCE MRI and IVIM DWI measurements were assessed by Spearman's test. To exclude false positive results under multiple testing, the false discovery rate (FDR) procedure was applied. The Mann-Whitney test was used to evaluate the differences between all variables in patients with non-myxoid and myxoid STT. No significant relationship was found between IVIM parameters and any DCE MRI parameters. Higher f and D*f values were found in non-myxoid tumors compared with myxoid tumors (p?=?0.004 and p?=?0.003, respectively). MSI was significantly higher in non-myxoid tumors than in myxoid tumors (p?=?0.029). From the visual assessments of single clinical cases, both f and D*f maps were in satisfactory agreement with DCE maps in the extreme cases of an avascular mass and a highly vascularized mass, whereas, for tumors with slight vascularity or with a highly heterogeneous perfusion pattern, this association was not straightforward. Although IVIM DWI was demonstrated to be feasible in STT, our data did not support evident relationships between perfusion-related IVIM parameters and perfusion measured by DCE MRI. Copyright 2015 John Wiley & Sons, Ltd. PMID:26602061

  11. Integrating diffusion kurtosis imaging, dynamic susceptibility-weighted contrast-enhanced MRI, and short echo time chemical shift imaging for grading gliomas

    PubMed Central

    Van Cauter, Sofie; De Keyzer, Frederik; Sima, Diana M.; Croitor Sava, Anca; D'Arco, Felice; Veraart, Jelle; Peeters, Ronald R.; Leemans, Alexander; Van Gool, Stefaan; Wilms, Guido; Demaerel, Philippe; Van Huffel, Sabine; Sunaert, Stefan; Himmelreich, Uwe

    2014-01-01

    Background We assessed the diagnostic accuracy of diffusion kurtosis imaging (DKI), dynamic susceptibility-weighted contrast-enhanced (DSC) MRI, and short echo time chemical shift imaging (CSI) for grading gliomas. Methods In this prospective study, 35 patients with cerebral gliomas underwent DKI, DSC, and CSI on a 3 T MR scanner. Diffusion parameters were mean diffusivity (MD), fractional anisotropy, and mean kurtosis (MK). Perfusion parameters were mean relative regional cerebral blood volume (rrCBV), mean relative regional cerebral blood flow (rrCBF), mean transit time, and relative decrease ratio (rDR). The diffusion and perfusion parameters along with 12 CSI metabolite ratios were compared among 22 high-grade gliomas and 14 low-grade gliomas (MannWhitney U-test, P < .05). Classification accuracy was determined with a linear discriminant analysis for each MR modality independently. Furthermore, the performance of a multimodal analysis is reported, using a decision-tree rule combining the statistically significant DKI, DSC-MRI, and CSI parameters with the lowest P-value. The proposed classifiers were validated on a set of subsequently acquired data from 19 clinical patients. Results Statistically significant differences among tumor grades were shown for MK, MD, mean rrCBV, mean rrCBF, rDR, lipids over total choline, lipids over creatine, sum of myo-inositol, and sum of creatine. DSC-MRI proved to be the modality with the best performance when comparing modalities individually, while the multimodal decision tree proved to be most accurate in predicting tumor grade, with a performance of 86%. Conclusions Combining information from DKI, DSC-MRI, and CSI increases diagnostic accuracy to differentiate low- from high-grade gliomas, possibly providing diagnosis for the individual patient. PMID:24470551

  12. Plasma-Enhanced Atomic Layer Deposition of Ruthenium-Titanium Nitride Mixed-Phase Layers for Direct-Plate Liner and Copper Diffusion Barrier Applications

    NASA Astrophysics Data System (ADS)

    Gildea, Adam James

    Current interconnect networks in semiconductor processing utilize a sputtered TaN diffusion barrier, Ta liner, and Cu seed to improve the adhesion, microstructure, and electromigration resistance of electrochemically deposited copper that fills interconnect wires and vias. However, as wire/via widths shrink due to device scaling, it becomes increasingly difficult to have the volume of a wire/via be occupied with ECD Cu which increases line resistance and increases the delay in signal propagation in IC chips. A single layer that could serve the purpose of a Cu diffusion barrier and ECD Cu adhesion promoter could allow ECD Cu to occupy a larger volume of a wire/via, leading to a decrease in line resistance and decrease in signal delay. Previous work has shown RuTaN, RuWCN, and RuCo films can act as Cu diffusion barriers and be directly platable to thickness of 2-3nm. However, other material selections may prove as effective or possibly better. Mixed-phase films of ruthenium titanium nitride grown by atomic layer deposition (ALD) were investigated for their performance as a Cu diffusion barrier and as a surface for the direct plating of ECD Cu. All Ru was deposited by plasma-enhanced atomic layer deposition (PEALD) while TiN was deposited by either thermal ALD or PEALD. RuTiN, films with thermal ALD TiN and a Ru:Ti of 20:1 showed barrier performance comparable to PVD TaN at 3-4 nm thickness and 15 nm planar films were directly platable. Follow up work is certainly needed for this material set, yet initial results indicate RuTiN could serve as an effective direct plate liner for Cu interconnects.

  13. Water vapor exchange system using a hydrophilic microporous layer coated gas diffusion layer to enhance performance of polymer electrolyte fuel cells without cathode humidification

    NASA Astrophysics Data System (ADS)

    Kitahara, Tatsumi; Nakajima, Hironori; Morishita, Masashi

    2012-09-01

    Polymer electrolyte fuel cells (PEFCs) generally have external humidifiers to supply humidified hydrogen and oxidant gases, which prevents dehydration of the membrane. If a PEFC could be operated without humidification, then external humidifiers could be removed, which would result in a simplified PEFC system with increased total efficiency and reduced cost. A water vapor exchange system installed in the PEFC was developed to enhance the performance without cathode humidification. A gas diffusion layer (GDL) coated with a hydrophobic microporous layer (MPL) was used at the active reaction area. A GDL coated with a hydrophilic MPL consisting of polyvinyl alcohol (PVA) and carbon black was used at the cathode water vapor exchange area to promote water transport from the cathode outlet wet gas to the anode inlet dry gas. This is effective for reducing the IR overpotential, which enhances the PEFC performance. Appropriate enhancement of hydrophilicity by increasing the PVA content in the MPL to 20 mass% is effective to increase water transport from the cathode to anode. At the anode water exchange area, a GDL without the hydrophilic MPL is effective to promote water transport from the water exchange area to the active reaction area, which enhances the PEFC performance.

  14. Enhanced Ca+ influx through cardiac L-type Ca+ channels maintains the systolic Ca+ transient in early cardiac atrophy induced by mechanical unloading.

    PubMed

    Schwoerer, A P; Neef, S; Broichhausen, I; Jacubeit, J; Tiburcy, M; Wagner, M; Biermann, D; Didi, M; Vettel, C; Maier, L S; Zimmermann, W H; Carrier, L; Eschenhagen, T; Volk, T; El-Armouche, A; Ehmke, H

    2013-12-01

    Cardiac atrophy as a consequence of mechanical unloading develops following exposure to microgravity or prolonged bed rest. It also plays a central role in the reverse remodelling induced by left ventricular unloading in patients with heart failure. Surprisingly, the intracellular Ca(2+) transients which are pivotal to electromechanical coupling and to cardiac plasticity were repeatedly found to remain unaffected in early cardiac atrophy. To elucidate the mechanisms underlying the preservation of the Ca(2+) transients, we investigated Ca(2+) cycling in cardiomyocytes from mechanically unloaded (heterotopic abdominal heart transplantation) and control (orthotopic) hearts in syngeneic Lewis rats. Following 2 weeks of unloading, sarcoplasmic reticulum (SR) Ca(2+) content was reduced by ~55 %. Atrophic cardiac myocytes also showed a much lower frequency of spontaneous diastolic Ca(2+) sparks and a diminished systolic Ca(2+) release, even though the expression of ryanodine receptors was increased by ~30 %. In contrast, current clamp recordings revealed prolonged action potentials in endocardial as well as epicardial myocytes which were associated with a two to fourfold higher sarcolemmal Ca(2+) influx under action potential clamp. In addition, Cav1.2 subunits which form the pore of L-type Ca(2+) channels (LTCC) were upregulated in atrophic myocardium. These data suggest that in early cardiac atrophy induced by mechanical unloading, an augmented sarcolemmal Ca(2+) influx through LTCC fully compensates for a reduced systolic SR Ca(2+) release to preserve the Ca(2+) transient. This interplay involves an electrophysiological remodelling as well as changes in the expression of cardiac ion channels. PMID:23842739

  15. Enhanced localization, energy anomalous diffusion and resonant mode in harmonic chains with correlated mass-spring disorder.

    PubMed

    de Albuquerque, S S; dos Santos, J L L; de Moura, F A B F; Lyra, M L

    2015-05-01

    In this work, we study the vibrational modes and energy spreading in a harmonic chain model with diluted second-neighbors couplings and correlated mass-spring disorder. While all nearest neighbor masses are coupled by an elastic spring, second neighbors springs are introduced with a probability pD. The masses are randomly distributed according to the site connectivity mi = m0 (1 + 1/n(?)(I), where ni is the connectivity of the site i and ? is a tunable exponent. We show that maximum localization of the vibrational modes is achieved for ? ? 3/4. The time-evolution of the energy wave-packet is followed after an initial localized excitation. While the participation number remains finite, the energy spread is shown to be sub-diffusive after a displacement and super-diffusive after an impulse excitation. These features are related to the development of a power-law tail in the wave-packet distribution. Further, we unveil that the spring dilution leads to the emergence of a resonant localized state which is signaled by a van Hove singularity in the density of states. PMID:25836635

  16. The chemistry of transient dense cores

    NASA Astrophysics Data System (ADS)

    Garrod, R. T.; Williams, D. A.; Hartquist, T. W.; Rawlings, J. M. C.; Viti, S.

    2005-01-01

    We investigate the chemistry of a transient density fluctuation, with properties similar to those of a dense core within a molecular cloud. We run a multipoint chemical code through a core's condensation from a diffuse medium to its eventual dispersion, over a period of ~1 Myr. We find a significant enhancement of the chemical composition of the core material on its return to diffuse conditions, whilst the expansion of the core as it disperses moves this material out to large distances from the core centre. This process transports molecular species formed in the high-density regions out into the diffuse medium. Chemical enrichment of the cloud as a whole also occurs, as other cores of various sizes, life-spans and separations evolve throughout. Enrichment is strongly affected by freeze-out on to dust grains, which takes place in high-density, high visual extinction regions. As the core disperses after reaching its peak density and the visual extinction drops below a critical value, grain mantles are evaporated back into the gas phase, initiating more chemistry. The influence of the sizes, masses and cycle periods of cores will be large both for the level of chemical enrichment of a dark cloud and ultimately for the low-mass star formation rate. We also consider the case of a self-gravitating core, by holding its peak density conditions for a further 0.4 Myr. We find that the differences are generally small, and the resultant column densities do not provide definitive criteria for detection of this condition. However, increases in fractional abundances due to reinjection of mantle-borne species may provide a criterion for a negative detection.

  17. An assessment of the cost-effectiveness of magnetic resonance, including diffusion-weighted imaging, in patients with transient ischaemic attack and minor stroke: a systematic review, meta-analysis and economic evaluation.

    PubMed Central

    Wardlaw, Joanna; Brazzelli, Miriam; Miranda, Hector; Chappell, Francesca; McNamee, Paul; Scotland, Graham; Quayyum, Zahid; Martin, Duncan; Shuler, Kirsten; Sandercock, Peter; Dennis, Martin

    2014-01-01

    BACKGROUND Patients with transient ischaemic attack (TIA) or minor stroke need rapid treatment of risk factors to prevent recurrent stroke. ABCD2 score or magnetic resonance diffusion-weighted brain imaging (MR DWI) may help assessment and treatment. OBJECTIVES Is MR with DWI cost-effective in stroke prevention compared with computed tomography (CT) brain scanning in all patients, in specific subgroups or as 'one-stop' brain-carotid imaging? What is the current UK availability of services for stroke prevention? DATA SOURCES Published literature; stroke registries, audit and randomised clinical trials; national databases; survey of UK clinical and imaging services for stroke; expert opinion. REVIEW METHODS Systematic reviews and meta-analyses of published/unpublished data. Decision-analytic model of stroke prevention including on a 20-year time horizon including nine representative imaging scenarios. RESULTS The pooled recurrent stroke rate after TIA (53 studies, 30,558 patients) is 5.2% [95% confidence interval (CI) 3.9% to 5.9%] by 7 days, and 6.7% (5.2% to 8.7%) at 90 days. ABCD2 score does not identify patients with key stroke causes or identify mimics: 66% of specialist-diagnosed true TIAs and 35-41% of mimics had an ABCD2 score of ≥ 4; 20% of true TIAs with ABCD2 score of < 4 had key risk factors. MR DWI (45 studies, 9078 patients) showed an acute ischaemic lesion in 34.3% (95% CI 30.5% to 38.4%) of TIA, 69% of minor stroke patients, i.e. two-thirds of TIA patients are DWI negative. TIA mimics (16 studies, 14,542 patients) make up 40-45% of patients attending clinics. UK survey (45% response) showed most secondary prevention started prior to clinic, 85% of primary brain imaging was same-day CT; 51-54% of patients had MR, mostly additional to CT, on average 1 week later; 55% omitted blood-sensitive MR sequences. Compared with 'CT scan all patients' MR was more expensive and no more cost-effective, except for patients presenting at > 1 week after symptoms to diagnose haemorrhage; strategies that triaged patients with low ABCD2 scores for slow investigation or treated DWI-negative patients as non-TIA/minor stroke prevented fewer strokes and increased costs. 'One-stop' CT/MR angiographic-plus-brain imaging was not cost-effective. LIMITATIONS Data on sensitivity/specificity of MR in TIA/minor stroke, stroke costs, prognosis of TIA mimics and accuracy of ABCD2 score by non-specialists are sparse or absent; all analysis had substantial heterogeneity. CONCLUSIONS Magnetic resonance with DWI is not cost-effective for secondary stroke prevention. MR was most helpful in patients presenting at > 1 week after symptoms if blood-sensitive sequences were used. ABCD2 score is unlikely to facilitate patient triage by non-stroke specialists. Rapid specialist assessment, CT brain scanning and identification of serious underlying stroke causes is the most cost-effective stroke prevention strategy. FUNDING The National Institute for Health Research Health Technology Assessment programme. PMID:24791949

  18. Low temperature plasma-enhanced atomic layer deposition of thin vanadium nitride layers for copper diffusion barriers

    SciTech Connect

    Rampelberg, Geert; Devloo-Casier, Kilian; Deduytsche, Davy; Detavernier, Christophe; Blasco, Nicolas

    2013-03-18

    Thin vanadium nitride (VN) layers were grown by atomic layer deposition using tetrakis(ethylmethylamino)vanadium and NH{sub 3} plasma at deposition temperatures between 70 Degree-Sign C and 150 Degree-Sign C on silicon substrates and polymer foil. X-ray photoelectron spectroscopy revealed a composition close to stoichiometric VN, while x-ray diffraction showed the {delta}-VN crystal structure. The resistivity was as low as 200 {mu}{Omega} cm for the as deposited films and further reduced to 143 {mu}{Omega} cm and 93 {mu}{Omega} cm by annealing in N{sub 2} and H{sub 2}/He/N{sub 2}, respectively. A 5 nm VN layer proved to be effective as a diffusion barrier for copper up to a temperature of 720 Degree-Sign C.

  19. Triple microporous layer coated gas diffusion layer for performance enhancement of polymer electrolyte fuel cells under both low and high humidity conditions

    NASA Astrophysics Data System (ADS)

    Kitahara, Tatsumi; Nakajima, Hironori; Inamoto, Masaoki; Shinto, Kosuke

    2014-02-01

    Enhancement of the performance of polymer electrolyte fuel cells (PEFCs) requires an appropriate water balance between the conservation of membrane humidity and the discharge of excess water produced in the cell. In the present study, a novel triple microporous layer (MPL) coated gas diffusion layer (GDL), in which a hydrophilic layer was coated on a hydrophobic double MPL, was developed to enhance the PEFC performance under both low and high humidity. The thin hydrophilic layer in the triple MPL is effective at conserving the humidity of the membrane electrode assembly (MEA) under low humidity, while the hydrophobic double MPL between the hydrophilic layer and the carbon paper substrate prevents removal of water from the hydrophilic layer. This results in a significant enhancement of the ability of the GDL to prevent dehydration of the MEA. The triple MPL coated GDL, where the polytetrafluoroethylene (PTFE) content in the hydrophobic MPL in contact with the hydrophilic layer is set to 30 mass% and that in contact with the substrate is set to 10 mass%, is effective at expelling excess water from the catalyst layer, which results in much higher PEFC performance under high humidity than that for a conventional hydrophobic MPL coated GDL.

  20. Transient Expression of Secretory IgA In Planta is Optimal Using a Multi-Gene Vector and may be Further Enhanced by Improving Joining Chain Incorporation

    PubMed Central

    Westerhof, Lotte B.; Wilbers, Ruud H. P.; van Raaij, Debbie R.; van Wijk, Christina Z.; Goverse, Aska; Bakker, Jaap; Schots, Arjen

    2016-01-01

    Secretory IgA (sIgA) is a crucial antibody in host defense at mucosal surfaces. It is a promising antibody isotype in a variety of therapeutic settings such as passive vaccination and treatment of inflammatory disorders. However, heterologous production of this heteromultimeric protein complex is still suboptimal. The challenge is the coordinate expression of the four required polypeptides; the alpha heavy chain, the light chain, the joining chain, and part of the polymeric-Ig-receptor called the secretory component, in a 4:4:1:1 ratio. We evaluated the transient expression of three sIgAκ variants, harboring the heavy chain isotype α1, α2m1, or α2m2, of the clinical antibody Ustekinumab in planta. Ustekinumab is directed against the p40 subunit that is shared by the pro-inflammatory cytokines interleukin (IL)-12 and IL-23. A sIgA variant of this antibody may enable localized treatment of inflammatory bowel disease. Of the three different sIgA variants we obtained the highest yield with sIgA1κ reaching up to 373 μg sIgA/mg total soluble protein. The use of a multi-cassette vector containing all four expression cassettes was most efficient. However, not the expression strategy, but the incorporation of the joining chain turned out to be the limiting step for sIgA production. Our data demonstrate that transient expression in planta is suitable for the economic production of heteromultimeric protein complexes such as sIgA. PMID:26793201

  1. Transient Faults in Computer Systems

    NASA Technical Reports Server (NTRS)

    Masson, Gerald M.

    1993-01-01

    A powerful technique particularly appropriate for the detection of errors caused by transient faults in computer systems was developed. The technique can be implemented in either software or hardware; the research conducted thus far primarily considered software implementations. The error detection technique developed has the distinct advantage of having provably complete coverage of all errors caused by transient faults that affect the output produced by the execution of a program. In other words, the technique does not have to be tuned to a particular error model to enhance error coverage. Also, the correctness of the technique can be formally verified. The technique uses time and software redundancy. The foundation for an effective, low-overhead, software-based certification trail approach to real-time error detection resulting from transient fault phenomena was developed.

  2. Transient Dimers of Allergens

    PubMed Central

    Rouvinen, Juha; Jnis, Janne; Laukkanen, Marja-Leena; Jylh, Sirpa; Niemi, Merja; Pivinen, Tero; Mkinen-Kiljunen, Soili; Haahtela, Tari; Sderlund, Hans; Takkinen, Kristiina

    2010-01-01

    Background Allergen-mediated cross-linking of IgE antibodies bound to the Fc?RI receptors on the mast cell surface is the key feature of the type I allergy. If an allergen is a homodimer, its allergenicity is enhanced because it would only need one type of antibody, instead of two, for cross-linking. Methodology/Principal Findings An analysis of 55 crystal structures of allergens showed that 80% of them exist in symmetric dimers or oligomers in crystals. The majority are transient dimers that are formed at high protein concentrations that are reached in cells by colocalization. Native mass spectrometric analysis showed that native allergens do indeed form transient dimers in solution, while hypoallergenic variants of them exist almost solely in the monomeric form. We created a monomeric Bos d 5 allergen and show that it has a reduced capability to induce histamine release. Conclusions/Significance The results suggest that dimerization would be a very common and essential feature for allergens. Thus, the preparation of purely monomeric variants of allergens could open up novel possibilities for specific immunotherapy. PMID:20140203

  3. Fluorescence-guided bone resection by using Visually Enhanced Lesion Scope in diffuse chronic sclerosingosteomyelitis of the mandible: Clinical and pathological evaluation

    PubMed Central

    Sasaguri, Masaaki; Matsuo, Kou; Yoshida, Sei; Uehara, Masataka; Habu, Manabu; Haraguchi, Kazuya; Tanaka, Tatsurou; Morimoto, Yasuhiro; Yoshioka, Izumi; Tominaga, Kazuhiro

    2015-01-01

    Diffuse chronic sclerosingosteomyelitis (DCSO) is a refractory disease, becausethe etiology and pathogenesis remain poorly understood and to determine the border betweenunhealthy boneandhealthybone is difficult. However, progressive inflammation, clinical symptoms and a high recurrence rate of DCSO were the reasons for surgical treatment. We report a case of a 66-year old woman with DCSO of the right side of mandible who was treated with hemimandibulectomy and simultaneous reconstruction by vascularized free fibula flap. After preoperative administration of minocycline for 1 month, the bone fluorescence was successfully monitored by using a Visually Enhanced Lesion Scope (VELscope®). Intraoperatively, we could determine the resection boundaries. We investigated the clinical and histopathological findings. The fluorescence findings were well correlated with histopathological findings. Using a VELscope®was handy and useful to determine the border between DCSO lesion andhealthybone.The free fibula flap under the minocycline-derived bone fluorescence by using a VELscope®offered a good quality of mandibular bone and the successful management of an advanced and refractory DCSO. Key words:Fluorescence-guided bone resection, fibular free flap, osteomyelitis of the mandible, diffuse chronicosteomyelitis, VELscope®. PMID:26535106

  4. Depth-compensated diffuse optical tomography enhanced by general linear model analysis and an anatomical atlas of human head.

    PubMed

    Tian, Fenghua; Liu, Hanli

    2014-01-15

    One of the main challenges in functional diffuse optical tomography (DOT) is to accurately recover the depth of brain activation, which is even more essential when differentiating true brain signals from task-evoked artifacts in the scalp. Recently, we developed a depth-compensated algorithm (DCA) to minimize the depth localization error in DOT. However, the semi-infinite model that was used in DCA deviated significantly from the realistic human head anatomy. In the present work, we incorporated depth-compensated DOT (DC-DOT) with a standard anatomical atlas of human head. Computer simulations and human measurements of sensorimotor activation were conducted to examine and prove the depth specificity and quantification accuracy of brain atlas-based DC-DOT. In addition, node-wise statistical analysis based on the general linear model (GLM) was also implemented and performed in this study, showing the robustness of DC-DOT that can accurately identify brain activation at the correct depth for functional brain imaging, even when co-existing with superficial artifacts. PMID:23859922

  5. Influence of high-intensity turbulence on laminar boundary layer development on a cylindrical leading edge: Enhancement to eddy diffusivity

    NASA Astrophysics Data System (ADS)

    Pearson, Juli K.

    The growing demand for increased efficiency in turbine engine designs has sparked a growing interest for research of air flow around curved surfaces. The turbine's operating conditions result in material property constraints, especially in the first stage turbine vanes and blades. These turbine vane components experience extreme loading conditions of both high temperature and high turbulence intensities exiting the combustor. The surface of the turbine blades has cylindrical leading edges that promote stabilizing flow accelerations. These convex surfaces can cause a reduced eddy diffusivity across the boundary layer. This thesis reviews measurements of velocity and turbulence intensities taken just shy of the thirty degrees offset from the stagnation line of a two-dimensional cylindrical leading edge under a wide range of turbulence and flow conditions flow conditions. Flow conditions and velocity measurements were gathered with respect to the distance to the surface. The length of the measurements extended from the surface to beyond the boundary layer's edge. The instrumentation used to collect data was a single wire driven by a constant temperature anemometer bridge. The hot wire is specially modified to measure data near the cylindrical leading edges curved surface. The traversing system allowed the acquisition of high-resolution boundary layer data. The traversing system was installed internally to the cylindrical leading edge to reduce probe blockage.

  6. Depth-compensated diffuse optical tomography enhanced by general linear model analysis and an anatomical atlas of human head

    PubMed Central

    Tian, Fenghua; Liu, Hanli

    2013-01-01

    One of the main challenges in functional diffuse optical tomography (DOT) is to accurately recover the depth of brain activation, which is even more essential when differentiating true brain signals from task-evoked artifacts in the scalp. Recently, we developed a depth-compensated algorithm (DCA) to minimize the depth localization error in DOT. However, the semi-infinite model that was used in DCA deviated significantly from the realistic human head anatomy. In the present work, we incorporated depth-compensated DOT (DC-DOT) with a standard anatomical atlas of human head. Computer simulations and human measurements of sensorimotor activation were conducted to examine and prove the depth specificity and quantification accuracy of brain atlas-based DC-DOT. In addition, node-wise statistical analysis based on the general linear model (GLM) was also implemented and performed in this study, showing the robustness of DC-DOT that can accurately identify brain activation at the correct depth for functional brain imaging, even when co-existing with superficial artifacts. PMID:23859922

  7. Enhanced blue light shielding property of light-diffusion polycarbonate composites by CeO2-coated silicate microspheres

    NASA Astrophysics Data System (ADS)

    Zhao, Yu; Shi, Liyi; Tang, Anjie; Song, Na; Tang, Shengfu; Ding, Peng

    2015-07-01

    The CeO2 coated silicate microspheres (SMSs) core-shell particles (SMS-CeO2) were synthesized for enhancing blue light shielding property of polycarbonate (PC) composites. The structure analysis showed that CeO2 particles were homogenously coated on SMS by Ce-O-Si bonds. The optical analysis indicated that the transmittance of PC/SMS-CeO2 composites were enhanced to 63.2% from 42.9% for PC/SMS/CeO2 composites when 0.6 wt.% fillers were loaded, while there was no obvious influence on the haze of the composites. UV-Vis analysis showed that the absorbance at 450-nm wavelength of blue-light increased from 24% of PC/SMS to 50% of PC/SMS-CeO2 composites, while the absorbance at 650-nm wavelength of red-light was unchanged. These results indicated that the PC/SMS-CeO2 composites had blue light shielding property and better performance on transmitting other visible lights.

  8. Transient IL-10 receptor blockade can enhance CD8(+) T cell responses to a simian adenovirus-vectored HIV-1 conserved region immunogen.

    PubMed

    Clutton, Genevieve; Bridgeman, Anne; Reyes-Sandoval, Arturo; Hanke, Tomas; Dorrell, Lucy

    2015-01-01

    Viral vector vaccines designed to elicit CD8(+) T cells in non-human primates exert potent control of immunodeficiency virus infections; however, similar approaches have been unsuccessful in humans. Adenoviral vectors elicit potent T cell responses but also induce production of immunosuppressive interleukin-10 (IL-10), which can limit the expansion of T cell responses. We investigated whether inhibiting IL-10 signaling prior to immunization with a candidate adenovirus vectored-HIV-1 vaccine, ChAdV63.HIVconsv, could modulate innate and adaptive immune responses in BALB/c mice. Transient IL-10 receptor blockade led to a modest but significant increase in the total magnitude CD8(+) T cell response to HIVconsv, but did not affect T cell responses to immunodominant epitopes. Anti-IL-10R-treated animals also exhibited greater expression of CD86 on CD11c(+) dendritic cells. Our data support further investigation and optimization of IL-10 blocking strategies to improve the immunogenicity of vaccines based on replication-defective adenoviruses. PMID:25751015

  9. Deletion of mitochondrial uncoupling protein-2 increases ischemic brain damage after transient focal ischemia by altering gene expression patterns and enhancing inflammatory cytokines

    PubMed Central

    Haines, Bryan A; Mehta, Suresh L; Pratt, Serena M; Warden, Craig H; Li, P Andy

    2010-01-01

    Mitochondrial hyperpolarization inhibits the electron transport chain and increases incomplete reduction of oxygen, enabling production of reactive oxygen species (ROS). The consequence is mitochondrial damage that eventually causes cell death. Uncoupling proteins (UCPs) are inner mitochondrial membrane proteins that dissipate the mitochondrial proton gradient by transporting H+ across the inner membrane, thereby stabilizing the inner mitochondrial membrane potential and reducing the formation of ROS. The role of UCP2 in neuroprotection is still in debate. This study seeks to clarify the role of UCP2 in transient focal ischemia (tFI) and to further understand the mechanisms of ischemic brain damage. Both wild-type and UCP2-knockout mice were subjected to tFI. Knocking out UCP2 significantly increased the infarct volume to 61% per hemisphere as compared with 18% in wild-type animals. Knocking out UCP2 suppressed antioxidant, cell-cycle, and DNA repair genes, including Sod1 and Sod2, Gstm1, and cyclins. Furthermore, knocking out UCP2 significantly upregulated the protein levels of the inflammatory cytokines, including CTACK, CXCL16, Eotaxin-2, fractalkine, and BLC. It is concluded that knocking out the UCP2 gene exacerbates neuronal death after cerebral ischemia with reperfusion and this detrimental effect is mediated by alteration of antioxidant genes and upregulation of inflammatory mediators. PMID:20407461

  10. Recombinant tissue-type plasminogen activator transiently enhances blood-brain barrier permeability during cerebral ischemia through vascular endothelial growth factor-mediated endothelial endocytosis in mice.

    PubMed

    Suzuki, Yasuhiro; Nagai, Nobuo; Yamakawa, Kasumi; Muranaka, Yoshinori; Hokamura, Kazuya; Umemura, Kazuo

    2015-12-01

    Recombinant tissue-type plasminogen activator (rt-PA) modulates cerebrovascular permeability and exacerbates brain injury in ischemic stroke, but its mechanisms remain unclear. We studied the involvement of vascular endothelial growth factor (VEGF)-mediated endocytosis in the increase of blood-brain barrier (BBB) permeability potentiated by rt-PA after ischemic stroke. The rt-PA treatment at 4 hours after middle cerebral artery occlusion induced a transient increase in BBB permeability after ischemic stroke in mice, which was suppressed by antagonists of either low-density lipoprotein receptor families (LDLRs) or VEGF receptor-2 (VEGFR-2). In immortalized bEnd.3 endothelial cells, rt-PA treatment upregulated VEGF expression and VEGFR-2 phosphorylation under ischemic conditions in an LDLR-dependent manner. In addition, rt-PA treatment increased endocytosis and transcellular transport in bEnd.3 monolayers under ischemic conditions, which were suppressed by the inhibition of LDLRs, VEGF, or VEGFR-2. The rt-PA treatment also increased the endocytosis of endothelial cells in the ischemic brain region after stroke in mice. These findings indicate that rt-PA increased BBB permeability via induction of VEGF, which at least partially mediates subsequent increase in endothelial endocytosis. Therefore, inhibition of VEGF induction may have beneficial effects after thrombolytic therapy with rt-PA treatment after stroke. PMID:26219596

  11. Transient Wellbore Fluid Flow Model

    Energy Science and Technology Software Center (ESTSC)

    1982-04-06

    WELBORE is a code to solve transient, one-dimensional two-phase or single-phase non-isothermal fluid flow in a wellbore. The primary thermodynamic variables used in solving the equations are the pressure and specific energy. An equation of state subroutine provides the density, quality, and temperature. The heat loss out of the wellbore is calculated by solving a radial diffusion equation for the temperature changes outside the bore. The calculation is done at each node point in themore » wellbore.« less

  12. Out-diffused silver island films for surface-enhanced Raman scattering protected with TiO2 films using atomic layer deposition

    PubMed Central

    2014-01-01

    We fabricated self-assembled silver nanoisland films using a recently developed technique based on out-diffusion of silver from an ion-exchanged glass substrate in reducing atmosphere. We demonstrate that the position of the surface plasmon resonance of the films depends on the conditions of the film growth. The resonance can be gradually shifted up to 100nm towards longer wavelengths by using atomic layer deposition of titania, from 3 to 100nm in thickness, upon the film. Examination of the nanoisland films in surface-enhanced Raman spectrometry showed that, in spite of a drop of the surface-enhanced Raman spectroscopy (SERS) signal after the titania spacer deposition, the Raman signal can be observed with spacers up to 7nm in thickness. Denser nanoisland films show slower decay of the SERS signal with the increase in spacer thickness. PACS 78.67.Sc (nanoaggregates; nanocomposites); 81.16.Dn (self-assembly); 74.25.nd (Raman and optical spectroscopy) PMID:25170333

  13. Reduced boron diffusion under interstitial injection in fluorine implanted silicon

    SciTech Connect

    Kham, M. N.; Matko, I.; Chenevier, B.; Ashburn, P.

    2007-12-01

    Point defect injection studies are performed to investigate how fluorine implantation influences the diffusion of boron marker layers in both the vacancy-rich and interstitial-rich regions of the fluorine damage profile. A 185 keV, 2.3x10{sup 15} cm{sup -2} F{sup +} implant is made into silicon samples containing multiple boron marker layers and rapid thermal annealing is performed at 1000 deg. C for times of 15-120 s. The boron and fluorine profiles are characterized by secondary ion mass spectroscopy and the defect structures by transmission electron microscopy (TEM). Fluorine implanted samples surprisingly show less boron diffusion under interstitial injection than those under inert anneal. This effect is particularly noticeable for boron marker layers located in the interstitial-rich region of the fluorine damage profile and for short anneal times (15 s). TEM images show a band of dislocation loops around the range of the fluorine implant and the density of dislocation loops is lower under interstitial injection than under inert anneal. It is proposed that interstitial injection accelerates the evolution of interstitial defects into dislocation loops, thereby giving transient enhanced boron diffusion over a shorter period of time. The effect of the fluorine implant on boron diffusion is found to be the opposite for boron marker layers in the interstitial-rich and vacancy-rich regions of the fluorine damage profile. For marker layers in the interstitial-rich region of the fluorine damage profile, the boron diffusion coefficient decreases with anneal time, as is typically seen for transient enhanced diffusion. The boron diffusion under interstitial injection is enhanced by the fluorine implant at short anneal times but suppressed at longer anneal times. It is proposed that this behavior is due to trapping of interstitials at the dislocation loops introduced by the fluorine implant. For boron marker layers in the vacancy-rich region of the fluorine damage profile, suppression of boron diffusion is seen for short anneals and then increased diffusion after a critical time, which is longer for inert anneal than interstitial injection. This behavior is explained by the annealing of vacancy-fluorine clusters, which anneal quicker under interstitial injection because the injected interstitials annihilate vacancies in the clusters.

  14. Nonmonotonic diffusion in crowded environments

    PubMed Central

    Putzel, Gregory Garbs; Tagliazucchi, Mario; Szleifer, Igal

    2015-01-01

    We study the diffusive motion of particles among fixed spherical crowders. The diffusers interact with the crowders through a combination of a hard-core repulsion and a short-range attraction. The long-time effective diffusion coefficient of the diffusers is found to depend non-monotonically on the strength of their attraction to the crowders. That is, for a given concentration of crowders, a weak attraction to the crowders enhances diffusion. We show that this counterintuitive fact can be understood in terms of the mesoscopic excess chemical potential landscape experienced by the diffuser. The roughness of this excess chemical potential landscape quantitatively captures the nonmonotonic dependence of the diffusion rate on the strength of crowder-diffuser attraction; thus it is a purely static predictor of dynamic behavior. The mesoscopic view given here provides a unified explanation for enhanced diffusion effects that have been found in various systems of technological and biological interest. PMID:25302920

  15. Transient drainage summary report

    SciTech Connect

    1996-09-01

    This report summarizes the history of transient drainage issues on the Uranium Mill Tailings Remedial Action (UMTRA) Project. It defines and describes the UMTRA Project disposal cell transient drainage process and chronicles UMTRA Project treatment of the transient drainage phenomenon. Section 4.0 includes a conceptual cross section of each UMTRA Project disposal site and summarizes design and construction information, the ground water protection strategy, and the potential for transient drainage.

  16. An uncommon cause of transient neurological dysfunction.

    PubMed

    Farooq, Muhammad U; Bhatt, Archit; Chang, Howard T

    2014-07-01

    Transient neurological dysfunction may be associated with uncommon disorders and should prompt consideration of a broad differential diagnosis when assessing patients with episodic symptoms. The most common causes of transient neurological dysfunction include transient ischemic attack (TIA), seizure disorder, and migraine and its variants. However, underlying unusual pathophysiological processes such as brain tumors can also cause transient neurological dysfunction. Here we present a case of a 68-year-old male with oligodendroglial gliomatosis cerebri (OGC) who presented with TIA-like symptoms. Brain magnetic resonance imaging revealed multiple diffuse T2 hyperintensities within the white and gray matter. Magnetic resonance spectroscopy was suggestive of gliomatosis cerebri and was particularly helpful in this case. The diagnosis of OGC was confirmed by histopathology and molecular genetic studies on brain biopsy tissue. In this report, we discuss the clinical and radiological characteristics of OGC and highlight the unusual presentation of this case. PMID:24982718

  17. An Uncommon Cause of Transient Neurological Dysfunction

    PubMed Central

    Bhatt, Archit; Chang, Howard T.

    2014-01-01

    Transient neurological dysfunction may be associated with uncommon disorders and should prompt consideration of a broad differential diagnosis when assessing patients with episodic symptoms. The most common causes of transient neurological dysfunction include transient ischemic attack (TIA), seizure disorder, and migraine and its variants. However, underlying unusual pathophysiological processes such as brain tumors can also cause transient neurological dysfunction. Here we present a case of a 68-year-old male with oligodendroglial gliomatosis cerebri (OGC) who presented with TIA-like symptoms. Brain magnetic resonance imaging revealed multiple diffuse T2 hyperintensities within the white and gray matter. Magnetic resonance spectroscopy was suggestive of gliomatosis cerebri and was particularly helpful in this case. The diagnosis of OGC was confirmed by histopathology and molecular genetic studies on brain biopsy tissue. In this report, we discuss the clinical and radiological characteristics of OGC and highlight the unusual presentation of this case. PMID:24982718

  18. Long-lived anomalous thermal diffusion induced by elastic cell membranes on nearby particles

    NASA Astrophysics Data System (ADS)

    Daddi-Moussa-Ider, Abdallah; Guckenberger, Achim; Gekle, Stephan

    2016-01-01

    The physical approach of a small particle (virus, medical drug) to the cell membrane represents the crucial first step before active internalization and is governed by thermal diffusion. Using a fully analytical theory we show that the stretching and bending of the elastic membrane by the approaching particle induces a memory in the system, which leads to anomalous diffusion, even though the particle is immersed in a purely Newtonian liquid. For typical cell membranes the transient subdiffusive regime extends beyond 10 ms and can enhance residence times and possibly binding rates up to 50%. Our analytical predictions are validated by numerical simulations.

  19. {ital Ab Initio} Pseudopotential calculations of dopant diffusion in Si

    SciTech Connect

    Zhu, J., LLNL

    1997-04-28

    The ab initio pseudopotential method is used to study transient-enhanced-diffusion (TED) related processes. The electronic degrees of freedom are included explicitly, together with the fully self-consistent treatment of the electron charge density. A large supercell and a fine k-point mesh are used to ensure numerical convergence. Such method has been demonstrated to give quantitative description of defect energetic. We will show that boron diffusion is significantly enhanced in the presence of the Si interstitial due to the substantial lowering of the migrational barrier through a kick-out mechanism. The resulting mobile boron can also be trapped by another substitutional boron, forming an immobile and elect rically inactive two-boron pair. Similarly, carbon diffusion is also enhanced significantly due to the pairing with Si interstitial. However, carbon binds to Si interstitial much more strongly than boron does, taking away most Si interstitial from boron at sufficiently large carbon concentration, which causes the suppression of the boron TED. We will also show that Fermi level effect plays an important role in both Si interstitial and boron diffusion.

  20. Quantitative Evaluation of Diffusion and Dynamic Contrast-Enhanced MR in Tumor Parenchyma and Peritumoral Area for Distinction of Brain Tumors

    PubMed Central

    Zhao, Jing; Yang, Zhi-yun; Luo, Bo-ning; Yang, Jian-yong; Chu, Jian-ping

    2015-01-01

    Purpose To quantitatively evaluate the diagnostic efficiency of parameters from diffusion and dynamic contrast-enhanced MR which based on tumor parenchyma (TP) and peritumoral (PT) area in classification of brain tumors. Methods 45 patients (male: 23, female: 22; mean age: 46 y) were prospectively recruited and they underwent conventional, DCE-MR and DWI examination. With each tumor, 10–15 regions of interest (ROIs) were manually placed on TP and PT area. ADC and permeability parameters (Ktrans, Ve, Kep and iAUC) were calculated and their diagnostic efficiency was assessed. Results In TP, all permeability parameters and ADC value could significantly discriminate Low- from High grade gliomas (HGG) (p<0.001); among theses parameters, Ve demonstrated the highest diagnostic power (iAUC: 0.79, cut-off point: 0.15); the most sensitive and specific index for gliomas grading were Ktrans (84%) and Kep (89%). While, in PT area, only Ktrans could help in gliomas grading (P = 0.009, cut-off point: 0.03 min-1). Moreover, in TP, mean Ve and iAUC of primary central nervous system lymphoma (PCNSL) and metastases were significantly higher than that in HGG (p<0.003). Further, in PT area, mean Ktrans (p≤0.004) could discriminate PCNSL from HGG and ADC (p≤0.003) could differentiate metastases with HGG. Conclusions Quantitative ADC and permeability parameters from Diffusion and DCE-MR in TP and PT area, especially DCE-MR, can aid in gliomas grading and brain tumors discrimination. Their combined application is strongly recommended in the differential diagnosis of these tumor entities. PMID:26384329

  1. Secondary porosity in a transient vadose zone

    SciTech Connect

    Frederick, W.T.; Grasso, T.X. Jr. )

    1993-03-01

    The Western New York Nuclear Service Center is the site of low and high level radioactive waster buried in a series of trenches excavated in a 28 m thick, Lavery-age silty clay diamicton that exhibits a 6 meter thick transient vadoes zone where exposed at the surface. Hydrostratigraphy of this till includes a 0.25 m thick poorly developed macroporous soil, a 3.5 m thick weathered zone of densely spaced and randomly orientated horizontal and vertical fractures, a 2 m thick unweathered zone of intermittently spaced fractures exhibiting east-west orientations, and a massive 23 m thick unweathered till zone that exhibits isolated, east-west orientated fractures. Bulk hydraulic conductivity of this active flow zone decreases with depth from 10[sup [minus]5] to 10[sup [minus]8] cm/s. The specific discharge of vertically flowing groundwater in the massive till zone is 1.25 cm/yr. A water surplus in the recharge season saturates the fractured zone to grade with up to 7.37 cm/yr of net infiltration. Tritium and radionuclides from the waste trenches and surrounding soil matrix hydrodynamically disperse into the field-saturated fracture network that contains meteoric recharge water. A soil moisture deficit in discharge season produces a vadose zone of widened fractures that via capillarity enhances the diffusion of contaminants into the soil matrix. These enlarged connecting conduits laterally channel the excess infiltration from the recharge season and diffused contaminants to local lowlands and incised streams that truncate the unweathered till. The current vadose and phreatic zone flow study will be used in numeric simulations that will delineate the areal extend and temporal duration of these seepage faces and the time frame of possible surfaces water contamination.

  2. Enhanced Oxygen Diffusion Within the Internal Oxidation Zone of Alloy 617 in Controlled Impurity Helium Environments from 1023 K to 1123 K (750 °C to 850 °C)

    NASA Astrophysics Data System (ADS)

    Gulsoy, Gokce; Was, Gary S.

    2015-04-01

    Alloy 617 was exposed to He-CO-CO2 environments with of either 9 or 1320 at temperatures from 1023 K to 1123 K (750 °C to 850 °C) to determine the oxygen diffusion coefficients within the internal oxidation zone of the alloy. The oxygen diffusion coefficients determined based on both intergranular and transgranular oxidation rates were several orders of magnitude greater than those reported in pure nickel and in nickel-based binary alloys, indicating that the rapid internal aluminum oxidation of Alloy 617 was primarily due to enhanced oxygen diffusion along the incoherent Al2O3-alloy interfaces. The range of activation energy values determined for oxygen diffusion associated with the intergranular aluminum oxidation was from 149.6 to 154.7 kJ/mol, and that associated with the transgranular aluminum oxidation was from 244.7 to 283.5 kJ/mol.

  3. Transient repetitive exposure to low level light therapy enhances collateral blood vessel growth in the ischemic hindlimb of the tight skin mouse.

    PubMed

    Zaidi, Maria; Krolikowki, John G; Jones, Deron W; Pritchard, Kirkwood A; Struve, Janine; Nandedkar, Sandhya D; Lohr, Nicole L; Pagel, Paul S; Weihrauch, Dorothe

    2013-01-01

    The tight skin mouse (Tsk(-/+)) is a model of scleroderma characterized by impaired vasoreactivity, increased oxidative stress, attenuated angiogenic response to VEGF and production of the angiogenesis inhibitor angiostatin. Low-level light therapy (LLLT) stimulates angiogenesis in myocardial infarction and chemotherapy-induced mucositis. We hypothesize that repetitive LLLT restores vessel growth in the ischemic hindlimb of Tsk(-/+) mice by attenuating angiostatin and enhancing angiomotin effects in vivo. C57Bl/6J and Tsk(-/+) mice underwent ligation of the femoral artery. Relative blood flow to the foot was measured using a laser Doppler imager. Tsk(-/+) mice received LLLT (670 nm, 50 mW cm(-2), 30 J cm(-2)) for 10 min per day for 14 days. Vascular density was determined using lycopersicom lectin staining. Immunofluorescent labeling, Western blot analysis and immunoprecipitation were used to determine angiostatin and angiomotin expression. Recovery of blood flow to the ischemic limb was reduced in Tsk(-/+) compared with C57Bl/6 mice 2 weeks after surgery. LLLT treatment of Tsk(-/+) mice restored blood flow to levels observed in C57Bl/6 mice. Vascular density was decreased, angiostatin expression was enhanced and angiomotin depressed in the ischemic hindlimb of Tsk(-/+) mice. LLLT treatment reversed these abnormalities. LLLT stimulates angiogenesis by increasing angiomotin and decreasing angiostatin expression in the ischemic hindlimb of Tsk(-/+) mice. PMID:23231468

  4. Response of HT29 Colorectal Xenograft Model to Cediranib Assessed with 18F-FMISO PET, Dynamic Contrast-Enhanced and Diffusion-Weighted MRI

    PubMed Central

    Bokacheva, Louisa; Kotedia, Khushali; Reese, Megan; Ricketts, Sally-Ann; Halliday, Jane; Le, Carl H.; Koutcher, Jason A.; Carlin, Sean

    2012-01-01

    Cediranib (AZD2171, AstraZeneca, UK) is a small-molecule pan-VEGFR inhibitor. The tumor response to short-term cediranib treatment was studied using dynamic contrast-enhanced (DCE) and diffusion-weighted (DW) MRI at 7 T as well as 18F-fluoromisonidazle (18F-FMISO) PET and histological markers. Rats bearing subcutaneous HT29 human colorectal tumors were imaged at baseline, then received three doses of cediranib (3 mg/kg per dose daily) or vehicle (dosed daily), with follow up imaging performed 2 hours after the final cediranib or vehicle dose. Tumors were excised and evaluated for the perfusion marker Hoechst 33342, endothelial cell marker CD31, smooth muscle actin (SMA), intercapillary distance (ICD) and tumor necrosis. DCE-MRI-derived parameters decreased significantly in cediranib-treated tumors relative to pre-treatment values: the muscle-normalized initial area under the gadolinium concentration curve (nIAUC90) by 48% (p = 0.002), the enhancing fraction (EnF) by 43% (p = 0.003) and Ktrans by 57% (p = 0.003), but remained unchanged in controls. No change between pre- and post-treatment tumor apparent diffusion coefficient (ADC) in either cediranib- or vehicle-treated group was observed over the course of this study. 18F-FMISO SUVmean decreased by 33% (p = 0.008) in the cediranib group, but showed no significant change in the control group. Histological analysis showed that the number of CD31-positive vessels (59 per mm2), the fraction of SMA-positive vessels (80 to 87%) and ICD (0.17 mm) were similar in cediranib- and vehicle-treated groups. The fraction of perfused blood vessels in cediranib-treated tumors (817%) was lower than in vehicle controls (913%, p = 0.02). The necrotic fraction was slightly higher in cediranib-treated rats (3412%) than in controls (2610%, p = 0.23). These findings suggest that short-term treatment with cediranib causes a decrease of tumor perfusion/permeability across the tumor cross-section, but changes in vascular morphology, vessel density or tumor cellularity do not manifest at this early time point. PMID:22777834

  5. Titan's Magic Island: Transient features in a Titan sea

    NASA Astrophysics Data System (ADS)

    Hofgartner, J. D.; Hayes, A. G., Jr.; Lunine, J. I.; Zebker, H. A.; Stiles, B. W.; Sotin, C.; Barnes, J. W.; Turtle, E. P.; Baines, K. H.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Encrenaz, P.; Kirk, R. L.; Le Gall, A. A.; Lopes, R. M. C.; Lorenz, R. D.; Malaska, M. J.; Mitchell, K. L.; Nicholson, P. D.; Paillou, P.; Radebaugh, J.; Wall, S. D.; Wood, C. A.

    2014-12-01

    Transient bright features, popularly referred to as Titan's Magic Island, were observed in Cassini Synthetic Aperture Radar (SAR) images of the northern sea, Ligeia Mare, in July 2013 (Hofgartner et al., 2014, Nature Geosci. 7, 493). Images obtained prior and subsequent to the July 2013 detection do not include these bright features. The features are not consistent with ambiguities, scalloping, gain control or edge effects and are not considered to be standard SAR image artifacts. We compared the measured radar cross-sections from the region of the anomalies to a suite of quasi-specular plus diffuse backscatter models and found that this class of models for a permanent structure can be ruled out to 88% confidence. Thus we conclude that the appearance of the features is the result of a transformation and the subsequent non-detections indicate that they were transient. The observational constraints do not permit tides and/or sea level change to be the dominant cause of the transient expression. We suggest that ephemeral phenomena such as surface waves, rising bubbles, and suspended or floating solids best explain these features. Local meteorology could stimulate or enhance these phenomena, but we are unable to constrain its role in the appearance of these transients. These enigmatic features and the waves reportedly detected in Punga Mare (Barnes et al., 2014, Planetary Science, accepted) are likely the first glimpses of dynamic processes that are commencing in the northern lakes and seas as summer nears in the northern hemisphere. It is plausible that they are an expression of the changing seasons and as Titan's northern hemisphere continues transitioning toward summer they may occur with increased frequency. Ligeia Mare, including the region of the transients, will be observed again during the Cassini Titan flyby on August 21, 2014 and this observation could be diagnostic of the nature of these features. For example, if the transients are waves and waves are detectable at the 12 degrees incidence of the upcoming radar measurements, the predicted increase in wind speeds should result in a higher spatial density of these features.

  6. Transient regimes and crossover for epitaxial surfaces.

    PubMed

    Haselwandter, Christoph A; Vvedensky, Dimitri D

    2010-02-01

    We apply a formalism for deriving stochastic continuum equations associated with lattice models to obtain equations governing the transient regimes of epitaxial growth for various experimental scenarios and growth conditions. The first step of our methodology is the systematic transformation of the lattice model into a regularized stochastic equation of motion that provides initial conditions for differential renormalization-group (RG) equations for the coefficients in the regularized equation. The solutions of the RG equations then yield trajectories that describe the original model from the transient regimes, which are of primary experimental interest, to the eventual crossover to the asymptotically stable fixed point. We first consider regimes defined by the relative magnitude of deposition noise and diffusion noise. If the diffusion noise dominates, then the early stages of growth are described by the Mullins-Herring (MH) equation with conservative noise. This is the classic regime of molecular-beam epitaxy. If the diffusion and deposition noise are of comparable magnitude, the transient equation is the MH equation with nonconservative noise. This behavior has been observed in a recent report on the growth of aluminum on silicone oil surfaces [Z.-N. Fang, Thin Solid Films 517, 3408 (2009)]. Finally, the regime where deposition noise dominates over diffusion noise has been observed in computer simulations, but does not appear to have any direct experimental relevance. For initial conditions that consist of a flat surface, the Villain-Lai-Das Sarma (VLDS) equation with nonconservative noise is not appropriate for any transient regime. If, however, the initial surface is corrugated, the relative magnitudes of terms can be altered to the point where the VLDS equation with conservative noise does indeed describe transient growth. This is consistent with the experimental analysis of growth on patterned surfaces [H.-C. Kan, Phys. Rev. Lett. 92, 146101 (2004); T. Tadayyon-Eslami, Phys. Rev. Lett. 97, 126101 (2006)]. PMID:20365573

  7. Gas diffusion layers coated with a microporous layer containing hydrophilic carbon nanotubes for performance enhancement of polymer electrolyte fuel cells under both low and high humidity conditions

    NASA Astrophysics Data System (ADS)

    Kitahara, Tatsumi; Nakajima, Hironori; Okamura, Kosuke

    2015-06-01

    Gas diffusion layers (GDLs) coated with a hydrophobic microporous layer (MPL) composed of carbon black and polytetrafluoroethylene (PTFE) have been commonly used to improve the water management characteristics of polymer electrolyte fuel cells (PEFCs). However, the hydrophobic MPL coated GDL designed to prevent dehydration of the membrane under low humidity conditions is generally inferior at reducing flooding under high humidity conditions. It is therefore important to develop a robust MPL coated GDL that can enhance the PEFC performance regardless of the humidity conditions. In the present study, a GDL coated with an MPL containing hydrophilic carbon nanotubes (CNTs) was developed. The less hydrophobic pores incorporating CNTs are effective at conserving the membrane humidity under low humidity conditions. The MPL with CNTs is also effective at expelling excess water from the catalyst layer while maintaining oxygen flow pathways from the GDL substrate, allowing the mean flow pore diameter to be decreased to 2 ?m without reducing the ability of the MPL to prevent flooding under high humidity conditions. An MPL coated GDL with a CNT content of 4 mass% exhibits significantly higher performance under both low and high humidity conditions than a hydrophobic MPL coated GDL.

  8. A modified spontaneous emulsification solvent diffusion method for the preparation of curcumin-loaded PLGA nanoparticles with enhanced in vitro anti-tumor activity

    NASA Astrophysics Data System (ADS)

    Chen, Cen; Yang, Wei; Wang, Dan-Tong; Chen, Chao-Long; Zhuang, Qing-Ye; Kong, Xiang-Dong

    2014-12-01

    To improve the anti-tumor activity of hydrophobic drug curcumin, we prepared curcumin-loaded PLGA nanoparticles (PLGA-Cur NPs) through a modified spontaneous emulsification solvent diffusion (modified-SESD) method. The influence of main preparation parameters was investigated, such as the volume ratio of binary organic solvents and the concentration of surfactant. Results indicated that the synthesized regular spherical PLGA NPs with the average diameter of 189.7 nm exhibited relatively higher yield (58.9%), drug loading (11.0% (w/w)) and encapsulation efficiency (33.5%), and also a controllable drug release profile. In order to evaluate the in vitro cytotoxicity of the prepared NPs, MTT assay was conducted, and results showed that the NPs could effectively inhibit HL60 and HepG2 cells with lower IC50 values compared with free curcumin. Furthermore, confocal microscopy together with flow cytometry analysis proved the enhanced apoptosis-inducing ability of PLGA-Cur NPs. Polymeric NP formulations are potential to be used for hydrophobic drug delivery systems in cancer therapy.

  9. PGE(2) transiently enhances DC expression of CCR7 but inhibits the ability of DCs to produce CCL19 and attract naive T cells.

    PubMed

    Muthuswamy, Ravikumar; Mueller-Berghaus, Jan; Haberkorn, Uwe; Reinhart, Todd A; Schadendorf, Dirk; Kalinski, Pawel

    2010-09-01

    Prostaglandin E(2) (PGE(2)) is an inflammatory mediator often used to increase CCR7 expression in the dendritic cells (DCs) used as cancer vaccines and to enhance their responsiveness to lymph node-associated chemokines. Here, we show that high surface expression of CCR7 on PGE(2)-matured DCs is associated with their suppressed production of the endogenous CCR7 ligand, CCL19, and is reversible by exogenous CCL19. In contrast to the PGE(2)-matured DCs, DCs matured in the presence of toll-like receptor (TLR) ligands and interferons produce high levels of both CCL19 and CCR7 mRNA/protein, but show selectively reduced expression of surface CCR7, which is compensated after DC removal from the CCL19-rich maturation environment. In accordance with these findings, PGE(2)-matured DCs show significantly higher in vitro migratory responsiveness to lymph node-associated chemokines directly after DC generation, but not after additional short-term culture in vitro, nor in vivo in patients injected with (111)indium-labeled DCs. The differences in CCL19-producing ability imprinted during DC maturation result in their different abilities to attract CCR7(+) naive T cells. Our data help to explain the impact of PGE(2) on CCR7 expression in maturing DCs and demonstrate a novel mechanism of regulatory activity of PGE(2), mediated by the inhibition of DCs ability to attract naive T cells. PMID:20498301

  10. Transient global amnesia.

    PubMed

    Szabo, Kristina

    2014-01-01

    Transient global amnesia (TGA) is a sudden and severe anterograde memory disturbance accompanied by various degrees of retrograde amnesia and sometimes executive dysfunction. TGA affects elderly individuals and men and women equally. During the episode, patients cannot recall novel episodic information and therefore repeatedly ask the same questions. They are not fully oriented to space and time. Diagnostic criteria first established in 1985, and elaborated in 1990, demand that there is no clouding of consciousness, other impairments of cognition, or a history of epilepsy or head trauma. An episode of TGA resolves within 24 h leaving a memory gap for the length of the attack. While in rare cases TGA might happen repeatedly, it mostly occurs as a single attack. TGA is considered a benign disorder as memory deficits resolve completely and do not lead to long-term sequelae. In up to 90% of reported TGA cases, a precipitating event - mainly described as physical or emotional stress - is present. The cause of TGA has been a matter of long-standing debate among researchers. In search of an answer, several possible causes (ischemia, migraine, epileptic seizures, or, more recently, a disturbance of venous hemodynamics) have been hypothesized. However, to date there is no scientific proof of any of these mechanisms. By using diffusion-weighted MRI 24-48 h after a TGA episode, small dot-like lesions have been detected in the hippocampus. This has led to the implication that the selective vulnerability of CA1 neurons to metabolic stress might play a role in the pathophysiology of TGA. PMID:24777137

  11. [Contribution of arterial spin labeling to the diagnosis of sudden and transient neurological deficit].

    PubMed

    Yger, M; Villain, N; Belkacem, S; Bertrand, A; Rosso, C; Crozier, S; Samson, Y; Dormont, D

    2015-02-01

    MRI is the gold standard exploration for sudden transient neurological events. If diffusion MRI is negative, there may be a diagnostic doubt between transient ischemic attack and other causes of transient neurological deficit. We illustrate how sequence arterial spin labeling (ASL), which evaluates cerebral perfusion, contributes to the exploration of transient neurological events. An ASL sequence was performed in seven patients with a normal diffusion MRI explored for a transient deficit. Cortical hyperperfusion not systematized to an arterial territory was found in three and hypoperfusion systematized to an arterial territory in four. ASL helped guide early management of these patients. PMID:25555846

  12. Transient Voltage Recorder

    NASA Astrophysics Data System (ADS)

    Medelius, Pedro J.; Simpson, Howard J.

    2002-09-01

    A voltage transient recorder can detect lightning induced transient voltages. The recorder detects a lightning induced transient voltage and adjusts input amplifiers to accurately record transient voltage magnitudes. The recorder stores voltage data from numerous monitored channels, or devices. The data is time stamped and can be output in real time, or stored for later retrieval. The transient recorder, in one embodiment, includes an analog-to-digital converter and a voltage threshold detector. When an input voltage exceeds a pre-determined voltage threshold, the recorder stores the incoming voltage magnitude and time of arrival. The recorder also determines if its input amplifier circuits clip the incoming signal or if the incoming signal is too low. If the input data is clipped or too low, the recorder adjusts the gain of the amplifier circuits to accurately acquire subsequent components of the lightning induced transients.

  13. High-energy transients.

    PubMed

    Gehrels, Neil; Cannizzo, John K

    2013-06-13

    We present an overview of high-energy transients in astrophysics, highlighting important advances over the past 50 years. We begin with early discoveries of ?-ray transients, and then delve into physical details associated with a variety of phenomena. We discuss some of the unexpected transients found by Fermi and Swift, many of which are not easily classifiable or in some way challenge conventional wisdom. These objects are important insofar as they underscore the necessity of future, more detailed studies. PMID:23630376

  14. Transient isotachophoresis focusing of DNA and DNA-protein complexes is essentially enhanced by spontaneously dissolved aerial carbon dioxide in electrolytes.

    PubMed

    Liu, Shengquan; Zhang, Dapeng; Wang, Hailin

    2015-01-01

    The formation of a highly adapted high-E zone is critical to isotachophoresis separation and focusing. Recently, we discovered that the high-E zone is present only in a small portion of electrophoresis channel in the presence of EOF (Liu, S. Q. et al. J. Am. Chem. Soc. 2013, 135, 4644-4647). Accordingly, a much narrower high-E zone is presumably present in t-ITP. If so, it is hard to achieve efficient t-ITP focusing. Indeed, by online coupling t-ITP with CE-LIF immunoassay, the immunocomplexes of carcinogenic BPDE-dG adducts are not efficiently focused using a freshly prepared background electrolyte. Intriguingly, we observed that 20-day stored background electrolyte displays a 10-fold better focusing efficiency. We hypothesize that the unexpected phenomenon is associated with the dissolution of aerial carbon dioxide, which is mainly converted to ionic HCO3(-) in the weak alkaline background electrolyte. Consequently, HCO3(-) of high electrophoretic mobility will be continuously injected into the capillary along with the background electrolyte and act as an alternative leading ion to improve the focusing. By addition of dry ice (without causing significant pH decrease, ?pH < 0.4) to freshly prepared background electrolytes, we immediately observed the enhanced focusing of immunocomplexes of the DNA adducts. NH4HCO3 and Na2CO3, included in the background electrolyte, also improve the focusing efficiency and reproducibility. All these consistently support our hypothesis. To understand the underlying mechanism, an advanced CE-SMFI was exploited to monitor in real time the motion of single DNA molecules and the E change throughout t-ITP. We uncovered that t-ITP can induce a local high-E zone, but the presence of HCO3(-) in the background electrolyte could greatly increase the E value in the high-E zone, which allows more DNA molecules to rapidly move backward and to be efficiently stacked at LE/TE boundary. This study provides new insight into nonuniform electric field-induced electrophoresis focusing. PMID:25437902

  15. Motion of a disordered polypeptide chain as studied by paramagnetic relaxation enhancements, 15N relaxation, and molecular dynamics simulations: how fast is segmental diffusion in denatured ubiquitin?

    PubMed

    Xue, Yi; Skrynnikov, Nikolai R

    2011-09-21

    Molecular dynamics (MD) simulations have been widely used to analyze dynamic conformational equilibria of folded proteins, especially in relation to NMR observables. However, this approach found little use in the studies of disordered proteins, where the sampling of vast conformational space presents a serious problem. In this paper, we demonstrate that the latest advances in computation technology make it possible to overcome this limitation. The experimentally validated (calibrated) MD models allow for new insights into structure/dynamics of disordered proteins. As a test system, we have chosen denatured ubiquitin in solution with 8 M urea at pH 2. High-temperature MD simulations in implicit solvent have been carried out for the wild-type ubiquitin as well as MTSL-tagged Q2C, D32C, and R74C mutants. To recalibrate the MD data (500 K) in relation to the experimental conditions (278 K, 8 M urea), the time axes of the MD trajectories were rescaled. The scaling factor was adjusted such as to maximize the agreement between the simulated and experimental (15)N relaxation rates. The resulting effective length of the trajectories, 311 μs, ensures good convergence properties of the MD model. The constructed MD model was validated against the array of experimental data, including additional (15)N relaxation parameters, multiple sets of paramagnetic relaxation enhancements (PREs), and the radius of gyration. In each case, a near-quantitative agreement has been obtained, suggesting that the model is successful. Of note, the MD-based approach rigorously predicts the quantities that are inherently dynamic, i.e., dependent on the motional correlation times. This cannot be accomplished, other than in empirical fashion, on the basis of static structural models (conformational ensembles). The MD model was further used to investigate the relative translational motion of the MTSL label and the individual H(N) atoms. The derived segmental diffusion coefficients proved to be nearly uniform along the peptide chain, averaging to D = 0.49-0.55 × 10(-6) cm(2)/s. This result was verified by direct analysis of the experimental PRE data using the recently proposed Ullman-Podkorytov model. In this model, MTSL and H(N) moieties are treated as two tethered spheres undergoing mutual diffusion in a harmonic potential. The fitting of the experimental data involving D as a single adjustable parameter leads to D = 0.45 × 10(-6) cm(2)/s, in good agreement with the MD-based analyses. This result can be compared with the range of estimates obtained from the resonance energy transfer experiments, D = 0.2-6.0 × 10(-6) cm(2)/s. PMID:21819149

  16. Detection of false transients

    NASA Astrophysics Data System (ADS)

    Galleani, Lorenzo; Cohen, Leon; Nelson, Douglas J.

    2005-08-01

    When one calculates a time-frequency distribution of white noise there sometimes appear transients of short duration. Superficially, these transients appear to be real signals but they are not. This comes about by random chance in the noise and also because particular types of distributions do not resolve components well in time. These fictitious signals can be misclassified by detectors and hence it is important to understand their origin and statistical properties. We present experimental studies regarding these false transients, and by simulation we statistically quantify their duration for various distributions. We compare the number and duration of the false transients when different distributions are used.

  17. Nocistatin excites rostral agranular insular cortex-periaqueductal gray projection neurons by enhancing transient receptor potential cation conductance via G(alphaq/11)-PLC-protein kinase C pathway.

    PubMed

    Chen, Y L; Li, A H; Yeh, T H; Chou, A H; Weng, Y S; Wang, H L

    2010-06-16

    Rostral agranular insular cortex (RAIC) projects to periaqueductal gray (PAG) and inhibits spinal nociceptive transmission by activating PAG-rostral ventromedial medulla (RVM) descending antinociceptive circuitry. Despite being generated from the same precursor prepronociceptin, nocistatin (NST) and nociceptin/orphanin FQ (N/OFQ) produce supraspinal analgesic and hyperalgesic effects, respectively. Prepronociceptin is highly expressed in the RAIC. In the present study, we hypothesized that NST and N/OFQ modulate spinal pain transmission by regulating the activity of RAIC neurons projecting to ventrolateral PAG (RAIC-PAG). This hypothesis was tested by investigating electrophysiological effects of N/OFQ and NST on RAIC-PAG projection neurons in brain slice. Retrogradely labeled RAIC-PAG projection neurons are layer V pyramidal cells and express mRNA of vesicular glutamate transporter subtype 1, a marker for glutamatergic neurons. N/OFQ hyperpolarized 25% of RAIC-PAG pyramidal neurons by enhancing inwardly rectifying potassium conductance via pertussis toxin-sensitive G(alphai/o). In contrast, NST depolarized 33% of RAIC-PAG glutamatergic neurons by causing the opening of canonical transient receptor potential (TRPC) cation channels through G(alphaq/11)-phospholipase C-protein kinase C pathway. There were two separate populations of RAIC-PAG pyramidal neurons, one responding to NST and the other one to N/OFQ. Our results suggest that G(alphaq/11)-coupled NST receptor mediates NST excitation of RAIC-PAG glutamatergic neurons, which is expected to cause the supraspinal analgesia by enhancing the activity of RAIC-PAG-RVM antinociceptive pathway. Opposite effects of NST and N/OFQ on supraspinal pain regulation are likely to result from their opposing effects on RAIC-PAG pyramidal neurons. PMID:20359524

  18. A Broad G Protein-Coupled Receptor Internalization Assay that Combines SNAP-Tag Labeling, Diffusion-Enhanced Resonance Energy Transfer, and a Highly Emissive Terbium Cryptate

    PubMed Central

    Levoye, Angélique; Zwier, Jurriaan M.; Jaracz-Ros, Agnieszka; Klipfel, Laurence; Cottet, Martin; Maurel, Damien; Bdioui, Sara; Balabanian, Karl; Prézeau, Laurent; Trinquet, Eric; Durroux, Thierry; Bachelerie, Françoise

    2015-01-01

    Although G protein-coupled receptor (GPCR) internalization has long been considered as a major aspect of the desensitization process that tunes ligand responsiveness, internalization is also involved in receptor resensitization and signaling, as well as the ligand scavenging function of some atypical receptors. Internalization thus contributes to the diversity of GPCR-dependent signaling, and its dynamics and quantification in living cells has generated considerable interest. We developed a robust and sensitive assay to follow and quantify ligand-induced and constitutive-induced GPCR internalization but also receptor recycling in living cells. This assay is based on diffusion-enhanced resonance energy transfer (DERET) between cell surface GPCRs labeled with a luminescent terbium cryptate donor and a fluorescein acceptor present in the culture medium. GPCR internalization results in a quantifiable reduction of energy transfer. This method yields a high signal-to-noise ratio due to time-resolved measurements. For various GPCRs belonging to different classes, we demonstrated that constitutive and ligand-induced internalization could be monitored as a function of time and ligand concentration, thus allowing accurate quantitative determination of kinetics of receptor internalization but also half-maximal effective or inhibitory concentrations of compounds. In addition to its selectivity and sensitivity, we provided evidence that DERET-based internalization assay is particularly suitable for characterizing biased ligands. Furthermore, the determination of a Z′-factor value of 0.45 indicates the quality and suitability of DERET-based internalization assay for high-throughput screening (HTS) of compounds that may modulate GPCRs internalization. PMID:26617570

  19. Incremental Value of Diffusion Weighted and Dynamic Contrast Enhanced MRI in the Detection of Locally Recurrent Prostate Cancer after Radiation Treatment: Preliminary Results

    PubMed Central

    Akin, Oguz; Gultekin, David; Vargas, Hebert Alberto; Zheng, Junting; Moskowitz, Chaya; Pei, Xin; Sperling, Dahlia; Schwartz, Lawrence; Hricak, Hedvig; Zelefsky, Michael

    2013-01-01

    Objectives To assess the incremental value of diffusion-weighted and dynamic contrast-enhanced MRI to T2-weighted MRI in detecting locally recurrent prostate cancer after radiotherapy. Methods Twenty-four patients (median age, 70 years) with a history of radiotherapy-treated prostate cancer underwent multi-parametric MRI (MP-MRI) and transrectal prostate biopsy. Two readers independently scored the likelihood of cancer on a 1-5 scale, using T2WI alone and then adding DWI and DCE-MRI. Areas under receiver operating characteristic curves (AUCs) were estimated at the patient and prostate-side levels. The ADC from DW-MRI and the Ktrans, kep, ve, AUGC90 and AUGC180 from DCE-MRI were recorded. Results Biopsy was positive in 16/24 (67%) and negative in 8/24 (33%) patients. AUCs for readers 1 and 2 increased from 0.64 and 0.53 to 0.95 and 0.86 with MP-MRI, at the patient level, and from 0.73 and 0.66 to 0.90 and 0.79 with MP-MRI, at the prostate-side level (p values <0.05). Biopsy-positive and biopsy-negative prostate sides differed significantly in median ADC [1.44 vs. 1.68 ( 10-3 mm2/s)], median Ktrans [1.07 vs. 0.34 (1/min)], and kep [2.06 vs 1.0 ( 1/min)] (p values <0.05). Conclusions MP-MRI was significantly more accurate than T2WI alone in detecting locally recurrent prostate cancer after radiotherapy PMID:21533634

  20. Gas diffusion ultrabarriers on polymer substrates using Al{sub 2}O{sub 3} atomic layer deposition and SiN plasma-enhanced chemical vapor deposition

    SciTech Connect

    Carcia, P. F.; McLean, R. S.; Groner, M. D.; Dameron, A. A.; George, S. M.

    2009-07-15

    Thin films grown by Al{sub 2}O{sub 3} atomic layer deposition (ALD) and SiN plasma-enhanced chemical vapor deposition (PECVD) have been tested as gas diffusion barriers either individually or as bilayers on polymer substrates. Single films of Al{sub 2}O{sub 3} ALD with thicknesses of >=10 nm had a water vapor transmission rate (WVTR) of <=5x10{sup -5} g/m{sup 2} day at 38 deg. C/85% relative humidity (RH), as measured by the Ca test. This WVTR value was limited by H{sub 2}O permeability through the epoxy seal, as determined by the Ca test for the glass lid control. In comparison, SiN PECVD films with a thickness of 100 nm had a WVTR of approx7x10{sup -3} g/m{sup 2} day at 38 deg. C/85% RH. Significant improvements resulted when the SiN PECVD film was coated with an Al{sub 2}O{sub 3} ALD film. An Al{sub 2}O{sub 3} ALD film with a thickness of only 5 nm on a SiN PECVD film with a thickness of 100 nm reduced the WVTR from approx7x10{sup -3} to <=5x10{sup -5} g/m{sup 2} day at 38 deg. C/85% RH. The reduction in the permeability for Al{sub 2}O{sub 3} ALD on the SiN PECVD films was attributed to either Al{sub 2}O{sub 3} ALD sealing defects in the SiN PECVD film or improved nucleation of Al{sub 2}O{sub 3} ALD on SiN.

  1. Added value of diffusion-weighted MRI in detection of cervical cancer recurrence: comparison with morphologic and dynamic contrast-enhanced MRI sequences

    PubMed Central

    Lucas, Rita; Dias, João Lopes; Cunha, Teresa Margarida

    2015-01-01

    PURPOSE We aimed to evaluate the added value of diffusion-weighted imaging (DWI) to standard magnetic resonance imaging (MRI) for detecting post-treatment cervical cancer recurrence. The detection accuracy of T2-weighted (T2W) images was compared with that of T2W MRI combined with either dynamic contrast-enhanced (DCE) MRI or DWI. METHODS Thirty-eight women with clinically suspected uterine cervical cancer recurrence more than six months after treatment completion were examined with 1.5 Tesla MRI including T2W, DCE, and DWI sequences. Disease was confirmed histologically and correlated with MRI findings. The diagnostic performance of T2W imaging and its combination with either DCE or DWI were analyzed. Sensitivity, positive predictive value, and accuracy were calculated. RESULTS Thirty-six women had histologically proven recurrence. The accuracy for recurrence detection was 80% with T2W/DCE MRI and 92.1% with T2W/DWI. The addition of DCE sequences did not significantly improve the diagnostic ability of T2W imaging, and this sequence combination misclassified two patients as falsely positive and seven as falsely negative. The T2W/DWI combination revealed a positive predictive value of 100% and only three false negatives. CONCLUSION The addition of DWI to T2W sequences considerably improved the diagnostic ability of MRI. Our results support the inclusion of DWI in the initial MRI protocol for the detection of cervical cancer recurrence, leaving DCE sequences as an option for uncertain cases. PMID:26200480

  2. A Broad G Protein-Coupled Receptor Internalization Assay that Combines SNAP-Tag Labeling, Diffusion-Enhanced Resonance Energy Transfer, and a Highly Emissive Terbium Cryptate.

    PubMed

    Levoye, Anglique; Zwier, Jurriaan M; Jaracz-Ros, Agnieszka; Klipfel, Laurence; Cottet, Martin; Maurel, Damien; Bdioui, Sara; Balabanian, Karl; Przeau, Laurent; Trinquet, Eric; Durroux, Thierry; Bachelerie, Franoise

    2015-01-01

    Although G protein-coupled receptor (GPCR) internalization has long been considered as a major aspect of the desensitization process that tunes ligand responsiveness, internalization is also involved in receptor resensitization and signaling, as well as the ligand scavenging function of some atypical receptors. Internalization thus contributes to the diversity of GPCR-dependent signaling, and its dynamics and quantification in living cells has generated considerable interest. We developed a robust and sensitive assay to follow and quantify ligand-induced and constitutive-induced GPCR internalization but also receptor recycling in living cells. This assay is based on diffusion-enhanced resonance energy transfer (DERET) between cell surface GPCRs labeled with a luminescent terbium cryptate donor and a fluorescein acceptor present in the culture medium. GPCR internalization results in a quantifiable reduction of energy transfer. This method yields a high signal-to-noise ratio due to time-resolved measurements. For various GPCRs belonging to different classes, we demonstrated that constitutive and ligand-induced internalization could be monitored as a function of time and ligand concentration, thus allowing accurate quantitative determination of kinetics of receptor internalization but also half-maximal effective or inhibitory concentrations of compounds. In addition to its selectivity and sensitivity, we provided evidence that DERET-based internalization assay is particularly suitable for characterizing biased ligands. Furthermore, the determination of a Z'-factor value of 0.45 indicates the quality and suitability of DERET-based internalization assay for high-throughput screening (HTS) of compounds that may modulate GPCRs internalization. PMID:26617570

  3. Gamma Ray Transients

    NASA Astrophysics Data System (ADS)

    Gehrels, N.

    Almost every source in the gamma-ray sky is variable. Transient classification therefore depends on the definition of ``transient'' and on instrument sensitivity thresholds. The sources that most clearly fall in the transient category are those that have large intensity differences between their low (or off) states and their high states and have well defined high states with durations less than about a year. Examples are gamma-ray bursts, solar flares, X-ray novae, jet transients, bursting pulsars and Be binary pulsars. Generally, most accreting neutron stars, galactic black holes and AGN are variable with periods of high intensity that can be labeled as transient outbursts. Supernovae and novae form another class of gamma-ray transient driven by explosive nucleosynthesis. The Compton Gamma Ray Observatory (CGRO) has been observing the gamma-ray sky for 6 years. Many of the scientific discoveries from the mission have related to transient observations. The BATSE instrument onboard is a powerful all-sky monitor with 50 m Crab detection sensitivity above 20 keV. The OSSE instrument has a narrow field-of-view with limited sky coverage, but has excellent sensitivities above 50 keV for specific objects. At higher MeV and GeV energies the COMPTEL and EGRET instruments have wide fields-of-view that give reasonable coverage of the sky. In this talk I will review the different classes of gamma-ray transient and present results from CGRO observations.

  4. Perception of acoustic transients

    NASA Astrophysics Data System (ADS)

    Howard, J. H., Jr.

    1984-01-01

    The research investigates the role of knowledge based or top-down processing in the perception of nonlinguistic, transient signals. The experiments address issues in transient pattern classification, target observation, attentional focusing, auditory induction, and computer based performance aids. The theoretical significance and naval relevance of the research is considered.

  5. Diffusion MRI

    NASA Astrophysics Data System (ADS)

    Fukuyama, Hidenao

    Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.

  6. Portable vapor diffusion coefficient meter

    DOEpatents

    Ho, Clifford K.

    2007-06-12

    An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.

  7. The Effective Vertical Advection-Diffusion Balance

    NASA Astrophysics Data System (ADS)

    Huber, M.; Tailleux, R.; Ferreira, D.; Kuhlbrodt, T.; Gregory, J. M.

    2014-12-01

    The capacity of the world ocean to transfer heat to deeper levels is a crucial factor in setting the magnitude and temporal evolution of the global temperature response under transient climate change. A traditional framework to discuss the vertical ocean heat balance is the classic upwelling-diffusive model of Munk [1966] between upwelling of cold abyssal waters and downward diffusion of warm waters. This simple framework is also often used to interpret (and predict) transient heat uptake under climate change. However, this is done in an ad-hoc manner, with little acknowledgment of the complex physics hidden behind the vertical velocity w and diffusivity k? of the classic model (advection of heat by the mean and eddy circulation, diffusion along and across surfaces of constant density, deep convection). Here, we derive an effective vertical velocity and an effective diffusivity for each advective and diffusive process from the steady-state temperature tendencies of two models, an eddy-parameterizing (HadCM3) and an eddy-permitting climate model (HiGEM). For both models, we find that both the effective vertical velocity and diffusivity change sign in mid-depth, highlighting the two physical regimes in which the residual advection is balanced by diapycnal diffusion (deep ocean) and isopycnal diffusion (upper to mid-depths). These findings are at odds with common practices which assume that w and k? are positive constants (in space and time), but is consistent with previous studies of the modeled heat balance. We further present the time-evolution of the effective quantities under an idealized transient climate change simulation. We demonstrate that these spatial and time variations are key to evaluate the transient heat uptake. Implications for the use of simple upwelling-diffusive models to interpret transient heat uptake will be discussed.

  8. Impact on the deuterium retention of simultaneous exposure of tungsten to a steady state plasma and transient heat cycling loads

    NASA Astrophysics Data System (ADS)

    Huber, A.; Sergienko, G.; Wirtz, M.; Steudel, I.; Arakcheev, A.; Brezinsek, S.; Burdakov, A.; Dittmar, T.; Esser, H. G.; Kreter, A.; Linke, J.; Linsmeier, Ch; Mertens, Ph; Möller, S.; Philipps, V.; Pintsuk, G.; Reinhart, M.; Schweer, B.; Shoshin, A.; Terra, A.; Unterberg, B.

    2016-02-01

    The impact on the deuterium retention of simultaneous exposure of tungsten to a steady-state plasma and transient cyclic heat loads has been studied in the linear PSI-2 facility with the main objective of qualifying tungsten (W) as plasma-facing material. The transient heat loads were applied by a high-energy laser, a Nd:YAG laser (λ = 1064 nm) with an energy per pulse of up to 32 J and a duration of 1 ms. A pronounced increase in the D retention by a factor of 13 has been observed during the simultaneous transient heat loads and plasma exposure. These data indicate that the hydrogen clustering is enhanced by the thermal shock exposures, as seen on the increased blister size due to mobilization and thermal production of defects during transients. In addition, the significant increase of the D retention during the simultaneous loads could be explained by an increased diffusion of D atoms into the W material due to strong temperature gradients during the laser pulse exposure and to an increased mobility of D atoms along the shock-induced cracks. Only 24% of the retained deuterium is located inside the near-surface layer (d<4 μm). Enhanced blister formation has been observed under combined loading conditions at power densities close to the threshold for damaging. Blisters are not mainly responsible for the pronounced increase of the D retention.

  9. Plasmapause diffusion

    NASA Technical Reports Server (NTRS)

    Horwitz, J. L.

    1983-01-01

    The Bohm diffusion coefficient and observed electrostatic wave scattering are used as the bases of estimates of the smoothing effect that diffusion may have on steep plasmapause density gradients. The estimate for diffusion resulting from scattering by observed electrostatic waves is found to be much lower than that of the perpendicular Bohm diffusion coefficient for characteristic plasma temperatures and magnetic fields. This diffusion rate estimate may be too small, however, if the wave amplitudes are significantly higher for steep plasmapauses. The effects are therefore negligible for most considerations of macroscopic plasmapause dynamics, but may be significant in limiting drift wave instabilities and similar phenomena driven by the steepness of the plasmapause density gradient.

  10. Coronal transient--eruptive prominence of 1980 August 5

    SciTech Connect

    Fisher, R.; Garcia, C.J.; Seagraves, P.

    1981-06-15

    A coronal transient was observed in association with an eruptive prominence event using the Mauna Loa experiment system. The transient, a rarefaction, formed before the acceleration of the eruptive prominence. Upward velocities of various features, as seen in the plane of the sky, show a marked difference as a function of time between the transient and the eruptive prominence. A region of enhanced electron density formed slowly in front of the rarefaction.

  11. Transient nucleation in glasses

    NASA Technical Reports Server (NTRS)

    Kelton, K. F.

    1991-01-01

    Nucleation rates in condensed systems are frequently not at their steady state values. Such time dependent (or transient) nucleation is most clearly observed in devitrification studies of metallic and silicate glasses. The origin of transient nucleation and its role in the formation and stability of desired phases and microstructures are discussed. Numerical models of nucleation in isothermal and nonisothermal situations, based on the coupled differential equations describing cluster evolution within the classical theory, are presented. The importance of transient nucleation in glass formation and crystallization is discussed.

  12. Luminous Extragalactic Transients

    NASA Astrophysics Data System (ADS)

    O'Brien, Paul; Jonker, Peter; Athena Explosive Transients Working Group

    2015-09-01

    The ESA Athena X-ray observatory mission will combine exceptionally high throughout with high spectral-energy resolution and will revolutionise many aspects of high-energy astrophysics. Many of the most powerful transient sources, including gamma-ray bursts and tidal disruptions events, are bright X-ray sources. Athena will be designed to have a fast-response capability permitting efficient observations of many transients. We will summarise the proposed capability of the mission and illustrate science programs to study transients ranging from the most distant GRBs to nuclear activity in nearby galaxies.

  13. Combined use of diffusion tensor tractography and multifused contrast-enhanced FIESTA for predicting facial and cochlear nerve positions in relation to vestibular schwannoma.

    PubMed

    Yoshino, Masanori; Kin, Taichi; Ito, Akihiro; Saito, Toki; Nakagawa, Daichi; Ino, Kenji; Kamada, Kyousuke; Mori, Harushi; Kunimatsu, Akira; Nakatomi, Hirofumi; Oyama, Hiroshi; Saito, Nobuhito

    2015-12-01

    OBJECT The authors assessed whether the combined use of diffusion tensor tractography (DTT) and contrast-enhanced (CE) fast imaging employing steady-state acquisition (FIESTA) could improve the accuracy of predicting the courses of the facial and cochlear nerves before surgery. METHODS The population was composed of 22 patients with vestibular schwannoma in whom both the facial and cochlear nerves could be identified during surgery. According to DTT, depicted fibers running from the internal auditory canal to the brainstem were judged to represent the facial or vestibulocochlear nerve. With regard to imaging, the authors investigated multifused CE-FIESTA scans, in which all 3D vessel models were shown simultaneously, from various angles. The low-intensity areas running along the tumor from brainstem to the internal auditory canal were judged to represent the facial or vestibulocochlear nerve. RESULTS For all 22 patients, the rate of fibers depicted by DTT coinciding with the facial nerve was 13.6% (3/22), and that of fibers depicted by DTT coinciding with the cochlear nerve was 63.6% (14/22). The rate of candidates for nerves predicted by multifused CE-FIESTA coinciding with the facial nerve was 59.1% (13/22), and that of candidates for nerves predicted by multifused CE-FIESTA coinciding with the cochlear nerve was 4.5% (1/22). The rate of candidates for nerves predicted by combined DTT and multifused CE-FIESTA coinciding with the facial nerve was 63.6% (14/22), and that of candidates for nerves predicted by combined DTT and multifused CE-FIESTA coinciding with the cochlear nerve was 63.6% (14/22). The rate of candidates predicted by DTT coinciding with both facial and cochlear nerves was 0.0% (0/22), that of candidates predicted by multifused CE-FIESTA coinciding with both facial and cochlear nerves was 4.5% (1/22), and that of candidates predicted by combined DTT and multifused CE-FIESTA coinciding with both the facial and cochlear nerves was 45.5% (10/22). CONCLUSIONS By using a combination of DTT and multifused CE-FIESTA, the authors were able to increase the number of vestibular schwannoma patients for whom predicted results corresponded with the courses of both the facial and cochlear nerves, a result that has been considered difficult to achieve by use of a single modality only. Although the 3D image including these prediction results helped with comprehension of the 3D operative anatomy, the reliability of prediction remains to be established. PMID:26053235

  14. Diffusion-weighted MR imaging of acute stroke: Correlation with T2-weighted and magnetic susceptibility-enhanced MR imaging in cats

    SciTech Connect

    Moseley, M.E.; Kucharczyk, J.; Mintorovitch, J.; Cohen, Y.; Kurhanewicz, J.; Derugin, N.; Asgari, H.; Norman, D. )

    1990-05-01

    We evaluated the temporal and anatomic relationships between changes in diffusion-weighted MR image signal intensity, induced by unilateral occlusion of the middle cerebral artery in cats, and tissue perfusion deficits observed in the same animals on T2-weighted MR images after administration of a nonionic intravascular T2 shortening agent. Diffusion-weighted images obtained with strong diffusion-sensitizing gradient strengths (5.6 gauss/cm, corresponding to gradient attenuation factor, b, values of 1413 sec/mm2) displayed increased signal intensity in the ischemic middle cerebral artery territory less than 1 hr after occlusion, whereas T2-weighted images without contrast usually failed to detect injury for 2-3 hr after stroke. After contrast administration (0.5-1.0 mmol/kg by Dy-DTPA-BMA, IV), however, T2-weighted images revealed perfusion deficits (relative hyperintensity) within 1 hr after middle cerebral artery occlusion that corresponded closely to the anatomic regions of ischemic injury shown on diffusion-weighted MR images. Close correlations were also found between early increases in diffusion-weighted MR image signal intensity and disrupted phosphorus-31 and proton metabolite levels evaluated with surface coil MR spectroscopy, as well as with postmortem histopathology. These data indicate that diffusion-weighted MR images more accurately reflect early-onset pathophysiologic changes induced by acute cerebral ischemia than do T2-weighted spin-echo images.

  15. Anticipated and abnormal transients in nuclear power plants

    SciTech Connect

    Karam, R.A. )

    1987-01-01

    This book contains the proceedings of an international conference on Anticipated and Abnormal Transients in Nuclear Power Plants. Included are the following papers: Comparative evaluation of recent water hammer events in light water reactors, Rick reduction through enhanced human performance, Assessment of the performance of an emergency boration system for anticipated transients without trip faults, Emergency procedure planning to mitigate event progression.

  16. High energy transients

    NASA Technical Reports Server (NTRS)

    Woosley, S. E.

    1984-01-01

    A meeting was convened on the campus of the University of California at Santa Cruz during the two-week interval July 11 through July 22, 1983. Roughly 100 participants were chosen so as to give broad representation to all aspects of high energy transients. Ten morning review sessions were held in which invited speakers discussed the current status of observations and theory of the above subjects. Afternoon workshops were also held, usually more than one per day, to informally review various technical aspects of transients, confront shortcomings in theoretical models, and to propose productive courses for future research. Special attention was also given to the instrumentation used to study high energy transient and the characteristics and goals of a dedicated space mission to study transients in the next decade were determined. A listing of articles written by various members of the workshop is included.

  17. Gamma ray transients

    NASA Technical Reports Server (NTRS)

    Cline, Thomas L.

    1987-01-01

    The discovery of cosmic gamma ray bursts was made with systems designed at Los Alamos Laboratory for the detection of nuclear explosions beyond the atmosphere. HELIOS-2 was the first gamma ray burst instrument launched; its initial results in 1976, seemed to deepen the mystery around gamma ray transients. Interplanetary spacecraft data were reviewed in terms of explaining the behavior and source of the transients.

  18. Transient amnesic syndromes.

    PubMed

    Bartsch, Thorsten; Butler, Christopher

    2013-02-01

    Transient amnesic syndromes are striking clinical phenomena that are commonly encountered by physicians in acute medical settings. Diagnosis of such syndromes can be challenging, and their causes have been debated for over 50 years. Critical clinical distinctions, such as between transient global amnesia (TGA) and transient epileptic amnesia (TEA), as well as important clues to the underlying pathophysiology, have recently been revealed. TGA is characterized by the sudden onset of a profound anterograde and retrograde amnesia that lasts for up to 24 h, with neuroimaging after an acute TGA event showing transient perturbation of specific hippocampal circuits that are involved in memory processing. Some cases of transient amnesia are attributable to focal seizure activity and are termed TEA, which has a clinical presentation similar to that of TGA, but can be distinguished from the latter by the brevity and frequency of amnesic attacks. Moreover, TEA carries a risk of persistent memory impairment that can be mistaken for dementia. Here, we summarize clinically relevant aspects of transient amnesic syndromes, giving practical recommendations for diagnosis and patient management. We describe results from imaging and epidemiological studies that have shed light on the functional anatomy and pathophysiological mechanisms underlying these conditions. PMID:23296343

  19. Osmosis and Diffusion

    ERIC Educational Resources Information Center

    Sack, Jeff

    2005-01-01

    OsmoBeaker is a CD-ROM designed to enhance the learning of diffusion and osmosis by presenting interactive experimentation to the student. The software provides several computer simulations that take the student through different scenarios with cells, having different concentrations of solutes in them.

  20. Model of Transient Response of Semiconductor Gas Sensors

    NASA Astrophysics Data System (ADS)

    Fujimoto, Akira; Kuwahara, Takashi

    The model of transient response of semiconductor gas sensor under modulation heating has been constructed successfully. The model consists of the heat conduction process from heater to the sensor surface, the reaction process on the sensor surface and diffusion process near the sensor surface to supply the inflammable gas. The calculated sensor response agreed well with experimental result under step power supplying to the heater. We can predict the sensor transient response so that the model will be useful to distinguish gases and smells by using transient response of semiconductor gas sensors.

  1. The interstitial fraction of diffusivity of common dopants in Si

    NASA Astrophysics Data System (ADS)

    Gossmann, H.-J.; Haynes, T. E.; Stolk, P. A.; Jacobson, D. C.; Gilmer, G. H.; Poate, J. M.; Luftman, H. S.; Mogi, T. K.; Thompson, M. O.

    1997-12-01

    The relative contributions of interstitials and vacancies to diffusion of a dopant A in silicon are specified by the interstitial fraction of diffusivity, fA. Accurate knowledge of fA is required for predictive simulations of Si processing during which the point defect population is perturbed, such as transient enhanced diffusion. While experimental determination of fA is traditionally based on an underdetermined system of equations, we show here that it is actually possible to derive expressions that give meaningful bounds on fA without any further assumptions but that of local equilibrium. By employing a pair of dopants under the same point-defect perturbance, and by utilizing perturbances very far from equilibrium, we obtain experimentally fSb?0.012 and fB?0.98 at temperatures of 800 C, which are the strictest bounds reported to date. Our results are in agreement with a theoretical expectation that a substitutional dopant in Si should either be a pure vacancy, or a pure interstitial(cy) diffuser.

  2. The Radio Transient Sky

    NASA Astrophysics Data System (ADS)

    Lazio, J.; Ray, P. S.; Ellingson, S.; Close, S.; Crane, P.; Hyman, S. D.; Jacoby, B. A.; Junor, W.; Kassim, N. E.; Kulkarni, S. R.; Pihlstrom, Y. M.; Taylor, G. B.; Werthimer, D.

    2006-08-01

    Transient radio sources are necessarily compact and usually are the locations of explosive or dynamic events, therefore offering unique opportunities for probing fundamental physics and astrophysics. In addition, short-duration transients are powerful probes of intervening media owing to dispersion, scattering, and Faraday rotation that modify the signals. While radio astronomy has an impressive record obtaining high time resolution, usually it is achieved in quite narrow fields of view. Consequently, the dynamic radio sky is poorly sampled, in contrast to the situation in the X-ray and ?-ray bands. Operating in the 20-80 MHz range, the Long Wavelength Array (LWA) is one of a suite of next-generation radio telescopes that will explore the radio transient sky. Composed of phased "stations" of dipoles, the LWA can probe the sky for transients on a range of angular and temporal scales, by using an individual station to scan much of the sky or correlating the signals from multiple stations to monitor possible transients. Numerous classes of radio transients, both known and hypothesized, are accessible to the LWA, ranging from cosmic ray air showers and Jovian emission, to bursts from extrasolar planets or other coherent emitters and prompt emission from ?-ray bursts, to possible electromagnetic counterparts of gravitational wave burst sources. We summarize the scientific potential of radio transient observations with the LWA as well as some of the technical challenges, the most notable of which is the robust excision or avoidance of radio frequency interference (RFI). Basic research in radio astronomy at the NRL is supported by the Office of Naval Research.

  3. Asymmetric Diffusional Solidification during Transient Liquid Phase Bonding of Dissimilar Materials

    NASA Astrophysics Data System (ADS)

    Ghoneim, A.; Ojo, O. A.

    2012-03-01

    A theoretical analysis of diffusional solidification during transient liquid phase (TLP) bonding of dissimilar materials was performed in conjunction with experimental verification. A fully implicit, two-dimensional, finite element numerical simulation model, without the inherent symmetry assumption, was developed and used for the theoretical calculations, and good correlations between the model predictions and experimental results were observed. The study showed that an asymmetric distribution of residual interlayer liquid during a dissimilar joining of polycrystal and single crystal alloys is attributable to a mismatch between their lattice diffusion coefficients or solute solubility, irrespective of enhanced intergranular diffusion as was assumed previously. Also, notwithstanding increased solute diffusivity with temperature, it was found that an increase in bonding temperature can result in the prolongation of processing time t f that is required to prevent the formation of deleterious eutectic during bonding of dissimilar materials. The occurrence of this seemingly anomalous behavior, however, reduces when a material is coupled with another type that exhibits a higher solute solubility or better capability of accommodating diffusing melting point depressant solute from the liquid interlayer.

  4. Uphill diffusion in multicomponent mixtures.

    PubMed

    Krishna, Rajamani

    2015-05-21

    Molecular diffusion is an omnipresent phenomena that is important in a wide variety of contexts in chemical, physical, and biological processes. In the majority of cases, the diffusion process can be adequately described by Fick's law that postulates a linear relationship between the flux of any species and its own concentration gradient. Most commonly, a component diffuses down the concentration gradient. The major objective of this review is to highlight a very wide variety of situations that cause the uphill transport of one constituent in the mixture. Uphill diffusion may occur in multicomponent mixtures in which the diffusion flux of any species is strongly coupled to that of its partner species. Such coupling effects often arise from strong thermodynamic non-idealities. For a quantitative description we need to use chemical potential gradients as driving forces. The transport of ionic species in aqueous solutions is coupled with its partner ions because of the electro-neutrality constraints; such constraints may accelerate or decelerate a specific ion. When uphill diffusion occurs, we observe transient overshoots during equilibration; the equilibration process follows serpentine trajectories in composition space. For mixtures of liquids, alloys, ceramics and glasses the serpentine trajectories could cause entry into meta-stable composition zones; such entry could result in phenomena such as spinodal decomposition, spontaneous emulsification, and the Ouzo effect. For distillation of multicomponent mixtures that form azeotropes, uphill diffusion may allow crossing of distillation boundaries that are normally forbidden. For mixture separations with microporous adsorbents, uphill diffusion can cause supra-equilibrium loadings to be achieved during transient uptake within crystals; this allows the possibility of over-riding adsorption equilibrium for achieving difficult separations. PMID:25761383

  5. On Asymmetric Diffusional Solidification During Transient Liquid Phase Bonding

    NASA Astrophysics Data System (ADS)

    Ghobadi Bigvand, A.; Ojo, Olanrewaju A.

    2014-04-01

    The underlying cause of asymmetric diffusion solidification which alters microstructure during transient liquid phase bonding under low temperature gradient was studied. A new solute-conserving asymmetric numerical model coupled with experimental verification showed that a transition from bi-directional to unidirectional solidification, under a constant temperature gradient, is controlled by competition between liquid and solid-state diffusion at one of the two liquid-solid interfaces. This mechanistic understanding would aid a more effective use of the process.

  6. Transient Uncoupling Induces Synchronization.

    PubMed

    Schrder, Malte; Mannattil, Manu; Dutta, Debabrata; Chakraborty, Sagar; Timme, Marc

    2015-07-31

    Finding conditions that support synchronization is a fertile and active area of research with applications across multiple disciplines. Here we present and analyze a scheme for synchronizing chaotic dynamical systems by transiently uncoupling them. Specifically, systems coupled only in a fraction of their state space may synchronize even if fully coupled they do not. While for many standard systems coupling strengths need to be bounded to ensure synchrony, transient uncoupling removes this bound and thus enables synchronization in an infinite range of effective coupling strengths. The presented coupling scheme therefore opens up the possibility to induce synchrony in (biological or technical) systems whose parameters are fixed and cannot be modified continuously. PMID:26274420

  7. The Zwicky Transient Facility

    NASA Astrophysics Data System (ADS)

    Bellm, Eric Christopher; Kulkarni, Shrinivas R.; ZTF Collaboration

    2015-01-01

    The Zwicky Transient Facility (ZTF) is a next-generation optical synoptic survey. Building on the experience and infrastructure of the Palomar Transient Factory (PTF), ZTF will use a new 47-square degree survey camera on the 48-inch Palomar Oschin Schmidt Telescope. ZTF will survey more than an order of magnitude faster than PTF, enabling an unprecedented wide area, high-cadence survey. Its major science goals include discovering young supernovae, searching for electromagnetic counterparts to gravitational wave sources, identifying stellar variables, and detecting Near-Earth Asteroids. Public surveys and data releases will enable broad utilization of the ZTF data.

  8. Role of thermal diffusion in cw IR laser absorption in gas mixtures.

    PubMed

    Maleissye, J T; Lempereur, F

    1982-01-15

    The absorption of radiation from a cw CO(2) laser by a mixture of absorbing SF(6) and transparent buffer gases has been measured as a function of pressure of added transparent gas (C(4)H(10)). The results are analyzed in terms of thermal diffusion of excited SF6 molecules out of the irradiation zone. In the 60-400-Torr pressure range, thermal difusion depletes the concentration of SF(6) so that the overall absorption is decreased and competes with the various channels of collisional relaxation which enhance absorption. An approximate semiempirical expression is used to determine the transient perturbation of concentration which occurs inside the laser beam. PMID:20372450

  9. Diffuse radiation

    NASA Technical Reports Server (NTRS)

    1981-01-01

    A diffuse celestial radiation which is isotropic at least on a course scale were measured from the soft X-ray region to about 150 MeV, at which energy the intensity falls below that of the galactic emission for most galactic latitudes. The spectral shape, the intensity, and the established degree of isotropy of this diffuse radiation already place severe constraints on the possible explanations for this radiation. Among the extragalactic theories, the more promising explanations of the isotropic diffuse emission appear to be radiation from exceptional galaxies from matter antimatter annihilation at the boundaries of superclusters of galaxies of matter and antimatter in baryon symmetric big bang models. Other possible sources for extragalactic diffuse gamma radiation are discussed and include normal galaxies, clusters of galaxies, primordial cosmic rays interacting with intergalactic matter, primordial black holes, and cosmic ray leakage from galaxies.

  10. Quantum diffusion

    NASA Astrophysics Data System (ADS)

    Tsekov, Roumen

    2011-03-01

    Quantum diffusion (QD) is studied via dissipative Madelung hydrodynamics. Initially, the wave packet spreads ballistically, then passes for an instant through normal diffusion and later tends asymptotically to a sub-diffusive law. It is shown that the apparent QD coefficient is not a universal physical parameter because it depends on the initial wave packet preparation. The overdamped QD of an electron in the field of a periodic potential is also investigated; in this case, the wave packet spreads logarithmically in time. Thermo-QD of heavier particles such as hydrogen, deuterium and tritium atoms in periodic potentials is studied and a simple estimate of the tunneling effect is obtained in the framework of a quasi-equilibrium semiclassical approach. The effective thermo-quantum temperature is also discussed in relation to the known temperature dependence of muon diffusivity in solids.

  11. Analyzing hydraulic transients

    SciTech Connect

    Logan, T.H.

    1992-03-01

    The operational mode of a hydroturbine determines hydraulic pressures and flows. The more starts and stops the turbine makes, the more pressure changes will occur. The faster the flow changes, the greater their magnitude. Analyses of hydraulic transients-known as waterhammer-should be part of preliminary engineering studies of any proposed hydro project that will operate as a peaking plant.

  12. Rotor transient analysis

    NASA Technical Reports Server (NTRS)

    Allaire, P. E.; Choy, K. C.; Gunter, E. J.

    1980-01-01

    Undamped modes approximate dynamic behavior of rotors and bearings. Application of modal analysis to uncouple equations of motion simplifies stability, steady-state unbalance response, and transient response analysis of system; nonlinear stability is predicted from calculated frequency spectra. Analysis provides designers with complete information without involving large-scale computational costs. Programs are written in FORTRAN IV for use on CDC 6600 computer.

  13. Unsteady behavior of locally strained diffusion flames affected by curvature and preferential diffusion

    SciTech Connect

    Yoshida, Kenji; Takagi, Toshimi

    1999-07-01

    Experimental and numerical studies are made of transient H{sub 2}/N{sub 2}--air counterflow diffusion flames unsteadily strained by an impinging micro jet. Two-dimensional temperature measurements by laser Rayleigh scattering method and numerical computations taking into account detailed chemical kinetics are conducted paying attention to transient local extinction and reignition in relation to the unsteadiness, flame curvature and preferential diffusion effects. The results are as follows. (1) Transient local flame extinction is observed where the micro jet impinges. But, the transient flame can survive instantaneously in spite of quite high stretch rate where the steady flame cannot exist. (2) Reignition is observed after the local extinction due to the micro air jet impingement. The temperature after reignition becomes significantly higher than that of the original flame. This high temperature is induced by the concentration of H{sub 2} species due to the preferential diffusion in relation to the concave curvature. The predicted behaviors of the local transient extinction and reignition are well confirmed by the experiments. (3) The reignition is induced after the formation of combustible premixed gas mixture and the consequent flame propagation. (4) The reignition is hardly observed after the extinction by micro fuel jet impingement. This is due to the dilution of H{sub 2} species induced by the preferential diffusion in relation to the convex curvature. (5) The maximum flame temperature cannot be rationalized by the stretch rate but changes widely depending on the unsteadiness and the flame curvature in relation with preferential diffusion.

  14. Inhomogeneous Forcing and Transient Climate Sensitivity

    NASA Technical Reports Server (NTRS)

    Shindell, Drew T.

    2014-01-01

    Understanding climate sensitivity is critical to projecting climate change in response to a given forcing scenario. Recent analyses have suggested that transient climate sensitivity is at the low end of the present model range taking into account the reduced warming rates during the past 10-15 years during which forcing has increased markedly. In contrast, comparisons of modelled feedback processes with observations indicate that the most realistic models have higher sensitivities. Here I analyse results from recent climate modelling intercomparison projects to demonstrate that transient climate sensitivity to historical aerosols and ozone is substantially greater than the transient climate sensitivity to CO2. This enhanced sensitivity is primarily caused by more of the forcing being located at Northern Hemisphere middle to high latitudes where it triggers more rapid land responses and stronger feedbacks. I find that accounting for this enhancement largely reconciles the two sets of results, and I conclude that the lowest end of the range of transient climate response to CO2 in present models and assessments (less than 1.3 C) is very unlikely.

  15. Continuous Processing of Multi-Walled Carbon Nanotube-Studded Carbon Fiber Tapes for Enhanced Through-Thickness Thermal Diffusivity Composites.

    PubMed

    Craddock, John D; Qian, Dali; Lester, Catherine; Matthews, JohnJ; Mansfield, J Patrick W; Foedinger, Richard; Weisenberger, Matthew C

    2015-09-01

    Carbon fiber reinforced polymer (CFRP) composites offer advantages over traditional metallic structures, particularly specific strength and stiffness, but at much reduced thermal conductivity. Moreover, fiber-to-fiber heat conduction in the composite transverse directions is significantly lower. When these structures contain electronics (heat generators), shortfalls in heat transport can be problematic. Here we report the achievement of a continuous, reel-to-reel process for growing short multiwalled carbon nanotubes (MWCNT) on the surfaces of spread-tow carbon fiber tapes. These tapes were subsequently prepregged with an epoxy matrix, and laid up into multi-ply laminate panels, cured and tested for through-thickness thermal diffusivity. The results showed up to a 57% increase in through thickness thermal diffusivity compared to the baseline composite with no MWCNT. PMID:26716256

  16. Pharmacological enhancement of disc diffusion and differentiation of healthy, ageing and degenerated discs : Results from in-vivo serial post-contrast MRI studies in 365 human lumbar discs.

    PubMed

    Rajasekaran, S; Venkatadass, K; Naresh Babu, J; Ganesh, K; Shetty, Ajoy P

    2008-05-01

    Degenerative disc disease (DDD) is still a poorly understood phenomenon because of the lack of availability of precise definition of healthy, ageing and degenerated discs. Decreased nutrition is the final common pathway for DDD and the status of the endplate (EP) plays a crucial role in controlling the extent of diffusion, which is the only source of nutrition. The vascular channels in the subchondral plate have muscarinic receptors but the possibility of enhancing diffusion pharmacologically by dilation of these vessels has not been probed. Although it is well accepted that EP damage will affect diffusion and thereby nutrition, there is no described method to quantify the extent of EP damage. Precise definitions with an objective method of differentiating healthy, ageing and degenerated discs on the basis of anatomical integrity of the disc and physiological basis of altered nutrition will be useful. This information is an urgent necessity for better understanding of DDD and also strategizing prevention and treatment. Seven hundred and thirty endplates of 365 lumbar discs from 73 individuals (26 healthy volunteers and 47 patients) with age ranging from 10-64 years were evaluated by pre-contrast and 10 min, 2, 4, 6 and 12 h post contrast MRI after IV injection of 0.3 mmol/kg of Gadodiamide. End plates were classified according to the extent of damage into six grades and an incremental score was given for each category. A total endplate score (TEPS) was derived by adding the EP score of the two endplates for each concerned disc. The base line value (SI(base)) and the signal intensity at particular time periods were used to derive the enhancement percentage for each time period (Enhancement (%) = SI(tp) - SI(base)/SI(base) x 100). The enhancement percentage for each time period, the time for peak enhancement (T-max) and the time intensity curve (TIC) over 12 h were used to study and compare the diffusion characteristics. The differences in pattern of diffusion were obvious visually at 4 h which was categorized into five patterns-Pattern A representing normal diffusion to Pattern E representing a total abnormality in diffusion. Degeneration was classified according to Pfirrmann's grading and this was correlated to the TEPS and the alterations in diffusion patterns. The relationship of TEPS on the increase in DDD was evaluated by a logistic curve and the cut point for severe DDD was found by ROC curve. The influence of the variables of age, level, Modic changes, instability, annulus fibrosis defect (DEBIT), TEPS and diffusion patterns on DDD was analyzed by multiple and stepwise regression analysis. Oral nimodipine study: Additional forty lumbar end-plates from four young healthy volunteers were studied to document the effect of oral nimodipine. Pre-drug diffusion levels were studied by pre and post contrast MRI (0.3 mmol/kg of gadodiamide) at 10 min, 2, 4, 6, 12 and 24 h. Oral nimodipine was administered (30 mg QID) for 5 days and post-contrast MRI studies were performed similarly. Enhancement was calculated at vertebral body-VB; subchondral bone-SCB; Endplate Zone-EPZ and at superior and inferior peripheral nucleus pulposus-PNP and central nucleus pulposus-CNP, using appropriate cursors by a blinded investigator. Paired sample t test and area under curve (AUC) measurements were done.The incidence of disc degeneration had a significant correlation with increasing TEPS (Trend Chi-square, P < 0.01). Only one out of 83 (1.2%) disc had either Pfirrmann Grade IV or V when the score was 4 or below when compared to 34/190 (17.9%) for scores 5-7; 41 of 72 (56.9%) for scores 8-10 and 18 of 20 (90%) for scores 11 and 12 (P < 0.001 for all groups). Pearson's correlation between TEPS and DDD was statistically significant, irrespective of the level of disc or different age groups (r value was above 0.6 and P < 0.01 for all age groups). Logistic curve fit analysis and ROC curve analysis showed that the incidence of DDD increased abruptly when the TEPS crossed six. With a progressive increase of end plate damage, five different p

  17. Analytical boron diffusivity model in silicon for thermal diffusion from boron silicate glass film

    NASA Astrophysics Data System (ADS)

    Kurachi, Ikuo; Yoshioka, Kentaro

    2015-09-01

    An analytical boron diffusivity model in silicon for thermal diffusion from a boron silicate glass (BSG) film has been proposed in terms of enhanced diffusion due to boron-silicon interstitial pair formation. The silicon interstitial generation is considered to be a result of the silicon kick-out mechanism by the diffused boron at the surface. The additional silicon interstitial generation in the bulk silicon is considered to be the dissociation of the diffused pairs. The former one causes the surface boron concentration dependent diffusion. The latter one causes the local boron concentration dependent diffusion. The calculated boron profiles based on the diffusivity model are confirmed to agree with the actual diffusion profiles measured by secondary ion mass spectroscopy (SIMS) for a wide range of the BSG boron concentration. This analytical diffusivity model is a helpful tool for p+ boron diffusion process optimization of n-type solar cell manufacturing.

  18. Transient and diffusion analysis of HgCdTe

    NASA Technical Reports Server (NTRS)

    Clayton, J. C.

    1982-01-01

    Solute redistribution during directional solidification of HgCdTe is addressed. Both one-dimensional and two-dimensional models for solute redistribution are treated and model results compared to experiment. The central problem studied is the cause of radial inhomogeneities found in directionally solidified HgCdTe. A large scale gravity-driven interface instability, termed shape instability, is postulated to be the cause of radial inhomogeneities. Recommendations for future work, along with appropriate computer programs, are included.

  19. Diffusion of Hydrogen in Silica under Transient Conditions

    NASA Technical Reports Server (NTRS)

    Palosz, W.

    2003-01-01

    Development of hydrogen in sealed silica glass ampoules during annealing at elevated temperatures was investigated. The dependence of hydrogen pressure in the ampoules as a function of time, for different temperatures and ampoule parameters was measured. The process was modeled assuming chemical solution of hydrogen according to the reaction: silica + H2 = H- Si= + H-O-Si=. The equilibrium constant of the reaction was determined by fitting the theoretical curves to the experimental data. The Gibbs function for this reaction was estimated at deltaG = -25.8 + 54T.

  20. Diffusion in silicon isotope heterostructures

    NASA Astrophysics Data System (ADS)

    Silvestri, Hughes Howland

    The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and 28Si enriched layers, enables the observation of 30Si self-diffusion from the natural layers into the 28Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale features have created the need for precise physical models of atomic diffusion in Si. The modeling of the experimental profiles of simultaneous diffusion of B and Si under p-type extrinsic conditions revealed that both species are mediated by neutral and singly, positively charged Si self-interstitials. The diffusion of As and Si under extrinsic n-type conditions yielded a model consisting of the interstitialcy and vacancy mechanisms of diffusion via singly negatively charged self-interstitials and neutral vacancies. The simultaneous diffusion of P and Si has been modeled on the basis of neutral and singly negatively charged self-interstitials and neutral and singly positively charged P species. Additionally, the temperature dependence of the diffusion coefficient of Si in Ge was measured over the temperature range of 550C to 900C using a buried Si layer in an epitaxially grown Ge layer.

  1. Diffusion in silicon isotope heterostructures

    SciTech Connect

    Silvestri, Hughes Howland

    2004-05-14

    The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and {sup 28}Si enriched layers, enables the observation of {sup 30}Si self-diffusion from the natural layers into the {sup 28}Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale features have created the need for precise physical models of atomic diffusion in Si. The modeling of the experimental profiles of simultaneous diffusion of B and Si under p-type extrinsic conditions revealed that both species are mediated by neutral and singly, positively charged Si self-interstitials. The diffusion of As and Si under extrinsic n-type conditions yielded a model consisting of the interstitialcy and vacancy mechanisms of diffusion via singly negatively charged self-interstitials and neutral vacancies. The simultaneous diffusion of P and Si has been modeled on the basis of neutral and singly negatively charged self-interstitials and neutral and singly positively charged P species. Additionally, the temperature dependence of the diffusion coefficient of Si in Ge was measured over the temperature range of 550 C to 900 C using a buried Si layer in an epitaxially grown Ge layer.

  2. Optimal Network Modularity for Information Diffusion

    NASA Astrophysics Data System (ADS)

    Nematzadeh, Azadeh; Ferrara, Emilio; Flammini, Alessandro; Ahn, Yong-Yeol

    2014-08-01

    We investigate the impact of community structure on information diffusion with the linear threshold model. Our results demonstrate that modular structure may have counterintuitive effects on information diffusion when social reinforcement is present. We show that strong communities can facilitate global diffusion by enhancing local, intracommunity spreading. Using both analytic approaches and numerical simulations, we demonstrate the existence of an optimal network modularity, where global diffusion requires the minimal number of early adopters.

  3. Bright Transients discovered by PSST

    NASA Astrophysics Data System (ADS)

    Smith, K. W.; Wright, D.; Smartt, S. J.; Huber, M.; Chambers, K. C.; Flewelling, H.; Willman, M.; Primak, N.; Schultz, A.; Gibson, B.; Magnier, E.; Waters, C.; Tonry, J.; Wainscoat, R. J.; Foley, R. J.; Jha, S. W.; Rest, A.; Scolnic, D.

    2016-03-01

    Seven bright transients have been discovered as part of the Pan-STARRS Survey for Transients (PSST). Information on all objects discovered by the Pan-STARRS Survey for Transients is available at http://star.pst.qub.ac.uk/ps1threepi/ (see Huber et al. ATel #7153).

  4. Transient global amnesia.

    PubMed

    Arena, Julieta E; Rabinstein, Alejandro A

    2015-02-01

    Transient global amnesia (TGA) is a clinical syndrome characterized by the sudden onset of anterograde amnesia (the inability to encode new memories), accompanied by repetitive questioning, sometimes with a retrograde component, lasting up to 24 hours, without compromise of other neurologic functions. Herein, we review current knowledge on the epidemiology, pathophysiology, clinical diagnosis, and prognosis of TGA. For this review, we conducted a literature search of PubMed, with no date limitations, using the following search terms (or combinations of them): transient global amnesia, etiology, pathophysiology, venous hypertension, migraine, magnetic resonance imaging, computed tomography, electroencephalography, prognosis, and outcome. We also reviewed the bibliography cited in the retrieved articles. Transient global amnesia is a clinical diagnosis, and recognition of its characteristic features can avoid unnecessary testing. Several pathophysiologic mechanisms have been proposed (venous insufficiency, arterial ischemia, and migrainous or epileptic phenomena), but none of them has been proved to consistently explain cases of TGA. Brain imaging may be considered and electroencephalography is recommended when episodes are brief and recurrent, but otherwise no investigations are necessary in most cases. Data on long-term prognosis are limited, but available information suggests that the relapse rate is low, the risk of stroke and seizures is not considerably increased, and cognitive outcome is generally good. PMID:25659242

  5. ON DETECTING TRANSIENT PHENOMENA

    SciTech Connect

    Belanger, G.

    2013-08-10

    Transient phenomena are interesting and potentially highly revealing of details about the processes under observation and study that could otherwise go unnoticed. It is therefore important to maximize the sensitivity of the method used to identify such events. In this article, we present a general procedure based on the use of the likelihood function for identifying transients which is particularly suited for real-time applications because it requires no grouping or pre-processing of the data. The method makes use of all the information that is available in the data throughout the statistical decision-making process, and is suitable for a wide range of applications. Here we consider those most common in astrophysics, which involve searching for transient sources, events or features in images, time series, energy spectra, and power spectra, and demonstrate the use of the method in the case of a weak X-ray flare in a time series and a short-lived quasi-periodic oscillation in a power spectrum. We derive a fit statistic that is ideal for fitting arbitrarily shaped models to a power density distribution, which is of general interest in all applications involving periodogram analysis.

  6. Advanced PFBC transient analysis

    SciTech Connect

    White, J.S.; Bonk, D.L.

    1997-05-01

    Transient modeling and analysis of advanced Pressurized Fluidized Bed Combustion (PFBC) systems is a research area that is currently under investigation by the US Department of Energy`s Federal Energy Technology Center (FETC). The object of the effort is to identify key operating parameters that affect plant performance and then quantify the basic response of major sub-systems to changes in operating conditions. PC-TRAX{trademark}, a commercially available dynamic software program, was chosen and applied in this modeling and analysis effort. This paper describes the development of a series of TRAX-based transient models of advanced PFBC power plants. These power plants burn coal or other suitable fuel in a PFBC, and the high temperature flue gas supports low-Btu fuel gas or natural gas combustion in a gas turbine topping combustor. When it is utilized, the low-Btu fuel gas is produced in a bubbling bed carbonizer. High temperature, high pressure combustion products exiting the topping combustor are expanded in a modified gas turbine to generate electrical power. Waste heat from the system is used to raise and superheat steam for a reheat steam turbine bottoming cycle that generates additional electrical power. Basic control/instrumentation models were developed and modeled in PC-TRAX and used to investigate off-design plant performance. System performance for various transient conditions and control philosophies was studied.

  7. Advanced PFBC transient analysis

    SciTech Connect

    White, J.S.; Bonk, D.L.; Rogers, L.

    1996-12-31

    Transient modeling and analysis of Advanced Pressurized Fluidized Bed Combustion (PFBC) systems is a research area that is currently under investigative study by the United States Department of Energy`s Morgantown Energy Technology Center (METC). The object of the effort is to identify key operating parameters affecting plant performance and then quantify the basic response of major sub-systems to changes in operating conditions. PC-TRAX, a commercially available dynamic software program, was chosen and applied in this modeling and analysis effort. This paper summarizes and describes the development of a series of TRAX-based transient models of Advanced PFBC power plants. These power plants generate a high temperature flue gas by burning coal or other suitable fuel in a PFBC. The high temperature flue gas supports low-Btu fuel gas or natural gas combustion in a gas turbine topping combustor. When utilized, low-Btu fuel gas is produced in a bubbling bed carbonizer. High temperature, high pressure combustion products exiting the topping combustor are expanded in a modified gas turbine to generate electrical power. Waste heat from the system is used to generate and superheat steam for a reheat steam turbine bottoming cycle that generates additional electrical power. Basic control/instrumentation models were developed and modeled in PC-TRAX and used to investigate off-design plant performance. System performance for various transient conditions and control philosophies was studied.

  8. Influence of defects on excess charge carrier kinetics studied by transient PC and transient PA

    SciTech Connect

    Feist, H.; Kunst, M.; Swiatkowski, C.

    1997-07-01

    By comparison of transient photoconductivity (TPC) and transient photoinduced absorption (PA) the influence of the density of states in the bandgap on excess charge carrier kinetics is studied for a-Si:H films deposited at different temperatures and for state of the art a-Si:H films in two different states of light soaking. In both series the rising deep defect density leads to an enhancement of electron trapping rather than recombination via deep defects. The samples deposited at temperatures lower than 250 C additionally show a lower effective electron mobility, i.e., a broader conduction band tail.

  9. Anomalous effects of ultradilute impurities on heat diffusion in liquids

    NASA Astrophysics Data System (ADS)

    Ambast, Deepak K. S.; Mondal, Richarj; Pati, Palas Baran; Zade, Sanjio S.; Bansal, Bhavtosh; Pal, Bipul

    2015-01-01

    We analyze the applicability of transient thermal lens (TL) z-scan technique as a sensitive tool to measure heat diffusivity of liquids. Suitable dyes at very low concentrations were added to the host liquid to enhance the TL effect through improved optical absorption. We investigate if these dye impurities, besides improving light absorption, have any effect on the thermal properties of the host liquid. We find that even a trace amount of impurity significantly alters the thermal properties of a solvent. Time-evolution of TL showed pronounced asymmetry about laser focus revealing anomalous behavior in thermal blooming of the laser beam. Heat transport was strongly dependent on the rise in sample temperature by light absorption. Important effects of nonlinear heat transport in time-resolved TL z-scan experiments were revealed.

  10. Transient lesion in the splenium of the corpus callosum due to rotavirus infection.

    PubMed

    Mazur-Melewska, Katarzyna; Jonczyk-Potoczna, Katarzyna; Szpura, Krystyna; Biega?ski, Grzegorz; Mania, Anna; Kemnitz, Pawe?; S?u?ewski, Wojciech; Figlerowicz, Magdalena

    2015-06-01

    Transient signal changes in magnetic resonance imaging (MRI) of the splenium of the corpus callosum (SCC) can result from many different reasons, including encephalitis and encephalopathy caused by infection, seizures, metabolic disorders and asphyxia. We report a case of a 6-year-old Polish girl with rotavirus infection demonstrating a reversible SCC lesion on diffusion-weighted MRI images. She presented six episodes of generalized tonic seizures with mild acute gastroenteritis. Stool test for rotavirus antigen was positive. At the time of admission imaging showed the hyperintense region in T2-weighted and fluid-attenuated inversion-recovery MRI, a well-defined lesion in the splenium of the corpus callosum with restricted diffusion in diffusion-weighted MRI and no enhancement in post contrast T1-weighted imaging. Her first EEG showed slow brain activity in the posterior occipitotemporal portion, consisting mainly of theta waves with a frequency of 4.5-5.5 Hz and amplitude of 40 uV. The lesion had completely disappeared on follow-up MRI 10 days later. The patient recovered fully without any sequelae. PMID:25686898

  11. Defusing Diffusion

    ERIC Educational Resources Information Center

    Dou, Remy; Hogan, DaNel; Kossover, Mark; Spuck, Timothy; Young, Sarah

    2013-01-01

    Diffusion has often been taught in science courses as one of the primary ways by which molecules travel, particularly within organisms. For years, classroom teachers have used the same common demonstrations to illustrate this concept (e.g., placing drops of food coloring in a beaker of water). Most of the time, the main contributor to the motion

  12. Demonstrating Diffusion

    ERIC Educational Resources Information Center

    Foy, Barry G.

    1977-01-01

    Two demonstrations are described. Materials and instructions for demonstrating movement of molecules into cytoplasm using agar blocks, phenolphthalein, and sodium hydroxide are given. A simple method for demonstrating that the rate of diffusion of a gas is inversely proportional to its molecular weight is also presented. (AJ)

  13. Relativistic diffusion.

    PubMed

    Haba, Z

    2009-02-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed. PMID:19391727

  14. Defusing Diffusion

    ERIC Educational Resources Information Center

    Dou, Remy; Hogan, DaNel; Kossover, Mark; Spuck, Timothy; Young, Sarah

    2013-01-01

    Diffusion has often been taught in science courses as one of the primary ways by which molecules travel, particularly within organisms. For years, classroom teachers have used the same common demonstrations to illustrate this concept (e.g., placing drops of food coloring in a beaker of water). Most of the time, the main contributor to the motion…

  15. Transient electrochemistry: beyond simply temporal resolution.

    PubMed

    Zhou, X-S; Mao, B-W; Amatore, C; Compton, R G; Marignier, J-L; Mostafavi, M; Nierengarten, J-F; Maisonhaute, E

    2016-01-01

    Some physicochemical intrigues for which transient electrochemistry was necessary to solve the problem are summarized in this feature article. First, we highlight the main constraints to be aware of to access to low time scales, and particularly focus on the effects of stray capacitances. Then, the electron transfer rate constant measured for redox molecules in a self-assembled monolayer configuration is compared to the conductance measured through the same systems, but at the single molecule level. This evidences strong conformational changes when molecules are trapped in the nanogap created between both electrodes. We also report about dendrimers, for which a short electrochemical perturbation induces creation of a diffusion layer within the molecule, allowing the electron hopping rate to be measured and analyzed in terms of molecular motions of the redox centers. Finally, we show that transient electrochemistry provides also useful information when coupled to other methodologies. For example, when an ultrasonic field drives very fast movements of a bubble situated above the electrode surface, the motion can be detected indirectly through a modification of the diffusion flux. Another field concerns pulse radiolysis, and we describe how the reactivity (at the electrode or within the solution) of radicals created by a radiolytic pulse can be quantified, widening the possibilities of electrochemistry to operate in biological media. PMID:26561921

  16. Direct Numerical Simulations of Transient Dispersion

    NASA Astrophysics Data System (ADS)

    Porter, M.; Valdes-Parada, F.; Wood, B.

    2008-12-01

    Transient dispersion is important in many engineering applications, including transport in porous media. A common theoretical approach involves upscaling the micro-scale mass balance equations for convection- diffusion to macro-scale equations that contain effective medium quantities. However, there are a number of assumptions implicit in the various upscaling methods. For example, results obtained from volume averaging are often dependent on a given set of length and time scale constraints. Additionally, a number of the classical models for dispersion do not fully capture the early-time dispersive behavior of the solute for a general set of initial conditions. In this work, we present direct numerical simulations of micro-scale transient mass balance equations for convection-diffusion in both capillary tubes and porous media. Special attention is paid to analysis of the influence of a new time- decaying coefficient that filters the effects of the initial conditions. The direct numerical simulations were compared to results obtained from solving the closure problem associated with volume averaging. These comparisons provide a quantitative measure of the significance of (1) the assumptions implicit in the volume averaging method and (2) the importance of the early-time dispersive behavior of the solute due to various initial conditions.

  17. Diffusion in linearly sheared granular packing

    NASA Astrophysics Data System (ADS)

    Dijksman, Joshua; Ren, Jie; Behringer, Robert

    2013-11-01

    We study shear-induced diffusion in a linearly sheared, dense disordered packing of frictional photoelastic disks. We can track both displacements and rotational motion, and measure interparticle forces obtained from the photoelastic response of the disks. In these experiments, volume fraction and shear amplitude are the control parameters. We probe the non-affine displacements, both in the transient of a single shear deformation, and during cyclic shear. We observe fine structure in the nonffine displacement fields and find that the diffusion anisotropy shows nontrivial dynamics. Additionally, we find that both rotational and translational diffusion increases with density for all but the highest densities. Currently at Merck & Co.

  18. Transient Numerical Modeling of Catalytic Channels

    NASA Technical Reports Server (NTRS)

    Struk, Peter M.; Dietrich, Daniel L.; Miller, Fletcher J.; T'ien, James S.

    2007-01-01

    This paper presents a transient model of catalytic combustion suitable for isolated channels and monolith reactors. The model is a lumped two-phase (gas and solid) model where the gas phase is quasi-steady relative to the transient solid. Axial diffusion is neglected in the gas phase; lateral diffusion, however, is accounted for using transfer coefficients. The solid phase includes axial heat conduction and external heat loss due to convection and radiation. The combustion process utilizes detailed gas and surface reaction models. The gas-phase model becomes a system of stiff ordinary differential equations while the solid phase reduces, after discretization, into a system of stiff ordinary differential-algebraic equations. The time evolution of the system came from alternating integrations of the quasi-steady gas and transient solid. This work outlines the numerical model and presents some sensitivity studies on important parameters including internal transfer coefficients, catalytic surface site density, and external heat-loss (if applicable). The model is compared to two experiments using CO fuel: (1) steady-state conversion through an isothermal platinum (Pt) tube and (2) transient propagation of a catalytic reaction inside a small Pt tube. The model requires internal mass-transfer resistance to match the experiments at lower residence times. Under mass-transport limited conditions, the model reasonably predicted exit conversion using global mass-transfer coefficients. Near light-off, the model results did not match the experiment precisely even after adjustment of mass-transfer coefficients. Agreement improved for the first case after adjusting the surface kinetics such that the net rate of CO adsorption increased compared to O2. The CO / O2 surface mechanism came from a sub-set of reactions in a popular CH4 / O2 mechanism. For the second case, predictions improved for lean conditions with increased external heat loss or adjustment of the kinetics as in the first case. Finally, the results show that different initial surface-species distribution leads to different steady-states under certain conditions. These results demonstrate the utility of a lumped two-phase model of a transient catalytic combustor with detailed chemistry.

  19. DIFFUSION MEASUREMENTS DURING PERVAPORATION THROUGH A ZEOLITE MEMBRANE

    EPA Science Inventory


    An isotopic-transient technique was used to directly measure diffusion times of H2O, methanol, ethanol, 2-propanol, and acetone in pure and binary mixture feeds transporting through a zeolite membrane under steady-state pervaporation conditions. Diffusivities can be determ...

  20. Magnetic Diffusion in Star Formation

    NASA Astrophysics Data System (ADS)

    Basu, Shantanu; Dapp, Wolf B.

    2011-04-01

    Magnetic diffusion plays a vital role in star formation. We trace its influence from interstellar cloud scales down to star-disk scales. On both scales, we find that magnetic diffusion can be significantly enhanced by the buildup of strong gradients in magnetic field structure. Large scale nonlinear flows can create compressed cloud layers within which ambipolar diffusion occurs rapidly. However, in the flux-freezing limit that may be applicable to photoionized molecular cloud envelopes, supersonic motions can persist for long times if driven by an externally generated magnetic field that corresponds to a subcritical mass-to-flux ratio. In the case of protostellar accretion, rapid magnetic diffusion (through Ohmic dissipation with additional support from ambipolar diffusion) near the protostar causes dramatic magnetic flux loss. By doing so, it also allows the formation of a centrifugal disk, thereby avoiding the magnetic braking catastrophe.

  1. The effect of excimer laser pretreatment on diffusion and activation of boron implanted in silicon

    SciTech Connect

    Monakhov, E.V.; Svensson, B.G.; Linnarsson, M.K.; La Magna, A.; Italia, M.; Privitera, V.; Fortunato, G.; Cuscuna, M.; Mariucci, L.

    2005-11-07

    We have investigated the effect of excimer laser annealing (ELA) on transient enhanced diffusion (TED) and activation of boron implanted in Si during subsequent rapid thermal annealing (RTA). It is observed that ELA with partial melting of the implanted region causes reduction of TED in the region that remains solid during ELA, where the diffusion length of boron is reduced by a factor of {approx}4 as compared to the as-implanted sample. This is attributed to several mechanisms such as liquid-state annealing of a fraction of the implantation induced defects, introduction of excess vacancies during ELA, and solid-state annealing of the defects beyond the maximum melting depth by the heat wave propagating into the Si wafer. The ELA pretreatment provides a substantially improved electrical activation of boron during subsequent RTA.

  2. How are Forbush decreases related to interplanetary magnetic field enhancements?

    NASA Astrophysics Data System (ADS)

    Arunbabu, K. P.; Antia, H. M.; Dugad, S. R.; Gupta, S. K.; Hayashi, Y.; Kawakami, S.; Mohanty, P. K.; Oshima, A.; Subramanian, P.

    2015-08-01

    Aims: A Forbush decrease (FD) is a transient decrease followed by a gradual recovery in the observed galactic cosmic ray intensity. We seek to understand the relationship between the FDs and near-Earth interplanetary magnetic field (IMF) enhancements associated with solar coronal mass ejections (CMEs). Methods: We used muon data at cutoff rigidities ranging from 14 to 24 GV from the GRAPES-3 tracking muon telescope to identify FD events. We selected those FD events that have a reasonably clean profile, and magnitude >0.25%. We used IMF data from ACE/WIND spacecrafts. We looked for correlations between the FD profile and that of the one-hour averaged IMF. We wanted to find out whether if the diffusion of high-energy protons into the large scale magnetic field is the cause of the lag observed between the FD and the IMF. Results: The enhancement of the IMF associated with FDs occurs mainly in the shock-sheath region, and the turbulence level in the magnetic field is also enhanced in this region. The observed FD profiles look remarkably similar to the IMF enhancement profiles. The FDs typically lag behind the IMF enhancement by a few hours. The lag corresponds to the time taken by high-energy protons to diffuse into the magnetic field enhancement via cross-field diffusion. Conclusions: Our findings show that high-rigidity FDs associated with CMEs are caused primarily by the cumulative diffusion of protons across the magnetic field enhancement in the turbulent sheath region between the shock and the CME. Appendices are available in electronic form at http://www.aanda.org

  3. Thermal transient anemometer

    DOEpatents

    Bailey, James L. (829 S. Bruner, Hinsdale, IL 60521); Vresk, Josip (4013 N. Park, Westmont, IL 60559)

    1989-01-01

    A thermal transient anemometer having a thermocouple probe which is utilized to measure the change in temperature over a period of time to provide a measure of fluid flow velocity. The thermocouple probe is located in the fluid flow path and pulsed to heat or cool the probe. The cooling of the heated probe or the heating of the cooled probe from the fluid flow over a period of time is measured to determine the fluid flow velocity. The probe is desired to be locally heated near the tip to increase the efficiency of devices incorporating the probe.

  4. The Rapid Transient Surveyor

    NASA Astrophysics Data System (ADS)

    Baranec, Christoph; Tonry, John; Wright, Shelley; Tully, R. Brent; Lu, Jessica R.; Takamiya, Marianne Y.; Hunter, Lisa

    2016-01-01

    The next decade of astronomy will be dominated by large area surveys (see the detailed discussion in the Astro-2010 Decadal survey and NRC's recent OIR System Report). Ground-based optical transient surveys, e.g., LSST, ZTF and ATLAS and space-based exoplanet, supernova, and lensing surveys such as TESS and WFIRST will join the Gaia all-sky astrometric survey in producing a flood of data that will enable leaps in our understanding of the universe. There is a critical need for further characterization of these discoveries through high angular resolution images, deeper images, spectra, or observations at different cadences or periods than the main surveys. Such follow-up characterization must be well matched to the particular surveys, and requires sufficient additional observing resources and time to cover the extensive number of targets.We describe plans for the Rapid Transient Surveyor (RTS), a permanently mounted, rapid-response, high-cadence facility for follow-up characterization of transient objects on the U. of Hawai'i 2.2-m telescope on Maunakea. RTS will comprise an improved robotic laser adaptive optics system, based on the prototype Robo-AO system (formerly at the Palomar 1.5-m and now at the Kitt Peak 2.2-m telescope), with simultaneous visible and near-infrared imagers as well as a near-infrared integral field spectrograph (R~100, λ = 850 - 1830 nm, 0.15″ spaxels, 8.7″×6.0″ FoV). RTS will achieve an acuity of ~0.07″ in visible wavelengths and < 0.16″ in the near infrared leading to an increase of the infrared point-source sensitivity against the sky background by a factor of ~9, crucial for efficient near-infrared spectroscopy.RTS will allow us to map the dark matter distribution in the z < 0.1 local universe with ten times better accuracy and precision than previous experiments. ATLAS will discover several thousand SNIae per year, measuring SNIa peak brightness, and decline rates, while RTS will measure reddening by dust, confirm SN type and confirm redshifts of the host galaxies. This unique combination of automated detection and characterization of astrophysical transients during a sustained observing campaign will yield the necessary statistics to precisely map dark matter in the local universe.

  5. Workshop on Radio Transients

    NASA Astrophysics Data System (ADS)

    Croft, Steve; Gaensler, Bryan

    2012-04-01

    abstract-type="normal">SummaryWe are entering a new era in the study of variable and transient radio sources. This workshop discussed the instruments and the strategies employed to study those sources, how they are identified and classified, how results from different surveys can be compared, and how radio observations tie in with those at other wavelengths. The emphasis was on learning what common ground there is between the plethora of on-going projects, how methods and code can be shared, and how best practices regarding survey strategy could be adopted. The workshop featured the four topics below. Each topic commenced with a fairly brief introductory talk, which then developed into discussion. By way of preparation, participants had been invited to upload and discuss one slide per topic to a wiki ahead of the workshop. 1. Telescopes, instrumentation and survey strategy. New radio facilities and on-going projects (including upgrades) are both studying the variability of the radio sky, and searching for transients. The discussion first centred on the status of those facilities, and on projects with a time-domain focus, both ongoing and planned, before turning to factors driving choices of instrumentation, such as phased array versus single pixel feeds, the field of view, spatial and time resolution, frequency and bandwidth, depth, area, and cadence of the surveys. 2. Detection, pipelines, and classification. The workshop debated (a) the factors that influence decisions to study variability in the (u,v) plane, in images, or in catalogues, (b) whether, and how much, pipeline code could potentially be shared between one project and another, and which software packages are best for different approaches, (c) how data are stored and later accessed, and (d) how transients and variables are defined and classified. 3. Statistics, interpretation, and synthesis. It then discussed how (i) the choice of facility and strategy and (ii) detection and classification schemes influence what is seen (in terms of types of object and rates) by different surveys, (iii) how results from different surveys could be compared, and (iv) how what we know from existing surveys drives choices (i) and (ii), particularly as regards finding new classes of object. 4. Multiwavelength approaches. The workshop concluded by discussing what information is needed from wavelengths other than radio in order to classify transients and variables adequately and predict their rates as a function of topics (1), (2) and (3). It asked what the constraints are on responding to, and issuing triggers for, follow-up observations, and how that might feed back into considerations for designing our telescopes and surveys.

  6. Transient mantle convection on Venus: The paradoxical coexistence of highlands and coronae in the BAT region

    NASA Astrophysics Data System (ADS)

    Robin, Catherine M. I.; Jellinek, A. Mark; Thayalan, Vid; Lenardic, Adrian

    2007-04-01

    The coexistence of Venusian highlands, attributed to long-lived axisymmetric mantle plumes, and uncompensated coronae, attributed to transient discrete mantle 'thermals', is difficult to reconcile with models of mantle convection under thermally steady-state conditions. However, cratering and geological studies indicate a uniformly young surface age ( 700 Myr) as well as a comparable timescale for resurfacing ( 100 to 400 Myr), possibly consistent with a recent lithospheric overturn and a transient mantle thermal regime. We use laboratory experiments on free and forced thermal convection at high Rayleigh number ( Ra 10 7) in a variable viscosity fluid to investigate the steady-state and transient thermal regimes preceding and following such an overturn. From analyses of shadowgraph images and time series of global and local variations in temperature, basal heat flux and viscosity, we establish steady-state stagnant- and active-lid states and characterize two intermediate transient regimes. Flow in steady-state stagnant lid is in the form of intermittent thermals, consistent with published work. During the transition to active-lid convection the stagnant lid is stirred into the interior using a conveyor belt. Spreading of this cold fluid along the hot boundary leads to a transition to a "mixed mode" of flow from the hot boundary: approximately isoviscous thermals rise from the thermal boundary layer ahead of the advancing cold front and low viscosity plumes rise from behind the front, as a result of an enhanced temperature contrast. The longevity of this regime and the timescale for the transient depends on the rate of overturn (Pe) and the aspect ratio of the system (A). The magnitude of local temperature, viscosity and heat flux variations increases with Pe and can exceed steady-state values for active-lid convection. Additional numerical simulations show that the mixed mode regime will occur in the presence of internal heating, and for no- and free-slip boundaries. In contrast, the transition from active-lid to stagnant-lid convection is marked by a change from a flow composed of plumes and large-scale overturning motions to a regime dominated by rising and sinking thermals on a timescale of thermal diffusion. Applied to Venus, our results support a hypothesis that the contemporaneous coexistence of the Atla and Beta highlands regions with interspersed uncompensated coronae is consistent with a transient thermal regime following a lithospheric overturn. It is also expected that such coronae formed > 250 Myr after the uplift of the highlands. Implications of the thermal origin of coronae for Venusian mantle structure are also explored.

  7. Analysis of transient hydrogen uptake by metal alloy particles

    SciTech Connect

    Zhang, W.; Srinivasan, S.; Ploehn, H.J.

    1996-12-01

    This paper describes a new approach to solving the equations comprising the shrinking core model for diffusion and reaction of a chemical species in a solid spherical particle. The reactant adsorbs on the particle surface, diffuses into the particle`s interior, and reacts with the particle to form a solid product. The shrinking core model assumes a fast reaction rate compared to reactant diffusion so that the reaction is localized in the interfacial zone between the unreacted solid core and the surrounding shell of reacted product. Analytical solutions of the governing conservation equations usually invoke the pseudo-steady state (PSS) approximation which neglects the transient mass accumulation and diffusion-induced convection terms in the continuity equation for the diffusing reactant. However, small particle radii and slow reactant diffusion cast doubt on the validity of the PSS approximation. Dimensional analysis reveals an approximation that is less restrictive than PSS, yet enables a semi-analytical solution for the diffusing reactant distribution and interface velocity. For sufficiently large values of the surface mass fraction of the diffusing reactant, the PSS approximation leads to serious errors in the time dependence of the interface position and fractional conversion. However, the estimate of the surface mass fraction of hydrogen in LaNi{sub 5} particles suggests the validity of the PSS approximation for hydriding of metal alloy particles. The shrinking core model thus enables an estimate of hydrogen diffusivity in metal alloy particles.

  8. Diffusion of Ellipsoids in Bacterial Suspensions

    NASA Astrophysics Data System (ADS)

    Peng, Yi; Lai, Lipeng; Tai, Yi-Shu; Zhang, Kechun; Xu, Xinliang; Cheng, Xiang

    2016-02-01

    Active fluids such as swarming bacteria and motile colloids exhibit exotic properties different from conventional equilibrium materials. As a peculiar example, a spherical tracer immersed inside active fluids shows an enhanced translational diffusion, orders of magnitude stronger than its intrinsic Brownian motion. Here, rather than spherical tracers, we investigate the diffusion of isolated ellipsoids in a quasi-two-dimensional bacterial bath. Our study shows a nonlinear enhancement of both translational and rotational diffusions of ellipsoids. More importantly, we uncover an anomalous coupling between particles' translation and rotation that is strictly prohibited in Brownian diffusion. The coupling reveals a counterintuitive anisotropic particle diffusion, where an ellipsoid diffuses fastest along its minor axis in its body frame. Combining experiments with theoretical modeling, we show that such an anomalous diffusive behavior arises from the generic straining flow of swimming bacteria. Our work illustrates an unexpected feature of active fluids and deepens our understanding of transport processes in microbiological systems.

  9. Diffusion of Ellipsoids in Bacterial Suspensions.

    PubMed

    Peng, Yi; Lai, Lipeng; Tai, Yi-Shu; Zhang, Kechun; Xu, Xinliang; Cheng, Xiang

    2016-02-12

    Active fluids such as swarming bacteria and motile colloids exhibit exotic properties different from conventional equilibrium materials. As a peculiar example, a spherical tracer immersed inside active fluids shows an enhanced translational diffusion, orders of magnitude stronger than its intrinsic Brownian motion. Here, rather than spherical tracers, we investigate the diffusion of isolated ellipsoids in a quasi-two-dimensional bacterial bath. Our study shows a nonlinear enhancement of both translational and rotational diffusions of ellipsoids. More importantly, we uncover an anomalous coupling between particles' translation and rotation that is strictly prohibited in Brownian diffusion. The coupling reveals a counterintuitive anisotropic particle diffusion, where an ellipsoid diffuses fastest along its minor axis in its body frame. Combining experiments with theoretical modeling, we show that such an anomalous diffusive behavior arises from the generic straining flow of swimming bacteria. Our work illustrates an unexpected feature of active fluids and deepens our understanding of transport processes in microbiological systems. PMID:26919019

  10. The Palomar transient factory

    NASA Astrophysics Data System (ADS)

    Nugent, Peter; Cao, Yi; Kasliwal, Mansi

    2015-01-01

    Astrophysics is transforming from a data-starved to a data-swamped discipline, fundamentally changing the nature of scientific inquiry and discovery. New technologies are enabling the detection, transmission, and storage of data of hitherto unimaginable quantity and quality across the electromagnetic, gravity and particle spectra. The observational data obtained during this decade alone will supersede everything accumulated over the preceding four thousand years of astronomy. Currently there are 4 large-scale photometric and spectroscopic surveys underway, each generating and/or utilizing hundreds of terabytes of data per year. Some will focus on the static universe while others will greatly expand our knowledge of transient phenomena. Maximizing the science from these programs requires integrating the processing pipeline with high-performance computing resources. These are coupled to large astrophysics databases while making use of machine learning algorithms with near real-time turnaround. Here we present an overview of one of these programs, the Palomar Transient Factory (PTF). We will cover the processing and discovery pipeline we developed at LBNL and NERSC for it and several of the great discoveries made during the 4 years of observations with PTF.

  11. Diffusible signal factor (DSF) quorum sensing signal and structurally related molecules enhance the antimicrobial efficacy of antibiotics against some bacterial pathogens

    PubMed Central

    2014-01-01

    Background Extensive use of antibiotics has fostered the emergence of superbugs that are resistant to multidrugs, which becomes a great healthcare and public concern. Previous studies showed that quorum sensing signal DSF (diffusible signal factor) not only modulates bacterial antibiotic resistance through intraspecies signaling, but also affects bacterial antibiotic tolerance through interspecies communication. These findings motivate us to exploit the possibility of using DSF and its structurally related molecules as adjuvants to influence antibiotic susceptibility of bacterial pathogens. Results In this study, we have demonstrated that DSF signal and its structurally related molecules could be used to induce bacterial antibiotic susceptibility. Exogenous addition of DSF signal (cis-11-methyl-2-dodecenoic acid) and its structural analogues could significantly increase the antibiotic susceptibility of Bacillus cereus, possibly through reducing drug-resistant activity, biofilm formation and bacterial fitness. The synergistic effect of DSF and its structurally related molecules with antibiotics on B. cereus is dosage-dependent. Combination of DSF with gentamicin showed an obviously synergistic effect on B. cereus pathogenicity in an in vitro model. We also found that DSF could increase the antibiotic susceptibility of other bacterial species, including Bacillus thuringiensis, Staphylococcus aureus, Mycobacterium smegmatis, Neisseria subflava and Pseudomonas aeruginosa. Conclusion The results indicate a promising potential of using DSF and its structurally related molecules as novel adjuvants to conventional antibiotics for treatment of infectious diseases caused by bacterial pathogens. PMID:24575808

  12. The role of external electric fields in enhancing ion mobility, drift velocity, and drift-diffusion rates in aqueous electrolyte solutions

    NASA Astrophysics Data System (ADS)

    Murad, Sohail

    2011-03-01

    Molecular simulations have been carried out using the method of molecular dynamics to investigate the role of external electric fields on the ion mobility, drift velocity, and drift-diffusion rate of ions in aqueous electrolyte solutions. These properties are critical for a range of processes including electrodialysis, electro-deionization, electrophoresis, and electroosmosis. Our results show that external electric fields relax the hydrated ion structure at significantly larger time scales (between 300 and 800 ps), than most other relaxation processes in solutions (generally of the order of 1 ps). Previous studies that did not account for the much longer relaxation times did not observe this behavior for ions even with very high electric fields. External electric fields must also overcome several (at least two or more) activation energy barriers to significantly change the structure of hydrated ions. As a result, the dynamic behavior changes almost in bands as a function of electric field strengths, rather than linearly. Finally, the effect of the field is much less dramatic on water than the ions. Thus electric fields will be of more significance in processes that involve the transport of ions (such as electro-deionization) than the transport of water (electroosmosis).

  13. On Transients in Detached Bridgman Growth

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Volz, M. P.

    2011-01-01

    In detached Bridgman growth, a gap exists between the growing crystal and the crucible wall. According to crystal shape stability theory, only specific gap widths will be dynamically stable. Beginning with a crystal diameter that differs from stable conditions, the transient crystal growth process is analyzed. The transient shapes are calculated assuming that the growth angle is constant. Anisotropy and dynamic contact angle effects are considered. In microgravity, dynamic stability depends only on capillary effects and is decoupled from heat transfer. However, heat transfer will influence the crystal-melt interface shape. The local angles and the crystal-melt-vapor triple junction are analyzed and the applicability of the Herring formula is discussed. A potential microgravity experiment is proposed which would enhance our understanding of the detached growth dynamic stability problem.

  14. Differences between thermal and laser-induced diffusion.

    PubMed

    Zaum, Ch; Meyer-Auf-der-Heide, K M; Mehlhorn, M; McDonough, S; Schneider, W F; Morgenstern, K

    2015-04-10

    A combination of femtosecond laser excitation with a low-temperature scanning tunneling microscope is used to study long-range interaction during diffusion of CO on Cu(111). Both thermal and laser-driven diffusion show an oscillatory energy dependence on the distance to neighboring molecules. Surprisingly, the phase is inverted; i.e., at distances at which thermal diffusion is most difficult, it is easiest for laser-driven diffusion and vice versa. We explain this unexpected behavior by a transient stabilization of the negative ion during diffusion as corroborated by ab initio calculations. PMID:25910140

  15. Differences Between Thermal and Laser-Induced Diffusion

    NASA Astrophysics Data System (ADS)

    Zaum, Ch.; Meyer-auf-der-Heide, K. M.; Mehlhorn, M.; McDonough, S.; Schneider, W. F.; Morgenstern, K.

    2015-04-01

    A combination of femtosecond laser excitation with a low-temperature scanning tunneling microscope is used to study long-range interaction during diffusion of CO on Cu(111). Both thermal and laser-driven diffusion show an oscillatory energy dependence on the distance to neighboring molecules. Surprisingly, the phase is inverted; i.e., at distances at which thermal diffusion is most difficult, it is easiest for laser-driven diffusion and vice versa. We explain this unexpected behavior by a transient stabilization of the negative ion during diffusion as corroborated by ab initio calculations.

  16. Alfvenic Generation of Magnetotail Transients During Substorms

    NASA Astrophysics Data System (ADS)

    Song, Y.; Lysak, B. L.

    2012-12-01

    Recent observations show that substorm associated phenomena before and after onsets are often transient and localized. These phenomena include bursty bulk flows (BBFs), dipolarization fronts (DFs) and plasma bubbles observed in the magnetotail, and poleward boundary intensifications (PBIs) and streamers observed in the ionosphere. The observations of the transients imply that the interaction between the solar wind and the magnetosphere-ionosphere (M-I) coupling system is of Alfvenic nature. Substorms are the dynamic response of the M-I coupling system to external perturbations in the solar wind driving conditions. The creation of the tail transients is directly associated with the total body force acting in the tail as well as their temporal changes and spatial distributions. The force is determined ultimately by the momentum transfer from the solar wind into the magnetosphere, and by internal conditions in the M-I coupling system, which include the generation of localized parallel electric fields in the auroral acceleration region or in the tail current sheets causing the localized breakdown of the frozen-in condition, as well as the changes in ionospheric parameters. We will discuss how a decrease in momentum transfer from the solar wind into the magnetosphere can produces a strong earthward body force acting in the magnetotail, exciting fast mode waves, causing BBFs, DFs and other magnetotail transients. An estimate of the increase of the earthward body force due to a given decrease in momentum transfer from the solar wind will be presented. The generation of parallel electric fields in the auroral acceleration region can redistribute perpendicular mechanical and magnetic stresses in the tail which may trigger a further sudden release of the tail energy enhancing the signatures of the tail transients and causing the substorm onset.

  17. The joy of transient chaos

    NASA Astrophysics Data System (ADS)

    Tl, Tams

    2015-09-01

    We intend to show that transient chaos is a very appealing, but still not widely appreciated, subfield of nonlinear dynamics. Besides flashing its basic properties and giving a brief overview of the many applications, a few recent transient-chaos-related subjects are introduced in some detail. These include the dynamics of decision making, dispersion, and sedimentation of volcanic ash, doubly transient chaos of undriven autonomous mechanical systems, and a dynamical systems approach to energy absorption or explosion.

  18. The Zwicky Transient Facility

    NASA Astrophysics Data System (ADS)

    Kulkarni, Shrinivas R.

    2016-01-01

    The Zwicky Transient Facility (ZTF) has been designed with a singular focus: a systematic exploration of the night sky at a magnitude level well suited for spectral classification and follow up with the existing class of 4-m to 10-m class telescopes. ZTF is the successor to the Palomar Transient Factory (PTF). The discovery engine for ZTF is a 47 square degree camera (realized through 16 e2V monolithic CCDs) that fills the entire focal plane of the 48-inch Oschin telescope of the Palomar Observatory. Single 30-s epoch sensitivity is about 20.5 in g and R bands. The Infarared Processing & Analysis Center (IPAC) is the data center for ZTF. ZTF is a public-private partnership with equal contributions from a consortium of world-wide partners and an NSF MSIP grant. Forty percent of ZTF time is set aside for two major community surveys: a 3-day cadence survey of high latitudes (to mimic LSST) and a time domain survey of the entire Northern Galactic plane. We expect first light in February 2017 and begin a 3-year survey starting summer of 2017. The first year will be spent on building up deep reference images of the sky (a must for transient surveys). During the second year IPAC will deliver near archival quality photometric products within 12 hours of observations. By comparison to reference images photometric alerts will be sent out. Year 3 will see the near real-time release of image differencing products. A Community Science Advisory Committee (CSAC), chaired by S. Ridgway (NOAO), has been set up to both advise the PI and to ensure that the US community's interests are well served. Astronomers interested in getting a head start on ZTF may wish to peruse the data releases from PTF. Young people (or young at heart) may wish to attend the annual summer school on PTF/ZTF (August, Caltech campus). The Principal Investigator (PI) for the project is S. Kulkarni and the Project Scientist is Eric Bellm.For further details please consult http://www.ptf.caltech.edu/ztf

  19. Atlas-guided volumetric diffuse optical tomography enhanced by generalized linear model analysis to image risk decision-making responses in young adults.

    PubMed

    Lin, Zi-Jing; Li, Lin; Cazzell, Mary; Liu, Hanli

    2014-08-01

    Diffuse optical tomography (DOT) is a variant of functional near infrared spectroscopy and has the capability of mapping or reconstructing three dimensional (3D) hemodynamic changes due to brain activity. Common methods used in DOT image analysis to define brain activation have limitations because the selection of activation period is relatively subjective. General linear model (GLM)-based analysis can overcome this limitation. In this study, we combine the atlas-guided 3D DOT image reconstruction with GLM-based analysis (i.e., voxel-wise GLM analysis) to investigate the brain activity that is associated with risk decision-making processes. Risk decision-making is an important cognitive process and thus is an essential topic in the field of neuroscience. The Balloon Analog Risk Task (BART) is a valid experimental model and has been commonly used to assess human risk-taking actions and tendencies while facing risks. We have used the BART paradigm with a blocked design to investigate brain activations in the prefrontal and frontal cortical areas during decision-making from 37 human participants (22 males and 15 females). Voxel-wise GLM analysis was performed after a human brain atlas template and a depth compensation algorithm were combined to form atlas-guided DOT images. In this work, we wish to demonstrate the excellence of using voxel-wise GLM analysis with DOT to image and study cognitive functions in response to risk decision-making. Results have shown significant hemodynamic changes in the dorsal lateral prefrontal cortex (DLPFC) during the active-choice mode and a different activation pattern between genders; these findings correlate well with published literature in functional magnetic resonance imaging (fMRI) and fNIRS studies. PMID:24619964

  20. Enhanced fluorescence diffuse optical tomography with indocyanine green-encapsulating liposomes targeted to receptors for vascular endothelial growth factor in tumor vasculature.

    PubMed

    Zanganeh, Saeid; Xu, Yan; Hamby, Carl V; Backer, Marina V; Backer, Joseph M; Zhu, Quing

    2013-12-01

    To develop an indocyanine green (ICG) tracer with slower clearance kinetics, we explored ICG-encapsulating liposomes (Lip) in three different formulations: untargeted (Lip/ICG), targeted to vascular endothelial growth factor (VEGF) receptors (scVEGF-Lip/ICG) by the receptor-binding moiety single-chain VEGF (scVEGF), or decorated with inactivated scVEGF (inactive-Lip/ICG) that does not bind to VEGF receptors. Experiments were conducted with tumor-bearing mice that were placed in a scattering medium with tumors located at imaging depths of either 1.5 or 2.0 cm. Near-infrared fluorescence diffuse optical tomography that provides depth-resolved spatial distributions of fluorescence in tumor was used for the detection of postinjection fluorescent signals. All liposome-based tracers, as well as free ICG, were injected intravenously into mice in the amounts corresponding to 5 nmol of ICG/mouse, and the kinetics of increase and decrease of fluorescent signals in tumors were monitored. A signal from free ICG reached maximum at 15-min postinjection and then rapidly declined with t1/2 of ~20 min. The signals from untargeted Lip/ICG and inactive-Lip/ICG also reached maximum at 15-min postinjection, however, declined somewhat slower than free ICG with t1/2 of ~30 min. By contrast, a signal from targeted scVEGF-Lip/ICG grew slower than that of all other tracers, reaching maximum at 30-min postinjection and declined much slower than that of other tracers with t1/2 of ~90 min, providing a more extended observation window. Higher scVEGF-Lip/ICG tumor accumulation was further confirmed by the analysis of fluorescence on cryosections of tumors that were harvested from animals at 400 min after injection with different tracers. PMID:24346856

  1. Enhanced fluorescence diffuse optical tomography with indocyanine green-encapsulating liposomes targeted to receptors for vascular endothelial growth factor in tumor vasculature

    PubMed Central

    Zanganeh, Saeid; Xu, Yan; Hamby, Carl V.; Backer, Marina V.; Backer, Joseph M.; Zhu, Quing

    2013-01-01

    Abstract. To develop an indocyanine green (ICG) tracer with slower clearance kinetics, we explored ICG-encapsulating liposomes (Lip) in three different formulations: untargeted (Lip/ICG), targeted to vascular endothelial growth factor (VEGF) receptors (scVEGF-Lip/ICG) by the receptor-binding moiety single-chain VEGF (scVEGF), or decorated with inactivated scVEGF (inactive-Lip/ICG) that does not bind to VEGF receptors. Experiments were conducted with tumor-bearing mice that were placed in a scattering medium with tumors located at imaging depths of either 1.5 or 2.0cm. Near-infrared fluorescence diffuse optical tomography that provides depth-resolved spatial distributions of fluorescence in tumor was used for the detection of postinjection fluorescent signals. All liposome-based tracers, as well as free ICG, were injected intravenously into mice in the amounts corresponding to 5 nmol of ICG/mouse, and the kinetics of increase and decrease of fluorescent signals in tumors were monitored. A signal from free ICG reached maximum at 15-min postinjection and then rapidly declined with t1/2 of ?20??min. The signals from untargeted Lip/ICG and inactive-Lip/ICG also reached maximum at 15-min postinjection, however, declined somewhat slower than free ICG with t1/2 of ?30??min. By contrast, a signal from targeted scVEGF-Lip/ICG grew slower than that of all other tracers, reaching maximum at 30-min postinjection and declined much slower than that of other tracers with t1/2 of ?90??min, providing a more extended observation window. Higher scVEGF-Lip/ICG tumor accumulation was further confirmed by the analysis of fluorescence on cryosections of tumors that were harvested from animals at 400min after injection with different tracers. PMID:24346856

  2. Enhanced fluorescence diffuse optical tomography with indocyanine green-encapsulating liposomes targeted to receptors for vascular endothelial growth factor in tumor vasculature

    NASA Astrophysics Data System (ADS)

    Zanganeh, Saeid; Xu, Yan; Hamby, Carl V.; Backer, Marina V.; Backer, Joseph M.; Zhu, Quing

    2013-12-01

    To develop an indocyanine green (ICG) tracer with slower clearance kinetics, we explored ICG-encapsulating liposomes (Lip) in three different formulations: untargeted (Lip/ICG), targeted to vascular endothelial growth factor (VEGF) receptors (scVEGF-Lip/ICG) by the receptor-binding moiety single-chain VEGF (scVEGF), or decorated with inactivated scVEGF (inactive-Lip/ICG) that does not bind to VEGF receptors. Experiments were conducted with tumor-bearing mice that were placed in a scattering medium with tumors located at imaging depths of either 1.5 or 2.0 cm. Near-infrared fluorescence diffuse optical tomography that provides depth-resolved spatial distributions of fluorescence in tumor was used for the detection of postinjection fluorescent signals. All liposome-based tracers, as well as free ICG, were injected intravenously into mice in the amounts corresponding to 5 nmol of ICG/mouse, and the kinetics of increase and decrease of fluorescent signals in tumors were monitored. A signal from free ICG reached maximum at 15-min postinjection and then rapidly declined with t of 20 min. The signals from untargeted Lip/ICG and inactive-Lip/ICG also reached maximum at 15-min postinjection, however, declined somewhat slower than free ICG with t of 30 min. By contrast, a signal from targeted scVEGF-Lip/ICG grew slower than that of all other tracers, reaching maximum at 30-min postinjection and declined much slower than that of other tracers with t of 90 min, providing a more extended observation window. Higher scVEGF-Lip/ICG tumor accumulation was further confirmed by the analysis of fluorescence on cryosections of tumors that were harvested from animals at 400 min after injection with different tracers.

  3. Transient Dentritic Solidification Experiment

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The Transient Dentritic Solidification Experiment (TDSE) is being developed as a candidate for flight aboard the International Space Station. TDSE will study the growth of dentrites (treelike crystalline structures) in a transparent material (succinonitrile or SCN) that mimics the behavior of widely used iron-based metals. Basic work by three Space Shuttle flights (STS-62, STS-75, and STS-87) of the Isothermal Dendritic Growth Experiment (IDGE) is yielding new insights into virtually all industrially relevant metal and alloy forming operations. The TDSE is similar to IDGE, but will maintain a constant temperature while varying pressure on the dentrites. Shown here is a cutaway of the isothermal bath containing its growth cell at the heart of the TDSE. The principal investigator is Matthew Koss of College of the Holy Cross in Worcester, MA. Note: an Acrobat PDF version is available from http://microgravity.nasa.gov/gallery

  4. Perturbations for transient acceleration

    SciTech Connect

    Vargas, Cristofher Zuiga; Zimdahl, Winfried; Hiplito-Ricaldi, Wiliam S. E-mail: hipolito@ceunes.ufes.br

    2012-04-01

    According to the standard ?CDM model, the accelerated expansion of the Universe will go on forever. Motivated by recent observational results, we explore the possibility of a finite phase of acceleration which asymptotically approaches another period of decelerated expansion. Extending an earlier study on a corresponding homogeneous and isotropic dynamics, in which interactions between dark matter and dark energy are crucial, the present paper also investigates the dynamics of the matter perturbations both on the Newtonian and General Relativistic (GR) levels and quantifies the potential relevance of perturbations of the dark-energy component. In the background, the model is tested against the Supernova type Ia (SNIa) data of the Constitution set and on the perturbative level against growth rate data, among them those of the WiggleZ survey, and the data of the 2dFGRS project. Our results indicate that a transient phase of accelerated expansion is not excluded by current observations.

  5. 100-liter transient transfection.

    PubMed

    Girard, Philippe; Derouazi, Madiha; Baumgartner, Gwendoline; Bourgeois, Michaela; Jordan, Martin; Jacko, Barbara; Wurm, Florian M

    2002-01-01

    This is the first report of two successful 100 l scale transienttransfections in a standard stirred bioreactor. More than half a gram of a monoclonal antibody (IgG) were produced in less than 10 days using a technology called large-scale transient gene expression(LS-TGE). Suspension adapted HEK 293 EBNA SF cells were transfectedwithin a 150 l (nominal) bioreactor by a modified calcium phosphateco-precipitation method with more than 75 mg of plasmid DNA per run.A mixture of three different plasmids, one encoding for the heavychain of a human recombinant immunoglobulin, the other for the corresponding light chain and a third one for the green fluorescent protein (GFP, 2-4% of DNA in transfection cocktail)were co-transfected. The GFP vector was chosen to monitor transfection efficiency. Expression of GFP could be registered asearly as 20 h after DNA addition, using fluorescence microscopy. We demonstrate that transient transfection can be done at the100 l scale, thus providing a new tool to produce hundreds of milligrams or even gram amounts of recombinant protein. Akey advantage of LS-TGE resides in its speed. In the presentedcases, the entire production process for the synthesis of halfa gram of a recombinant antibody, including DNA preparationand necessary expansion of cells prior to transfection, wasexecuted in less than a month. Having an established transfection/expression process allows to run productioncampaigns for any given protein, within one facility, with onesingle host cell line and therefore only one single seed train. Without any need to create and maintain stable cell lines, expression of new r-proteins is not only faster and more economical but also more flexible. PMID:19003082

  6. An Upregulation in the Expression of Vanilloid Transient Potential Channels 2 Enhances Hypotonicity-Induced Cytosolic Ca2+ Rise in Human Induced Pluripotent Stem Cell Model of Hutchinson Gillford Progeria

    PubMed Central

    Ho, Jenny Chung-Yee; Siu, Chung-Wah; Cheung, Sin-Ying; Tang, Nelson L.; Yu, Shan; Tse, Hung-Fat; Yao, Xiaoqiang

    2014-01-01

    Hutchinson-Gillford Progeria Syndrome (HGPS) is a fatal genetic disorder characterized by premature aging in multiple organs including the skin, musculoskeletal and cardiovascular systems. It is believed that an increased mechanosensitivity of HGPS cells is a causative factor for vascular cell death and vascular diseases in HGPS patients. However, the exact mechanism is unknown. Transient receptor potential (TRP) channels are cationic channels that can act as cellular sensors for mechanical stimuli. The aim of this present study was to examine the expression and functional role of TRP channels in human induced pluripotent stem cell-derived endothelial cells (iPSC-ECs) from the patients with HGPS. The mRNA and protein expression of TRP channels in HGPS and control (IMR90) iPSC-ECs were examined by semi-quantitative RT-PCRs and immunoblots, respectively. Hypotonicity-induced cytosolic Ca2+ ([Ca2+]i) rise in iPSC-ECs was measured by confocal microscopy. RT-PCRs and immunoblots showed higher expressional levels of TRPV2 in iPSC-ECs from HGPS patients than those from normal individuals. In functional studies, hypotonicity induced a transient [Ca2+]i rise in iPSC-ECs from normal individuals but a sustained [Ca2+]i elevation in iPSC-ECs from HGPS patients. A nonselective TRPV inhibitor, ruthenium red (RuR, 20 M), and a specific TRPV2 channel inhibitor, tranilast (100 M), abolished the sustained phase of hypotonicity-induced [Ca2+]i rise in iPSC-ECs from HGPS patients, and also markedly attenuated the transient phase of the [Ca2+]i rise in these cells. Importantly, a short 10 min hypotonicity treatment caused a substantial increase in caspase 8 activity in iPSC-ECs from HGPS patients but not in cells from normal individuals. Tranilast could also inhibit the hypotonicity-induced increase in caspase 8 activity. Taken together, our data suggest that an up-regulation in TRPV2 expression causes a sustained [Ca2+]i elevation in HGPS-iPSC-ECs under hypotonicity, consequently resulting in apoptotic cell death. This mechanism may contribute to the pathogenesis of vascular diseases in HGPS patients. PMID:24475260

  7. Mechanisms of boron diffusion in silicon and germanium

    NASA Astrophysics Data System (ADS)

    Mirabella, S.; De Salvador, D.; Napolitani, E.; Bruno, E.; Priolo, F.

    2013-01-01

    B migration in Si and Ge matrices raised a vast attention because of its influence on the production of confined, highly p-doped regions, as required by the miniaturization trend. In this scenario, the diffusion of B atoms can take place under severe conditions, often concomitant, such as very large concentration gradients, non-equilibrium point defect density, amorphous-crystalline transition, extrinsic doping level, co-doping, B clusters formation and dissolution, ultra-short high-temperature annealing. In this paper, we review a large amount of experimental work and present our current understanding of the B diffusion mechanism, disentangling concomitant effects and describing the underlying physics. Whatever the matrix, B migration in amorphous (?-) or crystalline (c-) Si, or c-Ge is revealed to be an indirect process, activated by point defects of the hosting medium. In ?-Si in the 450-650 C range, B diffusivity is 5 orders of magnitude higher than in c-Si, with a transient longer than the typical amorphous relaxation time. A quick B precipitation is also evidenced for concentrations larger than 2 1020 B/cm3. B migration in ?-Si occurs with the creation of a metastable mobile B, jumping between adjacent sites, stimulated by dangling bonds of ?-Si whose density is enhanced by B itself (larger B density causes higher B diffusivity). Similar activation energies for migration of B atoms (3.0 eV) and of dangling bonds (2.6 eV) have been extracted. In c-Si, B diffusion is largely affected by the Fermi level position, occurring through the interaction between the negatively charged substitutional B and a self-interstitial (I) in the neutral or doubly positively charged state, if under intrinsic or extrinsic (p-type doping) conditions, respectively. After charge exchanges, the migrating, uncharged BI pair is formed. Under high n-type doping conditions, B diffusion occurs also through the negatively charged BI pair, even if the migration is depressed by Coulomb pairing with n-type dopants. The interplay between B clustering and migration is also modeled, since B diffusion is greatly affected by precipitation. Small (below 1 nm) and relatively large (5-10 nm in size) BI clusters have been identified with different energy barriers for thermal dissolution (3.6 or 4.8 eV, respectively). In c-Ge, B motion is by far less evident than in c-Si, even if the migration mechanism is revealed to be similarly assisted by Is. If Is density is increased well above the equilibrium (as during ion irradiation), B diffusion occurs up to quite large extents and also at relatively low temperatures, disclosing the underlying mechanism. The lower B diffusivity and the larger activation barrier (4.65 eV, rather than 3.45 eV in c-Si) can be explained by the intrinsic shortage of Is in Ge and by their large formation energy. B diffusion can be strongly enhanced with a proper point defect engineering, as achieved with embedded GeO2 nanoclusters, causing at 650 C a large Is supersaturation. These aspects of B diffusion are presented and discussed, modeling the key role of point defects in the two different matrices.

  8. Formation of Magnetized Prestellar Cores with Ambipolar Diffusion and Turbulence

    NASA Astrophysics Data System (ADS)

    Chen, Che-Yu; Ostriker, Eve

    2014-07-01

    We investigate the roles of magnetic fields and ambipolar diffusion during prestellar core formation in turbulent giant molecular clouds (GMCs), using three-dimensional numerical simulations. Our simulations focus on the shocked layer produced by a converging flow within a GMC, and survey varying ionization and angle between the upstream flow and magnetic field. We also include ideal magnetohydrodynamic (MHD) and hydrodynamic models. From our simulations, we identify hundreds of self-gravitating cores that form within 1 Myr, with masses M~0.04-2.5 solar-mass and sizes L~0.015-0.07 pc, consistent with observations of the peak of the core mass function (CMF). Median values are M=0.47 solar-mass and L=0.03 pc. Core masses and sizes do not depend on either the ionization or upstream magnetic field direction. In contrast, the mass-to-magnetic flux ratio does increase with lower ionization, from twice to four times the critical value. The higher mass-to-flux ratio for low ionization is the result of enhanced transient ambipolar diffusion when the shocked layer first forms. However, ambipolar diffusion is not necessary to form low-mass supercritical cores. For ideal MHD, we find similar masses to other cases. These masses are 1-2 orders of magnitude lower than the value that defines a magnetically supercritical sphere under post-shock ambient conditions. This discrepancy is the result of anisotropic contraction along field lines, which is clearly evident in both ideal MHD and diffusive simulations. We interpret our numerical findings using a simple scaling argument which suggests that gravitationally critical core masses will depend on the sound speed and mean turbulent pressure in a cloud, regardless of magnetic effects.

  9. Formation of Magnetized Prestellar Cores with Ambipolar Diffusion and Turbulence

    NASA Astrophysics Data System (ADS)