These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Transient enhanced diffusion from decaborane molecular ion implantation  

NASA Astrophysics Data System (ADS)

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

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

1998-10-01

2

Transient enhanced diffusion from decaborane molecular ion implantation  

SciTech Connect

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

Agarwal, A.; Gossmann, H.; Jacobson, D.C.; Eaglesham, D.J. [Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974 (United States)] [Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974 (United States); Sosnowski, M.; Poate, J.M. [New Jersey Institute of Technology, University Heights, Newark, New Jersey (United States)] [New Jersey Institute of Technology, University Heights, Newark, New Jersey (United States); Yamada, I.; Matsuo, J. [Kyoto University, Sakyo, Kyoto 606-01 (Japan)] [Kyoto University, Sakyo, Kyoto 606-01 (Japan); Haynes, T.E. [Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)] [Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

1998-10-01

3

Modeling of the effects of dose, dose rate, and implant temperature on transient enhanced diffusion  

NASA Astrophysics Data System (ADS)

Atomistic simulations are used to study the effects of implant parameters on transient enhanced diffusion (TED). We analyze 10 keV Si implants in a wide range of doses from 108 to 1014ions/cm2, dose rates from 1010 to 1014ions/cm2 s, and implant temperature from room temperature to 1000 °C. Different regimes with different dependence of TED on these parameters are observed. For high doses, high dose rates, and low implant temperatures, the Frenkel pairs are accumulated during ion implantation, and the resulting damage is very dense. During the postimplant annealing, the recombination of Frenkel pairs is efficient, and the extra interstitials generated by the implanted ions provide the main contribution to the enhanced diffusivity. For low doses, low dose rates, and high implant temperatures, there is little interaction between neighboring cascades during annealing. The recombination of Frenkel pairs is not complete, and many interstitials and vacancies from each cascade survive recombination and contribute significantly to TED.

Pelaz, Lourdes; Gilmer, G. H.; Venezia, V. C.; Gossmann, H.-J.; Jaraiz, M.; Barbolla, J.

1999-04-01

4

Effective diffusivity in transient state  

NASA Astrophysics Data System (ADS)

The effective diffusivity in a polymer matrix modified with inclusions is usually calculated based on Kalnin-Kotomin's model [J. R. Kalnin, E. A. Kotomin, and J. Maier, J. Phys. Chem. Solids 63, 449-456 (2002)], 10.1016/S0022-3697(01)00159-7, which extends the well known Maxwell-Garnett formula. Kalnin-Kotomin's model correctly predicts effective diffusivity for stationary diffusion or for infinite media. In the present paper diffusion in composite media is studied for finite systems under transient conditions. The process of diffusion is modeled numerically and effective diffusion coefficient in the transient state is estimated, which, under certain conditions, is different from the predictions of the Kalnin-Kotomin's model. An analytical model is proposed to explain deviations of the transient effective coefficient of diffusion from the stationary case.

Tabor, Zbis?aw; Nowak, Pawe?; Krzak, Ma?gorzata; Warszy?ski, Piotr

2013-08-01

5

Acoustic Enhancement of Surface Diffusion Chengping Wu,  

E-print Network

Acoustic Enhancement of Surface Diffusion Chengping Wu, Vladimir Yu. Zaitsev,, and Leonid V, Russia *S Supporting Information ABSTRACT: The idea of acoustic activation of surface diffusion by surface acoustic waves is possible via (1) transient surface strain- induced modification of the diffusion

Zhigilei, Leonid V.

6

Transient Diffusion of Beryllium and Silicon in Gallium Arsenide  

NASA Astrophysics Data System (ADS)

Transient diffusion is an increasingly important phenomenon as thermal budgets for real processes decrease and diffusion during sample growth becomes more important. To fully characterize dopant diffusion in gallium arsenide, an understanding must be developed of the dominant atomistic processes for a given dopant, as well as the sources of transient effects under a given set of experimental conditions. Theoretical, experimental, and simulation results were obtained to understand transient diffusivities of beryllium and silicon in grown-in and implanted samples. In implanted samples, by understanding implant damage and modeling the evolution of point defect populations, the observed transient effects can be explained. Such phenomena cannot account for the time-dependent diffusivity observed when the dopant is introduced during molecular beam epitaxial growth. Transient diffusivities for grown-in beryllium were investigated and explained by modeling the evolution of point defect populations as they increase beyond their equilibrium levels at the growth temperature to achieve equilibrium at the anneal temperature.

Haddara, Yaser M.; Bravman, John C.

1998-08-01

7

Discriminating between Anomalous Diffusion and Transient Behavior in Microheterogeneous Environments  

PubMed Central

Diffusion in macrohomogeneous and microheterogeneous media can be described as effective free diffusion only at sufficiently long times. At intermediate times, the mean-square displacement of a diffusing object shows a transient behavior that can be misinterpreted as anomalous subdiffusion. We discuss how to discriminate between the two. PMID:24461027

Berezhkovskii, Alexander M.; Dagdug, Leonardo; Bezrukov, Sergey M.

2014-01-01

8

Enhanced diffusion welding  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

9

Transient Anomalous Diffusion in Pipe Poiseuille Flow  

Microsoft Academic Search

In this paper we revisit the classical problem of dispersion of a point-discharge of tracer in laminar pipe Poiseuille flow. We show that in the limit of small non-dimensional diffusion, D, that tracer dispersion can be divided into three regimes. For small times (t << D-1\\/3),diffusion dominates advection yielding a roughly spherically symmetric dispersion cloud. At large times (t >>

Marco Latini; Andrew J. Bernoff

2000-01-01

10

Adsorption and diffusion properties of zeolite membranes by transient permeation  

Microsoft Academic Search

Adsorption isotherms and diffusion coefficients for light gases and butane isomers were measured for the transport pathways involved in gas permeation through H-ZSM-5 membranes by a transient permeation technique. The permeate responses to step changes in the feed were measured, and the transport was modeled as Maxwell—Stefan diffusion with single-site Langmuir adsorption in the zeolite. Isotherms measured for N2, CO2,

Tracy Q. Gardner; John L. Falconer; Richard D. Noble

2002-01-01

11

Enhancing Rotational Diffusion Using Oscillatory Shear  

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

12

Enhanced diffusion of phosphorus at grain boundaries  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

13

Enhanced nitrogen diffusion induced by atomic attrition  

SciTech Connect

The nitrogen diffusion in steel is enhanced by previous atomic attrition with low energy xenon ions. The noble gas bombardment generates nanoscale texture surfaces and stress in the material. The atomic attrition increases nitrogen diffusion at lower temperatures than the ones normally used in standard processes. The stress causes binding energy shifts of the Xe 3d{sub 5/2} electron core level. The heavy ion bombardment control of the texture and stress of the material surfaces may be applied to several plasma processes where diffusing species are involved.

Ochoa, E.A.; Figueroa, C.A.; Czerwiec, T.; Alvarez, F. [Instituto de Fisica 'Gleb Wataghin', Universidade Estadual de Campinas, Unicamp 13083-970, Campinas, Sao Paulo (Brazil)

2006-06-19

14

Transient decrease in cerebral white matter diffusivity on MR imaging in human herpes virus-6 encephalopathy  

Microsoft Academic Search

We report a 16-month-old boy with human herpes virus-6 (HHV-6) encephalopathy showing transient abnormalities of the cerebral white matter on magnetic resonance imaging. Diffusion-weighted imaging (DWI) demonstrated diffuse high signal intensity in the bilateral cerebral white matter areas. The signal changes on DWI subsequently resolved, and cerebral atrophy resulted. The transient decrease in the cerebral white matter diffusivity seen in

Manami Akasaka; Makoto Sasaki; Shigeru Ehara; Atsushi Kamei; Shoichi Chida

2005-01-01

15

Review of enhanced vapor diffusion in porous media  

SciTech Connect

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.

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

1998-08-01

16

Test of the hypothesis of transient molten state diffusion for swift-heavy-ion induced mixing  

SciTech Connect

The recently proposed hypothesis that swift-heavy-ion induced mixing is a consequence of a transient molten state diffusion is tested by studying 230 MeV Au ion induced mixing at an Fe/Si interface monitored online by elastic recoil detection analysis. An extensive data analysis has been made to determine the experimental intrinsic diffusivities of Fe in Si, and vice versa. The required size and duration of the transient melt phase have been calculated theoretically from the thermal spike model. The close resemblance of the experimental diffusivities to the liquid state diffusivities reported in the literature is a verification of the hypothesis.

Srivastava, S.K. [Nuclear Science Centre, Aruna Asaf Ali Marg, P. O. Box 10502, New Delhi 110067 (India); Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse-3, 70569 Stuttgart (Germany); Avasthi, D.K. [Nuclear Science Centre, Aruna Asaf Ali Marg, P. O. Box 10502, New Delhi 110067 (India); Assmann, W. [Sektion Physik, Universitaet Muenchen, D-85748 Garching (Germany); Wang, Z.G. [Centre Interdisciplinaire de Recherches avec les Ions Lourds, Laboratoire mixte CEA-CNRS, rue Claude Bloch, Boite Postale 5133, 14040 Caen Cedex (France); Kucal, H.; Jacquet, E.; Toulemonde, M. [Centre Interdisciplinaire de Recherches Ion Laser, CIRIL, Boite Postale 5133, F-14070 Caen Cedex 5 (France); Carstanjen, H.D. [Max-Planck-Institut fuer Metallforschung, Heisenbergstrasse-3, 70569 Stuttgart (Germany)

2005-05-15

17

Analytical model of transient compressive stress evolution during growth of high diffusivity thin films on substrates  

Microsoft Academic Search

We present an analytical model of transient compressive stress evolution during growth of thin films with high surface and grain boundary diffusivities on substrates. The model provides a closed-form analytical solution which compares well with numerical analysis as well as recent experimental data on transient stress evolution during electrodeposition of Sn films on substrates.

Tanmay K. Bhandakkar; Eric Chason; Huajian Gao

2010-01-01

18

Thermal diffusivity measurements in organic liquids using transient thermal lens calorimetry  

E-print Network

Thermal diffusivity measurements in organic liquids using transient thermal lens calorimetry C. V. Thermal diffusivity measurements are carried out in certain organic liquids using the pulsed dual beam and it is closely related to thermal conductivity, specific heat and thermal expansion. An ex- tensive review

Harilal, S. S.

19

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

NASA Astrophysics Data System (ADS)

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, 1.5G or varied gravity level conditions can be generated during flight experiments. On the sudden change of gravity level from microgravity to 1.5G, different ap-pearances in the transient diffusion fields could be observed. The mass diffusion coefficient depends on measurement time. From this phenomenon, it is possible to guess that the dynamic re-clustering process may occur in the solutions.

Komiya, Atsuki; Maruyama, Shigenao

20

A transient heating technique for measuring the thermal diffusivity of metals  

SciTech Connect

A transient heating technique, improving the constant-rate-heating technique for the measurements of thermal diffusivities of metals, is proposed. For a physical model of a specimen to be measured, the transient heat-conduction equation was solved with some boundary conditions, and the solution obtained was used as the principle of the present transient heating technique for determining the thermal diffusivity of the specimen. Additionally, a thermal analysis was made to satisfy a boundary condition involved in the principle, that is, the condition of radiative thermal insulation at the two end surfaces of the specimen. To verify the validity of the present technique, the thermal diffusivity of iron, whose thermophysical properties are well-known, was measured with the same apparatus as used in the previous work, and the experimental results are discussed. Moreover, thermal diffusivities of thermocouple materials, namely, constantan, chromel, and alumel, were measured by the technique in the temperature range of 360 to 680 K.

Sasaki, S.; Takahashi, H. [Ichinoseki National Coll. of Technology (Japan)] [Ichinoseki National Coll. of Technology (Japan); Masuda, H. [Tohoku Gakuin Univ., Tagajo (Japan). Faculty of Technology] [Tohoku Gakuin Univ., Tagajo (Japan). Faculty of Technology; Kou, H. [Daebul Univ., Chonnam (Korea, Republic of). Faculty of Mechanical and Industrial System Engineering] [Daebul Univ., Chonnam (Korea, Republic of). Faculty of Mechanical and Industrial System Engineering

1998-01-01

21

Case-II diffusion in polymers. I. Transient swelling  

Microsoft Academic Search

The swelling of a polymer glass by sorption of a small molecule penetrant is considered in a regime characterized by so-called case-II diffusion. Attention is focused on the polymer so that the swelling process can be investigated apart from diffusion. The model of Thomas and Windle (TW) is used to predict the surface swelling as a function of exposure time.

C.-Y. Hui; K.-C. Wu; Ronald C. Lasky; Edward J. Kramer

1987-01-01

22

Fracture-Flow-Enhanced Solute Diffusion into Fractured Rock  

SciTech Connect

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

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

2007-12-15

23

ENHANCED SEVERE TRANSIENT ANALYSIS FOR PREVENTION TECHNICAL PROGRAM PLAN  

SciTech Connect

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

Gougar, Hans [Idaho National Laboratory

2014-09-01

24

Transient model of an intermediate surge system for the Paducah Gaseous Diffusion Plant  

SciTech Connect

Engineering design work (Reference 1) is underway for intermediate surge systems to be added to the Paducah Gaseous Diffusion Plant (PGDP) cascade as part of the Process Inventory Control System (PICS) project. These systems would be located between 000 buildings and lower half 00 buildings and would remove or add inventory during cascade transients in order to protect cascade compressors from overload and surge. Similar systems were operated in the Oak Ridge Gaseous Diffusion Plant cascade and are operated in the Portsmouth Gaseous Diffusion Plant cascade. A steady state flow analysis of the system to be installed at the PGDP has been made. The flow analysis did not address response of the surge system to the cascade transients, nor did it address automatic control of the system. The need to address these issues prompted development of the transient model described in this report. 2 refs., 8 figs., 2 tabs.

Beard, B.; Blankenship, J.G.; McGrady, P.W.

1989-09-01

25

TRANSIENT ANOMALOUS SUB-DIFFUSION ON BOUNDED DOMAINS  

PubMed Central

This paper develops strong solutions and stochastic solutions for the tempered fractional diffusion equation on bounded domains. First the eigenvalue problem for tempered fractional derivatives is solved. Then a separation of variables and eigenfunction expansions in time and space are used to write strong solutions. Finally, stochastic solutions are written in terms of an inverse subordinator. PMID:24639592

MEERSCHAERT, MARK M.; NANE, ERKAN; VELLAISAMY, P.

2013-01-01

26

Transient and diffusion analysis of Hg Cd Te  

NASA Technical Reports Server (NTRS)

The solution of the one dimensional planar interface solidification problem is presented. Numerical solutions are applied to experimental solute profiles to determine the effective diffusion constant for Hg Co Te. Progress on the design and construction of a high gradient furnace is reported.

Clayton, J. C.

1980-01-01

27

Stratification of heterogeneous diffusion MRI ischemic lesion with kurtosis imaging – Evaluation of mean diffusion and kurtosis MRI mismatch in an animal model of transient focal ischemia  

PubMed Central

Background and Purpose Ischemic tissue damage is heterogeneous, resulting in complex patterns in the widely used diffusion-weighted MRI (DWI). Our study examined the spatiotemporal characteristics of diffusion kurtosis imaging (DKI) in an animal model of transient middle cerebral artery occlusion (MCAO). Methods Adult male Wistar rats (N = 18) were subjected to 90min MCAO. Multi-parametric MRI were obtained during MCAO and 20 min after reperfusion, with DWI obtained using eight b-values from 250 to 3000 s/mm2 in six diffusion gradient directions. Diffusion and kurtosis lesions were outlined in shuffled images by two investigators independently. T2 MRI was obtained 24 hr after MCAO to evaluate stroke outcome. Results Mean diffusion (MD) lesion (23.5±8.1%, percentage of the brain slice) was significantly larger than mean kurtosis (MK) lesion (13.2±2.0%) during MCAO. MD lesion decreased significantly after reperfusion (13.8±4.3%) while MK lesion showed little change (13.0±2.5%), with their lesion size difference being insignificant. Conclusions We demonstrated that MD/MK mismatch recovered reasonably well upon reperfusion while regions with concurrent MD and MK deficits showed poor recovery. DKI may help stratify heterogeneous DWI lesion for enhanced characterization of ischemic tissue injury. PMID:22773558

Cheung, Jerry S.; Wang, Enfeng; Lo, Eng H; Sun, Phillip Zhe

2012-01-01

28

Partial transient liquid phase diffusion bonding of Zircaloy4 to stabilized austenitic stainless steel 321  

Microsoft Academic Search

An innovative method was applied for bonding Zircaloy-4 to stabilized austenitic stainless steel 321 using an active titanium interlayer. Specimens were joined by a partial transient liquid phase diffusion bonding method in a vacuum furnace at different temperatures under 1MPa dynamic pressure of contact. The influence of different bonding temperatures on the microstructure, microindentation hardness, joint strength and interlayer thickness

M. Mazar Atabaki; A. Talebi Hanzaei

2010-01-01

29

Numerical modelling of transient liquid phase bonding and other diffusion controlled phase changes  

Microsoft Academic Search

Diffusion in material of inhomogeneous composition can induce phase changes, even at a constant temperature. A transient liquid phase (TLP), in which a liquid layer is formed and subsequently solidifies, is one example of such an isothermal phase change. This phenomenon is exploited industrially in TLP bonding and sintering processes. Successful processing requires an understanding of the behaviour of the

T. C. I LLINGWORTH; I. O. GOLOSNOY; T. W. C LYNE

2005-01-01

30

Transient Anomalous Diffusion of Telomeres in the Nucleus of Mammalian Cells  

NASA Astrophysics Data System (ADS)

We measured individual trajectories of fluorescently labeled telomeres in the nucleus of eukaryotic cells in the time range of 10-2-104sec? by combining a few acquisition methods. At short times the motion is subdiffusive with ?r2?˜t? and it changes to normal diffusion at longer times. The short times diffusion may be explained by the reptation model and the transient diffusion is consistent with a model of telomeres that are subject to a local binding mechanism with a wide but finite distribution of waiting times. These findings have important biological implications with respect to the genome organization in the nucleus.

Bronstein, I.; Israel, Y.; Kepten, E.; Mai, S.; Shav-Tal, Y.; Barkai, E.; Garini, Y.

2009-07-01

31

Enhancing phosphorylation cascades by anomalous diffusion  

NASA Astrophysics Data System (ADS)

A key event in many cellular signaling cascades is the multiple phosphorylation of proteins by specialized kinases. A prototypical example is the mitogen-activated protein kinase (MAPK) that alters the cell's gene transcription after having been phosphorylated twice by the same kinase. Here, we show that anomalous diffusion, induced, for example, by cytoplasmic crowding, can significantly improve the activation of MAPK. Our results on anomalous diffusion with the characteristics of fractional Brownian motion and obstructed diffusion compare favorably to very recent biochemical data on MAPK activation at varying degrees of cytoplasmic crowding. Our results predict any Michaelis-Menten scheme in which a substrate is modified by the same enzyme several times to show an increased performance due to anomalous diffusion when dissociation rates of the intermediate enzyme-substrate complexes are high while the irreversible catalytic step is slow. Thus, crowding-induced anomalous diffusion can strongly alter the behavior of many cellular signaling pathways.

Hellmann, M.; Heermann, D. W.; Weiss, M.

2012-03-01

32

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

NASA Astrophysics Data System (ADS)

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

Yaras, M. I.; Orsi, P.

33

Numerical modelling of transient liquid phase bonding and other diffusion controlled phase changes  

Microsoft Academic Search

Diffusion in material of inhomogeneous composition can induce phase changes, even at a constant temperature. A transient liquid\\u000a phase (TLP), in which a liquid layer is formed and subsequently solidifies, is one example of such an isothermal phase change.\\u000a This phenomenon is exploited industrially in TLP bonding and sintering processes. Successful processing requires an understanding\\u000a of the behaviour of the

T. C. Illingworth; I. O. Golosnoy; V. Gergely; T. W. Clyne

2005-01-01

34

Enhanced diffusion of tracer particles in dilute bacterial suspensions.  

PubMed

Swimming bacteria create long-range velocity fields that stir a large volume of fluid and move around passive particles dispersed in the fluid. Recent experiments and simulations have shown that long-time mean-squared displacement of passive particles in a bath of swimming bacteria exhibits diffusive behaviour with an effective diffusion coefficient significantly larger than its thermal counterpart. A comprehensive theoretical prediction of this effective diffusion coefficient and the understanding of the enhancement mechanism remain a challenge. Here, we adapt the kinetic theory by Lin et al., J. Fluid Mech., 2011, 669, 167 developed for 'squirmers' to the bacterial case to quantitatively predict enhanced diffusivity of tracer particles in dilute two- and three-dimensional suspensions of swimming bacteria. We demonstrate that the effective diffusion coefficient is a product of the bacterial number density, their swimming speed, a geometric factor characterising the velocity field created by a single bacterium, and a numerical factor. We show that the numerical factor is, in fact, a rather strong function of the system parameters, most notably the run length of the bacteria, and that these dependencies have to be taken into account to quantitatively predict the enhanced diffusivity. We perform molecular-dynamics-type simulations to confirm the conclusions of the kinetic theory. Our results are in good agreement with the values of enhanced diffusivity measured in recent two- and three-dimensional experiments. PMID:24668266

Morozov, Alexander; Marenduzzo, Davide

2014-04-28

35

Imaging transient formation of diffusion layers with fluorescence-enabled electrochemical microscopy.  

PubMed

Fluorescence-enabled electrochemical microscopy (FEEM) is demonstrated as a new technique to image transient concentration profiles of redox species generated on ultramicroelectrodes (UMEs). FEEM converts an electrical signal into an optical signal by electrically coupling a conventional redox reaction to a fluorogenic reporter reaction on a closed bipolar electrode. We describe the implementation of FEEM for diffusion layer imaging and use an array of thousands of parallel bipolar electrodes to image the diffusion layers of UMEs in two and three dimensions. This new technique provides a way to image an entire 2-dimensional lateral cross section of a dynamic diffusion layer in a single experiment. By taking several of these lateral cross sections at different axial positions in the diffusion layer, a 3-dimensional image of the diffusion layer can be built. We image the diffusion layer of a 10 ?m diameter carbon fiber electrode over the course of a cyclic voltammetry experiment and compare the FEEM-generated images to concentration profiles generated from numerical simulation. We also image the diffusion layer of a two electrode array consisting of two 10 ?m diameter carbon fibers over the course of a potential step experiment. PMID:25398201

Oja, Stephen M; Zhang, Bo

2014-12-16

36

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

SciTech Connect

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

Eaglesham, D.J.; Stolk, P.A.; Cheng, J.Y.; Gossmann, H.J.; Poate, J.M. [AT and T Bell Labs., Murray Hill, NJ (United States); Haynes, T.E. [Oak Ridge National Lab., TN (United States). Solid State Div.

1995-04-01

37

Persistent Reversal of Enhanced Amphetamine Intake by Transient CaMKII Inhibition  

E-print Network

Amphetamine exposure transiently increases Ca2+/calmodulin-dependent protein kinase II (CaMKII) ? expression in the nucleus accumbens (NAcc) shell and this persistently increases local GluA1 S831 phosphorylation and enhances ...

Loweth, Jessica A.

38

Generation of the photoacoustic effect through heat diffusion: Transient grating measurements in reverse micellar solutions  

SciTech Connect

We report the application of the transient grating method to measurement of radii of inverse micelles. A theoretical model is used to calculate the time evolution of the grating as a function of the solution thermal properties and the radii of the micelles. The method is based on the large difference in the thermal expansion coefficients between water and organic solvents: energy deposited in the aqueous interior of the micelles by the optical exciting beams does not result in sizable photoacoustic effect until heat diffuses into the surrounding organic solvent. The time profile of the transient grating signal is shown to be a function of the micellar radius, and the thermal conductivity and thermal diffusivity of the aqueous and organic subphases. For water-in-alkane reverse micelles, heat deposition is limited to the aqueous interior of the micelles through the use of ionic dyes. Experiments are reported using 1-3 GHz acoustic waves in solutions containing micelles with diameters in the range 10-30 nm. The correspondence between radii determined by the thermal diffusion method and those from dynamic light scattering measurements is discussed. 34 refs., 4 figs., 1 tab.

Cao, Y.N.; Chen, H.X.; Diebold, G.J.; Sun, T.; Zimmt, M.B. [Brown Univ., Providence, RI (United States)] [Brown Univ., Providence, RI (United States)

1997-04-10

39

Dynamics of surface thermal expansion and diffusivity using two-color reflection transient gratings  

SciTech Connect

We report ultrafast measurements of the dynamic thermal expansion of a surface and the temperature dependent surface thermal diffusivity using a two-color reflection transient grating technique. Studies were performed on p-type, n-type, and undoped GaAs(100) samples at several temperatures. Using a 75 fs ultraviolet probe with visible excitation beams, the electronic effects that dominate single color experiments become negligible; thus surface expansion due to heating and the subsequent contraction caused by cooling provide the dominant influence on the diffracted probe. The diffracted signal was composed of two components, thermal expansion of the surface and heat flow away from the surface, allowing the determination of the rate of expansion as well as the surface thermal diffusivity. At room temperature a signal rise due to thermal expansion was observed, corresponding to a maximum average displacement of {approx} 1 {angstrom} at 32 ps. Large fringe spacings were used, thus the dominant contributions to the signal were expansion and diffusion perpendicular to the surface. Values for the surface thermal diffusivity of GaAs were measured and found to be in reasonable agreement with bulk values above 50{degrees}K. Below 50{degrees}K, the diffusivity at the surface was more than an order of magnitude slower than in the bulk due to increased phonon boundary scattering. Comparison of the results with a straightforward thermal model yields good agreement over a range of temperatures (12--300{degrees}K). The applicability and advantages of the transient grating technique for studying photothermal and photoacoustic phenomena are discussed.

Pennington, D.M.; Harris, C.B. [California Univ., Berkeley, CA (United States). Dept. of Chemistry

1993-02-01

40

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

41

Modified anisotropic diffusion for image smoothing and enhancement  

NASA Astrophysics Data System (ADS)

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.

Tang, Zhong; Whitaker, Ross T.

2001-05-01

42

Enhancement of Diffusive Transport by Nonequilibrium Thermal Fluctuations  

E-print Network

) in quasi-two dimensional systems, while in three dimensions it grows as L-1 0 - L-1 , where L0-state diffusive flux in a finite system subject to a concentration gradient is enhanced because of long-range cor-order mode-mode coupling analysis, are compared to results from particle simulations and a finite

43

Process Model Verification for Dopant Segregation and Oxidation Enhanced Diffusion  

Microsoft Academic Search

This paper describes a case study of semiconductor process modeling verification which has been implemented in the silicon processing course within the Microelectronic Engineering Department at the Rochester Institute of Technology. The study focuses on fully-coupled modeling and fabrication of ion implanted profiles that are annealed in a steam ambient, causing oxidation enhanced diffusion. Silvaco's Athena process simulation software is

R. E. Pearson; K. D. Hirschman; R. Manley

2008-01-01

44

Improved Diffusion Imaging through SNR-Enhancing Joint Reconstruction  

PubMed Central

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

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

2012-01-01

45

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

46

Numerical studies on transient double-diffusive and mixed convection in cylindrical enclosures  

NASA Astrophysics Data System (ADS)

Numerical studies on transient convection phenomena are introduced. The studies are related to computation and description of time dependent flow, temperature and concentration fields. Two topics related with convection phenomena in cylindrical enclosures are presented, the first being double diffusive natural convection in cylindrical vessels. The subject of research is concerned with the liquid-liquid interface stability and its relationship with the different flow and mixing characteristics observed in the system. Interface penetration phenomena during transient double diffusive convection in a vertical cylinder is analyzed through direct numerical simulation. The fluid is initially motionless with a pre-existent two-layers density stratification featuring a diffusion-like interface. The flow is initiated when a uniform heat flux is applied from the sidewall. The influence of relevant parameters on velocity of interface penetration and intensity of mixing are analyzed. Two regimes of interface penetration were identified and characterized namely: convective and diffusive-convective regimes of interface penetration. The second topic is mixed natural and forced convection. In this case the investigation is focused on transient oscillatory convection and its suppression in the Czochralski growth melt. A numerical analysis assuming axisymmetric flow and temperature fields in a cylindrical enclosure was performed in which the swirl component of velocity is included in the computation to account for rotational effects. Temperature and flow field oscillations were computed for natural and forced convection dominant flow regimes. Numerical predictions are in excellent agreement with previously reported experimental results. Computational results are presented which disclose relevant features of oscillatory thermal and flow fields. Parametric studies were carried out to evaluate the effect of crystal radius and melt depth variations on the oscillatory flows. It was shown that non-oscillatory striation free conditions can be attained, for both natural convection dominant or forced convection dominant flow modes by reducing the radius fraction rc/Rc, and increasing the crucible aspect ratio Rc/H. The effect of a circular flat plate immersed in the melt was also evaluated for different vertical positions of the baffle. It was found that inserting a baffle with a radius slightly larger than the crystal radius at an appropriate vertical position can effectively attenuate thermal fluctuations.

Rujano Maldonado, Jose Raul

1999-10-01

47

A hybrid superconducting fault current limiter for enhancing transient stability in Korean power systems  

NASA Astrophysics Data System (ADS)

Additional power generation sites have been limited in Korea, despite the fact load demands are gradually increasing. In order to meet these increasing demands, Korea’s power system company has begun constructing new generators at existing sites. Thus, multi-unit plants can create problems in terms of transient stability when a large disturbance occurs. This paper proposes a hybrid superconducting fault current limiter (SFCL) application to enhance the transient stability of multi-unit power plants. SFCLs reduce fault currents, and limitation currents decrease the imbalance of the mechanical and electrical torque of the generators, resulting in an improvement in transient stability.

Seo, Sangsoo; Kim, Seog-Joo; Moon, Young-Hwan; Lee, Byongjun

2013-11-01

48

Superplastic deformation enhanced diffusion bonding of aluminum alloy 7475  

SciTech Connect

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

Sunwoo, A.; Lum, R. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States)

1995-08-15

49

Enhancing chemical identification efficiency by SAW sensor transients through a data enrichment and information fusion strategy—a simulation study  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

50

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

SciTech Connect

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

Atabaki, M. Mazar, E-mail: m.mazaratabaki@gmail.com [Department of Materials Engineering, Faculty of Mechanical Engineering, University Technology Malaysia, 81310 (Malaysia); Hanzaei, A. Talebi [Department of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran (Iran, Islamic Republic of)

2010-10-15

51

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

52

Enhanced diffusion and ordering of self-propelled rods  

E-print Network

Starting from a minimal physical model of self propelled hard rods on a substrate in two dimensions, we derive a modified Smoluchowski equation for the system. Self -propulsion enhances longitudinal diffusion and modifies the mean field excluded volume interaction. From the Smoluchowski equation we obtain hydrodynamic equations for rod concentration, polarization and nematic order parameter. New results at large scales are a lowering of the density of the isotropic-nematic transition and a strong enhancement of boundary effects in confined self-propelled systems.

Aparna Baskaran; M. Cristina Marchetti

2008-06-27

53

Enhanced photocoagulation with catheter-based diffusing optical device  

NASA Astrophysics Data System (ADS)

A novel balloon catheter-based diffusing optical device was designed and evaluated to assist in treating excessive menstrual bleeding. A synthetic fused-silica fiber was micro-machined precisely to create scattering segments on a 25 mm long fiber tip for uniform light distribution. A visible wavelength (?=532 nm) was used to specifically target the endometrium due to the high vascularity of the uterine wall. Optical simulation presented 30% wider distribution of photons along with approximately 40% higher irradiance induced by addition of a glass cap to the diffuser tip. Incorporation of the optical diffuser with a polyurethane balloon catheter considerably enhanced coagulation depth and area (i.e., 3.5 mm and 18.9 cm2 at 1 min irradiation) in tissue in vitro. The prototype device demonstrated the coagulation necrosis of 2.8±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.

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

2012-11-01

54

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

NASA Astrophysics Data System (ADS)

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: UO 2 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.

Williamson, R. L.

2011-08-01

55

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

SciTech Connect

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.

R. L. Williamson; D. A. Knoll

2009-09-01

56

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, ...

57

Transient Stability Assessment of Power Systems using Probabilistic Neural Network with Enhanced Feature Selection and Extraction  

Microsoft Academic Search

This paper presents transient stability assessment of a large actual 87-bus system and the IEEE 39-bus system using the probabilistic neural network (PNN) with enhanced feature selection and extraction methods. The investigated power systems are divided into smaller areas depending on the coherency of the areas when subjected to disturbances. This is to reduce the amount of data sets collected

Noor Izzri Abdul Wahab; Azah Mohamed

2009-01-01

58

Transient stability enhancement in power system with distributed static series compensator (DSSC)  

Microsoft Academic Search

Long distance AC transmission system is often subjected to stability problems which limit the transmission capability. Large power systems often suffer from weakly damped swings between synchronous generators. This paper aims to enhance the transient stability of the power system with the use of distributed static series compensator (DSSC). First of all, a detailed simulation model of the DSSC has

S. Golshannavaz; M. Mokhtari; M. Khalilian; D. Nazarpour

2011-01-01

59

Enhanced self-diffusion of adsorbed methanol in silica aerogel  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

60

Non-Gaussian diffusion imaging for enhanced contrast of brain tissue affected by ischemic stroke.  

PubMed

Recent diffusion MRI studies of stroke in humans and animals have shown that the quantitative parameters characterising the degree of non-Gaussianity of the diffusion process are much more sensitive to ischemic changes than the apparent diffusion coefficient (ADC) considered so far as the "gold standard". The observed changes exceeded that of the ADC by a remarkable factor of 2 to 3. These studies were based on the novel non-Gaussian methods, such as diffusion kurtosis imaging (DKI) and log-normal distribution function imaging (LNDFI). As shown in our previous work investigating the animal stroke model, a combined analysis using two methods, DKI and LNDFI provides valuable complimentary information. In the present work, we report the application of three non-Gaussian diffusion models to quantify the deviations from the Gaussian behaviour in stroke induced by transient middle cerebral artery occlusion in rat brains: the gamma-distribution function (GDF), the stretched exponential model (SEM), and the biexponential model. The main goal was to compare the sensitivity of various non-Gaussian metrics to ischemic changes and to investigate if a combined application of several models will provide added value in the assessment of stroke. We have shown that two models, GDF and SEM, exhibit a better performance than the conventional method and allow for a significantly enhanced visualization of lesions. Furthermore, we showed that valuable information regarding spatial properties of stroke lesions can be obtained. In particular, we observed a stratified cortex structure in the lesions that were well visible in the maps of the GDF and SEM metrics, but poorly distinguishable in the ADC-maps. Our results provided evidence that cortical layers tend to be differently affected by ischemic processes. PMID:24586610

Grinberg, Farida; Farrher, Ezequiel; Ciobanu, Luisa; Geffroy, Françoise; Le Bihan, Denis; Shah, N Jon

2014-01-01

61

Non-Gaussian Diffusion Imaging for Enhanced Contrast of Brain Tissue Affected by Ischemic Stroke  

PubMed Central

Recent diffusion MRI studies of stroke in humans and animals have shown that the quantitative parameters characterising the degree of non-Gaussianity of the diffusion process are much more sensitive to ischemic changes than the apparent diffusion coefficient (ADC) considered so far as the “gold standard”. The observed changes exceeded that of the ADC by a remarkable factor of 2 to 3. These studies were based on the novel non-Gaussian methods, such as diffusion kurtosis imaging (DKI) and log-normal distribution function imaging (LNDFI). As shown in our previous work investigating the animal stroke model, a combined analysis using two methods, DKI and LNDFI provides valuable complimentary information. In the present work, we report the application of three non-Gaussian diffusion models to quantify the deviations from the Gaussian behaviour in stroke induced by transient middle cerebral artery occlusion in rat brains: the gamma-distribution function (GDF), the stretched exponential model (SEM), and the biexponential model. The main goal was to compare the sensitivity of various non-Gaussian metrics to ischemic changes and to investigate if a combined application of several models will provide added value in the assessment of stroke. We have shown that two models, GDF and SEM, exhibit a better performance than the conventional method and allow for a significantly enhanced visualization of lesions. Furthermore, we showed that valuable information regarding spatial properties of stroke lesions can be obtained. In particular, we observed a stratified cortex structure in the lesions that were well visible in the maps of the GDF and SEM metrics, but poorly distinguishable in the ADC-maps. Our results provided evidence that cortical layers tend to be differently affected by ischemic processes. PMID:24586610

Geffroy, Françoise; Le Bihan, Denis; Shah, N. Jon

2014-01-01

62

Anomalous enhancement in interfacial perpendicular magnetic anisotropy through uphill diffusion  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

63

Anomalous enhancement in interfacial perpendicular magnetic anisotropy through uphill diffusion.  

PubMed

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. PMID:24937637

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

2014-01-01

64

Anomalous enhancement in interfacial perpendicular magnetic anisotropy through uphill diffusion  

PubMed Central

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. PMID:24937637

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

2014-01-01

65

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

66

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

DOEpatents

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.

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

1982-01-01

67

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

68

Enhanced detection in CT colonography using adaptive diffusion filtering  

NASA Astrophysics Data System (ADS)

Computer-aided detection (CAD) is a computerized procedure in medical science that supports the medical team's interpretations and decisions. CAD often uses information from a medical imaging modality such as Computed Tomography to detect suspicious lesions. Algorithms to detect these lesions are based on geometric models which can describe the local structures and thus provide potential region candidates. Geometrical descriptive models are very dependent on the data quality which may affect the false positive rates in CAD. In this paper we propose an efficient adaptive diffusion technique that adaptively controls the diffusion flux of the local structures in the data using robust statistics. The proposed method acts isotropically in the homogeneous regions and anisotropically in the vicinity of jump discontinuities. This method structurally enhances the data and makes the geometrical descriptive models robust. For the iterative solver, we use an efficient gradient descent flow solver based on a PDE formulation of the problem. The whole proposed strategy, which makes use of adaptive diffusion filter coupled with gradient descent flows has been developed and evaluated on clinical data in the application to colonic polyp detection in Computed Tomography Colonography.

Douiri, Abdel; Siddique, Musib; Ye, Xujiong; Beddoe, Gareth; Slabaugh, Greg

2009-02-01

69

Half-transient liquid phase diffusion welding: An approach for diffusion welding of SiC p \\/A356 with Cu interlayer  

Microsoft Academic Search

Aluminum matrix composite SiCp\\/A356 was welded by half-transient liquid Phase diffusion welding (HTLPDW) with a Cu interlayer. The effects of welding parameters\\u000a and interlayer thickness on the properties of the welded joint were investigated, and the optimal welding parameters were\\u000a subsequently put forward. The relationship between the tensile strength of the joint and the microstructure was studied by\\u000a analyzing the

Meng Hua; Wei Guo; Hang Wai Law; John Kin Lim Ho

2008-01-01

70

Dynamics of Enhanced Tracer Diffusion in Suspensions of Swimming Microorganisms  

NASA Astrophysics Data System (ADS)

We observe and statistically quantify the enhanced transport of passive tracer particles in suspensions of swimming microalgae, Chlamydomonas reinhardtii. These bi-flagellated, single-celled eukaryotes (10 ?m diameter) swim with a breast-stroke motion of their flagella at speeds of about 100 ?m/s and exhibit a heterogeneous trajectory shapes. Fluorescent tracer particles (2 ?m diameter) allowed us to quantify the enhanced mixing caused by the swimmers, which is relevant to marine ecology. As the swimmer concentration increases, the probability density functions (PDFs) of tracer displacements develop strong exponential tails, and the Gaussian core broadens; the diffusivity grows linearly with concentration. For a given swimmer concentration, the displacement PDFs show self-similar behavior and diffusive scaling in time. High-speed imaging of tracer-swimmer interactions demonstrates the importance of flagellar beating in creating oscillatory flows that exceed Brownian motion out to about 5 cell radii from the swimmers.footnotetextK.C. Leptos et al., submitted to Phys. Rev. Lett (2009)

Gollub, J. P.; Guasto, J. S.; Leptos, K. C.; Pesci, A. I.; Goldstein, R. E.

2009-11-01

71

Transient decrease in nociceptor GRK2 expression produces long–term enhancement in inflammatory pain  

PubMed Central

In heterozygous mice, attenuation of G-protein-coupled receptor kinase 2 (GRK2) level in nociceptors is associated with enhanced and prolonged inflammatory hyperalgesia. To further elucidate the role of GRK2 in nociceptor function we reversibly decreased GRK2 expression using intrathecal antisense oligodeoxynucleotide (AS-ODN). GRK2 AS-ODN administration led to an enhanced and prolonged hyperalgesia induced by prostaglandin E 2, epinephrine and carrageenan. Morover, this effect persisted unattenuated 2 weeks after the last dose of antisense, well after GRK2 protein recovered, suggesting that transient attenuation of GRK2 produced neuroplastic changes in nociceptor function. Unlike hyperalgesic priming induced by transient attenuation of GRK2 produced neuroplastic changes in nociceptor function. Unlike hyperalgesic priming induced by transient activation of protein kinase C epsilon (PKC?), (Aley et al., 2000, Parada et al., 2003b), the enhanced and prolonged hyperalgesia following attenuation of GRK2 is PKC?- and cytoplasmic polyadenylation element binding protein (CPEB)-independent and is protein kinase A (PKA)- and Src tyrosine kinase (Src)-dependent. Finally, rats treated with GRK2 AS-ODN exhibited enhanced and prolonged hyperalgesia induced by direct activation of second messengers, adenyl cyclase, Epac or PKA, suggesting changes downstream of G-protein-coupled receptors. Because inflammation can produce a decrease in GRK2, such a mechanism could help explain a predilection to develop chronic pain, after resolution of acute inflammation. PMID:22796071

Ferrari, Luiz F.; Bogen, Oliver; Alessandri–Haber, Nicole; Levine, Emma; Gear, Robert W.; Levine, Jon D.

2012-01-01

72

Boron doping of diamond powder by enhanced diffusion and forced diffusion: Diffusion concentrations, mechanical, chemical and optical properties  

NASA Astrophysics Data System (ADS)

Diamond, with its unique mechanical properties, is an excellent material for a wide range of applications. However, there exist some problems. One such problem is integration of diamond of diamond into tool's (usually tungsten-carbide) lattice matrix for the purpose of increasing its performance. The presence of cobalt in the matrix, which acts as a poison for diamond, causes graphitization and degradation of diamond. In addition, diamond graphitizes at sintering temperatures (1770 K). The results of this work suggest that boron has produced a protective layer for diamond, thus reducing the effects of annealing at high temperatures. Boron has been introduced into single crystal high pressure, high temperature diamond powder by enhanced diffusion and forced diffusion techniques. Enhanced diffusion resulted in higher concentrations of boron in diamond powder. Total boron concentrations of 500 to 600 ppm, and 10sp{20} cmsp{-3} at a depth of 0.5 micrometer, have been achieved. Hardness tests performed on doped samples reveal that diamond did not lose its strength due to diffusion at elevated temperatures. Raman spectroscopy and X-ray diffraction analysis did not show any change in the "quality" of diamond due to doping. Oxidation experiments performed on doped and undoped samples revealed that the samples with the highest boron concentrations had superior performance and resistance to oxidation. Final weight loss in these samples was much less than in undoped samples and samples with low boron concentrations. Scanning electron microscopy of these samples showed that degradation due to oxidation of heavily doped diamond samples was significantly less than other samples.

Golshani, Fariborz

73

Diffusion-controlled intermolecular electron transfer studied by transient absorption and degenerate four-wave mixing measurements  

NASA Astrophysics Data System (ADS)

The time dependence of intermolecular electron transfer kinetics is studied by two experimental techniques: transient absorption measurements and degenerate four-wave mixing after excitation of the donor molecules by picosecond UV pulses. In the system perylene/phthalic anhydride the electron transfer rate depends strongly on the concentration of the acceptor molecule phthalic anhydride. The value agrees with theoretical calculations based on a diffusion-controlled process.

Assel, M.; Höfer, T.; Laubereau, A.; Kaiser, W.

1995-03-01

74

Interactive effect of oxygen diffusion and volatiles advection on transient thermal degradation of poly methyl methacrylate (PMMA)  

Microsoft Academic Search

A transient, one-dimensional model has been presented to formulate the substantial role of polymer gasification in the early\\u000a stages of fire growth. The present model comprises the interaction between the oxygen diffusion and the released volatiles\\u000a on the rate of polymer gasification, when the polymeric sample is subjected to an external radiative source. The model also\\u000a includes different mechanisms affecting

Arash Kashani; Javad Abolfazli Esfahani

2008-01-01

75

Incorporating Diffusion-Weighted Magnetic Resonance Imaging into an Observation Unit Transient Ischemic Attack Pathway  

PubMed Central

Background and Purpose: National guidelines advocate for early, aggressive transient ischemic attack (TIA) evaluations and recommend diffusion-weighted magnetic resonance imaging (MRI) for brain imaging. The purpose of this study is to examine clinician compliance, the yield of MRI, and patient-centered clinical outcomes following implementation of an emergency department observation unit (EDOU) clinical pathway incorporating routine MRI into the acute evaluation of patients with TIA. Methods: This is a prospective observational study of patients with TIA admitted from the ED. Patients with low-risk TIA were transferred to an EDOU for diagnostic testing including MRI; high-risk patients were directed to hospital admission. Clinical variables, diagnostic tests, and treatment were recorded for all patients. The primary clinical outcome was the rate of stroke or recurrent TIA, determined through telephone follow-up and medical record review at 7 and 30 days. Results: A total of 116 patients with TIA were enrolled. In all, 92 (79.3%) patients were transferred to the EDOU, of whom 69 (59.5%) were discharged without hospitalization. Compliance with the EDOU pathway was 83 (91.2%) of 92. Magnetic resonance imaging demonstrated acute infarct in 16 (15.7%) of 102 patients. Stroke (n = 2) or TIA (n = 3) occurred in 5 patients with TIA (4.3%, 95% confidence interval: 1.6%-10.0%) within 30 days; no strokes occurred after discharge. Conclusions: Implementation of a TIA clinical pathway incorporating MRI effectively encouraged guideline-compliant diagnostic testing; however, patient-important outcomes appear similar to diagnostic protocols without routine MRI. Further study is needed to assess the benefits and costs associated with routinely incorporating MRI into TIA evaluation. PMID:24707334

Oostema, J. Adam; DeLano, Mark; Bhatt, Archit; Brown, Michael D.

2014-01-01

76

Transient experimental technique for the determination of the thermal diffusivity of fibrous insulation  

Microsoft Academic Search

The current investigation is an attempt to develop a transient technique that will circumvent these long experiment times. The present technique is fundamentally different from the hot-wire and hot-strip techniques, currently the only practical (but limited) transient techniques available for determining the thermal conductivity of insulators. In 1983, a step heat technique involving planar geometry was presented (Bittle, 1983; Bittle

S. P. Rooke; R. E. Taylor

1988-01-01

77

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

NASA Astrophysics Data System (ADS)

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

Atieh, Anas Mahmoud

78

Fluorine-enhanced boron diffusion in amorphous silicon J. M. Jacques,a)  

E-print Network

Fluorine-enhanced boron diffusion in amorphous silicon J. M. Jacques,a) L. S. Robertson, and K. S annealing at 550 °C, secondary ion mass spectroscopy determined that the diffusivity of boron in amorphous increases the boron diffusivity by approximately five orders of magnitude at 550 °C. It is proposed

Florida, University of

79

Enhanced diffusion of nonswimmers in a three-dimensional bath of motile bacteria.  

PubMed

We show, using differential dynamic microscopy, that the diffusivity of nonmotile cells in a three-dimensional (3D) population of motile E. coli is enhanced by an amount proportional to the active cell flux. While nonmotile mutants without flagella and mutants with paralyzed flagella have quite different thermal diffusivities and therefore hydrodynamic radii, their diffusivities are enhanced to the same extent by swimmers in the regime of cell densities explored here. Integrating the advective motion of nonswimmers caused by swimmers with finite persistence-length trajectories predicts our observations to within 2%, indicating that fluid entrainment is not relevant for diffusion enhancement in 3D. PMID:24229108

Jepson, Alys; Martinez, Vincent A; Schwarz-Linek, Jana; Morozov, Alexander; Poon, Wilson C K

2013-10-01

80

Enhanced diffusion of non-swimmers in a 3D bath of motile bacteria  

E-print Network

We show using differential dynamic microscopy that the diffusive motion of non-motile cells in a three-dimensional population of motile E. coli is enhanced by an amount that is strictly proportional to the active cell flux. While non-motile mutants without flagella and mutants with paralysed flagella have quite different thermal diffusivities and therefore hydrodynamic radii, their diffusivities are enhanced to the same extent by swimmers in the regime of cell densities explored here. Integrating the motion of non-swimmers caused by swimmers with finite persistence-length trajectories predicts quantitatively the observed linear dependence of enhanced diffusivity and active cell flux.

Jepson, A; Schwarz-Linek, J; Morozov, A; Poon, W C K

2013-01-01

81

Enhanced diffusion of nonswimmers in a three-dimensional bath of motile bacteria  

NASA Astrophysics Data System (ADS)

We show, using differential dynamic microscopy, that the diffusivity of nonmotile cells in a three-dimensional (3D) population of motile E. coli is enhanced by an amount proportional to the active cell flux. While nonmotile mutants without flagella and mutants with paralyzed flagella have quite different thermal diffusivities and therefore hydrodynamic radii, their diffusivities are enhanced to the same extent by swimmers in the regime of cell densities explored here. Integrating the advective motion of nonswimmers caused by swimmers with finite persistence-length trajectories predicts our observations to within 2%, indicating that fluid entrainment is not relevant for diffusion enhancement in 3D.

Jepson, Alys; Martinez, Vincent A.; Schwarz-Linek, Jana; Morozov, Alexander; Poon, Wilson C. K.

2013-10-01

82

Diffuse dispersive delay and the time convolution/attenuation of transients  

NASA Technical Reports Server (NTRS)

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.

Bittner, Burt J.

1991-01-01

83

Exciton diffusion in semiconducting single-walled carbon nanotubes studied by transient absorption microscopy  

E-print Network

Spatiotemporal dynamics of excitons in isolated semiconducting single-walled carbon nanotubes are studied using transient absorption microscopy. Differential reflection and transmission of an 810-nm probe pulse after excitation by a 750-nm pump...

Ruzicka, Brian A.; Wang, Rui; Lohrman, Jessica; Ren, Shenqiang; Zhao, Hui

2012-11-09

84

Enhancement of inhibitory synaptic transmission in large aspiny neurons after transient cerebral ischemia.  

PubMed

Large aspiny neurons and most of the GABAergic interneurons survive transient cerebral ischemia while medium spiny neurons degenerate in 24 h. Expression of a long-term enhancement of excitatory transmission in medium spiny neurons but not in large aspiny neurons has been indicated to contribute to this selective vulnerability. Because neuronal excitability is determined by the counterbalance of excitation and inhibition, the present study examined inhibitory synaptic transmission in large aspiny neurons after ischemia in rats. Transient cerebral ischemia was induced for 22 min using the four-vessel occlusion method and whole-cell voltage-clamp recording was performed on striatal slices. The amplitudes of evoked inhibitory postsynaptic currents in large aspiny neurons were significantly increased at 3 and 24 h after ischemia, which was mediated by the increase of presynaptic release. Postsynaptic responses were depressed at 24 h after ischemia. Inhibitory postsynaptic currents could be evoked in large aspiny neurons at 24 h after ischemia, suggesting that they receive GABAergic inputs from the survived GABAergic interneurons. Muscimol, a GABA(A) receptor agonist, presynaptically facilitated inhibitory synaptic transmission at 24 h after ischemia. Such facilitation was dependent on the extracellular calcium and voltage-gated sodium channels. The present study demonstrates an enhancement of inhibitory synaptic transmission in large aspiny neurons after ischemia, which might reduce excitotoxicity and contribute, at least in part, to the survival of large aspiny neurons. Our data also suggest that large aspiny neurons might receive inhibitory inputs from GABAergic interneurons. PMID:19167464

Li, Y; Lei, Z; Xu, Z C

2009-03-17

85

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

PubMed

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

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

2005-01-01

86

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

PubMed

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

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

2013-02-01

87

Fractional diffusion analysis of the electromagnetic fields generated by a transient straight current source over a porous geological media  

NASA Astrophysics Data System (ADS)

An interpretation based on the Continuous Time Random Walk theory (CTRW) to the diffusion of electromagnetic fields generated by a transient straight current source over a porous geological media is presented here. The CTRW theory is demonstrated to be a powerful tool to concisely and more accurately model a transport process in a fractal medium with complex structures, comparing to the classical transport theory. In the controlled-source electromagnetic (EM) induction setting, the time dependent evolution of the EM field of some sources over a rough medium are governed by the fractional diffusion EM equation in a CTRW sense. The master equation can be solved for a uniform conducting half-space in the Laplace domain semi-analytically. We use 2D finite difference method to calculate the solution numerically for the assigned space and transform to time domain with Gaver-Stehfest algorithm. Here we adopt a spatially uniform roughness parameter ? in the solution to characterize the complexity of the geoelectrical structure of the geological medium. To introduce the heterogeneity to our model, we set up the space as several 2 D blocks with different conductivities and ?s. Then we compare our results with the synthetic data we got from the high resolution numerical simulations. We are able to show that by introducing the heterogeneity to the fractional diffusion perspective, our approach is competent for tracing the diffusion process with less model parameters.

Ge, J.; Everett, M. E.; Weiss, C. J.

2010-12-01

88

Numerical Analysis of Effect of Backplate Diffusivity on the Transient Temperature in Friction Stir Welding  

NASA Astrophysics Data System (ADS)

It is still not clearly known as to what extent the temperature field of friction stir welding joint is influenced by backplate diffusivity owing to the limitation of temperature measuring points. In the present study, therefore, the effect of backplate diffusivity on the temperature field of the workpiece was systematically investigated based on the numerical analysis. Simulated results show that the backplate diffusivity has a significant influence on not only the peak temperature but the final temperature distribution. More heat is dissipated by using a high thermal conductivity backplate during FSW. With increasing the backplate diffusivity, the peak temperature decreases gradually and the average cooling rate increases first and then slightly decreases. In addition, the time spent above 195 °C presents a nearly linear decrease with increasing the backplate diffusivity. Moreover, the width of temperature region higher than 195 °C in the transverse direction is remarkably diminished by using the backplate of a high conductivity, and changes little during the entire process.

Zhang, Zhihan; Li, Wenya; Li, Jinglong; Chao, Y. J.

2013-09-01

89

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

E-print Network

Structural dynamics of hydrogen bonded methanol oligomers: Vibrational transient hole burning donate and receive hydrogen bonds have an inhomogeneously broadened hydroxyl stretch absorption line the dynamics are attributed to fluctuations in the local hydrogen bond network, which is consistent with recent

Fayer, Michael D.

90

Diffuse-charge effects on the transient response of electrochemical cells  

E-print Network

We present theoretical models for the time-dependent voltage of an electrochemical cell in response to a current step, including effects of diffuse charge (or “space charge”) near the electrodes on Faradaic reaction kinetics. ...

van Soestbergen, M.

91

Uphill diffusion, zero-flux planes and transient chemical solitary waves in garnet  

NASA Astrophysics Data System (ADS)

Diffusion profiles in minerals are increasingly used to determine the duration of geological events. For this purpose, the distinction between growth and diffusion zoning is critical; it requires the understanding of complex features associated with multicomponent diffusion. Seed-overgrowth interdiffusion experiments carried out in the range 1,050-1,250°C at 1.3 GPa have been designed to quantify and better understand Fe-Mg-Ca interdiffusion in garnet. Some of the diffusion profiles measured by analytical transmission electron microscope show characteristic features of multicomponent diffusion such as uphill diffusion, chemical solitary waves, zero-flux planes and complex diffusion paths. We implemented three different methods to calculate the interdiffusion coefficients of the D matrix from the experimental penetration curves and determined that with Ca as the dependent component, the crossed coefficients of the D matrix are negative. Experiments and numerical simulations indicate that: (1) uphill diffusion in garnet can be observed indifferently on the three components Fe, Mg and Ca, (2) it takes the form of complementary depletion/repletion waves and (3) chemical waves occur preferentially on initially flat concentration profiles. Derived D matrices are used to simulate the fate of chemical waves in time, in finite crystals. These examples show that the flow of atoms in multicomponent systems is not necessarily unidirectional for all components; it can change both in space along the diffusion profile and in time. Moving zero-flux planes in finite crystals are transitory features that allow flux reversals of atoms in the diffusion zone. Interdiffusion coefficients of the D matrices are also analyzed in terms of eigenvalues and eigenvectors. This analysis and the experimental results show that depending on the composition of the diffusion couple, (1) the shape of chemical waves and diffusion paths changes; (2) the width of the diffusion zone for each component may or may not be identical; and (3) the width of diffusion calculated at a given D and duration may greatly vary. D matrices were retrieved from thirteen sets of diffusion profiles. Data were cast in Arrhenius relations. Linear regressions of the data yield activation energies equal to 368, 148, 394, 152 kJ mol-1 at 1 bar and frequency factors Do equal to 2.37 × 10-6, -4.46 × 10-16, -1.31 × 10-5, 9.85 × 10-15 m2 s-1 for tilde{D}_{FeFe}^{Ca} , tilde{D}_{FeMg}^{Ca} , tilde{D}_{MgFe}^{Ca} , tilde{D}_{MgMg}^{Ca} , respectively. These values can be used to calculate interdiffusion coefficients in Fe-Mg-Ca garnets and determine the duration of geological events in high temperature metamorphic or magmatic garnets.

Vielzeuf, D.; Saúl, A.

2011-05-01

92

Transient expression directed by homologous and heterologous promoter and enhancer sequences in fish cells.  

PubMed Central

In order to construct fish specific expression vectors for studies on gene regulation in vitro and in vivo a variety of heterologous enhancers and promoters from mammals and from viruses of higher vertebrate cells were tested for expression of the bacterial chloramphenicol acetyl transferase reporter gene in three teleost fish cell lines. Several viral enhancers were found to be constitutively active at high levels. The human metallothionein promoter showed inducible expression in the presence of heavy metal ions. A fish sequence was isolated that can be used as a homologous constitutively active promoter for expression of foreign genes. Using the human growth hormone gene with an active promoter in fish cells for transient expression insufficient splicing and lack of translation were observed, pointing to limitations in the use of heterologous genes in gene transfer experiments. On the contrary, some heterologous promoters and enhancers functioned in fish cells as well as in their cell type of origin, indicating that corresponding transcription factors are sufficiently conserved between fish and human over a period of 900 million years of independent evolution. Images PMID:2356120

Friedenreich, H; Schartl, M

1990-01-01

93

Transient expression directed by homologous and heterologous promoter and enhancer sequences in fish cells.  

PubMed

In order to construct fish specific expression vectors for studies on gene regulation in vitro and in vivo a variety of heterologous enhancers and promoters from mammals and from viruses of higher vertebrate cells were tested for expression of the bacterial chloramphenicol acetyl transferase reporter gene in three teleost fish cell lines. Several viral enhancers were found to be constitutively active at high levels. The human metallothionein promoter showed inducible expression in the presence of heavy metal ions. A fish sequence was isolated that can be used as a homologous constitutively active promoter for expression of foreign genes. Using the human growth hormone gene with an active promoter in fish cells for transient expression insufficient splicing and lack of translation were observed, pointing to limitations in the use of heterologous genes in gene transfer experiments. On the contrary, some heterologous promoters and enhancers functioned in fish cells as well as in their cell type of origin, indicating that corresponding transcription factors are sufficiently conserved between fish and human over a period of 900 million years of independent evolution. PMID:2356120

Friedenreich, H; Schartl, M

1990-06-11

94

Enhancement of gas-phase diffusion in the presence of liquid  

NASA Astrophysics Data System (ADS)

Gas diffusion in porous media occurs in both the gas and liquid phases. In many instances, gas diffusion in the liquid phase is ignored. However, under many conditions, gas diffusion in the liquid phase may be more important than gas diffusion in the gas phase. Two different cases will be examined in this work. The first case is a continuous liquid path between the gas concentrations of interest modeled after Jury et al. (1984). The second case is the situation at low liquid saturation where liquid islands exist. For the first case, Jury's model can be rewritten as a ratio of the total gas diffusion in the gas and liquid phases to that just in the gas phase. The liquid diffusion coefficient is approximately 10-4 times the gas diffusion coefficient consistent with Jury et al. (1984). The ratio of total diffusion to gas-phase diffusion is then only a function of Henry's constant and the liquid saturation. For higher values of Henry's constant, such as for CO2 and O2, the effect of diffusion in the liquid phase is small except at high liquid saturations. For small values of Henry's constant, such as for some VOCs and explosive compounds, diffusion in the liquid phase dominates for low and moderate liquid saturation values. The second case is the enhancement of diffusion caused by liquid islands at low liquid saturation. Enhanced vapor diffusion across liquid islands has been observed and modeled by Webb and Ho (1999), where condensation and evaporation occur on opposite ends of the liquid island. Vapor diffusion enhancement of up to a factor of 10 has been observed. Similarly, gas can diffuse through the liquid island. For high values of Henry's constant, gas diffusion through liquid islands is negligible and can be ignored. For small values of Henry's constant, diffusion through liquid islands may be much greater than diffusion through gas, so the rate is enhanced. The work was sponsored by the Geneva International Center for Humanitarian Demining (GICHD) under the direction of Havard Bach. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.

Webb, S.; Angert, A.

2003-04-01

95

Astroglial-neural networks, diffusion-enhancement bilayers, and spatio-temporal grouping dynamics  

Microsoft Academic Search

Summary form only given, as follows. Spatiotemporal grouping phenomena were examined in the context of static and time-varying imagery. The dynamics of a biologically plausible diffusion-enhancement bilayer was developed that exhibits grouping of static features on multiple scales as a function of time, and long-range apparent motion between time-varying inputs. The architecture consists of a diffusion layer and a contrast-enhancement

R. Cunningham; A. M. Waxman

1991-01-01

96

Transient Natural Convection Flow with Cosinusoidally Fluctuating Thermal and Mass Diffusion  

NASA Astrophysics Data System (ADS)

The problem of a transient natural convection flow of a viscous incompressible fluid past a permeable (porous) flat plate with the temperature and concentration cosinusoidally fluctuating with time is considered. The equations of mass, momentum, and energy conservation that govern the heat and mass transfer problem are solved analytically with the use of the regular perturbation technique. Explicit expressions for the velocity, temperature, and concentration are obtained. Numerical evaluation of the analytical results is performed, and graphical results for the flow characteristics, skin friction, and the rate of heat transfer are presented and discussed.

Sharma, P. K.; Saini, S. K.

2014-11-01

97

Search for muon enhancement at sea level from transient solar activity  

SciTech Connect

This paper presents first results of an ongoing study of a possible association between muon enhancements at ground observed by the TUPI telescope and transient events such as the Sun's X-ray activity. The analysis of the observed phenomenon by using the GOES satellite archive data seems to indicate that on most cases the Ground Level Enhancements (GLEs) could potentially be associated with solar flares. We show that small-scale solar flares, those with prompt X-ray emission classified as C class (power above 10{sup -6} Watts m{sup -2} at 1 AU) may give rise to GLEs, probably associated with solar protons and ions arriving to the Earth as a coherent particle pulse. The TUPI telescope's high performance with these energetic solar particles arises mainly from: (i) its high counting rate (up to {approx}100 KHz). This value in most cases is around 100 times higher than other detectors at ground and (ii) due to its tracking system. The telescope is always looking near the direction of the IMF lines. The GLE's delay in relation of the X-ray prompt emission suggest that shock driven by corona mass ejection (CME) is an essential requirement for the particle acceleration efficiency.

Augusto, C.R.A.; Navia, C.E.; Robba, M.B. [Instituto de Fisica, Universidade Federal Fluminense, 24210-130, Niteroi, RJ (Brazil)

2005-05-15

98

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

NASA Astrophysics Data System (ADS)

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

Bermúdez, Vicente; Pastor, José V.; López, J. Javier; Campos, Daniel

2014-06-01

99

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

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

100

Crossing-Preserving Coherence-Enhancing Diffusion on Invertible Orientation Scores  

E-print Network

and bifurcating line structures. This is for example important in High Angular Resolution Diffusion Imaging (HARDI, catheters, neural fibers, and contours of organs in noisy medical image data. Many methods for enhancing, Remco Duits March 13, 2008 Abstract Many medical image processing problems require enhancement

Eindhoven, Technische Universiteit

101

Electrostatic Enhancement of Diffusion-controlled ProteinProtein Association: Comparison of Theory  

E-print Network

Electrostatic Enhancement of Diffusion-controlled Protein±Protein Association: Comparison of Theory and Digestive Kidney Diseases, National Institutes of Health, Bethesda MD 20892, USA The electrostatic mutations are found to correlate well with experimental results for the electrostatic rate enhancement

Weston, Ken

102

Enhancement of epitaxial lateral overgrowth by vapor-phase diffusion  

E-print Network

heterostructure lasers, electroadsorption modulators, light-emitting diodes, etc. [1,2]. Micrometer nanostructures by MBE [10­12]. The advances in experimental field of SAG stimulate the interest in fundamental growth mechanism and ignore diffusion in vapor phase; the effect of vapor phase is reduced

Khenner, Mikhail

103

Performance enhancement of PV solar system by diffused reflection  

Microsoft Academic Search

Various methods are being adopted to enhance the performance of a solar panel. The most common method is to track the sun for performance enhancement. Such method needs complicated control and drive circuits for implementation. Also, the power required for the tracking motor has to be provided by the solar panel and the battery system. Although better performance is achievable

Rizwan ur Rahman; Dewan Ishtiaque Ahmed; Mufrad Ahmed Fahmi; Tithi Tasnuva; M. Fayyaz Khan

2009-01-01

104

Cardiac Amyloidosis: Typical Imaging Findings and Diffuse Myocardial Damage Demonstrated by Delayed Contrast-Enhanced MRI  

SciTech Connect

Amyloidosis is a rare systemic disease. However, involvement of the heart is a common finding and is the most frequent cause of death in amyloidosis. We report the sonographic, scintigraphic, and MRI features of a pathologically proven case of cardiac amyloidosis. Delayed contrast-enhanced MR images, using an inversion recovery prepped gradient-echo sequence, revealed diffuse enhancement in the wall of both left and right ventricles. This enhancement suggested expansion of the extracellular space of the myocardium caused by diffuse myocardial necrosis secondary to deposition of amyloid.

Sueyoshi, Eijun, E-mail: EijunSueyoshi@aol.com; Sakamoto, Ichiro; Okimoto, Tomoaki; Hayashi, Kuniaki [Nagasaki University School of Medicine, Department of Radiology (Japan); Tanaka, Kyouei; Toda, Genji [Nagasaki University School of Medicine, Department of Cardiology (Japan)

2006-08-15

105

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

NASA Technical Reports Server (NTRS)

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.

Gokoglu, Suleyman A.

2003-01-01

106

First-principles calculation of self-diffusion, arsenic diffusion, and surface segregation in silicon  

Microsoft Academic Search

Integrated circuit device densities have increased more than 2000 times since Gordon Moore's observation of exponential growth in 1965. Modern devices are thus sensitive to minute variations in diffusion, such as the transient-enhanced diffusivity resulting from ion implantation, concentration-dependent diffusivity of dopants due to changes in the Fermi level, and the effects of high stresses and stress gradients (resulting from

Scott A. Centoni

2003-01-01

107

Transient coherent anti-Stokes Raman scattering spectroscopy as a tool for measuring the diffusion coefficient and size of gas molecules  

SciTech Connect

Formulas are derived for evaluating the diffusion coefficient and size of gas molecules from transient coherent anti-Stokes Raman scattering measurements. Numerical estimates are presented for hydrogen. (special issue devoted to the 80th birthday of S.A. Akhmanov)

Nikitin, Sergei Yu [M. V. Lomonosov Moscow State University, Faculty of Physics, Moscow (Russian Federation)

2009-07-31

108

2.5D Fractional Diffusion Analysis of The Electromagnetic Field Generated By A Transient Loop Source In Fractured Mediums  

NASA Astrophysics Data System (ADS)

A 2.5D finite difference (FD) frequency-domain modeling based on the Continuous Time Random Walk theory (CTRW) to the diffusion of electromagnetic fields generated by a transient loop source over a porous geological media is presented. The CTRW theory is demonstrated to be a powerful tool to concisely describe a transport process in fractal mediums with complex structures (Scher and Lax 1973, Metzler and Klafter 2000). In the controlled-source electromagnetic (CSEM) induction setting, the diffusion of Eddy currents in a rough medium is governed by the fractional differential EM equations in a CTRW sense (Everett 2009). We use staggered finite difference (FD) approach to discretize the equations in frequency domain. The biconjugate gradient iterative solver is implemented to solve sparse matrix equations. We compare the FD solutions with analytical solutions to a half space model to verify the accuracy of our code. Then FD solutions are calculated for a model with a 2D block fractured structures included in a homogeneous space. Via displaying the high sensitivity of the spatial variation of Ey fields to the geoelectrical properties and roughness of the block, we are able to show the potential of combination of CTRW theory with CSEM method in detecting unknown fractured targets in subsurface.

Ge, J.; Everett, M. E.; Weiss, C. J.

2011-12-01

109

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

PubMed

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. PMID:23005055

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

2012-06-01

110

Cholesterol enhances surface water diffusion of phospholipid bilayers.  

PubMed

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 (1)H Overhauser dynamic nuclear polarization (ODNP) NMR relaxometry that enables the sensitive and selective determination of water diffusion within 5-10 Å of a nitroxide-based spin label, positioned off the surface of the polar headgroups or within the nonpolar core of lipid membranes. The Chol-rich membrane systems were prepared from mixtures of Chol, dipalmitoyl phosphatidylcholine and/or dioctadecyl phosphatidylcholine lipid that are known to form liquid-ordered, raft-like, domains. Our data reveal that the translational diffusion of local water on the surface and within the hydrocarbon volume of the bilayer is significantly altered, but in opposite directions: accelerated on the membrane surface and dramatically slowed in the bilayer interior with increasing Chol content. Electron paramagnetic resonance (EPR) lineshape analysis shows looser packing of lipid headgroups and concurrently tighter packing in the bilayer core with increasing Chol content, with the effects peaking at lipid compositions reported to form lipid rafts. The complementary capability of ODNP and EPR to site-specifically probe the hydration dynamics and lipid ordering in lipid membrane systems extends the current understanding of how Chol may regulate biological processes. One possible role of Chol is the facilitation of interactions between biological constituents and the lipid membrane through the weakening or disruption of strong hydrogen-bond networks of the surface hydration layers that otherwise exert stronger repulsive forces, as reflected in faster surface water diffusivity. Another is the concurrent tightening of lipid packing that reduces passive, possibly unwanted, diffusion of ions and water across the bilayer. PMID:25494784

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

2014-12-14

111

Cholesterol enhances surface water diffusion of phospholipid bilayers  

NASA Astrophysics Data System (ADS)

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 surface water diffusivity. Another is the concurrent tightening of lipid packing that reduces passive, possibly unwanted, diffusion of ions and water across the bilayer.

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

2014-12-01

112

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

SciTech Connect

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.

Hirsch, Cordula [Institute of Molecular Medicine and Cell Research, Albert-Ludwigs-University Freiburg Stefan-Meier-Str. 17, D-79104 Freiburg (Germany); Campano, Louise M. [Institute of Molecular Medicine and Cell Research, Albert-Ludwigs-University Freiburg Stefan-Meier-Str. 17, D-79104 Freiburg (Germany); Woehrle, Simon [Institute of Molecular Medicine and Cell Research, Albert-Ludwigs-University Freiburg Stefan-Meier-Str. 17, D-79104 Freiburg (Germany); Hecht, Andreas [Institute of Molecular Medicine and Cell Research, Albert-Ludwigs-University Freiburg Stefan-Meier-Str. 17, D-79104 Freiburg (Germany)]. E-mail: andreas.hecht@mol-med.uni-freiburg.de

2007-02-01

113

Enhancement of microhomology-mediated genomic rearrangements by transient loss of mouse Bloom syndrome helicase  

PubMed Central

Bloom syndrome, an autosomal recessive disorder of the BLM gene, confers predisposition to a broad spectrum of early-onset cancers in multiple tissue types. Loss of genomic integrity is a primary hallmark of such human malignancies, but many studies using disease-affected specimens are limited in that they are retrospective and devoid of an appropriate experimental control. To overcome this, we devised an experimental system to recapitulate the early molecular events in genetically engineered mouse embryonic stem cells, in which cells undergoing loss of heterozygosity (LOH) can be enriched after inducible down-regulation of Blm expression, with or without site-directed DNA double-strand break (DSB) induction. Transient loss of BLM increased the rate of LOH, whose breakpoints were distributed along the chromosome. Combined with site-directed DSB induction, loss of BLM synergistically increased the rate of LOH and concentrated the breakpoints around the targeted chromosomal region. We characterized the LOH events using specifically tailored genomic tools, such as high-resolution array comparative genomic hybridization and high-density single nucleotide polymorphism genotyping, revealing that the combination of BLM suppression and DSB induction enhanced genomic rearrangements, including deletions and insertions, whose breakpoints were clustered in genomic inverted repeats and associated with junctional microhomologies. Our experimental approach successfully uncovered the detailed molecular mechanisms of as-yet-uncharacterized loss of heterozygosities and reveals the significant contribution of microhomology-mediated genomic rearrangements, which could be widely applicable to the early steps of cancer formation in general. PMID:23908384

Yamanishi, Ayako; Yusa, Kosuke; Horie, Kyoji; Tokunaga, Masahiro; Kusano, Kohji; Kokubu, Chikara; Takeda, Junji

2013-01-01

114

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

NASA Astrophysics Data System (ADS)

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.

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

115

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

PubMed

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

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

2006-03-01

116

Enhanced anomalous diffusion of sputtered atoms in nanosized pores  

E-print Network

and enhancing their catalytic effi- ciency [1, 2, 3]. The catalytic efficiency of these advanced porous a rele- vant way for designing catalytic thin films [1, 2, 6, 7, 8, 9]. The growth of the active layer to 50 min at argon pressure of 3.10-3 mbar. The morphology of the Pt coated AAO templates were analyzed

Boyer, Edmond

117

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

SciTech Connect

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

Shestakov, A I; Offner, S R

2007-03-02

118

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

SciTech Connect

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

Shestakov, A I; Offner, S R

2006-09-21

119

Enhanced texture in die-upset nanocomposite magnets by Nd-Cu grain boundary diffusion  

NASA Astrophysics Data System (ADS)

Bulk anisotropic nanocomposite Nd2Fe14B/?-Fe magnets were prepared by hot pressing and die upsetting coupled with Nd-Cu grain boundary diffusion. The hot workability of nanocomposite magnets is enhanced dramatically by grain boundary diffusion of low melt point Nd-Cu alloy, resulting in a strong anisotropy by die upsetting. The microstructure of die-upset nanocomposite magnets is identical with that of the traditional die-upset rare earth-rich magnets. The coercivity, remanence, and squareness degree of demagnetization curves are optimized. The observation for microstructures and the analysis of magnetic properties suggest that the grain boundary diffusion mainly occurs in the hot deformation process.

Tang, Xin; Chen, Renjie; Yin, Wenzong; Wang, Jinzhi; Tang, Xu; Lee, Don; Yan, Aru

2013-02-01

120

Cosolute Paramagnetic Relaxation Enhancements Detect Transient Conformations of Human Uracil DNA Glycosylase (hUNG)  

PubMed Central

The human DNA repair enzyme uracil DNA glycosylase (hUNG) locates and excises rare uracil bases that arise in DNA from cytosine deamination or through dUTP incorporation by DNA polymerases. Previous NMR studies of hUNG have revealed millisecond time scale dynamic transitions in the enzyme-nonspecific DNA complex, but not the free enzyme, that were ascribed to a reversible clamping motion of the enzyme as it scans along short regions of duplex DNA in its search for uracil. Here we further probe the properties of the nonspecific DNA binding surface of {2H12C}{15N}-labeled hUNG using a neutral chelate of a paramagnetic Gd3+ cosolute (Gd(HP-DO3A)). Overall, the measured paramagnetic relaxation enhancements (PREs) on R2 of the backbone amide protons for free hUNG and its DNA complex were in good agreement with those calculated based on their relative exposure observed in the crystal structures of both enzyme forms. However, the calculated PREs systematically underestimated the experimental PREs by large amounts in discrete regions implicated in DNA recognition and catalysis: active site loops involved in DNA recognition (268–274, 246–250), the uracil binding pocket (143–148, 169–170), a transient extrahelical base binding site (214–216), and a remote hinge region (129–132) implicated in dynamic clamping. These reactive hot spots were not correlated with electrostatic, structural or hydrophobic properties that might be common to these regions, leaving the possibility that the effects arise from dynamic sampling of exposed conformations that are distinct from the static structures. Consistent with this suggestion, the above regions have been previously shown to be flexible based on relaxation dispersion measurements and course-grained normal mode analysis. A model is suggested where the intrinsic dynamic properties of these regions allows sampling of transient conformations where the backbone amide groups have greater average exposure to solvent as compared to the static structures. We conclude that PREs derived from the paramagnetic cosolute reveal dynamic hot spots in hUNG and that these regions are highly correlated with substrate binding and recognition. PMID:22077282

Sun, Yan; Friedman, Joshua I.; Stivers, James T.

2011-01-01

121

Wrinkles enhance the diffuse reflection from the dragonfly Rhyothemis resplendens.  

PubMed

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

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

2015-02-01

122

Water diffusion-exchange effect on the paramagnetic relaxation enhancement in off-resonance rotating frame  

PubMed Central

The off-resonance rotating frame technique based on the spin relaxation properties of off-resonance T1? can significantly increase the sensitivity of detecting paramagnetic labeling at high magnetic fields. However, the in vivo detectable dimension for labeled cell clusters/tissues in T1? -weighted images is limited by the water diffusion-exchange between mesoscopic scale compartments. An experimental investigation of the effect of water diffusion-exchange between compartments on the paramagnetic relaxation enhancement of paramagnetic agent compartment is presented for in vitro/in vivo models. In these models, the size of paramagnetic agent compartment is comparable to the mean diffusion displacement of water molecules during the long RF pulses that are used to generate the off-resonance rotating frame. The three main objectives of this study were: (1) to qualitatively correlate the effect of water diffusion-exchange with the RF parameters of the long pulse and the rates of water diffusion, (2) to explore the effect of water diffusion-exchange on the paramagnetic relaxation enhancement in vitro, and (3) to demonstrate the paramagnetic relaxation enhancement in vivo. The in vitro models include the water permeable dialysis tubes or water permeable hollow fibers embedded in cross-linked proteins gels. The MWCO of the dialysis tubes was chosen from 0.1 to 15 kDa to control the water diffusion rate. Thin hollow fibers were chosen to provide sub-millimeter scale compartments for the paramagnetic agents. The in vivo model utilized the rat cerebral vasculatures as a paramagnetic agent compartment, and intravascular agents (Gd-DTPA)30-BSA were administrated into the compartment via bolus injections. Both in vitro and in vivo results demonstrate that the paramagnetic relaxation enhancement is predominant in the T1? -weighted imaging in the presence of water diffusion exchange. The T1? contrast has substantially higher sensitivity than the conventional T1 contrast in detecting paramagnetic agents, especially at low paramagnetic agent volumetric fractions, low paramagnetic agent concentrations, and low RF amplitudes. Short pulse duration, short pulse recycle delay and efficient paramagnetic relaxation can reduce the influence of water diffusion-exchange on the paramagnetic enhancement. This study paves the way for the design of off-resonance rotating experiments to detect labeled cell clusters/tissue compartments in vivo at a sub-millimeter scale. PMID:17412624

Zhang, Huiming; Xie, Yang; Ji, Tongyu

2007-01-01

123

Enhancement by Li+ of the diffusion of Mn2+ in MgF2 crystals  

NASA Astrophysics Data System (ADS)

A particularly striking example of solute enhancement of cationic diffusion is observed in the case of Mn2+ diffusion in MgF2 crystals doped with Li+. Mn2+ is diffused in from the vapor at 920°C and detected by its electron-spin-resonance spectrum. In the absence of Li+, DMn at 920°C is <~9×10-11 cm2/sec, but in the presence of ~600-ppm Li+, values ~= 2×10-9 cm2/sec are obtained. This large enhancement apparently originates in the fact that Li+ enters the lattice predominantly as interstitials, thereby greatly increasing the cation vacancy concentration. The present results also permit lower-limit estimates to be made for the formation enthalpy of the predominant intrinsic defect in MgF2.

Toulouse, J.; Nowick, A. S.; Halliburton, L. E.

1982-09-01

124

Analysis of model equations for stress-enhanced diffusion in coal  

E-print Network

Analysis of model equations for stress-enhanced diffusion in coal layers Andro Mikeli´c Andro coal seams. A typical procedure is the injection of carbon dioxide via deviated wells drilled inside the coal seams. Carbon dioxide displaces the methane adsorbed on the internal surface of the coal

Segatti, Antonio

125

Normal and inverse laminar jet-diffusion flames under oxygen enhancement and gravity-variation  

Microsoft Academic Search

A computational study (emphasizing the effects of oxygen enhancement, gravity and inverse burning on species mass-fraction, velocity, temperature, radiative losses, transport properties, reaction rates, species emission and flame size) has been performed for ethane fueled laminar gas jet diffusion flames. Fire safety, efficient energy utilization and fundamental research, both on earth and in space, are the areas where this study

Pramod Bhatia

2008-01-01

126

Enhanced Diffusion due to Active Swimmers at a Solid Surface Gaston Min~o,1  

E-print Network

Enhanced Diffusion due to Active Swimmers at a Solid Surface Gasto´n Min~o,1 Thomas E. Mallouk,2 2010; published 25 January 2011) We consider two systems of active swimmers moving close to a solid field hydrodynamic forces that become prevalent and require a complex treatment of the lubrication

127

Enhanced diffusion due to active swimmers at a solid surface Gaston Mi~no1  

E-print Network

Enhanced diffusion due to active swimmers at a solid surface Gast´on Mi~no1 , Thomas E. Mallouk2 of active swimmers moving close to a solid surface, one being a living population of wild-type E. coli the close field hydrodynamic forces that become prevalent and require a complex treatment of the lubrication

128

The Cerebral Vascular Enhancement Effect in Establishing Diffusion Tensor Imaging Protocols  

Microsoft Academic Search

The focus of this paper is to investigate the significance of the cerebral vascular enhancement effect on diffusion tensor imaging (DTI) datasets and in establishing appropriate DTI imaging protocols. Two DTI scans are performed on each subject during the same imaging session. Between DTI scans, 22 minutes of a visual tracking experiment and 3 minutes of an alternating breath hold

Rajbir Jaswal; Tara L. Alvarez; Yelda Alkan; Eun Kim; Bharat B. Biswal

2009-01-01

129

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

130

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

131

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

PubMed

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

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

2014-11-01

132

Microstructural evolution in the partial transient liquid phase diffusion bonding of Zircaloy4 to stainless steel 321 using active titanium filler metal  

Microsoft Academic Search

Microstructural evolution of the partial transient liquid phase diffusion bonded Zircaloy-4 and stainless steel 321 using an active Ti-base interlayer were studied at different temperatures. Additionally, simple analytical models were developed to predict the evolution of the interlayer and intermetallics during the bonding operation. Bonds were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. Precision measurement of the

M. Mazar Atabaki

2010-01-01

133

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

134

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

NASA Astrophysics Data System (ADS)

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

Mahdad, Belkacem; Srairi, K.

2013-12-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

136

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

PubMed Central

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

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

2012-01-01

137

Diffusion  

NSDL National Science Digital Library

Diffusion is the net movement of particles from areas of high concentration (number of particles per unit area) to low concentration. In this activity, students use a molecular dynamics model to view the behavior of diffusion in gases and liquids.

2012-07-19

138

Development of Enhanced Electric Arc Furnace Models for Transient Analysis Gilsoo Jang  

E-print Network

- plement the chaotic load models in the EMTP--Electromagnetic Transients Program. The simulation results impact on the power system. Some researchers used the stochastic models to represent the operation-shaped chaotic model uses the patterns detected in the EAF current to characterize its variation. In addition

139

Enhanced selectivity of MOSFET gas sensors by systematical analysis of transient parameters  

Microsoft Academic Search

Transient response curves from Pt-MOSFET gas sensors exposed to mixtures of hydrogen and ethanol were studied. Parameters of two types were extracted from the response curves: simple parameters like pulse heights, derivatives and integrals, and coefficients from different curve fitting algorithms. All parameters were evaluated with respect to their signal to standard deviation ratio, the correlations in a principal component

Tomas Eklöv; Per Mårtensson; Ingemar Lundström

1997-01-01

140

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

PubMed Central

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

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

141

Discovery and characterization of super-enhancer-associated dependencies in diffuse large B cell lymphoma.  

PubMed

Diffuse large B cell lymphoma (DLBCL) is a biologically heterogeneous and clinically aggressive disease. Here, we explore the role of bromodomain and extra-terminal domain (BET) proteins in DLBCL, using integrative chemical genetics and functional epigenomics. We observe highly asymmetric loading of bromodomain 4 (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

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

2013-12-01

142

Combustion and radiation characteristics of oxygen-enhanced inverse diffusion flame  

Microsoft Academic Search

The characteristics of combustion and radiation heat transfer of an oxygen-enhanced diffusion flame was experimentally analyzed.\\u000a An infrared radiation heat flux gauge was used to measure the thermal radiation of various types of flames with fuel, air\\u000a and pure oxygen. And the Laser Induced Incandescence (LII) technique was applied to characterize the soot concentrations which\\u000a mainly contribute to the continuum

Sang Soon Hwang; Jay P Gore

2002-01-01

143

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

SciTech Connect

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.

Turinsky, P.J.; Al-Chalabi, R.M.K.; Engrand, P.; Sarsour, H.N.; Faure, F.X.; Guo, W. [North Carolina State Univ., Raleigh, NC (United States)

1994-06-01

144

Enhancement of the superfluid transition temperature in liquid 3He due to transient polarization  

NASA Astrophysics Data System (ADS)

We have produced polarized liquid 3He by rapid melting of polarized solid 3He grown from the superfluid phase. The superfluid transition temperature of transiently polarized 3He is shown to be above the equilibrium transition tempearture in the external field of 9.2 T. The quadratic term in the increase of the transition temperature with polarization seems lower than is predicted recently.

Wiegers, S. A. J.; Hata, T.; Van de Haar, P. G.; Roobol, L. P.; Van Woerkens, C. M. C. M.; Jochemsen, R.; Frossati, G.

1990-08-01

145

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

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

146

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

SciTech Connect

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.

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

1999-01-01

147

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

NASA Astrophysics Data System (ADS)

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

Wang, Bo; Jiang, Shaosong; Zhang, Kaifeng

2012-09-01

148

Does diffusion-weighted magnetic resonance imaging enable detection of early ischemic change following transient cerebral ischemia?  

Microsoft Academic Search

To examine the usefulness of diffusion-weighted imaging for detecting neuronal damage following ischemia, dynamic changes in diffusion-, T1- and T2-weighted images of rats subjected to 10 min of 4-vessel occlusion and of humans who had suffered 10–20 min of cardiac arrest were observed. In rats, no remarkable alteration was observed on day 1. On day 3, however, diffusion-weighted images showed

Hidero Kawahara; Yoshimasa Takeda; Akio Tanaka; Osamu Nagano; Hiroshi Katayama; Masahisa Hirakawa; Yoshio Hiraki

2000-01-01

149

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

NASA Astrophysics Data System (ADS)

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, ?, 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.

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

2009-10-01

150

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

PubMed

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. PMID:23218277

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

2013-01-30

151

Entropy-driven enhanced self-diffusion in confined reentrant supernematics.  

PubMed

We present a molecular dynamics study of reentrant nematic phases using the Gay-Berne-Kihara model of a liquid crystal in nanoconfinement. At densities above those characteristic of smectic A phases, reentrant nematic phases form that are characterized by a large value of the nematic order parameter S?1. Along the nematic director these "supernematic" phases exhibit a remarkably high self-diffusivity, which exceeds that for ordinary, lower-density nematic phases by an order of magnitude. Enhancement of self-diffusivity is attributed to a decrease of rotational configurational entropy in confinement. Recent developments in the pulsed field gradient NMR technique are shown to provide favorable conditions for an experimental confirmation of our simulations. PMID:21231424

Mazza, Marco G; Greschek, Manuel; Valiullin, Rustem; Kärger, Jörg; Schoen, Martin

2010-11-26

152

Enhanced Diffusion, Chemotaxis, and Pumping by Active Enzymes: Progress toward an Organizing Principle of Molecular Machines.  

PubMed

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

Astumian, R Dean

2014-12-23

153

Entropy-Driven Enhanced Self-Diffusion in Confined Reentrant Supernematics  

NASA Astrophysics Data System (ADS)

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

Mazza, Marco G.; Greschek, Manuel; Valiullin, Rustem; Kärger, Jörg; Schoen, Martin

2010-11-01

154

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

PubMed Central

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

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

2012-01-01

155

Single file diffusion enhancement in a fluctuating modulated quasi-1D channel  

NASA Astrophysics Data System (ADS)

We show that the diffusion of a single file of particles moving in a fluctuating modulated quasi-1D channel is enhanced with respect to the one in a bald pipe. This effect, induced by the fluctuations of the modulation, is favoured by the incommensurability between the channel potential modulation and the moving file periodicity. This phenomenon could be of importance in order to optimize the critical current in superconductors, in particular in the case where mobile vortices move in 1D channels designed by patterns of pinning sites.

Coupier, G.; Saint Jean, M.; Guthmann, C.

2007-03-01

156

Enhancement of mixing and adsorption in microfluidic devices by shear-induced diffusion and topography-induced secondary flow  

NASA Astrophysics Data System (ADS)

Continuum simulations are used to assess the effects of shear-induced diffusion and secondary flow kinematics on the enhancement of mixing and adsorption during flow of suspensions in microfluidic channels. Unidirectional flow in rectangular channels is considered, as well as flow in channels with a topographically patterned wall that generates transverse flow. Patterns that lead both to chaotic and nonchaotic kinematics are considered. Effects of shear-induced diffusion due to the presence of suspended particles are incorporated via an empirical shear-rate dependent diffusivity. It is observed that for the bulk mixing case the most significant enhancement is due to convection. Channels with chaotic flow have the best mixing characteristics, followed by channels with swirling, nonchaotic flow. Only a small increase in mixing due to shear-induced diffusion is observed. For the case of adsorption from the bulk to a channel wall, on the other hand, it is observed that the most significant enhancement is due to shear-induced diffusion. Channels with secondary flows, both chaotic and nonchaotic, circulate solute-depleted fluid away from the adsorbing boundary but this is not sufficient to guarantee high fluxes toward the surface when the diffusivities are small. The most effective way to enhance adsorption is through the combination of both secondary flow and shear-induced diffusion. Secondary flow circulates fluid between bulk and boundary layer, while shear-induced diffusion enhances transport across the boundary layer. Nevertheless, under the large Peclet number conditions considered here, only a maximum of 30% of the solute is adsorbed to the surface for channels with length of 300 channel heights; for smooth channels without shear-induced diffusion this fraction is only 3%.

Lopez, Mauricio; Graham, Michael D.

2008-05-01

157

Transient MR Signal Changes in Patients with Generalized Tonicoclonic Seizure or Status Epilepticus: Periictal Diffusion-weighted Imaging  

Microsoft Academic Search

BACKGROUND AND PURPOSE:Our purpose was to investigate transient MR signal chang- es on periictal MR images of patients with generalized tonicoclonic seizure or status epilepticus and to evaluate the clinical significance of these findings for differential diagnosis and under- standing of the pathophysiology of seizure-induced brain changes. METHODS: Eight patients with MR images that were obtained within 3 days after

Jeong-Ah Kim; Jin Il Chung; Pyeong Ho Yoon; Dong Ik Kim; Tae-Sub Chung; Eun-Ju Kim; Eun-Kee Jeong

158

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

PubMed Central

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

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

2014-01-01

159

Transient Inhibition of ATM Kinase Is Sufficient to Enhance Cellular Sensitivity to Ionizing Radiation  

Microsoft Academic Search

In response to DNA damage, the ATM protein kinase activates signal transduction pathways essential for coordinating cell cycle progression with DNA repair. In the human disease ataxia-telangiectasia, mutation of the ATM gene results in multiple cellular defects, including enhanced sensitivity to ionizing radiation (IR). This phenotype highlights ATM as a potential target for novel inhibitors that could be used to

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

2008-01-01

160

Pharmacological enhancement of disc diffusion and differentiation of healthy, ageing and degenerated discs  

PubMed Central

Degenerative disc disease (DDD) is still a poorly understood phenomenon because of the lack of availability of precise definition of healthy, ageing and degenerated discs. Decreased nutrition is the final common pathway for DDD and the status of the endplate (EP) plays a crucial role in controlling the extent of diffusion, which is the only source of nutrition. The vascular channels in the subchondral plate have muscarinic receptors but the possibility of enhancing diffusion pharmacologically by dilation of these vessels has not been probed. Although it is well accepted that EP damage will affect diffusion and thereby nutrition, there is no described method to quantify the extent of EP damage. Precise definitions with an objective method of differentiating healthy, ageing and degenerated discs on the basis of anatomical integrity of the disc and physiological basis of altered nutrition will be useful. This information is an urgent necessity for better understanding of DDD and also strategizing prevention and treatment. Seven hundred and thirty endplates of 365 lumbar discs from 73 individuals (26 healthy volunteers and 47 patients) with age ranging from 10–64 years were evaluated by pre-contrast and 10 min, 2, 4, 6 and 12 h post contrast MRI after IV injection of 0.3 mmol/kg of Gadodiamide. End plates were classified according to the extent of damage into six grades and an incremental score was given for each category. A total endplate score (TEPS) was derived by adding the EP score of the two endplates for each concerned disc. The base line value (SIbase) and the signal intensity at particular time periods were used to derive the enhancement percentage for each time period (Enhancement (%) = SItp – SIbase/SIbase × 100). The enhancement percentage for each time period, the time for peak enhancement (T-max) and the time intensity curve (TIC) over 12 h were used to study and compare the diffusion characteristics. The differences in pattern of diffusion were obvious visually at 4 h which was categorized into five patterns—Pattern A representing normal diffusion to Pattern E representing a total abnormality in diffusion. Degeneration was classified according to Pfirrmann’s grading and this was correlated to the TEPS and the alterations in diffusion patterns. The relationship of TEPS on the increase in DDD was evaluated by a logistic curve and the cut point for severe DDD was found by ROC curve. The influence of the variables of age, level, Modic changes, instability, annulus fibrosis defect (DEBIT), TEPS and diffusion patterns on DDD was analyzed by multiple and stepwise regression analysis. Oral nimodipine study: Additional forty lumbar end-plates from four young healthy volunteers were studied to document the effect of oral nimodipine. Pre-drug diffusion levels were studied by pre and post contrast MRI (0.3 mmol/kg of gadodiamide) at 10 min, 2, 4, 6, 12 and 24 h. Oral nimodipine was administered (30 mg QID) for 5 days and post-contrast MRI studies were performed similarly. Enhancement was calculated at vertebral body-VB; subchondral bone-SCB; Endplate Zone-EPZ and at superior and inferior peripheral nucleus pulposus-PNP and central nucleus pulposus-CNP, using appropriate cursors by a blinded investigator. Paired sample t test and area under curve (AUC) measurements were done. The incidence of disc degeneration had a significant correlation with increasing TEPS (Trend Chi-square, P < 0.01). Only one out of 83 (1.2%) disc had either Pfirrmann Grade IV or V when the score was 4 or below when compared to 34/190 (17.9%) for scores 5–7; 41 of 72 (56.9%) for scores 8–10 and 18 of 20 (90%) for scores 11 and 12 (P < 0.001 for all groups). Pearson’s correlation between TEPS and DDD was statistically significant, irrespective of the level of disc or different age groups (r value was above 0.6 and P < 0.01 for all age groups). Logistic curve fit analysis and R

Venkatadass, K.; Naresh Babu, J.; Ganesh, K.; Shetty, Ajoy P.

2008-01-01

161

Enhanced Li adsorption and diffusion in single-walled silicon nanotubes: an ab initio study.  

PubMed

We report a first-principles investigation of Li adsorption and diffusion in single-walled Si nanotubes (SWSiNTs) of interest to Li-ion battery anodes. We calculate Li insertion characteristics in SWSiNTs and compare them with the respective ones in carbon nanotubes (CNTs) and other silicon nanostructures. From our calculations, SWSiNTs show higher reactivity toward the adsorption of Li adatoms than CNTs and Si nanoclusters. Considering the importance of Li kinetics, we demonstrate that the interior of SWSiNTs may serve as a fast Li diffusion channel. The important advantage of SWSiNTs over their carbon analogues is a sevenfold reduction in the energy barrier for the penetration of the Li atoms into the nanotube interior through the sidewalls. This prepossesses easier Li diffusion inside the tube and subsequent utilization of the interior sites, which enhances Li storage capacity of the system. The improvements in both Li uptake and Li mobility over their analogues support the great potential of SWSiNTs as Li-ion battery anodes. PMID:23564742

Kulish, Vadym V; Ng, Man-Fai; Malyi, Oleksandr I; Wu, Ping; Chen, Zhong

2013-04-15

162

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

SciTech Connect

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

Kruk, D., E-mail: danuta.kruk@matman.uwm.edu.pl [Faculty of Mathematics and Computer Science, University of Warmia and Mazury in Olsztyn, S?oneczna 54, 10-710 Olsztyn (Poland); Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth (Germany); Korpa?a, A. [Department of Biophysics, Jagiellonian University Medical College, ?azarza 16, 31-530 Kraków (Poland) [Department of Biophysics, Jagiellonian University Medical College, ?azarza 16, 31-530 Kraków (Poland); Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków (Poland); Taheri, S. Mehdizadeh; Förster, S. [Department of Physical Chemistry I, Universität Bayreuth, 95440 Bayreuth (Germany)] [Department of Physical Chemistry I, Universität Bayreuth, 95440 Bayreuth (Germany); Koz?owski, A. [NU-MED Group Inc., Center of Radiotherapy and Improvements in Elbl?g, Królewiecka 146, 82-300 Elbl?g (Poland)] [NU-MED Group Inc., Center of Radiotherapy and Improvements in Elbl?g, Królewiecka 146, 82-300 Elbl?g (Poland); Rössler, E. A. [Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth (Germany)] [Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth (Germany)

2014-05-07

163

Multispecies diffusion models: A study of uranyl species diffusion  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

164

Fermi\\/GBM Detection of Transient Enhanced Emission from SGR J1550-5418  

Microsoft Academic Search

On 2009 January 22, SGR J1550-5418 (previously known as AXP 1E 1547.0-5408) went into a very active bursting episode, and Fermi\\/GBM detected ˜450 bursts from this source on this day alone. Within the GBM data at the onset of this intense bursting period, we identified underlying enhanced persistent emission with coherent pulsation. We present the detailed timing and spectral analysis

Yuku Kaneko; Ersin Gogus; Chryssa Kouveliotou; Jonathan Granot; Enrico Ramirez-Ruiz; Alexander J. van der Horst; Anna L. Watts; Mark H. Finger; Neil Gehrels; Asaf Pe'Er; Michiel van der Klis; Andreas von Kienlin; Stefanie Wachter; Colleen A. Wilson-Hodge; Peter M. Woods

2010-01-01

165

Enhanced activation of the transient receptor potential channel TRPA1 by ajoene, an allicin derivative.  

PubMed

TRPA1 is a calcium-permeable, nonselective cation channel expressed in the dorsal root ganglion and trigeminal ganglia nociceptive neurons. It is activated by the pungent compounds in mustard oil (AITC, allyl isothiocyanate), cinnamon (cinnamaldehyde), garlic (allicin), and is believed to mediate the inflammatory actions of environmental irritants and proalgesic agents. Thiosulfinate (allicin) and isothiocyanate (AITC) compounds contain reactive electrophilic chemical groups that react with cysteine residues within the TRPA1 channel N terminus, leading to channel activation. Ajoene also contains reactive electrophilic chemical groups likely to target TRPA1 channel. Here, we have used voltage-clamp recordings to show that TRPA1-responses are enhanced by ajoene application in a Xenopus oocyte expression system. Though ajoene alone did not activate TRPA1, subsequent application of ajoene enhanced the AITC-, allicin- and depolarization-induced responses of TRPA1. Moreover, when increasing concentrations of ajoene were applied along with constant concentrations of allicin or AITC, stronger responses were elicited. These findings suggest that ajoene is a novel TRPA1 channel enhancer, operating in a channel-opening-dependent manner. PMID:19808063

Yassaka, Ricardo Tsuneo; Inagaki, Hidetoshi; Fujino, Tsuchiyoshi; Nakatani, Kei; Kubo, Tai

2010-01-01

166

Diffusion  

NSDL National Science Digital Library

Diffusion is the movement of particles from an area of high concentration to an area of low concentration. The molecules move until equilibrium is reached. If a perfume is sprayed on one side of the room, the perfume molecules will eventually spread out all over the room until there are equal concentrations of the molecules throughout the space.

Christopher Thomas (None;)

2006-11-09

167

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

SciTech Connect

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

Fred J. Molz, III

2010-05-28

168

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

PubMed Central

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

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

2014-01-01

169

Diffusion  

NSDL National Science Digital Library

Since the advent of the internet, a number of artists and related organizations have become interested in utilizing the web to promulgate new forms of artistic creation and their subsequent dissemination. Supported by the Arts Council of England, these Diffusion eBooks are essentially pdf files that readers can download, print out and make into booklets. As the site suggests, "the Diffusion format challenges conventions of interactivity-blending the physical and the virtual and breaking the dominance of mouse and screen as the primary forms of human computer interaction...the format's aim is to take the reader away from the screen and computer and engage them in the process of production." There are a number of creative booklets available here for visitors, complete with instruction on how to assemble them for the desired effect. For anyone with even a remote interest in the possibilities afforded by this rather curious new form of expression, this website is worth a look.

170

Diffusivity transients and radiative recombination in intermixed In0.5Ga0.5As/GaAs quantum structures  

NASA Astrophysics Data System (ADS)

The effects of thermally induced compositional disordering on the luminescence from two-dimensional and zero-dimensional In0.5Ga0.5As/GaAs structures are examined. Quantum-mechanical numerical calculations modeling changes in the quantum-well (QW) confining potential with interdiffusion have been used to obtain values for diffusivities. These show transient behavior. Activation energies for interdiffusion (3.5+/-0.3 eV) are found to be similar to values reported for low-indium-content InxGa1-xAs/GaAs QW's. In quantum-dot structures, larger blueshifts can be obtained than in QW's under similar conditions. Interdiffusion decreased activation energies for radiative recombination, reflecting changes in confining potentials, and affecting lifetime ratios in recombination processes. The latter were observed in all intermixed heterostructures regardless of dimensionality.

Leon, R.; Williams, D. R. M.; Krueger, J.; Weber, E. R.; Melloch, M. R.

1997-08-01

171

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

PubMed

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. PMID:24928353

Pan, Y-Z; Rutecki, P A

2014-09-01

172

Recurrent transient apical cardiomyopathy (tako-tsubo-like left ventricular dysfunction) in a postmenopausal female with diffuse esophageal spasms.  

PubMed

Transient apical cardiomyopathy, also known as Takot-tsubo-like left ventricular dysfunction, is a clinical syndrome characterized by reversible left ventricular dysfunction at the apex with preserved basal contractility, in the setting of new ST and T wave changes suggestive of ischemia but no evidence of obstructive coronary artery disease on angiography. The main mechanism appears to be intense neuroadrenergic myocardial stimulation with endothelial dysfunction of the coronary vasculature. It has been noted that patients with esophageal spasms also have a tendency for coronary spasms. We present the case of a postmenopausal female with documented severe esophageal spasms who presented with atypical angina and recurrent Tako-tsubo cardiomyopathy. PMID:24695751

Brenes Salazar, Jorge A

2013-10-01

173

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

PubMed Central

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

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

2014-01-01

174

Enhancement of Terrestrial Diffuse X-Ray Emission Associated with Coronal Mass Ejection and Geomagnetic Storm  

NASA Astrophysics Data System (ADS)

We present an analysis of a Suzaku observations taken during the geomagnetic storm of 2005 August 23-24. We found a time variation of diffuse soft X-ray emission when a coronal mass ejection hit Earth and caused a geomagnetic storm. The diffuse emission consisted of fluorescent scattering of solar X-rays and an exospheric solar wind charge exchange. The former is characterized by a neutral oxygen emission line due to strong heating of the upper atmosphere during the storm time, while the latter is dominated by the sum of C V, C VI, N VI, N VII, O VII, and O VIII emission lines due to an enhanced solar wind flux in the vicinity of the exosphere. Using the solar-wind data taken with the ACE and WIND satellites, a time correlation between the solar wind and the strong O VII line flux was investigated. We estimated necessary column densities for the solar X-ray scattering and exospheric SWCX. From these results, we argue that a part of the solar-wind ions enters inside the magnetosphere and causes the SWCX reaction.

Ezoe, Yuichiro; Miyoshi, Yoshizumi; Yoshitake, Hiroshi; Mitsuda, Kazuhisa; Terada, Naoki; Oishi, Shihoko; Ohashi, Takaya

2011-11-01

175

Saikosaponin a Enhances Transient Inactivating Potassium Current in Rat Hippocampal CA1 Neurons  

PubMed Central

Saikosaponin a (SSa), a main constituent of the Chinese herb Bupleurum chinense DC., has been demonstrated to have antiepileptic activity. Recent studies have shown that SSa could inhibit NMDA receptor current and persistent sodium current. However, the effects of SSa on potassium (K+) currents remain unclear. In this study, we tested the effect of SSa on 4AP-induced epileptiform discharges and K+ currents in CA1 neurons of rat hippocampal slices. We found that SSa significantly inhibited epileptiform discharges frequency and duration in hippocampal CA1 neurons in the 4AP seizure model in a dose-dependent manner with an IC50 of 0.7??M. SSa effectively increased the amplitude of ITotal and IA, significantly negative-shifted the activation curve, and positive-shifted steady-state curve of IA. However, SSa induced no significant changes in the amplitude and activation curve of IK. In addition, SSa significantly increased the amplitude of 4AP-sensitive K+ current, while there was no significant change in the amplitude of TEA-sensitive K+ current. Together, our data indicate that SSa inhibits epileptiform discharges induced by 4AP in a dose-dependent manner and that SSa exerts selectively enhancing effects on IA. These increases in IA may contribute to the anticonvulsant mechanisms of SSa. PMID:23554830

Xie, Wei; Yu, Yun Hong; Du, Yong Ping; Zhao, Yun Yan; Li, Chang Zheng; Yu, Lin; Duan, Jian Hong; Xing, Jun Ling

2013-01-01

176

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

NASA Astrophysics Data System (ADS)

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

Atabaki, M. Mazar

2010-11-01

177

Solvent-enhanced dye diffusion in polymer thin films for color tuning of organic light-emitting diodes  

E-print Network

only one color. Ink-jet printing of polymer solution,4­7 or screen printing of the polymer8 have been-jet printing of a dye solution on a substrate previously coated with polymer,9 or photobleaching of a dye.10Solvent-enhanced dye diffusion in polymer thin films for color tuning of organic light

178

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

NASA Astrophysics Data System (ADS)

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

Gischig, Valentin S.; Wiemer, Stefan

2013-08-01

179

A feed-forward artificial neural network with enhanced feature selection for power system transient stability assessment  

Microsoft Academic Search

This paper describes an approach where an artificial neural network is used to predict the stability status of the power system. This efficient and robust approach combines the advantages of the time–domain integration schemes and artificial neural network for on-line transient stability assessment of the power system. The transient stability index has been obtained by the extended equal area criterion

Harinder Sawhney; B. Jeyasurya

2006-01-01

180

Hepatic Cavernous Hemangiomas: Relationship between Speed of Intratumoral Enhancement during Dynamic MRI and Apparent Diffusion Coefficient on Diffusion-Weighted Imaging  

PubMed Central

Objective To investigate the relationships between the apparent diffusion coefficients (ADCs) on diffusion-weighted imaging (DWI) and the speed of contrast-enhancement in hepatic hemangiomas. Materials and Methods Sixty-nine hepatic hemangiomas (? 1 cm) were evaluated with DWI, by using multiple b values (b = 50, 400, 800 s/mm2), followed by a gadolinium-enhanced dynamic MRI. The lesions were classified into three groups, according to the speed of contrast-enhancement on the portal phase. ADCs were measured on the ADC map automatically, and were calculated by using the two different b values (mADC50-400 with b values = 50 and 400; mADC400-800 with b values = 400 and 800 s/mm2). Results The mean ADCs (× 10-3 mm2/s) were significantly higher in the rapid group (1.9 ± 0.44) than in the intermediate (1.7 ± 0.35, p = 0.046) or the slow groups (1.4 ± 0.34, p = 0.002). There were significant differences between the rapid and the slow groups in mADC50-400 (2.12 vs. 1.48; p = 0.008) and mADC400-800 (1.68 vs. 1.22, p = 0.010), and between the rapid and the intermediate groups in mADC50-400 (2.12 vs. 1.79, p = 0.049). Comparing mADC50-400 with mADC400-800, there was a significant difference only in the rapid group (p = 0.001). Conclusion Higher ADCs of rapidly-enhancing hemangiomas may be related to richer intralesional vascular perfusion. Also, the restricted diffusion may be attributed to the difference of structural characteristics of hemangioma. PMID:23118571

Nam, Se Jin; Park, Kae Young; Chung, Jae-Joon; Kim, Joo Hee; Kim, Ki Whang

2012-01-01

181

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

PubMed

Diffusion anisotropy is a critical property in predicting migration of substances in sedimentary formations with very low permeability. The diffusion anisotropy of sedimentary rocks has been evaluated mainly from laboratory diffusion experiments, in which the directional diffusivities are separately estimated by through-diffusion experiments using different rock samples, or concurrently by in-diffusion experiments in which only the tracer profile in a rock block is measured. To estimate the diffusion anisotropy from a single rock sample, this study proposes an axisymmetric diffusion test, in which tracer diffuses between a cylindrical rock sample and a surrounding solution reservoir. The tracer diffusion between the sample and reservoir can be monitored from the reservoir tracer concentrations, and the tracer profile could also be obtained after dismantling the sample. Semi-analytical solutions are derived for tracer concentrations in both the reservoir and sample, accounting for an anisotropic diffusion tensor of rank two as well as the dilution effects from sampling and replacement of reservoir solution. The transient and steady-state analyses were examined experimentally and numerically for different experimental configurations, but without the need for tracer profiling. These experimental configurations are tested for in- and out-diffusion experiments using Koetoi and Wakkanai mudstones and Shirahama sandstone, and are scrutinized by a numerical approach to identify favorable conditions for parameter estimation. The analysis reveals the difficulty in estimating diffusion anisotropy; test configurations are proposed for enhanced identifiability of diffusion anisotropy. Moreover, it is demonstrated that the axisymmetric diffusion test is efficient in obtaining the sorption parameter from both steady-state and transient data, and in determining the effective diffusion coefficient if isotropic diffusion is assumed. Moreover, measuring reservoir concentrations in an axisymmetric diffusion experiment coupled with tracer profiling may be a promising approach to estimate of diffusion anisotropy of sedimentary rocks. PMID:21288593

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

2011-04-25

182

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

SciTech Connect

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

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

2011-02-01

183

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

SciTech Connect

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.

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

2012-05-01

184

Pyruvate Induces Transient Tumor Hypoxia by Enhancing Mitochondrial Oxygen Consumption and Potentiates the Anti-Tumor Effect of a Hypoxia-Activated Prodrug TH-302  

PubMed Central

Background TH-302 is a hypoxia-activated prodrug (HAP) of bromo isophosphoramide mustard that is selectively activated within hypoxic regions in solid tumors. Our recent study showed that intravenously administered bolus pyruvate can transiently induce hypoxia in tumors. We investigated the mechanism underlying the induction of transient hypoxia and the combination use of pyruvate to potentiate the anti-tumor effect of TH-302. Methodology/Results The hypoxia-dependent cytotoxicity of TH-302 was evaluated by a viability assay in murine SCCVII and human HT29 cells. Modulation in cellular oxygen consumption and in vivo tumor oxygenation by the pyruvate treatment was monitored by extracellular flux analysis and electron paramagnetic resonance (EPR) oxygen imaging, respectively. The enhancement of the anti-tumor effect of TH-302 by pyruvate treatment was evaluated by monitoring the growth suppression of the tumor xenografts inoculated subcutaneously in mice. TH-302 preferentially inhibited the growth of both SCCVII and HT29 cells under hypoxic conditions (0.1% O2), with minimal effect under aerobic conditions (21% O2). Basal oxygen consumption rates increased after the pyruvate treatment in SCCVII cells in a concentration-dependent manner, suggesting that pyruvate enhances the mitochondrial respiration to consume excess cellular oxygen. In vivo EPR oxygen imaging showed that the intravenous administration of pyruvate globally induced the transient hypoxia 30 min after the injection in SCCVII and HT29 tumors at the size of 500–1500 mm3. Pretreatment of SCCVII tumor bearing mice with pyruvate 30 min prior to TH-302 administration, initiated with small tumors (?550 mm3), significantly delayed tumor growth. Conclusions/Significance Our in vitro and in vivo studies showed that pyruvate induces transient hypoxia by enhancing mitochondrial oxygen consumption in tumor cells. TH-302 therapy can be potentiated by pyruvate pretreatment if started at the appropriate tumor size and oxygen concentration. PMID:25254649

Takakusagi, Yoichi; Matsumoto, Shingo; Saito, Keita; Matsuo, Masayuki; Kishimoto, Shun; Wojtkowiak, Jonathan W.; DeGraff, William; Kesarwala, Aparna H.; Choudhuri, Rajani; Devasahayam, Nallathamby; Subramanian, Sankaran; Munasinghe, Jeeva P.; Gillies, Robert J.; Mitchell, James B.; Hart, Charles P.; Krishna, Murali C.

2014-01-01

185

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

PubMed Central

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

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

2006-01-01

186

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

PubMed

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

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

2006-01-01

187

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

NASA Astrophysics Data System (ADS)

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

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

1999-01-01

188

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

Microsoft Academic Search

We have experimentally assessed the quantitative nature of planar laser-induced fluorescence (PLIF) measurements of NO concentration in an atmospheric-pressure, laminar, inverse diffusion flame (IDF). The PLIF measurements were assessed relative to a two-dimensional array of separate laser-saturated fluorescence (LSF) measurements. Furthermore, we have proposed, demonstrated and evaluated several experimentally -based procedures for enhancing the quantitative nature of PLIF concentration images.

William Powell Partridge Jr.

1995-01-01

189

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

PubMed Central

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

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

2014-01-01

190

The Experience of Using a Neural Assistor to Enhance the Transient Characteristics of well-defined Control Systems  

Microsoft Academic Search

Neural networks (NN) as controllers, are generally nonlinear ones in nature, the input command range in such a system is limited in advance. For different input, the controller may behave in different way. A NN can be used together with a conventional controller such as a PID one, in this condition; NN can further improve the transient of the control

PenChen Chou; TsiChow Chang; TsiChian Hwang

2006-01-01

191

Convection-enhanced delivery of topotecan into diffuse intrinsic brainstem tumors in children.  

PubMed

Convection-enhanced delivery (CED) for the treatment of malignant gliomas is a technique that can deliver chemotherapeutic agents directly into the tumor and the surrounding interstitium through sustained, low-grade positive-pressure infusion. This allows for high local concentrations of drug within the tumor while minimizing systemic levels that often lead to dose-limiting toxicity. Diffuse intrinsic pontine gliomas (DIPGs) are universally fatal childhood tumors for which there is currently no effective treatment. In this report the authors describe CED of the topoisomerase inhibitor topotecan for the treatment of DIPG in 2 children. As part of a pilot feasibility study, the authors treated 2 pediatric patients with DIPG. Stereotactic biopsy with frozen section confirmation of glial tumor was followed by placement of bilateral catheters for CED of topotecan during the same procedure. The first patient underwent CED 210 days after initial diagnosis, after radiation therapy and at the time of tumor recurrence, with a total dose of 0.403 mg in 6.04 ml over 100 hours. Her Karnofsky Performance Status (KPS) score was 60 before CED and 50 posttreatment. Serial MRI initially demonstrated a modest reduction in tumor size and edema, but the tumor progressed and the patient died 49 days after treatment. The second patient was treated 24 days after the initial diagnosis prior to radiation with a total dose of 0.284 mg in 5.30 ml over 100 hours. Her KPS score was 70 before CED and 50 posttreatment. Serial MRI similarly demonstrated an initial modest reduction in tumor size. The patient subsequently underwent fractionated radiation therapy, but the tumor progressed and she died 120 days after treatment. Topotecan delivered by prolonged CED into the brainstem in children with DIPG is technically feasible. In both patients, high infusion rates (> 0.12 ml/hr) and high infusion volumes (> 2.8 ml) resulted in new neurological deficits and reduction in the KPS score, but lower infusion rates (< 0.04 ml/hr) were well tolerated. While serial MRI showed moderate treatment effect, CED did not prolong survival in these 2 patients. More studies are needed to improve patient selection and determine the optimal flow rates for CED of chemotherapeutic agents into DIPG to maximize safety and efficacy. Clinical trial registration no.: NCT00324844. PMID:23240851

Anderson, Richard C E; Kennedy, Benjamin; Yanes, Candix L; Garvin, James; Needle, Michael; Canoll, Peter; Feldstein, Neil A; Bruce, Jeffrey N

2013-03-01

192

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

NASA Astrophysics Data System (ADS)

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.

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

2004-07-01

193

Diffusion kurtosis imaging and log-normal distribution function imaging enhance the visualisation of lesions in animal stroke models.  

PubMed

In this work, we report a case study of a stroke model in animals using two methods of quantification of the deviations from Gaussian behaviour: diffusion kurtosis imaging (DKI) and log-normal distribution function imaging (LNDFI). The affected regions were predominantly in grey rather than in white matter. The parameter maps were constructed for metrics quantifying the apparent diffusivity (evaluated from conventional diffusion tensor imaging, DKI and LNDFI) and for those quantifying the degree of deviations (mean kurtosis and a parameter ? characterising the width of the distribution). We showed that both DKI and LNDFI were able to dramatically enhance the visualisation of ischaemic lesions in comparison with conventional methods. The largest relative change in the affected versus healthy regions was observed in the mean kurtosis values. The average changes in the mean kurtosis and ? values in the lesions were a factor of two to three larger than the relative changes observed in the mean diffusivity. In conclusion, the applied methods promise valuable perspectives in the assessment of stroke. PMID:22461260

Grinberg, Farida; Ciobanu, Luisa; Farrher, Ezequiel; Shah, N Jon

2012-11-01

194

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

195

Dual Orexin Actions on Dorsal Raphe and Laterodorsal Tegmentum Neurons: Noisy Cation Current Activation and Selective Enhancement of Ca2+ Transients Mediated by L-Type Calcium Channels  

PubMed Central

The hypocretin/orexins (Hcrt/Orxs) are hypothalamic neuropeptides that regulate stress, addiction, feeding, and arousal behaviors. They depolarize many types of central neurons and can increase [Ca2+]i in some, including those of the dorsal raphe (DR) and laterodorsal tegmental (LDT) nuclei—two structures likely to contribute to the behavioral actions of Hcrt/Orx. In this study, we used simultaneous whole cell and Ca2+-imaging methods in mouse brain slices to compare the Hcrt/Orx-activated current in DR and LDT neurons and to determine whether it contributes to the Ca2+ influx evoked by Hcrt/Orx. We found Hcrt/Orx activates a similar noisy cation current that reversed near 0 mV in both cell types. Contrary to our expectation, this current did not contribute to the somatic Ca2+ influx evoked by Hcrt/Orx. In contrast, Hcrt/Orx enhanced the Ca2+ transients produced by voltage steps (?60 to ?30 mV) by ?30% even in neurons lacking an inward current. This effect was abolished by nifedipine, augmented by Bay-K and abolished by bisindolylmaleimide I. Thus Hcrt/Orx has two independent actions: activation of noisy cation channels that generate depolarization and activation of a protein kinase C (PKC)-dependent enhancement of Ca2+ transients mediated by L-type Ca2+ channels. Immunocytochemistry verified that both these actions occurred in serotonergic and cholinergic neurons, indicating that Hcrt/Orx can function as a neuromodulator in these key neurons of the reticular activating system. Because regulation of Ca2+ transients mediated by L-channels is often linked to the control of transcriptional signaling, our findings imply that Hcrt/Orxs may also function in the regulation of long-term homeostatic or trophic processes. PMID:18667550

Kohlmeier, K. A.; Watanabe, S.; Tyler, C. J.; Burlet, S.; Leonard, C. S.

2008-01-01

196

Gas sensing enhancement of aluminum-doped ZnO nanovase structure with many gas facile diffusivity paths  

NASA Astrophysics Data System (ADS)

Al-doped ZnO nanovase structures were synthesized by thermal evaporation method with a fast temperature rise speed. It was found that there were a good amount of nanovase structures with a large aperture on the top of it and many short nanorods grew from their surface to generate many holes or channels enough for gas to quickly diffuse from surface to the inside of nanovase. Gas sensors were fabricated using the Al-doped ZnO nanostructures to examine the responses to 500 ppm C2H5OH, CO, NH3, and CH4 gases. The Al-doped ZnO nanovases exhibited a better response and selectivity toward ethanol as high as 34.1 at 300 °C. These results showed that Al-doped ZnO nanovases are highly promising for ethanol sensor applications, as the gas diffusion and mass transportation in sensing materials are significantly enhanced by their unique structures.

Lingmin, Yu; Xinhui, Fan; Lei, Cao; Lijun, Qi; Wen, Yan

2013-01-01

197

Myofibre segmentation in H&E stained adult skeletal muscle images using coherence-enhancing diffusion filtering  

PubMed Central

Background The correct segmentation of myofibres in histological muscle biopsy images is a critical step in the automatic analysis process. Errors occurring as a result of incorrect segmentations have a compounding effect on latter morphometric analysis and as such it is vital that the fibres are correctly segmented. This paper presents a new automatic approach to myofibre segmentation in H&E stained adult skeletal muscle images that is based on Coherence-Enhancing Diffusion filtering. Methods The procedure can be broadly divided into four steps: 1) pre-processing of the images to extract only the eosinophilic structures, 2) performing of Coherence-Enhancing Diffusion filtering to enhance the myofibre boundaries whilst smoothing the interior regions, 3) morphological filtering to connect unconnected boundary regions and remove noise, and 4) marker controlled watershed transform to split touching fibres. Results The method has been tested on a set of adult cases with a total of 2,832 fibres. Evaluation was done in terms of segmentation accuracy and other clinical metrics. Conclusions The results show that the proposed approach achieves a segmentation accuracy of 89% which is a significant improvement over existing methods. PMID:25352214

2014-01-01

198

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

DOEpatents

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.

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

199

Enhanced reliability of drift-diffusion approximation for electrons in fluid models for nonthermal plasmas  

SciTech Connect

Common fluid models used for the description of electron transport in nonthermal discharge plasmas are subject to substantial restrictions if the electron energy transport significantly influences the discharge behaviour. A drift-diffusion approach is presented which is based on a multiterm approximation of the electron velocity distribution function and overcomes some of these restrictions. It is validated using a benchmark model and applied for the analysis of argon discharge plasmas at low and atmospheric pressure. The results are compared to those of common drift-diffusion models as well as to experimental data. It is pointed out that fluid models are able to describe nonlocal phenomena caused by electron energy transport, if the energy transport is consistently described. Numerical difficulties that frequently occur when the conventional drift-diffusion model is consistently applied are avoided by the proposed method.

Becker, M. M.; Loffhagen, D. [Leibniz Institute for Plasma Science and Technology, Felix-Hausdorff-Str. 2, 17489 Greifswald (Germany)

2013-01-15

200

GLP-1 and Exendin-4 Transiently Enhance GABAA Receptor-Mediated Synaptic and Tonic Currents in Rat Hippocampal CA3 Pyramidal Neurons.  

PubMed

Glucagon-like peptide-1 (GLP-1) is a hormone that stimulates insulin secretion. Receptors for GLP-1 are also found in the brain, including the hippocampus, the center for memory and learning. Diabetes is a risk factor for decreased memory functions. We studied effects of GLP-1 and exendin-4, a GLP-1 receptor agonist, on ?-aminobutyric acid (GABA) signaling in hippocampal CA3 pyramidal neurons. GABA is the main inhibitory neurotransmitter and decreases neuronal excitability. GLP-1 (0.01-1 nmol/L) transiently enhanced synaptic and tonic currents, and the effects were blocked by exendin (9-39). Ten pmol/L GLP-1 increased both the spontaneous inhibitory postsynaptic current (sIPSC) amplitudes and frequency by a factor of ?1.8. In 0.1, 1 nmol/L GLP-1 or 10, 50, or 100 nmol/L exendin-4, only the sIPSC frequency increased. The tonic current was enhanced by 0.01-1 nmol/L GLP-1 and by 0.5-100 nmol/L exendin-4. When action potentials were inhibited by tetrodotoxin (TTX), inhibitory postsynaptic currents decreased and currents were no longer potentiated by GLP-1 or exendin-4. In contrast, although the tonic current decreased in TTX, it was still enhanced by GLP-1 or exendin-4. The results demonstrate GLP-1 receptor regulation of hippocampal function and are consistent with GLP-1 receptor agonists enhancing GABAA signaling by pre- and postsynaptic mechanisms. PMID:25114295

Korol, Sergiy V; Jin, Zhe; Babateen, Omar; Birnir, Bryndis

2015-01-01

201

Is 3-Tesla Gd-EOB-DTPA-Enhanced MRI with Diffusion-Weighted Imaging Superior to 64-Slice Contrast-Enhanced CT for the Diagnosis of Hepatocellular Carcinoma?  

PubMed Central

Objectives To compare 64-slice contrast-enhanced computed tomography (CT) with 3-Tesla magnetic resonance imaging (MRI) using Gd-EOB-DTPA for the diagnosis of hepatocellular carcinoma (HCC) and evaluate the utility of diffusion-weighted imaging (DWI) in this setting. Methods 3-phase-liver-CT was performed in fifty patients (42 male, 8 female) with suspected or proven HCC. The patients were subjected to a 3-Tesla-MRI-examination with Gd-EOB-DTPA and diffusion weighted imaging (DWI) at b-values of 0, 50 and 400 s/mm2. The apparent diffusion coefficient (ADC)-value was determined for each lesion detected in DWI. The histopathological report after resection or biopsy of a lesion served as the gold standard, and a surrogate of follow-up or complementary imaging techniques in combination with clinical and paraclinical parameters was used in unresected lesions. Diagnostic accuracy, sensitivity, specificity, and positive and negative predictive values were evaluated for each technique. Results MRI detected slightly more lesions that were considered suspicious for HCC per patient compared to CT (2.7 versus 2.3, respectively). ADC-measurements in HCC showed notably heterogeneous values with a median of 1.2±0.5×10?3 mm2/s (range from 0.07±0.1 to 3.0±0.1×10?3 mm2/s). MRI showed similar diagnostic accuracy, sensitivity, and positive and negative predictive values compared to CT (AUC 0.837, sensitivity 92%, PPV 80% and NPV 90% for MRI vs. AUC 0.798, sensitivity 85%, PPV 79% and NPV 82% for CT; not significant). Specificity was 75% for both techniques. Conclusions Our study did not show a statistically significant difference in detection in detection of HCC between MRI and CT. Gd-EOB-DTPA-enhanced MRI tended to detect more lesions per patient compared to contrast-enhanced CT; therefore, we would recommend this modality as the first-choice imaging method for the detection of HCC and therapeutic decisions. However, contrast-enhanced CT was not inferior in our study, so that it can be a useful image modality for follow-up examinations. PMID:25375778

Maiwald, Bettina; Lobsien, Donald; Kahn, Thomas; Stumpp, Patrick

2014-01-01

202

Significant Enhancement of Electronic Thermal Conductivity of Two-Dimensional Zero-Gap Systems by Bipolar-Diffusion Effect  

NASA Astrophysics Data System (ADS)

Electrical conductivity (?), thermopower (S), electronic thermal conductivity (?e), and Lorentz ratio (L = ?e/?T) are examined for two-dimensional (2D) zero-gap systems. The bipolar-diffusion (BD) effect in 2D Dirac cones is discussed for the first time. Semiclassical calculations show that L is enhanced by a factor of 200–400% as compared with the conventional Sommerfeld value L0 = 2.45 × 10?8 W·?·K?2 due to the BD effect. It is, however, shown that this enhancement is not due to the linear dispersion of the Dirac cones but due to the zero band gap and is widely expected to occur in all zero-gap systems under its charge neutrality condition. Calculations taking into account electron–hole puddles revealed that the BD effect is suppressed in pristine graphene devices affected by charged-impurity potentials.

Yoshino, Harukazu; Murata, Keizo

2015-02-01

203

Simulations of normal and inverse laminar diffusion flames under oxygen enhancement and gravity variation  

Microsoft Academic Search

Steady-state global chemistry calculations for 20 different flames were carried out using an axisymmetric Computational Fluid Dynamics (CFD) code. Computational results for 16 flames were compared with flame images obtained at the NASA Glenn Research Center. The experimental flame data for these 16 flames were taken from Sunderland et al. [4] which included normal and inverse diffusion flames of ethane

P. Bhatia; V. R. Katta; S. S. Krishnan; Y. Zheng; P. B. Sunderland; J. P. Gore

2012-01-01

204

ON THE COMBINED FORWARD AND BACKWARD ANISOTROPIC DIFFUSION SCHEME FOR THE MULTISPECTRAL IMAGE ENHANCEMENT  

E-print Network

ON THE COMBINED FORWARD AND BACKWARD ANISOTROPIC DIFFUSION SCHEME FOR THE MULTISPECTRAL IMAGE is proposed and evaluated. The new algorithm is based on the combined forward and backward anisotropic refers to time or iteration step in the dis- crete case and ´� Ý �µ is a monotonically decreasing con

Kedem, Klara

205

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

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.

Shiba, Takahiro; Tamai, Takuma; Sahara, Yurina; Kurohane, Kohta [Laboratory of Microbiology and Immunology, School of Pharmaceutical Sciences, University of Shizuoka, 52?1 Yada, Suruga-ku, Shizuoka City, Shizuoka 422?8526 (Japan)] [Laboratory of Microbiology and Immunology, School of Pharmaceutical Sciences, University of Shizuoka, 52?1 Yada, Suruga-ku, Shizuoka City, Shizuoka 422?8526 (Japan); Watanabe, Tatsuo [Laboratory of Food Chemistry, School of Food and Nutritional Sciences, University of Shizuoka, 52?1 Yada, Suruga-ku, Shizuoka City, Shizuoka 422?8526 (Japan)] [Laboratory of Food Chemistry, School of Food and Nutritional Sciences, University of Shizuoka, 52?1 Yada, Suruga-ku, Shizuoka City, Shizuoka 422?8526 (Japan); Imai, Yasuyuki, E-mail: imai@u-shizuoka-ken.ac.jp [Laboratory of Microbiology and Immunology, School of Pharmaceutical Sciences, University of Shizuoka, 52?1 Yada, Suruga-ku, Shizuoka City, Shizuoka 422?8526 (Japan)] [Laboratory of Microbiology and Immunology, School of Pharmaceutical Sciences, University of Shizuoka, 52?1 Yada, Suruga-ku, Shizuoka City, Shizuoka 422?8526 (Japan)

2012-11-01

206

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

NASA Technical Reports Server (NTRS)

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.

Partridge, William P.; Laurendeau, Normand M.

1997-01-01

207

Diffusion tube  

NASA Technical Reports Server (NTRS)

The diffusion tube was designed to operate below about 0.25 percent of water supersaturation. It is simply a long tube lined on the inside with a damp chamois cloth, and heated isothermally to a few degrees centigrade above the incoming air. The diffusion coefficient for water vapor is slightly larger than that for heat, making it possible to supersaturate the airflow. This is the same principle by which transient supersaturations may occur in parallel plate cloud chambers. Only the diffusion of vapor and heat from the walls into the moving air are considered.

Leaitch, R.; Megaw, W. J.

1981-01-01

208

The Monitoring Population Density of Pests Based on Edge-enhancing Diffusion Filtering and Image Processing  

Microsoft Academic Search

As is known, agriculture is very important in China, but the problem about pests has hampered the further development of Chinese\\u000a agriculture. Digital image-processing technology and mathematical morphology are referred to as the main research methods,\\u000a and tiny pets like aphids among field are referred to as the research objects. Image processing technology such as edgeenhancing\\u000a diffusion filtering, mathematical morphology

Yuehuan Wang; Guirong Weng

2007-01-01

209

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

PubMed

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

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

2012-11-01

210

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

NASA Astrophysics Data System (ADS)

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

Cooke, Kavian O.

2012-06-01

211

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

NASA Astrophysics Data System (ADS)

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

Kang, Jinbum; Yoo, Yangmo

2014-03-01

212

Hepatocyte-targeted MR contrast agents: contrast enhanced detection of liver cancer in diffusely damaged liver.  

PubMed

The performance of hepatocyte-targeted magnetic resonance (MR) contrast agents in the detection of liver tumor was tested in rats with hepatitis. Hepatocyte-targeted MR contrast agents (paramagnetic hepatobiliary complex [manganese-DPDP] and superparamagnetic iron oxide coated with arabinogalactan [SPIO-AG]) were injected into normal rats and rats with carbon tetrachloride-induced hepatitis. Before and after injection of either contrast agent, ex vivo relaxometry (0.94T) or in vivo MR imaging (1.0T) were performed. The obtained liver and tumor T1 and T2 relaxation times, liver and tumor signal-to-noise ratios (SNR), and tumor-liver contrast-to-noise ratios (CNR) of control rats and rats with hepatitis were compared. Both relaxometry and MR imaging showed that MnDPDP and SPIO-AG selectively enhanced liver tissue in controls and in rats with hepatitis to the same degree, and little tumor enhancement was seen in either group. As a result, no significant difference between control rats and rats with hepatitis was observed in the postcontrast tumor-liver CNR. For a MnDPDP-enhanced CNR with spin echo (SE) of 310/15, the results were -10.4+/-3.6 in control rats vs. -11.5+/-1.4 in rats with hepatitis; for a SPIO-AG-enhanced CNR with SE 2000/45 and 2000/90, respectively, the results were 30.7+/-9.2 and 18.7+/-4.7 in control rats vs. 31.9+/-7.1 and 17.7+/-2.4 in rats with hepatitis. These results indicate that hepatocyte-targeted contrast agents effectively enhance liver tissue and enhance liver-tumor image contrast despite hepatocellular dysfunction. PMID:16340158

Tanimoto, Akihiro; Kuribayashi, Sachio

2005-01-01

213

Hydroxylamine Diffusion Can Enhance N2O Emissions in Nitrifying Biofilms: A Modeling Study.  

PubMed

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

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

2015-02-01

214

Transient Photoreceptor Deconstruction by CNTF Enhances rAAV-Mediated Cone Functional Rescue in Late Stage CNGB3-Achromatopsia  

PubMed Central

Achromatopsia is a genetic disorder of cones, and one of the most common forms is a channelopathy caused by mutations in the ?-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. PMID:23568263

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

2013-01-01

215

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

PubMed

Achromatopsia is a genetic disorder of cones, and one of the most common forms is a channelopathy caused by mutations in the ?-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. PMID:23568263

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

216

Mapping of the Mouse Olfactory System with Manganese-Enhanced Magnetic Resonance Imaging and Diffusion Tensor Imaging  

PubMed Central

As the power of studying mouse genetics and behavior advances, research tools to examine systems level connectivity in the mouse are critically needed. In this study, we compared statistical mapping of the olfactory system in adult mice using manganese-enhanced MRI (MEMRI) and diffusion tensor imaging (DTI) with probabilistic tractography. The primary goal was to determine whether these complementary techniques can determine mouse olfactory bulb connectivity consistent with known anatomical connections. For MEMRI, 3D T1 weighted images were acquired before and after bilateral nasal administration of MnCl2 solution. Concomitantly, high resolution diffusion-tensor images were obtained ex vivo from a second group of mice and processed with a probabilistic tractography algorithm originating in the olfactory bulb. Incidence maps were created by co-registering and overlaying data from the two scan modalities. The resulting maps clearly show pathways between the olfactory bulb and amygdala, piriform cortex, caudate putamen, and olfactory cortex in both the DTI and MEMRI techniques that are consistent with the known anatomical connections. These data demonstrate that MEMRI and DTI are complementary, high-resolution neuroimaging tools that can be applied to mouse genetic models of olfactory and limbic system connectivity. PMID:22527121

Gutman, David A.; Magnuson, Matthew; Majeed, Waqas; Keifer, Orion P.; Davis, Michael; Ressler, Kerry J.; Keilholz, Shella

2012-01-01

217

Enhancement of fiber orientation distribution reconstruction in diffusion-weighted imaging by single channel blind source separation.  

PubMed

In diffusion-weighted imaging (DWI), reliable fiber tracking results rely on the accurate reconstruction of the fiber orientation distribution function (fODF) in each individual voxel. For high angular resolution diffusion imaging (HARDI), deconvolution-based approaches can reconstruct the complex fODF and have advantages in terms of computational efficiency and no need to estimate the number of distinct fiber populations. However, HARDI-based methods usually require relatively high b-values and a large number of gradient directions to produce good results. Such requirements are not always easy to meet in common clinical studies due to limitations in MRI facilities. Moreover, most of these approaches are sensitive to noise. In this study, we propose a new framework to enhance the performance of the spherical deconvolution (SD) approach in low angular resolution DWI by employing a single channel blind source separation (BSS) technique to decompose the fODF initially estimated by SD such that the desired fODF can be extracted from the noisy background. The results based on numerical simulations and two phantom datasets demonstrate that the proposed method achieves better performance than SD in terms of robustness to noise and variation in b-values. In addition, the results show that the proposed method has the potential to be applied to low angular resolution DWI which is commonly used in clinical studies. PMID:22020665

Jing, Min; McGinnity, T Martin; Coleman, Sonya; Zhang, Huaizhong; Fuchs, Armin; Kelso, J A Scott

2012-02-01

218

Evaluation of patients with diffuse unilateral subacute neuroretinitis by spectral domain optical coherence tomography with enhanced depth imaging  

PubMed Central

Background The purpose of this study was to determine the value of spectral domain optical coherence tomography (SD-OCT) in assessing patients with diffuse unilateral subacute neuroretinitis (DUSN). Methods This was an observational case series with clinical imaging correlation performed at the Retina and Vitreous Institute of Londrina and State University of Londrina, Paraná, Brazil. The series comprised ten consecutive patients with a confirmed diagnosis of DUSN, ie, seven patients with late-stage disease and three with early-stage disease, who were assessed by SD-OCT for mean macular, retinal nerve fiber layer, and choroidal thickness using enhanced depth imaging software. Results Comparing the affected eye with the healthy fellow eye, significant diffuse atrophy of the retinal layers with a decrease in mean macular (P=0.004) and retinal nerve fiber layer (P=0.002) thickness was found in all cases. There was no difference in choroidal thickness (P=0.262). Conclusion The correlation of SD-OCT results with central vision and funduscopic findings may explain the profound loss of visual function in patients with DUSN. PMID:24940045

Berbel, Rodrigo F; Casella, Antonio Marcelo B; de Souza, Eduardo C; Farah, Michel E

2014-01-01

219

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

220

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

NASA Astrophysics Data System (ADS)

We have experimentally assessed the quantitative nature of planar laser-induced fluorescence (PLIF) measurements of NO concentration in an atmospheric-pressure, laminar, inverse diffusion flame (IDF). The PLIF measurements were assessed relative to a two-dimensional array of separate laser-saturated fluorescence (LSF) measurements. Furthermore, we have proposed, 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. Prior to the PLIF assessment, we experimentally assessed the influence of interferences on both narrow -band and broad-band fluorescence measurements at atmospheric and high pressures. On this basis, optimum excitation and detection schemes were determined for the LSF and PLIF measurements. As a result, a new methodology has been established for excitation/filter selection for broad-band detection measurements. An LSF/PLIF optical-diagnostics facility and a unique axial IDF burner were developed for the PLIF assessment. We found that ~84% of the uncorrected PLIF measurements were equivalent to the corresponding LSF measurements to within the uncertainty in the LSF measurements. Single -input and multiple-input, experimentally-based PLIF enhancement procedures were developed for application in test environments with both negligible and significant error gradients due to variations in the electronic quenching rate coefficient. A minimal-input procedure was also demonstrated which uses existing knowledge of the test environment to optimize the design of the correction procedure. Each experimentally -based procedure provides a ~50% enhancement in the quantitative nature of the PLIF measurements, and results in concentration images that are nominally as quantitative as a single LSF point measurement. Furthermore, these experimentally-based PLIF 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.

Partridge, William Powell, Jr.

1995-01-01

221

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

PubMed

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

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

2014-10-17

222

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

PubMed Central

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

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

2014-01-01

223

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

PubMed

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

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

2014-06-01

224

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

NASA Astrophysics Data System (ADS)

Organic photovoltaic cells (OPVs) have the potential to become a low-cost source of renewable energy due to their compatibility with high throughput processing techniques and the demonstration of power conversion efficiencies exceeding 10%. In the simplest planar heterojunction OPVs, photoconversion is limited by a short exciton diffusion length (LD) that restricts migration to the dissociating electron donor-acceptor (D-A) 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 alternate approach that seeks to directly engineer LD by optimizing the intermolecular separation and consequently, the photophysical parameters responsible for excitonic energy transfer. By diluting the electron donor boron subphthalocyanine chloride (SubPc) into a wide energy gap host material, we optimize the degree of interaction between donor molecules and observe a nearly 50% increase in LD. Using this approach, we construct planar heterojunction OPVs with a power conversion efficiency of 4.4%, 30% larger than the case of optimized devices containing an undiluted donor layer. It is worth noting that this efficiency also rivals those realized in optimized, bulk heterojunction OPVs based on SubPc and C60. The underlying correlation between LD and the degree of molecular interaction has wide implications for the design of both OPV active materials and device architectures.

Holmes, Russell J.

2013-03-01

225

CXCR4 expression enhances diffuse large B cell lymphoma dissemination and decreases patient survival.  

PubMed

The chemokine receptor CXCR4 has been implicated in the migration and trafficking of malignant B cells in several haematological malignancies. Over-expression of CXCR4 has been identified in haematological tumours, but data concerning the role of this receptor in diffuse large B cell lymphoma (DLBCL) are lacking. CXCR4 is a marker of poor prognosis in various neoplasms, correlating with metastatic disease and decreased survival of patients. We studied CXCR4 involvement in cell migration in vitro and dissemination in vivo. We also evaluated the prognostic significance of CXCR4 in 94 biopsies of DLBCL patients. We observed that the level of expression of CXCR4 in DLBCL cell lines correlated positively with in vitro migration. Expression of the receptor was also associated with increased engraftment and dissemination, and decreased survival time in NOD/SCID mice. Furthermore, administration of a specific CXCR4 antagonist, AMD3100, decreased dissemination of DLBCL cells in a xenograft mouse model. In addition, we found that CXCR4 expression is an independent prognostic factor for shorter overall survival and progression-free survival in DLBCL patients. These results show that CXCR4 mediates dissemination of DLBCL cells and define for the first time its value as an independent prognostic marker in DLBCL patients. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. PMID:25231113

Moreno, María José; Bosch, Rosa; Dieguez-Gonzalez, Rebeca; Novelli, Silvana; Mozos, Ana; Gallardo, Alberto; Pavón, Miguel Ángel; Céspedes, María Virtudes; Grañena, Albert; Alcoceba, Miguel; Blanco, Oscar; Gonzalez-Díaz, Marcos; Sierra, Jorge; Mangues, Ramon; Casanova, Isolda

2015-02-01

226

Role of Diffusion Weighted Imaging and Contrast-Enhanced MRI in the Evaluation of Intrapelvic Recurrence of Gynecological Malignant Tumor  

PubMed Central

Background and Purpose To investigate the diagnostic performance of diffusion-weighted imaging (DWI) and contrast-enhanced imaging in combination with T2-weighted imaging (T2WI) for magnetic resonance imaging (MRI) evaluation of intrapelvic recurrence of gynecological malignancies. Materials and Methods Sixty-two patients with suspected intrapelvic recurrence of gynecological malignancies underwent pelvic MRI including T2WI DWI, and contrast-enhanced imaging. Diagnostic performance for detection of local recurrence, pelvic lymph node and bone metastases, and peritoneal lesions was evaluated by consensus reading of two experienced radiologists using a 5-point scoring system, and compared among T2WI with unenhanced T1-weighted imaging (T1WI) (protocol A), a combination of protocol A and DWI (protocol B), and a combination of protocol B and contrast-enhanced imaging (protocol C). Final diagnoses were obtained by histopathological examinations, radiological imaging and clinical follow-up for at least 6 months. Receiver operating characteristic (ROC) analysis and McNemar test were employed for statistical analysis. Results Locally recurrent disease, lymph node recurrence, peritoneal dissemination and bone metastases were present in 48.4%, 29.0%, 16.1%, and 6.5% of the patients, respectively. The patient-based sensitivity, specificity, accuracy, and area under the ROC curve (AUC) for detection of intrapelvic recurrence were 55.0, 81.8, 64.5% and 0.753 for protocol A, 80.0, 77.3, 79.0% and 0.838 for protocol B, and 80.0, 90.9, 83.9% and 0.862 for protocol C, respectively. The sensitivity, accuracy, and AUC were significantly better for protocols B and C than for protocol A (p<0.001). There was no significant difference between protocols B and C. Conclusion MRI using a combination of DWI and T2WI gives comparatively acceptable results for assessment of intrapelvic recurrence of gynecological malignancies. PMID:25629156

Kitajima, Kazuhiro; Tanaka, Utaru; Ueno, Yoshiko; Maeda, Tetsuo; Suenaga, Yuko; Takahashi, Satoru; Deguchi, Masashi; Miyahara, Yoshiya; Ebina, Yasuhiko; Yamada, Hideto; Tsurusaki, Masakatsu; Tamaki, Yukihisa; Sugimura, Kazuro

2015-01-01

227

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

NASA Astrophysics Data System (ADS)

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 ?M 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.

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

2013-12-01

228

In vivo evaluation of retinal and callosal projections in early postnatal development and plasticity using manganese-enhanced MRI and diffusion tensor imaging  

Microsoft Academic Search

The rodents are an excellent model for understanding the development and plasticity of the visual system. In this study, we explored the feasibility of Mn-enhanced MRI (MEMRI) and diffusion tensor imaging (DTI) at 7T for in vivo and longitudinal assessments of the retinal and callosal pathways in normal neonatal rodent brains and after early postnatal visual impairments. Along the retinal

Kevin C. Chan; Joe S. Cheng; Shujuan Fan; Iris Y. Zhou; Jian Yang; Ed X. Wu

229

Solvent-enhanced Dye Diffusion in Polymer This-Films for OLED Application F. Pschenitzka, K. Long, and J. C. Sturm  

E-print Network

Solvent-enhanced Dye Diffusion in Polymer This-Films for OLED Application F. Pschenitzka, K. Long in polymer films for organic light-emitting diode (OLED) application is introduced. After an initial dye by 150 °C. OLEDs with 0.4% external quantum efficiency were demonstrated. The materials used

230

Enhanced Oxygen Diffusion Within the Internal Oxidation Zone of Alloy 617 in Controlled Impurity Helium Environments from 1023 K to 1123 K (750 °C to 850 °C)  

NASA Astrophysics Data System (ADS)

Alloy 617 was exposed to He-CO-CO2 environments with P_{{CO}} /P_{{{{CO}}2 }} of either 9 or 1320 at temperatures from 1023 K to 1123 K (750 °C to 850 °C) to determine the oxygen diffusion coefficients within the internal oxidation zone of the alloy. The oxygen diffusion coefficients determined based on both intergranular and transgranular oxidation rates were several orders of magnitude greater than those reported in pure nickel and in nickel-based binary alloys, indicating that the rapid internal aluminum oxidation of Alloy 617 was primarily due to enhanced oxygen diffusion along the incoherent Al2O3-alloy interfaces. The range of activation energy values determined for oxygen diffusion associated with the intergranular aluminum oxidation was from 149.6 to 154.7 kJ/mol, and that associated with the transgranular aluminum oxidation was from 244.7 to 283.5 kJ/mol.

Gulsoy, Gokce; Was, Gary S.

2015-01-01

231

The marine polyether gambierol enhances muscle contraction and blocks a transient K(+) current in skeletal muscle cells.  

PubMed

Gambierol is a complex marine toxin first isolated with ciguatoxins from cell cultures of the toxic dinoflagellate Gambierdiscus toxicus. Despite the chemical complexity of the polycyclic ether toxin, the total successful synthesis of gambierol has been achieved by different chemical strategies. In the present work the effects of synthetic gambierol on mouse and frog skeletal neuromuscular preparations and Xenopus skeletal myocytes have been studied. Gambierol (0.1-5 muM) significantly increased isometric twitch tension in neuromuscular preparations stimulated through the motor nerve. Less twitch augmentation was observed in directly stimulated muscles when comparing twitch tension-time integrals obtained by nerve stimulation. Also, gambierol induced small spontaneous muscle contraction originating from presynaptic activity that was completely inhibited by d-tubocurarine. Gambierol slowed the rate of muscle action potential repolarization, triggered spontaneous and/or repetitive action potentials, and neither affected action potential amplitude nor overshoot in skeletal muscle fibers. These results suggest that gambierol through an action on voltage-gated K(+) channels prolongs the duration of action potentials, enhances the extent and time course of Ca(2+) release from the sarcoplasmic reticulum, and increases twitch tension generation. Further evidence is provided that gambierol at sub-micromolar concentrations blocks a fast inactivating outward K(+) current that is responsible for action potential prolongation in Xenopus skeletal myocytes. PMID:20540957

Schlumberger, Sébastien; Ouanounou, Gilles; Girard, Emmanuelle; Sasaki, Makoto; Fuwa, Haruhiko; Louzao, M Carmen; Botana, Luis M; Benoit, Evelyne; Molgó, Jordi

2010-10-01

232

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

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

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

2014-01-01

233

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)

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 ( ?X) 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 debris-laden environments (cosmic dust), heat transfer in forest fire spread, geochemical contamination and ceramic materials processing.

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

2009-11-01

234

Visualization of Hydrogen Diffusion in a Hydrogen-Enhanced Fatigue Crack Growth in Type 304 Stainless Steel  

NASA Astrophysics Data System (ADS)

To study the influence of hydrogen on the fatigue strength of AISI type 304 metastable austenitic stainless steel, specimens were cathodically charged with hydrogen. Using tension-compression fatigue tests, the behavior of fatigue crack growth from a small drill hole in the hydrogen-charged specimen was compared with that of noncharged specimen. Hydrogen charging led to a marked increase in the crack growth rate. Typical characteristics of hydrogen effect were observed in the slip band morphology and fatigue striation. To elucidate the behavior of hydrogen diffusion microscopically in the fatigue process, the hydrogen emission from the specimens was visualized using the hydrogen microprint technique (HMT). In the hydrogen-charged specimen, hydrogen emissions were mainly observed in the vicinity of the fatigue crack. Comparison between the HMT image and the etched microstructure image revealed that the slip bands worked as a pathway for hydrogen to move preferentially. Hydrogen-charging resulted in a significant change in the phase transformation behavior in the fatigue process. In the noncharged specimen, a massive type ?' martensite was observed in the vicinity of the fatigue crack. On the other hand, in the hydrogen-charged specimen, large amounts of ? martensite and a smaller amount of ?' martensite were observed along the slip bands. The results indicated that solute hydrogen facilitated the ? martensitic transformation in the fatigue process. Comparison between the results of HMT and EBSD inferred that martensitic transformations as well as plastic deformation itself can enhance the mobility of hydrogen.

Matsunaga, Hisao; Noda, Hiroshi

2011-09-01

235

Chemically enhanced physical vapor deposition (CEPVD) of tantalum nitride-based films for diffusion barrier layers used in ULSI devices  

NASA Astrophysics Data System (ADS)

To address future ULSI barrier/liner deposition needs, we have investigated a hybrid approach to film deposition, referred to as chemically enhanced physical vapor deposition (CEPVD), attempting to provide Ionized Physical Vapor Deposition (IPVD)-like film quality and Chemical Vapor Deposition (CVD)-like step coverage. In CEPVD, a chemical precursor is introduced to the substrate during IPVD to provide a CVD component to the overall deposition process. The isotropic precursor flux is intended to provide film deposition on surfaces that are not impacted by the directional ions, such as the lower sidewall of a narrow via or trench. The kinetic energy delivered to the surface by the flux of ionized metal may serve to enhance chemical component deposition. We have focused on the Ta-N material system since Ta/TaN is widely used as a diffusion barrier in Cu damascene processing. CEPVD was carried out by introducing a Ta-containing, organometallic precursor (tert-butylimino tris(diethylamino) tantalum, or TBTDET) to the substrate during IPVD. Film thickness and step coverage were determined by cross-sectional SEM. Film atomic composition, molecular composition, chemical state, roughness, crystalline structure and resistivity were characterized using AES, SIMS, XPS, AFM, XRD and four-point-probe respectively. A zero-order semi-empirical model is established allowing the attachment of physical understanding and CEPVD experimental phenomena. The model stems from the knowledge of reactive sputtering and PECVD processes as well as the acquired CEPVD experiment results. It correlates the processing parameters with the target and film surface coverage by Ta, TaN and organic sites, from which one can predict the operation mode, either metallic or poison, and the film elemental composition. The organic by-products accounting for the detection of carbon on the substrate by AES analysis and poisoning of the target during the processing are categorized into non-volatile product (OR1) and volatile product (OR2) in a lump-sum assumption. Electron impact, H reducing and ion bombardment are considered as the enhancing mechanisms between the physical and chemical components and included as the reactants of the chemical reactions. Simulation results compare favorably with the experimental data.

Li, Ning

236

Pulse mitigation and heat transfer enhancement techniques. Volume 3: Liquid sodium heat transfer facility and transient response of sodium heat pipe to pulse forward and reverse heat load  

Microsoft Academic Search

This report presents the description of a liquid sodium heat transfer facility (sodium loop) constructed to support the study of transient response of heat pipes. The facility, consisting of the loop itself, a safety system, and a data acquisition system, can be safely operated over a wide range of temperature and sodium flow rate. The transient response of a heat

L. C. Chow; O. J. Hahn; H. X. Nguyen

1992-01-01

237

[Transient diplopia].  

PubMed

Transient binocular diplopia is a frequent complaint in an everyday ophthalmic practice. Since the objective clinical examination is most often within normal limits between the diplopia attacks, a thorough history is mandatory to determine the possible causes and precipitating factors. Although transient diplopia can herald visual or even life-threatening associated conditions, it is most often related to benign diseases. An appropriate work-up depends on the history and the clinical evaluation, targeting specific underlying causes. PMID:19944482

Milea, D

2009-12-01

238

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

SciTech Connect

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

Giovanni Pastore; Michael R. Tonks; Derek R. Gaston; Richard L. Williamson; David Andrs; Richard Martineau

2014-03-01

239

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)

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.

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

240

Solid state chemistry and non-steady state radiation enhanced diffusion (NSRED): Part I. Synthesis and characterization of some lithium-tin and lithium-silver-tin polar intermetallics. Part II. Titanium diffusion in ion-modified magnesium oxide surfaces  

NASA Astrophysics Data System (ADS)

Part I of this thesis centers on the investigation of the structural, electronic and physical properties of Li-Sn based novel polar intermetallic compounds. In spite of both scientific and technological interests, the understanding of structure-property relationships of polar intermetallics based on Li-Sn system have not been extensively studied. Our exploratory studies focus on the chemistry of the Li-richest binary phase, Li4.4Sn, as well as on the discovery of new ternary Li-rich phases. Careful phase analyses coupled with X-ray and neutron diffraction studies resulted in the reformulation of Li4.4Sn as Li17Sn4. Exploratory synthesis in the Li-rich side of the ternary Li-Ag-Sn system also led to the discovery of two novel ternary lithium silver stannides phases: Li32.54Ag 9.46Sn10 and Li17Ag3Sn6. The new ternary compounds represent examples of two new crystal structure-types. Li32.54Ag9.46Sn10 exhibits high Li content, and a structure with covalent Ag-Sn framework with significant Li/Ag defects indicating its potential as an anode material for Li-ion batteries. Li 17Ag3Sn6 represents the first example of a quasi-2-dimensional polar intermetallic of the Li-Ag-Sn system. Its high lithium content also suggests it is a viable candidate for Li-battery anode applications. Part II of this thesis focuses on the investigation of defect production upon inert and chemically reactive energetic ion irradiated single crystals of MgO (100). Ti diffusion in ion pre-irradiated (low-energy ion beams of Ar+, Cl+ and Cr+ of 7keV) MgO (100) surfaces was selected as a model system in this work. The annealing process followed ion-irradiation treatment. Diffusion was conducted in an inert atmosphere. In these conditions, non-steady state concentration defects were created and a new type of diffusion termed as Non-Steady State Radiation Enhanced Diffusion (NSRED) was developed. NSRED is obtained by using the following: ion irradiation in the keV range followed by annealing; the diffusion range overlaps heavily with the central region of the collision cascade; the diffusing species are evaporated on the pre-irradiated surfaces. Secondary Ion Mass Spectrometry was used to measure the diffusion coefficients versus ion irradiation conditions as well as their time dependence. A theoretical model was formulated to calculate the depth-dependent bulk diffusion coefficients and the following order was obtained: DTi/Cr/MgO > DTi/Ar/MgO > DTi/Cl/MgO (where D stands for the depth-dependent diffusion coefficient of samples bombarded with Cr, Ar and Cl, respectively). Monte-Carlo (TRIM) simulations, lattice deformation effects, electrical neutrality requirements as well as nature of vacancies were used to explain the observed trend. Additional kinetic studies and HRXRD experiments were performed to further explain the DTi/Ar/MgO > DTi/Cl/MgO trend. A modified Kapinos-Platonov model was used to include the chemical effect observed. Larger vacancies cluster are assumed to form after relaxation processes under Cl+ bombardment versus Ar+ bombardment. The model accounts for: (1) enhanced diffusion obtained due to the vacancy cluster dissociation during the annealing process, the so-called post-irradiation annealing effect; (2) enhanced diffusion obtained due to the chemical properties of the ions, the so-called chemical effect.

Lupu, Corina

241

Chemo-nociceptive signalling from the colon is enhanced by mild colitis and blocked by inhibition of transient receptor potential ankyrin 1 channels  

PubMed Central

Background and purpose: Transient receptor potential ankyrin 1 (TRPA1) channels are expressed by primary afferent neurones and activated by irritant chemicals including allyl isothiocyanate (AITC). Here we investigated whether intracolonic AITC causes afferent input to the spinal cord and whether this response is modified by mild colitis, morphine or a TRPA1 channel blocker. Experimental approach: One hour after intracolonic administration of AITC to female mice, afferent signalling was visualized by expression of c-Fos in laminae I–IIo of the spinal dorsal horn at sacral segment S1. Mild colitis was induced by dextran sulphate sodium (DSS) added to drinking water for 1 week. Key results: Relative to vehicle, AITC (2%) increased expression of c-Fos in the spinal cord. Following induction of mild colitis by DSS (2%), spinal c-Fos responses to AITC, but not vehicle, were augmented by 41%. Colonic inflammation was present (increased myeloperoxidase content and disease activity score), whereas colonic histology, locomotion, feeding and drinking remained unchanged. Morphine (10 mg·kg?1) or the TRPA1 channel blocker HC-030031 (300 mg·kg?1) inhibited the spinal c-Fos response to AITC, in control and DSS-pretreated animals, whereas the response to intracolonic capsaicin (5%) was blocked by morphine but not HC-030031. Conclusions and implications: Activation of colonic TRPA1 channels is signalled to the spinal cord. Mild colitis enhanced this afferent input that, as it is sensitive to morphine, is most likely of a chemonociceptive nature. As several irritant chemicals can be present in chyme, TRPA1 channels may mediate several gastrointestinal pain conditions. PMID:20590633

Mitrovic, Martina; Shahbazian, Anaid; Bock, Elisabeth; Pabst, Maria A; Holzer, Peter

2010-01-01

242

Pre- and posttreatment with edaravone protects CA1 hippocampus and enhances neurogenesis in the subgranular zone of dentate gyrus after transient global cerebral ischemia in rats.  

PubMed

Edaravone is clinically used for treatment of patients with acute cerebral infarction. However, the effect of double application of edaravone on neurogenesis in the hippocampus following ischemia remains unknown. In the present study, we explored whether pre- and posttreatment of edaravone had any effect on neural stem/progenitor cells (NSPCs) in the subgranular zone of hippocampus in a rat model of transient global cerebral ischemia and elucidated the potential mechanism of its effects. Male Sprague-Dawley rats were divided into three groups: sham-operated (n?=?15), control (n?=?15), and edaravone-treated (n?=?15) groups. Newly generated cells were labeled by 5-bromo-2-deoxyuridine. Immunohistochemistry was used to detect neurogenesis. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling was used to detect cell apoptosis. Reactive oxygen species (ROS) were detected by 2,7-dichlorofluorescien diacetate assay in NSPCs in vitro. Hypoxia-inducible factor-1? (HIF-1?) and cleaved caspase-3 proteins were quantified by western blot analysis. Treatment with edaravone significantly increased the number of NSPCs and newly generated neurons in the subgranular zone (p?enhances neurogenesis by protecting NSPCs from apoptosis in the hippocampus, which is probably mediated by decreasing ROS generation and inhibiting protein expressions of HIF-1? and cleaved caspase-3 after cerebral ischemia. PMID:25388889

Lei, Shan; Zhang, Pengbo; Li, Weisong; Gao, Ming; He, Xijing; Zheng, Juan; Li, Xu; Wang, Xiao; Wang, Ning; Zhang, Junfeng; Qi, Cunfang; Lu, Haixia; Chen, Xinlin; Liu, Yong

2014-01-01

243

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

PubMed

The ?-carbonic anhydrases (CAs) are zinc-containing enzymes that catalyze the interconversion of CO2 and HCO3 (-). Here, we focus on human CA II (CA II), a ubiquitous cytoplasmic enzyme. In the second paper in this series, we examine CA IV at the extracellular surface. After microinjecting recombinant CA II in a Tris solution (or just Tris) into oocytes, we expose oocytes to 1.5% CO2/10 mM HCO3 (-)/pH 7.50 while using microelectrodes to monitor intracellular pH (pHi) and surface pH (pHS). CO2 influx causes the familiar sustained pHi fall as well as a transient pHS rise; CO2 efflux does the opposite. Both during CO2 addition and removal, CA II increases the magnitudes of the maximal rate of pHi change, (dpHi/dt)max, and the maximal change in pHS, ?pHS. Preincubating oocytes with the inhibitor ethoxzolamide eliminates the effects of CA II. Compared with pHS, pHi begins to change only after a delay of ~9 s and its relaxation has a larger (i.e., slower) time constant (?pHi > ?pHS ). Simultaneous measurements with two pHi electrodes, one superficial and one deep, suggest that impalement depth contributes to pHi delay and higher ?pHi . Using higher CO2/HCO3 (-) levels, i.e., 5%/33 mM HCO3 (-) or 10%/66 mM HCO3 (-), increases (dpHi/dt)max and ?pHS, though not in proportion to the increase in [CO2]. A reaction-diffusion mathematical model (described in the third paper in this series) accounts for the above general features and supports the conclusion that cytosolic CA-consuming entering CO2 or replenishing exiting CO2-increases CO2 fluxes across the cell membrane. PMID:24965587

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

2014-11-01

244

Modeling the Effect of Intra-Voxel Diffusion of Contrast Agent on the Quantitative Analysis of Dynamic Contrast Enhanced Magnetic Resonance Imaging  

PubMed Central

Quantitative dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) provides estimates of physiologically relevant parameters related to tissue blood flow, vascular permeability, and tissue volume fractions which can then be used for prognostic and diagnostic reasons. However, standard techniques for DCE-MRI analysis ignore intra-voxel diffusion, which may play an important role in contrast agent distribution and voxel signal intensity and, thus, will affect quantification of the aforementioned parameters. To investigate the effect of intra-voxel diffusion on quantitative DCE-MRI, we developed a finite element model of contrast enhancement at the voxel level. For diffusion in the range of that expected for gadolinium chelates in tissue (i.e., 1×10?4 to 4×10?4 mm2/s), parameterization errors range from ?58% to 12% for Ktrans, ?9% to 8% for ve, and ?60% to 213% for vp over the range of Ktrans, ve, vp, and temporal resolutions investigated. Thus the results show that diffusion has a significant effect on parameterization using standard techniques. PMID:25275536

Barnes, Stephanie L.; Quarles, C. Chad; Yankeelov, Thomas E.

2014-01-01

245

Dynamic Contrast-Enhanced and Diffusion MRI Show Rapid and Dramatic Changes in Tumor Microenvironment in Response to Inhibition of HIF-1? Using PX478  

Microsoft Academic Search

PX-478 is a new agent known to inhibit the hypoxia- responsivetranscriptionfactor,HIF-1A,inexperimental tumors. The current study was undertaken in prepa- ration for clinical trials to determine which noninvasive imaging endpoint(s) is sensitive to this drug's actions. Dynamic contrast-enhanced (DCE) and diffusion- weighted (DW) magnetic resonance imaging (MRI) were used to monitor acute effects on tumor hemo- dynamics and cellularity, respectively. Mice

Bénédicte F. Jordan; Matthew Runquist; Natarajan Raghunand; Amanda Baker; Ryan Williams; Lynn Kirkpatrickb; Garth Powis; Robert J. Gillies

2005-01-01

246

An enhanced transient expression system in plants based on suppression of gene silencing by the p19 protein of tomato bushy stunt virus  

Microsoft Academic Search

Summary Transient gene expression is a fast, flexible and reproducible approach to high-level expression of useful proteins. In plants, recombinant strains of Agrobacterium tumefaciens can be used for transient expression of genes that have been inserted into the T-DNA region of the bacterial Ti plasmid. A bacterial culture is vacuum-infiltrated into leaves, and upon T-DNA transfer, there is ectopic expression

Olivier Voinnet; Susana Rivas; Pere Mestre; David Baulcombe

2003-01-01

247

Boron diffusion in ultra low-energy (<1 keV\\/atom) decaborane (B 10H14) ion implantation  

Microsoft Academic Search

High performance 40 nm p-MOSFETs with ultra shallow junction have been fabricated, using decaborane (B10H14) ion implantation. It has been experimentally demonstrated that ultra low-energy implantation of B10H14 in Si(100) at 2 keV does not cause the transient enhanced diffusion (TED) of boron atoms during annealing at 900°C for 10 sec. In order to reveal the diffusion mechanism of B

Takuya Kusaba; Norihiro Shimada; Takaaki Aoki; Jiro Matsuo; I. Yamada; K. Goto; T. Sugii

1998-01-01

248

Self- and dopant diffusion in extrinsic boron doped isotopically controlled silicon multilayer structures  

SciTech Connect

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.

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

249

Acute psychological and physical stress transiently enhances brachial artery flow-mediated dilation stimulated by exercise-induced increases in shear stress.  

PubMed

Exercise elevates conduit artery shear stress and stimulates flow-mediated dilation (FMD). However, little is known regarding the impact of acute psychological and physical stress on this response. The purpose of this study was to examine the impact of the Trier Social Stress Test (TSST (speech and arithmetic tasks)) and a cold pressor test (CPT) with and without social evaluation (SE) on exercise-induced brachial artery FMD (EX-FMD). A total of 59 healthy male subjects were randomly assigned to 1 of 3 conditions: TSST, CPT, or CPT with SE. During 6 min of handgrip exercise, brachial artery EX-FMD was assessed before and 15 and 35 min poststress with echo and Doppler ultrasound. Shear stress was estimated as shear rate, calculated as brachial artery mean blood velocity/brachial artery diameter. Results are means ± SD. All conditions elicited significant physiological stress responses. Salivary cortisol increased from 4.6 ± 2.4 nmol/L to 10.0 ± 5.0 nmol/L (p < 0.001; condition effect: p = 0.292). Mean arterial pressure increased from 98.6 ± 12.1 mm Hg to 131.9 ± 18.7 mm Hg (p < 0.001; condition effect: p = 0.664). Exercise shear rate did not differ between conditions (p = 0.592), although it was modestly lower poststress (prestress: 72.3 ± 4.5 s(-1); 15 min poststress: 70.8 ± 5.4 s(-1); 35 min poststress: 70.6 ± 6.1 s(-1); trial effect: p = 0.011). EX-FMD increased from prestress to 15 min poststress in all conditions (prestress: 6.2% ± 2.8%; 15 min poststress: 7.9% ± 3.2%; 35 min poststress: 6.6% ± 2.9%; trial effect: p < 0.001; condition effect: p = 0.611). In conclusion, all conditions elicited similar stress responses that transiently enhanced EX-FMD. This response may help to support muscle perfusion during stress. PMID:24921439

Szijgyarto, Ingrid C; Poitras, Veronica J; Gurd, Brendon J; Pyke, Kyra E

2014-08-01

250

A stabilized method for transient transport equations  

NASA Astrophysics Data System (ADS)

We present a stabilized method for the transient advective-reactive-diffusive equation. The discretization is based on Rothe’s method, which discretizes in time before the spatial discretization. The resulting steady state advective-reactive-diffusive equation is approximated by the Unusual Stabilized Finite Element Method (USFEM).

Henao, Carlos A. A.; Coutinho, Alvaro L. G. A.; Franca, Leopoldo P.

2010-01-01

251

Phenomenon of enhanced diffusion of lithium-ion in LiMn 2O 4 induced by electrochemical cycling  

Microsoft Academic Search

Lithium-ion diffusion in insertion-host materials is of significant interest because of its importance in improving the power density of lithium-ion batteries. In this study, the dependence of the chemical diffusion coefficient (D) of lithium-ion in spinel LiMn2O4 cathode material on electrochemical cycling has been investigated by the capacity intermittent titration technique (CITT). Results show that there are two minimum peaks

Xin-Cun Tang; Li-Qing Li; Bai-Yun Huang; Yue-Hui He

2006-01-01

252

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

NASA Astrophysics Data System (ADS)

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.

Kann, Z. R.; Skinner, J. L.

2014-09-01

253

Dynamic Contrast-Enhanced and Diffusion-Weighted Magnetic Resonance Imaging Noninvasive Evaluation of Vascular Disrupting Treatment on Rabbit Liver Tumors  

PubMed Central

Evaluation of vascular disrupting treatment (VDT) is generally based on tumor size and enhancement on conventional magnetic resonance imaging (MRI) which, unfortunately, may be limited in providing satisfactory information. The purpose of the study is to evaluate consecutive changes of 20 rabbit VX2 liver tumors after VDT by dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI) at a 3.0 T MR unit. Twenty four hours after intravenous injection of Combretastatin A-4-phosphate (CA4P) at 20 mg/kg, DCE-MRI derived Maximum Slope of Increase (MSI) and Positive Enhancement Integral (PEI) decreased sharply due to sudden shutting down of tumor feeding vessels. DWI derived Apparent Diffusion Coefficient (ADC) in tumor periphery decreased because of ischemic cell edema. On day 4, an increase of MSI was probably caused by the recovery of blood supply. A remarkable increase of ADC represented a large scale of necrosis among tumors. On day 8, the blood perfusion further decreased and the extent of necrosis further increased, reflected by lower MSI and PEI values and higher ADC value. On day 12, a second decrease of ADC was noticed because the re-growth of periphery tumor. The experimental data indicate that the therapeutic effects of VDT may be noninvasively monitored with DCE-MRI (reflecting tumor blood perfusion) and DWI (reflecting the changes of histology), which provide powerful measures for assessment of anticancer treatments. PMID:24376560

Shao, Haibo; Ni, Yicheng; Zhang, Jian; Chen, Feng; Dai, Xu; Fan, Guoguang; Sun, Ziping; Xu, Ke

2013-01-01

254

Three-Tesla magnetic resonance elastography for hepatic fibrosis: Comparison with diffusion-weighted imaging and gadoxetic acid-enhanced magnetic resonance imaging  

PubMed Central

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

Park, Hee Sun; Kim, Young Jun; Yu, Mi Hye; Choe, Won Hyeok; Jung, Sung Il; Jeon, Hae Jeong

2014-01-01

255

Direct Observation of Dopant Atom Diffusion in a Bulk Semiconductor Crystal Enhanced by a Large Size Mismatch  

NASA Astrophysics Data System (ADS)

Diffusion is one of the fundamental processes that govern the structure, processing, and properties of materials and it plays a crucial role in determining device lifetimes. However, direct observations of diffusion processes have been elusive and limited only to the surfaces of materials. Here we use an aberration-corrected electron microscope to locally excite and directly image the diffusion of single Ce and Mn dopants inside bulk wurtzite-type AlN single crystals, identifying correlated vacancy-dopant and interstitial-dopant kick-out mechanisms. Using a 200 kV electron beam to supply energy, we observe a higher frequency of dopant jumps for the larger and heavier Ce atoms than the smaller Mn atoms. These observations confirm density-functional-theory-based predictions of a decrease in diffusion barrier for large substitutional atoms. The results show that combining depth sensitive microscopy with theoretical calculations represents a new methodology to investigate diffusion mechanisms, not restricted to surface phenomena, but within bulk materials.

Ishikawa, Ryo; Mishra, Rohan; Lupini, Andrew R.; Findlay, Scott D.; Taniguchi, Takashi; Pantelides, Sokrates T.; Pennycook, Stephen J.

2014-10-01

256

Effects of Lewis Number on Temperatures of Spherical Diffusion Flames  

NASA Technical Reports Server (NTRS)

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%.

Santa, K. J.; Sun, Z.; Chao, B. H.; Sunderland, P. B.; Axelbaum, R. I.; Urban, D. L.; Stocker, D. P.

2007-01-01

257

Early Annihilation and Diffuse Backgrounds in Models of Weakly Interacting Massive Particles in Which the Cross Section for Pair Annihilation Is Enhanced by 1/v  

NASA Astrophysics Data System (ADS)

Recent studies have considered modifications to the standard weakly interacting massive particle scenario in which the pair annihilation cross section (times relative velocity v) is enhanced by a factor 1/?10-3 in the Galaxy, enough to explain several puzzling Galactic radiation signals. We show that in these scenarios a burst of weakly interacting massive particle annihilation occurs in the first collapsed dark-matter halos. We show that severe constraints to the annihilation cross section derive from measurements of the diffuse extragalactic radiation and from ionization and heating of the intergalactic medium.

Kamionkowski, Marc; Profumo, Stefano

2008-12-01

258

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

DOEpatents

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.

Christophorou, Loucas G. (Oak Ridge, TN); Hunter, Scott R. (Oak Ridge, TN)

1990-01-01

259

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

DOEpatents

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.

Christophorou, L.G.; Hunter, S.R.

1988-06-28

260

IMAGE SEGMENTATION AND EDGE DETECTION VIA CONSTRAINED DIFFUSION AND ADAPTIVE MORPHOLOGY: A CNN APPROACH TO BUBBLE-DEBRIS IMAGE ENHANCEMENT  

Microsoft Academic Search

In this paper, a cellular neural network (CNN) based locally adaptive scheme is presented for image segmentation and edge detection. It is shown that combining a constrained (linear or nonlinear) diffusion approach with adaptive morphology leads to a robust segmentation algorithm for an important class of image models. These images comprise of simple geometrical objects, each having a homogeneous gray-scale

Csaba Rekeczky; Abraham Schultz; István Szatmári; Tamás Roska; Leon O. Chua

261

Slowing the adoption and diffusion process to enhance brand repositioning: The consumer driven repositioning of Dunlop Volley  

Microsoft Academic Search

What should you do when your brand becomes ‘hot’ overnight among influential endorsers? Do you exploit this sudden rise in popularity and mainstream the brand, or do you attempt to slow the diffusion process and seek to understand how to market to these consumers? Drawing on the case of Dunlop Volley in Australia, we argue that mainstreaming the brand by

Michael Beverland; Michael Ewing

2005-01-01

262

Pulse mitigation and heat transfer enhancement techniques. Volume 4: Transient behavior of heat pipe with thermal energy storage under pulse heat loads  

Microsoft Academic Search

A novel design of a high-temperature axially grooved heat pipe (HP), which utilizes thermal energy storage (TES) to mitigate pulse heat loads, was presented. Phase-change material (PCM) encapsulated in cylindrical containers was used for thermal energy storage. The transient responses of the HP\\/TES system under two types of pulse heat loads were studied numerically. The first type is pulse heat

L. C. Chow; M. J. Chang

1992-01-01

263

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

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. PMID:25569941

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

2014-08-01

264

Enhance  

NSDL National Science Digital Library

It doesn't take a Photoshop expert to create attractive graphics for the Web. To prove this, the folks at MicroFrontier have released three graphic creation/editing packages for the Macintosh, each aimed at a different user level. All three applications support Photoshop 3.0 compatible plug-ins and basic features such as scanner support, image and resolution scaling, and basic image enhancement. Enhance, aimed at the graphics professionals, adds even more features, including multiple layers, opacity control, sixteen levels of undo, convolution filter effects, and CYMK support. A save-disabled demo version of each application is available at the MicroFrontier Website. The price for Enhance is $100 .

1998-01-01

265

Plasma-Enhanced Atomic Layer Deposition of Ruthenium-Titanium Nitride Mixed-Phase Layers for Direct-Plate Liner and Copper Diffusion Barrier Applications  

NASA Astrophysics Data System (ADS)

Current interconnect networks in semiconductor processing utilize a sputtered TaN diffusion barrier, Ta liner, and Cu seed to improve the adhesion, microstructure, and electromigration resistance of electrochemically deposited copper that fills interconnect wires and vias. However, as wire/via widths shrink due to device scaling, it becomes increasingly difficult to have the volume of a wire/via be occupied with ECD Cu which increases line resistance and increases the delay in signal propagation in IC chips. A single layer that could serve the purpose of a Cu diffusion barrier and ECD Cu adhesion promoter could allow ECD Cu to occupy a larger volume of a wire/via, leading to a decrease in line resistance and decrease in signal delay. Previous work has shown RuTaN, RuWCN, and RuCo films can act as Cu diffusion barriers and be directly platable to thickness of 2-3nm. However, other material selections may prove as effective or possibly better. Mixed-phase films of ruthenium titanium nitride grown by atomic layer deposition (ALD) were investigated for their performance as a Cu diffusion barrier and as a surface for the direct plating of ECD Cu. All Ru was deposited by plasma-enhanced atomic layer deposition (PEALD) while TiN was deposited by either thermal ALD or PEALD. RuTiN, films with thermal ALD TiN and a Ru:Ti of 20:1 showed barrier performance comparable to PVD TaN at 3-4 nm thickness and 15 nm planar films were directly platable. Follow up work is certainly needed for this material set, yet initial results indicate RuTiN could serve as an effective direct plate liner for Cu interconnects.

Gildea, Adam James

266

First-principles calculation of self-diffusion, arsenic diffusion, and surface segregation in silicon  

NASA Astrophysics Data System (ADS)

Integrated circuit device densities have increased more than 2000 times since Gordon Moore's observation of exponential growth in 1965. Modern devices are thus sensitive to minute variations in diffusion, such as the transient-enhanced diffusivity resulting from ion implantation, concentration-dependent diffusivity of dopants due to changes in the Fermi level, and the effects of high stresses and stress gradients (resulting from thermal oxidation and other surface treatments). Arsenic diffusion and self-diffusion in Si are caused by both types of intrinsic defects, vacancies and self-interstitials. Surprisingly, the mechanisms of Si self-diffusion remain unclear: equilibrium defect concentrations are too low to measure, and defect diffusivities are obscured by the relatively large concentrations of C and O traps. The aim of the present work is to develop a physically based, quantitative understanding of dopant diffusion during IC processing, as well as the non-equilibrium limits to dopant concentrations. Density functional theory, a first-principles techniques, has been used (with the PW91 functional) to calculate properties of intrinsic defects not directly accessible to experiment. Density functional calculations of the formation enthalpies and volumes of vacancies and interstitials in silicon are presented in each low-energy geometry and charge state. The effect of pressure (up to 30 kbar) and doping (moving the Fermi level from the valence band maximum to the conduction band minimum) on the stability and diffusivity of defects is discussed. In the presence of electronic or optical excitation, both defects are mobile even at cryogenic temperatures. Vacancy diffusion is found to be enhanced by n-type doping, while p-type doping inhibits interstitial migration. Relaxation volume tensors extracted from these calculations express the response of the defects to non-hydrostatic stress states. The interstitial-mediated diffusion of As is shown to have a similar activation barrier to vacancy-mediated diffusion, despite much lower binding energies. The presence of multiple low-energy As interstitial configurations suggests a high diffusion entropy.

Centoni, Scott A.

267

Triple microporous layer coated gas diffusion layer for performance enhancement of polymer electrolyte fuel cells under both low and high humidity conditions  

NASA Astrophysics Data System (ADS)

Enhancement of the performance of polymer electrolyte fuel cells (PEFCs) requires an appropriate water balance between the conservation of membrane humidity and the discharge of excess water produced in the cell. In the present study, a novel triple microporous layer (MPL) coated gas diffusion layer (GDL), in which a hydrophilic layer was coated on a hydrophobic double MPL, was developed to enhance the PEFC performance under both low and high humidity. The thin hydrophilic layer in the triple MPL is effective at conserving the humidity of the membrane electrode assembly (MEA) under low humidity, while the hydrophobic double MPL between the hydrophilic layer and the carbon paper substrate prevents removal of water from the hydrophilic layer. This results in a significant enhancement of the ability of the GDL to prevent dehydration of the MEA. The triple MPL coated GDL, where the polytetrafluoroethylene (PTFE) content in the hydrophobic MPL in contact with the hydrophilic layer is set to 30 mass% and that in contact with the substrate is set to 10 mass%, is effective at expelling excess water from the catalyst layer, which results in much higher PEFC performance under high humidity than that for a conventional hydrophobic MPL coated GDL.

Kitahara, Tatsumi; Nakajima, Hironori; Inamoto, Masaoki; Shinto, Kosuke

2014-02-01

268

Enhanced performance of organic thin film solar cells using electrodes with nanoimprinted light-diffraction and light-diffusion structures.  

PubMed

An ITO substrate with periodic surface nanostructures was used to induce strong diffusion and diffraction of incident light. The nanostructures were fabricated using nanoimprint lithography on photoresist followed by coating of the ITO layer and organic materials with uniform morphology. The nanostructures embedded into the ITO layer were found to increase absorption in poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester solar devices. The short-circuit current of the nanostructured organic solar cells improved from 7.07 to 10.76 mA/cm2. This improvement was due to the increased effective optical path of absorbed light resulting from the trapping and scattering by the nanostructures. PMID:24735241

Chen, Jheng-Yuan; Yu, Ming-Hung; Chang, Chih-Yu; Chao, Yi-Hsiang; Sun, Kien Wen; Hsu, Chain-Shu

2014-05-14

269

Low temperature plasma-enhanced atomic layer deposition of thin vanadium nitride layers for copper diffusion barriers  

SciTech Connect

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.

Rampelberg, Geert; Devloo-Casier, Kilian; Deduytsche, Davy; Detavernier, Christophe [Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, B-9000 Ghent (Belgium)] [Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, B-9000 Ghent (Belgium); Schaekers, Marc [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium)] [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Blasco, Nicolas [Air Liquide Electronics US, L.P., 46401 Landing Parkway, Fremont, California 94538 (United States)] [Air Liquide Electronics US, L.P., 46401 Landing Parkway, Fremont, California 94538 (United States)

2013-03-18

270

Crossover from normal to anomalous diffusion in field-aligned dipolar systems  

E-print Network

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 cage-like 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.

Jelena Jordanovic; Sabine H. L. Klapp

2010-09-23

271

Numerical simulation of transient liquid phase bonding under temperature gradient.  

E-print Network

??Transient Liquid Phase bonding under Temperature Gradient (TG-TLP bonding) is a relatively new process of TLP diffusion bonding family for joining difficult-to-weld aerospace materials. Earlier… (more)

Ghobadi Bigvand, Arian

2013-01-01

272

An enhanced International Prognostic Index (NCCN-IPI) for patients with diffuse large B-cell lymphoma treated in the rituximab era.  

PubMed

The International Prognostic Index (IPI) has been the basis for determining prognosis in patients with aggressive non-Hodgkin lymphoma (NHL) for the past 20 years. Using raw clinical data from the National Comprehensive Cancer Network (NCCN) database collected during the rituximab era, we built an enhanced IPI with the goal of improving risk stratification. Clinical features from 1650 adults with de novo diffuse large B-cell lymphoma (DLBCL) diagnosed from 2000-2010 at 7 NCCN cancer centers were assessed for their prognostic significance, with statistical efforts to further refine the categorization of age and normalized LDH. Five predictors (age, lactate dehydrogenase (LDH), sites of involvement, Ann Arbor stage, ECOG performance status) were identified and a maximum of 8 points assigned. Four risk groups were formed: low (0-1), low-intermediate (2-3), high-intermediate (4-5), and high (6-8). Compared with the IPI, the NCCN-IPI better discriminated low- and high-risk subgroups (5-year overall survival [OS]: 96% vs 33%) than the IPI (5 year OS: 90% vs 54%), respectively. When validated using an independent cohort from the British Columbia Cancer Agency (n = 1138), it also demonstrated enhanced discrimination for both low- and high-risk patients. The NCCN-IPI is easy to apply and more powerful than the IPI for predicting survival in the rituximab era. PMID:24264230

Zhou, Zheng; Sehn, Laurie H; Rademaker, Alfred W; Gordon, Leo I; Lacasce, Ann S; Crosby-Thompson, Allison; Vanderplas, Ann; Zelenetz, Andrew D; Abel, Gregory A; Rodriguez, Maria A; Nademanee, Auayporn; Kaminski, Mark S; Czuczman, Myron S; Millenson, Michael; Niland, Joyce; Gascoyne, Randy D; Connors, Joseph M; Friedberg, Jonathan W; Winter, Jane N

2014-02-01

273

Depth-compensated diffuse optical tomography enhanced by general linear model analysis and an anatomical atlas of human head.  

PubMed

One of the main challenges in functional diffuse optical tomography (DOT) is to accurately recover the depth of brain activation, which is even more essential when differentiating true brain signals from task-evoked artifacts in the scalp. Recently, we developed a depth-compensated algorithm (DCA) to minimize the depth localization error in DOT. However, the semi-infinite model that was used in DCA deviated significantly from the realistic human head anatomy. In the present work, we incorporated depth-compensated DOT (DC-DOT) with a standard anatomical atlas of human head. Computer simulations and human measurements of sensorimotor activation were conducted to examine and prove the depth specificity and quantification accuracy of brain atlas-based DC-DOT. In addition, node-wise statistical analysis based on the general linear model (GLM) was also implemented and performed in this study, showing the robustness of DC-DOT that can accurately identify brain activation at the correct depth for functional brain imaging, even when co-existing with superficial artifacts. PMID:23859922

Tian, Fenghua; Liu, Hanli

2014-01-15

274

Metadherin interference inhibits proliferation and enhances chemo-sensitivity to doxorubicin in diffuse large B cell lymphoma  

PubMed Central

Metadherin (MTDH) is highly expressed in many tumors and is involved in the proliferation, metastasis and drug resistance of tumor cells by regulating multiple signaling pathways. Our previous studies demonstrated that MTDH is overexpressed in diffuse large B cell lymphoma (DLBCL) and involved in apoptosis resistance, in part, via Wnt signaling. Here, we investigated the role of MTDH in the chemo-sensitivity of DLBCL. The study was performed in the DLBCL cell line LY8 to investigate the relationship between MTDH expression and doxorubicin (DOX) sensitivity in DLBCL. A MTDH interference model was developed in LY8 cells by transfected with lentivirus which is carrying MTDH interference sequence. Western blot was used to detect the protein expression. A CCK-8 assay was used to evaluate cell proliferation. The results showed that DOX treatment had no effect on the intracellular MTDH expression of LY8 cells. The proliferation of LY8 cells was inhibited after MTDH interference. MTDH interference increased the DOX sensitivity in the LY8 cell lines. The results suggested that MTDH is a potential therapeutic target in DLBCL, and it cooperates with DOX in treatment of DLBCL. PMID:25232390

Li, Pei-Pei; Feng, Li-Li; Chen, Na; Lu, Kang; Meng, Xiao-Hui; Ge, Xue-Ling; Lv, Xiao; Wang, Xin

2014-01-01

275

Response of HT29 colorectal xenograft model to cediranib assessed with 18 F-fluoromisonidazole positron emission tomography, dynamic contrast-enhanced and diffusion-weighted MRI.  

PubMed

Cediranib is a small-molecule pan-vascular endothelial growth factor receptor inhibitor. The tumor response to short-term cediranib treatment was studied using dynamic contrast-enhanced and diffusion-weighted MRI at 7 T, as well as (18) F-fluoromisonidazole positron emission tomography and histological markers. Rats bearing subcutaneous HT29 human colorectal tumors were imaged at baseline; they then received three doses of cediranib (3 mg/kg per dose daily) or vehicle (dosed daily), with follow-up imaging performed 2 h after the final cediranib or vehicle dose. Tumors were excised and evaluated for the perfusion marker Hoechst 33342, the endothelial cell marker CD31, smooth muscle actin, intercapillary distance and tumor necrosis. Dynamic contrast-enhanced MRI-derived parameters decreased significantly in cediranib-treated tumors relative to pretreatment values [the muscle-normalized initial area under the gadolinium concentration curve decreased by 48% (p=0.002), the enhancing fraction by 43% (p=0.003) and K(trans) by 57% (p=0.003)], but remained unchanged in controls. No change between the pre- and post-treatment tumor apparent diffusion coefficients in either the cediranib- or vehicle-treated group was observed over the course of this study. The (18) F-fluoromisonidazole mean standardized uptake value decreased by 33% (p=0.008) in the cediranib group, but showed no significant change in the control group. Histological analysis showed that the number of CD31-positive vessels (59 per mm(2) ), the fraction of smooth muscle actin-positive vessels (80-87%) and the intercapillary distance (0.17 mm) were similar in cediranib- and vehicle-treated groups. The fraction of perfused blood vessels in cediranib-treated tumors (81 ± 7%) was lower than that in vehicle controls (91 ± 3%, p=0.02). The necrotic fraction was slightly higher in cediranib-treated rats (34 ± 12%) than in controls (26 ± 10%, p=0.23). These findings suggest that short-term treatment with cediranib causes a decrease in tumor perfusion/permeability across the tumor cross-section, but changes in vascular morphology, vessel density or tumor cellularity are not manifested at this early time point. PMID:22777834

Bokacheva, Louisa; Kotedia, Khushali; Reese, Megan; Ricketts, Sally-Ann; Halliday, Jane; Le, Carl H; Koutcher, Jason A; Carlin, Sean

2013-02-01

276

Transient Dimers of Allergens  

PubMed Central

Background Allergen-mediated cross-linking of IgE antibodies bound to the Fc?RI receptors on the mast cell surface is the key feature of the type I allergy. If an allergen is a homodimer, its allergenicity is enhanced because it would only need one type of antibody, instead of two, for cross-linking. Methodology/Principal Findings An analysis of 55 crystal structures of allergens showed that 80% of them exist in symmetric dimers or oligomers in crystals. The majority are transient dimers that are formed at high protein concentrations that are reached in cells by colocalization. Native mass spectrometric analysis showed that native allergens do indeed form transient dimers in solution, while hypoallergenic variants of them exist almost solely in the monomeric form. We created a monomeric Bos d 5 allergen and show that it has a reduced capability to induce histamine release. Conclusions/Significance The results suggest that dimerization would be a very common and essential feature for allergens. Thus, the preparation of purely monomeric variants of allergens could open up novel possibilities for specific immunotherapy. PMID:20140203

Rouvinen, Juha; Jänis, Janne; Laukkanen, Marja-Leena; Jylhä, Sirpa; Niemi, Merja; Päivinen, Tero; Mäkinen-Kiljunen, Soili; Haahtela, Tari; Söderlund, Hans; Takkinen, Kristiina

2010-01-01

277

Experimental Investigation of Radio-Turbulence Induced Diffusion -- Final Report  

SciTech Connect

The outcome of this research project suggests that the transport of radon in water is significantly greater than that predicted solely by molecular diffusion. The original study was related to the long term storage of {sup 226}Ra-bearing sand at the DOE Fernald site and determining whether a barrier of water covering the sand would be effective in reducing the emanation of {sup 222}Rn from the sand. Initial observations before this study found the transport of radon in water to be greater than that predicted solely by molecular diffusion. Fick's law on diffusion was used to model the transport of radon in water including the impact associated with radioactive decay. Initial measurements suggested that the deposition of energy in water associated with the radioactive decay process influences diffusion and enhances transport of radon. A multi-region, one-dimensional, steady-state transport model was used to analyze the movement of radon through a sequential column of air, water and air. An effective diffusion coefficient was determined by varying the thickness of the water column and measuring the time for transport of {sup 222}Rn through of the water barrier. A one-region, one-dimensional transient diffusion equation was developed to investigate the build up of radon at the end of the water column to the time when a steady-state, equilibrium condition was achieved. This build up with time is characteristic of the transport rate of radon in water and established the basis for estimating the effective diffusion coefficient for {sup 222}Rn in water. Several experiments were conducted using different types and physical arrangements of water barriers to examine how radon transport is influenced by the water barrier. Results of our measurements confirm our theoretical analyses which suggest that convective forces other than pure molecular diffusion impact the transport of {sup 222}Rn through the water barrier. An effective diffusion coefficient is defined that includes effects of molecular diffusion and convection to describe the transport of radon in water. The effective diffusion coefficients measured in these experiments are 6.8 x 10{sup -4} {+-} 28% and 3.5 x 10{sup -4} {+-} 34% cm{sup 2} sec{sup -1} for the steady-state and transient diffusion conditions, respectively. Water barriers ranging in thickness from 30-50 cm reduce the amount of radon released from the radium-bearing source material by a factor of 0.3-0.1, respectively.

Spitz, H. B.; Usman, S.

2005-07-07

278

Transient heat flux shielding using thermal metamaterials  

NASA Astrophysics Data System (ADS)

We have developed a heat shield based on a metamaterial engineering approach to shield a region from transient diffusive heat flow. The shield is designed with a multilayered structure to prescribe the appropriate spatial profile for heat capacity, density, and thermal conductivity of the effective medium. The heat shield was experimentally compared to other isotropic materials.

Narayana, Supradeep; Savo, Salvatore; Sato, Yuki

2013-05-01

279

Diffusion and Electrophoretic Mobility of Single-Stranded RNA from Molecular Dynamics Simulations  

PubMed Central

Hydrodynamic properties of small single-stranded RNA homopolymers with three and six nucleotides in free solution are determined from molecular dynamics simulations in explicit solvent. We find that the electrophoretic mobility increases with increasing RNA length, consistent with experiment. Diffusion coefficients of RNA, corrected for finite-size effects and solvent viscosity, agree well with those estimated from experiments and hydrodynamic calculations. The diffusion coefficients and electrophoretic mobilities satisfy a Nernst-Einstein relation in which the effective charge of RNA is reduced by the charge of transiently bound counterions. Fluctuations in the counterion atmosphere are shown to enhance the diffusive spread of RNA molecules drifting along the direction of the external electric field. As a consequence, apparent diffusion coefficients measured by capillary zone electrophoresis can be significantly larger than the actual values at certain experimental conditions. PMID:14747307

Yeh, In-Chul; Hummer, Gerhard

2004-01-01

280

Nanoparticle dispersion in polymer nanocomposites by spin-diffusion-averaged paramagnetic enhanced NMR relaxometry: scaling relations and applications.  

PubMed

Scaling relationships are identified between NMR longitudinal relaxation times and clay dispersion quality in polymer-paramagnetic clay nanocomposites. Derived from a previously published analytical relationship developed from a lamella-based model, the scaling relationships are based on the enhancement of NMR relaxation rates with increasing exfoliation and dispersion homogeneity. The paramagnetic contribution to the NMR relaxation rate is inversely proportional to the square of the clay interparticle spacing, and directly proportional to the square of the clay weight fraction. These scaling relationships allow the prediction of relative exfoliation of clay particles for a given series of polymer-clay nanocomposites. With independent knowledge of clay exfoliation in a single sample (e.g., from transmission electron microscopy), NMR relaxometry data may be converted into absolute measures of exfoliation. These scaling relations are confirmed with samples of fully exfoliated poly(vinyl alcohol)-montmorillonite nanocomposites, and then used to reveal exfoliation and dispersion quality in a series of nylon-6-montmorillonite nanocomposites. This characterization route is advantageous because NMR relaxometry can more rapidly provide clay dispersion information that is averaged over larger sample volumes than transmission electron microscopy. PMID:25000915

Xu, Bo; Leisen, Johannes; Beckham, Haskell W

2014-08-21

281

An uncommon cause of transient neurological dysfunction.  

PubMed

Transient neurological dysfunction may be associated with uncommon disorders and should prompt consideration of a broad differential diagnosis when assessing patients with episodic symptoms. The most common causes of transient neurological dysfunction include transient ischemic attack (TIA), seizure disorder, and migraine and its variants. However, underlying unusual pathophysiological processes such as brain tumors can also cause transient neurological dysfunction. Here we present a case of a 68-year-old male with oligodendroglial gliomatosis cerebri (OGC) who presented with TIA-like symptoms. Brain magnetic resonance imaging revealed multiple diffuse T2 hyperintensities within the white and gray matter. Magnetic resonance spectroscopy was suggestive of gliomatosis cerebri and was particularly helpful in this case. The diagnosis of OGC was confirmed by histopathology and molecular genetic studies on brain biopsy tissue. In this report, we discuss the clinical and radiological characteristics of OGC and highlight the unusual presentation of this case. PMID:24982718

Farooq, Muhammad U; Bhatt, Archit; Chang, Howard T

2014-07-01

282

An Uncommon Cause of Transient Neurological Dysfunction  

PubMed Central

Transient neurological dysfunction may be associated with uncommon disorders and should prompt consideration of a broad differential diagnosis when assessing patients with episodic symptoms. The most common causes of transient neurological dysfunction include transient ischemic attack (TIA), seizure disorder, and migraine and its variants. However, underlying unusual pathophysiological processes such as brain tumors can also cause transient neurological dysfunction. Here we present a case of a 68-year-old male with oligodendroglial gliomatosis cerebri (OGC) who presented with TIA-like symptoms. Brain magnetic resonance imaging revealed multiple diffuse T2 hyperintensities within the white and gray matter. Magnetic resonance spectroscopy was suggestive of gliomatosis cerebri and was particularly helpful in this case. The diagnosis of OGC was confirmed by histopathology and molecular genetic studies on brain biopsy tissue. In this report, we discuss the clinical and radiological characteristics of OGC and highlight the unusual presentation of this case. PMID:24982718

Bhatt, Archit; Chang, Howard T.

2014-01-01

283

Transient tachypnea - newborn  

MedlinePLUS

TTN; Wet lungs - newborns; Retained fetal lung fluid; Transient RDS; Prolonged transition ... Transient tachypnea is a respiratory disorder seen shortly after delivery in full-term or late preterm babies. ...

284

Transient familial hyperbilirubinemia  

MedlinePLUS

Transient familial hyperbilirubinemia is a metabolic disorder that is passed down through families. Babies with this disorder ... Transient familial hyperbilirubinemia is an inherited disorder. It occurs when the body does not properly break down ( ...

285

Transcription factor CCAAT/enhancer-binding protein alpha and critical circadian clock downstream target gene PER2 are highly deregulated in diffuse large B-cell lymphoma  

PubMed Central

Disturbances of circadian rhythms and mammalian clock genes have been implicated in the etiologies of many chronic illnesses, including cancer. We show that transcription factor CCAAT/enhancer-binding protein alpha (C/EBPalpha)-regulated PER2 activation is a potential tumor suppressor pathway in diffuse large B-cell lymphoma (DLBCL), one of the commonest types of mature B-cell lymphoma. Expression analysis of human B-cell lymphoma samples including DLBCL (n = 50), mantle cell (n = 21), follicular (n = 25) and Burkitt (n = 18) lymphoma revealed markedly down-regulated CEBPA and PER2 mRNA levels exclusively in DLBCL samples compared to control lymphatic tissue. We demonstrated direct regulation of the circadian core clock gene PER2 by C/EBPalpha in the pro-B cell line Ba/F3, and forced expression of PER2 resulted in decreased proliferation, GO/G1 cell cycle arrest and increased rates of apoptosis. Interestingly, treatment of human DLBCL cell lines with the histone deacetylase-inhibitor suberoylanilide hydroxamic acid (SAHA) significantly increased the expression of C/EBPalpha and Per2, accompanied by cell growth inhibition; in contrast, siRNA knockdown of CEBPA reduced the anti-proliferative effect of SAHA treatment. Our results show for the first time that C/EBPalpha with its associated direct core clock gene target, PER2, are highly deregulated in DLBCL, suggesting an important tumor suppressive pathway in the pathogenesis of this lymphoma entity. PMID:22260161

Thoennissen, Nils H.; Thoennissen, Gabriela B.; Abbassi, Sam; Nabavi-Nouis, Shayan; Sauer, Tim; Doan, Ngan B.; Gery, Sigal; Müller-Tidow, Carsten; Said, Jonathan W.; Koeffler, H. Phillip

2013-01-01

286

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)

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.

Chen, Cen; Yang, Wei; Wang, Dan-Tong; Chen, Chao-Long; Zhuang, Qing-Ye; Kong, Xiang-Dong

2014-12-01

287

The Truncate Mutation of Notch2 Enhances Cell Proliferation through Activating the NF-?B Signal Pathway in the Diffuse Large B-Cell Lymphomas  

PubMed Central

The Notch2 is a critical membrane receptor for B-cell functions, and also displays various biological roles in lymphoma pathogenesis. In this article, we reported that 3 of 69 (4.3%) diffuse large B-cell lymphomas (DLBCLs) exhibited a truncate NOTCH2 mutation at the nucleotide 7605 (G/A) in the cDNA sequence, which led to partial deletion of the C-terminal of PEST (proline-, glutamic acid-, serine- and threonine-rich) domain. The truncate Notch2 activated both the Notch2 and the NF-?B signals and promoted the proliferation of B-cell lymphoma cell lines, including DLBCL and Burkitt's lymphoma cell lines. Moreover, the ectopic proliferation was completely inhibited by ammonium pyrrolidinedithiocarbamate (PDTC), an NF-?B inhibitor. Simultaneously, PDTC also reduced the expression level of Notch2. Based on these results, we conclude that the Notch2 receptor with PEST domain truncation enhances cell proliferation which may be associated with the activation of the Notch2 and the NF-?B signaling. Our results are expected to provide a possible target for new DLBCL therapies by suppressing the Notch2 and the NF-?B signaling. PMID:25314575

Zhang, Xinxia; Shi, Yaoyao; Weng, Yuanyuan; Lai, Qian; Luo, Taobo; Zhao, Jing; Ren, Guoping; Li, Wande; Pan, Hongyang; Ke, Yuehai; Zhang, Wei; He, Qiang; Wang, Qingqing; Zhou, Ren

2014-01-01

288

Transient drainage summary report  

SciTech Connect

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.

NONE

1996-09-01

289

Transient regimes and crossover for epitaxial surfaces.  

PubMed

We apply a formalism for deriving stochastic continuum equations associated with lattice models to obtain equations governing the transient regimes of epitaxial growth for various experimental scenarios and growth conditions. The first step of our methodology is the systematic transformation of the lattice model into a regularized stochastic equation of motion that provides initial conditions for differential renormalization-group (RG) equations for the coefficients in the regularized equation. The solutions of the RG equations then yield trajectories that describe the original model from the transient regimes, which are of primary experimental interest, to the eventual crossover to the asymptotically stable fixed point. We first consider regimes defined by the relative magnitude of deposition noise and diffusion noise. If the diffusion noise dominates, then the early stages of growth are described by the Mullins-Herring (MH) equation with conservative noise. This is the classic regime of molecular-beam epitaxy. If the diffusion and deposition noise are of comparable magnitude, the transient equation is the MH equation with nonconservative noise. This behavior has been observed in a recent report on the growth of aluminum on silicone oil surfaces [Z.-N. Fang, Thin Solid Films 517, 3408 (2009)]. Finally, the regime where deposition noise dominates over diffusion noise has been observed in computer simulations, but does not appear to have any direct experimental relevance. For initial conditions that consist of a flat surface, the Villain-Lai-Das Sarma (VLDS) equation with nonconservative noise is not appropriate for any transient regime. If, however, the initial surface is corrugated, the relative magnitudes of terms can be altered to the point where the VLDS equation with conservative noise does indeed describe transient growth. This is consistent with the experimental analysis of growth on patterned surfaces [H.-C. Kan, Phys. Rev. Lett. 92, 146101 (2004); T. Tadayyon-Eslami, Phys. Rev. Lett. 97, 126101 (2006)]. PMID:20365573

Haselwandter, Christoph A; Vvedensky, Dimitri D

2010-02-01

290

Transient Isotachophoresis Focusing of DNA and DNA-Protein Complexes Is Essentially Enhanced by Spontaneously Dissolved Aerial Carbon Dioxide in Electrolytes.  

PubMed

The formation of a highly adapted high-E zone is critical to isotachophoresis separation and focusing. Recently, we discovered that the high-E zone is present only in a small portion of electrophoresis channel in the presence of EOF (Liu, S. Q. et al. J. Am. Chem. Soc. 2013, 135, 4644-4647). Accordingly, a much narrower high-E zone is presumably present in t-ITP. If so, it is hard to achieve efficient t-ITP focusing. Indeed, by online coupling t-ITP with CE-LIF immunoassay, the immunocomplexes of carcinogenic BPDE-dG adducts are not efficiently focused using a freshly prepared background electrolyte. Intriguingly, we observed that 20-day stored background electrolyte displays a 10-fold better focusing efficiency. We hypothesize that the unexpected phenomenon is associated with the dissolution of aerial carbon dioxide, which is mainly converted to ionic HCO3(-) in the weak alkaline background electrolyte. Consequently, HCO3(-) of high electrophoretic mobility will be continuously injected into the capillary along with the background electrolyte and act as an alternative leading ion to improve the focusing. By addition of dry ice (without causing significant pH decrease, ?pH < 0.4) to freshly prepared background electrolytes, we immediately observed the enhanced focusing of immunocomplexes of the DNA adducts. NH4HCO3 and Na2CO3, included in the background electrolyte, also improve the focusing efficiency and reproducibility. All these consistently support our hypothesis. To understand the underlying mechanism, an advanced CE-SMFI was exploited to monitor in real time the motion of single DNA molecules and the E change throughout t-ITP. We uncovered that t-ITP can induce a local high-E zone, but the presence of HCO3(-) in the background electrolyte could greatly increase the E value in the high-E zone, which allows more DNA molecules to rapidly move backward and to be efficiently stacked at LE/TE boundary. This study provides new insight into nonuniform electric field-induced electrophoresis focusing. PMID:25437902

Liu, Shengquan; Zhang, Dapeng; Wang, Hailin

2015-01-01

291

Persistent distension and enhanced diffusive extravasation of tumor vessels improved uniform tumor targeting of radioimmunoconjugate in mice administered with angiotensin II and kininase inhibitor.  

PubMed

Induced hypertension with angiotensin II (AT-II) and the inhibition of kininase with enalapril maleate may increase the tumor targeting of radiolabeled monoclonal antibodies (MAbs). We previously found that short-period infusion of 2.0 microg/kg/min of AT-II enhanced tumor targeting of MAb without an impact on normal tissue distribution. In this study, we aimed to optimize the manipulation with these agents, and examine the possible mechanism of their effects on MAb distribution. Effect of the manipulation on tissue circulation was assessed in mice bearing colon cancer xenografts by 201Tl and 99mTc-human serum albumin (HSA) as markers of tissue blood flow and tissue blood volume and/or vascular permeability. A dose finding study of enalapril ranging from 3 to 300 microg showed that 30 microg of enalapril in combination with AT-II infusion produced the best improvement in tumor uptake of 99Tc-HSA without altering 201Tl distribution, suggesting that the increase of vascular permeability was caused by enalapril. AT-II infusion for longer than 1 h affected renal blood flow and caused subcutaneous edema. Tumor uptake of (111)In-A7, a murine IgG1, was 1.62-fold improved 72 h postinjection (P < 0.001) and intratumoral distribution became uniform with 2.0 microg/kg/min of AT-II for 1 h and 30 microg of enalapril. Vessels in manipulated tumors were distended even 48 h after the cessation of AT-II infusion. In conclusion, it was suggested that persistent distension of tumor vessels and the increase of diffusive extravasation of MAb caused by short-period-induced hypertension and inhibition of bradykinin degradation produced favorable effect for the MAb distribution in tumors. PMID:10367936

Kinuya, S; Yokoyama, K; Yamamoto, W; Kawashima, A; Konishi, S; Hiramatsu, T; Tega, H; Shuke, N; Aburano, T; Watanabe, N; Takayama, T; Michigishi, T; Tonami, N

1998-01-01

292

Gas diffusion ultrabarriers on polymer substrates using Al{sub 2}O{sub 3} atomic layer deposition and SiN plasma-enhanced chemical vapor deposition  

SciTech Connect

Thin films grown by Al{sub 2}O{sub 3} atomic layer deposition (ALD) and SiN plasma-enhanced chemical vapor deposition (PECVD) have been tested as gas diffusion barriers either individually or as bilayers on polymer substrates. Single films of Al{sub 2}O{sub 3} ALD with thicknesses of >=10 nm had a water vapor transmission rate (WVTR) of <=5x10{sup -5} g/m{sup 2} day at 38 deg. C/85% relative humidity (RH), as measured by the Ca test. This WVTR value was limited by H{sub 2}O permeability through the epoxy seal, as determined by the Ca test for the glass lid control. In comparison, SiN PECVD films with a thickness of 100 nm had a WVTR of approx7x10{sup -3} g/m{sup 2} day at 38 deg. C/85% RH. Significant improvements resulted when the SiN PECVD film was coated with an Al{sub 2}O{sub 3} ALD film. An Al{sub 2}O{sub 3} ALD film with a thickness of only 5 nm on a SiN PECVD film with a thickness of 100 nm reduced the WVTR from approx7x10{sup -3} to <=5x10{sup -5} g/m{sup 2} day at 38 deg. C/85% RH. The reduction in the permeability for Al{sub 2}O{sub 3} ALD on the SiN PECVD films was attributed to either Al{sub 2}O{sub 3} ALD sealing defects in the SiN PECVD film or improved nucleation of Al{sub 2}O{sub 3} ALD on SiN.

Carcia, P. F.; McLean, R. S. [DuPont Central Research and Development, Wilmington, Delaware 19880 (United States); Groner, M. D.; Dameron, A. A. [Deparment of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309 (United States); George, S. M. [Deparment of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309 (United States); Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado 80309 (United States)

2009-07-15

293

Modeling transient radiation effects in power MOSFETS  

NASA Astrophysics Data System (ADS)

Using standard device specifications and simple assumptions, the transient radiation response of vertical-conduction double-diffused metal-oxide-semiconductor (VDMOS) MOSFETs can be modeled in a standard circuit analysis program. The device model consists of a body diode, a parasitic bipolar transistor, and elements to simulate high-current reduced breakdown. The proposed photocurrent model emulates response to any pulse shape and accounts for bias-dependent depletion regions. The model can be optimized to best fit available test data.

Hoffman, J. Russell; Hall, Wallace E.; Dunn, Douglas E.

1987-12-01

294

Vaneless diffusers  

Microsoft Academic Search

The influence of vaneless diffusers on flow in centrifugal compressors, particularly on surge, is discussed. A vaneless diffuser can demonstrate stable operation in a wide flow range only if it is installed with a backward leaning blade impeller. The circumferential distortion of flow in the impeller disappears quickly in the vaneless diffuser. The axial distortion of flow at the diffuser

Y. Senoo

1984-01-01

295

Diffusion /Osmosis  

NSDL National Science Digital Library

This project is use to review the concepts of diffusion and osmosis 1. Watch the tutorials on diffusion and osmosis. Take the online quiz at the end of each one. Diffusion Animation Osmosis Animation 2. Do the interactive lab on diffusion. Stop when you get to the calculating water potential section. Diffusion/Osmosis Interactive Demo 3. Play the Quia review games. Quia Games- matching/concetration Quia Jeopardy 4. Check out the Elodea leaf cells. Be able to ...

Jensen

2007-11-26

296

The effects of neglecting displacement currents when studying transient wave propagation in the Earth  

Microsoft Academic Search

Diffusion approximations are often used to study the interaction of transient electromagnetic waves with the Earth. If a frequency-independent conductivity and permittivity are assumed, then neglecting the displacement currents in the Earth reduces the wave equation to the diffusion equation, which sometimes can be solved analytically using elementary special functions. We study the validity of the diffusion approximation for a

Hsueh-Yuan Pao; Steven L. Dvorak; D. G. Dudley

1996-01-01

297

The Radio Transient Sky  

Microsoft Academic Search

Transient radio sources are necessarily compact and usually are the locations of explosive or dynamic events, therefore offering unique opportunities for probing fundamental physics and astrophysics. In addition, short-duration transients are powerful probes of intervening media owing to dispersion, scattering, and Faraday rotation that modify the signals. While radio astronomy has an impressive record obtaining high time resolution, usually it

J. Lazio; P. S. Ray; S. Ellingson; S. Close; P. Crane; S. D. Hyman; B. A. Jacoby; W. Junor; N. E. Kassim; S. R. Kulkarni; Y. M. Pihlstrom; G. B. Taylor; D. Werthimer

2006-01-01

298

Coronal transient phenomena  

Microsoft Academic Search

Solar coronal transients, particularly those caused by flares and eruptive prominences, play a major role in the fields of solar-terrestrial physics and astrophysics. In the former field, coronal transients and their associated interplanetary disturbances are responsible for solar and galactic cosmic ray modulations, as well as planetary magnetospheric and ionospheric disturbances. In the latter field, supernovae remnants are scaled-up manifestations

M. Dryer

1982-01-01

299

Asymmetric Diffusional Solidification during Transient Liquid Phase Bonding of Dissimilar Materials  

NASA Astrophysics Data System (ADS)

A theoretical analysis of diffusional solidification during transient liquid phase (TLP) bonding of dissimilar materials was performed in conjunction with experimental verification. A fully implicit, two-dimensional, finite element numerical simulation model, without the inherent symmetry assumption, was developed and used for the theoretical calculations, and good correlations between the model predictions and experimental results were observed. The study showed that an asymmetric distribution of residual interlayer liquid during a dissimilar joining of polycrystal and single crystal alloys is attributable to a mismatch between their lattice diffusion coefficients or solute solubility, irrespective of enhanced intergranular diffusion as was assumed previously. Also, notwithstanding increased solute diffusivity with temperature, it was found that an increase in bonding temperature can result in the prolongation of processing time t f that is required to prevent the formation of deleterious eutectic during bonding of dissimilar materials. The occurrence of this seemingly anomalous behavior, however, reduces when a material is coupled with another type that exhibits a higher solute solubility or better capability of accommodating diffusing melting point depressant solute from the liquid interlayer.

Ghoneim, A.; Ojo, O. A.

2012-03-01

300

Transient nucleation in glasses  

NASA Technical Reports Server (NTRS)

Nucleation rates in condensed systems are frequently not at their steady state values. Such time dependent (or transient) nucleation is most clearly observed in devitrification studies of metallic and silicate glasses. The origin of transient nucleation and its role in the formation and stability of desired phases and microstructures are discussed. Numerical models of nucleation in isothermal and nonisothermal situations, based on the coupled differential equations describing cluster evolution within the classical theory, are presented. The importance of transient nucleation in glass formation and crystallization is discussed.

Kelton, K. F.

1991-01-01

301

Investigation Of A Transient Energetic Charge Exchange Fux Enhancement (?spike-on-tail?) Observed In Neutral-beam-heated H-mode Discharges In The National Spherical Torus Experiment  

SciTech Connect

In the National Spherical Torus Experiment (NSTX), a large increase in the charge exchange neutral flux localized at the Neutral Beam (NB) injection full energy is measured by the E||B (superimposed parallel electric and magnetic fields) Neutral Particle Analyzer (NPA). Termed the High-Energy Feature (HEF), it appears on the NB-injected energetic ion spectrum only in discharges where tearing or kink-type modes (f < 50 kHz) are absent, Toroidal Alfvén Eigenmode (TAE) activity (f ~ 50 - 150 kHz) is weak and Global Alfvén Eigenmode (GAE) activity (f ~ 400 – 1000 kHz) is robust. Compressional Alfvén eigenmode (CAE) activity (f > 1000 kHz) is usually sporadic or absent during the HEF event. The HEF exhibits growth times of ?t ~ 20 - 80 ms, durations of ~ 100 – 600 ms and peak-to-base flux ratios up to H = Fmax /Fmin ~ 10. In infrequent cases, a slowing down distribution below the HEF energy can develop that continues to evolve over periods > 100 ms, a time scale long compared with the typical fast ion equilibration times. HEFs are Transient energetic charge exchange flux enhancement (?spike-on-tail?) 2 observed only in H-mode (not L-mode) discharges with injected power Pb ? 4 MW and in the pitch range ? = vll /v ~ 0.7 – 0.9; i.e. only for passing particles. Increases of ~ 10 - 30 % in the measured neutron yield and total stored energy that are observed to coincide with the feature appear to be driven by concomitant broadening of measured Te(r), Ti(r) and ne(r) profiles and not the HEF itself. While the HEF has minimal impact on plasma performance, it nevertheless poses a challenging wave-particle interaction phenomenon to understand. Candidate mechanisms for HEF formation are developed based on quasilinear theory of wave-particle interaction. The only mechanism found to lead to the large NPA flux ratios, H = Fmax /Fmin , observed in NSTX is the quasilinear evolution of the energetic ion distribution, Fb(E,?,r), in phase space and the concomitant loss of some particles, which occurs due to the cyclotron interaction of the particles with destabilized modes having sufficiently high frequencies, F ~ 700 - 1000 kHz, in the plasma frame that are tentatively identified as Global Alfvén Eigenmodes.

S.S. Medley et. al.

2011-08-04

302

Osmosis and Diffusion  

ERIC Educational Resources Information Center

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.

Sack, Jeff

2005-01-01

303

Femtosecond Transient Imaging  

E-print Network

This thesis proposes a novel framework called transient imaging for image formation and scene understanding through impulse illumination and time images. Using time-of-flight cameras and multi-path analysis of global light ...

Kirmani, Ahmed (Ghulam Ahmed)

2010-01-01

304

Measurement of transient reflectance  

NASA Technical Reports Server (NTRS)

Real-time reflectometer, adjusted to a fraction of a second, monitors transient effects and allows sample to be exposed to environment continuously. Reflectance and reference signals share same optical path, minimizing extraneous effects.

Zwiener, J. M.

1976-01-01

305

Gamma ray transients  

NASA Technical Reports Server (NTRS)

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.

Cline, Thomas L.

1987-01-01

306

Transient growth of Ekman-Couette flow.  

PubMed

Coriolis force effects on shear flows are important in geophysical and astrophysical contexts. We report a study on the linear stability and the transient energy growth of the plane Couette flow with system rotation perpendicular to the shear direction. External rotation causes linear instability. At small rotation rates, the onset of linear instability scales inversely with the rotation rate and the optimal transient growth in the linearly stable region is slightly enhanced ?Re2. The corresponding optimal initial perturbations are characterized by roll structures inclined in the streamwise direction and are twisted under external rotation. At large rotation rates, the transient growth is significantly inhibited and hence linear stability analysis is a reliable indicator for instability. PMID:24580314

Shi, Liang; Hof, Björn; Tilgner, Andreas

2014-01-01

307

Temperature Dependence of Digital Single-Event Transients in Bulk and Fully-Depleted SOI Technologies  

E-print Network

Factors that affect single-event transient pulse widths, such as drift, diffusion, and parasitic bipolar transistor parameters, are also strong functions of operating temperature. In this paper, SET pulse-width measurements ...

Gouker, Pascale M.

308

Lateral Diffusion in an Archipelago  

PubMed Central

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

Saxton, Michael J.

1982-01-01

309

Transient fission gas behavior in uranium nitride fuel under proposed space applications  

Microsoft Academic Search

In order to investigate whether fission gas swelling and release would be significant factors in a space based nuclear reactor operating under the Strategic Defense Initiative (SDI) program, the finite element program REDSTONE (Routine For Evaluating Dynamic Swelling in Transient Operational Nuclear Environments) was developed to model the 1-D, spherical geometry diffusion equations describing transient fission gas behavior in a

Daniel L. Deforest

1991-01-01

310

Transient fission-gas behavior in uranium nitride fuel under proposed space applications. Doctoral thesis  

Microsoft Academic Search

In order to investigate whether fission gas swelling and release would be significant factors in a space based nuclear reactor operating under the Strategic Defense Initiative (SDI) program, the finite element program REDSTONE (Routine For Evaluating Dynamic Swelling in Transient Operational Nuclear Environments) was developed to model the 1-D, spherical geometry diffusion equations describing transient fission gas behavior in a

Deforest

1991-01-01

311

Low Temperature Transient Liquid Phase (LTTLP) Bonding for Au/Cu  

E-print Network

) ) M. M. Hou Low Temperature Transient Liquid Phase (LTTLP) Bonding for Au/Cu and Cu of Technology, Cambridge, MA 02139 TheLow Temperature TransientLiquidPhase Diffusion Bonding (LTTLP) process has been bonded to copper heatsink.s at temperatures less than 160"C, using /n-Sn eutectic solders. After

Eagar, Thomas W.

312

Complex Diffusion Based Level Set Method  

Microsoft Academic Search

Complex diffusion has been applied to image denoising and enhancement. However, whether it is suitable for image segmentation or not is needed to further study. In this paper complex diffusion is combined with level set method without re-initiation and then complex diffusion based level set method is proposed. And the new algorithm is applied to insect image segmentation. Experimental results

Huang Shiguo; Li Xiaolin; Geng Guohua; Zhou Mingquan

2010-01-01

313

Validation model for the transient analysis of tightly coupled reactors  

Microsoft Academic Search

Both the static and transient analysis of tightly coupled reactors differ from those of the loosely coupled systems. In these reactors, highly absorbing regions are interspaced with low absorbing regions. That raises questions of the acceptability of diffusion theory approximations. Also, the spectral shapes change drastically throughout the core and can be altered significantly by perturbations. Accurate analysis requires at

T. Bahadir; A. F. Henry

1996-01-01

314

On the theory of stress-assisted diffusion, II  

Microsoft Academic Search

Summary Similarity and general steady-state solutions of a recently developed strees-assisted diffusion theory are derived. General transient solutions are obtained analytically for certain classes of stress distributions. For general stress distributions a perturbation method is employed to produce transient solutions. Under appropriate conditions the derived solutions are reduced to previous formulae that have unsystematically appeared in the literature. Examples of

D. J. Unger; E. C. Aifantis

1983-01-01

315

On some applications of diffusion processes for image processing  

NASA Astrophysics Data System (ADS)

We propose a new algorithm inspired by the properties of diffusion processes for image filtering. We show that purely nonlinear diffusion processes ruled by Fisher equation allows contrast enhancement and noise filtering, but involves a blurry image. By contrast, anisotropic diffusion, described by Perona and Malik algorithm, allows noise filtering and preserves the edges. We show that combining the properties of anisotropic diffusion with those of nonlinear diffusion provides a better processing tool which enables noise filtering, contrast enhancement and edge preserving.

Morfu, S.

2009-06-01

316

DSN Transient Observatory  

NASA Astrophysics Data System (ADS)

Detection of radio transients, in particular those transients with time scales of less than a second, provide a window into some of nature's most extreme conditions. There are now several dedicated transient search programs underway or in planning phase around the globe. The Deep Space Network (DSN) with its multitude of antennas spread across three complexes around the globe, offers a unique capability to search for such short-lived events. Additionally, downlink tracks of planetary orbiters offer an opportunity to search for planetary emissions, such as electrostatic discharges. We will describe a prototype system operating at the DSN Goldstone facility and the preliminary results obtained from monitoring Mars during spacecraft downlink tracks. We will discuss the system architecture, detection algorithms, and strategies for vetoing non-astrophysical events. We will also describe our future plans in terms of expansion of the program to other DSN complexes.

Kuiper, T. B.; Lazio, T. J.; Majid, W. A.; Navarro, R.; Teitelbaum, L. P.; Trinh, J. T.

2013-01-01

317

Transient photoconductivity spectroscopy of polycrystalline diamond films  

SciTech Connect

Photoexcitation spectra of nonequilibrium charge carriers in polycrystalline diamond films were measured in the visible region (430 - 690 nm) by the contact-less transient photoconductivity technique with a tunable optical parametric oscillator. Preliminary irradiation of samples by intense UV laser pulses resulted in the redistribution of the population of deep trap levels and was accompanied by substantial long-term enhancement of photoconductivity in the spectral band at 2 eV. (laser applications and other topics in quantum electronics)

Klimentov, Sergei M; Garnov, Sergei V [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Pimenov, S M; Konov, Vitalii I [Natural Science Center, A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Gloor, S; Luthy, W; Weber, H P [Institute of Applied Physics, University of Bern (Switzerland)

2000-05-31

318

Anomalous effects of ultradilute impurities on heat diffusion in liquids  

NASA Astrophysics Data System (ADS)

We analyze the applicability of transient thermal lens (TL) z-scan technique as a sensitive tool to measure heat diffusivity of liquids. Suitable dyes at very low concentrations were added to the host liquid to enhance the TL effect through improved optical absorption. We investigate if these dye impurities, besides improving light absorption, have any effect on the thermal properties of the host liquid. We find that even a trace amount of impurity significantly alters the thermal properties of a solvent. Time-evolution of TL showed pronounced asymmetry about laser focus revealing anomalous behavior in thermal blooming of the laser beam. Heat transport was strongly dependent on the rise in sample temperature by light absorption. Important effects of nonlinear heat transport in time-resolved TL z-scan experiments were revealed.

Ambast, Deepak K. S.; Mondal, Richarj; Pati, Palas Baran; Zade, Sanjio S.; Bansal, Bhavtosh; Pal, Bipul

2015-01-01

319

The Zwicky Transient Facility  

NASA Astrophysics Data System (ADS)

The Zwicky Transient Facility (ZTF) is a next-generation optical synoptic survey. Building on the experience and infrastructure of the Palomar Transient Factory (PTF), ZTF will use a new 47-square degree survey camera on the 48-inch Palomar Oschin Schmidt Telescope. ZTF will survey more than an order of magnitude faster than PTF, enabling an unprecedented wide area, high-cadence survey. Its major science goals include discovering young supernovae, searching for electromagnetic counterparts to gravitational wave sources, identifying stellar variables, and detecting Near-Earth Asteroids. Public surveys and data releases will enable broad utilization of the ZTF data.

Bellm, Eric Christopher; Kulkarni, Shrinivas R.; ZTF Collaboration

2015-01-01

320

Diffuse leptomeningeal oligodendrogliomatosis: radiologic/pathologic correlation.  

PubMed

We present the radiologic and pathologic findings in a boy who presented with diffuse leptomeningeal enhancement and whose clinical status deteriorated over the course of 5 years. During this period, MR images showed progression of the enhancement in the subarachnoid spaces, formation of intraaxial cysts, and hydrocephalus. Autopsy findings revealed diffuse oligodendroglioma throughout the leptomeninges of the brain and spine, with no definite intraaxial focus. The radiologic and pathologic features of diffuse leptomeningeal oligodendrogliomatosis are reviewed. PMID:10871026

Armao, D M; Stone, J; Castillo, M; Mitchell, K M; Bouldin, T W; Suzuki, K

2000-01-01

321

Influence of defects on excess charge carrier kinetics studied by transient PC and transient PA  

SciTech Connect

By comparison of transient photoconductivity (TPC) and transient photoinduced absorption (PA) the influence of the density of states in the bandgap on excess charge carrier kinetics is studied for a-Si:H films deposited at different temperatures and for state of the art a-Si:H films in two different states of light soaking. In both series the rising deep defect density leads to an enhancement of electron trapping rather than recombination via deep defects. The samples deposited at temperatures lower than 250 C additionally show a lower effective electron mobility, i.e., a broader conduction band tail.

Feist, H.; Kunst, M.; Swiatkowski, C.

1997-07-01

322

Dynamic characterization of hydrophobic and hydrophilic solutes in oleic-acid enhanced transdermal delivery using two-photon fluorescence microscopy  

NASA Astrophysics Data System (ADS)

In this letter, we propose an efficient methodology of investigating dynamic properties of sulforhodamine B and rhodamine B hexyl ester molecules transporting across ex-vivo human stratum corneum with and without oleic acid enhancement. Three-dimensional, time-lapse fluorescence images of the stratum corneum can be obtained using two-photon fluorescence microscopy. Furthermore, temporal quantifications of transport enhancements in diffusion parameters can be achieved with the use of Fick's second law. Dynamic characterization of solutes transporting across the stratum corneum is an effective method for understanding transient phenomena in transdermal delivery of probe molecules, leading to improved delivery strategies of molecular species for therapeutic purposes.

Tseng, Te-Yu; Yang, Chiu-Sheng; Tsai, Tsung-Hua; Chen, Yang-Fang; Dong, Chen-Yuan

2014-10-01

323

Quantum diffusion: A simple, exactly solvable model  

NASA Astrophysics Data System (ADS)

We propose a simple quantum mechanical model describing the time dependent diffusion current between two fermion reservoirs that were initially disconnected and characterized by different densities or chemical potentials. The exact, analytical solution of the model yields the transient behavior of the coupled fermion systems evolving to a final steady state, whereas the long-time behavior is determined by a power law rather than by exponential decay. Similar results are obtained for the entropy production which is proportional to the diffusion current.

Magnus, Wim; Nelissen, Kwinten

2015-01-01

324

Quantum diffusion: a simple, exactly solvable model  

E-print Network

We propose a simple quantum mechanical model describing the time dependent diffusion current between two fermion reservoirs that were initially disconnected and characterized by different densities or chemical potentials. The exact, analytical solution of the model yields the transient behavior of the coupled fermion systems evolving to a final steady state, whereas the long-time behavior is determined by a power law rather than by exponential decay. Similar results are obtained for the entropy production which is proportional to the diffusion current.

Wim Magnus; Kwinten Nelissen

2012-12-06

325

Optimal Network Modularity for Information Diffusion  

NASA Astrophysics Data System (ADS)

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.

Nematzadeh, Azadeh; Ferrara, Emilio; Flammini, Alessandro; Ahn, Yong-Yeol

2014-08-01

326

Transient separation of multicomponent liquid mixtures in thermogravitational columns.  

PubMed

Transient separation of the individual components in a multicomponent liquid mixture in a thermogravitational column can be used to determine the thermal and molecular diffusion coefficients. Two models of the transient behavior are developed. First, a classical model where density only depends on temperature. Second, a general model where the compositional effect on density is also taken into account. Diffusion coefficients can be determined by fitting experimental data to either model. The procedure is demonstrated for a ternary liquid mixture. The results reveal that the classical model is very unreliable even though composition variation only contributes to the total buoyancy by one-third. Diffusion coefficients can be obtained reliably from the general model provided the experimental noise does not exceed +/-1% of steady-state separation. This level of accuracy in composition measurements is achievable. PMID:17949173

Haugen, Kjetil B; Firoozabadi, Abbas

2007-10-21

327

Rotor transient analysis  

NASA Technical Reports Server (NTRS)

Undamped modes approximate dynamic behavior of rotors and bearings. Application of modal analysis to uncouple equations of motion simplifies stability, steady-state unbalance response, and transient response analysis of system; nonlinear stability is predicted from calculated frequency spectra. Analysis provides designers with complete information without involving large-scale computational costs. Programs are written in FORTRAN IV for use on CDC 6600 computer.

Allaire, P. E.; Choy, K. C.; Gunter, E. J.

1980-01-01

328

Shock Wave and EUV Transient During a Flare  

NASA Technical Reports Server (NTRS)

A metric type II burst and a 'brow' type enhancement in EUV were observed during the hard X-ray flare of 1997 April 15 from a newly emerging region, AR 8032. The position of the type II burst obtained from the Nancay radioheliograph coincided with the EUV transient. The type II burst and the EUV transient were in the equatorial streamer region to the north of the flaring region. This observation suggests that the EUV transient may be the manifestation of the MHD shock responsible for the type II burst.

Gopalswamy, N.; Kaiser, M. L.; Sato, J.; Pick, Monique

2000-01-01

329

Mathematical Modeling and Experimental Investigations of Isothermal Solidification during Transient Liquid Phase Bonding of Nickel  

E-print Network

of diffusion, was used to predict the time required to complete isothermal solidification and to determine with the experimentally determined values. The obtained activation energies for diffusion of boron were very close welding [1], transient liquid phase bonding evolved as an effective way to join these superalloys. TLP

Medraj, Mamoun

330

Short-Time Transient Analysis of Intercalation of an Ion into a Sphere  

E-print Network

. These parameters are exchange current density, double-layer capacitance, and diffusion coefficient. The effects to represent the battery potential at moderate discharge rates.11 The periodic steady-state solution and frequency on the transient response revealed the possibility of estimating the diffusion coefficient

331

Diffusion in silicon isotope heterostructures  

SciTech Connect

The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and {sup 28}Si enriched layers, enables the observation of {sup 30}Si self-diffusion from the natural layers into the {sup 28}Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale features have created the need for precise physical models of atomic diffusion in Si. The modeling of the experimental profiles of simultaneous diffusion of B and Si under p-type extrinsic conditions revealed that both species are mediated by neutral and singly, positively charged Si self-interstitials. The diffusion of As and Si under extrinsic n-type conditions yielded a model consisting of the interstitialcy and vacancy mechanisms of diffusion via singly negatively charged self-interstitials and neutral vacancies. The simultaneous diffusion of P and Si has been modeled on the basis of neutral and singly negatively charged self-interstitials and neutral and singly positively charged P species. Additionally, the temperature dependence of the diffusion coefficient of Si in Ge was measured over the temperature range of 550 C to 900 C using a buried Si layer in an epitaxially grown Ge layer.

Silvestri, Hughes Howland

2004-05-14

332

Noninvasive monitoring of therapy-induced microvascular changes in a pancreatic cancer model using dynamic contrast-enhanced magnetic resonance imaging with P846, a new low-diffusible gadolinium-based contrast agent.  

PubMed

A predictive technique in the management of patients with cancer could improve the therapeutic index by allowing better individualization of treatment. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a noninvasive technique that can provide anatomical and physiological information on the tumor and its microenvironment. We studied the effect of chemotherapy (gemcitabine), anti-angiogenesis therapy (sunitinib) and radiotherapy on the kinetics of DCE-MRI parameters in a preclinical model of pancreatic cancer using P846, a new low-diffusible contrast agent. Mice underwent DCE-MRI before treatment (MRI1), after 1 week of treatment (MRI2), and after 1 additional week (MRI3). Combined treatment with radiotherapy and sunitinib had a synergistic effect on tumor growth. In radiotherapy/sunitinib-treated mice, a decrease in K(trans) at MRI2 predicted its superior antivascular and antitumor effect at an early time. An increased K(trans) at MRI2, as seen in gemcitabine- and gemcitabine/sunitinib-treated mice, reflects increased permeability for P846 and might predict a smaller therapeutic effect at this early time. This study shows that the kinetics of DCE-MRI parameters depends on the contrast agent used. P846 appears to be a promising low-diffusible agent to monitor therapeutic effects in this preclinical cancer model, but further studies are needed to compare its behavior with Gd-DTPA and macromolecular-weight contrast agents. Sunitinib as a radiosensitizer is promising for future clinical trials in human pancreatic cancer. PMID:21175342

Casneuf, Veerle F; Delrue, Louke; Van Damme, Nancy; Demetter, Pieter; Robert, Philippe; Corot, Claire; Duyck, Philippe; Ceelen, Wim; Boterberg, Tom; Peeters, Marc

2011-01-01

333

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...

334

Diffuse radiation  

NASA Technical Reports Server (NTRS)

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.

1981-01-01

335

Transient Numerical Modeling of Catalytic Channels  

NASA Technical Reports Server (NTRS)

This paper presents a transient model of catalytic combustion suitable for isolated channels and monolith reactors. The model is a lumped two-phase (gas and solid) model where the gas phase is quasi-steady relative to the transient solid. Axial diffusion is neglected in the gas phase; lateral diffusion, however, is accounted for using transfer coefficients. The solid phase includes axial heat conduction and external heat loss due to convection and radiation. The combustion process utilizes detailed gas and surface reaction models. The gas-phase model becomes a system of stiff ordinary differential equations while the solid phase reduces, after discretization, into a system of stiff ordinary differential-algebraic equations. The time evolution of the system came from alternating integrations of the quasi-steady gas and transient solid. This work outlines the numerical model and presents some sensitivity studies on important parameters including internal transfer coefficients, catalytic surface site density, and external heat-loss (if applicable). The model is compared to two experiments using CO fuel: (1) steady-state conversion through an isothermal platinum (Pt) tube and (2) transient propagation of a catalytic reaction inside a small Pt tube. The model requires internal mass-transfer resistance to match the experiments at lower residence times. Under mass-transport limited conditions, the model reasonably predicted exit conversion using global mass-transfer coefficients. Near light-off, the model results did not match the experiment precisely even after adjustment of mass-transfer coefficients. Agreement improved for the first case after adjusting the surface kinetics such that the net rate of CO adsorption increased compared to O2. The CO / O2 surface mechanism came from a sub-set of reactions in a popular CH4 / O2 mechanism. For the second case, predictions improved for lean conditions with increased external heat loss or adjustment of the kinetics as in the first case. Finally, the results show that different initial surface-species distribution leads to different steady-states under certain conditions. These results demonstrate the utility of a lumped two-phase model of a transient catalytic combustor with detailed chemistry.

Struk, Peter M.; Dietrich, Daniel L.; Miller, Fletcher J.; T'ien, James S.

2007-01-01

336

Using the Transient Surveys  

NASA Astrophysics Data System (ADS)

(Abstract only) We are starting the era of all-sky surveys. While some, like APASS, have specific goals in mind (sky calibration, exoplanets, asteroids, and so on), others have begun releasing real-time alerts of interesting objects. The easily available surveys with alerts will be discussed, along with the kind of objects they are detecting and some hints about how to make use of the transient information.

Henden, A. A.

2014-06-01

337

Transient neonatal Behçet's disease  

PubMed Central

A term neonate with a transient form of Behçet's disease (BD) is described. The mother had a 3-year history of BD treated with corticosteroids, which remained in remission during pregnancy. On day 1 of life, the neonate was noted to have papulopustular lesions of the labia and perineum. She remained clinically well and bacterial and viral infection screens were negative. The lesions disappeared within 3?weeks without scarring. No recurrence has been reported. PMID:23391945

Antonelou, Marilina; Braha, Nirit

2013-01-01

338

Advanced PFBC transient analysis  

SciTech Connect

Transient modeling and analysis of advanced Pressurized Fluidized Bed Combustion (PFBC) systems is a research area that is currently under investigation by the US Department of Energy`s Federal Energy Technology Center (FETC). The object of the effort is to identify key operating parameters that affect plant performance and then quantify the basic response of major sub-systems to changes in operating conditions. PC-TRAX{trademark}, a commercially available dynamic software program, was chosen and applied in this modeling and analysis effort. This paper describes the development of a series of TRAX-based transient models of advanced PFBC power plants. These power plants burn coal or other suitable fuel in a PFBC, and the high temperature flue gas supports low-Btu fuel gas or natural gas combustion in a gas turbine topping combustor. When it is utilized, the low-Btu fuel gas is produced in a bubbling bed carbonizer. High temperature, high pressure combustion products exiting the topping combustor are expanded in a modified gas turbine to generate electrical power. Waste heat from the system is used to raise and superheat steam for a reheat steam turbine bottoming cycle that generates additional electrical power. Basic control/instrumentation models were developed and modeled in PC-TRAX and used to investigate off-design plant performance. System performance for various transient conditions and control philosophies was studied.

White, J.S. [Parsons Power Group, Inc., Reading, PA (United States); Bonk, D.L. [USDOE Federal Energy Technology Center, Morgantown, WV (United States)

1997-05-01

339

Advanced PFBC transient analysis  

SciTech Connect

Transient modeling and analysis of Advanced Pressurized Fluidized Bed Combustion (PFBC) systems is a research area that is currently under investigative study by the United States Department of Energy`s Morgantown Energy Technology Center (METC). The object of the effort is to identify key operating parameters affecting plant performance and then quantify the basic response of major sub-systems to changes in operating conditions. PC-TRAX, a commercially available dynamic software program, was chosen and applied in this modeling and analysis effort. This paper summarizes and describes the development of a series of TRAX-based transient models of Advanced PFBC power plants. These power plants generate a high temperature flue gas by burning coal or other suitable fuel in a PFBC. The high temperature flue gas supports low-Btu fuel gas or natural gas combustion in a gas turbine topping combustor. When utilized, low-Btu fuel gas is produced in a bubbling bed carbonizer. High temperature, high pressure combustion products exiting the topping combustor are expanded in a modified gas turbine to generate electrical power. Waste heat from the system is used to generate and superheat steam for a reheat steam turbine bottoming cycle that generates additional electrical power. Basic control/instrumentation models were developed and modeled in PC-TRAX and used to investigate off-design plant performance. System performance for various transient conditions and control philosophies was studied.

White, J.S. [Parsons Power Group, Inc., Reading, PA (United States); Bonk, D.L.; Rogers, L. [USDOE Morgantown Energy Technology Center, WV (United States)

1996-12-31

340

Transient critical heat flux  

SciTech Connect

The term Critical Heat Flux (CHF) is used in boiling heat transfer to describe the local value of the heat flux at which a characteristic reduction in the heat transfer coefficient first occurs. A major limitation on the thermal design of a light-water reactor (LWR) is the necessity to maintain an adequate safety margin between the CHF and the local heat flux. Extended operations at local power levels in excess of the CHF can lead to high-temperature oxidation and embrittlement or melting of the zircaloy cladding, thus jeopardizing the fuel rod's integrity. In nuclear reactors, the CHF level is more likely to be reached during abnormal (transient) operating conditions, rather than during normal (steady) operations. For accurate nuclear reactor modeling, the accurate prediction of CHF as a function of time-dependent, thermal-hydraulic conditions is essential. This research was a two-fold study. In the first part, the quasi-steady approach in predicting the CHF is defined and analyzed. Data from blowdown experiments are compared to commonly used steady-state correlations on a local-instantaneous basis. In the second part, faster transients, where the quasi-steady approach is unable to predict the CHF, are considered. A new theory is developed to predict the CHF in power transients, which are typical of Reactivity Initiated Accidents (RIA) in LWRs.

Pasamehmetoglu, K.O.

1986-01-01

341

Kinesin Motor Transport is Altered by Macromolecular Crowding and Transiently Associated Microtubule-Associated Proteins  

E-print Network

Intracellular transport of vesicular cargos, organelles, and other macromolecules is an essential process to move large items through a crowded, and inhomogeneous cellular environment. In an effort to dissect the fundamental effects of crowding and an increasingly complex cellular environment on the transport of individual motor proteins, we have performed in vitro reconstitution experiments with single kinesin-1 motors walking on microtubules in the presence of crowding agents and transient microtubule-associated proteins that more closely emulate the cellular environment. Macromolecular crowding due to inert polymers caused enhanced run lengths of motors, but displayed an increased tendency for non-specific motor association and diffusion, most likely due to depletion interactions. We found that transiently bound associated proteins slowed forward motion, but did not drastically affect the association times, in opposition to previously reported obstacle properties of stably associated microtubule-associated proteins, such as the neuronal protein tau. Such studies of the transport properties of molecular motors in increasingly complex reconstituted environments are important to illuminate the fundamental biophysical principles underlying the essential process of intracellular cargo transport.

Leslie Conway; Jennifer L. Ross

2014-09-11

342

Diagnostic assessment by dynamic contrast-enhanced and diffusion-weighted magnetic resonance in differentiation of breast lesions under different imaging protocols  

PubMed Central

Background The apparent diffusion coefficient (ADC) is a highly diagnostic factor in discriminating malignant and benign breast masses in diffusion-weighted magnetic resonance imaging (DW-MRI). The combination of ADC and other pictorial characteristics has improved lesion type identification accuracy. The objective of this study was to reassess the findings on an independent patient group by changing the magnetic field from 1.5-Tesla to 3.0-Tesla. Methods This retrospective study consisted of a training group of 234 female patients, including 85 benign and 149 malignant lesions, imaged using 1.5-Tesla MRI, and a test group of 95 female patients, including 19 benign and 85 malignant lesions, imaged using 3.0-Tesla MRI. The lesion of interest was segmented from the raw image and four sets of measurements describing the morphology, kinetics, DW-MRI, and texture of the pictorial properties of each lesion were obtained. Each lesion was characterized by 28 features in total. Three classical machine-learning algorithms were used to build prediction models on the training group, which evaluated the prognostic performance of the multi-sided features in three scenarios. To reduce information redundancy, five highly diagnostic factors were selected to obtain a compact yet informative characterization of the lesion status. Results Three classification models were built on the training of 1.5-Tesla patients and were tested on the independent 3.0-Tesla test group. The following results were found. i) Characterization of breast masses in a multi-sided way dramatically increased prediction performance. The usage of all features gave a higher performance in both sensitivity and specificity than any individual feature groups or their combinations. ii) ADC was a highly effective factor in improving the sensitivity in discriminating malignant from benign masses. iii) Five features, namely ADC, Sum Average, Entropy, Elongation, and Sum Variance, were selected to achieve the highest performance in diagnosis of the 3.0-Tesla patient group. Conclusions The combination of ADC and other multi-sided characteristics can increase the capability of discriminating malignant and benign breast lesions, even under different imaging protocols. The selected compact feature subsets achieved a high diagnostic performance and thus are promising in clinical applications for discriminating lesion type and for personalized treatment planning. PMID:24885156

2014-01-01

343

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)

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.

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

2013-11-01

344

Diffusible signal factor (DSF) quorum sensing signal and structurally related molecules enhance the antimicrobial efficacy of antibiotics against some bacterial pathogens  

PubMed Central

Background Extensive use of antibiotics has fostered the emergence of superbugs that are resistant to multidrugs, which becomes a great healthcare and public concern. Previous studies showed that quorum sensing signal DSF (diffusible signal factor) not only modulates bacterial antibiotic resistance through intraspecies signaling, but also affects bacterial antibiotic tolerance through interspecies communication. These findings motivate us to exploit the possibility of using DSF and its structurally related molecules as adjuvants to influence antibiotic susceptibility of bacterial pathogens. Results In this study, we have demonstrated that DSF signal and its structurally related molecules could be used to induce bacterial antibiotic susceptibility. Exogenous addition of DSF signal (cis-11-methyl-2-dodecenoic acid) and its structural analogues could significantly increase the antibiotic susceptibility of Bacillus cereus, possibly through reducing drug-resistant activity, biofilm formation and bacterial fitness. The synergistic effect of DSF and its structurally related molecules with antibiotics on B. cereus is dosage-dependent. Combination of DSF with gentamicin showed an obviously synergistic effect on B. cereus pathogenicity in an in vitro model. We also found that DSF could increase the antibiotic susceptibility of other bacterial species, including Bacillus thuringiensis, Staphylococcus aureus, Mycobacterium smegmatis, Neisseria subflava and Pseudomonas aeruginosa. Conclusion The results indicate a promising potential of using DSF and its structurally related molecules as novel adjuvants to conventional antibiotics for treatment of infectious diseases caused by bacterial pathogens. PMID:24575808

2014-01-01

345

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)

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).

Murad, Sohail

2011-03-01

346

On Transients in Detached Bridgman Growth  

NASA Technical Reports Server (NTRS)

In detached Bridgman growth, a gap exists between the growing crystal and the crucible wall. According to crystal shape stability theory, only specific gap widths will be dynamically stable. Beginning with a crystal diameter that differs from stable conditions, the transient crystal growth process is analyzed. The transient shapes are calculated assuming that the growth angle is constant. Anisotropy and dynamic contact angle effects are considered. In microgravity, dynamic stability depends only on capillary effects and is decoupled from heat transfer. However, heat transfer will influence the crystal-melt interface shape. The local angles and the crystal-melt-vapor triple junction are analyzed and the applicability of the Herring formula is discussed. A potential microgravity experiment is proposed which would enhance our understanding of the detached growth dynamic stability problem.

Mazuruk, K.; Volz, M. P.

2011-01-01

347

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

PubMed

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. PMID:23197994

Annan, Kodwo

2012-01-01

348

Anomalous anisotropic diffusion dynamics of hydration water at lipid membranes.  

PubMed

The diffusional water dynamics in the hydration layer of a dipalmitoylphosphatidylcholine bilayer is studied using molecular dynamics simulations. By mapping the perpendicular water motion on the ordinary diffusion equation, we disentangle free energetic and friction effects and show that perpendicular diffusion is strongly reduced. The lateral water motion exhibits anomalous diffusion up to several nanoseconds and is characterized by even further decreased diffusion coefficients, which by comparison with coarse-grained simulations are explained by the transient corrugated effective free energy landscape imposed by the lipids. This is in contrast to homogenous surfaces, where boundary hydrodynamic theory quantitatively predicts the anisotropy of water diffusion. PMID:24074121

von Hansen, Yann; Gekle, Stephan; Netz, Roland R

2013-09-13

349

Mechanisms of boron diffusion in silicon and germanium  

NASA Astrophysics Data System (ADS)

B migration in Si and Ge matrices raised a vast attention because of its influence on the production of confined, highly p-doped regions, as required by the miniaturization trend. In this scenario, the diffusion of B atoms can take place under severe conditions, often concomitant, such as very large concentration gradients, non-equilibrium point defect density, amorphous-crystalline transition, extrinsic doping level, co-doping, B clusters formation and dissolution, ultra-short high-temperature annealing. In this paper, we review a large amount of experimental work and present our current understanding of the B diffusion mechanism, disentangling concomitant effects and describing the underlying physics. Whatever the matrix, B migration in amorphous (?-) or crystalline (c-) Si, or c-Ge is revealed to be an indirect process, activated by point defects of the hosting medium. In ?-Si in the 450-650 °C range, B diffusivity is 5 orders of magnitude higher than in c-Si, with a transient longer than the typical amorphous relaxation time. A quick B precipitation is also evidenced for concentrations larger than 2 × 1020 B/cm3. B migration in ?-Si occurs with the creation of a metastable mobile B, jumping between adjacent sites, stimulated by dangling bonds of ?-Si whose density is enhanced by B itself (larger B density causes higher B diffusivity). Similar activation energies for migration of B atoms (3.0 eV) and of dangling bonds (2.6 eV) have been extracted. In c-Si, B diffusion is largely affected by the Fermi level position, occurring through the interaction between the negatively charged substitutional B and a self-interstitial (I) in the neutral or doubly positively charged state, if under intrinsic or extrinsic (p-type doping) conditions, respectively. After charge exchanges, the migrating, uncharged BI pair is formed. Under high n-type doping conditions, B diffusion occurs also through the negatively charged BI pair, even if the migration is depressed by Coulomb pairing with n-type dopants. The interplay between B clustering and migration is also modeled, since B diffusion is greatly affected by precipitation. Small (below 1 nm) and relatively large (5-10 nm in size) BI clusters have been identified with different energy barriers for thermal dissolution (3.6 or 4.8 eV, respectively). In c-Ge, B motion is by far less evident than in c-Si, even if the migration mechanism is revealed to be similarly assisted by Is. If Is density is increased well above the equilibrium (as during ion irradiation), B diffusion occurs up to quite large extents and also at relatively low temperatures, disclosing the underlying mechanism. The lower B diffusivity and the larger activation barrier (4.65 eV, rather than 3.45 eV in c-Si) can be explained by the intrinsic shortage of Is in Ge and by their large formation energy. B diffusion can be strongly enhanced with a proper point defect engineering, as achieved with embedded GeO2 nanoclusters, causing at 650 °C a large Is supersaturation. These aspects of B diffusion are presented and discussed, modeling the key role of point defects in the two different matrices.

Mirabella, S.; De Salvador, D.; Napolitani, E.; Bruno, E.; Priolo, F.

2013-01-01

350

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

PubMed

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

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

2014-08-01

351

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

PubMed Central

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

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

2014-01-01

352

Enhanced fluorescence diffuse optical tomography with indocyanine green-encapsulating liposomes targeted to receptors for vascular endothelial growth factor in tumor vasculature.  

PubMed

To develop an indocyanine green (ICG) tracer with slower clearance kinetics, we explored ICG-encapsulating liposomes (Lip) in three different formulations: untargeted (Lip/ICG), targeted to vascular endothelial growth factor (VEGF) receptors (scVEGF-Lip/ICG) by the receptor-binding moiety single-chain VEGF (scVEGF), or decorated with inactivated scVEGF (inactive-Lip/ICG) that does not bind to VEGF receptors. Experiments were conducted with tumor-bearing mice that were placed in a scattering medium with tumors located at imaging depths of either 1.5 or 2.0 cm. Near-infrared fluorescence diffuse optical tomography that provides depth-resolved spatial distributions of fluorescence in tumor was used for the detection of postinjection fluorescent signals. All liposome-based tracers, as well as free ICG, were injected intravenously into mice in the amounts corresponding to 5 nmol of ICG/mouse, and the kinetics of increase and decrease of fluorescent signals in tumors were monitored. A signal from free ICG reached maximum at 15-min postinjection and then rapidly declined with t1/2 of ~20 min. The signals from untargeted Lip/ICG and inactive-Lip/ICG also reached maximum at 15-min postinjection, however, declined somewhat slower than free ICG with t1/2 of ~30 min. By contrast, a signal from targeted scVEGF-Lip/ICG grew slower than that of all other tracers, reaching maximum at 30-min postinjection and declined much slower than that of other tracers with t1/2 of ~90 min, providing a more extended observation window. Higher scVEGF-Lip/ICG tumor accumulation was further confirmed by the analysis of fluorescence on cryosections of tumors that were harvested from animals at 400 min after injection with different tracers. PMID:24346856

Zanganeh, Saeid; Xu, Yan; Hamby, Carl V; Backer, Marina V; Backer, Joseph M; Zhu, Quing

2013-12-01

353

Transient and diffusion analysis of HgCdTe  

NASA Technical Reports Server (NTRS)

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.

Clayton, J. C.

1982-01-01

354

The Transient Receptor Potential Vanilloid 2 Cation Channel Is Abundant in Macrophages Accumulating at the Peri-Infarct Zone and May Enhance Their Migration Capacity towards Injured Cardiomyocytes following Myocardial Infarction  

PubMed Central

Purpose A novel family of transient receptor potential (TRP) channels, that may hold a role in calcium homeostasis, has recently been described. By employing a GeneChip array analysis we have demonstrated a clear and specific upregulation of the TRP vanilloid 2 (TRPV2) mRNA in the left ventricles (LV) 3–5 days post-acute myocardial infarction (MI) compared to sham-operated controls, both in rats and in mice. We sought to characterize the cardiac cellular subpopulations in which TRPV2 is overexpressed upon acute MI. Methods Lewis rats underwent an acute MI by ligation of the left anterior descending artery or chest opening only (sham). The animals were terminated at various time points and an immunohistochemical (IHC) and immunofloerescent (IFC) staining of the LV sections as well as a flow cytometry analysis of LV-derived cells were carried out, using anti-TRPV2 and anti-monocyte/macrophage antibodies. Rat alveolar macrophage cells, NR8383, transiently transfected with TRPV2 siRNA were allowed to migrate towards hypoxic conditioned media of the rat cardiac myoblast line H9C2 using a trans-well migration assay. The macrophage cells migrating to the bottom side of the inserts were counted. Results The IHC and IFC staining as well as the flow cytometry data demonstrated a substantial expression of TRPV2 in infiltrating macrophages in the peri-infarct region 3–5 days post-acute MI. The in vitro migration assay data demonstrated that following inhibition of the TRPV2 channel, the number of migrating macrophages towards conditioned medium of hypoxic cardiomyocytes was significantly reduced. Conclusions TRPV2 is highly expressed on the peri-infarct infiltrating macrophages and may play an important role in post-MI phagocytosis. Better characterization of this channel may pave the way for identifying a new target for modulating the dramatic post-MI immune reactions. PMID:25136832

Goryainov, Pavel; Landa, Natalie; Barshack, Iris; Avivi, Camila; Semo, Jonathan; Keren, Gad

2014-01-01

355

Thermal transient anemometer  

DOEpatents

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.

Bailey, J.L.; Vresk, J.

1989-07-18

356

Thermal transient anemometer  

DOEpatents

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.

Bailey, James L. (829 S. Bruner, Hinsdale, IL 60521); Vresk, Josip (4013 N. Park, Westmont, IL 60559)

1989-01-01

357

Transient and steady-state selection in the striatal microcircuit  

PubMed Central

Although the basal ganglia have been widely studied and implicated in signal processing and action selection, little information is known about the active role the striatal microcircuit plays in action selection in the basal ganglia-thalamo-cortical loops. To address this knowledge gap we use a large scale three dimensional spiking model of the striatum, combined with a rate coded model of the basal ganglia-thalamo-cortical loop, to asses the computational role the striatum plays in action selection. We identify a robust transient phenomena generated by the striatal microcircuit, which temporarily enhances the difference between two competing cortical inputs. We show that this transient is sufficient to modulate decision making in the basal ganglia-thalamo-cortical circuit. We also find that the transient selection originates from a novel adaptation effect in single striatal projection neurons, which is amenable to experimental testing. Finally, we compared transient selection with models implementing classical steady-state selection. We challenged both forms of model to account for recent reports of paradoxically enhanced response selection in Huntington's disease patients. We found that steady-state selection was uniformly impaired under all simulated Huntington's conditions, but transient selection was enhanced given a sufficient Huntington's-like increase in NMDA receptor sensitivity. Thus our models provide an intriguing hypothesis for the mechanisms underlying the paradoxical cognitive improvements in manifest Huntington's patients. PMID:24478684

Tomkins, Adam; Vasilaki, Eleni; Beste, Christian; Gurney, Kevin; Humphries, Mark D.

2014-01-01

358

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 Central

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. PMID:25531391

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

359

Critical current density enhancement by ion irradiation for thick YBa2Cu3O7-? films prepared by diffusion reaction technique  

NASA Astrophysics Data System (ADS)

In the present work we have investigated the effect of 200 MeV Ag ions on YBa2Cu3O7-?/Y2O3 (5 wt.% and 10 wt.%) composite thick films. The samples were characterized using temperature dependent resistivity and magnetization measurements. The residual resistivity, mean field transition temperature and the zero resistance state are appreciably modified due to swift heavy ion irradiation (SHI). With the increase in defect density for 10 wt.% Y2O3 added samples irradiated with ? ? 5 × 1011 ions/cm2 shows semiconducting behavior above the transition temperature marked by broadening of transition width. Pseudogap temperature regime estimated from the deviation of linear behaviour from resistivity data indicates a shift to lower temperature zone. Synergetic effect of SHI and Y2O3 show enhancement of critical current density and flux pinning at 40 K for 5 wt.% Y2O3 inclusions. However, 10 wt.% Y2O3 added films after ion bombardment records lower values of critical current density and flux pinning. The results are explained on the basis of interplay of defect density and pinning of vortices in the YBCO matrix.

Kujur, A.; Asokan, K.; Behera, D.

2015-01-01

360

Two-stage diffusion and nanoparticle formation in heavily implanted polycrystalline Al 2O 3  

NASA Astrophysics Data System (ADS)

Two-stage diffusion was experimentally observed for the first time in polycrystalline alumina. Samples were heavily implanted by Ti ions and the concentration depth profiles were determined by Rutherford backscattering spectrometry (RBS) with 2 MeV He + ions. The Arrhenius-plot, derived from the RBS spectra, shows two different diffusion mechanisms for the implanted Ti ions between RT and 900°C: (i) radiation enhanced diffusion (RED) up to 730°C; (ii) transient thermal-like diffusion between 730°C and 900°C. The extrapolation to zero-value at 710°C agrees well with the temperature, reported in (G.P. Pells, J. Am. Ceram. Soc. 77 (2) (1994) 368). At this temperature the annealing of F-centres is already completed. High resolution scanning electron microscopy (HSEM) with energy dispersive X-ray analysis (EDX) showed Ti-enriched nanoparticles with a typical diameter of about 10-15 nm on samples, implanted at RT. The nanoparticles agglomerate into larger particles at an implantation temperature of about 830°C. Combining RBS, HSEM, X-ray photoelectron spectroscopy (XPS) measurements with TRIM simulations (J.F. Ziegler, J.P. Biersack, U. Littmark, The Stopping and Range of Ions in Solids, Pergamon, New York, 1985), more detailed information on depth and lateral distribution of Ti atoms was obtained.

Duvanov, Sergei M.; Balogh, Adam G.

2000-12-01

361

Defusing Diffusion  

ERIC Educational Resources Information Center

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…

Dou, Remy; Hogan, DaNel; Kossover, Mark; Spuck, Timothy; Young, Sarah

2013-01-01

362

Measurand transient signal suppressor  

NASA Technical Reports Server (NTRS)

A transient signal suppressor for use in a controls system which is adapted to respond to a change in a physical parameter whenever it crosses a predetermined threshold value in a selected direction of increasing or decreasing values with respect to the threshold value and is sustained for a selected discrete time interval is presented. The suppressor includes a sensor transducer for sensing the physical parameter and generating an electrical input signal whenever the sensed physical parameter crosses the threshold level in the selected direction. A manually operated switch is provided for adapting the suppressor to produce an output drive signal whenever the physical parameter crosses the threshold value in the selected direction of increasing or decreasing values. A time delay circuit is selectively adjustable for suppressing the transducer input signal for a preselected one of a plurality of available discrete suppression time and producing an output signal only if the input signal is sustained for a time greater than the selected suppression time. An electronic gate is coupled to receive the transducer input signal and the timer output signal and produce an output drive signal for energizing a control relay whenever the transducer input is a non-transient signal which is sustained beyond the selected time interval.

Bozeman, Richard J., Jr. (inventor)

1994-01-01

363

Peach Bottom Transients Analysis with TRAC/BF1-VALKIN  

SciTech Connect

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.

Verdu, G.; Miro, R.; Sanchez, A.M.; Rosello, O.; Ginestar, D.; Vidal, V. [Universidad Politecnica de Valencia (Spain)

2004-10-15

364

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

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, C16:1?7c, and iso–C17:1?9c. 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 C17:1?8c. 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

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

2014-01-01

365

Thermal Diffusivity and Viscosity of Suspensions of Disc Shaped Nanoparticles  

E-print Network

In this work we conduct a transient heat conduction experiment with an aqueous suspension of nanoparticle disks of Laponite JS, a sol forming grade, using laser light interferometry. The image sequence in time is used to measure thermal diffusivity and thermal conductivity of the suspension. Imaging of the temperature distribution is facilitated by the dependence of refractive index of the suspension on temperature itself. We observe that with the addition of 4 volume % of nano-disks in water, thermal conductivity of the suspension increases by around 30%. A theoretical model for thermal conductivity of the suspension of anisotropic particles by Fricke as well as by Hamilton and Crosser explains the trend of data well. In turn, it estimates thermal conductivity of the Laponite nanoparticle itself, which is otherwise difficult to measure in a direct manner. We also measure viscosity of the nanoparticle suspension using a concentric cylinder rheometer. Measurements are seen to follow quite well, the theoretical relation for viscosity of suspensions of oblate particles that includes up to two particle interaction. This result rules out the presence of clusters of particles in the suspension. The effective viscosity and thermal diffusivity data show that the shape of the particle has a role in determining enhancement of thermophysical properties of the suspension.

Susheel S. Bhandari; K. Muralidhar; Yogesh M Joshi

2014-03-05

366

Transient analysis of tritium migration in a fusion reactor vessel  

NASA Astrophysics Data System (ADS)

Transient analysis of tritium migration after implantation into the INTOR-like stainless steel first wall and W/Cu divertor is performed using a computer code TRIP. Effects of thermal diffusion, protium from (n, p) reactions, tritium decay, surface conditions and trap characters on the tritium permeation and inventory are estimated. The influence of the bakeout procedure on the outgassing and inventory through the structures after shut-down is also discussed in detail.

Ashibe, K.; Ebisawa, K.

1984-12-01

367

Transient response of a gas-controlled heat pipe  

Microsoft Academic Search

The paper presents a combined analytical and experimental investigation of the transient response of a gas-controlled heat pipe with an absorption gas reservoir. A mathematical model which considers the heat conduction in the condenser wall, the overall vapor core temperature, the diffusion of the vapor-gas interface, and the absorption of the control gas in the working fluid\\/wick structure matrix of

K. N. Shukla

1981-01-01

368

[Proliferative diffuse glomerulonephritis (author's transl)].  

PubMed

Some aspects of the diffuse proliferative glomerulonephritis have been examined: initial renal failure, evolution of the lesions, crioglobulinemia. Thirty-five of 88 cases presented high urea levels, in 3 of them with acute renal failure transient hemodialysis treatment was needed, only one case progressed toward chronic renal failure. Anatomic alterations either in the case of exudative or proliferative damages improved but not up to complete healing: mesangial tickening and local proliferation has been observed. Crioglobulinemia was found in 14 of 21 cases. The disappearance in two cases of the crioglobulinemia was accompanied by a significative improvement of the hystology; a persistent crioglobulinemia usually accompanies unmodified histologic alterations. PMID:786322

Richet, G C

1975-01-01

369

Specific and nonspecific interactions in ultraweak protein-protein associations revealed by solvent paramagnetic relaxation enhancements.  

PubMed

Weak and transient protein-protein interactions underlie numerous biological processes. However, the location of the interaction sites of the specific complexes and the effect of transient, nonspecific protein-protein interactions often remain elusive. We have investigated the weak self-association of human growth hormone (hGH, KD = 0.90 ± 0.03 mM) at neutral pH by the paramagnetic relaxation enhancement (PRE) of the amide protons induced by the soluble paramagnetic relaxation agent, gadodiamide (Gd(DTPA-BMA)). Primarily, it was found that the PREs are in agreement with the general Hwang-Freed model for relaxation by translational diffusion (J. Chem. Phys. 1975, 63, 4017-4025), only if crowding effects on the diffusion in the protein solution are taken into account. Second, by measuring the PREs of the amide protons at increasing hGH concentrations and a constant concentration of the relaxation agent, it is shown that a distinction can be made between residues that are affected only by transient, nonspecific protein-protein interactions and residues that are involved in specific protein-protein associations. Thus, the PREs of the former residues increase linearly with the hGH concentration in the entire concentration range because of a reduction of the diffusion caused by the transient, nonspecific protein-protein interactions, while the PREs of the latter residues increase only at the lower hGH concentrations but decrease at the higher concentrations because of specific protein-protein associations that impede the access of gadodiamide to the residues of the interaction surface. Finally, it is found that the ultraweak aggregation of hGH involves several interaction sites that are located in patches covering a large part of the protein surface. PMID:24969589

Johansson, Helle; Jensen, Malene Ringkjøbing; Gesmar, Henrik; Meier, Sebastian; Vinther, Joachim M; Keeler, Camille; Hodsdon, Michael E; Led, Jens J

2014-07-23

370

Diffusion in membranes: Toward a two-dimensional diffusion map  

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

371

The fast diffusion of Au IN Pb  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

372

Perturbations for transient acceleration  

SciTech Connect

According to the standard ?CDM model, the accelerated expansion of the Universe will go on forever. Motivated by recent observational results, we explore the possibility of a finite phase of acceleration which asymptotically approaches another period of decelerated expansion. Extending an earlier study on a corresponding homogeneous and isotropic dynamics, in which interactions between dark matter and dark energy are crucial, the present paper also investigates the dynamics of the matter perturbations both on the Newtonian and General Relativistic (GR) levels and quantifies the potential relevance of perturbations of the dark-energy component. In the background, the model is tested against the Supernova type Ia (SNIa) data of the Constitution set and on the perturbative level against growth rate data, among them those of the WiggleZ survey, and the data of the 2dFGRS project. Our results indicate that a transient phase of accelerated expansion is not excluded by current observations.

Vargas, Cristofher Zuñiga; Zimdahl, Winfried [Universidade Federal do Espírito Santo, Departamento de Física, Av. Fernando Ferrari, 514, Campus de Goiabeiras, CEP 29075-910, Vitória, Espírito Santo (Brazil); Hipólito-Ricaldi, Wiliam S., E-mail: win_unac@hotmail.com, E-mail: hipolito@ceunes.ufes.br, E-mail: winfried.zimdahl@pq.cnpq.br [Universidade Federal do Espírito Santo, Departamento de Ciências Naturais, Grupo de Física Teórica, Rodovia BR 101 Norte, km 60, Campus de São Mateus, CEP 29932-540, São Mateus, Espírito Santo (Brazil)

2012-04-01

373

Transient Dentritic Solidification Experiment  

NASA Technical Reports Server (NTRS)

The Transient Dentritic Solidification Experiment (TDSE) is being developed as a candidate for flight aboard the International Space Station. TDSE will study the growth of dentrites (treelike crystalline structures) in a transparent material (succinonitrile or SCN) that mimics the behavior of widely used iron-based metals. Basic work by three Space Shuttle flights (STS-62, STS-75, and STS-87) of the Isothermal Dendritic Growth Experiment (IDGE) is yielding new insights into virtually all industrially relevant metal and alloy forming operations. The TDSE is similar to IDGE, but will maintain a constant temperature while varying pressure on the dentrites. Shown here is a cutaway of the isothermal bath containing its growth cell at the heart of the TDSE. The principal investigator is Matthew Koss of College of the Holy Cross in Worcester, MA. Note: an Acrobat PDF version is available from http://microgravity.nasa.gov/gallery

2000-01-01

374

Line transients with corona  

SciTech Connect

This paper investigates the effect of corona on the electromagnetic transients along high voltage overhead lines. A method is presented to simulate the line by dividing it into a number of sections connected in cascade. For {ital n} line sections, the number of the unknown variables is 2{ital n} + 1. The method allows any waveform of the exciting voltage function, as well as any impedance loading condition. The corona is represented by voltage-dependent shunt current sources. A systematic way for writing a sufficient number of differential equations is shown. For their solution, a digital computer subroutine based on the Runge--Kutta--Verner method was used. An artificial frequency-dependent damping by means of linear resistors was used to suppress the Gibb's oscillations in the solution. The proposed method is applied to study the transients on a 40 km high voltage line with 30-ft flat phase spacing and a single 1.4 inch ACSR conductor per phase. The exciting voltage has a double-exponential impulse waveform. Solutions are given for three values of resistive loads Z{sub {ital c}}2Z{sub {ital c}} and Z{sub {ital c}}/2, where Z{sub {ital c}} is the line surge impedance. The results of two interesting cases of inductive and capacitive loads are also given. Physical interpretations for the different solutions are given. Also, the current-voltage duality between inductive and capacitive loads is recognized. The corona was found to attenuate and distort the travelling waves. For example, during one wave excursion, the reduction of the current wave peaks can reach values as high as 8.5%. The effect is more noticeable in the current than in the voltage waves. As expected, it increases also with the line corona losses. The effect of the increase of the line effective capacitance due to the corona discharge is also demonstrated.

Saied, M.M.; Safar, Y.A.; Salama, M.H. (Kuwait Univ. (Kuwait))

1987-01-01

375

100-liter transient transfection.  

PubMed

This is the first report of two successful 100 l scale transienttransfections in a standard stirred bioreactor. More than half a gram of a monoclonal antibody (IgG) were produced in less than 10 days using a technology called large-scale transient gene expression(LS-TGE). Suspension adapted HEK 293 EBNA SF cells were transfectedwithin a 150 l (nominal) bioreactor by a modified calcium phosphateco-precipitation method with more than 75 mg of plasmid DNA per run.A mixture of three different plasmids, one encoding for the heavychain of a human recombinant immunoglobulin, the other for the corresponding light chain and a third one for the green fluorescent protein (GFP, 2-4% of DNA in transfection cocktail)were co-transfected. The GFP vector was chosen to monitor transfection efficiency. Expression of GFP could be registered asearly as 20 h after DNA addition, using fluorescence microscopy. We demonstrate that transient transfection can be done at the100 l scale, thus providing a new tool to produce hundreds of milligrams or even gram amounts of recombinant protein. Akey advantage of LS-TGE resides in its speed. In the presentedcases, the entire production process for the synthesis of halfa gram of a recombinant antibody, including DNA preparationand necessary expansion of cells prior to transfection, wasexecuted in less than a month. Having an established transfection/expression process allows to run productioncampaigns for any given protein, within one facility, with onesingle host cell line and therefore only one single seed train. Without any need to create and maintain stable cell lines, expression of new r-proteins is not only faster and more economical but also more flexible. PMID:19003082

Girard, Philippe; Derouazi, Madiha; Baumgartner, Gwendoline; Bourgeois, Michaela; Jordan, Martin; Jacko, Barbara; Wurm, Florian M

2002-01-01

376

Differential Diagnosis of Transient Amnesia  

Microsoft Academic Search

In a group of 39 consecutive patients attending neurological clinics with transient amnesia patients with transient global amnesia formed the largest group; others suffered from epilepsy, migraine, temporal lobe encephalitis, or psychogenic fugues. In most cases the clinical features suggested the aetiology, but an electroencephalogram recorded as soon after the attack as possible may help in distinguishing amnesia due to

P. B. Croft; K. W. G. Heathfield; M. Swash

1973-01-01

377

CFD modeling of a transient hollow fiber ultrafiltration system for protein concentration  

Microsoft Academic Search

A transient model based on the finite element method (CFD Comsol) to simulate numerically the flow (momentum equation) and the concentration (diffusion–convection equation) in an ultrafiltration unit is presented. The CFD model was developed by solving the 2D Navier–Stokes equation and the mass conservation equation for transient conditions. A resistance model was used to link the retained protein concentration, the

Bernard Marcos; Christine Moresoli; Jana Skorepova; Brandi Vaughan

2009-01-01

378

Fine-scale transient arcs seen in a shock aurora  

NASA Astrophysics Data System (ADS)

report, for the first time, fine-scale transient arcs that emerged successively within the initial 1-2 min evolutionary interval of a postnoon shock aurora on 14 July 2012. Data were acquired from ~2 Hz temporal resolution imaging of dayside aurora with a white light all-sky camera (ASC) at South Pole Station (magnetic latitude = -74.3°, magnetic local time = UT -3.5 h). Just after 1809:50 UT at which the initial response to an interplanetary (IP) shock was detected in the postnoon geosynchronous magnetic field, the ASC observed three successive transient arcs of which the locations shifted equatorward with an abrupt jump by ~0.2° in latitude. All of the transient arcs occurred in a closed field line region, ~1.0°-1.5° equatorward of the polar cap or open/closed field line boundary inferred from the intensity ratio of I630.0/I557.7 but just poleward of the shock-induced proton and diffuse-type electron aurorae. Each of the transient arcs had a latitudinal width of ~0.1° and a short lifetime of ~20-30 s. Although the obvious mechanism has still remained unclear, possible interpretations of the fine-scale transient arc features are discussed in terms of a local process of each of the magnetospheric origin (mode conversion) and ionospheric origin (feedback interaction) that may be induced by IP shock.

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

2014-08-01

379

Validation model for the transient analysis of tightly coupled reactors  

SciTech Connect

Both the static and transient analysis of tightly coupled reactors differ from those of the loosely coupled systems. In these reactors, highly absorbing regions are interspaced with low absorbing regions. That raises questions of the acceptability of diffusion theory approximations. Also, the spectral shapes change drastically throughout the core and can be altered significantly by perturbations. Accurate analysis requires at least two-dimensional, multigroup transport methods. Although, such methods can be applied for static cases, for transient analysis they would be almost impossibly expensive. Recently a transient nodal model accounting for transport corrections has been developed for tightly coupled reactors. In this model, few-group, node-averaged cross sections and discontinuity factors are edited from full-core, higher order reference results such as Monte Carlo or fine-mesh, multigroup, discrete ordinate transport solutions for various conditions expected during transients. Tables of nodal parameters are constructed, and their values as the transient proceeds are found by interpolation. Although the static part of this few-group model can be tested easily by comparing nodal results with the reference transport solution, without a time-dependent transport code (at least a two-dimensional, multigroup, discrete ordinate code), doing the analogous validation for the time-dependent problem is not possible.

Bahadir, T.; Henry, A.F. [Massachusetts Inst. of Technology, Cambridge, MA (United States)

1996-12-31

380

Anomalous cross-field diffusion in a magnetic trap  

NASA Astrophysics Data System (ADS)

We numerically simulated the diffusion of a charged Brownian particle confined to a plane under the action of an orthogonal magnetic field with intensity depending on the distance from a center. Despite its apparent simplicity, this system exhibits anomalous diffusion. For positive field gradients, radial and angular dynamics are asymptotically subdiffusive, with exponents given by simple analytical expressions. In contrast, when driven by a weakly decaying field, the particle attains normal diffusion only after exceedingly long superdiffusive transients. These mechanisms can be related to Bohm diffusion in magnetized plasmas.

Savel'ev, Sergey E.; Marchesoni, Fabio

2014-12-01

381

Influence of process parameters on microstructure of transient liquid phase bonded Inconel 738LC superalloy with Amdry DF3 interlayer  

Microsoft Academic Search

The effect of bonding temperature and time on microstructure of diffusion brazed joint of nickel base superalloy Inconel 738LC using Amdry DF-3 filler, alloy was investigated. It was observed that the formation of eutectic microconstituents, within the joint regions, was significantly influenced by the brazing temperature and time. A deviation from the conventional transient liquid phase (TLP) bonding diffusion models

N. P. Wikstrom; O. A. Ojo; M. C. Chaturvedi

2006-01-01

382

Ambipolar diffusion of photocarriers in electrolyte-filled, nanoporous TiOâ  

Microsoft Academic Search

The authors report transient photocurrent measurements on solar cell structures based on dye-sensitized, porous TiOâ films filled with a liquid electrolyte. The measurements are interpreted as ambipolar diffusion; under most measurement conditions, the ambipolar diffusion coefficient is dominated by electrons diffusing in the TiOâ matrix. The authors report a strong dependence of the ambipolar diffusion coefficient upon the photoexcitation density,

N. Kopidakis; E. A. Schiff; N.-G. Park; J. van de Lagemaat; A. J. Frank

2000-01-01

383

Accelerated kinetics and mechanism of growth of boride layers on titanium under isothermal and cyclic diffusion  

NASA Astrophysics Data System (ADS)

The tendency of titanium (Ti) and its alloys to wear, gall and seize during high contact stresses between sliding surfaces severely limits their applications in bearings, gears etc. One way to mitigate these problems is to modify their surfaces by applying hard and wear resistant surface coatings. Boriding, which involves solid state diffusion of boron (B) into Ti, thereby forming hard surface layers consisting of TiB2 and TiB compounds has been shown to produce extremely high wear resistant surfaces in Ti and its alloys. The growth kinetics of these layers are, however, limited by the low diffusivities of B in the high melting TiB2 and TiB compounds. On the basis of the fact that HCP metals such as Ti show enhanced (anomalous) self-diffusion near the phase transition temperature, the first hypothesis of this work has been that the diffusivity enhancement should cause rapid ingress of B atoms, thereby accelerating the growth of the hard boride layers. Isothermal boriding experiments were performed close to phase transition temperature (890, 910, and 915°C) for time periods ranging from 3 to 24 hours. It was found that indeed a much deeper growth of TiB into the Ti substrate (˜75 mum) occurred at temperatures very close to the transition temperature (910°C), compared to that obtained at 1050°C. A diffusion model based on error-function solutions of Fick's second law was developed to quantitatively illustrate the combined effects of the normal B diffusion in the TiB phase and the anomalous B diffusion in Ti phase in accelerating TiB layer growth. Furthermore, isothermal boriding experiments close to transition temperature (900°C) for a period of 71 hours resulted in coating thickness well above 100 mum, while at 1050°C, the layer growth saturated after about 24 hours of treatment time. In the second part of this work, a novel approach named "cyclic-phase-changediffusion, (CPCD)," to create deeper TiB2 and TiB coating layers on CP-Ti by cyclic thermal processing, has been investigated. It was found that thermal cyclic B diffusion in Ti across the alpha(alpha)-beta(beta) phase transition temperature led to highly hardened surface layers enriched with TiB whiskers that grow to depths exceeding 120 mum. By solving the transient heat transport problem for cyclic changes in surface temperatures, it was found that there is a "heat-packet" that travels back and forth from the surface to the interior of the material. This heat-packet appears to transport B dissolved in beta-Ti into interior causing increased coating depths.

Sarma, Biplab

2011-12-01

384

Analysis of the transient calibration of heat flux sensors: One dimensional case  

NASA Technical Reports Server (NTRS)

The effect of transient heat flux on heat flux sensor response and calibration is analyzed. A one dimensional case was studied in order to elucidate the key parameters and trends for the problem. It has the added advantage that the solutions to the governing equations can be obtained by analytic means. The analytical results obtained to date indicate that the transient response of a heat flux sensor depends on the thermal boundary conditions, the geometry and the thermal properties of the sensor. In particular it was shown that if the thermal diffusivity of the sensor is small, then the transient behavior must be taken into account.

Dybbs, A.; Ling, J. X.

1989-01-01

385

Ambipolar Diffusion  

NASA Astrophysics Data System (ADS)

When magnetic forces are present in a partially ionized medium, the plasma drifts with respect to the neutrals. This plasma—neutral drift, which is known as ambipolar diffusion, occurs in all partially ionized astrophysical systems, including portions of the interstellar medium, protostellar accretion disks, and the chromosphere of the Sun and other cool stars. Ambipolar drift redistributes magnetic flux, which can trigger star formation. It affects short wavelength interstellar turbulence, the structure of interstellar shocks, flow driven instabilities, and the nature of magnetic reconnection. Energy dissipated by ion-neutral friction can be an important source of heat. This chapter reviews ambipolar drift as a process and discusses some of the implications.

Zweibel, Ellen G.

386

Stroke: transient ischemic attack.  

PubMed

The definitions of transient ischemic attack (TIA) and stroke have evolved with advancements in medical imaging. Approximately one-third of events that last less than 24 hours are associated with new infarctions on modern imaging sequences. These events, previously called apoplexy, are now called strokes. Approximately 10% of patients with TIA will have a stroke within 90 days without urgent evaluation and management; 50% of these events will occur within the first 48 hours. The ABCD(2) and ABCD(3)-I scores are validated measures that can help predict which patients are at greatest risk. With urgent evaluation and management, the rate of stroke after TIA can be reduced by up to 80%. Measures that reduce the rate of recurrence include rapid diagnosis and management of atrial fibrillation, identification and repair of carotid artery stenosis, early antithrombotic management, and use of statins for appropriate patients. Dual antiplatelet management with aspirin and clopidogrel may be useful in the first 30 days after TIA, but these drugs should not be used in combination after that time. Adverse events, including major bleeding and mortality, occur more frequently than with monotherapy with no reduction in ischemic events. Patients also should be encouraged to adopt lifestyle changes, such as regular exercise and weight loss. PMID:24818554

Silver, Brian; Wulf Silver, Rachel

2014-05-01

387

MULTIMOMENT RADIO TRANSIENT DETECTION  

SciTech Connect

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.

Spitler, L. G.; Cordes, J. M.; Chatterjee, S. [Astronomy Department and NAIC, Cornell University, Ithaca, NY 14853 (United States); Stone, J., E-mail: lspitler@astro.cornell.edu [Department of Physics and Astronomy, Barnard College, New York, NY 10027 (United States)

2012-04-01

388

Omnidirectional superfluorescence transients  

NASA Astrophysics Data System (ADS)

A dense sample of atomic rubidium vapor excited by a short (4 ps) transform-limited laser pulse two-photon resonant with the 5S-5D transition in a large Fresnel number geometry emits a delayed omnidirectional infrared superfluorescence pulse (coherent flash) on the 5D-6 P transition. This superfluorescence emission involves a coherent population transfer to the 6P level and results in prompt directional yoked UV emission and coherent population transfer back to the ground 5S state. This emission completes the process of parametric four- wave mixing, selectively involving only those atoms on the 6 P level whose 5D- 6P emission satisfies the phase-matching condition. The unique feature of this four-wave mixing radiation is that it occurs after the termination of the pump pulse, as evidenced by direct measurement of emission timing. The multidirectional character of superfluorescent emission is confirmed by the observation of noncollinear parametric four wave mixing when exciting the sample by two simultaneous overlapping pulses, for a wide range of beam angles. Also observed and investigated is superfluorescent transient diffraction that appears when the sample is excited by a sequence of three laser pulses.

Lvovsky, Alexander Isayevich

389

Transient catalytic combustor model  

NASA Technical Reports Server (NTRS)

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.

Tien, J. S.

1981-01-01

390

Transient regional osteoporosis.  

PubMed

Transient regional osteoporosis (TRO) is a disease that predisposes to fragility fracture in weight bearing joints of mid-life women and men. Pregnant women may also suffer the process, usually at the hip. The prevalence of TRO is lower than the systemic form, associated with postmenopause and advanced age, but may be falsely diminished by under-diagnosis. The disease may be uni- or bilateral, and may migrate to distinct joints. One main feature of TRO is spontaneous recovery. Pain and progressive limitation in the functionality of the affected joint(s) are key symptoms. In the case of the form associated with pregnancy, difficulties in diagnosis derive from the relatively young age at presentation and from the clinical overlapping with the frequent aches during gestation. Densitometric osteoporosis in the affected region is not always present, but bone marrow edema, with or without joint effusion, is detected by magnetic resonance. There are not treatment guidelines, but the association of antiresorptives to symptomatic treatment seems to be beneficial. Surgery or other orthopedic interventions can be required for specific indications, like hip fracture, intra-medullary decompression, or other. PMID:24582491

Cano-Marquina, Antonio; Tarín, Juan J; García-Pérez, Miguel-Ángel; Cano, Antonio

2014-04-01

391

Numerical Simulation of Transient Liquid Phase Bonding under Temperature Gradient  

NASA Astrophysics Data System (ADS)

Transient Liquid Phase bonding under Temperature Gradient (TG-TLP bonding) is a relatively new process of TLP diffusion bonding family for joining difficult-to-weld aerospace materials. Earlier studies have suggested that in contrast to the conventional TLP bonding process, liquid state diffusion drives joint solidification in TG-TLP bonding process. In the present work, a mass conservative numerical model that considers asymmetry in joint solidification is developed using finite element method to properly study the TG-TLP bonding process. The numerical results, which are experimentally verified, show that unlike what has been previously reported, solid state diffusion plays a major role in controlling the solidification behavior during TG-TLP bonding process. The newly developed model provides a vital tool for further elucidation of the TG-TLP bonding process.

Ghobadi Bigvand, Arian

392

Study of anisotropic moisture diffusion in paper material  

NASA Astrophysics Data System (ADS)

The influence of moisture on the final use of paper has been a critical issue for papermakers. In this thesis, we studied transient and steady state moisture diffusion in paper under different humidity conditions and its relationship to sheet structure. Moisture transport through this medium occurs by a number of mechanisms, which the most important are: diffusion through the pores, diffusion of condensed water through the cell-wall of the fibers, surface diffusion and capillary transport. In the first part of this work, we investigated the sorption of moisture by paper sheets exposed to rapid changes in the external humidity. We found that transient moisture transported in paper material is Non-Fickian, most likely being caused by two sequential diffusion steps: the first being a rapid diffusion through the pores followed by a slow diffusion through the fibers/cell wall material. External boundary layers cause further departures from Fickian sorption. The porous structure of paper significantly impacts its diffusion characteristics. At low to moderate moisture contents, it is the pore space that conducts water vapor by diffusion: transport is therefore proportional to the sheet porosity and is inversely proportional to the tortuosity. Pulp refining reduces the porosity and increases tortuosity, decreasing the moisture diffusivity. Since the pore structure is strongly anisotropic, reflecting the layered structure of paper, diffusion is also anisotropic and is usually greater in the lateral (in-plane or XY) dimensions as compared to the transverse (through plane or ZD) dimension. In machine made paper, there could be a weak dependence on the in-plane fiber orientation giving rise to higher diffusion in the machine direction (MD) as compared to the cross machine direction, (CD). Parameters describing the moisture diffusivity in paper are necessary for calculating transport rates and moisture profiles. Therefore, we present diffusion parameters for moisture transport through the pore space (Dp) and the non-linear diffusivity of condensed phase moisture (D q0 and m) for sheets made from bleached kraft softwood pulps refined to different levels. We demonstrate the utility of the diffusion parameters by estimating moisture profiles through a stack of sheets using a mathematical model for transient moisture transport. The model predictions agreed with our measurements of the moisture profiles showing the usefulness of these diffusion parameters. Keywords: moisture diffusion, paper, water vapor, bound water.

Massoquete, A.

393

Atomic transport in metastable compounds: Case study of self-diffusion in Si-C-N films using neutron reflectometry  

NASA Astrophysics Data System (ADS)

The investigation of atomic mobilities in transient metastable phases is a challenging task in diffusion science. For amorphous silicon carbonitrides we identified a transient metastable bonding configuration by Fourier-transform infrared spectroscopy on samples annealed in a defined time-temperature domain. We demonstrate that it is possible to determine nitrogen self-diffusivities in this state using neutron reflectometry. The results revealed that the diffusion experiments on this system are feasible only if very short diffusion lengths on the order of 1 nm and very low diffusivities can be measured, as it is the case for neutron reflectometry technique applied in our studies.

Hüger, E.; Schmidt, H.; Stahn, J.; Braunschweig, B.; Geckle, U.; Bruns, M.; Markwitz, A.

2009-12-01

394

Geometric considerations for diffusion in polycrystalline solids  

NASA Astrophysics Data System (ADS)

Mass transport in polycrystals is usually enhanced by short-circuit diffusion along various defect paths, e.g., grain boundaries, dislocation cores, and triple junctions. In the "kinetic-A" regime, diffusion fields associated with the various diffusion paths overlap each other, forming a macroscopically homogeneous diffusion profile that can be described by an effective diffusion coefficient. Here, we develop a composite diffusion model for polycrystals based on realistic arrangements between various microstructural elements, which usually exhibit complex network morphologies. Asymmetric effective medium equations and power-law scaling relationships are used to evaluate the effective diffusivity of a general isotropic polycrystal, and are compared to predictions of the simple arithmetic rule of mixtures used frequently in the literature. We also examine the grain size and temperature dependence of polycrystalline diffusion in terms of the apparent grain size exponent and activation energy, which in turn provide the basis by which we assess dominant diffusion processes and construct generalized diffusion mechanism maps. Implications of geometry on experimental diffusivity measurements are also discussed.

Chen, Ying; Schuh, Christopher A.

2007-03-01

395

Sensor for gas analysis based on thermal conductivity, specific heat capacity and thermal diffusivity  

Microsoft Academic Search

We investigate a new method of gas analysis based on the determination of thermal conductivity, specific heat capacity and thermal diffusivity. A silicon micro-wire surrounded by the gas is supplied with transient heat power (sinusoidal or square wave signal). The induced transient changes in gas temperature are detected in several well defined distances from the heater. We demonstrate the detection

K. Kliche; S. Billat; F. Hedrich; C. Ziegler; R. Zengerle

2011-01-01

396

Transient Heat Transfer in TCAP Coils  

SciTech Connect

The Thermal Cycling Absorption Process (TCAP) is used to separate isotopes of hydrogen. TCAP involves passing a stream of mixed hydrogen isotopes through palladium deposited on kieselguhr (Pd/k) while cycling the temperature of the Pd/k. Kieselguhr is a silica mineral also called diatomite. To aid in the design of a full scale facility, the Thermal Fluids Laboratory was used by the Chemical and Hydrogen Technology Section to compare the heat transfer properties of three different configurations of stainless steel coils containing kieselguhr and helium. Testing of coils containing Pd/k and hydrogen isotopes would have been more prototypical but would have been too expensive. Three stainless steel coils filled with kieselguhr were tested; one made from 2.0 inch diameter tubing, one made from 2.0 inch diameter tubing with foam copper embedded in the kieselguhr and one made from 1.25 inch diameter tubing. It was known prior to testing that increasing the tubing diameter from 1.25 inch to 2.0 inch would slow the rate of temperature change. The primary purpose of the testing was to measure to what extent the presence of copper foam in a 2.0" tubing coil would compensate for the effect of larger diameter. Each coil was connected to a pressure gage and the coil was evacuated and backfilled with helium gas. Helium was used instead of a mixture of hydrogen isotopes for reasons of safety. Each coil was quickly immersed in a stirred bath of ethylene glycol at a temperature of approximately 100 degrees Celsius. The coil pressure increased, reflecting the increase in average temperature of its contents. The pressure transient was recored as a function of time after immersion. Because of the actual process will use Pd/k instead of kieselguhr, additional tests were run to determine the differences in thermal properties between the two materials. The method was to position a thermocouple at the center of a hollow sphere and pack the sphere with Pd/k. The sphere was sealed, quickly submerged in a bath of boiling water and the temperature transient was recorded. There sphere was then opened, the Pd/k was replaced with kieselguhr and the transient was repeated. The response was a factor of 1.4 faster for Pd/k than for kieselguhr, implying a thermal diffusivity approximately 40 percent higher than for kieselguhr. Another implication is that the transient tests with the coils would have proceeded faster if the coils had been filled with Pd/k rather than kieselguhr.

Steimke, J.L.

1999-03-09

397

Anisotropy Induced by Macroscopic Boundaries: Surface-Normal Mapping using Diffusion-Weighted Imaging  

Microsoft Academic Search

In MRI, macroscopic boundaries lead to a diffusion-related increase in signal intensity near them—an effect commonly referred to as edge-enhancement. In diffusion-weighted imaging protocols where the signal attenuation due to diffusion results predominantly from the application of magnetic field gradients, edge-enhancement will depend on the orientation of these diffusion gradients. The resulting diffusion anisotropy can be exploited to map the

Evren Özarslan; Uri Nevo; Peter J. Basser

2008-01-01

398

Parameter recovery for transient signals  

E-print Network

Transient signals naturally arise in numerous disciplines for which the decay rates and amplitudes carry some informational significance. Even when the decay rates are known, solving for the amplitudes results in an ...

Lahlou, Tarek A. (Tarek Aziz)

2013-01-01

399

Analytical solution of the advection-diffusion transport equation using a change-of-variable and integral transform technique  

Technology Transfer Automated Retrieval System (TEKTRAN)

This paper presents a formal exact solution of the linear advection-diffusion transport equation with constant coefficients for both transient and steady-state regimes. A classical mathematical substitution transforms the original advection-diffusion equation into an exclusively diffusive equation. ...

400

Opportunistic Transient-Fault Detection  

Microsoft Academic Search

CMOS scaling increases susceptibility of microprocessors to transient faults. Most current proposals for transient-fault detection use full redundancy to achieve perfect coverage while incurring significant performance degradation. However, most commodity systems do not need or provide perfect coverage. A recent paper explores this leniency to reduce the soft-error rate of the issue queue during L2 misses while incurring minimal performance

Mohamed A. Gomaa; T. N. Vijaykumar

2005-01-01

401

Opportunistic transient-fault detection  

Microsoft Academic Search

CMOS scaling increases susceptibility of microprocessors to transient faults. Most current proposals for transient-fault detection use full redundancy to achieve perfect coverage while incurring significant performance degradation. However, most commodity systems do not need or provide perfect coverage. A recent paper explores this leniency to reduce the soft-error rate of the issue queue during L2 misses while incurring minimal performance

Mohamed A. Gomaa; T. N. Vijaykumar

2005-01-01

402

Opportunistic Transient-Fault Detection  

Microsoft Academic Search

CMOS scaling increases susceptibility of microprocessors to transient faults. Most current proposals for transient-fault detection use full redundancy to achieve perfect coverage while incurring significant performance degradation. How- ever, most commodity systems do not need or provide perfect coverage. A recent paper explores this leniency to reduce the soft-error rate of the issue queue during L2 misses while incur- ring

Mohamed A. Gomaa; T. N. Vijaykumar

2006-01-01

403

Photoacoustic thermal diffusion flowmetry.  

PubMed

Thermal Diffusion Flowmetry (TDF) (also called Heat Clearance Method or Thermal Clearance Method) is a longstanding technique for measuring blood flow or blood perfusion in living tissues. Typically, temperature transients and/or gradients are induced in a volume of interest and the temporal and/or spatial temperature variations which follow are measured and used for calculation of the flow. In this work a new method for implementing TDF is studied theoretically and experimentally. The heat deposition which is required for TDF is implemented photothermally (PT) and the measurement of the induced temperature variations is done by photoacoustic (PA) thermometry. Both excitation light beams (the PT and the PA) are produced by directly modulated 830 nm laser diodes and are conveniently delivered to the volume under test by the same optical fiber. The method was tested experimentally using a blood-filled phantom vessel and the results were compared with a theoretical prediction based on the heat and the photoacoustic equations. The fitting of a simplified lumped thermal model to the experimental data yielded estimated values of the blood velocity at different flow rates. By combining additional optical sources at different wavelengths it will be possible to utilize the method for non-invasive simultaneous measurement of blood flow and oxygen saturation using a single fiber probe. PMID:22574267

Sheinfeld, Adi; Eyal, Avishay

2012-04-01

404

Analytical solution for transient partitioning and reaction of a condensing vapor species in a droplet  

NASA Astrophysics Data System (ADS)

We present the exact analytical solution of the transient equation of gas-phase diffusion of a condensing vapor to, and diffusion and reaction in, an aqueous droplet. Droplet-phase reaction is represented by first-order chemistry. The solution facilitates study of the dynamic nature of the vapor uptake process as a function of droplet size, Henry's law coefficient, and first-order reaction rate constant for conversion in the droplet phase.

Liu, Albert Tianxiang; Zaveri, Rahul A.; Seinfeld, John H.

2014-06-01

405

Implementation of Wavelet-Based Neural Network for the detection of Very Low Frequency (VLF) Whistlers Transients  

NASA Astrophysics Data System (ADS)

Abstract: In this paper, a wavelet-based neural network system for the detection and identification of four types of VLF whistler’s transients (i.e. dispersive, diffuse, spiky and multipath) is implemented and tested. The discrete wavelet transform (DWT) technique is integrated with the feed forward neural network (FFNN) model to construct the identifier. First, the multi-resolution analysis (MRA) technique of DWT and the Parseval’s theorem are employed to extract the characteristics features of the transients at different resolution levels. Second, the FFNN identifies these extracted features to identify the transients according to the features extracted. The proposed methodology can reduce a great quantity of the features of transients without losing its original property; less memory space and computing time are required. Various transient events are tested; the results show that the identifier can detect whistler transients efficiently. Keywords: Discrete wavelets transform, Multi-resolution analysis, Parseval’s theorem and Feed forward neural network

Sondhiya, Deepak Kumar; Gwal, Ashok Kumar; Verma, Shivali; Kasde, Satish Kumar

406

Is Arnold diffusion relevant to global diffusion?  

E-print Network

Global diffusion of Hamiltonian dynamical systems is investigated by using a coupled standard maps. Arnold web is visualized in the frequency space, using local rotation numbers, while Arnold diffusion and resonance overlaps are distinguished by the residence time distributions at resonance layers. Global diffusion in the phase space is shown to be accelerated by diffusion across overlapped resonances generated by the coupling term, rather than Arnold diffusion along the lower-order resonances. The former plays roles of hubs for transport in the phase space, and accelerate the diffusion.

Seiichiro Honjo; Kunihiko Kaneko

2003-07-27

407

Transient Tsunamis in Lakes  

NASA Astrophysics Data System (ADS)

A large number of lakes are surrounded by steep and unstable mountains with slopes prone to failure. As a result, landslides are likely to occur and impact water sitting in closed reservoirs. These rare geological phenomena pose serious threats to dam reservoirs and nearshore facilities because they can generate unexpectedly large tsunami waves. In fact, the tallest wave experienced by contemporary humans occurred because of a landslide in the narrow bay of Lituya in 1958, and five years later, a deadly landslide tsunami overtopped Lake Vajont's dam, flooding and damaging villages along the lakefront and in the Piave valley. If unstable slopes and potential slides are detected ahead of time, inundation maps can be drawn to help people know the risks, and mitigate the destructive power of the ensuing waves. These maps give the maximum wave runup height along the lake's vertical and sloping boundaries, and can be obtained by numerical simulations. Keeping track of the moving shorelines along beaches is challenging in classical Eulerian formulations because the horizontal extent of the fluid domain can change over time. As a result, assuming a solid slide and nonbreaking waves, here we develop a nonlinear shallow-water model equation in the Lagrangian framework to address the problem of transient landslide-tsunamis. In this manner, the shorelines' three-dimensional motion is part of the solution. The model equation is hyperbolic and can be solved numerically by finite differences. Here, a 4th order Runge-Kutta method and a compact finite-difference scheme are implemented to integrate in time and spatially discretize the forced shallow-water equation in Lagrangian coordinates. The formulation is applied to different lake and slide geometries to better understand the effects of the lake's finite lengths and slide's forcing mechanism on the generated wavefield. Specifically, for a slide moving down a plane beach, we show that edge-waves trapped by the shoreline and free-waves moving away from it coexist. On an open coast, these two types of waves would never interact, but because of the lake's finite dimensions, here we show that local inundation height maxima are due to wave superposition on the shoreline. These interactions can be dramatic near the lake's corners. For instance, in a rectangular lake delimited by two opposite and plane beaches and two vertical walls, we find that a landslide tsunami results in an inundation height at a corner 50% larger than anywhere else. The nonlinear and linear models produce different inundation maps, and here we show that maximum wave runups can be increased by up to 56% when nonlinear terms are included.

Couston, L.; Mei, C.; Alam, M.

2013-12-01

408

The Transient Radio Sky  

NASA Astrophysics Data System (ADS)

The high time-resolution radio sky represents unexplored astronomical territory where the discovery potential is high. In this thesis I have studied the transient radio sky, focusing on millisecond scales. As such, this work is concerned primarily with neutron stars, the mostpopulous member of the radio transient parameter space. In particular, I have studied the well known radio pulsars and the recently identified group of neutron stars which show erratic radio emission, known as RRATs, which show radio bursts every few minutes to every few hours. When RRATs burst onto the scene in 2006, it was thought that they represented a previously unknown, distinct class of sporadically emitting sources. The difficulty in their identification implies a large underlying population, perhaps larger than the radio pulsars. The first question investigated in this thesis was whether the large projected population of RRATs posed a problem, i.e. could the observed supernova rate account for so many sources. In addition to pulsars and RRATs, the various other known neutron star manifestations were considered, leading to the conclusion that distinct populations would result in a `birthrate problem'. Evolution between the classes could solve this problem -- the RRATs are not a distinct population ofneutron stars.Alternatively, perhaps the large projected population of RRATs is an overestimate. To obtain an improved estimate, the best approach is to find more sources. The Parkes Multi-beam Pulsar Survey, wherein the RRATs were initially identified, offered an opportunity to do just this. Abouthalf of the RRATs showing bursts during the survey were thought to have been missed, due to the deleterious effects of impulsive terrestrial interference signals. To remove these unwanted signals, so that we could identify the previously shrouded RRATs, we developed newinterference mitigation software and processing techniques. Having done this, the survey was completely re-processed, resulting in the discovery of 19 new sources. Of these, 12 have been re-detected on multiple occasions, whereas the others have not been seen to re-emitsince the initial discovery observations, and may be very low burst-rate RRATs, or, isolated burst events. These discoveries suggest that the initial population estimate was not over-estimated -- RRATs, though not a distinct population, are indeed numerous.In addition to finding new sources, characterisation of their properties is vital. To this end, a campaign of regular radio observations of the newly discovered sources, was mounted, at theParkes Observatory, in Australia. In addition, some of the initially identified RRATs were observed with the Lovell Telescope at Jodrell Bank. These have revealed glitches in J1819-1458, with anomalous post-glitch recovery of the spin-down rate. If such glitches werecommon, it would imply that the source was once a magnetar, neutron stars with the strongest known magnetic fields of up to 10^{15} gauss. The observations have also been used to perform`timing' observations of RRATs, i.e. determination of their spin-down characteristics. At the beginning of this thesis, 3 of the original sources had `timing solutions' determined. This has since risen to 7, and furthermore, 7 of the newly discovered sources now also have timing solutions. With this knowledge, we can see where RRATs lie in period-period derivative space. The Parkes RRATs seem to be roughly classifiable into three groupings, with high observed nulling fractions -- normal pulsars, high magnetic field pulsars and old,`dying' pulsars.It seems that RRATs and pulsars are one and the same. When a pulsar is more easily detected in searches for single bright pulses, as opposed to in periodicity searches, we label it a RRAT. Such searches impart a selection effect on the parameter space of possible sources, in bothnulling fraction and rotation period. In this sense, an observational setup could be designed to make any pulsar appear as a RRAT. For realistic survey parameters however, this is not the case, and the groups mentioned above s

Keane, E. F.

2010-11-01

409

A new era for low frequency Galactic center transient monitoring  

NASA Astrophysics Data System (ADS)

An upgrade of the low frequency observing system of the VLA developed by NRL and NRAO, called low band (LB), will open a new era of Galactic center (GC) transient monitoring. Our previous searches using the VLA and GMRT have revealed a modest number of radio-selected transients, but have been severely sensitivity and observing time limited. The new LB system, currently accessing the 236--492 MHz frequency range, promises ?5 × improved sensitivity over the legacy VLA system. The new system is emerging from commissioning in time to catch any enhanced sub-GHz emission from the G2 cloud event, and we review existing limits based on recent observations. We also describe a proposed 24/7 commensal system, called the LOw Band Observatory (LOBO). LOBO offers over 100 VLA GC monitoring hours per year, possibly revealing new transients and helping validate ASTRO2010's anticipation of a new era of transient radio astronomy. A funded LOBO pathfinder called the VLA Low Frequency Ionosphere and Transient Experiment (VLITE) is under development. Finally, we consider the impact of LB and LOBO on our GC monitoring program.

Kassim, N. E.; Hyman, S. D.; Intema, H.; Lazio, T. J. W.

2014-05-01

410

The role of stationary and transient atmospheric waves in the Martian water cycle  

NASA Astrophysics Data System (ADS)

Extensive studies of the water cycle on Mars has resulted in detailed monitoring of the atmo-spheric water vapor contents, clouds, frosts, surface and subsurface ices during several consecu-tive Martian years. With help of simulations based on GCM models, this allowed for evaluation of the contribution of water different inventories and transport mechanisms in the water cycle. We present a detailed model of the Martian climate based on GFDL general circulation model with high resolution and comprehensive treatment of the microphysical processes in clouds and the interactions between the atmosphere and the planet's surface. Due to highly detailed description of cloud microphysics with a hybrid grid-moment scheme the model is able to re-produce such phenomena as formation of clouds, fogs, and precipitation. The mutual influence between frost deposition rates and water diffusion into the regolith from one side, and the surface thermal inertia from the other, provides notable feedback that may explain observed variations in the bound water contents in the upper soil layer. Another possible phenomenon that causes zonal variations in water deposition on the surface is the global and mesoscale wave activity in the atmosphere. Stationary wave 2 feature persists in the tropical atmosphere during the equinoctial seasons, while several times during the solstice season, a short-living wave-3 transients occur. Such transient waves, possibly caused by the inertial instability in the circumpolar vortex due to seasonally determined meridional velocity shear change, provide significant enhancement of the water transport between polar reservoirs and the tropical and extratropical atmosphere.

Rodin, Alexander V.; Burlakov, Alexey; Evdokimova, Nadezda; Fedorova, Anna; Kuzmin, Ruslan; Wilson, R. John

411

Parallel flow diffusion battery  

DOEpatents

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.

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

1984-01-01

412

Transient Turbulent Friction in Smooth Pipe Flows  

NASA Astrophysics Data System (ADS)

A weighting function model of unsteady skin friction in smooth-walled, one-dimensional ducts is derived using an idealized form of the radial viscosity distribution. The model is an enhancement of earlier work by the authors in which additional simplifying assumptions were made. Important improvements include (1) replacing the assumption of uniform (solid) behaviour in an extensive core region by an assumption of uniform turbulent viscosity and (2) relating the wall shear stress to the mean flow velocity instead of to the maximum velocity. The resulting model can be used directly in numerical analyses of transient flows in pipes. It can also be used to deduce numerical values of an empirical coefficient in a popular alternative model of skin friction in which the unsteady contribution is assumed to be proportional to the instantaneous mean acceleration.

Vardy, A. E.; Brown, J. M. B.

2003-01-01

413

FRACTIONAL PEARSON DIFFUSIONS  

PubMed Central

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

Leonenko, Nikolai N.; Meerschaert, Mark M.

2013-01-01

414

Effect of non-ionic surfactants on transient cavitation in a megasonic field M. Keswani  

E-print Network

of ferricyanide species con- centrated at the liquid­vapor interface of a transient cavity at the end of its, power density and percent duty cycle) and solution parameters (temperature, dissolved gas content diffusion by allowing more gas to enter inside the bubble during expansion than it leaves during compression

Deymier, Pierre