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1

Characteristic lengths affecting evaporative drying of porous media.

Evaporation from porous media involves mass and energy transport including phase change, vapor diffusion, and liquid flow, resulting in complex displacement patterns affecting drying rates. Force balance considering media properties yields characteristic lengths affecting the transition in the evaporation rate from a liquid-flow-based first stage limited only by vapor exchange with air to a second stage controlled by vapor diffusion through the medium. The characteristic lengths determine the extent of the hydraulically connected region between the receding drying front and evaporating surface (film region) and the onset of flow rate limitations through this film region. Water is displaced from large pores at the receding drying front to supply evaporation from hydraulically connected finer pores at the surface. Liquid flow is driven by a capillary pressure gradient spanned by the width of the pore size distribution and is sustained as long as the capillary gradient remains larger than gravitational forces and viscous dissipation. The maximum extent of the film region sustaining liquid flow is determined by a characteristic length L_{C} combining the gravity characteristic length L_{G} and viscous dissipation characteristic length L_{V} . We used two sands with particle sizes 0.1-0.5 mm ("fine") and 0.3-0.9 mm ("coarse") to measure the evaporation from columns of different lengths under various atmospheric evaporative demands. The value of L_{G} determined from capillary pressure-saturation relationships was 90 mm for the coarse sand and 140 mm for the fine sand. A significant decrease in drying rate occurred when the drying front reached the predicted L_{G} value (viscous dissipation was negligibly small in sand and L_{C} approximately L_{G} ). The approach enables a prediction of the duration of first-stage evaporation with the highest water losses from soil to the atmosphere. PMID:18643163

Lehmann, Peter; Assouline, Shmuel; Or, Dani

2008-05-01

2

Diffusion lengths in amphoteric GaAs heteroface solar cells

NASA Technical Reports Server (NTRS)

Minority-carrier diffusion lengths in amphoteric GaAs:Si were investigated. Electron and hole diffusion lengths in p- and n-type, respectively, were determined to be 13 microns and 7 microns. Preliminary efficiency measurements on heteroface structures based on amphoteric GaAs:Si p-n junctions indicated that these devices should make excellent solar cells.

Ashley, K. L.; Beal, S. W.

1978-01-01

3

Thirty years since diffuse sound reflection by maximum length

This year celebrates the 30th anniversary of Schroeder's seminal paper on sound scattering from maximum length sequences. This paper, along with Schroeder's subsequent publication on quadratic residue diffusers, broke new ground, because they contained simple recipes for designing diffusers with known acoustic performance. So, what has happened in the intervening years? As with most areas of engineering, the room acoustic

Trevor J. Cox; Peter D'Antonio

2005-01-01

4

Thirty years since diffuse sound reflection by maximum length

NASA Astrophysics Data System (ADS)

This year celebrates the 30th anniversary of Schroeder's seminal paper on sound scattering from maximum length sequences. This paper, along with Schroeder's subsequent publication on quadratic residue diffusers, broke new ground, because they contained simple recipes for designing diffusers with known acoustic performance. So, what has happened in the intervening years? As with most areas of engineering, the room acoustic diffuser has been greatly influenced by the rise of digital computing technologies. Numerical methods have become much more powerful, and this has enabled predictions of surface scattering to greater accuracy and for larger scale surfaces than previously possible. Architecture has also gone through a revolution where the forms of buildings have become more extreme and sculptural. Acoustic diffuser designs have had to keep pace with this to produce shapes and forms that are desirable to architects. To achieve this, design methodologies have moved away from Schroeder's simple equations to brute force optimization algorithms. This paper will look back at the past development of the modern diffuser, explaining how the principles of diffuser design have been devised and revised over the decades. The paper will also look at the present state-of-the art, and dreams for the future.

Cox, Trevor J.; D'Antonio, Peter

2005-09-01

5

Beta Irradiation of Silicon Junction Devices: Effects on Diffusion Length

The effects of electron irradiation on the minority carrier diffusion length in silicon devices has been studied by utilizing Pm-147 and Kr-85 beta sources. The beta spectra of Pm-147 and Kr-85 are characterized by maximum beta-particle energies of 230 and 670 kev, respectively. Short-circuit current for Li-doped p+n and n+p cells has been measured while the devices are continually irradiated.

L. C. Olsen

1972-01-01

6

NASA Astrophysics Data System (ADS)

Ion dynamics in lithium bismuth borate conducting glasses have been reported in wide composition and temperature ranges. The activation energy for the dc conduction has been analysed using Anderson-Stuart model and a correlation between the dc conductivity and the doorway radius has been predicted. The characteristic length scales for ion dynamics, such as mean square displacement and spatial extent of sub-diffusive motion of lithium ions have been determined from the ac conductivity and dielectric spectra, respectively. A direct connection between the ion dynamics and the characteristic length scales and the network structural units have been established.

Shaw, A.; Ghosh, A.

2013-09-01

7

NASA Technical Reports Server (NTRS)

Quantitative analysis of the electron beam-induced current and the dependence of the effective diffusion length of the minority carriers on the penetration depth of the electron beam were employed for the analysis of the carrier recombination characteristics in heavily doped silicon layers. The analysis is based on the concept of the effective excitation strength of the carriers which takes into consideration all possible recombination sources. Two dimensional mapping of the surface recombination velocity of P-diffused Si layers will be presented together with a three dimensional mapping of minority carrier lifetime in ion implanted Si. Layers heavily doped with As exhibit improved recombination characteristics as compared to those of the layers doped with P.

Gatos, H. C.; Watanabe, M.; Actor, G.

1977-01-01

8

Changes in diffusion path length with old age in diffuse optical tomography

NASA Astrophysics Data System (ADS)

Diffuse, optical near infrared imaging is increasingly being used in various neurocognitive contexts where changes in optical signals are interpreted through activation maps. Statistical population comparison of different age or clinical groups rely on the relative homogeneous distribution of measurements across subjects in order to infer changes in brain function. In the context of an increasing use of diffuse optical imaging with older adult populations, changes in tissue properties and anatomy with age adds additional confounds. Few studies investigated these changes with age. Duncan et al. measured the so-called diffusion path length factor (DPF) in a large population but did not explore beyond the age of 51 after which physiological and anatomical changes are expected to occur [Pediatr. Res. 39(5), 889-894 (1996)]. With increasing interest in studying the geriatric population with optical imaging, we studied changes in tissue properties in young and old subjects using both magnetic resonance imaging (MRI)-guided Monte-Carlo simulations and time-domain diffuse optical imaging. Our results, measured in the frontal cortex, show changes in DPF that are smaller than previously measured by Duncan et al. in a younger population. The origin of these changes are studied using simulations and experimental measures.

Bonnéry, Clément; Leclerc, Paul-Olivier; Desjardins, Michèle; Hoge, Rick; Bherer, Louis; Pouliot, Philippe; Lesage, Frédéric

2012-05-01

9

Gate control of the electron spin-diffusion length in semiconductor quantum wells

The spin diffusion length is a key parameter to describe the transport properties of spin polarized electrons in solids. Electrical spin injection in semiconductor structures, a major issue in spintronics, critically depends on this spin diffusion length. Gate control of the spin diffusion length could be of great importance for the operation of devices based on the electric field manipulation and transport of electron spin. Here we demonstrate that the spin diffusion length in a GaAs quantum well can be electrically controlled. Through the measurement of the spin diffusion coefficient by spin grating spectroscopy and of the spin relaxation time by time-resolved optical orientation experiments, we show that the diffusion length can be increased by more than 200% with an applied gate voltage of 5?V. These experiments allow at the same time the direct simultaneous measurements of both the Rashba and Dresselhaus spin-orbit splittings. PMID:24052071

Wang, G.; Liu, B. L.; Balocchi, A.; Renucci, P.; Zhu, C. R.; Amand, T.; Fontaine, C.; Marie, X.

2013-01-01

10

Infinite characteristic length on small-world systems

It was recently claimed that on d-dimensional small-world networks with a\\u000adensity p of shortcuts, the typical separation s(p) ~ p^{-1\\/d} between\\u000ashortcut-ends is a characteristic length for shortest-paths{cond-mat\\/9904419}.\\u000aThis contradicts an earlier argument suggesting that no finite characteristic\\u000alength can be defined for bilocal observables on these systems\\u000a{cont-mat\\/9903426}. We show analytically, and confirm by numerical simulation,\\u000athat shortest-path

Cristian F. Moukarzel; Marcio Argollo de Menezes

1999-01-01

11

NASA Astrophysics Data System (ADS)

Acids generated upon exposure to radiation induce the polarity change of the polymer through catalytic chain reactions in chemically amplified resists. With the reduction of feature size, the acid diffusion length increasingly becomes an important issue. In this study, we investigated the acid diffusion length in line-and-space patterns fabricated using a small field exposure tool for extreme ultraviolet (EUV) lithography and the EIDEC standard resist to clarify the acid diffusion length in a state-of-the-art resist. The acid diffusion length depended on the nominal line width and exposure dose. Upon exposure to EUV radiation with an exposure dose of 16 mJ cm-2, the acid diffusion length (three-dimensional) in a line-and-space pattern with 21 nm nominal line width was 9.5 nm.

Kozawa, Takahiro; Santillan, Julius Joseph; Itani, Toshiro

2013-07-01

12

Diffusion Correction to Slow Invariant Manifolds in a Short Length Scale Limit

Diffusion Correction to Slow Invariant Manifolds in a Short Length Scale Limit Joshua D. Mengers Abstract-- Slow Invariant Manifolds (SIM) are calculated for isothermal closed reaction-diffusion systems as a model reduction technique. Diffusion effects are examined using a Galerkin projection that rigorously

13

Diffusivity determination in bulk materials on nanometric length scales using neutron reflectometry

NASA Astrophysics Data System (ADS)

An approach based on neutron reflectometry and isotope heterostructures is presented in order to determine self-diffusivities in bulk materials on small length scales of 1-10 nm. The method is demonstrated for lithium self-diffusion in LiNbO3 single crystals at low temperatures of 200 and 250 °C using 6LiNbO3 (amorphous film)/natLiNbO3 (single crystal) structures for analysis. Lithium diffusivities are derived from neutron reflectivity patterns in good agreement with results obtained by secondary ion mass spectrometry on the same type of samples but on larger length scales up to 90 nm, as given in literature. In addition, neutron reflectivity simulations were performed in order to investigate the influence of diffusion length and scattering length density on the quality of the results. The limitation of the method is discussed.

Hüger, E.; Rahn, J.; Stahn, J.; Geue, T.; Schmidt, H.

2012-06-01

14

Characterizing Tumor Response to Chemotherapy at Various Length Scales Using Temporal Diffusion

Characterizing Tumor Response to Chemotherapy at Various Length Scales Using Temporal Diffusion biomarkers for monitoring tumor response to treatment. However, conventional pulsed-gradient spin echo (PGSE) were significantly lower in treated tumors, consistent with increased intracellular restrictions

Xu, Junzhong

15

Diffusion length damage coefficient and annealing studies in proton-irradiated InP

NASA Technical Reports Server (NTRS)

We report on the measurement of the diffusion length damage coefficient (K(sub L)) and the annealing characteristics of the minority carrier diffusion length (L(sub n)) in Czochralski-grown zinc-doped indium phosphide (InP), with a carrier concentration of 1 x 10(exp l8) cm(exp -3). In measuring K(sub L) irradiations were made with 0.5 MeV protons with fluences ranging from 1 x 10(exp 11) to 3 x 10(exp 13) cm(exp -2). Pre- and post-irradiation electron-beam induced current (EBIC) measurements allowed for the extraction of L(sub n) from which K(sub L) was determined. In studying the annealing characteristics of L(sub n) irradiations were made with 2 MeV protons with fluence of 5 x 10(exp 13) cm(exp -2). Post-irradiation studies of L(sub n) with time at room temperature, and with minority carrier photoinjection and forward-bias injection were carried out. The results showed that recovery under Air Mass Zero (AMO) photoinjection was complete. L(sub n) was also found to recover under forward-bias injection, where recovery was found to depend on the value of the injection current. However, no recovery of L(sub n) after proton irradiation was observed with time at room temperature, in contrast to the behavior of 1 MeV electron-irradiated InP solar cells reported previously.

Hakimzadeh, Roshanak; Vargas-Aburto, Carlos; Bailey, Sheila G.; Williams, Wendell

1993-01-01

16

SLOWING DOWN AND DIFFUSION LENGTHS OF NEUTRONS IN GRAPHITE-BISMUTH SYSTEMS

Exponential experiments were performed to measure the slowing down ; lengths and diffusion lengths of neutrons in graphite-bismuth lattices. The ; lattices were composed of graphite and bismuth bars, each approximately 1 x 1 x ; 24 in., with a small amount of aluminum foil, which will eventually be replaced ; by uranium foils for experiments related to neutron multiplication.

J. M. Hendrie; J. P. Phelps; G. A. Price; E. V. Weinstock

1958-01-01

17

Diffusion lengths in GaN obtained from steady state photocarrier gratings (SSPG)

NASA Astrophysics Data System (ADS)

We present diffusion length measurements in gallium nitride (GaN) and AlXGa1-XN/GaN multilayers with aluminium contents up to Xmax = 37 at.%. The opto-electrical method employed is the steady-state photocarrier grating (SSPG), which uses two interfering laser beams to induce a periodic resistivity modulation normal to the sense current lines. We experimentally refined the SSPG, using a double beamsplitter technique and introducing a variable ND filter. We measured diffusion lengths of single GaN and AlXGa1-XN/GaN double layers, and analysed the obtained diffusion lengths as function of the aluminium concentration, comparing them with the respective drift lengths. Finally, we critically discuss the common interpretation in terms of ambipolar transport. We suggest a new model in which minority carriers are rapidly trapped in acceptor-like valence band tails and participate in the grating blurring passively, as spatially localized recombination centres.

Niehus, M.; Schwarz, R.

2006-06-01

18

On the scaling of the visible lengths of jet diffusion flames

Length of jet diffusion flames is of direct importance in many industrial processes (e.g., in flaring applications in the petroleum industry) and is analyzed by applying scaling method directly to the governing partial differential equations. It is shown that for jet-momentum-dominated diffusion flames, when the buoyancy effects are neglected, the flame length normalized by the burner exit diameter increases linearly with the Reynolds number at the burner exit in the laminar burning regime and decreases in inverse proportion to the Reynolds number in the transitional regime. For turbulent diffusion flames, the normalized flame lengths are independent of the burner exit flow conditions. It is further found that for vertical upward flames, the buoyancy effect increases the flame length in the laminar and transitional regime and reduces the length in the turbulent regime; while for vertical downward flames, the buoyancy effect decreases the flame length in the laminar and transitional regime and increases the length in the turbulent regime, provided that jet momentum is dominated, and there is no flame spreading out and then burning upward like a downward-facing pool fire. Hence, for turbulent flames the flame lengths depend on the Froude number, Fr, and increase (or decrease) slightly as Fr increases for upward (or downward) flames. By comparison, it is found that the foregoing theoretical results are in good agreement with the experimental observations reported in literature.

Li, X. [Univ. of Victoria, British Columbia (Canada). Dept. of Mechanical Engineering

1996-06-01

19

Determination of spin diffusion length in Germanium by optical and electrical spin injection

NASA Astrophysics Data System (ADS)

We report on the measurements of spin diffusion length and lifetime in Germanium with both magneto-electro-optical and magneto-electrical techniques. Magneto-electro-optical measurements were made by optically inject in Fe/MgO/Ge spin-photodiodes a spin polarized population around the ? point of the Brillouin zone of Ge at different photon energies. The spin diffusion length is obtained by fitting by a mathematical model the photon energy dependence of the spin signal, due to switching of the light polarization from left to right, leading to a spin diffusion length of 0.9±0.2 ?m at room temperature. Non-local four-terminals and Hanle measurements performed on Fe/MgO/Ge lateral devices, at room temperature, instead lead to 1.2±0.2 ?m. The compatibility of these values among the different measurement methods validates the use all of all of them to determine the spin diffusion length in semiconductors. While electrical methods are well known in semiconductor spintronics, in this work we demonstrate that the optical pumping versus photon energy is an alternative and reliable method for the determination of the spin diffusion length whereas the band structure of the semiconductor allows for a non-negligible optical spin orientation.

Rinaldi, Christian; Bertoli, Stefano; Cantoni, Matteo; Manzoni, Cristian; Marangoni, Marco; Cerullo, Giulio; Bianchi, Massimiliano; Sordan, Roman; Bertacco, Riccardo

2014-08-01

20

Characteristic lengths for evaporation suppression from patchy porous surfaces

NASA Astrophysics Data System (ADS)

For non-uniformly wet porous surfaces, evaporation rates vary nonlinearly with mean surface water content and with the areal fraction of wet patches. The nonlinearity stems from the complex vapor field forming over individual pores and patches that could enhance vapor fluxes from pores surrounded by dry area (relative to fluxes from the same area of free water surface). The resulting evaporation rates from such a surface are similar to free water surface evaporation despite considerably lower evaporating area (low surface water content). Theoretically, such flux compensation could be suppressed by lumping isolated pores into clusters with equal mean water content. The resulting arrangement in wet patches ensures nearly 1D conditions within the patch and some flux enhancement at the periphery. The interplay between patch water content, patch size, and mean surface water content within a prescribed air flow boundary layer was modeled analytically using single pore diffusion as a building block. Results show existence of a characteristic cluster size that yields the largest evaporation suppression for a given boundary layer thickness and spacing between patches. For patches larger than this size, the relative evaporation rate from patchy surface (relative to free water surface evaporation) reaches a predictable rate equal to the fractional area of clusters. Model predictions for the relation between pore cluster size and evaporation suppression were evaluated numerically and in a series of wind tunnel experiments using porous surfaces with different pore clusters. The findings could be used for the design of optimal porous covers for suppressing evaporation losses from water reservoirs, or for controlling evaporative drying from engineered porous surfaces.

Lehmann, Peter; Or, Dani

2014-05-01

21

Measurements of apparent diffusion coefficient (ADC) using magnetic resonance imaging (MRI) have been suggested as potential imaging biomarkers for monitoring tumor response to treatment. However, conventional pulsed-gradient spin echo (PGSE) methods incorporate relatively long diffusion times, and are usually sensitive to changes in cell density and necrosis. Diffusion temporal spectroscopy using the oscillating gradient spin echo (OGSE) sequence is capable of probing short length scales, and may detect significant intracellular microstructural changes independent of gross cell density changes following anti-cancer treatment. To test this hypothesis, SW620 xenografts were treated by barasertib (AZD1152), a selective inhibitor of Aurora B kinase which causes SW620 cancer cells to develop polyploidy and increase in size following treatment, ultimately leading to cell death through apoptosis. Following treatment, the ADC values obtained by both the PGSE and low frequency OGSE methods increased. However, the ADC values at high gradient frequency (i.e. short diffusion times) were significantly lower in treated tumors, consistent with increased intracellular restrictions/hindrances. This suggests that ADC values at long diffusion times are dominated by tumor microstructure at long length scales, and may not convey unambiguous information of subcellular space. While the diffusion temporal spectroscopy provides more comprehensive means to probe tumor microstructure at various length scales. This work is the first study to probe intracellular microstructural variations due to polyploidy following treatment using diffusion MRI in vivo. It is also the first observation of post-treatment ADC changes occurring in opposite directions at short and long diffusion times. The current study suggests that temporal diffusion spectroscopy potentially provides pharmacodynamic biomarkers of tumor early response which distinguish microstructural variations following treatment at both the subcellular and supracellular length scales. PMID:22911846

Xu, Junzhong; Li, Ke; Smith, R. Adam; Waterton, John C.; Zhao, Ping; Chen, Heidi; Does, Mark D.; Manning, H. Charles; Gore, John C.

2012-01-01

22

Determination of the Pt spin diffusion length by spin-pumping and spin Hall effect

The spin diffusion length of Pt at room temperature and at 8 K is experimentally determined via spin pumping and spin Hall effect in permalloy/Pt bilayers. Voltages generated during excitation of ferromagnetic resonance from the inverse spin Hall effect and anisotropic magnetoresistance effect were investigated with a broadband approach. Varying the Pt layer thickness gives rise to an evolution of the voltage line shape due to the superposition of the above two effects. By studying the ratio of the two voltage components with the Pt layer thickness, the spin diffusion length of Pt can be directly extracted. We obtain a spin diffusion length of ?1.2 nm at room temperature and ?1.6 nm at 8 K.

Zhang, Wei; Pearson, John E.; Hoffmann, Axel [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Vlaminck, Vincent [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Colegio de Ciencias e Ingenería, Universidad San Fransciso de Quito, Quito (Ecuador); Divan, Ralu [Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States)] [Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States); Bader, Samuel D. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States) [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, Illinois 60439 (United States)

2013-12-09

23

NASA Technical Reports Server (NTRS)

A systematic and quantitative analysis is carried out to investigate the effects of the shape (point, cube, Gaussian) and size of the generation volume, the surface recombination velocity, and the diffusion length on the electron-beam-induced current (EBIC) and its derivative (DEIC). Thick homogeneously doped samples exhibiting diffusion lengths in the low micron and submicron range are considered. The results are presented in computed EBIC curves as a function of scanning distance and of the ratio true diffusion length/effective diffusion length. Shown using these curves are: (1) a simple and yet rigorous method for the determination of the true diffusion length, taking into consideration all of the factors cited above, (2) a method for the rapid determination of the surface recombination velocity, (3) the condition under which the source shape becomes insignificant, and (4) a new value for the lower limit of the diffusion length which can be determined by the EBOC technique.

Luke, K. L.; Von Roos, O.; Cheng, L.-J.

1985-01-01

24

Disconnected Glass-Glass Transitions and Diffusion Anomalies in a Model with Two Repulsive Length-coupling-theory calculations, we report a novel scenario for multiple glass tran- sitions in a purely repulsive spherical potential: the square shoulder. The liquid-glass transition lines exhibit both melting by cooling

Zaccarelli, Emanuela

25

National Technical Information Service (NTIS)

The temperature dependence of diffusion length for PU-BE neutrons in distilled water poisoned with boric acid was studied using concentrations of 1.0, 8.0, 16.0, and 30.0 grams per liter. Runs at each concentration were made at temperatures of 95, 131, an...

J. A. Frew

1970-01-01

26

Diffusion length measurements in solar cells: An analysis and comparison of techniques

NASA Technical Reports Server (NTRS)

A brief review of the major techniques for measuring minority carrier diffusion lengths in solar cells is given. Emphasis is placed on comparing limits of applicability for each method, especially as applied to silicon cells or to gallium arsenide cells, including the effects of radiation damage.

Woollam, J. A.; Khan, A. A.; Soukup, R. J.; Hermann, A. M.

1982-01-01

27

Soundproof characteristics of finite length orthotropic honeycomb shells

Acoustic radiation emanating from the walls of orthotropic honeycomb shells is studied analytically for the case of axisymmetric acoustic mode transmission within the shell. The shell has a finite vibrating length and is mounted on an infinite rigid baffle in a free field. The problem is studied on the basis of a shell theory in which it is assumed that

S. Chonan

1989-01-01

28

NASA Astrophysics Data System (ADS)

We have presented conductivity spectra at different temperatures for mixed network former silver borophosphate glasses. By mapping the conductivity spectra onto time dependence of the mean square displacement of mobile ions in the framework of linear response theory, we have obtained two characteristic lengths of ion dynamics viz characteristic mean square displacement at which crossover from diffusive to subdiffusive ion dynamics and spatial extent of localized motion of mobile silver ions occur. We have shown that the mixed network effect in these glasses is correlated to these characteristic lengths which are strongly influenced by the Coulomb repulsion between the mobile silver ions as well as the interaction between the mobile ions and the glass network.

Kabi, S.; Ghosh, A.

2012-10-01

29

Temporal scaling characteristics of diffusion as a new MRI contrast: Findings in rat hippocampus

Features of the diffusion-time dependence of the diffusion-weighted magnetic resonance imaging (MRI) signal provide a new contrast that could be altered by numerous biological processes and pathologies in tissue at microscopic length scales. An anomalous diffusion model, based on the theory of Brownian motion in fractal and disordered media, is used to characterize the temporal scaling (TS) characteristics of diffusion-related quantities, such as moments of the displacement and zero-displacement probabilities, in excised rat hippocampus specimens. To reduce the effect of noise in magnitude-valued MRI data, a novel numerical procedure was employed to yield accurate estimation of these quantities even when the signal falls below the noise floor. The power-law dependencies characterize the TS behavior in all regions of the rat hippocampus, providing unique information about its microscopic architecture. The relationship between the TS characteristics and diffusion anisotropy is investigated by examining the anisotropy of TS, and conversely, the TS of anisotropy. The findings suggest the robustness of the technique as well as the reproducibility of estimates. TS characteristics of the diffusion-weighted signals could be used as a new and useful marker of tissue microstructure. PMID:22306798

Ozarslan, Evren; Shepherd, Timothy M.; Koay, Cheng Guan; Blackband, Stephen J.; Basser, Peter J.

2012-01-01

30

Which range of structures contribute to light scattering in a continuous random media such as biological tissue? In this Letter, we present a model to study the structural length-scale sensitivity of scattering in continuous random media under the Born approximation. The scattering coefficient ?s, backscattering coefficient ?b, anisotropy factor g, and reduced scattering coefficient ?s? as well as the shape of the diffuse reflectance profile are calculated under this model. For media with a biologically relevant Henyey-Greenstein phase function with g ~ 0.93 at wavelength ? = 633 nm, we report that ?s? is sensitive to length-scales from 46.9 nm to 2.07 ?m (i.e. ?/13 to 3?), ?b is sensitive from 26.7 nm to 320 nm (i.e. ?/24 to ?/2), and the diffuse reflectance profile is sensitive from 30.8 nm to 2.71 ?m (i.e. ?/21 to 4?). PMID:23258058

Radosevich, Andrew J.; Yi, Ji; Rogers, Jeremy D.; Backman, Vadim

2013-01-01

31

Surface preparation for determining diffusion length by the surface photovoltage method

A method of treating the surface of a sample of n-type silicon material in preparation for measurements for determining the minority carrier diffusion length of the material by the surface photovoltage method comprises applying a strong oxidizing agent to an appropriately prepared surface of a semiconductor material such as silicon. The oxidizing agent is taken from the group consisting of potassium permanganate (KMnO/sub 4/), potassium dichromate (K/sub 2/Cr/sub 2/O/sub 7/), and ammonium dichromate ((NH/sub 4/)/sub 2/Cr/sub 2/O/sub 7/). The surface preparation assures a consistently large surface photovoltage that is stable during the surface photovoltage measurement for minority carrier diffusion length.

Goodman, A.M.

1985-03-26

32

Characteristic length of an AdS/CFT superconductor

We investigate in more detail the holographic model of a superconductor recently found by Hartnoll, Herzog, and Horowitz [Phys. Rev. Lett. 101, 031601], which is constructed from a condensate of a charged scalar field in AdS_4-Schwarzschild background. By analytically studying the perturbation of the gravitational system near the critical temperature T_c, we obtain the superconducting coherence length proportional to 1/\\sqrt{1-T/T_c} via AdS/CFT correspondence. By adding a small external homogeneous magnetic field to the system, we find that a stationary diamagnetic current proportional to the square of the order parameter is induced by the magnetic field. These results agree with Ginzburg-Landau theory and strongly support the idea that a superconductor can be described by a charged scalar field on a black hole via AdS/CFT duality.

Kengo Maeda; Takashi Okamura

2008-09-18

33

Minority carrier diffusion length and edge surface-recombination velocity in InP

NASA Technical Reports Server (NTRS)

A scanning electron microscope was used to obtain the electron-beam-induced current (EBIC) profiles in InP specimens containing a Schottky barrier perpendicular to the scanned (edge) surface. An independent technique was used to measure the edge surface-recombination velocity. These values were used in a fit of the experimental EBIC data with a theoretical expression for normalized EBIC (Donolato, 1982) to obtain the electron (minority carrier) diffusion length.

Hakimzadeh, Roshanak; Bailey, Sheila G.

1993-01-01

34

Method and apparatus for determining minority carrier diffusion length in semiconductors

Method and apparatus are provided for determining the diffusion length of minority carriers in semiconductor material, particularly amorphous silicon which has a significantly small minority carrier diffusion length using the constant-magnitude surface-photovoltage (SPV) method. An unmodulated illumination provides the light excitation on the surface of the material to generate the SPV. A manually controlled or automatic servo system maintains a constant predetermined value of the SPV. A vibrating Kelvin method-type probe electrode couples the SPV to a measurement system. The operating optical wavelength of an adjustable monochromator to compensate for the wavelength dependent sensitivity of a photodetector is selected to measure the illumination intensity (photon flux) on the silicon. Measurements of the relative photon flux for a plurality of wavelengths are plotted against the reciprocal of the optical absorption coefficient of the material. A linear plot of the data points is extrapolated to zero intensity. The negative intercept value on the reciprocal optical coefficient axis of the extrapolated linear plot is the diffusion length of the minority carriers.

Goldstein, Bernard (Princeton, NJ); Dresner, Joseph (Princeton, NJ); Szostak, Daniel J. (Mercerville, NJ)

1983-07-12

35

Improvement of carrier diffusion length in silicon nanowire arrays using atomic layer deposition

NASA Astrophysics Data System (ADS)

To achieve a high-efficiency silicon nanowire (SiNW) solar cell, surface passivation technique is very important because a SiNW array has a large surface area. We successfully prepared by atomic layer deposition (ALD) high-quality aluminum oxide (Al2O3) film for passivation on the whole surface of the SiNW arrays. The minority carrier lifetime of the Al2O3-depositedSiNW arrays with bulk silicon substrate was improved to 27 ?s at the optimum annealing condition. To remove the effect of bulk silicon, the effective diffusion length of minority carriers in the SiNW array was estimated by simple equations and a device simulator. As a result, it was revealed that the effective diffusion length in the SiNW arrays increased from 3.25 to 13.5 ?m by depositing Al2O3 and post-annealing at 400°C. This improvement of the diffusion length is very important for application to solar cells, and Al2O3 deposited by ALD is a promising passivation material for a structure with high aspect ratio such as SiNW arrays.

Kato, Shinya; Kurokawa, Yasuyoshi; Miyajima, Shinsuke; Watanabe, Yuya; Yamada, Akira; Ohta, Yoshimi; Niwa, Yusuke; Hirota, Masaki

2013-08-01

36

Improvement of carrier diffusion length in silicon nanowire arrays using atomic layer deposition.

To achieve a high-efficiency silicon nanowire (SiNW) solar cell, surface passivation technique is very important because a SiNW array has a large surface area. We successfully prepared by atomic layer deposition (ALD) high-quality aluminum oxide (Al2O3) film for passivation on the whole surface of the SiNW arrays. The minority carrier lifetime of the Al2O3-depositedSiNW arrays with bulk silicon substrate was improved to 27 ?s at the optimum annealing condition. To remove the effect of bulk silicon, the effective diffusion length of minority carriers in the SiNW array was estimated by simple equations and a device simulator. As a result, it was revealed that the effective diffusion length in the SiNW arrays increased from 3.25 to 13.5 ?m by depositing Al2O3 and post-annealing at 400°C. This improvement of the diffusion length is very important for application to solar cells, and Al2O3 deposited by ALD is a promising passivation material for a structure with high aspect ratio such as SiNW arrays. PMID:23968156

Kato, Shinya; Kurokawa, Yasuyoshi; Miyajima, Shinsuke; Watanabe, Yuya; Yamada, Akira; Ohta, Yoshimi; Niwa, Yusuke; Hirota, Masaki

2013-01-01

37

Finite gradient pulse lengths are traditionally considered a nuisance in q-space diffusion NMR and MRI, since the simple Fourier relation between the acquired signal and the displacement probability is invalidated. Increasing the value of the pulse length leads to an apparently smaller value of the estimated compartment size. We propose that q-space data at different gradient pulse lengths, but with

Carin Malmborg; Martin Sjöbeck; Sara Brockstedt; Elisabeth Englund; Olle Söderman; Daniel Topgaard

2006-01-01

38

Thermal diffusion of oligosaccharide solutions: the role of chain length and structure.

We investigated the chain length dependence of the thermodiffusion behavior of oligosaccharides by the infrared thermal diffusion forced Rayleigh scattering (IR-TDFRS) technique. Three disaccharides, sucrose, cellobiose and maltose, two trisaccharides, melezitose and raffinose, and a tetrasaccharide, stachyose, have been studied. We determined the thermal diffusion (D(T)), mass diffusion (D), and Soret (S(T)) coefficient as a function of temperature and concentration. While monosaccharides in water accumulate at the cold side in the investigated temperature (20-50 degrees C) and concentration (0.2-0.6667 wt) range, oligosaccharides enrich on the warm side with decreasing temperature or increasing sugar concentration. Additionally, we determined the kinematic viscosity (nu), the density (rho), and the thermal expansion coefficient (alpha) of the mixtures in order to check the linear correlation between D(T) and the ratio alpha/nu, which has been recently found for aqueous solutions of monosaccharides and for alkane mixtures. Finally, we found that D(T) and D decay with increasing chain length of the oligosaccharides in the whole studied range of temperatures, in contradiction with experimental results for nonpolar mixtures and theoretical predictions. PMID:20684655

Blanco, Pablo; Kriegs, Hartmut; Arlt, Bastian; Wiegand, Simone

2010-08-26

39

Introduction This study aims to identify whether patient-level or provider-level characteristics are most influential on a patient’s length of stay in the acute care hospital. Materials and Methods A dataset containing a nationally representative sample of inpatient discharge abstracts was used. Multi-level linear regression models were used to evaluate the associations between patient- and provider-level characteristics on patients’ lengths of stay. Results The target population included 322,894 discharges with a primary procedure code for primary total knee arthroplasty and 193,553 discharges for total hip arthroplasty. The variables associated with the greatest increases in length of stay were a higher co-morbidity level among patient level attributes (+17.4%) and low surgeon volume among provider-level characteristics (+18.8%). Discussion Provider-level characteristics, particularly provider volume, had a greater impact on length of stay. PMID:21277159

Styron, Joseph F.; Koroukian, Siran; Klika, Alison; Barsoum, Wael K.

2010-01-01

40

Indium phosphide (InP) solar cells are more radiation resistant than gallium arsenide (GaAs) and silicon (Si) solar cells, and their growth by heteroepitaxy offers additional advantages leading to the development of light weight, mechanically strong, and cost-effective cells. Changes in heteroepitaxial InP cell efficiency under 0.5- and 3-MeV proton irradiations have been explained by the variation in the minority-carrier diffusion length. The base diffusion length versus proton fluence was calculated by simulating the cell performance. The diffusion length damage coefficient, K[sub L], was also plotted as a function of proton fluence.

Jain, R.K.; Weinberg, I.; Flood, D.J.

1993-04-01

41

NASA Technical Reports Server (NTRS)

Diffusion lengths and surface recombination velocities were measured in GaAs diodes and InP finished solar cells. The basic technique used was charge collection microscopy, also known as electron beam induced current (EBIC). The normalized currents and distances from the pn junction were read directly from the calibrated curves obtained while using the line-scan mode in an SEM. These values were then equated to integral and infinite series expressions resulting from the solution of the diffusion equation with both extended-generation and point-generation functions. This expands previous work by examining both thin and thick samples. The surface recombination velocity was either treated as an unknown in a system of two equations or measured directly using low e(-) beam accelerating voltages. These techniques give accurate results by accounting for the effects of surface recombination and the finite size of the generation volume.

Leon, R. P.

1987-01-01

42

NASA Technical Reports Server (NTRS)

Diffusion lengths and surface recombination velocities were measured in GaAs diodes and InP finished solar cells. The basic techniques used was charge collection microscopy also known as electron beam induced current (EBIC). The normalized currents and distances from the pn junction were read directly from the calibrated curves obtained while using the line scan mode in an SEM. These values were then equated to integral and infinite series expressions resulting from the solution of the diffusion equation with both extended generation and point generation functions. This expands previous work by examining both thin and thick samples. The surface recombination velocity was either treated as an unknown in a system of two equations, or measured directly using low e(-) beam accelerating voltages. These techniques give accurate results by accounting for the effects of surface recombination and the finite size of the generation volume.

Leon, R. P.

1987-01-01

43

Cross-field diffusion in low-temperature plasma discharges of finite length

NASA Astrophysics Data System (ADS)

The long-standing problem of plasma diffusion across a magnetic field (B-field) is reviewed, with emphasis on low-temperature linear devices of finite length with the magnetic field aligned along an axis of symmetry. In these partially ionized plasmas, cross-field transport is dominated by ion–neutral collisions and can be treated simply with fluid equations. Nonetheless, electron confinement is complicated by sheath effects at the endplates, and these must be accounted for to get agreement with experiment. ).

Curreli, Davide; Chen, Francis F.

2014-12-01

44

Temperature dependence of diffusion length, lifetime and minority electron mobility in GaInP

The mobility of electrons in double heterostructures of p-type Ga{sub 0.50}In{sub 0.50}P has been determined by measuring minority carrier diffusion length and lifetime. The minority electron mobility increases monotonically from 300?K to 5?K, limited primarily by optical phonon and alloy scattering. Comparison to majority electron mobility over the same temperature range in comparably doped samples shows a significant reduction in ionized impurity scattering at lower temperatures, due to differences in interaction of repulsive versus attractive carriers with ionized dopant sites. These results should be useful in modeling and optimization for multi-junction solar cells and other optoelectronic devices.

Schultes, F. J.; Haegel, N. M., E-mail: nmhaegel@nps.edu [Physics Department, Naval Postgraduate School, Monterey, California 93943 (United States); Christian, T.; Alberi, K.; Fluegel, B. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States)] [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Jones-Albertus, R.; Pickett, E.; Liu, T.; Misra, P.; Sukiasyan, A.; Yuen, H. [Solar Junction, Inc., San Jose, California 95131 (United States)] [Solar Junction, Inc., San Jose, California 95131 (United States)

2013-12-09

45

Temperature dependence of diffusion length, lifetime and minority electron mobility in GaInP

NASA Astrophysics Data System (ADS)

The mobility of electrons in double heterostructures of p-type Ga0.50In0.50P has been determined by measuring minority carrier diffusion length and lifetime. The minority electron mobility increases monotonically from 300 K to 5 K, limited primarily by optical phonon and alloy scattering. Comparison to majority electron mobility over the same temperature range in comparably doped samples shows a significant reduction in ionized impurity scattering at lower temperatures, due to differences in interaction of repulsive versus attractive carriers with ionized dopant sites. These results should be useful in modeling and optimization for multi-junction solar cells and other optoelectronic devices.

Schultes, F. J.; Christian, T.; Jones-Albertus, R.; Pickett, E.; Alberi, K.; Fluegel, B.; Liu, T.; Misra, P.; Sukiasyan, A.; Yuen, H.; Haegel, N. M.

2013-12-01

46

Diffusion lengths in irradiated N/P InP-on-Si solar cells

NASA Technical Reports Server (NTRS)

Indium phosphide (InP) solar cells were made on silicon (Si) wafers (InP/Si) by to take advantage of both the radiation-hardness properties of the InP solar cell and the light weight and low cost of Si wafers. The InP/Si cell application is for long duration and/or high radiation orbit space missions. Spire has made N/P InP/Si cells of sizes up to 2 cm by 4 cm with beginning-of-life (BOL) AM0 efficiencies over 13% (one-sun, 28C). These InP/Si cells have higher absolute efficiency and power density after a high radiation dose than gallium arsenide (GaAs) or silicon (Si) solar cells after a fluence of about 2e15 1 MeV electrons/sq. cm. In this work, we investigate the minority carrier (electron) base diffusion lengths in the N/P InP/Si cells. A quantum efficiency model was constructed for a 12% BOL AM0 N/P InP/Si cell which agreed well with the absolutely measured quantum efficiency and the sun-simulator measured AM0 photocurrent (30.1 mA/sq. cm). This model was then used to generate a table of AM0 photocurrents for a range of base diffusion lengths. AM0 photocurrents were then measured for irradiations up to 7.7e16 1 MeV electrons/sq. cm (the 12% BOL cell was 8% after the final irradiation). By comparing the measured photocurrents with the predicted photocurrents, base diffusion lengths were assigned at each fluence level. A damage coefficient K of 4e-8 and a starting (unirradiated) base electron diffusion length of 0.8 microns fits the data well. The quantum efficiency was measured again at the end of the experiment to verify that the photocurrent predicted by the model (25.5 mA/sq. cm) agreed with the simulator-measured photocurrent after irradiation (25.7 mA/sq. cm).

Wojtczuk, Steven; Colerico, Claudia; Summers, Geoffrey P.; Walters, Robert J.; Burke, Edward A.

1996-01-01

47

National Technical Information Service (NTIS)

Electron Beam Induced Current (EBIC) measurements were performed on GaN nanowires to determine minority charge carrier diffusion length, Ld. Although EBIC has been used to characterize bulk and thin film materials, very little is known about near contact ...

C. P. Ong

2009-01-01

48

NASA Astrophysics Data System (ADS)

Finite gradient pulse lengths are traditionally considered a nuisance in q-space diffusion NMR and MRI, since the simple Fourier relation between the acquired signal and the displacement probability is invalidated. Increasing the value of the pulse length leads to an apparently smaller value of the estimated compartment size. We propose that q-space data at different gradient pulse lengths, but with the same effective diffusion time, can be used to identify and quantify components with free or restricted diffusion from multiexponential echo decay curves obtained on cellular systems. The method is demonstrated with experiments on excised human brain white matter and a series of model systems with well-defined free, restricted, and combined free and restricted diffusion behavior. Time-resolved diffusion MRI experiments are used to map the spatial distribution of the intracellular fraction in a yeast cell suspension during sedimentation, and observe the disappearance of this fraction after a heat treatment.

Malmborg, Carin; Sjöbeck, Martin; Brockstedt, Sara; Englund, Elisabeth; Söderman, Olle; Topgaard, Daniel

2006-06-01

49

Time-reversal Characteristics of Quantum Normal Diffusion

This paper concerns with the time-reversal characteristics of intrinsic normal diffusion in quantum systems. Time-reversible properties are quantified by the time-reversal test; the system evolved in the forward direction for a certain period is time-reversed for the same period after applying a small perturbation at the reversal time, and the separation between the time-reversed perturbed and unperturbed states is measured

Hiroaki S. Yamada; Kensuke S. Ikeda

2011-01-01

50

Flow distribution characteristics and control in marine gas turbine diffusers

The object of this study was to investigate flow distribution characteristics and control in the marine gas turbine diffusers most suitable for waste heat recovery systems. The major technical problems associated with nonuniform flow distributions in heat-exchanger or flow-equipment systems were reviewed. Various means to alleviate or minimize these undesirable problems were evaluated. Four sets of candidate flow-distribution data were

M. K. Ellingsworth; Ho-Tine Shu; S. C. Kuo

1984-01-01

51

NASA Astrophysics Data System (ADS)

Magnetic braking is essential for cloud contraction and star formation. Ambipolar diffusion is unavoidable in self-gravitating, magnetic clouds and leads to single-stage (as opposed to hierarchical) fragmentation (or core formation) and protostar formation. Magnetic forces dominate thermal-pressure and centrifugal forces over scales comparable to molecular cloud radii. Magnetic support of molecular clouds and the imperfect collisional coupling between charged and neutral particles introduce a critical magnetic length scale (?M,cr = 0.62?A?ff) and an Alfvén length scale ((?A = ??A?ni), respectively, in the problem which together with a critical thermal length scale (?T,cr = 1.09Ca?ff) explain naturally the formation of fragments (or cores) in otherwise quiescent clouds and determine the sizes and masses of these fragments during the subsequent stages of contraction. (The quantity ?A is the Alfvén speed, ?ni the mean neutral-ion collision time, Ca the adiabatic speed of sound, and ?ff the free4all time scale.) Numerical calculations based on new adaptive-grid techniques follow the formation of fragments by ambipolar diffusion and their subsequent collapse up to an enhancement in central density above its initial equilibrium value by a factor ?106 with excellent spatial resolution. The results confirm the existence and relevance of the three length scales and extend the analytical understanding of fragmentation and star formation derived from them. The ultimately bimodal opposition to gravity (by magnetic forces in the envelope and by thermal-pressure forces in the core) introduces a break in the slope of the log pn -log r profile. The relation Bc ? pkc between the magnetic field strength and the gas density in cloud cores holds with K = 0.4 - 0.5 even in the presence of ambipolar diffusion up to densities ˜109 cm-3 for a wide variety of clouds. The value K ? ½ is fairly typical. At the late stages of evolution, for example, at a central density of about 3 × 108 cm-3, a typical core is relatively uniform, contains 0.1 Msun and a magnetic field ? 3 mG, and is surrounded by a spatially rapidly decreasing, highly nonspherical (disklike) density distribution. The amount of mass available for accretion onto the compact core is limited by magnetic forces, and is typically ?1 Msun. These results are built into the detailed scenario for star formation described recently elsewhere.

Mouschovias, Telemachos Ch.

1991-05-01

52

NASA Astrophysics Data System (ADS)

We have studied the mixed network former effect on the dynamics of lithium ions in borotellurite glasses in wide composition and temperature ranges. The length scales of ion dynamics, such as characteristic mean square displacement and spatial extent of sub-diffusive motion of lithium ions have been determined from the ac conductivity and dielectric spectra, respectively, in the framework of linear response theory. The relative concentrations of different network structural units have been determined from the deconvolution of the FTIR spectra. A direct correlation between the ion dynamics and the characteristic length scales and the relative concentration of BO4 units has been established for different compositions of the borotellurite glasses.

Shaw, A.; Ghosh, A.

2014-10-01

53

Temporal evolution of characteristic length and fractal dimension for a non-Euclidean system

NASA Astrophysics Data System (ADS)

In order to understand some yet incomprehensible experimental observations on temporal evolution of characteristic length and fractal dimension of a dynamical system, a model simulation has been attempted. It has been shown that the present simulation corroborates well with the trend of the experimentally observed temporal evolutions of fractal dimension and characteristic length during light water hydration of calcium silicates ( C3S and C2S ) and ordinary Portland cement. The dynamical scaling of the scattering functions was found to be valid during hydration, particularly in intermediate and in late stages of hydration process.

Sen, D.; Mazumder, S.; Bahadur, J.

2009-04-01

54

Time-reversal Characteristics of Quantum Normal Diffusion

This paper concerns with the time-reversal characteristics of intrinsic\\u000anormal diffusion in quantum systems. Time-reversible properties are quantified\\u000aby the time-reversal test; the system evolved in the forward for a certain\\u000aperiod is time-reversed for the same period after applying a small\\u000aperturbation, and the separation between the time-reversed perturbed and\\u000aunperturbed states is measured as the function of perturbation

Hiroaki S. Yamada; Kensuke S. Ikeda

2011-01-01

55

Characteristics of Gaseous Diffusion Flames with High Temperature Combustion Air in Microgravity

NASA Technical Reports Server (NTRS)

The characteristics of gaseous diffusion flames have been obtained using high temperature combustion air under microgravity conditions. The time resolved flame images under free fall microgravity conditions were obtained from the video images obtained. The tests results reported here were conducted using propane as the fuel and about 1000 C combustion air. The burner included a 0.686 mm diameter central fuel jet injected into the surrounding high temperature combustion air. The fuel jet exit Reynolds number was 63. Several measurements were taken at different air preheats and fuel jet exit Reynolds number. The resulting hybrid color flame was found to be blue at the base of the flame followed by a yellow color flame. The length and width of flame during the entire free fall conditions has been examined. Also the relative flame length and width for blue and yellow portion of the flame has been examined under microgravity conditions. The results show that the flame length decreases and width increases with high air preheats in microgravity condition. In microgravity conditions the flame length is larger with normal temperature combustion air than high temperature air.

Ghaderi, M.; Gupta, A. K.

2003-01-01

56

A new method of determination of the minority carrier diffusion length (L) in the base region of an n[sup +]-p-p[sup +] silicon solar cell using the spectral response of the cell in a middle wavelength ([lambda]) range is presented. The minority carrier diffusion length (L) in the base region of an n[sup +]-p or n[sup +]-p-p[sup +] silicon solar cell has a profound effect on the solar cell performance. In this paper the authors report a new method of determination of diffusion length using the middle wavelength spectral response (MWSR) of the cell. It has been developed using a model of n[sup +]-p-p[sub +] silicon solar cells given by Singh and Jain and making some simplifying assumptions. It is equally applicable to cells with d/L > 2.5 and d/L < 2.5. In the following they give the theoretical basis of the method and present the result of the measurement of diffusion length of a few N[sup +]-p-p[sup +] silicon solar cells with d/L in the range 1.3--4.1 by using this method and the LWSR method.

Basu, P.K.; Singh, S.N.; Arora, N.K.; Chakravarty, B.C. (National Physical Lab., New Delhi (India))

1994-03-01

57

NASA Technical Reports Server (NTRS)

Accurate evaluations of diffusion lengths for heavily to moderately doped III-V semiconductors and/or radiation damaged solar cells have been made possible by using experimental and numerical techniques. The techniques employed were electron beam induced current and low voltage electron microscopy.

Leon, R. P.

1987-01-01

58

Measurement of the Minority Carrier Diffusion Length and Edge Surface-Recombination Velocity in InP.

National Technical Information Service (NTIS)

A scanning electron microscope (SEM) was used to measure the electron (minority carrier) diffusion length (L(sub n)) and the edge surface-recombination velocity (V(sub s)) in zinc-doped Czochralski-grown InP wafers. Electron-beam-induced current (EBIC) pr...

S. G. Bailey, R. Hakimzadeh

1993-01-01

59

Flow development and turbulence length scales within an annular gas turbine exhaust diffuser

This paper presents the experimental investigation of a scaled down model of a PGT10 gas turbine diffuser by Nuovo Pignone S.p.A. The model was designed to operate in geometric and Reynolds number similarity with the GT diffuser, and 24 guide vanes are mounted at inlet to reproduce typical inlet conditions of an industrial gas turbine diffuser. The PGT10 diffuser has

Stefano Ubertini; Umberto Desideri

2000-01-01

60

Background To analyze the longitudinal length accuracy of gross tumor volume (GTV) delineation with diffusion weighted magnetic resonance imaging for esophageal squamous cell carcinoma (SCC). Methods Forty-two patients from December 2011 to June 2012 with esophageal SCC who underwent radical surgery were analyzed. Routine computed tomography (CT) scan, T2-weighted MRI and diffusion weighted magnetic resonance imaging (DWI) were employed before surgery. Diffusion-sensitive gradient b-values were taken at 400, 600, and 800 s/mm2. Gross tumor volumes (GTV) were delineated using CT, T2-weighted MRI and DWI on different b-value images. GTV longitude length measured using the imaging modalities listed above was compared with pathologic lesion length to determine the most accurate imaging modality. CMS Xio radiotherapy planning system was used to fuse DWI scans and CT images to investigate the possibility of delineating GTV on fused images. Results The differences between the GTV length according to CT, T2-weighted MRI and pathology were 3.63?±?12.06 mm and 3.46?±?11.41 mm, respectively. When the diffusion-sensitive gradient b-value was 400, 600, and 800 s/mm2, the differences between the GTV length using DWI and pathology were 0.73?±?6.09 mm, -0.54?±?6.03 mm and ?1.58?±?5.71 mm, respectively. DWI scans and CT images were fused accurately using the radiotherapy planning system. GTV margins were depicted clearly on fused images. Conclusions DWI displays esophageal SCC lengths most precisely when compared with CT or regular MRI. DWI scans fused with CT images can be used to improve accuracy to delineate GTV in esophageal SCC. PMID:23829638

2013-01-01

61

NASA Astrophysics Data System (ADS)

Mass transfer characteristics of gas diffusion layer (GDL) are closely related to performance of polymer electrolyte fuel cells. Therefore, it is necessary to clarify the characteristics of water distribution relating to the microscopic conformation and oxygen diffusivity of GDL. A hybrid type carbon paper GDL with planar-distributed wettability is investigated for control of liquid water movement and distribution due to hydrophobic to hydrophilic areas that provide wettability differences in GDL and to achieve enhancement of both oxygen diffusion and moisture retention. Hybrid GDLs with different PTFE content were fabricated in an attempt to improve the oxygen diffusion characteristics. The effects of different PTFE contents on the oxygen diffusivity and water distribution were simultaneously measured and observed using galvanic cell oxygen absorber and X-ray radiography. The PTFE distribution was observed using scanning electron microscopy. The formation of oxygen diffusion paths was confirmed by X-ray radiography, where voids in the hybrid GDL were first formed in the hydrophobic regions and then spread to the untreated wetting region. Thus, the formation of oxygen diffusion paths enhanced the oxygen diffusion. In addition, the effects of local PTFE content in the hydrophobic region and the optimal amount of PTFE for hybrid GDL were elucidated.

Koresawa, Ryo; Utaka, Yoshio

2014-12-01

62

NASA Astrophysics Data System (ADS)

Experiments on leading-edge vortex (LEV) growth and detachment from a plunging profile have been conducted in a free-surface water tunnel. Direct-force and velocity-field measurements have been performed at a Reynolds number of Re = 10,000, a reduced frequency of k = 0.25, and a Strouhal number of St = 0.16, for three varying leading-edge geometries. The leading-edge shape is shown to influence the shear layer feeding the LEV, and thus to some extent the development of the LEV and associated flow topology. This effect in turn influences the arrival time of the rear (LEV) stagnation point at the trailing edge, which, once breached, constitutes a detachment of the LEV. It is found that despite minor phase changes in LEV detachment through leading-edge shape, the position of the trailing edge (chord length) should be chosen as the characteristic length scale for the vortex separation process.

Rival, David E.; Kriegseis, Jochen; Schaub, Pascal; Widmann, Alexander; Tropea, Cameron

2014-01-01

63

National Technical Information Service (NTIS)

We report values of minority carrier diffusion length in n-type 6H SiC measured using a planar Electron Beam Induced Current (EBIC) method. Values of hole diffusion length in defect free regions of n-type 6H SiC, with a doping concentration of 1.7El7 1/cu...

M. Tabib-Azar

1997-01-01

64

We have studied the mixed network former effect on the dynamics of lithium ions in borotellurite glasses in wide composition and temperature ranges. The length scales of ion dynamics, such as characteristic mean square displacement and spatial extent of sub-diffusive motion of lithium ions have been determined from the ac conductivity and dielectric spectra, respectively, in the framework of linear response theory. The relative concentrations of different network structural units have been determined from the deconvolution of the FTIR spectra. A direct correlation between the ion dynamics and the characteristic length scales and the relative concentration of BO4 units has been established for different compositions of the borotellurite glasses. PMID:25362322

Shaw, A; Ghosh, A

2014-10-28

65

Path-length-resolved diffusive particle dynamics in spectral-domain optical coherence tomography.

We describe a new method to measure the decorrelation rate of the optical coherence tomography (OCT) magnitude simultaneously in space and time. We measure the decorrelation rate of the OCT magnitude in a Fourier-domain OCT system for a large range of translational diffusion coefficients by varying the sphere diameter. The described method uses the sensitivity advantage of Fourier-domain OCT over time-domain OCT to increase the particle diffusion imaging speed by a factor of 200. By coherent gating, we reduce the contribution of multiple scattering to the detected signal, allowing a quantitative study of diffusive particle dynamics in high concentration samples. We demonstrate that this technique is well suited to image diffusive particle dynamics in samples with a complex geometry as we measure the morphology and diffusive particle dynamics simultaneously with both high spatial and high temporal resolution. PMID:21231201

Kalkman, J; Sprik, R; van Leeuwen, T G

2010-11-01

66

NASA Astrophysics Data System (ADS)

A method is proposed for measuring the diffusion length and surface recombination velocity of Interdigitated Back Contact (IBC) solar cells by means of a simple linear regression on experimental quantum efficiency values versus the inverse of the absorption coefficient. This method is extended to the case of Front Surface Field (FSF) solar cells. Under certain conditions, the real or the effective surface recombination velocity may be measured.

Verlinden, Pierre; Van de Wiele, Fernand

1985-03-01

67

We examine by molecular dynamics simulation the solubility of small apolar solutes in a solvent whose particles interact via the Jagla potential, a spherically symmetric ramp potential with two characteristic lengths: an impenetrable hard core and a penetrable soft core. The Jagla fluid has been recently shown to possess water-like structural, dynamic, and thermodynamic anomalies. We find that the solubility exhibits a minimum with respect to temperature at fixed pressure and thereby show that the Jagla fluid also displays water-like solvation thermodynamics. We further find low-temperature swelling of a hard-sphere chain dissolved in the Jagla fluid and relate this phenomenon to cold unfolding of globular proteins. Our results are consistent with the possibility that the presence of two characteristic lengths in the Jagla potential is a key feature of water-like solvation thermodynamics. The penetrable core becomes increasingly important at low temperatures, which favors the formation of low-density, open structures in the Jagla solvent. PMID:18077365

Buldyrev, Sergey V.; Kumar, Pradeep; Debenedetti, Pablo G.; Rossky, Peter J.; Stanley, H. Eugene

2007-01-01

68

Effect on fan flow characteristics of length and axial location of a cascade thrust reverser

NASA Technical Reports Server (NTRS)

A series of static tests were conducted on a model fan with a diameter of 14.0 cm to determine the fan operating characteristics, the inlet static pressure contours, the fan-exit total and static pressure contours, and the fan-exit pressure distortion parameters associated with the installation of a partial-circumferential-emission cascade thrust reverser. The tests variables included the cascade axial length, the axial location of the reverser, and the type of fan inlet. It was shown that significant total and static pressure distortions were produced in the fan aft duct, and that some configurations induced a static pressure distortion at the fan face. The amount of flow passed by the fan and the level of the flow distortions were dependent upon all the variables tested.

Dietrich, D. A.

1975-01-01

69

NASA Technical Reports Server (NTRS)

Minority-Carrier diffusion lengths of n-type 6H-SiC were measured using the electron-beam induced current (EBIC) technique. Experimental values of primary beam current, EBIC, and beam voltage were obtained for a variety of SIC samples. This data was used to calculate experimental diode efficiency vs. beam voltage curves. These curves were fit to theoretically calculated efficiency curves, and the diffusion length and metal layer thickness were extracted. The hole diffusion length in n-6H SiC ranged from 0.93 +/- 0.15 microns.

Hubbard, S. M.; Tabib-Azar, M.; Balley, S.; Rybickid, G.; Neudeck, P.; Raffaelle, R.

2004-01-01

70

NASA Astrophysics Data System (ADS)

The near-field electron beam induced current technique is used to study the minority carrier effective diffusion length versus electron beam energy on structures containing spherical Ge nanocrystals (NCs) with diameters of 50 nm and 70 nm formed by a two step dewetting/nucleation process. For both nanocrystal sizes, the effective diffusion length increases with the electron beam energy and then decreases from a threshold energy, which depends on the nanocrystal size. The effective diffusion length is smaller at low energy for NCs of larger size because of their larger surface recombination velocity, due to a better charge trapping efficiency.

Doan, Quang-Tri; El Hdiy, Abdelillah; Troyon, Michel

2011-07-01

71

Diffusion length variation and proton damage coefficients for InP/In(x)Ga(1-x)As/GaAs solar cells

NASA Technical Reports Server (NTRS)

Indium phosphide solar cells are more radiation resistant than gallium arsenide and silicon solar cells, and their growth by heteroepitaxy offers additional advantages leading to the development of lighter, mechanically strong and cost-effective cells. Changes in heteroepitaxial InP cell efficiency under 0.5 and 3 MeV proton irradiations are explained by the variation in the minority-carrier diffusion length. The base diffusion length versus proton fluence is calculated by simulating the cell performance. The diffusion length damage coefficient K(L) is plotted as a function of proton fluence.

Jain, R. K.; Weinberg, I.; Flood, D. J.

1993-01-01

72

PREDICTION OF CHARACTERISTIC LENGTH AND FRACTURE TOUGHNESS IN DUCTILE-BRITTLE TRANSITION

Finite element method was used to analyze the three-point bend experimental data of A533B-1 pressure vessel steel obtained by Sherry, Lidbury, and Beardsmore [1] from -160 to -45 C within the ductile-brittle transition regime. As many researchers have shown, the failure stress ({sigma}{sub f}) of the material could be approximated as a constant. The characteristic length, or the critical distance (r{sub c}) from the crack tip, at which {sigma}{sub f} is reached, is shown to be temperature dependent based on the crack tip stress field calculated by the finite element method. With the J-A{sub 2} two-parameter constraint theory in fracture mechanics, the fracture toughness (J{sub C} or K{sub JC}) can be expressed as a function of the constraint level (A{sub 2}) and the critical distance r{sub c}. This relationship is used to predict the fracture toughness of A533B-1 in the ductile-brittle transition regime with a constant {sigma}{sub f} and a set of temperature-dependent r{sub c}. It can be shown that the prediction agrees well with the test data for wide range of constraint levels from shallow cracks (a/W= 0.075) to deep cracks (a/W= 0.5), where a is the crack length and W is the specimen width.

Lam, P

2008-04-15

73

NASA Astrophysics Data System (ADS)

The supersonic biplane is well known as the airfoil that has zero wave drag at the supersonic speed. This paper investigates aerodynamic characteristics of the supersonic biplane with the finite span length and effects of the aspect and taper ratios by comparing with the two-dimensional supersonic biplane which has the infinite span length using the computational fluid dynamics. The rectangular wing was employed to examine the effect of the aspect ratio and tapered wing was employed to inspect the effect of the taper ratio. Both the rectangular wing and the two-dimensional supersonic biplane choke at the high angle of attack. The drag of the three-dimensional wing becomes smaller when it has a higher aspect ratio. The drag polar curve of the three-dimensional wing approaches asymptotically to the drag polar curve of the two-dimensional supersonic biplane when it has a higher taper ratio. The drag of the tapered wing becomes smaller when it has an adequate taper ratio.

Yonezawa, Masahito; Obayashi, Shigeru

74

The long-range diffusion coefficients of isoprenoid quinones in a model of lipid bilayer were determined by a method avoiding fluorescent probe labeling of the molecules. The quinone electron carriers were incorporated in supported dimyristoylphosphatidylcholine layers at physiological molar fractions (<3 mol%). The elaborate bilayer template contained a built-in gold electrode at which the redox molecules solubilized in the bilayer were reduced or oxidized. The lateral diffusion coefficient of a natural quinone like UQ10 or PQ9 was 2.0 +/- 0.4 x 10(-8) cm2 s(-1) at 30 degrees C, two to three times smaller than the diffusion coefficient of a lipid analog in the same artificial bilayer. The lateral mobilities of the oxidized or reduced forms could be determined separately and were found to be identical in the 4-13 pH range. For a series of isoprenoid quinones, UQ2 or PQ2 to UQ10, the diffusion coefficient exhibited a marked dependence on the length of the isoprenoid chain. The data fit very well the quantitative behavior predicted by a continuum fluid model in which the isoprenoid chains are taken as rigid particles moving in the less viscous part of the bilayer and rubbing against the more viscous layers of lipid heads. The present study supports the concept of a homogeneous pool of quinone located in the less viscous region of the bilayer. PMID:9545054

Marchal, D; Boireau, W; Laval, J M; Moiroux, J; Bourdillon, C

1998-01-01

75

Measurement of the minority carrier diffusion length and edge surface-recombination velocity in InP

NASA Technical Reports Server (NTRS)

A scanning electron microscope (SEM) was used to measure the electron (minority carrier) diffusion length (L(sub n)) and the edge surface-recombination velocity (V(sub s)) in zinc-doped Czochralski-grown InP wafers. Electron-beam-induced current (EBIC) profiles were obtained in specimens containing a Schottky barrier perpendicular to the scanned (edge) surface. An independent technique was used to measure V(sub s), and these values were used in a theoretical expression for normalized EBIC. A fit of the experimental data with this expression enabled us to determine L(sub n).

Bailey, Sheila G.; Hakimzadeh, Roshanak

1993-01-01

76

Ballistic versus diffusive base transport in the high-frequency characteristics of bipolar a universal character both in the diffusion limit ( W)Z,,) and the ballistic limit (I,,. IV). In the latter ("ballistic") limit Z& W, the second term in Eqs. (4) and (5) is negligible 2770 Appl. Phys. Lett. 60 (22), 1

Luryi, Serge

77

NASA Astrophysics Data System (ADS)

An innovative multilayer growth of InAs quantum dots on GaAs(100) is demonstrated to lead to self-aggregation of correlated quantum dot chains over mesoscopic distances. The fundamental idea is that at critical growth conditions is possible to drive the dot nucleation only at precise locations corresponding to the local minima of the Indium chemical potential. Differently from the known dot multilayers, where nucleation of new dots on top of the buried ones is driven by the surface strain originating from the dots below, here the spatial correlations and nucleation of additional dots are mostly dictated by a self-engineering of the surface occurring during the growth, close to the critical conditions for dot formation under the fixed oblique direction of the incoming As flux, that drives the In surface diffusion.

Placidi, E.; Arciprete, F.; Latini, V.; Latini, S.; Magri, R.; Scuderi, M.; Nicotra, G.; Patella, F.

2014-09-01

78

NASA Astrophysics Data System (ADS)

The characteristics of the voltage-induced metal insulator transition (MIT) of VO2 film devices are investigated as a function of ambient temperature and length. At the onset of voltage-induced MIT, an abrupt formation of a conduction channel is observed within the insulating phase. The carrier density of the device varies with ambient temperature (TA) and device length (L) across MIT. As the device length is reduced, a statistically random appearance of the conduction channel is observed. Our results suggest that the primary operation principles of the VO2 device can be chosen between Joule heating effect and the electric field effect.

Yoon, Joonseok; Lee, Giyong; Park, Changwoo; Mun, Bongjin Simon; Ju, Honglyoul

2014-08-01

79

NASA Technical Reports Server (NTRS)

An investigation was made in the Langley 300 MPH 7- by 10-foot tunnel to determine the aerodynamic characteristics of a flying-boat hull of a length-beam ratio of 15 in the presence of a wing. The investigation was an extension of previous tests made on hulls of length-beam ratios of 6, 9, and 12; these hulls were designed to have approximately the same hydrodynamic performance with respect to spray and resistance characteristics. Comparison with the previous investigation at lower length-beam ratios indicated a reduction in minimum drag coefficients of 0.0006 (10 peroent)with fixed transition when the length-beam ratio was extended from 12 to 15. As with the hulls of lower length-beam ratio, the drag reduction with a length-beam ratio of 15 occurred throughout the range of angle of attack tested and the angle of attack for minimum drag was in the range from 2deg to 3deg. Increasing the length-beam ratio from 12 to 15 reduced the hull longitudinal instability by an mount corresponding to an aerodynamic-center shift of about 1/2 percent of the mean aerodynamic chord of the hypothetical flying boat. At an angle of attack of 2deg, the value of the variation of yawing-moment coefficient with angle of yaw for a length-beam ratio of 15 was 0.00144, which was 0.00007 larger than the value for a length-beam ratio of 12.

Riebe, John M.; Naeseth, Rodger L.

1951-01-01

80

We report on the thermoelectric characteristics of p-type silicon nanowires (NWs) on plastics in the relatively low temperature regime below 47 °C, and for temperature differences of less than 10 K in ambient air. Thermal profile images are utilized to directly determine the temperature difference in the NWs generated by Joule heating in air. The Seebeck coefficient of the NWs increases from 294 to 414 ?V K(-1) as the NW length varies from 40 to 280 ?m. For a temperature difference of 7 K, the maximal Seebeck voltage can be estimated to be 2.7 mV for NWs with a length of 280 ?m. In contrast, the output power is maximized for NWs length of 240 ?m. The maximized output power obtained experimentally in this study is 2.1 pW at a temperature difference of 6 K. The thermoelectric characteristics are analyzed and discussed. PMID:24141226

Choi, Jinyong; Cho, Kyoungah; Kim, Sangsig

2013-11-15

81

Muscle length influences the contractile properties of muscle in that when muscle is lengthened the relaxation phase of the muscle twitch is prolonged and when muscle is shortened, the relaxation phase is shorter in duration. As a result, the force exerted by active motor units varies with muscle length during voluntary contractions. To determine if motoneuron spike trains were adjusted

D. W. Vander Linden; C. G. Kukulka; G. L. Soderberg

1991-01-01

82

The effects of operating temperature on an osmotic sucrose solution with a selected concentration pattern (30-50-70 °Brix) on mass transfer characteristics during the diffusion process in bilimbi fruits in a dehydration system were investigated. Half-ripe bilimbi fruits were used. In the pretreatment step, all fruits were blanched in boiling water for 1 min to soften the fruit for better diffusion.

Chairat SIRIPATANA

83

Morphologic characteristics and immunohistochemical profile of diffuse intrinsic pontine gliomas

Tumors of the CNS are the second most common malignancy in children. In particular, diffuse intrinsic pontine gliomas (DIPGs) are aggressive tumors with poor prognosis and account for 10–25% of pediatric brain tumors. The majority of DIPGs are astrocytic, infiltrative and localized to the pons. Studies have shown median survival times of less than a year with 90% of children dying within 2 years. We built multi-tissue arrays with 24 post-mortem DIPG samples and analyzed the morphology and expression of several proteins (p53, EGFR, GFAP, MIB1, BMI1, B-catenin, p16, Nanog, Nestin, OCT4, OLIG2, Sox2) with the goal of identifying potential treatment targets and improving our understanding of the biology of these tumors. The majority of DIPGs were high-grade gliomas (22) with 18 cases having features of glioblastoma (WHO grade IV), and 4 cases with high-grade features consistent with anaplastic astrocytoma (WHO grade-III). One case was low grade (WHO grade II) and one case showed intermediate features between a grade II and grade III glioma (low mitotic rate, but increased cellularity and cell atypia), being difficult to grade precisely.. The majority of the tumors were positive for GFAP (24/24), MIB1 (23/24), OLIG2 (22/24), p16 (20/24), p53 (20/24), Sox2 (19/24), EGFR (16/24) and BMI1 (9/24). Our results suggest that dysregulation of EGFR and p53 may play an important role in the development of DIPGs. The majority of DIPGs express stem cell makers such as SOX2 and OLIG2, consistent with a role for tumor stem cells in the origin and maintenance of these tumors. Targeted therapies against these proteins could be beneficial in treatment. PMID:24076776

Ballester, Leomar Y.; Wang, Zengfeng; Shandilya, Shaefali; Miettinen, Markku; Burger, Peter C.; Eberhart, Charles G.; Rodriguez, Fausto J.; Raabe, Eric; Nazarian, Javad; Warren, Katherine; Quezado, Martha M.

2013-01-01

84

Characteristics of methane diffusion flame in a reacting vortex ring

NASA Astrophysics Data System (ADS)

Direct numerical simulations of non-premixed methane flame vortex ring interactions are performed. The methane combustion was modelled using a detailed kinetic mechanism which consists of 36 species and 217 elementary reactions and involves C1, C2, and a small set of C3 kinetics. The vortex ring is generated by a brief discharge of cold fuel into a quiescent oxidizer ambient. The much higher oxidizer temperature leads to the auto-ignition of the vortex ring. The effects of fuel and oxidizer dilution and vortex ring strength on the dynamics of the interaction are studied. Three flame regions, front, top, and wake, are identified. Several combustion regimes are defined in the reacting vortex ring configuration. For the range of parameters accessible, unsteady, curvature and thickening effects on the flame structure are observed. Flame structure comparisons with steady counterflow diffusion flame (CFDF) results show that for a Damköhler number greater than 25, the unsteady effects on the flame become small. The contributions of time varying straining, fuel temperature and concentration to the unsteady effects on the front flame structure are separated through comparisons with unsteady CFDF simulations. For high initial Damköhler number simulations, none of these contributions are important since the flame becomes quasi-steady shortly after ignition. For intermediate initial Damköhler number simulations the unsteady effects are important at early times. At later times, a decrease in the straining and an increase in the fuel temperature reduce these effects. However, a decrease in the fuel concentration extends the duration for which the unsteady effects are important. If the initial Damköhler number is sufficiently low, the decrease in the fuel concentration overcomes the effects of straining and fuel temperature, and the flame remains unsteady for the entire simulation. Thickening and curvature effects on the flame structure are observed for the intermediate and low Damköhler number simulations. For runs with the flame close to the vortex ring, the curvature effects on the flame are important in the wake of the ring while the thickening effects are small. The curvature effects are small and the wake flame is thicker for the runs with the flame far from the ring. This article was chosen from Selected Proceedings of the Third International Symposium on Turbulence and Shear Flow Phenomena (Sendai, Japan, 24 27 June 2003) ed N Kasagi et al.

Safta, C.; Madnia, C. K.

2004-09-01

85

The purpose of the present study was to investigate muscle mechanical properties and mechanical interaction between muscles in the lower hindlimb of the spastic mutant rat. Length-force characteristics of gastrocnemius (GA), soleus (SO), and plantaris (PL) were assessed in anesthetized spastic and normally developed Han-Wistar rats. In addition, the extent of epimuscular myofascial force transmission between synergistic GA, SO, and PL, as well as between the calf muscles and antagonistic tibialis anterior (TA), was investigated. Active length-force curves of spastic GA and PL were narrower with a reduced maximal active force. In contrast, active length-force characteristics of spastic SO were similar to those of controls. In reference position (90° ankle and knee angle), higher resistance to ankle dorsiflexion and increased passive stiffness was found for the spastic calf muscle group. At optimum length, passive stiffness and passive force of spastic GA were decreased, whereas those of spastic SO were increased. No mechanical interaction between the calf muscles and TA was found. As GA was lengthened, force from SO and PL declined despite a constant muscle-tendon unit length of SO and PL. However, the extent of this interaction was not different in spastic rats. In conclusion, the effects of spasticity on length-force characteristics were muscle specific. The changes observed for GA and PL muscles are consistent with the changes in limb mechanics reported for human patients. Our results indicate that altered mechanics in spastic rats cannot be attributed to differences in mechanical interaction, but originate from individual muscular structures. PMID:25190742

Olesen, Annesofie T; Jensen, Bente R; Uhlendorf, Toni L; Cohen, Randy W; Baan, Guus C; Maas, Huub

2014-11-01

86

NASA Astrophysics Data System (ADS)

We have evaluated the diffusion length of minority carriers (holes) in single-crystalline n-type ?-FeSi2 bulk grown by chemical vapor transport by means of electron-beam-induced current (EBIC) technique in the edge-scan configuration. The EBIC line-scan data showed a clear exponential dependence of distance from the Al electrode. The diffusion length was estimated to be 20?m at room temperature, and increased upon high-temperature annealing, reaching approximately 30?m after annealing at 800°C for 8h. This result explained the improvement of photoresponsivity in the Al /n-?-FeSi2 Schottky diodes by high-temperature annealing.

Ootsuka, Teruhisa; Suemasu, Takashi; Chen, Jun; Sekiguchi, Takashi

2008-01-01

87

NASA Astrophysics Data System (ADS)

We have studied the influence of molecular beam epitaxy (MBE) of ?- FeSi films on minority-carrier diffusion length of an n-type Si(111) substrate. It was found from electron beam induced current technique that the diffusion length was less influenced in sample formed with a ?- FeSi template prior to the MBE growth than that in sample grown without the template. The size of ?- FeSi grains measured by electron back-scatter diffraction was also discussed.

Kawakami, H.; Suzuno, M.; Akutsu, K.; Chen, J.; Fuxing, Y.; Sekiguchi, T.; Suemasu, T.

88

Water Transport Characteristics of Gas Diffusion Layer in a PEM Fuel Cell

A presentation addressing the following: Water transport in PEM Fuel Cells - a DoE Project 1. Gas Diffusion Layer--Role and Characteristics 2. Capillary Pressure Determinations of GDL Media 3. Gas Permeability Measurements of GDL Media 4. Conclusions and Future Activities

Ashok S. Damle; J. Vernon Cole

2008-11-01

89

National Technical Information Service (NTIS)

Minority-Carrier diffusion lengths of n-type 6H-SiC were measured using the electron-beam induced current (EBIC) technique. Experimental values of primary beam current, EBIC, and beam voltage were obtained for a variety of SIC samples. This data was used ...

S. M. Hubbard, M. Tabib-Azar, S. Balley, G. Rybickid, P. Neudeck, R. Raffaelle

2004-01-01

90

Diffusion-weighted imaging characteristics of biopsy-proven demyelinating brain lesions

Objectives: To describe lesional diffusion-weighted imaging characteristics in a cohort of patients with biopsy-proven CNS inflammatory demyelinating disease (IDD) and compare diffusion characteristics of ring-enhancing CNS IDD lesions vs abscesses and tumors. Methods: Forty prebiopsy apparent diffusion coefficient (ADC) maps were reviewed from 30 patients with CNS IDD. Lesions were analyzed for size, T2-weighted (T2W) hypointense rim, enhancement, and ADC pattern. ADC patterns of CNS IDD ring-enhancing lesions were compared with a published cohort of 35 patients with ring-enhancing tumors and abscesses. Results: IDD lesions displayed a spectrum of peripheral ADC patterns at the lesion edge: restricted diffusion (low ADC), 33%; increased diffusion (high ADC), 60%; and normal diffusion (homogeneously isointense), 7%. Of biopsied lesions, 93% enhanced (ring, 52%; heterogeneous, 34%; homogeneous, 7%). A hypointense T2W rim was observed in 53%. A ring pattern on ADC (isointense or dark) was associated with T2W hypointense rims (p = 0.02) but not with ring enhancement. On serial imaging, 4 of 7 (57%) patients demonstrated changes in ADC patterns. Peripheral restriction was more common in IDD (p = 0.006) than in tumors or abscesses, whereas central restriction was only observed in abscesses. Restricted lesions in the same stage were more common in the non-IDD cohort (42% vs 20%), with a uniform restricted pattern seen only in abscesses. Conclusions: In ring-enhancing lesions, peripheral diffusion restriction is more common in IDD than in tumors/abscesses, whereas central restriction is more common among abscesses. Rapid ADC pattern changes in IDD probably reflect dynamic lesion evolution and may distinguish IDD from tumors. PMID:22573639

Abou Zeid, N.; Erickson, B.; Weigand, S.D.; Thomsen, K.M.; Scheithauer, B.; Parisi, J.E.; Giannini, C.; Linbo, L.

2012-01-01

91

Background An in-vitro setup was established in order to determine a) the diffusion activities of eight otic preparations (Aurizon®, Eas Otic®, Epi Otic®, Otifree®, Otomax®, Panolog®, Posatex®, Surolan®) through synthetic cerumen, and b) the ceruminolytic capacity and impregnation effects of these products. The main lipid classes of canine cerumen produced with moderate, non-purulent otitis externa were determined by thin layer chromatography and were subsequently used to produce a standardised synthetic cerumen (SCC). SCC was filled into capillary tubes, all of which were loaded with six commercially available multipurpose otic medications and two ear cleaners, each mixed with two markers in two experimental setups. These two marker compounds (Oil red O and marbofloxacin) were chosen, since they exhibit different physicochemical drug characteristics by which it is possible to determine and verify the diffusion activity of different types of liquids (i.e. the otic preparations). A synthetic cerumen described in the literature (JSL) was also used for comparison as its lipid composition was different to SCC. The diffusion activities of the otic preparations through both types of synthetic cerumen were studied over 24 hours. A second in-vitro experiment determined both the ceruminolytic activity and impregnation effect of the otic preparations by comparing the weight loss or weight gain after repeated incubation of JSL. Results Canine cerumen is mainly composed of triglycerides, sterol esters, fatty acid esters and squalene. The diffusion experiments showed a high diffusion efficacy along with a high impregnation effect for one test product. All the other products exhibited a lower diffusion activity with a mild to moderate impregnation effect. A mild ceruminolytic activity was observed for the two ear cleaners but not for any of the otic medications. Conclusions The present study demonstrates that there are significant differences in the diffusion characteristics and ceruminolytic properties of the eight tested otic preparations. PMID:23574753

2013-01-01

92

Channel characteristics analysis of diffuse indoor cellular optical wireless communication systems

NASA Astrophysics Data System (ADS)

In this paper, two models for diffuse indoor cellular optical wireless communication (OWC) systems with and without a holographic light shaping diffuser (LSD) are presented. For both models, the power distribution, the impulse response of the channels and root mean square (RMS) delay are described and analyzed. We perform a computer simulation to compare the channel characteristics of the typical indoor cellular OWC systems with that employing the holographic LSD. The results show that the system with the holographic LSD provides a more uniform power distribution and a less RMS delay spread for the same divergence angles.

Wu, D.; Ghassemlooy, Z.; Le-Minh, H.; Rajbhandari, S.; Chao, L.

2011-12-01

93

Diffusion characteristics of large molecules assessed by proton MRS on a whole-body MR system.

Methods for examinations of diffusion of large molecules of the size of fatty acids or triglycerides were developed for whole body MR units. Samples of aliphatic molecules were examined to study the influence of chain length. Feasibility under in vivo conditions was tested on lard samples at 37 degrees C and on human subjects Three stimulated echo sequences with maximum b-values of 2000 s/mm(2), 20000 s/mm(2), and 80000 s/mm(2) were used to assess a wide range of mobility. Sequence timing was optimized to minimize relaxation losses of fatty tissue. Apparent diffusion coefficients (ADC) were determined from five spectra with different diffusion weighting. In-vitro experiments were performed on butanol, decanol, and oleic acid to study the influence of chain length. In vivo conditions were mimicked using lard at 37 degrees C representing a composition of substances of various chain lengths. Subcutaneous fat and tibial bone marrow were studied in three healthy volunteers. ADC of muscular lipids of the lower leg was determined in two subjects. ADC values of pure aliphatic substances were in the range between 3.2 x 10(-5) mm(2)/s for oleic acid and 37.8 x 10(-5) mm(2)/s for butanol. In vivo investigations revealed ADC values of 1.11-1.24 x 10(-5) mm(2)/s for tibial bone marrow and 1.21-2.05 x 10(-5) mm(2)/s for subcutaneous fat. Diffusion coefficients of extra- and intramyocellular lipids were 1.83-3.65 x 10(-5) mm(2)/s and 2.22-3.60 x 10(-5) mm(2)/s, respectively. The proposed technique enables determination of ADC values of relatively large molecules and of lipid tissue compartments under in vivo conditions. Diffusion properties in several human lipid compartments are reported for the first time. Incoherent voxel motion influences the in vivo results to an unknown degree because of high motion sensitivity. In vitro experiments revealed ADC values depending on the chain length of the substances, indicating a residual dependence of measured ADC's on sequence timing. PMID:14972393

Lehnert, A; Machann, J; Helms, G; Claussen, C D; Schick, F

2004-01-01

94

NASA Astrophysics Data System (ADS)

One of the most accurate methods for measuring the compressibility of liquids is resonance measurement of sound velocity in a fixed-length interferometer. This method combines high sensitivity, accuracy, and small sample volume of the test liquid. The measuring principle is to study the resonance properties of a composite resonator that contains a test liquid sample. Ealier, the phase-locked loop (PLL) scheme was used for this. In this paper, we propose an alternative measurement scheme based on digital analysis of harmonic signals, describe the implementation of this scheme using commercially available data acquisition modules, and give examples of test measurements with accuracy evaluations of the results.

Astashev, M. E.; Belosludtsev, K. N.; Kharakoz, D. P.

2014-05-01

95

Photovoltaic characteristics of diffused P/+N bulk GaAs solar cells

NASA Technical Reports Server (NTRS)

The photovoltaic characteristics of P(+)N junction solar cells fabricated on bulk GaAs by an open tube diffusion technique are described in this paper.Spectral response measurements were analyzed in detail and compared to a computer simulation in order to determine important material parameters. It is projected that proper optimization of the cell parameters can increase the efficiency of the cells from 12.2 percent to close to 20 percent.

Borrego, J. M.; Keeney, R. P.; Bhat, I. B.; Bhat, K. N.; Sundaram, L. G.; Ghandhi, S. K.

1982-01-01

96

Photovoltaic characteristics of diffused P\\/sup +\\/N bulk GaAs solar cells

This paper describes the photovoltaic characteristics of P\\/sup +\\/N junction solar cells fabricated on bulk GaAs by an open tube diffusion technique. Spectral response measurements were analyzed in detail and compared to computer simulation in order to determine important material parameters. It is projected that proper optimization of the cell parameters can increase the efficiency of the cells from 12.2%

J. M. Borrego; I. B. Bhat; K. N. Bhat; S. K. Ghandhi; R. P. Kenney; L. Sundaram

1982-01-01

97

Photovoltaic characteristics of diffused P\\/+N bulk GaAs solar cells

The photovoltaic characteristics of P(+)N junction solar cells fabricated on bulk GaAs by an open tube diffusion technique are described in this paper.Spectral response measurements were analyzed in detail and compared to a computer simulation in order to determine important material parameters. It is projected that proper optimization of the cell parameters can increase the efficiency of the cells from

J. M. Borrego; R. P. Keeney; I. B. Bhat; K. N. Bhat; L. G. Sundaram; S. K. Ghandhi

1982-01-01

98

Radiant emission characteristics of isothermal diffuse cylindrical-inner-cone cavities

NASA Astrophysics Data System (ADS)

A new calculation of the local hemispherical effective emissivities along an isothermal diffuse cylindrical-inner-cone cavity has been made. Results are presented for cylindrical inner cones with dimensions such that the effective emissivities along the inner cones and the surface nearby are very close to unity. Comparison is made between Bedford-Ma techniques and the present method for a cone half-angle of 90 deg. Results show that high accuracy can be obtained with the method, especially for cavities with high surface emissivity, long cylinder length, and small aperture radius.

Chu, Z.; Chen, S.; Chen, H.

1980-10-01

99

Freezing lines of colloidal Yukawa spheres. II. Local structure and characteristic lengths

NASA Astrophysics Data System (ADS)

Using the Rogers-Young (RY) integral equation scheme for the static pair correlation functions combined with the liquid-phase Hansen-Verlet freezing rule, we study the generic behavior of the radial distribution function and static structure factor of monodisperse charge-stabilized suspensions with Yukawa-type repulsive particle interactions at freezing. In a related article, labeled Paper I [J. Gapinski, G. Nägele, and A. Patkowski, J. Chem. Phys. 136, 024507 (2012)], this hybrid method was used to determine two-parameter freezing lines for experimentally controllable parameters, characteristic of suspensions of charged silica spheres in dimethylformamide. A universal scaling of the RY radial distribution function maximum is shown to apply to the liquid-bcc and liquid-fcc segments of the universal freezing line. A thorough analysis is made of the behavior of characteristic distances and wavenumbers, next-neighbor particle coordination numbers, osmotic compressibility factor, and the Ravaché-Mountain-Streett minimum-maximum radial distribution function ratio.

Gapinski, Jacek; Nägele, Gerhard; Patkowski, Adam

2014-09-01

100

Freezing lines of colloidal Yukawa spheres. II. Local structure and characteristic lengths.

Using the Rogers-Young (RY) integral equation scheme for the static pair correlation functions combined with the liquid-phase Hansen-Verlet freezing rule, we study the generic behavior of the radial distribution function and static structure factor of monodisperse charge-stabilized suspensions with Yukawa-type repulsive particle interactions at freezing. In a related article, labeled Paper I [J. Gapinski, G. Nägele, and A. Patkowski, J. Chem. Phys. 136, 024507 (2012)], this hybrid method was used to determine two-parameter freezing lines for experimentally controllable parameters, characteristic of suspensions of charged silica spheres in dimethylformamide. A universal scaling of the RY radial distribution function maximum is shown to apply to the liquid-bcc and liquid-fcc segments of the universal freezing line. A thorough analysis is made of the behavior of characteristic distances and wavenumbers, next-neighbor particle coordination numbers, osmotic compressibility factor, and the Ravaché-Mountain-Streett minimum-maximum radial distribution function ratio. PMID:25273449

Gapinski, Jacek; Nägele, Gerhard; Patkowski, Adam

2014-09-28

101

NASA Astrophysics Data System (ADS)

The vegetation canopy has a significant impact on various physical and biological processes such as forest microclimate, rainfall evaporation distribution and climate change. Most scaled laboratory experimental studies have used canopy element models that consist of rigid vertical strips or cylindrical rods that can be typically represented through only one or a few characteristic length scales, for example the diameter and height for cylindrical rods. However, most natural canopies and vegetation are highly multi-scale with branches and sub-branches, covering a wide range of length scales. Fractals provide a convenient idealization of multi-scale objects, since their multi-scale properties can be described in simple ways (Mandelbrot 1982). While fractal aspects of turbulence have been studied in several works in the past decades, research on turbulence generated by fractal objects started more recently. We present an experimental study of boundary layer flow over fractal tree-like objects. Detailed Particle-Image-Velocimetry (PIV) measurements are carried out in the near-wake of a fractal-like tree. The tree is a pre-fractal with five generations, with three branches and a scale reduction factor 1/2 at each generation. Its similarity fractal dimension (Mandelbrot 1982) is D ~ 1.58. Detailed mean velocity and turbulence stress profiles are documented, as well as their downstream development. We then turn attention to the turbulence mixing properties of the flow, specifically to the question whether a mixing length-scale can be identified in this flow, and if so, how it relates to the geometric length-scales in the pre-fractal object. Scatter plots of mean velocity gradient (shear) and Reynolds shear stress exhibit good linear relation at all locations in the flow. Therefore, in the transverse direction of the wake evolution, the Boussinesq eddy viscosity concept is appropriate to describe the mixing. We find that the measured mixing length increases with increasing streamwise locations. Conversely, the measured eddy viscosity and mixing length decrease with increasing elevation, which differs from eddy viscosity and mixing length behaviors of traditional boundary layers or canopies studied before. In order to find an appropriate length for the flow, several models based on the notion of superposition of scales are proposed and examined. One approach is based on spectral distributions. Another more practical approach is based on length-scale distributions evaluated using fractal geometry tools. These proposed models agree well with the measured mixing length. The results indicate that information about multi-scale clustering of branches as it occurs in fractals has to be incorporated into models of the mixing length for flows through canopies with multiple scales. The research is supported by National Science Foundation grant ATM-0621396 and AGS-1047550.

Meneveau, C. V.; Bai, K.; Katz, J.

2011-12-01

102

NASA Astrophysics Data System (ADS)

The reflection signal from a defect in the process of guided wave-based pipeline inspection usually includes sufficient information to detect and define the defect. In previous research, it has been found that the reflection of guided waves from even a complex defect primarily results from the interference between reflection components generated at the front and the back edges of the defect. The respective contribution of different parameters of a defect to the overall reflection can be affected by the features of the two primary reflection components. The identification of these components embedded in the reflection signal is therefore useful in characterizing the concerned defect. In this research, we propose a method of model-based parameter estimation with the aid of the Hilbert-Huang transform technique for the purpose of decomposition of a reflection signal to enable characterization of the pipeline defect. Once two primary edge reflection components are decomposed and identified, the distance between the reflection positions, which closely relates to the axial length of the defect, could be easily and accurately determined. Considering the irregular profiles of complex pipeline defects at their two edges, which is often the case in real situations, the average of varied axial lengths of such a defect along the circumference of the pipeline is used in this paper as the characteristic value of actual axial length for comparison purpose. The experimental results of artificial defects and real corrosion in sample pipes were considered in this paper to demonstrate the effectiveness of the proposed method.

Wang, Xiaojuan; Tse, Peter W.; Dordjevich, Alexandar

2011-02-01

103

A microbial fuel cell (MFC) is a bio-electrochemical converter that can extract electricity from biomass by the catabolic reaction of microorganisms. This work demonstrates the impact of a small characteristic length in a Geobacteraceae-enriched, micro-scale microbial fuel cell (MFC) that achieved a high power density. The small characteristic length increased the surface-area-to-volume ratio (SAV) and the mass transfer coefficient. Together, these factors made it possible for the 100-µL MFC to achieve among the highest areal and volumetric power densities - 83 ?W/cm(2) and 3300 ?W/cm(3), respectively - among all micro-scale MFCs to date. Furthermore, the measured Coulombic efficiency (CE) was at least 79%, which is 2.5-fold greater than the previously reported maximum CE in micro-scale MFCs. The ability to improve these performance metrics may make micro-scale MFCs attractive for supplying power in sub-100 µW applications, especially in remote or hazardous conditions, where conventional powering units are hard to establish. PMID:24956566

Ren, Hao; Torres, César I; Parameswaran, Prathap; Rittmann, Bruce E; Chae, Junseok

2014-11-15

104

NASA Astrophysics Data System (ADS)

The intramolecular diffusive motions associated with the creation and annihilation of gauche defects in intermediate-length alkane molecules adsorbed on a solid surface are relatively slow and on a time scale of nanoseconds. This has been shown by molecular dynamics (MD) simulations and by high-energy-resolution quasielastic neutron scattering (QNS) on monolayers of tetracosane (n-C24H50) adsorbed on graphite basal-plane surfaces. QNS with the high energy resolution makes it now possible to probe diffusive motions on the same time scale as in nuclear magnetic resonance (NMR) experiments and, in addition, to obtain information about length scales and character of motions through the wavevector dependence of the QNS.

Hansen, F. Y.; Taub, H.

2004-04-01

105

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

106

Background Diffusion-weighted MRI (DWI) has been used in neurosurgical practice mainly to distinguish cerebral metastases from abscess and glioma. There is evidence from other solid organ cancers and metastases that DWI may be used as a biomarker of prognosis and treatment response. We therefore investigated DWI characteristics of cerebral metastases and their peritumoral region recorded pre-operatively and related these to patient outcomes. Methods Retrospective analysis of 76 cases operated upon at a single institution with DWI performed pre-operatively at 1.5T. Maps of apparent diffusion coefficient (ADC) were generated using standard protocols. Readings were taken from the tumor, peritumoral region and across the brain-tumor interface. Patient outcomes were overall survival and time to local recurrence. Results A minimum ADC greater than 919.4 × 10-6 mm2/s within a metastasis predicted longer overall survival regardless of adjuvant therapies. This was not simply due to differences between the types of primary cancer because the effect was observed even in a subgroup of 36 patients with the same primary, non-small cell lung cancer. The change in diffusion across the tumor border and into peritumoral brain was measured by the “ADC transition coefficient” or ATC and this was more strongly predictive than ADC readings alone. Metastases with a sharp change in diffusion across their border (ATC >0.279) showed shorter overall survival compared to those with a more diffuse edge. The ATC was the only imaging measurement which independently predicted overall survival in multivariate analysis (hazard ratio 0.54, 95% CI 0.3 – 0.97, p = 0.04). Conclusions DWI demonstrates changes in the tumor, across the tumor edge and in the peritumoral region which may not be visible on conventional MRI and this may be useful in predicting patient outcomes for operated cerebral metastases. PMID:25086595

2014-01-01

107

Watershed Best Management Practices (BMPs) are often designed to reduce loading from particle-borne contaminants, but the temporal lag between BMP implementation and improvement in receiving water quality is difficult to assess because particles are only moved downstream episodically, resting for long periods in storage between transport events. A theory is developed that describes the downstream movement of suspended sediment particles accounting for the time particles spend in storage given sediment budget data (by grain size fraction) and information on particle transit times through storage reservoirs. The theory is used to define a suspended sediment transport length scale that describes how far particles are carried during transport events, and to estimate a downstream particle velocity that includes time spent in storage. At 5 upland watersheds of the mid-Atlantic region, transport length scales for silt-clay range from 4 to 60 km, while those for sand range from 0.4 to 113 km. Mean sediment velocities for silt-clay range from 0.0072 km/yr to 0.12 km/yr, while those for sand range from 0.0008 km/yr to 0.20 km/yr, 4–6 orders of magnitude slower than the velocity of water in the channel. These results suggest lag times of 100–1000 years between BMP implementation and effectiveness in receiving waters such as the Chesapeake Bay (where BMPs are located upstream of the characteristic transport length scale). Many particles likely travel much faster than these average values, so further research is needed to determine the complete distribution of suspended sediment velocities in real watersheds.

Pizzuto, James; Schenk, Edward R.; Hupp, Cliff R.; Gellis, Allen; Noe, Greg; Williamson, Elyse; Karwan, Diana L.; O'Neal, Michael; Marquard, Julia; Aalto, Rolf; Newbold, Denis

2014-01-01

108

Effects of phenotypic characteristics on the length of stay of dogs at two no kill animal shelters.

Adoption records from 2 no kill shelters in New York State were examined to determine how age, sex, size, breed group, and coat color influenced the length of stay (LOS) of dogs at these shelters. Young puppies had the shortest length of stay; LOS among dogs increased linearly as age increased. Neither coat color nor sex influenced LOS. Considering only size classifications, medium-size dogs had the greatest LOS, and extra small dogs and puppies remained in shelters for the least amount of time. Considering only breed groupings, dogs in the guard group had the greatest LOS and those in the giant group had the shortest LOS. The lack of effect of coat color was not expected, nor was the shorter LOS among "fighting" breeds compared with other breed groups. Coat color and breed may have only local effects on LOS that do not generalize to all shelters, including traditional shelters. Understanding the traits of dogs in a specific shelter and the characteristics of these nonhuman animals desired by adopters are critical to improving the welfare of animals served by that shelter. PMID:23282290

Brown, William P; Davidson, Janelle P; Zuefle, Marion E

2013-01-01

109

Thermal Characteristics and Structure of Fully-Modulated, Turbulent Diffusion Flames in Microgravity

NASA Technical Reports Server (NTRS)

Turbulent jet diffusion flames are studied in microgravity and normal gravity under fully-modulated conditions for a range of injection times and a 50% duty cycle. Diluted ethylene was injected through a 2-mm nozzle at a Reynolds number of 5,000 into an open duct, with a slow oxidizer co-flow. Microgravity tests are conducted in NASA's 2.2 Second Drop Tower. Flames with short injection times and high duty cycle exhibit a marked increase in the ensemble-averaged flame length due to the removal of buoyancy. The cycle-averaged centerline temperature profile reveals higher temperatures in the microgravity flames, especially at the flame tip where the difference is about 200 K. In addition, the cycle-averaged measurements of flame radiation were about 30% to 60% greater in microgravity than in normal gravity.

Hermanson, J. C.; Johari, H.; Stocker, D. P.; Hegde, U. G.

2003-01-01

110

NASA Astrophysics Data System (ADS)

High-speed directly modulated microlasers are potential light sources for on-chip optical interconnection and photonic integrated circuits. In this Letter, dynamic characteristics are studied for microring lasers by rate equation analysis considering radial carrier hole burning and diffusion and experimentally. The coupled modes with a wide radial field pattern and the injection current focused in the edge area of microring resonator can greatly improve the high speed response curve due to the less carrier hole burning. The small-signal response curves of a microring laser connected with an output waveguide exhibit a larger 3 dB bandwidth and smaller roll-off at low frequency than that of the microdisk laser with the same radius of 15 ?m, which accords with the simulation results.

Lv, Xiao-Meng; Huang, Yong-Zhen; Yang, Yue-De; Zou, Ling-Xiu; Long, Heng; Liu, Bo-Wen; Xiao, Jin-Long; Du, Yun

2014-04-01

111

NASA Astrophysics Data System (ADS)

We present the results of a statistical study using optical images from ALIS (Auroral Large Imaging System) to investigate the spatial and temporal variations of structures in diffuse aurora. Analysis of conjugate Reimei data shows that such fine structures are a result of modulation of high-energy precipitating electrons. Pitch angle diffusion into the loss cone due to interaction of whistler mode waves with plasma sheet electrons is the most feasible mechanism leading to high-energy electron precipitation. This suggests that the fine structure is an indication of modulations of the efficiency of the wave-particle interaction. The scale sizes and variations of these structures, mapped to the magnetosphere, can give us information about the characteristics of the modulating wave activity. We found the scale size of the auroral stripes and the spacing between them to be on average 13-14 km, which corresponds to 3-4 ion gyro radii for protons with an energy of 7 keV. The structures move southward with a speed close to zero in the plasma convection frame.

Axelsson, K.; Sergienko, T.; Nilsson, H.; Brändström, U.; Ebihara, Y.; Asamura, K.; Hirahara, M.

2012-12-01

112

We show that the averaged characteristic polynomial and the averaged inverse characteristic polynomial, associated with Hermitian matrices whose elements perform a random walk in the space of complex numbers, satisfy certain partial differential, diffusion-like, equations. These equations are valid for matrices of arbitrary size. Their solutions can be given an integral representation that allows for a simple study of their asymptotic behaviors for a broad range of initial conditions.

Jean-Paul Blaizot; Jacek Grela; Maciej A. Nowak; Piotr Warcho?

2014-05-20

113

Chromatin repeat length in somatic hybrids.

In order to study the mechanisms by which a characteristic repeat length is inherited in somatic cells, it was necessary to develop a method for determining repeat length with a precision of 1 to 2 base pairs. Hybrid clones between parental cell lines differing in repeat length by 6 base pairs were isolated. The four independent hybrid clones characterized had repeat lengths intermediate between those of the parental lines; however, it could be demonstrated that these repeat lengths are unique values and do not arise from a double distribution of the parental repeat lengths. It therefore is concluded that repeat length in somatic cells is determined by a common pool of diffusible substances. Images PMID:6930661

Sperling, L; Tardieu, A; Weiss, M C

1980-01-01

114

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

115

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.

116

NASA Astrophysics Data System (ADS)

The principle difficulty when joining magnesium (Mg)-aluminium (Al) lies in the existence of formation of oxide films and brittle intermetallic in the bond region. However, diffusion bonding can be used to join these alloys without much difficulty. Temperature, pressure, and holding time are the three main variables which govern the integrity of a diffusion bond. This paper focuses on the effect of these parameters on diffusion layer thickness, hardness and strength of AZ31B magnesium-AA2024 aluminium dissimilar joints. The experiments were conducted based on three factors, five-level, and central composite rotatable design with full replications technique. Empirical relationships were developed to predict diffusion layer thickness, hardness and strength using response surface methodology. From this investigation, it is found that bonding temperature has predominant effect on bond characteristics.

Mahendran, G.; Babu, S.; Balasubramanian, V.

2010-07-01

117

This paper is the second part of the experimental study on exploring the feasibility of inverse diffusion flame (IDF) for impingement heating. The structures and heat transfer characteristics of an impinging IDF jet have been studied. Four types of impinging flame structure have been identified and reported. The distributions of the wall static pressure are measured and presented. The influences

L. L. Dong; C. S. Cheung; C. W. Leung

2007-01-01

118

The report gives results of Phase I of a laboratory assessment of the permeability and diffusion characteristics of Florida concretes. (NOTE: The ability of concrete to permit air flow under pressure (permeability) and the passage of radon gas without any pressure difference (dif...

119

120

Characteristics of a highly efficient propeller type small wind turbine with a diffuser

We studied the improved effects a diffuser had on the output power of small wind turbine systems, aiming to introduce these systems to radio relay stations as an independent power supply system. A frustum-shaped diffuser was chosen from an economical standpoint and wind speed distribution. The effect the diffuser's shape had on the wind speed was analyzed by simulation and

Toshio Matsushima; Shinya Takagi; Seiichi Muroyama

2006-01-01

121

NASA Astrophysics Data System (ADS)

Synchrotron-based, spectrally resolved x-ray beam-induced current (SR-XBIC) is introduced as a technique to locally measure the minority carrier diffusion length in semiconductor devices. Equivalence with well-established diffusion length measurement techniques is demonstrated. The strength of SR-XBIC is that it can be combined in situ with other synchrotron-based analytical techniques, such as x-ray fluorescence microscopy (?-XRF) and x-ray absorption microspectroscopy (?-XAS), yielding information about the distribution, elemental composition, chemical nature, and effect on minority carrier diffusion length of individual transition metal species in multicrystalline silicon. SR-XBIC, ?-XRF, and ?-XAS measurements were performed on intentionally contaminated multicrystalline silicon, revealing a strong correlation between local concentrations of copper and nickel silicide precipitates and a decrease of minority carrier diffusion length. In addition, the reduction of minority carrier diffusion length due to submicron-sized Cu3Si and NiSi2 precipitates could be decoupled from the influence of homogeneously distributed nanoprecipitates and point defects.

Buonassisi, T.; Istratov, A. A.; Pickett, M. D.; Marcus, M. A.; Hahn, G.; Riepe, S.; Isenberg, J.; Warta, W.; Willeke, G.; Ciszek, T. F.; Weber, E. R.

2005-07-01

122

NASA Astrophysics Data System (ADS)

The effects of two different carbon powders (oil-furnace carbon black and acetylene-black) as materials for carbon cloth-based cathode gas diffusion layers on the performance of polymer electrolyte fuel cell (PEFC) electrodes were investigated. The carbon powder characteristics affect the reversible potential of the cell ( E°) and both the linear and non-linear polarization components. The best fuel cell performance was obtained at an oxygen pressure of 5 atm with acetylene-black in the cathode gas diffusion layer.

Antolini, E.; Passos, R. R.; Ticianelli, E. A.

123

Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) mapping are functional magnetic resonance imaging techniques for detecting water diffusion. DWI and the ADC map were performed for intracranial lesions in two dogs. In necrotizing leukoencephalitis, cavitated lesions contained a hypointense center with a hyperintense periphery on DWI, and hyperintense signals on the ADC maps. In metastatic sarcoma, masses including a necrotic region were hypointense with DWI, and hyperintense on the ADC map with hyperintense perilesional edema on DWI and ADC map. Since DWI and ADC data reflect the altered water diffusion, they can provide additional information at the molecular level. PMID:24675836

Kim, Boeun; Yi, Kangjae; Jung, Sunyoung; Ji, Seoyeon; Choi, Mincheol

2014-01-01

124

Effects of MRTI sampling characteristics on estimation of HIFU SAR and tissue thermal diffusivity

While the non-invasive and three-dimensional nature of magnetic-resonance temperature imaging (MRTI) makes it a valuable tool for high-intensity focused ultrasound (HIFU) treatments, random and systematic errors in MRTI measurements may propagate into temperature-based parameter estimates used for pretreatment planning. This study assesses the MRTI effects of zero-mean Gaussian noise (SD=0.0-2.0°C), temporal sampling (tacq=1.0-8.0 s), and spatial averaging (Res=0.5-2.0 mm isotropic) on HIFU temperature measurements and temperature-based estimates of the amplitude and full width half maximum (FWHM) of the HIFU specific absorption rate (SAR) and of tissue thermal diffusivity. The ultrasound beam used in simulations and ex vivo pork loin experiments has lateral and axial FWHM dimensions of 1.4 mm and 7.9 mm respectively. For spatial averaging simulations, beams with lateral FWHM varying from 1.2-2.2 mm are also assessed. Under noisy conditions, parameter estimates are improved by fitting to data from larger voxel regions. Varying the temporal sampling results in minimal changes in measured temperatures (<2% change) and parameter estimates (<5% change). For the HIFU beams studied, a spatial resolution of 1×1×3 mm3 or smaller is required to keep errors in temperature and all estimated parameters less than 10%. By quantifying the errors associated with these sampling characteristics, this work provides researchers with appropriate MRTI conditions for obtaining estimates of parameters essential to pretreatment modeling of HIFU thermal therapies. PMID:24077026

Dillon, C R; Todd, N; Payne, A; Parker, D L; Christensen, D A; Roemer, R B

2013-01-01

125

Clinico-radiologic characteristics of long-term survivors of diffuse intrinsic pontine glioma

Diffuse intrinsic pontine glioma (DIPG) is the deadliest central nervous system tumor in children. The survival of affected children has remained poor despite treatment with radiation therapy (RT) with or without chemotherapy. We reviewed the medical records of all surviving patients with DIPG treated at our institution between October 1, 1992 and May 31, 2011. Blinded central radiologic review of the magnetic resonance imaging at diagnosis of all surviving patients and 15 controls with DIPG was performed. All surviving patients underwent neurocognitive assessment during follow-up. Five (2.6%) of 191 patients treated during the study period were surviving at a median of 9.3 years from their diagnosis (range, 5.3 to 13.2 years). Two patients were younger than 3 years, one lacked signs of pontine cranial nerve involvement, and three had longer duration of symptoms at diagnosis. One patient had a radiologically atypical tumor and one had a tumor originating in the medulla. All five patients received RT. Chemotherapy was variable among these patients. Neurocognitive assessments were obtained after a median interval of 7.1 years. Three of four patients who underwent a detailed evaluation showed cognitive function in the borderline or mental retardation range. Two patients experienced disease progression at 8.8 and 13 years after diagnosis. A minority of children with DIPG experienced long-term survival with currently available therapies. These patients remained at high risk for tumor progression even after long follow-ups. Four of our long-term survivors had clinical and radiologic characteristics at diagnosis associated with improved outcome. PMID:23813229

Jackson, Sadhana; Patay, Zoltan; Howarth, Robyn; Pai Panandiker, Atmaram S.; Onar-Thomas, Arzu; Gajjar, Amar; Broniscer, Alberto

2013-01-01

126

NASA Astrophysics Data System (ADS)

The flow characteristics of turbulent jets with and without flame are evaluated at the low Reynolds numbers of 2,000 and 3,000, with fuel-rich mixtures of propane and air. Radial and axial time mean velocities and fluctuation velocities were measured by a fine thermocouple and a photomultiplier, respectively.

Tanaka, Hidenori; Saima, Atsushi

1992-02-01

127

NASA Astrophysics Data System (ADS)

The Holocene epoch as seen in the water isotopic records of polar ice cores is described by a relatively stable climate characterized by minimal fluctuations in temperature. Arguably, the most commonly used proxy in ice core studies, the ratios of water's stable isotopes, provide an insight in past temperatures via a linear relationship with temperature, commonly referred to as the isotope slope. However, the validity of this slope has been extensively debated. Based on borehole thermometry and gas isotope fractionation studies, it has been shown that temperature changes over the Bølling - Allerød and Younger Dryas transitions as well as several interstadial events have been underestimated by the water isotope slope. Additionally, isotopic artifacts related to ice sheet elevation changes, apparent between 6 and 10 ka b2k, result in a poor or even absent representation of the Holocene climatic optimum in the ?18O record from Greenland ice cores, contrary to what other paleoclimatic records from Northern latitudes indicate. In this study we present ongoing work on the use of the firn isotopic diffusion lengths as a high resolution proxy of the snow and firn temperature. Our reconstruction is based on the high resolution ?18O dataset from NGRIP. Water isotope diffusion is a process that occurs after deposition of the precipitation and takes place in the porous space of the firn until the close off depth. Assuming a diffusivity parameterization and based on a densification and strain rate history, it is possible to investigate the effects of temperature and accumulation on the diffusion length. By inverting the model we produce a temperature reconstruction for the last 15 ka. This temperature signal is independent of factors like the water vapor source location and temperature, the intensity of the atmospheric inversion over the deposition site and the presence or not of clear sky precipitation. In order for the reconstruction to reproduce the long term climate signal, a correction for the thinning function is required. Under the assumption that the GICC05 chronology is the best available estimate for the age - depth relationship in the ice, that would require about 10 - 15% lower accumulation rates at the time of the climatic optimum. The temperature reconstruction is able to infer a Younger Dryas warming signal very close to what previous borehole thermometry and gas isotope fractionation studies indicate. A strong 8.2 ky event can be seen in the record and seems to occur in a two stage fashion and last longer than the raw ?18O signal indicates. Overall, the inferred temperature signal reveals a significant variance with climatic events that are initially not reflected in the ?18O record. Some of those events are supported by the findings of other northern hemispheric climatic or historical records (Medieval and Roman warm periods). The most profound of those events is a rapid warming occurring between 4 and 5 ky b2k, indicating a clear mid - Holocene optimum and ending with a rapid cooling at approximately 4.2 ky b2k. We will comment on the validity of those results as well as the feasibility of the magnitude of the temperature shifts and propose ways to constrain the findings further.

Gkinis, Vasileios; Simonsen, Sebastian B.; Buchardt, Susanne L.; Vinther, Bo M.; White, James W. C.

2013-04-01

128

In this work, we highlight several unusual characteristics of adsorption and diffusion of a variety of guest molecules, such as linear and branched alkalies with a number of C atoms in the 1-6 range, CO2, and Ar in microporous structures such as zeolites (FAU, NaY) and metal organic frameworks (IRMOF-1, CuBTC, MIL-47, MIL-53 (Cr)-1p, PCN-6') that have channel or cavity

Rajamani Krishna; Baten van J. M

2010-01-01

129

Two swirl-stabilized flames, a premixed flame (PMF-s) and an inverse diffusion flame (IDF-s), were investigated experimentally in order to obtain information on their thermal, emission and heat transfer characteristics. The two flames, having different global air\\/fuel mixing mechanisms, were compared under identical air and fuel flow rates. Results showed that the two flames have similar visual features such as flame

H. S. Zhen; C. W. Leung; C. S. Cheung

2011-01-01

130

NASA Astrophysics Data System (ADS)

In this paper, a stable and diffuse dielectric barrier discharge plasma excited by bipolar nanosecond pulse is obtained under a needle-array electrode at atmospheric pressure in air. The images of the diffuse discharge, electric characteristics, and the optical emission spectra emitted from the diffuse discharge are investigated under mono and multi needle electrodes configuration. The peak value of discharge current, the average power, the power density, the emission intensity of N2 (C3?u ?B3?g, 0-0), and the gas temperature of the diffuse dielectric barrier discharge plasmas are investigated under different needle electrode numbers based on the waveforms of pulse voltage-current and the optical emission spectra. Moreover, the plasma area is obviously enlarged in the transverse direction when the needle electrode number is increased from 1 to 13. An area approximately 65 × 45 mm2 diffuse discharge plasma region under 13 needle electrodes can be obtained and the discharge plasma still keeps good uniformity, which could be used for large-area surface processing in several fields spanning from biological sterilization and plasma medicine to surface modification of materials and synthesis of functional materials.

Liu, Zhi-jie; Wang, Wen-chun; Zhang, Li; Wang, Sen; Yang, De-zheng; Zhang, Shuai; Tang, Kai

2014-05-01

131

We have epitaxially grown undoped {beta}-FeSi{sub 2} films on Si(111) substrates via atomic-hydrogen-assisted molecular-beam epitaxy. {beta}-FeSi{sub 2} films grown without atomic hydrogen exhibited p-type conduction with a hole density of over 10{sup 19} cm{sup -3} at room temperature (RT). In contrast, those prepared with atomic hydrogen showed n-type conduction and had a residual electron density that was more than two orders of magnitude lower than the hole density of films grown without atomic hydrogen (of the order of 10{sup 16} cm{sup -3} at RT). The minority-carrier diffusion length was estimated to be approximately 16 {mu}m using an electron-beam-induced current technique; this value is twice as large as that for {beta}-FeSi{sub 2} prepared without atomic hydrogen. This result could be well explained in terms of the minority-carrier lifetimes measured by a microwave photoconductance decay technique. The 1/e decay time using a 904 nm laser pulse was approximately 17 {mu}s, which is much longer than that for {beta}-FeSi{sub 2} prepared without atomic hydrogen (3 {mu}s). The photoresponsivity reached 13 mA/W at 1.31 {mu}m, which is the highest value ever reported for {beta}-FeSi{sub 2} films.

Akutsu, Keiichi; Kawakami, Hideki; Suzuno, Mitsushi; Yaguchi, Takashi [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Jiptner, Karolin; Chen, Jun; Sekiguchi, Takashi [National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Ootsuka, Teruhisa [National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8568 (Japan); Suemasu, Takashi [Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan); Japan Science and Technology Agency, CREST, Chiyoda-ku, Tokyo 102-0075 (Japan)

2011-06-15

132

NASA Astrophysics Data System (ADS)

We have epitaxially grown undoped ?-FeSi2 films on Si(111) substrates via atomic-hydrogen-assisted molecular-beam epitaxy. ?-FeSi2 films grown without atomic hydrogen exhibited p-type conduction with a hole density of over 1019 cm-3 at room temperature (RT). In contrast, those prepared with atomic hydrogen showed n-type conduction and had a residual electron density that was more than two orders of magnitude lower than the hole density of films grown without atomic hydrogen (of the order of 1016 cm-3 at RT). The minority-carrier diffusion length was estimated to be approximately 16 ?m using an electron-beam-induced current technique; this value is twice as large as that for ?-FeSi2 prepared without atomic hydrogen. This result could be well explained in terms of the minority-carrier lifetimes measured by a microwave photoconductance decay technique. The 1/e decay time using a 904 nm laser pulse was approximately 17 ?s, which is much longer than that for ?-FeSi2 prepared without atomic hydrogen (3 ?s). The photoresponsivity reached 13 mA/W at 1.31 ?m, which is the highest value ever reported for ?-FeSi2 films.

Akutsu, Keiichi; Kawakami, Hideki; Suzuno, Mitsushi; Yaguchi, Takashi; Jiptner, Karolin; Chen, Jun; Sekiguchi, Takashi; Ootsuka, Teruhisa; Suemasu, Takashi

2011-06-01

133

The effects of low-temperature annealing in 8.2 MeV electron-irradiated 4H-SiC Schottky diodes were investigated. Deep-level transient spectroscopy and minority-carrier diffusion length (L{sub d}) measurements were carried out on not-irradiated samples and on irradiated samples before and after thermal treatments up to T=450 deg. C. We found that several deep levels in the upper half band gap (S1 with enthalpy E{sub T}=0.27 eV, S2 with E{sub T}=0.35 eV, S4 with E{sub T}=0.71 eV, and S5 with E{sub T}=0.96 eV) anneal out or modify at temperature values lower or equal to T=450 deg. C, whereby their progressive annealing out is accompanied by a net increase of L{sub d}, up to 50% of the value in the as-irradiated sample. We drew some conclusions regarding the microscopic nature of the defects related to the deep levels, according to their annealing behavior.

Castaldini, A.; Cavallini, A.; Rigutti, L.; Pizzini, S.; Le Donne, A.; Binetti, S. [Dipartimento di Fisica, Universita di Bologna, Viale Berti Pichat 6/2, 40127 Bologna (Italy); Dipartimento di Scienza dei Materiali, Universita di Milano Bicocca, Via Cozzi 53, 20125 Milan (Italy)

2006-02-01

134

A methodology has been established to estimate the radon emanation rates and back diffusion rates of different building materials in small chamber tests. The two parameters, emanation rate and back diffusion rate, can be obtained from the growth curve of the chamber radon activity. Small impervious containers with a volume of 14900c.c. were used in the measurement and solid-state radon

Christopher Y. H. Chao; Thomas C. W. Tung; Daniel W. T. Chan; John Burnett

1997-01-01

135

NASA Astrophysics Data System (ADS)

A method for the determination of the blockage area function of a duct or pipe from a single measurement of its transfer function is presented. The technique extends a method developed by de Salis and Oldham (Journal of Sound and Vibration221, 180-186) [1] where the duct blockage area function reconstruction is achieved as a function of the resonance and anti-resonance frequencies of the unblocked and partially blocked duct. In each case the resonance and anti-resonance frequencies are determined from maximum length sequence measurements (MLS). The advantage of using MLS analysis is that it has inherently high noise immunity and as such gives a sufficiently large signal-to-noise ratio to reveal the positions of the anti-resonance frequencies in the duct transfer function. In the current paper the technique is further simplified as the resonance and anti-resonance frequencies of the unblocked and the partially blocked duct are determined from a single MLS measurement in the partially blocked duct using an approximation suggested by Wu 1994 (Applied Acoustics41, 229-236) [2]. However, Wu's approach utilized resonance frequency information alone and was thus limited to blockage area functions with no degree of symmetry in the longitudinal plane. In earlier work Wu and Fricke 1990 (Journal of the Acoustical Society of America87, 67-75) [3] have demonstrated that the method using resonance frequencies measured under two sets of boundary conditions could be applied to functions of all degrees of symmetry. In this paper it is shown that the additional determination of the duct anti-resonance frequencies enables Wu's limited reconstruction technique (Wu 1994 Applied Acoustics41, 229-236) [2] to achieve results equivalent to the two boundary condition technique (Wu and Fricke 1990 Journal of the Acoustical Society of America87, 67-75) [3]. Accuracy is enhanced as filtration of the measured transfer function is used to further reduce extraneous noise thus improving the resolution of the transfer function. The determination of the duct area function is achieved utilizing resonance and anti-resonance frequency information alone which renders the determination of the duct length unnecessary. The accuracy of the shift approximation method in achieving a reconstruction technique for the blockage area function of a finite length duct or pipe from a single measurement is demonstrated.

DE SALIS, M. H. F.; OLDHAM, D. J.

2001-06-01

136

The characteristics of vacuum arc with stationary diffuse spot on non-thermionic cathode

The vacuum arc with stationary diffuse spot on the solid cathode from chromium has been studied. The arc current was 30-220 A, cathode temperature 1800-2100 K. The mean current density on the cathode 10-10 2 A\\/cm2. The part of thermionic current at the cathode was less than 0.1 % from arc current. Observations of cathode surface during arcing with help

V. M. Batenin; L. I. Klimovsky; V. P. Polistchook; V. A. Sinel'shchikov

2000-01-01

137

Characteristics of Diffuse X-Ray Line Emission within 20 Parsecs of the Galactic Center

Over the last three years, the Galactic center region has been monitored with the Chandra X-Ray Observatory. Besides the X-ray emission from the target object, Sgr A*, diffuse X-ray emission was detected throughout most of the 17'×17' field of view. With 11 Chandra observations through 2002 June, the total effective exposure reaches ~590 ks, providing significant photon statistics on much

Sangwook Park; Michael P. Muno; Frederick K. Baganoff; Yoshitomo Maeda; Mark Morris; Christian Howard; Mark W. Bautz; Gordon P. Garmire

2004-01-01

138

Characteristics of Diffuse X-Ray Line Emission within 20 pc of the Galactic Center

Over the last 3 yrs, the Galactic center (GC) region has been monitored with\\u000athe Chandra X-Ray Observatory. With 11 Chandra observations through 2002 June,\\u000athe total effective exposure reaches ~590 ks, providing significant photon\\u000astatistics on the faint, filamentary, diffuse X-ray emission. The true-color\\u000aX-ray image and the equivalent width (EW) images for the detected elemental\\u000aspecies demonstrate that

Sangwook Park; Michael P. Muno; Frederick K. Baganoff; Yoshitomo Maeda; Mark Morris; Christian Howard; Mark W. Bautz; Gordon P. Garmire

2003-01-01

139

This study examined how content characteristics of antitobacco messages affect smokers' selective exposure to and social sharing of those messages. Results from an experiment revealed that content features predicting smokers' selection of antismoking messages are different from those predicting whether those messages are shared. Antismoking messages smokers tend to select are characterized by strong arguments (odds ratio = 2.02, P = .02) and positive sentiments (odds ratio = 3.08, P = .03). Once selected, the messages more likely to be retransmitted by smokers were those with novel arguments (B = .83, P = .002) and positive sentiments (B = 1.65, P = .005). This research adds to the literature about the content characteristics driving the social diffusion of antitobacco messages and contributes to our understanding of the role of persuasive messages about smoking cessation in the emerging public communication environment. PMID:24395989

Kim, Hyun Suk; Lee, Sungkyoung; Cappella, Joseph N; Vera, Lisa; Emery, Sherry

2013-12-01

140

The characteristics of diffuse glow discharges in pure argon and the Ar + 1%N{sub 2} mixture at pressures of 2-80 Torr were studied experimentally and numerically. The discharge operated in a molybdenumglass tube with an inner diameter of 2.8 cm and interelectrode distance of 75 cm. The current-voltage characteristic of the discharge and the populations of the N{sub 2}(B{sup 3{Gamma}}{sub g}) and N{sub 2}(C{sup 3{Gamma}}{sub u}) states were measured. It is shown that, at relatively low pressures (P < 10 Torr), the current-voltage characteristic of a discharge in the argon-nitrogen mixture lies higher than that in pure argon. In contrast, at higher pressures (P > 15 Torr), the current-voltage characteristic of a discharge in the mixture lies lower than that in pure argon. As the pressure increases, the effect of the reduction in the discharge voltage becomes more pronounced. A self-consistent zero-dimensional kinetic model is developed that allows one to calculate the characteristics of the positive column of a discharge in pure argon and Ar:N{sub 2} mixtures under the conditions of high vibrational excitation of nitrogen. A detailed description of the model is presented, and the calculated results are compared with experimental data. The model adequately reproduces the observed change in the current-voltage characteristic in Ar and the Ar + 1%N{sub 2} mixture with increasing gas pressure. It is shown that the main ionization mechanism in the Ar + 1%N{sub 2} mixture at moderate pressures is the associative ionization of excited nitrogen atoms.

Dyatko, N. A. [Troitsk Institute for Innovation and Fusion Research (Russian Federation); Ionikh, Yu. Z.; Meshchanov, A. V. [St. Petersburg State University (Russian Federation); Napartovich, A. P. [Troitsk Institute for Innovation and Fusion Research (Russian Federation); Barzilovich, K. A. [St. Petersburg State University (Russian Federation)

2010-12-15

141

Characteristics of diffusion-tensor imaging for healthy adult rhesus monkey brains

Diffusion-tensor imaging can be used to observe the microstructure of brain tissue. Fractional sotropy reflects the integrity of white matter fibers. Fractional anisotropy of a young adult brain is low in gray matter, high in white matter, and highest in the splenium of the corpus callosum. Thus, we selected the anterior and posterior limbs of the internal capsule, head of the caudate nucleus, semioval center, thalamus, and corpus callosum (splenium and genu) as regions of interest when using diffusion-tensor imaging to observe fractional anisotropy of major white matter fiber tracts and the deep gray matter of healthy rhesus monkeys aged 4–8 years. Results showed no laterality ferences in fractional anisotropy values. Fractional anisotropy values were low in the head of date nucleus and thalamus in gray matter. Fractional anisotropy values were highest in the splenium of corpus callosum in the white matter, followed by genu of the corpus callosum and the posterior limb of the internal capsule. Fractional anisotropy values were lowest in the semioval center and posterior limb of internal capsule. These results suggest that fractional anisotropy values in major white matter fibers and the deep gray matter of 4–8-year-old rhesus monkeys are similar to those of healthy young people.

Zhao, Xinxiang; Pu, Jun; Fan, Yaodong; Niu, Xiaoqun; Yu, Danping; Zhang, Yanglin

2013-01-01

142

The stria terminalis (ST) connects the amygdale (AM) with the hypothalamus, anterior commissure, preoptic area, and septal region. Many animal studies have reported on the anatomy and function of the ST; in contrast, little is known about its anatomy and function in the human brain. In the current study, we attempted to investigate the anatomical characteristics of the ST in

Hyeok Gyu Kwon; Woo Mok Byun; Sang Ho Ahn; Su Min Son; Sung Ho Jang

2011-01-01

143

of Silicon F-N Junctions. (December 19~&6) Ku~w-Chun Andrew Huang, B. S. , exas ARM University Chairman of Advisory Committee: Dr. W. A. Porter Mater' al and electrical characteristics of semiconductor- . junctions formed by impurity diffusion using... characteristics measurements include: surf'ace sheet resistance, junction dep . h, impurity profile, chemical etch, X-ray topography and X-ray diffractive power measurement Electrical characteristics measurements include: forward 'oias, reverse breakdown...

Huang, Kuan-Chun Andrew

2012-06-07

144

NASA Astrophysics Data System (ADS)

As essential electrochromic (EC) materials are related to energy savings in fenestration technology, tungsten oxide (WO3) films have been intensively studied recently. In order to achieve better understanding of the mechanism of EC properties, and thus facilitate optimization of device performance, clarification of the correlation between cation storage and transfer properties and the coloration performance is needed. In this study, transparent polycrystalline and amorphous WO3 thin films were deposited on SnO2:F-coated glass substrates by the pulsed laser deposition technique. Investigation into optical transmittance in a wavelength range of 400-800 nm measured at a current density of 130 ?A · cm-2 with the applied potential ranging from 3.2 to 2.2 V indicates that polycrystalline films have a larger optical modulation of ~ 30% at 600 nm and a larger coloration switch time of 95 s in the whole wavelength range compared with amorphous films (~ 24% and 50 s). Meanwhile, under the same conditions, polycrystalline films show a larger lithium storage capacity corresponding to a Li/W ratio of 0.5, a smaller lithium diffusion coefficient (2×10-12 cm2·s-1 for Li/W=0.24) compared with the amorphous ones, which have a Li/W ratio of 0.29 and a coefficient of ~2.5×10-11 cm2·s-1 as Li/W=0.24. These results demonstrate that the large optical modulation relates to the large lithium storage capacity, and the fast coloration transition is associated with fast lithium diffusion.

Yu, Peng-Fei; Cui, Zhong-Hui; Fan, Wu-Gang; Guo, Xiang-Xin

2013-03-01

145

NASA Astrophysics Data System (ADS)

A single-wavelength Brillouin laser is demonstrated by using a 3-m-long erbium doped fiber (EDF) in a ring cavity. The EDF is used to provide both nonlinear and linear gains to generate a stimulated Brillouin scattering (SBS) and to amplify the generated SBS, respectively. The Brillouin erbium fiber laser (BEFL) operates at 1561.5 nm, where the operating wavelength is up-shifted by 0.08nm from the Brillouin pump. The operation wavelength is also tunable within 1560.6-1562.6 nm. The BEFL also shows a self-pulsing characteristic with repetition of 66.7 kHz when the BP is set around the threshold pump power of 13mW. Compared to the conventional Brillouin fiber laser with a long cavity length, the proposed BEFL exhibits a significantly lower amplitude of pulse. This laser has many potential applications, such as in optical communication and sensors.

Zarei, A.; Z. R. R. Rosdin, R.; M. Ali, N.; H., Ahmad; W. Harun, S.

2014-05-01

146

NASA Technical Reports Server (NTRS)

A study of the flow strength, creep resistance and diffusion welding characteristics of the titanium alloy Ti-6Al-2Nb-1Ta-0.8Mo was conducted. Two mill-processed forms of this alloy were examined. The forged material was essentially processed above the beta transus while the rolled form was subjected to considerable work below the beta transus. Between 1150 and 1250 K, the forged material was stronger and more creep resistant than the rolled alloy. Both forms exhibit superplastic characteristics in this temperature range. Strain measurements during diffusion welding experiments at 1200 K reveal that weld interfaces have no measurable effect on the overall creep deformation. Significant deformation appears to be necessary to produce a quality diffusion weld between superplastic materials. A 'soft' interlayer inserted between faying surfaces would seemingly allow manufacture of quality diffusion welds with little overall deformation.

Whittenberger, J. D.; Moore, T. J.

1977-01-01

147

A preliminary study of the shape and the extinction characteristics of a diffusion flame established over a circular liquid fuel surface under the influence of an opposed air flow, is presented. Renewable liquid fuel such as ethanol is employed. A simple heterogeneous combustion setup, which consists of a cylindrical tube containing ethanol located at the bottom, is exposed to an opposed air flow from a coaxial circular pipe of same size located at the top at a fixed separation distance. Axial and radial extents of flame for different air flow rates are qualitatively analyzed. Burning rates of ethanol for different separation distances and air flow rates are recorded. For a fixed separation distance, at a particular air flow rate the flame extinction takes place. Extinction air flow rates and corresponding strain rates for different separation distances are presented. (author)

Sen, Anirudh; Raghavan, Vasudevan; Shet, U.S.P. [Department of Mechanical Engineering, Indian Institute of Technology Madras, 206A TDCE Lab., Chennai 600036 (India)

2009-03-15

148

NASA Astrophysics Data System (ADS)

Management of liquid water transported through the reactant-gas-supply channels is a significant problem in proton exchange membrane fuel cells. Typically these channels have three smooth, impermeable walls and a fourth wall consisting of a porous carbon paper called the gas-diffusion layer (GDL). This research addresses microchannel fuel cells where the channel height is comparable to the GDL thickness and both gas and liquid may move longitudinally through either the channel or the porous layer. Transparent test structures were built with 500 ?m wide by 200 ?m deep by 15 cm long channels with one of the 500 ?m wide channel walls bounded by a 190 or 390 ?m thick GDL layer. A controlled flow of water was injected into the backside of the GDL at 4 equally distributed points along the channel. Two phase flow regimes in the channel were observed to be a function of the water and gas flow rates, GDL hydrophobicity, GDL thickness and channel wall hydrophobicity. Generally the flow regime evolves from plug flow, to wavy annular flow, to stratified flow as the gas flow rate increases. The transition points are determined by the system parameters and the hysteresis of the flow regime is observed with the direction of gas flow variation. Modeling of the system requires correct accounting for a significant gas flow passing longitudinally through a partially-saturated GDL.

Lee, Eon Soo; Steinbrenner, Julie; Wang, Fu-Min; Hidrovo, Carlos; Goodson, Kenneth; Eaton, John

2006-11-01

149

An indigenous Cellulosimicrobium cellulans GS6 isolate able to solubilize insoluble phosphate complexes in soil is a potential bacterial fertilizer. Enclosure of the phosphate-solubilizing bacterium (PSB) in biodegradable capsules may protect the PSB cells inoculated into soil and, in the meantime, enable the control of cell release that confers long-term fertilizing effects. In this study, calcium alginate (CA) was used as the core matrix to encapsulate cells of C. cellulans GS6. The cell-liberating properties of the CA-based capsules were modified by blending with a variety of supplemental materials (SM), including chitin, cellulose, olive oil, and gelatin. The experimental results showed that the maximum cell-release percentage (MCR%) of the capsules decreased in the order of CA-cellulose>CA-olive oil>CA-chitin>CA-gelatin>CA. Furthermore, a mass transport model was developed to accurately describe the kinetics of cell release results for each capsule. The diffusion coefficient (D(e)) of each capsule was also determined from the model simulation. We found that the estimated D(e) values are positively correlated to the release rate with rare exceptions. Lastly, as our results underscored the crucial roles that the type of capsules plays in the rate and amount of cell release, controlled release of the bacterial fertilizer (C. cellulans GS6 cells) may be achieved via the design of capsule materials. PMID:17482812

Liu, Chien-Hung; Wu, Jane-Yii; Chang, Jo-Shu

2008-04-01

150

Diffuse large B-cell lymphoma (DLBCL) is an aggressive non-Hodgkin lymphoma with marked biologic heterogeneity. We analyzed 100 cases of DLBCL to evaluate the prognostic value of immunohistochemical markers derived from the gene expression profiling-defined cell origin signature, including MYC, BCL2, BCL6, and FOXP1 protein expression. We also investigated genetic alterations in BCL2, BCL6, MYC and FOXP1 using fluorescence in situ hybridization and assessed their prognostic significance. BCL6 rearrangements were detected in 29% of cases, and BCL6 gene alteration (rearrangement and/or amplification) was associated with the non-germinal center B subtype (non-GCB). BCL2 translocation was associated with the GCB phenotype, and BCL2 protein expression was associated with the translocation and/or amplification of 18q21. MYC rearrangements were detected in 15% of cases, and MYC protein expression was observed in 29% of cases. FOXP1 expression, mainly of the non-GCB subtype, was demonstrated in 37% of cases. Co-expression of the MYC and BCL2 proteins, with non-GCB subtype predominance, was observed in 21% of cases. We detected an association between high FOXP1 expression and a high proliferation rate as well as a significant positive correlation between MYC overexpression and FOXP1 overexpression. MYC, BCL2 and FOXP1 expression were significant predictors of overall survival. The co-expression of MYC and BCL2 confers a poorer clinical outcome than MYC or BCL2 expression alone, whereas cases negative for both markers had the best outcomes. Our study confirms that DLBCL, characterized by the co-expression of MYC and BCL2 proteins, has a poor prognosis and establishes a significant positive correlation with MYC and FOXP1 over-expression in this entity. PMID:24887414

Bellas, Carmen; Garcia, Diego; Vicente, Yolanda; Kilany, Linah; Abraira, Victor; Navarro, Belen; Provencio, Mariano; Martin, Paloma

2014-01-01

151

Standard Length versus Total Length

In an effort to determine the length measurement most representative of the bulk of the fish, the standard length and the total length were each compared with the weight of the fish. This comparison was made for four species of game fish, yellow perch (Perca flavescens), wall-eyed pike (Stizostedion v. vitreum), rock bass (Ambloplites rupestris), and lake trout (Cristivomer n.

William F. Royce

1942-01-01

152

NASA Technical Reports Server (NTRS)

An experimental investigation of the aerodynamic noise and flow field characteristics of internal-flow jet-augmented flap configurations (abbreviated by the term jet flap throughout the study) is presented. The first part is a parametric study of the influence of the Mach number (subsonic range only), the slot nozzle aspect ratio and the flap length on the overall radiated sound power and the spectral composition of the jet noise, as measured in a reverberation chamber. In the second part, mean and fluctuating velocity profiles, spectra of the fluctuating velocity and space correlograms were measured in the flow field of jet flaps by means of hot-wire anemometry. Using an expression derived by Lilley, an attempt was made to estimate the overall sound power radiated by the free mixing region that originates at the orifice of the slot nozzle (primary mixing region) relative to the overall sound power generated by the free mixing region that originates at the trailing edge of the flap (secondary mixing region). It is concluded that at least as much noise is generated in the secondary mixing region as in the primary mixing region. Furthermore, the noise generation of the primary mixing region appears to be unaffected by the presence of a flap.

Schrecker, G. O.; Maus, J. R.

1974-01-01

153

The soil of several floodplain areas along large European rivers shows increased levels of heavy metals as a relict from past sedimentation of contaminants. These levels may pose risks of accumulation in food webs and toxicologic effects on flora and fauna. However, for floodplains, data on heavy-metal concentrations in vertebrates are scarce. Moreover, these environments are characterised by periodical flooding cycles influencing ecologic processes and patterns. To investigate whether the suggested differences in accumulation risks for insectivores and carnivores, omnivores, and herbivores are reflected in the actual heavy-metal concentrations in the species, we measured the current levels of Zn, Cu, Pb, and Cd in 199 specimens of 7 small mammal species (voles, mice, and shrews) and in their habitats in a diffusely polluted floodplain. The highest metal concentrations were found in the insectivorous and carnivorous shrew, Sorex araneus. Significant differences between the other shrew species, Crocidura russula, and the vole and mouse species was only found for Cd. The Cu concentration in Clethrionomys glareolus, however, was significantly higher than in several other vole and mouse species. To explain the metal concentrations found in the specimens, we related them to environmental variables at the trapping locations and to certain characteristics of the mammals. Variables taken into account were soil total and CaCl2-extractable metal concentrations at the trapping locations; whether locations were flooded or nonflooded; the trapping season; and the life stage; sex; and fresh weight of the specimens. Correlations between body and soil concentrations and location or specimen characteristics were weak. Therefore; we assumed that exposure of small mammals to heavy-metal contamination in floodplains is significantly influenced by exposure time, which is age related, as well as by dispersal and changes in foraging and feeding patterns under influence of periodic flooding. PMID:17387425

Leuven, R. S. E. W.; van der Velde, G.; Jungheim, G.; Koelemij, E. I.; de Vries, F. T.; Eijsackers, H. J. P.; Smits, A. J. M.

2007-01-01

154

NASA Astrophysics Data System (ADS)

We analyze the multi-dimensional, solution-dependent family of discontinuous finite element and characteristic methods in the thick, diffusive limit in Cartesian geometry on an arbitrary grid of polygons or polyhedra. We develop various conditions that must be satisfied by the weight and basis functions in order for an individual spatial discretization to have any chance of succeeding in this limit. In addition, we emphasize the various deviations required by this analysis from the solution-independent families. We provide several specific one and two-dimensional spatial discretizations within this family and analyze them in this limit to validate the results of the general analysis. We stress properties of each method's weight and/or basis functions that result in the method's success or failure in this limit. We further provide several relevant numerical examples for each of the individual methods considered to emphasize the utility and predictive capability of the general analysis. We describe in great detail how the algebraically nonlinear spatial discretization equations are solved. We present a modified Newton-Raphson iterative scheme used to eliminate the basis function coefficients in favor of known quantities. Furthermore, we propose an extension to the transport synthetic acceleration (TSA) algorithm for accelerating source iteration as applied to the class of solution-dependent spatial discretizations. We then test this acceleration scheme on a simple family of problems with variable scattering ratios. Finally, we select two different solution-dependent spatial discretizations contained in these families and analyze them in other limits of interest.

Castrianni, Christopher Lee

155

Damage and recovery characteristics of lithium-containing solar cells.

NASA Technical Reports Server (NTRS)

Damage and recovery characteristics were measured on lithium-containing solar cells irradiated by 1-MeV electrons. Empirical expressions for cell recovery time, diffusion-length damage coefficient immediately after irradiation, and diffusion-length damage coefficient after recovery were derived using results of short-circuit current, diffusion-length, and reverse-bias capacitance measurements. The damage coefficients were expressed in terms of a single lithium density parameter, the lithium gradient. A fluence dependence was also established, this dependence being the same for both the immediate-post-irradiation and post-recovery cases. Cell recovery rates were found to increase linearly with lithium gradient.

Faith, T. J.

1971-01-01

156

Ballistic-Diffusive Heat-Conduction Equations

We present new heat-conduction equations, named ballistic-diffusive equations, which are derived from the Boltzmann equation. We show that the new equations are a better approximation than the Fourier law and the Cattaneo equation for heat conduction at the scales when the device characteristic length, such as film thickness, is comparable to the heat-carrier mean free path and\\/or the characteristic time,

Gang Chen; Gang

2001-01-01

157

AIM: To investigate dynamic characteristics and pathological mechanism of signal in rabbit VX-2 tumor model on diffusion-weighted imaging (DWI) after chemoembolization. METHODS: Forty New Zealand rabbits were included in the study and forty-seven rabbit VX-2 tumor models were raised by implanting directly and intrahepatically after abdominal cavity opened. Forty VX-2 tumor models from them were divided into four groups. DWI was performed periodically and respectively for each group after chemoembolization. All VX-2 tumor samples of each group were studied by pathology. The distinction of VX-2 tumors on DWI was assessed by their apparent diffusion coefficient (ADC) values. The statistical significance between different time groups, different area groups or different b-value groups was calculated by using SPSS12.0 software. RESULTS: Under b-value of 100 s/mm2, ADC values were lowest at 16 h after chemoembolization in area of VX-2 tumor periphery, central, and normal liver parenchyma around tumor, but turned to increase with further elongation of chemoembolization treatment. The distinction of ADC between different time groups was significant respectively (F = 7.325, P < 0.001; F = 2.496, P < 0.048; F = 6.856, P < 0.001). Cellular edema in the area of VX-2 tumor periphery or normal liver parenchyma around tumor, increased quickly in sixteen h after chemoembolization but, from the 16th h to the 48th h, cellular edema in the area of normal liver parenchyma around tumor decreased gradually and that in the area of VX-2 tumor periphery decreased lightly at, and then increased continually. After chemoembolization, Cellular necrosis in the area of VX-2 tumor periphery was more significantly high than that before chemoembolization. The areas of dead cells in VX-2 tumors manifested low signal and high ADC value, while the areas of viable cells manifested high signal and low ADC value. CONCLUSION: DWI is able to detect and differentiate tumor necrotic areas from viable cellular areas before and after chemoembolization. ADC of normal liver parenchyma and VX-2 tumor are influenced by intracellular edema, tissue cellular death and microcirculation disturbance after chemoembolization. PMID:17963295

Yuan, You-Hong; Xiao, En-Hua; Liu, Jian-Bin; He, Zhong; Jin, Ke; Ma, Cong; Xiang, Jun; Xiao, Jian-Hua; Chen, Wei-Jian

2007-01-01

158

Characteristics of hydrogen–hydrocarbon composite fuel turbulent jet flames

The characteristics (flame length, pollutant emission, radiative heat loss fraction, and volumetric soot concentration) of hydrogen–hydrocarbon composite fuel turbulent jet diffusion flames are presented. A correlation of flame length with hydrogen concentration in the fuel mixture is shown. The reactivity of fuel mixture increases with the increase of hydrogen concentration, which ultimately shortens the combustion time, and thereby reduces the

Ahsan R. Choudhuri; S. R. Gollahalli

2003-01-01

159

NASA Astrophysics Data System (ADS)

Using extrusion compounding followed by compression molding processes, polycarbonate-based optical diffusers with uniform dispersion of diffusing particles could be prepared for application in direct-lit LED backlight unit. Inorganic porous silica and organic silicone microsphere particles were employed as diffusing agents. The inclusion of diffusing particles up to 3 wt % substantially improved the luminance uniformity with respect to both location and viewing angle, and the effect was shown to be more prominent for the silicone particles. Alternatively, inorganic silica particles could yield diffusers with enhanced absolute luminance and thermal resistance property. The thermo-mechanical property of the elastic modulus was revealed to be improved upon addition of diffusing particles of silica and silicone with cross-linked structure.

Kim, Hyo Jin; Kim, Dong Won; Kim, Seong Woo

2013-10-01

160

In an attempt to find out whether the length of the alkyl chain on the imidazolium cation has a bearing on solute rotation, temperature-dependent fluorescence anisotropies of three structurally similar solutes have been measured in a series of 1-alkyl-3-methylimidazolium (alkyl = methyl, ethyl, propyl, butyl, and hexyl) bis(trifluoromethylsulfonyl)imides. Solute-solvent coupling constants obtained from the experimentally measured reorientation times with the aid of Stokes-Einstein-Debye hydrodynamic theory indicate that there is no influence of the length of the alkyl chain on the rotation of nonpolar, anionic, and cationic solutes 9-phenylanthracene (9-PA), fluorescein (FL), and rhodamine 110 (R110), respectively. It has also been noticed that the rotational diffusion of 9-PA is closer to the predictions of slip hydrodynamics, whereas the rotation of negatively charged FL and positively charged R110 is almost identical and follows stick hydrodynamics in these ionic liquids. Despite having similar shape and size, ionic solutes rotate slower by a factor of 3-4 compared to the nonpolar solute. Interplay of specific and electrostatic interactions between FL and the imidazolium cation of the ionic liquids, and between R110 and the bis(trifluoromethylsulfonyl)imide anion, appear to be responsible for the observed behavior. These results are an indication that the length of the alkyl chain on the imidazolium cation does not alter their physical properties in a manner that has an effect on solute rotation. PMID:23013036

Gangamallaiah, V; Dutt, G B

2012-10-25

161

A large meteorological wind tunnel was used to simulate a suburban atmospheric boundary layer. The model-prototype scale was 1:300 and the roughness length was approximately 1.0 m full scale. The model boundary layer simulated full scale dispersion from ground-level and elevated ...

162

NASA Astrophysics Data System (ADS)

With the continuing aggressive scaling of interconnect dimensions and introduction of lower k materials, back-end-of-line (BEOL) dielectric time-dependent dielectric breakdown (TDDB) reliability margin is greatly reduced. In this paper, a comprehensive investigation on abnormal low-k TDDB characteristics, a systematic degradation of Weibull slopes, and a systematic increase of field acceleration at lower stress voltages due to massive Cu diffusion were conducted for Cu interconnect with low-k dielectric. Based on data from extensive electrical and physical analysis, such abnormal TDDB characteristics were attributed to slow metallic diffusion in bulk low-k under bias and temperature stress. A TDDB model based on invasion percolation was proposed to model the observed abnormalities. Cu interconnects with robust liner and capping layer, to ensure metal free low-k film, have become important for BEOL low-k TDDB.

Chen, Fen; Shinosky, Michael; Aitken, John; Yang, Chih-Chao; Edelstein, Daniel

2012-12-01

163

Diffusive resistance of the upper and lower leaf surfaces of Abutilon theophrasti Medic, was measured with an automatic diffusive resistance meter. Plants were maintained in growth chambers under 4 different environments: 1. high humidity, well-watered, 2. high humidity, dry, 3. low humidity, well-watered, 4. low humidity, dry. Diffusive resistance measurements were obtained every 4 h for up to 3 days when the plants were subjected to either daily regimes consisting of 15 h of light followed by 9 h of darkness or to continuous illumination. Leaf movements were also monitored. Diffusive resistance was rhythmic (circadian) under all the environmental conditions examined. The pattern of diffusive resistance was the same regardless of whether the humidity and/or soil moisture were high or low. The rhythms of diffusive resistance of the upper and lower leaf surfaces differed, however, in amplitude and in the phase at which the minimum value was reached. Diffusive resistance of the leaf was highest (peak of the rhythm) when the leaf blade was in a nearly horizontal position. PMID:7140475

Fuhrman, M H; Koukkari, W L

1982-01-01

164

NASA Astrophysics Data System (ADS)

The electrical properties of defects in a p-?-FeSi2/n-Si heterostructures were investigated by deep level transient spectroscopy (DLTS) and the electron-beam-induced current (EBIC) technique. DLTS revealed the presence of trap levels for holes, caused by defects in the n-Si layer near the interface during the ?-FeSi2 film fabrication. The defect density became small when a 20-nm-thick ?-FeSi2 template layer was grown on the n-Si prior to molecular beam epitaxy (MBE) of a 700-nm-thick ?-FeSi2 layer. The diffusion length of minority carriers in the n-Si was found to be approximately 15 µm by EBIC. This is much larger than the value of approximately 3 µm for the n-Si obtained when the template layer was not inserted.

Kawakami, Hideki; Suzuno, Mitsushi; Akutsu, Keiichi; Chen, Jun; Jiptner, Karolin; Sekiguchi, Takashi; Suemasu, Takashi

2011-04-01

165

NSDL National Science Digital Library

Although life experience plays a huge role in shaping who we are, the foundations of our personality begin in the womb. This Science Update describes a recent study that looks to finger length for signs of a man's pre-natal exposure to testosterone.

Science Update;

2005-03-28

166

The paper deals with technique for visualizing thermally induced flow at high Grashof numbers. The flow is generated inside a relatively tall chamber by means of an electrically heated rectangular slab. Visualization is accomplished by adding metaldehyde particles to the air flow and photographing the luminous diffusion against a dark background. Flow patterns obtained by the technique are given and

P. Barrera; C. Cardella; P. Testa

1977-01-01

167

NSDL National Science Digital Library

This Science Update explores male agression patterns and their correlation to pre-natal testosterone exposure. Although life experience plays a huge role in shaping who we are, the foundations of our personality begin in the womb. One recent study looks to finger length for signs of a man's pre-natal exposure to testosterone.n women, the index and ring finger are roughly equal in length. But in most men, the ring finger is longer. That's a result of fetal exposure to testosterone. Psychologists Alison Bailey and Pete Hurd, of the University of Alberta in Canada, studied these finger ratios in male college students. And they found that men with more dramatic differences tended to be more aggressive. Additional links to resources are given for further inquiry.

American Association for the Advancement of Science (;)

2005-03-28

168

The axial homogeneity of preparative-scale chromatography columns was studied by measuring the overall properties of similar columns differing only by their lengths. The properties investigated were the packing density, the external porosity, the permeability and the column efficiency. Two different materials were used, one made of large, irregular silica particles compressed under either a high or a low degree of

Joon-Ho Koh; Georges Guiochon

1998-01-01

169

National Technical Information Service (NTIS)

A wind-tunnel investigation has been conducted at Mach numbers of 1.50, 2.16, and 2.86 to obtain axial-force data on a metric rectangular-box cavity with various length-to-depth ratios. The model was tested at angles of attack from -4 deg to -2 deg. The r...

A. B. Blair, R. L. Stallings

1986-01-01

170

Diblock/silica films with multi-bilayer vesicular mesostructures of large characteristic length scales were synthesized through evaporation-induced self-assembly of PS-b-PEO. The present system is believed to be the first to yield diblock/silica films with multi-bilayer vesicular mesostructures through solvent evaporation-induced self-assembly (EISA). The ready formation in the present system is argued to be the polydispersity of polymer chains.

YU,KUI; BRINKER,C. JEFFREY; HURD,ALAN J.; EISENBERG,ADI

2000-11-22

171

NASA Technical Reports Server (NTRS)

Sideline noise and takeoff field length were varied for two types of Mach 2.32 cruise airplane to determine their effect on engine cycle selection. One of these airplanes was the NASA/Langley-LTV arrow wing while the other was a Boeing modified delta-plus-tail derived from the earlier 2707-300 concept. Advanced variable cycle engines were considered. A more conventional advanced low bypass turbofan engine was used as a baseline for comparison. Appropriate exhaust nozzle modifications were assumed, where needed, to allow all engines to receive either an inherent co-annular or annular jet noise suppression benefit. All the VCE's out-performed the baseline engine by substantial margins in a design range comparison, regardless of airplane choice or takeoff restrictions. The choice among the three VCE's considered, however, depends on the field length, noise level, and airplane selected.

Whitlow, J. B., Jr.

1976-01-01

172

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

173

Tuberculosis remains one of the most prevalent and fatal infectious diseases in spite of considerable improvements in medical science. The diagnosis and treatment of extrapulmonary tuberculosis involving the abdomen is still complicated owing to vague or non-specific clinical features. Although rare, isolated splenic involvement is one of the important manifestations of extrapulmonary tuberculosis, and imaging suspicion of the disease is essential. We report a case of surgically confirmed mass-forming splenic tuberculosis showing a layered pattern consisting of caseous necrosis with profound restriction of water molecules surrounded by an irregular rind of granulation tissue with less diffusion restriction on diffusion-weighted magnetic resonance imaging (DWI). In the differential diagnosis of neoplastic or non-neoplastic mass-forming lesions involving the spleen, this unique DWI feature could be helpful in characterizing splenic tuberculosis. The patient has been in clinically disease free status for nearly 20 months after splenectomy. PMID:21394320

Lim, Jihe; Hong, Soon Won; Chung, Jae-Joon; Kim, Joo Hee; Kim, Ki Whang

2011-01-01

174

A total of 220 enteroadherent Escherichia coli were identified from 729 Egyptian children with diarrhea using the HEp-2 adherence assay. Enteropathogenic E.coli (EPEC = 38) was common among children <6 months old and provoked vomiting, while diffuse-adhering E.coli (DAEC = 109) induced diarrheal episodes of short duration, and enteroaggregative E.coli (EAEC = 73) induced mild non-persistent diarrhea. These results suggest that EPEC is associated with infantile diarrhea in Egyptian children. PMID:25122630

Ahmed, Salwa F; Shaheen, Hind I; Abdel-Messih, Ibrahim Adib; Mostafa, Manal; Putnam, Shannon D; Kamal, Karim A; Sayed, Abdel Nasser El; Frenck, Robert W; Sanders, John W; Klena, John D; Wierzba, Thomas F

2014-10-01

175

Background Many households in sub-Saharan Africa utilize the private sector as a primary source of treatment for malaria episodes. Expanding access to effective treatment in private drug shops may help reduce incidence of severe disease and mortality. This research leveraged a longitudinal survey of stocking of subsidized artemisinin combination therapies (ACTs), an effective anti-malarial, in Accredited Drug Dispensing Outlets (ADDOs) in two regions of Tanzania. This provided a unique opportunity to explore shop and market level determinants of product diffusion in a developing country retail market. Methods 356 ADDOs in the Rukwa and Mtwara regions of Tanzania were surveyed at seven points between Feb 2011 and May 2012. Shop level audits were used to measure the availability of subsidized ACTs at each shop. Data on market and shop level factors were collected during the survey and also extracted from GIS layers. Regression and network based methodologies were used. Shops classified as early and late adopters, following Rogers’ model of product diffusion, were compared. The Bass model of product diffusion was applied to determine whether shops stocked ACTs out of a need to imitate market competitors or a desire to satisfy customer needs. Results Following the introduction of a subsidy for ACTs, stocking increased from 12% to nearly 80% over the seven survey rounds. Stocking was influenced by higher numbers of proximal shops and clinics, larger customer traffic and the presence of a licensed pharmacist. Early adopters were characterized by a larger percentage of customers seeking care for malaria, a larger catchment and sourcing from specific wholesalers/suppliers. The Bass model of product diffusion indicated that shops were adopting products in response to competitor behavior, rather than customer demand. Conclusions Decisions to stock new pharmaceutical products in Tanzanian ADDOs are influenced by a combination of factors related to both market competition and customer demand, but are particularly influenced by the behavior of competing shops. Efforts to expand access to new pharmaceutical products in developing country markets could benefit from initial targeting of high profile shops in competitive markets and wholesale suppliers to encourage faster product diffusion across all drug retailers. PMID:24350611

2013-01-01

176

Incommensurate Diffusion in Confined Systems

NASA Astrophysics Data System (ADS)

Molecular simulations corroborate the existence of the disputed window effect, i.e., an increase in diffusion rate by orders of magnitude when the alkane chain length increases so that the shape of the alkane is no longer commensurate with that of a zeolite cage. This window effect is shown to be characteristic for molecular sieves with pore openings that approach the diameter of the adsorbate. Furthermore, the physical compatibility between the adsorbate and the adsorbent has a direct effect on the heat of adsorption, the Henry coefficients, the activation energy, and the frequency factors.

Dubbeldam, D.; Calero, S.; Maesen, T. L.; Smit, B.

2003-06-01

177

Scaling and Crossovers in Diffusion Limited Aggregation

We discuss the scaling of characteristic lengths in diffusion limited aggregation clusters in light of recent developments using conformal maps. We are led to the conjecture that the apparently anomalous scaling of lengths is due to one slow crossover. This is supported by an analytical argument for the scaling of the penetration depth of newly arrived random walkers, and by numerical evidence on the Laurent coefficients which uniquely determine each cluster. We find common crossover behavior for the squares of the characteristic lengths and the penetration depth of the form N{sup 2/D}({alpha}+{beta}N{sup -{phi}} ) with {phi} in the range -0.3{+-}0.1 suggesting that there is a single dominant correction to scaling. (c) 1999 The American Physical Society.

Somfai, E. [Department of Physics, The University of Michigan, Ann Arbor, Michigan 48109-1120 (United States)] [Department of Physics, The University of Michigan, Ann Arbor, Michigan 48109-1120 (United States); Sander, L. M. [Department of Physics, The University of Michigan, Ann Arbor, Michigan 48109-1120 (United States)] [Department of Physics, The University of Michigan, Ann Arbor, Michigan 48109-1120 (United States); Ball, R. C. [Department of Physics, The University of Warwick, Coventry CV4 7AL, (United Kingdom)] [Department of Physics, The University of Warwick, Coventry CV4 7AL, (United Kingdom)

1999-12-27

178

Experimental study of vortex diffusers

This report documents experimental research performed on vortex diffusers used in ventilation and air-conditioning systems. The main objectives of the research were (1) to study the flow characteristics of isothermal jets issuing from vortex diffusers, (2) to compare the vortex diffuser`s performance with that of a conventional diffuser, and (3) to prepare a report that disseminates the results to the designers of ventilation and air-conditioning systems. The researchers considered three diffusers: a conventional round ceiling diffuser and two different styles of vortex diffusers. Overall, the vortex diffusers create slightly more induction of ambient air in comparison to the conventional diffuser.

Shakerin, S.; Miller, P.L. [National Renewable Energy Lab., Golden, CO (United States)

1995-11-01

179

Diffusion Geometry Diffusion Geometry

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

180

The natural biodegradation of seven polycyclic aromatic hydrocarbons (PAHs) by native microorganisms was studied in five soils from Normandy (France) from diffusely polluted areas, which can also pose a problem in terms of surfaces and amounts of contaminated soils. Bioavailability tests using cyclodextrin-based extractions were performed. The natural degradation of low molecular weight (LMW) PAHs was not strongly correlated to their bioavailability due to their sorption to geosorbents. Conversely, the very low degradation of high molecular weight (HMW) PAHs was partly correlated to their poor availability, due to their sorption on complexes of organic matter and kaolinites or smectites. A principal component analysis allowed us to distinguish between the respective degradation behaviors of LMW and HMW PAHs. LMW PAHs were degraded in less than 2-3 months and were strongly influenced by the relative percentage of phenanthrene-degrading bacteria over total bacteria in soils. HMW PAHs were not significantly degraded, not only because they were less bioavailable but also because of a lack of degrading microorganisms. Benzo[a]pyrene stood apart since it was partly degraded in acidic soils, probably because of a catabolic cooperation between bacteria and fungi. PMID:24671402

Crampon, M; Bureau, F; Akpa-Vinceslas, M; Bodilis, J; Machour, N; Le Derf, F; Portet-Koltalo, F

2014-07-01

181

Amplitude of Supersonic Diffuser Flow Pulsations

NASA Technical Reports Server (NTRS)

A theoretical method for evaluating the stability characteristics and the amplitude and the frequency of pulsation of ram-jet engines without heat addition is presented herein. Experimental verification of the theoretical results are included where data were available. Theory and experiment show that the pulsation amplitude of a high mass-flow-ratio diffuser having no cone surface flow separation increases with decreasing mass flow. The theoretical trends for changes in amplitude, frequency, and mean-pressure recovery with changes in plenum-chamber volume were experimentally confirmed. For perforated convergent-divergent-type diffusers, a stability hysteresis loop was predicted on the pressure-recovery mass-flow-ratio curve. At a given mean mass-flow ratio, the higher.value of mean pressure recovery corresponded to oscillatory flow in the diffuser while the lower branch was stable. This hysteresis has been observed experimentally. The theory indicates that for a ram-jet engine of given diameter, the amplitude of pulsation of a supersonic diffuser is increased by decreasing the relative size of the plenum chamber with respect to the diffuser volume down to a critical value at which oscillations cease. In the region of these critical values, the stable mass-flow range of the diffuser may be increased either by decreasing the combustion chamber volume or by increasing the length of the diffuser.

Sterbentz, William H.; Davids, Joseph

1952-01-01

182

NASA Technical Reports Server (NTRS)

A methodological evaluation for two-finite differencing schemes for computer-aided gas turbine design is presented. The two computational schemes include; a Bounded Skewed Finite Differencing Scheme (BSUDS); and a Quadratic Upwind Differencing Scheme (QSDS). In the evaluation, the derivations of the schemes were incorporated into two-dimensional and three-dimensional versions of the Teaching Axisymmetric Characteristics Heuristically (TEACH) computer code. Assessments were made according to performance criteria for the solution of problems of turbulent, laminar, and coannular turbulent flow. The specific performance criteria used in the evaluation were simplicity, accuracy, and computational economy. It is found that the BSUDS scheme performed better with respect to the criteria than the QUDS. Some of the reasons for the more successful performance BSUDS are discussed.

Syed, S. A.; Chiappetta, L. M.

1985-01-01

183

Hereditary diffuse leukoencephalopathy with spheroids (HDLS) is an early-onset dementia that predominantly affects the cerebral white matter. After the discovery of a gene encoding the colony stimulating factor 1 receptor (CSF-1R) as a causative gene in patients with HDLS, gene analysis of CSF-1R enabled the diagnosis of HDLS without histopathological evidence. To clarify the genetic and clinical characteristics of HDLS, here, we reviewed the characteristics of patients with HDLS with CSF-1R mutations in the literature. Seventy-three patients from 54 pedigrees with HDLS from various ethnic backgrounds have been reported. Among them, Japanese patients account for 22% (16 patients from 15 pedigrees). Mean age at onset was 45 years (18 to 78 years). A wide range of clinical features including cognitive decline, behavioral changes, seizures, pyramidal signs, and parkinsonism have been described in these patients. Various kinds of mutations were found in the tyrosine kinase domain of CSF-1R. A frameshift mutation causing nonsense-mediated mRNA decay was also described. This suggests that haploinsufficiency of CSF-1R is sufficient to cause HDLS. Neuropathological analysis revealed that microglia in the brains of patients demonstrated distinct morphology and distribution. These results suggest that primary microglial dysfunction due to CSF-1R signaling perturbation may underlie the pathogenesis of HDLS. PMID:24807373

Konno, Takuya; Tada, Masayoshi; Tada, Mari; Nishizawa, Masatoyo; Ikeuchi, Takeshi

2014-05-01

184

ESTIMATION OF TURBULENT DIFFUSIVITY WITH DIRECT NUMERICAL SIMULATION OF STELLAR CONVECTION

We investigate the value of horizontal turbulent diffusivity {eta} by numerical calculation of thermal convection. In this study, we introduce a new method whereby the turbulent diffusivity is estimated by monitoring the time development of the passive scalar, which is initially distributed in a given Gaussian function with a spatial scale d{sub 0}. Our conclusions are as follows: (1) assuming the relation {eta} = L{sub c} v{sub rms}/3, where v{sub rms} is the root-mean-square (rms) velocity, the characteristic length L{sub c} is restricted by the shortest one among the pressure (density) scale height and the region depth. (2) The value of turbulent diffusivity becomes greater with the larger initial distribution scale d{sub 0}. (3) The approximation of turbulent diffusion holds better when the ratio of the initial distribution scale d{sub 0} to the characteristic length L{sub c} is larger.

Hotta, H.; Iida, Y.; Yokoyama, T., E-mail: hotta.h@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2012-05-20

185

Probe diffusion in phase-separated bicontinuous biopolymer gels.

Probe diffusion was determined in phase separated bicontinuous gels prepared by acid-induced gelation of the whey protein isolate-gellan gum system. The topological characterization of the phase-separated gel systems is achieved by confocal microscopy and the diffusion measurements are performed using pulsed field gradient (PFG) NMR and fluorescence recovery after photo-bleaching (FRAP). These two techniques gave complementary information about the mass transport at different time- and length scales, PFG NMR provided global diffusion rates in the gel systems, while FRAP enabled the measurements of diffusion in different phases of the phase-separated gels. The results revealed that the phase-separated gel with the largest characteristic wavelength had the fastest diffusion coefficient, while the gel with smaller microstructures had a slower probe diffusion rate. By using the diffusion data obtained by FRAP and the structural data from confocal microscopy, modelling through the lattice-Boltzmann framework was carried out to simulate the global diffusion and verify the validity of the experimental measurements. With this approach it was found that discrepancies between the two experimental techniques can be rationalized in terms of probe distribution between the different phases of the system. The combination of different techniques allowed the determination of diffusion in a phase-separated biopolymer gel and gave a clearer picture of this complex system. We also illustrate the difficulties that can arise if precautions are not taken to understand the system-probe interactions. PMID:25189146

Wassén, Sophia; Bordes, Romain; Gebäck, Tobias; Bernin, Diana; Schuster, Erich; Lorén, Niklas; Hermansson, Anne-Marie

2014-11-01

186

NSDL National Science Digital Library

This is a description for a learning module from Maricopa Advanced Technology Education Center. This PDF describes the module; access may be purchased by visiting the MATEC website. In an orderly and comprehensive set of lectures, lessons, and laboratory activities, MATEC explicates for your learners the complex process of diffusion. Beginning with an overview of diffusion's purpose in altering a wafer's electrical characteristics, the module then drills down to specifics: process parameters, different techniques of diffusion, the use of a hot probe to evaluate diffusion, and wafer handling. Your learners demonstrate their new knowledge by diffusing selected dopants into a silicon wafer.

2012-12-05

187

The relationship between skin cancer and non-Hodgkin lymphoma (NHL) suggests common genetic, host or environmental causes. Ultraviolet radiation (UVR), pigmentary characteristics have been linked with both malignancies, and for skin cancer, the melanocortin 1 receptor (MC1R) which influences pigmentation has also been implicated. This paper reports on the relationship between MC1R, skin, hair and eye colour, time spent outdoors, and diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL). Persons carrying MC1R homozygote variant alleles at R151C, R160W, D294H and D84E were more likely to have fair skin, red hair and to spend less time outdoors than those who did not. The variant allele at V92M was associated with FL (odds ratio (OR)=1.61, 95% confidence interval (CI) 1.08-2.39) and the r:wild type genotype with DLBCL (OR=0.58, 95% CI 0.38-0.89). Interactions between MC1R genotypes and skin colour influenced DLBCL risk; the RR genotype increased risk in individuals with medium or dark skin, based on 5 cases and no controls, but decreased risk among those of fair skin. On the whole, DLBCL and FL risk were not related to genetic variation in MC1R, pigmentation or time spent outdoors. PMID:20129839

Kane, Eleanor V; Painter, Dan; Roman, Eve; Allan, James; Law, Graham; Lightfoot, Tracy

2010-04-01

188

A nonlinear equation for ionic diffusion in a strong binary electrolyte

The problem of the one dimensional electro-diffusion of ions in a strong binary electrolyte is considered. The mathematical description, known as the Poisson-Nerst-Planck (PNP) system, consists of a diffusion equation for each species augmented by transport due to a self consistent electrostatic field determined by the Poisson equation. This description is also relevant to other important problems in physics such as electron and hole diffusion across semi-conductor junctions and the diffusion of ions in plasmas. If concentrations do not vary appreciably over distances of the order of the Debye length, the Poisson equation can be replaced by the condition of local charge neutrality first introduced by Planck. It can then be shown that both species diffuse at the same rate with a common diffusivity that is intermediate between that of the slow and fast species (ambipolar diffusion). Here we derive a more general theory by exploiting the ratio of Debye length to a characteristic length scale as a small asymptotic parameter. It is shown that the concentration of either species may be described by a nonlinear partial differential equation which provides a better approximation than the classical linear equation for ambipolar diffusion but reduces to it in the appropriate limit. PMID:21818176

Ghosal, Sandip; Chen, Zhen

2011-01-01

189

Diffusion in correlated random potentials, with applications to DNA

NASA Astrophysics Data System (ADS)

Many biological processes involve one-dimensional diffusion over a correlated inhomogeneous energy landscape with a correlation length ?c . Typical examples are specific protein target location on DNA, nucleosome repositioning, or DNA translocation through a nanopore, in all cases with ?c ?10 nm . We investigate such transport processes by the mean first passage time (MFPT) formalism, and find diffusion times which exhibit strong sample to sample fluctuations. For a displacement N , the average MFPT is diffusive, while its standard deviation over the ensemble of energy profiles scales as N3/2 with a large prefactor. Fluctuations are thus dominant for displacements smaller than a characteristic Nc ?c : typical values are much less than the mean, and governed by an anomalous diffusion rule. Potential biological consequences of such random walks, composed of rapid scans in the vicinity of favorable energy valleys and occasional jumps to further valleys, is discussed.

Slutsky, Michael; Kardar, Mehran; Mirny, Leonid A.

2004-06-01

190

Charged Particle Diffusion in Isotropic Random Static Magnetic Fields

NASA Astrophysics Data System (ADS)

Study of the transport and diffusion of charged particles in a turbulent magnetic field remains a subject of considerable interest. Research has most frequently concentrated on determining the diffusion coefficient in the presence of a mean magnetic field. Here we consider Diffusion of charged particles in fully three dimensional statistically isotropic magnetic field turbulence with no mean field which is pertinent to many astrophysical situations. We classify different regions of particle energy depending upon the ratio of Larmor radius of the charged particle to the characteristic outer length scale of turbulence. We propose three different theoretical models to calculate the diffusion coefficient each applicable to a distinct range of particle energies. The theoretical results are compared with those from computer simulations, showing very good agreement.

Subedi, P.; Sonsrettee, W.; Matthaeus, W. H.; Ruffolo, D. J.; Wan, M.; Montgomery, D.

2013-12-01

191

Pivoted document length normalization

Automatic information retrieval systems have to deal with documents of varying lengths in a text collection. Document length normalization is used to fairly retrieve documents of all lengths. In this study, we ohserve that a normalization scheme that retrieves documents of all lengths with similar chances as their likelihood of relevance will outperform another scheme which retrieves documents with chances

Amit Singhal; Chris Buckley; Manclar Mitra

1996-01-01

192

DIFFUSE SCATTERING Hercules 2008

- Barium IV: self-hosting incommensurate structure - Nanotubes@zeolite: structural characteristics-kind disorder Average structure ORDER Bragg peaks 2-body correlations DISORDER Diffuse scattering Average long Same scattering patterns! Scattering experiments: probe 2-body correlations Ambiguities can exist

Paris-Sud 11, UniversitÃ© de

193

Diffusion in Dense Inhomogeneous Colloid Suspensions in Narrow Channels

NASA Astrophysics Data System (ADS)

We report the results of a study of single particle diffusion in dense colloid fluids confined in a ribbon channel geometry that is intermediate between quasi-one-dimensional (q1D) and quasi-two-dimensional (q2D). In all of the systems studied the colloid density distribution transverse to the ribbon channel is stratified with peak amplitudes that depend on the colloid density. Although the virtual walls that confine a stratum are structured with a scale length of the colloid diameter, that structure does not have an apparent influence on the single particle diffusion, which shows the characteristic features of diffusion in a q1D channel with smooth walls. We find that for all channel widths and packing fractions studied the single particle transverse diffusion coefficient in a stratum is smaller than the single particle longitudinal diffusion coefficient in the same stratum, and that the single particle longitudinal diffusion coefficient varies very little from stratum to stratum, being only slightly smaller in the dense strata next to the walls than in central strata. The lack of variation of the longitudinal diffusion coefficient with apparent stratum density is explained by application of the Fischer-Methfessel approximation to the local density in an inhomogeneous liquid. The ratio of the transverse to longitudinal diffusion coefficients varies very slowly with ribbon width, implying a very slow transition from q1D to q2D behavior.

Lin, Binhua; Wonder, Emily; Rice, Stuart A.

2012-02-01

194

Diffused junction p(+)-n solar cells in bulk GaAs. II - Device characterization and modelling

NASA Astrophysics Data System (ADS)

The photovoltaic characteristics of p(+)-n junction solar cells fabricated on bulk GaAs by an open tube diffusion technique are presented in detail. Quantum efficiency measurements were analyzed and compared to computer simulations of the cell structure in order to determine material parameters such as diffusion length, surface recombination velocity and junction depth. From the results obtained it is projected that proper optimization of the cell parameters can increase the efficiency of the cells to close to 20 percent.

Keeney, R.; Sundaram, L. M. G.; Rode, H.; Bhat, I.; Ghandhi, S. K.; Borrego, J. M.

1984-02-01

195

Invariant lengths using existing Special Relativity

A field of random space-time events exhibiting complete spatial-temporal randomness appears statistically identical to all observers. Boost invariant lengths naturally emerge when we examine fluctuation scales of this field such as the nearest neighbor distance. If we interpret Planck's length as the characteristic fluctuation scale of quantum gravity, its boost invariance can then be understood without modifying Special Relativity.

Christopher D. Burton

2009-12-14

196

Characteristic scale lengths of nonthermal X-rays from the SN1006 NE rim,\\u000awhich are observed by Chandra, are interpreted in the context of the diffusive\\u000ashock acceleration on the assumption that the observed spatial profile of\\u000anonthermal X-rays corresponds to that of accelerated electrons with energies of\\u000aa few tens of TeV. To explain the observed scale lengths, we construct two

Ryo Yamazaki; Tatsuo Yoshida; Toshio Terasawa; Aya Bamba; Katsuji Koyama

2003-01-01

197

ERIC Educational Resources Information Center

Everyone with a thorough knowledge of single variable calculus knows that integration can be used to find the length of a curve on a given interval, called its arc length. Fortunately, if one endeavors to pose and solve more interesting problems than simply computing lengths of various curves, there are techniques available that do not require an…

Boudreaux, Gregory M.; Wells, M. Scott

2007-01-01

198

Measuring Thermodynamic Length

Thermodynamic length is a metric distance between equilibrium thermodynamic states. Among other interesting properties, this metric asymptotically bounds the dissipation induced by a finite time transformation of a thermodynamic system. It is also connected to the Jensen-Shannon divergence, Fisher information, and Rao's entropy differential metric. Therefore, thermodynamic length is of central interestin understanding matter out of equilibrium. In this Letter, we will consider how to denethermodynamic length for a small system described by equilibrium statistical mechanics and how to measure thermodynamic length within a computer simulation. Surprisingly, Bennett's classic acceptance ratio method for measuring free energy differences also measures thermodynamic length.

Crooks, Gavin E

2007-09-07

199

NASA Astrophysics Data System (ADS)

A series of gas nitriding and gas nitrocarburizing experiments was performed at 823 K (550 °C) to investigate the growth kinetics of ?-Fe3(N,C)1+ x /?'-Fe4N1- z -double layers on pure ?-iron substrates. The growth rate and composition of the (sub)layers were determined by (sub)layer-thickness measurements using light optical microscopy and electron-probe microanalyses (EPMA), respectively. Models for the growth of bilayers into a substrate, controlled by the interstitial diffusion of two elements (N and C), were applied to the experimental data to determine the intrinsic diffusion coefficients of N and C in ?-Fe3(N,C)1+ x as well as the self-diffusion coefficient of N in ?'-Fe4N1- z . For ?-Fe3(N,C)1+ x , it was found that the four components of the diffusion matrix, D_{{NN}}^{\\varepsilon } , D_{{CC}}^{\\varepsilon } , D_{{NC}}^{\\varepsilon } and D_{{CN}}^{\\varepsilon } , are all positive. The significant values of the off-diagonal diffusivities D_{{NC}}^{\\varepsilon } and D_{{CN}}^{\\varepsilon } indicate profound interaction of both interstitial species. Thereby, additional information is obtained about the thermodynamic properties of the ? phase in the ternary Fe-N-C system.

Woehrle, T.; Leineweber, A.; Mittemeijer, E. J.

2013-06-01

200

Numerical analysis of nuclear magnetic resonance relaxation-diffusion responses of sedimentary rock

NASA Astrophysics Data System (ADS)

The nuclear magnetic resonance (NMR) relaxation-diffusion response of porous reservoir rock is frequently used, e.g. in oil field applications, to extract characteristic length scales of pore space or information about saturating fluids. External gradients are typically applied to encode for diffusion. In reservoir rocks, field inhomogeneities due to internal gradients can even at low fields be strong enough to interfere with this encoding. Furthermore, the encoding for diffusion coefficients of fluids takes a finite amount of time, during which diffusing fluid molecules can experience restricted diffusion. Both effects can combine to make the interpretation of the diffusion dimension of a relaxation-diffusion measurement difficult. We use x-ray-CT images of porous rock samples to define the solid and fluid phases of reservoir rock and simulate the full experimental pulse sequence, taking into account the static applied field, external gradients and internal gradients as a function of susceptibility of each component, and surface and bulk relaxation properties of fluids and fluid-fluid and fluid-solid interfaces. We carry out simulations of NMR relaxation-diffusion measurements, while explicitly tracking the time-dependent diffusion coefficient in each fluid as well as associated local gradients. This allows us to quantify the influence of restricted diffusion and internal gradients for common choices of experimental parameters.

Arns, Christoph H.; AlGhamdi, Tariq; Arns, Ji-Youn

2011-01-01

201

In the TREC collection—a large full-text experimental text collection with widely varying document lengths—we observe that the likelihood of a document being judged relevant by a user increases with the document length. We show that a retrieval strategy, such as the vector-space cosine match, that retrieves documents of different lengths with roughly equal chances, will not optimally retrieve useful documents

Amit Singhal; Gerard Salton; Mandar Mitra; Chris Buckley

1996-01-01

202

Combustion characteristics of hydrogen–hydrocarbon hybrid fuels

A comparative study of the flame structure and characteristics of diffusion flames of the mixture of hydrogen–hydrocarbon (natural gas and propane) hybrid fuel in a slow co-flowing stream of air is presented. The volumetric content of natural gas and propane in the mixture was varied from 0–35%. The burner exit Reynolds number was varied from 150–3000. Measurements include flame length,

Ahsan R Choudhuri; S. R Gollahalli

2000-01-01

203

The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status. PMID:24616525

Trinkaus, Erik; Holliday, Trenton W.; Auerbach, Benjamin M.

2014-01-01

204

Novel Diffusivity Measurement Technique

NASA Technical Reports Server (NTRS)

A common-path interferometer (CPI) system was developed to measure the diffusivity of liquid pairs. The CPI is an optical technique that can be used to measure changes in the gradient of the refraction index of transparent materials. This system uses a shearing interferometer that shares the same optical path from a laser light source to the final imaging plane. Hence, the molecular diffusion coefficient of liquids can be determined using the physical relations between changes in the optical path length and the liquid phase properties. The data obtained with this interferometer were compared with similar results from other techniques and demonstrated that the instrument is superior in measuring the diffusivity of miscible liquids while keeping the system very compact and robust. CPI can also be used for studies in interface dynamics and other diffusion-dominated-process applications.

Rashidnia, Nasser

2001-01-01

205

NSDL National Science Digital Library

The GR Proper Length program simulates the distance between points using the Schwarzschild metric. It displays the proper length between two points and the light-travel path. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the gr_properlength.jar file will run the program if Java is installed. GR Proper Length is part of a suite of Open Source Physics programs that model aspects of General Relativity. Other programs provide additional visualizations. They can be found by searching ComPADRE for Open Source Physics, OSP, or General Relativity.

Christian, Wolfgang; Belloni, Mario; Cox, Anne

2008-05-14

206

Contact Diffusion Interaction of Materials with Cladding.

National Technical Information Service (NTIS)

Consideration is given to problems arising from diffusion interaction between materials and their claddings and the film of condensate formed on their surfaces. Topics include: characteristics of diffusion in condensates formed on a hot cladding; diffusio...

A. A. Babad-Zakhryapina

1967-01-01

207

Myofilament Length Dependent Activation

The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca2+ ions at a longer sarcomere length, commonly referred to as myofilament length dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the “Frank-Starling law of the heart” constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development. PMID:20053351

de Tombe, Pieter P.; Mateja, Ryan D.; Kittipong-Tachampa; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C.

2010-01-01

208

Myofilament length dependent activation

The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca{sup 2+} ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the 'Frank-Starling law of the heart' constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

de Tombe, Pieter P.; Mateja, Ryan D.; Tachampa, Kittipong; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C. (IIT); (Loyola)

2010-05-25

209

Measurements at high spatial resolution by DGT (diffusive gradients in thin films) require a binding agent that is homogeneously distributed in the binding layer. Formation of ferrihydrite by in situ precipitation within a hydrogel has been previously shown to meet these requirements for the measurement of oxyanions by DGT. Here, we report for the first time detailed performance characteristics of the binding gel and associated DGT devices obtained by deployment in known solutions. To allow comparison of measured and theoretical accumulation of As(V), Se(VI), V(V), and Sb(V), their diffusion coefficients were determined using an independent diffusion cell. Theoretical responses were obtained irrespective of ionic strength (1-100 mmol L(-1)) and pH (3-8), except for Se above pH 7.8 and V below pH 5. Calculated detection limits, based on deployment times of 1 day, were lower than those for devices made with a binding gel cast with a ferrihydrite slurry, and the measured capacity of the binding layer was also superior. There was no evidence for interference from other oxyanions, but binding performance showed some deterioration after 38 days of storage. The potential capability for measuring labile forms of these oxyanions in acidic to neutral, fresh to brackish waters was demonstrated. PMID:20936784

Luo, Jun; Zhang, Hao; Santner, Jakob; Davison, William

2010-11-01

210

NSDL National Science Digital Library

This lesson plan for teachers of kindergarten students involves activities that introduce the concepts of using a non-standard unit to measure length and associating a measurement with a number. After introducing the lesson with a literature connection, students cut out their own measuring cards and use them to compare lengths, and measure distance along a path using a line of ladybug beans and a non-standard tape. Materials, handouts, and suggestions for extensions and parental involvement are included.

Lessonplans, Utah

2006-06-24

211

Technological changes have moved publishing to electronic-first publication where the print version has been relegated to simply another display mode. Distribution in HTML and EPUB formats, for example, changes the reading environment and reduces the need for strict pagination. Therefore, in an effort to streamline the calculation of length, the APS journals will no longer use the printed page as the determining factor for length. Instead the journals will now use word counts (or word equivalents for tables, figures, and equations) to establish length; for details please see http://publish.aps.org/authors/length-guide. The title, byline, abstract, acknowledgment, and references will not be included in these counts allowing authors the freedom to appropriately credit coworkers, funding sources, and the previous literature, bringing all relevant references to the attention of readers. This new method for determining length will be easier for authors to calculate in advance, and lead to fewer length-associated revisions in proof, yet still retain the quality of concise communication that is a virtue of short papers.

Sprouse, Gene D. [American Physical Society (United States)

2011-07-15

212

Universality of modulation length exponents

NASA Astrophysics Data System (ADS)

We study systems (classical or quantum) with general pairwise interactions. Our prime interest is in frustrated spin systems. First, we focus on systems with a crossover temperature T^* across which the correlation function changes from exhibiting commensurate to incommensurate modulations. We report on a new exponent, ?L, characterizing the universal nature of this crossover. Near the crossover, the characteristic wave-vector k on the incommensurate side differs from that on the commensurate side, q by |k-q||T-T^*|^?L. We find, in general, that ?L=1/2, or in some special cases, other rational numbers. We discuss applications to the axial next nearest neighbor Ising model, Fermi systems (with application to the metal to band insulator transition) and Bose systems. Second, we obtain a universal form of the high temperature correlation function in general systems. From this, we show the existence of a diverging correlation length in the presence of long range interactions. Such a correlation length tends to the screening length in the presence of screening. We also find a way of obtaining the pairwise interaction potentials in the high temperature phase from the correlation functions.

Chakrabarty, Saurish; Seidel, Alexander; Nussinov, Zohar

2012-02-01

213

Diffusion-Aware Sampling and Estimation in Information Diffusion Networks

Partially-observed data collected by sampling methods is often being studied to obtain the characteristics of information diffusion networks. However, these methods usually do not consider the behavior of diffusion process. In this paper, we propose a novel two-step (sampling/estimation) measurement framework by utilizing the diffusion process characteristics. To this end, we propose a link-tracing based sampling design which uses the infection times as local information without any knowledge about the latent structure of diffusion network. To correct the bias of sampled data, we introduce three estimators for different categories; link-based, node-based, and cascade-based. To the best of our knowledge, this is the first attempt to introduce a complete measurement framework for diffusion networks. We also show that the estimator plays an important role in correcting the bias of sampling from diffusion networks. Our comprehensive empirical analysis over large synthetic and real datasets demonstrates that in av...

Mehdiabadi, Motahareh Eslami; Salehi, Mostafa

2014-01-01

214

On collisional diffusion in a stochastic magnetic field

The effect of particle collisions on the transport in a stochastic magnetic field in tokamaks is investigated. The model of resonant magnetic perturbations generated by external coils at the plasma edge is used for the stochastic magnetic field. The particle collisions are simulated by a random walk process along the magnetic field lines and the jumps across the field lines at the collision instants. The dependencies of the local diffusion coefficients on the mean free path ?{sub mfp}, the diffusion coefficients of field lines D{sub FL}, and the collisional diffusion coefficients, ?{sub ?} are studied. Based on these numerical data and the heuristic arguments, the empirical formula, D{sub r}=?{sub ?}+v{sub ||}D{sub FL}/(1+L{sub c}/?{sub mfp}), for the local diffusion coefficient is proposed, where L{sub c} is the characteristic length of order of the connection length l{sub c}=?qR{sub 0}, q is the safety factor, R{sub 0} is the major radius. The formula quite well describes the results of numerical simulations. In the limiting cases, the formula describes the Rechester-Rosenbluth and Laval scalings.

Abdullaev, S. S. [Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung - Plasmaphysik, EURATOM Association, 52425 Jülich (Germany)] [Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung - Plasmaphysik, EURATOM Association, 52425 Jülich (Germany)

2013-08-15

215

NASA Astrophysics Data System (ADS)

A study of signals originating near the lithium-diffused n+ contact of p-type point contact (PPC) high purity germanium detectors (HPGe) is presented. The transition region between the active germanium and the fully dead layer of the n+ contact is examined. Energy depositions in this transition region are shown to result in partial charge collection. This provides a mechanism for events with a well defined energy to contribute to the continuum of the energy spectrum at lower energies. A novel technique to quantify the contribution from this source of background is introduced. Experiments that operate germanium detectors with a very low energy threshold may benefit from the methods presented herein.

Aguayo, E.; Amman, M.; Avignone, F. T.; Barabash, A. S.; Barton, P. J.; Beene, J. R.; Bertrand, F. E.; Boswell, M.; Brudanin, V.; Busch, M.; Chan, Y.-D.; Christofferson, C. D.; Collar, J. I.; Combs, D. C.; Cooper, R. J.; Detwiler, J. A.; Doe, P. J.; Efremenko, Yu.; Egorov, V.; Ejiri, H.; Elliott, S. R.; Esterline, J.; Fast, J. E.; Fields, N.; Finnerty, P.; Fraenkle, F. M.; Galindo-Uribarri, A.; Gehman, V. M.; Giovanetti, G. K.; Green, M. P.; Guiseppe, V. E.; Gusey, K.; Hallin, A. L.; Hazama, R.; Henning, R.; Hoppe, E. W.; Horton, M.; Howard, S.; Howe, M. A.; Johnson, R. A.; Keeter, K. J.; Kidd, M. F.; Knecht, A.; Kochetov, O.; Konovalov, S. I.; Kouzes, R. T.; Laferriere, B. D.; Leon, J.; Leviner, L. E.; Loach, J. C.; Looker, Q.; Luke, P. N.; Macmullin, S.; Marino, M. G.; Martin, R. D.; Merriman, J. H.; Miller, M. L.; Mizouni, L.; Nomachi, M.; Orrell, J. L.; Overman, N. R.; Perumpilly, G.; Phillips, D. G.; Poon, A. W. P.; Radford, D. C.; Rielage, K.; Robertson, R. G. H.; Ronquest, M. C.; Schubert, A. G.; Shima, T.; Shirchenko, M.; Snavely, K. J.; Steele, D.; Strain, J.; Timkin, V.; Tornow, W.; Varner, R. L.; Vetter, K.; Vorren, K.; Wilkerson, J. F.; Yakushev, E.; Yaver, H.; Young, A. R.; Yu, C.-H.; Yumatov, V.; Majorana Collaboration

2013-02-01

216

A study of signals originating near the lithium-diffused n+ contact of p-type point contact (PPC) high purity germanium detectors (HPGe) is presented. The transition region between the active germanium and the fully dead layer of the n+ contact is examined. Energy depositions in this transition region are shown to result in partial charge collection. This provides a mechanism for events with a well defined energy to contribute to the continuum of the energy spectrum at lower energies. A novel technique to quantify the contribution from this source of background is introduced. Experiments that operate germanium detectors with a very low energy threshold may benefit from the methods presented herein.

Aguayo, E. [Pacific Northwest National Laboratory (PNNL); Amman, M. [Lawrence Berkeley National Laboratory (LBNL); Avignone, F. T. [University of South Carolina/ORNL; Barabash, A.S. [Institute of Theoretical & Experimental Physics, Moscow, Russia; Barton, P. J. [Lawrence Berkeley National Laboratory (LBNL); Beene, James R [ORNL; Bertrand Jr, Fred E [ORNL; Boswell, M. [Los Alamos National Laboratory (LANL); Brudanin, V. [Joint Institute for Nuclear Research, Dubna, Russia; Busch, M. [Duke University; Chan, Y-D [Lawrence Berkeley National Laboratory (LBNL); Christofferson, C. D. [South Dakota School of Mines & Technology, Rapid City, SD; Collar, Juan I. [University of Chicago; Combs, D. C. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Cooper, Reynold J [ORNL; Detwiler, J.A. [Lawrence Berkeley National Laboratory (LBNL); Doe, P. J. [University of Washington; Efremenko, Yuri [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Egorov, V. [Joint Institute for Nuclear Research, Dubna, Russia; Ejiri, H. [Osaka University; Elliott, S. R. [Los Alamos National Laboratory (LANL); Esterline, J. [Duke University; Fast, J.E. [Pacific Northwest National Laboratory (PNNL); Fields, N. [University of Chicago; Finnerty, P. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Fraenkle, F. M. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Galindo-Uribarri, Alfredo {nmn} [ORNL; Gehman, V. M. [Los Alamos National Laboratory (LANL); Giovanetti, G. K. [Univ, of North Carolina & Triangle Universities Nucl. Lab - Durham, NC; Green, M. P. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Guiseppe, V.E. [University of South Dakota; Gusey, K. [Joint Institute for Nuclear Research, Dubna, Russia; Hallin, A. L. [University of Alberta, Edmonton, Canada; Hazama, R. [Osaka University; Henning, R. [Univ, of North Carolina & Triangle Universities Nucl. Lab - Durham, NC; Hoppe, E.W. [Pacific Northwest National Laboratory (PNNL); Horton, M. [South Dakota School of Mines & Technology, Rapid City, SD; Howard, S. [South Dakota School of Mines and Technology; Howe, M. A. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Johnson, R. A. [University of Washington, Seattle; Keeter, K.J. [Black Hills State University, Spearfish, SD; Kidd, M. F. [Los Alamos National Laboratory (LANL); Knecht, A. [University of Washington, Seattle; Kochetov, O. [Joint Institute for Nuclear Research, Dubna, Russia; Konovalov, S.I. [Institute of Theoretical & Experimental Physics, Moscow, Russia; Kouzes, R. T. [Pacific Northwest National Laboratory (PNNL); LaFerriere, B. D. [Pacific Northwest National Laboratory (PNNL); Leon, J. [University of Washington, Seattle; Leviner, L. E. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Loach, J.C. [Lawrence Berkeley National Laboratory (LBNL); Looker, Q. [Lawrence Berkeley National Laboratory (LBNL); Luke, P.N. [Lawrence Berkeley National Laboratory (LBNL); MacMullin, S. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Marino, M. G. [University of Washington, Seattle; Martin, R.D. [Lawrence Berkeley National Laboratory (LBNL); Merriman, J. H. [Pacific Northwest National Laboratory (PNNL); Miller, M. L. [University of Washington, Seattle; Mizouni, L. [PPNL/Univ. of South Carolina; Nomachi, M. [Osaka University; Orrell, John L. [Pacific Northwest National Laboratory (PNNL); Overman, N. R. [Pacific Northwest National Laboratory (PNNL); Perumpilly, G. [University of South Dakota; Phillips II, D. G. [University of North Carolina / Triangle Universities Nuclear Lababoratory, Durham; Poon, A.W.P. [Lawrence Berkeley National Laboratory (LBNL); et al.

2013-01-01

217

Anomalous Diffusion: In diffusion-weighted magnetic resonance imaging (MRI) of neural tissue modeled diffusion in neural tissue from the perspective of a continuous time random walk. Here, the characteristic diffusion decay is represented by the Mittag- Leffler function (see figure), which relaxes

McQuade, D. Tyler

218

Correlated Diffusion of Colloidal Particles near a Liquid-Liquid Interface

Optical microscopy and multi-particle tracking are used to investigate the cross-correlated diffusion of quasi two-dimensional colloidal particles near an oil-water interface. The behaviors of the correlated diffusion along longitudinal and transverse direction are asymmetric. It is shown that the characteristic length for longitudinal and transverse correlated diffusion are particle diameter and the distance from particle center to the interface, respectively, for large particle separation . The longitudinal and transverse correlated diffusion coefficient and are independent of the colloidal area fraction when , which indicates that the hydrodynamic interactions(HIs) among the particles are dominated by HIs through the surrounding fluid for small . For high area fraction , the power law exponent for the spatial decay of begins to decrease, which suggests the HIs are more contributed from the 2D particle monolayer self for large . PMID:24465498

Zhang, Wei; Chen, Song; Li, Na; Zhang, Jia zheng; Chen, Wei

2014-01-01

219

Upper Extremity Length Equalization

Significant upper extremity length inequality is uncommon but can cause major functional problems. The ability to position and use the hand may be impaired by shortness of any of the long bones of the upper extremity. In many respects upper and lower extremity length problems are similar. They most commonly occur after injury to a growing bone and the treatment modalities utilized in the lower extremity may be applied to the upper extremity. These treatment options include epiphysiodesis, shortening osteotomy, angulatory correction osteotomy and lengthening. This report reviews the literature relative to upper extremity length inequality and equalization and presents an algorithm for evaluation and planning appropriate treatment for patients with this condition. This algorithm is illustrated by two clinical cases of posttraumatic shortness of the radius which were effectively treated. ImagesFigure 1Figure 2Figure 3

DeCoster, Thomas A.; Ritterbusch, John; Crawford, Mark

1992-01-01

220

Accuracy of Reporting of Menstrual Cycle Length

There are many studies based on self-reported menstrual cycle length, yet little is known about the validity of this measure. The authors used data collected in 1990 from 352 women born in Chicago, Illinois, aged 37–39 years. Women reported their usual cycle length and behavioral and reproductive characteristics at study enrollment and then completed daily menstrual diaries for up to 6 months. The authors compared this observed cycle length (geometric mean) with the reported length by using kappa coefficients. To assess systematic effects, they performed linear regression of the difference between reported and observed cycle length. Agreement between observed and reported cycle length was moderate. The crude overall kappa coefficient was 0.33; the kappa adjusted for within-woman sampling variability was 0.45 (95% confidence interval: 0.36, 0.55). On average, women overestimated their cycle length by 0.7 days (95% confidence interval: 0.3, 1.0). Reporting by sexually active women and women with a history of infertility was more accurate. Parity, body mass index, prior medical evaluation for irregular cycles, and exercise were all associated with systematic reporting differences. Studies that rely on self-reported cycle length could be prone to artifactual findings because of systematic covariate effects on reporting. PMID:17928401

Weinberg, Clarice R.; Wilcox, Allen J.; McConnaughey, D. Robert; Hornsby, Paige; Baird, Donna D.

2008-01-01

221

NSDL National Science Digital Library

This website includes an animation which illustrates the diffusion process. The two models that have been developed to explain the mechanism for the diffusion of dopants into silicon are the Vacancy model and the Interstitial model. It is the different bonding characteristics of the dopants with silicon that determine the diffusion mechanism. Although each model is based on these differences, they are not mutually exclusive. Objective: Explain the difference between the Vacancy and Interstitial diffusion models. You can find this animation under the heading "Process & Equipment III." This simulation is from Module 019 of the Process & Equipment III Cluster of the MATEC Module Library (MML). To view other clusters or for more information about the MML visit http://matec.org/ps/library3/process_I.shtmlKey

2012-11-22

222

Characteristic 0 Positive characteristic

Characteristic 0 Positive characteristic Unlikely formal intersections Piotr Kowalski Instytut Matematyczny Uniwersytetu Wroclawskiego June 14, 2012 Kowalski Unlikely formal intersections #12;Characteristic(A) + dim(V ) - dim(W). Kowalski Unlikely formal intersections #12;Characteristic 0 Positive characteristic

Kowalski, Piotr

223

Two-dimensional network simulation of diffusion-driven coarsening of foam inside a porous medium

In order to use foams in subsurface applications, it is necessary to understand their stability in porous media. Diffusion-driven coarsening of a stationary or nonflowing foam in a porous medium results in changing gas pressures and a coarsening of the foam texture. A two-dimensional network simulation has been created that predicts the behavior of foam in a porous medium by physically specifying the locations of all the lamellae in the system and by solving the complete set of Young-Laplace and diffusion equations. An hourglass approximates the shape of the pores, and the pore walls are considered to be highly water wet. A singularity arises in the system of differential algebraic equations due to the curvature of the pore walls. This singularity is a signal that the system must undergo oscillations or sudden lamellar rearrangements before the diffusion process can continue. Newton-Raphson iteration is used along with Keller`s method of arc-length continuation and a new jump resolution technique to locate and resolve bifurcations in the system of coupled lamellae. Gas bubbles in pore throats are regions of encapsulated pressure. As gas is released from these bubbles during diffusion, the pressure of the bubbles in the pore bodies increases. When the pressure increase is scaled by the characteristic Young-Laplace pressure, the equilibrium time for the diffusion process is scaled by the ratio of the square of the characteristic length to the gas diffusivity and two dimensionless groups. One describes the ease with which gas can diffuse through a lamella, and the second represents the amount of gas encapsulated within the pore throats initially. Given this scaling, the resulting plots of pressure versus time and normalized lamellae positions versus time are universal for all system sizes and characteristics. This is true as long as the initial lamella distribution is the same in each case.

Cohen, D.; Radke, C.J. [Lawrence Berkeley National Lab., CA (United States)] [Lawrence Berkeley National Lab., CA (United States); Patzek, T.W. [Univ. of California, Berkeley, CA (United States)] [Univ. of California, Berkeley, CA (United States)

1996-05-10

224

Two-dimensional network simulation of diffusion driven coarsening of foam inside a porous medium

In order to use foams in subsurface applications, it is necessary to understand their stability in porous media. Diffusion driven coarsening of a stationary or nonflowing foam in a porous medium results in changing gas pressures and a coarsening of the foam texture. A two-dimensional network simulation has been created that predicts the behavior of foam in a porous medium by physically specifying the locations of all the lamellae in the system and by solving the complete set of Young-Laplace and diffusion equations. An hourglass approximates the shape of the pores, and the pore walls are considered to be highly water wet. A singularity arises in the system of differential algebraic equations due to the curvature of the pore walls. This singularity is a signal that the system must undergo oscillations or sudden lamellar rearrangements before the diffusion process can continue. Newton-Raphson iteration is used along with Keller`s method of arc-length continuation and a new jump resolution technique to locate and resolve bifurcations in the system of coupled lamellae. Gas bubbles in pore throats are regions of encapsulated pressure. As gas is released from these bubbles during diffusion, the pressure of the bubbles in the pore bodies increases. When the pressure increase is scaled by the characteristic Young-Laplace pressure, the equilibrium time for the diffusion process is scaled by the ratio of the square of the characteristic length to the gas diffusivity and two dimensionless groups. One describes the ease with which gas can diffuse through a lamella, the second represents the amount of gas encapsulated within the pore throats initially. Given this scaling, the resulting plots of pressure versus time and normalized lamellae positions versus time are universal for all system sizes and characteristics. This is true as long as the initial lamella distribution is the same in each case.

Cohen, D.; Patzek, T.W.; Radke, C.J.

1996-04-01

225

Liquid diffusion in fibrous insulation

Vapor condensation in insulated structures degrades their physical properties as well as thermal performance. Motion of the condensate within the insulation is a crucial factor in analyzing this phenomenon. The liquid diffusion can be caused by several driving potentials. A model for isothermal liquid transport in fibrous insulation is presented. The model relates liquid diffusion to the characteristics of the

S. Motakef; M. A. El-Masri

1983-01-01

226

Power-law distributions are the main functional form for the distribution of repeat size and repeat copy number in the human genome. When the genome is broken into fragments for sequencing, the limited size of fragments and reads may prevent an unique alignment of repeat sequences to the reference sequence. Repeats in the human genome can be as long as 104 bases, or 105 ? 106 bases when allowing for mismatches between repeat units. Sequence reads from these regions are therefore unmappable when the read length is in the range of 103 bases. With a read length of 1000 bases, slightly more than 1% of the assembled genome, and slightly less than 1% of the 1 kb reads, are unmappable, excluding the unassembled portion of the human genome (8% in GRCh37/hg19). The slow decay (long tail) of the power-law function implies a diminishing return in converting unmappable regions/reads to become mappable with the increase of the read length, with the understanding that increasing read length will always move toward the direction of 100% mappability.

Li, Wentian; Freudenberg, Jan

2014-01-01

227

Diffusion in an absorbing porous medium : from microscopic geometry to macroscopic transport

Two physical models of diffusion in absorbing porous media are proposed on two length scales. One models diffusion in the pore space of a random medium with absorbing interfaces while the other is a reaction diffusion model ...

Forney, David C., III

2007-01-01

228

Mesoscopic diffusion thermopower in two-dimensional electron gases

NASA Astrophysics Data System (ADS)

The diffusion of energy that is locally deposited into two-dimensional electron gases by Joule heating generates transverse voltages across devices with broken symmetry. For mesoscopic structures characterized by device dimensions comparable to the energy diffusion length, the resulting thermopower strongly depends on details of the potential profile defined by electric gates. We discuss these mesoscopic features within a diffusion thermopower model and propose schemes to measure the energy diffusion length and its dependence on gate voltage.

Rojek, Stephan; König, Jürgen

2014-09-01

229

This author's recent proposal of interferometric tests of Planck-scale-related properties of space-time is here revisited from a strictly phenomenological viewpoint. The results announced previously are rederived using elementary dimensional considerations. The dimensional analysis is then extended to the other two classes of experiments (observations of neutral kaons at particle accelerators and observations of the gamma rays we detect from distant astrophysical sources) which have been recently considered as opportunities to explore "foamy" properties of space-time. The emerging picture suggests that there is an objective and intuitive way to connect the sensitivities of these three experiments with the Planck length. While in previous studies the emphasis was always on some quantum-gravity scenario and the analysis was always primarily aimed at showing that the chosen scenario would leave a trace in a certain class of doable experiments, the analysis here reported takes as starting point the experiments and, by relating in a direct quantitative way the sensitivities to the Planck length, provides a model-independent description of the status of Planck-length phenomenology.

Giovanni Amelino-Camelia

2000-08-04

230

Thermal Expansion and Diffusion Coefficients of Carbon

Thermal Expansion and Diffusion Coefficients of Carbon Nanotube-Polymer Composites Chenyu Wei* NASA for polymer-nanotube interface are used to investigate the thermal expansion and diffusion characteristics to increase the glass transition temperature Tg, and thermal expansion and diffusion coefficients

Wei, Chenyu

231

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

232

NASA Technical Reports Server (NTRS)

The performance characteristics of InP-based In(x)Ga(1-x)As/In(0.52)Al(0.48)As (0.53 is less than or equal to x is less than or equal to 0.70) pseudomorphic modulation-doped field-effect transistors (MODFET's) as a function of strain in the channel, gate, length, and temperature were investigated analytically and experimentally. The strain in the channel was varied by varying the In composition x. The temperature was varied in the range of 40-300 K and the devices have gate lengths L(sub g) of 0.8 and 0.2 microns. Analysis of the device was done using a one-dimensional self consistent solution of the Poisson and Schroedinger equations in the channel, a two-dimensional Poisson solver to obtain the channel electric field, and a Monte Carlo simulation to estimate the carrier transit times in the channel. An increase in the value of the cutoff frequency is predicted for an increase in In composition, a decrease in temperature, and a decrease in gate length. The improvements seen with decreasing temperature, decreasing gate length, and increased In composition were smaller than those predicted by analysis. The experimental results on pseudomorphic InGaAs/InAlAs MODFET's showed that there is a 15-30 percent improvement in cutoff frequency in both the 0.8- and 0.2-micron gate length devices when the temperature is lowered from 300 to 40 K.

Lai, Richard; Bhattacharya, Pallab K.; Yang, David; Brock, Timothy L.; Alterovitz, Samuel A.; Downey, Alan N.

1993-01-01

233

Fokker-Planck . . . Diffusion . . .

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

234

Approximate sample sizes required to estimate length distributions

The sample sizes required to estimate fish length were determined by bootstrapping from reference length distributions. Depending on population characteristics and species-specific maximum lengths, 1-cm length-frequency histograms required 375-1,200 fish to estimate within 10% with 80% confidence, 2.5-cm histograms required 150-425 fish, proportional stock density required 75-140 fish, and mean length required 75-160 fish. In general, smaller species, smaller populations, populations with higher mortality, and simpler length statistics required fewer samples. Indices that require low sample sizes may be suitable for monitoring population status, and when large changes in length are evident, additional sampling effort may be allocated to more precisely define length status with more informative estimators. ?? Copyright by the American Fisheries Society 2007.

Miranda, L. E.

2007-01-01

235

Indeterminate-length quantum coding

The quantum analogues of classical variable-length codes are indeterminate-length quantum codes, in which codewords may exist in superpositions of different lengths. This paper explores some of their properties. The length observable for such codes is governed by a quantum version of the Kraft-McMillan inequality. Indeterminate-length quantum codes also provide an alternate approach to quantum data compression.

Benjamin Schumacher; Michael D. Westmoreland

2000-11-02

236

Protein self-diffusion in crowded solutions

Macromolecular crowding in biological media is an essential factor for cellular function. The interplay of intermolecular interactions at multiple time and length scales governs a fine-tuned system of reaction and transport processes, including particularly protein diffusion as a limiting or driving factor. Using quasielastic neutron backscattering, we probe the protein self-diffusion in crowded aqueous solutions of bovine serum albumin on nanosecond time and nanometer length scales employing the same protein as crowding agent. The measured diffusion coefficient D(?) strongly decreases with increasing protein volume fraction ? explored within 7% ? ? ? 30%. With an ellipsoidal protein model and an analytical framework involving colloid diffusion theory, we separate the rotational Dr(?) and translational Dt(?) contributions to D(?). The resulting Dt(?) is described by short-time self-diffusion of effective spheres. Protein self-diffusion at biological volume fractions is found to be slowed down to 20% of the dilute limit solely due to hydrodynamic interactions. PMID:21730176

Roosen-Runge, Felix; Hennig, Marcus; Zhang, Fajun; Jacobs, Robert M. J.; Sztucki, Michael; Schober, Helmut; Seydel, Tilo; Schreiber, Frank

2011-01-01

237

NASA Technical Reports Server (NTRS)

Payload customers for the Space Shuttle have recently expressed concerns about the possibility of their payloads at an adjacent pad being contaminated by plume effluents from a shuttle at an active pad as they await launch on an inactive pad. As part of a study to satisfy such concerns a ring of inexpensive dosimeters was deployed around the active pad at the inter-pad distance. However, following a launch, dosimeters cannot be read for several hours after the exposure. As a consequence factors such as different substrates, solvent systems, and possible volatilization of HCl from the badges were studied. This observation led to the length of stain (LOS) dosimeters of this invention. Commercial passive LOS dosimeters are sensitive only to the extent of being capable of sensing 2 ppm to 20 ppm if the exposure is 8 hours. To map and quantitate the HCl generated by Shuttle launches, and in the atmosphere within a radius of 1.5 miles from the active pad, a sensitivity of 2 ppm HCl in the atmospheric gases on an exposure of 5 minutes is required. A passive length of stain dosimeter has been developed having a sensitivity rendering it capable of detecting a gas in a concentration as low as 2 ppm on an exposure of five minutes.

Lueck, Dale E. (inventor)

1994-01-01

238

Layered superconducting ferromagnetic nanosystems Cu(32 nm)/V(40-80 nm)/Fe(0.5-4 nm)/MgO(001) have been investigated by reflectometry and the diffuse scattering of synchrotron radiation. The data obtained make it possible to determine the important characteristics of samples such as the layer thickness and the rms heights and lateral correlation lengths of roughness at the interfaces.

Nikitin, A. M., E-mail: am.nikitin@physics.msu.ru [Moscow State University (Russian Federation); Borisov, M. M.; Mukhamedzhanov, E. Kh.; Kovalchuk, M. V. [National Research Center Kurchatov Institute (Russian Federation); Sajti, S.; Tancziko, F.; Deak, L.; Bottyan, L. [Hungarian Academy of Sciences, KFKI Research Institute for Particle and Nuclear Physics (Hungary); Khaydukov, Yu. N.; Aksenov, V. L. [Moscow State University (Russian Federation)

2011-09-15

239

Permeability characteristics have been determined for isolated ribbons of the basement membrane of the intestine ofAscaris suum. The solute permeability coefficient (Pc) was measured for a series of hydrophobic, nonionic molecules of graded molecular size. The geometric pore area per unit path length (Ao\\/?x) was estimated to be 24.0 cm from the diffusion rates for the various solute molecules. A

Manus J. Donahue; Calvin G. Beames; Karen Sue Bost

1983-01-01

240

Effects of diffusion boundary layer on reaction kinetics of immunoassay in a biosensor

NASA Astrophysics Data System (ADS)

Specific binding reaction is a natural characteristic that is applied to design biosensors. This work simulates the binding reaction kinetics of two commonly used proteins, C-reactive protein and immunoglobulin G, in a reaction chamber (microchannel) of a biosensor. For a diffusion-limited protein, the diffusion boundary layer on the reaction surface of the biosensor would hinder the binding reaction from association and dissociation. Several crucial factors, which influence the binding reaction curves in the simulation, are discussed, including the concentration of analyte, the inlet flow velocity, the channel height, and the length of the reaction surface. A higher channel causes the diffusive transport of the analyte to take longer time to reach the reaction surface, which in turn decreases the reaction rate of the protein pairs. The length of the reaction surface plays an important role in the formation of the boundary layer. For longer reaction surface, it takes more time to allow diffusion to overcome the larger zone of the diffusion boundary layer, resulting in a slower binding rate and a longer time to reach saturation. The presented data of simulation are useful in designing the biosensors.

Yang, Chih-Kai; Chang, Jeng-Shian; Chao, Sheng D.; Wu, Kuang-Chong

2008-04-01

241

Arc-Length-Based Axial Deformation and Length Preserving Deformation

This paper presents an arc-length preserving axial deformation along a B-spline curve based on arc-length parameterization of the axial curve. Space spanned by arc length and rotation minimizing frame on the axis is taken as the embedded space. As in real life, the length of an object's skeleton usually remains constant when it is axially deformed such as a swimming

Qunsheng Peng; Xiaogang Jin; Jieqing Feng

242

NASA Astrophysics Data System (ADS)

Parameterizations of the vertical eddy diffusivity over homogeneous terrain in neutral, stable and unstable conditions for the entire atmospheric boundary layer are proposed using the mixing length theory. The formulation utilizes the theoretically derived local mixing length scale that is composed of three component length scales. Proposed profiles of the eddy diffusivity in various stability conditions are compared to those reported in the literature. The proposed profiles of the eddy diffusivity are used in a generalized analytical model for dispersion of pollutants released from a continuous source in the atmospheric boundary layer. The dispersion model describing the crosswind integrated concentrations is briefly presented. By considering the proposed and other commonly applied parameterizations of eddy diffusivity, the dispersion model is evaluated with the tracer observations obtained from Copenhagen diffusion experiment in unstable conditions, Prairie Grass experiment in both unstable and stable conditions and Hanford experiment in stable conditions. The dispersion model with proposed parameterizations of the eddy diffusivity is performing reasonably well with the observations and demonstrates throughout a consistent and good performance in the concentration estimation for elevated and surface releases from a continuous point source in various stability conditions. Though the magnitudes of the various eddy diffusivities are different from the proposed one, the profiles of all parameterizations in terms of the shape have almost similar characteristics. The differences in the magnitudes of diffusion produced by various parameterizations cause minor but noticeable changes in the simulation of ground level concentrations from the dispersion model. In very stable conditions, the agreement of the model evaluations with measurements is less satisfactory and none of the parameterizations used here including proposed one is adequate to describe the atmospheric dispersion process in these conditions.

Kumar, Pramod; Sharan, Maithili

2012-03-01

243

Women experience a series of specific transitions in their reproductive function with age. Shortening of the menstrual cycle begins in the mid to late 30s and is regarded as the first sign of reproductive aging. Other early changes include elevation and increased variance of serum FSH levels, increased incidences of oocyte spindle aberrations and aneuploidy, and declining fertility. The goal of this study was to investigate whether the mouse strain senescence-accelerated mouse-prone-8 (SAMP8) is a suitable model for the study of these midlife reproductive aging characteristics. Midlife SAMP8 mice aged 6.5-7.85 months (midlife SAMP8) exhibited shortened estrous cycles compared with SAMP8 mice aged 2-3 months (young SAMP8, P = .0040). Midlife SAMP8 mice had high FSH levels compared with young SAMP8 mice, and mice with a single day of high FSH exhibited statistically elevated FSH throughout the cycle, ranging from 1.8- to 3.6-fold elevation on the days of proestrus, estrus, metestrus, and diestrus (P < .05). Midlife SAMP8 mice displayed more variance in FSH than young SAMP8 mice (P = .01). Midlife SAMP8 ovulated fewer oocytes (P = .0155). SAMP8 oocytes stained with fluorescently labeled antitubulin antibodies and scored in fluorescence microscopy exhibited increased incidence of meiotic spindle aberrations with age, from 2/126 (1.59%) in young SAMP8 to 38/139 (27.3%) in midlife SAMP8 (17.2-fold increase, P < .0001). Finally, SAMP8 exhibited declining fertility from 8.9 pups/litter in young SAMP8 to 3.5 pups/litter in midlife SAMP8 mice (P < .0001). The age at which these changes occur is younger than for most mouse strains, and their simultaneous occurrence within a single strain has not been described previously. We propose that SAMP8 mice are a model of midlife human female reproductive aging. PMID:24654787

Bernstein, Lori R; Mackenzie, Amelia C L; Kraemer, Duane C; Morley, John E; Farr, Susan; Chaffin, Charles L; Merchenthaler, István

2014-06-01

244

Two new zinc coordination complexes, namely [Zn2(tib)4/3(L(1))2]·DMA (1) and [Zn2(tib)4/3(L(2))2]·H2O (2) (tib = 1,3,5-tris(1-imidazolyl)benzene, H2L(1) = biphenyl-4,4'-dicarboxylic acid, H2L(2) = 4,4'-(2,2'-oxybis(ethane-2,1-diyl)bis(oxy))dibenzoic acid and DMA = N,N-dimethylacetamide), are obtained using achiral mixed ligands and characterized using elemental analysis, IR and X-ray crystallography. Compounds 1 and 2 both display intriguing structural features of both interpenetration and self-catenation. By careful inspection of the two structures, we found that the Zn(ii) cations, the tib ligands, and the dicarboxylic anions show the same coordination modes or analogous configurations. Compound 1 is chiral, which was confirmed by measuring the optical rotation of the bulk samples using solid-state circular dichroism (CD). It is comprised of two crystallographically independent interpenetrated 3D motifs, each containing interlaced triple-stranded right- and left-handed Zn-L(1)-Zn helical chains and chiral 2D [Zn(tib)2/3] layers. Both motifs display binodal (3,4)-coordinated 3D self-catenated networks with the point symbol (10(3))2(10(6))3 and the vertex symbols [1013·1013·1013] and [107·107·108·1010·1011·1011]. However, the two types of helical chains are not racemic due to the differences between the two kinds of L(1) anions, and the two types of chiral 2D [Zn(tib)2/3](2+) layers are not enantiomeric either due to the different configurations of the tib ligands. Therefore, the two motifs are not enantiomers. Compound 2 is achiral, containing Zn-L(2)-Zn zigzag chains that span into three directions and chiral 2D [Zn(tib)2/3] layers. The overall 3D network is a new binodal (3,4)-coordinated self-catenated network with the point symbol (10(3))2(10(6))3 and the vertex symbols [107·107·107] and [102·104·105·105·105·105]. Two of these networks interpenetrate. Their chiral and achiral structures are mainly modulated by the length of the dicarboxylates. As expected, compounds 1 and 2 show photoluminescence behaviors and compound 1 shows a ferroelectric behavior. Thermogravimetric studies of 1 and 2 have also been performed. We examined all 48 known structures containing the tib ligand and drew the conclusion that the metal + tib combination, modulated by the prolonged L ligands, can be a good basis for new chiral and catenated structures. PMID:25182167

Wang, Yue; Qi, Yan; Blatov, Vladislav A; Zheng, Jimin; Li, Qun; Zhang, Chao

2014-10-28

245

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

246

Multiscale Analytical\\/Numerical Theory of the Diffusivity of Concrete

The ionic diffusivity of a concrete is a function of its microstructure at many length scales, ranging from nanometers to millimeters. The microstructure is largely controlled by the initial concrete mixture proportions and the ultimate curing conditions. Linking a property like ionic diffusivity to the microstructure then requires a multiscale approach. A multiscale microstructural computer model for ionic diffusivity has

Edward J. Garboczi; Dale P. Bentz

1998-01-01

247

Revealing mesoscopic structural universality with diffusion

Measuring molecular diffusion is widely used for characterizing materials and living organisms noninvasively. This characterization relies on relations between macroscopic diffusion metrics and structure at the mesoscopic scale commensurate with the diffusion length. Establishing such relations remains a fundamental challenge, hindering progress in materials science, porous media, and biomedical imaging. Here we show that the dynamical exponent in the time dependence of the diffusion coefficient distinguishes between the universality classes of the mesoscopic structural complexity. Our approach enables the interpretation of diffusion measurements by objectively selecting and modeling the most relevant structural features. As an example, the specific values of the dynamical exponent allow us to identify the relevant mesoscopic structure affecting MRI-measured water diffusion in muscles and in brain, and to elucidate the structural changes behind the decrease of diffusion coefficient in ischemic stroke. PMID:24706873

Novikov, Dmitry S.; Jensen, Jens H.; Helpern, Joseph A.; Fieremans, Els

2014-01-01

248

Coaxial atomizer liquid intact lengths

NASA Technical Reports Server (NTRS)

Average intact lengths of round liquid jets generated by airblast coaxial atomizer were measured from over 1500 photographs. The intact lengths were studied over a jet Reynolds number range of 18,000 and Weber number range of 260. Results are presented for two different nozzle geometries. The intact lengths were found to be strongly dependent on Re and We numbers. An empirical equation was derived as a function of these parameters. A comparison of the intact lengths for round jets and flat sheets shows that round jets generate shorter intact lengths.

Eroglu, Hasan; Chigier, Norman; Farago, Zoltan

1991-01-01

249

Kinetic diffusion in polymer gels

NASA Astrophysics Data System (ADS)

Heuristics for determining whether of not Fick's first law can govern the diffusion of small molecules in polymers are discussed. Two types of integrals of Fickian diffusion equations are known to exhibit the characteristics of non-Fickian diffusion; integrals of each type are given for a nonlinear asymptotic description of Fickian swelling in free volume limited materials. Kinetic criteria, based on the Kramers theory of activated processes, are used to characterize types of molecular relaxations that can be represented by such “non-Fickian” solutions to Fick's second law. It is concluded that these solutions cannot represent the swelling dynamics of typical polymeric materials.

Lightfoot, Edwin J.

1990-11-01

250

Length control of He atmospheric plasma jet plumes: Effects of discharge parameters and ambient air

NASA Astrophysics Data System (ADS)

The effects of various discharge parameters and ambient gas on the length of He atmospheric plasma jet plumes expanding into the open air are studied. It is found that the voltage and width of the discharge-sustaining pulses exert significantly stronger effects on the plume length than the pulse frequency, gas flow rate, and nozzle diameter. This result is explained through detailed analysis of the I-V characteristics of the primary and secondary discharges which reveals the major role of the integrated total charges of the primary discharge in the plasma dynamics. The length of the jet plume can be significantly increased by guiding the propagating plume into a glass tube attached to the nozzle. This increase is attributed to elimination of the diffusion of surrounding air into the plasma plume, an absence which facilitates the propagation of the ionization front. These results are important for establishing a good level of understanding of the expansion dynamics and for enabling a high degree of control of atmospheric pressure plasmas in biomedical, materials synthesis and processing, environmental and other existing and emerging industrial applications.

Xiong, Q.; Lu, X.; Ostrikov, K.; Xiong, Z.; Xian, Y.; Zhou, F.; Zou, C.; Hu, J.; Gong, W.; Jiang, Z.

2009-04-01

251

NASA Astrophysics Data System (ADS)

The optical characteristics of absorption and scattering of irradiated tissue determine light spatial distribution and the subsequent biological effects, which could decide the dosimetry for laser medical applications. Studys have shown that the optical properties of bio-tissue could be determined through some fitting algorithms with spatially resolved diffuse reflectance theory based on the measurement of diffuse reflectance. The regression of reflectance data with by diffusion theory model was important for optical properties estimation. In the paper, the reflectance versus distance data acquired from Monte Carlo method was by fit to diffusion theory model by the nonliear least-squares fitting algorithm to study the produre and mothod of determination of optical properties. And attention was especially paid to the influence of the radial step width ?r, length of radial distance rL and start value of radial distance r0 on the regression results. Preliminary results indicated that the radial step width and length of radial distance rL both have little influence on the fitting. Nevertheless, the start value of radial distance r0 of reflectance data has great influence on the fitting. Fitting deviation would become little while the start value of radial distance r0 grow greater. and an appropriate r0 was important for data fitting. Study also showd a more accurate light diffuse reflectance theoretical model was need for estimate the optical parameters by fitting the diffuse reflectance data accurately. Our work maybe be helpful to the experiment measurement of light diffuse reflectance data for noninvasive optical properties determination.

Peng, Dong-qing; Li, Hui

2012-12-01

252

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

253

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

254

Dynamics on Multiple Time and Length Scales in Complex Fluids Formed by Conjugated Polymers

NASA Astrophysics Data System (ADS)

Even though tremendous effort takes place to incorporate conjugated polymers into device applications, there is a significant gap in performance of the optimal desired devices developed. While the photo physics of highly conjugated polymers has been intensively investigated, the factors that affect the conformation and assembly and the dynamics on multiple length scales, that ultimately control the electro-optical response, have not been resolved. Using poly(paraphenyleneethynylene)s (PPE) as a model system for conjugated polymers, our studies have identified the driving forces for different association modes of PPEs as a function of their chemical structure and their interactions with solvents. X-ray and neuron scattering, probing dimensions from 0.1 to 100nm, revealed that PPEs dissolved in toluene form a rich variety of complex fluids. At high temperature the molecules are isolated and assume extended configuration. As the temperature decreases, the molecules associate and eventually form gels of different nature. In higher concentrations ordered phases are formed. Inelastic Neutron Back Scattering together with Neutron Spin Echo were used to study the dynamics on multiple length scales at the different complex fluids, exploring processes of 5-100 nano seconds. The dynamic scattering function incorporates the center of mass diffusion together with intramolecular motions. With decreasing temperature the PPE molecules aggregate and their center of mass diffusion is hindered. At the gellation transition the center of mass diffusion is no longer observed where as the intramolecular dynamics is retained in all phases. Cooperative dynamics of the solvent and PPE molecules has been observed in both molecular solution and micellar phase. The phases formed by PPEs are optically active where the dynamic processes affect directly their optical characteristics.

Perahia, Dvora

2010-03-01

255

Computer simulation of a wind tunnel test section with discrete finite-length wall slots

NASA Technical Reports Server (NTRS)

A computer simulation of a slotted wind tunnel test section which includes a discrete, finite-length wall slot representation with plenum chamber constraints and accounts for the nonlinear effects of the dynamic pressure of the slot outflow jet and of the low energy of slot inflow air was developed. The simulation features were selected to be those appropriate for the intended subsequent use of the simulation in a wall interference assessment procedure using sparsely located wall pressure measurements. It is demonstrated that accounting for slot discreteness is important in interpreting wall pressure measured between slots, and that accounting for nonlinear slot flow effects produces significant changes in tunnel-induced velocity distributions and, in particular, produces a longitudinal component of tunnel-induced velocity due to model lift. A characteristic mode of tunnel flow interaction with constraints imposed by the plenum chamber and diffuser entrance is apparent in simulation results and is derived analytically through a simplified analysis.

Kemp, W. B., Jr.

1986-01-01

256

Single-particle diffusion in dense inhomogeneous colloid suspensions in ribbon channels.

We report the results of a study of single-particle diffusion in dense colloid fluids confined in a ribbon channel geometry that is intermediate between quasione dimensional (q1D) and quasitwo dimensional (q2D). This paper complements a previous paper about pair diffusion in the same system [Phys. Rev. E 82, 031403 (2010)]. In all of the systems studied, the colloid density distribution transverse to the ribbon channel is stratified with peak amplitudes that depend on the colloid density. Although the virtual walls that confine a stratum are structured with a scale length of the colloid diameter, that structure does not have an apparent influence on the single-particle diffusion, which shows the characteristic features of diffusion in a q1D channel with smooth walls. We find that, for all channel widths and packing fractions studied, the single-particle transverse diffusion coefficient in a stratum is smaller than the single-particle longitudinal diffusion coefficient in the same stratum and that the single-particle longitudinal diffusion coefficient varies very little from stratum to stratum, being only slightly smaller in the dense strata next to the walls than in the central strata. The lack of variation in the longitudinal diffusion coefficient with apparent stratum density is explained by the application of the Fischer-Methfessel approximation to the local density in an inhomogeneous liquid. The ratio of the transverse to longitudinal diffusion coefficients varies very slowly with ribbon width, implying a very slow transition from q1D to q2D behavior. PMID:22181142

Wonder, Emily; Lin, Binhua; Rice, Stuart A

2011-10-01

257

Exploratory laboratory study of lateral turbulent diffusion at the surface of an alluvial channel

In natural streams turbulent diffusion is one of the principal mechanisms by which liquid and suspended-particulate contaminants are dispersed in the flow. A knowledge of turbulence characteristics is therefore essential in predicting the dispersal rates of contaminants in streams. In this study the theory of diffusion by continuous movements for homogeneous turbulence is applied to lateral diffusion at the surface of an open channel in which there is uniform flow. An exploratory-laboratory investigation was conducted in which the lateral dispersion at the water surface of a sand-Led flume was studied by measuring the lateral spread from a point source of small floating polyethylene articles. The experiment was restricted to a single set of low and channel geometry conditions. The results of the study indicate that with certain restrictions lateral dispersion in alluvial channels may be successfully described by the theory of diffusion by continuous movements. The experiment demonstrates a means for evaluating the lateral diffusion coefficient and also methods for quantitatively estimating fundamental turbulence properties, such as the intensity and the Lagrangian integral scale of turbulence in an alluvial channel. The experimental results show that with increasing distance from the source the coefficient of lateral turbulent diffusion increases initially but tends toward a constant limiting value. This result is in accordance with turbulent diffusion theory. Indications are that the distance downstream from the source required for the diffusion coefficient to reach its limiting value is actually very small when compared to the length scale of most diffusion phenomena in natural streams which are of practical interest.

Sayre, William W.; Chamberlain, A. R.

1964-01-01

258

Single-particle diffusion in dense inhomogeneous colloid suspensions in ribbon channels

NASA Astrophysics Data System (ADS)

We report the results of a study of single-particle diffusion in dense colloid fluids confined in a ribbon channel geometry that is intermediate between quasione dimensional (q1D) and quasitwo dimensional (q2D). This paper complements a previous paper about pair diffusion in the same system [Phys. Rev. EPRESCM1539-375510.1103/PhysRevE.82.031403 82, 031403 (2010)]. In all of the systems studied, the colloid density distribution transverse to the ribbon channel is stratified with peak amplitudes that depend on the colloid density. Although the virtual walls that confine a stratum are structured with a scale length of the colloid diameter, that structure does not have an apparent influence on the single-particle diffusion, which shows the characteristic features of diffusion in a q1D channel with smooth walls. We find that, for all channel widths and packing fractions studied, the single-particle transverse diffusion coefficient in a stratum is smaller than the single-particle longitudinal diffusion coefficient in the same stratum and that the single-particle longitudinal diffusion coefficient varies very little from stratum to stratum, being only slightly smaller in the dense strata next to the walls than in the central strata. The lack of variation in the longitudinal diffusion coefficient with apparent stratum density is explained by the application of the Fischer-Methfessel approximation to the local density in an inhomogeneous liquid. The ratio of the transverse to longitudinal diffusion coefficients varies very slowly with ribbon width, implying a very slow transition from q1D to q2D behavior.

Wonder, Emily; Lin, Binhua; Rice, Stuart A.

2011-10-01

259

The existence of a critical length scale in regularised friction

NASA Astrophysics Data System (ADS)

We study a regularisation of Coulomb's friction law on the propagation of local slip at an interface between a deformable and a rigid solid. This regularisation, which was proposed based on experimental observations, smooths the effect of a sudden jump in the contact pressure over a characteristic length scale. We apply it in numerical simulations in order to analyse its influence on the behaviour of local slip. We first show that mesh convergence in dynamic simulations is achieved without any numerical damping in the bulk and draw a convergence map with respect to the characteristic length of the friction regularisation. By varying this length scale on the example of a given slip event, we observe that there is a critical length below which the friction regularisation does not affect anymore the propagation of the interface rupture. A spectral analysis of the regularisation on a periodic variation of Coulomb's friction is conducted to confirm the existence of this critical length. The results indicate that if the characteristic length of the friction regularisation is smaller than the critical length, a slip event behaves as if it was governed by Coulomb's law. We therefore propose that there is a domain of influence of the friction regularisation depending on its characteristic length and on the frequency content of the local slip event. A byproduct of the analysis is related to the existence of a physical length scale characterising a given frictional interface. We establish that the experimental determination of this interface property may be achieved by experimentally monitoring slip pulses whose frequency content is rich enough.

Kammer, D. S.; Yastrebov, V. A.; Anciaux, G.; Molinari, J. F.

2014-02-01

260

Solute transport in clay-rich aquitards is characterized as molecular diffusion- or advection-dominated based on the Péclet number (P(e)). However, few field-based measurements of the coefficient of molecular diffusion (D(e)) exist, and none with a range of advection- or diffusion-dominated conditions in the same aquitard. In this long-term field experiment, standing water in a recovering well was spiked with deuterium ((2)H), then water-level recovery and ?(2)H values were monitored as the well returned to static conditions over 1054 days. After a second (2)H spike, water levels and ?(2)H values were monitored to day 1644 while under near static conditions. Modeling of the second spike was used to define the D(e) of (2)H as (3-4)× 10(-10)m(2)s(-1) for an accessible porosity of 0.31. Reservoir concentrations from the initial spike were modeled to define the transition from advection- to diffusion-dominated transport. This occurred after 200 days, consistent with a transition in P(e) from <1 to >1 when the length term is taken as the radial extent of the tracer plume (normalized concentration <0.05). This study verifies plume extent as the characteristic length term in the calculation of P(e) and demonstrates the transition from advection- to diffusion-dominated transport as the value of P(e) decreases below unity. PMID:22343012

Barbour, S Lee; Hendry, M Jim; Wassenaar, Leonard I

2012-04-01

261

NSDL National Science Digital Library

This is Lesson 1 of a five lesson unit. "This lesson focuses students' attention on the attributes of length and develops their knowledge of and skill in using nonstandard units of measurement, their feet. It provides practice with and remediation of the measurable attributes of length." (from NCTM Illuminations)

Math, Illuminations N.

2009-01-28

262

Diffusion of an alkane molecule in siliceous zeolite beta Matthew Aronson

1 Diffusion of an alkane molecule in siliceous zeolite beta Matthew was performed to study the diffusion of an alkane molecule in siliceous zeolite beta, as a function of chain length and temperature. The alkane was modeled

Shell, M. Scott

263

Introduction Diffusion Tensor Imaging

Introduction Diffusion Tensor Imaging Diffusion Kurtosis Imaging D-Eigenvalues and . . . Further Â·Full Screen Â·Close Â·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

264

Coarsening of precipitation patterns in a moving reaction-diffusion front

NASA Astrophysics Data System (ADS)

Precipitation patterns emerging in a two-dimensional moving front are investigated on the example of NaOH diffusing into a gel containing AlCl3 . The time evolution of the precipitate Al(OH)3 can be observed since the precipitate redissolves in the excess outer electrolyte NaOH and thus it exists only in a narrow optically accessible region of the reaction front. The patterns display self-similar coarsening with a characteristic length ? increasing with time as ?(t)˜t . A theory based on the Cahn-Hilliard phase-separation dynamics, including redissolution, is shown to yield agreement with the experiments.

Volford, A.; Lagzi, I.; Molnár, F., Jr.; Rácz, Z.

2009-11-01

265

Linear study of Rayleigh-Taylor instability in a diffusive quantum plasma

The linear Rayleigh-Taylor (RT) instability in an incompressible quantum plasma is investigated on the basis of quantum magnetohydrodynamic model. It is shown that the occurrence of RT instability depends on density-temperature inhomogeneity (characteristic lengths) on one hand, and the system layer size on the other. It is also observed that the combined effects of external magnetic field, diffusivity, and quantum pressure significantly modify the dispersion properties of system in both the parallel and perpendicular directions. For any case, the imaginary and real parts of dispersion relation are presented and the possibility and conditions for the instability growth rate are discussed.

Momeni, Mahdi [Faculty of Physics, Shahrood University, Shahrood (Iran, Islamic Republic of)] [Faculty of Physics, Shahrood University, Shahrood (Iran, Islamic Republic of)

2013-08-15

266

Determination of local diffusion properties in heterogeneous biomaterials.

The coupling between structure and diffusion properties is essential for the functionality of heterogeneous biomaterials. Structural heterogeneity is defined and its implications for time-dependent diffusion are discussed in detail. The effect of structural heterogeneity in biomaterials on diffusion and the relevance of length scales are exemplified with regard to different biomaterials such as gels, emulsions, phase separated biopolymer mixtures and chocolate. Different diffusion measurement techniques for determination of diffusion properties at different length and time scales are presented. The interplay between local and global diffusion is discussed. New measurement techniques have emerged that enable simultaneous determination of both structure and local diffusion properties. Special emphasis is given to fluorescence recovery after photobleaching (FRAP). The possibilities of FRAP at a conceptual level is presented. The method of FRAP is briefly reviewed and its use in heterogeneous biomaterials, at barriers and during dynamic changes of the structure is discussed. PMID:19481193

Lorén, Niklas; Nydén, Magnus; Hermansson, Anne-Marie

2009-08-30

267

The word-length effect in reading: a review.

The finding that visual processing of a word correlates with the number of its letters has an extensive history. In healthy subjects, a variety of methods, including perceptual thresholds, naming and lexical decision times, and ocular motor parameters, show modest effects that interact with high-order effects like frequency. Whether this indicates serial processing of letters under some conditions or indexes low-level visual factors related to word length is unclear. Word-length effects are larger in pure alexia, where they probably reflect a serial letter-by-letter strategy, due to failure of lexical whole-word processing and variable dysfunction in letter encoding. In pure alexia, the word-length effect is systematically related to mean naming latency, with the word-length effect becoming proportionally greater as naming latency becomes more delayed in severe cases. Other conditions may also generate enhanced word-length effects. This occurs in right hemianopia: Computer simulations suggest a criterion of 160?ms/letter to distinguish hemianopic dyslexia from pure alexia. Normal reading development is accompanied by a decrease in word-length effects, whereas persistently elevated word-length effects are characteristic of developmental dyslexia. Little is known about word-length effects in other reading disorders. We conclude that the word-length effect captures the efficiency of the perceptual reading process in development, normal reading, and a number of reading disorders, even if its mechanistic implications are not always clear. PMID:24665973

Barton, Jason J S; Hanif, Hashim M; Eklinder Björnström, Laura; Hills, Charlotte

2014-01-01

268

Depletion lengths in semiconductor nanostructures

NASA Astrophysics Data System (ADS)

We calculate the depletion length, W( R), at the surface of a cylindrical nanostructure of radius R and show that W( R) satisfies the inequality Wp? W( R)? Rc, where W p= 2? ?/(e 2N d) is the depletion length at a planar interface ( ? is the surface potential energy barrier, ? is the dielectric constant and Nd is the doping density), and R c= 2W p is, as we show, a critical radius below which, for R? Rc, the structure is fully depleted. The standard result Wp therefore underestimates the depletion length in a finite structure. The discrepancy between W( R) and Wp becomes significant when the dimensions of the structure becomes comparable to the depletion length, as can occur in nanostructure devices.

Luscombe, J. H.; Frenzen, C. L.

2002-06-01

269

SLOW DIFFUSIVE GRAVITATIONAL INSTABILITY BEFORE DECOUPLING

Radiative diffusion damps acoustic modes at large comoving wavenumber (k) before decoupling ('Silk damping'). In a simple WKB analysis, neglecting moments of the temperature distribution beyond the quadrupole (the tight-coupling limit), damping appears in the acoustic mode as a term of order ik{sup 2}tau-dot{sup -1}, where tau-dot is the scattering rate per unit conformal time. Although the Jeans instability is stabilized on scales smaller than the adiabatic Jeans length, I show that the medium is linearly unstable to first order in tau-dot{sup -1} to a slow diffusive mode. At large comoving wavenumber, the characteristic growth rate becomes independent of spatial scale and constant: (t{sub KH} a){sup -1} approx (128piG/9kappa{sub T} c)(rho{sub m}/rho{sub b}), where a is the scale factor, rho{sub m} and rho{sub b} are the matter and baryon energy density, respectively, and kappa{sub T} is the Thomson opacity. This is the characteristic timescale for a fluid parcel to radiate away its total thermal energy content at the Eddington limit, analogous to the Kelvin-Helmholz (KH) timescale for a radiation pressure-dominated massive star or the Salpeter timescale for black hole growth. Although this mode grows at all times prior to decoupling and on scales smaller than roughly the horizon, the growth time is long, about 100 times the age of the universe at decoupling. Thus, it modifies the density and temperature perturbations on small scales only at the percent level. The physics of this mode in the tight-coupling limit is already accounted for in the popular codes CMBFAST and CAMB, but is typically neglected in analytic studies of the growth of primordial perturbations. The goal of this work is to clarify the physics of this diffusive instability in the epoch before decoupling, and to emphasize that the universe is formally unstable on scales below the horizon, even in the limit of very large tau-dot. Analogous instabilities that might operate at yet earlier epochs are also mentioned.

Thompson, Todd A., E-mail: thompson@astronomy.ohio-state.ed [Department of Astronomy and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States)

2010-02-01

270

NASA Astrophysics Data System (ADS)

Working in the limit in which the localization length scale is large compared to other relevant length scales, we examine three experimental situations with the continuous-spontaneous-localization (CSL) model, a well-motivated alternative to standard quantum theory. These are the two-slit experiment, scattering from a potential barrier, and release of two noninteracting particles simultaneously from a potential trap. In each case we calculate the diagonal part of the time-evolved density matrix giving a probability density function over final measured states. The case of the two-slit experiment is already well understood and we reproduce some known conditions for observing loss of interference. The other examples have not previously been examined in the context of CSL. For scattering from a potential barrier we find that the probability of reflection is unchanged by CSL; however, the momentum state is spread in a characteristic way. For the case of two particles released simultaneously from a trap we find that it is more likely that the particles diffuse in the same direction than would happen if the particles behaved independently. We assess the possibility of observing these effects.

Bedingham, D. J.

2014-03-01

271

We present results on dendritic growth of electrohydrodynamic convection in a nematic liquid crystal subject to parallel magnetic and electric fields. Previous work found that these dendrites have many properties in common with crystalline dendrites. Nevertheless, crystalline dendrites are significantly different from the system studied here. Specifically, the length selection mechanism for these dendrites is substantially richer than that which controls crystalline dendritic growth. In contrast with the sharp selection mechanism operating in the case of crystalline dendrites, these dendrites show only partial selection. As the separation between electrodes and the magnetic field becomes larger, the selection becomes even less sharp. We quantify the selection by measuring two important characteristics of these dendrites, their length scale, as reflected by the tip radius of curvature, and their growth speed. We measure these quantities as functions of the most important control parameters: the spacing of the liquid crystal cell, the magnetic field, and the applied voltage. A nontrivial scaling relationship is found for the tip radius of curvature. These dendrites occur in a system containing only one state of matter, and they are defined not by an abrupt boundary but by a diffuse interface. We find that the width of that interface is determined solely by the applied magnetic field. PMID:12513506

Gheorghiu, N; Gleeson, J T

2002-11-01

272

NASA Astrophysics Data System (ADS)

We present results on dendritic growth of electrohydrodynamic convection in a nematic liquid crystal subject to parallel magnetic and electric fields. Previous work found that these dendrites have many properties in common with crystalline dendrites. Nevertheless, crystalline dendrites are significantly different from the system studied here. Specifically, the length selection mechanism for these dendrites is substantially richer than that which controls crystalline dendritic growth. In contrast with the sharp selection mechanism operating in the case of crystalline dendrites, these dendrites show only partial selection. As the separation between electrodes and the magnetic field becomes larger, the selection becomes even less sharp. We quantify the selection by measuring two important characteristics of these dendrites, their length scale, as reflected by the tip radius of curvature, and their growth speed. We measure these quantities as functions of the most important control parameters: the spacing of the liquid crystal cell, the magnetic field, and the applied voltage. A nontrivial scaling relationship is found for the tip radius of curvature. These dendrites occur in a system containing only one state of matter, and they are defined not by an abrupt boundary but by a diffuse interface. We find that the width of that interface is determined solely by the applied magnetic field.

Gheorghiu, N.; Gleeson, J. T.

2002-11-01

273

NONLINEAR DIFFUSION Erkut Erdem

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

274

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

275

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.

276

Continuously variable focal length lens

A material preferably in crystal form having a low atomic number such as beryllium (Z=4) provides for the focusing of x-rays in a continuously variable manner. The material is provided with plural spaced curvilinear, optically matched slots and/or recesses through which an x-ray beam is directed. The focal length of the material may be decreased or increased by increasing or decreasing, respectively, the number of slots (or recesses) through which the x-ray beam is directed, while fine tuning of the focal length is accomplished by rotation of the material so as to change the path length of the x-ray beam through the aligned cylindrical slows. X-ray analysis of a fixed point in a solid material may be performed by scanning the energy of the x-ray beam while rotating the material to maintain the beam's focal point at a fixed point in the specimen undergoing analysis.

Adams, Bernhard W; Chollet, Matthieu C

2013-12-17

277

Screening length in plasma winds

We study the screening length L_s of a heavy quark-antiquark pair in strongly coupled gauge theory plasmas flowing at velocity v. Using the AdS/CFT correspondence we investigate, analytically, the screening length in the ultra-relativistic limit. We develop a procedure that allows us to find the scaling exponent for a large class of backgrounds. We find that for conformal theories the screening length is (boosted energy density)^{-1/d}. As examples of conformal backgrounds we study R-charged black holes and Schwarzschild-anti-deSitter black holes in (d+1)-dimensions. For non-conformal theories, we find that the exponent deviates from -1/d and as examples we study the non-extremal Klebanov-Tseytlin and Dp-brane geometries. We find an interesting relation between the deviation of the scaling exponent from the conformal value and the speed of sound.

Elena Caceres; Makoto Natsuume; Takashi Okamura

2006-07-28

278

Facilitated diffusion buffers noise in gene expression

1. 4 1. 6 1. 8 2. 0 sliding length (bp) Fa n o fa ct or ? ? ? ? ? ? ? ? ? lacI 3D lacI WT FIG. 4. Dependence of the mRNA Fano factor on sliding length. The dissociation rate was changed accordingly to keep average mRNA levels constant. Analytic... independently searching lac tetramers per cell. 3. Sliding length sl The root-mean-square deviation during one slide on the DNA was estimated to be sl,RMSD = ? 2D1D/kd = (45 ± 10) bp [3], where D1D is the 1D diffusion constant and kd is the DNA dissociation rate...

Schoech, Armin; Zabet, Nicolae Radu

2014-09-02

279

Characterising cosmic inhomogeneity with anomalous diffusion

Dark matter (DM) clustering at the present epoch is investigated from a fractal viewpoint to determine the scale where the self-similar scaling property of the DM halo distribution transits to homogeneity. Methods based on well-established counts-in-spheres, as well as new methods based on anomalous diffusion and random walks, are applied both to DM halos of the biggest N-Body simulation in the `Dark Sky Simulations' (DS) and an equivalent randomly distributed catalogue. Results for the smaller `Millennium Run' (MR) simulation are revisited. It is found that the MR simulation volume is too small and prone to bias to reliably identify the onset of homogeneity. Transition to homogeneity is defined when the fractal dimension of the clustered and random distributions cannot be distinguished within the associated uncertainties. The `counts-in-spheres' method applied to the DS simulation then yields a homogeneity scale roughly consistent with previous work ($\\sim 150$ Mpc/h). The characteristic length-scale for ano...

Kraljic, David

2014-01-01

280

AMBIPOLAR DIFFUSION HEATING IN TURBULENT SYSTEMS

The temperature of the gas in molecular clouds is a key determinant of the characteristic mass of star formation. Ambipolar diffusion (AD) is considered one of the most important heating mechanisms in weakly ionized molecular clouds. In this work, we study the AD heating rate using two-fluid turbulence simulations and compare it with the overall heating rate due to turbulent dissipation. We find that for observed molecular clouds, which typically have Alfven Mach numbers of {approx}1 and AD Reynolds numbers of {approx}20, about 70% of the total turbulent dissipation is in the form of AD heating. AD has an important effect on the length scale where energy is dissipated: when AD heating is strong, most of the energy in the cascade is removed by ion-neutral drift, with a comparatively small amount of energy making it down to small scales. We derive a relation for the AD heating rate that describes the results of our simulations to within a factor of two. Turbulent dissipation, including AD heating, is generally less important than cosmic-ray heating in molecular clouds, although there is substantial scatter in both.

Li, Pak Shing [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Myers, Andrew [Physics Department, University of California, Berkeley, CA 94720 (United States); McKee, Christopher F., E-mail: psli@astron.berkeley.edu, E-mail: atmyers@berkeley.edu, E-mail: cmckee@berkeley.edu [Physics Department and Astronomy Department, University of California, Berkeley, CA 94720 (United States)

2012-11-20

281

Parallel flow diffusion battery

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

282

Parallel flow diffusion battery

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

283

Normal and Anomalous Diffusion: A Tutorial

The purpose of this tutorial is to introduce the main concepts behind normal and anomalous diffusion. Starting from simple, but well known experiments, a series of mathematical modeling tools are introduced, and the relation between them is made clear. First, we show how Brownian motion can be understood in terms of a simple random walk model. Normal diffusion is then treated (i) through formalizing the random walk model and deriving a classical diffusion equation, (ii) by using Fick's law that leads again to the same diffusion equation, and (iii) by using a stochastic differential equation for the particle dynamics (the Langevin equation), which allows to determine the mean square displacement of particles. (iv) We discuss normal diffusion from the point of view of probability theory, applying the Central Limit Theorem to the random walk problem, and (v) we introduce the more general Fokker-Planck equation for diffusion that includes also advection. We turn then to anomalous diffusion, discussing first its formal characteristics, and proceeding to Continuous Time Random Walk (CTRW) as a model for anomalous diffusion. It is shown how CTRW can be treated formally, the importance of probability distributions of the Levy type is explained, and we discuss the relation of CTRW to fractional diffusion equations and show how the latter can be derived from the CTRW equations. Last, we demonstrate how a general diffusion equation can be derived for Hamiltonian systems, and we conclude this tutorial with a few recent applications of the above theories in laboratory and astrophysical plasmas.

Loukas Vlahos; Heinz Isliker; Yannis Kominis; Kyriakos Hizanidis

2008-05-05

284

Propagation of sound and thermal waves in diffuse molecular clouds

The phase velocity and the scale length for the damping of sound and thermal waves propagating in a diffuse molecular cloud are calculated as functions of the frequency of the driven wave. The cloud is assumed to be heated by cosmic rays and grain photoelectron heating, cooled by a schematized cooling rate exp(-alpha\\/T), and with a heat diffusion by neutral

Nestor Sanchez

1995-01-01

285

Equation-free, multiscale computation for unsteady random diffusion

We present an ``equation-free'' multiscale approach to the simulation of unsteady diffusion in a random medium. The diffusivity of the medium is modeled as a random field with short correlation length, and the governing equations are cast in the form of stochastic differential equations. A detailed fine-scale computation of such a problem requires discretization and solution of a large system

DONGBIN XIUAND; Ioannis G. Kevrekidis

2005-01-01

286

Telomere Length Wildlife Aging Technique

2/22/2009 1 Telomere Length as a Wildlife Aging Technique Forestry, Wildlife and Fisheries GraduateNon-invasive genetic sampling Telomeres: Â· Form Â· Function Â· Methods of measuring Â· Telomeres in wildlife aging #12;2/22/2009 4 Telomere Form: Â·Short repeated sequences of DNA Â·Found at the ends of linear eukaryotic

Gray, Matthew

287

Incubation length of dabbling ducks

We collected unincubated eggs from wild Mallard (Anas platyrhynchos), Gadwall (A. strepera), Blue-winged Teal (A. discors), and Northern Shoveler (A. clypeata) nests and artificially incubated them at 37.5??C. Average incubation lengths of Mallard, Gadwall, and Northern Shoveler eggs did not differ from their wild-nesting counterparts, but artificially incubated Blue-winged Teal eggs required an additional 1.7 days to hatch, suggesting that wild-nesting teal incubated more effectively. A small sample of Mallard, Gadwall, and Northern Shoveler eggs artificially incubated at 38.3??C hatched 1 day sooner, indicating that incubation temperature affected incubation length. Mean incubation length of Blue-winged Teal declined by 1 day for each 11-day delay in nesting, but we found no such seasonal decline among Mallards, Gadwalls, or Northern Shovelers. There is no obvious explanation for the seasonal reduction in incubation length for Blue-winged Teal eggs incubated in a constant environment, and the phenomenon deserves further study. ?? The Cooper Ornithological Society 2005.

Wells-Berlin, A. M.; Prince, H.H.; Arnold, T.W.

2005-01-01

288

Finite length Taylor Couette flow

NASA Technical Reports Server (NTRS)

Axisymmetric numerical solutions of the unsteady Navier-Stokes equations for flow between concentric rotating cylinders of finite length are obtained by a spectral collocation method. These representative results pertain to two-cell/one-cell exchange process, and are compared with recent experiments.

Streett, C. L.; Hussaini, M. Y.

1987-01-01

289

Nanoparticle Diffusion in Polymer Nanocomposites

Large-scale molecular dynamics simulations show that nanoparticle (NP) diffusivity in weakly interacting mixtures of NPs and polymer melts has two very different classes of behavior depending on their size. NP relaxation times and their diffusivities are completely described by the local, Rouse dynamics of the polymer chains for NPs smaller than the polymer entanglement mesh size. The motion of larger NPs, which are comparable to the entanglement mesh size, is significantly slowed by chain entanglements, and is not describable by the Stokes-Einstein relationship. Our results are in essentially quantitative agreement with a force-level generalized Langevin equation theory for all the NP sizes and chain lengths explored, and imply that for these lightly entangled systems, activated NP hopping is not important.

Kalathi, Jagannathan [Columbia University, New York] [Columbia University, New York; Yamamoto, Umi [University of Illinois, Urbana-Champaign] [University of Illinois, Urbana-Champaign; Schweizer, Kenneth [University of Illinois] [University of Illinois; Grest, Gary S. [Sandia National Laboratories (SNL)] [Sandia National Laboratories (SNL); Kumar, Sanat [Columbia University, New York] [Columbia University, New York

2014-01-01

290

The effect of cavitation on the hydrofoil dynamic characteristics

NASA Astrophysics Data System (ADS)

Cavitation in hydraulic machinery usually causes a change of fluid dynamic characteristics. In order to predict the effect of cavitation on hydrofoil characteristics, the cavitation around a hydrofoil was studied numerically. The full cavitation model and a modified RNG k ?-turbulence model were used. The finite volume method with the SIMPLEC scheme was used to discretize the time-dependent equations. The second-order upwind scheme was used for the convection terms with the central difference scheme used for the diffusion terms. Fluid dynamic characteristics including cavity's length, shedding frequency, pressure coefficient and lift and drag force coefficients features in a range of cavitation number were analyzed. Computations were made on the three-dimensional flow field around a NACA66 hydrofoil at 8° angle of attack. The recording force signals exhibit periodic behaviours with the time. And the cavity shedding frequency increases with the cavitation number, however the length of cavity decreases with the cavitation number, which result in changing of lift-drag ratio. Especially for larger cavitation numbers, the lift drag ratio of cavitation field is getting closer and closer to that of non-cavitation field.

Yang, J.; Zhou, L. J.; Wang, Z. W.; Zhi, F. L.

2013-12-01

291

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

292

Bunch Length Measurements using Coherent Radiation

The accelerating field that can be obtained in a beam-driven plasma wakefield accelerator depends on the current of the electron beam that excites the wake. In the E-167 experiment, a peak current above 10 kA will be delivered at a particle energy of 28 GeV. The bunch has a length of a few ten micrometers and several methods are used to measure its longitudinal profile. Among these, autocorrelation of coherent transition radiation (CTR) is employed. The beam passes a thin metallic foil, where it emits transition radiation. For wavelengths greater than the bunch length, this transition radiation is emitted coherently. This amplifies the long-wavelength part of the spectrum. A scanning Michelson interferometer is used to autocorrelate the CTR. However, this method requires the contribution of many bunches to build an autocorrelation trace. The measurement is influenced by the transmission characteristics of the vacuum window and beam splitter. We present here an analysis of materials, as well as possible layouts for a single shot CTR autocorrelator.

Ischebeck, Rasmus; Barnes, Christopher; Blumenfeld, Ian; Decker, Franz-Josef; Hogan, Mark; Iverson, Richard H.; Krejcik, Patrick; Siemann, Robert H.; Walz, Dieter; /SLAC; Kirby, Neil; /Stanford U., Phys. Dept.; Clayton, Chris; Huang, Chengkun; Johnson, Devon K.; Lu, Wei; Marsh, Ken; /UCLA; Deng, Suzhi; Oz, Erdem; /Southern California U.

2005-06-24

293

Aeolian sand transport: Length and height distributions of saltation trajectories

NASA Astrophysics Data System (ADS)

We report wind-tunnel measurements on aeolian sand transport aiming at characterizing the distribution of the length and height of trajectories of the saltating particles. We employ a simple horizontal sand trap device to assess the distribution of saltation length while the distribution of saltation height is inferred from the measurements of the particle lift-off velocity by means of particle velocimetry tracking techniques. Our measurements reveal that the saltation length and height present a continuum distribution which decreases monotonously and exhibits a long tail that can be well described by a lognormal law. Interestingly, these distributions are found almost invariant with the flow strength. As a consequence, the mean saltation length (l¯) and height (h¯) are independent of the flow strength confirming previous indirect measurements. The influence of the flow strength is only seen through the tail of the saltation length distribution: the higher the Shields number, the flatter the distribution tail. Finally, experiments carried out with sand of different sizes show that the mean saltation length and height are not related to the sand grain size through a simple manner but depend instead linearly with the height zf of the Bagnold focus point: l??6zf and h??0.6zf. This last result emphasizes that the focus height is an important characteristic length scale of the saltation transport.

Ho, T. D.; Valance, A.; Dupont, P.; Ould El Moctar, A.

2014-03-01

294

Telomere length dynamics in aging mice.

??Leukocyte telomere length (TL) shortens with age and is associated with age-related pathologies. However, inherited and acquired variation in telomere length in individuals complicates clinical… (more)

Comartin, Paul J

2012-01-01

295

To evaluate diffusion sampling as an alternative method to monitor volatile organic compound (VOC) concentrations in ground water, concentrations in samples collected by traditional pumped-sampling methods were compared to concentrations in samples collected by diffusion-sampling methods for 89 monitoring wells at or near the Massachusetts Military Reservation, Cape Cod. Samples were analyzed for 36 VOCs. There was no substantial difference between the utility of diffusion and pumped samples to detect the presence or absence of a VOC. In wells where VOCs were detected, diffusion-sample concentrations of tetrachloroethene (PCE) and trichloroethene (TCE) were significantly lower than pumped-sample concentrations. Because PCE and TCE concentrations detected in the wells dominated the calculation of many of the total VOC concentrations, when VOC concentrations were summed and compared by sampling method, visual inspection also showed a downward concentration bias in the diffusion-sample concentration. The degree to which pumped- and diffusion-sample concentrations agreed was not a result of variability inherent within the sampling methods or the diffusion process itself. A comparison of the degree of agreement in the results from the two methods to 13 quantifiable characteristics external to the sampling methods offered only well-screen length as being related to the degree of agreement between the methods; however, there is also evidence to indicate that the flushing rate of water through the well screen affected the agreement between the sampling methods. Despite poor agreement between the concentrations obtained by the two methods at some wells, the degree to which the concentrations agree at a given well is repeatable. A one-time, well-bywell comparison between diffusion- and pumped-sampling methods could determine which wells are good candidates for the use of diffusion samplers. For wells with good method agreement, the diffusion-sampling method is a time-saving and cost-effective alternative to pumped-sampling methods in a long-term monitoring program, such as at the Massachusetts Military Reservation.

Archfield, Stacey A.; LeBlanc, Denis R.

2005-01-01

296

Buoyancy Effects on Flow Transition in Hydrogen Gas Jet Diffusion Flames

NASA Technical Reports Server (NTRS)

Experiments were performed in earth-gravity to determine how buoyancy affected transition from laminar to turbulent flow in hydrogen gas jet diffusion flames. The jet exit Froude number characterizing buoyancy in the flame was varied from 1.65 x 10(exp 5) to 1.14 x 10(exp 8) by varying the operating pressure and/or burner inside diameter. Laminar fuel jet was discharged vertically into ambient air flowing through a combustion chamber. Flame characteristics were observed using rainbow schlieren deflectometry, a line-of-site optical diagnostic technique. Results show that the breakpoint length for a given jet exit Reynolds number increased with increasing Froude number. Data suggest that buoyant transitional flames might become laminar in the absence of gravity. The schlieren technique was shown as effective in quantifying the flame characteristics.

Albers, Burt W.; Agrawal, Ajay K.; Griffin, DeVon (Technical Monitor)

2000-01-01

297

NASA Astrophysics Data System (ADS)

In this work, a multilayered dielectric film and metallic film are used as reflecting surface to fabricate light pipe. Linearly polarized laser beam with wave length of 532nm enters into the light pipe. After multi-reflection process, laser beam come out from the light pipe. We have found that the polarization state of linearly polarized incident light after reflection are different for the light pipe coated with metal and multilayered dielectric film. We also found a distributed polarization characteristic in the output optical field. The polarization degree has been simulated by using ZEMAX software. Laser speckle contrast from a glass diffuser is measured to exam the simulated result.

Zhao, PengFei; Zhang, Shengtao; Wang, Yanhong; Shi, Yunbo; Chen, XuYuan

2012-11-01

298

Diffusion, dimensionality and noise in transcriptional regulation

The precision of biochemical signaling is limited by randomness in the diffusive arrival of molecules at their targets. For proteins binding to the specific sites on the DNA and regulating transcription, the ability of the proteins to diffuse in one dimension by sliding along the length of the DNA, in addition to their diffusion in bulk solution, would seem to generate a larger target for DNA binding, consequently reducing the noise in the occupancy of the regulatory site. Here we show that this effect is largely cancelled by the enhanced temporal correlations in one dimensional diffusion. With realistic parameters, sliding along DNA has surprisingly little effect on the physical limits to the precision of transcriptional regulation.

Gasper Tkacik; William Bialek

2007-12-12

299

Characteristic Time Scales of Characteristic Magmatic Processes and Systems

NASA Astrophysics Data System (ADS)

Every specific magmatic process, regardless of spatial scale, has an associated characteristic time scale. Time scales associated with crystals alone are rates of growth, dissolution, settling, aggregation, annealing, and nucleation, among others. At the other extreme are the time scales associated with the dynamics of the entire magmatic system. These can be separated into two groups: those associated with system genetics (e.g., the production and transport of magma, establishment of the magmatic system) and those due to physical characteristics of the established system (e.g., wall rock failure, solidification front propagation and instability, porous flow). The detailed geometry of a specific magmatic system is particularly important to appreciate; although generic systems are useful, care must be taken to make model systems as absolutely realistic as possible. Fuzzy models produce fuzzy science. Knowledge of specific time scales is not necessarily useful or meaningful unless the hierarchical context of the time scales for a realistic magmatic system is appreciated. The age of a specific phenocryst or ensemble of phenocrysts, as determined from isotopic or CSD studies, is not meaningful unless something can be ascertained of the provenance of the crystals. For example, crystal size multiplied by growth rate gives a meaningful crystal age only if it is from a part of the system that has experienced semi-monotonic cooling prior to chilling; crystals entrained from a long-standing cumulate bed that were mechanically sorted in ascending magma may not reveal this history. Ragged old crystals rolling about in the system for untold numbers of flushing times record specious process times, telling more about the noise in the system than the life of typical, first generation crystallization processes. The most helpful process-related time scales are those that are known well and that bound or define the temporal style of the system. Perhaps the most valuable of these times comes from the observed durations and rates of volcanism. There can be little doubt that the temporal styles of volcanism are the same as those of magmatism in general. Volcano repose times, periodicity, eruptive fluxes, acoustic emission structures, lava volumes, longevity, etc. must also be characteristic of pluton-dominated systems. We must therefore give up some classical concepts (e.g., instantaneous injection of crystal-free magma as an initial condition) for any plutonic/chambered system and move towards an integrated concept of magmatism. Among the host of process-related time scales, probably the three most fundamental of any magmatic system are (1) the time scale associated with crystal nucleation (J) and growth (G) (tx}=C{1(G3 J)-{1}/4; Zieg & Marsh, J. Pet. 02') along with the associated scales for mean crystal size (L) and population (N), (2) the time scale associated with conductive cooling controlled by a local length scale (d) (tc}=C{2 d2/K; K is thermal diffusivity), and (3) the time scale associated with intra-crystal diffusion (td}=C{3 L2/D; D is chemical diffusivity). It is the subtle, clever, and insightful application of time scales, dovetailed with realistic system geometry and attention paid to the analogous time scales of volcanism, that promises to reveal the true dynamic integration of magmatic systems.

Marsh, B. D.

2004-05-01

300

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

301

The Diffuse Interstellar Bands: Contributed papers

NASA Technical Reports Server (NTRS)

Drawing a coherent picture of the observational characteristics of the Diffuse Interstellar Bands (DIB's) and the physical and chemical properties of its proposed carriers was the focus of this NASA sponsored conference. Information relating to absoption spectra, diffuse radiation carriers, carbon compounds, stellar composition, and interstellar extinction involving T-Tauri stars, Reflection Nebulae, Red Giants, and accretion discs are discussed from those papers presented at the conference, which are included in this analytic.

Tielens, Alexander G. G. M. (editor)

1994-01-01

302

Microcavity effects on the generation,fluorescence, and diffusion of excitons in organic solar cells

We compute the short-circuit diffusion current of excitons in an organic solar cell, with special emphasis on fluorescence losses. The exciton diffusion length is not uniform but varies with its position within the device, even with moderate fluorescence quantum efficiency. With large quantum efficiencies, the rate of fluorescence can be strongly reduced with proper choices of the geometrical and dielectric parameters. In this way, the diffusion length can be increased and the device performance significantly improved.

Kozyreff, G; Vuong, L T; Silleras, O Nieto; Martorell, J

2013-01-01

303

Diffusive-Ballistic Heat Conduction of Carbon Nanotubes and Nanographene Ribbons Junichiro Shiomi-3-5800-6983 Abstract Investigations of diffusive-ballistic heat conduction of finite-length single-walled carbon of the balance between ballistic and diffusive heat conduction. For both systems, the profile indicates

Maruyama, Shigeo

304

Numerical study of a macroscopic finite pulse model of the diffusion MRI signal

NASA Astrophysics Data System (ADS)

Diffusion magnetic resonance imaging (dMRI) is an imaging modality that probes the diffusion characteristics of a sample via the application of magnetic field gradient pulses. The dMRI signal from a heterogeneous sample includes the contribution of the water proton magnetization from all spatial positions in a voxel. If the voxel can be spatially divided into different Gaussian diffusion compartments with inter-compartment exchange governed by linear kinetics, then the dMRI signal can be approximated using the macroscopic Karger model, which is a system of coupled ordinary differential equations (ODEs), under the assumption that the duration of the diffusion-encoding gradient pulses is short compared to the diffusion time (the narrow pulse assumption). Recently, a new macroscopic model of the dMRI signal, without the narrow pulse restriction, was derived from the Bloch-Torrey partial differential equation (PDE) using periodic homogenization techniques. When restricted to narrow pulses, this new homogenized model has the same form as the Karger model. We conduct a numerical study of the new homogenized model for voxels that are made up of periodic copies of a representative volume that contains spherical and cylindrical cells of various sizes and orientations and show that the signal predicted by the new model approaches the reference signal obtained by solving the full Bloch-Torrey PDE in O (?2) , where ? is the ratio between the size of the representative volume and a measure of the diffusion length. When the narrow gradient pulse assumption is not satisfied, the new homogenized model offers a much better approximation of the full PDE signal than the Karger model. Finally, preliminary results of applying the new model to a voxel that is not made up of periodic copies of a representative volume are shown and discussed.

Li, Jing-Rebecca; Nguyen, Hang Tuan; Van Nguyen, Dang; Haddar, Houssem; Coatléven, Julien; Le Bihan, Denis

2014-11-01

305

Diffusive Logistic Model Towards Predicting Information Diffusion in Online Social Networks

Online social networks have recently become an effective and innovative channel for spreading information and influence among hundreds of millions of end users. Many prior work have carried out empirical studies and proposed diffusion models to understand the information diffusion process in online social networks. However, most of these studies focus on the information diffusion in temporal dimension, that is, how the information propagates over time. Little attempt has been given on understanding information diffusion over both temporal and spatial dimensions. In this paper, we propose a Partial Differential Equation (PDE), specifically, a Diffusive Logistic (DL) equation to model the temporal and spatial characteristics of information diffusion in online social networks. To be more specific, we develop a PDE-based theoretical framework to measure and predict the density of influenced users at a given distance from the original information source after a time period. The density of influenced users over tim...

Wang, Feng; Xu, Kuai

2011-01-01

306

Laser glass marking: influence of pulse characteristics

NASA Astrophysics Data System (ADS)

Laser glass marking is currently used in several glass materials for different purposes, such as bar codes for product tracking, brand logos or just decoration. Systems with a variety of different laser sources, with inherent power ranges, wavelengths and pulse regimes have been used, namely CO2, Nd:YAG, Excimer, Ti-Sapphire lasers. CO2 Lasers systems, although being a reliable tool for materials processing, and very compact in the case of sealed low power lasers, are usually associated with a localized thermal loading on the material, causing brittle materials like glass to crack around the irradiated area. In this experimental study a pulsed CO2 laser was used to direct marking the glass surface. The temporal characteristics of the laser pulse--pulse length, period and duty cycle were varied, and glass materials with different thermal properties were used in order to correlate the marking process--cracking or softening with or without material removal with the laser and material characteristics. Glass materials with major industrial application, such as soda-lima, borosilicate (PYREX) glasses and crystal have been investigated. Laser marked areas have been characterized in terms of surface optical properties, like diffuse and direct reflectance and transmittance for white light, directly related with marked surface quality.

Rolo, Ana; Coelho, João; Pires, Margarida

2005-09-01

307

An unresolved problem in physics is how the thermodynamic arrow of time arises from an underlying time reversible dynamics. We contribute to this issue by developing a measure of time-symmetry breaking, and by using the work fluctuation relations, we determine the time asymmetry of recent single molecule RNA unfolding experiments. We define time asymmetry as the Jensen-Shannon divergencebetween trajectory probability distributions of an experiment and its time-reversed conjugate. Among other interesting properties, the length of time's arrow bounds the average dissipation and determines the difficulty of accurately estimating free energy differences in nonequilibrium experiments.

Feng, Edward H.; Crooks, Gavin E.

2008-08-21

308

Haploinsufficiency and telomere length homeostasis.

In humans, autosomal dominant or X-linked disease can arise through a phenomenon termed haploinsufficiency, where one remaining wild-type allele is insufficient for function. In model organisms, the impact of heterozygosity can be tested directly with engineered mutant alleles or in a hemizygous state where the expression of one allele is abrogated completely. This review will focus on haploinsufficiency as it relates to telomerase and telomere length maintenance and, citing selected examples in various model organisms, it will discuss how the problem of gene dosage relates to telomere function in normal and diseased states. PMID:22100521

Harrington, Lea

2012-02-01

309

NSDL National Science Digital Library

In this math lesson, learners explore the concept of using units to measure length. Learners first read "How Big is a Foot" by Rolf Myller and learn about units. Then, learners visit four measurement centers. In each center, learners will measure items with various kinds of units. Learners use non-standard units to measure their shoes, the distance between beanbags and a bullâs-eye target, their body parts (arms, legs, etc.), and some everyday objects. This lesson guide includes instructions on how to set up a "Shoe Store" dramatic play area that can be used to introduce learners to measurement prior to this activity.

Lyman, Nichol

2012-09-26

310

Tau Protein Diffuses along the Microtubule Lattice*

Current models for the intracellular transport of Tau protein suggest motor protein-dependent co-transport with microtubule fragments and diffusion of Tau in the cytoplasm, whereas Tau is believed to be stationary while bound to microtubules and in equilibrium with free diffusion in the cytosol. Observations that members of the microtubule-dependent kinesin family show Brownian motion along microtubules led us to hypothesize that diffusion along microtubules could also be relevant in the case of Tau. We used single-molecule total internal reflection fluorescence microscopy to probe for diffusion of individual fluorescently labeled Tau molecules along microtubules. This allowed us to avoid the problem that microtubule-dependent diffusion could be masked by excess of labeled Tau in solution that might occur in in vivo overexpression experiments. We found that approximately half of the individually detected Tau molecules moved bidirectionally along microtubules over distances up to several micrometers. Diffusion parameters such as diffusion coefficient, interaction time, and scanned microtubule length did not change with Tau concentration. Tau binding and diffusion along the microtubule lattice, however, were sensitive to ionic strength and pH and drastically reduced upon enzymatic removal of the negatively charged C termini of tubulin. We propose one-dimensional Tau diffusion guided by the microtubule lattice as one possible additional mechanism for Tau distribution. By such one-dimensional microtubule lattice diffusion, Tau could be guided to both microtubule ends, i.e. the sites where Tau is needed during microtubule polymerization, independently of directed motor-dependent transport. This could be important in conditions where active transport along microtubules might be compromised. PMID:23019339

Hinrichs, Maike H.; Jalal, Avesta; Brenner, Bernhard; Mandelkow, Eckhard; Kumar, Satish; Scholz, Tim

2012-01-01

311

Restricted diffusion in annular geometrical pores

NASA Astrophysics Data System (ADS)

Nuclear magnetic resonance (NMR) diffusion (including diffusion MRI) experiments are only as powerful as the models used to analyse the NMR diffusion data. A major problem, especially with measurements on biological systems, is that the existing models are only very poor approximations of cellular shape. Here, diffusion propagators and pulsed gradient spin-echo attenuation equations are derived in the short gradient pulse limit for diffusion within the annular region of a concentric cylinder of finite length and, similarly, within the annular region of a concentric sphere. The models include the possibility of relaxation at the boundaries and, in the case of the concentric cylinder, having the cylinder arbitrarily oriented with respect to the direction of the applied field gradient. The two models are also of interest due to their direct analogy to optical double slit diffraction. Also expressions for the mean square displacements, which are very useful information for determining the diffusion coefficient within these complex geometries, are obtained as well as for the limiting cases of diffusion on cylindrical and spherical shells and in a ring.

Ghadirian, Bahman; Torres, Allan M.; Yadav, Nirbhay N.; Price, William S.

2013-03-01

312

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

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.

313

Fibreoptic diffuse-light irradiators of biological tissues

We report techniques for the fabrication of laser radiation diffusers for interstitial photodynamic therapy. Using chemical etching of the distal end of silica fibre with a core diameter of 200 - 600 {mu}m, we have obtained long (up to 40 mm) diffusers with good scattering uniformity. Laser ablation has been used to produce cylindrical diffusers with high emission contrast and a scattering uniformity no worse than {approx}10 % in their middle part. The maximum length of the diffusers produced by this method is 20 - 25 mm. (laser applications and other topics in quantum electronics)

Volkov, Vladimir V; Loshchenov, V B; Konov, Vitalii I; Kononenko, Vitalii V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2010-10-15

314

Diffusion of water in nanoporous NF polyamide membrane

NASA Astrophysics Data System (ADS)

Diffusion of water sorbed in a nanofiltration (NF) polyamide membrane as studied by quasielastic neutron scattering (QENS) is reported here. The trimesoyl chloride-piperazine based NF membrane was synthesized by interfacial polymerization technique and was characterized by positron annihilation lifetime spectroscopy (PALS) and SEM techniques. PALS data shows that the membrane has an average pore size ˜4.6 Å. QENS data from water sorbed NF membrane show that the diffusion in the sorbed water occurs through jump diffusion with the jump lengths distributed randomly. Translational diffusion coefficient obtained for water sorbed in the NF membrane is found to be smaller than that of bulk water.

Sharma, V. K.; Singh, P. S.; Gautam, S.; Mitra, S.; Mukhopadhyay, R.

2009-08-01

315

Microfabricated diffusion source

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

316

In this thesis the instruments explore two main aspects of organic optoelectronic devices. One instrument characterizes exciton diffusion and the other patterns organic thin films. Exciton diffusion characteristics are ...

Mendoza, Hiroshi Antonio

2012-01-01

317

Bilateral Filtering of Diffusion Tensor MR Images Ghassan Hamarneh and Judith Hradsky

- sion tensor magnetic resonance imaging (DTMRI) records the diffusion characteristics of water molecules progression and treatment evaluation on fiber connectivity and diffusion properties [1], [2]. In DTMRI of treatment and disease progression, and statistical analysis of structural and functional variability

Hamarneh, Ghassan

318

Mathematical model of alternative mechanism of telomere length maintenance

Biopolymer length regulation is a complex process that involves a large number of subprocesses acting simultaneously across multiple spatial and temporal scales. An illustrative example important for genomic stability is the length regulation of telomeres---nucleo-protein structures at the ends of linear chromosomes. Maintenance of telomeres is often facilitated by the enzyme telomerase but, particularly in telomerase-free systems, the maintenance of chromosomal termini depends on alternative lengthening of telomeres (ALT) mechanisms mediated by recombination. Various linear and circular DNA structures were identified to participate in ALT, however, dynamics of the whole process is still poorly understood. We propose a chemical kinetics model of ALT with kinetic rates systematically derived from the biophysics of DNA diffusion and looping. The reaction system is reduced to a coagulation-fragmentation system by quasi-steady state approximation. The detailed treatment of kinetic rates yields explicit formulae f...

Kollár, Richard; Nosek, Jozef; Tomaska, Lubomir

2014-01-01

319

Drying characteristics and kinetics of okra

Air-drying characteristics of okra were investigated in a laboratory scale hot-air dryer for a temperature range 50–70°C, and a relative humidity range 8–25%. Results indicated that drying took place in the falling rate period. Moisture transfer from okra was described by applying the Fick’s diffusion model, and the effective diffusivity was calculated. Effective diffusivity increased with increasing temperature. An Arrhenius

?brahim Doymaz

2005-01-01

320

Real-Valued Semigroups and (Causal) Diffusion

It can be shown that a process modeled by a strongly continuous real-valued semigroup (that has a space convolution operator as infinitesimal generator) cannot satisfy causality. By causality we mean that a characteristic feature of a process like an interface or a front must propagate with a finite speed. We present and discuss a causal model of diffusion that satisfies the semigroup property at a discrete set of time instants M:={l_brace}m{tau}|m is an element of N{sub 0}{r_brace} and that in contrast to the classical diffusion model is not smooth. More precisely, if v denotes the concentration of a substance diffusing with constant speed, then v is continuous but its time derivative is discontinuous at the discrete set M of time instants. It is this property of (causal) diffusion that forbids the classical limit procedure {tau}{yields}0 that leads to the noncausal diffusion model in Stochastics. Finally, we give two explanations why in some cases the discretization of the noncausal diffusion model can be considered as an approximation of the causal diffusion model. In particular, we present an inhomogeneous wave equation with a time dependent coefficient that is satisfied by causal diffusion.

Kowar, Richard [Department of Mathematics, University of Innsbruck, Technikerstrasse 21a/2, A-6020, Innsbruck (Austria)

2011-09-22

321

Holographic diffuser by use of a silver halide sensitized gelatin process

NASA Astrophysics Data System (ADS)

Diffusers play an important role in liquid-crystal display (LCD) application as a beam-shaping device, a brightness homogenizer, a light-scattering device, and an imaging screen. The transmittance and diffusing angle of the diffusers are the critical aspects for the applications to the LCD. The holographic diffusers by use of various processing methods have been investigated. The diffusing characteristics of different diffusing materials and processing methods have been evaluated and compared. The micro-structures of holographic diffusers have been investigated by use of using scanning electron microscopy. The holographic diffusers by use of the silver halide sensitized gelatin (SHSG) method have the structural merits for the improvement of the quality of diffusers. The features of holographic diffuser were exceptional in terms of transmittance and diffusing angle. The replication method by use of the SHSG process can be directly used for the manufacturing of diffusers for the display application.

Kim, Sun Il; Choi, Yoon Sun; Ham, Yong Nam; Park, Chong Yun; Kim, Jong Man

2003-05-01

322

UPDATING APPLIED DIFFUSION MODELS

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...

323

Factors affecting length at maturity and other important reproductive characteristics have not been investigated for Idaho redband trout Oncorhynchus mykiss gairdneri residing in desert streams. Prespawning redband trout were collected from nine streams, and estimates of length at sexual maturity, median age at maturity, sex ratio, and fecundity were developed along with models predicting length at maturity from physical stream

Daniel J. Schill; George W. LaBar; Elizabeth R. J. M. Mamer; Kevin A. Meyer

2010-01-01

324

Handbook on atmospheric diffusion

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

325

DT-MRI regularization using 3D nonlinear gradient vector flow anisotropic diffusion

In DT-MRI, diffusion-weighted multislice echoplanar images (EPIs) are processed to represent water diffusion characteristics as a diffusion tensor, reflecting the amount of diffusion in 3D. However imaging quality is generally compromised by several factors including the number of imaging slices, averages, diffusion sensitization steps (b-values), voxel size, and gradient directions, resulting in suboptimal SNR. In this study, we focus on

T.-S. Kim; S. Kim; D. Hwang; M. Singh

2004-01-01

326

Rumor Diffusion in an Interests-Based Dynamic Social Network

To research rumor diffusion in social friend network, based on interests, a dynamic friend network is proposed, which has the characteristics of clustering and community, and a diffusion model is also proposed. With this friend network and rumor diffusion model, based on the zombie-city model, some simulation experiments to analyze the characteristics of rumor diffusion in social friend networks have been conducted. The results show some interesting observations: (1) positive information may evolve to become a rumor through the diffusion process that people may modify the information by word of mouth; (2) with the same average degree, a random social network has a smaller clustering coefficient and is more beneficial for rumor diffusion than the dynamic friend network; (3) a rumor is spread more widely in a social network with a smaller global clustering coefficient than in a social network with a larger global clustering coefficient; and (4) a network with a smaller clustering coefficient has a larger efficiency. PMID:24453911

Mao, Xinjun; Guessoum, Zahia; Zhou, Huiping

2013-01-01

327

Dinosaur Skull and Body Length Predictions

NSDL National Science Digital Library

In this activity (located on page 2 of PDF), learners will look for a relationship between skull size and body length among various dinosaurs. Starting from a list of dinosaur measurements, learners will compare dinosaur sizes to common objects and create a chart that plots body length against skull length to see if the data predicts other dinosaurs' length from skull size. Relates to the linked video, DragonflyTV GPS: Baby Dinosaurs.

Twin Cities Public Television, Inc.

2007-01-01

328

Finite element modeling of aponeurotomized rat extensor digitorium longus muscle was performed to investigate the acute effects\\u000a of proximal aponeurotomy. The specific goal was to assess the changes in lengths of sarcomeres within aponeurotomized muscle\\u000a and to explain how the intervention leads to alterations in muscle length–force characteristics. Major changes in muscle length–active\\u000a force characteristics were shown for the aponeurotomized

Can A. Yucesoy; Bart H. F. J. M. Koopman; Henk J. Grootenboer; Peter A. Huijing

2007-01-01

329

Many properties of industrial Ti-Al alloys, such as high-temperature stability of the lamellar structure and creep resistance, are determined by diffusion rates in the phases and along the interfaces. The knowledge of diffusion characteristics and fundamental understanding of diffusion mechanisms are of great importance to the research and design of industrial Ti-Al alloys. This paper gives an overview of recent progress in experimental and theoretical studies of diffusion behavior in the phases of the Ti-Al system. The experimental methods used in modern diffusion measurements are briefly described, and recent experimental results for Ti and Al diffusion in {alpha}-Ti(Al), {beta}-Ti(Al), and intermetallic phases {alpha}{sub 2}-Ti{sub 3}Al and {gamma}-TiAl, are summarized. The results for interdiffusion and impurity diffusion in these phases are also discussed in detail. The second part of the paper provides an overview of current understanding of point defects and diffusion mechanisms in Ti{sub 3}Al and TiAl. A statistical model of point-defect disorder in ordered compounds is presented and applied to Ti{sub 3}Al and TiAl using input data generated with embedded-atom potentials. Possible atomic mechanisms of diffusion in these compounds are analyzed in detail, and methods of diffusion calculations under different mechanisms are reviewed. The relative importance of different mechanisms in Ti{sub 3}Al and TiAl is evaluated by comparing their estimated activation energies. Prospective topics of further experimental and theoretical research in this area are outlined.

Mishin, Y.; Herzig, C.

2000-02-09

330

Compact noninvasive electron bunch-length monitor

A compact rf cavity was constructed that simultaneously resonates at many harmonic modes when excited by a repetitive bunched electron beam passing through its bore. The excitation of these modes provides a Fourier description of the temporal characteristics of the bunch train. The cavity was used to noninvasively characterize electron bunches produced from thin and thick GaAs photocathodes inside a DC high voltage photogun illuminated with 37 ps (full width half maximum, FWHM) laser pulses at repetition rates near 1500 MHz, at average beam current from 5 to 500????A , and at beam energy from 75 to 195 keV. The cavity bunch-length monitor could detect electron bunches as short as 57 ps (FWHM) when connected directly to a sampling oscilloscope, and could clearly distinguish bunches with varying degrees of space-charge induced growth and with different tail signatures. Efforts are under way to detect shorter bunches by designing cavities with increased bandwidth. This demonstration lends credibility to the idea that these cavities could also be used for other applications, including bunching and shaping, when driven with external rf.

Roberts, B.; Mammei, R. R.; Poelker, M.; McCarter, J. L.

2012-12-01

331

Fission track length distributions in multi-system thermochronology (Invited)

NASA Astrophysics Data System (ADS)

Fission track length distributions contain a unique record of past temperature variations and therefore play a key role in low-temperature thermochronology, for which there is no exact equivalent in any other method. Confined track lengths closely approximate the true etchable ranges of latent fission tracks [1] and are therefore favoured for fission track studies, but they still have a number of practical limitations. These include small numbers of suitable tracks, especially when only horizontal confined tracks are measured. Using only track-in-track events for measurement further limits the sample size. These restrictions become acute for low track-density samples, where length measurements may be impossible. Irradiating the surface with 252Cf tracks [2] can substantially increase the number of confined tracks, but many researchers do not have access to a Cf source. An even more significant issue has emerged from inter-laboratory comparison experiments that demonstrate a disturbingly poor reproducibility of length measurements between observers [3], a problem compounded by a lack of standardisation in measurement techniques. As a result, individual observers may measure different positions for the end of a track, contributing significantly to variability, and consequently blurring the thermal histories obtained. New digital microscopes open up important opportunities for improved track length measurements by reducing restrictions on sample size, and eliminating some sources of inter-observer bias. We have developed a track length measurement system that enables precise determination of vertical as well as horizontal track dimensions, allowing 3D lengths to be obtained. Lengths are measured on captured image stacks that can be analysed easily and may also be shared, for greater standardisation between laboratories. Length measurements are highly reproducible between different observers using this system, suggesting that at least one source of variability can be eliminated. The selection of lengths for imaging, however, still remains a source of potential bias between observers. The new measurement system also enables measurement of 3D lengths of surface-intersecting ';semi-tracks', the distributions of which have been well understood theoretically [1,4], but have not been used in practice because of difficulties of measuring vertical dimensions on older microscopes. Semi-track lengths are, of course, a degraded measure compared to confined tracks because they are randomly truncated. However, this is more than compensated by their very much greater abundance, by a factor of >60, compared to confined tracks. They are also more amenable to semi- or fully-automated measurement techniques than confined tracks. Moreover the distribution characteristics of semi-track lengths relative to confined track lengths are well understood so that in principle the two types could be used together in modelling thermal histories. The implementation of these new approaches for track length measurement should significantly improve the precision and standardisation of track length measurements at every stage of their utilisation, from annealing studies to thermal history modelling of unknowns. [1] Galbraith (2003) Statistics for FT Analysis, Chapman & Hall [2] Donelick et al. (2005) Rev Min Geochem 58, 49-94 [3] Ketcham et al. (2009) Ear Planet Sci Lett 284, 504-515 [4] Jonckheere & Van den haute (1999) Rad Meas 30, 155-179

Gleadow, A. J.; Seiler, C.

2013-12-01

332

Forced convective heat transfer in curved diffusers

Measurements of the velocity characteristics of the flows in two curved diffusers of rectangular cross section with C and S-shaped centerlines are presented and related to measurements of wall heat transfer coefficients along the heated flat walls of the ducts. The velocity results were obtained by laser-Doppler anemometry in a water tunnel and the heat transfer results by liquid crystal

J. Rojas; J. H. Whitelaw; M. Yianneskis

1987-01-01

333

The feasibility of obtaining general impurity distributions by diffusion

Although it is possible to optimize selected characteristics of semiconductor devices by controlling the net impurity distribution, present methods used for fabricating planar devices by diffusion techniques invariably produce profiles which are approximately either Gaussian or complementary error functions. The purpose of this paper is to examine the feasibility of obtaining a general impurity profile within intrinsic material using diffusion

A. H. Marshak; D. J. Hamilton

1970-01-01

334

An epidemic model for information diffusion in MANETs

Choosing appropriate information dissemination strategies is crucial in mobile ad hoc networks (MANET) due to the frequent topology changes. Flooding-based approaches like diffusion have a strong similarity with epidemic spreading of diseases. Applying epidemiological models to information diffusion allows the evaluation of such strategies depending on the MANET characteristics, e.g. the node density. In order to choose appropriate strategies at

Abdelmajid Khelil; Christian Becker; Jing Tian; Kurt Rothermel

2002-01-01

335

High-power diffusing-tip fibers for interstitial photocoagulation

NASA Astrophysics Data System (ADS)

A line of optical fiber based diffusing tips has been designed, developed, and tested that are capable of distributing tens of watts of cw laser power over lengths ranging from two millimeters to over 10 cm. The result is a flexible non-stick diffuser capable of coagulating large volumes of tissue in reasonably short exposures of 3 - 5 minutes. Sub-millimeter diameter devices have a distinct effect on reducing the force needed to insert the applicator interstitially into tissue. Utilizing our design approach, we have produced diffusers based on 200 micrometer core fiber that has delivered over 35 watts of Nd:YAG energy over diffusion lengths as short as 4 mm. These applicators are being tested for applications in oncology, cardiology, electrophysiology, urology and gynecology.

Sinofsky, Edward L.; Farr, Norman; Baxter, Lincoln; Weiler, William

1997-05-01

336

Characteristic 0 Characteristic p > 0

Kowalski Instytut Matematyczny Uniwersytetu Wroclawskiego May 22, 2010 Kowalski Transcendence in positive Algebraic independence Kowalski Transcendence in positive characteristic #12;Set-up Characteristic 0 independent modulo C, then trdegC (x, y) n + 1. Kowalski Transcendence in positive characteristic #12;Set

Kowalski, Piotr

337

Diffusion laws in dendritic spines

Dendritic spines are small protrusions on a neuronal dendrite that are the main locus of excitatory synaptic connections. Although their geometry is variable over time and along the dendrite, they typically consist of a relatively large head connected to the dendritic shaft by a narrow cylindrical neck. The surface of the head is connected smoothly by a funnel or non-smoothly to the narrow neck, whose end absorbs the particles at the dendrite. We demonstrate here how the geometry of the neuronal spine can control diffusion and ultimately synaptic processes. We show that the mean residence time of a Brownian particle, such as an ion or molecule inside the spine, and of a receptor on its membrane, prior to absorption at the dendritic shaft depends strongly on the curvature of the connection of the spine head to the neck and on the neck's length. The analytical results solve the narrow escape problem for domains with long narrow necks. PMID:22655862

2011-01-01

338

Inheritance of Telomere Length in a Bird

Telomere dynamics are intensively studied in human ageing research and epidemiology, with many correlations reported between telomere length and age-related diseases, cancer and death. While telomere length is influenced by environmental factors there is also good evidence for a strong heritable component. In human, the mode of telomere length inheritance appears to be paternal and telomere length differs between sexes, with females having longer telomeres than males. Genetic factors, e.g. sex chromosomal inactivation, and non-genetic factors, e.g. antioxidant properties of oestrogen, have been suggested as possible explanations for these sex-specific telomere inheritance and telomere length differences. To test the influence of sex chromosomes on telomere length, we investigated inheritance and sex-specificity of telomere length in a bird species, the kakapo (Strigops habroptilus), in which females are the heterogametic sex (ZW) and males are the homogametic (ZZ) sex. We found that, contrary to findings in humans, telomere length was maternally inherited and also longer in males. These results argue against an effect of sex hormones on telomere length and suggest that factors associated with heterogamy may play a role in telomere inheritance and sex-specific differences in telomere length. PMID:21364951

Horn, Thorsten; Robertson, Bruce C.; Will, Margaret; Eason, Daryl K.; Elliott, Graeme P.; Gemmell, Neil J.

2011-01-01

339

On Quasilinear Perpendicular Diffusion

Quasilinear perpendicular diffusion of charged particles in fluctuating electromagnetic fields is the focus of this paper. A general transport parameter for perpendicular diffusion is presented being valid for an arbitrary turbulence geometry and a plasma wave dispersion relation varying arbitrarily in wavevector. The new diffusion coefficient is evaluated in detail for slab turbulence geometry for two special cases: (1) Alfv\\'enic turbulence and (2) dynamical magnetic turbulence. Furthermore, perpendicular diffusion in 2D geometry is considered for a purely dynamical magnetic turbulence. The derivations and numerical calculations presented here cast serious doubts on the applicability of quasilinear theory for perpendicular diffusion. Furthermore, they emphasize that nonlinear effects play a crucial role in the context of perpendicular diffusion.

O. Stawicki

2005-03-26

340

Translational displacement of molecules within cells is a key process in cellular biology. Molecular motion potentially depends on many factors, including active transport, cytosol viscosity and molecular crowding, tortuosity resulting from cytoskeleton and organelles, and restriction barriers. However, the relative contribution of these factors to molecular motion in the cytoplasm remains poorly understood. In this work, we designed an original diffusion-weighted magnetic resonance spectroscopy strategy to probe molecular motion at subcellular scales in vivo. This led to the first observation of anomalous diffusion, that is, dependence of the apparent diffusion coefficient (ADC) on the diffusion time, for endogenous intracellular metabolites in the brain. The observed increase of the ADC at short diffusion time yields evidence that metabolite motion is characteristic of hindered random diffusion rather than active transport, for time scales up to the dozen milliseconds. Armed with this knowledge, data modeling based on geometrically constrained diffusion was performed. Results suggest that metabolite diffusion occurs in a low-viscosity cytosol hindered by ?2-?m structures, which is consistent with known intracellular organization. PMID:22929443

Marchadour, Charlotte; Brouillet, Emmanuel; Hantraye, Philippe; Lebon, Vincent; Valette, Julien

2012-01-01

341

Self-gravitational structure formation theory for astrophysics and cosmology is revised using nonlinear fluid mechanics. Gibson's 1996-2000 theory balances fluid mechanical forces with gravitational forces and density diffusion with gravitational diffusion at critical viscous, turbulent, magnetic, and diffusion length scales termed Schwarz scales. Instability occurs for scales larger than the largest Schwarz scale rather than only for scales larger than the

Carl H. Gibson

2000-01-01

342

Multinomial diffusion equation

We describe a new, microscopic model for diffusion that captures diffusion induced fluctuations at scales where the concept of concentration gives way to discrete particles. We show that in the limit as the number of particles N {yields} {infinity}, our model is equivalent to the classical stochastic diffusion equation (SDE). We test our new model and the SDE against Langevin dynamics in numerical simulations, and show that our model successfully reproduces the correct ensemble statistics, while the classical model fails.

Balter, Ariel I.; Tartakovsky, Alexandre M.

2011-06-24

343

Noninvasive measurements of microstructure in materials, cells, and in biological tissues, constitute a unique capability of gradient-assisted NMR. Diffusion-diffraction MR approaches pioneered by Callaghan demonstrated this ability; Oscillating-Gradient Spin-Echo (OGSE) methodologies tackle the demanding gradient amplitudes required for observing diffraction patterns by utilizing constant-frequency oscillating gradient pairs that probe the diffusion spectrum, D(?). Here we present a new class of diffusion MR experiments, termed Non-uniform Oscillating-Gradient Spin-Echo (NOGSE), which dynamically probe multiple frequencies of the diffusion spectral density at once, thus affording direct microstructural information on the compartment's dimension. The NOGSE methodology applies N constant-amplitude gradient oscillations; N-1 of these oscillations are spaced by a characteristic time x, followed by a single gradient oscillation characterized by a time y, such that the diffusion dynamics is probed while keeping (N-1)x+y?TNOGSE constant. These constant-time, fixed-gradient-amplitude, multi-frequency attributes render NOGSE particularly useful for probing small compartment dimensions with relatively weak gradients - alleviating difficulties associated with probing D(?) frequency-by-frequency or with varying relaxation weightings, as in other diffusion-monitoring experiments. Analytical descriptions of the NOGSE signal are given, and the sequence's ability to extract small compartment sizes with a sensitivity towards length to the sixth power, is demonstrated using a microstructural phantom. Excellent agreement between theory and experiments was evidenced even upon applying weak gradient amplitudes. An MR imaging version of NOGSE was also implemented in ex vivo pig spinal cords and mouse brains, affording maps based on compartment sizes. The effects of size distributions on NOGSE are also briefly analyzed. PMID:24140623

Shemesh, Noam; Alvarez, Gonzalo A; Frydman, Lucio

2013-12-01

344

NASA Astrophysics Data System (ADS)

Noninvasive measurements of microstructure in materials, cells, and in biological tissues, constitute a unique capability of gradient-assisted NMR. Diffusion-diffraction MR approaches pioneered by Callaghan demonstrated this ability; Oscillating-Gradient Spin-Echo (OGSE) methodologies tackle the demanding gradient amplitudes required for observing diffraction patterns by utilizing constant-frequency oscillating gradient pairs that probe the diffusion spectrum, D(?). Here we present a new class of diffusion MR experiments, termed Non-uniform Oscillating-Gradient Spin-Echo (NOGSE), which dynamically probe multiple frequencies of the diffusion spectral density at once, thus affording direct microstructural information on the compartment's dimension. The NOGSE methodology applies N constant-amplitude gradient oscillations; N - 1 of these oscillations are spaced by a characteristic time x, followed by a single gradient oscillation characterized by a time y, such that the diffusion dynamics is probed while keeping (N - 1)x + y ? TNOGSE constant. These constant-time, fixed-gradient-amplitude, multi-frequency attributes render NOGSE particularly useful for probing small compartment dimensions with relatively weak gradients - alleviating difficulties associated with probing D(?) frequency-by-frequency or with varying relaxation weightings, as in other diffusion-monitoring experiments. Analytical descriptions of the NOGSE signal are given, and the sequence's ability to extract small compartment sizes with a sensitivity towards length to the sixth power, is demonstrated using a microstructural phantom. Excellent agreement between theory and experiments was evidenced even upon applying weak gradient amplitudes. An MR imaging version of NOGSE was also implemented in ex vivo pig spinal cords and mouse brains, affording maps based on compartment sizes. The effects of size distributions on NOGSE are also briefly analyzed.

Shemesh, Noam; Álvarez, Gonzalo A.; Frydman, Lucio

2013-12-01

345

Diffusion of single-walled carbon nanotube under physiological conditions.

Single-walled carbon nanotube (SWNT) can be functionalized to target cells for drug delivery or cancer cells for their detection and therapy. Understanding their transport phenomena in vivo is a necessary step to unlock their medical potential. This work estimates the diffusion characteristics of SWNTs and their DNA-conjugated bio-hybrids under simulated or postulated physiological conditions using EPI-fluorescence microscopy (EFM). SWNT was shortened and dispersed in aqueous solution with the average length and diameter of 253 nm (+/-30.6 nm) and 1.6 nm (+/-0.34 nm), respectively, and tagged with a fluorophore, 1-pyrenebutanoic succinimidyl ester (PSE), through non-covalent pi stacking. DNA was attached to the PSE-SWNTs through carboxiimide based coupling procedure. Using the EFM, real-time videos were recorded under four different viscosities corresponding to four kinds of human body fluids: lymph (1.4 cP), bile (2.4 cP), blood (3-6 cP), and cytoplasm (10-30 cP), and processed to calculate diffusion coefficients based on random walk and speed. At 37 degreeC, diffusion coefficients of the SWNTs were estimated to be: 1.45 (+/-0.652) x 10(4) nm2/s (lymph), 0.91 (+/-0.205) x 10(4) nm2/s (bile), 0.59 (+/-0.179)x 10(4) nm2/s (blood), and 0.26 (+/-0.114)x 10(4) nm2/s (cytoplasm). Estimated diffusion coefficients of SWNT-DNA bio-hybrids were: 1.45 (+/-0.402) x 10(4) nm2/s (plasma), 0.62 (+/-0.212) x 10(4) nm2/s (bile), 0.41 (+/-0.142) x 10(4) nm2/s (blood), 0.38 (+/-0.257) x 10(4) nm2/s (cytoplasm). These outcomes should serve as key data for developing mathematical models of SWNT-based drug delivery, cell targeting, and its biodistribution. PMID:23858971

Judkins, John; Lee, Hyun Ho; Tung, Steve; Kim, Jin-Woo

2013-06-01

346

A study of diffusion in binary solutions using spin echoes

the concentration dependence of the A and B intrinsic diffusion coefficients and the mutual diffusion coefficient characteristic of the AB solution. Hahn has discovered that the application of a sequence of two RP pulses to a sample containing magnetic nuclei.... The decay of the echo signal can be related to the diffusion of the magnetic nuclei through the sample. Thus, a very use- ful experimental technique for the study of diffusion is asso- ciated with the observation of spin echoes. The spin-echo method has...

Rousseau, Cecil Clyde

2012-06-07

347

Length asymmetry of the bovine digits

The lengths of the digital bones of the fore- and hind-limbs obtained post mortem from 40 cattle of different ages were measured using digital radiographs. The lengths of the individual digital bones and the overall length of the digit were determined using computer software.The lateral metacarpal\\/metatarsal condyle, and lateral P1 and P2 were significantly longer than their medial counterparts, whereas

E. Muggli; C. Sauter-Louis; U. Braun; K. Nuss

2011-01-01

348

Measuring Crack Length in Coarse Grain Ceramics

NASA Technical Reports Server (NTRS)

Due to a coarse grain structure, crack lengths in precracked spinel specimens could not be measured optically, so the crack lengths and fracture toughness were estimated by strain gage measurements. An expression was developed via finite element analysis to correlate the measured strain with crack length in four-point flexure. The fracture toughness estimated by the strain gaged samples and another standardized method were in agreement.

Salem, Jonathan A.; Ghosn, Louis J.

2010-01-01

349

Bond-length relaxation in pseudobinary alloys

NASA Astrophysics Data System (ADS)

The bond-length relaxation in pseudobinary alloys can be predicted by a simple radial force model. In tetrahedral structure alloys the bond-length deviation of the solute in the dilute solution is a quarter of the bond-length difference between the two components. This result agrees with the experimental work done on the Ga1-x InxAs system performed by Mikkelsen and Boyce.

Shih, C. K.; Spicer, W. E.; Harrison, W. A.; Sher, Arden

1985-01-01

350

Microtubule Length Regulation by Molecular Motors

NASA Astrophysics Data System (ADS)

Length regulation of microtubules (MTs) is essential for many cellular processes. Molecular motors like kinesin-8, which move along MTs and also act as depolymerases, are known as key players in MT dynamics. However, the regulatory mechanisms of length control remain elusive. Here, we investigate a stochastic model accounting for the interplay between polymerization kinetics and motor-induced depolymerization. We determine the dependence of MT length and variance on rate constants and motor concentration. Moreover, our analyses reveal how collective phenomena lead to a well-defined MT length.

Melbinger, Anna; Reese, Louis; Frey, Erwin

2012-06-01

351

Mathematical modeling of molecular diffusion through mucus

The rate of molecular transport through the mucus gel can be an important determinant of efficacy for therapeutic agents delivered by oral, intranasal, intravaginal/rectal, and intraocular routes. Transport through mucus can be described by mathematical models based on principles of physical chemistry and known characteristics of the mucus gel, its constituents, and of the drug itself. In this paper, we review mathematical models of molecular diffusion in mucus, as well as the techniques commonly used to measure diffusion of solutes in the mucus gel, mucus gel mimics, and mucosal epithelia. PMID:19135488

Cu, Yen; Saltzman, W. Mark

2008-01-01

352

Experimental Evidence of Non-Diffusive Thermal Transport in Si and GaAs

The length-scales at which thermal transport crosses from the diffusive to ballistic regime are of much interest particularly in the design and improvement of nano-structured materials. In this work, we demonstrate that ...

Johnson, Jeremy A.

353

ERIC Educational Resources Information Center

A review of the general literature on diffusion, innovation, and social change is worthwhile as a basis for developing more effective methods for facilitating the adoption of computer-based technologies. Much of the research on diffusion has focused on (1) characteristics of the innovation which influence the diffusion process, (2) a description…

Stewart, David W.

354

Diffusion model and empirical analysis of China-Brazil Earth Resource Satellite image

Applications Satellite Industry is national strategic high-tech industry, and the key tache for its industrialization is to deepen Image diffusion in more economic and social fields. Based on the market structure and diffusion process of CBERS (China-Brazil Earth Resource Satellite) image, this paper analyses the characteristics of distribution and establishes three diffusion models of network channels, price strategies and competitive

Zhang Lei; Yan Xiang-bin

2009-01-01

355

Transverse spin diffusion in strongly interacting Fermi gases

NASA Astrophysics Data System (ADS)

We compute spin diffusion in a dilute Fermi gas at arbitrary temperature, polarization, and strong interaction in the normal phase using kinetic theory. While the longitudinal spin diffusivity D? depends weakly on polarization and diverges for small temperatures, the transverse spin diffusivity D? has a strong polarization dependence and approaches a finite value for T?0 in the Fermi liquid phase. For a 3D unitary Fermi gas at infinite scattering length, the diffusivities reach a minimum near the quantum limit of diffusion ?/m in the quantum degenerate regime and are strongly suppressed by medium scattering, and we discuss the importance of the spin-rotation effect. In two dimensions, D? attains a minimum at strong coupling -1?ln(kFa2D)?1 and reaches D?˜0.2...0.3?/m at large polarization. These values are consistent with recent measurements of two-dimensional ultracold atomic gases in the strong coupling regime.

Enss, Tilman

2013-09-01

356

Single-particle tracking: the distribution of diffusion coefficients.

In single-particle tracking experiments, the diffusion coefficient D may be measured from the trajectory of an individual particle in the cell membrane. The statistical distribution of single-trajectory diffusion coefficients is examined by Monte Carlo calculations. The width of this distribution may be useful as a measure of the heterogeneity of the membrane and as a test of models of hindered diffusion in the membrane. For some models, the distribution of the short-range diffusion coefficient is much narrower than the observed distribution for proteins diffusing in cell membranes. To aid in the analysis of single-particle tracking measurements, the distribution of D is examined for various definitions of D and for various trajectory lengths. PMID:9083678

Saxton, M J

1997-01-01

357

Coiled to diffuse: Brownian motion of a helical bacterium.

We employ real-time three-dimensional confocal microscopy to follow the Brownian motion of a fixed helically shaped Leptospira interrogans (LI) bacterium. We extract from our measurements the translational and the rotational diffusion coefficients of this bacterium. A simple theoretical model is suggested, perfectly reproducing the experimental diffusion coefficients, with no tunable parameters. An older theoretical model, where edge effects are neglected, dramatically underestimates the observed rates of translation. Interestingly, the coiling of LI increases its rotational diffusion coefficient by a factor of 5, compared to a (hypothetical) rectified bacterium of the same contour length. Moreover, the translational diffusion coefficients would have decreased by a factor of ~1.5, if LI were rectified. This suggests that the spiral shape of the spirochaete bacteria, in addition to being employed for their active twisting motion, may also increase the ability of these bacteria to explore the surrounding fluid by passive Brownian diffusion. PMID:22891749

Butenko, Alexander V; Mogilko, Emma; Amitai, Lee; Pokroy, Boaz; Sloutskin, Eli

2012-09-11

358

The diffusion coefficient of a circular shaped inclusion in a liquid membrane is investigated by taking into account the interaction between membranes and bulk solvents of arbitrary thickness. As illustrative examples, the diffusion coefficients of two types of inclusions - a circular domain composed of fluid with the same viscosity as the host membrane and that of a polymer chain embedded in the membrane are studied.The diffusion coefficients are expressed in terms of the hydrodynamic screening lengths which vary according to the solvent thickness. When the membrane fluid is dragged by the solvent of finite thickness, via stick boundary conditions, multiple hydrodynamic screening lengths together with the weight factors to the diffusion coefficients are obtained from the dispersion relation. The condition for which the diffusion coefficients can be approximated by the expression including only a single hydrodynamic screening length are also shown.

Kazuhiko Seki; Sanoop Ramachandran; Shigeyuki Komura

2011-05-19

359

Relations between anisotropic diffusion and robust statis tics are described in this pa- per. Specifically, we show that anisotropic diffusion can be seen as a robust estimation procedure that estimates a piecewise smooth image from a noi sy input image. The \\

Michael J. Black; Guillermo Sapiro; David H. Marimont; David Heeger

1998-01-01

360

Investigating Diffusion with Technology

ERIC Educational Resources Information Center

The activities described here allow students to explore the concept of diffusion with the use of common equipment such as computers, webcams and analysis software. The procedure includes taking a series of digital pictures of a container of water with a webcam as a dye slowly diffuses. At known time points, measurements of the pixel densities…

Miller, Jon S.; Windelborn, Augden F.

2013-01-01

361

Nonisothermal, Nonstationary Diffusion.

National Technical Information Service (NTIS)

The theory of nonisothermal, nonstationary diffusion in a two-bulb geometry is corrected and extended. Two major corrections to simple theory are necessary: one for the variation with time of the thermal diffusion ratio, and one for the deviations from a ...

E. A. Mason, B. K. Annis, A. E. Humphreys

1968-01-01

362

Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions ''hop'' in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter {Gamma}=175 to Coulomb parameters up to {Gamma}=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

Hughto, J.; Schneider, A. S.; Horowitz, C. J.; Berry, D. K. [Department of Physics and Nuclear Theory Center, Indiana University, Bloomington, Indiana 47405 (United States); University Information Technology Services, Indiana University, Bloomington, Indiana 47408 (United States)

2011-07-15

363

Diffusion in coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants $D$ from molecular dynamics simulations. We find that $D$ for coulomb crystals with relatively soft-core $1/r$ interactions may be larger than $D$ for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ring-like configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from coulomb parameter $\\Gamma=175$ to coulomb parameters up to $\\Gamma=1750$, is fast enough so that the system starts to crystallize during long simulation runs. These results strongly suggest that coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous.

J. Hughto; A. S. Schneider; C. J. Horowitz; D. K. Berry

2011-04-25

364

16 Diffusion Tensor MRI Visualization

16 Diffusion Tensor MRI Visualization 16.1 Introduction Diffusion Tensor Magnetic Resonance Imaging the diffusion of water molecules. The direction of fastest diffusion is aligned with fiber orientation in a pattern that can be numerically modeled by a diffusion tensor. DTI is the only modality for noninva

Utah, University of

365

NONLINEAR DIFFUSION PDES Erkut Erdem

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

366

The length of the new crescent Moon

Danjon noticed that the length (cusp to cusp) of the new crescent moon was less than 180 degrees and suggested that the cause of the shortening is the shadows of the lunar mountains. McNally, however, attributed the crescent shortening to atmospheric seeing, while Schaefer suggests that length shortening is due to sharp falling off of the brightness towards the cusps.

A. H. Sultan

2005-01-01

367

Environmental Stresses Disrupt Telomere Length Homeostasis

Environmental Stresses Disrupt Telomere Length Homeostasis Gal Hagit Romano1,2,3. , Yaniv Harari1, United States of America Abstract Telomeres protect the chromosome ends from degradation and play crucial psychological stress, telomere length, and health outcome in humans. However, studies have not yet explored

Shamir, Ron

368

Juvenile recidivism and length of stay

Official data maintained by the Florida Department of Juvenile Justice of 16,779 juveniles released from commitment programs to the community or aftercare between July 1, 1998 and June 30, 2000 were examined in this study. No consistent relationship between length of confinement and recidivism was found. The effects of length of stay were mediated based on the risk level of

Kristin Parsons Winokur; Alisa Smith; Stephanie R. Bontrager; Julia L. Blankenship

2008-01-01

369

Linking SNPs to CAG repeat length in

Linking SNPs to CAG repeat length in Huntington's disease patients Wanzhao Liu1, Lori A Kennington1) is a promising therapy for human trinucleotide repeat diseases such as Huntington's disease. Linking SNP repeat length and nucleotide identity of heterozygous SNPs using Huntington's disease patient peripheral

Cai, Long

370

371

Code of Federal Regulations, 2010 CFR

...longer if grandfathered. (4) Maxi-cube vehicle. No State shall impose a length limit on a maxi-cube vehicle, as defined in § 658.5 of...drawbar or hitching device. For maxi-cubes with an adjustable length drawbar or...

2010-04-01

372

Code of Federal Regulations, 2011 CFR

...longer if grandfathered. (4) Maxi-cube vehicle. No State shall impose a length limit on a maxi-cube vehicle, as defined in § 658.5 of...drawbar or hitching device. For maxi-cubes with an adjustable length drawbar or...

2011-04-01

373

Code of Federal Regulations, 2013 CFR

...longer if grandfathered. (4) Maxi-cube vehicle. No State shall impose a length limit on a maxi-cube vehicle, as defined in § 658.5 of...drawbar or hitching device. For maxi-cubes with an adjustable length drawbar or...

2013-04-01

374

Code of Federal Regulations, 2012 CFR

2012-04-01

375

Multiparameter Comparison of Cotton Fiber Length Distribution

Length distributions obtained from a broad range of cottons were examined and revealed complex patterns with, in many instances, clear evidence of bimodality. With such complex distributional features, the summary parameters typically used to describe fiber length (means, percentiles, SFC…) are not representative of the distribution, and often show clear insufficiencies in characterizing its alterations during mechanical processing. This paper

Mourad Krifa

376

Conductive Gage for Crack Length Measurement.

National Technical Information Service (NTIS)

The determination of crack lengths in an accurate and straight forward manner is very useful in studying and preventing load created flaws and cracks. A crack length sensor according to the present invention is fabricated in a rectangular or other geometr...

R. Prabhakaran, O. F. Lopez

1991-01-01

377

The Length of the Filamentous Pseudomonas aeruginosa

SUMMARY The length of the Pseudomonas aeruginosa filamentous bacteriophage Pf was found to be 1915 +77 nm, as measured in the electron microscope using the Kleinschmidt spreading technique. Pf is thus the longest filamentous phage so far isolated. Coliphage If, the I-specific filamentous phage, is nearest to it with a length of I3OO nm. Bacteriophage Pf, which is the only

Bacteriophage Pf

1973-01-01

378

Estimating upper extremity tendon slack lengths

Tendon slack lengths are used in a dynamic muscle and limb model to animate the upper extremity based on user supplied activation levels. This paper provides tendon slack length estimates for actuators crossing the elbow and inserting on the radius or ulna. These values were not previously available as a complete see for the upper extremity. Muscle parameters used in

Brian R. von Konsky

1995-01-01

379

NSDL National Science Digital Library

These 3 activities, part of the Mathematics Developmental Continuum of the State of Victoria, Australia, are intended to introduce young learners to the measurable attribute of length as distinguished from others. Students compare lengths of two or more objects directly or indirectly. Teaching suggestions and progress indicators are included.

2009-09-25

380

Fully Modulated Turbulent Diffusion Flames in Microgravity*

NASA Astrophysics Data System (ADS)

Fully modulated, turbulent diffusion flames are studied in microgravity in 2.2 s drop-tower tests with a co-flow combustor. The fuel consists of pure ethylene or a 50/50 mixture with nitrogen; the oxidizer is either normal air or up to 40% oxygen in nitrogen. A fast solenoid valve is used to fully modulate (completely shut off) the fuel flow. The injection times range from 5 to 400 ms with a duty-cycle of 0.1 - 0.5. The fuel nozzle is 2 mm in diameter with a jet Reynolds number of 5000. The shortest injection times yield compact puffs with a mean flame length as little as 20% of that of the steady-state flame. The reduction in flame length appears to be somewhat greater in microgravity than in normal gravity. As the injection time increases, elongated flames result with a mean flame length comparable to that of a steady flame. The injection time for which the steady-state flame length is approached is shorter for lower air/fuel ratios. For a given duty-cycle, the separation between puffs is greater in microgravity than in normal gravity. For compact puffs, increasing the duty-cycle appears to increase the flame length more in microgravity than in normal gravity. The microgravity flame puffs do not exhibit the vortex-ring-like structure seen in normal gravity.

Sangras, Ravikiran; Hermanson, James C.; Johari, Hamid; Stocker, Dennis P.; Hegde, Uday G.

2001-11-01

381

Helium diffusion in carbonates

NASA Astrophysics Data System (ADS)

The abundance and large grain size of carbonate minerals make them a potentially attractive target for 4He thermochronology and 3He cosmogenic dating, although the diffusive properties of helium in carbonates remain poorly understood. This work characterizes helium diffusion in calcite and dolomite to better understand the crystal-chemical factors controlling He transport and retentivity. Slabs of cleaved natural calcite and dolomite, and polished sections of calcite cut parallel or normal to c, were implanted with 3He at 3 MeV with a dose of 5x1015/cm2. Implanted carbonates were heated in 1-atm furnaces, and 3He distributions following diffusion anneals were profiled with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For 3He transport normal to cleavage surfaces in calcite, we obtain the following Arrhenius relation over the temperature range 78-300°C: Dcalcite = 9.0x10-9exp(-55 × 6 kJ mol-1/RT) m2sec-1. Diffusion in calcite exhibits marked anisotropy, with diffusion parallel to c about two orders of magnitude slower than diffusion normal to cleavage faces. He diffusivities for transport normal to the c-axis are similar in value to those normal to cleavage surfaces. Our findings are broadly consistent with helium diffusivities from step-heating measurements of calcite by Copeland et al. (2007); these bulk degassing data may reflect varying effects of diffusional anisotropy. Helium diffusion normal to cleavage surfaces in dolomite is significantly slower than diffusion in calcite, and has a much higher activation energy for diffusion. For dolomite, we obtain the following Arrhenius relation for He diffusion over the temperature range 150-400°C: Ddolomite = 9.0x10-8exp(-92 × 9 kJ mol-1/RT) m2sec-1. The role of crystallographic structure in influencing these differences among diffusivities was evaluated using the maximum aperture approach of Cherniak and Watson (2011), in which crystallographic structures are sectioned along possible diffusion directions and the maximum interstitial apertures in each 'slice' in the structure are identified. Preliminary results show that observed differences in diffusivities are consistent with the size of the smallest maximum aperture along each diffusion direction. In calcite, the smallest maximum apertures are ~0.92 and ~0.66 angstroms for cleavage-normal and c-axis parallel directions respectively. In dolomite, the smallest maximum aperture is ~0.78 angstroms for the cleavage normal direction. Work is in progress on characterizing helium diffusion for other orientations in dolomite, and in other carbonates, including aragonite and magnesite, and in implementing these diffusion findings in the interpretation and modeling of bulk volume diffusion in heterogeneous calcite crystals common in many geologic applications. Copeland et al. (2007) GCA 71, 4488-4511 Cherniak and Watson, (2011) Chem. Geo. 288, 149-161

Amidon, W. H.; Cherniak, D. J.; Watson, E. B.; Hobbs, D.

2013-12-01

382

NASA Astrophysics Data System (ADS)

Diffusion of helium has been characterized in natural Fe-bearing olivine (~Fo90) and synthetic forsterite. Polished, oriented slabs of olivine were implanted with 3He, at 100 keV at a dose of 5x1015/cm2 or at 3.0 MeV at a dose of 1x1016/cm2. A set of experiments on the implanted olivine were run in 1-atm furnaces. In addition to the one-atm experiments, experiments on implanted samples were also run at higher pressures (2.6 and 2.7 GPa) to assess the potential effects of pressure on He diffusion and the applicability of the measured diffusivities in describing He transport in the mantle. The high-pressure experiments were conducted in a piston-cylinder apparatus using an "ultra-soft" pressure cell, with the diffusion sample directly surrounded by AgCl. 3He distributions following experiments were measured with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. This direct profiling method permits us to evaluate anisotropy of diffusion, which cannot be easily assessed using bulk-release methods. For diffusion in forsterite parallel to c we obtain the following Arrhenius relation over the temperatures 250-950°C: D = 3.91x10-6exp(-159 ± 4 kJ mol-1/RT) m2/sec. The data define a single Arrhenius line spanning more than 7 orders of magnitude in D and 700°C in temperature. Diffusion parallel to a appears slightly slower, yielding an activation energy for diffusion of 135 kJ/mol and a pre-exponential factor of 3.73x10-8 m2/sec. Diffusion parallel to b is slower than diffusion parallel to a (by about two-thirds of a log unit); for this orientation an activation energy of 138 kJ/mol and a pre-exponential factor of 1.34x10-8 m2/sec are obtained. This anisotropy is broadly consistent with observations for diffusion of Ni and Fe-Mg in olivine. Diffusion in Fe-bearing olivine (transport parallel to b) agrees within uncertainty with findings for He diffusion in forsterite. The higher-pressure experiments yield diffusivities in agreement with those from the 1-atm experiments, indicating that the results reported here can be reasonably applied to modeling He transport in the upper mantle. The insensitivity of He diffusion to pressure over the investigated range of conditions suggests that compression of the mineral lattice is not sufficient to significantly influence migration of the relatively small helium atoms, which likely diffuse via crystal interstices. The He diffusivities in this work are generally consistent with results from the study of Futagami et al. (1993), who measured He diffusion in natural olivine by outgassing 4He implanted samples, and with the diffusivities measured by bulk-release of 4He and 3He by Shuster et al. (2003), but are about 2 orders of magnitude slower than the recent findings of Tolstikhin et al. (2010) and Blard et al. (2008) . An up-temperature extrapolation of our data also show reasonable agreement with the higher-temperature measurements of Hart (1984). Blard et al. (2008) GCA 72, 3788-3803; Futagami et al. (1993) GCA 57, 3177-3194; Hart (1984) EPSL 70, 297-302; Shuster et al.( 2003) EPSL 217, 19-32; Tolstikhin et al. (2010) GCA 74, 1436-1447

Cherniak, D. J.; Watson, E. B.

2011-12-01

383

Buoyancy Effects in Fully-Modulated, Turbulent Diffusion Flames

NASA Technical Reports Server (NTRS)

Pulsed combustion appears to have the potential to provide for rapid fuel/air mixing, compact and economical combustors, and reduced exhaust emissions. The objective of this experiment (PuFF, for Pulsed-Fully Flames) is to increase the fundamental understanding of the fuel/air mixing and combustion behavior of pulsed, turbulent diffusion flames by conducting experiments in microgravity. In this research the fuel jet is fully-modulated (i.e., completely shut off between pulses) by an externally controlled valve system. This gives rise to drastic modification of the combustion and flow characteristics of flames, leading to enhanced fuel/air mixing compared to acoustically excited or partially-modulated jets. Normal-gravity experiments suggest that the fully-modulated technique also has the potential for producing turbulent jet flames significantly more compact than steady flames with no increase in exhaust emissions. The technique also simplifies the combustion process by avoiding the acoustic forcing generally present in pulsed combustors. Fundamental issues addressed in this experiment include the impact of buoyancy on the structure and flame length, temperatures, radiation, and emissions of fully-modulated flames.

Hermanson, J. C.; Johari, H.; Ghaem-Maghami, E.; Stocker, D. P.; Hegde, U. G.; Page, K. L.

2003-01-01

384

Zero-flux planes, flux reversals and diffusion paths in ternary and quaternary diffusion

During isothermal multicomponent diffusion, interdiffusion fluxes of individual components can go to zero at zero-flux planes (ZFP) and exhibit flux reversals from one side to the other of such planes. Interdiffusion fluxes as well as the locations and compositions of ZFPs for components are determined directly from the concentration profiles of diffusion couples without the need for prior knowledge of interdiffusion coefficients. The development and identification of ZFPs is reviewed with the aid of single phase and two-phase diffusion couples investigated in the Cu-Ni-Zn system at 775/sup 0/C. ZFP locations in the diffusion zone nearly correspond to sections where the activity of a component is the same as its activity in either of the terminal alloys of a couple. Path slopes at ZFPs are uniquely dictated by the atomic mobility and thermodynamic data for the components. Discontinuous flux reversals for the components can also occur at interfaces in multiphase couples. Identification of ZFPs is also presented for diffusion in the Cu-Ni-Zn-Mn quaternary system. Analytical representation of diffusion paths for both ternary and quaternary diffusion couples is presented with the aid of characteristic path parameters.

Dayananda, M.A.

1986-05-23

385

Oxygen diffusion in titanite: Lattice diffusion and fast-path diffusion in single crystals

Oxygen diffusion in titanite: Lattice diffusion and fast-path diffusion in single crystals X June 2006 Editor: P. Deines Abstract Oxygen diffusion in natural and synthetic single-crystal titanite cold-seal pressure vessels for durations of 1 day to several weeks. Diffusive uptake profiles of 18 O

Watson, E. Bruce

386

Global Optimization by Adapted Diffusion

In this paper, we study a diffusion stochastic dynamics with a general diffusion coefficient. The main result is that adapting the diffusion coefficient to the Hamiltonian allows to escape local wide minima and to speed ...

Poliannikov, Oleg V.

387

Macromolecule diffusion into muscle tissue

NSDL National Science Digital Library

Diffusion in spherical coordinates from a small device into fibrous muscle tissue, with discussion of something like a boundary layer, mass transfer coefficient, anisotropic diffusion, and biological complications to diffusion.

Powell, Adam C., IV

2004-07-08

388

Supersonic minimum length nozzle design for dense gases

NASA Technical Reports Server (NTRS)

Recently, dense gases have been investigated for many engineering applications such as for turbomachinery and wind tunnels. Supersonic nozzle design for these gases is complicated by their nonclassical behavior in the transonic flow regime. In this paper a method of characteristics (MOC) is developed for two-dimensional (planar) and, primarily, axisymmetric flow of a van der Waals gas. Using a straight aortic line assumption, a centered expansion is used to generate an inviscid wall contour of minimum length. The van der Waals results are compared to previous perfect gas results to show the real gas effects on the flow properties and inviscid wall contours.

Aldo, Andrew C.; Argrow, Brian M.

1993-01-01

389

NASA Technical Reports Server (NTRS)

Diffusion flames are commonly used for industrial burners in furnaces and flares. Oxygen/fuel burners are usually diffusion burners, primarily for safety reasons, to prevent flashback and explosion in a potentially dangerous system. Furthermore, in most fires, condensed materials pyrolyze, vaporize, and burn in air as diffusion flames. As a result of the interaction of a diffusion flame with burner or condensed-fuel surfaces, a quenched space is formed, thus leaving a diffusion flame edge, which plays an important role in flame holding in combustion systems and fire spread through condensed fuels. Despite a long history of jet diffusion flame studies, lifting/blowoff mechanisms have not yet been fully understood, compared to those of premixed flames. In this study, the structure and stability of diffusion flames of gaseous hydrocarbon fuels in coflowing air at normal earth gravity have been investigated experimentally and computationally. Measurements of the critical mean jet velocity (U(sub jc)) of methane, ethane, or propane at lifting or blowoff were made as a function of the coflowing air velocity (U(sub a)) using a tube burner (i.d.: 2.87 mm). By using a computational fluid dynamics code with 33 species and 112 elementary reaction steps, the internal chemical-kinetic structures of the stabilizing region of methane and propane flames were investigated. A peak reactivity spot, i.e., reaction kernel, is formed in the flame stabilizing region due to back-diffusion of heat and radical species against an oxygen-rich incoming flow, thus holding the trailing diffusion flame. The simulated flame base moved downstream under flow conditions close to the measured stability limit.

Takahashi, Fumiaki; Katta, V. R.

2006-01-01

390

NASA Technical Reports Server (NTRS)

Diffusion flames are commonly used for industrial burners in furnaces and flares. Oxygen/fuel burners are usually diffusion burners, primarily for safety reasons, to prevent flashback and explosion in a potentially dangerous system. Furthermore, in most fires, condensed materials pyrolyze, vaporize, and burn in air as diffusion flames. As a result of the interaction of a diffusion flame with burner or condensed-fuel surfaces, a quenched space is formed, thus leaving a diffusion flame edge, which plays an important role in flame holding in combustion systems and fire spread through condensed fuels. Despite a long history of jet diffusion flame studies, lifting/blowoff mechanisms have not yet been fully understood, compared to those of premixed flames. In this study, the structure and stability of diffusion flames of gaseous hydrocarbon fuels in coflowing air at normal earth gravity have been investigated experimentally and computationally. Measurements of the critical mean jet velocity (U(sub jc)) of methane, ethane, or propane at lifting or blowoff were made as a function of the coflowing air velocity (U(sub a)) using a tube burner (i.d.: 2.87 mm) (Fig. 1, left). By using a computational fluid dynamics code with 33 species and 112 elementary reaction steps, the internal chemical-kinetic structures of the stabilizing region of methane and propane flames were investigated (Fig. 1, right). A peak reactivity spot, i.e., reaction kernel, is formed in the flame stabilizing region due to back-diffusion of heat and radical species against an oxygen-rich incoming flow, thus holding the trailing diffusion flame. The simulated flame base moved downstream under flow conditions close to the measured stability limit.

Takahashi, Fumiaki; Katta, Viswanath R.

2007-01-01

391

Diffusion of sucrose and dextran through agar gel membranes.

Mass transfer limitations severely impede the performance of bioreactions involving large molecules by gel-entrapped microorganisms. This paper describes a quantitative investigation of such diffusional limitations in agar gel membranes. Sucrose and commercial dextran fractions with (weight-average) molecular weights ranging from 10,000 to 2,000,000 Da were used as standard diffusants. For all tested solutes but sucrose, the values of the agar/water partition coefficients highlighted steric hindrance at the entrance of the membrane pores. The effective diffusivity of sucrose in agar was similar to that in water. All dextran fractions, however, displayed restricted diffusion in the agar membranes. Their effective diffusivities were a decreasing function of the agar content of the gel membrane (0.5, 1.0, or 1.5% w/v). The effective diffusivity in a given membrane decreased as the molecular weight of the diffusing molecule increased. T500 (Mw = 470,000 Da) and T2000 (Mw = 1,950,000 Da) fractions were unable to diffuse through 1.0 or 1.5% agar membranes. The diffusion data did not agree with the classical (Renkin) model for a hard sphere diffusing through a cylindrical pore. These results are discussed in terms of gel and diffusant characteristics. PMID:7505595

Lebrun, L; Junter, G A

1993-12-01

392

Diffusion mechanism of chromium in GaAs

NASA Astrophysics Data System (ADS)

The diffusion of the substitutional Cr atoms (Crs) in GaAs results from the rapid migration of the interstitial atoms (Cri) and their subsequent changeover to occupy Ga sites (or vise versa), a typical substitutional-interstitial-diffusion (SID) process. There are two possible ways for the Cri-Crs changeover to occur: the kick-out mechanism in which Ga self-interstitials are involved, and the dissociative mechanism in which Ga vacancies are involved. The Crs in-diffusion profiles are of characteristic shapes indicating the dominance of the kick-out mechanism, while the Crs out-diffusion profiles are error-function shaped, indicating the dominance of the dissociative mechanism. In this study, an integrated SID mechanism, which takes into account both the kick-out and dissociative mechanisms, is used to analyze Cr diffusion results. Going beyond just qualitative consistency, the Cr in- and out-diffusion features in GaAs are explained on a quantitative basis. It is confirmed that the kick-out mechanism dominates Cr in-diffusion while the dissociative mechanism dominates Cr out-diffusion. Parameters used to fit existing experimental results provided quantitative information on the Ga self-interstitial contribution to the Ga self-diffusion coefficient. The values obtained are consistent with those obtained from a study of Zn diffusion in GaAs, and with available experimentally determined Al-Ga interdiffusion coefficients.

Yu, S.; Tan, T. Y.; Gösele, U.

1991-11-01

393

Knowledge of the diffusion coefficient is necessary for modeling gas transport in soils and other porous media. This study was con- ducted to determine the relationship between the diffusion coeffi- cient and pore structure parameters, such as the fractal dimension of pores (Dmp), the shortest path length through the medium (lmin), and the fractal dimension of the shortest path (Dmin).

Gang Liu; Baoguo Li; Kelin Hu; M. Th. van Genuchten

2006-01-01

394

DCT-Based Characterization of Milk Products Using Diffuse Reflectance Images

. These images are obtained by il lumination of a hyperspectral coherent laser (460-1000 nm) into the surface of diffuse reflectance images of laser illumination on milk products in different wave lengths. BasedDCT-Based Characterization of Milk Products Using Diffuse Reflectance Images Sara Sharifzadeh

395

Diffusion of neutral and ionic species in charged membranes: Boric acid, arsenite, and water

Dynamic ion speciation using DMT (Donnan membrane technique) requires insight into the physicochemical characteristics of diffusion in charged membranes (tortuosity, local diffusion coefficients) as well as ion accumulation. The latter can be precluded by studying the diffusion of neutral species, such as boric acid, B(OH)30(aq), arsenite, As(OH)30(aq), or water. In this study, the diffusion rate of B(OH)30 has been evaluated

E. Goli; T. Hiemstra; Riemsdijk van W. H; R. Rahnemaie; M. J. Malakouti

2010-01-01

396

A new determination of the upper limit to the cosmic diffuse background radiation, at ~110 nm, of 300 photons s-1 cm-2 sr-1 nm-1, is placed in the context of diffuse background measurements across the entire electromagnetic spectrum, including new optical, infrared, visible, and gamma-ray background measurements. The possibility that observed excess diffuse visible radiation is due to redshifted cosmological Lyman alpha recomination radiation is explored. Also, a new standard of units for the display of spectra is advocated.

Richard C. Henry

1999-03-18

397

ESTIMATING THE LENGTHS OF MEMORY WORDS 1 Estimating the Lengths of Memory Words

ESTIMATING THE LENGTHS OF MEMORY WORDS 1 Estimating the Lengths of Memory Words GusztÂ´av Morvai w AK is called a memory word if the conditional probability of X0 given the past is constant of the longest minimal memory word and show that no such universal estimator exists for the length

Morvai, GusztÃ¡v

398

Fabrication of periodic Ti:LiNbO3 waveguides by single and double diffusion

Periodic index waveguides have been successfully fabricated by diffusing a 200-A?-thick titanium film containing a grating pattern into Y-cut LiNbO3 substrates. Bragg deflectors with efficiencies of up to 64% have been demonstrated in devices having a grating length of 750 ?m and a diffusion time of 3 h. Similar devices have also been fabricated using a double-diffusion process to obtain

Alfredo Yi-Yan; I. Andonovic; E. Y. B. Pun; B. Bjortorp

1983-01-01

399

Self-diffusion of Rod-like Viruses Through Smectic Layer

We report the direct visualization at the scale of single particles of mass transport between smectic layers, also called permeation, in a suspension of rod-like viruses. Self-diffusion takes place preferentially in the direction normal to the smectic layers, and occurs by quasi-quantized steps of one rod length. The diffusion rate corresponds with the rate calculated from the diffusion in the nematic state with a lamellar periodic ordering potential that is obtained experimentally.

M. Paul Lettinga; Eric Grelet

2007-10-31

400

Phase-Resolved DPIV Investigation of Vortex-Flame Interactions in Hydrogen Jet Diffusion Flames

Turbulent diffusion flames consist of countless vortex-flame interactions with length- and time-scales that vary over several orders of magnitude. These vortex-flame interactions are the fundamental building blocks of turbulent diffusion flames. In this experiment, a hydrogen jet diffusion flame is driven with a loud speaker located below a cylindrical fuel tube. The modulation of the fuel velocity in the tube

Sivaram Gogineni; Robert Hancock; Frederick Schauer; Robert Lucht

1997-01-01

401

Algorithms of Ancestral Gene Length Reconstruction

Ancestral sequence reconstruction is a well-known problem in molecular evolution. The problem presented in this study is inspired by sequence reconstruction, but instead of leaf-associated sequences we consider only their lengths. We call this problem ancestral gene length reconstruction. It is a problem of finding an optimal labeling which minimizes the total length's sum of the edges, where both a tree and nonnegative integers associated with corresponding leaves of the tree are the input. In this paper we give a linear algorithm to solve the problem on binary trees for the Manhattan cost function s(v, w) = |?(v) ? ?(w)|. PMID:24371824

Bolshoy, Alexander; Kirzhner, Valery M.

2013-01-01

402

Effect of Minimal lengths on Electron Magnetism

We study the magnetic properties of electron in a constant magnetic field and confined by a isotropic two dimensional harmonic oscillator on a space where the coordinates and momenta operators obey generalized commutation relations leading to the appearance of a minimal length. Using the momentum space representation we determine exactly the energy eigenvalues and eigenfunctions. We prove that the usual degeneracy of Landau levels is removed by the presence of the minimal length in the limits of weak and strong magnetic field.The thermodynamical properties of the system, at high temperature, are also investigated showing a new magnetic behavior in terms of the minimal length.

Khireddine Nouicer

2007-07-13

403

Antenatal measurement of scapula length using ultrasound.

In 76 fetuses from 14 weeks of gestation through to term, measurements of the scapula were made using ultrasound. Statistical analysis of the results revealed a highly significant correlation between scapula measurements and gestational age, biparietal diameter, fetal femur length and fetal abdominal circumference (r = 0.93, 0.91, 0.95, and 0.91, respectively). In particular, values related to length of the scapula were highly correlated with femur length. These findings show that this measurement is useful as an adjunct to assessing development as well as growth of the femur and dating parameters of the fetus in utero. PMID:2695411

Murao, F; Shibukawa, T; Takamiya, O; Yamamoto, K; Hasegawa, K

1989-01-01

404

NASA Astrophysics Data System (ADS)

Segmental dynamic heterogeneity of short-chain grafted poly(dimethylsiloxane) (PDMS) on pyrogenic silica was investigated using 1H NMR spin-diffusion. A double-quantum dipolar filter was employed for selection of the interface (rigid) region. One-dimensional spin-diffusion equations were solved numerically for a space distribution of spin diffusivity D( x) of the mobile PDMS chains. The degree of heterogeneity can be quantified by the parameters of Gaussian and exponential diffusivity distribution functions which yield similar diffusivities. The rigid and mobile domain sizes and spin diffusivities were correlated with the PDMS chain length, the temperature, and 1H residual dipolar couplings.

Bertmer, Marko; Demco, Dan E.; Wang, Mingfei; Melian, Claudiu; Marcean-Chelcea, Ramona I.; Fechete, Radu; Baias, Maria; Blümich, Bernhard

2006-11-01

405

NASA Astrophysics Data System (ADS)

A series of 223Ra (t1/2 = 11.4 d) and 224Ra (t1/2 = 3.66 d) measurements made in the Mid-Atlantic Bight yield eddy diffusivity (K) estimates of 1.2 ± 0.3 × 102 m2 s-1 and 1.4 ± 0.2 × 102 m2 s-1, respectively. These results fall in line with previous studies from multiple locations throughout the ocean, in which 224Ra-based eddy diffusivities invariably exceed those determined using 223Ra. Such a pattern conflicts with the Fickian model for eddy diffusivity, in which K is constant. Moreover, this trend runs counter to the length scale-dependent view of eddy diffusion, which suggests that K values estimated using 223Ra should exceed those of 224Ra, because the length scale of the former is greater than that of the latter. A finite mixing-length model based on the concept of differential diffusion is used to provide an explanation for this discrepancy.

Stachelhaus, Scott L.; Moran, S. Bradley

2012-03-01

406

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

Pereyra, Victor; Milchev, Andrey; Fleurov, Victor

1994-12-01

407

Chemiluminescent Detection of Diffusion

NSDL National Science Digital Library

This activity engages students in observing the results of diffusion through a selectively permeable membrane, monitoring the concentration of solute in water, learning the simple test for starch, and quantitating the chemiluminescence by exposure to photographic paper.

Evelyn Bradshaw (Cleveland Heights High School)

1995-07-01

408

Diffusion between evolving interfaces

Diffusion in an evolving environment is studied by continuos-time Monte Carlo simulations. Diffusion is modelled by continuos-time random walkers on a lattice, in a dynamic environment provided by bubbles between two one-dimensional interfaces driven symmetrically towards each other. For one-dimensional random walkers constrained by the interfaces, the bubble size distribution domi- nates diffusion. For two-dimensional random walkers, it is also controlled by the topography and dynamics of the interfaces. The results of the one-dimensional case are recovered in the limit where the interfaces are strongly driven. Even with simple hard-core repulsion between the interfaces and the particles, diffusion is found to depend strongly on the details of the dynamical rules of particles close to the interfaces. Article reference: Journal of Physics: Condensed Matter 22, 465402 (2010).

Janne Juntunen; Juha Merikoski

2010-11-19

409

NSDL National Science Digital Library

Students create a STELLA model of two marine terrace platforms separated in elevation by a cliff, using the hillslope flux equation to simulate the change in the cliff face over time as diffusive processes tear it down.

Menking, Kirsten

410

A phenomenological analysis of the distribution of Wilson loops in SU(2) Yang-Mills theory is presented in which Wilson loop distributions are described as the result of a diffusion process on the group manifold. It is shown that, in the absence of forces, diffusion implies Casimir scaling and, conversely, exact Casimir scaling implies free diffusion. Screening processes occur if diffusion takes place in a potential. The crucial distinction between screening of fundamental and adjoint loops is formulated as a symmetry property related to the center symmetry of the underlying gauge theory. The results are expressed in terms of an effective Wilson loop action and compared with various limits of SU(2) Yang-Mills theory.

A. M. Brzoska; F. Lenz; J. W. Negele; M. Thies

2004-12-01

411

Adaptive multigroup radiation diffusion

This thesis describes the development and implementation of an algorithm for dramatically increasing the accuracy and reliability of multigroup radiation diffusion simulations at low group counts. This is achieved by ...

Williams, Richard B., Sc. D. Massachusetts Institute of Technology

2005-01-01

412

National Technical Information Service (NTIS)

The need to reduce the cost and weight of aerospace metallic structures has led to increased interest in solid state and liquid phase diffusion bonding processes, especially in combination with superplastic forming. The bonding mechanisms and bonding tech...

P. G. Partridge

1989-01-01

413

Canonical Transformations for Diffusions.

National Technical Information Service (NTIS)

Morphisms of backward heat equations, preserve in the appropriate sense, the forward Lagrangian, as well as the forward (Newton's) equations of motion for a general class of diffusions. Time reflection yields results for forward heat equations, in particu...

B. Djehiche, T. Kolsrud

1995-01-01

414

Factorized Diffusion Map Approximation

Diffusion maps are among the most powerful Machine Learning tools to analyze and work with complex high-dimensional datasets. Unfortunately, the estimation of these maps from a finite sample is known to suffer from the curse of dimensionality. Motivated by other machine learning models for which the existence of structure in the underlying distribution of data can reduce the complexity of estimation, we study and show how the factorization of the underlying distribution into independent subspaces can help us to estimate diffusion maps more accurately. Building upon this result, we propose and develop an algorithm that can automatically factorize a high dimensional data space in order to minimize the error of estimation of its diffusion map, even in the case when the underlying distribution is not decomposable. Experiments on both the synthetic and real-world datasets demonstrate improved estimation performance of our method over the standard diffusion-map framework. PMID:25309676

Amizadeh, Saeed; Valizadegan, Hamed; Hauskrecht, Milos

2013-01-01

415

Mechanisms of large length fluctuations during actin filament growth

NASA Astrophysics Data System (ADS)

Prior TIRF microscopy experiments monitoring the growth of single actin filaments have indicated that the magnitude of growth rate fluctuations, characterized by a ``length diffusion coefficient'' D, is much larger than the value expected from a simple monomer-by-monomer polymerization process. Several theoretical studies have explored mini-catastrophes or oligomeric annealing and fragmentation as sources of enhanced fluctuations. We used numerical simulations and analytical theory to examine additional mechanisms that contribute to length fluctuations. Fluctuations caused by cooperative kinetics, in which the rate of monomer addition and/or subtraction depends on the type of nucleotide bound to neighboring actin subunits exhibit qualitatively distinct dependence on actin monomer concentration and on concentration of phosphate than those caused by ``short pauses.'' By comparing to analysis of experimental data, we show that the experimentally measured D values can be distinguished from random noise. Further we propose experiments that will distinguish these sources of fluctuations. We relate our findings to other one-dimensional directed processes, such as in molecular motor walks.

Smith, Matthew B.; Vavylonis, Dimitrios

2009-03-01

416

Diffusion in active magnetic colloids

NASA Astrophysics Data System (ADS)

Properties of active colloids of circle swimmers are reviewed. As a particular example of active magnetic colloids the magnetotactic bacteria under the action of a rotating magnetic field is considered. The relation for a diffusion coefficient due to the random switching of the direction of rotation of their rotary motors is derived on the basis of the master equation. The obtained relation is confirmed by the direct numerical simulation of random trajectory of a magnetotactic bacterium under the action of the Poisson type internal noise due to the random switching of rotary motors. The results obtained are in qualitative and quantitative agreement with the available experimental results and allow one to determine the characteristic time between the switching events of a rotary motor of the bacterium.

Taukulis, R.; Cebers, A.

2014-11-01

417

Load Diffusion in Composite and Smart Structures

NASA Technical Reports Server (NTRS)

The research carried out here builds on our previous NASA supported research on the general topic of edge effects and load diffusion in composite structures. Further fundamental solid mechanics studies were carried out to provide a basis for assessing the complicated modeling necessary for the multi-functional large scale structures used by NASA. An understanding of the fundamental mechanisms of load diffusion in composite subcomponents is essential in developing primary composite structures. Some specific problems recently considered were those of end effects in smart materials and structures, study of the stress response of pressurized linear piezoelectric cylinders for both static and steady rotating configurations, an analysis of the effect of pre-stressing and pre-polarization on the decay of end effects in piezoelectric solids and investigation of constitutive models for hardening rubber-like materials. Our goal in the study of load diffusion is the development of readily applicable results for the decay lengths in terms of non-dimensional material and geometric parameters. Analytical models of load diffusion behavior are extremely valuable in building an intuitive base for developing refined modeling strategies and assessing results from finite element analyses.

Horgan, Cornelius O.; Ambur, D. (Technical Monitor); Nemeth, M. P. (Technical Monitor)

2003-01-01

418

Effects of N 2 gas on preheated laminar LPG jet diffusion flame

This paper presents an experimental investigation of the inert gas effect on flame length, NOx and soot free length fraction (SFLF) in a laminar LPG diffusion flame. Besides this, flame radiant fraction and temperature are also measured to explain observed NOx emission and SFLF. The inert is added to both air and fuel stream at each base line condition by

D. P. Mishra; P. Kumar

2010-01-01

419

Diffusive behavior of a greedy traveling salesman.

Using Monte Carlo simulations we examine the diffusive properties of the greedy algorithm in the d-dimensional traveling salesman problem. Our results show that for d=3 and 4 the average squared distance from the origin (r(2)) is proportional to the number of steps t. In the d=2 case such a scaling is modified with some logarithmic corrections, which might suggest that d=2 is the critical dimension of the problem. The distribution of lengths also shows marked differences between d=2 and d>2 versions. A simple strategy adopted by the salesman might resemble strategies chosen by some foraging and hunting animals, for which anomalous diffusive behavior has recently been reported and interpreted in terms of Lévy flights. Our results suggest that broad and Lévy-like distributions in such systems might appear due to dimension-dependent properties of a search space. PMID:21797310

Lipowski, Adam; Lipowska, Dorota

2011-06-01

420

Diffusion induced stresses in buckling battery electrodes

NASA Astrophysics Data System (ADS)

Highly networked nanostructured battery electrode materials offer the possibility of achieving both rapid battery charge-discharge rates and high storage capacity. Recently, lithium ion battery (LIB) electrodes based on a 2-D honeycomb architecture were shown to undergo remarkable and reversible morphological changes during the lithiation process. Charge-discharge rates in 3-D composite electrode have also been shown to benefit from sandwiching the electrolytically active material between highly conductive ion and electron transport pathways to reduce electrical resistance and solid-state diffusion lengths. In the present work we simulate and analyze the observed morphological changes in honeycomb electrodes, with and without the presence of conductive pathways, during the lithiation-delithiation process. Diffusion induced stresses are analyzed for such structures undergoing elastic-plastic deformation during cycling. The results show that such a periodic, nanostructured electrode geometry allows for the presence of buckling-like deformation modes, which effectively reduce the resulting mechanical stresses that lead to electrode failure.

Bhandakkar, Tanmay K.; Johnson, Harley T.

2012-06-01

421

Diffusion in low-dimensional lipid membranes.

The diffusion behavior of biological components in cellular membranes is vital to the function of cells. By collapsing the complexity of planar 2D membranes down to one dimension, fundamental investigations of bimolecular behavior become possible in one dimension. Here we develop lipid nanolithography methods to produce membranes, under fluid, with widths as low as 6 nm but extending to microns in length. We find reduced lipid mobility, as the width is reduced below 50 nm, suggesting different lipid packing in the vicinity of boundaries. The insertion of a membrane protein, M2, into these systems, allowed characterization of protein diffusion using high-speed AFM to demonstrate the first membrane protein 1D random walk. These quasi-1D lipid bilayers are ideal for testing and understanding fundamental concepts about the roles of dimensionality and size on physical properties of membranes from energy transfer to lipid packing. PMID:25166509

Heath, George R; Roth, Johannes; Connell, Simon D; Evans, Stephen D

2014-10-01

422

Instabilities and patterns in coupled reaction-diffusion layers.

We study instabilities and pattern formation in reaction-diffusion layers that are diffusively coupled. For two-layer systems of identical two-component reactions, we analyze the stability of homogeneous steady states by exploiting the block symmetric structure of the linear problem. There are eight possible primary bifurcation scenarios, including a Turing-Turing bifurcation that involves two disparate length scales whose ratio may be tuned via the interlayer coupling. For systems of n-component layers and nonidentical layers, the linear problem's block form allows approximate decomposition into lower-dimensional linear problems if the coupling is sufficiently weak. As an example, we apply these results to a two-layer Brusselator system. The competing length scales engineered within the linear problem are readily apparent in numerical simulations of the full system. Selecting a sqrt[2]:1 length-scale ratio produces an unusual steady square pattern. PMID:22463307

Catllá, Anne J; McNamara, Amelia; Topaz, Chad M

2012-02-01

423

The length of the world's glaciers - a new approach for the global calculation of center lines

NASA Astrophysics Data System (ADS)

Glacier length is an important measure of glacier geometry. Nevertheless, global glacier inventories are mostly lacking length data. Only recently semi-automated approaches to measure glacier length have been developed and applied regionally. Here we present a first global assessment of glacier length using an automated method that relies on glacier surface slope, distance to the glacier margins and a set of trade-off functions. The method is developed for East Greenland, evaluated for East Greenland as well as for Alaska and eventually applied to all ~ 200 000 glaciers around the globe. The evaluation highlights accurately calculated glacier length where digital elevation model (DEM) quality is high (East Greenland) and limited accuracy on low-quality DEMs (parts of Alaska). Measured length of very small glaciers is subject to a certain level of ambiguity. The global calculation shows that only about 1.5% of all glaciers are longer than 10 km, with Bering Glacier (Alaska/Canada) being the longest glacier in the world at a length of 196 km. Based on the output of our algorithm we derive global and regional area-length scaling laws. Differences among regional scaling parameters appear to be related to characteristics of topography and glacier mass balance. The present study adds glacier length as a key parameter to global glacier inventories. Global and regional scaling laws might prove beneficial in conceptual glacier models.

Machguth, H.; Huss, M.

2014-09-01

424

Code of Federal Regulations, 2010 CFR

...AGRICULTURE COMMODITY STANDARDS AND STANDARD CONTAINER REGULATIONS TOBACCO INSPECTION Standards Official Standard Grades for Flue-Cured Tobacco (u.s. Types 11, 12, 13, 14 and Foreign Type 92) § 29.1032 Length. The linear...

2010-01-01

425

A length operator for canonical quantum gravity

We construct an operator that measures the length of a curve in four-dimensional Lorentzian vacuum quantum gravity. We work in a representation in which a $SU(2)$ connection is diagonal and it is therefore surprising that the operator obtained after regularization is densely defined, does not suffer from factor ordering singularities and does not require any renormalization. We show that the length operator admits self-adjoint extensions and compute part of its spectrum which like its companions, the volume and area operators already constructed in the literature, is purely discrete and roughly is quantized in units of the Planck length. The length operator contains full and direct information about all the components of the metric tensor which faciliates the construction of a new type of weave states which approximate a given classical 3-geometry.

T. Thiemann

1996-06-29

426

Method of continuously determining crack length

NASA Technical Reports Server (NTRS)

The determination of crack lengths in an accurate and straight forward manner is very useful in studying and preventing load created flaws and cracks. A crack length sensor according to the present invention is fabricated in a rectangular or other geometrical form from a conductive powder impregnated polymer material. The long edges of the sensor are silver painted on both sides and the sensor is then bonded to a test specimen via an adhesive having sufficient thickness to also serve as an insulator. A lead wire is connected to each of the two outwardly facing silver painted edges. The resistance across the sensor changes as a function of the crack length in the specimen and sensor. The novel aspect of the present invention includes the use of relatively uncomplicated sensors and instrumentation to effectively measure the length of generated cracks.

Prabhakaran, Ramamurthy (inventor); Lopez, Osvaldo F. (inventor)

1993-01-01

427

A computational kinetic model of diffusion for molecular systems

Regulation of biomolecular transport in cells involves intra-protein steps like gating and passage through channels, but these steps are preceded by extra-protein steps, namely, diffusive approach and admittance of solutes. The extra-protein steps develop over a 10–100 nm length scale typically in a highly particular environment, characterized through the protein's geometry, surrounding electrostatic field, and location. In order to account for solute energetics and mobility of solutes in this environment at a relevant resolution, we propose a particle-based kinetic model of diffusion based on a Markov State Model framework. Prerequisite input data consist of diffusion coefficient and potential of mean force maps generated from extensive molecular dynamics simulations of proteins and their environment that sample multi-nanosecond durations. The suggested diffusion model can describe transport processes beyond microsecond duration, relevant for biological function and beyond the realm of molecular dynamics simulation. For this purpose the systems are represented by a discrete set of states specified by the positions, volumes, and surface elements of Voronoi grid cells distributed according to a density function resolving the often intricate relevant diffusion space. Validation tests carried out for generic diffusion spaces show that the model and the associated Brownian motion algorithm are viable over a large range of parameter values such as time step, diffusion coefficient, and grid density. A concrete application of the method is demonstrated for ion diffusion around and through the Eschericia coli mechanosensitive channel of small conductance ecMscS. PMID:24089741

Teo, Ivan; Schulten, Klaus

2013-01-01

428

A computational kinetic model of diffusion for molecular systems.

Regulation of biomolecular transport in cells involves intra-protein steps like gating and passage through channels, but these steps are preceded by extra-protein steps, namely, diffusive approach and admittance of solutes. The extra-protein steps develop over a 10-100 nm length scale typically in a highly particular environment, characterized through the protein's geometry, surrounding electrostatic field, and location. In order to account for solute energetics and mobility of solutes in this environment at a relevant resolution, we propose a particle-based kinetic model of diffusion based on a Markov State Model framework. Prerequisite input data consist of diffusion coefficient and potential of mean force maps generated from extensive molecular dynamics simulations of proteins and their environment that sample multi-nanosecond durations. The suggested diffusion model can describe transport processes beyond microsecond duration, relevant for biological function and beyond the realm of molecular dynamics simulation. For this purpose the systems are represented by a discrete set of states specified by the positions, volumes, and surface elements of Voronoi grid cells distributed according to a density function resolving the often intricate relevant diffusion space. Validation tests carried out for generic diffusion spaces show that the model and the associated Brownian motion algorithm are viable over a large range of parameter values such as time step, diffusion coefficient, and grid density. A concrete application of the method is demonstrated for ion diffusion around and through the Eschericia coli mechanosensitive channel of small conductance ecMscS. PMID:24089741

Teo, Ivan; Schulten, Klaus

2013-09-28

429

Multispecies diffusion models: A study of uranyl species diffusion

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

430

NASA Technical Reports Server (NTRS)

A model has been proposed for the momentum eddy diffusivity induced by free stream turbulence intensity and integral length scale. The eddy diffusivity model is applied to a cylinder situated in a uniform crossflow in the presence of free stream turbulence. Numerical solution of the governing momentum and energy equations with the proposed eddy diffusivity model yielded results for the skin friction coefficient and the Nusselt number. The numerical predictions of the present work are compared with experimental data and the agreement between the two is seen to be very good.

Gorla, R. S. R.; Nemeth, N.

1982-01-01

431

Diffusion Maps for Changing Data Diffusion Maps for Changing Data

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn Department of Mathematics Yale University November 5, 2012 University of Houston Image Analysis Seminar #12;Diffusion Maps;Diffusion Maps for Changing Data How to compare images across sensors? Figure: Sokolov Mine in 2009 and 2010

Hirn, Matthew

432

Diffusion Maps for Changing Data Diffusion Maps for Changing Data

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn Department in Honor of the 70th Birthday of David R. Larson #12;Diffusion Maps for Changing Data Collaborators Joint work with Ronald Coifman and Roy Lederman. #12;Diffusion Maps for Changing Data High Dimensional Data

Hirn, Matthew

433

Diffusion: Diffusive initial value problems and how to solve them

84 #12;Chapter 6 Diffusion: Diffusive initial value problems and how to solve them Selected Reading of the simplest partial dif- ferential equations for diffusive initial value problems in the absence of advection be written T t = Â· T (6.0.1) where T is the temperature and = k/(cP ) is the thermal diffusivity (which has

Spiegelman, Marc W.

434

Diffusion Maps for Changing Data Diffusion Maps for Changing Data

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn Department of Mathematics Yale University October 2, 2012 University of Maryland, Norbert Wiener Center #12;Diffusion Maps;Diffusion Maps for Changing Data How to compare images across sensors? Figure: Sokolov Mine in 2009 (visible

Hirn, Matthew

435

Diffusion Maps for Changing Data Diffusion Maps for Changing Data

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn Department;Diffusion Maps for Changing Data Collaborators Ronald Coifman (Yale University) Roy Lederman (Yale University) #12;Diffusion Maps for Changing Data How to compare images across sensors? Figure: Sokolov Mine

Hirn, Matthew

436

Diffusion Maps for Changing Data Diffusion Maps for Changing Data

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn September 3, 2013 #12;Diffusion Maps for Changing Data Collaborators Simon Adar, Tel Aviv University Eyal Ben Dor, Tel, Clarkson University Yoel Shkolnisky, Tel Aviv University #12;Diffusion Maps for Changing Data Heat equation

Hirn, Matthew

437

Diffusion Maps for Changing Data Diffusion Maps for Changing Data

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn Department of Mathematics Yale University November 29, 2012 Kansas State University Colloquium #12;Diffusion Maps;Diffusion Maps for Changing Data How to compare images across sensors? Figure: Sokolov Mine in 2009 and 2010

Hirn, Matthew

438

Diffusion Maps for Changing Data Diffusion Maps for Changing Data

Diffusion Maps for Changing Data Diffusion Maps for Changing Data Matthew J. Hirn Department of Mathematics Yale University July 26, 2012 Bell Labs #12;Diffusion Maps for Changing Data Collaborators Joint work with Ronald Coifman and Roy Lederman. #12;Diffusion Maps for Changing Data Overview 1 High

Hirn, Matthew

439

Journal Diffusion Factors a measure of diffusion? Tove Faber Frandsen

1 Journal Diffusion Factors Â a measure of diffusion? Tove Faber Frandsen Royal School of Library In this paper we show that the measure of diffusion introduced by Ian Rowlands called the Journal Diffusion Factor (JDF) is highly negatively correlated with the number of citations, leading highly cited journals

Paris-Sud XI, UniversitÃ© de

440

Linear Modeling - Forearm Length vs. Height

NSDL National Science Digital Library

The main purpose of this lab is to explore the proportionality of forearm length and height. The students will record their heights and forearm lengths, first plotting on a table. Each group will plot their 12 points on the given graph paper, and then draw a "best-fit-line". Each group will be asked to give the linear equation--in both slope-intercept form as well as standard form.

2011-01-01

441

Cold Bose Gases with Large Scattering Lengths

NASA Astrophysics Data System (ADS)

We calculate the energy and condensate fraction for a dense system of bosons interacting through an attractive short range interaction with positive s-wave scattering length a. At high densities n>>a-3, the energy per particle, chemical potential, and square of the sound speed are independent of the scattering length and proportional to n2/3, as in Fermi systems. The condensate is quenched at densities na3~=1.

Cowell, S.; Heiselberg, H.; Mazets, I. E.; Morales, J.; Pandharipande, V. R.; Pethick, C. J.

2002-05-01

442

Process for fabricating continuous lengths of superconductor

A process for manufacturing a superconductor. The process is accomplished by depositing a superconductor precursor powder on a continuous length of a first substrate ribbon, overlaying a continuous length of a second substrate ribbon on said first substrate ribbon, and applying sufficient pressure to form a bound layered superconductor precursor between said first substrate ribbon and said second substrates ribbon. The layered superconductor precursor is then heat treated to form a super conductor layer.

Kroeger, Donald M. (Knoxville, TN); List, III, Frederick A. (Andersonville, TN)

1998-01-01

443

NASA Astrophysics Data System (ADS)

Diffusion rates in natural ilmenite of composition Fe0.842+ Fe0.163+Mn0.07Mg0.01Ti 0.92O3 from the Vishnevye Mountains (Urals, Russia) have been measured at 1000° C. Experiments were carried out in a one atmosphere furnace with oxygen fugacity controlled by flow of a CO-CO2 gas mixture, over a period of four hours. The diffusant source was a synthetic ilmenite (FeTiO3) powder doped with trace amounts of Mg, Co, Ni, Zr, Hf, V, Nb, Ta, Al, Cr, Ga and Y. Since, the natural ilmenite crystal contained Mn it was also possible to study diffusion of Mn from the ilmenite crystal. The experiments were analysed using the electron microprobe and scanning laser ablation ICP-MS. Diffusion profiles were measured for Al, Mg, Mn, Co, Ni, Ga, and Y. Diffusion of Cr, Hf, Zr, V, Nb and Ta was too slow to allow diffusion profiles to be accurately measured for the times and temperatures studied so far. The preliminary results show that diffusion in ilmenite is fast, with the diffusivity determined in this study on the order of 10-13 to 10-16 m2s-1. For comparison, Chakraborty (1997) found interdiffusion of Fe and Mg in olivine at 1000° C on the order of 10-17 to 10-18m2s-1 and Dieckmann (1998) found diffusivity of Fe, Mg, Co in magnetite at 1200° C to be on the order of 10-13 to 10-14 m2s-1. The order in which the diffusivity of the elements decreases is Mn > Co > Mg ? Ni > Al ? Y ? Ga, that is to say that Mn diffuses the fastest and Ga the slowest. Overall, this study intends to determine diffusion parameters such as frequency factor, activation energy and activation volume as a function of temperature and oxygen fugacity. This research is taking place in the context of a larger study focusing on the use of the garnet-ilmenite system as a geospeedometer. Examination of the consequences of simultaneous diffusion of multiple elements is a necessity if we are to develop an understanding of the crystal-chemical controls on diffusion (cf Spandler & O'Neill, in press). Chakraborty, S. (1997). Rates and mechanisms of Fe-Mg interdiffusion in olivine at 980° C -1300° C. Journal of geophysical research 102 (B6) p.12317-12331. Dieckmann, R. (1998). Point defects and transport in non-stoichiometric oxides: solved and unsolved problems. Journal of Physics and Chemistry of Solids 59 (4) p. 507-525. Spandler, C., O'Neill, H. St. C. (in press). Diffusion and partition coefficients of minor and trace elements in San Carlos olivine at 1300° C with some geochemical implications. Contributions to Mineralogy and Petrology doi: 10.1007/s00410-009-0456-8.

Stenhouse, Iona; O'Neill, Hugh; Lister, Gordon

2010-05-01

444

Exploitable length correlations in peptide nanofibres

NASA Astrophysics Data System (ADS)

Sequence-prescribed biomolecular assemblies find increasing use in the development of novel nanostructured materials. Critical requirements for emerging designs remain in matching form with function. Peptide assembly diversifies form and supports function, but lacks control over both. Herein we exploit length correlations in peptide nanoscale fibres (form) using a model helical template. We establish that different assembly patterns result from a synergistic interplay between peptide length, net charge and folding and supra-molecular cooperativity, while correlating with increases in cell proliferation (function) as a function of peptide length. The revealed correlations offer an efficient rationale for the programming of longitudinally finite and biologically active nanoscale fibres.Sequence-prescribed biomolecular assemblies find increasing use in the development of novel nanostructured materials. Critical requirements for emerging designs remain in matching form with function. Peptide assembly diversifies form and supports function, but lacks control over both. Herein we exploit length correlations in peptide nanoscale fibres (form) using a model helical template. We establish that different assembly patterns result from a synergistic interplay between peptide length, net charge and folding and supra-molecular cooperativity, while correlating with increases in cell proliferation (function) as a function of peptide length. The revealed correlations offer an efficient rationale for the programming of longitudinally finite and biologically active nanoscale fibres. Electronic supplementary information (ESI) available: Materials and methods together with additional tables and figures. See DOI: 10.1039/c4nr03328k

de Santis, Emiliana; Faruqui, Nilofar; Noble, James E.; Ryadnov, Maxim G.

2014-09-01

445

Dynamical Length-Regulation of Microtubules

NASA Astrophysics Data System (ADS)

Microtubules (MTs) are vital constituents of the cytoskeleton. These stiff filaments are not only needed for mechanical support. They also fulfill highly dynamic tasks. For instance MTs build the mitotic spindle, which pulls the doubled set of chromosomes apart during mitosis. Hence, a well-regulated and adjustable MT length is essential for cell division. Extending a recently introduced model [1], we here study length-regulation of MTs. Thereby we account for both spontaneous polymerization and depolymerization triggered by motor proteins. In contrast to the polymerization rate, the effective depolymerization rate depends on the presence of molecular motors at the tip and thereby on crowding effects which in turn depend on the MT length. We show that these antagonistic effects result in a well-defined MT length. Stochastic simulations and analytic calculations reveal the exact regimes where regulation is feasible. Furthermore, the adjusted MT length and the ensuing strength of fluctuations are analyzed. Taken together, we make quantitative predictions which can be tested experimentally. These results should help to obtain deeper insights in the microscopic mechanisms underlying length-regulation. [4pt] [1] L.Reese, A.Melbinger, E.Frey, Biophys. J., 101, 9, 2190 (2011)

Melbinger, Anna; Reese, Louis; Frey, Erwin

2012-02-01

446

Modelling of dynamic contact length in rail grinding process

NASA Astrophysics Data System (ADS)

Rails endure frequent dynamic loads from the passing trains for supporting trains and guiding wheels. The accumulated stress concentrations will cause the plastic deformation of rail towards generating corrugations, contact fatigue cracks and also other defects, resulting in more dangerous status even the derailment risks. So the rail grinding technology has been invented with rotating grinding stones pressed on the rail with defects removal. Such rail grinding works are directed by experiences rather than scientifically guidance, lacking of flexible and scientific operating methods. With grinding control unit holding the grinding stones, the rail grinding process has the characteristics not only the surface grinding but also the running railway vehicles. First of all, it's important to analyze the contact length between the grinding stone and the rail, because the contact length is a critical parameter to measure the grinding capabilities of stones. Moreover, it's needed to build up models of railway vehicle unit bonded with the grinding stone to represent the rail grinding car. Therefore the theoretical model for contact length is developed based on the geometrical analysis. And the calculating models are improved considering the grinding car's dynamic behaviors during the grinding process. Eventually, results are obtained based on the models by taking both the operation parameters and the structure parameters into the calculation, which are suitable for revealing the process of rail grinding by combining the grinding mechanism and the railway vehicle systems.

Zhi, Shaodan; Li, Jianyong; Zarembski, A. M.

2014-09-01

447

Modelling of dynamic contact length in rail grinding process

NASA Astrophysics Data System (ADS)

Rails endure frequent dynamic loads from the passing trains for supporting trains and guiding wheels. The accumulated stress concentrations will cause the plastic deformation of rail towards generating corrugations, contact fatigue cracks and also other defects, resulting in more dangerous status even the derailment risks. So the rail grinding technology has been invented with rotating grinding stones pressed on the rail with defects removal. Such rail grinding works are directed by experiences rather than scientifically guidance, lacking of flexible and scientific operating methods. With grinding control unit holding the grinding stones, the rail grinding process has the characteristics not only the surface grinding but also the running railway vehicles. First of all, it's important to analyze the contact length between the grinding stone and the rail, because the contact length is a critical parameter to measure the grinding capabilities of stones. Moreover, it's needed to build up models of railway vehicle unit bonded with the grinding stone to represent the rail grinding car. Therefore the theoretical model for contact length is developed based on the geometrical analysis. And the calculating models are improved considering the grinding car's dynamic behaviors during the grinding process. Eventually, results are obtained based on the models by taking both the operation parameters and the structure parameters into the calculation, which are suitable for revealing the process of rail grinding by combining the grinding mechanism and the railway vehicle systems.

Zhi, Shaodan; Li, Jianyong; Zarembski, A. M.

2014-08-01

448

Single-file nanochannel persistence lengths from NMR.

Crystalline solids composed of one-dimensional channels with cross-sectional dimensions below 1 nm represent an intriguing class of materials with important potential applications. A key characteristic for certain applications is the average open channel persistence length, i.e., the ensemble average distance from a channel opening to the first obstruction. This paper introduces an NMR-based methodology to measure this quantity. The protocol is applied to polycrystalline specimens of two different dipeptide nanotubes: l-Ala-l-Val and its retro-analog l-Val-l-Ala. Persistence lengths derived from the NMR measurements are found to be comparable to the typical crystallite dimensions seen in scanning electron microscopy (SEM) images, indicating that the crystals of these AV and VA specimens are essentially hollow with practically no blockages. Applications of the method to an AV sample that has been pulverized in a mortar and pestle showed that the open channel persistence length was reduced from 50 to 6.6 ?m, consistent with the crystallite sizes observed in SEM images. PMID:24432853

Dvoyashkin, Muslim; Bhase, Hrishi; Mirnazari, Navid; Vasenkov, Sergey; Bowers, Clifford R

2014-02-18

449

Causal Baryon Diffusion and Colored Noise

We construct a model of baryon diffusion which has the desired properties of causality and analyticity. The model also has the desired property of colored noise, meaning that the noise correlation function is not a Dirac delta function in space and time; rather, it depends on multiple time and length constants. The model can readily be incorporated in 3+1 dimensional second order viscous hydro-dynamical models of heavy ion collisions, which is particularly important at beam energies where the baryon density is large.

J. I. Kapusta; C. Young

2014-04-18

450

Causal baryon diffusion and colored noise

NASA Astrophysics Data System (ADS)

We construct a model of baryon diffusion which has the desired properties of causality and analyticity. The model also has the desired property of colored noise, meaning that the noise correlation function is not a Dirac delta function in space and time; rather, it depends on multiple time and length constants. The model can readily be incorporated in 3+1-dimensional second-order viscous hydrodynamical models of heavy-ion collisions, which is particularly important at beam energies where the baryon density is large.

Kapusta, J. I.; Young, C.

2014-10-01

451

Using synchrotron X-ray scattering to study the diffusion of water in a weakly-hydrated clay sample

We study the diffusion of water in weakly-hydrated samples of the smectite clay Na-fluorohectorite. The quasi one-dimensional samples are dry compounds of nano-layered particles consisting of ~ 80 silicate platelets. Water diffuses into a sample through the mesoporosity in between the particles, and can subsequently intercalate into the adjacent particles. The samples are placed under controlled temperature. They are initially under low humidity conditions, with all particles in a 1WL intercalation state. We then impose a high humidity at one sample end, triggering water penetration along the sample length. We monitor the progression of the humidity front by monitoring the intercalation state of the particles in space and time. This is done by determining the characteristic spacing of the nano-layered particles in situ, from synchrotron wide-angle X-ray scattering measurements. The spatial width of the intercalation front is observed to be smaller than 2mm, while its velocity decreases with time, as expected from a diffusion process.

Y. Meheust; B. Sandnes; G. Lovoll; K. J. Maloy; J. O. Fossum; G. J. da Silva; M. S. P. Mundim; R. Droppa; D. d. Miranda Fonseca

2005-09-10

452

Lateral Diffusion Length Changes in HgCdTe Detectors in a Proton Environment

NASA Technical Reports Server (NTRS)

This paper presents a study of the performance degradation in a proton environment of very long wavelength infrared (VLWIR) HgCdTe detectors. The energy dependence of the Non-Ionizing Energy Loss (NIEL) in HgCdTe provides a framework for estimating the responsivity degradation in VLWIR HgCdTe due to on orbit exposure from protons. Banded detector arrays that have different detector designs were irradiated at proton energies of 7, 12, and 63 MeV. These banded detector arrays allovedin sight into how the fundamental detector parameters degraded in a proton environment at the three different proton energies. Measured data demonstrated that the detector responsivity degradation at 7 MeV is 5 times larger than the degradation at 63 MeV. The comparison of the responsivity degradation at the different proton energies suggests that the atomic Columbic interaction of the protons with the HgCdTe detector is likely the primary mechanism responsible for the degradation in responsivity at proton energies below 30 MeV.

Hubbs, John E.; Marshall, Paul W.; Marshall, Cheryl J.; Gramer, Mark E.; Maestas, Diana; Garcia, John P.; Dole, Gary A.; Anderson, Amber A.

2007-01-01

453

Diffusion in compacted clays is often studied in sandwich-like arrangements where the clay is confined by porous filter plates in order to control its swelling. In some clays (for example, Na-montmorillonite) equilibrated with dilute electrolyte solutions, the fluxes of cationic radiotracers can be quite high due to cation-exchange reactions. Accordingly, the diffusion resistance of clay layers can become comparable with or even smaller than the diffusion resistance of porous filters (such layers are called "thin" in this study). In view of the typical uncertainties (ca. 20%) of diffusion permeability of porous filters reported in the literature, the diffusion resistance of clay layers cannot be reliably determined from the steady-state diffusion permeability of the filter-clay-filter "sandwich" in this case. In this study, it is shown that, rather unexpectedly, information on the diffusion permeability of "thin" clay layers can be obtained from the time dependence of diffusant flux into the outlet compartment because at very short times, there is a characteristic flux delay that does not occur in the limiting case of infinitely large diffusion permeability of clay. The flux behavior at longer times is controlled by the diffusion permeability of the filters, which makes possible its determination directly from through-diffusion data and makes superfluous independent diffusion experiments with filters. This approach has been validated via theoretical interpretation of literature data on the diffusion of (22)Na radiotracers through confined compacted montmorillonite equilibrated with 0.01 M NaClO(4) solution. The filter and clay properties estimated in this way are in good agreement with the literature data. PMID:19552916

Yaroshchuk, Andriy E; Glaus, Martin A; Van Loon, Luc R

2009-09-15