Science.gov

Sample records for transient enhanced diffusion

  1. Implantation induced extended defects and transient enhanced diffusion in silicon

    SciTech Connect

    Chen, J.; Liu, J.; Listebarger, J.; Krishnamoorthy, W.; Zhang, L.; Jones, K.S.

    1995-08-01

    Transient enhanced diffusion (TED) of dopant in silicon caused by point defects during annealing of implanted. Si has become one of the essential concerns in miniaturization of silicon device technology. In order to control and minimize the TED effect, a fundamental understanding of the evolution of the point defects upon annealing and the interaction between point defects and extended defects and their effects on dopant diffusion is necessary. Our studies were carried out by two parts; (1) For understanding the evolution of <311> and <110> defects, B{sup +} and Si{sup +} implantation at energies (from 5 keV to 40 keV) and doses in the range from 5 x 10{sup 12} to 1 x 10{sup 14}/cm{sup 2} were used. The annealing kinetics were investigated using a N{sub 2} ambient with temperatures for time ranging from 500{degrees}C to 1100{degrees}C for time ranging from 3 min to 3 hours. A matrix of implant energy vs. dose on formation threshold of <311> and <110> defect, interstitials napped and dissolved condition were obtained. (2) For Understanding the interaction between Type II dislocation loop and point defect a B doped buried marker layer was used. The oxidation of silicon surface used as a interstitials injection source and a buried type II loop layer as a point defect detector used to quantify the flux of interstitials injected. Combining the flux measured by loops and dopant diffusion the D{sub I} C{sub I} was determined. The diffusion limited kinetics was concluded. The TED from <311> and EOR (End of Range) <110> defect was studied using 8keV B{sup +} implanted Si to a dose of the le14 and 190keV Ge{sub +} implanted to a dose of le15. Subsequent anneals are done for 5 min and 30 min, respectively, These defects affect dopant diffusion by trapping and releasing point defects.

  2. 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.

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

    SciTech Connect

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

    2015-10-15

    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.

  4. 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.

  5. 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.

  6. 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.

  7. Transient diffusion in a tube with dead ends.

    PubMed

    Dagdug, Leonardo; Berezhkovskii, Alexander M; Makhnovskii, Yurii A; Zitserman, Vladimir Yu

    2007-12-14

    A particle diffusing in a tube with dead ends, from time to time enters a dead end, spends some time in the dead end, and then comes back to the tube. As a result, the particle spends in the tube only a part of the entire observation time that leads to slowdown of its diffusion along the tube. We study the transient diffusion in a tube with periodic identical dead ends formed by cavities of volume V(cav) connected to the tube by cylindrical channels of length L and radius a, which is assumed to be much smaller than the tube radius R and the distance l between neighboring dead ends. Assuming that the particle initial position is uniformly distributed over the tube, we analyze the monotonic decrease of the particle diffusion coefficient D(t) from its initial value D(0)=D, which characterizes diffusion in the tube without dead ends, to its asymptotic long-time value D(infinity)=D(eff)

  8. Diffusive-light invisibility cloak for transient illumination

    NASA Astrophysics Data System (ADS)

    Orazbayev, B.; Beruete, M.; Martínez, A.; García-Meca, C.

    2016-12-01

    Invisibility in a diffusive-light-scattering medium has been recently demonstrated by employing a scattering-cancellation core-shell cloak. Unlike nondiffusive cloaks, such a device can be simultaneously macroscopic, broadband, passive, polarization independent, and omnidirectional. Unfortunately, it has been verified that this cloak, as well as more sophisticated ones based on transformation optics, fail under pulsed illumination, invalidating their use for a variety of applications. Here, we introduce a different approach based on unimodular transformations that enables the construction of unidirectional diffusive-light cloaks exhibiting a perfect invisibility effect, even under transient conditions. Moreover, we demonstrate that a polygonal cloak can extend this functionality to multiple directions with a nearly ideal behavior, while preserving all other features. We propose and numerically verify a simple cloak realization based on a layered stack of two isotropic materials. The studied devices have several applications not addressable by any of the other cloaks proposed to date, including shielding from pulse-based detection techniques, cloaking undesired scattering elements in time-of-flight imaging or high-speed communication systems for diffusive environments, and building extreme optical security features. The discussed cloaking strategy could also be applied to simplify the implementation of thermal cloaks.

  9. 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.

  10. 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.

  11. 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.

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

    PubMed

    Stanislavsky, Aleksander; Weron, Karina; Weron, Aleksander

    2014-02-07

    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.

  13. Diffusion-Weighted Imaging and Diagnosis of Transient Ischemic Attack

    PubMed Central

    Brazzelli, Miriam; Chappell, Francesca M; Miranda, Hector; Shuler, Kirsten; Dennis, Martin; Sandercock, Peter A G; Muir, Keith; Wardlaw, Joanna M

    2014-01-01

    Objective Magnetic resonance (MR) diffusion-weighted imaging (DWI) is sensitive to small acute ischemic lesions and might help diagnose transient ischemic attack (TIA). Reclassification of patients with TIA and a DWI lesion as “stroke” is under consideration. We assessed DWI positivity in TIA and implications for reclassification as stroke. Methods We searched multiple sources, without language restriction, from January 1995 to July 2012. We used PRISMA guidelines, and included studies that provided data on patients presenting with suspected TIA who underwent MR DWI and reported the proportion with an acute DWI lesion. We performed univariate random effects meta-analysis to determine DWI positive rates and influencing factors. Results We included 47 papers and 9,078 patients (range = 18–1,693). Diagnosis was by a stroke specialist in 26 of 47 studies (55%); all studies excluded TIA mimics. The pooled proportion of TIA patients with an acute DWI lesion was 34.3% (95% confidence interval [CI] = 30.5–38.4, range = 9–67%; I2 = 89.3%). Larger studies (n > 200) had lower DWI-positive rates (29%; 95% CI = 23.2–34.6) than smaller (n < 50) studies (40.1%; 95% CI = 33.5–46.6%; p = 0.035), but no other testable factors, including clinician speciality and time to scanning, reduced or explained the 7-fold DWI-positive variation. Interpretation The commonest DWI finding in patients with definite TIA is a negative scan. Available data do not explain why ⅔ of patients with definite specialist-confirmed TIA have negative DWI findings. Until these factors are better understood, reclassifying DWI-positive TIAs as strokes is likely to increase variance in estimates of global stroke and TIA burden of disease. ANN NEUROL 2014;75:67–76 PMID:24085376

  14. 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.

  15. In trans promoter activation by enhancers in transient transfection.

    PubMed

    Smirnov, N A; Akopov, S B; Didych, D A; Nikolaev, L G

    2017-03-01

    Earlier, it was reported that the strong cytomegalovirus enhancer can activate the cytomegalovirus promoter in trans, i.e. as a separate plasmid co-transfected with a promoter-reporter gene construct. Here we demonstrate that the ability of enhancers to activate promoters in trans in transient transfection experiments is a property of not only viral regulatory elements but also of various genomic enhancers and promoters. Enhancer-promoter activation in trans is promoter- and cell type-specific, and accompanied by physical interaction between promoter and enhancer as revealed by chromosome conformation capture assays. Thus, promoter activation in transient co-transfection of promoters and enhancers shares a number of important traits with long-distance promoter activation by enhancers in living cells and may therefore serve as a model of this fundamental cellular process.

  16. Evaluation of the Effect of Gravity Force on Transient Mass Diffusion Fields

    NASA Astrophysics Data System (ADS)

    Komiya, Atsuki; Maruyama, Shigenao

    In this study, the relationship between gravitational force and diffusion phenomena in aque-ous solutions is discussed. The microgravity environment gives a high quality crystal growth condition which produces high quality medicines or foods. In this condition, a natural con-vection can be neglected and diffusion phenomenon without convection is observed. The mass diffusion coefficient is one of the most important thermophysical properties to investigate that mass transport system. However, the available experimental data of mass diffusion coefficients in microgravity conditions is not enough. Because it is quite a few opportunity that exper-iments can be conducted using facilities which produce microgravity environment for a long time. Then we have developed an observation system of small transient diffusion fields within 20 seconds. The experimental apparatus is composed of phase shifting interferometer, special designed signal processing unit and recorder. The mechanism of test cell used in this study has a unique performance that the transient diffusion fields can be produced continuously with no change of solutions and cell. Therefore this system can be applied to short-time microgravity experiment which is generated by the parabolic flight of an airplane. By using this system, the transient diffusion field of Sodium Chloride (NaCl) solution in microgravity conditions could be clearly observed and the mass diffusion coefficient was estimated from the obtained data. In microgravity condition, the transient diffusion fields have different appearances from the normal gravity condition. A slight acceleration governs the transient diffusion fields because of no density difference, so vibrations applied the apparatus disturb the transient diffusion fields. The measured mass diffusion coefficient has been estimated as a smaller value compared with ones under normal gravity condition. Using the airplane as a facility, not only microgravity condition but also 0.8G, 1

  17. 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.

  18. Enhanced diffusion for oscillatory viscoelastic flow

    NASA Astrophysics Data System (ADS)

    Manopoulos, C.; Tsangaris, S.

    2014-08-01

    This paper examines the enhanced axial solute dispersion of a linear viscoelastic fluid, subjected to a longitudinal pressure gradient sinusoidal oscillation, in a duct between parallel walls. The viscoelastic fluid follows the material law of the Jeffrey fluid. An extension of Watson’s theory, developed in 1983, is used to solve the problem analytically. The diffusivity enhancement results are shown in dimensionless form and are presented as functions of the dimensionless group β = h(2ω/ν)1/2 as defined by Watson, the dimensionless retardation time, and the Schmidt, elasticity, and Euler dimensionless numbers. This paper compares the dispersion enhancement of the Jeffrey fluid, in relation to the Newtonian one, for several intervals of the dimensionless parameters. The results indicate very high dispersion enhancement in several cases, especially for high realistic Schmidt number values, and peaks appear at certain dimensionless parameter β values.

  19. 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.

  20. Transient interfacial tension and dilatational rheology of diffuse polymer-polymer interfaces

    NASA Astrophysics Data System (ADS)

    Peters, Gerrit W. M.; Zdravkov, Alexander N.; Meijer, Han E. H.

    2005-03-01

    We demonstrate the influence of molecular weight and molecular weight asymmetry across an interface on the transient behavior of the interfacial tension. The interfacial tension was measured as a function of time for a range of polymer combinations with a broad range of interfacial properties using a pendant/sessile drop apparatus. The results show that neglecting mutual solubility, assumed to be a reasonable approximation in many cases, very often does not sustain. Instead, a diffuse interface layer develops in time with a corresponding transient interfacial tension. Depending on the specific combination of polymers, the transient interfacial tension is found to increase or decrease with time. The results are interpreted in terms of a recently proposed model [Shi et al., Macromolecules 37, 1591 (2004)], giving relative characteristic diffusion time scales in terms of molecular weight, molecular weight distribution, and viscosities. However, the time scales obtained from this theoretical approach do not give a conclusive trend. Using oscillatory dilatational interfacial experiments the viscoelastic behavior of these diffusive interfaces is demonstrated. The time evolution of the interfacial tension and the dilatational elasticity show the same trend as predicted by the theory of diffuse interfaces, supporting the idea that the polymer combinations under consideration indeed form diffuse interfaces. The dilatational elasticity and the dilatational viscosity show a frequency dependency that is described qualitatively by a simple Fickian diffusion model and quantitatively by a Maxwell model. The characteristic diffusion times provided by the latter show that the systems with thick interfaces (tens of microseconds and more) can be considered as slower diffusive systems compared to the systems with thinner interfaces (a few micrometers in thickness and less) can be considered as fast diffusive systems.

  1. Transient spatio-temporal dynamics of a diffusive plant-herbivore system with Neumann boundary conditions.

    PubMed

    Yu, Fang; Wang, Lin; Watmough, James

    2016-12-01

    In many existing predator-prey or plant-herbivore models, the numerical response is assumed to be proportional to the functional response. In this paper, without such an assumption, we consider a diffusive plant-herbivore system with Neumann boundary conditions. Besides stability of spatially homogeneous steady states, we also derive conditions for the occurrence of Hopf bifurcation and steady-state bifurcation and provide geometrical methods to locate the bifurcation values. We numerically explore the complex transient spatio-temporal behaviours induced by these bifurcations. A large variety of different types of transient behaviours including oscillations in one or both of space and time are observed.

  2. Transient anomalous diffusion in periodic systems: ergodicity, symmetry breaking and velocity relaxation

    PubMed Central

    Spiechowicz, Jakub; Łuczka, Jerzy; Hänggi, Peter

    2016-01-01

    We study far from equilibrium transport of a periodically driven inertial Brownian particle moving in a periodic potential. As detected for a SQUID ratchet dynamics, the mean square deviation of the particle position from its average may involve three distinct intermediate, although extended diffusive regimes: initially as superdiffusion, followed by subdiffusion and finally, normal diffusion in the asymptotic long time limit. Even though these anomalies are transient effects, their lifetime can be many, many orders of magnitude longer than the characteristic time scale of the setup and turns out to be extraordinarily sensitive to the system parameters like temperature or the potential asymmetry. In the paper we reveal mechanisms of diffusion anomalies related to ergodicity of the system, symmetry breaking of the periodic potential and ultraslow relaxation of the particle velocity towards its steady state. Similar sequences of the diffusive behaviours could be detected in various systems including, among others, colloidal particles in random potentials, glass forming liquids and granular gases. PMID:27492219

  3. 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

  4. 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.

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

    SciTech Connect

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

    2015-09-21

    Si self-diffusion in the presence of end-of-range (EOR) defects is investigated using {sup nat}Si/{sup 28}Si 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 {sup 30}Si self-diffusion. The experimental {sup 30}Si 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 {sup 30}Si profiles.

  6. Benchmarking report for WIGGLE: A one-dimensional transient diffusion theory code

    SciTech Connect

    Pevey, R.E.

    1990-11-01

    WIGGLE is a static/transient one-dimensional diffusion theory calculation written to estimate the axial power profile while safety rods are falling during a scram. The code is used in the LOCA Limits Analysis Package (LLAP), a part of the SRS system for calculating thermal-hydraulic limits. Since WIGGLE was designed to be implemented through LLAP and not as a stand-alone code, it consists entirely of subroutines; the problem data must be passed to it from a driver routine. This project concerned the verification of WIGGLE, which limited it to the determination that WIGGLE is correctly implementing the transient 1D diffusion equation. The approach was to compare the results of the code with three analytic solutions: a static homogeneous calculation of the pre-accident power profile (without end-fittings); a static heterogeneous calculation of the pre-accident power profile (includes end-fittings); and a transient calculation designed to test the time-dependent calculational ability. The results of all three calculations were essentially identical to the analytical solutions, thus giving us confidence that WIGGLE is correctly solving the one-dimensional time-dependent diffusion equation.

  7. 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 in Pe due 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 aquifer–aquitard complexes.

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

    PubMed

    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 in Pe due 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 aquifer-aquitard complexes.

  9. Transient Treg depletion enhances therapeutic anti‐cancer vaccination

    PubMed Central

    Aston, Wayne J.; Chee, Jonathan; Khong, Andrea; Cleaver, Amanda L.; Solin, Jessica N.; Ma, Shaokang; Lesterhuis, W. Joost; Dick, Ian; Holt, Robert A.; Creaney, Jenette; Boon, Louis; Robinson, Bruce; Lake, Richard A.

    2016-01-01

    Abstract Introduction Regulatory T cells (Treg) play an important role in suppressing anti‐ immunity and their depletion has been linked to improved outcomes. To better understand the role of Treg in limiting the efficacy of anti‐cancer immunity, we used a Diphtheria toxin (DTX) transgenic mouse model to specifically target and deplete Treg. Methods Tumor bearing BALB/c FoxP3.dtr transgenic mice were subjected to different treatment protocols, with or without Treg depletion and tumor growth and survival monitored. Results DTX specifically depleted Treg in a transient, dose‐dependent manner. Treg depletion correlated with delayed tumor growth, increased effector T cell (Teff) activation, and enhanced survival in a range of solid tumors. Tumor regression was dependent on Teffs as depletion of both CD4 and CD8 T cells completely abrogated any survival benefit. Severe morbidity following Treg depletion was only observed, when consecutive doses of DTX were given during peak CD8 T cell activation, demonstrating that Treg can be depleted on multiple occasions, but only when CD8 T cell activation has returned to base line levels. Finally, we show that even minimal Treg depletion is sufficient to significantly improve the efficacy of tumor‐peptide vaccination. Conclusions BALB/c.FoxP3.dtr mice are an ideal model to investigate the full therapeutic potential of Treg depletion to boost anti‐tumor immunity. DTX‐mediated Treg depletion is transient, dose‐dependent, and leads to strong anti‐tumor immunity and complete tumor regression at high doses, while enhancing the efficacy of tumor‐specific vaccination at low doses. Together this data highlight the importance of Treg manipulation as a useful strategy for enhancing current and future cancer immunotherapies. PMID:28250921

  10. Fixation, transient landscape, and diffusion dilemma in stochastic evolutionary game dynamics.

    PubMed

    Zhou, Da; Qian, Hong

    2011-09-01

    Agent-based stochastic models for finite populations have recently received much attention in the game theory of evolutionary dynamics. Both the ultimate fixation and the pre-fixation transient behavior are important to a full understanding of the dynamics. In this paper, we study the transient dynamics of the well-mixed Moran process through constructing a landscape function. It is shown that the landscape playing a central theoretical "device" that integrates several lines of inquiries: the stable behavior of the replicator dynamics, the long-time fixation, and continuous diffusion approximation associated with asymptotically large population. Several issues relating to the transient dynamics are discussed: (i) multiple time scales phenomenon associated with intra- and inter-attractoral dynamics; (ii) discontinuous transition in stochastically stationary process akin to Maxwell construction in equilibrium statistical physics; and (iii) the dilemma diffusion approximation facing as a continuous approximation of the discrete evolutionary dynamics. It is found that rare events with exponentially small probabilities, corresponding to the uphill movements and barrier crossing in the landscape with multiple wells that are made possible by strong nonlinear dynamics, plays an important role in understanding the origin of the complexity in evolutionary, nonlinear biological systems.

  11. Tracing the origins of transient overshoots for binary mixture diffusion in microporous crystalline materials.

    PubMed

    Krishna, Rajamani

    2016-06-21

    Separation of mixtures using microporous crystalline materials is normally achieved by exploiting differences in the adsorption strengths of the constituent species. The focus of the current investigation is on diffusion-selective separations that exploit differences in intra-crystalline diffusivities of guest molecules. A number of experimental investigations report overshoots in intra-crystalline loadings of the more mobile species during transient mixture uptake. Analogous overshoots in fluxes occur for mixture permeation across thin microporous membrane layers. The attainment of supra-equilibrium loadings is a common characteristic of diffusion-selective separations; this allows the over-riding of adsorption selectivities. The primary objective of the current investigation is to demonstrate that the Maxwell-Stefan diffusion formulation, using chemical potential gradients as driving forces, is capable of providing a quantitative description of the temporal and spatial overshoots found in diverse experimental studies. The origins of the overshoots can be traced to thermodynamic coupling effects that emanate from sizable off-diagonal contributions of the matrix of thermodynamic correction factors. If thermodynamic coupling effects are neglected, the overshoots are not realized. It is also demonstrated that while the transport of the more mobile partner is uphill of its loading gradient, its transport is downhill the gradient of its chemical potential. The deliberate exploitation of uphill diffusion to achieve difficult separations is highlighted.

  12. Anomalous diffusion process applied to magnetic resonance image enhancement.

    PubMed

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

    2015-03-21

    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.

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

    NASA Astrophysics Data System (ADS)

    Nargelas, S.; Jarašiunas, K.; Bertulis, K.; Pačebutas, 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 ΔEa=46 meV of diffusivity and low hole mobility value μh=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/τR∝Bi(x )3.2 indicated an increasing structural disorder in the alloy.

  14. Deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase-epitaxy n-GaAs

    NASA Technical Reports Server (NTRS)

    Partin, D. L.; Chen, J. W.; Milnes, A. G.; Vassamillet, L. F.

    1979-01-01

    The paper presents deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase epitaxy n-GaAs. Nickel diffused into VPE n-GaAs reduces the hole diffusion length L sub p from 4.3 to 1.1 microns. Deep-level transient spectroscopy was used to identify energy levels in Ni-diffused GaAs; the as-grown VPE GaAs contains traces of these levels and an electron trap. Ni diffusion reduces the concentration of this level by an amount that matches the increase in concentration of each of the two Ni-related levels. A technique for measuring minority-carrier capture cross sections was developed, which indicates that L sub p in Ni-diffused VPE n-GaAs is controlled by the E sub c - 0.39 eV defect level.

  15. Vessel enhancing diffusion: a scale space representation of vessel structures.

    PubMed

    Manniesing, Rashindra; Viergever, Max A; Niessen, Wiro J

    2006-12-01

    A method is proposed to enhance vascular structures within the framework of scale space theory. We combine a smooth vessel filter which is based on a geometrical analysis of the Hessian's eigensystem, with a non-linear anisotropic diffusion scheme. The amount and orientation of diffusion depend on the local vessel likeliness. Vessel enhancing diffusion (VED) is applied to patient and phantom data and compared to linear, regularized Perona-Malik, edge and coherence enhancing diffusion. The method performs better than most of the existing techniques in visualizing vessels with varying radii and in enhancing vessel appearance. A diameter study on phantom data shows that VED least affects the accuracy of diameter measurements. It is shown that using VED as a preprocessing step improves level set based segmentation of the cerebral vasculature, in particular segmentation of the smaller vessels of the vasculature.

  16. Overcoming diffusion-limited processes using enhanced advective fields

    SciTech Connect

    Rasmussen, T.C.

    1995-12-31

    Many subsurface cleanup activities focus on the remediation of organic contaminants using induced advective fields. Subsurface heterogeneities cause most advective transport to occur in more permeable zones, with transport from the lower permeability units being limited by diffusion to the higher permeable units. While diffusion rates can be enhanced using thermal sources, many of the treatment strategies, including pump and treat, vapor extraction and bioremediation, are limited by mass exchange rates between the higher and lower permeability sand and clay mixtures. Instead of relying on the enhancement of diffusion rates, it is proposed that remediation strategies should focus on the enhancement of induced advective transport rates through the lower permeability units. Injection-extraction strategies using crosshole and huff-and-puff methods are presented for maximizing advective transport through lower permeability units. Optimization of the design can incorporate diffusion-enhancement technologies, bionourishment, capillary confinement in the unsaturated zone, and DNAPL slurping.

  17. Substrate catalysis enhances single-enzyme diffusion.

    PubMed

    Muddana, Hari S; Sengupta, Samudra; Mallouk, Thomas E; Sen, Ayusman; Butler, Peter J

    2010-02-24

    We show that diffusion of single urease enzyme molecules increases in the presence of urea in a concentration-dependent manner and calculate the force responsible for this increase. Urease diffusion measured using fluorescence correlation spectroscopy increased by 16-28% over buffer controls at urea concentrations ranging from 0.001 to 1 M. This increase was significantly attenuated when urease was inhibited with pyrocatechol, demonstrating that the increase in diffusion was the result of enzyme catalysis of urea. Local molecular pH changes as measured using the pH-dependent fluorescence lifetime of SNARF-1 conjugated to urease were not sufficient to explain the increase in diffusion. Thus, a force generated by self-electrophoresis remains the most plausible explanation. This force, evaluated using Brownian dynamics simulations, was 12 pN per reaction turnover. These measurements demonstrate force generation by a single enzyme molecule and lay the foundation for a further understanding of biological force generation and the development of enzyme-driven nanomotors.

  18. 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.

  19. 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.

  20. Structural dynamics of hydrogen bonded methanol oligomers: Vibrational transient hole burning studies of spectral diffusion

    NASA Astrophysics Data System (ADS)

    Piletic, I. R.; Gaffney, K. J.; Fayer, M. D.

    2003-07-01

    Frequency resolved pump-probe experiments have been conducted on the deuterated hydroxyl stretch of methanol-d in a solution containing 0.8% methanol-d/23% methanol-h in carbon tetrachloride. Methanol-d molecules that both donate and receive hydrogen bonds have an inhomogeneously broadened hydroxyl stretch absorption line centered at 2487 cm-1. With a laser tuned to 2513 cm-1, the high-frequency side of the absorption spectrum is excited. The equilibration of the excited state peak and the ground-state hole results in the time-dependent shift in the frequency of the signal, which is used to monitor the dynamics of spectral diffusion. Model calculations were conducted to address the influence of spectral diffusion in the ground and excited states on the experimental observables when the vibrational lifetime is comparable to the spectral diffusion time. The model calculations illustrate the influence on the signal of absorbers in the ground state that have relaxed from the excited state. This aspect of the problem has not been addressed in previous descriptions of frequency resolved pump-probe spectroscopy. The calculations were used to fit the time-dependent peak maximum, resulting in a bi-exponential frequency-frequency correlation function, with a fast time constant of roughly 0.1 ps and a slower time constant of 1.6±0.3 ps. The observed dynamics have been compared with the predictions of dielectric continuum theory. The inability of a simple dielectric continuum theory to predict the observed spectral diffusion dynamics suggests that these dynamics do not result from the long-wavelength, collective orientational relaxation of the solvent. Instead the dynamics are attributed to fluctuations in the local hydrogen bond network, which is consistent with recent molecular-dynamics simulations of vibrational transient hole burning in water.

  1. A transient divided-bar method for simultaneous measurements of thermal conductivity and thermal diffusivity

    NASA Astrophysics Data System (ADS)

    Bording, Thue S.; Nielsen, Søren B.; Balling, Niels

    2016-04-01

    Accurate information on thermal conductivity and thermal diffusivity of materials is of central importance in relation to geoscience and engineering problems involving the transfer of heat. Within the geosciences, this applies to all aspects regarding the determination of terrestrial heat flow and subsurface temperature modelling. Several methods, including the classical divided-bar technique, are available for laboratory measurements of thermal conductivity, and much fewer for thermal diffusivity. We have generalized the divided-bar technique to the transient case, in which thermal conductivity and volumetric heat capacity, and thereby also thermal diffusivity, are measured simultaneously. As the density of samples is easily determined independently, specific heat capacity may also be determined. Finite element formulation provides a flexible forward solution for heat transfer across the bar and thermal properties are estimated by inverse Monte Carlo modelling. This methodology enables a proper quantification of experimental uncertainties on measured thermal properties. The developed methodology was applied to laboratory measurements of various materials, including a standard ceramic material and different rock samples, and measuring results were compared with results applying traditional steady-state divided-bar and an independent line-source method. All measurements show highly consistent results and with excellent reproducibility and high accuracy. For conductivity, uncertainty is typically 1-3 %, and for diffusivity uncertainty may be reduced to about 3-5 %. The main uncertainty originates from the presence of thermal contact resistance associated with the internal interfaces of the bar. They are not resolved during inversion, and it is highly important that they are minimized by careful sample preparation.

  2. Moderate MAS enhances local (1)H spin exchange and spin diffusion.

    PubMed

    Roos, Matthias; Micke, Peter; Saalwächter, Kay; Hempel, Günter

    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 nm(2)/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.

  3. 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, ...

  4. Modified anisotropic diffusion for image smoothing and enhancement

    NASA Astrophysics Data System (ADS)

    Tang, Zhong; Whitaker, Ross T.

    2001-05-01

    This paper discusses an improved nonlinear filtering approach based on anisotropic diffusion technique. This modified anisotropic diffusion method smooths along curve directions, i.e. the directions of level sets. The upwind scheme for level set is used to solve the diffusion equation. Compared with the conventional anisotropic diffusion, which depends only on the local gradient of intensities of the processed image, this modified scheme overcomes the defect of indefinite edge enhancement associated with Perona-Malik model while depressing noises in a better performance. Moreover, a multi-scale diffusion technique is applied to limit blurring by the presence of edges as measured at the scale of interest, so that accurate information about boundaries of objects could be preserved and small details that fall below the scale of interest be removed. Then an extension into vector-valued diffusion is also presented in this paper, which is capable of smoothing small objects while maintaining boundaries information in vector-valued images. Experiments on gray-scale and color images demonstrate the efficacy of this method in image smoothing as well as image enhancement.

  5. 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.

  6. SL9 Impacts and Simulations of Enhanced Radial Diffusion

    NASA Astrophysics Data System (ADS)

    de Pater, Imke; Brecht, Stephen H.

    2001-05-01

    We present detailed calculations on enhanced radial diffusion models and show that many, though not all, of the phenomena observed during the week that Comet Shoemaker-Levy 9 crashed into Jupiter can be explained by a sudden increase in the radial diffusion coefficient. Our calculations use estimates for the enhancement in the diffusion coefficient which come from self-consistent calculations of the electromagnetic turbulence generated by the impacts (Brecht et al. 2001, Icarus). These calculations suggest that the diffusion coefficient is enhanced at least a few million times above the nominal value during a short period of time (minutes). Our model shows that Jupiter's main radiation peaks brighten up much more than the high latitude regions, as is indeed observed following impacts during the first few days of the impact week. The calculations also suggest that the largest enhancements in intensity and largest inward shift of the radiation peaks occur at jovicentric longitudes ˜100°≲λ III≲250°, i.e., the longitude range where the B=constant contours are furthest from the planet. This longitude range agrees with the region where the strongest enhancements have indeed been observed. The dramatic increase in the intensity of the high latitude peaks following impacts which took place later in the week is attributed to a direct acceleration of electrons by the upward propagating shock. Finally, compared to the observations, the radial diffusion models predict much larger enhancements in the radiation peaks than observed. We attribute this, as well as the initial decrease in intensity on July 16-17, to a large loss of electrons caused by pitch angle scattering.

  7. Performance Enhancement of the NPS Transient Electromagnetic Scattering Laboratory

    DTIC Science & Technology

    1991-09-01

    MASTER OF SCIENCE IN ELECTRICAL ENGINEERING MASTER OF SCIENCE IN SYSTEMS ENGINEERING (ELECTRONIC WARFARE) from NAVAL POSTGRADUATE S OOL Author: JvAlo...Bresani Approved by: Michael A. Morgan, Thesis Advisor Jeffrey B. Knorr, Second Reader Michael A. Morgan, Chairman, Department of Electrical & Computer...SYSTEM REPRESENTATION ... .......... 13 B. MATHEMATICAL MODEL ......... ..... 15 C. TRANSIENT RESPONSE EVALUATION .. ......... . 17 IV. MEASUREMENT

  8. 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.

  9. 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

  10. 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.

  11. Enhanced Diffusion Weighting Generated by Selective Adiabatic Pulse Trains

    PubMed Central

    Sun, Ziqi; Bartha, Robert

    2007-01-01

    A theoretical description and experimental validation of the enhanced diffusion weighting generated by selective adiabatic full passage (AFP) pulse trains is provided. Six phantoms (Ph-1 to Ph-6) were studied on a 4T Varian/Siemens whole body MRI system. Phantoms consisted of 2.8 cm diameter plastic tubes containing a mixture of 10 μm ORGASOL polymer beads and 2 mM Gd-DTPA dissolved in 5% agar (Ph-1) or nickel(II) ammonium sulphate hexahydrate doped (56.3 mM – 0.8 mM) water solutions (Ph-2 to Ph-6). A customized localization by adiabatic selective refocusing (LASER) sequence containing slice selective AFP pulse trains and pulsed diffusion gradients applied in the phase encoding direction was used to measure 1H2O diffusion. The b-value associated with the LASER sequence was derived using the Bloch-Torrey equation. The apparent diffusion coefficients measured by LASER were comparable to those measured by a conventional pulsed gradient spin-echo (PGSE) sequence for all phantoms. Image signal intensity increased in Ph-1 and decreased in Ph-2 – Ph-6 as AFP pulse train length increased while maintaining a constant echo-time. These experimental results suggest that such AFP pulse trains can enhance contrast between regions containing microscopic magnetic susceptibility variations and homogeneous regions in which dynamic dephasing relaxation mechanisms are dominant. PMID:17600741

  12. 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.

  13. Low Energy Boron Implantation in Silicon: (1) Reduction of Channeling Tail by Careful Alignments. (2) Transient Diffusion during Rapid Thermal Annealing

    NASA Astrophysics Data System (ADS)

    Cho, Keelho

    The channeling tail in dopant distribution formed during low energy ion implantation into crystal targets is one of the major problems in shallow junction technology. The problem is more significant for implantation of light ions such as boron since it is difficult for light ions to render the crystalline target amorphous during room temperature implantation. In this thesis an attempt is made to minimize the channeling tail by implantation along a random equivalent direction following a careful alignment of the target. In order to analytically determine the random equivalent directions, critical angles for channeling are mapped on a stereogram. Boron ions with energies of 17 and 45 keV are implanted along specified directions determined from the map. The depth distribution of the dopant is profiled by SIMS and the effects of wafer orientation upon the channeling tail are noted. Industrial common use of a 7(DEGREES) tilt is not optimum. However, implantation with the wafer tilted at 5.5 (+OR-) 0.5(DEGREES) from the surface normal and rotated at 7.0 (+OR-) 0.5(DEGREES) from a (100) plane shows the least channel-tail compared to implantation along other directions. Rapid thermal annealing (RTA) is a promising annealing method for shallow junction formation. Transient enhanced diffusion of implanted boron is observed. Two different mechanisms for the boron diffusion enhancement have been suggested; namely the fast diffusion of boron interstitials or the enhancement by point defects generated during RTA. However, no experimental evidence exists so far. In this work experiments are performed with various annealing sequences of ('11)B implanted silicon combined with post-implantation of ('10)B or Si and SIMS profiling of the boron distribution. The data show that enhanced diffusion of boron during RTA is not caused by fast diffusion of boron interstitials. Rather, the enhancement is associated with an enhancement due to point defects generated during RTA. Two

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

    DOE PAGES

    Riedel, Clement; Gabizon, Ronen; Wilson, Christian A. M.; ...

    2014-12-10

    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 theorymore » 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). We find 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.« less

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

    SciTech Connect

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

    2014-12-10

    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). We find 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.

  16. Anomalous enhancement in interfacial perpendicular magnetic anisotropy through uphill diffusion.

    PubMed

    Das, Tanmay; Kulkarni, Prabhanjan D; Purandare, S C; Barshilia, Harish C; Bhattacharyya, Somnath; Chowdhury, Prasanta

    2014-06-17

    We observed interfacial chemical sharpening due to uphill diffusion in post annealed ultrathin multilayer stack of Co and Pt, which leads to enhanced interfacial perpendicular magnetic anisotropy (PMA). This is surprising as these elements are considered as perfectly miscible. This chemical sharpening was confirmed through quantitative energy dispersive x-ray (EDX) spectroscopy and intensity distribution of images taken on high angle annular dark field (HAADF) detector in Scanning Transmission Electron Microscopic (STEM) mode. This observation demonstrates an evidence of miscibility gap in ultrathin coherent Co/Pt multilayer stacks.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

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

    PubMed

    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.

  3. 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.

  4. Active Mediation of Plasmon Enhanced Localized Exciton Generation, Carrier Diffusion and Enhanced Photon Emission.

    PubMed

    Haq, Sharmin; Addamane, Sadhvikas; Kafle, Bijesh; Huang, Danhong; Balakrishnan, Ganesh; Habteyes, Terefe G

    2017-04-13

    Understanding the enhancement of charge carrier generation and their diffusion is imperative for improving the efficiency of optoelectronic devices particularly infrared photodetectors that are less developed than their visible counterpart. Here, using gold nanorods as model plasmonic systems, InAs quantum dots (QDs) embedded in an InGaAs quantum well as an emitter, and GaAs as an active mediator of surface plasmons for enhancing carrier generation and photon emission, the distance dependence of energy transfer and carrier diffusion have been investigated both experimentally and theoretically. Analysis of the QD emission enhancement as a function of distance reveals a Förster radius of 3.85 ± 0.15 nm, a near-field decay length of 4.8 ± 0.1 nm and an effective carrier diffusion length of 64.0 ± 3.0 nm. Theoretical study of the temporal-evolution of the electron-hole occupation number of the excited states of the QDs indicates that the emission enhancement trend is determined by the carrier diffusion and capture rates.

  5. 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.

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

    SciTech Connect

    Weber, Christopher Phillip

    2005-01-01

    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.

  7. 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.

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

    DOEpatents

    Cresap, Richard L.; Taylor, Carson W.; Kreipe, Michael J.

    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.

  9. 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

  10. 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.

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

    SciTech Connect

    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 the 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.

  12. Diffusion-like recommendation with enhanced similarity of objects

    NASA Astrophysics Data System (ADS)

    An, Ya-Hui; Dong, Qiang; Sun, Chong-Jing; Nie, Da-Cheng; Fu, Yan

    2016-11-01

    In the last decade, diversity and accuracy have been regarded as two important measures in evaluating a recommendation model. However, a clear concern is that a model focusing excessively on one measure will put the other one at risk, thus it is not easy to greatly improve diversity and accuracy simultaneously. In this paper, we propose to enhance the Resource-Allocation (RA) similarity in resource transfer equations of diffusion-like models, by giving a tunable exponent to the RA similarity, and traversing the value of this exponent to achieve the optimal recommendation results. In this way, we can increase the recommendation scores (allocated resource) of many unpopular objects. Experiments on three benchmark data sets, MovieLens, Netflix and RateYourMusic show that the modified models can yield remarkable performance improvement compared with the original ones.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Current-pulse-induced enhancement of transient photodetective effect in tilted manganite film.

    PubMed

    Ni, H; Zhao, K; Xi, J F; Feng, X; Xiang, W F; Zhao, S Q; Kong, Y-C; Wong, H K

    2012-12-17

    A current-pulse-induced enhancement effect of transient photovoltage has been discovered in tilted manganite La(2/3)Ca(1/3)MnO(3) film at room temperature. Here, by applying a pulsed current stimulus before pulse laser irradiation, we observed a significant enhancement of more than 50% in photovoltaic sensitivity. The current-pulse-induced photovoltaic enhancement can be tuned not only by the stimulating current value but also by the stimulating time. Such enhancement is time-sensitive and reproducible. This electrically induced effect, observed at room temperature, has both the benefit of a discovery in materials properties and the promise of applications for thin film manganites in photodetectors.

  19. 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.

  20. Catalytic systems used for polymerization, biomass conversion, and enhancing diffusion

    NASA Astrophysics Data System (ADS)

    Pong, Frances

    A significant amount of research has been dedicated towards the study and improvement of catalysts. A better understanding of how catalysts work can lead to developing more cost-efficient catalytic systems for a variety of applications. My research is focuses on catalytic systems used in three different fields, which are (i) organometallic polymerization catalysts, (ii) molecular motors and (iii) biomass conversion. Researchers have long studied and modified organometallic catalysts for use in the direct co- and homopolymerization of monomers with polar functional groups. The ability to add polar moieties to polymers, which can potentially yield materials with a wider range of physical properties, is highly desirable. In this study (i), a series of naphthoxyimine palladium(II) catalysts -- in which the naphthyl backbone had been functionalized with different moieties -- were synthesized and systematically studied to determine the ligand structure's impact on catalytic activity. The study showed that slight modifications of the naphthyl backbone led to significant changes in the polymer's molecular weight and polydispersity index. The catalysts were also displayed some ability to co-polymerize ethylene and functionalized norbornene. These positive results suggest that further exploration of naphthoxyimine palladium (II) catalysts may be fundamentally interesting. The effect of active, motile particles at the nanoscale has been vigorously researched during the past decade. By understanding how such active suspensions behave, researchers can gain new insights which can potentially provide new applications in many fields. Here (ii) the momentum transfer of active catalysts (Grubbs' 2nd generation catalyst with a hydrodynamic radius of 6A) to their immediate surroundings is observed in an organic suspension. This phenomenon, which has been coined "enhanced diffusion," has not been well studied at the angstrom scale until now. Diffusion-NMR spectroscopy surprisingly

  1. Convection-Enhanced Delivery for Diffuse Intrinsic Pontine Glioma Treatment.

    PubMed

    Zhou, Zhiping; Singh, Ranjodh; Souweidane, Mark M

    2017-01-01

    Convection-enhanced delivery (CED) is a technique designed to deliver drugs directly into the brain or tumors. Its ability to bypass the blood-brain barrier (BBB), one of the major hurdles in delivering drugs to the brain, has made it a promising drug delivery method for the treatment of primary brain tumors. A number of clinical trials utilizing CED of various therapeutic agents have been conducted to treat patients with supratentorial high-grade gliomas. Significant responses have been observed in certain patients in all of these trials. However, the insufficient ability to monitor drug distribution and pharmacokinetics hampers CED from achieving its potentials on a larger scale. Brainstem CED for diffuse intrinsic pontine glioma (DIPG) treatment is appealing because this tumor is compact and has no definitive treatment. The safety of brainstem CED has been established in small and large animals, and recently in early stage clinical trials. There are a few current clinical trials of brainstem CED in treating DIPG patients using targeted macromolecules such as antibodies and immunotoxins. Future advances for CED in DIPG treatment will come from several directions including: choosing the right agents for infusion; developing better agents and regimen for DIPG infusion; improving instruments and technique for easier and accurate surgical targeting and for allowing multisession or prolonged infusion to implement optimal time sequence; and better understanding and control of drug distribution, clearance and time sequence. CED-based therapies for DIPG will continue to evolve with new understanding of the technique and the disease.

  2. A diffusible signal from arbuscular mycorrhizal fungi elicits a transient cytosolic calcium elevation in host plant cells.

    PubMed

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

    2007-06-01

    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 Ca(2+) indicator aequorin to detect intracellular Ca(2+) 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 Ca(2+) were recorded, indicating that diffusible molecules released by the mycorrhizal fungus are perceived by host plant cells through a Ca(2+)-mediated signaling. Similar responses were also triggered by two Glomus isolates. The fungal molecules active in generating the Ca(2+) transient were constitutively released in the medium, and the induced Ca(2+) 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 Ca(2+) 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.

  3. Single-file diffusion of particles in a box: Transient behaviors

    NASA Astrophysics Data System (ADS)

    Delfau, Jean-Baptiste; Coste, Christophe; Saint Jean, Michel

    2012-06-01

    We consider a finite number of particles with soft-core interactions, subjected to thermal fluctuations and confined in a box with excluded mutual passage. Using numerical simulations, we focus on the influence of the longitudinal confinement on the transient behavior of the longitudinal mean squared displacement. We exhibit several power laws for its time evolution according to the confinement range and to the rank of the particle in the file. We model the fluctuations of the particles as those of a chain of springs and point masses in a thermal bath. Our main conclusion is that actual system dynamics can be described in terms of the normal oscillation modes of this chain. Moreover, we obtain complete expressions for the physical observables, in excellent agreement with our simulations. The correct power laws for the time dependency of the mean squared displacement in the various regimes are recovered, and analytical expressions of the prefactors according to the relevant parameters are given.

  4. 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.

  5. 3D transient electromagnetic simulation using a modified correspondence principle for wave and diffusion fields

    NASA Astrophysics Data System (ADS)

    Hu, Y.; Ji, Y.; Egbert, G. D.

    2015-12-01

    The fictitious time domain method (FTD), based on the correspondence principle for wave and diffusion fields, has been developed and used over the past few years primarily for marine electromagnetic (EM) modeling. Here we present results of our efforts to apply the FTD approach to land and airborne TEM problems which can reduce the computer time several orders of magnitude and preserve high accuracy. In contrast to the marine case, where sources are in the conductive sea water, we must model the EM fields in the air; to allow for topography air layers must be explicitly included in the computational domain. Furthermore, because sources for most TEM applications generally must be modeled as finite loops, it is useful to solve directly for the impulse response appropriate to the problem geometry, instead of the point-source Green functions typically used for marine problems. Our approach can be summarized as follows: (1) The EM diffusion equation is transformed to a fictitious wave equation. (2) The FTD wave equation is solved with an explicit finite difference time-stepping scheme, with CPML (Convolutional PML) boundary conditions for the whole computational domain including the air and earth , with FTD domain source corresponding to the actual transmitter geometry. Resistivity of the air layers is kept as low as possible, to compromise between efficiency (longer fictitious time step) and accuracy. We have generally found a host/air resistivity contrast of 10-3 is sufficient. (3)A "Modified" Fourier Transform (MFT) allow us recover system's impulse response from the fictitious time domain to the diffusion (frequency) domain. (4) The result is multiplied by the Fourier transformation (FT) of the real source current avoiding time consuming convolutions in the time domain. (5) The inverse FT is employed to get the final full waveform and full time response of the system in the time domain. In general, this method can be used to efficiently solve most time-domain EM

  6. Verification of high-order mixed FEM solution of transient Magnetic diffusion problems

    SciTech Connect

    Rieben, R; White, D A

    2005-05-12

    We develop and present high order mixed finite element discretizations of the time dependent electromagnetic diffusion equations for solving eddy current problems on 3D unstructured grids. The discretizations are based on high order H(grad), H(curl) and H(div) conforming finite element spaces combined with an implicit and unconditionally stable generalized Crank-Nicholson time differencing method. We develop three separate electromagnetic diffusion formulations, namely the E (electric field), H (magnetic field) and the A-{phi} (potential) formulations. For each formulation, we also provide a consistent procedure for computing the secondary variables F (current flux density) and B (magnetic flux density), as these fields are required for the computation of electromagnetic force and heating terms. We verify the error convergence properties of each formulation via a series of numerical experiments on canonical problems with known analytic solutions. The key result is that the different formulations are equally accurate, even for the secondary variables J and B, and hence the choice of which formulation to use depends mostly upon relevance of the Natural and Essential boundary conditions to the problem of interest. In addition, we highlight issues with numerical verification of finite element methods which can lead to false conclusions on the accuracy of the methods.

  7. Accurate simulation of transient landscape evolution by eliminating numerical diffusion: the TTLEM 1.0 model

    NASA Astrophysics Data System (ADS)

    Campforts, Benjamin; Schwanghart, Wolfgang; Govers, Gerard

    2017-01-01

    Landscape evolution models (LEMs) allow the study of earth surface responses to changing climatic and tectonic forcings. While much effort has been devoted to the development of LEMs that simulate a wide range of processes, the numerical accuracy of these models has received less attention. Most LEMs use first-order accurate numerical methods that suffer from substantial numerical diffusion. Numerical diffusion particularly affects the solution of the advection equation and thus the simulation of retreating landforms such as cliffs and river knickpoints. This has potential consequences for the integrated response of the simulated landscape. Here we test a higher-order flux-limiting finite volume method that is total variation diminishing (TVD-FVM) to solve the partial differential equations of river incision and tectonic displacement. We show that using the TVD-FVM to simulate river incision significantly influences the evolution of simulated landscapes and the spatial and temporal variability of catchment-wide erosion rates. Furthermore, a two-dimensional TVD-FVM accurately simulates the evolution of landscapes affected by lateral tectonic displacement, a process whose simulation was hitherto largely limited to LEMs with flexible spatial discretization. We implement the scheme in TTLEM (TopoToolbox Landscape Evolution Model), a spatially explicit, raster-based LEM for the study of fluvially eroding landscapes in TopoToolbox 2.

  8. Enhancing Cation Diffusion and Suppressing Anion Diffusion via Lewis-Acidic Polymer Electrolytes.

    PubMed

    Savoie, Brett M; Webb, Michael A; Miller, Thomas F

    2017-02-02

    Solid polymer electrolytes (SPEs) have the potential to increase both the energy density and stability of lithium-based batteries, but low Li(+) conductivity remains a barrier to technological viability. SPEs are designed to maximize Li(+) diffusivity relative to the anion while maintaining sufficient salt solubility. It is thus remarkable that poly(ethylene oxide) (PEO), the most widely used SPE, exhibits Li(+) diffusivity that is an order of magnitude smaller than that of typical counterions at moderate salt concentrations. We show that Lewis-basic polymers like PEO favor slow cation and rapid anion diffusion, while this relationship can be reversed in Lewis-acidic polymers. Using molecular dynamics, polyboranes are identified that achieve up to 10-fold increases in Li(+) diffusivities and significant decreases in anion diffusivities, relative to PEO in the dilute-ion regime. These results illustrate a general principle for increasing Li(+) diffusivity and transference number with chemistries that exhibit weaker cation and stronger anion coordination.

  9. Enhanced transient reactivity of an O-sputtered Au(111) surface

    SciTech Connect

    Biener, M M; Biener, J; Friend, C M

    2004-12-02

    The interaction of SO{sub 2} with oxygen-sputtered Au(111) surfaces ({theta}{sub oxygen} {le} 0.35 ML) was studied by monitoring the oxygen and sulfur coverages as a function of SO{sub 2} exposure. Two reaction regimes were observed: oxygen depletion followed by sulfur deposition. An enhanced, transient sulfur deposition rate is observed at the oxygen depletion point. This effect is specifically pronounced if the Au surface is continuously exposed to SO{sub 2}. The enhanced reactivity towards S deposition seems to be linked to the presence of highly reactive, under-coordinated Au atoms. Adsorbed oxygen appears to stabilize, but also to block these sites. In absence of the stabilization effect of adsorbed oxygen, i.e. at the oxygen depletion point, the enhanced reactivity decays on a timescale of a few minutes. These observations shed a new light on the catalytic reactivity of highly dispersed gold nanoparticles.

  10. Modelled isotopic fractionation and transient diffusive release of methane from potential subsurface sources on Mars

    NASA Astrophysics Data System (ADS)

    Stevens, Adam H.; Patel, Manish R.; Lewis, Stephen R.

    2017-01-01

    We calculate transport timescales of martian methane and investigate the effect of potential release mechanisms into the atmosphere using a numerical model that includes both Fickian and Knudsen diffusion. The incorporation of Knudsen diffusion, which improves on a Fickian description of transport given the low permeability of the martian regolith, means that transport timescales from sources collocated with a putative martian water table are very long, up to several million martian years. Transport timescales also mean that any temporally varying source process, even in the shallow subsurface, would not result in a significant, observable variation in atmospheric methane concentration since changes resulting from small variations in flux would be rapidly obscured by atmospheric transport. This means that a short-lived 'plume' of methane, as detected by Mumma et al. (2009) and Webster et al. (2014), cannot be reconciled with diffusive transport from any reasonable depth and instead must invoke alternative processes such as fracturing or convective plumes. It is shown that transport through the martian regolith will cause a significant change in the isotopic composition of the gas, meaning that methane release from depth will produce an isotopic signature in the atmosphere that could be significantly different than the source composition. The deeper the source, the greater the change, and the change in methane composition in both δ13C and δD approaches -1000 ‰ for sources at a depth greater than around 1 km. This means that signatures of specific sources, in particular the methane produced by biogenesis that is generally depleted in 13CH4 and CH3D, could be obscured. We find that an abiogenic source of methane could therefore display an isotopic fractionation consistent with that expected for biogenic source processes if the source was at sufficient depth. The only unambiguous inference that can be made from measurements of methane isotopes alone is a measured

  11. 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.

  12. Transient aggregation and long-time diffusion of bacterial suspensions in time periodic flows

    NASA Astrophysics Data System (ADS)

    Qin, Boyang; Winter, Rebecca; Gurjar, Madhura; Gagnon, David; Patteson, Alison; Arratia, Paulo

    2016-11-01

    In this talk, the transport dynamics of swimming bacteria in time-periodic flows is investigated in experiments and simulations. Experiments are performed by introducing swimming bacteria (Vibrio cholerae) in a low Reynolds number, two-dimensional flow driven electromagnetically. We observe two distinct transport regimes: (i) entrapment of bacteria inside vortex and near elliptic points and (ii) aggregation and subsequent transport along the flow manifolds. These time-dependent behaviors are set by the interaction between swimmer kinematics (e.g. speed, tumbling frequency, etc) and flow properties. Numerical simulation using a stochastic Langevin model are able to capture the main experimental results including the entrapment of bacteria near elliptic points and the rapid spreading along manifolds. Results show a significant reduction in long-time effective diffusion of the swimmer as vortex strength is increased. The conditions for bacterial entrapment in vortex flows are discussed.

  13. 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.

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

    DOE PAGES

    Rettig, L.; Cortés, R.; Chu, J. -H.; ...

    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

  15. Deciphering mechanisms of enhanced-retarded oxygen diffusion in doped Si

    NASA Astrophysics Data System (ADS)

    Timerkaeva, Dilyara; Caliste, Damien; Pochet, Pascal

    2013-12-01

    We study enhanced/retarded diffusion of oxygen in doped silicon by means of first principle calculations. We evidence that the migration energy of oxygen dimers cannot be significantly affected by strain, doping type, or concentration. We attribute the enhanced oxygen diffusion in p-doped silicon to reduced monomer migration energy and the retarded oxygen diffusion in Sb-doped to monomer trapping close to a dopant site. These two mechanisms can appear simultaneously for a given dopant leading to contradictory experimental results. More generally, our findings cast a new light on phenomena involving oxygen diffusion: precipitation, thermal donors formation, and light induced degradation.

  16. Evolution Nonlinear Diffusion-Convection PDE Models for Spectrogram Enhancement

    NASA Astrophysics Data System (ADS)

    Dugnol, B.; Fernández, C.; Galiano, G.; Velasco, J.

    2008-09-01

    In previous works we studied the application of PDE-based image processing techniques applied to the spectrogram of audio signals in order to improve the readability of the signal. In particular we considered the implementation of the nonlinear diffusive model proposed by Álvarez, Lions and Morel [1](ALM) combined with a convective term inspired by the differential reassignment proposed by Chassandre-Mottin, Daubechies, Auger and Flandrin [2]-[3]. In this work we consider the possibility of replacing the diffusive model of ALM by diffusive terms in divergence form. In particular we implement finite element approximations of nonlinear diffusive terms studied by Chen, Levine, Rao [4] and Antontsev, Shmarev [5]-[8] with a convective term.

  17. 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

  18. 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

  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. Phase-Resolved Heterodyne-Detected Transient Grating Enhances the Capabilities of 2D IR Echo Spectroscopy.

    PubMed

    Jin, Geun Young; Kim, Yung Sam

    2017-02-09

    2D IR echo spectroscopy, with high sensitivity and femtosecond time resolution, enables us to understand structure and ultrafast dynamics of molecular systems. Application of this experimental technique on weakly absorbing samples, however, had been limited by the precise and unambiguous phase determination of the echo signals. In this study, we propose a new experimental scheme that significantly increases the phase stability of the involved IR pulses. We have demonstrated that the incorporation of phase-resolved heterodyne-detected transient grating (PR-HDTG) spectroscopy greatly enhances the capabilities of 2D IR spectroscopy. The new experimental scheme has been used to obtain 2D IR spectra on weakly absorbing azide ions (N3(-)) in H2O (absorbance ∼0.025), free of phase ambiguity even at large waiting times. We report the estimated spectral diffusion time scale (1.056 ps) of azide ions in aqueous solution from the 2D IR spectra and the vibrational lifetime (750 ± 3 fs) and the reorientation time (1108 ± 24 fs) from the PR-HDTG spectra.

  1. Numerical Simulation of Transient Development of Flame, Temperature and Velocity under Reduced Gravity in a Methane Air Diffusion Flame

    NASA Astrophysics Data System (ADS)

    Bhowal, Arup Jyoti; Mandal, Bijan Kumar

    2017-02-01

    A methane air co flow diffusion flame has been numerically simulated with the help of an in-house developed code at normal gravity, 0.5 G, and 0.0001 G (microgravity) for the study of transient behavior of the flame in terms of flame shape, temperature profile and velocity (streamlines). The study indicates that lower is the gravity level, the higher is the time of early transience. The flame developments during transience are marked by the formation of a secondary flamelet at different heights above the primary flame at all gravity levels. The development of temperature profile at microgravity takes a much longer time to stabilize than the flame development. At normal gravity and 0.5 G gravity level, streamlines, during transience, show intermediate vortices which are finally replaced by recirculation of ambient air from the exit plane. At microgravity, neither any vortex nor any recirculation at any stage is observed. Centerline temperature plots, at all gravity levels during transience, demonstrate a secondary peak at some instants as a consequence of the secondary flamelet formation. The centerline velocity at microgravity decreases gradually during transience, unlike at other two gravity levels where the fall is very sharp and is indicative of negligible buoyancy at microgravity.

  2. Transient Enhancement of Inhibitory Synaptic Transmission in Hippocampal CA1 Pyramidal Neurons after Cerebral Ischemia

    PubMed Central

    Liang, Rui; Pang, Zhi-Ping; Deng, Ping; Xu, Zao C.

    2009-01-01

    Pyramidal neurons in hippocampal CA1 regions are highly sensitive to cerebral ischemia. Alterations of excitatory and inhibitory synaptic transmission may contribute to the ischemia-induced neuronal degeneration. However, little is known about the changes of GABAergic synaptic transmission in the hippocampus following reperfusion. We examined the GABAA receptor-mediated inhibitory postsynaptic currents (IPSCs) in CA1 pyramidal neurons 12 hours and 24 hours after transient forebrain ischemia. The amplitudes of evoked IPSCs (eIPSCs) were increased significantly 12 hours after ischemia and returned to control levels 24 hours following reperfusion. The potentiation of eIPSCs was accompanied by an increase of miniature IPSCs (mIPSCs) amplitude, and an enhanced response to exogenous application of GABA, indicating the involvement of postsynaptic mechanisms. Furthermore, there was no obvious change of the paired-pulse ratio (PPR) of eIPSCs and the frequency of mIPSCs, suggesting that the potentiation of eIPSCs might not be due to the increased presynaptic release. Blockade of adenosine A1 receptors led to a decrease of eIPSCs amplitude in post-ischemic neurons but not in control neurons, without affecting the frequency of mIPSCs and the PPR of eIPSCs. Thus, tonic activation of adenosine A1 receptors might, at least in part, contribute to the enhancement of inhibitory synaptic transmission in CA1 neurons after forebrain ischemia. The transient enhancement of inhibitory neurotransmission might temporarily protect CA1 pyramidal neurons, and delay the process of neuronal death after cerebral ischemia. PMID:19258028

  3. Parametric study of diffusion-enhancement networks for spatiotemporal grouping in real-time artificial vision

    NASA Astrophysics Data System (ADS)

    Cunningham, Robert K.; Waxman, Allen M.

    1991-06-01

    This is the first Annual Technical Summary of the MIT Lincoln Laboratory effort into the parametric study of diffusion-enhancement networks for spatiotemporal grouping in real-time artificial vision. Spatiotemporal grouping phenomena are examined in the context of static and time-varying imagery. Dynamics that exhibit static feature grouping on multiple scales as a function of time and long-range apparent motion between time-varying inputs are developed for a biologically plausible diffusion-enhancement bilayer. The architecture consists of a diffusion and a contrast-enhancement layer coupled by feedforward and feedback connections: input is provided by a separate feature extracting layer. The model is cast as an analog circuit that is realizable in VLSI, the parameters of which are selected to satisfy a psychophysical database on apparent motion. Specific topics include: neural networks, astrocyte glial networks, diffusion enhancement, long-range apparent motion, spatiotemporal grouping dynamics, and interference suppression.

  4. 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.

  5. Image segmentation and edge enhancement with stabilized inverse diffusion equations.

    PubMed

    Pollak, I; Willsky, A S; Krim, H

    2000-01-01

    We introduce a family of first-order multidimensional ordinary differential equations (ODEs) with discontinuous right-hand sides and demonstrate their applicability in image processing. An equation belonging to this family is an inverse diffusion everywhere except at local extrema, where some stabilization is introduced. For this reason, we call these equations "stabilized inverse diffusion equations" (SIDEs). Existence and uniqueness of solutions, as well as stability, are proven for SIDEs. A SIDE in one spatial dimension may be interpreted as a limiting case of a semi-discretized Perona-Malik equation. In an experiment, SIDE's are shown to suppress noise while sharpening edges present in the input signal. Their application to image segmentation is also demonstrated.

  6. 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

  7. Cholesterol enhances surface water diffusion of phospholipid bilayers

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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 1H 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

  8. 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.

  9. Enhancing scattering images for orientation recovery with diffusion map

    SciTech Connect

    Winter, Martin; Saalmann, Ulf; Rost, Jan M.

    2016-02-12

    We explore the possibility for orientation recovery in single-molecule coherent diffractive imaging with diffusion map. This algorithm approximates the Laplace-Beltrami operator, which we diagonalize with a metric that corresponds to the mapping of Euler angles onto scattering images. While suitable for images of objects with specific properties we show why this approach fails for realistic molecules. Here, we introduce a modification of the form factor in the scattering images which facilitates the orientation recovery and should be suitable for all recovery algorithms based on the distance of individual images. (C) 2016 Optical Society of America

  10. 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 43°C) and divided into three groups. They were then allowed to recover in a room at 24°C 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-1β instead of LPS, the 1-day post-HS rabbits did not respond with enhanced fevers. The plasma levels of TNFα 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.

  11. Transient stability enhancement of modern power grid using predictive Wide-Area Monitoring and Control

    NASA Astrophysics Data System (ADS)

    Yousefian, Reza

    This dissertation presents a real-time Wide-Area Control (WAC) designed based on artificial intelligence for large scale modern power systems transient stability enhancement. The WAC using the measurements available from Phasor Measurement Units (PMUs) at generator buses, monitors the global oscillations in the system and optimally augments the local excitation system of the synchronous generators. The complexity of the power system stability problem along with uncertainties and nonlinearities makes the conventional modeling non-practical or inaccurate. In this work Reinforcement Learning (RL) algorithm on the benchmark of Neural Networks (NNs) is used to map the nonlinearities of the system in real-time. This method different from both the centralized and the decentralized control schemes, employs a number of semi-autonomous agents to collaborate with each other to perform optimal control theory well-suited for WAC applications. Also, to handle the delays in Wide-Area Monitoring (WAM) and adapt the RL toward the robust control design, Temporal Difference (TD) is proposed as a solver for RL problem or optimal cost function. However, the main drawback of such WAC design is that it is challenging to determine if an offline trained network is valid to assess the stability of the power system once the system is evolved to a different operating state or network topology. In order to address the generality issue of NNs, a value priority scheme is proposed in this work to design a hybrid linear and nonlinear controllers. The algorithm so-called supervised RL is based on mixture of experts, where it is initialized by linear controller and as the performance and identification of the RL controller improves in real-time switches to the other controller. This work also focuses on transient stability and develops Lyapunov energy functions for synchronous generators to monitor the stability stress of the system. Using such energies as a cost function guarantees the convergence

  12. 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

  13. Real-time vessel image enhancement system with forward and backward diffusion based on DSP

    NASA Astrophysics Data System (ADS)

    Zhang, Zhao; Wang, An; Sun, Jian-Zhao; Xia, Ying-Wei; Zhang, Long; Liu, Yong

    2016-10-01

    In order to help medical personnel to make accurate clinical judgment, we built a DSP real-time image enhancement system to enhance and sharpening the hand vein distribution image. First, we use 760 nm and 960 nm mixed near-infrared light as the light source to decrease the skin scattering and absorption of the incident light, and gain a distinct original image. Then, we analyzed the vascular model in the multi-scale method, and using the vascular response function to take the place of gradient in diffusion equation, constructed the Forward And Backward Diffusion (FABD) coefficients. Then, we realized it in the DM642 DSP hardware platform; finally, the proposed enhancement algorithms implemented on the hardware platform, and compared with anisotropic diffusion algorithm and forward and backward diffusion algorithm. The results showed that, the proposed system to enhance the images standard deviation than the original increased by 11.4971, and increased by 2.2530 and 1.1500 than the anisotropic diffusion algorithm and forward and backward diffusion algorithm respectively. The proposed system's processing time was 28.0ms, and met real time requirements. The system was stable, reliable and met the medical needs.

  14. 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

  15. A hybrid preprocessing method using geometry based diffusion and elective enhancement filtering for pulmonary nodule detection

    NASA Astrophysics Data System (ADS)

    Dhara, Ashis K.; Mukhopadhyay, Sudipta

    2012-03-01

    The computer aided diagnostic (CAD) system has been developed to assist radiologist for early detection and analysis of lung nodules. For pulmonary nodule detection, image preprocessing is required to remove the anatomical structure of lung parenchyma and to enhance the visibility of pulmonary nodules. In this paper a hybrid preprocessing technique using geometry based diffusion and selective enhancement filtering have been proposed. This technique provides a unified preprocessing framework for solid nodule as well as ground glass opacity (GGO) nodules. Geometry based diffusion is applied to smooth the images by preserving the boundary. In order to improve the sensitivity of pulmonary nodule detection, selective enhancement filter is used to highlight blob like structure. But selective enhancement filter sometimes enhances the structures like blood vessel and airways other than nodule and results in large number of false positive. In first step, geometry based diffusion (GBD) is applied for reduction of false positive and in second step, selective enhancement filtering is used for further reduction of false negative. Geometry based diffusion and selective enhancement filtering has been used as preprocessing step separately but their combined effect was not investigated earlier. This hybrid preprocessing approach is suitable for accurate calculation of voxel based features. The proposed method has been validated on one public database named Lung Image Database Consortium (LIDC) containing 50 nodules (30 solid and 20 GGO nodule) from 30 subjects and one private database containing 40 nodules (25 solid and 15 GGO nodule) from 30 subjects.

  16. Enhanced Diffusion of Molecular Motors in the Presence of Adenosine Triphosphate and External Force

    NASA Astrophysics Data System (ADS)

    Shinagawa, Ryota; Sasaki, Kazuo

    2016-06-01

    The diffusion of a molecular motor in the presence of a constant external force is considered on the basis of a simple theoretical model. The motor is represented by a Brownian particle moving in a series of parabolic potentials placed periodically on a line, and the potential is switched stochastically from one parabola to another by a chemical reaction, which corresponds to the hydrolysis or synthesis of adenosine triphosphate (ATP) in motor proteins. It is found that the diffusion coefficient as a function of the force exhibits peaks. The mechanism of this diffusion enhancement and the possibility of observing it in F1-ATPase, a biological rotary motor, are discussed.

  17. Enhanced ionic diffusion in ionomer-filled nanopores

    SciTech Connect

    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.

  18. 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.

  19. 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.

  20. 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.

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

    PubMed

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

    2015-02-06

    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 µm 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.

  2. 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 µm 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

  3. Multispectral image fusion based on diffusion morphology for enhanced vision applications

    NASA Astrophysics Data System (ADS)

    Knyaz, Vladimir A.; Vygolov, Oleg V.; Vizilter, Yury V.; Zheltov, Sergey Y.; Vishnyakov, Boris V.

    2016-05-01

    Existing image fusion methods based on morphological image analysis, that expresses the geometrical idea of image shape as a label image, are quite sensitive to the quality of image segmentation and, therefore, not sufficiently robust to noise and high frequency distortions. On the other hand, there are a number of methods in the field of dimensionality reduction and data comparison that give possibility of avoiding an image segmentation step by using diffusion maps techniques. The paper proposes a new approach for multispectral image fusion based on the combination of morphological image analysis and diffusion maps theory (i.e. Diffusion Morphology). A new image fusion algorithm is described that uses a matched diffusion filtering procedure instead of morphological projection. The algorithm is implemented for a three channels Enhanced Vision System prototype. The comparative results of image fusion are shown on real images acquired in flight experiments.

  4. Obstruction enhances the diffusivity of self-propelled rod-like particles.

    PubMed

    Khalilian, Hamidreza; Fazli, Hossein

    2016-10-28

    Diffusion of self-propelled particles in the presence of randomly distributed obstacles is studied in three dimensions (3D) using Langevin dynamics simulations. It is found that depending on the magnitude of the propelling force and the particle aspect ratio, the diffusion coefficient can be a monotonically decreasing or a non-monotonic concave function of the obstructed volume fraction. Counterintuitive enhancement of the particle diffusivity with increasing the obstacle crowd is shown to be resulted from interplay of self-propulsion and anisotropy in the particle shape. On the propelling force-aspect ratio plane, regions that correspond to monotonic and non-monotonic dependence of the diffusivity on obstacle density are specified using the simulation results and the boundary between the two regions is described.

  5. Vacancy–Vacancy Interaction Induced Oxygen Diffusivity Enhancement in Undoped Nonstoichiometric Ceria

    SciTech Connect

    Yuan, Fenglin; Zhang, Yanwen; Weber, William J.

    2015-05-19

    In this paper, molecular dynamics simulations and molecular static calculations have been used to systematically study oxygen vacancy transport in undoped nonstoichiometric ceria. A strong oxygen diffusivity enhancement appears in the vacancy concentration range of 2–4% over the temperature range from 1000 to 2000 K. An Arrhenius ion diffusion mechanism by vacancy hopping along the (100) direction is unambiguously identified, and an increasing trend of both the oxygen migration barrier and the prefactor with increasing vacancy concentration is observed. Within the framework of classical diffusion theory, a weak concentration dependence of the prefactor in oxygen vacancy migration is shown to be crucial for explaining the unusual fast oxygen ion migration in the low concentration range and consequently the appearance of a maximum in oxygen diffusivity. Finally, a representative (100) direction interaction model is constructed to identify long-range vacancy–vacancy interaction as the structural origin of the positive correlation between oxygen migration barrier and vacancy concentration.

  6. Enhanced Translational Diffusion of 9,10-bis(phenylethynyl)anthracene (BPEA) in Polystyrene

    NASA Astrophysics Data System (ADS)

    Wang, Chia-Ying; Ediger, M. D.

    1997-03-01

    We have used a holographic fluorescence recovery after photobleaching (FRAP) techanique to measure translational diffusion coefficients of tracer levels of 9,10-bis(phenylethynyl)anthracene (BPEA) in polystyrene. Values for the diffusion coefficient DT ranged from 10-8 to 10-14 cm^2/sec over the temperature range T_g+90K to Tg (Tg = 373K). DT has a considerably weaker temperature dependence than matrix viscosity η. In contrast, the rotational correlation time τ c for BPEA has the same temperature dependence as η. At T_g, translational diffusion of BPEA is enhanced over rotation by 2.4 decades. These results support the idea that spatially heterogeneous dynamics are responsible for enhanced translation and are an important feature of dynamics at T_g.

  7. Enhanced Diffusion of Chlorinated Organic Compounds into Aquitards due to Cracking

    NASA Astrophysics Data System (ADS)

    Ayral, D.; Otero, M.; Chung, S.; Goltz, M. N.; Huang, J.; Demond, A. H.

    2012-12-01

    Despite great efforts, remediation of sites contaminated with dense non-aqueous phase liquids (DNAPLs) is very challenging because, even at residual saturations, DNAPLs can act as a long-term source for a dissolved phase contaminant plume. Current models consider the possibility of diffusion and storage of these compounds in unfractured low permeability layers. However, there is a need to consider the impact of cracks, whether naturally occurring or induced by the interaction between low permeable layers and DNAPLs. To evaluate the impact on diffusive fluxes, diffusion coefficients were measured in low permeability materials representative of aquitards at steady-state using the time-lag method. The experimental setup comprised silty soil, packed into a retaining ring, sandwiched in between two reservoirs. The analytical solution for the time-lag method requires constant conditions in the upper and lower reservoirs. The lower reservoir contained pure trichloroethylene (TCE), while the upper reservoir was maintained at a concentration of zero by bubbling air through it, sweeping TCE into toluene trap. In order to predict the flux, the experimental effective diffusion coefficients were used to calculate the flux through uncracked matrix whereas bulk diffusion coefficient was used to calculate flux through the cracks. By using the experimentally-obtained diffusion coefficients and experimentally-measured crack intensity factors (the ratio of the area of cracks to the uncracked area), the total flux was estimated over extended time periods. These calculations, based on experimental data, were used to evaluate if diffusive-based fluxes in the presence of cracks were significantly greater than in the case of diffusion into an uncracked matrix. The enhanced diffusive fluxes were evaluated to determine whether there is the potential for significantly greater storage in the low permeable layers in the case of cracks, or whether the possibility of advective fluxes into the

  8. Retinal Image Enhancement Using Robust Inverse Diffusion Equation and Self-Similarity Filtering

    PubMed Central

    Fu, Shujun; Xu, Lingzhong; Zhao, Kun; Zhang, Caiming

    2016-01-01

    As a common ocular complication for diabetic patients, diabetic retinopathy has become an important public health problem in the world. Early diagnosis and early treatment with the help of fundus imaging technology is an effective control method. In this paper, a robust inverse diffusion equation combining a self-similarity filtering is presented to detect and evaluate diabetic retinopathy using retinal image enhancement. A flux corrected transport technique is used to control diffusion flux adaptively, which eliminates overshoots inherent in the Laplacian operation. Feature preserving denoising by the self-similarity filtering ensures a robust enhancement of noisy and blurry retinal images. Experimental results demonstrate that this algorithm can enhance important details of retinal image data effectively, affording an opportunity for better medical interpretation and subsequent processing. PMID:27388503

  9. 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

  10. An evaluation of the contributions of diffusion and exchange in relaxation enhancement by MRI contrast agents

    NASA Astrophysics Data System (ADS)

    Gossuin, Yves; Roch, Alain; Muller, Robert N.; Gillis, Pierre

    2002-09-01

    Magnetic compounds are known to enhance water proton relaxation, either by diffusion or by proton exchange. An experimental procedure to distinguish both mechanisms is proposed and validated by relaxation measurements made in water-methanol solutions of Dy 3+, Ni 2+, Gd 3+, Tempo, and AMI-25. The test discriminates according to the character of the transverse relaxation in water-methanol solutions: a mono-exponential decay corresponds to diffusion, while a bi-exponential decay indicates the contribution of a proton exchange. The study of ferritin and akaganeite particle solutions confirms the occurrence of a proton exchange between protons belonging to hydroxyl groups of the particle surface and free water protons.

  11. 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 (ΔpHS) and decreases time constants for pHi changes (τpHi ) and pHS relaxations (τpHS ). 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) τpHS , 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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

    Lafranceschina, Jacopo; Wackerbauer, Renate

    2015-01-01

    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.

  14. 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.

  15. Enhanced diffusion self-stimulated by micro-algae in an active, aerotactic bacterial suspension

    NASA Astrophysics Data System (ADS)

    Peaudecerf, François; Goldstein, Raymond E.

    2014-11-01

    Suspensions of swimming bacteria form a new class of active fluids that generate complex phenomena. An ``active bath'' of bacteria for instance produces fluid flows which move passive colloids in a random-like walk, associated with an effective diffusion coefficient higher than for Brownian motion. The value of this enhanced diffusion coefficient depends on the local density of bacteria and their swimming behavior. However, with aerotactic, obligate aerobic bacteria such as B. subtilis, the local oxygen concentration impacts on the distribution of cells and their swimming behavior. We consider the specific case in which non-motile photosynthetic algal cells interacting with a B. subtilis suspension not only play the role of passive colloids, but also produce oxygen under light. We demonstrate that this new kind of active suspension, under heterogeneous illumination, can induce an effective negative phototaxis of the passive algal cells. We explain the origin of this novel phenomenon as the combination of algal oxygen production, diffusion, chemotaxis and motility switching in bacteria resulting in an heterogeneous enhanced diffusion. Finally, we present potential applications for algal cell mixing and sorting, that can inspire new methods for bioengineering. Supported by ERC, Raymond and Beverly Sackler Foundation, and Mines ParisTech.

  16. Enhanced exciton diffusion in an organic photovoltaic cell by energy transfer using a phosphorescent sensitizer

    NASA Astrophysics Data System (ADS)

    Luhman, Wade A.; Holmes, Russell J.

    2009-04-01

    We demonstrate enhanced exciton diffusion in an organic photovoltaic cell through the incorporation of a phosphorescent sensitizer. The increase in exciton diffusion length (LD) is realized using a composite electron donor layer consisting of a N ,N'-bis(naphthalen-1-yl)-N ,N'-bis(phenyl)-benzidine (NPD) host doped with the phosphorescent guest fac-tris(2-phenylpyridine) iridium [Ir(ppy)3]. The presence of the phosphor at low concentration allows for the population of the long-lived NPD triplet state and an increase in LD. An increase in the NPD LD from 6.5±0.3 to 11.8±0.6 nm is extracted from measurements of the external quantum efficiency for donor layers containing 5 wt % Ir(ppy)3. This enhancement leads to a ˜80% improvement in the power conversion efficiency relative to devices containing an undoped donor layer.

  17. Transient Liquid Phase Diffusion Bonding of 6061Al-15 wt.% SiC p Composite Using Mixed Cu-Ag Powder Interlayer

    NASA Astrophysics Data System (ADS)

    Roy, Pallab; Pal, Tapan Kumar; Maity, Joydeep

    2016-08-01

    Microstructure and shear strength of transient liquid phase diffusion bonded (560 °C, 0.2 MPa) 6061Al-15 wt.% SiCp extruded composite using a 50-µm-thick mixed Cu-Ag powder interlayer have been investigated. During isothermal solidification that took 2 h for completion, a ternary liquid phase formed due to diffusion of Cu and Ag in Al. Subsequent cooling formed a ternary phase mixture (α-Al + CuAl2 + Ag2Al) upon eutectic solidification. With mixed Cu-Ag powder interlayer, isothermal solidification was faster than for pure Al joints made using a 50-µm-thick Cu foil interlayer and for the composite joints made using a 50-µm-thick Cu foil/powder interlayer under similar conditions. The presence of brittle eutectic phase mixture (CuAl2 + Ag2Al) led to poor joint strength at short TLP bonding times. The mixture disappeared upon isothermal solidification with a 2-h hold yielding improved joint strength even with solidification shrinkage in the joint. Increased holding time (6 h) erased shrinkage via solid state diffusion and yielded the highest joint strength (87 MPa) and fair joint efficiency (83%).

  18. Parametric Study of Diffusion-Enhancement Networks for Spatiotemporal Grouping in Real-Time Artificial Vision

    DTIC Science & Technology

    1993-04-01

    Neuronal Networks 18 4.4 Interactions 19 4.5 Useful Biological Parameters 19 5. DIFFUSION-ENHANCEMENT BILAYER MODEL 21 5.1 DEB Network Architecture 21...substrate of the long-range communication process, while neuronal networks provide focusing to create and reinforce the localized percept. There are strong...later neuronal activity. Either of these mechanisms may be responsible for the long-range interactions simulated here. 4.3 Neuronal Networks Many cells

  19. Wavy membranes and the growth rate of a planar chemical garden: Enhanced diffusion and bioenergetics

    PubMed Central

    Ding, Yang; Batista, Bruno; Steinbock, Oliver; Cardoso, Silvana S. S.

    2016-01-01

    To model ion transport across protocell membranes in Hadean hydrothermal vents, we consider both theoretically and experimentally the planar growth of a precipitate membrane formed at the interface between two parallel fluid streams in a 2D microfluidic reactor. The growth rate of the precipitate is found to be proportional to the square root of time, which is characteristic of diffusive transport. However, the dependence of the growth rate on the concentrations of hydroxide and metal ions is approximately linear and quadratic, respectively. We show that such a difference in ionic transport dynamics arises from the enhanced transport of metal ions across a thin gel layer present at the surface of the precipitate. The fluctuations in transverse velocity in this wavy porous gel layer allow an enhanced transport of the cation, so that the effective diffusivity is about one order of magnitude higher than that expected from molecular diffusion alone. Our theoretical predictions are in excellent agreement with our laboratory measurements of the growth of a manganese hydroxide membrane in a microfluidic channel, and this enhanced transport is thought to have been needed to account for the bioenergetics of the first single-celled organisms. PMID:27486248

  20. Wavy membranes and the growth rate of a planar chemical garden: Enhanced diffusion and bioenergetics.

    PubMed

    Ding, Yang; Batista, Bruno; Steinbock, Oliver; Cartwright, Julyan H E; Cardoso, Silvana S S

    2016-08-16

    To model ion transport across protocell membranes in Hadean hydrothermal vents, we consider both theoretically and experimentally the planar growth of a precipitate membrane formed at the interface between two parallel fluid streams in a 2D microfluidic reactor. The growth rate of the precipitate is found to be proportional to the square root of time, which is characteristic of diffusive transport. However, the dependence of the growth rate on the concentrations of hydroxide and metal ions is approximately linear and quadratic, respectively. We show that such a difference in ionic transport dynamics arises from the enhanced transport of metal ions across a thin gel layer present at the surface of the precipitate. The fluctuations in transverse velocity in this wavy porous gel layer allow an enhanced transport of the cation, so that the effective diffusivity is about one order of magnitude higher than that expected from molecular diffusion alone. Our theoretical predictions are in excellent agreement with our laboratory measurements of the growth of a manganese hydroxide membrane in a microfluidic channel, and this enhanced transport is thought to have been needed to account for the bioenergetics of the first single-celled organisms.

  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

  2. Discovery and Characterization of Super-Enhancer Associated Dependencies in Diffuse Large B-Cell Lymphoma

    PubMed Central

    Chapuy, Bjoern; McKeown, Michael R.; Lin, Charles Y.; Monti, Stefano; Roemer, Margaretha G.M.; Qi, Jun; Rahl, Peter B.; Sun, Heather H.; Yeda, Kelly T.; Doench, John G; Reichert, Elaine; Kung, Andrew L.; Rodig, Scott J.; Young, Richard A.; Shipp, Margaret A.; Bradner, James E.

    2014-01-01

    Summary Diffuse Large B-Cell Lymphoma (DLBCL) is a biologically heterogeneous and clinically aggressive disease. Here, we explore the role of BET bromodomain proteins in DLBCL, using integrative chemical genetics and functional epigenomics. We observe highly asymmetric loading of BRD4 at enhancers, with approximately 33% of all BRD4 localizing to enhancers at 1.6% of occupied genes. These super-enhancers prove particularly sensitive to bromodomain inhibition, explaining the selective effect of BET inhibitors on oncogenic and lineage-specific transcriptional circuits. Functional study of genes marked by super-enhancers identifies DLBCLs dependent on OCA-B and suggests a strategy for discovering unrecognized cancer dependencies. Translational studies performed on a comprehensive panel of DLBCLs establish a therapeutic rationale for evaluating BET inhibitors in this disease. PMID:24332044

  3. 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.

  4. 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.

  5. Determination of Reduced Number and Suitable Locations of Fuzzy Logic Controlled Braking Resistors for Transient Stability Enhancement

    NASA Astrophysics Data System (ADS)

    Ali, Mohd. Hasan; Murata, Toshiaki; Tamura, Junji

    Braking resistor is known to be a very powerful tool for transient stability improvement in electric power systems. Usually, in a large power system braking resistors are placed at each generator terminal bus which requires a high installation as well as operation cost. Also, heavy computation is required for the controllers used for the switching of the resistors. From these viewpoints, this paper directs to the study of installation of reduced number of fuzzy logic controlled braking resistors at suitable locations for transient stability enhancement. Groups of coherent generators in the power system are determined. Then one braking resistor is installed in each of the coherent group and at each of the remaining generator terminal bus. Thus, the number of braking resistors is reduced and hence the installation and operation cost as well as computational burden for the controllers are minimized. The suitable location for the braking resistor in each coherent group of generators is determined according to the values of the transient stability index as calculated for a 3LG (Three-phase-to-ground) fault at the points near the generators of the coherent group without considering the braking resistors in the system. The effectiveness of the proposed method is demonstrated through EMTP simulations for the IEEJ West-10 machine model system.

  6. Enhanced Vapor-Phase Diffusion in Porous Media - LDRD Final Report

    SciTech Connect

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

    1999-01-01

    As part of the Laboratory-Directed Research and Development (LDRD) Program at Sandia National Laboratories, an investigation into the existence of enhanced vapor-phase diffusion (EVD) in porous media has been conducted. A thorough literature review was initially performed across multiple disciplines (soil science and engineering), and based on this review, the existence of EVD was found to be questionable. As a result, modeling and experiments were initiated to investigate the existence of EVD. In this LDRD, the first mechanistic model of EVD was developed which demonstrated the mechanisms responsible for EVD. The first direct measurements of EVD have also been conducted at multiple scales. Measurements have been made at the pore scale, in a two- dimensional network as represented by a fracture aperture, and in a porous medium. Significant enhancement of vapor-phase transport relative to Fickian diffusion was measured in all cases. The modeling and experimental results provide additional mechanisms for EVD beyond those presented by the generally accepted model of Philip and deVries (1957), which required a thermal gradient for EVD to exist. Modeling and experimental results show significant enhancement under isothermal conditions. Application of EVD to vapor transport in the near-surface vadose zone show a significant variation between no enhancement, the model of Philip and deVries, and the present results. Based on this information, the model of Philip and deVries may need to be modified, and additional studies are recommended.

  7. A transient assay for recombination demonstrates that Arabidopsis SNM1 and XRCC3 enhance non-homologous recombination.

    PubMed

    Johnson, R A; Hellens, R P; Love, D R

    2011-09-16

    Replacement of endogenous genes by homologous recombination is rare in plants; the majority of genetic modifications are the result of transforming DNA molecules undergoing random genomic insertion by way of non-homologous recombination. Factors that affect chromatin remodeling and DNA repair are thought to have the potential to enhance the frequency of homologous recombination in plants. Conventional tools to study the frequencies of genetic recombination often rely on stable transformation-based approaches, with these systems being rarely capable of high-throughput or combinatorial analysis. We developed a series of vectors that use chemiluminescent (LUC and REN) reporter genes to assay the relative frequency of homologous and non-homologous recombination in plants. These transient assay vectors were used to screen 14 candidate genes for their effects on recombination frequencies in Nicotiana benthamiana plants. Over-expression of Arabidopsis genes with sequence similarity to SNM1 from yeast and XRCC3 from humans enhanced the frequency of non-homologous recombination when assayed using two different donor vectors. Transient N. benthamiana leaf systems were also used in an alternative assay for preliminary measurements of homologous recombination frequencies, which were found to be enhanced by over-expression of RAD52, MIM and RAD51 from yeast, as well as CHR24 from Arabidopsis. The findings for the assays described here are in line with previous studies that analyzed recombination frequencies using stable transformation. The assays we report have revealed functions in non-homologous recombination for the Arabidopsis SNM1 and XRCC3 genes, so the suppression of these genes' expression offers a potential means to enhance the gene targeting frequency in plants. Furthermore, our findings also indicate that plant gene targeting frequencies could be enhanced by over-expression of RAD52, MIM, CHR24, and RAD51 genes.

  8. 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.

  9. Drug diffusion from disperse systems with a hydrophobically modified polysaccharide: Enhancer vs Franz cells.

    PubMed

    Lucero, María Jesús; Claro, Carmen; Casas, Marta; Jiménez-Castellanos, María Rosa

    2013-01-30

    This study assesses the capacity of a new hydrophobically modified polysaccharide -hydroxypropyl cellulose-methyl methacrylate - to control drug release in semisolid formulations. The dispersed systems contain the new polymer, Igepal CO520 as surfactant and theophylline as model drug at three concentrations (0.5, 1 and 1.5%, w/w). Drug release study shows that the systems containing 0.5% (w/w) of drug have faster release and higher diffusion coefficient than the other two concentrations. These results can be explained by two different structures ("relaxed" and "structured") found from a rheological point of view. Also, this paper compares two different devices for testing drug release and diffusion. It has been obtained more reliable and reproducible results with Enhancer Cell respect to Franz diffusion cell. In both cases, Fickian diffusion was the mechanism predominant for all systems. Finally, the utility of this polymer has been demonstrated to make three-dimensional gel structure and control theophylline release from systems in topical application.

  10. Vacancy–Vacancy Interaction Induced Oxygen Diffusivity Enhancement in Undoped Nonstoichiometric Ceria

    DOE PAGES

    Yuan, Fenglin; Zhang, Yanwen; Weber, William J.

    2015-05-19

    In this paper, molecular dynamics simulations and molecular static calculations have been used to systematically study oxygen vacancy transport in undoped nonstoichiometric ceria. A strong oxygen diffusivity enhancement appears in the vacancy concentration range of 2–4% over the temperature range from 1000 to 2000 K. An Arrhenius ion diffusion mechanism by vacancy hopping along the (100) direction is unambiguously identified, and an increasing trend of both the oxygen migration barrier and the prefactor with increasing vacancy concentration is observed. Within the framework of classical diffusion theory, a weak concentration dependence of the prefactor in oxygen vacancy migration is shown tomore » be crucial for explaining the unusual fast oxygen ion migration in the low concentration range and consequently the appearance of a maximum in oxygen diffusivity. Finally, a representative (100) direction interaction model is constructed to identify long-range vacancy–vacancy interaction as the structural origin of the positive correlation between oxygen migration barrier and vacancy concentration.« less

  11. An extended convection diffusion model for red blood cell-enhanced transport of thrombocytes and leukocytes

    NASA Astrophysics Data System (ADS)

    Hund, S. J.; Antaki, J. F.

    2009-10-01

    Transport phenomena of platelets and white blood cells (WBCs) are fundamental to the processes of vascular disease and thrombosis. Unfortunately, the dilute volume occupied by these cells is not amenable to fluid-continuum modeling, and yet the cell count is large enough that modeling each individual cell is impractical for most applications. The most feasible option is to treat them as dilute species governed by convection and diffusion; however, this is further complicated by the role of the red blood cell (RBC) phase on the transport of these cells. We therefore propose an extended convection-diffusion (ECD) model based on the diffusive balance of a fictitious field potential, Ψ, that accounts for the gradients of both the dilute phase and the local hematocrit. The ECD model was applied to the flow of blood in a tube and between parallel plates in which a profile for the RBC concentration field was imposed and the resulting platelet concentration field predicted. Compared to prevailing enhanced-diffusion models that dispersed the platelet concentration field, the ECD model was able to simulate a near-wall platelet excess, as observed experimentally. The extension of the ECD model depends only on the ability to prescribe the hematocrit distribution, and therefore may be applied to a wide variety of geometries to investigate platelet-mediated vascular disease and device-related thrombosis.

  12. 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

  13. 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.

  14. Varying total population enhances disease persistence: Qualitative analysis on a diffusive SIS epidemic model

    NASA Astrophysics Data System (ADS)

    Li, Huicong; Peng, Rui; Wang, Feng-Bin

    2017-01-01

    This paper performs qualitative analysis on an SIS epidemic reaction-diffusion system with a linear source in spatially heterogeneous environment. The main feature of our model lies in that its total population number varies, compared to its counterpart proposed by Allen et al. [2]. The uniform bounds of solutions are derived, based on which, the threshold dynamics in terms of the basic reproduction number is established and the global stability of the unique endemic equilibrium is discussed when spatial environment is homogeneous. In particular, the asymptotic profile of endemic equilibria is determined if the diffusion rate of the susceptible or infected population is small or large. The theoretical results show that a varying total population can enhance persistence of infectious disease, and therefore the disease becomes more threatening and harder to control.

  15. Enhanced Corrosion Resistance of a Transient Liquid Phase Bonded Nickel-Based Superalloy

    NASA Astrophysics Data System (ADS)

    Adebajo, O. J.; Ojo, O. A.

    2017-01-01

    Electrochemical analysis of corrosion performance of a transient liquid phase (TLP) bonded nickel-based superalloy was performed. The TLP bonding process resulted in significant reduction in corrosion resistance due to the formation of non-equilibrium solidification reaction micro-constituents within the joint region. The corrosion resistance degradation is completely eliminated through a new application of composite interlayer that had been previously considered unusable for joining single-crystal superalloys. The effectiveness of the new approach becomes more pronounced as the severity of environment increases.

  16. Predicting diffuse light-enhancement of GPP from plant functional traits: A multi-site synthesis

    NASA Astrophysics Data System (ADS)

    O'Halloran, T. L.; Barr, J. G.; Cook, B.; Goeckede, M.; Law, B. E.; Kueppers, L. M.; Riley, W. J.

    2013-12-01

    Diffuse light enhances canopy-scale photosynthesis because isotropic diffuse light penetrates deeper into the canopy, involves more leaf area in photosynthesis, and prevents the top of the canopy from becoming light saturated. However, the observational and modeling communities still have little understanding of how the 'Diffuse light Enhancement Effect' (DEE) varies across plant functional types or is constrained by factors such as nitrogen availability and plant structure. So far, variability in the strength of DEE across plant functional types (PFTs) remains poorly constrained, but canopy models indicate leaf area index (LAI) is a primary controller. While the very few existing multi-site, measurement-based syntheses of the DEE have provided valuable information on the variability of the DEE across a few plant functional types, no study has correlated measured metrics of DEE magnitude with direct measurements of canopy physical traits across a wide range of plant functional types. Here we report a new metric that is suitable for quantifying the DEE in both flux measurements and land surface models. We also present, for the first time, an examination of the relationship between the DEE metric and plant functional traits. Results from our 70+ site AmeriFlux and FLUXNET synthesis indicate that LAI is the strongest controller of the DEE across sites and PFTs, with less significant influences from foliar nitrogen, canopy height, and mean annual precipitation. Our results will enable direct evaluation and improvement of remote sensing algorithms and light use efficiency models (e.g. MODIS GPP), which to this point regard diffuse light fraction as a source of noise. Additionally, improving resolution of the DEE in prognostic land surface models, such as the Community Land Model (CLM), will greatly improve our ability to forecast future feedbacks to terrestrial carbon sequestration from changes in cloudiness and aerosol amount.

  17. 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.

  18. 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.

  19. Silver mirror for enhancing the detection ability of near-infrared diffuse reflectance spectroscopy.

    PubMed

    Wang, Cuicui; Wang, Shuyu; Cai, Wensheng; Shao, Xueguang

    2017-01-01

    Near-infrared diffuse reflectance spectroscopy (NIRDRS) has been proved to be a convenient and fast quantitative method for complex samples. The sensitivity or the detection limit, however, has been the obstacle in practical uses, although great efforts have been made through experimental and chemometric approaches. Due to the strong reflectivity of silver in near-infrared region, a novel method that utilizes silver layer as the adsorption substrate was developed to enhance the detection ability of NIRDRS in this study. For investigating the enhancement effect of the method, lysozyme samples with different concentrations were spotted on the silver layer and NIR spectra were measured. Then quantitative determination was performed using multivariate calibration. For comparison, the comparative experiment was performed using the copper sheet as the substrate. The results show that the intensity of diffuse reflection can be enhanced, and the background variation was reduced by taking the mirror layer as the substrate. A linear variation was obtained between the concentrations and the intensities of the spectral response at a wavenumber. Using multivariate calibration for quantitative analysis, the optimal PLS model was obtained. The maximum deviation of the prediction results can be as low as 12.8µg. Therefore, this study made a progress for NIRDRS technique in microanalysis.

  20. Extreme Mountain Ultra-Marathon Leads to Acute but Transient Increase in Cerebral Water Diffusivity and Plasma Biomarkers Levels Changes.

    PubMed

    Zanchi, Davide; Viallon, Magalie; Le Goff, Caroline; Millet, Grégoire P; Giardini, Guido; Croisille, Pierre; Haller, Sven

    2016-01-01

    Background: Pioneer studies demonstrate the impact of extreme sport load on the human brain, leading to threatening conditions for athlete's health such as cerebral edema. The investigation of brain water diffusivity, allowing the measurement of the intercellular water and the assessment of cerebral edema, can give a great contribution to the investigation of the effects of extreme sports on the brain. We therefore assessed the effect of supra-physiological effort (extreme distance and elevation changes) in mountain ultra-marathons (MUMs) athletes combining for the first time brain magnetic resonance imaging (MRI) and blood parameters. Methods:This longitudinal study included 19 volunteers (44.2 ± 9.5 years) finishing a MUM (330 km, elevation + 24000 m). Quantitative measurements of brain diffusion-weighted images (DWI) were performed at 3 time-points: Before the race, upon arrival and after 48 h. Multiple blood biomarkers were simultaneously investigated. Data analyses included brain apparent diffusion coefficient (ADC) and physiological data comparisons between three time-points. Results:The whole brain ADC significantly increased from baseline to arrival (p = 0.005) and then significantly decreased at recovery (p = 0.005) to lower values than at baseline (p = 0.005). While sodium, potassium, calcium, and chloride as well as hematocrit (HCT) changed over time, the serum osmolality remained constant. Significant correlations were found between whole brain ADC changes and osmolality (p = 0.01), cholesterol (p = 0.009), c-reactive protein (p = 0.04), sodium (p = 0.01), and chloride (p = 0.002) plasma level variations. Conclusions:These results suggest the relative increase of the inter-cellular volume upon arrival, and subsequently its reduction to lower values than at baseline, indicating that even after 48 h the brain has not fully recovered to its equilibrium state. Even though serum electrolytes may only indirectly indicate modifications at the brain level due

  1. Extreme Mountain Ultra-Marathon Leads to Acute but Transient Increase in Cerebral Water Diffusivity and Plasma Biomarkers Levels Changes

    PubMed Central

    Zanchi, Davide; Viallon, Magalie; Le Goff, Caroline; Millet, Grégoire P.; Giardini, Guido; Croisille, Pierre; Haller, Sven

    2017-01-01

    Background: Pioneer studies demonstrate the impact of extreme sport load on the human brain, leading to threatening conditions for athlete's health such as cerebral edema. The investigation of brain water diffusivity, allowing the measurement of the intercellular water and the assessment of cerebral edema, can give a great contribution to the investigation of the effects of extreme sports on the brain. We therefore assessed the effect of supra-physiological effort (extreme distance and elevation changes) in mountain ultra-marathons (MUMs) athletes combining for the first time brain magnetic resonance imaging (MRI) and blood parameters. Methods:This longitudinal study included 19 volunteers (44.2 ± 9.5 years) finishing a MUM (330 km, elevation + 24000 m). Quantitative measurements of brain diffusion-weighted images (DWI) were performed at 3 time-points: Before the race, upon arrival and after 48 h. Multiple blood biomarkers were simultaneously investigated. Data analyses included brain apparent diffusion coefficient (ADC) and physiological data comparisons between three time-points. Results:The whole brain ADC significantly increased from baseline to arrival (p = 0.005) and then significantly decreased at recovery (p = 0.005) to lower values than at baseline (p = 0.005). While sodium, potassium, calcium, and chloride as well as hematocrit (HCT) changed over time, the serum osmolality remained constant. Significant correlations were found between whole brain ADC changes and osmolality (p = 0.01), cholesterol (p = 0.009), c-reactive protein (p = 0.04), sodium (p = 0.01), and chloride (p = 0.002) plasma level variations. Conclusions:These results suggest the relative increase of the inter-cellular volume upon arrival, and subsequently its reduction to lower values than at baseline, indicating that even after 48 h the brain has not fully recovered to its equilibrium state. Even though serum electrolytes may only indirectly indicate modifications at the brain level due

  2. Stress enhanced self-diffusion in Si: Entropy effect in anisotropic elastic environment

    NASA Astrophysics Data System (ADS)

    Rushchanskii, Konstantin Z.; Pochet, Pascal; Lançon, Frédéric

    2008-04-01

    We present a multiscale analysis on stress enhanced vacancy-mediated diffusion in strained Si that explicitly includes the Jahn-Teller structural distortion around vacancies. The resulting anisotropy combined with biaxial deformations applied to (100)-oriented films lead to an orientational dependency of the vacancy formation energy. At finite temperatures, it results in a strong entropy effect when thermal activation allows occupancy of high energy defect states. Kinetic Lattice Monte Carlo simulations reveal that the effective activation energy is a strongly nonlinear function of strain at small deformations. At larger deformations, it becomes linear where as the occupancy of the excited states becomes insignificant.

  3. 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.

  4. Diffusion consistent calibrations for improved chemical imaging using nanoparticle enhanced optical sensors.

    PubMed

    Hakonen, Aron; Strömberg, Niklas

    2012-01-21

    A basic square root function was successfully used as a diffusion consistent calibration function that considers depletion mechanisms often occurring within optical chemical sensors. This continuous function improved image quality and simplified the calibration process. It may be a universal tool for the typical response function of reversible diffusion controlled sensing reactions. Further, we demonstrate that the gold nanoparticle interaction based ammonium fluorosensor is suitable for non-invasive high-resolution quantitative imaging of complex samples. The plasmon sensitized optical sensors were utilized as a bioanalytical tool for chemical imaging of natural degradation processes occurring in biological tissues. Analytical performance of the nanoparticle enhanced sensors confirmed superior sensitivity, reversibility, durability and overall image quality over non-doped sensing membranes. Although applied in a complex matrix of high potassium (major interferent) and very high sodium (interferent) excellent performance is achieved. The nanoparticle interaction/coextraction based sensing scheme utilized in this study is general and can be used for numerous ions, preferably combined with the diffusion consistent calibrations for superior analytical performance. A table with 44 commercially available ionophores is provided to guide potential users of this sensor configuration.

  5. 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.

  6. 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

  7. Understanding spatial and temporal patterning of astrocyte calcium transients via interactions between network transport and extracellular diffusion

    NASA Astrophysics Data System (ADS)

    Shtrahman, E.; Maruyama, D.; Olariu, E.; Fink, C. G.; Zochowski, M.

    2017-02-01

    Astrocytes form interconnected networks in the brain and communicate via calcium signaling. We investigate how modes of coupling between astrocytes influence the spatio-temporal patterns of calcium signaling within astrocyte networks and specifically how these network interactions promote coordination within this group of cells. To investigate these complex phenomena, we study reduced cultured networks of astrocytes and neurons. We image the spatial temporal patterns of astrocyte calcium activity and quantify how perturbing the coupling between astrocytes influences astrocyte activity patterns. To gain insight into the pattern formation observed in these cultured networks, we compare the experimentally observed calcium activity patterns to the patterns produced by a reduced computational model, where we represent astrocytes as simple units that integrate input through two mechanisms: gap junction coupling (network transport) and chemical release (extracellular diffusion). We examine the activity patterns in the simulated astrocyte network and their dependence upon these two coupling mechanisms. We find that gap junctions and extracellular chemical release interact in astrocyte networks to modulate the spatiotemporal patterns of their calcium dynamics. We show agreement between the computational and experimental findings, which suggests that the complex global patterns can be understood as a result of simple local coupling mechanisms.

  8. 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.

  9. Systematic analysis of diffuse rear reflectors for enhanced light trapping in silicon solar cells

    SciTech Connect

    Pfeffer, Florian; Eisenlohr, Johannes; Basch, Angelika; Hermle, Martin; Lee, Benjamin G.; Goldschmidt, Jan Christoph

    2016-08-01

    Simple diffuse rear reflectors can enhance the light path length of weakly absorbed near infrared light in silicon solar cells and set a benchmark for more complex and expensive light trapping structures like dielectric gratings or plasmonic particles. We analyzed such simple diffuse rear reflectors systematically by optical and electrical measurements. We applied white paint, TiO2 nanoparticles, white backsheets and a silver mirror to bifacial silicon solar cells and measured the enhancement of the external quantum efficiency for three different solar cell geometries: planar front and rear side, textured front and planar rear side, and textured front and rear side. We showed that an air-gap between the solar cell and the reflector decreases the absorption enhancement significantly, thus white paint and TiO2 nanoparticles directly applied to the rear cell surface lead to the highest short circuit current density enhancements. The short circuit current density gains for a 200 um thick planar solar cell reached up to 1.8 mA/cm2, compared to a non-reflecting black rear side and up to 0.8 mA/cm2 compared to a high-quality silver mirror rear side. For solar cells with textured front side the short circuit current density gains are in the range between 0.5 and 1.0 mA/cm2 compared to a non-reflecting black rear side and do not significantly depend on the angular characteristic of the rear side reflector but mainly on its absolute reflectance.

  10. First-principles study of hydrogen-enhanced phosphorus diffusion in silicon

    SciTech Connect

    The Anh, Le Lam, Pham Tien; Manoharan, Muruganathan; Matsumura, Hideki; Otsuka, Nobuo; Hieu Chi, Dam; Tien Cuong, Nguyen; Mizuta, Hiroshi

    2016-01-28

    We present a first-principles study on the interstitial-mediated diffusion process of neutral phosphorus (P) atoms in a silicon crystal with the presence of mono-atomic hydrogen (H). By relaxing initial Si structures containing a P atom and an H atom, we derived four low-energy P-H-Si defect complexes whose formation energies are significantly lower than those of P-Si defect complexes. These four defect complexes are classified into two groups. In group A, an H atom is located near a Si atom, whereas in group B, an H atom is close to a P atom. We found that the H atom pairs with P or Si atom and changes the nature bonding between P and Si atoms from out-of-phase conjugation to in-phase conjugation. This fact results in the lower formation energies compare to the cases without H atom. For the migration of defect complexes, we have found that P-H-Si defect complexes can migrate with low barrier energies if an H atom sticks to either P or Si atom. Group B complexes can migrate from one lattice site to another with an H atom staying close to a P atom. Group A complexes cannot migrate from one lattice site to another without a transfer of an H atom from one Si atom to another Si atom. A change in the structure of defect complexes between groups A and B during the migration results in a transfer of an H atom between P and Si atoms. The results for diffusion of group B complexes show that the presence of mono-atomic H significantly reduces the activation energy of P diffusion in a Si crystal, which is considered as a summation of formation energy and migration barrier energy, leading to the enhancement of diffusion of P atoms at low temperatures, which has been suggested by recent experimental studies.

  11. First-principles study of hydrogen-enhanced phosphorus diffusion in silicon

    NASA Astrophysics Data System (ADS)

    The Anh, Le; Tien Cuong, Nguyen; Lam, Pham Tien; Manoharan, Muruganathan; Mizuta, Hiroshi; Matsumura, Hideki; Otsuka, Nobuo; Hieu Chi, Dam

    2016-01-01

    We present a first-principles study on the interstitial-mediated diffusion process of neutral phosphorus (P) atoms in a silicon crystal with the presence of mono-atomic hydrogen (H). By relaxing initial Si structures containing a P atom and an H atom, we derived four low-energy P-H-Si defect complexes whose formation energies are significantly lower than those of P-Si defect complexes. These four defect complexes are classified into two groups. In group A, an H atom is located near a Si atom, whereas in group B, an H atom is close to a P atom. We found that the H atom pairs with P or Si atom and changes the nature bonding between P and Si atoms from out-of-phase conjugation to in-phase conjugation. This fact results in the lower formation energies compare to the cases without H atom. For the migration of defect complexes, we have found that P-H-Si defect complexes can migrate with low barrier energies if an H atom sticks to either P or Si atom. Group B complexes can migrate from one lattice site to another with an H atom staying close to a P atom. Group A complexes cannot migrate from one lattice site to another without a transfer of an H atom from one Si atom to another Si atom. A change in the structure of defect complexes between groups A and B during the migration results in a transfer of an H atom between P and Si atoms. The results for diffusion of group B complexes show that the presence of mono-atomic H significantly reduces the activation energy of P diffusion in a Si crystal, which is considered as a summation of formation energy and migration barrier energy, leading to the enhancement of diffusion of P atoms at low temperatures, which has been suggested by recent experimental studies.

  12. 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

  13. Coregistration of dynamic contrast enhanced MRI and broadband diffuse optical spectroscopy for characterizing breast cancer.

    PubMed

    Hsiang, David; Shah, Natasha; Yu, Hon; Su, Min-Ying; Cerussi, Albert; Butler, John; Baick, Choong; Mehta, Rita; Nalcioglu, Orhan; Tromberg, Bruce

    2005-10-01

    A hand-held scanning probe based on broadband Diffuse Optical Spectroscopy (DOS) was used in combination with dynamic contrast enhanced MRI (DCE-MRI) to quantitatively characterize locally-advanced breast cancers in six patients. Measurements were performed sequentially using external fiducial markers for co-registration. Tumor patterns were categorized according to MRI morphological data, and 3D DCE-MRI slices were converted into a volumetric matrix with isotropic voxels to generate views that coincided with the DOS scanning plane. Tumor volume and depth at each DOS measurement site were determined, and a tissue optical index (TOI) that reflects both angiogenic and stromal characteristics was derived from broadband DOS data. In all six cases, optical scans showed significant TOI contrast corresponding to MRI morphological information. Sharp TOI peaks were recovered for well-circumscribed masses. A reduction in TOI was found inside a tumor with a necrotic center. A broadened peak was observed for a diffuse tumor pattern, and an inflammatory septal case provided two TOI peaks that correlated qualitatively with MRI enhancement. These results provide qualitative confirmation of the common signal origin and complementary information content that can be achieved by combining optical and MR imaging for breast cancer detection and clinical management.

  14. Transient enhancement of spike-evoked calcium signaling by a serotonergic interneuron.

    PubMed

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

    2008-11-01

    Enhancement of presynaptic Ca(2+) 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 Ca(2+) 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 Ca(2+) signals in C2 without altering basal Ca(2+) 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 Ca(2+) 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 Ca(2+) 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 Ca(2+) signals in the distal neurites of C2.

  15. Energy deprivation transiently enhances rhythmic inhibitory events in the CA3 hippocampal network in vitro.

    PubMed

    Gee, C E; Benquet, P; Demont-Guignard, S; Wendling, F; Gerber, U

    2010-07-14

    Oxygen glucose deprivation (OGD) leads to rapid suppression of synaptic transmission. Here we describe an emergence of rhythmic activity at 8 to 20 Hz in the CA3 subfield of hippocampal slice cultures occurring for a few minutes prior to the OGD-induced cessation of evoked responses. These oscillations, dominated by inhibitory events, represent network activity, as they were abolished by tetrodotoxin. They were also completely blocked by the GABAergic antagonist picrotoxin, and strongly reduced by the glutamatergic antagonist NBQX. Applying CPP to block NMDA receptors had no effect and neither did UBP302, an antagonist of GluK1-containing kainate receptors. The gap junction blocker mefloquine disrupted rhythmicity. Simultaneous whole-cell voltage-clamp recordings from neighboring or distant CA3 pyramidal cells revealed strong cross-correlation of the incoming rhythmic activity. Interneurons in the CA3 area received similar correlated activity. Interestingly, oscillations were much less frequently observed in the CA1 area. These data, together with the observation that the recorded activity consists primarily of inhibitory events, suggest that CA3 interneurons are important for generating these oscillations. This transient increase in inhibitory network activity during OGD may represent a mechanism contributing to the lower vulnerability to ischemic insults of the CA3 area as compared to the CA1 area.

  16. Extended gene expression by medium exchange and repeated transient transfection for recombinant protein production enhancement.

    PubMed

    Cervera, Laura; Gutiérrez-Granados, Sonia; Berrow, Nicholas Simon; Segura, Maria Mercedes; Gòdia, Francesc

    2015-05-01

    Production of recombinant products in mammalian cell cultures can be achieved by stable gene expression (SGE) or transient gene expression (TGE). The former is based on the integration of a plasmid DNA into the host cell genome allowing continuous gene expression. The latter is based on episomal plasmid DNA expression. Conventional TGE is limited to a short production period of usually about 96 h, therefore limiting productivity. A novel gene expression approach termed extended gene expression (EGE) is explored in this study. The aim of EGE is to prolong the production period by the combination of medium exchange and repeated transfection of cell cultures with plasmid DNA to improve overall protein production. The benefit of this methodology was evaluated for the production of three model recombinant products: intracellular GFP, secreted GFP, and a Gag-GFP virus-like particles (VLPs). Productions were carried out in HEK 293 cell suspension cultures grown in animal-derived component free media using polyethylenimine (PEI) as transfection reagent. Transfections were repeated throughout the production process using different plasmid DNA concentrations, intervals of time, and culture feeding conditions in order to identify the best approach to achieve sustained high-level gene expression. Using this novel EGE strategy, the production period was prolonged between 192 and 240 h with a 4-12-fold increase in production levels, depending on the product type considered.

  17. 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.

  18. Enhancement of electron-positron pair creation due to transient excitation of field-induced bound states

    NASA Astrophysics Data System (ADS)

    Jiang, M.; Lv, Q. Z.; Sheng, Z. M.; Grobe, R.; Su, Q.

    2013-04-01

    We study the creation of electron-positron pairs induced by two spatially separated electric fields that vary periodically in time. The results are based on large-scale computer simulations of the time-dependent Dirac equation in reduced spatial dimensions. When the separation of the fields is very large, the pair creation is caused by multiphoton transitions and mainly determined by the frequency of the fields. However, for small spatial separations a coherence effect can be observed that can enhance or reduce the particle yield compared to the case of two infinitely separated fields. If the travel time for a created electron or positron between both field locations becomes comparable to the period of the oscillating fields, we observe peaks in the energy spectrum which can be explained in terms of field-induced transient bound states.

  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; Muñuzuri, A P; Pérez-Muñuzuri, 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.

  20. 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.

  1. Diffusion of Paramagnetically Labeled Proteins in Cartilage: Enhancement of the 1-D NMR Imaging Technique

    NASA Astrophysics Data System (ADS)

    Foy, Brent D.; Blake, Joseph

    2001-01-01

    Quantifying the diffusive transport of large molecules in avascular cartilage tissue is important both for planning potential pharamacological treatments and for gaining insight into the molecular-scale structure of cartilage. In this work, the diffusion coefficients of gadolinium-DTPA and Gd-labeled versions of four proteins-lysozyme, trypsinogen, ovalbumin, and bovine serum albumin (BSA) with molecular weights of 14,300, 24,000, 45,000, and 67,000, respectively-have been measured in healthy and degraded calf cartilage. The experimental technique relies on the effect of the paramagnetic on the relaxation properties of the surrounding water, combined with the time course of a 1-dimensional spatial profile of the water signal in the cartilage sample. The enhanced technique presented here does not require a prior measurement of the relaxivity of the paramagnetic compound in the sample of interest. The data are expressed as the ratio of the diffusion coefficient of a compound in cartilage to its diffusion coefficient in water. For healthy cartilage, this ratio was 0.34 ± 0.07 for Gd-DTPA, the smallest compound, and fell to 0.3 ± 0.1 for Gd-lysozyme, 0.08 ± 0.04 for Gd-trypsinogen, and 0.07 ± 0.04 for Gd-ovalbumin. Gd-BSA did not appear to enter healthy cartilage tissue beyond a surface layer. After the cartilage had been degraded by 24-h trypsinization, these ratios were 0.60 ± 0.03 for Gd-DTPA, 0.40 ± 0.08 for Gd-lysozyme, 0.42 ± 0.09 for Gd-trypsinogen, 0.16 ± 0.14 for Gd-ovalbumin, and 0.11 ± 0.05 for Gd-BSA. Thus, degradation of the cartilage led to increases in the diffusion coefficient of up to fivefold for the Gd-labeled proteins. These basic transport parameters yield insights on the nature of pore sizes and chemical-matrix interactions in the cartilage tissue and may prove diagnostically useful for identifying the degree and nature of damage to cartilage.

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

    PubMed

    Pérez-Gómez, 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 μM) 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 μM, 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.

  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

    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.

  5. 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.

  6. Diffusion of Chlorinated Organic Contaminants into Aquitards: Enhanced by the Flocculation of Clay?

    NASA Astrophysics Data System (ADS)

    Ayral, D.; Otero, M.; Demond, A. H.; Goltz, M. N.; Huang, J.

    2011-12-01

    Waste organic contaminants stored in low permeability subsurface layers serve as long-term sources for dissolved phase contaminant plumes. Current models consider the movement into and out of aquitards or other low permeability layers to occur through transverse diffusion. Yet, field evidence suggests higher transport rates of contaminants than can be accounted for by diffusion alone. Waste organic liquids contain both organic liquid solvents as well as surface-active solutes. Measurements using montmorillonite in contact with pure chlorinated organic liquids such as trichloroethylene (TCE) showed that the basal spacing is similar to the case of montmorillonite in contact with air, thus suggesting that these fluids have similar flocculation effects. On the other hand, the basal spacing increased in contact with aqueous surfactant solutions. Measurements of the basal spacing in contact with a TCE waste gave the same results as with pure TCE, suggesting that effect on basal spacing is dominated by the organic solvent matrix rather than by the surfactant content. Since flocculation can lead to cracking, this behavior suggests that aquitards underlying aquifers contaminated with chlorinated organic wastes may develop cracks, thus enhancing the transport into low permeability layers.

  7. On the stabilizing role of species diffusion in chemical enhanced oil recovery

    NASA Astrophysics Data System (ADS)

    Daripa, Prabir; Gin, Craig

    2015-11-01

    In this talk, the speaker will discuss a problem on the stability analysis related to the effect of species diffusion on stabilization of fingering in a Hele-Shaw model of chemical enhanced oil recovery. The formulation of the problem is motivated by a specific design principle of the immiscible interfaces in the hope that this will lead to significant stabilization of interfacial instabilities, there by improving oil recovery in the context of porous media flow. Testing the merits of this hypothesis poses some challenges which will be discussed along with some numerical results based on current formulation of this problem. Several open problems in this context will be discussed. This work is currently under progress. Supported by the grant NPRP 08-777-1-141 from the Qatar National Research Fund (a member of The Qatar Foundation).

  8. In situ synthesis of nano silver/lecithin on wool: enhancing nanoparticles diffusion.

    PubMed

    Barani, Hossein; Montazer, Majid; Samadi, Nasrin; Toliyat, Tayebeh

    2012-04-01

    Silver nanoparticles are being used increasingly in various applications because of their antibacterial properties. It is necessary to lower their direct contact with the skin by embedding in a polymer reducing their side effects. In this study, silver nanoparticles were synthesized inside the wool fibers acted as a polyfunctional ligands. Lecithin as a biological lipid was used to enhance the diffusion of silver ions and nanoparticles into the wool fibers reducing cytotoxicity effects of the nano silver loaded wool. The highest loading efficiency and inhibition zone was observed on the wool with the highest lecithin concentration. Presence of lecithin reduced the rate of nano silver release which results in decreasing the specific coefficient of lethality. Also, the extracted solution of the synthesized silver nanoparticles on the wool has not altered the morphology of L929 fibroblast cells.

  9. 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

  10. Contrast Enhancement without Transient Map Expansion for Species-Specific Vocalizations in Core Auditory Cortex during Learning

    PubMed Central

    Shepard, Kathryn N.; Chong, Kelly K.

    2016-01-01

    Tonotopic map plasticity in the adult auditory cortex (AC) is a well established and oft-cited measure of auditory associative learning in classical conditioning paradigms. However, its necessity as an enduring memory trace has been debated, especially given a recent finding that the areal expansion of core AC tuned to a newly relevant frequency range may arise only transiently to support auditory learning. This has been reinforced by an ethological paradigm showing that map expansion is not observed for ultrasonic vocalizations (USVs) or for ultrasound frequencies in postweaning dams for whom USVs emitted by pups acquire behavioral relevance. However, whether transient expansion occurs during maternal experience is not known, and could help to reveal the generality of cortical map expansion as a correlate for auditory learning. We thus mapped the auditory cortices of maternal mice at postnatal time points surrounding the peak in pup USV emission, but found no evidence of frequency map expansion for the behaviorally relevant high ultrasound range in AC. Instead, regions tuned to low frequencies outside of the ultrasound range show progressively greater suppression of activity in response to the playback of ultrasounds or pup USVs for maternally experienced animals assessed at their pups’ postnatal day 9 (P9) to P10, or postweaning. This provides new evidence for a lateral-band suppression mechanism elicited by behaviorally meaningful USVs, likely enhancing their population-level signal-to-noise ratio. These results demonstrate that tonotopic map enlargement has limits as a construct for conceptualizing how experience leaves neural memory traces within sensory cortex in the context of ethological auditory learning. PMID:27957529

  11. Enhanced excitatory synaptic network activity following transient group I metabotropic glutamate activation.

    PubMed

    Pan, Y-Z; Rutecki, P A

    2014-09-05

    Prolonged activation of group I metabotropic glutamate receptors (mGluRs) using the agonist (S)-3,5-dihydroxyphenylglycine (DHPG) produces long-lasting changes in the CA3 region of the hippocampal slice. Changes in CA3 pyramidal neuron excitability that follow DHPG exposure result in abnormal network activity manifest by epileptiform activity that consists of interictal and longer lasting ictal epileptiform discharges. In this study we evaluated changes in synaptic activity of CA3 neurons in rat hippocampal slices that occurred after exposure to DHPG. Whole-cell voltage-clamp recordings were made from visually identified CA3 neurons in control artificial cerebrospinal fluid at times greater than 1h after DHPG exposure. Compared to control slices, neurons from slices exposed to DHPG showed enhanced amplitude and frequency of spontaneously occurring excitatory postsynaptic currents (EPSCs) without a concurrent change in inhibitory postsynaptic current (IPSC) amplitude or frequency. Miniature EPSCs were not affected by DHPG exposure but mIPSCs occurred less frequently and were of reduced amplitude. IPSCs recorded in the presence of ionotropic glutamate receptor blockade occurred less frequently in neurons that had been exposed to DHPG. Monosynaptic-evoked IPSPs were also reduced in amplitude in neurons that had been exposed to DHPG. Taken together, these findings demonstrated an enhanced network excitability of the CA3 region and failure of compensatory synaptic inhibition. We propose that prolonged activation of group I mGluR that may occur under conditions of pathological glutamate release results in long-lasting changes in CA3 synaptic network activity and epileptiform activity driven by excessive synaptic excitation.

  12. Co-transport of polycyclic aromatic hydrocarbons by motile microorganisms leads to enhanced mass transfer under diffusive conditions.

    PubMed

    Gilbert, Dorothea; Jakobsen, Hans H; Winding, Anne; Mayer, Philipp

    2014-04-15

    The environmental chemodynamics of hydrophobic organic chemicals (HOCs) are often rate-limited by diffusion in stagnant boundary layers. This study investigated whether motile microorganisms can act as microbial carriers that enhance mass transfer of HOCs through diffusive boundary layers. A new experimental system was developed that allows (1) generation of concentration gradients of HOCs under the microscope, (2) exposure and direct observation of microorganisms in such gradients, and (3) quantification of HOC mass transfer. Silicone O-rings were integrated into a Dunn chemotaxis chamber to serve as sink and source for polycyclic aromatic hydrocarbons (PAHs). This resulted in stable concentration gradients in water (>24 h). Adding the model organism Tetrahymena pyriformis to the experimental system enhanced PAH mass transfer up to hundred-fold (benzo[a]pyrene). Increasing mass transfer enhancement with hydrophobicity indicated PAH co-transport with the motile organisms. Fluorescence microscopy confirmed such transport. The effective diffusivity of T. pyriformis, determined by video imaging microscopy, was found to exceed molecular diffusivities of the PAHs up to four-fold. Cell-bound PAH fractions were determined to range from 28% (naphthalene) to 92% (pyrene). Motile microorganisms can therefore function as effective carriers for HOCs under diffusive conditions and might significantly enhance mobility and availability of HOCs.

  13. 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

  14. Structure enhancement diffusion and contour extraction for electron tomography of mitochondria

    PubMed Central

    Miller, Michelle; Blomgren, Peter

    2009-01-01

    The interpretation and measurement of the architectural organization of mitochondria depend heavily upon the availability of good software tools for filtering, segmenting, extracting, measuring, and classifying the features of interest. Images of mitochondria contain many flow-like patterns and they are usually corrupted by large amounts of noise. Thus, it is necessary to enhance them by denoising and closing interrupted structures. We introduce a new approach based on anisotropic nonlinear diffusion and bilateral filtering for electron tomography of mitochondria. It allows noise removal and structure closure at certain scales, while preserving both the orientation and magnitude of discontinuities without the need for threshold switches. This technique facilitates image enhancement for subsequent segmentation, contour extraction, and improved visualization of the complex and intricate mitochondrial morphology. We perform the extraction of the structure-defining contours by employing a variational level set formulation. The propagating front for this approach is an approximate signed distance function which does not require expensive re-initialization. The behavior of the combined approach is tested for visualizing the structure of a HeLa cell mitochondrion and the results we obtain are very promising. PMID:19254765

  15. 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+).

  16. Cilostazol attenuates ischemic brain injury and enhances neurogenesis in the subventricular zone of adult mice after transient focal cerebral ischemia.

    PubMed

    Tanaka, Y; Tanaka, R; Liu, M; Hattori, N; Urabe, T

    2010-12-29

    Evidence suggests that neurogenesis occurs in the adult mammalian brain, and that various stimuli, for example, ischemia/hypoxia, enhance the generation of neural progenitor cells in the subventricular zone (SVZ) and their migration into the olfactory bulb. In a mouse stroke model, focal ischemia results in activation of neural progenitor cells followed by their migration into the ischemic lesion. The present study assessed the in vivo effects of cilostazol, a type 3 phosphodiesterase inhibitor known to activate the cAMP-responsive element binding protein (CREB) signaling, on neurogenesis in the ipsilateral SVZ and peri-infarct area in a mouse model of transient middle cerebral artery occlusion. Mice were divided into sham operated (n=12), vehicle- (n=18) and cilostazol-treated (n=18) groups. Sections stained for 5-bromodeoxyuridine (BrdU) and several neuronal and a glial markers were analyzed at post-ischemia days 1, 3 and 7. Cilostazol reduced brain ischemic volume (P<0.05) and induced earlier recovery of neurologic deficit (P<0.05). Cilostazol significantly increased the density of BrdU-positive newly-formed cells in the SVZ compared with the vehicle group without ischemia. Increased density of doublecortin (DCX)-positive and BrdU/DCX-double positive neural progenitor cells was noted in the ipsilateral SVZ and peri-infarct area at 3 and 7 days after focal ischemia compared with the vehicle group (P<0.05). Cilostazol increased DCX-positive phosphorylated CREB (pCREB)-expressing neural progenitor cells, and increased brain derived neurotrophic factor (BDNF)-expressing astrocytes in the ipsilateral SVZ and peri-infarct area. The results indicated that cilostazol enhanced neural progenitor cell generation in both ipsilateral SVZ and peri-infarct area through CREB-mediated signaling pathway after focal ischemia.

  17. 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

    2015-01-01

    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 μg 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.

  18. MO-FG-BRA-08: A Preliminary Study of Gold Nanoparticles Enhanced Diffuse Optical Tomography

    SciTech Connect

    Xu, K; Dogan, N; Yang, Y

    2015-06-15

    Purpose: To develop an imaging method by using gold nanoparticles (GNP) to enhance diffuse optical tomography (DOT) for better tumor detection. Methods: Experiments were performed on a tissue-simulating cylindrical optical phantom (30mm diameter, 60mm length). The GNP used are gold nanorods (10nm diameter, 44nm length) with peak light absorption at 840nm. 0.085ml GNP colloid of 96nM concentration was loaded into a 6mm diameter cylindrical hole in the phantom. An 856nm laser beam (14mW) was used as light source to irradiate the phantom at multiple locations through rotating and elevating the phantom. A CCD camera captured the light transmission through the phantom for each irradiation with total 40 projections (8 rotation angles in 45degree steps and 5 elevations with 3mm apart). Cone beam CT of the phantom was used to generate the three-dimensional mesh for DOT reconstruction and to identify the true location of the GNP volume. A forward simulation was performed with known phantom optical properties to establish a relationship between the absorption coefficient and concentration of the GNP by matching the simulated and measured transmission. DOT image reconstruction was performed to restore the GNP within the phantom. In addition, a region-constrained reconstruction was performed by confining the solutions within the GNP volume detected from CT. Results: The position of the GNP volume was reconstructed with <2mm error. The reconstructed average GNP concentration within an identical volume was 104nM, 8% difference from the truth. When the CT was used as “a priori”, the reconstructed average GNP concentration was 239nM, about 2.5 times of the true concentration. Conclusion: This study is the first to demonstrate GNP enhanced DOT with phantom imaging. The GNP can be differentiated from their surrounding background. However, the reconstruction methods needs to be improved for better spatial and quantification accuracy.

  19. Parameterized source term in the diffusion approximation for enhanced near-field modeling of collimated light

    NASA Astrophysics Data System (ADS)

    Jia, Mengyu; Wang, Shuang; Chen, Xueying; Gao, Feng; Zhao, Huijuan

    2016-03-01

    Most analytical methods for describing light propagation in turbid medium exhibit low effectiveness in the near-field of a collimated source. Motivated by the Charge Simulation Method in electromagnetic theory as well as the established discrete source based modeling, we have reported on an improved explicit model, referred to as "Virtual Source" (VS) diffuse approximation (DA), to inherit the mathematical simplicity of the DA while considerably extend its validity in modeling the near-field photon migration in low-albedo medium. In this model, the collimated light in the standard DA is analogously approximated as multiple isotropic point sources (VS) distributed along the incident direction. For performance enhancement, a fitting procedure between the calculated and realistic reflectances is adopted in the nearfield to optimize the VS parameters (intensities and locations). To be practically applicable, an explicit 2VS-DA model is established based on close-form derivations of the VS parameters for the typical ranges of the optical parameters. The proposed VS-DA model is validated by comparing with the Monte Carlo simulations, and further introduced in the image reconstruction of the Laminar Optical Tomography system.

  20. Numerical Simulations of Transverse Beam Diffusion Enhancement by the Use of Electron Lens in the Tevatron Collider

    SciTech Connect

    Previtali, V.; Stancari, G.; Valishev, A.; Shatilov, D.N.; /Novosibirsk, IYF

    2012-05-01

    Transverse beam diffusion for the Tevatron machine has been calculated using the Lifetrac code. The following effects were included: random noise (representing residual gas scattering, voltage noise in the accelerating cavities) lattice nonlinearities and beam-beam interactions. The time evolution of particle distributions with different initial amplitudes in Hamiltonian action has been simulated for 6 million turns, corresponding to a time of about 2 minutes. For each particle distribution, several cases have been considered: a single beam in storage ring mode, the collider case and the effects of a hollow electron beam collimator. The diffusion coefficient for some representative points in the amplitude space has been calculated by fitting the time evolution of delta-like particle distributions using the diffusion equation, for different machine conditions. The results confirm a strong efficiency of the electron lens as an halo diffusive enhancer, leading to diffusion coefficients which are at least a factor 10K higher than the values obtained for the collision case. This result is confirmed by the Frequency Map Analysis, which shows a clear intensification of resonance lines for particle amplitudes larger than the electron lens inner radius. If compared with past experiments, the simulations successfully reproduce the diffusion coefficients for the beam core, but still present a large discrepancy for halo particles, still under investigation.

  1. 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

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

    PubMed

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

    2006-12-20

    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

  3. Cranberry derivatives enhance biofilm formation and transiently impair swarming motility of the uropathogen Proteus mirabilis HI4320.

    PubMed

    O'May, Che; Amzallag, Olivier; Bechir, Karim; Tufenkji, Nathalie

    2016-06-01

    Proteus mirabilis is a major cause of catheter-associated urinary tract infection (CAUTI), emphasizing that novel strategies for targeting this bacterium are needed. Potential targets are P. mirabilis surface-associated swarming motility and the propensity of these bacteria to form biofilms that may lead to catheter blockage. We previously showed that the addition of cranberry powder (CP) to lysogeny broth (LB) medium resulted in impaired P. mirabilis swarming motility over short time periods (up to 16 h). Herein, we significantly expanded on those findings by exploring (i) the effects of cranberry derivatives on biofilm formation of P. mirabilis, (ii) whether swarming inhibition occurred transiently or over longer periods more relevant to real infections (∼3 days), (iii) whether swarming was also blocked by commercially available cranberry juices, (iv) whether CP or cranberry juices exhibited effects under natural urine conditions, and (v) the effects of cranberry on medium pH, which is an indirect indicator of urease activity. At short time scales (24 h), CP and commercially available pure cranberry juice impaired swarming motility and repelled actively swarming bacteria in LB medium. Over longer time periods more representative of infections (∼3 days), the capacity of the cranberry material to impair swarming diminished and bacteria would start to migrate across the surface, albeit by exhibiting a different motility phenotype to the regular "bull's-eye" swarming phenotype of P. mirabilis. This bacterium did not swarm on urine agar or LB agar supplemented with urea, suggesting that any potential application of anti-swarming compounds may be better suited to settings external to the urine environment. Anti-swarming effects were confounded by the ability of cranberry products to enhance biofilm formation in both LB and urine conditions. These findings provide key insights into the long-term strategy of targeting P. mirabilis CAUTIs.

  4. Radial expansion rates and tumor growth kinetics predict malignant transformation in contrast-enhancing low-grade diffuse astrocytoma

    PubMed Central

    Hathout, Leith; Pope, Whitney B; Lai, Albert; Nghiemphu, Phioanh L; Cloughesy, Timothy F; Ellingson, Benjamin M

    2015-01-01

    Summary Background Contrast-enhancing low-grade diffuse astrocytomas are an understudied, aggressive subtype at increased risk because of few radiographic indications of malignant transformation. In the current study, we tested whether tumor growth kinetics could identify tumors that undergo malignant transformation to higher grades. Methods Thirty patients with untreated diffuse astrocytomas (WHO II) that underwent tumor progression were enrolled. Contrast-enhancing and T2 hyperintense tumor regions were segmented and the radius of tumor at two time points leading to progression was estimated. Radial expansion rates were used to estimate proliferation and invasion rates using a biomathematical model. Results Radial expansion rates for both contrast-enhancing (p = 0.0040) and T2 hyperintense regions (p = 0.0016) were significantly higher in WHO II–IV tumors compared with nontransformers. Similarly, model estimates showed a significantly higher proliferation (p = 0.0324) and invasion rate (p = 0.0050) in WHO II–IV tumors compared with nontransformers. Conclusion Tumor growth kinetics can identify contrast-enhancing diffuse astrocytomas undergoing malignant transformation. PMID:26095141

  5. 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.

  6. Adaptive diffusion regularization for enhancement of microcalcifications in digital breast tomosynthesis (DBT) reconstruction

    NASA Astrophysics Data System (ADS)

    Lu, Yao; Chan, Heang-Ping; Fessler, Jeffrey A.; Hadjiiski, Lubomir; Wei, Jun; Goodsitt, Mitchell M.

    2011-03-01

    Digital breast tomosynthesis (DBT) has been shown to increase mass detection. Detection of microcalcifications in DBT is challenging because of the small, subtle signals to be searched in the large breast volume and the noise in the reconstructed volume. We developed an adaptive diffusion (AD) regularization method that can differentially regularize noise and potential signal regions during reconstruction based on local contrast-to-noise ratio (CNR) information. This method adaptively applies different degrees of regularity to signal and noise regions, as guided by a CNR map for each DBT slice within the image volume, such that potential signals will be preserved while noise is suppressed. DBT scans of an American College of Radiology phantom and the breast of a subject with biopsy-proven calcifications were acquired with a GE prototype DBT system at 21 angles in 3° increments over a +/-30° range. Simultaneous algebraic reconstruction technique (SART) was used for DBT reconstruction. The AD regularization method was compared to the non-convex total p-variation (TpV) method and SART with no regularization (NR) in terms of the CNR and the full width at half maximum (FWHM) of the central gray-level line profile in the focal plane of a calcification. The results demonstrated that the SART regularized by the AD method enhanced the CNR and preserved the sharpness of microcalcifications compared to reconstruction without regularization. The AD regularization was superior to the TpV method for subtle microcalcifications in terms of the CNR while the FWHM was comparable. The AD regularized reconstruction has the potential to improve the CNR of microcalcifications in DBT for human or machine detection.

  7. Diffusion-enhanced Förster resonance energy transfer and the effects of external quenchers and the donor quantum yield.

    PubMed

    Jacob, Maik H; Dsouza, Roy N; Ghosh, Indrajit; Norouzy, Amir; Schwarzlose, Thomas; Nau, Werner M

    2013-01-10

    The structural and dynamic properties of a flexible peptidic chain codetermine its biological activity. These properties are imprinted in intrachain site-to-site distances as well as in diffusion coefficients of mutual site-to-site motion. Both distance distribution and diffusion determine the extent of Förster resonance energy transfer (FRET) between two chain sites labeled with a FRET donor and acceptor. Both could be obtained from time-resolved FRET measurements if their individual contributions to the FRET efficiency could be systematically varied. Because the FRET diffusion enhancement (FDE) depends on the donor-fluorescence lifetime, it has been proposed that the FDE can be reduced by shortening the donor lifetime through an external quencher. Benefiting from the high diffusion sensitivity of short-distance FRET, we tested this concept experimentally on a (Gly-Ser)(6) segment labeled with the donor/acceptor pair naphthylalanine/2,3-diazabicyclo[2.2.2]oct-2-ene (NAla/Dbo). Surprisingly, the very effective quencher potassium iodide (KI) had no effect at all on the average donor-acceptor distance, although the donor lifetime was shortened from ca. 36 ns in the absence of KI to ca. 3 ns in the presence of 30 mM KI. We show that the proposed approach had to fail because it is not the experimentally observed but the radiative donor lifetime that controls the FDE. Because of that, any FRET ensemble measurement can easily underestimate diffusion and might be misleading even if it employs the Haas-Steinberg diffusion equation (HSE). An extension of traditional FRET analysis allowed us to evaluate HSE simulations and to corroborate as well as generalize the experimental results. We demonstrate that diffusion-enhanced FRET depends on the radiative donor lifetime as it depends on the diffusion coefficient, a useful symmetry that can directly be applied to distinguish dynamic and structural effects of viscous cosolvents on the polymer chain. We demonstrate that the

  8. Exciton diffusion length in complex quantum systems: the effects of disorder and environmental fluctuations on symmetry-enhanced supertransfer.

    PubMed

    Abasto, D F; Mohseni, M; Lloyd, S; Zanardi, P

    2012-08-13

    Symmetric couplings among aggregates of n chromophores increase the transfer rate of excitons by a factor n(2), a quantum-mechanical phenomenon called 'supertransfer'. In this work, we demonstrate how supertransfer effects induced by geometrical symmetries can enhance the exciton diffusion length by a factor n along cylindrically symmetric structures, consisting of arrays of rings of chromophores, and along spiral arrays. We analyse both closed-system dynamics and open quantum dynamics, modelled by combining a random bosonic bath with static disorder. In the closed-system case, we use the symmetries of the system within a short-time approximation to obtain a closed analytical expression for the diffusion length that explicitly reveals the supertransfer contribution. When subject to disorder, we show that supertransfer can enhance excitonic diffusion lengths for small disorders and characterize the crossover from coherent to incoherent motion. Owing to the quasi-one-dimensional nature of the model, disorder ultimately localizes the excitons, diminishing but not destroying the effects of supertransfer. When dephasing effects are included, we study the scaling of diffusion with both time and number of chromophores and observe that the transition from a coherent, ballistic regime to an incoherent, random-walk regime occurs at the same point as the change from supertransfer to classical scaling.

  9. Diffusion of myosin light chain kinase on actin: A mechanism to enhance myosin phosphorylation rates in smooth muscle.

    PubMed

    Hong, Feng; Brizendine, Richard K; Carter, Michael S; Alcala, Diego B; Brown, Avery E; Chattin, Amy M; Haldeman, Brian D; Walsh, Michael P; Facemyer, Kevin C; Baker, Josh E; Cremo, Christine R

    2015-10-01

    Smooth muscle myosin (SMM) light chain kinase (MLCK) phosphorylates SMM, thereby activating the ATPase activity required for muscle contraction. The abundance of active MLCK, which is tightly associated with the contractile apparatus, is low relative to that of SMM. SMM phosphorylation is rapid despite the low ratio of MLCK to SMM, raising the question of how one MLCK rapidly phosphorylates many SMM molecules. We used total internal reflection fluorescence microscopy to monitor single molecules of streptavidin-coated quantum dot-labeled MLCK interacting with purified actin, actin bundles, and stress fibers of smooth muscle cells. Surprisingly, MLCK and the N-terminal 75 residues of MLCK (N75) moved on actin bundles and stress fibers of smooth muscle cell cytoskeletons by a random one-dimensional (1-D) diffusion mechanism. Although diffusion of proteins along microtubules and oligonucleotides has been observed previously, this is the first characterization to our knowledge of a protein diffusing in a sustained manner along actin. By measuring the frequency of motion, we found that MLCK motion is permitted only if acto-myosin and MLCK-myosin interactions are weak. From these data, diffusion coefficients, and other kinetic and geometric considerations relating to the contractile apparatus, we suggest that 1-D diffusion of MLCK along actin (a) ensures that diffusion is not rate limiting for phosphorylation, (b) allows MLCK to locate to areas in which myosin is not yet phosphorylated, and (c) allows MLCK to avoid getting "stuck" on myosins that have already been phosphorylated. Diffusion of MLCK along actin filaments may be an important mechanism for enhancing the rate of SMM phosphorylation in smooth muscle.

  10. Enhanced sedimentation beneath particle-laden flows in lakes and the ocean due to double-diffusive convection

    NASA Astrophysics Data System (ADS)

    Davarpanah Jazi, Shahrzad; Wells, Mathew G.

    2016-10-01

    The transport rate of particles beneath sediment-laden overflows and interflows in lakes and the ocean can be enhanced by double-diffusive and settling-driven convection. In previous experiments with sediment-laden fluid overlaying a saline layer, visual measurements could only be made in the optically clear lower layer. Hence, there was difficulty distinguishing the two processes, hindering predictions of when enhanced sedimentation occurs. We used an Acoustic Doppler Velocimeter to measure velocities and turbulence above and below the initial sediment/salt interface. The velocity of the sediment fingers in the lower layer were always larger than the Stokes settling velocity of the particles, leading to an asymmetry in the flow field of the two convective layers. Sediment fingers only dominated when there were marginal density differences between the two layers. We conclude that double-diffusive sediment fingers control sedimentation beneath interflows in most lakes, whereas settling-driven convection is dominant in most oceanic overflows.

  11. Enhanced hot-carrier cooling and ultrafast spectral diffusion in strongly coupled PbSe quantum-dot solids.

    PubMed

    Gao, Yunan; Talgorn, Elise; Aerts, Michiel; Trinh, M Tuan; Schins, Juleon M; Houtepen, Arjan J; Siebbeles, Laurens D A

    2011-12-14

    PbSe quantum-dot solids are of great interest for low cost and efficient photodetectors and solar cells. We have prepared PbSe quantum-dot solids with high charge carrier mobilities using layer-by-layer dip-coating with 1,2-ethanediamine as substitute capping ligands. Here we present a time and energy resolved transient absorption spectroscopy study on the kinetics of photogenerated charge carriers, focusing on 0-5 ps after photoexcitation. We compare the observed carrier kinetics to those for quantum dots in dispersion and show that the intraband carrier cooling is significantly faster in quantum-dot solids. In addition we find that carriers diffuse from higher to lower energy sites in the quantum-dot solid within several picoseconds.

  12. 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

    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.

  13. Transient Transport in Binary and Ternary Semiconductors.

    DTIC Science & Technology

    1986-02-27

    transport; Semiconductors, Microelectronics, Quantum transport , Boltzmann transport, Drift and diffusion, Gallium arsende, Aluminum gallium arsenide, Indium gallium arsenide, and Transient transport.

  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. Enhancement of Lateral Diffusion in Catanionic Vesicles during Multilamellar-to-Unilamellar Transition.

    PubMed

    Mitra, S; Sharma, V K; Garcia-Sakai, V; Orecchini, A; Seydel, T; Johnson, M; Mukhopadhyay, R

    2016-04-21

    Catanionic vesicles are formed spontaneously by mixing cationic and anionic dispersions in aqueous solution in suitable conditions. Because of spontaneity in formation, long-term stability, and easy modulation of size and charge, they have numerous advantages over conventional lipid-based vesicles. The dynamics of such vesicles is of interest in the field of biomedicine, as they can be used to deliver drug molecules into the cell membrane. Dynamics of catanionic vesicles based on sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) have been studied using incoherent elastic and quasielastic neutron scattering (QENS) techniques. Neutron scattering experiments have been carried out on two backscattering spectrometers, IRIS and IN16B, which have different energy resolutions and energy transfer windows. An elastic fixed-window scan carried out using IN16B shows a phase transition at ∼307 K during the heating cycle, whereas on cooling the transition occurred at ∼294 K. DSC results are found to be in close agreement with the elastic scan data. This transition is ascribed to a structural rearrangement from a multilamellar to a unilamellar phase [ Andreozzi J. Phys. Chem. B 2010 , 114 , 8056 - 8060 ]. It is found that a model in which the surfactant molecules undergo both lateral and internal motions can describe the QENS data quite well. While the data from IRIS have contributions from both dynamical processes, the data from IN16B probe only lateral motions, as the internal motions are too fast for the energy window of the spectrometer. It is found that, through the transition, the fraction of surfactant molecules undergoing lateral motion increases of a factor of 2 from the multilamellar to the unilamellar phase, indicating an enhanced fluidity of the latter. The lateral motion is found to be Fickian in nature, while the internal motion has been described by a localized translational diffusion model. The results reported here could have direct

  16. In Vivo Evaluation of the Visual Pathway in Streptozotocin-Induced Diabetes by Diffusion Tensor MRI and Contrast Enhanced MRI

    PubMed Central

    Kancherla, Swarupa; Kohler, William J.; van der Merwe, Yolandi

    2016-01-01

    Visual function has been shown to deteriorate prior to the onset of retinopathy in some diabetic patients and experimental animal models. This suggests the involvement of the brain's visual system in the early stages of diabetes. In this study, we tested this hypothesis by examining the integrity of the visual pathway in a diabetic rat model using in vivo multi-modal magnetic resonance imaging (MRI). Ten-week-old Sprague-Dawley rats were divided into an experimental diabetic group by intraperitoneal injection of 65 mg/kg streptozotocin in 0.01 M citric acid, and a sham control group by intraperitoneal injection of citric acid only. One month later, diffusion tensor MRI (DTI) was performed to examine the white matter integrity in the brain, followed by chromium-enhanced MRI of retinal integrity and manganese-enhanced MRI of anterograde manganese transport along the visual pathway. Prior to MRI experiments, the streptozotocin-induced diabetic rats showed significantly smaller weight gain and higher blood glucose level than the control rats. DTI revealed significantly lower fractional anisotropy and higher radial diffusivity in the prechiasmatic optic nerve of the diabetic rats compared to the control rats. No apparent difference was observed in the axial diffusivity of the optic nerve, the chromium enhancement in the retina, or the manganese enhancement in the lateral geniculate nucleus and superior colliculus between groups. Our results suggest that streptozotocin-induced diabetes leads to early injury in the optic nerve when no substantial change in retinal integrity or anterograde transport along the visual pathways was observed in MRI using contrast agent enhancement. DTI may be a useful tool for detecting and monitoring early pathophysiological changes in the visual system of experimental diabetes non-invasively. PMID:27768755

  17. Thaumatin crystallization aboard the International Space Station using liquid-liquid diffusion in the Enhanced Gaseous Nitrogen Dewar (EGN).

    PubMed

    Barnes, Cindy L; Snell, Edward H; Kundrot, Craig E

    2002-05-01

    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 77 to 273 K in about 4 d, about the same time it took to warm from 273 to 293 K. The temperature within the EGN was 293-297 K 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 A, comparable to previous studies of space-grown thaumatin crystals. The resolution of the best ground-control crystal was only 1.47 A. It is not clear if the difference in diffraction limit arises from factors other than crystal size. Improvements in temperature control and the elimination of air gaps are needed, but the results show that the EGN on the ISS can be used to produce space-grown crystals that diffract to high resolution.

  18. 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.

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

    DOEpatents

    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.

  20. Enhanced Absorption and Diffusion Properties of Lithium on B,N,VC-decorated Graphene

    PubMed Central

    Jin, Mengting; Yu, L. C.; Shi, W. M.; Deng, J. G.; Zhang, Y. N.

    2016-01-01

    Systematic first-principles calculations were performed to investigate the adsorption and diffusion of Li on different graphene layers with B/N-doping and/or C-vacancy, so as to understand why doping heteroatoms in graphene anode could significantly improve the performance of lithium-ion batteries. We found that the formation of single or double carbon vacancies in graphene are critical for the adsorption of Li atoms. While the N-doping facilitates the formation of vacancies, it introduces over binding issue and hinders the Li diffusion. The presence of B takes the excessive electrons from Li and N and reduces the energy barrier of Li diffusion on substrates. We perceive that these clear insights are crucial for the further development of graphene based anode materials for lithium-ion batteries. PMID:27897202

  1. Enhanced Absorption and Diffusion Properties of Lithium on B,N,VC-decorated Graphene

    NASA Astrophysics Data System (ADS)

    Jin, Mengting; Yu, L. C.; Shi, W. M.; Deng, J. G.; Zhang, Y. N.

    2016-11-01

    Systematic first-principles calculations were performed to investigate the adsorption and diffusion of Li on different graphene layers with B/N-doping and/or C-vacancy, so as to understand why doping heteroatoms in graphene anode could significantly improve the performance of lithium-ion batteries. We found that the formation of single or double carbon vacancies in graphene are critical for the adsorption of Li atoms. While the N-doping facilitates the formation of vacancies, it introduces over binding issue and hinders the Li diffusion. The presence of B takes the excessive electrons from Li and N and reduces the energy barrier of Li diffusion on substrates. We perceive that these clear insights are crucial for the further development of graphene based anode materials for lithium-ion batteries.

  2. Impact of Modified Anisotropic Diffusion-based Enhancement Method in Computer-Aided Classification of Focal Liver Lesions.

    PubMed

    Mittal, Deepti

    2017-03-01

    This work is presented with the objective to assess quantitatively the impact of modified anisotropic diffusion-based enhancement method of Mittal et al. in computer-aided classification of focal liver lesions. This assessment was made before and after enhancement of clinically acquired ultrasound images with the comparison of (a) discrimination capability of radiologically important texture contrast feature using box plot and p-value statistics and (b) test results of designed computer-aided classification schemes to detect/classify focal liver tissues using receiver operating characteristic curves. The results reveal that the application of enhancement method on clinically acquired ultrasound image may effectively improve the confidence of clinicians/radiologists in computer-aided diagnostic solutions to detect and classify focal liver lesions.

  3. Enhanced nonlinear inspection of diffusion bonded interfaces using reflected non-collinear ultrasonic wave mixing

    NASA Astrophysics Data System (ADS)

    Zhang, Ziyin; Nagy, Peter B.; Hassan, Waled

    2016-02-01

    Ultrasonic wave mixing has shown promising potential for assessing otherwise hidden subtle imperfections in imperfect diffusion bonds between Ti-6Al-4V components. When interrogating a diffusion bonded specimen using non-collinear shear wave mixing, both bulk and interface nonlinearity will contribute to the transmitted nonlinear signal. Although a recent study has shown that changing the transducer alignment can suppress the intrinsic nonlinearity of the surrounding material to some extent so that the interface nonlinearity could be detected more selectively, it is still difficult to distinguish different levels of bond quality based on the detected transmitted signal only. Analytical and numerical studies showed that an imperfect interface generates the same amount of nonlinear displacement in the reflected and transmitted fields. In this study, we used the reflected nonlinear interface signature to characterize diffusion bonded interfaces. Our results indicate that it is better to use the reflected nonlinear interface signature to assess the bond quality, which is in agreement with our previous analytical and numerical predictions. However, the observed random phase of the reflected signature indicates that existing nonlinear interface models are insufficient for accurately describing the nonlinear interaction of shear incident waves with high-quality diffusion bonded interfaces.

  4. ICG enhanced co-registered diffuse optical tomography and photoacoustic tomography

    NASA Astrophysics Data System (ADS)

    Xu, Chen; Kumavor, Patrick D.; Xu, Yan; Zhu, Quing

    2013-03-01

    To overcome the intensive light scattering in the biological tissue, diffuse optical tomography (DOT) in the near infrared range for breast lesion detection usually is combined with other imaging modalities such as ultrasound, X-ray, and MRI, to provide guidance. However, the guided imaging modalities may depend on different contrast mechanics compared to the optical contrast in the DOT. As a result, they can't provide reliable guidance for diffuse optical tomography because some lesions may not be detectable by a non-optical modality but yet have high optical contrast. An imaging modality which can provide the guidance from optical contrast is desirable for DOT. In this paper, we present a system that combines diffuse optical tomography and photoacoustic tomography (PAT), to detect and characterize the deeply-seated targets embedded in a turbid medium. Photoacoustic tomography utilizes a short-pulsed laser beam to penetrate into tissue diffusively. Upon absorption of the light by the target, photoacoustic waves are generated and used to reconstruct, at ultrasound resolution, the optical absorption distribution that reveals optical contrast. The combined system used in the experiment combines a 64-channel photoacoustic system with a frequency-domain diffused optical system. To further improve the contrast, the exogenous contrast agent, indocyanine green (ICG) is used. Our experiment results show that the combined system can detect a tumormimicking phantom up to 2.5 cm in depth and 10 μM in concentration. Mice experiments also confirmed that the combined system can detect the tumor region and monitor the ICG uptake and washout in the tumor region. This method can potentially improve the accuracy to detect the small breast lesions or any lesions which are sensitive to the reference change, such as the lesions located on the chest wall.

  5. Transient receptor potential vanilloid 2 activation by focal mechanical stimulation requires interaction with the actin cytoskeleton and enhances growth cone motility.

    PubMed

    Sugio, Shouta; Nagasawa, Masami; Kojima, Itaru; Ishizaki, Yasuki; Shibasaki, Koji

    2016-12-22

    We have previously reported that transient receptor potential vanilloid 2 (TRPV2) can be activated by mechanical stimulation, which enhances axonal outgrowth in developing neurons; however, the molecular mechanisms that govern the contribution of TRPV2 activation to axonal outgrowth remain unclear. In the present study, we examined this mechanism by using PC12 cells as a neuronal model. Overexpression of TRPV2 enhanced axonal outgrowth in a mechanical stimulus-dependent manner. Accumulation of TRPV2 at the cell surface was 4-fold greater in the growth cone compared with the soma. In the growth cone, TRPV2 is not static, but dynamically accumulates (within ∼100 ms) to the site of mechanical stimulation. The dynamic and acute clustering of TRPV2 can enhance very weak mechanical stimuli via focal accumulation of TRPV2. Focal application of mechanical stimuli dramatically increased growth cone motility and caused actin reorganization via activation of TRPV2. We also found that TRPV2 physically interacts with actin and that changes in the actin cytoskeleton are required for its activation. Here, we demonstrated for the first time to our knowledge that TRPV2 clustering is induced by mechanical stimulation generated by axonal outgrowth and that TRPV2 activation is triggered by actin rearrangements that result from mechanical stimulation. Moreover, TRPV2 activation enhances growth cone motility and actin accumulation to promote axonal outgrowth. Sugio, S., Nagasawa, M., Kojima, I., Ishizaki, Y., Shibasaki, K. Transient receptor potential vanilloid 2 activation by focal mechanical stimulation requires interaction with the actin cytoskeleton and enhances growth cone motility.

  6. Stability Test for Transient-Temperature Calculations

    NASA Technical Reports Server (NTRS)

    Campbell, W.

    1984-01-01

    Graphical test helps assure numerical stability of calculations of transient temperature or diffusion in composite medium. Rectangular grid forms basis of two-dimensional finite-difference model for heat conduction or other diffusion like phenomena. Model enables calculation of transient heat transfer among up to four different materials that meet at grid point.

  7. Enhanced diffusion and anomalous transport of magnetic colloids driven above a two-state flashing potential

    NASA Astrophysics Data System (ADS)

    Tierno, Pietro; Shaebani, M. Reza

    We combine experiment and theory to investigate the diffusive and subdiffusive dynamics of paramagnetic colloids driven above a two-state flashing potential. The magnetic potential was realized by periodically modulating the stray field of a magnetic bubble lattice in a uniaxial ferrite garnet film. At large amplitudes of the driving field, the dynamics of particles resembles an ordinary random walk with a frequency-dependent diffusion coefficient. However, subdiffusive and oscillatory dynamics at short time scales is observed when decreasing the amplitude. We present a persistent random walk model to elucidate the underlying mechanism of motion, and perform numerical simulations to demonstrate that the anomalous motion originates from the dynamic disorder in the structure of the magnetic lattice, induced by slightly irregular shape of bubbles.

  8. 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

  9. 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

    2015-05-04

    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.

  10. 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.

    2016-04-01

    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.

  11. Monitoring radiation belt particle precipitation - automatic detection of enhanced transient ionisation in the lower plasmasphere using subionospheric narrow band VLF signals

    NASA Astrophysics Data System (ADS)

    Steinbach, P.; Lichtenberger, J.; Ferencz, Cs.

    2009-04-01

    Signals of naval VLF transmitters, propagating long distances along the Earth-ionosphere waveguide (EIWG) have been widely applied as effective tools for monitoring transient ionization at mesospheric altitudes. Perturbations in recorded amplitude and/or phase data series of stable frequency signals may refer to the effect of transient enhanced ionization in the EIWG, due to e.g. loss-cone precipitation of trapped energetic electrons (Carpenter et al., 1984, Dowden and Adams, 1990), burst of solar plasma particles (Clilverd et al., 2001). The contribution of precipitating particles are thought to be substantial in certain Sun-to-Earth energy flow processes in the upper atmosphere (Rodger et al., 2005). Narrow band VLF measuring network has been set up, developed and operated in Hungary, running in the last decade almost continuously, dedicated to monitor ionization enhancement regions along numerous transmitter-receiver paths. This setup is based on Omnipal and Ultra-MSK equipment, logging amplitude and phase data of received signals, sampled at frequencies of selected VLF transmitters. Signal trajectories, selected for recording represent proper configuration to survey transient ionization caused by energetic particles in the sub-polar region, such as effect of scattered particles of the inner radiation belt. Reprocessing of the mass archived recordings has been started using a newly developed signal processing code, detecting and classifying different sort of perturbations automatically on narrow band VLF series. Occurrence rates, daily and seasonal variation, statistics of transient ionization enhancements, their geographic distribution within the surveyed range and time period, and correlation with intense geomagnetic and/or Solar event is yielded by this analysis. References: Carpenter, D.L., Inan, U.S., Trimpi, M.L., Helliwell, R.A., and Katsufrakis, J.P.: Perturbations of subionospheric LF and MF signals due to whistler-induced electron precipitation burst

  12. Discrete or diffuse intramedullary tumor? Contrast-enhanced intraoperative ultrasound in a case of intramedullary cervicothoracic hemangioblastomas mimicking a diffuse infiltrative glioma: technical note and case report.

    PubMed

    Vetrano, Ignazio G; Prada, Francesco; Nataloni, Ilaria F; Bene, Massimiliano Del; Dimeco, Francesco; Valentini, Laura G

    2015-08-01

    Hemangioblastomas are benign, highly vascularized intramedullary lesions that may also extend into the intradural space. Surgery represents the standard therapy, with the goal of obtaining complete resection even at the risk of neurological morbidity. MRI is the gold standard for diagnosis and assessment of intramedullary tumors. Nevertheless, sometimes MRI may not accurately differentiate between different types of intramedullary tumors, in particular if they are associated with syringes or intra- and peritumoral cysts. This could subsequently affect surgical strategies. Intraoperative ultrasound (ioUS) has become in the last few years a very useful tool for use during neurosurgical procedures. Various ioUS modalities such as B-mode and Doppler have been applied during neurosurgical procedures. On the other hand, the use of contrast-enhanced ultrasound (CEUS) is not yet well defined and standardized in this field. We report a case of a young patient harboring a cervicothoracic intramedullary tumor, for which the preoperative neuroradiologi-cal diagnosis was in favor of a diffuse astrocytoma with nodular components whereas ioUS demonstrated 3 distinct intramedullary nodules. CEUS showed highly vascularized lesions, compatible with hemangioblastomas. These findings, particularly those obtained with CEUS, allowed better definition of the lesions for diagnosis, enhanced understanding of the physiopathological aspects, and permitted the localization of all 3 nodules, thus limiting spinal cord manipulation and allowing complete resection of the lesions, with an uneventful postoperative neurological course. To the best of our knowledge, this is the first report of the use of intraoperative CEUS in a case of intramedullary hemangioblastoma.

  13. Multiparametric MR Imaging of Diffusion and Perfusion in Contrast-enhancing and Nonenhancing Components in Patients with Glioblastoma.

    PubMed

    Boonzaier, Natalie R; Larkin, Timothy J; Matys, Tomasz; van der Hoorn, Anouk; Yan, Jiun-Lin; Price, Stephen J

    2017-02-27

    Purpose To determine whether regions of low apparent diffusion coefficient (ADC) with high relative cerebral blood volume (rCBV) represented elevated choline (Cho)-to-N-acetylaspartate (NAA) ratio (hereafter, Cho/NAA ratio) and whether their volumes correlated with progression-free survival (PFS) and overall survival (OS) in patients with glioblastoma (GBM). Materials and Methods This retrospective analysis was approved by the local research ethics committee. Volumetric analysis of imaging data from 43 patients with histologically confirmed GBM was performed. Patients underwent preoperative 3-T magnetic resonance imaging with conventional, diffusion-weighted, perfusion-weighted, and spectroscopic sequences. Patients underwent subsequent surgery with adjuvant chemotherapy and radiation therapy. Overlapping low-ADC and high-rCBV regions of interest (ROIs) (hereafter, ADC-rCBV ROIs) were generated in contrast-enhancing and nonenhancing regions. Cho/NAA ratio in ADC-rCBV ROIs was compared with that in control regions by using analysis of variance. All resulting ROI volumes were correlated with patient survival by using multivariate Cox regression. Results ADC-rCBV ROIs within contrast-enhancing and nonenhancing regions showed elevated Cho/NAA ratios, which were significantly higher than those in other abnormal tumor regions (P < .001 and P = .008 for contrast-enhancing and nonenhancing regions, respectively) and in normal-appearing white matter (P < .001 for both contrast-enhancing and nonenhancing regions). After Cox regression analysis controlling for age, tumor size, resection extent, O-6-methylguanine-DNA methyltransferase-methylation, and isocitrate dehydrogenase mutation status, the proportional volume of ADC-rCBV ROIs in nonenhancing regions significantly contributed to multivariate models of OS (hazard ratio, 1.132; P = .026) and PFS (hazard ratio, 1.454; P = .017). Conclusion Volumetric analysis of ADC-rCBV ROIs in nonenhancing regions of GBM can be used to

  14. Transient nonlinear optically-thick radiative-convective double-diffusive boundary layers in a Darcian porous medium adjacent to an impulsively started surface: Network simulation solutions

    NASA Astrophysics Data System (ADS)

    Anwar Bég, O.; Zueco, J.; Takhar, H. S.; Bég, T. A.; Sajid, A.

    2009-11-01

    A boundary-layer model is described for the two-dimensional nonlinear transient thermal convection heat and mass transfer in an optically-thick fluid in a Darcian porous medium adjacent to an impulsively started vertical surface, in the presence of significant thermal radiation and buoyancy forces in an (X∗,Y∗,t∗) coordinate system. An algebraic approximation is employed to simplify the integro-differential equation of radiative transfer for unidirectional flux normal to the plate into the boundary-layer regime, by incorporating this flux term in the energy conservation equation. The conservation equations are non-dimensionalized into an (X,Y,T) coordinate system and solved using the Network Simulation Method (NSM), a robust numerical technique which demonstrates high efficiency and accuracy. The transient variation of non-dimensional streamwise velocity component (u) and temperature (T) and concentration (C) functions is computed for various selected values of Stark number (radiation-conduction interaction parameter) and Darcy number. Transient velocity (u) and steady-state local skin friction (τX) are also studied for various thermal Grashof number (Gr), species Grashof number (Gm), Schmidt number (Sc) and Stark number (N) values. These computations for the infinite permeability case (Da → ∞) are compared with previous finite difference solutions [Prasad et al. Int J Therm Sci 2007;46(12):1251-8] and shown to be in excellent agreement. An increase in Darcy number is seen to accelerate the flow and boost velocity. A decrease in Stark number (corresponding to an increase in thermal radiation heat transfer contribution) is shown to increase the velocity values. Temperature function is observed to fall in value with a rise in Da and increase with decrease in N (corresponding to an increase in thermal radiation heat transfer contribution). Applications of the study include rocket combustion chambers, astrophysical flows, spacecraft thermal fluid dynamics in

  15. An Enhanced Method for Scheduling Observations of Large Sky Error Regions for Finding Optical Counterparts to Transients

    NASA Astrophysics Data System (ADS)

    Rana, Javed; Singhal, Akshat; Gadre, Bhooshan; Bhalerao, Varun; Bose, Sukanta

    2017-04-01

    The discovery and subsequent study of optical counterparts to transient sources is crucial for their complete astrophysical understanding. Various gamma-ray burst (GRB) detectors, and more notably the ground-based gravitational wave detectors, typically have large uncertainties in the sky positions of detected sources. Searching these large sky regions spanning hundreds of square degrees is a formidable challenge for most ground-based optical telescopes, which can usually image less than tens of square degrees of the sky in a single night. We present algorithms for better scheduling of such follow-up observations in order to maximize the probability of imaging the optical counterpart, based on the all-sky probability distribution of the source position. We incorporate realistic observing constraints such as the diurnal cycle, telescope pointing limitations, available observing time, and the rising/setting of the target at the observatory’s location. We use simulations to demonstrate that our proposed algorithms outperform the default greedy observing schedule used by many observatories. Our algorithms are applicable for follow-up of other transient sources with large positional uncertainties, such as Fermi-detected GRBs, and can easily be adapted for scheduling radio or space-based X-ray follow-up.

  16. 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.

    2016-03-01

    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.

  17. TiO2-NiO p-n nanocomposite with enhanced sonophotocatalytic activity under diffused sunlight.

    PubMed

    Vinoth, R; Karthik, P; Devan, K; Neppolian, B; Ashokkumar, Muthupandian

    2017-03-01

    TiO2-NiO composites with p-n junction were developed by assembling p-type NiO on n-type TiO2 using ultrasound assisted wet impregnation method. The sonophotocatalytic efficiencies of pure TiO2 and TiO2-NiO composites were evaluated under diffused sunlight using methyl orange (MO) as a model pollutant. The impregnation of NiO nanoparticles on TiO2 considerably enhanced the optical absorption in visible region (500-800nm) due to the formation of p-n junctions at the interface between TiO2 and NiO. The internal electric field induced by the p-n junction led to effective separation of electron-hole pairs and thereby generating a large amount of reactive species for the degradation of MO. The individual effect of ultrasound and diffused sunlight for the degradation of MO was found to be 30% and 6%, respectively. A synergy of 4.8 fold was achieved when ultrasound was combined with photocatalytic degradation process in the presence of diffused sunlight. The sonophotocatalytic activity of TiO2-NiO photocatalysts with different NiO loading was also evaluated and 10wt% NiO loading was found to be optimal. Moreover, 66% of Total Organic Carbon (TOC) removal was achieved with the optimized TiO2-NiO composite in 140min. In addition, the TiO2-NiO composite exhibited an enhanced photocurrent response under visible light illumination.

  18. Increasing the sensitivity of NMR diffusion measurements by paramagnetic longitudinal relaxation enhancement, with application to ribosome–nascent chain complexes

    PubMed Central

    Cassaignau, Anaïs M. E.; Cabrita, Lisa D.

    2016-01-01

    The translational diffusion of macromolecules can be examined non-invasively by stimulated echo (STE) NMR experiments to accurately determine their molecular sizes. These measurements can be important probes of intermolecular interactions and protein folding and unfolding, and are crucial in monitoring the integrity of large macromolecular assemblies such as ribosome–nascent chain complexes (RNCs). However, NMR studies of these complexes can be severely constrained by their slow tumbling, low solubility (with maximum concentrations of up to 10 μM), and short lifetimes resulting in weak signal, and therefore continuing improvements in experimental sensitivity are essential. Here we explore the use of the paramagnetic longitudinal relaxation enhancement (PLRE) agent NiDO2A on the sensitivity of 15N XSTE and SORDID heteronuclear STE experiments, which can be used to monitor the integrity of these unstable complexes. We exploit the dependence of the PLRE effect on the gyromagnetic ratio and electronic relaxation time to accelerate recovery of 1H magnetization without adversely affecting storage on Nz during diffusion delays or introducing significant transverse relaxation line broadening. By applying the longitudinal relaxation-optimized SORDID pulse sequence together with NiDO2A to 70S Escherichia coli ribosomes and RNCs, NMR diffusion sensitivity enhancements of up to 4.5-fold relative to XSTE are achieved, alongside ~1.9-fold improvements in two-dimensional NMR sensitivity, without compromising the sample integrity. We anticipate these results will significantly advance the use of NMR to probe dynamic regions of ribosomes and other large, unstable macromolecular assemblies. PMID:26253948

  19. 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.

  20. Metal based gas diffusion layers for enhanced fuel cell performance at high current densities

    NASA Astrophysics Data System (ADS)

    Hussain, Nabeel; Van Steen, Eric; Tanaka, Shiro; Levecque, Pieter

    2017-01-01

    The gas diffusion layer strongly influences the performance and durability of polymer electrolyte fuel cells. A major drawback of current carbon fiber based GDLs is the non-controlled variation in porosity resulting in a random micro-structure. Moreover, when subjected to compression these materials show significant reduction in porosity and permeability leading to water management problems and mass transfer losses within the fuel cell. This study investigated the use of uniform perforated metal sheets as GDLs in conjunction with microchannel flowfields. A metal sheet design with a pitch of 110 μm and a hole diameter of 60 μm in combination with an MPL showed superior performance in the high current density region compared to a commercially available carbon paper based GDL in a single cell environment. Fuel cell testing with different oxidants (air, heliox and oxygen) indicate that the metal sheet offers both superior diffusion and reduced flooding in comparison to the carbon based GDL. The presence of the MPL has been found to be critical to the functionality of the metal sheet suggesting that the MPL design may represent an important optimisation parameter for further improvements in performance.

  1. Enhancement of oxygen transfer efficiency in diffused aeration systems using liquid-film-forming apparatus.

    PubMed

    Zhu, H; Imai, T; Tani, K; Ukita, M; Sekine, M; Higuchi, T; Zhang, Z J

    2007-05-01

    Surface transfer and bubble transfer both contribute significantly to oxygen transfer in a diffused aeration system. In the present study, liquid-film-forming apparatus is successfully developed on a laboratory scale to improve considerably the surface transfer via the unique liquid film transfer technique. The experimental results show that the volumetric mass transfer coefficient for liquid-film-forming apparatus alone is found to be as much as 5.3 times higher than that for water surface and that the total volumetric mass transfer coefficient for liquid film aeration system increases by 37 % in comparison with conventional aeration system. Additionally, by tuning finely the structural parameters of the liquid-film-forming apparatus, it can also lead to high dissolved oxygen water with the dissolved oxygen percent saturation greater than 90 %. More importantly, this result is accomplished by simply offering a single-pass aeration at the depth as shallow as 26 cm. As a result, the objective of economical energy consumption in diffused aeration systems can be realized by lowering the aeration depth without sacrificing the aeration efficiency.

  2. A general strategy for anisotropic diffusion in MR image denoising and enhancement.

    PubMed

    Tong, Chenchen; Sun, Ying; Payet, Nicolas; Ong, Sim-Heng

    2012-12-01

    Anisotropic diffusion (AD) has proven to be very effective in the denoising of magnetic resonance (MR) images. The result of AD filtering is highly dependent on several parameters, especially the conductance parameter. However, there is no automatic method to select the optimal parameter values. This paper presents a general strategy for AD filtering of MR images using an automatic parameter selection method. The basic idea is to estimate the parameters through an optimization step on a synthetic image model, which is different from traditional analytical methods. This approach can be easily applied to more sophisticated diffusion models for better denoising results. We conducted a systematic study of parameter selection for the AD filter, including the dynamic parameter decreasing rate, the parameter selection range for different noise levels and the influence of the image contrast on parameter selection. The proposed approach was validated using both simulated and real MR images. The model image generated using our approach was shown to be highly suitable for the purpose of parameter optimization. The results confirm that our method outperforms most state-of-the-art methods in both quantitative measurement and visual evaluation. By testing on real images with different noise levels, we demonstrated that our method is sufficiently general to be applied to a variety of MR images.

  3. Enhancing tumor apparent diffusion coefficient histogram skewness stratifies the postoperative survival in recurrent glioblastoma multiforme patients undergoing salvage surgery.

    PubMed

    Zolal, Amir; Juratli, Tareq A; Linn, Jennifer; Podlesek, Dino; Sitoci Ficici, Kerim Hakan; Kitzler, Hagen H; Schackert, Gabriele; Sobottka, Stephan B; Rieger, Bernhard; Krex, Dietmar

    2016-05-01

    Objective To determine the value of apparent diffusion coefficient (ADC) histogram parameters for the prediction of individual survival in patients undergoing surgery for recurrent glioblastoma (GBM) in a retrospective cohort study. Methods Thirty-one patients who underwent surgery for first recurrence of a known GBM between 2008 and 2012 were included. The following parameters were collected: age, sex, enhancing tumor size, mean ADC, median ADC, ADC skewness, ADC kurtosis and fifth percentile of the ADC histogram, initial progression free survival (PFS), extent of second resection and further adjuvant treatment. The association of these parameters with survival and PFS after second surgery was analyzed using log-rank test and Cox regression. Results Using log-rank test, ADC histogram skewness of the enhancing tumor was significantly associated with both survival (p = 0.001) and PFS after second surgery (p = 0.005). Further parameters associated with prolonged survival after second surgery were: gross total resection at second surgery (p = 0.026), tumor size (0.040) and third surgery (p = 0.003). In the multivariate Cox analysis, ADC histogram skewness was shown to be an independent prognostic factor for survival after second surgery. Conclusion ADC histogram skewness of the enhancing lesion, enhancing lesion size, third surgery, as well as gross total resection have been shown to be associated with survival following the second surgery. ADC histogram skewness was an independent prognostic factor for survival in the multivariate analysis.

  4. 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.

  5. Insights into Surface Interactions between Metal Organic Frameworks and Gases during Transient Adsorption and Diffusion by In-Situ Small Angle X-ray Scattering

    PubMed Central

    Dumée, Ludovic F.; He, Li; Hodgson, Peter; Kong, Lingxue

    2016-01-01

    The fabrication of molecular gas sieving materials with specific affinities for a single gas species and able to store large quantities of materials at a low or atmospheric pressure is desperately required to reduce the adverse effects of coal and oil usage in carbon capture. Fundamental understanding of the dynamic adsorption of gas, the diffusion mechanisms across thin film membranes, and the impact of interfaces play a vital role in developing these materials. In this work, single gas permeation tests across micro-porous membrane materials, based on metal organic framework crystals grown on the surface of carbon nanotubes (ZiF-8@CNT), were performed for the first time in-situ at the Australian Synchrotron on the small angle X-ray scattering beamline in order to reveal molecular sieving mechanisms and gas adsorption within the material. The results show that specific chemi-sorption of CO2 across the ZiF-8 crystal lattices affected the morphology and unit cell parameters, while the sieving of other noble or noble like gases across the ZiF-8@CNT membranes was found to largely follow Knudsen diffusion. This work demonstrates for the first time a novel and effective technique to assess molecular diffusion at the nano-scale across sub-nano-porous materials by probing molecular flexibility across crystal lattice and single cell units. PMID:27598211

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

    PubMed

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

    2016-01-29

    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 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.

  7. 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.

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

    SciTech Connect

    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 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. Lastly, such interfaces may be used to create materials with unprecedented resistance to radiation-induced damage.

  9. 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

  10. Contrast enhanced high-resolution diffuse optical tomography of the human brain using ICG

    PubMed Central

    Habermehl, Christina; Schmitz, Christoph H.; Steinbrink, Jens

    2011-01-01

    Non-invasive diffuse optical tomography (DOT) of the adult brain has recently been shown to improve the spatial resolution for functional brain imaging applications. Here we show that high-resolution (HR) DOT is also advantageous for clinical perfusion imaging using an optical contrast agent. We present the first HR-DOT results with a continuous wave near infrared spectroscopy setup using a dense grid of optical fibers and indocyanine green (ICG) as an exogenic contrast agent. We find an early arrival of the ICG bolus in the intracerebral tissue and a delayed arrival of the bolus in the extracerebral tissue, achieving the separation of both layers. This demonstrates the method’s potential for brain perfusion monitoring in neurointensive care patients. PMID:21935232

  11. 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.

  12. Enhancement of electron hot spot relaxation in photoexcited plasmonic structures by thermal diffusion

    NASA Astrophysics Data System (ADS)

    Spitzer, F.; Glavin, B. A.; Belotelov, V. I.; Vondran, J.; Akimov, I. A.; Kasture, S.; Achanta, V. G.; Yakovlev, D. R.; Bayer, M.

    2016-11-01

    We demonstrate that in confined plasmonic metal structures subject to ultrafast laser excitation, electron thermal diffusion (ETD) can provide spatial redistribution of excess energy faster than its transfer to the lattice. This relaxation occurs after the excitation of nanometer-sized hot spots in the confined structure, changing sensitively the optical parameters in these regions. The changes become essential when the plasmonic resonance condition is met for both excitation and detection, as evidenced by a pump-probe experiment on plasmonic gold lattices: Subpicosecond relaxation with characteristic times well described by a two-temperature model involving ETD is observed. The results suggest that the dynamical optical response in plasmonic structures can be tuned by the selection of the structural geometry as well as the choice of wavelength and polarization of the excitation and detection light.

  13. Enhancing a diffusion algorithm for 4D image segmentation using local information

    NASA Astrophysics Data System (ADS)

    Lösel, Philipp; Heuveline, Vincent

    2016-03-01

    Inspired by the diffusion of a particle, we present a novel approach for performing a semiautomatic segmentation of tomographic images in 3D, 4D or higher dimensions to meet the requirements of high-throughput measurements in a synchrotron X-ray microtomograph. Given a small number of 2D-slices with at least two manually labeled segments, one can either analytically determine the probability that an intelligently weighted random walk starting at one labeled pixel will be at a certain time at a specific position in the dataset or determine the probability approximately by performing several random walks. While the weights of a random walk take into account local information at the starting point, the random walk itself can be in any dimension. Starting a great number of random walks in each labeled pixel, a voxel in the dataset will be hit by several random walks over time. Hence, the image can be segmented by assigning each voxel to the label where the random walks most likely started from. Due to the high scalability of random walks, this approach is suitable for high throughput measurements. Additionally, we describe an interactively adjusted active contours slice by slice method considering local information, where we start with one manually labeled slice and move forward in any direction. This approach is superior with respect to accuracy towards the diffusion algorithm but inferior in the amount of tedious manual processing steps. The methods were applied on 3D and 4D datasets and evaluated by means of manually labeled images obtained in a realistic scenario with biologists.

  14. Surfactant-enhanced aquifer remediation at the Portsmouth Gaseous Diffusion Plant

    SciTech Connect

    Jackson, R.E.; Londergan, J.T.; Pickens, J.F.

    1995-10-01

    Many DOE facilities are situated in areas of sand and gravel which have become polluted with dense, non-aqueous phase liquids or DNAPLs, such as chlorinated solvents, from the various industrial operations at these facilities. The presence of such DNAPLs in sand and gravel aquifers is now recognized as the principal factor in the failure of standard ground-water remediation methods. The principal objective of this study, as stated in the Statement of Work of the contract (DE-AC21-92MC29111), is to demonstrate that multi-component DNAPLs can be readily solubilized in sand and gravel aquifers by dilute surfactant solutions. The specific objectives of the contract are: to identify dilute surfactants or blends of surfactants in the laboratory that will efficiently extract multi-component DNAPLs from sand and gravel aquifers by micellar solubilization (Phase 1); 2. to test the efficacy of the identified surfactants or blends of surfactants to solubilize in situ perchloroethylene (PCE) and trichloroethylene (TCE) DNAPLs by the injection and the subsequent extraction through an existing well or wells at a government-owned contaminated site (Phase 1); and 3. to demonstrate the full-scale operation of this remedial technology at a government-owned contaminated site (Phase 2). Specific objective number 1 has been completed and reported to DOE. However, the results of the test referred to in specific objective number 2, conducted at Paducah Gaseous Diffusion Plant in 1994, were inconclusive. Following this first test, it was decided by DOE and INTERA to move the test site elsewhere due to difficulties with obtaining core samples of the sand and gravel aquifer containing the DNAPL and with ascertaining the location of the DNAPL relative to the injection well. The solubilization test at the Portsmouth Gaseous Diffusion Plant (PORTS) will constitute the second test of Phase 1 of this contract.

  15. Neuropeptide Y rapidly enhances [Ca2+]i transients and Ca2+ sparks in adult rat ventricular myocytes through Y1 receptor and PLC activation.

    PubMed

    Heredia, María del Puy; Delgado, Carmen; Pereira, Laetitia; Perrier, Romain; Richard, Sylvain; Vassort, Guy; Bénitah, Jean-Pierre; Gómez, Ana María

    2005-01-01

    Neuropeptide Y (NPY) is the most abundant peptide in the mammalian heart, but its cardiac actions are not fully understood. Here we investigate the effect of NPY in intracellular Ca2+ release, using isolated rat cardiac myocytes and confocal microscopy. Cardiac myocytes were field-stimulated at 1 Hz. The evoked [Ca2+]i transient was of higher amplitude and of faster decay in the presence of 100 nM NPY. Cell contraction was also increased by NPY. We analyzed the occurrence of Ca2+ sparks and their characteristics after NPY application. NPY significantly increased Ca2+ sparks frequency in quiescent cells. The Ca2+ spark amplitude was enhanced by NPY but the other characteristics of Ca2+ sparks were not significantly altered. Because cardiac myocytes express both Y1 and Y2 NPY receptors, we repeated the experiments in the presence of the receptor blockers, BIBP3226 and BIIE0246. We found that Y1 NPY receptor blockade completely inhibited NPY effects on [Ca2+]i transient. PTX-sensitive G-proteins and/or phospholypase C (PLC) have been invoked to mediate NPY effects in other cell types. We tested these two hypotheses. In PTX-treated myocytes NPY was still effective, which suggests that the observed NPY actions are not mediated by PTX-sensitive G-proteins. In contrast, the increase in [Ca2+]i transient by NPY was completely inhibited by the PLC inhibitor U73122. In conclusion, we find that NPY has a positive inotropic effect in isolated rat cardiac myocytes, which involves increase in Ca2+ release after activation of Y1 NPY receptor and subsequent stimulation of PLC.

  16. 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.

  17. MRI Edge Enhancement as a Diffusive Discord of Spin Phase Structure

    NASA Astrophysics Data System (ADS)

    Stepišnik, Janez; Duh, Andrej; Mohorič, Aleš; Serša, Igor

    1999-03-01

    The enhancement of magnetic resonance image intensity near impermeable boundaries can be nicely described by a new approach where the diffusional spin echo attenuation is linked to the correlation function of molecular motion. In this method the spin phase structure created by the applied gradient is considered to be a composition of plane waves with the wave vectors representing feasible momentum states of a particle in confinement. The enhancement of edges on the magnetic resonance images (MRI) comes out as a discord of plane waves due to particle motion. It results from the average of the wave phase by using the cumulant expansion in the Gaussian approximation. The acquired analytical expression describes the MRI signal space distribution where the enhancement of edges depends on the intensity and the duration of gradient sequence as well as on the length of the mean squared particle displacement in restricted geometry. This new method works well with gradients of general waveform and is, therefore, suitable for imaging sequences where finite or even modulated gradients are usually used.

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

    DOE PAGES

    Vattré, A.; Jourdan, T.; Ding, H.; ...

    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

  19. Site-selective transient photoluminescence enhancement of impurity-trapped excitons in NaMgF3:Yb2+

    NASA Astrophysics Data System (ADS)

    Hughes-Currie, Rosa B.; Senanayake, Pubudu S.; Wells, Jon-Paul R.; Reid, Michael F.; Berden, Giel; Reeves, Roger J.; Meijerink, Andries

    2013-09-01

    The excited-state structure of impurity-trapped excitons are measured in a multisite system. We use a two-color (UV-IR) pulsed photoluminescence enhancement technique, which probes the interlevel transitions and dynamics of impurity-trapped excitons in doped insulating phosphor materials. The technique is applied to NaMgF3:Yb2+, which exhibits emission from two charge-compensation centers with peaks at 22300 cm-1 (448 nm) and 24000 cm-1 (417 nm). The observed photoluminescence enhancement is caused by a combination of intraexcitonic excitation and electron trap liberation. The electron traps are inferred to have a depth of approximately 800 cm-1.

  20. Robust Anisotropic Diffusion Based Edge Enhancement for Level Set Segmentation and Asymmetry Analysis of Breast Thermograms using Zernike Moments.

    PubMed

    Prabha, S; Sujatha, C M; Ramakrishnan, S

    2015-01-01

    Breast thermography plays a major role in early detection of breast cancer in which the thermal variations are associated with precancerous state of breast. The distribution of asymmetrical thermal patterns indicates the pathological condition in breast thermal images. In this work, asymmetry analysis of breast thermal images is carried out using level set segmentation and Zernike moments. The breast tissues are subjected to Tukey’s biweight robust anisotropic diffusion filtering (TBRAD) for the generation of edge map. Reaction diffusion level set method is employed for segmentation in which TBRAD edge map is used as stopping criterion during the level set evolution. Zernike moments are extracted from the segmented breast tissues to perform asymmetry analysis. Results show that the TBRAD filter is able to enhance the edges near infra mammary folds and lower breast boundaries effectively. It is observed that segmented breast tissues are found to be continuous and has sharper boundary. This method yields high degree of correlation (98%) between the segmented output and the ground truth images. Among the extracted Zernike features, higher order moments are found to be significant in demarcating normal and carcinoma breast tissues by 9%. It appears that, the methodology adopted here is useful in accurate segmentation and differentiation of normal and carcinoma breast tissues for automated diagnosis of breast abnormalities.

  1. 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.

  2. Transient photoreceptor deconstruction by CNTF enhances rAAV-mediated cone functional rescue in late stage CNGB3-achromatopsia.

    PubMed

    Komáromy, András M; Rowlan, Jessica S; Corr, Amanda T Parton; Reinstein, Shelby L; Boye, Sanford L; Cooper, Ann E; Gonzalez, Amaliris; Levy, Britt; Wen, Rong; Hauswirth, William W; Beltran, William A; Aguirre, Gustavo D

    2013-06-01

    Achromatopsia is a genetic disorder of cones, and one of the most common forms is a channelopathy caused by mutations in the β-subunit, CNGB3, of the cone cyclic nucleotide-gated (CNG) channel. Recombinant adeno-associated virus of serotype 5 (rAAV5)-mediated gene transfer of human CNGB3 cDNA to mutant dog cones results in functional and structural rescue in dogs <0.5 years of age, but treatment is minimally effective in dogs >1 year. We now test a new therapeutic concept by combining gene therapy with the administration of ciliary neurotrophic factor (CNTF). Intravitreal CNTF causes transient dedifferentiation of photoreceptors, a process called deconstruction, whereby visual cells become immature with short outer segments, and decreased retinal function and gene expression that subsequently return to normal. Cone function was successfully rescued in all mutant dogs treated between 14 and 42 months of age with this strategy. CNTF-mediated deconstruction and regeneration of the photoreceptor outer segments prepares the mutant cones optimally for gene augmentation therapy.

  3. Interaction with Dopamine D2 Receptor Enhances Expression of Transient Receptor Potential Channel 1 at the Cell Surface

    PubMed Central

    Hannan, Meredith A.; Kabbani, Nadine; Paspalas, Constantinos D.; Levenson, Robert

    2008-01-01

    Receptor signaling is mediated by direct protein interaction with various types of cytoskeletal, adapter, effector, and additional receptor molecules. In brain tissue and in cultured neurons, activation of dopamine D2 receptors (D2Rs) has been found to impact cellular calcium signaling. Using a yeast two-hybrid approach, we have uncovered a direct physical interaction between the D2R and the transient receptor potential channel (TRPC) subtypes 1, 4 and 5. The TRPC/D2R interaction was further validated by GST-pulldown assays and coimmunoprecipitation from mammalian brain. Ultrastructural analysis of TRPC1 and D2R expression indicates colocalization of the two proteins within the cell body and dendrites of cortical neurons. In cultured cells, expression of D2Rs was found to increase expression of TRPC1 at the cell surface by 50%. These findings shed new light on the constituents of the D2R signalplex, and support the involvement of D2Rs in cellular calcium signaling pathways via a novel link to TRPC channels. PMID:18261457

  4. Transient Depletion of Kupffer Cells Leads to Enhanced Transgene Expression in Rat Liver Following Retrograde Intrabiliary Infusion of Plasmid DNA and DNA Nanoparticles

    PubMed Central

    Dai, Hui; Jiang, Xuan; Leong, Kam W.

    2011-01-01

    Abstract In this report, we have demonstrated that by temporarily removing Kupffer cells (KCs), the transgene expression levels mediated by retrograde intrabiliary infusion (RII) of plasmid DNA, polyethylenimine-DNA, and chitosan nanoparticles were enhanced by 1,927-, 131-, and 23,450-fold, respectively, in comparison with the respective groups without KC removal. KC removal also led to significantly prolonged transgene expression in the liver that received all three carriers. This increased transgene expression was correlated with significantly reduced serum tumor necrosis factor-α level as an indicator for KC activation. These results suggest that KC activation is a significant contributing factor to the lowered transgene expression by polycation-DNA nanoparticles delivered by RII. More importantly, the combination of RII and transient removal of KCs may be adopted as an effective approach to achieving high and persistent transgene expression in the liver mediated by nonviral nanoparticles. PMID:21091274

  5. Enhanced Li Adsorption and Diffusion on MoS2 Zigzag Nanoribbons by Edge Effects: A Computational Study.

    PubMed

    Li, Yafei; Wu, Dihua; Zhou, Zhen; Cabrera, Carlos R; Chen, Zhongfang

    2012-08-16

    By means of density functional theory computations, we systematically investigated the adsorption and diffusion of Li on the 2-D MoS2 nanosheets and 1-D zigzag MoS2 nanoribbons (ZMoS2NRs), in comparison with MoS2 bulk. Although the Li mobility can be significantly facilitated in MoS2 nanosheets, their decreased Li binding energies make them less attractive for cathode applications. Because of the presence of unique edge states, ZMoS2NRs have a remarkably enhanced binding interaction with Li without sacrificing the Li mobility, and thus are promising as cathode materials of Li-ion batteries with a high power density and fast charge/discharge rates.

  6. Quantitative measurements of enhanced soot production in a flickering methane/air diffusion flame

    SciTech Connect

    Shaddix, C.R.; Harrington, J.E.; Smyth, K.C. . Building and Fire Research Lab.)

    1994-12-01

    Integrated models of soot production and oxidation 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 of soot concentrations against experimental measurements obtained in time-varying flowfields. This paper reports quantitative measurements of the local soot volume fraction in a co-flowing, flickering CH[sub 4]/air diffusion flame burning at atmospheric pressure. Acoustic forcing of the fuel flow rate is used to phase lock the periodic flame flicker close to the natural flicker frequency. Measurements show that soot production is four time greater for a forcing condition in which flame tip clipping occurs, compared with a steady flame burning with the same mean fuel flow velocity. The soot field in the flickering flame has been characterized using tomographic reconstruction of extinction data obtained at 632.8 nm, laser-induced incandescence (LII) images calibrated against steady CH[sub 4]/air extinction results, and vertically polarized scattering data. 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 of these results suggests that the flickering flame exhibits similar number densities but larger particle sizes that the corresponding steady flame.

  7. Cold welding of gold nanoparticles on mica substrate: Self-adjustment and enhanced diffusion

    PubMed Central

    Cha, Song-Hyun; Park, Youmie; Han, Jeong Woo; Kim, Kyeounghak; Kim, Hyun-Seok; Jang, Hong-Lae; Cho, Seonho

    2016-01-01

    From the images of HR-TEM, FE-SEM, and AFM, the cold welding of gold nanoparticles (AuNPs) on a mica substrate is observed. The cold-welded gold nanoparticles of 25 nm diameters are found on the mica substrate in AFM measurement whereas the size of cold welding is limited to 10 nm for nanowires and 2~3 nm for nanofilms. Contrary to the nanowires requiring pressure, the AuNPs are able to rotate freely due to the attractive forces from the mica substrate and thus the cold welding goes along by adjusting lattice structures. The gold nanoparticles on the mica substrate are numerically modeled and whose physical characteristics are obtained by the molecular dynamic simulations of LAMMPS. The potential and kinetic energies of AuNPs on the mica substrate provide sufficient energy to overcome the diffusion barrier of gold atoms. After the cold welding, the regularity of lattice structure is maintained since the rotation of AuNPs is allowed due to the presence of mica substrate. It turns out that the growth of AuNPs can be controlled arbitrarily and the welded region is nearly perfect and provides the same crystal orientation and strength as the rest of the nanostructures. PMID:27597438

  8. Tailored exciton diffusion in organic photovoltaic cells for enhanced power conversion efficiency.

    PubMed

    Menke, S Matthew; Luhman, Wade A; Holmes, Russell J

    2013-02-01

    Photoconversion in planar-heterojunction organic photovoltaic cells (OPVs) is limited by a short exciton diffusion length (L(D)) that restricts migration to the dissociating electron donor/acceptor interface. Consequently, bulk heterojunctions are often used to realize high efficiency as these structures reduce the distance an exciton must travel to be dissociated. Here, we present an alternative approach that seeks to directly engineer L(D) by optimizing the intermolecular separation and consequently, the photophysical parameters responsible for excitonic energy transfer. By diluting the electron donor boron subphthalocyanine chloride into a wide-energy-gap host material, we optimize the degree of interaction between donor molecules and observe a ~50% increase in L(D). Using this approach, we construct planar-heterojunction OPVs with a power conversion efficiency of (4.4 ± 0.3)%, > 30% larger than the case of optimized devices containing an undiluted donor layer. The underlying correlation between L(D) and the degree of molecular interaction has wide implications for the design of both OPV active materials and device architectures.

  9. Enhancing electron collection efficiency and effective diffusion length in dye-sensitized solar cells.

    PubMed

    Wong, Daniel Kwan-Pang; Ku, Chen-Hao; Chen, Yen-Ru; Chen, Guan-Ren; Wu, Jih-Jen

    2009-10-19

    Intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy are employed to measure the dynamics of electron transport and recombination in the ZnO nanowire (NW) array-ZnO/layered basic zinc acetate (LBZA) nanoparticle (NP) composite dye-sensitized solar cells (DSSCs). The roles of the vertical ZnO NWs and insulating LBZA in the electron collection and transport in DSSCs are investigated by comparing the results to those in the TiO(2)-NP, horizontal TiO(2)-NW and vertical ZnO-NW-array DSSCs. The electron transport rate and electron lifetime in the ZnO NW/NP composite DSSC are superior to those in the conventional TiO(2)-NP cell due to the existence of the vertical ZnO NWs and insulating LBZA. It indicates that the ZnO NW/NP composite anode is able to sustain efficient electron collection over much greater thickness than the TiO(2)-NP cell does. Consequently, a larger effective electron diffusion length is available in the ZnO composite DSSC.

  10. 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.

  11. 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; Cáceres, Mónica; Becerra, Alvaro; Cabello-Verrugio, Claudio; Elorza, Alvaro A; Riedel, Claudia; Tapia, Pablo; Velásquez, 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.

  12. Exposure of nondividing populations of primary human fibroblasts to UV (254 nm) radiation induces a transient enhancement in capacity to repair potentially lethal cellular damage

    SciTech Connect

    Tyrrell, R.M.

    1984-02-01

    Nondividing (arrested) populations of primary human fibroblasts from normal individuals exposed to an intial dose (1.5 or 3 Jm/sup -2/) of far-UV (254 nm) radiation and then incubated in medium containing low (0.5%) serum develop enhanced resistance to inactivation of cloning efficiency by a second (challenge) dose of UV. The resistance develops within 2-4 days, after which there is a decline. Resistance develops to a higher degree and more rapidly (1-2 days) in cells derived from patients with the variant form of xeroderma pigmentosum. Excision-deficient cells from xeroderma pigmentosum complementation group A individuals also develop UV resistance after a lower (0.2 Jm/sup -2/) exposure to UV. Enhanced UV resistance does not develop in UV-irradiated cell populations incubated with the protein synthesis inhibitor cycloheximide (5 ..mu..M). These observations are consistent with the interpretation that exposure of human fibroblasts to low doses of UV induces synthesis of a protein involved in a metabolic pathway that transiently enhances the capacity of cells to repair potentially lethal damage resulting from a subsequent dose of UV.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  14. 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.

  15. Loss of the tectorial membrane protein CEACAM16 enhances spontaneous, stimulus-frequency, and transiently evoked otoacoustic emissions.

    PubMed

    Cheatham, Mary Ann; Goodyear, Richard J; Homma, Kazuaki; Legan, P Kevin; Korchagina, Julia; Naskar, Souvik; Siegel, Jonathan H; Dallos, Peter; Zheng, Jing; Richardson, Guy P

    2014-07-30

    α-Tectorin (TECTA), β-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.

  16. On-column labeling of gram-positive bacteria with a boronic acid functionalized squarylium cyanine dye for analysis by polymer-enhanced capillary transient isotachophoresis.

    PubMed

    Saito, Shingo; Massie, Tara L; Maeda, Takeshi; Nakazumi, Hiroyuki; Colyer, Christa L

    2012-03-06

    A new asymmetric, squarylium cyanine dye functionalized by boronic acid ("SQ-BA") was designed and synthesized for on-capillary labeling of gram-positive bacteria to provide for high sensitivity detection by way of a modified form of capillary electrophoresis with laser induced fluorescence detection (CE-LIF). The CE-based separation employed a polymer-enhanced buffer with capillary transient isotachophoresis in a new hybrid method dubbed "PectI." It was found that the addition of various monosaccharides to SQ-BA in a batch aqueous solution greatly enhanced the emission of the boronic acid functionalized dye by a factor of up to 18.3 at a long wavelength (λ(ex) = 630 nm, λ(em) = 660 nm) with a high affinity constant (K = ~10(2.80) M(-1)) superior to other sugar probes. Semiempirical quantum mechanics calculations suggest that the mechanism for this high enhancement may involve the dissociation of initially nonemissive dye associates (stabilized by an intramolecular hydrogen bond) upon complex formation with sugars. The fluorescence emission of SQ-BA was also significantly enhanced in the presence of a gram-positive bacterial spore, Bacillus globigii (Bg), which serves as a simulant of B. anthracis (or anthrax) and which possesses a peptidoglycan (sugar)-rich spore coat to provide ample sites for interaction with the dye. Several peaks were observed for a pure Bg sample even with polyethyleneoxide (PEO) present in the CE separation buffer, despite the polymer's previously demonstrated ability to focus microoorganisms to a single peak during migration. Likewise, several peaks were observed for a Bg sample when capillary transient isotachophoresis (ctITP) alone was employed. However, the new combination of these techniques as "PectI" dramatically and reproducibly focused the bacteria to a single peak with no staining procedure. Using PectI, the trace detection of Bg spores (corresponding to approximately three cells per injection) along with separation efficiency

  17. Synergistic efficacy of salicylic acid with a penetration enhancer on human skin monitored by OCT and diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhao, Qingliang; Dai, Cuixia; Fan, Shanhui; Lv, Jing; Nie, Liming

    2016-10-01

    Salicylic acid (SA) has been frequently used as a facial chemical peeling agent (FCPA) in various cosmetics for facial rejuvenation and dermatological treatments in the clinic. However, there is a tradeoff between therapeutic effectiveness and possible adverse effects caused by this agent for cosmetologists. To optimize the cosmetic efficacy with minimal concentration, we proposed a chemical permeation enhancer (CPE) azone to synergistically work with SA on human skin in vivo. The optical properties of human skin after being treated with SA alone and SA combined with azone (SA@azone) were successively investigated by diffuse reflectance spectroscopy (DRS) and optical coherence tomography (OCT). Our results revealed that as the SA concentration increased, the light reflectance decreased and the absorption increased. We also found that SA@azone exhibited a synergistic effect on enhancing light penetration and OCT imaging depth. We demonstrated that the combination of DRS and OCT techniques could be used as a noninvasive, rapid and accurate measurement method to monitor the subtle changes of skin tissue after treatment with FCPA and CPE. The approach will greatly benefit the development of clinical cosmetic surgery, dermatosis diagnosis and therapeutic effect inspection in related biomedical studies.

  18. Synergistic efficacy of salicylic acid with a penetration enhancer on human skin monitored by OCT and diffuse reflectance spectroscopy.

    PubMed

    Zhao, Qingliang; Dai, Cuixia; Fan, Shanhui; Lv, Jing; Nie, Liming

    2016-10-10

    Salicylic acid (SA) has been frequently used as a facial chemical peeling agent (FCPA) in various cosmetics for facial rejuvenation and dermatological treatments in the clinic. However, there is a tradeoff between therapeutic effectiveness and possible adverse effects caused by this agent for cosmetologists. To optimize the cosmetic efficacy with minimal concentration, we proposed a chemical permeation enhancer (CPE) azone to synergistically work with SA on human skin in vivo. The optical properties of human skin after being treated with SA alone and SA combined with azone (SA@azone) were successively investigated by diffuse reflectance spectroscopy (DRS) and optical coherence tomography (OCT). Our results revealed that as the SA concentration increased, the light reflectance decreased and the absorption increased. We also found that SA@azone exhibited a synergistic effect on enhancing light penetration and OCT imaging depth. We demonstrated that the combination of DRS and OCT techniques could be used as a noninvasive, rapid and accurate measurement method to monitor the subtle changes of skin tissue after treatment with FCPA and CPE. The approach will greatly benefit the development of clinical cosmetic surgery, dermatosis diagnosis and therapeutic effect inspection in related biomedical studies.

  19. Synergistic efficacy of salicylic acid with a penetration enhancer on human skin monitored by OCT and diffuse reflectance spectroscopy

    PubMed Central

    Zhao, Qingliang; Dai, Cuixia; Fan, Shanhui; Lv, Jing; Nie, Liming

    2016-01-01

    Salicylic acid (SA) has been frequently used as a facial chemical peeling agent (FCPA) in various cosmetics for facial rejuvenation and dermatological treatments in the clinic. However, there is a tradeoff between therapeutic effectiveness and possible adverse effects caused by this agent for cosmetologists. To optimize the cosmetic efficacy with minimal concentration, we proposed a chemical permeation enhancer (CPE) azone to synergistically work with SA on human skin in vivo. The optical properties of human skin after being treated with SA alone and SA combined with azone (SA@azone) were successively investigated by diffuse reflectance spectroscopy (DRS) and optical coherence tomography (OCT). Our results revealed that as the SA concentration increased, the light reflectance decreased and the absorption increased. We also found that SA@azone exhibited a synergistic effect on enhancing light penetration and OCT imaging depth. We demonstrated that the combination of DRS and OCT techniques could be used as a noninvasive, rapid and accurate measurement method to monitor the subtle changes of skin tissue after treatment with FCPA and CPE. The approach will greatly benefit the development of clinical cosmetic surgery, dermatosis diagnosis and therapeutic effect inspection in related biomedical studies. PMID:27721398

  20. Fast diffusion kurtosis imaging (DKI) with Inherent COrrelation-based Normalization (ICON) enhances automatic segmentation of heterogeneous diffusion MRI lesion in acute stroke.

    PubMed

    Zhou, Iris Yuwen; Guo, Yingkun; Igarashi, Takahiro; Wang, Yu; Mandeville, Emiri; Chan, Suk-Tak; Wen, Lingyi; Vangel, Mark; Lo, Eng H; Ji, Xunming; Sun, Phillip Zhe

    2016-12-01

    Diffusion kurtosis imaging (DKI) has been shown to augment diffusion-weighted imaging (DWI) for the definition of irreversible ischemic injury. However, the complexity of cerebral structure/composition makes the kurtosis map heterogeneous, limiting the specificity of kurtosis hyperintensity to acute ischemia. We propose an Inherent COrrelation-based Normalization (ICON) analysis to suppress the intrinsic kurtosis heterogeneity for improved characterization of heterogeneous ischemic tissue injury. Fast DKI and relaxation measurements were performed on normal (n = 10) and stroke rats following middle cerebral artery occlusion (MCAO) (n = 20). We evaluated the correlations between mean kurtosis (MK), mean diffusivity (MD) and fractional anisotropy (FA) derived from the fast DKI sequence and relaxation rates R1 and R2 , and found a highly significant correlation between MK and R1 (p < 0.001). We showed that ICON analysis suppressed the intrinsic kurtosis heterogeneity in normal cerebral tissue, enabling automated tissue segmentation in an animal stroke model. We found significantly different kurtosis and diffusivity lesion volumes: 147 ± 59 and 180 ± 66 mm(3) , respectively (p = 0.003, paired t-test). The ratio of kurtosis to diffusivity lesion volume was 84% ± 19% (p < 0.001, one-sample t-test). We found that relaxation-normalized MK (RNMK), but not MD, values were significantly different between kurtosis and diffusivity lesions (p < 0.001, analysis of variance). Our study showed that fast DKI with ICON analysis provides a promising means of demarcation of heterogeneous DWI stroke lesions.

  1. AS04, an aluminum salt- and TLR4 agonist-based adjuvant system, induces a transient localized innate immune response leading to enhanced adaptive immunity.

    PubMed

    Didierlaurent, Arnaud M; Morel, Sandra; Lockman, Laurence; Giannini, Sandra L; Bisteau, Michel; Carlsen, Harald; Kielland, Anders; Vosters, Olivier; Vanderheyde, Nathalie; Schiavetti, Francesca; Larocque, Daniel; Van Mechelen, Marcelle; Garçon, Nathalie

    2009-11-15

    Adjuvant System 04 (AS04) combines the TLR4 agonist MPL (3-O-desacyl-4'-monophosphoryl lipid A) and aluminum salt. It is a new generation TLR-based adjuvant licensed for use in human vaccines. One of these vaccines, the human papillomavirus (HPV) vaccine Cervarix, is used in this study to elucidate the mechanism of action of AS04 in human cells and in mice. The adjuvant activity of AS04 was found to be strictly dependent on AS04 and the HPV Ags being injected at the same i.m. site within 24 h of each other. During this period, AS04 transiently induced local NF-kappaB activity and cytokine production. This led to an increased number of activated Ag-loaded dendritic cells and monocytes in the lymph node draining the injection site, which further increased the activation of Ag-specific T cells. AS04 was also found to directly stimulate those APCs in vitro but not directly stimulate CD4(+) T or B lymphocytes. These AS04-induced innate responses were primarily due to MPL. Aluminum salt appeared not to synergize with or inhibit MPL, but rather it prolonged the cytokine responses to MPL at the injection site. Altogether these results support a model in which the addition of MPL to aluminum salt enhances the vaccine response by rapidly triggering a local cytokine response leading to an optimal activation of APCs. The transient and confined nature of these responses provides further supporting evidence for the favorable safety profile of AS04 adjuvanted vaccines.

  2. The potential of theragnostic 124I-8H9 convection-enhanced delivery in diffuse intrinsic pontine glioma

    PubMed Central

    Luther, Neal; Zhou, Zhiping; Zanzonico, Pat; Cheung, Nai-Kong; Humm, John; Edgar, Mark A.; Souweidane, Mark M.

    2014-01-01

    Background Reasons for failure in prior human glioma convection-enhanced delivery (CED) clinical trials remain unclear. Concentration-dependent volume of distribution (Vd) measurement of CED-infused agents in the human brain is challenging and highlights a potential technical shortcoming. Activity of iodine isotope 124 (124I ) in tissue can be directly measured in vivo with high resolution via PET. With the potential therapeutic utility of radioimmunotherapy, we postulate 124I conjugated to the antiglioma monoclonal antibody 8H9 may serve as a “theragnostic” agent delivered via CED to diffuse intrinsic pontine glioma. Methods Fifteen rats underwent CED of 0.1–1.0 mCi of 131I-8H9 to the pons for toxicity evaluation. Six additional rats underwent CED of 10 µCi of 124I-8H9 to the pons for dosimetry, with serial microPET performed for 1 week. Two primates underwent CED of gadolinium-albumin and 1.0 mCi of 124I-8H9 to the pons for safety and dosimetry analysis. Serial postoperative PET, blood, and CSF radioactivity counts were performed. Results One rat (1.0 mCi 131I-8H9 infusion) suffered toxicity necessitating early sacrifice. PET analysis in rats yielded a pontine absorbed dose of 37 Gy/mCi. In primates, no toxicity was observed, and absorbed pontine dose was 3.8 Gy/mCi. Activity decreased 10-fold with 48 h following CED in both animal models. Mean Vd was 0.14 cc3 (volume of infusion [Vi] to Vd ratio = 14) in the rat and 6.2 cc3 (Vd/Vi = 9.5) in primate. Conclusion The safety and feasibility of 124I dosimetry following CED via PET is demonstrated, establishing a preclinical framework for a trial evaluating CED of 124I-8H9 for diffuse intrinsic pontine glioma. PMID:24526309

  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

  4. 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.

  5. Virtual-source diffusion approximation for enhanced near-field modeling of photon-migration in low-albedo medium.

    PubMed

    Jia, Mengyu; Chen, Xueying; Zhao, Huijuan; Cui, Shanshan; Liu, Ming; Liu, Lingling; Gao, Feng

    2015-01-26

    Most analytical methods for describing light propagation in turbid medium exhibit low effectiveness in the near-field of a collimated source. Motivated by the Charge Simulation Method in electromagnetic theory as well as the established discrete source based modeling, we herein report on an improved explicit model for a semi-infinite geometry, referred to as "Virtual Source" (VS) diffuse approximation (DA), to fit for low-albedo medium and short source-detector separation. In this model, the collimated light in the standard DA is analogously approximated as multiple isotropic point sources (VS) distributed along the incident direction. For performance enhancement, a fitting procedure between the calculated and realistic reflectances is adopted in the near-field to optimize the VS parameters (intensities and locations). To be practically applicable, an explicit 2VS-DA model is established based on close-form derivations of the VS parameters for the typical ranges of the optical parameters. This parameterized scheme is proved to inherit the mathematical simplicity of the DA approximation while considerably extending its validity in modeling the near-field photon migration in low-albedo medium. The superiority of the proposed VS-DA method to the established ones is demonstrated in comparison with Monte-Carlo simulations over wide ranges of the source-detector separation and the medium optical properties.

  6. SUB-ALFVENIC NON-IDEAL MAGNETOHYDRODYNAMIC TURBULENCE SIMULATIONS WITH AMBIPOLAR DIFFUSION. III. IMPLICATIONS FOR OBSERVATIONS AND TURBULENT ENHANCEMENT

    SciTech Connect

    Li, Pak Shing; Klein, Richard I.; McKee, Christopher F. E-mail: cmckee@astro.berkeley.edu

    2012-01-01

    Ambipolar diffusion (AD) is believed to be a crucial process for redistributing magnetic flux in the dense molecular gas that occurs in regions of star formation. We carry out numerical simulations of this process in regions of low ionization using the heavy-ion approximation. The simulations are for regions of strong field (plasma {beta} = 0.1) and mildly supersonic turbulence (M=3, corresponding to an Alfven Mach number of 0.67). The velocity power spectrum of the neutral gas changes from an Iroshnikov-Kraichnan spectrum in the case of ideal MHD to a Burgers spectrum in the case of a shock-dominated hydrodynamic system. The magnetic power spectrum shows a similar behavior. We use a one-dimensional radiative transfer code to post-process our simulation results; the simulated emission from the CS J = 2-1 and H{sup 13}CO{sup +} J = 1-0 lines shows that the effects of AD are observable in principle. Linewidths of ions are observed to be less than those of neutrals, and we confirm previous suggestions that this is due to AD. We show that AD is unlikely to affect the Chandrasekhar-Fermi method for inferring field strengths unless the AD is stronger than generally observed. Finally, we present a study of the enhancement of AD by turbulence, finding that AD is accelerated by factor 2-4.5 for non-self-gravitating systems with the level of turbulence we consider.

  7. Enhanced effect of diffused Ohmic contact metal atoms for device scaling in AlGaN/GaN heterostructure field-effect transistors

    NASA Astrophysics Data System (ADS)

    Liu, Huan; Cheng, Aijie; Lin, Zhaojun; Cui, Peng; Liu, Yan; Fu, Chen; Lv, Yuanjie; Feng, Zhihong; Luan, Chongbiao

    2017-03-01

    Using measured capacitance-voltage and current-voltage curves for the AlGaN/GaN heterostructure field-effect transistors with different source-drain spacing, the electron mobility under the gate region was obtained. By comparing mobility variation and analyzing polarization charge distribution, it is found that with device scaling, the effect of the diffused Ohmic contact metal atoms on the electron mobility is enhanced. Then, a theoretical calculation related to different scattering mechanisms was adopted and it was verified this enhanced effect is due to the enhanced polarization Coulomb field (PCF) scattering.

  8. Performance of Enhanced Liver Fibrosis test and comparison with transient elastography in the identification of liver fibrosis in patients with chronic hepatitis B infection.

    PubMed

    Trembling, P M; Lampertico, P; Parkes, J; Tanwar, S; Viganò, M; Facchetti, F; Colombo, M; Rosenberg, W M

    2014-06-01

    Assessment of liver fibrosis is important in determining prognosis, disease progression and need for treatment in patients with chronic hepatitis B (CHB). Limitations to the use of liver biopsy in assessing fibrosis are well recognized, and noninvasive tests are being increasingly evaluated including transient elastography (TE) and serum markers such as the Enhanced Liver Fibrosis (ELF) test. We assessed performance of ELF and TE in detecting liver fibrosis with reference to liver histology in a cohort of patients with CHB (n = 182), and compared the performance of these modalities. Median age was 46 and mean AST 70 IU/L. Cirrhosis was reported in 20% of liver biopsies. Both modalities performed well in assessing fibrosis at all stages. Area under receiver operator characteristic (AUROC) curves for detecting METAVIR fibrosis stages F ≥ 1, F ≥ 2, F ≥ 3 and F4 were 0.77, 0.82, 0.80 and 0.83 for ELF and 0.86, 0.86, 0.90 and 0.95 for TE. TE performed significantly better in the assessment of severe fibrosis (AUROC 0.80 for ELF and 0.90 for TE, P < 0.01) and cirrhosis (0.83 for ELF and 0.95 for TE, P < 0.01). This study demonstrates that ELF has good performance in detection of liver fibrosis in patients with CHB, and when compared, TE performs better in detection of severe fibrosis/cirrhosis.

  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. Performance of Enhanced Liver Fibrosis test and comparison with transient elastography in the identification of liver fibrosis in patients with chronic hepatitis B infection

    PubMed Central

    Trembling, P M; Lampertico, P; Parkes, J; Tanwar, S; Viganò, M; Facchetti, F; Colombo, M; Rosenberg, W M

    2014-01-01

    Assessment of liver fibrosis is important in determining prognosis, disease progression and need for treatment in patients with chronic hepatitis B (CHB). Limitations to the use of liver biopsy in assessing fibrosis are well recognized, and noninvasive tests are being increasingly evaluated including transient elastography (TE) and serum markers such as the Enhanced Liver Fibrosis (ELF) test. We assessed performance of ELF and TE in detecting liver fibrosis with reference to liver histology in a cohort of patients with CHB (n = 182), and compared the performance of these modalities. Median age was 46 and mean AST 70 IU/L. Cirrhosis was reported in 20% of liver biopsies. Both modalities performed well in assessing fibrosis at all stages. Area under receiver operator characteristic (AUROC) curves for detecting METAVIR fibrosis stages F ≥ 1, F ≥ 2, F ≥ 3 and F4 were 0.77, 0.82, 0.80 and 0.83 for ELF and 0.86, 0.86, 0.90 and 0.95 for TE. TE performed significantly better in the assessment of severe fibrosis (AUROC 0.80 for ELF and 0.90 for TE, P < 0.01) and cirrhosis (0.83 for ELF and 0.95 for TE, P < 0.01). This study demonstrates that ELF has good performance in detection of liver fibrosis in patients with CHB, and when compared, TE performs better in detection of severe fibrosis/cirrhosis. PMID:24750297

  11. Bilateral high-frequency stimulation of the subthalamic nucleus on attentional performance: transient deleterious effects and enhanced motivation in both intact and parkinsonian rats

    PubMed Central

    Baunez, Christelle; Christakou, Anastasia; Chudasama, Yogita; Forni, Claude; Robbins, Trevor W.

    2007-01-01

    It is now well established that subthalamic nucleus high-frequency stimulation (STN HFS) alleviates motor problems in Parkinson's disease. However, its efficacy for cognitive function remains a matter of debate. The aim of this study was to assess the effects of STN HFS in rats performing a visual attentional task. Bilateral STN HFS was applied in intact and in bilaterally dopamine (DA)-depleted rats. In all animals, STN HFS had a transient debilitating effect on all the variables measured in the task. In DA-depleted rats, STN HFS did not alleviate the deficits induced by the DA lesion such as omissions and latency to make correct responses, but induced perseverative approaches to the food magazine, an indicator of enhanced motivation. In sham-operated controls, STN HFS significantly reduced accuracy and induced perseverative behaviour, mimicking partially the effects of bilateral STN lesions in the same task. These results are in line with the hypothesis that STN HFS only partially mimics inactivation of STN produced by lesioning and confirm the motivational exacerbation induced by STN inactivation. PMID:17331214

  12. 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.

  13. 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

  14. 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

  15. Atomistic modeling of intrinsic and radiation-enhanced fission gas (Xe) diffusion in UO2±x: Implications for nuclear fuel performance modeling

    NASA Astrophysics Data System (ADS)

    Andersson, D. A.; Garcia, P.; Liu, X.-Y.; Pastore, G.; Tonks, M.; Millett, P.; Dorado, B.; Gaston, D. R.; Andrs, D.; Williamson, R. L.; Martineau, R. C.; Uberuaga, B. P.; Stanek, C. R.

    2014-08-01

    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. UO2±x), 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 UO2±x non-stoichiometry were 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 UO2±x 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.

  16. Enhancement and retardation of thermal boron diffusion in silicon from atmospheric pressure chemical vapor deposited boron silicate glass film

    NASA Astrophysics Data System (ADS)

    Kurachi, Ikuo; Yoshioka, Kentaro

    2014-03-01

    Thermal boron diffusion into silicon from boron silicate glass (BSG) prepared by atmospheric pressure CVD (AP-CVD) has been investigated in terms of the BSG boron concentration dependence on diffusion mechanism for N-type solar cell applications. With thermal diffusion at 950 °C in N2 for 20 min, the sheet resistance of the boron-diffused layer decreases with BSG boron concentration up to approximately 4 × 1021 cm-3 at which a boron-rich layer (BRL) is formed at the surface. However, the resistance increases with BSG boron concentration when the BSG boron concentration is higher than 4 × 1021 cm-3. It is also confirmed that the diffusion depth decreases with increasing BSG boron concentration within this BSG concentration region. To clarify this mechanism, the BSG boron concentration dependence on boron diffusivity has also been studied. From extracted diffusivities, the anomalous diffusion can be explained by silicon interstitials formed owing to kick-out by diffused boron atoms and by silicon interstitial generation-degradation due to BRL formation.

  17. Assessment of Blood-Brain Barrier Permeability by Dynamic Contrast-Enhanced MRI in Transient Middle Cerebral Artery Occlusion Model after Localized Brain Cooling in Rats

    PubMed Central

    Kim, Eun Soo; Kwon, Mi Jung; Lee, Phil Hye; Ju, Young-Su; Yoon, Dae Young; Kim, Hye Jeong; Lee, Kwan Seop

    2016-01-01

    Objective The purpose of this study was to evaluate the effects of localized brain cooling on blood-brain barrier (BBB) permeability following transient middle cerebral artery occlusion (tMCAO) in rats, by using dynamic contrast-enhanced (DCE)-MRI. Materials and Methods Thirty rats were divided into 3 groups of 10 rats each: control group, localized cold-saline (20℃) infusion group, and localized warm-saline (37℃) infusion group. The left middle cerebral artery (MCA) was occluded for 1 hour in anesthetized rats, followed by 3 hours of reperfusion. In the localized saline infusion group, 6 mL of cold or warm saline was infused through the hollow filament for 10 minutes after MCA occlusion. DCE-MRI investigations were performed after 3 hours and 24 hours of reperfusion. Pharmacokinetic parameters of the extended Tofts-Kety model were calculated for each DCE-MRI. In addition, rotarod testing was performed before tMCAO, and on days 1-9 after tMCAO. Myeloperoxidase (MPO) immunohisto-chemistry was performed to identify infiltrating neutrophils associated with the inflammatory response in the rat brain. Results Permeability parameters showed no statistical significance between cold and warm saline infusion groups after 3-hour reperfusion 0.09 ± 0.01 min-1 vs. 0.07 ± 0.02 min-1, p = 0.661 for Ktrans; 0.30 ± 0.05 min-1 vs. 0.37 ± 0.11 min-1, p = 0.394 for kep, respectively. Behavioral testing revealed no significant difference among the three groups. However, the percentage of MPO-positive cells in the cold-saline group was significantly lower than those in the control and warm-saline groups (p < 0.05). Conclusion Localized brain cooling (20℃) does not confer a benefit to inhibit the increase in BBB permeability that follows transient cerebral ischemia and reperfusion in an animal model, as compared with localized warm-saline (37℃) infusion group. PMID:27587960

  18. 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 α-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, ΔpHS. 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 (τpHi > τpHS). Simultaneous measurements with two pHi electrodes, one superficial and one deep, suggest that impalement depth contributes to pHi delay and higher τpHi. Using higher CO2/HCO3− levels, i.e., 5%/33 mM HCO3− or 10%/66 mM HCO3−, increases (dpHi/dt)max and ΔpHS, 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

  19. 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; Tröltzsch, Michael; Schütz, 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 (4.6/2.6–75 and 6.7/2.9–21.3 kPa) and ARFI (2.1/0.7–3.7 and 2.0/0.7–3.8 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

  20. Blocking transient receptor potential vanilloid 2 channel in astrocytes enhances astrocyte-mediated neuroprotection after oxygen-glucose deprivation and reoxygenation.

    PubMed

    Zhang, Han; Xiao, Jun; Hu, Zheng; Xie, Minjie; Wang, Wei; He, Dan

    2016-10-01

    Astrocytes play important roles in homeostatic regulation in the central nervous system and are reported to influence the outcome of ischemic injury. Regulating Ca(2+) signaling of astrocytes is a promising strategy for stroke therapy. Herein, we report for the first time that transient receptor potential vanilloid 2 (TRPV2), a Ca(2+) -permeable channel that is important in osmotic balance regulation, expresses in rat cortical astrocytes by immunofluorescence. Moreover, oxygen-glucose deprivation and reoxygenation (OGD/R) treatment enhanced the expression. The TRPV2 is functional because Ca(2+) imaging showed that activating the TRPV2 channel in cultured astrocytes increased intracellular Ca(2+) level and the increment of intracellular Ca(2+) level expanded when astrocytes were treated with OGD/R. Staining with 5-ethynyl-2'-deoxyuridine (EdU) revealed that while blocking the TRPV2, it promoted the proliferation of astrocytes. Additionally, blocking the TRPV2 in astrocytes increased the synthesis of nerve growth factor (NGF) mRNA and the secretion of NGF by real-time PCR and enzyme-linked immunosorbent assay respectively. We further found that the increased secretion of NGF could be reversed by c-JunN-terminalkinase (JNK) inhibitor and blocking the TRPV2 caused the phosphorylation of JNK. These indicated that blocking the TRPV2 induced NGF secretion via the mitogen-activated protein kinase (MAPK)-JNK signaling pathway. As the promoted proliferation of astrocytes and secretion of NGF were reported to have neuroprotective effects in the early stage of stroke, we concluded that targeting the TRPV2 channel in astrocytes might be a potential new therapeutic strategy in ischemic stroke.

  1. Enhanced production of secretory glycoprotein VSTM1-v2 with mouse IgGκ 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 IgGκ 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, 3.6 mg/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 0.5 mg/L to 3.6 mg/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.

  2. Effect of the initial field's phase dislocation on the intensity enhancement factor of the laser beam backscattered off a diffuse target

    NASA Astrophysics Data System (ADS)

    Banakh, V. A.; Rytchkov, D. S.

    2014-11-01

    The given article presents the results of the investigation of the vortex laser beam reflection off a diffuse target in turbulent medium. Expressions of the mutual coherence function (MCF) and the relative intensity enhancement factor (REF) of a laser beam at the receiver plane are derived. The effect of the initial phase dislocation in the laser field distribution on the MCF and the REF of a backward wave at the receiver plane is investigated.

  3. Enhanced slow wave sleep and improved sleep maintenance after gaboxadol administration during seven nights of exposure to a traffic noise model of transient insomnia.

    PubMed

    Dijk, D-J; Stanley, N; Lundahl, J; Groeger, J A; Legters, A; Trap Huusom, A K; Deacon, S

    2012-08-01

    Slow wave sleep (SWS) has been reported to correlate with sleep maintenance, but whether pharmacological enhancement of SWS also leads to improved sleep maintenance is not known. Here we evaluate the time-course of the effects of gaboxadol, an extra-synaptic gamma-aminobutyric acid (GABA) agonist, on SWS, sleep maintenance, and other sleep measures in a traffic noise model of transient insomnia. After a placebo run-in, 101 healthy subjects (20-78 y) were randomized to gaboxadol (n = 50; 15 mg in subjects <65 y and 10 mg in subjects ≥65 y) or placebo (n = 51) for 7 nights (N1-N7). The model caused some disruption of sleep initiation and maintenance, with greatest effects on N1. Compared with placebo, gaboxadol increased SWS and slow wave activity throughout N1 to N7 (p < 0.05). Gaboxadol reduced latency to persistent sleep overall (N1-N7) by 4.5 min and on N1 by 11 min (both p < 0.05). Gaboxadol increased total sleep time (TST) overall by 16 min (p < 0.001) and on N1 by 38 min (p < 0.0001). Under gaboxadol, wakefulness after sleep onset was reduced by 11 min overall (p < 0.01) and by 29 min on N1 (p < 0.0001), and poly-somnographic awakenings were reduced on N1 (p < 0.05). Gaboxadol reduced self-reported sleep onset latency overall and on N1 (both p < 0.05) and increased self-reported TST overall (p < 0.05) and on N1 (p < 0.01). Subjective sleep quality improved overall (p < 0.01) and on N1 (p < 0.0001). Increases in SWS correlated with objective and subjective measures of sleep maintenance and subjective sleep quality under placebo and gaboxadol (p < 0.05). Gaboxadol enhanced SWS and reduced the disruptive effects of noise on sleep initiation and maintenance.

  4. Can Dynamic Contrast-Enhanced MRI (DCE-MRI) and Diffusion-Weighted MRI (DW-MRI) Evaluate Inflammation Disease

    PubMed Central

    Zhu, Jianguo; Zhang, Faming; Luan, Yun; Cao, Peng; Liu, Fei; He, Wenwen; Wang, Dehang

    2016-01-01

    Abstract The aim of the study was to investigate diagnosis efficacy of dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted MRI (DW-MRI) in Crohn's disease (CD). To find out the correlations between functional MRI parameters including Ktrans, Kep, Ve, Vp, and apparent diffusion coefficient (ADC) with a serologic biomarker. The relationships between pharmacokinetic parameters and ADC were also studied. Thirty-two patients with CD (22 men, 10 women; mean age: 30.5 years) and 18 healthy volunteers without any inflammatory disease (10 men, 8 women; mean age, 34.11 years) were enrolled into this approved prospective study. Pearson analysis was used to evaluate the correlation between Ktrans, Kep, Ve, Vp, and C-reactive protein (CRP), ADC, and CRP respectively. The diagnostic efficacy of the functional MRI parameters in terms of sensitivity and specificity were analyzed by receiver operating characteristic (ROC) curve analyses. Optimal cut-off values of each functional MRI parameters for differentiation of inflammatory from normal bowel were determined according to the Youden criterion. Mean value of Ktrans in the CD group was significantly higher than that of normal control group. Similar results were observed for Kep and Ve. On the contrary, the ADC value was lower in the CD group than that in the control group. Ktrans and Ve were shown to be correlated with CRP (r = 0.725, P < 0.001; r = 0.533, P = 0.002), meanwhile ADC showed negative correlation with CRP (r = −0.630, P < 0.001). There were negative correlations between the pharmacokinetic parameters and ADC, such as Ktrans to ADC (r = −0.856, P < 0.001), and Ve to ADC (r = −0.451, P = 0.01). The area under the curve (AUC) was 0.994 for Ktrans (P < 0.001), 0.905 for ADC (P < 0.001), 0.806 for Ve (P < 0.001), and 0.764 for Kep (P = 0.002). The cut-off point of the Ktrans was found to be 0.931 min–1. This value provided the best trade-off between

  5. 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.

  6. 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.

  7. A scaled-ionic-charge simulation model that reproduces enhanced and suppressed water diffusion in aqueous salt solutions.

    PubMed

    Kann, Z R; Skinner, J L

    2014-09-14

    Non-polarizable models for ions and water quantitatively and qualitatively misrepresent the salt concentration dependence of water diffusion in electrolyte solutions. In particular, experiment shows that the water diffusion coefficient increases in the presence of salts of low charge density (e.g., CsI), whereas the results of simulations with non-polarizable models show a decrease of the water diffusion coefficient in all alkali halide solutions. We present a simple charge-scaling method based on the ratio of the solvent dielectric constants from simulation and experiment. Using an ion model that was developed independently of a solvent, i.e., in the crystalline solid, this method improves the water diffusion trends across a range of water models. When used with a good-quality water model, e.g., TIP4P/2005 or E3B, this method recovers the qualitative behaviour of the water diffusion trends. The model and method used were also shown to give good results for other structural and dynamic properties including solution density, radial distribution functions, and ion diffusion coefficients.

  8. 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

    2016-03-08

    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 β1 Na(+)-K(+) pump subunit, a reversible oxidative modification that inhibits the pump. Susceptibility of the β1 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

  9. Performance enhancement of polymer electrolyte fuel cells by combining liquid removal mechanisms of a gas diffusion layer with wettability distribution and a gas channel with microgrooves

    NASA Astrophysics Data System (ADS)

    Utaka, Yoshio; Koresawa, Ryo

    2016-08-01

    Although polymer electrolyte fuel cells (PEFCs) are commercially available, there are still many problems that need to be addressed to improve their performance and increase their usage. At a high current density, generated water accumulates in the gas diffusion layer and in the gas channels of the cathode. This excess water obstructs oxygen transport, and as a result, cell performance is greatly reduced. To improve the cell performance, the effective removal of the generated water and the promotion of oxygen diffusion in the gas diffusion layer (GDL) are necessary. In this study, two functions proposed in previous reports were combined and applied to a PEFC: a hybrid GDL to form an oxygen diffusion path using a wettability distribution and a gas separator with microgrooves to enhance liquid removal. For a PEFC with a hybrid GDL and a gas separator with microgrooves, the concentration overvoltage of the PEFC was reduced, and the current density limit and maximum power density were increased compared with a conventional PEFC. Moreover, the stability of the cell voltage was markedly improved.

  10. Poly(vinylidene fluoride-co-hexafluoropropylene) phase inversion coating as a diffusion layer to enhance the cathode performance in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Yang, Wulin; Zhang, Fang; He, Weihua; Liu, Jia; Hickner, Michael A.; Logan, Bruce E.

    2014-12-01

    A low cost poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) phase inversion coating was developed as a cathode diffusion layer to enhance the performance of microbial fuel cells (MFCs). A maximum power density of 1430 ± 90 mW m-2 was achieved at a PVDF-HFP loading of 4.4 mg cm-2 (4:1 polymer:carbon black), with activated carbon as the oxygen reduction cathode catalyst. This power density was 31% higher than that obtained with a more conventional platinum (Pt) catalyst on carbon cloth (Pt/C) cathode with a poly(tetrafluoroethylene) (PTFE) diffusion layer (1090 ± 30 mW m-2). The improved performance was due in part to a larger oxygen mass transfer coefficient of 3 × 10-3 cm s-1 for the PVDF-HFP coated cathode, compared to 1.7 × 10-3 cm s-1 for the carbon cloth/PTFE-based cathode. The diffusion layer was resistant to electrolyte leakage up to water column heights of 41 ± 0.5 cm (4.4 mg cm-2 loading of 4:1 polymer:carbon black) to 70 ± 5 cm (8.8 mg cm-2 loading of 4:1 polymer:carbon black). This new type of PVDF-HFP/carbon black diffusion layer could reduce the cost of manufacturing cathodes for MFCs.

  11. 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%.

  12. Hydrodynamic enhancement of the diffusion rate in the region between two fluctuating membranes in close opposition: a theoretical and computational study.

    PubMed

    Pannuzzo, Martina; Grassi, Antonio; Raudino, Antonio

    2014-07-24

    Periodic variation of the distance between two weakly adhering bodies gives rise to a huge tangential motions of the sandwiched solvent layer (squeezing flow). Oscillations either can be induced by an external applied field or can spontaneously arise from the coupling with the solvent heat bath. First we calculated by the Navier-Stokes equation the components of the fluid velocity near two oscillating juxtaposed plates. Then we evaluated the influence of plate oscillations on the transport properties of a trace diffusant dissolved at t = 0 in the outer medium for both deterministic and stochastic excitations. By employing both analytical (Fokker-Planck) and coarse-grained molecular dynamics (MD) simulations, we proved that the entry and migration rates of the diffusant sharply increases with the oscillation amplitudes. Enhancement was related to relevant parameters like oscillation frequency, fluid layer thickness, fluid viscosity, and temperature. An extension to the case of oscillating multistacked lamellae has been also made. Theoretical and MD results suggest a significant enhancement of the diffusant flux even in the worse situation of thermally excited small amplitude fluctuations. Excitation arising from other sources (e.g., microwave or ultrasound irradiation of solid-fluid layered systems) could have a dramatic effect on the transport phenomena. Possible implications to relevant biological problems have been discussed.

  13. Superresolution microscopy with transient binding.

    PubMed

    Molle, Julia; Raab, Mario; Holzmeister, Susanne; Schmitt-Monreal, Daniel; Grohmann, Dina; He, Zhike; Tinnefeld, Philip

    2016-06-01

    For single-molecule localization based superresolution, the concentration of fluorescent labels has to be thinned out. This is commonly achieved by photophysically or photochemically deactivating subsets of molecules. Alternatively, apparent switching of molecules can be achieved by transient binding of fluorescent labels. Here, a diffusing dye yields bright fluorescent spots when binding to the structure of interest. As the binding interaction is weak, the labeling is reversible and the dye ligand construct diffuses back into solution. This approach of achieving superresolution by transient binding (STB) is reviewed in this manuscript. Different realizations of STB are discussed and compared to other localization-based superresolution modalities. We propose the development of labeling strategies that will make STB a highly versatile tool for superresolution microscopy at highest resolution.

  14. Enhanced intensity variation for multiple-plane phase retrieval using a spatial light modulator as a convenient tunable diffuser.

    PubMed

    Almoro, Percival F; Pham, Quang Duc; Serrano-Garcia, David Ignacio; Hasegawa, Satoshi; Hayasaki, Yoshio; Takeda, Mitsuo; Yatagai, Toyohiko

    2016-05-15

    In the multiple-plane phase retrieval method, a tedious-to-fabricate phase diffuser plate is used to increase the axial intensity variation for a nonstagnating iterative reconstruction of a smooth object wavefront. Here we show that a spatial light modulator (SLM) can be used as an easily controllable diffuser for phase retrieval. The polarization modulation at the SLM facilitates independent formation of orthogonally polarized scattered and specularly reflected beams. Through an analyzer, the polarization states are filtered enabling beam interference, thereby efficiently encoding the phase information in the axially diverse speckle intensity measurements. The technique is described using wave propagation and Jones calculus, and demonstrated experimentally on technical and biological samples.

  15. Concentration-dependent diffusion of ion-implanted silicon in In0.53Ga0.47As

    NASA Astrophysics Data System (ADS)

    Aldridge, H. L.; Lind, A. G.; Law, M. E.; Hatem, C.; Jones, K. S.

    2014-07-01

    In contrast to prior reports, evidence of concentration-dependent diffusion is reported for Si implanted In0.53Ga0.47As. The Fickian and concentration-dependent components of diffusivities were extracted using the Florida object oriented process and device simulator. The migration energy for silicon diffusion in In0.53Ga0.47As was calculated to be 2.4 and 1.5 eV for the Fickian and concentration dependent components of diffusion, respectively. A lack of change in diffusivities at given anneal temperatures suggest that transient-enhanced diffusion has not occurred. Due to these findings, silicon diffusion at high doping concentrations (>1 × 1020 cm-3) should be better characterized and understood for future complimentary metal-oxide semiconductor applications.

  16. Transient space-charge-limited current pulse shapes in molecularly doped polymers

    NASA Astrophysics Data System (ADS)

    Goldie, D. M.

    1999-12-01

    The transient current response of molecularly doped polymers have been numerically modelled under space-charge-limited (SCL) conditions for the situation in which a step potential is applied to an ideal injecting contact. Under trap-free conditions, the transient SCL current pulse shape is found to be sensitive not only to the underlying field dependence of the injected carrier mobilities and diffusivities, but also to the magnitude of the applied step potential. A progressive reduction in the ratio of the peak current density jp to the final steady-state magnitude jss is obtained by increasing either the field strength of the mobility or the relative amount of diffusion. It is demonstrated, however, that for times preceding the location tp of the current peak, the rate of current increase displays a gradual transition from a super-linear to linear time dependence upon the introduction of diffusion. The diminishing observability of jp/jss is accompanied by a shift in the position of tp relative to the space-charge-free carrier transit time t0. The classical fixed-mobility value tp/t0 = 0.786 is modestly reduced as the field strength of the mobility or amount of carrier diffusion is enhanced. The numerical predictions are compared with experimental SCL current transients obtained from hydrazone doped polyester samples fitted with gold contacts.

  17. 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.

  18. Binary and ternary gas mixtures with temperature enhanced diffuse glow discharge characteristics for use in closing switches

    DOEpatents

    Christophorou, Loucas G.; Hunter, Scott R.

    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.

  19. 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.

  20. Unexpected transient effect.

    PubMed

    Chame, A; Villain, J

    2001-02-01

    When a grooved periodic profile cut in a crystalline surface relaxes through surface diffusion, flatter parts appear at the top and bottom in the transient state which precedes complete smoothing. This has been attributed to a tendency of successive steps of identical sign to draw closer to one another. This kind of kinetic interaction is a consequence of the finite value of the interatomic distance, and is present even if no interaction between steps is taken into account. We investigate this effect in a very simplified model, namely, a one-dimensional profile with alternating pairs of up and down steps, where no annihilation of steps is allowed. The quantitative effect is partly treated analytically.

  1. 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.

  2. Enlarged extracellular space of aquaporin-4-deficient mice does not enhance diffusion of Alexa Fluor 488 or dextran polymers.

    PubMed

    Xiao, F; Hrabetová, S

    2009-06-16

    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 a real-time iontophoretic (RTI) method demonstrated an increase of about 25% in the ECS volume fraction (alpha) in the neocortex of AQP4(-/-) mice compared to AQP4(+/+) mice but no change in the hindrance imposed to diffusing molecules (tortuosity lambda). In contrast, other diffusion studies employing large molecules (dextran polymers) and a fluorescence recovery after photobleaching (FRAP) method measured a decrease of about 10%-20% in lambda in the neocortex of AQP4(-/-) mice. These conflicting findings on lambda 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 (molecular weight [MW] 547, lambda(AF)) and two large dextran polymers (MW 3000, lambda(dex3) and MW 75,000, lambda(dex75)) in the in vitro neocortex of AQP4(+/+) and AQP4(-/-) mice. We found that lambda(AF)=1.59, lambda(dex3)=1.76 and lambda(dex75)=2.30 obtained in AQP4(-/-) mice were not significantly different from lambda(AF)=1.61, lambda(dex3)=1.76, and lambda(dex75)=2.33 in AQP4(+/+) mice. These IOI results demonstrate that lambda 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.

  3. 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, Rüdiger; 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 board–approved 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 material–enhanced 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

  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. 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

  6. Enhanced coercivity thermal stability realized in Nd-Fe-B thin films diffusion-processed by Nd-Co alloys

    NASA Astrophysics Data System (ADS)

    Zhong, Hui; Fu, Yanqing; Li, Guojian; Liu, Tie; Cui, Weibin; Liu, Wei; Zhang, Zhidong; Wang, Qiang

    2017-03-01

    A proposed Nd2Fe14B-core/Nd2(Fe, Co)14B-shell microstructure was realized by diffusion-processing textured Nd14Fe77B9 single-layer film with Nd100-xCox (x=10, 20 and 40) alloys to improve the coercivity thermal stability. The ambient coercivity was increased from around 1 T in single-layer film to nearly 2 T in diffusion-processed films, which was due to the Nd-rich grain boundaries as seen from transmission electron microscopy (TEM) images. The coercivity thermal stability was improved by the core/shell microstructure because Nd-rich grain boundaries provided the high ambient coercivity and Co-rich shell provided the improved coercivity stability.

  7. Enlarged extracellular space of aquaporin-4-deficient mice does not enhance diffusion of Alexa Fluor 488 or dextran polymers

    PubMed Central

    Xiao, Fanrong; Hrabětová, 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 (α) in the neocortex of AQP4−/− mice compared to AQP4+/+ mice but no change in the hindrance imposed to diffusing molecules (tortuosity λ). In contrast, other diffusion studies employing large molecules (dextran polymers) and fluorescence recovery after photobleaching (FRAP) method measured a decrease of about 10–20% in λ in the neocortex of AQP4−/− mice. These conflicting findings on λ 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, λAF) and two large dextran polymers (MW 3,000, λdex3 and MW 75,000, λdex75) in the in vitro neocortex of AQP4+/+ and AQP4−/− mice. We found that λAF = 1.59, λdex3 = 1.76 and λdex75 = 2.30 obtained in AQP4−/− mice were not significantly different from λAF = 1.61, λdex3 = 1.76, and λdex75 = 2.33 in AQP4+/+ mice. These IOI results demonstrate that λ 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

  8. Anisotropic diffusion filter based edge enhancement for the segmentation of carotid intima-media layer in ultrasound images using variational level set method without re-initialisation.

    PubMed

    Sumathi, K; Anandh, K R; Mahesh, V; Ramakrishnan, S

    2014-01-01

    In this work an attempt has been made to enhance the edges and segment the boundary of intima-media layer of Common Carotid Artery (CCA) using anisotropic diffusion filter and level set method. Ultrasound B mode longitudinal images of normal and abnormal images of common carotid arteries are used in this study. The images are subjected to anisotropic diffusion filter to generate edge map. This edge map is used as a stopping boundary in variational level set method without re-initialisation to segment the intima-media layer. Geometric features are extracted from this layer and analyzed statistically. Results show that anisotropic diffusion filtering is able to extract the edges in both normal and abnormal images. The obtained edge maps are found to have high contrast and sharp edges. The edge based variational level set method is able to segment the intima-media layer precisely from common carotid artery. The extracted geometrical features such as major axis and extent are found to be statistically significant in differentiating normal and abnormal images. Thus this study seems to be clinically useful in diagnosis of cardiovascular disease.

  9. 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. PMID:27026795

  10. Pulse Mitigation and Heat Transfer Enhancement Techniques. Volume 4. Transient Behavior of Heat Pipe With Thermal Energy Storage Under Pulse Heat Loads

    DTIC Science & Technology

    1992-08-01

    the remarkable properties of the heat pipe have become appreciated, and serious developmental work is still taking place. A heat pipe consists of a...transient liquid flow model requires knowledge of the saturation dependence of the capillary flow properties , which can only be determined by experiment...their discretization equations which are physically unrealistic. In light of the above observation, an improved ADI method is proposed. The

  11. 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.

  12. DIFFUSION PUMP

    DOEpatents

    Levenson, L.

    1963-09-01

    A high-vacuum diffusion pump is described, featuring a novel housing geometry for enhancing pumping speed. An upright, cylindrical lower housing portion is surmounted by a concentric, upright, cylindrical upper housing portion of substantially larger diameter; an uppermost nozzle, disposed concentrically within the upper portion, is adapted to eject downwardly a conical sheet of liquid outwardly to impinge upon the uppermost extremity of the interior wall of the lower portion. Preferably this nozzle is mounted upon a pedestal rising coaxially from within the lower portion and projecting up into said upper portion. (AEC)

  13. Anomalous diffusion of a polymer chain in an unentangled melt

    NASA Astrophysics Data System (ADS)

    Farago, Jean; Meyer, Hendrik; Semenov, Alexander

    2012-02-01

    Contrary to common belief, the hydrodynamic interactions (HI) in polymer melts are not screened beyond the monomer length and are important in transient regimes. We show that the viscoelastic HI effects (VHI) lead to anomalous dynamics of a tagged chain in an unentangled melt at t < tN (tN, the Rouse time). The chain centre-of-mass (CM) mean-square displacement is enhanced (as compared to the Rouse diffusion) by a large factor increasing with chain length. We develop an analytical theory of VHI-controlled chain dynamics yielding negative CM velocity autocorrelation function which quantitatively agrees with our MD simulations without any fitting parameter. It is also shown that the Langevin friction force, when added in the model, strongly affects the short-t CM dynamics which, however, can remain strongly enhanced. The transient VHI effects thus provide the dominant contribution to the subdiffusive CM motion universally observed in simulations and experiments on polymer melts.

  14. The transient behavior of Peltier junctions pulsed with supercooling

    NASA Astrophysics Data System (ADS)

    Mao, J. N.; Chen, H. X.; Jia, H.; Qian, X. L.

    2012-07-01

    There exists the transient thermoelectric supercooling effect that can be enhanced by keeping on increasing the Peltier cooling effect to compensate for the Joule heating effect and Fourier heat conduction effect arriving at the cold junction, in which a transient cold spike can be produced by superimposing an additional shaped current pulse of a large magnitude on the original steady-state optimum value. Most previous work on the transient supercooling mainly focused on the minimum supercooling temperature achievable and separately analyzed the beneficial or detrimental effects on the transient supercooling performance, which was not clarified quantitatively to what extent the interactional effects were on the enhancement of the transient supercooling performance. In this work, we systematically investigate a numerical solution involving time-dependent imposed voltage pulse and time-dependent thermal boundary conditions on the transient supercooling behavior as well as the response of characteristic time and cold-junction temperature distribution to the pulse operation parameters during the periods of pulse start-up, pulse-on time, and pulse-off time, which is served as a theoretical basis for exploiting the coupling interaction of the thermoelectric effects on the heat diffusion from or to the cold junction interrelated with the amount of the availably electrical conversion in the short time scale. Additionally, the advantage of certain pulse forms over others is described. The results indicate that Peltier supercooling capacity shows a decreasing monotonic trend in proportion to the total amount of electrical conversion, and the maximum coefficient of performance for cooling state is about 0.5 to be achieved at steady state. Taking advantage of the temporary Peltier effect focused electrical conversion as the additional cooling for a period long enough against the earlier arrival of the excessively Joule heating dominated heat accumulation is the key parameter

  15. 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.

  16. 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.

  17. Stationary and transient Soret separation in a binary mixture with a consolute critical point.

    PubMed

    Ryzhkov, Ilya I; Kozlova, Sofia V

    2016-12-01

    The stationary and transient Soret separation in a binary mixture with a consolute critical point is studied theoretically. The mixture is placed between two parallel plates kept at different temperatures. A polymer blend is used as a model system. Analytical solutions are constructed to describe the stationary separation in a binary mixture with variable Soret coefficient. The latter strongly depends on temperature and concentration and enhances near a consolute critical point due to reduced diffusion. As a result, a large concentration gradient is observed locally, while much smaller concentration variations are found in the rest of the layer. It is shown that complete separation can be obtained by applying a small temperature difference first, waiting for the establishment of stationary state, and then increasing this difference again. In this case, the critical temperature lies between hot and cold wall temperatures, while the mixture still remains in the one-phase region. When the initial (mean) temperature or concentration are shifted away from the near-critical values, the separation decreases. The analysis of transient behavior shows that the Soret separation occurs much faster than diffusion to the homogeneous state when the initial concentration is close to the critical one. It happens due to the decrease (increase) of the local relaxation time during the Soret (Diffusion) steps. The transient times of these steps become comparable for small temperature differences or off-critical initial concentrations. An unusual (non-exponential) separation dynamics is observed when the separation starts in the off-critical domain, and then enhances greatly when the system enters into the near-critical region. It is also found that the transient time decreases with increasing the applied temperature difference.

  18. Severe Left Ventricular Hypertrophy, Small Pericardial Effusion, and Diffuse Late Gadolinium Enhancement by Cardiac Magnetic Resonance Suspecting Cardiac Amyloidosis: Endomyocardial Biopsy Reveals an Unexpected Diagnosis

    PubMed Central

    Hofmann, Nina P.; Giusca, Sorin; Klingel, Karin; Nunninger, Peter; Korosoglou, Grigorios

    2016-01-01

    Left ventricular (LV) hypertrophy can be related to a multitude of cardiac disorders, such as hypertrophic cardiomyopathy (HCM), cardiac amyloidosis, and hypertensive heart disease. Although the presence of LV hypertrophy is generally associated with poorer cardiac outcomes, the early differentiation between these pathologies is crucial due to the presence of specific treatment options. The diagnostic process with LV hypertrophy requires the integration of clinical evaluation, electrocardiography (ECG), echocardiography, biochemical markers, and if required CMR and endomyocardial biopsy in order to reach the correct diagnosis. Here, we present a case of a patient with severe LV hypertrophy (septal wall thickness of 23 mm, LV mass of 264 g, and LV mass index of 147 g/m2), severely impaired longitudinal function, and preserved radial contractility (ejection fraction = 55%), accompanied by small pericardial effusion and diffuse late gadolinium enhancement (LGE) by cardiac magnetic resonance (CMR). Due to the imaging findings, an infiltrative cardiomyopathy, such as cardiac amyloidosis, was suspected. However, amyloid accumulation was excluded by endomyocardial biopsy, which revealed the presence of diffuse myocardial fibrosis in an advanced hypertensive heart disease. PMID:27247807

  19. Low-Dose PET/CT and Full-Dose Contrast-Enhanced CT at the Initial Staging of Localized Diffuse Large B-Cell Lymphomas

    PubMed Central

    Sabaté-Llobera, Aida; Cortés-Romera, Montserrat; Mercadal, Santiago; Hernández-Gañán, Javier; Pomares, Helena; González-Barca, Eva; Gámez-Cenzano, Cristina

    2016-01-01

    Computed tomography (CT) has been used as the reference imaging technique for the initial staging of diffuse large B-cell lymphoma until recent days, when the introduction of positron emission tomography (PET)/CT imaging as a hybrid technique has become of routine use. However, the performance of both examinations is still common. The aim of this work was to compare the findings between low-dose 2-deoxy-2-(18F)fluoro-d-glucose (18F-FDG) PET/CT and full-dose contrast-enhanced CT (ceCT) in 28 patients with localized diffuse large B-cell lymphoma according to PET/CT findings, in order to avoid the performance of ceCT. For each technique, a comparison in the number of nodal and extranodal involved regions was performed. PET/CT showed more lesions than ceCT in both nodal (41 vs. 36) and extranodal localizations (16 vs. 15). Disease staging according to both techniques was concordant in 22 patients (79%) and discordant in 6 patients (21%), changing treatment management in 3 patients (11%). PET/CT determined a better staging and therapeutic approach, making the performance of an additional ceCT unnecessary. PMID:27559300

  20. Enhancing the electron lifetime and diffusion coefficient in dye-sensitized solar cells by patterning the layer of TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Sajedi Alvar, Mohammad; Javadi, Mohammad; Abdi, Yaser; Arzi, Ezatollah

    2016-03-01

    In order to fulfill fast electron transport and low recombination rate in dye-sensitized solar cells, we propose to utilize a micro-patterned anode based on TiO2 nanoparticles. The micro-structures of the mesoporous TiO2 films were patterned by Si molds (microimprint technique). A series of measurements including the time of flight, open circuit voltage decay, and charge extraction is carried out to investigate the electron transport in these structures. Our measurement confirms the fast electron transport and high electron lifetime in the micro-patterned structures, which is in agreement with the previously reported simulations. The results have shown that for columnar 20 × 20 μm2 micro-structures, the electron diffusion coefficient is increased by 60% from 3.9 × 10-5 cm 2 / s to 6.3 × 10-5 cm 2 / s . In addition, the electron lifetime has considerably (about one order of magnitude) increased in the cells based on TiO2 micro-structures. These enhancements in the electron transport have significantly improved the power conversion efficiency of dye-sensitized solar cells, which is increased by 69% from 5.16% to 8.73%. The results are explained in terms of directional diffusion and extra trap states in the micro-structures of porous TiO2 films.

  1. 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

  2. Towards combined electrochemistry and surface-enhanced resonance Raman of heme proteins: Improvement of diffusion electrochemistry of cytochrome c at silver electrodes chemically modified with 4-mercaptopyridine.

    PubMed

    Millo, Diego; Ranieri, Antonio; Koot, Wynanda; Gooijer, Cees; van der Zwan, Gert

    2006-08-01

    To date, a successful combination of surface-enhanced resonance Raman spectroscopy (SERRS) and electrochemistry to study heme proteins is inhibited by the problems raised by the prerequisite to use silver as electrode metal. This paper indicates an approach to overcome these problems. It describes a quick and reproducible procedure to prepare silver electrodes chemically modified with 4-mercaptopyridine suitable to perform diffusion electrochemistry of cytochrome c (cyt c). The method involves the employment of a mechanical and a chemical treatment and avoids the use of alumina slurries and any electrochemical pretreatment. Cyclic voltammetry (CV) was used to test the electrochemical response of cyt c, and the CV signals were found identical with those obtained on gold electrodes under the same experimental conditions. Compared to previous literature, a significant improvement of the CV signal of cyt c at silver electrodes was achieved. Preliminary results show that this treatment can be also successfully employed for the preparation of SERRS-active electrodes.

  3. Enhanced Islet Cell Nucleomegaly Defines Diffuse Congenital Hyperinsulinism in Infancy but Not Other Forms of the Disease

    PubMed Central

    Han, Bing; Newbould, Melanie; Batra, Gauri; Cheesman, Edmund; Craigie, Ross J.; Mohamed, Zainab; Rigby, Lindsey; Padidela, Raja; Skae, Mars; Mironov, Aleksandr; Starborg, Tobias; Kadler, Karl E.; Banerjee, Indraneel

    2016-01-01

    Objectives: To quantify islet cell nucleomegaly in controls and tissues obtained from patients with congenital hyperinsulinism in infancy (CHI) and to examine the association of nucleomegaly with proliferation. Methods: High-content analysis of histologic sections and serial block-face scanning electron microscopy were used to quantify nucleomegaly. Results: Enlarged islet cell nuclear areas were 4.3-fold larger than unaffected nuclei, and the mean nuclear volume increased to approximately threefold. Nucleomegaly was a normal feature of pediatric islets and detected in the normal regions of the pancreas from patients with focal CHI. The incidence of nucleomegaly was highest in diffuse CHI (CHI-D), with more than 45% of islets containing two or more affected cells. While in CHI-D nucleomegaly was negatively correlated with cell proliferation, in all other cases, there was a positive correlation. Conclusions: Increased incidence of nucleomegaly is pathognomonic for CHI-D, but these cells are nonproliferative, suggesting a novel role in the pathobiology of this condition. PMID:27334808

  4. 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.

  5. 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.

  6. 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

  7. Use of ambroxol and bromhexine as mucolytics for enhanced diffusion of furaltadone into tracheobronchial secretions in broilers.

    PubMed

    Sumano, H; Gracia, I; Capistrán, A; Meade, G; Rivero, A; Ruiz-Ramírez, L

    1995-07-01

    1. Ambroxol and bromhexine were evaluated as mucolytics and to enhance the passage of furaltadone into tracheobronchial secretions (TBS) in chronic complicated respiratory disease-affected broilers. 2. Viscosity of TBS was noticeably increased in the ambroxol-treated birds and only slightly increased in the bromhexine groups; however, the physical (nature) of TBS was superior in the ambroxol-treated broilers. 3. There was a clear increase in the passage of furaltadone into tracheobronchial secretions only in the ambroxol-treated birds. 4. Everyday use of ambroxol in broilers is discussed.

  8. Thalidomide enhanced the efficacy of CHOP chemotherapy in the treatment of diffuse large B cell lymphoma: A phase II study

    PubMed Central

    Ji, Dongmei; Li, Qiu; Cao, Junning; Guo, Ye; Lv, Fangfang; Liu, Xiaojian; Wang, Biyun; Wang, Leiping; Luo, Zhiguo; Chang, Jianhua; Wu, Xianghua; Hong, Xiaonan

    2016-01-01

    Cyclophosphamide, doxorubicin, vincristine, and prednisolone plus rituximab (R-CHOP) is the standard treatment for patients with diffuse large B cell lymphoma (DLBCL). However, rituximab cannot be popularly applied in a considerable number of patients with DLBCL because of economic reasons. To develop a new regimen to improve the outcome of these patients is extremely important. In our study, sixty five patients with DLBCL were randomly assigned to thalidomide plus CHOP group (n=32) or to CHOP alone group (n=33). Objective response rates (ORR) and complete remission rates (CRR) were 96.7% and 80.6% in T-CHOP group versus 78.9 % and 57.8 % in CHOP group, respectively (P <0.05). At a median follow-up of 96 months, median PFS for T-CHOP group was still not reached yet, and in CHOP group it was 22.9 months (95% CI [0-50.4]). (P=0.163). Median overall survival (OS) for T-CHOP group was also not reached, and the estimated median OS for CHOP group was 83.5 months, the difference of OS between the two groups is not significant (p=0.263). But, in patients with Bcl-2 positive and Bcl-6 negative, the median PFS in T-CHOP group was longer than that in CHOP group (111.0 vs 8.5 months (P=0.017). In addition, thalidomide did not significantly increase the grade 3/4 toxicity of CHOP. We concluded that the addition of thalidomide to the CHOP regimen significantly improved the CRR and showed a trend of improving clinical outcome in patients with DLBCL, especially for patients with Bcl-2 positive and Bcl-6 negative B-cell phenotype, without increased toxicity. PMID:27129176

  9. Crossover from normal to anomalous diffusion in systems of field-aligned dipolar particles.

    PubMed

    Jordanovic, Jelena; Jäger, Sebastian; Klapp, Sabine H L

    2011-01-21

    Using molecular dynamics simulations we investigate the translational dynamics of particles with dipolar interactions in homogenous external fields. For a broad range of concentrations, we find that the anisotropic, yet normal diffusive behavior characterizing weakly coupled systems becomes anomalous both parallel and perpendicular to the field at sufficiently high dipolar coupling and field strength. After the ballistic regime, chain formation first yields cagelike motion in all directions, followed by transient, mixed diffusive-superdiffusive behavior resulting from cooperative motion of the chains. The enhanced dynamics disappears only at higher densities close to crystallization.

  10. 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.

  11. Transient tachypnea - newborn

    MedlinePlus

    TTN; Wet lungs - newborns; Retained fetal lung fluid; Transient RDS; Prolonged transition; Neonatal - transient tachypnea ... As the baby grows in the womb, the lungs make a special fluid. This fluid fills the ...

  12. On the reaction of D-amino acid oxidase with dioxygen: O2 diffusion pathways and enhancement of reactivity.

    PubMed

    Rosini, Elena; Molla, Gianluca; Ghisla, Sandro; Pollegioni, Loredano

    2011-02-01

    Evidence is accumulating that oxygen access in proteins is guided and controlled. We also have recently described channels that might allow access of oxygen to pockets at the active site of the flavoprotein D-amino acid oxidase (DAAO) that have a high affinity for dioxygen and are in close proximity to the flavin. With the goal of enhancing the reactivity of DAAO with oxygen, we have performed site-saturation mutagenesis at three positions that flank the putative oxygen channels and high-affinity sites. The most interesting variants at positions 50, 201 and 225 were identified by a screening procedure at low oxygen concentration. The biochemical properties of these variants have been studied and compared with those of wild-type DAAO, with emphasis on the reactivity of the reduced enzyme species with dioxygen. The substitutions at positions 50 and 225 do not enhance this reaction, but mainly affect the protein conformation and stability. However, the T201L variant shows an up to a threefold increase in the rate constant for reaction of O(2) with reduced flavin, together with a fivefold decrease in the K(m) for dioxygen. This effect was not observed when a valine is located at position 201, and is thus attributed to a specific alteration in the micro-environment of one high-affinity site for dioxygen (site B) close to the flavin that plays an important role in the storage of oxygen. The increase in O(2) reactivity observed for T201L DAAO is of great interest for designing new flavoenzymes for biotechnological applications.

  13. 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.

  14. Magnetic field enhanced convective diffusion of iron oxide nanoparticles in an osmotically disrupted cell culture model of the blood–brain barrier

    PubMed Central

    Sun, Zhizhi; Worden, Matthew; Wroczynskyj, Yaroslav; Yathindranath, Vinith; van Lierop, Johan; Hegmann, Torsten; Miller, Donald W

    2014-01-01

    Purpose The present study examines the use of an external magnetic field in combination with the disruption of tight junctions to enhance the permeability of iron oxide nanoparticles (IONPs) across an in vitro model of the blood–brain barrier (BBB). The feasibility of such an approach, termed magnetic field enhanced convective diffusion (MFECD), along with the effect of IONP surface charge on permeability, was examined. Methods The effect of magnetic field on the permeability of positively (aminosilane-coated [AmS]-IONPs) and negatively (N-(trimethoxysilylpropyl)ethylenediaminetriacetate [EDT]-IONPs) charged IONPs was evaluated in confluent monolayers of mouse brain endothelial cells under normal and osmotically disrupted conditions. Results Neither IONP formulation was permeable across an intact cell monolayer. However, when tight junctions were disrupted using D-mannitol, flux of EDT-IONPs across the bEnd.3 monolayers was 28%, increasing to 44% when a magnetic field was present. In contrast, the permeability of AmS-IONPs after osmotic disruption was less than 5%. The cellular uptake profile of both IONPs was not altered by the presence of mannitol. Conclusions MFECD improved the permeability of EDT-IONPs through the paracellular route. The MFECD approach favors negatively charged IONPs that have low affinity for the brain endothelial cells and high colloidal stability. This suggests that MFECD may improve IONP-based drug delivery to the brain. PMID:25018630

  15. 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.

  16. Diffusible iodine-based contrast-enhanced computed tomography (diceCT): an emerging tool for rapid, high-resolution, 3-D imaging of metazoan soft tissues.

    PubMed

    Gignac, Paul M; Kley, Nathan J; Clarke, Julia A; Colbert, Matthew W; Morhardt, Ashley C; Cerio, Donald; Cost, Ian N; Cox, Philip G; Daza, Juan D; Early, Catherine M; Echols, M Scott; Henkelman, R Mark; Herdina, A Nele; Holliday, Casey M; Li, Zhiheng; Mahlow, Kristin; Merchant, Samer; Müller, Johannes; Orsbon, Courtney P; Paluh, Daniel J; Thies, Monte L; Tsai, Henry P; Witmer, Lawrence M

    2016-06-01

    Morphologists have historically had to rely on destructive procedures to visualize the three-dimensional (3-D) anatomy of animals. More recently, however, non-destructive techniques have come to the forefront. These include X-ray computed tomography (CT), which has been used most commonly to examine the mineralized, hard-tissue anatomy of living and fossil metazoans. One relatively new and potentially transformative aspect of current CT-based research is the use of chemical agents to render visible, and differentiate between, soft-tissue structures in X-ray images. Specifically, iodine has emerged as one of the most widely used of these contrast agents among animal morphologists due to its ease of handling, cost effectiveness, and differential affinities for major types of soft tissues. The rapid adoption of iodine-based contrast agents has resulted in a proliferation of distinct specimen preparations and scanning parameter choices, as well as an increasing variety of imaging hardware and software preferences. Here we provide a critical review of the recent contributions to iodine-based, contrast-enhanced CT research to enable researchers just beginning to employ contrast enhancement to make sense of this complex new landscape of methodologies. We provide a detailed summary of recent case studies, assess factors that govern success at each step of the specimen storage, preparation, and imaging processes, and make recommendations for standardizing both techniques and reporting practices. Finally, we discuss potential cutting-edge applications of diffusible iodine-based contrast-enhanced computed tomography (diceCT) and the issues that must still be overcome to facilitate the broader adoption of diceCT going forward.

  17. Differentiation of pancreatic carcinoma and mass-forming focal pancreatitis: qualitative and quantitative assessment by dynamic contrast-enhanced MRI combined with diffusion-weighted imaging

    PubMed Central

    Zhang, Ting-Ting; Wang, Li; Liu, Huan-huan; Zhang, Cai-yuan; Li, Xiao-ming; Lu, Jian-ping; Wang, Deng-bin

    2017-01-01

    Differentiation between pancreatic carcinoma (PC) and mass-forming focal pancreatitis (FP) is invariably difficult. For the differential diagnosis, we qualitatively and quantitatively assessed the value of dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI) in PC and FP in the present study. This study included 32 PC and 18 FP patients with histological confirmation who underwent DCE-MRI and DWI. The time-signal intensity curve (TIC) of PC and FP were classified into 5 types according to the time of reaching the peak, namely, type I, II, III, IV, and V, respectively, and two subtypes, namely, subtype-a (washout type) and subtype-b (plateau type) according to the part of the TIC profile after the peak. Moreover, the mean and relative apparent diffusion coefficient (ADC) value between PC and FP on DWI were compared. The type V TIC was only recognized in PC group (P < 0.01). Type IV b were more frequently observed in PC (P = 0.036), while type- IIa (P < 0.01), type- Ia (P = 0.037) in FP. We also found a significant difference in the mean and relative ADC value between PC and FP. The combined image set of DCE-MRI and DWI yielded an excellent sensitivity, specificity, and diagnostic accuracy (96.9%, 94.4%, and 96.0%). The TIC of DCE-MRI and ADC value of DWI for pancreatic mass were found to provide reliable information in differentiating PC from FP, and the combination of DCE-MRI and DWI can achieve a higher sensitivity, specificity, and diagnostic accuracy. PMID:27661003

  18. Neoadjuvant Systemic Therapy in Breast Cancer: Association of Contrast-enhanced MR Imaging Findings, Diffusion-weighted Imaging Findings, and Tumor Subtype with Tumor Response.

    PubMed

    Santamaría, Gorane; Bargalló, Xavier; Fernández, Pedro Luis; Farrús, Blanca; Caparrós, Xavier; Velasco, Martin

    2016-11-22

    Purpose To investigate the performance of tumor subtype and various magnetic resonance (MR) imaging parameters in the assessment of tumor response to neoadjuvant systemic therapy (NST) in patients with breast cancer and to outline a model of pathologic response, considering pathologic complete response (pCR) as the complete absence of any residual invasive cancer or ductal carcinoma in situ (DCIS). Materials and Methods This was an institutional review board-approved retrospective study, with waiver of the need to obtain informed consent. From November 2009 to December 2014, 111 patients with histopathologically confirmed invasive breast cancer who were undergoing NST were included (mean age, 54 years; range, 27-84 years). Breast MR imaging was performed before and after treatment. Presence of late enhancement was assessed. Apparent diffusion coefficients (ADCs) were obtained by using two different methods. ADC ratio (mean posttreatment ADC/mean pretreatment ADC) was calculated. pCR was defined as absence of any residual invasive cancer or DCIS. Multivariate regression analysis and receiver operating characteristic analysis were performed. Results According to their immunohistochemical (IHC) profile, tumors were classified as human epidermal growth factor receptor 2 (HER2) positive (n = 51), estrogen receptor (ER) positive/HER2 negative (n = 40), and triple negative (n = 20). pCR was achieved in 19% (21 of 111) of cases; 86% of them were triple-negative or HER2-positive subtypes. Absence of late enhancement at posttreatment MR imaging was significantly associated with pCR (area under the curve [AUC], 0.85). Mean ADC ratio significantly increased when pCR was achieved (P < .001). A κ value of 0.479 was found for late enhancement (P < .001), and the intraclass correlation coefficient for ADCs was 0.788 (P < .001). Good correlation of ADCs obtained with the single-value method and those obtained with the mean-value methods was observed. The model combining the IHC

  19. Electrical Conductivity and Chemical Diffusion Coefficient of Strontium-Doped Lanthanum Manganites

    NASA Astrophysics Data System (ADS)

    Yasuda, Isamu; Hishinuma, Masakazu

    1996-05-01

    Electrical conductivity and chemical diffusion coefficient of Sr-doped lanthanum manganites, La 1- xSr xMnO 3±δ( x= 0.05 - 0.20), were measured by the dc four-probe technique and relaxation type experiments where a sudden change of oxygen chemical potential was imposed on the pre-equilibrated sample and the change of electrical conductivity was followed as a function of elapsed time. A defect model is proposed to elucidate the oxygen partial pressure dependence of the measured conductivity and the reported oxygen nonstoichiometry. The transient conductivity behavior after an abrupt change of oxygen partial pressure was successfully described by a diffusion model with consideration of partial control by surface reaction. The determined chemical diffusion coefficients, of the order of 10 -5to 10 -4cm 2s -1at 1000°C, increased with decreased oxygen partial pressure due to the thermodynamic enhancement effect. Using the enhancement factor estimated by combination of the proposed defect model and the ambipolar diffusion theory, the oxygen vacancy diffusion coefficients were derived. High vacancy diffusivity comparable to that of Fe- or Co-based perovskites predicts fast oxide ion diffusion under conditions where the manganites show oxygen deficient type non-stoichiometry.

  20. Transient thermal camouflage and heat signature control

    NASA Astrophysics Data System (ADS)

    Yang, Tian-Zhi; Su, Yishu; Xu, Weikai; Yang, Xiao-Dong

    2016-09-01

    Thermal metamaterials have been proposed to manipulate heat flux as a new way to cloak or camouflage objects in the infrared world. To date, however, thermal metamaterials only operate in the steady-state and exhibit detectable, transient heat signatures. In this letter, the theoretical basis for a thermal camouflaging technique with controlled transient diffusion is presented. This technique renders an object invisible in real time. More importantly, the thermal camouflaging device instantaneously generates a pre-designed heat signature and behaves as a perfect thermal illusion device. A metamaterial coating with homogeneous and isotropic thermal conductivity, density, and volumetric heat capacity was fabricated and very good camouflaging performance was achieved.

  1. Guide tube flow diffuser

    SciTech Connect

    Berringer, R.T.; Myron, D.L.

    1980-11-04

    A nuclear reactor upper internal guide tube has a flow diffuser integral with its bottom end. The guide tube provides guidance for control rods during their ascent or descent from the reactor core. The flow diffuser serves to divert the upward flow of reactor coolant around the outside of the guide tube thereby limiting the amount of coolant flow and turbulence within the guide tube, thus enhancing the ease of movement of the control rods.

  2. 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.

  3. 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.

  4. Transient Effects and Disturbed Conditions

    NASA Astrophysics Data System (ADS)

    Wibberenz, G.; Le Roux, J. A.; Potgieter, M. S.; Bieber, J. W.

    1998-01-01

    In the present phase of the solar cycle no big transients leading to strong modulation had been observed after 1991. Apart from a few minor disturbances cosmic rays were still recovering to a new intensity maximum. It was suggested, therefore, that existing literature from previous cycles should be critically reviewed. The scene was set by the introductory papers on - phenomenology of cosmic ray modulation in successive solar cycles throughout the heliosphere, - the present state of models for long term modulation and their shortcomings, - the relation between cosmic ray variations and the magnitude of the interplanetary magnetic field (the CR-B-relation), - charge dependent effects. In the discussions, the study of propagating diffusive disturbances and the CR-B-relation played a central role. The difference was stressed between isolated transient disturbances in the inner solar system (Forbush decreases), and the long lasting, step-like decreases caused by merged interaction regions in the outer heliosphere. The recovery rates following the step-like decreases vary with the phase in the 22-year solar cycle. In some cases this requires a modification of existing drift models. In the outer heliosphere, the CR-B-relation leads to the result Κ alpha 1/Β between the diffusion coefficient Κ and the field magnitude Β. This simple result is a challenge for theoreticians to derive the perpendicular diffusion coefficient fromfirst principles. The three articles in this report essentially follow the list of open points and arguments just presented. The article "Observations and Simple Models" is organised around the model of a propagating diffusive barrier, its application to Forbush effects in the inner heliosphere and to decreases caused by merged interaction regions in the outer heliosphere. Acomparison of observed Forbush decreases with model predictions requires a careful separation of the two steps related to the turbulent region behind the shock front and the

  5. 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.

  6. 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

  7. 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, 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.

  8. Griffith diffusers

    NASA Technical Reports Server (NTRS)

    Yang, T.-T.; Nelson, C. D.

    1979-01-01

    Contoured wall diffusers are designed by using an inverse method. The prescribed wall velocity distribution(s) was taken from the high lift airfoil designed by A. A. Griffith in 1938; therefore, such diffusers are named Griffith diffusers. First the formulation of the inverse problem and the method of solution are outlined. Then the typical contour of a two-dimensional diffuser and velocity distributions across the flow channel at various stations are presented. For a Griffith diffuser to operate as it is designed, boundary layer suction is necessary. Discussion of the percentage of through-flow required to be removed for the purpose of boundary layer control is given. Finally, reference is made to the latest version of a computer program for a two-dimensional diffuser requiring only area ratio, nondimensional length and suction percentage as inputs.

  9. Preclinical evaluation of convection-enhanced delivery of liposomal doxorubicin to treat pediatric diffuse intrinsic pontine glioma and thalamic high-grade glioma.

    PubMed

    Sewing, A Charlotte P; Lagerweij, Tonny; van Vuurden, Dannis G; Meel, Michaël H; Veringa, Susanna J E; Carcaboso, Angel M; Gaillard, Pieter J; Peter Vandertop, W; Wesseling, Pieter; Noske, David; Kaspers, Gertjan J L; Hulleman, Esther

    2017-02-17

    OBJECTIVE Pediatric high-grade gliomas (pHGGs) including diffuse intrinsic pontine gliomas (DIPGs) are primary brain tumors with high mortality and morbidity. Because of their poor brain penetrance, systemic chemotherapy regimens have failed to deliver satisfactory results; however, convection-enhanced delivery (CED) may be an alternative mode of drug delivery. Anthracyclines are potent chemotherapeutics that have been successfully delivered via CED in preclinical supratentorial glioma models. This study aims to assess the potency of anthracyclines against DIPG and pHGG cell lines in vitro and to evaluate the efficacy of CED with anthracyclines in orthotopic pontine and thalamic tumor models. METHODS The sensitivity of primary pHGG cell lines to a range of anthracyclines was tested in vitro. Preclinical CED of free doxorubicin and pegylated liposomal doxorubicin (PLD) to the brainstem and thalamus of naïve nude mice was performed. The maximum tolerated dose (MTD) was determined based on the observation of clinical symptoms, and brains were analyzed after H & E staining. Efficacy of the MTD was tested in adult glioma E98-FM-DIPG and E98-FM-thalamus models and in the HSJD-DIPG-007-Fluc primary DIPG model. RESULTS Both pHGG and DIPG cells were sensitive to anthracyclines in vitro. Doxorubicin was selected for further preclinical evaluation. Convection-enhanced delivery of the MTD of free doxorubicin and PLD in the pons was 0.02 mg/ml, and the dose tolerated in the thalamus was 10 times higher (0.2 mg/ml). Free doxorubicin or PLD via CED was ineffective against E98-FM-DIPG or HSJD-DIPG-007-Fluc in the brainstem; however, when applied in the thalamus, 0.2 mg/ml of PLD slowed down tumor growth and increased survival in a subset of animals with small tumors. CONCLUSIONS Local delivery of doxorubicin to the brainstem causes severe toxicity, even at doxorubicin concentrations that are safe in the thalamus. As a consequence, the authors could not establish a therapeutic

  10. Anomalous extracellular diffusion in rat cerebellum.

    PubMed

    Xiao, Fanrong; Hrabe, Jan; Hrabetova, Sabina

    2015-05-05

    Extracellular space (ECS) is a major channel transporting biologically active molecules and drugs in the brain. Diffusion-mediated transport of these substances is hindered by the ECS structure but the microscopic basis of this hindrance is not fully understood. One hypothesis proposes that the hindrance originates in large part from the presence of dead-space (DS) microdomains that can transiently retain diffusing molecules. Because previous theoretical and modeling work reported an initial period of anomalous diffusion in similar environments, we expected that brain regions densely populated by DS microdomains would exhibit anomalous extracellular diffusion. Specifically, we targeted granular layers (GL) of rat and turtle cerebella that are populated with large and geometrically complex glomeruli. The integrative optical imaging (IOI) method was employed to evaluate diffusion of fluorophore-labeled dextran (MW 3000) in GL, and the IOI data analysis was adapted to quantify the anomalous diffusion exponent dw from the IOI records. Diffusion was significantly anomalous in rat GL, where dw reached 4.8. In the geometrically simpler turtle GL, dw was elevated but not robustly anomalous (dw = 2.6). The experimental work was complemented by numerical Monte Carlo simulations of anomalous ECS diffusion in several three-dimensional tissue models containing glomeruli-like structures. It demonstrated that both the duration of transiently anomalous diffusion and the anomalous exponent depend on the size of model glomeruli and the degree of their wrapping. In conclusion, we have found anomalous extracellular diffusion in the GL of rat cerebellum. This finding lends support to the DS microdomain hypothesis. Transiently anomalous diffusion also has a profound effect on the spatiotemporal distribution of molecules released into the ECS, especially at diffusion distances on the order of a few cell diameters, speeding up short-range diffusion-mediated signals in less permeable

  11. Anomalous Extracellular Diffusion in Rat Cerebellum

    PubMed Central

    Xiao, Fanrong; Hrabe, Jan; Hrabetova, Sabina

    2015-01-01

    Extracellular space (ECS) is a major channel transporting biologically active molecules and drugs in the brain. Diffusion-mediated transport of these substances is hindered by the ECS structure but the microscopic basis of this hindrance is not fully understood. One hypothesis proposes that the hindrance originates in large part from the presence of dead-space (DS) microdomains that can transiently retain diffusing molecules. Because previous theoretical and modeling work reported an initial period of anomalous diffusion in similar environments, we expected that brain regions densely populated by DS microdomains would exhibit anomalous extracellular diffusion. Specifically, we targeted granular layers (GL) of rat and turtle cerebella that are populated with large and geometrically complex glomeruli. The integrative optical imaging (IOI) method was employed to evaluate diffusion of fluorophore-labeled dextran (MW 3000) in GL, and the IOI data analysis was adapted to quantify the anomalous diffusion exponent dw from the IOI records. Diffusion was significantly anomalous in rat GL, where dw reached 4.8. In the geometrically simpler turtle GL, dw was elevated but not robustly anomalous (dw = 2.6). The experimental work was complemented by numerical Monte Carlo simulations of anomalous ECS diffusion in several three-dimensional tissue models containing glomeruli-like structures. It demonstrated that both the duration of transiently anomalous diffusion and the anomalous exponent depend on the size of model glomeruli and the degree of their wrapping. In conclusion, we have found anomalous extracellular diffusion in the GL of rat cerebellum. This finding lends support to the DS microdomain hypothesis. Transiently anomalous diffusion also has a profound effect on the spatiotemporal distribution of molecules released into the ECS, especially at diffusion distances on the order of a few cell diameters, speeding up short-range diffusion-mediated signals in less permeable

  12. Decomposition of the supersaturated solid solutions at the stage of coalescence under conditions of passage from dislocation-controlled to volume diffusion

    NASA Astrophysics Data System (ADS)

    Ustyugov, Yu. M.

    2007-11-01

    The object of a theoretical examination is here the heterogeneous isomorphic continuous decomposition of supersaturated solid solutions for the case of binary aging alloys with a developed dislocation structure under enhanced temperatures in the unsteady stage of coalescence, whose transient nature is caused by the instability with respect to a change in the mechanism of mass transfer acting in the system, which controls coarsening of the disperse heterophase structure. For the quasi-stationary diffusion regime, a complete analytical description of the evolution of the second-phase-size distribution function is given for the stage of the transient kinetics, when the initially prevailing diffusion along dislocations, which supply the alloying component to the precipitation phase, is succeeded by volume diffusion at the last stages of decomposition.

  13. 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.

  14. Tracer counterpermeation analysis of diffusivity in finite-length nanopores with and without single-file dynamics

    NASA Astrophysics Data System (ADS)

    Ackerman, David M.; Evans, James W.

    2017-01-01

    We perform a tracer counterpermeation (TCP) analysis for a stochastic model of diffusive transport through a narrow linear pore where passing of species within the pore is inhibited or even excluded (single-file diffusion). TCP involves differently labeled but otherwise identical particles from two decoupled infinite reservoirs adsorbing into opposite ends of the pore, and desorbing from either end. In addition to transient behavior, we assess steady-state concentration profiles, spatial correlations, particle number fluctuations, and diffusion fluxes through the pore. From the profiles and fluxes, we determine a generalized tracer diffusion coefficient Dtr(x ) , at various positions x within the pore. Dtr(x ) has a plateau value in the pore center scaling inversely with the pore length, but it is enhanced near the pore openings. The latter feature reflects the effect of fluctuations in adsorption and desorption, and it is also associated with a nontrivial scaling of the concentration profiles near the pore openings.

  15. [Transient epileptic amnesia].

    PubMed

    Muramatsu, Kazuhiro; Yoshizaki, Takahito

    2016-03-01

    Transient amnesia is one of common clinical phenomenon of epilepsy that are encountered by physicians. The amnestic attacks are often associated with persistent memory disturbances. Epilepsy is common among the elderly, with amnesia as a common symptom and convulsions relatively uncommon. Therefore, amnesia due to epilepsy can easily be misdiagnosed as dementia. The term 'transient epileptic amnesia (TEA)' was introduced in the early 1990s by Kapur, who highlighted that amnestic attacks caused by epilepsy can be similar to those occurring in 'transient global amnesia', but are distinguished by features brevity and recurrence. In 1998, Zeman et al. proposed diagnostic criteria for TEA.

  16. 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.

  17. 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.

  18. Transient cortical blindness after coronary angiography.

    PubMed

    Alp, B N; Bozbuğa, N; Tuncer, M A; Yakut, C

    2009-01-01

    Transient cortical blindness is rarely encountered after angiography of native coronary arteries or bypass grafts. This paper reports a case of transient cortical blindness that occurred 72 h after coronary angiography in a 56-year old patient. This was the patient's fourth exposure to contrast medium. Neurological examination demonstrated cortical blindness and the absence of any focal neurological deficit. A non-contrast-enhanced computed tomographic scan of the brain revealed bilateral contrast enhancement in the occipital lobes and no evidence of cerebral haemorrhage, and magnetic resonance imaging of the brain showed no pathology. Sight returned spontaneously within 4 days and his vision gradually improved. A search of the current literature for reported cases of transient cortical blindness suggested that this is a rarely encountered complication of coronary angiography.

  19. 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.

  20. Increased papillae growth and enhanced short-chain fatty acid absorption in the rumen of goats are associated with transient increases in cyclin D1 expression after ruminal butyrate infusion.

    PubMed

    Malhi, Moolchand; Gui, Hongbing; Yao, Lei; Aschenbach, Jörg R; Gäbel, Gotthold; Shen, Zanming

    2013-01-01

    We tested the hypothesis that the proliferative effects of intraruminal butyrate infusions on the ruminal epithelium are linked to upregulation in cyclin D1 (CCND1), the cyclin-dependent kinase 4 (CDK4), and their possible association with enhanced absorption of short-chain fatty acids (SCFA). Goats (n=23) in 2 experiments (Exp.) were fed 200 g/d concentrate and hay ad libitum. In Exp. 1, goats received an intraruminal infusion of sodium butyrate at 0.3 (group B, n=8) or 0 (group C, n=7) g/kg of body weight (BW) per day before morning feeding for 28 d and were slaughtered 8 h after the butyrate infusion. In Exp. 2, goats (n=8) received butyrate infusion and feeding as in Exp. 1. On d 28, epithelial samples were biopsied from the antrium ruminis at 0, 3, and 7 h after the last butyrate infusion. In Exp. 1, the ruminal molar proportional concentration of butyrate increased in group B by about 110% after butyrate infusion and remained elevated for 1.5 h; thereafter, it gradually returned to the baseline (preinfusion) level. In group C, the molar proportional concentration of butyrate was unchanged over the time points. The length and width of papillae increased in B compared with C; this was associated with increased numbers of cells and cell layers in the epithelial strata and an increase in the surface area of 82%. The mRNA expression of CCND1 increased transiently at 3 h but returned to the preinfusion level at 7 h following butyrate infusion in Exp. 2. However, it did not differ between B and C in Exp. 1, in which the ruminal epithelium was sampled at 8 h after butyrate infusion. The mRNA expression of the monocarboxylate transporter MCT4, but not MCT1, was stably upregulated in B compared with C. The estimated absorption rate of total SCFA (%/h) increased in B compared with C. We conclude that transient increases in cyclin D1 transcription contribute to butyrate-induced papillae growth and subsequently to the increased absorption of SCFA in the ruminal epithelium

  1. Transient topographical amnesia.

    PubMed Central

    Stracciari, A; Lorusso, S; Pazzaglia, P

    1994-01-01

    Ten healthy middle aged or elderly women experienced isolated episodes of topographical amnesia without an obvious aetiology. It is likely a benign cognitive disorder, similar to transient global amnesia. PMID:7964826

  2. Transient Global Amnesia

    MedlinePlus

    ... global amnesia is a sudden, temporary episode of memory loss that can't be attributed to a ... know well. But that doesn't make your memory loss less disturbing. Fortunately, transient global amnesia is ...

  3. Transient Astrophysics Observatory (TAO)

    NASA Astrophysics Data System (ADS)

    Racusin, J. L.; TAO Team

    2016-10-01

    The Transient Astrophysics Observatory (TAO) is a NASA MidEx mission concept (formerly known as Lobster) designed to provide simultaneous wide-field gamma-ray, X-ray, and near-infrared observations of the sky.

  4. 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.

  5. 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.

  6. Transient multivariable sensor evaluation

    DOEpatents

    Vilim, Richard B.; Heifetz, Alexander

    2017-02-21

    A method and system for performing transient multivariable sensor evaluation. The method and system includes a computer system for identifying a model form, providing training measurement data, generating a basis vector, monitoring system data from sensor, loading the system data in a non-transient memory, performing an estimation to provide desired data and comparing the system data to the desired data and outputting an alarm for a defective sensor.

  7. 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.

  8. Efficiency enhancement of CIGS compound solar cell fabricated using homomorphic thin Cr2O3 diffusion barrier formed on stainless steel substrate

    NASA Astrophysics Data System (ADS)

    Sim, Jae-Kwan; Lee, Seung-Kyu; Kim, Jin-Soo; Jeong, Kwang-Un; Ahn, Haeng-Keun; Lee, Cheul-Ro

    2016-12-01

    It is known that the efficiency of flexible Cu(In,Ga)Se2 (CIGS) solar cells fabricated on stainless-steel (STS) substrates deteriorates due to iron (Fe) and Cr impurities diffusing into the CIGS absorber layer. To overcome this problem, a nanoscale homomorphic chromium oxide layer was formed as a diffusion barrier by thermal oxidation on the surface of STS substrates for 1 min at 600 °C in oxygen atmosphere. By TEM and grazing-incidence X-ray diffraction (GIXRD), it was confirmed that the formed oxide layer on surface of STS substrates was a Cr2O3 layer. It was found that the formed homomorphic Cr2O3 thin layer of about 15 nm thickness was an effective diffusion barrier to reduce impurity diffusion into the CIGS layer by secondary ion mass spectroscopy (SIMS). In contrast to the efficiency of CIGS solar cell without homomorphic Cr2O3 diffusion layer is 8.6%, whereas with diffusion barrier it increases to 10.6% because of impurities such as Fe and Cr from the STS substrate into the CIGS layer. It reveals that the layer formed on the surface of STS substrate by thermal oxidation process plays an important role in increasing the performance of CIGS solar cells.

  9. Plasma enhanced chemical vapor deposition of metalboride interfacial layers as diffusion barriers for nanostructured diamond growth on cobalt containing alloys CoCrMo and WC-Co

    NASA Astrophysics Data System (ADS)

    Johnston, Jamin M.

    This work is a compilation of theory, finite element modeling and experimental research related to the use of microwave plasma enhanced chemical vapor deposition (MPECVD) of diborane to create metal-boride surface coatings on CoCrMo and WC-Co, including the subsequent growth of nanostructured diamond (NSD). Motivation for this research stems from the need for wear resistant coatings on industrial materials, which require improved wear resistance and product lifetime to remain competitive and satisfy growing demand. Nanostructured diamond coatings are a promising solution to material wear but cannot be directly applied to cobalt containing substrates due to graphite nucleation. Unfortunately, conventional pre-treatment methods, such as acid etching, render the substrate too brittle. Thus, the use of boron in a MPECVD process is explored to create robust interlayers which inhibit carbon-cobalt interaction. Furthermore, modeling of the MPECVD process, through the COMSOL MultiphysicsRTM platform, is performed to provide insight into plasma-surface interactions using the simulation of a real-world apparatus. Experimental investigation of MPECVD boriding and NSD deposition was conducted at surface temperatures from 700 to 1100 °C. Several well-adhered metal-boride surface layers were formed: consisting of CoB, CrB, WCoB, CoB and/or W2CoB2. Many of the interlayers were shown to be effective diffusion barriers against elemental cobalt for improving nucleation and adhesion of NSD coatings; diamond on W2CoB2 was well adhered. However, predominantly WCoB and CoB phase interlayers suffered from diamond film delamination. Metal-boride and NSD surfaces were evaluated using glancing-angle x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), cross-sectional scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), micro-Raman spectroscopy, nanoindentation, scratch testing and epoxy pull testing. COMSOL MultiphysicsRTM was used to construct a

  10. Diffusion barriers

    NASA Technical Reports Server (NTRS)

    Nicolet, M. A.

    1983-01-01

    The choice of the metallic film for the contact to a semiconductor device is discussed. One way to try to stabilize a contact is by interposing a thin film of a material that has low diffusivity for the atoms in question. This thin film application is known as a diffusion barrier. Three types of barriers can be distinguished. The stuffed barrier derives its low atomic diffusivity to impurities that concentrate along the extended defects of a polycrystalline layer. Sacrificial barriers exploit the fact that some (elemental) thin films react in a laterally uniform and reproducible fashion. Sacrificial barriers have the advantage that the point of their failure is predictable. Passive barriers are those most closely approximating an ideal barrier. The most-studied case is that of sputtered TiN films. Stuffed barriers may be viewed as passive barriers whose low diffusivity material extends along the defects of the polycrystalline host.

  11. 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.

  12. A semi-analytical method for simulating matrix diffusion in numerical transport models

    NASA Astrophysics Data System (ADS)

    Falta, Ronald W.; Wang, Wenwen

    2017-02-01

    A semi-analytical approximation for transient matrix diffusion is developed for use in numerical contaminant transport simulators. This method is an adaptation and extension of the heat conduction method of Vinsome and Westerveld (1980) used to simulate heat losses during thermally enhanced oil recovery. The semi-analytical method is used in place of discretization of the low permeability materials, and it represents the concentration profile in the low permeability materials with a fitting function that is adjusted in each element at each time-step. The resulting matrix diffusion fluxes are added to the numerical model as linear concentration-dependent source/sink terms. Since only the high permeability zones need to be discretized, the numerical formulation is extremely efficient compared to traditional approaches that require discretization of both the high and low permeability zones. The semi-analytical method compares favorably with the analytical solution for transient one-dimensional diffusion with first order decay, with a two-layer aquifer/aquitard solution, with the solution for transport in a fracture with matrix diffusion and decay, and with a fully numerical solution for transport in a thin sand zone bounded by clay with variable decay rates.

  13. A semi-analytical method for simulating matrix diffusion in numerical transport models.

    PubMed

    Falta, Ronald W; Wang, Wenwen

    2017-02-01

    A semi-analytical approximation for transient matrix diffusion is developed for use in numerical contaminant transport simulators. This method is an adaptation and extension of the heat conduction method of Vinsome and Westerveld (1980) used to simulate heat losses during thermally enhanced oil recovery. The semi-analytical method is used in place of discretization of the low permeability materials, and it represents the concentration profile in the low permeability materials with a fitting function that is adjusted in each element at each time-step. The resulting matrix diffusion fluxes are added to the numerical model as linear concentration-dependent source/sink terms. Since only the high permeability zones need to be discretized, the numerical formulation is extremely efficient compared to traditional approaches that require discretization of both the high and low permeability zones. The semi-analytical method compares favorably with the analytical solution for transient one-dimensional diffusion with first order decay, with a two-layer aquifer/aquitard solution, with the solution for transport in a fracture with matrix diffusion and decay, and with a fully numerical solution for transport in a thin sand zone bounded by clay with variable decay rates.

  14. Lateral Diffusion in an Archipelago

    PubMed Central

    Saxton, Michael J.

    1982-01-01

    Lateral diffusion of molecules in lipid bilayer membranes can be hindered by the presence of impermeable domains of gel-phase lipid or of proteins. Effective-medium theory and percolation theory are used to evaluate the effective lateral diffusion constant as a function of the area fraction of fluid-phase lipid and the permeability of the obstructions to the diffusing species. Applications include the estimation of the minimum fraction of fluid lipid needed for bacterial growth, and the enhancement of diffusion-controlled reactions by the channeling effect of solid patches of lipid. PMID:7052153

  15. Palomar Transient Factory

    NASA Astrophysics Data System (ADS)

    Kulkarni, S.; Quimby, R.

    2010-12-01

    The Palomar Transient Factory (PTF) was designed to explicitly to chart the transient sky with a particular focus on events which lie in the nova-supernova gap. With its innovative two-telescope architecture it achieves both high cadence and large areal rate of coverage. PTF was commissioned during the summer of 2009. PTF is now finding an extragalactic transient every 20 minutes and a Galactic (strong) variable every 10 minutes. Spectroscopy undertaken at Keck and Palomar has allowed us: identify an emerging class of ultra-luminous supernovae, discover luminous red novae, undertake UV spectroscopy of Ia supernovae, discover supernovae powered by something other than Nickel-56, clarification of sub-classes of core collapse and thermo-nuclear explosions, map the systematics of core collapse supernovae, a trove of eclipsing binaries and many others.

  16. Na-Diffusion Enhanced p-type Conductivity in Cu(In,Ga)Se 2 : A New Mechanism for Efficient Doping in Semiconductors

    SciTech Connect

    Yuan, Zhen-Kun; Chen, Shiyou; Xie, Yun; Park, Ji-Sang; Xiang, Hongjun; Gong, Xin-Gao; Wei, Su-Huai

    2016-08-30

    A new mechanism responsible for the hole concentration increase in the CIGS thin films after Na doping is proposed. At high temperature, a high concentration of Na is doped into the grains. After cooling and water rinsing, the solubility of Na becomes lower, so Na diffuses out of the grains with high concentration of Cu vacancies and hole carriers formed.

  17. Connecting molecular structure and exciton diffusion length in rubrene derivatives.

    PubMed

    Mullenbach, Tyler K; McGarry, Kathryn A; Luhman, Wade A; Douglas, Christopher J; Holmes, Russell J

    2013-07-19

    Connecting molecular structure and exciton diffusion length in rubrene derivatives demonstrates how the diffusion length of rubrene can be enhanced through targeted functionalization aiming to enhance self-Förster energy transfer. Functionalization adds steric bulk, forcing the molecules farther apart on average, and leading to increased photoluminescence efficiency. A diffusion length enhancement greater than 50% is realized over unsubstituted rubrene.

  18. Primary diffuse leptomeningeal gliosarcomatosis.

    PubMed

    Moon, Ju Hyung; Kim, Se Hoon; Kim, Eui Hyun; Kang, Seok-Gu; Chang, Jong Hee

    2015-04-01

    Primary diffuse leptomeningeal gliomatosis (PDLG) is a rare condition with a fatal outcome, characterized by diffuse infiltration of the leptomeninges by neoplastic glial cells without evidence of primary tumor in the brain or spinal cord parenchyma. In particular, PDLG histologically diagnosed as gliosarcoma is extremely rare, with only 2 cases reported to date. We report a case of primary diffuse leptomeningeal gliosarcomatosis. A 68-year-old man presented with fever, chilling, headache, and a brief episode of mental deterioration. Initial T1-weighted post-contrast brain magnetic resonance imaging (MRI) showed diffuse leptomeningeal enhancement without a definite intraparenchymal lesion. Based on clinical and imaging findings, antiviral treatment was initiated. Despite the treatment, the patient's neurologic symptoms and mental status progressively deteriorated and follow-up MRI showed rapid progression of the disease. A meningeal biopsy revealed gliosarcoma and was conclusive for the diagnosis of primary diffuse leptomeningeal gliosarcomatosis. We suggest the inclusion of PDLG in the potential differential diagnosis of patients who present with nonspecific neurologic symptoms in the presence of leptomeningeal involvement on MRI.

  19. Transient lingual papillitis.

    PubMed

    Kornerup, Ida M; Senye, Mireya; Peters, Edmund

    2016-01-01

    A case of recurrent, clinically innocuous, but painful papules involving the tongue dorsum of a 25-year-old man is presented. The lesions were interpreted to represent a transient lingual papillitis. This a poorly understood, but benign and self-limited condition involving the tongue fungiform papillae, which does not appear to be widely recognized.

  20. Transient familial hyperbilirubinemia

    MedlinePlus

    ... please enable JavaScript. Transient familial hyperbilirubinemia is a metabolic disorder that is passed down through families. Babies with ... M. Editorial team. Related MedlinePlus Health Topics Jaundice Metabolic Disorders Browse the Encyclopedia A.D.A.M., Inc. ...

  1. Lightning-Transient Recorder

    NASA Technical Reports Server (NTRS)

    Grumm, R. L.

    1984-01-01

    Battery-powered system operates for more than one year. Recorder digitizes and records up to 146 current samples at selected intervals during lightning stroke. System continues to store time tags of lightning strokes even if transient current memory is full.

  2. Diffusion in silicon isotope heterostructures

    SciTech Connect

    Silvestri, Hughes Howland

    2004-01-01

    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

  3. Nonergodic subdiffusion from transient interactions with heterogeneous partners

    NASA Astrophysics Data System (ADS)

    Charalambous, C.; Muñoz-Gil, G.; Celi, A.; Garcia-Parajo, M. F.; Lewenstein, M.; Manzo, C.; García-March, M. A.

    2017-03-01

    Spatiotemporal disorder has been recently associated to the occurrence of anomalous nonergodic diffusion of molecular components in biological systems, but the underlying microscopic mechanism is still unclear. We introduce a model in which a particle performs continuous Brownian motion with changes of diffusion coefficients induced by transient molecular interactions with diffusive binding partners. In spite of the exponential distribution of waiting times, the model shows subdiffusion and nonergodicity similar to the heavy-tailed continuous time random walk. The dependence of these properties on the density of binding partners is analyzed and discussed. Our work provides an experimentally testable microscopic model to investigate the nature of nonergodicity in disordered media.

  4. 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.

  5. 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.

  6. 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…

  7. 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)

  8. 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.

  9. Vacancy-enhanced mechanism for helium diffusion along Σ7 grain boundary in α-Al2O3: A first principle study

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Lai, Wensheng; Li, Rusong; He, Bin; Li, Sufen

    2017-02-01

    Helium migration behavior in the bulk and along the rhombohedral Σ7 grain boundary (GB) of α-Al2O3 has been studied via first-principles calculations based on the projector-augmented wave method. It turns out that the formation energies of helium in the α-Al2O3 bulk and in the rhombohedral Σ7 GB area are 2.12 eV and 3.15 eV, respectively. The energy barrier for helium migration in bulk is 2.28 eV, indicating that helium is difficult to diffuse. Moreover, the calculations also reveal that the radiation-induced O vacancies are favored to aggregate to the Σ7 GB plane, forming a zigzag O vacancy chain. In such circumvent, however, the energy barrier for helium diffusion along vacancy chain is significantly reduced to 0.61 eV, suggesting such O vacancy chain would provide the fast diffusion path for helium to escape from α-Al2O3 due to its large positive formation energy in the bulk.

  10. 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.

  11. Transient effects in laser cooling

    SciTech Connect

    Padua, S.; Xie, C.; Gupta, R.; Batelaan, H.; Bergeman, T.; Metcalf, H.

    1993-05-01

    Transient laser cooling (TLC) can produce cooling and heating, but often with the opposite detuning from that found in steady state. In TLC the time scale is set by the optical pumping (OP) rate to a state not coupled by the laser field. The combination of such OP processes and the conservative light shift potential U{sub o}sin{sup 2}kz leads to TLC. The average PE of atoms entering a standing wave is U{sub o}/2. They experience the optical force until undergoing OP to an uncoupled state, which is more likely to happen at high light intensity, near an antinode. For {delta} > 0 this means higher PE and thus lower KE, and conversely for {delta} < 0. In TLC there is no final {open_quotes}temperature{close_quotes} resulting from competition between a damping force and diffusive heating. Instead the changes in KE are bounded by U{sub o} so that the signal widths decrease with intensity. This can result in sub-Doppler widths. We have made two independent theoretical studies of these experiments. In a semiclassical calculation we evolve the motion for a calculated OP time and calculate the velocity distribution. We have also performed fully quantum mechanical calculations of the motion of atoms in the standing wave whose basis set consists of product states of internal and external atomic coordinates.

  12. Tailoring of electron diffusion through TiO2 nanowires

    NASA Astrophysics Data System (ADS)

    Jose, R.; Yusoff, M. M.

    2012-11-01

    Charge transport through a random network of onedimensional TiO2 nanostructures such as nanorods, nanowires, and nanofibers developed by electrospinning technique has been studied in the presence of an electrolyte by electrochemical impedance spectroscopy and transient photocurrent measurements. The results have been compared with the charge transport parameters of random TiO2 nanoparticle (25 nm) network. The charge transport was discussed under the framework of hopping transport. Continuous nanofibers had longer charge collecting times and short nanorods have enhanced scattering losses. The TiO2 films containing random network of nanowires of aspect ratio 10:1 can have an order of magnitude higher diffusion coefficient than other morphologies. Furthermore, charge transport through Nb-doped anatase TiO2 nanofibers was studied. It was observed that the Fermi level of TiO2 rise close to its conduction band and result in a band-edge type diffusion mechanism even at low bias voltages when 2 wt% Nb atoms replaces the Ti atoms in the anatase lattice. The Nb-doped anatase electrospun nanofibers showed high chemical capacitance, high effective diffusion coefficient, and lower transport resistance compared to the undoped samples and conventional nanoparticles.

  13. Photoacoustic transient imagery

    NASA Astrophysics Data System (ADS)

    Franceschi, J. L.; Marty-Dessus, D.; Severac, H.; Boucher, Jean-Marc; Bastie, A.

    1993-01-01

    A collimated laser diode associated with a small, short focal length objective lens produces a focused laser beam on the top of a sample glued onto a piezoelectric transducer. This laser beam is horizontally scanned on the surface and its intensity is modulated by a square wave using a TTL signal generator. This system induces acoustic waves in the sample. With a specially designed control circuitry, by combining this acoustic signal and the scanned laser beam, imaging of the subsurface is possible. The transient analysis developed is described and we show how to select cut-away views of the subsurface specimen with some applications in failure analysis of integrated circuits. We present the apparatus, the transient photoacoustic signal theory, and make a comparison between scanning photoacoustic (SPAM) and scanning electron acoustic microscopy (SEAM).

  14. Unusual CRTS Transient

    NASA Astrophysics Data System (ADS)

    Drake, A. J.; Mahabal, A.; Djorgovski, S. G.; Williams, R.; Graham, M. J.; Beshore, E. C.; Larson, S. M.; Christensen, E.; Christensen, E.; Beshore, E. C.; Larson, S. M.

    2008-10-01

    We have detected an optical transient of unknown nature in Catalina 0.7m Schmidt telescope images from 28 Sep 2008 UT. The object has the following parameters:

    CSS080928:160837+041626 2008-09-28 UT 02:50:49 RA 16:08:37.23 Dec 04:16:26.7 Mag 17.7 Type ?
    A possible uncataloged match to the transient is present in SDSS images with magnitude r~22.5.

  15. Synthesized light transients.

    PubMed

    Wirth, A; Hassan, M Th; Grguras, I; Gagnon, J; Moulet, A; Luu, T T; Pabst, S; Santra, R; Alahmed, Z A; Azzeer, A M; Yakovlev, V S; Pervak, V; Krausz, F; Goulielmakis, E

    2011-10-14

    Manipulation of electron dynamics calls for electromagnetic forces that can be confined to and controlled over sub-femtosecond time intervals. Tailored transients of light fields can provide these forces. We report on the generation of subcycle field transients spanning the infrared, visible, and ultraviolet frequency regimes with a 1.5-octave three-channel optical field synthesizer and their attosecond sampling. To demonstrate applicability, we field-ionized krypton atoms within a single wave crest and launched a valence-shell electron wavepacket with a well-defined initial phase. Half-cycle field excitation and attosecond probing revealed fine details of atomic-scale electron motion, such as the instantaneous rate of tunneling, the initial charge distribution of a valence-shell wavepacket, the attosecond dynamic shift (instantaneous ac Stark shift) of its energy levels, and its few-femtosecond coherent oscillations.

  16. 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...

  17. Transient Pulse Monitor

    DTIC Science & Technology

    1988-05-20

    connection to the test solar array pannels . One radiated electromagnetic signal sensor will be placed on one of the solar array panels (Figures 6 and 7). The...22 02 Spacecraft, Charging , Discharge, Transient, Environment 19. ABSTRACT (Cmntnue on mromN ifesor AWMI endwtfr by blok numfber) SRI International is...6 2.1.2 Particle Interactions with Satellite Materials: Charging ........................ 6 2.1.3 Discharges and Their Effects on Systems

  18. Coherent Transient Systems Evaluation

    DTIC Science & Technology

    1993-06-17

    europium doped yttrium silicate in collaboration with IBM Almaden Research Center. Research into divalent ion doped crystals as photon gated materials...demonstration of the coherent transient continuous optical processor was performed in europium doped yttrium silicate. Though hyperfine split ground...materials. Research into divalent samarium doped into other hosts is incomplete and may produce better results. Preliminary measurements on Tm:KCl revealed

  19. Transient Detection Using Wavelets.

    DTIC Science & Technology

    1995-03-01

    signaL and transients are nonstationary. A new technique for the analysis of this type of signal, called the Wavelet Transform , was applied to artificial...and real signals. A brief theoretical comparison between the Short Time Fourier Transform and the Wavelet Transform is introduced A multisolution...analysis approach for implementing the transform was used. Computer code for the Discrete Wavelet Transform was implemented. Different types of wavelets to use as basis functions were evaluated. (KAR) P. 2

  20. Lunar transient phenomena

    NASA Astrophysics Data System (ADS)

    Cameron, W. S.

    1991-03-01

    Lunar transient phenomena (LTP) sightings are classified into five categories: brightenings, darkenings, reddish colorations, bluish colorations, and obscurations. There is evidence that the remaining LTP's are of lunar origin. A substantial number of sightings are independently confirmed. They have been recorded on film and spectrograms, as well as with photoelectric photometers and polarization equipment. It suggested that the LTP's may be gentle outgassings of less-than-volcanic proportions.

  1. 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.

  2. Diffusion bonding

    DOEpatents

    Anderson, Robert C.

    1976-06-22

    1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

  3. Climate Variability and Vadose Zone Controls on Damping of Transient Recharge Fluxes

    NASA Astrophysics Data System (ADS)

    Corona, C.; Gurdak, J. J.; Dickinson, J.; Ferré, T. P. A.

    2015-12-01

    We investigate the effects of interannual to multidecadal climate variability on groundwater resources by exploring the physical processes in the vadose zone that partially control transient infiltration and recharge fluxes. The vadose zone connects climate variability modes to groundwater systems by influencing infiltration events. Infiltration events become time-varying water flux through the vadose zone and are controlled by highly nonlinear, complex interactions between mean infiltration flux, infiltration period, soil textures, and depth to water table. We focus on the behavior and damping depth of water flux in the vadose zone. The damping depth is defined as the depth that the flux variation damps to 5% of the land surface variation. When the damping depth is above the water table, recharge may be considered steady; when the damping depth is below the water table, recharge may be considered transient. Previous work shows that the damping depth is sensitive to the frequency of the infiltration pattern and the unsaturated hydraulic properties of the media. We examine controls on the damping depth by modeling transient water fluxes at the land surface using the Gardner-Kozeny soil model for diffuse unsaturated flow in HYDRUS 1-D. Results for homogeneous profiles show that shorter-period oscillations, smaller mean fluxes, and finer-grained soil textures generally produce damping depths closer to land surface. Modeling layered soil textures indicates similar, but more complicated responses in the damping depth. Model results indicate that finer-textured layers in a coarser soil profile generally result in damping depths closer to land surface, while coarser-textured layers in a coarser soil profile result in damping depths deeper in the vadose zone. Findings from this study will enhance understanding of the vadose zone's influence on transient water flux and improve the simulation of recharge processes and climate variability effects in groundwater models.

  4. Diffusion of Small Solute Particles in Viscous Liquids: Cage Diffusion, a Result of Decoupling of Solute-Solvent Dynamics, Leads to Amplification of Solute Diffusion.

    PubMed

    Acharya, Sayantan; Nandi, Manoj K; Mandal, Arkajit; Sarkar, Sucharita; Bhattacharyya, Sarika Maitra

    2015-08-27

    We study the diffusion of small solute particles through solvent by keeping the solute-solvent interaction repulsive and varying the solvent properties. The study involves computer simulations, development of a new model to describe diffusion of small solutes in a solvent, and also mode coupling theory (MCT) calculations. In a viscous solvent, a small solute diffuses via coupling to the solvent hydrodynamic modes and also through the transient cages formed by the solvent. The model developed can estimate the independent contributions from these two different channels of diffusion. Although the solute diffusion in all the systems shows an amplification, the degree of it increases with solvent viscosity. The model correctly predicts that when the solvent viscosity is high, the solute primarily diffuses by exploiting the solvent cages. In such a scenario the MCT diffusion performed for a static solvent provides a correct estimation of the cage diffusion.

  5. Diagnosing transient ionization in dynamic events

    NASA Astrophysics Data System (ADS)

    Doyle, J. G.; Giunta, A.; Madjarska, M. S.; Summers, H.; O'Mullane, M.; Singh, A.

    2013-09-01

    Aims: The present study aims to provide a diagnostic line ratio that will enable the observer to determine whether a plasma is in a state of transient ionization. Methods: We use the Atomic Data and Analysis Structure (ADAS) to calculate line contribution functions for two lines, Si iv 1394 Å and O iv 1401 Å, formed in the solar transition region. The generalized collisional-radiative theory is used. It includes all radiative and electron collisional processes, except for photon-induced processes. State-resolved direct ionization and recombination to and from the next ionization stage are also taken into account. Results: For dynamic bursts with a decay time of a few seconds, the Si iv 1394 Å line can be enhanced by a factor of 2-4 in the first fraction of a second with the peak in the line contribution function occurring initially at a higher electron temperature due to transient ionization compared to ionization equilibrium conditions. On the other hand, the O iv 1401 Å does not show such any enhancement. Thus the ratio of these two lines, which can be observed with the Interface Region Imaging Spectrograph, can be used as a diagnostic of transient ionization. Conclusions: We show that simultaneous high-cadence observations of two lines formed in the solar transition region may be used as a direct diagnostic of whether the observed plasma is in transient ionization. The ratio of these two lines can change by a factor of four in a few seconds owing to transient ionization alone.

  6. 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.

  7. Current transients in single nanoparticle collision events.

    PubMed

    Xiao, Xiaoyin; Fan, Fu-Ren F; Zhou, Jiping; Bard, Allen J

    2008-12-10

    Electrochemical hydrazine oxidation and proton reduction occur at a significantly higher rate at Pt than at Au or C electrodes. Thus, the collision and adhesion of a Pt particle on a less active Au or C electrode leads to a large current amplification by electrocatalysis at single nanoparticles (NPs). At low particle concentrations, the collision of Pt NPs was characterized by current transients composed of individual current profiles that rapidly attained a steady state, signaling single NP collisions. The characteristic steady-state current was used to estimate the particle size. The fluctuation in collision frequency with time indicates that the collision of NPs at the detector electrodes occurs in a statistically random manner, with the average frequency a function of particle concentration and diffusion coefficient. A longer term current decay in single current transients, as opposed to the expected steady-state behavior, was more pronounced for proton reduction than for hydrazine oxidation, revealing microscopic details of the nature of the particle interaction with the detector electrode and the kinetics of electrocatalysis at single NPs. The study of single NP collisions allows one to screen particle size distributions and estimate NP concentrations and diffusion coefficients.

  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. Atomic scale models of Ion implantation and dopant diffusion in silicon

    SciTech Connect

    Caturla, M; Johnson, M; Lenosky, T; Sadigh, B; Theiss, S K; Zhu, J; de la Rubia, T D

    1999-03-01

    We review our recent work on an atomistic approach to the development of predictive process simulation tools. First principles methods, molecular dynamics simulations, and experimental results are used to construct a database of defect and dopant energetics in Si. This is used as input for kinetic Monte Carlo simulations. C and B trapping of the Si self- interstitial is shown to help explain the enormous disparity in its measured diffusivity. Excellent agreement is found between experiments and simulations of transient enhanced diffusion following 20-80 keV B implants into Si, and with those of 50 keV Si implants into complex B-doped structures. Our simulations predict novel behavior of the time evolution of the electrically active B fraction during annealing.

  10. 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

  11. Enhancing the effectiveness of HIV/AIDS prevention programs targeted to unique population groups in Thailand: lessons learned from applying concepts of diffusion of innovation and social marketing.

    PubMed

    Svenkerud, P J; Singhal, A

    1998-01-01

    Diffusion of innovations theory and social marketing theory have been criticized for their limited applicability in influencing unique population groups (e.g., female commercial sex workers (CSWs) working in low-class brothels). This study investigated the applicability of these two theoretical frameworks in outreach efforts directed to unique populations at high risk for HIV/AIDS in Bangkok, Thailand. Further, this study examined Thai cultural characteristics that influence communication about HIV/AIDS prevention. The results suggest that certain concepts and strategies drawn from the two frameworks were used more or less by effective outreach programs, providing several policy-relevant lessons. Cultural constraints, such as the lack of visibility of the disease and traditional sexual practices, influenced communication about HIV/AIDS prevention.

  12. 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

  13. Transient transformation of plants.

    PubMed

    Jones, Huw D; Doherty, Angela; Sparks, Caroline A

    2009-01-01

    Transient expression in plants is a valuable tool for many aspects of functional genomics and promoter testing. It can be used both to over-express and to silence candidate genes. It is also scaleable and provides a viable alternative to microbial fermentation and animal cell culture for the production of recombinant proteins. It does not depend on chromosomal integration of heterologous DNA so is a relatively facile procedure and can lead to high levels of transgene expression. Recombinant DNA can be introduced into plant cells via physical methods, via Agrobacterium or via viral vectors.

  14. Thermal transient anemometer

    DOEpatents

    Bailey, J.L.; Vresk, J.

    1989-07-18

    A thermal transient anemometer is disclosed 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. 12 figs.

  15. Thermal transient anemometer

    DOEpatents

    Bailey, James L.; Vresk, Josip

    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.

  16. 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

  17. Surface self-diffusion of organic glasses.

    PubMed

    Brian, Caleb W; Yu, Lian

    2013-12-19

    Surface self-diffusion coefficients have been determined for the organic glass Nifedipine using the method of surface grating decay. The flattening of 1000 nm surface gratings occurs by viscous flow at 12 K or more above the glass transition temperature and by surface diffusion at lower temperatures. Surface diffusion is at least 10(7) times faster than bulk diffusion, indicating a highly mobile surface. Nifedipine glasses have faster surface diffusion than the previously studied Indomethacin glasses, despite their similar bulk relaxation times. Both glasses exhibit fast surface crystal growth, and its rate scales with surface diffusivity. The observed rate of surface diffusion implies substantial surface rearrangement during the preparation of low-energy glasses by vapor deposition. The Random First Order Transition Theory and the Coupling Model successfully predict the large surface-enhancement of mobility and its increase on cooling, but disagree with the experimental observation of the faster surface diffusion of Nifedipine.

  18. Thermal Soret Diffusion in the Liquid Phase Epitaxial Growth of Binary Iii-V Compounds

    NASA Astrophysics Data System (ADS)

    Chien, Chung-Ping

    The conditions necessary for stable nucleation and growth in the liquid phase epitaxial growth of GaAs and InP are analytically established and, in the former, experimentally confirmed in this research. A transient thermodynamic transport treatment of supersaturated to undersaturated melts, which includes the coupling between solute and heat transport(thermal Soret diffusion), has been solved in closed form. The thermal Soret diffusion effect has been found to be a very important factor for the stabilization of solute transport. For steady-state LPE growth, the thermal Soret diffusion will give rise to a separation effect that forces the steady -state solute concentration to exceed the equilibrium liquidus concentration at a noninteracting interface. This increased concentration, near the growth interface, can cause localized nonuniformities in the melt which leads to terrace, miniscus -line and/or hillock growth morphologies. When nucleation and growth are initiated at near equilibrium liquidus conditions, at the substrate interface with a temperature gradient, meltback and spontaneous nucleation are minimized. To enhance stable uniform growth, the substrate should be brought into contact with the melt at a very critical time, during melt saturation, when the equilibrium liquidus concentration is reached at the noninteracting interface of the slider. The critical melt saturation time for the transient concentration to reach the liquidus concentration at this interface has been analytically determined and experimentally confirmed. In this analysis, the Soret thermal diffusion coefficient has also been evaluated in terms of the solute and solvent masses and the temperature dependence of the solute diffusion coefficient. The critical time determined in this analysis appears to be in close agreement with the experimental results for LPE GaAs. When near steady-state solute transport is achieved at the initiation of growth on the substrate, i.e., the liquidus solute

  19. Selective ion changes during spontaneous mitochondrial transients in intact astrocytes.

    PubMed

    Azarias, Guillaume; Chatton, Jean-Yves

    2011-01-01

    The bioenergetic status of cells is tightly regulated by the activity of cytosolic enzymes and mitochondrial ATP production. To adapt their metabolism to cellular energy needs, mitochondria have been shown to exhibit changes in their ionic composition as the result of changes in cytosolic ion concentrations. Individual mitochondria also exhibit spontaneous changes in their electrical potential without altering those of neighboring mitochondria. We recently reported that individual mitochondria of intact astrocytes exhibit spontaneous transient increases in their Na(+) concentration. Here, we investigated whether the concentration of other ionic species were involved during mitochondrial transients. By combining fluorescence imaging methods, we performed a multiparameter study of spontaneous mitochondrial transients in intact resting astrocytes. We show that mitochondria exhibit coincident changes in their Na(+) concentration, electrical potential, matrix pH and mitochondrial reactive oxygen species production during a mitochondrial transient without involving detectable changes in their Ca(2+) concentration. Using widefield and total internal reflection fluorescence imaging, we found evidence for localized transient decreases in the free Mg(2+) concentration accompanying mitochondrial Na(+) spikes that could indicate an associated local and transient enrichment in the ATP concentration. Therefore, we propose a sequential model for mitochondrial transients involving a localized ATP microdomain that triggers a Na(+)-mediated mitochondrial depolarization, transiently enhancing the activity of the mitochondrial respiratory chain. Our work provides a model describing ionic changes that could support a bidirectional cytosol-to-mitochondria ionic communication.

  20. Chemotherapeutic drug-specific alteration of microvascular blood flow in murine breast cancer as measured by diffuse correlation spectroscopy

    PubMed Central

    Ramirez, Gabriel; Proctor, Ashley R.; Jung, Ki Won; Wu, Tong Tong; Han, Songfeng; Adams, Russell R.; Ren, Jingxuan; Byun, Daniel K.; Madden, Kelley S.; Brown, Edward B.; Foster, Thomas H.; Farzam, Parisa; Durduran, Turgut; Choe, Regine

    2016-01-01

    The non-invasive, in vivo measurement of microvascular blood flow has the potential to enhance breast cancer therapy monitoring. Here, longitudinal blood flow of 4T1 murine breast cancer (N=125) under chemotherapy was quantified with diffuse correlation spectroscopy based on layer models. Six different treatment regimens involving doxorubicin, cyclophosphamide, and paclitaxel at clinically relevant doses were investigated. Treatments with cyclophosphamide increased blood flow as early as 3 days after administration, whereas paclitaxel induced a transient blood flow decrease at 1 day after administration. Early blood flow changes correlated strongly with the treatment outcome and distinguished treated from untreated mice individually for effective treatments. PMID:27699124

  1. Diffusion in membranes: Toward a two-dimensional diffusion map

    NASA Astrophysics Data System (ADS)

    Toppozini, Laura; Garcia-Sakai, Victoria; Bewley, Robert; Dalgliesh, Robert; Perring, Toby; Rheinstädter, Maikel C.

    2015-01-01

    For decades, quasi-elastic neutron scattering has been the prime tool for studying molecular diffusion in membranes over relevant nanometer distances. These experiments are essential to our current understanding of molecular dynamics of lipids, proteins and membrane-active molecules. Recently, we presented experimental evidence from X-ray diffraction and quasi-elastic neutron scattering demonstrating that ethanol enhances the permeability of membranes. At the QENS 2014/WINS 2014 conference we presented a novel technique to measure diffusion across membranes employing 2-dimensional quasi-elastic neutron scattering. We present results from our preliminary analysis of an experiment on the cold neutron multi-chopper spectrometer LET at ISIS, where we studied the self-diffusion of water molecules along lipid membranes and have the possibility of studying the diffusion in membranes. By preparing highly oriented membrane stacks and aligning them horizontally in the spectrometer, our aim is to distinguish between lateral and transmembrane diffusion. Diffusion may also be measured at different locations in the membranes, such as the water layer and the hydrocarbon membrane core. With a complete analysis of the data, 2-dimensional mapping will enable us to determine diffusion channels of water and ethanol molecules to quantitatively determine nanoscale membrane permeability.

  2. Effects of electrode properties and fabricated pressure on Li ion diffusion and diffusion-induced stresses in cylindrical Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Zhang, Tao; Guo, Zhansheng

    2014-03-01

    The effects of electrode properties and fabricated pressure on Li ion diffusion and diffusion-induced stress in a cylindrical Li-ion battery are studied. It is found that hydrostatic pressure or elastic modulus variation in the active layer have little effect on the distribution of Li ions for a higher diffusivity coefficient, but both can facilitate Li ion diffusion for a lower diffusivity coefficient. The elastic modulus variation has a significant effect on the distribution of stress and hydrostatic pressure can reduce the surface stress for the lower diffusivity coefficient. A higher charging rate causes a more transient response in the stress history, but a linear charging history is observed for slow charging rates. A higher charging rate would not inflict extra damage on the electrode for the higher diffusivity coefficient and the stress history becomes highly transient and charging rate dependent for the lower diffusivity coefficient. The effect of fabricated pressure can be neglected.

  3. Calculating transient rates from surveys

    NASA Astrophysics Data System (ADS)

    Carbone, D.; van der Horst, A. J.; Wijers, R. A. M. J.; Rowlinson, A.

    2017-03-01

    We have developed a method to determine the transient surface density and transient rate for any given survey, using Monte Carlo simulations. This method allows us to determine the transient rate as a function of both the flux and the duration of the transients in the whole flux-duration plane rather than one or a few points as currently available methods do. It is applicable to every survey strategy that is monitoring the same part of the sky, regardless the instrument or wavelength of the survey, or the target sources. We have simulated both top-hat and Fast Rise Exponential Decay light curves, highlighting how the shape of the light curve might affect the detectability of transients. Another application for this method is to estimate the number of transients of a given kind that are expected to be detected by a survey, provided that their rate is known.

  4. Enhanced performance of polybenzimidazole-based high temperature proton exchange membrane fuel cell with gas diffusion electrodes prepared by automatic catalyst spraying under irradiation technique

    NASA Astrophysics Data System (ADS)

    Su, Huaneng; Pasupathi, Sivakumar; Bladergroen, Bernard Jan; Linkov, Vladimir; Pollet, Bruno G.

    2013-11-01

    Gas diffusion electrodes (GDEs) prepared by a novel automatic catalyst spraying under irradiation (ACSUI) technique are investigated for improving the performance of phosphoric acid (PA)-doped polybenzimidazole (PBI) high temperature proton exchange membrane fuel cell (PEMFC). The physical properties of the GDEs are characterized by pore size distribution and scanning electron microscopy (SEM). The electrochemical properties of the membrane electrode assembly (MEA) with the GDEs are evaluated and analyzed by polarization curve, cyclic voltammetry (CV) and electrochemistry impedance spectroscopy (EIS). Effects of PTFE binder content, PA impregnation and heat treatment on the GDEs are investigated to determine the optimum performance of the single cell. At ambient pressure and 160 °C, the maximum power density can reach 0.61 W cm-2, and the current density at 0.6 V is up to 0.38 A cm-2, with H2/air and a platinum loading of 0.5 mg cm-2 on both electrodes. The MEA with the GDEs shows good stability for fuel cell operating in a short term durability test.

  5. 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).

  6. Formation of magnetized prestellar cores with ambipolar diffusion and turbulence

    SciTech Connect

    Chen, Che-Yu; Ostriker, Eve C. E-mail: eco@astro.princeton.edu

    2014-04-10

    We investigate the roles of magnetic fields and ambipolar diffusion during prestellar core formation in turbulent giant molecular clouds, using three-dimensional numerical simulations. Our simulations focus on the shocked layer produced by a converging large-scale flow and survey varying ionization and the 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 M {sub ☉} and sizes L ∼ 0.015-0.07 pc, consistent with observations of the peak of the core mass function. Median values are M = 0.47 M {sub ☉} 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-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 one to two orders of magnitude lower than the value M {sub mag,} {sub sph} = 0.007B {sup 3}/(G {sup 3/2}ρ{sup 2}) 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 that suggests that gravitationally critical core masses will depend on the sound speed and mean turbulent pressure in a cloud, regardless of magnetic effects.

  7. Fluid diffusion in porous silica

    NASA Astrophysics Data System (ADS)

    McCann, Lowell I.

    Fluid motion in porous media has received a great deal of theoretical and experimental attention due to its importance in systems as diverse as ground water aquifers, catalytic processes, and size separation schemes. Often, the motion of interest is the random thermal motion of molecules in a fluid undergoing no net flow. This diffusive motion is particularly important when the size of the pores is nearly the same as the size of the molecules. In this study, fluid diffusion is measured in several varieties of porous silica whose pore structure is determined by the process by which it is made. The samples in this study have porosities (φ, the ratio of the pore volume to the total sample volume) that vary from 0.3 to 0.75 and average pore radii that range from approximately 15 to 120 A. Determining the effect of the pore structure on the diffusion of a liquid in a porous material is complicated by the chemical interactions between the diffusing molecules and the pore surface. In this study, ions in a hydrophilic fluid are used to block the adsorption of the diffusing dye molecules to the hydroxyl groups covering the silica surface. This technique is unlike typical surface treatments of silica in that it does not permanently alter the pore geometry. In this work, fluid diffusion is measured with a transient holographic grating technique where interfering laser beams create a periodic refractive index modulation in the fluid. The diffraction of a third laser off this grating is monitored to determine how quickly the grating relaxes, thereby determining the diffusion coefficient of the molecules in the fluid. Varying the grating periodicity controls the length scale of the diffusion measurement from 1.2 to 100 μm which is much larger than the average pore sizes of the samples. Therefore, over these large scales, we measure 'normal' diffusion, where the mean squared displacement of a diffusing particle varies linearly with time. In one particular type of porous silica

  8. The joy of transient chaos

    SciTech Connect

    Tél, Tamás

    2015-09-15

    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.

  9. 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

  10. Double-diffusive layer formation

    NASA Astrophysics Data System (ADS)

    Zaussinger, Florian; Kupka, Friedrich; Hücker, Sebastian; Egbers, Christoph

    2015-04-01

    Double-diffusive convection plays an important role in geo- and astrophysical applications. The special case, where a destabilising temperature gradient counteracts a stabilising solute gradient leads to layering phenomena under certain conditions. Convectively mixed layers sandwiched in diffusive interfaces form a so-called stack. Well-known double-diffusive systems are observed in rift lakes in Africa and even from the coffee drink Latte Macciatto. Stacks of layers are also predicted to occur inside massive stars and inside giant planets. Their dynamics depend on the thermal, the solute and the momentum diffusivities, as well on the ratio of the gradients of the opposing stratifications. Since the layering process cannot be derived from linear stability analysis, the full nonlinear set of equations has to be investigated. Numerical simulations have become feasible for this task, despite the physical processes operate on a vast range of length and time scales, which is challenging for numerical hydrodynamical modelling. The oceanographically relevant case of fresh and salty water is investigated here in further details. The heat and mass transfer is compared with theoretical results and experimental measurements. Additionally, the initial dynamic of layering, the transient behaviour of a stack and the long time evolution are presented using the example of Lake Kivu and the interior of a giant planet.

  11. Perturbations for transient acceleration

    SciTech Connect

    Vargas, Cristofher Zuñiga; Zimdahl, Winfried; Hipólito-Ricaldi, Wiliam S. E-mail: hipolito@ceunes.ufes.br

    2012-04-01

    According to the standard ΛCDM 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.

  12. DSN Transient Observatory

    NASA Astrophysics Data System (ADS)

    Kuiper, T. B. H.; Monroe, R. M.; White, L. A.; Miro, C. Garcia; Levin, S. M.; Majid, W. A.; Soriano, M.

    The Deep Space Network (DSN) Transient Observatory (DTO) is a signal processing facility that can monitor up to four DSN downlink bands for astronomically interesting signals. The monitoring is done commensally with reception of deep space mission telemetry. The initial signal processing is done with two CASPERa ROACH1 boards, each handling one or two baseband signals. Each ROACH1 has a 10 GBe interface with a GPU-equipped Debian Linux workstation for additional processing. The initial science programs include monitoring Mars for electrostatic discharges, radio spectral lines, searches for fast radio bursts and pulsars and SETI. The facility will be available to the scientific community through a peer review process.

  13. Single file diffusion in microtubules

    NASA Astrophysics Data System (ADS)

    Rutenberg, Andrew; Farrell, Spencer; Brown, Aidan

    2015-03-01

    We investigate the single file diffusion (SFD) of large particles entering a confined tubular geometry, such as luminal diffusion of proteins inside microtubules or flagella. While single-file effects have no effect on particle density, we report significant single-file effects for individually-tracked tracer particle motion. Both exact and approximate ordering statistics of particles entering semi-infinite tubes agree well with our stochastic simulations. Considering initially empty semi-infinite tubes, with particles entering at one end starting from an initial time t = 0 , tracked particles display super-diffusive effective exponents just after they enter the system and trends towards diffusive exponents at later times. Equivalently, if diffusive exponents are assumed the effective diffusivity is reduced at early times and enhanced at later times through a logarithmic factor logN , where N is the number of particles in the tube. When we number each particle from the first (n = 1) to the most recent (n = N), we find good scaling collapse of the effective diffusivity for all n. Techniques that track individual particles, or local groups of particles, such as photo-activation or photobleaching, will exhibit single-file effects.

  14. Cytoplasmic hydrogen ion diffusion coefficient.

    PubMed Central

    al-Baldawi, N F; Abercrombie, R F

    1992-01-01

    The apparent cytoplasmic proton diffusion coefficient was measured using pH electrodes and samples of cytoplasm extracted from the giant neuron of a marine invertebrate. By suddenly changing the pH at one surface of the sample and recording the relaxation of pH within the sample, an apparent diffusion coefficient of 1.4 +/- 0.5 x 10(-6) cm2/s (N = 7) was measured in the acidic or neutral range of pH (6.0-7.2). This value is approximately 5x lower than the diffusion coefficient of the mobile pH buffers (approximately 8 x 10(-6) cm2/s) and approximately 68x lower than the diffusion coefficient of the hydronium ion (93 x 10(-6) cm2/s). A mobile pH buffer (approximately 15% of the buffering power) and an immobile buffer (approximately 85% of the buffering power) could quantitatively account for the results at acidic or neutral pH. At alkaline pH (8.2-8.6), the apparent proton diffusion coefficient increased to 4.1 +/- 0.8 x 10(-6) cm2/s (N = 7). This larger diffusion coefficient at alkaline pH could be explained quantitatively by the enhanced buffering power of the mobile amino acids. Under the conditions of these experiments, it is unlikely that hydroxide movement influences the apparent hydrogen ion diffusion coefficient. PMID:1617134

  15. Atlas-guided volumetric diffuse optical tomography enhanced by generalized linear model analysis to image risk decision-making responses in young adults

    PubMed Central

    Lin, Zi-Jing; Li, Lin; Cazzell, Mary; Liu, Hanli

    2014-01-01

    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

  16. Finite volume scheme for double convection-diffusion exchange of solutes in bicarbonate high-flux hollow-fiber dialyzer therapy.

    PubMed

    Annan, Kodwo

    2012-01-01

    The efficiency of a high-flux dialyzer in terms of buffering and toxic solute removal largely depends on the ability to use convection-diffusion mechanism inside the membrane. A two-dimensional transient convection-diffusion model coupled with acid-base correction term was developed. A finite volume technique was used to discretize the model and to numerically simulate it using MATLAB software tool. We observed that small solute concentration gradients peaked and were large enough to activate solute diffusion process in the membrane. While CO(2) concentration gradients diminished from their maxima and shifted toward the end of the membrane, HCO(3)(-) concentration gradients peaked at the same position. Also, CO(2) concentration decreased rapidly within the first 47 minutes while optimal HCO(3)(-) concentration was achieved within 30 minutes of the therapy. Abnormally high diffusion fluxes were observed near the blood-membrane interface that increased diffusion driving force and enhanced the overall diffusive process. While convective flux dominated total flux during the dialysis session, there was a continuous interference between convection and diffusion fluxes that call for the need to seek minimal interference between these two mechanisms. This is critical for the effective design and operation of high-flux dialyzers.

  17. Finite Volume Scheme for Double Convection-Diffusion Exchange of Solutes in Bicarbonate High-Flux Hollow-Fiber Dialyzer Therapy

    PubMed Central

    Annan, Kodwo

    2012-01-01

    The efficiency of a high-flux dialyzer in terms of buffering and toxic solute removal largely depends on the ability to use convection-diffusion mechanism inside the membrane. A two-dimensional transient convection-diffusion model coupled with acid-base correction term was developed. A finite volume technique was used to discretize the model and to numerically simulate it using MATLAB software tool. We observed that small solute concentration gradients peaked and were large enough to activate solute diffusion process in the membrane. While CO2 concentration gradients diminished from their maxima and shifted toward the end of the membrane, HCO3 − concentration gradients peaked at the same position. Also, CO2 concentration decreased rapidly within the first 47 minutes while optimal HCO3 − concentration was achieved within 30 minutes of the therapy. Abnormally high diffusion fluxes were observed near the blood-membrane interface that increased diffusion driving force and enhanced the overall diffusive process. While convective flux dominated total flux during the dialysis session, there was a continuous interference between convection and diffusion fluxes that call for the need to seek minimal interference between these two mechanisms. This is critical for the effective design and operation of high-flux dialyzers. PMID:23197994

  18. Transient Spatiotemporal Chaos in a Synaptically Coupled Neural Network

    NASA Astrophysics Data System (ADS)

    Lafranceschina, Jacopo; Wackerbauer, Renate

    2014-03-01

    Spatiotemporal chaos is transient in a diffusively coupled Morris-Lecar neural network. This study shows that the addition of synaptic coupling in the ring network reduces the average lifetime of spatiotemporal chaos for small to intermediate coupling strength and almost all numbers of synapses. For large coupling strength, 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 Lyaponov exponent and degree of phase coherence as the number of synaptic links increases. The presence of transient spatiotemporal chaos in a network of coupled neurons and the associated chaotic saddle provides a possibility for switching between metastable states observed in information processing and brain function. This research is supported by the University of Alaska Fairbanks.

  19. Transient forcing effects on mixing of two fluids for a stable stratification

    NASA Astrophysics Data System (ADS)

    Pool, María.; Dentz, Marco; Post, Vincent E. A.

    2016-09-01

    Mixing and dispersion in coastal aquifers are strongly influenced by periodic temporal flow fluctuations on multiple time scales ranging from days (tides), seasons (pumping and recharge) to glacial cycles (regression and transgressions). Transient forcing effects lead to a complex space and time-dependent flow response which induces enhanced spreading and mixing of dissolved substances. We study effective mixing and solute transport in temporally fluctuating one-dimensional flow for a stable stratification of two fluids of different density using detailed numerical simulation as well as accurate column experiments. We quantify the observed transport behaviors and interface evolution by a time-averaged model that is obtained from a two-scale expansion of the full transport problem, and derive explicit expressions for the center of mass and width of the mixing zone between the two fluids. We find that the magnitude of transient-driven mixing is mainly controlled by the hydraulic diffusivity, the period, and the initial interface location. At an initial time regime, mixing can be characterized by an effective dispersion coefficient and both the interface position and width evolve linearly in time. At larger times, the spatial variability of the flow velocity leads to a deceleration of the interface and a compression of its width, which is manifested by a subdiffusive evolution of its width as t1/2.

  20. Peach Bottom Transients Analysis with TRAC/BF1-VALKIN

    SciTech Connect

    Verdu, G.; Miro, R.; Sanchez, A.M.; Rosello, O.; Ginestar, D.; Vidal, V.

    2004-10-15

    The TRAC/BF1-VALKIN code is a new time domain analysis code for studying transients in a boiling water reactor. This code uses the best-estimate code TRAC/BF1 to give an account of the heat transfer and thermal-hydraulic processes and a three-dimensional neutronics module. This module has two options: the MODKIN option that makes use of a modal method based on the assumption that the neutronic flux can be approximately expanded in terms of the dominant lambda modes associated with a static configuration of the reactor core, and the NOKIN option that uses a one-step backward discretization of the neutron diffusion equation. To check the performance of the TRAC/BF1-VALKIN code, the Peach Bottom turbine trip transient has been simulated, because this transient is a dynamically complex event where neutron kinetics is coupled with thermal hydraulics in the reactor primary system, and reactor variables change very rapidly.

  1. Quantifying protein diffusion and capture on filaments.

    PubMed

    Reithmann, Emanuel; Reese, Louis; Frey, Erwin

    2015-02-17

    The functional relevance of regulating proteins is often limited to specific binding sites such as the ends of microtubules or actin-filaments. A localization of proteins on these functional sites is of great importance. We present a quantitative theory for a diffusion and capture process, where proteins diffuse on a filament and stop diffusing when reaching the filament's end. It is found that end-association after one-dimensional diffusion is the main source for tip-localization of such proteins. As a consequence, diffusion and capture is highly efficient in enhancing the reaction velocity of enzymatic reactions, where proteins and filament ends are to each other as enzyme and substrate. We show that the reaction velocity can effectively be described within a Michaelis-Menten framework. Together, one-dimensional diffusion and capture beats the (three-dimensional) Smoluchowski diffusion limit for the rate of protein association to filament ends.

  2. Inferring transient particle transport dynamics in live cells.

    PubMed

    Monnier, Nilah; Barry, Zachary; Park, Hye Yoon; Su, Kuan-Chung; Katz, Zachary; English, Brian P; Dey, Arkajit; Pan, Keyao; Cheeseman, Iain M; Singer, Robert H; Bathe, Mark

    2015-09-01

    Live-cell imaging and particle tracking provide rich information on mechanisms of intracellular transport. However, trajectory analysis procedures to infer complex transport dynamics involving stochastic switching between active transport and diffusive motion are lacking. We applied Bayesian model selection to hidden Markov modeling to infer transient transport states from trajectories of mRNA-protein complexes in live mouse hippocampal neurons and metaphase kinetochores in dividing human cells. The software is available at http://hmm-bayes.org/.

  3. The MWA Transients Survey (MWATS).

    NASA Astrophysics Data System (ADS)

    Bell, M.; Murphy, T.; Kaplan, D. L.; Croft, S. D.; Hancock, P.; Rowlinson, A.; Wayth, R.; Gaensler, B.; Hurley-Walker, N.; Offringa, A.; Loi, C.; Bannister, K.; Trott, C.; Marquart, J.

    2017-01-01

    We propose the continuation of the MWA transients survey to search for and monitor low frequency transient and variable radio sources in the southern sky. This proposal is aimed at commensally utilising data from the GLEAM-X (G0008) project in semester 2017-A. The aim of this commensal data acquisition is to commission long baseline observations for transient science. In particular this will involve studying the impact of the ionosphere on calibration and imaging, and developing the techniques needed to produce science quality data products. The proposed drift scans with LST locking (see G0008 proposal) are particularly exciting as we can test image subtraction for transient and variable identification. This survey is targeted at studying objects such as AGN (intrinsic and extrinsic variability), long duration synchrotron emitters, pulsars and transients of unknown origin. The maps generated from this survey will be analysed with the Variables and Slow Transients (VAST) detection pipeline. The motivation for this survey is as follows: (i) To obtain temporal data on an extremely large and robust sample of low frequency sources to explore and quantify both intrinsic and extrinsic variability; (ii) To search and find new classes of low frequency radio transients that previously remained undetected and obscured from multi-wavelength discovery; (iii) To place rigorous statistics on the occurrence of both transients and variables prior to the Australian SKA era.

  4. Summer 1993 Transient Student Report.

    ERIC Educational Resources Information Center

    Kent State Univ., Warren, OH. Office of Institutional Research.

    A study was conducted by the Trumbull Campus (TC) of Kent State University, in Ohio, to determine the motivations, objectives, and level of satisfaction of transient students, or students pursuing a degree at another institution but enrolled in courses at TC. Surveys were mailed to 50 transient students enrolled in summer 1993, with completed…

  5. Neoclassical diffusion in a turbulent plasma

    SciTech Connect

    Yushmanov, P. . Inst. Atomnoj Ehnergii Texas Univ., Austin, TX . Inst. for Fusion Studies)

    1991-11-01

    This work describes a new approach to plasma transport where the toroidal drift motion is considered as a perturbation to the fluctuating velocity. Percolation theory is used to determine the scaling of the diffusion coefficient. Several neoclassical phenomena should persist even when diffusion is enhanced from neoclassical predictions. Numerical simulation results support the theoretical scaling arguments.

  6. The fast diffusion of Au IN Pb

    NASA Technical Reports Server (NTRS)

    Mclellan, R. B.; Ko, C.; Brotzen, F. R.

    1990-01-01

    A treatment of the phenomenon of fast diffusion in lead is presented. The model used is based upon the fast diffusion of free solute interstitials. The very large negative enhancement coefficients found in the Pb-(Au, Ag) systems is explained by the formation of first and second order clusters of vacancies and substitutional solute atoms.

  7. Perspectives of transient tracer applications and limiting cases

    NASA Astrophysics Data System (ADS)

    Stöven, T.; Tanhua, T.; Hoppema, M.; Bullister, J. L.

    2015-09-01

    Currently available transient tracers have different application ranges that are defined by their temporal input (chronological transient tracers) or their decay rate (radioactive transient tracers). Transient tracers range from tracers for highly ventilated water masses such as sulfur hexafluoride (SF6) through tritium (3H) and chlorofluorocarbons (CFCs) up to tracers for less ventilated deep ocean basins such as argon-39 (39Ar) and radiocarbon (14C). In this context, highly ventilated water masses are defined as water masses that have been in contact with the atmosphere during the last decade. Transient tracers can be used to empirically constrain the transit time distribution (TTD), which can often be approximated with an inverse Gaussian (IG) distribution. The IG-TTD provides information about ventilation and the advective/diffusive characteristics of a water parcel. Here we provide an overview of commonly used transient tracer couples and the corresponding application range of the IG-TTD by using the new concept of validity areas. CFC-12, CFC-11 and SF6 data from three different cruises in the South Atlantic Ocean and Southern Ocean as well as 39Ar data from the 1980s and early 1990s in the eastern Atlantic Ocean and the Weddell Sea are used to demonstrate this method. We found that the IG-TTD can be constrained along the Greenwich Meridian south to 46° S, which corresponds to the Subantarctic Front (SAF) denoting the application limit. The Antarctic Intermediate Water (AAIW) describes the limiting water layer in the vertical. Conspicuous high or lower ratios between the advective and diffusive components describe the transition between the validity area and the application limit of the IG-TTD model rather than describing the physical properties of the water parcel. The combination of 39Ar and CFC data places constraints on the IG-TTD in the deep water north of the SAF, but not beyond this limit.

  8. Diffusion in isotopically controlled semiconductor systems

    NASA Astrophysics Data System (ADS)

    Bracht, H.

    1999-12-01

    Isotopically controlled heterostructures of 28Si/natSi and Al71GaAs/Al69GaAs/71GaAs have been used to study the self-diffusion process in this elemental and compound semiconductor material. The directly measured Si self-diffusion coefficient is compared with the self-interstitial and vacancy contribution to self-diffusion which were deduced from metal diffusion experiments. The remarkable agreement between the Si self-diffusion coefficients and the individual contributions to self-diffusion shows that both self-interstitials and vacancies mediate Si self-diffusion. The Ga self-diffusion in undoped AlGaAs was found to decrease with increasing Al concentration. The activation enthalpy of Ga and Al diffusion in GaAs and of Ga diffusion in AlGaAs all lie in the range of (3.6±0.1) eV, but with different pre-exponential factors. The doping dependence of Ga self-diffusion reveals a retardation (enhancement) of Ga diffusion under p-type (n-type) doping compared to intrinsic conditions. All experimental results on the group-III atom diffusion are accurately described if vacancies on the group-III sublattice are assumed to mediate the Ga self- and Al-Ga interdiffusion in undoped AlGaAs and the Ga self-diffusion in Be- and Si-doped GaAs with an active dopant concentration of 3×1018 cm-3. The doping dependence of Ga self-diffusion in GaAs provides strong evidence that neutral, singly and doubly charged Ga vacancies govern the self-diffusion process.

  9. Diffusion archeology for diffusion progression history reconstruction.

    PubMed

    Sefer, Emre; Kingsford, Carl

    2016-11-01

    Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring - perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial diffusion data. Here, we tackle the problem of reconstructing a diffusion history from one or more snapshots of the diffusion state. This ability can be invaluable to learn when certain computer nodes are infected or which people are the initial disease spreaders to control future diffusions. We formulate this problem over discrete-time SEIRS-type diffusion models in terms of maximum likelihood. We design methods that are based on submodularity and a novel prize-collecting dominating-set vertex cover (PCDSVC) relaxation that can identify likely diffusion steps with some provable performance guarantees. Our methods are the first to be able to reconstruct complete diffusion histories accurately in real and simulated situations. As a special case, they can also identify the initial spreaders better than the existing methods for that problem. Our results for both meme and contaminant diffusion show that the partial diffusion data problem can be overcome with proper modeling and methods, and that hidden temporal characteristics of diffusion can be predicted from limited data.

  10. Transient leukoencephalopathy after intrathecal methotrexate mimicking stroke.

    PubMed

    Agarwal, Amit; Vijay, Kanupriya; Thamburaj, Krishnamoorthy; Ouyang, Tao

    2011-08-01

    Methotrexate (MTX) is an indispensable antimetabolite for the treatment of oncological and immunological disorders in all age groups. It can be administrated intravenously as well as intrathecally and may be used alone or in combination with other drugs. Chronic leukoencephalopathy is a well-known side effect of MTX, especially in conjunction with intrathecal administration. However, acute neurotoxicity with confusion, disorientation, seizures, and focal deficits may also be seen. This can clinically mimic stroke with restricted diffusion on MRI. However, unlike stroke, there is resolution of clinical and imaging findings within 1-4 weeks. We report two cases of transient leukoencephalopathy following intrathecal methotrexate, with complete clinical and radiological resolutions on follow-up.

  11. Theoretical comparison of the self diffusion and mutual diffusion of interacting membrane proteins.

    PubMed Central

    Scalettar, B A; Abney, J R; Owicki, J C

    1988-01-01

    Self diffusion and mutual diffusion in two-dimensional membrane systems are analyzed. It is shown that interprotein interactions can produce markedly different density-dependent changes in the diffusion coefficients describing these two processes; the qualitative differences are illustrated by using a theoretical formalism valid for dilute solutions. Results are obtained for three analytical potentials: hard-core repulsions, soft repulsions, and soft repulsions with weak attractions. Self diffusion is inhibited by all three interactions. In contrast, mutual diffusion is inhibited by attractions but is enhanced by repulsions. It is shown that such interaction-dependent differences in self diffusion and mutual diffusion could underlie, among other things, the disparity in protein diffusion coefficients extracted from fluorescence recovery after photobleaching and postelectrophoresis relaxation data. PMID:3413121

  12. 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

    Lo, Chun-Yin; Tjong, Yung-Wui; 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 µM), and a specific TRPV2 channel inhibitor, tranilast (100 µM), 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

  13. Transient catalytic combustor model

    NASA Technical Reports Server (NTRS)

    Tien, J. S.

    1981-01-01

    A quasi-steady gas phase and thermally thin substrate model is used to analyze the transient behavior of catalytic monolith combustors in fuel lean operation. The combustor response delay is due to the substrate thermal inertia. Fast response is favored by thin substrate, short catalytic bed length, high combustor inlet and final temperatures, and small gas channel diameters. The calculated gas and substrate temperature time history at different axial positions provides an understanding of how the catalytic combustor responds to an upstream condition change. The computed results also suggest that the gas residence times in the catalytic bed in the after bed space are correlatable with the nondimensional combustor response time. The model also performs steady state combustion calculations; and the computed steady state emission characteristics show agreement with available experimental data in the range of parameters covered. A catalytic combustor design for automotive gas turbine engine which has reasonably fast response ( 1 second) and can satisfy the emission goals in an acceptable total combustor length is possible.

  14. MULTIMOMENT RADIO TRANSIENT DETECTION

    SciTech Connect

    Spitler, L. G.; Cordes, J. M.; Chatterjee, S.; Stone, J.

    2012-04-01

    We present a multimoment technique for signal classification and apply it to the detection of fast radio transients in incoherently dedispersed data. Specifically, we define a spectral modulation index in terms of the fractional variation in intensity across a spectrum. A signal whose intensity is distributed evenly across the entire band has a lower modulation index than a spectrum whose intensity is localized in a single channel. We are interested in broadband pulses and use the modulation index to excise narrowband radio frequency interference by applying a modulation index threshold above which candidate events are removed. The technique is tested both with simulations and using data from known sources of radio pulses (RRAT J1928+15 and giant pulses from the Crab pulsar). The method is generalized to coherent dedispersion, image cubes, and astrophysical narrowband signals that are steady in time. We suggest that the modulation index, along with other statistics using higher order moments, should be incorporated into signal detection pipelines to characterize and classify signals.

  15. Transient internal probe

    NASA Astrophysics Data System (ADS)

    Jarboe, Thomas R.; Mattick, Arthur T.

    1993-12-01

    The Transient Internal Probe (TIP) diagnostic is a novel method for probing the interior of hot magnetic fusion plasmas that are inaccessible with ordinary stationary probes. A small probe of magneto-optic (Verdet) material is fired through a plasma at speeds of several km/sec, illuminated by a laser beam. The beam's polarization is rotated in the probe by the local magnetic field and retroreflection back to a polarimetry detector allows determination of the B-field profile across the diameter of a plasma at a spatial resolution of better than 1-cm and an absolute B-field resolution of a few tens of Gauss. The principal components of a TIP diagnostic system were developed and tested. A two-stage light gas gun was constructed that accelerates 30-caliber projectiles to 3 km/sec, and methods were examined for stripping a lexan sabot from a probe prior to entry into a plasma. Probes of CdMnTe and FR-5 Verdet glass were fabricated, and a polarimetry system was constructed for resolving polarization to within 0.25 deg. The diagnostic was validated by measuring a static B-field with a moving (dropped) TIP probe, and finding agreement with Hall-probe measurements to within experimental accuracy (40 Gauss).

  16. Transient catalytic combustor model

    NASA Astrophysics Data System (ADS)

    Tien, J. S.

    1981-05-01

    A quasi-steady gas phase and thermally thin substrate model is used to analyze the transient behavior of catalytic monolith combustors in fuel lean operation. The combustor response delay is due to the substrate thermal inertia. Fast response is favored by thin substrate, short catalytic bed length, high combustor inlet and final temperatures, and small gas channel diameters. The calculated gas and substrate temperature time history at different axial positions provides an understanding of how the catalytic combustor responds to an upstream condition change. The computed results also suggest that the gas residence times in the catalytic bed in the after bed space are correlatable with the nondimensional combustor response time. The model also performs steady state combustion calculations; and the computed steady state emission characteristics show agreement with available experimental data in the range of parameters covered. A catalytic combustor design for automotive gas turbine engine which has reasonably fast response ( 1 second) and can satisfy the emission goals in an acceptable total combustor length is possible.

  17. Detecting Thermal Cloaks via Transient Effects

    PubMed Central

    Sklan, Sophia R.; Bai, Xue; Li, Baowen; Zhang, Xiang

    2016-01-01

    Recent research on the development of a thermal cloak has concentrated on engineering an inhomogeneous thermal conductivity and an approximate, homogeneous volumetric heat capacity. While the perfect cloak of inhomogeneous κ and inhomogeneous ρcp is known to be exact (no signals scattering and only mean values penetrating to the cloak’s interior), the sensitivity of diffusive cloaks to defects and approximations has not been analyzed. We analytically demonstrate that these approximate cloaks are detectable. Although they work as perfect cloaks in the steady-state, their transient (time-dependent) response is imperfect and a small amount of heat is scattered. This is sufficient to determine the presence of a cloak and any heat source it contains, but the material composition hidden within the cloak is not detectable in practice. To demonstrate the feasibility of this technique, we constructed a cloak with similar approximation and directly detected its presence using these transient temperature deviations outside the cloak. Due to limitations in the range of experimentally accessible volumetric specific heats, our detection scheme should allow us to find any realizable cloak, assuming a sufficiently large temperature difference. PMID:27605153

  18. Clinical utility of multimodality imaging with dynamic contrast-enhanced MRI, diffusion-weighted MRI, and 18F-FDG PET/CT for the prediction of neck control in oropharyngeal or hypopharyngeal squamous cell carcinoma treated with chemoradiation.

    PubMed

    Ng, Shu-Hang; Lin, Chien-Yu; Chan, Sheng-Chieh; Lin, Yu-Chun; Yen, Tzu-Chen; Liao, Chun-Ta; Chang, Joseph Tung-Chieh; Ko, Sheung-Fat; Wang, Hung-Ming; Chang, Chee-Jen; Wang, Jiun-Jie

    2014-01-01

    The clinical usefulness of pretreatment imaging techniques for predicting neck control in patients with oropharyngeal or hypopharyngeal squamous cell carcinoma (OHSCC) treated with chemoradiation remains unclear. In this prospective study, we investigated the role of pretreatment dynamic contrast-enhanced perfusion MR imaging (DCE-PWI), diffusion-weighted MR imaging (DWI), and [18F]fluorodeoxyglucose-positron emission tomography (18F-FDG PET)/CT derived imaging markers for the prediction of neck control in OHSCC patients treated with chemoradiation. Patients with untreated OHSCC scheduled for chemoradiation between August, 2010 and July, 2012 were eligible for the study. Clinical variables and the following imaging parameters of metastatic neck lymph nodes were examined in relation to neck control: transfer constant, volume of blood plasma, and volume of extracellular extravascular space (Ve) on DCE-PWI; apparent diffusion coefficient (ADC) on DWI; maximum standardized uptake value, metabolic tumor volume, and total lesion glycolysis on 18F-FDG PET/CT. There were 69 patients (37 with oropharynx SCC and 32 with hypopharynx SCC) with successful pretreatment DCE-PWI and DWI available for analysis. After a median follow-up of 31 months, 25 (36.2%) participants had neck failure. Multivariate analysis identified hemoglobin level <14.3 g/dL (P = 0.019), Ve <0.23 (P = 0.040), and ADC >1.14×10-3 mm2/s (P = 0.003) as independent prognostic factors for 3-year neck control. A prognostic scoring system was formulated by summing up the three significant predictors of neck control. Patients with scores of 2-3 had significantly poorer neck control and overall survival rates than patients with scores of 0-1. We conclude that hemoglobin levels, Ve, and ADC are independent pretreatment prognostic factors for neck control in OHSCC treated with chemoradiation. Their combination may identify a subgroup of patients at high risk of developing neck failure.

  19. The Growth of Steroidobacter agariperforans sp. nov., a Novel Agar-Degrading Bacterium Isolated from Soil, is Enhanced by the Diffusible Metabolites Produced by Bacteria Belonging to Rhizobiales

    PubMed Central

    Sakai, Masao; Hosoda, Akifumi; Ogura, Kenjiro; Ikenaga, Makoto

    2014-01-01

    An agar-degrading bacterium was isolated from soil collected in a vegetable cropping field. The growth of this isolate was enhanced by supplying culture supernatants of bacteria belonging to the order Rhizobiales. Phylogenetic analysis based on 16S rRNA gene sequences indicated the novel bacterium, strain KA5–BT, belonged to the genus Steroidobacter in Gammaproteobacteria, but differed from its closest relative, Steroidobacter denitrificans FST, at the species level with 96.5% similarity. Strain KA5–BT was strictly aerobic, Gram-negative, non-motile, non-spore forming, and had a straight to slightly curved rod shape. Cytochrome oxidase and catalase activities were positive. The strain grew on media containing culture supernatants in a temperature range of 15–37°C and between pH 4.5 and 9.0, with optimal growth occurring at 30°C and pH 6.0–8.0. No growth occurred at 10 or 42°C or at NaCl concentrations more than 3% (w/v). The main cellular fatty acids were iso–C15:0, C16:1ω7c, and iso–C17:1ω9c. The main quinone was ubiquinone-8 and DNA G+C content was 62.9 mol%. In contrast, strain FST was motile, did not grow on the agar plate, and its dominant cellular fatty acids were C15:0 and C17:1ω8c. Based on its phylogenetic and phenotypic properties, strain KA5–BT (JCM 18477T = KCTC 32107T) represents a novel species in genus Steroidobacter, for which the name Steroidobacter agariperforans sp. nov. is proposed. PMID:24621511

  20. Enhancement of physicochemical properties of nanocolloidal carrier loaded with cyclosporine for topical treatment of psoriasis: in vitro diffusion and in vivo hydrating action

    PubMed Central

    Musa, Siti Hajar; Basri, Mahiran; Fard Masoumi, Hamid Reza; Shamsudin, Norashikin; Salim, Norazlinaliza

    2017-01-01

    Psoriasis is a chronic autoimmune disease that cannot be cured. It can however be controlled by various forms of treatment, including topical, systemic agents, and phototherapy. Topical treatment is the first-line treatment and favored by most physicians, as this form of therapy has more patient compliance. Introducing a nanoemulsion for transporting cyclosporine as an anti-inflammatory drug to an itchy site of skin disease would enhance the effectiveness of topical treatment for psoriasis. The addition of nutmeg and virgin coconut-oil mixture, with their unique properties, could improve cyclosporine loading and solubility. A high-shear homogenizer was used in formulating a cyclosporine-loaded nanoemulsion. A D-optimal mixture experimental design was used in the optimization of nanoemulsion compositions, in order to understand the relationships behind the effect of independent variables (oil, surfactant, xanthan gum, and water content) on physicochemical response (particle size and polydispersity index) and rheological response (viscosity and k-value). Investigation of these variables suggests two optimized formulations with specific oil (15% and 20%), surfactant (15%), xanthan gum (0.75%), and water content (67.55% and 62.55%), which possessed intended responses and good stability against separation over 3 months’ storage at different temperatures. Optimized nanoemulsions of pH 4.5 were further studied with all types of stability analysis: physical stability, coalescence-rate analysis, Ostwald ripening, and freeze–thaw cycles. In vitro release proved the efficacy of nanosize emulsions in carrying cyclosporine across rat skin and a synthetic membrane that best fit the Korsmeyer–Peppas kinetic model. In vivo skin analysis towards healthy volunteers showed a significant improvement in the stratum corneum in skin hydration.

  1. Diffusion of oxygen in cork.

    PubMed

    Lequin, Sonia; Chassagne, David; Karbowiak, Thomas; Simon, Jean-Marc; Paulin, Christian; Bellat, Jean-Pierre

    2012-04-04

    This work reports measurements of effective oxygen diffusion coefficient in raw cork. Kinetics of oxygen transfer through cork is studied at 298 K thanks to a homemade manometric device composed of two gas compartments separated by a cork wafer sample. The first compartment contains oxygen, whereas the second one is kept under dynamic vacuum. The pressure decrease in the first compartment is recorded as a function of time. The effective diffusion coefficient D(eff) is obtained by applying Fick's law to transient state using a numerical method based on finite differences. An analytical model derived from Fick's law applied to steady state is also proposed. Results given by these two methods are in close agreement with each other. The harmonic average of the effective diffusion coefficients obtained from the distribution of 15 cork wafers of 3 mm thickness is 1.1 × 10(-9) m(2) s(-1) with a large distribution over four decades. The statistical analysis of the Gaussian distribution obtained on a 3 mm cork wafer is extrapolated to a 48 mm cork wafer, which length corresponds to a full cork stopper. In this case, the probability density distribution gives a mean value of D(eff) equal to 1.6 × 10(-9) m(2) s(-1). This result shows that it is possible to obtain the effective diffusion coefficient of oxygen through cork from short time (few days) measurements performed on a thin cork wafer, whereas months are required to obtain the diffusion coefficient for a full cork stopper. Permeability and oxygen transfer rate are also calculated for comparison with data from other studies.

  2. NIST Diffusion Data Center

    National Institute of Standards and Technology Data Gateway

    NIST Diffusion Data Center (Web, free access)   The NIST Diffusion Data Center is a collection of over 14,100 international papers, theses, and government reports on diffusion published before 1980.

  3. Parallel flow diffusion battery

    DOEpatents

    Yeh, Hsu-Chi; Cheng, Yung-Sung

    1984-08-07

    A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

  4. Parallel flow diffusion battery

    DOEpatents

    Yeh, H.C.; Cheng, Y.S.

    1984-01-01

    A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.

  5. TU-F-CAMPUS-J-02: Evaluation of Textural Feature Extraction for Radiotherapy Response Assessment of Early Stage Breast Cancer Patients Using Diffusion Weighted MRI and Dynamic Contrast Enhanced MRI

    SciTech Connect

    Xie, Y; Wang, C; Horton, J; Chang, Z

    2015-06-15

    Purpose: To investigate the feasibility of using classic textural feature extraction in radiotherapy response assessment, we studied a unique cohort of early stage breast cancer patients with paired pre - and post-radiation Diffusion Weighted MRI (DWI-MRI) and Dynamic Contrast Enhanced MRI (DCE-MRI). Methods: 15 female patients from our prospective phase I trial evaluating preoperative radiotherapy were included in this retrospective study. Each patient received a single-fraction radiation treatment, and DWI and DCE scans were conducted before and after the radiotherapy. DWI scans were acquired using a spin-echo EPI sequence with diffusion weighting factors of b = 0 and b = 500 mm{sup 2} /s, and the apparent diffusion coefficient (ADC) maps were calculated. DCE-MRI scans were acquired using a T{sub 1}-weighted 3D SPGR sequence with a temporal resolution of about 1 minute. The contrast agent (CA) was intravenously injected with a 0.1 mmol/kg bodyweight dose at 2 ml/s. Two parameters, volume transfer constant (K{sup trans} ) and k{sub ep} were analyzed using the two-compartment Tofts kinetic model. For DCE parametric maps and ADC maps, 33 textural features were generated from the clinical target volume (CTV) in a 3D fashion using the classic gray level co-occurrence matrix (GLCOM) and gray level run length matrix (GLRLM). Wilcoxon signed-rank test was used to determine the significance of each texture feature’s change after the radiotherapy. The significance was set to 0.05 with Bonferroni correction. Results: For ADC maps calculated from DWI-MRI, 24 out of 33 CTV features changed significantly after the radiotherapy. For DCE-MRI pharmacokinetic parameters, all 33 CTV features of K{sup trans} and 33 features of k{sub ep} changed significantly. Conclusion: Initial results indicate that those significantly changed classic texture features are sensitive to radiation-induced changes and can be used for assessment of radiotherapy response in breast cancer.

  6. FRACTIONAL PEARSON DIFFUSIONS.

    PubMed

    Leonenko, Nikolai N; Meerschaert, Mark M; Sikorskii, Alla

    2013-07-15

    Pearson diffusions are governed by diffusion equations with polynomial coefficients. Fractional Pearson diffusions are governed by the corresponding time-fractional diffusion equation. They are useful for modeling sub-diffusive phenomena, caused by particle sticking and trapping. This paper provides explicit strong solutions for fractional Pearson diffusions, using spectral methods. It also presents stochastic solutions, using a non-Markovian inverse stable time change.

  7. FRACTIONAL PEARSON DIFFUSIONS

    PubMed Central

    Leonenko, Nikolai N.; Meerschaert, Mark M.

    2013-01-01

    Pearson diffusions are governed by diffusion equations with polynomial coefficients. Fractional Pearson diffusions are governed by the corresponding time-fractional diffusion equation. They are useful for modeling sub-diffusive phenomena, caused by particle sticking and trapping. This paper provides explicit strong solutions for fractional Pearson diffusions, using spectral methods. It also presents stochastic solutions, using a non-Markovian inverse stable time change. PMID:23626377

  8. Initiation of a coronal transient

    SciTech Connect

    Low, B.C.; Munro, R.H.; Fisher, R.R.

    1982-03-01

    This paper analyzes the coronal transient/eruptive prominence event of 1980 August 5 observed by the Mauna Loa experiment system. This event yielded data on the early development of the transient in the low corona between 1.2 R/sub sun/ and 2.2 R/sub sun/, information which was not available when earlier attempts were made to explain transient phenomena. The transient's initial appearance in the form of a rising density-depleted structure, prior to the eruption of the associated prominence, can be explained as an effect of magnetic buoyancy. The data indicate that this transient has a density depletion of 17% to 33% relative to an undisturbed corona which is approximately isothermal with a temperature of 1.5 x 10/sup 6/ K and a coronal density of 1.0 x 10/sup 9/ cm/sup -3/ at the base of the corona. The height versus base length relationship of the evolving transient resembles, remarkably well, the theoretical predictions obtained from a quasi-static model of a margnetically buoyant loop system. By matching this relationship with the theoretical model, we estimate the magnetic field at the base of the transient to be between 2 and 3 gauss. It is also shown that the initial, nearly constant speed of the top of the transient, 80 +- 20 km s/sup -1/, is consistent with a theoretical estimate calculated from the quasi-static model. These results suggest that some transients are not initiated impulsively, the initial stage of the development being driven by a quasi-static response to a slow change in magnetic field conditions at the base of the corona.

  9. Fine-scale transient arcs seen in a shock aurora

    NASA Astrophysics Data System (ADS)

    Motoba, T.; Ebihara, Y.; Kadokura, A.; Weatherwax, A. T