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1

Suppression of boron transient enhanced diffusion in SiGe heterojunction bipolar transistors by carbon incorporation  

E-print Network

Suppression of boron transient enhanced diffusion in SiGe heterojunction bipolar transistors-4 Record high-frequency npn Si/Si1 xGex /Si bipolar transistor performance has been achieved by reducing postgrowth thermal process- ing or implantation and annealing due to transient enhanced diffusion TED effects

2

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

3

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

SciTech Connect

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

Nakashima, Yoshiki; Hamamoto, Nariaki; Nagayama, Tsutomu; Koga, Yuji; Umisedo, Sei; Kawamura, Yasunori; Hashimoto, Masahiro; Onoda, Hiroshi [Nissin Ion Equipment Co., Ltd., 575 Kuze Tonoshiro-cho, Minami-ku, Kyoto, 601-8205 (Japan)

2012-11-06

4

A Predictive Model for Transient Enhanced Diffusion Based on Evolution of f311g Defects  

E-print Network

A Predictive Model for Transient Enhanced Diffusion Based on Evolution of f311g Defects Alp H observed that f311g defects form, grow and eventually dissolve during annealing of Si implanted silicon wafers. The fact that for sub­amorphizing silicon implants f311g defects initially contain the full net

Dunham, Scott

5

The effect of boron implant energy on transient enhanced diffusion J. Liu and V. Krishnamoorthy  

E-print Network

sources of TED for boron implants B-I: short time component that decays rapidly consistent with nonvisibleThe effect of boron implant energy on transient enhanced diffusion in silicon J. Liu and V after low energy boron implantation and annealing was investigated using boron-doping superlattices DSLs

Florida, University of

6

The effect of boron implant energy on transient enhanced diffusion J. Liu and V. Krishnamoorthy  

E-print Network

sources of TED for boron implants B-I : short time component that decays rapidly consistentThe effect of boron implant energy on transient enhanced diffusion in silicon J. Liu and V after low energy boron implantation and annealing was investigated using boron-doping superlattices DSLs

Florida, University of

7

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.

8

Enhanced Diffusion by Reciprocal Swimming  

NASA Astrophysics Data System (ADS)

Purcell’s scallop theorem states that swimmers deforming their shapes in a time-reversible manner (“reciprocal” motion) cannot swim. Using numerical simulations and theoretical calculations we show here that, in a fluctuating environment, reciprocal swimmers undergo, on time scales larger than that of their rotational diffusion, diffusive dynamics with enhanced diffusivities, possibly by orders of magnitude, above normal translational diffusion. Reciprocal actuation does therefore lead to a significant advantage over nonmotile behavior for small organisms such as marine bacteria.

Lauga, Eric

2011-04-01

9

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

10

Ultrasonic enhancement of battery diffusion.  

PubMed

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

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

2014-03-01

11

A stable transient boundary element method (BEM) for diffuser scattering  

Microsoft Academic Search

Boundary element methods (BEM) may be used to model scattering from hard rigid surfaces such as diffusers. They have the advantage over volumetric methods that only the surface need be meshed and the surface velocity potential found. Unlike the more widely used single frequency methodology, transient BEM discretizes integral equations to produce an iterative system that is marched on in

Jonathan A. Hargreaves; Trevor J. Cox

2005-01-01

12

Anomalous diffusion and enhancement of diffusion in a vibrational motor  

NASA Astrophysics Data System (ADS)

The diffusion properties of a vibrational motor, in which an additional time-dependent driving brings the system out of equilibrium and the other time-periodic driving fills the role usually played by noise, are investigated. Within the tailored parameter regime, the diffusion coefficient evolving after a considerably long time develops a sharp peak closely related to the inflection points of the mean velocity upon an increase of the damping constant. The diffusion peak here depends on the superdiffusion motion of the particle. Also, negative velocity (for a positive bias) depending on the subdiffusive motion, i.e. dispersionless transport in the asymptotic long time limit, is obtained. Moreover, an enhancement of diffusion phenomenon can be observed. These results may be helpful for separating particles under some conditions by adjusting the external forces applied.

Guo, Wei; Du, Lu-Chun; Mei, Dong-Cheng

2014-04-01

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

Edge preserving image enhancement using anisotropic diffusion  

NASA Astrophysics Data System (ADS)

Enhancing an image in such a way that maintains image edges is a difficult problem. Many current methods for image enhancement either smooth edges on a small scale while improving contrast on a global scale or enhance edges on a large scale while amplifying noise on a small scale. One method which has been proposed for overcoming this is anisotropic diffusion, which views each image pixel as an energy sync which interacts with the surrounding pixels based upon the differences in pixel intensities and conductance values calculated from local edge estimates. In this paper, we propose a novel image enhancement method which makes use of these smoothed images produced by diffusion methods. The basic steps of this algorithm are: a) decompose an image into a smoothed image and a difference image, for example by using anisotropic diffusion or as in Lee's Algorithm [14]; b) apply two image enhancement algorithms, such as alpha rooting [7] or logarithmic transform shifting [15]; c) fuse these images together, for example by weighting the two enhanced images and summing them for the final image. Computer simulations comparing the results of the proposed method and current state-of-the-art enhancement methods will be presented. These simulations show the higher performance, both on the basis of subjective evaluation and objective measures, of the proposed method over current methods.

Wharton, Eric J.; Panetta, Karen A.; Agaian, Sos S.

2008-02-01

15

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

PubMed

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

Stanislavsky, Aleksander; Weron, Karina; Weron, Aleksander

2014-02-01

16

Anomalous diffusion induced by enhancement of memory.  

PubMed

We introduced simple microscopic non-Markovian walk models which describe the underlying mechanism of anomalous diffusions. In the models, we considered the competitions between randomness and memory effects of previous history by introducing the probability parameters. The memory effects were considered in two aspects: one is the perfect memory of whole history and the other is the latest memory enhanced with time. In the perfect memory model superdiffusion was induced with the relation of the Hurst exponent H to the controlling parameter p as H = p for p>1/2, while in the latest memory enhancement models, anomalous diffusions involving both superdiffusion and subdiffusion were induced with the relations H = (1+?)/2 and H = (1-?)/2 for 0 ? ? ? 1, where ? is the parameter controlling the degree of the latest memory enhancement. Also we found that, although the latest memory was only considered, the memory improved with time results in the long-range correlations between steps and the correlations increase as time goes on. Thus we suggest the memory enhancement as a key origin describing anomalous diffusions. PMID:25122247

Kim, Hyun-Joo

2014-07-01

17

Impurity-concentration profile for an exponentially decaying diffusion coefficient in irradiation enhanced diffusion  

Microsoft Academic Search

The diffusion equation is solved for a semi-infinite region in the case of irradiation-enhanced diffusion produced by a diffusion coefficient falling off exponentially in the medium. Near the surface the concentration profile due to enhanced diffusion has a larger concentration than the profile due to thermal diffusion; conversely far from the surface the enhanced-diffusion profile has a lower concentration than

J. Kowall; D. Peak; J. W. Corbett

1976-01-01

18

Fission enhanced diffusion of uranium in zirconia  

NASA Astrophysics Data System (ADS)

This paper deals with the comparison between thermal and Fission Enhanced Diffusion (FED) of uranium into zirconia, representative of the inner face of cladding tubes. The experiments under irradiation are performed at the Institut Laue Langevin (ILL) in Grenoble using the Lohengrin spectrometer. A thin 235UO 2 layer in direct contact with an oxidised zirconium foil is irradiated in the ILL high flux reactor. The fission product flux is about 10 11 ions cm -2 s -1 and the target temperature is measured by an IR pyrometer. A model is proposed to deduce an apparent uranium diffusion coefficient in zirconia from the energy distribution broadening of two selected fission products. It is found to be equal to 10 -15 cm 2 s -1 at 480 °C and compared to uranium thermal diffusion data in ZrO 2 in the same pressure and temperature conditions. The FED results are analysed in comparison with literature data.

Bérerd, N.; Chevarier, A.; Moncoffre, N.; Sainsot, Ph.; Faust, H.; Catalette, H.

2005-11-01

19

Fission Enhanced diffusion of uranium in zirconia  

E-print Network

This paper deals with the comparison between thermal and Fission Enhanced Diffusion (FED) of uranium into zirconia, representative of the inner face of cladding tubes. The experiments under irradiation are performed at the Institut Laue Langevin (ILL) in Grenoble using the Lohengrin spectrometer. A thin $^{235}UO\\_2$ layer in direct contact with an oxidized zirconium foil is irradiated in the ILL high flux reactor. The fission product flux is about 10$^{11}$ ions cm$^{-2}$ s$^{-1}$ and the target temperature is measured by an IR pyrometer. A model is proposed to deduce an apparent uranium diffusion coefficient in zirconia from the energy distribution broadening of two selected fission products. It is found to be equal to 10$^{-15}$ cm$^2$ s$^{-1}$ at 480$\\circ$C and compared to uranium thermal diffusion data in ZrO$\\_2$ in the same pressure and temperature conditions. The FED results are analysed in comparison with literature data.

Bérerd, N; Moncoffre, N; Sainsot, P; Faust, H; Catalette, H

2005-01-01

20

Enhanced diffusion for oscillatory viscoelastic flow  

NASA Astrophysics Data System (ADS)

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

Manopoulos, C.; Tsangaris, S.

2014-08-01

21

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

22

Substrate Catalysis Enhances Single-Enzyme Diffusion Hari S. Muddana,  

E-print Network

autocorrelated and fit by a multicomponent 3D diffusion model to determine the diffusion coefficientSubstrate Catalysis Enhances Single-Enzyme Diffusion Hari S. Muddana, Samudra Sengupta, Thomas E. In addition, catalysis-enhanced diffusion at the single-molecule scale has not been reported. Because

23

Assessing Guest Diffusivities in Porous Hosts from Transient Concentration Profiles Lars Heinke,1  

E-print Network

Assessing Guest Diffusivities in Porous Hosts from Transient Concentration Profiles Lars Heinke,1 to n-butane as guest molecules, transient concen- tration profiles during uptake or release (via representative of a novel family of nanoporous materials (the metal organic frameworks), were recorded. Analyzing

Li, Jing

24

Measurement of thermal diffusivity at high pressure using a transient heating technique  

E-print Network

1 Measurement of thermal diffusivity at high pressure using a transient heating technique Pierre submitted to Applied Physics Letters 09/20/2007 Abstract: We describe a flash-heating procedure designed to measure thermal diffusivity of materials at high pressure and temperature in diamond anvil cells

Militzer, Burkhard

25

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

26

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

E-print Network

We present a parareal in time algorithm for the simulation of neutron diffusion transient model. The method is made efficient by means of a coarse solver defined with large time steps and steady control rods model. Using finite element for the space discretization, our implementation 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 (LMW) benchmark [1].

Baudron, Anne-Marie A -M; Maday, Yvon; Riahi, Mohamed Kamel; Salomon, Julien

2014-01-01

27

Induced nuclear fission viewed as a diffusion process: Transients  

Microsoft Academic Search

Induced nuclear fission is viewed as a diffusion process of the fission degree of freedom over the fission barrier. We describe this process in terms of a Fokker-Planck equation which contains the fission variable and its canonically conjugate momentum. We solve this equation numerically for several energies (temperatures) of the fissioning nucleus neglecting changes of the fission barrier due to

P. Grangé; Li Jun-Qing; H. A. Weidenmueller

1983-01-01

28

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

29

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

30

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

Microsoft Academic Search

Udimet 720 has been selected for use on Stirling power converters for space applications. Because Udimet 720 is generally considered susceptible to strain age cracking if traditional fusion welding is used, other joining methods are being considered. A process for transient liquid phase diffusion bonding of Udimet 720 has been theoretically developed in an effort to eliminate the strain age

Donald L. Mittendorf; William G. Baggenstoss

1992-01-01

31

Enhanced Diffuse Field Model for Ad Hoc Microphone Array Calibration  

E-print Network

Enhanced Diffuse Field Model for Ad Hoc Microphone Array Calibration Mohammad J. Taghizadeha), Switzerland Abstract In this paper, we investigate the diffuse field coherence model for microphone array and algorithms are evaluated on simulated and real data recordings for calibration of microphone array geometry

Garner, Philip N.

32

Fundamental Modeling of Transient Enhanced Diffusion through Extended Defect Evolution  

E-print Network

, S. Chakravarthi, I. Clejan, and S.T. Dunham Department of Electrical and Computer Engineering Boston. These extended defects act to store excess interstitials generated by implantation, reducing the initial DEACTIVATION 2.1. Energetics of the model We model the evolution of an extended defect population or dopant

Dunham, Scott

33

‘Footprints’ of Transient Ischemic Attacks: A Diffusion-Weighted MRI Study  

Microsoft Academic Search

Objective: Diffusion-weighted imaging (DWI) conveys temporal as well as anatomic information about brain infarction, and is therefore well suited to identify ischemic injury that has occurred simultaneously, or closely linked in time, with a transient ischemic attack (TIA). We aimed to determine the proportion and clinical characteristics of patients with TIA who harbor infarction(s) on DWI. Methods: Using T2-weighted imaging

Hakan Ay; Jamary Oliveira-Filho; Ferdinando S. Buonanno; Pamela W. Schaefer; Karen L. Furie; Yuchiao Chang; Guy Rordorf; Lee H. Schwamm; R. Gilberto Gonzalez; Walter J. Koroshetz

2002-01-01

34

Color Histogram Diffusion for Image Enhancement  

NASA Technical Reports Server (NTRS)

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

Kim, Taemin

2011-01-01

35

Level Set Diffusion for MRE Image Enhancement  

Microsoft Academic Search

\\u000a Magnetic resonance elastography (MRE) is an emerging technique for noninvasive imaging of tissue elasticity. Proprietary algorithms\\u000a are used to reconstruct tissue elasticity from the images of wave propagation within soft tissue. Elasticity reconstruction\\u000a suffers from interfering noise and outliers. The interference causes biased elasticity and undesired artifacts in the reconstructed\\u000a elasticity map. Anisotropic geometric diffusion is able to suppress image

Bing Nan Li; Chee-Kong Chui; Sim Heng Ong; Stephen Chang; Etsuko Kobayashi

2010-01-01

36

A generalised approach to transient security enhancement in power markets  

Microsoft Academic Search

Ensuring transient security usually requires the re-dispatch of generators to eliminate potential transient instability after a contingency, but this has commercial implications in a power market. A further complication is that different candidate contingencies may motivate different re-dispatch strategies because the advanced generator group is different in each case, or the sensitivity of the stability margin to power exchanges between

X. J. Lin; C. W. Yu; A. K. David; C. Y. Chung

2004-01-01

37

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

NASA Astrophysics Data System (ADS)

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

Zhou, Da; Qian, Hong

2011-09-01

38

{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

39

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

NASA Astrophysics Data System (ADS)

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

Mittendorf, Donald L.; Baggenstoss, William G.

40

Radiation-enhanced self- and boron diffusion in germanium  

NASA Astrophysics Data System (ADS)

We report experiments on proton radiation-enhanced self- and boron (B) diffusion in germanium (Ge) for temperatures between 515 ?C and 720 ?C. Modeling of the experimental diffusion profiles measured by means of secondary ion mass spectrometry is achieved on the basis of the Frenkel pair reaction and the interstitialcy and dissociative diffusion mechanisms. The numerical simulations ascertain concentrations of Ge interstitials and B-interstitial pairs that deviate by several orders of magnitude from their thermal equilibrium values. The dominance of self-interstitial related defects under irradiation leads to an enhanced self- and B diffusion in Ge. Analysis of the experimental profiles yields data for the diffusion of self-interstitials (I) and the thermal equilibrium concentration of BI pairs in Ge. The temperature dependence of these quantities provides the migration enthalpy of I and formation enthalpy of BI that are compared with recent results of atomistic calculations. The behavior of self- and B diffusion in Ge under concurrent annealing and irradiation is strongly affected by the property of the Ge surface to hinder the annihilation of self-interstitials. The limited annihilation efficiency of the Ge surface can be caused by donor-type surface states favored under vacuum annealing, but the physical origin remains unsolved.

Schneider, S.; Bracht, H.; Klug, J. N.; Hansen, J. Lundsgaard; Larsen, A. Nylandsted; Bougeard, D.; Haller, E. E.

2013-03-01

41

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.

42

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

43

Reduction of boride enhanced diffusion in MeV-implanted silicon  

NASA Astrophysics Data System (ADS)

We demonstrated that implantation of MeV Si ions into a Si substrate can suppress boride-enhanced diffusion (BED) normally associated with a high B concentration layer. In this study, a molecular-beam-epitaxy grown Si layer with a B concentration of 1021/cm3 over a 10 nm region capped with 100 nm Si was used as a source of BED. A sequence of four B delta-doped layers with 100 nm Si spacers was grown prior to the source layer to monitor the diffusion. Half of the sample was implanted with 1 MeV Si ions at a dose of 1016/cm2, followed by annealing at 800, 900, and 1000 °C for different periods of time. For control samples without the MeV Si implant, BED was observed with enhancements of around 40 while the MeV Si-implanted sample showed a reduced, yet nonvanishing, BED with an enhancement of around 8 after annealing at 800 °C for 1 h. Both BED and suppressed BED with MeV implant show transient behavior with decay after annealing for long periods of time. The effect of high energy implant on B diffusion from surface deposited B layer was also discussed.

Shao, Lin; Thompson, Phillip E.; Bleiler, Roger J.; Baumann, Scott; Wang, Xuemei; Chen, Hui; Liu, Jiarui; Chu, Wei-Kan

2002-11-01

44

Modeling of the transient interstitial diffusion of implanted atoms during low-temperature annealing of silicon substrates  

E-print Network

It has been shown that many of the phenomena related to the formation of "tails" in the low-concentration region of ion-implanted impurity distribution are due to the anomalous diffusion of nonequilibrium impurity interstitials. These phenomena include boron implantation in preamorphized silicon, a "hot" implantation of indium ions, annealing of ion-implanted layers et cetera. In particular, to verify this microscopic mechanism, a simulation of boron redistribution during low-temperature annealing of ion-implanted layers has been carried out under different conditions of transient enhanced diffusion suppression. Due to the good agreement with the experimental data, the values of the average migration length of nonequilibrium impurity interstitials have been obtained. It has been shown that for boron implanted into a silicon layer preamorphized by germanium ions the average migration length of impurity interstitials at the annealing temperature of 800 Celsius degrees be reduced from 11 nm to approximately 6 nm due to additional implantation of nitrogen. The further shortening of the average migration length is observed if the processing temperature is reduced to 750 Celsius degrees. It is also found that for implantation of BF2 ions into silicon crystal, the value of the average migration length of boron interstitials is equal to 7.2 nm for thermal treatment at a temperature of 800 Celsius degrees.

O. I. Velichko; A. P. Kavaliova

2011-08-21

45

Enhanced translational diffusion of rubrene in sucrose benzoate  

NASA Astrophysics Data System (ADS)

The translational diffusion of rubrene in the fragile molecular glass former, sucrose benzoate (SB) (fragility index m~94), has been studied from Tg+6 K to Tg+71 K(Tg=337 K) by using the technique of holographic fluorescence recovery after photobleaching. In the temperature range of the measurements, the translational relaxation functions were observed to decay exponentially, indicating that Fick's law of diffusion governs the translational motion of rubrene in sucrose benzoate. The value of the translational diffusion coefficient DT obtained from the 1/e time of the translational relaxation function varied from 5.3×10-15 cm2 s-1 at 343 K to 5.0×10-9 cm2 s-1 at 408 K. The temperature dependence of DT for diffusion of rubrene in SB is compared with that of the viscosity and the dielectric relaxation time ?D of SB. The temperature dependence of DT is weaker than that of T/? for T<1.2Tg but tracks the reciprocal of the dielectric relaxation time 1/?D for 1.05Tgdiffusion coefficient at Tg is enhanced by a factor of ~ 2.5×102 over the value predicted by the Stokes-Einstein equation. The decoupling of probe diffusion from the viscosity is characterized by a scaling law, DT~?-?, with ?=0.729.

Rajesh Rajian, Justin; Huang, Wei; Richert, Ranko; Quitevis, Edward L.

2006-01-01

46

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

47

Enhancement of the ultrasound images by modified anisotropic diffusion method.  

PubMed

Speckle is a primary factor which degrades the contrast resolution and masks the meaningful texture information present in an ultrasound image. Its presence severely hampers the interpretation and analysis of ultrasound images. When speckle reduction technique is applied for visual enhancement of ultrasound images, it is to be kept in mind that blurring associated with speckle reduction should be less and fine details are properly enhanced. With these points in consideration, the modified speckle reduction anisotropic diffusion (MSRAD) method is proposed in the present study to improve the visual quality of the ultrasound images. In the proposed MSRAD method, the four neighboring pixel template in speckle reduction anisotropic diffusion (SRAD) method of Yu and Acton (IEEE Trans Image Process 11:1260-1270, 2002) have been replaced by a new template of larger number of neighboring pixels to calculate the diffusion term. To enhance visual quality of ultrasound images, nonquadratic regularization (Yu and Yadegar, Proceedings of the IEEE international conference on image processing, 2006) is incorporated with MSRAD method and accordingly changes in parameter settings have been made. The performance of MSRAD method was evaluated using clinical ultrasound images, interpretation by the medical experts and results of MSRAD method by subjective and objective criteria. PMID:20574722

Mittal, Deepti; Kumar, Vinod; Saxena, Suresh Chandra; Khandelwal, Niranjan; Kalra, Naveen

2010-12-01

48

Anxiety Enhances Threat Processing Without Competition Among Multiple Inputs: A Diffusion Model Analysis  

E-print Network

Anxiety Enhances Threat Processing Without Competition Among Multiple Inputs: A Diffusion Model is necessary for enhanced threat processing. Implications for theories of anxiety are discussed. Keywords: diffusion model, lexical decision, anxiety, threat bias, processing competition Numerous studies have

Segraves, Kari A.

49

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

50

Diffusivity and Transient Localization of Filler Particles in Polymer Melts and Crosslinked Systems  

NASA Astrophysics Data System (ADS)

Building on recent progress in describing the microscopic equilibrium structure of polymer nanocomposites (PRISM theory), as well as the na"ive mode coupling and nonlinear Langevin equation approaches for predicting localization and activated barrier hopping, we have initiated the study of dynamical phenomena in nanocomposites at finite filler loading. A colloidal suspension perspective is adopted whereby the polymer dynamics are assumed to remain unperturbed by fillers. Both entangled polymer melts and crosslinked systems are studied. The long time behavior of a tagged nanoparticle (localization and diffusivity) is calculated for various melt (tube diameter, polymer radius of gyration) and nanoparticle (filler size and volume fraction, polymer-filler attraction strength) parameters. For transiently localized particles, a dynamic free energy is constructed and employed to compute the nanoparticle localization length, mean barrier hopping time, and self-diffusion constant. The influence of filler-filler interactions on the Stokes-Einstein violation phenomenon in entangled melts is established. In addition, the influence of nanocomposite statistical structure (e.g., in the depletion, steric stabilization, or bridging regimes) on slow dynamics and localization is investigated.

Dell, Zachary E.; Schweizer, Kenneth S.

2013-03-01

51

Measurement of transient behavior of the thermal diffusivity of flowing polymer melt  

NASA Astrophysics Data System (ADS)

Molecular orientation of polymer molecules created by shear force due to the flow of the polymer melt in a duct rapidly relaxes after the change in the shear rate. This relaxation causes the changes in anisotropic behavior of mechanical. thermal, and optical properties which have strong effect in precision forming of casted polymer products. Among these properties, thermal diffusivity is one of the most difficult properties to measure by the conventional techniques. The present paper describes and discusses the subsecond measurement of relaxation characteristics in thermal dilfusivity anisotropy of flowing polymer melt in conjunction with measurements of some typical flow characteristics. The method used was the forced Rayleigh scattering method, an optical method which was developed and modified by the authors' group for applying to oriented polymer materials. The measuring lime of I ms can trace the relaxation occurred in the order of several seconds. Measured results of thermal diffusivity anisotropy were compared with transient characteristics of the now and quantitatively showed a good agreement with estimated behavior of oriented polymer molecules.

Miyamoto, H.; Nagashima, A.

1996-09-01

52

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

SciTech Connect

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

Mohamed, M. Shadi, E-mail: m.s.mohamed@durham.ac.uk [School of Engineering and Computing Sciences, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Seaid, Mohammed; Trevelyan, Jon [School of Engineering and Computing Sciences, University of Durham, South Road, Durham DH1 3LE (United Kingdom)] [School of Engineering and Computing Sciences, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Laghrouche, Omar [Institute for Infrastructure and Environment, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)] [Institute for Infrastructure and Environment, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)

2013-10-15

53

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

SciTech Connect

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

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

1996-05-01

54

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

55

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

56

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

57

Enhanced diffusion of dopants in vacancy supersaturation produced by MeV implantation  

SciTech Connect

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

Venezia, V.C. [Oak Ridge National Lab., TN (United States). Solid State Div.]|[Univ. of North Texas, Denton, TX (United States). Dept. of Physics; Haynes, T.E. [Oak Ridge National Lab., TN (United States). Solid State Div.; Agarwal, A. [Oak Ridge National Lab., TN (United States). Solid State Div.]|[Lucent Technologies, Murray Hill, NJ (United States). Bell Lab.; Gossmann, H.J.; Eaglesham, D.J. [Lucent Technologies, Murray Hill, NJ (United States). Bell Lab.

1997-04-01

58

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, Francoise; Le Bihan, Denis; Shah, N. Jon

2014-01-01

59

Error diffusion with vivid color enhancement and noise reduction  

NASA Astrophysics Data System (ADS)

A novel error diffusion technique with vivid color enhancement and noise reduction has been developed to achieve high quality, high resolution color ink jet printing. Conventional error diffusion produces halftones with worm-like and salt-and-pepper-like noises. Each halftoned pixel may be one of the 8 colors: RGBCMYKW. Depending on the printing device characteristics (including printer dot size, registration, resolution, ink, and media), color interference between the 8 possible colors may occur. This color interference produces visible salt-and-pepper noise. In order to remove the noise, we classify the 8 colors into three clusters. Each cluster contains a set of harmonic colors. We exclude non-harmonic color halftones to be mixed. Any smooth color area in an input image uses a cluster (i.e., a set of colors) to make the halftone color more vivid and to minimize the non-harmonic color interference. In the error diffusion processing, inter-frame information between RGB plans are used to enforce the color cluster rules to achieve no salt-and-pepper noise and more vivid color halftones. Experimental results are provided to show the effectiveness of the technique.

Shu, Joseph S.

1996-04-01

60

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

61

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

62

Transient Stability Enhancement of Wind Generator by a New Logical Pitch Controller  

NASA Astrophysics Data System (ADS)

In order to investigate the impacts of the integration of wind farms into utilities networks, transient stability should be analyzed before connecting wind turbine generator system (WTGS) to the power system. In this paper, a new logical pitch controller equipped with fuzzy logic controller (FLC) has been proposed, which can enhance the transient performance of WTGS during severe network disturbances. Moreover, it can maintain the output power at rated level when wind speed is over the rated speed. Before transient stability analysis, it is necessary to determine initial values of WTGS connected to the external network. In this paper, the initial value calculation method of WTGS is discussed at different wind conditions. Finally, in order to evaluate the effectiveness of the proposed controller in improving the transient stability, simulations have been carried out for severe network disturbances and windy conditions, considering mechanical dead zone of the pitch actuation system. Simulation results clearly indicate that the proposed controller can enhance the transient stability of wind generator at any network, fault or windy condition, and maintain output power of wind generator at rated level when wind speed is over the rated speed.

Muyeen, S. M.; Ali, Mohd. Hasan; Takahashi, Rion; Murata, Toshiaki; Tamura, Junji

63

Large enhancement of transient photovoltage induced by the absorption of the metal Al  

NASA Astrophysics Data System (ADS)

The transient photovoltage of ITO/CuPc/Al is studied. The transient photovoltage under the Al side illumination is much greater than that under ITO side illumination. It is not negligible while light is almost completely absorbed by the Al layer. It seems that the light absorption of the Al layer could enhance the generation of the photoinduced carriers in the organic layer, which is further shown by the transient photovoltage study of ITO/Al/NPB/Au. A possible mechanism proposed is that the holes generated in the Al are because of light absorption that is injected from the Al to organic materials. This results in further charge separation by the internal built-in electric field.

Wu, Bo; Sun, XiaoYu; Sun, ZhengYi; You, YinTao; Lu, Min; Ding, XunMin; Hou, XiaoYuan

2012-07-01

64

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

65

Comparison between the Predictions of Diffusion-Reaction Models and Localized Ca2+ Transients in Amphibian Skeletal Muscle Fibers  

PubMed Central

We developed a three-dimensional cylindrical diffusion-reaction model of a single amphibian myofibril in which Ca2+ release occurred only at the Z-line. The model incorporated diffusion of Ca2+, Mg2+, and all relevant buffer species, as well as the kinetic binding reactions between the buffers and appropriate ions. Model data was blurred according to a Gaussian approximation of the point spread function of the microscope and directly compared with experimental data obtained using the confocal spot methodology. The flux parameters were adjusted until the simulated Z-line transient matched the experimental one. This model could not simultaneously predict key parameters of the experimental M- and Z-line transients, even when model parameters were adjusted to unreasonably extreme values. Even though the model was accurate in predicting the Z-line transient under conditions of high [EGTA], it predicted a significantly narrower Ca2+ domain than observed experimentally. We modified the model to incorporate a broader band of release centered at the Z-line. This extended release model was superior both in simultaneously predicting critical features of the Z- and M-line transients as well as the domain profile under conditions of high [EGTA]. We conclude that a model of release occurring exclusively at the Z-line cannot explain our experimental data and suggest that Ca2+ may be released from a broader region of the sarcoplasmic reticulum than just the T-tubule-sarcoplasmic reticulum junction. PMID:12885654

Novo, David; DiFranco, Marino; Vergara, Julio L.

2003-01-01

66

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

67

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

PubMed

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

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

2011-04-01

68

Comparison of homogenized and enhanced diffusion solutions of model PWR problems  

SciTech Connect

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

Lewis, E. E. [Dept. of Mechanical Engineering, Northwestern Univ., 2145 Sheridan Rd., Evanston, IL 60208 (United States); Smith, M. A. [Nuclear Engineering Div., Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439 (United States)

2012-07-01

69

Kinetic Ignition Enhancement of Diffusion Flames by Nonequilibrium Magnetic Gliding Arc Plasma  

E-print Network

Kinetic Ignition Enhancement of Diffusion Flames by Nonequilibrium Magnetic Gliding Arc Plasma efficiently for ignition enhancement. I. Introduction THE development of hypersonic airbreathing propulsion combustor. Therefore, the total heat release, thrust, and propulsive efficiency cannot fully be realized

Ju, Yiguang

70

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

71

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

72

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

73

Fission Enhanced diffusion of uranium in zirconia N. Brerd, A. Chevarier, N. Moncoffre,  

E-print Network

Fission Enhanced diffusion of uranium in zirconia N. Bérerd, A. Chevarier, N. Moncoffre, Institut and Fission Enhanced Diffusion (FED) of uranium into zirconia, representative of the inner face of cladding using the Lohengrin spectrometer. A thin 235 UO2 layer in direct contact with an oxidized zirconium foil

Paris-Sud XI, Université de

74

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

SciTech Connect

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

Weber, Christopher P.

2005-12-15

75

Determination of the Liquid Water Diffusivity from Transient Moisture Transfer Experiments  

Microsoft Academic Search

The Boltzmann transformation method is used to determine the liquid water diffusivity from moisture content profiles as measured in a capillary water absorption experiment. An inter-laboratory comparison for analyzing the reliability of the determination method showed that the inaccuracy in the liquid water diffusivity is caused by scatter in the transformed data and by uncertainty in the boundary conditions at

J. Carmeliet; H. Hens; S. Roels; OCG Adan; HJP Brocken; R. Cerny; Z. Pavlik; C. Hall; K. Kumaran; L. Pel

2004-01-01

76

Pore-scale modeling of enhanced vapor diffusion in porous media  

SciTech Connect

Vapor diffusion in porous media in the presence of its liquid has often been analyzed like air diffusion. The diffusion rate 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. The mechanisms postulated to lead to this enhancement include condensation/evaporation across isolated liquid islands in the porous media and an increased temperature gradient in the gas phase. In order to try to understand the mechanisms involved in such an enhancement, pore-scale models have been developed. Vapor diffusion in the presence of liquid islands has been evaluated for a one-dimensional pore network under a concentration gradient. The simulations show that significant enhancement of vapor diffusion is indeed possible in the presence of liquid islands, while air diffusion decreases slightly. While the present pore-scale model indicates that enhanced vapor diffusion is possible, only experimental data can confirm the relevant processes.

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

1997-10-01

77

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.

78

Transient diffusion of radionuclides from a cylindrical waste solid into fractured porous rock  

SciTech Connect

This paper presents the numerical results of an analytical study for mass transfer and transport of radionuclides released from a cylindrical waste solid into water-saturated fractured porous rock. The purposes of this study are (1) to predict the diffusive mass flux from a cylindrical waste solid into a planar fracture and the surrounding rock matrix for the low-flow conditions wherein near-field mass transfer is expected to be controlled by molecular diffusion and (2) to investigate the effects of cylindrical geometry and of multidimensional matrix diffusion including diffusion in the directions parallel to the fracture plane. In the paper are presented the derivation of an analytical solution for the time-dependent mass transfer from the cylinder for low-flow conditions and computer-code implementation and numerical results. The problem was first proposed and solved analytically by Chambre. Numerical results are shown for (1) the diffusive mass fluxes from the cylindrical waste solid into the fracture and into the rock matrix, (2) the diffusive mass flux across the rock/fracture interface, and (3) the instantaneous concentration isopleths in the fracture and in the rock matrix. Comparison of the present cylindrical model with previous planar models, wherein contaminant was assumed to be released only into the fracture and diffusion in the rock matrix was assumed to be one-dimensional perpendicular to the fracture plane, shows that the cylindrical model is more conservative than the planar models with respect to the mass transfer from the source into the fracture and with respect to the far-field transport, provided that diffusion is dominant in the fracture. 21 refs., 10 figs., 3 tabs.

Ahn, J. (Tokyo Univ. (Japan). Faculty of Engineering); Chambre, P.L.; Pigford, T.H. (California Univ., Berkeley, CA (USA). Dept. of Nuclear Engineering Lawrence Berkeley Lab., CA (USA))

1990-09-01

79

A novel speckle reduction and contrast enhancement method based on fuzzy anisotropic diffusion  

Microsoft Academic Search

Two major problems of ultrasound imaging are low-contrast and speckle noise. Traditionally, before speckle reduction, an enhancement algorithm is employed to improve the quality of the image. However, the noise is enhanced as well. To overcome this drawback, we introduce a novel fuzzy anisotropic diffusion approach for speckle reduction and contrast enhancement. Maximum fuzzy entropy principle is used to map

Yingtao Zhang; H. D. Cheng; Jiawei Tian; Jianghua Huang

2010-01-01

80

Enhanced magnetospheric/boundary layer plasma flows observed during transient magnetopause crossings  

NASA Astrophysics Data System (ADS)

We observed enhanced plasma flows inside the magnetopause while the Geotail satellite briefly crossed the magnetopause. The enhanced flows were mainly in the MN plane of the LMN coordinates. Some of them showed a bipolar signature, i.e., inward flow before the outbound (from the magnetosphere to the magnetosheath) crossing and then outward flow after the inbound (from the magnetosheath to the magnetosphere) crossing, in the component normal to the nominal magnetopause. We found two different types of the bipolar flow: one is roughly symmetric with respect to the center of the event, that is, the peak amplitudes of the inward and outward flows are comparable, and the other is strongly asymmetric, that is, the outward flow speed is much larger than the inward flow speed. Using a simple qualitative model, we show that the symmetric bipolar flow is consistent with a vortical plasma motion from the E×B drift. The source of the electric field E may be attributed to briefly compressed magnetopause moving tailward, which is induced by a transient external (solar wind/foreshock) pressure pulse. In the asymmetric case, the strong outward flows were accompanied by a depressed magnetic field strength. This suggests that the strong outward plasma motion is associated with transient magnetospheric expansion driven by external pressure pulse variations.

Kim, K.-H.; Lin, N.; Cattell, C. A.; Lee, D.-H.; Kokubun, S.; Mukai, T.; Tsuruda, K.

81

Evolution Nonlinear Diffusion-Convection PDE Models for Spectrogram Enhancement  

NASA Astrophysics Data System (ADS)

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

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

2008-09-01

82

Enhanced anomalous diffusion of sputtered atoms in nanosized pores  

E-print Network

domains such as transport in fractal media [11], solid surface diffusion [12] or hydrodynamics (rotating, an argon plasma is created in a 80 liter cylindrical stainless steel chamber by an external planar antenna

Boyer, Edmond

83

Electric Field Enhanced Diffusion of Salicylic Acid through Polyacrylamide Hydrogels  

NASA Astrophysics Data System (ADS)

The release mechanisms and the diffusion coefficients of salicylic acid -loaded polyacrylamide hydrogels were investigated experimentally by using a modified Franz-diffusion cell at 37 ^oC to determine the effects of crosslinking ratio and electric field strength. A significant amount of salicylic acid is released within 48 hours from the hydrogels of various crosslinking ratios, with and without electric field. The release characteristic follows the Q vs. t^1/2 linear relationship. Diffusion coefficient initially increases with increasing electric field strength and reaches the maximum value at electric field strength of 0.1 V; beyond that it decreases with electric field strength and becomes saturated at electric field strength of 5 V. The diffusion coefficient increases at low electric field strength (less 0.1 V) as a result of the electrophoresis of the salicylic acid, the expansion of pore size, and the induced pathway in pigskin. For electric field strength higher than 0.1 V, the decrease in the diffusion coefficient is due to the reduction of the polyacrylamide pore size. The diffusion coefficient obeys the scaling behavior D/Do=(drug size/pore size)^m, with the scaling exponent m equal to 0.93 and 0.42 at electric fields of 0 and 0.1 V, respectively.

Niamlang, Sumonman; Sirivat, Anuvat

2008-03-01

84

Approach to asymptotically diffusive behavior for Brownian particles in periodic potentials: extracting information from transients.  

PubMed

A Langevin process describing diffusion in a periodic potential landscape has a time-dependent diffusion constant, which means that its average mean-squared displacement (MSD) only becomes linear at late times. The long-time, or effective diffusion, constant can be estimated from the slope of a linear fit of the MSD at late times. Due to the crossover between a short time microscopic diffusion constant, which is independent of the potential, to the effective late-time diffusion constant, a linear fit of the MSD will not in general pass through the origin and will have a nonzero constant term. Here we address how to compute the constant term and provide explicit results for Brownian particles in one dimension in periodic potentials. We show that the constant is always positive and that at low temperatures it depends on the curvature of the minimum of the potential. For comparison we also consider the same question for the simpler problem of a symmetric continuous time random walk in discrete space. Here the constant can be positive or negative and can be used to determine the variance of the hopping time distribution. PMID:25215694

Dean, David S; Oshanin, Gleb

2014-08-01

85

Concurrent MRI and diffuse optical tomography of breast after indocyanine green enhancement  

E-print Network

Concurrent MRI and diffuse optical tomography of breast after indocyanine green enhancement Vasilis agents MRI coregistration Diffuse optical tomography (DOT) in the near-infrared (NIR) is an emerging 19104-6089 Contributed by Britton Chance, December 23, 1999 We present quantitative optical images

Yodh, Arjun G.

86

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

NASA Astrophysics Data System (ADS)

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.

Nikitin, Sergei Yu

2009-07-01

87

Diffusion enhancement due to low-energy ion bombardment during sputter etching and deposition  

Microsoft Academic Search

The effects of low-energy ion bombardment on enhancing elemental diffusion rates at both heterojunction interfaces during film deposition and over the compositionally altered layer created during sputter etching alloy targets have been considered. Depth dependent enhanced interdiffusion coefficients, expressed as D*(x)=D*(0) exp(?x\\/Ld), where D*(0) is more than five orders of magnitude greater than thermal diffusion values, were measured in InSb\\/GaSb

A. H. Eltoukhy; J. E. Greene

1980-01-01

88

Diffusion enhancement due to low-energy ion bombardment during sputter etching and deposition  

Microsoft Academic Search

The effects of low-energy ion bombardment on enhancing elemental diffusion rates at both heterojunction interfaces during film deposition and over the compositionally altered layer created during sputter etching alloy targets have been considered. Depth dependent enhanced interdiffusion coefficients, expressed as D*(x)=D*(0) exp(-x\\/Ld), where D*(0) is more than five orders of magnitude greater than thermal diffusion values, were measured in InSb\\/GaSb

A. H. Eltoukhy; J. E. Greene

1980-01-01

89

Transient Heat-transfer analysis of scaled down SSME Test-Stand Diffuser  

NASA Astrophysics Data System (ADS)

the scaled-down high altitude test-stand simulator is a metalic cylinder where combussed rocket fuels pass through with speed of Mach 4 or 5. The Temperature at diffuser wall can reach as high as 1800 R. These conditions dictate special design for diffuser. Dominant mode of heat transfer is conduction and convection. An analysis using lumped capacitance method is done the result is a 1st order non- homogeneous differential equation with following solution. T(t)=b/a+(T0-b/a)exp(-at) Where T and t represent temperature and time, a , b and T0 are constants containing physical properties and initial conditions. MAJO POINTS i- Conducton and convection are dominant modes of heat transfer ii-Lumped capacitance method, although simple, provides reasonable first approaximation. The rsult indicates that diffuser wall average temperature varies from nozzle entrance through the length of the diffuser. The maximum appears 30-50 sec after the start of the test and varies from 710-940 R. This was part of the summer faculy fellowship at NASA SSC

Aceil, Sam

2000-11-01

90

Measurement of transient behavior of the thermal diffusivity of flowing polymer melt  

Microsoft Academic Search

Molecular orientation of polymer molecules created by shear force due to the flow of the polymer melt in a duct rapidly relaxes after the change in the shear rate. This relaxation causes the changes in anisotropic behavior of mechanical. thermal, and optical properties which have strong effect in precision forming of casted polymer products. Among these properties, thermal diffusivity is

H. Miyamoto; A. Nagashima

1996-01-01

91

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

92

1D scattering experiments with ultra-cold atoms: transient enhancement of high momenta  

NASA Astrophysics Data System (ADS)

During the scattering of a particle from a repulsive potential, the particle can exhibit an enhancement of high momentum components. This effect is transient in the sense that it only exists when there is an overlap between the particle's wavefunction and the scattering potential, and is inherently a quantum mechanical phenomenon. This effect has been shown to be strongest for scattering potentials that are weak such that the wavepacket is entirely transmitted [1]. In our experiment we use an ultra-cold gas interacting with a thin optical dipole barrier to observe this effect. If time permits, we will discuss experiments in progress to investigate tunneling of our ultra-cold gas in 1D. [4pt] [1] S. Brouard and J. G. Muga , Phys. Rev. Lett. 81, 2621-2625 (1998)

Chang, Rockson; Ellenor, Chris; Siercke, Mirco; Potnis, Shreyas; Steinberg, Aephraim

2011-06-01

93

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

94

Image restoration and enhancement based on tunable forward-and-backward diffusion  

NASA Astrophysics Data System (ADS)

In order to improve signal-to-noise ratio (SNR) and contrast-to-noise ratio, we introduces a novel tunable forward-and-backward (TFAB) diffusion approach for image restoration and edge enhancement. In the TFAB algorithm, an alternative forward-and-backward (FAB) diffusion process is presented, where it is possible to better modulate all aspects of the diffusion behavior and it shows better algorithm behavior compared to the existing FAB diffusion approaches. In addition, there is no necessity to laboriously determine the value of the gradient threshold. We believe the TFAB diffusion to be an adaptive mechanism for image restoration and enhancement. Qualitative experiments, based on various general digital images and a magnetic resonance image, show significant improvements when the TFAB diffusion algorithm is used versus the existing anisotropic diffusion and the previous FAB diffusion algorithms for enhancing edge features and improving image contrast. Quantitative analyses, based on peak SNR and the universal image quality index, confirm the superiority of the proposed algorithm.

Wang, Yi; Niu, Ruiqing; Yu, Xin; Zhang, Liangpei; Shen, Huanfeng

2010-05-01

95

Coupled glide-climb diffusion-enhanced crystal plasticity  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

96

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

97

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

98

Transiently enhanced LPS-induced fever following hyperthermic stress in rabbits  

NASA Astrophysics Data System (ADS)

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

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

2005-11-01

99

Application Of The EIKONIX Diffusion Model Transformation For Electro-Optical Image Enhancement  

NASA Astrophysics Data System (ADS)

This paper reviews briefly some of the previous work done with the EIKONIX Diffusion Model Transformation (DMT) as an image enhancement algorithm for electro-optical imagery. It also compares the technique to some other common forms of image enhancement, such as: - linear high pass filtering - homomorphic high pass filtering - histogram remapping The DMT produced results superior to the other enhancement methods. A combination of the DMT and histogram equalization proved still better.

Rudomen, Bennett; Liff, Harold

1981-07-01

100

Experimental demonstration of diffusion signal enhancement in 2D DESIRE images  

NASA Astrophysics Data System (ADS)

In magnetic resonance microscopy based on conventional Fourier encoding techniques, molecular self-diffusion leads to a loss in signal to noise ratio while also limiting the spatial resolution. As opposed to standard diffusion-weighted sequences, the DESIRE (Diffusion Enhancement of SIgnal and REsolution) method gains signal through diffusion via a signal difference measurement, corresponding to the total number of spins saturated by a localized pulse applied for a given amount of time. The higher the diffusion coefficient at that location, the larger the number of spins effectively saturated and thus the higher the difference in signal. While the method has been previously demonstrated in 1D, the availability of higher magnetic fields and gradient strengths has recently brought its development within reach in 2D. Here we report the implementation of 2D DESIRE and the first experimental evaluation of enhancements in water and thin silicone oil. Enhancement levels obtained by saturating a 60 ?m diameter region (effectively ˜140 ?m) and allowing diffusion lengths of 28 ?m or 7 ?m, respectively, are consistent with theoretical predictions. The typical enhancement values are 100% in water and 20% in silicone oil.

Jelescu, Ileana O.; Boulant, Nicolas; Le Bihan, Denis; Ciobanu, Luisa

2012-05-01

101

Forward-and-backward diffusion for hyperspectral remote sensing image smoothing and enhancement  

NASA Astrophysics Data System (ADS)

Among all enhancement techniques being developed over the past two decades, anisotropic diffusion has received a lot of attention and has experienced significant developments, with promising results and applications in several specific domains. The elegant property of the technique is that it can enhance images by reducing undesirable intensity variability within the objects in image, while improving signal-to-noise ratio (SNR) and enhancing the contrast of the edges in scalar and, more recently, in vector-valued images, such as color, multispectral and hyperspectral imagery. In this paper, we firstly analyze two complementary schemes-variational methods and nonlinear diffusion partial differential equations (PDEs), in terms of edge enhancement. Based on these analyses, a general flexible class of hyperspectral forward-and-backward (FAB) diffusion process will be proposed, which can achieve the main requirements for edgepreserving regularization with image enhancement. In addition, we use additive operator splitting (AOS) scheme to speedup the numerical evolution of the nonlinear diffusion equation with respect to traditional explicit schemes. The performance of the vector-valued FAB diffusion PDE is studied using some hyperspectral remote sensing images. Experimental results on these images are shown the validity and effectiveness of the proposed method.

Wang, Yi; Niu, Ruiqin; Shen, Huanfeng; Yu, Xin

2008-12-01

102

EFFECTS OF SERIES AND SHUNT FACTS DEVICES IN TRANSIENT STABILITY ENHANCEMENT OF MULTI-MACHINE POWER SYSTEMS  

Microsoft Academic Search

In this paper a study is performed on Transient Stability enhancement in multi-machine power systems using Unified Power Flow Controller (UPFC). The paper uses the Injection Model of UPFC and series quadrature voltage injection and shunt compensation used for oscillation damping and then the effects of series and shunt compensation separately and together analyzed. Then different locations for UPFC in

S. Javad Sajjadi; M. Hasan Mohseninejad; Saeed Afsharnia

103

Low-cost enhancement of the signal-averaging capability of transient recorders using a small computer  

Microsoft Academic Search

Where the signal to be observed is repetitive, a microcomputer may be used to enhance the effective sampling rate of a transient recorder by interleaving successive records in the computer memory. A system is described using a Datalab DL 920 recorder which permits the averaging of weak signals with a time resolution of 10 ns.

P. C. Landers; M. O. Norris; S. J. Rogers

1978-01-01

104

How Much Would Performing Diffusion-Weighted Imaging for All Transient Ischemic Attacks Increase MRI Utilization?  

PubMed Central

Objectives The American Heart Association recently redefined transient ischemic attack (TIA) to exclude patients with infarction on neuroimaging. Given its advantages, MRI/DWI was recommended as the preferred imaging modality. We determined how frequently MRI/DWI was performed for TIA and ascertained the proportion of clinically-defined TIA patients who had ischemic lesions on DWI in our community in 2005. Methods All clinically-defined TIA cases among residents of a five-county region around Cincinnati who presented to emergency departments were identified during 2005. Demographics and medical history, whether MRI/DWI was done, and DWI findings were recorded. Generalized estimating equations were used to compare groups in order to account for the design of the study and multiple events per patient. Results Of 834 TIA events in 799 patients, 323 events (40%) had MRI/DWI performed. Patients who had MRI/DWI were younger (mean 66 vs. 70yrs, p=0.03), had less severe pre-stroke disability (baseline modified Rankin Scale zero, 44% vs. 34%, p=0.02), were less likely to have prior stroke or TIA (42% vs 56%, p=0.002), and were less likely to have atrial fibrillation (10% vs. 16%, p=0.01). Of the 323 events with DWI, 51 (15%) had evidence of acute infarction. Patients with positive DWI were older (75 vs. 64yrs, p=0.0001) and more likely to have atrial fibrillation (21% vs. 7%, p=0.002). Conclusion Performing MRI/DWI on all clinically-defined TIA patients in our community would reveal more cases of actual infarction, but would more than double current use. Future studies should assess whether MRI/DWI is warranted for all TIA patients. PMID:20798366

Adeoye, Opeolu; Heitsch, Laura; Moomaw, Charles J.; Alwell, Kathleen; Khoury, Jane; Woo, Daniel; Flaherty, Matthew L.; Ferioli, Simona; Khatri, Pooja; Broderick, Joseph P.; Kissela, Brett M.; Kleindorfer, Dawn

2010-01-01

105

Diffusive transport enhancement by isolated resonances and distribution tails growth in hadronic beams  

SciTech Connect

The escape rates and evolution of a distribution of particles are considered for a 2-D model of transverse motion of particles in hadronic storage rings, when nonlinear resonances and external diffusion are present. Dynamic enhancement of diffusion inside separatrices can develop under a certain geometry of resonance oscillations and relatively wide resonances, leading to the fast growth of distribution tails and escape rates. The phenomenon is absent in 1-D. 10 refs., 4 figs.

Gerasimov, A.

1990-12-06

106

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

107

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

108

Enhancement of an anti-tumor immune response by transient blockade of central T cell tolerance  

PubMed Central

Thymic central tolerance is a critical process that prevents autoimmunity but also presents a challenge to the generation of anti-tumor immune responses. Medullary thymic epithelial cells (mTECs) eliminate self-reactive T cells by displaying a diverse repertoire of tissue-specific antigens (TSAs) that are also shared by tumors. Therefore, while protecting against autoimmunity, mTECs simultaneously limit the generation of tumor-specific effector T cells by expressing tumor self-antigens. This ectopic expression of TSAs largely depends on autoimmune regulator (Aire), which is expressed in mature mTECs. Thus, therapies to deplete Aire-expressing mTECs represent an attractive strategy to increase the pool of tumor-specific effector T cells. Recent work has implicated the TNF family members RANK and RANK-Ligand (RANKL) in the development of Aire-expressing mTECs. We show that in vivo RANKL blockade selectively and transiently depletes Aire and TSA expression in the thymus to create a window of defective negative selection. Furthermore, we demonstrate that RANKL blockade can rescue melanoma-specific T cells from thymic deletion and that persistence of these tumor-specific effector T cells promoted increased host survival in response to tumor challenge. These results indicate that modulating central tolerance through RANKL can alter thymic output and potentially provide therapeutic benefit by enhancing anti-tumor immunity. PMID:24752296

Khan, Imran S.; Mouchess, Maria L.; Zhu, Meng-Lei; Conley, Bridget; Fasano, Kayla J.; Hou, Yafei; Fong, Lawrence; Su, Maureen A.

2014-01-01

109

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

110

Enhancement of an anti-tumor immune response by transient blockade of central T cell tolerance.  

PubMed

Thymic central tolerance is a critical process that prevents autoimmunity but also presents a challenge to the generation of anti-tumor immune responses. Medullary thymic epithelial cells (mTECs) eliminate self-reactive T cells by displaying a diverse repertoire of tissue-specific antigens (TSAs) that are also shared by tumors. Therefore, while protecting against autoimmunity, mTECs simultaneously limit the generation of tumor-specific effector T cells by expressing tumor self-antigens. This ectopic expression of TSAs largely depends on autoimmune regulator (Aire), which is expressed in mature mTECs. Thus, therapies to deplete Aire-expressing mTECs represent an attractive strategy to increase the pool of tumor-specific effector T cells. Recent work has implicated the TNF family members RANK and RANK-Ligand (RANKL) in the development of Aire-expressing mTECs. We show that in vivo RANKL blockade selectively and transiently depletes Aire and TSA expression in the thymus to create a window of defective negative selection. Furthermore, we demonstrate that RANKL blockade can rescue melanoma-specific T cells from thymic deletion and that persistence of these tumor-specific effector T cells promoted increased host survival in response to tumor challenge. These results indicate that modulating central tolerance through RANKL can alter thymic output and potentially provide therapeutic benefit by enhancing anti-tumor immunity. PMID:24752296

Khan, Imran S; Mouchess, Maria L; Zhu, Meng-Lei; Conley, Bridget; Fasano, Kayla J; Hou, Yafei; Fong, Lawrence; Su, Maureen A; Anderson, Mark S

2014-05-01

111

Ion-bombardment-enhanced diffusion during the growth of sputtered superlattice thin films  

Microsoft Academic Search

A technique is presented for determining the enhancement in solid-state diffusion caused by low-energy ion bombardment. In this technique, superlattice films are grown under varying conditions of ion bombardment and the amplitude of the resulting composition modulation wave is determined by analyzing x-ray diffraction satellite peaks surrounding the central Bragg peaks. The amplitude is in turn related to the enhanced

A. H. Eltoukhy; J. E. Greene

1978-01-01

112

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

113

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

NASA Astrophysics Data System (ADS)

The influence of proton diffusion on nuclear magnetic resonance (NMR) relaxation was investigated in the presence of horse spleen ferritin at 7 T. Binary mixtures of water and glycerol were used to control diffusion within the range of 0.6-2.0 × 10-9 m2/s, which was confirmed by pulsed gradient techniques. The effect of chemical exchange by hydrolysis between water and glycerol on relaxation was characterized with Carr-Purcell-Meiboom-Gill (CPMG) dispersion experiments. The relaxation rate enhancement of the protons due to ferritin was found to be inversely proportional to the diffusion coefficient. The enhancement increased by a factor of 3.6 over the range of diffusion coefficients, while the hydroxyl proton concentration decreased by a factor of 1.3. This result is in disagreement with the proton exchange dephasing model, which is independent of diffusion but predicts an inverse dependence on the hydroxyl concentration. Our data indicate that the role of diffusion dominates and must be considered when relaxation rates are used to determine iron concentration in vivo.

Boss, Michael A.; Chris Hammel, P.

2012-04-01

114

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

115

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 motors dispersed in a fluid display emergent properties that differ strongly from passive suspensions

116

Concurrent MRI and diffuse optical tomography of breast after indocyanine green enhancement  

Microsoft Academic Search

We present quantitative optical images of human breast in vivo. The images were obtained by using near-infrared diffuse optical tomog- raphy (DOT) after the administration of indocyanine green (ICG) for contrast enhancement. The optical examination was performed con- currently with a magnetic resonance imaging (MRI) exam on patients scheduled for excisional biopsy or surgery so that accurate image coregistration and

Vasilis Ntziachristos; A. G. Yodh; Mitchell Schnall; Britton Chance

2000-01-01

117

Pyramidal flux in an anisotropic diffusion scheme for enhancing structures in 3D images  

Microsoft Academic Search

Pyramid based methods in image processing provide a helpful framework for accelerating the propagation of information over large spatial domains, increasing the efficiency for large scale applications. Combined with an anisotropic diffusion scheme tailored to preserve the boundaries at a given level, an efficient way for enhancing large structures in 3D images is presented. In our approach, the partial differential

Oscar Acosta; Hans Frimmel; Aaron Fenster; Olivier Salvado; Sébastien Ourselin

2008-01-01

118

Dynamics of Enhanced Tracer Diffusion in Suspensions of Swimming Eukaryotic Microorganisms  

E-print Network

Dynamics of Enhanced Tracer Diffusion in Suspensions of Swimming Eukaryotic Microorganisms Kyriacos of nonmotile particles and their advection by flows from swimming microorganisms. As a laboratory realization by microorganisms has remained largely unsolved, even in the dilute swimmer limit in which interactions between

Goldstein, Raymond E.

119

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.

Consortium, The C.

2011-12-11

120

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

PubMed

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

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

2014-11-12

121

Neuron, Vol. 45, 469477, February 3, 2005, Copyright 2005 by Elsevier Inc. DOI 10.1016/j.neuron.2004.12.039 Transient Attention Enhances Perceptual  

E-print Network

.neuron.2004.12.039 Transient Attention Enhances Perceptual Performance and fMRI Response in Human Visual in the visual cortex. For instance, in single-unitNew York, New York 10003 recording studies, researchers have-Trujillo and Treue, 2002; Reynolds et al., attention, producing a transient improvement of per- 2000

Carrasco, Marisa

122

November 18, 2007 1:11 WSPC -Proceedings Trim Size: 9in x 6in ChennuNCPW10 TRANSIENT ATTENTIONAL ENHANCEMENT  

E-print Network

November 18, 2007 1:11 WSPC - Proceedings Trim Size: 9in x 6in ChennuNCPW10 TRANSIENT ATTENTIONAL-relevant item, a spatially specific Transient Attentional Enhancement (TAE), called the blaster, is triggered pattern of the blaster in the model matches the N2pc compo- nent in human ERP recordings, for targets

Kent, University of

123

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

124

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

125

Diffusion enhancement due to low-energy ion bombardment during sputter etching and deposition  

SciTech Connect

The effects of low-energy ion bombardment on enhancing elemental diffusion rates at both heterojunction interfaces during film deposition and over the compositionally altered layer created during sputter etching alloy targets have been considered. Depth dependent enhanced interdiffusion coefficients, expressed as D*(x)=D*(0) exp(-x/L/sub d/), where D*(0) is more than five orders of magnitude greater than thermal diffusion values, were measured in InSb/GaSb multilayer structures deposited by multitarget bias sputering. D*(0) was determined from the amplitude u of the compositional modulation in the multilayered films (layer thicknesses between 20 and 45 A) as measured by superlattice x-ray diffraction techniques. The value of D*(0) was found to increase from 3 x 10/sup -17/ to 1 x 10/sup -16/ cm/sup 2//sec as the applied substrate bias was increased from 0 to -75 V. However even at V/sub a/=0, the diffusion coefficient was enhanced owing to an induced substrate potential with respect to the positive space-charge region in the Ar discharge. The diffusion length of L/sub d/ of the ion bombardment created defects was approx.1000 A. Enhanced diffusion also has a significiant effect on the altered layer thickness x/sub e/ and the total sputtering time t/sub e/ (or ion dose) required to reach steady state during ion etching of multielement targets. The effects of using an exponentially depth dependent versus a constant value of the enhanced diffusion coefficient on calculated values of x/sub e/ and t/sub e/ in single-phase binary alloys were considered. The results show that both x/sub e/ and t/sub e/ are considerably larger using a depth dependent D*(x), when L/sub d/D*(0)/v, the usual case for most sputtering applications, the two solutions approach each other.

Eltoukhy, A.H.; Greene, J.E.

1980-08-01

126

Cascade defect production and irradiation enhanced diffusion in Cu/sub 3/Au  

SciTech Connect

By using the ordering alloy Cu/sub 3/Au and measuring resistivity changes during and following fast-neutron irradiations at IPNS, we have studied cascade defect production and irradiation enhanced diffusion between 10 and 460/sup 0/K. Ordering and disordering rates were measured as functions of irradiation temperature, neutron dose, neutron dose rate, time following cessation of flux, and step annealing. Free and clustered vacancy production was observed. The temperature dependence of the production of total migrating vacancy concentrations was determined. Vacancy sink production was linear with neutron dose and is compared with recent transmission electron microscopy experiments on the production of dislocation loops in this alloy. Time dependent and quasi-steady state vacancy concentrations were measured and compared with solutions of reaction rate equations for irradiation enhanced diffusion. The influence of recombination of vacancies with interstitials is observed at low sink concentrations (low neutron doses).

Kirk, M.A.; Funk, L.L.

1986-03-01

127

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

128

Enhanced production of HD and D_2 molecules on small dust grains in diffuse clouds  

E-print Network

Motivated by recent observations of deuterated molecules in the interstellar medium, we examine the production of HD and D$_2$ molecules on dust grain surfaces. A mechanism for the enhanced production of these deuterated molecules is studied. This mechanism applies on grain surfaces on which D atoms stick more strongly than H atoms, under conditions of low flux and within a suitable range of temperatures. It is shown that under these conditions the production rates of HD and D$_2$ are greatly enhanced (vs. the H$_2$ production rate) compared with the expected rates based on the adsorption of gas-phase atomic abundances of D and H. The enhancement in the formation rate of HD is comparable with the enhancement due to gas-phase ion-molecule reactions in diffuse clouds.

Azi Lipshtat; Ofer Biham; Eric Herbst

2003-11-23

129

Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth  

E-print Network

Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth Guus of the ferromagnetic oxide SrRuO3 on TiO2-terminated SrTiO3 , we observe a self-organized conversion of the terminating prerequisites to utilize all opportunities. SrRuO3 has been subject to many studies because of its unique

Eom, Chang Beom

130

Enhanced surface diffusion through termination conversion during epitaxial SrRuO3 growth  

Microsoft Academic Search

During the initial growth of the ferromagnetic oxide SrRuO3 on TiO2-terminated SrTiO3, we observe a self-organized conversion of the terminating atomic layer from RuO2 to SrO. This conversion induces an abrupt change in growth mode from layer by layer to growth by step advancement, indicating a large enhancement of the surface diffusivity. This growth mode enables the growth of single-crystalline

Guus Rijnders; Dave H. A. Blank; Junghoon Choi; Chang-Beom Eom

2004-01-01

131

Strong stress-enhanced diffusion in amorphous lithium alloy nanowire electrodes  

NASA Astrophysics Data System (ADS)

Diffusion-induced stress (DIS) development and stress-enhanced diffusion (SED) in amorphous lithium alloy nanowire battery electrodes are investigated using a finite deformation model, accounting for full two-way coupling between diffusion and stress evolution. Analytical solutions are derived using a perturbation method. The analyses reveal significant contributions to the driving force for diffusion by stress gradient, an effect much stronger than those seen in cathode lattices but so far has been neglected for alloy-based anodes. The contribution of stress to diffusion is small at low lithium concentrations, this lack of SED leads to significantly higher DIS levels in early stages of a charging cycle. As lithium concentration increases, SED becomes more pronounced, leading to lower DIS levels. The long-term DIS level in the material scales with charging rate, nanowire radius, and the mobility of Li ions as modulated by the effect of stress. The solutions obtained provide guidance for lowering stresses during charging. In particular, lower charging rates should be used during the initial stages of charging cycles.

Gao, Y. F.; Zhou, M.

2011-01-01

132

Relativistic electron loss due to ultralow frequency waves and enhanced outward radial diffusion  

NASA Astrophysics Data System (ADS)

Using the THEMIS and GOES satellites and ground-based magnetometers, the loss of outer zone radiation belt electrons through the magnetopause in response to ultralow frequency (ULF) waves is examined. A 2 orders of magnitude decrease in >2 MeV electron flux observed at geosynchronous orbit, starting at 00 UT on 25 June 2008, is attributed to a rapid (1-4 h) nonadiabatic loss process. ULF waves were observed by the THEMIS-A, -D, and -E probes in the afternoon-to-dusk sector from the magnetopause to geosynchronous altitude. Estimates of the electron resonant energies indicate strong drift resonant interactions occurring between the energetic electrons and the observed waves. The rate of outward radial diffusion was estimated for MeV electrons using the observed ULF wave azimuthal electric field and compressional magnetic field and the diffusion time (˜2.5 h) was found to be in good agreement with the observed time for nonadiabatic flux decreases at geosynchronous orbit. The magnetopause was compressed inside of its nominal position because of increased solar wind dynamic pressure. The electron loss is interpreted as a combination of magnetopause shadowing (from the compressed magnetosphere) and enhanced outward diffusion from ULF wave-particle drift resonant interactions. The enhanced day-night asymmetry of the MeV electron drift path from the compression suggests that enhanced losses may have also occurred around local noon as well as in the afternoon-to-dusk sector.

Loto'Aniu, T. M.; Singer, H. J.; Waters, C. L.; Angelopoulos, V.; Mann, I. R.; Elkington, S. R.; Bonnell, J. W.

2010-12-01

133

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

134

Effects of low-dose Si implantation damage on diffusion of phosphorus and arsenic in Si  

E-print Network

Effects of low-dose Si implantation damage on diffusion of phosphorus and arsenic in Si Heemyong of defects.In the caseof arsenic,previous resultscontradict eachother. Someresearchersshowedini- tial transient enhanced diffusion of arsenic during RTA,13*14while others observedno initial transient,15or only

Florida, University of

135

Energy function based neural networks UPFC for transient stability enhancement of network-preserving power systems  

Microsoft Academic Search

An energy function based unified power flow controller (UPFC) is developed for improving transient stability of network-preserving power systems. In order to consider model uncertainties, we also propose a forward neural networks controller to deal with such model uncertainties. This controller can be treated as neural network approximations of energy function control actions and provides online learning ability. Simulations on

Chia-Chi Chu; Hung-Chi Tsai

2010-01-01

136

Comparison of SMES and SFCL for transient stability enhancement of wind generator system  

Microsoft Academic Search

Superconducting magnetic energy storage (SMES) and superconducting fault current limiters (SFCL) can be used to stabilize the wind generator system. While both SMES and SFCL use superconducting coils for their operations, this paper makes a comparative study of these two devices in case of their applications in the wind generator system. The comparison is done on the basis of transient

M. H. Ali; R. A. Dougal

2010-01-01

137

Enhanced neutron diagnostics data acquisition system based on a time digitizer and transient recorder hybrid module  

Microsoft Academic Search

This paper proposes a new transient recorder (TR)–time digitizer (TD) hybrid system to be used to pull out higher performance of presently used techniques for measuring the collimated flux and the spectrum of the neutron emission from fusion plasmas of either deuterium or deuterium–tritium, as well as to apply to new neutron measuring techniques, with demanding specific requirements in plasma

R. C. Pereira; A. Combo; N. Cruz; Jorge Sousa; C. Correia; C. Varandas; S. Conroy; J. Källne

2006-01-01

138

A total internal reflection fluorescence microscopy study of mass diffusion enhancement in water-based alumina nanofluids  

NASA Astrophysics Data System (ADS)

Mass diffusion of rhodamine 6G (R6G) in water-based alumina nanofluids is studied by means of total internal reflection fluorescence (TIRF) microscopy. We report a mass diffusivity enhancement that reaches an order of magnitude in a 2 vol % nanofluid when compared to the value in deionized water. Since experiments were performed with positively charged R6G, interfacial complexation between the dye and the nanoparticles was not observed. The effect of local density variations on mass diffusivity measurements is also addressed. An explanation for the enhancement of mass diffusion is presented using arguments based on dispersion, and it is shown that it correctly describes the order of magnitude differences between the thermal conductivity and mass diffusivity enhancements reported in the literature.

Veilleux, Jocelyn; Coulombe, Sylvain

2010-11-01

139

Using coupled inductors to enhance transient performance of multi-phase buck converters  

Microsoft Academic Search

Motivated by modern microprocessors' demand for high-current, low-voltage power with large transient load steps, a scalable multi-phase coupled inductor buck circuit is presented which delivers 80 A at 1.2 V from a 12 V input. 4-phase coupling and 1 MHz per-phase switching frequency enable the use of 50 nil per-phase leakage inductance so that the system is capable of supporting

Jieli Li; Anthony Stratakos; Aaron Schultz; Charles R. Sullivan

2004-01-01

140

Enhanced long-wavelength transient photoresponsiveness of WO3 induced by tellurium doping.  

PubMed

Tungsten trioxide (WO3) films doped with 0.25 atom% tellurium synthesised by a sol-gel route, show strong transient photocurrents under chopped sub-bandgap illumination (hnu=1.8 eV

Yang, Bin; Luca, Vittorio

2008-10-01

141

Proton diffusion along the membrane surface of thylakoids is not enhanced over that in bulk water  

PubMed Central

In photosynthesis and respiration ATP synthesis is powered by a transmembrane protonmotive force. Membrane bound proton pumps and proton translocating ATPsynthases are coupled by lateral proton flow. Whether it leads through the aqueous bulk phases (chemiosmotic theory) or whether it is confined to the membrane or the membrane water interface, is still controversial. Another related controversy is whether or not proton diffusion along the interface between a phospholipid membrane and water is enhanced over the one in bulk water. Thylakoid membranes of plant chloroplasts are intrinsically closely apposed (?5 nm). To study lateral proton diffusion along the narrow interfacial domain between adjacent thylakoid membranes, we stimulated the proton pumps by a flash of light. This generates an alkalinization jump. In the absence of ADP the membrane is relatively proton tight. Therefore, the alkalinization jump relaxes into the medium. The relaxation kinetics as function of pH and added buffers were studied by flash spectrophotometry. The results were compared with a theory dealing with the diffusion of protons, hydroxyl ions, and mobile buffers plus the action of fixed buffers. We came to the conclusion that the lateral diffusion coefficient both, for H+ and for OH- was less or of same magnitude as in bulk water. PMID:19431743

Polle, Andrea; Junge, Wolfgang

1989-01-01

142

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

143

Transient grating measurement of in-plane ambipolar diffusion in a 4-micron-band-gap, four-layer superlattlce  

Microsoft Academic Search

We describe time-resolved transient grating measurements of in-plane ambipolar transport in a narrowband-gap superlattice that has a period comprised of four layers: InAs\\/GaInSb\\/InAs\\/AlGaInAsSb. The structure was designed as an active region for mid-infrared semiconductor lasers. Two 140-fs, 840-nm pulses from a mode-locked Ti:sapphire laser were interfered in the superlattice to create the transient grating, which was subsequently interrogated in a

S. A. Anson; J. T. Olesberg; M. E. Flatte; T. C. Hasenberg; T. F. Boggess

1999-01-01

144

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.

145

Multispecies diffusion models: A study of uranyl species diffusion  

SciTech Connect

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

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

2011-12-14

146

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

NASA Astrophysics Data System (ADS)

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 1H spin-lattice relaxation for decalin and toluene solutions of various Fe2O3 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 1H 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 1H spin-lattice relaxation resulting from the electronic properties of the crystals and the solvent diffusion were explained.

Kruk, D.; Korpa?a, A.; Taheri, S. Mehdizadeh; Koz?owski, A.; Förster, S.; Rössler, E. A.

2014-05-01

147

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

SciTech Connect

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

Pipon, Yves; Moncoffre, Nathalie; Bererd, Nicolas; Jaffrezic, Henri [Universite de Lyon / Universite Claude Bernard Lyon 1 / IUT A Chimie, CNRS/IN2P3/IPNL, 4 rue Enrico Fermi, Villeurbanne, 69622 (France); Toulhoat, Nelly [Universite de Lyon / Universite Claude Bernard Lyon 1 / IUT A Chimie, CNRS/IN2P3/IPNL, 4 rue Enrico Fermi, Villeurbanne, 69622 (France)]|[Commissariat a l'Energie Atomique, DEN, CEN Saclay, Gif sur Yvette cedex, 91191 (France); Barthe, Marie France; Desgardin, Pierre [CNRS, Centre d'Etudes et de Recherches par Irradiation, 3A rue de la Ferollerie Orleans cedex2, 45071 (France); Raimbault, Louis [Ecole des Mines, Centre d'Informatique Geologique (CIG), 35 rue Saint Honore, Fontainebleau cedex, 77305 (France); Scheidegger, Andre M. [Paul Scherrer Institut, Nuclear Energy and Safety Department (NES), Laboratory for Waste Management, Villigen, 5235 (Switzerland); Carlot, Gaelle [Commissariat a l'Energie Atomique, DEN/DEC/SESC/LLCC, Centre de Cadarache, Saint Paul lez Durance, 13108 (France)

2007-07-01

148

Force enhancement in lengthening contractions of cat soleus muscle in situ: transient and steady-state aspects  

PubMed Central

Force enhancement (FE) associated with lengthening is a well-accepted phenomenon of active skeletal muscle, but the underlying mechanism(s) remain unknown. Similar to force depression (FD) following active shortening, the mechanism of FE may be attributed, at least in part, to cross-bridge kinetics. To examine this relationship, a post hoc analysis was performed on the transient force relaxation phase of previous in-situ FE experiments in soleus muscle-tendon units of anesthetized cats. For each muscle (n = 8), nine eccentric lengthenings (3 amplitudes, 3 velocities) were performed while tetanically stimulated (3T at 30 Hz, 3× ? motorneuron, 35 ± 1°C). To determine transient aspects of FE, the period immediately following stretching was fit with an exponential decay function (R2 > 0.95). Statistical analyses revealed that total steady-state FE (FESS) increased with stretching amplitude and applied mechanical work. A positive relationship was observed between the active FESS and rate of force decay (k), indicating that a kinetic mechanism may explain active FE. However, for all muscles and stretch conditions, there was no correlation between the total amount of FESS and rate of decay. Therefore, FE cannot be explained solely by an active FE mechanism involving the interaction of actin and myosin. Rather, these findings suggest a combination of underlying mechanisms, including a kinetic mechanism for active FE, contributions of a passive elastic element, and possibly an activatable passive component operating outside of actin–myosin cross-bridging. Moreover, this transient analysis identifies that FE is not simply the opposite of FD, and its underlying mechanism(s) cannot simply be the opposite in nature. PMID:24303106

Koppes, Ryan A; Herzog, Walter; Corr, David T

2013-01-01

149

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

150

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

PubMed

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

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

2013-03-13

151

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

152

Determination of Thermal Diffusivities, Thermal Conductivities, and Sound Speeds of Room-Temperature Ionic Liquids by the Transient Grating Technique  

E-print Network

, does not significantly influence the sound speed or the thermal diffusivity of the RTILs. Introduction-temperature1-8 lubricants. It is probable that industrial applications of RTILs in chemistry, engineering-11 and can be used to determine thermophysical properties of solids, liquids, and gases. The method is based

Reid, Scott A.

153

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

NASA Astrophysics Data System (ADS)

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

Foy, Brent D.; Blake, Joseph

2001-01-01

154

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

155

Recurrent Transient Apical Cardiomyopathy (Tako-Tsubo-Like Left Ventricular Dysfunction) in a Postmenopausal Female with Diffuse Esophageal Spasms  

PubMed Central

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

2013-01-01

156

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

PubMed

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

Pérez-Gómez, Anabel; Tasker, R Andrew

2014-05-01

157

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

158

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

PubMed

Silver nanoparticles are being used increasingly in various applications because of their antibacterial properties. It is necessary to lower their direct contact with the skin by embedding in a polymer reducing their side effects. In this study, silver nanoparticles were synthesized inside the wool fibers acted as a polyfunctional ligands. Lecithin as a biological lipid was used to enhance the diffusion of silver ions and nanoparticles into the wool fibers reducing cytotoxicity effects of the nano silver loaded wool. The highest loading efficiency and inhibition zone was observed on the wool with the highest lecithin concentration. Presence of lecithin reduced the rate of nano silver release which results in decreasing the specific coefficient of lethality. Also, the extracted solution of the synthesized silver nanoparticles on the wool has not altered the morphology of L929 fibroblast cells. PMID:22178185

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

2012-04-01

159

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

PubMed

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

2014-10-01

160

Enhancing tracer diffusivity by tuning interparticle interactions and coordination shell structure  

E-print Network

This study uses a combination of stochastic optimization, statistical mechanical theory, and molecular simulation to test the extent to which the long-time dynamics of a single tracer particle can be enhanced by rationally modifying its interactions--and hence static correlations--with the other particles of a dense fluid. Specifically, a simulated annealing strategy is introduced that, when coupled with test-particle calculations from an accurate density functional theory, finds interactions that maximize either the tracer's partial molar excess entropy or a related pair-correlation measure (i.e., two quantities known to correlate with tracer diffusivity in other contexts). The optimized interactions have soft, Yukawa-like repulsions, which extend beyond the hard-sphere interaction and disrupt the coordination-shell cage structure surrounding the tracer. Molecular and Brownian dynamics simulations find that tracers with these additional soft repulsions can diffuse more than three times faster than bare hard spheres in a moderately supercooled fluid, despite the fact that the former appear considerably larger than the latter by conventional definitions of particle size.

James Carmer; Gaurav Goel; Mark J. Pond; Jeffrey R. Errington; Thomas M. Truskett

2011-10-11

161

Enhanced Electro-Static Modulation of Ionic Diffusion through Carbon Nanotube Membranes by Diazonium Grafting Chemistry  

PubMed Central

A membrane structure consisting of an aligned array of open ended carbon nanotubes (~ 7 nm i.d.) spanning across an inert polymer matrix allows the diffusive transport of aqueous ionic species through CNT cores. The plasma oxidation process that opens CNTs tips inherently introduces carboxylic acid groups at the CNT tips, which allows for a limited amount of chemical functional at the CNT pore entrance. However for numerous applications, it is important to increase the density of carboxylic acid groups at the pore entrance for effective separation processes. Aqueous diazonium based electro-chemistry significantly increases the functional density of carboxylic acid groups. pH dependent dye adsorption-desorption and interfacial capacitance measurements indicate ~ 5–6 times increase in functional density. To further control the spatial location of the functional chemistry, a fast flowing inert liquid column inside the CNT core is found to restrict the diazonium grafting to the CNT tips only. This is confirmed by the increased flux of positively charged Ru(bi-py)3+2 with anionic functionality. The electrostatic enhancement of ion diffusion is readily screened in 0.1(M) electrolyte solution consistent with the membrane pore geometry and increased functional density. PMID:25132719

Majumder, Mainak; Keis, Karin; Zhan, Xin; Meadows, Corey; Cole, Jeggan

2013-01-01

162

The response of a propane-air counter-flow diffusion flame subjected to a transient flow field  

Microsoft Academic Search

OH planar laser-induced fluorescence (PLIF) and particle image velocimetry have been used to study the frequency response of laminar C3H8-air counterflow diffusion flames to assess the adequacy of the steady-flamelet models. Particle image velocimetry was used to determine the flame strain rate, while OH PLIF was used both to measure temperature at the flame front, using the two-line PLIF technique,

Eric J. Welle; William L. Roberts; Campbell D. Carter; Jeffrey M. Donbar

2003-01-01

163

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

PubMed

The environmental chemodynamics of hydrophobic organic chemicals (HOCs) are often rate-limited by diffusion in stagnant boundary layers. This study investigated whether motile microorganisms can act as microbial carriers that enhance mass transfer of HOCs through diffusive boundary layers. A new experimental system was developed that allows (1) generation of concentration gradients of HOCs under the microscope, (2) exposure and direct observation of microorganisms in such gradients, and (3) quantification of HOC mass transfer. Silicone O-rings were integrated into a Dunn chemotaxis chamber to serve as sink and source for polycyclic aromatic hydrocarbons (PAHs). This resulted in stable concentration gradients in water (>24 h). Adding the model organism Tetrahymena pyriformis to the experimental system enhanced PAH mass transfer up to hundred-fold (benzo[a]pyrene). Increasing mass transfer enhancement with hydrophobicity indicated PAH co-transport with the motile organisms. Fluorescence microscopy confirmed such transport. The effective diffusivity of T. pyriformis, determined by video imaging microscopy, was found to exceed molecular diffusivities of the PAHs up to four-fold. Cell-bound PAH fractions were determined to range from 28% (naphthalene) to 92% (pyrene). Motile microorganisms can therefore function as effective carriers for HOCs under diffusive conditions and might significantly enhance mobility and availability of HOCs. PMID:24625194

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

2014-04-15

164

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

SciTech Connect

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

Lu Yao; Chan, Heang-Ping; Wei Jun; Hadjiiski, Lubomir M. [Department of Radiology, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2010-11-15

165

1732 IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 42, NO. 8, AUGUST 2007 A Transient-Enhanced Low-Quiescent  

E-print Network

1732 IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 42, NO. 8, AUGUST 2007 A Transient-Enhanced Low. INTRODUCTION POWER management is essential in all battery-powered portable devices such as cellular phones and PDAs in order to reduce the standby power and prolong the battery runtime. Low-dropout regulators (LDOs

Lee, Hoi

166

Transient Activation of the PI3K-AKT Pathway by Hepatitis C Virus to Enhance Viral Entry*  

PubMed Central

The PI3K-AKT signaling pathway plays an important role in cell growth and metabolism. Here we report that hepatitis C virus (HCV) transiently activates the PI3K-AKT pathway. This activation was observed as early as 15 min postinfection, peaked by 30 min, and became undetectable at 24 h postinfection. The activation of AKT could also be mediated by UV-inactivated HCV, HCV pseudoparticle, and the ectodomain of the HCV E2 envelope protein. Because antibodies directed against CD81 and claudin-1, but not antibodies directed against scavenger receptor class B type I or occludin, could also activate AKT, the interaction between HCV E2 and its two co-receptors CD81 and claudin-1 probably triggered the activation of AKT. This activation of AKT by HCV was important for HCV infectivity, because the silencing of AKT by siRNA or the treatment of cells with its inhibitors or with the inhibitor of its upstream regulator PI3K significantly inhibited HCV infection, whereas the expression of constitutively active AKT enhanced HCV infection. The PI3K-AKT pathway is probably involved in HCV entry, because the inhibition of this pathway could inhibit the entry of HCV pseudoparticle but not the VSV pseudoparticle into cells. Furthermore, the treatment of cells with the AKT inhibitor AKT-V prior to HCV infection inhibited HCV infection, whereas the treatment after HCV infection had no obvious effect. Taken together, our studies indicated that HCV transiently activates the PI3K-AKT pathway to facilitate its entry. These results provide important information for understanding HCV replication and pathogenesis and raised the possibility of targeting this cellular pathway to treat HCV patients. PMID:23095753

Liu, Zhe; Tian, Yongjun; Machida, Keigo; Lai, Michael M. C.; Luo, Guangxiang; Foung, Steven K. H.; Ou, Jing-hsiung James

2012-01-01

167

Follicle-stimulating hormone enhances the proliferation of ovarian cancer cells by activating transient receptor potential channel C3  

PubMed Central

Recent studies have suggested that follicle-stimulating hormone (FSH) plays an important role in ovarian epithelial carcinogenesis. We demonstrated that FSH stimulates the proliferation and invasion of ovarian cancer cells, inhibits apoptosis, and facilitates neovascularisation. Our previous work has shown that transient receptor potential channel C3 (TRPC3) contributes to the progression of human ovarian cancer. In this study, we further investigated the interaction between FSH and TRPC3. We found that FSH stimulation enhanced the expression of TRPC3 at both the mRNA and protein levels. SiRNA-mediated silencing of TRPC3 expression inhibited the ability of FSH to stimulate proliferation and blocked apoptosis in ovarian cancer cell lines. FSH stimulation was associated with the upregulation of TRPC3, while also facilitating the influx of Ca2+ after treatment with a TRPC-specific agonist. Knockdown of TRPC3 abrogated FSH-stimulated Akt/PKB phosphorylation, leading to decreased expression of downstream effectors including survivin, HIF1? and VEGF. Ovarian cancer specimens were analysed for TRPC3 expression; higher TRPC3 expression levels correlated with early relapse and worse prognosis. Association with poor disease-free survival and overall survival remained after adjusting for clinical stage and grade. In conclusion, TRPC3 plays a significant role in the stimulating activity of FSH and could be a potential therapeutic target for the treatment of ovarian cancer, particularly in postmenopausal women with elevated FSH levels. PMID:23580589

Tao, Xiang; Zhao, Naiqing; Jin, Hongyan; Zhang, Zhenbo; Liu, Yintao; Wu, Jian; Bast, Robert C.; Yu, Yinhua; Feng, Youji

2013-01-01

168

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

NASA Astrophysics Data System (ADS)

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

An, Yonghao; Jiang, Hanqing

2013-10-01

169

The Effect of Multipole-Enhanced Diffusion on the Joule Heating of a Cold Non-Neutral Plasma  

E-print Network

One proposed technique for trapping anti-atoms is to superimpose a Ioffe-Pritchard style magnetic-minimum neutral trap on a standard Penning trap used to trap the charged atomic constituents. Adding a magnetic multipole field in this way removes the azimuthal symmetry of the ideal Penning trap and introduces a new avenue for radial diffusion. Enhanced diffusion will lead to increased Joule heating of a non-neutral plasma, potentially adversely affecting the formation rate of anti-atoms and increasing the required trap depth. We present a model of this effect, along with an approach to minimizing it, with comparison to measurements from an intended anti-atom trap.

Chapman, Steven Francis

170

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

171

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

172

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

173

Improving the prediction of stroke or death after transient ischemic attack (TIA) by adding diffusion-weighted imaging lesions and TIA etiology to the ABCD2 score.  

PubMed

The present study investigated the addition of transient ischemic attack (TIA) etiology and diffusion-weighted imaging (DWI) to the ABCD2 score, creating the ABCDE+ score, to improve the predictive ability of stroke risk or death at 6 months after TIA. We performed a cohort study of 150 consecutive patients with TIA. All patients underwent DWI and all had an etiologic workup and were followed up for 6 months. The area under the receiver operating characteristic curve (AUC) was used to compare the scores' ability to predict the outcome of stroke or death. Multivariate Cox regression analysis was performed to evaluate the association between the measured variables and subsequent stroke or death. Thirty patients (20%) experienced future stroke, and 12 patients (8%) died within the 6-month follow-up. A comparison of AUCs demonstrated the superiority of the ABCDE+ score over the ABCD2 score for predicting stroke (0.64 vs 0.60) and for predicting death (0.62 vs 0.56). ABCD2 score >4, ABCDE+ score >6, large-artery disease, and lesions detected on DWI were found to be independent predictors of future stroke, and ABCDE+ score >6, age, and heart disease were independent predictors of death. We conclude that incorporating DWI positivity and etiology of TIA into the ABCD2 score can improve the ability to predict stroke and death within 6 months after TIA. PMID:22609319

Arhami Dolatabadi, Ali; Meisami, Amirhosein; Hatamabadi, Hamidreza; Mansori, Behnam; Shahrami, Ali; Amini, Afshin; Jamali, Kazem

2013-10-01

174

DIFFUSION OF INNOVATION: ENHANCING THE DISSEMINATION OF THE PONSETI METHOD IN LATIN AMERICA THROUGH VIRTUAL FORUMS  

PubMed Central

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

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

2011-01-01

175

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

176

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

177

Comparison of Dynamic and Liver-Specific Gadoxetic Acid Contrast-Enhanced MRI versus Apparent Diffusion Coefficients  

PubMed Central

Background Hepatic lesions often present diagnostic connundrums with conventional MR techniques. Hepatobiliary phase contrast-enhanced imaging with gadoxetic acid can aid in the characterization of such lesions. However, quantitative measures describing late-phase enhancement must be assessed relative to their accuracy of hepatic lesion classification. Purpose: To compare quantitative parameters in gadoxetic acid contrast-enhanced dynamic and hepatobiliary phase imaging versus apparent diffusion coefficients in hepatic lesion characterization. Material and Methods 57 patients with focal hepatic lesions on gadoxetic acid MR were included. Lesion enhancement at standard post-contrast time points and in the hepatobiliary phase (HB; 15 and 25 minutes post-contrast) was assessed via calculation of contrast (CR) and enhancement ratios (ER). Apparent diffusion coefficient (ADC) values were also obtained. Values for these parameters were compared among lesions and ROC analyses performed. Results: HB enhancement was greatest with FNH and adenomas. HB ER parameters but not HB CR could distinguish HCC from benign entities (0.9 ER ROC AUC versus 0.5 CR ROC AUC). There was no statistically significant difference found between the 15 and 25 minutes HB time points in detection of any lesion (p>0.4). ADC values were statistically significantly higher with hemangiomas (p<0.05) without greater accuracy in lesion detection relative to HB phase parameters. Conclusion Hepatobiliary phase gadoxetic acid contrast-enhanced MR characterizes focal hepatic lesions more accurately than ADC and conventional dynamic post-contrast time point enhancement parameters. ER values are generally superior to CR. No discernible benefit of 25 minute versus 15 minute delayed imaging is demonstrated. PMID:23805174

Morelli, John N.; Michaely, Henrik J.; Meyer, Mathias M.; Rustemeyer, Thassilo; Schoenberg, Stefan O.; Attenberger, Ulrike I.

2013-01-01

178

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

PubMed

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

2014-07-15

179

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

180

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

181

Enhanced diffusion in conic channels by means of geometric stochastic resonance.  

PubMed

Geometric stochastic resonance of Brownian particles diffusing across a converging conic channel subject to oscillating forces is studied in this paper. Conic channel geometries have been previously considered as a model for transport of particles in biological membranes, zeolites, and nanostructures. For this system, a broad excess peak of the effective diffusion above the free diffusion limit is exhibited over a wide range of frequencies, suggesting a synchronization effect in the confining geometry as particles respond to the periodic modulation of the external force. This indicates that the geometric stochastic resonance effect with unbiased ac forces can be exploited for improving the transport of particles in complex geometries. PMID:22070287

Vazquez, M V; Valdes-Parada, F J; Dagdug, L; Alvarez-Ramirez, J

2011-11-01

182

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

PubMed Central

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

Zhang, L H; Kerr, A

1991-01-01

183

Improved Diagnostic Accuracy of Breast MRI through Combined Apparent Diffusion Coefficients and Dynamic Contrast-Enhanced Kinetics  

PubMed Central

This study investigated the relationship between apparent diffusion coefficient (ADC) measures and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) kinetics in breast lesions, and evaluated the relative diagnostic value of each quantitative parameter. Seventy-seven women with 100 breast lesions (27 malignant and 73 benign) underwent both DCE-MRI and diffusion weighted MRI (DWI). DCE-MRI kinetic parameters included peak initial enhancement, predominant delayed kinetic curve type (persistent, plateau or washout), and worst delayed kinetic curve type (washout>plateau>persistent). Associations between ADC and DCE-MRI kinetic parameters and predictions of malignancy were evaluated. Results showed that ADC was significantly associated with predominant curve type (ADC was higher for lesions exhibiting predominantly persistent enhancement compared to those exhibiting predominantly washout or plateau, p=0.006), but was not significantly associated with peak initial enhancement or worst curve type (p>0.05). Univariate analysis showed significant differences between benign and malignant lesions in both ADC (p<0.001) and worst curve (p =0.003). In multivariate analysis, worst curve type and ADC were significant independent predictors of benign versus malignant outcome and in combination produced the highest area under the ROC curve (AUC = 0.85, AUC=0.78 with 5-fold cross-validation). PMID:21254208

Partridge, SC; Rahbar, H; Murthy, R; Chai, X; Kurland, BF; DeMartini, WB; Lehman, CD

2011-01-01

184

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

PubMed

This paper reports results from the first biological crystal-growth experiment on the International Space Station (ISS). Crystals of thaumatin were grown using liquid-liquid diffusion in Tygon tubing transported in the Enhanced Gaseous Nitrogen Dewar (EGN). Different volume ratios and concentrations of protein and precipitant were used to test different adaptations of the vapor-diffusion crystallization recipe to the liquid-liquid diffusion method. The EGN warmed up from 77 to 273 K in about 4 d, about the same time it took to warm from 273 to 293 K. The temperature within the EGN was 293-297 K for the majority of the experiment. Air gaps that blocked liquid-liquid diffusion formed in the tubes. Nonetheless, crystals were grown. Synchrotron diffraction data collected from the best space-grown crystal extended to 1.28 A, comparable to previous studies of space-grown thaumatin crystals. The resolution of the best ground-control crystal was only 1.47 A. It is not clear if the difference in diffraction limit arises from factors other than crystal size. Improvements in temperature control and the elimination of air gaps are needed, but the results show that the EGN on the ISS can be used to produce space-grown crystals that diffract to high resolution. PMID:11976485

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

2002-05-01

185

Resolution enhancement of diffusion-weighted images by local fiber profiling.  

PubMed

Diffusion-weighted imaging (DWI), while giving rich information about brain circuitry, is often limited by insufficient spatial resolution and low signal-to-noise ratio (SNR). This paper describes an algorithm that will increase the resolution of DW images beyond the scan resolution, allowing for a closer investigation of fiber structures and more accurate assessment of brain connectivity. The algorithm is capable of generating a dense vector-valued field, consisting of diffusion data associated with the full set of diffusion-sensitizing gradients. The fundamental premise is that, to best preserve information, interpolation should always be performed along fiber streamlines. To achieve this, at each spatial location, we probe neighboring voxels in various directions to gather diffusion information for data reconstruction. Based on the fiber orientation distribution (FOD), directions that are more likely to be traversed by fibers will be given greater weights during interpolation and vice versa. This ensures that data reconstruction is only contributed by diffusion data coming from fibers that are aligned with a specific direction. This approach respects local fiber structures and prevents blurring resulting from averaging of data from significantly misaligned fibers. Evaluations suggest that this algorithm yields results with significantly less blocking artifacts, greater smoothness in anatomical structures, and markedly improved structural visibility. PMID:23286109

Yap, Pew-Thian; Shen, Dinggang

2012-01-01

186

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

187

Selective sharpness enhancement of corrupted old film sequences by coupled nonlinear reaction-diffusion time-evolution  

NASA Astrophysics Data System (ADS)

In old movie film, most of sharp brightness transitions have been blurred, and film materials are often corrupted by several distortions such as blotches. To restore original edge sharpness without augmenting visibility of such distortions, first we characterize such distortion areas, repair them and then sharpen only blurred edges selectively. This paper presents a locally-adaptive sharpening method based on the coupled nonlinear reaction-diffusion time-evolution equipped with a second-order nonlinear smoothing term, a reaction term and an overshooting term. The overshooting term adds an overshoot only to the blurred edges. The coupled nonlinear reaction-diffusion method utilizes information about local image contents and the characterized film distortions, to control the degree of the second-order smoothing and the magnitude of the overshoot to be added. Our method sharpens blurred edges selectively much better than our previously presented adaptive peaking method. Our method, of course, is applicable to sharpness enhancement of general blurred images.

Saito, Takahiro; Yashiro, Kentarou; Satsumabayashi, Jun; Komatsu, Takashi

2002-01-01

188

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

189

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

190

Bicarbonate and other buffer systems can enhance the rate of H+ diffusion through mucus in vitro.  

PubMed

The effect of various diffusible buffers on mucus H+ permeability, and in particular the potency of the HCO3-/CO2 buffer system relative to other selected buffers is reported here. The diffusional resistance of mucus and water was demonstrated to be dependent on buffer concentration, and the contrast between the two types of layer was most pronounced for low DH+ values near neutrality. This concentration dependence was most marked with mucus layers in the buffer systems investigated. Furthermore, the nature and pKa values of the diffusible buffer systems used in this study had a profound effect on measured DH+. The effect was particularly striking in the case of HCO3- buffer with mucus. Possible implications of these in vitro findings in mucosal protection from acid are discussed. PMID:1311604

Desai, M A; Vadgama, P M

1992-03-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

192

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

Microsoft Academic Search

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 by MRI. 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

Huiming Zhang; Yang Xie; Tongyu Ji

2007-01-01

193

Vapor diffusion in partially saturated packed beds  

SciTech Connect

The objective of this experimental and numerical study is to quantify the vapor diffusion enhancement factor resulting from pore-level evaporation/condensation in porous media subjected to a temperature gradient. In an earlier paper the enhancement factor {beta}, extracted from nonisothermal diffusion experiments, was shown to increase to approximately 1.0, which is equivalent to the free space diffusion coefficient, as average saturation in the packed bed increases from 0 to 0.2. The results of a drying experiment involving an initially partially saturated bed are presented in this paper. Numerical simulations of the nonisothermal diffusion and drying experiments using the TOUGH2 code were performed. The predicted vapor fluxes in both transient and quasi-steady simulations for the nonisothermal diffusion experiment are in good agreement with the experimental results when the experimentally determined enhancement factor is incorporated into the code. Simulated saturation profiles for drying are in qualitative agreement with experimental results. In both simulations the discrepancy between the predicted and observed saturation distributions may be the result of capillary hysteresis which is not included in the TOUGH2 code. Comparison between the experiments and simulations supports the existence of the enhanced vapor diffusion mechanism and indicates that the enhancement factor ranges from 0.3 to 1.0 depending on the moisture content.

Gu, L.; Ho, C.K.; Plumb, O.A.; Webb, S.W.

1999-07-01

194

Dynamics of Enhanced Tracer Diffusion in Suspensions of Swimming Eukaryotic Microorganisms  

NASA Astrophysics Data System (ADS)

In contexts such as suspension feeding in marine ecologies there is an interplay between Brownian motion of nonmotile particles and their advection by flows from swimming microorganisms. As a laboratory realization, we study passive tracers in suspensions of eukaryotic swimmers, the alga Chlamydomonas reinhardtii. While the cells behave ballistically over short intervals, the tracers behave diffusively, with a time-dependent but self-similar probability distribution function of displacements consisting of a Gaussian core and robust exponential tails. We emphasize the role of flagellar beating in creating oscillatory flows that exceed Brownian motion far from each swimmer.

Leptos, Kyriacos C.; Guasto, Jeffrey S.; Gollub, J. P.; Pesci, Adriana I.; Goldstein, Raymond E.

2009-11-01

195

Enhanced Carbon Diffusion in Austenitic Stainless Steel Carburized at Low Temperature  

Microsoft Academic Search

Austenitic stainless steel AISI 316L was carburized by a novel, low-temperature gas-phase process. Using a calibrated scanning\\u000a Auger microprobe (SAM) analysis of cross-sectional specimens under dynamic sputtering, we determined the fraction–depth profile\\u000a of carbon. The profile is concave—very different from the shape expected for concentration-independent diffusion—and indicates\\u000a a carbide-free solid solution with carbon levels up to 15 at. pct and

F. Ernst; A. Avishai; H. Kahn; X. Gu; G. M. Michal; A. H. Heuer

2009-01-01

196

Diffusion-weighted imaging in uterine artery embolisation: do findings correlate with contrast enhancement and volume reduction?  

PubMed Central

Objectives The objective of this study was to determine the role of diffusion-weighted imaging (DWI) in uterine artery embolisation (UAE), and to assess the apparent diffusion coefficient (ADC) of the dominant fibroid and its relationship to contrast enhancement and fibroid volume reduction. Methods We carried out a retrospective study of 15 patients who underwent UAE. Calculations were performed at baseline and 6 months post-embolisation. Fibroid ADC (expressed in 10?3 mm2 s?1) was calculated using b=0 and b=1000 DWI values. Fibroid enhancement was compared with background myometrium by measuring signal-difference-to-noise ratio (SDNR). Fibroid volume was calculated using a prolate ellipse formula. Results There was a significant reduction (p<0.001) in fibroid ADC at 6 months (0.48; standard deviation, SD=0.26) as compared with baseline (1.01; SD=0.39). No significant change (p=0.07) was identified in 6-month myometrial ADC (1.09; SD=0.28) as compared with baseline (1.24; SD=0.20). Moderately strong and significant positive correlation was identified between baseline ADC and 6-month percentage volume reduction of the fibroid (correlation=0.66, p=0.007). No correlation was identified between SDNR and ADC at baseline or 6 months (r=0.01, p=0.97 and r=?0.13, p=0.64, respectively) or SDNR and percentage volume reduction at 6 months (correlation r=0.18, p=0.51). Conclusion Baseline ADC of dominant fibroids shows a moderately strong correlation with subsequent volume reduction at 6 months following UAE. No correlation was identified between ADC values and contrast enhancement on the baseline or 6-month scans. Further prospective evaluation is needed before DWI can be utilised in clinical practice. Advances in knowledge DWI imaging may provide additional information about UAE and possibly help to predict uterine volume reduction. PMID:22898156

Ananthakrishnan, G; Macnaught, G; Hinksman, L; Gilmour, H; Forbes, K P; Moss, J G

2012-01-01

197

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

198

Enhanced Boiling Heat Transfer in Parallel Microchannels With Diffusion Brazed Wire Mesh  

Microsoft Academic Search

Flow boiling is an important process in energy conversion applications such as power generation and heating, ventilating, and air conditioning systems. Recently, it has drawn interest in the high heat flux electronics cooling community. Flow boiling enhancement, in addition, has the benefit of early onset of nucleate boiling, potentially lowering wall superheat, and increasing the heat transfer coefficient and critical

Hailei Wang; Richard B. Peterson

2010-01-01

199

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

200

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

NASA Astrophysics Data System (ADS)

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

Cooper, R. F.; McCarthy, C.

2012-12-01

201

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

NASA Astrophysics Data System (ADS)

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

Hirschfeld, J. A.; Lustfeld, H.

2014-01-01

202

Low energy ion bombardment enhanced diffusion, segregation, and phase transformations in Cu:In alloys  

Microsoft Academic Search

Scanning transmission electron microscopy and Auger electron spectroscopy were used to investigate the effects of low energy (200–3000 eV) Ar+ ion bombardment of supersaturated Cu: In alloys. Ion bombardment always resulted in the preferential sputtering of In although for sample temperatures T8 ? 250°C, In loss due to preferential sputtering was increasingly compensated by radiation enhanced surface segregation. Even at

L. Rivaud; A. H. Eltoukhy; J. E. Greene

1982-01-01

203

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

SciTech Connect

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

Tyrrell, R.M.

1984-02-01

204

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

205

Systematic Review of Associations Between the Presence of Acute Ischemic Lesions on Diffusion-Weighted Imaging and Clinical Predictors of Early Stroke Risk After Transient Ischemic Attack  

Microsoft Academic Search

Background and Purpose—Early risk of stroke after a transient ischemic attack can be reliably predicted with risk scores based on clinical features of the patient and of the ischemic event, but it is unclear how these features correlate with findings on brain imaging. Methods—We performed a systematic review of the literature and identified all previous studies which reported patient characteristics

Jessica N. E. Redgrave; Shelagh B. Coutts; Ursula G. Schulz; Dennis Briley; Peter M. Rothwell

2009-01-01

206

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

207

Sparsity enhanced spatial resolution and depth localization in diffuse optical tomography  

PubMed Central

Abstract: In diffuse optical tomography (DOT), researchers often face challenges to accurately recover the depth and size of the reconstructed objects. Recent development of the Depth Compensation Algorithm (DCA) solves the depth localization problem, but the reconstructed images commonly exhibit over-smoothed boundaries, leading to fuzzy images with low spatial resolution. While conventional DOT solves a linear inverse model by minimizing least squares errors using L2 norm regularization, L1 regularization promotes sparse solutions. The latter may be used to reduce the over-smoothing effect on reconstructed images. In this study, we combined DCA with L1 regularization, and also with L2 regularization, to examine which combined approach provided us with an improved spatial resolution and depth localization for DOT. Laboratory tissue phantoms were utilized for the measurement with a fiber-based and a camera-based DOT imaging system. The results from both systems showed that L1 regularization clearly outperformed L2 regularization in both spatial resolution and depth localization of DOT. An example of functional brain imaging taken from human in vivo measurements was further obtained to support the conclusion of the study. PMID:22567587

Kavuri, Venkaiah C.; Lin, Zi-Jing; Tian, Fenghua; Liu, Hanli

2012-01-01

208

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

Komaromy, Andras 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

209

NONLINEAR DIFFUSION Erkut Erdem  

E-print Network

NONLINEAR DIFFUSION Erkut Erdem Hacettepe University March 9th, 2013 CONTENTS 1 Perona-Malik Type Nonlinear Diffusion 1 2 Total Variation (TV) Regularization 5 3 Edge Enhancing Diffusion 8 References 11 1 PERONA-MALIK TYPE NONLINEAR DIFFUSION The main theory behind nonlinear diffusion models is to use

Erdem, Erkut

210

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

211

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

PubMed

?-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

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

2014-07-30

212

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

213

Diagnosis of Breast Masses from Dynamic Contrast-Enhanced and Diffusion-Weighted MR: A Machine Learning Approach  

PubMed Central

Purpose Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is increasingly used for breast cancer diagnosis as supplementary to conventional imaging techniques. Combining of diffusion-weighted imaging (DWI) of morphology and kinetic features from DCE-MRI to improve the discrimination power of malignant from benign breast masses is rarely reported. Materials and Methods The study comprised of 234 female patients with 85 benign and 149 malignant lesions. Four distinct groups of features, coupling with pathological tests, were estimated to comprehensively characterize the pictorial properties of each lesion, which was obtained by a semi-automated segmentation method. Classical machine learning scheme including feature subset selection and various classification schemes were employed to build prognostic model, which served as a foundation for evaluating the combined effects of the multi-sided features for predicting of the types of lesions. Various measurements including cross validation and receiver operating characteristics were used to quantify the diagnostic performances of each feature as well as their combination. Results Seven features were all found to be statistically different between the malignant and the benign groups and their combination has achieved the highest classification accuracy. The seven features include one pathological variable of age, one morphological variable of slope, three texture features of entropy, inverse difference and information correlation, one kinetic feature of SER and one DWI feature of apparent diffusion coefficient (ADC). Together with the selected diagnostic features, various classical classification schemes were used to test their discrimination power through cross validation scheme. The averaged measurements of sensitivity, specificity, AUC and accuracy are 0.85, 0.89, 90.9% and 0.93, respectively. Conclusion Multi-sided variables which characterize the morphological, kinetic, pathological properties and DWI measurement of ADC can dramatically improve the discriminatory power of breast lesions. PMID:24498092

Chen, Minsheng; Li, Li

2014-01-01

214

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

215

Transient, sparsely populated compact states of apo and calcium-loaded calmodulin probed by paramagnetic relaxation enhancement: interplay of conformational selection and induced fit.  

PubMed

Calmodulin (CaM) is the universal calcium sensor in eukaryotes, regulating the function of numerous proteins. Crystallography and NMR show that free CaM-4Ca(2+) exists in an extended conformation with significant interdomain separation, but clamps down upon target peptides to form a highly compact structure. NMR has revealed substantial interdomain motions in CaM-4Ca(2+), enabled by a flexible linker. In one instance, CaM-4Ca(2+) has been crystallized in a compact configuration; however, no direct evidence for transient interdomain contacts has been observed in solution, and little is known about how large-scale interdomain motions contribute to biological function. Here, we use paramagnetic relaxation enhancement (PRE) to characterize transient compact states of free CaM that are too sparsely populated to observe by traditional NMR methods. We show that unbound CaM samples a range of compact structures, populated at 5-10%, and that Ca(2+) dramatically alters the distribution of these configurations in favor of states resembling the peptide-bound structure. In the absence of Ca(2+), the target peptide binds only to the C-terminal domain, and the distribution of compact states is similar with and without peptide. These data suggest an alternative pathway of CaM action in which CaM remains associated with its kinase targets even in the resting state. Only CaM-4Ca(2+), however, shows an innate propensity to form the physiologically active compact structures, suggesting that Ca(2+) activates CaM not only through local structural changes within each domain but also through more global remodeling of interdomain interactions. Thus, these findings illustrate the subtle interplay between conformational selection and induced fit. PMID:21999431

Anthis, Nicholas J; Doucleff, Michaeleen; Clore, G Marius

2011-11-23

216

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

E-print Network

Poly(vinylidene fluoride-co-hexafluoropropylene) phase inversion coating as a diffusion layer(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) phase inversion coating was developed as a cathode diffusion

217

Vaccination with a T-cell-priming Gag peptide of caprine arthritis encephalitis virus enhances virus replication transiently in vivo.  

PubMed

CD4+ T cells are involved in several immune response pathways used to control viral infections. In this study, a group of genetically defined goats was immunized with a synthetic peptide known to encompass an immunodominant helper T-cell epitope of caprine arthritis encephalitis virus (CAEV). Fifty-five days after challenge with the molecularly cloned CAEV strain CO, the vaccinated animals had a higher proviral load than the controls. The measurement of gamma interferon and interleukin-4 gene expression showed that these cytokines were reliable markers of an ongoing immune response but their balance did not account for more or less efficient control of CAEV replication. In contrast, granulocyte-macrophage colony-stimulating factor appeared to be a key cytokine that might support virus replication in the early phase of infection. The observation of a potential T-cell-mediated enhancement of virus replication supports other recent findings showing that lentivirus-specific T cells can be detrimental to the host, suggesting caution in designing vaccine candidates. PMID:17412991

Nenci, Chiara; Zahno, Marie-Luise; Vogt, Hans-Rudolf; Obexer-Ruff, Gabriela; Doherr, Marcus G; Zanoni, Reto; Peterhans, Ernst; Bertoni, Giuseppe

2007-05-01

218

Combined prostate Diffusion Tensor Imaging and Dynamic Contrast Enhanced MRI at 3T - quantitative correlation with biopsy  

PubMed Central

The purpose of this work was to compare diagnostic accuracy of Diffusion Tensor Imaging (DTI), Dynamic Contrast Enhanced MRI (DCE MRI), and their combination in diagnosing prostate cancer. Twenty five patients with clinical suspicion of prostate cancer underwent MRI, prior to transrectal ultrasound (TRUS)-guided biopsies. MRI data were correlated to biopsy results. Logistic regression models were constructed for the DTI parameters, DCE MRI parameters, and their combination. The areas under the Receiver Operator Characteristic curves (AUC) were compared between the models. The nonparametric Wilcoxon signed rank test was used for statistical analysis. The sensitivity and specificity values were respectively 81% (74% – 87%) and 85% (79% – 90%) for DTI and 63% (55% – 70%) and 90% (85% – 94%) for DCE. The combination “DTI or DCE MRI” had 100% (97% – 100%) sensitivity and 77% (69% – 83%) specificity, while “DTI and DCE MRI” had 44% (37% – 52%) sensitivity and 98% (94% – 100%) specificity. The AUC for DTI + DCE parameters was significantly higher than that for either DTI (0.96 vs. 0.92, p = 0.0143) or DCE MRI parameters (0.96 vs. 0.87, p = 0.00187) alone. In conclusion, the combination of DTI and DCE MRI has significantly better accuracy in prostate cancer diagnosis than either technique alone. PMID:20392586

Kozlowski, Piotr; Chang, Silvia D.; Meng, Ran; Madler, Burkhard; Bell, Robert; Jones, Edward C.; Goldenberg, S. Larry

2010-01-01

219

Enhanced dissolution rate of felodipine using spherical agglomeration with Inutec SP1 by quasi emulsion solvent diffusion method.  

PubMed

Felodipine is a second generation calcium channel blocker widely used as antihypertensive and antianginal drug which belongs to BCS class II category. Hence, its low water solubility limits the pharmacological effect. The aim of this study was to improve the dissolution rate of felodipine using spherical agglomeration technique with acetone, water and dichloromethane as good solvent, poor solvent and bridging liquid, respectively. The quasi emulsion solvent diffusion technique was used as a method for spherical agglomeration. Inutec SP1 was used as an emulsion stabilizer and as hydrophilic polymer in agglomeration process. The FTIR and DSC results showed no change in the drug after crystallization process. PXRD studies showed sharp peaks in the diffractograms of spherical agglomerates with minor reduction in height of the peaks. The particle size of spherical agglomerates (FI-2) was about 134.33 ± 13.57 µm, n=3 and the dissolution efficiency of felodipine up to 120 min increased to about 4-fold in phosphate buffer containing 1.8% Tween 80 (pH 6.8). Spherical agglomerates showed enhanced solubility compared to untreated powder possibly due to the partial conversion to amorphous form. PMID:21589802

Tapas, A R; Kawtikwar, P S; Sakarkar, D M

2009-07-01

220

Sensitive analysis of aminoglycoside antibiotics via hyphenation of transient moving substitution boundary with field-enhanced sample injection in capillary electrophoresis.  

PubMed

A novel field-enhanced sample injection coupled with transient moving substitution boundary method in capillary electrophoresis was developed for aminoglycoside antibiotic (AG) analysis using 18-crown-6-tetracarboxylic acid (18C6H4) as a pseudostationary phase. Results indicated that the stacking mechanism of moving substitution boundary relied on the substitution reaction between 18C6H4-bonded AG complexes and Na(+) at the substitution boundary. The stacking mechanism as well as important parameters governing pre-concentration and separation have been investigated in order to obtain maximum resolution and sensitivity. Under optimized conditions, using a sample prepared in a low-conductivity matrix, the limits of detection for streptomycin, neomycin, and kanamycin were 0.62, 5.9 and 8.6 nM (S/N=3), respectively, and the detection sensitivities were improved 940-, 692-, and 415-fold, respectively. The method also gave accurate and reliable results in the analysis of AGs in river water samples. PMID:23669327

Ge, Shuli; Tang, Wanrong; Han, Ruobing; Zhu, Yan; Wang, Qingjiang; He, Pingang; Fang, Yuzhi

2013-06-21

221

Robust TaN{sub x} diffusion barrier for Cu-interconnect technology with subnanometer thickness by metal-organic plasma-enhanced atomic layer deposition  

SciTech Connect

TaN{sub x} diffusion barriers with good barrier properties at subnanometer thickness were deposited by plasma-enhanced atomic layer deposition (PE-ALD) from pentakis(dimethylamino)Ta. Hydrogen and/or nitrogen plasma was used as reactants to produce TaN{sub x} thin films with a different nitrogen content. The film properties including the carbon and oxygen impurity content were affected by the nitrogen flow during the process. The deposited film has nanocrystalline grains with hydrogen-only plasma, while the amorphous structure was obtained for nitrogen plasma. The diffusion barrier properties of deposited TaN films for Cu interconnects have been studied by thermal stress test based on synchrotron x-ray diffraction. The results indicate that the PE-ALD TaN films are good diffusion barriers even at a small thickness as 0.6 nm. Better diffusion barrier properties were obtained for higher nitrogen content. Based on a diffusion kinetics analysis, the nanocrystalline microstructure of the films was responsible for the better diffusion barrier properties compared to polycrystalline PE-ALD TaN films deposited from TaCl{sub 5}.

Kim, H.; Detavenier, C.; Straten, O. van der; Rossnagel, S.M.; Kellock, A.J.; Park, D.-G. [Department of Materials Science and Technology, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); International Business Machines Corporation (IBM) T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); International Business Machines Corporation (IBM) Almaden Research Center, San Jose, California 95120 (United States); International Business Machines Corporation (IBM) Microelectronics Division Hopewell Junction, New York 12533 (United States)

2005-07-01

222

Quantification of fibrosis in infarcted swine hearts by ex vivo late gadolinium-enhancement and diffusion-weighted MRI methods.  

PubMed

Many have speculated that MRI signal characteristics can be used to identify regions of heterogeneous infarct associated with an arrhythmogenic substrate; however, direct evidence of this relationship is limited. The aim of this study was to demonstrate the remodelling characteristics of fibrosis by means of histology and high-resolution MR imaging. For this purpose, we performed whole-mount histology in heart samples (n = 9) collected from five swine at six weeks post-infarction and compared the extent of fibrosis in the infarcted areas delineated in these histological images with that obtained ex vivo by MRI using late gadolinium-enhancement (LGE) and diffusion-weighted imaging (DWI) methods. All MR images were obtained at a submillimetre resolution (i.e., voxel size of 0.6×0.6×1.2 mm(3)). Specifically, in the histology images, we differentiated moderate fibrosis (consisting of a mixture of viable and non-viable myocytes, known as border zone, BZ) from severe fibrosis (i.e., the dense scar). Correspondingly, tissue heterogeneities in the MR images were categorized by a Gaussian mixture model into healthy, BZ and scar. Our results showed that (a) both MRI methods were capable of qualitatively distinguishing sharp edges between dense scar and healthy tissue from regions of heterogeneous BZ; (b) the BZ and dense scar areas had intermediate-to-high increased values of signal intensity in the LGE images and of apparent diffusion coefficient in the DWI, respectively. In addition, as demonstrated by the Picrosirius Red and immunohistochemistry stains, the viable bundles in the BZ were clearly separated by thin collagen strands and had reduced expression of Cx43, whereas the core scar was composed of dense fibrosis. A quantitative analysis demonstrated that the comparison between BZ/scar extent in LGE and DWI to the corresponding areas identified in histology yielded very good correlations (i.e., for the scar identified by LGE, R(2) was 0.96 compared to R(2) = 0.93 for the scar identified in ADC maps, whereas the BZ had R(2) = 0.95 for the correlation between LGE and histology compared to R(2) = 0.91 obtained for ADC). This novel study represents an intermediate step in translating such research to the in vivo stages, as well as in establishing the best and most accurate MR method to help identify arrhythmia substrate in patients with structural heart disease. PMID:23833042

Pop, Mihaela; Ghugre, Nilesh R; Ramanan, Venkat; Morikawa, Lily; Stanisz, Greg; Dick, Alexander J; Wright, Graham A

2013-08-01

223

Quantification of fibrosis in infarcted swine hearts by ex vivo late gadolinium-enhancement and diffusion-weighted MRI methods  

NASA Astrophysics Data System (ADS)

Many have speculated that MRI signal characteristics can be used to identify regions of heterogeneous infarct associated with an arrhythmogenic substrate; however, direct evidence of this relationship is limited. The aim of this study was to demonstrate the remodelling characteristics of fibrosis by means of histology and high-resolution MR imaging. For this purpose, we performed whole-mount histology in heart samples (n = 9) collected from five swine at six weeks post-infarction and compared the extent of fibrosis in the infarcted areas delineated in these histological images with that obtained ex vivo by MRI using late gadolinium-enhancement (LGE) and diffusion-weighted imaging (DWI) methods. All MR images were obtained at a submillimetre resolution (i.e., voxel size of 0.6×0.6×1.2 mm3). Specifically, in the histology images, we differentiated moderate fibrosis (consisting of a mixture of viable and non-viable myocytes, known as border zone, BZ) from severe fibrosis (i.e., the dense scar). Correspondingly, tissue heterogeneities in the MR images were categorized by a Gaussian mixture model into healthy, BZ and scar. Our results showed that (a) both MRI methods were capable of qualitatively distinguishing sharp edges between dense scar and healthy tissue from regions of heterogeneous BZ; (b) the BZ and dense scar areas had intermediate-to-high increased values of signal intensity in the LGE images and of apparent diffusion coefficient in the DWI, respectively. In addition, as demonstrated by the Picrosirius Red and immunohistochemistry stains, the viable bundles in the BZ were clearly separated by thin collagen strands and had reduced expression of Cx43, whereas the core scar was composed of dense fibrosis. A quantitative analysis demonstrated that the comparison between BZ/scar extent in LGE and DWI to the corresponding areas identified in histology yielded very good correlations (i.e., for the scar identified by LGE, R2 was 0.96 compared to R2 = 0.93 for the scar identified in ADC maps, whereas the BZ had R2 = 0.95 for the correlation between LGE and histology compared to R2 = 0.91 obtained for ADC). This novel study represents an intermediate step in translating such research to the in vivo stages, as well as in establishing the best and most accurate MR method to help identify arrhythmia substrate in patients with structural heart disease.

Pop, Mihaela; Ghugre, Nilesh R.; Ramanan, Venkat; Morikawa, Lily; Stanisz, Greg; Dick, Alexander J.; Wright, Graham A.

2013-08-01

224

Sensitivity of Climate Change on Diapycnal Diffusion in Global Warming Experiments  

Microsoft Academic Search

This study seeks understanding of the role played by the diapycnal diffusivity in determining the transient climate evolution in a scenario with enhanced atmospheric CO2 concentration. We use an Earth system Model of Intermediate Complexity (EMIC) composed of a 3D Ocean Model with idealized topography and a 2D Atmospheric Model. The model is spun up to equilibrium for three different

F. Dalan; P. H. Stone; A. Sokolov

2002-01-01

225

Preoperative diagnosis and staging of rectal cancer using diffusion-weighted and water imaging combined with dynamic contrast-enhanced scanning  

PubMed Central

The aim of the present study was to evaluate the value of diffusion-weighted imaging (DWI) and water imaging combined with dynamic contrast-enhanced scanning for the preoperative diagnosis and staging of rectal cancer. In total, 72 patients with pathologically confirmed rectal cancer were selected for examination using magnetic resonance imaging (MRI) with phased-array coils, DWI, water imaging and dynamic contrast-enhanced scanning. The patients were divided into two groups, experimental (simple enhanced scanning plus diffusion combined with water imaging) and control (simple enhanced scanning), for the pathological observations. The sensitivity, specificity and accuracy for the T staging of the carcinomas using scan enhancement with DWI and the evaluation of cancer using water imaging were 98.5% (65/66), 66.7% (4/6) and 95.8% (69/72), respectively, and the accuracy for N staging was 89%. Whereas, the sensitivity, specificity and accuracy for the T staging of the carcinomas using simple scan enhancement were 85.7% (42/49), 78.3% (18/23) and 83.3% (60/72), respectively, and the accuracy for N staging was 61%. Therefore, the combination of multiple MRI techniques may be of high value for the early diagnosis and exact staging of rectal cancer. PMID:25360178

ZHAO, QILI; LIU, LIJIAN; WANG, QIUYAN; LIANG, ZEXIA; SHI, GAOFENG

2014-01-01

226

Theoretical model and computer simulation results of enhanced diffusion of high-temperature implanted aluminum in silicon carbide  

NASA Astrophysics Data System (ADS)

The wide-spread use of silicon carbide (SiC) films in the production of microelectronic devices make predictions of the doping profiles during and/or after thermal treatment especially important. A macroscopic kinetic model of enhanced diffusion of aluminum in SiC films during ion bombardment at high temperatures has been considered. The set of equations describing the kinetic model takes into account the generation of VC and VSi vacancies during bombardment, migration of mobile species (Aluminum) towards the surface and reactions of Al atoms with VC and VSi vacancies, as well as Al evolution from the film. Numerical simulation of the equations have been carried out to obtain the concentration profile of Al implanted into SiC, the special distribution of immobile Al atoms substituting Si and C sites in SiC lattice, mobile Al atoms, and the number of Al atoms which leave the film. The calculations were carried out for the flux of Al ions with the energy of 40 keV and current density 20 ?A/cm 2 to a dose 2×10 16 cm-2 at 1800°C. The calculations have shown that the Al content in SiC at these conditions does not exceed 40%. The calculated profile of Al is in good agreement with the experimental data (A.V. Suvorov, I.O. Usov, V.V. Sokolov, A.A. Suvorova, in: D.B. Poker, D. Ila, Y.-S. Cheng, L.R. Harriot, T.W. Sigmon (Eds.), Ion-Solid Interaction for Materials Modification and Processing, PA, 1996, pp. 239-242).

Gadiyak, G. V.

1998-07-01

227

Transient performance  

NASA Astrophysics Data System (ADS)

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

Curnock, Barry

228

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

229

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

2014-10-01

230

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

231

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

232

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

PubMed

Periodic variation of the distance between two weakly adhering bodies gives rise to a huge tangential motions of the sandwiched solvent layer (squeezing flow). Oscillations either can be induced by an external applied field or can spontaneously arise from the coupling with the solvent heat bath. First we calculated by the Navier-Stokes equation the components of the fluid velocity near two oscillating juxtaposed plates. Then we evaluated the influence of plate oscillations on the transport properties of a trace diffusant dissolved at t = 0 in the outer medium for both deterministic and stochastic excitations. By employing both analytical (Fokker-Planck) and coarse-grained molecular dynamics (MD) simulations, we proved that the entry and migration rates of the diffusant sharply increases with the oscillation amplitudes. Enhancement was related to relevant parameters like oscillation frequency, fluid layer thickness, fluid viscosity, and temperature. An extension to the case of oscillating multistacked lamellae has been also made. Theoretical and MD results suggest a significant enhancement of the diffusant flux even in the worse situation of thermally excited small amplitude fluctuations. Excitation arising from other sources (e.g., microwave or ultrasound irradiation of solid-fluid layered systems) could have a dramatic effect on the transport phenomena. Possible implications to relevant biological problems have been discussed. PMID:24992344

Pannuzzo, Martina; Grassi, Antonio; Raudino, Antonio

2014-07-24

233

NONLINEAR DIFFUSION PDES Erkut Erdem  

E-print Network

NONLINEAR DIFFUSION PDES Erkut Erdem Hacettepe University March 5th, 2012 CONTENTS 1 Perona-Malik Type Nonlinear Diffusion 1 2 Edge Enhancing Diffusion 5 References 7 1 PERONA-MALIK TYPE NONLINEAR DIFFUSION The main theory behind nonlinear diffusion models is to use nonlinear PDEs to create a scale space

Erdem, Erkut

234

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

235

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

236

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

237

Investigation of starting transients in the thermally choked ram accelerator  

NASA Technical Reports Server (NTRS)

An experimental investigation of the starting transients of the thermally choked ram accelerator is presented in this paper. Construction of a highly instrumented tube section and instrumentation inserts provide high resolution experimental pressure, luminosity, and electromagnetic data of the starting transients. Data obtained prior to and following the entrance diaphragm show detailed development of shock systems in both combustible and inert mixtures. With an evacuated launch tube, starting the diffuser is possible at any Mach number above the Kantrowitz Mach number. The detrimental effects and possible solutions of higher launch tube pressures and excessive obturator leakage (blow-by) are discussed. Ignition of a combustible mixture is demonstrated with both perforated and solid obturators. The relative advantages and disadvantages of each are discussed. Data obtained from these starting experiments enhance the understanding of the ram accelerator, as well as assist in the validation of unsteady, chemically reacting CFD codes.

Burnham, E. A.; Hinkey, J. B.; Bruckner, A. P.

1992-01-01

238

Investigation of starting transients in the thermally choked ram accelerator  

NASA Astrophysics Data System (ADS)

An experimental investigation of the starting transients of the thermally choked ram accelerator is presented in this paper. Construction of a highly instrumented tube section and instrumentation inserts provide high resolution experimental pressure, luminosity, and electromagnetic data of the starting transients. Data obtained prior to and following the entrance diaphragm show detailed development of shock systems in both combustible and inert mixtures. With an evacuated launch tube, starting the diffuser is possible at any Mach number above the Kantrowitz Mach number. The detrimental effects and possible solutions of higher launch tube pressures and excessive obturator leakage (blow-by) are discussed. Ignition of a combustible mixture is demonstrated with both perforated and solid obturators. The relative advantages and disadvantages of each are discussed. Data obtained from these starting experiments enhance the understanding of the ram accelerator, as well as assist in the validation of unsteady, chemically reacting CFD codes.

Burnham, E. A.; Hinkey, J. B.; Bruckner, A. P.

1992-10-01

239

Aggressive Angiomyxoma with Diffusion-Weighted Magnetic Resonance Imaging and Dynamic Contrast Enhancement: A Case Report and Review of the Literature  

PubMed Central

Introduction Aggressive angiomyxoma (AA) is a rare benign soft tissue tumour usually affecting the pelvis and perineum of young women. Magnetic resonance imaging (MRI) is crucial in the management of AA patients for its diagnostic contribution and for the preoperative assessment of the actual tumour extension. Given the current development of less aggressive therapeutics associated with a higher risk of recurrence, close follow-up with MRI is fundamental after treatment. In this context, diffusion-weighted (DW) imaging has already shown high efficacy in the detection of early small relapses in prostate or rectal cancer. Case Report We report here a case of pelvic AA in a 51-year-old woman examined with dynamic contrast enhancement and DW-MRI, including apparent diffusion coefficient mapping and calculation. Conclusion To our knowledge, this is the first description of DW-MRI in AA reported in the literature. Here, knowledge about imaging features of AA will be reviewed and expanded. PMID:23904848

Brunelle, S.; Bertucci, F.; Chetaille, B.; Lelong, B.; Piana, G.; Sarran, A.

2013-01-01

240

Chandra TOOs for Fermi Galactic Plane Transients  

NASA Astrophysics Data System (ADS)

Fermi detected hundreds of transients with short (sec to hr) and long (months) variability timescales. However, so far no systematic search of transients on weekly timescales has been performed. The Fermi All-sky Variability Analysis (FAVA) allows us to systematically search all-sky for weekly transients. The novelty of FAVA resides in using the mission-long data to provide an estimate of the average sky intensity against which weekly data are compared. This makes FAVA an unbiased and fast tool to find transients in the Galactic plane where the diffuse emission is the brightest. FAVA detects 1 plane transient every 8 weeks. We propose to use Chandra to follow up on 2 new transients. The population of Galactic transients is under-sampled and detecting even 1 source will have a large impact

Ajello, Marco

2014-09-01

241

Diffusion Geometry Diffusion Geometry  

E-print Network

Diffusion Geometry Diffusion Geometry for High Dimensional Data Matthew J. Hirn July 3, 2013 #12;Diffusion Geometry Introduction Embedding of closed curve Figure: Left: A closed, non-self-intersecting curve in 3 dimensions. Right: Its embedding as a circle. #12;Diffusion Geometry Introduction Cartoon

Hirn, Matthew

242

Short-term changes in Jupiter's synchrotron radiation at 325 MHz: Enhanced radial diffusion in Jupiter's radiation belt driven by solar UV/EUV heating  

NASA Astrophysics Data System (ADS)

The total flux density of Jupiter's synchrotron radiation (JSR) at 325 MHz was observed in 2007 with the Iitate Planetary Radio Telescope to investigate short-term variations in Jupiter's radiation belt with a time scale of a few days to a month. The total flux density showed a series of short-term increases and subsequent decreases. The variations in JSR and the Mg II solar UV/EUV index showed positive correlations, but the variations in JSR were preceded by those of the Mg II index by 3-5 days. The positive correlation supports a theoretical prediction that an enhancement in the radial diffusion driven by thermospheric winds in the upper atmosphere causes changes in relativistic electron distributions in both the radiation belt and the total flux density of JSR. The radial diffusion model was used to examine the hypothesis that temporal changes in the radial diffusion rate could be an origin of the short-term variation. The model includes physical processes such as radial diffusion, energy degradation by the synchrotron radiation, and several loss processes. We applied a radial diffusion coefficient of 3 × 10-8 L3/s and found a suitable solution that accounted for both the time scale of the short-term variations and the 4 day time lag. The model also showed that strong electron loss processes other than the synchrotron radiation are needed to explain the electron distribution in low L regions. An empirical electron distribution model showed that the synchrotron radiation does not act as a loss of electrons in such areas.

Tsuchiya, F.; Misawa, H.; Imai, K.; Morioka, A.

2011-09-01

243

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

244

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

245

Early annihilation and diffuse backgrounds in models of weakly interacting massive particles in which the cross section for pair annihilation is enhanced by 1/upsilon.  

PubMed

Recent studies have considered modifications to the standard weakly interacting massive particle scenario in which the pair annihilation cross section (times relative velocity v) is enhanced by a factor 1/upsilon to approximately 10(-3) in the Galaxy, enough to explain several puzzling Galactic radiation signals. We show that in these scenarios a burst of weakly interacting massive particle annihilation occurs in the first collapsed dark-matter halos. We show that severe constraints to the annihilation cross section derive from measurements of the diffuse extragalactic radiation and from ionization and heating of the intergalactic medium. PMID:19437633

Kamionkowski, Marc; Profumo, Stefano

2008-12-31

246

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

247

Magnetic Field Diffusion and Enhanced Resistivity in 12-cm-Diameter 200-ns 3.5MA Pinch Implosions  

Microsoft Academic Search

Investigations of magnetic field diffusion and plasma resistivity in 12-cm-diameter triple-gas-puff Ar Z-pinch implosions were carried out by using planar laser-induced fluorescence (PLIF), a laser shearing interferometer (LSI), and a laser wavefront analyzer (LWA) on a 3.5-MA 200-ns generator. The PLIF measurements gave the initial Ar gas distributions. The implosion velocity and electron density profiles were measured from LWA and\\/or

Niansheng Qi; B. H. Failor; J. S. Levine; J. Goyer; H. Sze; A. Verma

2010-01-01

248

Dopamine enhances a voltage-dependent transient K+ current in the MMQ cell, a clonal pituitary line expressing functional D2 dopamine receptors.  

PubMed

The influence of dopamine on voltage-dependent K+ current (IK) was studied in cultured MMQ cells using the whole-cell patch-clamp technique. IK in nearly all MMQ cells revealed a transient outward current component and inactivated during maintained depolarization lasting 60 ms. The transient component was inhibited by prepulse potentials more positive than -40 mV or by addition of 4 mM 4-aminopyridine to the bathing solution and was insensitive to the external Ca2+ concentration. Thus, this transient K+ current resembled the A-current (IA) found in other cells. Dopamine at 1 microM increased by 50% (P less than 0.001) the peak of IK evoked by a test potential to +80 mV and the response was prevented by pretreatment with 100 nM haloperidol, a D2 receptor antagonist. These data suggest that MMQ clonal pituitary cells possess a voltage-gated K+ A-current and that this current can be modulated by dopamine via D2 receptors. PMID:2137361

Login, I S; Pancrazio, J J; Kim, Y I

1990-01-01

249

Compressive Diffusion Strategies Over Distributed Networks for Reduced Communication Load  

NASA Astrophysics Data System (ADS)

We study the compressive diffusion strategies over distributed networks based on the diffusion implementation and adaptive extraction of the information from the compressed diffusion data. We demonstrate that one can achieve a comparable performance with the full information exchange configurations, even if the diffused information is compressed into a scalar or a single bit. To this end, we provide a complete performance analysis for the compressive diffusion strategies. We analyze the transient, steady-state and tracking performance of the configurations in which the diffused data is compressed into a scalar or a single-bit. We propose a new adaptive combination method improving the convergence performance of the compressive diffusion strategies further. In the new method, we introduce one more freedom-of-dimension in the combination matrix and adapt it by using the conventional mixture approach in order to enhance the convergence performance for any possible combination rule used for the full diffusion configuration. We demonstrate that our theoretical analysis closely follow the ensemble averaged results in our simulations. We provide numerical examples showing the improved convergence performance with the new adaptive combination method.

Sayin, Muhammed O.; Kozat, Suleyman S.

2014-10-01

250

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

251

Microgravity Turbulent Gas-Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

A gas-jet diffusion flame is similar to the flame on a Bunsen burner, where a gaseous fuel (e.g., propane) flows from a nozzle into an oxygen-containing atmosphere (e.g., air). The difference is that a Bunsen burner allows for (partial) premixing of the fuel and the air, whereas a diffusion flame is not premixed and gets its oxygen (principally) by diffusion from the atmosphere around the flame. Simple gas-jet diffusion flames are often used for combustion studies because they embody the mechanisms operating in accidental fires and in practical combustion systems. However, most practical combustion is turbulent (i.e., with random flow vortices), which enhances the fuel/air mixing. These turbulent flames are not well understood because their random and transient nature complicates analysis. Normal gravity studies of turbulence in gas-jet diffusion flames can be impeded by buoyancy-induced instabilities. These gravitycaused instabilities, which are evident in the flickering of a candle flame in normal gravity, interfere with the study of turbulent gas-jet diffusion flames. By conducting experiments in microgravity, where buoyant instabilities are avoided, we at the NASA Lewis Research Center hope to improve our understanding of turbulent combustion. Ultimately, this could lead to improvements in combustor design, yielding higher efficiency and lower pollutant emissions. Gas-jet diffusion flames are often researched as model flames, because they embody mechanisms operating in both accidental fires and practical combustion systems (see the first figure). In normal gravity laboratory research, buoyant air flows, which are often negligible in practical situations, dominate the heat and mass transfer processes. Microgravity research studies, however, are not constrained by buoyant air flows, and new, unique information on the behavior of gas-jet diffusion flames has been obtained.

1996-01-01

252

REDUCED CHEMISTRY-DIFFUSION COUPLING  

Microsoft Academic Search

In reacting flow problems involving large numbers of chemical species and reactions, reduced chemistry modeling is used to approximately describe, with fewer unknowns, the slow chemical evolutions after the rapid but brief initial transients have decayed. Diffusion transport terms, if present, are modified by the reduced chemistry approximations. This article reiterates that the use of unmodified diffusion terms along with

S. H. LAM

2007-01-01

253

Anomalous diffusion of a polymer chain in an unentangled melt  

NASA Astrophysics Data System (ADS)

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

Farago, Jean; Meyer, Hendrik; Semenov, Alexander

2012-02-01

254

Enhanced yellow fluorescent protein photoconversion to a cyan fluorescent protein-like species is sensitive to thermal and diffusion conditions  

Microsoft Academic Search

Ongoing research efforts into fluorescent proteins continuously generates new mutation variants, some of which can become photoactivated or photoconverted to a red-shifted color upon intense UV or blue light illumination. We report a built-in propensity for enhanced yellow fluorescent protein (EYFP) to undergo irreversible photoconversion into a cyan fluorescent protein (CFP)-like species upon green-light illumination. The photoconversion is thermally activated,

Merete K. Raarup; Anja W. Fjorback; Stig M. R. Jensen; Heidi K. Müller; Maj M. Kjærgaard; Hanne Poulsen; Ove Wiborg; Jens R. Nyengaard

2009-01-01

255

Transient detector apparatus  

Microsoft Academic Search

A transient detector apparatus utilizing peak and slope detectors to determine the presence of transient signal in a logic signal. Individual slope measurements of the input signal are compared with a logic criteria to establish the occurrence of a transient. The peak voltage and pulse width of a transient are digitized in order to time tag or isolate a transient

Lapeyrolerie

1985-01-01

256

Transient-fault recovery using simultaneous multithreading  

Microsoft Academic Search

We propose a scheme for transient-fault recovery called Simultaneously and Redundantly Threaded processors with Recovery (SRTR) that enhances a previously proposed scheme for transient-fault detection, called Simultaneously and Redundantly Threaded (SRT) processors. SRT replicates an application into two communicating threads, one executing ahead of the other. The trailing thread repeats the computation performed by the leading thread, and the values

T. N. Vijaykumar; Irith Pomeranz; Karl Cheng

2002-01-01

257

Dynamic Contrast-Enhanced and Diffusion MRI Show Rapid and Dramatic Changes in Tumor Microenvironment in Response to Inhibition of HIF-1? Using PX-4781  

PubMed Central

Abstract PX-478 is a new agent known to inhibit the hypoxia-responsive transcription factor, HIF-1?, in experimental tumors. The current study was undertaken in preparation 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 hemodynamics and cellularity, respectively. Mice bearing human xenografts were treated either with PX-478 or vehicle, and imaged over time. DW imaging was performed at three b values to generate apparent diffusion coefficient of water (ADCw) maps. For DCE-MRI, a macromolecular contrast reagent, BSA-Gd-DTPA, was used to determine vascular permeability and vascular volume fractions. PX-478 induced a dramatic reduction in tumor blood vessel permeability within 2 hours after treatment, which returned to baseline by 48 hours. The anti-VEGF antibody, Avastin, reduced both the permeability and vascular volume. PX-478 had no effect on the perfusion behavior of a drug-resistant tumor system, A-549. Tumor cellularity, estimated from ADCw, was significantly decreased 24 and 36 hours after treatment. This is the earliest significant response of ADC to therapy yet reported. Based on these preclinical findings, both of these imaging endpoints will be included in the clinical trial of PX-478. PMID:15967100

Jordan, Benedicte F; Runquist, Matthew; Raghunand, Natarajan; Baker, Amanda; Williams, Ryan; Kirkpatrick, Lynn; Powis, Garth; Gillies, Robert J

2005-01-01

258

Dynamic contrast-enhanced and diffusion MRI show rapid and dramatic changes in tumor microenvironment in response to inhibition of HIF-1alpha using PX-478.  

PubMed

PX-478 is a new agent known to inhibit the hypoxia-responsive transcription factor, HIF-1alpha, in experimental tumors. The current study was undertaken in preparation 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 hemodynamics and cellularity, respectively. Mice bearing human xenografts were treated either with PX-478 or vehicle, and imaged over time. DW imaging was performed at three b values to generate apparent diffusion coefficient of water (ADCw) maps. For DCE-MRI, a macromolecular contrast reagent, BSA-Gd-DTPA, was used to determine vascular permeability and vascular volume fractions. PX-478 induced a dramatic reduction in tumor blood vessel permeability within 2 hours after treatment, which returned to baseline by 48 hours. The anti-VEGF antibody, Avastin, reduced both the permeability and vascular volume. PX-478 had no effect on the perfusion behavior of a drug-resistant tumor system, A-549. Tumor cellularity, estimated from ADCw, was significantly decreased 24 and 36 hours after treatment. This is the earliest significant response of ADC to therapy yet reported. Based on these preclinical findings, both of these imaging endpoints will be included in the clinical trial of PX-478. PMID:15967100

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

2005-05-01

259

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

PubMed

1. Ambroxol and bromhexine were evaluated as mucolytics and to enhance the passage of furaltadone into tracheobronchial secretions (TBS) in chronic complicated respiratory disease-affected broilers. 2. Viscosity of TBS was noticeably increased in the ambroxol-treated birds and only slightly increased in the bromhexine groups; however, the physical (nature) of TBS was superior in the ambroxol-treated broilers. 3. There was a clear increase in the passage of furaltadone into tracheobronchial secretions only in the ambroxol-treated birds. 4. Everyday use of ambroxol in broilers is discussed. PMID:7583380

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

1995-07-01

260

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.

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

2014-01-01

261

Out-diffused silver island films for surface-enhanced Raman scattering protected with TiO2 films using atomic layer deposition  

PubMed Central

We fabricated self-assembled silver nanoisland films using a recently developed technique based on out-diffusion of silver from an ion-exchanged glass substrate in reducing atmosphere. We demonstrate that the position of the surface plasmon resonance of the films depends on the conditions of the film growth. The resonance can be gradually shifted up to 100 nm towards longer wavelengths by using atomic layer deposition of titania, from 3 to 100 nm in thickness, upon the film. Examination of the nanoisland films in surface-enhanced Raman spectrometry showed that, in spite of a drop of the surface-enhanced Raman spectroscopy (SERS) signal after the titania spacer deposition, the Raman signal can be observed with spacers up to 7 nm in thickness. Denser nanoisland films show slower decay of the SERS signal with the increase in spacer thickness. PACS 78.67.Sc (nanoaggregates; nanocomposites); 81.16.Dn (self-assembly); 74.25.nd (Raman and optical spectroscopy) PMID:25170333

2014-01-01

262

Dopant and self-diffusion in extrinsic n-type silicon isotopically controlled heterostructures  

SciTech Connect

We present experimental results of dopant- and self-diffusion in extrinsic silicon doped with As. Multilayers of isotopically controlled {sup 28}Si and natural silicon enable simultaneous analysis of {sup 30}Si diffusion into the {sup 28}Si enriched layers and dopant diffusion throughout the multilayer structure. In order to suppress transient enhanced self- and dopant diffusion caused by ion implantation, we adopted a special approach to dopant introduction. First, an amorphous 250-nm thick Si layer was deposited on top of the Si isotope heterostructure. Then the dopant ions were implanted to a depth such that all the radiation damage resided inside this amorphous cap layer. These samples were annealed for various times and temperatures to study the impact of As diffusion and doping on Si self-diffusion. The Si self-diffusion coefficient and the dopant diffusivity for various extrinsic n-type conditions were determined over a wide temperature range. We observed increased diffusivities that we attribute to the increase in the concentration of the native defect promoting the diffusion.

Silvestri, Hughes H.; Sharp, Ian D.; Bracht, Hartmut A.; Nicols, Sam P.; Beeman, Jeff W.; Hansen, John; Nylandsted-Larsen, Arme; Haller, Eugene E.

2002-04-01

263

Novel transient-fault detection circuit featuring enhanced bulk built-in current sensor with low-power sleep-mode  

E-print Network

with low-power sleep-mode . R. Possamai Bastosa,*1 , F. Sill Torresb , G. Di Natalea , M. Flottesa , B and enhanced with low-power sleep-mode. In addition, a calibration method for bulk built-in current sensors. This strategy is exemplified through system's recovery schemes fired in function of the indication of concurrent

Paris-Sud XI, Université de

264

Transient Faults in Computer Systems  

NASA Technical Reports Server (NTRS)

A powerful technique particularly appropriate for the detection of errors caused by transient faults in computer systems was developed. The technique can be implemented in either software or hardware; the research conducted thus far primarily considered software implementations. The error detection technique developed has the distinct advantage of having provably complete coverage of all errors caused by transient faults that affect the output produced by the execution of a program. In other words, the technique does not have to be tuned to a particular error model to enhance error coverage. Also, the correctness of the technique can be formally verified. The technique uses time and software redundancy. The foundation for an effective, low-overhead, software-based certification trail approach to real-time error detection resulting from transient fault phenomena was developed.

Masson, Gerald M.

1993-01-01

265

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

266

Transient Repetitive Exposure To Low Level Light Therapy Enhances Collateral Blood Vessel Growth In The Ischemic Hindlimb Of The Tight Skin Mouse  

PubMed Central

The tight skin mouse (Tsk?/+) is a model of scleroderma characterized by impaired vasoreactivity, increased oxidative stress, attenuated angiogenic response to VEGF, and production of the angiogenesis inhibitor angiostatin. Low level light therapy (LLLT) stimulates angiogenesis in myocardial infarction and chemotherapy-induced mucositis. We hypothesize repetitive LLLT restores vessel growth in the ischemic hindlimb of Tsk?/+ mice by attenuating angiostatin and enhancing angiomotin effects in vivo. C57Bl/6J and Tsk?/+ mice underwent ligation of the femoral artery. Relative blood flow to the foot was measured using a laser Doppler imager. Tsk?/+ mice received LLLT (670 nm, 50 mW cm2, 30 J/cm2) for 10 min/day for 14 days. Vascular density was determined using lycopersicom lectin staining. Immunofluorescent labeling, western blot analysis, and immunoprecipitation were used to determine angiostatin and angiomotin expression. Recovery of blood flow to the ischemic limb was reduced in Tsk?/+ compared with C57Bl/6 mice two weeks after surgery. LLLT treatment of Tsk?/+ mice restored blood flow to levels observed in C57Bl/6 mice. Vascular density was decreased, angiostatin expression was enhanced and angiomotin depressed in the ischemic hindlimb of Tsk?/+ mice. LLLT treatment reversed these abnormalities. LLLT stimulates angiogenesis by increasing angiomotin and decreasing angiostatin expression in the ischemic hindlimb of Tsk?/+ mice. PMID:23231468

Zaidi, Maria; Krolikowki, John G.; Jones, Deron W.; Pritchard, Kirkwood A.; Struve, Janine; Nandedkar, Sandhya D.; Lohr, Nicole L.; Pagel, Paul S.; Weihrauch, Dorothee

2012-01-01

267

Attempts to characterize the NBD heterodimer of MRP1: transient complex formation involves Gly771 of the ABC signature sequence but does not enhance the intrinsic ATPase activity  

PubMed Central

MRP1 (multidrug-resistance-associated protein 1; also known as ABCC1) is a member of the human ABC (ATP-binding cassette) transporter superfamily that confers cell resistance to chemotherapeutic agents. Considering the structural and functional similarities to the other ABC proteins, the interaction between its two NBDs (nucleotide-binding domains), NBD1 (N-terminal NBD) and NBD2 (C-terminal NBD), is proposed to be essential for the regulation of the ATP-binding/ATP-hydrolysis cycle of MRP1. We were interested in the ability of recombinant NBD1 and NBD2 to interact with each other and to influence ATPase activity. We purified NBD1 (Asn642–Ser871) and NBD2 (Ser1286–Val1531) as soluble monomers under native conditions. We measured extremely low intrinsic ATPase activity of NBD1 (10?5 s?1) and NBD2 (6×10?6 s?1) and no increase in the ATP-hydrolysis rate could be detected in an NBD1+NBD2 mixture, with concentrations up to 200 ?M. Despite the fact that both monomers bind ATP, no stable NBD1·NBD2 heterodimer could be isolated by gel-filtration chromatography or native-PAGE, but we observed some significant modifications of the heteronuclear single-quantum correlation NMR spectrum of 15N-NBD1 in the presence of NBD2. This apparent NBD1·NBD2 interaction only occurred in the presence of Mg2+ and ATP. Partial sequential assignment of the NBD1 backbone resonances shows that residue Gly771 of the LSGGQ sequence is involved in NBD1·NBD2 complex formation. This is the first NMR observation of a direct interaction between the ABC signature and the opposite NBD. Our study also reveals that the NBD1·NBD2 heterodimer of MRP1 is a transient complex. This labile interaction is not sufficient to induce an ATPase co-operativity of the NBDs and suggests that other structures are required for the ATPase activation mechanism. PMID:16014004

2005-01-01

268

Transient Heliosheath Modulation  

E-print Network

Voyager 1 has explored the solar wind-interstellar medium interaction region between the terminal shock and heliopause following the intensity distribution of galactic cosmic ray protons above 200 MeV energy. Before this component reached the galactic level at 121.7 AU, 4 episodes of rapid intensity change occured similar to the Forbush Decreases found near the sun, rather than the expected result of models related to those describing Long Term Modulation in the inner solar system. Because the mean solar wind flow is both expected and observed to be perpendicular to the radial direction close to the heliopause, explanation is given in terms of transient radial flows related to possible heliopause boundary flapping. It is necessary that radial flows are at the sound speed found for conditions downstream of the teminal shock and that the relevant perpendicular cosmic ray diffusion is controlled by 'slab' field fluctuations accounting for 20 percent or less of the total power in field variance. However, addition...

Quenby, J J

2014-01-01

269

TIA (Transient Ischemic Attack)  

MedlinePLUS

TIA (Transient Ischemic Attack) Updated:Oct 2,2014 Excerpted from “ Why Rush? ”, Stroke Connection January/February 2009 (Science update October 2012) While transient ischemic attack (TIA) is often labeled “mini-stroke,” ...

270

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

271

Lithium diffusion in (Li, K, Na)NbO3 piezoeletric thin films and the resulting approach for enhanced performance properties  

NASA Astrophysics Data System (ADS)

Dramatic out-diffusion of lithium from (Li, K, Na)NbO3 (KNN-LN) thin films into substrate was identified as the cause of seriously degraded electrical properties. Utilizing the strong diffusion ability of lithium, lithium composition could be effectively introduced to the KNN film through the diffusion from the surface to the film. The distributions of the lithium diffused across the KNN films were found complementary to that of potassium, as lithium tended to be retained where A-site vacancies existed. With more lithium retained and reduced A-site vacancies, outstandingly large piezoelectric strain coefficient and voltage coefficient were demonstrated in the resulting Li-KNN film.

Chin Goh, Phoi; Yao, Kui; Chen, Zhong

2011-08-01

272

Complex transient epileptic amnesia  

Microsoft Academic Search

Transient epileptic amnesia is a rare but probably underrecognized form of temporal lobe epilepsy, which typically manifests as episodic isolated memory loss. Consequently, transient epileptic amnesia may be readily misdiagnosed as a nonepileptic memory dysfunction in older individuals. When appropriately recognized, it has been described as a treatment-responsive syndrome amenable to antiepileptic drugs. We describe a patient with drug-resistant transient

Ryan D. Walsh; Robert E. Wharen; William O. Tatum

2011-01-01

273

Analysis of coupled bimolecular reaction kinetics and diffusion by two-color fluorescence correlation spectroscopy: enhanced resolution of kinetics by resonance energy transfer.  

PubMed Central

In two-color fluorescence correlation spectroscopy (TCFCS), the fluorescence intensities of two fluorescently-labeled species are cross-correlated over time and can be used to identify static and dynamic interactions. Generally, fluorophore labels are chosen that do not undergo Förster resonance energy transfer (FRET). Here, a general TCFCS theory is presented that accounts for the possibility of FRET between reactants in the reversible bimolecular reaction, [reaction: see text] where k(f) and k(b) are forward and reverse rate constants, respectively (dissociation constant K(d) = k(b)/k(f)). Using this theory, we systematically investigated the influence on the correlation function of FRET, reaction rates, reactant concentrations, diffusion, and component visibility. For reactants of comparable size and an energy-transfer efficiency of approximately 90%, experimentally measurable cross-correlation functions should be sensitive to reaction kinetics for K(d) > 10(-8) M and k(f) >or= approximately 10(7) M(-1)s(-1). Measured auto-correlation functions corresponding to donor and acceptor labels are generally less sensitive to reaction kinetics, although for the acceptor, this sensitivity increases as the visibility of the donor increases relative to the acceptor. In the absence of FRET or a significant hydrodynamic difference between reactant species, there is little effect of reaction kinetics on the shape of auto- and cross-correlation functions. Our results suggest that a subset of biologically relevant association-dissociation kinetics can be measured by TCFCS and that FRET can be advantageous in enhancing these effects. PMID:12080140

Hom, Erik F Y; Verkman, A S

2002-01-01

274

ON THE X-RAY OUTBURSTS OF TRANSIENT ANOMALOUS X-RAY PULSARS AND SOFT GAMMA-RAY REPEATERS  

SciTech Connect

We show that the X-ray outburst light curves of four transient anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), namely, XTE J1810-197, SGR 0501+4516, SGR 1627-41, and CXOU J164710.2-455216, can be produced by the fallback disk model that was also applied to the outburst light curves of persistent AXPs and SGRs in our earlier work. The model solves the diffusion equation for the relaxation of a disk that has been pushed back by a soft gamma-ray burst. The sets of main disk parameters used for these transient sources are very similar to each other and to those employed in our earlier models of persistent AXPs and SGRs. There is a characteristic difference between the X-ray outburst light curves of transient and persistent sources. This can be explained by the differences in the disk surface density profiles of the transient and persistent sources in quiescence indicated by their quiescent X-ray luminosities. Our results imply that a viscous disk instability operating at a critical temperature in the range of {approx}1300-2800 K is a common property of all fallback disks around AXPs and SGRs. The effect of the instability is more pronounced and starts earlier for the sources with lower quiescent luminosities, which leads to the observable differences in the X-ray enhancement light curves of transient and persistent sources. A single active disk model with the same basic disk parameters can account for the enhancement phases of both transient and persistent AXPs and SGRs. We also present a detailed parameter study to show the effects of disk parameters on the evolution of the X-ray luminosity of AXPs and SGRs in the X-ray enhancement phases.

Cal Latin-Small-Letter-Dotless-I skan, Sirin; Ertan, Uenal [Sabanc Latin-Small-Letter-Dotless-I University, Orhanl Latin-Small-Letter-Dotless-I -Tuzla, Istanbul, 34956 (Turkey)

2012-10-20

275

Transient regimes and crossover for epitaxial surfaces  

NASA Astrophysics Data System (ADS)

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)].

Haselwandter, Christoph A.; Vvedensky, Dimitri D.

2010-02-01

276

Transient Voltage Recorder  

NASA Technical Reports Server (NTRS)

A voltage transient recorder can detect lightning induced transient voltages. The recorder detects a lightning induced transient voltage and adjusts input amplifiers to accurately record transient voltage magnitudes. The recorder stores voltage data from numerous monitored channels, or devices. The data is time stamped and can be output in real time, or stored for later retrieval. The transient recorder, in one embodiment, includes an analog-to-digital converter and a voltage threshold detector. When an input voltage exceeds a pre-determined voltage threshold, the recorder stores the incoming voltage magnitude and time of arrival. The recorder also determines if its input amplifier circuits clip the incoming signal or if the incoming signal is too low. If the input data is clipped or too low, the recorder adjusts the gain of the amplifier circuits to accurately acquire subsequent components of the lightning induced transients.

Medelius, Pedro J. (Inventor); Simpson, Howard J. (Inventor)

2002-01-01

277

Portable vapor diffusion coefficient meter  

DOEpatents

An apparatus for measuring the effective vapor diffusion coefficient of a test vapor diffusing through a sample of porous media contained within a test chamber. A chemical sensor measures the time-varying concentration of vapor that has diffused a known distance through the porous media. A data processor contained within the apparatus compares the measured sensor data with analytical predictions of the response curve based on the transient diffusion equation using Fick's Law, iterating on the choice of an effective vapor diffusion coefficient until the difference between the predicted and measured curves is minimized. Optionally, a purge fluid can forced through the porous media, permitting the apparatus to also measure a gas-phase permeability. The apparatus can be made lightweight, self-powered, and portable for use in the field.

Ho, Clifford K. (Albuquerque, NM)

2007-06-12

278

Transient Effects and Disturbed Conditions  

NASA Astrophysics Data System (ADS)

In the present phase of the solar cycle no big transients leading to strong modulation had been observed after 1991. Apart from a few minor disturbances cosmic rays were still recovering to a new intensity maximum. It was suggested, therefore, that existing literature from previous cycles should be critically reviewed. The scene was set by the introductory papers on - phenomenology of cosmic ray modulation in successive solar cycles throughout the heliosphere, - the present state of models for long term modulation and their shortcomings, - the relation between cosmic ray variations and the magnitude of the interplanetary magnetic field (the CR-B-relation), - charge dependent effects. In the discussions, the study of propagating diffusive disturbances and the CR-B-relation played a central role. The difference was stressed between isolated transient disturbances in the inner solar system (Forbush decreases), and the long lasting, step-like decreases caused by merged interaction regions in the outer heliosphere. The recovery rates following the step-like decreases vary with the phase in the 22-year solar cycle. In some cases this requires a modification of existing drift models. In the outer heliosphere, the CR-B-relation leads to the result ? alpha 1/? between the diffusion coefficient ? and the field magnitude ?. This simple result is a challenge for theoreticians to derive the perpendicular diffusion coefficient fromfirst principles. The three articles in this report essentially follow the list of open points and arguments just presented. The article "Observations and Simple Models" is organised around the model of a propagating diffusive barrier, its application to Forbush effects in the inner heliosphere and to decreases caused by merged interaction regions in the outer heliosphere. Acomparison of observed Forbush decreases with model predictions requires a careful separation of the two steps related to the turbulent region behind the shock front and the closed magnetic field regions of the ejecta (the interplanetary counterparts of coronal mass ejections). It is shown that models for propagating disturbances can be used to derive values of the diffusion coefficients phenomenologically, not only during the disturbance, but also in the ambient medium. The "Modeling of Merged Interaction Regions" summarizes the dynamic and time-dependent process of cosmic ray modulation in the heliosphere. Numerical models with only a time-dependent neutral sheet prove to be successful when moderate to low solar activity occurs but fail to describe large and discrete steps in modulated cosmic rays when solar activity is high. To explain this feature of heliospheric modulation, the concept of global merged interaction regions is required. The com-bination of gradient, curvature and neutral sheet drifts with these global merged interaction regions has so far been the most successful approach in explaining the 11-year and 22-year cycles in the long-term modulation of cosmic rays. The "Remarks on the Diffusion Tensor in the Heliosphere" describe available theories of perpen-dicular diffusion and drift, and discuss their relevance to cosmic rays in the heliosphere. In addition, the information about diffusion coefficients and spatial gradients obtained from the analysis of steady state anisotropies at neutron monitor energies is summarized. These topics are intimately related to the other two articles. They are also part of the general discussion about the "Diffusion Tensor throughout the Heliosphere" which played an important role in all working groups.

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

1998-01-01

279

Electromagnetic Transients from Supernovae  

NASA Astrophysics Data System (ADS)

A core-collapse supernova (SN) would produce an expanding shell of charged particles which interact with the surrounding magnetic field of the progenitor star producing a transient radio pulse. Approximately one supernova event per century is expected in a galaxy. Such a pulse may be detected by a transient radio array. We present details of an ongoing such for such events by the Eight-meter-wavelength Transient Array (ETA). )

Kothari, Manthan

2010-02-01

280

Laboratory Study of Transient Stress Effects on Fault Stability  

Microsoft Academic Search

Transient dynamic stresses, such as seismic waves and Earth tides, can destabilize fault slip and trigger earthquakes. Understanding the effects of transient stressing on fault zone frictional strength would enhance our understanding of the earthquake cycle. Earthquake triggering does not depend simply on the magnitude of the trigger but rather might be a function of the dynamic stress associated with

H. M. Savage; C. J. Marone

2004-01-01

281

Force-induced diffusion in microrheology.  

PubMed

We investigate the force-induced diffusive motion of a tracer particle inside a glass-forming suspension when a strong external force is applied to the probe (active nonlinear microrheology). A schematic model of mode-coupling theory introduced recently is extended to describe the transient dynamics of the probe particle, and used to analyze recent molecular-dynamics simulation data. The model describes non-trivial transient displacements of the probe before a steady-state velocity is reached. The external force also induces diffusive motion in the direction perpendicular to its axis. We address the relation between the transverse diffusion coefficient D(perpendicular) and the force-dependent nonlinear friction coefficient ?. Non-diffusive fluctuations in the direction of the force are seen at long times in the MD simulation, while the model describes cross-over to long-time diffusion. PMID:23114229

Harrer, Ch J; Winter, D; Horbach, J; Fuchs, M; Voigtmann, Th

2012-11-21

282

Short-term changes in Jupiter's synchrotron radiation at 325 MHz: Enhanced radial diffusion in Jupiter's radiation belt driven by solar UV\\/EUV heating  

Microsoft Academic Search

Evidence of short-term changes in Jupiter's synchrotron radiaion at 325 MHzRadial diffusion rate of 3 × 10?8 L3 \\/s is suitable in Jupiter's radiation beltThe synchrotron emission does not contribute electron loss in the radiation belt

F. Tsuchiya; H. Misawa; K. Imai; A. Morioka

2011-01-01

283

Detection of non-palpable breast cancer in asymptomatic women by using unenhanced diffusion-weighted and T2-weighted MR imaging: comparison with mammography and dynamic contrast-enhanced MR imaging  

Microsoft Academic Search

Objective  To compare the detectability of non-palpable breast cancer in asymptomatic women by using mammography (MMG), dynamic contrast-enhanced\\u000a MR imaging (DCE-MRI) and unenhanced MR imaging with combined diffusion-weighted and T2-weighted images (DWI?+?T2WI).\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Forty-two lesions in 42 patients with non-palpable breast cancer in asymptomatic women were enrolled. For the reading test,\\u000a we prepared a control including 13 normal and 8 benign cases.

Hidetake Yabuuchi; Yoshio Matsuo; Shunya Sunami; Takeshi Kamitani; Satoshi Kawanami; Taro Setoguchi; Shuji Sakai; Masamitsu Hatakenaka; Makoto Kubo; Eriko Tokunaga; Hidetaka Yamamoto; Hiroshi Honda

2011-01-01

284

Prognosis Prediction of Measurable Enhancing Lesion after Completion of Standard Concomitant Chemoradiotherapy and Adjuvant Temozolomide in Glioblastoma Patients: Application of Dynamic Susceptibility Contrast Perfusion and Diffusion-Weighted Imaging  

PubMed Central

Purpose To assess the prognosis predictability of a measurable enhancing lesion using histogram parameters produced by the normalized cerebral blood volume (nCBV) and normalized apparent diffusion coefficient (nADC) after completion of standard concomitant chemoradiotherapy (CCRT) and adjuvant temozolomide (TMZ) medication in glioblastoma multiforme (GBM) patients. Materials and Methods This study was approved by the institutional review board (IRB), and the requirement for informed consent was waived. A total of 59 patients with newly diagnosed GBM who received standard CCRT with TMZ and adjuvant TMZ for six cycles underwent perfusion-weighted and diffusion-weighted imaging. Twenty-seven patients had a measurable enhancing lesion and 32 patients lacked a measurable enhancing lesion based on the Response Assessment in Neuro-Oncology (RANO) criteria in the follow-up MRI, which was performed within 3 months after adjuvant TMZ therapy was completed. We measured the nCBV and nADC histogram parameters based on the measurable enhancing lesion. The progression free survival (PFS) was analyzed by the Kaplan-Meier method with the use of the log-rank test. Results The median PFS of patients lacking measurable enhancing lesion was longer than for those with measurable enhancing lesions (17.6 vs 3.3 months, P<.0001). There was a significant, positive correlation between the 99th percentile nCBV value of a measurable enhancing lesion and the PFS (P?=?.044, R2?=?.152). In addition, the median PFS was longer in patients with a 99th percentile nCBV value ?4.5 than it was in those with a value <4.5 (4.4 vs 3.1 months, P?=?.036). Conclusion We found that the nCBV value can be used for the prognosis prediction of a measurable enhancing lesion after the completion of standard treatment for GBM, wherein a high 99th percentile nCBV value (?4.5) suggests a better PFS for GBM patients. PMID:25419975

Kim, Jae Hyun; Choi, Seung Hong; Ryoo, Inseon; Yun, Tae Jin; Kim, Tae Min; Lee, Se-Hoon; Park, Chul-Kee; Kim, Ji-Hoon; Sohn, Chul-Ho; Park, Sung-Hye; Kim, Il Han

2014-01-01

285

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

286

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

287

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

288

Transient Response Analysis  

NASA Technical Reports Server (NTRS)

Transient Response Analysis Program, TRAP aids in analysis of frequency response of force-transmission and shock-damping devices. Devices analyzed with TRAP include hydraulic actuators, automotive shock absorbers and electromechanical actuators.

Blackman, L. D.

1985-01-01

289

Transient monocular visual loss.  

PubMed

Transient monocular visual loss may be caused by a variety of ophthalmic and systemic conditions. Management depends on identifying the cause. Embolic occlusions of arteries supplying the eye are a most important cause. Such emboli often arise from the heart, aorta, and internal carotid arteries. The most common embolic substances are white platelet-fibrin and red erythrocyte-fibrin thrombi, cholesterol crystals, and calcific particles. Retinal vasoconstriction is another important cause of transient monocular visual loss. The conditions that cause anterior ischemic optic neuropathy may occasionally cause transient visual loss. Transient monocular visual loss may also be related to conditions that cause papilledema and some conditions intrinsic to the eye, such as optic disk drusen and colobomas. PMID:17540127

Amick, Amy; Caplan, Louis R

2007-01-01

290

Complex transient epileptic amnesia.  

PubMed

Transient epileptic amnesia is a rare but probably underrecognized form of temporal lobe epilepsy, which typically manifests as episodic isolated memory loss. Consequently, transient epileptic amnesia may be readily misdiagnosed as a nonepileptic memory dysfunction in older individuals. When appropriately recognized, it has been described as a treatment-responsive syndrome amenable to antiepileptic drugs. We describe a patient with drug-resistant transient epileptic amnesia treated with unilateral temporal lobectomy. Prolonged postictal slowing in the mesial temporal structures was evident on invasive electroencephalography 5 hours after the occurrence of a brief focal seizure. These findings support the theory of a Todd phenomenon as the underlying pathophysiological mechanism in transient epileptic amnesia. PMID:21262589

Walsh, Ryan D; Wharen, Robert E; Tatum, William O

2011-02-01

291

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

292

Multiresolution transient detection  

Microsoft Academic Search

Designs and studies the performance of a multiresolution-based transient detector. The transients the authors are interested in consist of wide-band, pulse-like, coherent structures in a turbulent flow. To take advantage of the fast pyramidal wavelet algorithm, an important point when processing large amounts of experimental data, the detector makes use of the discrete wavelet transform. The authors show how the

Patrice Abry; Patrick Flandrin

1994-01-01

293

Hillslope diffusion  

NSDL National Science Digital Library

This lab is designed to help students apply hillslope diffusion equations (derived in class prior to the lab) to understand real-world hillslopes. The major goal is a deeper understanding of hillslope processes and the equations used to describe hillslope diffusion by observing the same factors described in the equations on real-world hillslopes.

Mcdermott, Jeni

294

Penetration Enhancers for Human Skin: Mode of Action of 2Pyrrolidone and Dimethylformamide on Partition and Diffusion of Model Compounds Water, n-Alcohols, and Caffeine  

Microsoft Academic Search

Penetration-enhancing solvents may modify diffusional routes through the stratum corneum and the partitioning of drugs into these pathways. To investigate the mechanisms of action of enhancers, steady-state fluxes were measured in vitro for polar methanol, nonpolar octanol, and an intermediate compound, caffeine. selected as model penetrants; human stratum corneum conditioned on both sides with water or accelerants (2-pyrrolidone or dimethylformamide

Diane Southwell; Brian W. Barry

1983-01-01

295

Fokker-Planck . . . Diffusion . . .  

E-print Network

Fokker-Planck . . . Diffusion . . . Diffusion- . . . Application: . . . Summary and . . . First #12;Fokker-Planck . . . Diffusion . . . Diffusion- . . . Application: . . . Summary and . . . Topics: 1. Fokker-Planck transport equation 2. Diffusion approximation 3. Diffusion-convection transport

296

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

297

Transient growth of Ekman-Couette flow  

NASA Astrophysics Data System (ADS)

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.

Shi, Liang; Hof, Björn; Tilgner, Andreas

2014-01-01

298

Laminar diffusion flames under micro-gravity conditions  

NASA Technical Reports Server (NTRS)

Laminar methane and propane gas-jet diffusion flames have been theoretically and experimentally studied at NASA-Lewis under microgravity conditions. It is noted that laminar diffusion flames are strongly affected by the combined effects of kinetics, radiation, and such transient phenomena as flame ignition, stabilization, and extinction. Observations on the distinctive nature of the flame color and luminosity parameters in microgravity are presented, and flame behavior under transient, high-deceleration rates is discussed. Test hardware and instrumentation design are described.

Edelman, Raymond B.; Bahadori, Yousef; Olson, Sandra L.; Stocker, Dennis P.

1988-01-01

299

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.

300

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

301

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

302

Diffuser Test  

NASA Technical Reports Server (NTRS)

Tests begun at Stennis Space Center's E Complex Sept. 13 evaluated a liquid oxygen lead for engine start performance, part of the A-3 Test Facility Subscale Diffuser Risk Mitigation Project at SSC's E-3 Test Facility. Phase 1 of the subscale diffuser project, completed Sept. 24, was a series of 18 hot-fire tests using a 1,000-pound liquid oxygen and gaseous hydrogen thruster to verify maximum duration and repeatability for steam generation supporting the A-3 Test Stand project. The thruster is a stand-in for NASA's developing J-2X engine, to validate a 6 percent scale version of A-3's exhaust diffuser. Testing the J-2X at altitude conditions requires an enormous diffuser. Engineers will generate nearly 4,600 pounds per second of steam to reduce pressure inside A-3's test cell to simulate altitude conditions. A-3's exhaust diffuser has to be able to withstand regulated pressure, temperatures and the safe discharge of the steam produced during those tests. Before the real thing is built, engineers hope to work out any issues on the miniature version. Phase 2 testing is scheduled to begin this month.

2007-01-01

303

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

304

Transient growth without inertia  

NASA Astrophysics Data System (ADS)

We study transient growth in inertialess plane Couette and Poiseuille flows of viscoelastic fluids. For streamwise-constant three-dimensional fluctuations, we demonstrate analytically the existence of initial conditions that lead to quadratic scaling of both the kinetic energy density and the elastic energy with the Weissenberg number, We. This shows that in strongly elastic channel flows of viscoelastic fluids, both velocity and polymer stress fluctuations can exhibit significant transient growth even in the absence of inertia. Our analysis identifies the spatial structure of the initial conditions (i.e., components of the polymer stress tensor at t =0) responsible for this large transient growth. Furthermore, we show that the fluctuations in streamwise velocity and the streamwise component of the polymer stress tensor achieve O(We) and O(We2) growth, respectively, over a time scale O(We) before eventual asymptotic decay. We also demonstrate that the large transient responses originate from the stretching of polymer stress fluctuations by a background shear and draw parallels between streamwise-constant inertial flows of Newtonian fluids and streamwise-constant creeping flows of viscoelastic fluids. One of the main messages of this paper is that at the level of velocity fluctuation dynamics, polymer stretching and the Weissenberg number in elasticity-dominated flows of viscoelastic fluids effectively assume the role of vortex tilting and the Reynolds number in inertia-dominated flows of Newtonian fluids.

Jovanovi?, Mihailo R.; Kumar, Satish

2010-02-01

305

Transient RC Circuits Applet  

NSDL National Science Digital Library

This applet simulates the transient behavior of a simple RC circuit. The user can change the magnitudes of the resistance, capacitance, and the voltage of the battery, as well as flip a switch between its two positions. The applet then graphs the voltage and current in the circuit as functions of time, and displays visual representations of those two quantities on a circuit diagram.

Hwang, Fu-Kwun.

2008-08-05

306

Lightning-Transient Recorder  

NASA Technical Reports Server (NTRS)

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

Grumm, R. L.

1984-01-01

307

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

308

The role of external electric fields in enhancing ion mobility, drift velocity, and drift-diffusion rates in aqueous electrolyte solutions.  

PubMed

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). PMID:21428629

Murad, Sohail

2011-03-21

309

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

310

Comparison of arsenic and phosphorus diffusion behavior in silicongermanium alloys  

E-print Network

Comparison of arsenic and phosphorus diffusion behavior in silicon­germanium alloys S. Eguchia of ion-implanted arsenic and phosphorus in relaxed Si0.8Ge0.2 has been investigated. Under equilibrium is roughly seven for arsenic, and roughly two for phosphorus. Under transient diffusion conditions

311

Diffusion behaviour of charge carriers in thin films of phthalocyanines  

Microsoft Academic Search

Phthalocyanine (Pc) thin films were prepared by the vacuum-evaporating method. The diffusion behaviour of the charge carriers in these films was investigated by means of transient photovoltage (Dember effect) measurements. The experiments imply that the dominant charge carriers in phthalocyanines are electrons which diffuse from the surface closest to the light to the internal bulk. As a comparative system, photovoltic

He Tian; Kong-Chang Chen

1995-01-01

312

Demonstrating Diffusion  

ERIC Educational Resources Information Center

Two demonstrations are described. Materials and instructions for demonstrating movement of molecules into cytoplasm using agar blocks, phenolphthalein, and sodium hydroxide are given. A simple method for demonstrating that the rate of diffusion of a gas is inversely proportional to its molecular weight is also presented. (AJ)

Foy, Barry G.

1977-01-01

313

Diffusion Models  

NSDL National Science Digital Library

Web-based intructional material describing the use of diffusion models in population ecology. This page is part of a set of on-line lectures on Quantitative Population Ecology produced by Alexei Sharov in the Department of Entomology at Virginia Tech.

Sharov, Alexei

314

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

315

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

316

Thermally induced transient trigeminal sensory neuropathy: imaging findings.  

PubMed

We report the clinical and imaging features of a patient with transient partial trigeminal sensory neuropathy thought to have been induced by thermal injury to the tongue. Abnormal thickening and enhancement of the mandibular division of the trigeminal nerve was revealed by MR imaging. The diagnostic considerations for mass-like enlargement of the trigeminal nerve should include transient/inflammatory processes, as well as more common and sinister conditions, such as tumor. PMID:10669251

Chan, L L; DeMonte, F; Ginsberg, L E

2000-01-01

317

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

318

Diffusion of Hydrogen in Silica under Transient Conditions  

NASA Technical Reports Server (NTRS)

Development of hydrogen in sealed silica glass ampoules during annealing at elevated temperatures was investigated. The dependence of hydrogen pressure in the ampoules as a function of time, for different temperatures and ampoule parameters was measured. The process was modeled assuming chemical solution of hydrogen according to the reaction: silica + H2 = H- Si= + H-O-Si=. The equilibrium constant of the reaction was determined by fitting the theoretical curves to the experimental data. The Gibbs function for this reaction was estimated at deltaG = -25.8 + 54T.

Palosz, W.

2003-01-01

319

Effects of turbulent diffusion on the chemistry of diffuse clouds  

E-print Network

Aims. We probe the effect of turbulent diffusion on the chemistry at the interface between a cold neutral medium (CNM) cloudlet and the warm neutral medium (WNM). Methods. We perform moving grid, multifluid, 1D, hydrodynamical simulations with chemistry including thermal and chemical diffusion. The diffusion coefficients are enhanced to account for turbulent diffusion. We post-process the steady-states of our simulations with a crude model of radiative transfer to compute line profiles. Results. Turbulent diffusion spreads out the transition region between the CNM and the WNM. We find that the CNM slightly expands and heats up: its CH and H$_2$ content decreases due to the lower density. The change of physical conditions and diffusive transport increase the H$^+$ content in the CNM which results in increased OH and H$_2$O. Diffusion transports some CO out of the CNM. It also brings H$_2$ into contact with the warm gas with enhanced production of CH$^+$, H$_3^+$, OH and H$_2$O at the interface. O lines are sensitive to the spread of the thermal profile in the intermediate region between the CNM and the WNM. Enhanced molecular content at the interface of the cloud broadens the molecular line profiles and helps exciting transitions of intermediate energy. The relative molecular yield are found higher for bigger clouds. Conclusions. Turbulent diffusion can be the source of additional molecular production and should be included in chemical models of the interstellar medium (ISM). It also is a good candidate for the interpretation of observational problems such as warm H$_2$, CH$^+$ formation and presence of H$_3^+$.

P. Lesaffre; M. Gerin; P. Hennebelle

2007-04-24

320

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

321

Transient cerebral ischemia.  

PubMed Central

Stroke is a major cause of disability and death in North America. About 30% to 40% of patients with stroke have had transient ischemic attacks (TIAs). The recognition and treatment of TIAs and possibly of asymptomatic stenoses of the carotid arteries may be beneficial in preventing stroke. We review the epidemiologic features, natural history, pathogenetic features, clinical presentation, methods of investigation and management of patients with TIAs. PMID:2642394

Cusimano, M D; Ameli, F M

1989-01-01

322

Transient Detection and Classification  

Microsoft Academic Search

I provide an incomplete inventory of the astronomical variability that will\\u000abe found by next-generation time-domain astronomical surveys. These phenomena\\u000aspan the distance range from near-Earth satellites to the farthest Gamma Ray\\u000aBursts. The surveys that detect these transients will issue alerts to the\\u000agreater astronomical community; this decision process must be extremely robust\\u000ato avoid a slew of ``false''

Andrew C. Becker

2008-01-01

323

Transient detection and classification  

Microsoft Academic Search

I provide an incomplete inventory of the astronomical variability that will be found by next-generation time-domain astronomical surveys. These phenomena span the distance range from near-Earth satellites to the farthest Gamma Ray Bursts. The surveys that detect these transients will issue alerts to the greater astronomical community; this decision process must be extremely robust to avoid a slew of ``false''

A. C. Becker

2008-01-01

324

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

325

Atomic transient recorder  

Microsoft Academic Search

In Bohr's model of the hydrogen atom, the electron takes about 150 attoseconds (1 as = 10-18s) to orbit around the proton, defining the characteristic timescale for dynamics in the electronic shell of atoms. Recording atomic transients in real time requires excitation and probing on this scale. The recent observation of single sub-femtosecond (1fs = 10-15s) extreme ultraviolet (XUV) light

R. Kienberger; E. Goulielmakis; M. Uiberacker; A. Baltuska; V. Yakovlev; F. Bammer; A. Scrinzi; Th. Westerwalbesloh; U. Kleineberg; U. Heinzmann; M. Drescher; F. Krausz

2004-01-01

326

Transient fault detectors  

Microsoft Academic Search

We present fault detectors for transient faults, (i.e., corruptions of the memory of the processors, but not of the code of\\u000a the processors). We distinguish fault detectors for tasks (i.e., the problem to be solved) from failure detectors for implementations (i.e., the algorithm that solves the problem). The aim of our fault detectors is to detect a memory corruption as

Joffroy Beauquier; Sylvie Delaët; Shlomi Dolev; Sébastien Tixeuil

2007-01-01

327

Lunar transient phenomena  

NASA Astrophysics Data System (ADS)

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

Cameron, W. S.

1991-03-01

328

ON DETECTING TRANSIENT PHENOMENA  

SciTech Connect

Transient phenomena are interesting and potentially highly revealing of details about the processes under observation and study that could otherwise go unnoticed. It is therefore important to maximize the sensitivity of the method used to identify such events. In this article, we present a general procedure based on the use of the likelihood function for identifying transients which is particularly suited for real-time applications because it requires no grouping or pre-processing of the data. The method makes use of all the information that is available in the data throughout the statistical decision-making process, and is suitable for a wide range of applications. Here we consider those most common in astrophysics, which involve searching for transient sources, events or features in images, time series, energy spectra, and power spectra, and demonstrate the use of the method in the case of a weak X-ray flare in a time series and a short-lived quasi-periodic oscillation in a power spectrum. We derive a fit statistic that is ideal for fitting arbitrarily shaped models to a power density distribution, which is of general interest in all applications involving periodogram analysis.

Belanger, G., E-mail: gbelanger@sciops.esa.int [European Space Astronomy Centre (ESA/ESAC), Science Operations Department, Villanueva de la Canada (Madrid) (Spain)

2013-08-10

329

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

330

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

331

Formation of Magnetized Prestellar Cores with Ambipolar Diffusion and Turbulence  

NASA Astrophysics Data System (ADS)

We investigate the roles of magnetic fields and ambipolar diffusion during prestellar core formation in turbulent giant molecular clouds (GMCs), using three-dimensional numerical simulations. Our simulations focus on the shocked layer produced by a converging flow within a GMC, and survey varying ionization and angle between the upstream flow and magnetic field. We also include ideal magnetohydrodynamic (MHD) and hydrodynamic models. From our simulations, we identify hundreds of self-gravitating cores that form within 1 Myr, with masses M~0.04-2.5 solar-mass and sizes L~0.015-0.07 pc, consistent with observations of the peak of the core mass function (CMF). Median values are M=0.47 solar-mass and L=0.03 pc. Core masses and sizes do not depend on either the ionization or upstream magnetic field direction. In contrast, the mass-to-magnetic flux ratio does increase with lower ionization, from twice to four times the critical value. The higher mass-to-flux ratio for low ionization is the result of enhanced transient ambipolar diffusion when the shocked layer first forms. However, ambipolar diffusion is not necessary to form low-mass supercritical cores. For ideal MHD, we find similar masses to other cases. These masses are 1-2 orders of magnitude lower than the value that defines a magnetically supercritical sphere under post-shock ambient conditions. This discrepancy is the result of anisotropic contraction along field lines, which is clearly evident in both ideal MHD and diffusive simulations. We interpret our numerical findings using a simple scaling argument which suggests that gravitationally critical core masses will depend on the sound speed and mean turbulent pressure in a cloud, regardless of magnetic effects.

Chen, Che-Yu; Ostriker, Eve

2014-07-01

332

Formation of Magnetized Prestellar Cores with Ambipolar Diffusion and Turbulence  

NASA Astrophysics Data System (ADS)

We investigate the roles of magnetic fields and ambipolar diffusion during prestellar core formation in turbulent giant molecular clouds, using three-dimensional numerical simulations. Our simulations focus on the shocked layer produced by a converging large-scale flow and survey varying ionization and the angle between the upstream flow and magnetic field. We also include ideal magnetohydrodynamic (MHD) and hydrodynamic models. From our simulations, we identify hundreds of self-gravitating cores that form within 1 Myr, with masses M ~ 0.04-2.5 M ? and sizes L ~ 0.015-0.07 pc, consistent with observations of the peak of the core mass function. Median values are M = 0.47 M ? and L = 0.03 pc. Core masses and sizes do not depend on either the ionization or upstream magnetic field direction. In contrast, the mass-to-flux ratio does increase with lower ionization, from twice to four times the critical value. The higher mass-to-flux ratio for low ionization is the result of enhanced transient ambipolar diffusion when the shocked layer first forms. However, ambipolar diffusion is not necessary to form low-mass supercritical cores. For ideal MHD, we find similar masses to other cases. These masses are one to two orders of magnitude lower than the value M mag, sph = 0.007B 3/(G 3/2?2) that defines a magnetically supercritical sphere under post-shock ambient conditions. This discrepancy is the result of anisotropic contraction along field lines, which is clearly evident in both ideal MHD and diffusive simulations. We interpret our numerical findings using a simple scaling argument that suggests that gravitationally critical core masses will depend on the sound speed and mean turbulent pressure in a cloud, regardless of magnetic effects.

Chen, Che-Yu; Ostriker, Eve C.

2014-04-01

333

Heat diffusion The objective of this laboratory is for you to use measurements of the diffusion of heat in a material to  

E-print Network

Heat diffusion Objective The objective of this laboratory is for you to use measurements of the diffusion of heat in a material to enhance your understanding of solutions of the diffusion equation, is the thermal diffusivity, D=/C. The MKS units of diffusivity are m2 /s. We can get a rough idea of the time

Braun, Paul

334

An upregulation in the expression of vanilloid transient potential channels 2 enhances hypotonicity-induced cytosolic Ca²? rise in human induced pluripotent stem cell model of Hutchinson-Gillford Progeria.  

PubMed

Hutchinson-Gillford Progeria Syndrome (HGPS) is a fatal genetic disorder characterized by premature aging in multiple organs including the skin, musculoskeletal and cardiovascular systems. It is believed that an increased mechanosensitivity of HGPS cells is a causative factor for vascular cell death and vascular diseases in HGPS patients. However, the exact mechanism is unknown. Transient receptor potential (TRP) channels are cationic channels that can act as cellular sensors for mechanical stimuli. The aim of this present study was to examine the expression and functional role of TRP channels in human induced pluripotent stem cell-derived endothelial cells (iPSC-ECs) from the patients with HGPS. The mRNA and protein expression of TRP channels in HGPS and control (IMR90) iPSC-ECs were examined by semi-quantitative RT-PCRs and immunoblots, respectively. Hypotonicity-induced cytosolic Ca²? ([Ca²?](i)) rise in iPSC-ECs was measured by confocal microscopy. RT-PCRs and immunoblots showed higher expressional levels of TRPV2 in iPSC-ECs from HGPS patients than those from normal individuals. In functional studies, hypotonicity induced a transient [Ca²?](i) rise in iPSC-ECs from normal individuals but a sustained [Ca²?](i) elevation in iPSC-ECs from HGPS patients. A nonselective TRPV inhibitor, ruthenium red (RuR, 20 µM), and a specific TRPV2 channel inhibitor, tranilast (100 µM), abolished the sustained phase of hypotonicity-induced [Ca²?](i) rise in iPSC-ECs from HGPS patients, and also markedly attenuated the transient phase of the [Ca²?](i) rise in these cells. Importantly, a short 10 min hypotonicity treatment caused a substantial increase in caspase 8 activity in iPSC-ECs from HGPS patients but not in cells from normal individuals. Tranilast could also inhibit the hypotonicity-induced increase in caspase 8 activity. Taken together, our data suggest that an up-regulation in TRPV2 expression causes a sustained [Ca²?](i) elevation in HGPS-iPSC-ECs under hypotonicity, consequently resulting in apoptotic cell death. This mechanism may contribute to the pathogenesis of vascular diseases in HGPS patients. PMID:24475260

Lo, Chun-Yin; Tjong, Yung-Wui; Ho, Jenny Chung-Yee; Siu, Chung-Wah; Cheung, Sin-Ying; Tang, Nelson L; Yu, Shan; Tse, Hung-Fat; Yao, Xiaoqiang

2014-01-01

335

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

336

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

NASA Astrophysics Data System (ADS)

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

Zhang, Tao; Guo, Zhansheng

2014-03-01

337

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

338

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

339

Workshop on Radio Transients  

NASA Astrophysics Data System (ADS)

abstract-type="normal">SummaryWe are entering a new era in the study of variable and transient radio sources. This workshop discussed the instruments and the strategies employed to study those sources, how they are identified and classified, how results from different surveys can be compared, and how radio observations tie in with those at other wavelengths. The emphasis was on learning what common ground there is between the plethora of on-going projects, how methods and code can be shared, and how best practices regarding survey strategy could be adopted. The workshop featured the four topics below. Each topic commenced with a fairly brief introductory talk, which then developed into discussion. By way of preparation, participants had been invited to upload and discuss one slide per topic to a wiki ahead of the workshop. 1. Telescopes, instrumentation and survey strategy. New radio facilities and on-going projects (including upgrades) are both studying the variability of the radio sky, and searching for transients. The discussion first centred on the status of those facilities, and on projects with a time-domain focus, both ongoing and planned, before turning to factors driving choices of instrumentation, such as phased array versus single pixel feeds, the field of view, spatial and time resolution, frequency and bandwidth, depth, area, and cadence of the surveys. 2. Detection, pipelines, and classification. The workshop debated (a) the factors that influence decisions to study variability in the (u,v) plane, in images, or in catalogues, (b) whether, and how much, pipeline code could potentially be shared between one project and another, and which software packages are best for different approaches, (c) how data are stored and later accessed, and (d) how transients and variables are defined and classified. 3. Statistics, interpretation, and synthesis. It then discussed how (i) the choice of facility and strategy and (ii) detection and classification schemes influence what is seen (in terms of types of object and rates) by different surveys, (iii) how results from different surveys could be compared, and (iv) how what we know from existing surveys drives choices (i) and (ii), particularly as regards finding new classes of object. 4. Multiwavelength approaches. The workshop concluded by discussing what information is needed from wavelengths other than radio in order to classify transients and variables adequately and predict their rates as a function of topics (1), (2) and (3). It asked what the constraints are on responding to, and issuing triggers for, follow-up observations, and how that might feed back into considerations for designing our telescopes and surveys.

Croft, Steve; Gaensler, Bryan

2012-04-01

340

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

341

RTDD: A Real-Time Communication Protocol for Directed Diffusion  

Microsoft Academic Search

In this paper, we propose Real-Time Directed Diffusion (RTDD), a real-time communication protocol for directed diffusion. Using the mechanisms provided by directed diffusion, we implement a prioritized scheduling policy over diffusion. With just a few extensions, RTDD significantly enhances the directed diffusion protocol, allowing time-critical flows to delivery more packets on time. We also propose two new scheduling policies which

Kenan Casey; Raghu Neelisetti; Alvin Lim

2008-01-01

342

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

343

Atomic transient recorder.  

PubMed

In Bohr's model of the hydrogen atom, the electron takes about 150 attoseconds (1 as = 10(-18) s) to orbit around the proton, defining the characteristic timescale for dynamics in the electronic shell of atoms. Recording atomic transients in real time requires excitation and probing on this scale. The recent observation of single sub-femtosecond (1 fs = 10(-15) s) extreme ultraviolet (XUV) light pulses has stimulated the extension of techniques of femtochemistry into the attosecond regime. Here we demonstrate the generation and measurement of single 250-attosecond XUV pulses. We use these pulses to excite atoms, which in turn emit electrons. An intense, waveform-controlled, few cycle laser pulse obtains 'tomographic images' of the time-momentum distribution of the ejected electrons. Tomographic images of primary (photo)electrons yield accurate information of the duration and frequency sweep of the excitation pulse, whereas the same measurements on secondary (Auger) electrons will provide insight into the relaxation dynamics of the electronic shell following excitation. With the current approximately 750-nm laser probe and approximately 100-eV excitation, our transient recorder is capable of resolving atomic electron dynamics within the Bohr orbit time. PMID:14985755

Kienberger, R; Goulielmakis, E; Uiberacker, M; Baltuska, A; Yakovlev, V; Bammer, F; Scrinzi, A; Westerwalbesloh, Th; Kleineberg, U; Heinzmann, U; Drescher, M; Krausz, F

2004-02-26

344

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

345

Introduction Diffusion Tensor Imaging  

E-print Network

Introduction Diffusion Tensor Imaging Diffusion Kurtosis Imaging D-Eigenvalues and . . . Further ·Full Screen ·Close ·Quit Diffusion Tensor and Diffusion Kurtosis Tensor in Biomedical Engineering Diffusion Tensor Imaging Diffusion Kurtosis Imaging D-Eigenvalues and . . . Further Discussion Home Page

Zhang, Shuzhong

346

Fluid diffusion in porous silica  

NASA Astrophysics Data System (ADS)

Fluid motion in porous media has received a great deal of theoretical and experimental attention due to its importance in systems as diverse as ground water aquifers, catalytic processes, and size separation schemes. Often, the motion of interest is the random thermal motion of molecules in a fluid undergoing no net flow. This diffusive motion is particularly important when the size of the pores is nearly the same as the size of the molecules. In this study, fluid diffusion is measured in several varieties of porous silica whose pore structure is determined by the process by which it is made. The samples in this study have porosities (?, the ratio of the pore volume to the total sample volume) that vary from 0.3 to 0.75 and average pore radii that range from approximately 15 to 120 A. Determining the effect of the pore structure on the diffusion of a liquid in a porous material is complicated by the chemical interactions between the diffusing molecules and the pore surface. In this study, ions in a hydrophilic fluid are used to block the adsorption of the diffusing dye molecules to the hydroxyl groups covering the silica surface. This technique is unlike typical surface treatments of silica in that it does not permanently alter the pore geometry. In this work, fluid diffusion is measured with a transient holographic grating technique where interfering laser beams create a periodic refractive index modulation in the fluid. The diffraction of a third laser off this grating is monitored to determine how quickly the grating relaxes, thereby determining the diffusion coefficient of the molecules in the fluid. Varying the grating periodicity controls the length scale of the diffusion measurement from 1.2 to 100 ?m which is much larger than the average pore sizes of the samples. Therefore, over these large scales, we measure 'normal' diffusion, where the mean squared displacement of a diffusing particle varies linearly with time. In one particular type of porous silica, manufactured to create a narrow distribution of pore sizes in each sample, the normalized diffusion coefficient depends upon ? as D/Do~ (/phi - ?c)1.5, as ? approaches a critical porosity ? c. Here, D o and D are the diffusion coefficients of the free fluid and the fluid within the porous sample, respectively. This result is compared with predictions of diffusion on a percolating cluster of identical pores as well as with continuum models based on networks with a distribution of pore sizes. While diffusion in these materials might be expected to behave according to a continuum model of porous networks based on the aggregation of spherical particles (the 'Swiss-cheese' model), the behavior seen agrees with the prediction for networks whose smallest bonds have a non-singular distribution of conductances. This experiment is unique in that the materials chosen appear to produce a system that is close enough to the percolation threshold to allow a measurement of the percolation exponents. The diffusion coefficient in these samples is also shown to depend on the average pore radius as D/Do ~ (Rp - Rc)0.49 a result which, while unpredicted, is shown to be consistent with a previous study of fluid diffusion in silica.

McCann, Lowell I.

347

Stability of composite tape superconductors against transient thermal disturbances  

NASA Astrophysics Data System (ADS)

A tape conductor composed of Nb 3Sn and Cu is presented to illustrate conductor design based on magnetic stability criterion. The tape can carry an overall current density in excess of 300 A mm -2 in a magnetic field of 10 T. The influence of transient thermal disturbances on the stability of the tape conductor has been theoretically analysed. Two distinct processes characterize the recovery of a transient temperature rise. One is the cool-down of copper due to heat transfer to the coolant and the other is controlled by thermal diffusion in Nb 3Sn. These two processes lead to the conditions required for stability provided that disturbances are of a transient distributed nature. It is shown that these conditions are equivalent to a single criterion of the magnetic stability. The energy density of the maximum tolerable disturbance is also discussed.

Ogasawara, T.

348

Transient vibrational circular dichroism spectrometer: technical development  

NASA Astrophysics Data System (ADS)

We recently reported the first measurements of transient VCD in the C-H-stretch region following visible excitation of cobalt(-)-spartein complex (Co(sp)Cl2) with picosecond time resolution [1]. This poster presents the detailed description of the setup based on the synchronization of a femtosecond laser system with a photo elastic modulator [2]. A very precise control of the probe pulse polarization is a requirement to avoid linear dichroism artefacts. This is particularly important in crossed polarizer “quasi-null” technique which can be used to significantly enhance chiral signals [3].

Bonmarin, M.; Helbing, J.

2010-06-01

349

Increasing the dynamic range of a transient recorder by using two analog-to-digital converters  

Microsoft Academic Search

This article describes an algorithm for recording transient voltages with enhanced dynamic range by using two 8-bit analog-to-digital\\u000a converters (ADCs). The method requires each transient to be recorded in both ADCs, with different input voltage gains. The\\u000a transients then are compared and combined to produce a single signal that has less digitization noise and greater dynamic\\u000a range than signals recorded

Ronald C. Beavis

1996-01-01

350

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

351

Transient Conjugated Forced Convection in Turbulent Pipe Flows  

Microsoft Academic Search

This work deals with the problem of transient conjugated forced convection heat transfer in turbulent pipe flows. The external surface of the pipe over a finite heated section is subjected to either uniform heat flux or uniform wall temperature. The governing parameters indentified in this work are the Reynolds number Re, the wall-to-fluid conductivity ratio K, the wall-to-fluid diffusivity ratio

Kuan-Tzong Lee; Wei-Mon Yan

1995-01-01

352

Point defect concentration relaxation and creep transients in binary oxides  

Microsoft Academic Search

In non-stoichiometric oxides (NiO, CoO, Cu2O…) two thermodynamic parameters (temperature T and partial pression of oxygen Po2) are necessary in order to fix the population of point defects. When one of these two parameters (T or Po2) is suddenly changed and a physical property is continuously recorded, a “transient” can be observed due to the diffusion of the point defects

M. Jiménez-Melendo; A. Domínguez-Rodríguez; J. Castaing

1995-01-01

353

Nonmonotonic diffusion of particles among larger attractive crowding spheres.  

PubMed

We study the diffusive motion of particles among fixed spherical crowders. The diffusers interact with the crowders through a combination of a hard-core repulsion and a short-range attraction. The long-time effective diffusion coefficient of the diffusers is found to depend nonmonotonically on the strength of their attraction to the crowders. That is, for a given concentration of crowders, a weak attraction to the crowders enhances diffusion. We show that this counterintuitive fact can be understood in terms of the mesoscopic excess chemical potential landscape experienced by the diffuser. The roughness of this excess chemical potential landscape quantitatively captures the nonmonotonic dependence of the diffusion rate on the strength of crowder-diffuser attraction; thus, it is a purely static predictor of dynamic behavior. The mesoscopic view given here provides a unified explanation for enhanced diffusion effects that have been found in various systems of technological and biological interest. PMID:25302920

Putzel, Gregory Garbès; Tagliazucchi, Mario; Szleifer, Igal

2014-09-26

354

Nonmonotonic Diffusion of Particles Among Larger Attractive Crowding Spheres  

NASA Astrophysics Data System (ADS)

We study the diffusive motion of particles among fixed spherical crowders. The diffusers interact with the crowders through a combination of a hard-core repulsion and a short-range attraction. The long-time effective diffusion coefficient of the diffusers is found to depend nonmonotonically on the strength of their attraction to the crowders. That is, for a given concentration of crowders, a weak attraction to the crowders enhances diffusion. We show that this counterintuitive fact can be understood in terms of the mesoscopic excess chemical potential landscape experienced by the diffuser. The roughness of this excess chemical potential landscape quantitatively captures the nonmonotonic dependence of the diffusion rate on the strength of crowder-diffuser attraction; thus, it is a purely static predictor of dynamic behavior. The mesoscopic view given here provides a unified explanation for enhanced diffusion effects that have been found in various systems of technological and biological interest.

Putzel, Gregory Garbès; Tagliazucchi, Mario; Szleifer, Igal

2014-09-01

355

Summer 1993 Transient Student Report.  

ERIC Educational Resources Information Center

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

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

356

Original article Mannitol enhances intracellular calcium diffusion  

E-print Network

Cedex 03, France b Department of Biostructure and Function, University of Connecticut Health Center intracellular calcium will raise the effective intracellular gradient and thereby amplify intracellular calcium]. It has been known for many years that sugars like lactose, or polyols like sorbitol or mannitol, when

Paris-Sud XI, Université de

357

Substrate Catalysis Enhances Single-Enzyme Diffusion  

Microsoft Academic Search

Self-propulsion of micro- and nanoscale objects can be achieved by harnessing the chemical free energy of the environment through substrate catalysis. For example, we and others have demonstrated that energy arising from catalytic reactions can drive the movement of asymmetric particles on the micrometer and submicrometer length scales by self-electrophoresis, self-diffusiophoresis, and bubble propulsion. 1 Autonomous motion of symmetric colloidal

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

2010-01-01

358

A review on techniques for the extraction of transients in musical signals  

E-print Network

applications, let us mention : adaptive audio effects (enhancement of attacks [1], time-stretching[2 identification). Furthermore, transients are known to play an important role in the perception of musicA review on techniques for the extraction of transients in musical signals Laurent Daudet

Paris 7 - Denis Diderot, Université

359

Observations of large transient magnetospheric electric fields  

NASA Technical Reports Server (NTRS)

Transient electric field events were observed with the long, double probe instrumentation carried by the IMP-6 satellite. Nine, clearly defined, exceptionally large amplitude events are presented here. The events are observed in the midnight sector at geocentric distances 3.5 to .5.5 R sub e at middle latitudes within a magnetic L-shell range of 4.8 to 7.5. They usually have a total duration of one to several minutes, with peak power spectra amplitudes occurring at a frequency of about 0.3 Hz. The events occur under magnetically disturbed conditions, and in most cases they can be associated with negative dH/dt excursions at magnetic observatories located near the foot of the magnetic field line intersecting IMP-6. The magnetospheric motions calculated for these electric fields indicated a quasi-stochastical diffusive process rather than the general inward magnetospheric collapsing motion expected during the expansive phases of auroral substorm activity.

Aggson, T. L.; Heppner, J. P.

1977-01-01

360

Photoacoustic thermal diffusion flowmetry  

PubMed Central

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

2012-01-01

361

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

362

Thermophysical property testing using transient techniques  

NASA Astrophysics Data System (ADS)

Transient techniques were applied to the study of energetic materials (AP, HMX, RDX and HTPB) used in solid rocket fuel to carbon/carbon materials used as rocket nozzles. Studies on AP included single crystals, pressed powders and AP/HTPB mixtures. It was found that the conductivity of AP can be considered isotropic, even the orthrohombic phase. The conductivity values for pure AP calculated from the AP/HTPB mixtures were somewhat larger than those measured directly on single crystals due to imperfections in the relatively large single crystals. Conductivity values for Beta HMX obtained on pressed powders are believed to be 20% below those that would be obtained on good single crystals if they were available. Delta phase values are believed representative. Conductivity data useful for modeling AP/binder and HMX/binder fuel from RT to combustion were obtained. Successful techniques for determining in-situ conductivity values for carbon fibers and matrix in c/c composites were developed. The relative roles of the fibers and matrix in c/c subject to transient heat fluxes were delineated. The advantages of off-axis testing were revealed. Diffusivity values corresponding to thermal conductivity results could be obtained. The presence of a surface layer in which interconstituent thermal gradients are important and beyond which they are negligible was demonstrated.

Taylor, R. E.; Shoemaker, R. L.; Stark, J. A.; Koshigoe, L. G.

1984-06-01

363

LINEAR DIFFUSION Erkut Erdem  

E-print Network

LINEAR DIFFUSION Erkut Erdem Hacettepe University February 24th, 2012 CONTENTS 1 Linear Diffusion 1 2 Appendix - The Calculus of Variations 5 References 6 1 LINEAR DIFFUSION The linear diffusion (heat (noisy) input image and u(x, t) be initialized with u(x, 0) = u0(x) = f (x). Then, the linear diffusion

Erdem, Erkut

364

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

365

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

366

Transient monocular blindness.  

PubMed

An attack of abrupt loss of vision in one eye that recovers completely after a short period is called "transient monocular blindness" (TMB) or amaurosis fugax. The most common cause of TMB is atherothromboembolism from the origin of the internal carotid artery (ICA), whereas atrial fibrillation is quite uncommon. TMB also can be caused by anterior optic nerve ischemia, that is usually caused by thrombosis in the posterior ciliary artery. Thrombosis in the central retinal vein may be another cause. Dissection of the ICA, vascular malformations, or fibromuscular dysplasia are other potential etiologies. Blurring of vision as compared with blackened vision or positive phenomena such as flashing is probably associated with a higher risk of future cardiovascular events, whereas involvement of the partial monocular field is associated with a relative benign prognosis. In patients with atherosclerosis, antiplatelet therapy is indicated and treatment of vascular risk factors should have high priority. Carotid endarterectomy should be performed only in case of an ICA stenosis of more than 70% in the presence of at least one other risk factor for stroke. PMID:16833032

Kappelle, L J; Donders, R C J M; Algra, A

2006-01-01

367

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

368

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, Hsu-Chi (Albuquerque, NM); Cheng, Yung-Sung (Albuquerque, NM)

1984-08-07

369

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

370

Transient heat conduction in homogeneous and non-homogeneous materials by the Laplace transform Galerkin boundary element method  

Microsoft Academic Search

The Green's function for three-dimensional transient heat conduction (diffusion equation) for functionally graded materials (FGMs) is derived. The thermal conductivity and heat capacitance both vary exponentially in one coordinate. In the process of solving this diffusion problem numerically, a Laplace transform (LT) approach is used to eliminate the dependence on time. The fundamental solution in Laplace space is derived and

Alok Sutradhar; Glaucio H. Paulino; L. J. Gray

2002-01-01

371

Pregnancy-induced remodelling and enhanced endothelium-derived hyperpolarization-type vasodilator activity in rat uterine radial artery: transient receptor potential vanilloid type 4 channels, caveolae and myoendothelial gap junctions.  

PubMed

In pregnancy, the vasculature of the uterus undergoes rapid remodelling to increase blood flow and maintain perfusion to the fetus. The present study determines the distribution and density of caveolae, transient receptor potential vanilloid type 4 channels (TRPV4) and myoendothelial gap junctions, and the relative contribution of related endothelium-dependent vasodilator components in uterine radial arteries of control virgin non-pregnant and 20-day late-pregnant rats. The hypothesis examined is that specific components of endothelium-dependent vasodilator mechanisms are altered in pregnancy-related uterine radial artery remodelling. Conventional and serial section electron microscopy were used to determine the morphological characteristics of uterine radial arteries from control and pregnant rats. TRPV4 distribution and expression was examined using conventional confocal immunohistochemistry, and the contribution of endothelial TRPV4, nitric oxide (NO) and endothelium-derived hyperpolarization (EDH)-type activity determined using pressure myography with pharmacological intervention. Data show outward hypertrophic remodelling occurs in uterine radial arteries in pregnancy. Further, caveolae density in radial artery endothelium and smooth muscle from pregnant rats was significantly increased by ~94% and ~31%, respectively, compared with control, whereas caveolae density did not differ in endothelium compared with smooth muscle from control. Caveolae density was significantly higher by ~59% on the abluminal compared with the luminal surface of the endothelium in uterine radial artery of pregnant rats but did not differ at those surfaces in control. TRPV4 was present in endothelium and smooth muscle, but not associated with internal elastic lamina hole sites in radial arteries. TRPV4 fluorescence intensity was significantly increased in the endothelium and smooth muscle of radial artery of pregnant compared with control rats by ~2.6- and 5.5-fold, respectively. The TRPV4 signal was significantly higher in the endothelium compared with the smooth muscle in radial artery of both control and pregnant rats, by ~5.7- and 2.7-fold, respectively. Myoendothelial gap junction density was significantly decreased by ~37% in radial artery from pregnant compared with control rats. Pressure myography with pharmacological intervention showed that NO contributes ~80% and ~30%, and the EDH-type component ~20% and ~70% of the total endothelium-dependent vasodilator response in radial arteries of control and pregnant rats, respectively. TRPV4 plays a functional role in radial arteries, with a greater contribution in those from pregnant rats. The correlative association of increased TRPV4 and caveolae density and role of EDH-type activity in uterine radial artery of pregnant rats is suggestive of their causal relationship. The decreased myoendothelial gap junction density and lack of TRPV4 density at such sites is consistent with their having an integral, albeit complex, interactive role in uterine vascular signalling and remodelling in pregnancy. PMID:24128141

Senadheera, Sevvandi; Bertrand, Paul P; Grayson, T Hilton; Leader, Leo; Murphy, Timothy V; Sandow, Shaun L

2013-12-01

372

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

373

2, 267283, 2006 Transient simulations  

E-print Network

/267/2006/ © Author(s) 2006. This work is licensed under a Creative Commons License. Climate of the Past Discussions out multi-millennial transient simulations, for example of the last deglaciation. For pragmatic

Boyer, Edmond

374

Real-time observation of impurity diffusion in silicon nanowires.  

PubMed

Solid-state diffusion of the transition metal impurities, gold (Au), nickel (Ni), and copper (Cu), in silicon (Si) nanowires was studied by in situ transmission electron microscopy. Compared to diffusion in a bulk crystal, Au diffusion is extremely slow when the amount of metal is limited but significantly enhanced when an unlimited supply is available. Cu and Ni diffusion leads to rapid silicide formation but slows considerably with physical encapsulation by a volume-restricting carbon shell. PMID:21786784

Holmberg, Vincent C; Collier, Katharine A; Korgel, Brian A

2011-09-14

375

Diffusing Diffusivity: A Model for Anomalous, yet Brownian, Diffusion  

NASA Astrophysics Data System (ADS)

Wang et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 15160 (2009)] have found that in several systems the linear time dependence of the mean-square displacement (MSD) of diffusing colloidal particles, typical of normal diffusion, is accompanied by a non-Gaussian displacement distribution G(x ,t), with roughly exponential tails at short times, a situation they termed "anomalous yet Brownian" diffusion. The diversity of systems in which this is observed calls for a generic model. We present such a model where there is diffusivity memory but no direction memory in the particle trajectory, and we show that it leads to both a linear MSD and a non-Gaussian G(x ,t) at short times. In our model, the diffusivity is undergoing a (perhaps biased) random walk, hence the expression "diffusing diffusivity". G(x ,t) is predicted to be exactly exponential at short times if the distribution of diffusivities is itself exponential, but an exponential remains a good fit for a variety of diffusivity distributions. Moreover, our generic model can be modified to produce subdiffusion.

Chubynsky, Mykyta V.; Slater, Gary W.

2014-08-01

376

Diffusion of single particles in cellular media  

NASA Astrophysics Data System (ADS)

In this work we suggest a model for diffusion of particles in cellular media in which the walls of cells are characterized by strongly reduced permeability. Our analytical results are obtained for a regular system and confirmed also by extensive Monte Carlo simulations. They reveal several distinct regimes of diffusion behavior in time whereby an initially normal diffusion at very short times turns into a transient one at a characteristic crossover time ?S and later, after a period marked by another characteristic time ?L, returns to normal. At fixed permeability p of the cell walls we find that these crossover times scale as ?S~L2 and?L~L with the cell size L, whereas for L=const one has ?L~p-1. These transitions from Gaussian to transient behavior are analyzed by cumulants of the mean quartic displacement . Our results are valid for a regular arrangement of walls; however, we find generally that the course of the mean-square displacement with time is very similar to results obtained in the past for diffusion in disordered media. The frequency-dependent conductivity ?(?) shows that at low frequency the real and imaginary parts of ?(?) vary as ?2 and ?, respectively, while saturating at constant values for ?-->?. By measuring the dc and ac conductivity of charge carriers it becomes possible to determine both the size of the cells and the permeability of their walls.

Pereyra, Victor; Milchev, Andrey; Fleurov, Victor

1994-12-01

377

Diffusion coefficients of endogenous cytosolic proteins from rabbit skinned muscle fibers.  

PubMed

Efflux time courses of endogenous cytosolic proteins were obtained from rabbit psoas muscle fibers skinned in oil and transferred to physiological salt solution. Proteins were separated by gel electrophoresis and compared to load-matched standards for quantitative analysis. A radial diffusion model incorporating the dissociation and dissipation of supramolecular complexes accounts for an initial lag and subsequent efflux of glycolytic and glycogenolytic enzymes. The model includes terms representing protein crowding, myofilament lattice hindrance, and binding to the cytomatrix. Optimization algorithms returned estimates of the apparent diffusion coefficients, D(r,t), that were very low at the onset of diffusion (?10(-10) cm(2) s(-1)) but increased with time as cytosolic protein density, which was initially high, decreased. D(r,t) at later times ranged from 2.11 × 10(-7) cm(2) s(-1) (parvalbumin) to 0.20 × 10(-7) cm(2) s(-1) (phosphofructose kinase), values that are 3.6- to 12.3-fold lower than those predicted in bulk water. The low initial values are consistent with the presence of complexes in situ; the higher later values are consistent with molecular sieving and transient binding of dissociated proteins. Channeling of metabolic intermediates via enzyme complexes may enhance production of adenosine triphosphate at rates beyond that possible with randomly and/or sparsely distributed enzymes, thereby matching supply with demand. PMID:24559981

Carlson, Brian E; Vigoreaux, Jim O; Maughan, David W

2014-02-18

378

Molecular crowding affects diffusion and binding of nuclear proteins in heterochromatin and reveals the fractal organization of chromatin  

PubMed Central

The nucleus of eukaryotes is organized into functional compartments, the two most prominent being heterochromatin and nucleoli. These structures are highly enriched in DNA, proteins or RNA, and thus thought to be crowded. In vitro, molecular crowding induces volume exclusion, hinders diffusion and enhances association, but whether these effects are relevant in vivo remains unclear. Here, we establish that volume exclusion and diffusive hindrance occur in dense nuclear compartments by probing the diffusive behaviour of inert fluorescent tracers in living cells. We also demonstrate that chromatin-interacting proteins remain transiently trapped in heterochromatin due to crowding induced enhanced affinity. The kinetic signatures of these crowding consequences allow us to derive a fractal model of chromatin organization, which explains why the dynamics of soluble nuclear proteins are affected independently of their size. This model further shows that the fractal architecture differs between heterochromatin and euchromatin, and predicts that chromatin proteins use different target-search strategies in the two compartments. We propose that fractal crowding is a fundamental principle of nuclear organization, particularly of heterochromatin maintenance. PMID:19927119

Bancaud, Aurelien; Huet, Sebastien; Daigle, Nathalie; Mozziconacci, Julien; Beaudouin, Joel; Ellenberg, Jan

2009-01-01

379

A Switching Surge Transient Recording Device  

Microsoft Academic Search

A switching surge transient recording device has been designed, built, and tested which serves as a continuous, unattended monitor of power system switching transients. Rather than reproduce the transient waveform, the recorder senses and records the positive and negative peak magnitudes of the transient to within a 4.0 per unit overvoltage limit, the maximum positive and maximum negative rates of

Dean Perry; Richard Raupach; C. A. E. Uhlig

1968-01-01

380

Reaction-diffusion textures  

Microsoft Academic Search

We present a method for texture synthesis based on the simulation of a process of local nonlinear interaction, called reaction-diffusion, which has been proposed as a model of biological pattern formation. We extend traditional reaction-diffusion systems by allowing anisotropic and spatially non-uniform diffusion, as well as multiple competing directions of diffusion. We adapt reaction-diffusion system to the needs of computer

Andrew P. Witkin; Michael Kass

1991-01-01

381

OSCILLATORY HYDROMAGNETIC DOUBLE-DIFFUSIVE CONVECTION IN A POROUS ENCLOSURE  

Microsoft Academic Search

The transient behavior of hydromagnetic double diffusive convection of a binary gas mixture in a porous enclosure subject to opposing thermal and compositional buoyancie is investigated numerically by employing the SIMPLE algorithm. Effects of several important parameters on the heat and mass transfer characteristics are studied. The fluid motion is reduced with the application of the magnetic field. For Ra

Chung-jen Tseng; Chia-lin Tseng

382

Simulation of SBWR startup transient and stability  

SciTech Connect

The Simplified Boiling Water Reactor (SBWR) designed by General Electric is a natural circulation reactor with enhanced safety features for potential accidents. It has a strong coupling between power and flow in the reactor core, hence the neutronic coupling with thermal-hydraulics is specially important. The potential geysering instability during the early part of a SBWR startup at low flow, low power and low pressure is of particular concern. The RAMONA-4B computer code developed at Brookhaven National Laboratory (BNL) for the SBWR has been used to simulate a SBWR startup transient and evaluate its stability, using a simplified four-channel representation of the reactor core for the thermal-hydraulics. This transient was run for 20,000 sec (5.56 hrs) in order to cover the essential aspect of the SBWR startup. The simulation showed that the SBWR startup was a very challenging event to analyze as it required accurate modeling of the thermal-hydraulics at low pressures. This analysis did not show any geysering instability during the startup, following the startup procedure as proposed by GE.

Cheng, H.S.; Khan, H.J.; Rohatgi, U.S.

1998-06-01

383

Solute transport under steady and transient conditions in biodegraded municipal solid waste  

NASA Astrophysics Data System (ADS)

The transport of a conservative tracer (lithium) in a large (3.5 m3) undisturbed municipal solid waste sample has been investigated under steady and fully transient conditions using a simple model. The model comprises a kinematic wave approximation for water movement, presented in a previous paper, and a strict convective solute flux law. The waste medium is conceptualized as a three-domain system consisting of a mobile domain (channels), an immobile fast domain, and an immobile slow domain. The mobile domain constitutes only a minor fraction of the medium, and the access to the major part of medium is constrained by diffusive transport. Thus the system is in a state of physical nonequilibrium. The fast immobile domain is the part of the matrix which surrounds the channels and forms the boundary between the channels and the matrix. Owing to its exposure to mobile water, which enhances the biodegradation process, this domain is assumed to be more porous and loose in its structure and therefore to respond faster to a change in solute concentration in the mobile domain compared to the regions deep inside the matrix. The diffusive mass exchange between the domains is modeled with two first-order mass transfer expressions coupled in series. Under transient conditions the system will also be in a state of hydraulic nonequilibrium. Hydraulic gradients build up between the channel domain and the matrix in response to the water input events. The gradients will govern a reversible flow and convective transport between the domains, here represented as a source/sink term in the governing equation. The model has been used to interpret and compare the results from a steady state experiment and an unsteady state experiment. By solely adjusting the size of the fraction of the immobile fast domain that is active in transferring solute, the model is capable of accurately reproducing the measured outflow breakthrough curves for both the steady and unsteady state experiments. During transient conditions the fraction of the immobile fast domain that is active in transferring solute is found to be about 65% larger than that under steady state conditions. It is therefore concluded that the water input pattern governs the size of the fraction of the immobile fast domain which, in turn, governs the solute residence time in the solid waste. It can be concluded that the contaminant transport process in landfills is likely to be in a state of both physical, hydraulic, and chemical nonequilibrium. The transport process for a conservative solute is here shown to be dominated by convective transport in the channels and a fast diffusive mass exchange with the surrounding matrix. This may imply that the observed leachate quality from landfills mainly reflects the biochemical conditions in these regions. The water input pattern is of great importance for the transport process since it governs the size of the fraction of the immobile fast domain which is active in transferring solute. This may be the reason for leachate quality to be seasonally or water flux dependent, which has been observed in several investigations. The result also has a significant practical implication for efforts to enhance the biodegradation process in landfills by recycling of the leachate.

Bendz, David; Singh, Vijay P.

1999-08-01

384

On Transient Phenomena in the Cusp Ionosphere (Invited)  

NASA Astrophysics Data System (ADS)

In this presentation we will discuss transient phenomena in the cusp ionosphere. One decade ago we were fortunate to use the EISCAT Svalbard Radar to reveal the detailed flow pattern around transients in the dayside aurora, the Poleward Moving Auroral Forms (PMAFs). Using a combination of fast azimuth and elevation scans we detected a series of meso-scale features in the F-region polar ionosphere, including meso-scale flow channel events and polar cap patches of enhanced electron density. These features are believed to be signatures of Flux Transfer Events (FTEs) and transient reconnection at the dayside magnetopause. This year we have installed multi-constellation TEC and scintillation receivers at four locations in Svalbard to study what effect that ionospheric irregularities generated by the same processes have on GNSS navigation systems. Here we present initial measurements from a campaign in January 2013. Enhanced scintillation was observed when a PMAF intersected the signal path of several GNSS spacecraft. Now we know that dayside transients may also represent a space weather challenge for society.

Oksavik, K.; van der Meeren, C.; Moen, J. I.; Lester, M.

2013-12-01

385

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

386

Transient aero-thermal simulations for TMT  

NASA Astrophysics Data System (ADS)

Aero-thermal simulations are an integral part of the design process for the Thirty Meter Telescope (TMT). These simulations utilize Computational Solid-Fluid Dynamics (CSFD) to estimate wind jitter and blur, dome and mirror seeing, telescope pointing error due to thermal drift, and to predict thermal effects on performance of components such as the primary mirror segments. Design guidance obtained from these simulations is provided to the Telescope, Enclosure, Facilities and Adaptive Optics groups. Computational advances allow for model enhancements and inclusion of phenomena not previously resolved, such as transient effects on wind loading and thermal seeing due to vent operation while observing or long exposure effects, with potentially different flow patterns corresponding to the beginning and end of observation. Accurate knowledge of the Observatory aero-thermal environment will result in developing reliable look-up tables for effective open loop correction of key active optics system elements, and cost efficient operation of the Observatory.

Vogiatzis, Konstantinos

2014-08-01

387

A magnetohydrodynamic theory of coronal loop transients  

NASA Technical Reports Server (NTRS)

The physical and geometrical characteristics of solar coronal loop transients are described in an MHD model based on Archimedes' MHD buoyancy force. The theory was developed from interpretation of coronagraphic data, particularly from Skylab. The brightness of a loop is taken to indicate the electron density, and successive pictures reveal the electron enhancement in different columns. The forces which lift the loop off the sun surface are analyzed as an MHD buoyancy force affecting every mass element by imparting an inertial force necessary for heliocentrifugal motion. Thermal forces are responsible for transferring the ambient stress to the interior of the loop to begin the process. The kinematic and hydrostatic buoyancy overcome the gravitational force, and a flux rope can then curve upward, spiralling like a corkscrew with varying cross section around the unwinding solar magnetic field lines.

Yeh, T.

1982-01-01

388

Particle acceleration during interactions between transient ion foreshock phenomena and Earth's bow shock  

NASA Astrophysics Data System (ADS)

Foreshocks are regions upstream of supercritical astrophysical shock waves that are in communication with the shock via suprathermal charged particles that have been energized and reflected by the shock and are counter-streaming into the incident plasma. These regions form upstream of the quasi-parallel region of the shock, in which the angle between the magnetic field in the incident plasma and the shock normal direction is less than ~40 deg. The relative drift between the reflected suprathermal particles and the incident bulk flow is a source of free energy, which is capable of producing a variety of kinetic plasma instabilities and enhanced wave activity. Simulations and observations of Earth's and other planetary foreshocks have shown that large-scale transient phenomena can also develop due to nonlinear processes and interactions between foreshock particles and discontinuities in the incident solar wind. Several of these transient ion foreshock phenomena (TIFP), such as short large-amplitude magnetic structures (SLAMS), hot flow anomalies (HFAs), and foreshock bubbles (FBs), can result in the development of nonlinear wave activity and additional shocks upstream of the main bow shock. We present in situ observations, made by NASA's THEMIS mission, of ion and electron distributions from within and without SLAMS, HFAs, and FBs, examining the particle heating and acceleration taking place within those TIFP. The observations are compared to theoretical expectations for shock-drift acceleration, Fermi acceleration, and energy diffusion via wave-particle interactions. Our preliminary results show that SLAMS, HFAs, and FBs can be ideal particle accelerators. Finally, we develop an understanding for the upper energy limits for ion and electron acceleration in each of these TIFP at Earth's bow shock and use this to investigate how TIFP may accelerate particles at other astrophysical shocks, such as planetary and astrospherical bow shocks, shocks in stellar winds, and supernova shocks.

Turner, Drew; Angelopoulos, Vassilis; Wilson, Lynn; Hietala, Heli; Omidi, Nick; Masters, Adam

2014-05-01

389

CALIOP receiver transient response study  

NASA Astrophysics Data System (ADS)

The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), an instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), was operated as an atmospheric lidar system to study the impact of clouds and aerosols on the Earth's radiation budget and climate. This paper discusses the receiver transient response of the CALIOP instrument, which is useful for getting a reliable attenuated backscatter profile from CALIOP data products. The noise tail effect (slow decaying rate) of PMT and broadening effect of the low-pass filter are both considered in modeling of the receiver transient response. An analytical expression of the CALIOP transient response function was obtained by the least square fitting of lidar measurements from land surfaces.

Lu, Xiaomei; Hu, Yongxiang; Liu, Zhaoyan; Zeng, Shan; Trepte, Charles

2013-09-01

390

Three-dimensional transient temperature field model for laser annealing  

SciTech Connect

A three-dimensional transient temperature field model (TTFM) is proposed for the general problem of laser-induced out-of-equilibrium annealing of a bilayer device, which is made up of a bulk material covered by a transparent layer. The TTFM solves the moving-boundary problem with a deterministic relation between the interface velocity and temperature in contrast to preceding problem-dependent models, which use an interface-tracking heuristic algorithm. The TTFM is the first step to model many temperature-driven phenomena such as diffusion and segregation in laser annealing. Both computed transient temperature field and melted-zone dimensions of a SiO{sub 2}/Si example device, which is irradiated by a focused visible (532 nm) laser, are in very good agreement with experimental measurements.

Degorce, Jean-Yves; Gillet, Jean-Numa; Magny, Francois; Meunier, Michel [Department of Engineering Physics, Ecole Polytechnique de Montreal, Laser Processing Laboratory, C.P. 6079, succ. Centre-ville, Montreal, Quebec H3C 3A7 (Canada)

2005-02-01

391

Transient thermal stress problem for a circumferentially cracked hollow cylinder  

NASA Technical Reports Server (NTRS)

The transient thermal stress problem for a hollow elasticity cylinder containing an internal circumferential edge crack is considered. It is assumed that the problem is axisymmetric with regard to the crack geometry and the loading, and that the inertia effects are negligible. The problem is solved for a cylinder which is suddenly cooled from inside. First the transient temperature and stress distributions in an uncracked cylinder are calculated. By using the equal and opposite of this thermal stress as the crack surface traction in the isothermal cylinder the crack problem is then solved and the stress intensity factor is calculated. The numerical results are obtained as a function of the Fourier number tD/b(2) representing the time for various inner-to-outer radius ratios and relative crack depths, where D and b are respectively the coefficient of diffusivity and the outer radius of the cylinder.

Nied, H. F.; Erdogan, F.

1982-01-01

392

Analysis of the transient production of a thermally stimulated well  

SciTech Connect

This paper presents a simple mathematical model to predict the oil production rate from a cyclic-steam-stimulated well. The oil volume flowing from the cold zone is estimated by numerically solving the diffusivity equation governing the radial transient flow of a fluid with a small and constant compressibility for three outer boundary conditions-infinite medium, constant pressure, and no flow-corresponding to different reservoir types. At the interface between the cold and hot zones, pressure is calculated by means of the superposition principle. Numerical solutions give pressure distribution as a function of radius and time. They also allow assessment of the effects of transient flow and outer boundary conditions on oil production rate. The numerical response of a cycle of steam injection strongly depends on the outer boundary condition. Excellent agreement is found between model-calculated and observed field rates.

Bidner, M.S. (Univ. of Buenos Aires (AR)); Kostiria, H.M.; Vampa, V.C. (Univ. Nacional de la Plata (AR))

1990-11-01

393

On the Outbursts of Soft X-ray Transients  

E-print Network

We suggest a new scenario to explain the outburst light curves of black hole soft X-ray transients together with the secondary maximum and the bump seen on their decay phases. Our explanations are based on the disk instability models considering the effect of X-ray irradiation. The scenario is consistent with the observed X-ray delays by a few days with respect to the optical rise for both the main outburst and the later maxima. We test our scenario by numerically solving the disk diffusion equation. The obtained model curve fits well to the observed X-ray outburst photon flux curve of the black hole soft X-ray transient GS/GRS 1124-68, a typical representative of the four BH SXTs with very similar light curves.

Unal Ertan; M. Ali Alpar

2002-07-10

394

Studies of Transient Meteor Activity  

NASA Technical Reports Server (NTRS)

Meteoroids bombard Earth's atmosphere daily, but occasionally meteor rates increase to unusual high levels when Earth crosses the relatively fresh ejecta of comets. These transient events in meteor activity provide clues about the whereabouts of Earth-threatening long-period comets, the mechanisms of large-grain dust ejection from comets, and the particle composition and size distribution of the cometary ejecta. Observations of these transient events provide important insight in natural processes that determine the large grain dust environment of comets, in natural phenomena that were prevalent during the time of the origin of life, and in processes that determine the hazard of civilizations to large impacts and of man-made satellites to the periodic blizzard of small meteoroids. In this proposal, three tasks form a coherent program aimed at elucidating various aspects of meteor outbursts, with special reference to planetary astronomy and astrobiology. Task 1 was a ground-based effort to observe periods of transient meteor activity. This includes: (1) stereoscopic imaging of meteors during transient meteor events for measurements of particle size distribution, meteoroid orbital dispersions and fluxes; and (2) technical support for Global-MS-Net, a network of amateur-operated automatic counting stations for meteor reflections from commercial VHF radio and TV broadcasting stations, keeping a 24h vigil on the level of meteor activity for the detection of new meteor streams. Task 2 consisted of ground-based and satellite born spectroscopic observations of meteors and meteor trains during transient meteor events for measurements of elemental composition, the presence of organic matter in the meteoroids, and products generated by the interaction of the meteoroid with the atmosphere. Task 3 was an airborne effort to explore the 2000 Leonid meteor outbursts, which are anticipated to be the most significant of transient meteor activity events in the remainder of the agreement period. This includes technical support for a multi-instrument aircraft campaign, Leonid MAC.

Jenniskens, Peter M. M.

2002-01-01

395

Transient heat conduction in one-dimensional composite slab. A ‘natural’ analytic approach  

Microsoft Academic Search

The transient response of one-dimensional multilayered composite conducting slabs to sudden variations of the temperature of the surrounding fluid is analysed. The solution is obtained applying the method of separation of variables to the heat conduction partial differential equation. In separating the variables, the thermal diffusivity is retained on the side of the modified heat conduction equation where the time-dependent

F. de Monte

2000-01-01

396

Transient mantle convection on Venus: The paradoxical coexistence of highlands and coronae in the BAT region  

E-print Network

Transient mantle convection on Venus: The paradoxical coexistence of highlands and coronae on a timescale of thermal diffusion. Applied to Venus, our results support a hypothesis that the contemporaneous convection; Venus; coronae; highlands; mantle thermals and mantle plumes Earth and Planetary Science Letters

Jellinek, Mark

397

Groundwater recharge simulation under the steady-state and transient climate conditions  

Microsoft Academic Search

Groundwater recharge simulation under the steady-state and transient climate conditions Diffusive groundwater recharge is a vertical water flux through the water table, i.e. through the boundary between the unsaturated and saturated zones. This flux features temporal and spatial changes due to variations in the climatic conditions, landscape the state of vegetation, and the spatial variability of vadoze zone characteristics. In

S. Pozdniakov; N. Lykhina

2010-01-01

398

Robotic Optical Transient Search Experiment  

NSDL National Science Digital Library

Astronomers have observed a visible light emitted at the same time as a gamma-ray burst for the first time on January 27, 1999. The Robotic Optical Transient Search Experiment (ROTSE) Detects Simultaneous Gamma-Ray Burst Optical Counterpart, provides detailed information pertaining to this discovery and ROTSE research in general. ROTSE's objective is to search for "astrophysical optical transients on time scales of a fraction of a second to a few hours." This project is sponsored by Lawrence Livermore National Laboratory (LLNL) and the University of Michigan.

399

Transient analysis of multicavity klystrons  

SciTech Connect

We describe a model for analytic analysis of transients in multicavity klystron output power and phase. Cavities are modeled as resonant circuits, while bunching of the beam is modeled using linear space-charge wave theory. Our analysis has been implemented in a computer program which we use in designing multicavity klystrons with stable output power and phase. We present as examples transient analyses of a relativistic klystron using a magnetic pulse compression modulator, and of a conventional klystron designed to use phase shifting techniques for rf pulse compression. 14 refs., 4 figs.

Lavine, T.L.; Miller, R.H.; Morton, P.L.; Ruth, R.D.

1989-03-01

400

A Mathematical Analysis of Obstructed Diffusion within Skeletal Muscle  

PubMed Central

Abstract Molecules are transported through the myofilament lattice of skeletal muscle fibers during muscle activation. The myofilaments, along with the myosin heads, sarcoplasmic reticulum, t-tubules, and mitochondria, obstruct the diffusion of molecules through the muscle fiber. In this work, we studied the process of obstructed diffusion within the myofilament lattice using Monte Carlo simulation, level-set and homogenization theory. We found that these intracellular obstacles significantly reduce the diffusion of material through skeletal muscle and generate diffusion anisotropy that is consistent with experimentally observed slower diffusion in the radial than the longitudinal direction. Our model also predicts that protein size has a significant effect on the diffusion of material through muscle, which is consistent with experimental measurements. Protein diffusion on the myofilament lattice is also anomalous (i.e., it does not obey Brownian motion) for proteins that are close in size to the myofilament spacing. The obstructed transport of Ca2+ and ATP-bound Ca2+ through the myofilament lattice also generates smaller Ca2+ transients. In addition, we used homogenization theory to discover that the nonhomogeneous distribution in the troponin binding sites has no effect on the macroscopic Ca2+ dynamics. The nonuniform sarcoplasmic reticulum Ca2+-ATPase pump distribution also introduces small asymmetries in the myoplasmic Ca2+ transients. PMID:19527637

Shorten, P.R.; Sneyd, J.

2009-01-01

401

Diffusion Confusion 8 4 Problem set #4: Fun with diffusion  

E-print Network

Diffusion Confusion 8 4 Problem set #4: Fun with diffusion Today's thrill packed exercise will be to deal with diffusion and advection-diffusion in one dimension. All exercises here will be in Matlab-nicolson diffusion of a gaussian initial condition with dirichlet boundary conditions (Diffusion/diffusion cn

Spiegelman, Marc W.

402

Microfabricated diffusion source  

DOEpatents

A microfabricated diffusion source to provide for a controlled diffusion rate of a vapor comprises a porous reservoir formed in a substrate that can be filled with a liquid, a headspace cavity for evaporation of the vapor therein, a diffusion channel to provide a controlled diffusion of the vapor, and an outlet to release the vapor into a gas stream. The microfabricated diffusion source can provide a calibration standard for a microanalytical system. The microanalytical system with an integral diffusion source can be fabricated with microelectromechanical systems technologies.

Oborny, Michael C. (Albuquerque, NM); Frye-Mason, Gregory C. (Cedar Crest, NM); Manginell, Ronald P. (Albuquerque, NM)

2008-07-15

403

Sound Exposure Calculations for Transient Events and Other Improvements to an Acoustical Tactical Decision Aid  

Microsoft Academic Search

Recent enhancements to an acoustical tactical decision aid, called the Acoustic Battlefield Aid (ABFA), are described. ABFA predicts the effects of the atmosphere and local terrain on the performance of acoustical sensors, using advanced sound propagation models. Among the enhancements are: (1) sound-exposure and detection calculations for moving and transient sources, (2) new display capabilities including loading of vector-map features

D. K. Wilson; V. A. Nguyen; Nassy Srour; John Noble

2002-01-01

404

Transient attenuation in optical fibers  

SciTech Connect

Low and high energy pulsed electron beams were used to generate radiation-induced transient attenuation in high-OH, Suprasil core, PCS fibers, demonstrating the energy dependence of the radiation damage and recovery mechanisms. A radiation resistant low-OH fiber was studied and its performance contrasted to that of high-OH materials. Several fibers with differing core compositions were also studied.

Hopkins, A.A.; Kelly, R.E.; Looney, L.D.; Lyons, P.B.

1984-01-01

405

Detection of transient fluorine atoms  

SciTech Connect

A KrF eximer laser with a fluence of 50 mJ/cm/sup 2/ was used to photolyze either uranium hexafluoride or molecular fluorine, yielding a transient number density of fluorine atoms. The rise and decay of the atomic fluorine density was observed by transient absorption of a 25-..mu..m Pb-salt diode laser. To prevent the diode laser wavelength from drifting out of resonance with the atomic fluorine line, part of the beam was split off and sent through a microwave discharge fluorine atom cell. This allowed a wavelength modulation-feedback technique to be used to lock the diode laser wavelength onto the atomic line. The remaining diode laser beam was made collinear with the eximer laser beam using a LiF window with a 45/sup 0/ angle of incidence to reflect the infrared beam while transmitting most of the uv beam. Using this setup along with a transient digitizer to average between 100 and 200 transient absorption profiles, fluorine atom number densities on the order of 10/sup 14/ cm/sup -3/ in a 1.7 m pathlength were detected. The signals observed were about a factor of two less than expected from known photolysis and atomic fluorine absorption cross-sections. 2 refs., 4 figs.

Loge, G.W.; Nereson, N.; Fry, H.A.

1986-01-01

406

Gamma-ray line transients  

SciTech Connect

Early interpretations of the variability of the narrow 0.511 MeV annihilation line from the Galactic center (GC) were confused by the unrecognized presence of a very extended component (mid 70s-mid 80s). Transient behavior was suggested by comparisons of measurements made by instruments with comparable fields of view, and by detection of other lines which could be interpreted as broadened and Doppler-shifted versions of the line. A new generation of instruments (late 80s-early 90s) provided more compelling evidence, by improved imaging capability (identifying a known transient high-energy candidate source, 1E 1740.7-2942), and by improved sensitivity. Additional broadened, shifted, and Compton-scattered derivatives of the annihilation line were detected from this and other sources. At the same time, theoretical developments suggested exciting new physics which might arise in the accretion regimes around black holes, of which these features would be important diagnostics. In the GRO era the existence of such transient lines has been brought into question by the failure of long-term monitoring to detect them. A seemingly critical observation of the GC by three different instruments simultaneously, in which transient emission was detected only by one, provides the strongest evidence that the earlier results were in error. Recent developments in accretion disk theory have weakened the theoretical case for the lines. I draw conclusions concerning the nature of scientific inquiry and public outreach efforts in science.

Harris, Michael J. [USRA/GVSP, Code 661, NASA/Goddard Spaceflight Center, Greenbelt, Maryland 20771 (United States)

1997-05-10

407

Study of transient jet gases  

Microsoft Academic Search

This work involves the use of flash lamp schlieren and the development of flash lamp light slicing (planar imaging) and their employment in visualization of transient gas jets discharging into the atmosphere and the mixing that ensues. Details of the flash lamp light slicing system design are provided. Visualization of flows from a pulsed valve discharge system and a shock

Aaron Jaan Saber

1988-01-01

408

A high speed transient recorder  

Microsoft Academic Search

The paper describes how the design of a high-speed oscillograph may be modified to produce a near-linear recordable sweep of 10-8 sec duration. The techniques necessary to reproduce photographically single transients of this order are discussed.

D R Hardy

1952-01-01

409

Characterization of fast and slow diffusion from diffusion-weighted MRI of pediatric Crohn's disease  

PubMed Central

Purpose To characterize fast and slow diffusion components in Diffusion-weighted MRI (DW-MRI) of pediatric Crohn’s disease (CD). Overall diffusivity reduction as measured by the apparent diffusion coefficient (ADC) in patients with CD has been previously demonstrated. However, the ADC reduction may be due to changes in either fast or slow diffusion components. In this study we distinguished between the fast and slow diffusion components in the DW-MRI signal decay of pediatric CD. Materials and Methods We acquired MRI from 24 patients, including MR enterography (MRE) and DW-MRI with 8 b-values [0–800 s/mm2]. We characterized fast and slow diffusivity by intra-voxel incoherent motion (IVIM) model parameters (f, D*, D), and overall diffusivity by ADC values. We determined which model best described the DW-MRI signal decay. We assessed the influence of the IVIM model parameters on the ADC. We evaluated differences in model parameter values between the enhancing and non-enhancing groups. Results The IVIM model described the observed data significantly better than the ADC model (p=0.0088). The ADC was correlated with f (r=0.67, p=0.0003), but not with D (r=0.39, p=0.062) and D* (r=?0.39, p=0.057). f values were significantly lower (p<0.003) and D* values were significantly higher (p=0.03) in the enhancing segments, while D values were not significantly different between the groups (p=0.14). Conclusion For this study population, the IVIM model provides a better description of the DW-MRI signal decay than the ADC model. The reduced ADC is related to changes in the fast diffusion rather than to changes in the slow diffusion. PMID:22927342

Freiman, Moti; Perez-Rossello, Jeannette M.; Callahan, Michael J.; Bittman, Mark; Mulkern, Robert V.; Bousvaros, Athos; Warfield, Simon K.

2012-01-01

410

UPDATING APPLIED DIFFUSION MODELS  

EPA Science Inventory

Most diffusion models currently used in air quality applications are substantially out of date with understanding of turbulence and diffusion in the planetary boundary layer. Under a Cooperative Agreement with the Environmental Protection Agency, the American Meteorological Socie...

411

Effect of transients in nuclear fission on multiplicity of prescission neutrons  

E-print Network

Transients in the fission of highly excited nuclei are studied in the framework of the Langevin equation. Time-dependent fission widths are calculated which show that after the initial transients, a steady flow towards the scission point is established not only for nuclei which have fission barriers but also for nuclei which have no fission barrier. It is shown from a comparison of the transient time and the fission life time that fission changes from a diffusive to a transient dominated process over a certain transition region as a function of the spin of the fissioning nucleus. Multiplicities of prescission neutrons are calculated in a statistical model with as well as without a single swoop description of fission and they are found to differ in the transition region. We however find that the difference is marginal and hence a single swoop picture of fission though not strictly valid in the transition region can still be used in the statistical model calculations.

Gargi Chaudhuri; Santanu Pal

2002-04-19

412

Transient Anomalous Subdiffusion: Effects of Specific and Non-specific Probe Binding with Actin Gels  

PubMed Central

When signaling molecules diffuse through the cytosol they encounter a wide variety of obstacles that hinder their mobility in space and time. Some of those factors include, but are not limited to, interactions with mobile and immobile targets or obstacles. Besides finding a crowded environment inside the cell, macromolecules assemble into molecular complexes that drive specific biological functions adding additional complexity to their diffusion. Thus, simple models of diffusion often fail to explain mobility through the cell interior and new approaches are needed. Here we used fluorescent correlation spectroscopy to measure diffusion of three molecules of similar size with different surface properties diffusing in actin gels. The fluorescent probes were a) quantum dots, b) yellow-green fluorescent spheres and c) the ? isoform of Ca2+ calmodulin-dependent protein kinase II tagged with green fluorescent protein. We compared various models for fitting the autocorrelation function (ACF) including single component, two-component, and anomalous diffusion. The two-component and anomalous diffusion models were superior and were largely indistinguishable based on a goodness of fit criteria. To better resolve differences between these two models, we modified the ACF to observe temporal variations in diffusion. We found in both simulated and experimental data, a transient anomalous subdiffusion between two freely diffusing regimes produced by binding interactions of the diffusive tracers with actin gels. PMID:20038146

Sanabria, Hugo; Waxham, M. Neal

2010-01-01

413

Fundamental Modeling of Transient Enhanced Diusion through Extended Defect Evolution  

E-print Network

. Chakravarthi, I. Clejan, and S.T. Dunham Department of Electrical and Computer Engineering Boston University. These extended defects act to store excess interstitials generated by implantation, reducing the initial dopant/defect diusion. 2. MODEL FOR EXTENDED DEFECTS AND DOPANT DEACTIVATION 2.1. Energetics of the model

Dunham, Scott

414

Handbook on atmospheric diffusion  

SciTech Connect

Basic meteorological concepts are covered as well as plume rise, source effects, and diffusion models. Chapters are included on cooling tower plumes and urban diffusion. Suggestions are given for calculating diffusion in special situations, such as for instantaneous releases over complex terrain, over long distances, and during times when chemical reactions or dry or wet deposition are important. (PSB)

Hanna, S.R.; Briggs, G.A.; Hosker, R.P. Jr.

1982-01-01

415

The transient gamma-ray spectrometer  

NASA Astrophysics Data System (ADS)

The authors describe the Transient Gamma-Ray Spectrometer (TGRS) to be flown onboard the WIND spacecraft. This instrument is designed to detect cosmic gamma-ray bursts over the energy range of 20 keV to 10 MeV with an expected spectroscopic resolution of 2 keV at 1 MeV (E/Delta-E = 500). The active detection element is a 215-cu cm high-purity n-type Ge crystal cooled to cryogenic temperatures by a passive radiative cooler. The geometric field of view (FOV) defined by the cooler is 170 deg FWFM. Burst data are stored directly in an onboard 2.75-Mb burst memory with an absolute timing accuracy of +/-1.5 ms. This capacity is sufficient to store the entire spectral data set of all but the largest bursts. In addition to burst measurements, the instrument will also study solar flares, search for possible diffuse background lines, and monitor the 511-keV positron annihilation radiation from the galactic center. The experiment is scheduled to be launched on a Delta II launch vehicle from Cape Canaveral on December 31, 1992.

Owens, A.; Baker, R.; Cline, T. L.; Gehrels, N.; Jermakian, J.; Nolan, T.; Ramaty, R.; Smith, G.; Stilwell, D. E.; Teegarden, B. J.

1991-04-01