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Sample records for characteristic diffusion length

  1. Effect of short wavelength illumination on the characteristic bulk diffusion length in ribbon silicon solar cells

    NASA Technical Reports Server (NTRS)

    Ho, C. T.; Mathias, J. D.

    1981-01-01

    The influence of short wavelength light on the characteristic bulk minority carrier diffusion length of the ribbon silicon photovoltaic cell has been investigated. We have measured the intensity and wavelength dependence of the diffusion length in an EFG ribbon cell, and compared it with a standard Czochralski grown silicon cell. While the various short wavelength illuminations have shown no influence on the diffusion length in the CZ cell, the diffusion lengths in the ribbon cell exhibit a strong dependence on the volume generation rate as well as on the wavelength of the superimposed lights. We have concluded that the trap-filling phenomenon at various depths in the bulk neutral region of the cell is consistent with the experimental observation.

  2. Diffusion length and resistivity distribution characteristics of silicon wafer by photoluminescence

    SciTech Connect

    Baek, Dohyun; Lee, Jaehyeong; Choi, Byoungdeog

    2014-10-15

    Highlights: Analytical photoluminescence efficiency calculation and PL intensity ratio method are developed. Wafer resistivity and diffusion length characteristics are investigated by PL intensity ratio. PL intensity is well correlated with resistivity, diffusion length or defect density on wafer measurement. - Abstract: Photoluminescence is a convenient, contactless method to characterize semiconductors. Its use for room-temperature silicon characterization has only recently been implemented. We have developed the PL efficiency theory as a function of substrate doping densities, bulk trap density, photon flux density, and reflectance and compared it with experimental data initially for bulk Si wafers. New developed PL intensity ratio method is able to predict the silicon wafer properties, such as doping densities, minority carrier diffusion length and bulk trap density.

  3. The investigation of the diffusion length of cathode materials in organic light emitting devices through impedance characteristics

    NASA Astrophysics Data System (ADS)

    Wu, I.-Wen; Chuang, Chia-Lin; Wang, Po-Sheng; Tseng, Wei-Hsuan; Wu, Chih-I.

    2012-04-01

    A non-destructive method to measure the diffusion length of the cathode materials into the organic layers in organic light emitting diodes (OLEDs) is demonstrated. The measurement is based on a correlation between the transition voltage in the impedance-voltage (Z-V) characteristics, the density of the accumulation charges, and the thickness of the electron transport layers (ETLs). The transition voltages in Z-V characteristics deviate from the theoretical values owing to the decrease of the effective ETL thickness caused by the diffusion of the cathode materials, which can be used to measure the diffusion length of metal ions into organic layers in OLEDs.

  4. Diffusion on two length scales

    SciTech Connect

    Cohen, R.H.; Nevins, W.M.; Rowlands, G.

    1981-08-01

    One-dimensional diffusion is considered for a system in which the diffusion coefficient D has a rapid oscillation in the spatial variable as well as a slow variation. For long times, the distribution function evolves diffusively with an effective diffusion coefficient given by averaging 1/D.

  5. Characteristic length of glass transition

    NASA Astrophysics Data System (ADS)

    Donth, E.

    1996-03-01

    The characteristic length of the glass transition (? _? ) is based on the concept of cooperatively rearranging regions (CRR's) by Adam & Gibbs (1965): ? _? is the diameter of one CRR. In the theoretical part of the talk a formula is derived how this length can be calculated from calorimetric data of the transformation interval. The approach is based on fluctuations in natural functional subsystems. The corresponding thermodynamics is represented e.g. in a book of the author (E. Donth, Relaxation and Thermodynamics in Polymers. Glass Transition, Akademie-Verlag, Berlin 1992). A typical value for this length is 3 nanometers. In the experimental part several examples are reported to enlarge the experimental evidence for such a length: Squeezing the glass transition in the amorphous layers of partially crystallized PET (C. Schick, Rostock), glass transition of small-molecule glass formers in a series of nanoscaled pores of porous glasses (F. Kremer, Leipzig), comparison with a concentration fluctuation model in homogeneous polymer mixtures (E.W. Fischer, Mainz), and, from our laboratory, backscaling to ? _? across the main transition from the entanglement spacing in several amorphous polymers such as PVAC, PS, NR, and some polymer networks. Rouse backscaling was possible in the ? ? splitting region of several poly(n alkyl methacrylates) resulting in small characteristic lengths of order 1 nanometer near the onset of ? cooperativity. In a speculative outlook a dynamic density pattern is presented, having a cellular structure with higher density and lower mobility of the cell walls. It will be explained, with the aid of different thermal expansion of wall and clusters, how the clusters within the cells maintain a certain mobility far below the glass temperature.

  6. The Influence of Spatial Variations of Diffusion Length on Charge Collected by Diffusion from Ion Tracks

    NASA Technical Reports Server (NTRS)

    Edmonds, L. D.

    1996-01-01

    Charge collected by diffusion from ion tracks in a semiconductor substrate may be influenced by the substrate diffusion length, which is related to recombination losses. A theoretical analysis shows that, excluding some extreme cases, charge collection is insensitive to spatial variations in the diffusion length funciton, so it is possible to define an effective diffusion length having the property that collected charge can be approximated by assuming a uniform diffusion length equal to this effective value.

  7. Characteristic length of the knotting probability revisited

    NASA Astrophysics Data System (ADS)

    Uehara, Erica; Deguchi, Tetsuo

    2015-09-01

    We present a self-avoiding polygon (SAP) model for circular DNA in which the radius of impermeable cylindrical segments corresponds to the screening length of double-stranded DNA surrounded by counter ions. For the model we evaluate the probability for a generated SAP with N segments having a given knot K through simulation. We call it the knotting probability of a knot K with N segments for the SAP model. We show that when N is large the most significant factor in the knotting probability is given by the exponentially decaying part exp(-N/NK), where the estimates of parameter NK are consistent with the same value for all the different knots we investigated. We thus call it the characteristic length of the knotting probability. We give formulae expressing the characteristic length as a function of the cylindrical radius rex, i.e. the screening length of double-stranded DNA.

  8. Diffusion lengths in amphoteric GaAs heteroface solar cells

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    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.

  9. Diffusion of Isolated DNA molecules: dependence on length and topology

    NASA Astrophysics Data System (ADS)

    Robertson, Rae M.; Laib, Stephan; Smith, Douglas E.

    2006-03-01

    Diffusion coefficients (D) for relaxed circular and linear DNA molecules ranging in length (L) from 5.9 to 287.1 kilobasepairs were measured by tracking the Brownian motion of single molecules. A topology independent scaling law, DL-0.58+/-0.016, was observed, in good agreement with the --0.588 exponent predicted by renormalization group theory. The measured ratio DCircular/DLinear = 1.32+/-0.014 fell between predictions of 1.18 for Kirkwood hydrodynamic theory and 1.45 for renormalization group theory and agreed best with a value 1.31 predicted using the Zimm model and an expression for the radius of gyration proposed by Bensafi, Maschke, and Benmouna. Measurements on supercoiled DNA molecules were also made and qualitatively compared to theoretical predictions.

  10. Length of intact plasma membrane determines the diffusion properties of cellular water

    PubMed Central

    Eida, Sato; Van Cauteren, Marc; Hotokezaka, Yuka; Katayama, Ikuo; Sasaki, Miho; Obara, Makoto; Okuaki, Tomoyuki; Sumi, Misa; Nakamura, Takashi

    2016-01-01

    Molecular diffusion in a boundary-free medium depends only on the molecular size, the temperature, and medium viscosity. However, the critical determinant of the molecular diffusion property in inhomogeneous biological tissues has not been identified. Here, using an in vitro system and a high-resolution MR imaging technique, we show that the length of the intact plasma membrane is a major determinant of water diffusion in a controlled cellular environment and that the cell perimeter length (CPL) is sufficient to estimate the apparent diffusion coefficient (ADC) of water in any cellular environment in our experimental system (ADC = −0.21 × CPL + 1.10). We used this finding to further explain the different diffusion kinetics of cells that are dying via apoptotic or non-apoptotic cell death pathways exhibiting characteristic changes in size, nuclear and cytoplasmic architectures, and membrane integrity. These results suggest that the ADC value can be used as a potential biomarker for cell death. PMID:26750342

  11. Diffusion length in nanoporous TiO{sub 2} films under above-band-gap illumination

    SciTech Connect

    Park, J. D.; Son, B. H.; Park, J. K.; Kim, Sang Yong; Park, Ji-Yong; Lee, Soonil; Ahn, Y. H.

    2014-06-15

    We determined the carrier diffusion lengths in TiO{sub 2} nanoporous layers of dye-sensitized solar cells by using scanning photocurrent microscopy using an ultraviolet laser. Here, we excited the carrier directly in the nanoporous layers where the diffusion lengths were found to 140 ?m as compared to that of visible illumination measured at 90 ?m. The diffusion length decreased with increasing laser modulation frequency, in which we determined the electron lifetimes and the diffusion coefficients for both visible and UV illuminations. The diffusion lengths have been studied in terms of the sintering temperatures for both cells with and without binding molecules. We found a strong correlation between the diffusion length and the overall light-to-current conversion efficiency, proving that improving the diffusion length and hence the interparticle connections, is key to improving cell efficiency.

  12. Surface recombination velocity and diffusion length of minority carriers in heavily doped silicon layers

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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.

  13. Scale length of mantle heterogeneities: Constraints from helium diffusion

    NASA Astrophysics Data System (ADS)

    Hart, S. R.; Kurz, M. D.; Wang, Z.

    2008-05-01

    A model of coupled He production/diffusion is used to constrain the question of whether Earth's peridotitic mantle contains ubiquitous mesoscale veins or slabs of other lithologies. The high diffusion rates of helium preclude survival of He isotope heterogeneities on scales smaller than a few tens of meters, especially if they represent long term in-growth of 4He in the mantle. For 1.5 Gyr residence times, and a diffusion coefficient of 10 - 10 m 2/s, 0.5 km slabs or 2 km cylinders will lose > 90% of in-grown 4He. However, substantial 3He/ 4He variations may persist in slabs or be induced in adjacent mantle, depending on initial He, U and Th contents. We have modeled three cases of 3He/ 4He equilibration between mantle domains: an ocean crust (OC) slab in depleted upper mantle (DMM) or in enriched mantle (BSE), and a BSE slab in DMM. For a 1 km OC slab in DMM (8 Ra today), the slab today will have 3He/ 4He of only 3 Ra, and will have influenced the surrounding mantle with 4He for > 7 km on either side. The average 3He/ 4He of this mixed zone will be < 7 Ra, even when sampled by melts over a total width of 20-50 km. For the case of a 1 km BSE slab in DMM (8 Ra today), the slab will be 37 Ra today, and will have infected a mantle domain > 16 km wide. Even with a 60 km melt sampling width, the average 3He/ 4He will be > 15 Ra. Slabs may lose their He signature by diffusion, but their presence will be recorded in the surrounding mantle. We have evaluated 3 along-axis N-MORB ridge-crest data sets in this context (MAR 25.7-26.5°S; EPR 19-23°S; SWIR 16-24° E), with a view to defining scale-lengths of He isotope variability. The average 3He/ 4He variability for these 3 areas is very small, and independent of spreading rate: 0.13, 0.19 and 0.21 Ra (± 1 σ). Since these ridges range from ultra-slow to very fast-spreading, the variability in size of along-axis magma chambers will lead inevitably to various scales of melt averaging. We conclude that these ridge areas are not sampling mantle that contains enriched veins or recycled oceanic crust slabs of significant size (> tens of meters). It appears difficult to sustain a view of the upper mantle as a ubiquitous mixture of veins and depleted matrix, with MORB always representing an averaging of this mixture.

  14. Performance Characteristics of Plane-Wall Two-Dimensional Diffusers

    NASA Technical Reports Server (NTRS)

    Reid, Elliott G

    1953-01-01

    Experiments have been made at Stanford University to determine the performance characteristics of plane-wall, two-dimensional diffusers which were so proportioned as to insure reasonable approximation of two-dimensional flow. All of the diffusers had identical entrance cross sections and discharged directly into a large plenum chamber; the test program included wide variations of divergence angle and length. During all tests a dynamic pressure of 60 pounds per square foOt was maintained at the diffuser entrance and the boundary layer there was thin and fully turbulent. The most interesting flow characteristics observed were the occasional appearance of steady, unseparated, asymmetric flow - which was correlated with the boundary-layer coalescence - and the rapid deterioration of flow steadiness - which occurred as soon as the divergence angle for maximum static pressure recovery was exceeded. Pressure efficiency was found to be controlled almost exclusively by divergence angle, whereas static pressure recovery was markedly influenced by area ratio (or length) as well as divergence angle. Volumetric efficiency. diminished as area ratio increased, and at a greater rate with small lengths than with large ones. Large values of the static-pressure-recovery coefficient were attained only with long diffusers of large area ratio; under these conditions pressure efficiency was high and. volumetric efficiency low. Auxiliary tests with asymmetric diffusers demonstrated that longitudinal pressure gradient, rather than wall divergence angle, controlled flow separation. Others showed that the addition of even a short exit duct of uniform section augmented pressure recovery. Finally, it was found that the installation of a thin, central, longitudinal partition suppressed flow separation in short diffusers and thereby improved pressure recovery

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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.

  16. Effects of venturi length on combustion characteristics on inshot burners

    SciTech Connect

    Rao, A.V.; Gollahalli, S.R.

    1996-12-31

    An experimental study of the changes caused in the flame structure and pollutant emission characteristics by the modifications of the primary-air venturi of an inshot burner used in residential natural gas furnaces is presented. The venturi modification examined in this study are the shape of the venturi inlet, and the venturi length. Modified venturi with curved inlets produce higher primary-air entrainment and slightly smaller (by 5 to 10%) emission indices of NOx and CO than the standard parallel side venturi. However, the changes in the venturi length for the modified geometry do not result in significant further changes.

  17. Low temperature diffusion length of excitons in gallium nitride measured by cathodoluminescence technique

    NASA Astrophysics Data System (ADS)

    Ino, Naoyuki; Yamamoto, Naoki

    2008-12-01

    Monochromatic cathodoluminescence (CL) images of threading dislocations in GaN epitaxial layers were observed using a transmission electron microscopy combined with CL system. The carrier diffusion lengths were derived from the free exciton emission intensity profile of the dislocation contrast in the CL images. The carrier diffusion lengths in Si-doped and Mg-doped GaN were nearly the same and shorter than that in undoped GaN in the temperature range from 20 to 140 K, respectively. Moreover, the temperature dependence of the diffusion length shows that the acoustic phonon scattering mainly affects the exciton diffusion process at low temperatures from 40 to 120 K.

  18. Acid Diffusion Length in Line-and-Space Resist Patterns Fabricated by Extreme Ultraviolet Lithography

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    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.

  19. Large diffusion lengths of excitons in perovskite and TiO2 heterojunction

    NASA Astrophysics Data System (ADS)

    Gevorkian, Zhyrair; Gasparian, Vladimir; Lozovik, Yurii

    2016-02-01

    Solar cells based on organometal halide perovskites have recently become very promising among other materials because of their cost-effective character and improvements in efficiency. Such performance is primarily associated with effective light absorption and large diffusion length of charge carriers. Our paper is devoted to the explanation of large diffusion lengths in these systems. The transport mean free path of charged carriers in a perovskite/TiO2 heterojunction that is an important constituent of the solar cells have been analyzed. Large transport length is explained by the planar diffusion of indirect excitons. Diffusion length of the coupled system increases by several orders compared to single carrier length due to the correlated character of the effective field acting on the exciton.

  20. Investigation of diffusion length distribution on polycrystalline silicon wafers via photoluminescence methods.

    PubMed

    Lou, Shishu; Zhu, Huishi; Hu, Shaoxu; Zhao, Chunhua; Han, Peide

    2015-01-01

    Characterization of the diffusion length of solar cells in space has been widely studied using various methods, but few studies have focused on a fast, simple way to obtain the quantified diffusion length distribution on a silicon wafer. In this work, we present two different facile methods of doing this by fitting photoluminescence images taken in two different wavelength ranges or from different sides. These methods, which are based on measuring the ratio of two photoluminescence images, yield absolute values of the diffusion length and are less sensitive to the inhomogeneity of the incident laser beam. A theoretical simulation and experimental demonstration of this method are presented. The diffusion length distributions on a polycrystalline silicon wafer obtained by the two methods show good agreement. PMID:26364565

  1. Investigation of diffusion length distribution on polycrystalline silicon wafers via photoluminescence methods

    NASA Astrophysics Data System (ADS)

    Lou, Shishu; Zhu, Huishi; Hu, Shaoxu; Zhao, Chunhua; Han, Peide

    2015-09-01

    Characterization of the diffusion length of solar cells in space has been widely studied using various methods, but few studies have focused on a fast, simple way to obtain the quantified diffusion length distribution on a silicon wafer. In this work, we present two different facile methods of doing this by fitting photoluminescence images taken in two different wavelength ranges or from different sides. These methods, which are based on measuring the ratio of two photoluminescence images, yield absolute values of the diffusion length and are less sensitive to the inhomogeneity of the incident laser beam. A theoretical simulation and experimental demonstration of this method are presented. The diffusion length distributions on a polycrystalline silicon wafer obtained by the two methods show good agreement.

  2. Cloud Shading Effects on Characteristic Boundary-Layer Length Scales

    NASA Astrophysics Data System (ADS)

    Horn, G. L.; Ouwersloot, H. G.; Vil-Guerau de Arellano, J.; Sikma, M.

    2015-11-01

    We studied the effects of shading by shallow cumulus (shallow Cu) and the subsequent effect of inducing heterogeneous conditions at the surface on boundary-layer characteristics. We placed special emphasis on quantifying the changes in the characteristic length and time scales associated with thermals, shallow Cu and induced thermal circulation structures. A series of systematic numerical experiments, inspired by Amazonian thermodynamic conditions, was performed using a large-eddy simulation model coupled to a land-surface model. We used four different experiments to disentangle the effects of shallow Cu on the surface and the response of clouds to these surface changes. The experiments include a `clear case', `transparent clouds', `shading clouds' and a case with a prescribed uniform domain and reduced surface heat flux. We also performed a sensitivity study on the effect of introducing a weak background flow. Length and time scales were calculated using autocorrelation and two-dimensional spectral analysis, and we found that shading controlled by shallow Cu locally lowers surface temperatures and consequently reduces the sensible and latent heat fluxes, thus inducing spatial and temporal variability in these fluxes. The length scale of this surface heterogeneity is not sufficiently large to generate circulations that are superimposed on the boundary-layer scale, but the heterogeneity does disturb boundary-layer dynamics and generates a flow opposite to the normal thermal circulation. Besides this effect, shallow Cu shading reduces turbulent kinetic energy and lowers the convective velocity scale, thus reducing the mass flux. This hampers the thermal lifetime, resulting in a decrease in the shallow Cu residence time (from 11 to 7 min). This reduction in lifetime, combined with a decrease in mass flux, leads to smaller clouds. This is partially compensated for by a decrease in thermal cell size due to a reduction in turbulent kinetic energy. As a result, inter-cloud distance is reduced, leading to a larger population of smaller clouds, while maintaining cloud cover similar to the non-shading clouds experiment. Introducing a 1 m s^{-1} background wind speed increases the thermal size in the sub-cloud layer, but the diagnosed surface-cloud coupling, quantified by characteristic time and length scales, remains.

  3. Contemplating Transport Characteristics by Augmenting the Length of Molecule

    NASA Astrophysics Data System (ADS)

    Kaur, Milanpreet; Sawhney, Ravinder Singh; Engles, Derick

    2013-11-01

    In this paper, we contemplated the transport characteristics of a single molecular device junction by augmenting the length of the molecule in the scattering region. The molecules considered here belongs to class of alkanedithiols (CnH2n+2S2). Specifically, we used a tight binding semi-empirical model to compute the transport characteristics of butanedithiol, pentanedithiol, hexanedithiol and heptanedithiol connected to semi-infinite gold electrodes through thiol anchoring elements. The exploration of transport properties of considered alkanes was completed for different bias voltages within the sphere of Keldysh's Non Equilibrium Green's Function (NEGF) and Extended Hckel Theory (EHT), for studying the self-consistent steady-state solution, analyzing the out-of-equilibrium electron distribution, and the behavior of the self-consistent potential. We perceived that the current and conductance retrenches with aggravation with the increase in length of the molecule with exhibition of single electron tunneling. We observed that the coupling regime shifts from strong coupling to weak for higher order alkanedithiols and the transmission is function of evenness or oddness of the carbon atoms forming an alkane.

  4. Diffusion length measurements using the scanning electron microscope. [in semiconductor devices

    NASA Technical Reports Server (NTRS)

    Weizer, V. G.

    1975-01-01

    A measurement technique employing the scanning electron microscope is described in which values of the true bulk diffusion length are obtained. It is shown that surface recombination effects can be eliminated through the application of highly doped surface field layers. The influence of high injection level effects and low-high junction current generation on the resulting measurement was investigated. Close agreement is found between the diffusion lengths measured by this method and those obtained using a penetrating radiation technique.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  6. Tracer diffusion through F-actin: effect of filament length and cross-linking.

    PubMed Central

    Jones, J D; Luby-Phelps, K

    1996-01-01

    We have determined diffusion coefficients for small (50- to 70-nm diameter) fluorescein-thiocarbamoyl-labeled Ficoll tracers through F-actin as a function of filament length and cross-linking. fx45 was used to regulate filament length and avidin/biotinylated actin or ABP-280 was used to prepare cross-linked actin gels. We found that tracer diffusion was generally independent of filament length in agreement with theoretical predictions for diffusion through solutions of rods. However, in some experiments diffusion was slower through short (< or = 1.0 micron) filaments, although this result was not consistently reproducible. Measured diffusion coefficients through unregulated F-actin and filaments of lengths > 1.0 micron were more rapid than predicted by theory for tracer diffusion through rigid, random networks, which was consistent with some degree of actin bundling. Avidin-induced cross-linking of biotinylated F-actin did not affect diffusion through unregulated F-actin, but in cases where diffusion was slower through short filaments this cross-linking method resulted in enhanced tracer diffusion rates indistinguishable from unregulated F-actin. This finding, in conjunction with increased turbidity of 1.0-micron filaments upon avidin cross-linking, indicated that this cross-linking method induces F-actin bundling. By contrast, ABP-280 cross-linking retarded diffusion through unregulated F-actin and decreased turbidity. Tracer diffusion under these conditions was well approximated by the diffusion theory. Both cross-linking procedures resulted in gel formation as determined by falling ball viscometry. These results demonstrate that network microscopic geometry is dependent on the cross-linking method, although both methods markedly increase F-actin macroscopic viscosity. PMID:8913611

  7. Estimation and calibration of the water isotope differential diffusion length in ice core records

    NASA Astrophysics Data System (ADS)

    van der Wel, G.; Fischer, H.; Oerter, H.; Meyer, H.; Meijer, H. A. J.

    2015-08-01

    Palaeoclimatic information can be retrieved from the diffusion of the stable water isotope signal during firnification of snow. The diffusion length, a measure for the amount of diffusion a layer has experienced, depends on the firn temperature and the accumulation rate. We show that the estimation of the diffusion length using power spectral densities (PSDs) of the record of a single isotope species can be biased by uncertainties in spectral properties of the isotope signal prior to diffusion. By using a second water isotope and calculating the difference in diffusion lengths between the two isotopes, this problem is circumvented. We study the PSD method applied to two isotopes in detail and additionally present a new forward diffusion method for retrieving the differential diffusion length based on the Pearson correlation between the two isotope signals. The two methods are discussed and extensively tested on synthetic data which are generated in a Monte Carlo manner. We show that calibration of the PSD method with this synthetic data is necessary to be able to objectively determine the differential diffusion length. The correlation-based method proves to be a good alternative for the PSD method as it yields precision equal to or somewhat higher than the PSD method. The use of synthetic data also allows us to estimate the accuracy and precision of the two methods and to choose the best sampling strategy to obtain past temperatures with the required precision. In addition to application to synthetic data the two methods are tested on stable-isotope records from the EPICA (European Project for Ice Coring in Antarctica) ice core drilled in Dronning Maud Land, Antarctica, showing that reliable firn temperatures can be reconstructed with a typical uncertainty of 1.5 and 2 C for the Holocene period and 2 and 2.5 C for the last glacial period for the correlation and PSD method, respectively.

  8. Acid diffusion length in contact hole imaging of chemically amplified extreme ultraviolet resists

    NASA Astrophysics Data System (ADS)

    Kozawa, Takahiro; Hirayama, Taku

    2014-01-01

    Contact holes and line-and-space patterns are the most basic elements in the fabrication of semiconductor devices. In this study, the chemical processes in contact hole imaging were investigated to clarify the optimum acid diffusion length in terms of the quality of latent images. The chemical processes were simulated using a Monte Carlo method based on the reaction mechanisms of chemically amplified extreme ultraviolet (EUV) resists. The theoretical dependence of the optimum acid diffusion length on the exposure dose and half-pitch (diameter) was clarified. At an exposure dose of 20 mJ cm-2, the optimum acid diffusion length (three-dimensional) was 10.7 nm for 28 nm contact holes (56 nm pitch). By decreasing the diameter to 16 nm (32 nm pitch), the optimum acid diffusion length (three-dimensional) was decreased to 8.9 nm, which was smaller than that of line-and-space patterns by 12%. The chemical reactions for the dissolution of resist polymers should be sufficiently induced within these acid diffusion lengths for contact hole imaging.

  9. Estimation of minority carrier diffusion lengths in InP/GaAs solar cells

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    Minority carrier diffusion length is one of the most important parameters affecting the solar cell performance. An attempt is made to estimate the minority carrier diffusion lengths is the emitter and base of InP/GaAs heteroepitaxial solar cells. The PC-1D computer model was used to simulate the experimental cell results measured at NASA Lewis under AMO (air mass zero) spectrum at 25 C. A 16 nm hole diffusion length in the emitter and a 0.42 micron electron diffusion length in the base gave very good agreement with the I-V curve. The effect of varying minority carrier diffusion lengths on cell short current, open circuit voltage, and efficiency was studied. It is also observed that the front surface recombination velocity has very little influence on the cell performance. The poor output of heteroepitaxial cells is caused primarily by the large number of dislocations generated at the interfaces that propagate through the bulk indium phosphide layers. Cell efficiency as a function of dislocation density was calculated and the effect of improved emitter bulk properties on cell efficiency is presented. It is found that cells with over 16 percent efficiencies should be possible, provided the dislocation density is below 10(exp 6)/sq cm.

  10. Lifetime and diffusion length measurements on silicon material and solar cells

    NASA Technical Reports Server (NTRS)

    Othmer, S.; Chen, S. C.

    1978-01-01

    Experimental methods were evaluated for the determination of lifetime and diffusion length in silicon intentionally doped with potentially lifetime-degrading impurities found in metallurgical grade silicon, impurities which may be residual in low-cost silicon intended for use in terrestrial flat-plate arrays. Lifetime measurements were made using a steady-state photoconductivity method. Diffusion length determinations were made using short-circuit current measurements under penetrating illumination. Mutual consistency among all experimental methods was verified, but steady-state photoconductivity was found preferable to photoconductivity decay at short lifetimes and in the presence of traps. The effects of a number of impurities on lifetime in bulk material, and on diffusion length in cells fabricated from this material, were determined. Results are compared with those obtained using different techniques. General agreement was found in terms of the hierarchy of impurities which degrade the lifetime.

  11. Probing sub-alveolar length scales with hyperpolarized-gas diffusion NMR

    NASA Astrophysics Data System (ADS)

    Miller, Wilson; Carl, Michael; Mooney, Karen; Mugler, John; Cates, Gordon

    2009-05-01

    Diffusion MRI of the lung is a promising technique for detecting alterations of normal lung microstructure in diseases such as emphysema. The length scale being probed using this technique is related to the time scale over which the helium-3 or xenon-129 diffusion is observed. We have developed new MR pulse sequence methods for making diffusivity measurements at sub-millisecond diffusion times, allowing one to probe smaller length scales than previously possible in-vivo, and opening the possibility of making quantitative measurements of the ratio of surface area to volume (S/V) in the lung airspaces. The quantitative accuracy of simulated and experimental measurements in microstructure phantoms will be discussed, and preliminary in-vivo results will be presented.

  12. Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber

    NASA Astrophysics Data System (ADS)

    Stranks, Samuel; Eperon, Giles; Grancini, Giulia; Menelaou, Christopher; Alcocer, Marcelo; Leijtens, Tomas; Herz, Laura; Petrozza, Annamaria; Snaith, Henry

    2014-03-01

    Organic-inorganic perovskites have shown promise as high-performance absorbers in solar cells, first as a coating on a mesoporous metal oxide scaffold and more recently as a solid layer in planar heterojunction architectures. Here, we report transient absorption and photoluminescence-quenching measurements to determine the electron-hole diffusion lengths, diffusion constants, and lifetimes in mixed halide (CH3NH3PbI3-xClx) and triiodide (CH3NH3PbI3) perovskite absorbers. We found that the diffusion lengths are greater than 1 micrometer in the mixed halide perovskite, which is an order of magnitude greater than the absorption depth. In contrast, the triiodide absorber has electron-hole diffusion lengths of order 100 nanometers. Finally, we fabricated solution-processed thin-film planar heterojunction devices, achieving power conversion efficiencies of over 12% using the mixed halide absorber but only 4% with the triiodide perovskite. Our results show that the long diffusion lengths justify the high efficiency of planar heterojunction perovskite solar cells, and identify a critical parameter to optimize for future perovskite absorber development.

  13. Interpretation of scanning electron microscope measurements of minority carrier diffusion lengths in semiconductors

    NASA Technical Reports Server (NTRS)

    Flat, A.; Milnes, A. G.

    1978-01-01

    In scanning electron microscope (SEM) injection measurements of minority carrier diffusion lengths some uncertainties of interpretation exist when the response current is nonlinear with distance. This is significant in epitaxial layers where the layer thickness is not large in relation to the diffusion length, and where there are large surface recombination velocities on the incident and contact surfaces. An image method of analysis is presented for such specimens. A method of using the results to correct the observed response in a simple convenient way is presented. The technique is illustrated with reference to measurements in epitaxial layers of GaAs. Average beam penetration depth may also be estimated from the curve shape.

  14. Minority carrier diffusion lengths and absorption coefficients in silicon sheet material

    SciTech Connect

    Dumas, K.A.; Swimm, R.T.

    1980-01-01

    One of the indicators which determine a material's potential for use as a solar cell is the minority carrier diffusion length (L/sub D/) of the material. To determine L/sub D/ a surface photovoltage (SPV) technique is used. This method is dependent upon an accurate knowledge of the optical absorption coefficient as function of wavelength. The results for the absorption coefficients for various types of silicon sheet material are compared to those previously used in the two models. The resultant effect upon the diffusion length is also discussed in detail. 7 refs.

  15. Direct measurements of exciton diffusion length limitations on organic solar cell performance.

    PubMed

    Kozub, Derek R; Vakhshouri, Kiarash; Kesava, Sameer Vajjala; Wang, Cheng; Hexemer, Alexander; Gomez, Enrique D

    2012-06-14

    Through a combination of X-ray scattering and energy-filtered electron microscopy, we have quantitatively examined the relationship between the mesostructure of the photoactive layer and device performance in PBTTT/PC(71)BM solar cells. We can predict device performance from X-ray structural data through a simple morphological model which includes the exciton diffusion length. PMID:22572808

  16. Water diffusion within hydrated model grafted polymeric membranes with bimodal side chain length distributions.

    PubMed

    Dorenbos, G

    2015-04-14

    The effect of bimodal side chain length distributions on pore morphology and solvent diffusion within hydrated amphiphilic polymeric membranes is predicted. Seven polymeric architectures are constructed from hydrophobic backbones from which at regular intervals side chains branch off that are alternatingly short (composed of p hydrophobic A fragments or beads) and long (q A fragments, q > p). The side chains are end-linked with a hydrophilic C fragment. Pore morphologies at a water volume fraction of 0.16 are calculated by dissipative particle dynamics (DPD). Water diffusion through the water containing pores is calculated by tracer diffusion calculations through 140 selected snapshots and from the water bead motions. Diffusion constants decrease with difference in side chain lengths, q - p. Overall, the distance between pores also decreases with q - p. The results are explained by counting for every architecture the average number of bonds 〈N(bond)〉 between an A and the nearest C fragment. These results are in line with a database that contains more than 60 architectures. Diffusion constants tend to increase linearly with 〈N(bond)〉|C|(-1)|A|, where |C| and |A| are the C and A bead fractions within the architecture. 〈N(bond)〉 is therefore expected to be an interesting design parameter for obtaining low percolation thresholds for solvent and/or proton diffusion. PMID:25703230

  17. Magnetic field dependence of the magnon spin diffusion length in the magnetic insulator yttrium iron garnet

    NASA Astrophysics Data System (ADS)

    Cornelissen, L. J.; van Wees, B. J.

    2016-01-01

    We investigated the effect of an external magnetic field on the diffusive spin transport by magnons in the magnetic insulator Y3Fe5O12 , using a nonlocal magnon transport measurement geometry. We observed a decrease in magnon spin diffusion length λm for increasing field strengths, where λm is reduced from 9.6 ±1.2 μ m at 10 mT to 4.2 ±0.6 μ m at 3.5 T at room temperature. In addition, we find that there must be at least one additional transport parameter that depends on the external magnetic field. Our results do not allow us to unambiguously determine whether this is the magnon equilibrium density or the magnon diffusion constant. These results are significant for experiments in the more conventional longitudinal spin Seebeck geometry, since the magnon spin diffusion length sets the length scale for the spin Seebeck effect as well and is relevant for its understanding.

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

    NASA Technical Reports Server (NTRS)

    Hakimzadeh, Roshanak; Bailey, Sheila G.

    1993-01-01

    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.

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

    PubMed

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

    2013-01-01

    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 400C. 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

  20. Method and apparatus for determining minority carrier diffusion length in semiconductors

    DOEpatents

    Goldstein, Bernard; Dresner, Joseph; Szostak, Daniel J.

    1983-07-12

    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.

  1. Effects of Coaxial Air on Nitrogen-Diluted Hydrogen Jet Diffusion Flame Length and NOx Emission

    SciTech Connect

    Weiland, N.T.; Chen, R.-H.; Strakey, P.A.

    2007-10-01

    Turbulent nitrogen-diluted hydrogen jet diffusion flames with high velocity coaxial air flows are investigated for their NOx emission levels. This study is motivated by the DOE turbine programs goal of achieving 2 ppm dry low NOx from turbine combustors running on nitrogen-diluted high-hydrogen fuels. In this study, effects of coaxial air velocity and momentum are varied while maintaining low overall equivalence ratios to eliminate the effects of recirculation of combustion products on flame lengths, flame temperatures, and resulting NOx emission levels. The nature of flame length and NOx emission scaling relationships are found to vary, depending on whether the combined fuel and coaxial air jet is fuel-rich or fuel-lean. In the absence of differential diffusion effects, flame lengths agree well with predicted trends, and NOx emissions levels are shown to decrease with increasing coaxial air velocity, as expected. Normalizing the NOx emission index with a flame residence time reveals some interesting trends, and indicates that a global flame strain based on the difference between the fuel and coaxial air velocities, as is traditionally used, is not a viable parameter for scaling the normalized NOx emissions of coaxial air jet diffusion flames.

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

    PubMed Central

    2013-01-01

    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 400C. 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

  3. Study of the spatial distribution of minority carrier diffusion length in epiplanar detector structures

    NASA Astrophysics Data System (ADS)

    Piotrowski, T.; Węgrzecki, M.; Stolarski, M.; Krajewski, T.

    2015-12-01

    One of the key parameters determining detection properties of silicon PIN detector structures (p+-ν-n+ or n+-ν-p+) is minority carrier diffusion length in p-n junction regions p-n (p+-ν or n+-ν). The parameter concerned strongly depends on quality of the starting material and technological processes conducted and has a significant impact on detector parameters, in particular dark current intensity. Thus, the parameter must be determined in order to optimise the design and technology of detectors. The paper presents a method for measuring the spatial distribution of effective carrier diffusion length in silicon detector structures, based on the measurement of photoelectric current of a non-polarised structure illuminated (spot diameter of 250 μm) with monochromatic radiation of two wavelengths λ1 = 500 nm (silicon penetration depth of around 0.9 μm) and λ2 = 900 nm (silicon penetration depth of around 33 μm). The value of diffusion length was determined by analysing the spatial distribution of optical carrier generation and values of photoelectric currents.

  4. Characterizing acid diffusion lengths in chemically amplified resists from measurements of deprotection kinetics

    NASA Astrophysics Data System (ADS)

    Patil, Abhijit A.; Pandey, Yogendra Narayan; Doxastakis, Manolis; Stein, Gila E.

    2014-10-01

    The acid-catalyzed deprotection of glassy poly(4-hydroxystyrene-co-tertbutyl acrylate) films was studied with infrared absorbance spectroscopy and stochastic simulations. Experimental data were interpreted with a simple description of subdiffusive acid transport coupled to second-order acid loss. This model predicts key attributes of observed deprotection rates, such as fast reaction at short times, slow reaction at long times, and a nonlinear dependence on acid loading. Fickian diffusion is approached by increasing the postexposure bake temperature or adding plasticizing agents to the polymer resin. These findings demonstrate that acid mobility and overall deprotection kinetics are coupled to glassy matrix dynamics. To complement the analysis of bulk kinetics, acid diffusion lengths were calculated from the anomalous transport model and compared with nanopattern line widths. The consistent scaling between experiments and simulations suggests that the anomalous diffusion model could be further developed into a predictive lithography tool.

  5. Effective optical path length for tandem diffuse cubic cavities as gas absorption cell

    NASA Astrophysics Data System (ADS)

    Yu, J.; Gao, Q.; Zhang, Y. G.; Zhang, Z. G.; Wu, S. H.

    2014-12-01

    Tandem diffuse cubic cavities designed by connecting two single diffuse cubic-shaped cavities, A and B, with an aperture (port fraction fap) in the middle of the connecting baffle was developed as a gas absorption cell. The effective optical path length (EOPL) was evaluated by comparing the oxygen absorption signal in the cavity and in air based on tunable diode laser absorption spectroscopy (TDLAS). Experimental results manifested an enhancement of EOPL for the tandem diffuse cubic cavities as the decrease of fap and can be expressed as the sum of EOPL of two single cubic cavities at fap < 0.01, which coincided well with theoretical analysis. The simulating EOPL was smaller than experimental results at fap > 0.01, which indicated that back scattering light from cavity B to cavity A cannot be ignored at this condition.

  6. Taylor-Couette Flow with Hourglass Geometry of Varying Lengths Simulated by Reaction-Diffusion

    NASA Astrophysics Data System (ADS)

    Zhao, Yunjie; Halmstad, Andrew; Olsen, Thomas; Wiener, Richard

    2008-11-01

    Previously, we have observed chaotic formation of Taylor-Vortex pairs in Modified Taylor- Couette Flow with Hourglass Geometry. In the experiment, the chaotic formation in a shorter system has been restricted to a narrow band about the waist of the hourglass. Such behavior has been modeled by The Reaction-Diffusion equation, which has been previously studied, by Riecke and Paap. Their calculation suggested that quadrupling length of the system would lead to spatial chaos in the vortex formation. We present a careful recreation of this result and consider an intermediate length. We demonstrate that doubling the length should be sufficient to observe spatially chaotic behavior. Richard J. Wiener et al, Phys. Rev. E 55, 5489 (1997). H. Riecke and H.-G. Paap, Europhys. Lett. 14, 1235 (1991).

  7. Characteristics of transitional and turbulent jet diffusion flames in microgravity

    NASA Technical Reports Server (NTRS)

    Bahadori, Yousef M.; Small, James F., Jr.; Hegde, Uday G.; Zhou, Liming; Stocker, Dennis P.

    1995-01-01

    This paper presents the ground-based results obtained to date in preparation of a proposed space experiment to study the role of large-scale structures in microgravity transitional and turbulent gas-jet diffusion flames by investigating the dynamics of vortex/flame interactions and their influence on flame characteristics. The overall objective is to gain an understanding of the fundamental characteristics of transitional and turbulent gas-jet diffusion flames. Understanding of the role of large-scale structures on the characteristics of microgravity transitional and turbulent flames will ultimately lead to improved understanding of normal-gravity turbulent combustion.

  8. Quantifying Characteristic Length Scales and Patterns in Topography

    NASA Astrophysics Data System (ADS)

    Schmiddunser, Matthias; Ehlers, Todd A.

    2014-05-01

    The geometry of mountain topography depends on climate, tectonic, and biologic processes that operate on different temporal and spatial scales. Quantitative measures of landscape geometry are of interest for a) identifying potential correlations with the different types of processes, and b) for comparing observed topography with calibrated landscape evolution models of different regions. Over the years, several of these geomorphic metrics have been developed and used. Most of these metrics are regional values, i.e. they are calculated over an area of specific extent. Usually a region's typical horizontal length scale, like the average ridge-to-valley-distance, is used for this. However, this value is often chosen arbitrarily from a visual assessment of the landscape. In this study we aim to develop a quantitative measure of landscape properties that identifies dominant trends in drainage spacing and orientation. This is done by taking into account variations in topographic relief on different wavelenghts. More specifically, we use an autocorrelation function that is evaluated for different directions, thereby identifying prevalent orientation of features. The area of interest is then subdivided into parts of the thus obtained size and the process repeated, so that higher order structures are revealed. The results not only provides a size for the area over which other geomorphic metrics can be calculated such as the mean slope or the hypsometric integral, but may also be used as an additional measure for the form of the landscape itself. The method is applied to three regions along the South American Pacific coastal areas between latitudes of 26S and 40S. The study areas have distinctly different climate and vegetation conditions, showing the effect of different landscape forms on the values obtained. Results indicate a systematic variation between the three investigated regions. In the northern drier part of the coast results indicate large variations in the obtained correlation lengths depending on orientation and distinct higher order features. This is in stark contrast to the southern most region where little variation in correlation length and only weak secondary structures can be seen.

  9. Charge Transfer Fluorescence and 34 nm Exciton Diffusion Length in Polymers with Electron Acceptor End Traps.

    PubMed

    Zaikowski, Lori; Mauro, Gina; Bird, Matthew; Karten, Brianne; Asaoka, Sadayuki; Wu, Qin; Cook, Andrew R; Miller, John R

    2015-06-18

    Photoexcitation of conjugated poly-2,7-(9,9-dihexylfluorene) polyfluorenes with naphthylimide (NI) and anthraquinone (AQ) electron-acceptor end traps produces excitons that form charge transfer states at the end traps. Intramolecular singlet exciton transport to end traps was examined by steady state fluorescence for polyfluorenes of 17-127 repeat units in chloroform, dimethylformamide (DMF), tetrahydrofuran (THF), and p-xylene. End traps capture excitons and form charge transfer (CT) states at all polymer lengths and in all solvents. The CT nature of the end-trapped states is confirmed by their fluorescence spectra, solvent and trap group dependence, and DFT descriptions. Quantum yields of CT fluorescence are as large as 46%. This strong CT emission is understood in terms of intensity borrowing. Energies of the CT states from onsets of the fluorescence spectra give the depths of the traps which vary with solvent polarity. For NI end traps, the trap depths are 0.06 (p-xylene), 0.13 (THF), and 0.19 eV (CHCl3). For AQ, CT fluorescence could be observed only in p-xylene where the trap depth is 0.27 eV. Quantum yields, emission energies, charge transfer energies, solvent reorganization, and vibrational energies were calculated. Fluorescence measurements on chains >100 repeat units indicate that end traps capture ?50% of the excitons, and that the exciton diffusion length is LD = 34 nm, which is much larger than diffusion lengths reported in polymer films or than previously known for diffusion along isolated chains. The efficiency of exciton capture depends on chain length but not on trap depth, solvent polarity, or which trap group is present. PMID:25531034

  10. Charge transfer fluorescence and 34 nm exciton diffusion length in polymers with electron acceptor end traps

    SciTech Connect

    Zaikowski, Lori; Mauro, Gina; Bird, Matthew; Karten, Brianne; Asaoka, Sadayuki; Wu, Qin; Cook, Andrew R.; Miller, John R.

    2014-12-22

    Photoexcitation of conjugated poly-2,7-(9,9-dihexylfluorene) polyfluorenes with naphthylimide (NI) and anthraquinone (AQ) electron-acceptor end traps produces excitons that form charge transfer states at the end traps. Intramolecular singlet exciton transport to end traps was examined by steady state fluorescence for polyfluorenes of 17 to 127 repeat units in chloroform, dimethylformamide (DMF), tetrahydrofuran (THF), and p-xylene. End traps capture excitons and form charge transfer (CT) states at all polymer lengths and in all solvents. The CT nature of the end-trapped states is confirmed by their fluorescence spectra, solvent and trap group dependence and DFT descriptions. Quantum yields of CT fluorescence are as large as 46%. This strong CT emission is understood in terms of intensity borrowing. Energies of the CT states from onsets of the fluorescence spectra give the depths of the traps which vary with solvent polarity. For NI end traps the trap depths are 0.06 (p-xylene), 0.13 (THF) and 0.19 eV (CHCl3). For AQ, CT fluorescence could be observed only in p-xylene where the trap depth is 0.27 eV. Quantum yields, emission energies, charge transfer energies, solvent reorganization and vibrational energies were calculated. Fluorescence measurements on chains >100 repeat units indicate that end traps capture ~50% of the excitons, and that the exciton diffusion length LD =34 nm, which is much larger than diffusion lengths reported in polymer films or than previously known for diffusion along isolated chains. As a result, the efficiency of exciton capture depends on chain length, but not on trap depth, solvent polarity or which trap group is present.

  11. Charge transfer fluorescence and 34 nm exciton diffusion length in polymers with electron acceptor end traps

    DOE PAGESBeta

    Zaikowski, Lori; Mauro, Gina; Bird, Matthew; Karten, Brianne; Asaoka, Sadayuki; Wu, Qin; Cook, Andrew R.; Miller, John R.

    2014-12-22

    Photoexcitation of conjugated poly-2,7-(9,9-dihexylfluorene) polyfluorenes with naphthylimide (NI) and anthraquinone (AQ) electron-acceptor end traps produces excitons that form charge transfer states at the end traps. Intramolecular singlet exciton transport to end traps was examined by steady state fluorescence for polyfluorenes of 17 to 127 repeat units in chloroform, dimethylformamide (DMF), tetrahydrofuran (THF), and p-xylene. End traps capture excitons and form charge transfer (CT) states at all polymer lengths and in all solvents. The CT nature of the end-trapped states is confirmed by their fluorescence spectra, solvent and trap group dependence and DFT descriptions. Quantum yields of CT fluorescence are asmore » large as 46%. This strong CT emission is understood in terms of intensity borrowing. Energies of the CT states from onsets of the fluorescence spectra give the depths of the traps which vary with solvent polarity. For NI end traps the trap depths are 0.06 (p-xylene), 0.13 (THF) and 0.19 eV (CHCl3). For AQ, CT fluorescence could be observed only in p-xylene where the trap depth is 0.27 eV. Quantum yields, emission energies, charge transfer energies, solvent reorganization and vibrational energies were calculated. Fluorescence measurements on chains >100 repeat units indicate that end traps capture ~50% of the excitons, and that the exciton diffusion length LD =34 nm, which is much larger than diffusion lengths reported in polymer films or than previously known for diffusion along isolated chains. As a result, the efficiency of exciton capture depends on chain length, but not on trap depth, solvent polarity or which trap group is present.« less

  12. Diffusion Characteristics of Upwind Schemes on Unstructured Triangulations

    NASA Technical Reports Server (NTRS)

    Wood, William A.; Kleb, William L.

    1998-01-01

    The diffusive characteristics of two upwind schemes, multi-dimensional fluctuation splitting and dimensionally-split finite volume, are compared for scalar advection-diffusion problems. Algorithms for the two schemes are developed for node-based data representation on median-dual meshes associated with unstructured triangulations in two spatial dimensions. Four model equations are considered: linear advection, non-linear advection, diffusion, and advection-diffusion. Modular coding is employed to isolate the effects of the two approaches for upwind flux evaluation, allowing for head-to-head accuracy and efficiency comparisons. Both the stability of compressive limiters and the amount of artificial diffusion generated by the schemes is found to be grid-orientation dependent, with the fluctuation splitting scheme producing less artificial diffusion than the dimensionally-split finite volume scheme. Convergence rates are compared for the combined advection-diffusion problem, with a speedup of 2-3 seen for fluctuation splitting versus finite volume when solved on the same mesh. However, accurate solutions to problems with small diffusion coefficients can be achieved on coarser meshes using fluctuation splitting rather than finite volume, so that when comparing convergence rates to reach a given accuracy, fluctuation splitting shows a 20-25 speedup over finite volume.

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

    PubMed Central

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

    2012-01-01

    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

  14. Defect density dependent photoluminescence yield and triplet diffusion length in rubrene

    NASA Astrophysics Data System (ADS)

    Irkhin, Pavel; Biaggio, Ivan; Zimmerling, Tino; Döbeli, Max; Batlogg, Bertram

    2016-02-01

    We investigate how excitonic processes in rubrene single crystals are affected by a deliberately implanted defect gradient induced by proton irradiation. Spatially resolved measurements show a gradually reduced photoluminescence quantum yield and triplet exciton diffusion length along the defect gradient. Both effects are caused by a decrease in the average triplet lifetime due to interaction with the implanted defects. The triplet lifetime was reduced by almost two orders of magnitude at the highest implanted defect density of 1017 cm-3. The strong sensitivity of the photoluminescence quantum yield to the defect density that is observed already at moderate excitation densities is caused by the combination of two effects: the dominant contribution of triplet-fusion to the observed photoluminescence and the long-range diffusion of triplet excitons.

  15. Diffusion length variation in 0.5- and 3-MeV-proton-irradiated, heteroepitaxial indium phosphide solar cells

    NASA Technical Reports Server (NTRS)

    Jain, Raj K.; Weinberg, Irving; Flood, Dennis J.

    1993-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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).

  17. Diffusion length measurement using the scanning electron microscope. [for silicon solar cell

    NASA Technical Reports Server (NTRS)

    Weizer, V. G.

    1975-01-01

    The present work describes a measuring technique employing the scanning electron microscope in which values of the true bulk diffusion length are obtained. It is shown that surface recombination effects can be eliminated through application of highly doped surface field layers. The effects of high injection level and low-high junction current generation are investigated. Results obtained with this technique are compared to those obtained by a penetrating radiation (X-ray) method, and a close agreement is found. The SEM technique is limited to cells that contain a back surface field layer.

  18. Gate-dependent carrier diffusion length in lead selenide quantum dot field-effect transistors.

    PubMed

    Otto, Tyler; Miller, Chris; Tolentino, Jason; Liu, Yao; Law, Matt; Yu, Dong

    2013-08-14

    We report a scanning photocurrent microscopy (SPCM) study of colloidal lead selenide (PbSe) quantum dot (QD) thin film field-effect transistors (FETs). PbSe QDs are chemically treated with sodium sulfide (Na2S) and coated with amorphous alumina (a-Al2O3) by atomic layer deposition (ALD) to obtain high mobility, air-stable FETs with a strongly gate-dependent conductivity. SPCM reveals a long photocurrent decay length of 1.7 ?m at moderately positive gate bias that decreases to below 0.5 ?m at large positive gate voltage and all negative gate voltages. After excluding other possible mechanisms including thermoelectric effects, a thick depletion width, and fringing electric fields, we conclude from photocurrent lifetime measurements that the diffusion of a small fraction of long-lived carriers accounts for the long photocurrent decay length. The long minority carrier lifetime is attributed to charge traps for majority carriers. PMID:23802707

  19. Method and apparatus for determining minority carrier diffusion length in semiconductors

    DOEpatents

    Moore, Arnold R. (Princeton, NJ)

    1984-02-21

    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. Steady or modulated illumination at several wavelengths 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 for each wavelength. A probe electrode immersed in an electrolyte solution containing redox couples (preferably quinhydrone) having an oxidation-reduction potential (E) in the order of +0.6 to -1.65 volts couples the SPV to a measurement system. The redox couple solution functions to create a liquid Schottky barrier at the surface of the material. The Schottky barrier is contacted by merely placing the probe in the solution. The redox solution is placed over and in contact with the material to be tested and light is passed through the solution to generate the SPV. To compensate for colored redox solutions a portion of the redox solution not over the material is also illuminated for determining the color compensated light intensity. Steady red light is also used as an optical bias to reduce deleterious space-charge effects that occur in amorphous silicon.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    Indium phosphide (InP) solar cells are being made on silicon (Si) wafers (InP/Si) to take advantage of both the radiation-hardness properties of the InP solar cell and the light weight and low cost of Si wafers compared to InP or germanium (Ge) wafers. The InP/Si cell application is for long duration and/or high radiation orbit space missions. InP/Si cells have higher absolute efficiency after a high radiation dose than gallium arsenide (GaAs) or silicon (Si) solar cells. In this work, base electron diffusion lengths in the N/P cell are extracted from measured AM0 short-circuit photocurrent at various irradiation levels out to an equivalent 1 MeV fluence of 1017 1 MeV electrons/sq cm for a 1 sq cm 12% BOL InP/Si cell. These values are then checked for consistency by comparing measured Voc data with a theoretical Voc model that includes a dark current term that depends on the extracted diffusion lengths.

  1. Absolute standard of diffusion length and lifetime of minority charge carriers in single-crystal silicon

    NASA Astrophysics Data System (ADS)

    Skidanov, V. A.

    2014-11-01

    A substantial difference in electron recombination cross sections on Fe-B complexes (?1) and on activated iron ions (?2) in boron-doped single-crystal silicon is used to independently determine the lifetime of electrons in the standard T st using the surface photo-emf method. Pairs of values of the lifetime T 1 and T 2 before and after the decomposition of the Fe-B complexes were measured for each of 600 ingots at arbitrary diffusion length L cal for the calibrating specimen and were placed on the plane ( T 1, T 2). At the boundary of the region filled with the points, ingots are presented that are only contaminated with iron ions, so that T 2/ T 1 = ?1/?2. The true values of L st and T st of the calibrating specimen and the ratio ?1/?2 = 12.5 0.5 are determined by selecting a new value of the diffusion length for the calibrating specimen, which straightens the boundary of the region filled with the points after the recalculation of the values of T 1 and T 2.

  2. Method and apparatus for determining minority carrier diffusion length in semiconductors

    DOEpatents

    Moore, Arnold R. (Princeton, NJ)

    1984-01-01

    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. Steady or modulated illumination at several wavelengths 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 for each wavelength. A drop of a transparent electrolyte solution containing redox couples (preferably quinhydrone) having an oxidation-reduction potential (E) in the order of +0.6 to -1.65 volts couples the SPV to a measurement system. The drop of redox couple solution functions to create a liquid Schottky barrier at the surface of the material. Illumination light is passed through a transparent rod supported over the surface and through the drop of transparent electrolyte. The drop is held in the gap between the rod and the surface. Steady red light is also used as an optical bias to reduce deleterious space-charge effects that occur in amorphous silicon.

  3. Determination of spin diffusion length of gold utilizing lateral spin valves

    NASA Astrophysics Data System (ADS)

    Ji, Yi

    2005-03-01

    Spin transport in lateral metallic structures is an intriguing, emerging area, which offers rich opportunities to explore complex spintronic devices. We demonstrate spin injection, diffusion, and detection in a series of lateral spin valves. A 220-nm wide and 20-nm thick gold wire is defined by e-beam lithography on a SiN substrate. Two permalloy (Py) electrodes, an injector and a detector, are subsequently overlaid on the Au wire. The charge current and spin current are separated by connecting current drain and voltage ground to opposite ends of the Au wire. A charge current that passes through the Py injector into the Au induces a spin accumulation, resulting in a split of the chemical potentials for the spin-up and spin-down electrons in the Au. The injected spins diffuse away on both sides of the injector, resulting in a spin current towards the detector even without a charge current. Depending on the relative orientations of the accumulated spin and the detector spin, a voltage contrast can be observed at the detector/Au interface. This separation of charge and spin currents results in a large percentage value of the spin signals, which rules out the possibilities of spurious effects such as AMR. By changing the injector-detector separation, we observe an exponential decay of the spin signals, and thus determine a spin diffusion length of 63 nm in Au at 10 K.

  4. Effective Channel Length Shortening and Mobility Increase of p-Channel Metal Oxide Semiconductor Transistors Resulting in Higher Drive Current Using Short Source-Drain Diffusion Length

    NASA Astrophysics Data System (ADS)

    See, Kwang-Seng; Lau, Wai-Shing; Liao, Hong; Eng, Chee-Wee; Tee, Kian-Meng; Quek, Elgin Kiok-Boone; Tee, Kheng-Chok; Chan, Lap-Hung

    2004-03-01

    Local lattice strain around the channel in metal oxide semiconductor (MOS) transistors of 0.13 ?m gate length using shallow trench isolation can be altered using different source-drain diffusion lengths (Lov). It is known that as Lov is reduced, the drive current of p-channel metal oxide semiconductor (PMOS) transistors can be increased due to stress-enhanced hole mobility. However, in this study, we found that as Lov is reduced below 0.62 ?m, the effective channel length (Leff) of the PMOS transistors is also reduced. This unexpected Leff shortening effect for very small Lov has instead led to a reduction of ?eff, as shown through our calculations. We thus propose that the drive current increase for Lov reduction is due to stress-enhanced hole mobility for larger Lov and that the Leff shortening due to stress-enhanced diffusion is the secondary and the more dominating mechanism for Lov values below 0.62 ?m.

  5. Transition to Spatio-Temporal Chaos with Increasing Length in the Reaction-Diffusion System

    NASA Astrophysics Data System (ADS)

    Trail, Collin; Tomlin, Brett; Olsen, Thomas; Wiener, Richard J.

    2003-11-01

    Calculations based up the Reaction-Diffusion model (H. Riecke and H.-G. Paap, Europhys. Lett. 14), 1235 (1991).have proven to be suggestive for a wide variety of pattern forming systems, including Taylor-Couette flow with hourglass geometry(Richard J. Wiener et al), Phys. Rev. E 55, 5489 (1997).. Seeking insight to guide experimental investigations, we extend these calculations. Previous calculations indicated that in smaller systems, only temporal chaos, located in a small region, would be observed, while in longer systems instabilities would form over a wide region. Our simulations explore this transition from purely temporal chaos to spatio-temporal chaos as the length of the system is increased.

  6. Minority carrier diffusion lengths and absorption coefficients in silicon sheet material

    NASA Technical Reports Server (NTRS)

    Dumas, K. A.; Swimm, R. T.

    1980-01-01

    Most of the methods which have been developed for the measurement of the minority carrier diffusion length of silicon wafers require that the material have either a Schottky or an ohmic contact. The surface photovoltage (SPV) technique is an exception. The SPV technique could, therefore, become a valuable diagnostic tool in connection with current efforts to develop low-cost processes for the production of solar cells. The technique depends on a knowledge of the optical absorption coefficient. The considered investigation is concerned with a reevaluation of the absorption coefficient as a function of silicon processing. A comparison of absorption coefficient values showed these values to be relatively consistent from sample to sample, and independent of the sample growth method.

  7. Diffusion characteristics of ethylene glycol in skeletal muscle.

    PubMed

    Oliveira, Luís M; Carvalho, Maria Inês; Nogueira, Elisabete M; Tuchin, Valery V

    2015-05-01

    Part of the optical clearing study in biological tissues concerns the determination of the diffusion characteristics of water and optical clearing agents in the subject tissue. Such information is sufficient to characterize the time dependence of the optical clearing mechanisms—tissue dehydration and refractive index (RI) matching. We have used a simple method based on collimated optical transmittance measurements made from muscle samples under treatment with aqueous solutions containing different concentrations of ethylene glycol (EG), to determine the diffusion time values of water and EG in skeletal muscle. By representing the estimated mean diffusion time values from each treatment as a function of agent concentration in solution, we could identify the real diffusion times for water and agent. These values allowed for the calculation of the correspondent diffusion coefficients for those fluids. With these results, we have demonstrated that the dehydration mechanism is the one that dominates optical clearing in the first minute of treatment, while the RI matching takes over the optical clearing operations after that and remains for a longer time of treatment up to about 10 min, as we could see for EG and thin tissue samples of 0.5 mm. PMID:25525766

  8. Diffusion characteristics of ethylene glycol in skeletal muscle

    NASA Astrophysics Data System (ADS)

    Oliveira, Luís M.; Carvalho, Maria Inês; Nogueira, Elisabete M.; Tuchin, Valery V.

    2015-05-01

    Part of the optical clearing study in biological tissues concerns the determination of the diffusion characteristics of water and optical clearing agents in the subject tissue. Such information is sufficient to characterize the time dependence of the optical clearing mechanisms-tissue dehydration and refractive index (RI) matching. We have used a simple method based on collimated optical transmittance measurements made from muscle samples under treatment with aqueous solutions containing different concentrations of ethylene glycol (EG), to determine the diffusion time values of water and EG in skeletal muscle. By representing the estimated mean diffusion time values from each treatment as a function of agent concentration in solution, we could identify the real diffusion times for water and agent. These values allowed for the calculation of the correspondent diffusion coefficients for those fluids. With these results, we have demonstrated that the dehydration mechanism is the one that dominates optical clearing in the first minute of treatment, while the RI matching takes over the optical clearing operations after that and remains for a longer time of treatment up to about 10 min, as we could see for EG and thin tissue samples of 0.5 mm.

  9. An explanation of the relationship between mass, metabolic rate and characteristic length for placental mammals

    PubMed Central

    2015-01-01

    The Mass, Metabolism and Length Explanation (MMLE) was advanced in 1984 to explain the relationship between metabolic rate and body mass for birds and mammals. This paper reports on a modernized version of MMLE. MMLE deterministically computes the absolute value of Basal Metabolic Rate (BMR) and body mass for individual animals. MMLE is thus distinct from other examinations of these topics that use species-averaged data to estimate the parameters in a statistically best fit power law relationship such as BMR = a(bodymass)b. Beginning with the proposition that BMR is proportional to the number of mitochondria in an animal, two primary equations are derived that compute BMR and body mass as functions of an individual animal’s characteristic length and sturdiness factor. The characteristic length is a measureable skeletal length associated with an animal’s means of propulsion. The sturdiness factor expresses how sturdy or gracile an animal is. Eight other parameters occur in the equations that vary little among animals in the same phylogenetic group. The present paper modernizes MMLE by explicitly treating Froude and Strouhal dynamic similarity of mammals’ skeletal musculature, revising the treatment of BMR and using new data to estimate numerical values for the parameters that occur in the equations. A mass and length data set with 575 entries from the orders Rodentia, Chiroptera, Artiodactyla, Carnivora, Perissodactyla and Proboscidea is used. A BMR and mass data set with 436 entries from the orders Rodentia, Chiroptera, Artiodactyla and Carnivora is also used. With the estimated parameter values MMLE can calculate characteristic length and sturdiness factor values so that every BMR and mass datum from the BMR and mass data set can be computed exactly. Furthermore MMLE can calculate characteristic length and sturdiness factor values so that every body mass and length datum from the mass and length data set can be computed exactly. Whether or not MMLE can calculate a sturdiness factor value so that an individual animal’s BMR and body mass can be simultaneously computed given its characteristic length awaits analysis of a data set that simultaneously reports all three of these items for individual animals. However for many of the addressed MMLE homogeneous groups, MMLE can predict the exponent obtained by regression analysis of the BMR and mass data using the exponent obtained by regression analysis of the mass and length data. This argues that MMLE may be able to accurately simultaneously compute BMR and mass for an individual animal. PMID:26355655

  10. The narrow pulse approximation and long length scale determination in xenon gas diffusion NMR studies of model porous media

    NASA Technical Reports Server (NTRS)

    Mair, R. W.; Sen, P. N.; Hurlimann, M. D.; Patz, S.; Cory, D. G.; Walsworth, R. L.

    2002-01-01

    We report a systematic study of xenon gas diffusion NMR in simple model porous media, random packs of mono-sized glass beads, and focus on three specific areas peculiar to gas-phase diffusion. These topics are: (i) diffusion of spins on the order of the pore dimensions during the application of the diffusion encoding gradient pulses in a PGSE experiment (breakdown of the narrow pulse approximation and imperfect background gradient cancellation), (ii) the ability to derive long length scale structural information, and (iii) effects of finite sample size. We find that the time-dependent diffusion coefficient, D(t), of the imbibed xenon gas at short diffusion times in small beads is significantly affected by the gas pressure. In particular, as expected, we find smaller deviations between measured D(t) and theoretical predictions as the gas pressure is increased, resulting from reduced diffusion during the application of the gradient pulse. The deviations are then completely removed when water D(t) is observed in the same samples. The use of gas also allows us to probe D(t) over a wide range of length scales and observe the long time asymptotic limit which is proportional to the inverse tortuosity of the sample, as well as the diffusion distance where this limit takes effect (approximately 1-1.5 bead diameters). The Pade approximation can be used as a reference for expected xenon D(t) data between the short and the long time limits, allowing us to explore deviations from the expected behavior at intermediate times as a result of finite sample size effects. Finally, the application of the Pade interpolation between the long and the short time asymptotic limits yields a fitted length scale (the Pade length), which is found to be approximately 0.13b for all bead packs, where b is the bead diameter. c. 2002 Elsevier Sciences (USA).

  11. Moisture diffusion parameter characteristics for epoxy composites and neat resins

    NASA Technical Reports Server (NTRS)

    Long, E. R., Jr.

    1979-01-01

    The moisture absorption characteristics of two graphite/epoxy composites and their corresponding cured neat resins were studied in high humidity and water immersion environments at elevated temperatures. Moisture absorption parameters, such as equilibrium moisture content and diffusion coefficient derived from data taken on samples exposed to high humidity and water soak environments, were compared. Composite swelling in a water immersion environment was measured. Tensile strengths of cured neat resin were measured as a function of their equilibrium moisture content after exposure to different moisture environments. The effects of intermittent moderate tensile loads on the moisture absorption parameters of composite and cured neat resin samples were determined.

  12. Study on electrical characteristics of barrier-free atmospheric air diffuse discharge generated by nanosecond pulses and long wire electrodes

    SciTech Connect

    Li, Lee Liu, Yun-Long; Teng, Yun; Liu, Lun; Pan, Yuan

    2014-07-15

    In room-temperature atmospheric air, the large-scale diffuse plasmas can be generated via high-voltage nanosecond pulses with short rise-time and wire electrodes. Diffuse discharge with the wire electrode length up to 110.0 cm and the discharge spacing of several centimeters has been investigated in this paper. Electrical characteristics of diffuse discharge have been analyzed by their optical photographs and measuring of the voltage and current waveforms. Experimental results show the electrode spacing, and the length of wire electrodes can influence the intensity and mode transition of diffuse discharge. The characteristic of current waveforms is that there are several current oscillation peaks at the time of applied pulsed voltage peak, and at the tail of applied pulse, the conduction current component will compensate the displacement one so that the measured current is unidirectional in diffuse discharge mode. The transition from diffuse discharge to arc discharge is always with the increasing of conduction current density. As for nanosecond pulses with long tail, the long wire electrodes are help for generating non-equilibrium diffuse plasmas.

  13. PbSe/PbSrSe MQW characteristic temperature relationship with laser cavity length

    NASA Astrophysics Data System (ADS)

    Khodr, M.

    2015-08-01

    A potential materials system that may play a key role in IR spectroscopy applications is PbSe/Pb0.934 Sr0.066Se quantum well structure. In this work, the characteristic temperature (T0) relationship with laser cavity length was studied for this material system at three temperature ranges 77lengths then decreases to an almost constant value after some critical length. The data were best fitted to a second degree polynomials which can be used to determine these critical values. Also, we analyzed the effects of quantum efficiency on the characteristic temperature values. Inclusion of theoretical values for the quantum efficiency due to Auger recombination and leakage current reduces the characteristic temperature T0 in these ranges. It was found that inclusion of the quantum efficiency decreases the characteristic temperature by 60% for a wide range of cavity lengths.

  14. Relation Between Discharge Length and Laser Pulse Characteristics in Longitudinally Excited CO2 Laser

    NASA Astrophysics Data System (ADS)

    Uno, Kazuyuki; Dobashi, Kazuma; Akitsu, Tetsuya; Jitsuno, Takahisa

    2013-04-01

    A longitudinally excited CO2 laser pumped by a fast discharge emits a short laser pulse, similarly to TEA and Q-switched CO2 lasers. We investigated the relation between the discharge length and the laser pulse characteristics to develop a longitudinally excited CO2 laser producing a high spike laser pulse. We examined discharge lengths of 30, 45, and 60 cm, using the same mirrors and the same excitation circuit with the same input energy. A longer discharge length increased the discharge volume and improved the laser output energy. However, the longer discharge length caused a long discharge formation time (a slow fall time of the discharge voltage) due to the higher discharge impedance, which resulted in a long laser pulse tail. Therefore, the longitudinally excited CO2 laser had optimum conditions for obtaining a high spike laser pulse effectively.

  15. CHARACTERISTIC LENGTH OF ENERGY-CONTAINING STRUCTURES AT THE BASE OF A CORONAL HOLE

    SciTech Connect

    Abramenko, V. I.; Yurchyshyn, V. B.; Goode, P. R.; Ahn, K.; Cao, W.; Zank, G. P.; Dosch, A.

    2013-08-20

    An essential parameter for models of coronal heating and fast solar wind acceleration that rely on the dissipation of MHD turbulence is the characteristic energy-containing length {lambda} of the squared velocity and magnetic field fluctuations (u{sup 2} and b{sup 2}) transverse to the mean magnetic field inside a coronal hole (CH) at the base of the corona. The characteristic length scale directly defines the heating rate. We use a time series analysis of solar granulation and magnetic field measurements inside two CHs obtained with the New Solar Telescope at Big Bear Solar Observatory. A data set for transverse magnetic fields obtained with the Solar Optical Telescope/Spectro-Polarimeter on board the Hinode spacecraft was utilized to analyze the squared transverse magnetic field fluctuations b{sub t}{sup 2}. Local correlation tracking was applied to derive the squared transverse velocity fluctuations u {sup 2}. We find that for u {sup 2} structures, the Batchelor integral scale {lambda} varies in a range of 1800-2100 km, whereas the correlation length sigmav and the e-folding length L vary between 660 and 1460 km. Structures for b{sub t}{sup 2} yield {lambda} Almost-Equal-To 1600 km, sigmav Almost-Equal-To 640 km, and L Almost-Equal-To 620 km. An averaged (over {lambda}, sigmav, and L) value of the characteristic length of u {sup 2} fluctuations is 1260 {+-} 500 km, and that of b{sub t}{sup 2} is 950 {+-} 560 km. The characteristic length scale in the photosphere is approximately 1.5-50 times smaller than that adopted in previous models (3-30 Multiplication-Sign 10{sup 3} km). Our results provide a critical input parameter for current models of coronal heating and should yield an improved understanding of fast solar wind acceleration.

  16. Energetic, crystallographic and diffusion characteristics of hydrogen isotopes in iron

    NASA Astrophysics Data System (ADS)

    Sivak, A. B.; Sivak, P. A.; Romanov, V. A.; Chernov, V. M.

    2015-06-01

    Energetic, crystallographic and diffusion characteristics of various interstitial configurations of H atoms and their complexes with self-point defects (SIA - self-interstitial atom, V - vacancy) in bcc iron have been calculated by molecular statics and molecular dynamics using Fe-H interatomic interaction potential developed by Ramasubramaniam et al. (2009) and modified by the authors of the present work and Fe-Fe matrix potential M07 developed by Malerba et al. (2010). The most energetically favorable configuration of an interstitial H atom is tetrahedral configuration. The energy barrier for H atom migration is 0.04 eV. The highest binding energy of all the considered complexes "vacancy - H atom" and "SIA - H atom" is 0.54 and 0.15 eV, respectively. The binding energy of H atom with edge dislocations in slip systems <1 1 1>{1 1 0}, <1 1 1>{1 1 2}, <1 0 0>{1 0 0}, <1 0 0>{1 1 0} is 0.32, 0.30, 0.45, 0.54 eV, respectively. The binding energy of H atom in VHn complexes (n = 1 … 15) decreases from 0.54 to 0.35 eV with increasing of n from 1 to 6. At n > 6, it decreases to ∼0.1 eV. The temperature dependences of hydrogen isotopes (P, D, T) diffusivities have been calculated for the temperature range 70-1800 K. Arrhenius-type dependencies describe the calculated data at temperatures T < 100 K. At T > 250 K, the temperature dependencies of the diffusivities DP, DD, DT have a parabolic form. The diffusivities of H isotopes are within 10% at room temperature. The isotope effect becomes stronger at higher temperatures, e.g., ratios DP/DD and DP/DT at 1800 K equal 1.23 and 1.40, respectively.

  17. The use of multiple EBIC curves and low voltage electron microscopy in the measurement of small diffusion lengths

    NASA Technical Reports Server (NTRS)

    Leon, R. P.

    1987-01-01

    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.

  18. Neighborhood Characteristics and Leukocyte Telomere Length: The Multi-Ethnic Study of Atherosclerosis

    PubMed Central

    Needham, Belinda L.; Carroll, Judith E.; Diez Roux, Ana V.; Fitzpatrick, Annette L.; Moore, Kari; Seeman, Teresa E.

    2014-01-01

    Telomeres are the protective caps at the ends of eukaryotic chromosomes. Telomeres get shorter each time a cell divides, and critically shortened telomeres trigger cellular senescence. Thus, telomere length is hypothesized to be a biological marker of aging. The purpose of this study was to examine the association between neighborhood characteristics and leukocyte telomere length. Using data from a subsample (n=978) of the Multi-Ethnic Study of Atherosclerosis, a population-based study of women and men aged 4584, we found that neighborhood social environment (but not neighborhood socioeconomic disadvantage) was associated with telomere length. Respondents who lived in neighborhoods characterized by lower aesthetic quality, safety, and social cohesion had shorter telomeres than those who lived in neighborhoods with a more salutary social environment, even after adjusting for individual-level socioeconomic status and biomedical and lifestyle factors related to telomere length. Telomere length may be one biological mechanism by which neighborhood characteristics influence an individuals risk of disease and death. PMID:24859373

  19. An Imaging System for Automated Characteristic Length Measurement of Debrisat Fragments

    NASA Technical Reports Server (NTRS)

    Moraguez, Mathew; Patankar, Kunal; Fitz-Coy, Norman; Liou, J.-C.; Sorge, Marlon; Cowardin, Heather; Opiela, John; Krisko, Paula H.

    2015-01-01

    The debris fragments generated by DebriSat's hypervelocity impact test are currently being processed and characterized through an effort of NASA and USAF. The debris characteristics will be used to update satellite breakup models. In particular, the physical dimensions of the debris fragments must be measured to provide characteristic lengths for use in these models. Calipers and commercial 3D scanners were considered as measurement options, but an automated imaging system was ultimately developed to measure debris fragments. By automating the entire process, the measurement results are made repeatable and the human factor associated with calipers and 3D scanning is eliminated. Unlike using calipers to measure, the imaging system obtains non-contact measurements to avoid damaging delicate fragments. Furthermore, this fully automated measurement system minimizes fragment handling, which reduces the potential for fragment damage during the characterization process. In addition, the imaging system reduces the time required to determine the characteristic length of the debris fragment. In this way, the imaging system can measure the tens of thousands of DebriSat fragments at a rate of about six minutes per fragment, compared to hours per fragment in NASA's current 3D scanning measurement approach. The imaging system utilizes a space carving algorithm to generate a 3D point cloud of the article being measured and a custom developed algorithm then extracts the characteristic length from the point cloud. This paper describes the measurement process, results, challenges, and future work of the imaging system used for automated characteristic length measurement of DebriSat fragments.

  20. Renal Water Molecular Diffusion Characteristics in Healthy Native Kidneys: Assessment with Diffusion Tensor MR Imaging

    PubMed Central

    Zheng, Zhenfeng; Shi, Huilan; Zhang, Jing; Zhang, Yunting

    2014-01-01

    Background To explore the characteristics of diffusion tensor imaging (DTI) and magnetic resonance (MR) imaging in healthy native kidneys. Methods Seventy-three patients without chronic kidney disease underwent DTI-MRI with spin echo-echo planar (SE-EPI) sequences accompanied by an array spatial sensitivity encoding technique (ASSET). Cortical and medullary mean, axial and radial diffusivity (MD, AD and RD), fractional anisotropy (FA) and primary, secondary and tertiary eigenvalues (?1, ?2, ?3) were analysed in both kidneys and in different genders. Results Cortical MD, ?2, ?3, and RD values were higher than corresponding medullary values. The cortical FA value was lower than the medullary FA value. Medullary ?1 and RD values in the left kidney were lower than in the right kidney. Medullary ?2, and ?3 values in women were higher than those in men. Medullary FA values in women were lower than those in men. Medullary FA (r?=?0.351, P?=?0.002) and ?1 (r?=?0.277, P?=?0.018) positively correlated with eGFR. Medullary FA (r?=??0.25, P?=?0.033) negatively correlated with age. Conclusions Renal water molecular diffusion differences exist in human kidneys and genders. Age and eGFR correlate with medullary FA and primary eigenvalue. PMID:25470776

  1. Characterization of Tissue Structure at Varying Length Scales Using Temporal Diffusion Spectroscopy

    PubMed Central

    Gore, John C.; Xu, Junzhong; Colvin, Daniel C.; Yankeelov, Thomas E.; Parsons, Edward C.; Does, Mark D.

    2011-01-01

    The concepts, theoretical behavior and experimental applications of temporal diffusion spectroscopy are reviewed and illustrated. Temporal diffusion spectra are obtained by using oscillating gradient waveforms in diffusion-weighted measurements, and represent the manner in which various spectral components of molecular velocity correlations vary in different geometrical structures that restrict or hinder free movements. Measurements made at different gradient frequencies reveal information on the scale of restrictions or hindrances to free diffusion, and the shape of a spectrum reveals the relative contributions of spatial restrictions at different distance scales. Such spectra differ from other so-called diffusion spectra which depict spatial frequencies and are defined at a fixed diffusion time. Experimentally, oscillating gradients at moderate frequency are more feasible for exploring restrictions at very short distances, which in tissues correspond to structures smaller than cells. We describe the underlying concepts of temporal diffusion spectra and provide analytical expressions for the behavior of the diffusion coefficient as a function of gradient frequency in simple geometries with different dimensions. Diffusion in more complex model media that mimic tissues has been simulated using numerical methods. Experimental measurements of diffusion spectra have been obtained in suspensions of particles and cells, as well as in vivo in intact animals. An observation of particular interest is the increased contrast and heterogeneity observed in tumors using oscillating gradients at moderate frequency compared to conventional pulse gradient methods, and the potential for detecting changes in tumors early in their response to treatment. Computer simulations suggest that diffusion spectral measurements may be sensitive to intracellular structures such as nuclear size, and that changes in tissue diffusion properties may be measured before there are changes in cell density. PMID:20677208

  2. Increasing polymer diffusivity by increasing the contour length: The surprising effect of YOYO-1 on DNA dynamics

    NASA Astrophysics Data System (ADS)

    Shin, Seunghwan; Dorfman, Kevin; Cheng, Xiang

    2015-03-01

    Double-stranded DNA (dsDNA) labeled with cyanine dyes such as YOYO-1 has been extensively used as a model to study equilibrium and dynamic properties of semiflexible polyelectrolytes. The ability to directly visualize the polymer dynamics is an attractive feature of these experiments, but positively charged cyanine dyes affect the physical properties of dsDNA, distorting the double helix and counterbalancing the intrinsic negative charge of the backbone. A variety of studies have been conducted to reveal the effect of the dye on the contour length and the persistence length of dsDNA. However, fewer efforts have been made to directly quantify the effect of dye on the diffusion behavior of dsDNA. In order to resolve this issue, we measured the in-plane diffusion coefficient of unconfined dsDNA using confocal microscopy. Although there is widespread consensus that intercalation increases the contour length of dsDNA, we find that increasing the dye:base pair ratio for YOYO-1 actually enhances the diffusion of dsDNA. This enhancement is more significant at lower ionic strengths, which implies that the increase in the diffusion coefficient by dye-DNA intercalation is mainly due to a reduction of excluded volume effect resulting from charge neutralization on the backbone.

  3. Identifying local characteristic lengths governing sound wave properties in solid foams

    NASA Astrophysics Data System (ADS)

    Tan Hoang, Minh; Perrot, Camille

    2013-02-01

    Identifying microscopic geometric properties and fluid flow through opened-cell and partially closed-cell solid structures is a challenge for material science, in particular, for the design of porous media used as sound absorbers in building and transportation industries. We revisit recent literature data to identify the local characteristic lengths dominating the transport properties and sound absorbing behavior of polyurethane foam samples by performing numerical homogenization simulations. To determine the characteristic sizes of the model, we need porosity and permeability measurements in conjunction with ligament lengths estimates from available scanning electron microscope images. We demonstrate that this description of the porous material, consistent with the critical path picture following from the percolation arguments, is widely applicable. This is an important step towards tuning sound proofing properties of complex materials.

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

    NASA Technical Reports Server (NTRS)

    Ghaderi, M.; Gupta, A. K.

    2003-01-01

    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.

  5. Factorial Moments Analyses Show a Characteristic Length Scale in DNA Sequences

    NASA Astrophysics Data System (ADS)

    Mohanty, A. K.; Narayana Rao, A. V. S. S.

    2000-02-01

    A unique feature of most of the DNA sequences, found through the factorial moments analysis, is the existence of a characteristic length scale around which the density distribution is nearly Poissonian. Above this point, the DNA sequences, irrespective of their intron contents, show long range correlations with a significant deviation from the Gaussian statistics, while, below this point, the DNA statistics are essentially Gaussian. The famous DNA walk representation is also shown to be a special case of the present analysis.

  6. Optimization design of strong and tough nacreous nanocomposites through tuning characteristic lengths

    NASA Astrophysics Data System (ADS)

    Ni, Yong; Song, Zhaoqiang; Jiang, Hongyuan; Yu, Shu-Hong; He, Linghui

    2015-08-01

    How nacreous nanocomposites with optimal combinations of stiffness, strength and toughness depend on constituent property and microstructure parameters is studied using a nonlinear shear-lag model. We show that the interfacial elasto-plasticity and the overlapping length between bricks dependent on the brick size and brick staggering mode significantly affect the nonuniformity of the shear stress, the stress-transfer efficiency and thus the failure path. There are two characteristic lengths at which the strength and toughness are optimized respectively. Simultaneous optimization of the strength and toughness is achieved by matching these lengths as close as possible in the nacreous nanocomposite with regularly staggered brick-and-mortar (BM) structure where simultaneous uniform failures of the brick and interface occur. In the randomly staggered BM structure, as the overlapping length is distributed, the nacreous nanocomposite turns the simultaneous uniform failure into progressive interface or brick failure with moderate decrease of the strength and toughness. Specifically there is a parametric range at which the strength and toughness are insensitive to the brick staggering randomness. The obtained results propose a parametric selection guideline based on the length matching for rational design of nacreous nanocomposites. Such guideline explains why nacre is strong and tough while most artificial nacreous nanocomposites aere not.

  7. Doping level dependence of electron irradiation-induced minority carrier diffusion length increase in Mg-doped GaN

    SciTech Connect

    Lopatiuk-Tirpak, O.; Chernyak, L.; Wang, Y. L.; Ren, F.; Pearton, S. J.; Gartsman, K.

    2007-08-27

    The electron irradiation-induced increase of minority carrier diffusion length was studied as a function of hole concentration in Mg-doped GaN. Variable-temperature electron beam induced current measurements yielded activation energies of 264, 254, 171, and 144 meV for samples with hole concentrations of 2x10{sup 16}, 9x10{sup 16}, 3x10{sup 18}, and 7x10{sup 18} cm{sup -3}, respectively. This carrier concentration dependence of the activation energy for the effects of electron irradiation was found to be consistent with Mg acceptors, indicating the involvement of the latter levels in the irradiation-induced diffusion length increase.

  8. The spin Hall angle and spin diffusion length of Pd measured by spin pumping and microwave photoresistance

    SciTech Connect

    Tao, X. D.; Feng, Z.; Miao, B. F.; Sun, L.; You, B.; Wu, D.; Du, J.; Zhang, W.; Ding, H. F.

    2014-05-07

    We present the experimental study of the spin Hall angle (SHA) and spin diffusion length of Pd with the spin pumping and microwave photoresistance effects. The Py/Pd bilayer stripes are excited with an out-of-plane microwave magnetic field. The pure spin current is thus pumped and transforms into charge current via the inverse spin Hall effect (ISHE) in Pd layer, yielding an ISHE voltage. The ISHE voltage can be distinguished from the unwanted signal caused by the anisotropic magnetoresistance according to their different symmetries. Together with Pd thickness dependent measurements of in and out-of-plane precessing angles and effective spin mixing conductance, the SHA and spin-diffusion length of Pd are quantified as 0.0056 ± 0.0007 and 7.3 ± 0.7 nm, respectively.

  9. Fluorescence Correlation Spectroscopy Measurements of the Membrane Protein TetA in Escherichia coli Suggest Rapid Diffusion at Short Length Scales

    PubMed Central

    Chow, David; Guo, Lin; Gai, Feng; Goulian, Mark

    2012-01-01

    Structural inhomogeneities in biomembranes can lead to complex diffusive behavior of membrane proteins that depend on the length or time scales that are probed. This effect is well studied in eukaryotic cells, but has been explored only recently in bacteria. Here we used fluorescence recovery after photobleaching (FRAP) and fluorescence correlation spectroscopy (FCS) to study diffusion of the membrane protein TetA-YFP in E. coli. We find that the diffusion constant determined from FRAP is comparable to other reports of inner membrane protein diffusion constants in E. coli. However, FCS, which probes diffusion on shorter length scales, gives a value that is almost two orders of magnitude higher and is comparable to lipid diffusion constants. These results suggest there is a population of TetA-YFP molecules in the membrane that move rapidly over short length scales (? 400 nm) but move significantly more slowly over the longer length scales probed by FRAP. PMID:23119068

  10. Characteristics of Cluster Implantation and Low Diffusion Annealing

    SciTech Connect

    Nagayama, Tsutomu; Hamamoto, Nariaki; Umisedo, Sei; Tanjyo, Masayasu; Ootsuka, Fumio; Aoyama, Takayuki

    2008-11-03

    Beyond 45 nm device fabrication, it is recognized that the ultra-shallow junction (USJ) formation is required, which is achieved by the ultra-low energy ion implantation and ultra-low diffusion annealing. For this purpose, Cluster ion implantation (CII) and the Flash lamp annealing (FLA) activation processes have been developed. In this paper, we introduce characteristics of activation using B{sub 18}Hx{sup +} implantation with FLA, which are applied to a source drain extension (SDE) for pMOSFET in Hgh-k/metal process. We will prove that the combined process of B{sub 18}Hx{sup +} and FLA can make the low sheet resistance and the fine crystal recovery for USJ formation such a SDE. Moreover, the combined process of C{sub 7}Hx{sup +} implantation and FLA can make the high stress region for nMOSFET by the high substitutional Carbon. If both of B{sub 18}Hx{sup +} implantation and C{sub 7}Hx{sup +} implantation with FLA are applied to High-k/metal process, it will give the highest performance. The combination of FLA and cluster ion implanter ''CLARIS'' which is developed for IC fabrication, will promise the most powerful performance beyond 45 nm node device.

  11. Air entry-based characteristic length improves permeability estimates for compacted earth materials

    NASA Astrophysics Data System (ADS)

    Assouline, S.; Or, D.

    2007-12-01

    The permeability, k, of porous media is required for quantifying flow and transport processes in hydrology, civil, agriculture and petroleum engineering and is often estimated from medium porosity and additional constraints. Changes in porosity of earth materials due to compaction by anthropogenic activities or overburden result in a reduction in mean pore sizes and a decrease of k. Permeability is often expressed as proportional to a characteristic length squared and inversely proportional to a porosity factor, pore shape, and tortuosity of the material. Various characteristic lengths for the porous medium were proposed such as the hydraulic radius of Kozeny-Carman, or limiting pore size derived from critical path analysis. We introduce a characteristic length related to the air entry value compatible with Aissen formula that accommodates complex pore shapes. The proposed model includes a geometrical (tortuosity) factor and links relative changes in porosity to concurrent changes in k. The model was evaluated for three different groups of natural porous media: sands, sandstones with different cementing agents, and unconsolidated soils. For clay-free sands and unconsolidated soils, the model provides reasonable predictions for the entire range of porosities found in laboratory or field experiments. However, for sandstones with cementing agents, the model is valid up to a critical porosity where pore structure seems to collapse and k reduces drastically. The geometrical factor for soils was influenced by silt-to-clay ratio, while for granular media, it was correlated with mean grain diameter. The model offers improvement in predicting k and provides a means for incorporating critical pore size (air entry) information in addition to porosity.

  12. Derivation of effective fission gas diffusivities in UO2 from lower length scale simulations and implementation of fission gas diffusion models in BISON

    SciTech Connect

    Andersson, Anders David Ragnar; Pastore, Giovanni; Liu, Xiang-Yang; Perriot, Romain Thibault; Tonks, Michael; Stanek, Christopher Richard

    2014-11-07

    This report summarizes the development of new fission gas diffusion models from lower length scale simulations and assessment of these models in terms of annealing experiments and fission gas release simulations using the BISON fuel performance code. Based on the mechanisms established from density functional theory (DFT) and empirical potential calculations, continuum models for diffusion of xenon (Xe) in UO2 were derived for both intrinsic conditions and under irradiation. The importance of the large XeU3O cluster (a Xe atom in a uranium + oxygen vacancy trap site with two bound uranium vacancies) is emphasized, which is a consequence of its high mobility and stability. These models were implemented in the MARMOT phase field code, which is used to calculate effective Xe diffusivities for various irradiation conditions. The effective diffusivities were used in BISON to calculate fission gas release for a number of test cases. The results are assessed against experimental data and future directions for research are outlined based on the conclusions.

  13. Dependence of cobaltocenium diffusion in ionic liquids on the alkyl chain length of 1-alkyl-3-methylimidazolium cations.

    PubMed

    Ueda, Hiroyuki; Nishiyama, Katsuhiko; Yoshimoto, Soichiro

    2016-02-01

    The electrochemical behavior of cobaltocenium (Cc(+)) on a Au(111) electrode was investigated in five 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([Cnmim][Tf2N], n = 2, 4, 6, 8, or 10) ionic liquids (ILs) in the temperature range from 293.15 to 343.15 K by cyclic voltammetry and chronoamperometry. The redox couple of Cc(+) exhibited a clear reversible one-electron reaction in all the [Cnmim][Tf2N] ILs. The diffusion coefficients of Cc(+) increased with an increase in the alkyl chain length of [Cnmim](+) and a decrease in the viscosity of the IL upon elevating the temperature. The viscosity of the IL plays an important role in determining the activation energy for the diffusion of Cc(+). The obtained results suggested that the alkyl chain length of [Cnmim](+) affects the strength of the interaction between Cc(+) and the surrounding ion species. The results also clarified that the equation proposed by Sutherland adequately describes the diffusion of Cc(+) in ILs when the effect of the type of IL and the temperature on the product of the Stokes radius of Cc(+) and the Sutherland coefficient is considered. PMID:26751148

  14. Characteristic length scale of input data in distributed models: implications for modeling grain size

    USGS Publications Warehouse

    Artan, Guleid A.; Neale, C. M. U.; Tarboton, D. G.

    2000-01-01

    The appropriate spatial scale for a distributed energy balance model was investigated by: (a) determining the scale of variability associated with the remotely sensed and GIS-generated model input data; and (b) examining the effects of input data spatial aggregation on model response. The semi-variogram and the characteristic length calculated from the spatial autocorrelation were used to determine the scale of variability of the remotely sensed and GIS-generated model input data. The data were collected from two hillsides at Upper Sheep Creek, a sub-basin of the Reynolds Creek Experimental Watershed, in southwest Idaho. The data were analyzed in terms of the semivariance and the integral of the autocorrelation. The minimum characteristic length associated with the variability of the data used in the analysis was 15 m. Simulated and observed radiometric surface temperature fields at different spatial resolutions were compared. The correlation between agreement simulated and observed fields sharply declined after a 10×10 m2 modeling grid size. A modeling grid size of about 10×10 m2 was deemed to be the best compromise to achieve: (a) reduction of computation time and the size of the support data; and (b) a reproduction of the observed radiometric surface temperature.

  15. Effect of Crystal Defects on Minority Carrier Diffusion Length in 6H SiC Measured Using the Electron Beam Induced Current Method

    NASA Technical Reports Server (NTRS)

    Tabib-Azar, Massood

    1997-01-01

    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 cm, ranged from 1.46 microns to 0.68 microns. We next introduce a novel variation of the planar method used above. This 'planar mapping' technique measured diffusion length along a linescan creating a map of diffusion length versus position. This map is then overlaid onto the EBIC image of the corresponding linescan, allowing direct visualization of the effect of defects on minority carrier diffusion length. Measurements of the above n-type 6H SiC resulted in values of hole diffusion length ranging from 1.2 micron in defect free regions to below 0.1 gm at the center of large defects. In addition, measurements on p-type 6H SiC resulted in electron diffusion lengths ranging from 1.42 micron to 0.8 micron.

  16. Moisture Diffusivity Characteristics of Rough Rice Under Infrared Radiation Heating

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To design an efficient infrared (IR) dryer for rough rice, it is important to understand the drying behavior of rice grains under infrared heating. The objective of this study was to determine the moisture diffusivity and moisture diffusivity coefficient of rough rice under IR heating and cooling. ...

  17. Diffusion-coupled molecular assembly: structuring of coordination polymers across multiple length scales.

    PubMed

    Hirai, Kenji; Reboul, Julien; Morone, Nobuhiro; Heuser, John E; Furukawa, Shuhei; Kitagawa, Susumu

    2014-10-22

    Porous coordination polymers (PCPs) are an intriguing class of molecular-based materials because of the designability of framework scaffolds, pore sizes and pore surface functionalities. Besides the structural designability at the molecular scale, the structuring of PCPs into mesoscopic/macroscopic morphologies has attracted much attention due to the significance for the practical applications. The structuring of PCPs at the mesoscopic/macroscopic scale has been so far demonstrated by the spatial localization of coordination reactions on the surface of templates or at the phase boundaries. However, these methodologies have never been applied to the fabrication of solid-solution or multivariate metal-organic frameworks (MOFs), in which multiple components are homogeneously mixed. Herein, we demonstrate the structuring of a box-type superstructure comprising of a solid-solution PCP by integrating a bidirectional diffusion of multiple organic ligands into molecular assembly. The parent crystals of [Zn2(ndc)2(bpy)]n were placed in the DMF solution of additional organic component of H2bdc, and the temperature was rapidly elevated up to 80 C (ndc = 1,4-naphthalenedicarboxylate, bpy = 4,4'-bipyridyl, bdc = 1,4-benzenedicarboxylate). The dissolution of the parent crystals induced the outward diffusion of components; contrariwise, the accumulation of the other organic ligand of H2bdc induced the inward diffusion toward the surface of the parent crystals. This bidirectional diffusion of multiple components spatially localized the recrystallization at the surface of cuboid parent crystals; therefore, the nanocrystals of a solid-solution PCP ([Zn2(bdc)1.5(ndc)0.5(bpy)]n) were organized into a mesoscopic box superstructure. Furthermore, we demonstrated that the box superstructures enhanced the mass transfer kinetics for the separation of hydrocarbons. PMID:25254320

  18. Dynamics of lithium ions in borotellurite mixed former glasses: Correlation between the characteristic length scales of mobile ions and glass network structural units

    SciTech Connect

    Shaw, A.; Ghosh, A.

    2014-10-28

    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 BO{sub 4} units has been established for different compositions of the borotellurite glasses.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  20. Measurement of N-Type 6H SiC Minority-Carrier Diffusion Lengths by Electron Bombardment of Schottky Barriers

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Hakimzadeh, Roshanak

    1993-01-01

    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).

  2. Cathodoluminescence of stacking fault bound excitons for local probing of the exciton diffusion length in single GaN nanowires

    SciTech Connect

    Nogues, Gilles Den Hertog, Martien; Auzelle, Thomas; Gayral, Bruno; Daudin, Bruno

    2014-03-10

    We perform correlated studies of individual GaN nanowires in scanning electron microscopy combined to low temperature cathodoluminescence, microphotoluminescence, and scanning transmission electron microscopy. We show that some nanowires exhibit well localized regions emitting light at the energy of a stacking fault bound exciton (3.42?eV) and are able to observe the presence of a single stacking fault in these regions. Precise measurements of the cathodoluminescence signal in the vicinity of the stacking fault give access to the exciton diffusion length near this location.

  3. Reaction-Diffusion Model Simulations relevant to Modified Taylor-Couette Flow in Systems of Varying Length

    NASA Astrophysics Data System (ADS)

    Halmstad, Andrew; Olsen, Thomas; Wiener, Richard

    2006-11-01

    Previously, we have observed a period-doubling cascade to chaos in Modified Taylor-Couette Flow with Hourglass Geometry. Such behavior had been predicted by The Reaction-Diffusion model simulations. The chaotic formation of Taylor-Vortex pair formation was restricted to a very narrow band about the waist of the hourglass. It was suggested that with increasing lengths of systems, the chaotic region would expand. We present a battery of simulations to determine the variation of the size of the chaotic region with length, seeking the transition to spatio- temporal chaos. Richard J. Wiener et al, Phys. Rev. E 55, 5489 (1997). H. Riecke and H.-G. Paap, Europhys. Lett. 14, 1235 (1991).

  4. Characteristics of Li diffusion on silicene and zigzag nanoribbon

    NASA Astrophysics Data System (ADS)

    Yan-Hua, Guo; Jue-Xian, Cao; Bo, Xu

    2016-01-01

    We perform a density functional study on the adsorption and diffusion of Li atoms on silicene sheet and zigzag nanoribbons. Our results show that the diffusion energy barrier of Li adatoms on silicene sheet is 0.25 eV, which is much lower than on graphene and Si bulk. The diffusion barriers along the axis of zigzag silicene nanoribbon range from 0.1 to 0.25 eV due to an edge effect, while the diffusion energy barrier is about 0.5 eV for a Li adatom to enter into a silicene nanoribbon. Our calculations indicate that using silicene nanoribbons as anodes is favorable for a Li-ion battery. Project supported by the National Natural Science Foundation of China (Grant Nos. 11074212 and 11204123) and the Natural Science Foundation of Jiangsu province, China (Grant No. BK20130945).

  5. Preliminary breakdown of intracloud lightning: Initiation altitude, propagation speed, pulse train characteristics, and step length estimation

    NASA Astrophysics Data System (ADS)

    Wu, Ting; Yoshida, Satoru; Akiyama, Yasuhiro; Stock, Michael; Ushio, Tomoo; Kawasaki, Zen

    2015-09-01

    Using a low-frequency lightning location system comprising 11 sites, we located preliminary breakdown (PB) processes in 662 intracloud (IC) lightning flashes during the summer of 2013 in Osaka area of Japan. On the basis of three-dimensional location results, we studied initiation altitude and upward propagation speed of PB processes. PB in most IC flashes has an initiation altitude that ranges from 5 to 10 km with an average of 7.8 km. Vertical speed ranges from 0.5 to 17.8 105 m/s with an average of 4.0 105 m/s. Vertical speed is closely related with initiation altitude, with IC flashes initiated at higher altitude having lower vertical speed during PB stage. Characteristics of PB pulse trains including pulse rate, pulse amplitude, and pulse width are also analyzed. The relationship between pulse rate and vertical speed has the strongest correlation, suggesting that each PB pulse corresponds to one step of the initial leader during the PB stage. Pulse rate, pulse amplitude, and pulse width all show decreasing trends with increasing initiation altitude and increasing trends with increasing vertical speed. Using a simple model, the step length of the initial leader during the PB stage is estimated. Most of initial leaders have step lengths that range from 40 to 140 m with an average of 113 m. Estimated step length has a strong correlation with initiation altitude, indicating that leaders initiated at higher altitude have longer steps. Based on the results of this study, we speculate that above certain altitude (~12 km), initial leaders in PB stages of IC flashes may only have horizontal propagations. PB processes at very high altitude may also have very weak radiation, so detecting and locating them would be relatively difficult.

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

    SciTech Connect

    Lam, P

    2008-04-15

    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.

  7. Manipulating surface diffusion and elastic interactions to obtain quantum dot multilayer arrangements over different length scales

    SciTech Connect

    Placidi, E. Arciprete, F.; Latini, V.; Latini, S.; Patella, F.; Magri, R.

    2014-09-15

    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.

  8. Reacto-Diffusive Length of N2O5 in Aqueous Sulfate- and Chloride-Containing Aerosol Particles.

    PubMed

    Gaston, Cassandra J; Thornton, Joel A

    2016-02-25

    Heterogeneous reactions of dinitrogen pentoxide (N2O5) on aerosol particles impact air quality and climate, yet aspects of the relevant physical chemistry remain unresolved. One important consideration is the competing effects of diffusion and the rate of chemical reaction within the particle, which determines the length that N2O5 travels within a particle before reacting, referred to as the reacto-diffusive length (l). Large values of l imply a dependence of the reactive uptake efficiency of N2O5, i.e., ?(N2O5), on particle size. We present measurements of the size dependence of ?(N2O5) on aqueous sodium chloride, ammonium sulfate, and ammonium bisulfate particles. ?(N2O5) on ammonium sulfate and ammonium bisulfate particles ranged from 0.016 0.005 to 0.036 0.001 as the surface-area-weighted particle radius increased from 39 to 127 nm, resulting in an estimated l of 32 6 nm. In contrast, ?(N2O5) on sodium chloride particles was independent of particle size, suggesting a near-surface reaction dominated the uptake of N2O5. Differences in the reactivity of the N2O5 intermediate, NO2(+), with water and chloride can explain the observed dependencies. These results allow for parameterizations in atmospheric models to determine a more robust population mean value of ?(N2O5) that accounts for the distribution of particle sizes. PMID:26836323

  9. Optical absorption coefficient and minority carrier diffusion length measurements in low-cost silicon solar cell material

    SciTech Connect

    Swimm, R.T.; Dumas, K.A.

    1982-11-01

    The optical absorption coefficient of silicon solar cell material grown by three low-cost growth methods was measured in the wavelength interval 0.8< or =lambda< or =1.0 ..mu..m, the wavelength region of interest in surface photovoltage measurements of the minority carrier diffusion length. The square root of the absorption coefficient was found to vary linearly with photon energy over the wavelengths studied, and the measured data agree with a linear empirical fit to within 0.5% RMS. The absorption coefficients obtained are slightly lower than those reported by Runyan, with the greatest disagreement at long wavelengths. Minority carrier diffusion lengths computed using the present absorption coefficients are approximately 16% greater than those calculated using Runyan's data. Excellent sample-to-sample agreement within and between lots indicates that for two of the growth methods studied, material quality as judged by optical properties has not been sacrificed by the use of low-cost growth methods. Samples grown by the third growth method studied showed measurably poorer optical quality.

  10. Electron-beam-induced current determination of minority-carrier diffusion length and surface recombination velocity in mercury-cadmium-telluride

    NASA Astrophysics Data System (ADS)

    Artz, B. E.

    1985-04-01

    A method is presented for determining the minority-carrier diffusion length and surface recombination velocity in passivated, shallow junction semiconductor devices. The method is particularly useful with devices where the minority-carrier diffusion length is comparable to the diameter of the electron beam interaction volume. A gaussian beam profile is convoluted with a theoretical model for electron-beam-induced current and the results used to determine the minority-carrier diffusion length from measured data. The surface recombination velocity is estimated from the dependence of the measured minority-carrier diffusion length on the electron beam accelerating voltage. The technique is applied to a photovoltaic infrared sensor device made in mercury-cadmium-telluride.

  11. The impact of network characteristics on the diffusion of innovations

    NASA Astrophysics Data System (ADS)

    Peres, Renana

    2014-05-01

    This paper studies the influence of network topology on the speed and reach of new product diffusion. While previous research has focused on comparing network types, this paper explores explicitly the relationship between topology and measurements of diffusion effectiveness. We study simultaneously the effect of three network metrics: the average degree, the relative degree of social hubs (i.e., the ratio of the average degree of highly-connected individuals to the average degree of the entire population), and the clustering coefficient. A novel network-generation procedure based on random graphs with a planted partition is used to generate 160 networks with a wide range of values for these topological metrics. Using an agent-based model, we simulate diffusion on these networks and check the dependence of the net present value (NPV) of the number of adopters over time on the network metrics. We find that the average degree and the relative degree of social hubs have a positive influence on diffusion. This result emphasizes the importance of high network connectivity and strong hubs. The clustering coefficient has a negative impact on diffusion, a finding that contributes to the ongoing controversy on the benefits and disadvantages of transitivity. These results hold for both monopolistic and duopolistic markets, and were also tested on a sample of 12 real networks.

  12. The effect of characteristic length on mean free path for confined gases

    NASA Astrophysics Data System (ADS)

    P. D., Sree Hari; Prabha, Sooraj K.; Sathian, Sarith P.

    2015-11-01

    Molecular Dynamics simulations are performed to investigate the influence of system boundaries and characteristic length (L) of the system on the mean free path (MFP) of rarefied gas confined to the walls of a nano-channel. Isothermal Lennard-Jones fluid confined between Reflective walls and platinum walls at different number densities (0.31 atoms/nm3 and 1.61 atoms/nm3) are independently considered. The MFP is calculated by the Lagrangian approach of tracking the trajectory of each atom and averaging the distance between successive collisions. The percentage of fluid-wall collisions is observed to predominate over fluid-fluid collisions at high levels of rarefaction. The influence of L (varying from 6 nm to 16 nm) on MFP is examined in this regime. At lower Knudsen number (Kn), it is observed that the effect of L on MFP is minimal. However, at higher rarefaction the characteristic dimension influences the MFP significantly for various wall configurations.

  13. Characterization of light transport in scattering media at sub-diffusion length scales with Low-coherence Enhanced Backscattering

    PubMed Central

    Turzhitsky, Vladimir; Rogers, Jeremy D.; Mutyal, Nikhil N.; Roy, Hemant K.; Backman, Vadim

    2009-01-01

    Low-coherence enhanced backscattering (LEBS) is a technique that has recently shown promise for tissue characterization and the detection of early pre-cancer. Although several Monte Carlo models of LEBS have been described, these models have not been accurate enough to predict all of the experimentally observed LEBS features. We present an appropriate Monte Carlo model to simulate LEBS peak properties from polystyrene microsphere suspensions in water. Results show that the choice of the phase function greatly impacts the accuracy of the simulation when the transport mean free path (ls*) is much greater than the spatial coherence length (LSC). When ls* < LSC, a diffusion approximation based model of LEBS is sufficiently accurate. We also use the Monte Carlo model to validate that LEBS can be used to measure the radial scattering probability distribution (radial point spread function), p(r), at small length scales and demonstrate LEBS measurements of p(r) from biological tissue. In particular, we show that pre-cancerous and benign mucosal tissues have different small length scale light transport properties. PMID:21037980

  14. Characteristic length of dynamic glass transition near T{sub g} for a wide assortment of glass-forming substances

    SciTech Connect

    Hempel, E.; Hempel, G.; Hensel, A.; Schick, C.; Donth, E.

    2000-03-23

    Dynamic heterogeneity is an active field of glass-transition research. the length scale of this heterogeneity is called the characteristic length. It can be calculated from complex heat capacity curves in the equilibrium liquid or from dynamic calorimetry curves corrected with regard to nonequilibrium. No molecular parameters or microscopic models are necessary for obtaining the length. The authors report the characteristic length near glass temperature for about 30 glass formers including small-molecule liquids, polymers, silicate glasses, a metallic glass, a liquid crystal, and a plastic crystal. The lengths are between 1.0 and 3.5 nm with certain accumulations between 1.0 and 2.0 nm and between 2.5 and 3.5 nm. To try a correlation to other properties, the authors find that at least two should be included, e.g., Angell's fragility and the distance of T{sub g} from the crossover temperature, T{sub c}.

  15. Determination of minority carrier diffusion length of sprayed-Cu2ZnSnS4 thin films

    NASA Astrophysics Data System (ADS)

    Courel, Maykel; Valencia-Resendiz, E.; Pulgarín-Agudelo, F. A.; Vigil-Galán, O.

    2016-04-01

    Despite Cu2ZnSnS4(CZTS) is a potential candidate for solar cell applications, so far, low efficiency values have been reported. In particular, for spray-deposited CZTS, efficiencies lower than 2% are commonly achieved. It is well known that one of the most important parameters governing solar cell performance is minority carrier diffusion length (Ln). In this work, CZTS thin film solar cells with different compositional ratios are fabricated in order to study its impact on Ln values. The Ln parameter is calculated for sprayed-CZTS layers using external quantum efficiency measurements in conjunction with optical absorption coefficient versus wavelength measurements - for the first time. Values in the range of 0.11-0.17 μm are obtained emphasizing the need for improving sprayed-CZTS crystalline quality.

  16. Lateral gas phase diffusion length of boron atoms over Si/B surfaces during CVD of pure boron layers

    NASA Astrophysics Data System (ADS)

    Mohammadi, V.; Nihtianov, S.

    2016-02-01

    The lateral gas phase diffusion length of boron atoms, LB, along silicon and boron surfaces during chemical vapor deposition (CVD) using diborane (B2H6) is reported. The value of LB is critical for reliable and uniform boron layer coverage. The presented information was obtained experimentally and confirmed analytically in the boron deposition temperature range from 700 °C down to 400 °C. For this temperature range the local loading effect of the boron deposition is investigated on the micro scale. A LB = 2.2 mm was determined for boron deposition at 700 °C, while a LB of less than 1 mm was observed at temperatures lower than 500 °C.

  17. Evaluating pedestal gradients and scale lengths without functional fits in order to test for non-diffusive transport processes

    NASA Astrophysics Data System (ADS)

    Eldon, D. P.; Tynan, G. R.; Groebner, R. J.; Osborne, T. H.; Bray, B. D.; Boivin, R. L.; Nazikian, R.

    2012-10-01

    The advent of the recent spatial resolution upgrade to the edge Thomson scattering diagnostic at DIII-D allows re-examination of methods for measuring electron density and temperature scale lengths. The modified hyperbolic tangent fit is widely used, however, this function is clearly inappropriate in some situations such as when density profiles are distorted by applied resonant magnetic perturbations (RMPs). In these cases, a flattening of the density profile is observed at or near the separatrix while the RMP is applied. However, no similar structure is observed in the temperature profile so far. Furthermore, the tanh fit is based on a diffusive model and recently observed differences between the tanh fit and measured profiles using newly available high spatial resolution data are revealing more subtle transport processes at the mm scale.

  18. Flow Characteristics in Compact Thermal Spray Coating Systems with Minimum Length Nozzle

    NASA Astrophysics Data System (ADS)

    Seung-Hyun, Kim; Youn-Jea, Kim

    2009-10-01

    In this study, numerical analysis is performed to adopt the equivalence ratio on the high velocity oxygen fuel (HVOF) thermal spray coating systems equipped with a minimum length nozzle. The analysis is applied to investigate the axisymmetric, steady-state, turbulent, and chemically combusting flow both within the torch and in a free jet region between the torch and the substrate to be coated. The combustion is modeled using a single-step and eddy-dissipation model which assumes that the reaction rate is limited by the turbulent mixing rate of the fuel and oxidant. As the diameter of the nozzle throat is increased, the location of the Mach shock disc moves backward from the nozzle exit. As the throat diameter and the divergent portion are 6 mm and 8 mm, respectively, the pressure in the HVOF system is the lowest at the chamber and the expanding gas is steadily maintained with both high velocity and high temperature for different equivalence ratios. Thus, relatively minor amendments of the equivalence ratio and the geometry of HVOF can lead to improved control over coating characteristics.

  19. Aerodynamic Characteristics of a Flying-Boat Hull Having a Length-Beam Ratio of 15, TED No. NACA 2206

    NASA Technical Reports Server (NTRS)

    Riebe, John M.; Naeseth, Rodger L.

    1951-01-01

    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.

  20. Effect of Length-Beam Ratio on the Aerodynamic Characteristics of Flying-Boat Hulls without Wing Interference

    NASA Technical Reports Server (NTRS)

    Lowry, John G.; Riebe, John M.

    1948-01-01

    Contains experimental results of an investigation of the aerodynamic characteristics of a family of flying boat hulls of length beam ratios 6, 9, 12, and 15 without wing interference. The results are compared with those taken on the same family of hulls in the presence of a wing.

  1. Determination of charge-carrier diffusion length in the photosensing layer of HgCdTe n-on-p photovoltaic infrared focal plane array detectors

    SciTech Connect

    Vishnyakov, A. V.; Stuchinsky, V. A. Brunev, D. V.; Zverev, A. V.; Dvoretsky, S. A.

    2014-03-03

    In the present paper, we propose a method for evaluating the bulk diffusion length of minority charge carriers in the photosensing layer of photovoltaic focal plane array (FPA) photodetectors. The method is based on scanning a strip-shaped illumination spot with one of the detector diodes at a low level of photocurrents j{sub ph} being registered; such scanning provides data for subsequent analysis of measured spot-scan profiles within a simple diffusion model. The asymptotic behavior of the effective (at j{sub ph} ≠ 0) charge-carrier diffusion length l{sub d} {sub eff} as a function of j{sub ph} for j{sub ph} → 0 inferred from our experimental data proved to be consistent with the behavior of l{sub d} {sub eff} vs j{sub ph} as predicted by the model, while the obtained values of the bulk diffusion length of minority carriers (electrons) in the p-HgCdTe film of investigated HgCdTe n-on-p FPA photodetectors were found to be in a good agreement with the previously reported carrier diffusion-length values for HgCdTe.

  2. Determination of bulk diffusion lengths for angle-lapped semiconductor material via the scanning electron microscope: A theoretical analysis

    NASA Technical Reports Server (NTRS)

    Vonroos, O.

    1978-01-01

    A standard procedure for the determination of the minority carrier diffusion length by means of a scanning electron microscope (SEM) consists in scanning across an angle-lapped surface of a P-N junction and measuring the resultant short circuit current I sub sc as a function of beam position. A detailed analysis of the I sub sc originating from this configuration is presented. It is found that, for a point source excitation, the I sub sc depends very simply on x, the variable distance between the surface and the junction edge. The expression for the I sub sc of a planar junction device is well known. If d, the constant distance between the plane of the surface of the semiconductor and the junction edge in the expression for the I of a planar junction is merely replaced by x, the variable distance of the corresponding angle-lapped junction, an expression results which is correct to within a small fraction of a percent as long as the angle between the surfaces, 2 theta sub 1, is smaller than 10 deg.

  3. Study of space spectral characteristics of the BRDF diffuse standard plate in visible and infrared bands

    NASA Astrophysics Data System (ADS)

    Wu, Houping; Feng, Guojin; Zheng, Chundi; Li, Ping; Wang, Yu

    2015-10-01

    The bidirectional reflectance distribution function (BRDF) diffuse plate as the standard of value transfer and carrier for BRDF, plays an important role in the study of radiometric calibration and scattering properties of. The space spectral characteristics of developed BRDF diffuse standard plate were measured by BRDF standard device. The standard BRDF values were given under more wavelengths and more geometric conditions in the visible to the infrared spectral bands, and the uncertainty is 1%. By comparison, the developed BRDF diffuse standard plate in visible and infrared bands reached the similar international standards plate level.

  4. Supersonic and hypersonic aerodynamic characteristics of two shuttle-orbiter configurations designed for reduced length

    NASA Technical Reports Server (NTRS)

    Stone, H. W.

    1974-01-01

    Performance, stability, and control tests at supersonic and hypersonic speeds have been performed on two versions of a shuttle orbiter configuration designed for reduced length. One of the test configurations had twin dorsal fins rolled out 15 deg the other a centerline single dorsal fin. Effects of elevon and body deg flap deflection, rudder flare, planform fillet, and aileron deflection were examined. The supersonic tests were over the Mach number range from 1.6 to 4.63 at a Reynolds number based on model length of 4,300,000. The hypersonic tests were conducted at a Mach number of 10.3 and Reynolds number of 670,000.

  5. Characteristics of laminar gas jet diffusion flames under the influence of elevated gravity

    NASA Technical Reports Server (NTRS)

    Altenkirch, R. A.; Eichhorn, R.; Hsu, N. N.; Brancic, A. B.; Cevallos, N. E.

    1977-01-01

    Laminar gas jet diffusion flames of hydrogen, methane, ethane, and propane, stabilized on small cylindrical burners, were studied at elevated gravity in a centrifuge to investigate the role of buoyancy in such flames. Photographic observation of the hydrocarbon flames indicated that length and carbon luminosity decreased with increasing buoyancy. These flames eventually separated from the burner rim and finally extinguished as gravity increased. Hydrogen flames, however, did not separate or extinguish up to about 31 times earth normal gravity. Length data are reported and interpreted with the aid of a simplified model which describes the flame as a heated vertical cylindrical sheet to which oxygen is supplied by a free convection boundary layer.

  6. [Effects of field border length for irrigation on the water consumption characteristics and grain yield of wheat].

    PubMed

    Ma, Shang-Yu; Yu, Zhen-Wen; Wang, Dong; Zhang, Yong-Li; Shi, Yu

    2012-09-01

    In the wheat growth seasons of 2009 -2010 and 2010-2011, six border lengths of 10, 20, 40, 60, 80 and 100 m were installed in a wheat field to study the effects of different border lengths for irrigation on the water consumption characteristics and grain yield of wheat. The results showed that with the increasing border length from 10 to 80 m, the irrigation amount and the proportion of irrigation amount to total water consumption amount, the water content in 0-200 cm soil layers and the soil water supply capacity at anthesis stage, as well as the wheat grain yield and water use efficiency increased, while the soil water consumption amount and the water consumption amount of wheat from jointing to anthesis stages as well as the total water consumption amount decreased. At the border length of <80 m, the irrigation amount was smaller, and the water content in upper soil layers was lower, as compared with those at the border length of 80 m, which led to the wheat to absorb more water from deeper soil layers, and thus, the total water consumption increased. At the border length of 100 m, the irrigation amount, soil water consumption amount, and total water consumption amount all increased, and, due to the excessive irrigation amount and the uneven distribution of irrigation water when irrigated once, the 1000-grain mass, grain yield, and water use efficiency decreased significantly, which was not conductive to the water-saving and high-yield cultivation. PMID:23286006

  7. Electron-hole diffusion lengths >175 μm in solution-grown CH3NH3PbI3 single crystals

    DOE PAGESBeta

    Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan; Mulligan, Padhraic; Qiu, Jie; Cao, Lei; Huang, Jinsong

    2015-02-27

    Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm–2) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smaller trap densities in the single crystals thanmore » in polycrystalline thin films. As a result, the long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.« less

  8. Electron-hole diffusion lengths >175 μm in solution-grown CH3NH3PbI3 single crystals

    DOE PAGESBeta

    Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan; Mulligan, Padhraic; Qiu, Jie; Cao, Lei; Huang, Jinsong

    2015-02-27

    Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm–2) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smaller trap densities in the single crystals thanmore »in polycrystalline thin films. As a result, the long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.« less

  9. Effective spin Hall properties of a mixture of materials with and without spin-orbit coupling: Tailoring the effective spin diffusion length

    NASA Astrophysics Data System (ADS)

    Yue, Z.; Prestgard, M. C.; Tiwari, A.; Raikh, M. E.

    2016-01-01

    We study theoretically the effective spin Hall properties of a composite consisting of two materials with and without spin-orbit (SO) coupling. In particular, we assume that SO material represents a system of grains in a matrix with no SO. We calculate the effective spin Hall angle and the effective spin diffusion length of the mixture. Our main qualitative finding is that, when the bare spin diffusion length is much smaller than the radius of the grain, the effective spin diffusion length is strongly enhanced, well beyond the "geometrical" factor. The physical origin of this additional enhancement is that, with small diffusion length, the spin current mostly flows around the grain without suffering much loss. We also demonstrate that the voltage, created by a spin current, is sensitive to a very weak magnetic field directed along the spin current, and even reverses sign in a certain domain of fields. The origin of this sensitivity is that the spin precession, caused by magnetic field, takes place outside the grains where SO is absent.

  10. Evaluation of spin diffusion length of AuW alloys using spin absorption experiments in the limit of large spin-orbit interactions

    NASA Astrophysics Data System (ADS)

    Laczkowski, P.; Jaffrs, H.; Savero-Torres, W.; Rojas-Snchez, J.-C.; Fu, Y.; Reyren, N.; Deranlot, C.; Notin, L.; Beign, C.; Attan, J.-P.; Vila, L.; George, J.-M.; Marty, A.

    2015-12-01

    The knowledge of the spin diffusion length, ?A, is a prerequisite for the estimation of the spin Hall angle of given materials. We investigate the spin-current absorption of materials with a short ?A using AuW stripes inserted in Cu-based lateral spin valves. Width variations of the AuW stripe lead to drastic changes of the spin absorption which cannot be explained by a conventional analysis. We show that the spin-current polarization and the spin-accumulation attenuation in Cu in the vicinity of the spin absorber must be precisely taken into account for an accurate estimation of ?A. We propose an analytical extension of the standard diffusion model of spin transport and spin absorption based on the existence of an effective spin diffusion length for Cu being in direct contact with AuW. The calculations are supported by numerical investigations which allow us to extract proper values of ?A.

  11. Cavity length and stripe width dependent lasing characteristics of InAs/InP(1 0 0) quantum dot lasers

    NASA Astrophysics Data System (ADS)

    Li, S. G.; Gong, Q.; Wang, X. Z.; Cao, C. F.; Zhou, Z. W.; Wang, H. L.

    2016-03-01

    The lasing characteristics of InAs/InP(1 0 0) quantum dot lasers grown by gas source molecular beam epitaxy were carefully studied by varying cavity length and stripe width. With the increase of injection current, the lasers having a longer cavity length and a wider stripe width exhibited simultaneously two-lasing peaks or/three-lasing peaks. The high-energy peak undergoes continuous buleshift, while the low-energy peaks are somewhat fixed. At the same times, the injection current density decreased as the stripe width increase. When the lasers were applied to external cavity system, the shorter cavity length of InAs/InP quantum dot laser had a wider tunable range.

  12. The effects of inlet temperature and turbulence characteristics on the flow development inside a gas turbine exhaust diffuser

    NASA Astrophysics Data System (ADS)

    Bomela, Christian Loangola

    The overall industrial gas turbine efficiency is known to be influenced by the pressure recovery in the exhaust system. The design and, subsequently, the performance of an industrial gas turbine exhaust diffuser largely depend on its inflow conditions dictated by the turbine last stage exit flow state and the restraints of the diffuser internal geometry. Recent advances in Computational Fluid Dynamics (CFD) tools and the availability of computer hardware at an affordable cost made the virtual tool a very attractive one for the analysis of fluid flow through devices like a diffuser. In this backdrop, CFD analyses of a typical industrial gas turbine hybrid exhaust diffuser, consisting of an annular diffuser followed by a conical portion, have been carried out with the purpose of improving the performance of these thermal devices using an open-source CFD code "OpenFOAM". The first phase in the research involved the validation of the CFD approach using OpenFOAM by comparing CFD results against published benchmark experimental data. The numerical results closely captured the flow reversal and the separated boundary layer at the shroud wall where a steep velocity gradient has been observed. The standard k --epsilon turbulence model slightly over-predicted the mean velocity profile in the casing boundary layer while slightly under-predicted it in the reversed flow region. A reliable prediction of flow characteristics in this region is very important as the presence of the annular diffuser inclined wall has the most dominant effect on the downstream flow development. The core flow region and the presence of the hub wall have only a minor influence as reported by earlier experimental studies. Additional simulations were carried out in the second phase to test the veracity of other turbulence models; these include RNG k--epsilon, the SST k--o, and the Spalart-Allmaras turbulence models. It was found that a high resolution case with 47.5 million cells using the SST k--o turbulence model produced a mean flow velocity profile at the middle of the annular diffuser portion that had the best overall match with the experiment. The RNG k --epsilon, however, better predicted the diffuser performance along the exhaust diffuser length by means of the pressure recovery coefficient. These results were obtained using uniform inflow conditions and steady-state simulations. As such, the last phase of our investigations involved varying the inflow parameters like the turbulence intensity, the inlet flow temperature, and the flow angularity, which constitute important characteristics of the turbine blade wake, to investigate their impact on the diffuser design and performance. These isothermal CFD simulations revealed that by changing the flow temperature from 15 to 427C, the pressure recovery coefficient significantly increased. However, it has been shown that the increase of temperature had no effects on the size of the reversed flow region and the thickness of the separated casing boundary layer, although the flow appears to be more turbulent. Furthermore, it has been established that an optimum turbulence intensity of about 4% produced comparable diffuser performance as the experiment. We also found that a velocity angle of about 2.5 at the last turbine stage will ensure a better exhaust diffuser performance.

  13. Performance characteristics of two annular dump diffusers using suction-stabilized vortex flow control

    NASA Technical Reports Server (NTRS)

    Juhasz, A. J.; Smith, J. M.

    1978-01-01

    The two diffusers employed in the investigation had the same overall area ratio but different prediffuser area ratios and suction slot geometries. Velocity profile and diffuser pressure recovery performance data were obtained at ambient pressure and temperature, with inlet Mach numbers ranging from 0.18 to 0.41 and suction rate varying from zero to 18% of total inlet mass flow rate. On the basis of the reported investigation it is concluded that suction stabilized vortex flow diffusers show promise for application in combustors because of relatively high static pressure recovery and low total pressure loss obtained in a short length. Performance obtained using a narrow angle (7 degree) prediffuser was superior to that obtained with a prediffuser having a 14 degree included angle.

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

    SciTech Connect

    Ashok S. Damle; J. Vernon Cole

    2008-11-01

    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

  15. Method for digital measurement of phase-frequency characteristics for a fixed-length ultrasonic spectrometer

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  16. Channel characteristics analysis of diffuse indoor cellular optical wireless communication systems

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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.

  17. The influences of thermodynamic characteristics on aerodynamic roughness length over land surface

    NASA Astrophysics Data System (ADS)

    Zhang, Qiang; Yao, Tong; Yue, Ping; Zhangf, Liyang; Zeng, Jian

    2013-04-01

    It has previously been shown that aerodynamic roughness length changes significantly along with nearsurface atmospheric thermodynamic state; however, at present, this phenomenon remains poorly understood, and very little research concerning this topic has been conducted. In this paper, by using the data of different underlying surfaces provided by the Experimental Co-observation and Integral Research in Semi-arid and Arid Regions over North China, aerodynamic roughness length ( z 0) values in stable, neutral, and unstable atmospheric stratifications are compared with one another, and the relationship between z 0 and atmospheric thermodynamic stability ( ζ) is analyzed. It is found that z 0 shows great differences among the stable, neutral, and unstable atmospheric thermodynamic states, with the difference in z 0 values between the fully thermodynamic stable condition and the neutral condition reaching 60% of the mean z 0. Furthermore, for the wind speed range in which the wind data are less sensitive to z 0, the surface z 0 changes more significantly with ζ, and is highly correlated with both the Monin-Obukhov stability ( ζ 0) and the overall Richardson number ( R ib), with both of their correlation coefficients greater than 0.71 and 0.47 in the stable and unstable atmospheric stratification, respectively. The empirical relation fitted with the experimental observations is quite consistent with the Zilitinkevich theoretical relation in the stable atmosphere, but the two are quite distinct and even show opposite variation tendencies in the unstable atmosphere. In application, however, verification of the empirical fitted relations by using the experimental data finds that the fitted relation is slightly more applicable than the Zilitinkevich theoretical relation in stable atmospheric stratification, but it is much more suitable than the Zilitinkevich relation in unstable atmospheric stratification.

  18. Electron irradiation-induced increase of minority carrier diffusion length, mobility, and lifetime in Mg-doped AlN/AlGaN short period superlattice

    SciTech Connect

    Lopatiuk-Tirpak, O.; Chernyak, L.; Borisov, B. A.; Kuryatkov, V. V.; Nikishin, S. A.; Gartsman, K.

    2007-10-29

    Minority carrier diffusion length in a p-type Mg-doped AlN/Al{sub 0.08}Ga{sub 0.92}N short period superlattice was shown to undergo a multifold and persistent (for at least 1 week) increase under continuous irradiation by low-energy beam of a scanning electron microscope. Since neither the diffusion length itself nor the rate of its increase exhibited any measurable temperature dependence, it is concluded that this phenomenon is attributable to the increase in mobility of minority electrons in the two-dimensional electron gas, which in turn is limited by defect scattering. Cathodoluminescence spectroscopy revealed {approx}40% growth of carrier lifetime under irradiation with an activation energy of 240 meV.

  19. Comparison of Hospitalists and Nonhospitalists in Inpatient Length of Stay Adjusting for Patient and Physician Characteristics

    PubMed Central

    Rifkin, William D; Holmboe, Eric; Scherer, Hannah; Sierra, Hernan

    2004-01-01

    OBJECTIVE To determine the independent effect of hospitalist status upon inpatient length of stay after controlling for case mix, as well as patient-level and provider-level variables such as age, years since physician medical school graduation, and volume status of provider. DESIGN Observational retrospective cohort study employing a hierarchical random intercept logistic regression model. SETTING Tertiary-care teaching hospital. PATIENTS All admissions during 2001 to the department of medicine not sent initially to the medical intensive care unit or coronary care unit. MEASUREMENTS Observed length of stay (LOS) compared to principle diagnosis related group (DRG)-specific mean LOS for hospitalist and nonhospitalist patients adjusting for patient age, gender, years since physician graduation from medical school, and physician volume status. MAIN RESULTS The 9 hospitalists discharged 2,027 patients while the nonhospitalists discharged 9,361 patients. On average, hospitalist patients were younger, 63.3 versus 73.3 years (P < .0001). Hospitalists were more recently graduated from medical school, 13.8 versus 22.5 years (P = .02). Each year of patient age was found to increase the likelihood of an above average LOS (odds ratio [OR], 1.01; 95% confidence interval [CI], 1.01 to 1.02; P < .001). In unadjusted analysis, hospitalists were less likely to have an above average LOS (OR, 0.51; 95% CI, 0.28 to 0.93; P = .03). Adjustment for effects of patient age and gender, physician gender, years since medical school graduation, and quintile of physician admission volume did not appreciably change the point estimate that hospitalist patients remained less likely to have above average LOS (OR, 0.60; 95% CI, 0.32 to 1.11; P = .11). CONCLUSIONS For a given principle DRG, hospitalist patients were less likely to exceed the average LOS than were nonhospitalist patients. This effect was rather large, in that hospitalist status reduced the likelihood of above average LOS by about 49%. Adjustment for patient age, years since physician graduation, and admission volume did not significantly alter this finding. Further research should focus on identifying specific practices that account for hospitalism's effects. PMID:15566442

  20. Temperature dependence of the characteristic length scale for glassy dynamics: Combination of dielectric and specific heat spectroscopy

    NASA Astrophysics Data System (ADS)

    Saiter, A.; Delbreilh, L.; Couderc, H.; Arabeche, K.; Schnhals, A.; Saiter, J.-M.

    2010-04-01

    The temperature dependence of characteristic length scales associated to the glass transition such as the cooperativity length scale introduced by Adam and Gibbs [cooperative rearranging region (CRR)] or the dynamic heterogeneity as estimated from the four point correlation function ?4 , is at the center of large interests. Broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry allow to study the CRR size temperature dependence in the temperature range of ergodicity loss for glass-forming liquids, starting from the onset of cooperativity in the crossover region down to the glass transition temperature. Furthermore, the correlation between these two techniques allows to explore a large frequency range (from 1 mHz to 10 MHz). The goal of this work is to follow the cooperativity evolution along the Arrhenius plot for two different polymeric systems: poly(ethylene 1,4-cyclohexylenedimethylene terephthalate glycol) and poly(bisphenol A carbonate).

  1. Diffusion characteristics and molecular size of DOM in plant and soil extracts

    NASA Astrophysics Data System (ADS)

    Fu, Roland; Zsolnay, dm.; Munch, Jean Charles

    2010-05-01

    The main sources of dissolved organic matter (DOM) in soil are plant litter, root exudates, soil fauna, and the un-dissolved soil organic matter pool. A strong spatial heterogeneity of these sources, even on the microscale, is observed in soil. Consequently diffusion of DOM is an important transport process, which connects "hot-spots" of microbial activity and substrates. Therefore an experiment was conducted in order to measure diffusion constants of DOM and 2 inorganic nutrients. Furthermore, hydrodynamic diameters were calculated from these constants, which give an approximation of molecular size. The diffusion characteristics of several parameters in aqueous extracts of two soils and of barley were investigated. They were: Ammonium, nitrate, dissolved organic nitrogen (DON), dissolved inorganic carbon, dissolved organic carbon (DOC), and 3 different fluorophore groups associated with DOM. The fluorophore groups were identified and quantified from fluorescence excitation emission spectra with the PARAFAC model. Two of the groups resembled groups, which have been used to imply the presence of humic substances (HS). Our results give reason to believe these groups can be regarded as indicators of dissolved HS in aqueous extracts only with caution. The other group, enriched in the barley extract, was the "tryptophan" group. However, its diffusion constant differed markedly between the soil and barley extracts, indicating that compounds other than tryptophan contributed to this fluorophore in soil extracts. When the Stokes-Einstein equation was applied to the diffusion coefficients of DOC (in all extracts about 0.27 x 10-5 cm2 s-1 at 4 C), a mean hydrodynamic diameter of 1.0 nm for the DOC was calculated. The diffusion constants for the other DOM parameters were also similar, regardless of source, with the exception of the "tryptophan" fluorophore group from barley, which diffused about 1.5 times faster than that from the soils and was in good agreement with the theoretical diffusion coefficient of tryptophan. There was no evidence of macromolecules in DOM. The diffusion of the inorganic nitrogen species was up to 4 times as rapid as that for DOC. Therefore, where in situ metabolism is fuelled by diffusion, diffusion rates of dissolved nitrogen are not likely to be the limiting factor.

  2. The effect of aminophylline on the force-length characteristics of the diaphragm.

    PubMed

    Wanke, T; Merkle, M; Zifko, U; Formanek, D; Lahrmann, H; Grisold, W; Zwick, H

    1994-06-01

    The aim of our study was to evaluate the effect of aminophylline on the contractile function of the human diaphragm during varying muscle fiber length. Ten healthy subjects were studied during maximal sniff maneuvers and bilateral phrenic nerve twitch stimulations, with and without intravenous infusion of aminophylline in a randomized fashion. The transdiaphragmatic pressures generated at various baseline lung volumes, from residual volume to 90% of total lung capacity, were recorded before and after the induction of diaphragm exhaustion. At all levels of lung volume, aminophylline did not have an effect on the contractility of the fresh diaphragm. In the exhausted diaphragm, however, the pressure values, induced by sniffs and twitch stimulations, were significantly improved by aminophylline. This positive effect on diaphragm contractility was also impressive at 60, 75, and 90% of total lung capacity. This indicates that aminophylline significantly improves the contractile function of the exhausted human diaphragm, even if the muscle fibers are shorter than optimal. This effect occurs regardless of the neuronal firing rate, whether it is low (twitch stimulation) or high (sniff maneuver). PMID:8004311

  3. From geometry and characteristic length scales to different relaxation regimes in Single-Chain Magnets

    NASA Astrophysics Data System (ADS)

    Vindigni, Alessandro

    2008-03-01

    The recently discovered Single-Chain Magnets can be considered a novel class of nanomagnets, representing the ultimate miniaturization limit of bistable magnetic nanowires. The name highlights the analogy with Single-Molecule Magnets: Both SMMs and SCMs show remanent magnetization in zero magnetic field due to slow dynamics, in spite of the reduced dimensionality (0D and 1D respectively) which forbids the occurrence of magnetic ordering. Beyond this common feature, the origin of slow dynamics is remarkably different. In particular, for a genuine 1D magnetic system slow dynamics at low temperature comes from the divergence of the relaxation time as the critical point, T=0, is approached. This scenario is actually encountered in SCMs at relatively high T in a regime where each spin chain behaves as if it were infinite. However, for a wide class of molecular chains (i) naturally occurring defects and (ii) non-collinearity between the single-spin anisotropy directions and the crystal axes break the site-by-site translational invariance along the chain. Both these phenomena affect slow relaxation. We will show how this fact can be accounted for through ad hoc extensions of Glauber dynamics. Different relaxation regimes are observed depending on the relationship between the correlation length and the actual distance between two defects, the lattice spacing and the domain-wall size.

  4. Estimating the spin diffusion length of semiconducting Indium Tin Oxide using Co/Indium Tin Oxide/Co spin valve junctions

    NASA Astrophysics Data System (ADS)

    Hakimi, A. M. H. R.; Banerjee, N.; Aziz, A.; Robinson, J. W. A.; Blamire, M. G.

    2010-03-01

    We have measured the transport behavior of Co/Indium Tin Oxide (ITO)/Co current-perpendicular-to-plane submicron spin-valve devices with ITO spacer thickness up to 20 nm, fabricated directly using a three-dimensional focused-ion beam etching technique. Using a simplified Valet-Fert model, we have determined a spin asymmetry ratio for Co of 0.55 and spin diffusion length of 61 nm in semiconducting ITO at room temperature.

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

    NASA Astrophysics Data System (ADS)

    Gapinski, Jacek; Ngele, Gerhard; Patkowski, Adam

    2014-09-01

    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. Ngele, 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 Ravach-Mountain-Streett minimum-maximum radial distribution function ratio.

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

    SciTech Connect

    Gapinski, Jacek Patkowski, Adam; Nägele, Gerhard

    2014-09-28

    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.

  7. Determination of critical diameters for intrinsic carrier diffusion-length of GaN nanorods with cryo-scanning near-field optical microscopy

    PubMed Central

    Chen, Y. T.; Karlsson, K. F.; Birch, J.; Holtz, P. O.

    2016-01-01

    Direct measurements of carrier diffusion in GaN nanorods with a designed InGaN/GaN layer-in-a-wire structure by scanning near-field optical microscopy (SNOM) were performed at liquid-helium temperatures of 10 K. Without an applied voltage, intrinsic diffusion lengths of photo-excited carriers were measured as the diameters of the nanorods differ from 50 to 800 nm. The critical diameter of nanorods for carrier diffusion is concluded as 170 nm with a statistical approach. Photoluminescence spectra were acquired for different positions of the SNOM tip on the nanorod, corresponding to the origins of the well-defined luminescence peaks, each being related to recombination-centers. The phenomenon originated from surface oxide by direct comparison of two nanorods with similar diameters in a single map has been observed and investigated. PMID:26876009

  8. Determination of critical diameters for intrinsic carrier diffusion-length of GaN nanorods with cryo-scanning near-field optical microscopy.

    PubMed

    Chen, Y T; Karlsson, K F; Birch, J; Holtz, P O

    2016-01-01

    Direct measurements of carrier diffusion in GaN nanorods with a designed InGaN/GaN layer-in-a-wire structure by scanning near-field optical microscopy (SNOM) were performed at liquid-helium temperatures of 10?K. Without an applied voltage, intrinsic diffusion lengths of photo-excited carriers were measured as the diameters of the nanorods differ from 50 to 800?nm. The critical diameter of nanorods for carrier diffusion is concluded as 170?nm with a statistical approach. Photoluminescence spectra were acquired for different positions of the SNOM tip on the nanorod, corresponding to the origins of the well-defined luminescence peaks, each being related to recombination-centers. The phenomenon originated from surface oxide by direct comparison of two nanorods with similar diameters in a single map has been observed and investigated. PMID:26876009

  9. Element diffusion ability in metasomatic agents and its effect on chemical characteristics of metasomatized peridotites

    NASA Astrophysics Data System (ADS)

    Yu, J.; O'Reilly, S. Y.

    2010-12-01

    Detailed in situ LM-ICPMS researches on the composite xenoliths from Yingfengling volcano of Leizhou Peninsula, South China, indicate that most incompatible trace elements of clinopyroxenes in composite xenoliths decrease spatially from pyroxenites to distal lherzolites, and compatible elements and HREE increase steeply. The increasing and decreasing rate is distinct for different trace elements, which give rise to element chromatographic fractionation within metasomatized lherzolites. The element chromatographic fractionation result actually from the difference in element diffusive rate in melts or fluids percolating through wallrock lherzolites. Based on element variation profiles in composite xenoliths this study indicates that Sr, Nb, La and Ce have the highest diffusive mobility, MREE-HREE are moderate, and Zr, Hf, Ti, Ga and Sc are very low in most cases. Higher diffusive rates of LREE than HREE would enlarge the REE fractionation of metasomatized peridotites, and lower diffusive rate of Zr, Hf and Ti relative to neighbor REEs with similar incompatibility would cause the relative depletion of these elements in metasomatized peridotites. Trace elements commonly have a higher diffusive rate in fluid-rich infiltrating melt, which will weaken element chromatographic fractionation during the metasomatism. The range of mantle metasomatism caused by silicate melt intrusion is very limited, generally within tens of centimeters wide. The width of metasomatized wallrock peridotites near the pyroxenite or horblendite veins was strictly controlled by both melt volume and chemical characteristics.

  10. Improved current and power density with a micro-scale microbial fuel cell due to a small characteristic length.

    PubMed

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

    2014-11-15

    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-L 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 W applications, especially in remote or hazardous conditions, where conventional powering units are hard to establish. PMID:24956566

  11. Unique sequence characteristics account for good DGGE separation of almost full-length 18S rDNAs.

    PubMed

    Huang, Zhiqing; Ke, Xinxin; Lv, Xiaodan; Liu, Zhibin; Ni, Li

    2016-03-01

    A major limiting factor for DGGE-based microbial community studies is that the fragments should not be much longer than 500 bp for successful analysis. However, relatively high-resolution was achieved based on DGGE of the long 18S rDNA fragment (>1500 bp), which might be surprising due to the known decrease in DGGE resolution of DNA molecules with large melted regions. A unique sequence characteristic was found in a specific region (ca. 275 bp, named the NS1-end region) of 18S rDNAs, and fungal communities separated from Hong Qu glutinous rice wine brewing system was used to reveal the relationship between high resolution capacity and the unique sequence characteristics. The results showed that DGGE separation of the long 18S rDNA fragments depended on their NS1-end regions. The region is composed of a sequence-variable and short-length GC-poor region (ca. 160 bp) and a GC-rich region (ca. 110 bp), which contribute to the high resolution capacity achieved for DGGE of the long 18S rDNA fragments. Thus DGGE of the long 18S rDNA fragment is recommended as a target fragment for studies of fungal communities whose 18S rDNAs possess similar sequence characteristics. Good resolution and almost full-length 18S rDNA sequences can thus be obtained to provide more accurate and reliable analysis of fungal communities. Since more sequences are obtained directly from the PCR product through the long rDNA fragment approach, this is a convenient and effective approach for sequence-based analysis without using other complementary methods such as an rDNA clone library method. PMID:26873559

  12. Experimental Investigation of the Effect of Vertical-tail Size and Length and of Fuselage Shape and Length on the Static Lateral Stability Characteristics of a Model with 45 Degree Sweptback Wing and Tail Surfaces

    NASA Technical Reports Server (NTRS)

    Queijo, M J; Wolhart, Walter D

    1951-01-01

    An investigation was made to determine the effects of vertical-tail size and length and of fuselage shape and length on the static lateral stability characteristics of a model with wing and vertical tails having the quarter-chord lines swept back 45 degrees. The results indicate that the directional instability of the various isolated fuselages was about two-thirds as large as that predicted by classical theory.

  13. Diffusion-weighted MRI characteristics of the cerebral metastasis to brain boundary predicts patient outcomes

    PubMed Central

    2014-01-01

    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

  14. Characteristic length scales and time-averaged transport velocities of suspended sediment in the mid-Atlantic Region, USA

    USGS Publications Warehouse

    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

    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.

  15. Characteristic length scales and time-averaged transport velocities of suspended sediment in the mid-Atlantic Region, USA

    NASA Astrophysics Data System (ADS)

    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

    2014-02-01

    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.

  16. [Cloning of full-length coding sequence of tree shrew CD3E and prediction of its molecular characteristics].

    PubMed

    Li, Yi-Jiang; Gao, Yue-Dong; Guo, Yan; Lu, Cai-Xia; Huang, Jing-Fei; Xia, Xue-Shan; Dai, Jie-Jie; Fan, Quan-Shui; Li, Zuo-Sheng; Zhang, Hua-Tang

    2010-10-01

    The use of tree shrews (Tupaia belangeri) in human disease studies demands essential research tools, in particular cellular markers and their monoclonal antibodies for immunological studies. Here we cloned the full-length cDNAs encoding CD3E from total RNA of the spleen, liver and peripheral blood of tree shrews and analyzed their structural characteristics in comparison with other mammals by Discovery Studio software. The results showed that the open reading frame sequence of tree shrew CD3E was 582 bp, encoding 194 amino acids. The overall structure of tree shrew CD3E protein was similar to its counterparts of other mammals, intracellular and transmembrane domain highly conserved. However, detailed analysis revealed two potential glycosylation sites and different surface charges in the extracellular domain. Availability of the entire open-reading-frame and related sequence information would therefore facilitate the preparation of monoclonal antibodies against tree shrew CD3 and further studies for its function. PMID:20979250

  17. A study of damage zones or characteristic lengths as related to the fracture behavior of graphite/epoxy laminates

    NASA Technical Reports Server (NTRS)

    Yeow, Y. T.; Brinson, H. F.

    1977-01-01

    Uniaxial tensile tests conducted on a variety of graphite/epoxy laminates, containing narrow rectangular slits, square or circular holes with various aspect ratios are discussed. The techniques used to study stable crack or damage zone growth--namely, birefringence coatings, COD gages, and microscopic observations are discussed. Initial and final fracture modes are discussed as well as the effect of notch size and shape, and laminate type on the fracture process. Characteristic lengths are calculated and compared to each other using the point, average and inherent flaw theories. Fracture toughnesses are calculated by the same theories and compared to a boundary integral equation technique. Finite width K-calibration factors are also discussed.

  18. Evaluation of the minority carrier diffusion length and surface-recombination velocity in GaAs p/n solar cells

    NASA Technical Reports Server (NTRS)

    Hakimzadeh, Roshanak; Moeller, Hans J.; Bailey, Sheila

    1991-01-01

    The minority carrier diffusion length (Lp) and the surface recombination velocity (Vs) were measured as a function of distance (x) from the p-n junction in GaAs p/n concentrator solar cells. The measured Vs values were used in a theoretical expression for the normalized electron-beam-induced current. A fitting procedure was then used to fit this expression with experimental values to obtain Lp. The results show that both Vs and Lp vary with x. Lp measured in irradiated cells showed a marked reduction. These values were compared to those measured previously which did not account for Vs.

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  20. Statistical investigation of the length-dependent deviations in the electrical characteristics of molecular electronic junctions fabricated using the direct metal transfer method.

    PubMed

    Jeong, Hyunhak; Kim, Dongku; Kwon, Hyukwoo; Hwang, Wang-Taek; Jang, Yeonsik; Min, Misook; Char, Kookrin; Xiang, Dong; Jeong, Heejun; Lee, Takhee

    2016-03-01

    We fabricated and analyzed the electrical transport characteristics of vertical type alkanethiolate molecular junctions using the high-yield fabrication method that we previously reported. The electrical characteristics of the molecular electronic junctions were statistically collected and investigated in terms of current density and transport parameters based on the Simmons tunneling model, and we determined representative current-voltage characteristics of the molecular junctions. In particular, we examined the statistical variations in the length-dependent electrical characteristics, especially the Gaussian standard deviation σ of the current density histogram. From the results, we found that the magnitude of the σ value can be dependent on the individual molecular length due to specific microscopic structures in the molecular junctions. The probable origin of the molecular length-dependent deviation of the electrical characteristics is discussed. PMID:26871992

  1. Statistical investigation of the length-dependent deviations in the electrical characteristics of molecular electronic junctions fabricated using the direct metal transfer method

    NASA Astrophysics Data System (ADS)

    Jeong, Hyunhak; Kim, Dongku; Kwon, Hyukwoo; Hwang, Wang-Taek; Jang, Yeonsik; Min, Misook; Char, Kookrin; Xiang, Dong; Jeong, Heejun; Lee, Takhee

    2016-03-01

    We fabricated and analyzed the electrical transport characteristics of vertical type alkanethiolate molecular junctions using the high-yield fabrication method that we previously reported. The electrical characteristics of the molecular electronic junctions were statistically collected and investigated in terms of current density and transport parameters based on the Simmons tunneling model, and we determined representative current–voltage characteristics of the molecular junctions. In particular, we examined the statistical variations in the length-dependent electrical characteristics, especially the Gaussian standard deviation σ of the current density histogram. From the results, we found that the magnitude of the σ value can be dependent on the individual molecular length due to specific microscopic structures in the molecular junctions. The probable origin of the molecular length-dependent deviation of the electrical characteristics is discussed.

  2. Pore-size dependence and characteristics of water diffusion in slitlike micropores

    NASA Astrophysics Data System (ADS)

    Diallo, S. O.

    2015-07-01

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (12 and 18 , denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. This suppression is accompanied by a systematic dependence of the average translational diffusion coefficient Dr and relaxation time of the restricted water on pore size and temperature. The observed Dr values are tested against a proposed scaling law, in which the translational diffusion coefficient Dr of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient Dc associated with the water bound to the pore walls and the ratio ? of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range.

  3. Pore-size dependence and characteristics of water diffusion in slitlike micropores.

    PubMed

    Diallo, S O

    2015-07-01

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (?12 and 18 , denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. This suppression is accompanied by a systematic dependence of the average translational diffusion coefficient D(r) and relaxation time ??(0)? of the restricted water on pore size and temperature. The observed D(r) values are tested against a proposed scaling law, in which the translational diffusion coefficient D(r) of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient D(c) associated with the water bound to the pore walls and the ratio ? of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range. PMID:26274167

  4. Large amplitude undulations of evening site diffuse aurorae. Optical characteristics and conditions of generation

    NASA Astrophysics Data System (ADS)

    Vorobjev, V. G.; Roldugin, V. C.; Yagodkina, O. I.

    2015-01-01

    Optical characteristics of large amplitude undulations (LAU) of diffuse aurorae observed by all-sky cameras at Kola Peninsula on December 28, 2010 were examined. Both interplanetary medium conditions and characteristics of magnetic activity before and during LAU were analyzed. It was shown that the development of undulations could be activated by sharp short-living of 20 minutes solar wind dynamic pressure impulse and existence of the undulations during about two hours was supported by electric field of stationary magnetospheric convection originated from large smoothly changed southward IMF Bz component of about -12nT. The altitude of undulation luminosity determined by triangulation method was 120 10 km. The undulations amplitude changed from about 100 to 300 km and the average wavelength was 250 km. The undulations were observed moving westward with the average phase velocity of 0.7 km/s. The pass of DMSP F16 spacecraft just along "the tongue" of undulations showed that the wave of luminosity was located in the region of the predominantly ion (proton) precipitation with the average energy of particles of 18 keV. Rayed auroral structures were observed continuously in the region of diffuse aurorae during time interval of LAU existence. These structures were observed moving westward with the velocity of about 2 km/s that corresponds to the northward electric field of 100 mV/m.

  5. Development of a variable-path-length diffusive sampler for ammonia and evaluation of ammonia pollution in the urban area of Rome, Italy

    NASA Astrophysics Data System (ADS)

    Perrino, C.; Catrambone, M.

    A variable-path-length diffusive sampler for the determination of atmospheric ammonia was developed and tested. Polyethylene was found to be the best material for the construction of the sampler, while a glass body sampler of similar design yielded unreliable results; phosphorous acid was the best collecting medium. The low level of the field blanks and the high operative capacity make this device able to operate in a very wide loading range (0.3-100 ?g); the possibility to vary the length of the diffusive pathway allows a further increase of the detectable concentration range (0.1-125 ?g m -3 during a 1-month exposure). Reproducibility is better than 5% and the comparison with reference denuders demonstrated a good accuracy of the method (deviation lower than 5%). The deployment of these samplers in some field campaigns carried out in Rome allowed us to confirm the close link between ammonia concentration and traffic emission and to get an insight into the spatial variability of this pollutant.

  6. Light-Induced Increase of Electron Diffusion Length in a p-n Junction Type CH3NH3PbBr3 Perovskite Solar Cell.

    PubMed

    Kedem, Nir; Brenner, Thomas M; Kulbak, Michael; Schaefer, Norbert; Levcenko, Sergiu; Levine, Igal; Abou-Ras, Daniel; Hodes, Gary; Cahen, David

    2015-07-01

    High band gap, high open-circuit voltage solar cells with methylammonium lead tribromide (MAPbBr3) perovskite absorbers are of interest for spectral splitting and photoelectrochemical applications, because of their good performance and ease of processing. The physical origin of high performance in these and similar perovskite-based devices remains only partially understood. Using cross-sectional electron-beam-induced current (EBIC) measurements, we find an increase in carrier diffusion length in MAPbBr3(Cl)-based solar cells upon low intensity (a few percent of 1 sun intensity) blue laser illumination. Comparing dark and illuminated conditions, the minority carrier (electron) diffusion length increases about 3.5 times from Ln = 100 50 nm to 360 22 nm. The EBIC cross section profile indicates a p-n structure between the n-FTO/TiO2 and p-perovskite, rather than the p-i-n structure, reported for the iodide derivative. On the basis of the variation in space-charge region width with varying bias, measured by EBIC and capacitance-voltage measurements, we estimate the net-doping concentration in MAPbBr3(Cl) to be 3-6 10(17) cm(-3). PMID:26266721

  7. Comments on ``Measurements of minority-carrier diffusion length in n-CuInSe2 by electron-beam-induced current method'' [J. Appl. Phys. 66, 5412 (1989)

    NASA Astrophysics Data System (ADS)

    Luke, Keung L.

    1990-10-01

    The recent findings of Scheer, Wilhelm, and Lewerenz[J. Appl. Phys. 66, 5412 (1989)] regarding the application of the electron-beam-induced current technique in both the vertical and planar configurations to determine the minority-carrier diffusion length in low-diffusion-length material are compared to the results of an earlier analysis [J. Appl. Phys. 57, 1978 (1985)] of the same subject. The differences are briefly discussed.

  8. High-pressure soot formation and diffusion flame extinction characteristics of gaseous and liquid fuels

    NASA Astrophysics Data System (ADS)

    Karatas, Ahmet Emre

    High-pressure soot formation and flame stability characteristics were studied experimentally in laminar diffusion flames. For the former, radially resolved soot volume fraction and temperature profiles were measured in axisymmetric co-flow laminar diffusion flames of pre-vaporized n-heptane-air, undiluted ethylene-air, and nitrogen and carbon dioxide diluted ethylene-air at elevated pressures. Abel inversion was used to re-construct radially resolved data from the line-of-sight spectral soot emission measurements. For the latter, flame extinction strain rate was measured in counterflow laminar diffusion flames of C1-4 alcohols and hydrocarbon fuels of n-heptane, n-octane, iso-octane, toluene, Jet-A, and biodiesel. The luminous flame height, as marked by visible soot radiation, of the nitrogen- and helium-diluted n-heptane and nitrogen- and carbon dioxide-diluted ethylene flames stayed constant at all pressures. In pure ethylene flames, flame heights initially increased with pressure, but changed little above 5 atm. The maximum soot yield as a function of pressure in nitrogen-diluted n-heptane diffusion flames indicate that n-heptane flames are slightly more sensitive to pressure than gaseous alkane hydrocarbon flames at least up to 7 atm. Ethylene's maximum soot volume fractions were much higher than those of ethane and n-heptane diluted with nitrogen (fuel to nitrogen mass flow ratio is about 0.5). Pressure dependence of the peak carbon conversion to soot, defined as the percentage of fuel's carbon content converted to soot, was assessed and compared to previous measurements with other gaseous fuels. Maximum soot volume fractions were consistently lower in carbon dioxide-diluted flames between 5 and 15 atm but approached similar values to those in nitrogen-diluted flames at 20 atm. This observation implies that the chemical soot suppression effect of carbon dioxide, previously demonstrated at atmospheric pressure, is also present at elevated pressures up to 15 atm, but fades off beyond 15 atm. In flame stability experiments, the extinction strain rates increased with decreasing dilution. In general, the fuels with higher carbon number and fuels with more compact structures were found to be more prone to extinction. Counterflow laminar diffusion flames established at the impingement of reactants with a top-hat (axially uniform) velocity profile were found to be more resistant to extinction than those with a parabolic exit velocity profile. Multiple solutions to the flame stability were observed for certain hydrocarbons.

  9. Influences of carrier diffusion and radial mode field pattern on high speed characteristics for microring lasers

    SciTech Connect

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

    2014-04-21

    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 μm, which accords with the simulation results.

  10. Microstructural characteristics of HIP-bonded monolithic nuclear fuels with a diffusion barrier

    NASA Astrophysics Data System (ADS)

    Jue, Jan-Fong; Keiser, Dennis D.; Breckenridge, Cynthia R.; Moore, Glenn A.; Meyer, Mitchell K.

    2014-05-01

    Due to the limitation of maximum uranium load achievable by dispersion fuel type, the Global Threat Reduction Initiative is developing an advanced monolithic fuel to convert US high-performance research reactors to low-enriched uranium. Hot-isostatic-press (HIP) bonding was the single process down-selected to bond monolithic U-Mo fuel meat to aluminum alloy cladding. A diffusion barrier was applied to the U-Mo fuel meat by roll-bonding process to prevent extensive interaction between fuel meat and aluminum-alloy cladding. Microstructural characterization was performed on fresh fuel plates fabricated at Idaho National Laboratory. Interfaces between the fuel meat, the cladding, and the diffusion barrier, as well as between the U-10Mo fuel meat and the Al-6061 cladding, were characterized by scanning electron microscopy. Preliminary results indicate that the interfaces contain many different phases while decomposition, second phases, and chemical banding were also observed in the fuel meat. The important attributes of the HIP-bonded monolithic fuel are: diffusion barrier with a thickness of 25 μm. A transverse cross section that exhibits relatively equiaxed grains with an average grain diameter of 10 μm. Chemical banding, in some areas more than 100 μm in length, that is very pronounced in longitudinal (i.e., rolling) direction with Mo concentration varying from 7-13 wt.%. Decomposed areas containing plate-shaped low-Mo phase. A typical Zr/cladding interaction layer with a thickness of 1-2 μm. A visible UZr2 bearing layer with a thickness of 1-2 μm. Mo-rich precipitates (mainly Mo2Zr, forming a layer in some areas) followed by a Mo-depleted sub-layer between the visible UZr2-bearing layer and the U-Mo matrix. No excessive interaction between cladding and the uncoated fuel edge. Cladding-to-cladding bonding that exhibits no cracks or porosity with second phases high in Mg, Si, and O decorating the bond line. Some of these attributes might be critical to the irradiation performance of monolithic U-10Mo nuclear fuel. There are several issues or concerns that warrant more detailed study, such as precipitation along the cladding-to-cladding bond line, chemical banding, uncovered fuel-zone edge, and the interaction layer between the U-Mo fuel meat and zirconium. Future post-irradiation examination results will focus, among other things, on identifying in-reactor failure mechanisms and, eventually, directing further fresh fuel characterization efforts.

  11. Microstructural Characteristics of HIP-bonded Monolithic Nuclear Fuels with a Diffusion Barrier

    SciTech Connect

    Jan-Fong Jue; Dennis D. Keiser, Jr.; Cynthia R. Breckenridge; Glenn A. Moore; Mitchell K. Meyer

    2014-05-01

    Due to the limitation of maximum uranium load achievable by dispersion fuel type, the Global Threat Reduction Initiative (GTRI) is developing an advanced monolithic fuel to convert US high performance research reactors to low-enriched uranium. Hot-isostatic-press bonding was the single process down-selected to bond monolithic U-Mo fuel meat to aluminum alloy cladding. A diffusion barrier was applied to the U–Mo fuel meat by roll-bonding process to prevent extensive interaction between fuel meat and aluminum-alloy cladding. Microstructural characterization was performed on fresh fuel plates fabricated at Idaho National Laboratory. Interfaces between fuel meat, cladding, and diffusion barrier, as well as U–10Mo fuel meat and Al–6061 cladding were characterized by scanning electron microscopy. Preliminary results indicate that the interfaces contain many different phases while decomposition, second phases, and chemical banding were also observed in the fuel meat. The important attributes of the HIP-bonded monolithic fuel are • A typical Zr diffusion barrier of thickness 25 µm • Transverse cross section that exhibits relatively equiaxed grains with an average grain diameter of 10 µm • Chemical banding, in some areas more than 100 µm in length, that is very pronounced in longitudinal (i.e., rolling) direction with Mo concentration varying from 7–13 wt% • Decomposed areas containing plate-shaped low-Mo phase • A typical Zr/cladding interaction layer of thickness 1-2 µm • A visible UZr2 bearing layer of thickness 1-2 µm • Mo-rich precipitates (mainly Mo2Zr, forming a layer in some areas) followed by a Mo-depleted sub-layer between the visible UZr2-bearing layer and the U–Mo matrix • No excessive interaction between cladding and the uncoated fuel edge • Cladding-to-cladding bonding that exhibits no cracks or porosity with second phases high in Mg, Si, and O decorating the bond line. • Some of these attributes might be critical to the irradiation performance of monolithic U-10Mo nuclear fuel. There are several issues or concerns that warrant more detailed study, such as precipitation along cladding-to-cladding bond line, chemical banding, uncovered fuel-zone edge, and interaction layer between U–Mo fuel meat and zirconium. Future post-irradiation examination results will focus, among other things, on identifying in-reactor failure mechanisms and, eventually, directing further fresh fuel characterization efforts.

  12. Investigation of doped calcium aluminosilicate glass: A coupling between thermal-expansion and thermal-diffusion models for assessment of nonradiative relaxation time and characteristic diffusion time

    NASA Astrophysics Data System (ADS)

    Souza Filho, N. E.; Nogueira, A. C.; Rohling, J. H.; Baesso, M. L.; Medina, A. N.; Siqueira, A. P. L.; Sampaio, J. A.; Vargas, H.; Bento, A. C.

    2009-11-01

    This paper discusses the use of photoacoustic models to obtain the nonradiative relaxation time (?) and characteristic diffusion time (??) for a sample showing visible absorption bands from fluorescent ion-doped low-silica calcium aluminosilicate glass. Two models allowing phase shift analyses, the thermal-expansion and thermal-diffusion models, are briefly reviewed. These models have limitations when the photoacoustic signal depends on both factors, in a coupling mechanism. An alternative model is proposed to take both thermal expansion and thermal diffusion into account with a single temperature solution for the heat-coupled differential equation. This model is simulated for absorbing samples near the thermally thick region. The model is applied to Eu-V codoped glass showing intermediate signal dependence from ?-1.0 to ?-3/2. The nonradiative time and characteristic diffusion time are derived with 33

  13. Performance characteristics of two annular dump diffusers using suction-stabilized vortex flow control

    NASA Technical Reports Server (NTRS)

    Juhasz, A. J.; Smith, J. M.

    1978-01-01

    Test results are described for two abrupt area change annular diffusers with provisions for maintaining suction stabilized toroidal vortices at the area discontinuity. Both diffusers had an overall area ratio of 4.0 with the prediffuser area ratio being 1.18 for diffuser A and 1.4 for diffuser B. Performance was evaluated at near atmospheric pressure and temperature for a range of inlet Mach numbers from 0.18 to 0.41 and suction rates from 0 to 18%. Static pressure recovery improved significantly as the suction rate was increased to approximately 11%. Results obtained with diffuser A were superior to that obtained with diffuser B. Flat radial profiles of exit velocity were not obtained since the flow showed preferential hub or tip attachment at moderate suction rates. At high suction rates the diffuser exit flow became circumferentially nonuniform and unstable.

  14. LABORATORY ASSESSMENT OF THE PERMEABILITY AND DIFFUSION CHARACTERISTICS OF FLORIDA CONCRETES - PHASE I. METHODS DEVELOPMENT AND TESTING

    EPA Science Inventory

    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...

  15. LABORATORY ASSESSMENT OF THE PERMEABILITY AND DIFFUSION CHARACTERISTICS OF FLORIDA CONCRETES - PHASE I - METHODS DEVELOPMENT AND TESTING

    EPA Science Inventory

    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...

  16. Characteristics of dynamic cerebral autoregulation in cerebral small vessel disease: Diffuse and sustained

    PubMed Central

    Guo, Zhen-Ni; Xing, Yingqi; Wang, Shuang; Ma, Hongyin; Liu, Jia; Yang, Yi

    2015-01-01

    Cerebral small vessel disease is a major cause of stroke and vascular dementia; however, the pathogenesis is largely unclear. In this study, we investigated the characteristics of the impairment of dynamic cerebral autoregulation (dCA) in lacunar infarction patients. Seventy-one lacunar infarction patients were enrolled in the study, including 46 unilateral middle cerebral artery (MCA) territory stroke patients and 25 unilateral posterior cerebral artery (PCA) territory stroke patients. Each group of patients was randomly divided into two subgroups. Group 1 underwent dCA assessments in the bilateral MCAs, and Group 2 underwent dCA assessments in the bilateral PCAs. All patients were followed up for 6 months. Transfer function analysis was applied to derive the autoregulatory parameters of gain and phase difference. In the unilateral MCA territory stroke patients, impairments of dCA were observed in both the MCAs and PCAs, and the same results were observed in the unilateral PCA territory stroke patients. These impairments remained unchanged during the 6-month follow-up. In lacunar infarction, which is most prevalent type of cerebral small vessel disease, though patients with unilateral MCA territory/PCA territory stroke, the impairments of dCA were global and sustained. This finding suggests that the physiological changes associated with lacunar infarction were diffuse. PMID:26469343

  17. Characteristics of dynamic cerebral autoregulation in cerebral small vessel disease: Diffuse and sustained.

    PubMed

    Guo, Zhen-Ni; Xing, Yingqi; Wang, Shuang; Ma, Hongyin; Liu, Jia; Yang, Yi

    2015-01-01

    Cerebral small vessel disease is a major cause of stroke and vascular dementia; however, the pathogenesis is largely unclear. In this study, we investigated the characteristics of the impairment of dynamic cerebral autoregulation (dCA) in lacunar infarction patients. Seventy-one lacunar infarction patients were enrolled in the study, including 46 unilateral middle cerebral artery (MCA) territory stroke patients and 25 unilateral posterior cerebral artery (PCA) territory stroke patients. Each group of patients was randomly divided into two subgroups. Group 1 underwent dCA assessments in the bilateral MCAs, and Group 2 underwent dCA assessments in the bilateral PCAs. All patients were followed up for 6 months. Transfer function analysis was applied to derive the autoregulatory parameters of gain and phase difference. In the unilateral MCA territory stroke patients, impairments of dCA were observed in both the MCAs and PCAs, and the same results were observed in the unilateral PCA territory stroke patients. These impairments remained unchanged during the 6-month follow-up. In lacunar infarction, which is most prevalent type of cerebral small vessel disease, though patients with unilateral MCA territory/PCA territory stroke, the impairments of dCA were global and sustained. This finding suggests that the physiological changes associated with lacunar infarction were diffuse. PMID:26469343

  18. Liquid water transport characteristics of porous diffusion media in polymer electrolyte membrane fuel cells: A review

    NASA Astrophysics Data System (ADS)

    Liu, Xunliang; Peng, Fangyuan; Lou, Guofeng; Wen, Zhi

    2015-12-01

    Fundamental understanding of liquid water transport in gas diffusion media (GDM) is important to improve the material and structure design of polymer electrolyte membrane (PEM) fuel cells. Continuum methods of two-phase flow modeling facilitate to give more details of relevant information. The proper empirical correlations of liquid water transport properties, such as capillary characteristics, water relative permeability and effective contact angle, are crucial to two phase flow modeling and cell performance prediction. In this work, researches on these properties in the last decade are reviewed. Various efforts have been devoted to determine the water transport properties for GDMs. However, most of the experimental studies are ex-situ measurements. In-situ measurements for GDMs and extending techniques available to study the catalyst layer and the microporous layer will be further challenges. Using the Leverett-Udell correlation is not recommended for quantitative modeling. The reliable Leverett-type correlation for GDMs, with the inclusion of the cosine of effective contact angle, is desirable but hard to be established for modeling two-phase flow in GDMs. A comprehensive data set of liquid water transport properties is needed for various GDM materials under different PEM fuel cell operating conditions.

  19. Effect of a long alkyl group on cyclopentadithiophene as a conjugated bridge for D-A-?-A organic sensitizers: IPCE, electron diffusion length, and charge recombination.

    PubMed

    Chai, Qipeng; Li, Wenqin; Wu, Yongzhen; Pei, Kai; Liu, Jingchuan; Geng, Zhiyuan; Tian, He; Zhu, Weihong

    2014-08-27

    The option of using conjugated ?-linkers is critical for rational molecular design toward an energy-level strategy for organic sensitizers. To further optimize photovoltaic performance, methyl- and octyl-substituted 4H-cyclopenta[2,1-b:3,4-b']dithiophene (CPDT) are introduced into D-A-?-A featured sensitizers. Along with CPDT, instead of thiophene as conjugated bridge, WS-39 and WS-43 exhibit an extended spectral response due to the excellent conjugation and coplanarity of CPDT. Specifically, we focused on the critical effect of length of the alkyl group linked to the bridging carbon atoms of CPDT on the photovoltaic performances. Octyl-substituted WS-39 shows a broader IPCE onset with an enhanced photovoltage relative to the analogue WS-5. In contrast, WS-43, with methyl substituted on the CPDT moiety, presents a relatively low quantum conversion efficiency within the whole spectral response region, along with low photocurrent density. WS-43 displays a distinctly low IPCE platform, predominately arising from the short electron diffusion length with significant electron loss during the electron transport. The relative movement of the conduction band edge (E(CB)) and charge transfer resistance as well as lifetime of injected electrons are studied in detail. Under standard AM 1.5 conditions, WS-39-based solar cells show a promising photovoltaic efficiency of 9.07% (J(SC) = 16.61 mA cm(-2), V(OC) = 770 mV, FF = 0.71). The octyl chains attached on CPDT can provide dual protection and exhibit a high propensity to prevent binding of the iodide-triiodide redox couple, producing an efficient shielding effect to retard the charge recombination and resulting in improvement of V(OC). Our research paves the way to explore more efficient sensitizers through ingenious molecular engineering. PMID:25062140

  20. Minority-carrier diffusion length, minority-carrier lifetime, and photoresponsivity of {beta}-FeSi{sub 2} layers grown by molecular-beam epitaxy

    SciTech Connect

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

    2011-06-15

    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.

  1. Clinical applications and characteristics of apparent diffusion coefficient maps for the brain of two dogs

    PubMed Central

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

    2014-01-01

    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

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

    PubMed Central

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

    2013-01-01

    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

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

    PubMed

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

    2013-10-21

    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 = 0.0-2.0C), temporal sampling (tacq= 1.0-8.0s), and spatial averaging (Res = 0.5-2.0mm isotropic) on HIFU temperature measurements and temperature-based estimates of the amplitude and full width half maximum (FWHM) of the HIFU specific absorption rate and of tissue thermal diffusivity. The ultrasound beam used in simulations and ex vivo pork loin experiments has lateral and axial FWHM dimensions of 1.4mm and 7.9mm respectively. For spatial averaging simulations, beams with lateral FWHM varying from 1.2-2.2mm 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 1נ1נ3mm(3)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

  4. White matter structure and clinical characteristics of stroke patients: A diffusion tensor MRI study.

    PubMed

    Ueda, Ryo; Yamada, Naoki; Kakuda, Wataru; Abo, Masahiro; Senoo, Atsushi

    2016-03-15

    Fractional anisotropy has been used in many studies that examined post-stroke changes in white matter. This study was performed to clarify cerebral white matter changes after stroke using generalized fractional anisotropy (GFA). White matter structure was visualized using diffusion tensor imaging in 72 patients with post-stroke arm paralysis. Exercise-related brain regions were examined in cerebral white matter using GFA. The relationship between GFA and clinical characteristics was examined. Overall, the mean GFA of the lesioned hemisphere was significantly lower than that of the non-lesioned hemisphere (P<0.05), the white matter of the lesioned side was severely affected by stroke. A weak negative correlation between GFA and time since stroke onset was found in Brodmann area 5 of the non-lesioned hemisphere. Age correlated negatively with GFA in Brodmann areas 5 and 7 of the lesioned hemisphere. Though these results may be due to a decrease in the frequency of use of the paralyzed limb over time, GFA overall was significantly and negatively affected by the subject's age. The GFA values of patients with paralysis of the dominant hand were significantly different from those of patients with paralysis of the nondominant hand in Brodmann areas 4 and 6 of the non-lesioned hemisphere and Brodmann area 4 of the lesioned hemisphere (P<0.05). The stroke size and location were not associated with GFA differences. Differences between the GFA of the lesioned and non-lesioned hemispheres varied depending on the affected brain region, age at onset of paralysis, and paralysis of the dominant or non-dominant hand. PMID:26783693

  5. Theoretical and experimental analyses of atom diffusion characteristics on wire bonding interfaces

    NASA Astrophysics Data System (ADS)

    Li, Junhui; Fuliang, Wang; Han, Lei; Zhong, Jue

    2008-07-01

    The features of ultrasonic bonding interface were inspected by using a high resolution transmission electron microscope. Stress of ultrasonic bonding interface was analysed by the finite elements simulation. Results show that the high stress of bonding interface was caused by ultrasonic vibration, which increased the dislocation density inside the metal crystalline lattice which provides the fast diffusion channels, and provided driving force for atom inter-diffusion. 'Short-circuit diffusion' during ultrasonic bonding is more prominent than crystal diffusion. For the given ultrasonic bonding parameters, depth of atom diffusion at Au/Al interface of ultrasonic bonding was about 100-300 nm in several ten milliseconds, which forms the bonding strength of 0.65 N, and it is an inter-metallic compound of AuAl2. These will be helpful for further analysis.

  6. Effects of Maternal and Infant Characteristics on Birth Weight and Gestation Length in a Colony of Rhesus Macaques (Macaca mulatta)

    PubMed Central

    Hopper, Kelly J; Capozzi, Denise K; Newsome, Joseph T

    2008-01-01

    A retrospective study using maternal and birth statistics from an open, captive rhesus macaque colony was done to determine the effects of parity, exposure to simian retrovirus (SRV), housing, maternal parity, and maternal birth weight on infant birth weight, viability and gestation length. Retrospective colony statistics for a 23-y period indicated that birth weight, but not gestation length, differed between genders. Adjusted mean birth weights were higher in nonviable infants. Mothers positive for SRV had shorter gestations, but SRV exposure did not affect neonatal birth weights or viability. Infants born in cages had longer gestations than did those born in pens, but neither birth weight nor viability differed between these groups. Maternal birth weight did not correlate with infant birth weight but positively correlated with gestation length. Parity was correlated with birth weight and decreased viability. Increased parity of the mother was associated with higher birth weight of the infant. A transgenerational trend toward increasing birth weight was noted. The birth statistics of this colony were consistent with those of other macaque colonies. Unlike findings for humans, maternal birth weight had little predictive value for infant outcomes in rhesus macaques. Nonviable rhesus infants had higher birth weights, unlike their human counterparts, perhaps due to gestational diabetes occurring in a sedentary caged population. Similar to the situation for humans, multiparity had a protective effect on infant viability in rhesus macaques. PMID:19149417

  7. High-Subsonic Performance Characteristics and Boundary-Layer Investigations of a 12 10-Inch-Inlet-Diameter Conical Diffuser

    NASA Technical Reports Server (NTRS)

    Little, B. H., Jr.; Wilbur, Stafford W.

    1950-01-01

    Performance and boundary-layer data were taken in a 12 degree 10-inch inlet-diameter conical diffuser of 2:1 exit- to inlet-area ratio. These data were taken for two inlet-boundary-layer conditions. The first condition was that of a thinner inlet boundary later (boundary-layer displacement thickness, delta* approximately equal to 0.034) produced by an inlet section approximately 1 inlet diameter in length between the entrance bell and the diffuser. The second condition was a thicker inlet boundary layer (delta* approximately equal to 0.120) produced by an additional inlet section length of approximately 6 diameters. Longitudinal static-pressure distributions were measured fro wall static orifices. Transverse total- and static-pressure surveys were made at the inlet and exit stations. Boundary-layer velocity distributions were measured at seven stations between the inlet and exit. These data were obtained for a Reynolds number (based on inlet diameter) range of 1 x 10(exp 6) to 3.9 x 10(exp 6). The corresponding Mach number range was from M = 0.2 to choking. At the maximum-power-available condition supersonic flow was obtained as far as 4.5 inches downstream from the diffuser inlet with a maximum Mach number of M approximately equal to 1.5. The total-pressure loss through the diffuser in percentage of inlet dynamic pressure was approximately 2.5 percent for the thinner inlet boundary later and 5.5 percent for the thicker inlet boundary later over the lower subsonic range. These valued increased with increasing flow rate- the values for the thicker inlet boundary later more than those for the thinner inlet boundary layer. The diffuser effectiveness, expressed as the ratio of the actual static-pressure rise to the ideal static-pressure rise, was about 85 percent for the thinner inlet boundary layer and about 67 percent for the thicker inlet boundary later in the lower subsonic range. These values decrease with increasing flow rate. Separated flow was observed for both inlet-boundary-layer conditions in the region of adverse pressure gradient just downstream of the transition curvature from inlet section to diffuser. The flow for the thinner-inlet-boundary-layer condition did not fully re-establish itself along the diffuser walls. The thicker inlet-boundary-layer flow, while not completely re-establishing the normal flow pattern downstream of the separated region, did re-establish more successfully than the thinner inlet boundary layer.

  8. Electron-hole diffusion lengths >175 ?m in solution-grown CH3NH3PbI3 single crystals

    SciTech Connect

    Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan; Mulligan, Padhraic; Qiu, Jie; Cao, Lei; Huang, Jinsong

    2015-02-27

    Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm2) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smaller trap densities in the single crystals than in polycrystalline thin films. As a result, the long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.

  9. Electron-hole diffusion lengths >175 μm in solution-grown CH3NH3PbI3 single crystals

    SciTech Connect

    Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan; Mulligan, Padhraic; Qiu, Jie; Cao, Lei; Huang, Jinsong

    2015-02-27

    Long, balanced electron and hole diffusion lengths greater than 100 nanometers in the polycrystalline organolead trihalide compound CH3NH3PbI3 are critical for highly efficient perovskite solar cells. We found that the diffusion lengths in CH3NH3PbI3 single crystals grown by a solution-growth method can exceed 175 micrometers under 1 sun (100 mW cm–2) illumination and exceed 3 millimeters under weak light for both electrons and holes. The internal quantum efficiencies approach 100% in 3-millimeter-thick single-crystal perovskite solar cells under weak light. These long diffusion lengths result from greater carrier mobility, longer lifetime, and much smaller trap densities in the single crystals than in polycrystalline thin films. As a result, the long carrier diffusion lengths enabled the use of CH3NH3PbI3 in radiation sensing and energy harvesting through the gammavoltaic effect, with an efficiency of 3.9% measured with an intense cesium-137 source.

  10. Altering length and velocity feedback during a neuro-musculoskeletal simulation of normal gait contributes to hemiparetic gait characteristics

    PubMed Central

    2014-01-01

    Background Spasticity is an important complication after stroke, especially in the anti-gravity muscles, i.e. lower limb extensors. However the contribution of hyperexcitable muscle spindle reflex loops to gait impairments after stroke is often disputed. In this study a neuro-musculoskeletal model was developed to investigate the contribution of an increased length and velocity feedback and altered reflex modulation patterns to hemiparetic gait deficits. Methods A musculoskeletal model was extended with a muscle spindle model providing real-time length and velocity feedback of gastrocnemius, soleus, vasti and rectus femoris during a forward dynamic simulation (neural control model). By using a healthy subjects base muscle excitations, in combination with increased feedback gains and altered reflex modulation patterns, the effect on kinematics was simulated. A foot-ground contact model was added to account for the interaction effect between the changed kinematics and the ground. The qualitative effect i.e. the directional effect and the specific gait phases where the effect is present, on the joint kinematics was then compared with hemiparetic gait deviations reported in the literature. Results Our results show that increased feedback in combination with altered reflex modulation patterns of soleus, vasti and rectus femoris muscle can contribute to excessive ankle plantarflexion/inadequate dorsiflexion, knee hyperextension/inadequate flexion and increased hip extension/inadequate flexion during dedicated gait cycle phases. Increased feedback of gastrocnemius can also contribute to excessive plantarflexion/inadequate dorsiflexion, however in combination with excessive knee and hip flexion. Increased length/velocity feedback can therefore contribute to two types of gait deviations, which are both in accordance with previously reported gait deviations in hemiparetic patients. Furthermore altered modulation patterns, in particular the reduced suppression of the muscle spindle feedback during swing, can contribute largely to an increased plantarflexion and knee extension during the swing phase and consequently to hampered toe clearance. Conclusions Our results support the idea that hyperexcitability of length and velocity feedback pathways, especially in combination with altered reflex modulation patterns, can contribute to deviations in hemiparetic gait. Surprisingly, our results showed only subtle temporal differences between length and velocity feedback. Therefore, we cannot attribute the effects seen in kinematics to one specific type of feedback. PMID:24885302

  11. Pressure dependence of separative characteristics of thermal diffusion column for H/sub 2/ - HT isotope separation

    SciTech Connect

    Yamamoto, I.; Kaba, A.; Kanagawa, A.

    1988-09-01

    Experiments of H/sub 2/-HT isotope separation were carried out with a hot wire column of 3 cm in diameter and 1.5 m in length. Separation factors were measured with cut changed from 0.1 to 0.9, and other operational conditions: pressure, feed rate and temperature difference, fixed. First, the feed rate was altered under the constant pressure, and next, pressure was changed. Experimental results were compared with those from an axisymmetric separative analysis, based on a Newton iterative solution of a convection-diffusion equation. Pressure dependence of separation factors agreed qualitatively with those from theory.

  12. Magnetic Resonance Diffusion Characteristics of Histologically Defined Prostate Cancer in Humans

    PubMed Central

    Xu, Junqian; Humphrey, Peter A.; Kibel, Adam S.; Snyder, Abraham Z.; Narra, Vamsidhar R.; Ackerman, Joseph J.H.; Song, Sheng-Kwei

    2010-01-01

    The contrast provided by diffusion-sensitive magnetic resonance offers the promise of improved tumor localization in organ-confined human prostate cancer (PCa). Diffusion tensor imaging (DTI) measurements of PCa were performed in vivo, in patients undergoing radical prostatectomy, and later, ex vivo, in the same patients prostatectomy specimens. The imaging data were coregistered to histological sections of the prostatectomy specimens, thereby enabling unambiguous characterization of diffusion parameters in cancerous and benign tissues. Increased cellularity, and hence decreased luminal spaces, in peripheral zone PCa led to approximately 40% and 50% apparent diffusion policy (ADC) decrease compared with benign peripheral zone tissues in vivo and ex vivo, respectively. In contrast, no significant diffusion anisotropy differences were observed between the cancerous and noncancerous peripheral zone tissues. However, the dense fibromuscular tissues in prostate, such as stromal tissues in benign prostatic hyperplasia in central gland, exhibited high diffusion anisotropy. A tissue classification method is proposed to combine DTI and T2-weighted image contrasts that may provide improved specificity of PCa detection over T2-weighted imaging alone. PCa identified in volume rendered MR images qualitatively correlates well with histologically determined PCa foci. PMID:19215051

  13. Clinical characteristics by topographical distribution of brain microbleeds, with a particular emphasis on diffuse microbleeds.

    PubMed

    Yakushiji, Yusuke; Yokota, Chiaki; Yamada, Naoaki; Kuroda, Yasuo; Minematsu, Kazuo

    2011-01-01

    From the perspective of the underlying pathogenesis of primary intracerebral hemorrhage (pICH), the topographical distribution of brain microbleeds (MBs) is divided into the lobar area and the deep brain or infratentorial areas. We investigated clinical features, including ambulatory blood pressure (ABP), of patients with MBs distributed in both areas (diffuse MBs). A total of 124 patients with first-ever acute stroke were enrolled prospectively. Gradient-echo T2?-weighted magnetic resonance imaging (MRI) was performed using a 1.5-T scanner. Patients were classified into 4 groups: MBs-negative group (n=68), those with MBs in lobar areas (lobar group; n=6), those with MBs in deep or infratentorial areas (deep or infratentorial group; n=31), and those with MBs in both areas (diffuse group; n=19). The admission casual BP (CBP) was recorded in all patients, and ABP was measured in the ischemic stroke patients. There were significant differences in the distribution of MBs (P=.004) among the 6 stroke subtypes. All stroke subtypes except transient ischemic attack had diffuse MBs; pICH had the highest prevalence of it (35%). The severity of white matter hyperintensity (WMH) differed among the 4 groups (P < .0001), with the diffuse group having the highest prevalence of early confluent (47%) and confluent types (21%). ABP and CBP were significantly higher in the deep and diffuse groups compared with the MBs-negative group, but did not differ between the lobar group and the MBs-negative group. Our data suggest that diffuse MBs are associated with hypertensive stroke, elevated BP, and severe WMH. The pathogenesis of diffuse MBs may be related to the more severe microangiopathy involved in hypertensive arteriopathy and cerebral amyloid angiopathy. PMID:20621512

  14. Effect of gate-length shortening on the terahertz small-signal and self-oscillations characteristics of field-effect transistors

    NASA Astrophysics Data System (ADS)

    Starikov, E.; Shiktorov, P.; Gruinskis, V.; Marinchio, H.; Palermo, C.; Varani, L.

    2015-12-01

    We investigate the shortening of the gate-length in submicrometric and nanometric field-effect transistors as a powerful tool to improve their self-oscillations performances in the terahertz frequency region due to the appearance of the Dyakonov-Shur instability. The theoretical model is based on the numerical solution of hydrodynamic equations for the electron transport in FETs/HEMTs channels. We show that a decrease of the gate length allows, on the one hand, to increase the intrinsic resonant frequencies near 1 THz and, on the other hand, to improve the conditions for the onset of the Dyakonov-Shur instability and related phenomena. The small-signal characteristics calculated under constant drain-voltage operation are compared with the drain-voltage self-oscillations calculated under constant drain-current operation.

  15. Electrical characteristics and short-channel effect of c-axis aligned crystal indium gallium zinc oxide transistor with short channel length

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yoshiyuki; Matsuda, Shinpei; Matsubayashi, Daisuke; Suzawa, Hideomi; Sakakura, Masayuki; Hanaoka, Kazuya; Okazaki, Yutaka; Yamamoto, Tsutomu; Hondo, Suguru; Hamada, Takashi; Sasagawa, Shinya; Nagai, Masaharu; Hata, Yuki; Maruyama, Tetsunori; Yamamoto, Yoshitaka; Yamazaki, Shunpei

    2014-01-01

    A channel length of a c-axis aligned crystal indium gallium zinc oxide (CAAC-IGZO) transistor having low off-state current at a yA/m level was decreased to 100 nm, and the electrical characteristics and short-channel effect of the CAAC-IGZO transistor were researched. As a result, we found that, in the CAAC-IGZO transistor with L = 100 nm, even with a gate insulator film having an equivalent oxide thickness (EOT) = 11 nm, an extremely small off-state current of 380 yA/m at 85 C is maintained, in addition channel length dependence of the electrical characteristics is hardly seen. Favorable values of characteristics of the CAAC-IGZO transistor can be obtained, such as subthreshold slope (SS) = 77 mV/dec, drain induced barrier lowering (DIBL) = 73 mV/V, threshold voltage (Vth) = 0.65 V, and on-state current (Ion) = 65 A/m. These results suggest the possibility that the CAAC-IGZO transistor can be applied to an LSI in a deep submicron region.

  16. Measurement of ZnO nanoparticles using diffusive gradients in thin films: binding and diffusional characteristics.

    PubMed

    Pouran, Hamid M; Martin, Francis L; Zhang, Hao

    2014-06-17

    Rapid growth in finding new applications for manufactured nanomaterials (MNM) has recently been accompanied by awareness about their related adverse toxicological and environmental impacts. Due to their intrinsic nature, measuring available concentrations of MNMs in the environment is a major challenge. This research is a launching point toward filling this gap, as it presents the potential of the well-established diffusive gradients in thin films (DGT) technique to determine MNMs concentrations in situ. Two binding layers commonly used in DGT devices were shown to be able to bind ZnO nanoparticles (ZnO NPs). The use of different types of diffusive layers demonstrated the critical role of their pore size for selective function of the DGT devices. The ZnO NPs can pass through the open pore diffusive layer used in standard DGT devices and be retained by the binding resin layer. However, the diffusion of ZnO NPs can be prevented when a 1000 MWCO (molecular weight cut off) dialysis membrane is placed in the front of the diffusive gel layer. A combination of two or more DGT devices with known diffusive layer properties should enable deduction of concentrations of available ZnO NPs in the environment. Unlike metal ions, determining diffusion coefficient values for ZnO NPs is challenging and greatly affected by shape, morphology, and solution-induced changes of the particles. Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) demonstrated that retention of ZnO NPs by Chelex and Metsorb binding layers occurs through chemisorption. The superior uptake kinetic for Chelex indicates that it is a better candidate for further development of DGT devices to measure ZnO NPs. These initial results are promising and important for further developing the DGT technique to measure available concentrations of manufactured nanomaterials in the different environmental media (waters, soils, and sediments). Further experiments investigating the effects of pH, ionic strength, and solution chemistry on the performance of DGT for measuring MNM concentrations are needed. PMID:24831848

  17. Numerical simulation of gas diffusion effects on charge/discharge characteristics of a solid oxide redox flow battery

    NASA Astrophysics Data System (ADS)

    Ohmori, Hiroko; Uratani, Syoichi; Iwai, Hiroshi

    2012-06-01

    Fundamental characteristics of a solid oxide redox flow battery consisting of solid oxide electrochemical cell (SOEC) and redox metal were studied by a gas-diffusion based time-dependent 1-D numerical simulation taking both the electrochemical and redox reactions into account. Close attention was paid to the distributions of the participating gas species and their effects on the charge/discharge performance. The volume expansion/reduction of the porous metal associated with the redox reaction was modeled as decrease/increase in local porosity. The numerical results for charge/discharge operation qualitatively showed the time-dependent distributions of the related physical quantities such as the gas concentrations, the active reaction region in the redox metal, and its local porosity. It was found that, to ensure effective redox reaction throughout the operation, the gas diffusion in the redox metal should be carefully designed.

  18. Molecular emission characteristics of various fluorides in a low-temperature-hydrogen diffusion flame.

    PubMed

    Dagnall, R M; Fleet, B; Risby, T H; Deans, D R

    1971-02-01

    A capillary burner supporting a nitrogen/hydrogen diffusion flame has been evaluated as a possible means of detection for several volatile fluorides after their gas-chromatographic separation. The fluorides of As, B, C, Ge, I, Mo, P, Re, S, Sb, Se, Si, Te and W were formed by the reaction of the element with chlorine trifluoride, and the intense molecular emission given by each was recorded. An attempt was made to identify the emitting species. PMID:18960872

  19. Diffusion barrier characteristics of co monolayer prepared by Langmuir Blodgett technique

    NASA Astrophysics Data System (ADS)

    Sharma, Sumit; Kumar, Mukesh; Rani, Sumita; Kumar, Dinesh

    2016-04-01

    Monolayers of Co over SiO2/Si substrate were deposited using Langmuir Blodgett (LB) technique. The diffusion barrier capability of Co layer was evaluated against copper diffusion. The structure of the deposited Co layer was analyzed using X-ray photoelectron spectroscopy (XPS), Energy Dispersive X-ray Spectroscopy (EDS) and Atomic force microscopy (AFM) techniques. Thermal stability of Cu/SiO2/Si and Cu/Co/SiO2/Si test structures was studied and compared using X-ray diffraction (XRD), scanning electron microscope (SEM) and four probe techniques. The samples were annealed at different temperatures starting from 200 °C up to 700 °C in vacuum for 30 min. XRD results indicated that combination of Co/SiO2 worked as diffusion barrier up to 550 °C whereas SiO2 alone could work as barrier only up to 300 °C. Sheet resistance of these samples was measured as a function of annealing temperature which also supports XRD results. C-V curves of these structures under the influence of Biased Thermal Stress (BTS) were analyzed. BTS was applied at 2.5 MV cm-1 at 150 °C. Results showed that in the presence of Co barrier layer there was no shift in the C-V curve even after 90 min of BTS while in the absence of barrier there was a significant shift in the C-V curve even after 30 min of BTS. Further these test structures were examined for leakage current density (jL) at same BTS conditions and leakage current density (jL) was plotted against the BTS duration. It was found that the Cu/Co/SiO2/Si test structure could survive about one and half time more than the Cu/SiO2/Si test structure.

  20. Application of continuum percolation theory for modeling single- and two-phase characteristics of anisotropic carbon paper gas diffusion layers

    NASA Astrophysics Data System (ADS)

    Ghanbarian, Behzad; Cheng, Ping

    2016-03-01

    Percolation theory is used to model intrinsic and relative permeabilities as well as tortuosity in anisotropic carbon paper gas diffusion layers (GDL) and compared with existing results from lattice-Boltzmann (LB) simulations and experimental measurements. Although single- and two-phase characteristics of the carbon paper GDL are mainly affected by medium geometrical and topological properties, e.g., pore-size distribution, connectivity, and pore geometry, analyzing capillary pressure curves implies that the pore-size distribution of the carbon paper GDL is very narrow. This suggests that its effect on tortuosity and wetting- and nonwetting-phase relative permeabilities is trivial. However, integrated effects of pore geometry, surface area, connectivity, and tortuosity on intrinsic permeability might be substantial. Universal power laws from percolation theory predict the tortuosity-porosity and relative permeability-saturation curves accurately, indicating both characteristics not affected by the pore-size distribution. The permeability-porosity relationship, however, conforms to nonuniversality.

  1. Content Characteristics Driving the Diffusion of Antismoking Messages: Implications for Cancer Prevention in the Emerging Public Communication Environment

    PubMed Central

    2013-01-01

    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

  2. Characteristics of red-emitting broad area stripe laser diodes with zinc diffused window structures

    NASA Astrophysics Data System (ADS)

    Ohno, Tomoki; Takiguchi, Mikio; Wakabayashi, Kazuya; Uchida, Hiroyuki; Naganuma, Kaori; Ohara, Maho; Ito, Satoshi; Hirata, Shoji

    2010-02-01

    We have applied zinc diffused window structures to 640 nm broad area stripe laser diodes (BALDs) for the first time. A solid-phase zinc diffusion technique was used for a thick single quantum well (SQW) in GaInP employing the short wavelength and disordered active layer possessed a blue shift of 58 nm in photoluminescence spectrum. We fabricated 10 mm arrays including twenty-five BALDs and each BALD consists of a 60 μm ridge stripe and a 1000 μm cavity. An initial catastrophic optical damage (COD) level of the window laser was increased by four times of a conventional none-window laser. A long-term reliability under automatic current control was investigated for initial output powers of 13W and 15W which overcome a previous demonstration of 7.2 W. Measured degradations within a period of 1000-hours were 5 % or less, in contrast a half-life period of our conventional none-window laser with an initial output power of 10 W was only 120-hours. Therefore the window structure improved the BALD in terms of the COD level and the long-term reliability.

  3. [Effects of irrigation with different length micro-sprinkling hoses on soil water distribution, water consumption characteristics of winter wheat, and its grain yield].

    PubMed

    Man, Jian-guo; Wang, Dong; Yu, Zhen-wen; Zhang, Yong-li; Shi, Yu

    2013-08-01

    Taking the high-yielding winter wheat variety Jimai 22 as test material, a field experiment was conducted in 2010-2012 to study the effects of irrigation with different length micro-sprinkling hoses on the soil water distribution in winter wheat growth period and the water consumption characteristics and grain yield of winter wheat. Three micro-sprinkling hose lengths were designed, i. e., 40 m (T40), 60 m (T60) and 80 m (T80). Under the micro-sprinkling irrigation at jointing and anthesis stages, the uniformity of the horizontal distribution of irrigation water in soil increased significantly with the decrease of hose length from 80 to 40 m. When irrigated at jointing stage, the water content of 0-200 cm soil layer in each space of wheat rows had no significant difference within the 0-40 m distanced from the border initial in treatments T40 and T60. When measured at the 38-40 m, 58-60 m, and 78-80 m distanced from the border initial in treatment T80 at jointing and anthesis stages, the water content in 0-200 cm soil layer had the same change pattern, i. e., decreased with the increasing distance from micro-sprinkling hose. The water consumption amounts in 40-60 cm soil layer from jointing to anthesis stages and in 20-80 cm soil layer from anthesis to maturing stages were higher in treatment T40 than in treatments T60 and T80. However, the soil water consumption amount, irrigation amount at anthesis stage, total irrigation amount, and total water consumption amount were significantly lower in treatment T40 than in treatments T60 and T80. The grain yield, yield water use efficiency increased with the hose length decreased from 80 to 40 m, but the flow decreased. Therefore, the effective irrigation area per unit time decreased with the same irrigation amounts. Considering the grain yield, water use efficiency, and the flow through micro-sprinkling hose, 40 and 60 m were considered to be the appropriate micro-sprinkling hose lengths under this experimental condition. PMID:24380337

  4. Brillouin Lasing with a Reduced Self-Pulsing Characteristic Using a Short-Length Erbium-Doped Fiber as the Nonlinear Gain Medium

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  5. Evaluation of the crack growth characteristics of glass and ceramics based on crack length measurement using an ion-sputtered film

    NASA Astrophysics Data System (ADS)

    Deng, G.; Sakamoto, K.; Ikeda, K.; Nakanishi, T.

    2008-12-01

    The crack length measurement method using an ion-sputtered film, proposed by the authors based on the change in the electric resistance of the film during the crack growth, was applied to the small crack growing in soda lime glass and alumina ceramics. Since the measurement system can record the electric resistance of the ion-sputtered film at a high sampling frequency of 125kHz, the crack lengths was measured almost continuously, and the relationship between the crack growth rate and the stress intensity factor were obtained in the whole regions from low crack growth rate to brittle fracture. The growth characteristics of the small crack under 1mm in alumina ceramics are clarified to be different from that of the large crack in the same materials; for example, the n values, which is defined as the constant in the Paris law relating the crack growth rate to the stress intensity factor, in the soda lime glass and the alumina ceramics obtained by this research are 74 to 96 and 530 to 580 respectively in the region I, and 12 to 15 and 17 to 25 respectively in the region II, that are different from the values obtained from a large crack, especially for the alumina ceramics.

  6. Diffusion characteristics and controlled release of bacterial fertilizers from modified calcium alginate capsules.

    PubMed

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

    2008-04-01

    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

  7. Immunohistochemical and Molecular Characteristics with Prognostic Significance in Diffuse Large B-Cell Lymphoma

    PubMed Central

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

    2014-01-01

    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

  8. Head Rotational Acceleration Characteristics Influence Behavioral and Diffusion Tensor Imaging Outcomes Following Concussion

    PubMed Central

    Stemper, Brian D.; Shah, Alok S.; Pintar, Frank A.; McCrea, Michael; Kurpad, Shekar N.; Glavaski-Joksimovic, Aleksandra; Olsen, Christopher; Budde, Matthew D.

    2015-01-01

    A majority of traumatic brain injuries (TBI) in motor vehicle crashes and sporting environments are mild and caused by high-rate acceleration of the head. For injuries caused by rotational acceleration, both magnitude and duration of the acceleration pulse were shown to influence injury outcomes. This study incorporated a unique rodent model of rotational acceleration-induced mild TBI (mTBI) to quantify independent effects of magnitude and duration on behavioral and neuroimaging outcomes. Ninety-two Sprague– Dawley rats were exposed to head rotational acceleration at peak magnitudes of 214 or 350 krad/s2 and acceleration pulse durations of 1.6 or 3.4 ms in a full factorial design. Rats underwent a series of behavioral tests including the Composite Neuroscore (CN), Elevated Plus Maze (EPM), and Morris Water Maze (MWM). Ex vivo diffusion tensor imaging (DTI) of the fixed brains was conducted to assess the effects of rotational injury on brain microstructure as revealed by the parameter fractional anisotropy (FA). While the injury did not cause significant locomotor or cognitive deficits measured with the CN and MWM, respectively, a main effect of duration was consistently observed for the EPM. Increased duration caused significantly greater activity and exploratory behaviors measured as open arm time and number of arm changes. DTI demonstrated significant effects of both magnitude and duration, with the FA of the amygdala related to both the magnitude and duration. Increased duration also caused FA changes at the interface of gray and white matter. Collectively, the findings demonstrate that the consequences of rotational acceleration mTBI were more closely associated with duration of the rotational acceleration impulse, which is often neglected as an independent factor, and highlight the need for animal models of TBI with strong biomechanical foundations to associate behavioral outcomes with brain microstructure. PMID:25344352

  9. "Smoking-Gun" Observables of Magnetic Reconnection: Spatiotemporal Evolution of Electron Characteristics Throughout the Diffusion Region

    NASA Astrophysics Data System (ADS)

    Shuster, J. R.; Chen, L. J.; Bessho, N.; Li, G.; Torbert, R. B.; Wang, S.; Argall, M. R.; Daughton, W. S.

    2014-12-01

    Electron distribution functions can provide "smoking-gun" evidence for the detection of electron diffusion regions in collisionless magnetic reconnection. Knowledge of the spatiotemporal evolution of electron distributions during reconnection is significantly lacking, and will further elucidate the outstanding questions of how, where, and when electrons are energized during reconnection. Based on spacecraft observations and PIC simulations of symmetric reconnection, electrons in the inflow region are known to exhibit a temperature anisotropy Te// > Te⊥. Studies of exhaust electrons have reported hot and isotropic electrons, while others have reported anisotropic exhaust structures. Electron distributions in the vicinity of the X-line have a triangular, 3D velocity space structure with distinct striations corresponding to the number of times electrons reflect within the electron current layer. Here, we report the spatial and temporal evolution of electron distributions from the vicinity of the X-line to the end of the electron outflow jet, with the discovery that the discrete striations swirl and rotate as electrons re-magnetize, forming arc and ring structures. Highly structured, time-dependent electron anisotropy develops in the exhaust distributions only near or after the peak reconnection rate, explaining the previous discrepancy concerning the degree of electron anisotropy in the exhaust, and suggesting a technique to infer the evolution stage of reconnection using spacecraft measurements. We also present a theory for predicting the spacing of the striations of electron distributions in the vicinity of the X-line based on local measurements, which could be directly tested by spacecraft observations. Electron data from Cluster magnetotail reconnection inflows and exhausts exhibit many anisotropic structures as predicted by simulation. Observed distributions near the reconnection mid-plane (Bx ~ 0 nT) are often highly structured with populations exhibiting Te⊥ > Te// in addition to lower energy field-aligned beams. Our work advances the understanding of electron distribution evolution, setting a foundation to successfully interpret the high resolution electron data anticipated from NASA's upcoming Magnetospheric Multi-Scale Mission.

  10. Immunohistochemical and molecular characteristics with prognostic significance in diffuse large B-cell lymphoma.

    PubMed

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

    2014-01-01

    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

  11. Elevated temperature flow strength, creep resistance and diffusion welding characteristics of Ti-6Al-2Nb-1Ta-0.8Mo

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    A study of the flow strength, creep resistance and diffusion welding characteristics of the titanium alloy Ti-6Al-2Nb-1Ta-0.8Mo has been conducted. Two mill-processed forms of this alloy were examined. The forged material had been processed above the beta transus (approximately 1275 K) while the rolled form had been subjected to 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.

  12. Elevated-temperature flow strength, creep resistance and diffusion welding characteristics of Ti-gAl-2Nb-1Ta-0.8Mo

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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.

  13. An invariance property of diffusive random walks

    NASA Astrophysics Data System (ADS)

    Blanco, S.; Fournier, R.

    2003-01-01

    Starting from a simple animal-biology example, a general, somewhat counter-intuitive property of diffusion random walks is presented. It is shown that for any (non-homogeneous) purely diffusing system, under any isotropic uniform incidence, the average length of trajectories through the system (the average length of the random walk trajectories from entry point to first exit point) is independent of the characteristics of the diffusion process and therefore depends only on the geometry of the system. This exact invariance property may be seen as a generalization to diffusion of the well-known mean-chord-length property (Case K. M. and Zweifel P. F., Linear Transport Theory (Addison-Wesley) 1967), leading to broad physics and biology applications.

  14. PS-b-PEO/Silica Films with Regular and Reverse Mesostructures of Large Characteristic Length Scales Prepared by Solvent Evaporation-Induced Self-Assembly

    SciTech Connect

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

    2000-11-22

    Since the discovery of surfactant-templated silica by Mobil scientists in 1992, mesostructured silica has been synthesized in various forms including thin films, powders, particles, and fibers. In general, mesostructured silica has potential applications, such as in separation, catalysis, sensors, and fluidic microsystems. In respect to these potential applications, mesostructured silica in the form of thin films is perhaps one of the most promising candidates. The preparation of mesostructured silica films through preferential solvent evaporation-induced self-assembly (EISA) has recently received much attention in the laboratories. However, no amphiphile/silica films with reverse mesophases have ever been made through this EISA procedure. Furthermore, templates employed to date have been either surfactants or poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) triblock copolymers, such as pluronic P-123, both of which are water-soluble and alcohol-soluble. Due to their relatively low molecular weight, the templated silica films with mesoscopic order have been limited to relatively small characteristic length scales. In the present communication, the authors report a novel synthetic method to prepare mesostructured amphiphilic/silica films with regular and reverse mesophases of large characteristic length scales. This method involves evaporation-induced self-assembly (EISA) of amphiphilic polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymers. In the present study, the PS-b-PEO diblocks are denoted as, for example, PS(215)-b-PEO(100), showing that this particular sample contains 215 S repeat units and 100 EO repeat units. This PS(215)-b-PEO(100) diblock possesses high molecular weight and does not directly mix with water or alcohol. To the authors knowledge, no studies have reported the use of water-insoluble and alcohol-insoluble amphiphilic diblocks as structure-directing agents in the synthesis of mesostructured silica films through EISA. It is believed that the present system is the first to yield amphiphile/silica films with regular and reverse mesophases, as well as curved multi-bilayer mesostructures, through EISA. The ready formation of the diblock/silica films with multi-bilayer vesicular mesostructures is discussed.

  15. Plasmapause diffusion

    NASA Technical Reports Server (NTRS)

    Horwitz, J. L.

    1983-01-01

    The Bohm diffusion coefficient and observed electrostatic wave scattering are used as the bases of estimates of the smoothing effect that diffusion may have on steep plasmapause density gradients. The estimate for diffusion resulting from scattering by observed electrostatic waves is found to be much lower than that of the perpendicular Bohm diffusion coefficient for characteristic plasma temperatures and magnetic fields. This diffusion rate estimate may be too small, however, if the wave amplitudes are significantly higher for steep plasmapauses. The effects are therefore negligible for most considerations of macroscopic plasmapause dynamics, but may be significant in limiting drift wave instabilities and similar phenomena driven by the steepness of the plasmapause density gradient.

  16. Noise characteristics of jet flap type exhaust flows. [effects of Mach number, slot nozzle aspect ratio, and flap length on radiated sound power

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    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.

  17. Heavy-Metal Concentrations in Small Mammals from a Diffusely Polluted Floodplain: Importance of Species- and Location-Specific Characteristics

    PubMed Central

    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

    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

  18. Characteristics of Optical Diffusers for Light-Emitting Diodes Backlight Unit Prepared by Melt-Extrusion Process

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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.

  19. Anomalous output characteristic shift for the n-type lateral diffused metal-oxide-semiconductor transistor with floating P-top layer

    NASA Astrophysics Data System (ADS)

    Liu, Siyang; Zhang, Chunwei; Sun, Weifeng; Su, Wei; Wang, Shaorong; Ma, Shulang; Huang, Yu

    2014-04-01

    Anomalous output characteristic shift of the n-type lateral diffused metal-oxide-semiconductor transistor with floating P-top layer is investigated. It shows that the linear drain current has obvious decrease when the output characteristic of fresh device is measured for two consecutive times. The charge pumping experiments demonstrate that the decrease is not from hot-carrier degradation. The reduction of cross section area for the current flowing, which results from the squeezing of the depletion region surrounding the P-top layer, is responsible for the shift. Consequently, the current capability of this special device should be evaluated by the second measured output characteristic.

  20. Anomalous output characteristic shift for the n-type lateral diffused metal-oxide-semiconductor transistor with floating P-top layer

    SciTech Connect

    Liu, Siyang; Zhang, Chunwei; Sun, Weifeng; Su, Wei; Wang, Shaorong; Ma, Shulang; Huang, Yu

    2014-04-14

    Anomalous output characteristic shift of the n-type lateral diffused metal-oxide-semiconductor transistor with floating P-top layer is investigated. It shows that the linear drain current has obvious decrease when the output characteristic of fresh device is measured for two consecutive times. The charge pumping experiments demonstrate that the decrease is not from hot-carrier degradation. The reduction of cross section area for the current flowing, which results from the squeezing of the depletion region surrounding the P-top layer, is responsible for the shift. Consequently, the current capability of this special device should be evaluated by the second measured output characteristic.

  1. DIFFUSION IN THE VICINITY OF STANDARD-DESIGN NUCLEAR POWER PLANTS-I. WIND-TUNNEL EVALUATION OF DIFFUSIVE CHARACTERISTICS OF A SIMULATED SUBURBAN NEUTRAL ATMOSPHERIC BOUNDARY LAYER

    EPA Science Inventory

    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 ...

  2. Variable ranking based on the estimated degree of separation for two distributions of data by the length of the receiver operating characteristic curve.

    PubMed

    Maswadeh, Waleed M; Snyder, A Peter

    2015-05-30

    Variable responses are fundamental for all experiments, and they can consist of information-rich, redundant, and low signal intensities. A dataset can consist of a collection of variable responses over multiple classes or groups. Usually some of the variables are removed in a dataset that contain very little information. Sometimes all the variables are used in the data analysis phase. It is common practice to discriminate between two distributions of data; however, there is no formal algorithm to arrive at a degree of separation (DS) between two distributions of data. The DS is defined herein as the average of the sum of the areas from the probability density functions (PDFs) of A and B that contain a≥percentage of A and/or B. Thus, DS90 is the average of the sum of the PDF areas of A and B that contain ≥90% of A and/or B. To arrive at a DS value, two synthesized PDFs or very large experimental datasets are required. Experimentally it is common practice to generate relatively small datasets. Therefore, the challenge was to find a statistical parameter that can be used on small datasets to estimate and highly correlate with the DS90 parameter. Established statistical methods include the overlap area of the two data distribution profiles, Welch's t-test, Kolmogorov-Smirnov (K-S) test, Mann-Whitney-Wilcoxon test, and the area under the receiver operating characteristics (ROC) curve (AUC). The area between the ROC curve and diagonal (ACD) and the length of the ROC curve (LROC) are introduced. The established, ACD, and LROC methods were correlated to the DS90 when applied on many pairs of synthesized PDFs. The LROC method provided the best linear correlation with, and estimation of, the DS90. The estimated DS90 from the LROC (DS90-LROC) is applied to a database, as an example, of three Italian wines consisting of thirteen variable responses for variable ranking consideration. An important highlight of the DS90-LROC method is utilizing the LROC curve methodology to test all variables one-at-a-time with all pairs of classes in a dataset. PMID:25998456

  3. Effective diffusivity of passive scalars in rotating turbulence.

    PubMed

    Imazio, P Rodriguez; Mininni, P D

    2013-02-01

    We use direct numerical simulations to compute turbulent transport coefficients for passive scalars in turbulent rotating flows. Effective diffusion coefficients in the directions parallel and perpendicular to the rotation axis are obtained by studying the diffusion of an imposed initial profile for the passive scalar, and calculated by measuring the scalar average concentration and average spatial flux as a function of time. The Rossby and Schmidt numbers are varied to quantify their effect on the effective diffusion. It is found that rotation reduces scalar diffusivity in the perpendicular direction. The perpendicular diffusion can be estimated from mixing length arguments using the characteristic velocities and lengths perpendicular to the rotation axis. Deviations are observed for small Schmidt numbers, for which turbulent transport decreases and molecular diffusion becomes more significant. PMID:23496621

  4. Supersonic axial-force characteristics of a rectangular-box cavity with various length-to-depth ratios in a flat plate

    NASA Technical Reports Server (NTRS)

    Blair, A. B., Jr.; Stallings, R. L., Jr.

    1986-01-01

    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 results are summarized to show variations in cavity axial-force coefficient for deep- and shallow-cavity configurations with detached and attached cavity flow fields, respectively. The results of the investigation indicate that for a wide range of cavity lengths and depths, good correlations of the cavity axial-force coefficients (based on cavity rear-face area) are obtained when these coefficients are plotted as a function of cavity length-to-depth ratio. Abrupt increases in the cavity axial-force coefficients at an angle of attack of 0 deg. reflect the transition from an open (detached) cavity flow field to a closed (attached) cavity flow field. Cavity length-to-depth ratio is the dominant factor affecting the switching of the cavity flow field from one type to the other. The type of cavity flow field (open or closed) is not dependent on the test angles of attack except near the critical value of length-to-depth ratio.

  5. A diffuser-based three-dimensional measurement of polarization-dependent scattering characteristics of optical films for 3D-display applications.

    PubMed

    Kim, Dae-Yeon; Seo, Jong-Wook

    2015-01-26

    We propose an accurate and easy-to-use three-dimensional measurement method using a diffuser plate to analyze the scattering characteristics of optical films. The far-field radiation pattern of light scattered by the optical film is obtained from the illuminance pattern created on the diffuser plate by the light. A mathematical model and calibration methods were described, and the results were compared with those obtained by a direct measurement using a luminance meter. The new method gave very precise three-dimensional polarization-dependent scattering characteristics of scattering polarizer films, and it can play an effective role in developing high performance polarization-selective screens for 3D display applications. PMID:25835866

  6. Boundary-layer analysis of subsonic inlet diffuser geometries for engines nacelles

    NASA Technical Reports Server (NTRS)

    Albers, J. A.; Felderman, E. J.

    1974-01-01

    Theoretical Mach number distributions and boundary-layer parameters are presented for subsonic nacelle inlet diffuser geometries with length to exit diameter ratios ranging from 0.4 to 1.6 and diffuser exit area to throat area ratios ranging from 1.1 to 2.0. The major portion of the study was done with a cubic diffuser contour with the inflection point at the midpoint of the diffuser, a diffuser throat Mach number of 0.6, and a free-stream Mach number of 0.12. Calculations were performed at both model (diffuser exit diameter, 30.5 cm) and full-scale (diffuser exit diameter, 183 cm) sizes. Separation limits were defined by establishing a separation boundary on plots of diffuser area ratio as a function of diffuser length to diameter ratio. The effects of diffuser contour, inlet lip geometry, and throat Mach number on the boundary-layer characteristics are illustrated. The major results of the study indicate that the separation boundary is shifted to greater area ratios by (1) increasing the diffuser length, (2) increasing the scale of the diffuser and, (3) moving the inflection point of the diffuser contour to or ahead of the midpoint of the diffuser.

  7. Effects of airplane characteristics and takeoff noise and field length constraints on engine cycle selection for a Mach 2.32 cruise application

    NASA Technical Reports Server (NTRS)

    Whitlow, J. B., Jr.

    1976-01-01

    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.

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

    DOEpatents

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

    1988-06-28

    An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc. 11 figs.

  9. LABORATORY ASSESSMENT OF THE PERMEABILITY AND DIFFUSION CHARACTERISTICS OF FLORIDA CONCRETES: PHASE II. FIELD SAMPLES AND ANALYSES

    EPA Science Inventory

    The report gives results of a study to: (1) establish the capability of measuring concrete's permeability and diffusivity, (2) measure these parameters in a small sampling of the typical types of Florida concrete, and (3) if possible, correlate the physical parameters of the conc...

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

    DOEpatents

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

    1990-06-26

    An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc. 11 figs.

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

    DOEpatents

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

    1990-01-01

    An improvement to the gas mixture used in diffuse glow discharge closing switches is disclosed which includes binary and ternary gas mixtures which are formulated to exhibit decreasing electron attachment with increasing temperature. This increases the efficiency of the conductance of the glow discharge and further inhibits the formation of an arc.

  12. Diffusion of subsidized ACTs in accredited drug shops in Tanzania: determinants of stocking and characteristics of early and late adopters

    PubMed Central

    2013-01-01

    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

  13. Biofouling of Polymer Hydrogel Materials and its Effect on Diffusion and Enzyme-Based Luminescent Glucose Sensor Functional Characteristics

    PubMed Central

    Roberts, Jason R.; Park, Jaebum; Helton, Kristen; Wisniewski, Natalie; McShane, Michael J.

    2012-01-01

    Background Continuous glucose monitoring is crucial to developing a successful artificial pancreas. However, biofouling and host response make in vivo sensor performance difficult to predict. We investigated changes in glucose diffusivity and sensor response of optical enzymatic glucose sensors due to biological exposure. Method Three hydrogel materials, poly(2-hydroxyethyl methacrylate) (pHEMA), poly(acrylamide) (pAM), and poly(2-hydroxyethyl methacrylate)-co-poly(acrylamide) (p(HEMA-co-AM)), were tested for glucose diffusivity before and after exposure to serum or implantation in rats for 1 month. Luminescent sensors based on these materials were measured to compare the response to glucose before and after serum exposure. Results Glucose diffusivity through the pHEMA [(8.1 0.38) 10-8 cm2/s] slabs was much lower than diffusivity through pAM [(2.7 0.15) 10-6 cm2/s] and p(HEMA-co-AM) [(2.5 0.08) 10-6]. As expected from these differences, sensor response was highly dependent on material type. The pHEMA sensors had a maximum sensitivity of 2.5%/(mg/dl) and an analytical range of 4.2356 mg/dl, while the p(HEMA-co-AM) sensors had a higher sensitivity [14.9%/(mg/dl)] and a narrower analytical range (17.670.5 mg/dl). After serum exposure, the pHEMA sensors were unaffected, whereas the p(HEMA-co-AM) sensors exhibited significantly decreased sensitivity and increased analytical range. Conclusions Decreases in glucose diffusivity in the polymers resulting from in vitro serum exposure and residence in vivo were shown to be similar, suggesting that serum incubation was a reasonable approximation of in vivo fouling. While biofouling is expected to affect the response of flux-based sensors, we have shown that this depended on the type of sensor and matrix used. Therefore, proper design and materials selection may minimize response alterations occurring upon implantation. PMID:23294771

  14. Explaining the variation in lamb longissimus shear force across and within ageing periods using protein degradation, sarcomere length and collagen characteristics.

    PubMed

    Starkey, Colin P; Geesink, Geert H; Oddy, V Hutton; Hopkins, David L

    2015-07-01

    Meat tenderness is known to be affected by sarcomere length (SL), proteolysis and collagen content (CC). Sixty lambs were slaughtered and the Longissimus muscle was sampled. Samples for shear force (SF), SL, proteolysis indicators (desmin degradation, particle size: PS) and CC were taken after the allotted ageing periods (1, 7, and 14 days). PS explained a large part of the variation in shear force (approximately 34%) when modelled across ageing periods. Other factors (CC, SL) combined with proteolysis indicators (PS, desmin degradation) explained just under 40% of the variation in shear force. Within ageing periods SL explained a small, but significant, part of the variation in shear force after 14 days of ageing (8%) and at day 1 of ageing desmin degradation explained 17% of the variation in shear force. Methods to improve the tenderness of lamb longissimus muscle should focus on increasing the extent of post-mortem proteolysis, when processing conditions are sufficient to prevent muscle fibre shortening. PMID:25768395

  15. Generalized Drift-Diffusion Model In Semiconductors

    SciTech Connect

    Mesbah, S.; Bendib-Kalache, K.; Bendib, A.

    2008-09-23

    A new drift-diffusion model is proposed based on the computation of the stationary nonlocal current density. The semi classical Boltzmann equation is solved keeping all the anisotropies of the distribution function with the use of the continued fractions. The conductivity is calculated in the linear approximation and for arbitrary collision frequency with respect to Kv{sub t} where K{sup -1} is the characteristic length scale of the system and V{sub t} is the thermal velocity. The nonlocal conductivity can be used to close the generalized drift-diffusion equations valid for arbitrary collisionality.

  16. Glycosyl linkage characteristics and classifications of exo-polysaccharides of some regionally different strains of Lentinula edodes by amplified fragment length polymorphism assay and cluster analysis.

    PubMed

    Lo, Tiffany Chien Ting; Kang, Ming Wei; Wang, Bor Cheh; Chang, C Allen

    2007-06-01

    We report here the first combined amplified fragment length polymorphism (AFLP) analysis of genomic DNA fingerprinting data and cluster analysis of the exo-polysaccharide glycosyl linkage data of 10 regionally different strains of Lentinula edodes to compare their genetic and structural similarities and differences. In addition, the monosaccharide compositions, molecular weights, glycosyl structural linkages were investigated for the exo-polysaccharides extracted from these different phylogenetic groups of regionally different L. edodes. All exo-polysaccharides had similar molecular weight distribution between 1x10(4) and 3x10(6) Da and the monosaccharide composition analysis revealed the presence of heterogeneous materials containing glucose, mannose, xylose, galactose, fucose, rhamnose and arabinose in different ratios. Among these monosaccharides, the glucose contents are the highest for all but one strain, indicating that glucose probably is the building block of the backbones of these exo-polysaccharides. The AFLP assay data helped to classify the 10 L. edodes strains into three distinct genetic groups. Gas chromatographic and mass spectrometric (GC-MS) data revealed five different glycosyl linkage types for these exo-polysaccharides. Most of the exo-polysaccharide backbone structures contain (1-->4)-linked-D-glucopyranosyl and (1-->6)-linked-D-glucopyranosyl moieties. Arabinose 1-->4 linkages and mannose 1-->2 linkages also exist in all strains. The only differences among these linkages are their monosaccharide compositions leading to different degree of backbone and branch formations. Cluster analyses of the GC-MS data of the exo-polysaccharides of the 10 strains resulted in 10 dendrograms. However, four of the 10 dendrograms were identical and were obtained using the average, Ward and weighted linkage type method of Manhattan distance and using the Ward method of Euclidean distance. The results of cluster analyses were not very much different from that of the AFLP assay and allowed the comparison of genetic and structural similarities and differences. PMID:17512819

  17. Discharge characteristics of He-Ne-Xe gas mixture with varying Xe contents and at varying sustain electrode gap lengths in the plasma display panel

    SciTech Connect

    Kwon, Ohyung; Whang, Ki-Woong; Bae, Hyun Sook

    2009-09-15

    The discharge characteristics of He-Ne-Xe gas mixture in the plasma display panel were investigated using a two-dimensional numerical simulation to understand the effects of adding He and varying the Xe contents in the gas mixture, and also varying sustain electrode gap. With 5% Xe content and 60 mum sustain electrode gap, decreased ionization led to the improvement of the vacuum ultraviolet (vuv) efficacy at increasing He mixing ratios. However, at 20% Xe content and 60 mum sustain electrode gap, increased electron heating improved the vuv efficacy until the He mixing ratio reached 0.7, but the efficacy decreased beyond the ratio of 0.7 due to the increased ionization of Xe atoms. At 5% Xe content and 200 mum sustain electrode gap, the vuv efficacy increased as a result of increased electron heating at the gap space at increasing He mixing ratios.

  18. Spatiotemporal evolution of electron characteristics in the electron diffusion region of magnetic reconnection: Implications for acceleration and heating

    NASA Astrophysics Data System (ADS)

    Shuster, J. R.; Chen, L.-J.; Hesse, M.; Argall, M. R.; Daughton, W.; Torbert, R. B.; Bessho, N.

    2015-04-01

    Based on particle-in-cell simulations of collisionless magnetic reconnection, the spatiotemporal evolution of electron velocity distributions in the electron diffusion region (EDR) is reported to illustrate how electrons are accelerated and heated. Approximately when the reconnection rate maximizes, electron distributions in the vicinity of the X line exhibit triangular structures with discrete striations and a temperature (Te) twice that of the inflow region. Te increases as the meandering EDR populations mix with inflowing electrons. As the distance from the X line increases within the electron outflow jet, the discrete populations swirl into arcs and gyrotropize by the end of the jet with Te about 3 times that of the X line. Two dominant processes increase Te and produce the spatially and temporally evolving EDR distributions: (1) electric field acceleration preferential to electrons which meander in the EDR for longer times and (2) cyclotron turning by the magnetic field normal to the reconnection layer.

  19. Diffusion MR Characteristics Following Concurrent Radiochemotherapy Predicts Progression-Free and Overall Survival in Newly Diagnosed Glioblastoma

    PubMed Central

    Chang, Warren; Pope, Whitney B.; Harris, Robert J.; Hardy, Anthony J.; Leu, Kevin; Mody, Reema R.; Nghiemphu, Phioanh L.; Lai, Albert; Cloughesy, Timothy F.; Ellingson, Benjamin M.

    2015-01-01

    The standard of care for newly diagnosed glioblastoma (GBM) is surgery, then radiotherapy (RT) with concurrent temozolomide (TMZ), followed by adjuvant TMZ. We hypothesized patients with low diffusivity measured using apparent diffusion coefficient (ADC) histogram analysis evaluated after RT+TMZ, prior to adjuvant TMZ, would have a significantly shorter progression-free (PFS) and overall survival (OS). To test this hypothesis we evaluated 120 patients with newly diagnosed GBM receiving RT+TMZ followed by adjuvant TMZ. MRI was performed after completion of RT+TMZ, prior to initiation of adjuvant TMZ. A double Gaussian mixed model was used to describe the ADC histograms within the enhancing tumor, where ADCL and ADCH were defined as the mean ADC value of the lower and higher Gaussian distribution, respectively. An ADCL value of 1.0 um2/ms and ADCH value of 1.6 um2/ms were used to stratify patients into high and low risk categories. Results suggest patients with low ADCL had significantly shorter PFS (Cox Hazard Ratio = 0.12, P = 0.0006). OS was significantly shorter with low ADCL tumors, showing a median OS of 407 vs. 644 days (Cox Hazard Ratio = 0.31, P = 0.047). ADCH was not predictive of PFS or OS when accounting for age and ADCL. In summary, newly diagnosed glioblastoma patients with low ADCL after completion of RT+TMZ are likely to progress and die earlier than patients with higher ADCL. Results suggest ADC histogram analysis may be useful for patient risk stratification following completion of RT+TMZ.

  20. MRI characteristics of acute and subacute brainstem and thalamic infarctions: value of T2- and diffusion-weighted sequences.

    PubMed

    Kker, Wilhelm; Weise, Jens; Krapf, Hilmar; Schmidt, Friederike; Friese, Sigrid; Bhr, Mathias

    2002-01-01

    MRI including diffusion-weighted sequences (DW-MRI) has demonstrated its high sensitivity for acute supratentorial ischemic lesions. In this study we examined the sensitivity of different MRI sequences for the detection of acute brainstem and isolated thalamic infarctions. Diffusion- and T2-weighted MRI of 45 consecutive patients with signs and symptoms of infratentorial and thalamic infarction between 6/1997 and 1/2000 were analysed. The time between the onset of symptoms and the first MRI varied between 2 hours to 7 days with a median of 2 days. MRI repeats were performed in 4 patients in whom the clinical brainstem infarction had not been detected initially. Lesion detectability and size were evaluated for different brainstem and thalamic localizations. An acute brainstem or thalamic infarction as defined by the clinical condition could be identified in all patients by comparison of DW-MRI and T2-weighted images. Pons in farctions were the largest, followed by midbrain and thalamic lesions. Medulla oblongata infarctions were small in comparison. Pons, mid-brain and thalamic infarctions were reliably identified beginning 12 hours after the onset of symptoms. In contrast, detectability of medulla oblongata infarctions varied within the first 24 hours and their overall visibility was worse than that of other brainstem infarctions corresponding to their small size. However, regardless of loca tion, none of the 3 infarctions examined within the first 5 hours after the onset of symptoms could be identified. These lesions were demonstrated in follow-up examinations. In conclusion, pontine, midbrain and thalamic infarctions can reliably be visualized by a combination of DW-MRI and T2-weighted images beginning 12 hours after the ischemic attack. However, sensitivity seems to be lower earlier than 12 hours after ischemia and for medulla oblongata lesions. PMID:11954866

  1. Characteristics of troponin C binding to the myofibrillar thin filament: extraction of troponin C is not random along the length of the thin filament.

    PubMed Central

    Swartz, D R; Moss, R L; Greaser, M L

    1997-01-01

    Troponin C (TnC) is the Ca(2+)-sensing subunit of troponin responsible for initiating the cascade of events resulting in contraction of striated muscle. This protein can be readily extracted from myofibrils with low-ionic-strength EDTA-containing buffers. The properties of TnC extraction have not been characterized at the structural level, nor have the interactions of TnC with the native myofibrillar thin filament been studied. To address these issues, fluorescein-labeled TnC, in conjunction with high-resolution digital fluorescence microscopy, was used to characterize TnC binding to myofibrils and to determine the randomness of TnC extraction. Fluorescein-5-maleimide TnC (F5M TnC) retained biological activity, as evidenced by reconstitution of Ca(2+)-dependent ATPase activity in extracted myofibrils and binding to TnI in a Ca(2+)-sensitive manner. The binding of F5M TnC to highly extracted myofibrils at low Ca2+ was restricted to the overlap region under rigor conditions, and the location of binding was not influenced by F5M TnC concentration. The addition of myosin subfragment 1 to occupy all actin sites resulted in F5M TnC being bound in both the overlap and nonoverlap regions. However, very little F5M TnC was bound to myofibrils under relaxing conditions. These results suggest that strong binding of myosin heads enhances TnC binding. At high Ca2+, the pattern of F5M TnC binding was concentration dependent: binding was restricted to the overlap region at low F5M TnC concentration, whereas the binding propagated into the nonoverlap region at higher levels. Analysis of fluorescence intensity showed the greatest binding of F5M TnC at high Ca2+ with S1, and these conditions were used to characterize partially TnC-extracted myofibrils. Comparison of partially extracted myofibrils showed that low levels of extraction were associated with greater F5M TnC being bound in the nonoverlap region than in the overlap region relative to higher levels of extraction. These results show that TnC extraction is not random along the length of the thin filament, but occurs more readily in the nonoverlap region. This observation, in conjunction with the influence of rigor heads on the pattern of F5M TnC binding, suggests that strong myosin binding to actin stabilizes TnC binding at low Ca2+. Images FIGURE 1 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 PMID:9199794

  2. Diffusion coefficient of an inclusion in a liquid membrane supported by a solvent of arbitrary thickness

    NASA Astrophysics Data System (ADS)

    Seki, Kazuhiko; Ramachandran, Sanoop; Komura, Shigeyuki

    2011-08-01

    The diffusion coefficient of an 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 characteristic equation. The conditions for which the diffusion coefficients can be approximated by the expression including only a single hydrodynamic screening length are also shown.

  3. Experimental study of vortex diffusers

    SciTech Connect

    Shakerin, S.; Miller, P.L.

    1995-11-01

    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.

  4. Length-Scale Dependent Viscosity in Semidilute Polyelectrolyte Solutions

    NASA Astrophysics Data System (ADS)

    Poling-Skutvik, Ryan; Krishnamoorti, Ramanan; Conrad, Jacinta

    2015-03-01

    Using optical microscopy and particle tracking algorithms, we measured the mean-squared displacements (MSDs) of fluorescent polystyrene particles with diameters ranging from 300 nm to 2 ?m suspended in semidilute solutions of high molecular weight partially hydrolyzed polyacrylamide. The solutions had polymer concentrations ranging from 0.67 to 67c*, where c* is the overlap concentration, and estimated correlation lengths of ~ 100 to 900 nm. At short times, the particles exhibited subdiffusive behavior characterized by MSD ~t? with ? < 1 . On long time scales, the particles transitioned to Fickian diffusion (? = 1) and their diffusivity was calculated from the slope of the MSD. Whereas the large particles agreed with predictions using the Stokes-Einstein equation and bulk zero-shear viscosity, the smaller particles diffused much faster than predicted. The relative diffusivities do not collapse onto a single curve, but rather form a continuum that varies with particle size. This indicates that the particles experience a size-dependent effective viscosity mediated by the ratio of particle diameter to characteristic length scales in the polymer solution.

  5. Role of electroless nickel diffusion barrier on the combinatorial plating characteristics of dense Pd/Ni/PSS composite membranes

    NASA Astrophysics Data System (ADS)

    Pujari, Murali; Agarwal, Amrita; Uppaluri, Ramgopal; Verma, Anil

    2014-06-01

    This work addresses the combinatorial plating characteristics of dense Pd/Ni/porous stainless steel (PSS) composite membranes in comparison with Pd/PSS membranes. While Pd/PSS membranes were fabricated using 0.1 μm nominal pore size PSS supports, Pd/Ni/PSS membranes were fabricated using 0.5 and 0.1 μm nominal pore size PSS supports. Both Ni and Pd films were deposited using an identified novel electroless plating process that characterizes the optimal utilization of surfactant, sonication and reducing agent contacting pattern in Pd electroless plating baths. It was observed that the combinatorial plating characteristics for Pd/Ni/PSS membranes were significantly different and poorer in comparison with those obtained for the Pd/PSS membranes. In summary, it has been inferred that the introduction of nickel interdiffusion barrier was not fruitful to reduce the critical thickness of dense Pd film without jeopardizing upon the pore densification.

  6. Correlations between PAH bioavailability, degrading bacteria, and soil characteristics during PAH biodegradation in five diffusely contaminated dissimilar soils.

    PubMed

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

    2014-01-01

    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

  7. Characteristics of the motions, turbulence intensity, diffusivity, flux of momentum and sensible heat in the upper atmosphere

    NASA Technical Reports Server (NTRS)

    Kao, S. K.; Lordi, N. J.

    1977-01-01

    Analyses of the meteorological rocket data obtained from an experiment conducted at 3-hour intervals at 8 western meridional rocket stations are presented. Large variations in the meridional wind contribute substantially to overall turbulence in the tropical stratosphere. The solar semidiurnal component of wind oscillations in the tropics was observed to be much higher than predicted by theory, often exceeding the magnitude of the diurnal amplitude throughout the stratosphere. The observed value of the solar diurnal amplitude in the stratosphere was in line with theoretical prediction. The solar terdiurnal amplitudes for temperature, meridional and zonal winds were non-negligible and must be considered in any harmonic analysis. Phase angle variation with height was rapid for all harmonics; however, there was general agreement between predicted and observed phase angles. Because of large changes in the mean winds in the mesosphere with season, harmonic determinations are difficult. There appear to be large zonal wind changes even within the same season as mentioned previously. Turbulence diffusivity in the upper stratosphere is greater near the equator than in the mid-latitudes.

  8. The effect of diffusion induced lattice stress on the open-circuit voltage in silicon solar cells

    NASA Technical Reports Server (NTRS)

    Weizer, V. G.; Godlewski, M. P.

    1984-01-01

    It is demonstrated that diffusion induced stresses in low resistivity silicon solar cells can significantly reduce both the open-circuit voltage and collection efficiency. The degradation mechanism involves stress induced changes in both the minority carrier mobility and the diffusion length. Thermal recovery characteristics indicate that the stresses are relieved at higher temperatures by divacancy flow (silicon self diffusion). The level of residual stress in as-fabricated cells was found to be negligible in the cells tested.

  9. Finite difference methods for reducing numerical diffusion in TEACH-type calculations. [Teaching Elliptic Axisymmetric Characteristics Heuristically

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    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.

  10. Amplitude of Supersonic Diffuser Flow Pulsations

    NASA Technical Reports Server (NTRS)

    Sterbentz, William H.; Davids, Joseph

    1952-01-01

    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.

  11. The back-diffusion effect of air on the discharge characteristics of atmospheric-pressure radio-frequency glow discharges using bare metal electrodes

    NASA Astrophysics Data System (ADS)

    Sun, Wen-Ting; Liang, Tian-Ran; Wang, Hua-Bo; Li, He-Ping; Bao, Cheng-Yu

    2007-05-01

    Radio-frequency (RF), atmospheric-pressure glow discharge (APGD) plasmas using bare metal electrodes have promising prospects in the fields of plasma-aided etching, deposition, surface treatment, disinfection, sterilization, etc. In this paper, the discharge characteristics, including the breakdown voltage and the discharge voltage for sustaining a stable and uniform α mode discharge of the RF APGD plasmas are presented. The experiments are conducted by placing the home-made planar-type plasma generator in ambient and in a vacuum chamber, respectively, with helium as the primary plasma-forming gas. When the discharge processes occur in ambient, particularly for the lower plasma-working gas flow rates, the experimental measurements show that it is the back-diffusion effect of air in atmosphere, instead of the flow rate of the gas, that results in the obvious decrease in the breakdown voltage with increasing plasma-working gas flow rate. Further studies on the discharge characteristics, e.g. the luminous structures, the concentrations and distributions of chemically active species in plasmas, with different plasma-working gases or gas mixtures need to be conducted in future work.

  12. Quantifying the electrical transport characteristics of electron-doped La0.7Ce0.3MnO3 thin films through hopping energies, Mn valence, and carrier localization length

    NASA Astrophysics Data System (ADS)

    Thiessen, A.; Beyreuther, E.; Werner, R.; Koelle, D.; Kleiner, R.; Eng, L. M.

    2015-05-01

    Cerium-doped LaMnO3 is widely discussed as one of the most prospective electron-doped thin-film prototype material that complements well-established hole-doped mixed-valence manganites. Here, we investigate La0.7Ce0.3MnO3 films with respect to their electrical properties and check whether they provide an effective electron doping with Mn-valences well below +3. Thin films of a variable thickness between 10 and 100 nm are characterized through resistance measurements over a broad temperature range between 90 and 300 K deducing their hopping energies, carrier localization lengths, and the Mn valence by comparing the experimental data to different transport models. While electronic transport above 300 K is well determined by the thermally activated diffusion of small polarons, we find the carrier localization by disorder to reveal a variable-range hopping-type transport for lower temperatures. From the several parameters investigated in the study, it is mainly the oxygen content and the degree of CeO2 phase segregation that are crucial to be controlled in such electron-doped thin-film manganites.

  13. The diffusive idealization of charged-particle transport in random magnetic fields. [cosmic ray propagation

    NASA Technical Reports Server (NTRS)

    Earl, J. A.

    1974-01-01

    The uniqueness and accuracy of the equations which describe the transport of charged particles diffusing in a random magnetic field parallel to a relatively large guiding field is examined. With regard to uniqueness, it is found that the same coefficient of diffusion is obtained by three methods that have apparently led to discrepancies in previous work. With regard to accuracy, it is found that two corrections must be added to Fick's law in which the diffusive flux is proportional to the gradient of the density. Explicit expressions are given for a characteristic time and a characteristic length which describe the corrections.

  14. Definition of Magnetic Exchange Length

    SciTech Connect

    Abo, GS; Hong, YK; Park, J; Lee, J; Lee, W; Choi, BC

    2013-08-01

    The magnetostatic exchange length is an important parameter in magnetics as it measures the relative strength of exchange and self-magnetostatic energies. Its use can be found in areas of magnetics including micromagnetics, soft and hard magnetic materials, and information storage. The exchange length is of primary importance because it governs the width of the transition between magnetic domains. Unfortunately, there is some confusion in the literature between the magnetostatic exchange length and a similar distance concerning magnetization reversal mechanisms in particles known as the characteristic length. This confusion is aggravated by the common usage of two different systems of units, SI and cgs. This paper attempts to clarify the situation and recommends equations in both systems of units.

  15. The extensibility of Aplysia nerve and the determination of true axon length.

    PubMed Central

    Koike, H

    1987-01-01

    1. Characteristics of Aplysia nerves in response to extension were examined in comparison with nerves of the cat, frog and lobster. 2. Only the Aplysia nerve was easily elongated up to about 5 times its resting or relaxing length without impairing propagation of the action potential along the axon in the nerve. 3. The conduction velocity along the elongated nerve increased linearly in proportion to the nerve length in the range from the relaxing length to about 1.2-1.5 times extension (the first phase). However, upon further extension it stayed constant regardless of the nerve length (the second phase). 4. In the relaxed nerve bundle the course of the axons was zigzagging and the axon membrane had numerous foldings or wrinklings. 5. The true length of the zigzagging axon was measured by analysing the length of intra-axonal diffusion following intracellular injection of radioactive acetylcholine ([3H]ACh) whose diffusion kinetics in the axoplasm have been studied in detail (Koike & Nagata, 1979). The length of the axon coincided with the nerve length at which the first phase shifted to the second phase. 6. Cat and frog nerves shrank after dissecting out from the body. When extended, they showed the first phase from the shortened length to their original length in the body. These nerves lacked the second phase. The lobster nerve did not shrink and lacked both phases. 7. Thus the zigzagging course of the axon is suggested to be responsible for the first phase during which the axon length did not change but took a straight course upon nerve extension. 8. On the other hand, the second phase appears to be caused by actual extension of the axon itself and could be explained by reduction of the wrinklings of the membrane. Images Fig. 1 Fig. 3 Fig. 4 Fig. 9 PMID:3502142

  16. Diffusing wave spectroscopy in Maxwellian fluids.

    PubMed

    Galvan-Miyoshi, J; Delgado, J; Castillo, R

    2008-08-01

    We present a critical assessment of the diffusing wave spectroscopy (DWS) technique for obtaining the characteristic lengths and for measuring the loss and storage moduli of a reasonable well-known wormlike micelle (WM) system. For this purpose, we tracked the Brownian motion of particles using DWS embedded in a Maxwellian fluid constituted by a wormlike micellar solution made of cetyltrimethylammonium bromide (CTAB), sodium salicylate (NaSal), and water. We found that the motion of particles was governed by the viscosity of the solvent at short times and by the stress relaxation mechanisms of the giant micelles at longer times. From the time evolution of the mean square displacement of particles, we could obtain for the WM solution the cage size where each particle is harmonically bound at short times, the long-time diffusion coefficient, and experimental values for the exponent that accounts for the broad spectrum of relaxation times at the plateau onset time found in the (deltar2(t)) vs. time curves. In addition, from the (deltar2(t)) vs. time curves, we obtained G'(omega) and G"(omega) for the WM solutions. All the DWS microreological information allowed us to estimate the characteristic lengths of the WM network. We compare our DWS microrheological results and characteristic lengths with those obtained with mechanical rheometers at different NaSal/CTAB concentration ratios and temperatures. PMID:19230210

  17. ESTIMATION OF TURBULENT DIFFUSIVITY WITH DIRECT NUMERICAL SIMULATION OF STELLAR CONVECTION

    SciTech Connect

    Hotta, H.; Iida, Y.; Yokoyama, T.

    2012-05-20

    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.

  18. Tailoring characteristic thermal stability of Ni-Au binary nanocrystals via structure and composition engineering: theoretical insights into structural evolution and atomic inter-diffusion

    SciTech Connect

    Li, Bangquan; Wang, Hailong; Xing, Guozhong; Wang, Rongming E-mail: rmwang@ustb.edu.cn

    2014-11-15

    We report on the structural evolution and atomic inter-diffusion characteristics of the bimetallic Ni-Au nanocrystals (NCs) by molecular dynamics simulations studies. Our results reveal that the thermal stability dynamics of Ni-Au NCs strongly depends on the atomic configurations. By engineering the structural construction with Ni:Au = 1:1 atomic composition, compared with core-shell Au@Ni and alloy NCs, the melting point of core-shell Ni@Au NCs is significantly enhanced up to 1215 K. Unexpectedly, with atomic ratio of Au:Ni= 1:9, the melting process initiates from the atoms in the shell of Ni@Au and alloy NCs, while starts from the core of Au@Ni NCs. The corresponding features and evolution process of structural motifs, mixing and segregation are illustrated via a series of dynamic simulations videos. Moreover, our results revealed that the face centered cubic phase Au{sub 0.75}Ni{sub 0.25} favorably stabilizes in NCs form but does not exist in the bulk counterpart, which elucidates the anomalies of previously reported experimental results on such bimetallic NCs.

  19. Probe diffusion in phase-separated bicontinuous biopolymer gels.

    PubMed

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

    2014-11-01

    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

  20. Arc Length Gone Global

    ERIC Educational Resources Information Center

    Boudreaux, Gregory M.; Wells, M. Scott

    2007-01-01

    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…

  1. Measuring Thermodynamic Length

    SciTech Connect

    Crooks, Gavin E

    2007-09-07

    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.

  2. Leg Length Inequality

    PubMed Central

    Sharpe, Colin R.

    1983-01-01

    Leg length inequality, a common abnormality, can cause musculoskeletal pain, scoliosis, and osteoarthritis of the hip. Seven percent of the asymptomatic population has a leg length inequality greater than 12 mm; the incidence is considerably higher (13%-22%) in individuals complaining of low back pain. Correction can usually be accomplished by shoe modification, and can result in dramatic relief of pain. Leg length inequality of more than half an inch is considered clinically significant. Leg length measurement should be routine in all patients complaining of low back pain, hip pain, and atypical flank and lower quadrant pain. Correction might prove very cost-effective. PMID:21283327

  3. Correlating anomalous diffusion with lipid bilayer membrane structure using single molecule tracking and atomic force microscopy.

    PubMed

    Skaug, Michael J; Faller, Roland; Longo, Marjorie L

    2011-06-01

    Anomalous diffusion has been observed abundantly in the plasma membrane of biological cells, but the underlying mechanisms are still unclear. In general, it has not been possible to directly image the obstacles to diffusion in membranes, which are thought to be skeleton bound proteins, protein aggregates, and lipid domains, so the dynamics of diffusing particles is used to deduce the obstacle characteristics. We present a supported lipid bilayer system in which we characterized the anomalous diffusion of lipid molecules using single molecule tracking, while at the same time imaging the obstacles to diffusion with atomic force microscopy. To explain our experimental results, we performed lattice Monte Carlo simulations of tracer diffusion in the presence of the experimentally determined obstacle configurations. We correlate the observed anomalous diffusion with obstacle area fraction, fractal dimension, and correlation length. To accurately measure an anomalous diffusion exponent, we derived an expression to account for the time-averaging inherent to all single molecule tracking experiments. We show that the length of the single molecule trajectories is critical to the determination of the anomalous diffusion exponent. We further discuss our results in the context of confinement models and the generating stochastic process. PMID:21663377

  4. Neandertal clavicle length

    PubMed Central

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

    2014-01-01

    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

  5. A Multiscale Analysis of Diffusions on Rapidly Varying Surfaces

    NASA Astrophysics Data System (ADS)

    Duncan, A. B.; Elliott, C. M.; Pavliotis, G. A.; Stuart, A. M.

    2015-04-01

    Lateral diffusion of molecules on surfaces plays a very important role in various biological processes, including lipid transport across the cell membrane, synaptic transmission, and other phenomena such as exo- and endocytosis, signal transduction, chemotaxis, and cell growth. In many cases, the surfaces can possess spatial inhomogeneities and/or be rapidly changing shape. Using a generalization of the model for a thermally excited Helfrich elastic membrane, we consider the problem of lateral diffusion on quasi-planar surfaces, possessing both spatial and temporal fluctuations. Using results from homogenization theory, we show that, under the assumption of scale separation between the characteristic length and timescales of the membrane fluctuations and the characteristic scale of the diffusing particle, the lateral diffusion process can be well approximated by a Brownian motion on the plane with constant diffusion tensor that depends on a highly nonlinear way on the detailed properties of the surface. The effective diffusion tensor will depend on the relative scales of the spatial and temporal fluctuations, and for different scaling regimes, we prove the existence of a macroscopic limit in each case.

  6. Characteristic oscillatory motion of a camphor boat sensitive to physicochemical environment

    NASA Astrophysics Data System (ADS)

    Nakata, S.; Yoshii, M.; Matsuda, Y.; Suematsu, N. J.

    2015-06-01

    A self-propelled camphor boat on water was investigated from the viewpoint of characteristic features of motion and mode-bifurcation depending on the diffusion length of camphor molecules. When a camphor disk was connected to the bottom of a larger plastic plate and then was placed on water, either oscillatory motion (repetition between rest and motion) or continuous motion was observed. In this paper, we report the novel features of this motion and mode-bifurcation as a function of the diffusion length of camphor molecules, e.g., multiple accelerations during oscillation, period-2 or irregular oscillatory motion, and reciprocating oscillation. These characteristic motion and mode-bifurcation are discussed in relation to the diffusion length of camphor molecules under the camphor boat and the development of camphor molecules from the camphor boat on water.

  7. Welding arc length control system

    NASA Technical Reports Server (NTRS)

    Iceland, William F. (Inventor)

    1993-01-01

    The present invention is a welding arc length control system. The system includes, in its broadest aspects, a power source for providing welding current, a power amplification system, a motorized welding torch assembly connected to the power amplification system, a computer, and current pick up means. The computer is connected to the power amplification system for storing and processing arc weld current parameters and non-linear voltage-ampere characteristics. The current pick up means is connected to the power source and to the welding torch assembly for providing weld current data to the computer. Thus, the desired arc length is maintained as the welding current is varied during operation, maintaining consistent weld penetration.

  8. Novel Diffusivity Measurement Technique

    NASA Technical Reports Server (NTRS)

    Rashidnia, Nasser

    2001-01-01

    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.

  9. Length Paradox in Relativity

    ERIC Educational Resources Information Center

    Martins, Roberto de A.

    1978-01-01

    Describes a thought experiment using a general analysis approach with Lorentz transformations to show that the apparent self-contradictions of special relativity concerning the length-paradox are really non-existant. (GA)

  10. Myofilament length dependent activation

    SciTech Connect

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

    2010-05-25

    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.

  11. Coefficients of Effective Length.

    ERIC Educational Resources Information Center

    Edwards, Roger H.

    1981-01-01

    Under certain conditions, a validity Coefficient of Effective Length (CEL) can produce highly misleading results. A modified coefficent is suggested for use when empirical studies indicate that underlying assumptions have been violated. (Author/BW)

  12. Equilibrium CO bond lengths

    NASA Astrophysics Data System (ADS)

    Demaison, Jean; Csszr, Attila G.

    2012-09-01

    Based on a sample of 38 molecules, 47 accurate equilibrium CO bond lengths have been collected and analyzed. These ultimate experimental (reEX), semiexperimental (reSE), and Born-Oppenheimer (reBO) equilibrium structures are compared to reBO estimates from two lower-level techniques of electronic structure theory, MP2(FC)/cc-pVQZ and B3LYP/6-311+G(3df,2pd). A linear relationship is found between the best equilibrium bond lengths and their MP2 or B3LYP estimates. These (and similar) linear relationships permit to estimate the CO bond length with an accuracy of 0.002 within the full range of 1.10-1.43 , corresponding to single, double, and triple CO bonds, for a large number of molecules. The variation of the CO bond length is qualitatively explained using the Atoms in Molecules method. In particular, a nice correlation is found between the CO bond length and the bond critical point density and it appears that the CO bond is at the same time covalent and ionic. Conditions which permit the computation of an accurate ab initio Born-Oppenheimer equilibrium structure are discussed. In particular, the core-core and core-valence correlation is investigated and it is shown to roughly increase with the bond length.

  13. Editorial: Redefining Length

    SciTech Connect

    Sprouse, Gene D.

    2011-07-15

    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.

  14. Diffusive-Compressive Acceleration of Charged Particles

    NASA Astrophysics Data System (ADS)

    Jokipii, J. R.; Giacalone, J.; Kta, J.

    2001-12-01

    We consider the transport of energetic particles in a medium through which gradual (non-shock) compressions exist and propagate. As is the case with shocks, these compressions can accelerate charged particles. We have previously considered such acceleration in the specific context of CIRs (Giacalone, J., Jokipii, and Kta, Joint SOHO-ACE Symposium Proceedings, in press, 2001). There we suggested that it may explain CIR-related energetic particles observed in the inner Heliosphere, near 1 AU, well inside of the radius where the co-rotating shock has formed. Here we extend this concept to the general problem of acceleration by non-shock compressions, and consider primarily the limit in which the particle motion is diffusive. The relevant dimensionless parameter is the ratio Rc of the characteristic compression length scale L to the diffusive skin depth ? D = ? /U , where U is the velocity and ? is the diffusion coefficient. Clearly, Rc = U L/? . If Rc << 1 , the results reduce to those of diffusive shock acceleration. We present the results from solving the transport equation for a variety of compressive disturbances with various values of Rc, and find significant charged-particle acceleration. We discuss the physics of this acceleration and the dependence on the various parameters. Possible applications of this mechanism to heliospheric and other contexts will be discussed. We sugggest that in some cases this new form of acceleration may help to explain observations.

  15. Diffusion MRI

    NASA Astrophysics Data System (ADS)

    Fukuyama, Hidenao

    Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.

  16. Relativistic Length Agony Continued

    NASA Astrophysics Data System (ADS)

    Redzic, D. V.

    2014-06-01

    We made an attempt to remedy recent confusing treatments of some basic relativistic concepts and results. Following the argument presented in an earlier paper (Redzic 2008b), we discussed the misconceptions that are recurrent points in the literature devoted to teaching relativity such as: there is no change in the object in Special Relativity, illusory character of relativistic length contraction, stresses and strains induced by Lorentz contraction, and related issues. We gave several examples of the traps of everyday language that lurk in Special Relativity. To remove a possible conceptual and terminological muddle, we made a distinction between the relativistic length reduction and relativistic FitzGerald-Lorentz contraction, corresponding to a passive and an active aspect of length contraction, respectively; we pointed out that both aspects have fundamental dynamical contents. As an illustration of our considerations, we discussed briefly the Dewan-Beran-Bell spaceship paradox and the 'pole in a barn' paradox.

  17. Variable focal length microlenses

    NASA Astrophysics Data System (ADS)

    L. G., Commander; Day, S. E.; Selviah, D. R.

    2000-04-01

    Refractive surface relief microlenses (150 ?m diameter) are immersed in nematic liquid crystal in a cell. Application of a variable voltage across the cell effectively varies the refractive index of the liquid crystal and results in a change of the focal length by the lensmakers formula (E. Hecht, Optics, 2nd edn., Addison-Wesley, Reading, Massachusetts, 1987, p. 138). We describe the cell design and construction and demonstrate a range of focal lengths from +490 to +1000 ?m for 2 to 12 V applied. A diverging lens results when the voltage is lower. Theoretical models are developed to account for some of the observed aberrations.

  18. Designing molecular devices by altering bond lengths.

    PubMed

    Lamba, Vijay; Wilkinson, Suman J; Arora, Charu

    2011-12-01

    The work focuses on a theoretical approach to investigating the electric field (EF) dependence of bond-length alternation, the geometric and electronic structures of molecular wires used in the design of molecular electronic devices, the EF dependence of SCF energy, and the spatial distribution of the frontier orbitals of the molecular wires. Just as the bond length is an important influence on the conductance of the molecular wire, the dependence of the conductance on the chain length was also studied. We have also investigated how the current-voltage (I-V) characteristics change with bond length, as the bond length plays an important role in determining the conductance of molecular wires. PMID:21369931

  19. [Maintaining telomere length].

    PubMed

    Wysoczańska, Barbara

    2013-01-01

    Telomeres protect the ends of chromosomes maintaining genome stability. The activity of telomerase enzyme, or alternatively the process of recombination, regulates the length of telomeres. In the absence of these mechanisms, excessive shortening of telomeres reach its critical level. Excessively shortened telomeres do not protect chromosome ends, the cell division cycle is stopped while the inactivity of replication process generates cellular senescence and cell death. On the other hand, critically shortened telomeres may promote chromosomal instability. These changes can lead to the development of carcinogenesis. In this process enzymatic activity of telomerase is reactivated. To maintain the protection of the chromosome ends, telomeres bind the stabilizing protein complex (shelterin). The presence of these protective proteins prevents undesirable DNA damage and initiates the repair system pathways. Molecular technologies enable the evaluation of telomere lengths, the analysis of telomerase expression and activity, and detection of mutations, polymorphic and epigenetic changes in telomere--shelterin--telomerase complex related genes. The purpose of research is to describe new mechanisms that affect the biology of telomere lengths, and to determine the impact on bone marrow failures, development of haematological malignancies, neurodegenerative diseases and others disorders associated with chromosomal instability. The model of modern therapies based on telomere biology explains the significance of the maintenance of telomere lengths in the process of cellular senescence and carcinogenesis. PMID:24379272

  20. Mappability and read length

    PubMed Central

    Li, Wentian; Freudenberg, Jan

    2014-01-01

    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. PMID:25426137

  1. Spin diffusion in ultracold spin-orbit-coupled 40K gas

    NASA Astrophysics Data System (ADS)

    Yu, T.; Wu, M. W.

    2015-07-01

    We investigate the steady-state spin diffusion for ultracold spin-orbit-coupled 40K gas by the kinetic spin Bloch equation approach both analytically and numerically. Four configurations, i.e., the spin diffusions along two specific directions with the spin polarization perpendicular (transverse configuration) and parallel (longitudinal configuration) to the effective Zeeman field are studied. It is found that the behaviors of the steady-state spin diffusion for the four configurations are very different, which are determined by three characteristic lengths: the mean free path l?, the Zeeman oscillation length l?, and the spin-orbit coupling oscillation length l?. It is analytically revealed and numerically confirmed that by tuning the scattering strength, the system can be divided into five regimes: I, weak scattering regime (l??l?,l? ); II, Zeeman field-dominated moderate scattering regime (l??l??l? ); III, spin-orbit coupling-dominated moderate scattering regime (l??l??l? ); IV, relatively strong scattering regime (l?c?l??l?,l? ); V, strong scattering regime (l??l?,l?,l?c ), with l?c representing the crossover length between the relatively strong and strong scattering regimes. In different regimes, the behaviors of the spacial evolution of the steady-state spin polarization are very rich, showing different dependencies on the scattering strength, Zeeman field and spin-orbit coupling strength. The rich behaviors of the spin diffusions in different regimes are hard to understand in the framework of the simple drift-diffusion model or the direct inhomogeneous broadening picture in the literature. However, almost all these rich behaviors can be well understood by means of our modified drift-diffusion model and/or modified inhomogeneous broadening picture. Specifically, several anomalous features of the spin diffusion are revealed, which are in contrast to those obtained from both the simple drift-diffusion model and the direct inhomogeneous broadening picture.

  2. Characteristics of Signals Originating Near the Lithium-Diffused N+ Contact of High Purity Germanium P-Type Point Contact Detectors

    SciTech Connect

    Aguayo Navarrete, Estanislao; Amman, M.; Avignone, F. T.; Barabash, A.; Barton, P. J.; Beene, Jim; Bertrand, F.; Boswell, M.; Brudanin, V.; Busch, Matthew; Chan, Yuen-Dat; Christofferson, Cabot-Ann; Collar, Juan; Combs, Dustin C.; Cooper, R. J.; Detwiler, Jason A.; Doe, Peter J.; Efremenko, Yuri; Egorov, Viatcheslav; Ejiri, H.; Elliott, S. R.; Esterline, James H.; Fast, James E.; Fields, N.; Finnerty, P.; Fraenkle, Florian; Galindo-Uribarri, A.; Gehman, Victor M.; Giovanetti, G. K.; Green, Matthew P.; Guiseppe, Vincente; Gusey, K.; Hallin, A. L.; Hazama, R.; Henning, Reyco; Hoppe, Eric W.; Horton, Mark; Howard, Stanley; Howe, Mark; Johnson, R. A.; Keeter, K.; Kidd, Mary; Knecht, A.; Kochetov, Oleg; Konovalov, S.; Kouzes, Richard T.; LaFerriere, Brian D.; Leon, Jonathan D.; Leviner, L.; Loach, J. C.; Looker, Ron L.; Luke, P.; MacMullin, S.; Marino, Michael G.; Martin, R. D.; Merriman, Jason H.; Miller, M. L.; Mizouni, Leila K.; Nomachi, Masaharu; Orrell, John L.; Overman, Nicole R.; Perumpilly, Gopakumar; Phillips, D.; Poon, Alan; Radford, Davis; Rielage, Keith; Robertson, R. G. H.; Ronquest, M. C.; Schubert, Alexis G.; Shima, T.; Shirchenko, M.; Snavely, Kyle J.; Steele, David; Strain, J.; Timkin, V.; Tornow, W.; Varner, R. L.; Vetter, Kai; Vorren, Kris R.; Wilkerson, J. F.; Yakushev, E.; Yaver, Harold; Young, A.; Yu, Chang-Hong; Yumatov, Vladimir

    2013-02-11

    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.

  3. Characteristics of Signals Originating near the Lithium-Diffused N+ Contact of High Purity Germanium P-Type Point Contact Detectors

    SciTech Connect

    Aguayo, E.; Amman, M.; Avignone, F. T.; Barton, P. J.; Beene, James R; Bertrand Jr, Fred E; Boswell, M.; Brudanin, V.; Busch, M.; Chan, Y-D; Christofferson, C. D.; Collar, Juan I.; Combs, D. C.; Detwiler, J.A.; Doe, P. J.; Efremenko, Yuri; Egorov, V.; Ejiri, H.; Elliott, S. R.; Esterline, J.; Fast, J.E.; Fields, N.; Finnerty, P.; Gehman, V. M.; Giovanetti, G. K.; Green, M. P.; Gusey, K.; Hallin, A. L.; Hazama, R.; Henning, R.; Hoppe, E.W.; Horton, M.; Howard, S.; Howe, M. 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.; Looker, Q.; Luke, P.N.; MacMullin, S.; Martin, R.D.; Merriman, J. H.; Miller, M. L.; Mizouni, L.; Orrell, John L.; Overman, N. R.; Perumpilly, G.; Phillips II, D. G.; et al.

    2013-01-01

    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.

  4. Performance characteristics of diffusive gradients in thin films equipped with a binding gel layer containing precipitated ferrihydrite for measuring arsenic(V), selenium(VI), vanadium(V), and antimony(V).

    PubMed

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

    2010-11-01

    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

  5. Dissipative charge transport in diffusive superconducting double-barrier junctions

    NASA Astrophysics Data System (ADS)

    Bezuglyi, E. V.; Bratus', E. N.; Shumeiko, V. S.

    2011-05-01

    We solve the coherent multiple Andreev reflection (MAR) problem and calculate current-voltage characteristics (IVCs) for Josephson SINIS junctions, where S are local-equilibrium superconducting reservoirs, I denotes tunnel barriers, and N is a short diffusive normal wire, the length of which is much smaller than the coherence length, and the resistance is much smaller than the resistance of the tunnel barriers. The charge transport regime in such junctions qualitatively depends on a characteristic value ?=?d? of relative phase shifts between the electrons and retroreflected holes accumulated during the dwell time ?d. In the limit of small electron-hole dephasing ??1, our solution recovers a known formula for a short mesoscopic connector extended to the MAR regime. At large dephasing, the subharmonic gap structure in the IVC scales with ?-1, which thus plays the role of an effective tunneling parameter. In this limit, the even gap subharmonics are resonantly enhanced, and the IVC exhibits portions with negative differential resistance.

  6. The dynamics of unsteady detonation with diffusion

    SciTech Connect

    Aslam, Tariq Dennis; Romick, Christopher; Powers, Joseph

    2010-01-01

    Here we consider an unsteady detonation with diffusion included. This introduces an interaction between the reaction length scales and diffusion length scales. Detailed kinetics introduce multiple length scales as shown though the spatial eigenvalue analysis of hydrogen-oxygen system; the smallest length scale is {approx} 10{sup 7} m and the largest {approx} 10{sup -2} m; away from equilibrium, the breadth can be larger. In this paper, we consider a simpler set of model equations, similar to the inviscid reactive compressible fluid equations, but include diffusion (in the form of thermal/energy, momentum, and mass diffusion). We will seek to reveal how the complex dynamics already discovered in one-step systems in the inviscid limit changes with the addition of diffusion.

  7. Ballistic to diffusive transition in a two-dimensional quantum dot lattice

    NASA Astrophysics Data System (ADS)

    Cleri, Fabrizio

    2015-12-01

    Two-dimensional networks of ordered quantum dots beyond the percolation threshold are studied, as a typical example of conducting nanostructures with quenched random disorder. Theory predicts anomalous diffusion with stretched-exponential relaxation at short distances, and computer simulations on lattices of crossing, straight paths of random length confirm such a behavior. Anomalous diffusion is interpreted as resulting from the higher probability of taking straight, or ballistic, paths, when the traveled distance is comparable or shorter than the lattice characteristic length. Diffusion turns over to normal for longer traveled distances, whence all paths tend to become equiprobable. Such random lattice structures may represent a model for realistic quantum dot networks, with potential applications in optoelectronics, photovoltaics, or spintronics.

  8. Diffusion of myelin water.

    PubMed

    Andrews, Trevor J; Osborne, Michael T; Does, Mark D

    2006-08-01

    We studied compartmentally specific characteristics of water diffusion in excised frog sciatic nerve by combining T1 or T2 selective acquisitions with pulse-gradient spin-echo (PGSE) diffusion weighting, with the specific objective of characterizing myelin water diffusion. Combining a PGSE with a Carr-Purcell-Meiboom-Gill (CPMG) acquisition provided apparent diffusion coefficients (ADCs) for each of the three T2 components found in nerve, including the short-lived component believed to be derived from myelin water. Double-inversion-recovery (DIR) preparation provided an alternate means of discriminating myelin water, and in combination with PGSE provided somewhat different measures of ADC. The DIR measures yielded myelin water ADCs of 0.37 microm2/ms (parallel to nerve) and 0.13 microm2/ms (perpendicular to nerve). These ADC estimates were postulated to be more accurate than those based on T2 discrimination, although the difference between the two findings is not clear. PMID:16767712

  9. Vowel length in Farsi

    NASA Astrophysics Data System (ADS)

    Shademan, Shabnam

    2001-05-01

    This study tests whether Farsi vowels are contrastive with respective to length. Farsi has a six-vowel system with three lax vowels and three tense vowels. Both traditional grammarians and modern linguists believe that Farsi tense vowels are longer than lax vowels, and that there are no vowel pairs that contrast only in length. However, it has been suggested that Farsi exhibits compensatory lengthening, which is triggered by the deletion of glottal consonants in coda position in informal speech (Darzi, 1991). As a result, minimal pairs such as [tar] and [tarh] should contrast only with respect to vowel length. A corpus of 90 words of the form CVC, CVCG, CVGC, and CVCC (where V=a vowel and G=a glottal consonant) was recorded, and durations of vowels in different contexts were measured and compared. Preliminary results show that lax vowel durations fall into three groups with CVCC longer than CVCG/CVGC, and the latter longer than CVC. It remains to be seen whether CVCG/CVGC words show compensatory lengthening when the glottal consonant is deleted.

  10. Optical and electrical investigation of a cylindrical diffuse-discharge chamber

    SciTech Connect

    Teng, Yun; Li, Lee Cheng, Yong; Ma, Ning; Peng, Ming-yang; Liu, Ming-hai

    2015-03-15

    More and more attention has been attached to atmospheric-pressure air diffuse plasma due to its enormous potential applications. In this paper, we designed a large-scale, cylindrical diffuse-plasma chamber using wire electrodes and a repetitive nanosecond pulse generator. The plasma chamber can be completely exposed in the open air without any barrier dielectric, and the length of cylindrical plasma chamber was extensible. Using optical and electrical measurements, we investigated the effects of electrode distance, electrode length, pulse repetition frequency, and electrode angle on the uniformity of discharge space. Four discharge regions were distinguished based on different spectral characteristics. Additionally, it was found that the discharge uniformity was improved as the electrode distance decreases, but remained almost constant with the variations of electrode length and pulse repetition frequency. Both of the plasma uniformity and the power density increased significantly as the electrode angle reduced.

  11. Diffusivity in turbulent fluid containing two dominant scales, and compressible shear layer according to a kinetic theory

    NASA Technical Reports Server (NTRS)

    Chung, P. M.

    1976-01-01

    The solution of the two nonequilibrium-degree kinetic equation was first determined for the effective length scale and turbulence energy for a spatially homogeneous turbulence field with two characteristic length scales, where the source for one family of eddies exists. This solution was applied to the evaluation of the eddy diffusivity in the combustion chamber of an internal combustion engine. The result was compared with another existing solution. This was carried out to demonstrate the feasibility of obtaining an effective length-scale equation within the context of the kinetic theory. A formulation and partial solution of the compressible plane shear layer are also presented.

  12. On collisional diffusion in a stochastic magnetic field

    SciTech Connect

    Abdullaev, S. S.

    2013-08-15

    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.

  13. Puzzle of the Electrostatic Persistence Length

    NASA Astrophysics Data System (ADS)

    Dobrynin, A. V.; Carrillo, J.-M. Y.

    2013-03-01

    Electrostatic interactions play an important role in controlling properties of synthetic and biological polyelectrolytes. The change in the ionic environment in such systems can significantly influence their conformational properties. For semiflexible polyelectrolyte chains with ionic groups interacting via the screened Debye-Huckel potential the electrostatic contribution to the chain persistence length scales quadratically with the Debye screening length (OSF model). However, recent computer simulations of flexible polyelectrolyte chains with explicit counterions and salt ions show that in the wide interval of the solution ionic strengths the electrostatic contribution to chain persistence length is proportional to the Debye screening length, rD. To understand the crossover between flexible and semiflexible chain behavior and elucidate the effect of explicit ions on chain conformations we performed molecular dynamics of polyelectrolyte chains with degree of polymerization N = 300 and different values of the chain bending rigidity varying between K = 1 and K = 160. Our simulations have shown that the bond-bond correlation function describing chain's orientational memory can be approximated by a sum of two exponential functions manifesting the existence of the two characteristic length scales. One describes the chain's bending rigidity at the distances along the polymer backbone shorter than rD while another controls the long-length scale chain's orientational correlations. The long-length scale bending rigidity is proportional to rD for chains with bending rigidity smaller than a crossover bending rigidity K*. NSF DMR-1004576

  14. Characterizing cosmic inhomogeneity with anomalous diffusion

    NASA Astrophysics Data System (ADS)

    Kraljic, D.

    2015-08-01

    Dark matter (DM) clustering at the present epoch is investigated from a fractal viewpoint in order 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-cells' as well as new methods based on anomalous diffusion and random walks are investigated. Both are applied to DM haloes of the biggest N-body simulation in the `Dark Sky Simulations' (DS) catalogue and an equivalent randomly distributed catalogue. Results based on the smaller `Millennium Run' (MR) simulation are revisited and improved. 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-cells' method applied to the DS then yields a homogeneity scale roughly consistent with previous work (˜150 h-1 Mpc). The characteristic length-scale for anomalous diffusion to behave homogeneously is found to be at about 250 h-1 Mpc. The behaviour of the fractal dimensions for a halo catalogue with the same two-point function as the original but with shuffled Fourier phases is investigated. The methods based on anomalous diffusion are shown to be sensitive to the phase information, whereas the `counts-in-cells' methods are not.

  15. Delayed feedback model of axonal length sensing.

    PubMed

    Karamched, Bhargav R; Bressloff, Paul C

    2015-05-01

    A fundamental question in cell biology is how the sizes of cells and organelles are regulated at various stages of development. Size homeostasis is particularly challenging for neurons, whose axons can extend from hundreds of microns to meters (in humans). Recently, a molecular-motor-based mechanism for axonal length sensing has been proposed, in which axonal length is encoded by the frequency of an oscillating retrograde signal. In this article, we develop a mathematical model of this length-sensing mechanism in which advection-diffusion equations for bidirectional motor transport are coupled to a chemical signaling network. We show that chemical oscillations emerge due to delayed negative feedback via a Hopf bifurcation, resulting in a frequency that is a monotonically decreasing function of axonal length. Knockdown of either kinesin or dynein causes an increase in the oscillation frequency, suggesting that the length-sensing mechanism would produce longer axons, which is consistent with experimental findings. One major prediction of the model is that fluctuations in the transport of molecular motors lead to a reduction in the reliability of the frequency-encoding mechanism for long axons. PMID:25954897

  16. Length of stain dosimeter

    NASA Technical Reports Server (NTRS)

    Lueck, Dale E. (Inventor)

    1994-01-01

    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.

  17. Odd Length Contraction

    NASA Astrophysics Data System (ADS)

    Smarandache, Florentin

    2013-09-01

    Let's denote by VE the speed of the Earth and byVR the speed of the rocket. Both travel in the same direction on parallel trajectories. We consider the Earth as a moving (at a constant speed VE -VR) spacecraft of almost spherical form, whose radius is r and thus the diameter 2r, and the rocket as standing still. The non-proper length of Earth's diameter, as measured by the astronaut is: L = 2 r√{ 1 -|/VE -VR|2 c2 } < 2 r . Therefore Earth's diameter shrinks in the direction of motion, thus Earth becomes an ellipsoid - which is untrue. Planet Earth may increase or decrease its diameter (volume), but this would be for other natural reasons, not because of a...flying rocket! Also, let's assume that the astronaut is laying down in the direction of motion. Therefore, he would also shrink, or he would die!

  18. Metagenomics: Read Length Matters?

    PubMed Central

    Wommack, K. Eric; Bhavsar, Jaysheel; Ravel, Jacques

    2008-01-01

    Obtaining an unbiased view of the phylogenetic composition and functional diversity within a microbial community is one central objective of metagenomic analysis. New technologies, such as 454 pyrosequencing, have dramatically reduced sequencing costs, to a level where metagenomic analysis may become a viable alternative to more-focused assessments of the phylogenetic (e.g., 16S rRNA genes) and functional diversity of microbial communities. To determine whether the short (?100 to 200 bp) sequence reads obtained from pyrosequencing are appropriate for the phylogenetic and functional characterization of microbial communities, the results of BLAST and COG analyses were compared for long (?750 bp) and randomly derived short reads from each of two microbial and one virioplankton metagenome libraries. Overall, BLASTX searches against the GenBank nr database found far fewer homologs within the short-sequence libraries. This was especially pronounced for a Chesapeake Bay virioplankton metagenome library. Increasing the short-read sampling depth or the length of derived short reads (up to 400 bp) did not completely resolve the discrepancy in BLASTX homolog detection. Only in cases where the long-read sequence had a close homolog (low BLAST E-score) did the derived short-read sequence also find a significant homolog. Thus, more-distant homologs of microbial and viral genes are not detected by short-read sequences. Among COG hits, derived short reads sampled at a depth of two short reads per long read missed up to 72% of the COG hits found using long reads. Noting the current limitation in computational approaches for the analysis of short sequences, the use of short-read-length libraries does not appear to be an appropriate tool for the metagenomic characterization of microbial communities. PMID:18192407

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

    SciTech Connect

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

    1996-04-01

    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.

  20. Diffuse radiation

    NASA Technical Reports Server (NTRS)

    1981-01-01

    A diffuse celestial radiation which is isotropic at least on a course scale were measured from the soft X-ray region to about 150 MeV, at which energy the intensity falls below that of the galactic emission for most galactic latitudes. The spectral shape, the intensity, and the established degree of isotropy of this diffuse radiation already place severe constraints on the possible explanations for this radiation. Among the extragalactic theories, the more promising explanations of the isotropic diffuse emission appear to be radiation from exceptional galaxies from matter antimatter annihilation at the boundaries of superclusters of galaxies of matter and antimatter in baryon symmetric big bang models. Other possible sources for extragalactic diffuse gamma radiation are discussed and include normal galaxies, clusters of galaxies, primordial cosmic rays interacting with intergalactic matter, primordial black holes, and cosmic ray leakage from galaxies.

  1. Quantum diffusion

    NASA Astrophysics Data System (ADS)

    Tsekov, Roumen

    2011-03-01

    Quantum diffusion (QD) is studied via dissipative Madelung hydrodynamics. Initially, the wave packet spreads ballistically, then passes for an instant through normal diffusion and later tends asymptotically to a sub-diffusive law. It is shown that the apparent QD coefficient is not a universal physical parameter because it depends on the initial wave packet preparation. The overdamped QD of an electron in the field of a periodic potential is also investigated; in this case, the wave packet spreads logarithmically in time. Thermo-QD of heavier particles such as hydrogen, deuterium and tritium atoms in periodic potentials is studied and a simple estimate of the tunneling effect is obtained in the framework of a quasi-equilibrium semiclassical approach. The effective thermo-quantum temperature is also discussed in relation to the known temperature dependence of muon diffusivity in solids.

  2. Helium-3 Diffusion MR Imaging of the Human Lung over Multiple Time Scales

    PubMed Central

    Mugler, John P.; Wang, Chengbo; Miller, G. Wilson; Cates, Gordon D.; Mata, Jaime F.; Brookeman, James R.; de Lange, Eduard E.; Altes, Talissa A.

    2008-01-01

    Rationale and Objectives Diffusion MRI with hyperpolarized 3He gas is a powerful technique for probing the characteristics of the lung microstructure. A key parameter for this technique is the diffusion time, which is the period during which the atoms are allowed to diffuse within the lung for measurement of the signal attenuation. The relationship between diffusion time and the length scales that can be explored is discussed, and representative, preliminary results are presented from ongoing studies of the human lung for diffusion times ranging from milliseconds to several seconds. Materials and Methods 3He diffusion MR imaging of the human lung was performed on a 1.5T Siemens Sonata scanner. Using gradient-echo-based and stimulated-echo-based techniques for short and medium-to-long diffusion times, respectively, measurements were performed for times ranging from 2 ms to 6.5 s in two healthy subjects, a subject with sub-clinical chronic obstructive pulmonary disease and a subject with bronchopulmonary dysplasia. Results In healthy subjects, the apparent diffusion coefficient decreased by about 10-fold, from approximately 0.2 to 0.02 cm2/s, as the diffusion time increased from approximately 1 ms to 1 s. Results in subjects with disease suggest that measurements made at diffusion times substantially longer than 1 ms may provide improved sensitivity for detecting certain pathological changes in the lung microstructure. Conclusion With appropriately designed pulse sequences it is possible to explore the diffusion of hyperpolarized 3He in the human lung over more than a 1000-fold variation of the diffusion time. Such measurements provide a new opportunity for exploring and characterizing the microstructure of the healthy and diseased lung. PMID:18486006

  3. Design and performance of thin cylindrical diffusers created in Ge-doped multimode optical fibers.

    PubMed

    Vesselov, Leonid; Whittington, William; Lilge, Lothar

    2005-05-10

    Cylindrical fiber diffusers have become common tools for various medical therapies. However, their large outer diameters and short lengths restrict their clinical application in some newly developed light therapies. Here, a 250-microm outer-diameter diffuser with an active length that exceeds 5 cm is presented. Diffusers are created in photosensitive optical fibers with outer cladding diameters of 140 microm by use of a structured beam from an excimer laser. Predetermined emission profiles can be achieved. Photometric characteristics, including longitudinal, polar, and azimuthal emission diagrams, were determined by use of a goniometer to assess the light-emission performance of the diffuser. Longitudinal isotropy of better than +/- 10% was achieved. Polar and azimuthal emissions were within +/- 15% of those of an ideal linear Lambertian emitter. Polar uniformity could be improved by an insignificant increase in the outer diameter by use of a diffusing recoating compound. The residual leakage of light at the distal end of the diffuser can be as little as 1%. Other physical parameters tested include minimal bending radius after recoating (< 5 mm) and maximum power handling (> 1.0W cm(-1)). All materials employed were biocompatible. PMID:15945145

  4. Channel length dependence of negative-bias-illumination-stress in amorphous-indium-gallium-zinc-oxide thin-film transistors

    NASA Astrophysics Data System (ADS)

    Um, Jae Gwang; Mativenga, Mallory; Migliorato, Piero; Jang, Jin

    2015-06-01

    We have investigated the dependence of Negative-Bias-illumination-Stress (NBIS) upon channel length, in amorphous-indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs). The negative shift of the transfer characteristic associated with NBIS decreases for increasing channel length and is practically suppressed in devices with L = 100-?m. The effect is consistent with creation of donor defects, mainly in the channel regions adjacent to source and drain contacts. Excellent agreement with experiment has been obtained by an analytical treatment, approximating the distribution of donors in the active layer by a double exponential with characteristic length LD Ln 10-?m, the latter being the electron diffusion length. The model also shows that a device with a non-uniform doping distribution along the active layer is in all equivalent, at low drain voltages, to a device with the same doping averaged over the active layer length. These results highlight a new aspect of the NBIS mechanism, that is, the dependence of the effect upon the relative magnitude of photogenerated holes and electrons, which is controlled by the device potential/band profile. They may also provide the basis for device design solutions to minimize NBIS.

  5. Pharmacologically induced erect penile length and stretched penile lengh are both good predictors of post-inflatable prosthesis penile length

    PubMed Central

    Osterberg, EC; Maganty, A; Ramasamy, R; Eid, JF

    2015-01-01

    Inflatable penile prosthesis (IPP) remains the gold standard for the surgical treatment of refractory erectile dysfunction; however, current literature to aid surgeons on how best to counsel patients on their postoperative inflated penile length is lacking. The aim of this study was to identify preoperative parameters that could better predict postoperative penile length following insertion of an IPP. Twenty men were enrolled in a prospective study examining penile lengths before and after IPP surgery. Patients with Peyronies disease were excluded from this analysis. Baseline preoperative characteristics, including body mass index, history of hypertension, diabetes, Sexual Health Inventory for Men scores and/or prior radical prostatectomy were recorded. All patients underwent implantation with a three-piece inflatable Coloplast penile prosthesis. We compared stretched penile length to pharmacologically induced erect lengths. Postoperatively, we measured inflated penile lengths at 6 weeks and assessed patients perception of penile size at 12 weeks. The median ( interquartile range) stretched penile length and pharmacologically induced erect penile length was 15 ( 3) and 14.25 ( 2) cm, respectively (P = 0.5). Median post-prosthesis penile length (13.5 2.13 cm) was smaller than preoperative pharmacologically induced length (P = 0.02) and preoperative stretched penile length (P = 0.01). The majority of patients (70%) had a decrease in penile length (median loss 0.5 1.5 cm); however, this loss was perceptible by 43% of men. Stretched penile length and pharmacologically induced erect penile length were equally good predictors of postoperative inflated length (Spearmans correlation 0.8 and 0.9, respectively). Pharmacologically induced erect penile length and stretched penile lengths are equal predictors of post-prosthesis penile length. The majority of men will experience some decrease in penile length following prosthesis implantation; however <50% report a subjective loss of penile length. PMID:24430278

  6. Gray zone lymphoma with features intermediate between classical Hodgkin lymphoma and diffuse large B-cell lymphoma: characteristics, outcomes, and prognostication among a large multicenter cohort.

    PubMed

    Evens, Andrew M; Kanakry, Jennifer A; Sehn, Laurie H; Kritharis, Athena; Feldman, Tatyana; Kroll, Aimee; Gascoyne, Randy D; Abramson, Jeremy S; Petrich, Adam M; Hernandez-Ilizaliturri, Francisco J; Al-Mansour, Zeina; Adeimy, Camille; Hemminger, Jessica; Bartlett, Nancy L; Mato, Anthony; Caimi, Paolo F; Advani, Ranjana H; Klein, Andreas K; Nabhan, Chadi; Smith, Sonali M; Fabregas, Jesus C; Lossos, Izidore S; Press, Oliver W; Fenske, Timothy S; Friedberg, Jonathan W; Vose, Julie M; Blum, Kristie A

    2015-09-01

    Gray zone lymphoma (GZL) with features between classical Hodgkin lymphoma and diffuse large B-cell lymphoma (DLBCL) is a recently recognized entity reported to present primarily with mediastinal disease (MGZL). We examined detailed clinical features, outcomes, and prognostic factors among 112 GZL patients recently treated across 19 North American centers. Forty-three percent of patients presented with MGZL, whereas 57% had non-MGZL (NMGZL). NMGZL patients were older (50 versus 37 years, P?=?0.0001); more often had bone marrow involvement (19% versus 0%, P?=?0.001); >1 extranodal site (27% versus 8%, P?=?0.014); and advanced stage disease (81% versus 13%, P?=?0.0001); but they had less bulk (8% versus 44%, P?=?0.0001), compared with MGZL patients. Common frontline treatments were cyclophosphamide-doxorubicin-vincristine-prednisone +/- rituximab (CHOP+/-R) 46%, doxorubicin-bleomycin-vinblastine-dacarbazine +/- rituximab (ABVD+/-R) 30%, and dose-adjusted etoposide-doxorubicin-cyclophosphamide-vincristine-prednisone-rituximab (DA-EPOCH-R) 10%. Overall and complete response rates for all patients were 71% and 59%, respectively; 33% had primary refractory disease. At 31-month median follow-up, 2-year progression-free survival (PFS) and overall survival rates were 40% and 88%, respectively. Interestingly, outcomes in MGZL patients seemed similar compared with that of NMGZL patients. On multivariable analyses, performance status and stage were highly prognostic for survival for all patients. Additionally, patients treated with ABVD+/-R had markedly inferior 2-year PFS (22% versus 52%, P?=?0.03) compared with DLBCL-directed therapy (CHOP+/-R and DA-EPOCH-R), which persisted on Cox regression (hazard ratio, 1.88; 95% confidence interval, 1.03-3.83; P?=?0.04). Furthermore, rituximab was associated with improved PFS on multivariable analyses (hazard ratio, 0.35; 95% confidence interval, 0.18-0.69; P?=?0.002). Collectively, GZL is a heterogeneous and likely more common entity and often with nonmediastinal presentation, whereas outcomes seem superior when treated with a rituximab-based, DLBCL-specific regimen. PMID:26044261

  7. Scattering Length Instability in Dipolar Bose-Einstein Condensates

    SciTech Connect

    Bortolotti, D. C. E.; Ronen, S.; Bohn, J. L.; Blume, D.

    2006-10-20

    We predict a new kind of instability in a Bose-Einstein condensate composed of dipolar particles. Namely, a comparatively weak dipole moment can produce a large, negative two-body scattering length that can collapse the Bose-Einstein condensate. To verify this effect, we validate mean-field solutions to this problem using exact, diffusion Monte Carlo methods. We show that the diffusion Monte Carlo energies are reproduced accurately within a mean-field framework if the variation of the s-wave scattering length with the dipole strength is accounted for properly.

  8. Characteristics of 0.8- and 0.2-microns gate length In(x)Ga(1-x) As/In(0.52)Al(0.48)As/InP (0.53 less than or equal to x less than or equal to 0.70) modulation-doped field-effect transistors at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  9. Spin diffusion in disordered organic semiconductors

    NASA Astrophysics Data System (ADS)

    Li, Ling; Gao, Nan; Lu, Nianduan; Liu, Ming; Bssler, Heinz

    2015-12-01

    An analytical theory for spin diffusion in disordered organic semiconductors is derived. It is based on percolation theory and variable range hopping in a disordered energy landscape with a Gaussian density of states. It describes universally the dependence of the spin diffusion on temperature, carrier density, material disorder, magnetic field, and electric field at the arbitrary magnitude of the Hubbard energy of charge pairs. It is found that, compared to the spin transport carried by carriers hopping, the spin exchange will hinder the spin diffusion process at low carrier density, even under the condition of a weak electric field. Importantly, under the influence of a bias voltage, anomalous spreading of the spin packet will lead to an abnormal temperature dependence of the spin diffusion coefficient and diffusion length. This explains the recent experimental data for spin diffusion length observed in Alq3.

  10. Tracer diffusion in silica inverse opals.

    PubMed

    Cherdhirankorn, Thipphaya; Retsch, Markus; Jonas, Ulrich; Butt, Hans-Juergen; Koynov, Kaloian

    2010-06-15

    We employed fluorescence correlation spectroscopy (FCS) to study the diffusion of small fluorescence tracers in liquid filled silica inverse opals. The inverse opals consisted of a nanoporous silica scaffold spanning a hexagonal crystal of spherical voids of 360 nm diameter connected by circular pores of 70 nm diameter. The diffusion of Alexa Fluor 488 in water and of perylene-3,4,9,10-tetracarboxylic diimide (PDI) in toluene was studied. Three diffusion modes could be distinguished: (1) Free diffusion limited by the geometric constraints given by the inverse opal, where, as compared to the free solution, this diffusion is slowed down by a factor of 3-4, (2) slow diffusion inside the nanoporous matrix of the silica scaffold, and (3) diffusion limited by adsorption. On the length scale of the focus of a confocal microscope of roughly 400 nm diffusion was non-Fickian in all cases. PMID:20232884

  11. Effect of Solder Joint Length on Fracture Under Bending

    NASA Astrophysics Data System (ADS)

    Akbari, Saeed; Nourani, Amir; Spelt, Jan K.

    2016-01-01

    Fracture tests were conducted on copper-solder-copper joints of various lengths using double-cantilever-beam (DCB) specimens under mode I loading conditions. The thickness and length of the solder joints were large enough to neglect any anisotropy associated with the solder microstructure. It was found that the critical strain energy release rate at crack initiation, G ci, was insensitive to the length of the solder joint; however, for joints shorter than a characteristic length which was a function of the thickness and the mechanical properties of the solder layer and the substrates, the fracture load increased with increasing solder joint length. A sandwich model was developed for the analysis of the stress and strain in solder joints, taking into account the influence of both the bending deformation and the shear deformation of the substrates on the solder joint stresses. Consistent with the experimental results, it was found that solder joints longer than the characteristic length have a maximum peel stress that remains unchanged with joint length, causing the joint strength to become independent of the joint length. A closed-form analytical solution was developed for the characteristic length of DCB specimens under mode I loading. The experimental results were in good agreement with the analytical model and with finite element results. The generality of the G ci failure criterion was demonstrated by comparing the experimental results and the fracture load predictions of mode I DCB solder joints with different lengths.

  12. Effect of Solder Joint Length on Fracture Under Bending

    NASA Astrophysics Data System (ADS)

    Akbari, Saeed; Nourani, Amir; Spelt, Jan K.

    2015-11-01

    Fracture tests were conducted on copper-solder-copper joints of various lengths using double-cantilever-beam (DCB) specimens under mode I loading conditions. The thickness and length of the solder joints were large enough to neglect any anisotropy associated with the solder microstructure. It was found that the critical strain energy release rate at crack initiation, G ci, was insensitive to the length of the solder joint; however, for joints shorter than a characteristic length which was a function of the thickness and the mechanical properties of the solder layer and the substrates, the fracture load increased with increasing solder joint length. A sandwich model was developed for the analysis of the stress and strain in solder joints, taking into account the influence of both the bending deformation and the shear deformation of the substrates on the solder joint stresses. Consistent with the experimental results, it was found that solder joints longer than the characteristic length have a maximum peel stress that remains unchanged with joint length, causing the joint strength to become independent of the joint length. A closed-form analytical solution was developed for the characteristic length of DCB specimens under mode I loading. The experimental results were in good agreement with the analytical model and with finite element results. The generality of the G ci failure criterion was demonstrated by comparing the experimental results and the fracture load predictions of mode I DCB solder joints with different lengths.

  13. Identifying anomalous diffusion and melting in dusty plasmas

    SciTech Connect

    Feng Yan; Goree, J.; Liu Bin

    2010-09-15

    Anomalous diffusion in liquids and the solid-liquid phase transition (melting) are studied in two-dimensional Yukawa systems. The self-intermediate scattering function (self-ISF), calculated from simulation data, exhibits a temporal decay, or relaxation, with a characteristic relaxation time. This decay is found to be useful for distinguishing normal and anomalous diffusion in a liquid, and for identifying the solid-liquid phase transition. For liquids, a scaling of the relaxation time with length scale is found. For the solid-liquid phase transition, the shape of the self-ISF curve is found to be a sensitive indicator of phase. Friction has a significant effect on the timing of relaxation, but not the melting point.

  14. A multi-length-scale theory of the anomalous mixing-length growth for tracer flow in heterogeneous porous media

    SciTech Connect

    Qiang Zhang )

    1992-01-01

    The author develops a multi-length-scale (multifractal) theory for the effect of rock heterogeneity on the growth of the mixing layer of the flow of a passive tracer through porous media. The multifractal exponent of the size of the mixing layer is determined analytically from the statistical properties of a random velocity (permeability) field. The anomalous diffusion of the mixing layer can occur both on finite and on asymptotic length scales.

  15. Towards an interpretation of the scale diffusivity in liquid atomization process: An experimental approach

    NASA Astrophysics Data System (ADS)

    Dumouchel, Christophe; Ménard, Thibaut; Aniszewski, Wojciech

    2015-11-01

    Recent investigations have presented an application of the scale entropy diffusion theory to model liquid atomization process. This theory describes multi-scale behavior by a diffusion equation of the scale entropy function. In atomization, this function is related to the scale-distribution which provides a measurement of the specific-length of the eroded liquid system according to the scale of erosion. The present paper performs a detailed description of the scale diffusion mechanism for the atomization process of a liquid jet emanating from a gasoline injector with the objective of determining the scale diffusivity parameter introduced by the diffusion theory. The 2-D description of the gasoline jet as a function of the injection pressure reveals that the scale space is divided into two regions according to the sign of the scale specific-length variation rate: The small-scale region refers to the scales that undergo an elongation mechanism whereas the large-scale region concerns the scales that undergo a contraction mechanism. Furthermore, two phases of the atomization process are identified depending on whether the elongation mechanism is governed by the jet dynamics or surface tension effects. A non-dimensional number segregating these two phases is established. During the atomization process, the contraction mechanism diffuses in the small scale region. This manifests by a temporal decrease of the scale with a zero specific-length variation. It is found that the scale diffusivity parameter can be determined from the evolution of this characteristic scale in the second phase of the atomization process.

  16. Use of cylindrical diffusing fibers as detectors for interstitial tissue spectroscopy

    NASA Astrophysics Data System (ADS)

    Baran, Timothy M.; Foster, Thomas H.

    2015-03-01

    Interstitial photodynamic therapy (iPDT) describes the use of implanted optical fibers for delivery of treatment light to activate photosensitizer in regions that can be located deep within the body. Since sensitive healthy structures are often located nearby, this requires careful treatment planning that is dependent on tissue optical properties. Determination of these values usually involves the insertion of additional fibers into the volume, or the use of flat-cleaved optical fibers as both treatment sources and detectors. The insertion of additional fibers is undesirable, and cylindrical diffusers have been shown to offer superior treatment characteristics compared to flat-cleaved fibers. Using cylindrical diffusers as detectors for spectroscopic measurement is therefore attractive. We describe the determination of the detection profile for a particular cylindrical diffuser design and derive the scatterer concentration gradient within the diffuser core. This detection profile is compared to previously characterized diffusers, and is shown to be dependent on the diffuser design. For diffusers with a constant scatterer concentration and distal mirror, the detection profile is localized to the proximal end of the diffusing region. For diffusers with variable scattering concentration along their length and no distal mirror, the detection profile is shown to be more uniform along the diffusing region. We also present preliminary results showing the recovery of optical properties using arrays of cylindrical diffusing fibers as sources and detectors, with a mean error of 4.4% in the determination of μeff. The accuracy of these results is comparable to those obtained with other methods of optical property recovery.

  17. Defusing Diffusion

    ERIC Educational Resources Information Center

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

    2013-01-01

    Diffusion has often been taught in science courses as one of the primary ways by which molecules travel, particularly within organisms. For years, classroom teachers have used the same common demonstrations to illustrate this concept (e.g., placing drops of food coloring in a beaker of water). Most of the time, the main contributor to the motion

  18. Demonstrating Diffusion

    ERIC Educational Resources Information Center

    Foy, Barry G.

    1977-01-01

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

  19. Relativistic diffusion.

    PubMed

    Haba, Z

    2009-02-01

    We discuss relativistic diffusion in proper time in the approach of Schay (Ph.D. thesis, Princeton University, Princeton, NJ, 1961) and Dudley [Ark. Mat. 6, 241 (1965)]. We derive (Langevin) stochastic differential equations in various coordinates. We show that in some coordinates the stochastic differential equations become linear. We obtain momentum probability distribution in an explicit form. We discuss a relativistic particle diffusing in an external electromagnetic field. We solve the Langevin equations in the case of parallel electric and magnetic fields. We derive a kinetic equation for the evolution of the probability distribution. We discuss drag terms leading to an equilibrium distribution. The relativistic analog of the Ornstein-Uhlenbeck process is not unique. We show that if the drag comes from a diffusion approximation to the master equation then its form is strongly restricted. The drag leading to the Tsallis equilibrium distribution satisfies this restriction whereas the one of the Jttner distribution does not. We show that any function of the relativistic energy can be the equilibrium distribution for a particle in a static electric field. A preliminary study of the time evolution with friction is presented. It is shown that the problem is equivalent to quantum mechanics of a particle moving on a hyperboloid with a potential determined by the drag. A relation to diffusions appearing in heavy ion collisions is briefly discussed. PMID:19391727

  20. Defusing Diffusion

    ERIC Educational Resources Information Center

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

    2013-01-01

    Diffusion has often been taught in science courses as one of the primary ways by which molecules travel, particularly within organisms. For years, classroom teachers have used the same common demonstrations to illustrate this concept (e.g., placing drops of food coloring in a beaker of water). Most of the time, the main contributor to the motion…

  1. Chromosome-length polymorphism in fungi.

    PubMed Central

    Zolan, M E

    1995-01-01

    The examination of fungal chromosomes by pulsed-field gel electrophoresis has revealed that length polymorphism is widespread in both sexual and asexual species. This review summarizes characteristics of fungal chromosome-length polymorphism and possible mitotic and meiotic mechanisms of chromosome length change. Most fungal chromosome-length polymorphisms are currently uncharacterized with respect to content and origin. However, it is clear that long tandem repeats, such as tracts of rRNA genes, are frequently variable in length and that other chromosomal rearrangements are suppressed during normal mitotic growth. Dispensable chromosomes and dispensable chromosome regions, which have been well documented for some fungi, also contribute to the variability of the fungal karyotype. For sexual species, meiotic recombination increases the overall karyotypic variability in a population while suppressing genetic translocations. The range of karyotypes observed in fungi indicates that many karyotypic changes may be genetically neutral, at least under some conditions. In addition, new linkage combinations of genes may also be advantageous in allowing adaptation of fungi to new environments. PMID:8531892

  2. Compressor and fan wake characteristics

    NASA Technical Reports Server (NTRS)

    Reynolds, B.; Hah, C.; Lakshminarayana, B.; Ravindranath, A.

    1978-01-01

    A triaxial probe and a rotating conventional probe, mounted on a traverse gear operated by two step motors were used to measure the mean velocities and turbulence quantities across a rotor wake at various radial locations and downstream stations. The data obtained was used in an analytical model developed to study how rotor flow and blade parameters and turbulence properties such as energy, velocity correlations, and length scale affect the rotor wake characteristics and its diffusion properties. The model, includes three dimensional attributes, can be used in predicting the discrete as well as broadband noise generated in a fan rotor, as well as in evaluating the aerodynamic losses, efficiency and optimum spacing between a rotor and stator in turbomachinery.

  3. Revealing mesoscopic structural universality with diffusion

    PubMed Central

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

    2014-01-01

    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

  4. Revealing mesoscopic structural universality with diffusion.

    PubMed

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

    2014-04-01

    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

  5. IMPEDANCE OF FINITE LENGTH RESISTOR

    SciTech Connect

    KRINSKY, S.; PODOBEDOV, B.; GLUCKSTERN, R.L.

    2005-05-15

    We determine the impedance of a cylindrical metal tube (resistor) of radius a, length g, and conductivity {sigma}, attached at each end to perfect conductors of semi-infinite length. Our main interest is in the asymptotic behavior of the impedance at high frequency, k >> 1/a. In the equilibrium regime, , the impedance per unit length is accurately described by the well-known result for an infinite length tube with conductivity {sigma}. In the transient regime, ka{sup 2} >> g, we derive analytic expressions for the impedance and wakefield.

  6. Steric effects on diffusion into bituminous coals

    SciTech Connect

    John W. Larsen; Doyoung Lee

    2006-02-01

    The reactions of maleic anhydride, cis-maleate esters, and acetylenedicarboxylate esters with Pittsburgh No. 8 or Illinois No. 6 coal using o-xylene or o-dichlorobenzene solvent are diffusion controlled. Diffusion is Fickian in all cases. The measured activation energies are between 5.4 and 7.6 kcal/mol. Diffusion rates decrease slowly with increasing alkyl chain length and sharply with branching. Diffusion rates are slightly faster with o-xylene than when o-dichlorobenzene is used. 40 refs., 5 figs., 4 tabs.

  7. Line Lengths and Starch Scores.

    ERIC Educational Resources Information Center

    Moriarty, Sandra E.

    1986-01-01

    Investigates readability of different line lengths in advertising body copy, hypothesizing a normal curve with lower scores for shorter and longer lines, and scores above the mean for lines in the middle of the distribution. Finds support for lower scores for short lines and some evidence of two optimum line lengths rather than one. (SKC)

  8. Experimental investigation on plasma parameter profiles on a wafer level with reactor gap lengths in an inductively coupled plasma

    NASA Astrophysics Data System (ADS)

    Kim, Ju-Ho; Kim, Young-Cheol; Chung, Chin-Wook

    2015-07-01

    The gap length effect on plasma parameters is investigated in a planar type inductively coupled plasma at various conditions. The spatial profiles of ion densities and the electron temperatures on the wafer level are measured with a 2D probe array based on the floating harmonic method. At low pressures, the spatial profiles of the plasma parameters rarely changed by various gap lengths, which indicates that nonlocal kinetics are dominant at low pressures. However, at relatively high pressures, the spatial profiles of the plasma parameter changed dramatically. These plasma distribution profile characteristics should be considered for plasma reactor design and processing setup, and can be explained by the diffusion of charged particles and the local kinetics.

  9. Length of 11-year solar cycles

    NASA Astrophysics Data System (ADS)

    Kramynin, A. P.; Mikhalina, F. A.

    2015-12-01

    Features of the dynamics and relationship between the parameters of 11-year solar cycles, which were found from different characteristic points of an 11-year cycle, are discussed. The cycle period is determined from the time of the appearance of the first sunspot of a new cycle, which makes it possible to exclude the contributions of cycle overlapping and asymmetry effects to variations in the cycle repetition interval, to reveal the dependence of the 11-year cycle repetition period on the secular cycle, and to ascertain a longer length of an even cycle as compared to an odd one. A change in the length of a 22-year cycle found by this technique is evidence of the presence of lags near secular cycle minima. A strong correlation between the length of the physical cycle decay and the interval between neighboring cycles is revealed. It is found that the dependence of the amplitude of an 11-year cycle on the length of the ascending branch depends on the secular cycle phase.

  10. Amosphous diffusion barriers

    NASA Technical Reports Server (NTRS)

    Kolawa, E.; So, F. C. T.; Nicolet, M-A.

    1986-01-01

    Amorphous W-Zr and W-N alloys were investigated as diffusion barriers in silicon metallization schemes. Data were presented showing that amorphous W-Zr crystallizes at 900 C, which is 200 C higher than amorphous W-Ni films, and that both films react with metallic overlayers at temperatures far below the crystllization temperature. Also, W-N alloys (crystalline temperature of 600 C) were successfully incorporated as a diffusion barrier in contact structures with both Al and Ag overlayers. The thermal stability of the electrical characteristics of shallow n(+)p junctions significantly improved by incorporating W-N layers in the contact system. One important fact demonstated was the critical influence of the deposition parameters during formation of these carriers.

  11. Phase behavior, diffusion, structural characteristics, and pH of aqueous hydrophobic ionic liquid confined media: insights into microviscosity and microporsity in the [C4C4im][NTf2] + water system.

    PubMed

    Nanda, Raju; Kumar, Anil

    2015-01-29

    We present our studies on the physicochemical properties of water confined in Dibutylimidazolium bis(trifluoromethanesulfonylimide) ([C4C4im][NTf2]) reverse micelles through the NMR relaxation measurements that provide us an understanding of microviscosity and pH in the confined condition. We present experimental results on phase behavior, diffusion, structural characteristics and pH in aqueous ionic liquid-confined media. The ternary phase diagram was constructed by the cloud point measurements and the microheterogeneous regions were detected by the measurement of bulk viscosity and diffusion coefficients of K4[Fe(CN)6] inside the homogeneous microemulsion systems through the cyclic voltammetric (CV) measurements. The size of the microemulsion systems was characterized by the dynamic light scattering (DLS) method. The (1)H NMR spectra of homogeneous microemulsion systems were taken which indicates the presence of bound and free water molecules inside the microemulsion system. The NMR spin-lattice relaxation time (T1) of water molecules in its homogeneous microemulsion systems were measured and the reorientational correlation time (?c) of water molecules obtained from it indicates that the fluidity of homogeneous confined media decreases with the decrease in the composition of water. Microviscosity of the aqueous confined media was calculated from the measured T1 relaxation time values by applying the Debye-Stokes equation and correlated with the bulk viscosity of the samples. It was observed that both the microviscosity and bulk viscosity show inverse relationship. The fraction of bound and free water molecules were calculated from the measured T1 values. NMR spin-spin relaxation time (T2) of water molecules in its homogeneous microemulsion systems were measured with the varying pH of the aqueous core. A change in the T2 relaxation time of the water proton was observed proposing an exchange of proton between the H2O and -OH group of the TX-100 molecules. Finally, methyl orange (MO) was used as a UV-vis spectrophotometric molecular probe and the measured ?max values of the probe were used for the detection of micropolarity of the homogeneous aqueous confined media and was found to be increase with the increase in the size of the confined media. PMID:25555212

  12. Diffusive acceleration

    NASA Astrophysics Data System (ADS)

    Scholer, Manfred

    This paper reviews the properties of diffuse energetic ions observed at the quasi-parallel bow shock and at quasi-parallel interplanetary shocks. The first-order Fermi or diffusive acceleration mechanism can consistently explain the many detailed observational facts. In this model, it is assumed that particles are scattered approximately elastically in the solar wind frame, and gain energy by repeated scattering between the converging upstream and downstream flows or between the upstream flow and the shock. An essential feature at both the bow shock and at interplanetary shocks are self-excited low-frequency waves representing the scattering irregularities. The seed particles for the acceleration process at the bow shock are most probably solar wind ions. However, how and with what efficiency a certain fraction of the thermal solar wind population is injected into the acceleration process is at present only poorly understood. Whether the seed particles for the acceleration at interplanetary shocks are solar wind ions or more energetic ions is an open question.

  13. A Systematic Comparison of Mathematical Models for Inherent Measurement of Ciliary Length: How a Cell Can Measure Length and Volume

    PubMed Central

    Ludington, William B.; Ishikawa, Hiroaki; Serebrenik, Yevgeniy V.; Ritter, Alex; Hernandez-Lopez, Rogelio A.; Gunzenhauser, Julia; Kannegaard, Elisa; Marshall, Wallace F.

    2015-01-01

    Cells control organelle size with great precision and accuracy to maintain optimal physiology, but the mechanisms by which they do so are largely unknown. Cilia and flagella are simple organelles in which a single measurement, length, can represent size. Maintenance of flagellar length requires an active transport process known as intraflagellar transport, and previous measurements suggest that a length-dependent feedback regulates intraflagellar transport. But the question remains: how is a length-dependent signal produced to regulate intraflagellar transport appropriately? Several conceptual models have been suggested, but testing these models quantitatively requires that they be cast in mathematical form. Here, we derive a set of mathematical models that represent the main broad classes of hypothetical size-control mechanisms currently under consideration. We use these models to predict the relation between length and intraflagellar transport, and then compare the predicted relations for each model with experimental data. We find that three models—an initial bolus formation model, an ion current model, and a diffusion-based model—show particularly good agreement with available experimental data. The initial bolus and ion current models give mathematically equivalent predictions for length control, but fluorescence recovery after photobleaching experiments rule out the initial bolus model, suggesting that either the ion current model or a diffusion-based model is more likely correct. The general biophysical principles of the ion current and diffusion-based models presented here to measure cilia and flagellar length can be generalized to measure any membrane-bound organelle volume, such as the nucleus and endoplasmic reticulum. PMID:25809250

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

    NASA Technical Reports Server (NTRS)

    Kemp, W. B., Jr.

    1986-01-01

    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.

  15. Study for noninvasive determination of optical properties of bio-tissue using spatially resolved diffuse reflectance

    NASA Astrophysics Data System (ADS)

    Peng, Dong-qing; Li, Hui

    2012-12-01

    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 Δr, 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.

  16. Feg-EPMA and Nanosims Profiles of Zoned Crystals for Diffusion Chronometry

    NASA Astrophysics Data System (ADS)

    Saunders, K.; Buse, B.; Kilburn, M.; Kearns, S.; Blundy, J. D.

    2014-12-01

    Diffusion chronometry is an alternative method that can be used to assess timescales of magmatic events. It relies on the chemical relaxation of chemical zoning within magmatic crystals. By studying a range of elements within a single crystal we can probe a range of magmatic processes and interrogate timescales of processes from days to millennia. Diffusion modifies the elemental concentrations of adjacent crystal zones. The timescales that can be investigated are limited not only by the diffusivity of an element and the available diffusion coefficients but also the resolution of the measured chemical profile and hence the analytical technique used to acquire these profiles. To obtained reliable diffusion timescales the analytical length scale must be shorter than the characteristic diffusion length. In addition sufficient analytical points must be present on the profile to ensure that the profile is 'real' and not a convolution artefact. Thus in some cases, sub-micron spatial resolution is required. Two such possible techniques that can achieve nanoscale resolution are field emission gun electron probe micro analyser (FEG-EPMA) and NanoSIMS. Plagioclase and pyroxene crystals were analysed by FEG-EPMA and NanoSIMS to investigate the achievable spatial resolution that could be attained. For quantitative analyses, analytical protocols for FEG-EPMA for plagioclase and pyroxene have been developed that can achieve spot analyses of down to 300 nm diameters with 300 nm spacing for major and trace elements. NanoSIMS can achieve a 200 nm spot diameter, but currently the chemical profiles are only qualitative. This increase in spatial resolution of analytical techniques has demonstrated that compositional boundaries within zoned crystals are relatively sharp (< 2 microns). Thus assuming step-profiles as an initial condition in simple 1D diffusion models is appropriate in many cases.

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

    USGS Publications Warehouse

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

    1964-01-01

    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.

  18. Ambipolar diffusion in complex plasma.

    PubMed

    Losseva, T V; Popel, S I; Yu, M Y; Ma, J X

    2007-04-01

    A self-consistent model of the ambipolar diffusion of electrons and ions in complex (dusty) plasmas accounting for the local electric fields, the dust grain charging process, and the interaction of the plasma particles with the dust grains and neutrals is presented. The dependence of the diffusion coefficient on the interaction of the electrons and ions with the dust grains as well as with the neutrals are investigated. It is shown that increase of the dust density leads to a reduction of the diffusion scale length, and this effect is enhanced at higher electron densities. The dependence of the diffusion scale length on the neutral gas pressure is found to be given by a power law, where the absolute value of the power exponent decreases with increase of the dust density. The electric field gradient and its effects are shown to be significant and should thus be taken into account in studies of complex plasmas with not very small dust densities. The possibility of observing localized coherent dissipative nonlinear dust ion-acoustic structures in an asymmetrically discharged double plasma is discussed. PMID:17501000

  19. Ambipolar diffusion in complex plasma

    SciTech Connect

    Losseva, T. V.; Popel, S. I.; Yu, M. Y.; Ma, J. X.

    2007-04-15

    A self-consistent model of the ambipolar diffusion of electrons and ions in complex (dusty) plasmas accounting for the local electric fields, the dust grain charging process, and the interaction of the plasma particles with the dust grains and neutrals is presented. The dependence of the diffusion coefficient on the interaction of the electrons and ions with the dust grains as well as with the neutrals are investigated. It is shown that increase of the dust density leads to a reduction of the diffusion scale length, and this effect is enhanced at higher electron densities. The dependence of the diffusion scale length on the neutral gas pressure is found to be given by a power law, where the absolute value of the power exponent decreases with increase of the dust density. The electric field gradient and its effects are shown to be significant and should thus be taken into account in studies of complex plasmas with not very small dust densities. The possibility of observing localized coherent dissipative nonlinear dust ion-acoustic structures in an asymmetrically discharged double plasma is discussed.

  20. The existence of a critical length scale in regularised friction

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

    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.

  1. Segmental conformational disorder and dynamics in the intrinsically disordered protein ?-synuclein and its chain length dependence.

    PubMed

    Grupi, Asaf; Haas, Elisha

    2011-02-01

    Conformational ensembles of fully disordered natural polypeptides represent the starting point of protein refolding initiated by transfer to folding conditions. Thus, understanding the transient properties and dimensions of such peptides under folding conditions is a necessary step in the understanding of their subsequent folding behavior. Such ensembles can also undergo alternative folding and form amyloid structures, which are involved in many neurological degenerative diseases. Here, we performed a structural study of this initial state using time-resolved fluorescence resonance energy transfer analysis of a series of eight partially overlapping double-labeled chain segments of the N-terminal and NAC domains of the ?-synuclein molecule. The distributions of end-to-end distance and segmental intramolecular diffusion coefficients were simultaneously determined for eight labeled chain segments. We used the coefficient of variation, C(v), as a measure of the conformational heterogeneity (i.e., structural disorder). With the exception of two segments, the C(v)s were characteristic of a fully disordered state of the chain. Subtle deviations from this behavior at the segment labeled in the NAC domain and the segment at the N termini reflected subtle conformational bias that might be related to the initiation of transition to amyloid aggregates. The chain length dependence of the mean segmental end-to-end distance followed a power law as predicted by Flory, but the dependence was steeper than previously predicted, probably due to the contribution of the excluded volume effect, which is more dominant for shorter-chain segments. The observed intramolecular diffusion coefficients (<10 to ?25?(2)/ns) are only an order of magnitude lower than the common diffusion coefficients of low molecular weight probes. This diffusion coefficient increased with chain length, probably due to the cumulative contributions of minor bond rotations along the chain. These results gave us a reference both for characteristics of a natural unfolded polypeptide at the moment of initiation of folding and for detection of possible initiation sites of the amyloid transition. PMID:21108951

  2. Tortuosity measurement and the effects of finite pulse widths on xenon gas diffusion NMR studies of porous media

    NASA Technical Reports Server (NTRS)

    Mair, R. W.; Hurlimann, M. D.; Sen, P. N.; Schwartz, L. M.; Patz, S.; Walsworth, R. L.

    2001-01-01

    We have extended the utility of NMR as a technique to probe porous media structure over length scales of approximately 100-2000 microm by using the spin 1/2 noble gas 129Xe imbibed into the system's pore space. Such length scales are much greater than can be probed with NMR diffusion studies of water-saturated porous media. We utilized Pulsed Gradient Spin Echo NMR measurements of the time-dependent diffusion coefficient, D(t), of the xenon gas filling the pore space to study further the measurements of both the pore surface-area-to-volume ratio, S/V(p), and the tortuosity (pore connectivity) of the medium. In uniform-size glass bead packs, we observed D(t) decreasing with increasing t, reaching an observed asymptote of approximately 0.62-0.65D(0), that could be measured over diffusion distances extending over multiple bead diameters. Measurements of D(t)/D(0) at differing gas pressures showed this tortuosity limit was not affected by changing the characteristic diffusion length of the spins during the diffusion encoding gradient pulse. This was not the case at the short time limit, where D(t)/D(0) was noticeably affected by the gas pressure in the sample. Increasing the gas pressure, and hence reducing D(0) and the diffusion during the gradient pulse served to reduce the previously observed deviation of D(t)/D(0) from the S/V(p) relation. The Pade approximation is used to interpolate between the long and short time limits in D(t). While the short time D(t) points lay above the interpolation line in the case of small beads, due to diffusion during the gradient pulse on the order of the pore size, it was also noted that the experimental D(t) data fell below the Pade line in the case of large beads, most likely due to finite size effects.

  3. Hand-ginned cotton length distributions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Instrumentation such as the Advanced Fiber Information System (AFIS) analyzes cotton (Gossypium hirsutum L.) fiber length distributions because variations in fiber length distribution impacts spinning performance. AFIS provides mean length, upper quartile length, fineness, and maturity for fibers ...

  4. Laminar smoke points of nonbuoyant jet diffusion flames

    SciTech Connect

    Sunderland, P.B; Mortazavi, S.; Faeth, G.M. . Dept. of Aerospace Engineering); Urban, D.L. . Microgravity Science Section)

    1994-01-01

    The laminar smoke point properties of jet diffusion flames -- the luminous flame length, the residence time, and the fuel flow rate, at the onset of soot emission from the flames -- have proven to be useful global measures of the soot properties of nonpremixed flames. These measures provide a means to rate several aspects of sooting properties: the relative tendency of various fuels to emit soot from flames the relative effects of fuel structure, flame temperature, and pressure on the soot properties of flames and the relative levels of continuum radiation from soot in flames. However, recent studies suggest potential for fundamental differences between the laminar smoke point properties of buoyant and non-buoyant flames. Thus, the overall objective of present investigation was to measure the laminar smoke point properties of nonbuoyant flames, due to their relevance to many industrial processes where effects of buoyancy are small. Prior to this work, no experiments have been reported to assess these potential effects of buoyancy on laminar smoke point properties. Thus, the present objective was to measure the laminar smoke point flame lengths and residence times of nonbuoyant flames. The scope of the study was limited to round ethylene and propane jet diffusion flames burning in slightly vitiated air at pressures of 0.5--2.0 atm. A low-gravity test environment was used to obtain nonbuoyant flames at the small flow velocities characteristic of laminar smoke point conditions.

  5. Persistence Length of Stable Microtubules

    NASA Astrophysics Data System (ADS)

    Hawkins, Taviare; Mirigian, Matthew; Yasar, M. Selcuk; Ross, Jennifer

    2011-03-01

    Microtubules are a vital component of the cytoskeleton. As the most rigid of the cytoskeleton filaments, they give shape and support to the cell. They are also essential for intracellular traffic by providing the roadways onto which organelles are transported, and they are required to reorganize during cellular division. To perform its function in the cell, the microtubule must be rigid yet dynamic. We are interested in how the mechanical properties of stable microtubules change over time. Some ``stable'' microtubules of the cell are recycled after days, such as in the axons of neurons or the cilia and flagella. We measured the persistence length of freely fluctuating taxol-stabilized microtubules over the span of a week and analyzed them via Fourier decomposition. As measured on a daily basis, the persistence length is independent of the contour length. Although measured over the span of the week, the accuracy of the measurement and the persistence length varies. We also studied how fluorescently-labeling the microtubule affects the persistence length and observed that a higher labeling ratio corresponded to greater flexibility. National Science Foundation Grant No: 0928540 to JLR.

  6. Diffusive Shock Acceleration

    NASA Astrophysics Data System (ADS)

    Baring, Matthew

    2003-04-01

    The process of diffusive acceleration of charged particles in shocked plasmas is widely invoked in astrophysics to account for the ubiquitous presence of signatures of non-thermal relativistic electrons and ions in the universe. This statistical energization mechanism, manifested in turbulent media, was first posited by Enrico Fermi in 1949 to explain the observed cosmic ray population, which exhibits an almost power-law distribution in rigidity. The absence of a momentum scale is a key characteristic of diffusive shock acceleration, and astrophysical systems generally only impose scales at the injection (low energy) and loss (high energy) ends of the particle spectrum. The existence of structure in the cosmic ray spectrum (the "knee") at around 3000 TeV has promoted contentions that there are at least two origins for cosmic rays, a galactic one supplying those up to the knee, and perhaps an extragalactic one that can explain even the ultra-high energy cosmic rays (UHECRs) seen at 1-300 EeV. Accounting for the UHECRs with familiar astrophysical sites of acceleration has historically proven difficult due to the need to assume high magnetic fields in order to reduce the shortest diffusive acceleration timescale, the ion gyroperiod, to meaningful values. Yet active galaxies and gamma-ray bursts remain strong and interesting candidate sources for UHECRs, turning the theoretical focus to relativistic shocks. This review summarizes properties of diffusive shock acceleration that are salient to the issue of UHECR generation. These include spectral indices, anisotropies, acceleration efficencies and timescales, as functions of the shock speed and mean field orientation, and also the degree of field turbulence. Astrophysical sites for UHECR production are also critiqued.

  7. When Does Length Cause the Word Length Effect?

    ERIC Educational Resources Information Center

    Jalbert, Annie; Neath, Ian; Bireta, Tamra J.; Surprenant, Aimee M.

    2011-01-01

    The word length effect, the finding that lists of short words are better recalled than lists of long words, has been termed one of the benchmark findings that any theory of immediate memory must account for. Indeed, the effect led directly to the development of working memory and the phonological loop, and it is viewed as the best remaining

  8. Point defect diffusion in ?-Zr

    NASA Astrophysics Data System (ADS)

    Hood, G. M.

    1988-10-01

    The present review of defects in ?-Zr is concerned with atomic and vacancy diffusion and with solute effects on radiation damage. The primary aim, in addressing atomic diffusion, is to try to expose the characteristics and systematics of intrinsic diffusion. This is done, both in a general context and in terms of problems and features more specifically associated with ?-Zr. Among the latter are the anisotropic crystal structure, the limited temperature interval of ?-phase stability, imposed by the ?-? (hcp-bcc) transformation, and the tendency for Zr to have high residual impurity levels. It is emphasized that reliable, intrinsic, diffusion data can only be obtained through the use of high-purity single-crystal material. Vacancy diffusion is considered in terms of experimental data on irradiation damage. Solute effects on irradiation damage are discussed on the basis of the interactions of solutes with vacancies and self-interstitial atoms (SIA). A consideration of atomic diffusion data indicates that self-diffusion in ?-Zr is intrinsically normal and that self-diffusion data associated with abnormal behaviour are probably expressive of diffusion dominated by extrinsic mechanisms: both structural and impurity-related defects appear to be important here. Intrinsic diffusion characteristics (diffusion coefficients ( D) and associated activation energies and pre-exponential factors) tend to scale in a remarkably simple manner with atomic size, with diffusion taking place by both interstitial and substitutional mechanisms. Small atoms diffuse mainly by interstitial paths, with associated D values which may be many orders of magnitude higher than those associated with substitutional solutes. Measurements of diffusion anisotropy show that diffusion is generally faster parallel to the c- axis than perpendicular to it: this is well established for fast-diffusing, interstitial-like solutes but not well known for substitutional solutes. The vacancy migration characteristics of ?-Zr present an ongoing enigma. Experimental data from electron microscopic and positron annihilation spectroscopic (PAS) measurements of irradiation damage recovery are readily interpreted in terms of abnormally facile vacancy migration, however there does not appear to be any evident theoretical support for such a phenomenon as an intrinsic process. This raises the possibility of an extrinsic mechanism. In addition, there seems to be sufficient ambiguity associated with the data to allow their interpretation in terms of a model wherein vacancy migration is inherently normal. Solute effects on irradiation damage and recovery are discussed in a general context with a consideration of the attraction of SIAs for small solute atoms and of solute-vacancy interactions in terms of electrostatic and bond-strength approaches. Specific attention is given to the role of Sn, since it is shown, from PAS measurements, that radiation damage and recovery in Zr can be profoundly altered by alloying additions of this element. Some understanding of these results can be found in terms of defect interactions with clustered configurations of solute atoms. The results suggest the basis of a general approach towards the development of irradiation-damage resistant alloys.

  9. Improvement of Spatial Uniformity of Nanosecond-Pulse Diffuse Discharges in a Multi-Needle-to-Plane Gap

    NASA Astrophysics Data System (ADS)

    Gu, Jianwei; Zhang, Cheng; Wang, Ruixue; Yan, Ping; Shao, Tao

    2016-03-01

    Large-scale non-thermal plasmas generated by nanosecond-pulse discharges have been used in various applications, including surface treatment, biomedical treatment, flow control etc. In this paper, atmospheric-pressure diffuse discharge was produced by a homemade nanosecond-pulse generator with a full width at half maximum of 100 ns and a rise time of 70 ns. In order to increase the discharge area, multi-needle electrodes with a 3×3 array were designed. The electrical characteristics of the diffuse discharge array and optical images were investigated by the voltage-current waveforms and discharge images. The experimental results showed that the intensity of diffuse discharges in the center was significantly weaker than those at the margins, resulting in an inhomogeneous spatial uniformity in the diffuse discharge array. Simulation of the electric field showed that the inhomogeneous spatial uniformity was caused by the non-uniform distribution of the electric field in the diffuse discharge array. Moreover, the spatial uniformity of the diffuse discharge array could be improved by increasing the length of the needle in the centre of the array. Finally, the experimental results confirmed the simulation results, and the spatial uniformity of the nanosecond-pulse diffuse discharge array was significantly improved. supported by National Natural Science Foundation of China (Nos. 51222701, 51477164) and the National Basic Research Program of China (No. 2014CB239505-3)

  10. Continuously variable focal length lens

    DOEpatents

    Adams, Bernhard W; Chollet, Matthieu C

    2013-12-17

    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.

  11. Graduated compression stockings: knee length or thigh length.

    PubMed

    Benk, T; Cooke, E A; McNally, M A; Mollan, R A

    2001-02-01

    The mechanisms by which graduated compression stockings prevent deep venous thrombosis are not completely understood. In the current study the physiologic effect of low-pressure graduated compression stockings on the venous blood flow in the lower limb and the practical aspects of their use were assessed. Patients having elective orthopaedic surgery at a university orthopaedic department were randomized into five groups to wear two different types of graduated compression stockings in thigh and knee lengths. Patients in the fifth control group did not wear graduated compression stockings. Venous occlusion strain gauge plethysmography was used to measure venous flow. After 20-minutes bed rest there was a highly significant increase in venous capacitance and venous outflow in patients in all of the four groups wearing stockings. There was no difference in the mean of the percentage change of venous capacitance in patients in the four groups wearing stockings. The knee length Brevet stockings were less efficient in increasing the venous outflow. There was no significant change in the venous capacitance and venous outflow in patients in the control group. Visual assessment of the fit and use of stockings was done, and patients' subjective opinion of comfort was sought. The knee length graduated compression stockings wrinkled significantly less, and significantly fewer patients reported discomfort with them. All stockings were reported to be difficult to use. Thigh and knee length stockings have a significant effect on decreasing venous stasis of the lower limb. Knee length graduated compression stockings are similarly efficient in decreasing venous stasis, but they are more comfortable to wear, and they wrinkle less. PMID:11210954

  12. Continuous lengths of oxide superconductors

    DOEpatents

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

    2000-01-01

    A layered oxide superconductor prepared by depositing a superconductor precursor powder on a continuous length of a first substrate ribbon. A continuous length of a second substrate ribbon is overlaid on the first substrate ribbon. Sufficient pressure is applied to form a bound layered superconductor precursor powder between the first substrate ribbon and the second substrate ribbon. The layered superconductor precursor is then heat treated to establish the oxide superconducting phase. The layered oxide superconductor has a smooth interface between the substrate and the oxide superconductor.

  13. Coherence length of neutron superfluids

    SciTech Connect

    De Blasio, F.V.; Hjorth-Jensen, M.; Lazzari, G.; Baldo, M.; Schulze, H.

    1997-10-01

    The coherence length of superfluid neutron matter is calculated from the microscopic BCS wave function of a Cooper pair in momentum space making use of recent nucleon-nucleon potential models and including polarization (RPA) effects. We find as our main result that the coherence length is proportional to the Fermi momentum to pairing gap ratio, in good agreement with simple estimates used in the literature, with a nearly interaction independent constant of proportionality. Our calculations can be applied to the problem of inhomogeneous superfluidity of hadronic matter in the crust of a neutron star. {copyright} {ital 1997} {ital The American Physical Society}

  14. Overview of bunch length measurements.

    SciTech Connect

    Lumpkin, A. H.

    1999-02-19

    An overview of particle and photon beam bunch length measurements is presented in the context of free-electron laser (FEL) challenges. Particle-beam peak current is a critical factor in obtaining adequate FEL gain for both oscillators and self-amplified spontaneous emission (SASE) devices. Since measurement of charge is a standard measurement, the bunch length becomes the key issue for ultrashort bunches. Both time-domain and frequency-domain techniques are presented in the context of using electromagnetic radiation over eight orders of magnitude in wavelength. In addition, the measurement of microbunching in a micropulse is addressed.

  15. Diffusion of bed load particles subject to different flow conditions

    NASA Astrophysics Data System (ADS)

    Cecchetto, Martina; Cotterle, Luca; Tregnaghi, Matteo; Tait, Simon; Marion, Andrea

    2015-04-01

    An in-depth understanding of sediment motion in rivers has acquired increasing importance lately in order to plan restoration activities that provide ecological benefit. River beds constitute the interfacial environment where several species live and mass exchange of sediments/nutrients/pollutants can take place. Moving grains interacting with the bed deposit and can locally change the bed surface topography they can also act as carriers for contaminants associated with the grains. Study the motion of grains on the bed, in particular the extent and variability of their travel distance with regards to the flow conditions can provide information on the transport of grain associated contaminants. The results of a series of experimental tests, in which increasing levels of boundary shear stress were applied over a bed deposit of natural river gravel, are reported. Image databases consisted of a series of bed images acquired at a frequency of 45 Hz were collected. Analysis of the images has provided time and position data to plot the trajectories of more than 200 moving grains for each test. This data enables the derivation of the statistics of the un-truncated probability distribution of the detected particles' step length, which is consider as the distance moved by a particle from the moment it is entrained to the instant it stops on the bed. In recent studies the movement of bed load material has been indicated as diffusive, but little is known about the spatial and temporal scales of this diffusion. The analysis of the longitudinal and transverse trajectories for the tracked particles has here revealed three regimes of diffusion: a ballistic diffusion which takes place at the very beginning of particles motion, an anomalous intermediate regime, and a normal subdiffusion which occurs for larger times. Characteristic time scales separate these three diffusive regimes. Results show that in experiments with higher shear stresses the time scale separating the ballistic from the intermediate regime decreases, whereas an opposite trend is observed for the boundary between the intermediate and the final subdiffusion regime. This suggests that flow intensity influences the particle traveling time depending on the diffusive regime. An equivalent pattern emerges for the transversal diffusion, even if it is characterized by much smaller time scales. The simultaneous measurement of the 3D near bed flow field via a PIV system has allowed the grain velocity to be linked to the spatial averaged fluid velocity. Understanding the type of advective and diffusive process along with its mechanics can potentially allow for derivation of bed-load transport rate equations, able to replicate this behaviour, without the need of experimental measurements.

  16. Turbulence reduces magnetic diffusivity in DTS liquid sodium experiment

    NASA Astrophysics Data System (ADS)

    Cabanes, S.; Schaeffer, N.; Nataf, H. C.

    2014-12-01

    Earth, Sun and many other astrophysical bodies produce their own magnetic field by dynamo action, where induction of magnetic field by fluid motion overcomes the Joule dissipation when the magnetic Reynolds number Rm = UL/η is large enough (U and L are characteristic velocity and length-scale and η the magnetic diffusivity). Large scale motion of a conducting medium shearing pre-existing magnetic field lines is a well known process to produce large scale magnetic field by omega-effect. However, such a process cannot sustain a self-excited dynamo and small-scale turbulent motions are usually invoked as the appropriate mechanism to dynamo action. The contribution of turbulent fluctuations to the induction of mean magnetic field is investigated in our liquid sodium spherical Couette experiment, with an imposed magnetic field. Many measurements are used through an inversion technique to obtain a radial profile of alpha and beta effects together with the mean flow at magnetic Reynolds number Rm = 100. It appears that the small scale turbulent fluctuations can be modeled as a strong contribution to the magnetic diffusivity which is negative in the interior region and positive close to the outer shell.Direct numerical simulations of our experiment support these results. The lowering of the effective magnetic diffusivity by small scale fluctuations implies that turbulence can actually help to achieve self-generation of large scale magnetic fields.

  17. Resolving and measuring diffusion in complex interfaces: Exploring new capabilities

    SciTech Connect

    Alam, Todd M.

    2015-09-01

    This exploratory LDRD targeted the use of a new high resolution spectroscopic diffusion capabilities developed at Sandia to resolve transport processes at interfaces in heterogeneous polymer materials. In particular, the combination of high resolution magic angle spinning (HRMAS) nuclear magnetic resonance (NMR) spectroscopy with pulsed field gradient (PFG) diffusion experiments were used to directly explore interface diffusion within heterogeneous polymer composites, including measuring diffusion for individual chemical species in multi-component mixtures. Several different types of heterogeneous polymer systems were studied using these HRMAS NMR diffusion capabilities to probe the resolution limitations, determine the spatial length scales involved, and explore the general applicability to specific heterogeneous systems. The investigations pursued included a) the direct measurement of the diffusion for poly(dimethyl siloxane) polymer (PDMS) on nano-porous materials, b) measurement of penetrant diffusion in additive manufactures (3D printed) processed PDMS composites, and c) the measurement of diffusion in swollen polymers/penetrant mixtures within nano-confined aluminum oxide membranes. The NMR diffusion results obtained were encouraging and allowed for an improved understanding of diffusion and transport processes at the molecular level, while at the same time demonstrating that the spatial heterogeneity that can be resolved using HRMAS NMR PFG diffusion experiment must be larger than ~μm length scales, expect for polymer transport within nanoporous carbons where additional chemical resolution improves the resolvable heterogeneous length scale to hundreds of nm.

  18. A model for the effective diffusion of gas or the vapor phase in a fractured media unsaturated zone driven by periodic atmospheric pressure fluctuations

    SciTech Connect

    Vold, E.L.

    1997-03-01

    There is evidence for migration of tritiated water vapor through the tuff in the unsaturated zone from the buried disposal shafts located on a narrow mesa top at Area G, Los Alamos, NM. Field data are consistent with an effective in-situ vapor phase diffusion coefficient of 1.5x10{sup {minus}3} m{sup s}/s, or a factor of 60 greater than the binary diffusion coefficient for water vapor in air. A model is derived to explain this observation of anomolously large diffusion, which relates an effective vapor or gas phase diffusion coefficient in the fractured porous media to the subsurface propagation of atmospheric pressure fluctuations (barometric pumping). The near surface (unattenuated) diffusion coefficient is independent of mode period under the simplified assumptions of a complete {open_quote}mixing mechanism{close_quote} for the effective diffusion process. The unattenuated effective diffusion driven by this barometric pumping is proportional to an average media permeability times the sum of the square of pressure mode amplitudes, while the attenuation length is proportional to the squarer root of the product of permeability times mode period. There is evidence that the permeability needed to evaluate the pressure attenuation length is the in-situ value, approximately that of the matrix. The diffusion which results using Area G parameter values is negligible in the matrix but becomes large at the effective permeability of the fractured tuff matrix. The effective diffusion coefficient predicted by this model, due to pressure fluctuations and the observed fracture characteristics, is in good agreement with the observed in-situ diffusion coefficient for tritium field measurements. It is concluded that barometric pumping in combination with the enhanced permeability of the fractured media is a likely candidate to account for the observed in-field migration of vapor in the near surface unsaturated zone at Area G.

  19. Incubation length of dabbling ducks

    USGS Publications Warehouse

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

    2005-01-01

    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.

  20. Persistent Criminality and Career Length

    ERIC Educational Resources Information Center

    Haapanen, Rudy; Britton, Lee; Croisdale, Tim

    2007-01-01

    This study is an examination of persistent offending and its implications for the understanding and investigation of desistance and career length. Persistence, especially as it is operationalized using official measures, is characterized as fundamentally a measure of resistance to formal social control: continued crime in the face of increasingly

  1. Persistent Criminality and Career Length

    ERIC Educational Resources Information Center

    Haapanen, Rudy; Britton, Lee; Croisdale, Tim

    2007-01-01

    This study is an examination of persistent offending and its implications for the understanding and investigation of desistance and career length. Persistence, especially as it is operationalized using official measures, is characterized as fundamentally a measure of resistance to formal social control: continued crime in the face of increasingly…

  2. Measurement of important parameters determining aqueous phase diffusion rates through crystalline rock matrices

    NASA Astrophysics Data System (ADS)

    Bradbury, M. H.; Green, A.

    1985-11-01

    One of the options being considered for the disposal of radioactive waste is deep burial in crystalline rocks such as granite. Recent theoretical studies on the migration of radionuclides in the groundwater circulating through the fissure networks, which are likely to be present to some extent in crystalline rocks, have indicated the importance of diffusion into the rock matrix as a retardation mechanism. Matrix diffusion will retard all radionuclides, but is of particular relevance to those exhibiting little or no sorption and which would otherwise migrate at or near the groundwater velocity. Diffusion measurements have been made on granites obtained from four different regions of the United Kingdom. In most of the experiments the weakly sorbed iodide ion was used as tracer, although the diffusion of Tc-99 (as the pertechnetate ion) has also been measured. Details of the experimental technique and method of analysis are set out and results given for the most important diffusion parameters, namely: Di, the intrinsic diffusion coefficient, ?, the rock capacity factor, and ?, a pore geometry parameter which is a characteristic of the rock type in question. In the pre-steady state region, a discrepancy between experiment and theory was observed. The cause of this has been interpreted as being due to the presence of two types of porosity; through-transport porosity, which carries the diffusion flux across the sample, and "dead-end" porosity, which comprises of cross-linking pores and pores closed at one end. A series of equations were set up and solved using this concept. From the analysis of experimental data in the pre-steady state region, estimates of the through-transport porosity, ?+, and mean length of "dead-end" pores, l?, were calculated. In addition, some initial results are given for diffusion through weathered fracture surfaces. Significant increases in both Di and ? were measured. The implications of these results are discussed.

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

    SciTech Connect

    Momeni, Mahdi

    2013-08-15

    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.

  4. Efficient document rendering with enhanced run length encoding

    NASA Astrophysics Data System (ADS)

    Feng, Guotong; Bouman, Charles A.

    2006-01-01

    Document imaging and transmission systems (typically MFPs) require both effective and efficient image rendering methods that support standard data formats for a variety of document types, and allow for real time implementation. Since most conventional raster formats (e. g. TIFF, PDF, JPEG) are designed for use with either black and white text, or continuous-tone images, more specialized rendering methods are often required for representing mixed content documents. The baseline TIFF format supports a few binary compression options: PackBits, CCITT G3 and G4. Conventionally, halftoning algorithms, such as error diffusion, can be used to create a binary representation of a document image in the TIFF format. However, PackBits, CCITT G3 and G4 compression generally do not produce desired compression on halftone images. In this paper, we propose an efficient error diffusion algorithm optimized for PackBits compression. This method, which we refer to as POED (PackBits optimized error diffusion), is a form of threshold modulation error diffusion which takes advantage of the byte-oriented run length structure of PackBits compression by encouraging repetition of bytes in the resulting binary image. To maintain the sharpness of text, a binary segmentation algorithm is provided to switch off the adaptive error diffusion procedure and switch on the Floyd Steinberg error diffusion procedure in text regions. The POED method with PackBits compression yields higher compression ratios than the conventional error diffusion method, while maintaining desirable visual quality with low computational and memory requirements. We show experimental results to compare our method with the Floyd Steinberg error diffusion method.

  5. Laminar Diffusion Flame Studies (Ground- and Space-Based Studies)

    NASA Technical Reports Server (NTRS)

    Dai, Z.; El-Leathy, A. M.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

    2000-01-01

    Laminar diffusion flames are of interest because they provide model flame systems that are far more tractable for analysis and experiments than more practical turbulent diffusion flames. Certainly, understanding flame processes within laminar diffusion flames must precede understanding these processes in more complex turbulent diffusion flames. In addition, many properties of laminar diffusion flames are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Laminar jet diffusion flame shapes (luminous flame boundaries) have been of particular interest since the classical study of Burke and Schumann because they are a simple nonintrusive measurement that is convenient for evaluating flame structure predictions. Thus, consideration of laminar flame shapes is undertaken in the following, emphasizing conditions where effects of gravity are small, due to the importance of such conditions to practical applications. Another class of interesting properties of laminar diffusion flames are their laminar soot and smoke point properties (i.e., the flame length, fuel flow rate, characteristic residence time, etc., at the onset of soot appearance in the flame (the soot point) and the onset of soot emissions from the flame (the smoke point)). These are useful observable soot properties of nonpremixed flames because they provide a convenient means to rate several aspects of flame sooting properties: the relative propensity of various fuels to produce soot in flames; the relative effects of fuel structure, fuel dilution, flame temperature and ambient pressure on the soot appearance and emission properties of flames; the relative levels of continuum radiation from soot in flames; and effects of the intrusion of gravity (or buoyant motion) on emissions of soot from flames. An important motivation to define conditions for soot emissions is that observations of laminar jet diffusion flames in critical environments, e.g., space shuttle and space station facilities, cannot involve soot emitting flames in order to ensure that test chamber windows used for experimental observations are not blocked by soot deposits, thereby compromising unusually valuable experimental results. Another important motivation to define conditions where soot is present in diffusion flames is that flame chemistry, transport and radiation properties are vastly simplified when soot is absent, making such flames far more tractable for detailed numerical simulations than corresponding soot-containing flames. Motivated by these observations, the objectives of this phase of the investigation were as follows: (1) Observe flame-sheet shapes (the location of the reaction zone near phi=1) of nonluminous (soot free) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of flame-sheet shapes for these conditions; (2) Observe luminous flame boundaries of luminous (soot-containing) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of luminous flame boundaries for these conditions. In order to fix ideas here, maximum luminous flame boundaries at the laminar smoke point conditions were sought, i.e., luminous flame boundaries at the laminar smoke point; (3) Observe effects of coflow on laminar soot- and smoke-point conditions because coflow has been proposed as a means to control soot emissions and minimize the presence of soot in diffusion flames.

  6. Parallel flow diffusion battery

    DOEpatents

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

    1984-01-01

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

  7. Parallel flow diffusion battery

    DOEpatents

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

    1984-08-07

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

  8. FRACTIONAL PEARSON DIFFUSIONS

    PubMed Central

    Leonenko, Nikolai N.; Meerschaert, Mark M.

    2013-01-01

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

  9. Critical waves and the length problem of biology.

    PubMed

    Laughlin, Robert B

    2015-08-18

    It is pointed out that the mystery of how biological systems measure their lengths vanishes away if one premises that they have discovered a way to generate linear waves analogous to compressional sound. These can be used to detect length at either large or small scales using echo timing and fringe counting. It is shown that suitable linear chemical potential waves can, in fact, be manufactured by tuning to criticality conventional reaction-diffusion with a small number substance. Min oscillations in Escherichia coli are cited as precedent resonant length measurement using chemical potential waves analogous to laser detection. Mitotic structures in eukaryotes are identified as candidates for such an effect at higher frequency. The engineering principle is shown to be very general and functionally the same as that used by hearing organs. PMID:26240329

  10. Critical waves and the length problem of biology

    PubMed Central

    Laughlin, Robert B.

    2015-01-01

    It is pointed out that the mystery of how biological systems measure their lengths vanishes away if one premises that they have discovered a way to generate linear waves analogous to compressional sound. These can be used to detect length at either large or small scales using echo timing and fringe counting. It is shown that suitable linear chemical potential waves can, in fact, be manufactured by tuning to criticality conventional reactiondiffusion with a small number substance. Min oscillations in Escherichia coli are cited as precedent resonant length measurement using chemical potential waves analogous to laser detection. Mitotic structures in eukaryotes are identified as candidates for such an effect at higher frequency. The engineering principle is shown to be very general and functionally the same as that used by hearing organs. PMID:26240329

  11. Diffusive Propagation of Ultra-High-Energy Cosmic Rays and the Propagation Theorem

    NASA Astrophysics Data System (ADS)

    Aloisio, R.; Berezinsky, V.

    2004-09-01

    We present a detailed analytical study of the propagation of ultra-high-energy (UHE) particles in extragalactic magnetic fields. The crucial parameter that affects the diffuse spectrum is the separation between sources. In the case of a uniform distribution of sources with a separation between them much smaller than all characteristic propagation lengths, the diffuse spectrum of UHE particles has a universal form, independent of the mode of propagation. This statement has the status of theorem. The proof is obtained using the particle number conservation during propagation and also using the kinetic equation for the propagation of UHE particles. This theorem can be also proved with the help of the diffusion equation. In particular, it is shown numerically how the diffuse fluxes converge to this universal spectrum, when the separation between sources diminishes. We study also the analytic solution of the diffusion equation in weak and strong magnetic fields with energy losses taken into account. In the case of strong magnetic fields and for a separation between sources large enough, the GZK cutoff can practically disappear, as it has been found early in numerical simulations. In practice, however, the source luminosities required are too large for this possibility.

  12. Design Optimization of Mixed-flow Pump Impellers and Diffusers in a Fixed Meridional Shape

    NASA Astrophysics Data System (ADS)

    Kim, Sung; Choi, Young-Seok; Lee, Kyoung-Yong

    2010-06-01

    In this paper, design optimization for mixed-flow pump impellers and diffusers has been studied by using a commercial CFD code and DOE(design of experiments). We also discussed how to improve the performance of the mixed-flow pump by designing the impeller and diffuser in the mixed-flow pump. Geometric design variables were defined by the vane plane development which indicates the blade-angle distributions and length of the impeller and the diffusers. The vane plane development was controlled by using blade-angle in a fixed meridional shape. First the design optimization of the defined impeller geometric variables was done, and then the flow characteristics were analyzed in the point of incidence angle at the diffuser leading edge for the optimized impeller. Then design optimizations of the defined diffuser shape variables were performed. The importance of the geometric design variables was analyzed by using 2k factorial designs, and the design optimization of the geometric variables were determined using the response surface method. The objective functions are defined as the total head and the total efficiency at the design flow-rate. From the comparison of CFD results between optimized pump and base design model, the reason for the performance improvement was discussed.

  13. Topological spin transport by Brownian diffusion of domain walls

    NASA Astrophysics Data System (ADS)

    Kim, Se Kwon; Takei, So; Tserkovnyak, Yaroslav

    2015-12-01

    We propose thermally populated domain walls (DWs) in an easy-plane ferromagnetic insulator as robust spin carriers between two metals. The chirality of a DW, which serves as a topological charge, couples to the metal spin accumulation via spin-transfer torque and results in the chirality-dependent thermal nucleation rates of DWs at the interface. After overpopulated DWs of a particular (net) chirality diffuse and leave the ferromagnet at the other interface, they reemit the spin current by spin pumping. The conservation of the topological charge supports an algebraic decay of spin transport as the length of the ferromagnet increases; this is analogous to the decaying behavior of superfluid spin transport but contrasts with the exponential decay of magnon spin transport. We envision that similar spin transport with algebraic decay may be implemented in materials with exotic spin phases by exploiting topological characteristics and the associated conserved quantities of their excitations.

  14. Variable focal length deformable mirror

    DOEpatents

    Headley, Daniel (Albuquerque, NM); Ramsey, Marc (Albuquerque, NM); Schwarz, Jens (Albuquerque, NM)

    2007-06-12

    A variable focal length deformable mirror has an inner ring and an outer ring that simply support and push axially on opposite sides of a mirror plate. The resulting variable clamping force deforms the mirror plate to provide a parabolic mirror shape. The rings are parallel planar sections of a single paraboloid and can provide an on-axis focus, if the rings are circular, or an off-axis focus, if the rings are elliptical. The focal length of the deformable mirror can be varied by changing the variable clamping force. The deformable mirror can generally be used in any application requiring the focusing or defocusing of light, including with both coherent and incoherent light sources.

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

    NASA Astrophysics Data System (ADS)

    Chubynsky, Mykyta V.; Slater, Gary W.

    2014-08-01

    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.

  16. Critical length limiting superlow friction.

    PubMed

    Ma, Ming; Benassi, Andrea; Vanossi, Andrea; Urbakh, Michael

    2015-02-01

    Since the demonstration of superlow friction (superlubricity) in graphite at nanoscale, one of the main challenges in the field of nano- and micromechanics was to scale this phenomenon up. A key question to be addressed is to what extent superlubricity could persist, and what mechanisms could lead to its failure. Here, using an edge-driven Frenkel-Kontorova model, we establish a connection between the critical length above which superlubricity disappears and both intrinsic material properties and experimental parameters. A striking boost in dissipated energy with chain length emerges abruptly due to a high-friction stick-slip mechanism caused by deformation of the slider leading to a local commensuration with the substrate lattice. We derived a parameter-free analytical model for the critical length that is in excellent agreement with our numerical simulations. Our results provide a new perspective on friction and nanomanipulation and can serve as a theoretical basis for designing nanodevices with superlow friction, such as carbon nanotubes. PMID:25699452

  17. An Experiment Investigation of Fully-Modulated, Turbulent Diffusion Flames in Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Hermanson, J. C.; Johari, H.; Usowicz, J. E.; Stocker, D. P.; Nagashima, T.; Obata, S.

    1999-01-01

    Pulsed combustion appears to have the potential to provide for rapid fuel/air mixing, compact and economical combustors, and reduced exhaust emissions. The ultimate objective of this program 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 can give rise to drastic modification of the combustion and flow characteristics of flames, leading to enhanced fuel/air mixing mechanisms not operative for the case of acoustically excited or partially-modulated jets. In addition, the fully-modulated injection approach avoids the strong acoustic forcing present in pulsed combustion devices, significantly simplifying the mixing and combustion processes. Relatively little is known of the behavior of turbulent flames in reduced-gravity conditions, even in the absence of pulsing. The goal of this Flight-Definition experiment (PUFF, for PUlsed-Fully Flames) is to establish the behavior of fully-modulated, turbulent diffusion flames under microgravity conditions. Fundamental issues to be addressed in this experiment include the mechanisms responsible for the flame length decrease for fully-modulated, turbulent diffusion flames compared with steady flames, the impact of buoyancy on the mixing and combustion characteristics of these flames, and the characteristics of turbulent flame puffs under fully momentum-dominated conditions.

  18. Nanoparticle diffusion in dense polymer melts

    NASA Astrophysics Data System (ADS)

    Kalathi, Jagannathan T.; Kumar, Sanat K.; Grest, Gary S.

    2013-03-01

    The diffusion of nanoparticles in melts and solutions of polymers facilitates understanding of the viscoelastic behavior of the respective polymers and their composites. It also plays a vital role in determining the equilibrium structure and morphology of polymer nanocomposites and hence, their mechanical properties. In this work, we present the diffusion coefficients of non-sticky smooth spherical particles of different sizes (1-10 ?) in an athermal mixture of particles and polymers of different chain lengths (N = 20 to 400) using molecular dynamics simulations. The diffusion of nanoparticles of size comparable to the polymer segment size (?) is independent of chain length and hence, nanoparticles apparently feel only the local viscosity, as predicted by scaling theories. When the nanoparticle becomes larger than a segment (or alternately the correlation length in the melt), then, the diffusion coefficient decreases. This is due to the fact that the mobility of the particles is retarded either by a chain section of size equivalent to the particle size or by entanglement mesh size depending on the nanoparticle size. We also elucidate the role of chain entanglements on diffusion of nanoparticles.

  19. AMBIPOLAR DIFFUSION HEATING IN TURBULENT SYSTEMS

    SciTech Connect

    Li, Pak Shing; Myers, Andrew; McKee, Christopher F. E-mail: atmyers@berkeley.edu

    2012-11-20

    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.

  20. Double-diffusive layer formation

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  1. Length Scale of the Spin Seebeck Effect.

    PubMed

    Kehlberger, Andreas; Ritzmann, Ulrike; Hinzke, Denise; Guo, Er-Jia; Cramer, Joel; Jakob, Gerhard; Onbasli, Mehmet C; Kim, Dong Hun; Ross, Caroline A; Jungfleisch, Matthias B; Hillebrands, Burkard; Nowak, Ulrich; Klui, Mathias

    2015-08-28

    We investigate the origin of the spin Seebeck effect in yttrium iron garnet (YIG) samples for film thicknesses from 20 nm to 50???m at room temperature and 50 K. Our results reveal a characteristic increase of the longitudinal spin Seebeck effect amplitude with the thickness of the insulating ferrimagnetic YIG, which levels off at a critical thickness that increases with decreasing temperature. The observed behavior cannot be explained as an interface effect or by variations of the material parameters. Comparison to numerical simulations of thermal magnonic spin currents yields qualitative agreement for the thickness dependence resulting from the finite magnon propagation length. This allows us to trace the origin of the observed signals to genuine bulk magnonic spin currents due to the spin Seebeck effect ruling out an interface origin and allowing us to gauge the reach of thermally excited magnons in this system for different temperatures. At low temperature, even quantitative agreement with the simulations is found. PMID:26371671

  2. Length Scale of the Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Kehlberger, Andreas; Ritzmann, Ulrike; Hinzke, Denise; Guo, Er-Jia; Cramer, Joel; Jakob, Gerhard; Onbasli, Mehmet C.; Kim, Dong Hun; Ross, Caroline A.; Jungfleisch, Matthias B.; Hillebrands, Burkard; Nowak, Ulrich; Klui, Mathias

    2015-08-01

    We investigate the origin of the spin Seebeck effect in yttrium iron garnet (YIG) samples for film thicknesses from 20 nm to 50 ? m at room temperature and 50 K. Our results reveal a characteristic increase of the longitudinal spin Seebeck effect amplitude with the thickness of the insulating ferrimagnetic YIG, which levels off at a critical thickness that increases with decreasing temperature. The observed behavior cannot be explained as an interface effect or by variations of the material parameters. Comparison to numerical simulations of thermal magnonic spin currents yields qualitative agreement for the thickness dependence resulting from the finite magnon propagation length. This allows us to trace the origin of the observed signals to genuine bulk magnonic spin currents due to the spin Seebeck effect ruling out an interface origin and allowing us to gauge the reach of thermally excited magnons in this system for different temperatures. At low temperature, even quantitative agreement with the simulations is found.

  3. (VDA) Vapor Diffusion Apparatus Tray

    NASA Technical Reports Server (NTRS)

    1994-01-01

    These Vapor Diffusion Apparatus (VDA) trays were first flown in the Thermal Enclosure System (TES) during the USMP-2 (STS-62) mission. Each tray can hold 20 protein crystal growth chambers. Each chamber contains a double-barrel syringe; one barrel holds protein crystal solution and the other holds precipitant agent solution. During the microgravity mission, a torque device is used to simultaneously retract the plugs in all 20 syringes. The two solutions in each chamber are then mixed. After mixing, droplets of the combined solutions are moved onto the syringe tips so vapor diffusion can begin. During the length of the mission, protein crystals are grown in the droplets. Shortly before the Shuttle's return to Earth, the experiment is deactivated by retracting the droplets containing protein crystals, back into the syringes.

  4. Nanoparticle Diffusion in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Kalathi, Jagannathan T.; Yamamoto, Umi; Schweizer, Kenneth S.; Grest, Gary S.; Kumar, Sanat K.

    2014-03-01

    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.

  5. Flux saturation length of sediment transport

    NASA Astrophysics Data System (ADS)

    Phtz, T.; Kok, J. F.

    2013-12-01

    Sediment transport along the surface ("bedload", "saltation") drives geophysical phenomena as diverse as wind erosion and dune formation. The main length-scale controlling the dynamics of sediment erosion and deposition is the saturation length L, which characterizes the flux response to a change in transport conditions. L partially determines the dynamics of bedforms, such as dunes, for instance by dictating the wavelength of elementary dunes on a sediment surface and the minimal size of crescent-shaped barchan dunes. Here, we present an analytical model predicting L as a function of the average sediment velocity under different physical environments. Our model accounts for both the characteristics of sediment entrainment and the saturation of particle and fluid velocities, and has only two physical parameters which we estimated directly from independent experiments. We show that our model is consistent with measurements of L in both aeolian and subaqueous transport regimes over at least five orders of magnitude in the ratio of fluid and particle density, including on Mars.

  6. Bunch Length Measurements using Coherent Radiation

    SciTech Connect

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

    2005-06-24

    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.

  7. Cylindrical diffuser performance using a truncated plug nozzle

    NASA Technical Reports Server (NTRS)

    Galanga, F. L.; Mueller, T. J.

    1976-01-01

    Cylindrical diffuser performance for a truncated plug nozzle without external flow was tested in a blowdown wind tunnel. The nozzle was designed for an exit Mach number of 1.9 and the plug was conical in shape from the throat and converged to the axis of symmetry at an angle of 10 degrees. The diffuser section was fashioned into two 13.97 cm lengths to facilitate boring of the duct diameter and to allow for testing of two different duct lengths. A slotted hypotube was installed in the base of the diffuser to measure pressure distribution down the centerline of the diffuser. The data obtained included: the typical centerline and sidewall pressure ratio variation along the diffuser, cell pressure ratio vs overall pressure ratio for long and short diffusers and a comparison of minimum experimental cell pressure ratio vs area ratio.

  8. Diffusion tensor MRI phantom exhibits anomalous diffusion.

    PubMed

    Ye, Allen Q; Hubbard Cristinacce, Penny L; Zhou, Feng-Lei; Yin, Ziying; Parker, Geoff J M; Magin, Richard L

    2014-01-01

    This paper reports diffusion weighted MRI measurements of cyclohexane in a novel diffusion tensor MRI phantom composed of hollow coaxial electrospun fibers (average diameter 10.2 ?m). Recent studies of the phantom demonstrated its potential as a calibration standard at low b values (less than 1000 s/mm<;sup>2<;/sup>) for mean diffusivity and fractional anisotropy. In this paper, we extend the characterization of cyclohexane diffusion in this heterogeneous, anisotropic material to high b values (up to 5000 s/mm<;sup>2<;/sup>), where the apparent diffusive motion of the cyclohexane exhibits anomalous behavior (i.e., the molecular mean squared displacement increases with time raised to the fractional power 2?/?). Diffusion tensor MRI was performed at 9.4 T using an Agilent imaging scanner and the data fit to a fractional order Mittag-Leffler (generalized exponential) decay model. Diffusion along the fibers was found to be Gaussian (2?/?=l), while diffusion across the fibers was sub-diffusive (2?/?<;l). Fiber tract reconstruction of the data was consistent with scanning electron micrograph images of the material. These studies suggest that this phantom material may be used to calibrate MR systems in both the normal (Gaussian) and anomalous diffusion regimes. PMID:25570066

  9. Robustness of compound Dirichlet priors for Bayesian inference of branch lengths.

    PubMed

    Zhang, Chi; Rannala, Bruce; Yang, Ziheng

    2012-10-01

    We modified the phylogenetic program MrBayes 3.1.2 to incorporate the compound Dirichlet priors for branch lengths proposed recently by Rannala, Zhu, and Yang (2012. Tail paradox, partial identifiability and influential priors in Bayesian branch length inference. Mol. Biol. Evol. 29:325-335.) as a solution to the problem of branch-length overestimation in Bayesian phylogenetic inference. The compound Dirichlet prior specifies a fairly diffuse prior on the tree length (the sum of branch lengths) and uses a Dirichlet distribution to partition the tree length into branch lengths. Six problematic data sets originally analyzed by Brown, Hedtke, Lemmon, and Lemmon (2010. When trees grow too long: investigating the causes of highly inaccurate Bayesian branch-length estimates. Syst. Biol. 59:145-161) are reanalyzed using the modified version of MrBayes to investigate properties of Bayesian branch-length estimation using the new priors. While the default exponential priors for branch lengths produced extremely long trees, the compound Dirichlet priors produced posterior estimates that are much closer to the maximum likelihood estimates. Furthermore, the posterior tree lengths were quite robust to changes in the parameter values in the compound Dirichlet priors, for example, when the prior mean of tree length changed over several orders of magnitude. Our results suggest that the compound Dirichlet priors may be useful for correcting branch-length overestimation in phylogenetic analyses of empirical data sets. PMID:22328570

  10. The Length of Time's Arrow

    SciTech Connect

    Feng, Edward H.; Crooks, Gavin E.

    2008-08-21

    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.

  11. Significance of Tumor Length as Prognostic Factor for Esophageal Cancer

    PubMed Central

    Zeybek, Arife; Erdo?an, Abdullah; Glkesen, Kemal Hakan; Ergin, Makbule; Sarper, Alpay; Dertsiz, Levent; Demircan, Abid

    2013-01-01

    Our study indicated the relationship between tumor length and clinicopathologic characteristics as well as long-term survival in esophageal cancer. A total of 116 patients who underwent curative surgery for thoracic esophageal cancer with standard lymphadenectomy in 2 fields between 2000 and 2010 were included in the study. The medical records of these patients were retrospectively reviewed. The patients with tumor length ?3 cm had a highly significant difference in the involvement of adventitia and lymph node stations. The patients with tumor length ?3 cm had significantly lower rates of involvement of the adventitia and lymph node stations. Tumor length could have a significant impact on both the overall survival and disease-free survival of patients with resected esophageal carcinomas and may provide additional prognostic value to the current tumor, node, and metastasis staging system before patients receive any cancer-specific treatment. PMID:23971777

  12. Control of arc length during gas metal arc welding

    SciTech Connect

    Madigan, R.B.; Quinn, T.P.

    1994-12-31

    An arc-length control system has been developed for gas metal arc welding (GMAW) under spray transfer welding conditions. The ability to monitor and control arc length during arc welding allows consistent weld characteristics to be maintained and therefore improves weld quality. Arc length control has only been implemented for gas tungsten arc welding (GTAW), where an automatic voltage control (AVC) unit adjusts torch-to-work distance. The system developed here compliments the voltage- and current-sensing techniques commonly used for control of GMAW. The system consists of an arc light intensity sensor (photodiode), a Hall-effect current sensor, a personal computer and software implementing a data interpretation and control algorithms. Arc length was measured using both arc light and arc current signals. Welding current was adjusted to maintain constant arc length. A proportional-integral-derivative (PID) controller was used. Gains were automatically selected based on the desired welding conditions. In performance evaluation welds, arc length varied from 2.5 to 6.5 mm while welding up a sloped workpiece (ramp in CTWD) without the control. Arc length was maintained within 1 mm of the desired (5 mm ) with the control.

  13. [Association study of telomere length with idiopathic male infertility].

    PubMed

    Shuyuan, Liu; Changjun, Zhang; Haiying, Peng; Xiaoqin, Huang; Hao, Sun; Keqin, Lin; Kai, Huang; Jiayou, Chu; Zhaoqing, Yang

    2015-11-01

    Telomeres are evolutionary conserved, multifunctional DNA-protein complexes located at the ends of eukaryotic chromosomes. Telomeres maintain chromosome stability and genome integrity and also play an important role in meiosis which aid in synapsis, homologous recombination, and segregation. Sperm telomere has been reported to play an important role in fertilization and embryo development. Nowadays, the association between telomere and reproduction is one of the major areas of interest, however whether sperm telomere associated with male infertility is not clear. In this study, in order to find out the association between Chinese idiopathic infertility and sperm telomere length, we analyzed the difference of sperm telomere length between idiopathic infertile men and normal fertile men, as well as the correlations between sperm telomere length and human semen characteristics. We analyzed 126 Chinese idiopathic infertile men and 138 normal fertile men for sperm telomere length by using quantitative PCR. We found that the relative sperm mean telomere length of infertile men was significantly shorter than that of fertile men (2.894 0.115 vs. 4.016 0.603, P=5.097 x 10??). Both sperm count and semen progressive motility are related with telomere length. Our results suggest that sperm telomere length is associated with idiopathic male infertility of China and we proposed the possibility that shorter telomeres in sperm chromosome will reduce spermatogenesis and sperm functions, which finally affected the fertility of male. PMID:26582527

  14. Length dependence of carbon nanotube thermal conductivity and the "problem of long waves"

    NASA Technical Reports Server (NTRS)

    Mingo, N.; Broido, D. A.

    2005-01-01

    We present the first calculations of finite length carbon nanotube thermal conductivity that extend from the ballistic to the diffusive regime, throughout a very wide range of lengths and temperatures. The long standing problem of vanishing scattering of the "long wavelength phonf dramatically here, making the thermal conductivity diverge as the nanotube length increases. We show that the divergence disappears if 3-phonon scattering processes are considered to second or higher order. Nevertheless, for defect free nanotubes, the thermal conductivity keeps increasing up to very large lengths (10 gm at 300 K). Defects in the nanotube are also able to remove the long wavelength divergence.

  15. NMR Measures of Heterogeneity Length

    NASA Astrophysics Data System (ADS)

    Spiess, Hans W.

    2002-03-01

    Advanced solid state NMR spectroscopy provides a wealth of information about structure and dynamics of complex systems. On a local scale, multidimensional solid state NMR has elucidated the geometry and the time scale of segmental motions at the glass transition. The higher order correlation functions which are provided by this technique led to the notion of dynamic heterogeneities, which have been characterized in detail with respect to their rate memory and length scale. In polymeric and low molar mass glass formers of different fragility, length scales in the range 2 to 4 nm are observed. In polymeric systems, incompatibility of backbone and side groups as in polyalkylmethacrylates leads to heteogeneities on the nm scale, which manifest themselves in unusual chain dynamics at the glass transition involving extended chain conformations. References: K. Schmidt-Rohr and H.W. Spiess, Multidimensional Solid-State NMR and Polymers,Academic Press, London (1994). U. Tracht, M. Wilhelm, A. Heuer, H. Feng, K. Schmidt-Rohr, H.W. Spiess, Phys. Rev. Lett. 81, 2727 (1998). S.A. Reinsberg, X.H. Qiu, M. Wilhelm, M.D. Ediger, H.W. Spiess, J.Chem.Phys. 114, 7299 (2001). S.A. Reinsberg, A. Heuer, B. Doliwa, H. Zimmermann, H.W. Spiess, J. Non-Crystal. Solids, in press (2002)

  16. Moving contact line dynamics: from diffuse to sharp interfaces

    NASA Astrophysics Data System (ADS)

    Kusumaatmaja, H.; Hemingway, E. J.; Fielding, S. M.

    2016-02-01

    We reconcile two scaling laws that have been proposed in the literature for the slip length associated with a moving contact line in diffuse interface models, by demonstrating each to apply in a different regime of the ratio of the microscopic interfacial width $l$ and the macroscopic diffusive length $l_D= (M\\eta)^{1/2}$, where $\\eta$ is the fluid viscosity and $M$ the mobility governing intermolecular diffusion. For small $l_D/l$ we find a diffuse interface regime in which the slip length scales as $\\xi \\sim(l_Dl)^{1/2}$. For larger $l_D/l>1$ we find a sharp interface regime in which the slip length depends only on the diffusive length, $\\xi \\sim l_D \\sim (M\\eta)^{1/2}$, and therefore only on the macroscopic variables $\\eta$ and $M$, independent of the microscopic interfacial width $l$. We also give evidence that modifying the microscopic interfacial terms in the model's free energy functional appears to affect the value of the slip length only the diffuse interface regime, consistent with the slip length depending only on macroscopic variables in the sharp interface regime. Finally, we demonstrate the dependence of the dynamic contact angle on the capillary number to be in excellent agreement with the theoretical prediction of \\cite{Cox1986}, provided we allow the slip length to be rescaled by a dimensionless prefactor. This prefactor appears to converge to unity in the sharp interface limit, but is smaller in the diffuse interface limit. The excellent agreement of results obtained using three independent numerical methods, across several decades of the relevant dimensionless variables, demonstrates our findings to be free of numerical artifacts.

  17. Calibration of the Mixing-length Theory for Convective White Dwarf Envelopes

    NASA Astrophysics Data System (ADS)

    Tremblay, P.-E.; Ludwig, H.-G.; Freytag, B.; Fontaine, G.; Steffen, M.; Brassard, P.

    2015-02-01

    A calibration of the mixing-length parameter in the local mixing-length theory (MLT) is presented for the lower part of the convection zone in pure-hydrogen-atmosphere white dwarfs. The parameterization is performed from a comparison of three-dimensional (3D) CO5BOLD simulations with a grid of one-dimensional (1D) envelopes with a varying mixing-length parameter. In many instances, the 3D simulations are restricted to the upper part of the convection zone. The hydrodynamical calculations suggest, in those cases, that the entropy of the upflows does not change significantly from the bottom of the convection zone to regions immediately below the photosphere. We rely on this asymptotic entropy value, characteristic of the deep and adiabatically stratified layers, to calibrate 1D envelopes. The calibration encompasses the convective hydrogen-line (DA) white dwarfs in the effective temperature range 6000 <= T eff (K) <=15, 000 and the surface gravity range 7.0 <= log g <= 9.0. It is established that the local MLT is unable to reproduce simultaneously the thermodynamical, flux, and dynamical properties of the 3D simulations. We therefore propose three different parameterizations for these quantities. The resulting calibration can be applied to structure and envelope calculations, in particular for pulsation, chemical diffusion, and convective mixing studies. On the other hand, convection has no effect on the white dwarf cooling rates until there is a convective coupling with the degenerate core below T eff ~ 5000 K. In this regime, the 1D structures are insensitive to the MLT parameterization and converge to the mean 3D results, hence they remain fully appropriate for age determinations.

  18. CALIBRATION OF THE MIXING-LENGTH THEORY FOR CONVECTIVE WHITE DWARF ENVELOPES

    SciTech Connect

    Tremblay, P.-E.; Ludwig, H.-G.; Freytag, B.; Fontaine, G.; Brassard, P.; Steffen, M.

    2015-02-01

    A calibration of the mixing-length parameter in the local mixing-length theory (MLT) is presented for the lower part of the convection zone in pure-hydrogen-atmosphere white dwarfs. The parameterization is performed from a comparison of three-dimensional (3D) CO5BOLD simulations with a grid of one-dimensional (1D) envelopes with a varying mixing-length parameter. In many instances, the 3D simulations are restricted to the upper part of the convection zone. The hydrodynamical calculations suggest, in those cases, that the entropy of the upflows does not change significantly from the bottom of the convection zone to regions immediately below the photosphere. We rely on this asymptotic entropy value, characteristic of the deep and adiabatically stratified layers, to calibrate 1D envelopes. The calibration encompasses the convective hydrogen-line (DA) white dwarfs in the effective temperature range 6000 ≤ T {sub eff} (K) ≤15, 000 and the surface gravity range 7.0 ≤ log g ≤ 9.0. It is established that the local MLT is unable to reproduce simultaneously the thermodynamical, flux, and dynamical properties of the 3D simulations. We therefore propose three different parameterizations for these quantities. The resulting calibration can be applied to structure and envelope calculations, in particular for pulsation, chemical diffusion, and convective mixing studies. On the other hand, convection has no effect on the white dwarf cooling rates until there is a convective coupling with the degenerate core below T {sub eff} ∼ 5000 K. In this regime, the 1D structures are insensitive to the MLT parameterization and converge to the mean 3D results, hence they remain fully appropriate for age determinations.

  19. Applicability of Mixing Length Theory to a Turbulent Vortex System

    NASA Technical Reports Server (NTRS)

    Ragsdale, Robert G.

    1961-01-01

    The ability of mixing length theory to correlate vortex data is evaluated. Expressions are derived for eddy diffusivity by applying the techniques of von Karman and Prandtl which have been established for pipe flow. Total and static pressures were measured from the outer radius to the exhaust-nozzle radius of a vortex generator for a range of mass flows. These data are combined with Navier-Stokes solutions for this region of a compressible vortex to determine turbulent Reynolds numbers. The Reynolds number is related to Prandtl and Karman functions for various assumed boundary conditions, and the experimental data are used to determine the usefulness of these expressions. The following conclusions were reached: (1) Mixing length functions developed by applying von Karman's similarity hypothesis to vortex motion correlate the data better than do Prandtl functions obtained with the assumption that mixing length is proportional to radius. (2) Some of the expressions developed do not adequately represent the experimental data. (3) The data are correlated with acceptable scatter by evaluating the fluid radial inertia at the outer boundary and the shear stress at the inner boundary. The universal constant K was found to be 0.04 to 0.08, rather than the value of 0.4 which is accepted for rectilinear flow. (4) The data are best correlated by a modified Karman expression which includes an effect of radial inertia, as well as shear stress, on eddy diffusivity.

  20. Ligand chain length conveys thermochromism.

    PubMed

    Ganguly, Mainak; Panigrahi, Sudipa; Chandrakumar, K R S; Sasmal, Anup Kumar; Pal, Anjali; Pal, Tarasankar

    2014-08-14

    Thermochromic properties of a series of non-ionic copper compounds have been reported. Herein, we demonstrate that Cu(II) ion with straight-chain primary amine (A) and alpha-linolenic (fatty acid, AL) co-jointly exhibit thermochromic properties. In the current case, we determined that thermochromism becomes ligand chain length-dependent and at least one of the ligands (A or AL) must be long chain. Thermochromism is attributed to a balanced competition between the fatty acids and amines for the copper(II) centre. The structure-property relationship of the non-ionic copper compounds Cu(AL)2(A)2 has been substantiated by various physical measurements along with detailed theoretical studies based on time-dependent density functional theory. It is presumed from our results that the compound would be a useful material for temperature-sensor applications. PMID:24943491

  1. Geometry of area without length

    NASA Astrophysics Data System (ADS)

    Ho, Pei-Ming; Inami, Takeo

    2016-01-01

    To define a free string by the Nambu-Goto action, all we need is the notion of area, and mathematically the area can be defined directly in the absence of a metric. Motivated by the possibility that string theory admits backgrounds where the notion of length is not well defined but a definition of area is given, we study space-time geometries based on the generalization of a metric to an area metric. In analogy with Riemannian geometry, we define the analogues of connections, curvatures, and Einstein tensor. We propose a formulation generalizing Einstein's theory that will be useful if at a certain stage or a certain scale the metric is ill defined and the space-time is better characterized by the notion of area. Static spherical solutions are found for the generalized Einstein equation in vacuum, including the Schwarzschild solution as a special case.

  2. Microfabricated diffusion source

    DOEpatents

    Oborny, Michael C.; Frye-Mason, Gregory C.; Manginell, Ronald P.

    2008-07-15

    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.

  3. Measuring charge carrier diffusion in coupled colloidal quantum dot solids.

    PubMed

    Zhitomirsky, David; Voznyy, Oleksandr; Hoogland, Sjoerd; Sargent, Edward H

    2013-06-25

    Colloidal quantum dots (CQDs) are attractive materials for inexpensive, room-temperature-, and solution-processed optoelectronic devices. A high carrier diffusion length is desirable for many CQD device applications. In this work we develop two new experimental methods to investigate charge carrier diffusion in coupled CQD solids under charge-neutral, i.e., undepleted, conditions. The methods take advantage of the quantum-size-effect tunability of our materials, utilizing a smaller-bandgap population of quantum dots as a reporter system. We develop analytical models of diffusion in 1D and 3D structures that allow direct extraction of diffusion length from convenient parametric plots and purely optical measurements. We measure several CQD solids fabricated using a number of distinct methods and having significantly different doping and surface ligand treatments. We find that CQD materials recently reported to achieve a certified power conversion efficiency of 7% with hybrid organic-inorganic passivation have a diffusion length of 80 10 nm. The model further allows us to extract the lifetime, trap density, mobility, and diffusion coefficient independently in each material system. This work will facilitate further progress in extending the diffusion length, ultimately leading to high-quality CQD solid semiconducting materials and improved CQD optoelectronic devices, including CQD solar cells. PMID:23701285

  4. Electronic states in diffused quantum wells

    NASA Astrophysics Data System (ADS)

    Vlaev, S.; Contreras-Solorio, D. A.

    1997-10-01

    In the present study we calculate the energy values and the spatial distributions of the bound electronic states in some diffused quantum wells. The calculations are performed within the virtual crystal approximation, sp3s* spin dependent empirical tight-binding model and the surface Green function matching method. A good agreement is found between our results and experimental data obtained for AlGaAs/GaAs quantum wells with thermally induced changes in the profile at the interfaces. Our calculations show that for diffusion lengths LD=0-20 the optical transition between the ground electron and hole states is less sensitive to the LD changes than the optical transitions between the excited electron and hole states. For diffusion lengths LD=20-100 , the optical transition between the second excited states is not sensitive to the diffusion length, but the other optical transitions display large "blue shifts" as LD increases. The observed dependence is explained in terms of the bound states spatial distributions.

  5. Attenuation characteristics of nonlinear pressure waves propagating in pipes

    NASA Technical Reports Server (NTRS)

    Shih, C. C.

    1974-01-01

    A series of experiments was conducted to investigate temporal and spatial velocity distributions of fluid flow in 3-in. open-end pipes of various lengths up to 210 ft, produced by the propagation of nonlinear pressure waves of various intensities. Velocity profiles across each of five sections along the pipes were measured as a function of time with the use of hot-film and hot-wire anemometers for two pressure waves produced by a piston. Peculiar configurations of the velocity profiles across the pipe section were noted, which are uncommon for steady pipe flow. Theoretical consideration was given to this phenomenon of higher velocity near the pipe wall for qualitative confirmation. Experimentally time-dependent velocity distributions along the pipe axis were compared with one-dimensional theoretical results obtained by the method of characteristics with or without diffusion term for the purpose of determining the attenuation characteristics of the nonlinear wave propagation in the pipes.

  6. Diffusion on spatial network

    NASA Astrophysics Data System (ADS)

    Hui, Zi; Tang, Xiaoyue; Li, Wei; Greneche, Jean-Marc; Wang, Qiuping A.

    2015-04-01

    In this work, we study the problem of diffusing a product (idea, opinion, disease etc.) among agents on spatial network. The network is constructed by random addition of nodes on the planar. The probability for a previous node to be connected to the new one is inversely proportional to their spatial distance to the power of ?. The diffusion rate between two connected nodes is inversely proportional to their spatial distance to the power of ? as well. Inspired from the Fick's first law, we introduce the diffusion coefficient to measure the diffusion ability of the spatial network. Using both theoretical analysis and Monte Carlo simulation, we get the fact that the diffusion coefficient always decreases with the increasing of parameter ? and ?, and the diffusion sub-coefficient follows the power-law of the spatial distance with exponent equals to -?-?+2. Since both short-range diffusion and long-range diffusion exist, we use anomalous diffusion method in diffusion process. We get the fact that the slope index ? in anomalous diffusion is always smaller that 1. The diffusion process in our model is sub-diffusion.

  7. The Diffuse Interstellar Bands: Contributed papers

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

  8. Delta-doping in diffusion studies

    NASA Astrophysics Data System (ADS)

    Bnire, Franois; Chaplain, Ren; Gauneau, Marcel; Reddy, Viswanatha; Rgrny, Andr

    1993-12-01

    The ?-doping where the dopant is confined on the length-scale of the lattice constant provides perfectly ideal conditions to study the atomic transport processes. We have studied MBE-grown GaAs samples ?-doped with Si and Al layers. Long time diffusion anneals have been performed in the temperature range 550 800 C. The distribution profiles are examined by SIMS-profiling. We obtain Si diffusion coefficients in good agreement with the other recent studies using different techniques (rapid thermal annealing, capacitance-voltage profiling, sandwiched diffusion source). This contrasts with the earlier measurements based on diffusion of implanted dopants which were much more widely spread. We conclude that the more accurate data allowed with the ?-doping show that the diffusion coefficient is an intrinsic parameter provided that the amount of dopant and the dislocation density are kept sufficiently small. Le dopage-delta, o le dopant est confin l'chelle du paramtre du rseau, fournit les conditions parfaitement idales pour tudier les processus de transport atomique. Nous avons tudi des chantillons de GaAs obtenus par pitaxie par jet molculaire dops par des couches-delta de Si et Al. Des traitements de diffusion de longue dure ont t raliss dans l'intervalle de temprature 550 800C. Les profils de distribution sont examins par spectromtrie d'mission d'ions secondaires. Nous obtenons des coefficients de diffusion de Si en bon accord avec les autres tudes rcentes utilisant des techniques diffrentes (traitement thermique ultrarapide, profil de distribution par la mthode capacit-voltage, diffusion d'une couche sandwich ). Ceci diffre des mesures antrieures qui, bases sur la diffusion de dopants implants, taient beaucoup plus disperses. Nous concluons que les donnes plus prcises rendues possibles par le dopage-delta montrent que le coefficient de diffusion est un paramtre intrinsque la condition que la quantit de dopant et la densit de dislocation demeurent assez faibles.

  9. Tau Protein Diffuses along the Microtubule Lattice*

    PubMed Central

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

    2012-01-01

    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

  10. An Efficient Variable-Length Data-Compression Scheme

    NASA Technical Reports Server (NTRS)

    Cheung, Kar-Ming; Kiely, Aaron B.

    1996-01-01

    Adaptive variable-length coding scheme for compression of stream of independent and identically distributed source data involves either Huffman code or alternating run-length Huffman (ARH) code, depending on characteristics of data. Enables efficient compression of output of lossless or lossy precompression process, with speed and simplicity greater than those of older coding schemes developed for same purpose. In addition, scheme suitable for parallel implementation on hardware with modular structure, provides for rapid adaptation to changing data source, compatible with block orientation to alleviate memory requirements, ensures efficiency over wide range of entropy, and easily combined with such other communication schemes as those for containment of errors and for packetization.

  11. Modeling Suomi-NPP VIIRS Solar Diffuser Degradation due to Space Radiation

    NASA Astrophysics Data System (ADS)

    Shao, X.; Cao, C.

    2014-12-01

    The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi-NPP uses a solar diffuser (SD) as on-board radiometric calibrator for the reflective solar band (RSB) calibration. Solar diffuser is made of Spectralon (one type of fluoropolymer) and was chosen because of its controlled reflectance in the VIS-NIR-SWIR region and its near-Lambertian reflectance profile. Spectralon is known to degrade in reflectance at the blue end of the spectrum due to exposure to space radiations such as solar UV radiation and energetic protons. These space radiations can modify the Spectralon surface through breaking C-C and C-F bonds and scissioning or cross linking the polymer, which causes the surface roughness and degrades its reflectance. VIIRS uses a SDSM (Solar Diffuser Stability Monitor) to monitor the change in the Solar Diffuser reflectance in the 0.4 - 0.94 um wavelength range and provide a correction to the calibration constants. The H factor derived from SDSM reveals that reflectance of 0.4 to 0.6um channels of VIIRS degrades faster than the reflectance of longer wavelength RSB channels. A model is developed to derive characteristic parameters such as mean SD surface roughness height and autocovariance length of SD surface roughness from the long term spectral degradation of SD reflectance as monitored by SDSM. These two parameters are trended to assess development of surface roughness of the SD over the operation period of VIIRS.

  12. UPDATING APPLIED DIFFUSION MODELS

    EPA Science Inventory

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

  13. Self-Diffusion of Symmetric Star Polymers

    NASA Astrophysics Data System (ADS)

    Frischknecht, Amalie; Milner, Scott T.

    2000-03-01

    We use a recent theory of arm retraction in star polymers, which successfully describes their distinctive rheology, to calculate the self-diffusion constant of symmetric stars. Star polymers can only take a diffusive step when an arm fully retracts to the center. Due to the wide separation of relaxation times along the star arms, star polymers obey dynamic dilution, in which the effective entanglement network dilutes as portions of the star arms relax. This implies a picture of self-diffusion in which the junction point hops a distance of order the dilated tube diameter ad associated with the diluted network, rather than a distance of order the original ``skinny'' tube diameter a0 defined by the entanglement molecular weight. The difference is substantial, since ad scales with arm length N as a_0N^2/7. However, comparing our results to self-diffusion data of Bartels et. al.,(C. R. Bartels, B. Crist, Jr., L. J. Fetters, and W. W. Graessley, Macromolecules 19), 785, 1986. we find that the data is more consistent with diffusive hops of a length scale a0 rather than a_d.

  14. Diffusion bonding aeroengine components

    NASA Astrophysics Data System (ADS)

    Fitzpatrick, G. A.; Broughton, T.

    1988-10-01

    The use of diffusion bonding processes at Rolls-Royce for the manufacture of titanium-alloy aircraft engine components and structures is described. A liquid-phase diffusion bonding process called activated diffusion bonding has been developed for the manufacture of the hollow titanium wide chord fan blade. In addition, solid-state diffusion bonding is being used in the manufacture of hollow vane/blade airfoil constructions mainly in conjunction with superplastic forming and hot forming techniques.

  15. Diffusion studies in the type-B kinetics regime using neutron reflectometry and isotope multilayers.

    PubMed

    Schmidt, Harald

    2011-03-16

    Neutron reflectometry in combination with isotope multilayers is an advanced method to determine ultra-low diffusion lengths and self-diffusivities in solids. An approach is presented which allows the extraction of volume self-diffusivities from reflectivity patterns in nanocrystalline materials in the type-B kinetics regime. PMID:21339579

  16. Comparison of diffusion- and pumped-sampling methods to monitor volatile organic compounds in ground water, Massachusetts Military Reservation, Cape Cod, Massachusetts, July 1999-December 2002

    USGS Publications Warehouse

    Archfield, Stacey A.; LeBlanc, Denis R.

    2005-01-01

    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.

  17. Reduce Confusion about Diffusion.

    ERIC Educational Resources Information Center

    Hebrank, Mary R.

    1997-01-01

    Presents activities that allow students to explore the fundamental but poorly understood concept of diffusion by appealing to their kinesthetic senses first, then challenging their analytical skills as they try to deduce the mathematical principle involved. Presents a computer simulation of diffusion and discusses diffusion's limitations and

  18. Handbook on atmospheric diffusion

    SciTech Connect

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

    1982-01-01

    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)

  19. Buoyancy Effects on Flow Transition in Hydrogen Gas Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  20. Radon Diffusion Measurement in Polyethylene based on Alpha Detection

    SciTech Connect

    Rau, Wolfgang

    2011-04-27

    We present a method to measure the diffusion of Radon in solid materials based on the alpha decay of the radon daughter products. In contrast to usual diffusion measurements which detect the radon that penetrates a thin barrier, we let the radon diffuse into the material and then measure the alpha decays of the radon daughter products in the material. We applied this method to regular and ultra high molecular weight poly ethylene and find diffusion lengths of order of mm as expected. However, the preliminary analysis shows significant differences between two different approaches we have chosen. These differences may be explained by the different experimental conditions.

  1. 28 CFR 551.4 - Hair length.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 28 Judicial Administration 2 2014-07-01 2014-07-01 false Hair length. 551.4 Section 551.4 Judicial... Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and clean. (b) The Warden shall require an inmate with long hair to wear a cap or hair net when working in food service...

  2. 28 CFR 551.4 - Hair length.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 28 Judicial Administration 2 2012-07-01 2012-07-01 false Hair length. 551.4 Section 551.4 Judicial... Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and clean. (b) The Warden shall require an inmate with long hair to wear a cap or hair net when working in food service...

  3. 28 CFR 551.4 - Hair length.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 28 Judicial Administration 2 2010-07-01 2010-07-01 false Hair length. 551.4 Section 551.4 Judicial... Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and clean. (b) The Warden shall require an inmate with long hair to wear a cap or hair net when working in food service...

  4. 28 CFR 551.4 - Hair length.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 28 Judicial Administration 2 2011-07-01 2011-07-01 false Hair length. 551.4 Section 551.4 Judicial... Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and clean. (b) The Warden shall require an inmate with long hair to wear a cap or hair net when working in food service...

  5. 28 CFR 551.4 - Hair length.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 28 Judicial Administration 2 2013-07-01 2013-07-01 false Hair length. 551.4 Section 551.4 Judicial... Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and clean. (b) The Warden shall require an inmate with long hair to wear a cap or hair net when working in food service...

  6. Real-Valued Semigroups and (Causal) Diffusion

    SciTech Connect

    Kowar, Richard

    2011-09-22

    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.

  7. Riemann equation for prime number diffusion.

    PubMed

    Chen, Wen; Liang, Yingjie

    2015-05-01

    This study makes the first attempt to propose the Riemann diffusion equation to describe in a manner of partial differential equation and interpret in physics of diffusion the classical Riemann method for prime number distribution. The analytical solution of this equation is the well-known Riemann representation. The diffusion coefficient is dependent on natural number, a kind of position-dependent diffusivity diffusion. We find that the diffusion coefficient of the Riemann diffusion equation is nearly a straight line having a slope 0.99734 in the double-logarithmic axis. Consequently, an approximate solution of the Riemann diffusion equation is obtained, which agrees well with the Riemann representation in predicting the prime number distribution. Moreover, we interpret the scale-free property of prime number distribution via a power law function with 1.0169 the scale-free exponent in respect to logarithmic transform of the natural number, and then the fractal characteristic of prime number distribution is disclosed. PMID:26026319

  8. Titanium diffusion in olivine

    NASA Astrophysics Data System (ADS)

    Cherniak, Daniele J.; Liang, Yan

    2014-12-01

    Diffusion of Ti has been characterized in natural olivine and synthetic forsterite. Experiments on the natural olivines were run under buffered conditions (IW and NNO), and those on synthetic forsterite were run in air. Titanium diffusion appears relatively insensitive to crystallographic orientation and oxygen fugacity under the range of investigated conditions, and diffusivities are similar for Fe-bearing olivine and forsterite. For Ti diffusion in synthetic forsterite, we obtain the following Arrhenius relation for diffusion over the temperature range 900-1400 °C:

  9. Diffusion in heterogeneous media

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Liu, L.

    2012-12-01

    Diffusion in heterogeneous media has been investigated for over forty years. However, the fundamental equations for bulk (effective) diffusivity in multi-phase systems were incorrect because of the use of an inappropriate similarity between diffusion and other physical properties such as thermal conductivity. The mistake has permeated through the literature and textbooks. Specifically, the role of concentration partitioning between different phases in diffusion was not considered in such similarity relations. In this work, we present the correct method to derive such relations in heterogeneous media. Barrer [1] used the similarity between diffusivity and thermal conductivity to derive the relation between the bulk (effective) diffusivity and the individual-phase diffusivities. The approach was followed by many others [2-4]. Unfortunately the similarity approach by Barrer [1] is incorrect because there is also dissimilarity. The key difference is that, even though heat conduction and mass diffusion are characterized by a similar flux equation, in heat conduction, T is continuous across phase boundaries, whereas in diffusion, C is usually not continuous across phase boundaries. The concentration in each phase plays a major role in controlling the contribution by the phase to the bulk diffusive flux and hence the bulk diffusivity. For example, if the concentration of a component in a phase is very low, even if the diffusivity in the phase is high, the contribution of diffusion in that phase to the bulk diffusion flux can still be negligible. Hence, previous models for diffusivity in composite materials or multi-mineral rocks, no matter how sophisticated, are fundamentally wrong because the foundation is a mistake. Correcting the mistake is straightforward. The mass flux can be written in terms of chemical potential and mobility [5,6]. Because chemical potential is continuous across phase boundaries, the relation between bulk mobility and individual-phase mobilities is the same as that between bulk heat conductivity and individual-phase heat conductivities. That is, all previous relations for diffusion cannot be directly applied to diffusivities, but can be applied to mobilities. Then, from the relation between diffusivity and mobility, the correct equations can be obtained, as will be shown in the presentation. [1] Barrer (1968) Diffusion in Polymers, Academic Press, 165. [2] Crank (1975) The Mathematics of Diffusion, Clarendon Press. [3] Brady (1983) Am. J. Sci. 283A, 181. [4] Torquato et al. (1999) J. Appl. Phys. 85, 1560. [5] Lesher (1994) J Geophys. Res. 99, 9585. [6] Zhang (1993) J Geophys. Res. 98, 11901.

  10. Study on Bezier Curve Variable Step-length Algorithm

    NASA Astrophysics Data System (ADS)

    Xiao, Guorong; Xu, Xuemiao

    Bessel Curve also known as Bezier Curve, through which the general vector graphics software accurately draws curves, as the Bezier curve is relatively easy to calculate and its stable characteristic, in many areas it has been widely applied. However, for the deficiency of less efficiency exists in the common Bezier Curve Generation Algorithm, the selection of the parameter step-length significantly affects the accuracy and efficiency of the generated curve. This paper aims at the efficiency available in the existing Bezier Curve Generation Algorithm to propose the Variable Step-length Algorithm; by changing the parameter step-length of the curve generation algorithm, it can significantly reduce the calculations of a large number of duplicate points in the point-by-point generation algorithm; the algorithm not only maintains a higher accuracy, but also significantly improves the efficiency generated in the curve, with better application.

  11. Compact noninvasive electron bunch-length monitor

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  12. Li diffusion in zircon

    NASA Astrophysics Data System (ADS)

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

    2010-09-01

    Diffusion of Li under anhydrous conditions at 1 atm and under fluid-present elevated pressure (1.0-1.2 GPa) conditions has been measured in natural zircon. The source of diffusant for 1-atm experiments was ground natural spodumene, which was sealed under vacuum in silica glass capsules with polished slabs of zircon. An experiment using a Dy-bearing source was also conducted to evaluate possible rate-limiting effects on Li diffusion of slow-diffusing REE+3 that might provide charge balance. Diffusion experiments performed in the presence of H2O-CO2 fluid were run in a piston-cylinder apparatus, using a source consisting of a powdered mixture of spodumene, quartz and zircon with oxalic acid added to produce H2O-CO2 fluid. Nuclear reaction analysis (NRA) with the resonant nuclear reaction 7Li(p,?)8Be was used to measure diffusion profiles for the experiments. The following Arrhenius parameters were obtained for Li diffusion normal to the c-axis over the temperature range 703-1.151C at 1 atm for experiments run with the spodumene source: D_{text{Li}} = 7.17 10^{ - 7} { exp }( - 275 11 {text{kJmol}}^{ - 1} /{text{RT}}){text{m}}2 {text{s}}^{ - 1}. Diffusivities are similar for transport parallel to the c-axis, indicating little anisotropy for Li diffusion in zircon. Similar Li diffusivities were also found for experiments run under fluid-present conditions and for the experiment run with the Dy-bearing source. Li diffusion is considerably faster than diffusion of other cations in zircon, with a smaller activation energy for diffusion. Although Li diffusion in zircon is comparatively rapid, zircons will be moderately retentive of Li signatures at mid-crustal metamorphic temperatures, but they are unlikely to retain this information for geologically significant times under high-grade metamorphism.

  13. Inherent structure length in metallic glasses: simplicity behind complexity

    PubMed Central

    Wu, Yuan; Wang, Hui; Cheng, Yongqiang; Liu, Xiongjun; Hui, Xidong; Nieh, Taigang; Wang, Yandong; Lu, Zhaoping

    2015-01-01

    One of the central themes in materials science is the structure-property relationship. In conventional crystalline metals, their mechanical behaviour is often dictated by well-defined structural defects such as dislocations, impurities, and twins. However, the structure-property relationship in amorphous alloys is far from being understood, due to great difficulties in characterizing and describing the disordered atomic-level structure. Herein, we report a universal, yet simple, correlation between the macroscopic mechanical properties (i.e., yield strength and shear modulus) and a unique characteristic structural length in metallic glasses (MGs). Our analysis indicates that this characteristic length can incorporate effects of both the inter-atomic distance and valence electron density in MGs, and result in the observed universal correlation. The current findings shed lights on the basic understanding of mechanical properties of MGs from their disordered atomic structures. PMID:26245801

  14. Trouble with diffusion: Reassessing hillslope erosion laws with a particle-based model

    NASA Astrophysics Data System (ADS)

    Tucker, Gregory E.; Bradley, D. Nathan

    2010-03-01

    Many geomorphic systems involve a broad distribution of grain motion length scales, ranging from a few particle diameters to the length of an entire hillslope or stream. Studies of analogous physical systems have revealed that such broad motion distributions can have a significant impact on macroscale dynamics and can violate the assumptions behind standard, local gradient flux laws. Here, a simple particle-based model of sediment transport on a hillslope is used to study the relationship between grain motion statistics and macroscopic landform evolution. Surface grains are dislodged by random disturbance events with probabilities and distances that depend on local microtopography. Despite its simplicity, the particle model reproduces a surprisingly broad range of slope forms, including asymmetric degrading scarps and cinder cone profiles. At low slope angles the dynamics are diffusion like, with a short-range, thin-tailed hop length distribution, a parabolic, convex upward equilibrium slope form, and a linear relationship between transport rate and gradient. As slope angle steepens, the characteristic grain motion length scale begins to approach the length of the slope, leading to planar equilibrium forms that show a strongly nonlinear correlation between transport rate and gradient. These high-probability, long-distance motions violate the locality assumption embedded in many common gradient-based geomorphic transport laws. The example of a degrading scarp illustrates the potential for grain motion dynamics to vary in space and time as topography evolves. This characteristic renders models based on independent, stationary statistics inapplicable. An accompanying analytical framework based on treating grain motion as a survival process is briefly outlined.

  15. The effect of cavitation on the hydrofoil dynamic characteristics

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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 ε-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.

  16. Non-linear diffusion paths in two-phase ternary diffusion couples

    NASA Astrophysics Data System (ADS)

    Yang, Hongwei

    2005-11-01

    Prediction of diffusion paths facilitates the understanding of interdiffusion microstructure development at the vicinity of a common interface between two alloys. Understanding the influence of interdiffusion on microstructure is critically important to the design of many advanced materials systems such as high temperature coatings. The current study using DICTRA finite difference software predicts non-linear features formed on the diffusion path as the initial interface is approached. The non-linear diffusion path deviates from the linear zigzag shape predicted by an error function model for multiphase diffusion couples. The deviations appear as "horns" that protrude from the linear paths. The horns were found to be of two types. When the two outer legs of the diffusion path bend in the same direction, a "single-horn" is formed. When they bend in opposite directions a "double-horn" is formed. The formation of horns is attributed to the concentration dependence of the diffusivity. It results in a shift on the maximum of the flux profile from the initial interface, which accordingly leads to a rapid rise or decrease of the precipitate fraction as the interface is approached. It was found that the horn length is proportional to the composition vector component along the major eigenvector of the effective diffusivity matrix. Applying these results to a study on Ni-Cr-Al diffusion couples prepared from gamma + beta alloys, it also was found that the formation of single-phase beta layers could be attributed to the horns pointing away from each other, in which case the diffusion path could intersect the single phase beta region of the phase diagram. Comparison between EPMA data and DICTRA simulation shows that existence of second phase could introduce microstructure effect on diffusion. This microstructure effect may be taken into account for promoting or blocking the diffusion.

  17. Scale length study in TFTR (Tokamak Fusion Test Reactor)

    SciTech Connect

    Hiroe, S.; Goldston, R.J.; Bitter, M.; Bush, C.E.; Efthimion, P.C.; Grek, B.; Johnson, D.W.; Murakami, M.; Schivell, J.; Towner, H.H.

    1988-12-01

    The scale lengths of the electron density (L/sub n//sub e/), temperature (L/sub T//sub e/), and pressure (L/sub p//sub e/) gradients were investigated during the 1985 operating period of the Tokamak Fusion Test Reactor (TFTR) for gas-fueled plasmas with neutral beam injection and movable limiter. Although the global energy confinement time degrades as the heating power increases or the plasma current decreases, the radial profiles of the scale lengths (L/sub T//sub e/ and L/sup p//sub e/) remain unchanged. Especially, the electron pressure profile is constrained not to change. This trend appears to hold over a fairly wide range of TFTR operational regimes. The radial profiles of L/sub n//sub e/ and /eta//sub e/ (= L/sub n//sub e//L/sub T//sub e/) also appear to remain unchanged, although the uncertainties of the experimental data for these quantities are greater than those for L/sub T//sub e/ and L/sub p//sub e/. The experimental parameters are used to evaluate theoretical predictions of the electron thermal diffusivity, and the results are compared with the empirical thermal diffusivity. 34 refs., 18 figs., 2 tabs.

  18. Constraining gas motions in the Centaurus cluster using X-ray surface brightness fluctuations and metal diffusion

    NASA Astrophysics Data System (ADS)

    Walker, S. A.; Sanders, J. S.; Fabian, A. C.

    2015-11-01

    We compare two different methods of constraining the characteristic velocity and spatial scales of gas motions in the X-ray bright, nearby Centaurus cluster, using new deep (760 ks) Chandra observations. The power spectrum of excess surface brightness fluctuations in the 0.5-6.0 keV band in a sector to west is measured and compared to theoretical expectations for Kolmogorov index fluctuations. The observed power spectrum is flatter than these expectations, and the surface brightness fluctuations are around the 8 per cent level on length-scales of 2 kpc. We convert the 2D power spectrum of fluctuations into a 3D power spectrum using the method of Churazov et al., and then convert this into constraints on the one-component velocity of the gas motions as a function of their length-scale. We find one-component velocities in the range 100-150 km s-1 on spatial scales of 4-10 kpc. An independent constraint on the characteristic velocity and length-scales of the gas motions is then found by considering the diffusion coefficient needed to explain the distribution of metals in the Centaurus cluster, combined with the need to balance the rate of gas cooling with the rate of heat dissipated by the gas motions. We find that these two methods of constraining the velocity and length-scales of the gas motions are in good agreement.

  19. Enhanced Nanorod Diffusion in Polymer Melts

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  20. Analysis of factors important for measurements of focal length of optical systems

    NASA Astrophysics Data System (ADS)

    Pokorný, P.; Opat, J.; Mikš, A.; Novák, J.; Novák, P.

    2015-09-01

    A focal length is a basic optical characteristic of an optical system. Thus, it is important to be able to measure this value for a given optical system very accurately in practice. At present there exist various physical principles of the focal length measurement which can achieve a different measurement accuracy. In our work we analyse several methods of measurement of the focal length with respect to factors, which are important for a measurement accuracy. The analysis is performed on examples.

  1. Static lengths in glass-forming monodisperse hard-sphere fluids from periodic array pinning.

    PubMed

    Zhou, Yuxing; Milner, Scott T

    2015-12-23

    We explore the static length in glass-forming hard-sphere liquids revealed by the response of dynamical properties (diffusion coefficient D and α relaxation time τα) to a regular array of pinned particles. By assuming a universal scaling form, we find data can be excellently collapsed onto a master curve, from which relative length scales can be extracted. By exploiting a crystal-avoiding simulation method that suppresses crystallization while preserving dynamics, we can study monodisperse as well as polydisperse systems. The static length obtained from dynamical property Q (τα and D) scales as log Q ∼ ξ, with ψ ≈ 1. PMID:26473276

  2. Dependence of Ion Dynamics on the Polymer Chain Length in Poly(ethylene oxide)-Based Polymer Electrolytes.

    PubMed

    Chattoraj, Joyjit; Knappe, Marisa; Heuer, Andreas

    2015-06-01

    It is known from experiments that in the polymer electrolyte system, which contains poly(ethylene oxide) chains (PEO), lithium-cations (Li(+)), and bis(trifluoromethanesulfonyl)imide-anions (TFSI(-)), the cation and the anion diffusion and the ionic conductivity exhibit a similar chain-length dependence: with increasing chain length, they start dropping steadily, and later, they saturate to constant values. These results are surprising because Li-cations are strongly correlated with the polymer chains, whereas TFSI-anions do not have such bonding. To understand this phenomenon, we perform molecular dynamics simulations of this system for four different polymer chain lengths. The diffusion results obtained from our simulations display excellent agreement with the experimental data. The cation transport model based on the Rouse dynamics can successfully quantify the Li-diffusion results, which correlates Li diffusion with the polymer center-of-mass motion and the polymer segmental motion. The ionic conductivity as a function of the chain length is then estimated based on the chain-length-dependent ion diffusion, which shows a temperature-dependent deviation for short chain lengths. We argue that in the first regime, counterion correlations modify the conductivity, whereas for the long chains, the system behaves as a strong electrolyte. PMID:25965904

  3. Quantitative diffusion coefficient maps using fast spin-echo MRI.

    PubMed

    Brockstedt, S; Thomsen, C; Wirestam, R; Holts, S; Sthlberg, F

    1998-10-01

    In this work, we have evaluated the performance of a diffusion-sensitive fast spin-echo (FSE) pulse sequence. The proposed pulse sequence utilises velocity-compensating diffusion-encoding gradients and includes the collection of navigator echoes. Spoiler gradients were inserted in the slice-selecting direction to minimise effects from stimulated echoes. Calculations of the b values showed that cross-terms between imaging gradients and diffusion gradients only led to a marginal increase of b values. Pixel-wise calculation of apparent diffusion coefficient (ADC) maps was performed numerically, considering cross-terms between diffusion-encoding and imaging gradients. The sequences investigated used echo train lengths of 16, 8 and 4 echoes and were encoded in either the slice-, frequency- or phase-encoding direction. In order to allow for higher b values a pulse-sequence version using non-motion compensating diffusion-encoding gradients was written. Phantom measurements were performed and the diffusion coefficients of water and acetone were reasonable. Seven healthy volunteers (age 28-50 years) were examined and apparent diffusion coefficient values agreed well with expected values. Diffusion-weighted images, apparent diffusion coefficient maps and images corresponding to the trace of the diffusion tensor of good quality were retrieved in vivo. PMID:9814769

  4. Turbulence generation and diffusion in coastal breaking waves

    NASA Astrophysics Data System (ADS)

    Rodriguez, A.; Mosso, C.; Serra, P.; Diez, M.

    2009-04-01

    Turbulence in the surf zone is a complex topic of study, of importance for both hydromorphodynamic and environmental studies. In this paper experimental results of turbulent flows for field tests in the Spanish Mediterranean coast are presented. The spatail and temporal resolution of measurements were limited by the ElectroMagnetic Sensors wich result in "filtering" out the small scales and observing; thus only macroturbulence due to breaking waves has been measured. The experimental field-results have been obtained during DELTA`93 and DELTA`96 largescale surf zone experiments in the Ebro Delta, (Spain), under Spilling/plungeing breaking waves (Rodriguez, 1997, PhD Thesis UPC, Barcelona). The field works include several measurements as topo-bathymetric surveys, water levels, 2DH and 2DV velocities, suspended sediment concentrations, sediment properties, meteorological conditions, etc. Several test across the surf zone with high vertical resolution were obtained, covering low, medium and high energy levels. Macroturbulence has been splitted from oscillatory fr irregular waves with a recent technique and then turbulent characteristics have been obtained. This turbulent properties are compared with state-of-art macroturbulence characteristics and a new semi-empirical length-scale formulation is proposed. Further measurements on structure functions of the velocity turbulent fluctuations are compared with the distributions of effective surface diffusivity.

  5. Influence of interface compounds on interface bonding characteristics of aluminium and silicon carbide

    SciTech Connect

    Sozhamannan, G.G.; Prabu, S. Balasivanandha

    2009-09-15

    The interface plays an important role in improving the mechanical properties of metal matrix composites. Hence, it is essential to evaluate interface bonding of Aluminium/Silicon carbide. The interface bonding of Aluminum/Silicon carbide samples were prepared by various processing temperatures at constant holding time. The interface compounds at the interface were evaluated by an energy dispersive spectroscope and diffusion length of compounds was calculated by Arrhenius equation. The interface structure was analyzed by a scanning electron microscope. The interface characteristics were evaluated by tensile test and microhardness test.

  6. Inheritance of telomere length in a bird.

    PubMed

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

    2011-01-01

    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

  7. Inheritance of Telomere Length in a Bird

    PubMed Central

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

    2011-01-01

    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

  8. Narrow groove welding gas diffuser assembly and welding torch

    SciTech Connect

    Rooney, Stephen J.

    2000-02-04

    A diffuser assembly is provided for narrow groove welding using an automatic gas tungsten arc welding torch. The diffuser assembly includes manifold adapted for adjustable mounting on the welding torch which is received in a central opening in the manifold. Laterally extending manifold sections communicate with a shield gas inlet such that shield gas supplied to the inlet passes to gas passages of the manifold sections. First and second tapered diffusers are respectively connected to the manifold sections in fluid communication with the gas passages thereof. The diffusers extend downwardly along the torch electrode on opposite sides thereof so as to release shield gas along the length of the electrode and at the distal tip of the electrode. The diffusers are of a transverse width which is on the order of the thickness of the electrode so that the diffusers can, in use, be inserted into a narrow welding groove before and after the electrode in the direction of the weld operation.

  9. Narrow groove welding gas diffuser assembly and welding torch

    DOEpatents

    Rooney, Stephen J.

    2001-01-01

    A diffuser assembly is provided for narrow groove welding using an automatic gas tungsten arc welding torch. The diffuser assembly includes a manifold adapted for adjustable mounting on the welding torch which is received in a central opening in the manifold. Laterally extending manifold sections communicate with a shield gas inlet such that shield gas supplied to the inlet passes to gas passages of the manifold sections. First and second tapered diffusers are respectively connected to the manifold sections in fluid communication with the gas passages thereof. The diffusers extend downwardly along the torch electrode on opposite sides thereof so as to release shield gas along the length of the electrode and at the distal tip of the electrode. The diffusers are of a transverse width which is on the order of the thickness of the electrode so that the diffusers can, in use, be inserted into a narrow welding groove before and after the electrode in the direction of the weld operation.

  10. Numerical study of a cylinder model of the diffusion MRI signal for neuronal dendrite trees

    NASA Astrophysics Data System (ADS)

    Van Nguyen, Dang; Grebenkov, Denis; Le Bihan, Denis; Li, Jing-Rebecca

    2015-03-01

    We study numerically how the neuronal dendrite tree structure can affect the diffusion magnetic resonance imaging (dMRI) signal in brain tissue. For a large set of randomly generated dendrite trees, synthetic dMRI signals are computed and fitted to a cylinder model to estimate the effective longitudinal diffusivity DL in the direction of neurites. When the dendrite branches are short compared to the diffusion length, DL depends significantly on the ratio between the average branch length and the diffusion length. In turn, DL has very weak dependence on the distribution of branch lengths and orientations of a dendrite tree, and the number of branches per node. We conclude that the cylinder model which ignores the connectivity of the dendrite tree, can still be adapted to describe the apparent diffusion coefficient in brain tissue.

  11. Double diffusive instabilities of chemical fronts

    NASA Astrophysics Data System (ADS)

    Zebib, A.; D'Hernoncourt, J.

    2005-11-01

    Gravitational Hele-Shaw fingering of an autocatalytic reaction diffusion interface is investigated theoretically. Dimensional analysis based on reaction diffusion length, time, and velocity scales reveal the dependence on the Lewis number Le, and thermal and concentration Rayleigh numbers RT and Rc. Linear stability analysis of a planar upward propagating (against the gravitational acceleration) interface results in an eigenvalue problem for each wavenumber k which we solve using a Chebyshev pseudospectral method. A novel light over heavy instability of an endothermic reaction was found when Le>1. It is shown that this instability is equivalent to that of a downward propagating exothermic wave. Nonlinear second-order Crank-Nicolson, finite volume simulations are in agreement with linear theory and also show the docile nature of the interface breakup. A displaced particle argument confirms that this unexpected instability is local, that it is subdued by a region of local stability, and elucidates its dependence on the underlying reaction diffusion mechanism.

  12. Diffusion in Solids

    NASA Astrophysics Data System (ADS)

    Wahnstrm, Gran

    A knowledge of diffusion in solids is necessary in order to describe the kinetics of various solid state reactions such as phase transformations, creep, annealing, precipitation, oxidation, corrosion, etc., all fundamental processes in materials science. There are two main approaches to diffusion in solids [1-5]: (i) the atomistic approach, where the atomic nature of the diffusing entities is explicitly considered; and (ii) the continuum approach, where the diffusing entities are treated as a continuous medium and the atomic nature of the diffusion process is ignored. Many useful results and general relations can be obtained within the continuum approach, but a more complete picture is obtained if the atomic motions are considered. Macroscopic quantities, such as diffusion fluxes, can then be related to microscopic quantities, such as atomic jump frequencies. Knowledge of how atoms move in solids is also intimately connected with the study of defects in solids.

  13. Hereditary Diffuse Infiltrating Retinoblastoma.

    PubMed

    Schedler, Katharina J E; Traine, Peter G; Lohmann, Dietmar R; Haritoglou, Christos; Metz, Klaus A; Rodrigues, Eduardo B

    2016-03-01

    Retinoblastoma is one of the most common childhood cancers. The diffuse infiltrating retinoblastoma is a rare subtype of this neoplasm. The majority of cases of diffuse infiltrating retinoblastoma are unilateral and occur sporadically. Herein we report on a family with three children affected by retinoblastoma, among them one girl with diffuse infiltrating retinoblastoma. This girl was diagnosed at the age of 8 years with a unilateral diffuse infiltrating retinoblastoma. By contrast, the two brothers became clinically apparent in the first 2 years of life with bilateral retinoblastoma. The parents were clinically unremarkable. Genetic analysis of RB1 gene was performed. The girl with diffuse infiltrating RB was found to be heterozygous for an oncogenic mutation in the RB1 gene that was also carried by both brothers and the father of the family. These results show that diffuse infiltrating retinoblastoma can develop on the background of a hereditary predisposition to retinoblastoma. PMID:24892564

  14. Multinomial diffusion equation

    SciTech Connect

    Balter, Ariel I.; Tartakovsky, Alexandre M.

    2011-06-24

    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.

  15. Subnanosecond spectral diffusion measurement using photon correlation

    NASA Astrophysics Data System (ADS)

    Sallen, G.; Tribu, A.; Aichele, T.; Andr, R.; Besombes, L.; Bougerol, C.; Richard, M.; Tatarenko, S.; Kheng, K.; Poizat, J.-Ph.

    2010-10-01

    Spectral diffusion is a result of random spectral jumps of a narrow line as a result of a fluctuating environment. It is an important issue in spectroscopy, because the observed spectral broadening prevents access to the intrinsic line properties. However, its characteristic parameters provide local information on the environment of a light emitter embedded in a solid matrix, or moving within a fluid, leading to numerous applications in physics and biology. We present a new experimental technique for measuring spectral diffusion based on photon correlations within a spectral line. Autocorrelation on half of the line and cross-correlation between the two halves give a quantitative value of the spectral diffusion time, with a resolution only limited by the correlation set-up. We have measured spectral diffusion of the photoluminescence of a single light emitter with a time resolution of 90 ps, exceeding by four orders of magnitude the best resolution reported to date.

  16. Rumor diffusion in an interests-based dynamic social network.

    PubMed

    Tang, Mingsheng; Mao, Xinjun; Guessoum, Zahia; Zhou, Huiping

    2013-01-01

    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

  17. Rumor Diffusion in an Interests-Based Dynamic Social Network

    PubMed Central

    Mao, Xinjun; Guessoum, Zahia; Zhou, Huiping

    2013-01-01

    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

  18. Development of Yttrium Stabilized Zirconia (YSZ) diffusion barrier coatings for mitigation of Fuel-Cladding Chemical Interactions

    NASA Astrophysics Data System (ADS)

    Firouzdor, Vahid; Brechtl, Jamieson; Wilson, Lucas; Semerau, Brandon; Sridharan, Kumar; Allen, Todd R.

    2013-07-01

    Fuel-Cladding Chemical Interactions (FCCIs) in a nuclear reactor occurs due to thermal and radiation enhanced inter-diffusion between the cladding and fuel materials. This can have the detrimental effects of reducing the effective cladding wall thickness and the formation of low melting point eutectic compounds. Deposition of thin diffusion barrier coatings in the inner surface of the cladding can potentially reduce or delay the onset of FCCI. This study examines the feasibility of using nanofluid-based electrophoretic deposition (EPD) process to deposit coatings of Yttrium Stabilized Zirconia (YSZ) as the diffusion barrier coating. The deposition parameters, including the nanofluid solvent, additive, particle size, current, and voltage were optimized using test flat substrates of T91 ferritic-martensitic steel. A post deposition sintering step was also conducted and optimized to improve the bonding and mechanical integrity of the coating. Diffusion characteristics of the coatings were investigated by diffusion couple experiments using cerium as a fuel fission product responsible for solid state FCCI. These diffusion couple studies performed at 575 C for 100 h showed that the YSZ coatings significantly reduced the solid state inter-diffusion between cerium and steel. A heat transfer model was developed to simulate the changes in temperature profile inside the fuel cladding by addition of YSZ coating. It was found that even though the temperature can increase in the coated cladding, the temperature falls below the melting point of uranium and eutectic temperature in Fe-U phase diagram. Using a co-axial configuration in conjunction with the EPD process, YSZ was successfully deposited uniformly on the inner surfaces of 12? length sections of cladding with 4 mm inner diameter. Such a coating is extremely hard to make by conventional coating technologies like thermal spray or vapor deposition.

  19. Macromolecular Diffusion in Dynamic Polymer Nanocomposite

    NASA Astrophysics Data System (ADS)

    Lin, Chia-Chun; Cargnello, Matteo; Clarke, Nigel; Winey, Karen; Composto, Russell

    2015-03-01

    We consider diffusion of tracer polymers in the presence of mobile nanoparticles in polymer nanocomposites (PNCs). These nanoparticles are mobile on the time scale of polymer diffusion and have dimensions less than the entanglement mesh size (i.e., tube diameter). The PNC consists of titanium dioxide nanorods (NR, diameter=4.5nm; length=30.1nm) grafted with phenyl groups uniformly dispersed in a polystyrene (P=650kg/mol; tube diameter=8nm) matrix up to 10 volume percent. Three deuterated polystyrenes (dPS; M=800, 1800 and 3200 kg/mol) are chosen because their diffusion relative to NR allows for investigating fixed and mobile NR by simply changing M. For all M, the reduced tracer diffusivities are observed to decrease monotonically as NR loading increases. However, the reduced diffusivity of dPS (3200 kg/mol) is faster than expected compared to the fixed NR case. These findings suggest that mobile NR do not effectively slow down tracer diffusion relative to fixed particles. To test this hypothesis, dPS diffusion is investigated in a high molecular weight matrix PS (2000 kg/mol) in order to slow down NR diffusion relative to dPS (3200 kg/mol). New models are needed to incorporate these mobility dependent entanglements into a comprehensive understanding of dynamics in PNCs. Primary fundings: NSF/EPSRC Materials World Network DMR-1210379 (KIW, RJC) and EP/5065373/1 (NC). Support also by the NSF/MRSEC-DMR 11-20901, and Polymer Programs DMR 09-07493.

  20. Back diffusion from thin low permeability zones.

    PubMed

    Yang, Minjune; Annable, Michael D; Jawitz, James W

    2015-01-01

    Aquitards can serve as long-term contaminant sources to aquifers when contaminant mass diffuses from the aquitard following aquifer source mass depletion. This study describes analytical and experimental approaches to understand reactive and nonreactive solute transport in a thin aquitard bounded by an adjacent aquifer. A series of well-controlled laboratory experiments were conducted in a two-dimensional flow chamber to quantify solute diffusion from a high-permeability sand into and subsequently out of kaolinite clay layers of vertical thickness 15 mm, 20 mm, and 60 mm. One-dimensional analytical solutions were developed for diffusion in a finite aquitard with mass exchange with an adjacent aquifer using the method of images. The analytical solutions showed very good agreement with measured breakthrough curves and aquitard concentration distributions measured in situ by light reflection visualization. Solutes with low retardation accumulated more stored mass with greater penetration distance in the aquitard compared to high-retardation solutes. However, because the duration of aquitard mass release was much longer, high-retardation solutes have a greater long-term back diffusion risk. The error associated with applying a semi-infinite domain analytical solution to a finite diffusion domain increases as a function of the system relative diffusion length scale, suggesting that the solutions using image sources should be applied in cases with rapid solute diffusion and/or thin clay layers. The solutions presented here can be extended to multilayer aquifer/low-permeability systems to assess the significance of back diffusion from thin layers. PMID:25478850

  1. Inpainting using airy diffusion

    NASA Astrophysics Data System (ADS)

    Lorduy Hernandez, Sara

    2015-09-01

    One inpainting procedure based on Airy diffusion is proposed, implemented via Maple and applied to some digital images. Airy diffusion is a partial differential equation with spatial derivatives of third order in contrast with the usual diffusion with spatial derivatives of second order. Airy diffusion generates the Airy semigroup in terms of the Airy functions which can be rewritten in terms of Bessel functions. The Airy diffusion can be used to smooth an image with the corresponding noise elimination via convolution. Also the Airy diffusion can be used to erase objects from an image. We build an algorithm using the Maple package ImageTools and such algorithm is tested using some images. Our results using Airy diffusion are compared with the similar results using standard diffusion. We observe that Airy diffusion generates powerful filters for image processing which could be incorporated in the usual packages for image processing such as ImageJ and Photoshop. Also is interesting to consider the possibility to incorporate the Airy filters as applications for smartphones and smart-glasses.

  2. Multicomponent diffusion revisited

    NASA Astrophysics Data System (ADS)

    Lam, S. H.

    2006-07-01

    The derivation of the multicomponent diffusion law is revisited. Following Furry [Am. J. Phys. 16, 63 (1948)], Williams [Am. J. Phys. 26, 467 (1958); Combustion Theory, 2nd ed. (Benjamin/Cummings , Menlo Park, CA,1985)] heuristically rederived the classical kinetic theory results using macroscopic equations, and pointed out that the dynamics of the mixture fluid had been assumed inviscid. This paper generalizes the derivation, shows that the inviscid assumption can easily be relaxed to add a new term to the classical diffusion law, and the thermal diffusion term can also be easily recovered. The nonuniqueness of the multicomponent diffusion coefficient matrix is emphasized and discussed.

  3. A Simple Single Step diffusion and Emitter Etching Process for High Efficiency Gallium Antimonide Thermophotovoltaic Devices

    SciTech Connect

    G. Rajagopalan; N.S. Reddy; E. Ehsani; I.B. Bhat; P.S. Dutta; R.J. Gutmann; G. Nichols; G.W. Charache; O. Sulima

    2003-08-29

    A single step diffusion followed by precise etching of the diffused layer has been developed to obtain a diffusion profile appropriate for high efficiency GaSb thermophotovoltaic cells. The junction depth was controlled through monitoring of light current-voltage (I-V) curves (photovoltaic response) during the post diffusion emitter etching process. The measured photoresponses (prior to device fabrication) have been correlated with the quantum efficiencies and the open circuit voltages in the fabricated devices. An optimum junction depth for obtaining highest quantum efficiency and open circuit voltage is presented based on diffusion lengths (or monitoring carrier lifetimes), carrier mobility and typical diffused impurity profile in GaSb.

  4. Control of exit velocity profile of an asymmetric annular diffuser using wall suction

    NASA Technical Reports Server (NTRS)

    Juhasz, A. J.

    1973-01-01

    An asymmetric annular diffuser equipped with wall bleed (suction) capability was tested for controllability of exit velocity profile. The diffuser area ratio was 3.2, and the length to inlet height ratio was 1.6. Results show that the diffuser radial exit velocity profile could be controlled from a hub peaked to a tip peaked form by selective use of bleed on the outer wall or on both diffuser walls. Based on these results, application of the diffuser bleed technique to gas turbine combustors may be possible. Diffuser bleed could be used to tailor the airflow distribution for optimizing combustor performance at a variety of operating conditions.

  5. The platinum microelectrode/Nafion interface - An electrochemical impedance spectroscopic analysis of oxygen reduction kinetics and Nafion characteristics

    NASA Technical Reports Server (NTRS)

    Parthasarathy, Arvind; Dave, Bhasker; Srinivasan, Supramaniam; Appleby, John A.; Martin, Charles R.

    1992-01-01

    The objectives of this study were to use electrochemical impedance spectroscopy (EIS) to study the oxygen-reduction reaction under lower humidification conditions than previously studied. The EIS technique permits the discrimination of electrode kinetics of oxygen reduction, mass transport of O2 in the membrane, and the electrical characteristics of the membrane. Electrode-kinetic parameters for the oxygen-reduction reaction, corrosion current densities for Pt, and double-layer capacitances were calculated. The production of water due to electrochemical reduction of oxygen greatly influenced the EIS response and the electrode kinetics at the Pt/Nafion interface. From the finite-length Warburg behavior, a measure of the diffusion coefficient of oxygen in Nafion and diffusion-layer thickness was obtained. An analysis of the EIS data in the high-frequency domain yielded membrane and interfacial characteristics such as ionic conductivity of the membrane, membrane grain-boundary capacitance and resistance, and uncompensated resistance.

  6. Roll diffusion bonding of titanium alloy panels

    NASA Technical Reports Server (NTRS)

    Bennett, J.; De Witt, T. E.; Jones, A. G.; Koeller, F.; Muser, C.

    1968-01-01

    Roll diffusion bonding technique is used for fabricating T-stiffened panel assemblies from titanium alloy. The single unit fabrication exhibits excellent strength characteristics under tensile and compressive loads. This program is applied to structures in which weight/strength ratio and integral construction are important considerations.

  7. Measuring Crack Length in Coarse Grain Ceramics

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan A.; Ghosn, Louis J.

    2010-01-01

    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.

  8. Laser glass marking: influence of pulse characteristics

    NASA Astrophysics Data System (ADS)

    Rolo, Ana; Coelho, João; Pires, Margarida

    2005-09-01

    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.

  9. Generalizations of Brandl's theorem on Engel length

    NASA Astrophysics Data System (ADS)

    Quek, S. G.; Wong, K. B.; Wong, P. C.

    2013-04-01

    Let n < m be positive integers such that [g,nh] = [g,mh] and assume that n and m are chosen minimal with respect to this property. Let gi = [g,n+ih] where i = 1,2,,m-n. Then ?(g,h) = (g1,,gm-n) is called the Engel cycle generated by g and h. The length of the Engel cycle is m-n. A group G is said to have Engel length r, if all the length of the Engel cycles in G divides r. In this paper we discuss the Brandl's theorem on Engel length and give some of its generalizations.

  10. Biomechanical implications of mild leg length inequality.

    PubMed Central

    McCaw, S T; Bates, B T

    1991-01-01

    The effect of mild leg length inequality (lower extremity length difference less than 3 cm) on posture and gait has been the source of much controversy. Many opinions have been expressed both for and against the need for intervention to reduce the magnitude of the discrepancy. This paper emphasizes the need for accurate and reliable assessment of leg length differences using a clinically functional radiographic technique, and reviews the biomechanical implications of leg length inequality as related to the development of stress fractures, low back pain and osteoarthritis. PMID:1913023

  11. Pi Bond Orders and Bond Lengths

    ERIC Educational Resources Information Center

    Herndon, William C.; Parkanyi, Cyril

    1976-01-01

    Discusses three methods of correlating bond orders and bond lengths in unsaturated hydrocarbons: the Pauling theory, the Huckel molecular orbital technique, and self-consistent-field techniques. (MLH)

  12. Island length distribution in genome sequencing.

    PubMed

    Percus, O E; Percus, J K

    1999-09-01

    We consider the general problem of constructing a physical map of a genome by welding islands of overlapping clones. Both distribution of clone length and non-uniform probability of overlap detection are taken into account, the latter restricted to the Markov case in which only the location of the end of the developing island is required. Exact results for the distribution of island length are obtained in the special cases of fixed clone length or rigid overlap criterion, and mean and variance for the general situation. Determination of ocean length distribution permits island number and contig number distributions to be found as well. PMID:10501922

  13. Simulating dislocation loop internal dynamics and collective diffusion using stochastic differential equations

    SciTech Connect

    Derlet, P. M.; Gilbert, M. R.; Dudarev, S. L.

    2011-10-01

    Nanoscale prismatic loops are modeled via a partial stochastic differential equation that describes an overdamped continuum elastic string, with a view to describing both the internal and collective dynamics of the loop as a function of temperature. Within the framework of the Langevin equation, expressions are derived that relate the empirical parameters of the model, the friction per unit length, and the elastic stiffness per unit length, to observables that can be obtained directly via molecular-dynamics simulations of interstitial or vacancy prismatic loop mobility. The resulting expressions naturally exhibit the properties that the collective diffusion coefficient of the loop (i) scales inversely with the square root of the number of interstitials, a feature that has been observed in both atomistic simulation and in situ TEM investigations of loop mobility, and (ii) the collective diffusion coefficient is not at all dependent on the internal interactions within the loop, thus qualitatively rationalizing past simulation results showing that the characteristic migration energy barrier is comparable to that of a single interstitial, and cluster migration is a result of individual (but correlated) interstitial activity.

  14. Fractality in the neuron axonal topography of the human brain based on 3-D diffusion MRI

    NASA Astrophysics Data System (ADS)

    Katsaloulis, P.; Ghosh, A.; Philippe, A. C.; Provata, A.; Deriche, R.

    2012-05-01

    In this work the fractal architecture of the neuron axonal topography of the human brain is evaluated, as derived from 3-D diffusion MRI (dMRI) acquisitions. This is a 3D extension of work performed previously in 2D regions of interest (ROIs), where the fractal dimension of the neuron axonal topography was computed from dMRI data. A group study with 18 subjects is here conducted and the fractal dimensions D f of the entire 3-D volume of the brains is estimated via the box counting, the correlation dimension and the fractal mass dimension methods. The neuron axon data is obtained using tractography algorithms on diffusion tensor imaging of the brain. We find that all three calculations of D f give consistent results across subjects, namely, they demonstrate fractal characteristics in the short and medium length scales: different fractal exponents prevail at different length scales, an indication of multifractality. We surmise that this complexity stems as a collective property emerging when many local brain units, performing different functional tasks and having different local topologies, are recorded together.

  15. High-power diffusing-tip fibers for interstitial photocoagulation

    NASA Astrophysics Data System (ADS)

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

    1997-05-01

    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.

  16. Assessment of the Characteristics of Orientation Distribution Functions in HARDI Using Morphological Metrics

    PubMed Central

    Sun, Chang-yu; Zhu, Yue-min; Chu, Chun-yu; Yang, Feng; Liu, Wan-yu; Korenberg, Julie R.; Hsu, Edward W.

    2016-01-01

    Orientation distribution functions (ODFs) are widely used to resolve fiber crossing problems in high angular resolution diffusion imaging (HARDI). The characteristics of the ODFs are often assessed using a visual criterion, although the use of objective criteria is also reported, which are directly borrowed from classic signal and image processing theory because they are intuitive and simple to compute. However, they are not always pertinent for the characterization of ODFs. We propose a more general paradigm for assessing the characteristics of ODFs. The idea consists in regarding an ODF as a three-dimensional (3D) point cloud, projecting the 3D point cloud onto an angle-distance map, constructing an angle-distance matrix, and calculating metrics such as length ratio, separability, and uncertainty. The results from both simulated and real data show that the proposed metrics allow for the assessment of the characteristics of ODFs in a quantitative and relatively complete manner. PMID:26919477

  17. Time and length scales within a fire and implications for numerical simulation

    SciTech Connect

    TIESZEN,SHELDON R.

    2000-02-02

    A partial non-dimensionalization of the Navier-Stokes equations is used to obtain order of magnitude estimates of the rate-controlling transport processes in the reacting portion of a fire plume as a function of length scale. Over continuum length scales, buoyant times scales vary as the square root of the length scale; advection time scales vary as the length scale, and diffusion time scales vary as the square of the length scale. Due to the variation with length scale, each process is dominant over a given range. The relationship of buoyancy and baroclinc vorticity generation is highlighted. For numerical simulation, first principles solution for fire problems is not possible with foreseeable computational hardware in the near future. Filtered transport equations with subgrid modeling will be required as two to three decades of length scale are captured by solution of discretized conservation equations. By whatever filtering process one employs, one must have humble expectations for the accuracy obtainable by numerical simulation for practical fire problems that contain important multi-physics/multi-length-scale coupling with up to 10 orders of magnitude in length scale.

  18. Chain length dependence of {alpha}-olefin readsorption in Fischer-Tropsch synthesis

    SciTech Connect

    Kuipers, E.W.; Vinkenburg, I.H.; Oosterbeek, H.

    1995-03-01

    The total product concentration and the paraffin/olefin ratio have been measured up to C{sub 14} for Fischer-Tropsch synthesis on polycrystalline Co foils. The influences due to surface area, a wax coating, the H{sub 2}/CO ratio and flow velocity on concentration and selectivity have been determined. The paraffin/olefin ratio increases exponentially with chain length which is attributed to a chain-length-dependent olefin readsorption mechanism. The probability of readsorption depends on the heat of physisorption of the olefins on the catalyst as well as on their heat of dissolution in and their diffusivity through the product wax. All three factors predict an increase of the paraffin/olefin ratio with carbon number. Physisorption and dissolution are shown to cause a much stronger chain-length dependence than diffusion and will usually dominate. 36 refs., 9 figs.

  19. Adaptation and Cultural Diffusion.

    ERIC Educational Resources Information Center

    Ormrod, Richard K.

    1992-01-01

    Explores the role of adaptation in cultural diffusion. Explains that adaptation theory recognizes the lack of independence between innovations and their environmental settings. Discusses testing and selection, modification, motivation, and cognition. Suggests that adaptation effects are pervasive in cultural diffusion but require a broader, more

  20. Cosmology with matter diffusion

    SciTech Connect

    Calogero, Simone; Velten, Hermano E-mail: velten@cce.ufes.br

    2013-11-01

    We construct a viable cosmological model based on velocity diffusion of matter particles. In order to ensure the conservation of the total energy-momentum tensor in the presence of diffusion, we include a cosmological scalar field ? which we identify with the dark energy component of the universe. The model is characterized by only one new degree of freedom, the diffusion parameter ?. The standard ?CDM model can be recovered by setting ? = 0. If diffusion takes place (? > 0) the dynamics of the matter and of the dark energy fields are coupled. We argue that the existence of a diffusion mechanism in the universe may serve as a theoretical motivation for interacting models. We constrain the background dynamics of the diffusion model with Supernovae, H(z) and BAO data. We also perform a perturbative analysis of this model in order to understand structure formation in the universe. We calculate the impact of diffusion both on the CMB spectrum, with particular attention to the integrated Sachs-Wolfe signal, and on the matter power spectrum P(k). The latter analysis places strong constraints on the magnitude of the diffusion mechanism but does not rule out the model.

  1. Phantom for Diffusion MRI

    Cancer.gov

    Combining a Diffusion MRI phantom with a resolution phantom would allow the same device to be used to calibrate an MR scanner''s image quality and the accuracy and precision of its diffusion measurements. This would be useful particularly for Radiological QA and for use in assuring data quality in longitudinal and multi-subject studies.

  2. Anatomy of Particle Diffusion

    ERIC Educational Resources Information Center

    Bringuier, E.

    2009-01-01

    The paper analyses particle diffusion from a thermodynamic standpoint. The main goal of the paper is to highlight the conceptual connection between particle diffusion, which belongs to non-equilibrium statistical physics, and mechanics, which deals with particle motion, at the level of third-year university courses. We start out from the fact

  3. Investigating Diffusion with Technology

    ERIC Educational Resources Information Center

    Miller, Jon S.; Windelborn, Augden F.

    2013-01-01

    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

  4. Investigating Diffusion with Technology

    ERIC Educational Resources Information Center

    Miller, Jon S.; Windelborn, Augden F.

    2013-01-01

    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…

  5. Anatomy of Particle Diffusion

    ERIC Educational Resources Information Center

    Bringuier, E.

    2009-01-01

    The paper analyses particle diffusion from a thermodynamic standpoint. The main goal of the paper is to highlight the conceptual connection between particle diffusion, which belongs to non-equilibrium statistical physics, and mechanics, which deals with particle motion, at the level of third-year university courses. We start out from the fact…

  6. Cosmology with matter diffusion

    NASA Astrophysics Data System (ADS)

    Calogero, Simone; Velten, Hermano

    2013-11-01

    We construct a viable cosmological model based on velocity diffusion of matter particles. In order to ensure the conservation of the total energy-momentum tensor in the presence of diffusion, we include a cosmological scalar field phi which we identify with the dark energy component of the universe. The model is characterized by only one new degree of freedom, the diffusion parameter ?. The standard ?CDM model can be recovered by setting ? = 0. If diffusion takes place (? > 0) the dynamics of the matter and of the dark energy fields are coupled. We argue that the existence of a diffusion mechanism in the universe may serve as a theoretical motivation for interacting models. We constrain the background dynamics of the diffusion model with Supernovae, H(z) and BAO data. We also perform a perturbative analysis of this model in order to understand structure formation in the universe. We calculate the impact of diffusion both on the CMB spectrum, with particular attention to the integrated Sachs-Wolfe signal, and on the matter power spectrum P(k). The latter analysis places strong constraints on the magnitude of the diffusion mechanism but does not rule out the model.

  7. The Diffusion of Innovation

    NASA Technical Reports Server (NTRS)

    Earabino, Gerard J.; Heyl, G. Christopher; Percorini, Thomas J.

    1987-01-01

    New ideas encounter obstacles on way to becoming products. Report examines process by which new ideas become products, processes, or accepted standards. Sequence of events called "the diffusion of innovation." Focuses on development of material processing in low gravity as case study in diffusion of innovation.

  8. Diffusion at High Pressure

    NASA Astrophysics Data System (ADS)

    Bjina, F.; Liebermann, R. C.; Jaoul, O.

    2002-05-01

    Atomic diffusion depends upon pressure only to the second-order, but at great depths in the interior of the Earth pressure can have non negligible effects. The rapid development of high pressure devices, and especially large volume multi-anvil apparatus, has made diffusion experiments under mantle conditions possible. One particular benefit of these technological improvements is that it is now possible to perform diffusion experiments in high-pressure mineral phases present in the upper and lower mantle (e.g. wadsleyite, ringwoodite, perovskite). We have now access to a wide new range of data in order to better understand and constrain physical and chemical processes in the Earth, and also we can now compare diffusion among polymorphs (e.g. olivine, wadsleyite, ringwoodite) in order to better understand the point-defect chemistry and the microscopic processes involved. In this presentation, we will give an overview of the latest diffusion techniques and results at high pressure, among which our current experiments on Mg diffusion in forsterite single crystal up to 10~GPa performed in the multi-anvil (USSA-2000) press at Stony Brook. In these experiments, we use {}26Mg as a tracer and measure the concentration profile using the nuclear reaction {}26Mg(p, ? ){}27Al using a Van de Graaff accelerator (GPS, Paris). We will also show the current state of new experiments we just started on diffusion in synthetic polycrystalline stishovite and wadsleyite. Finally, possible new techniques applicable to diffusion experiments at high pressure will be discussed.

  9. Diffusion in Coulomb crystals

    SciTech Connect

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

    2011-07-15

    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.

  10. Diffusion in Coulomb crystals.

    PubMed

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

    2011-07-01

    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 Γ=175 to Coulomb parameters up to Γ=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. PMID:21867316

  11. Segment lengths influence hill walking strategies.

    PubMed

    Sheehan, Riley C; Gottschall, Jinger S

    2014-08-22

    Segment lengths are known to influence walking kinematics and muscle activity patterns. During level walking at the same speed, taller individuals take longer, slower strides than shorter individuals. Based on this, we sought to determine if segment lengths also influenced hill walking strategies. We hypothesized that individuals with longer segments would display more joint flexion going uphill and more extension going downhill as well as greater lateral gastrocnemius and vastus lateralis activity in both directions. Twenty young adults of varying heights (below 155 cm to above 188 cm) walked at 1.25 m/s on a level treadmill as well as 6 and 12 up and downhill slopes while we collected kinematic and muscle activity data. Subsequently, we ran linear regressions for each of the variables with height, leg, thigh, and shank length. Despite our population having twice the anthropometric variability, the level and hill walking patterns matched closely with previous studies. While there were significant differences between level and hill walking, there were few hill walking variables that were correlated with segment length. In support of our hypothesis, taller individuals had greater knee and ankle flexion during uphill walking. However, the majority of the correlations were between tibialis anterior and lateral gastrocnemius activities and shank length. Contrary to our hypothesis, relative step length and muscle activity decreased with segment length, specifically shank length. In summary, it appears that individuals with shorter segments require greater propulsion and toe clearance during uphill walking as well as greater braking and stability during downhill walking. PMID:24968942

  12. Ginning, lint cleaning, fiber length and waste

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A study was done to determine how 1) the length distribution of a medium staple upland cultivar was affected by the possible range of ginning and lint cleaning treatments, 2) the length distribution of the fiber lost during increasing levels of lint cleaning changed and 3) changes in ginned fiber le...

  13. LENGTH SCALE OF TURBULENCE ABOVE ROUGH SURFACES

    EPA Science Inventory

    Results of analyses of data for two urban sites and a rural site suggest that the mixing length can be represented by the integral length scale of the turbulence derived from vertical velocity spectra. The result is apparently universal and permits the shear production of turbule...

  14. Anomalous diffusion of brain metabolites evidenced by diffusion-weighted magnetic resonance spectroscopy in vivo

    PubMed Central

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

    2012-01-01

    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

  15. Crystalline Bis-urea Nanochannel Architectures Tailored for Single-File Diffusion Studies.

    PubMed

    Bowers, Clifford R; Dvoyashkin, Muslim; Salpage, Sahan R; Akel, Christopher; Bhase, Hrishi; Geer, Michael F; Shimizu, Linda S

    2015-06-23

    Urea is a versatile building block that can be modified to self-assemble into a multitude of structures. One-dimensional nanochannels with zigzag architecture and cross-sectional dimensions of only ?3.7 4.8 are formed by the columnar assembly of phenyl ether bis-urea macrocycles. Nanochannels formed by phenylethynylene bis-urea macrocycles have a round cross-section with a diameter of ?9.0 . This work compares the Xe atom packing and diffusion inside the crystalline channels of these two bis-ureas using hyperpolarized Xe-129 NMR. The elliptical channel structure of the phenyl ether bis-urea macrocycle produces a Xe-129 powder pattern line shape characteristic of an asymmetric chemical shift tensor with shifts extending to well over 300 ppm with respect to the bulk gas, reflecting extreme confinement of the Xe atom. The wider channels formed by phenylethynylene bis-urea, in contrast, present an isotropic dynamically average electronic environment. Completely different diffusion dynamics are revealed in the two bis-ureas using hyperpolarized spin-tracer exchange NMR. Thus, a simple replacement of phenyl ether with phenylethynylene as the rigid linker unit results in a transition from single-file to Fickian diffusion dynamics. Self-assembled bis-urea macrocycles are found to be highly suitable materials for fundamental molecular transport studies on micrometer length scales. PMID:26035000

  16. Axial length effects on lean NOx trap performance

    SciTech Connect

    Prikhodko, Vitaly Y; Nguyen, Ke; Choi, Jae-Soon; Daw, C Stuart

    2009-01-01

    The effect of axial length on the NO{sub x} reduction performance of two different commercial Lean NO{sub x} Trap (LNT) monolithic catalysts was experimentally investigated in a bench flow reactor. The washcoat composition of one of the catalysts consisted of Pt and K on {gamma}-Al{sub 2}O{sub 3}; whereas the other catalyst contained a complex mixture of Pt, Pd, Rh, Ba, Ce, Zr, Mg, Al and others. The NO{sub x} removal characteristics of cylindrical monolith segments of constant diameter (2.22 cm) and axial lengths of 2.54, 5.08 and 7.62 cm were evaluated using a simulated lean engine exhaust containing water and carbon dioxide at a constant space velocity of 30,000 h{sup -1}. No significant effects of length were observed when the catalysts were fully reduced with hydrogen between NO{sub x} capture phases. However when the catalysts were only partially regenerated NO{sub x} reduction efficiency increased with monolith length. Intra-catalyst H{sub 2} measurements at different axial locations indicated that at least some of the efficiency loss during partial regeneration occurred when back-mixed H{sub 2} was directly oxidized and became unavailable for nitrate reduction.

  17. Roughness length and displacement height derived from building databases

    SciTech Connect

    Burian, S. J.; Brown, M. J.; Velugubantla, S. P.

    2002-01-01

    In air quality and meteorological models, the bulk drag and turbulence enhancement due to cities is often parameterized through the roughness length (z{sub 0}) and displacement height (d). These log-law parameters have traditionally been derived from meteorological measurements and building morphological characteristics (e.g., see Grimmond and Oke, 1999). We are in the midst of an effort to characterize the morphological properties of some of the major cities in the western U.S. At this time we have completed the analyses for Los Angeles, Phoenix, and Salt Lake City. We are currently working with datasets from Portland and Houston and anticipate analyzing more than five other cities in the near future. Morphological analysis of 3-D building databases produces a suite of urban canopy parameters that can be incorporated into mesoscale meteorological, surface energy budget, and pollutant dispersion models. Additional computations can be performed to derive roughness length and displacement height using several common morphological formulae described in the literature. This paper summarizes the derivation of roughness length and displacement height for a 12-km{sup 2} section of downtown Los Angeles, 16-km{sup 2} section of downtown Phoenix, and 6-km{sup 2} section of downtown Salt Lake City. We correlate the computed roughness length and displacement height to underlying land use type.

  18. Fiber bundle length and cognition: a length-based tractography MRI study.

    PubMed

    Behrman-Lay, Ashley M; Usher, Christina; Conturo, Thomas E; Correia, Stephen; Laidlaw, David H; Lane, Elizabeth M; Bolzenius, Jacob; Heaps, Jodi M; Salminen, Lauren E; Baker, Laurie M; Cabeen, Ryan; Akbudak, Erbil; Luo, Xi; Yan, Peisi; Paul, Robert H

    2015-12-01

    Executive function (EF) and cognitive processing speed (CPS) are two cognitive performance domains that decline with advanced age. Reduced EF and CPS are known to correlate with age-related frontal-lobe volume loss. However, it remains unclear whether white matter microstructure in these regions is associated with age-related decline in EF and/or CPS. We utilized quantitative tractography metrics derived from diffusion-tensor MRI to investigate the relationship between the mean fiber bundle lengths (FBLs) projecting to different lobes, and EF/CPS performance in 73 healthy aging adults. We measured aspects of EF and CPS with the Trail Making Test (TMT), Color-Word Interference Test, Letter-Number Sequencing (L-N Seq), and Symbol Coding. Results revealed that parietal and occipital FBLs explained a significant portion of variance in EF. Frontal, temporal, and occipital FBLs explained a significant portion of variance in CPS. Shorter occipital FBLs were associated with poorer performance on the EF tests TMT-B and CWIT 3. Shorter frontal, parietal, and occipital FBLs were associated with poorer performance on L-N Seq and Symbol Coding. Shorter frontal and temporal FBLs were associated with lower performance on CPS tests TMT-A and CWIT 1. Shorter FBLs were also associated with increased age. Results suggest an age-related FBL shortening in specific brain regions related to poorer EF and CPS performance among older adults. Overall, results support both the frontal aging hypothesis and processing speed theory, suggesting that each mechanism is contributing to age-related cognitive decline. PMID:25376332

  19. Diffusion of single-walled carbon nanotube under physiological conditions.

    PubMed

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

    2013-06-01

    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

  20. Tungsten diffusion in silicon

    SciTech Connect

    De Luca, A.; Texier, M.; Burle, N.; Oison, V.; Pichaud, B.; Portavoce, A.; Grosjean, C.

    2014-01-07

    Two doses (10{sup 13} and 10{sup 15}?cm{sup ?2}) of tungsten (W) atoms were implanted in different Si(001) wafers in order to study W diffusion in Si. The samples were annealed or oxidized at temperatures between 776 and 960?C. The diffusion profiles were measured by secondary ion mass spectrometry, and defect formation was studied by transmission electron microscopy and atom probe tomography. W is shown to reduce Si recrystallization after implantation and to exhibit, in the temperature range investigated, a solubility limit close to 0.15%0.2%, which is higher than the solubility limit of usual metallic impurities in Si. W diffusion exhibits unusual linear diffusion profiles with a maximum concentration always located at the Si surface, slower kinetics than other metals in Si, and promotes vacancy accumulation close to the Si surface, with the formation of hollow cavities in the case of the higher W dose. In addition, Si self-interstitial injection during oxidation is shown to promote W-Si clustering. Taking into account these observations, a diffusion model based on the simultaneous diffusion of interstitial W atoms and W-Si atomic pairs is proposed since usual models used to model diffusion of metallic impurities and dopants in Si cannot reproduce experimental observations.